EFFECT OF REACTIVITY ON CURE AND PHASE-SEPARATION BEHAVIOR IN EPOXY-RESIN MODIFIED WITH THERMOPLASTIC POLYMER - A MONTE-CARLO SIMULATION APPROACH

Structure development during the cure of epoxy resin modified with rub ber or thermoplastic polymer was investigated by a Monte Carlo simulat ion technique. The lattice model of bond-fluctuation algorithm propose d by Carmesin and Kremer was modified to be applied to the crosslinkin g reaction between epoxy resin and curing agent. The entropy driven ph ase separation behavior was monitored by a quantity of collective stru cture factor and was analyzed by the Flory-Huggins theory. Even though the phase separation behavior near the critical composition of the mi xture shows the spinodal decomposition irrespective of the cure rate, the phase separation mechanism at the off-critical composition is chan ged with the cure rate. The cure behavior seems to follow a second ord er reaction kinetics. As the volume fraction of added thermoplastic po lymer increases, the apparent kinetic rate constant decreases at the s ame reactivity. This can be interpreted as a diluent effect of the add ed thermoplastic polymer on the cure kinetics. Also, the gelation beha vior was compared with the Flory-Stockmayer branching theory.