Endre søk
Begrens søket
1234 151 - 179 of 179
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 151.
    Ottenhall, Anna
    et al.
    KTH, Skolan för kemivetenskap (CHE).
    Henschen, Jonatan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Illergård, Josefin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Bacteria adsorbing emergency water filters based on polyelectrolyte modified paperManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Water filtration is a popular way to remove particles and microorganisms from drinking water but is generally based on size exclusion of the particles. Bacteria can be modeled as small particles with a diameter of 1-2 µm, which is usually too small to be excluded by paper filters. In this article, commercial available paper filters have been surface modified by polyelectrolyte multilayer adsorption to create a positively charged filter that can trap the negatively charged bacteria through electrostatic interactions. The polyelectrolyte modified filters bind the bacteria to there surface and will thereby remove bacteria from the water instead of inactivated them through addition of biocides. The modified filters can remove more than 99.9 % of bacteria in water, depending on filter design, and has successfully been compared to a commercial cellulose water filter, based on the release of silver to inactivate bacteria. This cheap and easy modification of filter paper has potential to create disposable water purification filters that could be used in emergency situations to prevent outbreak of lethal diarrheal diseases.

  • 152.
    Ottenhall, Anna
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Henschen, Jonatan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Illergård, Josefin
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Cellulose-based water purification using paper filters modified with polyelectrolyte multilayers to remove bacteria from water through electrostatic interactions2018Inngår i: Environmental Science: Water Research & Technology, ISSN 2053-1400Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Filtration is a common way to obtain pure drinking water by removing particles and microorganisms based on size exclusion. Cellulose-based filters are affordable and biobased option for the removal of particles but bacteria are usually too small to be removed by size exclusion alone. In this article, the surfaces of cellulose fibres in two types of commercial paper filters have been given a positive net charge to trap bacteria through electrostatic interactions without releasing any biocides. The fibres were modified with the cationic polyelectrolyte polyvinylamine polymer in single layers (1 L) or in multilayers together with the anionic polyelectrolyte polyacrylic acid (3 L or 5 L) using a water-based process at room temperature. Filtration tests show that all filters, using both types of filter papers and a number of layers, can physically remove more than 99.9% of E. coli from water and that the 3 L modified filters can remove more than 97% of cultivatable bacteria from natural water samples. The bacterial reduction increased with increasing number of filter sheets used for the filtration and the majority of the bacteria were trapped in the top sheets of the filter. The results show the potential for creating water purification filters from bio-based everyday consumable products with a simple modification process. The filters could be used in the future for point-of-use water purification that may be able to save lives without releasing bactericides.

  • 153.
    Ottenhall, Anna
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Illergård, Josefin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Water purification using functionalized cellulose with non-leaching bacteria adsorbing propertiesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Portable purification systems are easy ways to obtain clean drinking water when there is no large-scale water treatment available. In this study, the potential to purify water using bacteria adsorbing cellulose functionalized with polyelectrolytes, according to the Layer-by-Layer method, is investigated. The adsorbed polyelectrolytes create a positive charge on the cellulose surface that physically attracts and bonds with bacteria. Three types of cellulose material have been modified and tested for the bacterial removal capacity in water. The time, material-water ratio and bacterial concentration dependence, as well as the bacterial removal capacity in water from natural sources, have been evaluated. Freely dispersed bacteria adsorbing cellulose can remove greater than 99.9% of Escherichia coli from non-turbid water, with the most notable reduction occurring within the first hour. For turbid water, a filtering approach using modified cellulose fibers is desirable. This bacteria adsorbing cellulose does not leach any biocides, and it is an environmentally sustainable and cheap option for disposable water purification devices.

