| 1. |
- Reddy, C. Nagendranatha, et al.
(författare)
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Review of microplastic degradation : Understanding metagenomic approaches for microplastic degrading organisms
- 2023
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Ingår i: Polymer testing. - : Elsevier BV. - 0142-9418 .- 1873-2348. ; 128, s. 108223-
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Forskningsöversikt (refereegranskat)abstract
- Environmental problems caused by plastic pollution are among the most pressing issues of our time. In recent years, metagenomics has become a powerful tool for understanding the microbial communities responsible for plastic biodegradation. In this review, recent developments and trends in metagenomics are discussed, and a comprehensive overview of the metagenomic methodology, analysis, and comparison of plastic-degrading bacteria is provided. In addition, the environmental consequences of plastic degradation are discussed, such as the impact on soil, water, and air quality, as well as the potential health risks posed by ingesting and inhaling microplastics. Possible solutions to the plastic degradation problem, such as using biodegradable materials and implementing recycling programs, are also explained. This review highlights the potential impact of metagenomics on the development of sustainable solutions to plastic pollution.
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| 2. |
- Bjurstrom, Anton, et al.
(författare)
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A Review of Polyolefin-Insulation Materials in High Voltage Transmission; From Electronic Structures to Final Products
- 2024
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095.
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Forskningsöversikt (refereegranskat)abstract
- This review focuses on the use of polyolefins in high-voltage direct-current (HVDC) cables and capacitors. A short description of the latest evolution and current use of HVDC cables and capacitors is first provided, followed by the basics of electric insulation and capacitor functions. Methods to determine dielectric properties are described, including charge transport, space charges, resistivity, dielectric loss, and breakdown strength. The semicrystalline structure of polyethylene and isotactic polypropylene is described, and the way it relates to the dielectric properties is discussed. A significant part of the review is devoted to describing the state of art of the modeling and prediction of electric or dielectric properties of polyolefins with consideration of both atomistic and continuum approaches. Furthermore, the effects of the purity of the materials and the presence of nanoparticles are presented, and the review ends with the sustainability aspects of these materials. In summary, the effective use of modeling in combination with experimental work is described as an important route toward understanding and designing the next generations of materials for electrical insulation in high-voltage transmission.
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| 3. |
- Gedde, Ulf W, et al.
(författare)
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Mass and charge transport in polyethylene – Structure, morphology and properties
- 2023
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 266
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Forskningsöversikt (refereegranskat)abstract
- Polyethylene is a model for semicrystalline polymers that provides the option to vary crystallinity within wide ranges and then to establish relationships between structure and mass and charge transport properties. Three different topics are covered: diffusion of n-hexane in polyethylene, extensive penetrant uptake kinetics, swelling and the design of a novel sensor, and finally electrical conduction in polyethylene, a field important to modern distribution of electric power (HVDC). This feature article presents past and ongoing studies at KTH Royal Institute of Technology using a variety of experimental methods and computer-aided simulation and modelling.
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| 4. |
- Holder, Shima L., et al.
(författare)
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Solubility and Diffusivity of Polar and Non-Polar Molecules in Polyethylene-Aluminum Oxide Nanocomposites for HVDC Applications
- 2020
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 13:3, s. 722-
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Tidskriftsartikel (refereegranskat)abstract
- The best commercial high-voltage insulation material of today is (crosslinked) ultra-pure low-density polyethylene (LDPE). A 100-fold decrease in electrical conductivity can be achieved by adding 1–3 wt.% of well-dispersed inorganic nanoparticles to the LDPE. One hypothesis is that the nanoparticle surfaces attract ions and polar molecules, thereby cleaning the surrounding polymer, and thus reducing the conductivity. LDPE-based nanocomposites with 1–12 wt.% octyl-coated aluminum oxide nanoparticles were prepared and the sorption and desorption of one polar compound (acetophenone, a crosslinking by-product) and one non-polar compound of a similar size (limonene) were examined. Since the uptake of acetophenone increased linearly with increasing filler content, whereas the uptake of limonene decreased, the surface attraction hypothesis was strengthened. The analytical functions for predicting composite solubility as a function of particle size and filler fraction were derived using experimental solubility measurements and Monte Carlo simulations.
