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Effect of Wood Constituents Oxidation of Unsaturated Fatty Acids
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. (Polymer Technology)
2011 (English)Licentiate thesis, monograph (Other academic)
Abstract [en]

This work presents the mechanisms of free radicals in a model system between fatty acids oxidation process and wood components. The aim is to create a better understanding of new environmentally friendly materials for exterior wood protection. The drying mechanisms of the unsaturated fatty acids with wood model system in the real time were monitored by using RT-IR. This method together with SEC and NMR are enormously powerful spectroscopy techniques to determine the physical and chemical properties of fatty acids-wood during the oxidation process over time. In the first part of this study the focus was in a molecular level on oxidation of methyl linoleate mixed with lignin model compounds (1 and 20 wt%). The effect of lignin structures on unsaturation fatty acids oxidation was determined with 1 wt% lignin model compounds. The interaction, coupling reaction and new structure formations were analyzed through 20 wt% of same lignin compounds mixed with 80 wt% methyl linoleate. The oil oxidation interaction mechanisms were also evaluated by using methyl linoleate, methyl oleate and Linola® on real/natural wood (Norwegian Spruce). In the second part of this work, FT-IR and different NMR methods were used as characterization techniques. The results showed that the oxidative drying process of unsaturated fatty acids was indeed affected by wood constituents. The most hydrophobic part of the wood; lignin, interacted with the oxidation process and some lignin structures inhibited or retarded the reaction. Not only the oil structures were affected but also the lignins were to some extent oxidized as a competing reaction with the oil oxidation. However, a formation of chemicals bonds between the oil and the lignin structures was not observed, i.e. the oils were not immobilized on lignin by covalent bond formation to any significant extent. Further, the focus was on oils in wood using NMR and FTIR demonstrated that highly reactive linoleic acid did react in wood significantly, while it was not immobilized to the same extent. Oleic acid on the other hand reacted more sluggish but the reactive part was immobilized in the wood structure. According to the results, it can be concluded that the structure of the oil is crucial in the overall protective performance of the system. This study indicated that the oxidation pattern of fatty acids behaved differently on wood surface. The wood model compounds minimize the complexity of all elements that exist normally in the natural wood. It can also be concluded that different wood components e.g. end group structures, affect the oil drying process in different ways. The fatty acids pattern will affect not only the structure of the oil dried itself but also the surrounding wood materials.

Abstract [sv]

Detta arbete beskriver friradikalmekanismerna i ett modellsystem mellan fettsyra oxidation och träs beståndsdelar för att skapa bättre förståelse för nya miljövänliga skyddssystem gällande trämaterial som används utomhus. Torkningsmekanismen av omättade fettsyror med trä modellsystem analyserades med hjälp av RT-IR i realtid. Denna metod tillsammans med SEC och NMR spektroskopier understödjer undersökningen av de fysikaliska och kemiska förändringarna av olja och träkomponenter under oxidationsprocessen. I den första delen av denna studie blandades metyl linoleate med ligninmodellföreningar (1 och 20 vikt%). Effekten av olika ligninstrukturer på omättade fettsyrors oxidation, bestämdes med 1vikt% ligninmodellföreningar. Samverkan och kemiska kopplingsreaktioner analyserades med 20 vikt% ligninföreningar genom att dessa kemikalier blandades med metyl linoleate (80 vikt%). Den andra delen av denna studie genomfördes på oljor som oxiderades på trä (gran). Detta genomfördes med hjälp av metyl linoleate, metyl oleat och Linola® på trä. FT-IR och olika NMR karaktäriseringsmetoder användandes i den sista delen av detta arbete. Resultaten visar ett flertal nya faktorer rörande den kemiska och fysikaliska samverkan mellan impregnerande olja och trä som har betydelse för ett optimalt fungerande skydd. Modellstudier mellan torkande oljor och olika ligninkomponenter visar att det sker en kemisk samverkan mellan ligninet och oljorna under oxidationsprocessen. En mycket viktig faktor är att oljan oxideras men att även en del av ligninstrukturerna förändras kemisk under denna process. Slutsatsen är att ligninet påverkar torkhastigheten hos oljan men att oxidationen av oljan också påverkar nedbrytning av ligninet. Studierna visar dock att ingen mätbar mängd olja reagerar kemisk med lignin dvs. oljan fastnar inte genom en kemisk koppling till lignin. NMR studier visar att olika oljor i trä är olika reaktiva, exempelvis reagerar linolja snabbt men merparten av dessa oxidationsreaktioner leder inte till att oljan immobilseras på en molekylär nivå. Mindre reaktiva oljor å andra sidan (exempelvis oljor med hög oljesyrahalt) torkar långsammare men att detta leder till att en större andel immobiliserad olja.

Genom att använda trämodellföreningar minimeras komplexiteten av alla element som normalt finns i trä. Från denna studie kan man dra slutsatsen att olika träkomponenter, t.ex. olika kemiska strukturer påverkar olja torkningsprocessen på olika sätt. Fettsyrans kolkedjor påverkar inte bara oljans struktur under sin torkningsmekanism utan även det omgivande trämaterialet.

 

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , 40 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2011:22
Keyword [en]
Wood constituents, oil, oxidation, unstatured fatty acids, lignin, model lignin compounds
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-33129ISBN: 978-91-7415-912-7OAI: oai:DiVA.org:kth-33129DiVA: diva2:413455
Presentation
2011-05-06, K2, KTH, Teknikringen 28, Stockholm, 14:00 (English)
Opponent
Supervisors
Funder
Formas, KFFB 633321Knut and Alice Wallenberg Foundation, KCAB 8202
Note
QC 20110429Available from: 2011-04-29 Created: 2011-04-28 Last updated: 2011-05-02Bibliographically approved

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