Preparation Of Nanosize Silica And Its Composite Polymer Emulsion

In this paper, nanosize silica were prepared via reverse microemulsion and elemental silicon methods. The surface of nanosize silica was modified by silane coupling agent. Then using modified nanosize silica prepared by elemental silicon method as seed, nano-SiO2/polymer composite emulsion was synthesized. First, monodisperse nanosize silica particles was synthesized by hydrolysis and condensation reaction of tetraethoxysilane(TEOS) in a polyoxyethylene nonylphenyl ether(NP-5)/cyclohexane/ammonium hydroxide reverse microemulsion system. The effects of reaction time, concentration of TEOS and concentration of ammonium hydroxide on mass fraction and particle size of nanosize silica in product were studied. The surface modification of produced nanosize silica was performed by silane coupling agent, methacryloxypropyltrimethoxysilane (KH-570), which improved the compatibility between nanosize silica and organic phase. Second, nanosize silica was prepared via elemental silicon method. The influences of reaction temperature, purity and dosage of elemental silicon, concentration of NaOH in water and reaction time on yield, size and size distribution of nanosize silica particle were studied. Then the surface of nanosize silica was modified by KH-570 too. Infrared spectrum (IR) confirmed the existence of chemical graft between nanosize silica and the coupling agent KH-570. Finally, using the surface modified nanosize silica as seed, styrene and butyl acrylate as monomers, seeded emulsion polymerization was carried out to synthesize nano-SiO2/polymer composite emulsion. Infrared spectrum (IR) analysis, Ultra-violet absorption analysis, film formation analysis and transmission electron microscope(TEM) were used to characterize the composite emulsion. The results showed that the polymer was chemically grafted onto nanosize silica particles. Shielding effect to ultraviolet radiation and mechanical properties of the film formed by the composite emulsion were improved due to the existence of nanosize silica.