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Sundqvist, Bror
Publications (10 of 11) Show all publications
Sundqvist, B., Westermark, U. & Eriksson, G. (2006). Cellulose degradation during hydrothermal treatment of birch wood (Betula pubescens Ehrh.) (ed.). Cellulose Chemistry and Technology, 40(3-4), 217-221
Open this publication in new window or tab >>Cellulose degradation during hydrothermal treatment of birch wood (Betula pubescens Ehrh.)
2006 (English)In: Cellulose Chemistry and Technology, ISSN 0576-9787, Vol. 40, no 3-4, p. 217-221Article in journal (Refereed) Published
Abstract [en]

Study of cellulose degradation during wood's heat treatment showed a considerable degradation in both commercially and laboratory heat-treated wood samples, probably due to the low pH induced by the heat treatment. Experimental series were performed for investigating cellulose degradation in birch wood, at different pH levels and times, during heat treatments performed at pH values of 4, 7 and 10, for 3 and 6 hours at 180°C. The results show that the selected span of pH and time of treatment clearly affects the size of the cellulose molecules. Study of cellulose degradation involved intrinsic viscosity measurements on α-cellulose from the samples. As a result of heat treatment, viscosity drops from 1430 mL/g (untreated wood) to less than or equal 700 mL/g and less than or equal 350 mL/g, for durations of 3 and 6 hours, respectively. The wood buffered in an aqueous solution at pH 4 showed a drop in intrinsic viscosity around 880 mL/g, while a sample of commercial "thermowood" yielded an intrinsic viscosity of 732 mL/g. For neutral and alkaline pH values, the drop in viscosity is considerably lower. At pH values of 7 and 10, a 3 hr treatment had almost no effect on the degree of polymerisation, while a 6 hr treatment gave intrinsic viscosities around 1000 mL/g and 1216 mL/g, respectively. There is a distinct relation between cellulose's molecular size and wood's strength properties. The decrease in cellulose length in unbuffered systems may affect the strength properties of the treated wood. The experiments show that pH is an important factor to consider.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-8409 (URN)6ebfd7e0-0d0b-11dc-8745-000ea68e967b (Local ID)6ebfd7e0-0d0b-11dc-8745-000ea68e967b (Archive number)6ebfd7e0-0d0b-11dc-8745-000ea68e967b (OAI)
Note

Validerad; 2006; 20070528 (cira)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-02-26Bibliographically approved
Sundqvist, B., Karlsson, O. & Westermark, U. (2006). Determination of formic-acid and acetic acid concentrations formed during hydrothermal treatment of birch wood and its relation to colour, strength and hardness (ed.). Paper presented at . Wood Science and Technology, 40(7), 549-561
Open this publication in new window or tab >>Determination of formic-acid and acetic acid concentrations formed during hydrothermal treatment of birch wood and its relation to colour, strength and hardness
2006 (English)In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 40, no 7, p. 549-561Article in journal (Refereed) Published
Abstract [en]

Formation of benzyl esters from acetic and formic acids during heat treatment of birch at 160-200°C has been studied by gas chromatography. High concentrations of formic and acetic acids formed by the wood itself during hydrothermal treatment were found. The concentrations of acids increased with both treatment time and temperature. The maximum formic- and acetic acid concentrations found at 180°C and after 4 h of treatment performed in this work were 1.1 and 7.2%, based on dry-weight wood, respectively. The treated wood material was characterised by mechanical testing [bending tests perpendicular to the grain, modulus of rupture, modulus of elasticity, Brinell hardness, impact bending and colour measurements (CIE colour space)]. The experiments, where high concentration of acids was formed, showed severe losses in mass and mechanical strength. Indications of possible enhanced mechanical properties for the treated, compared with untreated birch wood were found around 180-200°C at short treatment times. This paper discusses possible degradation reactions coupled with the colour and mechanical properties in relation to acid formation, and suggestions for process optimisations.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-12639 (URN)10.1007/s00226-006-0071-z (DOI)000240913700003 ()2-s2.0-33749363273 (Scopus ID)bccb28b0-f765-11db-ac79-000ea68e967b (Local ID)bccb28b0-f765-11db-ac79-000ea68e967b (Archive number)bccb28b0-f765-11db-ac79-000ea68e967b (OAI)
Note
Validerad; 2006; 20070430 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Westermark, U. & Sundqvist, B. (2005). Basic factors influencing the strength loss in heat treatment processes for production of durable wood (ed.). Paper presented at International Symposium on Wood, Fibre and Pulping Chemistry : 16/05/2005 - 19/05/2005. Paper presented at International Symposium on Wood, Fibre and Pulping Chemistry : 16/05/2005 - 19/05/2005.
Open this publication in new window or tab >>Basic factors influencing the strength loss in heat treatment processes for production of durable wood
2005 (English)Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

