Preparation of submicron SiO₂ PMMA GMA composite particles and their modification for epoxy

Based on the sol-gel method, the submicron SiO₂ particles with the polymerizable group on the surface were prepared.The SiO₂-poly(methyl methacrylate)(PMMA)-glycidyl methacrylate (GMA) composite particles with the core-shell structure were successfully prepared by emulsion polymerization on the surface of SiO₂, the structure of the composite particles was characterized by TEM, FTIR and TGA.In succession, the SiO₂-PMMA-GMA/epoxy composite materials were prepared and SEM was used to observe the fracture morphology, then the toughness mechanism of composite particles to epoxy was also put forward.The results indicate that SiO₂ is the core in the composite particles with about 180 nm diameter, the surface of SiO₂ is encapsulated by PMMA-GMA polymer with about 20 nm thickness.The mass ratio of PMMA-GMA polymer to original SiO₂ is 87.4%, the grafting ratio of PMMA-GMA polymer to original SiO₂ and effective grafting ratio of PMMA-GMA polymer are 77.0% and 88.1%, respectively.The impact strength of epoxy after curing increases to 42.0 kJ/m² from 19.2 kJ/m² when the content of the SiO₂-PMMA-GMA composite particles is 4wt% in the epoxy matrix.