Crystallinity and orientation development upon hot multistage drawing of PET multifilament yarn

Abstract

In this research, poly(ethylene terephthalate) (PET) multifilament yarn was drawn on an industrial drawing machine at hot multistage. By varying draw ratio, a number of drawn fibers with different internal structures were obtained. Total draw ratio was changed from 4.68 to 6.24. Crystallinity and molecular orientation of the drawn samples were investigated using differential scanning calorimetry, birefringence, infrared spectroscopy, and X-ray diffraction. The results show that the high population of gauche conformer in as-spun fiber decreased rapidly with fiber orientation. The absence of crystallization peak and clear T g in the drawn samples has been explained by orientation development as well as crystalline–amorphous interactions. Microstructural changes in the drawn PET fibers have been discussed in terms of the applied heat and mechanical deformation upon hot multistage drawing.