COMPUTER-SIMULATION OF CURING AND TOUGHENING OF EPOXY SYSTEMS

The crosslinking and toughening process of diglycidyl ether of bisphen ol A (DGEBA) resin was simulated by various computational techniques, using a commercial polymer modeling software package. First, curing of DGEBA resin with three different curing agents was simulated using a Monte Carlo simulation technique. Results calculated for crosslinking conversion of the formed network showed that deviation from an ideal n etwork due to loops and dangling chains increased with excess amounts of the curing agent and that the formed network is close to the ideal when stoichiometric concentrations are used. The maximal calculated mo dulus was an indication of the optimal curing agent concentration. The glassy modulus and T-g for the simulated systems were calculated usin g the group contribution method and semiempirical correlations. Second , the simulation results of multicomponent epoxy systems, comprising t wo curing agents, a reactive diluent and DGEBA resin, indicate that th ere is no difference in network quality compared with bicomponent epox y systems, comprising DGEBA and a single curing agent. The simulation results exemplified the ability to choose optimal components concentra tion in a complicated multicomponent epoxy system. Third, the tougheni ng process of amino-terminated butadiene acrylonitrile (ATBN) and carb oxyl-terminated butadiene acrylonitrile (CTBN) in DGEBA resin was anal yzed using the solubility parameter approach. This approach could expl ain the role of the rubber acrylonitrile group in epoxy/rubber blends. The interaction parameters of both systems (ATBN and CTBN) and their phase diagrams were estimated using modified Flory-Huggins theory. It was shown that this technique leads to good estimations of the optimal rubber concentration, leading to optimal mechanical properties.