| 1. |
- Pålsson, Bertil, 1951-, et al.
(författare)
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Nano-entities for surface modification of minerals : Implications for flotation
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 2. |
- 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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| 3. |
- Muraleedharan, Madhu Nair, et al.
(författare)
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Isolation and modification of nano-scale cellulose from organosolv-treated birch through the synergistic activity of LPMO and endoglucanases
- 2021
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier. - 0141-8130 .- 1879-0003. ; 183, s. 101-109
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Tidskriftsartikel (refereegranskat)abstract
- Nanocellulose isolation from lignocellulose is a tedious and expensive process with high energy and harsh chemical requirements, primarily due to the recalcitrance of the substrate, which otherwise would have been cost-effective due to its abundance. Replacing the chemical steps with biocatalytic processes offers opportunities to solve this bottleneck to a certain extent due to the enzymes substrate specificity and mild reaction chemistry. In this work, we demonstrate the isolation of sulphate-free nanocellulose from organosolv pretreated birch biomass using different glycosyl-hydrolases, along with accessory oxidative enzymes including a lytic polysaccharide monooxygenase (LPMO). The suggested process produced colloidal nanocellulose suspensions (ζ-potential −19.4 mV) with particles of 7–20 nm diameter, high carboxylate content and improved thermostability (To = 301 °C, Tmax = 337 °C). Nanocelluloses were subjected to post-modification using LPMOs of different regioselectivity. The sample from chemical route was the least favorable for LPMO to enhance the carboxylate content, while that from the C1-specific LPMO treatment showed the highest increase in carboxylate content.
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| 4. |
- Vuddanda, Parameswara Rao, et al.
(författare)
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Electrospun nanofiber Mats for ultrafast release of ondansetron
- 2016
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Ingår i: Reactive & functional polymers. - : Elsevier BV. - 1381-5148 .- 1873-166X. ; 99, s. 65-72
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Tidskriftsartikel (refereegranskat)abstract
- Nanofiber mats or films are promising platforms that can offer unique opportunities in oromucosoal drug delivery. However, the conventional film forming technologies are unable to produce mats with unique internal microstructure and properties. Thus, the present study was aimed to develop electrospun nanofiber mats of a model drug -ondansetron hydrochloride (OND) for ultrafast drug release. Polyvinyl alcohol (PVA), a water soluble synthetic polymer was used in the preparation of nanofiber mats and casting film. The OND nanofiber mats and conventional films were prepared by electrospinning and casting methods, respectively. Different electrospinning process variables (feed rate, electric voltage and tip to collector distance) were investigated. Nanofiber mats and casted films were characterized using Scanning electron microscopy (SEM), Atomic force microscopy (AFM), Differential scanning calorimetry (DSC), Powder X-ray diffraction (PXRD), and Attenuated total reflection – Fourier transform infrared spectroscopy (ATR-FTIR). The folding endurance, drug content, wetting behaviour and disintegration properties and in-vitro drug release studies were also performed.The SEM and AFM had revealed that the nanofiber mats were formed with smooth uniform texture. Solid state studies indicated that the OND was in amorphous state and uniformly dispersed in PVA mats and a film. The electrospun nanofiber mat and casted film of OND showed sufficient mechanical properties. Wet sponge method suggested that OND nanofiber mats were simultaneously wetted and disintegrated within 10 s, which is ultrafast compared to casted films. The total amount of OND was released in 90 s (1.5 min) and 1800 s (30 min) from OND-PVA electrospun nanofiber mats and casted film, respectively. OND nanofiber mats can be promising alternatives to existing solid dosage forms for ultrafast release of drugs.
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| 5. |
- Hooshmand, Saleh, et al.
(författare)
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All-cellulose nanocomposite fibers produced by melt spinning cellulose acetate butyrate and cellulose nanocrystals
- 2014
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Ingår i: Cellulose. - : Kluwer Academic Publishers. - 0969-0239 .- 1572-882X. ; 21:4, s. 2665-2678
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Tidskriftsartikel (refereegranskat)abstract
- Bio-based continuous fibers were prepared by melt spinning cellulose acetate butyrate (CAB), cellulose nanocrystals (CNC) and triethyl citrate. A CNC organo-gel dispersion technique was used and the prepared materials (2 and 10 wt% CNC) were melt spun using a twin-screw micro-compounder and drawn to a ratio of 1.5. The microscopy studies showed that the addition of CNC in CAB resulted in defect-free and smooth fiber surfaces. An addition of 10 wt% CNC enhanced the storage modulus and increased the tensile strength and Young’s modulus. Fiber drawing improved the mechanical properties further. In addition, a micromechanical model of the composite material was used to estimate the stiffness and showed that theoretical values were exceeded for the lower concentration of CNC but not reached for the higher concentration. In conclusion, this dispersion technique combined with melt spinning can be used to produce all-cellulose nanocomposites fibers and that both the increase in CNC volume fraction and the fiber drawing increased the mechanical performance.
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| 6. |
- Hooshmand, Saleh, et al.
