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  • 201.
    Skrifvars, Mikael
    et al.
    University of Borås, School of Engineering.
    Rajan, Rathish
    Riihivuori, Johanna
    Järvelä, Pentti
    Mechanical and water absorption behaviour of textile composites on chemical treatment of reinforcements2013Conference paper (Other academic)
  • 202.
    Skrifvars, Mikael
    et al.
    University of Borås, School of Engineering.
    Ramamoorthy, Sunil Kumar
    University of Borås, School of Engineering.
    Baghaei, Behnaz
    University of Borås, School of Engineering.
    Development Of Regenerated Cellulose Reinforcements And Their Use In Structural Composites For Automotive Applications2013Conference paper (Refereed)
    Abstract [en]

    There is need for the bio‐based materials which could fully or partly replace the synthetic materials in automotive components. Several studies have been suggested to incorporate natural fiber based materials into automotives, and regenerated cellulose fibers could have a great potential several automotive applications. In the paper we will describe ongoing research where we study non‐woven viscose and Lyocell as well as uniaxial continuous viscose filament reinforcements for the use in structural composites. Hybrid reinforcements based on regenerated cellulose fibers and glass fibers have also been studied, with the intention to optimize the reinforcement durability. The uniaxial viscose filament reinforcements were prepared by a winding technique, and we have also combined the viscose filament with continuous hemp yarns as well as different thermoplastic yarns. Both thermoset and thermoplastic composites were then produced by compression moulding with a pressure of 40 bar and at the temperature between 160‐170°C for 5 minutes. The resulting composites have been characterized regarding mechanical and thermal properties.

  • 203.
    Skrifvars, Mikael
    et al.
    University of Borås, School of Engineering.
    Rehnby, Weronika
    University of Borås, Swedish School of Textiles.
    Gustafsson, Maria
    Coating of textile fabrics with conductive polymers for smart textile applications2008Conference paper (Refereed)
  • 204.
    Skrifvars, Mikael
    et al.
    University of Borås, School of Engineering.
    Soroudi, Azadeh
    University of Borås, School of Engineering.
    Melt spinning of carbon nanotube modified polypropylene conducting nanocomposite fibres2009In: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, ISSN 1012-0394, Vol. 151, p. 43-47Article in journal (Refereed)
    Abstract [en]

    Blends of polypropylene with multi-walled carbon nanotubes (CNT) have been prepared and melt spun to fibre filaments. The resulted filaments have been characterised regarding conductivity, thermal properties, and morphology. DSC suggests that carbon nanotubes act as nucleating sites in polypropylene and the TGA shows a high increase in thermal stability. Conductivity around 0.001 S/cm are achieved for both as-spun fibre and drawn fibre. A higher load of CNT up to 15 wt % increases the conductivity to 2.8 S/cm in as-spun fibre, but due to a high fibre diameter variation during spinning resulting in fibre breakage, melt spinning is very difficult. This is due to a non-uniform stress distribution during the drawing steps which can be a result of a non-homogeneous PP-CNT blend and the spinning machine process limitations. Differences in conductivities for extruded rods, as-spun fibre and drawn fibre which are made from the same blends, suggests that the crystallinity can affect the conductivity of the PP/CNT fibre.

  • 205.
    Skrifvars, Mikael
    et al.
    University of Borås, School of Engineering.
    Soroudi, Azadeh
    University of Borås, School of Engineering.
    Melt spinning of carbon nanotube modified polypropylene for electrically conducting nanocomposite fibres2008Conference paper (Refereed)
  • 206.
    Skrifvars, Mikael
    et al.
    University of Borås, School of Engineering.
    Soroudi, Azadeh
    University of Borås, School of Engineering.
    Preparation of conducting fibres by melt spinning of polyaniline-polyproplene blends modified with carbon nanotubes2008Conference paper (Refereed)
  • 207.
    Skrifvars, Mikael
    et al.
    University of Borås, School of Engineering.
    Soroudi, Azadeh
    University of Borås, School of Engineering.
    Strategies for the preparation of conductive textile fibres for smart and functional textiles2008Conference paper (Refereed)
    Abstract [en]

    This presentation will discuss some on-going efforts regarding the development of conductive fibres by melt spinning of polyaniline-polypropylene blends. The blend was also modified with multi wall carbon nanotubes. The presentation will also review in the literature presented concepts regarding processing and manufacture of electrically conductive textile fibres.

