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  • 51.
    Das, Oisik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. Department of Civil and Environmental Engineering, Centre for Advanced Composite Materials, University of Auckland, New Zealand.
    Kim, Nam Kyeun
    Kalamkarov, Alexander L.
    Sarmah, Ajit K.
    Bhattacharyya, Debes
    Biochar to the rescue: Balancing the fire performance and mechanical properties of polypropylene composites2017In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 144, p. 485-496Article in journal (Refereed)
    Abstract [en]

    Biochar based wood/polypropylene (PP) composites were manufactured with two flame retardants (FRs): ammonium polyphosphate/APP and magnesium hydroxide/Mg(OH)(2). The amounts of wood and biochar were alternated for accommodating the FRs in each blend. Flammability and mechanical characterisation for both the batches containing different FRs were done. Having higher proportion of biochar and less wood is beneficial to reduce flammability. The thermally stable biochar contributes to formation of effective char to restrict O-2 transfer into PP. The higher weight ratio of biochar than wood in the composites compromised the tensile and flexural strengths to some extent as the APP and Mg(OH)(2) particles were trapped inside biochar pores consequently reducing the effectiveness of biochar pore infiltration by PP. In general, addition of biochar with a woody biomass (with FRs) to neat PP significantly impedes its flammability while enhancing certain mechanical properties, such as flexural strength and tensile/flexural moduli and preserving the tensile strength. (C) 2017 Elsevier Ltd. All rights reserved.

  • 52.
    Ekelund, Maria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Fantoni, P. F.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Thermal ageing assessment of EPDM-chlorosulfonated polyethylene insulated cables using line resonance analysis (LIRA)2011In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 30, no 1, p. 86-93Article in journal (Refereed)
    Abstract [en]

    Two cables with chlorosulfonated polyethylene jackets and EPDM core insulations, but having different designs and geometries, were aged at 140 degrees C for different periods of time mimicking ageing at 50 degrees C for an exposure time of more than one hundred years. The cable samples were aged in dry air and dry nitrogen. The cable samples were studied with indenter modulus measurements, tensile tests, infrared spectroscopy and line resonance analysis (LIRA). The main question was whether universal correlations could be established between the two classical methods (indenter and tensile testing) and LIRA. The global ageing indicator (CBAC2) obtained by LIRA showed good correlation with the indenter modulus of the jacketing and with the mechanical properties of the core insulation. Almost universal CBAC2 values were obtained for samples reaching a critical state; the latter being defined according to a criterion based on LOCA test data. Infrared spectroscopy showed that the core insulation degraded by an essentially oxygen-free mechanism, with a gradual increase in the concentration of vinyl and vinylene groups. (C) 2010 Elsevier Ltd. All rights reserved.

  • 53.
    Elwinger, Fredrik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Pourmand, Payam
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Diffusive Transport in Pores. Tortuosity and Molecular Interaction with the Pore Wall2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 25, p. 13757-13764Article in journal (Refereed)
    Abstract [en]

    The self-diffusion of neat water, dimethyl sulfoxide (DMSO), octanol, and the molecular components in a water-DMSO solution was measured by H-1 and H-2 NMR diffusion experiments for those fluids imbibed into controlled pore glasses (CPG). Their highly interconnected structure is scaled by pore size and shows invariant pore topology independent of the size. The nominal pore diameter of the explored CPGs varied from 7.5 to 72.9 nm. Hence, the about micrometer mean-square diffusional displacement during the explored diffusion tithes was much larger than the individual pore size, and the experiment yielded the average diffusion coefficient Great care was taken to establish the actual pore: volumes of the CPGs. Transverse relaxation experiments processed by inverse Laplace transformation were performed to verify that the liquids explored filled exactly the available pore volume. Relative to the respective diffusion coefficients obtained in bulk phases, we observe a reduction in the diffusion coefficient that is independent of pore size for the larger pores and becomes stronger toward the smaller pores. Geometric tortuosity governs the behavior at larger pore sizes, while the interaction with pore walls becomes the dominant factor at our smallest pore diameter. Deviation from the trends predicted by the Renkin equation indicates that the interaction with the pore wall is not a just simple steric one but is in part dependent on the specific features of the molecules explored here.

  • 54.
    Fang, Mei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Belova, Lyubov
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Rao, K. Venkat
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Rapid mixing: A route to synthesize magnetite nanoparticles with high moment2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 22, p. 222501-Article in journal (Refereed)
    Abstract [en]

    We demonstrate the impact of rapid mixing of the precursors in a time scale of milliseconds on the reaction rate and magnetic properties of co-precipitated magnetite with a custom-made mixer. The mixed volume is directed into a desk-top AC susceptometer to monitor the magnetic response from the growing particles in real-time. These measurements indicate that the reaction is mostly completed within a minute. The obtained superparamagnetic nanoparticles exhibit a narrow size distribution and large magnetization (87 Am(2) kg(-1)). Transmission electron micrographs suggest that rapid mixing is the key for better crystallinity and a more uniform morphology leading to the observed magnetization values.

  • 55.
    Galland, Sylvain
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Olsson, Richard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Strong and Moldable Cellulose Magnets with High Ferrite Nanoparticle Content2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 22, p. 20524-20534Article in journal (Refereed)
    Abstract [en]

    A major limitation in the development of highly functional hybrid nanocomposites is brittleness and low tensile strength at high inorganic nanoparticle content. Herein, cellulose nanofibers were extracted from wood and individually decorated with cobalt-ferrite nanoparticles and then for the first time molded at low temperature (<120 degrees C) into magnetic nanocomposites with up to 93 wt % inorganic content. The material structure was characterized by TEM and FE-SEM and mechanically tested as compression molded samples. The obtained porous magnetic sheets were further impregnated with a thermosetting epoxy resin, which improved the load-bearing functions of ferrite and cellulose material. A nanocomposite with 70 wt % ferrite, 20 wt % cellulose nanofibers, and 10 wt % epoxy showed a modulus of 12.6 GPa, a tensile strength of 97 MPa, and a strain at failure of ca. 4%. Magnetic characterization was performed in a vibrating sample magnetometer, which showed that the coercivity was unaffected and that the saturation magnetization was in proportion with the ferrite content. The used ferrite, CoFe2O4 is a magnetically hard material, demonstrated by that the composite material behaved as a traditional permanent magnet. The presented processing route is easily adaptable to prepare millimeter-thick and moldable magnetic objects. This suggests that the processing method has the potential to be scaled-up for industrial use for the preparation of a new subcategory of magnetic, low-cost, and moldable objects based on cellulose nanofibers.

  • 56.
    Galland, Sylvain
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Andersson, Richard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Salajkova, Michaela
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Olsson, Richard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Cellulose nanofibers decorated with magnetic nanoparticles: synthesis, structure and use in magnetized high toughness membranes for a prototype loudspeaker2013In: Journal of Materials Chemistry C, ISSN 2050-7526, Vol. 1, no 47, p. 7963-7972Article in journal (Refereed)
    Abstract [en]

    Magnetic nanoparticles are the functional component for magnetic membranes, but they are difficult to disperse and process into tough membranes. Here, cellulose nanofibers are decorated with magnetic ferrite nanoparticles formed in situ which ensures a uniform particle distribution, thereby avoiding the traditional mixing stage with the potential risk of particle agglomeration. The attachment of the particles to the nanofibrils is achieved via aqueous in situ hydrolysis of metal precursors onto the fibrils at temperatures below 100 °C. Metal adsorption and precursor quantification were carried out using Induction Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). FE-SEM was used for high resolution characterization of the decorated nanofibers and hybrid membranes, and TEM was used for nanoparticle size distribution studies. The decorated nanofibers form a hydrocolloid. Large (200 mm diameter) hybrid cellulose/ferrite membranes were prepared by simple filtration and drying of the colloidal suspension. The low-density, flexible and permanently magnetized membranes contain as much as 60 wt% uniformly dispersed nanoparticles (thermogravimetric analysis data). Hysteresis magnetization was measured by a Vibrating Sample Magnetometer; the inorganic phase was characterized by XRD. Membrane mechanical properties were measured in uniaxial tension. An ultrathin prototype loudspeaker was made and its acoustic performance in terms of output sound pressure was characterized. A full spectrum of audible frequencies was resolved.

