Study On The Influence Of SiO₂ On Suspension Polymerization Of PMMA And The Properties Of The Composites

Since the introduction of suspension polymerization product of poly(methyl methacrylate) (PMMA)as a denture base material, it has suffered from having relatively poor mechanical properties. So many methods of improving its strength have been investigated. Nano-SiO₂ has been widely used as fillers to enhance the mechanical properties of polymers. However, until now, Polymer/ SiO₂ prepared via suspension polymerization. has not been reported.In this paper, PMMA/SiO₂ nanocomposites were prepared via in situ suspension polymerization. The surfaces of nano-SiO₂ need to be modified to make it homogeneous disperse in the monomer MMA. Four types of modifier such as KH570, A151, CT201, and lauryl alcohol were used to modify nano-SiO₂. Then with the aid of coupler (A151, KH570) on the surface of nano-SiO₂, PMMA molecular chains were grafted onto the surface of nano-SiO₂ through in-situ solution polymerization of MMA monomer and gained compound nano particles encapsulated by polymers. The modified nano-SiO₂ was characterized with Fourier transform infrared spectroscopy (FI-IR), thermal gravimetric analysis (TGA), sedimentation experiment, transmission electron microscopy (TEM). It was shown that nano-SiO₂ had been well modified and had better dispersion in MMA.The microstructure of nanocomposites was characterized with TEM, FT-IR. The influence of different reaction conditions on molecular weight of PMMA, the particle shape and size, and the mechanical and thermal properties of the composites were investigated.The results indicate that, PMMA/SiO₂ nanocomposites with modified SiO₂ could be successfully prepared via suspension polymerization. The presence of SiO₂ and the content influenced the molecular weight of PMMA and the shape and size of composite particles. Well modified SiO₂ could improve mechanical properties to a large degree and improve the thermal properties. It has been found that grafting polymer is an effective way to modify the surface of nano particle for the purpose of in situ suspension polymerization.