Preparation And Performance Of Hybrid Benzoxazine And Aerogel Composite

Aiming at the use requirement of the heatshield of space reentry,the ablator materials should be lightweight,low thermal conductivity and low ablator rate.In this dissertation,a low curing temperature and high char yield hybrid benzoxazine was synthesized by liquid silazane and allyl containing benzoxazine.Then,the benzoxazine aerogel was prepared by sol-gel method.Last,a lightweight and low thermal conductive thermal protection material was fabricated by benzoxazine aerogel and carbon felt preform.Both Bisphenol A and Biphenol were react with allylamine and paraformaldehyde to synthesis allyl containing benzoxazine Bala and BPala.The DSC cruve peak of Bala and BPala is 270?.After curing at 250? for 3 hours,the Tg of Bala and BPala is 320?,the char yeld of Bala is 29.24%and the char yeld of BPala is 40.45%.Hybrid benzoxazine were synthesized by allyl containing benzoxazine and liquid silazane(LSZ).When 0.2%mol NiAA added in hybrid benzoxazine,with the addition of LSZ,the DSC cruve peak temperature of BL system can be decreased from 270?to 168?.Add 0.5%mol NiAA into hybrid benzoxazine,the DSC cruve peak temperature of hybrid benzoxazine(BL200-050)can be decreased to 132?.After curing,the char yield of LSZ modified Bala increased from 29.24%to 68.78%,and the maximum char yield of LSZ modified BPala is 80.95%(BPL200-020).The char yield of BPL200-020 is 12.17%higher than BL200-020.Carbon felt preform(CFP)was fabricated by hybrid benzoxazine(BPL200-020)solution and carbon felt.After impregnated,dried at room temperature and cured at 220?,the BPL resin enriched in the carbon bundle of z direction.When the mass concentration of BPL increase from 10%to 50%,the density of CFP increased from 0.128 g/cm~3 to 0.407 g/cm~3,the 10%compression strength of CFP increased from 0.256 MPa to 2.246 MPa,but the elastic compression deformation of CFP decreased from 0.065 mm/mm to 0.03 mm/mm.Hybrid benzoxazine aerogel was synthesised with TDI as a curing agent,the room temperature reactivity of BPLT system increase with the increase of TDI.But after gel,the high temperature reactivity of BPLT gel system decrease with the increase of TDI.The char yield of BPLT resin first increase and then decrease with the increase of TDI.The lightweight aerogel composite was prepared by vacuum impregnated and sol-gel method and consist by benzoxazine aerogel and CFP.With the density of CFP/A increase from 0.249 g/cm~3 to 0.474g/cm~3,the heat capcity of CFP/A increase from 1.7 J/g·K to 2.2 J/g·K,heat diffusion decrease from 0.485 mm~2/s to 0.242 mm~2/s,and the heat thermal conductivity increase from 0.225 W/m·K to 0.252 W/m·K.In 60 seconds butane ablation test,with the density fo CFP/A increase from 0.249 g/cm~3 to 0.474 g/cm~3,the mass ablation rate of CFP/A increase from 1.300 mg/s to2.967 mg/s,the liner ablation rate of CFP/A first increase from 2.317?m/s to 2.933?m/s and then decrease to 0.617?m/s.The compression strength of CFP/A is between 0.40 MPa to 2.42MPa,after carbonization at 800?for 1 hour,the compression strength of carbonized CFP/A is between 0.176 MPa to 0.457 MPa.