| 1. |
- Gordobil, Oihana, et al.
(författare)
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Surface chemistry and bioactivity of colloidal particles from industrial kraft lignins
- 2022
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 220, s. 1444-1453
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Tidskriftsartikel (refereegranskat)abstract
- The morphology control of lignin through particle size reduction to nanoscale seems to be a suitable conversion technology to overcome the intrinsic limitations of its native form to develop a wide range of biomaterials with high performance. Colloidal lignin particles (CLPs) in the range of 150-200 nm were synthesised from hardwood and softwood kraft lignins by the solvent shifting method. The initial molecular features of kraft lignins were evaluated in terms of purity, molecular weight distribution, and chemical functionalities. The impact of the lignin source and structure on the morphology, size distribution, and surface chemistry of CLPs was evaluated by particle size analyser, SEM, TEM and H-1 NMR. The results evidenced the influence of the botanical origin on the morphology and surface chemistry of particles. Furthermore, the antioxidant properties and cytotoxicity of lignins and corresponding CLPs, towards lung fibroblast cells were compared. CLPs from hardwood kraft lignins exhibited higher antioxidant power against DPPH free radical and a higher cytotoxic effect (IC30 = 67-70 mu g/mL) against lung fibroblast when compared to CLPs from softwood kraft lignin (IC30 = similar to 91 mu g/mL). However, the cytotoxicity of these biomaterials was dose-dependent, suggesting their potential application as active ingredients in cosmetic and pharmaceutic products at low concentrations.
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| 2. |
- Li, Huisi, et al.
(författare)
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A comparative study of lignin-containing microfibrillated cellulose fibers produced from softwood and hardwood pulps
- 2024
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Ingår i: Cellulose. - 0969-0239 .- 1572-882X. ; 31:2, s. 907-926
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Tidskriftsartikel (refereegranskat)abstract
- The expanding field of lignin-containing nanocellulose offers a sustainable alternative to fossil-based substances in applications such as packaging, coatings, and composites. This has underscored the importance to explore the impact of raw materials due to the complexities of lignin structures and different raw fiber characteristics, which plays a significant role in determining the properties of the resultant lignin-rich cellulose materials. This study presents a detailed investigation and comparison on the production and structure-property relationships of lignin-containing microfibrillated cellulose (LMFC) fibers prepared from unbleached softwood and hardwood kraft pulps. The microfibrillation process was analyzed for both softwood and hardwood pulps, comparing the results across various stages of fibrillation. Distinguishing features of lignin structures in softwood and hardwood pulps were identified through Py-GC/MS analysis. Additionally, Digital Image Correlation was employed to investigate the varying failure patterns in LMFC films derived from different wood species. Softwood-derived LMFC films demonstrate less strain-concentrated regions and strain variation, attributed to the formation of more physical crosslinking joints by the elongated fibers. Consequently, softwood-origin LMFC films displayed superior load-sharing and enhanced tensile strength (287 MPa) compared to those derived from hardwood. Additionally, the denser lignin structures in unbleached softwood pulp further boosted the stiffness of resultant softwood-derived films. Upon recycling, LMFC films exhibited superior recovery of mechanical properties following drying, suggesting their significant potential for widespread commercial use.
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| 3. |
- Li, Huisi, et al.
(författare)
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Enhancing the Strength and Flexibility of Microfibrillated Cellulose Films from Lignin-Rich Kraft Pulp
- 2023
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 11:47, s. 16793-16805
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Tidskriftsartikel (refereegranskat)abstract
- Recent progress in nanocellulose production favors lignin-rich raw fibers due to their cost effectiveness, higher yield of unbleached pulp, and added benefits from residual lignin, positioning them as ideal substitutes for fossil-based materials in composites and packaging. Nonetheless, their application has been impeded due to their inferior mechanical properties. This study introduces a simplified method to enhance the strength of lignin-containing microfibrillated cellulose (LMFC) films using water as a plasticizer during drying. Both LMFC from unbleached pulps and lignin-free microfibrillated cellulose (MFC) from fully bleached industrial kraft pulp were prepared through an environmentally friendly and scalable method. Given the charged carboxylic groups from hemicellulose and residual lignin, the LMFC gel demonstrated greater colloidal stability compared to MFC. Moreover, lignin-rich films displayed heightened hydrophobicity and exceptional thermal stability (T-max > 345 degrees C). A significant improvement in tensile strength and Young's modulus of LMFC films was achieved with an elevated drying temperature from 40 degrees C to above 90 degrees C, increasing tensile strength from 248 to 283 MPa and Young's modulus by 84%. These improvements are attributed to the thermoplastic nature of lignin and the plasticizing effect of water at elevated temperatures. The longer fibers in microfibrillated films also improved the resistance to cracking in a folded state. The study highlights that enhancement of the properties of lignin-rich films can occur during the film making step itself, hinting at a sustainable, innovative method for creating robust and scalable materials for flexible devices, biocomposites, and packaging.
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