SURFACE MODIFICATION | ADDITIVES


Fighting friction and wear


With plastics being used in increasingly demanding mechanical applications, the pressure is on to improve wear and reduce friction.Peter Mapleston reviews the latest developments


As plastics find increasing use in technical applications that call on high resistance to friction and wear, additive and compound companies are coming up with new, better and more sustainable ways to create compounds that are fit for purpose. Several of them were discussed at the first Wear- Resistant Plastics conference, organised last year by Compounding World publisher AMI. This article takes a look at some of the most recent developments. Fluoropolymers, especially PTFE micropowders,


are frequently used to reduce friction between contacting surfaces. When used in engineering plastics, PTFE can eliminate the need for external lubrication, reduce wear rates, achieve lower and more consistent frictional responses, and eliminate ‘stick-slip’ issues, chatter and other motion-induced noise. But PTFE is not a perfect solution and several companies are working on alternatives. “Whereas PTFE lubricants – typically added to the thermoplastic material in the range of 10- 20wt% – improve wear and friction performance, a fine balance is needed to maintain mechanical properties or processability of the base polymer,”


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says Claus-Peter Keller, New Business Development Manager with AGC Chemicals Europe. AGC Chemicals is a leading manufacturer of modified fluoropolymers, offering a range of anhydride-functionalised grades under the brand name of Fluon+. Well-established applications include double and triple-layer fuel lines, where an inner liner made of ETFE (ethylene tetrafluoroethylene) is coextruded with an outer liner of PA12. During processing, the anhydride groups react with end groups in the PA12 to provide the necessary adhesion. Keller says AGC Chemicals recently investigated the use of anhydride-functionalised fluoropolymers as compounding additives in PTFE-filled thermoplastics. “First results show that an anhydride modified PFA (perfluoroalkoxy alkane) can improve the blending of PTFE into thermoplastics due to its higher surface energy in combination with its good compatibility with PTFE,” he says. Tested with a PPS blend, there was seen to be a significant improvement in wear and friction performance. Adding 1phr of an anhydride- functionalised Fluon+ PFA EA2000 into an 80:20


Main image: Plastic


compounds for production of gears such as these need particularly good


tribological properties and resistance to wear


February 2019 | COMPOUNDING WORLD 17


PHOTO: STOCK IMAGES/COLLOIDS


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