  • 57.
    Gedde, Ulf
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hjertberg, Thomas
    Borealis.
    Costa, Francis
    Borealis/Linz.
    Oderkerk, Jeroen
    Borealis.
    Polyolefin composition with increased resistance against degradation caused by chlorine dioxide2011Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The present invention relates to a polyolefin composition with increased resistance to degradation caused by ClO2-containing water and to an article made of such a polyolefin composition. The polyolefin composition comprises a polyolefin base resin (A), at least one antioxidant (B) having an initial oxygen induction time (OIT190°C) of more than 35 min., determined according to the OIT190°C test described herein and having a slope of the curve, when OIT190°C, in minutes, is recorded as a function of exposure time, in minutes, in a chlorine dioxide degradation test as described herein, of at least -0.07, and c) at least one antioxidant (C) having an initial oxygen induction time (OIT190°C) of not more than 35 min., determined according to the OIT190°C test described herein and having a slope of the curve, when OIT190°C, in minutes, is recorded as a function of exposure time, in minutes, in a chlorine dioxide degradation test as described herein, of less than -0.07, wherein said polyolefin composition shows a resistance against water containing 10 ppm chlorine dioxide at 70 °C and a pH of 6.8 ± 0.1 of at least 450 min., expressed as the time to reach 50% of the initial oxygen induction time at 210 °C (OIT(210°C),50%), determined according to the chlorine dioxide degradation test as described herein. The present invention further relates to the use of the polyolefin composition for the production of an article, e.g. a pipe, a fitting or a storage container and to the use of the polyolefin composition for increasing the resistance of an article against degradation caused by contact with ClO2-containing water.

  • 58.
    Gedde, Ulf W
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Untitled2016In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 55, p. A2-A2Article in journal (Other academic)
  • 59.
    Guex, Leonard Gaston
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Sacchi, B.
    Peuvot, Kevin F.
    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.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Farris, S.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Experimental review: chemical reduction of graphene oxide (GO) to reduced graphene oxide (rGO) by aqueous chemistry2017In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, no 27, p. 9562-9571Article, review/survey (Refereed)
    Abstract [en]

    The electrical conductivity of reduced graphene oxide (rGO) obtained from graphene oxide (GO) using sodium borohydride (NaBH4) as a reducing agent has been investigated as a function of time (2 min to 24 h) and temperature (20 degrees C to 80 degrees C). Using a 300 mM aqueous NaBH4 solution at 80 degrees C, reduction of GO occurred to a large extent during the first 10 min, which yielded a conductivity increase of 5 orders of magnitude to 10 S m(-1). During the residual 1400 min of reaction, the reduction rate decreased significantly, eventually resulting in a rGO conductivity of 1500 S m(-1). High resolution XPS measurements showed that C/O increased from 2.2 for the GO to 6.9 for the rGO at the longest reaction times, due to the elimination of oxygen. The steep increase in conductivity recorded during the first 8-12 min of reaction was mainly due to the reduction of C-O (e.g., hydroxyl and epoxy) groups, suggesting the preferential attack of the reducing agent on C-O rather than C=O groups. In addition, the specular variation of the percentage content of C-O bond functionalities with the sum of Csp(2) and Csp(3) indicated that the reduction of epoxy or hydroxyl groups had a greater impact on the restoration of the conductive nature of the graphite structure in rGO. These findings were reflected in the dramatic change in the structural stability of the rGO nanofoams produced by freeze-drying. The reduction protocol in this study allowed to achieve the highest conductivity values reported so far for the aqueous reduction of graphene oxide mediated by sodium borohydride. The 4-probe sheet resistivity approach used to measure the electrical conductivity is also, for the first time, presented in detail for filtrate sheet assemblies' of stacked GO/rGO sheets.

  • 60. Harrisson, Simon
    et al.
    Drisko, Glenna L.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hult, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Wooley, Karen L.
    Hybrid Rigid/Soft and Biologic/Synthetic Materials: Polymers Grafted onto Cellulose Microcrystals2011In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, no 4, p. 1214-1223Article in journal (Refereed)
    Abstract [en]

    Rigid nanoscale polymer rods were prepared by grafting preformed amine-terminated poly(styrene) and poly(tert-butyl acrylate) onto oxidized cellulose microcrystals. Low polydispersity polymers, grown using atom transfer radical polymerization, were characterized and purified prior to cellulose attachment. Oxidation of the cellulose microcrystal led to the formation of carboxylic acids on the surface of the microcrystals. Covalent attachment of the polymers onto the cellulose microcrystals was achieved via a carbodiimide-mediated amidation reaction. The length and diameter of the polymer-cellulose composites increased upon surface modification. Typically, polymer-cellulose composites are synthesized by a grafting-from method because it can be difficult to obtain sufficient graft density using a grafting-to preparation. However, the composites reported here comprised 60-64% grafted polymer by mass. This degree of grafting-to allowed the composite to form stable suspensions in organic solvents.

  • 61. Introzzi, Laura
    et al.
    Blomfeldt, Thomas O. J.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Trabattoni, Silvia
    Tavazzi, Silvia
    Santo, Nadia
    Schiraldi, Alberto
    Piergiovanni, Luciano
    Farris, Stefano
    Ultrasound-Assisted Pullulan/Montmorillonite Bionanocomposite Coating with High Oxygen Barrier Properties2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 30, p. 11206-11214Article in journal (Refereed)
    Abstract [en]

    In this paper, the preparation and characterization of oxygen barrier pullulan sodium montmorillonite (Na+-MMT) nanocomposite coatings are presented for the first time. Full exfoliation of platelets during preparation of the coating water dispersions was mediated by ultrasonic treatment, which turned out to be a pivotal factor in the oxygen barrier performance of the final material even at high relative humidity (RH) conditions [oxygen permeability coefficients similar to 1.43 +/- 0.39 and 258.05 +/- 13.78 mL.mu m.m(-2).(24 h)(-1).atm(-1) at 23 degrees C and 0% RH and 70% RH, respectively]. At the micro- and nanoscale, the reasons are discussed. The final morphology of the coatings revealed that clay lamellae were stacked on top of one another, probably due to the forced confinement of the platelets within the coating thickness after solvent evaporation. This was also confirmed by modeling the experimental oxygen permeability data with the well-known Nielsen and Cussler permeation theoretical models, which suggested a reasonable aspect ratio (alpha) of similar to 100. Electron microscopic analyses also disclosed a peculiar cell-like arrangement of the platelets. The stacking of the clay lamellae and the cell-like arrangement create the excellent oxygen barrier properties. Finally, we demonstrated that the slight haze increase in the bionanocomposite coating materials arising from the addition of the clays depends on the clay concentration but not so much on the sonication time, due to the balance of opposite effects after sonication (an increase in the number of scattering centers but a reduction in their size).

