| 1. |
- Aaen, Ragnhild, et al.
(författare)
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Oil-in-Water Emulsions Stabilized by Cellulose Nanofibrils-The Effects of Ionic Strength and pH.
- 2019
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Pickering o/w emulsions prepared with 40 wt % rapeseed oil were stabilized with the use of low charged enzymatically treated cellulose nanofibrils (CNFs) and highly charged 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized CNFs. The emulsion-forming abilities and storage stability of the two qualities were tested in the presence of NaCl and acetic acid, at concentrations relevant to food applications. Food emulsions may be an important future application area for CNFs due to their availability and excellent viscosifying abilities. The emulsion characterization was carried out by visual inspection, light microscopy, viscosity measurements, dynamic light scattering and mild centrifugation, which showed that stable emulsions could be obtained for both CNF qualities in the absence of salt and acid. In addition, the enzymatically stabilized CNFs were able to stabilize emulsions in the presence of acid and NaCl, with little change in the appearance or droplet size distribution over one month of storage at room temperature. The work showed that enzymatically treated CNFs could be suitable for use in food systems where NaCl and acid are present, while the more highly charged TEMPO-CNFs might be more suited for other applications, where they can contribute to a high emulsion viscosity even at low concentrations.
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| 2. |
- Aaen, Ragnhild, et al.
(författare)
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The potential of TEMPO-oxidized cellulose nanofibrils as rheology modifiers in food systems
- 2019
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Ingår i: Cellulose. - : Springer Netherlands. - 0969-0239 .- 1572-882X. ; 26:9, s. 5483-5496
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Cellulose nanofibrils (CNFs) have been proposed for use in low-fat food products due to their availability and excellent viscosifying and gel forming abilities. As the CNFs are negatively charged, the presence of other components in foods, such as electrolytes and food additives such as xanthan gum is likely to affect their rheological properties. Hence, the study of these interactions can contribute valuable information of the suitability of CNFs as rheology modifiers and fat replacers. Rheological measurements on aqueous dispersions of TEMPO-oxidized CNFs were performed with variations in concentration of CNFs, concentration of electrolytes and with varying CNF/xanthan ratios. UV–Vis Spectroscopy was used to evaluate the onset of CNF flocculation/aggregation in the presence of electrolytes. The CNF dispersions followed a power-law dependency for viscosity and moduli on CNF concentration. Low electrolyte additions strengthened the CNF network by allowing for stronger interactions, while higher additions led to fibril aggregation, and loss of viscosity, especially under shear. The CNF/xanthan ratio, as well as the presence of electrolytes were shown to be key factors in determining whether the viscosity and storage modulus of CNF dispersions increased or decreased when xanthan was added. Graphical abstract: [Figure not available: see fulltext.].
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| 3. |
- Brodin, Fredrik Wernersson, et al.
(författare)
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Displacement washing of TEMPO-oxidized softwood kraft pulp : Effects of change in fiber properties
- 2013
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; :3, s. 366-376
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Tidskriftsartikel (refereegranskat)abstract
- Bleached softwood kraft pulp fibers were treated using TEMPO oxidation at two different dosages of NaClO. A batch of non-oxidized reference pulp was also prepared with a concentration of the tracer (Na) similar to the oxidized batches. A total of 15 washing experiments were conducted and the dispersion model was used to characterize washing behavior. TEMPO oxidation resulted in a major increase in the amount of carboxylate groups in the pulps and a considerable decrease in fiber/particle size in relation to the reference pulp fibers. Oxidized fibers also had less fiber curl than reference fibers. Water retention values were greater in the oxidized pulps and the oxidized fibers exhibited major swelling during the washing operation, while reference fibers had only minorswelling. The amount of sodium in the filter cakes after washing corresponded to the amount of carboxylate groups in the pulps. Swelling of oxidized pulp fibers needs to be considered in order to describe filtration and washing. The average specific filtration resistance for all pulps in this study was in the order of 1010-1011 m/kg, i.e. moderately easy to filter. The most oxidized pulp had the highest average specific filtration resistance and the lowest value for the estimated effective longitudinal dispersion coefficient, in agreement with theory.
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| 4. |
- 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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| 5. |
- Celaya Romeo, Javier, et al.
(författare)
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Pyrolysis oil based fuel emulsions for marine engines
- 2016
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Ingår i: European Biomass Conference and Exhibition Proceedings. ; , s. 1740-1745
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The International Convention for the Prevention of Pollution from Ships (MARPOL) is reducing the allowed amount of sulphur in marine fuels and these reductions will continue in the future. Bio-oil is a sulphur-free liquid fuel and it constitutes a potential biofuel for the marine sector because it may be produced at industrial scale through pyrolysis of residues coming from the wood processing industry. Due to some of its challenging characteristics, it cannot substitute conventional fuels directly or be blended with them, but it might be used as a component of an emulsified drop-in fuel. The objective of this work is to determine the best conditions to produce an emulsified marine drop-in fuel. These conditions include the percentages of each component (marine gas oil or biodiesel, bio-oil, surfactant, type and combination of surfactants and the hydrophilic-lipophilic value (HLB) of the surfactant blend. Stability of the emulsions has been analysed by light scattering and visual observation at different times. This work forms part of the ReShip Project partly funded by the Research Council of Norway (The ENERGIX programme).
