Study On Synthesis And Surface Functionalization Of Colloidal Silica With High Performance In Silicone Rubber

Silica as one of the fillers is widely used in the reinforcement of siliconerubber. Aiming this contradiction of mechanical properties and creekresistance that silica exhibits, it presents important practical significance todesign and synthesize a kind of silica with high performance. In this paper,silica nanoparticles were synthesized by sol-gel method, based on the siliconresource of tetraethyl orthosilicate(TEOS). And this study involves preparingconditions for silica sol, effects of in-situ and ex-situ modification on surfacearea of silica, modified conditions for silica by VTES(A-151) and effects ofvinyl-functionalized silica on curing behavior and mechanical properties.The structures and properties were characterized using laser particlesize analyzer, surface area and pore size analyzer, X-ray diffraction(XRD),fourier transform infrared spectroscopy(FTIR), TGA/DSC simultaneousthermal analyzer(TGA/DSC), field emission scanning electron microscope(FESEM), transmission electron microscope(TEM). The results show that,preparing conditions for silica sol: concentration of ammonia0.5M,preparing temperature50oC, stirring speed1730rpm, drop rate of TEOS2.0mL/min. Compared with ex-situ modification, in-situ modification is betterfor preparation of silica with high surface area. Vinyl group is successfullygrafted to the silica surface and the conditions for graft: the amount of VTES5mL, the amount of hydrochloric acid(0.5M)5mL, stirring speed1730rpm,modifying temperature50oC.Dynamic mechanical thermal analyzer(DMTA) and differential scanningcalorimeter(DSC) were carried out to study the effects of vinyl-grafted silicaon curing behavior and mechanical properties. The results show that, Vinylgroup on the silica surface participate in the cross-linking reaction during thecuring process of silicone rubber, which increases the interaction betweensilica and silicone rubber. Introduce of vinyl-functionalized silica on siliconerubber can improve the reaction rate on the first stage of reaction, thecorresponding curing temperature is120oC and the value of rate constantwas0.527.120oC as the curing temperature is appropriate. For silicone rubber containing VTES-modified silica, the normal force is309g, thenormal stress is2.12MPa, the elongation at break is184.8%.DTMA was used to test the curing behavior and mechanical propertiesof silicone rubbers containing10-undecen-1-ol-modified silica and1-undecanol-modified silica, respectively. The results show that, carbonchain length of modifier is increased appropriatly, which is beneficial to thereinforcement of silicone rubber.10-undecen-1-ol-modified silica presentsphysico-chemical synergistic reinforcement effect on silicone rubber. Forsilicone rubber containing10-undecen-1-ol-modified silica, the normal forceis324g, the normal stress is2.34MPa, the elongation at break is256.8%.The creek resistance of vulcanized silicone rubber is enhanced due to vinylgrafted to the silica surface.