| 1. |
- 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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| 2. |
- Jönsson, Christina, et al.
(författare)
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Biocatalysis in the Recycling Landscape for Synthetic Polymers and Plastics towards Circular Textiles
- 2021
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 14:19, s. 4028-4040
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Tidskriftsartikel (refereegranskat)abstract
- Although recovery of fibers from used textiles with retained material quality is desired, separation of individual components from polymer blends used in today's complex textile materials is currently not available at viable scale. Biotechnology could provide a solution to this pressing problem by enabling selective depolymerization of recyclable fibers of natural and synthetic origin, to isolate constituents or even recover monomers. We compiled experimental data for biocatalytic polymer degradation with a focus on synthetic polymers with hydrolysable links and calculated conversion rates to explore this path The analysis emphasizes that we urgently need major research efforts: beyond cellulose-based fibers, biotechnological-assisted depolymerization of plastics so far only works for polyethylene terephthalate, with degradation of a few other relevant synthetic polymer chains being reported. In contrast, by analyzing market data and emerging trends for synthetic fibers in the textile industry, in combination with numbers from used garment collection and sorting plants, it was shown that the use of difficult-to-recycle blended materials is rapidly growing. If the lack of recycling technology and production trend for fiber blends remains, a volume of more than 3400 Mt of waste will have been accumulated by 2030. This work highlights the urgent need to transform the textile industry from a biocatalytic perspective.
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| 3. |
- 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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| 4. |
- Seoane, Fernando, et al.
(författare)
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Conductive Polymer Films as Textrodes for Biopotential Sensing
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: After several years of progresses in textile technology and wearable measurement instrumentation, applications of wearable textile-electronics systems are arising providing a stable background for commercial applications. So far, the available commercial solutions are centered on fitness applications and mostly based in the acquisition of heart rate through Textile Electrodes (Textrodes) based on metallic threads or on conductive rubber compounds. Methods and Materials: In this work a novel material approach is presented to produce Textrodes for acquisition of Electrocardiographic (ECG) signals using a conductive polypropylene (PP1386 from Premix, Finland) polymer material. The polymer was film extruded into thin films, and used as such in the Textrode. Conductive Polymer Films (CPF) have been used to produce Textrodes, and its measurement performance has been compared with the ECG signals obtained with commercial Textrode fabrics and conventional Ag/AgCl electrodes. In order to set up the same measurement conditions, a chest strap tailored to host the testing electrodes has been used. Results: The close resemblance of the ECG acquired with the textile fabric electrodes, the Ag/AgCl electrodes and the PP1386 CPF electrodes suggest that the Polymer Electrodes PP1386 are a feasible alternative to the current textile fabrics that use silver thread as conductive material and also to conductive rubber material. Discussion & Conclusion: The availability of the Conductive Polymer Electrode PP1386 in a film form allows the manufacturing of electrodes by conventional textile processes, like lamination or sewing, therefore facilitating the transition from lab prototyping to industrial manufacturing. Replacing the traditional silver thread as conductive element in the fabrication of Textrodes will definitely reduce the material cost per Textrode. Biocompatibility issues and manufacturability issues must be addressed but the exhibited functional performance is showing encouraging results.
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| 5. |
- 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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| 6. |
- Lei, Yu, et al.
(författare)
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Graphene and Beyond: Recent Advances in Two-Dimensional Materials Synthesis, Properties, and Devices
- 2022
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Ingår i: ACS Nanoscience Au. - : American Chemical Society (ACS). - 2694-2496. ; 2:6, s. 450-485
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Forskningsöversikt (refereegranskat)abstract
- Since the isolation of graphene in 2004, two-dimensional (2D) materials research has rapidly evolved into an entire subdiscipline in the physical sciences with a wide range of emergent applications. The unique 2D structure offers an open canvas to tailor and functionalize 2D materials through layer number, defects, morphology, moiré pattern, strain, and other control knobs. Through this review, we aim to highlight the most recent discoveries in the following topics: theory-guided synthesis for enhanced control of 2D morphologies, quality, yield, as well as insights toward novel 2D materials; defect engineering to control and understand the role of various defects, including in situ and ex situ methods; and properties and applications that are related to moiré engineering, strain engineering, and artificial intelligence. Finally, we also provide our perspective on the challenges and opportunities in this fascinating field.
