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  • 4301. Wolf, A.
    et al.
    Vidlund, Anna
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Andersson, E.
    Energy-efficient pellet production in the forest industry - a study of obstacles and success factors2006In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 30, no 1, p. 38-45Article in journal (Refereed)
    Abstract [en]

    With an expanding market for upgraded biofuel in many countries, it is important to develop efficient production methods for upgrading wet biomass. The possibilities for heat recovery can be improved if the upgrading process is integrated with other energy-intensive processes, as for example a pulp mill or a sawmill, in a biofuel combine. This work evaluates obstacles and Success factors for forming such biofuel combines with the forest industry. Case Studies and calculations on theoretical cases have been used together with literature references to evaluate how a biofuel combine can be realised and to compile obstacles and success factors for a combine. It could be seen from the case studies that an excess of by-products and waste heat, together with an existing need for investments are important driving forces for the formation of biofuel combines in the forest industry. The market was also identified as an important factor, which can be both an obstacle and a success factor depending on the situation. It was concluded that the existence of a small-scale pellet market near the plant is important for economic feasibility when sawdust is used as raw material. The conditions for the biofuel combine are different depending on the form of ownership. When a pulp mill or sawmill owns the pellet factory, it was concluded that minimising the risk by using well-known technologies can be an important factor for the realisation of the combine.

  • 4302.
    Wolf, Jens
    KTH, Superseded Departments, Chemical Engineering and Technology.
    CO2 mitigation in advanced power cycles2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis encompasses CO2 mitigation using three different processes: i) natural gas-fired combined cycle with chemical looping combustion (CLC), ii) trigeneration of electrical power, hydrogen and district heating with extended CLC, iii) steam-based gasification of biomass integrated in an advanced power cycle.

    In CLC, a solid oxygen carrier circulates between two fluidised-bed reactors and transports oxygen from the combustion air to the fuel; thus, the fuel is not mixed with air and an inherent CO2 separation occurs. In this thesis, CLC has been studied as an alternative process for CO2 capture in a natural gas-fired combined cycle (NGCC). The potential efficiency of such a process using a turbine inlet temperature of 1200 °C and a pressure ratio of 13 is between 52 and 53 % when including the penalty for CO2 compression to 110 bar. It is shown that this efficiency cannot be further improved by including an additional CO2 turbine. Two conceivable reactor designs for CLC in an NGCC are presented. Top-firing has been studied as an option to overcome a temperature limitation in the CLC reactor system. The degree of CO2 capture is shown versus the temperature in the CLC reactor and its combustion efficiency. CLC has the potential to reach both a higher efficiency and a higher degree of CO2 capture than conventional post combustion CO2 capture technique. However, further research is needed to solve technical problems as, for example, temperature limitations in the reactor to reach this potential.

    Extended CLC (exCLC) is introduced, in which hydrogen is not only produced but also inherently purified. The potential efficiency of a novel tri-generation process for hydrogen, electricity and district heating using exCLC for CO2 capture is investigated. The results show that a thermal efficiency of about 54% might be achieved.

    A novel power process named evaporative biomass air turbine (EvGT-BAT) for biomass feedstock is presented. This process contains a steam-based gasification of biomass, which is integrated in an externally fired gas turbine cycle with top-firing. In the EvGT-BAT process, the steam-based gasification is conducted in an entrained-flow tubular reactor that is installed in the SFC as a heat exchanger. The EvGT-BAT process has the potential to generate electrical power from biomass with an efficiency of 41 %.

  • 4303.
    Wolf, Jens
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Yan, Jinyue
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Cogeneration of hydrogen and electrical power in an extended chemical-looping combustion2004In: Energy-Efficient, Cost-Effective and Environmentally-Sustainable Systems and Processes, Vols 1-3 / [ed] Rivero, R; Monroy, L; Pulido, R; Tsatsaronis, G, MEXICO: INST MEXICANO DEL PETROLEO , 2004, p. 1151-1160Conference paper (Refereed)
    Abstract [en]

    This paper presents an extended chemical-looping combustion (exCLC), which may be the core process in an advanced power generation system with CO2-capture that cogenerates hydrogen and electrical power. This paper focuses on the description of the exCLC and its novelty compared to the classic chemical-looping combustion (CLC), which is known as all efficient alternative for CO2-capture. In CLC. a solid oxygen carrier circulates between two fluidised-bed reactors and transports oxygen from the combustion air to the fuel, thus, the fuel is not mixed with air and an inherent CO2 separation occurs. In addition to the classic CLC, the exCLC inherently separates the CO2 and hydrogen, that is produced by the process. A thermo-chemical study of the exCLC provides the required operating conditions of each step. The results indicate that the production of hydrogen is possible as well as an inherent separation of hydrogen and CO2.

  • 4304.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Bränsleceller och material: Rapport från arbetsseminarium 16 juni 20112011Report (Other (popular science, discussion, etc.))
  • 4305.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Aguinaga, Luis Guerrero
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Oyarce, Alejandro
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ubeda, Diego
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ingratta, Mark
    Jannasch, Patric
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Fuel cell performance using a phosphonated polysulphone ionomer (PSUgPVPA) in the PEM cathode electrode2013In: Fuel Cell Membranes, Electrode Binders, And Mea Performance, Electrochemical Society, 2013, no 23, p. 33-45Conference paper (Refereed)
    Abstract [en]

    Inexpensive and environmentally friendly electrolyte polymers that can be operated at higher temperatures and drier conditions are highly interesting for PEM fuel cells for automotive, portable power and stationary electricity generation applications. In this study an ionomer based on polysulfone grafted with poly(vinylphosphonic acid) (PSUgPVPA) in the cathode Pt/C catalyst layer (CL) was electrochemically characterized and compared to Nafion (R). The performance at different levels of humidity at 80 degrees C was evaluated by polarization and cyclic voltammetry. The results show that the performance of the PSUgPVPA-based cathode CL is comparable to that of Nafion (R) at 100% relative humidity (RH) but with some instabilities. However, at drier conditions significant losses of performance for the PSUgPVPA-based cathode was observed, concomitant to a reduced electrochemical surface area. The lower performance at low humidity is concluded to be due to a combination of lower proton conductivity and wettability or interference with oxygen reduction reaction at lower RH.

  • 4306.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hildebrandt, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Polymera bränsleceller (PEMFC): Teknikbevakningsrapport 20092009Report (Other (popular science, discussion, etc.))
  • 4307.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Kortsdottir, Katrin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Pérez Ferriz, Francisco Javier
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Conde Lopez, Julio Jose
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    The Effect of Hydrocarbon Impurities in the Hydrogen Fuel on the Anode Activity in PEMFC2013Conference paper (Refereed)
    Abstract [en]

    The reformate fuel cell has recently gained increasing attention both for APUs in vehicles

    operating on diesel and in stationary applications such as micro-CHP operating on natural

    or biogas. In addition to hydrogen gas, reformate contain considerable amounts of CO2,

    nitrogen, water vapour and traces of CO, sulphur species and hydrocarbons. CO and H2S

    are well known poisons to the anode [1] but the influence of hydrocarbon species in the

    fuel cell has not been much investigated. We have previously investigated toluene [2] and

    ethene [3] on the anode Pt/C catalyst in the PEM fuel cell. In this paper we will discuss the

    influences of alkenes and alkanes in the light of some novel results on the effect of

    propene, propane and methane in the PEM fuel cell. We have especially focused on the

    adsorption and deactivation phenomena of low concentrations of contaminant on a Pt/C

    catalyst. In the experiments, in situ stripping voltammetry and on-line mass spectrometer

    were employed. The effects of adsorption potential and temperature are discussed. We

    show that propene is more poisonous to the Pt/C catalyst than ethene as it is adsorbed on

    the catalyst surface within the Hupd region and forms an adlayer that can be oxidized in two

    steps between 0.5-1 V (at 80°C, 90%RH) or be hydrogenated to propane in the Hupd region

    and in the presence of hydrogen.

