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Wågberg, Lars
Publications (10 of 23) Show all publications
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
Fält, S. & Wågberg, L. (2003). Influence of electrolytes on the swelling and strength of kraft-liner pulps. Nordic Pulp & Paper Research Journal, 18(1), 69-73
Open this publication in new window or tab >>Influence of electrolytes on the swelling and strength of kraft-liner pulps
2003 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, no 1, p. 69-73Article in journal (Refereed) Published
Abstract [en]

In the present paper, the effect of common process electrolytes NaCl, Na2SO4 and CaCl2 on fibre swelling and paper strength has been investigated. Results show that there is an initial increase in the water retention value (WRV) of the fibres when the salt concentration is increased at a pH of 5 in the solution surrounding the fibres. At higher salt concentrations, the WRV decreases. This behaviour is most pronounced for Na2SO4 and smaller for NaCl and CaCl2.The increase in swelling is explained as being due to an increase in pH in the fibre wall and a subsequent increased dissociation of the carboxyl groups during the initial increase in ionic strength. When the electrolyte concentration is further increased, the difference in osmotic pressure between the interior of the fibre wall and the surrounding solution decreases and eventually the pressure difference drops to zero. It is also found that there is no unique relationship between the WRV and the strength of paper formed from the fibres treated with different electrolyte concentrations.

National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-13649 (URN)10.3183/NPPRJ-2003-18-01-p069-073 (DOI)000182384600011 ()2-s2.0-0038680580 (Scopus ID)
Available from: 2011-04-19 Created: 2011-04-19 Last updated: 2017-12-11Bibliographically approved
Fält, S., Wågberg, L. & Vesterlind, E.-L. (2003). Swellling of model films of cellulose having different charge densities and comparison to the swelling behavior of corresponding fibers. Langmuir, 19(19), 7895-7903
Open this publication in new window or tab >>Swellling of model films of cellulose having different charge densities and comparison to the swelling behavior of corresponding fibers
2003 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, no 19, p. 7895-7903Article in journal (Refereed) Published
Abstract [en]

Cellulose model films with different charge densities were prepared by spin-coating dissolved cellulose in N-methylmorpholine-N-oxide onto SiO2 surfaces. The swelling of the model cellulose films due to exposure to solutions of different electrolytes and at different ionic strengths and pH values were studied using QCM-D (quartz crystal microbalance with dissipation monitoring). Results show that at pH 5, there is a swelling of the film at a low electrolyte concentration (10(-4)-10(-2) M), whereas the deswelling of the film was observed at a high electrolyte concentration (10(-1)-1 M). A considerable swelling of the films is seen when they are treated with deionized water with an increasing pH. The swelling of the films is accompanied by an increase in dissipation, that is, a softening of the material, and the deswelling by a decrease in dissipation, that is, a stiffening of the material. Furthermore, exposure of the films to solutions of different electrolytes affected the swelling of the layer. In this respect, the swelling response of Na2SO4 differs from that of NaCl and CaC1(2) by showing simultaneously high swelling and low dissipation values. The results also show that the rate of swelling reaches its lowest value as the electrolyte concentration reaches the detected limit for the deswelling. The QCM-D results are compared to the swelling of the corresponding carboxymethylated fibers, where a similar behavior was found. However, for the fibers a marked deswelling occurred at a high electrolyte concentration, but only a minor deswelling of the cellulose film was observed. This difference between the materials can be ascribed to noncovalent bonds within the film that will not reform when the swelling forces are decreased at high electrolyte concentrations. A direct measurement of the thickness changes was performed using atomic force microscopy, which shows that the change in frequency measured with QCM-D for the films treated with different NaCl electrolyte concentrations corresponds to changes of 1-2%.