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| 7. |
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| 8. |
- Jeong, Seung Hee, 1978-
(författare)
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Soft Intelligence : Liquids Matter in Compliant Microsystems
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Soft matter, here, liquids and polymers, have adaptability to a surrounding geometry. They intrinsically have advantageous characteristics from a mechanical perspective, such as flowing and wetting on surrounding surfaces, giving compliant, conformal and deformable behavior. From the behavior of soft matter for heterogeneous surfaces, compliant structures can be engineered as embedded liquid microstructures or patterned liquid microsystems for emerging compliant microsystems.Recently, skin electronics and soft robotics have been initiated as potential applications that can provide soft interfaces and interactions for a human-machine interface. To meet the design parameters, developing soft material engineering aimed at tuning material properties and smart processing techniques proper to them are to be highly encouraged. As promising candidates, Ga-based liquid alloys and silicone-based elastomers have been widely applied to proof-of-concept compliant structures.In this thesis, the liquid alloy was employed as a soft and stretchable electrical and thermal conductor (resistor), interconnect and filler in an elastomer structure. Printing-based liquid alloy patterning techniques have been developed with a batch-type, parallel processing scheme. As a simple solution, tape transfer masking was combined with a liquid alloy spraying technique, which provides robust processability. Silicone elastomers could be tunable for multi-functional building blocks by liquid or liquid-like soft solid inclusions. The liquid alloy and a polymer additive were introduced to the silicone elastomer by a simple mixing process. Heterogeneous material microstructures in elastomer networks successfully changed mechanical, thermal and surface properties.To realize a compliant microsystem, these ideas have in practice been useful in designing and fabricating soft and stretchable systems. Many different designs of the microsystems have been fabricated with the developed techniques and materials, and successfully evaluated under dynamic conditions. The compliant microsystems work as basic components to build up a whole system with soft materials and a processing technology for our emerging society.
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| 9. |
- Decrop, Deborah, et al.
(författare)
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Single-step manufacturing of femtoliter microwell arrays in a novel surface energy mimicking polymer
- 2015
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Ingår i: 18th International Conference on Solid-State Sensors, Actuators and Microsystems (IEEE TRANSDUCER 2015). - : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- We report a novel polymer material formulation and stamp-molding technique that enable rapid single-step manufacturing of hydrophilic-in-hydrophobic microwell arrays. We developed a modified thiol-ene-epoxy polymer (mOSTE+) formulation that mimics the surface energy of its mold during polymerization. The polymer inherits the surface energy from the mold through molecular self-assembly, in which functional monomers self-assemble at the interface between the liquid prepolymer and the mold surface. Combining this novel mOSTE+ material with a stamp-molding process leads to simultaneous surface energy mimicking and micro-structuring. This method was used to manufacture microwells with hydrophilic bottom and hydrophobic sidewall, depressed in a surrounding hydrophobic surface. The microwell arrays were successfully tested for the self-assembly of 62’000 femtoliter-droplets. Such femtoliter droplet arrays are useful for, e.g., digital ELISA and single cell/molecule analysis applications.
