| 1. |
- Åkerfeldt, Maria, 1982, et al.
(författare)
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Textile piezoelectric sensors – melt spun bi-component poly(vinylidene fluoride) fibres with conductive cores and poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) coating as the outer electrode
- 2014
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Ingår i: Fashion and Textiles. - : Springer Science and Business Media LLC. - 2198-0802. ; 1:1
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Tidskriftsartikel (refereegranskat)abstract
- The work presented here addresses the outer electroding of a fully textile piezoelectric strain sensor, consisting of bi-component fibre yarns of β-crystalline poly(vinylidene fluoride) (PVDF) sheath and conductive high density polyethylene (HDPE)/carbon black (CB) core as insertions in a woven textile, with conductive poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) coatings developed for textile applications. Two coatings, one with a polyurethane binder and one without, were compared for the application and evaluated as electrode material in piezoelectric testing, as well as tested for surface resistivity, tear strength, abrasion resistance and shear flexing. Both coatings served their function as the outer electrodes in the system and no difference in this regard was detected between them. Omission of the binder resulted in a surface resistivity one order of magnitude less, of 12.3 Ω/square, but the surface resistivity of these samples increased more upon abrasion than the samples coated with binder. The tear strength of the textile coated with binder decreased with one third compared to the uncoated substrate, whereas the tear strength of the coated textile without binder increased with the same amount. Surface resistivity measurements and scanning electron microscopy (SEM) images of the samples subjected to shear flexing showed that the coatings without the binder did not withstand this treatment, and that the samples with the binder managed this to a greater extent. In summary, both of the PEDOT:PSS coatings could be used as outer electrodes of the piezoelectric fibres, but inclusion of binder was found necessary for the durability of the coating.
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| 2. |
- Henrysson, Erica, 1987, et al.
(författare)
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Conceptual Design and Analysis of Membrane Structures
- 2016
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Ingår i: Proceedings of 29th Nordic Seminar on Computational Mechanics – NSCM29.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this work one approach for formfinding and analysing tension membranestructures is described. Focus has been on the conceptual stage. For this the computersoftware SMART Form has been further developed, enabling the possibility to do real-timeformfinding and analysis of fabric structures. The software is based on a method where theorthotropic membrane is modeled with a triangular mesh, where the mass is lumped on thenodes. As a computational tool dynamic relaxation is used to find the static equilibriumconfiguration for the structure. The advantage with this is that there is no need for formulationand manipulation of matrices common in the finite element method.
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| 3. |
- Lund, Anja, et al.
(författare)
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Melt spinning of beta-phase poly(vinylidene fluoride) yarns with and without a conductive core
- 2011
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Ingår i: Journal of Applied Polymer Science. - : Wiley Periodicals, Inc.. - 0021-8995 .- 1097-4628. ; 120:2, s. 1080-1089
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Tidskriftsartikel (refereegranskat)abstract
- When poly(vinylidene fluoride) (PVDF) is to be used as a piezoelectric material, the processing must include the formation of polar β-phase crystallites, as well as the application of electrically conducting charge collectors, that is, electrodes. In this article, results from the melt spinning of PVDF yarns and a novel bicomponent PVDF-yarn with a conductive carbon black/polypropylene (CB/PP) core are presented. Melt spinning has been done under conditions typical for industrial large-scale fiber production. The effects on the resulting crystalline structure of varying the spinning velocity, draw rate, and draw temperature are discussed. The results show that, for maximum α-to-β phase transformation, cold drawing should take place at a temperature between 70 and 90°C, and both the draw ratio and the draw rate should be as high as possible. It was observed that the cold drawing necessary to form β-phase crystallinity simultaneously leads to a decrease in the core conductivity of the bicomponent yarns. In this work, the melt spinning of bicomponent fibers with high-β-phase PVDF in the sheath and a CB/PP core was successfully accomplished. The core material remained electrically conductive, paving the way for the use of a CB-polymer compound as inner electrode in the melt spinning of piezoelectric bicomponent fibers.
