| 1. |
- Anugwom, I, et al.
(författare)
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Selective Extraction of Hemicelluloses from Spruce using Switchable Ionic Liquids
- 2012
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 87:3, s. 2005-2011
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Tidskriftsartikel (refereegranskat)abstract
- Switchable Ionic Liquids (SILs) made from alcohols, either hexanol or butanol, and CO2 together with an amidine (1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU)) were investigated as dissolution/fractionation solvents for wood material. Both native spruce (Picea abies), and pre-extracted spruce were treated with either butanol SIL (SIL1) or hexanol SIL (SIL 2) for 5 days at 55 °C under normal pressure. The SILs were formed by bubbling CO2 through an equimolar mixture of either 1-hexanol or 1-butanol and DBU. The viscosity of the mixture increased from 7.1 mPas to 2980 mPas for SIL 2 and 5.1 to 1600 mPas for SIL 1. Melting points of the SILs 1 and 2 were at 8 and 14 °C, respectively. After the treatment time (5 days), the undissolved fraction contained 38 wt % less hemicelluloses compared to native spruce. There was an increase in the glucose content of the milled spruce treated with both SILs, since the milling step reduced the cellulose crystallinity of the wood and facilitated an easier SIL access into the wood. The solvents were very neutral in terms of lignin removal. Consequently, only about 2% of the lignin was removed from native wood. Moreover, a priori removal of the wood extractives did not influence the lignin removal. Highlights► Switchable Ionic Liquids made from, either hexanol or butanol, and CO2 together with an amidine (DBU) were studies as dissolution/fractionation solvents for spruce wood. ► After the treatment undissolved fraction contained 38 wt-% less hemicelluloses. ► We conclude that Switchable ionic liquids are effective solvent for fractionation of wood material, and they are easily recycled and can be reused.
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| 2. |
- Bergström, Elina Mabasa, et al.
(författare)
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Plasticized xyloglucan for improved toughness-Thermal and mechanical behaviour
- 2012
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 87:4, s. 2532-2537
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Tidskriftsartikel (refereegranskat)abstract
- Tamarind seed xyloglucan is an interesting polysaccharide of high molar mass with excellent thermomechanical properties. Several plasticizers were studied in order to facilitate thermal processing and improve toughness (work to fracture) of xyloglucan film materials: sorbitol, urea, glycerol and polyethylene oxide. Films of different compositions were cast and studied by thermogravimetric analysis (TGA), calorimetry (DSC), dynamic mechanical thermal analysis (DMA) and tensile tests. Results are analysed and discussed based on mechanisms and practical considerations. Highly favourable characteristics were found with XG/sorbitol combinations, and the thermomechanical properties motivate further work on this material system, for instance as a matrix in biocomposite materials.
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| 3. |
- Carlstedt, Jonas, et al.
(författare)
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Hydration and the phase diagram of acid hydrolyzed potato starch
- 2014
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Ingår i: Carbohydrate Polymers. - : Elsevier. - 0144-8617 .- 1879-1344. ; 112, s. 569-577
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Tidskriftsartikel (refereegranskat)abstract
- We investigated hydration of acid hydrolyzed potato starch (maltodextrin) employing a multi-method approach. In particular, synchrotron radiation X-ray scattering and differential scanning calorimetry were used, and, for the first time, the material was investigated with sorption calorimetry and a newly developed quartz crystal microbalance with humidity scanning. The dry starch was found to be in an amorphous state. During hydration it exhibits a glass transition in both bulk and thin film samples, followed by an exothermic event where the starch crystallized. Recrystallized bulk samples displayed neither a pronounced glass transition nor crystallization upon hydration whereas both events occurred in thin film samples. The hydration-driven crystallization resulted in an X-ray pattern consistent with the coexistence of A and B type crystallites; however, at higher water concentrations only the B form occurred. The results were used to construct the first ever acid hydrolyzed starch–water phase diagram.
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| 4. |
- Dax, Daniel, et al.