Heat treatment of wood leads to improvement of properties such as durability and dimensional stability but also to loss in strength which can be an obstacle for use in wood products. The underlying explanation is often attributed to the degradation of hemicelluloses and lignin. In this work degradation by acid hydrolysis of cellulose is proposed to be a major cause for strength loss in heat treated wood. Hydrothermal treatment was performed at 180°C in a sealed autoclave where the wood samples were soaked in non-buffered and in buffered solutions at pH 4, 7 and 10. Also industrially produced samples of heat treated wood were analysed. The molecular chain length of cellulose was characterized by viscosimetric measurements of dissolved α-cellulose after mild delignification of the samples. The results clearly show that non-buffered systems similar to industrially heat treatment lead to a considerable degradation of cellulose. In the non-buffered systems the pH drops to approximately 3 (room temperature) as a result of heat treatment. Samples from industrially heat treated wood also show cellulose degradation to similar extent as the non-buffered samples. In buffered conditions at pH 7 and pH 10 the degradation of cellulose is clearly diminished. The results indicate that the cellulose degradation can be avoided by modifications that controls or minimizes the effect of acid hydrolysis during the heat treatment process

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-39146 (URN)dc74c3c0-0637-11dc-b09b-000ea68e967b (Local ID)dc74c3c0-0637-11dc-b09b-000ea68e967b (Archive number)dc74c3c0-0637-11dc-b09b-000ea68e967b (OAI)
Conference
International Symposium on Wood, Fibre and Pulping Chemistry : 16/05/2005 - 19/05/2005
Note
Godkänd; 2005; Bibliografisk uppgift: Titel på proceedings: 59th Appita Annual Conference and Exhibition : incorporating the 13th ISWFPC Undertitel på proceedings: proceedings Sider: 417-419; 20070519 (ysko)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically approved
Westermark, U., Steenberg, B. & Sundqvist, B. (2005). Impregnation with PEG and solvolysis of wood: reflections from analysis of the ancient warship Vasa (ed.). Paper presented at International Symposium on Wood, Fibre and Pulping Chemistry : 16/05/2005 - 19/05/2005. Paper presented at International Symposium on Wood, Fibre and Pulping Chemistry : 16/05/2005 - 19/05/2005.
Open this publication in new window or tab >>Impregnation with PEG and solvolysis of wood: reflections from analysis of the ancient warship Vasa
2005 (English)Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

The paper raises the question if PEG impregnation of wood is a durable method for preservation of waterlogged items or if unexpected chemical reactions under unfavourable conditions can destroy the impregnated wood. In recent years it has been found that polyethylene glykol is an excellent reagent for solvolysis of wood. This means that polyethylene glycol and low concentration of acid completely and rapidly can degrade wood to low molecular weight products (wood liquefacation).

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-34953 (URN)94562100-0638-11dc-b09b-000ea68e967b (Local ID)94562100-0638-11dc-b09b-000ea68e967b (Archive number)94562100-0638-11dc-b09b-000ea68e967b (OAI)
Conference
International Symposium on Wood, Fibre and Pulping Chemistry : 16/05/2005 - 19/05/2005
Note
Godkänd; 2005; Bibliografisk uppgift: Titel på proceedings: 59th Appita Annual Conference and Exhibition : incorporating the 13th ISWFPC Undertitel på proceedings: proceedings Sider: 229-231; 20070519 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Sundqvist, B. (2004). Colour changes and acid formation in wood during heating (ed.). (Doctoral dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Colour changes and acid formation in wood during heating
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Heating wood has since ancient times been a method to dry and modify its properties. Nowadays heat is used in industrial processes for the same reasons. Treatment at temperatures above 150ºC can change the colour, improve resistance to biodegradation and enhance dimensional stability. However, losses in the mechanical strength of wood may also occur, and this drawback is a limitation for the use of heat-treated wood in a broad range of products. This thesis suggests that cellulose degradation can contribute to the loss of mechanical strength in wood under high-temperature treatment. The formation of formic and acetic acid during heat treatment of birch wood has been studied. Substantial amounts of acetic acid (at most 7.2% by weight) and formic acid (at most 1.1% by weight) were found in autoclave experiments at temperatures between 160ºC and 200ºC. It was also found that the average molecular size of both commercially heat-treated birch wood and birch wood treated in laboratory experiments under acidic pH conditions was considerably reduced (42%–53%) in comparison to untreated birch wood. It is reasonable to think that the formation of acid and the accompanying decrease in average cellulose molecular size have a crucial influence on the observed decrease of mechanical strength in heat-treated wood. The thesis suggests that wood can be heat-treated while maintaining mechanical strength through a process design that keeps the wood in neutral to alkaline conditions. This thesis also describes studies of colour development in birch, Norway spruce and Scots pine wood during hydrothermal treatment, with special reference to treatment at temperatures between 65ºC and 95ºC with high moisture content. The colour responses of wood that had been heat treated or kiln dried have been investigated, and the colour coordinates Lightness (L*), Chroma (Cab*), hue (h) and colour difference DEab* are presented. It is shown that colour changes associated with heat treatment at high temperatures can be obtained by treatment for long periods at temperatures around 100ºC. Such treatments will lead to changes in colour, but presumably no change in dimensional stability or resistance to biodegradation. The origin of colour formation in wood as a result of heating is briefly investigated and discussed. Colour stability during accelerated UV/Visible light exposure of heat-treated samples has been tested and the results are presented in this thesis. The colour responses of birch, Norway spruce and Scots pine wood were measured after drying in laboratory kiln experiments in the interval of 40º– 111ºC, and it was concluded that the average wood colour of a batch can be controlled by regulating time and temperature. There are some results that show an increase (around 20%) in the mechanical strength of birch wood for heat treatment around 180º–200ºC for approximately 1 hour and that colour measurements may be used as a way to monitor and control the phenomenon. However, further experiments will have to be made to confirm these indications.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2004. p. 50
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544 ; 2004:10
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-26190 (URN)d16d8230-6f85-11db-962b-000ea68e967b (Local ID)d16d8230-6f85-11db-962b-000ea68e967b (Archive number)d16d8230-6f85-11db-962b-000ea68e967b (OAI)
Note
Godkänd; 2004; 20061030 (haneit)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-24Bibliographically approved
Sundqvist, B. (2003). Värmebehandling av trä: från ett historiskt perspektiv till kommersiell produktion av idag (ed.). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Värmebehandling av trä: från ett historiskt perspektiv till kommersiell produktion av idag
2003 (Swedish)Report (Other academic)
Abstract [sv]