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| 10. |
- Kroon, Martin
(författare)
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An 8-chain Model for Rubber-like Materials Accounting for Non-affine Chain Deformations and Topological Constraints
- 2011
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Ingår i: Journal of elasticity. - : Springer Science and Business Media LLC. - 0374-3535 .- 1573-2681. ; 102:2, s. 99-116
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Tidskriftsartikel (refereegranskat)abstract
- Several industrial applications involve rubber and rubber-like materials, and it is important to be able to predict the constitutive response of these materials. In the present paper, a new constitutive model for rubber-like solids is proposed. The model is based on the 8-chain concept introduced by Arruda and Boyce (J. Mech. Phys. Solids 41, 389-412, 1993) to which two new components are added. Real polymer networks do not deform affinely, and in the proposed model this is accounted for by the inclusion of an elastic spring, acting in series with the representative polymer chain. Furthermore, real polymer chains are not completely free to move, which is modelled by imposing a topological constraint on the transverse motions of the representative polymer chain. The model contains five model parameters and these need to be determined on the basis of experimental data. Three: experimental studies from the literature were used to assess the proposed model. The model was able to reproduce experimental data performed under conditions of uniaxial tension, generalised plane deformation, and biaxial tension with an excellent accuracy. The strong predictive abilities together with the numerically efficient structure of the model make it suitable for implementation in a finite element context.
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| 11. |
- Pardon, Gaspard, 1983-
(författare)
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From Macro to Nano : Electrokinetic Transport and Surface Control
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today, the growing and aging population, and the rise of new global threats on human health puts an increasing demand on the healthcare system and calls for preventive actions. To make existing medical treatments more efficient and widely accessible and to prevent the emergence of new threats such as drug-resistant bacteria, improved diagnostic technologies are needed. Potential solutions to address these medical challenges could come from the development of novel lab-on-chip (LoC) for point-of-care (PoC) diagnostics.At the same time, the increasing demand for sustainable energy calls for the development of novel approaches for energy conversion and storage systems (ECS), to which micro- and nanotechnologies could also contribute.This thesis has for objective to contribute to these developments and presents the results of interdisciplinary research at the crossing of three disciplines of physics and engineering: electrokinetic transport in fluids, manufacturing of micro- and nanofluidic systems, and surface control and modification. By combining knowledge from each of these disciplines, novel solutions and functionalities were developed at the macro-, micro- and nanoscale, towards applications in PoC diagnostics and ECS systems.At the macroscale, electrokinetic transport was applied to the development of a novel PoC sampler for the efficient capture of exhaled breath aerosol onto a microfluidic platform.At the microscale, several methods for polymer micromanufacturing and surface modification were developed. Using direct photolithography in off-stoichiometry thiol-ene (OSTE) polymers, a novel manufacturing method for mold-free rapid prototyping of microfluidic devices was developed. An investigation of the photolithography of OSTE polymers revealed that a novel photopatterning mechanism arises from the off-stoichiometric polymer formulation. Using photografting on OSTE surfaces, a novel surface modification method was developed for the photopatterning of the surface energy. Finally, a novel method was developed for single-step microstructuring and micropatterning of surface energy, using a molecular self-alignment process resulting in spontaneous mimicking, in the replica, of the surface energy of the mold.At the nanoscale, several solutions for the study of electrokinetic transport toward selective biofiltration and energy conversion were developed. A novel, comprehensive model was developed for electrostatic gating of the electrokinetic transport in nanofluidics. A novel method for the manufacturing of electrostatically-gated nanofluidic membranes was developed, using atomic layer deposition (ALD) in deep anodic alumina oxide (AAO) nanopores. Finally, a preliminary investigation of the nanopatterning of OSTE polymers was performed for the manufacturing of polymer nanofluidic devices.
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| 12. |
- 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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| 13. |
- Hosseini, Seyedehsan, 1994, et al.
(författare)
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Alkyl ketene dimer modification of thermomechanical pulp promotes processability with polypropylene
- 2024
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Ingår i: Polymer Composites. - 1548-0569 .- 0272-8397. ; 45:1, s. 825-835
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Tidskriftsartikel (refereegranskat)abstract
- Alkyl ketene dimers (AKDs) are known to efficiently react with cellulose with a dual polarity in their structure: a polar component and a nonpolar component. AKD of three different carbon chain lengths, 4, 10, and 16 carbons have been synthesized, and thermomechanical pulp (TMP) fibers were modified by them. The modification of TMP fibers with AKD resulted in an increased water contact angle, showing the presence of the AKDs on the TMP fibers and a new carbonyl peak in the IR spectra, suggesting modification of the TMP fibers with AKD groups. Calculating the Hansen solubility parameters of AKD and AKD conjugated to TMP in polypropylene (PP) indicates improved compatibility, especially of longer chain AKD and TMP AKD. The rheological studies of the composites showed that the AKD with the longest carbon chain decreases the melt viscosity of the PP-TMP-AKD composite, which combined with the shape and the color of the extruded composite filaments indicates improved flow properties and reduced stress build up during processing. The research findings demonstrate the ability of AKD to enhance the dispersibility and compatibility of natural fibers with PP.
