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  • 1.
    Lindström, Stefan B.
    et al.
    FSCN Research Centre, Mid Sweden University, Sundsvall, SE-851 70, Sweden.
    Amjad, Rabab
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Gåhlin, Elin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Andersson, Linn
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Kaarto, Marcus
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Liubytska, Kateryna
    FSCN Research Centre, Mid Sweden University, Sundsvall, SE-851 70, Sweden; Applied Mathematics Department, National Technical University “Kharkiv Polytechnic Institute”, Kharkiv, 61000, Ukraine.
    Persson, Johan
    FSCN Research Centre, Mid Sweden University, Sundsvall, SE-851 70, Sweden.
    Berg, Jan Erik
    FSCN Research Centre, Mid Sweden University, Sundsvall, SE-851 70, Sweden.
    Engberg, Birgitta A.
    FSCN Research Centre, Mid Sweden University, Sundsvall, SE-851 70, Sweden.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials. FSCN Research Centre, Mid Sweden University, Sundsvall, SE-851 70, Sweden.
    Pulp Particle Classification Based on Optical Fiber Analysis and Machine Learning Techniques2024In: Fibers, E-ISSN 2079-6439, Vol. 12, no 1, article id 2Article in journal (Refereed)
    Abstract [en]

    In the pulp and paper industry, pulp testing is typically a labor-intensive process performed on hand-made laboratory sheets. Online quality control by automated image analysis and machine learning (ML) could provide a consistent, fast and cost-efficient alternative. In this study, four different supervised ML techniques—Lasso regression, support vector machine (SVM), feed-forward neural networks (FFNN), and recurrent neural networks (RNN)—were applied to fiber data obtained from fiber suspension micrographs analyzed by two separate image analysis software. With the built-in software of a commercial fiber analyzer optimized for speed, the maximum accuracy of 81% was achieved using the FFNN algorithm with Yeo–Johnson preprocessing. With an in-house algorithm adapted for ML by an extended set of particle attributes, a maximum accuracy of 96% was achieved with Lasso regression. A parameter capturing the average intensity of the particle in the micrograph, only available from the latter software, has a particularly strong predictive capability. The high accuracy and sensitivity of the ML results indicate that such a strategy could be very useful for quality control of fiber dispersions.

  • 2.
    Krantz, Gustav
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Moretti, Christian
    Department of Environmental Systems Science, ETH Zürich, Universitätstrasse 22, Zürich, 8092, Switzerland, Universitätstrasse 22.
    Brandão, Miguel
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Sustainability Assessment and Management.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials. DivisioFSCN Research Centre, Mid Sweden University, Sundsvall, SE-85170, Sweden.
    Assessing the Environmental Impact of Eight Alternative Fuels in International Shipping: A Comparison of Marginal vs. Average Emissions2023In: Environments, E-ISSN 2076-3298, Vol. 10, no 9, article id 155Article in journal (Refereed)
    Abstract [en]

    Global warming and other environmental concerns drive the search for alternative fuels in international shipping. A life-cycle analysis (LCA) can be utilized to assess the environmental impact of different fuels, thereby enabling the identification of the most sustainable alternative among the candidate fuels. However, most LCA studies do not consider marginal emissions, which are important when predicting the effects of large-scale fuel transitions. The research purpose of this study was to assess the marginal emissions of several currently available marine fuels to facilitate the identification of the most promising marine fuel. Thus, marginal and average emissions for eight marine fuels (high-sulfur fuel oil, very-low-sulfur fuel oil, marine gas oil, liquified natural gas, biomethane, biomethanol, fossil methanol, and hydro-treated vegetable oil) were compared in terms of their environmental impact. Non-intuitively, the results indicate that biofuels exhibit equally or higher marginal greenhouse gas emissions than conventionally used fuel oils (162–270 versus 148–174 kg CO2/MJ propulsion), despite their significantly lower average emissions (19–73 vs. 169–175 kg CO2/MJ). This discrepancy is attributed to the current limited availability of climate-efficient biofuels. Consequently, a large-scale shift to biofuels cannot presently yield substantial reductions in the shipping industry’s climate impact. Additional measures, such as optimized trading routes, more energy-efficient ships, and research on more climate-friendly biofuels and electro-fuels, are thus required to significantly reduce the climate footprint of shipping.

  • 3.
    Liu, Sirui
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Bettelli, Mercedes A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Wei, Xin-Feng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Capezza, Antonio Jose
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Sochor, Benedikt
    Deutsches Elektronen-Synchrotron, DESY, Notkestraße 85, Hamburg, D-22607, Germany, Notkestraße 85.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Johansson, Eva
    Department of Plant Breeding, Swedish University of Agricultural Sciences, P.O. Box 190, Lomma, SE-234 22, Sweden, P.O. Box 190.
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials. Deutsches Elektronen-Synchrotron, DESY, Notkestraße 85, Hamburg, D-22607, Germany, Notkestraße 85.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Design of Hygroscopic Bioplastic Products Stable in Varying Humidities2023In: Macromolecular materials and engineering, ISSN 1438-7492, E-ISSN 1439-2054, Vol. 308, no 2, article id 2200630Article in journal (Refereed)
    Abstract [en]

    Hygroscopic biopolymers like proteins and polysaccharides suffer from humidity-dependent mechanical properties. Because humidity can vary significantly over the year, or even within a day, these polymers will not generally have stable properties during their lifetimes. On wheat gluten, a model highly hygroscopic biopolymer material, it is observed that larger/thicker samples can be significantly more mechanically stable than thinner samples. It is shown here that this is due to slow water diffusion, which, in turn, is due to the rigid polymer structure caused by the double-bond character of the peptide bond, the many bulky peptide side groups, and the hydrogen bond network. More than a year is required to reach complete moisture saturation (≈10 wt.%) in a 1 cm thick plate of glycerol-plasticized wheat gluten, whereas this process takes only one day for a 0.5 mm thick plate. The overall moisture uptake is also retarded by swelling-induced mechanical effects. Hence, hygroscopic biopolymers are better suited for larger/thicker products, where the moisture-induced changes in mechanical properties are smeared out over time, to the extent that the product remains sufficiently tough over climate changes, for example, throughout the course of a year.

  • 4.
    Qu, Muchao
    et al.
    Guangdong Polytech Normal Univ, Sch Automobile & Transportat Engn, Guangzhou 510450, Peoples R China..
    Xie, Zixin
    Guangdong Polytech Normal Univ, Sch Automobile & Transportat Engn, Guangzhou 510450, Peoples R China..
    Liu, Shuiyan
    Guangzhou Highteen Plast Co Ltd, Guangzhou 510800, Peoples R China..
    Zhang, Jinzhu
    Guangzhou Highteen Plast Co Ltd, Guangzhou 510800, Peoples R China..
    Peng, Siyao
    Guangdong Polytech Normal Univ, Sch Automobile & Transportat Engn, Guangzhou 510450, Peoples R China..
    Li, Zhitong
    Guangdong Polytech Normal Univ, Sch Automobile & Transportat Engn, Guangzhou 510450, Peoples R China..
    Lin, Cheng
    Guangdong Polytech Normal Univ, Sch Automobile & Transportat Engn, Guangzhou 510450, Peoples R China..
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials. Mid Sweden Univ, FSCN Res Ctr, SE-10392 Sundsvall, Sweden..
    Electric Resistance of Elastic Strain Sensors-Fundamental Mechanisms and Experimental Validation2023In: Nanomaterials, E-ISSN 2079-4991, Vol. 13, no 12, article id 1813Article in journal (Refereed)
    Abstract [en]

    Elastic strain sensor nanocomposites are emerging materials of high scientific and commercial interest. This study analyzes the major factors influencing the electrical behavior of elastic strain sensor nanocomposites. The sensor mechanisms were described for nanocomposites with conductive nanofillers, either dispersed inside the polymer matrix or coated onto the polymer surface. The purely geometrical contributions to the change in resistance were also assessed. The theoretical predictions indicated that maximum Gauge values are achieved for mixture composites with filler fractions slightly above the electrical percolation threshold, especially for nanocomposites with a very rapid conductivity increase around the threshold. PDMS/CB and PDMS/CNT mixture nanocomposites with 0-5.5 vol.% fillers were therefore manufactured and analyzed with resistivity measurements. In agreement with the predictions, the PDMS/CB with 2.0 vol.% CB gave very high Gauge values of around 20,000. The findings in this study will thus facilitate the development of highly optimized conductive polymer composites for strain sensor applications.

  • 5.
    Hoogendoorn, Billy W.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Xiao, Xiong
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Polisetti, Veerababu
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Tjus, Kåre
    IVL Svenska Miljöinstitutet.
    Forsberg, Kerstin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Resource recovery.
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Formation of Different Zinc Oxide Crystal Morphologies Using Cellulose as Nucleation Agent in the Waste Valorization and Recycling of Zn-Ion Batteries2023In: Rare Metal Technology 2023, Springer, 2023Conference paper (Refereed)
    Abstract [en]

    The formation of zinc oxide particles of different hierarchical morphologies was investigated. By performing elemental analysis on samples extracted from the supernatant solution during precipitations yielding two distinctly different morphologies, the consumption of zinc ions was used to follow the liquid-to-solid phase formation. While a rapid Zn-ion consumption was synonymous with the formation of predominantly oxygen terminated flower-shaped ZnO-particles, with half of the zinc ions being precipitated during the first minute, less than 10% of the zinc ions were converted to sea urchin-shaped ZnO-particles (with mixed terminations) after 1 min of the reaction. The unique ZnO-particle morphologies may therefore be related to the precipitation rates, which can be further explored as a tool for understanding how ZnO-particles with differently facetted surfaces form. Interestingly, the different formation rates remained with identical patterns when 0.5 g/L cellulose (0.005 wt%) was added to the reactions as nucleating agent for improved yields. The controlled formation of specific functional ZnO-particle surfaces is an important method for recycling inexpensive zinc waste from batteries to high value materials useful in a variety of catalytic applications.

