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  • 201.
    Ariza, David
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Becerra, Marley
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Hollertz, Rebecca
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pitois, Claire
    ABB AB Corporate Research.
    First Mode Negative Streamers along Mineral Oil-solid Interfaces2017Ingår i: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 24, nr 4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This document presents an experimental study on the propagation of first mode negative streamers along mineral oil-solid interfaces. Samples made of an oil impregnated kraft paper and a low-porosity paper made from cellulosic micro and nano fibrils, as well as different polymeric films (low density polyethylene (LDPE), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF)) are used as the solid. A comparison of the length, charge and velocity of streamers for all different mineral oil-solid interfaces is reported. It is shown that streamers propagate longer and faster along mineral oil-solid interfaces with low surface roughness, low porosity and higher electrical permittivity than mineral oil. Those streamers show a quasi-continuous injection of charge in the early stage of their propagation. This quasi-continuous charge injection consists of a sequence of small charge steps separated by few tens of nanoseconds in between. In comparison, the streamers that propagate along surfaces with similar permittivity to the mineral oil have lower injection of charge and higher stopping voltage conditions than streamers propagating free in the liquid without any solid barrier.

  • 202.
    Ariza, David
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Becerra, Marley
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Methling, Ralf
    INP - Leibniz Institute for Plasma Science and Technology.
    Gortchakow, Sergey
    INP Leibniz Institute for Plasma Science and Technology.
    Hollertz, Rebecca
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Influence of Paper Properties on Streamers Creepingin Mineral Oil2017Ingår i: Proceedings of IEEE International Conference on Dielectric Liquids, ISSN 2153-3725, E-ISSN 2153-3733Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work presents an experimental study ofsecond mode positive streamers propagating along mineral oilpaperinterfaces. A point-plane arrangement immersed inmineral oil with the paper inclined 60 degrees to the planeelectrode is used to create the liquid-solid interface. Kraft paperand a kraft fibril paper, made from cellulosic micro and nanofibrils, with higher density and lower surface roughness are usedas the solid materials. High speed shadowgraphy and chargerecordings are used to compare the propagation of second modepositive streamers along the mineral oil-kraft paper and mineraloil-kraft fibril paper. Streamers creeping along the mineral oilkraftpaper interface propagate mainly into the liquid, with oneor two main filaments. In comparison, the streamers propagatingalong the kraft fibril paper show a strong reduction of thebranching; these streamers consist of a single filament thatpropagates exactly on the solid surface. Streamers along the kraftfibril paper also have longer propagation time than for the casewith kraft paper. Mutual electrostatic shielding betweenfilaments is observed for the streamers creeping on the kraftpaper. An electrostatic analysis of the influence of permittivity,density and surface roughness of the solid in the electricalproperties of the streamer filaments is also performed.

  • 203.
    Ariza, David
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Hollertz, Rebecca
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Beccera, Marley
    Pitois, Claire
    KTH.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    First mode negative streamers at mineral oil-solid interfacesManuskript (preprint) (Övrigt vetenskapligt)
  • 204.
    Ariza, David
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Hollertz, Rebecca
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Methling, Ralf
    Gortschakow, Sergey
    Influence of paper properties on streamers creeping in mineral oilManuskript (preprint) (Övrigt vetenskapligt)
  • 205.
    Arnling Bååth, Jenny
    et al.
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Giummarella, Nicola
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Klaubauf, Sylvia
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Lawoko, Martin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Olsson, Lisbeth
    Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    A glucuronoyl esterase from Acremonium alcalophilum cleaves native lignin-carbohydrate ester bonds2016Ingår i: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 590, nr 16, s. 2611-2618Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Glucuronoyl esterases (GE) have been proposed to target lignin-carbohydrate (LC) ester bonds between lignin moieties and glucuronic acid side groups of xylan, but to date, no direct observations of enzymatic cleavage on native LC ester bonds have been demonstrated. In the present investigation, LCC fractions from spruce and birch were treated with a recombinantly produced GE originating from Acremonium alcalophilum (AaGE1). A combination of size exclusion chromatography and 31P NMR analyses of phosphitylated LCC samples, before and after AaGE1 treatment provided the first evidence for cleavage of the LC ester linkages existing in wood.

  • 206. Arvidson, K.
    et al.
    Abdallah, B. M.
    Applegate, L. A.
    Baldini, N.
    Cenni, E.
    Gomez-Barrena, E.
    Granchi, D.
    Kassem, M.
    Konttinen, Y. T.
    Mustafa, K.
    Pioletti, D. P.
    Sillat, T.
    Finne-Wistrand, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Bone regeneration and stem cells2011Ingår i: Journal of Cellular and Molecular Medicine (Print), ISSN 1582-1838, E-ISSN 1582-4934, Vol. 15, nr 4, s. 718-746Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Introduction Bone fracture healing and healing problems Biomaterial scaffolds and tissue engineering in bone formation Bone tissue engineering Biomaterial scaffolds Synthetic scaffolds Micro- and nanostructural properties of scaffolds Conclusion Mesenchymal stem cells and osteogenesis Bone tissue Origin of osteoblasts Isolation and characterization of bone marrow derived MSC In vitro differentiation of MSC into osteoblast lineage cells In vivo differentiation of MSC into bone Factors and pathways controlling osteoblast differentiation of hMSC Defining the relationship between osteoblast and adipocyte differentiation from MSC MSC and sex hormones Effect of aging on osteoblastogenesis Conclusion Embryonic, foetal and adult stem cells in osteogenesis Cell-based therapies for bone Specific features of bone cells needed to be advantageous for clinical use Development of therapeutic biological agents Clinical application concerns Conclusion Platelet-rich plasma (PRP), growth factors and osteogenesis PRP effects in vitro on the cells involved in bone repair PRP effects on osteoblasts PRP effects on osteoclasts PRP effects on endothelial cells PRP effects in vivo on experimental animals The clinical use of PRP for bone repair Non-union Distraction osteogenesis Spinal fusion Foot and ankle surgery Total knee arthroplasty Odontostomatology and maxillofacial surgery Conclusion Molecular control of osteogenesis TGF-beta signalling FGF signalling IGF signalling PDGF signalling MAPK signalling pathway Wnt signalling pathway Hedgehog signalling Notch signalling Ephrin signalling Transcription factors regulating osteoblast differentiation Conclusion Summary This invited review covers research areas of central importance for orthopaedic and maxillofacial bone tissue repair, including normal fracture healing and healing problems, biomaterial scaffolds for tissue engineering, mesenchymal and foetal stem cells, effects of sex steroids on mesenchymal stem cells, use of platelet-rich plasma for tissue repair, osteogenesis and its molecular markers. A variety of cells in addition to stem cells, as well as advances in materials science to meet specific requirements for bone and soft tissue regeneration by addition of bioactive molecules, are discussed.

