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Dagbro, Ola
Publications (7 of 7) Show all publications
Torniainen, P., Elustondo, D. & Dagbro, O. (2016). Industrial Validation of the Relationship between Color Parameters in Thermally Modified Spruce and Pine (ed.). BioResources, 11(1), 1369-1381
Open this publication in new window or tab >>Industrial Validation of the Relationship between Color Parameters in Thermally Modified Spruce and Pine
2016 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 1, p. 1369-1381Article in journal (Refereed) Published
Abstract [en]

Thermal modification causes the darkening of wood throughout its cross-section because of chemical changes in the wood. After treatment, naturally light wood species look darker or even tropical, depending predominantly on the treatment temperature and processing time. This study investigates the suitability of using color measurement to determine treatment intensity at the industrial scale. The color was determined using the L*, a*, and b* color space, also referred to as CIELab, and the relationship between lightness (L*) and the color parameters (a*) and (b*) was investigated for thermal modification treatments at 190 and 212 °C. The wood species studied were pine (Pinus sylvestris L.) and spruce (Picea abies L.). The results showed that yellowness (+b*) and redness (+a*) had a significant prediction ability for class treatments at 190 and 212 °C, respectively. After treatment, there were no noticeable differences in color between the species, but sapwood was darker than heartwood in both untreated and thermally modified wood. The thickness of the boards had a proportionally darkening effect on the color values.

National Category
Other Mechanical Engineering
Research subject
Wood Science and Engineering
Identifiers
urn:nbn:se:ltu:diva-16140 (URN)fbad5e9a-10d5-4673-a1be-ba514c493eba (Local ID)fbad5e9a-10d5-4673-a1be-ba514c493eba (Archive number)fbad5e9a-10d5-4673-a1be-ba514c493eba (OAI)
Note

Validerad; 2016; Nivå 2; 20151219 (dieelu)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Dagbro, O. (2016). Studies on Industrial-Scale Thermal Modification of Wood (ed.). (Doctoral dissertation). Paper presented at . : Luleå tekniska universitet
Open this publication in new window or tab >>Studies on Industrial-Scale Thermal Modification of Wood
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Wood as a raw material is useful for many purposes even though some properties are less than optimal, for example, dimensional stability and durability. These characteristics can however be improved by different treatment methods. Environmental awareness has led to an increased demand for environmentally friendly processes like thermal modification that does not add any chemicals to the wood in contrast to, for example, CCA-impregnated wood.This thesis mainly focuses on thermally modified wood from species such as pine, spruce and birch. The thesis present studies of physical attributes such as color, and chemical analysis of water-soluble compounds and degradation products. Treatment intensity is compared between two different industrial processes referred as Thermowood and WTT, which use respectively superheated steam and pressurized steam as heating media.Thermal modification processes darken the color of wood throughout its cross-section. The formation of darker color is related to a degradation processes that takes place during thermal modification. During thermal modification wood is exposed to temperatures between 160 - 220°C, and the temperature causes physical and chemical transformations that change some of the wood properties. Dimensional stability and durability are typically improved, but mechanical strength properties are usually negatively affected by the treatment.The studied wood species were Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L.) and Birch (Betula pendula L.). Treatments using pressurized steam were carried out under temperatures of 160°C, 170°C and 180°C, and treatments using superheated steam at normal air pressure were carried out at temperatures of 190°C and 212°C. Results showed that similar L* (lightness) can be reached at lower temperatures using pressurized steam compared to superheated steam. The residual moisture content after completed thermal modification was approximately 10% higher in wood treated with the pressurized steam process. It was found that despite an approximately 25°C lower treatment temperature, birch modified in pressurized steam was more acidic compared to birch modified in superheated steam. This will likely have further consequences, requiring more research concerning surface treatment and fixation.The thesis also includes the development of an industrial-quality control procedure based on nondestructive color measurements verified in industrial environment. Treatment intensity in industry is today certified by inspection of documented process schedule and measuring the temperature and time of the process. Quality control in this context refers to the measurement of wood color as an indirect measure of treatment intensity. The color in our study was measured using L*C*H color space. The study shows that it is possible for quality control purposes to measure the color of thermally modified wood from the surfaces of planed boards instead of sawdust or board cross sections that have been used in other studies.The thesis has a final section about academia-industry collaboration that describes how trust building was established through a fruitful relationship involving academia and regional wood products industry in northern Sweden. The study presents an example of a successful research and development alliance between university and a group of small- and medium-sized enterprises (SMEs). This alliance has been a great example on international collaboration involving researchers originating from Finland, China, Bangladesh, Spain, Russia and Sweden. Through an in-depth multi-year study of how the research cooperation developed, the paper describes how the involved companies successfully entered into a new segment of the market.

