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BETA
Segerholm, KristofferORCID iD iconorcid.org/0000-0001-7014-6230
Publications (10 of 43) Show all publications
Joffre, T., Segerholm, K., Persson, C., Bardage, S., Luengo Hendriks, C. L. & Isaksson, P. (2017). Characterization of interfacial stress transfer ability in acetylation-treated wood fibre composites using X-ray microtomography. Industrial crops and products (Print), 95, 43-49
Open this publication in new window or tab >>Characterization of interfacial stress transfer ability in acetylation-treated wood fibre composites using X-ray microtomography
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2017 (English)In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 95, p. 43-49Article in journal (Refereed) Published
Abstract [en]

The properties of the fibre/matrix interface contribute to stiffness, strength and fracture behaviour of fibre-reinforced composites. In cellulosic composites, the limited affinity between the hydrophilic fibres and the hydrophobic thermoplastic matrix remains a challenge, and the reinforcing capability of the fibres is hence not fully utilized. A direct characterisation of the stress transfer ability through pull-out tests on single fibres is extremely cumbersome due to the small dimension of the wood fibres. Here a novel approach is proposed: the length distribution of the fibres sticking out of the matrix at the fracture surface is approximated using X-ray microtomography and is used as an estimate of the adhesion between the fibres and the matrix. When a crack grows in the material, the fibres will either break or be pulled-out of the matrix depending on their adhesion to the matrix: good adhesion between the fibres and the matrix should result in more fibre breakage and less pull-out of the fibres than poor adhesion. The effect of acetylation on the adhesion between the wood fibres and the PLA matrix was evaluated at different moisture contents using the proposed method. By using an acetylation treatment of the fibres it was possible to improve the strength of the composite samples soaked in the water by more than 30%.

Keywords
Acetylation, Adhesion, CT analysis, PLA, Wood fibres, Fiber reinforced plastics, Fibers, Fracture, Fracture mechanics, Polymer matrix composites, Reinforcement, Tensile strength, Tomography, Different moisture contents, Fibre reinforced composites, Fibre/matrix interfaces, Interfacial stress transfer, Length distributions, Thermoplastic matrices, Wood fibre, X ray microtomography, Wood
National Category
Materials Engineering
Identifiers
urn:nbn:se:ri:diva-29197 (URN)10.1016/j.indcrop.2016.10.009 (DOI)2-s2.0-84991689339 (Scopus ID)
Available from: 2017-04-03 Created: 2017-04-03 Last updated: 2019-01-22Bibliographically approved
Kymäläinen, M., Hautamäki, S., Lillqvist, K., Segerholm, K. & Rautkari, L. (2017). Surface modification of solid wood by charring. Journal of Materials Science, 52(10), 6111-6119
Open this publication in new window or tab >>Surface modification of solid wood by charring
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2017 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 52, no 10, p. 6111-6119Article in journal (Refereed) Published
Abstract [en]

Most wooden structures for outdoor applications require repetitive maintenance operations to protect the surfaces from adverse effects of weathering. One-sided surface modification of boards with a relatively fast charring process has the potential to increase the durability and service life of wooden claddings. To assess some weathering-related effects on surface charred wood, spruce and pine sapwood were subjected to a series of long charring processes (30–120 min) at a moderate temperature of 250 °C and to a short one (30 s) at a high temperature of 400 °C. The wettability and contact angles of treated samples were investigated, and the heat transfer was measured along with the micromorphological changes taking place in the material. The result revealed an increased moisture resistance of charred spruce sapwood and an increased water uptake of pine sapwood. The contact angles of both wood species improved compared to references. Heat conduction measurement revealed that only a thin section of the wood was thermally modified. Some micromorphological changes were recorded, especially on the inside walls of the lumina. The results show that spruce sapwood has an improved resistance towards moisture-induced weathering, but more studies are needed to unlock the potential of surface charred wood.