  • 207.
    Arzpeima, Minoodokht
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Björling, Gunilla
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Antimicrobial Efficacy and Degradation Route of Silver-Based Coated Endotracheal Tubes2012Konferensbidrag (Refereegranskat)
  • 208.
    Arzpeima, Minoodokht
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Rosén, Annika
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Sanchez, Javier
    Björling, Gunilla
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Chemotherapy-Induced Surface Degradation and Thrombogenicity of Intravascular Catheters: A Preliminary In-Vitro Study with Focus on Breast Cancer2012Konferensbidrag (Refereegranskat)
  • 209.
    Asem, Heba
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Polymeric Nanoparticles Explored for Drug-Delivery Applications2018Ingår i: Gels and Other Soft Amorphous Solids, American Chemical Society (ACS), 2018, s. 315-331Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    The main drawback of conventional chemotherapeutics is their non-specific distribution in the body which causes serious side effects to healthy cells. As a consequence, the drug concentration reaching the tumor is reduced, resulting in suboptimal therapeutic efficacy. The discovery that polymer-based nanomaterials can be used for controlled drug delivery systems offers well-defined reservoirs for a wide spectrum of pharmaceutical agents, with the ability to reduce the toxic response. The most widely explored polymeric nanocarriers, including biodegradable polymers, amphiphilic copolymers and polymers that form unimolecular micelles, are discussed in this brief chapter.

  • 210. Asp, Leif
    et al.
    Gamstedt, Kristofer
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gibson, Geoff
    13th European Conference on Composite Materials2009Ingår i: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, nr 2-4, s. 47-48Artikel i tidskrift (Övrigt vetenskapligt)
  • 211.
    Atari Jabarzadeh, Sevil
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Prevention of Biofilm Formation on Silicone Rubber Materials for Outdoor High Voltage Insulators2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 212.
    Atari Jabarzadeh, Sevil
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Mendoza Álvarez, Ana Isabel
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Hillborg, Henrik
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material. ABB, Corporated Resarch, Sweden.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material. Univ Skovde, S-54128 Skovde, Sweden.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Design of nanocomposite surfaces with antibiofouling properties for outdoor insulation applicationsManuskript (preprint) (Övrigt vetenskapligt)
  • 213.
    Atari Jabarzadeh, Sevil
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Nilsson, Fritjof
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material. ABB, Corp Res, S-72178 Vasteras, Sweden.
    Hillborg, Henrik
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material. ABB, Corp Res, S-72178 Vasteras, Sweden.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material. Univ Skovde, S-54128 Skovde, Sweden.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Image Analysis Determination of the Influence of Surface Structure of Silicone Rubbers on Biofouling2015Ingår i: International Journal of Polymer Science, ISSN 1687-9422, E-ISSN 1687-9430, artikel-id 390292Artikel i tidskrift (Refereegranskat)
    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.

  • 214.
    Atari Jabarzadeh, Sevil
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Salas Lacamprett, Carla
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material. Univ Skovde, S-54128 Skovde, Sweden.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Use of essential oils for the prevention of biofilm formation on silicone rubber high voltage insulators2015Ingår i: Polymers from Renewable Resources, ISSN 2041-2479, Vol. 6, nr 4, s. 119-136Artikel i tidskrift (Refereegranskat)
    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.

  • 215.
    Atarijabarzadeh, Sevil
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Biofilm adhesion on silicone materials2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 216.
    Atarijabarzadeh, Sevil
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Biofilm formation on silicone materials containing various antimicrobial agents2010Konferensbidrag (Refereegranskat)
    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.

  • 217.
    Atarijabarzadeh, Sevil
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Biofilm formation on silicone nanocomposites containing different antimicrobial agents2010Konferensbidrag (Refereegranskat)
    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.

  • 218.
    Atarijabarzadeh, Sevil
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Design of antimicrobial silicone nanocomposites for high voltage insulationManuskript (preprint) (Övrigt vetenskapligt)
  • 219.
    Atarijabarzadeh, Sevil
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Inhibition of biofilm formation on silicone rubber samples using various antimicrobial agents2011Ingår i: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 65, nr 8, s. 1111-1118Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-temperature-cured silicone rubber samples (silicone rubber (SIR) based on polydimethylsiloxane (PDMS)) and SIR samples containing three different antimicrobial agents, sodium benzoate (NaB), DCOIT (4,5 Dichloro-2-octyl-2H-isothiazolone-one) and p-aminobenzoic acid (PABA) were inoculated with fungal spore suspensions and incubated for 28 days at 29 +/- 1 degrees C and >= 90% humidity, according to the ISO 846:1997(E) protocol. Prior to the biodegradation test, a powder test was conducted to study the efficacy of the chosen antimicrobial compounds and to determine the correct concentration of the compounds for sample preparation. The extent of the microbial growth was studied visually and by Scanning Electron Microscopy (SEM). Changes in surface hydrophobicity and surface chemical composition were studied by contact angle measurements and Fourier Transform Infrared (FTIR) spectroscopy, respectively. Microbial growth and biofilm formation were observed on the surface of reference samples. DCOIT was the most effective antimicrobial agent, as demonstrated by the lack of microbial growth and unaltered surface hydrophobicity. On the surface of samples containing NaB, an initiation of microbial growth and therefore a slight change in surface hydrophobicity was observed. PABA did not inhibit the fungal growth.