  • 208.
    Skrifvars, Mikael
    et al.
    University of Borås, School of Engineering.
    Soroudi, Azadeh
    University of Borås, School of Engineering.
    Bashir, Tariq
    University of Borås, School of Engineering.
    Preparation of conductive textile fibres by melt spinning and coating methods by utilising carbon nanotubes and conjugated polymers2009Conference paper (Refereed)
  • 209.
    Skrifvars, Mikael
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Åkesson, Dan
    University of Borås, Faculty of Textiles, Engineering and Business.
    Mabille, Coline
    Wojno, Sylwia
    Zhang, Zhongyi
    University of Portsmouth.
    Dhakal, Hom
    University of Portsmouth.
    Warp knitted and carded regenerated cellulose reinforced biocomposites2015Conference paper (Other academic)
  • 210.
    Skrifvars, Mikael
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Pettersson, C.
    Andreassson, S.
    Återvinning av kompositer genom mikrovågspyrolys2010Conference paper (Other academic)
  • 211.
    Soroudi, Azadeh
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Conductive polyblend fibers made of polyamide-6/ polypropylene/ polyaniline for smart textile applications: electrical and mechanical properties2010Conference paper (Refereed)
    Abstract [en]

    Ternary blends of polypropylene/polyamide-6/Polyaniline-complex and binary blends of PP/ Polyaniline-complex were prepared and melt spun to conductive fibers under different solid-state draw ratios. Both blends showed a dependency of the conductivity to the fiber draw ratio. Compared to the binary blend fibers, the ternary blend fibers showed a more linear voltage-resistance relationship, a smoother surface and more even fiber in SEM images, and could combine a good conductivity with a good mechanical strength, because their maximum conductivity was observed in fibers made under a higher draw-ratio where the fibers show a better mechanical strength. The mechanical properties were promising to be used in a knitted network.

  • 212.
    Soroudi, Azadeh
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business. University of Boras.
    Skrifvars, Mikael
    University of Borås, Faculty of Textiles, Engineering and Business.
    Electro-conductive polyblend fibers of Polyamide-6/polypropylene/polyaniline: electrical, morphological and mechanical characteristics2012In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 52, no 7, p. 1606-1612Article in journal (Refereed)
    Abstract [en]

    Melt spun drawn fibers were prepared using a ternary blend of PP/PA6/PANI-complex (polypropylene/polyamide-6/polyaniline-complex). Their electrical and mechanical properties were compared to those of binary blend fibers of PP/PANI-complex. The results of the morphological studies on 55:25:20 PP/PA6/PANI-complex ternary fibers were found to be in accordance with the predicted morphology for the observed conductivity vs. fiber draw ratio. The scanning electron microscopy (SEM) micrographs of the ternary blend illustrated at least a three-phase morphology of a matrix/core-shell dispersed phase style, with widely varying sizes of droplets. This resulted in a dispersed morphology that, in some parts of the blend, approached a bicontinuous/dispersed phase morphology due to coalescence of the small droplets. The matrix was PP and the core-shell dispersed phase was PA6 and PANI-complex, in which a part of the PANI-complex had encapsulated the PA6 phase and the remaining was solved/dispersed in the PA6 core, as later confirmed by X-ray mapping. When the ternary blend fibers were compared to the binary fibers, the formers were able to combine better conductivity (of an order of 10−3 S cm−1) with a greater tensile strength only at a draw ratio of 5. This indicated that the draw ratio is more critical for the ternary blend fibers, because both conductivity and tensile strength depended on the formation of fibrils from the core-shell dispersed phase of the PA6/PANI-complex.

