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  • 151.
    Hedenqvist, Mikael S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Merveille, A.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Bergman, G.
    Adhesion of microwave-plasma-treated fluoropolymers to thermoset vinylester2005In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 98, no 2, p. 838-842Article in journal (Refereed)
    Abstract [en]

    Poly(tetrafluoroethylene) and a fluoroethylene copolymer were surface treated with a 2.45-GHz microwave plasma to enhance their adhesion to a vinylester thermoset. The plasmas were generated with an inert gas (Ar) and with reactive gases (H-2, O-2, and N-2). The lap-joint shear stress was measured on fluoropolymer samples glued with the vinylester. In general, the stress at failure increased with increasing plasma-energy dose. The H, plasma yielded the best adhesion, and X-ray photoelectron spectroscopy revealed that it yielded the highest degree of defluorination of the fluoropolymer surface. The defluorination efficiency declined in the order H-2, Ar, O-2, and N-2. Contact angle measurements and scanning electron microscopy revealed that the surface roughness of the fluoropolymer depended on the rate of achieving the target energy dose. High power led to a smoother surface, probably because of a greater increase in temperature and partial melting.

  • 152.
    Hoglund, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Macromolecular design controls the degradation product pattern and mechanical properties of polyesters2012In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 244Article in journal (Other academic)
  • 153.
    Hua, Geng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Johan, Franzén
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    One-pot inimer promoted ROCP synthesis of branched copolyesters using α-hydroxy-γ-butyrolactone as the branching reagent2016In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 54, no 13, p. 1908-1918Article in journal (Refereed)
    Abstract [en]

    An array of branched poly(ɛ-caprolactone)s was successfully synthesized using an one-pot inimer promoted ring-opening multibranching copolymerization (ROCP) reaction. The biorenewable, commercially available yet unexploited comonomer and initiator 2-hydroxy-γ-butyrolactone was chosen as the inimer to extend the use of 5-membered lactones to branched structures and simultaneously avoiding the typical tedious work involved in the inimer preparation. Reactions were carried out both in bulk and in solution using stannous octoate (Sn(Oct)2) as the catalyst. Polymerizations with inimer equivalents varying from 0.01 to 0.2 were conducted which resulted in polymers with a degree of branching ranging from 0.049 to 0.124. Detailed ROCP kinetics of different inimer systems were compared to illustrate the branch formation mechanism. The resulting polymer structures were confirmed by 1H, 13C, and 1H-13C HSQC NMR and SEC (RI detector and triple detectors). The thermal properties of polymers with different degree of branching were investigated by DSC, confirming the branch formation. Through this work, we have extended the current use of the non-homopolymerizable γ-butyrolactone to the branched polymers and thoroughly examined its behaviors in ROCP.

  • 154.
    Hua, Geng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Exploiting Ring-Opening Aminolysis–Condensation as a Polymerization Pathway to Structurally Diverse Biobased Polyamides2018In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602Article in journal (Refereed)
    Abstract [en]

    A pathway to biobased polyamides (PAs) via ring-opening aminolysis–condensation (ROAC) under benign conditions with diverse structure was designed. Ethylene brassylate (EB), a plant oil-derived cyclic dilactone, was used in combination with an array of diamines of diverse chemical structure, and ring-opening of the cyclic dilactone EB was revealed as a driving force for the reaction. The ROAC reactions were adjusted, and reaction conditions of 100 °C under atmospheric pressure using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as a catalyst for 24 h were optimal. The structures of the polyamides were confirmed by mass spectroscopy, FTIR, and NMR, and the PAs had viscosity average molecular weights (Mη) of ∼5–8 kDa. Glassy or semicrystalline PAs with glass transition temperatures between 48 and 55 °C, melting temperatures of 120–200 °C for the semicrystalline PAs, and thermal stabilities above 400 °C were obtained and were comparable to the existing PAs with similar structures. As a proof-of-concept of their usage, one of the PAs was shown to form fibers by electrospinning and films by melt pressing. Compared to conventional methods for PA synthesis, the ROAC route portrayed a reaction temperature at least 60–80 °C lower, could be readily carried out without a low-pressure environment, and eliminated the use of solvents and toxic chemicals. Together with the plant oil-derived monomer (EB), the ROAC route provided a sustainable alternative to design biobased PAs.

