Toughening of crosslinked polystyrene with liquid rubber

The optimum conditions for preparing poly(styrene-co-divinylbenzene) were d etermined and the variation of the mechanical properties of the networks wi th the crosslinking density was evaluated. The molecular weight between cro sslinks was in the 800-12,000 range. The flexural modulus and flexural stre ngth were 5000 and 110 MPa, respectively, for the more crosslinked material s. When liquid rubber (hydroxyl-terminated polybutadiene) was incorporated into the glassy matrix, these values dropped to 2500 and 70 MPa, respective ly, but the impact resistance increased to 70 J/m. These values were compar able to some commercial grade high impact polystyrene resins. The particle size of the dispersed rubber phase was on the nanometer scale, and attempts to increase its dimensions should provide further improvement in the impac t properties. (C) 2001 John Wiley & Sons, Inc.