Preparation Of Mullite Fiber/inorganic Powder Filled Silicone Rubber Composites And Research On Fire And Shock Resistance

As a new fire prevention material,a hard ceramic layer can be formed by silicon rubber composites in the case of open fire or high temperature burning to play a good fire prevention role.The hard ceramic layer can be got by adding some certain amount of ceramic filler into the ordinary ceramic silicone rubber composites.However,some special materials,such as sealing materials for aircraft nacelles,not only need to meet their good fire resistance and sealing performance,but also need to have good anti-vibration performance.And it is difficult to form a good ceramic layer for the general ceramic fireproof silicone rubber composites under the influence of vibration field.In this article,mullite fiber(MF),glass bead(GB),refractory reinforcing filler(CaCO₃),silane coupling agent(KH570)modified MF and different softening point glass powders were added in the silicone rubber to prepare ceramic silicone rubber composites,and their effects on the fire-resistant performance under vibration of silicone rubber composites were systematically studied.The main contents are as follows:(1)The effects of MF and GB on the properties of silicone rubber composites were studied.The fire resistance of silicone rubber composites was significantly improved by filling with MF and GB.The fire resistance rating reached FV-0 level,the limit oxygen index reached 34.8%,and the composites could still meet the fire resistance and seismic performance requirements under the condition of 1050? flame,50 Hz frequency and 5 g horizontal acceleration for 15 min.However,its mechanical properties were greatly reduced.In addition,although the mechanical properties of the material was improved by modifying MF with KH570,the fire resistance,fire resistance and limiting oxygen index of the composites were reduced.Filling with CaCO₃ can not only improved the mechanical properties of the composites,but also kept the composites with relatively good fire resistance,and reduce the heat release rate and the total heat release amount of the material.(2)The effects of MF,GB and CaCO₃ contents on the fire resistance and seismic performance of silicone rubber composites were studied.Ceramic properties and the strength of ceramic layer were improved by filling with MF.The fire resistance of the composites increased obviously with the increase of MF.When the amount of MF was added to be 28 phr,the composites met the requirements of fire resistance performance,and the thickness of the ceramic layer gradually increased with the increase of MF.The limiting oxygen index and fire retardant rating of the composites could be improved by adding GB.With the increase of GB content,the flame retardant and fire retardant performance of the composites were gradually improved,the thermal conductivity of the composites was decreased,and the heat resistance was enhanced.CaCO₃ improved the mechanical properties of the composites,significantly reduced the linear ablation rate of the composites,and enhanced the bending strength of the composites.(3)The ceramization mechanism of silicone rubber composites was explored.At the beginning of the combustion vibration,the protective effect layer was provided by MF for generating internal ceramic.After a certain temperature and time,the other ceramic layer within it was formed,and the external ceramic layer was shaken off.The newly formed ceramic layer was strong enough to support the composites to withstand vibration and high temperature shock,the thickness of it increased gradually as time goes on.As a fluxing agent,GB bonded the residue of vibration combustion of silicone rubber composites to enhance the strength of ceramic layer through the function of"liquid bridge".As a precursor of silicate,CaCO₃ began to decompose at 600? and absorb heat to improve the refractory performance of the composites.The Ca O generated by its decomposition reacted with SiO₂ to generate calcium silicate,thus enhanced the ceramic strength of the composites.(4)The influence of glass powder(GB)with different softening points and the effects of GB on the fire resistance and seismic performance of silicone rubber composites were studied.In the process of combustion vibration,the lower softening point glass powder led to composites decomposition in advance,and reduced the refractory performance.However the intensity of the generated ceramic was relatively high.High melting point glass powder had good fireproof performance,but its ceramic strength dropped,in addition,the composites was burned through under the action of vibration force field and impact flame in the process of vibration combustion.Excellent fire resistance and fire resistance and seismic performance were obtained by adding GB.Therefore,compare with the glass powder in different softening points,GB had relatively good heat resistance and fire resistance and seismic performance.