Performance of clear coatings on modified wood exposed to the weather for 2 years in Australia

Abstract

We examine the performance of clear coatings on wood treated to improve its photostability. The treatments tested were: benzoyl chloride; chromic acid; modified PF resins; vinyl benzoate; and primers containing different photostabilisers. Treated panels were finished with clear coatings containing different types/levels of photostabilisers and exposed outdoors in Australia for 2 years. The coatings performed better on treated than untreated panels, except for coatings on panels treated with a primer containing cerium oxide nanoparticles. Clear coatings performed best on wood treated with chromic acid, vinyl benzoate or PF resin containing a hindered amine light stabiliser. However, the performance of the coatings was also strongly influenced by coating type. We conclude that the performance of clear coatings can be increased if they are applied to photostable wood substrates. However, coating performance is also dependent on coating flexibility, its propensity to form surface defects, and the level/types of photostabiliser in the coatings.

Keywords:

• Clear coatings
• Wood
• Performance
• Weathering
• Photostability
• Chemical modification
• Acrylic
• Alkyd
• Polyurethane

We thank Anwar Ahniyaz (YKI); Ylva Kärrfelt, Kenneth Möller, Sara Olsson, Emma Östmark, Magnus Wålinder and Mats Westin (SP Trätek); Charlotta Reimertz and Glenn Svensson (Akzo Nobel); and Steven Teding van Berkhout and Richard Eldridge (Kioloa coastal campus of The Australian National University); Sara Kraushaar Gibson and Mark Anderson (Arclin), for their assistance with this research. We thank Arclin, Ecobuild, NSERC and the Rix Family Foundation for financial support. PDE thanks Viance, Tolko and FP Innovations for their support of his BC Leadership Chair at UBC.

Notes

This paper is part of a special issue on the Sixth European Conference on Wood Modification