| 1. |
- Henriksson, Gunnar, 1965-, et al.
(författare)
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Monocomponent endoglucanases : an excellent tool in wood chemistry and pulp processing
- 2005
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Ingår i: 13th ISWFPC (International Symposium on Wood, Fibre and Pulping Chemistry), Auckland, New Zealand, 16-19 May 2005: Proceedings. ; , s. 503-508
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Konferensbidrag (refereegranskat)abstract
- Highly pure cellulases of endoglucanase type produced by genetically modified fungi are commercially available. They are useful tools both for analytical wood chemistry and potentially also as industrial chemicals for novel processes for the pulp and paper industry. Here the functionality of cellulases and some application of endoglucanases are reviewed. The mechanisms behind the effects of the enzyme are discussed.
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| 2. |
- Henriksson, Marielle, et al.
(författare)
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An environmentally friendly method for enzyme-assisted preparation of microfibrillated cellulose (MFC) nanofibers
- 2007
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 43:8, s. 3434-3441
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Tidskriftsartikel (refereegranskat)abstract
- Microfibrillated cellulose nanofibers (MFC) provide strong reinforcement in polymer nanocomposites. In the present study, cellulosic wood fiber pulps are treated by endoglucanases or acid hydrolysis in combination with mechanical shearing in order to disintegrate MFC from the wood fiber cell wall. After successful disintegration, the MFC nanofibers were studied by atomic force microscopy (AFM). Enzyme-treatment was found to facilitate disintegration, and the MFC nanofibers produced also showed higher average molar mass and larger aspect ratio than nanofibers resulting from acidic pretreatment.
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| 3. |
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| 4. |
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| 5. |
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| 6. |
- Dvinskikh, Sergey V., et al.
(författare)
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A multinuclear magnetic resonance imaging (MRI) study of wood with adsorbed water : Estimating bound water concentration and local wood density
- 2011
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 65:1, s. 103-107
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between moisture and the macromolecular wood tissue is of critical importance to wood properties. In this context, magnetic resonance imaging (MRI) is very promising as this method could deliver molecular information on the submillimeter scale (i.e., along concentration gradients) about both free and adsorbed water and the cell wall polymers. In the present study, it is demonstrated for the first time that wood containing adsorbed heavy water ((H2O)-H-2) can be studied by MRI based on separated images due to water (H-2 MRI) and cell wall polymers (H-1 MRI). Data confirm that in specimens equilibrated at controlled humidity there is a direct correlation between bound water content and relative density of the polymers in wood tissue; there is a strong variation across annual rings.
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| 7. |
- Dvinskikh, Sergey V., et al.
(författare)
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NMR imaging study and multi-Fickian numerical simulation of moisture transfer in Norway spruce samples
- 2011
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Ingår i: Engineering structures. - : Elsevier BV. - 0141-0296 .- 1873-7323. ; 33:11, s. 3079-3086
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Tidskriftsartikel (refereegranskat)abstract
- Wood has potential as a renewable material for a large variety of applications that often call for improved properties such as dimensional stability, moisture insensitivity, and durability. Moisture migration in wood is a particularly important factor in determining the cost-effective service life of wooden construction. Within the present research, proton NMR imaging was applied for recording the moisture spatial distribution of various samples of Norway Spruce. Moisture distribution along the radial, tangential and longitudinal directions in wood was monitored at different times upon three consecutive changes of relative humidity: (1) from 65% to 94%; (2) from 94% to 33%; (3) from 33% to 65%. Uncoated samples and specimens treated with different types of surface coatings were studied. The experiments were numerically simulated by using the multi-Fickian model. The model describes the moisture transport process in wood which is characterized by three phenomena: (a) bound water diffusion, (b) water vapor diffusion and (c) coupling between the two phases through sorption. The model is implemented into the Abaqus FEM code. The numerical results are found to be in agreement with the experimental data.
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| 8. |
- Fall, Andreas, et al.
