Thermal behavior of elastomer-resin mixtures used as friction materials

This study looks at the thermal behavior of mixtures of nitrile-butadiene r ubber (NBR) with a resol or a novolac resin. When heated in the 200-300 deg reesC range, NBR became hard and insoluble because of exothermic curing and cyclizing chain reactions involving the double bonds of its butadiene unit s and the nitrile groups of its acrylonitrile units. The NBR proved to be c ompatible with the novolac but not the resol. Heating increased the modulus of elasticity of the mixtures, which was due to crosslinking of the resin and the rubber. Preliminary linking of the resin resulted in phase separati on in the novolac and prevented curing of the rubber when the mixture was h eated. (C) 2001 John Wiley & Sons, Inc.