Hydrophobic silica composite aerogels using poly(methyl methacrylate) by rapid supercritical extraction process

摘要

A poly(methyl methacrylate) solution was mixed in an optimized tetraethoxysilane-based silica sol and a silica aerogel was obtained by a rapid supercritical extraction process. The hydrophobicity was enhanced by an addition of poly(methyl methacrylate), the silica aerogel prepared with 6 wt% poly(methyl methacrylate) has the contact angle of 156A degrees with low density (0.067 g/cm(3)), high surface area (829 m(2)/g), and low thermal conductivity (0.072 W/m center dot K). The thermogravimetric-differential thermal analysis also showed that the aerogels were hydrophobic up to a temperature of 393 A degrees C. An extra hydrophobicity could be expected for silica aerogel using poly(methyl methacrylate) through the surface modification of silica aerogel with generated -OCH3 and -CH3 radicals by the thermal decomposition of poly(methyl methacrylate) excluding poly(methyl methacrylate) itself. This study provided a simple and cost effective method that used an inexpensive polymer additive without using an expensive surface modification agent nor hydrophobic silica precursor.