Keywords
Cellulose, Swelling, Charge densities
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:miun:diva-3253 (URN)10.1021/la026984i (DOI)000185293500033 ()2-s2.0-0141508877 (Scopus ID)3213 (Local ID)3213 (Archive number)3213 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2017-12-12Bibliographically approved
Andreasson, B., Forsström, J. & Wågberg, L. (2003). The porous structure of pulp fibres with different yields and its influence on paper strength. Cellulose, 10(2), 111-123
Open this publication in new window or tab >>The porous structure of pulp fibres with different yields and its influence on paper strength
2003 (English)In: Cellulose, ISSN 0969-0239, Vol. 10, no 2, p. 111-123Article in journal (Refereed) Published
Abstract [en]

The porous structure of the interior of papermaking fibres is a well-known important property of the fibres. Changes of this structure will influence tensile and burst strength of paper formed from the fibres and a change in pore size of the pores within the fibre wall is also important for the ability of molecules to diffuse in and out of the fibre wall. Relevant examples of this latter effect are the removal of lignin during cooking and the addition of performance chemicals during papermaking. In this paper, pore sizes and the pore size distribution of unbleached softwood fibres have been studied. A well-characterised fibre material consisting of laboratory cooked spruce and pine pulp of various lignin contents was used. Pore size and pore size distribution were measured by studies of the relaxation behaviour of 2H in fibres saturated with 2H2O. Beside this the total and surface charge of the fibres were also measured together with strength properties of papers from unbeaten fibres. For both pulps, there is a maximum in pore radius at a yield around 46%. Calculations of fibre wall volume from water retention values and yield levels show that there is a discontinuity in pore radius as a function of the fibre wall volume around a yield of 51%. It is suggested that this discontinuity is caused by the breakdown of the hemicellulose/lignin matrix within the fibre wall at this yield level. The strength of the papers formed from the fibres shows a correlation with the surface charge of the fibres. Based on the change in surface charge with yield and the change in total charge with yield, this correlation is suggested to be due to an opening up of the external part of the fibre wall. This stresses the importance of the chemical composition and physical structure of the outer layer of the fibre wall.

Keywords
pores, fibres, yields, strength, NMR
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-2329 (URN)10.1023/A:1024055406619 (DOI)000184046200003 ()2-s2.0-0038500905 (Scopus ID)1810 (Local ID)1810 (Archive number)1810 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2016-10-27Bibliographically approved
Norgren, M., Edlund, H. & Wågberg, L. (2002). Aggregation of Lignin Derivatives under Alkaline Conditions. Kinetics and Aggregate Structure. Langmuir, 18(7), 2859-2865
Open this publication in new window or tab >>Aggregation of Lignin Derivatives under Alkaline Conditions. Kinetics and Aggregate Structure
2002 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, no 7, p. 2859-2865Article in journal (Refereed) Published
Abstract [en]

The kinetics of kraft lignin (KL) aggregation at alkaline conditions was studied by quasi-elastic light scattering (QELS) and turbidity measurements. Stability ratios (W) for KL were obtained at 70 °C and various concentrations of sodium chloride. By analyzing the early-time evolution data of aggregate growth obtained from QELS, fractal dimensions of flocs formed in both reaction-limited cluster-cluster aggregation regimes and diffusion-limited cluster-cluster aggregation regimes were determined. Correlations between the fractal dimension and the W-ratio were found in accordance to recent studies of a system containing monodisperse polystyrene colloids. By cryogenic transmission electron microscopy, the fractality of KL aggregate structures in the system was also shown. It was seen from stability studies of KL solutions that the effects of specific co- and counterions follow the Hofmeister series. From the outcome of the investigation, different modes of aggregation occurring in a KL system are proposed. Starting from the macromolecular state of KL and evolving through larger aggregates, the KL clusters finally exhibit a supramolecular structure similar to what earlier has been proposed for native softwood lignin.