  • 154.
    Ottenhall, Anna
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Seppänen, Tiinamari
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Purification of water using cellulose: A safe way to remove bacteria2017Inngår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 253Artikkel i tidsskrift (Annet vitenskapelig)
  • 155.
    Ottenhall, Anna
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Seppänen, Tiinamari
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Water-stable cellulose fiber foam with antimicrobial properties for bio based low-density materials2018Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, nr 4, s. 2599-2613Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    New bio-based packaging materials are highly interesting for replacing conventional fossil based products for a more sustainable society. Water-stable cellulose fiber foams have been produced in a simple one-batch foam-forming process with drying under ambient conditions. The cellulose fiber foams have a low density (33–66 kg/m3) and can inhibit microbial growth; two highly valuable features for insulating packaging materials, especially in combination with stability in water. Cationic chitosan and/or polyvinylamine have been added during the foam-forming process to give the foams water-stability and antimicrobial properties. The structural and mechanical properties of the cellulose fiber foams have been studied and the antimicrobial properties have been evaluated with respect to both Escherichia coli, a common model bacteria and Aspergillus brasiliensis, a sporulating mold. The cellulose foams containing chitosan had both good water-stability and good antibacterial and antifungal properties, while the foams containing PVAm did disintegrate in water and did not inhibit fungal growth when nutrients were added to the foam, showing that it is possible to produce a bio-based foam material with the desired characters. This can be an interesting low-density packaging material for protection from both mechanical and microbial damage without using any toxic compounds.

  • 156. Reitberger, Torbjorn
    et al.
    Eriksson, Tord
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ihren, Gunilla
    On the importance of radical species in TCF bleaching.1995Inngår i: Proceedings 8th Int. Symp. Wood Pulp. Chem., 1995, s. 301-307Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The present paper addresses the reasons behind the lack of selectivity in ozone bleaching of pulp.  The main cause for this is concluded to be a superoxide mediated chain reaction forming hydroxyl radicals in the fiber.  Therefore, a strategy to improve the selectivity must focus on possibilities to eliminate superoxide.  This may be achieved with efficient superoxide scavengers, in themselves stable under ozone bleaching conditions, or by performing ozone bleaching in the absence of oxygen, which seems to be a realistic alternative.  A preliminary study shows that phenolic compds. with α-carbonyl groups are particularly efficient in forming radicals in their reactions with ozone.  Therefore, measures to remove α-carbonyl groups before the ozone stage may be expedient.  The cellulose model Me-β-D-glucopyranoside does not produce radicals in its reactions with ozone.  Thermo-labile structures are formed in the pulp as a result of ozone bleaching.  This indicates that an ozone bleached pulp may undergo faster aging than pulp bleached conventionally.  However, this can be prevented if the ozone bleached pulp is treated with alkali or acid sulfite.

  • 157. Rosenqvist, Marie
    et al.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Optimized delignification of kraft pulps by regulating the interactions of cell wall structure.: Influence of alkali profile in the kraft cook on the bleachability of birch.2001Konferansepaper (Fagfellevurdert)
  • 158. Rosenqvist, Marie
    et al.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Photoyellowing of ECF and TCF bleached pulps.1994Inngår i: Proceedings 3rd European Workshop on Lignocellulosics and Pulp, 1994, s. 165-169Konferansepaper (Fagfellevurdert)
  • 159.
    Sevastyanova, Olena
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Use of Ionic Liquids for the pretreatment of cellulose fibre materials for improved rectivity and value added applications2009Konferansepaper (Annet vitenskapelig)
  • 160.
    Sevastyanova, Olena
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Helander, Mikaela
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Chowdhury, Sudip
    Wedin, Helena
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Kadla, John F.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Evaluation of physico-chemical properties and prediction of spinning parameters for high-quality lignins produced by ultra-filtration of industrial Kraft liquor2013Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 245Artikkel i tidsskrift (Annet vitenskapelig)
  • 161.
    Sevastyanova, Olena
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Li, Dongfang
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Evaluation of Ionic Liquids as direct solvents for the manufacturing of novel products from cellulose2010Konferansepaper (Fagfellevurdert)
  • 162.
    Sevasyanova, Olena
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Helander, Mikaela
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Chowdhury, Sudip
    Lange, Heiko
    Wedin, Helena
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Zhang, Liming
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Kadla, John F.
    Crestini, Claudia
    Lindström, Mikael F.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Tailoring the Molecular and Thermo-Mechanical Properties of Kraft Lignin by Ultrafiltration2014Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 131, nr 18, s. 9505-9515Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study has shown that ultrafiltration allows the selective extraction from industrial black liquors of lignin fraction with specific thermo-mechanical properties, which can be matched to the intended end uses. Ultrafiltration resulted in the efficient fractionation of kraft lignin according to its molecular weight, with an accumulation of sulfur-containing compounds in the low-molecular weight fractions. The obtained lignin samples had a varying quantities of functional groups, which correlated with their molecular weight with decreased molecular size, the lignin fractions had a higher amount of phenolic hydroxyl groups and fewer aliphatic hydroxyl groups. Depending on the molecular weight, glass-transition temperatures (T-g) between 70 and 170 degrees C were obtained for lignin samples isolated from the same batch of black liquor, a tendency confirmed by two independent methods, DSC, and dynamic rheology (DMA). The Fox-Flory equation adequately described the relationship between the number average molecular masses (M-n) and T-g's-irrespective of the method applied. DMA showed that low-molecular-weight lignin exhibits a good flow behavior as well as high-temperature crosslinking capability. Unfractionated and high molecular weight lignin (M-w > 5 kDa), on the other hand, do not soften sufficiently and may require additional modifications for use in thermal processings where melt-flow is required as the first step.

