Calorimetric study of diepoxide chain-extended poly(ethylene terephthalate)

A series of chain-extended PET samples were obtained by the use of different amounts of a diepoxide as chain extender, which was prepared for this purpose. These samples exhibited different intrinsic viscosities and degrees of branching or cross-linking. The effects of this differentiation on the thermal properties were studied by differential scanning calorimetry. The thermal parameters studied were the glass transition temperature (T-g), the cold-crystallization temperature (T-cc), the melting temperature (T-m), the enthalpy (Delta H-m) and the degree of crystallinity. The data revealed that, the higher the quantity of chain extender or the chain extension time, the higher T-g and T-cc but the lower T-m and Delta H-m, i.e. the more amorphous the chain-extended samples, as also shown by density measurements.