Keywords
solid wood, contact angle, heat conduction, heat transfer, moisture, surface treatment, weathering, wood product, wooden building
National Category
Wood Science
Identifiers
urn:nbn:se:ri:diva-30340 (URN)10.1007/s10853-017-0850-y (DOI)2-s2.0-85011878891 (Scopus ID)
Available from: 2017-08-18 Created: 2017-08-18 Last updated: 2019-01-21Bibliographically approved
Laine, K., Segerholm, K., Wålinder, M., Rautkari, L., Hughes, M. & Lankveld, C. (2016). Surface densification of acetylated wood. European Journal of Wood and Wood Products, 74(6), 829-835
Open this publication in new window or tab >>Surface densification of acetylated wood
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2016 (English)In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 74, no 6, p. 829-835Article in journal (Refereed) Published
Abstract [en]

The mechanical properties of wood can be improved by compressing its porous structure between heated metal plates. By adjusting the process parameters it is possible to target the densification only in the surface region of wood where the property improvements are mostly needed in applications, such as flooring. The compressed form is, however, sensitive to moisture and will recover to some extent in high humidity. In this study, therefore, acetylated radiata pine was utilised in the surface densification process in order to both reduce the set-recovery of densified wood and to improve the hardness of the acetylated wood. Pre-acetylation was found to significantly reduce the set-recovery of surface densified wood. However, after the second cycle the increase in set-recovery of acetylated wood was relatively higher than the un-acetylated wood. The acetylated samples were compressed by only 1 mm (instead of the target 2 mm), yet, the hardness and hardness recovery of the acetylated samples significantly increased as a result of densification. It was also discovered that rough (un-planed) surfaces may be surface densified, however, even if the surface became smooth to the touch, the appearance remained uneven.

Keywords
Acetylation, Densification, Hardness, Recovery, Acetylated wood, Densified wood, Mechanical properties of wood, Porous structures, Process parameters, Property improvement, Surface densification, Surface region, Wood
National Category
Agricultural Science, Forestry and Fisheries
Identifiers
urn:nbn:se:ri:diva-27590 (URN)10.1007/s00107-016-1077-3 (DOI)2-s2.0-84976477767 (Scopus ID)
Available from: 2016-12-19 Created: 2016-12-19 Last updated: 2019-06-19Bibliographically approved
Källbom, S., Rautkari, L., Wålinder, M., Johansson, L.-S., Campbell, J., Segerholm, K., . . . Laine, K. (2016). Water vapour sorption characteristics and surface chemical composition of thermally modified spruce (ed.). International Wood Products Journal, 7(3), 116-123
Open this publication in new window or tab >>Water vapour sorption characteristics and surface chemical composition of thermally modified spruce
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2016 (English)In: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 7, no 3, p. 116-123Article in journal (Refereed) Published
Abstract [en]

The objective of this work was to study the hygroscopicity and surface chemical composition of thermally modified (TM) spruce. An effort was also made to study if those features were influenced by a previous exposure to a significant increase in relative humidity (RH). TM and unmodified Norway spruce (Picea abies Karst) samples, both in solid and ground form, were prepared. Water vapour sorption characteristics of the ground samples were obtained by measuring sorption isotherms using a dynamic vapour sorption (DVS). The surface chemical composition of the solid samples, both acetone extracted and non-extracted, were analysed using X-ray photoelectron spectroscopy (XPS). The DVS analysis indicated that the TM wood exposed to the 75% RH revealed a decrease in isotherm hysteresis. The XPS analysis indicated a decrease of acetone extractable or volatile organic components and a relative increase of non-extractable components for the samples exposed to the increased RH condition.

Keywords
Dynamic vapour sorption (DVS), Extractives, Norway spruce, Surface chemical composition, Thermally modified wood, X-ray photoelectron spectroscopy (XPS)
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-6935 (URN)10.1080/20426445.2016.1160590 (DOI)31001 (Local ID)31001 (Archive number)31001 (OAI)
Available from: 2016-09-08 Created: 2016-09-08 Last updated: 2019-06-19Bibliographically approved
Laine, K., Segerholm, K., Wålinder, M., Rautkari, L. & Hughes, M. (2016). Wood densification and thermal modification: hardness, set-recovery and micromorphology. Wood Science and Technology, 50(5), 883-894
Open this publication in new window or tab >>Wood densification and thermal modification: hardness, set-recovery and micromorphology
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2016 (English)In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, no 5, p. 883-894Article in journal (Refereed) Published
Abstract [en]