  • 6.
    Mendoza, Ana
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Larroche, Pierre
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Hillborg, Henrik
    Hitachi Energy Res, S-72178 Västerås, Sweden..
    Moriana Torro, Rosana
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Image analysis of PDMS/ZnO nanocomposite surfaces for optimized superhydrophobic and self-cleaning surface design2023In: SURFACES AND INTERFACES, ISSN 2468-0230, Vol. 37, article id 102733Article in journal (Refereed)
    Abstract [en]

    Optimized superhydrophobic and self-cleaning nanocomposite surfaces were obtained by spraying surface modified ZnO nanoparticles (NPs) onto PDMS, using octadecylphosphonic acid and octadecanethiol as hydro-phobic modifiers. In this study, it is the first time to our knowledge that surface parameters such as topography, morphology, superhydrophobicity, and self-cleaning are correlated to particle surface distribution and agglomeration parameters obtained by image analysis. The topography, morphology, and wettability of the surfaces were analyzed using atomic force microscopy, scanning electron microscopy, static contact angle (SCA), and contact angle hysteresis measurements. Image analysis was performed using the new enhanced graphical user interface of a previously self-developed Matlab (R) algorithm. Both hydrophobization methodologies increased the NPs' surface coverage and the hierarchical rough structure formation on the substrates, resulting in more homogenous superhydrophobic self-cleaning surfaces. A higher coated fraction and lower degree of interconnected uncoated PDMS paths are correlated to an increase in SCA. The combination of a higher ag-glomerates fraction, lower agglomerate radius, and lower distance between agglomerates obtained for the sur-faces with hydrophobized ZnO-NPs rendered self-cleaning surfaces. The observed correlations increase the understanding of the design and modelling of superhydrophobic self-cleaning PDMS/ZnO nanocomposite sur-faces for use in high voltage outdoor insulators.

  • 7.
    Birdsong, Björn K.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hoogendoorn, Billy W.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials. Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 58 11428 Stockholm Sweden, Teknikringen 58.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials. Mid Sweden University Sundsvall 85170 Sweden.
    Andersson, Richard L.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Capezza, Antonio Jose
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Farris, Stefano
    DeFENS - Department of Food, Environmental and Nutritional Sciences Food Packaging Laboratory, Via Celoria 2 20133 Milan Italy, Via Celoria 2.
    Guerrero, Antonio
    Department of Chemical Engineering, Escuela Politécnica Superior, Universidad de Sevilla, 41011 Sevilla Spain.
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Large-scale synthesis of 2D-silica (SiOx) nanosheets using graphene oxide (GO) as a template material2023In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 15, no 31, p. 13037-13048Article in journal (Refereed)
    Abstract [en]

    Graphene oxide (GO) was used in this study as a template to successfully synthesize silicon oxide (SiOx) based 2D-nanomaterials, adapting the same morphological features as the GO sheets. By performing a controlled condensation reaction using low concentrations of GO (<0.5 wt%), the study shows how to obtain 2D-nanoflakes, consisting of GO-flakes coated with a silica precursor that were ca. 500 nm in lateral diameter and ca. 1.5 nm in thickness. XPS revealed that the silanes had linked covalently with the GO sheets at the expense of the oxygen groups present on the GO surface. The GO template was shown to be fully removable through thermal treatment without affecting the nanoflake morphology of the pure SiOx-material, providing a methodology for large-scale preparation of SiOx-based 2D nanosheets with nearly identical dimensions as the GO template. The formation of SiOx sheets using a GO template was investigated for two different silane precursors, (3-aminopropyl) triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS), showing that both precursors were capable of accurately templating the graphene oxide template. Molecular modeling revealed that the choice of silane affected the number of layers coated on the GO sheets. Furthermore, rheological measurements showed that the relative viscosity was significantly affected by the specific surface area of the synthesized particles. The protocol used showed the ability to synthesize these types of nanoparticles using a common aqueous alcohol solvent, and yield larger amounts (∼1 g) of SiOx-sheets than what has been previously reported.

  • 8.
    Gedde, Ulf W
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. NKT High Voltage Cables, Technology Consulting, SE-721 78 Västerås, Sweden.
    Unge, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials. NKT High Voltage Cables, Technology Consulting, SE-721 78 Västerås, Sweden.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials. FSCN research centre, Mid Sweden University, 85170 Sundsvall, Sweden.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Mass and charge transport in polyethylene – Structure, morphology and properties2023In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 266, article id 125617Article, review/survey (Refereed)
    Abstract [en]

    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.

  • 9.
    Qu, Muchao
    et al.
    School of Automobile and Transportation Engineering, Guangdong Polytechnic Normal University, Guangzhou, China.
    Cai, Jinfeng
    School of Automobile and Transportation Engineering, Guangdong Polytechnic Normal University, Guangzhou, China.
    Li, Xiaoqing
    School of Automobile and Transportation Engineering, Guangdong Polytechnic Normal University, Guangzhou, China.
    Wu, Jin
    School of Automobile and Transportation Engineering, Guangdong Polytechnic Normal University, Guangzhou, China.
    Chen, Hongji
    School of Automobile and Transportation Engineering, Guangdong Polytechnic Normal University, Guangzhou, China.
    Zheng, Zhenxing
    School of Automobile and Transportation Engineering, Guangdong Polytechnic Normal University, Guangzhou, China.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials. FSCN Research Centre, Mid Sweden University, Sundsvall, Sweden.
    Liu, Shuiyan
    Guangzhou Highteen Plastics Co., Ltd., Guangzhou, China.
    Gao, Qun
    School of Automobile and Transportation Engineering, Guangdong Polytechnic Normal University, Guangzhou, China.
    Mechanical and electrical properties of carbon nanotube/epoxy/glass-fiber composites intended for nondestructive testing2023In: Polymers for Advanced Technologies, ISSN 1042-7147, E-ISSN 1099-1581, Vol. 34, no 8, p. 2554-2563Article in journal (Refereed)
    Abstract [en]

    In this study, ternary polymer composites sheets comprising glass fiber (GF) reinforced epoxy with various fractions of carbon nanotubes (CNT) were manufactured using hot-pressing technology. A multiscale morphology analysis was presented using scanning electron microscopy. The thermal behavior of the glass fiber reinforced polymer (GFRP) was investigated using thermogravimetric analysis, DSC, and DMA, which indicated an application temperature up to 71°C for the composites. Mechanical uniaxial stretching and three-points bending tests showed that the addition of 0.1–0.2 wt% CNT decreased the dissipated energy of the specimen by 50% and increased the Young's modulus by more than 100%. During all stretching and bending measurements, the relative change in electrical resistance (RCR) was recorded as function of strain, revealing a relationship between the electrical signal and the applied deformation of the GFRP. Finally, the standard equation for fitting RCR versus strain was optimized, reducing the number of fitting parameters from five to three. The electrical and mechanical properties of the CNT/GF/epoxy composites show that they are suitable sensoring materials for wind-turbine blades and other glass-fiber reinforced epoxy constructions, especially for nondestructive testing.

  • 10.
    Elf, Patric
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Özeren, Hüsamettin Deniz
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Larsson, Per A.
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
    Larsson, Anette
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden.;Chalmers Univ Technol, FibRe Ctr Lignocellulose Based Thermoplast, SE-41296 Gothenburg, Sweden..
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Nilsson, Robin
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden.;Chalmers Univ Technol, FibRe Ctr Lignocellulose Based Thermoplast, SE-41296 Gothenburg, Sweden..
    Chaiyupatham, Poppy Thanaporn
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden..
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. Mid Sweden Univ, FSCN Res Ctr, S-85170 Sundsvall, Sweden..
    Molecular Dynamics Simulations of Cellulose and Dialcohol Cellulose under Dry and Moist Conditions2023In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 24, no 6, p. 2706-2720Article in journal (Refereed)
    Abstract [en]

    The development of wood-based thermoplastic polymersthat can replacesynthetic plastics is of high environmental importance, and previousstudies have indicated that cellulose-rich fiber containing dialcoholcellulose (ring-opened cellulose) is a very promising candidate material.In this study, molecular dynamics simulations, complemented with experiments,were used to investigate how and why the degree of ring opening influencesthe properties of dialcohol cellulose, and how temperature and presenceof water affect the material properties. Mechanical tensile properties,diffusion/mobility-related properties, densities, glass-transitiontemperatures, potential energies, hydrogen bonds, and free volumeswere simulated for amorphous cellulosic materials with 0-100%ring opening, at ambient and high (150 degrees C) temperatures, withand without water. The simulations showed that the impact of ringopenings, with respect to providing molecular mobility, was higherat high temperatures. This was also observed experimentally. Hence,the ring opening had the strongest beneficial effect on "processability"(reduced stiffness and strength) above the glass-transition temperatureand in wet conditions. It also had the effect of lowering the glass-transitiontemperature. The results here showed that molecular dynamics is avaluable tool in the development of wood-based materials with optimalthermoplastic properties.

