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Fibre/fibre joints: Their characterization and influence on different paper strength properties
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , ix, 71 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2006:29
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-11882OAI: oai:DiVA.org:kth-11882DiVA: diva2:287567
Public defence
2006-10-27, SCA salen, Mittuniversitetet, Holmgatan 10, Sundsvall, 10:00 (English)
Supervisors
Note
QC 20100923Available from: 2010-01-19 Created: 2010-01-19 Last updated: 2010-09-23Bibliographically approved
List of papers
1. Study of the joint strength between regenerated cellulose fibres and its influence on the sheet strength
Open this publication in new window or tab >>Study of the joint strength between regenerated cellulose fibres and its influence on the sheet strength
2003 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, no 4, 455-459 p.Article in journal (Refereed) Published
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 predrying 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.

Keyword
bonds, bonding strength, bonded area, fibre bonding, chemical bonding, electrostatic charge, joints, dry strength, strain, swelling, pulp fibers, paper, adhesion, surface
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-23161 (URN)10.3183/NPPRJ-2003-18-04-p455-459 (DOI)000188873000015 ()
Note
QC 20100525Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
2. Influence of electrostatic interactions on fibre/fibre joint and paper strength
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, 440-447 p.Article 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.

Keyword
bonded area, chemical bonds, dry strength, electrostatic charge, joints, regenerated cellulose, strain, swelling, kraft pulps, fiber
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-23981 (URN)10.3183/NPPRJ-2004-19-04-p440-447 (DOI)000226067800006 ()2-s2.0-11144313628 (Scopus ID)
Note
QC 20100525Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
3. The link between the fiber contact zone and the physical properties of paper: A way to control paper properties
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, 1619-1633 p.Article in journal (Refereed) Published
Abstract [en]

Paper is a composite of fibers, air and additives where the fiber/fiber joints keep the network structure together. A study was undertaken to establish the link between the properties of the contact zone between fibers and paper performance under mechanical loading. The contact zone between fibers was investigated using light microscopy. A staining technique was developed for evaluating the influence of surface charge on fiber/fiber joint strength. The joint strength was linearly correlated with paper tensile strength and with the average amplitude of the acoustic events measured by acoustic emission testing. The fiber surface conformability was improved by changing the surface charge. This resulted in increased fiber/fiber joint strength as the relative contact area became larger. Increasing the molecular adhesion in the contact zone with the aid of strength additives also improved the fiber/fiber joint strength.

Keyword
acoustic emission, wood fibers, bonded area, bonding strength, chemical bonds, paper strength, regenerated cellulose, kraft pulps, strength, joint
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-16863 (URN)10.1177/0021998306069875 (DOI)000248687500005 ()2-s2.0-34347351149 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
4. Fiber/Fiber crosses: Finite element modeling and comparison with experiment
Open this publication in new window or tab >>Fiber/Fiber crosses: Finite element modeling and comparison with experiment
2007 (English)In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 41, no 13, 1603-1618 p.Article in journal (Refereed) Published
Abstract [en]

Fiber/fiber joints were analyzed using finite element analysis in order to characterize the influence of fiber and contact region properties on the stress-strain behavior of a single fiber/fiber cross. The output of the models was validated by comparison with experimental load-deformation curves. The contact zone of the fiber/fiber 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 behavior of the fiber/fiber cross under tensile loading. The maximum stress and hence the fiber/fiber joint strength was, however, affected by the degree of contact. It was concluded that knowledge of the material behavior of the contact zone (such as local plastic behavior), and of chemical effects (such as work of adhesion) are needed to predict the fiber/fiber joint strength.

Keyword
bonded area, bonding strength, chemical bonds, joints, strength, paper, joint
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-16862 (URN)10.1177/0021998306069873 (DOI)000248687500004 ()2-s2.0-34347334461 (Scopus ID)
Note

QC 20150728

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
5. Influence of fibre/fibre joint strength and fibre flexibility on the strength of papers from unbleached kraft fibres
Open this publication in new window or tab >>Influence of fibre/fibre joint strength and fibre flexibility on the strength 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, 186-191 p.Article 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 around 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.

Keyword
bonded area, bonding strength, counter-ions, flexibility, hornification, joints, pulp yield, tensile strength, unbleached pulp
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-14887 (URN)10.3183/NPPRJ-2005-20-02-p186-191 (DOI)000230271800008 ()2-s2.0-20744441111 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
6. Tailoring of fibre/fibre joints in order to avoid the negative impacts of drying on paper properties
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, 411-418 p.Article 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.

Keyword
bonded area, bonding strength, chemical bonds, dry strength, joints, Kraft pulp, paper strength, polyelectrolyte, recycling, swelling, unbleached kraft fibers, weak polyelectrolytes, strength, flexibility, multilayers
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-16085 (URN)000241531500017 ()2-s2.0-33750380817 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
7. Surface modification of wood fibers using the polyelectrocyte multilayer technique: Effects on fiber joint and paper strength properties
Open this publication in new window or tab >>Surface modification of wood fibers using the polyelectrocyte multilayer technique: Effects on fiber joint and paper strength properties
2006 (English)In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 45, 5279-5286 p.Article 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.

Keyword
weak polyelectrolytes, dry strength, starch
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-6118 (URN)10.1021/ie060226w (DOI)000238973200014 ()2-s2.0-33746907494 (Scopus ID)
Note

QC 20100923

Available from: 2006-09-14 Created: 2006-09-14 Last updated: 2017-12-14Bibliographically approved

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Citation style
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  • modern-language-association-8th-edition
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  • nn-NO
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Output format
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  • asciidoc
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