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  • 1.
    Adekunle, Kayode
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Biobased Composites Prepared by Compression Molding with a Novel Thermoset Resin from Soybean Oil and a Natural-Fiber Reinforcement2010In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 116, no 3, p. 1759-1765Article in journal (Refereed)
    Abstract [en]

    Biobased composites were manufactured with a compression-molding technique. Novel thermoset resins from soybean oil were used as a matrix, and flax fibers were used as reinforcements. The air-laid fibers were stacked randomly, the woven fabrics were stacked crosswise (0/90 ), and impregnation was performed manually. The fiber/resin ratio was 60 : 40. The prepared biobased composites were characterized by impact and flexural testing. Scanning electron microscopy of knife-cut cross sections of the specimens was also done to investigate the fiber–matrix interface. Thermogravimetric analysis of the composites was carried out to provide indications of thermal stability. Three resins from soybean oil [methacrylated soybean oil, methacrylic anhydride modified soybean oil (MMSO), and acetic anhydride modified soybean oil] were used as matrices. The impact strength of the composites with MMSO resin reinforced with air-laid flax fibers was 24 kJ/m2, whereas that of the MMSO resin reinforced with woven flax fabric was between 24 and 29 kJ/m2. The flexural strength of the MMSO resin reinforced with air-laid flax fibers was between 83 and 118 MPa, and the flexural modulus was between 4 and 6 GPa, whereas the flexural strength of the MMSO resin reinforced with woven fabric was between 90 and 110 MPa, and the flexural modulus was between 4.87 and 6.1 GPa.

  • 2.
    Adekunle, Kayode
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Preparation of biobased composites using novel thermoset polymers from soybean oil and a natural fibre reinforcement2009Conference paper (Other academic)
    Abstract [en]

    Health related issues, stringent environmental protection policies, search for cost effective and alternative materials, crave for renewability and sustainability and quest for high performance materials for structural applications give the motivation for research in polymer composites and material science. Due to the health, safety and environmental concerns over the conventional synthetic materials and the legislation against their usage both in domestic and industrial applications, alternatives sources that will be comparable in properties are being sought. There is an emerging market for biodegradable polymers which is expected to increase substantially in the coming years.[1] Preparation of Composites Airlaid and woven flax fibre mats were first treated with 4% sodium hydroxide solution for one hour and then washed with plenty of water. This was done in order to remove any residual impurities. The fibres were dried at room temperature for 24 hr and then dried in a vacuum oven for 1hr at a temperature of 105°С. The 8 sheets of the fibre were hand laid cross- wisely and the impregnation was done manually. The fibre/ resin ratio was about 60% to 40%. Methacrylated soybean oil, methacrylic anhydride and acetic anhydride modified soybean oil were the synthesized matrices used. The compression moulding was done at a temperature of 170°С for 5 min at 40bar. Characterisations The tensile testing was performed based on an ISO-test method for tensile tests on plastic materials. The Charpy impact strength of unnotched specimens was evaluated in accordance with ISO 179 using a Zwick test instrument and scanning electron microscopy analysis was done on the fractured specimens. The composites showed various mechanical properties, having impact strengths between 24 and 63 kJ/m² and tensile strength up to 51MPa.

  • 3.
    Adekunle, Kayode
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Synthesis of reactive soybean oils for use as biobased thermoset resins in structural natural fibre composites2008Conference paper (Refereed)
  • 4.
    Adekunle, Kayode
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Synthetic modification of reactive soybean oils for use as biobased thermoset resins in structural natural fiber composites2008Conference paper (Other academic)
  • 5.
    Adekunle, Kayode
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Synthetic modification of reactive soybean oils for use as biobased thermoset resins in structural natural fiber composites2008In: Polymer Preprints, ISSN 0551-4657, Vol. 49, no 1, p. 279-Article in journal (Refereed)
  • 6. Ali, Majid
    et al.
    Bashir, Tariq
    University of Borås, School of Engineering.
    Persson, Nils-Krister
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Optimization of oCVD Process for the Production of Conductive Fibers2011Conference paper (Other academic)
    Abstract [en]

    Electro active textile fibers are key components in smart and interactive textile applications. In our previous study, we produced poly(3,4-ethylenedioxythiophene) (PEDOT) coat edviscose fibers by using oxidative chemical vapordeposition (OCVD) technique. We tried FeCl3 as oxidant and found optimum reaction conditions at which better electrical as well as mechanical properties of conductive fibers could be achieved.

  • 7.
    Baghaei, Behnaz
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Berglin, Lena
    University of Borås, Swedish School of Textiles.
    Manufacture and characterisation of thermoplastic composites made from PLA/hemp co-wrapped hybrid yarn prepregs2013In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 50, p. 93-101Article in journal (Refereed)
    Abstract [en]

    PLA/hemp co-wrapped hybrid yarns were produced by wrapping PLA filaments around a core composed of a 400 twists/m and 25 tex hemp yarn (Cannabis Sativa L) and 18 tex PLA filaments. The hemp content varied between 10 and 45 mass%, and the PLA wrapping density around the core was 150 and 250 turns/metre. Composites were fabricated by compression moulding of 0/90 bidirectional prepregs, and characterised regarding porosity, mechanical strength and thermal properties by dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). Mechanical tests showed that the tensile and flexural strengths of the composites markedly increased with the fibre content, reaching 59.3 and 124.2 MPa when reinforced with 45 mass% fibre, which is approximately 2 and 3.3 times higher compared to neat PLA. Impact strength of the composites decreased initially up to 10 mass% fibre; while higher fibre loading (up to 45 mass%) caused an increase in impact strength up to 26.3 KJ/m2, an improvement of about 2 times higher compared to neat PLA. The composites made from the hybrid yarn with a wrapping density of 250 turns/metre showed improvements in mechanical properties, due to the lower porosity. The fractured surfaces were investigated by scanning electron microscopy to study the fibre/matrix interface.

