Ändra sökning
Avgränsa sökresultatet
1234567 151 - 200 av 782
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 151.
    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.

  • 152.
    Cobo Sanchez, Carmen
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Inorganic and organic polymer-grafted nanoparticles: their nanocomposites and characterization2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Nanocomposites (NCs) have been widely studied in the past decades due to the promising properties that nanoparticles (NPs) offer to a polymer matrix, such as increased thermal stability and non-linear electrical resistivity. It has also been shown that the interphase between the two components is the key to achieving the desired improvements. In addition, polymer matrices are often hydrophobic while NPs are generally hydrophilic, leading to NP aggregation. To overcome these challenges, NPs can be surface-modified by adding specific molecules and polymers. In the present work, a range of organic and inorganic NPs have been surface-modified with polymers synthesized by atom transfer radical polymerization (ATRP) or surface-initiated ATRP (SI-ATRP).Cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) are highly crystalline NPs that can potentially increase the Young’s modulus of the NC. In this study, a matrix-free NC was prepared by physisorption of a block-copolymer containing a positively charged (quaternized poly(2-(dimethylamino)ethyl methacrylate), qPDMAEMA) and a thermo-responsive (poly di(ethylene glycol) methyl ether methacrylate, PDEGMA). The modified CNF exhibited a thermo-responsive, reversible behavior. CNCs were polymer-modified either via SI-ATRP or physisorbed with poly (butyl methacrylate) (PBMA) to improve the dispersion and interphase between them and a polycaprolactone (PCL) matrix during extrusion. The mechanical properties of the NCs containing CNC modified via SI-ATRP were superior to the reference and unmodified materials, even at a high relative humidity.Reduced graphene oxide (rGO) and aluminum oxide (Al2O3) are interesting for electrical and electronic applications. However, the matrices used for these applications, such as poly(ethylene-co-butyl acrylate) (EBA) and low density polyethylene (LDPE) are mainly hydrophobic, while the NPs are hydrophilic. rGO was modified via SI-ATRP using different chain lengths of PBMA and subsequently mixed with an EBA matrix. Al2O3 was modified with two lengths of poly(lauryl methacrylate) (PLMA), and added to LDPE prior to extrusion. Agglomeration and dispersion of the NCs were dependent on the lengths and miscibilities of the grafted polymers and the matrices. rGO-EBA NCs showed non-linear direct current (DC) resistivity upon modification, as the NP dispersion improved with increasing PBMA length. Al2O3-LDPE systems improved the mechanical properties of the NCs when low amounts of NPs (0.5 to 1 wt%) were added, while decreasing power dissipation on the material.Finally, PLMA-grafted NPs with high polymer quantities and two grafting densities in Al2O3 and silicon oxide (SiO2) nanoparticles were synthesized by de-attaching some of the silane groups from the surfaces, either by hydrolysis or by a mild tetrabutylammonium fluoride (TBAF) cleavage. These compounds were characterized and compared to the bulk PLMA, and were found to have very interesting thermal properties.

    Publikationen är tillgänglig i fulltext från 2020-04-24 14:42
  • 153.
    Cobo Sanchez, Carmen
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Malmström, Eva
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Matrix-free Nanocomposites based on Poly(lauryl methacrylate)-Grafted Nanoparticles: Effect of Graft Length and Grafting DensityManuskript (preprint) (Övrigt vetenskapligt)
    Publikationen är tillgänglig i fulltext från 2020-04-24 14:17
  • 154.
    Colson, Jerome
    et al.
    Univ Nat Resources & Life Sci Vienna, Dept Mat Sci & Proc Engn, Inst Wood Technol & Renewable Mat, Konrad Lorenz Str 24, A-3430 Tulin, Austria..
    Pettersson, Torbjörn
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Fiberteknologi.
    Asaadi, Shirin
    Aalto Univ, Sch Chem Engn, Dept Bioprod & Biosyst, Vuorimiehentie 1, Espoo 02150, Finland..
    Sixta, Herbert
    Aalto Univ, Sch Chem Engn, Dept Bioprod & Biosyst, Vuorimiehentie 1, Espoo 02150, Finland..
    Nypelo, Tiina
    Chalmers Univ Technol, Dept Chem & Chem Technol, Kemigarden 4, S-41296 Gothenburg, Sweden..
    Mautner, Andreas
    Univ Vienna, Fac Chem, Inst Mat Chem & Res, Wahringer Str 42, A-1090 Vienna, Austria..
    Konnerth, Johannes
    Univ Nat Resources & Life Sci Vienna, Dept Mat Sci & Proc Engn, Inst Wood Technol & Renewable Mat, Konrad Lorenz Str 24, A-3430 Tulin, Austria..
    Adhesion properties of regenerated lignocellulosic fibres towards poly (lactic acid) microspheres assessed by colloidal probe technique2018Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 532, s. 819-829Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the field of polymer reinforcement, it is important to understand the interactions involved between the polymer matrix and the reinforcing component. This paper is a contribution to the fundamental understanding of the adhesion mechanisms involved in natural fibre reinforced composites. We report on the use of the colloidal probe technique for the assessment of the adhesion behaviour between poly(lactic acid) microspheres and embedded cross-sections of regenerated lignocellulosic fibres. These fibres consisted of tailored mixtures of cellulose, lignin and xylan, the amount of which was determined beforehand. The influence of the chemical composition of the fibres on the adhesion behaviour was studied in ambient air and in dry atmosphere. In ambient air, capillary forces resulted in larger adhesion between the sphere and the fibres. Changing the ambient medium to a dry nitrogen atmosphere allowed reducing the capillary forces, leading to a drop in the adhesion forces. Differences between fibres of distinct chemical compositions could be measured only on freshly cut surfaces. Moreover, the surface energy of the fibres was assessed by inverse gas chromatography. Compared to fibres containing solely cellulose, the presence of lignin and/or hemicellulose led to higher adhesion and lower surface energy, suggesting that these chemicals could serve as natural coupling agents between hydrophobic and hydrophilic components.