(författare)
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The effect of ionic strength and pH on the dewatering rate of cellulose nanofibril dispersions
- 2022
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Ingår i: Cellulose. - : Springer Science and Business Media B.V.. - 0969-0239 .- 1572-882X. ; 29:14, s. 7649-7662
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibrils, CNFs, show great potential in many application areas. One main aspect limiting the industrial use is the slow and energy demanding dewatering of CNF suspensions. Here we investigate the dewatering with a piston press process. Three different CNF grades were dewatered to solid contents between approx. 20 and 30%. The CNF grades varied in charge density (30, 106 and 604 µmol/g) and fibrillation degree. The chemical conditions were varied by changing salt concentration (NaCl) and pH and the dewatering rates were compared before and after these changes. For the original suspensions, a higher charge provides slower dewatering with the substantially slowest dewatering for the highest charged CNFs. However, by changing the conditions it dewatered as fast as the two lower charged CNFs, even though the salt/acid additions also improved the dewatering rate for these two CNFs. Finally, by tuning the conditions, fast dewatering could be obtained with only minor effect on film properties (strength and oxygen barrier) produced from redispersed dispersion. However, dewatering gives some reduction in viscosity of the redispersed dispersions. This may be a disadvantage if the CNF application is as e.g. rheology modifier or emulsion stabilizer. Graphical abstract: [Figure not available: see fulltext.].
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| 9. |
- Heggset, Ellinor B, et al.
(författare)
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Cellulose nanofibrils as rheology modifier in mayonnaise – A pilot scale demonstration
- 2020
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Ingår i: Food Hydrocolloids. - : Elsevier B.V.. - 0268-005X .- 1873-7137. ; 108
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Tidskriftsartikel (refereegranskat)abstract
- The applicability of cellulose nanofibrils (CNFs) as viscosifying agent in a starch-reduced low-fat mayonnaise and in an oil-reduced full-fat mayonnaise has been considered. For low-fat mayonnaise a 50 wt% reduction in the ordinary starch content was performed, while for full-fat mayonnaise, the oil content was reduced from 79 to 70 wt%. To study if the stability was affected when CNFs were added, analyses as visual and accelerated stability tests, droplet size measurements and rheology studies, determining the shear viscosity, and the loss and storage moduli, were conducted after 1 day, 1 week and 1 month of storage in room temperature. Even though changes in droplet size distributions and rheological properties indicated some coalescence, the visual stability was not changed after 1 month of storage for any of the samples. The decrease in viscosity and moduli inflicted by reduction of starch or fat, could be regained by the addition of CNFs at 0.75 wt % and 0.42 wt %, respectively. Based on the results in this work, mayonnaise with reduced starch or fat content can be produced when CNFs are used as a viscosifying agent.
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| 10. |
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| 11. |
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| 12. |
- Henriksson, Marielle, 1976-
(författare)
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Cellulose Nanofibril Networks and Composites : Preparation, Structure and Properties
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Träbaserade cellulosananofibriller är intressanta som förstärkande fas i polymera nanokompositer; detta främst på grund av den kristallina cellulosans höga styvhet och på grund av nanofibrillernas förmåga att bilda nätverk. Cellulosananofibriller kan användas i form av mikrokristallin cellulosa, MCC, som har lågt längd/diameter förhållande, eller i form av mikrofibrillerad cellulosa, MFC, med högt längd/diameter förhållande. Målet med det här arbetet är att studera struktur-egenskapsförhållanden för nanofibrillnätverk och kompositer. Nanokompositer baserade på MCC och termoplastisk polyuretan tillverkades genom in-situ polymerisation. Cellulosafibrillerna var väl dispergerade i matrisfasen och kompositen visade ökad styvhet, styrka samt brottöjning. Dessa förbättningar antas bero på stark interaktion mellan polyuretan och cellulosananofibrillerna. En metod som underlättar mikrofibrillering av massafiberns cellvägg under homogenisering har utvecklats. Massan förbehandlades med ett enzym innan homogenisering. Den här metoden förenklade mikrofibrilleringen och mekanismerna diskuteras. De resulterande MFC-nanofibrillerna hade högt längd/diameter förhållande. Filmer har tillverkats av MFC-nanofibriller och filmernas struktur samt mekaniska egenskaper har studerats. Röntgendiffraktion och SEM visar att nanofibrilerna är mer orienterade i planet än i rymden. SEM och densitetsmätningar visar även att filmerna har en porös struktur. Resultaten från dragprovning visade att filmernas brottstyrka är beroende av molekylvikten för cellulosan. Nanofibrillerna med högst molekylvikt visade en E-modul på 13.2 GPa, brottstyrkan var 214 MPa och brottöjningen 10.1%. Kompositer med hög fiberhalt har tillverkats genom tillsats av melaminformaldehyd till MFC-filmer. Dessa kompositer visar ökad styvhet och styrka på bekostnad av brottöjningen. Kompositer har också tillverkats genom impregnering av MFC-nätverk med en hyperförgrenad polymer som tvärbands. DMA visar två Tg för kompositerna med 0.26 och 0.43 volymfraktion nanofibriller; matrisens Tg samt ytterligare ett Tg vid högre temperatur. Detta motsvarar molekyler med lägre mobilitet på grund av ökad interaktion med nanofibrillernas ytor.
