QUANTITATIVE INVESTIGATION OF WOOD COMPOSITION BY INTEGRATED FT-IR AND THERMOGRAVIMETRIC METHODS

A non-invasive integrated method for assessing cellulose and hemicelluloses/lignin ratio in different wooden pieces was developed by coupling infrared spectroscopy (FTIR-ATR) with thermo-gravimetric analysis (TGA). The method could be helpful for a precise assessment of the cellulose and hemicelluloses/lignin ratio necessary for the characterization of wooden artefacts. Thirteen wood species of hardwood lime (Tilia cordata), oak (Quercus robur), beech (Fagus sylvatica L.), poplar (Populus), maple (Acer palmatum), cherry tree (Prunus avium), horn beam (Carpinus betulus), walnut (Juglans regia L.), balsa, sycamore maple (Acer pseudo platanus), African pole (Pyrus communis), and two wood species of softwood fir (Abies), pine (Pinus silvestris) were investigated in fresh and dried state. The ratio between the normalized peak area A1370 (corresponding to the mass loss of cellulose and hemicelluloses) and A1505 (corresponding to the mass loss of lignin) was determined – from the FTIR spectra – as A1370/A1505 = R FTIR . From TGA data, the ratio between the mass loss of cellulose and hemicelluloses (ΔmHC) and the mass loss of lignin was calculated: ΔmL as ΔmHC/ΔmL = R TG . A good correlation was obtained, with a small variation between the difference in the two parameters, ∆R = R FTIR - R TG , related to the nature of wood (+0.015 in fresh softwood and +0.065 in fresh hardwood), (+0.265 in dried softwood and +0.18 in dried hardwood). The results obtained show that TGA (a quantitative and invasive method) may be successfully used as a complementary tool of FT-IR analysis (a qualitative and non-invasive method) for the rapid assessments required by the restoration processes as to the degradation stage of wooden artefacts.