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  • 101. Mathew, Aji P.
    et al.
    Packirisamy, S.
    Mahatma Gandhi University.
    Radusch, H.J.
    Martin Luther Universität.
    Thomas, Sabu
    Effect of initiating system, blend ratio and crosslink density on the mechanical properties and failure topography of nano-structured full-interpenetrating polymer networks from natural rubber and polystyrene2001In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 37, no 9, p. 1921-1934Article in journal (Refereed)
    Abstract [en]

    The mechanical performance of full-interpenetrating polymer networks (IPNs) based on natural rubber/polystyrene (NR/PS) system has been studied in detail. The IPNs were prepared using different initiators viz., benzoyl peroxide (BPO), azo-bis-isobutyronitrile (AIBN), and dicumyl peroxide (DCP) and the effect of initiating systems on the properties was studied. It was observed that in all cases the IPNs initiated using DCP showed a superior property compared to BPO and AIBN initiated ones. The crosslink density of the IPN was varied by varying the percent of divinyl benzene (crosslinking agent of PS) and the effect of crosslink density on the properties has been studied. The stress-strain behaviour, tensile strength, Young's modulus, elongation at break, tear strength, tension set and tensile set were determined. The effects of strain rate on tensile properties were analysed. The studies on the morphology using scanning electron microscopy showed an increase in phase mixing on increasing the PS content and PS crosslinking. However, high level of PS content and PS crosslinking lead to a decrease in phase mixing. The morphology studies using TEM revealed the interesting fact that NR/PS IPN system was nano-structured. The fracture surfaces of tensile and tear specimens were studied using scanning electron microscopy, to get a clear picture of the mechanism of failure.

  • 102. Mathew, Aji P.
    et al.
    Packirisamy, S.
    Vikram Sarabhai Space Centre.
    Stephen, Ranimol
    Mahatma Gandhi University.
    Thomas, Sabu
    Mahatma Gandhi University.
    Transport of aromatic solvents through natural rubber/polystyrene (NR/PS) interpenetrating polymer network membranes2002In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 20, no 1-2, p. 213-227Article in journal (Refereed)
    Abstract [en]

    A series of interpenetrating polymer network membranes have been synthesised from natural rubber and polystyrene by the sequential polymerisation technique. The transport of aromatic hydrocarbons through semi- and full-interpenetrating polymer network membranes (IPNs) have been studied in detail by tracing the solvent uptake up to equilibrium. The sorption was carried out in a series of aromatic solvents viz. benzene, toluene and xylene. The effect of temperature on swelling is studied by carrying out the experiments in toluene in the temperature range of 30-75 °C. The effects of blend ratio, crosslinker content and nature of initiator on the diffusion of various solvents were analysed. It was found that in all cases, the uptake value increased by about 50% as the PS content decreased from 70-30%. The diffusion, sorption and permeation coefficients were evaluated. As the crosslink density was increased, the uptake decreased by 40%. Kinetic and thermodynamic parameters were evaluated from diffusion experiments. The diffusion profiles were compared with theoretical predictions. The influence of swelling on the mechanical performance of the membranes has been investigated by conducting tensile testing of swollen specimens.

  • 103. Mathew, Aji P.
    et al.
    Packirisamy, S.
    PSC Division, VSSC.
    Thomas, Sabu
    Mahatma Gandhi University.
    Studies on the thermal stability of natural rubber/polystyrene interpenetrating polymer networks: thermogravimetric analysis2001In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 72, no 3, p. 423-439Article in journal (Refereed)
    Abstract [en]

    The thermal degradation of natural rubber/polystyrene (NR/PS) interpenetrating polymer networks (IPNs) was studied and the effects of blend ratio, crosslink level and initiating system were analysed. The thermogravimetric analysis (TGA) shows that the IPNs are more stable than the pure components. The full-IPNs have better stability than semi-IPNs which is due to higher entanglement density of full-IPNs. The initial decomposition temperature and temperature for 50% decomposition (T50) increase with increase in concentration and crosslinker level of the plastic phase. The kinetics of degradation were analysed using nine mechanistic equations. The kinetic parameters such as activation energy, Arrhenius parameter and entropy of activation were determined. Thermal ageing studies of the samples were also conducted. The IPNs aged for 72 h at 100°C showed enhanced mechanical strength due to crosslinking on post curing.

  • 104. Mathew, Aji P.
    et al.
    Thielemans, W.
    Ecole Française de Papeterie et des Industries Graphiques, Institut National Polytechique de Grenoble (EFPG-INGP).
    Dufresne, A.
    Centre de Recherches sur les Macromolécules Végétales (CERMAV-CNRS), Université Joseph Fourier.
    Mechanical properties of nanocomposites from sorbitol plasticized starch and tunicin whiskers2008In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 109, no 6, p. 4065-4074Article in journal (Refereed)
    Abstract [en]

    Nanocomposite materials were obtained using sorbitol plasticized waxy maize starch as matrix and tunicin whiskers as the reinforcement. The effect of filler load (0-25 wt % whiskers) and the relative humidity levels (0-98%) on the mechanical behavior of the films are discussed for linear and nonlinear deformation. The performance of the films is explained, based on the morphology and structural behavior of the composite materials (Mathew and Dufresne, Biomacromolecules 2002, 3, 609). The nanocomposites exhibit good mechanical strength due to the strong interaction between tunicin whiskers, matrix, plasticizer (sorbitol), and water, and due to the ability of the cellulose filler to form a rigid three-dimensional network. The evolution of Tg as a function of relative humidity level and filler load is studied in detail. A decrease in crystallinity of the amylopectin phase is observed at high filler loads, due to the resistance to chain rearrangement imposed by the whiskers. The mechanical strength increased proportionally with filler loads, showing an effective stress transfer from the matrix to the whiskers. An even distribution of whiskers (as determined by SEM) and plasticizer in the matrix contributes to the mechanical performance. The mechanical properties of the nanocomposites showed a strong dependence on relative humidity conditions

  • 105. Mathew, Aji P.
    et al.
    Thomas, Sabu
    Izod impact behavior of natural rubber/polystyrene interpenetrating polymer networks2001In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 50, no 2-3, p. 154-163Article in journal (Refereed)
    Abstract [en]

    The impact behavior of semi and full interpenetrating polymer networks based on natural rubber (NR) and polystyrene (PS) has been studied with special reference to blend ratio and cross-linking level of PS phase. As the PS cross-linker level increases up to 4% an increase in impact strength values was observed. This behavior was explained based on blend morphology and the fractography. It was also found that in moderately cross-linked IPNs, the blend composition with 70% PS showed maximum impact strength values. At higher cross-linking levels, samples with 60% PS showed maximum impact strength values. The fracture surface morphology satisfactorily explained the nature of failure and impact performance in all cases. Addition of NR to PS has changed the failure mechanism from crazing to shear yielding

  • 106.
    Mautner, Andreas
    et al.
    Polymer & Composite Engineering (PaCE) Group, Department of Chemical Engineering, Imperial College London, South Kensington Campus.
    Lee, Koon-Yang
    Department of Chemical Engineering, University College London.
    Tammelin, Tekla
    VTT Technical Research Centre of Finland, Espoo.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nedoma, Alisyn J.
    Polymer & Composite Engineering (PaCE) Group, Department of Chemical Engineering, Imperial College London, South Kensington Campus.
    Li, Kang
    Polymer & Composite Engineering (PaCE) Group, Department of Chemical Engineering, Imperial College London, South Kensington Campus.
    Bismarck, Alexander
    Vienna University of Technology, Polymer & Composite Engineering (PaCE) Group, Department of Chemical Engineering, Imperial College London, South Kensington Campus.
    Cellulose nanopapers as tight aqueous ultra-filtration membranes2015In: Reactive & functional polymers, ISSN 1381-5148, E-ISSN 1873-166X, Vol. 86, p. 209-214Article in journal (Refereed)
    Abstract [en]

    Recently, we have demonstrated the use of wood-derived nanocellulose papers, herein termed nanopapers, for organic solvent nanofiltration applications. In this study, we extend the use of these nanopapers to tight ultrafiltration (UF) membranes. The feasibility of such nanopaper-based UF membranes intended for use in water purification is shown. Four types of nanocelluloses, namely bacterial cellulose, wood-derived nanocellulose, TEMPO-oxidized cellulose nanofibrils and cellulose nanocrystals, were used as raw materials for the production of these nanopaper-based membranes. The resulting nanopapers exhibit a transmembrane permeance in the range of commercially available tight UF membranes with molecular weight cut-offs ranging from 6 to 25 kDa, which depends on the type of nanocellulose used. These molecular weight cut-offs correspond to average pore sizes of a few nanometres. The rejection performance of the nanopapers is on the border of nanofiltration and UF. We demonstrate that the pore size of the nanopapers can be controlled by using different types of nanocellulose fibrils.

