紫胶树脂-羟丙基甲基纤维素复合膜的热分解动力学试验

Study on Thermal Decomposition Kinetics of Shellac Resin-Hydroxypropyl Methylcellulose Composite Membrane

紫胶树脂(SHL)-羟丙基甲基纤维素(HPMC)复合膜是基于改善紫胶树脂亲水性、成膜的致密性而利用HPMC的亲水性凝胶骨架所制备的一种复合材料,为探究该复合材料在加热条件下的热分解行为及相关数据,采用热分解动力学研究方法,以氧气为吹扫气,监测复合膜由室温至高温条件范围内的热质量(TG)和差示扫描量热(DSC)曲线,利用相关软件绘制相应的微分热质量(DTG)曲线,分析复合膜热分解过程的特征参数变化;根据TG、DTG曲线,采用Kissinger法、Starink法计算复合膜的热分解活化能,对计算结果进行了线性相关性检验;应用Malek法计算并推断复合膜的热分解数学模型。结果表明:SHL-HPMC复合膜的热分解过程分两步进行,且热分解反应过程中,体系的放热量高于吸热量;由于SLR-HPMC复合膜具有聚合物特性,其热分解反应最大分解速率温度随升温速率的增大而增大;Kissinger法和Starink法的计算结果具有密切的线性相关性,其计算的热分解反应活化能分别为441.310 kJ/mol和349.410 kJ/mol;Malek法计算结果表明:SLR-HPMC复合膜的热分解反应最接近于J-M-A方程,其热分解反应机理为随机成核和随后生长。SLR-HPMC复合膜在10、15、20、25℃/min升温速率时粘流转变的起始、峰值及终止温度平均值分别为57.0、67.8、81.1℃,相应升温速率时的粘流转变热量变化均值为475.9 mJ。

The composite membrane of shellac resin(SHL)-hydroxypropyl methylcellulose(HPMC)is a composite material prepared by using the hydrophilic gel skeleton of HPMC to improve the hydrophilicity of shellac resin and the compactness of the film.In order to explore the thermal decomposition behavior and related data of the composite under heating conditions,the thermal decomposition kinetics method was used,with oxygen as the purge gas.The thermal mass(TG)and differential scanning calorimetry(DSC)curves of the composite membrane from room temperature to high temperature were monitored,and the corresponding differential thermal mass(DTG)curves were drawn by related software to analyze the changes in characteristic parameters in the thermal decomposition process of the composite membrane.According to the TG and DTG curves,the thermal decomposition activation energy of the composite mem-brane was calculated by Kissinger method and Starink method,followed by the linear correlation test.The Malek method was used to calculate and infer the thermal decomposition mathematical model of the com-posite membrane.The results show that the thermal decomposition process of SHL-HPMC composite membrane occurs in two steps,and the heat release of the system is higher than that of heat absorption in the thermal decomposition process.Due to the polymer characteristics of SLR-HPMC composite mem-brane,the maximum decomposition rate temperature increases with the increase of heating rate.There is a close linear correlation between the results of Kissinger method and Starink method.The thermal de-composition activation energy of SLR-HPMC composite film is 441.310 kJ/mol and 349.410 kJ/mol re-spectively.The Malek method results show that the thermal decomposition reaction of SLR-HPMC com-posite film is closest to J-M-A equation,and the thermal decomposition reaction mechanism is random nucleation and subsequent growth.The average values of initial,peak and end temperatures of viscous flow transition of SLR-HPMC composite films at 10,15,20 and 25℃/min are 57.0,67.8,81.1℃,respectively,and the average heat change of viscous flow transition at the corresponding heating rate is 475.9 mJ.