  • 8.
    Bakare, Fatimat
    et al.
    University of Borås, School of Engineering.
    Åkesson, Dan
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Bashir, Tariq
    University of Borås, School of Engineering.
    Ingman, Petri
    Srivastava, Rajiv
    Synthesis and characterization of unsaturated lactic acid based thermoset bio-resins2014In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 67, p. 570-582Article in journal (Refereed)
    Abstract [en]

    Bio-based thermoset resins have been synthesized using lactic acid oligomers, which were functionalized with carbon–carbon double bonds, in order to allow their crosslinking by a free radical mechanism. Two different resin structures were synthesized. One resin was composed of an allyl alcohol terminated lactic acid oligomer, which was end-functionalized with methacrylic anhydride (MLA resin). The second resin was a mixture of the same allyl alcohol-lactic acid oligomer, and penthaerythritol. This mixture was end-functionalized with methacrylic anhydride, in order to get a methacrylate functionalized lactic acid oligomer, and methacrylate functionalized penthaerythritol (PMLA resin). The synthesized resins were characterized using FT-IR, 1H NMR and 13C NMR spectroscopy, differential scanning calorimetry as well as dynamic mechanical analysis to confirm the resin structure and reactivity. The flow viscosities were also measured in order to evaluate the suitability of the resins to be used as a matrix in composite applications. The results showed that the PMLA resin has better mechanical, thermal and rheological properties than the MLA resin, and both had properties which were comparable with a commercial unsaturated polyester resin. The high biobased content of 90% and the high glass transition temperature at 100 °C for the PMLA resin makes it an attractive candidate for composite applications where crude oil based unsaturated polyester resins are normally used.

  • 9.
    Barghi, Hamidreza
    University of Borås, School of Engineering.
    Functionalization of Synthetic Polymers for Membrane Bioreactors2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Membrane bioreactors (MBRs) show great promise for productivity improvement and energy conservation in conventional bioprocesses for wastewater reclamation. In order to attain high productivity in a bioprocess, it is crucial to retain the microorganisms in the bioreactors by preventing wash out. This enables recycling of the microorganisms, and is consequently saving energy. The main feature of MBRs is their permeable membranes, acting as a limitative interface between the medium and the microorganisms. Permeation of nutrients and metabolites through the membranes is thus dependent on the membrane characteristics, i.e. porosity, hydrophilicity,and polarity. The present thesis introduces membranes for MBRs to be used in a continuous feeding process, designed in the form of robust, durable, and semi-hydrophilic films that constitute an effective barrier for the microorganisms, while permitting passage of nutrients and metabolites. Polyamide 46 (polytetramethylene adipamide), a robust synthetic polymer, holds the desired capabilities, with the exception of porosity and hydrophilicity. In order to achieve adequate porosity and hydrophilicity, bulk functionalization of polyamide 46 with different reagents was performed. These procedures changed the configuration from dense planar to spherical, resulting in increased porosity. Hydroxyethylation of the changed membranes increased the surface tension from 11.2 to 44.6 mJ/m2. The enhanced hydrophilicity of PA 46 resulted in high productivity of biogas formation in a compact MBR, due to diminished biofouling. Copolymerization of hydrophilized polyamide 46 with hydroxymethyl 3,4-ethylenedioxythiophene revealed electroconductivity and hydrophilic properties, adequate for use in MBRs. To find either the maximal pH stability or the surface charge of the membranes having undergone carboxymethylation, polarity and the isoelectric point (pI) of the treated membranes were studied by means of a Zeta analyzer. The hydroxylated PA 46 was finally employed in a multilayer membrane bioreactor and compared with hydrophobic polyamide and PVDF membranes. The resulting biogas production showed that the hydroxylated PA 46 membrane was, after 18 days without regeneration, fully comparable with PVDF membranes.

  • 10.
    Barghi, Hamidreza
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Taherzadeh, Mohammad J.
    University of Borås, School of Engineering.
    Catalytic Synthesis of Bulk Hydrophilic Acetaldehyde-Modified Polyamide 462014In: Current Organic Synthesis, ISSN 1570-1794, E-ISSN 1875-6271, Vol. 11, no 6, p. 288-294Article in journal (Refereed)
    Abstract [en]

    Hydrophilization of Polyamide 46 (PA46) via modification with acetaldehyde in continuous phase was studied. The chemical modification of PA 46 with acetaldehyde resulted in a water-swollen polymer with hydrophilic property. The polyamide 46 undergoes a nucleophilic addition with acetaldehyde in the presence of aluminum chloride as a catalyst. The extent of bulk hydroxyethylation using AlCl3 resulted in 95.65% modification counted as total N-hydroxyethylated polyamide 46. The modification resulted in improved hydrophilic properties, and a maximum surface free energy of 44.6 mJ/m2 was achieved after 3 h reaction, whereas the unmodified PA46 had a surface free energy of 11.2 mJ/m2. In addition, thermal properties of the polymers were studied using differential scanning calorimetry and thermogravimetric analyses. The functionalization leads to decrease in the crystallization energy from 88 J/g to 51 J/g, while the melting energy is changed from 110 J/g to 53 J/g. Furthermore, the thermal stability of the PA46 to pyrolysis was diminished after hydroxylation.

  • 11.
    Bashir, Tariq
    et al.
    University of Borås, School of Engineering.
    Ali, Majid
    Persson, Nils-Krister
    University of Borås, Swedish School of Textiles.
    Ramamoorthy, Sunil Kumar
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Stretch Sensing Properties of Conductive Knitted Structures of PEDOT-coated Viscose and Polyester Yarns2013In: Textile research journal, ISSN 0040-5175, E-ISSN 1746-7748, Vol. 84, no 3, p. 323-334Article in journal (Refereed)
    Abstract [en]

    Wearable textile-based stretch sensors for health-care monitoring allow physiological and medical evaluation without interfering in the daily routine of the patient. In our previous work, we successfully coated viscose and polyester (PES)fibers with the conjugated polymer poly(3,4-ethylenedioxythiophene) (PEDOT), using a chemical vapor deposition (CVD) process. In the present paper we report the possibility of producing a large quantity of PEDOT-coated conductive fibers with acceptable mechanical strength and frictional properties, so that knitted stretch sensors can be produced. In utilizing these knitted structures we have demonstrated the possibility of producing a textile-based monitoring device which is more readily integrated into wearable clothing than the previous metal-containing structures. The performance of viscose and PES knitted structures as stretch sensors has been investigated using a cyclic tester of our own design. For imitation of respiratory and joint movement, the variation in electrical properties of the knitted structures was examined at 5 to 50% elongation, and the performance of knitted viscose and PES structures was then compared on the basis of the cyclic testing results. In order to determine the effect of washing on PEDOT coatings and the knitted structures, two washing cycles were performed. After washing, the persistence of PEDOT coating on knitted structures was investigated using FT–IR spectroscopy and thermogravimetric analysis. In the case of PES fiber, it was revealed that stretch sensing behavior persisted even after the washing cycles. These structures thus have the potential to be utilized in medical textiles for monitoring the physiological activities of patients, such as breathing rate and joint movement.

