New technology for high-performance white coatings
Titanium dioxide is the most popular white pigment because of its brightness and very high refractive index, providing whiteness and opacity to everything from papers and paints to coatings and plastics. However, it is a scarce commodity and demand is projected to significantly increase over the next few years, its cost is gradually increasing and it largely contributes to the carbon footprint of its products. To address these serious problems facing the decorative painting industry, the EU-funded project DRYFOAM (Super-stabilised opaque foam coatings for architectural applications) introduced a novel approach to developing opaque paintings free of titanium dioxide without sacrificing coating performance. The key idea behind DRYFOAM’s innovative approach was the use of a stable foam structure containing air voids to provide opacity to decorative coatings. Air voids in the dried paint film reflect the incident light, giving a white paint its white appearance. Initial work was geared towards the preparation of a stable aqueous foam structure. To this end, researchers synthesised different polymers and surface-modified particles. Specific surfactants combined with latex nanoparticles demonstrated their ability to stabilise the foam structure and achieve the desired paint properties. Researchers then tested several methods to introduce air into the paints, including chemical blowing and gas expansion. Paints were dried and, when applied to a specially prepared plasterboard, showed excellent film appearance, opacity and scrub resistance comparable to a standard titanium dioxide-based paint. A novel emulsifier system helped improve the durability of the polymer latex films. Compared to state-of-the-art technology, this led to the synthesis of emulsion polymers offering higher scrub resistance up to 150 %. Compared to conventional paints that are formulated at high pigment volume concentrations and have poor scrub resistance, DRYFOAMS’ coatings are thicker and with better crack-bridging and anti-condensation properties. Technology will add increased value to products, and if further developed will not be limited to decorative paints.
Keywords
Coating, titanium dioxide, whiteness, DRYFOAM, foam structure, air voids