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| 5. |
- Shanmugam, Vigneshwaran, et al.
(författare)
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A Review on Combustion and Mechanical Behaviour of Pyrolysis Biochar
- 2022
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Ingår i: Materials Today Communications. - : Elsevier. - 2352-4928. ; 31
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Forskningsöversikt (refereegranskat)abstract
- Biochar has unique physical and chemical properties, making it a viable and sustainable future generation material for a variety of applications. The applications include power generation, composite production, construction (as a reinforcement), and soil amendment. The inherent good mechanical and combustion (or fire) resistance properties of biochar are attractive, however, there are limited reports, despite its effects on bulk material properties being well-documented. Comprehending these innate properties of biochar is critical for tailoring the mechanical and fire properties of biochar-based materials and structures. Therefore, an attempt has been made in this article to garner and analyse literatures reported on the mechanical and combustion properties of biochar without being integrated with a material or structural system (e.g. composite). Biochar produced at high pyrolysis temperatures (>500 ℃) showed high fire resistance property, because of the absence of the volatile matters and development of strong C-C covalent bonds. The mechanical and combustion properties of biocharcan be controlled by varying the biochar size, porus nature, and pyrolysis temperature. The information presented in this article is crucial and can be used as a guide to develop biochar-based materials and structures for mechanical and fire resistance applications.
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| 6. |
- Unge, Mikael, et al.
(författare)
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Coarse-Grained Model for Prediction of Hole Mobility in Polyethylene
- 2023
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 19:21, s. 7882-7894
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Tidskriftsartikel (refereegranskat)abstract
- Electrical conductivity measurements of polyethylene indicate that the semicrystalline structure and morphology influence the conductivity. To include this effect in atomistic charge transport simulations, models that explicitly or implicitly take morphology into account are required. In the literature, charge transport simulations of amorphous polyethylene have been successfully performed using short oligomers to represent the polymer. However, a more realistic representation of the polymer structure is desired, requiring the development of fast and efficient charge transport algorithms that can handle large molecular systems through coarse-graining. Here, such a model for charge transport simulations in polyethylene is presented. Quantum chemistry calculations were used to define six segmentation rules on how to divide a polymer chain into shorter segments representing localized molecular orbitals. Applying the rules to amorphous systems yields distributions of segments with mode and median segment lengths relatively close to the persistence length of polyethylene. In an initial test, the segments of an amorphous polyethylene were used as hopping sites in kinetic Monte Carlo (KMC) simulations, which yielded simulated hole mobilities that were within the experimental range. The activation energy of the simulated system was lower compared to the experimental values reported in the literature. A conclusion may be that the experimental result can only be explained by a model containing chemical defects that generate deep traps.
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| 7. |
- Unge, Mikael, et al.
(författare)
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Hole mobility in amorphous polyethylene - Impact of intra-chain electronic coupling
- 2023
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Ingår i: 2023 IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2023. - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350335620
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Konferensbidrag (refereegranskat)abstract
- Experimental results indicate that electrical conductivity in polyethylene depend on the morphology. In order to simulate mobility in polyethylene the morphology need to be included implicitly or explicitly. To include the morphology explicitly in atomic scale simulation of mobility the charge transport along the chain need to described. Marcus theory can be used to describe the hopping process. Here a ghost atom model was used to calculate electronic coupling both along and between chains. A factor 10 difference was seen between intra-chain electronic coupling obtained here compared to previous results. However, the charge transport in amorphous polyethylene was primarily limited by the inter-chain electronic coupling.
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| 8. |
- Wei, Xin-Feng, et al.
