Pawtucket, RI – Two leading plastics suppliers to the medical device industry have demonstrated a strong, chemical resistant bond between thermoplastic elastomers (TPEs) and a clear copolyester substrate known for its toughness and chemical resistance.
In 90 degree peel tests of test specimens produced in a two-shot molding process, three Medalist medical grade TPEs from Teknor Apex Company provided durable bonds to four of Eastman’s Tritan copolyesters. Specifically formulated to adhere to copolyester and other engineering thermoplastics, the Medalist compounds exhibited high levels of peel strength. The peel tests that showed high peel strengths with adhesive failures demonstrate excellent Tritan TPE over-molding performance. The combination of high peel strength and adhesive failure is considered desirable for over-molded applications.
The bond strength between Medalist TPEs and Tritan exhibited very little loss even after soaking test samples for 48 hours in disinfecting chemicals, including a 70 percent isopropyl alcohol, Clorox bleach and a 20 percent intralipids solution, which is a fat emulsion used as an intravenously administered nutrient.
Medalist compounds tested included three grades: MD-34940, MD-34950 and MD-34959, with durometer A hardnesses of 42, 50 and 59, respectively. Tritan grades MX711, MX811, MXF321 and MXF421 provided a good range of physical properties. All three Medalist compounds in combination with all four Tritan resins showed very little loss of bond strength after chemical exposure.
Over-molding thermoplastic elastomers (TPE) onto copolyester offers medical device designers a combination of hard and soft materials that are advantageous in medical components. Soft TPEs are desirable for grips, gaskets, seals and soft-touch elements on rigid medical housings and other components.
“By combining Medalist TPEs and Tritan copolyesters, manufacturers can improve the ergonomics, aesthetics or functionality of medical devices,” said Dr. Yubiao Liu, global medical technical platform lead, Eastman. “The combination of soft TPEs with rigid copolyester substrates can enhance grip, add texture or comfort, yield a tight seal or provide damping characteristics.”
Medalist TPEs combine the performance of thermoset rubber with the processing ease of thermoplastics, making them superior alternatives to silicones, PVC and TPUs, noted Ross van Royen, senior market manager for Teknor Apex. “We have developed Medalist TPEs to meet the most stringent requirements of the health care industry and produce them in multiple ISO 13485 certified facilities with only FDA listed food grade ingredients. All grades are biocompatible in accordance with ISO 10993-5, are RoHS and REACH SVHC compliant, and contain no phthalates, latex proteins or BPA.”