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  • Journal article
    Mishnaevsky L, Mikkelsen LP, Gaduan AN, Lee KY, Madsen Bet al., 2019,

    Nanocellulose reinforced polymer composites: Computational analysis of structure-mechanical properties relationships

    , Composite Structures, Vol: 224, ISSN: 0263-8223

    © 2019 Elsevier Ltd Structure-mechanical properties relationships of nanocellulose reinforced polymer composites are studied in computational experiments. A code for the generation of 3D unit cell finite element models of nanocellulose reinforced polymers with “snake”-shaped nanocellulose fibrils is developed. The code allows the generation of pre-defined nanocomposites structures, with varied angles between nanocellulose snakes segments and hydrogen bonds between nanocellulose fibrils. In a series of computational studies, it is demonstrated that the nanocellulose reinforcement leads to higher stiffness of the matrix polymer, but makes it more brittle.

  • Journal article
    Suwan K, Waramit S, Przystal J, Stoneham C, Bentayebi K, Asavarut P, Chongchai A, Pothachareon P, Lee K-Y, Topanurak S, Smith T, Gelovani J, Sidman R, Pasqualini R, Arap W, Hajitou Aet al., 2019,

    Next-generation of targeted AAVP vectors for systemic transgene delivery against cancer

    , Proceedings of the National Academy of Sciences of USA, ISSN: 0027-8424

    Bacteriophage (phage) have attractive advantages as delivery sys-tems compared to mammalian viruses, but have been consideredpoor vectors because they lack evolved strategies to confrontand overcome mammalian cell barriers to infective agents. Wereasoned that improved efficacy of delivery might be achievedthrough structural modification of the viral capsid to avoid pre-and post-internalization barriers to mammalian cell transduction.We generated multifunctional hybrid AAV/phage (AAVP) particlesto enable simultaneous display of targeting ligands on the phage’sminor pIII proteins and also degradation-resistance motifs on thevery numerous pVIII coat proteins. This genetic strategy of directedevolution, bestows a next-generation of AAVP particles that fea-ture resistance to fibrinogen adsorption or neutralizing antibodies,and ability to escape endolysosomal degradation. This results insuperior gene transfer efficacyin vitroand also in preclinicalmouse models of rodent and human solid tumors. Thus, the uniquefunctions of our next-generation AAVP particles enable improvedtargeted gene delivery to tumor cells.

  • Journal article
    Karim Z, Svedberg A, Lee K-Y, Khan MJet al., 2019,

    Processing-Structure-Property Correlation Understanding of Microfibrillated Cellulose Based Dimensional Structures for Ferric Ions Removal.

    , Sci Rep, Vol: 9

    In this research article, wood based microfibrillated cellulose (MFC) was studied to gain a better understanding of the process of dependent network formation. Networking potential and obtained properties of the produced dimensional structures could be controlled using opted processing routes. The fabricated dimensional structure, using freeze-drying (FD) is a highly open and porous network (98% porosity) compared to slightly tight, dense and less porous network produced after pressing at 200kN (96% porosity), followed by vacuum-filtered (VF) networks (33% porosity). The porosity (17%) was further decreased when the casting (CS) method was used, further producing a highly dense and compressed network. High water flux (180.8 ± 11 L/m2h) of pressed freeze-dried (PFD) followed by vacuum-filtered (VF) (11.4 ± 1.9 L/m2h) and casting CS (0.7 ± 0.01 L/m2h) were calculated using device. Furthermore, increased water flux (1.4 fold) of Experimental Paper Machine (XPM) based structures was reported in comparison with CS structures. Pore-sized distribution and surface area were measured using Hg porosimetry; they showed an average pore size of 16.5 μm for FD, followed by PFD (8.2 μm) structures. A 27-fold decrease in average pore-size was observed for CS structure in comparison with the FD structures. Highest tensile strength (87 ± 21 MPa) was recorded for CS structures, indicating a more highly compacted network formation compared to VF (82 ± 19 MPa) and PFD (1.6 ± 0.06 MPa). Furthermore, an attempt was made to upscale the VF structures using traditional paper making approach on XMP. Improved tensile strength (73 ± 11 MPa) in machine produced structures is due to alignment of fibers towards machine direction compared to cross directional (43 ± 9 MPa)

  • Journal article
    Dieckmann E, Eleftheriou K, Audic T, Lee KY, Sheldrick L, Cheeseman Cet al., 2019,

    New sustainable materials from waste feathers: Properties of hot-pressed feather/cotton/bi-component fibre boards

    , Sustainable Materials and Technologies, Vol: 20, ISSN: 2214-9937

    Feathers from poultry are an abundant, globally available waste. The current beneficial reuse for feathers involves autoclaving them to produce feather meal, an animal feed with low economic value. This paper reports on the production and performance of new feather-derived materials. These have potential to provide a higher value application for waste feathers. Feather fibres, cotton fibres and polyethylene/polypropylene bi-component fibres (blended 55:20:25 by weight) have been air-laid to form 20 mm thick non-woven pre-forms with a density of 0.14 g cm −2 . These were then hot pressed to produce materials with significantly higher density and improved properties. Optimum materials were formed by hot pressing between 150 and 160 °C at 6 MPa for 1 min. Lower temperatures resulted in poor fibre bonding and fibre pull-out during fracture. Higher temperatures caused thermal degradation of the feather fibres. The optimum feather fibre boards with a density of 0.77 g/cm 3 , corresponding to 31.3% porosity, had tensile strengths of 17.9 MPa a tensile modulus of 1.74 GPa and an elongation at fracture of 5.9%. These samples exhibited fibre fracture during tensile testing. Feather fibre boards have similar tensile strength, density and Young's modulus to particleboard, organic resin particleboard and flake board. Quantitative estimates of the economic and environmental benefits from using feather fibres to form feather fibre boards are discussed. The research advances sustainability by providing a new potential circular economy outlet for waste feathers and is part of on-going research to develop novel applications that exploit the unique properties of feathers.

  • Journal article
    Santmarti A, Teh JW, Lee K-Y, 2019,

    Transparent poly(methyl methacrylate) composites based on bacterial cellulose nanofibre networks with improved fracture resistance and impact strength

    , ACS Omega, Vol: 4, Pages: 9896-9903, ISSN: 2470-1343

    Cellulose nanofibers are often explored as biobased reinforcement for the production of high-performance composite materials. In this work, we fabricated transparent poly(methyl methacrylate) (PMMA) composites consisting of two-dimensional and three-dimensional bacterial cellulose (BC) nanofiber networks. Three different composite designs consisting of 1 vol % BC loading were fabricated and studied: (i) composites with a three-dimensional BC nanofiber network embedded uniformly throughout the PMMA matrix; (ii) sandwich-structured construction consisting of three-dimensional BC–PMMA sandwiched between two neat PMMA sheets; and (iii) dried and well-consolidated two-dimensional BC nanofiber network embedded in a PMMA matrix. All fabricated model BC–PMMA composites were found to be optically transparent, but PMMA composites consisting of the two-dimensional BC nanofiber network possessed higher light transmittance (73% @550 nm) compared to the three-dimensional BC nanofiber network counterparts (63% @550 nm). This is due to the higher specific surface area of the three-dimensional BC nanofiber network, which led to more light scattering. Nevertheless, it was found that both two-dimensional and three-dimensional BC nanofiber networks serve as excellent stiffening agents for PMMA matrix, improving the tensile modulus of the resulting composites by up to 30%. However, no improvement in tensile strength was observed. The use of three-dimensional BC nanofiber network led to matrix embrittlement, reducing the tensile strain-at-failure, fracture resistance, and Charpy impact strength of the resulting BC–PMMA composites. When the BC nanofiber network was used as two-dimensional reinforcement, cracks were observed to propagate through the debonding of BC nanofiber network, leading to higher fracture toughness and Charpy impact strength. These novel findings could open up further opportunities in the design of novel optically transparent polymeric composite lami

  • Journal article
    Fazli Wan Nawawi WM, Lee KY, Kontturi E, Murphy RJ, Bismarck Aet al., 2019,

    Chitin nanopaper from mushroom extract: natural composite of nanofibers and glucan from a single biobased source

    , ACS Sustainable Chemistry and Engineering, Vol: 7, Pages: 6492-6496, ISSN: 2168-0485

    An isolation method with mild mechanical agitation and no acidic extraction step from a mushroom substrate resulted in chitin nanofibers (ChNFs) with large shares of retained glucans (50-65%). The subsequent chitin nanopapers exhibited exceptionally high tensile strengths of >200 MPa and moduli of ca. 7 GPa, which were largely attributed to the preserved glucans in the mixture, imparting a composite nature to the nanopapers. The isolation method for ChNFs is notably different from the conventional process with crustacean chitin sources that do not incorporate glucans and where an acidic extraction step for the removal of minerals must always be included.

