Preparation,Thermal Insulation And Flame Retardant Properties Of Glucomannan-silicon Composite Biomass Aerogels

Polysaccharide-inorganic composite aerogels are one sort of advance materials for heat preservation,heat insulation and flame retardants due to their three-dimensional network structure,high specific surface area,high porosity,good mechanical properties and good thermal stabilitydue to the three-dimensional network structure.In this paper,konjac glucan-mannan（KGM）and ethyl orthosilicate（TEOS）were used as raw materials,and potato starch（starch,S）were used as auxiliary additive.The polysaccharide-inorganic composite aerogels were prepared via sol-gel and vacuum freeze-drying method,Their microstructure and physical properties were characterized,and their insulation flame retardant performance were tested.Si O₂aerogel microspheres（SA）were prepared by TEOS,and then KGM-Si O₂composite aerogels（K-SA）were obtained by sol-gel method with KGM and SA.Scanning electron microscopy（SEM）results showed that K-SA aerogels had a uniform closed pore network structure,of which KGM constituted a continuous three-dimensional porous skeleton,while the mesoporous SA particles interpenetrated and embedded on the pore wall of aerogels,making the pore structure of the composite aerogels more complex.Determing by the mechanical properties and microstructure of the aerogels,the optimal ratio was K1SA1.The compressive strength of K1SA1 was 14.25 k Pa,the specific surface area of K1SA1 was 192.341m²/g,the pore volume was of K1SA1 0.235 cm²/g,and the average pore diameter of K1SA1 was 6.309 nm.Compared with K1 aerogel,the thermal stability of K1SA1was not improved.SA was prepared by TEOS,and then KGM-S-Si O₂composite aerogels（K-S-SA）were obtained by sol-gel method co mbined with KGM and S.The results showed that with the increase of starch content,the compressive strength significantly increased,while the open poress of the aerogels decreases,the wall thickness increases,and the porosity increases.Determing by the mechanical properties and microstructure of the aerogels,the optimal ratio was K1S0.5SA1,and the compressive strength of K1S0.5SA1 was 30.38 k Pa.SEM results showed that the pore structure of K1S0.5SA1 was more complex than K1SA1 aerogel.The specific surface area of K1S0.5SA1 was 150.599 m²/g,the pore volume was 0.209 cm²/g,and average pore diameter of K1S0.5SA1 was 6.105 nm.Compared with K1S0.5 aerogel,the thermal stability of K1S0.5SA1 was not improved.KGM-Si O₂interpenetrating network aerogels（K-T）wre prepared by sol-gel blending with TEOS and KGM as precursors.Determing by the microstructure and mechanical properties of the aerogels,the optimal ratio was K1T2.The experimental results showed that the structure of K1T2 aerogel was homogeneous.Compared with K1SA1 aerogel and K1S0.5SA1 aerogel,the mechanical properties of K1T2 aerogel were significantly improved.The compressive strength of K1S0.5SA1 aerogel was43.49 k Pa.The specific surface area of K1S0.5SA1 was 180.694 m²/g,the pore volume of K1S0.5SA1 was 0.171 cm²/g,and the average pore diameter of K1S0.5SA1 was 3.676 nm.Compared with the maximum weight loss rate temperature of K1 aerogel（298.05℃）,those of K1T2（324.809℃）increased by8.9%,indicating that the thermal stability of K1T2 was significantly improved.The flame retardant and thermal conductivity of three kinds of composite aerogels were studied.The results showed that K-T series aerogels prepared by the co-precursor method showed the best flame retardant properties,and the heat release rate of K1T3 aerogels was the lowest,which was 17.5 W/K.Among the three kinds of composite aerogels,the thermal conductivity of K1S0.5SA1 aerogels is the lowest,which was 0.0324 W/m K.168 h hot air aging tests were conducted on three kinds of composite aerogels and pure KGM aerogels（K1）.The results showed that the microstructure of K1 and K1SA1 aerogels had no significant change after aging,but the compressive strength decreased significantly.The pore sizes of K1T2 and K1S0.5SA1 aerogels decreased significantly after aging,and the compressive strength decreased significantly,but still significantly higher than that of K1 aerogels.Three kinds of composite aerogels and K1 aerogels were hydrophobically modified by trichloromethylsilane.After modification,the contact angles of all the aerogels were increased to more than 120°,and the modified K1SA1 showed the best hydrophobicity with the water contact of129.2°.Three kinds of composite aerogels after hydrophobic modification were subjected to hot air aging test.The experimental results showed that the water contact angles of all the aerogels decreased,but still remained above 100°.The K1SA1showed the best hydrophobicity,and its water contact Angle was 122.7°.