Modification Of Nano SiO₂ And Properties Of SiO₂/silicone Rubber Composites

Silicone rubber has a widely used because of their odorless,non-toxic,excellent stability,low shrinkage,high transparency,electrical insulation,etc.However,the unreinforced silicone rubber has low mechanical properties,which seriously limits its scope of use.Fumed nano SiO₂is often used as a reinforcing material because of its superior stability,reinforcement,large specific surface area and industrialized production.However,a lots of silanol groups?Si-OH?contain in their surface.These Si-OH groups are easy to adsorb moisture in the air and forming agglomeration.Since the room temperature vulcanized liquid silicone rubber has no mixing process,the nano SiO₂ is difficult to be uniformly dispersed in the silicone rubber matrix.As a result,its transparency and mechanical properties are weakened.The aim of this paper is to synthesize a kind of liquid silicone rubber?room temperature vulcanized silicone rubber?,which can be reinforced by industrialized fumed nano SiO₂.Therefore,a nano SiO₂/silicone rubber composite with good mechanical properties and transparency was prepared,and the feasibility of the composites prepared in packaging materials was discussed.The paper carried out the following research work:?1?First,a kind of two-component room temperature vulcanized liquid silicone rubber was designed and prepared.The liquid silicone rubber with good transparency,high fluidity before molding and good mechanical properties after molding was obtained.Through Study on the types,addition amounts of raw material and reaction conditions for liquid silicone rubber and optimized process.?2?The double precursor surface modifier was designed to modify the nano SiO₂,and the chemical structure and morphology of nano SiO₂ before and after modification were tested by fourier transform infrared spectroscopy,transmission electron microscopy and video contact angle measuring instrument.The results showed that the surface of nano SiO₂ was grafted with silane coupling agent and hydroxy silicone oil after modification,and the structure did not change significantly.The hydrophobic properties of SiO₂ particles are significantly increased which laying the foundation for effective dispersion in silicone rubber.?3?The modified nano SiO₂ are combined with the liquid silicone rubber to prepare a composite material.The cross-sectional morphology and thermodynamic properties of nanoSiO₂/silicone rubber composites were analyzed by SEM,universal material testing machine and TG.The results show that the modified nano SiO₂ has good dispersibility in the silicone rubber matrix and has a good reinforcing effect on the silicone rubber.Compared with the unreinforced liquid silicone rubber,the silicone rubber composite with 5 wt%modified SiO₂ has a mechanical strength increased by about 180%and an elongation at break increased by about160%.Compared with the composite materials prepared by the same amount of unmodified nano SiO₂,the mechanical strength is increased by about 165%,and the elongation at break is increased by about 150%.The results shows that the modified nano SiO₂ has a greater reinforcing effect on liquid silicone rubber.?4?The application of the prepared modified nano SiO₂/silicone rubber in the field of packaging was discussed.To this end,a tackifier was designed to improve the bonding properties of the modified nano SiO₂/silicone rubber composite.The results show that the tackifier significantly improves the bonding strength of liquid silicone rubber.Adding proper content of modified nano SiO₂ can effectively improve the mechanical properties of liquid silicone rubber and further improve the bonding performance under the premise of ensuring the transparency of the composite.The experiment shows that the bond shear strength is 1.12 MPa,which meets some commercial product standards.