TUBING TALKS
Why PEEK is so hard to extrude The popular material for catheters and minimally invasive tubing can trip up novices when it comes to extrusion.
PEEK has a semi-crystalline structure, but can be extruded to maintain amorphous qualities or to a very hard finish. Image courtesy of Microspec
Heather Thompson | Senior Editor |
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Medical Design & Outsourcing
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Polyetheretherketone (PEEK) is known throughout the medical device industry for its toughness, strength and high heat thermal characteristics. It’s often used to replace metal components in medical devices; because it’s a thermoplastic it can be injection-molded or extruded into nearly limitless shapes, profiles and tubes. The material has a semi-crystalline structure but can be extruded to maintain amorphous qualities or to a very hard finish. It can withstand temperatures up to its glass transition point of 289°F, meaning it can withstand autoclave temperatures. The PEEK challenge Although PEEK has been used for more than 25 years in medical tubing applications, newcomers still make mistakes when it comes to its extrusion. “There’s a learning curve when it comes to PEEK,” said Tim Steele, one of the 1 • 2018
pioneers of PEEK medical extrusion and the founder and CEO of Microspec Corp. (Peterborough, N.H.) The first challenge in optimizing the PEEK extrusion process is understanding the melt characteristics of the material. Although much can be gleaned from the technical data sheet, that’s only the first step of many in developing a consistent extrusion process. After the technical data sheet, the first consideration is the size and design of the part to be extruded, as well as the size of the extruder and tools that are going to be used. There are various considerations including screw design, extrusion or crosshead design and the heat profile that plasticates or melts the polymer consistently in the barrel. If the melt is not even and consistent, the extruder output will be poor. If the extruder is not optimized, it can lead to waste and increased production time.
www.medicaldesignandoutsourcing.com
1/25/18 10:28 AM