Wood has a well-known susceptibility to ultra-violet light degradation, leading to premature replacement. A variety of products have been developed to protect against this damage, but most provide less than 12 months of protection and must be regularly reapplied. Developing improved coatings would help reduce wood losses and reduce maintenance costs. Nano-particles have a variety of attractive properties that may make them suitable UV protectants. The effects of nano-particles on surface appearance, colour, and wettability of radiata pine (Pinus radiata) sapwood samples were investigated over 20 weeks of outdoor exposure. Nanometer to micron-sized water dispersions of ZnO, α and γ Fe2O3, rutile and anatase TiO2, Fe3O4, Fe(OH)3, spherical and porous SiO2, and α and γ Al2O3 were used to evaluate the effects of concentration and crystal shape on UV performance. Surface colour changes were characterized by measuring CIE L*a*b* parameters, while surface wettability changes were assessed using water droplet contact angle. Wood appearance changed markedly over the 20-week exposure and mould fungi appeared on the surface. Nano-particles protected wood from photo-discoloration to differing degrees with rutile TiO2 and alpha Fe2O3 providing the most effective protection especially at higher concentrations. Larger micron-sized alpha Fe2O3 provided more sustained UV protection. Mould growth reduced the yellowness on wood surfaces and thus influenced overall colour change. Nano-particles did not reduce wettability of wood after UV exposure. While none of the systems completely prevented UV damage, some showed promise and further trials are underway using combinations of nano-particles.

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