| 1. |
- Sethi, Jatin, et al.
(författare)
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Water resistant nanopapers prepared by lactic acid modified cellulose nanofibers
- 2018
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Ingår i: Cellulose. - : Springer. - 0969-0239 .- 1572-882X. ; 25:1, s. 259-268
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Tidskriftsartikel (refereegranskat)abstract
- The current work reports a novel, completely water based approach to prepare the water resistant modified cellulose nanopapers. Lactic acid in aqueous medium was attached on cellulose nanofibers surface with the aid of ultra-sonication and later oligomerized (polymerized) by compression molding under high temperature and pressure, to obtain the modified nanopapers with enhanced mechanical properties. The modified nanopapers showed an increase of 32% in the elastic modulus and 30% in the yield strength over reference nanopapers. Additionally, the modified nanopaper was hydrophobic in nature and had superior storage modulus under moist conditions. The storage modulus of wet modified nanopaper was three times (2.4 GPa) compared to the reference nanopapers (0.8 GPa) after 1 h immersion in water. Finally, the thermal stability of the modified nanopaper was also higher than reference nanopaper. The material reported is 100% bio-based
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| 2. |
- Alemandar, Ayse, et al.
(författare)
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The effect of decreased fiber size in wheat straw/polyvinyl alchol composites
- 2009
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Ingår i: Journal of Biobased Materials and Bioenergy. - : American Scientific Publishers. - 1556-6560 .- 1556-6579. ; 3:1, s. 75-80
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Tidskriftsartikel (refereegranskat)abstract
- The reinforcing potential of micro and nano-size fibers from wheat straw in polyvinyl alcohol (PVA) was studied. The microfibers were obtained by alkali treatment and disintegration process of wheat straw while nanofibers were obtained after applying further mechanical treatment of this alkali treated wheat straw. The results showed that the alkali treatment increased the α-cellulose content of the fibers from 38% to 73% due to hydrolysis of the hemicelluloses and lignin from the straw walls. The morphology and thermal properties of the micro and nano-size fibers were determined to show their potential as reinforcements. The transmission electron microscopy study showed that the size of the wheat straw fibers was decreased from micro to nano-size by the defibrillation process. Thermogravimetric analysis demonstrated the alkali treatment dramatically increased the thermal properties of the wheat straw fibers. The morphologies and thermal properties of the prepared composites were investigated by scanning electron microscopy and thermogravimetric analysis. The thermal stability of the nanofiber-reinforced composites increased with respect to the neat PVA. The mechanical properties of the composites increased significantly with the addition of microfibers and further increment was obtained with nanofibers. The tensile modulus increased from 2.1 GPa of pure PVA to 3 GPa with the addition of micro sized fibers and further to 3.8 GPa with the decreased fiber size to nano scale. The composites strength showed similar trend.
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| 3. |
- Alemdar, Ayse, et al.
(författare)
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Reinforcement capability of wheat straw fibers from micro to nano size
- 2007
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Ingår i: 9th International Conference on Wood & Biofiber Plastic Composites. - Madison, Wis : Forest Products Society. - 1892529505
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Konferensbidrag (refereegranskat)abstract
- The goal of this study was to explore the reinforcement capability of micro and nano-size fibers from wheat straw. Microfibers were obtained by alkali treatment and disintegration processes of the wheat straw while nanofibers were obtained after applying further mechanical treatment of this alkali treated wheat straw. The morphology and thermal properties of both fiber types were determined to show their suitability as reinforcements. TEM images showed that the diameters of the wheat straw fibers were decreased from micro to nano-size by the defibrillation process. Thermogravimetric analysis showed the alkali treatment dramatically increased the thermal properties of the wheat straw fibers. The composites were produced using, respectively, the microfibers and nanofibers as reinforcement, with both polyvinyl alcohol (PVA) and cellulose acetate butyrate (CAB) as the matrix. The morphology and thermal properties of the composites were investigated by scanning electron microscopy and thermogravimetric analysis. The mechanical properties of the composites were compared with those of neat polymer matrix and found to be considerably improved.
