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  • 1.
    Akin, Danny E.
    et al.
    Richard B. Russell Agricultural Research Center, Agricultural Research Service, US Department of Agriculture, Athens.
    Henriksson, Gunnar
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Evans, J. D.
    South Central Poultry Research Laboratory, Agricultural Research Service, US Department of Agriculture, USA.
    Adamsen, A. S. P.
    Agro Business Par, Denmark.
    Foulk, J. A.
    Cotton Quality Research Station, Agricultural Research Service, US Department of Agriculture, USA.
    Dodd, R. B.
    Department of Agricultural and Biological Engineering, Clemson University.
    Progress in enzyme-retting of flax2004Ingår i: Journal of Natural Fibers, ISSN 1544-0478, Vol. 1, nr 1, s. 21-47Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    New methods for retting flax are sought to overcome problems in the current method of dew-retting of flax. Published data are reviewed and new data presented on the development and testing of a method to ret flax using pectinase-rich enzyme mixtures plus chelators based on cost and fiber yield and properties. In spray enzyme retting (SER), flax stems are crimped to physically disrupt the plant's protective barrier and then sprayed until soaked with, or briefly immersed in, an enzyme/ chelator formulation. Flax is then incubated at temperatures optimal for enzyme activity, washed, and dried. Pilot scale tests, conducted with 10 kg samples of flax retted with a series of formulations, showed that this method effectively retted flax stems from a variety of sources, including fiber flax, mature fiber flax, and linseed straw. Fiber yield, strength, and fineness were significantly influenced by variations in enzyme-chelator amounts. Cellulases in pectinase mixtures appeared to preferentially attack dislocations in fibers and fiber bundles resulting in loss of fiber strength. Polygalacturonases alone effectively separated fiber from non-fiber components. The SER method proved to be an effective framework for further tests on enzyme-chelator formulations that now must be integrated with physical processing to optimize the extraction of flax fibers based on cost and fiber yield and properties.

  • 2.
    Albertsson, Ann-Christine
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Synthesis of resorbable networks based on homo- and copolymers of poly(1,5-dioxepan-2-one) and poly(L-lactide).2004Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 228, s. U442-U442Artikel i tidskrift (Övrigt vetenskapligt)
  • 3. Andreasson, B.
    et al.
    Forsstrom, J.
    Wågberg, Lars
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    The porous structure of pulp fibres with different yields and its influence on paper strength2003Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 10, nr 2, s. 111-123Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The porous structure of the interior of papermaking fibres is a well-known important property of the fibres. Changes of this structure will influence tensile and burst strength of paper formed from the fibres and a change in pore size of the pores within the fibre wall is also important for the ability of molecules to diffuse in and out of the fibre wall. Relevant examples of this latter effect are the removal of lignin during cooking and the addition of performance chemicals during papermaking. In this paper, pore sizes and the pore size distribution of unbleached softwood fibres have been studied. A well-characterised fibre material consisting of laboratory cooked spruce and pine pulp of various lignin contents was used. Pore size and pore size distribution were measured by studies of the relaxation behaviour of H-2 in fibres saturated with (H2O)-H-2. Beside this the total and surface charge of the fibres were also measured together with strength properties of papers from unbeaten fibres. For both pulps, there is a maximum in pore radius at a yield around 46%. Calculations of fibre wall volume from water retention values and yield levels show that there is a discontinuity in pore radius as a function of the fibre wall volume around a yield of 51%. It is suggested that this discontinuity is caused by the breakdown of the hemicellulose/ lignin matrix within the fibre wall at this yield level. The strength of the papers formed from the fibres shows a correlation with the surface charge of the fibres. Based on the change in surface charge with yield and the change in total charge with yield, this correlation is suggested to be due to an opening up of the external part of the fibre wall. This stresses the importance of the chemical composition and physical structure of the outer layer of the fibre wall.

  • 4.
    Andronova, Natalia
    et al.
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Finne, Anna
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Fibrillar structure of resorbable microblock copolymers based on 1,5-dioxepan-2-one and epsilon-caprolactone2003Ingår i: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 41, nr 15, s. 2412-2423Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The copolymerization of 1,5-dioxepan-2-one (DXO) and E-caprolactone, initiated by a five-membered cyclic tin alkoxide initiator, was performed in chloroform at 60 degreesC. Copolymers with different molar ratios of DXO (25, 40, and 60%) were synthesized and characterized. C-13 NMR spectroscopy of the carbonyl region revealed the formation of copolymers with a blocklike structure. Differential scanning calorimetry measurements showed that all the copolymers had a single glass transition between -57 and -49 degreesC and a melting temperature in the range of 30.1-47.7 degreesC, both of which were correlated with the amount of DXO. An increase in the amount of DXO led to an increase in the glass-transition temperature and to a decrease in the melting temperature. Dynamic mechanical thermal analysis measurements confirmed the results of the calorimetric analysis, showing a single sharp drop in the storage modulus in the temperature region corresponding to the glass transition. Tensile testing demonstrated good mechanical properties with a tensile strength of 27-39 MPa and an elongation at break of up to 1400%. The morphology of the copolymers was examined with polarized optical microscopy and atomic force microscopy; the films that crystallized from the melt showed a short fibrillar structure (with a length of 0.05-0.4 mum) in contrast to the untreated solution-cast films. (C) 2003 Wiley Periodicals, Inc.

  • 5. Antonsson, S.
    et al.
    Lindström, Mikael
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Hogskolan, K. T.
    Ragnar, M.
    A comparative study of the impact of the cooking process on oxygen delignification2003Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, nr 4, s. 388-394Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The impact of oxygen delignification on chemical pulps of a given kappa number manufactured in different ways (using kraft, prehydrolysis kraft and magnesium sulphite cooking) has been investigated. The prehistory of the pulps proves to be a very important factor in determining the response to oxygen delignification, i.e. the degree of delignification. It is shown that this is not due to different amounts of hexenuronic acid (HexA) in the different pulps, although this is an important factor behind the high residual kappa number after oxygen delignification of birch kraft pulp. Oxygen delignification of sulphite pulps proves to be efficient even at kappa numbers significantly lower than 10. These pulps show the greatest yield loss over the oxygen delignification. It is likely that Lignin Carbohydrate Complexes (LCC) complexes play a very important role in limiting the speed of reaction of oxygen delignification. Due to the very different prehistories of the pulps investigated, it is probable that the LCC:s are native and not formed during cooking.

  • 6.
    Aulin, Christian
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Lindstrom, Tom
    STFI Packforsk, KTH STFI, SE-11486 Stockholm, Sweden..
    CELL 206-Preparation, characterization and wetting of fluorinated cellulose surfaces2008Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 235Artikel i tidskrift (Övrigt vetenskapligt)
  • 7.
    Axelsson, Patrik
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Aspects on birch kraft pulping and the relation between cooking conditions and pulp bleachability2004Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 8.
    Axelsson, Patrik
    et al.
    KTH, Tidigare Institutioner, Pappers- och massateknik.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner, Pappers- och massateknik.
    Lindström, Mikael
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Condensation reactions of lignin during birch Kraft pulping as studied by thioacidolysis2004Ingår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 30, nr 12, s. 317-322Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influences of kappa number and ionic strength during birch kraft cooking on the extent of lignin condensation have been studied using thioacidolysis and size exclusion chromatography. Thioacidolysis degrades alkyl-aryl ether bonds in lignin while leaving carbon-carbon and diaryl-ether bonds relatively intact. Therefore, the lignin structures not cleaved during thioacidolysis can be considered as relatively stable and may account,, for example,for the slow residual phase delignification in the kraft cook and for differences in bleachability. It was shown that condensed lignin structures are formed in the residual lignin during birch kraft cooking. The relative amount of such structures increased with decreasing kappa number or with increasing sodium ion concentration in the cook. These structures were also found in a xylan-lignin complex isolated from a birch kraft pulp. The condensed structures were only partly reactive during oxygen delignification.