(författare)
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Melt spun cellulose nanocomposite fibres : Comparison of two dispersion techniques
- 2014
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Ingår i: Plastics, rubber and composites. - : Maney Publishing. - 1465-8011 .- 1743-2898. ; 43:1, s. 15-24
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Tidskriftsartikel (refereegranskat)abstract
- Biobased fibres of cellulose acetate butyrate (CAB) and cellulose nanocrystals (CNC) and triethyl citrate (TEC) as plasticiser were prepared by melt spinning. To obtain homogeneous dispersion of CNC, two different dispersion techniques were studied. In the first, the water content of the CNC suspension was reduced and exchanged to ethanol using centrifugation. In the second, the water in the CNC suspension was completely exchanged to ethanol by sol–gel process. Results showed that tensile modulus and tensile strength of the nanocomposite fibres produced with the first technique were lower than CAB–TEC fibres, but the fibres produced by the sol–gel process showed an increase in the tensile modulus and had no decrease in the strength. Optical microscopy of the fibres indicated a few aggregations on the sol–gel prepared materials. The results indicate that the sol–gel process is enhancing the dispersion of CNC and can be a suitable way to prepare nanocomposite fibres.
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| 7. |
- Mikkonen, K. S., et al.
(författare)
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Glucomannan composite films with cellulose nanowhiskers
- 2010
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 17:1, s. 69-81
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Aitomäki, Yvonne, et al.
(författare)
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Impregnation of cellulose nanofibre networks with a thermoplastic polymer
- 2013
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The emphasis of this study have been to study if impregnation of cellulose nanofibre networks can be made using a thermoplastic polymer as a matrix and to estimate the reinforcing efficiency of the cellulose nanofibres in this composite. A nanofibre network with higher porosity that water-dried nanofibre network was prepared from a cellulose waste byproduct (sludge). This was impregnated using a diluted solution of cellulose acetate butyrate polymer to produce a 60 wt. % CNF/CAB composite. This composite was characterized using microscopy and mechanical testing. High porosity is seen in the SEM images of the acetone-dried fibre network and SEM and film transparency was used to qualitatively assess the impregnation of the network. A significant improvement in the visible light transmittance was observed for the nanocomposite film compared to the nanofibre network as a result of the impregnation. The reinforcing efficiency was calculated based on a model of the nanocomposite and compared to other nanocomposites in the literature. The efficiency factor takes into account the volume fraction and the stiffness of the matrix. This showed that this CNF/CAB combination is similar in efficiency to CNF/PLA nanocomposites and more efficient that nanocomposites using when using stiffer matrices. It was also more efficient CNF nanocomposites based on Chitosan, which has the same stiffness. It is still however not as efficient as traditional glass polymer composites due to the random orientation of the fibres nor nanocomposites with very soft matrices due to the dominating network effect of the CNF in such composites. In conclusion, CAB impregnated cellulose nanofibre networks are promising biocomposite materials that could be used in applications where transparency and good mechanical properties are of interest. The key elements in the impregnation process of the nanocomposites were the use of a porous networks and a low viscosity thermoplastic resin solution.
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| 9. |
- Bondeson, Daniel, et al.
(författare)
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Optimization of the Isolation of Nanocrystals from Microcrystalline Cellulose by Acid Hydrolysis
- 2006
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 13:2, s. 171-180
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this work was to find a rapid, high-yield process to obtain an aqueous stable colloid suspension of cellulose nanocrystals/whiskers. Large quantities are required since these whiskers are designed to be extruded into polymers in the production of nano-biocomposites. Microcrystalline cellulose (MCC), derived from Norway spruce (Picea abies), was used as the starting material. The processing parameters have been optimized by using response surface methodology. The factors that varied during the process were the concentration of MCC and sulfuric acid, the hydrolysis time and temperature, and the ultrasonic treatment time. Responses measured were the median size of the cellulose particles/whiskers and yield. The surface charge as calculated from conductometric titration, microscopic examinations (optical and transmission electron microscopy), and observation of birefringence were also investigated in order to determine the outcome (efficiency) of the process. With a sulfuric acid concentration of 63.5% (w/w), it was possible to obtain cellulose nanocrystals/whiskers with a length between 200 and 400 nm and a width less than 10 nm in approximately 2 h with a yield of 30% (of initial weight).
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| 10. |
- Bozic, Mojca, et al.
(författare)
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Enzymatic phosphorylation of cellulose nanofibers to new highly-ions adsorbing, flame-retardant and hydroxyapatite-growth induced natural nanoparticles
- 2014
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 21:4, s. 2713-2726
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Tidskriftsartikel (refereegranskat)abstract
- This study confirms the enzyme-mediated phosphorylation of cellulose nanofibers (CNF) by using hexokinase and adenosine-5’-triphosphate (ATP) in the presence of Mg-ions, resulting in a phosphate group’s creation predominantly at C-6-O positioned hydroxyl groups of cellulose monomer rings. A proof-of-concept is provided using 12C CPMAS, 31P MAS NMR, ATR-FTIR and XPS analyzing methods. The degree of substitution is determined for the first time by ATR-FTIR spectroscopy being in a correlation with XPS and potentiometric titration results. From the thermal degradation measurements using TGA, the C-6-O phosphorylation was found to noticeably prevent the CNF derivatives from weight loss in the pyrolysis process, thus, providing them flame-resistance functionality. Furthermore, phosphorylation significantly enhanced adsorption capacity of Fe3+ ions making them interesting for fabrication of biobased filters and membranes. Finally, the biomimetic growth of Ca-P crystals (hydroxyapatite) in simulated body fluid was characterized by SEM and showing further practicability for biomedical materials.
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