  • 11.
    Kim, Hyeri
    et al.
    Research Center for Bio-Based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44429, Republic of Korea.
    Shin, Giyoung
    Research Center for Bio-Based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44429, Republic of Korea.
    Jang, Min
    Research Center for Bio-Based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44429, Republic of Korea.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials. FSCN Research Centre, Mid Sweden University, Sundsvall 85170, Sweden.
    Hakkarainen, Minna
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.
    Kim, Hyo Jung
    Research Center for Bio-Based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44429, Republic of Korea.
    Hwang, Sung Yeon
    Research Center for Bio-Based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44429, Republic of Korea; Department of Plant & Environmental New Resources and Graduate School of Biotechnology, Kyung Hee University, Gyeonggi-do 17104, Republic of Korea.
    Lee, Junhyeok
    Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Republic of Korea.
    Park, Sung Bae
    Research Center for Bio-Based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44429, Republic of Korea.
    Park, Jeyoung
    Research Center for Bio-Based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44429, Republic of Korea; Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 04107, Republic of Korea.
    Oh, Dongyeop X.
    Research Center for Bio-Based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44429, Republic of Korea.
    Jeon, Hyeonyeol
    Research Center for Bio-Based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44429, Republic of Korea.
    Koo, Jun Mo
    Research Center for Bio-Based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Ulsan 44429, Republic of Korea; Department of Organic Materials Engineering, Chungnam National University, Daejeon 34134, Republic of Korea.
    Toward Sustaining Bioplastics: Add a Pinch of Seasoning2023In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 11, no 5, p. 1846-1856Article in journal (Refereed)
    Abstract [en]

    Modern society can no longer sustain accumulating plastic pollution without intervention; plastic waste has even found its way into the food that we consume. Unfortunately, biodegradable alternatives lack sound commercial and economic distinctiveness because mechanical strength and biodegradability are typically mutually exclusive. Inspired by fine cuisine, we introduce a novel synthetic method, referred to as “seasoning”, which consists of adding a minimal amount of a biobased multifunctional monomer to pinch the amorphous domains of poly(butylene succinate). Seasoning with only 0.03 mol % of a biobased monomer led to a significantly improved oxygen barrier, high strength (86 MPa), and excellent elongation at break (654%). To the best of our knowledge, this “seasoning” approach with the significant property improvement provided is unique in the bioplastics research field. The proposed approach is highly scalable, relies on existing industrial production, and has the potential to expand current biodegradable plastic applications through its simplicity.

  • 12. Qu, M.
    et al.
    Li, D.
    Qin, T.
    Luo, Z.
    Liu, X.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Gao, Q.
    Zheng, Z.
    Qin, Y.
    Carbon Black Nanoparticle/Polydopamine-Coated Core-Spun Yarns for Flexible Strain Sensors2022In: ACS Applied Nano Materials, E-ISSN 2574-0970, Vol. 5, no 11, p. 16996-17003Article in journal (Refereed)
    Abstract [en]

    A smart and flexible textile strain sensor was developed based on a commercial core-spun yarn coated with carbon black (CB) nanoparticles and polydopamine (PDA). The morphology of the textile was studied using scanning electron microscopy (SEM), and the distribution of CB and self-polymerized PDA was observed. Thermogravimetric analysis (TGA) revealed the applicable temperature range of the strain sensor. The smart textile showed an outstanding strain sensor response range up to 450%, and its mechanical properties were only slightly reduced as compared to the original textile. The cyclic strain sensor behavior of the smart textile was investigated by stretching the textile 100% for 100 cycles, yielding a stable and durable output electrical signal. Application tests for various human motions were also performed. Finally, two mathematical equations based on tunneling theory were proposed to accurately predict the electrical signal during stretching and to reveal the fundamental properties of the textile. Our findings clearly expand the current knowledge of strain sensors. 

  • 13. Soroudi, A.
    et al.
    Ouyang, Y.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials. FSCN research centre, Mid Sweden University, 85170 Sundsvall, Sweden.
    Östergren, I.
    Xu, X.
    Li, Z.
    Pourrahimi, A. M.
    Hedenqvist, M.
    Gkourmpis, T.
    Hagstrand, P. -O
    Müller, C.
    Highly insulating thermoplastic nanocomposites based on a polyolefin ternary blend for high-voltage direct current power cables2022In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 14, no 21, p. 7927-7933Article in journal (Refereed)
    Abstract [en]

    Octyl-silane-coated Al2O3 nanoparticles are found to be a promising conductivity-reducing additive for thermoplastic ternary blends comprising low-density polyethylene (LDPE), isotactic polypropylene and a styrenic copolymer. The ternary blend nanocomposites were prepared by compounding the blend components together with an LDPE-based masterbatch that contained the nanoparticles. The nanoparticles did not affect the superior stiffness of the ternary blends, compared to neat LDPE, between the melting temperatures of the two polyolefins. As a result, ternary blend nanocomposites comprising 38 wt% polypropylene displayed a storage modulus of more than 10 MPa up to at least 150 °C, independent of the chosen processing conditions. Moreover, the ternary blend nanocomposites featured a low direct-current electrical conductivity of about 3 × 10−15 S m−1 at 70 °C and an electric field of 30 kV mm−1, which could only be achieved through the presence of both polypropylene and Al2O3 nanoparticles. This synergistic conductivity-reducing effect may facilitate the design of more resistive thermoplastic insulation materials for high-voltage direct current (HVDC) power cables.

  • 14.
    Krantz, Gustav
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Brandao, Miguel
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Indirect CO2 emissions caused by the fuel demand switch in international shipping2022In: Transportation Research Part D: Transport and Environment, ISSN 1361-9209, E-ISSN 1879-2340, Vol. 102, p. 103164-, article id 103164Article in journal (Refereed)
    Abstract [en]

    In 2020 the fuel sulphur limit in international shipping was reduced from 3.5 to 0.5 wt%. Three adaptive measures dominate: (i) increased exhaust gas cleaning in the maritime industry enabling continued use of high-sulphur fuel oil, (ii) increased refining output ratio of low-sulphur fuels, and iii) increased use of blended fuels. As (i) and (ii) are insufficient to comply with the new demand, refiners will resort to (iii), which requires increased crude oil throughput. Extracted crude oil will typically oxidize completely over longer time periods, so increased crude oil throughput is synonymous with increased CO2 emissions of up to 323 Mton in 2020, corresponding to similar to 1% of the total global CO2 emissions from fossil fuels. Transferring demand from low-value to high-value oil products cause indirect CO2 emissions, and vice versa. CO2 emissions can be mitigated by prioritizing demand reduction according to oil product value starting with the most valuable products.

  • 15. Asem, H.
    et al.
    Zheng, W.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Zhang, Y.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hassan, M.
    Malmström, E.
    Functional Nanocarriers for Drug Delivery by Surface Engineering of Polymeric Nanoparticle Post-Polymerization-Induced Self-Assembly2021In: ACS Applied Bio Materials, E-ISSN 2576-6422, Vol. 4, no 1, p. 1045-1056Article in journal (Refereed)
    Abstract [en]

    Engineered polymeric nanoparticles (NPs) have been comprehensively explored as potential platforms for diagnosis and targeted therapy for several diseases including cancer. Herein, we designed functional poly(acrylic acid)-b-poly(butyl acrylate) (PAA-b-PBA) NPs using reversible addition-fragmentation chain-transfer (RAFT)-mediated emulsion polymerization via polymerization-induced self-assembly (PISA). The hydrophilic PAA-macroRAFT, forming a stabilizing shell (i.e., corona), was chain-extended using the hydrophobic monomer n-butyl acrylate (n-BA), resulting in stable, monodisperse, and reproducible PAA-b-PBA NPs, typically having a diameter of 130 nm. The surface engineering of the PAA-b-PBA NP post-PISA were explored using a two-step approach. The hydrophilic NP-shell corona was modified with allyl groups under mild conditions, using allylamine in water, which resulted in stable allyl-functional NPs (allyl-NPs) suitable for further bioconjugation. The allyl-NPs were subsequently conjugated with a thiol-functional fluorescent dye (BODIPY-SH) to the allyl groups using "thiol-ene"-click chemistry, to mimic the attachment of a thiol-functional target ligand. The successful attachment of BODIPY-SH to the allyl-NPs was corroborated by UV-vis spectroscopy, showing the characteristic absorbance of the BODIPY-fluorophore at 500 nm. Despite modification of NPs with allyl groups and attachment of BODIPY-SH, the NPs retained their colloidal stability and monodispersity as indicated by DLS. This demonstrates that post-PISA functionalization is a robust method for synthesizing functional NPs. Neither the NPs nor allyl-NPs showed significant cytotoxicity toward RAW264.7 or MCF-7 cell lines, which indicates their desirable safety profile. The cellular uptake of the NPs using J774A cells in vitro was found to be time and concentration dependent. The anti-cancer drug doxorubicin was efficiently (90%) encapsulated into the PAA-b-PBA NPs during NP formation. After a small initial burst release during the first 2 h, a controlled release pattern over 7 days was observed. The present investigation demonstrates a potential method for functionalizing polymeric NP post-PISA to produce carriers designed for targeted drug delivery.