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| 4. |
- Lund, Anja
(författare)
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Melt spun piezoelectric textile fibres : an experimental study
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Melt Spun Piezoelectric Textile Fibres - an Experimental Study ANJA LUND Department of Materials and Manufacturing Technology Chalmers University of Technology ABSTRACT The manufacturing and characterisation of piezoelectric textile fibres are described in this thesis. A piezoelectric material is one that generates an electric voltage when deformed, a property which exists in a number of materials. The polymer with the strongest known piezoelectric effect today is poly(vinylidene fluoride) (PVDF), however it must be processed under certain conditions to become piezoelectric. This study shows that piezoelectric bicomponent PVDF-based fibres can be produced by melt spinning, which is a common and relatively simple fibre spinning method. The melt spinning process must include cold drawing, as this introduces a polar crystalline structure in the polymer. The fibres must also be electroded, which is done by producing bicomponent fibres with a core-and-sheath structure. The core is electrically conductive and constitutes an inner electrode consisting of a carbon black/polymer compound, whereas the sheath is PVDF and constitutes the piezoelectric component. Being sensitive to both deformation and temperature changes, these fibres are anticipated to be useful in a number of sensor applications. The flexibility and small size of the fibres makes it possible to include them as miniature-sensors in structures or garment without affecting the shape or comfort.
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| 5. |
- Nilsson, Erik, 1976, et al.
(författare)
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Electrically conductive polymeric bi-component fibers containing a high load of low-structured carbon black
- 2015
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 132:29, s. art. no. 42255-
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Tidskriftsartikel (refereegranskat)abstract
- © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42255. © 2015 Wiley Periodicals, Inc. Melt spinning at semi-industrial conditions of carbon black (CB) containing textiles fibers with enhanced electrical conductivity suitable for heating applications is described. A conductive compound of CB and high density polyethylene (HDPE) was incorporated into the core of bi-component fibers which had a sheath of polyamide 6 (PA6). The rheological and fiber-forming properties of a low-structured and a high-structured CB/HDPE composite were compared in terms of their conductivity. The low-structured CB gave the best trade-off between processability and final conductivity. This was discussed in terms of the strength of the resulting percolated network of carbon particles and its effect on the spin line stability during melt spinning. The conductivity was found to be further enhanced with maintained mechanical properties by an in line thermal annealing of the fibers at temperatures in the vicinity of the melting point of HDPE. By an adequate choice of CB and annealing conditions a conductivity of 1.5 S/cm of the core material was obtained. The usefulness of the fibers for heating applications was demonstrated by means of a woven fabric containing the conductive fibers in the warp direction. By applying a voltage of 48 V the surface temperature of the fabric rose from 20 to 30°C.
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| 6. |
- Rasel, H., et al.
(författare)
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New bio-based plastics, from a non-edible plant oil side-stream, for film extrusion
- 2014
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Ingår i: 19th IAPRI World Conference on Packaging 2014. - : Victoria University. - 9781510821316 ; , s. 586-590
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Konferensbidrag (refereegranskat)abstract
- Renewable sourced PET, PA, PE, starch blends, etc, are fastly growing due to the processability and final performance, that is similar to their petroleum derived options. A bit in the shadow of the development of these plastics, development is ongoing on another group of plastics, made directly of the side-streams of agricultural products: oil plant residues and proteins. They can be used in edible applications but not all of them are suitable for food or forage. Industrial oilseed meal from crambe abyssinica contains relatively high levels of protein that is not suitable for human or animal consumption due to the presence of anti-nutritional compounds. This paper presents research on crambe meal as a base for new plastics, developed to extrude continuous, flexible plastic films based on crambe meal, blended with vital wheat gluten as an elastic component and urea as a protein denaturant. The effect of process parameters, such as screw speed, die temperature and pressure, and the effect of components were studied with regards to the final performance of the film extrudates. E.g. mechanical properties, oxygen permeability and moisture content were determined and surface and cross-section morphologies were examined with electron microscopy. The results showed that crambe-based blends can be extruded as continuous, flexible plastic films, which exhibit barrier properties towards oxygen. Recipes and methods for pelletizing of master batches for post-converting (e.g. extrusion or compression molding) were successfully developed. Addition of a renewable plasticizer improved the extrusion performance and resulted in less hygroscopic films, which further showed the overall highest tensile strength while the extensibility was nearly unaffected. The results provide a first basis to further develop the process and the blend towards potential industrial applications, for example as packaging materials to trays, pots and similar type of packages.
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| 7. |
- Gaska, Karolina, 1986, et al.
