Surface Tension of Silane-Modified Silica Dispersions

5 Surface Tension of Silane-Modified Silica Dispersions 

The surface tension of a silane-modified (0.6 glycerolpropylsilyl silane per nm surface area) and two other unmodified silica sols were measured as a function of the silica concentration [59]. The silica dispersions were diluted with pure water. A small amount of sodium chloride was added so that the concentration was 0.01 M NaCl for all silica concentrations. The instrument was a du Noiiy ring type equipped with a platinum/iridium ring (radius 9.54 mm and thickness 0.38 mm). 

However, the surface tension for the silane-modified silica dispersion decreases slightly at silica concentrations above 1 wt%. At pH 2, the surface tension for the silane-modified silica dispersion has dropped to about 66 mN/m at 10 wt% SiO, but at pH 7 the drop in surface tension is limited to about 69 mN/m. A part of the drop in surface tension can be explained by the presence of methanol, about 0.6 wt% in 10 wt% SiO dispersion. 

Silica dispersion number Degree of silane modification (glycerolpropyl-silyl per nm ) Observation cycle 1 Observation cycle 2 

1 0 White precipitates, no stable dispersion White precipitates, no stable dispersion 

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