  • 213.
    Soroudi, Azadeh
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Fabrication of melt spun electro-conductive fibres using multi-walled carbon nanotubes, polypropylene and compatibilizers2009Conference paper (Other academic)
  • 214.
    Soroudi, Azadeh
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Melt blending of carbon nanotubes/polyaniline/polypropylene compounds and their melt spinning to conductive fibres2010In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 160, no 11-12, p. 1143-1147Article in journal (Refereed)
    Abstract [en]

    Blends of polypropylene with polyaniline and multi-walled carbon nanotubes have been prepared and melt spun to fibre filaments. The resulted filaments have been characterised regarding conductivity, morphology, thermal and mechanical properties. DSC suggests that carbon nanotubes act as nucleating sites for PP/polyaniline blend. Electrical conductivity has been measured for blends with extruded rod shape, as-spun fibre filaments and fibres made under draw ratio of four. Polypropylene containing 20 wt% polyaniline polymer modified with 7.5 wt% carbon nanotubes shows the maximum conductivity among all the samples, about 0.16 S/cm.

  • 215.
    Soroudi, Azadeh
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Preparation of conductive polyaniline/polypropylene blends and their melt spinning to fibre filaments2008Conference paper (Refereed)
  • 216.
    Soroudi, Azadeh
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Preparation of melt spun conductive polypropylene/polyaniline fibres for smart textile applications2008Conference paper (Refereed)
  • 217.
    Soroudi, Azadeh
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Ternary composites made of carbon nanotubes/polypropylene/Polyaniline and melt spinning to conductive fibers2009Conference paper (Other academic)
    Abstract [en]

    Ternary blends of polyaniline-complex, polypropylene and multiwalled carbon nanotubes have been prepared and melt spun to fibre filaments. Prepared filaments have been characterised regarding electrical and thermal properties as well as microscopic morphology. Electrical conductivity measurements showed that the maximum conductivity is obtained in polypropylene containing both CNT and Polyaniline rather than polypropylene with only one of the conductive materials. In SEM images for cross section of as-spun fibres, PP/polyaniline-complex/CNT shows much more homogeneous structure than PP/polyaniline-complex prepared at the same blending and spinning conditions. Fibres made of PP/CNT and PP/ CNT/polyaniline-complex show the electrical resistance dependency on time as well as applied voltage within the chosen range of measurements.

  • 218.
    Soroudi, Azadeh
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    The influence of matrix viscosity on properties of polypropylene/polyaniline composite fibers: Rheological, electrical, and mechanical characteristics2010In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 119, no 5, p. 2800-2807Article in journal (Refereed)
    Abstract [en]

    Electrically conductive composites containing polypropylene (PP) and polyaniline (PANI) were prepared using PP with three different melt flow rates (MFRs) and a commercial PANI-complex in proportions of 80% by weight and 20%, respectively. Composite blends were melt-spun to fibers under different solid-state draw ratios. Rheological studies of dynamic viscosity, as well as the storage modulus and loss modulus showed that the prepared PANI-complex/PP blends exhibit different dynamic rheological behavior, depending on the PP used. This confirms the blends' morphological differences. PP matrix viscosity was found to play an important role in the electrical properties of the prepared fibers. Fibers prepared using the matrix with the lowest viscosity, showed a larger dispersed phase size in the cross-sectional SEM micrographs, maximum conductivity observed at higher draw ratios and a more linear resistance–voltage relationship than those of the fibers prepared using the higher viscosity matrices.

