How can we effectively use accelerated methods to predict the decorative properties of PVDF-based coatings? – A practical approach

Poly(vinylidene fluoride) (PVDF) resins are the dominant component of some of the most weatherable commercially available decorative coatings, which can have color retention and chalk resistance service lifetimes of decades. We have recently oultined a service life prediction model for the decorative properties of coatings of this type (Wood, 2009). The model is based on the “contraction” theory of gloss loss and chalking, coupled with simple assumptions about the photochemical kinetics of two-resin hybrid systems where one resin (PVDF) is much more weatherable than the other (in this case, an acrylic). Because different mechanisms account for gloss loss, color change, and chalking, the relative rates of change for each of these properties can be different, in accordance with experimental observations. In this paper, we combine insights from the model, empirical data from accelerated tests, and long-term weathering test data from solvent-based baked PVDF coatings, to predict the service life of new waterborne no-bake PVDF coatings.