The density of wood can be increased by compressing the porous structure under suitable moisture and temperature conditions. One aim of such densification is to improve surface hardness, and therefore, densified wood might be particularly suitable for flooring products. After compression, however, the deformed wood material is sensitive to moisture, and in this case, recovered up to 60 % of the deformation in water-soaking. This phenomenon, termed set-recovery, was reduced by thermally modifying the wood after densification. This study presents the influence of compression ratio (CR = 40, 50, 60 %) and thermal modification time (TM = 2, 4, 6 h) on the hardness and set-recovery of densified wood. Previously, set-recovery has mainly been studied separately from other properties of densified wood, while in this work, set-recovery was also studied in relation to hardness. The results show that set-recovery was almost eliminated with TM 6 h in the case of CR 40 and 50 %. Hardness significantly increased due to densification and even doubled compared to non-densified samples with a CR of 50 %. Set-recovery reduced the hardness of densified (non-TM) wood back to the original level. TM maintained the hardness of densified wood at an increased level after set-recovery. However, some reduction in hardness was recorded even if set-recovery was almost eliminated.

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2016
Keywords
Compression Ratio, Densified Wood, Wood Compression, Thermal Modification, Brinell Hardness
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-404 (URN)10.1007/s00226-016-0835-z (DOI)
Available from: 2016-06-22 Created: 2016-06-22 Last updated: 2019-06-19Bibliographically approved
Källbom, S., Wålinder, M., Segerholm, K. & Jones, D. (2015). Surface energy characterization of thermally modified spruce using inverse gas chromatography under cyclic humidity conditions (ed.). Wood and Fiber Science, 47(4), 410-420
Open this publication in new window or tab >>Surface energy characterization of thermally modified spruce using inverse gas chromatography under cyclic humidity conditions
2015 (English)In: Wood and Fiber Science, ISSN 0735-6161, Vol. 47, no 4, p. 410-420Article in journal (Refereed) Published
Abstract [en]

The surface energy of unmodified and thermally modified spruce wood components was researched at dry and moist conditions using inverse gas chromatography. The results indicate a more pronounced heterogeneous nature of the thermally modified wood surfaces in terms of the dispersive (nonpolar) component of the surface energy, compared with that of the unmodified wood surfaces. The dispersive component of the surface energy of the thermally modified wood ranged between 44 and 38 mJ/m2 corresponding to an increase in surface coverage from a low level and up to about 10%. Suggested explanations for the more distinct heterogeneity of the thermally modified wood sample arerelated to chemical changes of the wood substance which seem to result in certain micromorphological features observed by scanning electron microscopy as alternated fracture surfaces created in the grinding process; and also possible changes or redistribution of the wood extractives. An increase of the MC, representing a change from a dry condition of approximately 0% RH to ca 75% RH, of both the unmodified and thermally modified samples seemed to have a marginal influence on the dispersive component of the surface energy. Possible implications of the results in this study can be found in the tailoring of new compatible and durable material combinations, for example, when using thermally modified wood residuals as a component in new types of biocomposites.

Keywords
BET-specific surface area, Dispersive surface energy, Humidity cycling, Inverse gas chromatography, Norway spruce, Surface energy heterogeneity, Thermally modified wood
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-6925 (URN)2-s2.0-84991704745 (Scopus ID)30935 (Local ID)30935 (Archive number)30935 (OAI)
Available from: 2016-09-08 Created: 2016-09-08 Last updated: 2019-08-09Bibliographically approved
Laine, K., Segerholm, K., Wålinder, M., Rautkari, L., Ormondroyd, G., Hughes, M. & Jones, D. (2014). Micromorphological studies of surface densified wood (ed.). Journal of Materials Science, 49(5), 2027-2034
Open this publication in new window or tab >>Micromorphological studies of surface densified wood
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2014 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 5, p. 2027-2034Article in journal (Refereed) Published
Abstract [en]

