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首页> 外文期刊>Polymer Sciences >Kinetic Study of Thermal Degradation of Polydimethylsiloxane: The Effect of Molecular Weight on Thermal Stability in Inert Atmosphere
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Kinetic Study of Thermal Degradation of Polydimethylsiloxane: The Effect of Molecular Weight on Thermal Stability in Inert Atmosphere

机译：聚二甲基硅氧烷热降解的动力学研究：分子量对惰性气氛中热稳定性的影响

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Thermal degradation of polydimethylsiloxane (PDMS) of different molecular weights in inert and oxygen atmosphere is studied and discussed in detail. PDMS samples of different molecular weights were prepared by anionically initiated ring-opening polymerization of octamethylcyclotetrasiloxane in emulsion. The molecular weight of PDMS drastically affected the shape of TGA curve at higher temperatures when thermogravimetric (TGA) measurements were performed in the inert atmosphere. The thermal stability of PDMS decreased with increasing the average molecular weight of the sample, which could be explained by prevailing unzipping mechanism at lower molecular weights over intramolecular and intermolecular redistribution, which were more important at higher molecular weights. On the other hand, experiments in oxygen atmosphere showed zero effect of polydimethylsiloxane molecular weight on its thermal stability. In addition, a kinetic model describing the thermal degradation of PDMS in inert atmosphere as a function of PDMS molecular weight was proposed. The proposed kinetic model was composed of diffusion-limited kinetics step related to evaporation rates of the degradation products and of rate-determined step related to the formation of cyclic degradation products. As a result of mathematical modeling by fitting the calculated data to experimental data kinetic parameters were derived properly.
机译：研究和讨论了在惰性和氧气气氛中不同分子量的聚二甲基硅氧烷（PDMS）的热降解。通过乳液中八甲基环四硅氧烷的阴离子引发的开环聚合反应制备了不同分子量的PDMS样品。当在惰性气氛中进行热重分析（TGA）时，PDMS的分子量会在较高温度下严重影响TGA曲线的形状。 PDMS的热稳定性随样品平均分子量的增加而降低，这可以用较低分子量下的普遍解链机制来解释，而分子内和分子间的再分布则是重要的，这在较高分子量下更重要。另一方面，在氧气气氛下的实验表明聚二甲基硅氧烷分子量对其热稳定性的影响为零。此外，提出了动力学模型，该模型描述了惰性气氛中PDMS的热降解与PDMS分子量的关系。所提出的动力学模型由与降解产物的蒸发速率相关的扩散受限动力学步骤和与环状降解产物的形成相关的速率确定步骤组成。通过将计算的数据拟合到实验数据进行数学建模的结果是，正确地得出了动力学参数。

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