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Wood Nanocellulose Materials and Effects from Surface Modification of Nanoparticles
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanocellulose is an interesting natural material thatis gaining interest in the field of materials science, particularly nanocomposites. Depending on the disintegration route, nanocellulose can be isolated either in the form of long and flexible fibres (nanofibrillated cellulose, NFC), or stiff, rod-like crystals (cellulose nanocrystals, CNC). Nanocellulose can be utilized in nanocomposites either as a reinforcement element or as a network matrix due to its ability to form a strong network. In this thesis, nanocellulose based materials are prepared by evaporation of a liquid medium. The key step in this processing route is a good dispersion of the nanoparticles in the selected matrix. Therefore the importance of surface modification in order to ensure favourable nanocellulose dispersion is clarified in avariety of materials systems.

In Paper I, poly(methyl methacrylate) (PMMA) based fibres prepared by electrospinning were reinforced with nanofibrillated cellulose. Native NFC appeared to show a good compatibility with PMMA matrix in the electrospinning solution and resulting fibres. Furthermore, a new method for mechanical testing of mats with random fibre orientation as well as aligned fibres was developed.

In Paper II, commingled nanopaper structures with carbon nanotubes (CNTs) were prepared. Several surfactants were used to disperse hydrophobic CNTs in water. A nonylphenol phosphate ester (NPPE) was found to work well for both dispersing CNTs in water and providing compatibility with NFC through electrostatic repulsion between the phosphate ester groups of the surfactant and the carboxylate groups of NFC.

In Paper III, a new water based route for functionalization of cellulose nanocrystals was developed. In this approach, inspired by organo-modified layered silicates, quaternary ammonium salts were adsorbed. It was demonstrated that different functionalities (alkyl, phenyl, glycidylor diallyl) can be introduced onto the cellulose and the dispersibility in organic solvents was studied. Subsequently, in Paper IV, nanocomposites with poly(vinyl acetate) (PVAc)were prepared. The effect of modification on the degree of dispersion of the CNC within the matrix was studied as well as the strong effects on the properties of the resulting nanocomposites.

In Paper V, taking advantage of the entangled NFC network and the possibility to tailor the pore size and surface chemistry, lubricant-infused slippery films and coatings based on NFC were prepared for the first time.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , 55 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2013:40
Keyword [en]
Nanocellulose, nanoc omposite, dispersion, surface modification, surfa ctant, poly(methyl methacrylate), poly(vinyl acetate), carbon nanotubes, electrospinning, lubricant - infused surfaces
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:kth:diva-131469ISBN: 978-91-7501-866-9 (print)OAI: oai:DiVA.org:kth-131469DiVA: diva2:656547
Public defence
2013-11-01, F3, Lindstetsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20131016

Available from: 2013-10-16 Created: 2013-10-16 Last updated: 2013-10-16Bibliographically approved
List of papers
1. Micromechanical Tensile Testing of Cellulose-Reinforced Electrospun Fibers Using a Template Transfer Method (TTM)
Open this publication in new window or tab >>Micromechanical Tensile Testing of Cellulose-Reinforced Electrospun Fibers Using a Template Transfer Method (TTM)
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2012 (English)In: Journal of polymers and the environment, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 20, no 4, 967-975 p.Article in journal (Refereed) Published
Abstract [en]

A template transfer method (TTM) and a fiber fixation technique were established for fiber handling and micro tensile stage mounting of aligned and non-aligned electrospun fiber mats. The custom-made template had been precut to be mounted on a variety of collectors, including a rapidly rotating collector used to align the fibers. The method eliminated need for direct physical interaction with the fiber mats before or during the tensile testing since the fiber mats were never directly clamped or removed from the original substrate. By using the TTM it was possible to measure the tensile properties of aligned poly(methyl methacrylate) (PMMA) fiber mats, which showed a 250 % increase in strength and 450 % increase in modulus as compared to a non-aligned system. The method was further evaluated for aligned PMMA fibers reinforced with cellulose (4 wt%) prepared as enzymatically derived nanofibrillated cellulose (NFC). These fibers showed an additional increase of 30 % in both tensile strength and modulus, resulting in a toughness increase of 25 %. The fracture interfaces of the PMMA-NFC fibers showed a low amount of NFC pull-outs, indicating favorable phase compatibility. The presented fiber handling technique is universal and may be applied where conservative estimates of mechanical properties need to be assessed for very thin fibers.

Keyword
Cellulose crystals (NFC), Electrospinning, Micro mechanical tensile testing, PMMA, Template transfer method (TTM)
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-115467 (URN)10.1007/s10924-012-0486-6 (DOI)000312402900009 ()2-s2.0-84871263311 (Scopus ID)
Funder
Sida - Swedish International Development Cooperation Agency
Note

QC 20130116

Available from: 2013-01-16 Created: 2013-01-15 Last updated: 2017-12-06Bibliographically approved
2. Tough nanopaper structures based on cellulose nanofibers and carbon nanotubes
Open this publication in new window or tab >>Tough nanopaper structures based on cellulose nanofibers and carbon nanotubes
2013 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 87, 103-110 p.Article in journal (Refereed) Published
Abstract [en]

