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Surface study of DWA‐wetted TiO 2 pigments
Author(s) -
Johansson LeenaSisko,
Losoi Tuomo,
Juhanoja Jyrki
Publication year - 1993
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740200210
Subject(s) - materials science , adsorption , wetting , x ray photoelectron spectroscopy , contact angle , chemical engineering , coating , pigment , chemistry , composite material , organic chemistry , engineering
We present a study on the dispersion of coated TiO 2 pigments in acrylic‐isocyanate automotive paints, based both on the surface characterization of the pigment particles and on studies of the films prepared from the paint. We investigated how the Al 2 O 3 –SiO 2 coating on TiO 2 affects the adsorption of an organic dispersing and wetting agent (DWA) and what the effect of this surfactant is on the dispersibility of the pigment. The study also shows the value of surface methods in the characterization of powder surfaces. Five Al 2 O 3 ‐ and/or SiO 2 ‐ coated TiO 2 pigment samples were used as substrates. These were treated with varying amounts of a commercial organic DWA. The substrate surfaces were characterized with XPS and zeta potential measurements prior to the DWA treatment. The adsorption of the surfactant was analysed with carbon analysis, UV and IR spectroscopies, XPS techniques and with static SIMS. Results from both the XPS analyses and adsorption measurements showed that the substrate saturation point for DWA depended on the pigment surface, owing to variations in substrate acidity. The effect of the DWA treatment on pigment dispersion was studied in paints. The TiO 2 pigments with and without the treatment were dispersed in acrylic‐isocyanate automotive paints together with a DWA‐wetted red pigment. The TiO 2 dispersion from the paint films was studied with a mechanical rub‐out test, x‐ray microanalysis and XPS sputter profiling. The observed colour variations in rub‐out tests were clearly connected with DWA treatment. X‐ray microanalysis revealed differences in the TiO 2 pigment dispersion stage that probably caused these variations.