  • 155. Cozzolino, Carlo A.
    et al.
    Campanella, Gaetano
    Ture, Hasan
    Olsson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Farris, Stefano
    Microfibrillated cellulose and borax as mechanical, O-2-barrier, and surface-modulating agents of pullulan biocomposite coatings on BOPP2016Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 143, s. 179-187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multifunctional composite coatings on bi-oriented polypropylene (BOPP) films were obtained using borax and microfibrillated cellulose (MFC) added to the main pullulan coating polymer. Spectroscopy analyses suggested that a first type of interaction occurred via hydrogen bonding between the C-6-OH group of pullulan and the hydroxyl groups of boric acid, while monodiol and didiol complexation represented a second mechanism. The deposition of the coatings yielded an increase in the elastic modulus of the entire plastic substrate (from similar to 2 GPa of the neat BOPP to similar to 3.1 GPa of the P/B+/MFC-coated BOPP). The addition of MFC yielded a decrease of both static and kinetic coefficients of friction of approximately 22% and 25%, respectively, as compared to the neat BOPP. All composite coatings dramatically increased the oxygen barrier performance of BOPP, especially under dry conditions. The deposition of the high hydrophilic coatings allowed to obtain highly wettable surfaces (water contact angle of similar to 18 degrees).

  • 156.
    Cunha, Ana Gisela
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Zhou, Qi
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. INNVENTIA AB, Sweden.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Topochemical acetylation of cellulose nanopaper structures for biocomposites: mechanisms for reduced water vapour sorption2014Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, nr 4, s. 2773-2787Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Moisture sorption decreases dimensional stability and mechanical properties of polymer matrix biocomposites based on plant fibers. Cellulose nanofiber reinforcement may offer advantages in this respect. Here, wood-based nanofibrillated cellulose (NFC) and bacterial cellulose (BC) nanopaper structures, with different specific surface area (SSA), ranging from 0.03 to 173.3 m(2)/g, were topochemically acetylated and characterized by ATR-FTIR, XRD, solid-state CP/MAS C-13-NMR and moisture sorption studies. Polymer matrix nanocomposites based on NFC were also prepared as demonstrators. The surface degree of substitution (surface-DS) of the acetylated cellulose nanofibers is a key parameter, which increased with increasing SSA. Successful topochemical acetylation was confirmed and significantly reduced the moisture sorption in nanopaper structures, especially at RH = 53 %. BC nanopaper sorbed less moisture than the NFC counterpart, and mechanisms are discussed. Topochemical NFC nanopaper acetylation can be used to prepare moisture-stable nanocellulose biocomposites.

  • 157.
    Das, Oisik
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Johansson, E.
    Olsson, Richard
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Loho, T. A.
    Capezza, Antonio J.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Singh Raman, R. K.
    Holder, Shima
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    An all-gluten biocomposite: Comparisons with carbon black and pine char composites2019Ingår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 120, s. 42-48Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three different charcoals (gluten char, pine bark char and carbon black) were used to rectify certain property disadvantages of wheat gluten plastic. Pyrolysis process of gluten was investigated by analysing the compounds released at different stages. Nanoindentation tests revealed that the gluten char had the highest hardness (ca. 0.5 GPa) and modulus (7.8 GPa) followed by pine bark char and carbon black. The addition of chars to gluten enhanced the indenter-modulus significantly. Among all the charcoals, gluten char was found to impart the best mechanical and water resistant properties. The addition of only 6 wt% gluten char to the protein caused a substantial reduction in water uptake (by 38%) and increase of indenter-modulus (by 1525%). It was shown that it is possible to obtain protein biocomposites where both the filler and the matrix are naturally sourced from the same material, in this case, yielding an all-gluten derived biocomposite.

  • 158. Dax, Daniel
    et al.
    Soledad Chavez, Maria
    Xu, Chunlin
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Process Chemistry Centre, C/o Laboratory of Wood and Paper Chemistry, Åbo Akademi University, Finland .
    Willfor, Stefan
    Teixeira Mendonca, Regis
    Sanchez, Julio
    Cationic hemicellulose-based hydrogels for arsenic and chromium removal from aqueous solutions2014Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 111, s. 797-805Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work the synthesis of hemicellulose-based hydrogels and their application for the removal of arsenic and chromium ions is described. In a first step O-acetyl galactoglucomannan (GGM) was subjected to a transesterification applying glycidyl methacrylate (GMA) for the synthesis of novel GGM macromonomers. Two distinguished and purified GGM fractions with molar mass of 7.1 and 28 kDa were used as starting materials. The resulting GGM macromonomers (GGM-MA) contained well-defined amounts of methacrylate groups as determined by H-1 NMR spectroscopy. Selected GGM-MA derivatives were consecutively applied as a crosslinker in the synthesis of tailored hydrogels using [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MeDMA) as monomer. The swelling rate of the hydrogels was determined and the coherence between the swelling rate and the hydrogel composition was examined. The morphology of the GGM-based hydrogels was analysed by SEM and the hydrogels revealed a high surface area and were assessed in respect to their ability to remove arsenate and chromate ions from aqueous solutions. The presented bio-based hydrogels are of high interest especially for the mining industries as a sustainable material for the treatment of their highly contaminated wastewaters.

