The aim of this study was to evaluate some of the properties of densified poplar and birch wood earlier subjected to partial delignification of cell walls. The effects of delignification are presented as a comparison of the content of basic structural components in wood before and after chemical modification. In birch wood, the lignin content decreased by 20%, while that of cellulose decreased by 9.7% and that of hemicellulose decreased by 64.9%. In poplar, the lignin content decreased by 34.1%, that of cellulose decreaed by 13.5%, and that of hemicellulose decreased by 58.0%. The hardness of densified birch and poplar wood, after partial reduction of chemical components, was 147 and 111 MPa, respectively, and, compared with natural (non-densified) wood, was almost 4.5 times and 7 times higher, respectively. Poplar wood was more densified (without delignification 238% and after delignification 281%). In the case of birch wood, the density levels were 176% and 188%, respectively.

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The effects of thermomechanical pulp (TMP) bleaching with hydrogen peroxide under acidic and alkaline conditions were studied using different spectroscopic analytical methods. The results of hydroxyl radical determination in bleaching solutions, analyses of carbonyl and carboxyl groups contents in the pulp, and the cellulose fiber surface analysis by X-ray photoelectron spectroscopy (XPS) elucidate the chemistry of the hydrogen peroxide treatment. Diffuse reflectance laser flash photolysis (DRLFP) method showed the differences in the photochemical behavior that reflect the changes of the chromophoric system after the preliminary peroxide bleaching stage under acidic conditions. Fourier transform infrared (FTIR) spectroscopy confirmed the non-delignifying character of the bleaching process. Suppression of carbonyl and formation of carboxyl groups in the case of the two-stage peroxide bleaching performed in the presence of catalysts and stabilizers was also confirmed. FT-Raman studies showed the removal of coniferaldehyde groups after treatment under acidic and alkaline conditions.

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AbstractThe paper presents the results of studies on the deacidification of model papers (Whatman) using nanodispersions of magnesium hydroxide in 2-propanol. Preliminary experiments showed greater effectiveness of nanodispersion deacidification in comparison with the standard magnesium hydroxide reagent which was applied in the form of micrometric particles. Further analyses compared the effectiveness of deacidification by washing, spraying and brushing. Although all of the tested methods caused an increase in the pH of paper water extracts, the assays of magnesium contents using Atomic Absorption Spectrometry (AAS) and Scanning Electron Microscopy with an Energy Dispersive X-ray spectrometer (SEM-EDX) showed greatest effectiveness of deacidification by washing. Dispersion spraying requires repetition of the operation at least three times in order to provide an effect that would be comparable with that of washing. Brushing seems to be a less effective method of magnesium hydroxide application to paper. When comparing uniformity of magnesium application on the surface of the paper samples (mapping, SEM-EDX), it was found that the deacidifier was distributed more uniformly when sprayed than in the case of washing.

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This paper reports the results of neutral sulfite cooking of birch wood, with the addition of Miscanthus giganteus stalks as a complementary raw material. The results of the experiments indicate the potential use of miscanthus as an additive in industrial processes.