  • 62. Johansson, E.
    et al.
    Malik, A. H.
    Hussain, A.
    Rasheed, F.
    Newson, W. R.
    Plivelic, T.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, M.
    Kuktaite, R.
    Wheat gluten polymer structures: The impact of genotype, environment, and processing on their functionality in various applications2013In: Cereal Chemistry, ISSN 0009-0352, E-ISSN 1943-3638, Vol. 90, no 4, p. 367-376Article in journal (Refereed)
    Abstract [en]

    For a number of applications, gluten protein polymer structures are of the highest importance in determining end-use properties. The present article focuses on gluten protein structures in the wheat grain, genotype- and environment-related changes, protein structures in various applications, and their impact on quality. Protein structures in mature wheat grain or flour are strongly related to end-use properties, although influenced by genetic and environment interactions. Nitrogen availability during wheat development and genetically determined plant development rhythm are the most important parameters determining the gluten protein polymer structure, although temperature during plant development interacts with the impact of the mentioned parameters. Glutenin subunits are the main proteins incorporated in the gluten protein polymer in extracted wheat flour. During dough mixing, gliadins are also incorporated through disulfide-sulfhydryl exchange reactions. Gluten protein polymer size and complexity in the mature grain and changes during dough formation are important for breadmaking quality. When using the gluten proteins to produce plastics, additional proteins are incorporated in the polymer through disulfide-sulfhydryl exchange, sulfhydryl oxidation, β-eliminations with lanthionine formation, and isopeptide formation. In promising materials, the protein polymer structure is changed toward β-sheet structures of both intermolecular and extended type and a hexagonal close-packed structure is found. Increased understanding of gluten protein polymer structures is extremely important to improve functionality and end-use quality of wheat- and gluten-based products.

  • 63.
    Jäverberg, Nadejda
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Venkatesulu, Bandapalle
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Edin, Hans
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hillborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Prebreakdown Current and Breakdown Strength of Alumina-filled Poly(ethylene co-butyl acrylate) Nanocomposites: Part I - Breakdown StrengthIn: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135Article in journal (Other academic)
  • 64.
    Jäverberg, Nadejda
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Venkatesulu, Bandapalle
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Edin, Hans
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hillborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Prebreakdown Current and Breakdown Strength of Alumina-filled Poly(ethylene co-butyl acrylate) Nanocomposites: Part II - Prebreakdown CurrentsIn: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135Article in journal (Other academic)
  • 65.
    Kaali, Peter
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Antimicrobial Polymer Composites for Medical Applications2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The current study and discuss the long-term properties of biomedical polymers in vitro and invivo and presents means to design and manufacture antimicrobial composites. Antimicrobialcomposites with reduced tendency for biofilm formation should lead to lower risk for medicaldevice associated infection.The first part analyse in vivo degradation of invasive silicone rubber tracheostomy tubes andpresents degradation mechanism, degradation products and the estimated lifetime of thematerials.. It was found that silicone tubes undergo hydrolysis during the long-term exposurein vivo, which in turn results in decreased stability of the polymer due to surface alterationsand the formation of low molecular weight compounds.The second part of the study presents the manufacturing of composites with single, binary andternary ion-exchanged zeolites as an antimicrobial agent. The ion distribution and release ofthe zeolites and the antimicrobial efficiency of the different systems showed that single silverion-exchanged zeolite was superior to the other samples. Antimicrobial composites wereprepared by mixing the above-mentioned zeolites and pure zeolite (without any ion) withdifferent fractions into polyether (TPU), polyether (PEU) polyurethane and silicone rubber.The antimicrobial efficiency of binary and ternary ion-exchanged samples was similar whichis thought to be due to the ion distribution in the crystal structure.The changes in the mechanical and surface properties of the composites due to the zeolitecontent demonstrated that the increasing zeolite content reduced the mechanical propertieswhile the surface properties did not change significantly. The antimicrobial tests showed thatthe silver-containing composite was the most efficient among all the other samples. Thebinary and ternary ion-exchanged composites expressed similar antimicrobial efficiency as itwas seen previously for the different zeolite systems. Biocompatibility was studied byexposure to artificial body fluids to simulate the degradation of the composites in the humanbody. Significant changes were observed in the morphology, the surface properties and the chemical structure.

  • 66.
    Kaali, Peter
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Pérez-Madrignal, Maria M.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Czel, Gyorgy
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    The influence of Ag(+), Zn(2+) and Cu(2+) exchanged zeolite on antimicrobial and long term in vitro stability of medical grade polyether polyurethane2011In: Express Polymer letters, ISSN 1788-618X, Vol. 5, no 12, p. 1028-1040Article in journal (Refereed)
    Abstract [en]

    This study aims to investigate the limitations and applicability of different ion exchanged zeolites as antimicrobial additive in thermoplastic polyether type polyurethanes. These composites were designed to improve the health quality of hospitalized patients by expressing both biocompatibility and relevant antimicrobial activity. The zeolites were exchanged with silver, copper and zinc ions and single, binary and ternary ion-exchanged zeolite-polyurethane composites were prepared. The antimicrobial activity and the resistance of the composites against the human environment play vital role in the applicability of the materials as a medical device therefore these properties were investigated. The antimicrobial test were performed on Methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa and Candida tropicalis. The tests showed that the efficiency of the silver ions is superior to the other single ionic systems. Besides, the binary and ternary ion-exchanged samples had similar antimicrobial efficiency regardless the type of the ions in the zeolite. The biocompatibility tests were carried out in-vitro in artificial body fluids for a period of 12 weeks. As a result of the in-vitro test, degradation of the composites were observed and the structural changes of the materials were detected and described by Scanning Electron Microscopy, Contact Angle measurements and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy.

  • 67.
    Kaali, Peter
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Czel, Gyoergy
    Department of Polymer Engineering, University of Miskolc.
    Momcilovic, Dane
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Antimicrobial properties of Ag+ loaded zeolite polyester polyurethane and silicone rubber and long-term properties after exposure to in-vitro ageing2010In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, no 9, p. 1456-1465Article in journal (Refereed)
    Abstract [en]

    In biomedical applications, tubes (e.g. catheters etc.) are commonly produced from polyurethane (PU) and silicone rubber which are known to be biocompatible materials. Several studies have shown that tubes, which are connected to the body (invasive) (especially urinary, tracheotomy and central venous catheters) are associated with infections. The present study reports the development of a new method aiming at obtaining antibacterial properties for PU and silicone rubber by mixing respective material with a natural antibacterial agent (Ag+ loaded zeolite) in different weight fractions. The influence of the zeolite content on the antimicrobial properties were analysed by exposure to bacteria (ISO 22196) and mixtures of fungi (ISO 846). The materials were also subject to artificial body fluids (Artificial Lysosomal Fluid (ALF) and Gamble's solution) for periods up to three months and the subsequent changes in the chemical properties after in-vitro exposure were determined by Matrix Assisted Laser Deposition/Ionization Time Of Flight Mass Spectrometry (MALDI-TOF MS) and Attenuated Total Reflection Fourier Transform Infra Red spectroscopy (ATR-FTIR). It was established that the antimicrobial effect of the materials increased with the increase of the zeolite content. The wettability of the materials was found to decrease significantly during the in-vitro exposure, but this could not be correlated to the zeolite content. In the PU samples, the formation of free carbonyl and -OH groups was observed, which corresponds to oxidative degradation. In case of the silicone rubber the ratio of cyclic PDMS to linear PDMS (H, CH3 and dimethyl terminated) decreased, which indicates a change in the concentration of the compounds. The formation and increase of the O-H bond during the exposure was also confirmed by the infrared spectra of the material which corresponds to hydrolysis of the silicone rubber.

