Publications
132 results found
Mautner A, Mayer F, Hervy M, et al., 2017, Better together: synergy in nanocellulose blends, Philosophical Transactions of the Royal Society A. Mathematical, Physical and Engineering Sciences, Vol: 376, ISSN: 1364-503X
Cellulose nanopapers have gained significantattention in recent years as large-scale reinforcementfor high-loading cellulose nanocomposites, substratesfor printed electronics and filter nanopapers forwater treatment. The mechanical properties ofnanopapers are of fundamental importance forall these applications. Cellulose nanopapers cansimply be prepared by filtering a suspension ofnanocellulose, followed by heat consolidation. It wasalready demonstrated that the mechanical propertiesof cellulose nanopapers can be tailored by the finenessof the fibrils used or by modifying nanocellulosefibrils for instance by polymer adsorption, butnanocellulose blends remain underexplored. In thiswork, we show that the mechanical and physicalproperties of cellulose nanopapers can be tuned bycreating nanopapers from blends of various gradesof nanocellulose, i.e. (mechanically refined) bacterialcellulose or cellulose nanofibrils extracted fromnever-dried bleached softwood pulp by chemical andmechanical pre-treatments. We found that nanopapersmade from blends of two or three nanocellulosegrades show synergistic effects resulting in improvedstiffness, strength, ductility, toughness and physicalproperties.This article is part of a discussion meeting issue‘New horizons for cellulose nanotechnology’.
Kontturi KS, Biegaj K, Mautner A, et al., 2017, Noncovalent Surface Modification of Cellulose Nanopapers by Adsorption of Polymers from Aprotic Solvents, LANGMUIR, Vol: 33, Pages: 5707-5712, ISSN: 0743-7463
Basic adsorption of hydrophobic polymers from aprotic solvents was introduced as a platform technology to modify exclusively the surfaces of cellulose nanopapers. Dynamic vapor sorption demonstrated that the water vapor uptake ability of the nanopapers remained unperturbed, despite strong repellency to liquid water caused by the adsorbed hydrophobic polymer on the surface. This was enabled by the fact that the aprotic solvents used for adsorption did not swell the nanopaper unlike water that is generally applied as the adsorption medium in such systems. As case examples, the adsorptions of polystyrene (PS) and poly(trifluoroethylene) (PF3E) were followed by X-ray photoelectron spectroscopy and water contact angle measurements, backed up with morphological analysis by atomic force microscopy. The resulting nanopapers are useful in applications like moisture buffers where repellence to liquid water and ability for moisture sorption are desired qualities.
Lee K, Daud NJ, 2017, Surface Modification of Nanocellulose, Handbook of Nanocellulose and Cellulose Nanocomposites, 2 Volume Set, Editors: Kargarzadeh, Ahmad, Thomas, Dufresne, Publisher: John Wiley & Sons, Pages: 101-122, ISBN: 9783527338665
With its coverage of a wide variety of materials, important characterization tools and resulting applications, this is an essential reference for beginners as well as experienced researchers.
Hervy M, Santmarti A, Lahtinen P, et al., 2017, Sample geometry dependency on the measured tensile properties of cellulose nanopapers, Materials & Design, Vol: 121, Pages: 421-429, ISSN: 0261-3069
Miniaturised test specimens are often used for the tensile testing of cellulose nanopapers as there are currently no standardised test geometries to evaluate their tensile properties. In this work, we report the influence of test specimen geometries on the measured tensile properties of plant-derived cellulose nanofibres (CNF) and microbially synthesised bacterial cellulose (BC) nanopapers. Four test specimen geometries were studied: (i) miniaturised dog bone specimen with 2 mm width, (ii) miniaturised rectangular specimen with 5 mm width, (iii) standard dog bone specimen with 5 mm width and (iv) standard rectangular specimen with 15 mm width. It was found that the tensile moduli of both CNF and BC nanopapers were not significantly influenced by the test specimen geometries if an independent strain measurement system (video extensometer) was employed. The average tensile strength of the cellulose nanopapers is also influenced by test specimen geometries. It was observed that the smaller the test specimen width, the higher the average tensile strength of the cellulose nanopapers. This can be described by the weakest link theory, whereby the probability of defects present in the cellulose nanopapers increases with increasing test specimen width. The Poisson's ratio and fracture resistance of CNF and BC nanopapers are also discussed.
