Computational modeling and simulation of temperature field evolution during the chemical foaming of epoxy foams

Abstract

The evolution and control of the temperature field during the chemical foaming of epoxy resin are of paramount importance because the foam structure results from the competition of resin crosslinking and foaming, both of which are highly dependent on temperature distributions. Herein, the epoxy foams, consisting of diglycidyl ether of bisphenol A, glycidyl amine‐type epoxy resin, and 4,4′‐diamino diphenyl sulfone hardener, are prepared using azodicarbonamide and 4,4′‐oxydibenzenesulfonyl hydrazide as a chemical foaming agent (CFA). Kinetic models for heat release and CFA decomposition are established using the auto‐catalytic and n‐th order models, respectively. By integrating the transient flow of resin during the foaming process, numerical simulations of the temperature field evolution within the self‐expanding geometry are conducted to investigate the effects of foaming temperature, heat transfer coefficient, and mold diameter on spatial temperature distributions. A comparison of the kinetic parameters of epoxy curing and CFA decomposition at various foaming temperatures (433, 443, and 453 K) reveals that the acceleration of the curing rate is consistent with that of the decomposition rate as the foaming temperature increases, then the foam structure remains largely unchanged across different foaming temperatures. However, local overheating is unavoidable for the foams at 443 and 453 K. This study offers a method for optimizing the processing parameters in preparing epoxy foams.Highlights Auto‐catalytic model for predicting heat released rate is well established. The decomposition kinetics of the chemical foaming agent is described by n‐th model. Nonisothermal simulation is implemented to study the self‐expanded process of epoxy foam. The foam structure is predicted by comparing the kinetic between the curing and expansion processes.