  • 9.
    Axelsson, Patrik
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Lindström, Mikael
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Influence of the conditions during birch kraft cooking on unbleached brightness, and on ECF- and TCF-bleachability2004Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 3, s. 309-317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influences on ECF and TCF bleachability of the hydroxide ion, hydrogen sulphide ion and sodium ion concentrations as well as of the amount of dissolved wood components (DWC) in a birch kraft cook were investigated. The pulping was carried out using a so-called constant composition cooking technique, where a high liquor-to-wood ratio enables an almost constant concentration of the cooking chemicals during the entire cook. This cooking method also renders possible to vary each cooking variable separately. The pulps were oxygen-delignified and bleached in a D(EOP)DD and a Q(OP)Q(PO) sequence. The presence of DWC caused a significant rate increasing effect on the delignification. An increase in hydroxide ion concentration, an increase in hydrogen sulphide ion concentration or a decrease in sodium ion concentration improved both the ECF and the TCF bleachability, but the DWC had no significant effect on the bleachability. Further a correlation was found between the bleachability and the brightness of the oxygen-delignified pulp.

  • 10.
    Backman, Anna
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Lange, Jakob
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Tidigare Institutioner, Polymerteknologi.
    Transport properties of uniaxially oriented aliphatic polyketone2004Ingår i: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 42, nr 6, s. 947-955Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The oxygen, carbon dioxide, and water-transport properties of a uniaxially oriented aliphatic polyketone were determined. The polyketone was drawn to 5-10 times its original length. The transport properties were related to changes in crystallinity estimated by differential scanning calorimetry and density measurements and by changes in the molecular and crystal orientation assessed by, respectively, infrared and X-ray spectroscopy. The film structures were characterized by confocal scanning laser microscopy and scanning electron microscopy. Stress-strain tests on the drawn specimens enabled the impacts of orientation on the transport and mechanical properties to be compared. A draw-induced increase in crystallinity and molecular orientation yielded permeabilities at a draw ratio of 10 that were 30-40% of the original value, and the percentage decrease was basically independent of the type of gas/vapor molecule. Also, the diffusivities of oxygen and carbon dioxide decreased by an order of magnitude. The fact that the amorphous permeability was peaking at a draw ratio of about 5 was a consequence of a peak in amorphous solubility, which was very high for oxygen and absent for water. It was suggested that the peak in solubility was mainly caused by the destruction of the polymer hydrogen-bond network during drawing and crystal reorientation. The impact of structural reorganization within the polymer and presence of surface valleys seemed to have less impact on the mechanical properties than on the transport properties. This suggested that transport data are more sensitive than mechanical data in probing material defects and changes in molecular packing and morphology.

  • 11.
    Berggren, Rickard
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Cellulose degradation in pulp fibers studied as changes in molar mass distributions2003Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this thesis, size-exclusion chromatography (SEC) of woodpolymers dissolved in lithium chloride/N,N-dimethylacetamide(LiCl/DMAc) has been used to characterize the molar massdistributions (MMD) of wood polymers in pulp fibers afterchemical degradation.

    Characterization of birch kraft pulps subjected to ozonedegradation and acid hydrolysis, respectively, rendereddifferent changes in the MMD. Ozone degradation resulted inlarge redistributions of the original MMD, observed as thedevelopment of a distinct fraction of cellulose withintermediate molar mass. Acid hydrolysis resulted in minorchanges of the original MMD compared to ozonation. Fiberssubjected to acid hydrolysis were considerably weaker thanozonated fibers. These results indicated that there aredifferences in how the two chemicals degrade the fiber.

    The solubility of softwood kraft pulp fibers was enhanced byderivatization of the fiber polymers with ethyl-isocyanateduring simultaneous dissolution in LiCl/DMAc. Thederivatization made it possible to achieve reliable estimationsof the MMD, and hence molar masses, of softwood kraft pulps.The derivatization procedure made it possible to dissolve 90 %of softwood kraft pulps with kappa numbers over 50.

    Severe alkaline degradation of birch and Norway spruce woodchips was studied both by varying the pulping time and byvarying the initial alkali concentration. Differences werefound in the MMD of the two fiber types, and the alkalinedegradation was found to affect polymers in the entire MMD.

    Multi-angular laser light scattering (MALLS) was used as adetection technique with SEC on cellulosic samples. The MMD andaverage molar masses obtained through directstandardcalibration with commercial standards were compared with MMDand molar masses as obtained by MALLS-detection. Largediscrepancies were found, and two methods of correcting forthese discrepancies were developed.

    Theoretical simulations of polymer degradation wereperformed. Random, or homogeneous degradation was used as amodel for alkaline cellulose chain scission, and a resemblancewith experimental data was observed. End-wise depolymerizationof cellulose was also simulated and the results are discussedin the light of experimentally observed MMD.

    Keywords:cellulose, kraft pulp, birch, spruce,ozonation, acid hydrolysis, degradation, MMD, sizeexclusionchromatography, light scattering, molar mass, chainscission

  • 12.
    Bergström, Jonas
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Fiber Suspension Velocity Measurements in a Cylindrical Through-Flow Hydrocyclone: Evaluation of Pitometer and Ultrasonic Techniques2004Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 13.
    Bergström, Roger
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Fibre flocculation during twin-wire roll forming2003Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    At the division of Paper Technology a forming unitconsisting of headbox, forming roll unit and reservoir systemfor suspension recirculation has been constructed, with themain purpose to experimentally study the paper forming event byvisually following the fibre flow phenomena in the formingzone.

    The effect of various running parameters upon the pressuredistribution, which is in correlation to the flow phenomenaoccuring during forming, has been studied with a flush mountedpressure sensor. Some combinations of running parametersresulted in highly oscillating pressure pulses, which wereevaluated by their wavelength.

    The visualisation was made with a high-speed video cameraand a pulsed laser light source. The forming zone was observedvia a mirror mounted on the forming roll, thus following aspecific small area of the forming zone. This made it possibleto follow floc motions relative to the forming roll/wire. Theflocs were found to move towards the wire due to the dewateringflow wereupon the bottom part of the floc was pinned to thewire. If the suspensionspeed is different from the wire speedthe floc will be stretched out, because the upper part of thefloc has a slightly different speed in comparison to the bottompart. If this speed difference is high enough, the flocs maysplit and thus contribute to fragmentation.

    The floc-floc interaction has been studied in a Couetteapparatus. It has been observed that voids in the suspensionplay a central role for the floc break-up process. The reasonis belived to be that voids induce movement inside thesuspension, which is a prerequisite for floc break-up. Thefloc-floc relative movements have been found to obey simplelaws of rack-and-pinion principles.

  • 14. Bexell, U.
    et al.
    Olsson, M.
    Sundell, P. E.
    Johansson, Mats K. G.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Carlsson, P.
    Hellsing, A.
    A ToF-SIMS study of linseed oil bonded to mercapto silane treated aluminium2004Ingår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 231-2, s. 362-365Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    ToF-SIMS has been used to analyse an aluminium surface treated with a vegetable oil using a mercapto silane as a coupling agent between the aluminium substrate and the vegetable oil. The coupling between the vegetable oil and the mercapto silane was obtained through a photoinduced thiol-ene reaction using UV-radiation. The ToF-SIMS results show that the desired thiolene reaction has taken place between the unsaturated parts of the vegetable oil and the thiol groups of the mercapto silane via the thiol-ene reaction forming a surface film.

  • 15.
    Bjarnestad, Sofia
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Characterization of the carbohydrate composition of pulp fibers2003Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 16.
    Brunius, Carl F.
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Syntheses and degradation of poly (N-vinyl-2-pyrrolidone) based graft copolymers: in search of hydrosoluble degradable materials for biomedical applications2002Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 17.
    Brännvall, Elisabet
    et al.
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Gustafsson, R.
    Teder, A.
    Properties of hyperalkaline polysulphide pulps2003Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, nr 4, s. 436-440Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The term hyperalkaline polysulphide pulping is used to denote a process utilising a polysulphide pretreatment step at high alkalinity. The stabilising effect of polysulphide on carbohydrates is enhanced by higher alkali concentrations. The high alkali concentration in the stabilisation stage also increases the delignification rate in the subsequent cooking stage. In order to keep the alkali at a high level, hyperalkaline polysulphide pulping employs two pretreatment stages. In the first stage, the alkali charge is aimed to neutralise the acids formed of the wood components. The succeeding stage is the actual hyperalkaline polysulphide stage. It has a noticeably higher alkali concentration, thus promoting an efficient carbohydrate stabilisation by the polysulphide. The hyperalkaline polysulphide pretreatment makes it possible to obtain a pulp with high viscosity and yields good bleachability and good strength properties. The pulps however, need more beating energy to reach a high tensile strength than kraft and normal polysulphide pulps.

