Weidmann Plastics Technology AG in Switzerland overmolds thermoplastic elastomer (TPE) sealing lips onto cowl vent substrates made from glass-reinforced polypropylene (PP).
Cowl vents sit between the windshield and the engine compartment of Peugeot 207 and 307 Series cars, span the vehicle width, and pass fresh air from the outside to the cabin. The overmolded sealing lips are up to 1.5 m (nearly 5 ft) long and are part of a single molding cycle for the three-component part that includes the structural PP substrate, the TPE sealing lip, and a molded in viewport for reading the vehicle chassis number.
The Tekron TPE, supplied in Europe by Chem Polymer, a unit of Teknor Apex, Pawtucket, R.I., provides flow properties necessary to maintain precise tolerances and a smooth, attractive surface along the entire length of the cowl vent part, reports Weidmann. The TPE features good weather resistance, as well as the heat stability and low compression set for maintaining seal integrity at the elevated temperatures seen in the cowl vent just above the engine bay.
Teknor TPEs are based on styrenic-block copolymers. They withstand temperatures to 120°C and stay flexible below 60°C. “One key benefit that Tekron TPEs provide for Weidmann’s cowl vent seal is their essentially nonreactive response to oxygen and ozone,” says Nick Sandland, Teknor Apex’s European market manager for TPEs.