(författare)
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High-performance glass-fibre reinforced biobased aromatic polyamide in automotive biofuel supply systems
- 2020
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Ingår i: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 263
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Tidskriftsartikel (refereegranskat)abstract
- The increase in service temperature and the use of renewable but also more aggressive biofuels such as biodiesel have remarkably raised demands for the durability of polymer components used in automotive fuel systems. The commonly used aliphatic polyamides (PAs) can here be problematic to use in (bio)diesel systems at high temperature in locations such as fuel pipes and fuel filter housings. In the present work, the ageing behaviour of a new class of easily melt-processable glass fibre-reinforced highly-biobased semi-aromatic polyamides (polyphthalamide, PPA) was investigated in very demanding environments (petroleum diesel (B0) and its commercial blend with 20 vol% biodiesel (B20)) at high temperature. The results showed that the PPA matrix had better barrier properties towards both petroleum and bio-based diesel compared to conventional PA12, as revealed by its lower and slower fuel uptake. The sorbed fuels plasticized the composite, decreasing the glass transition temperature (Tg), with B20 having a larger plasticizing effect on PPA than B0. Notably, the mechanical properties of the PPA composite were not negatively affected even after long exposure to both B0 and B20. This was due to the low level of fuel uptake, high Tg and intact interface between the glass fibres and PPA matrix.
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| 9. |
- Alipour, Nazanin
(författare)
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Interactions between polymers and the environment
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation addresses the structure and properties of a number of polymer-based materials when they come into contact with specific environments. The first part describes the migration and depletion of active substances from insecticide-impregnated polyethylene sheets in water and air at different humidity levels and higher temperatures. In the second part, the structure, crystallization kinetics, and mechanical and transport properties of multilayer polymer films, consisting of metallocene (mPE) and low-density (LDPE) polyethylene layers, and in some cases also with layers of poly(ethylene-co-vinyl alcohol) and a polyethylene compatibilizer were investigated. Furthermore, inhomogeneous swelling was observed in the 2-layer films containing mPE and LDPE due to differences in the uptake of n-hexane (and limonene) in the respective film layers. These differences caused a bending/curvature of the film upon exposure to the vapour. This effect was further evaluated to determine whether solvent-induced bending could be used as a passive sensor to detect the presence and content of volatile organic compounds in air (VOC). The third part of this thesis describes the possibility of producing biopolymer materials based on larvae from the black soldier fly. After adding a plasticizer to the degreased larval material, protein-based biopolymer films were prepared via compression-moulding. The lipid extracted from the degreasing operation could potentially be used in various applications, such as those involving lubricants. In the last part of this work the release of micro- and nano-particles were determined from a polypropylene nanoclay-composite in a commonly occurring environment for plastics (air at elevated temperature). A prototype exposure chamber was built, and a method was developed to allow aging (degradation) of the sample in this chamber and analyze the effects of aging on the sample.
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| 10. |
- Alipour, Nazanin, et al.
(författare)
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Release of micro- and nanoparticles from a polypropylene/clay nanocomposite, a methodology for controlled degradation and evaluation
- 2021
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Ingår i: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 319
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Tidskriftsartikel (refereegranskat)abstract
- A methodology was developed for qualitative assessment and characterisation of particle losses from nanocomposites during service life. The methodology can be generalised to other systems where the material fragments during ageing and can be extended to quantitative analysis. A chamber was constructed for ageing of selected materials, which enabled effective collection and subsequent analysis of released particles. A combination of scanning and transmission electron microscopy and energy dispersive X-ray spectroscopy was found to be suitable for characterising particles in terms of size, shape and content. The methodology was tested on a common nanoclay composite with polypropylene as the matrix. There was no need for physical/mechanical wear to generate particles, slow flow of air and elevated temperature led to cracking and fragmentation of the material, and subsequent release of nanocomposite particles containing embedded or protruding clay. The release of pure clay particles and polypropylene particles was also detected. Using the methodology, it was observed that even in ‘mild’ degradation conditions (pure thermo-oxidation with no wear), fillers and nanocomposite particles can be released to the environment, which is an environmental and health concern. © 2021 The Authors
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