| 1. |
- Hii, Collin, et al.
(författare)
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The effect of MFC on the pressability and paper properties of TMP and GCC based sheets
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:2, s. 388-396
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Tidskriftsartikel (refereegranskat)abstract
- Different qualities of microfibrillated cellulose (MFC) were blended with thermomechanical pulp (TMP) and ground calcium carbonate (GCC) filler. The addition of MFC reduced the drainage of the pulp suspension but improved strength properties. Wet pressing experiments showed that optimal use of MFC and filler could enhance the strength and optical properties without reducing the solids content after wet pressing. Field-emission scanning electron microscopy (FESEM) revealed that MFC adsorbed onto and contributed to the bonding of the filler particles and fibres. The MFC binds the filler-MFC-fines aggregates to the fibre network and partially filled the pore network. As a result, MFC addition increased the air resistance and internal bonding of the sheet.
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| 2. |
- Hii, Collin, et al.
(författare)
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The effect of Newsprint furnish composition and sheet structure on wet pressing efficiency
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:4, s. 790-797
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Tidskriftsartikel (refereegranskat)abstract
- The dewatering ability and wet sheet structure after pressing was studied using a dynamic wet pressing simulator in combination with electron microscopy and image analysis. Deinked pulp (DIP) that contains 5% ash dewaters more easily than thermo-mechanical pulp (TMP) when pressed with single roll pulse. The in-plane moisture flow (crushing) in DIP samples started at higher peak pressure and higher solids content compared to TMP samples. The TMP sample showed higher springback after wet pressing compared to DIP samples. When both TMP and DIP samples were designed to have a higher amount of small pores at the dewatering side surface layers, the samples with coarser TMP pulp could achieve similar dryness as DIP samples when pressed with higher nip pressure. In addition, the DIP samples with higher number of small pores in the outermost 10 μm thick surface layer in the dewatering side resulted in lower dryness after pressing with a single roll pulse. The effect of filler distribution in paper z-direction on dryness and sheet structure after wet pressing using an 8 milliseconds roll pulse was also studied. In this study the distribution of filler does not affect the maximum achievable dryness (41%) after wet pressing when the total amount of filler in the sheets remains constant, 13.5%. In addition, the samples with more filler in the dewatering layer dewater more easily and yield the maximum achievable dryness (40%) after wet pressing at lower nip pressure (2.5 MPa) when compared to samples made from TMP (36% at 4.4 MPa) and DIP pulps (40% at 4.9 MPa).
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| 3. |
- Hii, Collin, et al.
(författare)
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The web structure in relation to the furnish composition and shoe press pulse profiles during wet pressing
- 2012
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 27:4, s. 798-805
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Tidskriftsartikel (refereegranskat)abstract
- This study shows that wet-pressing TMP and DIP with a shoe press pulse may yield similar after-press solids, provided that an adequate shoe pulse length with similar pressure profile is applied. A wet web with more porous structure in the sheet dewatering (felt) layer seems to contribute to the increased dewatering during wet pressing. In addition, a shoe press pulse with high peak pressure at the end yields higher solids content after wet-pressing and higher bulk compared to a pulse with a peak pressure in the beginning. The increased dewatering during wet-pressing implies a reduction of steam consumption in the dryer.
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| 4. |
- Rodionova, Galina, et al.
(författare)
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Gas-phase esterification of microfibrillated cellulose (MFC) films
- 2013
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 20:3, s. 1167-1174
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Tidskriftsartikel (refereegranskat)abstract
- The barrier properties of microfibrillated cellulose (MFC) films were improved by heterogeneous gas-phase esterification using various combinations of trifluoroacetic acid anhydride, acetic acid and acetic anhydride. The temperature, reagent ratio and reaction time were varied in the experimental design. The effects of two different purification procedures on the barrier properties of esterified MFC films were investigated. Washing with water did not affect the barrier properties compared to those of the films that were not washed, while the use of diethyl ether led to improved barrier properties as measured by the contact angle (CA) of water. The chemical composition of the modified films was studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Alterations in hydrophobicity and oxygen permeability were evaluated using dynamic CA and oxygen transmission rate measurements, respectively.
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| 5. |
- Rodionova, Galina, et al.
(författare)
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Mechanical and oxygen barrier properties of films prepared from fibrillated dispersions of TEMPO-oxidized Norway spruce and Eucalyptus pulps
- 2012
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 19
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Tidskriftsartikel (refereegranskat)abstract
- TEMPO-oxidized cellulose nanofibers (TOCN) were obtained from commercial Norway spruce and mixed Eucalyptus cellulose pulps using TEMPO/sodium bromide (NaBr)/sodium hypochlorite (NaClO) system at pH 10 and 22 °C. After reaction, the fibrillated TEMPO-oxidized celluloses were used for preparation of self-standing films and casting of laminate films on 50 μm thick polyethylene terephthalate. Significant differences between N. spruce and Eucalyptus TOCN were registered. The tensile strength of the films showed a maximum value for spruce samples oxidized with addition of 10 mmol g -1 of NaClO. Oxygen permeability decreased with increasing oxidation levels, being lower for N. spruce TOCN compared to Eucalyptus.
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| 6. |
- Rodionova, Galina, et al.
