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  • 101.
    Bergström, L. Magnus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Aratono, Makoto
    Synergistic effects in mixtures of two identically charged ionic surfactants with different critical micelle concentrations2011Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, nr 19, s. 8870-8879Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Expressions for the critical micelle concentration (cmc) and activity coefficients as functions of surfactant composition in mixtures of two identically charged monovalent ionic surfactants are derived from the nonlinear Poisson-Boltzmann (PB) theory. For the special case of no added salt, the simple expression cmc(alpha) = xcmc(1)(alpha) + (1 - x)cmc(2)(alpha) is deduced, where the exponential parameter alpha > 1 depends on the number of ionic species in a surfactant molecule as well as the curvature of the self-assembled interface. Theoretical predictions are compared with cmc values obtained with some different experimental techniques for mixtures of the two cationic surfactants didodecyldimethylammonium bromide (DDAB) and dodecyltrimethylammonium bromide (DTAB) in water and in the absence of added salt. It is demonstrated that the PB theory generates significantly better agreement with experimental data than predicted by ideal behaviour or the regular mixture theory. We find that maximum synergistic effects occur at a DDAB mole fraction in solution y = 0.005. According to the PB theory, this very low value of y corresponds to a mole fraction of DDAB in the self-assembled interfacial aggregates equal to x = 0.995. Moreover, our calculations of the surfactant composition in the self-assembled interfacial aggregates above cmc demonstrate that the transition from small micelles to large bilayer aggregates is found to consistently occur at a mole fraction of DDAB equal to about x = 0.41-0.42, irrespective of the surfactant molar ratio in solution. Experimental observations strongly support the fact that concentrations of free surfactant, as well as the surfactant composition in the self-assembled interfacial aggregates, may be accurately calculated from the non-linear Poison-Boltzmann theory. On the other hand, a micelle-to-bilayer transition induced by changes in surfactant mole fraction in the self-assembled interfacial aggregates is consistent with neither ideal surfactant behaviour nor synergistic behaviour according to the regular mixture theory.

  • 102.
    Bi, Ran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lignocellulose Degradation by Soil Micro-organisms2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lignocellulosic biomass is a sustainable resource with abundant reserves. Compared to petroleum ‐ based products, the biomass ‐ derived polymers and chemicals give better environmental profiles. A lot of research interest is focused on understanding the lignocellulose structures.

    Lignin, among the three major wood components, represents most difficulty for microbial degradation because of its complex structure and because cross ‐ linking to hemicellulose makes wood such a compact structure. Nevertheless, wood is naturally degraded by wood ‐ degrading micro ‐ organisms and modified and partly degraded residual of lignin goes into soil. Therefore soil serves as a good environment in which to search for special lignin ‐ degraders. In this thesis, different types of lignin have been used as sole carbon sources to screen for lignin ‐ degrading soil micro ‐ organisms. Eleven aerobic and three anaerobic microbe strains have been isolated and identified as able to grow on lignin. The lignin degradation patterns of selected strains have been studied and these partly include an endwise cleavage of  β‐ O ‐ 4 bonds in lignin and is more complex than simple hydrolytic degradation.

    As lignin exists in wood covalently bonded to hemicellulose, one isolated microbe strain, Phoma herbarum, has also been studied with regards to its ability to degrade covalent lignin polysaccharide networks (LCC). The results show that its culture filtrate can attack lignin ‐ polysaccharide networks in a manner different from that of the commercial enzyme product, Gammanase, possibly by selective cleavage of phenyl glucoside bonds. The effects on LCC of Phoma herbarum also enhance polymer extractability. Hot ‐ water extraction of a culture filtrate of Phoma herbarum ‐ treated fiberized spruce wood material gave an amount of extracted galactoglucomannan more than that given by the Gammanase ‐ treated material and non ‐ enzyme ‐ treated material.

    Over millions of years of natural evolution, micro ‐ organisms on the one hand develop so that they can degrade all wood components to get energy for growth, while plants on the other hand also continuously develop to defend from microbial attack. Compared with lignin and cellulose, hemicelluloses as major components of plant cell walls, are much more easily degraded, but hemicelluloses differ from cellulose in that they are acetylated to different extents. The biological functions of acetylation are not completely understood, but it is suggested is that one function is to decrease the microbial degradability of cell walls. By cultivation of soil micro ‐ organisms using mannans acetylated to deffernent degrees as sole carbon source on agar plates, we were able to see significant trends where the resistance towards microbial degradation of glucomannan and galactomannan increased with increasing degree of acetylation. Possible mechanisms and the technological significance of this are discussed. Tailoring the degree of acetylation of polysaccharide materials might slow down the biodegradation, making it possible to design a material with a degradation rate suited to its application.

  • 103.
    Bi, Ran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Azhar, Shoaib
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Mckee, Lauren
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Culture Filtrates from a Soil Organism Enhances Extractability of Polymers from Fiberised Spruce WoodManuskript (preprint) (Annet vitenskapelig)
  • 104.
    Bi, Ran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Jennie
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Vilaplana, Francisco
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    McKee, Lauren
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    The Degree Of Acetylation Affects The Microbial Degradability Of HemicellulosesManuskript (preprint) (Annet vitenskapelig)
  • 105.
    Bi, Ran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Huang, Shan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. Linnaus University, Sweden.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Isolation of exceedingly low oxygen consuming fungal strains able to utilize lignin as carbon sourceInngår i: Cellulose Chemistry and Technology, ISSN 0576-9787Artikkel i tidsskrift (Fagfellevurdert)
  • 106.
    Bi, Ran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lawoko, Martin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Phoma herbarum, a soil fungus able to grow on natural lignin and synthetic lignin (DHP) as sole carbon source and cause lignin degradationManuskript (preprint) (Annet vitenskapelig)
  • 107.
    Bi, Ran
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Oinonen, Petri
    Ecohelix AB, Teknikringen 38, 10044 Stockholm, Sweden.
    Wang, Yan
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    A Method for Studying Effects on Lignin-Polysaccharide Networks during Biological Degradation and Technical Processes of Wood2016Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, nr 1, s. 1307-1318Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Woody tissues consist primarily of a mixture of cellulose, hemicelluloses, and lignin. Covalent bonds between lignin and polysaccharides likely play a central role in determining the mechanical and physical properties of wood. Intact and defined lignin-polysaccharide networks have not been isolated in large quantities because of the recalcitrance of lignin, which demands harsh chemical treatments that alter its structure. This report presents a method for preparing large quantities of lignin-polysaccharide networks similar to those naturally present in wood based on the enzymatic oxidation of hemicellulose from Norway spruce. Fungal enzymes produced from various carbon sources were used to depolymerize these networks. The method was used for simulating "enzyme mining" - a concept in biorefineries, giving a possible explanation for its mechanisms.

  • 108.
    Bladholm, Viktor
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Organic Fillers for Solid Rocket Fuel2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Idag är de vanligaste använda raketerna flytande-bränsle- och fast-bränsle- raketer. Flytande-bränsle-raketer har fördelen att det kan manövreras men de har en komplex design och problem med förvaring. Fast-bränsle-raketer har en enkel design och kan förvaras men de har en miljöpåverkan och bränslet kan vara svårhanterligt. En tredje typ av raketer, hybridraketer, kan kombinera enkelheten från fasta-bränsle-raketer med manövreringsbarheten från vätske-bränsle-raketer. Trots fördelarna med hybridraketer används de inte på grund av att bränslet har låg regressionshastighet och låg densitet. Organiska additiv har visat sig förbättra dessa egenskaper. 50 organiska additiv granskades med avseende på deras specifika impuls, densitet, kostnad och användarvänlighet. De mest lovande organiska additiven utvärderades sedan experimentellt. Termogravimetrisk analys (TGA), isotermviktförlust, kompatibilitet och differentiell svepkalorimetri (DSC) användes. Resultaten indikerar att hexamin, fluorene, anthracene och 1,4-dicyanobenzene har mest potential att förbättra bränslet i hybridraketer.

