New Low Cost High Performance Materials for Automotive Connectors and Light Sockets 2002-01-1322
The QUESTRA* Crystalline Polymer product family, based on syndiotactic polystyrene (SPS), has been improved to meet the needs of the automotive connector and light socket applications in a very cost effective manner. In this paper, the attributes of two new SPS formulations, SPS/polyamide (PA) blends and low gas SPS formulations, are compared to existing SPS formulations and competitive resins. It is shown that the SPS/PA blends have significantly improved strength and ductility over existing SPS formulations. This improves the SPS formulation technology to include the full range of strength and ductility options the designer of automotive connectors needs to achieve the terminal retention forces and latch deflection distances necessary for the smaller connectors like the .64 mm terminal systems that the automotive industry is migrating towards. It is shown that the SPS/PA blends have a unique combination of low and high shear rate rheology compared to other materials which leads to improved processability in thin walled parts. The fundamentals of how the decreased cycle time and the dimensional stability inherent with SPS are transferred to PA are discussed. How the hydrophobic nature of SPS decreases the moisture sensitivity of PA and permits the SPS/PA blends to have excellent USCAR performance is detailed. It is demonstrated that the excellent creep resistance of PA improves the high temperature creep performance of the SPS/PA blends over that of existing SPS formulation. Formulations of SPS have been developed to yield the lowest condensation of out-gas in light socket applications during operation. The performance of these formulations is briefly discussed. Finally, examples where the SPS formulations have been proven to yield the lowest total cost for connector manufacturers are given.