  • 155.
    Hua, Geng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    From Food Additive to High-Performance Heavy Metal Adsorbent: A Versatile and Well-Tuned Design2016In: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485Article in journal (Refereed)
    Abstract [en]

    A biosourced, cross-linked hydrogel-type heavy metal adsorbent is presented. Various factors such as the highly efficient chemical interactions, the various network structures, the decreased energy consumption during cross-linking, and the negligible amount of generated waste are considered when designing the adsorbent. The widely applied, naturally occurring food additive δ-gluconolactone is studied as a building block for the adsorbent. Aminolysis reactions were applied to form linear dimer precursors between diamines and δ-gluconolactones. The abundant hydroxyl groups on the dimers from δ-gluconolactone were fully exploited by using them as the cross-linking sites for reactions with ethylenediaminetetraacetic dianhydride, a well-known metal-chelating moiety. The versatility of the adsorbent and its metal-ion binding capacity is well tuned using dimers with different structures and by controlling the feed ratios of the precursors. Buffers with different pH values were used as the conditioning media to examine the swelling properties and the mechanical properties of the hydrogels, revealing that both properties can be controlled. High heavy metal chelating performance of the adsorbent was determined by isothermal adsorption kinetics, titration, and thermal gravimetric analysis. The adsorbent exhibits an outstanding chelating ability toward the three tested heavy metals (Cu(II), Co(II), Ni(II)), and the maximum adsorption capacity (qm ∼ 121 mg·g–1) is higher than that of the majority of the reported biosourced adsorbents.

  • 156.
    Hua, Geng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Isocyanate-Free, UV-Crosslinked Poly(Hydroxyurethane) Networks: A Sustainable Approach toward Highly Functional Antibacterial Gels2017In: Macromolecular Bioscience, ISSN 1616-5187, E-ISSN 1616-5195Article in journal (Refereed)
    Abstract [en]

    An increased sustainabile awarness has inspired the development of new polymeric networks in a remarkable way and this strive should be combined with environmentally concerned end-uses. Therefore, a UV-crosslinked polyhydroxyurethane film with antibacterial properties is developed. First, a hydroxyurethane precursor is synthesized using aminolysis condensation, circumventing the use of isocyanates. The films are subsequently crosslinked under solvent-free conditions through a UV-triggered thiol-ene mechanism. The reactions are monitored by 1H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy, and the networks have gel contents above 90%, and are transparent, hydrophilic, and highly flexible. Antibacterial properties are achieved by a controlled quaternization of the network's tertiary-amine and methylation of thiol-ether functionality, resulting in quaternary ammonium compounds (QACs) and sulfonium compounds. The antibacterial properties are evaluated against both Escherichia coli and Staphylococcus aureus using the agar plate diffusion and tube shaking methods. The QAC-loaded films exhibit outstanding bactericide properties (>99.9%) and the antibacterial mechanism is demonstrated to be a dual killing mechanism, i.e., diffusion killing and contact active killing.

  • 157.
    Höglund, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Migration and Hydrolysis of Hydrophobic Polylactide Plasticizer2010In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 11, no 1, p. 277-283Article in journal (Refereed)
    Abstract [en]

    Hydrophobic plasticizer protects polylactide (PLA) against hydrolytic degradation but still migrates to aging medium and there undergoes further hydrolysis contributing to the spectrum of degradation products. PLA plasticized with hydrophobic acetyl tributyl citrate (ATC) plasticizer showed a slower degradation rate compared with pure PLA because of the increased hydrophobicity of the material. The enhanced bulk hydrophobicity also overcame the degradation enhancing effect of hydrophilic surface grafting. In addition to plasticization with ATC, some of the samples were also surface grafted with acrylic acid. The materials were subjected to hydrolysis at 37 and 60 degrees C for up to 364 days to compare the effect of hydrophobic and hydrophilic bulk and surface modifications. Although considered insoluble in water, the plasticizer was detected in the water solutions immediately upon immersion of the materials, and the relative abundance of the ATC degradation products increased with hydrolysis time.

  • 158.
    Höglund, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Surface Modification Changes the Degradation Process and Degradation Product Pattern of Polylactide2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 1, p. 378-383Article in journal (Refereed)
    Abstract [en]

    The effect of surface modification on the degradation process and degradation product patterns of degradable polymers is still a basically unexplored area even though it significant effect can be expected. Polylactide (PLA) and PLA grafted with acrylic acid (PLA-AA) were, thus, subjected to hydrolytic degradation, and water-soluble degradation products were determined by electrospray ionization-mass spectrometry (ESI-MS) after different time periods. Low molar mass Compounds migrated from surface-grafted PLA already during the first 7 days at 37 degrees C, while it Look 133 days in the case of nongrafted PLA before any low molar mass compounds were detected in the aging water. In addition, the degradation product pattern of surface-grafted PLA showed significant variation as a function of hydrolysis time with the evolution of short and long AA-grafted lactic acid oligomers as well as plain lactic acid oligomers after different time periods, The degradation up to 13 lactic acid units. Surface grafting, thus, changed the degradation product patterns and accelerated the formation of water-soluble degradation products.

  • 159.
    Höglund, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Lindqvist, Anna
    Psykologiska institutionen, Stockholms universitet.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Berglund, Birgitta
    Psykologiska institutionen, Stockholms universitet.
    Odour perception - A rapid and easy method to detect early degradation of polymers2012In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 4, p. 481-487Article in journal (Refereed)
    Abstract [en]

    Human perception of odour is presented as a tool to detect early degradation of polymeric materials. Polyamide 66 (PA66) was selected as model material and subjected to accelerated ageing through thermo-oxidation. After different degradation times, participants smelled at the headspace of jars with aged polymer and scaled their perceived odour intensity. In parallel, conventional analysis by GC-MS and tensile testing was performed to measure the volatile compounds released and accompanying changes in mechanical properties during degradation. Perceived odour intensity correlated with a significant deterioration in mechanical properties and the release profiles of eight degradation products. This relationship was detected at a very early stage of degradation before any significant changes could be observed in thermal and surface properties. Odour perception, thus, constitutes a rapid and convenient method to determine the quality of plastic materials.

