Time‐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.

The film-forming behavior of falling film flow with a high-viscosity fluid in clamped channels was investigated numerically and experimentally. The present work puts forward and deeply investigates a new method of falling film flow in the field of industrial engineering. The new findings from computational fluid dynamics (CFD) agree well with the experimental results. Flow patterns can be observed and divided into three flow patterns: columnar flow, partial curtain flow, and curtain flow. In terms of different flow patterns, the evolution of the liquid film along the direction of gravity was diversified, mainly including coalescence, break-up, shrinkage, and expansion. In addition, the shape of the free surface depended mainly on the physical properties of the fluid, the geometrical structure of the channel, and the spray density. The convex ratio k of the liquid film varied between 0 and 1.2, and such a wide range indicated that the free surface of the liquid film would be visually bent, resulting in a large area for the gas–liquid interface and a very high level of the film-forming efficiency. More interestingly, the desired shape of the liquid film was obtained by regulating the structural factors r and d. Based on the above conclusions, the method concerning falling film flow down clamped channels could be beneficial to enhance the heat and mass transfer in the process intensification of industrial engineering.

Abstract:The blending of aliphatic polyolefins and aromatic poly(ethylene terephthalate) (PET) based on different intrinsic viscosities (IV) was conducted in a torque rheometer. The comparison of blend components in terms of low density polythene (LDPE) and polypropylene (PP) in blending with PET was investigated, and the effects of the IV and proportion of PET on polymer blends are discussed in detail. Polymer blends with or without compatibilizer were examined by using a differential scanning calorimeter, thermogravimetric analyzer, rotary rheometer, field-emission scanning electron microscopy and a universal testing machine. It was found that the blending led to an increase in processability and a decrease in thermal stability for blends. The morphological analysis revealed that the incompatibility of blends was aggravated by a higher IV of PET, while this situation could be improved by the addition of compatibilizer. Results showed that there was an opposite effect for the tensile strength and the elongation at break of the polymer blend in the presence of a compatibilizer, wherein the influence of IV of PET was complicated.

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