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| 6. |
- Celaya Romeo, Javier, et al.
(författare)
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Re-homogenization of phase separated forest residue pyrolysis oil by blending
- 2016
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Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 163, s. 60-66
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Tidskriftsartikel (refereegranskat)abstract
- The wood processing industry generates large amounts of forest residues like branches and tops which represent a significant unexploited resource for sustainable biofuel production. A feasible thermochemical route to valorise these residues is fast pyrolysis. However, the main product of this technology, pyrolysis oil or bio-oil, shows several disadvantages in comparison with conventional fuels. One of the main drawbacks of bio-oil is its instability which results in liquid phase separation in many cases. The purpose of this study is to verify whether homogenous single-phase heating fuels for district heating etc. can be formed from aged, phase separated forest residue pyrolysis oils by blending. Aged, phase separated pyrolysis oils were blended with either methanol or 1-butanol and the amount of alcohol needed to form homogeneous and storage stable fuel blends was evaluated. Homogeneity of the fuel blends was analysed by water concentration profile analysis and image analysis. Storage stability was analysed by analysing homogeneity as function of storage time. Essential fuel characteristics were analysed. The results revealed that phase separated forest residue pyrolysis oil can be homogenized by adding moderate amounts of alcohol and that some of the blends are stable longer than two months. Alcohol addition also improves essential product properties for pyrolysis oils as heating fuels. This work forms part of the ReShip Project partly funded by the Research Council of Norway (The ENERGIX programme).
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| 7. |
- Wernersson Brodin, Fredrik, 1983, et al.
(författare)
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A comparison of softwood and birch kraft pulp fibers as raw materials for production of TEMPO-oxidized pulp, MFC and superabsorbent foam
- 2013
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 20:6, s. 2825-2838
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Tidskriftsartikel (refereegranskat)abstract
- This study compares the suitability of using birch kraft pulp or softwood kraft pulp in the preparation of TEMPO-oxidized pulp, MFC and superabsorbent foam. TEMPO oxidation was performed using five different dosages of primary oxidant. The time of disintegration treatment was varied to study its influence on the properties of the produced MFCs and foams. Both the birch and the softwood pulps could be used for producing superabsorbent foams, depending on the process conditions, the absorption capacities were about the same for the two pulps and varied between 25 and 55 g saline solution/g absorbent. The foams based on birch pulp had, however, on average, 30 % higher retention capacity than the foams based on softwood pulp. The maximum retention capacity obtained was 16.6 g saline solution/g absorbent. The greater retention capacity of birch-based foams is not fully understood, but a smaller pore size may be the reason, which in turn would generate greater capillary forces. In addition to this, it was found that birch pulps, contrary to softwood pulps, had a substantial amount of fibers that were relatively unaffected by the disintegration treatment. These oxidized fibers are likely to reinforce the foam, thereby making the foam more resistant to external pressures, which is in accordance with earlier findings.
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| 8. |
- Wernersson Brodin, Fredrik, 1983, et al.
(författare)
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Absorbent materials based on kraft pulp: Preparation and material characterization
- 2012
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Ingår i: BioResources. - : BioResources. - 1930-2126 .- 1930-2126. ; 7:2, s. 1666-1683
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Tidskriftsartikel (refereegranskat)abstract
- Today, petroleum-based superabsorbents are widely used, but interest in renewable alternatives is on the rise. This study presents two wood-based absorbent materials suitable for various absorption applications as an alternative to petroleum-based products. Never-dried bleached kraft pulp was treated with TEMPO-oxidation, and new carboxylate and aldehyde groups were introduced. It was found that the aldehyde groups contributed to the wet integrity of the absorbent materials, possibly by the formation of hemiacetal bonds. After oxidation, the pulp fibers were gradually disintegrated, and size analysis showed that the disintegration rate was enhanced by an increase in the charge of the oxidant. Freeze drying produced a porous foam with a large surface area that enabled a rapid absorption rate as well as a reasonably high absorption capacity even for absorption under load. Air drying formed a compact film with a slow absorption rate but with a high final capacity for absorption.