  • 107.
    Mautner, Andreas
    et al.
    Imperial College London, Polymer & Composite Engineering (PaCE) Group, Institute for Materials Chemistry & Research, University of Vienna.
    Maples, Henry A.
    Polymer & Composite Engineering (PaCE) Group, Department of Chemical Engineering, Imperial College London, South Kensington Campus.
    Sehaqui, Houssine
    Applied Wood Materials Laboratory, Swiss Federal Laboratories for Materials Science and Technology (EMPA), CH-8600 Dübendorf, Swiss Federal Laboratories for Materials Testing and Research (EMPA).
    Zimmermann, Tanja
    Swiss Federal Laboratories for Materials Testing and Research (EMPA), Applied Wood Materials Laboratory, Swiss Federal Laboratories for Materials Science and Technology (EMPA), CH-8600 Dübendorf.
    Larraya, Uxua Perez de
    Cemitec, Polígono Mocholí, Navarra.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lai, Chi Yan
    Department of Chemical Engineering, Imperial College London.
    Li, Kang
    Imperial College London, Department of Chemical Engineering, London.
    Bismarck, Alexander
    Vienna University of Technology, Polymer & Composite Engineering (PaCE) Group, Department of Chemical Engineering, Imperial College London, South Kensington Campus.
    Nitrate removal from water using a nanopaper ion-exchanger2016In: Environmental Science: Water Research & Technology, ISSN 2053-1400, Vol. 2, p. 117-124Article in journal (Refereed)
    Abstract [en]

    Nitrates seriously affect drinking water quality. We herein present a process for the efficient removal of nitrates from water using a nanopaper ion-exchanger, which can be operated in flow-through conditions. The nanopaper ion-exchanger was produced from nanofibrillated cellulose obtained from fibre sludge, a paper-production waste stream, using a simple paper-making process. The cellulose nanofibrils were modified with quaternary trimethylammonium groups. The performance of these cationic nanopaper ion-exchangers was assessed with respect to their permeance and nitrate adsorption. Nitrates could be successfully captured onto the cationic nanopaper and thus rejected from contaminated water during dynamic filtration experiments. The ion-exchange nanopaper had adsorption capacities in the range of commercial available adsorbers but with the advantage of reduced contact time.

  • 108.
    Mikkonen, Kirsi
    et al.
    Department of Applied Chemistry and Microbiology, University of Helsinki.
    Mathew, Aji P.
    Pirkkalainen, Kari
    Department of Physics, University of Helsinki.
    Serimaa, Ritva
    Department of Physics, University of Helsinki.
    Xu, Chunlin
    Process Chemistry Centre, Åbo Akademi University.
    Willför, Stefan
    Process Chemistry Centre, Åbo Akademi University.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Tenkanen, Maija
    Department of Applied Chemistry and Microbiology, University of Helsinki.
    Glucomannan composite films with cellulose nanowhiskers2010In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 17, no 1, p. 69-81Article in journal (Refereed)
    Abstract [en]

    Spruce galactoglucomannans (GGM) and konjac glucomannan (KGM) were mixed with cellulose nanowhiskers (CNW) to form composite films. Remarkable effects of CNW on the appearance of the films were detected when viewed with regular and polarizing optical microscopes and with a scanning electron microscope. Addition of CNW to KGM-based films induced the formation of fiberlike structures with lengths of several millimeters. In GGM-based films, rodlike structures with lengths of several tens of micrometers were formed. The degree of crystallinity of mannan in the plasticized KGM-based films increased slightly when CNW were added, from 25 to 30%. The tensile strength of the KGM-based films not containing glycerol increased with increasing CNW content from 57 to 74 MPa, but that of glycerol-plasticized KGM and GGM films was not affected. Interestingly, the notable differences in the film structure did not appear to be related to the thermal properties of the films

  • 109.
    Mikkonen, Krisi S.
    et al.
    Helsinki University.
    Mathew, Aji P.
    Xu, Chunlin
    Åbo Akademi.
    Willfor, Stefan M.
    Åbo Akademi.
    Tenkanen, Maija
    Helsinki University.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mannan-cellulose nanocomposites2008In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 235, no 228Article in journal (Other academic)
  • 110.
    Mtibe, A.
    et al.
    CSIR Materials Science and Manufacturing, Polymers and Composites Competence Area, Nonwovens and Composites Research Group, P.O. Box 1124, 4 Gomery Avenue, Summerstrand, Port Elizabeth.
    Linganiso, Linda Z.
    CSIR Materials Science and Manufacturing, Polymers and Composites Competence Area, Nonwovens and Composites Research Group, P.O. Box 1124, 4 Gomery Avenue, Summerstrand, Port Elizabeth.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    John, Maya
    CSIR Materials Science and Manufacturing, Fibres and Textiles Competence Area, Port Elizabeth, CSIR, Materials Science and Manufacturing, Polymers and Composites, Port Elizabeth.
    Anandjiwala, Rejesh D.
    CSIR Materials Science and Manufacturing, Polymers and Composites Competence Area, Nonwovens and Composites Research Group, P.O. Box 1124, 4 Gomery Avenue, Summerstrand, Port Elizabeth.
    A comparative study on properties of micro and nanopapers produced from cellulose and cellulose nanofibres2015In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 118, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Cellulose nanocrystals (CNCs) and cellulose nanofibres (CNFs) were successfully extracted from cellulose obtained from maize stalk residues. A variety of techniques, such as Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used for characterization and the experimental results showed that lignin and hemicellulose were removed to a greater extent by following the chemical methods. Atomic force microscopy (AFM) results confirmed that the diameters of CNCs and CNFs were ranging from 3 to 7 nm and 4 to10 nm, respectively, with their lengths in micro scale. CNCs suspension showed a flow of birefringence, however, the same was not observed in the case of suspension containing CNFs. XRD analysis confirmed that CNCs had high crystallinity index in comparison to cellulose and CNFs. Nanopapers were prepared from CNCs and CNFs by solvent evaporation method. Micropapers were also prepared from cellulose pulp by the same technique. Nanopapers made from CNFs showed less transparency as compared to nanopapers produced from CNCs whereas high transparency as compared to micropaper. Nanopapers produced from CNFs provided superior mechanical properties as compared to both micropaper and nanopapers produced from CNCs. Also, nanopapers produced from CNFs were thermally more stable as compared to nanopapers produced from CNCs but thermally less stable as compared to micropapers.

  • 111.
    Naseri, Narges
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Algan, C.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Electrospun chitosan nanofiber random mats reinforced with cellulose nanowhiskers: Poster Presentation2013Conference paper (Refereed)
    Abstract [en]

    Chitosan is a non-toxic, antibacterial, biodegradable and biocompatible biopolymer used extensively for biomedical applications such as tissue engineering, drug and gene delivery, wound healing etc. Electrospinning of chitosan solution in acetic acid (50%) was carried out at 25 kV, gap distance of 155 mm, flow rate 13 mL/h. Cellulose nanowhiskers having diameters of 5-10 nm and aspect ratio of ≈150, were isolated from microcrystalline cellulose (MCC) and used as the reinforcement in the electrospun random mats. The mats were further crosslinked using genipin to improve mechanical properties. The electrospun fibers had diameters in the range of 130-300 nm. With inclusion of the whiskers decreased 50% of average fiber diameters. The mechanical properties of electrospun mats increased as a function of nanowhisker addition as well as crosslinking. These electrospun mats are expected to find application in wound dressing, burn healing etc.

  • 112.
    Naseri, Narges
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Algan, Constance
    Luleå tekniska universitet.
    Jacobs, Valencia
    CSIR Materials Science and Manufacturing, Fibres and Textiles Competence Area, Port Elizabeth.
    John, Maya
    CSIR Materials Science and Manufacturing, Fibres and Textiles Competence Area, Port Elizabeth.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Electrospun chitosan-based nanocomposite mats reinforced with chitin nanocrystals for wound dressing2014In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 109, p. 7-15Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to develop electrospun chitosan/polyethylene oxide- based randomly oriented fiber mats reinforced with chitin nanocrystals (ChNC) for wound dressing. Microscopy studies showed porous mats of smooth and beadless fibers with diameters between 223-966 nm. The addition of chitin nanocrystals as well as crosslinking had a positive impact on the mechanical properties of the mats, and the crosslinked nanocomposite mats with a tensile strength of 64.9 MPa and modulus of 10.2 GPa were considered the best candidate for wound dressing application. The high surface area of the mats (35 m2.g−1) was also considered beneficial for wound healing. The water vapor transmission rate of the prepared mats was between 1290-1548 g.m−2.day−1, and was in the range for injured skin or wounds. The electrospun fiber mats showed compatibility towards adipose derived stem cells, further confirming their potential use as wound dressing materials.

