二甲基苯基硅氧基封端聚(二甲基-甲基苯基)硅氧烷共聚物的热分解性能及动力学研究

以1,1,3,3-四甲基二苯基二硅氧烷为封端剂,八甲基环四硅氧烷与甲基苯基环硅氧烷混合物为共聚单体,在阴离子催化剂作用下合成了二甲基苯基硅氧基封端的聚(二甲基-甲基苯基)硅氧烷共聚物。采用非等温TG技术,在惰性气氛和5.0、10.0、15.0和40.0 K min 1线性升温速率条件下,考察了共聚物非等温热降解机理及反应动力学,采用Friedman-Reich-Levi、Flynn-Wall-Ozawa和Kissinger等方法对非等温动力学数据进行分析,所得平均表观活化能分别为113.64、115.69和145.80 kJ mol 1。采用等转化率法确定出共聚物热分解反应符合Avrami-Erofeev方程,反应机理为随机成核和随后生长。采用Crane和Doyle方法研究了不同升温速率对反应级数、活化能和指前因子的影响,结果表明降解反应为一级反应,反应活化能介于152.46~183.13 kJ mol 1之间,指前因子介于4.25×109~4.02×109s 1。同时采用等温TG技术得到失重5%和10%条件下的寿命方程,对共聚物的寿命进行了预测。

Thermal Decomposition Properties and Kinetic Studies of the Dimethylphenylsiloxyl Terminated Poly(dimethyl-methylphenyl)siloxane Copolymer

Dimethylphenylsiloxyl terminated poly(dimethyl-methylphenyl)siloxane copolymer was prepared through anionic polymerization with 1,1,3,3-tetramethyldiphenyldisiloxane as the end-blocking agent and octamethylcyclosiloxane and methylphenyl cyclic oligomers as the monomers.The thermal decomposition mechanism and kinetics of copolymer were investigated by means of non-isothermal TG at different heating rates of 5.0,10.0,15.0 and 40.0 K min 1 in an inert atmosphere.The TG data were analyzed by the Friedman-Reich-Levi method,the Flynn-Wall-Ozawa method and the Kissinger method,and the obtained apparent activation energies are 113.64,115.69 and 145.80 kJ mol 1,respectively.The decomposition mechanism was identified by isoconversion method and the results show that the most probable kinetic function of the thermal decomposition is the Avrami-Erofeev equation.The corresponding decomposition mechanism is random nucleation following by subsequent growth.The influences of heating rate on reaction order,activation energy and preexponential factor were also investigated by the Crane method and the Doyle method.The results indicate that the thermal decomposition is a first order reaction,the calculated activation energy ranges from 152.46 to 183.13 kJ mol 1and the preexponential factor ranges from 4.25×109 to 4.02×109 s 1.The lifetime equation at weight loss of 5% and 10% were further deduced by isothermal TG analysis and the lifetime of copolymer was predicted.