Effects of surface modification of fumed silica on interfacial structures and mechanical properties of poly(vinyl chloride) composites

Poly(vinyl chloride) (PVC)-based composites were prepared by blending PVC with nano-SiO2 particles, which were treated with dimethyl dichlorosilane (DMCS), γ-methylacryloxypropyl trimethoxy silane (KH570). The dispersion and interfacial compatibility of nano-SiO2 particles in PVC matrix was characterized by SEM, which indicated that DDS had a better dispersion and compatibility than UTS but worse than KHS. The mechanical properties, processability and effective interfacial interaction of nano-SiO2/PVC composites were studied. The nano-SiO2 particles treated with KH570 or DMCS significantly reinforced and toughened the PVC composites. The maximum impact strength of PVC composites was achieved at a weight ratio of nano-SiO2/PVC:4/100. The tensile yield stress increased with increasing the content of treated inorganic particles. The incorporation of untreated nano-SiO2 particles adversely affected the tensile strength of the composite. Although the equilibrium torques of all nano-SiO2/PVC composites were higher than that of pure PVC, the surface treatments did reduce the equilibrium torque. The interfacial interaction parameter, B, and interfacial immobility parameter, b, calculated respectively from tensile yield stress and loss module of nano-SiO2/PVC composites, were employed to quantitatively characterize the effective interfacial interaction between the nano-SiO2 particles and PVC matrix. It was demonstrated that the nano-SiO2 particles treated with KH570 had stronger effective interface interaction with PVC matrix than those treated with DMCS, which also had stronger effective interface interaction than the untreated nano-SiO2 particles.