Preparation And Properties Of Halogen-free Flame Retardant Thermally Conductive Room Temperature Vulcanized Silicone Rubber

Since the commercialization of silicone rubber in the 1940s,the development of silicone rubber products has been making continuous progress,and various new products have emerged in an endless stream,which has become an important part of the national economy.Silicone rubber is widely used in the fields of biology,medical treatment,transportation,food hygiene,electronic appliances,etc.due to its excellent biocompatibility,chemical resistance,insulation,weather resistance and other advantages.The main structural unit of the silicone rubber is inorganic-Si-O-,but due to the presence of a large amount of C and H on the side groups of the main chain of the molecule,it is flammable,and it is very prone to smoldering at high temperatures to release a lot of heat in a short time.In addition,like most polymer materials,the thermal conductivity of silicone rubber is quite low.The flammability and low thermal conductivity of silicone rubber limit its further application in many fields or places.In order to broaden its application fields,the research on flame-retardant and thermally conductive silicone rubber has received extra attention.Therefore,following research was carried out in this article:First,a new halogen-free phosphorus-nitrogen flame retardant(HACP)was synthesized in one step method using hexachlorocyclotriphosphazene and acetaminophen as raw materials,and a two-component flame retardant silicone rubber(ALSR/HACP)was prepared using this as a flame retardant,and analyzed it using FT-IR,NMR,TG and other characterization methods;after vertical burner,oxygen index tester and cone calorimeter,thermogravimetric analyzer,Py-GC/MS,SEM,EDS and other tests and characterizations have investigated the flame retardant mechanism.When the content of HACP reaches 30 phr,the flame-retardant silicone rubber passes the UL-94 V-0 rating.In order to further improve the thermal conductivity of flame retardant silicone rubber,phosphazene derivatives are compounded with different thermally conductive fillers such as carbon fiber,multilayer graphene(m-MG)and spherical alumina to prepare flame retardant thermally conductive silicone rubber.The results show that the three thermally conductive fillers can not only significantly improve the thermal conductivity of silicone rubber,but also improve the thermal stability of flame retardant silicone rubber to a certain extent,and all have different degrees of synergistic flame retardant effect.Carbon fiber and spherical alumina can make silicone rubber have a higher thermal decomposition temperature;m-MG has the highest residual carbon rate when silicone rubber burns due to the better barrier effect.When 10 phr m-CFP,m-MG and m-AP are added to silicone rubber alone,the thermal conductivity of silicone rubber increases by 220%,313%and 173%,respectively.In addition,graphene was modified with hexachlorocyclotriphosphazene to prepare cyclophosphazene-modified graphene(FGO),and then FGO and HACP were used to prepare flame retardant thermally conductive silicone rubber.Using FT-IR,TG,vertical combustion test,oxygen index test,cone calorimeter and heat flow thermal conductivity instrument and other characterization and test methods,the preparation process of modified graphene and the flame retardant performance of the compound on silicone rubber were discussed With the effect of thermal conductivity.When 1 phr FGO and 19 phr HACP were added,the vertical combustion of silicone rubber reached V-0 level,the LOI value reached 31.4%,and the peak heat release rate was 222.67 k W/m~2.When 5 phr GO and FGO were added,the thermal conductivity of silicone rubber increased by 306%and 247%,respectively.