In joint testing by Teknor Apex and Eastman, Medalist® TPEs over-molded onto Eastman Tritan™ copolyester yielded durable bond for grips, gaskets, and other soft/rigid items  


PAWTUCKET, RI, U.S.A., June 21, 2021: 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% isopropyl alcohol, Clorox® bleach, and a 20% 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 Shore A durometers 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.”

PHOTO CAPTIONS: 01. Graph shows peel strength test results for one Medalist® TPE over-molded onto four Tritan substrates. Blue shows average peel strength, while peak peel strength is indicated by gray in background. 02. Peel strength was measured in 90-degree pull test on a Zwick tensionometer with 100 mm/min. pulling rate in accordance with DIN EN 1464.

About Teknor Apex. Teknor Apex Company, a privately held firm founded in 1924, is one of the world’s leading custom compounders of plastics.  Teknor Apex produces flexible and rigid vinyl, thermoplastic elastomers, nylons, color masterbatches, specialty chemicals, and hoses. The company is headquartered in Pawtucket, RI, U.S.A. and operates thirteen manufacturing facilities worldwide in the United States, Belgium, Germany, China, and Singapore. To learn more visit:

About Eastman

Founded in 1920, Eastman is a global specialty materials company that produces a broad range of products found in items people use every day. With the purpose of enhancing the quality of life in a material way, Eastman works with customers to deliver innovative products and solutions while maintaining a commitment to safety and sustainability. The company’s innovation-driven growth model takes advantage of world-class technology platforms, deep customer engagement, and differentiated application development to grow its leading positions in attractive end markets such as transportation, building and construction, and consumables. As a globally inclusive and diverse company, Eastman employs approximately 14,500 people around the world and serves customers in more than 100 countries. The company had 2020 revenues of approximately $8.5 billion and is headquartered in Kingsport, Tennessee, USA. For more information, visit

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