  • 220. Atlas, Salima
    et al.
    Raihane, Mustapha
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Lahcini, Mohammed
    Ameduri, Bruno
    Radical copolymerization of acrylonitrile with 2,2,2-trifluoroethyl acrylate for dielectric materials: Structure and characterization2013Ingår i: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 51, nr 18, s. 3856-3866Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Radical copolymerization based on acrylonitrile (AN) and 2,2,2-Trifluoroethyl acrylate (ATRIF) initited by AIBN was investigated in acetonitrile solution. The resulting poly(AN-co-ATRIF) copolymers were characterized by 1 H, 13 C, and 19 F NMR and IR spectroscopy, and size exclusion chromatography (SEC). Their compositions were assessed by 1 H NMR. The kinetics of radical copolymerization of AN with ATRIF was investigated from sereval experiments achieved at 70 degrees C from initial [AN](0)/[ATRIF](0) molar ratios ranging between 20/80 and 80/20 and was enabled to determine the reactivity ratios of both comonomers. From the monomer-polymer copolymerization curve, the Fineman-Ross and Kelen-Tudos laws enabled to assess the reactivity ratios (r(AN) = r(1) = 1.25 +/- 0.04 and r(ATRIF) = r(2) = 0.93 +/- 0.05 at 70 degrees C) while the revised patterns scheme led to r(12) = r(AN) = 1.03, and r(21) = r(ATRIF) = 0.78 at 70 degrees C. In all cases, rAN x rATRIF product was close to unity, which indicates that poly(AN-co-ATRIF) copolymers exhibit a random structure. This was also confirmed by the Igarashi's and Pyun's laws which revealed the presence of AN-ATRIF, AN-AN, and ATRIF-ATRIF dyads. The Q and e values for ATRIF were also assessed (Q(2) = 0.62 and e(2) = 0.93). The glass transition temperature values, Tg, of these copolymers increased from 17 to 61 degrees C as the molar percentage of ATRIF decreased from 77 to 16% in the copolymer. Thermogravimetry analysis of poly(AN-co-ATRIF) copolymers showed a good thermal stability compared to that of poly(ATRIF) homopolymer due to incorporation of AN comonomer.

  • 221.
    Aulin, Christian
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Novel oil resistant cellulosic materials2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The aim of this study has been to prepare and characterise oil resistant cellulosic materials, ranging from model surfaces to papers and aerogels. The cellulosic materials were made oil resistant by chemical and topographic modifications, based on surface energy, surface roughness and barrier approaches. Detailed wetting studies of the prepared cellulosic materials were made using contact angle measurements and standardised penetration tests with different alkanes and oil mixtures.

    A significant part of the activities were devoted to the development of model cellulosic surfaces with different degrees of crystalline ordering for the wetting studies. Crystalline cellulose I, II and amorphous cellulose surfaces were prepared by spin-coating of cellulose nanocrystal or microfibrillated cellulose (MFC) dispersions, with Langmuir-Schaefer (LS) films or by a layer-by-layer (LbL) deposition technique. The formation of multilayers consisting of polyethyleneimine (PEI)/anionic MFC or cationic MFC/anionic MFC was further studied and optimized in terms of total layer thickness and adsorbed amount by combining Dual Polarization Interferometry (DPI) or Stagnation Point Adsorption Reflectrometry (SPAR) with a Quartz Crystal Microbalance with Dissipation (QCM-D).

    The smooth cellulosic surfaces prepared had different molecular and mesostructure properties and different surface energies as shown by X-ray diffraction, Atomic Force Microscopy (AFM) imaging, ellipsometry measurements and contact angle measurements.

    The cellulose model surfaces were found to be ideal for detailed wetting studies, and after the surface has been coated or covalently modified with various amounts of fluorosurfactants, the fluorinated cellulose films were used to follow the spreading mechanisms of different oil mixtures. The viscosity and surface tension of the oil mixtures, as well as the dispersive surface energy of the cellulose surfaces, were found to be essential parameters governing the spreading kinetics. A strong correlation was found between the surface concentration of fluorine, the dispersive surface energy and the measured contact angle of the oil mixtures.

    Silicon surfaces possessing structural porous characteristics were fabricated by a plasma etching process. The structured silicon surfaces were coated with sulfate-stabilized cellulose I nanocrystals using the LbL technique. These artificial intrinsically oleophilic cellulose surfaces were made highly oleophobic when coated with a thin layer of fluorinated silanes. By comparison with flat cellulose surfaces, which are oleophilic, it is demonstrated that the surface energy and the surface texture are essential factors preventing oil from spreading on the surface and, thus, inducing the observed macroscopic oleophobic properties.

    The use of the MFC for surface coating on base papers demonstrated very promising characteristics as packaging materials. Environmental-Scanning Electron Microscopy (E-SEM) micrographs indicated that the MFC layer reduced the sheet porosity, i.e. the dense structure formed by the nanofibers resulted in superior oil barrier properties. Attempts were made to link the procedure for preparation of the MFC dispersions to the resulting microstructure of the coatings, and film porosity and the film moisture content to the resulting permeability properties.

    Finally, MFC aerogels were successfully prepared by freeze-drying. The surface texture of the porous aerogels was carefully controlled by adjusting the concentration of the MFC dispersion used for the freeze-drying. The different scales of roughness of the MFC aerogels were utilised, together with the very low surface energy created by fluorination of the aerogel, to induce highly oleophobic properties.

  • 222.
    Aulin, Christian
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Preparation, characterisation and wetting of fluorinated cellulose surfaces2007Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis deals with the wetting by oil mixtures of two different model cellulose surfaces. The surfaces studied were a regenerated cellulose (RG) surface prepared by spin-coating, and a film consisting of polyelectrolyte multilayers (PEM) of Poly(ethyleneimine) (PEI) and a carboxymethylated Microfibrillated Cellulose (MFC). After coating or covalently modifying the cellulose surfaces with various amounts of fluorosurfactants, the fluorinated cellulose films were used to follow the spreading mechanisms of the different oil mixtures. The viscosity and surface tension of the oil, as well as the dispersive surface energy of the cellulose surface, are essential parameters governing the spreading kinetics. X-ray Photoelectron Spectroscopy (XPS) and dispersive surface energy measurements were made on the cellulose films treated with fluorosurfactants. A strong correlation between the surface coverage of fluorine, the dispersive surface energy and the measured contact angle of the oil mixtures was found. For example, a dispersive surface energy less than 18 mN/m was required in order for the cellulose surface to be non-wetting (θe > 90º) by castor oil.

    Significant parts of this work were devoted to the development of cellulose surfaces for the wetting studies. The formation of a PEM consisting of PEI and MFC was studied and the total layer thickness and adsorbed amount were optimized by combining Dual Polarization Interferometry (DPI) with a Quartz Crystal Microbalance with Dissipation (QCM-D). The adsorption behaviour as well as the influence of the charge density, pH and electrolyte concentration of PEI, and electrolyte concentration of the MFC dispersion on the adsorbed amount of MFC were investigated. Results indicate that a combination of a high pH, a fairly high electrolyte concentration for PEI solution together with low or zero electrolyte concentration for the MFC resulted in the largest possible adsorbed amounts of the individual PEI and MFC layers.

    The structures of the two cellulose surfaces were characterised with atomic force microscopy measurements and a difference in terms of surface structure and roughness were observed. Both surfaces were however very smooth with calculated RMS roughness values in the range of a few nanometers.

    The adsorption behaviour of water-dispersible fluorosurfactants physically adsorbed at various concentrations onto the two model cellulose surfaces was investigated using DPI. The aggregate structure of an anionic fluorosurfactant, perfluorooctadecanoic acid, dispersed in water was studied by Cryo Transmission Electron Microscopy (Cryo-TEM). The fluorosurfactants had an adsorption and desorption behaviour in water which was dependent on the fluorinated chain length and the aggregation form of the fluorosurfactant. Perfluorooctanoic acid and a commercial cationic fluorosurfactant with a formal composition of CF3 (CF2)nSO2NH(CH2)3-4N(CH3)3+I- was found to desorb from the MFC and RG surfaces upon rinsing with water, whereas perfluorooctadecanoic acid was strongly adsorbed to the surfaces. It is essential for a fluorosurfacatant to be strongly adsorbed to the cellulose surface even after rinsing to yield hydrophobic and lipophobic (oleophobic) properties with a large contact angle for oils and water.

  • 223.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Gallstedt, Mikael
    Lindström, Tom
    Oxygen and oil barrier properties of microfibrillated cellulose films and coatings2010Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 17, nr 3, s. 559-574Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The preparation of carboxymethylated microfibrillated cellulose (MFC) films by dispersion-casting from aqueous dispersions and by surface coating on base papers is described. The oxygen permeability of MFC films were studied at different relative humidity (RH). At low RH (0%), the MFC films showed very low oxygen permeability as compared with films prepared from plasticized starch, whey protein and arabinoxylan and values in the same range as that of conventional synthetic films, e.g., ethylene vinyl alcohol. At higher RH's, the oxygen permeability increased exponentially, presumably due to the plasticizing and swelling of the carboxymethylated nanofibers by water molecules. The effect of moisture on the barrier and mechanical properties of the films was further studied using water vapor sorption isotherms and by humidity scans in dynamic mechanical analysis. The influences of the degree of nanofibrillation/dispersion on the microstructure and optical properties of the films were evaluated by field-emission scanning electron microscopy (FE-SEM) and light transmittance measurements, respectively. FE-SEM micrographs showed that the MFC films consisted of randomly assembled nanofibers with a thickness of 5-10 nm, although some larger aggregates were also formed. The use of MFC as surface coating on various base papers considerably reduced the air permeability. Environmental scanning electron microscopy (E-SEM) micrographs indicated that the MFC layer reduced sheet porosity, i.e., the dense structure formed by the nanofibers resulted in superior oil barrier properties.

  • 224.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Johansson, E.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, T.
    Adsorption behaviour, structural and adhesive properties of microfibrillated cellulose-based multilayersArtikel i tidskrift (Refereegranskat)
  • 225.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Innventia AB, Sweden.
    Johansson, Erik
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Structure and Properties of Layer-by-Layer Films from Combinations of Cellulose Nanofibers, Polyelectrolytes and Colloids2014Ingår i: HANDBOOK OF GREEN MATERIALS, VOL 3: SELF - AND DIRECT - ASSEMBLING OF BIONANOMATERIALS, World Scientific, 2014, s. 57-77Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    The formation of nanometer-thin films of cellulose nanofibers (CNFs), polyelectrolytes, and/or nanoparticles has opened up new possibilities of manufacturing interactive devices with controlled mechanical properties. By controlling the charge of the CNF and the charge and 3D structure of the polyelectrolytes, it is possible to control the buildup, i.e., the thickness, the adsorbed amount, and the immobilized water of layer-by-layer (LbL) films of these materials. The charge balance between the components is not the only factor controlling the LbL formation. The structure of these adsorbed layers in combination with the properties of the constituent components will in turn control how these layers interact with, for example moist air. The mechanical properties of the LbLs can be tuned by combining the high-modulus CNF with different components. This has been shown by using a microbuckling technique where the mechanical properties of ultra-thin films can be measured. In combination with, for example, moisture-sensitive poly(ethylene imine) (PEI), the Young's modulus of CNF/PEI films can be changed by one order of magnitude when the humidity is increased from 0% RH to 50% RH. The incorporation of high-modulus nanoparticles such as SiO2 particles can also be used to prepare LbLs with a higher modulus. Examples are also given where it is shown that the color of an LbL film can be used as a non-contact moisture sensor since the thickness is related to the amount of adsorbed moisture. By chemical modification of the CNF, it is also possible to tailor the interaction between the CNF and multivalent metal ions, enabling a specific interaction between multivalent for example metal surfaces in water and modified CNF.

  • 226.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Johansson, Erik
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Lindström, Tom
    Self-Organized Films from Cellulose I Nanofibrils Using the Layer-by-Layer Technique2010Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 11, nr 4, s. 872-882Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The possibility of forming self-organized films using only charge-stabilized dispersions of cellulose I nanofibrils with opposite charges is presented, that is, the multilayers were composed solely of anionically and cationically modified microfibrillated cellulose (MFC) with a low degree of substitution. The build-up behavior and the properties of the layer-by-layer (LbL)-constructed films were studied using a quartz crystal microbalance with dissipation (QCM-D) and stagnation point adsorption reflectometry (SPAR). The adsorption behavior of cationic/anionic MFC was compared with that of polyethyleneimine (PEI)/anionic MFC. The water contents of five bilayers of cationic/anionic MFC and PEI/anionic MFC were approximately 70 and 50%, respectively. The MFC surface coverage was studied by atomic force microscopy (AFM) measurements, which clearly showed a more dense fibrillar structure in the five bilayer PEI/anionic MFC than in the five bilayer cationic/anionic MFC. The forces between the cellulose-based multilayers were examined using the AFM colloidal probe technique. The forces on approach were characterized by a combination of electrostatic and steric repulsion. The wet adhesive forces were very long-range and were characterized by multiple adhesive events. Surfaces covered by PEU/anionic MFC multilayers required more energy to be separated than surfaces covered by cationic/anionic MFC multilayers.

  • 227.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Josefsson, Peter
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nanoscale Cellulose Films with Different Crystallinities and Mesostructures: Their Surface Properties and Interaction with Water2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 13, s. 7675-7685Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A systematic study of the degree of molecular ordering and swelling of different nanocellulose model films has been conducted. Crystalline cellulose II surfaces were prepared by spin-coating of the precursor cellulose solutions onto oxidized silicon wafers before regeneration in water or by using the Langmuir-Schaefer (LS) technique. Amorphous cellulose films were also prepared by spin-coating of a precursor cellulose solution onto oxidized silicon wafers. Crystalline cellulose I surfaces were prepared by spin-coating wafers with aqueous suspensions of sulfate-stabilized cellulose nanocrystals and low-charged microfibrillated cellulose (LC-MFC). In addition, a dispersion of high-charged MFC was used for the buildup of polyelectrolyte multilayers with polyetheyleneimine on silica with the aid of the layer-by-layer (LbL) technique. These preparation methods produced smooth thin films on the nanometer scale Suitable for X-ray diffraction and swelling measurements. The surface morphology and thickness of the cellulose films were characterized in detail by atomic force microscopy (AFM) and ellipsometry measurements, respectively. To determine the surface energy of the cellulose surfaces, that Is, their ability to engage in different interactions with different materials, they were characterized through contact angle measurements against water, glycerol, and methylene iodide. Small incidence angle X-ray diffraction revealed that the nanocrystal and MFC films exhibited a cellulose I crystal structure and that the films prepared from N-methylmorpholine-N-oxide (NMMO), LiCl/DMAc solutions, using the LS technique, possessed a cellulose II structure. The degree of crystalline ordering was highest in the nanocrystal films (similar to 87%), whereas the MFC, NMMO, and LS films exhibited a degree of crystallinity of about 60%. The N,N-dimethylacetamide(DMAc)/LiCl film possessed very low crystalline ordering (<15%). It was also established that the films ha different mesostructures, that is, structures around 10 nm, depending on the preparation conditions. The LS and LiCl/DMAc films are smooth without any clear mesostructure, whereas the other films have a clear mesostructure in which the dimensions are dependent oil the size of the nanocrystals, fibrillar cellulose, and electrostatic charge of the MFC. The swelling of the films was studied using a quartz crystal microbalance with dissipation. To understand the swelling properties of the films, it was necessary to consider both the difference in crystalline ordering and the difference in mesostructure of the films.

  • 228.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Karabulut, Erdem
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Tran, Amy
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lindström, Tom
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Transparent Nanocellulosic Multilayer Thin Films on Polylactic Acid with Tunable Gas Barrier Properties2013Ingår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, nr 15, s. 7352-7359Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The layer-by-layer (LbL) deposition method was used for the build-up of alternating layers of nanofibrillated cellulose (NFC) or carboxymethyl cellulose (CMC) with a branched, cationic polyelectrolyte, polyethyleneimine (PEI) on flexible poly (lactic acid) (PLA) substrates. With this procedure, optically transparent nanocellulosic films with tunable gas barrier properties were formed. 50 layer pairs of PEI/NFC and PEI/CMC deposited on PLA have oxygen permeabilities of 0.34 and 0.71 cm(3).mu m/m(2).day.kPa at 23 degrees C and 50% relative humidity, respectively, which is in the same range as polyvinyl alcohol and ethylene vinyl alcohol. The oxygen permeability of these multilayer nanocomposites outperforms those of pure NFC films prepared by solvent-casting. The nanocellulosic LbL assemblies on PLA substrates was in detailed characterized using a quartz crystal microbalance with dissipation (QCM-D). Atomic force microscopy (AFM) reveals large structural differences between the PEI/NFC and the PEI/CMC assemblies, with the PEI/NFC assembly showing a highly entangled network of nanofibrils, whereas the PEI/CMC surfaces lacked structural features. Scanning electron microscopy images showed a nearly perfect uniformity of the nanocellulosic coatings on PLA, and light transmittance results revealed remarkable transparency of the LbL-coated PLA films. The present work demonstrates the first ever LbL films based on high aspect ratio, water-dispersible nanofibrillated cellulose, and water-soluble carboxymethyl cellulose polymers that can be used as multifunctional films and coatings with tailorable properties, such as gas barriers and transparency. Owing to its flexibility, transparency and high-performance gas barrier properties, these thin film assemblies are promising candidates for several large-scale applications, including flexible electronics and renewable packaging.

  • 229.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindqvist, Josefina
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Shchukarev, Andrei
    Umeå Universitet.
    Lindström, Tom
    Wetting kinetics of oil mixtures on fluorinated model cellulose surfaces2008Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 317, s. 556-567Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The wetting of two different model cellulose surfaces has been studied; a regenerated cellulose (RG) surface prepared by spin-coating, and a novel multilayer film of poly(ethyleneimine) and a carboxymethylated microtibrillated cellulose (MFC). The cellulose films were characterized in detail using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM indicates smooth and continuous films on a nanometer scale and the RMS roughness of the RG cellulose and MFC surfaces was determined to be 3 and 6 nm, respectively. The cellulose films were modified by coating with various amounts of an anionic fluorosurfactant, perfluorooctadecanoic acid, or covalently modified with pentadecafluorooctanyl chloride. The fluorinated cellulose films were used to follow the spreading mechanisms of three different oil mixtures. The viscosity and surface tension of the oils were found to be essential parameters governing the spreading kinetics on these surfaces. XPS and dispersive surface energy measurements were made on the cellulose films coated with perfluorooctadecanoic acid. A strong correlation was found between the surface concentration of fluorine, the dispersive surface energy and the contact angle of castor oil on the surface. A dispersive surface energy less than 18 mN/m was required in order for the cellulose surface to be non-wetting (theta(e) > 90 degrees) by castor oil.

  • 230.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lindström, Tom
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Biopolymer Coatings for Paper and Paperboard2011Ingår i: Biopolymers: New Materials for Sustainable Films and Coatings / [ed] David Plackett, Chichester: John Wiley & Sons, 2011, s. 255-276Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 231.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Netrval, Julia
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Lindström, Tom
    Aerogels from nanofibrillated cellulose with tunable oleophobicity2010Ingår i: SOFT MATTER, ISSN 1744-683X, Vol. 6, nr 14, s. 3298-3305Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation of structured porous aerogels of nanofibrillated cellulose (NFC) by freeze-drying has been demonstrated. The aerogels have a high porosity, as shown by FE-SEM and nitrogen adsorption/desorption measurements, and a very low density ( < 0.03 g cm(-3)). The density and surface texture of the aerogels can be tuned by selecting the concentration of the NFC dispersions before freeze-drying. Chemical vapor deposition (CVD) of 1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane (PFOTS) was used to uniformly coat the aerogel to tune their wetting properties towards non-polar liquids. An XPS analysis of the chemical composition of the PFOTS-modified aerogels demonstrated the reproducibility of the PFOTS-coating and the high atomic fluorine concentration (ca. 51%) in the surfaces. The modified aerogels formed a robust composite interface with high apparent contact angles (theta* >> 90 degrees) for castor oil (gamma(1v) = 35.8 mN m(-1)) and hexadecane (gamma(1v) = 27.5 mN m(-1)).

  • 232.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Netrval, Julia
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Tom
    Ultra light-weight microfibrillated cellulose aerogels with tunable oleophobicityArtikel i tidskrift (Refereegranskat)
  • 233.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Salazar-Alvarez, German
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lindström, Tom
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    High strength, flexible and transparent nanofibrillated cellulose-nanoclay biohybrid films with tunable oxygen and water vapor permeability2012Ingår i: Nanoscale, ISSN 2040-3364, Vol. 4, nr 20, s. 6622-6628Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel, technically and economically benign procedure to combine vermiculite nanoplatelets with nanocellulose fibre dispersions into functional biohybrid films is presented. Nanocellulose fibres of 20 nm diameters and several micrometers in length are mixed with high aspect ratio exfoliated vermiculite nanoplatelets through high-pressure homogenization. The resulting hybrid films obtained after solvent evaporation are stiff (tensile modulus of 17.3 GPa), strong (strength up to 257 MPa), and transparent. Scanning electron microscopy (SEM) shows that the hybrid films consist of stratified nacre-like layers with a homogenous distribution of nanoplatelets within the nanocellulose matrix. The oxygen barrier properties of the biohybrid films outperform commercial packaging materials and pure nanocellulose films showing an oxygen permeability of 0.07 cm(3) mu m m(-2) d(-1) kPa(-1) at 50% relative humidity. The oxygen permeability of the hybrid films can be tuned by adjusting the composition of the films. Furthermore, the water vapor barrier properties of the biohybrid films were also significantly improved by the addition of nanoclay. The unique combination of excellent oxygen barrier behavior and optical transparency suggests the potential of these biohybrid materials as an alternative in flexible packaging of oxygen sensitive devices such as thin-film transistors or organic light-emitting diode displays, gas storage applications and as barrier coatings/laminations in large volume packaging applications.

  • 234.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Ström, Göran
    Multilayered Alkyd Resin/Nanocellulose Coatings for Use in Renewable Packaging Solutions with a High Level of Moisture Resistance2013Ingår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 52, nr 7, s. 2582-2589Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A surprisingly simple and rapid methodology for large-area, lightweight, and thin laminate coatings with remarkable moisture barrier properties is introduced. Commercially available paperboards are coated with thin layers of nanocellulose. The nanocellulose coating induces a surface smoothening effect on the coated sheets as characterized by environmental scanning electron microscopy and white light interferometry. A moisture-protective layer of renewable alkyd resins is deposited on the nanocellulose precoated sheets using a water-borne dispersion coating process or lithographic printing. Through an auto-oxidation process, the applied alkyd resins are transformed into moisture sealant layers. The moisture barrier properties are characterized in detail by water vapor permeability measurements at different levels of relative humidity. The water vapor barrier properties of the nanocellulose precoated substrates were significantly improved by thin layers of renewable alkyd resins. The effect of the alkyd resin properties, coating technologies, and base paper substrates on the final barrier performance of the sheets were studied. It was found that the nanocellulose coating had a notable effect on the homogeneity and barrier performance of the alkyd resin layers and in particular those alkyd resin layers that were applied by printing. The concept is environmentally friendly, energy-efficient, and economic and is ready for scaling-up via continuous roll-to-roll processes. Large-scale renewable coatings applicable for sustainable packaging solutions are foreseen.

  • 235.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Varga, Imre
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Lindström, Tom
    STFI-Packforsk AB.
    Buildup of Polyelectrolyte Multilayers of Polyethyleneimine and Microfibrillated Cellulose Studied by in situ Dual Polarization Interferometry and Quartz Crystal Microbalance with Dissipation2008Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, nr 6, s. 2509-2518Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyethyleneimine (PEI) and Microfibrillated cellulose (MFC) have been used to buildup polyelectrolyte multilayers (PEM) on silicone oxide and silicone oxynitride surfaces at different pH values and with different electrolyte and polyelectrolyte/colloid concns. of the components.  Consecutive adsorption on these surfaces was studied by in situ dual-polarization interferometry (DPI) and quartz crystal microbalance measurements.  The adsorption data obtained from both the techniques showed a steady buildup of multilayers.  High pH and electrolyte concn. of the PEI soln. was found to be beneficial for achieving a high adsorbed amt. of PEI, and hence of MFC, during the buildup of the multilayer.  On the other hand, an increase in the electrolyte concn. of the MFC dispersion was found to inhibit the adsorption of MFC onto PEI.  The adsorbed amt. of MFC was independent of the bulk MFC concn. in the investigated concn. range (15-250 mg/L).  At. force microscopy measurements were used to image a MFC-treated silicone oxynitride chip from DPI measurements.  The surface was found to be almost fully covered by randomly oriented microfibrils after the adsorption of only one bilayer of PEI/MFC.  The surface roughness expressed as the rms-roughness over 1 μm2 was calcd. to be 4.6 nm (1 bilayer).  The adsorbed amt. of PEI and MFC and the amt. of water entrapped by the individual layers in the multilayer structures were estd. by combining results from the two anal. techniques using the de Feijter formula.  These results indicate a total water content of ca. 41% in the PEM.

  • 236.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Lindstrom, Tom
    STFI Packforsk, KTH STFI, SE-11486 Stockholm, Sweden..
    CELL 206-Preparation, characterization and wetting of fluorinated cellulose surfaces2008Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 235Artikel i tidskrift (Övrigt vetenskapligt)
  • 237.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Yun, Sang Ho
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Lindström, Tom
    Design of Highly Oleophobic Cellulose Surfaces from Structured Silicon Templates2009Ingår i: Applied Materials and Interfaces, ISSN 1944-8244, Vol. 1, nr 11, s. 2443-2452Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Structured silicon surfaces, possessing hierarchical porous characteristics consisting of micrometer-sized cavities superimposed upon a network of nanometer-sized pillars or wires, have been fabricated by a plasma-etching process. These surfaces have superoleophobic properties, after being coated with fluorinated organic trichlorosilanes, on intrinsically oleophilic surfaces. By comparison with flat silicon surfaces, which are oleophilic, it has been demonstrated that a combination of low surface energy and the structured features of the plasma-etched surface is essential to prevent oil from penetrating the surface cavities and thus induce the observed macroscopic superoleophobic phenomena with very low contact-angle hysteresis and low roll-off angles. The structured silicon surfaces were coated with cellulose nanocrystals using the polyelectrolyte multilayer technique. The cellulose surfaces prepared in this way were then coated with a monolayer of fluorinated trichlorosilanes. These porous cellulose films displayed highly nonwetting properties against a number of liquids with low surface tension, including alkanes such as hexadecane and decane. The wettability and chemical composition of the cellulose/silicon surfaces were characterized with contact-angle goniometry and X-ray photoelectron spectroscopy, respectively. The nano/microtexture features of the cellulose/silicon surfaces were also studied with field-emission scanning electron microscopy. The highly oleophobic structured cellulose surfaces are very interesting model surfaces for the development of biomimetic self-cleaning surfaces in a vast array of products, including green constructions, packaging materials, protection against environmental fouling, sports, and outdoor clothing, and microfluidic systems.

  • 238. Auty, Sam E. R.
    et al.
    Andrén, Oliver C. J.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hern, Faye Y.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Rannard, Steven P.
    One-pot' sequential deprotection/functionalisation of linear-dendritic hybrid polymers using a xanthate mediated thiol/Michael addition2015Ingår i: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 6, nr 4, s. 573-582Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thiol-Michael addition chemistry is a powerful tool for the preparation of functional materials. In this first report of xanthate-functional linear-dendritic polymer hybrids, the preparation of four generations of xanthate-functionalised dendron atom transfer radical polymerisation macroinitiators is described using an orthogonal chemical strategy. The controlled polymerisation of tertiary butyl methacrylate is demonstrated to high conversion and without interference from the xanthate surface groups. Modification of the peripheral xanthate groups of dendrons at the hybrid polymer chain-end has been studied using a one-pot deprotection/functionalisation strategy and a range of commercially available and bespoke acrylate monomers to form complex polymer architectures from feedstock polymers, differing in the number of modified end groups and the surface chemistry of the dendron chain end.

  • 239. Auty, Sam E. R.
    et al.
    Andrén, Oliver
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik.
    Rannard, Steven P.
    The first peripherally masked thiol dendrimers: a facile and highly efficient functionalization strategy of polyester dendrimers via one-pot xanthate deprotection/thiol-acrylate Michael addition reactions2014Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 50, nr 50, s. 6574-6577Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Introducing multiple reactive functional groups at the periphery of dendrimer materials presents considerable challenges if the functionality is able to self-react. An efficient and facile approach to introducing masked thiols at the surface of polyester dendrimers is presented. One-pot, deprotection/thiol-acrylate Michael addition from the xanthate-functional dendritic substrates (generation zero to two) has been achieved for the first time, with high efficiency demonstrated using three acrylates of varying chemistry and avoiding disulfide formation.

  • 240.
    Avalos, Arturo Salazar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Superiorly Plasticized PVC/PBSA Blends through Crotonic and Acrylic Acid Functionalization of PVC2017Ingår i: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 9, nr 3, artikel-id 84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Superior plasticization efficiency was achieved by a grafting from functionalization of the PVC backbone. This was deduced to a synergistic effect of internal plasticization and improved intermolecular interactions between PVC and an oligomeric poly(butylene succinate-co-adipate) ( PBSA) plasticizer. A mild grafting process for functionalization of the PVC chain by crotonic acid ( CA) or acrylic acid ( AA) was used. The formation of PVC-g-CA and PVC-g-AA was confirmed by FTIR and H-1 NMR. Grafting with the seemingly similar monomers, CA and AA, resulted in different macromolecular structures. AA is easily homopolymerized and long hydrophilic poly( acrylic acid) grafts are formed resulting in branched materials. Crotonic acid does not easily homopolymerize; instead, single crotonic acid units are located along the PVC chain, leading to basically linear PVC chains with pendant crotonic acid groups. The elongation of PVC-g-CA and PVC-g-AA in comparison to pure PVC were greatly increased from 6% to 128% and 167%, respectively, by the grafting reactions. Blending 20% ( w/w) PBSA with PVC, PVC-AA or PVC-CA further increased the elongation at break to 150%, 240% and 320%, respectively, clearly showing a significant synergistic effect in the blends with functionalized PVC. This is a clearly promising milestone towards environmentally friendly flexible PVC materials.

  • 241. Axegard, Peter
    et al.
    Bergnor, Elisabeth
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ekholm, Ulrika
    Bleaching of softwood kraft pulps with H2O2, O3, and ClO21996Ingår i: TAPPI Journal, ISSN 0734-1415, Vol. 79, nr 1, s. 113-119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ozone or chlorine dioxide bleaching prior to hydrogen peroxide bleaching greatly improves the performance of the hydrogen peroxide stage. The efficiency is further improved by a chelating treatment immediately after the ozone or chlorine dioxide stage. With an optimal metal ion profile, laboratory bleached (OAZQP) softwood kraft pulps can reach brightness levels above 90% ISO, with 5-10% lower pulp strength properties and bleaching costs comparable to ECF bleaching. It also is possible to obtain full brightness with only hydrogen peroxide provided the metal ion profile is optimal, e.g., by using multiple QP treatments. The chemical consumptions, expressed as oxidation equivalents per decreased kappa number are the same as for sequences including ozone or chlorine dioxide. Ozone and chlorine dioxide are comparable as far as delignification and brightness efficiency go.