  • 68.
    Kaali, Peter
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Czel, Gyorgy
    Modelling the ion distribution in single, binary and ternary ion exchanged Azeolite2011In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093Article in journal (Other academic)
  • 69.
    Kaali, Peter
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Prevention of Biofilm Associated Infections and Degradation of Polymeric Materials Used in Biomedical Applications2011In: Biomedical Engineering, Trends in Materials Science / [ed] Anthony N. Laskovski, InTech , 2011Chapter in book (Refereed)
  • 70.
    Kallio, Kai J.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    The Ageing of Fuel Lines Based on Polyamide-122010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Today, the use of bio-fuels for cars is increasing. There is a wide range of biofuelsavailable world wide, in Sweden ethanol containing fuels are favoured.For car manufacturers there is a need to be able to predict short and long termproperties of fuel lines subjected to ethanol containing fuels to ensure properlong term behaviour. The presented method for ageing in “close to real”environment involved circulating fuel inside the tubes and air on the outside attwo temperatures, 50°C and 110°C. The exposure time was extensive in the50°C case, almost 3 years, and the ageing at 110°C was conducted for 100days. Polyamide-12 was chosen as pipe material, which is also used in realparts. Tensile testing was used to assess the mechanical changes caused byageing. Long ageing times and high ethanol levels resulted in low extensibility.In the case of fuel with 25 vol.% ethanol at 110°C (100 days) the samplesshowed no macroscopic yielding. Even at 50°C a time induced loss ofextensibility was observed (80 vol.% ethanol). However, at ethanol levels of 0and 22 vol.% the extensibility was not reduced even after the 3 years of ageing.The changes at short times were interpreted as being due to loss of plasticizer.The changes at long ageing times were thoroughly investigated. The change incrystallinity, pipe swelling, leaching and the decrease in extensibility were allgreatest in the pipes subjected to ethanol. As expected, the molar massdecreased as the ethanol level increased and a good correlation between molarmass and extensibility was observed. A method for determining the fuelpermeation properties was developed. Fuel lines were subjected to circulatingfuels in the same manner as in the ageing tests and the surrounding air wasanalysed for fuel components with a flame ionisation detector. Higher level ofethanol increased the individual fuel component fluxes as well as the total fluxand also the temperature effect on the flux was significant. Finally it should bementioned, that ethanol was not always an unwanted ingredient; adding a smallamount of ethanol to the ethanol-free fuel prevented premature pipe failure at110°C.

  • 71.
    Kallio, Kai J.
    et al.
    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.
    Ageing properties of polyamide-12 pipes exposed to fuels with and without ethanol2008In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 93, no 10, p. 1846-1854Article in journal (Refereed)
    Abstract [en]

    The chemical and physical properties of polyamide-12 (PA12) fuel pipes/lines, aged for <= 2400 h at 110 degrees C, have been investigated. The pipes, containing fuel with or without ethanol, were either of a single PA12 layer, or of two PA12 layers surrounding a poly(vinylidene fluoride) barrier layer. The molar mass of the inner surface region obtained by size-exclusion chromatography was reduced during ageing. and optical microscopy revealed a surface that was partly dissolved in the presence of ethanol. Infrared spectroscopy revealed a rapid loss of plasticiser, especially in the presence of ethanol, and the fuel contained plasticiser and other polymer related components. Immersion tests at 60 degrees C showed that the swelling of the pipe and the amount of dissolved material were greatest for the fuels with intermediate ethanol content (50 vol.%). Aged samples experienced an increase in melting point, presumably, to a large extent, due to the loss of plasticiser and/or PA12-related components. In addition, for several samples, the crystallinity seemed to increase with ageing. (C) 2008 Elsevier Ltd. All rights reserved.

  • 72.
    Kallio, Kai J.
    et al.
    Volvo Car Corporation, Polymer Centre.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Effects of ethanol content and temperature on the permeation of fuel through polyamide-12-based pipes2010In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 29, no 5, p. 603-608Article in journal (Refereed)
    Abstract [en]

    A new test method has been developed which enables the fuel permeation properties of polyamide-12 (PA-12) - based pipes to be investigated. Fuel lines were exposed to circulating fuel with equal volume contents of toluene, isooctane and 0, 25 or 85 vol.% ethanol for up to 6 months at 60-110 degrees C. The pipes were either of a single PA12-layer or a multi-layer type, the latter having a poly(vinylidene fluoride) barrier layer between two PA12 sections. With a Thwing-Albert cup attached to the fuel line, it was possible to expose a pipe-section to surrounding air running in a separate pipe loop at a controlled flow-rate. Gas/vapour samples were collected from this loop using a syringe and, subsequently, analysed with a flame ionization detector. It was observed in the case of multi-layer pipes that the presence of ethanol increased the permeability (average values) of the "total" fuel as well as of the individual hydrocarbons. In addition, the 60 degrees C fuel permeability (85 vol.% ethanol) increased after a high temperature (110 degrees C peak) cycle, whereas the ethanol-free fuel flux seemed to decrease.

  • 73.
    Kallio, Kai J.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Degradation of Polyamide-12 pipes aged in fuelIn: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321Article in journal (Other academic)
    Abstract [en]

    In this work properties of polyamide-12 (PA12) fuel lines, exposed for ≤2400 h at 110°C and ≤26000 h at 50°C, containing fuels with different ethanol contents, were investigated. Dynamic mechanical thermal analysis indicated a sizeable loss of plasticiser during ageing. Viscosity measurements suggested that chain scission was an important mechanism of degradation at the higher temperature and size exclusion chromatography suggested that this was probably the case also at 50°C after long ageing times. The molar mass and polydispersity data indicated that the most degraded samples were those exposed to high ethanol contents at 110°C. Thermogravimetry showed that the onset temperature of the main degradation stage was 340-410°C (depending on heating rate). X-ray fluorescence spectroscopy and high performance liquid chromatography indicated migration of stabiliser and in the three-layered pipe, having two PA12 layers divided by a poly(vinylidene fluoride) barrier layer, the migration occurred preferentially from the inner pipe layer into the fuel.

  • 74.
    Kallio, Kai J.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Nageye, Arbi S.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ageing properties of car fuel-lines;accelerated testing in “close-to-real” service conditions2010In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 29, no 1, p. 41-48Article in journal (Refereed)
    Abstract [en]

    The use of ethanol-based fuels and tougher restrictions on fuel emissions put a higher demand on car fuel-line (pipe) systems. In this context, it is important to be able to establish and predict properties based on measurements on pipes exposed to real or “close-to-real” environments. This paper presents a new method to age pipes in accelerated “close-to-real” conditions. In this method, the pipe is exposed to circulating fuel on the inside and to air on the outside. The method/equipment allows for non-destructive mechanical testing on “continuous” pipes. The usefulness of the ageing method/system was illustrated on polyamide-12 (PA12) pipes exposed to fuels with varying ethanol content at 50 °C and 110 °C for a maximum of, respectively, ca 3 years and 100 days. “Non-destructive” three-point bending as well as tensile testing was used to assess the ageing-induced changes in mechanical properties. The most conclusive information was that the lowest pipe extensibility (ductility) of dried, previously fuel-exposed pipes was observed at the end of the ageing periods and at the higher ethanol contents. In fact, optical microscopy showed that the tensile fractured pipes, exposed to 25/30 vol. % ethanol at 110 °C (100 h), showed no signs of macroscopic yielding. The trends were interpreted, based also on findings from previous work, as being due to the loss of plasticiser (possibly also PA12 monomers/oligomers) and material “degradation/annealing” processes, the latter involving possibly stabiliser issues.