  • 16.
    Wei, Xin-Feng
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Yin, Haiyan
    RISE Res Inst Sweden, Div Bioecon & Hlth, SE-11486 Stockholm, Sweden..
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Microplastics Originating from Polymer Blends: An Emerging Threat?2021In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 55, no 8, p. 4190-4193Article in journal (Refereed)
    Abstract [en]

    No one can have missed the growing global environmental problems with plastics ending up as microplastics in food, water, and soil, and the associated effects on nature, wildlife, and humans. A hitherto not specifically investigated source of microplastics is polymer blends. A 1 g polymer blend can contain millions to billions of micrometer-sized species of the dispersed phase and therefore aging-induced fragmentation of the polymer blends can lead to the release of an enormous amount of microplastics. Especially if the stability of the dispersed material is higher than that of the surrounding matrix, the risk of microplastic migration is notable, for instance, if the matrix material is biodegradable and the dispersed material is not. The release can also be much faster if the matrix polymer is biodegradable. The purpose of writing this feature article is to arise public and academic attention to the large microplastic risk from polymer blends during their development, production, use, and waste handling.

  • 17.
    Nilsson, Fritjof
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Karlsson, Mattias E.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Gedde, Ulf W
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Kadar, Roland
    Chalmers Univ Technol, Dept Ind & Mat Sci, Engn Mat, SE-41296 Gothenburg, Sweden..
    Gaska, Karolina
    Univ Bristol, Dept Aerosp Engn, Bristol BS8 1TR, Avon, England..
    Mueller, Christian
    Chalmers Univ Technol, Dept Chem & Chem Engn, SE-41296 Gothenburg, Sweden..
    Hagstrand, Per-Ola
    Borealis AB, Innovat & Technol, SE-44486 Stenungsund, Sweden..
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Gkourmpis, Thomas
    Borealis AB, Innovat & Technol, SE-44486 Stenungsund, Sweden..
    Nanocomposites and polyethylene blends: two potentially synergistic strategies for HVDC insulation materials with ultra-low electrical conductivity2021In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 204, article id 108498Article in journal (Refereed)
    Abstract [en]

    Among the various requirements that high voltage direct current (HVDC) insulation materials need to satisfy, sufficiently low electrical conductivity is one of the most important. The leading commercial HVDC insulation material is currently an exceptionally clean cross-linked low-density polyethylene (XLPE). Previous studies have reported that the DC-conductivity of low-density polyethylene (LDPE) can be markedly reduced either by including a fraction of high-density polyethylene (HDPE) or by adding a small amount of a well dispersed, semiconducting nanofiller such as Al2O3 coated with a silane. This study demonstrates that by combining these two strategies a synergistic effect can be achieved, resulting in an insulation material with an ultra-low electrical conductivity. The addition of both HDPE and C-8-Al2O3 nanoparticles to LDPE resulted in ultra-insulating nanocomposites with a conductivity around 500 times lower than of the neat LDPE at an electric field of 32 kV/mm and 60-90 degrees C. The new nanocomposite is thus a promising material regarding the electrical conductivity and it can be further optimized since the polyethylene blend and the nanoparticles can be improved independently.

  • 18.
    Özeren, Hüsamettin Deniz
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Prediction of Real Tensile Properties using Extrapolations from Atomistic Simulations: An Assessment on Thermoplastic Starch2021In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 228, no 123919Article in journal (Refereed)
    Abstract [en]

    Atomistic molecular dynamics (MD) simulations can be used to predict mechanical properties, such as stiffness and strength, for polymers. A concern is unavoidably high strain rates in simulations compared with those in physical experiments. To quantitatively capture the mechanical properties of the ‘real’ material, i.e., to predict absolute values rather than just qualitative trends, extrapolation to realistic strain rates is required. In this study, different strain-rate extrapolation strategies involving time-temperature shifting with the Williams-Landel-Ferry equation (above Tg) and the Eyring equation (below Tg) were evaluated, using thermoplastic starch as an example. MD simulations were first used to compute the stiffness and strength at three (high) strain rates over a wide range of temperatures. The mechanical MD data were then horizontally time-temperature shifted, resulting in master curves with strain-rate (x-axis) versus mechanical properties (y-axis). The precision in the prediction of experimental data was quite good in several cases, but was dependent on the extrapolation method and the specific thermoplastic starch system. A notable finding was that the simulations could be simplified using fewer simulation strain rates and temperatures. The extrapolation techniques used here are expected to be valid for other polymer systems, but this remains to be validated.

  • 19.
    Özeren, Hüsamettin Deniz
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Wei, Xin-Feng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Role of Hydrogen Bonding in Wheat Gluten Protein Systems Plasticized with Glycerol and Water2021In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 232, p. 124149-Article in journal (Other academic)
    Abstract [en]

    Many biopolymers are stiff and brittle and require plasticizers. To optimize the choice and amount of plasticizer, the mechanisms behind plasticization need to be understood. For polar biopolymers, such as polysaccharides and proteins, plasticization depends to a large extent on the hydrogen bond network. In this study, glycerol-plasticized protein systems based on wheat gluten were investigated, in combination with the effects of water. The methodology was based on a combination of mechanical tests and molecular dynamics simulations (MD). The simulations accurately predicted the glycerol content where the experimental depression in glass transition temperature (Tg) occurred (between 20 and 30 wt.% plasticizer). They also predicted the strong water-induced depression in Tg. Detailed analysis revealed that in the dry system, the main effect of glycerol was to break protein-protein hydrogen bonds. In the moist system, glycerol was partly outcompeted by water in forming hydrogen bonds with the protein, making the glycerol plasticizer less effective than in dry conditions. These results show that MD can successfully predict the plasticizer concentration at which the onset of efficient plasticization occurs. MD can therefore be an important tool for understanding plasticizer mechanisms, even in a complex system, on a level of detail that is impossible with experiments.

  • 20.
    Linde, Erik
    et al.
    Sandia Natl Labs, Organ Mat Sci Dept 1853, POB 5800,MS 1411, Albuquerque, NM 87185 USA..
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Barrett, Matija
    Sandia Natl Labs, Organ Mat Sci Dept 1853, POB 5800,MS 1411, Albuquerque, NM 87185 USA..
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Celina, Mathew C.
    Sandia Natl Labs, Organ Mat Sci Dept 1853, POB 5800,MS 1411, Albuquerque, NM 87185 USA..
    Time- and Feedback-Dependent DLO Phenomena in Oxidative Polymer Aging2021In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 189, article id 109598Article in journal (Refereed)
    Abstract [en]

    Polymer degradation under oxidative conditions, particularly under accelerated stresses such as increased temperatures and irradiation, often exhibits spatially heterogeneous oxidation profiles. This well-known behavior is the result of diffusion-limited oxidation (DLO), which occurs when the oxidation rate is faster than the resupply of oxygen through diffusion into the material. So far most theoretical model descriptions have focused on DLO in equilibrium situations in which the underlying material properties do not change with increasing degradation levels or are constant (i.e. time-independent) variables. An extension of a previously developed finite element model is now presented, which accommodates time-dependent variables that are either explicitly time-dependent (i.e. changes homogeneously throughout the material), or through a feedback mechanism driven by the localized degree of oxidation, which results in spatial variations in the material properties responsible for specific DLO behavior. This model is realized in COMSOL Multiphysics and is capable of geometries in 1D up to 3D. Additionally, specific theoretical cases in 1D are shown which relate to known non-stationary phenomena in polymer degradation. They illustrate the effect on the resulting oxidation profile, when the oxygen diffusivity, solubility or oxidation rate properties change over time and in space. With COMSOL based FEM, it is now possible to model DLO for whatever material behavior may exist or could be envisaged.

  • 21. Yang, G.
    et al.
    Schubert, D. W.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. Institute of Polymer Materials, Friedrich-Alexander-University Erlangen-Nuremberg.
    Qu, M.
    Redel, M.
    A Study of a Novel Synergy Definition for Ternary CB/CNT Composites Suggesting a Representative Model for CB and CNT2020In: Macromolecular Theory and Simulations, ISSN 1022-1344, E-ISSN 1521-3919, Vol. 29, no 5, article id 2000035Article in journal (Refereed)
    Abstract [en]

    For polymer composites containing two types of conductive fillers, the electrical conductivity can be predicted with a ternary mixing equation. However, a slight deviation from the foreseen trend is recently observed for ternary polymethyl methacrylate (PMMA) nanocomposites containing carbon nanotubes (CNT) and carbon black (CB). In this study, the reason for the deviation is examined. Representative composite geometries are generated with Monte-Carlo technique and the composite conductivity is calculated with Finite Element Modeling (FEM) Traditional FEM strategies would give results resembling the ternary mixing equation, but when the CB particles are modeled as solid spheres whereas the CNT are modeled as solid cylinders surrounded by soft, conductive shells, the composite conductivity gained the same shape as observed experimentally. One possible interpretation is that a small geometrical rearrangement of the CNT fibers has a larger impact on the composite conductivity than a corresponding movement of the spherical CB particles. As a consequence, the CNT/CB/PMMA nanocomposite exhibits a special kind of synergy ("synergism"), caused by the grape-shaped morphology. These findings can be utilized in the future development and optimization of conductive polymer nanocomposites. 

