Curing kinetics of epoxy resin for RFI process using isothermal DSC

To predict the curing behavior theoretically,  the isothermal differential scanning calorimetry (DSC) method was used to investigate the curing process of a hybrid epoxy resin system for resin film infusion (RFI) at 80，90，100，110 and 120℃，respectively. The curing system  is composed of hybrid epoxy resin of E-44/E-21(6/4，mass ratio) with GA-327(GA-327/resin=40/100，mass ratio) as curing agent，and a uniform film can be formed at room temperature and cured at 70～80℃. The corresponding parameters of the n-order curing model，the autocatalytic model and the Kamal model were determined by fitting the experimental data using Matlab software，respectively. According to the values of R² and the sum of square due to error (SSE) of the fitted data，a suitable curing reaction kinetic model was determined. It was found that the curing reaction of the hybrid epoxy resin system was of autocatalyzed and diffusion controlled characteristics，and the effect of the diffusion was much evident at a lower temperature. The data fitting results also indicate that the autocatalytic reaction kinetic model can be used to describe the cure kinetics of the curing system. The apparent activation energy E_a of the curing reactions is 56.7 kJ/mol and the pre-exponential factor A of the system is 1.18×10⁷ s^-1. The cure reaction order m and n are 0.529 and 1.561，respectively.