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Johansson, Dennis
Publications (8 of 8) Show all publications
Johansson, D. (2008). Heat treatment of solid wood: effects on absorption, strength and colour (ed.). (Doctoral dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Heat treatment of solid wood: effects on absorption, strength and colour
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Wood is a useful construction material, but it has less desirable properties such as poor durability and poor dimensional stability. These problems can be reduced by using various chemical treatments. Increased environmental awareness has raised the demand for more environmentally friendly methods. Heat treatment is an alternative method for improving these properties with no use of chemical additives. When wood is heated, chemical changes start to take place inside the wood structure. These changes result in increased durability and dimensional stability. In this thesis, a method developed in Finland called ThermoWood has been used in which wood is heated in an atmosphere of superheated steam that serves as a shielding gas. Various property changes due to heat treatment have been studied in this thesis: Colour and strength (Paper I), internal checking (Papers II & III) and capillary absorption (Papers IV-VII). Some smaller unpublished studies are also presented. Paper I focuses on colour and strength response of birch to heat treatment. A method for measuring colour heterogeneity was devised. The results show that there is measurable colour heterogeneity present in birch after heat treatment. Paper I also examines the possibility of using colour for predicting mechanical strength in heat-treated birch, but it is concluded that it is not a suitable method. Impact testing did not give any clear results in strength loss, but it showed significant changes in mechanical failure mechanisms; it showed that heat treatment increased the mechanical failures between fibres in birch. When heat-treating boards thicker than 50 mm, there is a risk of internal checking, especially in spruce. The results show that internal checking in heat-treated spruce is caused by both thermal degradation and drying, but drying has the greatest influence on crack formation. One of the main reasons for heat-treating wood is to reduce the hydroscopic properties. Heat-treated wood has lower equilibrium moisture content and lower wettability as demonstrated by contact angle measurement. Increased water uptake has been discovered when Scots pine treated at around 170°C is subjected to free water in such way that capillary absorption is possible. The results in Paper VII indicate that extractives are a contributing factor to this increased absorption. The results also show that extraction by water soaking causes capillary water absorption in Scots pine to decrease in samples dried at 60°C and cause an increase in samples treated at 200°C. After extraction by water soaking, the reducing effect of heat treatment on capillary water absorption had disappeared.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2008. p. 42
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544 ; 2008:53
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-17325 (URN)2d9465e0-abea-11dd-a7c5-000ea68e967b (Local ID)2d9465e0-abea-11dd-a7c5-000ea68e967b (Archive number)2d9465e0-abea-11dd-a7c5-000ea68e967b (OAI)
Note

Godkänd; 2008; 20081106 (ysko)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-02-26Bibliographically approved
Sehlstedt-Persson, M., Johansson, D. & Morén, T. (2006). Absorption of liquid water in pine, birch and spruce and the effect of heat treatment on the microstructure (ed.). Paper presented at Nordic-Baltic Network in Wood Material Science and Engineering : 30/10/2006 - 31/10/2006. Paper presented at Nordic-Baltic Network in Wood Material Science and Engineering : 30/10/2006 - 31/10/2006.
Open this publication in new window or tab >>Absorption of liquid water in pine, birch and spruce and the effect of heat treatment on the microstructure
2006 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

