Preparation And Properties Of UV And Ozone Resistant Silicone Rubber For Sealing Strip Of Disinfection Cabinet

With the improvement of human health consciousness,the industry of disinfection equipment is flourishing,and the researches on sealing strips for food contact have been attracting increasing attention.Silicone rubber(SiR)has excellent heat resistance,cold resistance,weather resistance,electrical properties and mechanical properties.With these unique characteristics,it is widely used to manufacture many kinds of rubber products such as composite insulators,gaskets,and sealing materials.However,considering the use in harsh environment of high ozone(O3)concentration and ultraviolet(UV)radiation intensity,there are still a lot of ageing problems for SiR seals to explore,such as the change in physical properties and rubber surface roughness.Therefore,it is of great significance to improve the resistance to UV aging and O3 aging of SiR.The ageing tests for silicone rubber exposed to UV-C radiation,O3 and UV/O3 atmosphere were carried out in the self-made accelerated device.The Fourier transform infrared spectroscopy(FT-IR),surface morphology,tensile strength,Shore A hardness,crosslinking density,X-ray photoelectron spectroscopic analysis(XPS)were recorded,respectively.The results were used to study the anti-ageing properties of SiR.The effect of additives on anti-ageing properties of SiR was also discussed.To improve the resistance to UV radiation,the ageing behavior of silicone rubber incorporated with titanium dioxide nanoparticles(nano-TiO2)was studied under UV-C radiation.It was found that nano-TiO2 was a good ultraviolet light stabilizer during the UV ageing process of SiR and the optimum content of nano-TiO2 was 2 phr.The surface modification of nano-TiO2 by silane coupling agents and the UV-C ageing behavior of SiR incorporated with modified nano-TiO2 were studied under UV-C radiation.The results showed that surface modification of nano-TiO2 with silane coupling agents improved particles dispersion.Besides,it was also confirmed that nano-TiO2 modified KH570 could further improve the anti-ageing property of SiR under UV-C radiation.Based on these results of crosslinking density,FT-IR and XPS,a possible UV ageing mechanism of SiR could be proposed.To improve the resistance to ozone ageing,the hindered amine light stabilizer(HALS)was introduced into the silicone rubber.The results of ageing tests showed that the treated SiR with HALS had better mechanical property.A novel stabilizer of nano-TiO2 immobilized hindered phenolic antioxidant(TiO2-KH550-AG)was prepared and its effect on ageing properties of SiR under ozone condition was studied.The results showed that the tensile strength and elongation at break of the SiR modified with TiO2-KH550-AG were obviously improved and the ozone resistance performance was obviously improved after 1000h ozone aging.Based on these results of crosslinking density,FT-IR and XPS,a possible O3 ageing mechanism of SiR could be proposed.The modified silicone rubber(M-SIR)containing 2phr inorganic ultraviolet light shielding agent(nano-TiO2),0.25phr organic UV absorbent and 0.25phr HALS was prepared.The effect of UV/O3 comprehensive aging on the unmodified silicone rubber(SIR)and M-SIR was studied.The results showed that compared with unmodified SiR,the modified SiR matained better mechanical properties with the increase of UV/O3 aging time.Compound additives could significantly improve the aging resistance of silicone rubber.When the retention ratio of mechanical properties was used as evaluation index,there was a synergistic effect between UV aging and ozone aging.