聚碳酸酯树脂的醇解反应及机理研究

Study on Glycolysis and Mechanism of Polycarbonate Resin

以醋酸锌(Zn(Ac)_2)为催化剂、乙二醇(EG)为醇解剂、四氢呋喃(THF)为溶剂,考察了不同醇解反应时间和温度条件下不同来源聚碳酸酯(PC-1、PC-2)树脂的醇解反应规律,得到相应的重均分子量与醇解反应速率参数,并通过红外特征吸收峰的变化推测其醇解反应机理。结果表明:延长反应时间、提高反应温度,PC的醇解率逐渐增大,重均分子量逐渐下降;其重均分子量的变化值(1/M_(wt)-1/M_(w0))与反应时间呈一级反应动力学规律;醇解反应速率常数随温度升高而增大,PC-1的醇解反应速率常数大于PC-2的,二者的醇解反应活化能分别为30.42kJ/mol和45.51kJ/mol。从降解机理来看,PC的醇解降解反应主要发生于碳酸酯键以及芳环-亚异丙基键接处。

The effect of reaction time and temperature on glycolysis of different type polycarbonate（PC-1,PC-2）resin was investigated,with zinc acetate（Zn（Ac）_2）as the catalyst,ethylene glycol（EG）as the glycolysis agent,tetrahydrofuran（THF）as the solvent.The weight-average molecular weight parameters and the glycolysis reaction rates were obtained.And the reaction mechanism was speculated according to the variation of characteristic infrared absorbance peaks of PC.The results showed that the glycolysis yield of PC increases and its weight-average molecular weight（Mw）decreases gradually with the reaction time and temperature.The relationship between 1/M_（wt）-1/M_（w0） and reaction time complys with a first-order reaction kinetics.The higher the reaction temperature is,the more the glycolysis reaction rate constant（K）becomes.Kof PC-1 is higher than that of PC-2.And their activation energy are 30.42 kJ/mol and45.51 kJ/mol,respectively.As for the decomposition mechanism of PC,the glycolysis mainly results from the scission of C—O bond belonging to carbonate group and C—C bond between aromatic ring and isopropylidene.