REINFORCEMENT STUDIES WITH POLYMERIC FILLERS.

This is a report on further studies which have been carried out on the use of finely-divided polymers, prepared by emulsion polymerization, as fillers for the reinforcement of SBR vulcanizates. It was found that the tensile strength of the filled vulcanizates was increased to a greater extent by fillers of greater rigidity, and that the effect of temperature on tensile strength also reflected the modulus-temperature relation of the filler. The tensile strength appeared to be relatively insensitive to the presence or absence of chemical bonds between the filler and the rubber, as determined by solvent extraction. The results offer a strong confirmation of the previous conclusions with regard to the mechanism of reinforcement of elastomers by rigid fillers, i. e. that fillers increase the strength by increasing the viscous response and hysteresis of the rubber.