An infra-red study of the structure of oriented poly(ethylene terephthalate) fibres

Abstract

Procedures have been developed for quantitative infra-red spectroscopic measurements on poly(ethylene terephthalate) fibres in conventional yarns. Following computer reconstruction methods already established for films, measurements of molecular orientation and trans/gauche conformer content have been carried out for a wide range of fibres produced by different processing routes. The trans bands can be separated into load-bearing and non-load-bearing conformations, where the former govern the modulus. It is also shown that a quantitative measure of amorphous orientation can be obtained from the infra-red measurements. While there are similarities between the development of overall molecular orientation and changes in molecular conformation for high wind-up speed yarns and drawn yarns produced from a low wind-up speed yarn, there are also major differences, which confirms previous work showing that these two classes of fibres are basically different in structure. These differences are shown by the relationships between the load-bearing trans conformations and the amorphous orientation with the overall orientation.