Attempt to protect wood colour against UV/visible light by using antioxidants bearing isocyanate groups and grafted to the material with microwave

Antioxidants such as a phenolic UV absorber containing the 3-(3'- benzotriazol-4'-hydroxy-5'-tert-butyl)phenylethane moiety, a polyethyleneglycol and two Hindered Amine Light Stabilizers(HALS) were derivatized to incorporate an isocyanate function. These were grafted on Middle Density Fiber (MDF) boards, fir ( Abies grandis) and oak woods by microwave activation without the need of any catalyst. The effect of the antioxidant grafting on the photodiscoloration of the materials was measured in the CIE-LAB system and expressed by the color differencenumber ΔE. The UV absorber was found the most efficient to photostabilize the woods and its action was enhanced when it is used in conjunction with the other additives.