1998-02-23

Advanced Liquid Injection Molded Silicone Technology for the Automotive Industry 980989

Liquid Injection Molded silicone elastomers represent a processing alternative to heat-cured silicone elastomers used in traditional compression molding processes. Higher injection speeds, cure speeds, and complex mold filling by Liquid Injection Molded materials offer rubber fabricators productivity gains that more than offset higher initial material and investment costs. However, the wide-spread acceptance of Liquid Injection Molded products in the automotive industry has been limited from a performance standpoint; up until now, Liquid Injection Molded products have not reached the level of underhood performance of heat-cured silicone elastomers in terms of heat age, compression set, and oil stability. We describe 2 breakthroughs in Liquid Injection Molded technology that will lead to much wider industry acceptance. A new Liquid Injection Molded formulation has been developed that offers consistently low compression set as-molded, but with none of the disadvantages associated with initial automotive liquid silicone rubber (LSR) offerings elsewhere in the industry. In particular, initial industry offerings achieved low compression set through the addition of extending precipitated fillers, which tended to negate the benefits of LSR processing.In contrast, new low compression set as-molded has been achieved through chemistry rather than the addition of inert fillers. Thus, the new automotive Liquid Injection Molded product has high flow, rapid mold fill, rapid cure, excellent release, low specific gravity, and outstanding tear resistance. These data are reported herein.Finally, new low compression set, high temperature Liquid Injection Molded materials are described. These products are simultaneously self-bonding to a variety of engineering thermoplastics and metals.

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