Influence of Temperature on the Tensile Strength of Carbon Filled Vulcanizates

Abstract

Abstract Despite undergoing a substantial reduction with increasing temperature the presence of carbon black added to the strength of both natural and styrenebutadiene rubber at temperatures up to 185° C. The magnitude of reinforcement was primarily dependent upon filler surface area although at the higher temperatures when this dependence is not so marked both high structure and particle activity appear advantageous. No theory of carbon black reinforcement can reasonably ignore the morphological characteristics of the material whose action it is attempting to explain. The concept of within aggregate voids, and occluded rubber envisaged by Medalia and used in this paper to describe the effect of fillers on rubber modulus, provides an interesting molecular meaning to the effects that have hitherto been explained on the basis of “shell” theories. Occluded rubber might reasonably be viewed as a type of shell since it undoubtedly represents a polymer zone in which molecular mobility is restricted. Furthermore the view of rubber being pulled from the interstices of an aggregate, manifestly a stress softening action, provides a source of plastic flow and mechanical hysteresis in the region of the aggregate—an apparent prerequisite for reinforcement.