Morphological changes of poly(ethylene terephthalate-co-isophthalate) during solid state polymerization

摘要

Poly(ethylene terephthalate-co-isophthalate) (PETI) prepolymer was submitted to solid state polymerization (SSP) at 184-230°C in a fixed bed reactor, to study the evolution of morphological changes during the process. Short reaction times were selected to investigate crystallization phenomena during nonisothermal (heating) and isothermal SSP phases. More specifically, multiple PETI melting behavior was observed and attributed to secondary crystallization, the rate of which increased significantly with SSP temperature. Reaction time was also found to exert a positive effect on solid-phase perfection of secondary crystals, leading at each temperature to melting points close to the value of bottle-grade poly(ethylene terephthalate). Finally, the mass fraction crystallinity of the SSP grades was found to comply with the crystal morphology encountered.