On acetylated wood.

Abstract

Experiments at the Forest Products Laboratory, Madison, have resulted in a new method of treating wood with chemical vapours to improve its dimensional stability when exposed to severe and prolonged high humidity or immersed in water over extended periods of time. The method involves treatment with vapours of a solution of acetic anhydride and pyridine, the pyridine being used to swell the wood and the acetic anhydride to replace the relatively hygroscopic hydroxyl groups in the wood with less hygroscopic acetyl groups. The pyridine also catalyses the acetyl anhydride reaction. The acetylation thus accomplished leaves the wood in a permanently swollen condition by means of the bulking action of the acetyl groups within the cell walls. Acetylation to about 20 per cent. acetyl content reduces shrinkage about 70 per cent. as compared with untreated wood. Limited tests indicate the treatment is permanent. Resistance to decay and shipworms is improved, and a few tests indicate that strength properties are not impaired and may in some cases be improved. Authors' summary.