(författare)
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Gas Barrier, Thermal, Mechanical and Rheological Properties of Highly Aligned Graphene-LDPE Nanocomposites
- 2017
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 9:7, s. 294-
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Tidskriftsartikel (refereegranskat)abstract
- This contribution reports on properties of low-density polyethylene-based composites filled with different amounts of graphene nanoplatelets. The studied samples were prepared in the form of films by means of the precoating technique and single screw melt-extrusion, which yields a highly ordered arrangement of graphene flakes and results in a strong anisotropy of composites morphology. The performed tests of gas permeability reveal a drastic decrease of this property with increasing filler content. A clear correlation is found between permeability and free volume fraction in the material, the latter evaluated by means of positron annihilation spectroscopy. A strong anisotropy of the thermal conductivity is also achieved and the thermal conductivity along the extrusion direction for samples filled with 7.5 wt % of GnP (graphene nanoplatelets) reached 2.2 W/m·K. At the same time, when measured through a plane, a slight decrease of thermal conductivity is found. The use of GnP filler leads also to improvements of mechanical properties. The increase of Young’s modulus and tensile strength are reached as the composites become more brittle.
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| 8. |
- Mellin, Pelle, 1985-, et al.
(författare)
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Nano-sized by-products from metal 3D printing, composite manufacturing and fabric production
- 2016
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Ingår i: Journal of Cleaner Production. - Sweden : Elsevier. - 0959-6526 .- 1879-1786. ; 139, s. 1224-1233
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Tidskriftsartikel (refereegranskat)abstract
- Recently, the health and environmental perspective of nano-materials has gained attention. Most previous work focused on Engineered Nanoparticles (ENP). This paper examines some recently introduced production routes in terms of generated nano-sized by-products. A discussion on the hazards of emitting such particles and fibers is included. Fine by-products were found in recycled metal powder after 3D printing by Selective Laser Melting (SLM). The process somehow generated small round metal particles (~1e2 mm) that are possibly carcinogenic and respirable, but not small enough to enter by skin-absorption. With preventive measures like closed handling and masks, any health related effects can be prevented. The composite manufacturing in particular generated ceramic and carbonaceous particles that are very small and respirable but do not appear to be intrinsically toxic. The smallest features in agglomerates were about 30 nm. Small particles and fibers that were not attached in agglomerates were found in a wide range of sizes, from 1 μm and upwards. Preventive measures like closed handling and masks are strongly recommended. In contrast, the more traditional production route of fabric production is investigated. Here, brushing residue and recycled wool from fabric production contained few nano-sized by-products.
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| 9. |
- Muneer, Faraz, et al.
(författare)
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Preparation, Properties, Protein Cross-Linking and Biodegradability of Plasticizer-Solvent Free Hemp Fibre Reinforced Wheat Gluten, Glutenin, and Gliadin Composites
- 2014
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Ingår i: BioResources. - : BioResources. - 1930-2126. ; 9:3, s. 5246-5261
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Tidskriftsartikel (refereegranskat)abstract
- The present study is aimed at evaluating the use of plant-based polymers and fibres for the production of sustainable biocomposites. For the first time, plasticiser/solvent-free hemp fibre-reinforced wheat gluten and hemp-gliadin and glutenin composites were obtained by compression moulding at different temperatures. The plasticiser/solvent-free sample preparation method developed in this study facilitated the use of a powdered protein matrix with a mat of randomly oriented hemp fibres. The tensile and protein cross-linking properties, as well as the biodegradability, were investigated. The addition of hemp fibre to the protein matrix increased the E-modulus by 20 to 60% at 130 degrees C. An increase in moulding temperature from 110 to 130 degrees C resulted in an increase in maximum stress due to the formation of intermolecular bonds between protein chains. The gliadin composites had higher E-modulus and maximum stress and showed a larger increase in protein polymerisation with increased temperature compared to the gluten in composites. A comparison of tensile properties revealed that the composites were stiffer and stronger compared to several similarly produced biobased composites. The composites were found to be fully biodegradable under a simulated soil environment after 180 days. Biocomposites produced in the present study were found to be environmentally friendly with fairly good mechanical properties.
