THERMODYNAMICS AND KINETICS OF ORIENTATIONAL CRYSTALLIZATION OF FLEXIBLE-CHAIN POLYMERS.

Crystallization of flexible-chain polymers from isotropic solutions and melts usually leads to the formation of folded-chain crystals. Mechanical properties, particularly the tenacity of these samples, are limited by the small number of tie chains. Crystallization in deformed melts proceeds by a substantially different mechanism involving extension of chains and formation of extended-chain crystals: this process is to some extent similar to that of crystallization of rigid-chain polymers leading to polymers of high tenacities. This method which promotes the formation of extended-chain crystals during crystallization of flexible-chain polymers - the orientational crystallization - is suitable for the preparation of polymer films and fibers from flexible-chain polymers with high tenacity and high modulus. The paper presents a comparison of orientational crystallization with other methods for obtaining high-strength polymer materials. Technological prospects of this method are also considered.