  • 22.
    Qu, Muchao
    et al.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, D-91058 Erlangen, Germany.;Guangdong Polytech Normal Univ, Sch Automobile & Transportat Engn, Guangzhou 510450, Peoples R China..
    Qin, Yijing
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, D-91058 Erlangen, Germany..
    Sun, Yue
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, D-91058 Erlangen, Germany..
    Xu, Huagen
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, D-91058 Erlangen, Germany..
    Schubert, Dirk W.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, D-91058 Erlangen, Germany..
    Zheng, Kai
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Biomat, D-91058 Erlangen, Germany..
    Xu, Wei
    Guangdong Polytech Normal Univ, Sch Automobile & Transportat Engn, Guangzhou 510450, Peoples R China..
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Biocompatible, Flexible Strain Sensor Fabricated with Polydopamine-Coated Nanocomposites of Nitrile Rubber and Carbon Black2020In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, no 37, p. 42140-42152Article in journal (Refereed)
    Abstract [en]

    A flexible, biocompatible, nitrile butadiene rubber (NBR)-based strain sensor with high stretchability, good sensitivity, and excellent repeatability is presented for the first time. Carbon black (CB) particles were embedded into an NBR matrix via a dissolving-coating technique, and the obtained NBR/CB composite was coated with polydopamine (PDA) to preserve the CB layer. The mechanical properties of the NBR films were found to be significantly improved with the addition of CB and PDA, and the produced composite films were noncytotoxic and highly biocompatible. Strain-sensing tests showed that the uncoated CB/NBR films possess a high sensing range (strain of similar to 550%) and good sensitivity (gauge factor of 52.2), whereas the PDA/NBR/CB films show a somewhat reduced sensing range (strain of similar to 180%) but significantly improved sensitivity (gauge factor of 346). The hysteresis curves obtained from cyclic strain-sensing tests demonstrate the prominent robustness of the sensor material. Three novel equations were developed to accurately describe the uniaxial and cyclic strain-sensing behavior observed for the investigated strain sensors. Gloves and knee/elbow covers were produced from the films, revealing that the signals generated by different finger, elbow, and knee movements are easily distinguishable, thus confirming that the PDA/NBR/CB composite films can be used in a wide range of wearable strain sensor applications.

  • 23.
    Qu, Muchao
    et al.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.;Bavarian Polymer Inst, Key LabAdv Fiber Technol, Dr Mack Str 77, D-90762 Furth, Germany..
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Qin, Yijing
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.;Bavarian Polymer Inst, Key LabAdv Fiber Technol, Dr Mack Str 77, D-90762 Furth, Germany..
    Yang, Guanda
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.;Bavarian Polymer Inst, Key LabAdv Fiber Technol, Dr Mack Str 77, D-90762 Furth, Germany..
    Gao, Qun
    Guangdong Polytech Normal Univ, Sch Automobile & Transportat Engn, Guangzhou 510450, Peoples R China..
    Xu, Wei
    Guangdong Polytech Normal Univ, Sch Automobile & Transportat Engn, Guangzhou 510450, Peoples R China..
    Liu, Xianhu
    Zhengzhou Univ, Natl Engn Res Ctr Adv Polymer Proc Technol, Minist Educ, Key Lab Mat Proc & Mold, 97-1 Wenhua, Zhengzhou 450002, Peoples R China..
    Schubert, Dirk W.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.;Bavarian Polymer Inst, Key LabAdv Fiber Technol, Dr Mack Str 77, D-90762 Furth, Germany..
    Electrical conductivity of anisotropic PMMA composite filaments with aligned carbon fibers - predicting the influence of measurement direction2020In: RSC Advances, E-ISSN 2046-2069, Vol. 10, no 7, p. 4156-4165Article in journal (Refereed)
    Abstract [en]

    In order to study the electrical conductivity of anisotropic PMMA/carbon fiber (CF) composites, cylindrical PMMA/CF filaments were extruded through a capillary rheometer, resulting in an induced CF orientation along the extrusion direction. The aspect ratios of the CFs in the filaments were accurately regulated using a two-step melt mixing process. By measuring the vertical and horizontal resistances of filaments where the outermost layer was successively peeled off, the anisotropic conductivities could be calculated. This was done using a novel analytical model where each cylindrical composite filament was defined as a structure consisting of three concentric cylinders with potentially different conductivities and CF orientations. The electrical conductivity increased with the degree of fiber orientation along the voltage direction and the effects of anisotropy and measurement direction were incorporated into the (isotropic) McLachlan equation. The required distance for electrical contact between the CFs was calculated to be 16 nm. Finite element (FEM) simulations were successfully utilized to confirm the data.

  • 24.
    Karlsson, Mattias E.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Xu, Xiangdong
    Chalmers Univ Technol, Dept Mat & Mfg Technol, SE-41296 Gothenburg, Sweden..
    Hillborg, Henrik
    ABB Power Grids Res, S-72178 Vasteras, Sweden..
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Lamellae-controlled electrical properties of polyethylene - morphology, oxidation and effects of antioxidant on the DC conductivity2020In: RSC Advances, E-ISSN 2046-2069, Vol. 10, no 8, p. 4698-4709Article in journal (Refereed)
    Abstract [en]

    Destruction of the spherulite structure in low-density polyethylene (LDPE) is shown to result in a more insulating material at low temperatures, while the reverse effect is observed at high temperatures. On average, the change in morphology reduced the conductivity by a factor of 4, but this morphology-related decrease in conductivity was relatively small compared with the conductivity drop of more than 2 decades that was observed after slight oxidation of the LDPE (at 25 degrees C and 30 kV mm(-1)). The conductivity of LDPE was measured at different temperatures (25-60 degrees C) and at different electrical field strengths (3.3-30 kV mm(-1)) for multiple samples with a total crystalline content of 51 wt%. The transformation from a 5 mu m coherent structure of spherulites in the LDPE to an evenly dispersed random lamellar phase (with retained crystallinity) was achieved by extrusion melt processing. The addition of 50 ppm commercial phenolic antioxidant to the LDPE matrix (e.g. for the long-term use of polyethylene in high voltage direct current (HVDC) cables) gave a conductivity ca. 3 times higher than that of the same material without antioxidants at 60 degrees C (the operating temperature for the cables). For larger amounts of antioxidant up to 1000 ppm, the DC conductivity remained stable at ca. 1 x 10(-14) S m(-1). Finite element modeling (FEM) simulations were carried out to model the phenomena observed, and the results suggested that the higher conductivity of the spherulite-containing LDPE stems from the displacement and increased presence of polymeric irregularities (formed during crystallization) in the border regions of the spherulite structures.

  • 25.
    Özeren, Hüsamettin Deniz
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Prediction of Plasticization in a Real Biopolymer System (Starch) using Molecular Dynamics Simulations2020In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 187, no 108387Article in journal (Refereed)
    Abstract [en]

    Virgin biopolymers are often brittle, which means that they need efficient, sustainable, non-toxic plasticizers for most practical applications. Although the mechanical properties of biopolymers plasticized with e.g. sugars have been extensively investigated, the explanation why efficient plasticization normally only occurs above 20 wt% plasticizer is still lacking. In this work, starch/glycerol was used as a model system to show that all-atom molecular dynamics (MD) simulations can be used to capture the transition region at 20–30 wt% plasticizer, where plasticization becomes pronounced. Tensile properties and PVT data (densities and glass transition temperatures) were obtained both from MD simulations and from measurements on real starch/glycerol materials, confirming that MD could capture the experimentally observed transition region. Also, the simulated glycerol diffusivity correlated well with the trends in the mechanical properties. Percolation theory was used to derive a probable explanation of the observed transition. The results indicate that the MD methodology can be used also for other polymer/plasticizer systems and has the potential to be a valuable tool for optimizing the type and amount of plasticizer in a given polymer, as well as being a tool for the design of new efficient plasticizers.

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  • 26.
    Özeren, Hüsamettin Deniz
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Guivier, Manon
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Ranking Plasticizers for Polymers with Atomistic Simulations; PVT, Mechanical Properties and the Role of Hydrogen Bonding in Thermoplastic Starch2020In: ACS Applied Polymer Materials, ISSN 2637-6105, Vol. 2, no 5, p. 2016-2026Article in journal (Refereed)
    Abstract [en]

    Virgin biopolymers are often brittle and, therefore, need the addition of plasticizers to obtain the required mechanical properties for practical applications, e.g. in bags and disposable kitchen items. In this article, based on a combined experimental and modelling approach, it is shown that it is possible to rank molecules with respect to their plasticization efficiency (depression in glass transition temperature with PVT data and reduced stiffness and strength) using molecular dynamics simulations. Starch was used as the polymeric matrix material due to its promising potential as a sustainable, eco-friendly, biobased replacement for fossil-based plastics. Three polyols (glycerol, sorbitol and xylitol), two ethanolamines and glucose were investigated. The results indicate that molecular simulations can be used to find the optimal plasticizer among a set of candidates, or to design/identify better plasticizers in a complex polymer system. Glycerol was the most efficient of the six plasticizers, explained by it forming the least amount of hydrogen bonds, having the shortest hydrogen bond lifetimes and low molecular rigidity. Hence, not only was it possible to rank plasticizers, the ranking results could also be explained by the simulations.

