Dynasylan® 40

Dynasylan® 40 is formed in the presence of water from tetraethyl silicate (Si[OEt]₄) by partial hydrolysis of the ethoxy groups to hydroxyl groups and subsequent condensation with formation of siloxane bonds (-Si-O-Si-). Dynasylan® 40 is a colorless, low-viscosity liquid with an SiO₂ content of 40% (the Si content of Dynasylan® 40 is calculated as SiO₂). The polysilicic acids still have a sufficient content of ethoxy groups which can be activated by acid- or base-catalyzed hydrolysis. Condensation starts even during hydrolysis, with the formation of relatively large polymeric molecules. During storage of these hydrolysates, condensation continues until a gel is formed, where the rate depends on the degree of hydrolysis. The action of the hydrolysates as binders is based on the continuation of the hydrolysis with subsequent gelation and dehydration to give polymeric SiO₂ structures.