  • 109.
    Blinkovskaja, Irina
    KTH, Skolan för kemivetenskap (CHE).
    Lanasol på bomull, ylle och fleece2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    A new type of natural, antimicrobial, biocompatible agent is presented. Lanasol--a brominated cyclic compound that can be extracted from red sea algae and occurs naturally was applied onto the three most commonly available fabrics: cotton, wool and fleece. Samples of the fabrics were tested for a series of properties such Antibacterial effectiveness, durability to laundering and flammability.

     

    The treated fabric surface and the Lanasol percentage present at the surface of the fabric were evaluated by performing SEM, IR and Density Archimedes. The antimicrobial activity of the coated fibres against fungi Fussarium, was assessed using qualitative Agar diffusion test.

     

    The Lanasol treated samples displayed very good antimicrobial properties compared to the untreated control samples.  It was observes that antibacterial effectives increased significantly with higher Lanasols solutions of 10% compared to 2,5%. Antibacterial properties remained effective after 10 washes but decreased visibly after 20 washes.  Anti-flammability properties were strongest in unwashed samples with considerable ignition time differences to the untreated control samples.

     

    The results obtained from the current study demonstrate that Lanasol, which has previously not been tested for textile durability, has significant potential as a new antibacterial agent. This concept opens the door to further research into the increasing the antimicrobials properties as well as enhancing the success of commercial application of Lanasol for textile treatment.

  • 110.
    Blomfeldt, Thomas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Freeze-Dried Wheat Gluten-Based Foams2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis presents wheat gluten foams as an alternative to the available commercialfoams. Polymeric foams, like all plastics, are mostly made from petroleum, and this isaffecting the environment negatively with the emission of greenhouse gases and generation oflandfills. During the past decades, there has been a drive to replace petroleum-based plasticswith alternatives made from renewable resources. Wheat gluten has interesting and promisingproperties as an alternative resource. As a large by-product in Europe from the biofuelindustry it is largely available and at a low price.In order to develop an insulation material based on this renewable resource, foammaterials have been made by freeze-drying frozen mixtures consisting of either acommercially available wheat gluten powder or various protein rich fractions of gliadins orglutenins extracted from the commercial powder. Some of the foams were further modifiedwith the addition of glycerol as plasticizer or bacterial cellulose as a reinforcing fiber. Theresulting cellular structure was shown to depend on the initial gluten concentration, and thefraction and type of additive used. The wheat gluten foam materials contained mainly an openpore structure with average pore diameters ranging from 20 to 70 μm.The addition of glycerol and/or bacterial cellulose changed the foam structure, theprotein structure and the mechanical properties. The addition of 20 wt.% glycerol wassufficient to plasticize the foam and to achieve a low modulus and a high strain recovery, butwith glycerol the average pores size increased due to the difference in freezing conditions.The bacterial cellulose gave a small and insignificant increase in stiffness and also a moreuniform cell structure. In addition, the glycerol-containing samples had a more polymerizedprotein structure, whereas the foams containing fibers had a lower degree of polymerization.Foams made from a glutenin rich fraction were much stiffer and stronger than gliadinrich foams. The glutenin rich foams had a higher degree of polymerization than the latter,foam the relatively mild heat treatment.The gluten foams were promising as insulation materials. The thermal conductivityvalues were 0.04-0.05 (W/m⋅°C), and were close to that of commercially available closed cellpolystyrene and polyurethane foams, that both have values at ca. 0.03 (W/m⋅°C).The wheat gluten foams showed also promising combustion properties with longignition times, no material dripping and a large content of residual char. The glycerolcontainingfoam however, exhibited a more rigorous bubbling and a larger flame.

  • 111.
    Bolakhrif, Sabah
    KTH, Skolan för kemivetenskap (CHE).
    Synthesis and application of PLA and PLA/GO fibers through thermo-responsive transformation of PLA particles2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    PLA nanofibers were successively produced by thermo-responsive transformation of PLA particles in water. The morphological structure of the nanofibers could be optimized by the heat treatment as well as the incorporation of GO to the fiber surface. PLA/GO fiber demonstrated a more stable morphology and GO provided good compatibility between PLA and starch. Both PLA and PLA/GO fibers incorporated in starch films resulted in increased thermal stability and mechanical properties. However, the most favorable properties were assigned starch films containing high concentration of PLA/GO fibers. These films with completely green components could possibly be utilized in biodegradable packaging applications.

                                                                                                                               

  • 112.
    Bor, Yasemin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Alin, Jonas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Polylactide stereocomplexation leads to reduced migration during microwave heating in contact with food simulants2014Inngår i: Journal of Food Engineering, ISSN 0260-8774, E-ISSN 1873-5770, Vol. 134, s. 1-4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of stereocomplexation on the stability and migration resistance of polylactide during microwave and conventional heating in contact with different food simulants was evaluated. The heating effects were followed through mass loss measurements, molecular weight measurements and identification of the individual migrants by electrospray ionization-mass spectrometry (ESI-MS). Increased mass losses were observed as a function of time and temperature, but approximately 50% smaller mass losses were always measured for PLA stereocomplex as compared to the corresponding regular PLEA material. The stability of the stereocomplex material was, thus, significantly higher. Microwave heating increased the mass loss as compared to the conventional heating at the same time and temperature. This effect was especially significant when 10% ethanol was used as food simulant instead of water. The amount of water-soluble migrants was in most cases under the detection limits, but when heating temperature was increased to 95 C, ESI-MS revealed the formation of homologous series of linear lactic acid oligomers. Results indicate that PEA stereocomplex materials could have potential in single-use microwave applications.

  • 113. Bose, Indranil
    et al.
    Ohlander, Anna
    Stich, Matthias I. J.
    Kiesl, Christian
    Hemmetzberger, Dieter
    Klink, Gerhard
    Trupp, Sabine
    Bock, Karlheinz
    Polymer opto-chemical-electronic based module as a detection system for volatile analytes on a foil substrate2012Inngår i: Proceedings of SPIE - The International Society for Optical Engineering, SPIE - International Society for Optical Engineering, 2012, Vol. 8479Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this paper, we report on a novel device that addresses the needs for an efficient, field deployable and disposable system in the field of bio-chemical sensors using organic semiconductors. The Fraunhofer Institute has enabled a complete roll-to-roll manufactured polymer-opto-chemical-electronic module on a foil substrate, wherein an electroluminescent light source has been hetero-integrated together with an organic TFT, working as a photo detector. A chemically sensitive, colour changing film is sandwiched in between the two elements to form an optical detection system for volatile analytes such as amines. The setup, henceforth referred to as the “PolyOpto” module, comprises of a dye coated layer that can detect specific chemical reactions by colour change inserted in between the EL light source and the OTFT photo-detector. A hole is laser cut through the system to allow the sensor layer to come in contact with the gases, which then through a chemical reaction, changes colour and initiates a different response in the output of the organic transistor. Hence, this allows for a disposable chemo-analytical system that can be used in various application fields. As compared to conventional systems, the advantage here lies in the direct integration of the different functionalities without any advanced assembly steps, simultaneous use of coatings for both components (transparent electrode and wiring layer) and roll-to-roll compatibility, thus rendering a disposable system. We believe that it aptly demonstrates the capabilities of polytronics in functional integration for low-cost bio-sensor manufacturing

