Issue
Korean Journal of Chemical Engineering,
Vol.19, No.1, 159-166, 2002
Fabrication and Thermophysical Characterization of Nano-Porous Silica-Polyurethane Hybrid Aerogel by Sol-Gel Processing and Supercritical Solvent Drying Technique
Thermally and mechanically enhanced nanoporous silica-polyurethane hybrid aerogel was synthesized by sol-gel processing and low temperature supercritical CO2 drying. A partially condensed silica solution and a polymeric MDI were used as the raw materials with a tertiary amine as a catalyst and 1,4-dioxiane as a dilution solvent. After the gelation reaction was completed, aged wet hybrid aerogel was dried by a low temperature supercritical CO2 drying technique. Also, thermophysical characteristics such as density, BET surface area, and thermal conductivity as a function of catalyst ratio and aging time of the synthesized hybrid aerogel were analyzed. It was found that, at a fixed target density, the lowest average pore size of the aerogel, 8 nm, was obtained when the catalyst ratio was 0.1 wt.%. Also, at these conditions, the BET surface area showed the highest surface area, 287.3 m2/g. It was found that with decreasing average pore size and with increasing BET surface area, thermal conductivity tends to decrease. At pressure 1 torr, the sample aerogel showed the lowest thermal conductivity, 0.0184 W/mK.
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