Infrared spectroscopic investigations of weathering effects on the surface of tropical wood

Abstract

 Two Fourier transform infrared spectroscopic techniques, photoacoustic and diffuse reflectance spectroscopy, were utilized to explore the physical and chemical changes in wood caused by weathering. Five tropical wood species (albizia, kapur, mahoni, nangka, puspa) were exposed to natural weathering for various periods. The contents of extracts, phenolics, and Klason lignin in unexposed samples of these wood species were determined by chemical analysis. Infrared spectra of the weathered surfaces were recorded by the two techniques. The photoacoustic spectra exhibited rapid decomposition and elusion of wood constituents containing benzene rings in the region closest to the exposed surface. Line maps of infrared spectra in the vertical direction obtained by diffuse reflectance infrared microspectroscopy were consistent with the view that the additive effects of water and ultraviolet irradiation play an important role in destroying the lignin-hemicellulose matrix of the cell wall. The infrared spectroscopic techniques are available for the analysis of weathered wood.