  • 114.
    Boujemaoui, Assya
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. 831220-7585.
    Polycaprolactone  Nanocomposites Reinforced  with   Cellulose Nanocrystals  Surface - modified  via  Covalent  Grafting  or  Physical Adsorption - a Comparative studyManuskript (preprint) (Annet vitenskapelig)
  • 115.
    Boujemaoui, Assya
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. 831220-7585.
    RAFT/MADIX Polymerization of Vinyl Acetate on Cellulose Nanocrystals for Nanocomposite ApplicationsManuskript (preprint) (Annet vitenskapelig)
  • 116.
    Boujemaoui, Assya
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik. 831220-7585.
    Surface Modification of Nanocellulose towards Composite Applications2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Nanocelluloses have attracted great interest during recent decades owing to their renewability, abundancy and remarkable physical and mechanical properties. The aim of this work was to investigate new strategies for surface modification and functionalization of nanocelluloses and their subsequent incorporation in polymer-host matrices.

    Nanocomposites of cellulose nanofibrils (CNF) and polycaprolactone (PCL) were produced by employing CNF nanopaper (NP) as a template and surface-initiated ring-opening polymerization (SI-ROP) of ε-caprolactone (ε-CL). SI-ROP of ε-CL from filter paper (FP) was also carried out for comparison. A larger amount of PCL was grafted from NP than from FP. The grafted NP had stronger mechanical properties than neat PCL.

    Cellulose nanocrystal (CNC)-reinforced polyvinyl acetate (PVAc) nanocomposites were also investigated. CNC were modified via “SI-reversible addition-fragmentation chain transfer and macromolecular design via the interchange of xanthate” (SI-RAFT/MADIX) polymerization of vinyl acetate (VAc). The resulting nanocomposites exhibited improved mechanical performance than the unmodified CNC.

    It is generally agreed that covalent grafting is superior to physical adsorption for the modification of a reinforcing agent. However, this hypothesis has never been thoroughly investigated. CNC was modified either through covalent grafting or through physical adsorption of poly(butyl methacrylate) (PBMA). Both methods resulted in improved mechanical performance than that of pure PCL or PCL containing unmodified CNC. However, covalent grafting gave the best mechanical performance even at high relative humidity.

    Functionalized CNC (F-CNC) were obtained through a versatile methodology employing organic acids bearing a functional group were employed for the simultaneous acid hydrolysis and esterification of cellulose fibers. This provided a facile route for the preparation of F-CNC.

  • 117.
    Boujemaoui, Assya
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Mazieres, Stephane
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Destarac, Mathias
    Carlmark, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    SI-RAFT/MADIX polymerization of vinyl acetate on cellulose nanocrystals for nanocomposite applications2016Inngår i: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 99, s. 240-249Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present work, poly(vinyl acetate) grafted cellulose nanocrystals (CNC-g-PVAc) were prepared via surface initiated reversible addition-fragmentation chain transfer and macromolecular design via the interchange of xanthates (SI-RAFT/MADIX) polymerization. Successful grafting of PVAc from CNC was confirmed by FT-IR and TGA analysis. PVAc nanocomposites reinforced with CNC-g-PVAc, as well as pristine CNC for comparison, of different weight percentages (0.5, 1, 3 and 5 wt%) of CNC were prepared via solvent casting. The PVAc reinforced with CNC-g-PVAc resulted in higher transparency and improved mechanical properties compared with unmodified CNC nanocomposites. The addition of 5 wt% CNC-g-PVAc increased the modulus of neat PVAc with as much as 154%. The proposed SI-RAFT/MADIX on CNC could be applied to wide range of monomers, and it is believed to be an efficient and robust method for CNC functionalization, thus expanding the potential applicability of CNC.

  • 118.
    Boujemaoui, Assya
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Mongkhontreerat, Surinthra
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Carlmark, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Preparation and characterization of functionalized cellulose nanocrystals2015Inngår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 115, s. 457-464Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, a series of functional nanocrystals (F-CNCs) was successfully produced by an efficient preparation method, combining acid hydrolysis and Fischer esterification with various organic acids. Functionalities such as ATRP initiators, double bonds, triple bonds, and thiols could be incorporated on CNCs. Surface modification was confirmed by FT-IR, XPS, and elemental analysis. Physical properties of FC-NCs were assessed by AFM, XRD and TGA. Moreover, ATRP initiator functionalized CNCs were utilized to graft poly(methyl methacrylate) via ATRP, thiol functionalized CNCs were reacted with Ellman's reagent to determine the thiol content and dye disperse red 13 was attached to alkyne functionalized CNCs to estimate the propiolate content. The herein presented method is a highly versatile and straightforward procedure for the preparation of F-CNCs which is believed to be a better alternative for the commonly utilized, extensive, multistep, and time consuming post functionalization methods.

  • 119.
    Bruce, Carl
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation.
    Surface Modification of Cellulose by Covalent Grafting and Physical Adsorption for Biocomposite Applications2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    There is an increasing interest to replace fossil-based materials with renewable alternatives. Cellulose fibers/nanofibrils (CNF) are sustainable options since they are biobased and biodegradable. In addition, they combine low weight with high strength; making them suitable to, for example, reinforce composites. However, to be able to use them as such, modifications are often necessary. This study therefore aimed at modifying cellulose fibers, model surfaces of cellulose and CNF. Cellulose fibers and CNF were thereafter incorporated into composite materials and evaluated.

    Surface-initiated ring-opening polymerization (SI-ROP) was performed to graft ε-caprolactone (ε-CL) from cellulose fibers. From these fibers, paper-sheet biocomposites were produced that could form laminate structures without the need for any addition of matrix polymer.

    By combining ROP and atom transfer radical polymerization (ATRP), diblock copolymers of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and PCL were prepared. Quaternized (cationic) PDMAEMA, allowed physical adsorption of block copolymers onto anionic surfaces, and, thereby, alteration of surface energy and adhesion to a potential matrix. Furthermore, the architecture of block copolymers of PCL and PDMAEMA was varied to investigate effects on morphology/crystallinity and adsorption behavior. In addition, poly(butadiene) was also evaluated as the hydrophobic block in the form of cationic and anionic triblock copolymers.

    Polystyrene (PS) was covalently grafted from CNF and used as reinforcement in PS-based composites. In an attempt to determine stress transfer from matrix to CNF, a method based on Raman spectroscopy was utilized.

    Covalent grafting and physical adsorption of PCL from/onto CNF were compared by incorporating modified CNF in PCL matrices. Both approaches resulted in improved mechanical properties compared to unmodified CNF, but even at low amounts of modified CNF, covalent grafting gave tougher materials and indicated higher interfacial adhesion.

  • 120.
    BRÄNNSTRÖM, SARA
    KTH, Skolan för kemivetenskap (CHE).
    En studie om hur koncentrerad saltsyra vid hög temperatur påverkar PP, PVC och CPVC2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Hydrochloric acid is commonly used in pickling plants where temperatures may be up to 90 °C. In such corrosive environments, pipes or containers of metals cannot be used and the use of plastic materials is therefore a more suitable option. For example it may be possible to use polypropylene (PP), polyvinyl chloride (PVC) and chlorinated PVC (CPVC) for these applications. Plastics are not standardized materials; therefore the chemical resistances of commercially available plastics need to be tested individually.