  • 18.
    Burman, L E
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Total luminescence intensity and chromatographic fingerprinting - Tools for early degradation detection and classification of degradable polyethylene films.2005Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 229, s. U971-U971Artikel i tidskrift (Övrigt vetenskapligt)
  • 19.
    Carlmark, Anna
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Complex Macromolecular Architectures by Atom Transfer Radical Polymerization2004Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Controlled radical polymerization has proven to be a viableroute to obtain polymers with narrow polydispersities (PDI's)and controlled molecular weights under simple reactionconditions. It also offers control over the chain-]ends of thesynthesized polymer. Atom transfer radical polymerization(ATRP) is the most studied and utilized of these techniques. Inthis study ATRP has been utilized as a tool to obtain differentcomplex macromolecular structures.

    In order to elaborate a system for which a multitude ofchains can polymerize in a controlled manner and in closeproximity to one another, a multifunctional initiator based onpoly(3-ethyl-3-(hydroxymethyl)oxetane was synthesized. Themacroinitiator was used to initiate ATRP of methyl acrylate(MA). The resulting dendritic-]linear copolymer hybrids hadcontrolled molecular weights and low PDI's. Essentially thesame system was used for the grafting of MA from a solidsubstrate, cellulose. A filter paper was used as cellulosesubstrate and the hydroxyl groups on the cellulose weremodified into bromo-]ester groups, known to initiate ATRP.Subsequent grafting of MA by ATRP on the cellulose made thesurface hydrophobic. The amount of polymer that was attached tothe cellulose could be tailored. In order to control that thesurface polymerization was -eliving-f and hence that thechain-]end functionality was intact, a second layer of ahydrophilic monomer, 2-hydroxyethyl methacrylate, was graftedonto the PMA- grafted cellulose. This dramatically changed thehydrophilicity of the cellulose.

    Dendronized polymers of generation one, two and three weresynthesized by ATRP of acrylic macromonomers based on2,2-bis(hydroxymethyl)propionic acid. In the macromonomerroute, macromonomers of each generation were polymerized byATRP. The polymerizations resulted in polymers with low PDI's.The kinetics of the reactions were investigated, and thepolymerizations followed first-order kinetics when ethyl2-bromopropionate was used as the initiator. In the-egraft-]onto-f route dendrons were divergently attached to adendronized polymer of generation one, that had been obtainedby ATRP.

  • 20.
    Carlmark, Anna
    et al.
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Malmström, Eva
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    ATRP grafting from cellulose fibers to create block-copolymer grafts2003Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 4, nr 6, s. 1740-1745Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellulose fibers, in the form of a conventional filter paper, have been modified by reacting the hydroxyl groups on the fiber surface with 2-bromoisobutyryl bromide, followed by grafting using ATRP conditions. The papers were first grafted with methyl acrylate (MA), rendering the paper very hydrophobic as reported in an earlier work. The papers were analyzed by gravimetry, FT-IR, ESCA, and AFM. To verify that the polymerization from the surface was living, a second layer of another, hydrophilic, polymer, 2-hydroxyethyl methacrylate (HEMA), was grafted upon the PMA layer, creating a block-copolymer graft from the fibers. After the layer of PHEMA had been attached, contact angle measurements were no longer possible, because of the absorbing nature of PHEMA-grafted layer. This indicates that a copolymer had indeed been formed on the surface. FT-IR showed a large increase in carbonyl content after the PHEMA-grafting, which further proves that a layer of PHEMA was attached to the PMA layer. This goes to show that the hydrophilic/ hydrophobic behavior of a cellulose surface can be tailored by the use of living/controlled radical polymerization methods such as ATRP.

  • 21.
    Carlmark, Anna
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Malmström, Eva E
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    ATRP of dendronized aliphatic macromonomers of generation one, two, and three2004Ingår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 37, nr 20, s. 7491-7496Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Atom transfer radical polymerization (ATRP) of dendritic, aliphatic macromonomers has been investigated. The macromonomers were based on acrylate functionalized 2,2-bis(methylol)propionic acid (bis-MPA) dendrons, with a flexible spacer of 10 carbons incorporated in the structure in between the polymerizable group and the dendritic wedge. Dendronized polymers of generation one, two, and three were successfully synthesized by ATRP. The polymerizations proceeded until over 80% conversion was reached, while maintaining control over polydispersity index (PDI). Plots of ln([M](0)/[M]) vs time for the polymerization of all three macromonomers showed a linear dependence, indicating that the number of propagating radicals in the reaction solution was constant throughout the reaction, when ethyl 2-bromopropionate (EBrP) was used as an initiator (i.e., radical termination was negligible). All of the resulting polymers had low PDI values and molecular weight close to the theoretical ones. The products were analyzed by H-1 and C-13 NMR spectroscopies, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF).

  • 22. Christiernin, M.
    et al.
    Henriksson, Gunnar
    KTH, Tidigare Institutioner                               , Pappers- och massateknik.
    Lindström, Mikael
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Brumer, Harry
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Teeri, Tuula T.
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Lindström, T.
    Laine, J.
    The effects of xyloglucan on the properties of paper made from bleached kraft pulp2003Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, nr 2, s. 182-187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Xyloglucan was adsorbed onto bleached soft-wood kraft pulp followed by preparation and analysis of handsheets with respect to sheet formation as well as sheet mechanical and optical properties. Adsorption of xyloglucan was found to be slow. After more than 20 hrs adsorption, equilibrium had not been reached. The amount of xyloglucan adsorbed increased with beating, but neither the rate of adsorption nor the quantity adsorbed was significantly affected by temperature. Xyloglucan was found to be practically irreversibly adsorbed onto the fibres and the effects of xyloglucan on paper sheet properties were investigated after thorough washing of the pulp. The adsorption characteristics of xyloglucan confirm observations by other authors on other cellulose substrates. Tensile index values for handsheets formed with the xyloglucan-containing pulps were higher than those measured for control pulps with a comparable beating degree. The light scattering coefficient was, however, not affected by xyloglucan adsorption. Hence, the increase in tensile strength is attributed to an increased relative bond strength between the fibres. Tensile strength versus tear strength relationship was similar for pulps with and without xyloglucan, but water retention value and dewatering resistance were lower for the xyloglucan treated pulps than for the reference pulps at the same tensile strength. In addition, formation was improved for pulps with adsorbed xyloglucan. The conclusion is that xyloglucan is a promising wet end additive that decreases the necessity for beating of the pulp and improves the formation of paper.

  • 23.
    Claesson, Hans
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Synthesis and Properties of Branched Semi-Crystalline Thermoset Resins2003Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis describes the synthesis and characterization ofbranched semi-crystalline polymers. Included in this work isthe SEC characterization of a series of dendrimers. Thebranched semi-crystalline polymers were synthesized in order toinvestigate the concept of their use as powder coatings resins.This concept being that the use of branched semi-crystallinepolymers in a UV-cured powder coating system may offer a lowertemperature alternative thus allowing the use of heat sensitivesubstrates and the added benefit of a reduced viscositycompared to linear polymers.

    A series of branched poly(ε-caprolactone)’s (PCL)(degree of polymerization: 5-200) initiated from hydroxylfunctional initiators were synthesized. The final architectureswere controlled by the choice of initiator structure;specifically the dendritic initiators yielded starbranchedPCL’s while the linear initiator yielded comb-branchedPCL’s. The dendritic initiators utilized were: (1) a3rd-generation Boltorn H-30, commercially availablehyperbranched polyester with approximately 32 hydroxyl groups,(2) a 3rd-generation dendrimer with 24 hydroxyl groups, and (3)a 3rd-generation dendron with 8 hydroxyl groups. Linear PCL wassynthesized for comparison. All dendritic initiators are basedon 2,2- bis(methylol) propionic acid. The comb-branchedpolymers were initiated from a modified peroxide functionalpolyacrylate. The resins were end-capped withmethylmethacrylate in order to produce a cross-linkable system.The polymers and films were characterized using 1H NMR, 13CNMR, SEC, DMTA, DSC, FT-IR, FT-Raman, rheometry and a rheometercoupled to a UV-lamp to measure cure behavior.