  • 12.
    Bashir, Tariq
    et al.
    University of Borås, School of Engineering.
    Naeem, Jawad
    Persson, Nils-Krister
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    FUNCTIONAL TEXTILES: Micro-porous Conductive Membranes for Bio-fuel Cell and Anti-static Air Filter Applications2013Conference paper (Refereed)
    Abstract [en]

    Conductive membranes are the highly demanding materials in the field of bio-fuel generation, bio-electrodes, sensors and anti-static air filter systems. The conductive membranes can effectively be utilized for above mentioned applications if they have better conductivity, lower weight, flexibility and cost effectiveness. Textile materials are extremely versatile in nature because their synergic combinations with other functional materials could be used for a wide range of applications, such as medical, sports, defence, energy generation and chemical industry. The non-woven micro-porous textile substrates can effectively be functionalized by coating them with conjugated polymers, such as PEDOT and polypyrrole. Coating with conjugated polymers not only gives better conductivity values but also maintain the lower molecular weight of the substrate material. In our research, we have prepared micro-porous conductive membranes by coating cellulosic non-woven fabrics with conductive polymer PEDOT. For coating purpose, we utilized most effective deposition technique, which is called chemical vapour deposition (CVD) process. The deposition of PEDOT by CVD process showed advantages over other conventionally used methods, such as the micro-pores were not blocked even after PEDOT deposition. The electrical characterization on produced conductive membranes was performed by using Kiethely 6000 picoammeter. The surface morphology was examined by scanning electron microscopy and structural properties were determined by ATR-FTIR analysis. In order to see the behaviour of these conductive membranes, electrochemical impedance scanning (EIS) was performed in different electrolyte solutions. The produced conductive membranes might have potential to be utilized as active electrode in bio-fuel cells and also can be used in anti-static air filter systems.

  • 13.
    Bashir, Tariq
    et al.
    University of Borås, School of Engineering.
    Naeem, Jawad
    Persson, Nils-Krister
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Functionalization of Textile Materials by Coating with Conjugated Polymers2013Conference paper (Refereed)
    Abstract [en]

    During the last decade, smart textiles have attracted an enormous attention of researchers and found extraordinary applications in biomedical, sports, defense, energy, and fashion industry. These textiles are able to accept the physical signals from external stimuli and then generate a reaction in the form of thermal, electrical, chemical and magnetic signals. They should be in the form of functionalized fabric or electro-active fibers. A numerous techniques for the production of electrically conductive fibers have already been developed. In this study, we have prepared relatively highly conductive fibers with better mechanical properties. For this purpose, we have functionalized the commercially available textile fibers by coating with intrinsically conductive polymer (ICP), poly(3,4-ethylenedioxythiophene) (PEDOT). An efficient coating technique, so called oxidative chemical vapor deposition (CVD) was utilized for making uniform, thin and highly conductive polymer layers on the surface of textile fibers. For our initial experiments, we used viscose and polyester fibers as substrate materials. After performing a series of experiments, we have optimized a number of reaction parameters at which good electro-mechanical properties of conductive fibers can be achieved. At specific reaction conditions, the conductivity level which we have attained is approximately 15 S/cm. The PEDOT coated viscose and polyester fibers were compared in order to find out the best suitable substrate material. For increasing the service life of obtained conductive fibers, a thin layer of silicon resin was applied on the surface of PEDOT coated fibers.

  • 14.
    Bashir, Tariq
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Persson, Nils-Krister
    University of Borås, School of Engineering.
    Production of conductive yarns by chemical vapour deposition technique of PEDOT viscose fibres2010Conference paper (Refereed)
  • 15.
    Bashir, Tariq
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Persson, Nils-Krister
    Surface Modification of Conductive PEDOT Coated Textile Yarns with Silicone Resin2011In: Materials technology (New York, N.Y.), ISSN 1066-7857, E-ISSN 1753-5557, Vol. 26, no 3, p. 135-139Article in journal (Refereed)
    Abstract [en]

    Electroactive textile fibres and fabrics have been used in smart and interactive clothing for medical,military and sports applications. The improved surface properties of conductive textiles are required for their successful integration in all of the above mentioned applications. This paper presents the production of conductive poly(3,4-ethylenedioxythiophene) (PEDOT) coated viscose yarns in longer length, i.e. 5 m, and the surface modification of the coated yarns by treating with silicone solution. The structural properties of silicone coated conductive yarns were then investigated by Fourier transform infrared spectroscopy and thermogravimetric analysis. The effect of silicone coating on the mechanical, electrical and hydrophobic properties was also evaluated and then compared with the PEDOT coated viscose yarns without surface treatment. Results show that the mechanical and hydrophobic properties of conductive yarns were improved by surface modification with silicone without affecting their structural properties. The surface modified PEDOT coated yarns could be used as pressure and stretch sensors in health care applications.

  • 16.
    Bohlén, Martin
    et al.
    University of Borås, School of Engineering.
    Yaghooby, Haleh
    Airola, Karri
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Film Extrusion of Hydroxyapapatite and β-Tricalciumphosphate Functionalized Polyactide Polymers for Biomedical Implants2010Conference paper (Other academic)
  • 17. Chalapati, Sachin
    et al.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Toluene mediated fluid catalytic cracking of low density polyethylene using ionic liquids2014Conference paper (Other academic)
  • 18.
    Cho, Sung-Woo
    University of Borås, School of Engineering.
    Aging and Heat-Sealing Properties of Films based on Wheat Gluten2007Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Recently the research interest of the possibility of using wheat gluten (WG) as packaging material has greatly increased due to its combination of high gas barrier, attractive mechanical, film-forming and renewable properties. The source is also readily available and inexpensive on a worldwide basis. The glycerol-plasticized WG films cast from pH 4 and pH 11 solutions were investigated in order to understand the mechanisms behind the undesired aging. The film prepared from the pH 11 solution was mechanically more stable upon aging than the pH 4 film, which was initially very ductile but turning brittle with time. It was revealed that the protein structure of the pH 4 film was initially less polymerized/aggregated and the polymerization increased during storage but it did not reach the degree of aggregation of the pH 11 film, whereas deamidation was occurred and increased in the pH 11 film. During aging, the pH 4 film lost more mass than the pH 11 film mainly due to migration of glycerol but also due to some loss of volatile mass and the greater plasticizer loss of pH 4 film was presumably due to its initial lower degree of protein aggregation /polymerization. The glycerol migration of cast films exposed to a porous paper was further investigated with respect to pH of cast solution, glycerol content and film thickness since it was the main reason for deterioration of the properties. The opacity was also characterized. The glycerol migration was quantified using GC method in order to determine only glycerol content, but not other volatile substances. Glycerol content did not significantly change the opacity and pH 4 films showed good contact clarity because of less Maillard reaction. Glycerol was extensively migrating to the paper support and the migration seemed to be diffusion controlled. The heat sealability of WG films was investigated, using an impulse-hear sealer. It was observed that the WG films were readily sealable keeping up their integrity. The sealing temperature had a negligible effect on the lap-shear strength, but the peel strength increased with sealing temperature. The lap-shear strength increased with increasing mold temperature and the failure mode changed.

