Semicrystalline Polymers

Abstract

AbstractThe crystalline state in polymers is distinguished from that in other materials by the fact that polymer crystals are not in a single phase having 100% crystallinity, but are only partially crystallized; therefore, they are called semicrystalline polymers. In a bulk semicrystalline polymer, one can find both crystalline and amorphous regions, and the crystalline region may form different aggregates in shapes in different length scales. These length scales are identified as follows: crystal unit cells in a length scale of a few tenth to one nanometer; single lamellar crystals having at least one dimension size less than a few tens of nanometers; lamellar aggregates in a length scale of a few hundreds of nanometers. Crystallinity is a concept in the macroscopic scale. Each structural or morphological level influences the ability of a polymer to respond to its environment. As a result, macroscopic properties are critically associated with different structural and morphological levels, which complicates structure–property relationships. This article, focuses on the formation mechanisms of the crystalline structures and morphologies in these length scales and tries to explore their interrelationships and interdependencies in semicrystalline polymers.