Preparation And Properties Of Phosphorus-nitrogen-silicon Hybrid Acrylate Flame Retardant Polymers

Most organic polymer materials are highly combustible,and the large amounts of smoke,toxic gases,heat and molten droplets produced during combustion cause immeasurable damage to human life and property each year.Although traditional flame retardant methods have achieved some satisfactory results,their application has encountered more and more difficulties with the increasing requirements of high flame retardant efficiency,strong persistence,low heat,smoke and toxic gas release.In this paper,three kinds of acrylate monomers modified with phosphorus-nitrogen-silicon flame retardant elements were designed and synthesized.By free radical chain polymerization,phosphorus-nitrogen-silicon hybrid flame retardant polymers with different polymer chain structures were prepared.The mechanical properties,thermal stability and combustion properties of the polymers were studied.At the same time,the flame retardant mechanism of polymer was explored.Specific research contents are as follows.1.Hydroxyethyl methacrylate（HEMA）and hexachlorocyclotriphosphazene（HCCP）were used as raw materials to synthesize ethyl hexamethacrylate etherized cyclotriphosphazene（EHEC）.Dimethacrylate ethyl oxy diphenyl silane（EDDSi）was synthesized from HEMA and diphenyl dichlorosilane（DPDSi）.Then,using azodiisobutyl（AIBN）as an initiator,EHEC and EDDSi were polymerized through free radical chain polymerization to synthesize the phospho-nitro-silicon hybrid acrylate binary flame retardant copolymer（P-N-SiHD）.The results show that when the mass ratio of EHEC:EDDSi is 1:1 and the initiator is 1%,the swelling degree of P-N-SiHD copolymer is 228.78%,the glass transition temperature（Tg）is 67.41℃,the breaking strength is 6.55 MPa,and the elongation at break is 19.17%.Initial decomposition temperature(T_5%)is 171.59℃,maximum combustion rate temperature(T_max)is 416.73℃,peak heat release（HRR）is 145.73 W/g,total heat release（THR）is 18.16 k J/g,combustion residual rate is 11.07%,LOI is 23.5%,V-2 level.When EHEC:EDDSi=2:1 and initiator is 3%,the swelling degree of P-N-SiHD is 206.06%,Tg is 60.63℃,breaking strength is 0.86 MPa,elongation at break is37.18%,T_5%is 205.41℃,T_max is 422.72℃,and combustion residual rate is 20.84%.HRR of126.05 W/g,THR of 18.74 k J/g,LOI of 27.2%,V-1 class.The types and proportions of monomers and the amount of initiator affect the mechanical properties,thermal stability and combustion properties of copolymers.With the increase of flame retardancy of P-N-SiHD,the mechanical properties decrease sharply,but the flame retardancy improvement is not obvious.2.Using HEMA and dichlorophenyl phosphate（PDCP）as raw materials,the monomer of ethyl dimethacrylate-phenyl phosphate（EDPP）was synthesized,and EHEC was used as a binary copolymer monomer system,and AIBN was used as an initiator to prepare high phosphorus-containing hybrid acrylate binary flame retardant copolymers（HDHPC）through free radical chain polymerization.The results showed that the cross-linking structure,mechanical properties,thermal stability(T_5%)and combustion properties of the polymer were affected by the monomer type,dosage and initiator dosage.When the mass ratio of EHEC:EDPP was 1:1 and the initiator was 1%,the swelling degree of HDHPC was 242.42%and Tg was 59.77℃.The fracture strength is 5.01 MPa,elongation at break is 43.5%,T_5%is208.38℃,combustion residual rate is 26.4%,HRR is 77.57 W/g,THR is 14.66 k J/g,LOI is24.4%,V-2 level.When the mass ratio of EHEC:EDPP was 2:1 and the initiator was 3%,the swelling degree of HDHPC was 170.76%,Tg was 59.63℃,breaking strength was 4.47 MPa,elongation at break was 43.51%,T_5%was 238.76℃,combustion residue rate was 27.9%,and HRR was 181.95 W/g.THR is 24.74 k J/g,LOI is 27.5%,V-1 class.The flame retardant mechanism of HDHPC copolymer is mainly condensed phase flame retardant.3.Phosphorus-nitrogen-silicon hybrid acrylate ternary flame retardant copolymer（P-N-SiHT）was synthesized by free radical chain polymerization using EHEC,EDDSi and EDPP as ternary copolymers and AIBN as initiator.The results show that when the mass ratio of EHEC:EDPP:EDDSi is 1:1:1 and the initiator is 1%,the swelling degree of P-N-SiHT is112.50%,Tg is 61.20℃,the breaking strength is 36.19 MPa,the elongation at break is 7.41%,and the impact energy is 135.87 J/m³.T_5%is 213.33℃,T_max is 421.03℃,HRR is 137.90 W/g,THR is 21.73 k J/g,combustion residual rate is 23.51%,LOI is 27.1%,V-1 level;When the mass ratio of EHEC:EDPP:EDDSi is 1:2:1 and the initiator is 1%,the swelling degree of P-N-SiHT is 180.00%,Tg is 64.50℃,breaking strength is 22.17 MPa,elongation at break is 5.53%,impact energy is 61.00 J/m³,T_5%is 220.59℃.T_max is 421.04℃,HRR is 155.69 W/g,THR is17.78 k J/g,combustion residual rate is 24.82%,LOI is 22.5%,V-2 grade.The type and amount of monomer affect the crosslinking structure,mechanical properties,thermal stability and flame retardant properties of terpolymer.The mechanical properties,thermal stability and combustion properties of terpolymer have comprehensive improvement advantages over those of binary copolymer.