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| 9. |
- Wernersson Brodin, Fredrik, 1983
(författare)
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Absorbent Materials from Kraft Pulp
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- SuperAbsorbent Polymers (SAPs) have, since being introduced in the 1980s, become an important constituent in hygiene products, such as disposable diapers. The design of disposable diapers has changed over the years and today thinner products can be produced partly because of the excellent absorption and retention properties of the petrochemical-based SAPs. The possibilities of producing alternative absorbent materials from a renewable resource, kraft pulp, are investigated in this thesis. In the experimental part, kraft pulp fibres were treated with TEMPO oxidation followed by disintegration of the fibres and drying by either freeze drying or air drying. Depending on the drying method, the final product was a porous foam (freeze drying) or a compact film (air drying). In an attempt to improve the performance of the foam, un-modified fibres were added before the drying step, thus forming a cellulosic composite material.Results showed that the freeze-dried foam had a more rapid absorption rate and a higher absorption capacity in saline solution than the air-dried film. The retention capacity of the foam was favoured by a high amount of oxidant. A high amount of oxidant was also beneficial to obtaining more efficient disintegration of pulp fibres. The ease of fibre disintegration was also favoured by a high reaction temperature, as the fibres at these conditions were more chemically degraded. The aldehyde groups introduced by TEMPO oxidation provided wet integrity in the material, possibly by the formation of hemiacetal bonds during the drying step. The addition of CTMP fibres prior to the drying step had a positive effect on the retention of the TEMPO-oxidized MFC, even though the total retention capacity decreased. At fibre contents around 85%, the retention capacities of the TEMPO-oxidized MFC were comparable with the capacity of commercial SAPs.
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| 10. |
- Wernersson Brodin, Fredrik, 1983
(författare)
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Absorbent Materials from Kraft Pulp
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Superabsorbent polymers (SAP) have, since being introduced in the 1980s, become an important constituent in hygiene products, such as disposable diapers. The design of disposable diapers has changed over the years and today thinner products can be produced partly because of the excellent absorption and retention properties of the petrochemical-based SAP. The possibilities of producing alternative absorbent materials from a renewable resource, kraft pulp, are investigated in this thesis. In this work, a four step process was developed using kraft pulp from either softwood or hardwood as the raw material. In the process, kraft pulp fibers were treated with TEMPO oxidation followed by washing, disintegration of the fibers into microfibrillar cellulose (MFC), and porous absorbent foam was then obtained by freeze drying the MFC. Process conditions were evaluated to optimize the properties of the obtained foams. In an attempt to improve the mechanical stability of the foam, un-modified fibres were added before the drying step, thus forming a cellulosic composite material.Tests of absorption properties showed that the absorbent foams had a more rapid absorption rate, similar absorption capacity and about half the retention capacity as compared to commercial SAP. In the foam, wet integrity was provided by the aldehyde groups introduced by TEMPO oxidation possibly through the formation of hemiacetal bonds. A high dosage of primary oxidant and the use of wood from birch as the raw material were the most favourable for maximizing liquid retention in the foams. An increase in the oxidation temperature from 25˚C to 50˚C decreased the reaction time, reduced the energy demand to disintegrate the fibers, while the retention capacity remained more or less unchanged. Washing experiments showed that in comparison with washing reference pulp, oxidized pulps had a higher specific filtration resistance and thus a larger filter area or longer hold-up time was needed for oxidized pulps. The addition of CTMP fibres increased the liquid retention capacity of the TEMPO-oxidized MFC. At fibre contents around 85%, the retention capacities of the TEMPO-oxidized MFC were comparable with the capacity of commercial SAP. The preparation of foam on the kilogram-scale showed that a similar morphology to gram-scale experiments was not achieved and consequently liquid retention was lower for kilogram-scale foams.
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| 11. |
- Wernersson Brodin, Fredrik, 1983, et al.
(författare)
-
Displacement washing of TEMPO-oxidized softwood kraft pulp: Effects of change in fiber properties
- 2013
-
Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 28:3, s. 366-376
-
Tidskriftsartikel (refereegranskat)abstract
- Bleached softwood kraft pulp fibers were treated using TEMPO oxidation at two different dosages of NaClO. A batch of non-oxidized reference pulp was also prepared with a concentration of the tracer (Na) similar to the oxidized batches. A total of 15 washing experiments were conducted and the dispersion model was used to characterize washing behavior. TEMPO oxidation resulted in a major increase in the amount of carboxylate groups in the pulps and a considerable decrease in fiber/particle size in relation to the reference pulp fibers. Oxidized fibers also had less fiber curl than reference fibers. Water retention values were greater in the oxidized pulps and the oxidized fibers exhibited major swelling during the washing operation, while reference fibers had only minor swelling. The amount of sodium in the filter cakes after washing corresponded to the amount of carboxylate groups in the pulps. Swelling of oxidized pulp fibers needs to be considered in order to describe filtration and washing. The average specific filtration resistance for all pulps in this study was in the order of 10(10)-10(11) m/kg, i.e. moderately easy to filter. The most oxidized pulp had the highest average specific filtration resistance and the lowest value for the estimated effective longitudinal dispersion coefficient, in agreement with theory.
