Effect of orientation and crystallinity on the photodegradation of poly(ethylene terephthalate) fibers

In this research, photodegradation of poly(ethylene terephthalate) (PET) fibers was investigated with emphasis on the morphological state of yarns. Two kinds of yarns, FDY (Fully Drawn Yarn) and POY (Partially Oriented Yarn), with different molecular orientation and crystallinity were applied in this research. FDY is spun in the same way as POY and subsequently drawn at high speed and then entangled before winding up. This sample has higher molecular orientation and crystallinity than the POY sample. Several analytical methods were applied in this study: viscometry, X-ray diffraction, FTIR spectroscopy, UV-Visible spectrophotometry, and mechanical testing. Viscometry was used to determine molecular weight as a monitoring factor for degradation. X-ray diagrams showed higher crystallinity for FDY samples during weathering process by irradiation. Results of mechanical testing indicated that the tenacity of the FDY fibers had less deterioration in comparison with the POY ones.