(författare)
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Cationic hemicellulose-based hydrogels for arsenic and chromium removal from aqueous solutions
- 2014
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 111, s. 797-805
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Tidskriftsartikel (refereegranskat)abstract
- In this work the synthesis of hemicellulose-based hydrogels and their application for the removal of arsenic and chromium ions is described. In a first step O-acetyl galactoglucomannan (GGM) was subjected to a transesterification applying glycidyl methacrylate (GMA) for the synthesis of novel GGM macromonomers. Two distinguished and purified GGM fractions with molar mass of 7.1 and 28 kDa were used as starting materials. The resulting GGM macromonomers (GGM-MA) contained well-defined amounts of methacrylate groups as determined by H-1 NMR spectroscopy. Selected GGM-MA derivatives were consecutively applied as a crosslinker in the synthesis of tailored hydrogels using [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MeDMA) as monomer. The swelling rate of the hydrogels was determined and the coherence between the swelling rate and the hydrogel composition was examined. The morphology of the GGM-based hydrogels was analysed by SEM and the hydrogels revealed a high surface area and were assessed in respect to their ability to remove arsenate and chromate ions from aqueous solutions. The presented bio-based hydrogels are of high interest especially for the mining industries as a sustainable material for the treatment of their highly contaminated wastewaters.
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| 5. |
- Djafari Petroudy, Seyed Rahman, et al.
(författare)
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Effects of bagasse microfibrillated cellulose and cationic polyacrylamide on key properties of bagasse paper
- 2014
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 99, s. 311-318
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Tidskriftsartikel (refereegranskat)abstract
- This study explores the benefits of using bagasse microfibrillated cellulose (MFC) in bagasse paper. Two different types of MFC were produced from DED bleached soda bagasse pulp. The MFC was added to soda bagasse pulp furnishes in different amounts. Cationic polyacrylamide (C-PAM) was selected as retention aid. The results show that addition of MFC increased the strength of paper as expected. Interestingly, 1% MFC in combination with 0.1% C-PAM yielded similar drainage time as the reference pulp, which did not contain MFC. In addition, the samples containing 1% MFC and 0.1% C-PAM yielded (i) a significant increment of the tensile index, (ii) a minor decrease of opacity and (iii) preserved Gurley porosity. Hence, this study proves that small fractions of MFC in combination with adequate retention aids can have positive effects with respect to paper properties, which is most interesting from an industrial point of view.
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| 6. |
- Eguees, Itziar, et al.
(författare)
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Corncob arabinoxylan for new materials
- 2014
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 102, s. 12-20
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Tidskriftsartikel (refereegranskat)abstract
- Corncob agricultural waste was used as a source of arabinoxylan for preparation of films. Three arabinoxylan samples were prepared: crude extract (CCAX), purified by a washing step, and purified by bleaching CCAX. Films prepared with untreated CCAX were water soluble, yellowish in color and had poor mechanical properties. After the purification processes the Young's modulus increased from similar to 293 MPa to similar to 1400-1600 MPa, and strength was improved from similar to 9 MPa to around 53 MPa, while the strain at break was kept at similar to 8% both in untreated and purified CCAX. The contact angle was increased from similar to 21.3 degrees to 67-74 degrees after washing or bleaching CCAX. Acetylation of bleached CCAX showed the highest thermal resistance (325 degrees C), had low T-g (125 degrees C) and a high contact angle (80 degrees), and its films were stronger (strength similar to 67 MPa; Young's modulus similar to 2241 MPa) and more flexible (similar to 13%). These characteristics make purified CCAX a suitable material to be used as a matrix for film applications.
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| 7. |
- Escalante, Alfredo, 1975, et al.
(författare)
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Flexible oxygen barrier films from spruce xylan
- 2012
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 87:4, s. 2381-2387
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Tidskriftsartikel (refereegranskat)abstract
- Arabinoglucuronoxylan was extracted from Norway spruce and films prepared by casting from aqueous solution. The sugar analysis and NMR confirmed that the spruce xylan was composed of arabinose, 4-O-methyl-glucuronic acid and xylose in a ratio of 1:2:11 respectively. Substitutions of 4-O-methyl-alpha-D-GlcpA at O-2 and of alpha-L-Araf at O-3 on the xylose backbone were found by NOE analysis. NOE cross-peaks indicated as well that there is at least one free xylose on the main chain present between two substitutions. Whether the distribution of side chains was random or in blocks was uncertain. The average molecular weight of the sample was determined by size exclusion chromatography to be 12,780 g/mol. Arabinoglucoronoxylan casting yielded transparent flexible films with an average stress at break of 55 MPa, strain at break of 2.7% and a Young's Modulus 2735 MPa. Wide-angle X-ray scattering analysis showed that the arabinoglucuronoxylan films were totally amorphous. Addition of sorbitol as plasticizer resulted in less strong but more flexible films (strain at break of 5%). Peaks of crystallinity could be seen in X-ray which corresponds to sorbitol crystallizing in distinct phases. The dynamic mechanical analysis showed that the arabinoglucuronoxylan film softened at a later relative humidity (80% RH) in comparison with plasticized films (60% RH). The films showed low oxygen permeability and thus have a potential application in food packaging.
