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  • 251.
    Azhar, Shoaib
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Wang, Yan
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lawoko, Martin
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Mikale E
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Chemoenzymatic separation of softwood polymers2011Ingår i: Proceedings of  the 16th international symposium of wood, fiber and pulp chemistry / [ed] Lijun Wan et al., 2011, s. 932-936Konferensbidrag (Refereegranskat)
    Abstract [en]

    Spruce wood chips were chemically pre-treated with sodium hydroxide to open up the compact structure of wood. The wood was then treated with enzymes (xylanase, gamanase and mannanase) and subjected to extraction with a mixture of methanol and alkali to efficiently isolate lignin and hemicelluloses. Chemical pre-treatment improved enzyme efficiency which consequently enhanced the extraction of lignocelluloses with higher average molar mass than the references.

  • 252.
    Azhdar, Bruska
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Improved high velocity cold copaction processing: polymer powder to high performance parts2005Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    A uniaxial High-Velocity Compaction (HVC) process for polymer powder using a cylindrical, hardened steel die and a new technique with relaxation assist was tested with a focus on the compactibility characteristics and surface morphology of the compacted materials using various heights of relaxation assist device with different compacting profiles.

    Relaxation assist device was presented as a new technique to reduce springback, pull-out phenomenon and to improve the compaction process.

    The basic phenomena associated with HVC are explained and the general energy principle is introduced to explain pull-out phenomenon during the decompacting stage. In this study, polyamide-11 powders with different particle size distributions have been compacted with the application of different compaction profiles, e.g. different energies and velocities. It was found that the relative green density is influenced more by the pre-compacting (primary compaction step) than by the post-compacting (secondary compaction step).

    Experimental results for different compaction profiles were presented showing the effect of varying the opposite velocity during the decompacting stage and how to improve the homogeneous densification between the upper and lower surface and the evenness of the upper surface of the compacted powder bed by using relaxation assists, and the influences of the relaxation assist device on the process characteristics. It was found that the relaxation assist improves the compaction of the polymer powder by locking the powder bed in the compacted form. In addition, the relative times of the compacting stage, decompacting stage and the reorganisation of the particles can be controlled by altering the height of the relaxation assist. It was found that the high-velocity compaction process is an interruption process and that the delay times between the pressure waves can be reduced by increasing the height of the relaxation assist device. Furthermore, the first gross instantaneous springback and the total elastic springback are reduced.

    Two bonding strain gauges and a high-speed video camera system were used to investigate the springback phenomenon during the compaction process. Scanning electron microscopy (SEM) and image computer board Camera (IC-PCI Imaging Technology) were used to the study the morphological characteristics, the limit of plastic deformation and particle bonding by plastic flow at contact points, and pull-out phenomena.

  • 253.
    Azhdar, Bruska
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Novel Technique to Improve High-Velocity Cold Compaction: Processing of Polymer Powders and Polymer-Based Nanocomposite High Performance Components2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Compaction of polymer powders and polymer-based nanocomposites by uniaxial high-velocity cold compaction (HVC), by high-energy ball milling (HEBM) and using a novel technique, relaxation assists, was investigated with a focus on the process parameters, the compactibility characteristics, surface morphology and friction. The basic phenomena associated with HVC are explained and the general energy principle is introduced to explain the pull-out phenomenon, springback gradient, delay time, relative time of the pressure wave, and stick-slip phenomenon during the compaction process. Experimental results for different compaction profiles, different particle size distributions and different milling system for polymer-based nanocomposite are presented, showing the effect of varying the process parameters on the compacted material; the compactibility in the compacted bed, the uniformity of the compacted surface, the pull-out phenomenon, the springback gradient, the stick-slip phenomenon and the homogeneity of the dispersions of nanoparticles in the polymer powders in the solid state. It was found that the high-velocity compaction process is an interruption process and that the opposite velocity and pressure loss during the compaction process have a major influence on the quality of the compacted material. The relaxation assist device is a novel technique that has been successfully developed to improve the compaction process. The relaxation assists are parts of the piston and they are regarded as projectile supports. They are constructed of the same material as the piston, and the diameters are the same but the lengths are different. The relaxation assist device leads to an improvement in the compaction of powders, polymer powders and polymer-based nanocomposites by giving a more homogeneous opposite velocity and a better locking of the powder bed in the compacted form during the compaction process with less change in dimensions in the case of both homogeneous and heterogeneous materials. If the movement of the particles is restricted the powder bed attains a higher density and the total elastic springback is minimized. In addition, there is a more homogeneous dispersion of nanoparticles in the case of a heterogeneous material. A much better transfer of the pressure through the powder bed and a smaller loss of pressure lead to a more homogenous stick-slip of the particles and a higher sliding coefficient due to the overall friction during the compaction process.

  • 254.
    Azhdar, Bruska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Stenberg, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Determination of dynamic and sliding friction, and observation of stick-slip phenomenon on compacted polymer powders during high-velocity compaction2006Ingår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 25, nr 8, s. 1069-1080Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dynamic friction, sliding friction, and the stick-slip phenomenon have been studied on compacted polymer powders during high-velocity compaction. It is particularly important from a practical point of view to distinguish the stick-slip mechanism and the sliding mechanism which occur concurrently. A practical experimental system has been successfully developed to study the dry frictional force and to measure the sliding coefficient between the polymer powder particles and the die wall during high-velocity compaction. Two new components have been introduced as relaxation assists to improve the compaction process by reducing the frictional forces. It was found that the relaxation assist device leads to an improvement in the polymer powder compaction process by giving a more homogeneous opposite velocity and a better locking of the powder bed in the compacted form with less change in dimensions. The subsequent movement of the particles can be reduced and the powder bed attains a higher density with a minimum total elastic spring-back. The relative time of the stick-slip phenomenon during the compacting stage is also reduced so that the time needed to transfer from an intermittent stick-slip state to a smooth sliding state is reduced and the powder bed slides smoothly. It was found that the dynamic, dry frictional force is intermittent (stick-slip mechanism) at low compaction rates but that at high compaction rates is becomes more smooth (sliding mechanism). Both mechanisms depend on the nature of the powder and on the compaction conditions. At the beginning of the compaction stage, the sliding coefficient decreases due to an increase in the radial to axial stress ratio until the maximum pressure has been reached. During the reorganization stage, more time is needed for large particles to move, rotate and slide due to their relatively large diameter and mass. As a result, the reorganization stage is extended and the stick-slip phenomenon is observed more with increasing particle size. Much better transfer of the pressure throughout the powder bed and less loss of pressure lead to a higher sliding coefficient due to the overall friction during the compaction process. It was found that the sliding coefficient is proportional to the density. A more homogeneous density distribution in the compacted powder and a smaller pressure loss during compaction has a major influence on the sliding coefficient and on the quality of the compacted material

  • 255.
    Azhdar, Bruska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Stenberg, Bengt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Determination of springback gradient in the die on compacted polymer powders during high-velocity compaction2006Ingår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 25, nr 1, s. 114-123Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A uniaxial high-velocity compaction process for polymer powder using a cylindrical, hardened steel die and a new technique with relaxation assist was tested with various heights. The influences of the relaxation assist device on the process characteristics are discussed. Two bonded strain gauges and a high-speed video camera system were used to investigate the springback phenomenon during the compaction process. It was found that the relaxation assist improves the compaction of the polymer powder by locking the powder bed in the compacted form. It is shown that the high-velocity compaction process is an interruption process and that the delay times between the pressure waves can be reduced by increasing the height of the relaxation assist device. The delay times between the pressure waves are also strongly dependent on the strain rate. If the height of the relaxation assist device is increased, the first gross instantaneous springback, and the total elastic springback, are reduced. In addition, the density of the powder bed is increased. The relative times of the compacting stage, decompacting stage and the reorganisation of the particles can be also controlled by altering the height of the relaxation assist.

