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Publications (10 of 41) Show all publications
Lecourt, M., Pöhler, T., Hornatowska, J., Salmen, L. & Jetsu, P. (2018). Density profiles of novel kraft pulp and TMP based foam formed thermal insulation materials observed by X-ray tomography and densitometry. Holzforschung
Open this publication in new window or tab >>Density profiles of novel kraft pulp and TMP based foam formed thermal insulation materials observed by X-ray tomography and densitometry
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2018 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434XArticle in journal (Refereed) In press
Abstract [en]

X-ray tomography and densitometry (XRT and XRD) were applied to characterise wood fibre based insulation materials, which were produced by the foam forming technology. XRT is a high resolution approach with long measurement times of around 29 h, while XRD measurement needs only a few minutes. The determination of density distribution of boards in the thickness direction was the focus of this study. Both approaches visualised well the impact of raw materials and manufacturing processes on the structure of the panels. The density profiles were dependent on the pulp applied for panel production, and the processing conditions were also influential. Air flow resistance correlated with the maximum density measured inside the board. Both XRT and XRD revealed similar trends, which are useful for the characterisation of insulation materials.

Keywords
kraft pulp, thermomechanical pulp, TMP, insulation, x-ray tomography, densitometry
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-33326 (URN)10.1515/hf-2017-0116 (DOI)2-s2.0-85042047233 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme
Available from: 2018-02-28 Created: 2018-02-28 Last updated: 2018-08-21Bibliographically approved
Salmen, L. & Stevanic Srndovic, J. (2018). Effect of drying conditions on cellulose microfibril aggregation and "€œhornification". Cellulose (London)
Open this publication in new window or tab >>Effect of drying conditions on cellulose microfibril aggregation and "€œhornification"
2018 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882XArticle in journal (Refereed) In press
Abstract [en]

Drying of chemical pulps results in a decreased swelling of the fibres, leading to lower density and strength properties of paper sheets. To investigate how variation of pulp pH, drying process temperature, and final moisture content affect this phenomenon, structural studies were performed on a cellulose-rich pulp. Interrupting the drying at moisture contents of around 20%, using drying temperatures of 80 °C and 140 °C, resulted in a more severe degree of hornification than if the pulp was completely dried at the same temperatures. This increased loss of swelling was accompanied by increased cellulose microfibril aggregation. No change of the cellulose microfibril size or of the cellulose crystallinity, as determined by NMR, could be seen. Further, the accessibility of the cellulose microfibril surfaces, including surfaces between microfibrils, was unaffected by the drying. Thus, hornification should not primarily be related to a reduction of accessible cellulosic surfaces.

Place, publisher, year, edition, pages
Springer Netherlands, 2018
Keywords
Cellulose derivatives, Deuterium, Drying, Moisture, Moisture determination, Nuclear magnetic resonance, Temperature, Cellulose crystallinity, Drying condition, Drying process, Drying temperature, Final moisture content, FTIR, Strength property, Structural studies, Cellulose
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-35313 (URN)10.1007/s10570-018-2039-1 (DOI)2-s2.0-85053563624 (Scopus ID)
Available from: 2018-10-15 Created: 2018-10-15 Last updated: 2018-10-15Bibliographically approved
Salmen, L. & Larsson, P. A. (2018). On the origin of sorption hysteresis in cellulosic materials. Carbohydrate Polymers, 182, 15-20
Open this publication in new window or tab >>On the origin of sorption hysteresis in cellulosic materials
2018 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 182, p. 15-20Article in journal (Refereed) Published
Abstract [en]

Moisture sorption and moisture sorption hysteresis of carbohydrates are phenomena which affect the utilisation of products made thereof. Although extensively studied, there is still no consensus regarding the mechanisms behind sorption hysteresis. Attempts have been made to link the behaviour to molecular properties, in particular to softening properties, and the moisture sorption hysteresis has therefore here been investigated by modifying cellulosic fibres to affect their softening properties. The results show that the moisture sorption hysteresis diminishes with decreasing softening temperature, and was even completely absent at the higher degrees of modification. The moisture sorption characteristics also changed from a type II sorption to a more type III sorption behaviour, a feature more prominent the higher the degree of modification and the higher the temperature. For the highest degree of modification studied the sorption characteristics changed from sorbing less water the higher the temperature to sorbing more water with increasing temperature.

