Browsing by Subject "Fibres"

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  • Ma, Yibo; Stubb, Jonas; Kontro, Inkeri; Nieminen, Kaarlo; Hummel, Michael; Sixta, Herbert (2018)
    Man-made lignocellulosic fibres were successfully prepared from unbleached birch kraft pulps by using the Ioncell-F technology. Pulps with different lignin content were produced by tailored kraft pulping with varying intensity. The degree of polymerization of the pulps was adjusted by acid-catalyzed hydrolysis and electron beam treatment. All substrates were completely soluble in 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH] OAc) and the respective solutions were spinnable to yield fibres with good to excellent mechanical properties despite the use of only mildly refined wood pulp. The tensile properties decreased gradually as the lignin concentration in the fibres increased. Changes in the chemical composition also affected the structure and morphology of the fibres. Both the molecular orientation and the crystallinity decreased while the presence of lignin enhanced the water accessibility. The effects of the crystallite size and lignin content on monolayer water adsorption are discussed.
  • Rasa, Kimmo; Vihera-Aarnio, Anneli; Rytkonen, Peetu; Hyvaluoma, Jari; Kaseva, Janne; Suhonen, Heikki; Jyske, Tuula (2021)
    Novel bioeconomic approaches call for increasingly faster production of lignocellulosic biomass and its bettertailored use for higher added value. The high-yield capacity and structural properties of willows (Salix spp.) suggest their excellent potential for the production of designed biochar for use in agronomic, electronic and technical applications. All these applications rely on the internal pore structure of biochar. However, we lack an in-depth quantitative understanding of the interlinkages between the feedstock properties and the physical quality of the biochar produced. We studied quantitatively how the clonal and within-plant properties of five different willow clones (hybrids of Salix schwerinii E.L. Wolf) affected the micrometre-scale pore properties of the produced biochars (pyrolyzed at + 462 ?C). The porosity and pore size distribution were analysed before and after slow pyrolysis by X-ray microtomography and image analysis. We also studied the potential of conventional low-cost fibre analysis techniques to be used to predict biochar pore properties directly from fresh feedstock. The total porosity (0.55?0.62) and the pore size distribution of willow wood and derived biochars varied between clones. Approximately two-thirds of the biochar total porosity was associated with pores formed by wood fibres. Pyrolysis levelled off the structural variation detected between and within the clones. Pyrolysis-induced shrinkage reduced the pore sizes and narrowed the pore size distribution. The results suggest that conventional fibre analysis techniques could be utilized to predict biochar homogeneity. Short rotation coppice willows are suitable feedstock to produce homogenous biochar precursor for production of bio-based carbon materials to be used in high value-added technical applications. The structural homogeneity of the feedstock and produced biochar can be enhanced by selecting proper harvesting strategy and clones used in plantations. From the industrial perspective, comprehensive understanding of feedstock properties helps to control quality of the produced biochar.