Preparation of hydrophobic CaCO3composite particles by mineralization with sodium trisilanolate in a methanol solution

Abstract

Hydrophobic CaCO₃ composite particles were prepared via crystallization of CaCO₃with a sodium trisilanolate [(c-C₅H₉)₇Si₇O₉(ONa)₃] in methanol. The molar ratio of calcium ion to the sodium trisilanolate was varied from 0.1 to 0.5. FT-IR and TGA analysis of the obtained product indicated that the trisilanol was bound to the crystalline CaCO₃. By changing the concentration of the trisilanol, composite particles with different shapes and polymorphism were obtained. Low concentration of the trisilanol gave stable vaterite crystals, the polymorph of which did not change when the composite was kept in water for more than 1 week. The contact angle of the modified vaterite was 62±4°. Dispersability of the composites in a polystyrene matrix was significantly improved compared with a bare CaCO₃. We have succeeded in surface modification of particles with the hydrophobic trisilanolate.