Scots pine (Pinus sylvestris L.) wood was surface densified in its radial direction in an open press with one heated plate to obtain a higher density on the wood surface whilst retaining the overall thickness of the sample. This study investigated the effect of temperature (100, 150 and 200 °C) and press closing speed (5, 10 and 30 mm/min, giving closing times of 60, 30 and 10 s, respectively) on the micromorphology of the cell-wall, as well as changes occurring during set-recovery of the densified wood. The micromorphology was analysed using scanning electron microscopy (SEM) combined with a sample preparation technique based on ultraviolet-excimer laser ablation. Furthermore, the density profiles of the samples were measured. Low press temperature (100 °C) and short closing time (10 s) resulted in more deformation through the whole thickness, whilst increasing the temperature (150 and 200 °C) and prolonging the closing time (30 and 60 s) enabled more targeted deformation closer to the heated plate. The deformation occurred in the earlywood regions as curling and twisting of the radial cell-walls, however, no apparent cell-wall disruption or internal fracture was observed, even at low temperatures and fast press closing speed, nor after soaking and drying of the samples. In the SEM-analysis after soaking and drying, it was noticed that the cells did not completely recover their original form. Thus, part of the deformation was considered permanent perhaps due to viscoelastic flow and plastic deformation of the cell-wall components.

National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-6606 (URN)10.1007/s10853-013-7890-8 (DOI)2-s2.0-84892440881 (Scopus ID)15449 (Local ID)15449 (Archive number)15449 (OAI)
Available from: 2016-09-08 Created: 2016-09-08 Last updated: 2019-08-01Bibliographically approved
Källbom, S., Ormondroyd, G., Segerholm, K., Jones, D. & Wålinder, M. (2014). Surface Energy Characteristics of Refined Fibres at Different Pressures (ed.). In: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014): . Paper presented at 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014).. Edinburgh Napier University
Open this publication in new window or tab >>Surface Energy Characteristics of Refined Fibres at Different Pressures
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2014 (English)In: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014), Edinburgh Napier University , 2014, , p. 134-138Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Edinburgh Napier University, 2014. p. 134-138
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-12430 (URN)19307 (Local ID)19307 (Archive number)19307 (OAI)
Conference
10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014).
Available from: 2016-09-13 Created: 2016-09-13 Last updated: 2018-08-13Bibliographically approved
Laine, K., Segerholm, K., Wålinder, M., Rautkari, L., Jones, D. & Hughes, M. (2014). The effect of process parameters on the micromorphology of surface densified wood (ed.). In: The seventh European Conference on Wood Modification : Book of Abstracts: . Paper presented at The seventh European Conference on Wood Modification. Lisboa, Portugal. March 10-12, 2014.
Open this publication in new window or tab >>The effect of process parameters on the micromorphology of surface densified wood
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2014 (English)In: The seventh European Conference on Wood Modification : Book of Abstracts, 2014Conference paper, Published paper (Refereed)
Series
The International Wood Products Journal, ISSN 2042-6445
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-12432 (URN)19310 (Local ID)19310 (Archive number)19310 (OAI)
Conference
The seventh European Conference on Wood Modification. Lisboa, Portugal. March 10-12, 2014
Available from: 2016-09-13 Created: 2016-09-13 Last updated: 2018-08-13Bibliographically approved
Segerholm, K. & Ibach, R. (2013). Moisture and Fungal Durability of Wood-Plastic Composites Made With Chemically Modified and Treated Wood Flour (ed.). In: Proceedings IRG Annual Meeting IRG/WP 13: . Paper presented at IRG Annual Meeting IRG/WP 13. Stockholm Sweden 16-20 June, 2013.
Open this publication in new window or tab >>Moisture and Fungal Durability of Wood-Plastic Composites Made With Chemically Modified and Treated Wood Flour
2013 (English)In: Proceedings IRG Annual Meeting IRG/WP 13, 2013, , p. 8Conference paper, Published paper (Other academic)
Publisher
p. 8
Series
PROCEEDINGS IRG ANNUAL MEETING, ISSN 2000-8953
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-12290 (URN)15405 (Local ID)15405 (Archive number)15405 (OAI)
Conference
IRG Annual Meeting IRG/WP 13. Stockholm Sweden 16-20 June, 2013
Note

IRG/WP 13-40648

Available from: 2016-09-13 Created: 2016-09-13 Last updated: 2018-08-13Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7014-6230

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