    The effect of hydrochloric acid (HCl) at high temperatures on commercially available materials from different manufacturers was studied. Totally five PP, five PVC and two CPVC materials were investigated. The materials were exposed to concentrated HCl at 60 °C for up to 8 weeks. The chemical changes were analyzed with Fourier Transfer Infrared Spectroscopy (FTIR). Differential Scanning Calorimetry (DSC) was used to measure the Oxidative Induction Time (OIT). The mechanical properties were studied with Charpy impact testing and tensile testing. An indicator technique was used to measure the diffusion of HCl in the materials. Quantification of how much HCl the materials absorb was performed with Ion chromatography (IC).

    The results showed that the PP samples lost antioxidants as seen in both FTIR spectra and changes in OIT. The PVC materials had a decrease in filler content where the acid had penetrated. The mechanical properties seemed to be unchanged after exposure for 8 weeks. Only two PVC materials seemed to have a decrease in stress at yield. Concluding, most of the tested PVC and CPVC materials are suitable for the use in contact with concentrated HCl. All PP, PVC and CPVC materials can be used in contact with concentrated HCl in 60 oC up to 8 weeks.

  • 121. Buchert, Johanna
    et al.
    Bergnor, Elisabeth
    Lindblad, Gunnar
    Viikari, Liisa
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Significance of xylan and glucomannan in the brightness reversion of kraft pulps1997Inngår i: TAPPI Journal, ISSN 0734-1415, Vol. 80, nr 6, s. 165-171Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The brightness reversion of kraft pulps is caused by the presence of residual lignin, chlorinated extractives, or oxidized carbohydrates. The effect of hemicellulose content, i.e., xylan (I) and glucomannan (II), on the thermal stability of modern bleached kraft pulps was investigated. Different O-delignified hard- and softwood kraft pulps were bleached with different bleaching sequences contg. ClO2, H2O2, or O3. Hemicellulose-degrading enzymes, i.e., xylanase or mannanase, were used for selective removal of the resp. hemicellulose from the pulps, and the role of partially removed I and II on the brightness stability of these pulps was studied. Because of the structure of kraft I, enzymic removal of I also resulted in a decreased carboxyl group content in the pulps, whereas II removal did not affect the carboxyl group content. By decreasing the carboxyl groups in the pulps in conjunction with I removal, the thermal aging of the pulps was significantly decreased. The role of II was less significant. Thus, the uronic acids present in the pulp participate in the brightness reversion of kraft pulps.

  • 122. Buchert, Johanna
    et al.
    Bergnor, Elisabeth
    Lindblad, Gunnar
    Viikari, Liisa
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    The role of xylan and glucomannan in yellowing of kraft pulps.1995Inngår i: Proceedings 8th Int. Symp. Wood Pulp. Chem., 1995, s. 43-48Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The effects of xylan and glucomannan on the thermal stability of unbleached, partially bleached, and fully bleached pine and birch kraft pulps were studied.  The choice of bleaching chems. strongly affected the brightness reversion.  Compared with hydrogen peroxide or chlorine dioxide, bleaching with ozone reduced the amt. of carboxyl groups and subsequently the pc-nos. of oxygen-delignified pulps.  Xylan removal reduced also the amt. of carboxyl groups in the pulps and this was reflected in improved brightness stability whereas glucomannan removal had no effect.  Thus, the uronic acids bound to pulp xylan were found to participate in the brightness reversion of kraft pulps.

  • 123. Buchert, Johanna
    et al.
    Tenkanen, Maija
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Teleman, Anita
    Vuorinen, Tapani
    Effect of pulping and bleaching on pulp carbohydrates and technical properties.1996Inngår i: Proceedings Int. Pulp Bleaching, 1996, s. 39-42Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Pulping and bleaching have a profound effect on the carbohydrate chem. of kraft pulps.  The chem. structure of xylan is modified due to the conversion of methylglucuronic acid side groups to hexenuronic acid side groups.  Pulping conditions strongly affect the amt. of hexenuronic acid present in the pulp and subsequently modified kraft pulps have different carboxyl group profiles as compared with conventionally cooked pulps.  Due to its reactivity, hexenuronic acid is readily degraded when chlorine dioxide or ozone are used as bleaching chems.  However, TCF-pulps bleached with peroxide and oxygen contain high amts. of hexenuronic acid.  Thus, depending on the pulping and bleaching method, the quality and quantity of carboxylic acids in different types of pulps varies significantly.  The differences in the uronic acid content are in turn reflected in the macroscale properties of the pulps, such as brightness stability.       

  • 124.
    Burman, Lina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Indicator products and chromatographic fingerprinting: New tools for degradation state and lifetime estimation2008Inngår i: CHROMATOGRAPHY FOR SUSTAINABLE POLYMERIC MATERIALS: RENEWABLE, DEGRADABLE AND RECYCLABLE, Berlin: Springer Verlag , 2008, Vol. 211, s. 1-22Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The demands on polymeric products are growing both with respect to their function and purity. There is a need for new high-throughput characterisation tools for rapid quality control and evaluation of materials. Precise control over degradation rate and service-life are also prerequisites for successful use of degradable polymers in an increasing number of applications. The chromatographic fingerprinting and indicator product concepts, presented in the current paper, are novel and attractive alternatives for rapid evaluation of the product quality, degradability, durability and service-life. The sensitivity of these techniques allows for detection of small initial changes in the materials and signs of early degradation. The possible applications include evaluation of different pro-oxidants or antioxidants, optimisation of processing parameters, evaluation of long-term properties or storage stability and lifetime prediction. The same principal could also be applied to process control and monitoring, acceptance or rejection of raw materials, intermediate and final products. The usefulness of indicator products and chromatographic fingerprinting is shown for estimation of the degradation state of degradable polyethylene. in addition, chromatographic fingerprinting together with multivariate data analysis is utilised to classify degradable polyethylene materials based on their incorporated pro-oxidant systems.

  • 125.
    Butchosa Robles, Núria
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Tailoring Cellulose Nanofibrils for Advanced Materials2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Cellulose nanofibrils (CNFs) are nanoscale fibers of high aspect ratio that can be isolated from a wide variety of cellulosic sources, including wood and bacterial cellulose. With high strength despite of their low density, CNFs are a promising renewable building block for the preparation of nanostructured materials and composites. To fabricate CNF-based materials with improved inherent rheological and mechanical properties and additional new functionalities, it is essential to tailor the surface properties of individual CNFs. The surface structures control the interactions between CNFs and ultimately dictate the structure and macroscale properties of the bulk material. In this thesis we have demonstrated different approaches, ranging from non-covalent adsorption and covalent chemical modification to modification of cellulose biosynthesis, to tailor the structure and surface functionalities of CNFs for the fabrication of advanced materials. These materials possess enhanced properties such as water-redispersibility, water absorbency, dye adsorption capacity, antibacterial activity, and mechanical properties.

    In Paper I, CNFs were modified via the irreversible adsorption of carboxymethyl cellulose (CMC). The adsorption of small amounts of CMC onto the surface of CNFs prevented agglomeration and co-crystallization of the nanofibrils upon drying, and allowed the recovery of rheological and mechanical properties after redispersion of dried CNF samples.

