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Polysaccharide-based wood adhesives
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.ORCID iD: 0000-0003-4831-006x
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

It is highly desirable to increase the use of renewable resources and reduce fossil-dependence due to sustainability concerns. As a consequence, it is expected that the use of the wood-based materials will increase in the future. Therefore, adhesives will have an important role since they allow for the use of lower-quality and recycled wood. At present, adhesives are mainly fossil-based and contain toxic components which can present a health risk. Extensive research is being conducted with the goal to replace fossil- with bio-based adhesives, and eliminate toxic components.

In this work, several polysaccharides have been investigated as wood adhesives, of which wood hemicelluloses are an interesting alternative. When applied between wood veneers, wood hemicelluloses alone do not exhibit sufficient strength, but combined with chitosan, they exhibit impressive strength and even sufficient water resistance. Since the molecular weight of hemicelluloses can affect the adhesive performance, locust bean gum has been used as a model in order to investigate this effect. An optimal molecular weight, 320-530 kDa in this case, is necessary for achieving the highest bond strength. These adhesives also show promising results in particleboards, and their internal bond strength fulfills the standard requirements for P2 boards (SS-EN 319), which are commonly used for furniture in dry conditions. High mat moisture contents are necessary for sufficient hydration of polysaccharides and internal bond strength; hence, a high mat moisture content (35-45 %), a pressing temperature of 150 °C, and pressing time of 15 min, yielded strong particleboards with no signs of steam blistering or delamination.

With the goal to partially replace fossil content in PVAc adhesives chitosan has been used in emulsion polymerization of VAc, as a surfactant and grafting site. Besides lowering the fossil content to 60 %, the water resistance was significantly improved.

Abstract [sv]

Ökad användning av förnybara resurser och minskat fossilberoendet är högst önskvärt ur miljösynpunkt. Som ett led i detta förväntas användningen av träbaserade material öka i framtiden och därmed kommer även lim att spela en viktig roll eftersom limning möjliggör användning av tex återvunnet trä av lägre kvalitet. De lim som används idag huvudsakligen fossilbaserade och de innehåller dessutom giftiga komponenter som kan utgöra en hälsorisk. Omfattande forskning bedrivs med målet att helt eller delvis ersätta fossila lim med biobaserade lim och att eliminera giftiga komponenter.

I detta arbete har flera polysackarider undersökts som trälim, varav trähemicellulosor är ett intressant alternativ. När trähemicellulosor appliceras mellan träfanér uppvisar de i sig själva inte tillräcklig bindningsstyrka, men i kombination med kitosan uppvisar de imponerande styrka och även godtagbar vattenbeständighet. Eftersom molekylvikten hos hemicellulosa kan påverka vidhäftningsförmågan har locust bean gum använts som modell för att undersöka denna effekt. En optimal molekylvikt, 320-530 kDa i detta fall, är nödvändig för att uppnå högsta bindningsstyrka. Dessa lim uppvisar också lovande resultat i spånskivor och deras inre bindningsstyrka uppfyller standardkraven för P2-skivor (SS-EN 319), vilka vanligtvis används för möbler i torra förhållanden. Höga fukthalter är nödvändiga för tillräcklig hydrering av polysackarider och intern bindningsstyrka; en hög spånskivefukthalt (35-45 %), en presstemperatur på 150 °C och presstid på 15 min gav därför starka spånskivor, utan tecken på ångblåsor eller delaminering.

Med målet att delvis ersätta mängden fossilbaserat material i PVAc-lim har kitosan använts i emulsionspolymerisation av VAc, som ytaktivt ämne och som substrat för ympning. Förutom att sänka fossilhalten till 60 % förbättrades också vattentåligheten avsevärt i det resulterande limmet.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2023. , p. 69
Series
TRITA-CBH-FOU ; 2023:9
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-325131ISBN: 978-91-8040-527-0 (print)OAI: oai:DiVA.org:kth-325131DiVA, id: diva2:1748306
Public defence
2023-04-28, F3, Lindstedtsvägen 26, via Zoom: https://kth-se.zoom.us/j/63528598963, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 2023-04-04

Available from: 2023-04-04 Created: 2023-04-03 Last updated: 2023-04-27Bibliographically approved
List of papers
1. Effect of hemicellulose molecular weight on bonding properties in biobased wood adhesives
Open this publication in new window or tab >>Effect of hemicellulose molecular weight on bonding properties in biobased wood adhesives
2022 (English)In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 10, no 47, p. 15372-15379Article in journal (Refereed) Published
Abstract [en]

