Effect of TiO2 on tannin migration in water-borne coatings

 
Acrylic polymer dispersions have proven their value as paint binders for exterior paints over many years. Overall exterior durability, particularly water resistance and flexibility are usually associated with an all- acrylic polymer backbone. Many of the failures still observed in acrylic exterior paints are associated with the capilar water intrusion through the paint film down to the substrate, particularly when the substrate is wood. The EN 927/5 norm sets a tough standard to quantify this parameter and set performance limits. Hard acrylics are less prone to water intrusion than soft ones. However, their reduced elasticity can lead to paint film cracking as a cold-check test can demonstrate. This paper demonstrates that there is a narrow window of heterogenity and composition that can take the performance of acrylic exterior paints a significant step forward in terms of water transmission resistance and flexibility.