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| 13. |
- Henriksson, Marielle, et al.
(författare)
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Cellulose nanopaper structures of high toughness
- 2008
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 9:6, s. 1579-1585
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose nanofibrils offer interesting potential as a native fibrous constituent of mechanical performance exceeding the plant fibers in current use for commercial products. In the present study, wood nanofibrils are used to prepare porous cellulose nanopaper of remarkably high toughness. Nanopapers of different porosities and from nanofibrils of different molar mass are prepared. Uniaxial tensile tests are performed and structure - property relationships are discussed. The high toughness of highly porous nanopaper is related to the nanofibrillar network structure and high mechanical nanofibril performance. Also, molar mass correlates with tensile strength. This indicates that nanofibril fracture controls ultimate strength. Furthermore, the large strain-to-failure means that mechanisms, such as interfibril slippage, also contributes to inelastic deformation in addition to deformation of the nanofibrils themselves. © 2008 American Chemical Society.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Henriksson, Marielle, et al.
(författare)
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Method of producing and the use of microfibrillated paper
- 2009
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Patent (populärvet., debatt m.m.)abstract
- The present invention relates to a method of producing a cellulose based paper, the paper itself and the use thereof where the paper exhibits enhanced mechanical properties. The method involves providing a suspension of well dispersed modified cellulose at a low concentration. The properties and the chemical structure of the paper make it suitable for in vivo applications such as implant material.
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| 18. |
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| 19. |
- Henriksson, Marielle, et al.
(författare)
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Novel nanocomposite concept based on cross-linking of hyperbranched polymers in reactive cellulose nanopaper templates
- 2011
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 71:1, s. 13-17
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Tidskriftsartikel (refereegranskat)abstract
- Cellulosic fibers offer interesting possibilities for good interfacial adhesion due to the high density of hydroxyl groups at the surface. in the present study, the potential of a new nanocomposite concept is investigated, where a porous cellulose nanofiber network is impregnated with a solution of reactive hyperbranched polyester. The polymer is chemically cross-linked to form a solid matrix. The resulting nanocomposite structure is unique. The matrix surrounds a tough nanopaper structure consisting of approximately 20 nm diameter nanofibers with an average interfiber distance of only about 6 nm. The cross-linked polymer matrix shows strongly altered characteristics when it is cross-linked in the confined space within the nanofiber network, including dramatically increased T-g, and this must be due to covalent matrix-nanofiber linkages.
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| 20. |
- Henriksson, Marielle, et al.
(författare)
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Producing paper, useful as e.g. filter paper, speaker membrane and suture, comprises providing modified nanofibrils of cellulose, providing suspension of modified nanofibrils, and filtering, dewatering and drying the nanofibrils
- 2009
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Patent (populärvet., debatt m.m.)abstract
- The present invention relates to a method of producing a cellulose based paper, the paper itself and the use thereof where the paper exhibits enhanced mechanical properties. The method involves providing a suspension of well dispersed modified cellulose at a low concentration. The properties and the chemical structure of the paper make it suitable for in vivo applications such as implant material.
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| 21. |
- Henriksson, Marielle, et al.
