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2020 Quarter 1 Vol. 6, No. 1

UV Curing Enables Wood Powder Coating Materials Enhance Coatings Sustainability Photoinitiator Effects Novel Optical Materials RadLaunch Winners Announced

RadTech 2020 Preview

Official Publication of RadTech International North America


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With a worldwide installation base unequaled in the industry that spans multiple markets and applications, our UV experience is OLWHUDOO\VHFRQGWRQRQH:HRIIHUWKHะบQHVWLQSURYHQ89WHFKQRORgy including LED, Traditional and Hybrid combinations of the two. When considering the addition of UV curing to your operation, let ,67SURYLGHWKHXOWLPDWH89VROXWLRQIRU\RXUFRPSDQ\7KHUHDUH lots of choices out there, as true UV professionals we can help you make an educated and informed decision on the right UV path to pursue to meet and exceed the needs of your company. IST AMERICA U.S. OPERATIONS 121-123 Capista Drive Shorewood, IL 60404-8851 Tel. +1 815 733 5345 info@usa.ist-uv.com, www.ist-uv.com


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FEATURES 6

RadTech 2020 Event Preview

18

Novel Bio-Based Energy-Curable Polyurethane Dispersions Enhance Coating Sustainability A new bio-based energy-curable product has been developed for clear and white-pigmented wood coatings, featuring a low film formation temperature and a reduced material carbon footprint. By Michel Tielemans, Guido Vanmeulder, Johan Van den Hauwe, Cédric d’Hulst and Michela Fusco, allnex Belgium

24

UV curing provides a decorating advantage at DVUV (Cleveland, Ohio) when powder coating MDF products. By Lara Copeland, contributing writer, UV+EB Technology

ON THE COVER

The cover was finished by Royle Printing Company, Sun Prairie, Wisconsin, using a multi-step UV-curing process called Rough Reticulated Strike-Through. First, the 4-color process was laid down and a UV varnish was applied as a spot application in the areas that did not receive the gloss UV treatment (photograph and copy). The UV varnish was cured with UV lights, and then an LED curing system was used to cure the 4-color process inks. A flood gloss UV was applied over the entire cover, which “reacted” to the UV varnish and created the matte varnish – staying glossy in the areas that were knocked out to receive the gloss UV. The final step was a pass under another UV curing system to cure the coating. This process was performed in one pass on press.

27

President’s Message ............................................ 4 Association News .............................................. 10 Technology Showcase ....................................... 42 Industry ............................................................... 48 New Faces .......................................................... 52 Regulatory News ............................................... 54 Calendar ............................................................. 56 Advertising Index .............................................. 56

2 | UV+EB Technology • Quarter 1, 2020

Plastics Market Outlook: Conflicting Calls to Action Industry challenges lead the headlines for the plastics industry, but opportunities are abundant. By Dianna Brodine, managing editor, UV+EB Technology

30

Photoinitiator Effect on Depth of Cure in Visible Light Cure Polymerization In this study, different visible photoinitiators were studied to understand the effect of photoinitiator type and concentration on the surface tackiness and depth of cure. By Shuhua Jin, Erik Kareliussen and Chih-Min Cheng, Henkel Corporation

44

DEPARTMENTS

UV-Cured Powder Coating Speeds MDF Application Process Time

Development of Novel Optical Materials Using Sulfur-Based Chemistry The value of sulfur-based reactions in the development of costefficient and useful optical materials is highlighted. By Darryl A. Boyd, Colin C. Baker, Jason D. Myers, Vinh Q. Nguyen, Woohong Ki and Jasbinder S. Sanghera, Optical Sciences Division, Naval Research Laboratory and Collin C. McClain and Christopher G. Brown, University Research Foundation

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TECHNOLOGY 2020 Quarter 1 Vol. 6, No. 1

CHAMPIONS THIS ISSUE

RadTech International North America’s Editorial Board facilitates the technical articles featured in UV+EB Technology. Smaller teams of Issue Champions review and approve articles and provide overall content management for each issue, as needed.

COLUMNS 12

Susan Bailey

UV Curing Technology Proper UV Cure Specifications are a Piece of Cake By Jim Raymont, EIT LLC

14

Innovations

Editorial Board Co-Chair Business Development Manager, Digital & Specialty Printing Michelman, Inc.

Syed T. Hasan

Editorial Board Co-Chair Key Account Manager, Security Inks BASF Corporation

MicroMaker 3D Speeds Prototyping of Tiny Technology By Nancy Cates, UV+EB Technology

16

Professor’s Corner Understanding Glass Transition Temperature: Part 1 By Byron K. Christmas, Ph.D., Professor of Chemistry, Emeritus

UV+EB TECHNOLOGY EDITORIAL BOARD Susan Bailey, Michelman, Inc. Co-Chair/Editor-in-Chief Syed Hasan, BASF Corporation Co-Chair/Editor-in-Chief Darryl Boyd, US Naval Research Laboratory Byron Christmas, Professor of Chemistry, Retired Amelia Davenport, Colorado Photopolymer Solutions Charlie He, Glidewell Laboratories Mike Higgins, Phoseon Technology Molly Hladik, Michelman, Inc.

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Mike J. Idacavage, Colorado Photopolymer Solutions JianCheng Liu, PPG Industries Sudhakar Madhusoodhanan, Applied Materials Gary Sigel, Armstrong Flooring Maria Muro-Small, Spectra Group Limited, Inc. Jacob Staples, Wausau Coated Products Chen Wang, National Renewable Energy Lab Huanyu Wei, Chase Corp. Sheng “Sunny” Ye, Facebook Reality Labs

Byron Christmas

Professor of Chemistry Retired

Gary Sigel

Senior Principle Scientist Armstrong Flooring

Mike Higgins

East Regional Sales Manager Phoseon Technology

UV+EB Technology • Quarter 1, 2020 | 3


PRESIDENT’S MESSAGE

W

elcome to RadTech 2020 … the world’s largest conference dedicated to UV and EB technology!

It recently was pointed out to me that we also are the world’s largest conference focused on UV 3D printing/additive manufacturing materials and also the world’s largest conference focused on UV/ EB graphic arts materials. The number Eileen Weber of applications, reach and interest in UV/ President EB exceeds the perception that we are just a niche technology. In fact, the growing interest in UV/EB coincides with the increasing emphasis on new manufacturing paradigms (manufacturing 4.0), sustainability and initiatives to develop a circular economy. I think this is no coincidence, as all of these trends are working toward many of the same goals. As our “circular economy” begins to form, UV/EB often is considered to be part of a sustainable future. Our profile is strong, as our equipment makers innovate to increase efficiency and use less energy; our processes significantly reduce harmful emissions, such as VOCs, HAPs and CO2; and the technology seems endlessly adaptable to new applications, materials and processes. And, with end user proclamations, such as Nestlé’s 2018 pledge that it would make all of its packaging recyclable or reusable by 2025, RadTech has created a sustainability committee to help guide our members’ efforts to help our customers achieve their goals. Our diverse membership, who represent every stage of the supply chain, is seeking data to offer their customers on how our technology fits into new consumer-driven sustainability requirements. Addressing these requirements is a task that will best be achieved by working together as an association.

Developing a circular economy implies the development of relationships, and that means RadTech members are working together and leading the way to learn from and contribute to the efforts of other groups embarking on similar journeys. While not always explicitly focused on sustainability, our industry is relentlessly pursuing technologies that offer significant advancements in products and processes. RadTech 2020 in Orlando is a showcase for this innovation and will help define how we fit into a more responsible, cleaner, sustainable economy. To help accelerate this effort, RadTech 2020 features a session on sustainability and a number of papers on important innovations. In addition, our RadLaunch initiative to foster start-up companies and ideas will celebrate new UV-curable, renewable bio-based materials, more efficient solvent-free formulations and cuttingedge 3D printing/additive manufacturing. And, RadLaunch also will tout how we may enable new end-use products that foster sustainability. For example, we will be awarding an application on next-generation energy storage with UV-cured electrolyte materials. We look forward to RadTech 2020 attendees interacting and sharing with our RadLaunch class. Finally, to further encourage innovation, at RadTech 2020 we also are announcing our charter members of the National Academy of Inventors. We celebrate the invention and innovation on which our industry is built and hope to inspire continued groundbreaking research and development. As the world’s largest UV/EB organization, with an extensive supply chain and across a multitude of industries, there is an important place in our evolving circular economy for our technology. By working together, we can best validate, document and advance our contributions to the future of sustainable manufacturing. I look forward to meeting you in Orlando! 

BOARD OF DIRECTORS

Published by:

President Eileen Weber – allnex USA., Inc.

TECHNOLOGY An official publication of: RADTECH INTERNATIONAL NORTH AMERICA 6935 Wisconsin Ave, Suite 207 Chevy Chase, MD 20815 240-497-1242 radtech.org EXECUTIVE DIRECTOR Gary M. Cohen gary@radtech.org SENIOR DIRECTOR Mickey Fortune

President-elect Jo Ann Arceneaux – allnex USA Inc. Secretary Susan Bailey – Michelman Treasurer Paul Elias – Miwon North America Immediate Past-President Lisa Fine – Ink Systems, Inc. Board of Directors Evan Benbow – Wikoff Color Corporation David Biro – Sun Chemical Mike Bonner – Saint Clair Systems, Inc. Todd Fayne – Pepsico Michael Gould – Rahn USA Jeffrey Klang – Sartomer Diane Marret – Red Spot Paint & Varnish Jim Raymont – EIT LLC Chris Seubert – Ford Motor Company P.K. Swain – Heraeus Noblelight America Karl Swanson – PCT Ebeam and Integration Hui Yang – Procter and Gamble Sheng “Sunny” Ye – Facebook Reality Labs

4 | UV+EB Technology • Quarter 1, 2020

2150 SW Westport Drive, Suite 101 Topeka, Kansas 66614 785-271-5801 petersonpublications.com Publisher Jeff Peterson

National Sales Director Janet Dunnichay janet@petersonpublications.com

Art Director Becky Arensdorf

Managing Editor Dianna Brodine dianna@petersonpublications.com

Contributing Editors Nancy Cates Liz Stevens

Circulation Manager Brenda Schell brenda@petersonpublications.com

ENews & Website Developer Mikell Burr

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March 8-11, 2020

Disney Coronado Springs Orlando, Florida C Co-Located with R RadTech 2020 2020 AMERICAS CONFERENCE

With more than 100 presentations, the latest innovations in UV LEDs, 3D printing and additive manufacturing materials, printing and packaging, industrial coatings, formulations and more will be featured. The event also offers short courses in polymer chemistry, Design of Experiments, and a special UV LED Bootcamp. RadTech Conference attendees will also have access to exhibitors and presentations at the co-located, 2020 IUVA Americas Conference with topics on UV disinfection for water, food and beverage, healthcare, and UV-C LED development.

SCHEDULE-AT-A-GLANCE SUNDAY, MARCH 8 Registration Express Check-In ................ 10:00 AM – 6:00 PM UV+EB University/Short Courses ............12:00 PM – 9:00 PM MONDAY, MARCH 9 Registration Express Check-In .................. 7:00 AM – 6:00 PM Conference Sessions ................................ 8:00 AM – 5:30 PM Exhibition ................................................. 10:00 AM – 6:30 PM Opening Reception ....................................5:30 PM – 6:30 PM TUESDAY, MARCH 10 Registration Express Check-In .................. 7:00 AM – 6:00 PM Conference Sessions ................................ 8:00 AM – 5:30 PM Exhibition ................................................. 10:00 AM – 6:30 PM President’s Reception................................5:30 PM – 6:30 PM Emerging Awards Dinner ...........................6:30 PM – 8:30 PM WEDNESDAY, MARCH 11 Registration Express Check-In ................ 7:00 AM – 12:00 PM Conference Sessions ................................ 8:00 AM – 3:15 PM Exhibition ................................................. 10:00 AM – 2:00 PM EXHIBITORS

As of February 3, 2020 Aal Chem Aceto US Adhesives & Sealants Industry Alberdingk Boley Allied Photochemical allnex Alpha-Purify American Ultraviolet Aquisense Technologies Austin Chemical Company, Inc. Azul3D, Inc. BASF Corporation BCH Boston Electronics BYK USA Canadian Finishing & Coatings Manufacturing Magazine Changzhou Tronly New Electronic Materials Co.,Ltd Chitec Technology Co, Ltd.

Coatings World Coinc LLC Colorado Photopolymer Solutions Converting Quarterly Crystal IS Daicel ChemTech, Inc. Double Bond Chemical Industries USA, Inc. Dowa International Corporation DSM Dymax Eindhoven University of Technology & TNO EIT Instrument Markets Energy Sciences Inc. Evonik Corporation Evoqua Water Technologies Excelitas Technologies Fermi National Accelerator Laboratory Foshan Comwin Light & Electricity Co., Ltd.

6 | UV+EB Technology • Quarter 1, 2020

HOTEL Alternative Option for Hotel Reservations Disney’s Port Orleans Resort – Riverside 1251 Riverside Drive Lake Buena Vista, FL 32830 A small number of rooms are available at Disney’s Port Orleans Resort – Riverside for $209 a night. Please note that transportation is not offered from Port Orleans to the conference so attendees will need to take an Uber or taxi. Make reservations via the link below or by calling (407) 939-4686. Visit radtech2020.com/hotel-travel-information for reservation information, discount Disney park tickets, directions, parking and shuttle service.

Hamamatsu Corporation Hampford Research Henkel Corporation Heraeus Noblelight America Hergy Lighting Technology Corp. Hitachi Chemical Company America Honle UV America Hubei Gurun Technology Co., Ltd. Hybrid Plastics Inc. IGM Resins USA, Inc. Ink World Innovations in Optics International Light Technologies IST America ITL Jarchem Industries, Inc. Jelight Company, Inc. Keyland Polymer Material Sciences Kowa American Corporation Kromachem Ltd. Lubrizol Advanced Materials, Inc. Luminus, Inc.

Miltec UV Miwon North America Nagase America National Academy of Inventors Nedap NewSun Poly Tech Co., Ltd. NICHIA Corporation Nippon Shokubai Co., Ltd. PCI Magazine PCT Ebeam and Integration, LLC Phoseon Technology Photon Wave Co., Ltd. PL Industries division of Esstech Porex Corporation Prime UV IR Systems Printed Electronics Now Promerus Pyran rad-solutions, llc RAHN USA Corporation Red Spot Paint & Varnish Co. San Esters Corporation

Sartomer Americas Schlenk Metallic Pigments Sensor Electronic Technology / Seoul Viosys Shamrock Technologies, Inc. Showa Denko America Siltech Corporation SUEZ Water Technologies & Solutions Surfacide LLC The Waterborne Symposium Tianjin Jiuri New Materials Co., Ltd. University of Colorado Ushio America UV Chem-Keys Co., Ltd. UV Solutions UV+EB Technology Violumas ZEXI USA LLC Zhejiang Yangfan New Materials Co., Ltd

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ASSOCIATION NEWS Vote Now for Best Posters Illustrating UV/EB Technology

parallel exhibition and a number of networking breaks. For more information visit www.iculta.com.

Once again, RadTech is partnering with the Technical Association for the Graphic Arts (TAGA) to encourage students to develop designs for a poster touting UV/EB technology and the upcoming RadTech 2020 conference.

Inaugural NAI Chapter Nominees to be Named at RadTech 2020 RadTech, the first nonprofit trade association to sponsor a chapter for the National Academy of Inventors, will celebrate the new chapter and its inaugural nominees at the RadTech 2020 UV+EB Technology Expo & Conference, March 9 through 11, 2020, in Orlando, Florida. The National Academy of Inventors is a nonprofit dedicated to encouraging inventors and innovators – and has shown significant interest in UV/EB technology. RadTech was allocated a limited number of individual memberships to NAI and is nominating those who have made significant contributions to UV/EB technology – whether through patents, papers or other efforts. For more information, visit www.academyofinventors.org.

