Preparation Of Silicon-phosphorus Flame Retardants And Their Applications In Flame Retardant Silicone Rubber

Room temperature vulcanized(RTV)silicone rubber has excellent biocompatibility,thermal stability,chemical resistance,low toxicity,and electrical properties,etc.Based on these unique properties,RTV silicone rubber has been widely used in various fields such as sealant,adhesives,coating,aerospace,electrical appliances.Although RTV silicone rubber has good high temperature performance,but RTV silicone rubber is considerably flammable,it can be ignited at low temperatures.Hence,it is essential to improve the flame retardancy of the RTV silicone rubber to meet the requirements for application.At present,various flame retardants such as aluminum hydroxide,magnesium hydroxide,montmorillonite,ammonium polyphosphate,melamine phosphate(MP)and expandable graphite have been used in RTV silicone rubber to improve its flame retardant properties.However,with the addition of these flame retardants,the mechanical properties of RTV silicone rubber significantly decreased.Mechanical properties greatly influence the performance of RTV silicone rubber.Therefore,the purpose of this paper is to prepare of a new type of flame retardant,which can improve the mechanical properties and flammability properties of the RTV silicone rubber simultaneously.The main contents include:1.One kind of silicon-phosphorus flame retardant(SPTES)with cross-linking effect was successfully synthesized with SPDPC and APTES.The effect of APTES on the mechanical properties and flame retardancy of RTV silicone rubber were studied.The results showed that the addition of PNTT can effectively improve the mechanical properties and flammability properties of the RTV silicone rubber simultaneously.It effectively solved the problem of the mechanical properties damages that originate from the traditional flame retardant.2.On the basis of the above method,a HCCP modified silicon-phosphorus flame retardant(PNTT)was prepared by the reaction of HCCP and APTES.The structure and properties of the PNTT were characterized by FT-IR,nuclear magnetic resonance(NMR)and thermogravimetric analysis(TG).Then PNTT was introduced into the silicone rubber system through cross-linking effect,a series of novel RTV flame-retardant silicone rubber were prepared.The structure change of novel RTV silicone rubber was studied by ATR-IR,the compatibility and dispersibility of PNTT in RTV silicone rubber were studied by SEM.The results showed that the PNTT were chemically bonded into PDMS polymer matrix successfully and PNTT has good compatibility with PDMS matrix and well-distributed in the silicone rubber.And the effect of PNTT on the thermal stability properties,mechanical properties and flammability properties of novel RTV silicone rubbers were studied by TG-IR analysis,universal tensile machine,shore A hardness test,swelling and extraction experiment,limiting oxygen index instrument and UL-94 test.The results show that when the dosage of PNTT reaches 25 phr,the limiting oxygen index increased from 20.8 to 23.9,the flame retardant grade from F to V-2.In addition,the flame retardant mechanism of PNTT in RTV silicone rabber was also studied.3.The effect of ATH and PNTT synergistic flame retardant on the flame retardancy and mechanical properties of RTV silicone rubber was studied by using ATH as synergistic flame retardant.The results showed that the flame retardancy of RTV silicone rubber was improved obviously when the ATH and PNTT were used together.When the dosage of ATH reached 20-30 phr,PNTT dosage of 30 phr,RTV silicone rubber has good flame retardant properties and mechanical properties.When the dosage of ATH was 30 phr,the comprehensive performance was the best,the tensile strength only decreased from 1.87 MPa to 1.82 MPa,the limit oxygen index raised from 24.0 to 36.3,and the flame retardant level raised from F to V-0.