  • 160.
    Höglund, Anders
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Målberg, Sofia
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Assessing the Degradation Profile of Functional Aliphatic Polyesters with Precise Control of the Degradation Products2012In: Macromolecular Bioscience, ISSN 1616-5187, E-ISSN 1616-5195, Vol. 12, no 2, p. 260-268Article in journal (Refereed)
    Abstract [en]

    The pre-polymer poly(but-2-ene-1,4-diyl malonate) (PBM) and a series of PBM-based materials are shown to be degradable under physiological conditions in vitro and they are therefore presented as potential materials for biomedical applications. Four different PBM-based materials are synthesized: a PBM homopolymer, crosslinked PBM with and without spacer, and a triblock copolymer of PBM and PLLA with the PBM as an amorphous middle block. The polymers are subjected to hydrolytic degradation in phosphate-buffered saline at pH = 7.4 and 37 °C. The results show that all the PBM-based materials degrade without a rapid release of acidic degradation products or any substantial lowering of the pH that might jeopardize their biocompatibility.

  • 161. Högström, P.-A.
    et al.
    Karlsson, S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Gedde, U.
    Effect of aging on the mechanical properties of UV curable optical fiber coatings2000In: International Journal of Polymeric Materials, ISSN 0091-4037, E-ISSN 1563-535X, Vol. 46, no 3-4, p. 403-421Article in journal (Refereed)
  • 162.
    Ibn Yaich, Anas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Strategies for Renewable Barriers with Enhanced Performance2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Forest biomass is expected to play an increasingly important role in tomorrow´s global bio-economy as one of the main renewable sources of materials, chemicals and energy. In the framework of the biorefinery concept, the forestry industry is looking for new processes to utilize several fractions in the biomass (cellulose, hemicelluloses, lignin etc.), thereby generating value-added by-products, an economically sustainable process, and new market opportunities. The work presented in this thesis aims to develop oxygen barrier films and coatings based on the hemicelluloses-rich biorefinery fraction, referred to as wood hydrolysate (WH). These WHs were obtained from the aqueous process liquor after the hydrothermal treatment of hardwood. The WH-based films and coatings are intended to meet the increasing demand of bio-based and biodegradable barrier materials in multi-layered laminates for the food-packaging sector. This work has employed four strategies to provide control and enhancement of the mechanical and barrier properties of WH: I) a selective choice of up-grading pre-treatments of the WH aqueous liquor, II) the incorporation of layer silicates into the barrier formulation, III) chain-extension of the hemicellulose chains present in the WH via reductive amination, and IV) the development of wood hydrolysate polyelectrolyte complexes (PEC) with quaternized cellulose (QC). It has been demonstrated that the crude WH, with almost no upgrading pre-treatment, produced coatings with the best performance in terms of low oxygen permeability. Furthermore, the addition of naturally occurring layered silicates into the WH-based film formulations led to a decrease in water vapor permeability, and a considerably lower oxygen permeability at 80% relative humidity. Moreover, the chain-extension approach was shown to significantly enhance the formability and mechanical performance of WH-based films, making it possible to produce cohesive films with a higher proportion of WH, 70–85% (w/w) and to reduce the content of co-components in the films. The WH/QC-PEC-based films exhibited by far the best tensile properties, better than those previously obtained with carboxymethyl cellulose as a co-component in an equal amount, with a tensile strain-at-break as high as 7 %.

  • 163.
    Ibn Yaich, Anas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Wood hydrolysate Barriers2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wood hemicellulose is an abundant but fairly unexploited renewable feedstock. Recent studies have shown that hemicelluloses have a large potential for use in the food packaging industry as a sustainable alternative to the conventional oxygen-barrier materials used today. Such hemicelluloses are the main components of wood hydrolysates (WH), which are released in large quantities in many forestry process side streams. Recovering these hemicellulose-rich WH fractions and turning them into food packaging materials would be beneficial from both, an environmental and an economic point of view. However, in the development of packaging materials for large-scale applications, the high production costs to obtain the highly purified hemicellulose and their high moisture sensitivity are considered to be the two main limiting factors.In this study, a selective choice of the upgrading conditions during the recovery of WH and the incorporation of layered silicate particles in WH-based films and coating formulations are used as tools to control and tailor the barrier and tensile performances of the materials, enabling the design of renewable oxygen-barrier materials that are cost-effective and with improved properties. The WH originated from the aqueous liquor from hardwood hydrothermal treatment and upgraded according to one of three alternative routes (ultrafiltration, ultrafiltration followed by diafiltration, and ethanol precipitation) resulting in hemicellulose-rich fractions with different structures, compositions, and properties, which in turn resulted in different performances in terms of mechanical and oxygen-permeability properties. WH in its crudest form gave rise to coatings with the best oxygen-barrier performance, higher than the oxygen-barrier performance of pure hemicellulose coatings. The addition of montmorillonite or talc layered silicates as mineral additives in the WH-based films resulted in better water-vapor-barrier properties, and considerably improved oxygen barrier performance at a relative humidity as high as 80 %. The application of the WH-based films was therefore extended to a wider range of relative humidity conditions.

