RJA April 2012 Latex

Rubber Journal Asia Latex Industry

Evolving latex industry

The global latex industry is facing unprecedented challenges at a time when the demand for latex-based products is on the rise across the globe, whether it is for gloves, condoms or balloons. A major challenge is the shortage of latex concentrate, which is directly linked to natural rubber (NR) prices.

This in fact is causing researchers to examine alternative rubber sources and their major impact in product performance as well as manufacturers to evaluate how these new discoveries translate to business speaks, says Lyn Cacha in this report on the Latex & Synthetic Polymer Dispersions Conference, organised by UK-based Smithers Rapra in Kuala Lumpur, Malaysia, recently.

Stiff competition looming he natural rubber latex (NRL) industry has grown tremendously, especially during the last 25 years. The industry is driven by the gloves market that has been responding to increased demand created by the heightened awareness for improved hygiene management. According to No Dock Moung from the Singapore-based International Rubber Study Group, over the next decade, this need will remain the central driver for the industry. “However, the industry will face stiff challenges as further developments will be made by nitrile (NBRL) gloves in its physical/chemical properties,� he added.

Traditionally, the cost of NBRL has been higher than NRL but in the past ten years, the cost advantage has been shared between the two, Moung explained. Over the same period, there has been an almost steady decline in the market share of NR latex gloves. Moung speculates that developments have been made in the physical/chemical properties of the NBRL glove market improving its attractiveness over NRL gloves.

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Turning the tide with guayule emand for NR continues to grow at a rate greater than new plantings of the traditional hevea and the latest discovery of the guayule plant is expected to fill this need.

Many efforts have been made to enhance worldwide rubber production through the domestication and commercialisation of guayule.

US company Yulex, for instance, commercially introduced the first domestic natural rubber latex source from guayule. Currently, more and more tyre companies are venturing into setting up own rubber sources. Cooper Tire and Bridgestone, for instance, are now assessing guayule for Katrina Cornish of Ohio State University is researching tyre applications. Some rubber the use of bio-based materials in latex products manufacturers, meanwhile, are taking a wait-and-see approach. According to some participants at the conference, for guayule to be a direct substitute for hevea it has to either perform the same functions at a lower cost or perform better at the same cost.

In line with the industry’s growing interest on guayule, Dr Katrina Cornish of Ohio State University presented in the conference the latest findings of her research that identified the contribution of several biobased components to the properties and performance of latex products.

Ten biobased materials were used including vegetable waste, eggshell calcium carbonate, cotton fibres, guayule bark bagasse, guayule bark baggase without resin and dandelion fluff were used. Among the ten biobased materials, guayule appeared to present the best properties that can be used for a wide variety of medical device applications and also has performance that is comparable if not better than hevea latex. Aside from lessening NR dependence, latex allergies to NRL have also led to the development of guayule.

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Latex Industry Guayule natural rubber latex (GNRL) contains very low levels of protein but current assessment tools being used are too insensitive to identify protein extractable from GNRL products. Hence, Dr David Kostyal of Akron Rubber Development Laboratory proposed a tool or standard that can be used to determine the actual level of extractable protein in finished GNRL products as well as improve and control quality during latex production.

Alternative fillers going green s the total glove market continues to increase by size, more and more waste latex gloves will be generated daily, thus contributing to solid waste disposal problems causing industries to look for eco-friendly materials that can help biodegrade gloves. Among these materials include natural starch that can be used as a filler in NRL gloves due to its ability to biodegrade. Recent studies show that starch speeds up biodegradation because it is consumed by microorganisms that hollow out the polymer matrix leading to a decrease in mechanical properties, an increase in permeability and the exhibition of a greater surface-to-volume ratio of polymeric materials.

Associate Prof. Dr Azura Rashid of University Science Malaysia (USM) showed how various starch (sago, corn and tapioca) loadings affect the mechanical properties of biodegradable NRL gloves. The trial testing used starches mixed with potassium hydroxide, anchoid and water and was ball milled at 20 rpm for 24 hours. Pre-vulcanised

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NRL films, meanwhile, were prepared by a dry coagulant dipping process. Using SEM analysis, research findings concluded that optimum mechanical properties of NRL films are achieved a 10 phr. Sago starch showed better mechanical and biodegradation properties to corn and tapioca starches.

Likewise, polyurethane dispersions (PUD) gloves are said to be friendlier to the environment. According to Rolf Irnich of Bayer MaterialSience, compared to conventional gloves, PUD gloves require a very simple formulation and are easier and cleaner to manufacture. They are also free from protein allergy, odour and powder. Moreover, PUDs component has no pot life and leads to material cost savings on the processing line. PUDs are water-based polymers and are much easier to dispose. At present, research work being carried out on breaking down polymers has not shown any level of concerned toxicity so far.

