Synthesis Of Macromolecular Phosphorus-silicon Containing Flame Retardant And Research Of Flame Retardant Silicone Rubber

Silicone rubber has widely used in transportation,electronics,biomedical and other industries for its excellent properties such as high and low temperature resistance,weather resistance,electrical insulation and physiological inertia.It is necessary to give silicone rubber excellent fire safety properties due to its flammability and flocculent substances were produced during combustion.Phosphorus-containing flame retardants have a good flame retardant effect on polymer materials.Additive flame retardants reduces the mechanical properties of polymers because of the compatibility with polymers.Therefore,it is of great significance and application value to design and develop phosphorus-containing flame retardants with good compatibility with silicone rubber and endow flame retardant silicone rubber with excellent comprehensive properties.Therefore,it has great significance and application value to endow flame retardant silicone rubber with excellent comprehensive properties through the design and development of phosphorus-containing flame retardants with good compatibility with silicone rubber.In this paper,a flame retardant additive poly 10(2-dihydro-9-oxa-10-phosphaphenanth rene-10-oxide siloxane)(DOPO-VMDS)was synthesized from 9,10-dihydro-9-oxa-10-phosphaphe nanthr-10-oxide(DOPO)and vinylmethyldimethoxy silane(VMDS)and its structure was characterized.DOPO-VMDS was added to room temperature vulcanized silicone rubber(RTV),The sample passed the UL-94 V-0 in the vertical combustion test.tensile strength reached 1.06 Mpa when the addition amount is 20 wt%.The DOPO-VMDS has good compatibility with the matrix because its similar chain structure with the material that the mechanical properties of the material was kept.The total heat release(THR)of flame retardant materials in cone calorimetry(CONE)decreased from 107.6 MJ/m2 of pure RTV to 74.2 MJ/m2.DOPO-VMDS was compounded with triazine charring agent(CFA)for improving flame retardant efficiency.The sample passed the UL-94 V-0 with the addition of 18 wt%when the mass ratio of DOPO-VMDS and CFA is 2:1.It is usually necessary to add 25%～30%flame retardant to achieve the same flame retardant effect.HRR and THR of RTV/DOPO-VMDS/CFA system has a significant reduction then pure RTV in CONE test.And the production of flocculent substances were inhibited.The addition of CFA promoted hard and dense char layer formd during combustion.The higher phosphorus content in the char layer can increase the density and strength of the char layer and effectively prevent the heat transfer.The phosphazene has the characteristics of high phosphorus content and excellent thermal stability.compared with DOPO.In this paper,KTP-DOPO with phosphazene and phosphaphenanthrene double functional groups,based on cyclotriphosphazene group was designed.TGA test shows that KTP-DOPO has good thermal stability,and the char residue of 800℃ is 34.2%,which meand that the flame retardant had good char forming properties.The FR-RTV passed the UL-94 V-0 with the addition amount of 18 wt%KTP-DOPO,HRR,THR,smoke release rate and total smoke release of the FR-RTV decreased by 46.1,37.6,46.7 and 46.6%.The mechanical test shows that the tensile strength of RTV is increased by 118.1%with the addition of flame retardant.Because the chain end of flame radetand is siloxane groups,which can form a cross-linked network structure in the vulcanization process,which increases the cross-linking density of the material,so the addition of KTP-DOPO can improve the mechanical properties of the material while achieving excellent flame retardant efficiency.