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Photoprotection of wood using metal acetylacetonates

University of British Columbia

Wood is a versatile material with a pleasant appearance that is widely used in architectural and interior applications. However, wood (including clear-coated wood) undergoes degradation when it is exposed outdoors. Wood can be protected from surface photodegradation (weathering) using reactive metal ions that are able to cross-link wood’s molecules and create complexes that are resistant to photodegradation. Metal acetylacetonates are coordination complexes of metal ions and the acetylacetonate anion. Metal acetylacetonates are used by industry to cross-link chemicals, and they have also been used as photostabilizers for polymers. One study has shown that titanium acetylacetonate can reduce the photodegradation of radiata pine veneers exposed to natural weathering. My general hypothesis is that metal acetylacetonates will be able to protect wood from photodegradation on their own or in combination with other protective systems, including clear finishes, oils and UV absorbers. I compared the photoprotective effects of six metal acetylacetonates on yellow cedar veneers and clear-coated yellow cedar and Scots pine panels. I found that the ability of metal acetylacetonates to photostabilize yellow cedar veneers varies depending on the metal in the coordination complex. Nickel, manganese, titanium and iron acetylacetonate were more effective than cobalt acetylacetonate at photostabilizing wood, based on the different measures I used to assess the degradation of weathered veneers. Iron acetylacetonate was more effective at photostabilizing lignin in weathered veneers than the other metal acetylacetonates. Manganese and titanium acetylacetonate had some positive effects on the performance of a clear polyurethane coating on Scots pine and particularly yellow cedar panels exposed to artificial accelerated weathering. Oils when combined with titanium acetylacetonate provided additional protection to wood surfaces, most notably water repellency, but the oils had negative effects (mould growth) on the appearance of panels exposed to natural weathering. I conclude that metal acetylacetonates can photostabilize wood surfaces and improve the performance of a clear polyurethane coating on wood, However, the effectiveness of metal acetylacetonates depends on the metal in the coordination complex and the wood species that are treated with the acetylacetonate. Finally, I conclude that metal acetylacetonates have potential as protective treatments, particular photoprotective primers for coatings.

Text

2019-01-31

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/64295

Forestry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/