  • Journal article
    Mohammed C, Mahabir S, Mohammed K, John N, Lee K-Y, Ward Ket al., 2019,

    Calcium Alginate Thin Films Derived from Sargassum natans for the Selective Adsorption of Cd2+, Cu2+, and Pb2+ Ions

    , Industrial & Engineering Chemistry Research, Vol: 58, Pages: 1417-1425, ISSN: 0888-5885

    The Caribbean has seen the influx of Sargassum, affecting the livelihood of communities. Sodium alginate extracted from Sargassum is known for its cross-linking properties, making the seaweed attractive as an adsorbent. Hence, the use of calcium alginate thin films can decrease the mass transfer resistance found in commonly used alginate beads, resulting in increased adsorption efficiency. This Article discusses the potential of calcium alginate thin films for Pb2+, Cu2+, and Cd2+ ion adsorption. Pb2+, Cu2+, and Cd2+ adsorption fitted the Langmuir isotherm well with capacities of 0.80, 0.10, and 0.02 mmol of metal/g, respectively, for Sargassum. Kinetic studies showed that the ions followed the pseudo-second-order model, elucidating that ion exchange governed adsorption. Furthermore, NMR characterization showed that G-block monomers influenced kinetic parameters and selectivity in the following order: Pb2+ > Cu2+ > Cd2+

  • Journal article
    Song W, Tagarielli VL, Lee KY, 2018,

    Enhancing the fracture resistance and impact toughness of mechanically frothed epoxy foams with hollow elastomeric microspheres

    , Macromolecular Materials and Engineering, Vol: 303, ISSN: 1438-7492

    Nonporous elastomeric particles are often employed to improve the toughness of brittle epoxy foams but this also decreases their compressive strength and stiffness. Herein, a novel strategy utilizing hollow elastomeric microspheres as toughening agent for epoxy foams is presented. The addition of 0.5 wt.% hollow elastomeric microspheres into epoxy foam leads to a 15% increase in critical stress intensity factor (K1c) to 0.38 MPa m0.5and 33% increase in Charpy impact strength (acU) to 1.05 kJ m−2, respectively, compared to unfilled epoxy foam (K1c = 0.33 MPa m0.5and acU= 0.79 kJ m−2). However, a further increase in the hollow elastomeric microsphere concentration to 1.0 wt.% leads to microsphere agglomeration, which reduces both K1cand acUto 0.35 MPa m0.5and 0.93 kJ m−2, respectively. Nevertheless, the added hollow elastomeric microspheres do not lead to a reduction in the quasi-static compressive properties of the epoxy foams.

  • Journal article
    Hervy M, Bock F, Lee KY, 2018,

    Thinner and better: (Ultra-)low grammage bacterial cellulose nanopaper-reinforced polylactide composite laminates

    , Composites Science and Technology, Vol: 167, Pages: 126-133, ISSN: 0266-3538

    One of the rate-limiting steps in the large-scale production of cellulose nanopaper-reinforced polymer composites is the time consuming dewatering step to produce the reinforcing cellulose nanopapers. In this work, we show that the dewatering time of bacterial cellulose (BC)-in-water suspension can be reduced by reducing the grammage of BC nanopaper to be produced. The influence of BC nanopaper grammage on the tensile properties of BC nanopaper-reinforced polylactide (PLLA) composites is also investigated in this work. BC nanopaper with grammages of 5, 10, 25 and 50 g m−2 were produced and it was found that reducing the grammage of BC nanopaper from 50 g m−2 to 5 g m−2 led to a three-fold reduction in the dewatering time of BC-in-water suspension. The porosity of the BC nanopapers, however, increased with decreasing BC nanopaper grammage. While the tensile properties of BC nanopapers were found to decrease with decreasing BC nanopaper grammage, no significant difference in the reinforcing ability of BC nanopaper with different grammages for PLLA was observed. All PLLA composite laminates reinforced with BC nanopapers possessed similar tensile modulus of 10.5–11.8 GPa and tensile strength of 95–111 MPa, respectively, at a BC loading fraction  = 39–53 vol.-%, independent of the grammage and tensile properties of the reinforcing BC nanopaper.

