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- Elegir, Graziano, et al.
(författare)
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Laccase-initiated cross-linking of lignocellulose fibres using a ultra-filtered lignin isolated from kraft black liquor
- 2007
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 77:4, s. 809-817
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the effect of Trametes pubescens laccase (TpL) used in combination with a low-molecular-weight ultra-filtered lignin (UFL) to improve mechanical properties of kraft liner pulp and chemi-thermo-mechanical pulp was studied. UFL was isolated by ultra-filtration from the kraft cooking black liquor obtained from softwood pulping. This by-product from the pulp industry contains an oligomeric lignin with almost twice the amount of free phenolic moieties than residual kraft pulp lignin. The reactivity of TpL on UFL and kraft pulp was studied by nuclear magnetic resonance spectroscopy and size exclusion chromatography. Laccase was shown to polymerise UFL and residual kraft pulp lignin in the fibres, seen by the increase in their average molecular weight and in the case of UFL as a decrease in the amount of phenolic hydroxyls. The laccase initiated cross-linking of lignin, mediated by UFL, which gives rise to more than a twofold increase in wet strength of kraft liner pulp handsheets without loosing other critical mechanical properties. Hence, this could be an interesting path to decrease mechano-sorptive creep that has been reported to lessen in extent as wet strength is given to papers. The laccase/2,2'azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) mediator system showed a greater increase in wet tensile strength of the resulting pulp sheets than the laccase/UFL system. However, other mechanical properties such as dry tensile strength, compression strength and Scott Bond internal strength were negatively affected by the laccase/ABTS system.
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| 2. |
- Gazzotti, Stefano, et al.
(författare)
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Cellulose nanofibrils as reinforcing agents for PLA-based nanocomposites : An in situ approach
- 2019
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 171, s. 94-102
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Tidskriftsartikel (refereegranskat)abstract
- One-pot in situ polymerization approach was explored for the preparation of polylactide (PLA)-cellulose nano-fibril (CNF) bio-nanocomposites. CNF were first prepared through enzymatic and mechanical treatment of bleached hardwood kraft pulp. The bio-nanocomposites- were then fabricated through ring opening polymerization (ROP) of L-lactide, in the presence of various amounts of fibrils. Molecular weight, thermal properties, surface morphology, mechanical and wettability properties of the PLA-CNF nanocomposites were evaluated. DSC analysis demonstrated the effect of CNF on crystallization and crystalline morphology of PLA. Improved modulus for the nanocomposites with respect to standard PLA was demonstrated, however, the differences in tensile stress were small probably due to the counteracting effects of reinforcement from CNF and the decreasing molecular weight as a function of CNF concentration. The absence of pulled-out fibers was assessed, highlighting the strong interface and covalent attachment of PLA chains on CNF surface. Finally, the covalent bonding of PLA chains on CNF surface was demonstrated by isolating the non-soluble part, consisting of PLA-grafted CNF, and characterization of this residue.
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