Heat-treated and matched boards dried at 60°C of Scots pine (Pinus silvestris), Norway spruce (Picea abies) and Birch (Betula pubescens) were submerged into water, allowing for water absorption in the longitudinal direction during two weeks in room climate. Heat treatment was performed according to the Thermo-wood process at 170°C and 200°C. Boards from pine and spruce boards contained both sap- and heartwood. During water absorption computer tomography scanning, CT-scanning, was performed intermittently in order to measure the ascent of capillary water. Longitudinal water absorption in heat-treated pine sapwood was substantial larger compared to untreated sapwood. In pine heartwood the ascent of water was low in heat-treated as well as in untreated boards. Spruce showed low water absorption in sap- and heartwood in heat-treated as well as in untreated boards. In birch the water absorption was lower in heat-treated wood compared to wood dried at 60°. SEM-studies of the anatomical microstructure, pits and pit membranes were performed on heat-treated as well as on untreated material. SEM-studies revealed damages in heat-treated and dried pine sapwood mainly in pit membranes in the fenestriform cross-field pits connecting longitudinal tracheids with radial ray parenchyma cells. These damages are believed to play an important role in explaining the differences in water absorption between pine and spruce since the piceoid cross field pits in spruce seemed to be unaffected by heat treatment. In birch no striking, visible observations were found when comparing the three different treatment temperatures that could shed light to the observed big difference in capillary water absorption.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-27002 (URN)04d667e0-f7d0-11db-ac79-000ea68e967b (Local ID)04d667e0-f7d0-11db-ac79-000ea68e967b (Archive number)04d667e0-f7d0-11db-ac79-000ea68e967b (OAI)
Conference
Nordic-Baltic Network in Wood Material Science and Engineering : 30/10/2006 - 31/10/2006
Note
Godkänd; 2006; Bibliografisk uppgift: Sider: 8; 20070501 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Johansson, D., Sehlstedt-Persson, M. & Morén, T. (2006). Effect of heat treatment on capillary water absorption of heat-treated pine, spruce and birch (ed.). In: (Ed.), R. Lagana; S. Kurjatko; J. Kudela (Ed.), Wood structure and properties '06: [proceedings of the 5th IUFRO Symposium Wood Structure and Properties '06 held on September 3-6, 2006 in Sliač - Sielnica, Slovakia]. Paper presented at International Symposium Wood Structure and Properties : 03/09/2006 - 06/09/2006 (pp. 251-255). Zvolen, Slovakia: Arbora Publishers
Open this publication in new window or tab >>Effect of heat treatment on capillary water absorption of heat-treated pine, spruce and birch
2006 (English)In: Wood structure and properties '06: [proceedings of the 5th IUFRO Symposium Wood Structure and Properties '06 held on September 3-6, 2006 in Sliač - Sielnica, Slovakia] / [ed] R. Lagana; S. Kurjatko; J. Kudela, Zvolen, Slovakia: Arbora Publishers , 2006, p. 251-255Conference paper, Published paper (Refereed)
Abstract [en]

Longitudinal absorption of water in matched heat-treated and untreated boards was studied. The boards are from three different species. Scots pine (Pious sylvestris), Norway spruce (Picea abies) and birch (Betula pubescens). The heat treatment was performed according to the Thermowood process at two different temperature levels (170 degrees C and 200 degrees C) for all three species. Computer tomography (CT) scanning was used to intermittently monitor the ascent of the water front. The use of CT scanning enables a study of the liquid water ascent in three dimensions over time. This means that it is possible to determine the influence of different treatment temperatures and species as well as the difference between heartwood and sapwood on capillary action.The results show that longitudinal water absorption in pine sapwood was substantially lamer when heat-treated at 170 degrees C compared to untreated pine sapwood. In pine heartwood, the ascent of water was low in heat-treated as well as in untreated boards. Spruce boards showed low water absorption in sap- and heartwood in heat-treated as well as in untreated boards. Birch showed a decreasing uptake of water with increasing treatment temperature

Place, publisher, year, edition, pages
Zvolen, Slovakia: Arbora Publishers, 2006
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-37157 (URN)b159cbf0-f817-11db-ac79-000ea68e967b (Local ID)80-968869-4-3 (ISBN)b159cbf0-f817-11db-ac79-000ea68e967b (Archive number)b159cbf0-f817-11db-ac79-000ea68e967b (OAI)
Conference
International Symposium Wood Structure and Properties : 03/09/2006 - 06/09/2006
Note
Godkänd; 2006; 20070501 (ysko)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically approved
Sehlstedt-Persson, M., Johansson, D. & Morén, T. (2006). Effect of heat treatment on the microstructure of pine, spruce and birch and the influence on capillary absorption (ed.). In: (Ed.), R. Lagana; S. Kurjatko; J. Kudela (Ed.), Wood structure and properties '06: [proceedings of the 5th IUFRO Symposium Wood Structure and Properties '06 held on September 3-6, 2006 in Sliač - Sielnica, Slovakia]. Paper presented at International Symposium Wood Structure and Properties : 03/09/2006 - 06/09/2006 (pp. 373-379). Zvolen, Slovakia: Arbora Publishers
Open this publication in new window or tab >>Effect of heat treatment on the microstructure of pine, spruce and birch and the influence on capillary absorption
2006 (English)In: Wood structure and properties '06: [proceedings of the 5th IUFRO Symposium Wood Structure and Properties '06 held on September 3-6, 2006 in Sliač - Sielnica, Slovakia] / [ed] R. Lagana; S. Kurjatko; J. Kudela, Zvolen, Slovakia: Arbora Publishers , 2006, p. 373-379Conference paper, Published paper (Refereed)
Abstract [en]