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| 8. |
- Fernandes, Susana C. M., et al.
(författare)
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Transparent chitosan films reinforced with a high content of nanofibrillated cellulose
- 2010
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 81:2, s. 394-401
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the preparation and characterization of nanocomposite films based on different chitosan matrices and nanofibrillated cellulose (NFC) for the purpose of improving strength properties. The nanocomposite films were prepared by a simple procedure of casting a water-based suspension of chitosan and NFC, and were characterized by several techniques: namely SEM, X-ray diffraction, visible spectrophotometry, TGA, tensile and dynamic-mechanical analysis. The films obtained were shown to be highly transparent (transmittance varying between 90 and 20% depending on the type of chitosan and NFC content), flexible, displayed better mechanical properties, with a maximum increment on the Young's modulus of 78% and 150% for high molecular weight (HCH) and water-soluble high molecular weight (WSHCH) filled chitosans, respectively; and of 200% and 320% for low molecular weight (LCH) and water-soluble filled (WSLCH) chitosans, respectively. The filled films also showed increased thermal stability, with, for example, an increase in the initial degradation temperature (Td(i)) from 227 degrees C in the unfilled LCH film up to 271 degrees C in filled LCHNFC50% nanocomposite films, and a maximum degradation temperature (Tdi) raising from 304 degrees C to 313 degrees C for the same materials.
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| 9. |
- Fortunati, E., et al.
(författare)
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Multifunctional bionanocomposite films of poly(lactic acid), cellulose nanocrystals and silver nanoparticles
- 2012
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 87:2, s. 1596-1605
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposite films were prepared by the addition of cellulose nanocrystals (CNCs) eventually surfactant modified (s-CNC) and silver (Ag) nanoparticles in the polylactic acid (PLA) matrix using melt extrusion followed by a film formation process. Multifunctional composite materials were investigated in terms of morphological, mechanical, thermal and antibacterial response. The nanocomposite films maintained the transparency properties of the PLA matrix. Thermal analysis showed increased values of crystallinity in the nanocomposites, more evident in the s-CNC based formulations that had the highest tensile Young modulus. The presence of surfactant favoured the dispersion of cellulose nanocrystals in the polymer matrix and the nucleation effect was remarkably enhanced. Moreover, an antibacterial activity against Staphylococcus aureus and Escherichia coil cells was detected for ternary systems, suggesting that these novel nanocomposites may offer good perspectives for food packaging applications which require an antibacterial effect constant over time. (C) 2011 Elsevier Ltd. All rights reserved.
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| 10. |
- Gillgren, T., et al.
(författare)
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Modulating rheo-kinetics of native starch films towards improved wet-strength
- 2011
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 83:2, s. 383-391
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Tidskriftsartikel (refereegranskat)abstract
- Starch directly functionalised in the plant by modulation of its biosynthesis by mutagenesis and transgene technology was exploited for its extended functionality beyond the normal variation In this study we investigated the theological and mechanical properties of films from such structurally highly different starch types derived from potato and cereal sources of normal and mutant and transgenic backgrounds A new improved technique was developed to permit the dynamic mechanical analysis of films in the presence of water It was found that the amylose content was decisive for the mechanical properties of the films - an increase in the amylose content resulted in both a higher stress and strain at break Interestingly there was no correlation between the speed of hydration and mechanical water resistance of the films Generally the films were clear and transparent even after wetting Transgenic potato starch with a low content of phosphate displayed an extraordinary combination of high robustness transparency mechanical strength and extensibility even in a wet condition The combination of optimal phosphate and amylose concentrations in this sample probably favoured hydration and amorphisation without compromising the inter-chain interactions of the polysaccharide network.
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