Thermal Crystallization of Poly(ethylene Terephthalate) and Its Copolyesters: Effect of Degree of Polymerization and Copolymerized Components

Abstract

The effect of the degree of polymerization and the copolymerized components on the thermal crystallization of poly(ethylene terephthalate) (PET) and its copolyesters was investigated at a temperature just above glass transition. The crystallinity of PET increased with the decrease of [ η], but the apparent activation energy of crystallization was scarcely influenced by [η]. Crystallization of PET appears to occur from a definite state of thermal motion of the polymer segment, the isoviscous state. Comparing undrawn PET with quenched bulk PET, the crystallinity and activation energy indicate that fiber formation near the spinning nozzle develops the aggregation polymer seg ments for crystallization. Crystallinity and the apparent activation energy of crystal lization for poly(ethylene terephthalate/isophthalate) and poly(ethylene terephthalate/ p-oxybenzoate) indicate behavior that is different from PET. The thermal motion of segments for copolyesters varies with the copolymerized components.