Heat-treated and matched boards of Scots pine (Pious sylvestris), Norway spruce (Picea abies) and Birch (Betula pubescens) were dried at 60 C and submerged into water, allowing for water absorption in the longitudinal direction during two weeks in an indoor climate. Heat treatment was performed according to the Thermo-Wood process at 170 degrees C and 200 degrees C. Boards from pine and spruce contained both sapwood and heartwood. During water absorption, computer tomography scanning (CT scanning) was performed intermittently in order to measure the ascent of capillary water. Longitudinal water absorption in heat-treated pine sapwood was substantially lamer than in untreated sapwood. In pine heartwood, the ascent of water was low in heat-treated as well as in untreated boards. Spruce showed low water absorption in sapwood and heartwood in heat-treated as well as in untreated boards. In birch, water absorption was lower in heat-treated wood than in wood dried at 60 degrees. SEM studies of the anatomical microstructure, the pits and pit membranes, were performed on heat-treated as well as on untreated material. SEM studies revealed damage in heat-treated and dried pine sapwood mainly in pit membranes in the fenestriform crossfield pits connecting longitudinal tracheids with radial ray parenchyma cells. This damage is believed to play an important role in explaining the differences in water absorption between pine and spruce, since the piceoid crossfield pits in spruce seemed to be unaffected by heat treatment. In comparing the three different treatment temperatures in birch, no striking, visible differences were found that could shed light on the observed large differences in capillary water absorption

Place, publisher, year, edition, pages
Zvolen, Slovakia: Arbora Publishers, 2006
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-35772 (URN)a70a8670-f818-11db-ac79-000ea68e967b (Local ID)80-968869-4-3 (ISBN)a70a8670-f818-11db-ac79-000ea68e967b (Archive number)a70a8670-f818-11db-ac79-000ea68e967b (OAI)
Conference
International Symposium Wood Structure and Properties : 03/09/2006 - 06/09/2006
Note
Godkänd; 2006; 20070501 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Johansson, D. (2006). Influences of drying on internal checking of spruce (Picea abies L.) heat-treated at 212°C (ed.). Holzforschung, 60(5), 558-560
Open this publication in new window or tab >>Influences of drying on internal checking of spruce (Picea abies L.) heat-treated at 212°C
2006 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 60, no 5, p. 558-560Article in journal (Refereed) Published
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-3380 (URN)10.1515/HF.2006.092 (DOI)000240350900017 ()2-s2.0-33747412970 (Scopus ID)133c1a60-bb52-11db-b560-000ea68e967b (Local ID)133c1a60-bb52-11db-b560-000ea68e967b (Archive number)133c1a60-bb52-11db-b560-000ea68e967b (OAI)
Note

Validerad; 2006; 20061016 (cira)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Johansson, D. & Morén, T. (2006). The potential of colour measurement for strength prediction of thermally treated wood (ed.). Paper presented at . European Journal of Wood and Wood Products, 64(2), 104-110
Open this publication in new window or tab >>The potential of colour measurement for strength prediction of thermally treated wood
2006 (English)In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 64, no 2, p. 104-110Article in journal (Refereed) Published
Abstract [en]