Värmebehandling av trä har uråldriga traditioner. Träet får bättre beständighet mot biologisk nedbrytning, får en i vissa fall estetiskt tilltalande mörk genomfärgning och blir mindre hygroskopiskt och mer formstabilt. Ideér om industriell värmebehandling började på 1910-talet i USA och patent på metoder finns från 1940-talet. På 1950- 1960-talet bedrevs forskning och utveckling främst i USA och Tyskland och detta fortsatte fram till 1980- talet i Tyskland. Från 1990-talet har intresset för värmebehandling ökat starkt i Finland, Tyskland, Holland och Frankrike. Detta har lett till kommersiell produktion i framförallt Finland och Holland. Olika industriella processer för värmebehandling finns. Gemensamt för dessa är att inverkan av syrgas reduceras i processen genom deplacering av inert gas eller mättad vattenånga eller genom nedsänkning i oljebad. Värmebehandlingen sker i temperaturer 150ºC till 250ºC upp till flera timmar, i ett eller flera steg. De egenskapsförbättringar som presenteras för värmebehandlat trä är främst ökad rötbeständighet och förbättrad dimensionsstabilitet. De mekaniska styrkegenskaperna minskar generellt tydligt. Sverige saknar både industriell tillverkning och FoU på värmebehandling av trä. Kännedomen om de fysikaliska och kemiska förändringarna under värmebhandling av trä är idag inte fullt kända. Noggrannare kontroll av tid, temperatur, fukt/vatten, tryck, pH, syrgas kan ge bättre egenskaperna för värmebehandlat trä.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2003. p. 29
Series
Technical report / Luleå University of Technology, ISSN 1402-1536 ; 2003:02
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-21770 (URN)00a1f480-2b43-11dd-8657-000ea68e967b (Local ID)00a1f480-2b43-11dd-8657-000ea68e967b (Archive number)00a1f480-2b43-11dd-8657-000ea68e967b (OAI)
Note
Godkänd; 2003; 20080526 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Sundqvist, B. (2002). Color response of Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula pubescens) subjected to heat treatment in capillary phase (ed.). Paper presented at . European Journal of Wood and Wood Products, 60(2), 106-114
Open this publication in new window or tab >>Color response of Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula pubescens) subjected to heat treatment in capillary phase
2002 (English)In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, no 2, p. 106-114Article in journal (Refereed) Published
Abstract [en]