Keywords
cellulose, chemical modification, glass transition temperature, dialcohol cellulose, kraft pulp, moisture sorption, sorption hysteresis, temperature
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-32794 (URN)10.1016/j.carbpol.2017.11.005 (DOI)2-s2.0-85032968676 (Scopus ID)
Available from: 2017-11-29 Created: 2017-11-29 Last updated: 2018-08-21Bibliographically approved
Salmen, L. (2018). Wood cell wall structure and organisation in relation to mechanics. In: Plant Biomechanics: From structure to function at multiple scales (pp. 3-19). Springer International Publishing
Open this publication in new window or tab >>Wood cell wall structure and organisation in relation to mechanics
2018 (English)In: Plant Biomechanics: From structure to function at multiple scales, Springer International Publishing , 2018, p. 3-19Chapter in book (Other academic)
Abstract [en]

The wood cell wall, as well as the entire wood structure, is a highly intermixed assembly of biopolymers building up various structural elements. The understanding of the organisation of these wood polymers and their interaction is a key to be able to better utilise wood materials. The complexity of the wood cell wall is here discussed regarding the cellulose fibrillar network, the cellulose aggregate structure and the arrangement of the matrix polymers of hemicelluloses and lignin. The ability to model the wood cell wall properties, based on the structural organisation within different cell wall structures, and the difficulties in relating predictions to actual measurements of cell wall properties are described. The deficiencies regarding our structural knowledge in relation to mechanical properties are also being defined.

Place, publisher, year, edition, pages
Springer International Publishing, 2018
Keywords
cell wall, cellulose, hemicellulose, humidity, lignin, microfibril, micromechanics, temperature, secondary cell wall
National Category
Wood Science
Identifiers
urn:nbn:se:ri:diva-35311 (URN)10.1007/978-3-319-79099-2_1 (DOI)2-s2.0-85053581145 (Scopus ID)978-3-319-79099-2 (ISBN)978-3-319-79098-5 (ISBN)
Available from: 2018-10-15 Created: 2018-10-15 Last updated: 2018-10-15Bibliographically approved
Guo, J., Yin, J., Zhang, Y., Salmen, L. & Yin, Y. (2017). Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin. Holzforschung, 71(6), 455-460
Open this publication in new window or tab >>Effects of thermo-hygro-mechanical (THM) treatment on the viscoelasticity of in-situ lignin
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2017 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, no 6, p. 455-460Article in journal (Refereed) Published
Abstract [en]

For producing wood products without fractures based on thermo-hygro-mechanical (THM) treatments, it is essential to understand how steaming and compression change the wood softening and cell wall components. In this paper, the effects of compression combined with steam treatment (CS) on the viscoelasticity of the in-situ lignin of Chinese fir has been investigated through dynamic mechanical analysis (DMA) under fully saturated conditions. Several variations were studied, such as the softening temperature (Tg) and apparent activation energy (ΔHa) of the softening process in response to CS treatment conditions (such as steam temperature and compression ratio) under separate consideration of earlywood (EW) and latewood (LW). No difference between EW and LW with respect to the viscoelasticity was noted. Tg and ΔHa of the lignin softening were nearly unaffected by the compression ratio, but were highly influenced by the steam temperature. The Tg decreased significantly with CS treatments at or above 160oC, but showed no appreciable change, compared to the native wood, at the lower steaming temperature of 140oC. ΔHa increased at higher steam temperatures, while ΔHa showed a decreasing tendency with decreasing Tg. This indicates that lignin undergoes a simultaneous depolymerization as well as a condensation during CS treatment.

Place, publisher, year, edition, pages
Walter de Gruyter GmbH, 2017
Keywords
Activation energy; Compression ratio (machinery); Dynamic mechanical analysis; Dynamics; Lignin; Steam; Viscoelasticity, Apparent activation energy; Dynamic mechanical analysis (DMA); Earlywood; Latewood; softening; Softening temperature; Steam temperature; Thermo-hygro-mechanical treatments, Wood
National Category
Chemical Engineering
Identifiers
urn:nbn:se:ri:diva-30032 (URN)10.1515/hf-2016-0201 (DOI)2-s2.0-85020397682 (Scopus ID)
Available from: 2017-07-04 Created: 2017-07-04 Last updated: 2018-08-21Bibliographically approved
Lindh, E. & Salmen, L. (2017). Surface accessibility of cellulose fibrils studied by hydrogena€“deuterium exchange with water. Cellulose (London), 24(1), 21-33
Open this publication in new window or tab >>Surface accessibility of cellulose fibrils studied by hydrogena€“deuterium exchange with water
2017 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 1, p. 21-33Article in journal (Refereed) Published
Abstract [en]