Song W, Barber K, Lee KY, 2017, Heat-induced bubble expansion as a route to increase the porosity of foam-templated bio-based macroporous polymers, Polymer, Vol: 118, Pages: 97-106, ISSN: 0032-3861
Macroporous polymers were prepared by mechanically frothing a bio-based epoxy resin and hardener mixture to first create air-in-resin liquid foams, followed by curing of these liquid foams. It was found that heating the air-in-resin liquid foams prior to their gelation decreased the viscosity of the resin mixture and increased the pressure of the air bubbles, leading to an isotropic expansion of the air bubbles. This resulted in an increase in the porosity of the resulting foam-templated macroporous polymers from 71% to 85%. Correspondingly, the compressive moduli (E) and strengths (σ) of the foam-templated macroporous polymers decreased from 231 MPa and 5.9 MPa, respectively, to 58 MPa and 1.9 MPa, respectively. This decrease is attributed to an increase in the porosity and pore throat frequency of the foam-templated macroporous polymers when heat was applied to the liquid foams. The deformation of the pores based on in situ SEM micro-compression test of the fabricated foam-templated macroporous polymers is also discussed.
Hervy M, Santmarti A, Lahtinen P, et al., 2017, Sample geometry dependency on the measured tensile properties of cellulose nanopapers, 253rd National Meeting of the American-Chemical-Society (ACS) on Advanced Materials, Technologies, Systems, and Processes, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Kontturi K, Biegaj K, Mautner A, et al., 2017, Exclusive surface modification of cellulose nanopapers by adsorption of polymers from non-aqueous solvents, 253rd National Meeting of the American-Chemical-Society (ACS) on Advanced Materials, Technologies, Systems, and Processes, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Tagarielli V, song Y, li Y, et al., 2017, Measurements of the mechanical response of unidirectional 3D-printed PLA, Materials & Design, Vol: 123, Pages: 154-164, ISSN: 0261-3069
Fully dense PLA blocks were manufactured by 3D-printing, depositing a polymer filament in a single direction via the fusion deposition method (FDM). Specimens were cut from printed blocks using conventional machining and were used to perform tension, compression and fracture experiments along different material directions. The elasto-plastic material response was found to be orthotropic and characterised by a strong tension-compression asymmetry; the material was tougher when loaded in the extrusion direction than in the transverse direction. The response of the unidirectional, 3D-printed material was compared to that of homogeneous injection-moulded PLA, showing that manufacturing by 3D-printing improves toughness; the effects of an annealing thermal cycle on the molecular structure and the mechanical response of the material were assessed.
Fortea-Verdejo M, Bumbaris E, Burgstaller C, et al., 2017, Plant fibre reinforced polymers: where do we stand in terms of tensile properties?, International Materials Reviews, Vol: 62, Pages: 441-464, ISSN: 1743-2804
Plant fibres have a unique set of properties ranging from being stiff and brittle, such as hemp and flax, to more ductile, such as coir, combining these properties with their cost and availability makes them attractive alternative reinforcements for the production of greener composites. This article reviews the tensileproperties ofvarious plant fibreor plant based natural fibre-reinforced polymersreported in the literature. We critically discuss the use of plant fibres as reinforcement for the production of bio-based,renewable or green polymer composites, showing the evolution of the properties of plant fibre composites. The reported tensile properties of plant fibre-reinforced polymer composites arecompared against various renewable and non-renewableengineering/commoditypolymers as well as the tensile propertiesof commercially available randomly oriented glass fibre-reinforced polymers (GFRP). Green composites containing random short plant fibres dohave similar properties to randomly oriented GFRP at a lower overall part weight. Unidirectional plant fibre-reinforced polymers offer better performance than randomly oriented GFRP and could have the potential to be adapted in applications requiring even higher mechanical performance, especially in areas where the useof costly synthetic fibres might be less attractive. Furthermore, plant fibres can also be regarded as effective fillers to replace more expensive polymersand improve the green credentialsof final composite parts. These features may motivate the industry to introduce more plant fibre-based products to the market.