     

  • 75. Kang, J.
    et al.
    Li, X.
    Xiong, B.
    Liu, Dongming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Chen, J.
    Yang, F.
    Cao, Y.
    Xiang, M.
    Investigation on the Tensile Behavior and Morphology Evolution of Isotactic Polypropylene Films Polymerized with Different Ziegler-Natta Catalysts2015In: Advances in Polymer Technology, ISSN 0730-6679, E-ISSN 1098-2329Article in journal (Refereed)
    Abstract [en]

    Stereodefect distribution is very important in determining the morphology and properties of isotactic polypropylene (iPP). In this study, two iPPs (PP-A and PP-B) with different uniformities of stereodefect distribution were prepared. The tensile behavior and morphology evolution of their cast films were studied. The morphology study of the cast films showed that compared with PP-B, PP-A with less uniform distribution of stereodefects has smaller spherulites and spheruilitic boundaries and higher degree of crystallinity. In uniaxial tensile measurements, PP-A exhibited higher yield strength and lower elongation at break. When strain was 500%, PP-A exhibits totally transparent appearance and highly oriented structures without cavities, whereas PP-B shows opaque appearance and mass of both nanometer- and micrometer-sized cavities. Moreover, calculation of rigid amorphous fraction (RAF) indicated that PP-B cast film has a higher amount of RAF, which might be the reason for the different morphology evolutions and tensile behaviors of the samples.

  • 76. Kaptan, Navid
    et al.
    Jafari, Seyed Hassan
    Mazinani, Saeedeh
    Akhlaghi, Shahin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Fazilat, Hakimeh
    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.
    Naderi, Ali
    Monfared, Alireza
    Thermal Behavior and Degradation Kinetics of Compatibilized Metallocene-Linear Low Density Polyethylene/Nanoclay Nanocomposites2014In: Polymer-plastics technology and engineering (Softcover ed.), ISSN 0360-2559, E-ISSN 1525-6111, Vol. 53, no 9, p. 890-902Article in journal (Refereed)
    Abstract [en]

    Morphology, thermal degradation and kinetics of metallocene-linear-low-density polyethylene (m-LLDPE)/m-LLDPE-graft-maleic anhydride (m-LLDPE-g-MA)/nanoclay nanocomposites were compared with m-LLDPE/nanoclay, m-LLDPE-g-MA/nanoclay and m-LLDPE/m-LLDPE-g-MA systems. X-ray diffraction measurements revealed intercalated and "highly intercalated'' morphologies for the nanocomposites. Thermogravimetric analysis demonstrated that although thermal degradation of m-LLDPE systems were delayed upon the inclusion of nanoclay in air, an inverse effect was perceived for the nanoclay under inert atmosphere. This conclusion was supported by kinetic analysis in terms of reaction order and activation energy. The results obtained from kinetics models also put forward the contribution of m-LLDPE-g-MA, as a compatibilizer, to the thermal stability enhancement through intermolecular cross-linking augmentation.

  • 77.
    Karlsson, Mattias
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Xu, Xiangdong
    Materials and Manufacturing Technology, Chalmers University of Technology.
    Gaska, Karolina
    Materials and Manufacturing Technology, Chalmers University of Technology.
    Hillborg, Henrik
    ABB AB, Power Technology, Corporate Research, SE-721 78 Västerås.
    Gubanski, Stanislaw
    Materials and Manufacturing Technology, Chalmers University of Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    DC Conductivity Measurements of LDPE: Influence of Specimen Preparation Method and Polymer Morphology2017In: Proceedings of the biannual nordic symposium on materials, components and diagnostics: Proceedings of the 25th Nordic Insulation Symposium / [ed] Frank Mauseth, Dr. Kari Lahti and Prof.dr. Hans Edin, 2017Conference paper (Refereed)
    Abstract [en]

    DC conductivity measurements are important for gaining fundamental understanding of conduction mechanisms of insulation materials, as well as in the development of HVDC power system components, such as extruded cable systems. In this study, the influence of sample processing on the morphology and DC conductivity of low-density polyethylene (LDPE) has been studied. Direct compression moulding of LDPE pellets is commonly used in research laboratories for obtaining plaque samples, whereas extrusion is an additional commonly used technique for dispersion of particles in nanocomposites prior to the compression moulding process. In this study LDPE plaques have been obtained by either compression moulding directly from pellets, or by extrusion followed by compression moulding. The morphology obtained in the first case consisted of banded spherulites, whereas the latter method yielded a morphology of small axialites. The difference in sample processing had also an impact on the DC conductivity. The DC conductivity at 22 °C and 3.3 kV mm-1  was of the order of 4x10–18  S m-1  for the plaques obtained by extrusion and compression moulding whereas the plaques obtained by direct compression moulding exhibited a conductivity of 1x10–16  S m-1 . In addition, the reproducibility of the performed DC conductivity measurements was also verified in a round robin test performed between the Royal Institute of Technology and Chalmers Technical University.

  • 78.
    Kittikorn, Thorsak
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Chemical surface modification of empty fruit bunch oil palm fibre in PP biocomposites2009Conference paper (Other academic)
  • 79.
    Kittikorn, Thorsak
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Comparison of Water Uptake as Function of Surface Modification of Empty Fruit Bunch Oil Palm Fibres in PP Biocomposites2013In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 2, p. 2998-3016Article in journal (Refereed)
    Abstract [en]

    Empty fruit bunch oil palm (EFBOP) fibres were surface modified by four different methods, propionylation, vinyltrimethoxy silanization, PPgMA dissolution modification, and PPgMA blending, and integrated into a polypropylene (PP) matrix. The designed biocomposites were subjected to an absorption process at different temperatures. Their water uptake behaviour was compared with the unmodified fibre biocomposites. An increased fibre content and temperature resulted in increased water uptake for all of the biocomposites. The biocomposites containing modified fibres showed a reduction in water uptake, rate of diffusion, sorption, and permeation in comparison with unmodified fibre composites. Comparing the 20 wt% fibre composites at ambient temperature, the performance in water absorption followed the sequence silanization < propionylation < PPgMA dissolution modification < PPgMA blending < no modification. Furthermore, the lowest water absorption was obtained from the silanized fibre/PP composite with 40% fibre content at ambient temperature. Dissolution or blending of PPgMA gave similar water uptake results. The reduction of diffusion, sorption, and permeation confirmed that the modification of fibres was potentially effective at resisting water penetration into the composites.

  • 80.
    Kittikorn, Thorsak
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Effect of surface modifications on microbial growth and biodegradation in sisal/PLA biocomposites2013Manuscript (preprint) (Other academic)
  • 81.
    Kittikorn, Thorsak
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Susceptibility to biodegradation by fungi for sisal/PLA and sisal/PHBV biocomposites2013Manuscript (preprint) (Other academic)
  • 82.
    Kittikorn, Thorsak
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. Skövde University.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    The mechanical properties of natural cellulosic fiber/biodegradable polymer biocomposites2011In: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, ISWFPC, 2011, p. 1330-1333Conference paper (Refereed)
    Abstract [en]

    The aim of this work was to investigate a methodology for the improvement of the mechanical properties of sustainable biodegradable biocomposites based on polylactide (PLA). Cellulosic fibre was incorporated as a reinforcing agent for improvement of the mechanical properties of the biocomposites. A coupling agent was synthesized and employed in order to enhance the interfacial adhesion of two components via a melt blending process. FT-IR spectra showed presences of specific functional groups of maleic anhydride on the backbone of the PLA after the grafting. The modulus of PLA was considerably raised after incorporation of the fibre. Furthermore, an addition of a coupling agent in PLA biocomposites was also able to remarkably increase the stiffness of the material.

