Controlling and tuning the dispersion properties of calcined kaolinite particles in various organic solvents via stepwise modification method using 3-glycidoxypropyltrimethoxysilane and dodecylamine

The chemical modification of calcined kaolinite particle surface via stepwise method using 3-glycidoxypropyltrimethoxysilane (GPS) and dodecylamine was investigated. Silylation of kaolinite particles was controlled by varying the amount of GPS under almost anhydrous condition. FT-IR and thermal analysis indicated that silylation monolayer coverage on kaolinite particle surface increased with the increasing of the amount of additive GPS, reaching a maximum value of 8.81 μmol/m2 when the mass ratio of kaolinite to GPS was up to 1:1. Further modification of the silylated kaolinite particle surfaces was accomplished using the modifier synthesized by the ring-open reaction of GPS and dodecylamine to form multilayer branches at the presence of H2O (pH = 12). The final modified kaolinite particle surfaces contained both hydrophobic long alkyl chains and hydrophilic groups, which were advantageous to homogeneous dispersion in low polar as well as polar solvents, respectively. Digital photographs and TEM images revealed that the final modified kaolinite particles were homogeneously dispersed in acetone, dioxane, ethanol, and THF, even better than raw kaolinite dispersed in ethanol. Meanwhile, the dispersion properties in low polar solvents such as xylene, cyclohexane and petroleum ether were also acceptable, and the aggregate particle size was near to primary particle size of raw kaolinite, or just a bit larger, increasing from 1.25 to 1.75-2.00 μm.