Shamsuddin SR, Lee KY, Bismarck A, 2016, Ductile unidirectional continuous rayon fibre-reinforced hierarchical composites, Composites Part A: Applied Science and Manufacturing, Vol: 90, Pages: 633-641, ISSN: 1359-835X
Endless rayon fibres (Cordenka®) were used to reinforce polyhydroxybutyrate (PHB) nanocomposites containing 2.5 wt.% nanofibrillated cellulose (NFC) to create truly green hierarchical composites. Unidirectional (UD) composites with 50–55% fibre volume fraction were produced using a solvent-free continuous wet powder impregnation method. The composites exhibit ductile failure behaviour with a strain-to-failure of more than 10% albeit using a very brittle matrix. Improvements at a model composite level were translated into higher mechanical properties of UD hierarchical composites. The Young’s moduli of rayon fibre-reinforced (NFC-reinforced) PHB composites were about 15 GPa. The tensile and flexural strength of hierarchical PHB composites increased by 15% and 33% as compared to the rayon fibre-reinforced neat PHB composites. This suggests that incorporation of NFC into the PHB matrix binds the rayon fibres, which does affect the load transfer between the constituents resulting in composites with better mechanical properties.
Ferguson A, Khan U, Walsh M, et al., 2016, Understanding the dispersion and assembly of bacterial cellulose in organic solvents, Biomacromolecules, Vol: 17, Pages: 1845-1853, ISSN: 1526-4602
The constituent nanofibrils of bacterial cellulose are of interest to many researchers because of their purity and excellent mechanical properties. Mechanisms to disrupt the network structure of bacterial cellulose (BC) to isolate bacterial cellulose nanofibrils (BCN) are limited. This work focuses on liquid-phase dispersions of BCN in a range of organic solvents. It builds on work to disperse similarly intractable nanomaterials, such as single-walled carbon nanotubes, where optimum dispersion is seen for solvents whose surface energies are close to the surface energy of the nanomaterial; bacterial cellulose is shown to disperse in a similar fashion. Inverse gas chromatography was used to determine the surface energy of bacterial cellulose, under relevant conditions, by quantifying the surface heterogeneity of the material as a function of coverage. Films of pure BCN were prepared from dispersions in a range of solvents; the extent of BCN exfoliation is shown to have a strong effect on the mechanical properties of BC films and to fit models based on the volumetric density of nanofibril junctions. Such control offers new routes to producing robust cellulose films of bacterial cellulose nanofibrils.
Kamal NAM, Lee K-Y, Bismarck A, 2016, Bovine biomass based microfibrillated cellulose composites, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Lee K, bismarck A, 2016, Single step functionalization of celluloses with differing degrees of reactivity as a route for in situ production of all-cellulose nanocomposites, Nanocomposites, Vol: 1, Pages: 214-222, ISSN: 2055-0332
A method of manufacturing all-cellulose nanocomposites using a single-step functionalization of two different celluloses with differing reactivities is presented. All-cellulose nanocomposites are produced by esterification of microcrystalline cellulose (MCC) in pyridine with hexanoic acid in the presence of bacterial cellulose (BC) followed by solvent removal. Neat MCC is more susceptible to esterification, with an accessible amount of hydroxyl groups of 1.79 compared to BC, with an accessible hydroxyl group content of 0.80. As a result, neat MCC undergoes severe bulk modification, turning into a toluene-soluble cellulose hexanoate (C6-MCC) while BC undergoes surface-only modification. Solution casted C6-MCC films have a tensile modulus and strength of 0.99 GPa and 23.1 MPa, respectively. The presence of 5 wt.% BC in C6-MCC leads to an increase in tensile modulus and strength of the resulting nanocomposites to 1.42 GPa and 28.4 MPa, respectively.
Lee K-Y, Bismarck A, 2016, Bacterial NanoCellulose as Reinforcement for Polymer Matrices, BACTERIAL NANOCELLULOSE: FROM BIOTECHNOLOGY TO BIO-ECONOMY, Editors: Gama, Dourado, Bielecki, Publisher: ELSEVIER SCIENCE BV, Pages: 109-122, ISBN: 978-0-444-63458-0
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- Citations: 9
Fortea-Verdejo M, Lee K-Y, Zimmermann T, et al., 2015, Upgrading flax nonwovens: nanocellulose as binder to produce rigid and robust flax fibre preforms, Composites Part A - Applied Science and Manufacturing, Vol: 83, Pages: 63-71, ISSN: 1359-835X
Typically in flax fibre nonwovens, the fibrous web is mechanically bonded (via entanglement and interlocking of fibres) or thermally bonded (by melting of polymer fibres). Recently, we showed that bacterial cellulose (BC) can be used as effective binder to produce rigid and robust natural fibre nonwovens without the need for polymer binders. Here, we further expand this work to manufacture flax nonwovens by utilising various types of (nano)cellulose, including nanofibrillated cellulose (NFC), BC and pulp fibres. Two preform manufacturing processes are investigated, namely single-step filtration and layer-by-layer filtration. Both BC and NFC serve as excellent binders for loose flax fibres due to their high surface area whilst pulp fibres are a poor binder for flax fibres. This is attributed to the low surface area of pulp compared to BC and NFC, which leads to a lower contact area between flax fibres and pulp. Furthermore, the larger fibre diameter of pulp results in a poorer packing efficiency and, therefore, a higher porosity of 67% compared to preforms made with BC or NFC as binder, which have a porosity of ∼60%. The manufactured preforms possess excellent tensile (View the MathML source, View the MathML source) and flexural (σ = 21.1 MPa, E = 2.2 GPa) properties. Layer-by-layer filtration process results in flax nonwovens, which exhibit even better tensile and flexural properties. This is hypothesised to be due to the better distribution of the fibrous nanocellulose network throughout the preform.
Hervy M, Evangelisti S, Lettieri P, et al., 2015, Life cycle assessment of nanocellulose-reinforced advanced fibre composites, Composites Science and Technology, Vol: 118, Pages: 154-162, ISSN: 0266-3538
The research and development of nanocellulose-reinforced polymer composites have dramatically increased in the recent years due to the possibility of exploiting the high tensile stiffness and strength of nanocellulose. In the work, the environmental impacts of bacterial cellulose (BC)- and nanofibrillated cellulose (NFC)-reinforced epoxy composites were evaluated using life cycle assessment (LCA). Neat polylactide (PLA) and 30% randomly oriented glass fibre-reinforced polypropylene (GF/PP) composites were used as benchmark materials for comparison. Our cradle-to-gate LCA showed that BC- and NFC-reinforced epoxy composites have higher global warming potential (GWP) and abiotic depletion potential of fossil fuels (ADf) compared to neat PLA and GF/PP even though the specific tensile moduli of the nanocellulose-reinforced epoxy composites were higher than neat PLA and GF/PP. However, when the use phase and the end-of-life of nanocellulose-reinforced epoxy composites were considered, the “green credentials” of nanocellulose-reinforced epoxy composites were comparable to that of neat PLA and GF/PP composites. Our life cycle scenario analysis showed that the cradle-to-grave GWP and ADf of BC- and NFC-reinforced epoxy composites could be lower than neat PLA when the composites contains more than 60 vol.-% nanocellulose. Our LCA model suggests that nanocellulose-reinforced epoxy composites with high nanocellulose loading is desired to produce materials with “greener credentials” than the best performing commercially available bio-derived polymer.
Lee K, Quero F, Coveney A, et al., 2015, Stress Transfer Quantification in Gelatin-Matrix Natural Composites with Tunable Optical Properties, Biomacromolecules, Vol: 16, Pages: 1784-1793, ISSN: 1526-4602
This work reports on the preparation and characterization of natural composite materials prepared from bacterial cellulose (BC) incorporated into a gelatin matrix. Composite morphology was studied using scanning electron microscopy and 2D Raman imaging revealing an inhomogeneous dispersion of BC within the gelatin matrix. The composite materials showed controllable degrees of transparency to visible light and opacity to UV light depending on BC weight fraction. By adding a 10 wt % fraction of BC in gelatin, visible (λ = 550 nm) and UV (λ = 350 nm) transmittances were found to decrease by ∼35 and 40%, respectively. Additionally, stress transfer occurring between the gelatin and BC fibrils was quantified using Raman spectroscopy. This is the first report for a gelatin–matrix composite containing cellulose. As a function of strain, two distinct domains, both showing linear relationships, were observed for which an average initial shift rate with respect to strain of −0.63 ± 0.2 cm–1%–1 was observed, followed by an average shift rate of −0.25 ± 0.03 cm–1%–1. The average initial Raman band shift rate value corresponds to an average effective Young’s modulus of 39 ± 13 GPa and 73 ± 25 GPa, respectively, for either a 2D and 3D network of BC fibrils embedded in the gelatin matrix. As a function of stress, a linear relationship was observed with a Raman band shift rate of −27 ± 3 cm–1GPa–1. The potential use of these composite materials as a UV blocking food coating is discussed.
