A thermodynamic approach to the stress‐induced crystallization in cross‐linked rubbers

Abstract

AbstractThe thermodynamic treatment of crystallization phenomena in a prestretched rubber was undertaken. Emphasis was put on defining conditions for the thermodynamic stability of the extendedor folded‐chain crystal structure. The extended‐chain structure is found to be stable thermodynamically at temperatures higher than the isotropic melting point of un‐cross‐linked polymer T in the stretched state, while the folded chain one is not. Below T, the stretch ratio of the network structure determines which crystal structure is more stable. The relation among the critical stretch ratio for the extended/folded crystalline structure transition, temperature, and molecular weight is also discussed. The crystallinity predicted by this work becomes zero at a temperature of T, the isotropic melting point of a cross‐linked system. The value of T decreases with increasing cross‐link density, and this is consistent with the experimental data reported in the literature.