  • 19.
    Cho, Sung-Woo
    University of Borås, School of Engineering.
    Protein-based packaging films, sheets and composites: process development and functional properties2009Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The depletion of the petroleum resources and a number of environmental concerns led to considerable research efforts in the field of biodegradable materials over the last few decades. Of the diverse range of biopolymers, wheat gluten (WG) stands out as an alternative to synthetic plastics in packaging applications due to its attractive combination of flexibility and strength, high gas barrier properties under low humidity conditions and renewability. The availability of raw materials has also been largely increased with an increase in the production of WG as a low-cost surplus material due to increasing demand for ethanol as fuel. In this study, WG was processed into films, sheets and composites using some of the most widely used techniques including solution casting, compression molding, extrusion and injection molding, accompanying process optimizations and characterization of their functional properties. This thesis consists mainly of six parts based on the purpose of the study. The first part addresses the aging and optical properties of the cast film in order to understand the mechanisms and reasons for the time-dependant physical and chemical changes. The films plasticized with glycerol were cast from acidic (pH 4) and basic (pH11) solutions. The film prepared from the pH 11 solution was mechanically more stable upon aging than the pH 4 film, which was initially very ductile but became brittle with time. It was revealed that the protein structure of the pH 4 film was initially less polymerized/aggregated and the polymerization increased during storage but it did not reach the degree of aggregation of the pH 11 film. During aging, the pH 4 film lost more mass than the pH 11 film mainly due to migration of glycerol but also due to some loss of volatile mass. In addition the greater plasticizer loss of the pH 4 film was presumably due to its initial lower degree of protein aggregation/polymerization. Glycerol content did not significantly change the opacity and pH 4 films showed good contact clarity because of less Maillard reaction. In the second part, the heat-sealability of WG films was investigated, using an impulse-heat sealer, as the sealability is one of the most important properties in the use of flexible packaging materials. It was observed that the WG films were readily sealable while preserving their mechanical integrity. The sealing temperature had a negligible effect on the lap-shear strength, but the peel strength increased with sealing temperature. The lap-shear strength increased with increasing mold temperature and the failure mode changed. The third part describes the possibility of using industrial hemp fibers to reinforce wheat gluten sheets based on evaluation of the fiber contents, fiber distribution and bonding between the fibers and matrix. It was found that the hemp fibers enhanced the mechanical properties, in which the fiber contents played a significant role in the strength. The fiber bonding was improved by addition of diamine as a cross-linker, while the fiber distribution needed to be improved. The fourth part presents a novel approach to improve the barrier and mechanical properties of extruded WG sheets with a single screw extruder at alkaline conditions using 3-5wt.% NaOH with or without 1 wt.% salicylic acid. The oxygen barrier, at dry conditions, was improved significantly with the addition of NaOH, while the addition of salicylic acid yielded poorer barrier properties. It was also observed that the WG sheets with 3 wt.% NaOH had the most suitable combination of low oxygen permeability and relatively small time-dependant changes in mechanical properties, probably due to low plasticizer migration and an optimal protein aggregation/polymerization. In the fifth part WG/PLA laminates were characterized for the purpose of improving the water barrier properties. The lamination was performed at 110°C and scanning electron microscopy showed that the laminated films were uniform in thickness. The laminates significantly suppressed the mass loss and showed promising water vapor barrier properties in humid conditions indicating possible applications in packaging. The final part addresses the development of injection molding processes for WG. Injection-molded nanocomposites of WG/MMT were also characterized. WG sheets were successively processed using injection molding and the process temperatures were found to preferably be in a range of 170-200°C, which was varied depending on the sample compositions. The clay was found to enhance the processability, being well dispersed in the matrix. The natural clay increased the tensile stiffness, whereas the modified clay increased the surface hydrophobicity. Both clays decreased the Tg and increased the thermal stability of the nanocomposites. The overall conclusion was that injection molding is a promising method for producing WG items of simple shapes. Further studies will reveal if gluten can also be used for making more complex shapes.

  • 20.
    Cho, Sung-Woo
    et al.
    University of Borås, School of Engineering.
    Adekunle, Kayode
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Mechanical properties of renewable thermoset composites reinforced with natural fibers2010Conference paper (Other academic)
    Abstract [en]

    The focus in this presentation has been to evaluate whether natural fibers can be used as reinforcement in composites based on renewable thermoset resin. Thermoset resins made from renewable resources as alternatives to crude oils are a relatively unexplored and important research area and could be used for a broad range of applications including coatings, inks, adhesives and composites. The common raw materials used in the preparation of biobased thermoset resins are vegetable oils such as soybean oil, rapeseed oil and linseed oil, which are low cost and abundant. Natural fibers as reinforcement have many advantages compared to synthetic fibers, for instance they are biodegradable, low weight and cost, nontoxic and recyclable. In the previous study, a novel thermoset resin [methacrylic anhydride modified soybean oil (MMSO)] was synthesized through the reaction of epoxidized soybean oil with methacrylic acid and used here as matrices. The studied composites based on the neat MMSO resin and the reisn blended with 30 wt.% styrene reinforced with non-woven flax fiber and woven flax fiber mats in different orientations [0°(warp direction), 45°, 90°(weft direction)] were manufactured using compression molding technique. The glass fiber reinforced composite was also prepared for the comparison purpose. The results show that it was possible to produce composite with high mechanical properties when the load is especially applied along the fiber direction, which implies that the structural composites having several plies of natural fiber mats in different orientations could be interesting candidates for use in technical applications.

  • 21.
    Cho, Sung-Woo
    et al.
    University of Borås, School of Engineering.
    Gällstedt, Mikael
    Hedenqvist, Mikael S.
    Effects of glycerol content and film thickness on the properties of vital wheat gluten films cast at pH 4 and 112010In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 117, no 6, p. 3506-3514Article in journal (Refereed)
    Abstract [en]

    This study deals with the optical properties and plasticizer migration properties of vital wheat gluten (WG) films cast at pH 4 and 11. The films contained initially 8, 16, and 25 wt.% glycerol and were aged at 23 °C and 50% relative humidity for at least 17 weeks on a paper support to simulate a situation where a paper packaging is laminated with an oxygen barrier film of WG. The films, having target thicknesses of 50 and 250 μm, were characterized visually and with ultraviolet/visible and infrared spectroscopy; the mass loss was measured by gravimetry or by a glycerol-specific gas chromatography method. The thin films produced at pH 4 were, in general, more heterogeneous than those produced at pH 11. The thin pH 4 films consisted of transparent regions surrounding beige glycerol-rich regions, the former probably rich in gliadin and the latter rich in glutenin. This, together with less Maillard browning, meant that the thin pH 4 films, in contrast to the more homogeneous (beige) thin pH 11 films, showed good contact clarity. The variations in glycerol content did not significantly change the optical properties of the films. All the films showed a significant loss of glycerol to the paper support but, after almost 9 months, the thick pH 11 film containing initially 25 wt.% glycerol was still very flexible and, despite a better contact to the paper, had a higher residual glycerol content than the pH 4 film, which was also more brittle.

