Molecular orientation and stress relaxation during strain-induced crystallization of vulcanized natural rubber

Abstract

Birefringence and tensile stress of vulcanized natural rubber samples were measured simultaneously. The effect of finite chain extensibility could be clearly detected. The increase in birefringence was related to the degree of orientation of amorphous chains to be incorporated into crystals. The normalized stress decreased in a manner that is almost independent of network-chain density. These experimental results could be successfully explained by assuming a certain fraction of network chains that behave in a manner similar to that of a fluid.