  • Journal article
    Mohammed A, Bissoon R, Bajnath E, Mohammed K, Lee T, Bissram M, John N, Jalsa NK, Lee KY, Ward Ket al., 2018,

    Multistage extraction and purification of waste Sargassum natans to produce sodium alginate: an optimization approach

    , Carbohydrate Polymers, Vol: 198, Pages: 109-118, ISSN: 0144-8617

    Sargassum in the Caribbean region has affected the livelihood of several coastal communities due to the influx of large quantities of the seaweed in recent times. This article seeks to explore how waste Sargassum natans can be utilized to produce sodium alginate. The novelty in this research lies in the optimization process, whereby multistage extraction and precipitation were investigated over commonly used single stage processing, in an effort to maximize both yield and purity. The results showed that a maximum yield of 19% was observed after 1 stage, while the purity was 74% after 4 stages. In addition, optimization of the multistage precipitation process using the Global Optimization Toolbox in MATLAB R2017b provided a novel model which indicated that a compromise between the maximum purity and yield can be obtained at 3 stages; 71–74% and 12–16% respectively. Furthermore, characterization was done using FTIR and NMR, with results comparable to a commercial sodium alginate brand, giving absorption bands at 1610 cm−1and 1395 cm-1and an M/G ratio of 0.51 respectively.

  • Journal article
    Narducci F, Lee K, Pinho ST, 2018,

    Realising damage-tolerant nacre-inspired CFRP

    , Journal of the Mechanics and Physics of Solids, Vol: 116, Pages: 391-402, ISSN: 0022-5096

    Inthiswork,anacre-inspiredCarbonFibreReinforcedPolymer(CFRP)compositeis designed,synthesisedandtested. Analyticalandnumericalmodelsareusedtodesign a tiled micro-structure, mimicking the staggered arrangement of ceramic platelets in nacreandexploitinggeometricalinterlocksforcrackdeflectionanddamagediffusion. The designed pattern of tiles is then laser-engraved in the laminate plies. In order to increase the damage-spreading capability of the material, a thin layer of poly(lactic acid) (PLA) is film-cast on the interlaminar region, both as a continuous film and as a pattern of fractal-shaped patches. Three-point bending tests show how the nacre-like micro-structure succeeds in deflecting cracks, with damage diffusion being significantly improved by the addition of PLA at the interface between tiles. It is observed that a texture of discontinuous fractal-shaped PLA patches can increase damage diffusion, by promoting the unlocking of tiles whilst preserving the interface strength.

  • Journal article
    Narducci F, Lee KY, Pinho ST, 2018,

    Interface micro-texturing for interlaminar toughness tailoring: a film-casting technique

    , Composites Science and Technology, Vol: 156, Pages: 203-214, ISSN: 0266-3538

    In this work, we developed a film-casting technique to deposit thin (13 μm) layers of poly(lactic acid) (PLA) on the interface of carbon/epoxy prepregs, with the aim of increasing the interlaminar toughness. PLA patches with fractal shape were explored, based on preliminary results showing that the toughening effect increases when PLA is deposited at multiple scales simultaneously. Double Cantilever Beam (DCB) and 4-point End-Notched Flexure (4ENF) tests showed an increase in interlaminar toughness of, respectively, up to 80% for Mode I and 12% for Mode II. This is specially remarkable because the interface thickness is only 13 μm. Moreover, it was demonstrated that this technique can promote interaction between neighbouring layers where PLA has been cast, thus triggering fibre bridging and leading to a further enhancement of toughness.