    The star-branched PCL’s exhibited considerably lowerviscosities than their linear counterparts with the samemolecular weight for the molecular region investigated (2-550kg mol-1). It was also found that the zero shear viscosityincreased roughly exponentially with M.

    The PCL star-branched resins are semi-crystalline and theirmelting points (Tm) range from 34-50°C; films can beformed and cured below 80°C. The viscoelastic behaviourduring the cure showed that the time to reach the gel point, afew seconds, increased linearly with molecular weight. Thecrossover of G’and G’’was used as the gelpoint. Measurement of mechanical properties of films showedthat the low molecular weight polymers were amorphous whilethose with high molecular weight were crystalline after cure.The polymerization of 5,5-dimethyl-1,3-dioxane-2-one (NPC) fromoligo- and multifunctional initiators was evaluated utilizingcoordination and cationic polymerization. Two tin basedcatalysts, stannous(II) 2-ethylhexanoate and stannous(II)trifluoromethane sulfonate, were compared with fumaric acid.Fumaric acid under bulk conditions resulted in lowerpolydispersity and less chance of gelling. The synthesis ofstar-branched polymers was confirmed by SEC data. The starpolymers exhibited a Tg at 20-30°C and a Tm at about100°C.

    All semi-crystalline resins exhibited a fast decrease inviscosity at Tm. Blends of combbranched semi-crystalline resinsand amorphous resins exhibited a transition behavior inbetweenthat of pure semi-crystalline resins and that of amorphousresins.

    The SEC characterization of a series of dendrimers withdifferent cores and terminal groups showed that the core had animpact on the viscosimetric radius of the core while theterminal groups appeared to have no effect.

    Keywords:star-branched, semi-crystalline,comb-branched, ring-opening polymerization,poly(ε-caprolactone), dendritic, thermoset, lowtemperature curing, powder coating, UVcuring,poly(5,5-dimethyl-1,3-dioxane-2-one), size exclusionchromatography, rheology, dendritic aliphatic polyester

  • 24.
    Claesson, Hans
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Scheurer, Curzio
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Malmström, Eva
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Johansson, Mats K. G.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Hult, Anders
    KTH, Tidigare Institutioner, Polymerteknologi.
    Paulus, W.
    Schwalm, R.
    Semi-crystalline thermoset resins: tailoring rheological properties in melt using comb structures with crystalline grafts2004Ingår i: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 49, nr 1, s. 13-22Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermosetting resins with semi-crystalline grafts have been synthesized. An amorphous resin with epoxide groups was first functionalized with hydroxyl groups using 2,2-bis(methylol) propionic acid, bis-MPA in bulk at 155 degreesC. Functionalization with bis-MPA was monitored using FT-IR, FT-Raman and SEC. The reaction was complete in 30 min. Grafts of poly(epsilon-caprolactone) were then grown from the hydroxyl functional resin and end capped with methacrylate groups. The polymerization Of epsilon-caprolactone, performed in bulk at 110 degreesC using Sn(Oct)(2), was characterized using H-1 NMR and SEC. The obtained molecular weights agreed well with theoretical values. The final end capping was performed using methacrylic anhydride, and monitored with SEC and H-1 NMR, which indicated full substitution. Two combs were synthesized with different arm lengths, DP 10 and 20, and the obtained M-W were close to calculated values. The complex viscosity was measured from low to high temperature for the crystalline resins, the amorphous resin and blends thereof. Rheological data show a rapid decrease in viscosity within a temperature change of 10-15 degreesC for the crystalline resins while the amorphous resin exhibited a slow softening. The blends exhibited a behavior in-between that of the crystalline and the amorphous resin. Films were prepared from the pure resins and the blends. The films were cured using UV irradiation. The comb architecture of these resins has advantages such as crystallinity, high molecular weight and low viscosity, facilitating leveling and resulting in smooth films. The final film properties varied with the ratio of crystalline to amorphous resin, where increase in the amount of crystalline resin correlated with increased the flexibility.

  • 25. Coullerez, G.
    et al.
    Lundmark, S.
    Malmström, Eva
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Hult, Anders
    KTH, Tidigare Institutioner                               , Polymerteknologi.
    Mathieu, H. J.
    ToF-SIMS for the characterization of hyperbranched aliphatic polyesters: probing their molecular weight on surfaces based on principal component analysis (PCA)2003Ingår i: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 35, nr 8, s. 693-708Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of 2,2-bis(hydroxymethyl)propionic acid (Bis-MPA) hyperbranched aliphatic polyesters with different molecular weights (generations) is analysed for the first time by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The main negative and positive low-mass fragments are identified in the fingerprint part of the spectra (m/z < 400) and are principally assigned to fragmentation of the Bis-MPA repeating units. In addition, it is shown that the fragmentation pattern is highly affected by the functional end-groups. This is illustrated for a phthalic acid end-capped hyperbranched polymer and for an acetonide-terminated dendrimer analog. Also, typical fragments assigned to the ethoxylated pentaerythritol core molecule are detected. These ions show decreasing intensities with increasing molecular weight. This intensity dependency on the generation is used to calibrate the molecular weight of hyperbranched polyesters on the surface. To obtain quantitative information, a principal component analysis WCA) multivariate statistical method is applied to the ToF-SIMS data. The influence of different normalization procedures prior to PCA calculation is tested, e.g. normalization to the total intensity, to the intensities of ions assigned to the Bis-MPA repeating unit or to intensities of fragments due to the core molecule. It is shown that only one principal component (PC1) is needed to describe most of the variance between the samples. In addition, PC1 takes into account the generation effect. However, different relationships between the PC1 scores and the hyperbranched mass average molecular weights are observed depending on the normalization procedure used. Normalization of data set ion intensities by ion intensities from the core molecule allows linearization of the SIMS intensities versus the molecular weight and allows the hyperbranched polymers to be discriminated up to the highest generations. In addition, PCA applied to ToF-SIMS data provides an extended interpretation of the spectra leading to further identification of the correlated mass peaks, such as those of the Bis-MPA repeating unit (terminal, dendritic and linear) and those of the core molecule. Finally, the work presented demonstrates the extreme potential of the static ToF-SIMS and PCA techniques in the analysis of dendritic molecules on solid surfaces.

  • 26.
    Coullerez, Geraldine
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Carlmark, Anna
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Malmström, Eva
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Jonsson, Mats
    KTH, Tidigare Institutioner, Kemi.
    Understanding copper-based atom-transfer radical polymerization in aqueous media2004Ingår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 108, nr 35, s. 7129-7131Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study investigates the mechanism of copper(I)-mediated living atom-transfer radical polymerization (ATRP) in aqueous media. It is shown that the ATRP apparent rate constant for polymerization of methoxycapped oligo(ethylene glycol) methacrylate (OEGMA) in water (k(P)(app)) at room temperature correlates with the redox potential (E-1/2) of the copper complexes. The results are discussed along with previously published results on the kinetics for bulk polymerization of methyl acrylate at 60 degreesC with the redox potentials measured in MeCN. The faster ATRP kinetics in water can mainly be attributed to a higher equilibrium concentration of propagating radicals [W] and to solvent effects on the rate of propagation k(p). It is shown that [R*] can be calculated from the redox properties of the alkyl halide and the copper complex. The values of [R*] in MeCN/bulk and in H2O were determined to be 8.2 x 10(-8) and 6.3 x 10(-5) M, respectively. The respective kp values are in good agreement with the literature values (3.6 x 10(3) M-1 s(-1) for OEGMA in water and 2.5 x 10(3) M-1 s(-1) for methyl acrylate in bulk).

