Study On The Flame Retardant Effects Of Ammonium Polyphosphate And Its Compounds With Inorganic Particles On Silicone Rubber

Silicone rubber is a type of essential and indispensable polymer in the national economy,due to its superior performances in bio-inert,weather ability,extreme temperature resistance,electrical insulation,ageing resistance and so on.It has been widely applied in many fields,such as food service industry,transportation,medical service,aerospace,electronic equipment,wire and cable.The fundamental structure of SR is the-Si-O-chain segment.Generally,it has good thermal stability and belongs to flame retardant material by the oxygen index as the evaluation standard.However,SR is prone to smoldering.Once being ignited,it rapidly turns into a constantly burning flame,and releases a large amount of heat.The combustibility of SR restricts its application in several areas.Due to these extreme requirements of SR,it is of great urgence to develop the novel flame retardancy SR and improve its flame resistance property.Ammonium polyphosphate(APP)is a kind of highly effective halogen-free flame retardant and has the characteristics of high nitrogen and phosphorus content,good flame retardant effect,high decomposition temperature and so on.It has the dual function of acid source and gas source in typical non halogen intumescent flame retardant.In recent years,it has become one of the hotspots in the field of flame retardant.Firstly,to study the effects of modification method on the flame retardancy and mechanical property for silicone rubber,APP modified by coupling agent(A-171)and mechanical milling separately,were incorporated in silicone rubber to prepare flame retardant silicone rubber composite(FRSR)by mechanical blending process and compared with the sample filled with unmodified APP.The interaction between APP and SR is fairly strong and the FRSR has the best flame retardant properties after modified by mechanical milling,but there is a slight agglomeration among APP.The compatibility between APP and SR becomes better and the FRSR has the best mechanical properties after modified by A-171?All FRSR samples have good flame retardant properties when the content of APP is larger than 20 phr.Then,to study the effects of different morphologies of inorganic particles on the flame retardancy and mechanical property for SR,acicular wollastonite(WS),tubular halloysite(HNTs),layered ?-Zirconium Phosphate(?-ZrP),modified by coupling agent,were selected to incorporate in silicone rubber together with APP to prepare FRSR by mechanical blending process.It has been comfirmed that OWS,OHNTs and OZrP are dispersed well in FRSR matrix as their original geometrical shape.When the content of inorganic particles and APP was 25 phr,the FRSR incorporated with 1phr OHNTs has higher mechanical property(tensile strength 8.8MPa,elongation at break 218.6%)compared that of FRSR incorporated with OWS and OZrP,the FRSR incorporated with 1phr OZrP has best thermal stability and flame retardancy(LOI value 32.3%,UL-94 V-0,T5% 312.9 ?C)compared that of FRSR incorporated with OWS and OHNTs.Among them,the barrier effect of lamellar OZrP was the best,and the surface of the residue was the most complete and stable,which can significantly reduce the smoke release rate and heat release rate.Finally,a novel functionalized ?-Zirconium Phosphate(F-ZrP)was synthesized by phosphazene derivative via in-situ intercalation reaction and the FRSR were prepared via incorporation of F-ZrP and APP with silicone rubber by mechanical blending process.It is found that the interlayer spacing of F-ZrP is larger compared with that of ?-ZrP and phosphazene derivative efficiently combined with ?-ZrP.What's more,F-ZrP existed with a structure of the intercalated components in FRSR.When the total content of the flame retardants was 20 phr and the mass ratio of F-ZrP to APP was 1:19,the LOI value of FRSR was increased from 30.0% to 31.4%,the UL-94 rating was enhanced to V-0 and the peak heat release rate was 265.3kW/m2.The results also suggested that the combination of F-ZrP and APP could make the char residue more stable,compact,and continuous,delaying the volatilization of decomposition product and inhibiting underlying FRSR from contacting heat and oxyen.All results indicated that there was a synergistic flame retardancy effect in gas phase and condensed phase between F-ZrP and APP for FRSR.