  • 22.
    Cho, Sung-Woo
    et al.
    University of Borås, School of Engineering.
    Gällstedt, Mikael
    Hedenqvist, Mikael S.
    Properties of Wheat Gluten/Poly(lactic acid) Laminates2010In: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 58, no 12, p. 7344-7350Article in journal (Refereed)
    Abstract [en]

    Laminates of compression-molded glycerol-plasticized wheat gluten (WG) films surrounded and supported by poly(lactic acid) (PLA) films have been produced and characterized. The objective was to obtain a fully renewable high gas barrier film with sufficient mechanical integrity to function in, for example, extrusioncoating paper/board applications. It was shown that the lamination made it possible to make films with a broad range of glycerol contents (0-30 wt.%) with greater strength than single unsupported WG films. The low plasticizer contents yielded laminates with very good oxygen barrier properties. In addition, whereas the unsupported WG films had an immeasurably high water vapor transmission rate (WVTR), the laminate showed values that were finite and surprisingly, in several cases, also lower than that of PLA. Besides being a mechanical support (as evidenced by bending and tensile data) and a shield between the WG and surrounding moisture, the PLA layer also prevented the loss of the glycerol plasticizer from the WG layer. This was observed after the laminate had been aged on an “absorbing” blotting paper for up to 17 weeks. The interlayer adhesion (peel strength) decreased with decreasing glycerol content and increasing WG film molding temperature (130 °C instead of 110 °C). The latter effect was probably due to a higher protein aggregation, as revealed by infrared spectroscopy. The lamination temperature (110-140 °C) did not, however, have a major effect on the final peel strength.

  • 23.
    Cho, Sung-Woo
    et al.
    University of Borås, School of Engineering.
    Gällstedt, Mikael
    Johansson, Eva
    Hedenqvist, Mikael S.
    Injection-molded nanocomposites and materials based on wheat gluten2011In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 48, no 1, p. 146-152Article in journal (Refereed)
    Abstract [en]

    This is, to our knowledge, the first study of the injection molding of materials where wheat gluten (WG) is the main component. In addition to a plasticizer (glycerol), 5 wt.% natural montmorillonite clay was added. X-ray indicated intercalated clay and transmission electron microscopy indicated locally good clay platelet dispersion. Prior to feeding into the injection molder, the material was first compression molded into plates and pelletized. The filling of the circular mold via the central gate was characterized by a divergent flow yielding, in general, a stronger and stiffer material in the circumferential direction. It was observed that 20–30 wt.% glycerol yielded the best combination of processability and mechanical properties. The clay yielded improved processability, plate homogeneity and tensile stiffness. IR spectroscopy and protein solubility indicated that the injection molding process yielded a highly aggregated structure. The overall conclusion was that injection molding is a very promising method for producing WG objects.

  • 24.
    Cho, Sung-Woo
    et al.
    University of Borås, School of Engineering.
    Gällstedt, Mikael
    Ullsten, Henrik
    Wretfors, Christer
    Johansson, Eva
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Hedenqvist, Mikael S.
    Protein-based bioplastics and nanocomposites from a processing perspective2010Conference paper (Other academic)
  • 25.
    Cho, Sung-Woo
    et al.
    University of Borås, School of Engineering.
    Persson, Maria
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Melt spun fibres of poly(lactic acid) and hydroxyapatite nanoparticles for use as tissue engineering scaffolds2011Conference paper (Refereed)
  • 26.
    Cho, Sung-Woo
    et al.
    University of Borås, School of Engineering.
    Persson, Maria
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Three dimensional woven bone tissue engineering scaffolds of melt-spun poly(lactic acid) fibres2011Conference paper (Refereed)
  • 27. Cho, Sung-Woo
    et al.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Hemanathan, Kumar
    Mahimaisenan, Pirabasenan
    Adekunle, Kayode
    University of Borås, School of Engineering.
    Regenerated cellulose fibre reinforced casein films: Effect of plasticizer and fibres on the film properties2014In: Macromolecular Research, ISSN 1598-5032, E-ISSN 2092-7673, Vol. 22, no 7, p. 701-709Article in journal (Refereed)
    Abstract [en]

    The idea of using man-made cellulosic fibres as reinforcement for casein films in this study was inspired by their well defined fibre diameter and availability in large quantity, eventually leading to a homogeneous high quality composite at low cost. The casein biofilms were fabricated by solution casting from an aqueous alkaline solution of the bovine milk protein casein in the presence of glycerol as a plasticizer, and the fibre-reinforced biocomposites were prepared by the addition of regenerated cellulose fibre to the casein casting solution with various amounts of glycerol. The effects of glycerol content and cellulose fibre reinforcements on the mechanical, thermal and physiological properties were characterized. The results showed that increasing glycerol content decreased the film strength, Young’s modulus and thermal stability with a gradual increase in the elongation. However, the tensile properties were noticeably improved when reinforced with cellulose fibre. The composite with 20 wt% glycerol and 20 wt% cellulose fibre showed the maximum tensile strength of 23.5 MPa and Young’s modulus of 1.5 GPa. The corresponding values for the composite with 30 wt% glycerol and the same fibre content were 15.1 MPa and 0.9 GPa, which were 2.3- and 3.2-fold higher compared to 30 wt% glycerol plasticized film. The thermal analysis revealed that the glass transition temperature and the thermal stability were decreased when the glycerol content was increased. Addition of cellulose fibres increased the glass transition temperature as well as the thermal stability. The gel electrophoresis (SDS-PAGE) analysis indicated that there was no significant decrease in the molecular weight of the casein protein during sample preparation. Scanning electron microscopy showed that the obtained composites with low glycerol content had adequate interfacial bonding, and Fourier transform IR spectroscopy confirmed the formation of molecular interactions between the cellulose fibres and the casein.

