Preparation And Performance Analysis Of Hydroxylated Glass Fiber Reinforced Silicon Aerogel At Normal Temperature And Pressure

Silicon aerogel is made up of nano-adhesive particles.The special network structure has the advantages of low density,high porosity and low thermal conductivity.However,the shortcomings of poor mechanical properties have always limited its production and application.On the one hand,experts and scholars at home and abroad continue to enhance the toughness of their bodies,and on the other hand,they improve their mechanical properties through composite reinforcements.In order to rapidly prepare a silicon aerogel with good toughness,hydrofluoric acid?HF?and ammonia water?NH₃·H₂0?were used as the acid-base catalyst,and the molar ratio of TEOS:EtOH:H2O=1:12:10 was used.The ratio is set to 2-3 when the hydrolysis is carried out,and the pH value is set to 7 when the base is polycondensed.The alcohol gel thus prepared not only has a short gel time but also optimizes the uniformity of the network structure.Thereafter,the aging is performed at a sealing temperature of 80?to enhance the strength of the network skeleton,and then the degree of shrinkage of the alcohol gel during drying is controlled by controlling the solvent displacement and surface modification processes,thereby obtaining a uniform network structure and high skeleton strength.A nanoporous silica aerogel with good porosity and a concentrated pore size distributed in the range of 2-50nm.The silicon aerogel prepared herein has a thermal conductivity of 0.018w/?m·k?,a density of 0.126g/cm³,an average pore diameter of 20nm,and a contact angle of140°.In order to improve the mechanical properties of silicon aerogel,the use of hydroxylated glass fiber for reinforcement,so the degree of glass fiber hydroxylation and the amount of hydroxylated glass fiber is particularly important.The glass fiber was treated with a hydrochloric acid solution at 100?×5mol/L for 8h to achieve maximum hydroxylation,and the Si-O structure was sufficiently exposed to a hydroxyl group content of 2.74/nm².Hydroxylated glass fibers are combined with silicon aerogels to form a tight bond between them.Not only physical bonding but also chemical bonding is achieved by condensation between hydroxyl groups,thus hydroxylated glass fibers to silicon aerogels The support effect is stronger,so the performance parameters of forming the composite material are also more excellent.When the optimal addition amount of hydroxylated glass fiber in the composite material is 20%,the thermal conductivity is 0.0198W/?m·K?,the density is 0.172g/cm³,the contact angle is 132°,and the compressive strength is 0.623MPa,the flexural strength was 0.86MPa.The loss of strength of the glass fiber after hydroxylation by hydrochloric acid erosion is large,and the two modification of the silane coupling agent can complete the hydroxylation under the condition of small loss of strength,The optimum treatment conditions are as follows:the glass fiber is firstly treated by 100?×1mol/L hydrochloric acid solution for 8h to complete the preliminary hydroxylation,and then the preliminary modification is completed in a kh550 solution with a volume fraction of 15%,and finally the mass fraction is 2wt%.The reaction was carried out for 3h in the kh560 solution,and the hydroxyl content on the glass fiber was3.53/nm².When the thus modified glass fiber is combined with the silicon aerogel,not only physical and chemical bonding can exist between each other,but also the performance of the silicon aerogel and the composite material is improved due to the introduction of the flexible carbon chain..Therefore,when the optimum addition amount of the modified glass fiber is 20%,the thermal conductivity is only 0.0185W/?m·K?,the density is as low as 0.167 g/cm³,the contact angle is 127°,and the compressive strength is 0.669MPa,the flexural strength is 1.042MPa.