Plastic and fracture behavior of nanosilica-filled poly(methyl methacrylate)

The plastic and fracture behavior of 'model' hybrid materials based on methyl methacrylate and methacryloxypropyl-grafted nanosilica was investigated. A four-step synthesis procedure allowed preparation of transparent nanosifica-poly(methyl methacrylate) networks of well-defined architecture, of variable particle diameter, volume fraction of particles, number of methacryloyl units grafted per surface unit of silica particles and nature of the grafting agent. Plasticity behavior was investigated through compression tests. The evolution of yield stress with volume fraction of fillers can be understood by taking into account the undeformability of particles and using the geometrical Kerner approach. The reduction of plastic flow plateau by a substantial strain hardening was imputed to the presence of crosslinks on the particles. Fracture properties were deduced from three-point bending experiments on notched samples. The effects on toughness of filler incorporation are tentatively related to plasticity and to the presence of crosslinks. (c) 2006 Society of Chemical Industry.