| 1. |
- Hasani, Merima, 1978, et al.
(författare)
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Nano-cellulosic materials: The impact of water on their dissolution in DMAc/LiCl
- 2013
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 98:2, s. 1565-1572
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Tidskriftsartikel (refereegranskat)abstract
- The dissolution behaviour of disassociated cellulosic materials in N,N-dimethylacetamide/lithium chloride (DMAc/LiCl) was investigated. The parameters monitored were chromatographic elution profiles and recovered mass by means of gel permeation chromatography (GPC) with RI detection. In order to elucidate the impact of the disassembly on cellulosic fibres, comparative studies were performed with the non-disassociated cellulose counterparts. The importance of the presence of water was addressed by Karl Fischer titration and solvent exchange experiments. Morphological changes during the dissolution process were studied by scanning electron microscopy (SEM). Dissolution of fibrillated cellulosic materials is impeded compared to the non-fibrillated material. This is a consequence of the high-surface-area fibrils prone to retain high amounts of water. Dissolution behaviour of nano-crystalline cellulosic materials appeared to be source-dependent. Due to the absence of entangled networks, these materials retain only water bound at the surface of the nano-crystallites, indicative of both the exposed surface area and solubility. The small cellulose nano-particles extracted from dissolving pulp show lower solubility compared to the large NCC particles from cotton.
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| 2. |
- Henniges, U., et al.
(författare)
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Electron Beam Irradiation of Cellulosic Materials-Opportunities and Limitations
- 2013
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 6:5, s. 1584-1598
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Tidskriftsartikel (refereegranskat)abstract
- The irradiation of pulp is of interest from different perspectives. Mainly it is required when a modification of cellulose is needed. Irradiation could bring many advantages, such as chemical savings and, therefore, cost savings and a reduction in environmental pollutants. In this account, pulp and dissociated celluloses were analyzed before and after irradiation by electron beaming. The focus of the analysis was the oxidation of hydroxyl groups to carbonyl and carboxyl groups in pulp and the degradation of cellulose causing a decrease in molar mass. For that purpose, the samples were labeled with a selective fluorescence marker and analyzed by gel permeation chromatography (GPC) coupled with multi-angle laser light scattering (MALLS), refractive index (RI), and fluorescence detectors. Degradation of the analyzed substrates was the predominant result of the irradiation; however, in the microcrystalline samples, oxidized cellulose functionalities were introduced along the cellulose chain, making this substrate suitable for further chemical modification.
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| 3. |
- Nypelö, Tiina, 1982, et al.
(författare)
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Submicron hierarchy of cellulose nanofibril films with etherified hemicelluloses
- 2017
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 177, s. 126-134
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Tidskriftsartikel (refereegranskat)abstract
- The lack of simple differentiation of all-polysaccharide-film components in nanoscale hinders unveiling their structure-property dependency. Submicron hierarchy of films of cellulose nanofibrils (CNFs) and carbohydrate-based additives was revealed via visualization of the components by their differentiating adhesion to an Atomic Force Microscope (AFM) tip. The differentiation of the film components revealed that distribution of hydroxypropylated hemicellulose in the CNF matrix could be tuned by addition of a plasticizer. The hemicellulose hydroxypropylation degree of substitution (DS) was detected to be another parameter affecting the film structure due to the water-solubility depending on the DS. This was further verified via Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). The translucent, self-standing films comprising CNFs, sorbitol and hydroxypropylated hemicellulose were tested for mechanical, optical and oxygen diffusion performance. The performance was linked to their structural evenness, which confirmed that the oxygen diffusion through the film is tremendously affected by the film nano hierarchy.
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