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Torgnysdotter, AnnSofie
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Publications (10 of 13) Show all publications
Torgnysdotter, A., Kulachenko, A., Gradin, P. & Wågberg, L. (2007). Fiber/Fiber crosses: Finite Element Modelling and Comparison with Experiment. Journal of composite materials, 41(13), 1603-1608
Open this publication in new window or tab >>Fiber/Fiber crosses: Finite Element Modelling and Comparison with Experiment
2007 (English)In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 41, no 13, p. 1603-1608Article in journal (Refereed) Published
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.

Keywords
Fibre/fibre cross, Bonded area, Bonding strength, Chemical bonds, Joints
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:miun:diva-5262 (URN)10.1177/0021998306069873 (DOI)000248687500004 ()2-s2.0-34347334461 (Scopus ID)4299 (Local ID)4299 (Archive number)4299 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2018-11-09Bibliographically approved
Torgnysdotter, A., Kulachenko, A., Gradin, P. & Wågberg, L. (2007). The Link Between the Fiber Contact Zone and the Physical Properties of Paper: A Way to Control Paper Properties. Journal of composite materials, 41(13), 1619-1633
Open this publication in new window or tab >>The Link Between the Fiber Contact Zone and the Physical Properties of Paper: A Way to Control Paper Properties
2007 (English)In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 41, no 13, p. 1619-1633Article in journal (Refereed) Published
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.

Keywords
Bonds, Bonding strength, Bonded area, Fibre bonding, Chemical bonding, joints, dry strength, swelling
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-1107 (URN)10.1177/0021998306069875 (DOI)000248687500005 ()2-s2.0-34347351149 (Scopus ID)4300 (Local ID)4300 (Archive number)4300 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2018-11-09Bibliographically approved
Torgnysdotter, A. (2006). Fibre/fibre joints : their characterization and influence on different paper strength properties. (Doctoral dissertation). Stockholm: KTH
Open this publication in new window or tab >>Fibre/fibre joints : their characterization and influence on different paper strength properties
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
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.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006
Series
Trita FPT-Report, ISSN 1652-2443 ; 2006:29
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-9105 (URN)
Public defence
(English)
Opponent
Supervisors
Available from: 2009-06-08 Created: 2009-06-08 Last updated: 2018-11-09Bibliographically approved
Eriksson, M., Torgnysdotter, A. & Wågberg, L. (2006). Surface modification of wood fibres using the polyelecrolyte multilayer technique: Effects on fibre joint and paper strength properties. Industrial & Engineering Chemistry Research, 45(15), 5279-5286
Open this publication in new window or tab >>Surface modification of wood fibres using the polyelecrolyte multilayer technique: Effects on fibre joint and paper strength properties
2006 (English)In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 45, no 15, p. 5279-5286Article in journal (Refereed) Published
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.

Keywords
fibre joints
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-832 (URN)10.1021/ie060226w (DOI)000238973200014 ()2-s2.0-33746907494 (Scopus ID)4574 (Local ID)4574 (Archive number)4574 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2018-11-09Bibliographically approved
Torgnysdotter, A. & Wågberg, L. (2006). Tailoring of fibre/fibre joints in order to avoid the negative impacts of drying on paper properties. Nordic Pulp & Paper Research Journal, 21(3), 411-418
Open this publication in new window or tab >>Tailoring of fibre/fibre joints in order to avoid the negative impacts of drying on paper properties
2006 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 21, no 3, p. 411-418Article in journal (Refereed) Published
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.

Keywords
Bonded area, Bonding strength, Chemical bonds, Dry strength, Joints, Kraft pulp, Paper strength, Polyelectrolyte, Recycling, Swelling
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-8676 (URN)10.3183/NPPRJ-2006-21-03-p411-418 (DOI)000241531500017 ()2-s2.0-33750380817 (Scopus ID)
Available from: 2009-02-26 Created: 2009-02-26 Last updated: 2018-11-09Bibliographically approved
Forsström, J., Torgnysdotter, A. & Wågberg, L. (2005). Influence of fibre/fibre joint strength and fibre flexibiity on the strentgh of papers from unbleached kraft fibres.. Nordic Pulp & Paper Research Journal, 20(2), 186-191
Open this publication in new window or tab >>Influence of fibre/fibre joint strength and fibre flexibiity on the strentgh of papers from unbleached kraft fibres.
2005 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, no 2, p. 186-191Article in journal (Refereed) Published
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.

Keywords
Bonded area, Bonding strength, Counter-ions, Flexibility, Hornification, Joints, Pulp yield, Tensile strength, Unbleached pulp
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-3129 (URN)10.3183/NPPRJ-2005-20-02-p186-191 (DOI)000230271800008 ()3040 (Local ID)3040 (Archive number)3040 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2018-11-09Bibliographically approved
Torgnysdotter, A. & Wågberg, L. (2004). Influence of electrostatic interactions on fibre/fibre joint and paper strength. Nordic Pulp & Paper Research Journal, 19(4), 440-447
Open this publication in new window or tab >>Influence of electrostatic interactions on fibre/fibre joint and paper strength
2004 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, no 4, p. 440-447Article in journal (Refereed) Published
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.

Keywords
Bonded area, Chemical bonds, Dry strength, Electrostatic charge, Joints, Regenerated cellulose, Strain, Swelling
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-3098 (URN)10.3183/NPPRJ-2004-19-04-p440-447 (DOI)000226067800006 ()2967 (Local ID)2967 (Archive number)2967 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2018-11-09Bibliographically approved
Torgnysdotter, A., Kulachenko, A., Gradin, P. & Wågberg, P. (2004). Modification of the Contact Zone to Control the Physical Behaviour of Paper - A Model Experiment: Pappersfysik konferens i Trondheim ?. In: : .
Open this publication in new window or tab >>Modification of the Contact Zone to Control the Physical Behaviour of Paper - A Model Experiment: Pappersfysik konferens i Trondheim ?
2004 (English)Conference paper, Published paper (Other academic)
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.

Keywords
Beam model, Bonds, Bonding strength, Bonded area, Fibre bonding, Chemical bonding, joints, dry strength, swelling.
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-6266 (URN)2968 (Local ID)2968 (Archive number)2968 (OAI)
Available from: 2009-06-08 Created: 2009-06-08 Last updated: 2018-11-09Bibliographically approved
Torgnysdotter, A. (2003). Fibre charge and paper forming. In: Fibernätverket- skogen som resurs: . Umeå
Open this publication in new window or tab >>Fibre charge and paper forming
2003 (English)In: Fibernätverket- skogen som resurs, Umeå, 2003Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Umeå: , 2003
Keywords
Fibre charge, joint
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-2225 (URN)1332 (Local ID)1332 (Archive number)1332 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2018-11-09Bibliographically approved
Torgnysdotter, A. (2003). Is there a relationship between the properties of the joint and the behaviour of paper. In: Sammanfattning av föredragen vid Ekmandagarna: . Stockholm: Svenska pappers och cellulosaingeniörsföreningen
Open this publication in new window or tab >>Is there a relationship between the properties of the joint and the behaviour of paper
2003 (English)In: Sammanfattning av föredragen vid Ekmandagarna, Stockholm: Svenska pappers och cellulosaingeniörsföreningen , 2003Conference paper, Published paper (Other academic)
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.

Place, publisher, year, edition, pages
Stockholm: Svenska pappers och cellulosaingeniörsföreningen, 2003
Keywords
Bond, joint
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-2223 (URN)1329 (Local ID)1329 (Archive number)1329 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2018-11-09Bibliographically approved
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