| 1. |
- Herrera, Natalia, et al.
(författare)
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Functionalized blown films of plasticized polylactic acid/chitin nanocomposite : Preparation and characterization
- 2016
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 92, s. 846-852
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Tidskriftsartikel (refereegranskat)abstract
- Bionanocomposite films prepared with melt compounding and film blowing were evaluated for packaging applications. The nanocomposite masterbatch with 75 wt% polylactic acid (PLA), 5 wt% chitin nanocrystals (ChNCs) and 20 wt% glycerol triacetate plasticizer (GTA) was melt compounded and then diluted to 1 wt% ChNCs with PLA and polybutylene adipate-co-terephthalate (PBAT) prior to film blowing. The morphological, mechanical, optical, thermal and barrier properties of the blown nanocomposite films were studied and compared with the reference material without ChNCs. The addition of 1 wt% ChNCs increased the tear strength by 175% and the puncture strength by 300%. Additionally, the small amount of chitin nanocrystals affected the glass transition temperature (Tg), which increased 4 °C compared with the reference material and slightly enhanced the films degree of crystallinity. The chitin nanocomposite also had lower fungal activity and lower electrostatic attraction between the film surfaces; leading to easy opening of the plastic bags. The barrier and optical properties as well as the thermal degradation of the films were not significantly influenced by the addition of chitin nanocrystals.
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| 2. |
- Esmaeili, Chakavak, et al.
(författare)
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Synergy Effect of Nanocrystalline Cellulose for the Biosensing Detection of Glucose
- 2015
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 15:10, s. 24681-24697
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Tidskriftsartikel (refereegranskat)abstract
- Integrating polypyrrole-cellulose nanocrystal-based composites with glucose oxidase (GOx) as a new sensing regime was investigated. Polypyrrole-cellulose nanocrystal (PPy-CNC)-based composite as a novel immobilization membrane with unique physicochemical properties was found to enhance biosensor performance. Field emission scanning electron microscopy (FESEM) images showed that fibers were nanosized and porous, which is appropriate for accommodating enzymes and increasing electron transfer kinetics. The voltammetric results showed that the native structure and biocatalytic activity of GOx immobilized on the PPy-CNC nanocomposite remained and exhibited a high sensitivity (ca. 0.73 μA·mM(-1)), with a high dynamic response ranging from 1.0 to 20 mM glucose. The modified glucose biosensor exhibits a limit of detection (LOD) of (50 ± 10) µM and also excludes interfering species, such as ascorbic acid, uric acid, and cholesterol, which makes this sensor suitable for glucose determination in real samples. This sensor displays an acceptable reproducibility and stability over time. The current response was maintained over 95% of the initial value after 17 days, and the current difference measurement obtained using different electrodes provided a relative standard deviation (RSD) of 4.47%.
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| 3. |
- Hassan, Mohammad L., et al.
(författare)
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Metallo-Terpyridine-Modified Cellulose Nanofiber Membranes for Papermaking Wastewater Purification
- 2018
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Ingår i: Journal of Inorganic and Organometallic Polymers and Materials. - : Springer. - 1574-1443 .- 1574-1451. ; 28:2, s. 439-447
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Tidskriftsartikel (refereegranskat)abstract
- Metallo-terpyridine compounds and polymers exhibit unique optical, electrical, magnetic and antimicrobial properties. Recently, metallo-terpyridine-modified cellulosic films with interesting porous structure, that exhibit these properties, have been prepared. Herein we report the use of Cu-terpyridine-modified oxidized cellulose nanofibers (OXCNF-Cu-Tpy) as membranes for treatment of effluents of paper mills to produce re-usable water. The OXCNF-Cu-Tpy was prepared by modification of TEMPO-oxidized CNF (OXCNF) using copper(II) complex of 4′-Chloro [2,2′:6′,2″] terpyridine. The modification was proven by elemental analysis and Fourier transform infrared spectroscopy. The prepared OXCNF-Cu-Tpy was also characterized using X-ray diffraction and transmission electron microscopy. The prepared membranes were evaluated regarding their microscopic structure using scanning electron microscopy, atomic force microscopy, contact angle measurement, water flux and rejection of sub-micron size suspended particles in papermaking wastewater effluent. Chemical modification of OXCNF with the Cu-Tpy groups significantly increased pure water flux of the membranes by about 52 and 194% depending on pressure used during filtration (0.5 and 1 MPa, respectively). Although both OXCNF and OXCNF-Cu-Tpy exhibited high efficiency in removing the sub-micron size suspended particles from wastewater effluent, OXCNF-Cu-Tpy membranes showed about 30% higher flux rate than OXCNF membranes.
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| 4. |
- Herrera, Natalia, et al.
(författare)
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Plasticized polylactic acid nanocomposite films with cellulose and chitin nanocrystals prepared using extrusion and compression molding with two cooling rates: Effects on mechanical, thermal and optical properties
- 2016
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 83, s. 89-97
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Tidskriftsartikel (refereegranskat)abstract
- Triacetate citrate plasticized poly lactic acid and its nanocomposites based on cellulose nanocrystals (CNC) and chitin nanocrystals (ChNC) were prepared using a twin-screw extruder. The materials were compression molded to films using two different cooling rates. The cooling rates and the addition of nanocrystals (1 wt%) had an impact on the crystallinity as well as the optical, thermal and mechanical properties of the films. The fast cooling resulted in more amorphous materials, increased transparency and elongation to break, (approx. 300%) when compared with slow cooling. Chitin nanocomposites were more transparent than cellulose nanocomposites; however, microscopy study showed presence of agglomerations in both materials. The mechanical properties of the plasticized PLA were improved with the addition of a small amount of nanocrystals resulting in PLA nanocomposites, which will be further evaluated for film blowing and thus packaging applications.
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| 5. |
- Herrera Vargas, Natalia, 1982-, et al.
(författare)
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Triethyl Citrate (TEC) as a Dispersing Aid in Polylactic Acid/Chitin Nanocomposites Prepared via Liquid-Assisted Extrusion
- 2017
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 9:9
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Tidskriftsartikel (refereegranskat)abstract
- The production of fully bio-based and biodegradable nanocomposites has gained attention during recent years due to environmental reasons; however, the production of these nanocomposites on the large-scale is challenging. Polylactic acid/chitin nanocrystal (PLA/ChNC) nanocomposites with triethyl citrate (TEC) at varied concentrations (2.5, 5.0, and 7.5 wt %) were prepared using liquid-assisted extrusion. The goal was to find the minimum amount of the TEC plasticizer needed to enhance the ChNC dispersion. The microscopy study showed that the dispersion and distribution of the ChNC into PLA improved with the increasing TEC content. Hence, the nanocomposite with the highest plasticizer content (7.5 wt %) showed the highest optical transparency and improved thermal and mechanical properties compared with its counterpart without the ChNC. Gel permeation chromatography confirmed that the water and ethanol used during the extrusion did not degrade PLA. Further, Fourier transform infrared spectroscopy showed improved interaction between PLA and ChNC through hydrogen bonding when TEC was added. All results confirmed that the plasticizer plays an important role as a dispersing aid in the processing of PLA/ChNC nanocomposites.
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| 6. |
- Hietala, M., et al.
(författare)
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Moisture stability and mechanical durability of peat biocomposites
- 2017
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Ingår i: ICCM21 Proceedings. - : ICCM, International Committee on Composite Materials.
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Konferensbidrag (refereegranskat)abstract
- Peat, the organic matter formed from incomplete degradation of vegetation in peatlands, was studied as lignocellulosic raw material in manufacture of biocomposites. Peat mosses with varying degree of decomposition, namely slightly decomposed peat (H2) and moderately decomposed peat (H6), were ground into different particle size fractions which were used to prepare peat-polypropylene (PP) composites with 50 wt% peat content using extrusion compounding. The moisture absorption and dimensional stability as well as the mechanical properties and microstructure before and after cyclic freeze-thaw conditioning of the peat-PP composites were analysed and compared to reference wood-plastic composite (WPC). The mechanical properties of peat-PP composites were better than the properties of reference WPC before the freeze-thaw conditioning, and the mechanical permanence of peat-PP composites was better after the cyclic conditioning. Especially when peat with higher decomposition degree was used (H6), the mechanical permanence of peat-PP composites was improved. Likewise, the moisture absorption and the dimensional stability properties were improved the more decomposed the used peat was. The particle size did not affect the composite properties as much as the decomposition degree of peat, though the dimensional stability of peat-PP composite with moderately decomposed peat was better with smaller particle size peat.
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| 7. |
- Mujica-Garcia, A, et al.
(författare)
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Poly(lactic acid) melt-spun fibers reinforced with functionalized cellulose nanocrystals
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 6, s. 9221-9231
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Tidskriftsartikel (refereegranskat)abstract
- Poly(lactic acid)-cellulose nanocrystals (PLA/CNC) nanocomposite fibers with 1% weight fraction of nanocrystals were prepared via melt-spinning. In order to improve the compatibility between PLA and the CNC, PLLA chains were grafted onto the CNC surface using a "grafting from" reaction. For comparison, melt-spun PLA fibers and nanocomposites with unmodified CNC were also prepared. The morphology and thermal and mechanical properties of the fibers with different draw ratios were determined. The results of this research show that the surface modification together with drawing resulted in improved fiber properties, which are expected to depend on the alignment of the CNC and PLA molecular chains. The modification is also expected to lead to a flexible interface, which leads to more stretchable fibers. The main conclusion is that PLLA grafting is a very promising approach to improve the dispersion of CNC in PLA, thus creating interfacial adhesion between the phases and making it possible to spin fibers that can be drawn with improved mechanical performance.
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| 8. |
- 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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| 9. |
- Singh, Shikha, et al.
(författare)
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Evaluation of mechanical properties of poly (lactic acid)/cellulose nanocrystal nanocomposites : A comparative study of conventional tensile test and small punch test
- 2019
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Ingår i: Texto de las comunicaciones presentadas en el. - : Grupo Español de fractura (GEF). ; , s. 226-231
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- El ácido poliláctico (PLA) ha ganado mucha atención debido a su potencial para sustituir algunos de los polímerosconvencionales basados en fuentes no renovables (petróleo), sin embargo, tiene algunos inconvenientes que restringen suuso. Una forma de mejorar las propiedades mecánicas y térmicas de PLA es mediante la adición de nanocargas como losnanocristales de celulosa (CNC).La dispersión de los CNC en la matriz de PLA representa un desafío, ya que los CNC tienen una tendencia a aglomerarse.En este trabajo, se favoreció la dispersión de los CNC en la matriz de PLA mediante ultrasonidos y agitación, así comocon la modificación de la superficie de los CNC con la técnica de polimerización por apertura de anillo (ROP). Parafacilitar el procesamiento, se prepararon microesferas de PLA / CNC (1% en peso) mediante nitrógeno líquido.Finalmente, las películas de nanocompuestos se prepararon por extrusión-calandra.El objetivo principal de esta investigación es analizar posibles efectos del refuerzo de los CNC sobre las propiedadesmecánicas del PLA. Las propiedades mecánicas de los nanocompuestos de PLA/CNC se evaluaron mediante ensayos detracción y análisis térmico mecánico dinámico (DMTA) y se compararon con los obtenidos utilizando el ensayo “smallpunch” (SPT).
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