Browsing by Author "Hummel, Michael, Dr., Aalto University, Department of Bioproducts and Biosystems, Finland"

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  • Fibre spinning from various low refined, recycled lignocelluloses using ionic liquid
    (2018) Ma, Yibo
     School of Chemical Technology | Doctoral dissertation (article-based)
    This dissertation presents the application of Ioncell technology to the production of man-made cellulosic fibres using recycled and low refined lignocellulosic materials. Ioncell technology consists of a dry-jet wet spinning process using ionic liquid (IL) as a polymer solvent. High performance regenerated cellulosic fibres have been produced with ionic liquid [DBNH]OAc (1,5-diazabi-cyclo[4.3.0]non-5-enium acetate)/dissolving grade pulp dopes. It is also found that [DBNH]OAc is a powerful solvent for low refined lignocelluloses. The effect of lignin and hemicellulose on the fibre spinning is studied using cellulose and lignin (isolated pure lignin) blends and unbleached kraft pulps (residue lignin in native form). Composite fibres can be produced with lignin content in blends up to 50 wt%. Fibres produced from cellulose and lignin blends reveal a decrease in the crystallinity and degree of orientation, while the lignin share increases. As a result, the tensile strength of the composite fibres drops. On the other hand, increases in lignin content enhance the hydrophobicity and the carbonisation yield at high temperature. The unbleached pulps with different lignin content are yielded by kraft pulping with varying intensity. Prior to dissolution in IL, the degree of polymerisation of the pulp is adjusted by using acid-catalysed hydrolysis and electron beam irradiation for producing dopes with optimal viscosity. Fibres could be spun even from only mild refined pulps. The fibre properties display a similar trend compared to composite fibre as lignin content in pulps raises. Unlike the fibre produced from pure lignin, fibres containing native lignin exhibit improved moisture accessibility due to the morphological changes of the fibres. This thesis also investigates the utilisation of waste fine paper, cardboard, and newsprints as raw materials. All these raw materials are refined gradually to examine the effect of the substrates' chemical composition on the spinnability. Except for untreated cardboard, newsprint, and low refined kraft newsprint, all substrates demonstrate high spinnability leading to fibres with high tensile properties. An environmentally friendly alkaline glycerol pulping process is found to be an optimal pre-treatment for newsprint. Ioncell is a promising process for the conversion of recycled and low refined lignocellulose into high-value textile products. Prototype fabrics are knitted with yarns that are produced from fibres spun from cellulose and lignin blends, recycled cardboard, and newsprint. The lignin contained in the fibre can be used as a natural dye. The shade of fibres depends on the lignin content exhibits, from beige to dark brown.