CMC/E44/DDM体系固化过程及动力学

摘要

采用红外光谱和非等温 DSC 法研究了羧甲基纤维素(CMC)/E44环氧树脂/4,4′-二氨基二苯基甲烷(DDM)体系的固化过程和动力学。红外光谱研究表明，CMC可促使E44/DDM体系在固化过程中生成更多的聚醚结构。DSC非等温固化反应动力学研究表明，CMC的加入在反应初始阶段降低了E44/DDM体系的反应活化能，促进固化反应的进行。采用等转化率法和自催化模型对固化反应的过程进行研究，建立动力学方程。由Starink等转化率法获得E44/DDM和CMC/E44/DDM体系的活化能随转化率的变化情况。E44/DDM体系的活化能随转化率升高而显著降低；CMC/E44/DDM 体系的活化能随转化率升高变化不明显，在相同含量时，相对分子质量高的CMC 体系活化能高。采用SB自催化模型研究E44/DDM和CMC/E44/DDM体系的固化过程并获得模型参数。对CMC/E44/DDM体系，SB模型对实验结果拟合较好；对E44/DDM体系，SB模型和实验结果吻合效果较差。由于E44/DDM体系活化能随固化度有显著变化，因此采用改进的变活化能自催化模型描述其实验现象，结果显示该法获得的模型能够较好地描述实验现象。动力学模型的建立能够为工艺参数的选择和工艺窗口优化提供理论依据。%The influence of sodium carboxy methyl cellulose (CMC) on the curing process of epoxy resin E44 with 4,4′-diamino diphenyl methane (DDM) was studied by using infrared spectra and thermal analytical methods. Infrared spectra indicated that the CMC contributed to forming more polyether structures during the curing process. The study of non-isothermal curing kinetics by differential scanning calorimeters (DSC) showed that CMC accelerated curing reaction of E44/DDM and reduced reaction activation energy in the initial reaction stage. The iso-conversional method and the autocatalytic model were used to analyze the curing process of E44/DDM and CMC/E44/DDM systems respectively. A kinetic model was built. The changes of activation energy (E)versus conversion (a) were obtained by the Starink’s iso-conversional method for E44/DDM system and CMC/E44/DDM systems respectively. The activation energy (E) of E44/DDM system was reduced obviously with increasing conversion. When CMC content was the same, activation energy of the CMC system with high molecular weight was higher than that with low molecular weight. However, for the CMC/E44/DDM system, as the degree of conversion increased, variation ofE was not obvious. The SB (m,n) autocatalytic kinetic model was used to describe the curing reaction process of the studied system. The model parameters were calculated by using the Levenberg-Marquardt method. The SB model showed a good agreement with experimental data of CMC/E44/DDM system. However, the SB model showed a relatively bad agreement with experimental data of E44/DDM system. AnE variable autocatalytic kinetic model was proposed to describe the curing process of E44/DDM system due to the obvious change of activation energy and the model parameters calculated with the Levenberg-Marquardt method. Compared with the SB model, this model showed a better agreement with the experimental data of E44/DDM system. The results of the research provide theoretical basis for improvement of manufacturing process and optimization of processing window.