STRUCTURAL-ANALYSIS OF POLY(ETHYLENE-TEREPHTHALATE) REINFORCED WITH GLASS-FIBER .1. A PHOTOACOUSTIC FOURIER-TRANSFORM INFRARED STUDY

Fourier transform infra-red spectroscopy coupled with photoacoustic de tection (PA-FTi.r.) has proved to be a useful tool for finding out abo ut quantitative structural changes in glass-fibre-reinforced poly(ethy lene terephthalate) (PET) obtained by compression moulding and subsequ ently annealed. Analysis of the photoacoustic parameters indicates tha t the photoacoustic characteristics of the composite are very similar to those of the isolated matrix. It was demonstrated that glass-fibre- reinforced PET satisfies the same two-phase conformational model as th e matrix. In contrast to the annealed matrix, the primary and secondar y isomerizations cannot be detected in the composite. Therefore, the t hermal treatment on the composite samples does not show further confor mational changes. As a result, the manufacturing process seems to dete rmine the composite microstructure, and its effect is quite similar to that observed in annealed matrix at the highest temperatures. Consequ ently, it can be considered that the trans isomer content in the amorp hous phase is negligible in the composite.