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Composite fibres that contain cellulose and lignin were produced from ionic liquid solutions by dry-jet wet spinning. Eucalyptus dissolving pulp and organosolv/kraft lignin blends in different ratios were dissolved in the ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate to prepare a spinning dope from which composite fibres were spun successfully. The composite fibres had a high strength with slightly decreasing values for fibres with an increasing share of lignin, which is because of the reduction in crystallinity. The total orientation of composite fibres and SEM images show morphological changes caused by the presence of lignin. The hydrophobic contribution of lignin reduced the vapour adsorption in the fibre. Thermogravimetric analysis curves of the composite fibres reveal the positive effect of the lignin on the carbonisation yield. Finally, the composite fibre was found to be a potential raw material for textile manufacturing and as a precursor for carbon fibre production.

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Ionic liquid-cosolvent systems have been proposed as selective solvent media for lignocellulosic materials.We present the ionic liquid-aided fractionation of silver birch (Betula pendula) combined with an autohydrolysis pretreatment. Contrary to untreated birchwood meal, autohydrolyzed birchwood meal reveals quantitative dissolution in 1-ethyl-3-methylimidazolium acetate and distinct separation into the individual wood polymers upon regeneration in acetone/water. The process yields two main fractions, a cellulose-rich precipitate with a residual lignin content of 13-15% and another virtually pure lignin fraction. No cellulose yield loss is observed during the ionic liquid processing step. A comprehensive mass balance of the process, including insoluble material, wash waters, and soluble residues, is provided. The product fractions are characterised for their chemical compositions, molar mass distributions and structural characteristics by Klason lignin and sugar analysis, 13 C NMR, GPC and WAXS. The study investigates the effects of wood particle size and autohydrolysis intensity on fractionation efficiency and selectivity.

This study describes a systematic characterization of lignin samples fractionated from industrial black liquor and an evaluation of their suitability as a component (50 wt.%) in thermoplastic blends with polyethylene with a special emphasis on tensile and impact properties. Industrial softwood kraft lignin was isolated from three different cooking stages and subsequently fractionated by sequential acid precipitation. Altogether, nine lignin fractions were subjected to several chemical/thermal analyses to compare their structural features and thermal decomposition properties. Lignin samples precipitated at pH 10.5 exhibited the highest molecular weight (M w) and purity, demonstrated by the lowest content of sulfur and polysaccharides. In contrast, samples precipitated at a low pH in general exhibited higher amount of impurities and low methoxyl group content. It was found that lignin precipitated at low pH contained the biggest share of sulfur present in kraft lignin. However, about 70 % of sulfur in these samples is present in non-bounded form and could be extracted with CS2. Additionally, low M w lignin exhibited a significantly lower T g value, which could favor material processing. A notable decrease in the thermal stability of the tested lignin samples was observed with a decrease in the molecular weight. In addition, lignin with a low M w, high phenolic hydroxyl groups, and lower number of double bonds seems to be favorable for increased tensile strength and elastic modulus of the polyethylene–lignin blend materials