    In Paper II, CNFs bearing permanent cationic charges were prepared through quaternization of wood pulp fibers followed by mechanical disintegration. The activation of the hydroxyl groups on pulp fibers by alkaline treatment was optimized prior to quaternization. This optimization resulted in individual CNFs with uniform width and tunable cationic charge densities. These cationic CNFs demonstrated ultrahigh water absorbency and high adsorption capacity for anionic dyes.

    In Paper III, via a similar approach as in Paper II, CNFs bearing polyethylene glycol (PEG) were prepared by covalently grafting PEG to carboxylated pulp fibers prior to mechanical disintegration. CNFs with a high surface chain density of PEG and a uniform width were oriented to produce macroscopic ribbons simply by mechanical stretching of the CNF hydrogel network before drying. The uniform grafted thin monolayer of PEG on the surface of individual CNFs prevented the agglomeration of CNFs and facilitated their alignment upon mechanical stretching, thus resulted in ribbons with ultrahigh tensile strength and modulus. These optically transparent ribbons also demonstrated interesting biaxial light scattering behavior.

    In Paper IV, bacterial cellulose (BC) was modified by the addition of chitin nanocrystals (ChNCs) into the growing culture medium of the bacteria Acetobacter aceti which secretes cellulose in the form of entangled nanofibers. This led to the in situ incorporation of ChNCs into the BC nanofibers network and resulted in BC/ChNC nanocomposites exhibiting bactericidal activity. Further, blending of BC nanofibers with ChNCs produced nanocomposite films with relatively lower tensile strength and modulus compared to the in situ cultivated ones. The bactericidal activity increased significantly with increasing amount of ChNCs for nanocomposites prepared by direct mixing of BC nanofibers and ChNCs.

    In Paper V, CNFs were isolated from suspension-cultured wild-type (WT) and cellulose-binding module (CBM) transformed tobacco BY-2 (Nicotiana tabacum L. cv bright yellow) cells. Results from strong sulfuric acid hydrolysis indicated that CNFs from transgenic cells overexpressing CBM consisted of longer cellulose nanocrystals compared to CNFs from WT cells. Nanopapers prepared from CNFs of transgenic cells demonstrated significantly enhanced toughness compared to CNFs of WT cells.

  • 126.
    Bäckström, Eva
    KTH, Skolan för kemivetenskap (CHE).
    Covalently modified starch with novel graphene oxide as biomaterial2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Today there is a large interest to develop new biomedical material to treat medical conditions. These materials need to be biocompatible and preferably bioresorbable. One option is the common biopolymer starch. Typically it needs reinforcement to allow usage. Nano-sized Graphene Oxide (GO) is promising reinforcing filler since it is nontoxic and strong. A method to produce starch-based hydrogels reinforced with nano-sized graphene oxide was demonstrated in this work. Graphene Oxide was derived from starch by microwave irradiation followed by oxidation. In turn the produced GO were covalently attached to starch by an esterification reaction using DCC and DMAP in DMSO to get the reinforced starch (STGO). Both GO and STGO were carefully investigated by TEM, SEM, DLS, AFM, NMR, FTIR, TGA and XRD. Starch hydrogels containing GO and STGO were produced in the presence of glycerol. Mineralization test on the gel proved that the carboxyl group present in GO functions as an anchoring site for the mineral Hydroxyapatite that is fundamental for enamel. Higher concentration of reinforced starch in the hydrogels showed better results with a higher density of mineral growth and a stoichiometric mineral. The STGO starch hydrogels thus show great potential to be utilized in dental applications to regenerate the demineralized teeth.

  • 127. Camacho, W.
    et al.
    Karlsson, S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Quality assessment of co-mingled recycled resins by fourier transform raman spectroscopy and multivariate calibration2001Inngår i: Polymer Recycling, Vol. 6, nr 2/3, s. 89-98Artikkel i tidsskrift (Fagfellevurdert)
  • 128. Camacho, Walker
    et al.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Quality determination of recycled plastic packaging waste by identification of contaminants by GC-MS after microwave assisted extraction (MAE)2001Inngår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 71, nr 1, s. 123-134Artikkel i tidsskrift (Fagfellevurdert)
  • 129. Camacho, Walker
    et al.
    Karlsson, Sigbritt
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Simultaneous determination of molecular weight and crystallinity of recycled HDPE by infrared spectroscopy and multivariate calibration2002Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 85, nr 2, s. 321-327Artikkel i tidsskrift (Fagfellevurdert)
  • 130. Cardoso, Marcos R.
    et al.
    Martins, Renato J.
    Dev, Apurba
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF.
    Voss, Tobias
    Mendonca, Cleber R.
    Highly hydrophobic hierarchical nanomicro roughness polymer surface created by stamping and laser micromachining2015Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 132, nr 24, artikkel-id 42082Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article describes the design and fabrication of hierarchical nanomicrostructured polymer surfaces with high hydrophobicity. The nanoscale roughness is achieved by stamping a ZnO nanowire film into PDMS. Subsequently, microstructures with different periodicities are created in the stamped PDMS sample by direct laser writing using femtosecond pulses. With this approach, we were able to produce hierarchical surface morphologies, composed of nano and microscale structures that exhibit water contact angles larger than 160 degrees.

  • 131.
    Carlborg, Carl Fredrik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Haraldsson, Tommy
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Stemme, Göran
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Wijngaart, Wouter van der
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    RELIABLE BATCH MANUFACTURING OF MINIATURIZED VERTICAL VIAS IN SOFT POLYMER REPLICA MOLDING2007Inngår i: 11th International Conference on Miniaturized Systems for Chemistry and Life Sciences (microTAS 2007), 2007, s. 527-529Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We introduce and have successfully tested an uncomplicated polydimethylsiloxane (PDMS) compatible method for batch manufacturing vertical microfluidic interconnects via a surface inhibition of cationic photopolymerization. The yield of the maskless method is 100%. Moreover, the method enhances bond strength with subsequently laminated polymer layers.

  • 132.
    Carlborg, Carl Fredrik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Haraldsson, Tommy
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Öberg, Kim
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    van der Wijngaart, Wouter
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    BEYOND PDMS:: OFF-STOCHIOMETRY THIOL-ENE BASED SOFT LITHOGRAPHY FOR RAPID PROTOTYPING OF MICROFLUIDIC DEVICES2010Inngår i: 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences (micro TAS 2010), 2010, s. 70-72Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present an easy to use, rapid fabrication platform for microfluidic systems, based on micro-molding of novel thiolene based polymer formulations. The novel fabrication platform addresses major drawbacks of PDMS by allowing large freedom in material and surface properties, including: (photo)patterning of stable surface modifications, bonding without plasma treatment, rapid UV or thermal curing, variable E-modulus, minimized leaching of uncured components [1] and suppressed non-specific binding of biomolecules [2]. This process is potentially suited for both rapid prototyping in the laboratory and medium-scale commercial production, bridging the “development gap”.

  • 133.
    Carlborg, Carl Fredrik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Saharil, Farizah
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Haraldsson, Tommy
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    Wijngaart, Wouter van der
    KTH, Skolan för elektro- och systemteknik (EES), Mikrosystemteknik (Bytt namn 20121201).
    LOW TEMPERATURE “CLICK” WAFER BONDING OF OFF-STOICHIOMETRY THIOL-ENE (OSTE) POLYMERS TO SILICON2011Inngår i: 15th International Conference on Miniaturized Systems for Chemistry and Life Sciences (microTAS 2011), 2011, s. 1143-1145Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present a low temperature (< 37°C) wafer-scale microfluidic batch packaging process using covalent, dry bonding of offstoichiometry thiol-ene polymers (OSTE), enabling rapid, bio-compatible integration of fluidics on wafer-scale in combination with excellent polymer properties.