  • 219.
    Soroudi, Azadeh
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Liu, Hewen
    Polyaniline: polypropylene melt-spun fiber filaments: The collaborative effects of blending conditions and fiber draw ratios on the electrical properties of fiber filaments2011In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 119, no 1, p. 558-564Article in journal (Refereed)
    Abstract [en]

    A melt-processable polyaniline complex was blended with polypropylene under different mixing conditions and melt-spun into fiber filaments under different draw ratios. The conductivity, electrical resistance at different voltages, and morphological characteristics of the prepared fibers were investigated. The morphology of this two-phase blend was demonstrated to have a large effect on the conductivity level and the linearity of the resistance–voltage relationship of the blend fibers. Two factors had substantial effects on the morphology and electrical properties of the fibers. They were the size of the initial dispersed conductive phase, which depended on the melt blending conditions, and the stress applied to orient this phase to a fibril-like morphology, which was controlled by the draw ratio of the fiber. The two factors were shown to be associated with each other to maintain an appropriate balance of fibril formation and breakage and to create continuous conductive pathways.

  • 220.
    Temmink, Robin
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Baghaei, Behnaz
    University of Borås, Faculty of Textiles, Engineering and Business.
    Skrifvars, Mikael
    University of Borås, Faculty of Textiles, Engineering and Business.
    Development of biocomposites from denim waste and thermoset bio-resins2018In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 106, p. 59-69Article in journal (Refereed)
    Abstract [en]

    This paper examines the use of post-consumer denim fabric in combination with thermoset bio-resins in composite manufacturing for structural applications. Bio-epoxy and acrylated epoxidized soybean oil resin (AESO) were used as bio-resins with four different manufacturing techniques in order to create a wide scope of possibilities for research. The four techniques are: compression moulding (COM), vacuum infusion (VAC), resin transfer moulding (RTM) and hand lay-up (HND). The bio-resins were compared to a conventional polyester resin, as this is highly used for structural applications. To determine suitability for structural applications, the biocomposites were tested for their mechanical and thermal properties. Fabricated composites were characterised regarding porosity, water absorption and analysed through microscopic images of the composite. Results show both bio-epoxy and AESO are suitable for use in structural applications over a range of manufacturing techniques. Furthermore, biocomposites from bio-epoxy are superior to those from AESO resin. The conventional polyester has shown to be unsuitable for structural applications.

  • 221. Viljanen, E.
    et al.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Vallittu, P.
    Analysis of residual monomers in dentritic methacrylate copolymers and composites by HPLC and headspace-CG/MS2006In: Dental Materials, ISSN 0109-5641, E-ISSN 1879-0097, Vol. 22, no 9, p. 845-851Article in journal (Refereed)
  • 222. Viljanen, E.
    et al.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Vallittu, P.
    Dendritic copolymers and particulate filler composites for dental applications: Degree of conversion and thermal properties2007In: Dental Materials, ISSN 0109-5641, E-ISSN 1879-0097, Vol. 23, no 11, p. 1420-1427Article in journal (Refereed)
  • 223.
    Vogt, Sarah
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Baghaei, Behnaz
    University of Borås, Faculty of Textiles, Engineering and Business.
    Kadi, Nawar
    University of Borås, Faculty of Textiles, Engineering and Business.
    Skrifvars, Mikael
    University of Borås, Faculty of Textiles, Engineering and Business.
    Determination of Processing Parameters for Thermoplastic Biocomposites Based on Hybrid Yarns Using Finite Elements Simulation2018In: Journal of Composites Science, ISSN 2504-477X, Vol. 2, no 1Article in journal (Refereed)
    Abstract [en]

    This paper investigates the processing parameters for the compression molding of hemp/PLA hybrid yarn biocomposites and their effect on the final mechanical properties. Finite element simulations are used to develop and assess the processing parameters, pressure, temperature, and time. These parameters are then evaluated experimentally by producing the composites by two different methods, to compare the results of experimentally determined processing conditions to parameters determined by the simulation analysis. The assessment of mechanical properties is done with several experimental tests, showing small improvements for the composites produced with the simulation method. The application of the simulation analysis results in considerably reduced processing times, from the initial 10 min to only three minutes, thereby vastly improving the processing method. While the employed methods are not yet able to produce composites with greatly improved mechanical properties, this study can be seen as a constructive approach, which has the ability to lead to further improvements.

