Application of ATR Infrared Spectroscopy in Wood

Acetylation is a chemical modification of wood to enhance its properties. IR-spectroscopy is a useful technique for proofing chemical bondings in wood and the Attenuated Total Reflection (ATR) Infrared Spectroscopy technique was applied as an easier technique over other IR-spectroscopies. In this research, different degrees of acetylation, weight percentage gains (WPGs) in beech and pine mini-stakes were achieved by using acetic anhydride. Acetylated samples were analyzed by applying an Attenuated Total Reflection (ATR) Infrared Spectroscopy technique. Comparison of the acetylated samples with non-acetylated woods showed that hydroxyl groups (O-H) were diminished at wave numbers of about 3,354-3,328 cm-1 due to the substitution of hydrophobic acetyl groups in cell wall polymers. A strong peak appeared at wave numbers of about 1,733-1,728 cm-1 in beech and 1,737-1,728 cm-1 in pine due to the carbonyl (C=O) stretching of acetyl groups. The magnitude of the bands increased with raising the weight percentage gains (WPGs). The methyl deformation of the acetyl groups induced at wave number 1369 cm-1 caused by the stretching of C-H in polysaccharides. There was also a clear increase in the magnitude of the wave numbers at about 1234-1226 cm-1 in beech and 1236-1226 cm-1 in pine due to the stretching of C-O and carbonyl deformation in the ester bonds during the acetylation of lignin.