Dimensional stability and photostability of octanoylated wood

摘要

The esterification of wood by fatty acids or their acid chlorides containing long hydrophobic chains can provide a water-repellent layer. A direct reaction between fatty acids and wood has low practical probability. Thiebaud and Borredon (1995) developed an esterification method with fatty-acid chlorides without using any solvent. The good hydrophobicity of the modified wood was even better with long-chain fatty-acid chlorides (Thiebaud et al. 1997). The thermal stability of the modified wood was also improved. The thermoplasticity of wood is increased by esterification of its hydroxyl groups with fatty-acid chlorides in a dinitrogen tetroxide-dimethylformamide-pyridine medium (Funakoshi et al. 1979; Shiraishi et al. 1979a,b), or with fatty acids combined with trifluoroacetic anhydride in benzene (Arni et al. 1961). The explanation for this is that the bulky substituents destroy the hydrogen bonds and increase the flexibility of the molecular chains and render possible sliding of the macromolecular layers (Nakano 1994). Hitherto, fatty-acid chlorides CH_3-(CH_2)_n-COCl with n = 6, 8, 10, 12, 14, 16 were used for wood modification. However, the dimensional stability and other weathering properties have not been evaluated. In this study we assessed the dimensional stability and photostability of solid wood blocks of Hevea brasiliensis (rubberwood) modified with octanoyl chloride.