  • 224.
    Åkesson, Dan
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bourmaud, Alain
    Beaugrand, Johnny
    Le Duigou, Antoine
    Skrifvars, Mikael
    University of Borås, Faculty of Textiles, Engineering and Business.
    Baley, Christophe
    Recycling of L-Poly-(lactide)-Poly-(butylene-succinate)-flax biocomposite2016In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 128, p. 77-88Article in journal (Refereed)
    Abstract [en]

    The development of new plant fibre composites is a key point in the development of semi-structural biodegradable or biobased parts, especially for automotive applications. The aim of this original and innovating work is to study, at different scales, the recycling ability of a fully biodegradable L-Poly-(lactide)-Poly-(butylene-succinate)-flax (PLLA-PBS-flax) biocomposite. The biocomposites were manufactured by twin-screw extrusion followed by injection moulding, then the recycling behaviour was studied during successive injection moulding cycles. Firstly, we investigated the length of the flax fibre after compounding and injection, as well as the cell wall stiffness and hardness, by in-situ nanoindentation tests. Secondly, we focused on the effects of recycling on thermal, rheological and tensile properties. We highlighted a severe evolution of the cell wall properties, especially concerning the polysaccharidic matrix after the first thermal cycle, nanoindentation properties remaining quasi-stable after this first drop. Furthermore, the biocomposites did not show any significant evolution of their mechanical performances during cycle three or four of the first injection cycles; after this plateau, the tensile strength and strain as well as impact energy were significantly altered due to the conjugated fibre length decrease and degradation of the PLLA, the latter being emphasized when the flax fibre is embedded. Nevertheless, this fully biodegradable composite exhibits a suitable recycling behaviour for 3 or 4 cycles, which is sufficient for industrial applications.

  • 225.
    Åkesson, Dan
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Fazelinejad, Samaneh
    Skrifvars, Ville-Viktor
    University of Borås, Faculty of Textiles, Engineering and Business.
    Skrifvars, Mikael
    University of Borås, Faculty of Textiles, Engineering and Business.
    Mechanical recycling of polylactic acid composites reinforced with wood fibres by multiple extrusion and hydrothermal ageing2016In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 35, no 16, p. 1248-1259Article in journal (Refereed)
  • 226.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Foltynowicz, Zenon
    Christeen, Jonas
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Products obtained from decomposition of glass fiber-reinforced composites using microwave pyrolysis2013In: Polimery, ISSN 0032-2725, Vol. 58, no 7-8, p. 582-586Article in journal (Refereed)
    Abstract [en]

    The possibility to obtain useful products from used glass fiber-reinforced composites using microwave pyrolysis were examined. A scrap of blade from a wind turbine was fragmented and microwave-pyrolysed. The oil and gas formed during the pyrolysis were characterized by gas chromatography-mass spectrometry (GC-MS). The oil from pyrolysis consisted mainly of various aromatic compounds and had an energy content of about 36 MJ/kg. The main component of the gaseous products was methane. The glass fiber recovered after pyrolysis represented 70 % of the initial mass of glass fiber-reinforced plastic.

  • 227.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Foltynowicz, Zenon
    Christéen, Jonas
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Microwave pyrolysis as a method of recycling glass fibre from used blades of wind turbines2012In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 31, no 17, p. 1136-1142Article in journal (Refereed)
    Abstract [en]

    The possibility of recycling glass fibre-reinforced composites by using microwave pyrolysis was examined. A scrap blade from a wind turbine was fragmented and microwave-pyrolysed. The glass fibre recovered after pyrolysis represented 70% of the initial mass of glass fibre-reinforced composites. The tensile strength of the glass fibre recovered was measured after pyrolysis and compared to the tensile strength of untreated glass fibre. The test showed that the fibres lost about 25% of their tenacity. Non-woven fibre mats were prepared from the recovered fibres. Laminates were then prepared from the non-woven mats obtained, together with virgin glass fibre mats. Mechanical testing of the laminates showed that it is possible to prepare composites using 25 wt% of recycled fibres, with relatively good mechanical properties.