(författare)
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TEMPO-mediated oxidation of Norway Spruce and Eucalyptus Pulps : Preparation and Characterization of Nanofibres and Nanofiber Dispersions
- 2013
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Ingår i: Journal of Polymers and the Environment. - : Springer Science and Business Media LLC. - 1566-2543 .- 1572-8919 .- 1572-8900. ; 21:1, s. 207-214
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Tidskriftsartikel (refereegranskat)abstract
- This study deals with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation of cellulose. Softwood and hardwood pulp fibers were suspended in water and oxidized to various extents at pH 10 and 22 °C using sodium hypochlorite in the presence of TEMPO radical and sodium bromide. This reaction system is known to be the most efficient one for the introduction of both surface carboxyl and aldehyde groups. Important relationships between formation of these functional groups and the fibrillation yield, light transmittance of the water dispersions and degree of polymerization of the oxidized softwood and hardwood pulps were established in the present study. A birefringence test confirmed the presence of nanofibers which according to atomic force microscopy analyses had diameters in the 1. 6-3. 8 nm range.
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| 7. |
- Rodionova, Galina, et al.
(författare)
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TEMPO-oxidized cellulose nanofiber films: : effect of surface morphology on water resistance
- 2012
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 19:4, s. 1115-1123
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Tidskriftsartikel (refereegranskat)abstract
- 2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibers were prepared from two kraft pulps (Norway spruce and mixed eucalyptus) using the TEMPO/NaBr/NaClO system at pH 10 and 22 °C. After reaction and mechanical treatment, the TEMPO-oxidized celluloses were used for preparation of self-standing films and coatings of laminate films on 50-μm-thick polyethylene terephthalate films. Characterization of the films was performed based on water contact angle measurements, laser profilometry, scanning electron microscopy, and field-emission scanning electron microscopy. The purpose of this study is to understand how the measured contact angles are affected by the film's physical properties (morphology, thickness, density, and roughness).
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| 8. |
- Rodionova, Galina, et al.
(författare)
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The formation and characterization of sustainable layered films incorporating microfibrillated cellulose (mfc)
- 2012
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Ingår i: BioResources. - 1930-2126. ; 7:3, s. 3690-3700
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Tidskriftsartikel (refereegranskat)abstract
- Microfibrillated cellulose (MFC), TEMPO-pretreated MFC, and hybrid polymer/MFC mix were used for the production of layered films with interesting properties for application in food packaging. The series of samples were prepared from MFC (base layers) using a dispersion-casting method. The same procedure as well as a bar coating technique was applied to form top layers of different basis weights. The barrier properties and formation of the layered films were investigated in relationship to the preparation procedures, combination of layers, and areal weight (basis weight). Characterization was done with respect to oxygen transmission rates (OTR), water vapor transmission rates (WVTR), tensile properties, and contact angles (CA) with water. The produced layered films yielded OTR values of 4 mL m-2 day-1 and fulfilled oxygen barrier requirements for a modified atmosphere packaging (MAP). Hornification of the MFC films, however, occurred during drying, which may result in a loss of the film's beneficial properties.
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| 9. |
- Brodin, Fredrik Wernersson, et al.
(författare)
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Preparation of individualised lignocellulose microfibrils based on thermomechanical pulp and their effect on paper properties
- 2015
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Ingår i: Nordic Pulp & Paper Research Journal. - : SPCI. - 0283-2631 .- 2000-0669. ; 30:3, s. 443-451
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Tidskriftsartikel (refereegranskat)abstract
- Although mechanical pulp can be considered as a potential raw material for preparation of microfibrils, suitable pre-treatment methods have been missing. Consequently, the objectives of this study were firstly to find a suitable procedure to prepare lignocellulose microfibrils (LCMF) from fractionated thermo-mechanical pulp (TMP) and secondly to evaluate if these TMP-based materials could be used as paper additives to increase paper strength. Carboxymethylation was found to be a suitable pretreatment for both TMP fines and TMP fibres to enable preparation of individualised LCMF after subsequent homogenisation treatment. After air drying, this material formed dense continuous films in conformity with films prepared from cellulose microfibrils (CMF) originating from chemical pulp. Homogenisation only or sulphonation followed by homogenisation did not fibrillate the TMP samples into individualised LCMF. Analysis of paper properties showed that addition of 20% LCMF to a standard TMP furnish improved tensile strength index by 15%. The LCMF-containing papers were also more brittle (less elongation) than the other paper sheets in this study. Similar tensile strength index was also obtained for TMP fines treated by sulphonation followed by homogenisation.
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| 10. |
- Chinga-Carrasco, Gary, et al.
(författare)
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Structural characteristics of pore networks affecting print-through
- 2008
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Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 34:1, s. 13-22
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Tidskriftsartikel (refereegranskat)abstract
- The pore structure of handsheets and of commercial newsprints is described in detail. The advantages and limitations of scanning electron microscopy and synchrotron radiation X-ray microtomography for pore-structure assessment are discussed. This gives insight into the two-dimensional and three-dimensional characteristics of the pore structure. A major achievement is the effective quantification of the submicron pores by scanning electron microscopy. It is demonstrated that submicron pores contribute positively to light scattering per unit thickness. The relationship between the pore structure, the light scattering and print-through is explored.
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