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首页> 外文期刊>Thermochimica Acta: An International Journal Concerned with the Broader Aspects of Thermochemistry and Its Applications to Chemical Problems >INVESTIGATION OF AN ENGINEERING THERMOPLASTIC POLYURETHANE BY MDSC
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INVESTIGATION OF AN ENGINEERING THERMOPLASTIC POLYURETHANE BY MDSC

机译：用MDSC研究工程热塑性聚氨酯

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摘要

A commercial engineering thermoplastic polyurethane (ETPU) resin was investigated by modulated-temperature DSC (MDSC). Use of this recently developed technique provided an accurate measurement of the changes in heat capacity resulting from crystallization and depolymerization processes. The former process was examined in a pseudo-isothermal experiment and the latter in a dynamic one. The ETPU resin investigated in this work is crystallizable but at such a slow rate that no crystalline regions are expected to be formed under normal processing conditions. Significant amounts of crystalline material are not formed until after 150 min at 160 degrees C and the crystallization process is not completely finished even after 700 min. It is shown that the endothermic activity observed upon heating is not a true melting process but is caused by a breakup of the crystalline regions by depolymerization. Heat capacity (C-p) traces obtained from a heat-cool-heat sequence of the amorphous material indicate that no significant irreversible changes to the resin have occurred during the time frame of the experiment. Starting from ca. 175 degrees C, a positive deviation in the linearity of the Cp VS. temperature relationship is observed. It is believed that this deviation is the result of a reversible depolymerization/repolymerization process. Number-average molecular weights, in line with expectations, have been calculated from the observed C-p changes using literature data for polystyrene. (C) 1997 Elsevier Science B.V. [References: 12]
机译：通过调制温度DSC（MDSC）研究了一种商用工程热塑性聚氨酯（ETPU）树脂。使用这种最新开发的技术可以准确测量结晶和解聚过程导致的热容变化。前一个过程在拟等温实验中进行了检验，而后一个过程在动态过程中进行了检验。在这项工作中研究的ETPU树脂是可结晶的，但是速度很慢，以至于在正常加工条件下不会形成结晶区。直到在160℃下150分钟之后，才形成大量的结晶材料，并且即使在700分钟之后，结晶过程也没有完全完成。已经表明，加热时观察到的吸热活性不是真正的熔融过程，而是由解聚作用导致的结晶区域破裂而引起的。从无定形材料的热-冷-热序列获得的热容（C-p）曲线表明，在实验时间范围内，未发生对树脂的重大不可逆变化。从ca开始。 175摄氏度，Cp VS的线性正偏差。观察到温度关系。认为该偏差是可逆解聚/再聚合过程的结果。使用聚苯乙烯的文献数据，由观察到的C-p变化计算出了符合预期的数均分子量。 （C）1997 Elsevier Science B.V. [参考：12]

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