  • 256.
    Azhdar, Bruska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Stenberg, Bengt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Development of a High-Velocity Compaction process for polymer powders2005Ingår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 24, nr 7, s. 909-919Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The High-Velocity Compaction (HVC) process for powder polymers has been studied, with a focus on the compactibility characteristics and surface morphology of the compacted materials, with and without relaxation assists, by increasing compacting quantity and direction. The basic phenomena associated with HVC are explained and the general energy principle is introduced to explain pull-out phenomena during the decompacting stage. Polyamide-11 powders with different particle size distributions have been compacted with the application of different compaction profiles, e.g. different energies and velocities. Scanning electron microscopy (SEM) and image computer board camera, (IC-PCI Imaging Technology) have been used to the study the morphological characteristics, the limit of plastic deformation and particle bonding by plastic flow at contact points, and pull-out phenomena. The relative green density is influenced more by the pre-compacting (primary compaction step) than by the post-compacting (secondary compaction step). The pressure and density distribution differences between the upper and lower surface are not uniform. Projectile supports or 'relaxation assists' are presented as a new technique to reduce pull-out phenomenon. Experimental results for different compaction profiles are presented showing the effect of varying the opposite velocity during the decompacting stage, and how to improve the homogeneous densification between the upper and lower surface and the evenness of the upper surface of the compacted powder bed by using relaxation assists.

  • 257.
    Azhdar, Bruska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Stenberg, Bengt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Polymer-nanofiller prepared by high-energy ball milling and high velocity cold compaction2008Ingår i: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 29, nr 3, s. 252-261Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High-energy ball milling using comilling in a solid state by low-temperature mechanical alloying to prepare nickel-ferrite (NiFe2O4) nanopowders and ultrafine poly(methyl methacrylate) (PMMA), dispersing nanoparticles in a polymer matrix, and a uniaxial high-velocity cold compaction process using a cylindrical, hardened steel die and a new technique with relaxation assists have been studied. The focus has been on the particle size distributions of the nanocomposite powder during the milling and on the surface morphology of the nanocomposite-compacted materials after compaction with and without relaxation assists. Experimental results for different milling systems are presented showing the effects of milling time and material ratio. It was found that a longer mixing time give a higher degree of dispersion of the nanopowder on the PMMA particle surfaces. Furthermore, with increasing content of NiFe2O4 nanopowder, the reduction of the particle size was more effective. Different postcompacting profiles, i.e. different energy distributions between the upper and lower parts of the compacted powder bed, lead to different movements of the various particles and particle layers. Uniformity, homogeneity, and densification on the surfaces in the compacted powder are influenced by the postcompacting magnitude and direction. It was found that the relaxation assist device leads to an improvement in the polymer powder compaction process by reducing the expansion of the compacted volume and by reducing the different opposite velocities, giving the compacted composite bed a more homogeneous opposite velocity during the decompacting stage and reducing the delay time between the successive pressure waves.

  • 258.
    Azhdar, Bruska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Yu, Wenbin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Reitberger, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    A new method for assessing the efficiency of stabilizers in polyolefins exposed to chlorinated water media2009Ingår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 28, nr 6, s. 661-667Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The chlorine used as disinfectant in tap water degrades most materials, including polyethylene. The most adequate (functional) test method, the pressure test, is complicated and expensive because the chlorinated aqueous media (Cl-2 or ClO2 in water) are unstable and they undergo reactions that are dependent on the pH. A new method which assesses the protection efficiency of phenolic antioxidants in polyolefins was developed. The method uses a liquid hydrocarbon analogue, squalane, in which antioxidants are dissolved. The organic phase was dispersed in the aqueous chlorinated phase (containing 10 ppm of either Cl-2 or ClO2; pH=6.8) at 70 degrees C by intense stirring. The depletion of antioxidant (Irganox 1010) was monitored by standard DSC determination of the oxidation induction time. It was shown that 300 min of exposure was sufficient to obtain useful data.

  • 259.
    Azwar, Edwin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Agro-Waste Derived Additives for Polylactide and Tapioca Starch2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Development of materials from renewable resources is one of the big challenges facing our world. In this thesis agro-industrial waste derivatives were developed and evaluated as additives for two common renewable polymer matrices, polylactide (PLA) and starch. Two waste products, wood flour (WF) and rice bran (RB) were evaluated in different forms. Milled WF and RB were either used directly to prepare PLA and starch biocomposites or they were liquefied by acid catalyzed hydrolysis to low molecular weight products. The complex polyol mixtures from liquefaction were tested directly as PLA and starch additives or utilized as monomers for synthesis of esters. The synthesized esters were evaluated as plasticizers for PLA and starch. The effect of different additives on tensile properties, miscibility, surface chemistry and morphology were evaluated by Instron, DSC, FTIR, FTIR imaging and SEM. In the case of polylactide films the influence of additives on hydrolytic degradation rate and process was evaluated by following the weight loss, surface changes, compositional changes and/or water-soluble migrants and degradation products by FTIR, SEM, pyrolysis-GC-MS and ESI-MS. The most marked difference in mechanical properties was observed in the case of PLA modified with liquefied wood flour derived ester plasticizer (PWF). Addition of 10 and 30 weight-% plasticizer increased the strain at break from a few percent for pure PLA to over 100 and 300%, respectively. The liquefied rice bran based ester, however, did not form miscible blends with PLA and it did not function as plasticizer. In some cases the impact of additives on the following degradation process was significant. Depending on the used additive, they could either concentrate in the matrix during the hydrolysis of polylactide or they were rapidly released to the surrounding water. In some cases clear hydrolysis catalyzing effects were observed. Liquefied rice bran in combination with mineral fillers and/or traditional plasticizers seemed to have the best potential as starch plasticizer.

  • 260.
    Azwar, Edwin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Liquefied Wood Flour and Rice Bran as Polylactide AdditivesArtikel i tidskrift (Övrigt vetenskapligt)
  • 261.
    Azwar, Edwin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Tuning the mechanical properties of tapioca starch by plasticizers, inorganic and agro-waste derived fillers2012Ingår i: Polymer science, ISSN 0965-545X, Vol. 2012, nr Article ID 463298Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mechanical properties of tapioca starch-based films were tuned by different additives and additive combinations. The additives included plasticizers (glycerol, sorbitol, and citric acid), inorganic fillers (halloysite and kaolin), and agrowaste-based fillers (milled wood flour and rice bran). In addition, new biobased additives were prepared from wood flour and rice bran through liquefaction reaction. Through different additive combinations, starch-based materials with significant differences in tensile properties were designed. Addition of halloysite nanoclay resulted in materials with improved tensile strength at break and rather low strain at break. The effect of kaolin on tensile strength was highly dependent on the used plasticizer. However, in most combinations the addition of kaolin resulted in materials with intermediate tensile strength and strain at break values. The addition of milled wood flour and rice bran improved the tensile strength, while the addition of liquefied fillers especially liquefied rice bran increased the strain at break indicating that liquefied rice bran could have potential as a plasticizer for starch blends.

  • 262.
    Azwar, Edwin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Vuorinen, Eino
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Pyrolysis-GC-MS reveals important differences in hydrolytic degradation process of wood flour and rice bran filled polylactide composites2012Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, nr 3, s. 281-287Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pyrolysis-GC-MS of polylactide (PLA) biocomposites before and after hydrolytic degradation revealed prominent differences in the hydrolytic degradation process of rice bran and wood flour filled biocomposites. The water uptake and mass loss for polylactide/wood flour composites were similar to that of plain PLA. Pyrolysis-GC-MS, however, showed that on prolonged ageing the hydrolysis of PLA led to increased wood flour concentration in the remaining biocomposite matrices. In contrast, the polylactide/rice bran composites exhibited larger water uptake and higher mass loss. Pyrolysis-GC-MS and FTIR analysis proved that the higher mass loss was caused by migration of rice bran from the composites. The type of natural filler could thus greatly influence the degradation process and/or the stability of the materials in aqueous or humid environments.

