基于热失重法的热塑性聚氨酯热氧老化特性分析及其降解动力学模型

采用热塑性聚氨酯（TPU）在40℃、50℃、60℃、70℃下进行人工加速热老化，利用热失重分析法（TG）对TPU热降解过程进行分析，探讨了TPU在老化过程中的热失重特性及其热降解动力学模型。测试结果表明，TPu热失重过程可分为硬段和软段热裂解两个阶段；硬段和软段各自最快热降解速率随老化温度和时间的增加没有明显变化。然而，通过对TPU热失重5％时对应的温度进行分析，得出该温度随着热氧老化时间的延长而逐渐下降，说明TPu的热稳定性随老化时间的延长而逐渐降低。采用Coats—Redfern方法对TPU的热降解动力学进行研究，结果表明，TPU的热降解符合0级反应动力学方程。

Characteristic Analysis and Evaluation Model of Thermal-Oxidative Aging of Thermoplastic Polyurethane Based on Thermogravimetry

An accelerated thermal-oxidative aging of thermoplastic polyurethane （TPU） at 40, 50, 60, 70 ℃ was carried out, and the thermal degradation kinetics with aging time and corresponding pyrolysis process were ana- lyzed via the thermogravimetry. The results showed that the weight loss in the pyrolysis process contains two stages, namely the hard segment and the soft segment of TPU, moreover, the fastest thermal degradation rate of the hard segment and the soft segment didnot change significantly with the aging temperature and time increasing. However, according to the temperatures of weight loss to 5% of TPU, the thermal stability of TPU with the durations showed the decreasing trend. The thermal degradation kinetic mechanism and model of TPU aging at different times and temperatures were determined by Coats-Redfern method, and then the nonisothermal kinetic equation of major deg- radation process was educed. The results showed that during the aging process, the reaction order n was 0, moreo- ver, the degeneration activation energy of TPU decreased gradually with the duration.