  • Book chapter
    Santmarti A, Lee K, 2018,

    Crystallinity and Thermal Stability of Nanocellulose

    , Nanocellulose and Sustainability Production, Properties, Applications, and Case Studies, Editors: Lee, Publisher: Taylor and Francis / CRC Press, Pages: 67-86, ISBN: 9781498761031
  • Book
    Lee K-Y, 2018,

    Nanocellulose and Sustainability: Production, Properties, Applications, and Case Studies

    , Publisher: CRC Press/Taylor Francis, ISBN: 9781498761031
  • Journal article
    Hervy M, Blaker JJ, Braz AL, Lee KYet al., 2017,

    Mechanical response of multi-layer bacterial cellulose nanopaper reinforced polylactide laminated composites

    , Composites Part A: Applied Science and Manufacturing, Vol: 107, Pages: 155-163, ISSN: 1359-835X

    In this study, we investigated the mechanical response of polylactide (PLLA) reinforced with multiple layers of BC nanopaper. Laminated composites consisting of 1, 3, 6 and 12 sheet(s) of BC nanopaper were produced. It was observed that increasing the number of BC nanopaper led to an increase in the porosity of the resulting BC nanopaper-reinforced PLLA laminated composites. The tensile moduli of the laminated composites were found to be ∼12.5 – 13.5 GPa, insensitive to the number of sheets of BC nanopaper in the composites. However, the tensile strength of the laminated composites decreased by 21% (from 121 MPa to 95 MPa) when the number of reinforcing BC nanopaper sheets increased from 1 to 12 sheets. This was attributed to the presence and severity of the scale-induced defects increased with increasing BC nanopaper sheets in the PLLA laminated composites.

  • Journal article
    Mautner A, Mayer F, Hervy M, Lee K-Y, Bismarck Aet 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’.

  • Journal article
    Kontturi KS, Biegaj K, Mautner A, Woodward RT, Wilson BP, Johansson L-S, Lee K-Y, Heng JYY, Bismarck A, Kontturi Eet 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.

  • Book chapter
    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.

  • Journal article
    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.

  • Journal article
    Tagarielli V, song Y, li Y, song W, yee K, lee KYet 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.

  • Journal article
    Hervy M, Santmarti A, Lahtinen P, Tammelin T, Lee Ket 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.

  • Journal article
    Fortea-Verdejo M, Bumbaris E, Burgstaller C, Bismarck A, Lee Ket 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.

  • Journal article
    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.

  • Book chapter
    Lee KY, Bismarck A, 2016,

    Bacterial NanoCellulose as Reinforcement for Polymer Matrices

    , Bacterial Nanocellulose: From Biotechnology to Bio-Economy, Pages: 109-122, ISBN: 9780444634580

    © 2016 Elsevier B.V. All rights reserved. Bacterial NanoCellulose (BNC) is a promising material for the production of high performance renewable composites because of its high tensile properties, low density, and low toxicity. In this chapter, we start with the discussion of both theoretical and experimental tensile properties of nanometer-scale cellulose fibrils, more commonly known as nanocellulose. This is then followed by what neat BNC offers as nanoreinforcement for polymers. The tensile properties of various neat BNC-reinforced polymer nanocomposites published in the literature to date were reviewed and are tabulated. In addition we critically discuss the micromechanical models that are suitable to describe the tensile properties of BNC-reinforced polymer nanocomposites.

  • Journal article
    Ferguson A, Khan U, Walsh M, Lee KY, Bismarck A, Shaffer MS, Coleman JN, Bergin SDet 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.

  • Journal article
    Lee K, bismarck A, Lee K, bismarck Aet al., 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.

  • Conference paper
    Lee KY, Bismarck A, Lee KY, Bismarck Aet al., 2016,

    Single step functionalisation of celluloses with differing degrees of reactivity as a route for in-situ production of all-cellulose nanocomposites

    © 2016, European Conference on Composite Materials, ECCM. All rights reserved. A method of manufacturing all-cellulose nanocomposites using a single step functionalisation 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. As a result, neat MCC undergoes severe bulk modification, turning into a toluene-soluble cellulose hexanoate (C6-MCC) whilst BC undergoes surface-only modification. The 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.

  • Journal article
    Fortea-Verdejo M, Lee K-Y, Zimmermann T, Bismarck Aet 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.

  • Journal article
    Hervy M, Evangelisti S, Lettieri P, Lee Ket 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.

  • Journal article
    Lee K, Quero F, Coveney A, Lewandowska AE, Richardson RM, Díaz-Calderón P, Eichhorn SJ, Ashraf Alam M, Enrione Jet 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.

