The results of the application of digital differential spectrometry in the processing of the results of the study of the structure of wood and wood materials by dynamic mechanical analysis (DMA) are shown. The experimental temperature dependences of the dynamic shear modulus G’ are smoothed using cubic splines. Smooth curves G‘(t) are obtained that are suitable for automated processing, including for finding the temperature derivatives of G’. The analysis of the temperature dependences of the first and second derivatives of the dynamic shear modulus allows us to determine the position, range, and intensity of temperature transitions in the components of the material under study. The results of the practical application of the DMA method and digital data processing are presented on the example of studying the dynamic mechanical characteristics of birch wood, apple wood, composite material made of hydrolyzed wood, particle board. It is shown that the use of digital processing of experimental data provides more accurate results, simplifies their interpretation, and expands the understanding of the processes occurring in wood materials at the level of intermolecular interaction.
Structural features and physical and mechanical characteristics of plate composite materials are investigated. The materials are obtained from hydrolyzed birch wood by hot pressing without the addition of binding components. Wood processing is carried out by the method of explosive autohydrolysis without chemical reagents. The influence of pre-moistening of wood on the structure and properties of the composite material is studied. The structural features of the amorphous and crystalline components of the composite material are studied. It was found that the composite material obtained from pre-dried and pre-moistened wood retains the crystalline phase that is present in the original wood. Changes in the structure of wood when obtaining composite materials based on it occur in the amorphous component. Based on the temperature dependences of the dynamic shear modulus and the tangent of the angle of mechanical losses, information on the glass transition temperature of a complex of amorphous components of a composite material is obtained. It was found that the region of transition of lignin and hemicellulose macrochains from a glassy to a highly elastic state in the composite material is shifted towards low temperatures in comparison with the original wood. The offset is more than 70K. It is assumed that structural plasticization is the main cause of the detected effect. Pre-moistening of wood does not affect the position of the temperature transition in the amorphous component of the composite material. The study of the diffusion and sorption of water vapor in the samples of the material shows the presence of large structural inhomogeneities. Diffusion processes obey Fick’s second law and correlate with the density of samples. Data on density, static bending strength, water absorption and swelling characteristics of composite material samples were obtained. It is shown that the use of pre-moistening of wood before barothermal treatment significantly improves the structural uniformity of the resulting material. The value of the dynamic shear modulus at room temperature in comparison with the same indicator for the material obtained on the basis of dry wood increases three times. Mechanical losses are reduced, mechanical strength increases.
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