  • 263.
    Azwar, Edwin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Yin, Bo
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Liquefied biomass derived plasticizer for polylactide2013Ingår i: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660, Vol. 88, nr 5, s. 897-903Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BACKGROUND: The valorization of renewable agro-industrial residues and their further utilization for production of polymers and polymer additives is a highly attractive alternative for replacement of oil-based materials. RESULTS: Liquefied wood flour and rice bran derived esters were synthesized and evaluated as novel green plasticizers for polylactide (PLA). The liquefied wood flour ester (PWF) showed good miscibility with PLA and good plasticization efficiency as shown by differential scanning calorimetry (DSC) and tensile testing. Tensile strain at break increased from a few percent for pure PLA to over 100 and 300% for the materials containing 10 and 30 wt-% of PWF. The addition of PWF accelerated the hydrolysis rate of PLA as shown by faster weight loss during aging in water and faster formation of water-soluble lactic acid oligomers, which was shown by electrospray ionization mass spectrometry (ESI-MS) analysis of the migrants. The liquefied rice bran based product (PRB) was not miscible with PLA and it did not improve the elongation at break of PLA. Rice bran is generally rich in arabinoxylans with only secondary less reactive alcohol groups. The larger number of un-reacted hydroxyl-groups in PRB was confirmed by Fourier transform infrared (FTIR) spectroscopy and could explain the immiscibility with PLA. CONCLUSIONS: The results demonstrate that the synthesized liquefied wood flour derived plasticizer could have great potential as a biobased polylactide plasticizer.

  • 264. Backa, Stefan
    et al.
    Ragnar, Martin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Pulp bleaching with peracetic acid generated from acetylated polymeric carbohydrates and hydrogen peroxide - Proof of principle2007Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 4, s. 409-414Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The generation of peracetic acid in the pulp mill may open up new opportunities to use this bleaching chemical. The generation of peracetic acid from acetylated carbohydrates and hydrogen peroxide followed by bleaching of pulp in a T stage was therefore studied with special emphasis on the COD content in the bleaching effluent from this stage. This preliminary work demonstrates that peracetic acid can be generated from acetylated polymeric carbohydrates and hydrogen peroxide, and that this peracetic acid will bleach pulp fibres as effectively as distilled peracetic acid. It is also shown that most of the deacetylated polymeric carbohydrate (in this case cationic starch) adsorbs to the fibre and does not affect the COD content of the filtrate after the T stage. The peracetic acid has been generated with and without pulp present. The peracetic acid yield from polymeric activators and hydrogen peroxide was lower than that from acetylated glucose. The peracetic acid yield can be further be optimised with respect to the acetylated polymer structure, process parameters and added peracetic acid stabilisers. No effect on the tensile strength was observed when cationic starch was used as an acetyl carrier in a TCF sequence with a final (PO) stage. Most of the cationic starch was probably removed in the washing after the (PO) stage pulp. To avoid this, the (PO) stage should be exchanged for a neutral or acidic bleaching stage or the cationic starch should be exchanged to a carbohydrate that better adsorbs to the fibre under alkaline conditions.

  • 265.
    Backman, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Björling, Gunilla
    Johansson, Unn-Britt
    Lysdahl, Michael
    Markström, Agneta
    Schedin, Ulla
    Aune, Ragnhild E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Frostell, Claes
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Material Wear of Polymeric Tracheostomy Tubes: A Six-Month Study2009Ingår i: The Laryngoscope, ISSN 0023-852X, E-ISSN 1531-4995, Vol. 119, nr 4, s. 657-664Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objectives: The objectives were to study long-term material wear of tracheostomy tubes made of silicone (Si), polyvinyl chloride (PVC), and polyurethane (PU) after 3 and 6 months of clinical use. Study Design: The study has a prospective and comparative design. Methods: Nineteen patients with long-term tracheostomy, attending the National Respiratory Center in Sweden, were included, n = 6 with Si tubes, n = 8 with PVC tubes, and n = 5 with PU tubes. The tubes were exposed to the local environment, in the trachea for 3 and 6 months and analyzed by scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and differential scanning calorimetry. Results: All tubes revealed severe surface changes. No significant differences were established after 3 or 6 months of exposure between the various materials. The changes had progressed significantly after this period, compared to previously reported changes after 30 days of exposure. The results from all analyzing techniques correlated well. Conclusions: All tubes, exposed in the trachea for 3-6 months, revealed major degradation and changes in the surface of the material. Polymeric tracheostomy tubes should be changed before the end of 3 months of clinical use.

  • 266. Backstrom, Marie
    et al.
    Jensen, Anna
    Brännvall, Elisabet
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Influence of chip presteaming conditions on kraft pulp composition and properties2016Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, nr 5, s. 393-399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Presteaming is a well-established technique in pulp mills, which improves cooking liquor impregnation by removing air from within and between chips. The aim of the study was to investigate how conditions during steaming affect the subsequent kraft cook and properties of the obtained pulp. It was found that higher pressure and temperature during chip presteaming led to increased degradation and dissolution of hemicelluloses. Lower refinability and tensile index was obtained for pulps cooked after presteaming at high pressure and for a long time.

  • 267.
    Backström, Eva
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Trash to Treasure: Microwave-Assisted Conversion of Polyethylene to Functional Chemicals2017Ingår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 56, nr 50, s. 14814-14821Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An effective microwave-assisted process for recycling low-density polyethylene (LDPE) waste into value-added chemicals was developed. To achieve fast and effective oxidative degradation aimed at production of dicarboxylic acids, nitric acid was utilized as an oxidizing agent. Different conditions were evaluated, where recycling time and concentration of oxidizing agent were varied and the end products were characterized by FTIR, NMR, and HPLC. After just 1 h of microwave irradiation at 180 degrees C in relatively dilute nitric acid solution (0.1 g/mL), LDPE powder was totally degraded. This transformation led to few well-defined water-soluble products, mainly succinic, glutaric, and adipic acids, as well as smaller amounts of longer dicarboxylic acids, acetic acid, and propionic acid. The length of the obtained dicarboxylic acids could to some extent be tuned by adjusting the reaction time, temperature, and amount of oxidizing agent. Finally, the developed process was verified by recycling LDPE freezer bags as model LDPE waste. The freezer bags were converted mainly into dicarboxylic acids with a yield of 71%, and the carbon efficiency of the process was 37%. The developed method can, thus, contribute to a circular economy and offers new possibilities to increase the value of plastic waste.

  • 268. Badia, J. D.
    et al.
    Kittikorn, Thorsak
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Santonja-Blasco, L.
    Martizez-Felipe, A.
    Ribes-Greus, A.
    Ek, Monica
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Water absorption and hydrothermal performance of PHBV/sisal biocomposites2014Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 108, s. 166-174Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The performance of biocomposites of poly(hydroxybutyrate-co-valerate) (PHBV) and sisal fibre subjected to hydrothermal tests at different temperatures above the glass transition of PHBV (T-H = 26, 36 and 46 degrees C) was evaluated in this study. The influences of both the fibre content and presence of coupling agent were focused. The water absorption capability and water diffusion rate were considered for a statistical factorial analysis. Afterwards, the physico-chemical properties of water-saturated biocomposites were assessed by Fourier-Transform Infrared Analysis, Size Exclusion Chromatography, Differential Scanning Calorimetry and Scanning Electron Microscopy. It was found that the water diffusion rate increased with both temperature and percentage of fibre, whereas the amount of absorbed water was only influenced by fibre content. The use of coupling agent was only relevant at the initial stages of the hydrothermal test, giving an increase in the diffusion rate. Although the chemical structure and thermal properties of water-saturated biocomposites remained practically intact, the physical performance was considerably affected, due to the swelling of fibres, which internally blew-up the PHBV matrix, provoking cracks and fibre detachment.