  • 27.
    Danielsson, Sverker
    et al.
    KTH.
    Brännvall, Elisabet
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Lindström, Mikael
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Xylan as a surface modifying agent in the kraft cook2006Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 231Artikel i tidskrift (Övrigt vetenskapligt)
  • 28.
    Ekevåg, Per
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Lindström, Tom
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Gellerstedt, Göran
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Lindström, Mikael
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Addition of carboxymethylcellulose to the kraft cook2004Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 2, s. 200-207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The physical attachment of carboxymethylcellulose (CMC) onto kraft pulps during cooking and the effects of subsequent bleaching in an OD(EOP)DD sequence were investigated. Two CMC grades with different molecular weights and different degrees of substitution (D.S.) were used, CMC Finnfix WRH and CMC Cekol DVG. The effect of the CMC was studied by measuring the increase in the total charge density as well as in the surface charge density. In this way, both the total amount of attached CMC and the amount of the CMC attached onto the surface of the fibres Could be determined. Hand-sheets were made to study the effects of CMC addition on the physical properties of the paper. Different amounts of CMC were added to find the optimum, which was determined to be 1% CMC on wood. The proportion of CMC attached at a level addition of 1% (on wood) was about 40%. It was, however, found that a large part of the CMC was degraded during the cook. Whereas high molecular weight CMC is attached onto the surface of fibres, the degraded CMC is attached to the interior of the cell wall, decreasing the efficiency of the CIVIC to enhance the joint strength between fibres. The tensile index increased significantly, approximately 10% after beating to 2000 PFI revolutions, when 1% CMC Finnfix WRH on wood was added. The CMC Cekol DVG grade showed the greatest increase in tensile index, approximately 12% at 2000 PFI revolutions. The results of the bleaching of a sample treated with CMC Finnfix WRH showed that a part of the effect of CMC remains after bleaching. Most of the reduction in the positive effect was due to a loss of CMC molecules from the fibre surface.

  • 29.
    Engström, Joakim
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Asem, Heba
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Brismar, Hjalmar
    KTH, Tidigare Institutioner (före 2005), Fysik. KTH, Centra, Science for Life Laboratory, SciLifeLab. KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Zhang, Yuning
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Malkoch, Michael
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi. KTH, Tidigare Institutioner (före 2005), Polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Malmström, Eva
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    In situ encapsulation of Nile red or Doxorubicinduring RAFT‐mediated emulsion polymerizationvia PISAManuskript (preprint) (Övrigt vetenskapligt)
  • 30.
    Eriksson, Malin
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Interaction between thin interfacial layers: the influence of polyelectrolyte multilayers on paper strength2004Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 31.
    Eriksson, Petter
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    New Approaches to Investigate and Prevent Oxidation of Polypropylene2002Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    When employing chemiluminescence to evaluate stabiliserperformance in a polymer, the induction time or the time toreach maximum chemiluminescence intensity is often used. Insuch an experiment the longest part of the experiment isnormally the time before the oxidation starts. In the presentwork oxidation was initiated in stabilised polypropylene (PP)by means of UV light or unstabilised PP, and the spreading ofoxidation was then followed using imaging chemiluminescence(ICL). As a result of this initiation, oxidation started at thebeginning of the experiment, which eliminated the inductiontime. The rate of the subsequent spreading of oxidation to therest of the sample was used to determine the performance ofdifferent stabilisers in PP. It was shown that such experimentsare reproducible and can be used to compare differentantioxidants with respect to their efficiency. However, therate of spreading accelerated during the experiments.

    The gaseous products formed during the experiment were foundto influence the results by increasing the rate of spreading.In order to remove the influence of the gas phase, a device wasconstructed that directed an air flow over the sample surface.Even without the gas phase the spreading of oxidation occurred,but was now ascribed to bulk phase spreading. This spreadingshowed a linear spreading rate and did not accelerate. Thecause of the acceleration is probably a build-up of reactivegaseous species in the sample chamber. In order to clarifypossible volatile oxidation products capable of spreadingoxidation via the gas phase, formaldehyde, acetic acid,ethylene, water and iso-butylene were added in small amounts tothe inlet air in the ICL sample chamber. Only formaldehyde andacetic acid were found to increase the spreading of oxidation.However, acetic acid did this by interacting with thestabiliser, whereas formaldehyde increased the oxidation alsoin unstabilised PP.

    To further study the oxidation of PP, a combined instrumentwas constructed where a microcalorimeter (MC) was connected toa photomultiplier via an optic fibre so that a simultaneous CL(Counts/s) and MC (Joule/s) signal could be collected. Thisinstrument provides complementary data that gives moreinformation than if each technique had been used separately. Sofar, it has been shown that the MC response occurs earlier thanthe CL response at low extents of oxidation. However, at higherextents of oxidation the reverse has been observed.

    In addition to studying commercial antioxidants for PP a newantioxidant concept based on a synergistic mixture of organotellurium compounds and hindered phenols was developed andfound to be superior to standard antioxidant formulations.Moreover, hyperbranched hindered phenols of differentgenerations were developed and tested in PP. The intention wasto discover low migrating antioxidants. These were found to besuperior to the commercial hindered phenol Irganox 1010 whenused in liquid, low viscous systems, but did not performequally well in PP. This is believed to be due to restrictedmobility. However when combining them with the organo telluriumantioxidants, mixtures that performed well also in PP wereachieved.

  • 32.
    Espert, Ana
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Natural fibres/polypropylene composites from residual and recycled materials2003Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Natural fibres fulfil all the requirements in order toreplace inorganic fillers in thermoplastic composites. Naturalfibres are inexpensive, renewable, biodegradable, present lowerdensity and their mechanical properties can be compared tothose of inorganic fillers. However, several disadvantagesappear when natural fibres are used for composites. First ofall, the poor compatibility between the hydrophilic fibres withthe hydrophobic thermoplastic matrix leads to a weak interface,which results in poor mechanical properties. On the other hand,the hydrophilic nature of the fibres makes them very sensitivetowards water absorption, which leads also to the loss ofproperties and the swelling and dimensional instability.

    In order to enhance the compatibility fibre-matrix, thefibres were chemically surface modified by five differentmethods: a) graft copolymerisation withpolypropylene-graftedmaleic anhydride copolymer (PPgMA), b)modification by PPgMA during processing, c) modification byorganosilanes, d) acetylation, e) modification with peroxideoligomers. Modified fibres led to improved mechanicalproperties and thermal behaviour when used in composites withpost-industrial polypropylene (PP) containing ethylene vinylacetate copolymer (EVA). Modification with peroxide oligomersshowed very promising results, but modification with PPgMA waschosen for further preparation of composites due to itssimplicity.

    Two sets of composites were prepared using two differentpolypropylene types as matrix: virgin polypropylene (PP) andthe above mentioned post-industrial polypropylene (PP/EVA).Four different types of cellulosic fibres were used as fillers:cellulose fibres from pulping, sisal fibres, coir fibres andLuffa sponge fibres. The mechanical properties of thecomposites were dependent mostly on the fibre loading andslightly on the type of fibre. The fibers changed thecharacteristics of the material leading a higher stiffness buta lower toughness.

    Water absorption of composites was studied at threedifferent temperatures: 23°C, 50°C and 70°C. Thewater absorption kinetics were studied and it was found thatwater is absorbed in composites following the kineticsdescribed by the Fickian diffusion theory. After absorption, animportant loss of properties was observed, due to thedestruction of the fibre structure due to the waterabsorbed.

  • 33.
    Espert, Ana
    et al.
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Karlsson, Sigbritt
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Novel PP/Montmorillonite/cellulose hybrid composites: study of the interaction between Montmorillonite clay and celluloseManuskript (preprint) (Övrigt vetenskapligt)
  • 34.
    Espert, Ana
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Vilaplana, Francisco
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Karlsson, Sigbritt
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Comparison of water absorption in natural cellulosic fibres from wood and one-year crops in polypropylene composites and its influence on their mechanical properties2004Ingår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 35, nr 11, s. 1267-1276Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Environmentally beneficial composites can be made by replacing glass fibres with various types of cellulose fibres. Fibres from pine or eucalyptus wood and also one-year crops such as coir, sisal, etc. are all good candidates. The poor resistance towards water absorption is one of the drawbacks of natural fibres/polypropylene composites. New natural fibres/polypropylene composites were made and the water absorption in them was studied by immersion of the composites in water at three different temperatures, 23, 50 and 70 degreesC. The process of absorption of water was found to follow the kinetics and mechanisms described by Fick's theory. In addition, the diffusivity coefficient was dependent on the temperature as estimated by means of Arrhenius law. A decrease in tensile properties of the composites was demonstrated, showing a great loss in mechanical properties of the water-saturated samples compared to the dry samples. The morphology change was monitored by scanning electron microscopy studies of the samples before and after exposure to water and the devastating effect of water on the fibre structure was shown.

