Advanced chemistry developed by Teknor Apex Company has yielded a new series of thermoplastic elastomers (TPEs) for over-molding that exhibit excellent adhesion to engineering plastic substrates while meeting the stringent requirements for use in medical devices. 
 
Medalist MD-30000 Series medical TPEs bond effectively to polycarbonate, ABS, PC/ABS, CoPe, PET, PBT, ASA, SAN, PMMA, POM, PA, and PS. Each compound in the series is chemically modified for adhesion to specific substrates (see table). Processable in either multi-shot or insert molding, the compounds are for use in wearable devices, ‘soft-touch’ or cosmetic grips for device housings, handheld devices, instruments, and seals and gaskets.
 
The new series includes grades with enhanced softness, translucence, low compression set for effective sealing properties, and resistance to lotions and other chemicals encountered by wearable devices. 
 
Unlike liquid silicones, over-molded TPEs do not require the use of a primer, have a shorter cycle time due to avoidance of a curing process, and can be processed on conventional injection molding equipment.
 
Three of the Medalist MD-30000 Series compounds were introduced earlier this year after successful completion of a joint project with Covestro LLC, in which the materials were over-molded onto medical grades of polycarbonate and PC alloys and tested for adhesion, processability, and chemical resistance.
 
“Over-molding Medalist TPEs onto rigid substrates enhances the ergonomic and aesthetic properties of medical devices, adds new functionalities such as molded-in seals and cushions, and provides the design freedom and cost savings associated with parts consolidation,” said Ross van Royen, senior market manager for Teknor Apex. “The Medalist MD-30000 Series is the latest addition to a large portfolio of TPEs developed by Teknor Apex for over-molding applications in medical devices as well as in the consumer product and automotive industries.” 
  
Medalist MD-30000 Series compounds are offered worldwide. Custom formulations are available. As medical-grade TPEs, they are subject to strict formulation controls, are made only with FDA-listed food-grade ingredients, are ISO 10993-5 compliant for biocompatibility, and are compliant with CONEG, RoHS, and California Proposition 65 requirements. Teknor Apex produces these compounds in multiple ISO-13485-certified facilities, ensuring security of supply.
 
Teknor Apex has developed an online resource for over-molding TPEs, which can be accessed at www.teknorapex.com/overmolding-academy. It contains basic information about over-molding and adhesion, guides to process and material selection, and case studies.