  • 228.
    Åkesson, Dan
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Fuchs, Torsten
    Stöss, Michael
    Root, Andrew
    MagSol, Helsinki, Finland.
    Stenvall, Erik
    Chalmers tekniska högskola.
    Skrifvars, Mikael
    University of Borås, Faculty of Textiles, Engineering and Business.
    Recycling of wood fiber-reinforced HDPE by multiple reprocessing2016In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 133, no 35Article in journal (Refereed)
    Abstract [en]

    The mechanical recycling of high-density polyethylene (HDPE) reinforced with wood fiber was studied by means of repeated injection moulding. The change in properties during the recycling was monitored by tensile and flexural tests, Charpy impact tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), FTIR spectroscopy, and by measuring the fiber lengths. Tests were also done where injection moulding was combined with subsequent accelerated thermo-oxidative ageing and thereafter repeated numerous times. The results showed that the HDPE composites were relatively stable toward both the ageing conditions and the repeated injection moulding. The change of the mechanical properties was mainly observed as an increased elongation at max. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43877. © 2016 Wiley Periodicals, Inc.

  • 229.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Khrishnamoorthi, Ramesh
    Foltynowicz, Zenon
    Christeen, Jonas
    Kalantar Mehrjerdi, Adib
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Glass Fibres Recovered by Microwave Pyrolysis as a Reinforcement for Polypropylene2013In: Polymers & polymer composites, ISSN 0967-3911, E-ISSN 1478-2391, Vol. 21, no 6, p. 333-339Article in journal (Refereed)
    Abstract [en]

    Glass fibre composites were recycled by microwave pyrolysis. The glass fibres recovered were evaluated as a reinforcement agent for polypropylene (PP). Samples were prepared with a micro-compounder and the resulting compounds were evaluated with tensile testing, flexural testing, Charpy impact testing and scanning electron microscopy (SEM). The adhesion between fibre and glass was relatively poor, and an attempt was made to improve it. Various coupling agents were evaluated, in addition to the use of maleic anhydride-grafted PP (MA-PP). Tests showed that MA-PP had a relatively strong effect on the mechanical properties.

  • 230.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Development of lactic acid and soy bean oil based thermoset resins and their natural fibre composites2007Conference paper (Refereed)
  • 231.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Mechanical recycling of polylactic acid reinforced with cellulose fibres2014Conference paper (Refereed)
    Abstract [en]

    The increased environmental awareness has drawn researchers’ attention to bio-based polymers and several polymers such as polylactic acid (PLA), Mater-bi and polyhydroxyalkanoates (PHA) have been studied extensively. It is not easy to replace conventional petro-based polymers and it is therefore likely that both petro- and bio-based polymers will coexists for a long time. The usage of bio-based polymers is however growing and this may have implications for the plastic recycling industry. The recycling of petro-based polymers is relatively well studied and, where it is cost effective, conventional, petro-based polymers are being recycled in the industry. However, the recycling of bio-based plastics and composites needs to be studied more in detail. While several bio-based polymers can be biologically degraded, it is of interest to study the mechanical recycling of these polymers. In order to minimize the energy usage and the consumption of renewable materials mechanical recycling can be a good option. PLA is an attractive polymer as it is both biodegradable and prepared from renewable materials. This polymer has received a lot of attention and several reviews have been written. Research has shown that neat PLA can be reprocessed several times without significant loss of mechanical properties. Biocomposites based on PLA reinforced with natural fibres have been studied extensively in the literature and there can be many industrial applications of these biocomposites, such as automotive components and materials for construction applications. However, the mechanical recycling of biocomposites is not well studied. Most studies in the literature concerns the recycling of polymers reinforced with wood flour. DuraPulp is a commercial quality consisting PLA fibres mixed with cellulose fibres. This biocomposite material can be processed with for example compression moulding. Adding cellulose fibres to the polymer matrix may significantly change how the material can be recycled. The purpose of this study was to study the mechanical recycling of this material. Sheets were first prepared from Durapulp. The sheets were then compression moulded, grinded and reprocessed again with compression moulding. The mechanical and thermal properties were characterized after each cycle. The feasibility to recycle Durapulp mechanically will be discussed.