  • 4308.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Teknikbevakning av polymera bränsleceller (PEFC)2011Report (Other (popular science, discussion, etc.))
  • 4309.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Oyarce, Alejandro
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Aguinaga, Luis Guerrero
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ubeda, Diego
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ingratta, Mark
    Jannasch, Patric
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Performance of Phosphonated Hydrocarbon Ionomer in the Fuel Cell Cathode Catalyst Layer2013In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 160, no 3, p. F269-F277Article in journal (Refereed)
    Abstract [en]

    Inexpensive and environmentally friendly electrolyte polymers that can be operated at higher temperatures and drier conditions are highly interesting for PEM fuel cells for automotive, portable power and stationary electricity generation applications. In this study an ionomer based on polysulfone grafted with poly(vinylphosphonic acid) (PSUgPVPA) in the cathode Pt/C catalyst layer was electrochemically characterized and compared to Nafion. The performance at different levels of humidity at 80 degrees C was evaluated by polarization measurements, cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results show that the performance of the PSUgPVPA-based cathode catalyst layer is comparable to that of Nafion-at 100% relative humidity (RH) but with some instabilities. However, at drier conditions significant losses of performance for the PSUgPVPA-based cathode was observed. This could be an effect of catalyst poisoning by the ionomer interfering with ORR. However, the concomitant decrease of the electrochemical surface area, double layer capacitance and increased imaginary impedance, indicate that the poorer performance at low humidity is mainly an effect of reduced catalyst wetting by the ionomer in combination with the decreased proton conduction in the ionomeric phase.

  • 4310.
    Wretfors, Christer
    et al.
    SLU, Alnarp.
    Cho, Sung-Woo
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael S
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Marttila, S
    SLU, Alnarp.
    Nimmermark, S
    SLU, Alnarp.
    Johansson, Eva
    SLU, Alnarp.
    Use of Industrial Hemp Fibers to Reinforce Wheat Gluten Plastics2009In: Journal of polymers and the environment, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 17, no 4, p. 259-266Article in journal (Refereed)
    Abstract [en]

    The next generation of manufactured products must be sustainable and industrially eco-efficient, making materials derived from plants an alternative of particular interest. Wheat gluten (WG) is an interesting plant material to be used for production of plastic similar materials due to its film-forming properties. For usage of plastics in a wider range of applications, composite materials with improved mechanical properties are demanded. The present study investigates the possibilities of reinforcing WG plastics with hemp fibers. Samples were manufactured using compression molding (130 A degrees C, 1600 bar, 5 min). Variation in fiber length, content (5, 10, 15 and 20 wt%) and quality (poor, standard, good) were evaluated. Mechanical properties and structure of materials were examined using tensile testing, light and scanning electron microscopy. Hemp fiber reinforcement of gluten plastics significantly influenced the mechanical properties of the material. Short hemp fibers processed in a high speed grinder were more homogenously spread in the material than long unprocessed fibers. Fiber content in the material showed a significant positive correlation with tensile strength and Young's modulus, and a negative correlation with fracture strain and strain at maximum stress. Quality of the hemp fibers did not play any significant role for tensile strength and strain, but the Young's modulus was significantly and positively correlated with hemp fiber quality. Despite the use of short hemp fibers, the reinforced gluten material still showed uneven mechanical properties within the material, a result from clustering of the fibers and too poor bonding between fibers and gluten material. Both these problems have to be resolved before reinforcement of gluten plastics by industrial hemp fibers is applicable on an industrial scale.

  • 4311.
    Wretfors, Christer
    et al.
    SLU, Alnarp.
    Cho, Sung-Woo
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Kuktaite, R.
    SLU, Alnarp.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Marttila, S
    SLU, Alnarp.
    Nimmermark, S
    SLU, Alnarp.
    Johansson, Eva
    SLU, Alnarp.
    Effects of fiber blending and diamines on wheat gluten materials reinforced with hemp fiber2010In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 45, no 15, p. 4196-4205Article in journal (Refereed)
    Abstract [en]

    Wheat gluten (WG) is a promising base material for production of "green" plastics, although reinforcement is needed in more demanding applications. Hemp fiber is a promising reinforcement source but difficulties exist in obtaining desired properties with a WG-based matrix. This study aimed at improving fiber dispersion and fiber-matrix interactions using a high speed blender and a diamine as a cross-linker. Samples were manufactured using compression molding, two types of blenders and addition of diamine. Mechanical properties were assessed with tensile testing. Tensile-fractured surfaces were examined with scanning electron microscopy (SEM). Protein polymerization and fiber-protein matrix interactions were examined using high performance liquid chromatography (HPLC) and confocal laser scanning microscopy (CLSM). The results showed that a higher-speed grinding yielded a more even distribution of fibers and a more polymerized protein structure compared to a lower-speed grinding. However, these improvements did not result in increased strength, stiffness, and extensibility for the higher-speed grinding. The strength was increased when the grinding was combined with addition of a diamine (Jeffamine(R) EDR-176). HPLC, SEM, and CLSM, indicated that diamine added samples showed a more "plastic" appearance together with a stiffer and stronger structure with less cracking compared to samples without diamine. The use of the diamine also led to an increased polymerization of the proteins, although no effect on the fiber-protein matrix interactions was observed using microscopical techniques. Thus, for future successful use of hemp fibers to reinforce gluten materials, an appropriate method to increase the fiber-protein matrix interaction is needed.

  • 4312.
    Wu, Duo
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Closed-loop strategy for recycling of starch and poly (lactic acid) into new materials2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Biopolymers such as starch and poly lactic acid (PLA) can be derived from agriculture and are among the most promising biobased plastics for packaging and other short term application. Considering the growing pressure of environmental safety and limited resources on our planet, it would be beneficial to retain the value of waste products by material recycling. A closed-loop strategy from feedstock recycling of biopolymers to utilization of the obtained degradation products as property enhancers in the same biopolymers was demonstrated in the thesis. 

  • 4313.
    Wu, Duo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bäckström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Starch Derived Nanosized Graphene Oxide Functionalized Bioactive Porous Starch Scaffolds2017In: Macromolecular Bioscience, ISSN 1616-5187, E-ISSN 1616-5195, Vol. 17, no 6Article in journal (Refereed)
    Abstract [en]

    A fully starch-derived bioactive 3D porous scaffold is developed. The bioactivity is introduced through nanosized graphene oxide (nGO) derived from starch by microwave-assisted degradation to carbon spheres and further oxidation to GO nanodots. nGO is covalently attached to starch to prepare functionalized starch (SNGO) via an esterification reaction. nGO and SNGO exhibit no cytotoxicity to MG63 at least up to 1000 µg mL−1 under (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Porous scaffolds consisting of starch and SNGO (S/SNGO) or nGO (S/nGO) are prepared by freeze drying. The porosity and water uptake ability of the scaffolds depend on the concentration of nGO. Moreover, nGO, as a bioactive nanofiller, functions as an effective anchoring site for inducing CaP recrystallization in simulated body fluid. Among all modified starch-based scaffolds, the S/SNGO scaffold containing the highest concentration of covalently attached SNGO (50%) induces the largest amount of hydroxyapatite, a type of CaP crystal that is closest to bone. The prepared 3D porous nGO functionalized scaffold, thus, exhibits potential promise for bone/cartilage tissue engineering. (Figure presented.).

  • 4314.
    Wu, Duo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    A Closed-Loop Process from Microwave-Assisted Hydrothermal Degradation of Starch to Utilization of the Obtained Degradation Products as Starch Plasticizers2014In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 2, no 9, p. 2172-2181Article in journal (Refereed)
    Abstract [en]

    A green closed-loop water-based process for chemical recycling of starch was demonstrated. The process starts from microwave-assisted controllable starch degradation to functional chemicals and continues to utilization of the formed degradation products, glucose and levulinic acid (LA), as starch plasticizers. The degradation process and the effect of process parameters on the formed degradation products and residues were carefully fingerprinted by multiple techniques, e.g., NMR, ESI-MS, FTIR imaging, UV-vis, and SEM. The degradation process took place in three steps, proceeding from rupture of starch granules and oligosaccharide formation to further hydrolysis to glucose. Finally, at well-defined time point rapid degradation of glucose to LA and formic acid (FA) was initiated through a 5-hydroxymethyl furfural (5-HMF) intermediate. 5-HMF also participated in carbonization reactions leading to formation of solid carbon spheres. Through selection of processing parameters, LA could be produced in high yield with 9596 selectivity. The results demonstrated that microwave-assisted degradation of starch leads to well-defined controllable degradation products. These products are directly reusable as plasticizers for new starch products, which suggest great opportunities for biomass and starch recycling, opening the door toward potential industrial applications.

  • 4315.
    Wu, Duo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Recycling PLA to multifunctional oligomeric compatibilizers for PLA/starch composites2015In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 64, p. 126-137Article in journal (Refereed)
    Abstract [en]

    Simple one-pot valorization of poly(lactic acid) (PLA) to green additives was demonstrated. PLA was thermally recycled in the presence of polyols, which accelerated the degradation process by reacting with PLA chains. As a result low molecular weight oligomers with polyols end-groups were formed. The reaction between PLA and multifunctional alcohols i.e. glycerol, sorbitol, glucose and starch were confirmed by FTIR, H-1 NMR, SEC and MALDI-MS. The resulting amphiphilic products were evaluated as compatibilizer candidates for PLA/starch blends. Multiple techniques demonstrated that the obtained oligomers strengthened the interfacial adhesion and improved the compatibility and flexibility of extruded and melt-blended PLA/starch composites. The developed one-pot procedure required no solvent or catalyst offering good possibilities for up-scaling. It was, thus, demonstrated that PLA can be recycled to low molecular weight compatibilizers by simple process of thermal heating in the presence of polyols. This provides profound promise for retaining the material value of old PLA products at the same time as biobased additives are produced.

  • 4316.
    Wu, Qiong
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Biofoams and Biocomposites based on Wheat Gluten Proteins2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Novel uses of wheat gluten (WG) proteins, obtained e.g. as a coproduct from bio-ethanol production, are presented in this thesis. A flame-retardant foam was prepared via in-situ polymerization of hydrolyzed tetraethyl orthosilicate (TEOS) in a denatured WG matrix (Paper I). The TEOS formed a well-dispersed silica phase in the walls of the foam. With silica contents ≥ 6.7 wt%, the foams showed excellent fire resistance. An aspect of the bio-based foams was their high sensitivity to fungi and bacterial growth. This was addressed in Paper II using a natural antimicrobial agent Lanasol. In the same paper, a swelling of 32 times its initial weight in water was observed for the pristine WG foam and both capillary effects and cell wall absorption contributed to the high uptake. In Paper III, conductive and flexible foams were obtained using carbon-based nanofillers and plasticizer. It was found that the electrical resistance of the carbon nanotubes and carbon black filled foams were strain-independent, which makes them suitable for applications in electromagnetic shielding (EMI) and electrostatic discharge protection (ESD). Paper IV describes a ‘water-welding’ method where larger pieces of WG foams were made by wetting the sides of the smaller cubes before being assembled together. The flexural strength of welded foams was ca. 7 times higher than that of the same size WG foam prepared in one piece. The technique provides a strategy for using freeze-dried WG foams in applications where larger foams are required.

    Despite the versatile functionalities of the WG-based materials, the mechanical properties are often limited due to the brittleness of the dry solid WG. WG/flax composites were developed for improved mechanical properties of WG (Paper V). The results revealed that WG, reinforced with 19 wt% flax fibres, had a strength that was ca. 8 times higher than that of the pure WG matrix. Furthermore, the crack-resistance was also significantly improved in the presence of the flax.

  • 4317.
    Wu, Qiong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindh, Vilhelm H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Johansson, E.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Freeze-dried wheat gluten biofoams; scaling up with water welding2017In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 97, p. 184-190Article in journal (Refereed)
    Abstract [en]

    This paper presents a simple and rapid wet welding technique that enables the scaling up of freeze-dried protein (wheat gluten (WG)) biofoams for e.g. thermal insulation applications. The welding occurred by first wetting faces of foam cubes in water and then pressing them together for a limited time period. The water plasticized thin cell-walls of the two foams formed a dense weld when the plasticized cells collapsed under the drying step. The welds were always stronger and stiffer than the surrounding cellular structure. Based on three-point bending, it was shown that welded specimens (four-cube samples) were 7 times stronger than specimens produced directly as one piece with similar total size. This illustrated the problem of freeze-drying larger products; by instead assembling smaller foams into a large object the overall foam structure became more homogeneous. In addition, the dense welds become “walls” that limit gas convection in the mainly open cell structure, beneficial for thermal insulation. This is the first report on combined freeze-drying and water welding. It shows the sustainable potential of the technique for foam production, since only water is used as a foaming/welding agent.

  • 4318.
    Wu, Qiong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Sundborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Andersson, Richard L.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Peuvot, Kevin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Guex, Leonard
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nilsson, Fritjof
    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.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Conductive biofoams of wheat gluten containing carbon nanotubes, carbon black or reduced graphene oxide2017In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, no 30, p. 18260-18269Article in journal (Refereed)
    Abstract [en]

    Conductive biofoams made from glycerol-plasticized wheat gluten (WGG) are presented as a potential substitute in electrical applications for conductive polymer foams from crude oil. The soft plasticised foams were prepared by conventional freeze-drying of wheat gluten suspensions with carbon nanotubes (CNTs), carbon black (CB) or reduced graphene oxide (rGO) as the conductive filler phase. The change in conductivity upon compression was documented and the results show not only that the CNT-filled foams show a conductivity two orders of magnitude higher than foams filled with the CB particles, but also that there is a significantly lower percolation threshold with percolation occurring already at 0.18 vol%. The rGO-filled foams gave a conductivity inferior to that obtained with the CNTs or CB particles, which is explained as being related to the sheet-like morphology of the rGO flakes. An increasing amount of conductive filler resulted in smaller pore sizes for both CNTs and CB particles due to their interference with the ice crystal formation before the lyophilization process. The conductive WGG foams with CNTs were fully elastic with up to 10% compressive strain, but with increasing compression up to 50% strain the recovery gradually decreased. The data show that the conductivity strongly depends on the type as well as the concentration of the conductive filler, and the conductivity data with different compressions applied to these biofoams are presented for the first time.

  • 4319.
    Wu, Qiong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Yu, Shun
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Kollert, Matthias
    Mtimet, Mekki
    Roth, Stephan V.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Johansson, Eva
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Highly Absorbing Antimicrobial Biofoams Based on Wheat Gluten and Its Biohybrids2016In: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 4, no 4, p. 2395-2404Article in journal (Refereed)
    Abstract [en]

    This paper presents the absorption, mechanical, and antimicrobial properties of novel types of biofoams based on wheat-gluten (WG) and its biohybrids with silica. The hybrid WG foams were in situ polymerized with silica using two different silanes. When immersed in water, the 90-95% porous WG and silica-modified hybrid WG foams showed a maximum water uptake between 32 and 11 times the original sample weight. The maximum uptake was only between 4.3 and 6.7 times the initial weight in limonene (a nonpolar liquid) but showed reversible absorption/desorption and that the foams could be dried into their original shape. The different foams had a cell size of 2-400 mu m, a density of 60-163 kg/m(3), and a compression modulus of 1-9 MPa. The integrity of the foams during swelling in water was improved by cross-linking with glutaraldehyde (GA) or by a thermal treatment at 130 degrees C, which polymerized the proteins. In the never-dried state, the foam acted as a sponge, and it was possible to squeeze out water and soak it repeatedly. If the foam was dried to its glassy state, then the cells collapsed and did not open again even if the solid foam was reimmersed in water, saving as a sensor mechanism that can be used to reveal unintended exposure to polar liquids such as water under a product's service life. Small-angle X-ray scattering revealed that the gliadin-correlated structure expanded and then disappeared in the presence of water. The foam was made antimicrobial by impregnation with a Lanasol solution (a bromophenol existing in algae). It was also shown that the foam can act as a transfer/storage medium for liquids such as natural oils (rapeseed oil) and as a slow-release matrix for surfactant chemicals.

  • 4320. Wu, X.
    et al.
    Bruschi, M.
    Waag, T.
    Schweeberg, T.
    Tian, Y.
    Meinhardt, T.
    Stigler, R.
    Larsson, K.
    Funk, M.
    Steinmueller-Nethl, D.
    Rasse, M.
    Krueger, A.
    Functionaliation of Bone Implants with Nanodiamd Particles and Angiopoitein-1 to Improve Vascularization and Bone Regeneration2017In: Journal of Materials Chemistry B, Vol. 5, no 32, p. 6629-Article in journal (Refereed)
  • 4321. Wu, Yan
    et al.
    Fang, Mei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Lan, Lvdeng
    Zhang, Ping
    Rao, K. Venkat
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Bao, Zhengyu
    Rapid and direct magnetization of goethite ore roasted by biomass fuel2012In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 94, p. 34-38Article in journal (Refereed)
    Abstract [en]

    Biomass is a renewable and carbon neutral solid fuel. Utilization of biomass in iron ore roasting process as heating agent and reducing agent contributes to energy conservation and emission reduction, and can partially replace for coal and coke. The biomass instead of coke was mixed together with iron ore powder from the north of Hainan province into ball roasting process to investigate the effects of mixture composition, reduction temperature, reaction time, the thermal reduction and magnetic properties of the mixture. The results show that the reduction temperature, reaction time and dosage of the biomass are correlated to the quality of the reduction and the magnetism of the iron ore, within the experimental conditions. The mechanism of the biomass reducing the weakly magnetic goethite into stronger magnetic iron oxide has been discussed. The results show that the goethite ores is dramatically reduced and magnetized by about 20 wt.% biomass at low roasting temperature. Application of biomass energy in iron ores roasting process is prospective to the effective use of biomass and for decreasing the consumption of fossil fuels in the steelmaking process.

  • 4322.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Passive and Active Micromixers2009In: Handbook of Micro Reactors: Vol.1: Fundamentals, Operations and Catalysts / [ed] V. Hessel, J.C. Schouten, A. Renken, and J.-I. Yoshida,, Weinheim: Wiley-VCH Verlagsgesellschaft, 2009, 1Chapter in book (Refereed)
  • 4323.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Surface modification of PDMS in Microfluidic Devices2014In: Concise Encycloppedia of High Performance Silicones / [ed] Atul Tiwari and Mark D Soucek, Salem, Massachusetts: John Wiley & Sons, 2014Chapter in book (Refereed)
    Abstract [en]

    Being one of the most used materials for fabrication of microfluidic devices, Polydimethylsiloxane (PDMS) attracts great attention for years since G M Whitesides’ group introduced soft lithography - a rapid prototyping of microfluidic systems with PDMS, into the scientific community in the early 1990s. Its advantages in both physical and chemical properties promote a lots of micro/nano applications. Great efforts have been put to enhance its ability as well as minimize its drawbacks. In this chapter, kinds of common used methods in PDMS surface modification with their characterization methods and their recent development are introduced and discussed.

  • 4324. Wulff, Josefin
    et al.
    Cornell, Ann M.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Cathodic current efficiency in the chlorate process2007In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 37, no 1, p. 181-186Article in journal (Refereed)
    Abstract [en]

    Sodium chlorate is produced in undivided electrolysis cells. Hydrogen is evolved on the cathodes, usually made of steel, while chloride ions are oxidised to chlorine on the anodes, usually DSA (R) s. Parasitic cathodic reactions, lowering the cathodic current efficiency (CE), are the reduction of hypochlorite and chlorate ions. These reactions are suppressed by the addition of Cr(VI) to the electrolyte. In this work the effects that time of the electrolysis, chromate concentration and interruption of the electrolysis process have on CE has been investigated. New steel, as well as steel samples cut from cathodes used in a chlorate plant, were used as cathode material. Laboratory experiments in a divided cell were made to determine the rate of hydrogen production, and thereby indirectly CE, at varying operating conditions. It was found that the chromate concentration is important for the CE in the range 0.5-6 g l(-1) Na2Cr2O7. The CE was higher on new steel than on the used steel, which had a more corroded and inhomogeneous surface. When starting the electrolysis the CE was initially low, at a value depending on the operating conditions, but increased with time of polarisation. The time to reach an approximate steady CE was generally in the order of hours. Electrolysis shut downs in the presence of hypochlorite (<= 3 g l(-1) NaClO) resulted in corrosion of iron and a low CE when restarting the process. After one such corrosion shut down the new steel showed as low CE as the used steel. When restarting the electrolysis after a shut down without hypochlorite the CE was higher than before the shut down. Current densities of a simulated bipolar plate during a shut down were measured to 50-150 A m(-2), resulting from oxidation of steel and reduction of oxy chlorides on the catalytic DSA (R) electrode.

  • 4325.
    Wäne, Gerd
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Fibre surface properties of kraft pulp: The influence of wood raw material, bleaching and storage2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis was to study the fibre surface properties of Birch (Betula ssp.), Eucalyptus (E. urograndis and E. globulus) and Spruce (Picea Abies) pulps bleached using two different methods: ECF (Elementary Chlorine Free) and TCF (Totally Chlorine Free). The hardwood pulps were subjected to a hot acidic stage prior to ECF bleaching in order to remove hexenuronic acid. The effect of prolonged storage (ageing) on the fibre surface properties was studied for all of the pulps.

    The characteristics of the fibre surfaces were determined by measuring the dynamic contact angle of single fibres (DCA) and by using Electron Spectroscopy for Chemical Analysis (ESCA) and Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). The correlation between the fibre surface properties and the sizing efficiency of the hardwood pulps were evaluated by measuring the amount of alkyl ketene dimer (AKD) needed to reach a certain water absorption level(measured as Cobb60).

    The birch pulp was more hydrophilic than the eucalyptus pulps, thus requiring more AKD to reach a certain water absorption value, and also had a lower DCA. The introduction of a hot acidic stage (A stage) in the ECF bleaching sequence applied to the hardwood pulps (i.e. A/D(EP)DD versus D(EP)DD) lowered, as expected, the total fibre charge due to the removal of hexenuronic acids groups (HexA). According to the DCA measurements all of the pulps became more hydrophilic after the A/D(EP)DD bleaching than after the D(EP)DD bleaching sequence. The sizing ability of the pulps, measured as the AKD demand to a certain Cobb60 value, showed that the AKD demand was more or less the same for the eucalyptus pulps regardless of the bleaching sequence used. The birch pulp, on the other hand, required somewhat less AKD in the A/D(EP)DD sequence than in the D(EP)DD.

    The AKD demand to a certain Cobb60 value decreased further for the bleached birch and E. globulus pulps after ageing due to an increase in the fibre surface hydrophobicity. ESCA analysis revealed an increase of surface extractives on the pulps after ageing, which was also supported by ToF-SIMS analysis. It was concluded that there was an increase in fatty acids, fatty acid salts and possibly even sterols and glycerides on the fibre surfaces due to ageing. A migration of these components from the interior of the fibre wall to the fibre surface during ageing was verified in this study.

    The TCF and ECF bleached softwood pulps also showed differences in their fibre surface properties that were tangible and thereby measurable. The dynamic contact angle was highest for the TCF bleached softwood fibres, i.e. these were more hydrophobic. Although changes caused by ageing were much more pronounced for the ECF fibres, all pulps became more hydrophobic upon ageing.

    The hydrophobicity of pulp fibres can be determined using DCA, which is a rather rapid and economically viable analysis. Using this information, a paper/board mill can base its sizing strategy on scientific findings.

    The ageing effects seen on the fibre surfaces in the form of the migration of extractives might be an important parameter from an industrial point of view, especially when pulps are stored and/or transported for a long time period. Nowadays it is quite common for pulps to be shipped around the world and subjected to warm and humid conditions. It is therefore probable that the properties of the pulp change in such a way that the papermaking process requires adjustment.

  • 4326.
    Wäne, Gerd
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Aspects on the AKD demand of hardwood kraft pulps before and after ageing2009In: Appita journal, ISSN 1038-6807, Vol. 62, no 2, p. 123-129Article in journal (Refereed)
  • 4327.
    Wäne, Gerd
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Pulp and Fibre surface properties of bleached hardwood Kraft Pulps: Influence of an A-stage2009In: Paperi ja puu, ISSN 0031-1243, Vol. 91, no 7-8, p. 58-64Article in journal (Refereed)
    Abstract [en]

    Hexenuronic acids in kraft pulps increase the demand for bleaching chemicals and cause brightness reversion of the bleached pulps during storage. They can, however, be removed by the use of hot acid treatments in e.g. the bleaching sequence, which is commonly used for eucalyptus in the pulp industry today. In this work three kraft hardwood pulps (two eucalyptus and one birch) were selected to study the influence on the surface properties of the pulps of a hot acidic stage (A stage) introduced prior to a standard ECF bleaching sequence. The sequences compared were A/D(EP)DD and D(EP)DD. The results were compared before and after the pulps were aged at room temperature for about eight months.

  • 4328.
    Wänglund, Josefin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Undersökning av SNCR som rökgasreningsmetod för att reducera utsläpp av NOx: En utredning gjord på SCA Östrands massafabrik2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    På SCA Östrands massafabrik i Timrå produceras två olika typer av pappersmassa,blekt sulfatmassa och kemitermomekanisk massa (CTMP). Idag produceras ungefär 430 000 ton blekt sulfatmassa och 95 000 ton CTMP per år. Just nu pågåren om- och nybyggnation av sulfatmassalinjen inom projektet Helios. Målet med projektet är att under 2018 ta i drift en fabrik med en kapacitet att producera 900 000 ton blekt sulfatmassa per år. I och med utbyggnaden har fabriken fått en ny miljödom (som ett resultat av verksamhetstillståndsansökan) med villkor attförhålla sig till. I miljödomen presenteras ett antal olika villkor; utredningsvillkor, utsläppsvillkor och riktvärden. Ett av villkoren är ett utredningsvillkor som gäller utredning av rökgasreningstekniken SNCR (selektiv icke-katalytisk reduktion) för att rena rökgaserna från fabrikens ångproducerande enheter, barkpannan (ÅP1)och sodapannan (SP6), från NOx. Syftet med examensarbetet var att i ett första steg i utredningen av utredningsvillkoret undersöka möjligheterna till att använda SNCR som rökgasrening på ÅP1 för att rena rökgaserna från NOx.

