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Westermark, Ulla
Publications (10 of 33) Show all publications
Terashima, N., Akiyama, T., Ralph, S., Evtuguin, D., Neto, C. P., Parkas, J., . . . Ralph, J. (2009). 2D-NMR (HSQC) difference spectra between specifically C-13-enriched and unenriched protolignin of Ginkgo biloba obtained in the solution state of whole cell wall material (ed.). Holzforschung, 63(4), 379-384
Open this publication in new window or tab >>2D-NMR (HSQC) difference spectra between specifically C-13-enriched and unenriched protolignin of Ginkgo biloba obtained in the solution state of whole cell wall material
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2009 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 63, no 4, p. 379-384Article in journal (Refereed) Published
Abstract [en]

In the structural analysis of lignins by 13C-NMR, signal overlap limits definitive assignment and accurate intensity measurement. Selective labeling by 13C-enrichment of a specific carbon in lignin enhances its signal intensity in the spectrum. Further enhancement of the specifically labeled carbons can be realized via difference spectra created from the enriched and unenriched samples. Difference 2D 13C-1H correlation (HSQC) NMR spectra, derived from the spectra of specifically 13C-enriched lignin model polymers (so-called dehydrogenation polymers) and their unenriched counterparts, take advantage of the enhanced dispersion afforded by both 13C and 1H chemical shifts, diminishing the difficulties arising from the signal-overlap problem and aiding in definitive signal assignments. In this research, protolignin in xylem cell walls was specifically 13C-enriched at all of the individual phenylpropanoid side-chain carbons by feeding 13C-enriched coniferins to growing stems of Ginkgo biloba. The whole xylem fractions containing 13C-enriched and unenriched protolignins were dissolved in a mixture of N-methylimidazole and DMSO, and then acetylated. Solution state 2D-NMR (HSQC) spectra of the acetylated whole cell wall were acquired. Difference spectra between the walls containing 13C-enriched and unenriched lignins afforded simplified 2D spectra in which well-separated signals were assigned exclusively to the specifically enriched carbons. This novel NMR technique provides a useful tool for elucidation of entire protolignin in the cell wall of ginkgo xylem.

Keywords
Forestry, agricultural sciences and landscape planning - Wood fibre and forest products, Skogs- och jordbruksvetenskap samt landskapsplanering - Träfiber- och virkeslära
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-13853 (URN)10.1515/HF.2009.074 (DOI)000267573200001 ()2-s2.0-67650309544 (Scopus ID)d26ab730-7ab2-11de-9f57-000ea68e967b (Local ID)d26ab730-7ab2-11de-9f57-000ea68e967b (Archive number)d26ab730-7ab2-11de-9f57-000ea68e967b (OAI)
Note

Validerad; 2009; 20090727 (ysko)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Pantze, A., Karlsson, O. & Westermark, U. (2008). Esterification of carboxylic acids on cellulosic material: solid state reactions (ed.). Paper presented at . Holzforschung, 62(2), 136-141
Open this publication in new window or tab >>Esterification of carboxylic acids on cellulosic material: solid state reactions
2008 (English)In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 2, p. 136-141Article in journal (Refereed) Published
Abstract [en]

In the present work, the formation of ester linkages in cellulosic materials during drying and heating was addressed. The results indicated that direct ester formation, without anhydride intermediate, occurs between carboxylic acids of suitable structure and cellulosic hydroxyls at 180 degrees C, even after reaction times as short as 5 min. The 2(R)-hydroxybutyric acid is most effective in ester formation, followed by 2-ketobutyric acid and 3-hydroxybutyric acid. Hexanoic acid is less effective and veratric acid produces no esters at all. At lower temperatures, 2-ketobutyric acid is the most reactive compound. One conclusion is that a hydroxyl or keto group in alpha position of the carboxylic acids favours ester formation. Another finding is that three pyrrolidine structures are produced after esterification and aminolysis of 2-ketobutyric acid. One of the structures indicates that 2-ketobutyric acid is reactive in two positions and could therefore be a potential cross-linker. A critical parameter for ester formation is pH, and the results indicate that pH < 2 strongly favours esterification, whereas almost no esters are produced at pH > 5-6. All experiments were performed in a solid-state model system (on cellulosic filter paper) with low moisture content. Esterification of five carboxylic acids was studied. Samples were heated constantly at 180 degrees C for 5 min or gradually from 22 degrees C to 180 degrees C over periods ranging from 5 to 45 min. Quantitative analysis of ester formation between the monocarboxylic acids and the hydroxyl groups of cellulose was performed by means of aminolysis and gas chromatography.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-12564 (URN)10.1515/HF.2008.027 (DOI)000253853200002 ()2-s2.0-38849126090 (Scopus ID)bb9817f0-0227-11dd-9241-000ea68e967b (Local ID)bb9817f0-0227-11dd-9241-000ea68e967b (Archive number)bb9817f0-0227-11dd-9241-000ea68e967b (OAI)
Note
Validerad; 2008; 20080404 (pafi)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Pantze, A., Karlsson, O. & Westermark, U. (2007). A model system to study esterification reactions in cellulosic or lignocellulosic material (ed.). Paper presented at . Journal of Pulp and Paper Science (JPPS), 33(4), 177-183
Open this publication in new window or tab >>A model system to study esterification reactions in cellulosic or lignocellulosic material
2007 (English)In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 33, no 4, p. 177-183Article in journal (Refereed) Published
Abstract [en]

