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Modification of Cellulose Nanofibers for Composites Applications
KTH, School of Chemical Science and Engineering (CHE).
2014 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Modifiering av cellulosananofibrer för kompositapplikationer (Swedish)
Abstract [en]

Cellulose nanofibrils (CNF) are assemblies of distinct polymeric units of cellulose chains. The low amount of structural defects and its rigidity gives good mechanical properties surpassing those of regular pulp fiber. The nanosize of CNF provides a high specific surface area and allows a high amount of interaction with its surrounding. CNFs desirable properties make it an interesting reinforcement in new bio composites. However, its hydrophilic nature makes it difficult to blend it with hydrophobic matrices. In this thesis TEMPO-oxidized CNF is modified with positively charged block-polyelectrolytes for a better miscibility with a hydrophobic polymer. Poly (dimethyl aminoethylmethacrylate) (PDMAEMA) macroinitiators and blocks with three different length of Poly (methyl methacrylate) (PMMA) were synthesized, quaternized and analyzed by NMR, SEC and polyelectrolyte titration (PET). Additionally, three different latexes with similar structure as the synthesized polyelectrolytes were provided by Linn Carlsson and Assya Boujemaoui at the Division of Coating Technology. One of the quaternized (PDMAEMA)-b-PMMA and the three Latexes were adsorbed to CNF and the adsorption was confirmed by TGA and FT-IR. Composites with 1, 2.5 and 5 wt% of latex modified CNF, with the respect of the pure fiber weight, were prepared. The composites were analyzed by tensile measurements, dynamic mechanical analysis (DMA), water uptake and scanning electron microscopy (SEM) to investigate the effect of the different modifications of the CNF. In this study poly(ε-caprolactone) (PCL) was utilized as a composite matrix. The polyelectrolytes were successfully adsorbed onto the CNF and it was shown that the amount of fiber content and length of the hydrophobic block had a positive effect on the composite materials increasing the Young’s modulus and max stress. The miscibility and compatibility of the materials has been increased through modifications of the CNF.

Abstract [sv]

Cellulosananofibriller (CNF) är sammansättningar av distinkta polymera enheter av cellulosa. Tack vare små strukturella defekter och dess styvhet har CNF goda mekaniska egenskaper som överstiger de hos vanlig massafiber. CNFs nanostorlek medför en hög specifik yta och tillåter en stor mängd interaktioner med dess omgivning. De önskvärda egenskaperna gör CNF till ett intressant material för förstärkning av biokompositer. Ett problem är att den naturliga hydrofilisiteten hos CNF gör den svår att blanda med hydrofoba matriser. I det här examensarbetet modifieras TEMPO-oxiderad CNF med hjälp av positivt laddade polyelektrolyter för en bättre blandbarhet med en hydrofob polymermatris. Poly (dimetyl aminometakrylat) (PDMAEMA) makroinitiatorer och block av poly (metylmetakrylat) (PMMA) i tre olika längder syntetiserades, kvartärniserades och analyserades med hjälp av NMR, SEC och polyelektrolytisk titrering (PET). Dessutom tillhandahölls tre olika latexar med liknande struktur som polyelektrolyterna från Linn Carlsson och Assya Boujemaoui på Avdelningen för Ytbehandlingsteknik. En av de kvartärniserade (PDMAEMA)-b-PMMA och de tre Latexarna adsorberades på CNF och adsorptionen bekräftades med TGA och FT-IR. Kompositer med 1, 2.5 och 5 vikt-% latexmodifierad CNF, med hänsyn till fibervikten, blandades och analyserades med dragprovning, DMA, vattenupptag och svepelektronmikroskop (SEM) för att undersöka effekten av de olika modifieringarna av CNF. I denna studie valdes polykaprolakton (PCL) till matris. Adsorption av polyelectrolyter till CNF lyckades och det kunde påvisas att fibermängden och längden på de hydrofoba blocken hade en positiv effekt på kompositmaterialen genom att öka styvheten och styrkan. Blandbarheten och kompatibiliteten hos materialen ökade genom modifieringen av CNF.

Place, publisher, year, edition, pages
2014.
Keyword [en]
Cellulose nanofibrils (CNF), polyelectrolytes, adsorption, atom transfer radical polymerization (ATRP), composite.
Keyword [sv]
Cellulosananofibriller (CNF), polyelektrolyter, adsorption, atom transfer radical polymerization (ATRP), komposit.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-158622OAI: oai:DiVA.org:kth-158622DiVA: diva2:778843
Available from: 2015-01-12 Created: 2015-01-12 Last updated: 2017-08-30Bibliographically approved

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