Place, publisher, year, edition, pages
Luleå tekniska universitet, 2016
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-26624 (URN)f421761d-62a6-480c-b378-3d1ba78a7a74 (Local ID)978-91-7583-626-3 (ISBN)978-91-7583-627-0 (ISBN)f421761d-62a6-480c-b378-3d1ba78a7a74 (Archive number)f421761d-62a6-480c-b378-3d1ba78a7a74 (OAI)
Note
För godkännande; 2016; 20160314 (olahof); Nedanstående person kommer att disputera för avläggande av teknologie doktorsexamen. Namn: Ola Dagbro Ämne: Träfysik/Wood Physics Avhandling: Studies on Industrial-Scale Thermal Modification of Wood Opponent: Associate Professor Lidia Gurau, Faculty of Wood Engineering, Transilvania University, Brasov, Romania. Ordförande: Professor Diego Elustondo, Avd för träteknologi, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet, Luleå. Tid: Torsdag 16 juni, 2016 kl 10.00 Plats: Luleå tekniska universitet, Campus SkellefteåAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-24
Karlsson, O., Dagbro, O. & Granlund, K. (2014). Soluble degradation products in thermally modified wood (ed.). In: (Ed.), Mojgan Vaziri; Dick Sandberg (Ed.), Final Cost Action FP0904 Conference: “Recent Advances in the Field of TH and THM Wood Treatment” : May 19-21, 2014, Skellefteå, Sweden : book of abstracts. Paper presented at Cost action FP0904 Conference : 19/05/2014 - 21/05/2014 (pp. 16-17). Skellefteå: Luleå tekniska universitet
Open this publication in new window or tab >>Soluble degradation products in thermally modified wood
2014 (English)In: Final Cost Action FP0904 Conference: “Recent Advances in the Field of TH and THM Wood Treatment” : May 19-21, 2014, Skellefteå, Sweden : book of abstracts / [ed] Mojgan Vaziri; Dick Sandberg, Skellefteå: Luleå tekniska universitet, 2014, p. 16-17Conference paper, Meeting abstract (Refereed)
Place, publisher, year, edition, pages
Skellefteå: Luleå tekniska universitet, 2014
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-37575 (URN)ba42a315-ef2e-4b50-b0aa-bf9b98d3b91f (Local ID)9789174399378 (ISBN)9789174399387 (ISBN)ba42a315-ef2e-4b50-b0aa-bf9b98d3b91f (Archive number)ba42a315-ef2e-4b50-b0aa-bf9b98d3b91f (OAI)
Conference
Cost action FP0904 Conference : 19/05/2014 - 21/05/2014
Note
Godkänd; 2014; 20140516 (andbra)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically approved
Karlsson, O., Torniainen, P., Dagbro, O., Granlund, K. & Morén, T. (2012). Presence of water-soluble compounds in thermally modified wood: carbohydrates and furfurals (ed.). Paper presented at . BioResources, 7(3), 3679-3689
Open this publication in new window or tab >>Presence of water-soluble compounds in thermally modified wood: carbohydrates and furfurals
Show others...
2012 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 3, p. 3679-3689Article in journal (Refereed) Published
Abstract [en]

With thermal modification, changes in properties of wood, such as the presence of VOC and water-soluble carbohydrates, may occur. Thermal modifications under saturated steam conditions (160°C or 170°C) and superheated steam conditions (170, 185, and 212°C) were investigated by analysing the presence of water-soluble 5-(hydroxymethyl)furfural (HMF), furfural, and carbohydrates in heat-treated wood. The influence of thermal modifications on Scots pine, Norway spruce, and silver birch was also studied. Furfurals were analysed using HPLC at 280 nm, while monosaccharides and water-soluble carbohydrates were determined by GC-FID as their acetylated alditiols and, after methanolysis, as their trimethylsilylated methyl-glycosides, respectively. The amount of furfurals was larger in boards thermally modified under saturated steam conditions than those treated under superheated steam conditions. Generally, more of HMF than furfural was found in the thermally modified boards. In process water, in which saturated steam conditions had been used, furfural and only traces of HMF were found. Higher content of water-soluble carbohydrates was found in boards treated in saturated steam rather than in superheated steam. After modification in saturated steam, substantial parts of the water-soluble carbohydrates were due to monosaccharides, but only traces of monosaccharides were found in boards treated under superheated steam conditions.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-8663 (URN)731ebb90-8616-479a-ad69-a3080ed42b6d (Local ID)731ebb90-8616-479a-ad69-a3080ed42b6d (Archive number)731ebb90-8616-479a-ad69-a3080ed42b6d (OAI)
Note
Validerad; 2012; 20120918 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Dagbro, O., Torniainen, P. & Morén, T. (2011). Thermal modification of birch using saturated and superheated steam (ed.). In: (Ed.), Erik Larnøy; Gry Alfredsen (Ed.), Proceedings of the 7th meeting of the Nordic-Baltic Network in Wood Material Science and Engineering (WSE): October 27-28, 2011, Oslo, Norway. Paper presented at Nordic-Baltic Network in Wood Material Science and Engineering : 27/10/2011 - 28/10/2011 (pp. 43-48). Ås: Norsk institutt for skog og landskap
Open this publication in new window or tab >>Thermal modification of birch using saturated and superheated steam
2011 (English)In: Proceedings of the 7th meeting of the Nordic-Baltic Network in Wood Material Science and Engineering (WSE): October 27-28, 2011, Oslo, Norway / [ed] Erik Larnøy; Gry Alfredsen, Ås: Norsk institutt for skog og landskap , 2011, p. 43-48Conference paper, Published paper (Refereed)
Abstract [en]

