Study On Rapid Preparation And Control Method Of Silica Aerogels For Thermal Insulations

Silica aerogel has extensive application prospect in the fields of aerospace, industry, architecture ect with ultra-low thermal conductivity. However, with low mechanical strength, long preparation period and many influence factors resulting unstable performance of samples, silica aerogel are greatly restricted produce and practical application. In this paper, TEOS as silicon source, ethanol as solvent, silica aerogel samples with good performance were prepared by sol-gel process and ambient pressure drying technology. Silica aerogel with low density and stable performance were obstained by compression modulus of alcogel as a comprehensive parameter. The influence of process parameters of silica aerogel and its composites on performance parameters of samples were researched with orthogonal experiment method and single-factor experiment method, and the optimal conditions of preparing silica aerogel and its composites were got. Compression modulus of alcogel as a comprehensive parameter, compression modulus of alcogel and densities of silica aerogels were tested, and the relationship between them was studied. The results show that density of silica aerogel lower than 100kg/m3 could be obtained as long as controlling compression modulus of alcogel within the range of 0.25~2.5 kPa.Influences of process parameters of silica aerogel, concluding hydrolysis time of TEOS, aging time, solvent exchange and surface modification time and washing time, on performance parameters of samples were researched with orthogonal experiment method and single-factor experiment method, and the preparation time was cut down. The results show that preparation cycle of 5 to 7 days was shorten to 1.5 days with one step solvent exchange and surface modification and optimization of process time, including sol-gel process, natual aging process, aging in solution process, and drying at room temprerature process, which has important reference value to rapid preparation method and scale production of silica aerogel.Complete massive of silica aerogel/ PET fiber composite was prapered with PET fiber as support material, and its thermal conductivity is as low as 0.024W/m·K, density is as low as 127kg/m3 and contact angle is as high as 144°. And the influence of process parameters on performance of composites was studied. The results show that composite with the lowest thermal conductivity of 0.024W/m·K(silica aerogel is about 0.02 W/m·K), lowest density of 127kg/m3 and maximum WVTR of 20g/m2·h( PET fiber is about 29g/m2·h) when PET fiber content is 10%. Silica aerogel/PET fiber composites maintain excellent insulation performance of silica aerogel and good air permeability of PET fiber, which may be desirable for heat-insulation in industry, architecture and clothing.