  • 27.
    Holder, Shima L.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Karlsson, Mattias E.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Olsson, Richard S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Solubility and Diffusivity of Polar and Non-Polar Molecules in Polyethylene-Aluminum Oxide Nanocomposites for HVDC Applications2020In: Energies, E-ISSN 1996-1073, Vol. 13, no 3, p. 722-Article in journal (Refereed)
    Abstract [en]

    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.

  • 28.
    Özeren, Hüsamettin Deniz
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Capezza, Antonio Jose
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Gharbi, Samy
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Guivier, Manon
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Starch/Alkane Diol Materials: Unexpected Ultraporous Surfaces, Near-Isoporous Cores, and Films Moving on Water2020In: ACS Omega, E-ISSN 2470-1343, Vol. 5, no 44, p. 28863-28869Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to find alternative starch plasticizers to glycerol that yielded a less tacky material in high-moisture conditions without leading to starch crystallization. A range of glycerol films containing different potential plasticizers (linear alkane diols) were therefore produced, and it was shown that 1,3-propanediol, in combination with glycerol, was a possible solution to the problem. Several additional interesting features of the starch films were however also revealed. The larger diols, instead of showing plasticizing features, yielded a variety of unexpected structures and film properties. Films with 1,6-hexanediol and 1,7-heptanediol showed an ultraporous film surface and near-isoporous core. The most striking feature was that starch films with these two diols moved/rotated over the surface when placed on water, with no other stimulus than the interaction with water. Films with 1,8-octanediol and 1,10-decanediol did not show these features, but there was clear evidence of a structure with phase-separated crystallized diol in a starch matrix, as observed in high-resolution scanning electron microscopy (SEM) images.

  • 29.
    Yang, Guanda
    et al.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Schubert, Dirk W.
    A Study of Finite Size Effects and Periodic Boundary Conditions to Simulations of a Novel Theoretical Self-Consistent Mean-Field Approach2019In: Macromolecular Theory and Simulations, ISSN 1022-1344, E-ISSN 1521-3919, article id 1900023Article in journal (Refereed)
    Abstract [en]

    In a previous work, a very promising mathematical model for predicting the electrical conductivity below the electrical percolation threshold, for both isotropic and anisotropic composites, was published by Schubert. In this work, periodic boundary condition of the simulation is utilized. The results are also compared to the previous work and other theoretical models. The truncated fibers due to finite size of the simulation volume are considered as two individual pieces so that the real aspect ratios will also be taken into consideration. A comparison is made between two groups, in which the length and the radius of the carbon fibers are changed, respectively, under certain aspect ratios. With three different sizes of the simulation volumes, the influence on the results due to the finite size effect is calculated.

  • 30.
    Sanchez, Carmen
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wåhlander, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Karlsson, Mattias E.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Quintero, Diana C. Marin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Hillborg, Henrik
    ABB Power Technol, SE-72178 Vasteras, Sweden..
    Malmström, Eva
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Characterization of Reduced and Surface-Modified Graphene Oxide in Poly(Ethylene-co-Butyl Acrylate) Composites for Electrical Applications2019In: Polymers, E-ISSN 2073-4360, Vol. 11, no 4, article id 740Article in journal (Refereed)
    Abstract [en]

    Promising electrical field grading materials (FGMs) for high-voltage direct-current (HVDC) applications have been designed by dispersing reduced graphene oxide (rGO) grafted with relatively short chains of poly (n-butyl methacrylate) (PBMA) in a poly(ethylene-co-butyl acrylate) (EBA) matrix. All rGO-PBMA composites with a filler fraction above 3 vol.% exhibited a distinct non-linear resistivity with increasing electric field; and it was confirmed that the resistivity could be tailored by changing the PBMA graft length or the rGO filler fraction. A combined image analysis- and Monte-Carlo simulation strategy revealed that the addition of PBMA grafts improved the enthalpic solubility of rGO in EBA; resulting in improved particle dispersion and more controlled flake-to-flake distances. The addition of rGO and rGO-PBMAs increased the modulus of the materials up to 200% and the strain did not vary significantly as compared to that of the reference matrix for the rGO-PBMA-2 vol.% composites; indicating that the interphase between the rGO and EBA was subsequently improved. The new composites have comparable electrical properties as today's commercial FGMs; but are lighter and less brittle due to a lower filler fraction of semi-conductive particles (3 vol.% instead of 30-40 vol.%).

  • 31.
    Nilsson, Fritjof
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Moyassari, Ali
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Bautista, Angela
    E2F, Plaza Benjamin Palencia 2-3,Entreplata 5, Albacete 02006, Spain..
    Castro, Abraham
    E2F, Plaza Benjamin Palencia 2-3,Entreplata 5, Albacete 02006, Spain..
    Arbeloa, Ignacio
    Amayuelas SL, C Orense 27,Esc B 5 Drch, Madrid 28020, Spain..
    Jarn, Mikael
    RISE Res Inst Sweden, Div Biosci & Mat, Box 5607, SE-11486 Stockholm, Sweden..
    Lundgren, Urban
    RISE Res Inst Sweden, Div Safety & Transport, Elect, Brinellgatan 4,Box 857, SE-50115 Boras, Sweden..
    Welinder, Jan
    RISE Res Inst Sweden, Div Safety & Transport, Elect, Brinellgatan 4,Box 857, SE-50115 Boras, Sweden..
    Johansson, Kenth
    RISE Res Inst Sweden, Div Biosci & Mat, Box 5607, SE-11486 Stockholm, Sweden..
    Modelling anti-icing of railway overhead catenary wires by resistive heating2019In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 143, article id 118505Article in journal (Refereed)
    Abstract [en]

    Aggregation of ice on electrical cables and apparatus can cause severe equipment malfunction and is thus considered as a serious problem, especially in arctic climate zones. In particular, cable damage caused by ice accumulation on railway catenary wires is in wintertime a common origin for delayed trains in the northern parts of Europe. This study examines how resistive heating can be used for preventing formation of ice on metallic, non-insulated electrical cables. The heat equation and the Navier Stokes equations were solved simultaneously with FEM in 3D in order to predict the cable temperature as function of external temperature, applied voltage, wind speed, wind direction, and heating time. An analytical expression for the heat transfer coefficient was derived from the FEM simulations and it was concluded that the influence of wind direction can typically be neglected. Experimental validation measurements were performed on Kanthal cables in a climate chamber, giving temperature increase results in good agreement with the simulation predictions. The resistive heating efficiency, i.e. the ratio between applied electrical energy and resulting thermal energy, was found to be approximately 68% in this particular study.

  • 32.
    Qu, Muchao
    et al.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.;BPI, Key Lab Adv Fiber Technol, Dr Mack Str 77, D-90762 Furth, Germany..
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Schubert, Dirk W.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.;BPI, Key Lab Adv Fiber Technol, Dr Mack Str 77, D-90762 Furth, Germany..
    Novel definition of the synergistic effect between carbon nanotubes and carbon black for electrical conductivity2019In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 30, no 24, article id 245703Article in journal (Refereed)
    Abstract [en]

    Anisotropic ternary composites comprising poly(methy-methacrylate) (PMMA), carbon black (CB), and carbon nanotubes (CNTs) were extruded using a capillary rheometer and the electrical conductivities of the composites were measured and presented in a detailed contour plot covering a large range of filler fractions (up to 30 vol% CNTs, 20 vol% CB). A recent generic conductivity model for ternary composites was successfully validated using the conductivity measurements. When analyzing the conductivity measurements using four traditional definitions of 'synergy' between two conductive fillers, no clear synergetic effect was observed between CB and CNT. Also, when all the conductivity data for ternary CNT/CB composites from the existing literature was carefully gathered and analyzed, the number of confirmed occurrences of strong and convincing CNT/CB synergies was surprisingly low. Finally, a novel definition of synergy based on the physical aspect, in particular, its maximum, the 'synergasm', was defined in order to obtain a more precise instrument for revealing regions of potential synergy.

  • 33.
    Holder, Shima
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Understanding and modelling the diffusion process of low molecular weight substances in polyethylene pipes2019In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, p. 301-309Article in journal (Refereed)
    Abstract [en]

    Peroxides are widely used as crosslinkers in polyethylene (PE) drinking water pipes. Cross-linked polyethylene (PEX) has better mechanical properties than PE, but peroxide decomposition by-products can migrate from PEX water pipes into the drinking water unless sufficient preventive actions are undertaken. This work systematically examines the migration of tert-Butyl methyl ether (MTBE), a dominating crosslinking by-product from PEX water pipes, into tap water by utilizing both experimental techniques and finite element (FEM) diffusion modeling. The effects of pipe geometry, tap water temperature (23–80 °C), boundary conditions (air or water interface) and degasing (at 180 °C) were considered. The MTBE diffusivity increased strongly with increasing temperature and it was concluded that a desired water quality can be achieved with proper degasing of the PEX pipes. As the FEM simulations were in excellent agreement with the experimental results, the model can accurately predict the MTBE concentration as a function of time, water temperature and PEX pipe geometry, and enable the pipe manufacturers to aid in ensuring desirable drinking water quality.

