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  • 1. Adekunle, Kayode
    et al.
    Cho, Sung-Woo
    Patzelt, Christian
    Blomfeldt, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Skrifvars, Mikael
    Impact and flexural properties of flax fabrics and Lyocell fiber-reinforced bio-based thermoset2011In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 30, no 8, p. 685-697Article in journal (Refereed)
    Abstract [en]

    A bio-based thermoset resin was reinforced with flax fabrics and Lyocell fiber. The effect of different weave architectures was studied with four flax fabrics with different architectures: plain, twill (two different types), and dobby. The effect of the outer ply thickness was studied and characterized with flexural and impact testing. Composites manufactured with plain weave reinforcement had the best mechanical properties. The tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength were 280MPa, 32GPa, 250MPa, 25GPa, and 75 kJ/m (2), respectively. Reinforcements with twill-weave architecture did not impart appreciable flexural strength or flexural modulus even when the outer thickness was increased. Plain- and dobby (basket woven style)-weave architectures gave better reinforcing effects and the flexural properties increased with an increase in outer thickness. Water absorption properties of the composites were studied and it was observed that the hybridization with Lyocell fiber reduced the water uptake. Field-emission scanning electron microscopy was used to study the micro-structural properties of the composites.

  • 2.
    Akhlaghi, Shahin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. Scania CV AB, Sweden.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Brana, Maria T. Conde
    Bellander, Martin
    Deterioration of automotive rubbers in liquid biofuels: A review2015In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 43, p. 1238-1248Article, review/survey (Refereed)
    Abstract [en]

    Concerns over the fast depletion of fossil fuels, environmental issues and stringent legislation associated with petroleum-based fuels have triggered a shift to bio-based fuels, as an alternative to meet the growing energy demand in the transportation sector. However, since conventional automobile fuel systems are adapted to petroleum-based fuels, switching to biofuels causes a severe deterioration in the performance of currently used rubber components. The degradation of the rubber materials in biofuels is complicated by the presence of different additives in biofuels and rubber compounds, by oxidation of biofuels and by the effects of thermomechanical loadings in the engine. This paper presents a comprehensive review of the effects of different types of biofuels, particularly biodiesel and bioethanol, on the physical, mechanical, morphological and thermal properties of elastomers under different exposure conditions. In addition, the literature data available on the variation of rubbers' resistance to biofuels with the changes in their monomer type and composition, cure system and additives content was also studied. The review essentially focuses on the compatibility of biofuels with acrylonitrile butadiene rubber, fluoroelastomers, polychloroprene rubber and silicon rubber, as the most commonly used automotive rubbers coming into contact with fuels during their service. The knowledge summarized in this study can help to develop a guideline on the selection of rubber for automotive parts designed to withstand biofuels.

  • 3.
    Akhlaghi, Shahin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Sjöstedt, C.
    Bellander, M.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Degradation of carbon-black-filled acrylonitrile butadiene rubber in alternative fuels: Transesterified and hydrotreated vegetable oils2016In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 123, p. 69-79Article in journal (Refereed)
    Abstract [en]

    The deterioration of acrylonitrile butadiene rubber (NBR), a common sealing material in automobile fuel systems, when exposed to rapeseed biodiesel and hydrotreated vegetable oil (HVO) was studied. The fuel sorption was hindered in HVO-exposed rubber by the steric constraints of bulky HVO molecules, but it was promoted in biodiesel-exposed rubber by fuel-driven cavitation in the NBR and by the increase in diffusivity of biodiesel after oxidation. The absence of a tan δ peak of the bound rubber and the appearance of carbon black particles devoid of rubber suggested that the cavitation was made possible in biodiesel-aged rubber by the detachment of bound rubber from particle surfaces. The HVO-exposed NBR showed a small decrease in strain-at-break due to the migration of plasticizer from the rubber, and a small increase in the Young’s modulus due to oxidative crosslinking. A drastic decrease in extensibility and Payne-effect amplitude of NBR on exposure to biodiesel was explained as being due to the damage caused by biodiesel to the continuous network of bound rubber-carbon black. A decrease in the ZnO crystal size with increasing exposure time suggested that the particles are gradually dissolved in the acidic components of oxidized biodiesel. The Zn2+ cations released from the dissolution of ZnO particles in biodiesel promoted the hydrolysis of the nitrile groups of NBR.

  • 4.
    Alipour, Nazanin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Structure and Mechanical/Transport properties of Single and Multilayer Polyethylene-based Materials2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The current study discusses the structure, mechanical and transport properties of polyethylene-based materials into two parts. The first part deals with the migration and chemical depletion of active substance such as insecticides from moulded polyethylene sheets. Deltamethrin (DM) and synergist piperonyl butoxide (PBO) are often used for insect control purpose. It was found that DM as a powder was incapable of recrystallization and remained in liquid state after cooling to room temperature, and that the evaporation of a DM/PBO solution was greater than that predicted from the evaporation rates of pristine separate material components. Infrared spectroscopy and liquid chromatography showed that the loss of DM and PBO through polyethylene sheets was negligible over 30 days, when aged in air at 80 °C (60 and 80 %RH). However, significant migration of the active species was observed in aged polyethylene sheets which were exposed in liquid water (at 80 and 95 °C). In the second part, the structure and properties of multi–layered polymer films were studied in terms of crystallization kinetics, mechanical and transport properties. Previously, it has been shown that when the layer thickness decreases from micrometre-scale to nanometre-scale, leading to improvement of the film performance such as crack propagation and oxygen barrier properties. In this work, two multi-layered systems were considered based on compatible (i) or incompatible layers (ii). In the first case (i), metallocene polyethylene (mPE) and low-density polyethylene (LDPE) where investigated as 2, 24, and 288 adjacent layers. In the second case (ii) poly(ethylene-co-vinyl alcohol) (EVOH) and polyethylene adhesive was evaluated as 5 and 19 layers. The crystallization kinetic studies showed that the crystallization rate was retarded as the layers became thinner with increasing number of layers in the multi-layered films as compared to the reference films (2 and 5 layers). The observation was suggested to stem from greater association between layers (inter layer mixing) in the case of mPE/LDPE films with 2 layers. Furthermore, the crack growth resistance increased with increasing number of layers. The x-ray scattering and tensile testing showed that the films were orientated more in extrusion direction than in the transverse direction, besides the EVOH films (the incompatible system) showed higher orientation in the extrusion direction than mPE/LDPE films. The uptake of n-hexane was reduced significantly in multi-layered EVOH films due to the effective protective role of EVOH. Furthermore, it was revealed that non-homogenous swelling causing a folding/curling of bilayer films when exposed to the vapour of the solvent.

  • 5.
    Alipour, Nazanin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Yu, Shun
    Roth, Stephan
    Brüning, Karsten
    Vieyres, Arnaud
    Schneider, Konrad
    Structure and properties of polyethylene-based and EVOH-based multilayered films with layer thicknesses of 150 nm and greater2015In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 64, p. 36-51Article in journal (Refereed)
    Abstract [en]

    This paper presents the structure and properties of two multilayered systems where polymers in adjacent layers were either miscible or immiscible. The miscible system consisted of 2, 17, 18, 24 and nominally 288 layers of alternating low-density (LDPE) and low-density/linear-low density (mPE) polyethylene layers with observed thicknesses ranging from 150 nm to 20 urn. The immiscible system consisted of 5 and 19 layer films with a combination of poly(ethylene-co-vinyl alcohol) (EVOH) (thickness: 9 and 1 gm, respectively), LDPE (17 and 7 gm) and a polyethylene adhesive (3 and 1 gm). The purpose of the multi-layering was to increase the crack growth resistance and, in the EVOH-based system, to decrease the oxygen transmission rate. Indeed, the crack growth resistance, as measured on tensile-tested notched films, increased with increasing number of layers. The thinnest polyethylene and polyethylene adhesive layers showed a clear ductile failure when fractured even in liquid nitrogen. Simultaneous synchrotron wide-angle/small-angle X-ray scattering and tensile testing indicated no new deformation features with changes in the layer thickness. The oxygen permeability was the same in the 5- and 19-layer EVOH-based films, but the uptake of n-hexane was strongly reduced in the 19-layer films, demonstrating the effective protective role of the EVOH layers. The n-hexane desorption data of the 2-layer LDPE/mPE film was successfully modeled using the diffusivities and solubilities of the single layers. Crystallization was slower and more confined in the films with thinner layers. The interlayer mixing in the melt (measured by isothermal crystallization from melts of initially layered polyethylene-based systems) was, as expected, significantly faster in the 24- and 288-multilayer films than in the 2-layer film.

  • 6. Amanizadeh, Farhad
    et al.
    Akhlaghi, Shahin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Mobarakeh, Hamid Salehi
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Starve fed emulsion copolymerization of vinyl acetate and 1-hexene at ambient pressure2014In: Polymer international, ISSN 0959-8103, E-ISSN 1097-0126, Vol. 63, no 10, p. 1850-1855Article in journal (Refereed)
    Abstract [en]

    A novel emulsion copolymer of vinyl acetate (VAc) and 1-hexene was synthesized at ambient pressure. The feeding technique, initiation system and reaction time of the copolymerization were optimized based on molecular characteristics such as the weight contribution of 1-hexene in the copolymer chains and glass transition temperature (T-g) as well as on bulk properties like minimum film-formation temperature (MFFT) and solid content. According to nuclear magnetic resonance spectroscopy and differential scanning calorimetry results, the combination of starve feeding and redox initiation, within a reaction time of 4h, effectively led to the copolymerization at ambient pressure between highly reactive polar VAc monomers and non-polar 1-hexene monomers of low reactivity. The copolymer showed a lower T-g and MFFT, and a reasonable solid content compared to the poly(vinyl acetate) (PVAc) homopolymer. The consumption rate, hydrolysis of acetate groups and chain transfer reactions during the polymerization were followed using infrared spectroscopy. Based on the results, the undesirable reactions between the VAc blocks were hindered by the neighbouring 1-hexene molecules. Tensile testing revealed an improvement in the toughness and elongation at break of VAc-1-hexene films compared to PVAc films.

  • 7.
    Andersson, Richard L.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Mallon, Peter E.
    Salajkova, Michaela
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Micromechanics of toughness improved electrospun PMMA fibers with embedded cellulose as tested under in-situ microscopyManuscript (preprint) (Other academic)
  • 8.
    Andersson, Richard L.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Salajkova, Michaela
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mallon, P. E.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Micromechanical Tensile Testing of Cellulose-Reinforced Electrospun Fibers Using a Template Transfer Method (TTM)2012In: Journal of polymers and the environment, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 20, no 4, p. 967-975Article in journal (Refereed)
    Abstract [en]

    A template transfer method (TTM) and a fiber fixation technique were established for fiber handling and micro tensile stage mounting of aligned and non-aligned electrospun fiber mats. The custom-made template had been precut to be mounted on a variety of collectors, including a rapidly rotating collector used to align the fibers. The method eliminated need for direct physical interaction with the fiber mats before or during the tensile testing since the fiber mats were never directly clamped or removed from the original substrate. By using the TTM it was possible to measure the tensile properties of aligned poly(methyl methacrylate) (PMMA) fiber mats, which showed a 250 % increase in strength and 450 % increase in modulus as compared to a non-aligned system. The method was further evaluated for aligned PMMA fibers reinforced with cellulose (4 wt%) prepared as enzymatically derived nanofibrillated cellulose (NFC). These fibers showed an additional increase of 30 % in both tensile strength and modulus, resulting in a toughness increase of 25 %. The fracture interfaces of the PMMA-NFC fibers showed a low amount of NFC pull-outs, indicating favorable phase compatibility. The presented fiber handling technique is universal and may be applied where conservative estimates of mechanical properties need to be assessed for very thin fibers.

  • 9.
    Andersson, Richard
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Cabedo, L.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Superparamagnetic [sic] nanofibers by electrospinning2016In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 26, p. 21413-21422Article in journal (Refereed)
    Abstract [en]

    The preparation of superparamagnetic thin fibers by electrospinning dispersions of nanosized magnetite (Fe3O4, SPIO/USPIO) in a PMMA/PEO polymer solution is reported. The saturation magnetization and coercivity were not affected by the concentration (0, 1, 10, 20 wt%) or fiber orientation, showing hysteresis loops with high magnetization (64 A m(2) kg(-1) @ 500 kA m(-1)) and record low coercivity (20 A m(-1)). AC susceptibility measurements vs. temperature at frequencies from 60 to 2 kHz confirmed superparamagnetism. The mechanical properties were only slightly dependent on the particle concentration because the nanoparticles were separately encapsulated by the polymer. A uniform fibre fracture cross section was found at all the investigated particle contents, which suggests a strong interaction at the polymer/particle interface. A theoretical value of the magnetic low field susceptibility was calculated from the Langevin function and compared with measured values. The results show a distinct but concentration-independent anisotropy, favoring magnetization along the fiber orientation with no sign of exchange interaction, explained by complete nanoparticle separation. Superparamagnetism cannot be inferred from particle size alone, so a relevant interpretation and criterion for superparamagnetism is presented, in accordance with Neel's original definition. From the measurements, it can be concluded that magnetic characterization can be used to elucidate the material morphology beyond the resolution of available microscopy techniques (TEM and SEM).

  • 10.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Micromechanical, Antimicrobial and Filtration Properties of Electrospun Fiber Mats2014Doctoral thesis, comprehensive summary (Other academic)
  • 11.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Structural properties and micromechanics of PMMA-based electrospun hybrid fibers2013Licentiate thesis, comprehensive summary (Other academic)
  • 12.
    Andersson, Richard L.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Martinez-Abad, Antonio
    Lagaron, Jose M.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Mallon, Peter E.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Antibacterial Properties of Tough and Strong Electrospun PMMA/PEO Fiber Mats Filled with Lanasol-A Naturally Occurring Brominated Substance2014In: International Journal of Molecular Sciences, ISSN 1422-0067, E-ISSN 1422-0067, Vol. 15, no 9, p. 15912-15923Article in journal (Refereed)
    Abstract [en]

    A new type of antimicrobial, biocompatible and toughness enhanced ultra-thin fiber mats for biomedical applications is presented. The tough and porous fiber mats were obtained by electrospinning solution-blended poly (methyl methacrylate) (PMMA) and polyethylene oxide (PEO), filled with up to 25 wt % of Lanasol-a naturally occurring brominated cyclic compound that can be extracted from red sea algae. Antibacterial effectiveness was tested following the industrial Standard JIS L 1902 and under agitated medium (ASTM E2149). Even at the lowest concentrations of Lanasol, 4 wt %, a significant bactericidal effect was seen with a 4-log (99.99%) reduction in bacterial viability against S. aureus, which is one of the leading causes of hospital-acquired (nosocomial) infections in the world. The mechanical fiber toughness was insignificantly altered up to the maximum Lanasol concentration tested, and was for all fiber mats orders of magnitudes higher than electrospun fibers based on solely PMMA. This antimicrobial fiber system, relying on a dissolved antimicrobial agent (demonstrated by X-ray diffraction and Infrared (IR)-spectroscopy) rather than a dispersed and "mixed-in" solid antibacterial particle phase, presents a new concept which opens the door to tougher, stronger and more ductile antimicrobial fibers.

  • 13.
    Andersson, Richard L.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Mallon, Peter E.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Micromechanics of ultra-toughened electrospun PMMA/PEO fibres as revealed by in-situ tensile testing in an electron microscope2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, p. 6335-Article in journal (Refereed)
    Abstract [en]

    A missing cornerstone in the development of tough micro/nano fibre systems is an understanding of the fibre failure mechanisms, which stems from the limitation in observing the fracture of objects with dimensions one hundredth of the width of a hair strand. Tensile testing in the electron microscope is herein adopted to reveal the fracture behaviour of a novel type of toughened electrospun poly(methyl methacrylate)/poly(ethylene oxide) fibre mats for biomedical applications. These fibres showed a toughness more than two orders of magnitude greater than that of pristine PMMA fibres. The in-situ microscopy revealed that the toughness were not only dependent on the initial molecular alignment after spinning, but also on the polymer formulation that could promote further molecular orientation during the formation of micro/nano-necking. The true fibre strength was greater than 150 MPa, which was considerably higher than that of the unmodified PMMA (17 MPa). This necking phenomenon was prohibited by high aspect ratio cellulose nanocrystal fillers in the ultra-tough fibres, leading to a decrease in toughness by more than one order of magnitude. The reported necking mechanism may have broad implications also within more traditional melt-spinning research.

  • 14. Arabasadi, Z.
    et al.
    Khorasani, M.
    Akhlaghi, Shahin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Fazilat, H.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Shiri, M. E.
    Prediction and optimization of fireproofing properties of intumescent flame retardant coatings using artificial intelligence techniques2013In: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 61, p. 193-199Article in journal (Refereed)
    Abstract [en]

    A multi-structured architecture of artificial intelligence techniques including artificial neural network (ANN), adaptive neuro-fuzzy-inference-system (ANFIS) and genetic algorithm (GA) were developed to predict and optimize the fireproofing properties of a model intumescent flame retardant coating including ammonium polyphosphate, pentaerythritol, melamine, thermoplastic acrylic resin and liquid hydrocarbon resin. By implementing ANN on heat insulation results of coating samples, prepared based on a L16 orthogonal array, mean fireproofing time (MFPT) values were properly predicted. The predicted data were then proved to be valid through performing closeness examinations on fuzzy inference systems results regarding their experimental counterparts. However, the possible deviations tapped into phenomena like foam detachment and char cracking were alleviated by ANFIS modeling embedded with pertinent fuzzy rules based on the sole and associative practical role of used additives. The contribution of each intumescent coating component on the formulation with optimized fireproofing behavior was then explored using GA modeling. A similar optimization procedure was also conducted using conventional Taguchi experimental design but the GA based optimized intumescent coating was found to exhibit higher MFPT value than that suggested by the Taguchi method.

  • 15.
    Atari Jabarzadeh, Sevil
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Prevention of Biofilm Formation on Silicone Rubber Materials for Outdoor High Voltage Insulators2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Microbial colonization on the surface of silicone rubber high voltage outdoor insulators often results in the formation of highly hydrated biofilm that influence the surface properties, such as surface hydrophobicity. The loss of hydrophobicity might lead to dry band formation, and, in the worst cases, flashover and failure of the insulator.

    In this work, the biocidal effects of various antimicrobial compounds in silicone rubber materials were determined. These materials were evaluated according to an ISO standard for the antimicrobial activity against the growth of aggressive fungal strains, and microorganisms that have been found colonizing the surfaces of outdoor insulators in several areas in the world. Several compounds suppressed microbial growth on the surfaces of the materials without compromising the material properties of the silicone rubber. A commercial biocide and thymol were very effective against fungal growth, and sodium benzoate could suppress the fungal growth to some extent. Thymol could also inhibit algal growth. However, methods for preservation of the antimicrobial agents in the bulk of the material need to be further developed to prevent the loss of the compounds during manufacturing. Biofilm formation affected the surface hydrophobicity and complete removal of the biofilm was not achieved through cleaning. Surface analysis confirmed that traces of microorganisms were still present after cleaning.

    Further, surface modification of the silicone rubber was carried out to study how the texture and roughness of the surface affect biofilm formation. Silicone rubber surfaces with regular geometrical patterns were evaluated to determine the influence of the surface texture on the extent of microbial growth in comparison with plane silicone rubber surfaces. Silicone rubber nanocomposite surfaces, prepared using a spray-deposition method that applied hydrophilic and hydrophobic nanoparticles to obtain hierarchical structures, were studied to determine the effects of the surface roughness and improved hydrophobicity on the microbial attachment. Microenvironment chambers were used for the determination of microbial growth on different modified surfaces under conditions that mimic those of the insulators in their outdoor environments. Different parts of the insulators were represented by placing the samples vertically and inclined. The microbial growth on the surfaces of the textured samples was evenly distributed throughout the surfaces because of the uniform distribution of the water between the gaps of the regular structures on the surfaces. Microbial growth was not observed on the inclined and vertical nanocomposite surfaces due to the higher surface roughness and improved surface hydrophobicity, whereas non-coated samples were colonized by microorganisms.

  • 16.
    Atari Jabarzadeh, Sevil
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Mendoza Álvarez, Ana Isabel
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hillborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. ABB, Corporated Resarch, Sweden.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. Univ Skovde, S-54128 Skovde, Sweden.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Design of nanocomposite surfaces with antibiofouling properties for outdoor insulation applicationsManuscript (preprint) (Other academic)
  • 17.
    Atari Jabarzadeh, Sevil
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. ABB, Corp Res, S-72178 Vasteras, Sweden.
    Hillborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. ABB, Corp Res, S-72178 Vasteras, Sweden.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. Univ Skovde, S-54128 Skovde, Sweden.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Image Analysis Determination of the Influence of Surface Structure of Silicone Rubbers on Biofouling2015In: International Journal of Polymer Science, ISSN 1687-9422, E-ISSN 1687-9430, article id 390292Article in journal (Refereed)
    Abstract [en]

    This study focuses on how the texture of the silicone rubber material affects the distribution of microbial growth on the surface of materials used for high voltage insulation. The analysis of surface wetting properties showed that the textured surfaces provide higher receding contact angles and therefore lower contact angle hysteresis. The textured surfaces decrease the risk for dry band formation and thus preserve the electrical properties of the material due to a more homogeneous distribution of water on the surface, which, however, promotes the formation of more extensive biofilms. The samples were inoculated with fungal suspension and incubated in a microenvironment chamber simulating authentic conditions in the field. The extent and distribution of microbial growth on the textured and plane surface samples representing the different parts of the insulator housing that is shank and shed were determined by visual inspection and image analysis methods. The results showed that the microbial growth was evenly distributed on the surface of the textured samples but restricted to limited areas on the plane samples. More intensive microbial growth was determined on the textured samples representing sheds. It would therefore be preferable to use the textured surface silicone rubber for the shank of the insulator.

  • 18.
    Atari Jabarzadeh, Sevil
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Salas Lacamprett, Carla
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. Univ Skovde, S-54128 Skovde, Sweden.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Use of essential oils for the prevention of biofilm formation on silicone rubber high voltage insulators2015In: Polymers from Renewable Resources, ISSN 2041-2479, Vol. 6, no 4, p. 119-136Article in journal (Refereed)
    Abstract [en]

    The prevention of biofilm formation on high voltage insulators is important to avoid changes in the surface properties of the material and the subsequent failure of the application. Antimicrobial silicone rubber samples were prepared by the addition of thymol and eugenol to Sylgard 184 to determine the possibility of using natural antimicrobial agents present in essential oils in materials used for high voltage insulators. The antimicrobial effects of thymol and eugenol were studied for different fungal strains and for green algae identified in the biofilms formed on insulators in Tanzania, Sri Lanka and Sweden. It was successfully demonstrated that samples containing high amount of eugenol and different concentrations of thymol could inhibit the fungal growth of strains from Sri Lanka and Tanzania and the growth of green algae. The growth of strains from Sweden was also suppressed. The addition of eugenol to the material resulted in a noncrosslinked system and therefore, the antimicrobial effect of the additive in the material could not be assessed. The addition of thymol did not significantly influence the thermal and mechanical properties of Sylgard184. Although thermal analysis revealed that a large amount of the antimicrobial agent was lost during sample preparation, the materials were effective against microbial growth, even at low thymol concentrations.

  • 19.
    Atarijabarzadeh, Sevil
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Biofilm adhesion on silicone materials2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Silicone composite high voltage insulators are sometimes contaminated by microorganisms in outdoor applications, which results in the insulator becoming conductive and thereafter failure of the insulators. In this work, it has been tried to develop silicone materials with antimicrobial properties. Silicone was blended with various antimicrobial agents. Affectivity and appropriate concentration of the biocides were decided through a fast test prior to the manufacturing of the samples.

    Samples were aged according to an international biodegradation test. To study the extent of the growth on the samples’ surface visual analysis and scanning electron microscopy (SEM) were performed. Samples were studied for changes in surface properties and surface chemical composition with carrying out dynamic contact angle measurements and Fourier transform infrared spectroscopy respectively. Results from the biodegradation test showed some biocides could inhibit the fungal growth comparing the results for the reference samples. Biofilm formation resulted in changes in surface hydrophobicity and surface chemical composition.

    Further, silicone materials were compounded with clay nanoparticles, which were modified with different organic compounds. Reference samples were manufactured with clay nanoparticles modified with a siloxane surfactant to make the dispersion of the particles into the silicone matrix easier. Clay nanoparticles were also grafted with two organic compounds with antimicrobial effect in order to synthesis organoclays, which have antimicrobial properties. Furthermore, grafting clay with these two compounds was also aimed to make the easy dispersion of the particles into silicone possible.

    Nanocomposites compounded with antimicrobial clay nanoparticles as well as reference nanocomposites were tested with quick test for microbial growth. Changes in the clay particles morphology were examined with x-ray diffraction as well as SEM. Manufactured nanocomposites were also examined with x-ray and SEM to study the dispersion of nanoparticles into the silicone matrix. Changes in clay morphology were observed due to modification with organic compounds. Microbial growth was inhibited on some samples due to presence of antimicrobial organoclays.

  • 20.
    Atarijabarzadeh, Sevil
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Biofilm formation on silicone materials containing various antimicrobial agents2010Conference paper (Refereed)
    Abstract [en]

    The colonisation of microorganisms and subsequent biofilm formation on the surface of polymeric high voltage insulators affect the surface properties and can lead to failure of the insulators.  In this study, silicone materials were prepared with different antimicrobial agents. The materials were analysed for the changes in the physical, chemical, surface and mechanical properties before and after biological growth test.

     

    Microorganisms used for the biological tests were fungi defined in the international standard test ISO 846 for electrical applications (Aspergillus niger van Tieghem, Penicillium funiculosum Thom, Paecilomyces variotii Bainier, Chaetomium globosum Kunze: Fries, Aspergillus terreus Thom, Aureobasidium pullulans (de Bary) Arnaud & Penicillium ochrochloron Biourge) and algae isolated from insulators in Sri Lanka and Tanzania (Chlorella vulgaris var. Autotrophica + various bacterial strains). Fungi growth test was performed by inoculation of the fungi on the surface of the materials and incubation in an oven at 28°C and 98% humidity for a specific period. Algae growth test was performed by inoculation on the material surface and subsequent incubation in room temperature under a constant fluorescent lamps for a specific period.

     

    The results indicated that some of the samples could prevent the biofilm formation on the surface of the materials while the microbial growth was unaffected on the pure silicone rubber.

  • 21.
    Atarijabarzadeh, Sevil
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Biofilm formation on silicone nanocomposites containing different antimicrobial agents2010Conference paper (Refereed)
    Abstract [en]

    In this study three types of clay/silicon nanocomposites were prepared. Clay was modified with two different antimicrobial agents (p-aminobenzoic acid and partially aminated poly(vinylbenzyl chloride) and used for preparation of the nanocomposites, which aimed to show antimicrobial properties and also easy dispersion of the clay into the polymeric matrix. Reference nanocomposites were made through the modification of the clay with a siloxane surfactant to make an easy dispersion of the clay into the silicone rubber. Nanocomposites were studied for resistancy against biological attack according to the international standard tests. Growth test results indicated that some of the nanocomposites can inhibit biological growth more than pristine nanocomposites. Modified clay was studied with x-ray diffraction technique. Materials were also studied with scanning electron microscopy before and after biological growth to analyse the biofilm formation on the surface.

  • 22. Badia, J. D.
    et al.
    Kittikorn, Thorsak
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Santonja-Blasco, L.
    Martizez-Felipe, A.
    Ribes-Greus, A.
    Ek, Monica
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Water absorption and hydrothermal performance of PHBV/sisal biocomposites2014In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 108, p. 166-174Article in journal (Refereed)
    Abstract [en]

    The performance of biocomposites of poly(hydroxybutyrate-co-valerate) (PHBV) and sisal fibre subjected to hydrothermal tests at different temperatures above the glass transition of PHBV (T-H = 26, 36 and 46 degrees C) was evaluated in this study. The influences of both the fibre content and presence of coupling agent were focused. The water absorption capability and water diffusion rate were considered for a statistical factorial analysis. Afterwards, the physico-chemical properties of water-saturated biocomposites were assessed by Fourier-Transform Infrared Analysis, Size Exclusion Chromatography, Differential Scanning Calorimetry and Scanning Electron Microscopy. It was found that the water diffusion rate increased with both temperature and percentage of fibre, whereas the amount of absorbed water was only influenced by fibre content. The use of coupling agent was only relevant at the initial stages of the hydrothermal test, giving an increase in the diffusion rate. Although the chemical structure and thermal properties of water-saturated biocomposites remained practically intact, the physical performance was considerably affected, due to the swelling of fibres, which internally blew-up the PHBV matrix, provoking cracks and fibre detachment.

  • 23. Badia, J. D.
    et al.
    Strömberg, E.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, A.
    Karlsson, S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    A statistical design of experiments for optimizing the MALDI-TOF-MS sample preparation of polymers. An application in the assessment of the thermo-mechanical degradation mechanisms of poly (ethylene terephthalate)2011In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 692, no 1-2, p. 85-95Article in journal (Refereed)
    Abstract [en]

    The sample preparation procedure for MALDI-TOF MS of polymers is addressed in this study by the application of a statistical Design of Experiments (DoE). Industrial poly (ethylene terephthalate) (PET) was chosen as model polymer. Different experimental settings (levels) for matrixes, analyte/matrix proportions and concentrations of cationization agent were considered. The quality parameters used for the analysis were signal-to-noise ratio and resolution. A closer inspection of the statistical results provided the study not only with the best combination of factors for the MALDI sample preparation, but also with a better understanding of the influence of the different factors, individually or in combination, to the signal. The application of DoE for the improvement of the MALDI measure of PET stated that the best combination of factors and levels was the following: matrix (dithranol), proportion analyte/matrix/cationization agent (1/15/1, V/V/V), and concentration of cationization agent (2 g L-1). In a second part, multiple processing by means of successive injection cycles was used to simulate the thermo-mechanical degradation effects on the oligomeric distribution of PET under mechanical recycling. The application of MALDI-TOF-MS showed that thermo-mechanical degradation primarily affected initially predominant cyclic species. Several degradation mechanisms were proposed, remarking intramolecular transesterification and hydrolysis. The ether links of the glycol unit in PET were shown to act as potential reaction sites, driving the main reactions of degradation.

  • 24. Badia, J. D.
    et al.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, A.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Assessing the MALDI-TOF MS sample preparation procedure to analyze the influence of thermo-oxidative ageing and thermo-mechanical degradation on poly (Lactide)2011In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 47, no 7, p. 1416-1428Article in journal (Refereed)
    Abstract [en]

    Multiple processing by means of successive injection cycles was used to simulate the thermo-mechanical degradation effects on the oligomeric distribution of PLA under mechanical recycling. Likewise, an accelerated thermal ageing over PLA glass transition was performed in order to simulate its service life. MALDI-TOF MS was used for the analysis and the sample preparation procedure was assessed by means of a statistical Design of Experiments (DoE). The quality effects in use for the analysis were signal-to-noise ratio and Resolution. Different matrixes, analyte/matrix proportions and the use of NaTFA as cationization agent were considered. A deep inspection of the statistical results provided a better understanding of the influence of the different factors, individually or in combination, to the signal. The application of DoE for the improvement of the MALDI measurement of PLA stated that the best combination of factors (levels) was the following: matrix (s-DHB), proportion analyte/matrix (1/5 V/V), and no use of cationization agent. Degradation primarily affected the initially predominant cyclic [LA(C)](n) and linear H-[LA(L)](n)-OH species, where LA stands for a PLA repeating unit. Intramolecular and intermolecular transesterifications as well as hydrolytic and homolytic reactions took place during the formation and disappearance of oligomeric species. In both degradation mechanisms induced by thermal ageing and thermo-mechanical degradation, the formation of H-[LA(L)](n)-O-CH(3) by intermolecular transesterifications was highlighted.

  • 25. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, A.
    Material valorisation of amorphous polylactide. Influence of thermo-mechanical degradation on the morphology, segmental dynamics, thermal and mechanical performance2012In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 4, p. 670-678Article in journal (Refereed)
    Abstract [en]

    This paper reports the effects of multiple mechanical recycling on the structure and properties of amorphous polylactide (PIA). The influence of the thermo-mechanical degradation induced by means of five successive injection cycles was initially addressed in terms of macroscopic mechanical properties and surface modification. A deeper inspection on the structure and morphology of PLA was associated to the thermal properties and viscoelastic behaviour. Although FT-IR analysis did not show significant changes in functional groups, a remarkable reduction in molar mass was found by viscometry. PIA remained amorphous throughout the reprocessing cycles, but the occurrence of a cold-crystallization during DSC and DMTA measurements, which enthalpy increased with each reprocessing step, suggested chain scission due to thermo-mechanical degradation. The effect of chain shortening on the glass-rubber relaxation studied by DMTA showed an increase in free volume affecting the segmental dynamics of PLA, particularly after the application of the second reprocessing step, in connection to the overall loss of performance showed by the remaining properties.

  • 26. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, A
    The role of crystalline, mobile amorphous and rigid amorphous fractions on the performance of recycled poly (ethylene terephthalate) (PET)2012In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 1, p. 98-107Article in journal (Refereed)
    Abstract [en]

    The action of thermo-mechanical degradation induced by mechanical recycling of poly(ethylene terephthalate) was simulated by successive injection moulding cycles. Degradation reactions provoked chain scissions and a reduction in molar mass mainly driven by the reduction of diethyleneglycol to ethylene glycol units in the flexible domain of the PET backbone, and the formation ofeOH terminated species with shorter chain length. The consequent microstructural changes were quantified taking into account a three-fraction model involving crystalline, mobile amorphous (MAF) and rigid amorphous fractions (RAF). A remarkable increase of RAF, to a detriment of MAF was observed, while the percentage of crystalline fraction remained nearly constant. A deeper analysis of the melting behaviour, the segmental dynamics around the glass-rubber relaxation, and the macroscopic mechanical performance, showed the role of each fraction leading to a loss of thermal, viscoelastic and mechanical features, particularly remarkable after the first processing cycle.

  • 27. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, Amparo
    Characterization of Induced Thermo-mechanical Degradation on Poly (ethylene terephthalate)2011Conference paper (Refereed)
  • 28. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ribes-Greus, Amparo
    STUDY OF THERMO-MECHANICAL AND THERMO-OXIDATIVE DEGRADATION OF POLYLACTIDE BYMALDI-TOF MS. A STATISTICAL DESIGN OF EXPERIMENTS TO OPTIMIZE THE SAMPLE PREPARATIONPROCEDURES2011Conference paper (Refereed)
  • 29. Banerjee, R.
    et al.
    Novak, J.
    Frank, C.
    Girleanu, M.
    Ersen, O.
    Brinkmann, M.
    Anger, F.
    Lorch, C.
    Dieterle, J.
    Gerlach, A.
    Drnec, J.
    Yu, Shun
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany .
    Schreiber, F.
    Structure and Morphology of Organic Semiconductor-Nanoparticle Hybrids Prepared by Soft Deposition2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 9, p. 5225-5237Article in journal (Refereed)
    Abstract [en]

    We present an extensive structural analysis of hybrid architectures prepared by the soft incorporation of gold nanoparticles (AuNPs) within an organic semiconductor matrix of diindenoperylene (DIP). Such soft or noninvasive deposition of nanoparticles within organic semiconducting host matrices not only minimizes the influence of the deposition process on the order and properties of the organic host molecules, but also offers additional control in the process of incorporation. The hybrid structures were characterized by X-ray scattering techniques including grazing incidence small angle X-ray scattering (GISAXS), grazing incidence X-ray diffraction (GIXD), X-ray reflectivity (XRR), and complemented by atomic force microscopy (AFM), photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM) measurements. We show that different strategies of incorporating the nanoparticles in the host matrix lead to drastically different structure and morphologies. Particularly remarkable is the morphological change observed in the matrix of DIP as well as the AuNPs due to the influence of organic solvents, as evidenced by TEM tomography measurements, which revealed the exact location of the AuNPs within the organic host. It is also demonstrated that AuNPs can be successfully used as tunable templates for the growth of the organic semiconductors with desired island sizes and distances.

  • 30. Bayley, G. M.
    et al.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Mallon, P. E.
    Large strain and toughness enhancement of poly(dimethyl siloxane) composite films filled with electrospun polyacrylonitrile-graft-poly(dimethyl siloxane) fibres and multi-walled carbon nanotubes2011In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 52, no 18, p. 4061-4072Article in journal (Refereed)
    Abstract [en]

    Unfilled cross-linked poly(dimethyl siloxane) (PDMS) is a weak material and is generally filled with high levels of particulate fillers such as silica, calcium carbonate and carbon black to improve its mechanical properties. The use of fibrous fillers such as electrospun nanofibres and multi-walled carbon nanotubes as fillers for PDMS has not been widely studied. In this study anew copolymer, polyacrylonitrile-graft-poly(dimethyl siloxane) (PAN-g-PDMS), is used as fibrous filler for PDMS. The graft copolymer is electrospun to produce the fibre filler material. It is shown how the PDMS content of the graft copolymer provides increased compatibility with silicone matrices and excellent dispersion of the fibre fillers throughout a silicone matrix. It is also shown that it is possible to include multi-walled carbon nanotubes in the electrospun fibres which are subsequently dispersed in the PDMS matrix. Fibre mats were used in the non-woven and the aligned forms. The differently prepared fibre composites have significantly different mechanical properties. Conventional composites using fibrous fillers usually show increased strength and stiffness but usually with a resultant loss of strain. In the case of the composites produced in this study there is a dramatic improvement in the extensibility of the non-woven PAN-g-PDMS fibre mat filled silicone films of up to 470%.

  • 31. Björling, Gunilla
    et al.
    Arzpeima, Minoodokht
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Considerations in Tube Selection2011Conference paper (Refereed)
  • 32. Björling, Gunilla
    et al.
    Lysdahl, Michael
    Markström, Agneta
    Schedin, Ulla
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Frostell, Claes
    Johansson, Unn-Britt
    Health-Related Quality of Life and Patient Experiences of Long-Term Tracheostomy2009Conference paper (Refereed)
  • 33.
    Blomfeldt, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Freeze-Dried Wheat Gluten-Based Foams2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents wheat gluten foams as an alternative to the available commercialfoams. Polymeric foams, like all plastics, are mostly made from petroleum, and this isaffecting the environment negatively with the emission of greenhouse gases and generation oflandfills. During the past decades, there has been a drive to replace petroleum-based plasticswith alternatives made from renewable resources. Wheat gluten has interesting and promisingproperties as an alternative resource. As a large by-product in Europe from the biofuelindustry it is largely available and at a low price.In order to develop an insulation material based on this renewable resource, foammaterials have been made by freeze-drying frozen mixtures consisting of either acommercially available wheat gluten powder or various protein rich fractions of gliadins orglutenins extracted from the commercial powder. Some of the foams were further modifiedwith the addition of glycerol as plasticizer or bacterial cellulose as a reinforcing fiber. Theresulting cellular structure was shown to depend on the initial gluten concentration, and thefraction and type of additive used. The wheat gluten foam materials contained mainly an openpore structure with average pore diameters ranging from 20 to 70 μm.The addition of glycerol and/or bacterial cellulose changed the foam structure, theprotein structure and the mechanical properties. The addition of 20 wt.% glycerol wassufficient to plasticize the foam and to achieve a low modulus and a high strain recovery, butwith glycerol the average pores size increased due to the difference in freezing conditions.The bacterial cellulose gave a small and insignificant increase in stiffness and also a moreuniform cell structure. In addition, the glycerol-containing samples had a more polymerizedprotein structure, whereas the foams containing fibers had a lower degree of polymerization.Foams made from a glutenin rich fraction were much stiffer and stronger than gliadinrich foams. The glutenin rich foams had a higher degree of polymerization than the latter,foam the relatively mild heat treatment.The gluten foams were promising as insulation materials. The thermal conductivityvalues were 0.04-0.05 (W/m⋅°C), and were close to that of commercially available closed cellpolystyrene and polyurethane foams, that both have values at ca. 0.03 (W/m⋅°C).The wheat gluten foams showed also promising combustion properties with longignition times, no material dripping and a large content of residual char. The glycerolcontainingfoam however, exhibited a more rigorous bubbling and a larger flame.

  • 34.
    Blomfeldt, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gluten Protein-Based Microcellular Foams and Composites: Development and Functional Properties2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Most common foams are produced from non-renewable resources (e.g., synthetic plastics),with a number of environmental concerns, hence there is a demand for alternative bio-derivedfoam materials. Wheat gluten protein is widely known to have excellent foaming properties(e.g., in bread making) and is a possible alternative resource for making foam products.Gluten foams were produced using a lyophilization process (freeze-drying) and variousgluten/water-based mixtures were studied. Foams with varying properties were obtained bymixing various amounts of wheat gluten with glycerol (plasticizer) and bacterial cellulosefibers (reinforcement). The gluten foams looked like bread with a beige color and few visuallydetectable surface pores. They were generally characterized as having an open cell structurewith a porosity in the range 75-85% and pore sizes ranging between 20 and 73 μm. Differentmechanical properties were obtained by using varying gluten concentrations and the differentadditives. Plasticizing with glycerol lead to increased flexibility of the foams, with the abilityto recover up to 95% after being compressed by 80%. By reinforcing with bacterial cellulosefibers the material became stiffer, with an increased elastic modulus. Confocal lasermicroscopy revealed that the fibers and gluten interacted. Analyzing the protein structure ofthe foams revealed that the different additives resulted in structures with different proteinpatterns. The samples containing glycerol were more polymerized and less extractable in SDS,whereas the fiber containing samples were only polymerized in small regions and easilyextracted in SDS. Generally the gluten foams had low conductivity values, with some valuesbelow 0.05 W/(m K), which was found to be dependant on density and pore structure. Glutenfoams were also shown to be more difficult to ignite when compared to other conventionalfoams. It was further observed that the foams did not drip making it increasingly difficult forthe fire to spread.

  • 35.
    Blomfeldt, Thomas O. J.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Kuktaite, Ramune
    Plivelic, Tomás S.
    Rasheed, Faiza
    Johansson, Eva
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Freeze-dried forms made from wheat glutenin- and gliadin-rich fractionsManuscript (preprint) (Other academic)
  • 36.
    Blomfeldt, Thomas O. J.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Holgate, Tim
    Xu, Jianxiao
    Johansson, Eva
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Thermal Conductivity and Combustion Properties of Wheat Gluten Foams2012In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 4, no 3, p. 1629-1635Article in journal (Refereed)
    Abstract [en]

    Freeze-dried wheat gluten foams were evaluated with respect to their thermal and fire-retardant properties, which are important for insulation applications. The thermal properties were assessed by differential scanning calorimetry, the laser flash method and a hot plate method. The unplasticised foam showed a similar specific heat capacity, a lower thermal diffusivity and a slightly higher thermal conductivity than conventional rigid polystyrene and polyurethane insulation foams. Interestingly, the thermal conductivity was similar to that of closed cell polyethylene and glass-wool insulation materials. Cone calorimetry showed that, compared to a polyurethane foam, both unplasticised and glycerol-plasticised foams had a significantly longer time to ignition, a lower effective heat of combustion and a higher char content. Overall, the unplasticised foam showed better fire-proof properties than the plasticized foam. The UL 94 test revealed that the unplasticised foam did not drip (form droplets of low viscous material) and, although the burning times varied, self-extinguished after flame removal. To conclude both the insulation and fire-retardant properties were very promising for the wheat gluten foam.

  • 37. Castro-Mayorga, J. L.
    et al.
    Fabra, M. J.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Lagaron, J. M.
    The impact of zinc oxide particle morphology as an antimicrobial and when incorporated in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) films for food packaging and food contact surfaces applications2017In: Food and Bioproducts Processing, ISSN 0960-3085, E-ISSN 1744-3571, Vol. 101, p. 32-44Article in journal (Refereed)
    Abstract [en]

    In this work, zinc oxide (ZnO) micron and nano sized-particles with different morphologies were synthesized by aqueous precipitation and evaluated as antimicrobial agents against foodborne pathogens. The most effective bactericide system was selected to prepare active poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films by three different methods (i) direct melt-mixing, (ii) melt-mixing of preincorporated ZnO into PHBV18 (18 mol% valerate content) fiber mats made by electrospinning, and, (iii) as a coating of the annealed electrospun PHBV18/ZnO fiber mats over compression molded PHBV. Results showed that ZnO successfully improved the thermal stability of the PHBV18, being the preincorporation method the most efficient in mitigating the negative impact that the PHBV18 had on the thermal stability, barrier and optical properties of the PHBV films. Similar behavior was found for the coating structure although this film showed effective and prolonged antibacterial activity against Listeria monocytogenes. This study highlights the suitability of the PHBV/ZnO nanostructures for active food packaging and food contact surface applications.

  • 38.
    Chen, Fei
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Chitosan and chitosan/wheat gluten blends: properties of extrudates, solid films and bio-foams2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents four different studis describing the characteristics and processing opportunities of two widely available biopolymers: chitosan and wheat gluten. The interest in these materials is mainly because they are bio-based and obtained as co- or by-products in the fuel and food sector

    In the first study, high solids content chitosan samples (60 wt.%) were successfully extruded. Chitosan extrusion has previously been reported but not chitosan extrusion with a high solids content, which decreases the drying time and increases the production volume. An orthogonal experimental design was used to assess the influence of formulation and processing conditions, and the optimal formulation and conditions were determined from the orthogonal experimental analysis and the qualities of the extrudates. The mechanical properties and processing-liquid mass loss of the optimized extrudates showed that the extrudates became stable within three days. The changes in the mechanical properties depended on the liquid mass loss.

    In a separate study, monocarboxylic (formic, acetic, propionic, and butyric) acid uptake and diffusion in chitosan films were investigated. It is of importance in order to be able to optimize the production of this material with the casting technique. The time of the equilibration uptake in the chitosan films exposed to propionic and butyric acid was nine months. This long equilibration time encouraged us study the exposed films further. The uptake and diffusivity of acid in the films decreased with increasing acid molecular size. A two-stage absorption curve was observed for the films exposed to propionic acid vapour. The films at the different stages showed different diffusivities. The acid transport was also affected by the structure of the chitosan films. X-ray diffraction suggested that the crystal structure of the original films disappeared after the films had been dried from their acid-swollen state, and that the microstructure of the dried films depended on the molecular size of the acid. Compared with the original films, the dried films retained their ductility, although a decrease in the molecular weight of the chitosan was detected. The water resistance of the acid-exposed films was increased, even though the crystallinity of these films was lower.

    The third study was devoted to chitosan/wheat gluten blend films cast from aqueous solutions. Different solvent types, additives and drying methods were used to examine their effects on the microstructures of the blended films. Chitosan and wheat gluten were immiscible in the aqueous blend, and the wheat gluten formed a discrete phase, and the homogeneity of the films was improved by using a reducing agent, compared with films prepared using only water/ethanol as cast media. Adding urea and surfactants resulted in a medium homogeneity of the films compared to those prepared with the reducing agents or with only water/ethanol. An elongated wheat gluten phase was observed in a film using glyoxal, in contrast to pure chitosan/wheat gluten blends. The opacity of the different films was studied. The mechanical properties and humidity uptake of the films increased with increasing chitosan content. The films containing 30 wt.% of wheat gluten showed the most promising mechanical properties, close to those of the pristine chitosan films.

    The final part describes the preparation and properties of a bio-foam composed of a blend of chitosan and wheat gluten. This foam was prepared without any porogen or frozen liquid phase to create porosity. A unique phase distribution of the chitosan and wheat gluten solutions formed without any agitation, and the foam was obtained when the liquid phase were withdrawn under vacuum. These foams showed high mass uptake of n-hexane and water in a short time due to their open pores and high porosity. The maximum uptake of n-hexane measured was 20 times the initial mass of the foam. The foams showed a high rebound resilience (94 % at 20 % compression strain) and they were not broken when subjected to bending.  

  • 39.
    Chen, Fei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, M.
    Olsson, Rickard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    A novel chitosan/wheat gluten biofoam fabricated by spontaneous mixing and vacuum-drying2015In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 114, p. 94191-94200Article in journal (Refereed)
    Abstract [en]

    A new type of chitosan and wheat gluten biofoam is presented. The pore structure achieved relied solely on the specific mixing and phase distribution when a film was cast from an aqueous mixture of chitosan/wheat gluten solution, in the absence of any chemical blowing agent, porogen or expanding gas. The foam was obtained when the liquid phase was removed by vacuum drying, without the need for the traditional freeze-drying that is frequently used for pore formation. Soft foam samples could be prepared with stiffnesses from 0.3 to 1.2 MPa and a high rebound resilience (64 and 94% at compressive strains of 80 and 20%, respectively). The foams were relatively ductile and did not require any plasticiser to allow for in-plane deformation (20% compression) and smaller bending. Only open pores with sizes of the order of 70-80 μm were observed by microscopy. The density of all the foams was ∼50 kg m-3, due to the high porosity (96% air). The foams showed a rapid and large uptake of both non-polar (limonene) and polar (water) liquids. When immersed in these liquids for 1 second, the maximum uptake recorded was 40 times the initial mass of the foam for limonene and 8 times for water.

  • 40.
    Chen, Fei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, Mikael
    Olsson, Richard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    A Novel Chitosan/Wheat Gluten Biofoam Fabricated by Mixing and Vacuum-dryingManuscript (preprint) (Other academic)
  • 41.
    Chen, Fei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, Mikael
    Olsson, Richard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Unusual Effects of Monocarboxylic Acids on The Structure and on The Transport and Mechanical Properties of Chitosan Films2015In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 132, p. 419-429Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to study the transport of monocarboxylic acids in chitosan films, since this is important for understanding and predicting the drying kinetics of chitosan from aqueous solutions. Despite the wealth of data on chitosan films prepared from aqueous monocarboxylic acid solutions, this transport has not been reported. Chitosan films were exposed to formic, acetic, propionic and butyric acid vapours, it was found that the rate of uptake decreased with increasing molecular size. The equilibration time was unexpectedly long, especially for propionic and butyric acid, nine months. A clear two-stage uptake curve was observed for propionic acid. Evidently, the rate of uptake was determined by acid-induced changes in the material. X-ray diffraction and infrared spectroscopy indicated that the structure of the chitosan acetate and buffered chitosan films changed during exposure to acid and during the subsequent drying. The dried films previously exposed to the acid showed less crystalline features than the original material and a novel repeating structure possibly involving acid molecules. The molar mass of the chitosan decreased on exposure to acid but tensile tests revealed that the films were always ductile. The films exposed to acid vapour (propionic and butyric acid) for the longest period of time were insoluble in the size-exclusion chromatography eluent, and they were also the most ductile/extensible of all samples studied.