  • 164.
    Ibn Yaich, Anas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Adapting wood hydrolysate barriers to high humidity conditions2014In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 100, p. 135-142Article in journal (Refereed)
    Abstract [en]

    The incorporation of layered silicates in bio-based barrier films resulted in lower water vapor permeability, and significantly lowered oxygen permeability at a relative humidity (RH) as high as 80%, with reduced moisture sensitivity of the wood hydrolysate (WH) based films. The applicability of WH based films was accordingly extended over a wider relative humidity condition range. Crude aqueous process liquor, the WH, was extracted from hardwood and utilized as a feed-stock for films without any upgrading pretreatment, yet producing superior oxygen barrier performance compared to partially upgraded WH and highly purified hemicelluloses. Films composed of crude WH and either one of two types of naturally occurring layered silicates, montmorillonite (MMT) or talc, as mineral additives, were evaluated with respect to oxygen and water vapor permeability, morphological, tensile and dynamic thermo-mechanical properties. Films with an oxygen permeability as low as 1.5 (cm(3) mu m)/(m(2) day kPa) at 80% RH was achieved.

  • 165.
    Ibn Yaich, Anas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Barriers from wood hydrolysate/quaternized cellulose polyelectrolyte complexes2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 3, p. 1977-1991Article in journal (Refereed)
    Abstract [en]

    Biobased polyelectrolyte complexes (PECs) were prepared by mixing negatively charged O-acetyl-4-O-methylglucuronoxylan-rich wood hydrolysate (WH) and positively charged quaternized cellulose (QC) in aqueous solution. The WH was obtained as an aqueous process liquor of the hydrothermal treatment of birch wood chips and partially upgraded by membrane filtration and dialysis. Three QC derivatives with different degrees of quaternization were synthesized, characterized in terms of molecular weight, charge density, crystallinity and solubility, and utilized for PEC production. The WH/QC PECs were designed to form free-standing films with high oxygen barrier performance and good mechanical integrity. The impact of the QC degree of quaternization on the oxygen permeability at both 50 and 80 % relative humidity, water vapor permeability and tensile properties was investigated. Films with a tensile strain-to-break as high as 7 % and an oxygen permeability as low as 1.3 (cm(3) mu m)/(m(2) - day kPa) at 80 % relative humidity were achieved.

  • 166.
    Ibn Yaich, Anas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Transfer of Biomatrix/Wood Cell Interactions to Hemicellulose-Based Materials to Control Water Interaction2017In: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 117, no 12, p. 8177-8207Article, review/survey (Refereed)
    Abstract [en]

    The family of hemicelluloses stands out as a very promising natural resource that can be utilized as a biobased materials feedstock. An in-depth understanding of the hemicellulose inherent structural and property features as well as the structure property relationships induced by the specific supramolecular hierarchical organization of lignocellulosic biopolymers will be a key enabling technology in the emerging biorefinery sector. This Review aims to give a perspective on these issues and demonstrate how the transfer of molecular wood cell interactions into hemicellulose-based materials may offer new design principles for material formulations.

  • 167.
    Ibn Yaich, Anas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Wood Hydrolysate Barriers: Performance Controlled via Selective Recovery2012In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 13, no 2, p. 466-473Article in journal (Refereed)
    Abstract [en]

    Films and coatings were produced from a noncellulosic polysaccaride-rich wood hydrolysate (WH) and the resulting oxygen barrier performance was improved by a selective choice of upgrading conditions. The WH was obtained from process water in the hydrothermal treatment of hardwood and subjected to one of three alternative upgrading treatments, resulting in xylan-rich fractions with significant differences in structure, composition, and properties of the recovered WH fractions, which in turn had a major impact on their performance with respect to tensile and oxygen barrier properties. The WH in the least upgraded state, the crudest fraction, produced films with the best performance in terms of oxygen permeability and was superior to corresponding films based on highly purified hemicellulose.