  • 269. Badia, J. D.
    et al.
    Reig-Rodrigo, P.
    Teruel-Juanes, R.
    Kittikorn, Thorsak
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. Prince of Songkla University, Thailand.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ribes-Greus, A.
    Effect of sisal and hydrothermal ageing on the dielectric behaviour of polylactide/sisal biocomposites2017Ingår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 149, s. 1-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dielectric properties of virgin polylactide (PLA) and its reinforced composites with different weight amounts of sisal fibres were assessed at broad temperature (from −130 °C to 130 °C) and frequency ranges (from 10−2–107 Hz), before and after being subjected to accelerated hydrothermal ageing. The synergetic effects of both the loading of sisal and hydrothermal ageing were analysed by means of dielectric relaxation spectra. The relaxation time functions were evaluated by the Havriliak-Negami model, substracting the ohmic contribution of conductivity. The intramolecular and intermolecular relaxations were respectively analysed by means of Arrhenius and Vogel-Fulcher-Tammann-Hesse thermal activation models. The addition of fibre increased the number of hydrogen bonds, which incremented the dielectric permittivity and mainly hindered the non-cooperative relaxations of the biocomposites by increasing the activation energy. Hydrothermal ageing enhanced the formation of the crystalline phase at the so-called transcrystalline region along sisal. This fact hindered the movement of the amorphous PLA fraction, and consequently decreased the dielectric permittivity and increased the dynamic fragility.

  • 270. Badia, J. D.
    et al.
    Strömberg, E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Ribes-Greus, A.
    Karlsson, S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    A statistical design of experiments for optimizing the MALDI-TOF-MS sample preparation of polymers. An application in the assessment of the thermo-mechanical degradation mechanisms of poly (ethylene terephthalate)2011Ingår i: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 692, nr 1-2, s. 85-95Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The sample preparation procedure for MALDI-TOF MS of polymers is addressed in this study by the application of a statistical Design of Experiments (DoE). Industrial poly (ethylene terephthalate) (PET) was chosen as model polymer. Different experimental settings (levels) for matrixes, analyte/matrix proportions and concentrations of cationization agent were considered. The quality parameters used for the analysis were signal-to-noise ratio and resolution. A closer inspection of the statistical results provided the study not only with the best combination of factors for the MALDI sample preparation, but also with a better understanding of the influence of the different factors, individually or in combination, to the signal. The application of DoE for the improvement of the MALDI measure of PET stated that the best combination of factors and levels was the following: matrix (dithranol), proportion analyte/matrix/cationization agent (1/15/1, V/V/V), and concentration of cationization agent (2 g L-1). In a second part, multiple processing by means of successive injection cycles was used to simulate the thermo-mechanical degradation effects on the oligomeric distribution of PET under mechanical recycling. The application of MALDI-TOF-MS showed that thermo-mechanical degradation primarily affected initially predominant cyclic species. Several degradation mechanisms were proposed, remarking intramolecular transesterification and hydrolysis. The ether links of the glycol unit in PET were shown to act as potential reaction sites, driving the main reactions of degradation.

  • 271. Badia, J. D.
    et al.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Kittikorn, Thorsak
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. Prince of Songkla University,Thailand.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Ribes-Greus, A.
    Relevant factors for the eco-design of polylactide/sisal biocomposites to control biodegradation in soil in an end-of-life scenario2017Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 143, s. 9-19Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The eco-design considers the factors to prepare biocomposites under an end-of-life scenario. PLA/sisal biocomposites were obtained from amorphous polylactide and sisal loadings of 10, 20 and 30 wt% with and without coupling agent, and subjected to biodegradation in soil according to standard ISO846. Mass-loss, differential scanning calorimetry and size-exclusion chromatography were used for monitoring biodegradation. A statistical factorial analysis based on the molar mass Mn and crystallinity degree XC pointed out the relevance and interaction of amount of fibre and use of coupling agent with the time of burial in soil. During the preparation of biocomposites, chain scission provoked a similar reduction of Mn for coupled and non-coupled biocomposites. The amount of fibre was relevant for the increase of XC due to the increase of nucleation sites. The coupling agent accelerated the evolution of both factors: reduction of Mn and the consequent increase of XC, mainly during biodegradation in soil. Both factors should be balanced to facilitate microbial assimilation of polymer segments, since bacterial digestion is enhanced by chain scission but blocked by the promotion of crystalline fractions.

  • 272. Badia, J. D.
    et al.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Ribes-Greus, A.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Assessing the MALDI-TOF MS sample preparation procedure to analyze the influence of thermo-oxidative ageing and thermo-mechanical degradation on poly (Lactide)2011Ingår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 47, nr 7, s. 1416-1428Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Multiple processing by means of successive injection cycles was used to simulate the thermo-mechanical degradation effects on the oligomeric distribution of PLA under mechanical recycling. Likewise, an accelerated thermal ageing over PLA glass transition was performed in order to simulate its service life. MALDI-TOF MS was used for the analysis and the sample preparation procedure was assessed by means of a statistical Design of Experiments (DoE). The quality effects in use for the analysis were signal-to-noise ratio and Resolution. Different matrixes, analyte/matrix proportions and the use of NaTFA as cationization agent were considered. A deep inspection of the statistical results provided a better understanding of the influence of the different factors, individually or in combination, to the signal. The application of DoE for the improvement of the MALDI measurement of PLA stated that the best combination of factors (levels) was the following: matrix (s-DHB), proportion analyte/matrix (1/5 V/V), and no use of cationization agent. Degradation primarily affected the initially predominant cyclic [LA(C)](n) and linear H-[LA(L)](n)-OH species, where LA stands for a PLA repeating unit. Intramolecular and intermolecular transesterifications as well as hydrolytic and homolytic reactions took place during the formation and disappearance of oligomeric species. In both degradation mechanisms induced by thermal ageing and thermo-mechanical degradation, the formation of H-[LA(L)](n)-O-CH(3) by intermolecular transesterifications was highlighted.

  • 273. Badia, J. D.
    et al.
    Vilaplana, Domingo Francisco Javier
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ribes-Greus, A.
    Thermal analysis as a quality tool for assessing the influence of thermo-mechanical degradation on recycled poly(ethylene terephthalate)2009Ingår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 28, nr 2, s. 169-175Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mechanical recycling of poly(ethylene terephthalate) (PET) was simulated by multiple processing to assess the effects of thermo-mechanical degradation, and characterized using rheological and thermal analysis techniques. Thermo-mechanical degradation under repeated extrusion induces chain scission reactions in PET, which result in a dramatic loss in the deformation capabilities and an increase in the fluidity of the polymer under reprocessing, reducing its recycling possibilities after four extrusion cycles. Multiple reprocessing severely affects the storage modulus and the microstructure of recycled PET, both in the amorphous and crystalline regions. Multimodal melting behavior is observed for reprocessed PET, indicating heterogeneous and segregated crystalline regions. A deconvolution procedure has been applied to individually characterize each crystalline population in terms of lamellar thickness distribution and partial crystallinity. Thermal analysis techniques such as differential scanning calorimetry (DSC) and dynamic-mechanical analysis (DMA) have proved to be suitable techniques for the quality assessment of recycled PET, giving unequivocal information about its degree of degradation compared to the common technological measurements of melt-mass flow rate (MFR) or oxidative stability (T-OX).

  • 274. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Ribes-Greus, A.
    Material valorisation of amorphous polylactide. Influence of thermo-mechanical degradation on the morphology, segmental dynamics, thermal and mechanical performance2012Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, nr 4, s. 670-678Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper reports the effects of multiple mechanical recycling on the structure and properties of amorphous polylactide (PIA). The influence of the thermo-mechanical degradation induced by means of five successive injection cycles was initially addressed in terms of macroscopic mechanical properties and surface modification. A deeper inspection on the structure and morphology of PLA was associated to the thermal properties and viscoelastic behaviour. Although FT-IR analysis did not show significant changes in functional groups, a remarkable reduction in molar mass was found by viscometry. PIA remained amorphous throughout the reprocessing cycles, but the occurrence of a cold-crystallization during DSC and DMTA measurements, which enthalpy increased with each reprocessing step, suggested chain scission due to thermo-mechanical degradation. The effect of chain shortening on the glass-rubber relaxation studied by DMTA showed an increase in free volume affecting the segmental dynamics of PLA, particularly after the application of the second reprocessing step, in connection to the overall loss of performance showed by the remaining properties.

  • 275. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Ribes-Greus, A
    The role of crystalline, mobile amorphous and rigid amorphous fractions on the performance of recycled poly (ethylene terephthalate) (PET)2012Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, nr 1, s. 98-107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The action of thermo-mechanical degradation induced by mechanical recycling of poly(ethylene terephthalate) was simulated by successive injection moulding cycles. Degradation reactions provoked chain scissions and a reduction in molar mass mainly driven by the reduction of diethyleneglycol to ethylene glycol units in the flexible domain of the PET backbone, and the formation ofeOH terminated species with shorter chain length. The consequent microstructural changes were quantified taking into account a three-fraction model involving crystalline, mobile amorphous (MAF) and rigid amorphous fractions (RAF). A remarkable increase of RAF, to a detriment of MAF was observed, while the percentage of crystalline fraction remained nearly constant. A deeper analysis of the melting behaviour, the segmental dynamics around the glass-rubber relaxation, and the macroscopic mechanical performance, showed the role of each fraction leading to a loss of thermal, viscoelastic and mechanical features, particularly remarkable after the first processing cycle.

  • 276. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Ribes-Greus, Amparo
    Characterization of Induced Thermo-mechanical Degradation on Poly (ethylene terephthalate)2011Konferensbidrag (Refereegranskat)
  • 277. Badia, J.D.
    et al.
    Strömberg, Emma
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Ribes-Greus, Amparo
    STUDY OF THERMO-MECHANICAL AND THERMO-OXIDATIVE DEGRADATION OF POLYLACTIDE BYMALDI-TOF MS. A STATISTICAL DESIGN OF EXPERIMENTS TO OPTIMIZE THE SAMPLE PREPARATIONPROCEDURES2011Konferensbidrag (Refereegranskat)
  • 278. Bamba, Yu
    et al.
    Ogawa, Yu
    Saito, Tsuguyuki
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Isogai, Akira
    Estimating the Strength of Single Chitin Nanofibrils via Sonication-Induced Fragmentation2017Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 18, nr 12, s. 4405-4410Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report the mechanical strength of native chitin nanofibrils. Highly crystalline alpha-chitiri nanofibrils Were purified from filaments produced by a microalgae Phaeocystis globosa, and two types of beta-chitin nariofibrils were purified from pens of a squid Loligo bleekeri and tubes of a tubeworm Lamellibrachia satsuma, with relatively low and high crystallinity, respectively. These chitin nanofibrils were fully dispersed in water. The strength of individualized nanofibrils was estimated using cavitation induced tensile fracture of nanoscale filaments in a liquid medium. Both types of beta-chitin nanofibrils exhibited similar strength values of approximately 3 GP; in contrast, the alpha-chitin nanofibrils exhibited a much lower strength value of 1.6 GPa. These strength estimates suggest that the tensile strength of chitin nanofibrils is governed by the molecular packing modes of chitin rather than their crystallinity.

  • 279.
    Banerjee, Indradumna
    et al.
    KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi.
    Salih, Tagrid
    KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi.
    Ramachandraiah, Harisha
    KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Erlandsson, Johan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Pettersson, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation. KTH, Tidigare Institutioner (före 2005), Kemi.
    Araújo, A. C.
    Karlsson, M.
    Russom, Aman
    KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Slipdisc: A versatile sample preparation platform for point of care diagnostics2017Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 7, nr 56, s. 35048-35054Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report a microfluidic sample preparation platform called "Slipdisc" based on slipchip technology. Slipdisc is a rotational slipchip that uses a unique hand-wound clockwork mechanism for precise movement of specially fabricated polycarbonate discs. In operation, the microchannels and microchambers carved on the closely aligned microfluidic discs convert from continuous filled paths to defined compartments using the slip movement. The clockwork mechanism introduced here is characterised by a food dye experiment and a conventional HRP TMB reaction before measuring lactate dehydrogenase (LDH) enzyme levels, which is a crucial biomarker for neonatal diagnostics. The colorimetry based detection of LDH was performed with an unmodified camera and an image analysis procedure based on normalising images and observing changes in red channel intensity. The analysis showed a close to unity coefficient of determination (R2 = 0.96) in detecting the LDH concentration when compared with a standard Chemical Analyser, demonstrating the excellent performance of the slipdisc platform with colorimetric detection. The versatile point of care sample preparation platform should ideally be suited for a multitude of applications at resource-limited settings.

  • 280. Banerjee, R.
    et al.
    Novak, J.
    Frank, C.
    Girleanu, M.
    Ersen, O.
    Brinkmann, M.
    Anger, F.
    Lorch, C.
    Dieterle, J.
    Gerlach, A.
    Drnec, J.
    Yu, Shun
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material. Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany .
    Schreiber, F.
    Structure and Morphology of Organic Semiconductor-Nanoparticle Hybrids Prepared by Soft Deposition2015Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, nr 9, s. 5225-5237Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present an extensive structural analysis of hybrid architectures prepared by the soft incorporation of gold nanoparticles (AuNPs) within an organic semiconductor matrix of diindenoperylene (DIP). Such soft or noninvasive deposition of nanoparticles within organic semiconducting host matrices not only minimizes the influence of the deposition process on the order and properties of the organic host molecules, but also offers additional control in the process of incorporation. The hybrid structures were characterized by X-ray scattering techniques including grazing incidence small angle X-ray scattering (GISAXS), grazing incidence X-ray diffraction (GIXD), X-ray reflectivity (XRR), and complemented by atomic force microscopy (AFM), photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM) measurements. We show that different strategies of incorporating the nanoparticles in the host matrix lead to drastically different structure and morphologies. Particularly remarkable is the morphological change observed in the matrix of DIP as well as the AuNPs due to the influence of organic solvents, as evidenced by TEM tomography measurements, which revealed the exact location of the AuNPs within the organic host. It is also demonstrated that AuNPs can be successfully used as tunable templates for the growth of the organic semiconductors with desired island sizes and distances.

  • 281. Bannow, J.
    et al.
    Benjamins, J. -W
    Wohlert, Jakob
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Löbmann, K.
    Svagan, Anna J.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Solid nanofoams based on cellulose nanofibers and indomethacin—the effect of processing parameters and drug content on material structure2017Ingår i: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 526, nr 1-2, s. 291-299Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The unique colloidal properties of cellulose nanofibers (CNF), makes CNF a very interesting new excipient in pharmaceutical formulations, as CNF in combination with some poorly-soluble drugs can create nanofoams with closed cells. Previous nanofoams, created with the model drug indomethacin, demonstrated a prolonged release compared to films, owing to the tortuous diffusion path that the drug needs to take around the intact air-bubbles. However, the nanofoam was only obtained at a relatively low drug content of 21 wt% using fixed processing parameters. Herein, the effect of indomethacin content and processing parameters on the foaming properties was analysed. Results demonstrate that a certain amount of dissolved drug is needed to stabilize air-bubbles. At the same time, larger fractions of dissolved drug promote coarsening/collapse of the wet foam. The pendant drop/bubble profile tensiometry was used to verify the wet-foam stability at different pHs. The pH influenced the amount of solubilized drug and the processing-window was very narrow at high drug loadings. The results were compared to real foaming-experiments and solid state analysis of the final cellular solids. The parameters were assembled into a processing chart, highlighting the importance of the right combination of processing parameters (pH and time-point of pH adjustment) in order to successfully prepare cellular solid materials with up to 46 wt% drug loading.

  • 282. Bartaula-Brevik, Sushma
    et al.
    Pedersen, Torbjorn O.
    Blois, Anna L.
    Papadakou, Panagiota
    Finne-Wistrand, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Xue, Ying
    Bolstad, Anne Isine
    Mustafa, Kamal
    Leukocyte transmigration into tissue-engineered constructs is influenced by endothelial cells through Toll-like receptor signaling2014Ingår i: Stem Cell Research & Therapy, E-ISSN 1757-6512, Vol. 5, s. 143-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Introduction: Inflammation plays a crucial role in tissue regeneration, wound healing, and the success of tissue-engineered constructs. The aim of this study was to investigate the influence of human umbilical vein endothelial cells (ECs) on leukocyte transmigration when co-cultured with primary human bone marrow-derived multipotent stromal cells (MSCs). Methods: MSCs with and without ECs were cultured in poly (L-lactide-co-1, 5-dioxepan-2-one) (poly (LLA-co-DXO)) scaffolds for 1 week in vitro in a bioreactor system, after which they were implanted subcutaneously in non-obese diabetic/severe combined immunodeficient mice. After 1 and 3 weeks, scaffolds were retrieved, and the mRNA expression of interleukin 1-beta (IL-1 beta), IL-6, IL-10, hypoxia-inducible factor 1-alpha (HIF-1 alpha), HIF-1 beta, and mammalian target of rapamycin was examined by real-time reverse transcription-polymerase chain reaction. Furthermore, immunofluorescent staining was performed for IL-1 beta, IL-6, neutrophils, and CD11b. In addition, Western blotting was done for IL-1 beta and IL-6. Leukocyte transmigration genes and genes in Toll-like receptor pathways, expressed by MSCs cultured in vitro with or without ECs, were further investigated with a microarray dataset. Results: In vitro, genes involved in leukocyte transmigration and Toll-like receptor pathways were clearly influenced by the addition of ECs. Platelet/endothelial cell adhesion molecule-1 (PECAM-1) and cadherin-5 (CDH5), both genes involved in leukocyte transmigration, were expressed significantly higher in the MSC/EC group. In vivo, the MSC/EC group showed higher mRNA expression of hypoxia-inducible factors HIF-1 alpha and HIF-1 beta. The mRNA expression of anti-inflammatory cytokine IL-10 showed no significant difference, whereas the mRNA and protein expression of pro-inflammatory cytokines IL-1 beta and IL-6 were lower in the MSC/EC group. The quantitative analysis of immunofluorescent staining revealed a significant difference in the number of neutrophils migrating into constructs, with the highest density found in the MSC/EC group. The number of macrophages positive for IL-6 and CD11b was significantly reduced in the MSC/EC group. Conclusions: The recruitment of leukocytes into tissue-engineered constructs with MSCs is strongly influenced by the addition of ECs via activation of leukocyte transmigration and Toll-like receptor pathways.

  • 283. Bartaula-Brevik, Sushma
    et al.
    Pedersen, Torbjorn O.
    Finne-Wistrand, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Bolstad, Anne Isine
    Mustafa, Kamal
    Angiogenic and Immunomodulatory Properties of Endothelial and Mesenchymal Stem Cells2016Ingår i: Tissue Engineering. Part A, ISSN 1937-3341, E-ISSN 1937-335X, Vol. 22, nr 3-4, s. 244-252Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It has been suggested that the effect of implanted cells on the local environment is important when selecting the appropriate cell type for tissue regeneration. Our aim was to compare the local tissue response to implanted human mesenchymal stem cells (MSC) and human umbilical vein endothelial cells (EC). MSC and EC were cultured in poly(l-lactide-co-1,5-dioxepan-2-one) scaffolds for 1 week in a bioreactor system, after which they were implanted subcutaneously in NOD/SCID mice. After 3 weeks, scaffolds were retrieved, and the mRNA expression of selected genes involved in hypoxia and inflammation was examined by real-time reverse transcription polymerase chain reaction and correlated with immunofluorescent staining for corresponding proteins. The Toll-like receptor signaling pathway was examined by superarray hybridization. The expression of 53 angiogenesis-related proteins was investigated by a proteome profiler angiogenesis antibody array kit. Vascularization was quantified using immunohistochemistry for CD31. The expression of hypoxia-inducible factors and biomarkers for angiogenesis was more strongly upregulated in response to implanted EC than to MSC, suggesting a higher sensitivity to low oxygen tension among EC. Hypoxic signaling was increased after implantation of EC compared with MSC, leading to a prolonged acute inflammatory phase that promoted ingrowth of vascular cells and establishment of the circulation. Inflammatory cytokines were also differently expressed at the gene and protein levels in the two experimental groups, resulting in altered recruitment of acute and chronic inflammatory cells. The end result of these differences was increased vessel formation within the constructs in the EC group.

  • 284. Battegazzore, Daniele
    et al.
    Alongi, Jenny
    Frache, Alberto
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Carosio, Federico
    Layer by Layer-functionalized rice husk particles: A novel and sustainable solution for particleboard production2017Ingår i: Materials Today Communications, ISSN 2352-4928, Vol. 13, s. 92-101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rice husk particles from agro-wastes have been treated with a Layer by Layer (LbL) deposition of polyelectrolytes and further assembled to prepare a bio-based particle board. The all polymer system employed uses a branched polyethyleneimine combined with a polyacrylic acid. The two polyelectrolytes show a super-linear growth as demonstrated by infrared spectroscopy. A schematic description of the mechanism behind the LbL deposition on rice husk particles is proposed and discussed on the basis of electron microscopy observations. The mechanical properties of the prepared LbL-joined particle boards are evaluated and related to the unique structure and intermolecular ionic interaction occurring between the assembled polyelectrolytes. Only 2 BLs allow for the preparation of a free-standing/self-supporting material. Boards assembled with 3 and 4 BL-coated particles yielded impressive storage moduli of 1.7 and 2.2 GPa, respectively, as measured by dynamic mechanical analyses performed at different temperatures and relative humidities. When tested by three points bending mechanical tests the same materials showed an elastic moduli up to 3.2 GPa and a tensile strengths up to 12 MPa. The presented results demonstrate that the LbL functionalization of agro-waste particles represents an attractive, functional and sustainable solution for the production of mechanically strong particleboards.

  • 285. Baumberger, Stephanie
    et al.
    Abaecherli, Alfred
    Fasching, Mario
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gosselink, Richard
    Hortling, Bo
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Saake, Bodo
    de Jong, Ed
    Molar mass determination of lignins by size-exclusion chromatography: towards standardisation of the method2007Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 61, nr 4, s. 459-468Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The reactivity and physicochemical properties of lignins are partly governed by their molar mass distribution. The development of reliable standard methods for determination of the molar mass distribution is not only relevant for designing technical lignins for specific applications, but also for monitoring and elucidating delignification and pulping processes. Size-exclusion chromatography (SEC) offers many advantages, such as wide availability, short analysis time, low sample demand, and determination of molar mass distribution over a wide range. A collaborative study has been undertaken within the Eurolignin European thematic network to standardise SEC analysis of technical lignins. The high-molar-mass fraction of polydisperse lignins was shown to be the main source of intra- and interlaboratory variations, depending on the gel type, elution solvent, detection mode, and calculation strategy. The reliability of two widespread systems have been tested: one based on alkali and a hydrophilic gel (e.g., TSK Toyopearl gel) and the other based on THF as solvent and polystyrene-based gels (e.g., Styragel). A set of practical recommendations has been deduced.

  • 286. Bayley, G. M.
    et al.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Mallon, P. E.
    Large strain and toughness enhancement of poly(dimethyl siloxane) composite films filled with electrospun polyacrylonitrile-graft-poly(dimethyl siloxane) fibres and multi-walled carbon nanotubes2011Ingår i: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 52, nr 18, s. 4061-4072Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Unfilled cross-linked poly(dimethyl siloxane) (PDMS) is a weak material and is generally filled with high levels of particulate fillers such as silica, calcium carbonate and carbon black to improve its mechanical properties. The use of fibrous fillers such as electrospun nanofibres and multi-walled carbon nanotubes as fillers for PDMS has not been widely studied. In this study anew copolymer, polyacrylonitrile-graft-poly(dimethyl siloxane) (PAN-g-PDMS), is used as fibrous filler for PDMS. The graft copolymer is electrospun to produce the fibre filler material. It is shown how the PDMS content of the graft copolymer provides increased compatibility with silicone matrices and excellent dispersion of the fibre fillers throughout a silicone matrix. It is also shown that it is possible to include multi-walled carbon nanotubes in the electrospun fibres which are subsequently dispersed in the PDMS matrix. Fibre mats were used in the non-woven and the aligned forms. The differently prepared fibre composites have significantly different mechanical properties. Conventional composites using fibrous fillers usually show increased strength and stiffness but usually with a resultant loss of strain. In the case of the composites produced in this study there is a dramatic improvement in the extensibility of the non-woven PAN-g-PDMS fibre mat filled silicone films of up to 470%.

