Abstract
The surface modification of titanium dioxide in aqueous dispersions of specially tailor-made periodic acrylic acid/isobutylene copolymers, poly(acrylic acid)/polystyrene graft copolymers, and hydrophobically modified polyethyleneoxide urethane (HEUR) by ultrasonic treatment was studied. The pigment surface modification by the above copolymers was comparatively investigated regarding conventional adsorption as contrasted to an ultrasonic treatment assisted procedure. The course and efficiency of the polymer adsorpption onto the pigment surface was quantified by electrokinetic sonic amplitude measurements. The higher efficiency of the pigment surface coating by the copolymers as achieved by ultrasonic treatment varies with the copolymer architecture and is a consequence of ultrasonically induced pigment surface activation.
Highlights
The homogeneous dispersing of pigments is im-p portant in coatings formulations
Acrylic acid (AA) based periodic copolymers P([IB-AA]-r-AA) consisting of alternating isobu-t tylene (IB) – AA sequences [IB-AA]m interrupted by (AA)n sequences, and graft copolymers PMAAg-PS consisting of poly(methacrylic acid) (PMAA) backbone and polystyrene (PS) grafts of various strructure were already shown to act as stabilizers of TiO2 aqueous dispersions [9, 10]
Earlier studies of the copoly-m mer-pigment interaction by means of the electrokinetic sonic amplitude (ESA) meth-o od had revealed that the saturation concentration SC increases with decreasing AA content and that the (AA)n homosequences act as anchor to the pigment, and electrosteric stabilization is predominantly achiieved through loops of alternating AA-IB sequences [9, 10]
Summary
For producing aquueous pigment dispersions, many approaches have been described in literature [1 - 3]. It was shown [4 - 6] that highly stable dispersions are obtained by ul-t trasonic treatment of pigment slurries in aqueous sollutions of polymer surfactants. We report on the dispersing of TiO2 in aqueous solutions of amphipolar copolymers of well-defined structures by ultrasonic treatment. For the preparation and investigation of the TiO2 pigment dispersions, amphipolar copolymers were predissolved in water, and the powdery pigment was added. The pigment-copolymer interaction and the formmation of the polymeric adsorption layer were inv-e estigated by ESA measurements as described earlier [7,11]. The obtained di-s spersions were poured into test-tubes and the sedimmentation kinetics were monitored by following the border line between the turbid and the transparent zones; the refraction index of the supernatant liquid was measured by standard optical devices
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