Thermally induced structural changes in low‐shrinkage poly(ethylene terephthalate) fibers

Abstract

This work studies the behavior of low shrinkage PET fibers during free-ends thermal annealing. The interest in this type of sample stems from the fact that it possesses an interesting structure characterized by the presence of crystalline and amorphous domains both in a highly extended and oriented state. Furthermore, thermal annealing is not able to produce a significant increase in the crystalline content. Thus, the lack of crystallization allows to isolate the effect of chain recoiling on the observed phenomena. To follow changes at molecular and microstructural levels, Fourier transform infrared spectroscopy with photoacoustic detection, differential scanning calorimetry, wide-angle x-ray diffraction and scanning electron microscopy techniques were employed. By their use, substantial structural changes in the amorphous and crystalline domains were found which, finally, were related to the macroscopical behavior of the material, mainly the observed shrinkage and the mechanical properties. © 1996 John Wiley & Sons, Inc.