  • 287. Bellier, Q.
    et al.
    Bouit, P. -A
    Kamada, K.
    Feneyrou, P.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Maury, O.
    Andraud, C.
    Design of near-infrared dyes for nonlinear optics: Towards optical limiting applications at telecommunication wavelengths2009Ingår i: Optical Materials in Defence Systems Technology VI, SPIE - International Society for Optical Engineering, 2009, s. 74870G-Konferensbidrag (Refereegranskat)
    Abstract [en]

    The rapid development of frequency-tunable pulsed lasers up to telecommunication wavelengths (1400-1600 nm) led to the design of new materials for nonlinear absorption in this spectral range. In this context, two families of near infra-red (NIR) chromophores, namely heptamethine cyanine and aza-borondipyrromethene (aza-bodipy) dyes were studied. In both cases, they show significant two-photon absorption (TPA) cross-sections in the 1400-1600 nm spectral range and display good optical power limiting (OPL) properties. OPL curves were interpreted on the basis of TPA followed by excited state absorption (ESA) phenomena. Finally these systems have several relevant properties like nonlinear absorption properties, gram scale synthesis and high solubility. In addition, they could be functionalized on several sites which open the way to numerous practical applications in biology, solid-state optical limiting and signal processing.

  • 288. Bengtsson, M.
    et al.
    Wallström, Stina
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gronlund, R.
    Anderson, B.
    Sjoholm, M.
    Larsson, A.
    Kroll, S.
    Svanberg, S.
    Development of a tool for remote detection of fungi and algae on electrical insulators using laser induced fluorescence combined with principal component analysis2005Ingår i: Conference on Lasers and Electro-Optics Europe - Technical Digest, 2005, s. 427-Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study a combination of laser induced fluorescence (LIF) and principal component analysis (PCA) is used in an attempt to develop a method to detect fungal growth on silicone rubber. Field experiments on aged insulators have been carried out to test whether LIF combined with PCA can give useful information about the fungal growth.

  • 289. Bengtsson, M.
    et al.
    Wallström, Stina
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Svanberg, S.
    Fluorescence lidar imaging of fungal growth on high-voltage outdoor composite insulators2005Ingår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 43, nr 6, s. 624-632Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Remote fluorescence imaging of fungal growth on polymeric high-voltage insulators was performed using a mobile lidar system with a laser wavelength of 355 nm. Insulator areas contaminated by fungal growth could be distinguished from clean surfaces and readily be imaged. The experiments were supported by detailed spectral studies performed in laboratory using a fibre-optic fluorosensor incorporating an optical multi-channel analyser system (OMA) and a nitrogen laser emitting radiation at 33 7 nm.

  • 290. Bengtsson, M.
    et al.
    Wallström, Stina
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Sjöholm, M.
    Grönlund, R.
    Anderson, B.
    Larsson, A.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Kröll, Stefan
    Svanberg, S.
    Fungus covered insulator materials studied with laser-induced fluorescence and principal component analysis2005Ingår i: Applied Spectroscopy, ISSN 0003-7028, E-ISSN 1943-3530, Vol. 59, nr 8, s. 1037-1041Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method combining laser-induced fluorescence and principal component analysis to detect and discriminate between algal and fungal growth on insulator materials has been studied. Eight fungal cultures and four insulator materials have been analyzed. Multivariate classifications were utilized to characterize the insulator material, and fungal growth could readily be distinguished from a clean surface. The results of the principal component analyses make it possible to distinguish between algae infected, fungi infected, and clean silicone rubber materials. The experiments were performed in the laboratory using a fiber-optic fluorosensor that consisted of a nitrogen laser and an optical multi-channel analyzer system.

  • 291.
    Benselfelt, Tobias
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Cranston, Emily D.
    Department of Chemical Engineering, McMaster University.
    Ondaral, Sedat
    Department of Pulp and Paper Technology, Karadeniz Technical University.
    Johansson, Erik
    Cellutech AB.
    Brumer, Harry
    The Michael Smith Laboratories and the Department of Chemistry, The University of British Columbia.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Adsorption of Xyloglucan onto Cellulose Surfaces of Different Morphologies: An Entropy-Driven Process2016Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, nr 9, s. 2801-2811Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The temperature-dependence of xyloglucan (XG) adsorption onto smooth cellulose model films regenerated from N-methylmorpholine N-oxide (NMMO) was investigated using surface plasmon resonance spectroscopy, and it was found that the adsorbed amount increased with increasing temperature. This implies that the adsorption of XG to NMMO-regenerated cellulose is endothermic and supports the hypothesis that the adsorption of XG onto cellulose is an entropy-driven process. We suggest that XG adsorption is mainly driven by the release of water molecules from the highly hydrated cellulose surfaces and from the XG molecules, rather than through hydrogen bonding and van der Waals forces as previously suggested. To test this hypothesis, the adsorption of XG onto cellulose was studied using cellulose films with different morphologies prepared from cellulose nanocrystals (CNC), semicrystalline NMMO-regenerated cellulose, and amorphous cellulose regenerated from lithium chloride/dimethylacetamide. The total amount of high molecular weight xyloglucan (XGHMW) adsorbed was studied by quartz crystal microbalance and reflectometry measurements, and it was found that the adsorption was greatest on the amorphous cellulose followed by the CNC and NMMO-regenerated cellulose films. There was a significant correlation between the cellulose dry film thickness and the adsorbed XG amount, indicating that XG penetrated into the films. There was also a correlation between the swelling of the films and the adsorbed amounts and conformation of XG, which further strengthened the conclusion that the water content and the subsequent release of the water upon adsorption are important components of the adsorption process.

  • 292.
    Benselfelt, Tobias
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Henschen, Jonatan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pettersson, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Polyelectrolyte multilayers on differently charged cellulose surfaces2016Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 251Artikel i tidskrift (Övrigt vetenskapligt)
  • 293.
    Benselfelt, Tobias
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Pettersson, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Influence of Surface Charge Density and Morphology on the Formation of Polyelectrolyte Multilayers on Smooth Charged Cellulose Surfaces2017Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 33, nr 4, s. 968-979Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To clarify the importance of the surface charge for the formation of polyelectrolyte multilayers, layer-by-layer (LbL) assemblies of polydiallyldimethylammonium chloride (pDADMAC) and polystyrenesulfonate (PSS) have been investigated on cellulose films with different carboxylic acid contents (20, 350, 870, and 1200 μmol/g) regenerated from oxidized cellulose. The wet cellulose films were thoroughly characterized prior to multilayer deposition using quantitative nanomechanical mapping (QNM), which showed that the mechanical properties were greatly affected by the degree of oxidation of the cellulose. Atomic force microscopy (AFM) force measurements were used to determine the surface potential of the cellulose films by fitting the force data to the DLVO theory. With the exception of the 1200 μmol/g film, the force measurements showed a second-order polynomial increase in surface potential with increasing degree of oxidation. The low surface potential for the 1200 μmol/g film was attributed to the low degree of regeneration of the cellulose film in aqueous media due to increasing solubility with increasing charge. The multilayer formation was characterized using a quartz crystal microbalance with dissipation (QCM-D) and stagnation-point adsorption reflectometry (SPAR). Extensive deswelling was observed for the charged films when pDADMAC was adsorbed due to the reduced osmotic pressure when ions inside the film were released, and the 1:1 charge compensation showed that all the charges in the films were reached by the pDADMAC. The multilayer formation was not significantly affected by the charge density above 350 μmol/g due to interlayer repulsions, but it was strongly affected by the salt concentration during the layer build-up.

