Abstract

Silicon esters are silicon compounds that contain an oxygen bridge from silicon to an organic group, ie, Si–OR. The most prevalent is tetraethoxysilane. The applications for tetraalkoxysilanes are classified roughly by whether the Si–OR bond is expected to remain intact or be hydrolyzed in the final application. Applications in which the Si–OR bond is hydrolyzed include as binders for foundry-mold sands used in investment and thin-shell castings; as binders for refractories; and as resins, coatings, sol–gel glasses, cross-linking agents, and adhesion promoters. Applications in which the Si–OR bond remains intact include as heat-transfer and hydraulic fluids. The hydrolysis reaction, which yields polymers of silicic acid that can be dehydrated to silicon dioxide, is of considerable commercial importance. The chemistry and properties of alkoxysilanes and related acyloxysilanes and aspects of commercial production and utilization are reviewed. Sol–gel technology is discussed.