TRISTYRYLPHENOL BASED SURFACTANTS AS EFFICIENT DISPERSANTS OF TIO2 PARTICLES IN DILUTE AND CONCENTRATED DISPERSIONS

This study presents two bulky surfactants, namely, tristyrylphenol ethoxylate (TSEO, uncharged) and tristyrylphenol ethoxylate phosphate (TSEO-P, negatively charged), for the stabilization of commercial TiO2 (Ti-Pure™ R-902+) particles at pH 8.0 (close to that used in the formulation of paints). X-ray photoelectron spectroscopy (XPS) revealed the presence of Ti, Al, Si, O and C on the surface of the commercial TiO2 particles. Batch adsorption experiments performed in the dilute range (1.0 wt%) indicated that the negatively charged TSEO-P adsorbed more efficiently on TiO2 particles (338 mg/g) than the TSEO surfactant did (qe = 222 mg/g), increasing the ζ-potential of TiO2 particles from – 24.4 ±1.0 mV to – 39.1 ±1.6 mV. Hydrophobic interaction between the hydrophobic tristyryl group and the organic molecules on the surface of the TiO2 particles favored the exposition of the phosphate groups to the medium. H bond between phosphate (HPO3-) and hydroxyl groups on the surface exposed the tristyryl groups to the aqueous medium, which could interact with other surfactant molecules by π-π interactions. Such structuring of surfactant (at 2.0 wt%) molecules on the TiO2 particles provided colloidal stability for TiO2 particles in the slurries (70 wt%) over 30 days at 25 oC and 52 oC, which was comparable to that provided by sodium polyacrylate (PAS, at 1.0 or 2.0 wt%). The flat paint film formulated with TSEO-P (2.0 wt%) presented a contact angle of 58.5 ± 1.0o, and superior wet scrub and leaching resistance in comparison to those prepared with sodium polyacrylate (2.0 wt%), which presented a contact angle of 52.8 ± 0.8o.