  • 159.
    de Carvalho, Danila Morais
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. Federal University of Viçosa, Brazil.
    Colodette, Jorge Luiz
    Comparative Study of Acid Hydrolysis of Lignin and Polysaccharides in Biomasses2017Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, nr 4, s. 6907-6923Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effects of different acid hydrolysis conditions were studied relative to the chemical transformations of lignin in eucalyptus, sugarcane bagasse, and sugarcane straw, and on the transformations of multiple polysaccharides in eucalyptus. The acid hydrolysis using 12 mol/L sulfuric acid followed by acid hydrolysis using approximately 0.41 mol/L sulfuric acid was used as the reference for the lignin and sugar analysis. During acid hydrolysis, the relative amount of lignin increased with longer reaction times and/or greater acid concentrations for all biomasses. The overestimation of lignin in harsher acidic conditions resulted from the summation of lignocellulosic-derivatives (pseudo- lignin) together with lignin itself. Lignin reactions (dissolution/deposition) for bagasse and straw occurred in a greater extent than for eucalyptus, considering similar conditions of acid hydrolysis. The sugar transformation during acid hydrolysis was also investigated for eucalyptus. The sugar content quantified in eucalyptus decreased as the acid concentration and/or reaction time in the second hydrolysis increased. Glucose, galactose, and mannose were more resistant to harsher acidic conditions than xylose and arabinose. However, the most severe conditions (121 degrees C, 90 min, and 6.15 mol/L H2SO4) caused complete sugar degradation.

  • 160.
    Decrop, Deborah
    et al.
    KU Leuven, Belgium.
    Pardon, Gaspard
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Kokalj, Tadej
    KU Leuven, Belgium.
    Robert, Puers
    KU Leuven, Belgium.
    Haraldsson, Tommy
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Lammertyn, Jeroen
    KU Leuven, Belgium.
    van der Wijngaart, Wouter
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Single-step manufacturing of femtoliter microwell arrays in a novel surface energy mimicking polymer2015Ingår i: 18th International Conference on Solid-State Sensors, Actuators and Microsystems (IEEE TRANSDUCER 2015), IEEE , 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    We report a novel polymer material formulation and stamp-molding technique that enable rapid single-step manufacturing of hydrophilic-in-hydrophobic microwell arrays. We developed a modified thiol-ene-epoxy polymer (mOSTE+) formulation that mimics the surface energy of its mold during polymerization. The polymer inherits the surface energy from the mold through molecular self-assembly, in which functional monomers self-assemble at the interface between the liquid prepolymer and the mold surface. Combining this novel mOSTE+ material with a stamp-molding process leads to simultaneous surface energy mimicking and micro-structuring. This method was used to manufacture microwells with hydrophilic bottom and hydrophobic sidewall, depressed in a surrounding hydrophobic surface. The microwell arrays were successfully tested for the self-assembly of 62’000 femtoliter-droplets. Such femtoliter droplet arrays are useful for, e.g., digital ELISA and single cell/molecule analysis applications.

  • 161.
    Dedic, Dina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Iversen, Tommy
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Cellulose degradation in the Vasa: The role of acids and rust2013Ingår i: Studies in Conservation, ISSN 0039-3630, E-ISSN 2047-0584, Vol. 58, nr 4, s. 308-313Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The oak timbers of the Swedish warship Vasa are deteriorating. High amounts of oxalic acid have been found along with a low pH and low molecular weight cellulose deep in the wood timbers. The iron-rich surface wood differs from the interior wood in that it displays higher pH and cellulose with higher molecular weight. The objective of this study was to determine why there is a difference in cellulose degradation, pH, and oxalic acid amount between the surface region and the interior of the Vasa timbers. Analysis of cellulose weight average molecular weight by size exclusion chromatography was performed, as well as quantification of oxalic acid and iron by high-performance anion exchange chromatography and atomic emission spectroscopy, respectively. It was found that a decrease in iron content coincides with an increase in oxalic acid concentration and a drop in pH at a certain depth from the wood surface. When iron-rich surface wood samples from the Vasa were mixed with an aqueous solution of oxalic acid, a fast increase of pH over time was observed. Neither interior wood poor in iron nor the fresh oak reference showed the same neutralizing effect during the time of measurement. This indicates that the presence of iron (rust) causes a neutralization of the wood, through the formation of iron(III) oxalato complexes, thus protecting the wood from oxalic acid hydrolysis. This effect was not observed to the same extent for other acids observed in Vasa wood (sulfuric, formic, glycolic, and acetic acids).

  • 162.
    Dedic, Dina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Iversen, Tommy
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Degradation reactions in vasa wood2011Ingår i: Shipwrecks 2011, 2011, s. 114-116Konferensbidrag (Refereegranskat)
  • 163.
    Dedic, Dina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Iversen, Tommy
    Sandberg, Teresia
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Chemical analysis of wood extractives and lignin in the oak wood of the 380 year old Swedish warship Vasa2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to map the source of oxalic acid in the interior wood of the Vasa ship, an analysis of wood extractives (tannins) was conducted. Samples used for analysis were PEG-impregnated dry Vasa wood, waterlogged Vasa wood and a reference material (fresh oak). The wood material was ground and extracted with an acetone/water-mixture. In the reference sample, several types of tannins were found such as the isomers castalagin/vescalagin and grandinin and their dimmers roburin A/D and roburin B/C respectively. The results have been confirmed by NMR spectroscopy and MALDI-TOF. The interior of the waterlogged Vasa wood contained small amounts of monomers, whereas the dry, PEG treated Vasa revealed no discernible amounts of hydrolysable tannins or other easily soluble compounds. Furthermore, an analysis of lignin was made by means of chemical degradation (thioacidolysis). A decrease in the amount of β-O-4 bonds in the lignin structure would imply a formation of easily oxidized free phenolics. The products were analyzed by GC-MS, which revealed no dramatic differences between the Vasa samples and the reference. The results were confirmed by CP/MAS NMR by analyzing the differences in the aromatic region (150∼160 ppm) as well as the carbonyl region (190∼200 ppm).

