Chain folding in highly oriented poly(ethylene terephthalate)

Abstract

A study intended to establish the relationship between chain folding and strength in oriented poly(ethylene terephthalate) (PET) led to the finding that the infrared absorption band at 988 cm⁻¹ does not disappear completely on drawing as reported before. Thus, it is concluded that complete elimination of chain folding in PET fibers and films cannot be achieved by conventional drawing techniques. The same conclusions are reached from an analysis of data of modulus and strength indicating a poor load transfer between the noncrystalline matrix and crystallites. A relationship between the intensity of the 988-cm⁻¹ band and ductility is observed indicating that samples having a large degree of regular chain folding are, in general, more plastic than those in which regularity in folding is low.