  • 168. Idris, Shaza B.
    et al.
    Dånmark, Staffan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Finne Wistrand, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Arvidson, Kristina
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Bolstad, Anne Isine
    Mustafa, Kamal
    Biocompatibility of Polyester Scaffolds with Fibroblasts and Osteoblast-like Cells for Bone Tissue Engineering2010In: Journal of bioactive and compatible polymers (Print), ISSN 0883-9115, E-ISSN 1530-8030, Vol. 25, no 6, p. 567-583Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to evaluate the in vitro cytotoxicity and cytocompatibility of the developed aliphatic polyester co-polymer scaffolds: poly(L-lactide-co-epsilon-caprolactone) and poly(L-lactide-co-1,5-dioxepan-2-one). The scaffolds were produced by solvent casting and particulate leaching, and tested by direct and indirect contact cytotoxicity assays on human osteoblast-like cells and mouse fibroblasts. Cell morphology was documented by light and scanning electron microscopy. Viability was assessed by the MTT, neutral red uptake, lactic dehydrogenase and apoptosis assays. Extraction tests confirmed that the scaffolds did not have a cytotoxic effect on the cells. The cells grew and spread well on the test scaffolds with good cellular attachment and viability. The scaffolds are noncytotoxic and biocompatible with the two cell types and warrant continued investigation as potential constructs for bone tissue engineering.

  • 169. Idris, Shaza B.
    et al.
    Isine Bolstad, Anne
    Ibrahim, Saleh O.
    Dånmark, Staffan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Finne Wistrand, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Arvidsson, Kristina
    Mustafa, Kamal
    Global Gene Expression Profile of Osteoblast-Like Cells Grown on Polyester Copolymer Scaffolds2011In: Tissue Engineering. Part A, ISSN 1937-3341, Vol. 17, no 21-22, p. 2817-2831Article in journal (Refereed)
    Abstract [en]

    One of the principal goals in tissue engineering is to produce scaffold materials that will guide cells to differentiate and regenerate functional replacement tissue at the site of injury. Poly(l-lactide-co-1,5-dioxepan-2-one) [Poly(LLA-co-DXO)], a potential scaffolding material for bone tissue engineering, has high hydrophilicity. Previous in vitro studies using human osteoblast-like cells (HOBs) demonstrated greater cytocompatibility and enhanced osteogenic differentiation when HOBs were seeded onto Poly(LLA-co-DXO) compared to Poly(llactide) [P(LLA)] scaffolds. The aim of the study was to identify the gene expression profiles of HOBs obtained from alveolar bone and grown on Poly(LLA-co-DXO) biodegradable polymer scaffolds compared to P(LLA) one. Illumina HumanWG-6 v3.0 Expression BeadChips were used for the gene expression analysis. Several genes were found as differentially expressed at 24 h and at 21 days. Expression of genes related to cell adhesion, cytoskeleton, antiapoptosis, proliferation, and bone mineralization was influenced by adding the monomer 1,5-dioxepan-2-one to the l-lactide. Genes related to three biological pathways involving Integrin, Notch, and Ras were found to be upregulated. For selected genes, results were confirmed by quantitative reverse transcriptase– polymerase chain reaction. Further, calcium content analysis revealed a significant enhancement of calcium deposition on both tested scaffolds. This observation was confirmed by Von Kossa and Alizarin Red S staining. Findings of this study are relevant to a better understanding of the molecular mechanisms underlying the behavior of HOBs in bone regenerative procedure.

  • 170. Inkinen, Saara
    et al.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Sodergard, Anders
    From Lactic Acid to Poly(lactic acid) (PLA): Characterization and Analysis of PLA and Its Precursors2011In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, no 3, p. 523-532Article, review/survey (Refereed)
    Abstract [en]

    The quality of the monomers lactic acid and lactide as well as the chemical changes induced during polymerization and processing are crucial parameters for controlling the properties of the resulting poly(lactic acid) (PLA) products. This review presents the most important analysis and characterization methods for quality assessment of PLA and its precursors. The impurities typically present in lactic acid or lactide monomers and their possible origins and effects on resulting PLA products are discussed. The significance of the analyses for the different polymer production stages is considered, and special applications of the methods for studying features specific for PLA-based materials are highlighted.

  • 171. Jansson, Mikael
    et al.
    Danielsson, Sverker
    Saadatmand, Soheil
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Upgrading of wood pre-hydrolysis liquor for renewable barrier design: a techno-economic consideration2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 3, p. 2045-2062Article in journal (Refereed)
    Abstract [en]

    A techno-economic assessment of an upgrading procedure and outtake of a pre-hydrolysate in a presumed dissolving pulp mill was performed. Pre-hydrolysis of spruce wood chips in pilot scale produced input data for energy and mass balances and was performed with and without subsequent membrane filtration to produce hydrolysate fractions rich in galactoglucomannan and with some lignin. The hydrolysate is a viable raw material for the production of renewable thin oxygen barrier films as demonstrated herein in the formulation of free standing films with very low oxygen permeability at both moderate and high relative humidities. Approximately 50,000 ton dry solid upgraded pre-hydrolysate suitable for production of oxygen barriers could be produced according to the presumed dissolving pulp mill producing about 500,000 air dry ton dissolving pulp per year and applying a liquor to wood ratio of 4:1. Utilization of the pre-hydrolysis liquor hence adds value to and realizes the dissolving plant as a biorefinery. A sensitivity analysis indicates that the market price of the upgraded pre-hydrolysate has the largest positive effect on the return on investment for separation and upgrading of a pre-hydrolysate. Increased investment cost and increased annuity factor show negative effects.