  • 164.
    Dedic, Dina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Sandberg, Teresia
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Iversen, Tommy
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Larsson, Tomas
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Analysisof lignin and extractives in the oak wood of the 17th century warship Vasa2011Manuskript (preprint) (Övrig (populärvetenskap, debatt, mm))
  • 165. Di Filippo, Maria
    et al.
    Alessi, Sabina
    Pitarresi, Giuseppe
    Sabatino, Maria Antonietta
    Zucchelli, Andrea
    Dispenza, Clelia
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. Univ Palermo, Italy.
    Hydrothermal aging of carbon reinforced epoxy laminates with nanofibrous mats as toughening interlayers2016Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 126, s. 188-195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electrospun mats have been applied as toughening interlayers in high performance carbon fiber epoxy composites. While the toughening mechanism exerted by the mat at the interface is the subject of several recent studies, no investigations are reported on the aging behaviour of laminates comprising these nanostructured elements. This work investigates the influence of the combined effect of water and temperature (90 degrees C) on laminates with Nylon 6,6 electrospun membranes placed either at the middle plane only or at each interlayer. The water-uptake behaviour is modelled by a two-stage diffusion model and compared with the behaviour of the neat resin and of the laminate without mats. Interestingly, a lower water uptake is observed for the laminates with mat-modified interfaces and this is possibly due to a significantly reduced porosity. The effect of hydrothermal aging on the thermal (Tg) and mechanical properties (transverse flexural modulus and interlaminar shear strength) of the various laminates is also investigated.

  • 166.
    Dinko, Lukes
    KTH, Skolan för kemivetenskap (CHE).
    Quantification of acid diffusion in fluoroplastic materials2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    To improve the service reliability of polymeric materials used in corrosive environments more corrosion data such as diffusion of acids is needed. The aim of this research was to investigate the diffusion of acids mainly in fluoroplastic materials by optimizing quantitative and qualitative methods to measure the diffusion. It was found that ion chromatography could be used to measure the acid concentration found inside the different polymers by desorption into a water solution. The amount of ions was then recalculated and presented as gacid/gpolymer. The polymeric materials were exposed in hydrochloric acid, nitric acid, hydrobromic acid and mixed acid. Very large spreading was seen within each series for the polymers in the different acids resulting in very high standard deviations on the concentrations of acids. The cause of the spreading was not found,  but analyses on the acid concentration using inductively coupled plasma (ICP) verified the large spreading seen from the ion chromatograph and conclusions were drawn that the ion chromatography did not cause the spreading. Changes to the experimental procedure were made but did not resolve the problem. The solubility of hydrogen chloride was measured in the fluoropolymers: perfluoroalkoxy (PFA), polyvinylidene fluoride (PVDF) and ethylene-chlorotrifluoroethylene (ECTFE) and compared to the polyolefins: polyethylene (PE) and polypropylene (PP). It was found that the polyolefins had the highest solubility of hydrogen chloride and ECTFE had the lowest. Chlorine dioxide solubility in PVDF was established through a different approach, the LGB-method, but the problem with spreading was seen on these results as well. An indicator technique was used to calculate diffusion rates of HCl in polypropylene samples with successful results. However, the indicator technique did not work for the ECTFE samples.

  • 167.
    Djahedi, Cyrus
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. Wallenberg Wood Science Center.
    Deformation of cellulose allomorphs studied by molecular dynamics2015Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Cellulose-based materials draw their good mechanical properties from the cellu-lose crystal. Improved understanding of crystal properties could lead to a wider range of applications for cellulose-based materials, Cellulose crystals show high axial Youngs modulus. Cellulose can attain several allomorphic forms which show unique structural arrangements in terms of both intra-molecular and inter-molecular bonding, as well as unit cell parameters and chain packing. Although several studies have confirmed that mechanical tensile properties of cellulose differ between different allomorphic forms, few reports have investigated the deformation mechanisms explaining the differences.In the first part of this thesis, the tensile elastic Youngs modulus of cellulose allo-morphs Iβ, II and III I were calculated under uniform conditions using Molecular Dynamics simulation techniques. As expected, a difference in modulus valuesc ould be observed, and the cooperative nature of energy contributions to crys-tal modulus is apparent. The allomorphs also show large differences in terms of how contributions to elastic energy are distributed between covalent bonds,angles, dihedrals, electrostatic forces, dispersion and steric forces.In the second part of this thesis, the cellulose Iβ and II allomorphs were sub-jected to a more detailed structural study. The purpose was to clarify how the deformation of the central glucosidic linkage between the monomer units depends on the hydrogen-bonding structures. This was carried out by studying simulated vibrational spectra and local deformations in the crystals.The results presented in this thesis confirm the differences in the tensile elastic properties of these cellulose allomorphs. These differences can in part be explained by the different intra-molecular hydrogen bonding patterns between allomorphs. Deformation mechanisms are discussed. The results are in supportof the so called ”leverage effect” proposed in the literature. The present analysis shows significant differences in details of deformation mechanisms compared with previous simpler analyses.

  • 168. Djahedi, Cyrus
    et al.
    Bergenstrahle-Wohlert, Malin
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wohlert, Jakob
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Role of hydrogen bonding in cellulose deformation: the leverage effect analyzed by molecular modeling2016Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, nr 4, s. 2315-2323Artikel i tidskrift (Refereegranskat)
  • 169.
    Duval, Antoine
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lawoko, Martin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    A review on lignin-based polymeric, micro- and nano-structured materials2014Ingår i: Reactive & functional polymers, ISSN 1381-5148, E-ISSN 1873-166X, Vol. 85, nr SI, s. 78-96Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Next to cellulose, lignin is the second most abundant biopolymer, and the main source of aromatic structures on earth. It is a phenolic macromolecule, with a complex structure which considerably varies depending on the plant species and the isolation process. Lignin has long been obtained as a by-product of cellulose in the paper pulp production, but had rather low added-value applications. Changes in the paper market have however stimulated the need to focus on other applications for lignins. In addition, the emergence of biorefinery projects to develop biofuels, bio-based materials and chemicals from carbohydrate polymers should also generate large amounts of lignin with the potential for value addition. These developments have brought about renewed interest in the last decade for lignin and its potential use in polymer materials. This review covers both the topics of the direct use of lignin in polymer applications, and of the chemical modifications of lignin, in a polymer chemistry perspective. The future trend toward micro- and nanostructured lignin-based materials is then addressed.

