The papermaking potential of bleached kraft pulps made from hemp stalks, hemp woody-core and hemp bast fibres was studied and compared with that of bleached birch pulp and pine kraft pulp. It has been shown that among the pulps from these raw materials, hemp stalk pulp has the most useful properties for papermaking. The disadvantages of hemp woody-core pulp and hemp bast fibre pulp as papermaking intermediates proved to be low tear resistance and low tensile strength, respectively. Results indicate that the main reasons for the low tensile strength of hemp bast fibre pulp are the low susceptibility of their fibres for internal fibrillation and low hemicellulose content. The technology used in this work for the processing of hemp bast fibres into papermaking pulp made it possible to obtain pulp with high a-cellulose content from this fibrous raw material with a high yield in a much simpler way than when such pulps are obtained from wood.
The absorption of 1-butyl-3-methylimidazolium chloride and acetate taken from commercial packaging was studied by means of UV-VIS and infrared spectroscopy with some differences observed. Further research showed that heating both 1-butyl-3-methylimidazolium chloride and acetate alone, as well as in the presence of wood pulp, causes the darkening of these ionic liquids. Changes in the colour of ionic liquids associated with a variation in the absorption characteristics of pure ionic liquids and wood solutions in these liquids in UV and visible light are expressed primarily in the widening of the absorption bands. The presence of coloured products formed during their heating, as well as dissolution of the chemical components of wood in ionic liquids, had relatively little effect on the position of individual absorption bands in the spectrum obtained by the FT-IR method. The small differences in the absorption of spruce groundwood solutions in ionic liquids in IR as compared to pure ionic liquids suggest that strong chromophore groups in ionic liquids are created without serious reconstruction of their structure.
The yield and kappa number of kraft pulps from tall wheatgrass, tall fescue, tall oatgrass, and Miscanthus were determined after pulping with 0.9% active alkali per 1% lignin content in raw materials. Fibre properties and test papers were also studied to evaluate the usefulness of these plants for papermaking. These results were compared with pulps prepared from birch and pine wood. Kraft pulps from the straws of grasses had yields similar to that of pulp from pine wood and lower kappa numbers than pulps from birch and pine wood. The tested pulps exhibited a favourable number of fibres in 1 g of pulp, and they resulted in papers with clearly differentiated properties from very resistant to rupture dense papers with very low air permeability, to less resistant to breaking more bulky papers.
The weight share of the pith, nodes and internodes in the stalks of Miscanthus, as well as the types of cells in these anatomical parts, were examined. Studies have shown that the pith contains mainly parenchyma cells, nodes-short fibres and palisade parenchyma cells, while internodes contains mainly fibres, which are accompanied by a certain amount of vessels and parenchyma cells. Then the whole stalks of Miscanthus were subjected to pulping using the kraft and soda pulping methods. These studies have shown that hard, regular, soft and very soft kraft pulps can be obtained using a lower amount of active alkali, with comparable or higher screened yield of pulp than is the case of pulping of birch. Furthermore, it was found that the content of knots and shives was lower in the digester hard and regular kraft pulps from Miscanthus compared to birch kraft pulp. Of the two pulping methods studied, kraft pulping gives better results than soda pulping concerning the considerably higher yield of pulp.
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