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| 10. |
- Hosseini, Seyedehsan, 1994
(författare)
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Additive-Driven Improvements in Interfacial Properties and Processing of TMP-Polymer Composites
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Efforts to address environmental concerns have resulted in new regulations designed to plan the reduction of plastic and synthetic polymer usage, necessitating the search for sustainable natural alternatives with comparable cost-effectiveness and mechanical performance. Thermomechanical pulp (TMP) fibres are one of the most affordable natural fibres that have no chemical refining in production, production have a high yield of 90-98% and TMP fibres have been demonstrated to improve the mechanical characteristics (strength, stiffness and toughness) of wood-polymer composites (WPCs) compared to the pure polymer. The integration of TMP fibres with non-polar synthetic polymers remains a challenge due to surface polarity differences. This PhD thesis aims to ease the processing of TMP fibre composites through the incorporation of additives. The hypothesis posits that incorporating magnesium stearate (MgSt), molybdenum disulfide (MoS2) and alkyl ketene dimer (AKD) as additives in TMP composites will enhance interfacial properties, resulting in improved processability and flow behaviour at high temperatures. MoS2 is known for its interaction with lignin, which exists in TMP and MgSt is recognised for its ability to improve flow in pharmaceutical processing when combined with cellulose, also a component of TMP. AKD modifies the hydrophilic properties of lignocellulosic surfaces. The experimental work explores the effect of these additives on the properties of TMP composites of ethylene acrylic acid copolymer (EAA) and polypropylene (PP) matrices. The dynamic mechanical analysis (DMA) and mechanical analysis results reveal that MoS2 exhibits superior interaction with TMP fibres, yielding enhanced interfacial properties compared to MgSt in between EAA and TMP fibres. Rheological studies elucidate the transition from a fluid-like state to a network-like structure upon the incorporation of TMP into the PP matrix. The incorporation of AKD with C18 reduces the viscosity of TMP-PP composites and PP itself, and, as determined through theoretical Hansen solubility parameter (HSP) calculations, increases compatibility between cellulose in TMP fibres and PP. The addition of AKD influences both the colour (lighter) and shape (smoother surface) of the extrudate filaments in the TMP-PP composites, indicative of improved processing. In addition, frictional analysis demonstrates the reduction of the coefficient of friction (COF) between metal and TMP fibre by MgSt and AKD treatments.
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| 11. |
- Anagnostopoulos, George, et al.
(författare)
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Strain Engineering in Highly Wrinkled CVD Graphene/Epoxy Systems
- 2018
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 10:49, s. 43192-43202
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Tidskriftsartikel (refereegranskat)abstract
- Chemical vapor deposition (CVD) is regarded as a promising fabrication method for the automated, large-scale, production of graphene and other two-dimensional materials. However, its full commercial exploitation is limited by the presence of structural imperfections such as folds, wrinkles, and even cracks that downgrade its physical and mechanical properties. For example, as shown here by means of Raman spectroscopy, the stress transfer from an epoxy matrix to CVD graphene is on average 30% of that of exfoliated monolayer graphene of over 10 μm in dimensions. However, in terms of electrical response, the situation is reversed; the resistance has been found here to decrease by the imposition of mechanical deformation possibly due to the opening up of the structure and the associated increase of electron mobility. This finding paves the way for employing CVD graphene/epoxy composites or coatings as conductive "networks" or bridges in cases for which the conductivity needs to be increased or at least retained when the system is under deformation. The tuning/control of such systems and their operative limitations are discussed here.
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| 12. |
- Andersson, Johanna, 1984
(författare)
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Surface tension-driven flow in soft porous materials — An investigation of the mechanism of capillary flow in microchannels of hydrogels
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Spontaneous spreading of liquids in porous materials is of great industrial relevance and occurs in, for example, diapers, fabrics, paper or paint. Often, it is necessary to manipulate the spreading rate of liquids to result in the desired mass transport, for example to soak up large liquid volumes, as in a diaper. To do this, it is necessary to know the precise mechanism of surface tension driven flow. However, the process is complex and so are the porous materials in terms of both chemical composition and geometry. The mathematical and physical description of the process is often limited to specific cases – for example, the well-known Lucas-Washburn equation describes the speed of a meniscus in capillaries with circular cross-section in a hard material without interconnections. The objective of this thesis is to deepen the understanding of the mechanism with which a liquid spreads in a soft porous material only driven by surface tension. To this end, the liquid dynamics of water and water-based liquids were investigated in various model systems which are similar to porous 3D materials. In an alginate gel, capillaries with circular cross-sections were produced and the spreading rate of water was determined and compared to existing models. Using a method, which involves 3D printing, it was possible to fabricate open channels with rectangular cross-sections in the same alginate gel. The liquid spreading in these channels in geometries of branched channel systems was investigated. The results revealed that the spreading rate in capillaries of circular cross-sections in soft materials was much slower than that anticipated in existing models, which describe hard materials. In open channels of rectangular cross-sections, the presence of side channels slowed down the meniscus in the main channel; the meniscus stopped when it encountered junctions. The stop duration was longer when the side channels were longer, when they were wider, and when their tilting angle was low with respect to the main channel. An analysis of the volume flow indicated that those geometries that had long side channels but are few in number, resulted in faster volume flow. In a porous 3D material, this suggests that the interconnectivity could decrease the volume flow rate. Finally, a calcium alginate gel with straight-aligned pores was produced and characterised as an example of optimal liquid transport. The outcome of this thesis can be used to adjust the geometrical design of porous materials to result in desired liquid transport properties. The stiffness of the material may influence the liquid transport. The thesis also contributes to the discussion on how the liquid takes selective pathways in porous materials.