  • 172.
    Karlsson, S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Nature - Model for new polymers1995In: Trends in Polymer Science, p. 311-Article in journal (Refereed)
  • 173.
    Karlsson, S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, A-C.
    Degradation products in degradable polymers1995In: Journal of macromolecular science. Pure and applied chemistry (Print), ISSN 1060-1325, E-ISSN 1520-5738, Vol. A32, no 4, p. 599-605Article in journal (Refereed)
  • 174.
    Karlsson, S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, A-C.
    Environmental interaction of polymers. Natural metabolites as opposed to the degradation products of synthetic polymers1997In: Macromolecular Symposia, ISSN 1022-1360, E-ISSN 1521-3900, Vol. 118, no 1, p. 733-737Article in journal (Refereed)
  • 175.
    Karlsson, S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, A-C.
    Plaster1992In: Svenska Folkets Miljölexikon, Höganäs: Bokförlaget Bra Böcker & Förlags AB Wiken , 1992, p. 204-Chapter in book (Refereed)
  • 176.
    Karlsson, S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, A-C.
    Techniques and mechanisms of polymer degradation1995In: Degradable Polymers: Principles and Applications, London: Chapman & Hall , 1995, p. 29-42Chapter in book (Refereed)
  • 177.
    Karlsson, S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, A-C.
    The biodegradation of a biopolymeric additive in building materials1990In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 23, no 137, p. 352-357Article in journal (Refereed)
  • 178.
    Karlsson, S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Banhidi, Z.G.
    Albertsson, A-C.
    Detection by high-performance liquid chromatography of polyamines formed by clostridial putrefaction of caseins1988In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 442, p. 267-277Article in journal (Refereed)
  • 179.
    Karlsson, S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Banhidi, Z.G.
    Albertsson, A-C.
    Gas chromatographic detection of volatile amines found in indoor air due to putrefactive degradation of casein-containing building materials1989In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 22, no 3, p. 163-169Article in journal (Refereed)
  • 180.
    Karlsson, S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Banhidi, Z.G.
    Albertsson, A-C
    Identification and characterization of alkali-tolerant clostridia isolated from biodeteriorated casein-containing building materials1988In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 28, no 3, p. 305-310Article in journal (Refereed)
  • 181.
    Karlsson, S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Ljungquist, O.
    Albertsson, A-C.
    Biodegradation of polyethylene and the influence of surfactants1988In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 21, no 3, p. 237-250Article in journal (Refereed)
  • 182.
    Karlsson, S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Sares, C.
    Renstad, R,
    Albertsson, A-C.
    Gas chromatographic, liquid chromatographic and gas chromatographic-mass spectrometric identification of degradation products in accelerated aged microbial polyhydroxyalkanoates1994In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 669, no 1-2, p. 97-102Article in journal (Refereed)
  • 183.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Use of GC-MS and MALDI to understand polymer degradation2002In: Polymer News, ISSN 0032-3918, Vol. 27, no 9, p. 305-309Article in journal (Refereed)
  • 184.
    Karlsson, Sigbritt
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    Abiotic and biotic degradation of aliphatic polyesters from "petro" versus "green" resources1998In: Macromolecular Symposia, ISSN 1022-1360, E-ISSN 1521-3900, Vol. 127, p. 219-225Article in journal (Refereed)
  • 185.
    Karlsson, Sigbritt
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    Biodegradable Polymers1998In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 38, no 8, p. 1251-Article in journal (Refereed)
  • 186.
    Karlsson, Sigbritt
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    Techniques and mechanisms of polymer degradation2002In: Degradable Polymers, the Netherlands: Kluwer Academic Publishers, 2002, 2nd, p. 51-69Chapter in book (Refereed)
  • 187.
    Karlsson, Sigbritt
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Erlandsson, Bengt
    Hakkarainen, Minna
    Albertsson, Ann-Christine
    Matrices effects as correlated with formation of degradation products in polyethylene1998In: Journal of environmental polymer degradation, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 70, p. 61-Article in journal (Refereed)
  • 188.
    Karlsson, Sigbritt
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Dicarboxylic acids and ketoacids formed in degradable polyethylenes by zip depolymerisation through a cyclic transition state1997In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 30, p. 7721-7728Article in journal (Refereed)
    Abstract [en]

    The intermediate and final degradation products formed in six different low-density polyethylene (LDPE) films modified with either starch and/or pro-oxidants or photosensitizers (Scott-Gilead formulation [SG]) were investigated. We propose that dicarboxylic acids and ketoacids, formed in the materials to varying degrees, are due to both secondary oxidation products and a zip depolymerization mechanism by backbiting through a cyclic transition state. Hydrocarbons, ketones, carboxylic acids and dicarboxylic acids are formed during early stages of photo-oxidation, and the ketones disappeared while several ketoacids appeared and the relative amount of dicarboxylic acids increased in the most severely degraded materials. During prolonged photo-oxidation, additional oxidation of ketones and monocarboxylic acids to dicarboxylic acids explains the high amount of dicarboxylic acids. In the thermooxidized samples the amount of ketones and monocarboxylic acids remained high even in the most degraded samples. Mono-and dicarboxylic acids were formed in several micrograms per 100 mg of polymer, while the ketones and ketoacids were formed in fewer micrograms per 100 mg of polymer. LDPE modified with the iron dimethyldithiocarbamate (SG1) was the most susceptible material to photooxidation, while LDPE containing starch and pro-oxidants (LDPE-MB) was the most susceptible material to thermo-oxidation. Degraded LDPE-MB demonstrated less formation of degradation products; e.g., only in UV-initiated samples thermally degraded at 80 degrees C for 5 weeks could degradation products be detected. Larger amounts of ketones and ketoacids were formed in the SG materials than in the starch-filled materials.

