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Microwave-Assisted Fractionation and Functionalization of Technical Lignin Towards Thermoset Resins
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. (Mats Johansson)ORCID iD: 0000-0002-1184-1310
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. (Mats Johansson)ORCID iD: 0000-0002-8127-9183
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology. (Minna Hakkarainen)ORCID iD: 0000-0002-6313-8539
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.ORCID iD: 0000-0002-7790-8987
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Lignin is the main source of aromatic natural polymers, with a potential to serve as a building block of rigid and thermally stable bio-based materials. However, because of its heterogeneity differences and not fully understood chemical structure it is still underutilized. Therefore, in this paper, technical softwood Kraft lignin is refined in to narrow-dispersity and relatively low molecular weight fractions by microwave-assisted processing. This process was carried out under non-catalytic conditions using a low boiling point solvent and higher pressure. The chemical properties of the retrieved fractions were investigated by 31P NMR, HSQC NMR, SEC, DSC, and TGA. One of the retrieved soluble lignin fractions was successfully chemically modified by microwave processing. The chemically modified lignin was characterized by 31P NMR and FTIR, which provided evidence of the introduction of the allyl moieties. Subsequently, the allylated lignin was cross-linked through thermally induced thiol-ene chemistry to produce lignin-based thermosets.

Keywords [en]
Softwood lignin, microwave-assisted fractionation, microwave-assisted functionalization, allylation, thiol-ene thermosets.
National Category
Polymer Chemistry Polymer Technologies Paper, Pulp and Fiber Technology
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-327223OAI: oai:DiVA.org:kth-327223DiVA, id: diva2:1758405
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20230524

Available from: 2023-05-22 Created: 2023-05-22 Last updated: 2024-05-23Bibliographically approved
In thesis
1. Lignin-Based Thermosets with Tunable Mechanical and Morphological Properties: A Study of Structure-Property Relationships
Open this publication in new window or tab >>Lignin-Based Thermosets with Tunable Mechanical and Morphological Properties: A Study of Structure-Property Relationships
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nowadays, there is an urgent need to decrease our dependence on fossilresources and shift towards the use of renewable resources for advancingsustainable development. Utilizing renewable and bio-based raw materials,such as lignocellulosic biomass, for designing new materials is a promisingapproach to promote this objective. The main components of lignocellulosicbiomass are cellulose, hemicellulose, and lignin. Lignin is the most abundantaromatic biopolymer in nature and it is produced on a large scale fromchemical pulping processes as technical lignin. Lignin has the potential as asustainable and renewable alternative to fossil-based aromatics in variousapplications, e.g. thermosetting resins.

Technical lignin has a complex and heterogeneous structure, with arelatively low chemical reactivity. It is characterized by a high dispersity, thepresence of various functional groups that are unevenly distributed along thelignin chains, and various interunit linkages between the monoaromatics. Toovercome the challenges associated with lignin heterogeneity, technicallignin can be fractionated and/or chemically modified.

In this work, LignoBoost Kraft lignin was used as a starting material toproduce lignin-based thiol-ene thermosets. Firstly, lignin was fractionatedusing two approaches: 1) sequential solvent fractionation, and 2) microwaveassistedextraction. These fractionation approaches enabled access to ligninfractions with unique and tunable properties. Subsequently, lignin waschemically modified, in particular through allylation. Two allylation reagentswere used: allyl chloride and diallyl carbonate. The use of allyl chlorideenables a selective allylation of the phenolic OH groups, leaving the aliphaticand carboxylic acid OH groups unmodified. On the other hand, diallylcarbonate can react with all the aforementioned OH groups, leading to ahigher degree of allylation. Subsequently, allylated lignin was thermallycross-linked with various polyfunctional thiols, leading to thiol-enethermosets. The structure-property relationships of the thermosets wereinvestigated by varying several parameters, including the lignin source,fractionation approach, chemical modification, and thiol cross-linker. Byadjusting these parameters, various thermosets with tunable mechanical andmorphological properties were produced. Understanding the structurepropertyrelationships of these bio-based materials is crucial for identifyingpotential applications.

