Moisture adsorption behaviour of esterified rubber wood (Hevea brasiliensis)

Rubber wood (Hevea brasiliensis) esterified with acetic anhydride, maleic a nhydride and phthalic anhydride was studied for moisture adsorption behavio ur. FTIR spectroscopic technique was used to analyse the chemical changes i n the wood through the correspondent reactions. Spectra indicated increasin g intensity of the C=O and C-O stretching bands, and reduction in O-H stret ching vibrations that reflects formation of less hygroscopic ester bonds wi th hydroxyl groups of cell wall polymers. Moisture adsorption isotherms sho w low equilibrium moisture content in esterified wood at all relative humid ity values as compared to a control. The adsorption data was analysed by ap plying Hailwood-Horrobin theory which separated the adsorbed water into hyd rated water and dissolved water corresponding to mono-layer and multi-layer adsorption. Curve for M-h and M-s were similar in pattern for esterified w ood and control with different magnitude. Low M-h and M-s in esterified woo d indicate reduction in moisture adsorption sites. Inaccessible fraction of wood for water vapour was increased by 43%, 32% and 26% in acetic, maleic and phthalic anhydride treated wood, respectively, compared to the control. Acetic anhydride treatment was found most effective in reducing hygroscopi city of wood.