  • 34. Yang, G.
    et al.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Schubert, D. W.
    Universal and anisotropic simulation platform for the study of electrical properties of conductive polymer composites2019In: AIP Conference Proceedings, American Institute of Physics (AIP), 2019, Vol. 2055, article id 050012Conference paper (Refereed)
    Abstract [en]

    In order to carry out a study on the synergistic relationship of variables which could affect the electrical properties of CPC, a universal and anisotropic platform of simulation, containing three simulation modules are explored. The simulation modules are: finite element modelling (FEM), percolation threshold modeling (PTM) and electrical networks modelling (ENM).

  • 35.
    Nakamura, Keisuke
    et al.
    Tohoku Univ, Dept Adv Free Rad Sci, Grad Sch Dent, Aoba Ku, 4-1 Seiryo Machi, Sendai, Miyagi 9808575, Japan..
    Ankyu, Shuhei
    Sweden Dent Sendai, Miyagino Ku, 1-6-2 Tsutsujigaoka, Sendai, Miyagi 9830852, Japan..
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Kanno, Taro
    Tohoku Univ, Dept Adv Free Rad Sci, Grad Sch Dent, Aoba Ku, 4-1 Seiryo Machi, Sendai, Miyagi 9808575, Japan..
    Niwano, Yoshimi
    Shumei Univ, Fac Nursing, 1-1 Daigaku Cho, Yachiyo, Chiba 2760003, Japan..
    von Steyern, Per Vult
    Malmo Univ, Fac Odontol, Dept Mat Sci & Technol, SE-20506 Malmo, Sweden..
    Örtengren, Ulf
    Univ Gothenburg, Sahlgrenska Acad, Inst Odontol, Dept Cariol, SE-40530 Gothenburg, Sweden.;Arctic Univ Norway, Fac Hlth Sci, Dept Clin Dent, N-9037 Tromso, Norway..
    Critical considerations on load-to-failure test for monolithic zirconia molar crowns2018In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 87, p. 180-189Article in journal (Refereed)
    Abstract [en]

    Application of monolithic zirconia crowns (MZCs) with reduced thickness to the molar region has been proposed, but potential complications have yet to be fully evaluated in laboratory tests. The present study aimed to develop a clinically relevant load-to-failure test in combination with fatigue treatments involving thermal and mechanical cycling (TC and MC) to evaluate the fracture resistance of molar MZCs. MZCs with a minimal thickness of 0.5 mm were bonded to dies made of resin-based composite (RBC), epoxy resin (EP), or polyoxymethylene-copolymer (POM-C). The samples were either untreated (UT) or subjected to TC (5-55 degrees C for 1 x 10(5) cycles) and MC (300 N for 2.4 x 10(6) cycles). The stress generated by TC and MC was simulated by finite element modeling. The load-to-failure test was performed using an inverse V-shaped two-plane indenter and was followed by fractographic analysis. The median values of fracture load for MZC/RBC and MZC/EP in the TC group were significantly lower than those in the UT group. MC also decreased the median value of fracture load for MZC/RBC significantly, but not that for MZC/EP and MZC/POM-C. Fractography revealed that the fracture started in the cervical area in all groups, which is similar to clinically failed crowns. The simulation confirmed stress concentration at the cervical area in both TC and MC groups. The present study suggests that the load-to-failure test using a two-plane indenter could induce clinically relevant fracture of MZCs, the vulnerability of the MZCs depends largely on the die material employed, and MZCs are more likely to be damaged by thermal fatigue than mechanical fatigue.

  • 36. Qu, M.
    et al.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Schubert, D. W.
    Effect of filler orientation on the electrical conductivity of carbon Fiber/PMMA composites2018In: Fibers, ISSN 2079-6439, Vol. 6, no 1, article id 3Article in journal (Refereed)
    Abstract [en]

    The electrical conductivity of extruded carbon fiber (CF)/Polymethylmethacrylate (PMMA) composites with controlled CF aspect ratio and filler fractions ranging from 0 to 50 vol. % has been investigated and analyzed. The composites were extruded through a capillary rheometer, utilizing either 1-mm or 3-mm diameter extrusion dies, resulting in cylindrical composite filaments of two different diameters. Since the average CF orientation becomes more aligned with the extrusion flow when the diameter of the extrusion dies decreases, the relationship between conductivity and average fiber orientation could therefore be examined. The room temperature conductivities of the extruded filaments as a function of CF fractions were fitted to theMcLachlan general effective medium (GEM) equation and the percolation thresholds were determined to 20.0 ± 2.5 vol. % and 32.0 ± 5.9 vol. % for the 3-mm (with CFs oriented less) and 1-mm(with CFs orientedmore) filaments, respectively. It turned out that the oriented CFs in the composite shift the percolation threshold to a higher value, however, the conductivity above the percolation threshold is higher for composites with oriented CFs. A novel approach based on the Balberg excluded volume theory was proposed to explain this counterintuitive phenomenon. 

  • 37.
    Yang, Guanda
    et al.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany..
    Schubert, Dirk W.
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany.;Bavarian Polymer Inst, Key Lab Adv Fiber Technol, Dr Mack Str 77, D-90762 Furth, Germany..
    Qu, Muchao
    Friedrich Alexander Univ Erlangen Nuremberg, Inst Polymer Mat, Martensstr 7, D-91058 Erlangen, Germany..
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Novel Theoretical Self-Consistent Mean-Field Approach to Describe the Conductivity of Carbon Fiber-Filled Thermoplastics: PART II. Validation by Computer Simulation2018In: Macromolecular Theory and Simulations, ISSN 1022-1344, E-ISSN 1521-3919, Vol. 27, no 4, article id 1700105Article in journal (Refereed)
    Abstract [en]

    The electrical conductivity of polymeric fiber composites is generally strongly dependent on the constituent conductivities, the fiber filler fraction, the fiber aspect ratio, and on the orientation of the fibers. Even though electrically conductive polymer composites are emerging materials of high scientific and commercial interest, accurate mathematical models for describing such materials are rare. A very promising mathematical model for predicting the electrical conductivity below the electrical percolation threshold, for both isotropic and anisotropic composites, is however recently published by Schubert. The shortcomings of that study are that the model includes so far only one predicted parameter and that it is not sufficiently validated. In the current study, finite element modeling is used to successfully validate the model of Schubert for isotropic fiber composites and to accurately determine the predicted parameter. These theoretical predictions are finally compared with experimental conductivity data for isotropic carbon fiber/poly(methyl methacrylate) (PMMA) composites with fiber filler fractions in the range 0-12 vol% and fiber aspect ratios from 5 to 30. The model forecasts, without any adjustable parameters, are satisfactory close to the experimental data.

  • 38.
    Özeren, Hüsamettin Deniz
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Olsson, Richard
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Prediction of plasticization mechanisms for biobased plastics through a combined experimental and molecular dynamics simulations approach2018In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 256Article in journal (Other academic)
  • 39.
    Wu, Qiong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Sundborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Peuvot, Kevin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Guex, Leonard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Conductive biofoams of wheat gluten containing carbon nanotubes, carbon black or reduced graphene oxide2017In: RSC Advances, E-ISSN 2046-2069, Vol. 7, no 30, p. 18260-18269Article in journal (Refereed)
    Abstract [en]

    Conductive biofoams made from glycerol-plasticized wheat gluten (WGG) are presented as a potential substitute in electrical applications for conductive polymer foams from crude oil. The soft plasticised foams were prepared by conventional freeze-drying of wheat gluten suspensions with carbon nanotubes (CNTs), carbon black (CB) or reduced graphene oxide (rGO) as the conductive filler phase. The change in conductivity upon compression was documented and the results show not only that the CNT-filled foams show a conductivity two orders of magnitude higher than foams filled with the CB particles, but also that there is a significantly lower percolation threshold with percolation occurring already at 0.18 vol%. The rGO-filled foams gave a conductivity inferior to that obtained with the CNTs or CB particles, which is explained as being related to the sheet-like morphology of the rGO flakes. An increasing amount of conductive filler resulted in smaller pore sizes for both CNTs and CB particles due to their interference with the ice crystal formation before the lyophilization process. The conductive WGG foams with CNTs were fully elastic with up to 10% compressive strain, but with increasing compression up to 50% strain the recovery gradually decreased. The data show that the conductivity strongly depends on the type as well as the concentration of the conductive filler, and the conductivity data with different compressions applied to these biofoams are presented for the first time.

