Dynamic automotive door seals are complex components generally constituted of a low-density sponge profile co-extruded onto a dense metal carrier. These seals contribute to the comfort inside the car by insulating from water and aerodynamic noises. They control the door closing force, assessed by load deflection measurements; and the long term sealing performance, assessed through compression set testing. Thermoplastic elastomers have started penetrating automotive weatherseal applications, offering light weight, easier processing and recyclability vs. traditional material. But TPV sponge seals have been limited in comparison to existing technology by several issues like rough surface aspect, high water absorption, compression load deflection, and compression set.
In this paper, we will describe general principles of a foaming technology suitable for thermoplastic elastomers, focusing on a new technique of foaming TPV by super critical fluid that creates a closed microcellular structure, and thus dramatically reduces water absorption and offers a better surface aspect.
In addition, TPV compositions adapted to this supercritical foaming technique can provide controlled cell morphology and improved performance. We believe that this new foaming process used in combination with such an adapted TPV grade can offer the performance required for dynamic automotive sealing systems.
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