  • 163.
    Sjödahl, Ragnar
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Lindström, Mikael E.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    The Effect of Sodium Ion Concentration and Dissolved Wood Components in the Kraft Cook of Softwood2004Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 3, s. 325-329Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of ionic strength and dissolved wood components (DWC) in form of industrial black liquor on the delignification rate and the brightness of the unbleached softwood kraft pulp has been investigated. A technique with a high liquor-to-wood ratio (75 L/kg) a so-called constant composition cook was used to separate the effects of the different parameters. The study showed that an increase in the ionic strength led to a decrease in the rate of delignification and gave a more coloured pulp, where as the presence of DWC gave a more coloured pulp and an increase in the delignification rate.

    The influence of the ionic strength and DWC on the bleachability of the softwood kraft pulp in an ECF-sequence (D(EOP)DD) was also investigated. The results show that the bleachability i.e. consumption of bleaching chemicals to reach a certain brightness, was not affected by the ionic strength during the cook. The addition of DWC, on the other hand, increased the consumption of bleaching chemicals to reach ISO brightness 89%.

  • 164.
    Sjödahl, Ragnar
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    The influence of industrial black liquor on the delignification rate in the kraft cooking2007Inngår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 33, nr 4, s. 240-245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of dissolved wood components in industrial black liquor on the rate of delignification in softwood kraft cooking has been studied The results show that, when industrial black liquor was added, the delignification rate increased significantly during the bulk phase and decreased during the residual phase. A softwood black liquor was fractionated with ceramic membranes with various cut-offs, to see the way the addition of various molecular weight fractions of the black-liquor lignin affected the delignification rate. The results show that the delignification rate is dependent more on the content of phenolic groups than on the size of the lignin fragments. However, a low molecular-weight lignin fraction has a higher content of phenolic groups than a high molecular-weight fraction does. These results may explain one reason for the positive effect of adding industrial black liquor to the bulk phase of a softwood kraft cook.

  • 165. Sjödahl, Ragnar
    et al.
    Keyoumu, Ayiguli
    Axelsson, Patrik
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Dissolved wood components in the kraft pulping liquor: -Effect on the rate of delignification and bleachability2003Konferansepaper (Fagfellevurdert)
  • 166. Sjödahl, Ragnar
    et al.
    Keyoumu, Ayiguli
    Axelsson, Patrik
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Dissolved wood components in the kraft pulping liquor: Effect on the rate of delignification and bleachability2003Konferansepaper (Fagfellevurdert)
  • 167. Sjödahl, Ragnar
    et al.
    Lindström, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    The influence of different cooking parameters on the bleachability of softwood kraft pulp.2002Inngår i: Proceedings 7th European Workshop on Lignocellulosics and Pulp, 2002Konferansepaper (Fagfellevurdert)
  • 168.
    Swensson, Beatrice
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Gray, Derek G.
    McGill Univ, Dept Chem, Pulp & Paper Bldg,3420 Univ St, Montreal, PQ H3A 2A7, Canada..
    In Situ Preparation of Silver Nanoparticles in Paper by Reduction with Alkaline Glucose Solutions2018Inngår i: ACS OMEGA, ISSN 2470-1343, Vol. 3, nr 8, s. 9449-9452Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Percolation of contaminated water through paper sheets containing silver nanoparticles is a promising way to provide emergency drinking water. The silver nanoparticles are deposited by the in situ reduction of silver nitrate on the cellulose fibers of an absorbent blotting paper sheet. Sodium borohydride has been used as the reductant but is toxic and expensive. Glucose is a benign alternative but is much less reactive. In this note, we demonstrate an improved way to produce silver nanoparticles in paper sheets by adding sodium hydroxide to the glucose reductant. The silver content of the sheets, measured by diffuse reflectance spectroscopy, was around 2-3 mg of silver per gram of dry paper. This was sufficient to reduce the concentration of a model Escherichia coli suspension after percolation through the sheet.

