Medical TPEs for Plunger Stoppers Enhance Syringe Function and Provide Processing Advantages over Rubber and TPVs


New medical-grade thermoplastic elastomers (TPEs) for injection molded plunger stoppers provide improved syringe performance, are less costly and easier to mold than natural and isoprene rubber, and provide processing advantages over thermoplastic vulcanizate (TPV) elastomers. Teknor Apex Company will introduce the compounds at NPE2018. 

Stoppers molded from the new Medalist® TPEs perform well in both glass and plastic syringe barrels, achieving a consistent piston release and travel force due to a low coefficient of friction. The compounds can be over-molded onto plungers, eliminating an assembly step. In addition to grades for over-molding onto polypropylene, specialty grades are available that, unlike TPVs, can be over-molded onto engineering resins like polycarbonate, ABS, PC / ABS, acrylic, acetal, PBT, and COPE. Also unlike most TPVs, the Medalist TPEs do not require pre-drying.

The Medalist TPEs exhibit improved compression set in comparison with competing TPEs, making possible a more secure seal. The compounds can be molded in high-cavitation tooling. All grades are sterilizable and are available in natural or black colors.  The Medalist compounds provide substantial advantages over rubber, which has been the predominant material for use in syringe stoppers. TPEs avoid the curing step required in rubber processing, eliminating concerns about extractables and leachables, and, unlike rubber, their scrap can be recycled. As thermoplastics, TPEs process in considerably shorter molding cycles and lend themselves to more intricate designs and tighter dimensional tolerances.

“Stoppers must move smoothly against the wall of the syringe barrel, provide an exceptional seal to preserve the integrity of the drug, and be chemically inert to prevent interaction with the syringe contents,” said Ross van Royen, senior market manager of regulated products. “Teknor Apex has developed a portfolio of Medalist TPEs that meet these performance requirements while providing substantial economic advantages because of their ease of processing.”  Teknor Apex produces Medalist compounds in ISO-13485 facilities in the USA and Singapore. All Medalist materials are made with FDA listed ingredients, are certified to ISO 10993-5 standards for biocompatibility, and are REACH SVHC compliant. They are free of DEHP and other phthalates, BPA, and latex. Standard grades are ADM-free.

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