  • 242. Axegård, Peter
    et al.
    Bergnor, Elisabeth
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ekholm, Ulrika
    The role of metal ions in TCF-bleaching of softwood kraft pulps.: Vol.31994Ingår i: Proceedings Tappi Pulping conf., 1994, s. 1161-1167Konferensbidrag (Refereegranskat)
  • 243. Axelsson, P.
    et al.
    Berggren, R.
    Berthold, F.
    Lindström, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Molecular mass distributions of lignin and lignin-carbohyd rate complexes in birch Kraft pulps: Changes caused by the conditions in the cook and their relation to unbleached pulp brightness and bleachability2005Ingår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 31, nr 1, s. 19-27Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lignin-carbohydrate complexes and their relationship to pulp bleachability and unbleached pulp brightness were studied in four birch kraft pulps produced at high and low hydroxide ion and sodium ion concentrations, using size-exclusion chromatography (SEC). About 75-80%of the lignin was found to be associated with carbohydrates, a larger part with hemicelluloses and a smaller part with cellulose. Easily bleached pulps, produced under high [OH-] or low [Na+] conditions, had more lignin associated with cellulose than their counterparts. Furthermore, a high [OH-] gave a residual lignin that was significantly more accessible in the residual lignin isolation, and where the inaccessible lignin was bonded to carbohydrates. Colour differences of pulps caused by variations in the cooking conditions, as studied in the SEC system, were associated with all the lignin, irrespective of whether it was associated with hemicelluloses or cellulose.

  • 244. Axelsson, Patrik
    et al.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Teder, Ants
    Bleachability of Alkaline Birch Pulps.2000Ingår i: Proceedings 6th European Workshop on Lignocellulosics and Pulp., 2000Konferensbidrag (Refereegranskat)
  • 245. Axelsson, Patrik
    et al.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Teder, Ants
    Influence of alkali profile in the kraft cook on the bleachability of birch.2001Ingår i: : Book:Vol I, 2001, s. 41-44Konferensbidrag (Refereegranskat)
  • 246.
    Azarian, Hamid Reza
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    MAE for Quantitative Determination of Antioxidant Irganox 1010 in Polypropylene Film2002Självständigt arbete på avancerad nivå (magisterexamen), 180 hpStudentuppsats (Examensarbete)
  • 247.
    Azhar, Shoaib
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Extraction of Polymeric Hemicelluloses from Spruce Wood2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Hemicelluloses are one of the three main components of spruce wood and constitute about 20% of the wood material. During mechanical pulping, 5–10% of the hemicelluloses are accumulated in waste waters, whereas during chemical pulping 70–80% of the hemicelluloses are lost in process liquors. The concept of integrated forest biorefinery involves the development of methods to extract these hemicelluloses prior to pulping in order to produce value-­added products besides pulp. This thesis describes some of the feasible possibilities of extracting hemicelluloses from wood at a high molecular weight prior to pulping in addition to presenting a deeper understanding of their degradation under mild treatment conditions.

    A major obstacle for the efficient extraction of hemicelluloses is the recalcitrance due to the network of lignin and polysaccharides. This network can be loosely opened by the use of enzymes and this improves the extraction of hemicelluloses. A chemical impregnation of the wood chips was performed to enhance the accessibility of the cell wall to enzymes. The ability of different additives to stabilize the hemicelluloses against peeling during the alkaline impregnation stage was also investigated in order to obtain a better yield in subsequent extraction.

    Increasing the surface area and decreasing the mass transport length could also improve the yield of hemicelluloses extracted from wood. This was achieved with a mild mechanical pre-­treatment of wood chips using an impressafiner and a fiberizer. Polymers mainly consisting of galactoglucomannan with an average molecular weight of 30 kDa were extracted from fiberized wood with water.

    Different pre-­treatment and extraction methods were combined to demonstrate the concept of material biorefinery based on wood.

    The kinetics of degradation of spruce galactoglucomannan were studied under alkaline conditions. It was degraded in two phases at two different rates. A kinetic model was developed to fit the experimental data and to estimate the activation energies. 

  • 248.
    Azhar, Shoaib
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Theliander, Hans
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Lindström, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Extraction of hemicelluloses from fiberized spruce wood2015Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 117, s. 19-24Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel mechanical pre-treatment method was used to separate the wood chips into fiber bundles in order to extract high molecular weight wood polymers. The mechanical pre-treatment involved chip compression in a conical plug-screw followed by defibration in a fiberizer. The fiberized wood was treated with hot water at various combinations of time and temperature in order to analyze the extraction yield of hemicelluloses at different conditions. Nearly 6 mg/g wood of galactoglucomannan was obtained at 90◦C/120min which was about three times more than what could be extracted from wood chips. The extracted carbohydrates had molecular weight ranging up to 60 kDa. About 10% of each of the extracted material had a molecular weight above 30 kDa. The extraction liquor could also be reused for consecutive extractions with successive increase in the extraction yield of hemicelluloses. 

  • 249.
    Azhar, Shoaib
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Wang, Yan
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lawoko, Martin
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Extraction of polymers from enzyme-treated softwood2011Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 6, nr 4, s. 4606-4614Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a biorefinery context it is an advantage to fractionate and extract different wood components in a relatively pure form. However, one major obstacle for efficient extraction of wood polymers (lignin, polysaccharides etc.) is the covalent lignin-polysaccharide networks present in lignified cell walls. Enzymatic catalysis might be a useful tool for a controlled degradation of these networks, thereby enhancing the extraction of high molecular weight polymers. In this work, a methanol-alkali mixture was used to extract two different wood samples treated with endoxylanase and gammanase, respectively. Wood chips were pretreated with alkali prior to enzymatic treatment to enhance the cell-wall accessibility to enzymes. Extractions were also carried out on non-enzyme-treated samples to evaluate the enzymatic effects. Results showed that the enzymatic treatment increased the extraction yield, with gammanase as the more efficient of the two enzymes. Furthermore, polymers extracted from xylanase-treated wood had a higher degree of polymerization than the reference.

  • 250.
    Azhar, Shoaib
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Wang, Yan
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lawoko, Martin
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Enhanced extraction of high-molecular-weight wood polymers with chemoenzymatic treatment2012Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 243Artikel i tidskrift (Övrigt vetenskapligt)
2345678 201 - 250 av 2733
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