Abstract: The two-stage process has been developed to generate the nanometer silica modified by acrylate monomer
(SiO₂-HPA) through surface-modification of silica with vinyl groups. The silica surfaces were treated with excess，4-toluene diisocynate (TDI)，and the residual isocyanate groups were converted into vinyl groups by reaction with hydroxypropylacrylate (HPA). The SiO₂-HPA/PVC nanocomposites were prepared via the melt blending method. The effects of silica content and interfacial property on the mechanical properties were investigated. It is found that the SiO₂-HPA/PVC nanocomposites have higher tensile and impact strength than the nanocomposites filled with unmodified silica or pure PVC，and the strength will achieve their maximum with silica mass fraction of 3%～4%. The interfacial interaction and compatibility between the silica and PVC have been greatly improved resulting in the reinforcing and toughening effects of the surface-modified silica on PVC. In addition，the reinforcing and toughening mechanisms of SiO₂-HPA based nanocomposites were studied in detail .