FOURIER-TRANSFORM RAMAN-STUDY OF GLASS-FIBER-REINFORCED POLY(ETHYLENE-TEREPHTHALATE)

FT-Raman spectroscopy has been proved as a useful tool to form the qua ntitative study of conformational changes in glass-fibre-reinforced an nealed poly(ethylene terephthalate) (PET). Based on composite Raman ba nds directly related to the ethylene glycol fragment in the trans and gauche conformations, it was observed that glass-fibre-reinforced PET exhibits the same two-phase conformational model as the isolated matri x. In contrast to the matrix, annealing thermal treatment of the compo site does not seem to affect the composite microstructure since the is omer contents remain constant with annealing temperature. Thus, the mi crostructure is mainly determined by the fabrication process and its e ffect is similar to that observed in an annealed matrix at the highest temperatures. Therefore, the disordered trans isomer content can be c onsidered negligible in the composite. In contrast to the spectroscopi c results, the crystallinity values of the composite obtained by diffe rential scanning calorimetry (DSC) only tend to coincide with those of the annealed matrix at temperatures above 150-degrees-C, and below th is temperature they are always lower. A comparison between the results obtained by FT-Raman and DSC techniques seems to indicate an improvem ent in the fibre-matrix interface in which an interfacial structure wi th a low degree of perfection changes to more perfect crystals.