PVC的热失重和热解动力学

Kinetics of Thermal Weightlessness and Decomposition of PVC

热重法对PVC树脂的热解研究表明,热解过程可分为3个阶段,250～350°C为第一失重阶段、350～400°C为稳定阶段、400～550°C为第二失重阶段;升温速率对热解有较显著的影响,随升温速率的增加,Tb、Tf和Tm随之提高,但各阶段的失重率并不改变;气氛对热解有重要的影响,在含氧气氛中总失重约为100%,而氢气中的总失重最低。热解动力学研究表明,PVC的热解为一级反应过程,3个阶段的热解活化能受气氛影响稍有差异,分别为170～200kJ/mol、10～20kJ/mol和50～80kJ/mol,各阶段活化能的较大幅度变化说明各阶段热解反应机理是不同的。

Thermal decomposition of PVC resin has been examined by thermogravimetric analysis. The results of the pyrolytic experiment indicate that the degradation process can be divided into three stages, the first weight loss stage of 250~350 °C, thermally stable stage of 350~400 °C and the second weight loss stage of 400~550 °C. The thermal degradation behaviors of PVC resin are affected greatly by heating rate. Tb、Tf and Tm increase with the increasing heating rate, while the ratio of weight loss at each weight loss stage changes little. Atmospheres have big effect on thermal decomposition. The total weight loss is lowest in hydrogen, but reaches 100% in air and oxygen. The reaction kinetics is studied by the division of PVC resin pyrolsis process into three stages, by which the process of PVC pyrolysis can be described by using three firstorder reaction correctly. The activation energy of three stages is 170~200 kJ/mol, 10~20 kJ/mol and 50~80 kJ/mol respectively. This shows that mechanism of thermal decomposition is different in each weight loss stage.