Photostabilisation of wood surfaces using a grafted benzophenone UV absorber

The photostability of polymers can be greatly improved using grafted photostabilisers. This approach was used here to improve the photostability of wood. 2-Hydroxy-4(2,3-epoxypropoxy)-benzophenone (HEPBP) was synthesised and the reaction conditions required to graft HEPBP to wood were examined. The photostability of grafted veneers during natural weathering was compared with veneers treated with 2,4-dihydroxybenzophenone (DHBP) or chromium trioxide. In the presence of dimethylbenzylamine, at temperatures in excess of 80°C, HEPBP reacted with wood resulting in permanent weight gains. FTIR and XPS spectra suggested grafting of the benzophenone to wood. Grafting of HEPBP restricted losses in veneer mass and tensile strength during weathering, whereas DHBP was ineffective. Grafting was generally as effective as chromium trioxide in restricting losses in veneer mass during weathering, and superior to chromium trioxide in terms of its effects on tensile strength. Grafting also reduced photochemical changes at exposed wood surfaces and improved the performance of clear finishes.