The lack of storage stability of organic-inorganic solvent-free sols is a well-known problem. We investigated the influence of different solvents in the acid catalyzed hydrolysis of various sols on their storage stability. Our experiments were based on two different silanes, 3-methacryloxypropyltrimethoxysilane (MPTS) and 1,1,1-tris(allyloxymethyl)-l-[[[3-(triethoxysilyl)propyl]aminocarbonyl]oxymethyl]methane (silane 31), synthesized by reaction of pentaerythritol triallyl ether and 3-isocyanatopropyltriethoxysilane. The employed solvents were alcohol, tetrahydofuran and tert-butyl methyl ether in a range of 95 wt% to 30 wt% in solution. In order to get comparable chemical conditions the degree of condensation of the various sols were adjusted between 75% and 85%. Furthermore, the sols were modified by silylation with trimethylchlorosilane. A comparison of silylated and not silylated silane 31 clearly showed that a decrease in residual silanol groups increase the storage stability. The results of the investigations demonstrated that both the kind and the amount of solvent used in hydrolysis affects the initial viscosity of solvent-free condensates of silane 31 and MPTS.
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