ESR Information during Tensile Deformation of Vulcanizates

Abstract

Electron spin resonance (ESR) and wide angle X-ray diffraction (WAXD) measurements under the tensile deformation were carried out for H-NBR, NBR and SBR vulcanizates with varying cross-link densities to discuss on the changes of network structure during tensile deformation. The H-NBR vulcanizates showed a strain-induced crystallization at room temperature, but the NBR and SBR vulcanizates did not. At a given stress, the radical concentration determined by ESR measurements was higher for H-NBR vulcanizates than for NBR and SBR vulcanizates. The degree of strain-induced crystallization at a given strain was likely to increase with the decrease of crosslink density. These results suggested that the strain-induced crystallization of H-NBR vulcanizates was accompanied by the partial breakdown of network structure in the vulcanizates.