| 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 .- 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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