Quantitative small-angle light scattering studies of the melting of poly(ethylene terephthalate)

Quantitative H_v small-angle light-scattering (SALS) studies of the melting of poly(ethylene terephthalate) (PET) have been performed. The results are compared with those from differential scanning calorimetry (DSC). It is found that fully grown spherulites melt over a temperature range of about 20°C without change in spherulite size, number, or internal disorder. The decrease in H_v SALS intensity is due to a decrease in spherulitic crystallinity over the melting range. The corrected experimental intensities are lower than, but in reasonable agreement with, the theoretically predicted intensities based on the DSC results. Procedures are presented for the quantitative analysis of H_v SALS intensities from spherulitic systems, including the corrections for the experimental, external disorder, and internal disorder effects.