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- Berglund, Lars A., 1956-, et al.
(författare)
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Eco-friendly high-strength composites based on hot-pressed lignocellulose microfibrils or fibers
- 2021
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society. - 2168-0485. ; 9:4, s. 1899-1910
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Tidskriftsartikel (refereegranskat)abstract
- Unbleached lignocellulosic wood fiber materials of low porosity are of great interest as eco-friendly load-bearing materials because their yield is much higher than that for “pure” wood cellulosics. The difference between comparable materials based on lignocellulose fibers or nanocellulose is investigated. The structure, surface area, mechanical properties, moisture sorption, and optical properties of films based on fibers or microfibrillated lignocellulose (MFLC) were characterized as a function of lignin content, and the environmental impact was compared. The modulus and tensile strength of comparable fiber and MFLC films (≈25% porosity) increased up to an optimum lignin content (11−17%) and then decreased at a very high lignin content. Hot-pressed MFLC films with little porosity showed excellent properties, 230−260 MPa strength, 17−20 GPa modulus, and 81 MPa wet strength. The mechanical property values of hot-pressed wood fibers with 25% porosity were also as high as 154 MPa strength and 13.2 GPa modulus, which are higher than those of comparable materials reported in the literature. Because hot-pressed lignocellulose fibers can be readily recycled and show low cumulative energy demand, they are candidates for semistructural engineering materials. MFLC is of great interest for coatings, films, adhesives, and as additives or in high-technology applications.
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| 2. |
- Larsson, Per Tomas, et al.
(författare)
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Bulking method for chemical pulps and its effect on cellulose structure - A CP/MAS 13C-NMR Study
- 2021
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Ingår i: TAPPICon LIVE. - : TAPPI Press. - 9781713848370 ; , s. 460-464
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Konferensbidrag (refereegranskat)abstract
- Cellulose-rich never-dried acetate grade Eucalyptus dissolving pulp was used to study the effects on the supramolecular structure of cellulose due to the addition of AlCl3 during drying from acidic conditions (pH 3.5). CP/MAS 13C-NMR was the analytical technique used for taking measures of the cellulose supramolecular structure. In this study AlCl3 was used as source of Al3+, but Al2(SO4)3 has been shown to give the same effect and it is believed that any salt of Al3+ will give the same effect. The presence of AlCl3 increased the average lateral fibril aggregate dimensions some 25% above that reached by the pulp dried without addition of AlCl3. The observed changes in cellulose supramolecular structure due to the addition of AlCl3 are large considering the low AlCl3 concentration that was used. No change in degree of crystallinity was observed as the result of drying, either with or without AlCl3 addition. Although the mechanism of action for AlCl3, causing the observed effects on the cellulose supramolecular structure, is currently not fully understood, the interpretation made was that the presence of AlCl3 increased the agglomeration of the cellulose that always take place during the first drying of cellulosic fibres. This can be seen as an increased degree of physical cross-linking in the cellulose network.
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