  • 35. Falt, S.
    et al.
    Wågberg, Lars
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Vesterlind, E. L.
    Swelling of model films of cellulose having different charge densities and comparison to the swelling behavior of corresponding fibers2003Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, nr 19, s. 7895-7903Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellulose model films with different charge densities were prepared by spin-coating dissolved cellulose in N-methylmorpholine-N-oxide onto SiO2 surfaces. The swelling of the model cellulose films due to exposure to solutions of different electrolytes and at different ionic strengths and pH values were studied using QCM-D (quartz crystal microbalance with dissipation monitoring). Results show that at pH 5, there is a swelling of the film at a low electrolyte concentration (10(-4)-10(-2) M), whereas the deswelling of the film was observed at a high electrolyte concentration (10(-1)-1 M). A considerable swelling of the films is seen when they are treated with deionized water with an increasing pH. The swelling of the films is accompanied by an increase in dissipation, that is, a softening of the material, and the deswelling by a decrease in dissipation, that is, a stiffening of the material. Furthermore, exposure of the films to solutions of different electrolytes affected the swelling of the layer. In this respect, the swelling response of Na2SO4 differs from that of NaCl and CaC1(2) by showing simultaneously high swelling and low dissipation values. The results also show that the rate of swelling reaches its lowest value as the electrolyte concentration reaches the detected limit for the deswelling. The QCM-D results are compared to the swelling of the corresponding carboxymethylated fibers, where a similar behavior was found. However, for the fibers a marked deswelling occurred at a high electrolyte concentration, but only a minor deswelling of the cellulose film was observed. This difference between the materials can be ascribed to noncovalent bonds within the film that will not reform when the swelling forces are decreased at high electrolyte concentrations. A direct measurement of the thickness changes was performed using atomic force microscopy, which shows that the change in frequency measured with QCM-D for the films treated with different NaCl electrolyte concentrations corresponds to changes of 1-2%.

  • 36. Falt, S.
    et al.
    Wågberg, Lars
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Vesterlind, E. L.
    Larsson, Per Tomas
    Model films of cellulose II - improved preparation method and characterization of the cellulose film2004Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 11, nr 2, s. 151-162Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An optimization study of the preparation of spin-coated cellulose model films from the NMMO/DMSO system on silicon wafers has been made. The study shows that the cellulose concentration in the solution determines the cellulose film thickness and that the temperature of the solution affects the surface roughness. A lower solution temperature results in a lower surface roughness at cellulose concentrations below 0.8%. Using the described method, it is possible to prepare films with thicknesses of 30-90 nm with a constant surface roughness by changing the cellulose concentration, i.e. by dilution with DMSO. On these films, water has a contact angle less than 20degrees and about 50% of the material can, according to CP/MAS C-13-NMR spectroscopy on corresponding fibrous material, be considered to consist of crystalline cellulose II type material. It has further been shown that AFM can be used to determine the thickness of cellulose films, in both dry and wet states. In this method, the difference in height between the top surface and the underlying wafer has been measured at an incision made into the cellulose film. The cellulose films have also been spin-coated with the same technique as on the silicon oxide wafer onto the crystal in a quartz crystal microbalance (QCM). These model films were found to be suitable for swelling measurements with the QCM. The films were very stable during this type of measurement and films with different amounts of charges gave different swelling responses depending on their charges. As expected, films with a higher charge showed a higher swelling.

  • 37.
    Farahani, Saina Kishani
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Vilaplana, Francisco
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Ruda, Marcus
    Hansson, Per
    Wågberg, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    The influence of solubility on the adsorption of different Xyloglucan fractions at Cellulose Water InterfacesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Xylogucan (XG) fractions with different molar masses were prepared while preserving the natural structure of the XG. The solubility of the fractions was investigated using light- scattering, chromatography and microscopy techniques. The conformational changes of the XG molecules and their association and phase separation were investigated together with concentration and molar mass changes. The knowledge gained was then applied to investigate the interaction of different XG fractions at cellulose model surfaces using a quartz crystal microbalance with dissipation. The results indicate that there is a cluster formation and phase separation of the XG molecules at the cellulose/water interface induced by the increase in XG concentration close to the surface. Concomitantly, the adsorption regimes are altered for the XG fractions depending on the solubility properties, indicating that the insolubility, association and phase separation of XGs in aqueous media affect their interaction with cellulose. The study is of vital importance for improving the functionality of sustainable materials made from xyloglucan/cellulose natural composites.

  • 38.
    Fateh-Alavi, Kamyar
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Stabilizers in crosslinked polydimethylsiloxane2003Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The loss and recovery of the surface hydrophobicity areimportant phenomena when highvoltage insulators, with a shedmaterial composed of polydimethylsiloxane (PDMS), are used. Theloss of hydrophobicity is mostly due to the oxidativecrosslinking which takes place on the PDMS surface duringexposure to electrical discharges, e. g. corona discharges. Thecrosslinking reaction leads to the formation of anoxygen-enriched, silica-like layer, which is brittle and henceprone to cracking, either spontaneously or upon mechanicaldeformation. Repetitive cracking leads to the propagation ofcracks into the core of the material, which is believed todeteriorate the insulator’s performance and reduce itsservice-life. Hence, an approach to make PDMS more resistant tothe build-up of the silica-like layer is beneficial for theperformance of PDMS in high voltage insulators.

    In this work the effect of antioxidative stabilizers on thecorona- and air-plasma-induced surface oxidation of PDMS isstudied. Three commercial stabilizers, a hindered phenol(Irganox® 1076), a hindered amine light stabilizer(Tinuvin® 770) and a bifunctional stabilizer withchainbreaking hindered phenol and secondary amine andhydroperoxide-decomposing sulfide moieties (Irganox® 565),have been used. Surface oxidation was achieved by exposure of amodel crosslinked PDMS to an air plasma or a corona discharge,and the surface characteristics of the exposed samples wereassessed by contact angle measurements, X-ray photoelectronspectroscopy, optical and scanning electron microscopy, andsurface profilometry before and after uniaxial stretching.

    A reliable rapid method for the assessment of stabilizerconcentration in PDMS was established. PDMS samples containingknown stabilizer concentrations of a phenolic antioxidant(Irganox® 1010) and a hindered amine stabilizer(Tinuvin® 144) were prepared. It was shown that thestabilizer concentration in PDMS could be determined by highperformance liquid chromatography (HPLC) of the microwaveassisted solvent extracts (MAE) of stabilized PDMS samplesusing acetone (a non-swelling solvent). This method wasemployed to measure the stabilizer concentration in PDMSsamples exposed to air plasma and corona discharges. Thestabilizer concentration in PDMS was varied by using diluteswelling solutions (0.005 wt% to 0.2 wt%) of the stabilizers inhexane. Samples stabilized with Irganox 565 showed stabilizerprecipitation on the surface after swelling in solutions with astabilizer concentration greater than 0.05 wt%. Samplescontaining Irganox 1076 and Tinuvin 770 showed no surfaceprecipitation except after swelling in a solution of 0.2 wt%stabilizer concentration.

    The air plasma and corona exposure time required for theformation of the silica-like surface layer increased,essentially, in a linear fashion with increasing stabilizerconcentration. Tinuvin 770 showed the strongest overallprotecting effect during, as well air plasma as coronaexposures, whereas Irganox 565 showed the strongest protectingeffect per mass fraction stabilizer during air plasmaexposures. Irganox 1076 was of moderate efficiency. The resultssuggest that efficient protection towards discharge-inducedsurface oxidation is achieved with hindered amine stabilizersor with stabilizers combining chain-breaking andhydroperoxide-decomposing functions.