    För att utreda möjligheterna att använda SNCR på ÅP1 gjordes temperaturmätningar av rökgaserna i pannans övre del och en temperaturprofil över pannan bestämdes. Vidare undersöktes olika metoder av SNCR och andra sekundära rökgasreningsmetoder i en litteraturstudie och i en undersökning av marknaden som bland annat innehöll referensbesök på anläggningar med olika SNCR-system.En grov kostnadsmässig analys genomfördes också genom att beräkna teoretiskautsläppsmängder för de nya förutsättningarna efter Helios, NOx-avgiften och kemikalieförbrukningen i ett hypotetiskt fall där SNCR installeras.

    Under de förutsättningar som temperaturmätningarna gjordes framkom det att det inte är möjligt att använda sig av SNCR för att reducera NOx-utsläppen från ÅP1. Mätningarna visade dock att det är möjligt att använda SNCR som reningsmetod vid laster högre än 72 ton ånga/h om det finns ett linjärt samband mellan last(ton ånga/h) och rökgastemperaturen.

  • 4329.
    Wärja, Mathias
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Björkqvist, Olof
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    A Systems Approach to Maintenance and Renewal Strategies2005In: CIRED 2005, 2005Conference paper (Other academic)
  • 4330.
    Wågberg, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Polyelectrolyte adsorption on cellulose fibres: a review2001Report (Other academic)
  • 4331.
    Wågberg, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Spreading of droplets of different liquids on specially structured papers2000Report (Other academic)
  • 4332. Wågberg, Lars
    et al.
    Decher, Gero
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Lindström, Tom
    Ankerfors, Mikael
    Axnäs, Karl
    The build-up of polyelectrolyte multilayers of microfibrillated cellulose and cationic polyelectrolytes2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 3, p. 784-795Article in journal (Refereed)
    Abstract [en]

    A new type of nanocellulosic material has been prepared by high-pressure homogenization of carboxymethylated cellulose fibers followed by ultrasonication and centrifugation. This material had a cylindrical cross-section as shown by transmission electron microscopy with a diameter of 5-15 nm and a length of up to 1 mu m. Calculations, using the Poisson-Boltzmann equation, showed that the surface potential was between 200 and 250 mV, depending on the pH, the salt concentration, and the size of the fibrils. They also showed that the carboxyl groups on the surface of the nanofibrils are not fully dissociated until the pH has reached pH = similar to 10 in deionized water. Calculations of the interaction between the fibrils using the Derjaguin-Landau-Verwey-Overbeek theory and assuming a cylindrical geometry indicated that there is a large electrostatic repulsion between these fibrils, provided the carboxyl groups are dissociated. If the pH is too low and/or the salt concentration is too high, there will be a large attraction between the fibrils, leading to a rapid aggregation of the fibrils. It is also possible to form polyelectrolyte multilayers (PEMs) by combining different types of polyelectrolytes and microfibrillated cellulose (MFC). In this study, silicon oxide surfaces were first treated with cationic polyelectrolytes before the surfaces were exposed to MFC. The build-up of the layers was monitored with ellipsometry, and they show that it is possible to form very well-defined layers by combinations of MFC and different types of polyelectrolytes and different ionic strengths of the solutions during the adsorption of the polyelectrolyte. A polyelectrolyte with a three-dimensional structure leads to the build-up of thick layers of MFC, whereas the use of a highly charged linear polyelectrolyte leads to the formation of thinner layers of MFC. An increase in the salt concentration during the adsorption of the polyelectrolyte results in the formation of thicker layers of MFC, indicating that the structure of the adsorbed polyelectrolyte has a large influence on the formation of the MFC layer. The films of polyelectrolytes and MFC were so smooth and well-defined that they showed clearly different interference colors, depending on the film thickness. A comparison between the thickness of the films, as measured with ellipsometry, and the thickness estimated from their colors showed good agreement, assuming that the films consisted mainly of solid cellulose with a refractive index of 1.53. Carboxymethylated MFC is thus a new type of nanomaterial that can be combined with oppositely charged polyelectrolytes to form well-defined layers that may be used to form, for example, new types of sensor materials.

  • 4333.
    Wågberg, Lars
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hägglund, R
    SCA Packaging Research.
    Kinetics of polyelectrolyte adsorption on cellulosic fibers2001In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 17, no 4, p. 1096-1103Article in journal (Refereed)
    Abstract [en]

    The present investigation has been focused on studying the adsorption of three different molecular mass fractions of a polydimethyldiallylammonium chloride (DMDAAC) (8750 (LMw), 48 000 (MMw), and 1 200 000 (HMw)) on bleached chemical fibers. Both kinetics of adsorption and equilibrium adsorption measurements have been conducted, and the adsorption has been measured by polyelectrolyte titration. The results show that the LMw polymer can reach all the charges in the fiber wall whereas the MMw and HMw can only reach the charges on the external surfaces of the fibers. It is also shown that the kinetics of adsorption of the LMw polymer is not at all affected by the presence of a saturated layer of HMw polymer on the surface of the fibers. Finally the results from the investigation show that it is possible to have a full coverage of the external surface of the fibers by a high molecular mass polymer and a full coverage of the internal surface of the fibers with a low molecular mass polymer provided that the high molecular mass polymer is adsorbed before addition of the low molecular mass polymer. This is true if the polymers are adsorbed to the same type of groups on the fibers. A simplistic model for describing ployelectrolyte adsorption in turbulent flow also shows good agreement with measured values for the low molecular mass polyelectrolyte whereas the agreement for the high molecular polyelectrolyte is not as good. For the high molecular mass polyelectrolyte a more sophisticated model is needed.

  • 4334.
    Wågberg, Lars
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hägglund, Rickard
    SCA packaging Research.
    Kinetics of polyelectrolyte adsorption on cellulosic fibres2000Report (Other academic)
  • 4335. Wågberg, Lars
    et al.
    Pettersson, Gunilla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Notley, Shannon
    Adsorption of bilayers and multilayers of cationic and anionic copolymers of acrylamide on silcon oxide2004In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 274, no 2, p. 480-488Article in journal (Refereed)
    Abstract [en]

    Silica surfaces were consecutively treated with copolymers of cationic and anionic polyacrylamides (C-PAM and A-PAM, respectively) and the layer-by-layer build-up was continuously monitored with the aid of stagnation point adsorption reflectometry (SPAR). Four different charge densities of the cationic polymer and one charge density of the anionic polymer were studied. The solid substrate used in the investigation was an oxidized Si wafer, the charge of which was varied by performing the measurements at different pH. Adsorption measurements were performed both in deionized water and with a background electrolyte concentration of 0.01 M NaCl The results show that the adsorption of C-PAM at pH 6 was dominated by electrostatic interactions. However, a significant nonionic contribution to the adsorption of C-PAM on SiO2 was detected-when the results of adsorption measurements conducted in deionized water and in 0.01 M NaCl were compared. At pH 9, the adsorption of C-PAM onto SiO2 was found to be geometrically restricted since the adsorption stoichiometry between the polymer charges and the charges on the surface was less than I irrespective of the charge of the C-PAM. Adsorption of the A-PAM onto the C-PAM covered surface increases as a function of the adsorbed charges in the first layer. Experiments showed that it was possible to form multilayers of polyelectrolytes on the SiO2 surface provided the charge of the C-PAM was high enough. The critical charge of the polyelectrolyte for the formation of multilayers was also dependent on the charge of the substrate; that is, the lower the surface charge the higher the critical charge of the C-PAM. The substrate affected the amount of polyelectrolyte adsorbed up to the fifth layer. For further layers there was almost a stoichiometric relationship between the charges of the polyelectrolytes in consecutive layers. Results from studies of the formed multilayers with a quartz crystal microbalance (QCM-D) indicated that there was a close correlation between energy dissipation into the multilayers and a decrease in the adsorption as detected with SPAR. This in turn indicates that a decrease in the reflectometer signal does not necessarily indicate a decrease in adsorption.

  • 4336.
    Wåhlander, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Gedde, Ulf W
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Edmondson, Steve
    School of Materials, University of Manchester.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Correction: Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states2016In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 8, p. 13522-13522Article in journal (Refereed)
    Abstract [en]

    Correction in Figure 8 for ‘Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states’ by Martin Wåhlander, et al., Nanoscale, 2016, DOI: 10.1039/c6nr01502f

  • 4337.
    Wåhlander, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Gedde, Ulf W
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Edmondson, Steve
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hydrophobic matrix-free graphene-oxide composites with isotropic and nematic states2016In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 8, p. 14730-14745Article in journal (Refereed)
    Abstract [en]

    We demonstrate a novel route to synthesise hydrophobic matrix-free composites of polymer-grafted graphene oxide (GO) showing isotropic or nematic alignment and shape-memory effects. For the first time, a cationic macroinitiator (MI) has been immobilised on anionic GO and subsequently grafted with hydrophobic polymer grafts. Dense grafts of PBA, PBMA and PMMA with a wide range of average graft lengths (MW: 1–440 kDa) were polymerised by surface-initiated controlled radical precipitation polymerisation from the statistical MI. The surface modification is designed similarly to bimodal graft systems, where the cationic MI generates nanoparticle repulsion, similar to dense short grafts, while the long grafts offer miscibility in non-polar environments and cohesion. The state-of-the-art dispersions of grafted GO were in the isotropic state. Transparent and translucent matrix-free GO-composites could be melt-processed directly using only grafted GO. After processing, birefringence due to nematic alignment of grafted GO was observed as a single giant Maltese cross, 3.4 cm across. Permeability models for composites containing aligned 2D-fillers were developed, which were compared with the experimental oxygen permeability data and found to be consistent with isotropic or nematic states. The storage modulus of the matrix-free GO-composites increased with GO content (50% increase at 0.67 wt%), while the significant increases in the thermal stability (up to 130 °C) and the glass transition temperature (up to 17 °C) were dependent on graft length. The tuneable matrix-free GO-composites with rapid thermo-responsive shape-memory effects are promising candidates for a vast range of applications, especially selective membranes and sensors.

  • 4338.
    Xia, Changjiu
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Research Institute of Petroleum Processing, SINOPEC, China.
    Ju, Long
    Zhao, Yi
    Xu, Hongyi
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zhu, Bin
    Gao, Feifei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lin, Min
    Dai, Zhenyu
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Shu, Xingtian
    Heterogeneous oxidation of cyclohexanone catalyzed by TS-1: Combined experimental and DFT studies2015In: Cuihuà xuébào, ISSN 0253-9837, E-ISSN 1872-2067, Vol. 36, no 6, p. 845-854Article in journal (Refereed)
    Abstract [en]

    The reaction mechanism of the oxidation of cyclohexanone catalyzed by titanium silicate zeolite Received 26 February 21515 TS-1 using aqueous H2O2 as the oxidant was investigated by combining density function theory (DFT) calculations with experimental studies. DFT calculations showed that H2O2 was adsorbed and activated at the tetrahedral Ti sites. By taking into account the adsorption energy, molecular size, steric hindrance and structural information, a reaction mechanism of Baeyer-Villiger oxidation catalyzed by TS-1 that involves the activation of H2O2 was proposed. Experimental studies showed that the major products of cyclohexanone oxidation by H2O2 catalyzed by a hollow TS-1 zeolite were epsilon-carprolactone, 6-hydroxyhexanoic acid, and adipic acid. These products were analyzed by GC-MS and were in good agreement with the proposed mechanism. Our studies showed that the reaction mechanism on TS-1 zeolite was different from that on Sn-beta zeolite.

  • 4339.
    Xia, Changjiu
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Research Institute of Petroleum Processing, SINOPEC, People’s Republic of China.
    Lin, Min
    Zheng, Aiguo
    Xiang, Yanjuan
    Zhu, Bin
    Xu, Guangtong
    Shu, Xingtian
    Irreversible deactivation of hollow TS-1 zeolite caused by the formation of acidic amorphous TiO2-SiO2 nanoparticles in a commercial cyclohexanone ammoximation process2016In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 338, p. 340-348Article in journal (Refereed)
    Abstract [en]

    Commercial deactivated HTS zeolite has been investigated by multiple characterization methods and catalytic evaluations. These indicate that structural and textural properties are not mainly ascribed to the irreversible deactivation, but some framework Ti species are transformed into Ti-rich nanoparticles. Both Bronsted and Lewis acid sites are observed in deactivated HTS zeolite, which agrees well with the spectroscopic characterization results and Tanabe's acidity theory on mixed binary oxides. Hence the acidic Ti-rich aggregates are attributed to the amorphous TiO2-SiO2 nanoparticles located on the external surface of the zeolite. Furthermore, it is demonstrated that the catalytic performance of deactivated HTS zeolite in phenol hydroxylation is seriously dependent on its acidity properties, which can accelerate the decomposition of H2O2. As a consequence, we conclude that the irreversible deactivation of HTS zeolite in the ammoximation process is caused by the formation of acidic amorphous TiO2-SiO2 nanoparticles catalyzing the fast H2O2 decomposition reaction.

  • 4340. Xiang, Q
    et al.
    Lee, YY
    Pettersson, Per O
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Torget, R
    Heterogeneous aspects of acid hydrolysis of alpha-cellulose2003In: Applied Biochemistry and Biotechnology, ISSN 0273-2289, E-ISSN 1559-0291, p. 505-514Article in journal (Refereed)
    Abstract [en]

    Hydrolysis of alpha-cellulose by H2SO4 is a heterogeneous reaction. As such the reaction is influenced by physical factors. The hydrolysis reaction is therefore controlled not only by the reaction conditions (acid concentration and temperature) but also by the physical state of the cellulose. As evidence of this, the reaction rates measured at the high-temperature region (above 200degreesC) exhibited a sudden change in apparent activation energy at a certain temperature, deviating from Arrhenius law. Furthermore, cc-cellulose, once it was dissolved into concentrated H2SO4 and reprecipitated, showed a reaction rate two orders of magnitude higher than that of untreated cellulose, about the same magnitude as cornstarch. The cc-cellulose when treated with a varying level of H2SO4 underwent an abrupt change in physical structure (fibrous form to gelatinous form) at about 65% H2SO4. The sudden shift of physical structure and reaction pattern in response to acid concentration and temperature indicates that the main factor causing the change in cellulose structure is disruption of hydrogen bonding. Finding effective means of disrupting hydrogen bonding before or during the hydrolysis reaction may lead to a novel biomass saccharification process.

  • 4341.
    Xie, Guoxin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Tsinghua Univ, State Key Lab Tribol, Peoples R China.
    Zhang, Fan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Adsorption and friction of Mussel Adhesive Protein (MAP) films under polarization2015In: PROCEEDINGS OF MALAYSIAN INTERNATIONAL TRIBOLOGY CONFERENCE 2015, 2015, p. 19-20Conference paper (Refereed)
    Abstract [en]

    Mussel Adhesive Protein (MAP) is an adhesive protein derived from blue mussel byssus, and has promising applications for a variety of functional coatings. In this work, different analytical techniques including cyclic voltammetry, chronocoulometry experiments, and microtribometer have been used to investigate the interfacial structures and the frictional properties of MAP film on the platinum (Pt) substrate under polarization. MAP adsorption could change electrostatically after polarization. The friction of adsorbed MAP film can be tuned effectively in a suitable potential range, which is promising for future active control over the adsorption and friction of MAP films.

  • 4342. Xie, L.
    et al.
    Xu, Huan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Li, Z. -M
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Structural Hierarchy and Polymorphic Transformation in Shear-Induced Shish-Kebab of Stereocomplex Poly(Lactic Acid)2016In: Macromolecular rapid communications, ISSN 1022-1336, E-ISSN 1521-3927, Vol. 37, no 9, p. 745-751Article in journal (Refereed)
    Abstract [en]

    The realization of hierarchical shish-kebab structures for stereocomplex poly(lactic acid) (PLA) is achieved by the application of a shear flow (100 s-1 for 1 s) mimicking what can be expected during polymer processing. Compared to the normal shearing scenarios, this transient and strong shear flow enables the creation of dense shish precursors in time- and energy-saving manner. The distribution of crystal form associated with the hierarchical structure is revealed by 2D Fourier transform infrared spectroscopy imaging, creating a unique visualization for both spatial resolution and polymorphism identification. Interestingly, in the shear stereocomplex chains are preferentially extended and crystallized as stable central cores with weak temperature dependence, whereas the development of lateral kebabs is defined by the distinct relation to the crystallization temperature. Below the melting point of homocrystals, both homo and stereocomplex crystallization are engaged in lamellar packing. Above that, exclusive stereocomplex crystals are organized into ordered lamellae. Combining the direct observations at multiscale, the ordered alignment of stereocomplex chains is recognized as the molecular origin of fibrillar extended chain bundles that constitute the central row-nuclei. The proposed hypothesis affords elucidation of shish-kebab formation and unique polymorphism in sheared stereocomplex PLA, which generates opportunities for engendering hierarchically structured PLA with improved performance. A transient and strong shear mimicking the typical melt processing scenario is used to create compact shish-kebab superstructures for stereocomplex poly(lactic acid). The highly oriented fibrillar extended chains are found to constitute the central shish, while 2D Fourier transform infrared spectroscopy imaging offered a direct visualization for determination of polymorphic transition that is associated with spatial hierarchy.

  • 4343.
    Xinhai, Yu
    et al.
    East China University of Science and Technology.
    Hongliang, Li
    East China University of Science and Technology.
    Shan-Tung, Tu
    East China University of Science and Technology.
    Yan, Jinyue
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Pt-Co catalyst-coated channel plate reactor for preferential CO oxidation2011In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 36, no 5, p. 3778-3788Article in journal (Other academic)
    Abstract [en]

    To achieve preferential CO oxidation, a PteCo catalyst-coated channel plate reactor (CCPR)was produced via conventional mechanical milling and catalyst coating. The proposedreactor performed well under a wide range of operating temperatures and providedsatisfactory results at low temperatures (CO concentrations of 1e10 ppm at 413e443 K and1e50 ppm at 413e453 K). In the proposed CCPR, significant deactivation was not observedduring continuous operation for 100 h. In addition, the reactor exhibited excellent toleranceto undesirable conditions, including reaction temperature runaway and feedingstream failure. Characterisation results indicated that the catalytic activity of the proposedCCPR was high due to the formation of Pt3Co intermetallic compounds and nanoscalemetal particles. The capacity per channel of the proposed CCPR was approximately 50e100times greater than those of conventional microchannel reactors; thus, problems associatedwith excessive reactors were significantly reduced. In general, the results indicated thatCCPR has great potential in the small-scale production of hydrogen for fuel cells.

  • 4344.
    Xu, Huan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Graphene Oxide Technology to Advance the Performance of Poly(lactic acid) Materials2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In the past two decades, a burgeoning biorefinery concept has grown in concert with the materials science, contributing to the rise of biobased materials that respect environment and are versatile for various applications. An excellent example is poly(lactic acid) (PLA) that exhibits high strength and desirable degradability. Unfortunately, PLA suffers from poor mechanical ductility and toughness, and low resistance to heat and water/gas permeation. In order to promote the performance of PLA and thus to broaden the application areas, this study brings to light the morphological and structural specificities for fabrication of high-performance PLA films. The proposed strategy hinges on innovative uses of graphene oxide (GO) nanostructures, giving the possibility to simultaneously tailor the crystalline morphology, mechanical and barrier properties, and degradation behavior for PLA.

    While recognizing the GO-enabled function in controlling the crystalline morphology of racemic PLA, the nucleation mechanism induced by GO nanosheets was elucidated as a first step. In addition to the observation of random lamellae induced by the basal planes of GO nanosheets, it was of particular interest to reveal that the ultrathin edges of nanosheets were ready to trigger the ordered alignment of PLA lamellae. The high nucleation activity of GO was further employed to preferentially accelerate the stereocomplex crystallization of PLA, which subsequently suppressed the development of homo-crystals by generation of spatial hindrance. As a result of the decoration of GO nanosheets with sterecomplex crystals, an impressive combination of barrier and thermal properties, and mechanical strength and ductility was achieved for the racemic PLA/GO composites.

    As a parallel approach, the morphology and structure of GO were tailored to enhance PLA-GO interactions and to improve GO dispersion: (1) few-layer nanosheets were firmly immobilized onto microsized starch particles by hydrogen bonding, permitting the creation of strong and active nanointerfaces in PLA biocomposites that enhanced interfacial interactions and facilitated filler dispersion; (2) the planar dimensionality of GO was shrunk to quasi-zero, conferring the generation of higher density of oxygen functional groups and enhanced interactions with PLA matrix, and resulting in higher nucleation activity and accelerated hydrolytic degradation.

    In addition to the fundamental insights into the PLA-GO interaction mechanisms, the methodologies proposed here can shape new routes to high-performance PLA materials with promising potential in a diversity of applications.

  • 4345.
    Xu, Huan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bai, Yuge
    Xie, Lan
    Li, Jinlai
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Heat-Resistant and Microwaveable Poly(Iactic acid) by Quantum-Dot Promoted Stereocomplexation2017In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 5, no 12, p. 11607-11617Article in journal (Refereed)
    Abstract [en]

    Nanofiller-tailored stereocomplexation signifies a promising and feasible pathway to develop heat-resistant poly (lactic acid) (PLA) materials. However, this pathway is thwarted by the potential adverse environmental issues of traditional nanofillers and the challenges in facilitating the nanofiller dispersion and selective formation of stereocomplex crystals (SCs). Here we unravel a microwave-assisted approach to exploit biobased quantum dots (QDs) featuring excellent capability to preferably nucleate PLA SCs. The combination of ultrasmall dimension and high oxygenation degree of QDs conferred intimate interactions with stereocomplexed PLA chains, readying complete exfoliation and uniform dispersion of QDs to promote stereocomplexation. The well-dispersed QDs provided perfect UV shielding for PLA composites, while sustaining high transmission to visible light comparable to pure PLA. Strong interfacial interactions and high concentration of SCs were created around the nanoscale surfaces of QDs, accounting for the greatly increased resistance to oxygen permeation, thermal deformation, and microwave heating. This was accompanied by substantial rise in tensile modulus and elongation at break (up to 74 and 51%) compared to that of pure PLA, affording the demonstration of unusual reinforcing and toughening mechanisms imparted by the PLA-affinitive QDs. The robust structural integrity under harsh usage environments, coupled with high gas barrier, prominent light management and evasion of flexibility and extensibility sacrifices, may prompt low-cost and ecofriendly PLA nanocomposites suitable for diverse applications including microwaveable food packaging.

  • 4346.
    Xu, Huan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology. College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu, China.
    Feng, Zhaoxuan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Xie, L.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Graphene Oxide-Driven Design of Strong and Flexible Biopolymer Barrier Films: From Smart Crystallization Control to Affordable Engineering2016In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 4, no 1, p. 334-349Article in journal (Refereed)
    Abstract [en]

    Development of multifunctional, versatile biobased polymers can greatly benefit from the discovery and application of 2D sheet-like materials. For instance, the hybrid system integrating graphene oxide (GO) nanosheets with enantiomeric poly(lactic acid) (PLA) showcases several key properties that can address emerging multifunction needs such as good gas barrier and high thermal resistance. Here we revealed that large specific surface area and homogeneous dispersion of GO conferred the construction of interconnected networks in PLA even with relatively low GO contents (0.1 and 0.5 wt %). These well-extended GO nanosheets were ready to provide enormous and active platforms to nucleate preferentially the neighboring stereocomplex chains, prompting the prevailing development of stereocomplex crystals (SCs). The notable scenario associated with the GO distribution was imaged by 2D Fourier transform infrared spectroscopy, and was further elucidated by dynamic crystallization. More importantly, the nanosheets decorated with ordered PLA lamellae, in turn, contributed to the impressive enhancement in barrier and mechanical properties and chemical resistance. For example, a distinct decrease of 98.5% in oxygen permeability coefficient was observed for the composite films containing 0.5 wt % GO (6.264 × 10-17 cm3 cm cm-2 s-1 Pa-1) compared to the control sample crystallized at 150 °C (4.214 × 10-15 cm3 cm cm-2 s-1 Pa-1). The performance distinction was accompanied by the unusual combination of high tensile strength (73.5 MPa) and high elongation (13.6%), displaying an increase of 31.7% and 183.3% compared to the counterpart, respectively. This may provide a broader context for exploiting 2D nanosheets as robust cells to advance the function and property of PLA, which helps to outline the roadmap for fashioning high-performance, affordable bioplastics.

  • 4347.
    Xu, Huan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wu, Duo
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Yang, Xi
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Xie, L.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Thermostable and impermeable "nano-barrier walls" constructed by poly(lactic acid) stereocomplex crystal decorated graphene oxide nanosheets2015In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 48, no 7, p. 2127-2137Article in journal (Refereed)
    Abstract [en]

    In contrast to the relatively clear understanding of epitaxial crystallization induced by one-dimensional nanofillers, the underlying interfacial interactions between polymer crystals and two-dimensional graphene oxide (GO) nanosheets are something of a mystery. Here, the GO-assisted formation of poly(lactic acid) (PLA) stereocomplex crystals (SCs) is disclosed from the quantitative structural analysis to the direct morphological observations at multiscale and the interaction mechanism at the molecular level. It is unexpected to observe that the edges of GO featuring rich grooves and ultralow thickness were ready to induce a layer of ordered lamellae, in clear contrast to the random growth of lamellae on the basal planes. The origin of GO-induced crystallization was appraised from the interaction point of view as indicated by the evident red-shift of a set of functional groups in the Fourier transform infrared spectroscopy spectra. More importantly, the GO nanosheets, albeit presented at an extremely low content (0.05 wt %), decorated by the preferred formation of SCs enabled the simultaneous enhancement of gas barrier properties and resistance to heat distortion. Specifically, the unique combination of greatly improved heat deformation temperature (HDT) and low oxygen permeability coefficient (P<inf>O</inf><inf>2</inf>) for the composite crystallized at 165 °C was demonstrated (146.5 °C and 0.95 × 10-15 cm3 cm cm-2 s-1 Pa-1), outperforming pure PLA with an increment of 75% and a decrease of 77% in HDT and P<inf>O</inf><inf>2</inf>, respectively. The proposed methodology affords elucidation of well-tailored thermal and barrier properties, which may motivate further extension of this rational design to other material combinations.

