Crystallographic texture, amorphization, and recrystallization in rolled and heat treated polyethylene terephthalate (PET)

This study is about crystallographic texture, deformation-induced decrystallization (disaggregation, amorphization), and subsequent recrystallization in rolled and heat treated semi-crystalline (triclinic) PET. Experiments are based on quantitative wide angle X-ray diffraction using an area detector. The change in crystallinity during rolling deformation and heating is analyzed in terms of X-ray data (peaks and background) that are integrated over the entire pole sphere. This method eliminates texture effects in the analysis of crystallinity. The rolling texture consists of a {100}<001> component and an incomplete fiber (<001>\\rolling direction). The texture is explained by crystallographic shear mainly on {100}<001> intralamellar shear systems. The X-ray analysis reveals that crystallinity drastically decreases during rolling. We suggest that amorphization (disaggregation, decrystallization) is a deformation mechanism which takes place as an alternative to crystallographic intralamellar shear depending on the orientation of the lamellae. Heat treatment (373, 473 K) leads to the recrystallization of amorphous material and to an enhancement of the original deformation texture. We explain the recrystallization texture in terms of an oriented nucleation mechanism where amorphous material aligns along existing crystalline lamellae. (C) 2004 Published by Elsevier Ltd.