(författare)
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Structure and Properties of Cellulose Nanocomposite Films Containing Melamine Formaldehyde
- 2007
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 106:4, s. 2817-2824
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Tidskriftsartikel (refereegranskat)abstract
- Films of high Young's modulus and low density are of interest for application as loudspeaker membranes. In the present study nanocomposite films were prepared from microfibrillated cellulose (MFC) and from MFC in combination with melamine formaldehyde (MF). The prepared materials were Studied with respect to structure as well as physical and mechanical properties. Studies in SEM and calculation of porosity showed that these materials have a dense paper-like structure. The moisture sorption isotherms were measured and showed that Moisture content decreased in the presence of ME Mechanical properties were studied by dynamical mechanical thermal measurements as well as by tensile tests. Cellulose films showed an average Young's modulus of 14 GPa while the nanocomposites showed an average Young's modulus as high as 16.6 GPa and average tensile strength as high as 142 M.Pa. By controlling composition and structure, the range of properties of these materials can extend the property range available for existing materials. The combination of comparatively high mechanical damping and high sound propagation velocity is of technical interest.
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| 22. |
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| 23. |
- Karim, Zoheb
(författare)
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Processing and characterization of membranes based on cellulose nanocrystals for water purification : Nanocellulose as functional entity
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Membrane technology is being extensively used in water purification as an energy efficient and low cost process. Nanostructured (NSM) and nanoenabled (NEM) membranes are favored in this context as nanoscaled entities are expected to provide high surface area, high mechanical properties and versatile surface chemistry as well as provide better control on the pore size and distribution, flux and selectivity of the membrane. Biobased nanoparticles as nanocrystals are expected to have a significant advantage in this context. Thus, the main aim of this work was to explore the use of cellulose nanocrystals as functional entities for the fabrication of nanoenabled composite membranes and apply these fabricated membranes for the removal of dyes and metal ions from polluted water. The first study deals with the isolation of cellulose nanocrystals (CNCBE) from wood using the bioethanol pilot scale setup. Cellulose was prepared from wood by diluted acid treatment in the bioethanol plant followed by dewaxing and bleaching. The cellulose was converted into cellulose nanocrystals by mechanical grinding using lab scale homogenizer. The isolated nanoparticles had a diameter of 5-15 nm and formed a thick gel at 2 wt%. X-ray photoelectron spectroscopy illustrated the presence of O=C-O surface functional groups, directly related to the negative zeta-potential values. Fabricated films of CNCBE denoted good mechanical properties, optical properties and cytocompatibility. Thus, a new isolation route that can be followed to produce nanocrystals in large quantities (600 g/ day) has been developed. In a second study, fully biobased nanocomposite membranes of cellulose nanocrystals and chitosan have been fabricated by freeze-drying and crosslinking with gluteraldehyde in vapor phase. The chitosan bound the CNCSL in a stable and nanoporous membrane network with thickness of 250-270 μm. Homogenous dispersion of CNCSL within chitosan matrix was reported based on scanning electron microscopy (SEM). The Brunauer Emmett and Teller (BET) studies showed a decrease in surface area (3.1 to 2.9 m2/g) and average pore size (17 to 13 nm) after crosslinking. The mechanical performance of composite membranes was low, being 0.98 ± 0.4 and 1.1 ± 0.3 MPa of tensile strength for uncross-linked and cross-linked membranes, respectively. In spite of low water flux (64 L m−2 h−1), the composite membranes successfully removed 98%, 84% and 70% respectively of positively charged dyes like Victoria Blue 2B, Methyl Violet 2B and Rhodamine 6G, from a model wastewater after a contact time of 24 h. In the third study layered membranes containing a highly porous support layer and a dense functional layer has been fabricated following a filtration and hot pressing method. Microsized cellulose fibers from sludge bioresidues was used as the support layer to provide mechanical stability and allow water flow without any hindrance. A nanocomposite system of nanocrystals (CNCSL, CNCBE and PCNCSL) with gelatin as matrix was used as the functional layer. Bubble point measurement confirmed the membrane pore sizes (5-6 m), in microfiltration range, which resulted in high water permeability < 4000 Lh-1m-2 at 1.5 bars. Efficient removal of Ag+, Cu2+ and Fe3+ from industrial wastewater was achieved using these membranes. The removal of metal ions was expected to be driven by the electrostatic attraction between negatively charged nanocellulose and the positively charged metal ions. The work has demonstrated that highly efficient water treatment membranes can be fabricated from nanocellulose via tailoring their ability to interact and selectively adsorb heavy metal ions and dyes.
