2000 Volume 7 Issue 285 Pages 92-98
The surface properties of calcium carbonate and silica which were modified with isopropyltriisostearoyltitanate were investigated. Especially, the reaction mechanism of surface modification, and the relationship between the surface structure of the modified samples and hydrophobic property were studied. It was realized that the modification reaction progressed when adsorbed water did not exist, from the examination of the modification reaction under the controlled amount of physisorbed water. Moreover, it was confirmed not to influence the value of the saturated surface density of the modifier by the adsorbed water existence. The saturated surface density of modifier on the silica and calcium carbonate was 0.3 nm-2 and 0.9 nm-2 respectively. This difference was presumed to be because of the steric hindrance of modifiers causing by the difference of site distribution on both samples. In addition, the mechanism of hydrophobic on the modified surface was examined by preferential dispersion test. As a result, both samples became hydrophobic at the same density of the modifier of about 0.2 nm-2, though the distribution of the initial reaction site on the surface of both samples is different. This value is considerably lower than the saturated surface density of modifier. From the above-mentioned, it was considered that hydrophobic property on the surface of the modification sample was influenced by the state of distribution of the modifier. Moreover, it was suggested that hydrophobic property increase by the thickness of modification layer, because the continuous structure of the modifier became close more than this density of the modifier.
