Silane Coupling Agent Effects in Ethylene Propylene Diene Terpolymers

The special performance properties noted for silane coupling agents in mineral filled EPDM compounds result from the interfacial effects related to the dual function reaction of the organofunctional silane. When common alkoxy substituted vinyl silanes are used, the nature of the hydrolyzable groups on the silicon atom is generally not a critical factor with adequate silane-filler bonding occurring under a variety of silane application techniques. It has been shown that to obtain optimum performance, the organofunctional group in the silane monomer must be generally reactive with the cure system being used, and have the ability to interact with the elastomer through co-polymerization or addition. It has been further shown that in the case of the copolymerizable vinyl silane (A-172) only a relatively low level of peroxide-induced vinyl silane-rubber bonding is obtained using standard levels of peroxide. Increasing the peroxide level in these vinyl silane-containing formulations results in a considerably higher level of filler-elastomer reinforcement producing dramatic improvements in modulus, tensile, and tear properties when compared with appropriate controls. In general, an enhanced utilization of silane at the elastomer-filler interface is realized. The use of the mercaptosilane (A-189) in sulfur curing mineral filled EPDM compounds improves the normal physical properties while dynamic testing also shows improvements in flex-life, abrasion, heat build-up, and road wear properties.