| Microwave is of the characteristics of acting deeply, operating conveniently, cleanness, high efficiency, security and so on. It has drawn more and more attention in many fields, such as rubber vulcanization, composite molding, and epoxy resin curing. Due to its good comprehensive performance, epoxy resin has been widely used in composite materials, adhesives, coatings, and so on. The curing technique of epoxy resin has been an important research field. However, it is a new attempt to use microwave in the curing of epoxy resin. At present, there is still a controversy over the mechanism of microwave radiation on the curing of epoxy resin. Some believe that it has only one manner of heating, i.e. thermal effect. Others argue that, besides thermal effect, it also has non-thermal effect. Studying on the mechanism can accelerate the applications of microwave in the epoxy resin curing. It is also important for enhancing the performance of epoxy resin. In this work, a set of temperature-constant equipment with microwave continuous irradiating was developed, which made it possible to study only the non-thermal effect under microwave irradiation in epoxy curing process without the interference of thermal effect. Using Fourier transform infrared spectroscopy (FTIR) to quantitatively analyze the process of epoxy resin curing was explored by comparing the chemical analytical method and FTIR. Results demonstrate that it is feasible to adopt neighboring valleys as the integral range, peak area as the absorption peak intensity, and the absorption peak of phenyl ring as the internal reference. Based on the method mentioned above, E-51/100A, E-51/DDM, E-51/DDS, E-51/DICY, E-44/100A, E-44/DDM, E-44/DDS, and E-44/DICY systems were cured under both conventional heating and microwave conditions. The curing processes were tracked by Fourier transform infrared spectroscopy. Results show that, compared with conventional thermal curing, microwave curing can accelerate the curing reaction rates; microwave radiation cannot change the structures of final products. The reason leading to the above phenomenon is that microwave radiation can reduce the reaction activation energy. The value being reduced is proportional to the activation energy under thermal curing. The ratio is around 0.07.At last, the curing mechanism of E-51/DICY system was proposed. Results suggest that, in this system, the H atom of primary amine reacts firstly with epoxy group. Then nitrile group reacts with hydroxyl group, which is accompanied by the reaction between the H atom of secondary amine and epoxy group. 100A can catalyze the reaction of the system. Microwave radiation can accelerate reaction rates although it cannot change the mechanism of reaction.The results achieved from this study can rationalize the effect of microwave radiation on chemical reactions. They can also direct the applications of microwave.
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