| 1. |
- Javed, Asif, 1982-, et al.
(författare)
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Lignin-containing coatings for packaging materials—pilot trials
- 2021
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 13:10
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Tidskriftsartikel (refereegranskat)abstract
- One severe weakness of most biopolymers, in terms of their use as packaging materials, is their relatively high solubility in water. The addition of kraft lignin to starch coating formulations has been shown to reduce the water solubility of starch in dry coatings. However, lignin may also migrate into aqueous solutions. For this paper, kraft lignin isolated using the LignoBoost process was used in order to examine the effect of pH level on the solubility of lignin with and without ammonium zirconium carbonate (AZC). Machine-glazed (MG) paper was coated in a pilot coating machine, with the moving substrate at high speed, and laboratory-coated samples were used as a reference when measuring defects (number of pinholes). Kraft lignin became soluble in water at lower pH levels when starch was added to the solution, due to the interactions between starch and lignin. This made it possible to lower the pH of the coating solutions, resulting in increased water stability of the dry samples; that is, the migration of lignin to the model liquids decreased when the pH of the coating solutions was reduced. No significant difference was observed in the water vapor transmission rate (WVTR) between high and low pH for the pilot-coated samples. The addition of AZC to the formulation reduced the migration of lignin from the coatings to the model liquids and led to an increase in the water contact angle, but also increased the number of pinholes in the pilot-coated samples. © 2021 by the authors
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| 2. |
- Sjöstrand, Björn, 1987-, et al.
(författare)
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Numerical model of water removal and air penetration during vacuum dewatering
- 2021
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Ingår i: Drying Technology. - : Taylor & Francis. - 0737-3937 .- 1532-2300. ; 39:10, s. 1349-1358
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Tidskriftsartikel (refereegranskat)abstract
- Dewatering and air flow in high vacuum suction boxes was examined. The work was mainly numerical and was based on, and compared with, previously published experimental results of vacuum dewatering from laboratory equipment and from a pilot paper machine. A previously published numerical model for wet pressing is used as the basis for this work. The aims of this study were to find new fitting parameters that allows the previous model to be used for vacuum dewatering instead of pressing, and to examine two extensions to the original model. The results indicate that the new vacuum dewatering model for moisture can predict the dewatering behavior for several different experimental data series both from laboratory equipment and a pilot paper machine using the same set of fitting parameters. Two different numerical models for air flow through the paper sheet, during vacuum dewatering, were developed based on postulating that the decrease in moisture permeability is accompanied by a simultaneous increase in air permeability. The models for air flow can also be fitted to experimental data and predict the magnitudes of air flow during vacuum dewatering. The data sets for air flow exhibit a certain degree of operator dependence though, so that one set of fitting parameters is not enough for obtaining good agreement with all data sets.
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| 3. |
- Sjöstrand, Björn, 1987-
(författare)
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Vacuum Dewatering of Cellulosic Materials : New insights into transport phenomena in the papermaking process
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Working towards sustainable development within the forest industry, the dewatering of pulp and paper must be fully understood along with the dewatering of other cellulose-based materials. Huge amounts of energy are used during paper manufacturing so there is a potential for making the processes more energy-efficient. This thesis attempts to gain understanding of vacuum dewatering in the forming section of the conventional papermaking process and its connection with energy consumption in order to suggest actions that may be taken not only to improve energy efficiency but also facilitate the introduction of new materials into existing processes. The main objective of this thesis is to develop a deeper understanding of the vacuum dewatering of forest-based cellulosic materials in existing paper manufacturing processes. Aspects of how rewetting, the structure of the forming fabric and additives of cellulosic materials affect vacuum dewatering are discussed in detail throughout. There is also a large section discussing the use of numerical models and software simulations of dewatering in the forming section of a papermaking machine. A brief background of the papermaking process is presented, along with useful numerical models used previously in that particular context. Three sets of experiments, including rewetting, forming fabrics and additions of cellulosic materials, compose the bulk of the thesis’ method along with two sets of simulations regarding fabrics and additives. This thesis shows how rewetting is both rapid and substantial after high vacuum suction boxes, the way in which the structure of the forming fabrics affects vacuum dewatering and how additions of micro-fibrillated cellulose and dialcohol cellulose affect vacuum dewatering. The results of the simulations and numerical models show how they can be used to explore ways of saving energy in the process as well as to facilitate the introduction of cellulosic additives into existing papermaking processes.
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