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| 24. |
- Mølgaard, Susanne, et al.
(författare)
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Cellulose-nanofiber/polygalacturonic acid coatings with high oxygen barrier and targeted release properties
- 2014
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 114, s. 179-182
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Tidskriftsartikel (refereegranskat)abstract
- A bio-inspired coating consisting of pectin (polygalacturonic acid) and cationic cellulose nanofibers were successfully produced by the layer-by-layer method. The build-up and the morphology of the resulting coatings were studied with spectroscopic ellipsometry and atomic force microscopy, respectively. The coating was able to survive the exposure of a simulated gastric fluid, but was partially degraded upon exposure to pectinase enzyme, which simulate the action of the microbial symbionts present in the human colon. Prior to exposure, the oxygen permeability coefficient of the coating (0.033 ml (STP) mm m-2 day-1 atm-1 at 23 °C and 20% RH) was in the same order of magnitude as for ethylene vinyl alcohol films (0.001-0.01 ml (STP) mm m-2 day-1 atm-1). However, after exposure to the mimicked gastrointestinal (GI) tract conditions, the contribution of coating to the overall barrier properties was not measurable.
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| 25. |
- Olsson, Richard T., et al.
(författare)
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Cellulose nanofillers for food packaging
- 2011
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Ingår i: Multifunctional and Nanoreinforced Polymers for Food Packaging. - Cambridge : Woodhead Publishing Limited. ; , s. 86-107
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter presents a review of methods for the extraction of cellulose nanofillers, as well as the most important characteristic features related to the exploration of these nanofillers in composite applications. Various methods for the extraction and surface modification of cellulose crystals are presented for the adaption of cellulose crystals in composite applications. A brief review of the different morphological characteristics as well as mechanical properties of different cellulose nanofillers are also presented.
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| 26. |
- Popescu, Carmen-Mihaela, et al.
(författare)
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Structural characterization and mechanical properties of wet-processed fibreboard based on chemo-thermomechanical pulp, furanic resin and cellulose nanocrystals
- 2020
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier. - 0141-8130 .- 1879-0003. ; 145, s. 586-593
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Tidskriftsartikel (refereegranskat)abstract
- Fibreboards are made of lignocellulosic fibres and synthetic adhesive which connect them. These synthetic adhesives, while relatively low-cost, are usually non-biodegradable and may cause health and environmental issues. Therefore, in recent years, there has been an increased demand for replacing these adhesives with bio-derived adhesives. The present study aims to develop fibreboards from chemo-thermomechanical pulp (CTMP) and a furanic resin based on prepolymers of furfuryl alcohol via wet-processing. To improve the bonding properties, maleic acid, aluminium sulphate, and cellulose nanocrystals (CNCs) were added. The resulting fibreboards were evaluated for their structural features and mechanical properties. The bending strength was improved when CNCs were added into the fibre's suspension, and the morphology indicated a more compact structure. The combination of the CTMP with CNC and Biorez resulted in the same mechanical behaviours as those noted for CTMP alone, the best performance being observed for the boards in which Al2(SO4)3 was added. Infrared spectroscopy and X-ray diffraction also proved the presence of cellulose nanocrystals and resin in the boards by increased specific bands intensity and crystallinity index, respectively.
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| 27. |
- Wu, Qiuju, et al.
(författare)
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A High Strength Nanocomposite Based on Microcrystalline Cellulose and Polyurethane
- 2007
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 8:12, s. 3687-3692
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Tidskriftsartikel (refereegranskat)abstract
- A high-strength elastomeric nanocomposite has successfully been prepared by dispersing microcrystalline cellulose in a polyurethane matrix. The resulting nanocomposites show increased strain-to-failure in addition to increased stiffness and strength compared to the unfilled polyurethane. The optimal composite contained 5 wt % cellulose. The average true strength for this composition was 257 MPa, compared with 39 MPa for the neat polyurethane, and showed the highest strain-to-failure. The improvements of stiffness, strength, as well as strain-to-failure are believed to be due to good interaction, by both covalent and hydrogen bonds, between the polyurethane and the cellulose nanofibrils.
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| 28. |
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