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| 12. |
- Wernersson Brodin, Fredrik, 1983, et al.
(författare)
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High Temperature TEMPO Oxidation in a Heterogeneous Reaction System: An Investigation of Reaction Kinetics, Pulp Properties, and Disintegration Behavior
- 2013
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Ingår i: BioResources. - : BioResources. - 1930-2126 .- 1930-2126. ; 8:4, s. 5925-5946
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Tidskriftsartikel (refereegranskat)abstract
- TEMPO oxidation was performed on never-dried bleached softwood kraft pulp fibres to study the influence of reaction temperature and the dosage of sodium hypochlorite in the oxidation treatment. It was found that oxidation at a high temperature shortened oxidation time, but it also resulted in more extensive degradation of the pulp. Harsh reaction conditions (high temperature and high dosage of sodium hypochlorite) enabled the rapid disintegration of pulp fibres with a low energy demand. The freeze-dried disintegrated pulp fibres had a high absorption capacity of saline liquid, 40 to 80 g/g, and retained 9 to 14 g saline liquid/g material in a standard centrifuge retention test. Four different models were investigated to describe the kinetics of TEMPO oxidation of pulp fibres. However, none of the models could adequately describe all the mechanisms involved in this reaction system. The results showed that the diffusion of hypochlorite ions was sufficiently fast compared to the chemical reactions. In contrast, the concentration of the catalytic compounds, NaBr and TEMPO, both had a strong influence on the reaction rate. Results show that the reactions have different phases, possibly with different rate-determining steps. It remains to be determined which reaction steps correspond to the different phases.
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| 13. |
- Wernersson Brodin, Fredrik, 1983, et al.
(författare)
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Preparation of Absorbent Foam Based on Softwood Kraft Pulp: Advancing from Gram to Kilogram Scale
- 2013
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Ingår i: BioResources. - : BioResources. - 1930-2126 .- 1930-2126. ; 8:2, s. 2099-2117
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Tidskriftsartikel (refereegranskat)abstract
- Absorbent foams were produced at both the gram scale and the kilogram scale by treating bleached softwood kraft pulp fibers to TEMPO oxidation, followed by washing, fiber disintegration, and freeze drying. Two reaction temperatures and three different dosages of primary oxidant were evaluated to find suitable oxidation conditions. It was found that the absorption and retention capacities were 50 to 70% lower for kilogram-scale foams than for gram-scale foams. SEM studies showed that the kilogram-scale foams had larger pores than the gram-scale foams; this explains the major differences in absorption and retention. The oxidation treatments performed in both scales resulted in a major increase in the amount of carboxylate groups and a major decrease in DPV, but only minor differences in these factors were found in a comparison between pulps from gram-and kilogram-scale experiments. However, the kilogram-scale dispersing equipment appeared to cause more fiber cutting, while the equipment used in the gram-scale experiments promoted the liberation of microfibrils to a greater extent. Furthermore, in both the gram- and kilogram-scale samples, a high dosage of primary oxidant and a low oxidation temperature were found to maximize the retention of liquid.
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| 14. |
- Wernersson Brodin, Fredrik, 1983, et al.
(författare)
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Reinforced absorbent material: a cellulosic composite of TEMPO-oxidized MFC and CTMP fibres
- 2012
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 19:4, s. 1413-1423
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Tidskriftsartikel (refereegranskat)abstract
- This research aims to develop new materials based on renewable resources that can fulfill the functions necessary in the absorption core of a disposable diaper. Absorbent foam was recently produced from softwood kraft pulp by TEMPO oxidation, disintegration and freeze drying. In this study, the TEMPO-oxidized MFC was mixed with pulp fibres, thus forming a cellulosic composite, in an attempt to improve the mechanical stability of the freeze-dried absorbent material. The fibres were added in different amounts and the freeze-dried materials were evaluated for their absorption and retention properties. The results of this study suggest that the composite material has a better mechanical stability than the absorbent foam without fibres. It was shown that using spruce CTMP fibres in the composite resulted in better absorption and retention capacities than in a composite with softwood kraft pulp fibres. The higher stiffness of the CTMP fibres is a probable explanation for this difference. For the composite material with CTMP fibres, liquid porosimetry showed that pore size distribution was more or less retained when put under load. Furthermore, it was seen that the retention properties reached a maximum around 85 % CTMP fibres and 15 % TEMPO-oxidized MFC. In the centrifuge retention test, the retention of the TEMPO-oxidized MFC in the composite material reached about the same capacity as conventional superabsorbent polymers.
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