  • 113.
    Naseri, Narges
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Algan, Constance
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Electrospun chitosan nanofiber random mats reinforced with chitin and cellulose nanocrystals for wound dressing application2013Conference paper (Refereed)
    Abstract [en]

    IntroductionProcessingof ultrafine continuous polymeric fibers ranging from tensof nanometers to a few micrometers using electtrospinning techniqueis well known1. In recent years, nanosized reinforcements have been usedto further improve/ tailor the mechanical properties and structural morphologyof electrospun fibers2. The current study is aimed to developrandomly oriented nanocomposite fiber mats by electrospinning,using cellulose and chitin nanocrystals as reinforcements3/ functionaladditives and explore the potential of the electrospun nanofiber mats for wounddressing application.Materials and methodsElectrospinning of chitosan solution in aceticacid (50%) was carried out at 25 kV, gap distance of 155mm, flow rate13 mL/h. Cellulose nanocrystal (CNCs) having diameters of5-10 nm were isolated from microcrystalline cellulose (MCC) by63% sulphuric acid hydrolysis using Bondeson et alprocedure3.Chitin nanocrystals (ChNCs) were produced from crab shells by HClhydrolysis. The concentrations of nanocrystals in all themats were kept at 50%. The spinning solution used was a mixture of1:1 (w/w) of chitosan-PEO in 50 wt% aqueous acetic acid, with a3 wt% total polymer concentration. The mats werefurther crosslinked using genipin in order to improvemechanical properties.Results and discussionCNCs and ChNCs werefound to be biocompatible and supported growth of adiposederived stem cells (ASC) and L929 cell line indicating thatthese nanomaterials are potential reinforcements/ functional additivesfor biomedical products. Randomly oriented nanofiber mats wereprepared and the effect of inclusion of CNCs and ChNCs on the structuralmorphology and diameter of electrospun nanofiber werestudied. Crosslinking of the mats resulted in more compact film likestructure for only matrix (M) and M-CNCH2SO4 while M-ChNC and MCNCHCLmats wereless affected. The electrospun fibers had diameters in the range of116-631 nm, which decreasedwith inclusion of nanocrystals except for M-CNCH2SO4 whereaggregation of CNCs probably occurred. The nanocrystals as well asthe crosslinking had positive impact on the mechanicalproperties of electrospun mats. The random mats showed porosity andare expected to facilitate cell growth, though porosity decreasedwith crosslinking probably due to dissolution of PEO. The matsexhibited water vapour permeability in the range of 1202-1879 g.m2day-1, which falls in the range of water vapour transmissionfor wounds and the permeability decreased slightlyafter crosslinking. ConclusionsRandomlyoriented nanofiber electrospun mats were successfully producedfrom chitosan/ PEO blend reinforced with CNCs orChNCs. Electrospun porous random mats reinforced withChNCs are the most promising materials (fibers free of defects).The crosslinking had positive impact on mechanicalstrength where as porosity and water vapour transmissiondecreased after crosslinking. The porous morphology of the matsfacilitated cell growth and water vapour transmission and is expectedto have potential application as wound healing materials. Acknowledgments Financial support fromVINNOVA (No. 2011-02071) under MNT-ERANET project, n-POSSCOG isacknowledged. EDUCELL, Slovenia and CSIR, S. Africa are acknowledgedfor biocomatibility studies and water vapour transmissionstudies respectievely.  References1. Son, W.K.; Youk,J.H. et al . J. Poly Sci. , 2004, 42 (1), 5-11.2. Oksman, K.;Mathew, A.P.; Sain, M., Plastics, Rubber &Composites, 2009, 38, 396-405.3. Bondeson, D.;Mathew, A. P.; Oksman, K. Cellulose, 2006,13, 171- 180.  Proceeding of the MiMeOctober 8-11, 2013 - Faenza, Italy1st InternationalConference on Materials in Medicine

  • 114.
    Naseri, Narges
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Deepa, B.
    Department of Chemistry, Bishop Moore College, Mavelikara, 690101, Kerala.
    Bárcena, José R.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    IPN Hydrogels Based on Nanocellulose for Soft Tissue Engineering2015Conference paper (Refereed)
    Abstract [en]

    In tissue engineering, development of materials, which positively interact with tissues, is very important.1 In this regard, hydrogels composed of three-dimensional polymeric networks, have become more attractive materials due to their ability to absorb high water content and swells without losing their structural integrity.2 Furthermore, hydrogels need to provide physico-mechanical support for cell growth, proliferation and new tissue formation.3 However, their low mechanical properties have found one drawback4 and therefore in this study, cellulose nanocrystals (CNCBE) isolated from bioethanol residue were used as reinforcement or functional additive. The objective of this work was to develop double-crosslinked Interpenetrating Polymeric Networks (IPNs) of nanocellulose-based hydrogels on alginate and gelatin and investigate the effect of IPN processing route on physico-chemical properties of the produced hydrogels as well as their potential in soft tissue engineering. Fully bio-based porous IPN scaffolds were processed through two freeze-drying steps and crosslinked using calcium chloride and genipin. The second freeze-drying was performed to induce more pores in the structure. The morphology studies showed highly porous structure (90-97% porosity), which is beneficial for cell attachment and growth, but resulted in lower mechanical performances under compression. Addition of CNCBE and crosslinking decreased the moisture uptake while increased the compression modulus. Furthermore, the development of extracellular matrix (ECM) is expected to improve the mechanical performances after implantation.AcknowledgementsFinancial support from VINNOVA (No. 2011-02071) under MNT-ERANET project, n-POSSCOG is acknowledged. References1. Silva, S. S.; Motta, A.; Rodrigues, M. T.; Pinheiro, A. F.; Gomes, M. E.; Mano, J. F.; Reis, R. L.; Migliaresi, C. Biomacromolecules 2008, 9, 2764-2774.2. Dragan, E. S.; Perju, M. M.; Dinu, M. V. Carbohydr. Polym. 2012, 88, 270-281.3. Drury, J. L.; Mooney, D. J. Biomaterials 2003, 24, 4337-4351.4. Matricardi, P.; Di Meo, C.; Coviello, T.; Hennink, W. E.; Alhaique, F. Adv. Drug Deliv. Rev. 2013, 65, 1172-1187.

  • 115.
    Naseri, Narges
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Girandon, Lenart
    Educell Ltd., Prevale 9, Trzin.
    Fröhlich, Mirjam
    Educell Ltd., Prevale 9, Trzin.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Porous electrospun nanocomposite mats based on chitosan-cellulose nanocrystals for wound dressing: Effect of surface characteristics of nanocrystals2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 1, p. 521-534Article in journal (Refereed)
    Abstract [en]

    Randomly oriented fiber mats of chitosan-polyethylene oxide matrix reinforced with cellulose nanocrystals (CNCs) were prepared by electrospinning technique. The cellulose nanocrystals used were isolated using hydrochloric acid (CNCHCl) or sulphuric acid (CNCH2SO4) and the CNCs concentration was 50 wt% in the electrospun mats. The surface characteristics of the nanocrystals were found to affect the dispersion, viscosity, conductivity and zeta-potential of the respective spinning solutions and resulted in better spinnability, homogeneity as well as crosslinking of CNCHCl based nanocomposite fiber mats compared to CNCH2SO4 ones. The microscopy studies showed that diameter of the electrospun fibers decreased by the inclusion of both types of nanocrystals and the crosslinking decreased the porosity of the mats. The tensile strength and tensile modulus of the mats increased with the addition of nanocrystals and increased further for the CNCHCl based mats (58 MPa, 3.1 GPa) after crosslinking. The as-spun CNCHCl based mats had average pore diameters of 1.6 μm and porosity of 38%. The water vapor permeability and the O2/CO2 transmission increased with the addition of CNCHCl. The used nanocrystals as well as electrospun mats showed non-cytotoxic impact towards adipose derived stem cells (ASCs) was considered favorable for wound dressing.

