THERMALLY-INDUCED STRUCTURAL-CHANGES IN LOW-SHRINKAGE POLY(ETHYLENE-TEREPHTHALATE) FIBERS

This work studies the behavior of low shrinkage PET fibers during free -ends thermal annealing. The interest in this type of sample stems fro m the fact that it possesses an interesting structure characterized by the presence of crystalline and amorphous domains both in a highly ex tended and oriented state. Furthermore, thermal annealing is not able to produce a significant increase in the crystalline content. Thus, th e lack of crystallization allows to isolate the effect of chain recoil ing on the observed phenomena. To follow changes at molecular and micr ostructural levels, Fourier transform infrared spectroscopy with photo acoustic detection, differential scanning calorimetry, wide-angle x-ra y diffraction and scanning electron microscopy techniques were employe d. By their use, substantial structural changes in the amorphous and c rystalline domains were found which, finally, were related to the macr oscopical behavior of the material, mainly the observed shrinkage and the mechanical properties. (C) 1996 John Wiley & Sons, Inc.