  • 42.
    Chen, Fei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Monnier, Xavier
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gällstedt, Mikael
    Innventia, Sweden.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Wheat gluten/chitosan blends: A new biobased material2014In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 60, p. 186-197Article in journal (Refereed)
    Abstract [en]

    Wheat gluten and chitosan are renewable materials that suffer from some poor properties that limit their use as a potential replacement of petroleum-based polymers. However, polymer blends based on wheat gluten and chitosan surprisingly reduced these shortcomings. Films were cast from acidic aqueous or water/ethanol solutions of wheat gluten and chitosan. Wheat gluten was the discontinuous phase in the 30-70 wt.% wheat gluten interval investigated. The most homogeneous films were obtained when reducing agents were used (alone or together with urea or glycerol). They consisted mainly of 1-2 mu m wheat gluten particles uniformly distributed in the continuous chitosan phase. Slightly smaller particles were also observed in the water/ethanol solvent system, but together with significantly larger particles (as large as 200 mu m). Both small and large particles were observed, albeit in different sizes and contents, when surfactants (both with and without a reducing agent) or urea (without a reducing agent) were used. The particles were often elongated, and preferably along the film, the most extreme case being observed when the glyoxal crosslinker was used together with sodium sulfite (reducing agent), showing particles with an average thickness of 0.6 mu m and an aspect ratio of 4.2. This film showed the highest transparency of all the blend films studied. For one of the most promising systems (with sodium sulfite), having good film homogeneity and small particles, the mechanical and moisture solubility/diffusivity properties were studied as a function of chitosan content. The extensibility, toughness and moisture solubility increased with increasing chitosan content, and the moisture diffusivity was highest for the pristine chitosan material. It is noteworthy that the addition of 30 wt.% wheat gluten to chitosan reduced the moisture uptake, while the extensibility/toughness remained unchanged.

  • 43.
    Chen, Fei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, M.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Chitosan extrusion at high solids content: An orthogonal experimental design study2014In: Polymers from Renewable Resources, ISSN 2041-2479, Vol. 5, no 1, p. 1-12Article in journal (Refereed)
    Abstract [en]

    For economic reasons and to save time there is a need to shorten the drying operation associated with the production of chitosan materials. Hence it is of interest to extrude chitosan at as high a solids content as possible. This is, to our knowledge, the first systematic study of the extrusion of chitosan at high solids content (60 wt%). An orthogonal experimental design was used to evaluate the effect of processing conditions and material factors on the extrudability of chitosan. This, together with the examination of the evenness and surface finish of the extrudate, made it possible to determine the best conditions for obtaining a readily extrudable high quality material. It was observed that a 1/1 ratio of chitosans with molar masses of 12 and 133 kDa, a process liquid containing 30 wt% acetic acid and 70 wt% water, and extrusion at 50 rpm and 50°C were the optimal material and processing conditions. Materials processed under these conditions were evaluated mechanically at different times after extrusion (stored at 50% RH) in order to see when the properties stabilized. Most mass loss occurred within the first three days after extrusion and this governed the mechanical properties (stiffness and extensibility), which also exhibited the largest changes within these three days (an increase in modulus from 18 to 830 MPa and a decrease in elongation at break from 17 to 3%).

  • 44.
    Cho, Sung-Woo
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Protein-based Packaging Films, Sheets and Composites: Process Development and Functional Properties2009Doctoral thesis, comprehensive summary (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.

  • 45.
    Cho, Sung-Woo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, Mikael
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Effects of glycerol content and film thickness on the properties of vital wheat gluten films cast at pH 4 and 12010In: 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 degrees 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 mu m, 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.

  • 46.
    Cho, Sung-Woo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, Mikael
    KTH.
    Hedenqvist, Mikael S
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    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, extrusion-coating 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 WO 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 degrees C instead of 110 degrees C). The latter effect was probably due to a higher protein aggregation, as revealed by infrared spectroscopy. The lamination temperature (110-140 degrees C) did not, however, have a major effect on the final peel strength.

  • 47.
    Cho, Sung-Woo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, Mikael
    Johansson, E.va
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    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.

  • 48.
    Cho, Sung-Woo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ullsten, Henrik
    STFI Packforsk AB.
    Gällstedt, Mikael
    STFI Packforsk AB.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Heat-sealing properties of compression-molded wheat gluten films2007In: Journal of Biobased Materials and Bioenergy, ISSN 1556-6560, Vol. 1, no 1, p. 56-63Article in journal (Refereed)
    Abstract [en]

    The impulse heat-sealing properties of wheat gluten films were investigated. Films containing 30 wt% glycerol were compression molded at 100-130 degrees C and then sealed in a lap-shear or peel-test geometry at 120-175 degrees C. The tensile properties of the pristine films and the lap-shear and peel strength of the sealed films were evaluated and the seals were examined by scanning electron microscopy. Glycerol was added to the film surfaces prior to sealing in an attempt to enhance the seal strength. It was observed that the wheat gluten films were readily sealable. At a 120 degrees C sealing temperature and without glycerol as adhesive, the lap-shear strength was greater than or similar to that of polyethylene film, although the peel strength was poorer. 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, especially in the absence of glycerol adhesive, from a cohesive (material failure) to an adhesive type. From previous results, it is known that the high-temperature (130 degrees C) compression-molded film was highly cross-linked and aggregated, and this prevents molecular interdiffusion and entanglement and thus leads to incomplete seal fusion and, in general, adhesive failure. The presence of glycerol adhesive had a beneficial affect on the peel strength but no, or only a minor, effect on the lap-shear strength.

  • 49. Cozzolino, C. A.
    et al.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Iotti, M.
    Sacchi, B.
    Piga, A.
    Farris, S.
    Exploiting the nano-sized features of microfibrillated cellulose (MFC) for the development of controlled-release packaging2013In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 110, p. 208-216Article in journal (Refereed)
    Abstract [en]

    Microfibrillated cellulose (MFC) was used in this study to prepare films containing an active molecule, lysozyme, which is a natural antimicrobial agent. The main goal of this research was to assess the potential for exploiting the nano-sized dimension of cellulose fibrils to slow the release of the antimicrobial molecule, thus avoiding a too-quick release into the surrounding medium, which is a major disadvantage of most release systems. For this purpose, the release kinetics of lysozyme over a 10-day period in two different media (pure water and water/ethanol 10. wt.%) were obtained, and the experimental data was fitted with a solution of Fick's second law to quantify the apparent diffusion coefficient (D). The results indicate that the MFC retained lysozyme, presumably due to electrostatic, hydrogen, and ion-dipole interactions, with the largest release of lysozyme-approximately 14%-occurring from the initial amount loaded on the films. As expected, ethanol as a co-solvent slightly decreased the diffusion of lysozyme from the MFC polymer network. The addition of two potential modulating release agents-glycerol and sodium chloride-was also evaluated. Findings from this work suggest that MFC-based films can be considered a suitable candidate for use in controlled-release packaging systems.

  • 50.
    Cozzolino, Carlo A.
    et al.
    University of Sassari.
    Blomfeldt, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Piga, Antonio
    University of Sassari.
    Piergiovanni, Luciano
    Farris, Stefano
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Dye release behavior from polyvinyl alcohol films in a hydro-alcoholic medium: Influence of physicochemical heterogeneity2012In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 403, p. 45-53Article in journal (Refereed)
    Abstract [en]

    In this paper we investigated the release kinetics of a model drug-like compound (Coomassie brilliant blue) from polyvinyl alcohol (PVOH) films into a hydro-alcoholic solution as a function of the physicochemical properties of the polymer matrix. After 33 days of monitoring, the total amount released ranged from 10% for the high hydrolysis degree/low molecular weight PVOH films to 60% for the low hydrolysis degree/low molecular weight films. Mathematical modeling allowed for an estimation of the two diffusion coefficients (D 1 and D 2) that characterized the release profile of the dye from the films. The degree of hydrolysis dramatically affected both the morphology and the physical structure of the polymer network. A high hydroxyl group content was also associated with the shifting of second order and first order transitions toward higher temperatures, with a concurrent increase in crystallinity. Moreover, the higher the degree of hydrolysis, the higher the affinity of the polymer to the negatively charged molecule dye. Selection of the polymer matrix based on physicochemical criteria may help in achieving different release patterns, thereby representing the first step for the production of polymer systems with modulated release properties.

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