  • 170.
    Dånmark, Staffan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Polyester scaffold: Material design and cell-protein-material interaction2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Konsten att med kroppens egna celler som utgångspunkt återskapa förlorad eller skadad vävnad, s.k. tissue engineering, har på senare tid blivit allt mer accepterad som ett alternativ  till dagens kliniska metoder. Inom ben-tissue engineering ingår oftast förutom celler, en nedbrytbar matris och lämpliga tillväxtfaktorer. För att kunna användas kliniskt ställs mycket höga krav på materialegenskaperna hos matrisen t.ex. dess utformning. Materialet ska vara biokompatibelt och matrisen ska i möjligaste mån efterlikna det naturliga proteinnätverk som finns mellan cellerna i benvävnaden. Eftertraktade egenskaper innefattar en 3-dimensionell porös struktur med förutsättnigar för adhesion, proliferering och differentiering av benceller.  Matrisens mekaniska egenskaper och nedbrytningshastighet är starkt beroende av varandra och bör anpassas efter den aktuella applikationen och vävnadens naturliga egenskaper.

    Den här avhandlingen beskriver utvecklandet av matriser baserade på alifatiska polyestrar med flera eftertraktade egenskaper inom ben-tissue egineering. Dessutom har alifatiska polyestrar används för att utveckla ett nytt mikrofluidikssystem för kontinuerlig visuell utvärdering av levande celler i porösa 3-dimensionella matriser.

    De nedbrytbara alifatiska polyestrarna poly(L-laktid-co-ε-kaprolakton) [poly(LLA-co-CL)], poly(L-laktid-co-1,5-dioxepan-2-on) [poly(LLA-co-DXO)] och poly(L-laktid) [poly(LLA)] användes för att tillverka matriser med hög grad av porositet, väl sammanbundna porer och varierande porstorlekar. De olika egenskaperna hos monomererna resulterade i matriser med mångsidiga egenskaper inom nedbrytningshastighet, mekanisk stabilitet, vätnings- och termiska-egenskaper.

    De framställda matriserna av alifatiska polyestrar visade sig stimulera proliferering och differentiering mot osteoblaster hos stamceller isolerade från benmärg (BMSC), vilket underströk potentialen hos dessa matriser för ben-tissue engineering. Vidare så förhöjdes potentialen hos poly(LLA-co-CL) matriser och andra kliniskt använda polyestrar genom att ytmodifiera materialen med den beninducerade tillväxtfaktorn, bone morphogenetic protein-2 (BMP-2). För detta ändamål utvecklades två separata immobiliseringsmetoder. I den ena metoden immobiliserades BMP-2 till heparinkopplade ytor och i den andra bands BMP-2 kovalent direkt till yt-ympade kopplingskedjor. I båda metoderna kunde BMP-2 immobiliseras med bibehållen biologisk aktivitet. Immobiliserat BMP-2 stimulerades i respektive metod till förhöjd proliferering hos embryonala C3H10T1/2 celler och ökat uttryck av gener starkt förknippade med mogna benceller samt proteinet osteocalcin i bencells-liknande celler.

    Nedbrytningsbeteendet och de mekaniska egenskaperna hos de elektronstråle-steriliserade polyestermatriser visade sig kraftigt beroende av materialens kemiska, fysiska och makroskopiska utfromning. Genom att inkorporera mer hydrofila monomerer i materialen påskyndades nedbrytningen och därmed förlusten av provens mekaniska stabilitet. Att istället sampolymerisera två hydrofoba monomerer med begränsade möjlighet till kristallisation, gav material med förlängd mekanisk stabilitet under nedbrytningen.

    BMSC och bencells-liknande celler visade normal utbredning och morfologi vid ahdesion till polyestrarna. Den initiala celladhesionen till syntetiska ytor sker vanligtvis genom ytadsorberade protein från omgivande biologiska vätskor. BMSCs initiala celladhesion till blodplasmabelagda polyestrar var starkt begränsade, oavsett polyestrarnas förmåga att adsorbera adhesiva protein ur blodplasma och att motsvarande proteinreceptorer återfanns på cellytan hos BMSC. Genom att istället adsorbera upprenade adhesiva protein till polyestrarna ökade adhesionen av BMSC till ytorna. Detta påvisade möjligheten att öka effektivitet av celladhesionen till polyestrar genom att på förhand belägga dem med adhesiva protein.

    Polyestrar kombinerades även med mikrofluidikteknik och mjuk litografi för att utveckla ett nytt system för högupplöst visuell observation av levande celler i porösa matriser. Systemet kunde användas till att kontinuerligt följa cell-proliferering och –differentiering på exakt samma plats i 3-dimensionella matriser under mer än 4 veckor. Det framtagna systemet kan med fördel användas till utvärdering av både material och celler som ska kan komma att användas inom tissue engineering.

    Slutsatsen blir att nedbrytbara matriser baserade på alifatiska polyester som grundligt utformas i avseende på makroskopisk struktur, bulkmaterial och ytkemi kan möta kraven för olika applikationer inom ben-tissue engineering. Dessutom kan alifatiska polyestrar kombineras med mikrofluidiskt system för att tillåta kontinuerligt högupplös visualisering av levande celler i porösa matriser med stor potential som utvärderingsmetod inom tissue engineering.