This paper investigates the effects of thermal treatment of birch with respect to colour and strength. Birch wood was treated at 175 °C and 200 °C for 0 h, 1 h, 3 h and 10 h. In bending-strength experiments, treatment was also performed at 185 °C for 2 h. Both static bending strength and impact bending strength were investigated using multivariate statistics (PLS) for correlation to process parameters, density, EMC, position in board, modulus of elasticity (only in static bending), colour and dimensions of samples. In static bending, two PLS models were designed, one based on process parameters and the other based on colour and EMC. From these models it was concluded that colour is not a useful parameter for prediction of strength. In impacted bending, the correlation was too small to give useful results. One test of static bending strength with matched samples was performed, and it showed a strength reduction of 43% when treatment was conducted at 200 °C for 3 h. Measurement of colour homogeneity of the treated boards showed that the colour is not homogeneous.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-13723 (URN)10.1007/s00107-005-0082-8 (DOI)000236001300004 ()2-s2.0-33644954475 (Scopus ID)d015a400-078b-11dc-b09b-000ea68e967b (Local ID)d015a400-078b-11dc-b09b-000ea68e967b (Archive number)d015a400-078b-11dc-b09b-000ea68e967b (OAI)
Note
Validerad; 2006; 20070521 (cira)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Johansson, D. (2005). Drying and heat treatment of wood: influences on internal checking (ed.). In: (Ed.), Trygve M. Eikevik (Ed.), Proceedings of the 3rd Nordic Drying Conference, NDC 2005: June 15th to 17th 2005, Karlstad, Sweden. Paper presented at Nordic Drying Conference : 15/06/2005 - 17/06/2005. Trondheim: sintef akademisk forlag
Open this publication in new window or tab >>Drying and heat treatment of wood: influences on internal checking
2005 (English)In: Proceedings of the 3rd Nordic Drying Conference, NDC 2005: June 15th to 17th 2005, Karlstad, Sweden / [ed] Trygve M. Eikevik, Trondheim: sintef akademisk forlag, 2005Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Trondheim: sintef akademisk forlag, 2005
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-34613 (URN)8db35d30-0643-11dc-b09b-000ea68e967b (Local ID)82-594-2873-3 (ISBN)8db35d30-0643-11dc-b09b-000ea68e967b (Archive number)8db35d30-0643-11dc-b09b-000ea68e967b (OAI)
Conference
Nordic Drying Conference : 15/06/2005 - 17/06/2005
Note
Godkänd; 2005; Bibliografisk uppgift: CD-ROM; 20070519 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Johansson, D. (2005). Strength and colour response of solid wood to heat treatment (ed.). (Licentiate dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Strength and colour response of solid wood to heat treatment
2005 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Heat treatment is a method for improving the durability and dimensional stability of wood. The treatment method used in this work is called Thermo Wood and is industrially applied in Finland. In 2004 production was 31146 m3. The method involves heating wood in a steam atmosphere where the heat causes chemical changes in the structure of the wood. The present work was done in order to improve the quality of the treated timber both by predicting strength through colour measurement and by understanding the mechanisms behind the internal checking in heat-treated wood. Besides the published papers there are some smaller unpublished studies presented in the thesis. In paper I the connection between colour and the strength reduction caused by the heat treatment is studied. The results show that colour measurements are not a good way of predicting strength loss on an industrial scale. However, they also show that on an experimental level it is an effective way to study the changes that occur in the wood during treatment. There is a problem with internal checking when heat treatment is performed on boards with dimensions greater than about 50 mm. In paper II the connection between internal checking and both mass loss and drying was investigated. The results showed that both mass loss and drying influence the development of internal checking. Paper III focuses on the effects of drying on internal checking. From studying the results from papers II and III together with the results of some of the unpublished studies, the conclusion is that drying stress is the main cause for internal checking in heat-treated wood.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2005. p. 34
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757 ; 2005:93
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-25830 (URN)b58e9220-8920-11db-8975-000ea68e967b (Local ID)b58e9220-8920-11db-8975-000ea68e967b (Archive number)b58e9220-8920-11db-8975-000ea68e967b (OAI)
Note
Godkänd; 2005; 20061211 (haneit)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-24Bibliographically approved

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