  • Journal article
    Mautner A, Lee K-Y, Tammelin T, Mathew AP, Nedoma AJ, Li K, Bismarck Aet al., 2015,

    Cellulose nanopapers as tight aqueous ultra-filtration membranes

    , REACTIVE & FUNCTIONAL POLYMERS, Vol: 86, Pages: 209-214, ISSN: 1381-5148
  • Journal article
    Lee K-Y, Aitomaki Y, Berglund LA, Oksman K, Bismarck Aet 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
  • Journal article
    Lee K-Y, Blaker JJ, Heng JYY, Murakami R, Bismarck Aet 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
  • Journal article
    Montrikittiphant T, Tang M, Lee K-Y, Williams CK, Bismarck Aet al., 2014,

    Bacterial Cellulose Nanopaper as Reinforcement for Polylactide Composites: Renewable Thermoplastic NanoPaPreg

    , MACROMOLECULAR RAPID COMMUNICATIONS, Vol: 35, Pages: 1640-1645, ISSN: 1022-1336
  • Journal article
    Blaker JJ, Lee K-Y, Walters M, Drouet M, Bismarck Aet 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%.

  • Journal article
    Yata T, Lee K-Y, Dharakul T, Songsivilai S, Bismarck A, Mintz PJ, Hajitou Aet al., 2014,

    Hybrid Nanomaterial Complexes for Advanced Phage-guided Gene Delivery

    , MOLECULAR THERAPY-NUCLEIC ACIDS, Vol: 3, ISSN: 2162-2531
  • Book chapter
    Lee K-Y, Bismarck A, 2014,

    Handbook of Green Materials (volume 3): Processing Technologies, Properties and Applications

    , Handbook of Green Materials: Processing Technologies, Properties and Applications (in 4 Volumes), Editors: Oksman, Mathew, Bismarck, ISBN: 9789814566452
  • Book chapter
    Lee K-Y, Bismarck A, 2014,

    Chemical surface modification and adhesion of nanocellulose

    , Handbook of Green Materials: Processing Technologies, Properties and Applications (in 4 Volumes), Editors: Oksman, Mathew, Bismarck, ISBN: 9789814566452
  • Book chapter
    Lee K-Y, Bismarck A, 2014,

    Advanced bacterial cellulose composites

    , Handbook of Green Materials: Processing Technologies, Properties and Applications (in 4 Volumes), Editors: Oksman, Mathew, Bismarck, ISBN: 9789814566452
  • Journal article
    Lee K-Y, Shamsuddin SR, Fortea-Verdejo M, Bismarck Aet al., 2014,

    Manufacturing Of Robust Natural Fiber Preforms Utilizing Bacterial Cellulose as Binder

    , Jove-Journal of Visualized Experiments, ISSN: 1940-087X
  • Journal article
    Mautner A, Lee K-Y, Lahtinen P, Hakalahti M, Tammelin T, Li K, Bismarck Aet al., 2014,

    Nanopapers for organic solvent nanofiltration

    , Chemical Communications, Vol: 50, Pages: 5778-5781, ISSN: 1364-548X

    Would it not be nice to have an organic solvent nanofiltration membrane made from renewable resources that can be manufactured as simply as producing paper? Here the production of nanofiltration membranes made from nanocellulose by applying a papermaking process is demonstrated. Manufacture of the nanopapers was enabled by inducing flocculation of nanofibrils upon addition of trivalent ions.

  • Book chapter
    Lee K-Y, Bismarck A, 2014,

    Creating hierarchical structures in (ligno)cellulosic fibres for green composites

    , Natural Fibre Composites, Editors: Hodzic, Shanks, Publisher: Woodhead Publishing, ISBN: 9780857099228
  • Journal article
    Lee K-Y, Blaker JJ, Murakami R, Heng JYY, Bismarck Aet al., 2014,

    Phase Behavior of Medium and High Internal Phase Water-in-Oil Emulsions Stabilized Solely by Hydrophobized Bacterial Cellulose Nanofibrils

    , LANGMUIR, Vol: 30, Pages: 452-460, ISSN: 0743-7463
  • Journal article
    Lee K-Y, Buldum G, Mantalaris A, Bismarck Aet al., 2014,

    More Than Meets the Eye in Bacterial Cellulose: Biosynthesis, Bioprocessing, and Applications in Advanced Fiber Composites

