MORPHOLOGY AND CRYSTALLIZATION OF POLY(ETHYLENE-TEREPHTHALATE)

The melting behaviour and the morphology of poly(ethylene terephthalate) crystallized from the melt are reported. In general, dual or triple melting endotherms are seen, and single endotherms are seen when the samples are crystallized above 215-degrees-C for long times. The location of the uppermost endotherm was found to be constant below T(c) = 230-degrees-C, and above that temperature the location depends on T(c). Therefore, we have shown that samples of PET which are crystallized above T(c) = 230-degrees-C contain perfect crystals only; below T(c) = 230-degrees-C, they contain perfect and imperfect crystals. Scanning electron microscopy showed that the perfect crystals are the dominant lamellae in the spherulitic structure, while the imperfect crystals are the subsidiary lamellae. The amorphous regions are located between individual lamellae.