Clearwood of Scots pine, Norway spruce, and birch was subjected to heat treatment while capillary water was kept in the wood. The treatments were performed on initially green wood from 65 °C to 95 °C from 0 to 6 days, followed by drying at 35 °C for 2 days. Color measurements, CIEL*C*h color space, were made on dry planed samples using a photoelectric colorimeter. Treatment time was more important than temperature for birch sapwood regarding the color responses, while time and temperature were of similar importance for pine and spruce. Birch sapwood became much redder and darker compared with pine and spruce. The darkening accelerated generally when treatment temperature exceeded approximately 80 °C. Pine and spruce showed generally similar color responses, untreated and treated, except for pine heartwood untreated, which showed a more saturated color. Pine treated at 65 °C and 80 °C showed red-yellow shift and yellow-red shift for sap- and heartwood respectively, as time elapsed. The color homogeneity was less for birch sapwood than for pine and spruce, and the homogeneity was generally indicated to decrease with increasing treatment temperature.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-3174 (URN)10.1007/s00107-001-0273-x (DOI)000175340600006 ()2-s2.0-0036555308 (Scopus ID)0f78ae90-b132-11db-bf9d-000ea68e967b (Local ID)0f78ae90-b132-11db-bf9d-000ea68e967b (Archive number)0f78ae90-b132-11db-bf9d-000ea68e967b (OAI)
Note
Validerad; 2002; 20070131 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Sundqvist, B. & Morén, T. (2002). The influence of wood polymers and extractives on wood colour induced by hydrothermal treatment (ed.). Paper presented at . European Journal of Wood and Wood Products, 60(5), 375-376
Open this publication in new window or tab >>The influence of wood polymers and extractives on wood colour induced by hydrothermal treatment
2002 (English)In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, no 5, p. 375-376Article in journal (Refereed) Published
Abstract [en]

A method to evaluate the influence of wood polymers and extractives on the color of wood subjected to hydrothermal treatment was proposed. As such, the technique used was extraction and color measurements. It was found that both degradation products from wood polymers and extractive compounds were indicated to be participating in the color formation of wood subjected to hydrothermal treatment.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-5742 (URN)10.1007/s00107-002-0320-2 (DOI)000179035400016 ()2-s2.0-0036803220 (Scopus ID)3ec466a0-bb53-11db-b560-000ea68e967b (Local ID)3ec466a0-bb53-11db-b560-000ea68e967b (Archive number)3ec466a0-bb53-11db-b560-000ea68e967b (OAI)
Note
Validerad; 2002; 20061016 (cira)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Sundqvist, B. (2002). Wood color control during kiln-drying (ed.). Paper presented at . Forest products journal, 52(2), 30-37
Open this publication in new window or tab >>Wood color control during kiln-drying
2002 (English)In: Forest products journal, ISSN 0015-7473, Vol. 52, no 2, p. 30-37Article in journal (Refereed) Published
Abstract [en]

Presents information on a study that investigated the coloration of wood during drying in a laboratory kiln. Research methods; Results and discussion on the study; Conclusions

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-7999 (URN)670d0fa0-a3f0-11dc-8fee-000ea68e967b (Local ID)670d0fa0-a3f0-11dc-8fee-000ea68e967b (Archive number)670d0fa0-a3f0-11dc-8fee-000ea68e967b (OAI)
Note
Validerad; 2002; 20071206 (cira)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
Sundqvist, B. (2000). Wood colour related to kiln drying (ed.). (Licentiate dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Wood colour related to kiln drying
2000 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Raised temperature in artificial drying has led to some changes of wood products such as colour and strength etc. For special treatment of wood-products with clearly modified properties, among them colour, is often high temperature and steam used industrially. Knowledge about the colour rendering from wood that is subjected to heat under humid conditions and/or artificial drying, especially kiln drying, is thus of interest. It is also of interest to understand the chemical background, for the colouring process, for future development of treatment and drying. The stability of the colour of wood exposed to UV/visible-light is also of concern when considering qualitative wood products. The colour response of Scots pine (Pinus sylvestris), Norway spruce (Picea Abies) and birch (Betula pubescens) was studied when exposed to heat and humid air, either as a hydrothermal treatment, where the wood contained capillary (free) water for certain times and temperatures, or a laboratory kiln drying. The wood subjected to hydrothermal treatment was also exposed to UV/visible-light to study the colour stability. The chemical background for the colour change during hydrothermal treatment was briefly investigated by using extraction, thin-layer chromatography (TLC) and UV/Visible-spectroscopy. The results show that multivariate modelling (PLS) of industrial wood-colour is possible as average values for the whole batch, "batch-colour". Quite strong colour changes (DE*ab > 10) were formed using hydrothermal treatment at 80-95ºC for 3-6 days. Furthermore, this quite strong colour formed is similarly stable when exposed to UV/Visible-light for 100 hours as untreated wood. Structure components (cellulose, hemicellulose and lignin) as well as extractive compounds, phenolic types, were both indicated to participate in the colour formation during hydrothermal treatment and the same is expected for kiln drying.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2000. p. 15
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757 ; 2000:38
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-26189 (URN)d153c080-d4ce-11db-8550-000ea68e967b (Local ID)d153c080-d4ce-11db-8550-000ea68e967b (Archive number)d153c080-d4ce-11db-8550-000ea68e967b (OAI)
Note
Godkänd; 2000; 20070317 (ysko)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-24Bibliographically approved
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