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| 14. |
- Nyflött, Åsa, 1986-
(författare)
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Structure-Performance Relations of Oxygen Barriers for Food Packaging
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Food packaging should ensure the safety and quality of food, minimize spoilage and provide an easy way of storing and handling it. Barrier coatings are generally used to meet the demands placed on fibre-based food packages, as these have the ability to regulate the amount of gases that can enter them. Some gases are detrimental to food quality: oxygen, for example, initiates lipid oxidation in fatty foods. Using both experimental data and computer modelling, this thesis explains some aspects of how the structure of barrier coatings influences the mass transport of oxygen with the aim of obtaining essential knowledge that can be used to optimize the performance of barriers.Barrier coatings are produced from polyvinyl alcohol and kaolin blends that are coated onto a polymeric support. The chemical and physical structures of these barriers were characterized according to their influence on permeability in various climates. At a low concentration of kaolin, the crystallinity of polyvinyl alcohol decreased; in the thinner films, the kaolin particles were orientated in the basal plane of the barrier coating. The experimental results indicated a complex interplay between the polymer and the filler with respect to permeability.A computer model for permeability incorporating theories for the filled polymeric layer to include the polymer crystallinity, addition of filler, filler aspect ratio and surrounding moisture was developed. The model shows that mass transport was affected by the aspect ratio of the clay in combination with the clay concentration, as well as the polymer crystallinity. The combined model agreed with the experiments, showing that it is possible to combine different theories into one model that can be used to predict the mass transport.Four barrier coatings: polyethylene, ethylene vinyl alcohol + kaolin, latex + kaolin and starch were evaluated using the parameters of greenhouse gas emissions and product costs. After the production of the barrier material, the coating process and the end-of-life handling scenarios were analysed, it emerged that starch had the lowest environmental impact and latex + kaolin had the highest.
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| 15. |
- Jeong, Seung Hee, 1978-, et al.
(författare)
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Stretchable Thermoelectric Generators Metallized with Liquid Alloy
- 2017
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 9:18, s. 15791-15797
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Tidskriftsartikel (refereegranskat)abstract
- Conventional thermoelectric generators (TEGs) are normally hard, rigid, and flat. However, most objects have curvy surfaces, which require soft and even stretchable TEGs for maximizing efficiency of thermal energy harvesting. Here, soft and stretchable TEGs using conventional rigid Bi2Te3 pellets metallized with a liquid alloy is reported. The fabrication is implemented by means of a tailored layer-by-layer fabrication process. The STEGs exhibit an output power density of 40.6 ?W/cm2 at room temperature. The STEGs are operational after being mechanically stretched-and-released more than 1000 times, thanks to the compliant contact between the liquid alloy interconnects and the rigid pellets. The demonstrated interconnect scheme will provide a new route to the development of soft and stretchable energy-harvesting avenues for a variety of emerging electronic applications.
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| 16. |
- 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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| 17. |
- Eriksson, Siw, et al.
