Study On Flame Retardant And Smoke Suppression Of Silicone Rubber Foam Containing Modified Expandable Graphite/Fe₂O₃

Silicone rubber foam(SRF)has been widely used because it combines the excellent properties of silicone rubber material and foam material.However,due to the flammability of its side chain and the bubble structure formed inside,a large amount of smoke will be generated in the event of fire,threatening the health and safety of personnel.Therefore,it must be treated with fire retardant and smoke suppression.Expandable graphite(GIC)is a kind of flame retardant which combines carbon source and gas source.It is cheap and green,and has been applied in many polymer foam materials.However,the "worm" carbon layer formed by GIC when used alone is sparse and loose,which cannot play a good flame retardant and smoke suppression effect.Zinc borate(ZB)has the advantages of smoke suppression,non-toxicity and promotion of carbon formation.It has a good flame retardant and smoke suppression effect in silicone rubber materials,and has an excellent synergistic flame retardant and smoke suppression effect when combined with the expansion flame retardant.Fe2O3 has strong synergistic effect and has shown good flame retardancy and smoke suppression ability in other polymer materials,but it has not been applied in SRF materials.Therefore,in order to improve the flame retardancy and smoke suppression performance of SRF,this study adopts graphite intercalation technology to introduce ZB into GIC layers to form a new flame retardancy modified expandable graphite(ZB-GIC),and uses the molten liquid formed under high temperature of ZB to fill the gap formed after GIC expansion to strengthen the carbon layer,so as to improve the flame retardancy and smoke suppression performance of GIC.The effect of ZB-GIC/Fe2O3 on SRF flame retardancy and smoke suppression was systematically studied by using various test methods,and the mechanism of flame retardancy and smoke suppression was revealed.The main innovative achievements are as follows:(1)ZB was introduced into GIC layers by graphite intercalation technology to form a new flame retardant ZB-GIC.SEM,XRD,laser particle size analysis and FTIR test show that the interlayer distance of ZB-GIC was obviously increased from 2.931 ? to 2.972?,and the particle size was obviously larger.The new peak positions correspond to ZB and phosphoric acid,which proved that ZB-GIC had been successfully prepared.(2)Flame retardant and smoke suppression performance and mechanical performance of GIC/SRF and ZB-GIC/SRF were studied by horizontal and vertical combustion test(UL-94),oxygen index test,conical calorimeter and universal tensile testing machine.The results showed that ZB-GIC was better than GIC in flame retardancy and smoke suppression of SRF materials.The flame retardance and smoke suppression performance of 5%ZB-GIC/SRF was the best,reaching UL-94 V0 rating,and the limiting oxygen index(LOI)increased to 42.6%,and the heat release rate(HRR),total heat release rate(THR),smoke release rate(SPR)and total smoke release rate(TSP)decreased obviously.ZB-GIC and GIC weaken the tensile properties of SRF to a certain extent,but ZB-GIC can improve the compressive strength of materials to a greater extent than GIC.(3)Flame retardant and smoke suppression performance and mechanical performance of Fe2O3/SRF and ZB-GIC/Fe2O3/SRF were studied by UL-94,LOI test,cone calorimeter and universal tensile testing machine.The results showed that Fe2O3 alone has good smoke suppression performance,but poor flame retardant effect,5%Fe2O3/SRF has the best comprehensive performance.When combined with 5%ZB-GIC/5%Fe2O3/SRF,the flame retardance and smoke suppression effect of 5%ZB-GIC/5%Fe2O3/SRF was the best,reaching UL-94 V0 rating,LOI value was 44.2%,peak heat release rate(PkHRR)decreased 67.42%,THR decreased 89.55%.The peak emission rate(PSPR)and TSP decreased by 76.86%and 91.81%respectively,which also had certain inhibition effect on CO and CO2.When the total compound content was less than 10%,the tensile properties of SRF materials were almost not affected,and the compressive strength of SRF materials could be slightly improved.(4)The macro-morphology and micro-morphology of carbon slags were analyzed by digital camera and SEM,and the thermal stability and pyrolysis products of SRF,5%ZB-GIC/SRF,5%Fe2O3/SRF and 5%ZB-GIC/5%Fe2O3/SRF were studied by thermogravimetric analysis(TGA)and thermogravimetric-fourier infrared spectroscopy(TG-FTIR).The results showed that the carbon residue of SRF could be made denser and more compact by the combination of the two,which could delay the decomposition temperature better and greatly improved the thermal stability of SRF materials.ZB-GIC/Fe2O3 mainly played the role of flame retardant and smoke suppression in condensed phase,and the high-strength carbon layer formed by the combination of ZB-GIC and Fe2O3 had the functions of heat insulation and oxygen isolation,and could prevent the smoke and heat generated by combustion from escaping.In addition,in the gas phase,the combination of the them would release more non-combustible gas and reduce the concentration of combustible gas in SRF matrix,thus achieving excellent flame retardant and smoke suppression effect.