Carbon nanotube (CNT) nanocomposites based on CNT in a polymer matrix typically have low strain to failure in tensile loading. Furthermore, mixing of more than a few percent of CNT with either molten thermoplastics or monomers in bulk often results in agglomeration of CNT. Here, multiwalled CNT (MWCNT) are mixed with nanofibrillated cellulose (NFC) in aqueous suspension and filtered into tough nanopaper structures with up to 17 wt% of MWCNT commingled with NFC nanofibrils. Carbon nanotubes were surface treated with a surfactant, and homogenous suspensions of carbon nanotubes in water miscible with the NFC suspension was obtained. NFC/CNT nanopaper structures were characterized for porosity using mercury displacement, and studied by FE-SEM and AFM. Mechanical properties were tested in uniaxial tension and electrical conductivity was measured. The processing route is environmentally friendly and leads to well-mixed structures. Thin coatings as well as thicker films can be prepared, which show a combination of high electrical conductivity, flexibility in bending and high tensile strength.

Keyword
Nanocomposite, Functional composite, Mechanical properties, Atomic force microscopy, Scanning electron microscopy
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-131462 (URN)10.1016/j.compscitech.2013.06.014 (DOI)000326134000015 ()2-s2.0-84883432820 (Scopus ID)
Note

QC 20131016

Available from: 2013-10-16 Created: 2013-10-16 Last updated: 2017-12-06Bibliographically approved
3. Hydrophobic cellulose nanocrystals modified with quaternary ammonium salts
Open this publication in new window or tab >>Hydrophobic cellulose nanocrystals modified with quaternary ammonium salts
2012 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 37, 19798-19805 p.Article in journal (Refereed) Published
Abstract [en]

An environmentally friendly procedure in aqueous solution for the surface modification of cellulose nanocrystals (CNCs) using quaternary ammonium salts via adsorption is developed as inspired by organomodified layered silicates. CNCs with a high carboxylate content of 1.5 mmol g(-1) were prepared by a new route, direct hydrochloric acid hydrolysis of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized nanofibrillated cellulose from a softwood pulp, and characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). Four quaternary ammonium cation surfactants bearing long alkyl, phenyl, glycidyl, and diallyl groups were successfully used to modify CNCs carrying carboxylic acid groups as characterized by Fourier transform infrared spectroscopy (FTIR). The modified CNCs can be redispersed and individualized in an organic solvent such as toluene as observed by scanning transmission electron microscopy (STEM). One may envision removing excess surfactant to obtain CNC with a monolayer of surfactant. The toluene suspension of the modified CNCs showed strong birefringence under crossed polars but no further chiral- nematic ordering was observed. The model surface prepared by the CNCs modified with quaternary ammonium salts bearing C18 alkyl chains showed a significant increase in water contact angle (71 degrees) compared to that of unmodified CNCs (12 degrees). This new series of modified CNCs can be dried from solvent and have the potential to form well-dispersed nanocomposites with non-polar polymers.

Keyword
Tempo-Mediated Oxidation, Radical Polymerization, Native Cellulose, Polyelectrolyte Multilayers, Nanocomposite Materials, Surface Oxidation, Organic-Compounds, Whiskers, Adsorption, Fibers
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-90883 (URN)10.1039/c2jm34355j (DOI)000308099900057 ()2-s2.0-84865706683 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20121109. Updated from manuscript to article in journal.

Available from: 2012-03-02 Created: 2012-03-02 Last updated: 2017-12-07Bibliographically approved
4. Strong surface treatment effects on reinforcement efficiency in biocomposites based on cellulose nanocrystals in poly(vinyl acetate) matrix
Open this publication in new window or tab >>Strong surface treatment effects on reinforcement efficiency in biocomposites based on cellulose nanocrystals in poly(vinyl acetate) matrix
2015 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 16, no 12, 3916-3924 p.Article in journal (Refereed) Published
Abstract [en]

In this work, the problem to disperse cellulose nanocrystals (CNC) in hydrophobic polymer matrices has been addressed through application of an environmentally friendly chemical modification approach inspired by clay chemistry. The objective is to compare the effects of unmodified CNC and modified CNC (modCNC) reinforcement, where degree of CNC dispersion is of interest. Hydrophobic functionalization made it possible to disperse wood-based modCNC in organic solvent and cast well-dispersed nanocomposite films of poly(vinyl acetate) (PVAc) with 1-20 wt % CNC. Composite films were studied by infrared spectroscopy (FT-IR), UV-vis spectroscopy, dynamic mechanical thermal analysis (DMTA), tensile testing, and field-emission scanning electron microscopy (FE-SEM). Strongly increased mechanical properties were observed for modCNC nanocomposites. The reinforcement efficiency was much lower in unmodified CNC composites, and specific mechanisms causing the differences are discussed.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2015
National Category
Biochemistry and Molecular Biology Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-131466 (URN)10.1021/acs.biomac.5b01245 (DOI)000366616700021 ()2-s2.0-84949844757 (Scopus ID)
Note

QC 20160115

Available from: 2013-10-16 Created: 2013-10-16 Last updated: 2017-12-06Bibliographically approved
5. Super-slippery omniphobic self-standing films and coatings based on nanocellulose
Open this publication in new window or tab >>Super-slippery omniphobic self-standing films and coatings based on nanocellulose
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:kth:diva-131468 (URN)
Note

QS 2013

Available from: 2013-10-16 Created: 2013-10-16 Last updated: 2014-11-03Bibliographically approved

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