The formation of natural ester cross-linkages in cellulosic or lignocellulosic composite materials during drying and heating is of interest for the production of paper and of wood composite boards and in giving cotton materials improved characteristics. A model system has been developed to study quantitatively the esterification of cellulosic material during drying and heating when solid-state conditions can be said to predominate. In the experiments, hexanoic acid and 3-hydroxybutyric acid were added to ordinary filter paper. Moisture content was adjusted, and samples were heated to temperatures ranging from 85 degrees C to 180 degrees C for between 15 and 45 minutes. Quantitative analysis of ester,formation, in this case between the monocarboxylic acids and the cellulose's hydroxyl groups, was performed using aminolysis/gas chromatography. The 3-hydroxybutyric acid was surprising v effective in ester formation. The results indicate that direct esterification of monocarboxylic acid can be an important reaction in lignocellulosic material at elevated temperatures.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-14383 (URN)dbc09e30-0a2e-11dd-ae49-000ea68e967b (Local ID)dbc09e30-0a2e-11dd-ae49-000ea68e967b (Archive number)dbc09e30-0a2e-11dd-ae49-000ea68e967b (OAI)
Note
Validerad; 2007; 20080414 (pafi)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
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
Karlsson, O., Westermark, U., Backlund, U. & Halvarsson, S. (2006). Environmentally friendly process for high density fibreboards (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 >>Environmentally friendly process for high density fibreboards
2006 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

Urea-formaldehyde (UF) resin is a common binder in many fibre- and particleboards today. However, formaldehyde is a fairly reactive compound with many negative affects on health and environment. This paper describes a process to make thin high density fibreboards without use of conventional resin such as UF. Initially we found that wood particles such as ones used in particle board had, when activated with hydrogen peroxide and iron catalyst, self-bonding capability when hot-pressed into boards. Low swelling board, although at somewhat higher density than conventional glued ones, could be formed by pressing activated wood particles at 170 oC in a laboratory press. We found that the activation technique was applicable to dry or semi-dry board processes and was considered to be well suited for fibreboards from refined wood fibers especially as their specific (contact) area is high. Activated wood fibres were produced at Metso Panelboards Pilot-refiner in Sundsvall and mats were also formed and pressed into boards 50x60 cm2 at fairly conventional pressing conditions. At a hydrogen peroxide charge of 4% boards made from birch fibres with good mechanical properties (in terms of bending strength and internal bonding) were produced. Thickness swelling in water was low (TS24h., 15-20%). At lower hydrogen peroxide charges (<2%) the swelling was higher. Development of the process to also include other wood species than birch is in our interest. Furthermore, properties of the boards were strongly dependent on the moisture content of fibres; at low moisture content (MC<8%) thickness swelling increased. We see a high potential in the process as the glue-free technique is estimated to reduce production cost of boards as well as give environmental advantages.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-36917 (URN)abd5ccf0-f7d2-11db-ac79-000ea68e967b (Local ID)abd5ccf0-f7d2-11db-ac79-000ea68e967b (Archive number)abd5ccf0-f7d2-11db-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: 9; 20070501 (ysko)Available from: 2016-10-03 Created: 2016-10-03 Last updated: 2017-11-25Bibliographically 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
Pantze, A., Westermark, U. & Karlsson, O. (2005). Formation of ester cross linkage in lignocellulosic materials during drying and heating (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 >>Formation of ester cross linkage in lignocellulosic materials during drying and heating
2005 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-27529 (URN)101b6130-0637-11dc-b09b-000ea68e967b (Local ID)101b6130-0637-11dc-b09b-000ea68e967b (Archive number)101b6130-0637-11dc-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: 297-300; 20070519 (ysko)Available from: 2016-09-30 Created: 2016-09-30 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
Parkås, J., Paulsson, M., Terashima, N., Westermark, U. & Ralph, S. (2004). Light-induced yellowing of selectively 13C-enriched dehydrogenation polymers (DHPs): Part 1. Side-chain 13C-enriched DHP (α-, β-, and γ-13C) (ed.). Paper presented at . Nordic Pulp & Paper Research Journal, 19(1), 29-36
Open this publication in new window or tab >>Light-induced yellowing of selectively 13C-enriched dehydrogenation polymers (DHPs): Part 1. Side-chain 13C-enriched DHP (α-, β-, and γ-13C)
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2004 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, no 1, p. 29-36Article in journal (Refereed) Published
Abstract [en]

Light-induced yellowing has been studied using side-chain (α, β, and γ) 13C-enriched DHP (dehydrogenation polymer) and quantitative solution state 13C NMR spectroscopy. The DHP was formed from 13C-enriched coniferin using an enzymatic system consisting of β-glucosidase, glucose oxidase, and peroxidase in a pH 6 buffer solution. The DHP was applied to filter paper, irradiated with UV/VIS light and the photodegraded DHP was extracted and analyzed. The NMR study revealed a drastic decrease in the amount of coniferyl alcohol end groups with the formation of end groups of the vanillin type and small amounts of end groups of the vanillic acid type. The results indicated a moderate formation of αcarbonyls, however, no significant decrease in the amount of βO-4 structures in the extractable part of the irradiated DHP could be established, based on difference spectra corresponding to the 13C-enriched DHP.

National Category
Bio Materials
Research subject
Wood Physics
Identifiers
urn:nbn:se:ltu:diva-11025 (URN)9eaa0750-0dbf-11dc-8745-000ea68e967b (Local ID)9eaa0750-0dbf-11dc-8745-000ea68e967b (Archive number)9eaa0750-0dbf-11dc-8745-000ea68e967b (OAI)
Note
Validerad; 2004; 20070529 (cira)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved

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