Abstract: This paper reported a study on the effect of molecular weight on stressoscillation behavior of poly(ethylene terephthalate) (PET) during the tensile experiment. Tensile test, differential scanning calorimetry and scanning electron microscopy were performed to investigate the stress-oscillation behavior, crystallinity, and macroscopic and microscopic morphologies in different regions of PET specimen. The results indicated that the stress-oscillation behavior of PET specimen was dependent on the relative molecular weight of PET resin and the tensile rate. Inhomogeneous voids observed inside the PET specimen were derived from the stress oscillation and considered as a microscopic result. The occurrence of stress oscillation was due to the difference of crystallinity degree within the bright-dark alternating bands during the process of stretch-induced crystallization.

Key words: poly(ethylene terephthalate), stress oscillation, cavitation, relative molecular weight, crystallinity degree