Evaluation of the effect of heat exposure time on the properties of dimethyl terephthalate-tetrahydrofuran copolymer and its products at different processing stages

   Purpose. In the process of processing the copolymer of dimethyl terephthalate and tetrahydrofuran into finished products, the initial elastomer is subjected to two high-temperature treatments, starting from the raw material preparation stage and including the actual process of converting the material into a finished product. Failure to comply with the drying and extrusion processes can result in a deterioration of the finished product's appearance and performance.

   The purpose of this study is to identify and explain these causes.

   Methods: IR-spectroscopy for structure analysis, physical and chemical methods for determining the fluidity and yield point of the melt, Shore hardness, compression testing, and product appearance control.

   Results. The paper evaluates the effect of heat treatment of a thermoplastic elastomer at the stage of raw material preparation, varying the pre-drying time of a copolymer of dimethyl terephthalate and tetrahydrofuran, on the properties and appearance of the finished product, with an analysis of possible chemical processes of hydrolytic degradation that lead to a deterioration in appearance. The negative impact of excessive melt residence time in the extruder on the performance properties of the finished product has been studied, along with the chemical processes and changes in the chemical structure of the material due to thermo-oxidative degradation.

   Conclusion. It has been established that the presence of moisture in the raw material due to non-compliance with storage conditions and the absence of methods for controlling the water content during the drying process leads to hydrolytic decomposition with the destruction of the polymer chain and the production of an unusable product. Failure to comply with the polymer melt exposure time in the extruder during the processing of the material results in its destruction during thermo-oxidative degradation, affecting the melt yield point and non-compliance with technological requirements.

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