STUDY ON THE RELATIONSHIP BETWEEN THE MECHANICAL-PROPERTIES AND PROCESSING FOR SELF-REINFORCED POLYMERS .1. A THEORY OF STRESS-INDUCED CRYSTALLIZATION FOR ENTANGLED POLYMER NETWORKS

A new theory of stress-induced crystallization for entangled polymer n etworks is presented. It is based on the theory of viscoelasticity wit h constraints of trapped entanglements and crystallites using a model of fibrillar and lamellar morphology engendered by the extended- and f olded-chain crystallization. The probability distribution function of the end-to-end vector for two kinds of constituent chains and the visc oelastic free energy of deformation for two kinds of network have been calculated. The relationships of stress to strain for four types of d eformation were derived. The theory is successful in relating the equi librium degree of crystallinity and the melting temperature to the ext ension ratio for networks with stress-induced crystallization. Further more, the theory provides a theoretical foundation for studying the de pendences of tensile modulus and strength on the processing and testin g conditions for self-reinformed polymers.