Preparation And Properties Of UV/Ozone Ageing Resistant Thermoplastic Vulcanizate

With the continuous improvement of the living standards of our residents,people's requirements for food safety are becoming stricter and stricter,therefore the disinfection cabinet industry ushered in a period of rapid development.At present,the combination of "short-wave ultraviolet(UV-C)" and "ozone(O3)" is generally applied in the disinfection cabinets on the market to disinfect food.The combination of the two disinfection methods not only enhances the disinfection effect,but also imposes stringent requirements on the UV resistance and ozone resistance of the sealing strip.Thermoplastic vulcanizates(TPV)is excellent in weather resistance,ozone resistance and heat resistance,and it is one of the ideal materials for manufacturing the sealing strip of the disinfection cabinet,with the advantages of superior processibility,non-toxic and environmental protection.However,when exposed in UV-C radiation and ozone environment for a long time,TPV still encounters severe aging problems,resulting in failure to meet the usage requirements.Therefore,it is important to improve the UV-C aging resistance and ozone aging resistance of TPV.The surface of the nano-TiO2 was modified with silane coupling agent(KH570).FTIR and TGA measurements confirmed the successful grafting of silane coupling agents onto the surface of TiO2 nanoparticles.The loading of KH570 on the surface of nano-TiO2 was approximately 8.04 wt.%.The contact angle and dispersion stability in non-polar organic solvent of nano-TiO2 increased after modification by silane coupling agent.UV-vis spectrum revealed that silane coupling agent modified nano-TiO2 could significantly improve the UV shielding performance of TPV.The effect of silane coupling agent modified nano-TiO2 on UV-C resistance of TPV was evaluated by the change of surface morphology,mechanical properties,gel content and carbonyl index during the ageing test.It was observed that the silane coupling agent modified nano-TiO2 could effectively inhibit the UV-C aging of TPV.N,N'-bis-(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine(HDM,a hindered amine stabilizer),?-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid(AG,a hindered phenolic antioxidant)and 2-mercaptobenzimidazole(MB,a sulfur-containing antioxidant)were added to TPV as stabilizer,respectively.The effects of three stabilizers on the ozone resistance of TPV were investigated by surface morphology,mechanical properties,gel content and carbonyl index.The results showed that HDM,AG and MB played positive roles in reducing the aging effect of ozone on TPV,and MB possessed the best thermal stability and ozone resistance among them.Antioxidant MB was immobilized on the surface of nano-TiO2 through the silane coupling agent KH570,and the nano-TiO2 immobilized antioxidant MB(TiO2-KH570-MB)was prepared.FT-IR,XPS and TGA confirmed the reaction between antioxidant MB and the modified TiO2.The loading amount of MB was approximately 5.19 wt.%.The lipophilic degree and sedimentation test showed that the immobilization of MB onto the surface of nano-TiO2 remarkably increased the lipophilicity of the nanoparticles.The measurement of tensile properties,hardness,Young's modulus and modulus of stress indicated that TiO2-KH570-MB could improve the mechanical properties of TPV.DMA results revealed that TiO2-KH570-MB could increase the storage modulus of TPV and the glass transition temperature of EPDM and PP.The dispersion of TiO2-KH570-MB was better than that of silane coupling agent modified nano-TiO2,and its migration resistance was better than that of antioxidant MB.The effect of TiO2-KH570-MB on the ageing resistance behavior of TPV against UV/O3 were investigated by surface morphology,mechanical properties,gel content and carbonyl index.The results indicated that the anti-aging efficiency against UV/O3 of TiO2-KH570-MB was superior to the corresponding mixture of TiO2-KH570 and MB.TPV/TiO2-KH570-MB performed excellent aging resistance against UV/O3.TiO2-KH570-MB could exert excellent UV shielding performance in TPV matrix,while TiO2-KH570-MB had the function of capturing free radicals and decomposing hydroperoxide,which can prevent photooxidation and ozonation of TPV.