Crosslinking of oriented rubber

Smoked sheet rubber, previously oriented in the calendering process, was crosslinked by exposure to 2 M.e.v. high energy electrons in the absence of vulcanizing agents. Even after annealing the resultant rubber showed anisotropic elastic properties, having a high elastic modulus and a low elongation at break in the direction of orientation. It is suggested that radiation in addition to crosslinking causes main chain fracture and stress relaxation in stressed molecular chains. The G value for crosslinking (1.05) by electron irradiation agrees well with that (1.1) previously found by elastic measurements of pile irradiated rubber.