    The diffusion of the stabilizers Irganox 1010 and Tinuvin144 from PDMS to water at elevated temperatures (75 °C and95 °C for Irganox 1010 and 95 °C for Tinuvin 144) wasstudied. For Irganox 1010 the diffusion constant (D), accordingto Fick’s second law for uni-dimensional penetrantdiffusion was assessed to 3.1 X 10-9cm2s-1at 95 °C and to 5.46 X 10-10cm2s-1at 75 °C. An estimate for the activationenergy for the diffusion of Irganox 1010 to the surroundingmedia was obtained (Ea=93 kJ mol-1), on the basis of the diffusion data. For Tinuvin144, no diffusion constant could be calculated due to poorseparation of the stabilizer peak from the impurities in theextract when using the HPLC method developed earlier.

  • 39.
    Fateh-Alavi, Kamyar
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Karlsson, Sigbritt
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Gedde, Ulf W.
    KTH, Tidigare Institutioner, Polymerteknologi.
    A rapid microwave-assisted solvent extraction method for assessment of stabilizer concentration in crosslinked polydimethylsiloxane2004Ingår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 93, nr 5, s. 2185-2192Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Crosslinked polyclimethylsiloxanes were prepared containing 0.05 to 0.2 wt % of either a phenolic antioxidant (Irganox(R) 1010) or a hindered amine stabilizer (Tinuvin(R) 144). The stabilizer concentration was assessed by HPLC and UV-Vis spectroscopy of Soxhlet and microwave-assisted solvent extracts. Almost complete recovery of stabilizer was achieved with Soxhlet extraction. High stabilizer recovery was achieved when acetone was used as the solvent in the microwave-assisted extraction. HPLC was shown to be an efficient method for determining the concentration of Irganox 1010. For Tinuvin 144 the selectivity of both UV-Vis spectroscopy and HPLC was poor, leading to imprecise evaluation of the antioxidant concentration. The loss of stabilizer by migration from polymer to hot water (75 and 95degreesC) was monitored for the systems stabilized with Irganox 1010 and the diffusion coefficient of the antioxidant in the polymer was determined.

  • 40.
    Finne Wistrand, Anna
    et al.
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Ryner, M.
    Albertsson, Ann-Christine
    KTH, Tidigare Institutioner                               , Polymerteknologi.
    Degradable polymers: Design, synthesis and testing2003Ingår i: Macromolecular Symposia, ISSN 1022-1360, E-ISSN 1521-3900, Vol. 195, s. 241-246Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The object for our research is to mimic Nature's perfectly designed resorbable materials to obtain important materials, which are biocompatible and degradable. We have therefore synthesized different architectures and copolymers of aliphatic polyesters with ring-opening polymerization. The first studies of these materials properties show that properties like hydrophilicity and tensile properties can be controlled.

  • 41.
    Finnveden, Maja
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi. KTH Royal Institute of Technology.
    Hendil-Forssell, Peter
    Claudino, Mauro
    Johansson, Mats
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Martinelle, Mats
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Industriell bioteknologi.
    Lipase Catalyzed Synthesis of renewable plant oil-based polyamidesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Enzyme catalyzed synthesis towards renewable polyamides was investigated using Candida antarctica lipase B. A fatty acid-derived AB-type functional monomer, having one amine and one methyl ester functionality was homopolymerized at 80 and 140°C. Additionally, the organobase 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was used as catalyst. The results from the two catalysts were comparable. However, the amount of lipase added was 1200 times lower showing that the lipase was a more efficient catalyst for this system as compared to TBD. Moreover, the AB type monomer was copolymerized with 1,12-diaminododecan to synthesize oligoamides of two different lengths.

  • 42.
    Fogelström, Linda
    et al.
    KTH, Tidigare Institutioner (före 2005), Fiber- och polymerteknologi.
    Antoni, P
    KTH.
    Malmström, Eva
    KTH, Tidigare Institutioner (före 2005), Polymerteknologi.
    Hult, Anders
    KTH, Tidigare Institutioner (före 2005), Polymerteknologi.
    UV-curable nanocomposite coatings.2005Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 229, s. U986-U986Artikel i tidskrift (Övrigt vetenskapligt)
  • 43. Forsstrom, J.
    et al.
    Wågberg, Lars
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Influence of different storage conditions on deinking efficiency of waterbased flexographic ink from model cellulose surfaces and sheets2004Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 2, s. 250-256Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of UV-Iight, temperature, atmospheric environment and storage time on the ink detachment of water-based flexographic ink printed on model cellulose surfaces was investigated using an impinging jet cell equipment. The printed surfaces were deinked using a NaOH solution (pH = 10) and the deinking process was monitored using a microscope equipped with a CCD camera. Images were collected at different time intervals during the detachment process and image analysis was used to quantify the ink detachment from the surface. Hand sheets, (the same pulp as used for model surface preparation) were also printed and stored under the same conditions, after which they were reslushed and deinked. The deinking efficiency of the recycled sheets was evaluated using brightness and ERIC (Effective Residual Ink Concentration) values. It was shown that UV-Iight had a negative effect on ink detachment both from the model cellulose surfaces and from the hand sheets. At storage temperatures of 55degreesC, (dark conditions were used) a large negative effect was observed for the cellulose surfaces while only a small effect on the ink detachment could be seen for the hand sheets. Ink detachment from the hand sheets became more difficult when increasing the storage temperature above 55degreesC, as detected as a decrease in brightness of the recycled and deinked sheets. A farther increase in the storage temperature to 105degreesC gave poorer ink detachment efficiency than storage under UV-Iight for the hand sheets. Air had a more negative effect on ink detachment than nitrogen.

  • 44.
    Forsström, Jennie
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Fundamental Aspects on the Re-use of Wood Based Fibres: Porous Structure of Fibres and Ink Detachment2004Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this work, different aspects on the re-use of wood based fibres have been studied, focusing on ink detachment of flexographic ink from model cellulose surfaces and changes in porous structure of kraft fibres following different treatments. New model systems for evaluation of ink detachment and ink-cellulose interactions were used. Ink detachment was studied using Impinging jet cell equipment, taking into consideration the influence of storage conditions, surface roughness and surface energy of the cellulose substrate. A micro adhesion measurement apparatus (MAMA) was used to directly study ink-cellulose interactions, from which the adhesive properties between ink and cellulose, having various surface energies, could be derived. UV-light, elevated temperatures, longer storage time, decreased surface energy, i.e. making the cellulose surface more hydrophobic, and high surface roughness all negatively affected ink detachment. Attenuated total reflectance - fourier transform infra red (ATR-FTIR) and atomic force microscopy (AFM) was used to evaluate structural and chemical changes of ink and cellulose upon storage at elevated temperature or under UV-light. After storage at elevated temperatures, ATR-FTIR spectra indicated that a hydrolysis or an oxidative reaction took place as a peak at 1710 cm-1 appeared. AFM revealed that storage at elevated temperatures caused the latex particles present in the ink to form a film, most likely due to annealing. Less ink detached from hydrophobic cellulose surfaces. Ink detachment decreased for rougher cellulose substrates due to an increased molecular contact area.

