THE ROLE OF ELASTOMERS IN THE STUDY OF POLYMER CRYSTALLIZATION

Abstract

Abstract Crystallization in polymers involves the development of three-dimensional order in the system. In this respect crystalline polymers resemble very closely the crystalline state of monomeric systems. In contrast to low molecular weight systems, however1 polymers never crystallize completely. The crystallinity level can vary from a few to 90% depending on the molecular constitution of the polymer chains and the external crystallization conditions. Consequently, a polycrystalline system having a complex morphology develops. When a polymer system crystallizes, either quiescently, or when held in a deformed state, there are major changes in properties from the typical rubber-like elasticity of noncrystalline (amorphous) polymers. These changes are particularly evident in many physical and mechanical properties. Therefore, it is important to understand the nature of the crystallization process and the structure and morphology that evolves. In addition to their intrinsic scientific interest these factors have great bearing on properties and the end-uses of polymeric substances. In this connection, elastomers, particularly natural rubber, have played a vital role that has led to our present understanding of the crystallization behavior of polymers, and the properties of the crystalline state. The significance of these pioneering contributions has not been generally recognized in today's study of the diverse number of crystalline polymers that constitute the present world of commerce.