  • 232.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Recycling of glass fibre reinforce plastics using microwave pyrolysis2012Conference paper (Other academic)
  • 233.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Recycling of thermoset composites by microwave pyrolysis2011Conference paper (Other academic)
    Abstract [en]

    A scrap blade from a wind turbine was microwave pyrolysed. The recovered glass fibres were characterised by SEM and TGA. The possibility to use the fibres to prepare new composites were evaluated. Laminates were prepared where fibres mats with virgin and recovered glass fibres were altered. Mechanical testing showed that it is possible to prepapare composite with up to 35 wt.-% recovered fibre without losing too much of the mechanical properties.

  • 234.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Technical Development of Biobased Thermoset REsins and Composites2007Conference paper (Other academic)
  • 235.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Thermoset composites based on polylactic acid2008Conference paper (Refereed)
  • 236.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Hagström, Bengt
    Walkenström, Pernilla
    University of Borås, Swedish School of Textiles.
    Seppälä, Jukka
    Processing of Structural Composites from Biobased Thermoset Resins and Natural Fibres by Compression Moulding2008In: Journal of Biobased Materials and Bioenergy, ISSN 1556-6560, E-ISSN 1556-6579, Vol. 3, no 3, p. 215-225Article in journal (Refereed)
    Abstract [en]

    With the aim of producing composites from renewable materials for the furniture industry, a number of thermoset prepregs were manufactured and evaluated. The applicability of two different biobased thermoset resins was evaluated. The first resin is based on soybean oil and the second on lactic acid. Both resins are cross-linkable and produced from renewable resources. Prepregs were manufactured from the two resins together with natural fibres (flax and cellulose). Furthermore, sheet moulding compound (SMC) was developed from lactic acid based resin together with glass fibre. Seat shells were produced from the prepregs by compression moulding. Curing of the composites was monitored using a response surface methodology. Further, the fibre ratio, mechanical properties as well as adhesion between the matrix and the fibre were evaluated. These prepregs offers short cycle times and yield products with suitable mechanical properties. Issues related to the preparation and the processing of the prepregs are discussed in the article.

  • 237.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Seppälä, J.
    Turunen, M.
    Martinelli, M.
    Matic, A.
    Synthesis and characterization of a lactic acid-based thermoset resin suitable for structural composites and coatings2009In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 115, no 1, p. 480-486Article in journal (Refereed)
    Abstract [en]

    A new biobased polyester resin was developed for thermoset composite applications. The resin is potentially inexpensive and can be produced industrially by relatively simple means. The resin consists of star-shaped methacrylated oligomers of lactic acid (LA). LA oligomers were synthesized in a two-step process: in the first step, oligomers of LA were polymerized by direct condensation of LA. In the second step, the oligomers were end-functionalized by methacrylic anhydride. The resin was characterized by differential scanning calorimetry, Raman spectroscopy, NMR, rubber process analyzer, and TOF-SIMS. Tests show that the resin can be crosslinked into a rigid network within a couple of minutes upon thermal initiation. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 480-486, 2010

  • 238.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Seppälä, Jukka
    Turunen, Minna
    Thermoset lactic acid-based resin as a matrix for flax fibers2010In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 119, no 5, p. 3004-3009Article in journal (Refereed)
    Abstract [en]

    Abstract Thermoset composites were produced from flax fibers and a novel lactic acid (LA)-based thermoset resin. This resin is based on methacrylated, star-shaped oligomers of LA. The main purpose of this work was to evaluate whether this resin can be used to produce structural composites from flax fibers. Composites were prepared by spray impregnation followed by compression molding at elevated temperature. The tests showed that composites can be produced with as much as 70 wt% fiber. The composites were evaluated by tensile testing, flexural testing, charpy impact test, dynamic mechanical thermal analysis (DMTA), and low-vacuum scanning electron microscopy. The ageing properties in high humid conditions were evaluated, the Young's modulus ranged from 3 GPa to 9 GPa in the best case. This work shows that structural composites can be produced from renewable material. It is clear from the results that these composites have properties that make them suitable for furniture, panels, or automotive parts.