  • 28. Damadzadeh, B
    et al.
    Jabari, H
    Airola, Karri
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Effect of level of ceramic nanofillers on the mechanical and thermal behaviour of PLA and PLGA composite materials for medical implants2009Conference paper (Other academic)
  • 29. Damadzadeh, B.
    et al.
    Jabari, H.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Airola, K.
    Moritz, N.
    Vallittu, P.
    Effect of ceramic filler content on the mechanical and thermal behaviour of poly-L-lactic acid and poly-L-lactic-co-glycolic acid composites for medical applications2010In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 21, no 9, p. 2523-2531Article in journal (Refereed)
    Abstract [en]

    One main application of resorbable poly-Llactic acid (PLLA) and poly-L-lactic-co-glycolic acid (PLGA) based materials is in medical implants. In this study composites were made from PLLA and PLGA with hydroxyapatite (HAp) respective b-tricalcium phosphate (b-TCP) fillers. The filler content and particle size were varied, and the thermal properties as well as the mechanical strength of the composites were investigated. The composites were made by an extrusion compounding process giving 2–2.5 mm diameter sized profiles. The results verified that the thermal stability of the composites was reasonable during the optimized compounding conditions. Scanning electron microscopy revealed that the fillers were well dispersed in the polymer matrices. The mechanical properties were improved by the addition of the fillers. The optimum mechanical properties for the extruded profiles were obtained with the HAp fillers. The E-modulus was increased from 3.3 to 4.6 GPa by addition of filler particles (30 wt%) whereas the flexural strength was reduced from 133 to 106 MPa.

  • 30. Ding, Xiangyu
    et al.
    Liu, Hewen
    Shi, Wenfang
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Form-fill-seal methodology for controlled encapsulation of small silver particles in hyperbranched polygycidol2009In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 112, no 3, p. 1209-1214Article in journal (Refereed)
  • 31. Dural Erem, A.
    et al.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Demirpek, U.
    Özcan, G.
    The Antimicrobial Efficiency of Polyamide 6/Silver Nanocomposites2010Conference paper (Other academic)
  • 32. Engström, Jonas
    et al.
    Hagström, Bengt
    Centrifugal spinning of nanofiber webs: A parameter study of a novel spinning process2009In: Nordic Textile Journal, ISSN 1404-2487Article in journal (Other academic)
  • 33. Engström, Jonas
    et al.
    Thorvaldsson, Anna
    Hagström, Bengt
    Walkenström, Pernilla
    University of Borås, Swedish School of Textiles.
    Nanofibers: small fibers with big potential2009In: Nordic Textile Journal, ISSN 1404-2487Article in journal (Other academic)
  • 34.
    Erdtman, Edvin
    et al.
    Linköping Universitet.
    Bohlén, Martin
    University of Borås, Faculty of Textiles, Engineering and Business.
    Ahlström, Peter
    University of Borås, Faculty of Textiles, Engineering and Business.
    Gkourmpis, Thomas
    Borealis AB.
    Berlin, Mikael
    Tetra Pak Packaging Solutions AB.
    Andersson, Thorbjörn
    Tetra Pak Packaging Solutions AB.
    Bolton, Kim
    University of Borås, Faculty of Textiles, Engineering and Business.
    A molecular-level computational study of the diffusion and solubility of water and oxygen in carbonaceous polyethylene nanocomposites2016In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 54, p. 589-602Article in journal (Refereed)
    Abstract [en]

    Monte Carlo and molecular dynamics simulations were performed to investigate the effect on the solubility, diffusion, and permeability of water and oxygen when adding graphene or single-walled carbon nanotubes (SWCNTs) to polyethylene (PE). When compared with pure PE, addition of graphene lowered the solubility of water, whereas at lower temperatures, the oxygen solubility increased because of the oxygen–graphene interaction. Addition of SWCNTs lowered the solubility of both water and oxygen when compared with pure PE. A detailed analysis showed that an ordered structure of PE is induced near the additive surface, which leads to a decrease in the diffusion coefficient of both penetrants in this region. The addition of graphene does not change the permeation coefficient of oxygen (in the direction parallel to the filler) and, in fact, may even increase this coefficient when compared with pure PE. In contrast, the water permeability is decreased when graphene is added to PE. The addition of SWCNTs decreases the permeability of both penetrants. Graphene can consequently be added to selectively increase the solubility and permeation of oxygen over water, at least at lower temperatures. 

  • 35. Erem, Aysin
    et al.
    Ozcan, Gulay
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Cakmak, Mukerrem
    In vitro assesment of antimicrobial activity and characteristics of polyamide 6/silver nanocomposite fibers2013In: Fibers And Polymers, ISSN 1229-9197, E-ISSN 1875-0052, Vol. 14, no 9, p. 1415-1421Article in journal (Refereed)
    Abstract [en]

    In this study, the preparation method and characteristics of silver (Ag) nanoparticle (NP) loaded polyamide 6 (PA6) nanocomposite and its antimicrobial activity against Klebsiella pneumonia and Staphylococcus aureus were investigated. The melt intercalation method was used to prepare a series of PA 6 nanocomposite fibers containing, 0; 1; 3; 5 % (wt.) Ag. PA6/Ag nanocomposite fibers exhibit increased antimicrobial efficiency with the increase of nanoparticle contents. On the other hand, thermal characterization tests show that the increased concentration of Ag nanoparticles reduces the mechanical properties due to their partial agglomeration leading to flaw generation. The crystallinity of the fibers was found to decrease about 10 % with increase of Ag to 5 %. This was attributed to faster cooling rate experienced in the presence of high thermal conductivity Ag particles.

  • 36. Fatarella, Enrico
    et al.
    Mylläri, Ville
    Ruzzante, Marco
    Pogni, Rathish
    Baratto, Maria
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Syrjälä, Seppo
    Järvelä, Pentti
    Sulfonated polyetheretherketone/polypropylene polymer blends for the production of photoactive materials2014In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 132, no 8Article in journal (Refereed)
    Abstract [en]

    Sulfonated polyetheretherketone (SPEEK) was synthesized via a mono-substitution reaction of PEEK in concentrated sulphuric acid and was blended with polypropylene (PP) in 2–10%w/w concentration to be used for the production of photoactive thermoplastic products. SPEEK and SPEEK/PP blends were characterized using FTIR, DSC, TGA, NMR, rheology, SEM, and EPR. Under UV-Vis irradiation, stable benzophenone ketyl (BPK) radicals were generated by hydrogen extraction from PP. By increasing the amount of SPEEK in the polymer blend a linear increase in the BPK radicals was achieved according to the EPR data. DSC and TGA tests indicated weaknesses in the thermal stability of SPEEK but according to the rheological tests this should not have a major effect on processabililty. The optimal amount of SPEEK in the blend was obtained at 5%w/w. This concentration provided a good compromise between radical concentration, material processability, and cost