  • 83.
    Kittikorn, Thorsak
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    The mechanical properties of natural cellulosic fibre/biodegradable polymer biocomposites2011In: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings, ISWFPC: Volume 2, 2011, p. 1330-1333Conference paper (Refereed)
    Abstract [en]

    Theaim of this work was to investigate a methodology fortheimprovement ofthemechanicalpropertiesof sustainablebiodegradablebiocompositesbased on polylactide (PLA).Cellulosicfibrewas incorporated as a reinforcing agent for improvement ofthemechanicalpropertiesofthebiocomposites. A coupling agent was synthesized and employed in order to enhancetheinterfacial adhesion of two components via a melt blending process. FT-IR spectra showed presences of specific functional groups of maleic anhydride onthebackbone ofthePLA afterthegrafting.Themodulus of PLA was considerably raised after incorporation ofthefibre. Furthermore, an addition of a coupling agent in PLAbiocompositeswas also able to remarkably increasethestiffness ofthematerial.

  • 84. Kuktaite, R.
    et al.
    Plivelic, T. S.
    Türe, Hasan
    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.
    Gällstedt, M.
    Marttila, S.
    Johansson, E.
    Changes in the hierarchical protein polymer structure: Urea and temperature effects on wheat gluten films2012In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 2, no 31, p. 11908-11914Article in journal (Refereed)
    Abstract [en]

    Understanding bio-based protein polymer structures is important when designing new materials with desirable properties. Here the effect of urea on the wheat gluten (WG) protein structure in WG-urea films was investigated. Small-angle X-ray scattering indicated the formation of a hexagonal close-packed (HCP) hierarchical structure in the WG-urea materials. The HCP structure was influenced significantly by the urea concentration and processing conditions. The interdomain distance d I between the HCP scattering objects increased with increasing content of urea and the objects seemed to be oriented in the extrusion direction. Additionally, the effect of temperature on the HCP structure was studied and it was shown that at ≥55°C the HCP structure disappeared. Transmission electron microscopy revealed a rather denatured pattern of both HMW-glutenins and gliadins in the WG-urea films. The molecular packing of the WG protein polymer can be highly affected by an additive and the processing method used.

  • 85. Kuktaite, Ramune
    et al.
    Türe, Hasan
    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.
    Gallstedt, Mikael
    Plivelic, Tomas S.
    Gluten Biopolymer and Nanoclay-Derived Structures in Wheat Gluten-Urea-Clay Composites: Relation to Barrier and Mechanical Properties2014In: ACS SUSTAIN CHEM ENG, ISSN 2168-0485, Vol. 2, no 6, p. 1439-1445Article in journal (Refereed)
    Abstract [en]

    Here, we investigated the structure of natural montmorillonite (MMT) and modified Cloisite C15A (MMT pre-intercalated with a dimethyl-dehydrogenated tallow quaternary ammonium surfactant) nanoclays in the wheat gluten-urea matrix in order to obtain a nanocomposite with improved barrier and mechanical properties. Small-angle X-ray scattering indicated that the characteristic hexagonal closed packed structure of the wheat gluten-urea matrix was not found in the CISA system and existed only in the 3 and 5 wt % MMT composites. SAXS/WAXS, TGA, and water vapor/oxygen barrier properties indicated that the dispersion of the C15A clay was somewhat better than the natural MMT clay. Confocal laser scanning microscopy showed MMT clay clusters and C15A clay particles dispersed in the protein matrix, and these were preferentially oriented in the extrusion direction only at 5 wt % of the CIS clay. The water vapor/oxygen barrier properties were improved with the presence of clay. Independent of the clay content used, the stiffness decreased and the extensibility increased in the presence of C15A due to the surfactant induced changes on the protein. The opposite "more expected" clay effect (increasing stiffness and decreasing extensibility) was observed for the MMT composites.

  • 86. Kömmling, Anja
    et al.
    Jaunich, Matthias
    Pourmand, Payam
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Wolff, Dietmar
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Influence of Ageing on Sealability of Elastomeric O-Rings2017In: MACROMOLECULAR SYMPOSIA, Wiley-VCH Verlagsgesellschaft, 2017, Vol. 373, no 1, article id UNSP 1600157Conference paper (Refereed)
    Abstract [en]

    At BAM, which is the federal institute for materials research and testing in Germany, it is one of our tasks to evaluate the safety of casks designed for transport and/or storage of radioactive material. This includes the assessment of the service lifetime of elastomeric seals that are part of the container lid system with regard to the requirements for long-term safety (40 years and more) of the containers. Therefore, we started an accelerated ageing programme with selected rubbers often used for seals (HNBR, EPDM and FKM) which are aged at four different temperatures (75 degrees C, 100 degrees C, 125 degrees C and 150 degrees C) up to 1.5 years. In order to assess sealability, O-rings are aged in compression by 25% (corresponding to the compression during service) between plates as well as in flanges that allow leakage rate measurements. For comparison, uncompressed O-rings are aged as well. Further methods characterising seal performance are compression stress relaxation (CSR) reflecting the loss of sealing force of a compressed seal over time, and compression set (CS) which represents the recovery behaviour of a seal after release from compression. Additionally, hardness is measured for information about the change of mechanical properties. The experimental results indicate that while hardness, CSR and CS show considerable degradation effects, the leakage rate stays relatively constant or even decreases until shrinkage combined with the loss of resilience of the aged seal leads to leakage. This demonstrates that static leakage rate, which is the only available direct seal performance criterion, has only limited sensitivity towards the degradation of the seal material. CS data is extrapolated using time-temperature shifts and Arrhenius graphs. An exemplary CS of 50% would be reached after approx. 1.2, 17 and 29 years at 60 degrees C for HNBR, EPDM and FKM respectively.

  • 87.
    Linde, Erik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Long-term performance of a DEHP-containing NBR membrane and a plasticised PVC cable2013Licentiate thesis, comprehensive summary (Other academic)
  • 88.
    Linde, Erik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Polymeric materials in nuclear power plants: Lifetime prediction, condition monitoring and simulation of ageing2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nuclear power plants generate a significant part of the world’s electrical power consumption. However, many plants are nearing the end of their designed lifetime, and to extend the lifetime it is important to verify that every component can withstand the added service time. This includes polymeric materials, which become brittle with time. By predicting their lifetime and monitoring their condition, unnecessary downtime of the plant can be avoided, and secure operation can be ensured. The lifetime can be predicted by extrapolating results from accelerated ageing to service conditions, or by simulation of the degradation process.

    In this study, lifetime predictions through extrapolation were performed on samples of a polyvinyl chloride (PVC) core insulation and an acrylonitrile butadiene rubber (NBR) membrane, which were thermally aged in air. The lifetime of the PVC cable was predicted using Arrhenius extrapolation, and using a method based on Langmuir, Clausius-Clapeyron, and Kirchhoff’s equations.

    The lifetime of the NBR membrane was predicted using extrapolation in the temperature domain using an Arrhenius approach coupled with an extrapolation in pressure-domain, yielding realistic lifetimes.

    Two cable insulations, one made from crosslinked polyethylene (XLPE) and the other from ethylene propylene rubber (EPR) were aged under the simultaneous effect of elevated temperature and γ-radiation investigated using several condition monitoring techniques. In particular, two non-destructive techniques, dielectric spectroscopy and nuclear magnetic resonance, showed promising results be developed and used in situ.

    Finally, a computer model simulating the diffusion and consumption of oxygen in XLPE was developed, based on assumptions that diffusion, consumption and solubility were dependent on the total degree of oxidation. The model showed promise for further development.

