Abstract
ABSTRACTTime‐resolved rheometry and size exclusion chromatography system [advanced polymer chromatography (APC)‐multi‐angle laser light scattering (MALLS)‐refractive index detector (RID)] were employed to investigate post‐polycondensation process of nonstirred high‐viscosity poly(ethylene terephthalate) (PET) of molten film forming by high‐flow inert gas sweeping at atmospheric pressure. In view of chemical reaction kinetics together with mass transfer to adjust reactive parameters, including moisture content of the sample, temperature, concentration of the active groups, residence time, and mass transfer factor, this work aims to distinguish the different reactions in reprocessing of high‐viscosity PET. Results indicated that hydrolysis is observed initially before thermal degradation and polycondensation reactions on remelting process. Promotion of thermal degradation is stronger than polycondensation with the increase in temperature. Fiber‐grade PET exhibits polycondensation as the dominant reaction at 275 °C in a reasonable reaction time, which leads to the increase of average molecular weight and the phenomenon of double distribution proved by APC‐MALLS‐RID system. However, the average molecular weight of industrial yarn‐grade PET is very difficult to improve when the thermal degradation reaction is not effectively inhibited. Importantly, the experimental study of the interfacial mass‐transfer area and mass‐transfer intensification demonstrated that mass transfer is the rate‐determining factor for the overall post‐polycondensation of high‐viscosity melt. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47484.
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