| 1. |
- Zhang, Renyun, et al.
(author)
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Soap-film coating : High-speed deposition of multilayer nanofilms
- 2013
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In: Scientific Reports. - Nature Publishing Group : Springer Science and Business Media LLC. - 2045-2322. ; 3, s. Art. no. 1477-
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Journal article (peer-reviewed)abstract
- The coating of thin films is applied in numerous fields and many methods are employed for the deposition of these films. Some coating techniques may deposit films at high speed; for example, ordinary printing paper is coated with micrometre-thick layers of clay at a speed of tens of meters per second. However, to coat nanometre thin films at high speed, vacuum techniques are typically required, which increases the complexity of the process. Here, we report a simple wet chemical method for the high-speed coating of films with thicknesses at the nanometre level. This soap-film coating technique is based on forcing a substrate through a soap film that contains nanomaterials. Molecules and nanomaterials can be deposited at a thickness ranging from less than a monolayer to several layers at speeds up to meters per second. We believe that the soap-film coating method is potentially important for industrial-scale nanotechnology.
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| 2. |
- Abdulgadir, Alamin, et al.
(author)
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Performance Simulation of a Composite Filter Material Containing Mechanical Pulp Fibers, Microfibrillated Cellulose, and Cellulose Nanofibers
- 2022
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In: Proceedings of the International Mechanical Pulping Conference. ; , s. 160-
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Conference paper (other academic/artistic)abstract
- Nonwoven fibrous materials with reticular support of an interconnected fiber network and a tortuous airflow pathway have been commonly used in filtration applications. To meet the criteria of filter efficiency and performance, the filter materials are recommended to contain different types of fibers such as mechanical pulp fibers, microfibrillated cellulose, cellulose nanofibers, and other polymer or synthetic fibers with a range of dimensions, i.e., length and diameter. Cellulose fibers in filter media possess irregular and complex structures with hollow or collapsed lumen structures owing to their refinement or pulping method. The development of an appropriate filter media model requires information on actual fiber characteristics. In this study, a simulation method was used to investigate the complex microstructures of filter media. The physical parameters such as fiber wall thickness, diameter, length, cross-section shapes, and curliness were obtained from fiber analyzers and scanning electron microscopy. Based on the experimental findings, GeoDict database comprising different types of common fiber models was constructed. 3-Dimensional fibrous models corresponding to the wet-laid binderless filter material were generated. Using the GeoDict modules, the pore size distributions, average pore sizes, air permeability, pressure drop and initial filter efficiency simulations were performed. The simulation results appear to be in close agreement with the experimental results. The incorporation of cellulose nanofibers resulted in reduced average pore sizes and air permeability of the filter material, thus enhancing the initial filter efficiency. The filter media developed a biobased material derived from pulp fibers for advanced applications such as medical facemask, and air filtration purposes.
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| 3. |
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| 4. |
- Joelsson, Tove, et al.
(author)
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Fibre morphology affects the bonding and densification of hot-pressed thermomechanical pulp-based paper
- 2022
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In: Proceedings of the International Mechanical Pulping Conference. ; , s. 142-148
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Conference paper (other academic/artistic)abstract
- A successful way to increase the strength properties for pulps based on lignin-rich fibres is to compress the fibre structure at high temperature by means of hot-pressing technology. The fundamental knowledge of how the fi-bre morphology influences the mechanical properties when a paper sheet is hot-pressed is still scarce. Paper sheets based on thermomechanical pulp (TMP) produced with single disc and double disc refiners were compared. The effect of degree of refining was studied as well as the effect of fibre shapes by fractionating pulp with hydrocyclones. Additionally, the effect of fines was studied. All pulps were produced at the Holmen Bra-viken Mill, Norrköping, Sweden with Norway Spruce (Picea abies) as raw material. Handsheets (100 g/m2) with 62% ± 3 dryness were hot-pressed at temperatures up to 260°C at a pressure around 8MPa. The hot-press-ing increased both dry and wet strength for all pulps studied. This was true even for pulps with low fines con-tent and low refining energy. Even thick-walled fibres normally giving lower strength showed an increase of 100% when hot-pressed. In summary, hot-pressing technology can make it possible to use different TMPs to produce strong packaging materials for use in dry and wet conditions.
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| 5. |
- Joelsson, Tove, et al.