  • 116.
    Naseri, Narges
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Electrospinnability of bionanocomposites with high nanocrystal loadings: The effect of nanocrystal surface characteristics2016In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 147, p. 464-472Article in journal (Refereed)
    Abstract [en]

    This paper deals with the effect of solution properties and nanoparticle surface chemistry on the spinnability of a chitosan/polyethylene oxide (PEO) with high concentration (50 wt%) of chitin and cellulose nanocrystals and the properties of the resultant nanocomposite fibers/fiber mats. Electrospinning dispersions with cellulose nanocrystals having sulphate surface groups showed poor spinnability compared to chitin nanocrystals with amide and amino groups. Chitin nanocrystal based dispersions showed good spinnability and continuous fiber formation whereas cellulose nanocrystal system showed discontinuous fibers and branching. The viscosity and surface tension are shown to impact this behavior, but conductivity did not. Poor spinnability observed for cellulose nanocrystal based fibers was attributed to the coagulation of negatively charged cellulose nanocrystals and positively charged chitosan. The study showed that the nanocrystal surface charge and interactions with the chitosan/PEO matrix have a significant impact on the spinnability of bionanocomposites.

  • 117.
    Naseri, Narges
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Interpenetrating Polymer Networks (IPN) hydrogels based on nanocellulose for soft tissue engineering2015Conference paper (Refereed)
    Abstract [en]

    Currently, the use of bio-based nanomaterials as reinforcements has attracted much interest especially in medical applications due to their cytocompatibility, good mechanical performance, good moisture stability, hydrophilicity and ability to form porous structure. In tissue engineering, development of materials, which positively interact with tissues, is very important. In this regard, hydrogels composed of three-dimensional polymeric networks, have become more attractive materials due to their ability to absorb high water content and swell without losing their structural integrity. Moreover, hydrogels need to provide physico-mechanical support for cell growth, proliferation and new tissue formation. However, their low mechanical properties have found one drawback. We attempted a novel technology to design double crosslinked interpenetrating polymer networks (IPN) of nanocellulose-based hydrogels of sodium alginate and gelatin with potential use in soft tissue engineering. Advanced, innovative fully bio-based porous IPN scaffolds have been prepared via freeze-drying and crosslinked using calcium chloride and genipin. Highly porous structure, which is considered beneficial for cells attachment and extracellular matrix (ECM) production was obtained. The addition of nanocellulose and crosslinking decreased the moisture uptake while increased the compression modulus. The study showed the potential use of these hydrogels based on nanocellulose in cartilage application.Key words: IPN hydrogel, nanocellulose, porous structure, mechanical performances, cytocompatibility, soft tissue engineering

  • 118.
    Naseri, Narges
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Porous electrospun nanocomposite mats based on cellulose/chitin nanocystals for wound dressing2016Conference paper (Refereed)
    Abstract [en]

    Recently, the use of bio-based nanomaterials has become more attractive in biomedical applications due to their cytocompatibility, good mechanical performances, good moisture stability and hydrophilicity as well as ability to form porous structures. In the current study, randomly oriented electrospun nanocomposites of chitosan/polyethylene oxide (PEO) with high concentration of chitin nanocrystals/ cellulose nanocrystals (50 wt%) were developed for potential application as wound dressing material.1,2 Nanocrystals with different surface characteristics were used to improve/tailor the pore structure as well as the mechanical and functional properties of the electrospun fibers. Furthermore, surface characteristics of nanocrystals had a significant impact on the electrospinning solution properties as well as properties of the resulting fibers. The structural morphology of the mats showed that diameter of the electrospun fibers were in the range of 223-1240 nm and decreased with incorporation of nanocrystals. The addition of nanocrystals as well as crosslinking had a positive impact on the mechanical properties of the nanocomposite mats. Chitin reinforced mats had the highest mechanical properties due to better compatibility with the matrix and increased further (tensile strength of 64.9 MPa and the modulus of 10.2 GPa) after crosslinking.1 The water vapor transmission rate and O2/CO2 permeability of the electrospun mats as well as cytocompatibility towards adipose derived stem cells were considered favorable for wound dressing.1,2 References:1. Naseri, Narges, et al. "Electrospun chitosan-based nanocomposite mats reinforced with chitin nanocrystals for wound dressing." Carbohydrate polymers109 (2014): 7-15.2. Naseri, Narges, et al. "Porous electrospun nanocomposite mats based on chitosan–cellulose nanocrystals for wound dressing: Effect of surface characteristics of nanocrystals." Cellulose 22.1 (2015): 521-534.

  • 119.
    Naseri, Narges
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Girandon, Lenart
    Fröhlich, Mirjam
    Porous nanocomposite scaffolds containing bio-based nanoreinforcements for biomedical applications2014Conference paper (Refereed)
    Abstract [en]

    Fully bio-based porous nanocomposite scaffolds based on nanocellulose and nanochitin were processed and characterized to explore the potential of these scaffolds in wound dressing and cartilage applications. The processing techniques involved electrospinning, freeze-drying and porogen leaching. Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) were isolated from pure cellulose sources through chemical and mechanical treatments. Chitin nanocrystals (ChNCs) were isolated via acid hydrolysis procedure from crab shells.CNCs, CNFs and ChNCs were found to be cytocompatible and supported growth of adipose derived (ASCs) stem cells and L929 cell line indicating the potential use of these nanoparticles in biomedical applications. Randomly oriented nanocomposite fiber mats containing chitosan/PEO reinforced with CNCs and ChNCs were produced using electrospinning technique. The nanocrystals as well as crosslinking showed positive impact on the mechanical properties of electrospun mats. The nanocomposite mats showed porous structures, which can support cell growth and interconnectivity. The water vapor permeability results are in the range of 1202-1879 g.m2d-1which is in the range of water vapour transmission for wounds. So these nanocomposite mats are expected to have potential in wound dressing application.Porous scaffolds containing biopolymer matrix reinforced with cellulose nanofibers (CNFs) were prepared by freeze-drying or porogen leaching and were crosslinked to enhance mechanical and dimensional stability. Pore size in the range of 20-200 μm was obtained, which is expected to facilitate the cell growth and interconnectivity. The freeze-dried scaffolds showed suitable mechanical properties while no considerable improvement was achieved after crosslinking in PBS medium. Short-term cytocompatibility studies showed non-cytotoxicity of the scaffolds for human chondrocytes after 7 days cell culturing.Acknowledgements:Financial support from VINNOVA (No. 2011-02071) under MNT-ERANET project, n-POSSCOG is acknowledged. Jean-Michel Poirier and Florence Rinn are acknowledged for the cartilage.

  • 120.
    Naseri, Narges
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Poirier, Jean-Michel
    Girandon, Lenart
    Educell Ltd., Prevale 9, Trzin.
    Fröhlich, Mirjam
    Educell Ltd., Prevale 9, Trzin.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    3-Dimensional Porous Nanocomposite Scaffolds Based on Cellulose Nanofibers for Cartilage Tissue Engineering2016In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 8, p. 5999-6007Article in journal (Refereed)
    Abstract [en]

    Fully bio-based three-dimensional porous scaffold for cartilage repair was prepared via freeze-drying where cellulose nanofibers, which were cytocompatible, were used as mechanical reinforcement (70-90 wt%) in a matrix of gelatin and chitosan (9:1) and crosslinked using genipin. Morphology studies showed that the scaffolds had interconnected pores with favorable pore diameters (< 250 μm) for cell growth. Compression modulus of the scaffolds (1-3 MPa) at room conditions was in the range for natural cartilage and decreased significantly (0.03-0.05 MPa) in phosphate buffered saline (PBS) at 37°C. The high PBS uptake shown by the scaffolds (< 3000 wt%) was attributed to liquid trapped in the pores during immersion in PBS. Furthermore, the scaffolds showed good cytocompatibility towards chondrocytes, which attached and proliferated properly. The scaffolds are considered to have potential in cartilage tissue engineering due to high porosity (≈ 95%) and good mechanical performance that promote cell attachment and extracellular matrix (ECM) production.