  • 171.
    Dånmark, Staffan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Finne-Wistrand, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Schander, K.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Arvidson, K.
    Mustafa, K.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    In vitro and in vivo degradation profile of aliphatic polyesters subjected to electron beam sterilization2011Ingår i: ACTA BIOMATERIALIA, ISSN 1742-7061, Vol. 7, nr 5, s. 2035-2046Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Degradation characteristics in response to electron beam sterilization of designed and biodegradable aliphatic polyester scaffolds are relevant for clinically successful synthetic graft tissue regeneration Scaffold degradation in vitro and in vivo were documented and correlated to the macroscopic structure and chemical design of the original polymer The materials tested were of inherently diverse hydrophobicity and crystallinity poly(L-lactide) (poly(LLA)) and random copolymers from L-lactide and epsilon-caprolactone or 1.5-dioxepan-2-one, fabricated into porous and non-porous scaffolds After sterilization, the samples underwent hydrolysis in vitro for up to a year In vivo, scaffolds were surgically implanted into rat calvarial defects and retrieved for analysis after 28 and 91 days In vitro, poly(L-lactide-co-1, 5-dioxepan-2-one) (poly(LLA-co-DXO)) samples degraded most rapidly during hydrolysis, due to the pronounced chain-shortening reaction caused by the sterilization. This was indicated by the rapid decrease in both mass and molecular weight of poly(LLA-co-DXO). Poly(L-lactide-co-epsilon-caprolactone) (poly(LLA-co-CL)) samples were also strongly affected by sterilization, but mass loss was more gradual; molecular weight decreased rapidly during hydrolysis Least affected by sterilization were the poly(LLA) samples, which subsequently showed low mass loss rate and molecular weight decrease during hydrolysis. Mechanical stability varied greatly. poly(LLA-co-CL) withstood mechanical testing for up to 182 days, while poly(LLA) and poly(LLA-co-DXO) samples quickly became too brittle Poly(LLA-co-DXO) samples unexpectedly degraded more rapidly in vitro than in vivo. After sterilization by electron beam irradiation, the three biodegradable polymers present widely diverse degradation profiles, both in vitro and in vivo. Each exhibits the potential to be tailored to meet diverse clinical tissue engineering requirements

  • 172. Edberg, Jesper
    et al.
    Malti, Abdellah
    Granberg, Hjalmar
    Hamedi, Mahiar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Crispin, Xavier
    Engquist, Isak
    Berggren, Magnus
    Electrochemical circuits from 'cut and stick' PEDOT: PSS-nanocellulose composite2017Ingår i: Flexible and Printed Electronics, ISSN 2058-8585, Vol. 2, nr 4, artikel-id 045010Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report a flexible self-standing adhesive composite made from PEDOT:PSS and nanofibrillated cellulose. The material exhibits good combined mechanical and electrical characteristics (an elastic modulus of 4.4 MPa, and an electrical conductivity of 30 S cm(-1)). The inherent self-adhesiveness of the material enables it to be laminated and delaminated repeatedly to form and reconfigure devices and circuits. This modular property opens the door for a plethora of applications where reconfigurability and ease-of-manufacturing are of prime importance. We also demonstrate a paper composite with ionic conductivity and combine the two materials to construct electrochemical devices, namely transistors, capacitors and diodes with high values of transconductance, charge storage capacity and current rectification. We have further used these devices to construct digital circuits such as NOT, NAND and NORlogic.

  • 173.
    Edlund, Ulrica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    A controlled radical polymerization route to polyepoxidated grafted hemicellulose materials2014Ingår i: Polimery, ISSN 0032-2725, Vol. 59, nr 1, s. 60-65Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyfunctional copolymers were prepared from the major softwood hemicellulose polysaccharide, i.e. O-acetylated galactoglucomannan (AcGGM) through a grafting-from controlled radical polymerization. AcGGM was functionalized with brominated pendant groups that served as initiating species in the subsequent Cu(0) mediated radical polymerization of glycidyl methacrylate (GMA). A linear relationship of ln[GMA](0)/[GMA] (the index 0 refers to the initial value) versus reaction time up to conversions of 80 % suggests a first order rate of propagation and a "living" polymerization.

  • 174.
    Edlund, Ulrica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Sauter, Tilman
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Covalent VEGF protein immobilization on resorbable polymeric surfaces2011Ingår i: Polymers for Advanced Technologies, ISSN 1042-7147, E-ISSN 1099-1581, Vol. 22, nr 12, s. 2368-2373Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vascular endothelial growth factor type protein (VEGF), a potent angiogenic effector molecule, was successfully covalently immobilized onto the surfaces of the resorbable polymers poly(L-lactic acid) (PLLA) and poly(epsilon-caprolactone) (PCL) through a three-step strategy. The surfaces were first covalently grafted with poly(acrylic acid) using non-destructive and solvent free vapor-phase grafting. A diamine spacer was coupled to the carboxylic acid pendant groups on the graft chains using EDC/NHS chemistry and VEGF was finally covalently attached to the amine linkers. The chemistry and topography of the modified substrates were quantitatively and qualitatively verified with XPS, ATR-FTIR, UV-VIS, SEM, and ELISA.

  • 175.
    Edlund, Ulrica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Svensson, Marie
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Microsphere valorization of forestry derived hydrolysates2012Ingår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 48, nr 2, s. 372-383Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A value-adding approach to the material utilization of non-cellulosic polysaccharides (NCPs) released from the lignocellulosic feedstock was realized via the formulation of renewable microspheres from wood hydrolysates using a purposely elaborated all edible water-in-oil emulsion technique. Four compositionally different hemicellulose rich wood hydrolysates were recovered from process waters in pulping and other hydrothermal treatments of hardwood and softwood. Multivariate screening designs were employed allowing for the identification and quantitation of significant process parameters and interaction effects governing the conversion of hydrolysates into small, smooth and well-defined microspheres with narrow size dispersity.