  • 134.
    Carlborg, Carl Fredrik
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Vastesson, Alexander
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Liu, Yitong
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    van der Wijngaart, Wouter
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Haraldsson, Tommy
    KTH, Skolan för elektro- och systemteknik (EES), Mikro- och nanosystemteknik.
    Functional Off-Stoichiometry Thiol-ene-epoxy Thermosets Featuring Temporally Controlled Curing Stages via an UV/UV Dual Cure Process2014Inngår i: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 52, nr 18, s. 2604-2615Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a facile two-stage UV/UV activation method for the polymerization of off-stoichiometry thiol-ene-epoxy, OSTE+, networks. We show that the handling and processing of these epoxy-based resins is made easier by introducing a material with a controlled curing technique based on two steps, where the first step offers excellent processing capabilities, and the second step yields a polymer with suitable end-properties. We investigate the sequential thiol-ene and thiol-epoxy reactions during these steps by studying the mechanical properties, functional group conversion, water absorption, hydrolytic stability, and thermal stability in several different thiol-ene-epoxy formulations. Finally, we conclude that the curing stages can be separated for up to 24 h, which is promising for the usefulness of this technique in industrial applications.

  • 135.
    Carlmark, Anna
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Complex Macromolecular Architectures by Atom Transfer Radical Polymerization2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

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

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

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

  • 136.
    Carlmark, Anna
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Malmström, Eva E
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    ATRP of dendronized aliphatic macromonomers of generation one, two, and three2004Inngår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 37, nr 20, s. 7491-7496Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 137.
    Carlsson, Linn
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Ytbehandlingsteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Surface Modification of Cellulose by Covalent Grafting and Physical Adsorption2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The interest in new environmentally friendly cellulose‐based productshas increased tremendously over the last years. At the same time theSwedish forest industry faces new challenges in its strive to increase the utilization of cellulose fibers in high‐value end‐products. The aim of this study was to expand the toolbox for surface modification of cellulose byemploying covalent surface‐initiated (SI) polymerizations or by physicaladsorption of polymers. SI‐ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) was performed from filter paper (FP) and high surface area nanopaper (NP).Larger amounts of polycaprolactone (PCL) were grafted from NP, compared to FP, owing to the higher amount of available initiating hydroxyl groups. Furthermore, the mechanical properties of PCL were improved by the grafting of FP and NP, as compared to pure PCL.It is challenging to characterize a polymer grafted from a surface. Hence, quartz crystal microbalance with dissipation (QCM‐D) was employed to investigate SI‐ROP in real time from a cellulose model surface. Furthermore, it was shown by colloidal probe AFM that increased lengthof grafted PCL, from cellulose microspheres, improved the interfacialadhesion to a pure PCL surface, suggesting that chain entanglements havea significant impact on the interfacial properties. Increased temperatureand time in contact also improved the adhesion.In order to investigate the degree of substitution (DS) and the degree of polymerization (DP), PCL‐grafted hydrolyzed cellulose cotton linters (HCCL) were studied by solid state NMR. It was found that despite a DS of only a few percent, the surface character changed considerably; furthermore, the DS was virtually independent of the DP. To increase theamount of grafted polymer, ring‐opening metathesis polymerization (ROMP) of norbornene was performed from FP. Short polymerizationtimes and low temperatures resulted in highly grafted surfaces. Alternatively, physical adsorption by electrostatic interactions was employed to modify a cellulose model surface in the QCM‐D. Cationic latex nanoparticles of poly(dimetylaminoethyl methacrylate‐co‐methacrylicacid)‐block‐poly(methyl methacrylate) were produced by reversible addition‐fragmentation chain‐transfer (RAFT)‐mediated surfactant‐freeemulsion polymerization by polymerization‐induced self‐assembly (PISA).This strategy does not require any organic solvents and could potentiallybe introduced in industrial processes.

  • 138.
    Carrick, Christopher
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Macro-, Micro- and Nanospheres from Cellulose: Their Preparation, Characterization and Utilization2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The structure of a polymeric material has a great influence in many fundamental scientific areas as well as in more applied science, since it affects the diffusion, permeability, mechanical strength, elasticity, and colloidal properties of the materials. The results in this thesis demonstrate that it is possible to fabricate solid and hollow cellulose spheres with a cellulose shell and encapsulated gas, liquid or solid particles and with a sphere size ranging from a few hundreds of nanometres to several millimetres, all with a tailored design and purpose.

    The sizes of the different spheres have been controlled by three different preparation methods: large cellulose macrospheres by a solution solidification procedure, hollow micrometre-sized cellulose spheres by a liquid flow-focusing technique in microchannels, and nanometre-sized cellulose spheres by a membrane emulsification technique. 

    The spheres were then modified in different ways in order to functionalize them into more advanced materials. This thesis demonstrates how to control the cellulose sphere dimensions and the wall-to-void volume ratio, the elasticity and the functionality of the spheres as such, where they were prepared to be pH-responsive, surface specific and X-ray active. These modifications are interesting in several different types of final materials such as packaging materials, drug release devices or advanced in vivo diagnostic applications.

    In the more fundamental science approach, surface-smooth solid cellulose spheres were prepared for characterization of the macroscopic work of adhesion when a cellulose surface is separated from another material. Using these ultra-smooth macroscopic cellulose probes, it is possible to measure the compatibility and the surface interactions between cellulose and other materials which provide an important tool for incorporating cellulose into different composite materials. 

  • 139.
    Carrick, Christopher
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Pendergraph, Samuel A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Nanometer Smooth, Macroscopic Spherical Cellulose Probes for Contact Adhesion Measurements2014Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, nr 23, s. 20928-20935Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose spheres were prepared by dissolving cellulose fibers and subsequently solidifying the solution in a nonsolvent. Three different solution concentrations were tested and several nonsolvents were evaluated for their effect on the formation of spheres. Conditions were highlighted to create cellulose spheres with a diameter of similar to 1 mm and a root-mean-square surface roughness of similar to 1 nm. These solid spheres were shown to be easily chemically modified without changing the mechanical properties significantly. Contact adhesion measurements were then implemented with these spheres against a poly(dimethylsiloxane) (PDMS) elastomer in order to quantify the adhesion. Using Johnson-Kendall-Roberts (JKR) theory, we quantified the adhesion for unmodified cellulose and hydrophobic cellulose spheres. We highlight the ability of these spheres to report more accurate adhesion information, compared to spin-coated thin films. The application of these new cellulose probes also opens up new possibilities for direct, accurate measurement of adhesion between cellulose and other materials instead of using uncertain surface energy determinations to calculate the theoretical work of adhesion between cellulose and different solid materials.

  • 140.
    Carvalho, Danila
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Study on the structure and properties of xylan extracted from eucalyptus, sugarcane bagasse and sugarcane straw2015Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lignocellulosic biomasses are an important source of chemical components such as cellulose, lignin and hemicelluloses, and can be used for a variety of purposes in both the pulp and paper and chemical conversion industries. Xylan, the main hemicellulose found in hardwood and grass plants, plays an important role during the pulping/pretreatment process reactions, including those used in 2nd generation bioethanol production. It may also play an important role in the production of certain novel materials.

