Formation of glass-like materials from ethyl silicate

The alkyl silicates, especially ethyl silicate, are used as binders in the foundry and refractory industries because they form rigid coherent gels which do not contain fluxing agents. The preparation of glass-like materials from technical ethyl silicate (SiO 2 equivalent of 40% w/w) has been studied, using certain four-covalent organotin compounds as catalysts for the neutral hydrolysis and gelation reactions. Clear, transparent, glass-like gels can be formed, particulary if the water content is greater than 16%. Systems with a water content under 16%, desirably between 8–16% show good fibre-forming ability, dibutyltin diacetate being the preferred catalyst. These systems show a better fibre-forming ability than do similar systems using tetraethoxysilane. Viscosity measurements suggest that this is because the technical ethyl silicate contains a mixture of linear polysilicate oligomers.