Exterior durability: the impact of TiO2 -polymer composite on gloss retention

 
Coating durability is a critical factor that drives the exterior paint market. In simple terms, customers want their homes to look freshly painted for as long possible. To the eye, a "freshly painted" appearance can be broken down into three main interrelated parts; excellent dirt pick-up resistance (DPUR), tint retention (TR) and gloss retention (GR). Interestingly, recent observations within Dow's technical community suggest that paints made with TiO2-polymer composites (Figure 1, later referred to simply as composites) have improved gloss retention verses conventional/non-composite paints under both accelerated and environmental weathering.1,2 Prior to the current study, the predominating assumptions for the observed gloss retention benefits could be broken down into five main groups: (1) The reduction in TiO2 level that accompanies the use of pre-composite polymers results in reduced free radical generation from the TiO2 upon UV exposure.3,4 (2) Pre-composite polymers enable a more homogeneous distribution of TiO2 which results in improved UV absorption to protect the binder from degradation.5 (3) A binder-rich layer that forms on the surface of coatings made with pre-composite polymers protects the bulk coating. (4) Precomposite polymers enable the formation of a less porous film that is less permeable to H2O and O2. 6,7 (5) Pre-composite polymers encase the TiO2 and circumvent the typical radical mediated polymer degradation pathway.