Thermal and Mechanical Properties of Crosslinked Epoxy Based on Molecular Dynamics

In this paper, the dynamic crosslinking process of epoxy materials containing diglycidyl ether of bisphenol A (DGEBA) as the epoxy monomer and 1, 3-benzenediamine (MPD) as hardener was studied using molecular simulation. An algorithm that can create the high-crosslinked epoxy was adopted, and the energy changes under different crosslinking processes were compared. The glass transition temperature (T_g) of the material under various crosslinking densities was determined as the temperature marking the discontinuity in slope of the temperature-density relationship. The Young's modulus was obtained through the linear regression by the elastic range in stress-strain relationship acquired by non-equilibration method. Simulation results show that the effectiveness of using simulated annealing method in the dynamic crosslinking process can reach higher degree of crosslinking while the molecular configuration is more desirable. Glass transition temperature grows with increasing the bulk crosslinking degree, the maximum T_g reaches roughly 431 K while the crosslinking degree is 80%. The Young's modulus is less sensitive to the strain rate, however, the large strain rate will lead to higher yield point. The Young's modulus will grow with increasing crosslinking degree. The thermal conductivity of crosslinked epoxy decreases with growing temperature before the glass transition temperature. Furthermore, the thermomechanical properties of the epoxy resin computed agree well with the existing theoretical or experimental values.