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| 13. |
- Bohlén, Martin, 1978
(författare)
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Computational studies of Poly(vinylidene fluoride) and Poly(vinylidene fluoride) - Single Wall Carbon Nanotube Composites
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Poly(vinylidene fluoride) (PVDF) exhibits properties that allows the material to be used in such diverse areas as wire and cable products, electronic devices, membranes, exterior coatings for constructions and in the chemical, pharmaceutical and food industry as fluid-handling equipment. It is the inherent molecular structure of PVDF, where every second backbone carbon is bonded to two fluorine atoms, that gives the polymer several unique properties, among them piezo- and pyroelectricity. However, to obtain a material with a high piezoelectric activity, the amount of the crystal phase with the largest polarization, the β crystal phase, has to be large. Possibly, this could be achieved by the addition of different types of additives, carbon nanotubes (CNTs) being one of them. In this study, molecular modeling of PVDF and PVDF-single wall carbon nanotubes (SWCNTs) composites has been performed. Also, the molecular structure of PVDF around and above the melting point has been investigated using both computational and experimental techniques. The results obtained from first principles, molecular mechanics (MM) and molecular dynamics (MD) studies indicate that PVDF molecules have a larger affinity to be in the all-trans structure similar to the polar β-phase at temperatures above the melting point. However, when melt or solution cast the main PVDF crystal phase obtained is the non-polar α-phase. A prevention of this phase transformation from β to α during crystallization could yield a material with a strong piezoelectric effect. Furthermore, MM and MD studies of the mechanical properties of PVDF and PVDF-SWCNT nanocomposites showed that the reinforcing effect of SWCNTs on PVDF is dependent on the alignment of the SWCNTs. When aligned in the direction of applied stress, an increase of the Young’s modulus of about 1 GPa could be observed. A simulation of a pullout of a SWCNT from a PVDF matrix revealed that the interfacial shear stress is in the same range as other polymer-SWCNT systems and that this interface possibly can be strengthened by functionalization of the pristine carbon nanotubes.
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| 14. |
- Hammarström, Thomas, 1974
(författare)
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Differences in partial discharge characteristics due to increased conductivity of the insulation material
- 2018
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Ingår i: Proceedings of the IEEE International Conference on Properties and Applications of Dielectric Materials. - 2160-9241. ; 2018-May, s. 148-151
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Konferensbidrag (refereegranskat)abstract
- This paper presents what influence the choice of PWM level and rise time has on the PD characteristics for two similar wire specimens insulated by different materials and exposed to short rise time voltage waveforms. The test objects were twisted pairs insulated by either polyamide-imid material (PAI) or the more conductive Cr 2 O 3 insulation. Here these test objects were fed from either two-, three-, four or five level inverter waveforms of similar type as used in actual applications. Observations are made on the importance of the voltage rise time, the size of the voltage step in relation to the extinction voltages (PDEV) and other observables. To compare the performances, measurements of the PD characteristics were conducted. Specifically, the total number of PDs and their average maximum amplitude per cycle were obtained together with the PRPDA pattern. Previous research suggests that the Cr 2 O 3 insulation shows improved degradation properties compared to conventional insulations for sinusoidal waveforms however less difference was observed when exposed to square and PWM waveforms. The experimental results presented in this work showed that the total summed PD magnitude (exposure) drops considerably already when applying a three or higher level inverter for both materials however the PD magnitude remains about the same for both materials tested. Thus to experience the expected advantages with the more conductive insulation a higher level than three appears required. Although in comparison both four and five levels show little influence in number of PDs, the maximum magnitude per cycle is reduced however for both insulation materials. The reduction is however more significant for the Cr 2 O 3 insulation. Initial studies suggest that the higher PWM level results in a reduction of the overvoltage level which helps reducing the PD amplitude. As the choice of material influences this phenomenon, the implications is that the advantages with an increased conductivity appears more significant at the higher PWM levels.
