Analysis of Curing Reaction for Epoxy Resin Used for Electrical Insulators: Part I Kinetic Analysis of Curing Reaction

摘要

Epoxy resins have been widely used as insulators in electronic devices because of the in excellent electrical properties. Cracking of the epoxy resin (interface) is a problem during the curing process, hence many experimental investigations on the causes have been performed. Few studies have dealt with this problem by numerical methods because the relationship among the reaction rate, temperature, stress, and strain is too complex to be expressed numerically. The finite element analysis method with a coupled matrix of the relationships is the most suitable for implementation. The results determined with numerical analysis is useful for designing electronic devices, although many parameters are necessary to accomplish the analysis. This paper reports on the kinetic analysis of the curing reaction between an epoxide (Epikote 828) and a carbonic acid anhydride (HN-2200) using a finite element analysis with a coupled matrix. The degree of reaction at a given temperature was determined by titration of the unreacted acid and epoxy groups in the system. Because the curing rates obtained by a power law model were not in good agreement with experiment, the curing rate was expressed as a function of temperature and the degree of reaction by means of a multiple regression analysis. To deal with the curing rate in the finite element analysis, the degree of reaction was defined as one of the variables at the Gaussian integration points in finite elements. Consequently, the analytical results with the new finite element model were in good agreement with the experimental data. This numerical method would be available for predicting the strain in epoxy resins and the degree of reaction throughout the curing process.