Lee K-Y, Bismarck A, 2015, Single step functionalization of cellulose to produce bacterial cellulose-reinforced derivatised all-cellulose nanocomposites, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Lee K-Y, Blaker J, Murakami R, et al., 2015, Phase behavior of water-in-oil emulsions stabilised solely by hydrophobised bacterial cellulose nanofibrils, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Mautner A, Lee K-Y, Li K, et al., 2015, Designing the porosity of bacterial cellulose nanopapers, Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Mautner A, Lee K-Y, Tammelin T, et al., 2015, Cellulose nanopapers as tight aqueous ultra-filtration membranes, REACTIVE & FUNCTIONAL POLYMERS, Vol: 86, Pages: 209-214, ISSN: 1381-5148
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- Citations: 121
Lee K-Y, Aitomaki Y, Berglund LA, et al., 2014, On the use of nanocellulose as reinforcement in polymer matrix composites, COMPOSITES SCIENCE AND TECHNOLOGY, Vol: 105, Pages: 15-27, ISSN: 0266-3538
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- Citations: 536
Lee K-Y, Blaker JJ, Heng JYY, et al., 2014, pH-triggered phase inversion and separation of hydrophobised bacterial cellulose stabilised Pickering emulsions, REACTIVE & FUNCTIONAL POLYMERS, Vol: 85, Pages: 208-213, ISSN: 1381-5148
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- Citations: 18
Montrikittiphant T, Tang M, Lee K-Y, et al., 2014, Bacterial Cellulose Nanopaper as Reinforcement for Polylactide Composites: Renewable Thermoplastic NanoPaPreg, MACROMOLECULAR RAPID COMMUNICATIONS, Vol: 35, Pages: 1640-1645, ISSN: 1022-1336
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- Citations: 25
Blaker JJ, Lee K-Y, Walters M, et al., 2014, Aligned unidirectional PLA/bacterial cellulose nanocomposite fibre reinforced PDLLA composites, Reactive & Functional Polymers, Vol: 85, Pages: 185-192, ISSN: 1381-5148
In an effort to enhance the properties of polylactide (PLA), we have developed melt-spinning techniques to produce both PLA/nanocellulose composite fibres, and a method akin to layered filament winding followed by compression moulding to produce self-reinforced PLA/nanocellulose composites. Poly(L-lactide) (PLLA) fibres were filled with 2 wt.% neat and modified bacterial cellulose (BC) in an effort to improve the tensile properties over neat PLA fibres. BC increased the viscosity of the polymer melt and reduced the draw-ratio of the fibres, resulting in increased fibre diameters. Nonetheless, strain induced chain orientation due to melt spinning led to PLLA fibres with enhanced tensile modulus (6 GPa) and strength (127 MPa), over monolithic PLLA, previously measured at 1.3 GPa and 61 MPa, respectively. The presence of BC also enhanced the nucleation and growth of crystals in PLA. We further produced PLA fibres with 7 wt.% cellulose nanocrystals (CNCs), which is higher than the percolation threshold (equivalent to 6 vol.%). These fibres were spun in multiple, alternating controlled layers onto spools, and subsequently compression moulded to produce unidirectional self-reinforced PLA composites consisting of 60 vol.% PLLA fibres reinforced with 7 wt.% CNC in a matrix of amorphous PDLLA, which itself contained 7 wt.% of CNC. We observed improvements in viscoelastic properties of up to 175% in terms of storage moduli in bending. Furthermore, strains to failure for PLLA fibre reinforced PDLLA were recorded at 17%.
Nawawi WMFW, Lee K-Y, Murphy RJ, et al., 2014, Fungal chitin-glucan: Renewable biopolymer for nanomaterial application, 248th National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Lee KY, Wong LLC, Bismarck A, 2014, Air-filled emulsions and oil foam templates for renewable macroporous polymers, 248th National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Lau T, Ibrahim D, Wong LLC, et al., 2014, Tailored for simplicity: Air-templated biobased macroporous polymers, 248th National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Lee K-Y, Montrikittiphant T, Min T, et al., 2014, Making the most out of bacterial cellulose: Sustainable thermoplastic "nano-PaPreg", 248th National Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Yata T, Lee K-Y, Dharakul T, et al., 2014, Hybrid Nanomaterial Complexes for Advanced Phage-guided Gene Delivery, MOLECULAR THERAPY-NUCLEIC ACIDS, Vol: 3, ISSN: 2162-2531
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- Citations: 30
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