    , Macromolecular Bioscience, Vol: 14, Pages: 10-32, ISSN: 1616-5195

    Bacterial cellulose (BC) nanofibers are one of the stiffest organic materials produced by nature. It consists of pure cellulose without the impurities that are commonly found in plant-based cellulose. This review discusses the metabolic pathways of cellulose-producing bacteria and the genetic pathways of Acetobacter xylinum. The fermentative production of BC and the bioprocess parameters for the cultivation of bacteria are also discussed. The influence of the composition of the culture medium, pH, temperature, and oxygen content on the morphology and yield of BC are reviewed. In addition, the progress made to date on the genetic modification of bacteria to increase the yield of BC and the large-scale production of BC using various bioreactors, namely static and agitated cultures, stirred tank, airlift, aerosol, rotary, and membrane reactors, is reviewed. The challenges in commercial scale production of BC are thoroughly discussed and the efficiency of various bioreactors is compared. In terms of the application of BC, particular emphasis is placed on the utilization of BC in advanced fiber composites to manufacture the next generation truly green, sustainable and renewable hierarchical composites.

  • Journal article
    Lau THM, Wong LLC, Lee K-Y, Bismarck Aet al., 2013,

    Tailored for simplicity: creating high porosity, high performance bio-based macroporous polymers from foam templates

    , Green Chemistry, Vol: 16, Pages: 1931-1940, ISSN: 1744-1560

    Mechanical frothing can be used to create gas–liquid monomer foams, which can then be subsequently polymerised to produce macroporous polymers. Until recently, this technique was limited to producing low porosity macroporous polymers with poor pore morphology and compression properties. In this study, we show that high porosity (75–80%) biobased macroporous polymers with excellent mechanical compression properties (E = 163 MPa, σ = 4.9 MPa) can be produced by curing of epoxy resin foams made by mechanical frothing. The key to this is to utilise the very viscous nature and very short working time of a biobased epoxy resin. It was found that increasing the frothing time of the biobased epoxy resin reduces the pore diameter of the resulting macroporous polymers. These macroporous polymers were also found to be partially interconnected. The compression properties of the macroporous polymers with smaller average pore diameter were found to be higher than those of foams with larger pore diameters. Unlike emulsion templating, which uses high internal phase emulsions to produce macroporous polymers, called polyHIPEs, the mechanical frothing technique has the advantage of creating macroporous polymers from monomers which cannot be easily emulsified.

  • Journal article
    Tang M, Purcell M, Steele JAM, Lee K-Y, McCullen S, Shakesheff KM, Bismarck A, Stevens MM, Howdle SM, Williams CKet al., 2013,

    Porous Copolymers of epsilon-Caprolactone as Scaffolds for Tissue Engineering

    , MACROMOLECULES, Vol: 46, Pages: 8136-8143, ISSN: 0024-9297
  • Journal article
    Seydibeyoglu MO, Misra M, Mohanty A, Blaker JJ, Lee K-Y, Bismarck A, Kazemizadeh Met al., 2013,

    Green polyurethane nanocomposites from soy polyol and bacterial cellulose

    , JOURNAL OF MATERIALS SCIENCE, Vol: 48, Pages: 2167-2175, ISSN: 0022-2461
  • Journal article
    Lee K-Y, Qian H, Tay FH, Blaker JJ, Kazarian SG, Bismarck Aet al., 2013,

    Bacterial cellulose as source for activated nanosized carbon for electric double layer capacitors

    , JOURNAL OF MATERIALS SCIENCE, Vol: 48, Pages: 367-376, ISSN: 0022-2461
  • Journal article
    Quero F, Eichhorn SJ, Nogi M, Yano H, Lee K-Y, Bismarck Aet al., 2012,

    Interfaces in Cross-Linked and Grafted Bacterial Cellulose/Poly(Lactic Acid) Resin Composites

    , JOURNAL OF POLYMERS AND THE ENVIRONMENT, Vol: 20, Pages: 916-925, ISSN: 1566-2543
  • Journal article
    Lee K-Y, Bharadia P, Blaker JJ, Bismarck Aet al., 2012,

    Short sisal fibre reinforced bacterial cellulose polylactide nanocomposites using hairy sisal fibres as reinforcement

    , COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING, Vol: 43, Pages: 2065-2074, ISSN: 1359-835X

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