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. The tests demonstrated a strong, chemical-resistant bond between a TPE and a clear copolyester substrate.
In 90-degree peel tests of test specimens produced in a two-shot molding process, three Medalist medical-grade TPEs from Teknor Apex provided durable bonds to four of Eastman’s Tritan copolyesters. 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.
Medalist compounds tested included three grades: MD-34940, MD-34950, 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.