(author)
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High strength paper from high yield pulps by means of hot-pressing
- 2020
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In: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 35:2, s. 195-204
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Journal article (peer-reviewed)abstract
- The hypothesis is that it should be possible to modify papermaking conditions in line with the softening properties of high yield pulp fibres and achieve similar strength properties to conventional chemical pulp based paper. We therefore investigated the rheological and physical properties of high yield pulp based papers during hot-pressing. Our results confirm that increased temperature combined with sufficient pressure enables permanent densification by softening of lignin, producing very high tensile strength. This treatment also significantly improved the wet tensile strength in comparison to bleached kraft pulp without using wet strength agents. The high yield pulps used here were spruce based thermomechanical pulp, chemi-thermomechanical pulp, and high temperature chemi-thermomechanical pulp, and birch-aspen based neutral sulphite semi chemical pulp, with spruce-pine based bleached kraft pulp as reference. Rapid Köhten sheets of 150 g/m 2 150\hspace{0.1667em}\text{g}/{\text{m}^{2}} and 50 % dryness were hot-pressed in a cylinder-press at 20-200 °C, 7 MPa, and 1 m/min. The mechanical properties showed great improvements in these high yield pulp papers, with tensile index increased to 75 kNm/kg and compression strength index to 45 kNm/kg; levels close to and better than bleached kraft. Wet strength increased to 16 Nm/g compared to 5 Nm/g for bleached kraft.
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| 6. |
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| 7. |
- Joelsson, Tove, et al.
(author)
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Improving paper wet-strength by means hot-pressing and increased lignin content in pulp fibers
- 2019
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In: Paper Conference and Trade Show, PaperCon 2019. - : TAPPI Press. - 9781510893948 ; , s. 704-713
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Conference paper (peer-reviewed)abstract
- The research presented here show ways to improve wet strength by means of hot-pressing without strength additives when using lignin containing pulps as unbleached softwood chemical pulps (NSK) and lignin rich softwood chemithermomechanical pulps (CTMP). NSK (Northern Softwood kraft) laboratory scale produced pulps of 3 different levels of natural lignin (or kappa number) and two commercial pulps, NBSK (Northern Bleached Softwood kraft) and CTMP, were compared evaluating dry- and wet-strength properties. Staining methods and light microscope were used to study cross sections of paper sheets. The CTMP fibers collapse to an increasing degree with pressing temperature whereas NBSK/NSK do not change. The microscopy methods show the distribution of lignin within the paper structure. Sheets made from NSK show a significant increase in wet strength from 4kNm/kg to 23kNm/kg, when increasing temperature from 20°C to 200°C. CTMP show corresponding increase from 2kNm/kg to 16kNm/kg. No increase in dry strength or in density can be observed in case of NBSK/NSK, while the CTMP show an increase of 53% and 100% respectively. The SCT values show an increase up to 35% for lignin-rich NSK based paper sheets when hot-pressing.
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| 8. |
- Joelsson, Tove, et al.
(author)
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Unique steel belt press technology for high strength papers from high yield pulp
- 2021
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In: SN Applied Sciences. - : Springer. - 2523-3963 .- 2523-3971. ; 3:5
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Journal article (peer-reviewed)abstract
- The dry strength properties of hot-pressed moist paper improved as stiff high-yield pulp fibers soften and the sheet density increased. Very high wet strength was also achieved without adding strengthening agents. This research focuses on a new hot-pressing methodology based on a steel belt-based pilot cylinder press with infrared heating. The heated steel belt transports the moist paper into the cylinder nip with two adjacent steel rollers with adjustable nip pressure. The temperature ranges up to 300 °C, maximum speed is 5 m/min, maximum pulling force from the steel belt is 70 kN and the line load in the two press nips is 15 kN/m each. High peak pressures are possible due to the hard press nip between steel rolls and steel belt, allowing a good heat transfer to the paper. The long dwell time allows strained drying of the paper which results to high density and high wet strength. Paper samples from high-yield pulps were tested at different nip pressures, temperatures and machine speeds while the dry content was kept constant at about 63%. High nip pressure showed the largest effect on densification and dry strength. While high temperature and long dwell time seem to be most important in achieving high wet strength.
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| 9. |
- Nordin, Tommy, et al.
(author)
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Industrially Relevant In-situ Production Of High Yield Pulp Based Nanocellulose Materials Optimized To Improve Strength In Packaging And Printing Papers : A Comparison Between CMC And MFC As The Anionic Component In Layer-by-Layer Technology
- 2018
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In: IMPC 2018. - Trondheim, Norway.
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Conference paper (peer-reviewed)abstract
- A key issue in papermaking is to understand how to improve strength without losing other important quality measures, like paper bulk. This must of course also be done in a cost efficient way. The trials described in this paper show some different aspects related to the replacement of the expensive anionic component CMC (carboxymethylcellulose) often used in Layer-by-Layer technology together with cationic starch in order to improve strength properties as z-strength and tensile strength of typical chemi-thermomechanical pulp (CTMP) often used as dominating component in industrial scale paper board production. The replacement for CMC investigated here is a MFC (micro-fibrillated cellulose) as the anionic component and paper sheets has been produced on an experimental paper machine at MoRe Research AB. This MFC is a commercially available product and it has not been treated in ways of increasing charge density. The trials were performed at a small pilot scale experimental paper machine (XPM) at MoRe Research in Örnsköldsvik, Sweden. This XPM is equipped with a unique setup to perform Layer-by-Layer-tests under very well controlled conditions. The general conclusion is that it could, with further developments, be feasible to replace CMC with MFC to improve bonding in typical CTMP based paper sheets.
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