  • 37.
    Hatamvand, Mohammad
    et al.
    Department of Textile Engineering, Yazd University, Yazd, Iran.
    Mirjalili, Seyed Abbas
    Department of Textile Engineering, Yazd University, Yazd, Iran.
    Fattahi, Saeid
    Department of Textile Engineering, Yazd University, Yazd, Iran.
    Bashir, Tariq
    University of Borås, Faculty of Textiles, Engineering and Business.
    Skrifvars, Mikael
    University of Borås, Faculty of Textiles, Engineering and Business.
    OPTIMUM DRAFTING CONDITIONS OF POLYESTER AND VISCOSE BLEND YARNS2016In: AUTEX Research Journal, ISSN 1470-9589, E-ISSN 2300-0929Article in journal (Refereed)
    Abstract [en]

    In this study, we used an experimental design to investigate the influence of the total draft, break draft, distancebetween the aprons (Clips) and production roller pressure on yarn quality in order to obtain optimum draftingconditions for polyester and viscose (PES/CV) blend yarns in ring spinning frame. We used PES fibers (1.4 dtex ×38 mm long) and CV fibers (1.6 dtex × 38 mm long) to spin a 20 Tex blend yarn of PES (70%)/CV (30%) blend ratio.When the break draft, adjustment of distance between of aprons and roller pressure is not reasonable, controllingand leading of the fibers is not sufficient for proper orientation of the fibers in the yarn structure to produce a highquality yarn. Experimental results and statistical analysis show that the best yarn quality will be obtained underdrafting conditions total draft of 38, 1.2 break draft, 2.8 mm distance between of aprons and maximum pressure ofthe production top roller.

  • 38. Hooshmand, Saleh
    et al.
    Aitomäki, Yvonne
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Mathew, Ali
    Oksman, Kristiina
    All-cellulose nanocomposite fibers produced by melt spinning cellulose acetate butyrate and cellulose nanocrystals2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 4, p. 2665-2678Article in journal (Refereed)
    Abstract [en]

    Bio-based continuous fibers were prepared by melt spinning cellulose acetate butyrate (CAB), cellulose nanocrystals (CNC) and triethyl citrate. A CNC organo-gel dispersion technique was used and the prepared materials (2 and 10 wt% CNC) were melt spun using a twin-screw micro-compounder and drawn to a ratio of 1.5. The microscopy studies showed that the addition of CNC in CAB resulted in defect-free and smooth fiber surfaces. An addition of 10 wt% CNC enhanced the storage modulus and increased the tensile strength and Young’s modulus. Fiber drawing improved the mechanical properties further. In addition, a micromechanical model of the composite material was used to estimate the stiffness and showed that theoretical values were exceeded for the lower concentration of CNC but not reached for the higher concentration. In conclusion, this dispersion technique combined with melt spinning can be used to produce all-cellulose nanocomposites fibers and that both the increase in CNC volume fraction and the fiber drawing increased the mechanical performance.

  • 39. Hooshmand, Saleh
    et al.
    Cho, Sung-Woo
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Mathew, Ali
    Oksman, Kristiina
    Melt spun cellulose nanocomposite fibres: Comparison of two dispersion techniques2014In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 43, no 1, p. 15-24Article in journal (Refereed)
    Abstract [en]

    Biobased fibres of cellulose acetate butyrate (CAB) and cellulose nanocrystals (CNC) and triethyl citrate (TEC) as plasticiser were prepared by melt spinning. To obtain homogeneous dispersion of CNC, two different dispersion techniques were studied. In the first, the water content of the CNC suspension was reduced and exchanged to ethanol using centrifugation. In the second, the water in the CNC suspension was completely exchanged to ethanol by sol–gel process. Results showed that tensile modulus and tensile strength of the nanocomposite fibres produced with the first technique were lower than CAB–TEC fibres, but the fibres produced by the sol–gel process showed an increase in the tensile modulus and had no decrease in the strength. Optical microscopy of the fibres indicated a few aggregations on the sol–gel prepared materials. The results indicate that the sol–gel process is enhancing the dispersion of CNC and can be a suitable way to prepare nanocomposite fibres.

  • 40. Hooshmand, Saleh
    et al.
    Soroudi, Azadeh
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Electroconductive composite fibers by melt spinning of polypropylene/polyamide/carbon nanotubes2011In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 161, no 15-16, p. 1731-1737Article in journal (Refereed)
    Abstract [en]

    In this study, the blends of polypropylene/polyamide with carbon nanotubes (CNTs) have been prepared and melt spun to as-spun and drawn fibers. Thermal analysis showed that increasing the polyamide content, decreased the degree of crystallinity in the blends. Characterization of fibers showed that both conductivity and tensile strength have been improved by increasing the amount of polyamide in the blends as well as the melt blending temperature; furthermore, the morphology, electrical and mechanical properties of the blends were significantly influenced by adding 1 phr compatibilizer to the blend. The comparison between as-spun fibers and drawn fibers proved that although mechanical properties were improved after drawing, the electrical conductivity was decreased from the order of E−02 to E−06 (S/cm), due to applied draw-ratio of three.

  • 41. Hooshmand, Saleh
    et al.
    Soroudi, Azadeh
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Preparation of conductive composite fibers made from polypropylene, polyamide and multi-walled carbon nanotubes: electrical, mechanical and thermal characteristics2011Conference paper (Refereed)
  • 42. Johansson, Eva
    et al.
    Newson, William
    Blomfeldt, Thomas
    Türe, Hasan
    Rasheed, F.
    Cho, Sung-Woo
    University of Borås, School of Engineering.
    Hedenqvist, Mikael
    Johansson, Therese
    Gällstedt, Mikael
    Kuktaite, Ramune
    Use of plant protein for materials production2011Conference paper (Other academic)
  • 43.
    Kalantar Mehrjerdi, Adib
    et al.
    University of Borås, School of Engineering.
    Adl-Zarrabi, Bijan
    Cho, Sung-Woo
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Mechanical and thermo-physical properties of high-density polyethylene modified with talc2013In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 129, no 4, p. 2128-2138Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to examine the physical, mechanical, and thermo-physical properties of high-density polyethylene (HDPE) modified with talc. Different weight fractions of talc (up to 35 wt %) were compounded with an HDPE matrix containing 2.5 wt % of carbon black (CB) in a twin-screw compounder. The composites were then processed by injection moulding to obtain specimens for testing. The results indicate that CB causes a significant decrease in the toughness, while talc not only enhances the thermal conductivity and thermo-physical properties of the composites but can also play a role in compensating for the negative effects of CB on impact resistance. The experimental data show that the presence of CB reduces the impact resistance of HDPE by up to 34%, while addition of up to 8 wt % talc can return this value to close to that of pure HDPE. No significant effect on the composite tensile yield and fracture strength was observed for either component at all concentrations. The thermal conductivity, thermal diffusivity, and specific density values of the composites increased almost linearly, but the increase in moisture absorption in the long term showed nonlinear behavior in the concentration range of the experiment.