A problem with cellulose-based materials is that they are highly influenced by moisture, leading to reduced strength properties with increasing moisture content. By achieving a more detailed understanding of the water–cellulose interactions, the usage of cellulose-based materials could be better optimized. Two different exchange processes of cellulose hydroxyl/deuteroxyl groups have been monitored by transmission FT-IR spectroscopy. By using line-shape-assisted deconvolution of the changing intensities, we have been able to follow the exchange kinetics in a very detailed and controlled manner. The findings reveal a hydrogen exchange that mainly is located at two different kinds of fibril surfaces, where the differences arise from the water accessibility of that specific surface. The slowly accessible regions are proposed to be located between the fibrils inside of the aggregates, and the readily accessible regions are suggested to be at the surfaces of the fibril aggregates. It was also possible to identify the ratio of slowly and readily accessible surfaces, which indicated that the average aggregate of cotton cellulose is built up by approximately three fibrils with an assumed average size of 12 × 12 cellulose chains. Additionally, the experimental setup enabled visualizing and discussing the implications of some of the deviating spectral features that are pronounced when recording FT-IR spectra of deuterium-exchanging cellulose: the insufficient red shift of the stretching vibrations and the vastly decreasing line widths.

National Category
Paper, Pulp and Fiber Technology Nano Technology
Identifiers
urn:nbn:se:ri:diva-27569 (URN)10.1007/s10570-016-1122-8 (DOI)2-s2.0-84995741409 (Scopus ID)
Available from: 2016-12-15 Created: 2016-12-15 Last updated: 2018-08-21Bibliographically approved
Rahman, H., Lindström, M. E., Sandström, P., Salmen, L. & Engstrand, P. (2017). The effect of increased pulp yield using additives in the softwood kraft cook on the physical properties of low-grammage handsheets. Nordic Pulp & Paper Research Journal, 32(2), 317-323
Open this publication in new window or tab >>The effect of increased pulp yield using additives in the softwood kraft cook on the physical properties of low-grammage handsheets
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2017 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, no 2, p. 317-323Article in journal (Refereed) Published
Abstract [en]

The effect of increasing the pulp yield by the addition of sodium borohydride (NaBH4) or polysulfide (PS) in softwood kraft cooking, i.e. enhancing the retention of glucomannan, on the physical properties of low-grammage handsheets was studied. In addition to the yield improvement, an increase in tensile index was observed, especially at lower degrees of beating. These higher yield pulps showed an increase in pore volume, indicating an increased degree of swelling of the fibres. Presumably, the increased flexibility of the fibres affects the bonding strength and leads to the higher tensile index observed.

Keywords
kappa number, polysulphide, tensile strength, porosimeter, z direction strength, softwood, handsheet, physical properties, yield
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-32950 (URN)10.3183/NPPRJ-2017-32-03-p317-323 (DOI)
Available from: 2018-01-02 Created: 2018-01-02 Last updated: 2018-08-23Bibliographically approved
Veguta, V. L., Stevanic, J. S., Lindström, M. E. & Salmen, L. (2017). Thermal and alkali stability of sodium dithionite studied using ATR-FTIR spectroscopy. BioResources, 12(2), 2496-2506
Open this publication in new window or tab >>Thermal and alkali stability of sodium dithionite studied using ATR-FTIR spectroscopy
2017 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 2, p. 2496-2506Article in journal (Refereed) Published
Abstract [en]

Sodium dithionite (Na2S2O4) may have the potential to be used as a reducing agent for the stabilization of glucomannan in kraft cooking for increased pulp yield. However, due to the fact that dithionite decomposes under the conditions of kraft pulping, studies of the effects of dithionite in kraft pulping are non-conclusive; sometimes clearly showing an increased yield, and in other studies no effect at all. The specific conditions influencing dithionite degradation are also unclear. For that reason, this study was conducted to determine the thermal and chemical stability of sodium dithionite with respect to specific factors, such as the pH, temperature, heating time, and the concentration of sodium dithionite solution. The study was performed under anaerobic conditions using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The thermal and alkali stability of the sodium dithionite solution was shown to decrease with increasing temperature, heating time, and concentration of the solution at the alkaline conditions studied. The thermal stability decreased rapidly at weak alkalinity (pH 9) as well as in high alkalinity (pH 14), whereas the sodium dithionite was rather stable at moderate alkalinity (pH 11.5 to pH 13).