  • 169. Villaverde, Juan Jos
    et al.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ligero, Pablo
    Vega, Alberto de
    Structural characterization of Acetosolve lignin from Miscanthus sinensis2008Inngår i: 10th EWLP: European Workshop on Lignocellulosics and Pulp, 2008, s. 262-265Konferansepaper (Fagfellevurdert)
  • 170. Villaverde, Juan Jos
    et al.
    Li, Jiebing
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ligero, Pablo
    Vega, Alberto de
    Structural characterization of Acetosolve lignin from Miscanthus sinensis2008Konferansepaper (Fagfellevurdert)
  • 171.
    Villaverde, Juan Jose
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ligero, Pablo
    de Vega, Alberto
    Native Lignin Structure of Miscanthus x giganteus and Its Changes during Acetic and Formic Acid Fractionation2009Inngår i: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 57, nr 14, s. 6262-6270Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Milled wood lignin (MWL) and acetic and formic acid lignin (AL and FL) from Miscanthus x giganteus bark were produced, respectively, before and after organosolv fractionations under optimal conditions, in terms of organic and hydrochloric acid concentrations, liquid/wood ratio, and reaction time. In order to study the M. x giganteus native lignin structure and its modifications during the fractionation process, the lignins were studied by two-dimensional heteronuclear single quantum coherence (2D-(HSQC)), C-13- and P-31 nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR), size-exclusion chromatography (SEC) both before and after thioacidolysis, and elemental analysis. In addition, chemical composition analysis was performed on ash, Klason lignin, and carbohydrate content. The analyses demonstrated that M. x giganteus native lignin (MWL) is highly acylated at the C-gamma of the lignin side chain (46%), possibly with p-coumarate and/or acetate groups. This is newsworthy since several earlier Studies showed that acylation at the gamma-carbon commonly occurs in C-3 and CAM grasses, whereas M. x giganteus is a C-4 grass. Furthermore, M. x giganteus showed a low S/G ratio (0.7) and a predominance of beta-O-4' linkages (up to 93% of all linkages). AL and FL lose part of these linkages during organosolv fractionation (up to 21 and 32%, respectively). The p-coumarate groups resist fractionation processes and are still present in high quantities in AL and FL. During the fractionation process, lignin is acetylated (acetic acid process) and condensed, with the G units condensing more than S units. M. x giganteus MWL contains a high content of carbohydrates (22.8%), suggesting that it is a lignin-carbohydrate complex (LCC). AL and FL showed low carbohydrate contents because of the breaking down of the LCC structures. AL and FL have high molecular weights and low polydispersities, and are high in phenolic content, qualities that make these suitable for different applications. These results suggest that refinement of M. x giganteus via organosolv processes could potentially turn this grass into a valuable source of both fiber and lignin.

  • 172.
    Westman, Eva-Helena
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Enarsson, Lars-Erik
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Assessment of Antibacterial Properties of Polyvinylamine (PVAm) with Different Charge Densities and Hydrophobic Modifications2009Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, nr 6, s. 1478-1483Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hydrophobically modified and unmodified polyvinylamines (PVAm), including a total of five polymers, were tested against both gram-negative (Escherichia coli) and gram-positive (Bacillus subtilis) bacteria for antimicrobial activity. The assessment of PVAm in solution against bacteria is described, and the influence of the charge density and of the hydrophobic modification of the polyelectrolyte is discussed. The antimicrobial activity was found to depend upon the concentration of PVAm and also on the type of bacteria used. The results also indicated that no direct relationship exists between antimicrobial activity and charge density of the different PVAms. It was, however, observed that an alkyl chain length of six or eight alkane units had a substantial effect on the bacteria investigated. The best combined antibacterial activity for the two bacteria tested was achieved for PVAm with a C-6 alkane substituent (PVAm C-6). To evaluate the antimicrobial activity on a solid substrate, PVAm C-6 was further studied after being deposited onto a glass slide and the results show a large reduction in bacterial infection.

  • 173.
    Westman, Eva-Helena
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Antimicrobial activity of polyelectrolyte multilayer-treated cellulose films2009Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 63, nr 1, s. 33-39Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A polyelectrolyte multilayer film with antimicrobial properties was prepared by the layer-by-layer technique on porous cellulose membranes by the alternate adsorption of hydrophobically modified polyvinylamine (PVAm) and polyacrylic acid. The approach included the introduction of negative charges onto cellulose membranes by NaBr and TEMPO-catalysed oxidation which created anchoring sites for the positively charged PVAm. The antibacterial activity of the cellulose membranes were tested with the Gram-negative bacterium Escherichia coli as organism. A significant decrease in bacterial growth was observed with increasing number of polymeric bilayers (between three and six layers of cationic polymer) on the cellulose membranes. The antimicrobial property was ascribed to the modified PVAm.

  • 174.
    Zheng, Chao
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Li, Dongfang
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Bio-based fire retardant and its application in cellulose-based thermal insulation materials2018Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Artikkel i tidsskrift (Annet vitenskapelig)
  • 175.
    Zheng, Chao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Li, Dongfang
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Cellulose-fiber-based insulation materials with improved reaction-to-fire properties2017Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, nr 3, s. 466-472Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The poor reaction-to-fire properties of cellulosic thermal insulation need to be improved to meet the safety regulations for building materials. In this study, cellulose-fiber-based insulation foams were prepared from formulations containing mechanical pulp and commercial fire retardants. Results of single-flame source tests showed that foams developed from the formulations with 20% expandable graphite (EG) or 25% synergetic (SY) fire retardants had substantially improved reaction-to-fire properties, and passed fire class E according to EN 13501-1. The results indicated that the foams could resist a small flame attack without serious flame spreading over a short period of time. Compared with the reference foam that contained no fire retardant, the peak heat release rate of the 20% EG and 25% SY foams decreased by 62% and 39% respectively when the samples were subjected to a radiance heat flux of 25 kW m-2 in a cone calorimeter, which suggested enhanced reaction-to-fire properties of these foams.

  • 176.
    Zheng, Chao
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Li, Dongfang
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardants2019Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 34, nr 1, s. 96-106Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sustainable thermal insulating materials produced from cellulosic fibers provide a viable alternative to plastic insulation foams. Industrially available, abundant, and inexpensive mechanical pulp fiber and recycled textile fiber provide potential raw materials to produce thermal insulating materials. To improve the fire retardancy of low-density thermal insulating materials produced from recycled cotton denim and mechanical pulp fibers, bio-based fire retardants, such as sulfonated kraft lignin, kraft lignin, and nanoclays, were coated onto sustainable insulating material surfaces to enhance their fire retardancy. Microfibrillated cellulose was used as a bio-based binder in the coating formula to disperse and bond the fire-retardant particles to the underlying thermal insulating materials. The flammability of the coated thermal insulating materials was tested using a single-flame source test and cone calorimetry. The results showed that sulfonated kraft lignin-coated cellulosic thermal insulating materials had a better fire retardancy compared with that for kraft lignin with a coating weight of 0.8 kg/m(2). Nanoclay-coated samples had the best fire retardancy and did not ignite under a heat flux of 25 kW/m(2), as shown by cone calorimetry and single-flame source tests, respectively. These cost-efficient and bio-based fire retardants have broad applications for improving fire retardancy of sustainable thermal insulating materials.