  • 176.
    Ejdeholm, Daniel
    KTH, Skolan för kemivetenskap (CHE).
    Mechanical Properties of Corroded Polypropylene2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    To improve the service reliability of polymeric materials used in pickling environments the aim for this research project was to investigate how the corrosion of PP, exposed to mixed acid, changes its mechanical properties. It was found that PPH-β and PPB has a better resistance to the mixed acid environment both in the corrosion rate and impact strength compared to PPH-α and PPR. Further investigation showed that the penetration depth of the nitration is equal in the material exposed to only nitric acid. A useful method has been developed that can, in a relative short time period, give answers to the selected material´s adequacy for this specific environment. Materials that were tested were in the form of commercially available pipes. The samples were exposed to mixed acid from the inside for 7-27 days at temperatures of 60°C and 80°C. The corrosion rates were determined by pH-indicator and FTIR line-scans. The results were compared to pipes that had been in service for 2 years. The impact strength was determined by Charpy impact testing both on the inside and outside of the pipe walls. No changes in impact properties were found from impacts made to the inside of the pipe.

  • 177.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Cellulose, cellulose regenerates and derivatives2009Konferensbidrag (Refereegranskat)
  • 178.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Delignification and bleaching of the future pulp mill2002Konferensbidrag (Refereegranskat)
  • 179.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    New Cell. Innovative Biopolymers2006Konferensbidrag (Refereegranskat)
  • 180.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    New Cellulose Derivatives from Wood for High Value Products2007Konferensbidrag (Refereegranskat)
  • 181.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    The Pulp Mill biorefinery2006Konferensbidrag (Refereegranskat)
  • 182.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Axegård, Peter
    Modern hydrogen peroxide bleaching.1994Konferensbidrag (Refereegranskat)
  • 183.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Engström, Ann-Charlott
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Increase Reactivity of Dissolving Pulps by different pretreatments2006Konferensbidrag (Refereegranskat)
  • 184.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Engström, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Vehviläinen, M
    Tamperere University.
    Heikkilä, S
    Temperere University.
    Agnemo, Roland
    Domsjö Fabriker.
    Cellulose derivatives: improved accessibility and reactivity2005Ingår i: 13th ISWFPC: Vol 2, 2005, s. 121-126Konferensbidrag (Refereegranskat)
  • 185.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Freiholtz, Anna
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Formation of oxalic acid during bleaching1996Konferensbidrag (Refereegranskat)
  • 186.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Freiholtz, Anna
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    On the formation of oxalic acid in bleaching.1996Konferensbidrag (Refereegranskat)
    Abstract [en]

    In modern pulp mills with prodn. of bleached chem. pulp the increased closure of the bleach plant effluent water system will lead to increased concns. of a variety of dissolved org. substances.  Among these oxalic acid is one of the most detrimental due to the facile formation of insol. calcium oxalate once the pH-value is low enough to liberate calcium ions from the pulp.  The ppt. may cause severe prodn. problems.  Therefore, the formation of oxalic acid from the bleaching of kraft pulps with a variety of bleaching agents have been analyzed.  Two methods of anal. have been employed, viz. ion chromatog. and enzymic oxidn. to hydrogen peroxide.  The former is a std. method requiring a certain sample treatment whereas the latter may be used on line.  Anal. of the aq. phase after each bleaching stage in a O D EO D sequence reveals that oxalic acid can be formed in all stages with the oxygen stage being the predominant contributor.  A comparison between different bleaching agents applied to the same pulp again reveals oxygen as a major producer of oxalic acid.  The oxalic acid can be formed from both lignin and polysaccharides but expts. with isolated lignin indicates that the predominant part of the oxalic acid is formed from carbohydrates.       

  • 187.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gierer, Josef
    Jansbo, Kerstin
    Study on the Selectivity of Bleaching with Oxygen-Containing Species1989Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 43, nr 6, s. 391-396Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the bleaching of pulp, the term Selectivity is widely used but poorly defined.This work is an attempt to quantify the selectivity of bleaching with Oxygen-containing species by generating hydroxil radicals and measuring their reaction rates with some lignin and carbohydrate models. Results of this investigation show that the selectivity factor defined as the ratio of the rate constants for a given pair of lignin and carbohydrate models, lies between 5 and 6.

  • 188.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gierer, Josef
    Jansbo, Kerstin
    Reitberger, Torbjoern
    Chemiluminescences as a means of observing hydroxyl radicals in bleaching processes.1987Ingår i: Proc. 4th int. Symp. Wood Pulp chem., Paris, France, 1987, s. 283-284Konferensbidrag (Refereegranskat)
  • 189.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gierer, Josef
    Reitberger, Torbjoern
    Hydroxyl radicals in oxygen bleaching1985Ingår i: Proc. 3rd Int. Symp. Wood Pulp. Chem., 1985, s. 209-210Konferensbidrag (Refereegranskat)
  • 190.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gustavsson, Catrin
    Kadiric, Jasmin
    Teder, Ants
    Formation and dissolution/degradation of hexenuronic acids during kraft pulping of Eucalyptus Globulus.2001Konferensbidrag (Refereegranskat)
  • 191.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ibarra, David
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Köpcke, Viviana
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Larsson, Per Tomas
    Jääskeläinen, Anna-Stiina
    Production of dissolving grade pulps from non-wood paper grade pulps using enzymatic and chemical pre-treatments for the viscose process2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cellulose is the most abundant biorenewable material, constitutes an important polymer since it is used as raw material for several products, e.g.  Paper and board but also cellulose-based products which have many important applications in the pharmaceutical, textile, food and paint industries.  A raw material with high cellulose content and low content of hemicelluloses, residual lignin, extractives and minerals is required for the prodn. of these products, e.g.  Cotton and dissolving grade pulp are used.  However, the high cost prodn. of dissolving grade pulps has aroused the possibility of upgrading paper grade pulps into dissolving pulps by selective removal of hemicelluloses and subsequent activation of the pulps.  This study reports the feasibility to produce dissolving grade pulps from different pulps, i.e.  Non-wood paper grade pulps and conventional hardwood kraft pulps, employing enzymic and chem. pretreatments.  A monocomponent endoglucanase and a xylanase followed by alk. extn. were tested in order to increase the accessibility and reactivity of the cellulose pulp and decrease the hemicellulose content, resp.  An optimization of these treatments in terms of enzyme dosage, incubation time and a possible combination of them was investigated.  The treatment effects on reactivity according to Fock's method, viscosity, hemicellulose content and mol. wt. distribution, using size exclusion chromatog. (SEC), were analyzed.  The characterization of cellulose structure after the enzymic and chem. treatments was investigated by different techniques.