Keywords
Alkalinity, ATR-FTIR, Concentration, Dithionite, Stability, Temperature
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-29742 (URN)10.15376/biores.12.2.2496-2506 (DOI)2-s2.0-85018871726 (Scopus ID)
Available from: 2017-05-30 Created: 2017-05-30 Last updated: 2018-08-23Bibliographically approved
Lindh, E. L., Terenzi, C., Salmen, L. & Furo, I. (2017). Water in cellulose: evidence and identification of immobile and mobile adsorbed phases by 2H MAS NMR. Physical Chemistry, Chemical Physics - PCCP, 19, 4360-4369
Open this publication in new window or tab >>Water in cellulose: evidence and identification of immobile and mobile adsorbed phases by 2H MAS NMR
2017 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, p. 4360-4369Article in journal (Refereed) Published
Abstract [en]

The organization of water molecules adsorbed onto cellulose and the supramolecular hydrated structure of microfibril aggregates represents, still today, one of the open and complex questions in the physical chemistry of natural polymers. Here, we investigate by 2H MAS NMR the mobility of water molecules in carefully 2H-exchanged, and thereafter re-dried, microcrystalline cellulose. By subtracting the spectral contribution of deuteroxyls from the spectrum of hydrated cellulose, we demonstrate the existence of two distinct 2H2O spectral populations associated with mobile and immobile water environments, between which the water molecules do not exchange at the NMR observation time scale. We conclude that those two water phases are located at differently-accessible adsorption sites, here assigned to the cellulose surfaces between and within the microfibril aggregates, respectively. The superior performance of 2H MAS NMR encourages further applications of the same method to other complex systems that expose heterogeneous hygroscopic surfaces, like wood cell walls.

Keywords
cellulose, water, adsorption, microcrystalline cellulose, nuclear magnetic resonance
National Category
Chemical Sciences Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-30307 (URN)10.1039/c6cp08219j (DOI)
Available from: 2017-08-14 Created: 2017-08-14 Last updated: 2018-08-21Bibliographically approved
Salmen, L., Stevanic Srndovic, J. & Olsson, A.-M. (2016). Contribution of lignin to the strength properties in wood fibres studied by dynamic FTIR spectroscopy and dynamic mechanical analysis (DMA). Holzforschung, 70(12), 1155-1163
Open this publication in new window or tab >>Contribution of lignin to the strength properties in wood fibres studied by dynamic FTIR spectroscopy and dynamic mechanical analysis (DMA)
2016 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 12, p. 1155-1163Article in journal (Refereed) Published
Abstract [en]

A deeper insight into the molecular interactions in the highly intermixed structure of the wood cell wall, from the point of view of both basic and applied science, is necessary. In particular, the role of the different matrix materials within the cell wall needs to be better understood, especially concerning how lignin contributes to the mechanical properties. In the present paper, the mechanical properties of spruce wood have been studied on a molecular scale by means of dynamic Fourier transform infrared (FTIR) spectroscopy. To this purpose, native spruce wood was subjected to chemical changes by impregnation and a mild pre-cooking with white liquor with a composition usual for kraft pulping. For comparison, lignin-rich primary cell wall material was also isolated by means of thermomechanical pulp (TMP) refining. Dynamic FTIR spectroscopy revealed that lignin took part in the stress transfer in all investigated samples. This finding is in contrast to literature data. A strong indirect coupling between lignin and cellulose was seen in the primary cell wall (P) material. In case of native wood, the lignin signal was much weaker and also indicated an indirect coupling to cellulose. In the case of pre-cooked wood samples (submitted to mild pulping), the interactions were modified so that the molecular straining of lignin was stronger and more directly related to that of cellulose. In other words, in these samples, lignin played a more active role in the stress transfer as compared to native wood. These findings were supported by a narrower lignin-softening region as measured by dynamic mechanical analysis (DMA). The interpretation is plausible in terms of the superior stiffness seen for high-yield pulps of a similar yield as the studied pre-cooked wood samples.

National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:ri:diva-27566 (URN)10.1515/hf-2016-0050 (DOI)2-s2.0-84998704967 (Scopus ID)
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Available from: 2016-12-15 Created: 2016-12-15 Last updated: 2018-08-21Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3534-1107

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