New Board of Director Members Announced by RadTech RadTech members are encouraged to vote on the top two of seven poster entries. Winning students will be presented with cash prizes and featured in UV+EB Technology magazine. Winners will be announced at the RadTech2020 awards dinner on March 10, 2020. At the dinner RadTech will also honor the best papers and celebrate RadLaunch winners, National Academy of Inventors charter members and more. To vote on your two favorite posters, visit: https://radtech2020.com/ radtech-student-poster-competition/

ICULTA Conference Set for April 26–29,2020 The Second International Conference on UV LED Technologies & Applications (ICULTA) will take place April 26 through 29, 2020, at the Melia Hotel in Berlin, Germany. Some 200 participants are expected to attend the conference, which will feature international invited, oral and poster presentations, a 10 | UV+EB Technology • Quarter 1, 2020

RadTech has announced the election of new members to its board of directors to serve a two-year term beginning in January 2020. New members include Karl Swanson, president of PCT Ebeam and Integration; Evan Benbow, director of R&D for Wikoff Color Corporation; and Diane Marret, product manager of UV Curable and Exterior Thermal technologies at Red Spot Paint & Varnish. In addition, Todd Fayne, PepsiCo, and Mike Bonner, Saint Clair Systems, were re-elected for second two-year terms. “With the continued significant growth of UV/EB in a number of applications, we are motivated to continue to develop new activities that help advance our technology,” said Eileen Weber of allnex, president of RadTech. “We are extremely excited to welcome our new Board members as their diverse experiences and expertise will greatly further our ability to do this.” Continuing Board members include Lisa Fine, Ink Systems Inc., immediate past president; JoAnn Arceneaux , allnex, presidentelect; Susan Bailey, Michelman, secretary; Paul Elias, Miwon NA, treasurer; David Biro, Sun Chemical; Michael Gould, Rahn USA; Jeffrey Klang, Sartomer; Jim Raymont, EIT; Chris Seubert, Ford Motor Co.; PK Swain, Heraeus; Hui Yang, Procter and Gamble; and Sheng “Sunny” Ye, Facebook Reality Labs.

RadLaunch Announces Start-up Technology Accelerator Class of 2020 RadLaunch, the unique idea accelerator for ultraviolet (UV) and electron beam (EB) technology start-ups, students and uvebtechnology.com + radtech.org


(,7Â&#x160;89%URDGEDQG0HDVXUHPHQW innovators, has selected five key technology developers for 2020 and three special recognition awards. RadTech, the nonprofit for UV/EB technology, created RadLaunch in recognition of the growing importance of the technology with the digitization of manufacturing and requirements for safe, clean, rapid processes in the fast-emerging circular economy. New innovations in materials, optics, design and data are propelling UV/EB in additive manufacturing/3D printing, inkjet, food packaging, automotive, medical, public health and electronics applications. ď&#x201A;ˇď&#x20AC; HARP (High-Area Rapid Printing), Azul 3D ď&#x201A;ˇď&#x20AC;  Solvent-free radical photopolymerization that continues its extensive post-conversion in the dark, Team from University of Colorado ď&#x201A;ˇď&#x20AC;  Next-Generation Energy Storage with UV Curing of Novel Polymer Electrolyte Materials, The Hosein Research Group, Syracuse University ď&#x201A;ˇď&#x20AC;  Bio-based 1,5-Pentanediol: A New Renewable Monomer for the Radcure Industry, Pyran LLC ď&#x201A;ˇď&#x20AC;  Real-time feedback-controlled monomer conversion: a new paradigm for UV curing process control, Eindhoven University of Technologyâ&#x20AC;&#x2122;s High Tech Systems Center and TNO (Eindhoven, The Netherlands) A special RadLaunch university award was presented for Novel UV-initiated Dual-curing thermoset materials suitable for 3D printing, Hamidreza Asemani, Professor Vijay Mannari; Coatings Research Institute, Eastern Michigan University, Ypsilanti, Michigan. The RadLaunch 2020 class all will give presentations at RadTech 2020, March 8 through 11, 2020. in Orlando, Florida. ď ľ

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Phone: 703-478-0700 Email: uv@eit.com Web: www.eit.com 309 Kellyâ&#x20AC;&#x2122;s Ford Plaza SE Leesburg, VA 20175

uvebtechnology.com + radtech.org

UV+EB Technology â&#x20AC;˘ Quarter 1, 2020 | 11


UV CURING TECHNOLOGY QUESTION & ANSWER

Proper UV Cure Specifications are a Piece of Cake B

on Appétit tracks down recipes of special dishes that readers have enjoyed at restaurants. Imagine obtaining the recipe of a decadent chocolate cake. You purchase, measure, sift, mix and blend the ingredients, and when it is ready to go in the oven, the recipe says to “bake for 20 minutes.” Having only the time is not helpful. What is the oven temperature? If the recipe directed you to “bake at 350 degrees” with no time listed, you would be equally puzzled. At a minimum, we expect the recipe to specify both the cook time and oven temperature. A better recipe would also specify the oven type (convection, standard), oven location (top rack, center rack), pan type (glass, metal), layer thickness and possibly any adjustments for altitude.

Like the cake recipe, many UV-curing specifications or data sheets have missing or incomplete information. Like the cake recipe, a UV specification should have both the time (energy density, J/cm2) and power (irradiance, W/ cm2) values specified.

4 Watts of irradiance, exposed for one second

Many cure specifications include only a Joule value, which can leave engineers, technicians and operators struggling to establish a process window and achieve proper UV cure. One Watt for One Second = One Joule. Having only Joules, a curing specification of 4 Joules could be achieved by any of the three exposures in Figure 1: These examples use “whole number” exposures and would lead to different characteristics in the material being cured. In the real world, a 4 Joule exposure does not fit into square blocks and looks more like the example in Figure 2. A radiometer is used to measure the irradiance and energy density. In order to properly replicate the curing process, a proper UV cure specification should at a minimum include: 1. The type of UV source (e.g. 395 nm LED, or iron additive mercury arc lamp) 2. The peak irradiance (Watts/cm2) 3. The required energy density (Joules/cm2)

2 Watts of irradiance, exposed for two seconds

With this information, you have a have a much better chance of replicating the process. Formulators will argue that they are being cautious and protecting their intellectual property. Establishing a process window requires work based on the specific application. Without a comprehensive specification, achieving proper UV cure is like rolling the dice. But when the stakes are high, leaving proper curing to chance can be a foolish bet. If available, further information also can be provided or established during tests to define the process window. Information on the UV source can be identified to the brand/model type. Examples include Heraeus 600 W/ 12 | UV+EB Technology • Quarter 1, 2020

1 Watt of irradiance, exposed for four seconds Figure 1. Irradiance and exposure examples uvebtechnology.com + radtech.org


Far too little effort is devoted to testing a “ladder” of settings that will provide good results so that the operators have a process window to work within. This is important since process conditions change over time. These changes sometimes occur naturally. For example, as an arc lamp ages, reflectors deteriorate. Or, over time, the glass on an LED array gets dirty. Other changes might be due to human error. For example, an operator might adjust a conveyor speed inaccurately or fail to properly reposition a lamp. Just like our cake recipe examples, there are likely to be a range of oven temperatures and cooking times that would produce an acceptable result. We would expect higher temperatures to require less time in the oven, to a point. However, it is unlikely that turning the dial up to 900°F will ever work. Figure 2. Four Joules in a more typical exposure

in. applied power, Light Hammer with “D” bulb or Excelitas 16 Watt 395 nm LED array. Other variables could indicate expected process speeds (e.g., 100 feet per minute), reflector type and/or distance between the substrate and the light source (e.g., a Phoseon LED 385 nm source, rated at 12 Watts, 3" from the glass.)

Such process windows have been a standard practice in other forms of curing. For example, a coating can be processed successfully at a number of different settings. This helps the operator to understand the limitations of the process and helps troubleshoot problems when they occur.

When specifying radiometer values, the type of radiometer used also should be specified. This is important because different makes and models of radiometers have different optic responses. A radiometer with a response of 250 to 420 nm will give a different reading than a radiometer with a response of 320 to 390 nm. A well-crafted specification will contain such information. Here are some examples of good, better and best process specifications: Good: Cure with 200 mW/cm2 and 1100 mJ/cm2 using a 395 nm LED. Better: Cure with 200 mW/cm2 and 1100 mJ/cm2 using an Excelitas AC7300-395 UV LED head, rated at 5 W/cm2, 15x300 mm @ 395 nm.

It would be great to see more UV formulators and processors work together to develop this kind of process window information. But in the meantime, I will be happy to see more of our customers hone their specifications so that they convey the information needed to make sure things are running properly.

Best: Cure with 200 mW/cm2 and 1100 mJ/cm2 using an Excelitas AC7300-395 UV LED head, rated at 5 W/cm2, 15x300 mm @ 395 nm and 25 fpm. Measured with an EIT L395 LEDCure radiometer.

Parting thought: With a proper UV cure specification, you can have your cake and eat it, too. 

In addition to differences in optic responses, radiometers also can have differences in dynamic range and suggested operating ranges, sampling rate and cosine response. These can lead to differences in the readings when trying to capture the process (Figure 2). When it comes to specifications, most of us set the bar too low. Even the Best specification provides only a snapshot of a set of parameters (peak irradiance and energy density) that deliver an acceptable cure. But, it would be even more helpful to know how much latitude this specification provides. uvebtechnology.com + radtech.org

See a sample UV specification sheet at www.uvebtechnology.com.

Jim Raymont Director of Sales EIT LLC jraymont@eit.com UV+EB Technology • Quarter 1, 2020 | 13


INNOVATIONS INDUSTRY ADVANCES WITH RADLAUNCH WINNERS

MicroMaker3D Speeds Prototyping of Tiny Technology By Nancy Cates, contributing editor, UV+EB Technology

W

ith the ability to 3D-print a structure smaller than a human hair, RadLaunch winner MicroMaker3D is ready to address the need for microfabrication-level rapid prototyping. “The production of small, light devices that consume less resources and use less power has enabled microsensors, wearable technology, hardware of IoT devices, point-of care devices for medical diagnostics, micro-robotics, aerospace applications and more,” said Andrea Bubendorfer, who leads the MicroMaker3D team. “Until now, there has been no rapid prototyping technology to make these tiny structures.” She explained that the group was especially interested in the opportunities the industry potentially provided, describing it as “a core technology that underpins these emerging high-value technologies. Miniaturization is critical for all these areas.” “MicroMaker3D uses our laminated resin printing (LRP) technology, our unique new patent-pending type of 3D printing,” she wrote in the application for RadTech International North America’s RadLaunch program. “Unlike other types of 3D printing, LRP uses elements of microfabrication, including extremeresolution UV imaging in concert with high-performance modern dry film photopolymer resins to achieve true 5-micron resolution. With LRP, we now can print structures smaller than a human hair, a level unprecedented with current 3D printing techniques.” The process can be used to print active structures – cantilevers, bridges and membranes – that respond to environmental stimuli. LRP accommodates such substrates as paper, fabric and printed circuit boards. Bubendorfer collaborates with engineer Andrew Best, who runs the New Zealand-based Callaghan Innovation microfabrication facility, and Business Manager Cath Andrews. “The MicroMaker project arose from some work we’d done earlier, looking initially at the New Zealand context for microfabrication,” Bubendorfer said. “Being a small country – population less than five million – as well as geographically distant from most of the world, we have few large companies working in the microfabrication space.” The group considered other means of lower-cost methods of microfabrication, seeing cleanrooms and other necessary

14 | UV+EB Technology • Quarter 1, 2020

equipment as cost-prohibitive. They began to develop techniques to scale down cost. “While others in the market were trying to do things better,” she continued, “with higher resolution, for example, we were focused on doing things simply and affordably. After a while, we realized our tools and techniques could be automated.” The result was MicroMaker – analogous to a 3D printer. Bubendorfer explained that the LRP technology was developed using fast UV projection with modern UV-activated highperformance photopolymers. “These are critical to reaching the extreme 5-micron resolution,” she said, “as well as providing fast patterning of the entire layer, with high speeds of only seconds per layer.” Micromaker3D was among the 2019 RadLaunch awardees recognized at the BIG IDEAS for UV+EB Conference last spring in Redondo Beach, California. “Being a RadLaunch winner was enormously exciting,” Bubendorfer said. “Being present at the meeting gave opportunities to talk to people in the field and see presentations that we wouldn’t otherwise have been able to. In particular, being based in New Zealand – the ability to talk to researchers and developers at the cutting edge was a fantastic opportunity to gain insights into the latest developments, markets and gain an understanding of end-user needs. “Since RadLaunch,” she continued, “we were finalists in the KiwiNet Research Commercialisation awards and winners of the New Zealand Engineering Vision (ENVI) award. Being able to claim a winning position in the RadLaunch Class of 2019 gave us prestige and credibility, which has helped with these ongoing opportunities.” Bubendorfer explained that Callaghan Innovation is New Zealand’s innovation agency. “We activate innovation and help businesses grow faster through a range of research and development services. KiwiNet is a New Zealand agency charged with getting publicly funded research to market faster. KiwiNet is made up of 18 partner research organizations, including Callaghan Innovation, working toward the common goal of transforming uvebtechnology.com + radtech.org


scientific discoveries into new businesses. In our case, MicroMaker was a project co-funded by both organizations.” One of MicroMaker3D’s first collaborations was providing a print service for a university research customer, printing structures from the researchers’ designs, “quickly and at low cost,” Bubendorfer said. “Since then, we have worked with a number of further customers, sometimes enabling entirely new capability. “The main competitor in the microfabrication field still is the manual tools and processes to develop microstructures,” she continued. “These are slow, skilled and costly techniques. Twophoton lithography – also known as two-photon polymerization – such as used by Nanoscribe, has been used to widely expand the possibilities in microfabrication, and some 3D printing techniques are increasingly developing toward printing small and high-resolution structures. Nevertheless, our process is inherently different – not just in the technical approach, but in outputs. The LRP technique of printing in 5-micron-thick solventless layers leads to a direct fabrication method to the basic micro-electromechanical systems (MEMS) springs – bridges, plates, cantilevers and membranes. “Since around the turn of the century, most of the world’s MEMS research and development has been in polymer photoresist materials, with the silicon industry reaching maturity,” she explained. “Polymer MEMS offers interesting new developments, with the material characteristics afforded by these photodefinable materials, including the flexibility seen by comparison with silicon, allowing much larger degrees of freedom of movement. I see immense opportunity for the future of photopolymers in MEMS development. It’s a very exciting field to be working in. LRP provides a route to accessing these opportunities. “These active devices move and respond to the environmental stimulus in a measurable way: Thus, we can print the basis of sensors. Combined with paths to metallize selected areas and the ability to print on a variety of substrates – printed electronics, paper, polymers etc. – provides the ability to print high-value active structures. uvebtechnology.com + radtech.org

“MicroMaker works by utilizing extreme resolution UV-sensitive photoresists, designed for the microfabrication industry as a consumable,” she continued. “Purchased off-the-shelf as dry film, these prepolymers are well tested with exceptional chemical and thermal properties, as well as high resolution in patterning and thickness. When exposed to patterns from a UV projector, each thin dry layer can be patterned with great sensitivity and speed. Many active microsensor devices are based on four basic springs – the cantilever, bridge, plate and membrane. The use of dry film is ideal – not just for forming the thin, active membranes and overhangs for MEMS devices – but the dry material makes the process very robust, eliminating the need for any solvent removal.” The resolution requires focused UV to provide enough energy to liberate a catalyst latent in the resin system, she continued. “3D structures are formed from the adhesiveless lamination of the UV-imaged resin films to form a stack. The selectively exposed areas are polymerized by heat cure with the precisely controlled catalyst. The result is an exceptionally strong, fully polymerized print with extreme chemical and thermal resistance. “A significant advantage of LRP is the ability to extend our rollbased operation to a full manufacturing scale roll-to-roll process. This means that prototyping to production, without the need for design change, now is uniquely enabled, so polymer MEMS may be able to compete in some areas with silicon technology.” MicroMaker3D’s first patent is pending. Bubendorfer said she hopes the next step will deliver LRP technology to end users, receiving feedback and gaining awareness. “What I see in the longer term is the ability to extend microstructure from expensive R&D institutes to small companies. This is a particularly exciting opportunity, as these smaller companies are able to be responsive and adaptive, and so are well positioned to create disruptions around them. Having a low-cost entry, as well as a path to manufacture, means we are creating a much larger pool of players and opportunities. At the end of the day, I hope to see much more creativity from democratizing microfabrication.”  UV+EB Technology • Quarter 1, 2020 | 15


