The Preparation Of Silica Areogel And Its Application

Silica aerogel has great potential in the field of thermal insulation materials, as a novel nanoporous material with extremely low density, low thermal conductivity dielectric constant and good hydrophobic ability. SiO2 aerogel has been prepared by the way of sol-gel.The insulation application of aerogel has been researched in different ways, such as direct immersion, load and insulation coating applied.Silica aerogel was synthesised using sodium silicate (Na2SiO3) as precursor, sulfuric acid catalyst by sol-gel process followed by the ambient pressure drying. The effects of sol-gel parameters such as NaiSiO3/methanol mass ratio, sulfuric acid concentration, gelation temperature on the structure and performance of the aerogel have been investigated. Results show that the prepared aerogel had typical three-dimensional network structure with the pore size of 25 nm, the bulk density of 0.046 g/cm3, the porosity of 94% and the thermal conductivity of 0.0198W/(m·k), under the conditions of sulphuric acid concentration of 1.5mol/L, mass ratio of water glass and ethanol of 1:6 and the gelation temperature of 50℃.A sandwich structure is made of thin and breathable fabric which is filled with SiO2 aerogel powder was tested by the infrared radiation. After 40 minutes, the temperature contrast between the inside of the sandwich structure as low as 13℃ than the original fabric, which shows better thermal insulation. Obviously, this structure has a great application potential in the insole, sleep mat or sleeping bag and other aspects. Hower, the powder is easy to run out of cloth fiber and needle along the front clearance.The sol and SiO2 aerogels were loaded onto polyester insulation batts for application research.Compared with the unmodified polyester batting, grooves or cracks appear on the fiber surface of polyester batting after an alcohol solution of NaOH treatment, which can load much more silica powders. Though insulation test, the temperature contrast between the inside of the sol @ modified polyester was lower about 5.5’C than the original piece.There were a lot of powders shake off the flakes with slight bend or warp, indicating that there is no noticeable force between aerogel and polyester fiber.Insulation coating was prepared with silica aerogels as functional particles and PA-5341, PU-2591, PTFE as well as PVDF-HFP as adhesive agent. Cotton fabric was coated with different kinds of insulation coating. The influences of the amount of silica aerogel and the amount of adhesive agent on the hermal conductivity, mechanical properties and insulation performance of coated fabric were studied. The PTFE and PVDF-HFP coated fabric showed much better performance than others.The best ratio for each component agent of insulation coatings is that:the mass ratio of the silica powders, adhesives, wetting agents and dispersing agents is 15%、 20%、 1.0% and 1.2%.At this ratio, with rate of elongation at break up to 140% and tearing strength of 15N and surface water absorption of about 1.2% with good abrasion fastness. The thermal conductivity of PTFE and PVDF-HFP coated fabric can as low as 0.027 W/(m·k) and 0.029 W/(m·k). The temperature contrast between the inside of them as low as 13℃ than the original one.