Carbon Black-Rubber Interactions and Bound Rubber

Abstract

Abstract The interaction of elastomers with fine particles has been a subject of great interest and much controversy for many years. This is easy to understand when it is remembered that reinforcement is one of the three great developments that underlie the extensive use of elastomers in our modern world. The other two are, of course the discovery of the principle of vulcanization, and the development of synthetic elastomers, including many having special properties superior to those of natural rubber. A large part of the controversy currently includes specifically the question of the special position—or lack of it—of carbon black as a particulate filler for elastomers. The resolution of this question is beyond the scope of our present knowledge, although strong opinions are held on both sides of the question. However, for two reasons, the present review will be restricted almost entirely to a consideration of the nature of the interaction of carbon black with hydrocarbon elastomers. The first reason for this is the undeniable technological importance of these systems. The second is the relatively small amount of work that has been reported on other types of fillers. In addition, the inclusion of other fillers would certainly add to the complexity of any attempt to analyze polymer-filler interactions at this time. However, it must be admitted that the possibility exists of explaining all polymer-filler interactions ultimately in similar and relatively nonspecific terms. In the past few years, an enormous amount of work has been reported that has a bearing on this problem. From the results of these investigations, a coherent explanation appears to be emerging. This paper attempts to review some of the more important work in this field in order to present an over-all picture of our present knowledge. The problem can be summarized in three questions: