Advancements in EPDM Sponge Compound Processing Using EPDM Bimodal Polymers

Ethylene-propylene-diene elastomers (EPDM elastomers) are the primary polymer choice for automotive weatherseal applications due to their outstanding weathering and heat resistance properties. Automotive sealing systems are complex in design; in particular, door seals are one of the most complex components of the sealing system, generally consisting of a low-density sponge profile co-extruded onto a dense metal carrier, as attachment to the car body. Door (or weather) seals contribute to the comfort inside the car by providing insulation from water, vibration and aerodynamic noises. The geometry of the sponge profile has become increasingly complex over the years to improve overall sealing performance. It controls the door closing force, assessed by load deflection measurements, and the long-term sealing performance, assessed through up to 1000 hours of compression set testing. In the last decade, the use of bimodal EPDM grades for the production of sponge profiles has grown significantly and contributed to increased productivity for door sealing systems.

This paper will review the recent advances in compound mixing and sponge extrusion using bimodal EPDM polymers. This report will also illustrate that such techniques can provide overall cost reduction and production efficiency without adverse effect on essential OEM requirements such as surface aspect, mechanical properties, compression load deflection and permanent set.