CELLULOSE CHEMISTRY AND TECHNOLOGY Cellulose Chem. Technol., 50 (1), 71-76 (2016) COLORIMETRIC AND FTIR ATR SPECTROSCOPY STUDIES OF DEGRADATIVE EFFECTS OF ULTRAVIOLET LIGHT ON THE SURFACE OF EXOTIC IPE (TABEBUIA SP.)WOOD MAGDALENA ZBOROWSKA, * AGATA STACHOWIAK-WENCEK, * BOGUSLAWA WALISZEWSKA * and WLODZIMIERZ PRDZYSKI ** * Institute of Chemical Wood Technology, Poznan University of Life Science, WojskaPolskiego 38/42, Pozna, Poland ** Institute of Wood Technology, Winiarska1, Pozna, Poland Corresponding author: Magdalena Zborowska, mzbor@up.poznan.pl Received June 22, 2014 The objective of the study was to characterize the UV light resistance of one of the exotic wood species –ipe (Tabebuia sp) – commonly used in the furniture industry, using the colorimetric and infrared spectroscopy analyses. A softwood species, Scots pine (Pinus sylvestris L.), was also studied for comparison purposes. Based on the results obtained after 100 h of light irradiation, colour changes were found in the samples of both analysed species, but the extentand pattern of the changes differed significantly. It was observed that the ipe wood was less influenced by light in comparison with the pine wood. The total colour difference of the pine wood amounted to 14.26 and for the ipe wood to merely 1.05. The most significant changes were observed in the case of chromatic coordinate “b”. Based on the infrared spectroscopic analysis, it was concluded that 340 UV irradiation yields the degradation of lignin structure. The infrared spectra gave an insight into the changes occurring in the range of carbonyl groups present in the structure of wood components and confirmed the resistance of carbohydrates to UV irradiation. Keywords: discoloration, exotic ipe wood (Tabebuia sp.), pine wood (Pinus sylvestris L.), FTIR ATR spectroscopy, colorimetry INTRODUCTION In recent years, exotic wood species have gained increasing popularity. Due to their characteristics, such as e.g. wide diameters, attractive colour and structure, high durability and resistance to decay, these species are more and more frequently used in parquet, plywood and the furniture industry. The physical and mechanical properties mentioned above result mainly from the chemical composition of exotic wood, which varies significantly among species. 1-3 As a natural material, exotic wood is subject to different kinds of degradation processes. 4-7 While exposed to outdoor environment, wood undergoes a weathering process induced by factors such as moisture, sunlight, heat and cold temperature. In the course of weathering, the surface of wood evidently changes, primarily leading to an alteration of its colour, lightness and gloss. 8 For example, under the influence of atmospheric factors, the brown, brown-grey or deep brown colour of untreated ipe wood turns to a patinaor deepens. The extent of colour changes depends on the chemical composition of wood, which may determine a significantly different sensitivity to light. Lignin is responsible for absorbing 80 to 95% of the total UV light absorbed by wood, carbohydrates 5 to 20% and extractives about 2%. 9 Several researchers have studied the weathering of exotic wood. 10-12 However, to the authors’ knowledge, there is still little information concerning the discoloration of exotic wood from the chemical point of view. It is well known that processes that occur during irradiation are complex physicochemical reactions, 13 which finally cause a decrease in the lignin content related to an increase of carbohydrates concentration. Light irradiation degrades the chromophore groups originally found in wood, 14 and leads to the formation of free radicals. The