Analysis of aggregation structure and orientation behavior of polyethylene terephthalate after confined drawing

ABSTRACT High-strength oriented PET products were prepared via the confined drawing process. The aggregation structure changes and orientation behavior of PET with different initial crystallinities (before and after drawing) were investigated by TMDSC, WAXD, and SAXS. Combined with the three-phase structure model, the generation and evolution process of highly-ordered rigid amorphous fraction (RAF) were further confirmed. Meanwhile, the effect of drawing temperature on the structure and properties of oriented PET was systematically explored. Consequently, below the cold crystallization temperature, limited mobility of crystalline regions results in two key evolutionary behaviors of PET during drawing: the transformation of the amorphous phase into highly-ordered RAF, and stress-induced crystallization under tensile force. Additionally, the annealing temperature is another key factor influencing the microstructural evolution of semicrystalline PET. The temperature at which the crystalline phase forms, it directly determines the mobility of the crystalline regions. The characterization results from TMDSC and X-ray techniques quantitatively analyzed the composition and variation law of the aggregation structure, providing guidance for the structure-property regulation of high-strength oriented PET.