  • 4348.
    Xu, Huan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. Sichuan University, Chengdu, China.
    Yang, Xi
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Xie, Lan
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Conformational Footprint in Hydrolysis-Induced Nanofibrillation and Crystallization of Poly(lactic acid)2016In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, no 3, p. 985-995Article in journal (Refereed)
    Abstract [en]

    The origin of hydrolysis-induced nanofibrillation and crystallization, at the molecular level, was revealed by mapping the conformational ordering during long-term hydrolytic degradation of initially amorphous poly(lactic acid) (PLA), a representative model for degradable aliphatic polyesters generally displaying strong interplay between crystallization and hydrolytic erosion. The conformational regularization of chain segments was essentially the main driving force for the morphological evolution of PLA during hydrolytic degradation. For hydrolysis at 37 degrees C, no significant structural variations were observed due to the immobilization of frozen PLA chains. In contrast, conformational ordering in PLA was immediately triggered during hydrolysis at 60 degrees C and was responsible for the transition from random coils to disordered trans and, further, to quasi-crystalline nanospheres. On the surfaces, the head-by-head absorption and joining of neighboring nanospheres led to nanofibrillar assemblies following a gluttonous snake-like manner. The length and density of nanofibers formed were in close relation to the hydrolytic evolution, both of which showed a direct rise in the initial 60 days and then a gradual decline. In the interior, presumably the high surface energy of the nanospheres allowed for the preferential anchoring and packing of conformationally ordered chains into lamellae. In accordance with the well-established hypothesis, the amorphous regions were attacked prior to the erosion of crystalline entities, causing a rapid increase of crystallinity during the initial 30 days, followed by a gradual fall until 90 days. In addition to adequate illustration of hydrolysis-induced variations of crystallinity, our proposed model elucidates the formation of spherulitic nuclei featuring an extremely wide distribution of diameters ranging from several nanometers to over 5 mu m, as well as the inferior resistance to hydrolysis observed for the primary nuclei. Our work fuels the interest in controlling nanofibrillation mechanism during hydrolysis of PLA, opening up possibilities for straightforward nanofiber formation.

  • 4349.
    Xu, Johanna
    et al.
    Lulea Univ Technol, Dept Engn Sci & Math, S-97189 Lulea, Sweden..
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering. KTH, Superseded Departments (pre-2005), Chemical Engineering and Technology.
    Varna, Janis
    Lulea Univ Technol, Dept Engn Sci & Math, S-97189 Lulea, Sweden..
    Multiphysics modeling of mechanical and electrochemical phenomena in structural composites for energy storage: Single carbon fiber micro-battery2018In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 37, no 10, p. 701-715Article in journal (Refereed)
    Abstract [en]

    This paper presents a framework for multiphysics modeling of a novel type of multifunctional composite material, structured on microscale, with ability to function as battery cell in addition to carry mechanical load. The micro-battery consists of a single carbon fiber surrounded by very thin solid electrolyte coating and embedded in a matrix which is a porous material containing active particles able to intercalate lithium. During battery operation (discharging and charging) the structural battery constituents undergo volume changes, caused by lithium-ion movement. The presented mathematical model is solved numerically using COMSOL software and results are used to analyze the physical phenomena occurring in the structural battery material. Parametric analysis is performed to reveal the significance of geometrical parameters like fiber volume fraction in the battery and the porosity content in the matrix on the multifunctional performance of the composite unit including its swelling/shrinking during charging/discharging.

  • 4350.
    Xu, Xueyan
    KTH, School of Chemical Science and Engineering (CHE).
    Development of Kraft Lignin and Coating Technique to Prepare Coated Urea Fertilisers with Increased Nutrient Use Efficiency2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Coating urea to prepare controlled release N-fertilizer has been considered as an effective way to increase its nutrient use efficiency, thus reduce its waste and the consequent harmful environmental impacts. Inorganic sulphur and synthetic polymers have been used in the industry as coating materials together with utilization of various types of expensive coating equipment which commonly requires also complicated technical setup and controls. As development trends, biopolymers are attention-grabbing to replace the synthetic polymers. Alternative simple coating technique is also desired. So far, polylactic acid (PLA) has been reported as a more promising biopolymer than several synthetic polymers for coating. On the other hand, highly purified industrial softwood kraft lignin (SKL) produced after LignoBoost process is now available in a large quantity, which should also be a promising biopolymer for the coating application. Aiming at increase of the efficiency of PLA-coated urea and development of alternative coating technique to generally make the preparation of control-released fertilizer more effective, economic and environmentally sustainable, in this study, SKL has been used in a PLA-SKL blending form as complex coating material and simple dip-coating technique has been investigated and applied.

    In order to lower the wettability of PLA-SKL coat layer, four different anhydrides, namely acetic anhydride, palmitic anhydride, lauric anhydride and trifluoroacetic anhydride, were used to esterify SKL to form AcSKL, PaSKL, LauSKL and TFASKL respectively before its utilization. NMR and FTIR analyses showed that the esterification reactions have been completed for AcSKL and PaSKL. LauSKL was partly esterified due to the low charge of lauric anhydride regent, while TFASKL was not esterified expectantly due to the steric hindrance between the three F atoms and polymeric SKL.

    In order to obtain organically bound nitrogen structure to also create slow-release type of N-fertilizer, Mannich reaction on SKL using diethylamine was also conducted to prepare ManSKL. The reaction was completed as shown by NMR and FTIR spectroscopy. To bring further functionality of metal chelation to open the possibility to also bring essential trace element into the final fertilizer, ethylenediaminetriacetic acid (ED3A) was synthesized and further used via Mannich reaction to modify SKL to form ED3ASKL. ED3A is not commercially available and it was synthesized successfully with an environmentally friendly method from commercial EDTA and the structure was verified by NMR spectroscopy. However, the Mannich reaction using ED3A was not very successful as shown by product’s NMR and FTIR spectra. In a comparison experiment using vanillyl alcohol as a lignin model structure, ED3A was successfully coupled onto the vanillyl alcohol structure as shown by NMR and FTIR spectra. Apparently there was a severe steric hindrance from SKL for the Mannich reaction using the larger molecule of ED3A than diethylamine for Mannich reaction.

    For utilization of dip-coating technique, dichloromethane(DCM) and tetrahydrofuran (THF) were chosen to dissolve PLA and SKL or the modified SKL respectively. Cast films of PLA/modified lignin complex were prepared using Teflon Petri-dishes. The optimal concentration of PLA in DCM and the effect of DCM/THF ratios on the prepared cast film which expectantly represents the quality of the complex coat in the coated urea were compared with SEM images and contact angle determination. It has been found that a 30 wt% of PLA in DCM was the best and this solution mixed with modified lignin solution (6 % in THF) in a ratio of DCM/THF =3/2 (v/v) had the best film performances and water barrier properties. Generally, the cast films from PLA/modified lignin complexes showed better properties compared with the neat PLA cast film. No pores and cracks were found on the surface. Comparatively, the LauSKL film showed the most homogeneous surface. But the AcSKL film had the best water barrier properties. The PLA/modified lignin complex coated urea was then prepared by dip-coating process. The coat thickness and weight increase showed statistically positive correlations against the repeating times of the dip-coating process. The coating layer also showed one single layer structure. The speed of urea releasing for coated urea was tested and the results showed that it was much slower than the un-coated or PLA-coated urea. The single-layered PLA/AcSKL and PLA/ManSKL were both observed with sound properties in delaying the release of urea cores in water.

    Conclusively, the PLA/modified SKL coated urea fertilizers prepared by dip-coating technique demonstrated in this study have highly efficiency with better effects of water barrier, organically N slow release, and nitrification inhibiting (due to free phenolic functional groups) properties. Both SKL and the dip-coating technique are promising in the fertilizer applications.

     

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