  • 239.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Seppälä, Jukka V.
    Walkenström, Pernilla
    University of Borås, Swedish School of Textiles.
    Preparation of Natural Fibre Composites from Biobased Thermoset Resins.2006Conference paper (Refereed)
  • 240.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Shichang, L.
    Shi, W.
    Adekunle, Kayode
    University of Borås, School of Engineering.
    Seppälä, J.
    Turunen, M.
    Preparation of nanocomposites from biobased thermoset resins by UV-curing2009In: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 67, no 3, p. 281-286Article in journal (Refereed)
    Abstract [en]

    Biobased thermoset resins were irradiated with utraviolet(UV) radiation in the presence of photoinitiators. Three different resins were evaluated-two resins were based on soybean oil and one was based on lactic acid. The cross-linking behaviour of these resins was characterized by real-time FTIR and Soxhlet extraction. All of the resins cured rapidly and formed rigid materials with a high degree of conversion. The cross-linked resins were characterized by mechanical testing, thermogravimetric analysis (TGA) as well as dynamic-mechanical thermal analysis (DMTA). The resins were reinforced with layered silicate, in order to form nanocomposite Structures. The resulting composites were characterized by DMTA and tensile testing. (C) 2009 Elsevier B.V. All rights reserved.

  • 241.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Walkenström, P.
    University of Borås, Swedish School of Textiles.
    Preparation of thermoset composites from natural fibres and acrylate modified soybean oil resins2009In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 114, no 4, p. 2502-2508Article in journal (Refereed)
    Abstract [en]

    Structural composites with a high content of renewable material were produced from natural fibres and an acrylated epoxidized soybean oil resin. Composites were prepared by spray impregnation followed by compression moulding at elevated temperature. The resulting composites good mechanical properties in terms of tensile strength flexural strength. Tensile testing as well as dynamical :hanical thermal analysis showed that increasing the e content, increased the mechanical properties. The resin be reinforced with up to 70 wt % fibre without sacrifice in processability. The tensile modulus ranged between 5.8 and 9.7 GPa depending on the type of fibre mat. The study of the adhesion by low vacuum scanning electron microscopy shows that the fibres are well impregnated in the matrix. The aging properties were finally evaluated. This study shows that composites with a very high content of renewable constituents can be produced from soy bean oil resins and natural fibres.

  • 242.
    Åkesson, Dan
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Vrignaud, Thomas
    Tissot, Clément
    Skrifvars, Mikael
    University of Borås, Faculty of Textiles, Engineering and Business.
    Mechanical Recycling of PLA Filled with a High Level of Cellulose Fibres2016In: Journal of polymers and the environment, ISSN 1566-2543, E-ISSN 1572-8919, Vol. 25, no 3, p. 185-195Article in journal (Refereed)
    Abstract [en]

    Composites consisting of 30 vol% PLA and 70 vol% cellulose fibres were prepared with compression moulding. In the first part of the study, the recyclability of this composite material was investigated by grinding the material and using the recyclate obtained as a filler for PLA. Thus, the recyclate was compounded with PLA in loadings ranging from 20 to 50 wt%. The composites obtained were characterised by tensile tests, Charpy impact tests, DMTA, and SEM. Tests showed that the recyclate had a relatively good reinforcing effect. Stress at break increased from about 50 to 77 MPa and the modulus increased from 3.6 to 8.5 GPa. In the second part of the study, the ability to mechanically recycle the composites obtained was evaluated by repeated processing. Composite with two loadings of the recyclate (20 wt% and 50 %) was injection moulded repeatedly, six times. Tests showed that the composite material with 20 wt% recyclate could withstand six cycles relatively well, while the composite with the higher load degraded much more quickly. For the composites with 50 wt% recyclate, signs of polymer degradation could be seen already after reprocessing the composite once.

2345 201 - 242 of 242
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