Modification of PET by reactive blending with sulfonated esters. II. Isothermal crystallization kinetics of PET-ionomers

摘要

The thermal properties of PET-ionomers, obtained by reactive blending between PET and a monofunctional ester containing an ionic group (-SO3Na), were studied using DSC, and results were compared with those of nonionic PET homopolymers. The presence of ionic groups located only at the chain ends induces significant modifications in the thermal behavior: the equilibrium melting temperature increases and the crystallization rate decreases with the ionic group content; moreover, the crystalline level remains high. All of these characteristics are interpreted as due to ionic associations between the sulfonated end groups, both in solid and in molten states, that cause an apparent increment in the molecular weight of ionomers. A confirmation of this simple molecular architecture is found in the growth regime analysis: the fold-surface free-energy values of ionomers do not vary compared to those of nonionic homopolymers, indicating that chain folding is not hindered by the presence of a complex network. [References: 37]