Today, the most commonly used adhesives in the wood industry are fossil-based, but the search for new, renewable and less hazardous, resources for adhesives is intensifying. Hemicelluloses show promising bonding performance when used as a component in wood adhesives. Since batch-to-batch variations can affect the use of hemicelluloses in a large-scale production, we have investigated the effect of hemicellulose molecular weight on important adhesive properties, such as viscosity and bond strength, by using locust bean gum as a hemicellulose model and varying the molecular weight through hydrolysis. Results showed that there is a nonlinear proportionality between bond strength and molecular weight. In the molecular weight range used in the study, 70–1460 kDa, anoptimum in the adhesive performance was achieved with intermediate molecular weights, 320 and 530 kDa, especially when considering applicability and bond strength. Adhesives with lower molecular weights, 70 and 150 kDa, did not exhibit sufficient cohesive strength; therefore, the bond strength was lower. The adhesive with higher molecular weight, 1460 kDa, was difficult to apply, especially since its maximum solid content was very low, 5 wt %.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2022
Keywords
Wood adhesive, Hemicellulose, Locust bean gum, Molecular weight, Tensile shear strength
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-325115 (URN)10.1021/acssuschemeng.2c03991 (DOI)000886600800001 ()2-s2.0-85142179298 (Scopus ID)
Funder
Swedish Research Council FormasSwedish Energy AgencyVinnova, 2017-05405Knut and Alice Wallenberg Foundation, 2018.0452
Note

QC 20230403

Available from: 2023-03-30 Created: 2023-03-30 Last updated: 2023-04-03Bibliographically approved
2. A fully bio-based wood adhesive valorising hemicellulose-rich sidestreams from the pulp industry
Open this publication in new window or tab >>A fully bio-based wood adhesive valorising hemicellulose-rich sidestreams from the pulp industry
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2021 (English)In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 23, no 9, p. 3322-3333Article in journal (Refereed) Published
Abstract [en]

Today, most wood adhesives are prepared from fossil-based polymers and contain hazardous components,e.g., formaldehyde. With the growing environmental concern there is an urge to develop bio-based and harmless substitutes. In this study, the ambition is to explore and valorise hemicelluloses, a biproduct from pulping, as the main component in wood adhesives. Wood adhesives were prepared from different sources: xylan from beech wood, hemicellulose-rich liquids obtained from hydrolysis of hardwood, and ultrafiltered softwood hemicellulose recovered from the process water of a thermomechanical pulp mill. Hemicelluloses themselves do not exhibit sufficient bonding performance, but excellent bond strength and water resistance were obtained in combination with poly(vinyl amine). It was also demonstrated that chitosan can be used as a bio-based amino-functional alternative to synthetic poly(vinyl amine), with similar or superior properties. Hemicelluloses alone show insufficient water resistance, but hemicelluloses in combination with chitosan exhibit exceptionally good bonding performance, especially regarding water resistance. Adhesives prepared from liquids rich in hardwood- and softwood hemicelluloses showed similar bond strength in combination with amino-functional polymers (poly(vinyl amine) and chitosan), regardless of their differences in structure. The current study constitutes an example on how sidestreams from the pulp industry in combination with chitosan can be used to substitute fossil-based materials in the quest for a more sustainable society.

Place, publisher, year, edition, pages
Royal Society of Chemistry (RSC), 2021
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-309867 (URN)10.1039/d0gc04273k (DOI)000642579700001 ()2-s2.0-85105870276 (Scopus ID)
Note

QC 20220314

Available from: 2022-03-14 Created: 2022-03-14 Last updated: 2023-04-03Bibliographically approved
3. Chitosan-graft-poly(vinyl acetate) for wood-adhesive applications
Open this publication in new window or tab >>Chitosan-graft-poly(vinyl acetate) for wood-adhesive applications
(English)Manuscript (preprint) (Other academic)
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-325128 (URN)
Note

QC 20230403

Available from: 2023-03-30 Created: 2023-03-30 Last updated: 2023-04-03Bibliographically approved
4. Locust bean gum as an adhesive for wood particleboards
Open this publication in new window or tab >>Locust bean gum as an adhesive for wood particleboards
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(English)Manuscript (preprint) (Other academic)
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-325127 (URN)
Note

QC 20230403

Available from: 2023-03-30 Created: 2023-03-30 Last updated: 2023-04-03Bibliographically approved
5. Fully biobased wood adhesives valorising hemicellulose-rich sidestreams and applied in particleboards
Open this publication in new window or tab >>Fully biobased wood adhesives valorising hemicellulose-rich sidestreams and applied in particleboards
(English)Manuscript (preprint) (Other academic)
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-325123 (URN)
Note

QC 20230403

Available from: 2023-03-30 Created: 2023-03-30 Last updated: 2023-04-03Bibliographically approved
6. Adhesives based on algae and chitosan for wood particleboards
Open this publication in new window or tab >>Adhesives based on algae and chitosan for wood particleboards
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(English)Manuscript (preprint) (Other academic)
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-325125 (URN)
Note

QC 20230403

Available from: 2023-03-30 Created: 2023-03-30 Last updated: 2023-04-03Bibliographically approved

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Todorovic, Tijana

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