LIGHT GELS BY CONVENTIONAL DRYING

Supercritical drying, the preparation route for aerogels gives high qu ality materials and very low density; however, the process is high ris k and has quite high cost. For a large scale application of aerogels, supercritical drying will most probably not give a cost effective prod uct. A process for preparing xerogels with a low density, i.e., aeroge l-like materials without the use of supercritical drying is of interes t. Shrinkage during drying of a gel is driven by the capillary pressur e and is resisted by the bulk modulus of the gel. Hence, it is of impo rtance to reduce the capillary pressure and increase the stiffness and strength of the wet gel without decreasing the pore size significantl y. An enhancement in stiffness and strength of wet gels can be perform ed by aging the wet gels in solutions of monomers. By this method mono lithic xerogels with a porosity up to 90% can be prepared. (C) 1998 El sevier Science B.V. All rights reserved.