SYNTHESIS AND APPLICATION OF CORE-SHELL PARTICLES AS TOUGHENING AGENTS FOR EPOXIES

Poly(butadiene-co-styrene) [P(B-S)] core-poly(methyl methacrylate) (PM MA) shell particles were prepared using a two-step emulsion polymeriza tion. These core-shell particles were used to toughen an epoxy polymer . The role of particle-epoxy interfaces were studied by systematically varying the shell compositions of the core-shell particles such as PM MA, P[MMA-acrylonitrile (AN)], P[MMA-glycidyl methacrylate (GMA)] and P[MMA-divinyl benzene(DVB)]. Therefore, the nature of the particle-epo xy interfaces is varied in terms of physical interactions and chemical bonding. The fracture toughness values of the toughened epoxies were measured using linear elastic fracture mechanics. Results indicate tha t the morphology of the dispersed particles in the epoxy matrix plays an important role in the toughening of epoxies. This degree of dispers ion can be varied by incorporating AN and GMA comonomers in the PMMA s hells or by crosslinking the shell. In summary, nanoscale interactions of the rubber-matrix interface do not directly influence fracture tou ghness, instead, it was found that the nanoscale interactions could be used to control the blend morphology which has a dramatic effect on t oughness. (C) 1995 John Wiley & Sons, Inc.