  • 294.
    Benyahia Erdal, Nejla
    et al.
    KTH, Skolan för kemivetenskap (CHE). Royal Inst Technol, Sch Chem Sci & Engn, Stockholm, Sweden..
    Adolfsson, Karin H.
    KTH, Skolan för kemivetenskap (CHE). Sch Chem Sci & Engn, Stockholm, Sweden..
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. Royal Inst Technol, Stockholm, Sweden..
    Silicone-hydrogel bandage lenses used in conjunction with pharmaceutical eye drops: An uptake and release study2016Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 251Artikel i tidskrift (Övrigt vetenskapligt)
  • 295.
    Benyahia Erdal, Nejla
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymerteknologi.
    Adolfsson, Karin H.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pettersson, Torbjörn
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Green Strategy to Reduced Nanographene Oxide through Microwave Assisted Transformation of Cellulose2018Ingår i: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 6, nr 1, s. 1245-1255Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A green strategy for fabrication of biobased reduced nanographene oxide (r-nGO) was developed. Cellulose derived nanographene oxide (nGO) type carbon nanodots were reduced by microwave assisted hydrothermal treatment with superheated water alone or in the presence of caffeic acid (CA), a green reducing agent. The carbon nanodots, r-nGO and r-nGO-CA, obtained through the two different reaction routes without or with the added reducing agent, were characterized by multiple analytical techniques including FTIR, XPS, Raman, XRD, TGA, TEM, AFM, UV-vis, and DLS to confirm and evaluate the efficiency of the reduction reactions. A significant decrease in oxygen content accompanied by increased number of sp2 hybridized functional groups was confirmed in both cases. The synergistic effect of superheated water and reducing agent resulted in the highest C/O ratio and thermal stability, which also supported a more efficient reduction. Interesting optical properties were detected by fluorescence spectroscopy where nGO, r-nGO, and r-nGO-CA all displayed excitation dependent fluorescence behavior. r-nGO-CA and its precursor nGO were evaluated toward osteoblastic cells MG-63 and exhibited nontoxic behavior up to 200 μg mL-1, which gives promise for utilization in biomedical applications.

  • 296.
    Bergenstrahle, Malin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Mazeau, Karim
    CNRS, Ctr Rech Macromol Vegetales, F-38041 Grenoble, France..
    CARB 18-Thermal response in crystalline cellulose: A molecular dynamics study2008Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 235Artikel i tidskrift (Övrigt vetenskapligt)
  • 297.
    Bergenstrahle-Wohlert, Malin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    d'Ortoli, Thibault Angles
    Sjoberg, Nils A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Widmalm, Goran
    Wohlert, Jakob
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    On the anomalous temperature dependence of cellulose aqueous solubility2016Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, nr 4, s. 2375-2387Artikel i tidskrift (Refereegranskat)
  • 298.
    Bergenstrahle-Wohlert, Malin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Wohlert, Jakob
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Vibrational spectrum of the cellulose-water interface investigated by atomistic simulations2014Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, s. 190-CELL-Artikel i tidskrift (Övrigt vetenskapligt)
  • 299.
    Bergenstråhle, Malin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Crystalline cellulose in bulk and at interfaces as studied by atomistic computer simulations2008Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Cellulosa förstärker cellväggen i växter i form av nanostrukturerade och mycketstarka fibriller. För utvecklingen av nya cellulosamaterial från dessa fibriller ären förståelse för cellulosans struktur och egenskaper viktig. Syftet med dennaavhandling är att med hjälp av en atomistisk modell och molekyldynamiskadatorsimuleringar (MD) öka kunskapen om cellulosa på atomär nivå.En atomistisk modell av kristallin cellulosa Iβ utvecklades och simuleradesmed simuleringsprogrampaketet GROMACS.Temperaturberoendet hos kristallin cellulosa i bulk undersöktes. Mellan350 K och 500 K skedde en gradvis kristallin strukturomvandling. Vid högre temperaturhade cellulosan annorlunda kristall-enhetscellsparametrar, vätebindingsmönsteroch elastisk modul jämfört med orginalstrukturen.Systemet cellulosa-vatten har stor praktisk betydelse. Spinn-gitter-relaxationstiderT1 beräknades därför från dynamiken hos C4-H4-vektorn i MD-simuleringaroch jämfördes med värden uppmätta med fastfas-NMR. De beräknadevärdena stämde väl överens med de experimentella och dynamiken vid ytan kanantas vara välreproducerad i modellen. Dessutom kunde en skillnad i T1 meden faktor 2 för C4-atomer på ytkedjor vid olika kristallografiska plan påvisas.Simuleringsresultaten stödjer därmed en tidigare föreslagen förklaring till endubblett för C4-atomer i cellulosans NMR-spektrum.Växelverkansenergier mellan cellulosa och polymeren PCL är intressant förnanokompositmaterial. Därför bestämdes växelverkansenergier mellan kristallincellulosa och vatten och cellulosa och 6-hydroxyhexanal (CL). Växelverkan mellancellulosa med vatten visade sig vara större än mellan cellulosa och CL.Ympning av CL-molekyler på cellulosaytan ledde till ökad växelverkan för såvälgränsytor mot vatten som mot CL. Elektrostatisk växelverkan dominerade vidsamtliga gränsytor, även om CL-ympning orsakade ökad andel av van der Waalskrafter.Polymerdesorption kan undersökas med hjälp av atomkraftmikroskopi (AFM).Ett simulerat experiment med MD utfördes därför genom att en cellulosaoktamerdrogs från en cellulosayta in i vatten eller cyklohexan. Det krävdes avsevärtmindre energi att dra loss oktameren i cyklohexan (300−400 kJ/mol) jämförtmed vatten (100 − 200 kJ/mol). Resultaten analyserades i termer av specifikväxelverkan mellan cellulosaoktameren och identifierbara kemiska grupper påcellulosaytan.MD har stor potential att öka förståelsen för cellulosa på molekylär nivå.MD-simuleringar kan inspirera experimentella mätningar genom upptäckter avnya fenomen. MD kan dessutom tillföra nya aspekter vid analys av experimentellaresultat. Det har i avhandlingen demonstrerats för metoder som NMR,AFM, mekanisk provning och mätning av termisk utvidgning

  • 300.
    Bergenstråhle, Malin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Mazeau, Karim
    CERMAV-CNRS .
    Thermal Response in Crystalline Iβ Cellulose: A Molecular Dynamics Study2007Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 111, nr 30, s. 9138-9145Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of temperature on structure and properties of the cellulose Iβ crystal was studied by molecular dynamics simulations with the GROMOS 45a4 force-field. At 300 K, the modeled crystal agreed reasonably with several sets of experimental data, including crystal density, corresponding packing and crystal unit cell dimensions, chain conformation parameters, hydrogen bonds, Young's modulus, and thermal expansion coefficient at room temperature. At high-temperature (500 K), the cellulose chains remained in sheets, despite differences in the fine details compared to the room-temperature structure. The density decreased while the a and b cell parameters expanded by 7.4% and 6%, respectively, and the c parameter (chain axis) slightly contracted by 0.5%. Cell angles α and β divided into two populations. The hydroxymethyl groups mainly adopted the gt orientation, and the hydrogen-bonding pattern thereby changed. One intrachain hydrogen bond, O2'H2'···O6, disappeared and consequently the Young's modulus decreased by 25%. A transition pathway between the low- and high-temperature structures has been proposed, with an initial step being an increased intersheet separation, which allowed every second cellulose chain to rotate around its helix axis by about 30°. Second, all hydroxymethyl groups changed their orientations, from tg to gg (rotated chains) and from tg to gt (non-rotated chains). When temperature was further increased, the rotated chains returned to their original orientation and their hydroxymethyl groups again changed their conformation, from gg to gt. A transition temperature of about 450 K was suggested; however, the transition seems to be more gradual than sudden. The simulated data on temperature-induced changes in crystal unit cell dimensions and the hydrogen-bonding pattern also compared well with experimental results.

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