  • 177.
    Zheng, Chao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Li, Dongfang
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Improving fire retardancy of cellulosic thermal insulating materials by coating with bio-based fire retardantsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Sustainable thermal insulating materials produced from cellulosic fibers provide a viable alternative to plastic insulation foams. Industrially available, abundant, and inexpensive mechanical pulp fiber and recycled textile fiber provide potential raw materials to produce thermal insulating materials. To improve the fire retardancy of low-density thermal insulating materials produced from recycled cotton denim and mechanical pulp fibers, bio-based fire retardants, such as sulfonated kraft lignin, kraft lignin, and nanoclays, were coated onto sustainable insulating material surfaces to enhance their fire retardancy. Microfibrillated cellulose was used as a bio-based binder in the coating formula to disperse and bond the fire-retardant particles to the underlying thermal insulating materials. The flammability of the coated thermal insulating materials was tested using a single-flame source test and cone calorimetry. The results showed that sulfonated kraft lignin-coated cellulosic thermal insulating materials had a better fire retardancy compared with that for kraft lignin with a coating weight of 0.8 kg/m2. Nanoclay-coated samples had the best fire retardancy and did not ignite under a heat flux of 25 kW/m2, as shown by cone calorimetry and single- flame source tests, respectively. These cost-efficient and bio-based fire retardants have broad applications as sustainable thermal insulating materials for improved fire retardancy.

  • 178.
    Zheng, Chao
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Li, Dongfang
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Mechanism and kinetics of thermal degradation of insulating materials developed from cellulose fiber and fire retardants2019Inngår i: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926, Vol. 135, nr 6, s. 3015-3027Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanism and kinetics of thermal degradation of materials developed from cellulose fiber and synergetic fire retardant or expandable graphite have been investigated using thermogravimetric analysis. The model-free methods such as Kissinger–Akahira–Sunose (KAS), Friedman, and Flynn–Wall–Ozawa (FWO) were applied to measure apparent activation energy (Ea).The increased Ea indicated a greater thermal stability because of the formation of a thermally stable char, and the decreased Ea after the increasing region related to the catalytic reaction of the fire retardants, which revealed that the pyrolysis of fire retardant-containing cellulosic materials through more complex and multi-step kinetics. The Friedman method can be considered as the best method to evaluate the Ea of fire-retarded cellulose thermal insulation compared with the KAS and two methods. A master-plots method such as the Criado method was used to determine the possible degradation mechanisms. The degradation of cellulose thermal insulation without a fire retardant is governed by a D3 diffusion process when the conversion value is below 0.6, but the materials containing synergetic fire retardant and expandable graphite fire retardant may have a complicated reaction mechanism that fits several proposed theoretical models in different conversion ranges. Gases released during the thermal degradation were identified by pyrolysis–gas chromatography/mass spectrometry. Fire retardants could catalyze the dehydration of cellulosic thermal insulating materials at a lower temperature and facilitate the generation of furfural and levoglucosenone, thus promoting the formation of char. These results provide useful information to understand the pyrolysis and fire retardancy mechanism of fire-retarded cellulose thermal insulation.

  • 179.
    Zheng, Chao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Li, Dongfang
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ottenhall, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Cellulose fiber based fungal and water resistant insulation materials2017Inngår i: International Journal of the Biology, Chemistry, Physics, and Technology of Wood, E-ISSN 1437-434X, Vol. 71, nr 7-8, s. 633-639Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The development of thermal insulation materials from sustainable, natural fibrous materials is desirable.In the present study, cellulose fiber based insulation foams made of bleached chemi thermo mechanical pulp(CTMP) have been investigated. To improve water resistance, the foams were impregnated with hydrophobic extractives from the outer bark of birch (Betula verrucosa)and dried. The surface morphology of the foams and the distribution of the deposited particles from the extractives were observed by scanning electron microscopy (SEM).The modified foams showed improved water resistance, as they did not disintegrate after immersion in water for7 days, whereas the unmodified foam did. Compared to the unmodified foam, the modified foams absorbed 50%less moisture within 24 h. The modification had no negative effects on the thermal insulation properties, fungal resistance or compressive strength of the foams. The proposed approach is simple and can be easily integrated into plants working based on the biorefinery concept.

1234 151 - 179 of 179
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf