| 1. |
- Bridarolli, Alexandra, et al.
(författare)
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Evaluation of the Adhesion and Performance of Natural Consolidants for Cotton Canvas Conservation
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society. - 1944-8244 .- 1944-8252. ; 10:39, s. 33652-33661
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Tidskriftsartikel (refereegranskat)abstract
- Recent developments in paper and canvas conservation have seen the introduction of nanocellulose (NC) as a compatible treatment for the consolidation of historical cellulosic artifacts and manuscripts. However, as part of the assessment of these new materials for canvas consolidation, the adhesion of the consolidation treatment (which takes place between the applied material and the substrate) has not yet been evaluated, and as a result, it is poorly understood by both the scientific and conservation communities. After evaluating the potential of NC treatments for the consolidation of cotton painting canvas, we investigate a route to promote the interaction between the existing canvas and the nanocellulose treatment, which is in our case made of cellulose nanofibrils (CNF). This was carried out by introducing a cationic polymer, polyamidoamine-epichlorohydrin (PAAE), as an intermediate layer between the canvas and the CNF. The morphological, chemical, and mechanical evaluation of the canvas samples at different relative humidity (RH) levels demonstrated how the adhesion of the added PAAE layer is a dominant factor in the consolidation process. Improvement in the coating of canvas single fibers by the CNF, higher adhesion energy between the canvas fibers and the CNF treatment, and finally overall stronger canvas reinforcement were observed following the introduction of PAAE. However, an increase in mechanical response to moisture sorption and desorption was also observed for the PAAE-treated canvases. Overall, this study shows the complexity of such systems and, as such, the relevance of using a multiscale approach for their assessment.
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| 2. |
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| 3. |
- Danyliv, Olesia, et al.
(författare)
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Self-Standing, Robust Membranes Made of Cellulose Nanocrystals (CNCs) and a Protic Ionic Liquid : Toward Sustainable Electrolytes for Fuel Cells
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society. - 2574-0962. ; 4:7, s. 6474-6485
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Tidskriftsartikel (refereegranskat)abstract
- Energy-conversion devices based on the phenomenon of proton conduction, for example, polymer electrolyte membrane fuel cells (PEMFCs), require low cost and sustainable electrolytes with high ionic conductivity and good mechanical properties under anhydrous conditions and at temperatures up to 150 °C. Biopolymers possess an intrinsic thermomechanical stability but an insufficient proton conductivity in the dry state, which however may be imparted by a protic ionic liquid (PIL). This work presents the preparation and properties of composite membranes made of cellulose nanocrystals (CNCs) and a PIL. The membranes are thermally stable and display an ionic conductivity within the range 10-4-10-3 S/cm for temperatures between 120 and 160 °C. Moreover, the analysis of the biopolymer's apparent dimensions at nanoscale reveals a dependence of the CNCs' defects, twisting, and aggregation in the presence of the PIL. Preliminary tests using a simple fuel cell setup demonstrate a response of the membranes to the inlet of H2 gas, with a generation of electrical current. These findings provide a solid groundwork for further development and future studies of biopolymer/PIL electrolytes for energy applications. © 2021 The Authors.
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| 4. |
- Kolman, Krzysztof, 1986, et al.
(författare)
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Combined Nanocellulose/Nanosilica Approach for Multiscale Consolidation of Painting Canvases
- 2018
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 1:5, s. 2036-2044
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Tidskriftsartikel (refereegranskat)abstract
- The restoration of painting canvases is a complex problem that, because of the hierarchical nature of the canvas, requires intervention at several length scales. We propose an approach combining polyelectrolyte-treated silica nanoparticles (SNP) and cellulose nanofibrils (CNF) for canvas consolidation. The formulations, applied on model degraded canvases, gave a total weight increase of
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| 5. |
- Kolman, Krzysztof, 1986, et al.
(författare)
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Preparation of silica/polyelectrolyte complexes for textile strengthening applied to painting canvas restoration
- 2017
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 532, s. 420-427
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Tidskriftsartikel (refereegranskat)abstract
- We here report three different approaches to prepare silica-polyelectrolyte complexes for mechanical strengthening of cotton fibers. In the first approach, polyvinylpyrrolidone (PVP) was used as a stabilizing polymer to delay the adsorption of a poly(quaternary ammonium) species, PQA (a copolymer of dimethylamine and epichlorohydrin), on the surface of silica. In the second approach cationic starch (CS), which is a branched polyelectrolyte, was used and the adsorption of CS resulted in formulations with good colloidal stability. The third approach was based on reduction of the charge density of silica to prevent PQA adsorption. Lowering the pH reduced the surface charge of the silica and enabled control of the adsorption. As a result, the aggregation was prevented and only a thin layer of polymer adsorbed. For all formulations a second polyelectrolyte, carboxymethyl cellulose (CMC) was subsequently adsorbed on the cationic polyelectrolyte layer. The silica/polyelectrolyte formulations were evaluated by dynamic light scattering (DLS). The obtained formulations were applied on model surfaces of degraded painting canvas. The performance of the silica particles coated either with one cationic polyelectrolyte and or with a layer of cationic polyelectrolyte followed by a layer of anionic polyelectrolyte were assessed by tensile testing and the morphology of the treated samples was investigated with SEM. The particles coated with a single cationic layer increased the maximum load at break by 29% at the cost of a reduction in strain. The particles coated with a double layer increased the maximum load to a lesser extent; however, higher values of strain were recorded. For all systems the mass uptake was limited to around 5 wt%.
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| 6. |
- Nagalakshmaiah, M., et al.
(författare)
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Melt extrusion of polystyrene reinforced with cellulose nanocrystals modified using poly (styrene)-co-(2-ethylhexyl acrylate) latex particles
- 2017
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057. ; 91, s. 297-306
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Tidskriftsartikel (refereegranskat)abstract
- Non-covalent modification of cellulose nanocrystals (CNC) was performed using a water based method with laboratory prepared statistical copolymer, viz. poly [(styrene)-co-(2-ethylhexyl acrylate)], by ionic interactions. The thermal, functional and morphological properties of modified CNC were characterized by thermogravimetric analysis (TGA), Fourier vansform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Their hydrophobic nature was investigated by contact angle measurements. These nanoparticles were used to prepare polystyrene (PS) nanocomposites by twin-screw extrusion. The thermomechanical performance of the ensuing composites was examined by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The morphology of the materials was also studied using scanning electron microscopy (SEM).
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| 7. |
- Nechyporchuk, Oleksandr, 1988, et al.
(författare)
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Accelerated ageing of cotton canvas as a model for further consolidation practices
- 2017
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Ingår i: Journal of Cultural Heritage. - : Elsevier BV. - 1296-2074. ; 28, s. 183-187
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Tidskriftsartikel (refereegranskat)abstract
- In order to assess the effectiveness of various practices for canvas consolidation, model substrates are needed. In this work, a method of rapid ageing of cotton canvas is described. The method consists of treatment of the canvas with a mixture of hydrogen peroxide and sulfuric acid at 40 degrees C during 72 hours to mimic to some extent the natural processes of oxidation and acid-catalysed hydrolysis of cellulose. Two protocols for canvas degradation were developed, which reduced the degree of polymerization of cellulose from ca.6250 to ca.1350 and 450. The reduction of the mechanical properties and the increase of the negative charge were also quantified. These samples were compared with a canvas degraded using a state-of-the-art method that takes up to 20 days. The results show that the developed method can provide a rapid procedure for preparing small samples for testing various consolidation strategies by conservators.
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| 8. |
- Nechyporchuk, Oleksandr, 1988, et al.
(författare)
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Cellulose Nanofibril-Based Coatings of Woven Cotton Fabrics for Improved Inkjet Printing with a Potential in E-Textile Manufacturing
- 2017
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Ingår i: ACS Sustainable Chemistry & Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 5:6, s. 4793-4801
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Tidskriftsartikel (refereegranskat)abstract
- The roughness of woven fabrics strongly limits print quality, which is particularly critical in printing of conductive circuits on fabrics. This work demonstrates the use of wood-derived cellulose nanofibrils (CNFs) mixed with a plasticizer as coatings of woven cotton fabrics for inkjet printing using (i) conventional water-based pigment inks and (ii) conductive silver nanoparticle inks. CNFs, being similar in nature to cotton, introduced minimal alteration to woven cotton fabrics by preserving their visual appearance as well as their mechanical properties. We also showed that the use of CNF-based coatings facilitated ink droplet settling on the substrate, which ensured high quality with the potential of higher printing speed production. The coatings of CNFs plasticized with glycerol enabled concentrating the pigment on the surface of the fabric, preventing its penetration into the fabric depth, which allows for increasing the resolution of the printed pattern. When used for color ink printing, it enhanced the print chroma and permitted reducing the amount of deposited ink, yielding similar color lightness. The CNF coatings allowed for substantial reduction of the amount of silver ink when printing the conductive tracks on fabrics. Furthermore, the nature of the coating imparts flexibility to the conductive layer, while maintaining electric signal quality, even when folded. This study provides a platform for manufacturing sustainable and disposable e-textiles.
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| 9. |
- Nechyporchuk, Oleksandr, et al.
(författare)
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Continuous Assembly of Cellulose Nanofibrils and Nanocrystals into Strong Macrofibers through Microfluidic Spinning
- 2018
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Ingår i: Advanced Materials Technologies. - : Wiley. - 2365-709X.
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Tidskriftsartikel (refereegranskat)abstract
- Microfluidic fiber spinning is a promising technique for assembling cellulose nanomaterials into macroscopic fibers. However, its implementation requires upscalabe fabrication processes while maintaining high strength of the fibers, which could not be previously achieved. Herein, a continuous wet spinning process based on microfluidic flow focusing is developed to produce strong fibers from cellulose nanofibrils (CNFs) and nanocrystals (CNCs). Fibers with an average breaking tenacity as high as 29.5 cN tex−1 and Young's modulus of 1146 cN tex−1 are reported for the first time, produced from nonhighly purified CNF grades. Using the same developed method, wet spinning of fibers from CNCs is achieved for the first time, reaching an average Young's modulus of 1263 cN tex−1 and a breaking tenacity of 10.6 cN tex−1, thus exhibiting strength twice as high as that of common CNC films. A rather similar stiffness of CNC and CNF spun fibers may originate from similar degrees of alignment, as confirmed by wide-angle X-ray scattering (WAXS) and birefringence measurements, whereas lower strength may primarily arise from the shorter length of CNCs compared to that of CNFs. The benefit of CNCs is their higher solids content in the dopes. By combining both CNCs and CNFs, the fiber properties can be tuned.
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| 10. |
- Nechyporchuk, Oleksandr, 1988, et al.
(författare)
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Current Progress in Rheology of Cellulose Nanofibril Suspensions
- 2016
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 17:7, s. 2311-2320
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Forskningsöversikt (refereegranskat)abstract
- Cellulose nanofibrils (CNFs) are produced and commonly used in the form of aqueous suspensions or gels. A number of studies have focused lately on rheological properties of CNF suspensions, which gives insight into properties of such materials and can reflect their behavior during handling. This Review summarizes the recent progress in rheological studies on CNF aqueous suspensions using rotational rheometry. Here, we discuss linear viscoelastic properties, i.e., frequency-dependent storage and loss moduli; shear flow behavior, i.e., apparent viscosity and shear stress as a function of shear rate; local flow characteristics, etc. In this Review, we point out that the rheological behavior of at least two types of CNF suspensions should be distinguished: (i) ones produced using mechanical fibrillation with or without enzymatic pretreatment (no surface chemical modification), which possess highly flocculated structure, and (ii) ones produced involving chemical modification pretreatments, e.g., carboxylation, carboxymethylation, quaternization, or sulfonation, which possess better colloidal stability and do not evidently flocculate.
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