During the thermal modification, wood is normally exposed to temperatures between 160 - 220°C. As a result physical and chemical changes are taking place and some of the wood properties are changed. Dimensional stability and weather resistance are improved. On the other hand the mechanical strength properties are usually negatively affected by the treatment. The visual appearance is also changed. There were two different types of thermal modification processes used in this study. One of them was using saturated steam and the other one superheated steam. Treatment temperature was 160°C in saturated steam process and 185°C in superheated steam. The wood specie used in this study was Silver birch (Betula pendula). In the chemistry part the acid content was investigated. Despite the 25°C lower treatment temperature, birch modified in saturated steam was more acidic compared to birch modified in superheated steam. Some differences in equilibrium moisture content (EMC) and dimensional stability were found mainly in the environment T=20°C and RH=85%. The colour of birch treated in saturated steam at 160°C was darker than the colour of birch treated in superheated steam at temperature 185°C.

Place, publisher, year, edition, pages
Ås: Norsk institutt for skog og landskap, 2011
Series
Report from Skog og landskap, ISSN 1891-7933 ; 15/2011
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-33985 (URN)812f83f0-9f9c-4d13-81a4-cee299555c09 (Local ID)978-82-311-0139-0 (ISBN)812f83f0-9f9c-4d13-81a4-cee299555c09 (Archive number)812f83f0-9f9c-4d13-81a4-cee299555c09 (OAI)
Conference
Nordic-Baltic Network in Wood Material Science and Engineering : 27/10/2011 - 28/10/2011
Note
Godkänd; 2011; 20120412 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Dagbro, O., Torniainen, P., Karlsson, O. & Morén, T. (2010). Colour responses from wood, thermally modified in superheated steam and pressurized steam atmospheres (ed.). Paper presented at . Wood Material Science & Engineering, 5(3), 211-219
Open this publication in new window or tab >>Colour responses from wood, thermally modified in superheated steam and pressurized steam atmospheres
2010 (English)In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 5, no 3, p. 211-219Article in journal (Refereed) Published
Abstract [en]

In this study, two different methods were used to produce thermally modified wood. One was carried out in a typical kiln drying chamber using superheated steam (SS) and the other used pressurized steam in an autoclave cylinder (PS). Overall, both processes followed the same principles and the wood was not treated with any chemicals. Two wood species were studied, Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). Treatments in the autoclave were carried out under pressure using temperatures of 160°C, 170°C and 180°C. Temperatures of 190°C and 212°C were used in treatments in the chamber at normal air pressure. The colour was measured using L*C*H colour space. Results for both species showed that similar L* (lightness) can be reached at lower (20-308C) temperatures using PS compared with SS treatment. The hue angle of PS-treated wood was smaller than that of SS-treated wood. No significant difference in C* (chroma) was detected. The difference in E value between PS- and SS-treated wood was smaller for Norway spruce than for Scots pine. The residual moisture content was about 10% higher in wood treated by the PS process compared with the SS process

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-5042 (URN)10.1080/17480272.2010.520739 (DOI)2-s2.0-78649531225 (Scopus ID)30faa350-0699-11e0-b767-000ea68e967b (Local ID)30faa350-0699-11e0-b767-000ea68e967b (Archive number)30faa350-0699-11e0-b767-000ea68e967b (OAI)
Note
Validerad; 2010; 20101213 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Dagbro, O. (2009). Spår i paneler: Delprojekt i det större projektet ”Sprickor i konstruktioner, utomhusexponering, optimering och simulering” (ed.). Paper presented at . : TräCentrum Norr
Open this publication in new window or tab >>Spår i paneler: Delprojekt i det större projektet ”Sprickor i konstruktioner, utomhusexponering, optimering och simulering”
2009 (Swedish)Report (Other (popular science, discussion, etc.))
Place, publisher, year, edition, pages
TräCentrum Norr, 2009. p. 61
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-23625 (URN)7bff34e6-c8b3-4c3a-b4cd-c938a352f5e4 (Local ID)7bff34e6-c8b3-4c3a-b4cd-c938a352f5e4 (Archive number)7bff34e6-c8b3-4c3a-b4cd-c938a352f5e4 (OAI)
Note
Godkänd; 2009; 20140416 (olahof)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
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