  • 40. Qu, M.
    et al.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Qin, Y.
    Yang, G.
    Pan, Y.
    Liu, X.
    Hernandez Rodriguez, G.
    Chen, J.
    Zhang, C.
    Schubert, D. W.
    Electrical conductivity and mechanical properties of melt-spun ternary composites comprising PMMA, carbon fibers and carbon black2017In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 150, p. 24-31Article in journal (Refereed)
    Abstract [en]

    In this study, the electrical conductivity of melt spun composites consisting of PMMA containing both aligned carbon fibers (CF) and carbon black (CB) has been investigated. A broad range of composite compositions (up to 50 vol % CF and 20 vol % CB) was studied. The percolation thresholds of binary PMMA/CF and PMMA/CB composites were determined to 31.8 and 3.9 vol %, respectively. Experimental conductivity contour plots for PMMA/CF/CB ternary composites were presented for the first time. Additionally, based on a model for predicting the percolation threshold of ternary composites, a novel equation was proposed to predict the conductivity of ternary composites, showing results in agreement with corresponding experimental data. Finally, two mechanical contour plots for elastic modulus and tensile strength were presented, showing how the decreasing tensile strength and increasing E-modulus of the PMMA/CF/CB ternary composites was depending on the CB and CF filling fractions. The systematic measurements and novel equations presented in this work are especially valuable when designing ternary conductive polymer composites with two different fillers.

  • 41.
    Moyassari, Ali
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Unge, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. ABB Corporate Research, Sweden.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    First-principle simulations of electronic structure in semicrystalline polyethylene2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 20, article id 204901Article in journal (Refereed)
    Abstract [en]

    In order to increase our fundamental knowledge about high-voltage cable insulation materials, realistic polyethylene (PE) structures, generated with a novel molecular modeling strategy, have been analyzed using first principle electronic structure simulations. The PE structures were constructed by first generating atomistic PE configurations with an off-lattice Monte Carlo method and then equilibrating the structures at the desired temperature and pressure using molecular dynamics simulations. Semicrystalline, fully crystalline and fully amorphous PE, in some cases including crosslinks and short-chain branches, were analyzed. The modeled PE had a structure in agreement with established experimental data. Linear-scaling density functional theory (LS-DFT) was used to examine the electronic structure (e.g., spatial distribution of molecular orbitals, bandgaps and mobility edges) on all the materials, whereas conventional DFT was used to validate the LS-DFT results on small systems. When hybrid functionals were used, the simulated bandgaps were close to the experimental values. The localization of valence and conduction band states was demonstrated. The localized states in the conduction band were primarily found in the free volume (result of gauche conformations) present in the amorphous regions. For branched and crosslinked structures, the localized electronic states closest to the valence band edge were positioned at branches and crosslinks, respectively. At 0 K, the activation energy for transport was lower for holes than for electrons. However, at room temperature, the effective activation energy was very low (similar to 0.1 eV) for both holes and electrons, which indicates that the mobility will be relatively high even belowthe mobility edges and suggests that charge carriers can be hot carriers above the mobility edges in the presence of a high electrical field.

  • 42.
    Liu, Dongming
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hoang, A. T.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pallon, Love K. H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gubanski, S. M.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Influence of Nanoparticle Surface Coating on Electrical Conductivity of LDPE/Al2O3 Nanocomposites for HVDC Cable Insulations2017In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 24, no 3, p. 1396-1404Article in journal (Refereed)
    Abstract [en]

    LDPE/metal oxide nanocomposites are promising materials for future high-voltage DC cable insulation. This paper presents data on the influence of the structure of the nanoparticle coating on the electrical conductivity of LDPE/Al2O3 nanocomposites. Al2O3 nanoparticles, 50 nm in size, were coated with a series of silanes with terminal alkyl groups of different lengths (methyl, n-octyl and n-octadecyl groups). The density of the coatings in vacuum was between 200 and 515 kg m(-3,) indicating substantial porosity in the coating. The dispersion of the nanoparticles in the LDPE matrix was assessed based on statistics for the nearest-neighbor particle distance. The electrical conductivity of the nanocomposites was determined at both 40 and 60 degrees C. The results show that an appropriate surface coating on the nanoparticles allowed uniform particle dispersion up to a filler loading of 10 wt.%, with a maximum reduction in the electrical conductivity by a factor of 35. The composites based on the most porous octyl-coated nanoparticles showed the greatest reduction in electrical conductivity and the lowest temperature coefficient of electrical conductivity of the composites studied.

  • 43.
    Nilsson, Fritjof
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Mattias
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pallon, Love K. H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Giacinti, Marco
    Olsson, Richard T.
    Venturi, Davide
    Gedde, Ulf W
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Influence of water uptake on the electrical DC-conductivity of insulating LDPE/MgO nanocomposites2017In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 152, p. 11-19Article in journal (Refereed)
    Abstract [en]

    Low-density polyethylene (LDPE), typically in cross-linked form, is currently the main insulation material for extruded high voltage cables. The DC-conductivity of LDPE can be reduced 100 times by adding 1-3 wt% well-dispersed metal-oxide nanoparticles (MgO, ZnO, Al2O3), but the underlying physics remain unclear. One of several feasible explanations is that the nanoparticles attract electrical charges, polar molecules (H2O and crosslinking by-products) and ions (H+, OH-, salts and ionic species originating from the crosslinking by-products), and thus clean the polymer. Effective media FEM simulations, assuming that the polymer conductivity is proportional to the moisture content, were used in order to examine this hypothesis. Water sorption measurements for LDPE and MgO/LDPE nanocomposites were conducted as experimental input. The simulations could conceptually predict the experimentally measured composite conductivities. The hypothesis was further strengthened by DC-conductivity measurements on LDPE and MgO/LDPE nanocomposites at 0 and 50% relative humidity (RH), showing a 100-fold conductivity increase for the nanocomposite at the elevated humidity. The DC-conductivity of the most insulating composite (3 wt% MgO) was below 10(-16) S/m after 64 h at 60 degrees C and 0% RH, using an electric field of ca 30 kV/mm. The long-term insulation efficiency of an insulating polymer nanocomposite is thus optimal if the material is carefully dried and surrounded by an impenetrable moisture barrier before use.

  • 44.
    Wåhlander, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hillborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. ABB AB.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Reduced and Surface-Modified Graphene Oxide with Nonlinear Resistivity2017In: Macromolecular rapid communications, ISSN 1022-1336, E-ISSN 1521-3927, Vol. 38, no 16, article id 1700291Article in journal (Refereed)
    Abstract [en]

    Field-grading materials (FGMs) are used to reduce the probability for electrical breakdowns in critical regions of electrical components and are therefore of great importance. Usually, FGMs are heavily filled (40 vol.%) with semi-conducting or conducting particles. Here, polymer-grafted reduced graphene oxide (rGO) is used as a filler to accomplish percolated networks at very low filling ratios (<2 vol.%) in a semi-crystalline polymer matrix: poly(ethylene-co-butyl acrylate) (EBA). Various simulation models are used to predict the percolation threshold and the flake-to-flake distances, to complement the experimental results. A substantial increase in thermal stability of rGO is observed after surface modification, either by silanization or subsequent polymerizations. The non-linear DC resistivity of neat and silanized rGO and its trapping of charge-carriers in semi-crystalline EBA are demonstrated for the first time. It is shown that the polymer-grafted rGO improve the dispersibility in the EBA-matrix and that the graft length controls the inter-flake distances (i.e. charge-carrier hopping distances). By the appropriate selection of graft lengths, both highly resistive materials at 10 kV mm-1 and FGMs with a large and distinct drop in resistivity (six decades) are obtained, followed by saturation. The nonlinear drop in resistivity is attributed to narrow inter-flake distance distributions of grafted rGO.

  • 45.
    Wåhlander, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Cobo Sanchez, Carmen
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Taylor, Nathaniel
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hillborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. ABB AB.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Tailoring Dielectric Properties using Designed Polymer-Grafted ZnO Nanoparticles in Silicone Rubber2017In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, p. 14241-14258, article id C6TA11237DArticle in journal (Refereed)
    Abstract [en]

    Polymer grafts were used to tailor the interphases between ZnO nanoparticles (NPs) and silicone matrices. The final electrical properties of the nanocomposites were tuned by the grafted interphases, by controlling the inter-particle distance and the NP-morphology. The nanocomposites can be used in electrical applications where control of the resistivity is desired. Hansen's solubility parameters were used to select a semi-compatible polymer for grafting to obtain anisotropic NP morphologies in silicone, and the grafted NPs self-assembled into various morphologies inside the silicone matrices. The morphologies in the semi-compatible nanocomposites could be tuned by steering the graft length of poly(n-butyl methacrylate) via entropic matrix-graft wetting using surface-initiated atom-transfer radical polymerization. Image analysis models were developed to calculate the radius of primary NPs, the fraction of aggregates, the dispersion, and the face-to-face distance of NPs. The dielectric properties of the nanocomposites were related to the morphology and the face-to-face distance of the NPs. The dielectric losses, above 100 Hz, for nanocomposites with grafted NPs were approximately one decade lower than those of pristine NPs. The isotropic nanocomposites increased the resistivity up to 100 times compared to that of neat silicone rubber, due to the trapping of charge carriers by the interphase of dispersed NPs and nanoclusters. On the other hand, the resistivity of anisotropic nanocomposites decreased 10–100 times when the inter-particle distance in continuous agglomerates was close to the hopping distance of charge carriers. The electrical breakdown strength increased for compatible isotropic nanocomposites, and the temperature dependence of the resistivity and the activation energy were ∼50% lower in the nanocomposites with grafted NPs. These flexible dielectric nanocomposites are promising candidates for low-loss high-voltage transmission cable accessories, mobile electronic devices, wearables and sensors.

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  • 46.