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| 4. |
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Cellulose nanocomposites : processing, characterization and properties
- 2005
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- The book will deal with new nanostructured composites, where both the reinforcement and the matrix are bio based. Cellulose combined with natural polymers led to the development of a new class of biodegradable and environmental friendly bionanocomposites. This new family of nanocomposites is expected to have remarkable improvement of material properties when compared with the matrix polymers or conventional micro- and macro-composite materials. Such improvements in properties typically include a higher modulus and strength, improved barrier properties, increased heat distortion temperature. This new class of renewable nanocomposites is expected to capture new market in transportation, medical and packaging applications. This book will include the raw materials which can be used for making these composites, separation/isolation technologies of cellulose based reinforcements from diverse natural resources and it will also include a brief overview of the recent advancements in the surface chemistry of nanocellulose. Characterization methods such as atomic force microscope (AFM), transmission electron microscope (TEM) and scanning electron microscope (SEM), Raman Spectroscopy, for the nano scale cellulose reinforcements and for the bio-nanocomposites will be discussed. Further, different processing methods for nanocomposites and their mechanical, thermal properties, barrier properties will be included. This will be the first book on the topic of cellulose based Nanocomposites! This is a relatively new research field and there are no books available on this topic. There is a growing interest on biopolymer based nanocomposites in developed and developing world (Japan, USA, Europe, China, South Africa, Australia) and especially if the nanocomposites are based totally on renewable raw materials. We can see several ongoing research projects on this topic in Europe and North America, and there is an emerging research trend for developing micro-and nano-fibre reinforced biopolymers.
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| 5. |
- Correia, Viviane da Costa, et al.
(författare)
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Grinding process for the production of nanofibrillated cellulose based on unbleached and bleached bamboo organosolv pulp
- 2016
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 23:5, s. 2971-2987
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Tidskriftsartikel (refereegranskat)abstract
- Nanofibrillated cellulose (NFC) is a type of nanomaterial based on renewable resources and produced by mechanical disintegration without chemicals. NFC is a potential reinforcing material with a high surface area and high aspect ratio, both of which increase reinforcement on the nanoscale. The raw materials used were unbleached and bleached bamboo organosolv pulp. Organosolv pulping is a cleaner process than other industrial methods (i.e. Kraft process), as it uses organic solvents during cooking and provides easy solvent recovery at the end of the process. The NFC was produced by treating unbleached and bleached bamboo organosolv pulps for 5, 10, 15 and 20 nanofibrillation cycles using the grinding method. Chemical, physical and mechanical tests were performed to determine the optimal condition for nanofibrillation. The delamination of the S2 layer of the fibers during nanofibrillation contributed to the partial removal of amorphous components (mainly lignin), which have low polarity and improved the adhesion of the fibers, particularly the unbleached cellulose. The transverse modulus of elasticity of the unbleached NFC was highest after 10 nanofibrillation cycles. Further treatment cycles decreased the modulus due to the mechanical degradation of the fibers. The unbleached NFC produced by 10 cycles have a greater transverse modulus of elasticity, the crystallite size showed increase with the nanofibrillation, and after 5 nanofibrillation cycles, no differences are observed in the morphology of the fibers.
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| 6. |
- Frisk, Nikolina, et al.
(författare)
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Nanocellulose reinforced bio-polyurethane foams as core in sandwich composite panels
- 2017
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Ingår i: ICCM21 Proceedings. - : ICCM, International Committee on Composite Materials.
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Konferensbidrag (refereegranskat)abstract
- The aim of this work was to reinforce bio-polyurethane (BPU) with cellulose nanofibers (CNF) to develop foams suitable for use as core in lightweight composite panels. The nanofibers were prepared using mechanical grinding of bleached carrot juice residue, a cheap and energy efficient process. The prepared foam properties were studied and compared to neat BPU foam properties. The results showed that the CNF reinforced foam had better mechanical properties compared to the neat bio-PU foams and the addition of cellulose nanofibers deceased the cell size and open cell content. Then the foam suitability for composite use was evaluated by manufacturing lightweight sandwich panels using vacuum infusion process with CNF reinforced BPU foam core. Kraft paper was used as a skin and epoxy resin was used as adhesive resin and the composite laminates were prepared using vacuum infusion technique. These nanofiber reinforced core materials resulted in sandwich panels with improved mechanical properties. X-ray tomography showed that the resin did not penetrate into the core but only the foam surface layer. Moreover, the results were evaluated in a material selection process by means of minimizing merit indices. A trend in the behaviour of compressive properties of the foam and flexural properties of the sandwich panels could be established. The addition of small amount of cellulose nanofibers to BPU based foams is leading to a foam which have similar properties as commercial rigid PU foams. © 2017 International Committee on Composite Materials.
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| 7. |
- Frisk, Nikolina, et al.
(författare)
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Novel Applications of Nanocellulose : Lightweight Sandwich Composites for Transportation
- 2015
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Ingår i: Reference module in materials science and materials engineering. - Amsterdam : Elsevier. - 9780128035818
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Bokkapitel (refereegranskat)abstract
- This chapter is focusing on improvement of the mechanical properties of bio-polyurethane (PU) foam by reinforcing the pre-resin with cellulose nanofibers (CNF). The prepared foam performance was evaluated by manufacturing lightweight sandwich panels using vacuum infusion process with CNF-reinforced bio-PU foam core. Cellulose fiber network (kraft paper) was used as a skin and epoxy resin was used as adhesive resin. The sandwich was tested and compared to a non-reinforced PU foam core sandwich in terms of compressive, flexural, and structural properties. The results showed that the CNF-reinforced foam resulted in sandwich panel with improved mechanical properties, and to foam with smaller cell size and lower open cell content. Moreover, the results were evaluated in a material selection process by means of minimizing merit indices. A trend in the behavior of compressive properties of the foam and flexural properties of the sandwich panels could be established. Overall, the results indicated that the mechanical properties of bio-PU foam was improved by reinforcing the pre-resin with small amounts of wet carrot CNF.Ultimately, this work shows a positive trend suggesting CNF-reinforced bio-PU foam has a great potential for use in commercialized products or structural components in future constructions.
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| 8. |
- Gezahegn, S., et al.
(författare)
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Lignin Spinning and Carbonization to Nano-Layered Graphitic Structure
- 2019
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Ingår i: Proceedings of the 2019 International Conference on Composite Materials. - : RMIT University. ; , s. 1482-1488
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Graphitic lignin-based nanocarbons were prepared from spun lignin/PVA nanofiber networks using dry pyrolysis (DP) at 900 oC and hydrothermal carbonization (HTC) at 200 oC under a pressure of ~200 psi. The graphite formations were confirmed in both DP and HTC treated samples using Transmission Electron Microscopy (TEM). The electrical conductivity of DP treated samples was improved by 14 % compared to the HTC treated samples, showing that DP converts lignin into more conductive graphite components. The photoluminescence of both charring methods showed similar patterns, with the highest emission at 320 nm. The DP samples had two times higher intensity than the HTC samples and were red-shifted, while the HTC samples showed more broad peaks. Corroborating with Fourier-Transform Infrared Spectroscopy (FTIR) results, functional groups from lignin residue were present in the HTC samples, while they were attenuated in the DP samples. The most important finding of this study is that spun Lignoboost lignin/PVA fibers prepared via two different charring methods yield layered graphitic materials.
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| 9. |
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| 10. |
- Mathew, Aji P., et al.
(författare)
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Mechanical properties of biodegradable composites from poly lactic acid (PLA) and microcrystalline cellulose (MCC)
- 2005
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 97:5, s. 2014-2025
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Tidskriftsartikel (refereegranskat)abstract
- Biodegradable composites were prepared using microcrystalline cellulose (MCC) as the reinforcement and polylactic acid (PLA) as a matrix. PLA is polyester of lactic acid and MCC is cellulose derived from high quality wood pulp by acid hydrolysis to remove the amorphous regions. The composites were prepared with different MCC contents, up to 25 wt %, and wood flour (WF) and wood pulp (WP) were used as reference materials. Generally, the MCC/PLA composites showed lower mechanical properties compared to the reference materials. The dynamic mechanical thermal analysis (DMTA) showed that the storage modulus was increased with the addition of MCC. The X-ray diffraction (XRD) studies on the materials showed that the composites were less crystalline than the pure components. However, the scanning electron microscopy (SEM) study of materials showed that the MCC was remaining as aggregates of crystalline cellulose fibrils, which explains the poor mechanical properties. Furthermore, the fracture surfaces of MCC composites were indicative of poor adhesion between MCC and the PLA matrix. Biodegradation studies in compost soil at 58°C showed that WF composites have better biodegradability compared to WP and MCC composites. The composite performances are expected to improve by separation of the cellulose aggregates to microfibrils and with improved adhesion
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