Medical TPEs from Teknor Apex
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.
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.