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| 15. |
- Larsson, Ragnar, 1960, et al.
(författare)
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Carbon-fibre composites with graphene filler for enhanced properties
- 2019
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Ingår i: Proceedings of XVIII Brazil MRS Meeting. - 9788563273406 ; , s. 558-
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Konferensbidrag (refereegranskat)abstract
- Carbon fibre reinforced polymer (CFRP) is often used in applications where lightweight design is essential. The material however suffers from inherent drawbacks such as high brittleness, low electrical conductivity. This Swedish-Brazilian collaboration combines experimental studies with modelling and simulation to investigate the improvement of the CFRP material properties after addition of graphene. Graphene exhibits excellent electrical and thermal conductivity, barrier properties, unique strength which makes it an optimal additive. In this industrial-driven project, the electrical percolation threshold is studied and the strength of the reinforced polymer around the threshold value is investigated. The improvement is dependent on dispersion techniques and the grade of exfoliation of graphene. This has been shown both experimentally and from the modeling.
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| 16. |
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| 17. |
- Chen, Jiajia, et al.
(författare)
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Characterization of Longitudinal Thermal Conductivity of Graphene Film
- 2021
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Ingår i: 2021 22nd International Conference on Electronic Packaging Technology, ICEPT 2021.
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Konferensbidrag (refereegranskat)abstract
- The chase of high performance by chip manufacturers has greatly increased the power consumption of integrated circuits, which brings great challenges to the heat dissipation of electronics systems. It has also slowed down following up of the Moore's Law, and it is expected to hit the wall soon [1]. Graphene film with high in-plane thermal conductivity is one of the key materials to make it possible for electronics industry to continue to follow the Moore's Law. However, there are few studies focusing on the longitudinal thermal conductivity of graphene films. The purpose of this study is to investigate the longitudinal thermal conductivity of graphene films according to ASTM D5470 [2]. The results show that the longitudinal thermal conductivity of the pressed graphene film is greater than that of the unpressurized graphene film. The longitudinal thermal conductivity is 10.6 W/m· K for the unpressurized graphene film and 20.6 W/m· K for the pressed graphene film.
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| 18. |
- Karlsson, Kristina, 1988
(författare)
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Foaming of cellulose derivatives and hemicellulose-containing materials
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fossil-based polymeric foams are important materials due to their good mechanical properties relative their low density, the low price and the possibility for large-scale production. They are widely used in cushioning, absorbing and insulation applications. There are however a few disadvantages with these foamed products. The raw-material originates from a non-renewable resource. In the foaming process some possible less environmentally friendly additives/blowing agents are used. Also, the relatively low price of these foamed articles makes them ideal for single-use packaging and, unfortunately, they often end up in nature where the slow degradation will ensure that they stay for a long time, causing problems for marine living and other species. One possible way to solve at least some of the issues relating to fossil-based foamed products would be to use a renewable, non-fossil, raw material. There are several polymers of a non-fossil origin which could serve a primary material for foams and in this thesis two different types of cellulose derivatives (hydroxypropyl methylcellulose (HPMC) and ethyl hydroxyethyl cellulose (EHEC)) as well as a number of different hemicelluloses (xylan, arabinoxylan (AX), β-glucan concentrate and galactoglucomannan (GGM)) were studied as possible and interesting candidates. The foaming ability of some different grades of the two cellulose derivatives, xylan, AX and GGM, was initially evaluated using a hot-mould process with water as the only blowing agent and plasticiser. A simulated foaming process was assessed using dynamical mechanical thermal analysis (DMTA) for HPMC and the rheological properties of the polymer-water mixtures were determined. Three grades of the HPMC derivatives were evaluated in a small-scale batch extrusion experiment using a capillary viscometer. Also, the β-glucan concentrate (mixed with water) was foamed in the capillary viscometer and its shear and extensional viscosities were evaluated. The results pointed towards the existence of a possible processing window for foaming and extrusion experiments were therefore performed with the HPMC and the β-glucan polymers. For HPMC, water was the only added plasticiser and blowing agent and for the β-glucan concentrate also sodium bicarbonate and citric acid were used along with the water. The final foams from both foaming techniques were characterised with regard to their apparent density and foam structure. In conclusion, cellulose derivatives and hemicelluloses could be suitable candidates for production of lightweight, foamed material originating from non-fossil, renewable resources.
