Investigation On Silica Grafted Polymer And Its Application

Nowadays, silica particles as reinforcing fillers are widely applied in many fields such as plastic, rubber, coating and so on, because of its excellent properties.Particularly, grafting functional polymer brush on the surface of silica particles can give silica particles more functional properties, which makes silica particles not only have the properties of inorganic particles with high strength and high resistance, but also have the flexibility of polymer brushes. So in this paper, we firstly adopts the atom transfer radical polymerization to graft two kinds of different polymers on the surface of silica particles respectively, then the silica particles grafted polymer brushes as fillers were added to the polyurethane foam and silicone rubber to prepare composite materials and study the influence of fillers on the performance of the composite materials. The results showed that:(1)3-triethoxysilylpropylamine and 2-bromoisobutyryi bromide were used gradually to modify the surface of silica and these process made silica graft the initiators which can induce atom transfer radical polymerization(ATRP) polymerization to occur on the surface of silica particles. Modified silica used as initiator to trigger monomer poly(ethylene glycol) methyl ether methacrylate(PEGMA) and methyl methacrylate(PMMA) to occur polymerization reaction on the surface of silica, then the hybrid particles including SiO2-g-P(PEGMA) and SiO2-g-PMMA were prepared respectively.The structure and morphology of ATRP initiators and grafting polymers on the surface of silica were analyzed and characterized using infrared(FTIR), X-ray photoelectron spectroscopy(XPS), thermal analysis(TGA) and the projection electron microscope(TEM). The results showed that ATRP initiators were successfully grafted on the surface of silica and its grafting density was 9.1 Br/nm2, and the tests also revealed the polymers including P(PEGMA) and PMMA were successfully grafted on the surface of silica. In addition the monomer PEGMA was polymerized respectively by ATRP method on the surface in different reaction conditions including different concentration of catalyst,ligand concentration, reaction time and concentration of monomer PEGMA.We discussed the effect of catalyst concentration, ligand concentration, reaction timeand concentration of monomer PEGMA on the amount of grafting polymer on the silica surface, and we concluded that the best reaction condition was: nmonomer:n Si O2-Br:nPMDETA:nCuBr: nCuBr2=100:1:1:1:0.2,the reaction time of 9 h.(2)The different amount of unmodified silica and silica grafted P(PEGMA)polymer as fillers, added to polyurethane foam to prepare composite materials, and explored the effect of silica grafting before and after and the different filler content on the pore morphology, thermal properties and compression performance of polyurethane foam. The experimental results showed when the filler content of SiO2-g-P(PEGMA)particles is 1 wt %, contrasted to polyurethane foam filled with unmodified silica particles,the average pore diameter of polyurethane foam filled with SiO2-g-P(PEGMA)particles decreased 81 um, and energy storage modulus of polyurethane foam increased by 53.9%, and compression strength increased by 7.9%.(3)The different amount of unmodified silica and silica grafted PMMA polymer as fillers, added to silicone rubber matrix to prepare composite materials, and researched the effect of silica grafting before and after and the different filler content on the dispersion of fillers, vulcanizing properties and mechanical properties of silicone rubber composite materials. The experimental results showed when the filler content of SiO2-g-PMMA was 10 wt%, contrasted to silicon rubber filled with unmodified silica particles, the shear modulus of silicon rubber filled with SiO2-g-PMMA particles before vulcanization increased by 15.6%, and loss modulus increased by 30.5%, and liquid viscosity increased increased 1.24 times; After vulcanization, the storage modulus of silicon rubber increased by 20.9%, and the torque increased by 19.7%, and the tensile elongation at break increased by 71.3%. These proved the PMMA chain on the surfac of silica paricles involved in the vulcanization reaction of silicon rubber. The PMMA chains tangle with silicon rubber molecular chains, which increased the crosslinking degree of silicon rubber.