  • 121.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Aitomäki, Yvonne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Siquiera, Gilberto
    Applied Wood Materials Laboratory, Swiss Federal Laboratories for Materials Science and Technology (EMPA), CH-8600 Dübendorf.
    Zhou, Qi
    School of Biotechnology, Royal Institute of Technology (KTH), AlbaNova University Centre, Stockholm.
    Butylina, Svetlana
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Tanpichai, Supachok
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Zhou, Xiaojian
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hooshmand, Saleh
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Review of the recent developments in cellulose nanocomposite processing2016In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 83, p. 2-18Article in journal (Refereed)
    Abstract [en]

    This review addresses the recent developments of the processing of cellulose nanocomposites, focusing on the most used techniques, including solution casting, melt-processing of thermoplastic cellulose nanocomposites and resin impregnation of cellulose nanopapers using thermoset resins. Important techniques, such as partially dissolved cellulose nanocomposites, nanocomposite foams reinforced with nanocellulose, as well as long continuous fibers or filaments, are also addressed. It is shown how the research on cellulose nanocomposites has rapidly increased during the last 10 years, and manufacturing techniques have been developed from simple casting to these more sophisticated methods. To produce cellulose nanocomposites for commercial use, the processing of these materials must be developed from laboratory to industrially viable methods.

  • 122.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jackson-Etang, Ayuk
    Mathew, Aji P.
    Jonoobi, Mehdi
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cellulose nanowhiskers separated from a bio-residue from wood bioethanol production2011In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 35, no 1, p. 146-152Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to explore the utilization of industrial bio-residues as a source of raw material for the industrial production of cellulose nanowhiskers. The used residue, obtained from a bioethanol pilot plant, was first purified using chemical extraction and bleaching, and then separated to nanowhiskers by mechanical treatments such as ultrasonication, high-pressure homogenization as well as chemical acid hydrolysis.The chemical compositions and characteristics of the bio-residue were studied before and after purification using a TAPPI standard, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The morphology of the isolated nanowhiskers was characterized using atomic force microscope (AFM). The chemical composition of the used bio-residue was found to be 49.5 wt% cellulose, 42.1 wt% lignin and 8.4 wt% extractives. The crystallinity of the bio-residue was 14.5% and it increased to more than 73% after the purification process. The nanowhiskers isolated using ultrasonication or high-pressure homogenization had better thermal stability than nanowhiskers isolated with acid hydrolysis. The AFM study showed that a simple ultrasonication and homogenization processes resulted in nanosize whiskers with diameters in the 10-20 nm range.

  • 123.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Composites based on cellulose nanofibers and natural rubber2009Conference paper (Other academic)
  • 124.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Melt Compounding Process of Cellulose Nanocomposites2014In: Handbook of Green Materials: Processing Technologies, Properties and Applications, Singapore: World Scientific and Engineering Academy and Society, 2014Chapter in book (Refereed)
  • 125.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Natural fibre composites manufactured using long fibre thermoplastic (LFT) and compression moulding2010In: 10th International Conference on Wood & Biofiber Plastic Composites and Cellulose NanoComposites Symposium, Forest Products Society, 2010Conference paper (Refereed)
  • 126.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Process and properties of bio-nanocomposites based on cellulose whiskers2007In: 9th International Conference on Wood & Biofiber Plastic Composites: held in Madison, Wisconsin, May 21 -23, 2007, Madison, Wis: Forest Products Society, 2007Conference paper (Refereed)
    Abstract [en]

    Inspired by the growing environmental awareness by all, there is a deliber­ate interest in finding new materials that are biodegradable and environmental friendly. Therefore materials derived from natural resources are studied extensively now days. Preparation of novel bio-nanocomposites based on biopolymers has drawn specific attention. It is expected that these type of nanocomposites will open new areas for medical, packaging and electronic applications. This presentation will deal with a novel processing technology of bio-nanocomposites based on cellulose whiskers and different biopolymers. Processing techniques for nanostructured materials includes drying, feeding and blending techniques. Characterization of the structure of nanocomposites will also be presented. Nanowhisker dispersion and size in the matrix polymer has shown to be difficult to characterize since both the matrix and reinforcement are soft, non-conductive and light materials. Cellulose nanowhiskers isolated from wooden source, by acid hydrolysis, have a size about 5 nm in width and 200-300 nm in length. These whiskers were blended with polylactic acid (PLA) and cellulose acetate butyrate (CAB) by melt compounding to achieve bio-nanocomposites. The composites mechanical and thermal properties as well as the nanostructure of cellulose whiskers and composites will be presented.

  • 127. Oksman, Kristiina
    et al.
    Mathew, Aji P.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Bondeson, Daniel
    Kvien, Ingvild
    Manufacturing process of cellulose whiskers/polylactic acid nanocomposites2006In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 66, no 15, p. 2776-2784Article in journal (Refereed)
    Abstract [en]

    Cellulose whiskers separated from commercially available microcrystalline cellulose (MCC) and polylactic acid (PLA) were used to develop novel nanostructured biocomposites by compounding extrusion. MCC was treated with N,N-dimethylacetamide (DMAc) containing lithium chloride (LiCl) in order to swell the MCC and partly separate the cellulose whiskers. The suspension of whiskers was pumped into the polymer melt during the extrusion process. Different microscopy techniques, thermogravimetric analysis, X-ray diffraction and mechanical testing were used to study the structure and properties of the whiskers and composites. The results showed that DMAc/LiCl can be used as swelling/separation agent for MCC but seems to cause degradation of the composites at high temperature processing. The structure of composites was made up of partly separated nanowhiskers when PEG was used as processing aid. The mechanical properties of nanocomposites were improved and compared to reference material the elongation to break was increased about 800% for one material combination. The future studies will be focused on process optimization, dispersion of nanowhiskers and finding a more suitable pumping medium to avoid thermal degradation of the composite.

  • 128.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jonoobi, Mehdi
    Hietala, Maiju
    Vargas, Natalia Herrera
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cellulose nanocomposites processing using extrusion2013In: Production and Applications of Cellulose Nanomaterials, TAPPI Press, 2013, p. 99-102Chapter in book (Refereed)
    Abstract [en]

    We have been working with development of compounding extrusion process for cellulose nanocomposites, since 2003. Feeding and dispersion of the nanocellulose materials are the main challenges and we have developed two specific processing routes; i) liquid feeding of the nanomaterials into the extruder and ii) dry feeding of nanomaterials as a master batch, to address the feeding problem. Composites with aggregated, partially dispersed or fully dispersed nanocellulose crystals or fibers have been obtained depending on the extent of the separation of cellulose nanocrystals or nanofibers in the liquid medium or in the master batch and the interaction of nanocelluloses with the polymer matrix. We aim to produce nanocomposites with good mechanical properties, thermal stability and transparency and at the same time develop an energy efficient and cost effective processing methodology, which can be up-scaled in industrial level.

  • 129.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jonoobi, Mehdi
    Siqueira, Gilberto
    Hietala, Maiju
    Aitomäki, Yvonne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cellulose nanofiber isolated from industrial side-streams2013In: Production and Applications of Cellulose Nanomaterials, TAPPI Press, 2013, p. 187-190Chapter in book (Refereed)
    Abstract [en]

    Isolation of cellulose nanofibers from industrial side-streams as raw material is interesting from several reasons; it will not only result in lower overall cost of the nanofibers but also add value for many different processes and products. We have used sludge, a residue from pulp production, carrot residue from juice production, and several agricultural waste products as the starting material to isolate nanofibers. The isolation process was made using a Masuko ultra fine friction grinder and our aim have been to optimize the processing parameters for the lowest energy consumption. In addition to developing the isolation process, the isolated nanofibers structure and properties were characterized. Typically, the isolated nanofibers are bundles with diameters lower than 100 nm. In particular, we found that carrot nanofibers have a uniform fiber size less than 50 nm. Scanning electron microscopy studies showed entangled nanofiber networks and the mechanical properties of nanofiber networks demonstrated a positive impact on modulus and strength when compared to networks with microsized fibers. The improvement is increased with decreased fiber size indicating more efficient fibrillation. From these studies, we have shown that industrial side-streams are excellent raw material sources for nanofiber preparation, being cheaper than other raw materials and consuming less energy for isolation while showing good properties.

  • 130.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Långström, Runar
    Swerea SICOMP AB.
    Nyström, Birgitha
    Swerea SICOMP AB.
    Joseph, Kuruvilla
    Indian Institute of Space Science and Technology.
    The influence of fibre microstructure on fibre breakage and mechanical properties of natural fibre reinforced polypropylene2009In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 69, no 11-12, p. 1847-1853Article in journal (Refereed)
    Abstract [en]

    The aim of the study was to investigate the influence of fibre morphology of different natural fibres on the composites mechanical properties and on the fibre breakage due to extrusion process. The composite materials were manufactured using LTF (long fibre thermoplastic) extrusion and compression moulding and the used fibres were sisal, banana, jute and flax, and the matrix was a polypropylene. The results showed that sisal composites had the best impact properties and the longest fibres after the extrusion. Generally, the composites flexural stiffness was increased with increased fibre content for all fibres, being highest for flax composites. The flexural strength was not affected by the addition of fibres because of the low compatibility. The addition of 2 wt% maleated polypropylene significantly improved the composites properties. Unlike the other three fibres, flax fibres were separated into individual elementary fibres during the process due to enzymatic retting and low lignin content.

  • 131.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Petersson, L.
    Kvien, Ingvild
    Bondeson, D.
    Tanem, B.-S.
    Processing of cellulose nanocomposites2004Conference paper (Refereed)
  • 132.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Sain, Mohini
    University of Toronto.
    Novel bionanocomposites: processing properties and potential applications2009In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, no 9-10, p. 396-405Article in journal (Refereed)
    Abstract [en]

    The demand for environmental sustainability has resulted in a great interest in finding new materials that are biodegradable and environmentally friendly. Therefore, materials derived from natural resources are now being extensively studied. Preparation of novel biocomposites based on nanocelluloses has drawn specific attention. It is expected that cellulose nanocomposites will open new areas for applications in medicine, packaging, electronics, the automotive sector, construction and other areas. This article presents a new research field of bionanocomposites where different types of nanocelluloses are used as reinforcements in biopolymers. Isolation of cellulose nanofibres and nanowhiskers from different sources, and processing technologies for the composites, are described and discussed. The main difficulty when producing cellulose based nanocomposites is to disperse the reinforcement in the polymer matrix without degradation of the biopolymer or the reinforcing phase. This can be addressed by improving the interaction (compatibility) between nanofibres and the matrix and by using suitable processing methods. The study of alignment of the nanocelluloses by using magnetic field is discussed and the nanocomposites' mechanical properties, based on the findings from different studies, are presented. Finally, some examples of future nanocomposites are discussed.

  • 133.
    Oksman, Kristiina
    et al.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Mathew, Aji P.
    Sain, Mohini
    University of Toronto.
    The effect of morphology and chemical characteristics of cellulose reinforcements on the crystallinity of polylactic acid2006In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 101, no 1, p. 300-310Article in journal (Refereed)
    Abstract [en]

    The aim of this work has been to study the crystallization behavior of composites based on polylactic acid (PLA) and three different types of cellulose reinforcements, viz., microcrystalline cellulose (MCC), cellulose fibers (CFs), and wood flour (WF). The primary interest was to determine how the size, chemical composition, and the surface topography of cellulosic materials affect the crystallization of PLA. The studied composite materials were compounded using a twin-screw extruder and injection-molded to test samples. The content of cellulose reinforcements were 25% by weight. The MCC and WF were shown to have a better nucleating ability than CFs based on differential scanning calorimetry and optical microscopy studies. It is difficult to visualize that transcrystallization will occur during melting process and this process is influenced by the morphological and chemical characteristics of the reinforcement. Bulk crystallization seems to be mainly dependent on the processing temperature. The cold crystallization process was shown to improve the thermal stability and storage modulus of the composites

  • 134. P, Deepalakshmi
    et al.
    PM, Visakh
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Chandra, Arup
    Thomas, Sabu
    Advances in Elastomers: Their blends and interpenetrating polymer networks: State of art, new challenges and oppurtunities2013In: Advances in Elastomers - I: Blends and Interpenetrating Networks, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2013, p. 1-9Chapter in book (Refereed)
  • 135.
    Petersson, L.
    et al.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Oksman, Kristiina
    Mathew, Aji P.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Using maleic anhydride grafted poly(lactic acid) as a compatibilizer in poly(lactic acid)/layered-silicate nanocomposites2006In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 102, no 2, p. 1852-1862Article in journal (Refereed)
    Abstract [en]

    The goal of this work was to prepare exfoliated poly(lactic acid) (PLA)/layered-silicate nanocomposites with maleic anhydride grafted poly(lactic acid) (PLA-MA) as a compatibilizer. Two different layered silicates were used in the study: bentonite and hectorite. The nanocomposites were prepared by the incorporation of each layered silicate (5 wt %) into PLA via solution casting. X-ray diffraction of the prepared nanocomposites indicated exfoliation of the silicates. However, micrographs from transmission electron microscopy showed the presence of intercalated and partially exfoliated areas. Tensile testing showed improvements in both the tensile modulus and yield strength for all the prepared nanocomposites. The results from the dynamic mechanical thermal analysis showed an improvement in the storage modulus over the entire temperature range for both layered silicates together with a shift in the tan peak to higher temperatures. The effect of using PLA-MA differed between the two layered silicates because of a difference in the organic treatment. The bentonite layered silicate showed a more distinct improvement in exfoliation and an increase in the mechanical properties because of the addition of PLA-MA in comparison with the hectorite layered silicate

  • 136.
    Petersson, Linnea
    et al.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Mathew, Aji P.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Dispersion and properties of cellulose nanowhiskers and layered silicates in cellulose acetate butyrate nanocomposites2009In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 112, no 4, p. 2001-2009Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to develop well dispersed nanocomposites, in a non water soluble polymer using a non aqueous, low polarity solvent as a dispersion medium. The nanoreinforcements were cellulose whiskers and layered silicates (LSs) and matrix was cellulose acetate butyrate (CAB). Before nanocomposite processing, a homogenizer was used in combination with sonification to achieve full dispersion of the nanoreinforcements in a medium of low polarity (ethanol). After processing, the cellulose nanowhiskers (CNW) showed flow birefringence in both ethanol and dissolved CAB, which indicated well dispersed whiskers. The microscopy studies indicated that the processing was successful for both nanocomposites. The CNW showed a homogeneous dispersion on nanoscale. The LS nanocomposite contained areas with lower degree of dispersion and separation of the LS sheets and formed mainly an intercalated structure. The produced materials were completely transparent, which indicated good dispersion. Transparency measurements also indicated that the nanocomposite containing CNW showed similar performance as the pure CAB. Dynamic mechanical thermal analysis (DMTA) showed improved storage modulus for a wide temperature range for both nanocomposites compared with the pure CAB matrix. This study indicated that CNW have a potential application in transparent nanocomposites based on fully renewable resources.

  • 137.
    PM, Visakh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Thomas, Sabu
    Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala.
    Starch-Based Bionanocomposites: Processing and Properties2012In: Polysaccharide building blocks: a sustainable approach to the development of renewable biomaterials, Hoboken: John Wiley & Sons Ltd , 2012, p. 287-306Chapter in book (Refereed)
  • 138.
    PM, Visakh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Thomas, Sabu
    Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Elastomeric nanocomposites: Potential of chitin and cellulose nanostructures as reinforcing phase2012In: Proceedings of the 15th European Conference on Composite Materials, Venice, 24-28 June 2012 / [ed] Marino Quaresimin; Laszlo Kollar; Leif Asp, Venice, 2012Conference paper (Refereed)
    Abstract [en]

    Cellulose and chitin are abundant, natural, renewable and biodegradable polymers which could be broken down into nano sized crystalline entities, using a top-down approach. In most cases, an aqueous suspension of these nano crystallites are prepared by acid hydrolysis process and has high specific mechanical properties making them potential reinforcements in various polymer matrices. In this work, we present the processing and characterization of nanoreinforcements from waste materials such as cellulose and chitin and their polymer nanocomposites using natural rubber matrix (NR) or synthetic rubber matrix, carboxylated styrene butadiene rubber (XSBR). The isolated chitin whiskers had a length ranging from 100 to 500 nm and diameter ranging from 10 to 80 nm and cellulose nanowhiskers had diameters between 4-14 nm. The addition of 4.32 wt of % chitin nanowhiskers resulted in an improvement of 1400 % for tensile strength. The cellulose nanowhiskers gave good mechanical and tensile improvements on NR matrixes and Atomic force microscopy (AFM) was carried out to examine the size and structure of chitin and cellulose nanowhiskers and scanning electron microscopy (SEM) used for the morphological study of both type of nanocomposites. It may be concluded that the biobased nanostructures have great potential in reinforcing natural and synthetic elastomers and the reinforcing potential depends on the dispersion and distribution of the nanocrystals in the matrix as well as the interaction between the phases.