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| 19. |
- Lund, Anja, 1971, et al.
(författare)
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Electrically conducting fibres for e-textiles: An open playground for conjugated polymers and carbon nanomaterials
- 2018
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Ingår i: Materials Science and Engineering: R: Reports. - : Elsevier BV. - 0927-796X .- 1879-212X. ; 126, s. 1-29
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Forskningsöversikt (refereegranskat)abstract
- Conducting fibres and yams promise to become an essential part of the next generation of wearable electronics that seamlessly integrate electronic function into one of the most versatile and most widely used form of materials: textiles. This review explores the many types of conducting fibres and yarns that can be realised with conjugated polymers and carbon materials, including carbon black, carbon nanotubes and graphene. We discuss how the interplay of materials properties and the chosen processing technique lead to fibres with a wide range of electrical and mechanical properties. Depending on the choice of conjugated polymer, carbon nanotube, graphene, polymer blend, or nanocomposite the electrical conductivity can vary from less than 10(-3) to more than 10(3) S cm(-1), accompanied by an increase in Young's modulus from 10 s of MPa to 100 s of GPa. Further, we discuss how conducting fibres can be integrated into electronic textiles (e-textiles) through e.g. weaving and knitting. Then, we provide an overview of some of the envisaged functionalities, such as sensing, data processing and storage, as well as energy harvesting e.g. by using the piezoelectric, thermoelectric, triboelectric or photovoltaic effect. Finally, we critically discuss sustainability aspects such as the supply of materials, their toxicity, the embodied energy of fibre and textile production and recyclability, which currently are not adequately considered but must be taken into account to ready carbon based conducting fibres for truly practical e-textile applications.
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| 20. |
- Xu, Yunsheng, et al.
(författare)
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Methacrylated lignosulfonate as compatibilizer for flax fiber reinforced biocomposites with soybean-derived polyester matrix
- 2020
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Ingår i: Composites Communications. - : Elsevier BV. - 2452-2139.
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Tidskriftsartikel (refereegranskat)abstract
- The poor adhesion between natural fibers and polymer matrix restricts the mechanical performance of natural fiber reinforced composites. Here, lignosulfonate was methacrylated and evaluated as a potential compatibilizer for flax fiber reinforced soybean-derived polyester thermosets. Significant improvement in both tensile and flexural properties of the fiber composites were achieved when the flax fiber mat was treated with methacrylated lignosulfonate solution. In particular, the flexural modulus and flexural strength more than doubled from 2.6 to 6.7 GPa and from 36 MPa to 76.8 MPa, respectively when the fibers were soaked in 5 wt % MLS solution. The SEM analysis revealed improved fiber-matrix interface and lower extent of fiber pull-out in the methacrylated lignosulfonate treated fiber composites, which correlates with the improved mechanical properties.
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| 21. |
- Ye, Xinchen
(författare)
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Materials Based on Protein Nanofibrils
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Protein nanofibrils (PNFs) prepared from whey protein isolate (WPI) at low pH and elevated temperature were processed into materials, i.e. hydrogels, films, foams, and fibres, for different applications where they could potentially be sustainable alternatives to petroleum-based polymers. WPI was chosen as the starting material due to the high accessibility of whey as an industrial side-stream product from cheese manufacturing, and its ability to easily grow PNFs.PNFs grown in the presence of different metal ions were generally curved and short, and they formed hydrogels, in contrast to the straight ones fibrillated without metal ions. The effect of metal ions with different acidity was systematically studied with respect to fibrillation kinetics and gelation behaviour. The protein fibrillation was accelerated by the addition of metal ions. The strength of the hydrogel increased with increasing acidity of the metal ion at the same ion concentration, as long as the ion did not precipitate as hydroxide/oxide. Protein nanocomposite films were prepared by adding separately grown PNFs into a non-fibrillar protein matrix from the same WPI starting material. The glycerol-plasticized composite films obtained an increased elastic modulus and decreased strain at break with increasing content of PNFs. The produced PNF foams showed high-temperature resistance during aging at 150 °C for as long as one month (maximum testing time), far exceeding the properties of many petroleum-based thermoplastics. The aged foams were also able to retain their properties in different solutions that normally degrade/dissolve protein materials.PNFs were also organized into microfibres using a flow-focusing method. Genipin was added as a natural crosslinker to improve the mechanical properties of the obtained fibre. The crosslinked fibre (using only 2% genipin) obtained a significantly higher stiffness and strength at break as compared to the fibre assembled without genipin.
