Dynasylan® A SQ
Dynasylan® A SQ represents a special quality of Dynasylan® A, the ethyl ester of orthosilicic acid.
Dynasylan® A SQ can replace Dynasylan® A in every application where higher purity is required. In the application of silic acid esters, use is often made of the option of preparing silicic acid by hydrolysis or thermally treatment. The resulting silicic acid bonds well to many inorganic substrates and can be deposited in situ in a controlled manner. The surfaces of glass, metals, pigments, fillers and synthetic fibres can be coated with a very thin SiO2 layer in order to improve chemical and thermal stability and mechanical properties. Other applications are: Dynasylan® A SQ is a suitable base material for the production of ultra high purity tetraethoxysilane (UHP TEOS) used in the electronic industry crosslinkers in silicone rubbers for electronic potting systems drying agents in sealing compositions for electronic applications. Dynasylan® A SQ is an important starting material for sol-gel processes, Hydrolysis leads to silanol groups which, in a subsequent condensation reaction, form very stable siloxane bonds (-Si-O-Si-). Condensation starts before hydrolysis is complete and, during storage of these hydrolysates, continues until a network is formed, where the rate depends on the degree of hydrolysis. Additional use of alkylalkoxysilanes (e. g. Dynasylan® MTES) can give the siloxane network a somewhat organic character as a result of the incorporation of alkyl groups. It is also possible to construct an inorganic/organic network by adding silanes containing organofunctional groups (e.g. aminopropyl groups) and polymerizing with organic precursors. This principle makes it possible to obtain highly scratch- and abrasion-resistant coatings. Dynasylan® A SQ is immiscible with water, so hydrolysis requires the use of a cosolvent as solubilizer. Suitable catalysts are acids or bases like mineral acids or ammonia, or even acetic acid and amines. Partial hydrolysis gives hydrolysates of Dynasylan® A SQ whose shelf life depends on the amount of water and solvent used. The amount of water determines the activity of the hydrolysate. Activity and shelf life are inversely proportional. The correct choice of the amount of water can give hydrolysates which have a shelf life of up to a year.