  • 192.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Illergård, Josefin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Biointeractive fibres: A sustainable way of fighting bacteria by using antibacterial cellulosic fibres2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Bacterial growth is a risk of infection.  Antibiotics did long time seem to be a soln. to the problem, but now the consequences are seen, as antibiotic-resistant strains are evolving.  The substances are also eventually released into the environment, where they often are harmful to living organisms.  Antibacterial surfaces state another option.  However, a majority of the now existing surfaces are of leaching type i.e. assocd. with the same problems as the antibiotics.  The non-leaching are a safer option, but until now the fabrication has been a problem with use of e.g. org. solvents.  We present a sustainable way of forming an antibacterial material onto cellulose by using the polyelectrolyte multilayer technique.  By step-wise adsorbing oppositely charged polyelectrolytes in an aq. soln. contg. fibers, at room-temp., the surface of the fibers are modified.  The result is a non-leaching material with bacteria inhibiting properties.  Also the fabrication is quite safe, as polymers have shown lower toxicity to humans than their monomeric counterparts.  Cellulose is an excellent substrate for antibacterial surfaces.  It is easy to modify with the present technique and is in itself a sustainable materials, with multiple applications.  Combined this gives us in total a new, antibacterial material which also opens up for sustainable cellulose-based products.

  • 193.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    From Cellulose Accessibility to Polymer and Product Properties of Cellulose Derivatives2009Konferensbidrag (Refereegranskat)
  • 194.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Fardim, Pedro
    Maunu, Sirkka Liisa
    University of Helsinki.
    Nousiainen, Pertti
    Siika-Aho5, Matti
    Walkenström, Pernilla
    New cellulose derivatives from wood for high value products2008Ingår i: TAPPSA: Technical Association of the Pulp and Paper Industry of Southern Africa, ISSN 1029-0109, nr September 2008Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Various pre-treatment methods to increase the accessibility of cellulose materials to swelling and reactive agents at different hierarchical levels, has been developed. It was demonstrated that enzymes are very efficient at increasing the cellulose reactivity. A new method to measure the reactivity and accessibility of the hydroxyl groups on cellulose was developed. Reversible addition-fragmentation chain transfer (RAFT) agents were synthesized and used further in esterification reactions with cellulose samples to prepare cellulose based graft-copolymers. MALDI-TOFMS was evaluated for characterization of cellulose derivatives. Methods to prepare electrospun fibres, casings, sponges and beads, were developed with target applications in pharmaceuticals and foods.

  • 195.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Köpcke, Viviana
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Ibarra, David
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Larsson, Per Tomas
    Characterization of dissolving pulps produced from Kraft pulps2009Konferensbidrag (Refereegranskat)
  • 196.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lennholm, Helena
    A studies on the mechanism of the photo-yellowing of partially acetylated ground wood pulps.1991Konferensbidrag (Refereegranskat)
  • 197.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lennholm, Helena
    Iversen, Tommy
    A comment on the effect of carbonyl groups on the light-induced reversion of groundwood pulp1990Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 5, nr 4, s. 159-160Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sodium borohydride redn. of stone groundwood pulp from spruce (Picea abies) had no dramatic effect on the light-induced brightness reversion.  This indicates that the direct scission of phenacyl aryl ether linkages is not an important step in the initial chromophore formation.

  • 198.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lennholm, Helena
    Lindblad, Gunnar
    Iversen, Tommy
    A study of the photochromic behaviour of UV-irradiated mechanical pulps.1992Ingår i: Proc. 2nd European Workshop Lignocellulosic Pulp (EWLP), 1992, s. 183-186Konferensbidrag (Refereegranskat)
  • 199.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lennholm, Helena
    Lindblad, Gunnar
    Iversen, Tommy
    The light-induced colour reversion of groundwood pulps1991Ingår i: Proc 6th Int. Symp. Wood Pulp Chem., Melbourne, Australia, 1991, s. 439-442Konferensbidrag (Refereegranskat)
  • 200.
    Ek, Monica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Westman, Eva-Helena
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Karlsson, Josefin
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    CELL 28-Biointeractive fibers with antibacterial properties2008Ingår i: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY: Volume: 235, 2008, s. 28-CELL-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Growth of bacteria on various surfaces may cause major concern if encountered in the wrong environment.  The ability to impart antimicrobial properties onto surfaces is therefore desirable.  Modification of both glass surfaces and cellulose membranes using weak polyelectrolytes as antimicrobial agent is presented.  The aim was to incorporate a known carrier of antimicrobial activity into a multilayer structure of adsorbed polyelectolytes at different surfaces and evaluate the antibacterial activities.  The approach involved screening for antimicrobial activity in soln. of modified and unmodified polymers.  The polymers were evaluated against gram-neg. E. coli and gram-pos. B. subtilis. In order to elucidate the mode of action of the polymers, the charge was detd.  This is done since earlier studies have shown that both charge and degree of hydrophobicity are of importance in terms of exerted activity.  Results show that the chosen polymers exert activity in the immobilized state.  Different techniques have been used to evaluate the mechanisms.

1234567 151 - 200 av 782
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf