miun.sePublikasjoner
Endre søk
Begrens søket
1 - 13 of 13
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Eriksson, Malin
    et al.
    Royal Institute of Technology, Stockholm.
    Torgnysdotter, Annsofie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Surface modification of wood fibres using the polyelecrolyte multilayer technique: Effects on fibre joint and paper strength properties2006Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 45, nr 15, s. 5279-5286Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyallylamine hydrochloride (PAH) and poly(acrylic acid) (PAA) were used to modify wood fibers by means of the polyelectrolyte multilayer (PEM) technique. Hand sheets and fiber crosses were prepared from the PEM-treated fibers. The sheet strength and fiber-fiber joint strength were evaluated, and the contact zone of the fiber-fiber joint was characterized using a recently developed staining technique. The nonjoined surface area of the paper sheets was estimated by determining nitrogen adsorption via BET analysis, and the results were compared with those of the light scattering measurements frequently used to determine the degree of “bonding” in paper. Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy was used to analyze chemical effects. It was shown that the PEM treatment of fibers increased the strength properties of the sheets through an increase in the number of fiber-fiber joints, increasing the degree of contact in a fiber-fiber joint and creating covalent bonding in the fiber-fiber joint.

  • 2.
    Forsström, Jennie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Torgnysdotter, Annsofie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Influence of fibre/fibre joint strength and fibre flexibiity on the strentgh of papers from unbleached kraft fibres.2005Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, nr 2, s. 186-191Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The joint strength between single fibres and its influence on strength properties of papers was evaluated, taking into account the effect of pulp yield, ionic form of the carboxyl groups and drying. Fibre/fibre joint strength stayed almost constant for pulps with yield between 45 % and 50 %. Further increasing the pulp yield increased the joint strength until a maximum value was reached at a pulp yield of 57 %, after which the joint strength decreased. Joint strength correlated well to paper tensile strength for never dried fibres, i.e. a lower joint strength resulted in lower sheet tensile index. The decrease in sheet tensile index was not as pronounced as the decrease in joint strength. Changing counter-ion from Na+ to Ca2+ or H+ did not affect fibre flexibility, although it reduced the joint strength as the molecular contact area decreased due to a reduced swelling upon changing the counter-ions. Drying the high yield pulp lowered both the joint strength and the sheet tensile index to the same extent. The sheet tensile index, for the low yield pulp, decreased much more than the fibre/fibre joint strength after drying the fibres. In conclusion, a combination of a lower fibre flexibility, resulting in fewer contact points between fibres in the sheet, and a lower joint strength after drying was responsible for the reduction in sheet tensile index.

  • 3.
    Torgnysdotter, Annsofie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Fibre charge and paper forming2003Inngår i: Fibernätverket- skogen som resurs, Umeå, 2003Konferansepaper (Annet vitenskapelig)
  • 4.
    Torgnysdotter, Annsofie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Fibre/fibre joints : their characterization and influence on different paper strength properties2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The main goal of this work was to gain knowledge of how to process the fibres for a certain enduse purpose. To reach this knowledge it must be clarified how different fibre properties, mechanical and chemical as well as surface and bulk properties, will influence the physical properties of the formed paper. The influence of adsorbed polyelectrolytes onto the fibres, and the conditions of the surrounding media were also included in the investigation, as those parameters will influence the interactions between the fibres during paper formation. The contact points between the fibres, the fibre/fibre joints, that are a key parameter of this work, were studied with respect to strength and appearance of the contact zone. The reason to the new nomenclature is the fact that the strength of the fibre/fibre joints is dependent on numerous other factors than just chemical bonds. In the present work the fibre/fibre joint has been investigated from an adhesion point of view where the physical appearance of the contact zone is one important parameter for the measured fibre/fibre joint strength. A new technique was developed for characterization of physical appearance of the contact zone, to create a link between contact zone properties, joint strength and the physical properties of paper.. Single fibre/fibre joint strength and the appearance of the contact zone were used to create a finite element model that described the stress-strain behaviour of fibre/fibre crosses under tensile loading. Electrostatics interactions between the fibres, polyelectrolytes, and the surrounding media in the stock will together with the mechanical properties of the fibres, such as fibre flexibility, control not only the number of contacts formed in the sheet during formation but also the fibre/fibre joint strength. It was found that the surface properties of the fibres and especially the surface charges, natural or introduced by chemical treatment, were important for the strength properties of the paper. Creating a fibre with a low surface elastic modulus will favour the formation of a large and homogeneous contact zone between the fibres and hence the strength of the fibre/fibre joint. The fibre/fibre joint strength is naturally also controlled by the molecular work of adhesion in the area of contact. Fibre surface modifications have a large potential in the design of paper with specific paper properties. By adsorbing polyelectrolytes at the surface of dried fibres the paper strength was enhanced beyond that of never dried fibres but with the density of paper made from dried fibres and a dewatering capacity as dried fibers.

  • 5.
    Torgnysdotter, Annsofie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Is there a relationship between the properties of the joint and the behaviour of paper2003Inngår i: Sammanfattning av föredragen vid Ekmandagarna, Stockholm: Svenska pappers och cellulosaingeniörsföreningen , 2003Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Paper is as a fibrous network where the fibres are joined together in fibre/fibre crossings and the main constituents of the paper dry strength is the joint strength between the fibres and the strength of the individual fibres. To study the link between chemical properties of the interface between two fibres and the physical properties of paper the single joint strength between fibres was measured. The specific strength of each fibre/fibre cross and the influence of chemical treatment of the fibres could then be quantified.

  • 6.
    Torgnysdotter, Annsofie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Kulachenko, Artem
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Gradin, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Wågberg, Lars
    KTH.
    Fiber/Fiber crosses: Finite Element Modelling and Comparison with Experiment2007Inngår i: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 41, nr 13, s. 1603-1608Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fibre/fibre joints were analysed using finite element analysis in order to characterise the influence of fibre and contact region properties on the stress strain behaviour of a single fibre/fibre cross. The output of the models was validated by comparison with experimental load deformation curves. The contact zone of the fibre/fibre joint was studied with respect to the appearance of the contact zone, the contact area, and the contact pattern; the work of adhesion of the contact areas was also considered. It was shown that the two-dimensional appearance of the contact zone had little influence on the stress strain behaviour of the fibre/fibre cross under tensile loading. The maximum stress and hence the fibre/fibre joint strength was, however, affected by the degree of contact. It was concluded that knowledge of the material behaviour of the contact zone (such as local plastic behaviour) and of chemical effects (such as work of adhesion) are needed to predict the fibre/fibre joint strength.

  • 7.
    Torgnysdotter, Annsofie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Kulachenko, Artem
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Gradin, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Wågberg, Lars
    KTH.
    The Link Between the Fiber Contact Zone and the Physical Properties of Paper: A Way to Control Paper Properties2007Inngår i: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 41, nr 13, s. 1619-1633Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In order to establish a link between the properties of the fibre surface and the paper performance under stress, the properties of single fibres and the properties of the joints between fibres were linked to the acoustic emission behaviour of paper of surface treated regenerated cellulose fibres under stress. Results show that the strength of the single fibre joint was influenced by the surfaces properties of the fibres and the interactions in the contact zone during joint formation, which in turn were dependent on both chemical and mechanical properties of the fibres surface. As the paper properties in this case were independent of the mechanical properties of the fibres, there was a strong link between the properties of the fibre-surface and joint properties and the behaviour of the paper under stress.

  • 8.
    Torgnysdotter, AnnSofie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Kulachenko, Artem
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Gradin, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Wågberg, P
    Modification of the Contact Zone to Control the Physical Behaviour of Paper - A Model Experiment: Pappersfysik konferens i Trondheim ?2004Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In order to establish a link between the properties of the fibre surface and the paper performance under stress, the properties of single fibres and the properties of the joints between fibres were linked to the acoustic emission behaviour of paper of surface treated regenerated cellulose fibres under stress. Results show that the strength of the single fibre joint was influenced by the surfaces properties of the fibres and the interactions in the contact zone during joint formation, which in turn were dependent on both chemical and mechanical properties of the fibres surface. As the paper properties in this case were independent of the mechanical properties of the fibres, there was a strong link between the properties of the fibre-surface and joint properties and the behaviour of the paper under stress.

  • 9.
    Torgnysdotter, Annsofie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lindström, Anna-Lena
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Possible links between the properties of paper and fibre contact zones: Poster, 5th International paper and coating chemistry symposium 2003, Montreal, Canada2003Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The mechanical behaviour of paper depends on both fibres and the properties of the fibre-fibre joints.The fibre surfaces will constitute the contact zone between the fibres and will hence be very important for paper strength. The links between the mechanical behaviour of single fibre joints and paper properties were studied by introducing negative charges to the surface and the bulk of regenerated cellulose fibres selectively. This will affect the properties of fibres and fibre surfaces differently. Both the chemical and mechanical properties were investigated.

  • 10.
    Torgnysdotter, Annsofie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    From Joint strength to strong paper2002Inngår i: Progress in paper physics seminar: Syracuse, NY, USA, 8-13 Sept. 2002, 2002, s. 3-9Konferansepaper (Annet vitenskapelig)
  • 11.
    Torgnysdotter, Annsofie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Influence of electrostatic interactions on fibre/fibre joint and paper strength2004Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 4, s. 440-447Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A study was undertaken to explore the influence of electrostatic interactions between the fibres during sheet forming and sheet consolidation on the strength of both the fibre/fibre joints and the paper. To establish this relationship, the joint strength between individual fibres was determined and compared with the strength of sheets made from these corresponding fibres. Regenerated cellulose fibres with their charge varied by carboxymethylation (anionic fibres) and by treatment with glycidyltrimethylamoniumchloride (GTAC) (cationic fibres) were investigated. In addition to joint strength and sheet strength measurements, the fibre charge together with wet fibre flexibility and fibre swelling, were evaluated for the differently treated fibres.The joint strength between individual fibres decreased with increasing ionic strength whereas the sheet strength measurements showed an increase in strength with increasing ionic strength for the bulk charged fibres. These results were found for both anionic and cationic bulk charged fibres. The wet flexibility of the fibres increased with increasing bulk charge, but there was no change in flexibility with an increase in salt concentration. Furthermore, there was no change in flexibility by increasing the surface charge of the fibres. It is suggested that the increase in sheet strength with increasing charge of the fibre is due to increasing joint strength and that the decrease in joint strength with increasing salt concentration is due to a decrease in the surface swelling of the fibres and hence a less favourable interaction between the fibres.The increase in sheet strength for the bulk charged fibres with increasing salt concentration is probably caused by an increased probability for joint formation in the fibre/fibre contacts due to decreased electrostatic repulsion between the fibres. This is discussed in terms of a balance between electrostatic repulsion and attractive capillary forces between the fibres during forming and consolidation of the paper.

  • 12.
    Torgnysdotter, Annsofie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Study of the joint strength between regenerated cellulose fibres and its influence on the sheet strength2003Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, nr 4, s. 455-459Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The joint strength between single fibres was investigated directly by measurements of perpendicular cross bonded fibres and compared with the corresponding paper properties. Regenerated cellulose fibres, rayon, were used. They were carboxymethylated in order to introduce charges to the fibres. Two different treatments were used to prepare fibres with charges located on the surface of the fibres and charges located throughout the bulk of the fibres. The charge characteristics, with respect to total charge and surface charge of the fibre were determined. The swelling caused by these charges was analysed with respect to pore volume distribution (NMR measurements) and water retention capacity (WRV). Charge characterisation showed that surface charged fibres could be produced by pre-drying fibres prior to carboxymethylation. Furthermore, WRV and NMR-relaxation measurements showed that an increase in the surface charge had no significant influence on the swelling whereas an increase in bulk charges had a large effect. The strength of the joints and the paper tensile properties are most affected by the surface charges, probably due to an increase in the molecular contact area with increasing charge. The results indicated that increased surface softness increased the critical strain of paper made from these modified fibres.

  • 13.
    Torgnysdotter, Annsofie
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    KTH, Stockholm.
    Tailoring of fibre/fibre joints in order to avoid the negative impacts of drying on paper properties2006Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, nr 3, s. 411-418Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work examines the possibility of changing the properties of the contact zone between fibres to control the physical properties of paper. This was done by linking the degree of contact of the contact zones in the fibre/fibre joints to joint strength, and furthermore, to the fibre and sheet properties. Kraft pulps of various yields were dried in order to collapse the fibre surface and fibre wall, to achieve a fibre with lower wet-fibre flexibility and fibre-surface deformability. This treatment produced fibres with lower water retention capacity and paper with lower sheet density, higher bending stiffness, and lower tensile strength. The changes in the sheet properties with drying were largely due to the decreased wet-fibre flexibility and deteriorated fibre contact-zone properties that reduced the fibre/fibre joint strength. By adding polyelectrolyte multilayers (PEM) or polyelectrolyte complexes (PEC), obtained from weak polyelectrolytes, to the dried pulp prior to fibre/fibre joint and sheet forming, the tensile and compression strength properties of the paper were significantly improved. Tensile strength increased up to 108% with no significant influence on either the sheet density or the water retention capacity of the fibres. Paper strength most likely increased due to the increase of the fibre/fibre joint strength arising from the improved contact-zone properties, where the increased work of adhesion and greater degree of contact of the fibre/fibre joints resulted in higher joint strength.

1 - 13 of 13
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf