Analysis of IR spectrograms of wood by the method of formalized modelling of the shape of absorption bands
Abstract
The problem of separating absorption bands in IR spectrograms of such a polymer composite as natural wood when analysing the changes in its moisture content is considered in the study. The use of well-known software packages in the analysis of such a composite as natural wood does not bring the desired effect, since the blurring of peaks is not caused by a high level of noise, but by the multicomponent composition and irregularity of the components.
The aim of this study was the demonstration of the possibilities of formalized modelling for separating bands in the IR spectrogram of natural wood after moistening the samples. As the experimental data, we used the IR spectra of microtome sections of natural pine wood with a thickness of 140-150 μm. The reference sample was atmospheric air in the measuring chamber under room conditions, the spectrum of which was determined immediately before each experiment. Research was carried out using infrared Fourier spectrometer FSM 2201 manufactured by OOO "Infraspek" (Russia, St. Petersburg).
Separation of absorption bands was carried out by modelling their shape with a normal distribution function with two parameters: the maximum value of the relative intensity and dispersion. For the determination of the parameters, the method of minimizing the standard deviation was used. The capabilities of the method are demonstrated in the article by analysing the change in the relative intensity of a double-peaked band in the range of 2360-2330 reciprocal centimetres in the IR spectrogram of wood before and after moistening.
The simulation results showed that a decrease in the intensity in the investigated part of the spectrogram after moistening was accompanied by a levelling off and a decreased intensity of these bands. This levelling and decrease indirectly indicated a decrease in the number of CO2 molecules in the pores of the wood, and, consequently, an increase in the concentration of water molecules in them after incubation in the weighing bottle. This conclusion was confirmed by the observed increase in the intensity of the absorption band corresponding to the concentration of associated water in the pores. Thus, the modelling of absorption bands allowed quantifying the relative change in the concentration of water molecules based on the change in the band intensity, and, therefore, unambiguously determine the level of change in the moisture content of wood. This method allowed specifying the mechanisms of moisture transfer in the micropores of wood and leads to the possibility of predicting the production of a material with specified hydrophobic and dielectric properties.
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References
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