Effects of organic modifiers on the properties of TiO2-coated CaCO3 composite pigments prepared by the hydrophobic aggregation of particles

In this study, TiO2-coated CaCO3 composite pigments were prepared by coating the modified CaCO3 particles with modified TiO2 in aqueous media according to the hydrophobic aggregation method. The experimental results revealed that the organic carbon chains of the modifiers adsorbed on the surfaces of the particles largely determined the formation of composite particles and the maintenance of the coating structure and pigment properties. The TiO2-coated CaCO3 composite pigments could not be obtained until both the CaCO3 and TiO2 particles were modified with organic modifiers and exhibited hydrophobicity. The prepared TiO2-coated CaCO3 composite pigments exhibited pigment properties equivalent to those of pure TiO2. The hiding power of the composite pigments with the mass ratio of TiO2 of 60% prepared using sodium stearate and sodium oleate as the modifiers respectively reached 90.18% and 93.50% of that of pure TiO2, and the water contact angles of the prepared composite pigments were larger than 100 degrees. Additionally, the binding mechanism analysis indicated that CaCO3 and TiO2 particles were combined together by the association among organic carbon chains on their surfaces. The results of ultrasonic experiments and binding force calculation showed that the binding force among particles was much stronger than Van der Waals force.