  • 44.
    Kalantar Mehrjerdi, Adib
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Mechanical and morphological properties of talc filled high density polyethylene2013Conference paper (Other academic)
  • 45. Krishnaprasad, R
    et al.
    Veena, N.R.
    Maria, H.J.
    Rajan, R
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Joseph, K
    Mechanical and thermal properties of bamboo microfibril reinforced polyhydroxybutyrate biocomposites2009In: Journal of environmental polymer degradation, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 17, no 2, p. 109-114Article in journal (Refereed)
    Abstract [en]

    In the present investigation, microfibrils were extracted from raw bamboo and characterized using scanning electron microscope. Composites based on polyhydroxybutyrate (PHB) and bamboo microfibril were prepared with various microfibril loading. The mechanical and thermal properties of the resulting composites were measured. Tensile strength and impact strength of the composites were found to be increasing with increase in the loading of bamboo microfibrils, reached an optimum and thereafter decreased with further increase in microfibril loading. Percentage crystallinity was found to be increasing with increase in fibril loading. Thermal stability of the composite was higher than that of pure PHB. The composite could be developed further for various structural applications.

  • 46. Kumar, Hemanathan
    et al.
    Mahimaisenan, Pirabasenan
    Cho, Sung-Woo
    University of Borås, School of Engineering.
    Adekunle, Kayode
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Casein films and its composites with regenerated cellulose fibre for packaging applications2011Conference paper (Other academic)
    Abstract [en]

    A novel approach in the production of protein based films and composites were performed, using the bovine milk protein casein and regenerated cellulose fibres (lyocell). The films were prepared by first dissolving the casein protein in an aqueous alkaline solution in the presence of glycerol as a plasticizer. Further the composite films were prepared by the addition of fibres on aqueous alkaline solution with casein. The casein films and composites were thereafter prepared by casting the solution mixture on Teflon coated glass plate and drying for 48 hr. The effects of glycerol content and lyocell fibre reinforcements on the mechanical, thermal and physiological properties of the casein films were characterized. The results revealed that the increase in the addition of glycerol content decreases the tensile strength, young’s modulus, thermal stability of the film and increases the elongation percentage. Tensile property and thermal stability of the films was improved by the increase in the addition of the fibre content with a gradual decrease in the elongation percentage. The casein film made of 20% glycerol and 20% fibre content showed the maximum tensile strength of 23.5 MPa, E-modulus of 1.5 GPa and glass transition temperature (Tg) of 67.1±1.5 ºC. The sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that there was no significant change in the molecular weight of the protein during sample preparation. The inter molecular networks have taken place in the casein films and composites, when analyzed under Fourier Transform Infrared Spectroscopy (FTIR), and proper bonding between fibres and protein was observed by scanning electron microscope (SEM).

  • 47. Naseri, Atefeh
    et al.
    Naseri, Narges
    Airola, Karri
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Microscale Compounding of Polycaprolactone with Hydroxyapatite,β-Tricalcium Phosphate and Bioactive Glass for Biomedical Implant Applications2010Conference paper (Other academic)
  • 48. Olabarrieta, Idoia
    et al.
    Cho, Sung-Woo
    University of Borås, School of Engineering.
    Gällstedt, Mikael
    Sarasua, Jose-Ramon
    Johansson, Eva
    Hedenqvist, Mikael S.
    Aging properties of films of plasticized vital wheat gluten cast from acidic and basic solutions2006In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 7, no 5, p. 1657-1664Article in journal (Refereed)
    Abstract [en]

    In order to understand the mechanisms behind the undesired aging of films based on vital wheat gluten plasticized with glycerol, films cast from water/ethanol solutions were investigated. The effect of pH was studied by casting from solutions at pH 4 and pH 11. The films were aged for 120 days at 50% relative humidity and 23 °C, and the tensile properties and oxygen and water vapor permeabilities were measured as a function of aging time. The changes in the protein structure were determined by infrared spectroscopy and size-exclusion and reverse-phase high-performance liquid chromatography, and the film structure was revealed by optical and scanning electron microscopy. The pH 11 film was mechanically more stable with time than the pH 4 film, the latter being initially very ductile but turning brittle toward the end of the aging period. The protein solubility and infrared spectroscopy measurements indicated that the protein structure of the pH 4 film was initially significantly less polymerized/aggregated than that of the pH 11 film. The polymerization of the pH 4 film increased during storage but it did not reach the degree of aggregation of the pH 11 film. Reverse-phase chromatography indicated that the pH 11 films were to some extent deamidated and that this increased with aging. At the same time a large fraction of the aged pH 11 film was unaffected by reducing agents, suggesting that a time-induced isopeptide cross-linking had occurred. This isopeptide formation did not, however, change the overall degree of aggregation and consequently the mechanical properties of the film. During aging, the pH 4 films lost more mass than the pH 11 films mainly due to migration of glycerol but also due to some loss of volatile mass. Scanning electron and optical microscopy showed that the pH 11 film was more uniform in thickness and that the film structure was more homogeneous than that of the pH 4 film. The oxygen permeability was also lower for the pH 11 film. The fact that the pH 4 film experienced a larger and more rapid change in its mechanical properties with time than the pH 11 film, as a consequence of a greater loss of plasticizer, was presumably due to its initial lower degree of protein aggregation/ polymerization. Consequently, the cross-link density achieved at pH 4 was too low to effectively retain volatiles and glycerol within the matrix.

  • 49. Persson, Maria
    et al.
    Berglin, Lena
    University of Borås, Swedish School of Textiles.
    Finnilä, Mikko
    Cho, Sung-Woo
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Tuukkanen, Juha
    3D Woven Scaffolds of Melt-spun PLA Composite Fibres for Bone Regeneration2013Conference paper (Other academic)
    Abstract [en]

    Fibres are the basic units of textiles and are desirable as scaffold matrix material since they provide a large surface area to volume ratio. Using the textile technology, fibres can also be processed to form a variety of shapes and sizes, thus be used in different biological and medical applications. Poly(lactic acid) is a widely investigated material for use as scaffold matrix material and may be transformed into fibres either by melt spinning or solution spinning [1]. However, its lack of cell recognition signal has limited its use in tissue engineering applications [2]. Hydroxyapatite (HA) particles, which mimics the natural bone mineral has been proven to stimulate and promote cell attachment [3]. From that point of view, the aim of this study was to produce a PLA/HA composite fibres that could be used in a 3D woven scaffold for bone regeneration.

  • 50.
    Persson, Maria
    et al.
    University of Borås, School of Engineering.
    Cho, Sung-Woo
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Woven Scaffolds of Melt-Spun Poly(lactic acid) Fibres for Bone Tissue Engineering2011Conference paper (Other academic)
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