Moisture sorption and quantitative assessment of acetylated African whitewood with infrared spectroscopic methods

Abstract

In this study, moisture absorption and reactivity of acetylated Triplochiton scleroxylon wood and its cell wall components was investigated. Wood samples were treated with acetic anhydride at 120 °C for 60, 120,180, 240 and 300 minutes. The moisture absorption was determined at relative humidity of 65% for eight weeks. The chemical constituents of the wood were determined by wet chemical analysis. The efficiency of the acetylation was assessed by Fourier Transform Infrared (FT-IR) Spectroscopy analysis. The ratio of the intensity of the major peaks at carbonyl (C=O) stretch region (1739 - 1730 cm -1), carbon-oxygen (C-H) stretch region (1370-1365 cm-1) and carbon-hydrogen (C-O) stretch region occurring at (1245-1000 cm-1) of the untreated samples to acetylated ones were determined. The moisture absorption (MA) of the untreated samples after 4 weeks and 8 weeks was 4.25% and 8.24% respectively while the acetylated ranged from 1.57-2.3% and 2.64-3.53% for 4 and 8 weeks respectively. The extracted acetylated and untreated wood components yielded milled wood lignin (6.24-9.8% and 5.40%), hemicelluloses (69.80-73.10% and 67.83%) and celluloses (42.40-44.0% and 42.20%) respectively. The ratio of intensity of IR transmission at the major peaks for acetylated whole wood, holocellulose, hemicellulose and lignin samples were found to be 3.4, 4.9, 1.4 and 4.2 times greater than their untreated counterparts. This suggested that all the wood components were chemically modified, and this is responsible for their significant lower moisture absorption.