    This thesis evaluates the composition of eucalyptus (Eucalyptus urophylla x Eucalyptus grandis), sugarcane bagasse and sugarcane straw, with a specific focus on the structure and properties of xylan. The chemical characterization of biomasses showed that sugarcane bagasse and straw contain larger amounts of extractives, ash and silica than eucalyptus. The large amount of silica leads to an overestimation of the Klason lignin content, if not corrected. By using a complete mass balance approach, sugarcane bagasse and straw were shown to contain smaller amounts of lignin (18.0% and 13.9%, respectively) than previously reported for these raw materials, and certainly a much smaller amount of lignin than was found in eucalyptus (27.4%). The hemicellulose content in sugarcane bagasse (28.7%) and straw (29.8%) was much higher than that in eucalyptus (20.3%).

    In order to investigate the structure of the xylan in greater detail, it was extracted with dimethyl sulfoxide from holocellulose, obtained by either peracetic acid or sodium chlorite delignification. The structure of the isolated xylans was confirmed by FTIR and 1H NMR analysis. In eucalyptus, the O-acetyl-(4-O-methylglucurono)xylan (MGX) was identified. This had a molar ratio of xylose units to branches of 4-O-methylglucuronic acid of 10:1.1 and a degree of acetylation of 0.39. All 4-O- methylglucuronic acid groups were attached to position O-2 of the xylose units, which had an acetyl group in position O-3. The acetyl groups were distributed in positions O-3 (64%), O-2 (26%) and O-2,3 (10%). The MGX had a molecular weight (Mw) of about 42 kDa.

    In bagasse and straw, arabinoxylan (AX) was identified. This had a molar ratio of xylose units to arabinosyl substitutions of 10:0.5 for bagasse and 10:0.6 for straw. A degree of acetylation was 0.29 and 0.08 for bagasse and straw, respectively. The arabinose units were attached preferentially to position O-3 in AX. In the xylan from bagasse, the acetyl groups were found in positions O-3 (60%), O-2 (13%) and O-2,3 (27%), while in the xylan from straw, the acetyl groups were distributed between positions O-3 (67%) and O-2 (33%). The AX had a molecular weight (Mw) of about 38 kDa and 30 kDa for bagasse and straw, respectively.

    The differences in the structure of xylan present in the various biomasses played an important role during hydrothermal pretreatment, which is often used as the first step in 2nd generation ethanol production. The varying amounts of uronic acid and acetyl groups resulted in different starting pH levels of liquor and, thus, affected the chemical transformation in the biomasses in different ways. The hydrothermal pretreatment resulted mostly in the removal and/or transformation of hemicelluloses, but also in the formation of a significant number of pseudo-lignin structures. In addition, in eucalyptus, pseudo-extractives structures were generated. The sugarcane straw showed the highest mass loss during the investigated pretreatment.

  • 141. Cataldi, A.
    et al.
    Dorigato, A.
    Deflorian, F.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Pegoretti, A.
    Polymer composite with micro- and nanocellulose for artwork protection and restoration2014Inngår i: 16th European Conference on Composite Materials, ECCM 2014, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Micro- and nanocomposites were prepared using Aquazol® 500 as a polymeric matrix and a microcrystalline cellulose (MCC), and suspensions of cellulose nanocrystals (CNC), as reinforcing agents. After a preliminary thermo-mechanical characterization that highlighted a stabilizing effect due to the micro- and nanofiller introduction, with an increase of the elastic modulus and a decrease of the thermal expansion coefficient and the creep compliance [1], these materials were applied as canvas lining adhesives. Single-lap shear tests both in quasi-static and creep conditions confirmed the dimensional stability provided by cellulose micro- and nanoparticles, with an important reduction of the adhesives compliance proportional to the filler content. Interestingly, MCC and CNC introduction did not impair the fracture behavior of the neat matrix.

  • 142.
    Celsi, Adrian
    KTH, Skolan för kemivetenskap (CHE).
    Developmental lignocellulose mapping in crop stems2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    With current techniques there is no rapid, one-step alternative to investigate plant composition and anatomy. In this study we present the use of luminescent

    conjugated oligothiophene (LCO), as a carbohydrate marker in unused cash crop stems. Stem samples were analyzed between day 0-75 using FTIR, gas

    chromatography, confocal laser scanning microscopy and spectral imaging analysis. Carbohydrate composition analysis confirmed cellulose presence in all

    time points tested and that fractions of monosaccharaides stay constant in the stem during growth. Using confocal and fluorescence microscopy, emission from

    LCO bound to cellulose was detected and stem composition and anatomy visualized.

    Overall, we demonstrate that LCOs can be utilized for compositional analyzes in plant tissues as a non-destructive and one-step alternative to today’s techniques.

    This method shows high applicability for structure and anatomy studies in plant tissues, but also as a compliment for current composition analysis techniques.

     

  • 143.
    Cervin, Nicholas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Porous Cellulose Materials from Nano Fibrillated Cellulose2012Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In the first part of this work a novel type of low-density, sponge-like material for the separation of mixtures of oil and water has been prepared by vapour deposition of hydrophobic silanes on ultra-porous nanocellulose aerogels. To achieve this, a highly porous (> 99 %) nanocellulose aerogel with high structural flexibility and robustness is first formed by freeze-drying an aqueous dispersion of the nanocellulose. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the nanocellulose dispersion before freeze-drying. The hydrophobic light-weight aerogels are almost instantly filled with the oil phase when they selectively absorb oil from water, with a capacity to absorb up to 45 times their own weight. The oil can also be drained from the aerogel and the aerogel can then be subjected to a second absorption cycle.In the second part of the work a novel, lightweight and strong porous cellulose material has been prepared by drying aqueous foams stabilized with surface-modified NanoFibrillated Cellulose (NFC). Confocal microscopy and high-speed video imaging show that the long-term stability of the wet foams can be attributed to the octylamine-coated, rod-shaped NFC nanoparticles residing at the air-liquid interface which prevent the air bubbles from collapsing or coalescing. Careful removal of the water yields a porous cellulose-based material with a porosity of 98 % and a density of 30 mg cm-3. These porous cellulose materials have a higher Young’s modulus than other cellulose materials made by freeze drying and a compressive energy absorption of 56 kJ m-3 at 80 % strain. Measurements with an autoporosimeter reveal that most pores are in the range of 300 to 500 μm.

  • 144.
    Cervin, Nicholas Tchang
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Johansson, E.
    Benjamins, J. -W
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Mechanisms behind the Stabilizing Action of Cellulose Nanofibrils in Wet-Stable Cellulose Foams2015Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 16, nr 3, s. 822-831Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The principal purpose of the investigation was to clarify the mechanisms behind the stabilizing action of cellulose nanofibrils (CNFs) in wet-stable cellulose foams. Following the basic theories for particle-stabilized foams, the investigation was focused on how the surface energy of the stabilizing CNF particles, their aspect ratio and charge density, and the concentration of CNF particles at the air-water interface affect the foam stability and the mechanical properties of a particle-stabilized air-liquid interface. The foam stability was evaluated from how the foam height changed over time, and the mechanical properties of the interface were evaluated as the complex viscoelastic modulus of the interface using the pendant drop method. The most important results and conclusions are that CNFs can be used as stabilizing particles for aqueous foams already at a concentration as low as 5 g/L. The major reasons for this were the small dimensions of the CNF and their high aspect ratio, which is important for gel-formation and the complex viscoelastic modulus of the particle-filled air-water interface. The influence of the aspect ratio was also demonstrated by a much higher foam stability of foams stabilized with CNFs than of foams stabilized by cellulose nanocrystals (CNC) with the same chemical composition. The charge density of the CNFs affects the level of liberation within larger aggregates and hence also the number of contact points at the interface and the gel formation and complex viscoelastic modulus of the air-water interface. The charges also result in a disjoining pressure related to the long-range repulsive electrostatic pressure between particle-stabilized bubbles and hence contribute to foam stability. (Figure Presented).

  • 145. Champ, Simon
    et al.
    Koch, Oliver
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Westman, Eva-Helena
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi.
    Feuerhake, Robert
    Haehnle, Hans-Joachim
    Biocidal coatings2006Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Biocidal multilayered system, characterized in that it comprises at least the following layers: - an anionic or cationic carrier, preferably cellulose as anionic carrier, - on this carrier alternating polymeric cationic and anionic layers starting with a layer having a charge opposite to that of the carrier, - wherein at least one layer is hydrophobically modified.

  • 146. Chang, B.
    et al.
    Schneider, K.
    Patil, N.
    Roth, Stephan V.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. DESY, Hamburg, Germany.
    Heinrich, G.
    Microstructure characterization in a single isotactic polypropylene spherulite by synchrotron microfocus wide angle X-ray scattering2018Inngår i: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 142, s. 387-393Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Position-resolved microstructure in a single spherulite of iPP is quantitatively studied by synchrotron microfocus wide angle X-ray scattering. The results show that the normal of mother lamellae in a spherulite is aligned mainly perpendicular to the radius, and the subsidiary daughter lamellae are inclined 80.75° with respect to that of the dominant mother lamellae. The crystallinity in the spherulite is in the range of 46%–56%, which is rarely influenced by the crystallization temperature. The ratio between the daughter lamellae and the mother lamellae is 0.18 when iPP crystallizes at 138 °C and it decreases to 0.11 as the crystallization temperature is decreased to 130 °C. The b-axis and c-axis in the mother lamellae tend to orient perpendicular to the radius direction, and the a-axis prefers to align in the radius direction.

  • 147.
    Chen, Chao
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Illergård, Josefin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Ek, Monica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Effect of cationic polyelectrolytes in contact-active antibacterial layer-by-layer functionalization2017Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, nr 7-8, s. 649-658Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Contact-active surfaces have been created by means of the layer-by-layer (LbL) modification technique, which is based on previous observations that cellulose fibers treated with polyelectrolyte multilayers with polyvinylamine (PVAm) are perfectly protected against bacteria. Several different cationic polyelectrolytes were applied, including PVAm, two different poly(diallyl dimethyl ammonium chloride) polymers and two different poly(allylamine hydrochloride) polymers. The polyelectrolytes were self-organized in one or three layers on cellulosic fibers in combination with polyacrylic acid by the LbL method, and their antibacterial activities were evaluated. The modified cellulose fibers showed remarkable bacterial removal activities and inhibited bacterial growth. It was shown that the interaction between bacteria and modified fibers is not merely a charge interaction because a certain degree of bacterial cell deformation was observed on the modified fiber surfaces. Charge properties of the modified fibers were determined based on polyelectrolyte titration and zeta potential measurements, and a correlation between high charge density and antibacterial efficiency was observed for the PVAm and PDADMAC samples. It was demonstrated that it is possible to achieve antibacterial effects by the surface modification of cellulosic fibers via the LbL technique with different cationic polyelectrolytes.

  • 148.
    Chen, Fei
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Monnier, Xavier
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gällstedt, Mikael
    Innventia, Sweden.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Wheat gluten/chitosan blends: A new biobased material2014Inngår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 60, s. 186-197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wheat gluten and chitosan are renewable materials that suffer from some poor properties that limit their use as a potential replacement of petroleum-based polymers. However, polymer blends based on wheat gluten and chitosan surprisingly reduced these shortcomings. Films were cast from acidic aqueous or water/ethanol solutions of wheat gluten and chitosan. Wheat gluten was the discontinuous phase in the 30-70 wt.% wheat gluten interval investigated. The most homogeneous films were obtained when reducing agents were used (alone or together with urea or glycerol). They consisted mainly of 1-2 mu m wheat gluten particles uniformly distributed in the continuous chitosan phase. Slightly smaller particles were also observed in the water/ethanol solvent system, but together with significantly larger particles (as large as 200 mu m). Both small and large particles were observed, albeit in different sizes and contents, when surfactants (both with and without a reducing agent) or urea (without a reducing agent) were used. The particles were often elongated, and preferably along the film, the most extreme case being observed when the glyoxal crosslinker was used together with sodium sulfite (reducing agent), showing particles with an average thickness of 0.6 mu m and an aspect ratio of 4.2. This film showed the highest transparency of all the blend films studied. For one of the most promising systems (with sodium sulfite), having good film homogeneity and small particles, the mechanical and moisture solubility/diffusivity properties were studied as a function of chitosan content. The extensibility, toughness and moisture solubility increased with increasing chitosan content, and the moisture diffusivity was highest for the pristine chitosan material. It is noteworthy that the addition of 30 wt.% wheat gluten to chitosan reduced the moisture uptake, while the extensibility/toughness remained unchanged.

  • 149.
    Chen, Fei
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Nilsson, Fritjof
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Gällstedt, M.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Chitosan extrusion at high solids content: An orthogonal experimental design study2014Inngår i: Polymers from Renewable Resources, ISSN 2041-2479, Vol. 5, nr 1, s. 1-12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For economic reasons and to save time there is a need to shorten the drying operation associated with the production of chitosan materials. Hence it is of interest to extrude chitosan at as high a solids content as possible. This is, to our knowledge, the first systematic study of the extrusion of chitosan at high solids content (60 wt%). An orthogonal experimental design was used to evaluate the effect of processing conditions and material factors on the extrudability of chitosan. This, together with the examination of the evenness and surface finish of the extrudate, made it possible to determine the best conditions for obtaining a readily extrudable high quality material. It was observed that a 1/1 ratio of chitosans with molar masses of 12 and 133 kDa, a process liquid containing 30 wt% acetic acid and 70 wt% water, and extrusion at 50 rpm and 50°C were the optimal material and processing conditions. Materials processed under these conditions were evaluated mechanically at different times after extrusion (stored at 50% RH) in order to see when the properties stabilized. Most mass loss occurred within the first three days after extrusion and this governed the mechanical properties (stiffness and extensibility), which also exhibited the largest changes within these three days (an increase in modulus from 18 to 830 MPa and a decrease in elongation at break from 17 to 3%).

  • 150.
    Claesson, Hans
    et al.
    KTH, Tidigare Institutioner, Polymerteknologi.
    Malmström, Eva
    KTH, Tidigare Institutioner, Polymerteknologi.
    Johansson, Mats K. G.
    KTH, Tidigare Institutioner, Polymerteknologi.
    Hult, Anders
    KTH, Tidigare Institutioner, Polymerteknologi.
    Doyle, M.
    Manson, J. A. E.
    Rheological behaviour during UV-curing of a star-branched polyester2002Inngår i: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 44, nr 1, s. 63-67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using a rheometer coupled with an UV-light generator, the viscoelastic behaviour during the fast cure of star-branched polyester is investigated. The 32 arm star polymers consist of a hyperbranched polyester core, Boltorn(TM) and linear grafts of poly(E-caprolactone) (degree of polymerisation: 20-52) with methacrylate end groups. The resins are crystalline and the melting points range from 34 to 50degreesC; films can be formed and cured below 80degreesC. The crossover of G' and G was used as the gel point. The time to reach the gel point, a few seconds, increases linearly with molecular weight.

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