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  • 51.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Preparation and Characterization of UV-cured Nano Reinforced Biobased Coatings2011Conference paper (Other academic)
    Abstract [en]

    Polymers are typically produced from crude oil which is a non-renewable resource. With the fast depletion of the petroleum resources, the development of materials based on renewable resources is becoming important. Polymers prepared from renewable resources are under development, but has mainly focused on thermoplastic polymers such as polylactic acid. For some applications, such as composites and coatings, thermoset polymers are often preferred. Consequently, it is important to develop thermoset resins from renewable resources as well. Plant oils, such as soybean oil and linseed oil, have been utilized by mankind for a long time. Soybean oil is produced in large quantities and soybean oil is an excellent starting material for the synthesis of thermoset resins. A possible strategy to prepare thermoset resins from plant oils is to introduce pendant methacrylate groups in the structure. Thus, the resins can be cured by a free radical polymerization. Such a resin is very susceptible to photopolymerization when exposed to ultraviolet (UV) radiation, which is a common technique to cure coatings. In the present study, three different thermoset resins were studied. Two of the resins were based on soybean oil while the third resin was based on lactic acid. The latter resin was prepared by a direct condensation of lactic acid and pentaerythritol and was finally end-capped with methacrylate groups. Several authors have studied the addition of nano-reinforcements to thermoset resins. One of the most promising nano-reinforcements is layered silicate which has shown to improve several properties. Layered silicate has been used to reinforce conventional resins with good results. The addition of layered silicates to the biobased resins can be used to improve the properties and to broaden the applications. The resins used in this study were therefore reinforced with layered silicate and UV-cured. The cured resins were characterized by Soxhlet extraction, photo-FTIR, DMTA and tensile tests which will be presented during the presentation.

  • 52.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Renewable composites prepared from biobased thermoset resins2009Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In our efforts to create a more sustainable society, several researchers have tried to prepare composites from renewable materials in recent years. The use of natural fibres for reinforcement of composites has been relatively well studied. To date, most studies of natural fibre-reinforced composites have either involved the use of conventional thermoset resins or thermoplastic biopolymers. While there are currently several thermoplastic polymers on the market that are produced from renewable resources, thermosets are inevitably produced from petroleum resources. The development of biobased thermoset resins is therefore of considerable importance. Such resins could be used in future for composite applications, for coating applications or in adhesives. This thesis describes the development of biobased thermoset resins for composite applications. Thermoset resins were synthesised from both epoxidised soybean oils as well as from lactic acid. These resins have been characterised neat as well as together with various reinforcements. The main objective has been to study these biobased resins together with natural fibres for reinforcement, though to some extent nano-reinforcements and glass fibres have also been used as reinforcements. Natural fibre-reinforced composites were prepared from several different biobased thermoset resins. Resins based on soybean oil as well as a resin based on lactic acid were evaluated. The soybean resins were prepared by introducing acrylate or methacrylate groups into the molecules of soybean oil. The second type of thermoset resin used was based on lactic acid. This resin consists of star-shaped methacrylated oligomers of lactic acid. Natural fibres were impregnated by several impregnation techniques. Composites were prepared from the biobased resins together with various natural fibres, such as flax and hemp fibres. The resulting composites were evaluated by tensile testing, flexural testing, impact testing, DMTA and SEM. The results show that composites prepared from biobased resin have relatively good mechanical properties and can be used for indoor applications such as furniture and construction elements.

  • 53.
    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.

  • 54.
    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)
  • 55.
    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.

  • 56.
    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.

  • 57.
    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.

  • 58.
    Åkesson, Dan
    et al.
    University of Borås, School of Engineering.
    Khrishnamoorthi, Ramesh
    Foltynowicz, Zenon
    Christeen, Jonas
    Kalantar Mehrjerdi, Adib
    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.

  • 59.
    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)
  • 60.
    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.

  • 61.
    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)
  • 62.
    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.

  • 63.
    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)
  • 64.
    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)
  • 65.
    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.

  • 66.
    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

  • 67.
    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.

  • 68.
    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)
  • 69.
    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.

  • 70.
    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.

  • 71.
    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.

12 51 - 71 of 71
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