  • 189.
    Karlsson, Sigbritt
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Identification by headspace gas chromatography-mass spectrometry of in vitro degradation products of homo-and copolymers of L- and D,L-lactide and 1,5-dioxepan-2-one1994In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 688, p. 251-259Article in journal (Refereed)
  • 190. Khabbaz, Farideh
    et al.
    Albertsson, Ann-Christine
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Trapping of volatile low molecular weight photoproducts in inert and enhanced degradable LDPE1998In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 61, no 2, p. 329-342Article in journal (Refereed)
  • 191.
    Kittikorn, Thorsak
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Comparison of Water Uptake as Function of Surface Modification of Empty Fruit Bunch Oil Palm Fibres in PP Biocomposites2013In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 2, p. 2998-3016Article in journal (Refereed)
    Abstract [en]

    Empty fruit bunch oil palm (EFBOP) fibres were surface modified by four different methods, propionylation, vinyltrimethoxy silanization, PPgMA dissolution modification, and PPgMA blending, and integrated into a polypropylene (PP) matrix. The designed biocomposites were subjected to an absorption process at different temperatures. Their water uptake behaviour was compared with the unmodified fibre biocomposites. An increased fibre content and temperature resulted in increased water uptake for all of the biocomposites. The biocomposites containing modified fibres showed a reduction in water uptake, rate of diffusion, sorption, and permeation in comparison with unmodified fibre composites. Comparing the 20 wt% fibre composites at ambient temperature, the performance in water absorption followed the sequence silanization < propionylation < PPgMA dissolution modification < PPgMA blending < no modification. Furthermore, the lowest water absorption was obtained from the silanized fibre/PP composite with 40% fibre content at ambient temperature. Dissolution or blending of PPgMA gave similar water uptake results. The reduction of diffusion, sorption, and permeation confirmed that the modification of fibres was potentially effective at resisting water penetration into the composites.

  • 192.
    Kittikorn, Thorsak
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Effect of surface modifications on microbial growth and biodegradation in sisal/PLA biocomposites2013Manuscript (preprint) (Other academic)
  • 193.
    Kittikorn, Thorsak
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Susceptibility to biodegradation by fungi for sisal/PLA and sisal/PHBV biocomposites2013Manuscript (preprint) (Other academic)
  • 194.
    Kittikorn, Thorsak
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    The effect of surface modifications on the mechanical and thermal properties of empty fruit bunch oil palm fibre PP biocomposites2012In: Polymers from Renewable Resources, ISSN 2041-2479, Vol. 3, no 3, p. 79-100Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to study the effect of chemical surface modifications on empty fruit bunch oil palm fibre/polypropylene composite properties. By FTIR spectra, propionylated fibre and PPgMA-modified fibre showed the presence of a carbonyl group of esters while vinyltrimethoxysilane-treated fibre showed a peak of silicate, confirming that the modifications were successful. PPgMAmodified fibre PP composite at fibre content 20% demonstrated the highest modulus of 0.71 GPa while the modulus of unmodified fibre PP composite was 0.56 GPa. By DSC analysis, PPgMA-modified fibre and vinyltrimethoxysilane-treated fibre PP composite at the same fibre content of 5% showed the highest crystallinity of 46% and 44% respectively whereas unmodified fibre PP composite showed a lower crystallinity of 38%. The DMTA analysis showed that after 60°C, the modified fibre PP composites exhibited a higher stiffness than pure polypropylene.

  • 195. Kleinhans, C.
    et al.
    Mohan, R.R.
    Vacun, G.
    Schwarz, T.
    Haller, B.
    Sun, Yang
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Kahlig, A.
    Kluger, P.
    Finne-Wistrand, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Walles, H.
    Hansmann, J.
    A perfusion bioreactor system efficiently generates cell-loaded bone substitute materials for addressing critical size bone defects2015In: Biotechnology Journal, ISSN 1860-6768, E-ISSN 1860-7314, Vol. 10, no 11, p. 1727-1738Article in journal (Refereed)
    Abstract [en]

    Critical size bone defects and non-union fractions are still challenging to treat. Cell-loaded bone substitutes have shown improved bone ingrowth and bone formation. However, a lack of methods for homogenously colonizing scaffolds limits the maximum volume of bone grafts. Additionally, therapy robustness is impaired by heterogeneous cell populations after graft generation. Our aim was to establish a technology for generating grafts with a size of 10.5 mm in diameter and 25 mm of height, and thus for grafts suited for treatment of critical size bone defects. Therefore, a novel tailor-made bioreactor system was developed, allowing standardized flow conditions in a porous poly(L-lactide-co-caprolactone) material. Scaffolds were seeded with primary human mesenchymal stem cells derived from four different donors. In contrast to static experimental conditions, homogenous cell distributions were accomplished under dynamic culture. Additionally, culture in the bioreactor system allowed the induction of osteogenic lineage commitment after one week of culture without addition of soluble factors. This was demonstrated by quantitative analysis of calcification and gene expression markers related to osteogenic lineage. In conclusion, the novel bioreactor technology allows efficient and standardized conditions for generating bone substitutes that are suitable for the treatment of critical size defects in humans.

  • 196. Kleinhans, C.
    et al.
    Vacun, G.
    Sun, Yang
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Haller, B.
    Kahlig, A
    Kluger, P. J.
    Finne-Wistrand, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Walles, H.
    Hansmann, J.
    Evaluation of a perfusion bioreactor for efficient seeding and advanced culture conditions of large bone substitute materials addressing critical size defectsManuscript (preprint) (Other academic)
  • 197.
    Krämer, Roland
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    On the intumescence of ethylene-acrylate copolymers blended with chalk and silicone2007In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 92, p. 1899-1910Article in journal (Refereed)
    Abstract [en]

    The combustion and melt dripping of poly(ethylene-co-butyl acrylate) (EBA), EBA blended with polypropylene (EBA-PP) and poly(ethylene-co-methacrylic acid) (EMAA), each blended with calcium carbonate and polydimethylsiloxane, were studied. In situ measurement of the temperature gradient in the cone calorimeter were combined with infrared spectroscopy measurements on specimens withdrawn and quenched at different times of the experiment. The reactions that govern the degradation at the high heating rates met in the combustion could be determined and the gap to analytical techniques such as thermogravimetry bridged. The interplay of mechanical char integrity and heat feedback by the flame determined how much time the specimen dwells in temperature range of 300-420 °C where char expansion due to calcium salt formation is effective and thereby affects the heat release rate strongly. Vertical cone calorimeter and vertical flame testing were used to assess melt dripping and char stability under flaming combustion. Plate-plate rheological measurements proofed to be of limited use to compare the effect of different degradation atmospheres on the melt viscosity. The EMAA formulation had the most effective intumescent process with a low heat release rate and good char stability even in vertical configuration. Electron-beam irradiated EMAA specimens with different levels of cross-links were tested in the cone calorimeter in order to understand the role of cross-links for the intumescent process.

  • 198.
    Krämer, Roland
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Heat release and structural collapse of flexible polyurethane foam2010In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, no 6, p. 1115-1122Article in journal (Refereed)
    Abstract [en]

    Flexible polyurethane foam used in upholstered furniture remains one of the major fire hazards to date. The heat release rate of burning items made of foam depends strongly on the foam’s physical behavior, notably its collapse to a burning liquid that can result in a pool fire. In this contribution, the cone calorimeter was used to study the physical processes and to determine their influence on foam combustion over a range of external heat fluxes. The initial stage of foam collapse can be described as the propagation of a liquid pyrolysis layer through the foam sample. The rate of propagation of the liquid layer was found to depend strongly on the convective heat transfer from the flame, which simultaneously defined and depended on the sample shape. The effective heat of combustion during foam collapse and pool fire was matched to the heat release potential of the components of the foam formulation to deduce which are consumed. The proposed analysis can serve to clarify the mechanism of flame retardant action, as demonstrated for a commercial brominated-phosphorous compound.

  • 199.
    Krämer, Roland
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    The role of depolymerization in simultaneous gasification and melt flow of polystyrene.Manuscript (preprint) (Other academic)
  • 200.
    Krämer, Roland
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Raza, Mohsin Ali
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf W
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Degradation of poly (ethylene-co-methacrylic acid)-calcium carbonate nanocomposites2007In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 92, no 10, p. 1795-1802Article in journal (Refereed)
    Abstract [en]

    Composites of poly(ethylene-co-methacrylic acid) with 5 mass fraction percent of precipitated calcium carbonate nanoparticles were prepared by melt extrusion on a miniature melt-blender and medium-scale production equipment. The composites consisted mostly of isolated particles. The ultimate mechanical properties of the nanocomposites were consequently largely superior to composites with micron-sized filler. The calcium carbonate particles were shown to offer a large surface area for calcium salt formation during the thermal degradation of the material. This imparted a stabilizing effect to the copolymer that was comparable to the neutralization of the methacrylic acid units with calcium ions. The rate of calcium salt formation was fast at temperatures above 350 degrees C. Stearic acid surface coatings did not interfere significantly with the calcium salt formation. The oxidative stability of the composites was further largely improved by the formation of a diffusion barrier.

1234567 151 - 200 of 348
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