| 11. |
- Ankerfors, Mikael, et al.
(författare)
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The use of microfibrillated cellulose in fine paper manufacturing : Results from a pilot scale papermaking trial
- 2014
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 29:3, s. 476-483
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Tidskriftsartikel (refereegranskat)abstract
- In this work the strength enhancing capabilities of microfibrillated cellulose (MFC) in highly filled papers was studied. Both the MFC production and the paper making were done in pilot scale under realistic industrial conditions. The results clearly show that MFC (2.5-5.0 wt-%) could improve the mechanical properties of highly filled papers (20-35 wt-% filler contents). All studied dry mechanical properties were improved and the improvements were most pronounced for Z-strength and fracture toughness. By combining the MFC with a C-starch dosage further improvements in mechanical properties could be achieved. The improvements in mechanical properties enabled increased filler content with retained properties. The filler increase could be achieved at the same time as the sheet formation and the dry content after pressing were improved.
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| 12. |
- Ankerfors, Mikael, et al.
(författare)
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Topo-chemical modification of fibres by grafting of carboxymethyl cellulose in pilot scale
- 2013
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; :1, s. 6-14
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to graft carboxymethyl cellulose (CMC) on to bleached softwood kraft pulp at temperatures below 100°C and to do a pilot paper machine trial in order to examine the influence of the CMC on dewatering, sheet formation and mechanical properties. During the pilot trial, one CMC grafted pulp was compared to a pulp with 3 different refining degrees. It was shown that CMC-grafting improves the mechanical properties of paper with only a minor effect on the sheet density. It was also shown that the CMC grafting is less detrimental to dewatering than refining and at a certain tensile index a higher dry content after pressing could be reached. The formation number of the paper produced in the FEX trial was not significantly affected by the addition of CMC.
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| 13. |
- Athley, Karin, et al.
(författare)
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Mechanical retention - Influence of filler floc size and grammage of the fibre web
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 202-207
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of the impact of particle size on the mechanical retention of particles in a fibre network has been conducted. The particles used were five sets of quartz particle fractions having fairly narrow particle size distributions with average particle size ranging from a few μm to around 100 μm. The particles were used to model flocculated filler aggregates as part of a larger study of the effect of pre-flocculation on mechanical retention. Pre-flocculation of the filler is a possible strategy to increase the filler content of paper without deterioration of strength properties. A modified laboratory hand sheet former, known as the Rapid Drainage Device (RDD) was used. The major modification consisted of a long pipe that acted as a suction leg, which provides a dewatering vacuum at the same level as on a paper machine. The experimental results showed that mechanical filler retention increased linearly with particle size and grammage of the fibre layer above a critical grammage which depended on particle size. The linear relation was also seen in a pilot scale trial on the FEX pilot-paper machine at Innventia. During this trial fine paper was produced using pre-flocculated filler where the mean particle size of the flocs and fibres was measured in the flow to the headbox. The results from this pilot trial show that mechanical retention is an important part of the total filler retention. Drainage time and therefore drainage resistance increased with the grammage of the fibre layer and amount of quartz particle added. Drainage time, compared at total grammage (i.e. the sum of fibre and quartz particle grammage) was lowest for a fraction of medium-sized particles, with a median size of 35 μm. There was no obvious effect on retention or drainage resistance of a change in the dewatering pressure from 27.5 to 41.5 kPa.
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| 14. |
- Blell, Rebecca, et al.
(författare)
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Generating in-Plane Orientational Order in Multilayer Films Prepared by Spray-Assisted Layer-by-Layer Assembly
- 2017
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 11:1, s. 84-94
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple yet efficient method for orienting cellulose nanofibrils in layer-by-layer assembled films through spray-assisted alignment. While spraying at 90° against a receiving surface produces films with homogeneous in-plane orientation, spraying at smaller angles causes a macroscopic directional surface flow of liquid on the receiving surface and leads to films with substantial in-plane anisotropy when nanoscale objects with anisotropic shapes are used as components. First results with cellulose nanofibrils demonstrate that such fibrils are easily aligned by grazing incidence spraying to yield optically birefringent films over large surface areas. We show that the cellulosic nanofibrils are oriented parallel to the spraying direction and that the orientational order depends for example on the distance of the receiving surface from the spray nozzle. The alignment of the nanofibrils and the in-plane anisotropy of the films were independently confirmed by atomic force microscopy, optical microscopy between crossed polarizers, and the ellipsometric determination of the apparent refractive index of the film as a function of the in-plane rotation of the sample with respect to the plane of incidence of the ellipsometer.
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| 15. |
- Duker, Elisabeth, et al.
(författare)
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The use of CMC as a dry strength agent - the interplay between CMC attachment and drying.
- 2008
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 23:1, s. 65-71
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the ability to use high molecular weight CMC as a dry strength agent in paper and how the drying of the pulp, either before or after the CMC attachment, affects the mechanical properties of the paper. The effect of the counter-ion form used during drying and reslushing was also investigated. In the case of the calcium and hydrogen counter-ion forms, drying after CMC attachment had no impact on the attached amount. The sodium form did, however, result in some detachment of CMC. When the pulp was dried prior to CMC treatment, the counter-ion form had no effect on the attached amount. It was also shown that drying of a CMC-treated pulp reduced the positive effect of CMC on the mechanical properties. Nevertheless, the mechanical properties were still better than those of paper made from the never-dried reference pulp. The relative effect of CMC on the mechanical properties was independent of the drying strategy used and the counter-ion form did not affect the mechanical properties. However, surface carboxymethylation prior to drying resulted in sheets with better final mechanical properties than sheets made from pulp that had first been dried and then surface carboxymethylated.
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| 16. |
- Fernández, A., et al.
(författare)
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Effects of ionizing radiation in ethylene-vinyl alcohol copolymers and in composites containing microfibrillated cellulose
- 2008
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 109:1, s. 126-134
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Tidskriftsartikel (refereegranskat)abstract
- This study reports on the effect of gamma radiation on morphological, thermal, and water barrier properties of pure ethylene vinyl alcohol copolymers (EVOH29 and EVOH44) and its biocomposites with the nanofiller microfibrillated cellulose (2 wt%). Added microfibrillated cellulose (MFC) preserved the transparency of EVOH films but led to a decrease in water barrier properties. Gamma irradiation at low (30 kGy) and high doses (60 kGy) caused some irreversible changes in the phase morphology of EVOH29 and EVOH44 copolymers that could be associated to crosslinking and other chemical alterations. Additionally, the EVOH copolymers and the EVOH composites reduced the number of hygroscopic hydroxyl functionalities during the irradiation processing and novel carbonyl based chemistry was, in turn, detected. As a result of the above alterations, the water barrier properties of both neat materials and composites irradiated at low doses were notably enhanced, counteracting the detrimental effect on water barrier of adding MFC to the EVOH matrix. © 2008 Wiley Periodicals, Inc.
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| 17. |
- Jin, H., et al.
(författare)
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Effects of different drying methods on textural properties of nanocellulose aerogels
- 2009
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Ingår i: ICCM International Conferences on Composite Materials.
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Konferensbidrag (refereegranskat)abstract
- There is increasing research interest in nanocellulose aerogels because they have low density, hierarchical structure and they are biodegradable and biocompatible. Typically, aerogels are made by supercritical drying, freeze drying and vacuum drying. This work will report the effects that different drying methods have on textural properties of aerogels.
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| 18. |
- Jin, Hua, et al.
(författare)
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Ionically interacting nanoclay and nanofibrillated cellulose lead to tough bulk nanocomposites in compression by forced self-assembly
- 2013
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Ingår i: Journal of Materials Chemistry B. - : Royal Society of Chemistry (RSC). - 2050-750X .- 2050-7518. ; 1:6, s. 835-840
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Tidskriftsartikel (refereegranskat)abstract
- Several approaches have recently been shown for self-assembled biomimetic composite films, aiming at combinations of high toughness, strength, and stiffness. However, it remains challenging to achieve high toughness using simple processes especially for bulk materials. We demonstrate that ionically interacting cationic native nanofibrillated cellulose (C-NFC) and anionic nanoclay, i.e. montmorillonite (MTM), allow local self-assemblies by a simple centrifugation process to achieve 3D bulk materials. The composite with MTM/C-NFC of 63/37 w/w has a high compressive strain to failure of 37% with distinct plastic deformation behaviour, a high work to fracture of 23.1 MJ m(-3), and a relatively high compression strength of 76 MPa. Unlike the conventionally used sequential deposition methods to achieve well-defined layers for the oppositely charged units as limited to films, the present one-step method allows quick formation of bulk materials and leads to local self-assemblies, however, having a considerable amount of nanovoids and defects between them. We suggest that the nanovoids and defects promote the plastic deformation and toughness. Considering the simple preparation method and bio-based origin of NFC, we expect that the present tough bulk nanocomposites in compression have potential in applications for sustainable and environmentally friendly materials in construction and transportation.
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| 19. |
- Karabulut, Erdem, 1983-, et al.
(författare)
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Adhesive Layer-by-Layer Films of Carboxymethylated Cellulose Nanofibril Dopamine Covalent Bioconjugates Inspired by Marine Mussel Threads
- 2012
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 6:6, s. 4731-4739
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Tidskriftsartikel (refereegranskat)abstract
- The preparation of multifunctional films and coatings from sustainable, low-cost raw materials has attracted considerable interest during the past decade. In this respect, cellulose-based products possess great promise due not only to the availability of large amounts of cellulose in nature but also to the new classes of nanosized and well-characterized building blocks of cellulose being prepared from trees or annual plants. However, to fully utilize the inherent properties of these nanomaterials, facile and also sustainable preparation routes are needed. In this work, bioinspired hybrid conjugates of carboxymethylated cellulose nanofibrils (CNFC) and dopamine (DOPA) have been prepared and layer-by-layer (LbL) films of these modified nanofibrils have been built up in combination with a branched polyelectrolyte, polyethyleneimine (PEI), to obtain robust, adhesive, and wet-stable nanocoatings on solid surfaces. It is shown that the chemical functionalization of CNFCs with DOPA molecules alters their conventional properties both in liquid dispersion and at the interface and also influences the LbL. film formation by reducing the electrostatic interaction. Although the CNFC-DOPA conjugates show a lower colloidal stability in aqueous dispersions due to charge suppression, it was possible to prepare the LbL films through the consecutive deposition of the building blocks. Adhesive forces between muttilayer films prepared using chemically functionalized CNFCs and a silica probe are much stronger in the presence of Fe3+ than those between a multilayer film prepared from unmodified nanofibrils and a silica probe. The present work demonstrates a facile way to prepare chemically functionalized cellulose nanofibrils whereby more extended applications can produce novel cellulose-based materials with different functionalities.
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| 20. |
- Klemm, Dieter, et al.
(författare)
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Nanocelluloses : A New Family of Nature-Based Materials
- 2011
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 50:24, s. 5438-5466
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Forskningsöversikt (refereegranskat)abstract
- Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species, such as water, organic and polymeric compounds, nanoparticles, and living cells. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the preparation of nanocrystalline cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants.
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