Abstract [sv]

Nuförtiden finns det ett akut behov av att minska vårt beroende av fossilaresurser och övergå till användningen av förnybara resurser och därmedavancera den hållbara utvecklingen. Att använda förnybara och biobaseraderåvaror, såsom lignocellulosabiomassa, för att designa nya material är ettlovande tillvägagångssätt för att uppnå detta mål. Huvudkomponenterna ilignocellulosabiomassa är cellulosa, hemicellulosa och lignin. Lignin ärnaturens vanligaste aromatiska biopolymer och den produceras i stor skalafrån kemiska massaprocesser som tekniskt lignin. Lignin kan fungera som etthållbart och förnybart alternativ till fossilbaserade aromater i olikatillämpningar, t.ex. g. värmehärdande hartser.

Tekniskt lignin har en komplex och heterogen struktur, med en relativt lågkemisk reaktivitet. Det kännetecknas av en hög dispersitet, närvaron av olikafunktionella grupper som är ojämnt fördelade längs ligninkedjorna, och olikatyper av enhetsbindningar mellan monoaromaterna. För att övervinna deutmaningar som är förknippade med ligninets heterogenitet kan ligninfraktioneras och/eller kemiskt modifieras.

I detta arbete användes LignoBoost Kraft-lignin som utgångsmaterial föratt tillverka ligninbaserade tiol-en-härdplaster. Först har lignin fraktioneratsmed hjälp av två olika metoder: 1) sekventiell lösningsmedelsfraktionering,och 2) mikrovågsassisterad extraktion. Dessa fraktioneringsmetoder gjordedet möjligt att erhålla ligninfraktioner med unika och skräddarsyddaegenskaper. Därefter modifierades ligninet kemiskt genom allylering. Tvåallyleringsreagens användes: allylklorid och diallylkarbonat. Användningenav allylklorid möjliggör selektiv allylering av de fenoliska OH-grupperna,samtidigt som de alifatiska och karboxylsyra-OH-grupperna lämnasomodifierade. Diallylkarbonat kan å andra sidan reagera med alla de tidigarenämnda OH-grupperna, vilket leder till en högre grad av allylering. Däreftertvärbands härdades allylerat lignin termiskt med olika polyfunktionellatioler, för att ge härdplast med tiol-en-tvärbindingar. Strukturegenskapsförhållandenaför härdplasterna undersöktes genom att varieraflera parametrar, inklusive ligninkällan, fraktioneringsmetod, kemiskmodifiering och tioltvärbindare. Genom att justera dessa parametrarproducerades olika härdplaster med skräddarsydda mekaniska ochmorfologiska egenskaper. Att förstå relationerna mellan struktur ochegenskaper av dessa biobaserade material är avgörande för att identifierapotentiella tillämpningar.

Place, publisher, year, edition, pages
Stockholm, Sweden: KTH Royal Institute of Technology, 2023. p. 66
Series
TRITA-CBH-FOU ; 2023:19
Keywords
Softwood, hardwood, technical lignin, solvent fractionation, allylation, thiol-ene thermosets, thioether linkage, wide-angle X-ray scattering, π-π stacking interactions, Barrträ, lövträ, tekniskt lignin, lösningsmedelsfraktionering, allylering, tiol-en-härdplaster, tioeterbindning, vidvinkelröntgenspridning, π-π staplingsinteraktioner
National Category
Organic Chemistry Polymer Chemistry Polymer Technologies Materials Chemistry
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-327306 (URN)978-91-8040-567-6 (ISBN)
Public defence
2023-06-15, F3, Lindstedtsvägen 26 & 28, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation
Note

QC 2023-05-23

Available from: 2023-05-23 Created: 2023-05-23 Last updated: 2023-05-25Bibliographically approved

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Truncali, AlessioRibca, IulianaYao, Jenevieve G.Hakkarainen, MinnaJohansson, Mats

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