(författare)
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Three-dimensional Fabrics as Medical Textiles
- 2015
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Ingår i: Advances in 3D Textiles. - : Woodhead Publishing Limited. - 9781782422143 - 9781782422198 ; , s. 305-340
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The number of 3D textile applications in medicine is rapidly increasing as new technology and procedures are introduced in health care. A first estimate of current medical applications of both general and 3D textiles is presented based on the medical devices classification system established by the US Food and Drug Administration. The textile specifics for these applications are covered from a textile technique perspective where the different 3D weaving as well as knitting, braiding and non-woven techniques are described and how their properties they can contribute in medical applications. In addition, emerging opportunities based on smart textiles as part of textile systems are described on a general level. The strong application areas of 3D medical textiles, i.e. wound management, vascular grafting and scaffolding for tissue engineering are covered in detail both from the medical and textiles perspective. Finally, some future lines of development are suggested and a short discussion on how new 3D textiles applications can be developed in close cooperation between the textile industry and the health care sector is presented.
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| 18. |
- Peterson, Joel, 1959-, et al.
(författare)
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Mechanical-Property-Based Comparison of Paper Yarn with Cotton, Viscose, and Polyester Yarns
- 2021
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Ingår i: Journal of Natural Fibers. - : Taylor & Francis Group. - 1544-0478 .- 1544-046X. ; 18:4, s. 492-501
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Tidskriftsartikel (refereegranskat)abstract
- Cotton and oil-based fibre consumption is highly problematic because the growth of these materials often requires fertilisers and toxic pesticides. Less environmentally damaging alternative fibres are urgently required. This study investigates Manila-hemp paper-yarn textile fabrics. Manila-hemp (abacá) is a species of banana grown as a commercial crop in the Philippines, Ecuador, and Costa Rica. Knitted structures of paper, cotton, viscose, and polyester yarns are tested and compared. Tensile strength tests are also performed. Paper yarn shows low shrinkage and no pilling, which are excellent characteristics for use in the textile and clothing industries. However, its poor handleability/knittability, high stiffness, and hard grip must be resolved for the widespread application of paper yarn in the textile industry in the future.
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| 19. |
- Pardon, Gaspard, 1983-, et al.
(författare)
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Simultaneous replication of hydrophilic and superhydrophobic micropatterns through area-selective monomer self-assembly
- 2016
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Ingår i: Advanced Materials Interfaces. - Weinheim : Wiley-VCH Verlagsgesellschaft. - 2196-7350. ; 3:17
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Tidskriftsartikel (refereegranskat)abstract
- The control and permanent modification of the surface properties of polymers is a critical enabler for many applications. Here, we demonstrate a strategy, which we call surface energy mimicking, for the spontaneous replication of micropatterns of surface energies ranging from hydrophilic to superhydrophobic from a mold to several replicas.We introduce surface energy mimicking, enabling spontaneous replication of micropatterns (2D and 2.5D) of different surface energies, and enabled by self-assembly of functional mimicking monomers within a polymer matrix. We demonstrate replication of surface energies ranging from hydrophilic to superhydrophobic, and self-assembly of picoliter-droplet arrays on replicated micropatterned arrays containing hydrophilic patches in a hydrophobic surface.
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| 20. |
- 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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| 21. |
- Kroon, Martin
(författare)
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Steady-state crack growth in rubber-like solids
- 2011
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Ingår i: International Journal of Fracture. - : Springer Science and Business Media LLC. - 0376-9429 .- 1573-2673. ; 169:1, s. 49-60
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Tidskriftsartikel (refereegranskat)abstract
- The fracture toughness of rubber-like materials depends on several factors. First there is the surface energy required to create new crack surface at the crack tip. Second, a significant amount of energy is dissipated through viscoelastic processes in the bulk material around the crack tip. Third, if the crack propagates very rapidly, inertia effects will come into play and contribute to the fracture toughness. In the present study, a computational framework for studying high-speed crack growth in rubber-like solids under conditions of steady-state is proposed. Effects of inertia, viscoelasticity and finite strains are included. The main purpose of the study is to study the contribution of viscoelastic dissipation to the total work of fracture required to propagate a crack in a rubber-like solid. The model was fully able to predict experimental results in terms of the local surface energy at the crack tip and the total energy release rate at different crack speeds. In addition, the predicted distributions of stress and dissipation around the propagating crack tip are presented.
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| 22. |
- 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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| 23. |
- 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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| 24. |
- 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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| 25. |
- 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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