1、Surface groups    
Neighboring hydroxyl groups (on adjacent silicon atoms), which are very important for the adsorption of polar substances; isolated hydroxyl groups, which are mainly present on the surface of silica with water removed. The content of this hydroxyl group is more in vapor phase silica than in precipitation, and it is not easily removed at elevated temperatures; double hydroxyl group, two hydroxyl groups attached to a silicon atom. The groups on the surface of silica have certain reactivity, and the reactions on the surface include: water loss and hydrolysis reaction, reaction with chlorine chloride, reaction with active hydrogen, formation of hydrogen bonds, etc. 2, the adsorption on the surface of silica has a certain degree of reactivity.
2、Adsorption on the surface of silica        
The surface of silica has strong chemical adsorption activity, which is related to the surface hydroxyl group. It can combine with water in the form of hydrogen bonds to form a polymolecular adsorption layer. In addition to this, it also adsorbs many organic small molecules. Polyfunctional amines or alcohols have higher adsorption properties than monofunctional ones, so polyfunctional compounds such as ethanolamine, ethylene glycol and triethanolamine are often used as active agents in SiO2 compounds.
3、Heat behavior       
Heating silica will release water, and the amount of released water increases with the increase of temperature. Before 150~200℃, the water released is the most, after 200℃, it tends to level off, and there is an obvious turning point. Before the turning point, it is mainly adsorption water desorption, and after the turning point, it is surface hydroxyl group shrinkage reaction.

Room termperature curing polysilazane, pls check IOTA 9150, IOTA 9150A. 
High termperature curing polysilazane, pls check IOTA 9108, IOTA 9118.