  • 139.
    PM, Visakh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Thomas, Sabu P.
    Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala.
    Natural polymers: Their blends, composites and nanocomposites: State of art, new challenges and opportunities2013In: Advances in Natural Polymers Composites and Nanocomposites, Dordrecht: Encyclopedia of Global Archaeology/Springer Verlag, 2013, p. 1-20Chapter in book (Refereed)
    Abstract [en]

    The present chapter deals with a brief account on various types of natural polymers such as cellulose, chitin, starch, soy protein, casein, hemicellu-loses, alginates, polylactic acid and polyhydroxyalkanoates etc. Blends, composites and nanocomposites based on these polymers have been very briefly discussed. Finally the applications, new challenges and opportunities of these biomaterials are also discussed

  • 140.
    PM, Visakh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Thomas, S.
    Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Effect of cellulose nanofibers isolated from bamboo pulp residue on vulcanized natural rubber2012In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 2, p. 2156-2168Article in journal (Refereed)
  • 141.
    PM, Visakh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Thomas, Sabu
    Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cellulose nanofibres and cellulose nanowhiskers based natural rubber composites: Diffusion, sorption, and permeation of aromatic organic solvents2012In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 124, no 2, p. 1614-1623Article in journal (Refereed)
    Abstract [en]

    This article investigates the transport behavior of three aromatic organic solvents, viz. benzene, toluene, and p-xylene in natural rubber nanocomposite membranes containing cellulose nanofibres (CNFs) and cellulose nanowhiskers (CNWs) isolated from bamboo pulp. The solvent molecules act as molecular probes to study the diffusion, sorption, and permeation through the nanocomposites, and provide information on the nanocomposite structure and matrix-filler interactions. Both the nanocelluloses were found to decrease the uptake of aromatic solvents in nanocomposite membranes, but the effect was more significant in the case on nanofibers compared to nanowhiskers. Furthermore, the uptake decreased with increased penetrant size; being the highest for benzene and the lowest for p-xylene. Transport parameters such as diffusion coefficient, sorption coefficient, and permeation coefficient have been calculated. Comparison of the experimental values of equilibrium solvent uptake with the predicted values indicated that both the nanocelluloses have restricted the molecular mobility at the interphase and thereby decreased the transport of solvents through the materials; being more significant for nanofibers. The results showed that both the used cellulosic nanomaterials act as functional additives capable of manipulating and tailoring the transport of organic solvents through elastomeric membranes, even at concentrations as low as 2.5 wt %.

  • 142.
    PM, Visakh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Thomas, Sabu
    Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Crosslinked natural rubber nanocomposites reinforced with cellulose whiskers isolated from bamboo waste: processing and mechanical/thermal properties2012In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 43, no 4, p. 735-741Article in journal (Refereed)
    Abstract [en]

    Crosslinked natural rubber (NR) nanocomposites were prepared using cellulose nanowhiskers (CNWs) that were extracted from bamboo pulp residue of newspaper production, as the reinforcing phase. The coagulated NR latex containing bamboo nanowhiskers (master batch) was compounded with solid NR and vulcanizing agents using a two-roll mill and subsequently cured to introduce crosslinks in the NR phase. No evidence of micro-scaled aggregates of cellulose nanowhiskers in NR matrix was observed in scanning electron microscopy (SEM) images. The addition of CNWs had a positive impact on the tensile strength, E-modulus, storage modulus, tan delta peak position and thermal stability of the crosslinked NR. Theoretical modeling of the mechanical properties showed a lower performance than predicated and therefore further process optimization and/or compatibilization are required to reach the maximum potential of these nanocomposites.

  • 143. Poirier, Jean-Michel
    et al.
    Naseri, Narges
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Porous nanocomposite scaffolds containing cellulose nanofibers for cartilage applications: mechanical properties and biocompatibility2013Conference paper (Refereed)
    Abstract [en]

    IntroductionNatural materials as cellulose extracted from wood and chitin extracted from crustaceans shells are promising biocompatible materials for tissue engineering applications. (1, 2) The study focuses on the processing of a novel biobased three -dimensional porous scaffolds for cartilage repair applications. A first phase of the study consists in optimising the composition and the process for suitable mechanical properties in simulated body conditions. In the second phase the biocompatibility of the material and the influence of the presence of chondrocytes extra cellular matrix (ECM) on its mechanical properties will be studied. Materials and methodsThe materials were prepared by freeze drying suspensions of cellulose nanofibers (CNFs) in a matrix of gelatin/chitosan. A single step freeze drying of a solution containing gelatin, CNFs, and chitosan, or a two steps freeze drying of a gelatin and CNFs solutions first, then impregnation with chitosan solution and subsequent freeze drying was performed. Cross-linking is carried out using genipin solution, followed by rinsing, and an additional freeze drying. The prepared materials were characterised by scanning electron microscopy (SEM), compression tests in dry and wet conditions, and Fourier transform Infrared spectroscopy. The porosity is measured by BET method. Cell attachment and proliferation were also evaluated.Results and discussionSEM observations of the freeze dried materials showed homogeneous pore structure. The structure observed shows a macroporous foam with pore size varying between 50 to 200 µm depending on the process and material, with a rough inner surface with nanosized wires formed by CNFs and chitosan. These nanowires are expected to enhance cell attachment and proliferation. The compression tests showed a compression strength of around 0.02 and 0.07 MPa and a compression modulus around 0.3 MPa and 3 MPa according to the initial concentration at 37°C and atmospheric moisture conditions, which is the in the same order of magnitude as natural cartilage i.e. between 0.4 and 0.8MPa according to the literature. (3) Biocompatibility tests also showed positive results and cell growth with the tested materials. Furthermore, the growth of chondrocytes within the samples and the production of ECM are expected to enhance the mechanical properties. (4)ConclusionsFreeze dried micro porous scaffolds of cellulose nanofiber based gelation/ chitosan nanocomposites showed promising mechanical properties and cell growth, with potential for cartilage application.AcknowledgmentsFinancial support from VINNOVA under MNT-ERANET project, n-POSSCOG is acknowledged. EDUCELL, Slovenia is acknowledged for biocompatibility data. References1. Mathew A, Oksman K, Pierron D, Harmad M. Cellulose. 2012 02/01; 19 (1): 139-50.2. Peter M, Ganesh N, Selvamurugan N, Nair SV, Furuike T, Tamura H, et al. Carbohydr Polym. 2010 5/5; 80 (3): 687-94.3. Mansour JM. Kinesiology: the Mechanics and Pathomechanics of Human Movement. 2003 (Ch 5): 66-79.4. Karageorgiou V, Kaplan D. Biomaterials. 2005 9; 26 (27): 5474-91.Proceeding of the MiMe October 8-11, 2013 - Faenza, Italy1st International Conference on Materials in Medicine

  • 144.
    Pålsson, Bertil
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Karlkvist, Tommy
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nano-entities for surface modification of minerals: Implications for flotation2017Conference paper (Other academic)
    Abstract [en]

    Adsorption of nano-entities (nano-cellulose and nano-chitin) on quartz and magnetite was investigated as a function of pH with measurement of Zeta potential as a tool. The results show strong adsorption of the nano-entities on both minerals, leading to charge reversal. However, the adsorption appears to be largely non-preferential over the concentration and pH ranges investigated.

    Micro-flotation results show that both nano-entities float quartz to the same extent, and that the same is true for magnetite. However, the amount floated is higher for quartz. There is also an indication that Chitin at pH 8 has some preference for quartz over magnetite.

    Mini-flotation results for mineral mixtures at pH 8 with Chitin and flotation reagents show that Chitin can selectively float quartz for the given conditions, but the recovery is low. If oleate is added, the selectivity is lost. This means that the nano-entity is probably not a cationic activator, rather it induces some little hydrophobicity to the quartz surface on its own.

  • 145.
    Samyn, P.
    et al.
    Albert-Ludwigs-Universität Freiburg, Institute for Forest Utilization and Works Science.
    Airoudj, A.
    Université de Haute-Alsace, Institut de Science des Matériaux de Mulhouse.
    laborie, M-P
    Albert-Ludwigs-Universität Freiburg, Institute for Forest Utilization and Works Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Roucoules, V.
    Université de Haute-Alsace, Institut de Science des Matériaux de Mulhouse.
    Plasma deposition of polymer composite films incorporating nanocellulose whiskers2011In: European Physical Journal: Applied physics, ISSN 1286-0042, E-ISSN 1286-0050, Vol. 56, no 2Article in journal (Refereed)
    Abstract [en]

    In a trend for sustainable engineering and functionalization of surfaces, we explore the possibilities of gas phase processes to deposit nanocomposite films. From an analysis of pulsed plasma polymerization of maleic anhydride in the presence of nanocellulose whiskers, it seems that thin nanocomposite films can be deposited with various patterns. By specifically modifying plasma parameters such as total power, duty cycle, and monomer gas pressure, the nanocellulose whiskers are either incorporated into a buckled polymer film or single nanocellulose whiskers are deposited on top of a polymeric film. The density of the latter can be controlled by modifying the exact positioning of the substrate in the reactor. The resulting morphologies are evaluated by optical microscopy, AFM, contact angle measurements and ellipsometry.

  • 146.
    Samyn, Pieter
    et al.
    Freiburg University, Institute for Forest Utilization and Works Science.
    Airoudj, Aissam
    Université de Haute-Alsace, Institut de Science des Matériaux de Mulhouse.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Roucoules, Vincent
    Université de Haute-Alsace, Institut de Science des Matériaux de Mulhouse.
    Haidara,, Hamidou
    Université de Haute-Alsace, Institut de Science des Matériaux de Mulhouse.
    Laborie, Marie-Pierre
    Freiburg University, Institute for Forest Utilization and Works Science.
    Metastable patterning of plasma nanocomposite films by incorporating cellulose nanowhiskers2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 2, p. 1427-1438Article in journal (Refereed)
    Abstract [en]

    A new method is presented for developing patterned thin nanocomposite films, by introducing cellulose nanowhiskers during pulsed plasma polymerisation of maleic anhydride. Metastable film structures develop as a combination of dewetting and buckling phenomena. By variation of the maleic anhydride monomer to nanocellulose weight ratio, the whiskers incorporate into a homogeneously covering patterned polymer film. An excess of nanowhiskers is required to prevent complete dewetting and deposit dimensionally stable films. The formation of anchoring points is assumed to stabilize the film through a ‘pinning’ effect to the substrate. The latter control the in-plane film stresses, similar to the effects of surface inhomogeneities such as artificial scratches. The different morphologies are evaluated by optical microscopy, AFM, contact angle measurements and ellipsometry. Further analysis by infrared spectroscopy and XPS suggests esterification between the maleic anhydride and cellulose moieties. The incorporation of renewable materials into a polymer film under solvent-free conditions demonstrates a further contribution to sustainable surface engineering, replacing traditional solvent-based processes.

  • 147.
    Sehaqui, Houssine
    et al.
    Applied Wood Materials Laboratory, Swiss Federal Laboratories for Materials Science and Technology (EMPA), CH-8600 Dübendorf.
    Larraya, Uxua Perez de
    Cemitec, Polígono Mocholí, Navarra.
    Liu, Peng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pfenninger, Numa
    Eawag, Dübendorf.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Zimmerman, Tanja
    Applied Wood Materials Laboratory, Swiss Federal Laboratories for Materials Science and Technology (EMPA), CH-8600 Dübendorf.
    Tingaut, Philippe
    Applied Wood Materials Laboratory, Swiss Federal Laboratories for Materials Science and Technology (EMPA), CH-8600 Dübendorf.
    Enhancing adsorption of heavy metal ions onto biobased nanofibers from waste pulp residues for application in wastewater treatment2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 4, p. 2831-2844Article in journal (Refereed)
    Abstract [en]

    Biobased nanofibers are increasingly considered in purification technologies due to their high mechanical properties, high specific surface area, versatile surface chemistry and natural abundance. In this work, cellulose and chitin nanofibers functionalized with carboxylate entities have been prepared from pulp residue (i.e., a waste product from the pulp and paper production) and crab shells, respectively, by chemically modifying the initial raw materials with the 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) mediated oxidation reaction followed by mechanical disintegration. A thorough investigation has first been carried out in order to evaluate the copper(II) adsorption capacity of the oxidized nanofibers. UV spectrophotometry, X-ray photoelectron spectroscopy and wavelength dispersive X-rays analysis have been employed as characterization tools for this purpose. Pristine nanofibers presented a relatively low content of negative charges on their surface thus adsorbing a low amount of copper(II). The copper adsorption capacity of the nanofibers was enhanced due to the oxidation treatment since the carboxylate groups introduced on the nanofibers surface constituted negative sites for electrostatic attraction of copper ions (Cu2+). The increase in copper adsorption on the nanofibers correlated both with the pH and carboxylate content and reached maximum values of 135 and 55 mg g−1 for highly oxidized cellulose and chitin nanofibers, respectively. Furthermore, the metal ions could be easily removed from the contaminated nanofibers through a washing procedure in acidic water. Finally, the adsorption capacity of oxidized cellulose nanofibers for other metal ions, such as nickel(II), chromium(III) and zinc(II), was also demonstrated. We conclude that TEMPO oxidized biobased nanofibers from waste resources represent an inexpensive and efficient alternative to classical sorbents for heavy metal ions removal from contaminated water.

  • 148.
    Shakeri, Alireza
    et al.
    Golestan University, Gorgan.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Self-reinforced nanocomposite by partial dissolution of cellulose microfibrils in ionic liquid2012In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 46, no 11, p. 1305-1311Article in journal (Refereed)
    Abstract [en]

    All-cellulose nanocomposite films with different ratios of cellulose I and II were produced by partial dissolution of microfibrillated cellulose using ionic liquid and subsequent film casting. The films were isotropic, transparent to visible light, highly crystalline, and contained different amounts of undissolved cellulose I crystallites in a matrix of dissolved cellulose. X-ray diffraction confirmed that cellulose I, i.e., the major polymorphic modification of cellulose in these nanocomposites, is rearranged to cellulose II crystal packing after the partial dissolution. The all-cellulose nanocomposite showed enhanced thermal properties, with thermal degradation temperature increased by 22% compared with thedissolved cellulose. The SEM and AFM studies verified that the nano-sized cellulose crystallites were well dispersed in the matrix. Results from DMA showed that the storage modulus was increased from 270 MPa for the dissolved cellulose to 1104 MPa for the nanocomposite with lower dissolution grade. This indicates that the all-cellulose nanocomposite films contained undissolved cellulose fragments – possibly cellulose I crystallites or aggregates of crystallites in a matrix of regenerated cellulose.

  • 149.
    Siqueira, Gilberto
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Processing of cellulose nanowhiskers/cellulose acetate butyrate nanocomposites using sol-gel process to facilitate dispersion2011In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 71, no 16, p. 1886-1892Article in journal (Refereed)
    Abstract [en]

    Biobased nanocomposites based on cellulose nanowhiskers (CNWs) and cellulose acetate butyrate (CAB) were prepared using solvent exchange of CNWs to ethanol by sol-gel method followed by casting. The strong flow birefringence of the solutions indicated evenly dispersed cellulose nanowhiskers in the dissolved polymer CAB. Scanning electron microscopy of the nanocomposites confirmed well dispersed CNWs in the CAB matrix, which was further supported by the high transparency exhibited by the nanocomposites. The results of tensile tests indicated significant improvements in the mechanical properties of nanocomposites by increasing the CNWs contents. The Young’s modulus and strength increased 83% and 70%, respectively, for nanocomposites with 12 wt% of CNW, and the strain was not suppressed compared to the neat CAB. The dynamic mechanical thermal analysis demonstrated significant improvement in storage modulus with increasing CNW contents, and the tan δ peak position was moved towards higher temperature when CNW was added. It is expected that solvent exchange by the sol-gel route followed by casting of nanocomposites from the same solvent will provide a promising route for obtaining cellulose nanocomposites with well dispersed CNW, leading to improved mechanical properties, even with low nanowhisker contents.

  • 150. Siqueira, Gilberto
    et al.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Tadokoro, Sandra K.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Re-dispersible carrot nanofibers with high mechanical properties and reinforcing capacity for use in composite materials2016In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 123, p. 49-56Article in journal (Refereed)
    Abstract [en]

    The separation of nanofibers from carrot juice residue and their reinforcing potential is demonstrated. Morphological properties, X-ray diffraction (XRD), and specific surface area (SSA) measurements showed that carrot nanofibers (CNF) have maintained the crystalline structure of native cellulose, while presenting a SSA as high as 246 m2.g-1 and diameters between 3 to 36 nm. CNF could be redispersed in water after drying, giving nanofibers with SSA and diameter comparable to properties of initial never-dried CNF. Finally, we propose possible uses of CNF either as strong nanopaper with excellent mechanical properties, i.e. modulus of 13.3 GPa and strength of 175 MPa, or as reinforcing phase in polymer matrices (CAB). Interesting properties of carrot nanofibers in terms of their possible transport and use from the dry state, as well as their remarkable mechanical properties afforded to nanopaper and nanocomposites may promote their use in environmentally benign constituent in industrial applications.

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