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| 22. |
- Lund, Anja, et al.
(författare)
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Piezoelectric polymeric bicomponent fibers produced by melt spinning
- 2012
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Ingår i: Journal of Applied Polymer Science. - : Wiley Periodicals, Inc.. - 0021-8995 .- 1097-4628. ; 126:2, s. 490-500
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Tidskriftsartikel (refereegranskat)abstract
- Melt spinning of a novel piezoelectric bicomponent fiber, with poly(vinylidene fluoride) as the electroactive sheath component, has been demonstrated. An electrically conductive compound of carbon black (CB) and high density polyethylene was used as core material, working as an inner electrode. A force sensor consisting of a number of fibers embedded in a soft CB/polyolefin elastomer matrix was manufactured for characterization. The fibers showed a clear piezoelectric effect, with a voltage output (peak-to-peak) of up to 40 mV under lateral compression. This continuous all-polymer piezoelectric fiber introduces new possibilities toward minimal single fiber sensors as well as large area sensors produced in standard industrial weaving machines.
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| 23. |
- Nilsson, Erik, 1976, et al.
(författare)
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Poling and characterization of piezoelectric polymer fibers for use in textile sensors
- 2013
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Ingår i: Sensors and Actuators A-Physical. - : Elsevier S.A.. - 0924-4247 .- 1873-3069. ; 201, s. 477-486
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Tidskriftsartikel (refereegranskat)abstract
- This study reports on the poling and characteristics of a melt-spun piezoelectric bicomponent fiber with poly(vinylidene fluoride) (PVDF) as its sheath component and a conductive composite with carbon black (CB) and high density polyethylene (HDPE) as its core component. The influence of poling conditions on the piezoelectric properties of the fibers has been investigated. The poling parameters temperature, time and poling voltage have been varied and the piezoelectric effect of both contact- and corona-poled yarns have been evaluated. The results show that a high piezoelectric effect is achieved when the poling voltage is high as possible and the poling temperature is between 60°C and 120°C. It was also shown that permanent polarization is achieved in a time as short as 2 second in corona-poled fibers. A yarn exposed to a sinusoidal axial tension of 0.07% strain (the corresponding force amplitude was 0.05 N) shows an intrinsic voltage output of 4 V. The mean power from a 25 mm length of yarn is estimated to be 15nW. To demonstrate the fibers sensor properties, they are woven into a textile fabric from which a force sensor is manufactured and used to detect the heartbeat of a human.
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| 24. |
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| 25. |
- Townsend, Philip, 1991, et al.
(författare)
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Stochastic modelling of 3D fiber structures imaged with X-ray microtomography
- 2021
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Ingår i: Computational materials science. - : Elsevier B.V.. - 0927-0256 .- 1879-0801. ; 194
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Tidskriftsartikel (refereegranskat)abstract
- Many products incorporate into their design fibrous material with particular levels of permeability as a way to control the retention and flow of liquid. The production and experimental testing of these materials can be expensive and time consuming, particularly if it needs to be optimised to a desired level of absorbency. We consider a parametric virtual fiber model as a replacement for the real material to facilitate studying the relationship between structure and properties in a cheaper and more convenient manner. 3D image data sets of a sample fibrous material are obtained using X-ray microtomography and the individual fibers isolated. The segmented fibers are used to estimate the parameters of a 3D stochastic model for generating softcore virtual fiber structures. We use several spatial measures to show the consistency between the real and virtual structures, and demonstrate with lattice Boltzmann simulations that our virtual structure has good agreement with respect to the permeability of the physical material. © 2021 The Author(s)
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