  • 89.
    Linde, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Plasticizer migration from PVC cable insulation - a case study testing different extrapolation methodsManuscript (preprint) (Other academic)
  • 90.
    Linde, Erik
    et al.
    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, Polymeric Materials.
    Plasticizer migration from PVC cable insulation - The challenges of extrapolation methods2014In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 101, no 1, p. 24-31Article in journal (Refereed)
    Abstract [en]

    A single strand PVC-P insulation including an internal metal conductor removed from the jacketed assemblies of a signal cable showed brittleness after 30 years service at 25 +/- 3 degrees C in air. The PVC compound contained diisodecyl phthalate (DIDP), di(2-ethylhexyl) phthalate (DEHP) and a sizeable fraction of filler. Single strand insulation samples with internal metal conductor were aged in air at elevated temperatures for different periods of time after which the strain at break, the Young's modulus and the plasticizer content were assessed by tensile testing and liquid chromatography. Isothermal evaporation rates from pristine DIDP and DEHP and solutions of the two plasticizers were obtained by thermogravimetry. Data for Young's modulus, strain at break and plasticizer contents were extrapolated to service temperature using two different extrapolation methods, Arrhenius extrapolation (constant activation energy) and a method based on models by Langmuir, Clausius-Clapeyron and Kirchhoff. These methods assume that evaporation of plasticizers to the surrounding gas phase is the dominant deterioration mechanism. Both methods predicted only a minor decrease in plasticizer content after 30 years of ageing at 28 degrees C and thus a material with adequate mechanical properties. Liquid chromatography showed that the single strand cable samples contained a very low DIDP content (4 wt.%) and an anomalously high DEHP content; a finding that cannot be explained by the expected evaporative loss mechanism. It is suggested that DIDP was efficiently extracted by contact with a DEHP-rich interface at the insulation surface, a process which is active during plant operation, but could not be simulated by controlled laboratory accelerated ageing studies.

  • 91.
    Linde, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Modelling of oxygen diffusion and consumption in an XLPE cableinsulation for nuclear power applications using an oxidationdependentdiffusion-reaction approachManuscript (preprint) (Other academic)
    Abstract [en]

    The oxidation profile of an XLPE conductor insulation after accelerated ageing atdifferent temperature/dose-rate combinations was assessed through infrared spectroscopy, tostudy heterogeneous oxidation in the samples. These profiles showed clear drops in oxidationdegree towards the centre of the cable, to such an extent that more than half of the thicknesswas essentially not oxidized. The oxygen diffusion and consumption was then modelledthrough computer simulations to obtain the diffusion coefficient and reaction rate, includingtheir possible dependencies on the oxidation degree. The model was based on the assumptionthat diffusion and consumption rates, and solubility of oxygen in polyethylene weredependent on the degree of oxidation relative to a maximum degree of oxidation. Good fitswith experimental data were obtained, and the model could be applied to data from literaturewith promising results.

  • 92.
    Linde, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Thomas, Blomfeldt
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Long-term performance of a DEHP-containing carbon-black-filled NBR membrane2014In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 34, no 1, p. 25-33Article in journal (Refereed)
    Abstract [en]

    A NBR membrane containing carbon black (36 wt.%) and di(2-ethylhexyl) phthalate (DEHP; 11 wt.%) that had been used at temperatures up to 45 C in pressurised air showed cracking after 2 years in service. Samples were aged in air at elevated temperatures and their mechanical properties were assessed by tensile testing, the glass transition temperature was obtained by DSC, and the DEHP content was determined by liquid chromatography. The loss of DEHP was controlled by the boundary conditions at low temperatures and the loss rate was constant at 90 C within a certain DEHP concentration range (8 to 11 wt.%). The presence of carbon black and DEHP made it impossible to determine oxidation products by infrared spectroscopy. Strain-at-break data were analysed in a way that enabled the effect of DEHP migration to be separated from the effect of thermal oxidation. This allowed extrapolation in both temperature and oxygen pressure domains of high temperature/low oxygen pressure data to the service conditions. The analysis showed that both DEHP evaporation and thermal oxidation had a significant impact on the strain-at-break, but that the latter was the more important. Data for the mechanical properties and the glass transition temperature indicated that oxidation was non-uniform with increasing depth in the specimens. This condition of the 4.5 mm thick samples meant that it was inappropriate to use the specimen Young's modulus for extrapolation purposes.

  • 93.
    Linde, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Verardi, Luca
    University of Bologna.
    Pourmand, Payam
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Davide, Fabiani
    University of Bologna.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Non-destructive condition monitoring of aged ethylene-propylenecopolymer cable insulation samples using dielectric spectroscopy and NMR spectroscopyManuscript (preprint) (Other academic)
    Abstract [en]

    The causes of changes in dielectric response as a result of thermal and irradiative ageingof a cable insulation of ethylene propylene copolymer rubber containing 38 wt.% filler wereinvestigated. Samples were aged in three different combinations of irradiation dose rate andtemperature, 0.42 kGy h–1 at 85 °C, and 1.58 kGy h–1 at 55 and 85 °C, and subsequentlystudied by dielectric spectroscopy, NMR spectroscopy using a portable spectrometer andtensile testing. The extractable mass fraction and density were determined, and related to theimaginary part of the dielectric permittivity at 100 kHz. The ageing led to an increase in thedielectric permittivity, stiffness, density and degree of oxidation, together with a decrease inboth strain-at-break and relaxation time, as revealed by NMR spectroscopy. Except for thestrain-at-break, the properties changed in a linear fashion with increasing imaginary part ofthe dielectric permittivity at 100 kHz, with a particularly good agreement with respect to thedensity. As these properties are affected by the degree of oxidation, the results show that bothNMR using a portable spectrometer and dielectric spectroscopy can be used as conditionmonitoring techniques to detect the degree of oxidation in complex systems such as filledcopolymers.

  • 94.
    Liu, Dongming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Functional polyethylene-aluminum oxide nanocomposites for insulation materials in high-voltage direct-current (HVDC) cables2015Licentiate thesis, comprehensive summary (Other academic)
  • 95.
    Liu, Dongming
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Polyethylene – metal oxide particle nanocomposites for future HVDC cable insulation: From interface tailoring to designed performance2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Low-density polyethylene (LDPE) nanocomposites containing metal oxide nanoparticles are considered as promising candidates for insulating materials in future high-voltage direct-current (HVDC) cables. The significant improvement in dielectric properties compared with unfilled polymer is attributed to the large and active interface between the nanoparticles and the polymer. The nanoparticles may also initiate cavitation under stress and potential accelerated aging risks due to the adsorption and inactivation of the protecting antioxidants. This study is focused on the possibilities of achieving well-balanced performances of the polyethylene nanocomposites for HVDC insulation via tailoring the particle interface in the nanocomposites.

    A facile and versatile surface coating method for metal oxide particles was developed based on silane chemistry. The developed method was successfully applied to 8.5 nm Fe3O4, 25 nm ZnO and 50 nm Al2O3 particles, with the aim to develop uniform coatings that universally could be applied on individual particles rather than aggregates of particles. The surface properties of the coatings were further tailored by applying silanes with terminal alkyl groups of different lengths, including methyl (C1-), octyl (C8-) and octadecyl (C18-) units. Transmission electron microscopy, infrared spectroscopy and thermal gravimetric analysis confirmed the presence of uniform coatings on the particle surface and importantly the coatings were found to be highly porous.