Stepping out in the ecological aspect, Joachim Storsberg of Fraunhofer Institute Applied Polymer Research (IAP) showed the feasibility of carbohydrates as good alternative fillers and additives to synthetic latexes.

Usually, synthetic latexes consist of petroleum-based components such as butadiene and styrene. Carbohydrates can substitute these ingredients and provide customised properties that can open up a broad spectrum of applications aside from classic ones such as paper, dipping goods, coatings and adhesives.

Rubber Journal Asia Latex Industry XSBR were prepared by latex stage compounding using two types of layered silicates, viz, sodium bentonite and flurohectorite. The extent of exfoliation and intercalation of polymer chain into the layers of nano-structured silicates were determined from x-ray diffraction pattern.

It was observed that the interlayer spacing of the clay galleries increased due to the diffusion of polymer chains into the inter galleries of the silicate layers.

Latex nanocomposites exhibited improved mechanical properties due to the enhanced polymer/filler interaction. Furthermore, the gas transport properties of NR and XSBR latex membranes also showed lower permeability to oxygen and nitrogen gasses due to enhanced polymer/filler interaction.

Joachim Storsberg of Fraunhofer Institute of Applied Polymer Research presented his studies on the use of carbohydrates as alternative fillers and additives to synthetic latexes

In his presentation, Storsberg said carbohydrates can be used in their natural form as fillers and additives and specially modified carbohydrates are used as excellent surfactant and stabiliser systems.

Through the use of thermo-labile functions that undergo a haemolytic splitting, carbohydrates can be used as surfactant-initiators in emulsion polymerisation processes.

Shifting to polyisoprene omfort and protection are among the major concerns with the increasing use of synthetic rubber (SR) to substitute the higher priced NR. Today, such concerns are waning as use of high quality polyisoprene in the healthcare industry is increasing.

This has been made evident with the growing interest in SR in medical devices. Adeline Kung Ai Lin of Ansell presented the company’s synthetic polyisoprene condom and its properties. Male latex condoms are usually made from NRL and non-NRL condoms available in the market are made from PU or other thermoplastic materials. Approved by the US FDA, the synthetic polyisoprene condom has been tested and results showed that its properties are comparable to NRL condoms in terms of safety, efficacy, quality and acceptability.

In the gloves field, Wouter de Jong of Kraton Innovation Centre Amsterdam presented a comparative study on commercially available surgical gloves made of various base materials. Mechanical properties evaluated include tensile strength, modulus and puncture resistance. Based on the findings, good quality polyisoprene surgical gloves offer mechanical protection comparable to NR gloves and are also said to be better than other synthetics in terms of comfort.

Although SR appears promising, barrier product makers continue to improve their NR products by offering the latest in superior protection. Eng Aik Hwee of Ansell presented the company’s first surgical gloves with antimicrobial coating on the inside. According to Eng, it is designed to reduce the microbial load on the inside surface of the glove in the event of a glove breach, thereby providing additional protection against microbial cross-contamination.

Using Ansell’s Antimicrobial Technology (AMT), the glove’s insides have an active ingredient – chlorhexidine gluconate – that helps kill more than 99% of an HCV surrogate virus and 99% of HIV-1 strain within a minute following exposure. It also kills 99.7% to 99.9% of eight clinically relevant bacteria.

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Zooming into nanoparticles hile the benefits of nanotechnology are widely publicised, the technology has not been picked up yet by rubber makers due to cost factors as well as the unknown potential effects of its widespread use in the consumer and industrial products.

During the conference, both the research and rubber manufacturing sectors were finding it extremely hard to argue the case due to the limited information available to support one side or the other.

It has been known that nanomaterials can easily enter the human body, however, how these impact human health and the environment in the long term is still unknown. Despite this, a growing number of studies in the research sector have been made to examine the potential benefits of nanomaterials.

According to Siby Varghese of Rubber Research Institute of India, nanotechnology offers some benefits to every application, such as its suitability to thin film products, ability for intimate mixing, low dosage requirement and low residual and toxicity. He believes that more product manufacturers will be incorporating nanotechnology.

Reduced protein content is one of the achievements of the introduction of nanofillers in latex condoms.

Presented by Dr Abi Santhosh of HLL Lifecare, the study shows how performance-enhancing nanofillers, specifically nanosilicates, can provide substantial improvements in mechanical properties of condoms.

Improved tensile and elongation as well as reduced moisture absorption and air permeability were achieved with the incorporation of nanosilicates.

In a similar vein, Dr Ranimol Stephen of St. Joseph’s College, India, compared the effects of nanoclay to the properties of NR and carboxylated styrene butadiene rubber (XSBR) lattices. In her research, NR and

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