Discussion

Doctor Blake has suggested a theory for the mechanism of filler dispersion and reënforcement. However, he deals only with carbon black in rubber. Carbon black is the most important reënforcing ingredient we have for a tire-tread compound. Being a conductor, it cannot be used in appreciable quantities in insulation. We might consider the possibility of finding a non-conducting reënforcing filler for insulation and also what should be done when the present supply of natural gas is depleted. What is needed is a material similar to clay which is cheap and has a small particle size. With present dispersing agents, clay does not, however, reënforce rubber to anywhere near the extent that carbon black does. For a filler to reënforce satisfactorily it must be well dispersed and adhere firmly to the rubber. The correct dispersing agent should bring this about. This agent should be a polar compound. One portion of the molecule should be soluble in the rubber hydrocarbon and another portion should be capable of being adsorbed by and adhering strongly to the surface of the clay.