    Fibre pore structure and water retaining ability influenced fibre/fibre joint strength and different paper strength properties. Investigations took into account the effect of pulp yield, counter-ion types, pH, salt, hornification and strength enhancing additives. Nuclear magnetic resonance relaxation (NMR), inverse size exclusion chromatography (ISEC) and water retention value (WRV) measured the changes that occur in the fibre wall upon varying the conditions. Each different measuring technique contained unique information such that a combination of the techniques was necessary to give as complete a picture as possible over the changes that occurred in the fibre wall upon varying the conditions for the fibre. A correlation between fibre pore radius and sheet strength properties was found, suggesting that fibres with larger pores allow for a larger molecular contact area between fibres to be formed during drying and consolidation of the paper. Fibre/fibre joint strength, fibre flexibility, and the number of efficient fibre/fibre contacts also controlled sheet strength. The effect of different strength enhancing additives on fibre pore structure and paper strength was investigated. Larger pores in the fibres allowed for additives to penetrate into the fibre wall. Additives with low molecular mass (Mw) penetrated into the fibre wall to a larger extent than additives with a high Mw, causing an embrittlement of the fibre. However, low Mw additives gave higher sheet tensile strength despite a leveling out in strength at high additions, indicating that the fibre wall can only adsorb a limited amount of chemical. Polyallylamine hydrochloride (PAH) and polyelectrolyte complexes (PEC) of PAH and polyacrylic acid (PAA) were added separately to the pulp. PEC significantly improved both tensile strength and Z-strength, whereas PAH alone did not increase the strength properties to the same extent unless the sheets were heated to 150°C for 10 minutes. The results suggested that the effect of PEC was dominated by an improvement in fibre/fibre joint strength, whereas the effect of PAH was significantly affected by an improvement of the intra-fibre bond strength

  • 45.
    Forsström, Jennie
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Ageing of flexographic printed model cellulose surfaces and determination of the mechanisms behind ageing2004Ingår i: Research Forum on Recycling, Proceedings, 2004, s. 21-25Konferensbidrag (Refereegranskat)
    Abstract [en]

    The influence of storage conditions on the ink detachment efficiency of water-based flexographic ink printed onto model cellulose surfaces and hand sheets were investigated. It was shown that UV-light, elevated temperatures, longer storage time, increasing surface roughness and increasing surface hydrophobicity all had a negative effect on ink detachment. It was also shown that the ink's chemical and structural characteristics changed when stored at elevated temperatures. No chemical or structural changes could be observed for the ink when stored under UV-light.

  • 46.
    Friman, Linda
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    The influence of iron and some other metals on the optical properties of themomechanical pulps2004Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 47.
    Fält, Susanna
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Model studies of cellulose fibers and films and their relation to paper strength2003Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The objectives of this work were (i) to develop a new methodfor the preparation of thin cellulose model films, (ii) to usethese model films for swelling measurements and (iii) to relatethe swelling of fibers and films to the dry strength ofpaper.

    In the new film preparation method, NMMO(N-methylmorpholine-N-oxide) was used to dissolve cellulose andDMSO (dimethyl sulfoxide) was added to control the viscosity ofthe cellulose solution. A dilute solution of the cellulose wasspin-coated onto a silicon oxide wafer and the cellulose filmthus prepared was then precipitated in deionised water. Asaturated layer of glyoxalated-polyacrylamide was used toanchor the film onto the silicon oxide wafer. This proceduregave films with thicknesses in the range of 20-270 nm. Thefilms were cleaned in deionised water and were found by ESCAanalysis and contact angle measurements (θ<20°)to be free from solvents. Solid state NMR measurements onfibers spun from NMMO also indicated that the model filmconsisted of about 50% crystalline material and that thecrystalline structure was of the cellulose II type.Determination of the molecular weight distribution of thecellulose surface material showed that the NMMO treatmentcaused only a minor breakdown of the cellulose chains and thatlow molecular mass oligomers of glucose were not created.

    It was further shown that atomic force microscopy (AFM)measurements could be used to determine the thicknessof thecellulose films, in both the dry and wet states. The thicknesswas determined as the height difference between the top surfaceand the underlying silica wafer measured at a position where anincision had been made in the cellulose film. The cellulosesolutions were also directly spin-coated onto the crystal usedin the Quartz crystal microbalance (QCM-D), pre-treated withthe same type of anchoring polymer. With this application,these model surfaces were shown to be suitable for swellingmeasurements with the QCM-D. The extent of swelling and theswelling kinetics in the presence of electrolytes, such asNaCl, CaCl2 and Na2SO4, and at different pH were measured inthis way. The films were found to be very stable during thesemeasurements and the results were comparable to the swellingresults obtained for the corresponding pulps. The swelling ofboth fibers and films followed the general behavior ofpolyelectrolyte gels in the presence of electrolytes and was inaccordance with the Donnan equilibrium theory. The films havebeen shown to differ from fibers with regard to the absence ofa covalent interior network. This influences the evaluation ofthe deswelling effects measured on the model films. Theswelling effect seen with different electrolytes has also beenconsidered in relation to the tensile strength of paperprepared from a kraftliner-pulp. In this study, it was foundthat there was no direct relationship between the swelling ofthe fibers, measured as WRV, and the strength of the paper inthe presence of different electrolytes at pH 5.

    KEYWORDS:absorption, carboxymethyl cellulose,cellulose, cellulose fibers, dissolving pulps, donnanequilibrium, electrolytes, film, ion exchange, ionization,kinetics, liner boards, microscopy, spinning, surfaces,swelling, tensile strength, water, water retention value.

  • 48.
    Gabig-Ciminska, Magdalena
    et al.
    KTH, Tidigare Institutioner, Bioteknologi.
    Los, M.
    Holmgren, Anders
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Albers, J.
    Czyz, A.
    Hintsche, R.
    Wegrzyn, G.
    Enfors, Sven-Olof
    KTH, Tidigare Institutioner, Bioteknologi.
    Detection of bacteriophage infection and prophage induction in bacterial cultures by means of electric DNA chips2004Ingår i: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 324, nr 1, s. 84-91Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Infections of bacterial cultures by bacteriophages are common and serious problems in many biotechnological laboratories and factories. A method for specific, quantitative, and quick detection of phage contamination, based on the use of electric DNA chip is described here. Different phages of Escherichia coli and Bacillus subtilis were analyzed. Phage DNA was isolated from bacterial culture samples and detected by combination of bead-based sandwich hybridization with enzyme-labeled probes and detection of the enzymatic product using silicon chips. The assay resulted in specific signals from all four tested phages without significant background. Although high sensitivity was achieved in 4h assay time, a useful level of sensitivity (10(7)-10(8) phages) is achievable within 25 min. A multiplex DNA chip technique involving a mixture of probes allows for detection of various types of phages in one sample.. These analyses confirmed the specificity of the assay.

  • 49.
    Gellerstedt, Göran
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Majtnerova, Andrea
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    On the structure of lignin in kraft pulping2004Ingår i: 2nd International Symposium on Technologies Of Pulping, Papermaking and Biotechnology on Fiber Plants, Proceedings / [ed] Jin, YC; Xie, HF, NANJING: NANJING FORESTRY UNIV , 2004, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    Lignin present in the residual delignification phase is difficult to dissolve and any further pulping leads to an increased loss of pulp strength and yield. In this work, a radical coupling mechanism during kraft pulping is suggested to contribute to the observed incomplete delignification. In such an electron transfer reaction, elemental sulfur may act as an initiator between the residual lignin in the pulp and phenolic structures present in the black liquor. To find support for such a mechanism, lignins from kraft cooks with kappa number of approximate to 30 prepared with and without a reactive phenol, 2,6-xylenol in the cook, were studied. GPC, GS-MS and NMR were the techniques used for analyses of isolated lignins and lignin samples obtained by thioacidolysis to support the suggested mechanism. The analytical data showed that the added phenol was incorporated into the polymeric lignin with a preferential formation of biphenyl structures.

  • 50.
    Gellerstedt, Göran
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Majtnerová, Andrea
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Zhang, Liming
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Towards a new concept of lignin condensation in kraft pulping. Initial results2004Ingår i: Comptes rendus. Biologies, ISSN 1631-0691, E-ISSN 1768-3238, Vol. 327, nr 9-10, s. 817-826Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In kraft pulping, a comparatively large amount of lignin remains in the fibres after the cook. Based on various analytical techniques for lignin, such as thioacidolysis, GPC and NMR, it is suggested that lignin condensation reactions take place during the cook. The reaction seems, however, not to involve ionic intermediates as has been suggested previously but rather a one-electron mechanism with elemental sulphur as the initiator. Support for such a reaction has been found through kraft cooks in the presence of an added phenol, 2,6-xylenol, as well as through NMR analysis of kraft lignin. It was found that the added phenol is incorporated in the pulp lignin with linkages indicative of radical coupling. Furthermore, kraft lignin was found to contain substantial amounts of chemically linked fatty acids. By complementary analyses of sulphur and polysulphide in an industrial black liquor, the presence of these compounds throughout a kraft cook was demonstrated.

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