Keywords
kraft lignin, aggregation, kinetics, NMR, QELS, Cryo-TEM, fractals, universality
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-1596 (URN)10.1021/la011627d (DOI)000174784400057 ()2-s2.0-0037007336 (Scopus ID)640 (Local ID)640 (Archive number)640 (OAI)
Available from: 2008-09-30 Created: 2008-09-30 Last updated: 2017-12-13Bibliographically approved
Rundlöf, M., Eriksson, M., Ström, H. & Wågberg, L. (2002). Effect of Mannanase and Lipase on the properties of colloidal wood extractives and their interaction with mechanical pulp fines. Cellulose (London), 9(2), 127-137
Open this publication in new window or tab >>Effect of Mannanase and Lipase on the properties of colloidal wood extractives and their interaction with mechanical pulp fines
2002 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 9, no 2, p. 127-137Article in journal (Refereed) Published
Abstract [en]

The effects of enzymatic treatments of dissolved and colloidal substances (DCS) released from thermomechanical pulp (TMP) have been investigated. A model dispersion of DCS was made by leaching several portions of TMP in distilled water and separating the fibrous material. Some samples were enriched in colloidal particles by removing dissolved substances using ultra-filtration. The DCS, which had been subjected to different enzymatic treatments, were added in a fixed quantity to TMP fines that had been made cationic, and were subsequently used to form handsheets. All DCS additions increased the content of lipophilic extractives in the sheets. Lipase gave a complete hydrolysation of triglycerides into free fatty acids. The untreated DCS gave no significant decrease in tensile strength, because of the relatively small addition. A treatment of the DCS with Lipase gave a higher extractives content and a tensile strength on the same level as the reference. A Mannanase treatment gave a decrease in strength compared with the reference at the same amount of extractives in the sheet. A combined treatment with Mannanase and Lipase gave a more pronounced decrease in tensile strength. Two possible reasons for the differences in strength at a given amount of extractives were suggested: (i) the destabilisation of the colloidal wood extractives due to the Mannanase could affect the distribution of the colloid in the sheet, making it more detrimental to sheet strength compared with the stable colloid. This would account for the observation that Lipase did not affect sheet strength as such, but the combination with Mannanase gave the lowest tensile strength; (ii) the decomposition of galactoglucomannans in aqueous solution would diminish their positive effect on tensile strength and/or affect the adsorption of the colloid. A reflectometry technique was used to quantify the adsorption of the differently treated DCS onto a model surface of the cationic fines. Colloidal wood extractives were identified on the surfaces after adsorption using staining and light microscopy. No variations in adsorbed amounts were found that could explain the differences in sheet strength, which indirectly suggests that the distribution of the colloid over the surface was affecting the ability of a strong bonded joint to be formed between two such surfaces.

Keywords
Adsorption, Dissolved and colloidal substances, Enzymes, Mechanical pulps, Reflectometry, Retention, Tensile strength, Wood resin
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-13632 (URN)10.1023/A:1020143825530 (DOI)000177946900004 ()2-s2.0-0036623781 (Scopus ID)
Available from: 2011-04-19 Created: 2011-04-19 Last updated: 2017-12-11Bibliographically approved
Gunnars, S., Wågberg, L. & Cohen Stuart, M. A. (2002). Model films of cellulose: I. Method development and initial results. Cellulose (London), 9(3/4), 239-249
Open this publication in new window or tab >>Model films of cellulose: I. Method development and initial results
2002 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 9, no 3/4, p. 239-249Article in journal (Refereed) Published
Abstract [en]

This report presents a new method for the preparation of thin cellulose films. NMMO (N- methylmorpholine- N-oxide) was used to dissolve cellulose and addition of DMSO (dimethyl sulfoxide) was used to control viscosity of the cellulose solution. A thin layer of the cellulose solution is spin- coated onto a silicon oxide wafer and the cellulose is precipitated in deionised water. The cellulose film is anchored onto the silicon oxide wafer by a saturated polymer layer. Among many different polymers tested, PVAm (polyvinylamine) and G- PAM (glyoxalated- polyacrylamide) worked well. The preparation of cellulose model films described in this paper resulted in films with thicknesses in the range 20- 270 nm and the thickness can be controlled by altering the concentration of cellulose solution by addition of different amounts of DMSO. The films were cleaned in deionised water and were found to be free from solvents by ESCA analysis and contact angle measurements. The molecular weight distribution of the cellulose surface material shows that there is only minor breakdown of the cellulose chains, mainly by cleavage of the longest molecular mass fraction and without creation of low molecular mass oligomers of glucose.

Keywords
Materials Science, Paper & Wood, Materials Science, Textiles, Polymer Science
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-13620 (URN)10.1023/A:1021196914398 (DOI)000179365000004 ()2-s2.0-0036764639 (Scopus ID)
Available from: 2011-04-19 Created: 2011-04-19 Last updated: 2017-12-11Bibliographically approved
Andreasson, U. & Wågberg, L. (2001). Ink release from printed surfaces: new methodology and initial insights to the true mechanisms behind ink detachment. Sundsvall: Mitthögskolan, FSCN
Open this publication in new window or tab >>Ink release from printed surfaces: new methodology and initial insights to the true mechanisms behind ink detachment
2001 (English)Report (Other academic)
Place, publisher, year, edition, pages
Sundsvall: Mitthögskolan, FSCN, 2001. p. 20
Series
Rapportserie FSCN, ISSN 1650-5387 ; 2001:02
Series
FSCN-rapport ; R-01-15
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-9299 (URN)
Available from: 2009-07-09 Created: 2009-07-09 Last updated: 2018-05-09Bibliographically approved
Wågberg, L. & Hägglund, R. (2001). Kinetics of polyelectrolyte adsorption on cellulosic fibers. Langmuir, 17(4), 1096-1103
Open this publication in new window or tab >>Kinetics of polyelectrolyte adsorption on cellulosic fibers
2001 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 4, p. 1096-1103Article in journal (Refereed) Published
Abstract [en]

The present investigation has been focused on studying the adsorption of three different molecular mass fractions of a polydimethyldiallylammonium chloride (DMDAAC) (8750 (LMw), 48 000 (MMw), and 1 200 000 (HMw)) on bleached chemical fibers. Both kinetics of adsorption and equilibrium adsorption measurements have been conducted, and the adsorption has been measured by polyelectrolyte titration. The results show that the LMw polymer can reach all the charges in the fiber wall whereas the MMw and HMw can only reach the charges on the external surfaces of the fibers. It is also shown that the kinetics of adsorption of the LMw polymer is not at all affected by the presence of a saturated layer of HMw polymer on the surface of the fibers. Finally the results from the investigation show that it is possible to have a full coverage of the external surface of the fibers by a high molecular mass polymer and a full coverage of the internal surface of the fibers with a low molecular mass polymer provided that the high molecular mass polymer is adsorbed before addition of the low molecular mass polymer. This is true if the polymers are adsorbed to the same type of groups on the fibers. A simplistic model for describing ployelectrolyte adsorption in turbulent flow also shows good agreement with measured values for the low molecular mass polyelectrolyte whereas the agreement for the high molecular polyelectrolyte is not as good. For the high molecular mass polyelectrolyte a more sophisticated model is needed.

Keywords
Bleached chemical fibers, Cellulosic fibers, Molecular mass fractions, Polydimethyldiallyammonium chloride
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-13606 (URN)10.1021/la000629f (DOI)000167064600020 ()2-s2.0-0035250123 (Scopus ID)
Available from: 2011-04-20 Created: 2011-04-19 Last updated: 2017-12-11Bibliographically approved
Wågberg, L. (2001). Polyelectrolyte adsorption on cellulose fibres: a review. Sundsvall: Mitthögskolan, FSCN
Open this publication in new window or tab >>Polyelectrolyte adsorption on cellulose fibres: a review
2001 (English)Report (Other academic)
Place, publisher, year, edition, pages
Sundsvall: Mitthögskolan, FSCN, 2001. p. 30
Series
FSCN-rapport ; R-00-7
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-9318 (URN)
Available from: 2009-07-09 Created: 2009-07-09 Last updated: 2012-02-12Bibliographically approved
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