PROFESSOR’S CORNER BACK TO THE BASICS OF UV/EB

Understanding Glass Transition Temperature: Part 1 I

n a previous edition of Professor’s Corner, a simple rubber band was used to illustrate how its macromolecular structure creates its unique properties.1 Among the most important and useful of these properties is its flexibility. The flexibility is a result of a very low glass transition temperature (Tg). While different rubber bands have different compositions and behave differently, a typical value for the Tg is -125°C.2 Under normal conditions of use, a rubber band may well be around 150°C above its Tg, making it very flexible and extensible. So, what is the Tg, anyway? Glass transition temperature: Part 1 The Tg is the temperature at which a glassy, brittle material becomes rubbery and flexible. For example, consider the flexibility of a garden hose in midsummer. It is quite flexible. Now consider it on a cold winter day at -4°F (-20°C). You could likely break it with your bare hands! In the former case, the hose is above its Tg, while in the latter, it is significantly below. To better understand the Tg, a brief discussion of morphology is helpful. Polymer morphology is defined by Malcolm Stevens as “…the structure, arrangement, and physical form of polymer molecules….”3 It depicts how the individual molecules relate to each other in 3-dimensional space. Broadly speaking, polymers possess two types of morphology: “amorphous” and “crystalline.” Amorphous polymers – those “without structure” – have very little order at the molecular scale, while crystalline polymers have a relatively high degree of order. The exceptionally long and entangled chain structure of polymers creates the amorphous regions and ensures that at least some degree of amorphous character is present in all polymers, including those that are UVor EB-polymerized. So, a typical polymer sample will contain regions or domains that are predominantly amorphous and those that are crystalline – regions with relatively ordered alignments of polymer chains. A simple “cooked spaghetti” model of a linear polymer is depicted in Figure 1. Looking closely, one can see areas where strands of spaghetti are strongly aligned with one another. These represent crystalline regions that are imbedded in a matrix of amorphous, randomly distributed, strands. Since no polymers are truly 100% “crystalline,” those containing some crystallinity are typically referred to as “semi-crystalline” and the crystalline domains within the polymer sample are called “microcrystalline regions” or “microcrystallites.” It is important to note that only the amorphous domains in a polymer sample will exhibit a Tg, a 16 | UV+EB Technology • Quarter 1, 2020

Figure 1. Linear polymer model using cooked spaghetti

secondary thermodynamic phase transition. The microcrystalline regions, on the other hand, if present, may go through a primary phase transition similar to melting rather than just “softening.” In addition to exhibiting a Tg, then, semi-crystalline materials may also exhibit a Tm – a crystalline melting temperature. While the examples given here represent linear polymers, branched and crosslinked polymers also contain significant amorphous character and, therefore, will, in principle, exhibit a Tg. Crosslinks do not inherently preclude segmental motion unless the crosslink density is too high. It should be noted that if the concentration of amorphous domains is too low, a polymer may not exhibit a Tg experimentally. Also, if a crosslinked polymer, such as those that are energy-cured, has a sufficiently high crosslink density, it may not exhibit a Tg because it may be too rigid to allow segmental motions, even when it is predominantly amorphous. What is happening at the molecular scale when a polymer goes through a Tg? Stevens refers to this transition as the onset of long-range segmental motion and describes a “segment” as 20 to 50 chain atoms.4 Below the Tg, amorphous regions within the sample are locked in a glassy, rigid structure. This means that as the temperature – a measure of the average kinetic energy of the molecules – rises, the sample is restricted to increased molecular vibrations rather than concerted segmental motions. At the Tg however, a number of changes begin to occur, any one of which, in principle, can be used to determine the Tg experimentally. These changes include – but are not limited to – changes in uvebtechnology.com + radtech.org


®

...if a crosslinked polymer, such as those that are energy-cured, has a sufficiently high crosslink density, it may not exhibit a Tg because it may be too rigid to allow segmental motions...

Transform the economics of UV

specific volume of the sample, changes in the heat capacity of the polymer, changes in the ability of the polymer to store or dissipate energy, and others. In the next edition of Professor’s Corner, Part 2 of this discussion of glass transition temperature will provide information about various key methods used to measure the Tg of polymers, including dilatometry, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). These methods will be compared and contrasted in terms of their accuracy and sensitivity. Different analytical methods often give different results for the Tg of a given polymer and possible reasons for these differences will be presented.  Technical questions? What are your technical questions about polymer science, photopolymerization or other topics concerning the chemistry and technology of UV/EB polymerization? Your questions will help guide future topic decisions for this column. Please submit your questions via email directly to Dianna Brodine, managing editor for UV+EB Technology, at dianna@petersonpublications.com. References for Further Study: 1. “Professor’s Corner,” UV+EB Technology, 5, No. 3, 3rd Quarter, 2019, pp. 12, 13. 2. https://science.howstuffworks.com/innovation/everydayinnovations/elastic5.htm 3. Stevens, Malcolm P. Polymer Chemistry: An Introduction, 3rd Edition, 1999, p. 61. 4. ibid., p. 70.

Byron K. Christmas, Ph.D. Professor of Chemistry, Emeritus University of Houston-Downtown b4christmas@gmail.com uvebtechnology.com + radtech.org

UV+EB Technology • Quarter 1, 2020 | 17


WOOD COATING By Michel Tielemans, Guido Vanmeulder, Johan Van den Hauwe, Cédric d’Hulst and Michela Fusco, allnex Belgium

Novel bio-based energycurable polyurethane dispersions enhance coating sustainability D

ecades ago, allnex pioneered sustainable coating technologies as a foundation for current waterborne, energy-curable, powder and crosslinker product ranges. Gradually, water-based and energy-curable products were merged with the development of novel energy-curable polyurethane dispersions (UVPUD), which combine the benefits of their parent technologies to boost performance and ecology to the next level of requirements. They constitute the fastest-growing product range in the wood coatings market today. In order to recognize the sustainable attributes of this product range, we must consider three dimensions inspired by Life Cycle Analysis (1). Composition. Products largely respond to environmental regulations due to their waterborne nature and low level of volatile organic compounds (VOCs). They can make use of renewable feedstock and safe raw materials – banning tin catalyst, volatile organic amines and alkoxylated alkyl phenol emulsifiers.

Performance-in-use. Products demonstrate low viscosity and are easily sprayable. Their minimum film formation temperature (MFFT) is low and does not require the use of additional coalescent materials, increasing air emissions. They keep the high productivity of instantaneous energy curing supported by new developments in low-energy UV-LED lamps. Lifetime and disposal. Products obtained after curing are characterized by a dense but flexible crosslinking network, resulting in superior substrate protection. They match outdoor applications, where light-fastness and weatherability become essential for durability. Recyclability and biodegradability can further reduce their environmental impact. Introduction Fossil resources decreased during the extensive industrialization in recent human history. The estimated reserves are expected to last 30 to 50 years, so their prices will start climbing as they rarify. The primary goal of the industry is to address survival scenarios and to facilitate a new world economy compatible with human wellness. This is imposing a slow but drastic change in the industry, one that we already comprehend with circular economy initiatives. Displacing fossil with renewable carbon feedstock to manufacture new bio-materials is fundamental to this transition. It is particularly relevant when paired with a substrate that is already a bio-material – natural (wood, leather, textile) or synthetic (plastic). This also immediately improves our environmental footprint by reducing the material carbon footprint as a fundamental value proposition for renewable coatings today. Of paramount concern is the massive release of greenhouse gas (such as CO2) in the atmosphere due to human activity. This is resulting in a slow but perceptible rise of the earth’s temperature, affecting life on this planet. There is a strong imbalance in the fossil carbon cycle, considering the rapid transformation of fossil carbon into CO2 (1 to 10 years) and the very slow fixation of this CO2 into fossil carbon (≈106 years). The use of renewable carbon addresses this cycle imbalance with a neutral carbon footprint proposition – considering 18 | UV+EB Technology • Quarter 1, 2020

uvebtechnology.com + radtech.org


“Biobasiert Geprüft” logo and the US Department of Agriculture (USDA) “certified bio-based” logo. In an effort to follow a bio-ethical vision to develop new renewable products, we seek to avoid interference with raw materials sourcing that is in direct competition with the human food chain.

Figure 1. A neutral carbon footprint proposition with a balanced rate of CO2 generation and fixation using renewable feedstock as opposed to fossil feedstock

that the CO2 released in the atmosphere is coming from the same quantity of CO2 fixed by plants during photosynthesis. It is depicted in Figure 1. Measurement of renewable carbon content and eco-certification Renewable materials are major components of our ecosphere. They are based on natural resources, which replenish quickly enough through natural biological processes and overcome depletion caused by intensive usage in a human lifetime scale. The renewable carbon content of an organic material is defined by its weight percentage of the total weight of organic carbon in the material. Bio-based polymers can be certified for their renewable carbon content as a basis for reduced material carbon footprint. This certification is provided after C14 / C12 quantification in the product, according to the dedicated ASTM D6866 standard. It includes distinct test methodologies, but a popular method involves the controlled combustion of the test sample into CO2 and its subsequent catalytic transformation into carbon – that is then introduced in high-energy accelerated mass spectroscopy (AMS) capable of quantifying the two isotopes. We can quantify the inherent material carbon footprint reduction from the measured renewable carbon content translated in CO2 emission savings (expressed in g/kg of dry product). Importantly, this value excludes the process carbon footprint and does not constitute a full life cycle analysis. Independent label programs are usually adopted and include, for instance, the Technical Inspection Association (TUV) “OK bio-based” logo, the DIN CERTCO certification organization uvebtechnology.com + radtech.org

Experimental The polymer composition, architecture and morphology of ionomeric polyurethane dispersions encompass an extremely wide range of possibilities to target desired performance (2). Our approach was to consider the weighted impact of building blocks constituting the polymer and to address prioritized substitution from renewable feedstock. It sounds like an evidence that the use of bio-sourced acrylic acid is prevalent for an easy dropin, but unfortunately, its cost-competitive availability is not expected within the next five years. The difficulty then is to stoichiometrically assemble bio-based polyurethane compositions with innovative bio-sourced molecules that preserve a high performance level (crosslinking density) together with possible additional benefits. Typically, raw materials with fixed renewable carbon content follow separate storage and manufacturing routes to guarantee the certification compliance. We developed a new green product with high-end performance suitable for clear and white-pigmented wood coatings. The product, referred to as UVPUD #1, has ~22% of bio-carbon content (ASTM D6866) resulting in the material carbon footprint reduction. The product is tin-free and APEO-free. It presents a good colloidal stability with a robust formulation and spray capability. It is physically drying (tack-free) before cure. The low minimum film formation temperature (MFFT) does not require additional co-solvents and dries easily, providing full performance level after energy-cure. The wet product characteristics are summarized in Table 1. Drying and film formation The drying efficiency of waterborne polymers is becoming a significant component of sustainability due to its energy impact. The film formation of polymer dispersions occurs in three distinct steps: (1) particles close contact, driven by water evaporation; (2) UVPUD #1 Solid content (%)

≈ 35

Viscosity (mPa.s)

≤ 200

pH

≈ 7.5

Average particle size (nm)

≤ 100

MFFT (°C)

≤5

Stability 60°C (day)

≥10

Table 1. Typical wet product characteristics for UVPUD #1

page 20  UV+EB Technology • Quarter 1, 2020 | 19


WOOD COATING  page 19 particles deform, driven by capillary forces; and (3) particles coalescence, driven by temperature – if above MFFT. Only a few protocols have been reported to accurately quantify the overall drying process. An example outside the academic world is the Adaptive Speckle Imaging Interferometry(3) (ASII) by FORMULACTION®, which is limited to ambient temperature. The drying of a coating is practically governed by time in an oven under controlled conditions of temperature, humidity and air flow. The water release of energy-curable polymer dispersions is often judged by the residual water in the coating during the second and third steps of film formation. Entrapped water may create coating defects, such as undesirable whitening due to the optical Figure 2. Drying kinetics at 40°C for UVPUD #1 (A/B) as a comparison with anisotropy between the polymer and the numerous REF #1 and REF #2 nanoclusters of water. The problem can be revealed and fixed for a prolonged period after energy A coating was applied on a glass plate at a wet thickness of curing. Thus, drying parameters need to be optimized for each ≈200 microns using a stainless steel cylindrical film applicator. product and substrate according to the wet coating thickness. The initial spectrum was taken at room temperature by putting the freshly coated glass plate (face down) above the detector A novel Near Infrared (NIR) spectroscopy protocol has been surface (fitted with four 2-mm-thick rubber pastilles to prevent developed to investigate the drying of the dispersions. The contact) and covering it with an NIR-compliant golden mirror for technique is robust because of its excellent sensitivity to water transflection measurements. The coated glass plate was placed and its ability to look through the whole coating thickness during in the middle of a Binder FD-53 ventilated oven at 40°C. The the drying operation without interaction with glass. coating was taken out after 60 seconds to fit the equipment and take the NIR spectrum (+20 seconds), before starting a new NIR spectroscopy is an analytical method based on the specific interaction between matter and radiated energy between 4,000 and drying cycle (+10 seconds). The measurements were taken every time at the same place of the coated glass plate. The absorbance 12,800 cm-1. The absorption occurring at a defined wavenumber corresponding to water at 5153 cm-1 and first overtone at 6850 is described by the Beer-Lambert law and provides information cm-1 were recorded and deducted from the baseline absorbance on the physico-chemical properties of the sample. It essentially above 8000 cm-1. The first overtone was selected for its good shows overtones and combination bands of transitions between vibrational energy levels of molecules. An overtone is a transition linear response (no saturation) over the whole experimental water content range and was normalized according to the absorbance from the ground state to any vibrational level higher than the first of acrylic double bonds at 6164 cm-1 as internal reference; it was level, while a combination band is defined as the combination of two or more fundamental transitions seen as a single absorption at normalized a second time based on the residual absorption of the organic background attributed to the absence of water. This a lower energy than the overtone. resulting absorbance was plotted as a function of residence time at 40°C for two distinct experiments using UVPUD #1 (A/B) as well We used the MB-3600 Laboratory FT-NIR Analyser from as for REF #1 and REF #2 (Figure 2). ABB. The NIR source is a halogen lamp connected to a sample compartment fitted for dynamic transflection measurements It is possible to extract from the drying curves some interesting and linked to an Indium Gallium Arsenide detector. The data descriptors like the characteristic time required for reaching treatment is ensured by a software, Horizon MBTM FT-NIR. 50% to 75% to 90% of residual water (t50-75-90). It also is possible to deduct the transition time (ttrans1) attributed tentatively to the The UVPUD #1 was assessed for drying performance against transition between the first and the second stage of film formation an internal bio-based reference (REF #1) and an external bio– corresponding to the strong inflection point in the drying curve. based benchmark (REF #2; 38% renewable carbon content). The The same can be done for the transition time (ttrans2) between the products were formulated with 0.5% BYK® 346 (wetting agent) second and the third stage of film formation – corresponding and 2% UCECOAT® 8460 (rheology modifier). In the case of tentatively to the weak inflection point in the drying curve. These REF #2, the product had to be formulated with additional Butyl transition points could be obtained precisely by calculating the Cellosolve (10%) because of the high MFFT of the dispersion page 22  (41°C). 20 | UV+EB Technology • Quarter 1, 2020

uvebtechnology.com + radtech.org


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RAYLOK® 1722 )RUFRPSRVLWHV ZRRGȴUHUHWDUGDQF\

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WOOD COATING  page 20 CLEAR

WHITE

UVPUD #1

REF #1

REF #2

UVPUD #1

REF #1

REF #2

100,0

100,0

100,0

100,0

100,0

100

Omnirad®500 – photoinitiator

1,5

1,5

1,0

1,5

1,5

1,0

Omnirad®819DW – photoinitiator

-

-

-

0,5

0,5

0,5

VXW6360 (50%) – thickener

2,0

2,0

2,0

2,0

2,0

2,0

Dispersion

Byk 028 – defoamer

-

-

0,5

-

-

0,5

Butyl cellosolve – coalescent

-

-

10,0

-

-

10,0

White pigment paste (proprietary)

-

-

-

25,0

25,0

25,0

®

Table 2. Formulation of UVPUD #1, REF #1 and REF #2 for clear and white coatings

The testing was always performed after one week at room temperature. We looked at the Persoz hardness of formulated products in several curing conditions. The coatings were applied with a 120μ wet thickness on a glass plate and dried 10 minutes at 60°C (condition a), followed by 12 days at room temperature (condition b), and finally UV cured at 5 m/min under 80 W/cm Ga lamp and 120 W/cm Hg lamp (condition c). As a comparison, the coatings were similarly dried 10 minutes at 60°C immediately followed by UV curing at 5 m/min under 80 W/cm Ga lamp and 120 W/cm Hg lamp (condition d) and followed by 6 days at room temperature (condition e). Figure 3. Persoz hardness (s) of UVPUD #1, REF #1 and REF #2 as a function of drying & curing conditions

intercept point from a linear regression of the associated points. Finally, it is worth indicating that residual water (%) at the drying plateau is stable (no evolution after an additional 3 hours at 80°C). Very good reproducibility is observed when duplicating the measurements for UVPUD #1 (A/B). All in all, the products show a comparable drying kinetic compatible with application lines, with some possible benefit for the UVPUD #1 during the second stage of film formation which is practically the most relevant for good water release (t90). The drying parameters from the table shed a useful fundamental light to the film formation that is not easily obtained with other techniques. At the end of the drying process, every product is physically drying (tack-free before cure). Results and discussion UVPUD #1 was designed to complement the high-performance product portfolio for wood coatings. The product and the two benchmarks were formulated for clear and white coatings according to the Table 2. They were applied on wood, glass, Leneta® or sanded melamine board (as a function of the test protocol) and cured at 5 m/min at 80 W/cm Ga and Hg lamps. 22 | UV+EB Technology • Quarter 1, 2020

Figure 3 immediately shows a significant difference between UVPUD #1 and REF #1 in comparison with REF #2. The first two products present a low hardness after drying but reach their full hardness potential immediately after UV curing. (Hardness always increases somewhat after several days at room temperature.) The REF #2 immediately starts with a moderate hardness after drying, which increases more significantly after some days at room temperature; in that case, the UV curing does not immediately deliver the full hardness, but it always is required to get a good solvent resistance. Figure 4 presents the comparative performance of the UVPUD #1 against the two benchmarks in clear formulation. Overall, the products present a balanced set of properties, comprising an excellent adhesion on wood with high gloss, good yellowing after cure and high hardness with superior chemical resistance. UVPUD #1 is close to the internal benchmark REF #1 but outperforms the external benchmark REF #2. Figure 5 similarly presents the performance in white formulation. UVPUD #1 presents an optimized chemical, mechanical and metal mark resistance in comparison with the internal benchmark REF #1 and is always superior or equal to the external benchmark REF #2. It is worth mentioning that the matting of UVPUD #1 is much improved compared to REF #1 or REF #2 with some uvebtechnology.com + radtech.org


Figure 4. Comparative performance of UVPUD #1 with REF #1 and REF #2 in clear formulation

specific pigment pastes and that this “self-matting” may be found advantageous for some applications (no matting agents required). Summary and conclusions  A novel bio-based, energy-curable polyurethane dispersion supported by clear technological differentiation builds on sustainable innovation.  UVPUD#1 (UCECOAT® 7999) contains more than 20% carbon from renewable feedstock (ASTM D6866) and significantly reduces its material carbon footprint.  The product has a low film formation temperature, requiring no co-solvent and provides immediate hardness after cure, along with excellent clear and white coating performance.  The drying kinetics of the coated product were studied using a novel NIR spectroscopy protocol capable of characterizing the film formation steps in a reproducible way. 

Figure 5. Comparative performance of UVPUD #1 with REF #1 and REF #2 in white formulation

global development projects for novel waterborne radiationcurable polymers and supporting coating market segments. He is the author of numerous articles and holds a Ph.D. in organic chemistry from Brussels University.

Selected references 1. Sustainable development of new water-based energy-curable PU dispersions for wood. M. Tielemans, G. Vanmeulder and M. Fusco. European Coating Journal 03-2019, 104-109. 2. Multiphase coatings from complex radiation curable polyurethane dispersions. M. Tielemans, P. Roose, C. Ngo, R. Lazzaroni and P. Leclère. Progress in Organic Coatings 75 (2012), 560-568. 3. Adaptive speckle imaging interferometry (ASII): New technology for advanced drying analysis of coatings. A. Brun, L. Brunel and P. Snabre. Surface Coatings International Part B: Coatings Transactions, September 2006, Volume 89, Issue 3, 251–254.

Michel Tielemans, an associate research fellow at allnex, is based in Drogenbos, Belgium. He occupied several technical and managerial positions in research and development, covering the development of waterborne acrylic and polyurethane polymers for the coating, adhesive and ink markets. He leads uvebtechnology.com + radtech.org

IST AMERICA U.S. OPERATIONS 121-123 Capista Drive Shorewood, IL 60404-8851 Tel. +1 815 733 5345 info@usa.ist-uv.com www.ist-uv.com

HANDCURE LED Mobile Curing

UV+EB Technology • Quarter 1, 2020 | 23


APPLICATION By Lara Copeland, contributing writer, UV+EB Technology

UV-Cured Powder Coating Speeds MDF Application Process Time L

ocated in Cleveland, Ohio, and occupying adjacent buildings, Keyland Polymer and DVUV have found ways to collaborate well beyond their physical proximity. As an innovator in the application of UVcured powder coating on medium-density fiberboard (MDF), DVUV specializes in custom powder-coated components or parts for the retail, store fixture, POP display, healthcare, educational and office furniture industries. Its largest volume application is contract furniture, but this mid- to high-volume manufacturer with an automated line also supplies finished components for products such as fixture/displays, tabletops, shelving, wall panels, cabinetry and signage. Keyland Polymer develops, formulates, manufactures and sells the UVcured powder coatings to DVUV and other customers for MDF, as well as other substrates including plastic, composites, metal and other materials. DVUV/Keyland Polymer Marketing Manager Rebecca Lonczak explained that DVUV does not work with natural wood and instead solely works with MDF due to its consistent uniformity of particle source, density and moisture content. “MDF is easily machinable and has a homogenous surface. Natural woods can be powder coated; however, the finish may be inconsistent, and issues can arise with outgassing and pinholes due to varying resin and moisture content in the wood,” she said. The density, fiber, resin and moisture content in natural woods vary greatly by wood type, in addition to the location where it is grown. Every tree is different, even within the same species. Since the powder-coating process uses heat to melt the powder, heat – even at a low temperature with short exposure – can cause an uncontrollable response in natural wood. This makes powder coating natural wood with a consistent finish especially problematic. UV powder coating of MDF produces a more consistent and visually pleasing finish.

24 | UV+EB Technology • Quarter 1, 2020

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of medium-pressure mercury vapor UV lamps are available for UV curing of powder coatings. Mercury lamps (“H” bulb) provide short wavelength UV energy (220–320 nm) that is suited for clear and tinted applications. Mercury lamps with an iron additive (“D” bulbs) provide higher wavelength energy (320–400 nm) that aid in curing for low-level pigmented systems. Lamps with a gallium additive (“V” bulb) provide a strong output of long wavelength energy (405–440 nm) and are the workhorse for pigmented systems. Long wavelength energy penetrates thicker and pigmented UV powder coatings.

Raw MDF parts are UV-cured during a powder coating process.

Keyland Polymer manufactures UV-cured powder coatings by combining resins, pigments, performance additives and photoinitiators. Photoinitiators are the key ingredient; they absorb the high-intensity ultraviolet light, producing and activating free radicals that crosslink the coating. This is a molecular crosslinking throughout the coating and is the instantaneous curing phase. “As soon as the photoinitiators are exposed to UV, crosslinking occurs, and the coating is cured instantly,” Lonczak said. Additives enhance the coating surface by modifying or adjusting a specific property – scratch or mar resistance, gloss and texture. Pigments produce color and opacity. UV powder coatings are produced in the same manner and on the same type of equipment as thermal powder coatings – blended, extruded, chilled, chipped, milled, classified, sieved and packaged. To achieve cure, it is necessary to match the photoinitiator type and amount to the UV source, including the proper combination of UV energy dose, intensity and wavelength. Several types

...the separation of the melt/ flow and the cure process functions is the differentiating characteristic between the two.

The DVUV UV-cured powder coating process is fast. “It is a 20-minute, singlestep process from raw MDF part to finished part ready to be packed and shipped,” Lonczak explained. To begin, the parts are hung on the line and prepared by spraying compressed air to remove any dust particles remaining from machining. Typically, surface sanding is not necessary prior to powder application. Next, the MDF parts enter a low-temperature preheat oven for one minute. “This allows the board to outgas before the coating is applied and brings the moisture in the MDF to the surface, making it conductive to attract the powder coating,” she added. The UV powder then is electrostatically applied on the part using an automatic spray gun system. After application, the powder is melted or gelled in a low-temperature oven for one minute. Once melted, the part is instantly cured by exposure to UV lamps. In 20 minutes, the part is fully finished and ready to be packed and shipped to the customer. UV-cured powder coatings were developed more than 20 years ago as an alternative to thermally cured powder coatings. Thermal curing requires 10 to 30 minutes or more to cure with high temperatures (around 400°F). The process time is longer and requires an additional cooling period prior to handling. As Lonczak pointed out, the main advantage UV curing has over thermal curing has to do with time and temperature. “The electrostatic powder application for UV-cured powder coating and thermoset powder coating are exactly the same; however, the separation of the melt/flow and the cure process functions is the differentiating characteristic between the two.” The UV curing process is instantaneous and only requires a short, one-minute preheat to melt/flow the powder with temperatures between 220°F and 240°F before curing with a UV source. The advantages of a significantly reduced process time and a lower page 26 

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UV+EB Technology • Quarter 1, 2020 | 25


APPLICATION ď ´ page 25 overall temperature make the UV-cured powder coating process important where MDF is concerned. â&#x20AC;&#x153;Excessive heat and time exposure can result in cracking and other defects,â&#x20AC;? she noted. Powder coating poses a few challenges, but DVUV has measures in place to overcome them. Moisture and temperature variances can alter the success of the finish, but are handled easily by controlling the process within a temperature-regulated plant. A humidifier ensures the MDF board maintains the correct moisture content prior to powder coating. Consistent product also is ensured by DVUVâ&#x20AC;&#x2122;s initial run set-ups and tests. Each part DVUV

          

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runs is custom based on the customerâ&#x20AC;&#x2122;s part specifications. â&#x20AC;&#x153;Line speed, spray gun distance and processing temperatures are different and modified for each job we run,â&#x20AC;? she concluded. The production team sets up trial runs in addition to performing checks during runs to ensure quality. A series of destructive and non-destructive tests are performed on the finished parts for quality control: a visual inspection comparing the part finish to the control standard, Tooke Gauge test (measures coating thickness), gloss level readings and MEK solvent-resistance tests. â&#x20AC;&#x153;Our production team also has a preventative maintenance, root cause analysis and corrective action plan when quality or process issues arise,â&#x20AC;? she concluded. The future for powder-coated MDF at DVUV is bright. Government and regulatory agencies are restricting or eliminating the use of solvent-based liquid coatings. Waterborne liquid coatings are difficult to use on MDF, making UV-cured powder coatings an ideal finishing solution for MDF. UV-cured powder coating is solvent free, non-toxic and contains no volatile organic compounds or hazardous air pollutants). No special permits are required for handling. DVUV is seeing an increased sales demand from furniture and MDF component manufacturers looking for a reliable supplier of high-quality, environmentally beneficial and cost-effective finished MDF components. ď ľ

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MARKETS By Dianna Brodine, managing editor, UV+EB Technology

Plastics Market Outlook: Conflicting Calls to Action D

espite a public and legislative outcry against plastics, the market outlook is strong for plastic film, flexible plastic and rigid plastic applications.

Led by increasing use in construction, automotive and electronics, “the global plastics market size was valued at USD 522.66 billion in 2017. It is poised to expand at a CAGR of 4.0% (to USD 721.14 billion) by 2025.”7 Plastic film used in packaging, plastic bags, labels, construction materials and more also is expected to grow worldwide at 3.9% CAGR over the next five years.6 Globally, packaging (both flexible and rigid formats) is the largest market for plastic resins, with construction, consumer goods and automotive following. “Demand for packaging is growing in both developed economies and in emerging markets as trends such as urbanization and rising wealth persist,” said a report from Grand View Research.3 However, the plastics industry has an image issue, and it must be mitigated for the trends in growth to continue. The siren call of sustainability Much like the sirens in ancient Greek tales, calls for greater sustainability are leading the plastics industry toward a crash on a rocky shore. Consumer sentiment is negative – particularly in the packaging segments. But, what the industry has is a recycling problem – not a materials problem. “Today, over 60 countries have introduced bans Global plastics market share, by application, 2017 (%) and levies on the use of plastics,” said a report from IHS Markit. “Both the public and private sectors are increasing the pace of efforts to curb consumption and improve management of singleuse plastics.” However, the report cautioned, “The actions are often driven by uninformed understanding of the consequences and available alternatives, or an underestimation of the ability of infrastructure to deliver.”4 There’s no doubt that the calls for increased Source: www.grandviewresearch.com recyclability have merit. Another IHS Markit report warned, “If overall plastics consumption continues with the same usage patterns, plastics waste in landfills and the environment will grow to over 10.5 billion metric tons by 2030.”5 Unfortunately, a significant barrier to increased plastics recycling exists – the existing technology and capacity can’t handle the volume. “Current mechanical recycling processes have scale and economics limitations, while processes such as chemical recycling are in their technology development infancy,” said IHS Markit.5 And, consumers seem to be ignoring the reasons plastics are used in many of its current industries. Alison Keane, president and CEO of the Flexible Packaging Association, explained, “Due to the environmental benefits of flexible packaging – including less water and energy usage, protection of the products with the least amount of packaging, transportation efficiency, food waste prevention, and reduced greenhouse gas emissions, among others – the industry still is growing, and we want to support that growth and not sacrifice these benefits in the rush to appease misguided public sentiment.” That doesn’t mean those involved in the plastics industry aren’t taking action to protect the environment – and the bottom line. “While the market for flexible packaging remains very strong – currently $31.8 billion in the page 28  uvebtechnology.com + radtech.org

UV+EB Technology • Quarter 1, 2020 | 27


MARKETS  page 27 US – the current anti-plastic sentiment has some consumer product companies moving to other substrates, like paper,” said Keane. “It also has converters developing mono-material packaging, plastic or otherwise, so that it can be fully recycled. Converters also are working on bio-based and compostable packaging and are heavily involved with activities in the US to increase the recovery and recycling of today’s packaging, much of it flexible.” Troy Nix, executive director of the Manufacturers Association for Plastics Processors, added, “When larger customers and OEMs – those who are supplied by these smaller processing companies – begin altering their business interest, it has a downstream ripple effect on the entire supply chain. Over just the last six months, companies like General Motors, Coke and Pepsi have realized and reacted to pressure from consumers and political organizations and have been forced to begin finding alternatives ways to do business. As a result, plastics processors are starting to look for innovative ways to aid their customers, like working to understand how to process new raw material bio-resins and other materials more friendly to the environment.” Areas of growth Opportunity: Medical “A group of well over 300 manufacturers representing the US plastics processing industry and the US mold building industry identified the medical products industry as the most optimistic industry for 2020,” said Nix. “Reasons for this include the aging population, increasing life expectancy and technological developments that are cross-pollinating from different markets, such as automotive LED lighting that has made its way into operating rooms and dental offices. These drivers are increasing demand for medical devices, such as surgical implants, electromedical equipment and sophisticated imaging systems.” Opportunity: Packaging The American Chemistry Council focused on packaging as a factor in the growth of US plastics resin use, indicating that North American retail sales are correlated with packaging resin demand. “In 2018, real retail sales in the US grew 2.3 percent,” its report said. “Growth in ‘non-store’ sales continues to outpace growth in traditional brick and mortar stores. Additionally, many traditional retailers also have significant online sales. This shift in sales and consumer behavior is impacting packaging demand because it creates demand for new types of packaging.”3 “Food packaging continues to be the biggest sector for flexible packaging, with 49% percent of the market and estimated at $15.6 billion,” added Keane. “If you add beverages, it becomes 58% and $24.6 billion. Within the food category, two segments stand out with projected growth – process fruits and vegetables by 4.6% and sweet spreads packaging by 3.5% (CAGR 2018-2023). Outside the food category, we see pet foods and personal care categories as having strong growth potential.” Opportunity: Automotive Automotive lightweighting will remain a factor in the growth of 28 | UV+EB Technology • Quarter 1, 2020

the plastics industry, as OEMs work to meet emissions and fuel economy goals. “Plastics facilitate fuel saving in automotive applications on account of reduced car weight and density as compared to conventional materials such as metals or rubber,” said a report by Grand View Research.7 Where does UV technology fit in? As the plastics industry continues on a trajectory of upward growth, the opportunities increase for UV technologies. This includes eco-friendly UV-curable resins that are seeing application in industrial and automotive markets. “Increasing emphasis on safe, odor-free, sustainable and green materials by various regulatory authorities across the globe has resulted in the surge in need of these products,” said Grand View Research.2 As applications increase, so too does the UV curing system market, which is estimated to grow from USD 3.7 billion in 2019 to USD 6.1 billion by 2024, at a CAGR of 10.3%. “The growth of the UV curing system market is driven by factors such as an inclination toward environmentally friendly products, along with stringent regulations regarding use of green products; and high performance and increased speed of UV curing systems than that of traditional curing systems,” said Market and Market. This includes growth in the medical markets as “medical device manufacturers across the globe are using UV curing technologies in their manufacturing process owing to its benefits such as reduction in friction between medical electronic devices, uniform adhesion and surface coverage, and coating homogeneity.”1 Packaging, too, is a growth opportunity. “The flexible packaging industry is the fastest growing segment of the packaging industry,” said Keane. “In the US, it is 19%, second to corrugated cardboard at 24%.” Globally, however, flexible packaging is at 41% – leaving room for the US market to catch up to its worldwide counterparts.  References 1. UV Curing System Market by Technology (Mercury Lamp (Microwave Lamp, Arc Lamp) and UV LED), Type (Spot Cure, Flood Cure, and Focused Beam), Pressure (High, Medium, and Low), Application, End-User Industry, and Geography - Global Forecast to 2024 2. Grand View Research Ultraviolet (UV) Curable Resins Market Analysis By Composition (Monomers, Oligomers, Photoinitiator), By Application, And Segment Forecasts To 2024 3. 2018 Resin Situation and Trends: American Chemistry Council (ACC) Plastics Industry Producers Statistics (PIPS) Group 4. IHS Markit Plastics Sustainability: Adapting your strategy 5. IHS Markit Plastics Sustainability: Risk and Strategy Implications, https://ihsmarkit.com/research-analysis/plastics-sustainability-risksand-strategy-implications.html 6. Plastic Films Market Size, Share 2020: Business Opportunities, Current Trends, Market Forecast & Global Industry Analysis by 2024, Market Watch 7. Plastics Market Size, Share & Trends Analysis Report By Product (PE, PP, PU, PVC, PET, Polystyrene, ABS, PBT, PPO, Epoxy Polymers, LCP, PC, Polyamide), By Application, And Segment Forecasts, 2019 – 2025, Grand View Research uvebtechnology.com + radtech.org


Plastics Impact the World Daily By Alex Hoffer, chief revenue officer, Hoffer Plastics Corporation Note from the Managing Editor: The plastics industry has been inundated with a wave of negative publicity, from pollution concerns to straw and bag bans. In October 2019, injection molder Alex Hoffer wrote this memo reminding consumers, brand owners and manufacturers that plastics are more than the latest news story.

D

espite its contributions to innovation, the plastics industry has garnered increasing criticism for its environmental impact. So, why do we continue to use plastics in the first place?

The technical answer is that plastic has a high strength-to-weight ratio and can be easily shaped into a wide variety of forms that are impermeable to liquids and are highly resistant to physical and chemical degradation. These materials can be produced at a relatively low cost, making it easier for companies to sell, scale, save, etc. The primary challenge is that the proliferation of plastics in our everyday use, in combination with poor end-of-life waste management, has resulted in widespread plastic pollution. However, consider that it is possible that the plastics industry is doing more good than harm, and that the environmental issues the industry faces have more to do with recycling than production. Plastics and the environment Austrian environmental consultancy Denkstatt recently conducted a study to determine the impact of farmers, retailers and consumers using recyclable products (wood, tins, glass bottles/jars and cardboard) to package their goods rather than plastic. What they found was that mass of packaging would increase by a whopping 3.6 times and would take more than double the energy to make, thereby increasing greenhouse gases by an astounding 2.7 times.

role in the preservation of food. In a world where many go hungry, it is advantageous to continue to support an industry that helps to keep food on tables, families fed and reduces food waste. Plastics and cars Turning our attention to plastics’ relationship with the automotive industry, let’s start with safety. The National Highway Traffic Safety Administration estimates that today’s seat belts, which are made with industrial strength plastics, have the potential to reduce auto fatalities by as much as 45% and serious injury by 50%, compared to not being buckled in. Also, car manufacturers rely on plastic to make lightweight materials that reduce the weight of automobiles so they can meet the Corporate Average Fuel Economy (CAFE) standard, which is set to be increased to 54.5 miles per gallon by 2025. I predict that the use of plastics to minimize the weight of cars will be an integral part of car manufacturers’ efforts to meet these new standards – ultimately increasing fuel efficiency and reducing the environmental footprint of vehicles. Plastics and healthcare Did you know that plastic materials increase the efficiency and hygiene of your physician’s office? Plastic syringes and tubing are disposable to reduce disease transmission. Plastic intravenous (IV) bags and tubing that store and deliver blood, fluid and medicine let healthcare workers more easily view dosages and replacement needs. Plastic heart valves and knee and hip joints save lives and make patients’ lives more comfortable. Plastic prostheses help amputees regain function and improve their quality of life.

One proposal for replacing plastics with different materials is to replace plastic bags with paper ones in grocery stores. While this may sound like a more sustainable solution, the data do not support it. By volume, paper takes up more room in landfills and does not disintegrate as rapidly as plastic. Because of this, plastic bags leave half the carbon footprint of cotton and paper bags.

Plastics and jobs Consider a world in which the plastics industry in America suddenly came to an end. While there would be some that celebrate this, I imagine that the cheers from those who are “anti-plastic” would very quickly be overshadowed by the 989,000 individuals in the US who collect our paychecks and support our families thanks to job opportunities within the plastics industry.

Plastics and food Consider the properties of plastic that make it so attractive for food packaging: It is durable, flexible and it does not shatter; it can breathe (or not); and it is extremely lightweight. As a result, food and drink are protected from damage and preserved for lengths of time previously unimaginable.

In 2019, the argument to remove plastics from our way of life entirely is not a feasible option. Plastics’ contribution to the health of our environment, the safety and durability of our healthcare products, the fuel efficiency on our roads and the growth of the economy – and so much more – tells us that it is worth putting our best efforts toward understanding this debate further. 

The European Packaging and Film Association (PAFA) says that the average spoilage of food between harvest and table is 3% in the developed world, compared to 50% in developing countries where plastic pallets, crates, trays, film and bags are not as commonly available. This data point shows us that plastics play an integral

Alex Hoffer is the vice president of sales and operations at Hoffer Plastics Corporation, a leading global supplier of tight-tolerance, custom injection molded parts across markets including flexible and rigid packaging, automotive, appliances and consumer industrial. For more information, visit www.hofferplastics.com.

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UV+EB Technology • Quarter 1, 2020 | 29


ADHESIVES By Shuhua Jin, Erik Kareliussen and Chih-Min Cheng, Henkel Corporation

This paper will be presented at RadTech 2020 in Orlando, Florida, March 9-11. For a full programming schedule, see pages 6-9.

Photoinitiator Effect on Depth of Cure in Visible Light Cure Polymerization Abstract he choice of photoinitiator (PI) is an important factor in the polymerization characteristics of light cure materials. This study investigated the influence of PI type and concentration on the surface tackiness and depth of cure (DOC) of experimental light cure acrylate formulations with several UV/visible photoinitiators. The chosen UV/visible photoinitiators include Type I PI phosphine oxide derivatives and Type II PI thioxanthone derivatives. Surface tackiness and DOC were also studied using two different radiation intensities emitted by LED 405 nm curing lights. A Design of Experiment (DOE) using Response Surface Methodology (RSM) was used to optimize thioxanthone and amine synergist concentrations for the most desired surface curing and DOC. The correlations of PI type and concentration with DOC help light cure material formulation to achieve a tack-free surface and suitable depth of cure, which are important in many adhesive applications.

T

Introduction UV-curable adhesives are single-part products that can be cured rapidly and on demand when exposed to UV light to form a high-strength material. Different UV adhesive products have been designed that cure with different wavelengths and at different cure speeds. Cured adhesive properties include adhesion to substrates, surface tackiness and depth of cure, as well as mechanical properties such as hardness and tensile strength, tensile elongation and modulus. Several factors affect light curing adhesive performances, including the materialâ&#x20AC;&#x2122;s composition, the choice of photoinitiators, the concentration of the initiators, the temperature, the peak wavelengths and bandwidth of the curing light, and the intensity of the light and the irradiation time.1-3 Depth of cure (DOC) is an important property to consider when evaluating adhesive curing performances and a guideline to applications. Some literature exists regarding the parameters affecting DOC of dental composites, but very little has been published regarding adhesive performance. Parameters affecting DOC include: 1. Light intensity (DOC in general increases with increasing intensity of the curing light). 2. Type of light. UV light with wavelengths below 365 nm will cure the surface extremely quickly, vitrifying the surface, blocking the UV light and preventing the material below from curing. UV to visible light, with wavelengths at 385 nm or higher, cures the material more uniformly and allows the UV to penetrate and cure adhesives in thicker sections. The closer the wavelength to visible range, the easier it is to cure through larger gaps. 3. Material opacity and color: Increasing opacity and color will decrease DOC. 4. Type of PI: Generally, PI Supplier Amine synergist Supplier there are two types of PIs. Norrish Type Omnirad 819 IGM Visiomer DMAPMA Evonik I PI produces free Omnirad TPO IGM radicals by PI cleavage. Omnirad L-TPO IGM Type II PI generates Genocure ITX Rahn free radicals, with PI abstracting hydrogen Genopol TX-2 Rahn from a co-initiator (amine IGM Omnipol TX synergist).4-5 PI should be Table 1. Visible photoinitiators and amine synergists chosen based on the UV 30 | UV+EB Technology â&#x20AC;˘ Quarter 1, 2020

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Component

Wt%

Urethane acrylate

45-55

LED 405nm Light intensity (W/cm2)

Curing time (sec)

Dosage (J/cm2)

Acrylate monomer

40-50

1.50

10

13.7

Visible PI

0.1-3

1.53

5

6.73

Amine synergist

0-5

Table 3. LED 405 nm flood lamp light intensity and dosage with two curing times

Table 2. General light cure formulas

5.

lamp, with a spectral output that peaks in the optimal range for the adhesive cure. Concentration of PI: It is PI dependent. It has been observed that, as the PI concentration is increased, the cure depth initially increases but then starts to decrease after reaching an optimal PI concentration.

Surface tackiness caused by atmospheric oxygen is also important for light cure acrylate adhesives. All the parameters affecting the DOC will influence surface tackiness of the cured adhesive. In this study, different visible photoinitiators (those that absorb at wavelengths >400 nm) were studied to understand the effect of PI type and concentration on the surface tackiness and DOC. Many methods – such as hardness tests, interaction with color dyes, translucency changes, double-bond conversion, NM tactile tests, penetration tests and scraping tests – have been used to measure the DOC. In this paper, DOC was measured using a scraping method adapted from ISO 4049.6 There are many surface tackiness tests. One easy, qualitative method is to dust silicon carbide or talcum powder on the cured surface and then remove the powder by gentle rubbing or brushing.7 Materials Table 1 is the list of the visible photoinitiators and amine synergists used in this study. Table 2 is a general formula containing different visible PI with or without amine synergists for this study.

and then cured using LED 405 nm flood lamps. Silicon carbide particles were applied on the cured resin surface and brushed lightly to remove the powder. It is considered tacky if the black particles remain and tack-free if no visible black particles remain. LED 405 nm light intensity and dosage: Samples were measured by LED visible UVV radiometer (Item # 1265282, Henkel ID: 5995, S/N UVV0059). Table 3 is the summary of LED 405 nm flood light intensity and dosage with two curing times. These are the curing conditions used for all the testing unless specified otherwise. Results and discussion UV/visible analysis of various visible photoinitiators Three Type I phosphine oxide-based visible PIs, Omnirad 819, TPO and L-TPO; one monomeric Type II PI, thioxanthone Genocure ITX; and two polymeric Type II PIs, thioxanthone derivatives, Genopol TX-2 and Omnipol TX; were studied. Figure 1 shows the PI absorbance spectra at wavelength 350 to 450 nm with 0.01 wt% of PI in acetonitrile solution. These PIs all have absorbance at visible range 400 to 410 nm. The absorbance values at 405 nm of each PI at concentration of 0.01, 0.1 and 1 wt% are listed in Table 4. The absorbance increases with concentration, but not linearly, as Beer’s law is not valid at higher concentrations.8 Among the six visible PIs page 32 

DOC test: Each sample, based on the formulation in Table 2, was put into a plastic cylinder with 13 mm height and 6 mm diameter. The surface was flattened using a spatula, and the sample was cured using LED 405 nm flood lamps. The sample was removed from cylinder. The bottom soft part was removed. The DOC is the height of the cured solid. Surface tackiness test: Each sample in Table 2 was applied on a glass slide to form a thin layer uvebtechnology.com + radtech.org

Absorbance

1

Sample preparation and testing methods Photoinitiator UV/visible absorbance spectrum: UV/visible spectrum of the PIs in Table 1 was acquired using ARM-1061 UV/Visible Spectrophotometric with each PI at three different concentrations 0.01, 0.1 and 1 wt% in acetonitrile.

0.8 0.6 0.4 0.2 0 350 360 370 380 390 400 410 420 430 440 450 Wavelength (nm) Gencure ITX

Genopol TX-2

Omnirad 819

Omnirad TPO-L

Omnipol TX

Omnirad TPO

Figure 1. UV/visible absorbance spectrum of four visible PIs at 0.01 wt% in Acetonitrile

UV+EB Technology • Quarter 1, 2020 | 31


ADHESIVES ď ´ page 31 tested, the absorbance of these PIs at 405 nm at 0.01% level has the order of: Omnipol TX > Genocure ITX > Omnirad 819 > Omnirad TPO > Omnirad TPO-L > Genopol TX-2. The trend is similar with other concentrations, but to a different extent. The absorbance at UV range 370 to 380 nm is bigger than the absorbance in the visible range. The PI absorbance is directly related to its reactivity at the wavelength light is emitted and impacts the DOC and surface tackiness tested in this study.

Omnipol TX

1.00%

0.6

2.82

3.27

0.21

1.78

2.87

0.12

1.21

3.3

Omnirad TPO

0.07

0.56

2.68

Omnirad TPO-L

0.03

0.33

2.32

Genopol TX-2

0.02

0.18

1.73

Table 4. PI 405 nm absorbance at different concentrations

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32 | UV+EB Technology â&#x20AC;˘ Quarter 1, 2020

0.10%

Omnirad 819

0RGHUQ3UREOHPV1HHG 1HZ,GHDV

ĎŽĎŽĎątĹ?Ä?ĹŹĆ?Ć&#x161;Ä&#x17E;Ä&#x17E;Ä&#x161;Ç&#x20AC;Ä&#x17E;ŜƾÄ&#x17E;Í&#x2013;dĹ˝Ć&#x152;ŽŜĆ&#x161;Ĺ˝Í&#x2022;KĹśĆ&#x161;Ä&#x201A;Ć&#x152;Ĺ?Ĺ˝Í&#x2022; Ä&#x201A;ĹśÄ&#x201A;Ä&#x161;Ä&#x201A;DĎ°,Ď­'Ďą dÄ&#x17E;ĹŻÍ&#x2014;͞ϰϭϲͿϰώϰͲϰϹϲϳÍ&#x2013;&Ä&#x201A;Ç&#x2020;Í&#x2014;͞ϰϭϲͿϰώϰͲϯϭϹϴ Ç Ç Ç Í&#x2DC;Ć?Ĺ?ĹŻĆ&#x161;Ä&#x17E;Ä?Ĺ&#x161;Í&#x2DC;Ä?Žž

0.01%

Genocure ITX

DOC and surface tackiness study DOC and surface tackiness of the formulas containing different PIs Three Type I phosphine oxide-based visible PIs, Omnirad 819, TPO and L-TPO; one monomeric Type II PI, thioxanthone Genocure ITX (ITX); and three polymeric Type II PI thioxanthone derivatives were studied, using the same curing condition. The PI loading for this testing was 1%. For Type II PIs, 2% of amine synergist Visiomer DMAPMA (DMAPMA) was added. The samples 1.1 to 1.5 were cured using LED 405 nm. Table 5 is the summary of the DOC and surface tackiness testing results of the formulas containing different PIs with 5s

6LOWHFK&RUSRUDWLRQ

PI concentration in acetonitrile

PI

and 10s curing time, respectively. Figure 2 is a graph showing the correlation of DOC and PI type. Results in Table 5 and Figure 2 showed that DOC is dependent on the PI used and curing time. DOC increases with curing time for all the PIs. For the three Type I Omnirad 819, TPO and L-TPO, it is demonstrated that the absorbance value or reactivity at 405 nm is in the order of 819 > TPO > L-TPO. For the three Type II PIs, ITX, TX-2 and TX, the absorbance or the reactivity at 405 nm is in the order of Omnipol TX > Genocure ITX > Genopol TX-2. However, DOC increases with decreasing reactivity at 405 nm. The results are consistent with both 5s and 10s curing. In this situation, lower PI reactivity favors DOC. On the contrary, surface tackiness tests of the formulations with different PIs showed good correlation of free surface tackiness with PI reactivity. The data showed a tack-free surface of the formulas with high reactivity PIs â&#x20AC;&#x201C; Omnirad 819, Genocure ITX and Omnipol TX. Other PIs with lower reactivity â&#x20AC;&#x201C; Omnirad TPO, L-TPO and Genopol TX-2 â&#x20AC;&#x201C; showed surface tackiness after both 5s and 10s curing, although DOC is relatively higher. DOC and surface tackiness of formulas containing PI with different concentrations In this study, different concentrations from 0.5% to 3% of Type I phosphine oxide-based visible PI Omnirad TPO-L and monomeric Type II PI thioxanthone Genocure ITX (ITX) were studied using the same resin compositions. For ITX , the amine synergist used is DMAPMA and ITX/DMAPMA, weight ratio 1:2. The previous

...surface tackiness tests of the formulations with different PIs showed good correlation of free surface tackiness with PI reactivity. page 34 ď ľ uvebtechnology.com + radtech.org


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ADHESIVES  page 32 samples 1.3 and 1.4 with 1% PI, and new samples 2.1-2.10 with other concentrations were cured using LED 405 nm for 5s. Table 6 is the summary of the DOC and surface tackiness of the formulas containing different concentrations of PI L-TPO 5 s cure Sample

PI

1.1

and PI ITX, amine DMAPMA, respectively. Figure 3 is a graph showing the correlation of DOC and PI concentration. Results in Table 6 and Figure 3 show that DOC decreases with increasing PI concentration for both PIs. The trend is opposite for surface tackiness tests. High PI concentration is beneficial to tack-free surface. Comparing formulations 10s cure with the same loading of TPO-L Surface and ITX, DOC is lower with DOC (mm) tackiness ITX, but the formulation with ITX results in a better tack-free 6.22 No surface. 13.00 Yes

DOC (mm)

Surface tackiness

Omnirad 819

4.30

No

1.2

Omnirad TPO

6.86

Yes

1.3

Omnirad L-TPO

9.45

Yes

13.00

Yes

1.4

Genocure ITX

4.15

No

6.21

No

DOC (mm)

Cure time effect on DOC and surface tackiness In this study, two formulas – 1.5 Genopol TX-2 6.50 Yes 13.00 Yes Sample 1.3 with 1% L-TPO and 1.6 Omnipol TX 1.65 No 2.53 No Sample 1.4 with 1% ITX and Table 5. Summary of the DOC and surface tackiness of the formulas containing different PIs 2% DMAPMA – were cured with LED 405 nm for different periods of time. Table 7 is the summary of the 14 DOC and surface tackiness of the two formulas 12 with different curing times. Figure 4 is a graph 10 showing the correlation of DOC and length of 8 cure time. 6 4 2 0

Omnirad 819

Omnirad TPO

Omnirad Genocure L-TPO ITX Visible PI 5s

10s

Genopol TX-2

Omnipol TX

Results in Table 7 and Figure 4 show that DOC increases with increasing cure time for both PIs. The DOC of Sample 1.3 showed DOC reached full depth of 13 mm after 7s. The surface still showed tackiness after 10s curing, due to the selected PI concentration. Increasing curing time in this case didn’t improve surface cure.

Curing light intensity effect on DOC and surface tackiness The two formulas, Sample 1.3 and 1.4, were cured with LED PI Sample PI Concentration (wt%) DOC (mm) Surface tackiness 405 nm under different intensity 2.1 0.5 11.00 Yes for 5s. Table 8 is the summary 2.2 1 9.45 Yes of the DOC of the two formulas with different curing intensity. 1.3 1.5 7.20 No Omnirad TPO-L Figure 5 is a graph showing the 2.3 2 5.40 No correlation of DOC and curing 2.4 2.5 5.37 No light intensity. Results in Table 8 and Figure 5 show that DOC 2.5 3 4.82 No increases with increasing curing 2.6 0.5 5.45 Yes light intensity for both PIs. 1.4 1 4.15 No The surface of Sample 1.3 still showed tackiness, even with 2.7 1.5 3.46 No ITX/ DMAPMA increased light intensity, due to 2.8 2 2.84 No the selected PI concentration. 2.9 2.5 2.29 No For Sample 1.4, surface turned from tacky to non-tacky after 2.10 3 1.55 No curing intensity increased. Table 6. Summary of the DOC of formulas containing different concentrations of PIs page 36 

Figure 2. DOC of the formulas containing different PIs

34 | UV+EB Technology • Quarter 1, 2020

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ADHESIVES  page 34 12

DOC (mm)

10 8 6 4 2 0 0

0.5

1

1.5 2 2.5 PI Concentration (wt%) L-TPO

3

3.5

ITX

Figure 3. DOC of formulas containing different concentrations of PI

Formula

Curing time (sec)

DOC (mm)

Surface tackiness

2

5.71

Yes

5

9.45

Yes

7

13.00

Yes

10

13.00

Yes

2

1.57

Yes

5

4.15

No

7

5.26

No

10

6.50

No

1.3

1.4

The results were analyzed by using Design Expert Version 11 software. Statistical analyses (regression and ANOVA analysis) of each response were carried out to determine the goodness of fit of each model and to estimate the coefficients of the polynomial equation. For response DOC, a reduced quadratic model was obtained with R2adj and R2pred of 0.905 and 0.789, respectively. For response surface tackiness, transformation with inverse square root was applied to have a linear model with R2adj and R2pred of 0.863 and 0.785, respectively. The final model equations are listed in Equation 1 for DOC and Equation 2 for surface tackiness. Their corresponding surface contour plots are shown in Figure 6.

Table 7. Summary of the DOC and surface tackiness of the formulas with different lengths of cure time

14

DOC (mm)

12 10 8 6 4 2 0 0

2

4

6 8 Curing time (s) TPO-L

10

ITX

Figure 4. DOC of the formulas with different lengths of curing time

36 | UV+EB Technology • Quarter 1, 2020

DOE study on formulations with ITX loading and DMAPMA/ITX ratio In this study, the DOC and surface tackiness performance are optimized by design of experiment using rotatable central composite design (CCD), which is one of the designs in response surface methodology design. There are two factors used in RSM study.9,10 Factor 1 is monomeric PI ITX loading, ranging from 0.17% to 2.13%. Factor 2 is the ratio of amine synergist (DMAPMA) to PI (ITX) loading, ranging from 0 to 4.0. The RSM design comprises 4 factor points, 4 axial points and 3 replicates of central points with a total of 11 runs. Adhesives are cured with 405 nm LED light for 5s. Response DOC is measured in the above-mentioned technique. Response surface tackiness was quantified by the relative amount of SiC powder remaining on the cured adhesive surface after brushing. If no SiC powder sticks to the surface, it is rated as “0,” and if all the powder remains on the surface, it is rated as “10.” Any values in between 0 and 10 were estimated based on the amount of SiC powder remaining. The RSM design points and response data are summarized in Table 9.

12

Equation 1: DOC = 5.917 – 5.166 * ITX loading + 2.173 * amine/ITX ratio + 1.337 * (ITX loading)2 – 0.380 * (DMAPMA/ITX ratio)2 Equation 2: 1/ Sqrt (tackiness-0.5) = 0.066 + 0.536* ITX loading + 0.038 * DMAPMA/ITX ratio page 38  uvebtechnology.com + radtech.org


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ADHESIVES  page 36 Formula

Curing Intensity (W/cm2)

DOC (mm)

Surface tackiness

0.61

5.52

Yes

1.07

7.27

Yes

1.5

9.45

Yes

2.18

13.00

Yes

0.61

2.11

Yes

1.07

3.03

Yes

1.3

1.4

1.5

4.15

No

2.18

4.70

No

... DOC decreases with increasing reactivity at 405 nm, however, less surface tackiness was observed with increasing PI reactivity.

Table 8. Summary of the DOC and surface tackiness of the formulas with different curing intensity

By applying multiple response optimization for maximum DOC and minimum surface tackiness, a high desirability of 0.7 is obtained to have predicted DOC of 5.6 mm and surface tackiness of 3.4. The optimized formulation is composed of 0.84% of ITX and DMAPMA/ITX loading ratio of 3.14. The optimization desirability plot is shown in Figure 7.

12

DOC (mm)

10 8 6 4 2 0 0

0.5

1 1.5 Light Intensity (w/cm2) TPO-L

2

2.5

ITX

Figure 5. DOC of the formulas with different light curing intensity

Factor 1

Factor 2

Response 1

Response 2

Std

ID

Run

A:ITX loading

B:DMAPMA/ITX ratio

DOC (mm)

Surface tackiness

1

1

3

0.30

0.27

4.90

10

2

2

5

2.00

0.27

1.90

8

3

3

4

0.30

4.00

7.80

10

4

4

1

2.00

4.00

2.67

0

5

5

6

0.17

2.14

7.50

4

6

6

2

2.13

2.14

4.30

0

7

7

7

1.15

0.00

1.50

2

8

8

10

1.15

4.28

4.25

1

9

9

8

1.15

2.14

5.00

2

11

9

9

1.15

2.14

4.20

2

10

9

11

1.15

2.14

4.80

2

Table 9. Summary of the DOC and surface tackiness of the formulas containing different ITX loading and DMAPMA/ITX ratio

38 | UV+EB Technology • Quarter 1, 2020

Conclusions This work examined the effect of visible photoinitiator type and concentration, as well as LED 405 nm intensity and curing time on the depth of cure and surface tackiness of an acrylate resin system under LED 405 nm light curing. UV/visible absorption spectra of the visible photoinitiators were used to obtain the PI absorbance at 405 nm. The 405 nm absorbance of the six PIs tested at 0.01% concentration has the order of: Omnipol TX > Genocure ITX > Omnirad 819 > Omnirad TPO > Omnirad TPO-L > Genopol TX-2. The PI absorbance correlates to its photocuring reactivity. The study proved, as literature reported, that DOC decreases with increasing reactivity at 405 nm; however, less surface tackiness was observed with increasing PI reactivity. With increasing PI concentration, the curing speed increased, resulting in less oxygen inhibition and less surface tackiness. The DOC decreased with increasing PI concentration due to the light blocking from the polymer gel formed on the resin surface. DOC increases with increasing curing intensity and time, as expected. Surface curing will be improved with curing time, although the tests in the study didn’t show any differences. It is important to understand how these parameters work together in order to optimize the surface curing and depth of cure of the selected resin page 40  uvebtechnology.com + radtech.org


ADHESIVES  page 38

Figure 6. Surface contour plots of response DOC and surface tackiness

systems, and DOE is a good tool for this optimization process. DOE using RSM allowed us to optimize Type II PI ITX concentration and amine synergist DMAPMA/ITX ratio for the most desired surface curing and DOC. A high desirability of 0.7 is obtained to have predicted DOC of 5.6 mm and surface tackiness of 3.4 with optimized formulation comprising 0.84% of ITX and DMAPMA/ITX of 3.14.  References 1. P. L. Fan, R. Schumacher, K. Azzolin, R. Geary, F. Eichmiller, “Curing Light Intensity and Depth of Cure of Resin- Based Composites Tested According to International Standards,” Journal of the American Dental Association, Volume: 133, Issue: No. 4 2. J.H. Lee et al., “Cure depth in photopolymerization: Experiments and theory,” J. Mater. Res., Vol. 16, No. 12, Dec 2001, p3536-3544 3. Alonso et al. “Photoinitiator concentration and modulated photoactivation: influence on polymerization characteristics of experimental composites,” Applied Adhesion Science 2014, 2:10, p1-8 4. Lambson technical bulletin “An Overview of Free Radical Photoinitiators” 5. Lambson technical bulletin “Photoinitiators for LED curing” 6. ISO 4049 (2009). International Standard, Dentistry- Polymer-based restorative materials, 4th Edition, Switzerland. 7. Mark W. Pressley, “Dual cure adhesive formulations,” US 2012/0145312 A1 8. David Harvey, “Spectroscopy Based on Absorption,” Analytical Chemistry 2.0 (Harvey), 10.2, P 5609 9. H.K. Kim, J.G. Kim, J.D. Cho, J.W. Hong, “Optimization and characterization of UV-curable adhesives for optical communications by response surface methodology,” Polymer Testing 22 (2003) 899–906

40 | UV+EB Technology • Quarter 1, 2020

Figure 7. Optimization desirability plot for DOC and surface tackiness 10. W. S. Chow, Y. P. Yap, “Optimization of process variables on flexural properties of epoxy/organo-montmorillonite nanocomposite by response surface methodology,” eXPRESS Polymer Letters Vol.2, No.1 (2008) 2–11

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TECHNOLOGY SHOWCASE Epson’s Newest UV Digital Label Press Now Available Technology firm Epson, with regional headquarters in Long Beach, California, has announced that the SurePress® L-6534VW UV digital label press is available and on display at the Epson Demo Center in Carson, California. The press enables high-speed printing that’s ideal for producing labels and packaging. Designed for label converters making first-time investments or looking to expand production facilities, the SurePress L-6534VW delivers a range of print speed modes, including “Standard” at 98 ft./minute and “Productivity” at 164 ft./minute. The press comes standard with the functions required for label production, including a Corona Treater, white ink, digital varnish and an additional UV curing unit. The print heads, inks, LED pinning and curing lamp units, media feeding and control system are developed, serviced and manufactured by Epson. For more information, visit www.epson.com.

Energy Sciences Offers Gelflex-EB Ink Energy Sciences, Inc., Wilmington, Massachusetts, a provider of low-voltage electron beam technology, now offers Gelflex-EB ink, which does not require a fully formed polymer. Gelflex-EB technology includes microscopic polymer chains that reduce resistance to flow. Using virtually no solvents, its gel-based technology allows ink to adhere almost instantly to a substrate by way of a covalent bond, resulting in no color bleed. In its reaction with an e-beam, Gelflex-EB crystallizes and cross-links polymer chains to create a contiguous and homogenous layer of polymerized print. The two-part gel and solvent EB inks have superior physical properties and dot gain, are fluid enough for flexo printing and thicken rapidly, providing effective ink trapping in the wet state as the solvent evaporates and a gel is formed. For more information, visit www.ebeam.com.

Innovations in Optics Offers UV-LED Systems for 3D Printing and Photolithography Innovations in Optics, Inc., Woburn, Massachusetts, offers solutions that pair high-power UV LED illuminators with precision driver/controllers for digital light processing (DLP®) applications in 3D printing and maskless photolithography. Optical power can exceed 35 watts of incident flux onto the active area of the DLP. The Model 3300 series of UV LED illuminators for DLP comprise a densely packed UV LED array. The illuminators support the larger of TI’s chipset families, DLP7000, DLP9000 and DLP9500. Standard LED center wavelengths range from 365 nm to 435 nm. Single or multi-wavelength configurations are possible. Up to 18-die integrated into the UV LED array can be driven and modulated independently. 42 | UV+EB Technology • Quarter 1, 2020

Recirculated liquid cooling allows the UV LED array to be operated at a very high current density. For more information, visit www.innovationsinoptics.com.

Phoseon Boosts Power of FireJet™ 800 Series Up to 50% with FJ801 Phoseon Technology, Hillsboro, Oregon, a manufacturer of UV LED curing solutions, has announced the launch of the FireJet™ FJ801 area curing solution, targeting electronics manufacturing adhesives cure applications and lab material/substrate curing. The new air-cooled solution provides increased power of up to 50% over its predecessor, the J800. The new FJ801 light source is designed primarily for production lines that require area curing, such as micro speakers and camera modules manufacturing. Starting from a base curing area of 100 mm x 100 mm, these modular products can scale in three directions to provide contiguous, uniform UV output. The FJ801 is available in 365 nm/385nm/395 nm/405 nm wavelengths. The FJ801 light source offers process stability with Phoseon’s patented TargetCure™ technology that provides users with precise and predictable UV output. For more information, visit www.phoseon.com.

EnvisionTEC and Sartomer Introduce E-Aquasol 3D Printing Resin EnvisionTEC – a global developer of professional-grade 3D printing solutions with US offices in Dearborn, Michigan – and Sartomer – a global supplier of specialty chemicals and a business line of Arkema, with US headquarters in Exton, Pennsylvania – introduce E-Aquasol water-soluble. Developed through a collaboration between the two companies, E-Aquasol resin is designed for use on EnvisionTEC’s proprietary cDLM® 3D printing platform and incorporates Sartomer’s N3xtDimension® UV-curable resin technology. Ideal for printing molds in a wide variety of industrial applications, the water-soluble 3D printing resin allows industrial manufacturers to shell-cast thin-walled parts with high feature resolution. Thanks to its high water solubility, E-Aquasol resin is an optimal choice for users who seek to avoid the use of more aggressive solvents. For more information, visit https://envisiontec.com/ and https://americas. sartomer.com/en/.

Infinite Material Solutions Develops New Water-Soluble 3D Printing Support Structure Material River Falls, Wisconsinbased Infinite Material Solutions, a development company for the additive manufacturing industry, has developed Aquasys 120, a high-performance, water-soluble 3D printing support material designed to be compatible with a wide range of engineering-grade 3D printing materials. AquaSys 120 uvebtechnology.com + radtech.org


is soluble in water, which significantly reduces finishing time for printed parts. AquaSys 120 has been proven to dissolve up to six times faster than PVA. And, unlike other PVA or BVOH filament materials, AquaSys 120 is extremely stable when higher temperatures or more demanding print conditions are needed. AquaSys 120 is available in 1.75 mm and 2.85 mm diameter filament for use in a variety of 3D printing platforms and materials. For more information, visit InfiniteMaterialSolutions.com.

and Sartomer, an Arkema Business Line, announced a partnership combining Continuous Compositesâ&#x20AC;&#x2122; patented continuous fiber 3D printing technology (CF3DÂŽ) with Sartomerâ&#x20AC;&#x2122;s N3xtDimensionÂŽ UV-curable resin solutions. Arkema has also partnered with 9T Labs (Zurich), a start-up specializing in the 3D printing of thermoplastic composites that has developed a technology automating the manufacture of composites using additive manufacturing (AM) and advanced software algorithms. For more information, visit www.arkema.com.

Arkema Expands Composite 3D Printing to Its High-Performance Material Range

Mimaki Announces Metallic Ink for UJF-7151 Plus Benchtop Flatbed Printer

Designer of materials and innovative solutions Arkema, Colombes Cedex, France, announced new partnerships and expansion of its high-performance solutions into 3D manufacturing of composite materials. This new technology combines the power of 3D printing and composite materials and will offer advances for the aeronautics, automotive, energy and construction sectors to meet the demand for lightweight materials. Continuous Composites

Mimaki USA, Suwanee, Georgia, a manufacturer of wide-format inkjet printers and cutters, announced new Metallic UV ink for its UJF-7151 Plus benchtop UV LED flatbed printer. With this new ink, the UJF-7151 Plus printer can directly image a surface without the need for added glitter or a foil transfer process. Gloss and matte finishes, as well as an emboss effect, are available. Metallic color effects can be created using metallic ink and RasterLink6 RIP software, which includes a swatch palette of 648 metallic colors that easily are selectable from IllustratorÂŽ software and can be utilized in a combination of custom colors. Mimaki MUH-100 Metallic Silver ink is packaged in a 200 ml bottle and is available for order now. For more information, visit www. mimakiusa.com. ď ľ

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UV+EB Technology â&#x20AC;˘ Quarter 1, 2020 | 43


POLYMERS By Darryl A. Boyd, Colin C. Baker, Jason D. Myers, Vinh Q. Nguyen, Woohong Ki and Jasbinder S. Sanghera, Optical Sciences Division, Naval Research Laboratory and Collin C. McClain and Christopher G. Brown, University Research Foundation, Greenbelt, Maryland

Development of Novel Optical Materials Using Sulfur-Based Chemistry Note from the Editor: The polymers described in the following proceeding are being developed for use as infrared (IR) transmitting materials to replace costlier, heavier and more difficult-to-process IR-transmitting materials currently on the market. These ‘ORMOCHALC’ polymers have been shown to transmit from the red-visible range all the way into the mid-wave IR. Abstract olymers containing the chalcogens sulfur and selenium show great promise as infrared transmissive materials. The chalcogen-based materials are synthesized using a process known as inverse vulcanization. Through this process, sulfur and selenium-rich polymers are fabricated, and these polymers possess unusually high refractive indices while also being transmissive far beyond the typical transmission range of most polymers. The results of this work highlight the value of sulfur-based reactions in the development of costefficient and useful optical materials.

P

Introduction Sulfur is an earth-abundant element that has several inherent beneficial qualities for the development of functional materials.1,2 ORganically MOdified CHALCogenide (ORMOCHALC) polymers are sulfur-rich materials that can be synthesized via inverse vulcanization.3 Inverse vulcanization is a recently developed process in which sulfur-based polymers can be synthesized through the use of elemental sulfur and carbonrich crosslinkers.4 First, sulfur, which exists as an eight-membered ring structure compound (i.e. S8), is heated to open the ring structure and make a linear sulfur chain. Upon ring-opening, radicals are revealed at either end of the sulfur chain. The radicals at the ends of the sulfur chain then can be reacted with crosslinking/ branching agents to produce stable ORMOCHALC polymers. The ORMOCHALC polymers fabricated using this process have valuable optical characteristics and have also found use in dye-sensitized solar cells,5 as well as in cathode materials for lithium sulfur batteries.4,6,7 Sulfur has elemental similarities with selenium, which sits just below sulfur in the periodic table of the elements. Due to their similarities,8,9 it is possible to combine the two elements and use this combination as an ORMOCHALC precursor material. The addition of selenium to the backbone of ORMOCHALC polymers has a direct and pronounced effect on the optical properties of the polymers produced. Most notable are the

Figure 1. Process to make ORMOCHALC precursor: (a) blending of sulfur and selenium, (b) conversion of S and Se from glassy to crystalline material

44 | UV+EB Technology • Quarter 1, 2020

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extension of the infrared transmission profile further into the mid-wave infrared region3 and the increased refractive indices of this class of polymers.10 The reported work presents the synthesis and optical characterization of ORMOCHALC polymers. Materials and methods Materials: Sulfur and selenium were purchased from All-Chemie Ltd. and distilled four times each. 1,3-diisopropenyl benzene (DIB) was purchased from TCI America and used as received. All polymers were fabricated with a “S-Se precursor” to “DIB comonomer” weight ratio of 70 to 30. Analysis Instrumentation: FT-IR data was obtained using an Analect Diamond-20 FT-IR. SWIR images of polymers were taken using an FJW Industries FIND-R-SCOPE.

Figure 2. Process to synthesize ORMOCHALC polymer: (a) ORMOCHALC precursor, (b) ORMOCHALC polymer, scale bar = 2.5 cm.

Figure 3. Photograph images showing (a) an ORMOCHALC polymer in visible light conditions and (b) the same ORMOCHALC polymer visualized using a short-wave infrared viewer

Preparation of crystalline sulfur-selenium compounds: Purified elemental sulfur (S) and purified elemental selenium (Se) were combined as previously described.3 Data presented are based on an S to Se ratio of 95:5. Fabrication of poly(SxSey-r-DIB) ORMOCHALC polymers: In a fume hood, a beaker containing a magnetic stir bar and crystalline S-Se compound was placed in a silicon oil bath that was preheated to ~180°C, covered with a watch glass and stirred on a magnetic stir plate. After the S-Se compound completely melted, DIB was added to the beaker and the mixture stirred until it became viscous and red in color. The viscous material was poured from the beaker into a mold, and the mold was then placed into a furnace that was preheated to 200°C and allowed to vitrify for 1 hour. The polymer was allowed to cool to room temperature and removed from its mold. Polymers in this study were made with 30 wt% DIB comonomer, while the subscript values given for sulfur and selenium within the precursor compounds represent atomic percentages. Results and discussion The blending of the elements sulfur and selenium together to uvebtechnology.com + radtech.org

form a uniform precursor material (Figure 1) is a nontrivial, but useful, process that allows for the synthesis of sulfur-selenium ORMOCHALC polymers.3 These multi-chalcogen precursors are used as comonomers and can be combined with a variety of crosslinking comonomers.6,11-13 In the work outlined, the crosslinking comonomer is 1,3-diisopropenyl benzene (DIB). The resulting polymers are generically named as poly(SxSey-rDIB), where S represents sulfur, Se represents selenium, DIB represents the comonomer, r represents the random nature of the crosslinking and the subscripts x and y represent the ratio of sulfur to selenium in the precursor, respectively. Elemental sulfur is typically yellow in color. Upon addition of selenium, the sulfur-selenium precursor becomes increasingly orange in color as the percentage of selenium increases. Once the solid precursor is heated to 120°C, it begins to melt and get darker in color (i.e. from yellow/orange to deep red) as the temperature approaches 200°C. The change in color is accompanied by an increase in viscosity, with the material becoming solid-like at 200°C. In the absence of a crosslinking comonomer, the sulfurselenium precursor will return to a yellow/orange, solid material. The addition of the DIB crosslinker at elevated temperatures page 46  UV+EB Technology • Quarter 1, 2020 | 45


POLYMERS  page 45 prevents the sulfur-selenium compound from turning back into a yellow/orange material, leaving behind a red, solid ORMOCHALC polymer (Figure 2b). Despite the red color of the ORMOCHALC polymers, they still are translucent to the naked eye (Figure 3a). When visualized in the short-wave infrared (SWIR) region of the electromagnetic spectrum, the polymers appear transparent, like clear glass (Figure 3b), demonstrating the useful infrared transmission character of these polymers. In agreement with what can be seen through a SWIR viewer (Figure 3b), FT-IR analysis demonstrates that the ORMOCHALC polymers indeed have broad optical transmission into the mid-wave infrared (MWIR) region of light (3 to 6 μm) (Figure 4). This transmission only is interrupted by the –CH absorbance bands that arise from the presence of the DIB comonomer within the ORMOCHALCs. Most polymers are incapable of transmitting light at high transmission percentages far into the infrared region, making ORMOCHALC polymers particularly valuable as possible replacements for costlier, heavier and more difficult to process IR-transmissive glasses. Conclusions Figure 4. FT-IR transmission plot for a poly(S-Se-r-DIB) ORMOCHALC Sulfur and selenium-rich materials, termed polymer ORMOCHALC polymers, can be fabricated via the inverse vulcanization process. A major benefit to ORMOCHALC research is that it offers an alternative use for the P.; Mackay, M. E.; Glass, R. S.; Char, K.; Pyun, J. RSC Advances large stores of excess sulfur that exist on the planet, and – with 2015, 5, 24718. 7. Gomez, I.; Mantione, D.; Leonet, O.; Blazquez, J. A.; Mecerreyes, the proper crosslinkers – can lead to the development of useful D. ChemElectroChem 2018, 5, 260. materials using completely renewable resources.14 Though red in 8. Eisenberg, A.; Tobolsky, A. V. Journal of Polymer Science 1960, color to the human eye, these materials provide transparency into 46, 19. the MWIR region of the electromagnetic spectrum, far beyond the 9. Tobolsky, A. V.; Eisenberg, A. Journal of the American Chemical typical transmission of most common organic polymers. Finally, Society 1959, 81, 780. the unique optical characteristics of these polymers can be further 10. Anderson, L. E.; Kleine, T. S.; Zhang, Y.; Phan, D. D.; Namnabat, enhanced by increasing the amount of selenium present in the S.; LaVilla, E. A.; Konopka, K. M.; Ruiz Diaz, L.; Manchester, polymer backbone.  M. S.; Schwiegerling, J.; Glass, R. S.; Mackay, M. E.; Char, K.; References 1. Boyd, D. A. Angewandte Chemie International Edition 2016, 55, 15486. 2. Boyd, D. A. Angewandte Chemie 2016, 128, 15712. 3. Boyd, D. A.; Baker, C. C.; Myers, J. D.; Nguyen, V. Q.; Drake, G. A.; McClain, C. C.; Kung, F. H.; Bowman, S. R.; Kim, W.; Sanghera, J. S. Chemical Communications 2017. 4. Chung, W. J.; Griebel, J. J.; Kim, E. T.; Yoon, H.; Simmonds, A. G.; Ji, H. J.; Dirlam, P. T.; Glass, R. S.; Wie, J. J.; Nguyen, N. A.; Guralnick, B. W.; Park, J.; SomogyiÁrpád; Theato, P.; Mackay, M. E.; Sung, Y.-E.; Char, K.; Pyun, J. Nat Chem 2013, 5, 518. 5. Liu, P.; Kloo, L.; Gardner, J. M. ChemPhotoChem 2017, 1, 363. 6. Dirlam, P. T.; Simmonds, A. G.; Kleine, T. S.; Nguyen, N. A.; Anderson, L. E.; Klever, A. O.; Florian, A.; Costanzo, P. J.; Theato,

46 | UV+EB Technology • Quarter 1, 2020

Norwood, R. A.; Pyun, J. ACS Macro Letters 2017, 6, 500. 11. Crockett, M. P.; Evans, A. M.; Worthington, M. J. H.; Albuquerque, I. S.; Slattery, A. D.; Gibson, C. T.; Campbell, J. A.; Lewis, D. A.; Bernardes, G. J. L.; Chalker, J. M. Angewandte Chemie International Edition 2016, 55, 1714. 12. Arslan, M.; Kiskan, B.; Yagci, Y. Macromolecules 2016, 49, 767. 13. Salman, M. K.; Karabay, B.; Karabay, L. C.; Cihaner, A. Journal of Applied Polymer Science 2016, 133, n/a. 14. Worthington, M. J. H.; Kucera, R. L.; Chalker, J. M. Green Chemistry 2017, 19, 2748.

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INDUSTRY Phoseon and CYNGIENT Combine Technologies, Increase Performance

Fujifilm Uvijet UV Inks Retain Greenguard Gold Certification

LED-based solution provider Phoseon Technology, Hillsboro, Oregon, is working closely with CYNGIENT, a Fairfield, New Jersey-based provider of inks, coating, adhesives and custom-built solutions, on UV LED-cured adhesives and adhesive development for the narrow web label industry and beyond. Technical support from CYNGIENT allows Phoseon to offer customers faster, more efficient leading-edge adhesive product support with predictable, consistent performance. HYPERcure™ LED /UV adhesives, combined with Phoseon’s global LED curing technology, offers customers peace of mind for turnkey cold foil and lamination products with stronger bonds and better cold foil transfer. HYPERcure™ branded adhesives deliver more predictable results with the consistent and reliable Phoseon LED curing systems. For more information, visit www.phoseon.com.

Fujifilm, an international company serving medical, graphic arts, optics, enterprise storage, motion picture and photography industries, announced that 25 of its Uvijet UV inks continue to retain GREENGUARD® Gold Certification. The certification standard includes health-based criteria for additional chemicals and requires lower total VOC emission levels to help ensure that products are acceptable for use in school and healthcare environments. For more information, visit www.fujifilmgraphics.com.

AMS Spectral UV Parent Company, Baldwin Technology, Launches New Website Baldwin Technology has launched a new website designed to provide better access to the company’s portfolio of leading technologies for the printing industry. The new website covers all areas, from AMS Spectral UV curing and drying systems and IR technologies through surface cleaning and precision spray dampening solutions and popular consumables. For more information, visit baldwintech.com.

Innovative Chemical Products Acquires Hi-Tech Coatings Specialty chemical manufacturer Innovative Chemical Products Group (ICP Group), Andover, Massachusetts, announced that it has acquired Hi-Tech Coatings, a developer and manufacturer of high-performance coatings located in the Netherlands and the United Kingdom, from Heidelberger Druckmaschinen AG (Heidelberg). Hi-Tech Coatings produces more than 1,000 products and formulations, primarily water-based and UVbased coatings. The transaction also established a strategic partnership between Heidelberg and ICP Group to ensure future sales of Heidelberg’s coating portfolio. The acquisition expands ICP ISG’s product offerings, and it diversifies and expands its international customer base in Europe, the Middle East and AsiaPacific regions. For more information, visit www.icpgroup.com and www.hitechcoatings.net. 48 | UV+EB Technology • Quarter 1, 2020

Van Technologies Launches New Website for GreenLight Coatings® Van Technologies, Inc., Duluth, Minnesota, a developer and producer of environmentally compliant coatings for the industrial wood, metal and plastic markets under the brand GreenLight Coatings®, has announced the launch of its newly redesigned website. The new site features a streamlined, modern design, improved functionality and easy access to essential information to help finishing professionals, technical and production managers, and owners become familiar with the company’s approach to the development of custom-engineered industrial coating solutions. The new website showcases the company’s dynamic laboratory service capabilities, including the latest in technology in color matching and finish performance testing. For more information, visit www.greenlightcoatings.com.

BASF Acquires 3D Printing Service Provider Sculpteo To expand its position as a service provider in the additive manufacturing sector, BASF New Business GmbH – part of German chemical producer BASF – has formally agreed to acquire the online 3D printing service provider Sculpteo, based in Paris, France, and San Francisco, California. The agreement was signed on November 14, 2019, and is expected to become page 50  uvebtechnology.com + radtech.org


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INDUSTRY  page 48 effective in the next few weeks pending regulatory approval by the relevant authorities. The acquisition of the 3D printing specialist will enable BASF 3D Printing Solutions GmbH, a wholly-owned subsidiary of BASF New Business GmbH, to market and establish new industrial 3D printing materials more quickly. Sculpteo’s management team fully supports the acquisition and will remain in place to provide customers and partners with this expanded service spectrum. For more information, visit www.forward-am.com and www.sculpteo.com.

Perstorp Breaks Ground in India to Boost Penta Business Sweden-based Perstorp, a specialty chemical company, will construct a new pentaerythritol (Penta) production facility in Gujarat, India. Representatives from the Executive Leadership Team, government officials, employees and guests attended a groundbreaking ceremony on last November. The world scale, greenfield plant will produce Penta, including the renewable grades of Voxtar™. Construction started in October 2019, with commercial production planned to start in the first quarter of 2022. When fully operational, the site will employ 120 people. The investment will expand Perstorp’s Penta production capacity, designed to produce 40 kilatons of Penta per year. Penta is an essential ingredient in coatings, synthetic lubricants and antioxidants. The Gujarat investment will reinforce Perstorp’s ability to meet growing demand and offer various Penta qualities including Penta Mono, Di-Penta and calcium formate. For more information, visit www.perstorp.com.

Pittsburgh International Airport Announces New Epicenter of Additive Manufacturing Pittsburgh International Airport has announced plans for Neighborhood 91, the world’s first development to condense and connect all components of the additive manufacturing/3D 50 | UV+EB Technology • Quarter 1, 2020

printing supply chain into one production neighborhood concept. Construction will begin next year. Neighborhood 91, developed in conjunction with the University of Pittsburgh, is the first development of the 195-acre Pittsburgh Airport Innovation Campus and will be adjacent to the airport terminal and runway. Argon gas supplier and recycler Arencibia has committed to be the anchor tenant. The University of Pittsburgh is a key partner – both for its research and development as well as workforce development. The site will contain all elements of the additive manufacturing supply chain, including an onsite communal supply of powder. For more information, visit www.Neighborhood91.com.

Global methyl methacrylate (MMA) Market to Register a Volume CAGR of 3.4% in 2018–2028 Persistence Market Research – a supplier of market intelligence reports and consulting services with US offices in New York, New York – has a recently published report that reveals the application of methyl methacrylate for the production of PMMA is projected to account for a major share of consumption (~50%) during the forecast period. The global methyl methacrylate market is pegged at approximately 3.9 million tons in terms of volume at present and is expected to expand with a CAGR of 3.4% to reach ~5.7 million tons by the end of 2028. Methyl methacrylate is an essential substance for PMMA and many other polymers. The global methyl methacrylate market is projected to register healthy growth over the forecast period. For more information, visit www. persistencemarketresearch.com.

Henkel Expands Portfolio with Sonderhoff Brand The 2 1/2 year integration phase of Cologne, Germanybased Sonderhoff Group into Düsseldorf, Germany-based adhesive company Henkel AG & Co. KGaA is complete. As of January 1, 2020, all Sonderhoff companies, which offer a technology platform for customized sealing, adhesive bonding and potting solutions, have been merged into the Adhesive Technologies business unit. The former Sonderhoff sites in Germany, Austria, Italy and the US now operate under the Henkel name. The Sonderhoff site in China will operate under its previous name. Customers will continue to be served from these locations. Sonderhoff’s activities will continue to be managed from Cologne and are assigned to a business area of Henkel Adhesive Technologies. The Sonderhoff portfolio will continue as the Sonderhoff brand of Henkel Adhesive Technologies. For more information, visit www.henkeladhesives.de and www.sonderhoff.com.

Solvay’s New HMW HALS Capacity Now Online Advanced materials and specialty chemicals company Solvay, Saddle Brook, New Jersey, has announced that its new high page 52  uvebtechnology.com + radtech.org


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INDUSTRY  page 50 molecular weight (HMW) hindered amine light stabilizer (HALS) capacity is now online, complementing existing HALS production at the Willow Island, West Virginia, USA, site. Solvay’s stateof-the-art facility was designed with the latest improvements in technology to ensure operator safety, reduce impact on the environment and improve the quality and consistency of Solvay’s HALS products. The core HALS products currently produced at the site are the foundation for the CYNERGY® and CYXTRA® polymer additives product families that enable Solvay’s customers to transform the performance characteristics of polyolefin plastics into advanced polymers for specialty applications in building and construction, agricultural films, and a host of consumer and industrial uses. For more information, visit www.solvay.com.

The board of directors of Sirrus, Inc., a chemical company with US headquarters in Loveland, Ohio, announced that Kenta Kanaida, currently a Sirrus director, will be appointed as the company’s new president and chief executive officer in early 2020, subject to board approval. In November 2019, Jeff Uhrig, president and CEO since 2013, resigned to pursue other opportunities. Kanaida brings more than 30 years of polymer science experience to Sirrus.

NEW FACES

Carbon Appoints Kullman President and CEO; DeSimone Named Executive Chairman

Michelman Appoints James Xue Country Manager for Greater China

Carbon, Redwood City, California, a digital manufacturing platform, announced that Ellen J. Kullman, former chairman and CEO of DuPont, has been named president and CEO of the company, and Dr. Joseph M. DeSimone has been named executive chairman of the board, effective immediately. Kullman also will remain on Carbon’s board of directors, where she has served since 2016. DeSimone is transitioning into the role of executive chairman to focus on growing mainstream adoption of the Carbon Digital Manufacturing Platform. 

Michelman, Cincinnati, Ohio, a global developer and manufacturer of advanced materials for industry, has announced the appointment of James Xue as country manager for greater China. Hired in 2017, Xue has more than 20 years of experience in the advanced materials industry sector. He began in 1996 as a Shanghai-based chemist, added sales and technical service expertise, and moved into sales management and senior

leadership. Before joining Michelman, he served with Huntsman Advanced Materials China and Dow Corning (China) Holding Co., Ltd.

Sirrus Announces Change in Executive Team

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REGULATORY NEWS 20 High Priority Chemicals Listed for TSCA Risk Evaluation The US Environmental Protection Agency (US EPA) is meeting a statutory requirement under the 2016 amendments to the Toxic Substances Control Act (TSCA) by proposing to designate 20 chemical substances as High-Priority Substances for upcoming risk evaluations. The proposed designation is a required step in a new process of reviewing chemical substances currently in commerce under the amended TSCA. Doreen M. Monteleone, Ph.D., director of sustainability & EHS initiatives, RadTech International North America doreen@ radtech.org

The EPA is issuing designation documents for each chemical substance describing the chemical-specific information, analysis and basis EPA used to support the proposed designation. The 20 proposed high-priority candidate chemicals include seven chlorinated solvents, six phthalates, four flame retardants, formaldehyde, a fragrance additive and a polymer precursor. Learn more at https://www.epa.gov/assessing-and-managingchemicals-under-tsca/chemical-substances-undergoing-prioritization-high. Updated Guide for Managing Hazardous Waste The US EPA has updated the guidebook entitled “Managing Hazardous Waste: A Guide for Small Businesses.” The guide provides an overview of the federal hazardous waste regulations to give business owners and operators a basic understanding of their hazardous waste management responsibilities. It answers questions such as, “Do hazardous waste regulations apply to me?” “How do I know which generator category I am?” and “What kinds of requirements do I have to follow?” The guide will help businesses determine proper hazardous waste management, a critical step in protecting human health and the environment. Although the guide is targeted to small businesses, the information may be helpful to any business managing hazardous waste. Learn more at https://www.epa.gov/hwgenerators/ managing-your-hazardous-waste-guide-small-businesses. SGP Announces New Supplier Certification The Sustainable Green Printing Partnership (SGP), the leading authority in sustainable printing certification, is pleased to announce a new certification for suppliers to the printing industry. The “SGP Supplier” certification is the next step in the organization’s mission to further sustainability throughout the printing supply chain. The criteria for SGP Supplier certification are similar to those for SGP Printers. The criteria specify the requirements for management and production operations that define sustainable practices encompassing people, planet and profit – the three P’s of sustainability. Draft criteria, based on SGP’s successful printer certification efforts, define the core elements of the SGP certification program, including development and adoption of a sustainability management system (SMS) and best practices. The criteria will be released in the first half of 2020.

News from the West Coast

RadTech Test Method Approved by SCAQMD Board In an unprecedented move, the South Coast Air Quality Management District (SCAQMD) Board voted unanimously to approve ASTM D7767-11 – the RadTech test method for thin film materials – thereby overriding their staff recommendation to continue to explore whether or not to approve ASTM D7767-11 for enforcement purposes. Rita Loof, director of regional environmental affairs, RadTech International North America rita@radtech.org

Decades ago, the Environmental Protection Agency (EPA) and the SCAQMD requested that RadTech develop a method for thin film materials as the methods used for conventional materials (EPA Method 24 and SCAQMD M313) are not valid for energy-curable materials, according to findings by both the EPA and the district. RadTech formed a committee of over 25 member companies and then invested significant time and resources to obtain approval from the ASTM. In 2011, ASTM D7767-11 was certified as a valid method to measure Volatile Organic Compounds (VOCs) from thin film energy-curable materials. While the district allowed the method for emission reporting and permitting, the agency had not specified which method it would use for compliance verification, leaving the industry in limbo. The issue kept coming up every time a new coatings rule was proposed, including the one at hand – Rule 1107 (Metal Coatings). Section (b) of Rule 1107 acknowledged ASTM D7767-11 and reads as follows: (b)(15) “ENERGY CURABLE COATINGS are single-component reactive products that cure upon exposure to visible-light, ultra-violet light or an electron beam. The VOC content of thin film energy-curable coatings may be measured

54 | UV+EB Technology • Quarter 1, 2020

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by manufacturers using ASTM D7767 – Standard Test Method to Measure Volatiles from Radiation Curable Acrylate Monomers, Oligomers, and Blends and Thin Coatings Made from Them.” The inclusion of the method in the definition section was progress, but ASTM D7767-11 was not listed as one of the Methods allowed under the Section (e) of the Rule “Methods of Analysis.” To complicate matters further, Section (e)(5) reads: “Multiple Test Methods: When more than one test method or set of methods are specified for any testing, a violation of any requirement of this rule established by any one of the specified test methods or set of test methods shall constitute a violation of the rule.” In essence, the language allows the district staff to fine companies whenever there is a dispute over the appropriate method. Since the district has no better method than ASTM D7767-11, RadTech requested listing the method in Section (e) with the other test methods, which would clarify test method requirements for businesses and allay fears that the district may take adverse enforcement action due to inconsistencies of test methods. Staff rejected the proposal. After engaging in a brief question and answer period with the staff, a board member suggested additional language that would compel suppliers to provide formulation date to the staff. A motion was made to accept the RadTech language without any changes and was seconded. The roll was called, and the motion passed 11-0 in favor of the RadTech proposal. The board decision means that for the first time in UV/EB history, the RadTech test method for thin films has been certified to prove compliance. Watch the testimony by Rita Loof, director of Environmental Affairs for RadTech and Doug Delong of Doctor UV at the following link (1:16 on the ribbon): http://www.aqmd.gov/home/news-events/webcast/livewebcast?ms=FhZzVdu3WGM PCBTF Now a Carcinogen in California Effective June 28, 2019, the California Office of Environmental Health Hazard Assessment (OEHHA) added p-chloro-α,α,α-trifluorotoluene (para-Chlorobenzotrifluoride, PCBTF) to the list of chemicals known to the State of California to cause cancer for purposes of Proposition 65. Under Prop 65, individuals must provide warnings prior to exposure to a chemical identified to cause cancer or reproductive harm. The duty to warn applies to product manufacturers, employers and individuals causing exposures in an affected area. PCBTF is used in field-applied architectural and industrial maintenance (AIM) coatings; marine coatings; auto-refinish coatings; factory-applied metal, plastic and wood coatings; and in adhesives and consumer products, including paint thinners. In 1994, the US Environmental Protection Agency (EPA) exempted PCBTF from its list of volatile organic compounds (VOCs). In addition, PCBTF sometimes is favored over other exempt compounds because it evaporates more slowly and has a higher flash point. Thus, it is less flammable than some exempt VOCs, such as acetone. According to OEHHA, the listing of PCBTF is based on formal identification by the National Toxicology Program (NTP) that the chemical causes cancer. The information OEHHA relied on primarily consisted of (1) studies on the toxicokinetics of PCBTF in rats, (2) studies investigating the potential for the chemical’s genotoxicity in bacterial and mammalian cell cultures, as well as in vivo in rodents, and (3) a lifetime cancer evaluation of PCBTF in B6C3F1/N mice and Hsd: Sprague Dawley SD rats carried out by NTP (2018). References found here: https://oehha.ca.gov/media/ downloads/crnr/pcbtfiur101819.pdf In October 2019, OEHHA released a proposed PCBTF cancer inhalation unit risk (IUR) factor. The state agency is in the process of finalizing the unit risk factor for PCBTF; once final, SCAQMD will utilize the unit risk factor to complete a risk assessment and could remove the PCBTF VOC exemption. The criteria used by OEHHA for the listing of chemicals under the “authoritative bodies” mechanism can be found in Title 27, Cal. Code of Regs., section 25306. But, industry representatives argue that the National Toxicology Program (NTP) Report on PCBTF and the data it provides do not satisfy the OEHHA listing criteria. If PCBTF’s VOC exemption is eliminated, SCAQMD may propose amendments to its Architectural Coatings rule (Rule 1113) to provide the industry additional time to reformulate products. Industry representatives have called for an increase in VOC limits in order to comply with rule requirements without the option of using products containing PCBTF. The district has indicated that any increase in emissions resulting from higher VOC limits would need to be offset with other additional VOC reductions to avoid “backsliding.”  uvebtechnology.com + radtech.org

UV+EB Technology • Quarter 1, 2020 | 55


CALENDAR MARCH 8-11: RadTech 2020, Disney Coronado Springs Resort, Orlando, Florida. For more information, visit https:// radtech2020.com/registration. 15-18: TAGA Annual Technical Conference, Sheraton Oklahoma City Downtown Hotel, Oklahoma City, Oklahoma. For more information, visit www.taga.org/conference. 29-April 2: SPE ANTEC 2020, Marriott Rivercenter, San Antonio, Texas. For more information, visit www.4spe.org. 31-April 2: American Coatings Show, Indiana Convention Center, Indianapolis, Indiana. For more information, visit www.american-coatings-show.com.

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ADVERTISING INDEX Alberdingk Boley ...................................................................... alberdingkusa.com ............................................................................................... 43 allnex.......................................................................................... allnex.com ............................................................................................................. 21 American Ultraviolet ................................................................. americanultraviolet.com ...................................................................................... 33 BCH North America Inc............................................................ bch-bruehl.com .................................................................................................... 49 Dymax ........................................................................................ dymax-oc.com/strength ...................................................................................... 37 EIT Instrument Markets ............................................................ eit.com ............................................................................................................ 11, 35 Excelitas Technologies ............................................................. excelitas.com .........................................................................................Back Cover GEW........................................................................................... gewuv.com ............................................................................................................ 17 Heraeus ..................................................................................... heraeus-noblelight.com....................................................................................... 39 Honle UV America Inc. ............................................................. honleuv.com ........................................................................................................... 5 IST America ............................................................................... ist-uv.com ............................................................................. Inside Front Cover, 23 Miwon Specialty Chemical Co., Ltd. ....................................... miramer.com ......................................................................................................... 41 Nagase ...................................................................................... nagaseamerica.com/radtech-2020 ..................................................................... 51 RadTech UV+EB 2020 ............................................................... radtech2020.com ........................................................................Inside Back Cover RAHN ......................................................................................... rahn-group.com...................................................................................................... 1 Siltech Corporation .................................................................. siltech.com ............................................................................................................ 32 Sun Chemical ............................................................................ sunchemical.com/energy_curable ...................................................................... 47 TopCon & Symposium ............................................................. plasticsdecorating.com/topcon .......................................................................... 53

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High-Performance OmniCure® UV LED Curing Solutions

• Enhance cure speeds and efficiencies with a range of optical output and wavelength options • Simplify integration with compact, air-cooled form factors • Achieve greater flexibility, reliability, and scalability • Improve product yields and reduce operational costs • Expand cure capabilities of adhesives, coatings, and inks

Visit us at:

www.excelitas.com omnicure@excelitas.com

RadTech UV+EB March 9 - 11, 2020 Orlando, FL | Booth #513

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