HDPE-hugging elastomers set for rollout

Thermoplastic elastomer (TPE) compounds with double the adhesive strength of standard TPEs when overmolded onto HDPE will debut at the MD&M West show organized by PlasticsToday owner Canon Communications in February.

Supplier Teknor Apex Co. (Pawtucket, RI) will deploy the technology in custom-compound TPEs in its Medalist range of medical-grade elastomers, according to Nick Sandland, senior market manager. “While device manufacturers are increasingly turning to multishot injection molding as a way to eliminate assembly, the existing ‘off-the-shelf’ TPEs available to them exhibit limited adhesion when overmolded into HDPE substrates,” Sandland says. “New formulation technology enables Teknor Apex to custom-compound TPEs that not only provide stronger bonds to HDPE, but also exhibit far less variation in bond strength, yielding a more consistent product.”
 

HDPE is commonly used in medical products because of its low level of extractables or leachables, resistance to many chemicals, and affordability. TPEs are typically overmolded onto rigid HDPE to serve as seals for vials and other fluid-storage vessels, and for connectors.

In a widely used 180° peel adhesion test, Teknor Apex compared HDPE samples overmolded with an HDPE-bonding Medalist TPE and samples with one of the company’s own standard hydrogenated styrenic block copolymer (HSBC) TPEs. The median adhesion, or peel strength, of the Medalist TPE was twice as great as that of the HSBC—42.086 lb per linear inch, vs. 21.412. In addition, the variation in peel strength among different test samples was less than half as great with Medalist as with HSBC.

Teknor Apex’s Medalist program for medical manufacturers includes a range of 33 standard high-purity elastomer compounds available with Shore A hardness from 5-87 as well as clear, translucent, and opaque formulations.—[email protected]