    The capacity of metal oxide particles to adsorb relevant polar species (e.g. moisture, acetophenone, cumyl alcohol and phenolic antioxidant) was further assessed due to its potential impact on electrical conductivity and long-term stability of the nanocomposites. The oxidative stability of the nanocomposites was affected by the adsorption of phenolic antioxidants on particles and transfer of catalytic impurities (ionic species) from metal oxide particles to polymer matrix. It was found that carefully coated metal oxide particles had much less tendency to adsorb antioxidants. They could, however, adsorb moisture, acetophenone and cumyl alcohol. The coated particles did not emit any destabilizing ionic species into the polymer matrix. 

    The inter-particle distance of the nanocomposites based on C8-coated nanoparticles showed only a small deviation from the ideal, theoretical value, indicating a good particle dispersion in the polymer. Scanning electron microscopy of strained nanocomposite samples suggested the cavitation mainly occurred at the polymer/nanoparticles interface. The microstructural changes at polymer/nanoparticle interface were studied by small-angle X-ray scattering coupled with tensile testing. The polymer/nanoparticle interface was fractal before deformation due to the existence of the bound polymers at the nanoparticle surface. Extensive de-bonding of particles and cavitation were observed when the nanocomposites were stretched beyond a critical strain. It was found that the composites based on carefully coated particles showed higher strain at cavitation than the composites based on uncoated particles. The composites based on C8-coated nanoparticles showed the largest decrease in electrical conductivity and the lowest temperature coefficient of the electrical conductivity among the composite samples studied.

  • 96.
    Liu, Dongming
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hoang, A.T
    Chalmers University of Technology.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Pallon, Love
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gubanski, Stanislaw
    Chalmers University of Technology.
    Ohlsson, Richard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Influence of nanoparticle surface coating on electrical conductivity of polyethylene/aluminium oxide nanocomposites for HVDC cable insulations2016In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135Article in journal (Refereed)
  • 97.
    Liu, Dongming
    et al.
    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.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Zhang, P.
    Diaz, A.
    Holler, M.
    Schneider, K.
    Olsson, Richard
    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.
    Yu, Shun
    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, Polymeric Materials.
    Cavitation in strained polyethylene/aluminium oxide nanocomposites2017In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 87, p. 255-265Article in journal (Refereed)
    Abstract [en]

    The incorporation of metal oxide (e.g. Al2O3) nanoparticles has a pronounced positive effect on low-density polyethylene (LDPE) as an insulating material for high-voltage direct-current (HVDC) cables, the electrical conductivity being decreased by one to two orders of magnitude and charge species being trapped by the nanoparticles. The risk of debonding between the nanoparticles and the polymer matrix leading to electrical treeing via electrical discharges in the formed cavities was the motivation for this study. Scanning electron microscope (SEM), small-angle X-ray scattering (SAXS) and X-ray ptychographic tomography were used to study a series of LDPE nanocomposites which contained Al2O3 nanoparticles treated with silanes having terminal alkyl groups of different lengths (methyl, octyl and octadecyl). When specimens were subjected to a tensile strain (a typical specimen stretched beyond the onset of necking consisted of three zones according to SEM of specimens that were studied after removal of the external force: an essentially cavitation-free zone with low local plastic strain, a transitional zone in which local plastic strain showed a marked increase and the revealed concentration of permanent cavities increased with increasing plastic strain and a highly strained zone with extensive cavitation), the cavitation occurred mainly at the polymer-nanoparticle interface according to SEM and X-ray ptychographic tomography and according to SEM progressed with increasing plastic strain through an initial phase with no detectable formation of permanent cavities to a period of very fast cavitation and finally almost an order of magnitude slower cavitation. The polymer/nanoparticle interface was fractal before deformation, as revealed by the profile of the Porod region in SAXS, presumably due to the existence of bound polymers at the nanoparticle surface. A pronounced decrease in the interface fractal dimension was observed when the strain exceeded a critical value; a phenomenon attributed to the stress-induced de-bonding of nanoparticles. The strain-dependence of the interface fractal dimension value at low strain levels between composites containing differently treated nanoparticles seems to be an indicator of the strength of the nanoparticle-polymer interface.

  • 98.
    Liu, Dongming
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pallon, Love
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Zhang, Peng
    Deutsches Elektronen-Synchrotron (DESY).
    Diaz, Ana
    Paul Scherrer Institut.
    Holler, Mirko
    Paul Scherrer Institut.
    Schneider, Konrad
    Leibniz Institut für Polymerforschung Dresden.
    Olsson, Richard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Yu, Shun
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Cavitation in strained polyethylene/aluminium oxide nanocomposites2016In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945Article in journal (Refereed)
  • 99.
    Liu, Dongming
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Pourrahimi, Amir Masoud
    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.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Influence of nanoparticle surface treatment on particle dispersion and interfacial adhesion in low-density polyethylene/aluminium oxide nanocomposites2015In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 66, p. 67-77Article in journal (Refereed)
    Abstract [en]

    The effect of silsesquioxane coating of aluminium oxide nanoparticles on their dispersion and on the interfacial strength between nanoparticles and polymer matrix in low-density polyethylene composites was studied. The surface chemistry of the nanoparticles was tailored from hydroxyl groups to alkyl groups with different lengths by reacting methyltrimethoxysilane (C1), octyltriethoxysilane (C8) or octadecyltrimethoxysilane (C18) with aluminium oxide nanoparticles. The core–shell structure of the coated nanoparticles was assessed by transmission electron microscopy, infrared spectroscopy and thermogravimetry. The inter-particle distance of the nanocomposite based on C8-coated nanoparticles showed only a small deviation from the ideal value, indicating a very good particle dispersion in the polymer. The interfacial adhesion between nanoparticles and matrix was determined by stretching nanocomposite specimens in a tensile testing machine to strains well beyond the yield point. A drop in the stress–strain curve indicated the onset of cavitation and necking in the nanocomposites. Samples stretched to different strain levels were studied by scanning electron microscopy and the cavitation was found to be confined to particle interfaces. The composite based on C18-coated nanoparticles showed the highest strain at cavitation/necking suggesting a high interfacial adhesion between nanoparticles and polymer.

  • 100.
    Liu, Dongming
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Pallon, Love K. H.
    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.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    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.
    Morphology and properties of silica-based coatings with different functionalities for Fe3O4, ZnO and Al2O3 nanoparticles2015In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 59, p. 48094-48103Article in journal (Refereed)
    Abstract [en]

    A facile single-step method for obtaining 2–3 nm thick silsesquioxane coatings on metal oxide nanoparticles using different carbon-functional silane precursors is presented. Iron oxide nanoparticles 8.5 nm in diameter were used as a model to evaluate the possibilities of forming different uniform carbon-functional coatings, ranging from hydrophobic to hydrophilic in character. Electron microscopy showed that all the coated nanoparticles could be described as core-shell nanoparticles with single Fe3O4 cores and carbon-functional silsesquioxane shells, without any core-free silicone oxide phase. Steric factors strongly influenced the deposited silicon oxide precursors with octyl-, methyl- or aminopropyl functionalities, resulting in coating densities ranging from 260 to 560 kg/m3. The methyl-functional coatings required several layers of silsesquioxane, 3–4, to build up the 2 nm structures, whereas only 1-2 layers were required for silsesquioxane with octyl groups. Pure silica coatings from tetraethoxysilanes were however considerably thicker due to the absence of steric hindrance during deposition, allowing the formation of 5–7 nm coatings of ca. 10 layers. The coating method developed for the iron oxide nanoparticles was generic and successfully transferred and up–scaled 30 and 325 times (by volume) to be applicable to 25 nm ZnO and 45 nm Al2O3 nanoparticles.

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