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  • 1.
    Alander, B.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Capezza, A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material. Department of Plant Breeding, The Swedish University of Agricultural Sciences, Box 101, Alnarp, Sweden.
    Wu, Q.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Johansson, E.
    Olsson, Richard T.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Hedenqvist, Mikael
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    A facile way of making inexpensive rigid and soft protein biofoams with rapid liquid absorption2018Ingår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 119, s. 41-48Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel and facile method to produce inexpensive protein biofoams suitable for sponge applications is presented. The protein used in the study was wheat gluten (WG), readily available as a by/co-product, but the method is expected to work for other cross-linkable proteins. The foams were obtained by high-speed stirring of pristine WG powder in water at room temperature followed by drying. Glutaraldehyde was used to crosslink the foam material in order to stabilize the dispersion, reduce its tackiness and improve the strength of the final foam. The foams were of medium to high density and absorbed readily both hydrophobic and hydrophilic liquids. The foam structure, consisting primarily of an open pore/channel system, led to a remarkably fast capillary-driven (pore-filling only) uptake of a hydrophobic liquid (limonene). Essentially all uptake occurred within the first second (to ca. 90% of the dry weight). In a polar liquid (water), the rapid pore-filling occurred in parallel with a more time-dependent swelling of the foam matrix material. Further improvement in the foam strength was achieved by making a denser foam or adding TEMPO-oxidized cellulose nanofibres. Soft foams were obtained by adding glycerol.

  • 2.
    Alipour, Nazanin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Andersson, Richard L.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    VOC-Induced Flexing of Single and Multilayer Polyethylene Films As Gas Sensors2016Ingår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, nr 15, s. 9946-9953Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The differential swelling and bending of multilayer polymeric films due to the dissimilar uptake of volatile organic compounds (VOCs; n-hexane, limonene) in the different layers was studied. Motions of thin polyethylene films triggered by the penetrant were investigated to learn more about how their deformation is related to VOC absorption. Single layers of metallocene or low-density polyethylene, and multilayers (2-288-layers) of these in alternating positions were considered. Single-, 24-, and 288 layer films displayed no motion when uniformly subjected to VOCs, but they could display simple curving modes when only one side of the film was wetted with a liquid VOC. Two-layer films displayed simple bending when uniformly subjected to VOCs due to the different swelling in the two layers, but when the VOC was applied to only one side of the film, more complex modes of motion as well as dynamic oscillations were observed (e.g., constant amplitude wagging at 2 Hz for ca. 50 s until all the VOC had evaporated). Diffusion modeling was used to study the transport behavior of VOCs inside the films and the different bending modes. Finally a prototype VOC sensor was developed, where the reproducible curving of the two-layer film was calibrated with n-hexane. The sensor is simple, cost-efficient, and nondestructive and requires no electricity.

  • 3.
    Andersson, Richard L.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Mallon, Peter E.
    Salajkova, Michaela
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Micromechanics of toughness improved electrospun PMMA fibers with embedded cellulose as tested under in-situ microscopyManuskript (preprint) (Övrigt vetenskapligt)
  • 4.
    Andersson, Richard L.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Salajkova, Michaela
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Mallon, P. E.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Micromechanical Tensile Testing of Cellulose-Reinforced Electrospun Fibers Using a Template Transfer Method (TTM)2012Ingår i: Journal of polymers and the environment, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 20, nr 4, s. 967-975Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A template transfer method (TTM) and a fiber fixation technique were established for fiber handling and micro tensile stage mounting of aligned and non-aligned electrospun fiber mats. The custom-made template had been precut to be mounted on a variety of collectors, including a rapidly rotating collector used to align the fibers. The method eliminated need for direct physical interaction with the fiber mats before or during the tensile testing since the fiber mats were never directly clamped or removed from the original substrate. By using the TTM it was possible to measure the tensile properties of aligned poly(methyl methacrylate) (PMMA) fiber mats, which showed a 250 % increase in strength and 450 % increase in modulus as compared to a non-aligned system. The method was further evaluated for aligned PMMA fibers reinforced with cellulose (4 wt%) prepared as enzymatically derived nanofibrillated cellulose (NFC). These fibers showed an additional increase of 30 % in both tensile strength and modulus, resulting in a toughness increase of 25 %. The fracture interfaces of the PMMA-NFC fibers showed a low amount of NFC pull-outs, indicating favorable phase compatibility. The presented fiber handling technique is universal and may be applied where conservative estimates of mechanical properties need to be assessed for very thin fibers.

  • 5.
    Andersson, Richard
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Cabedo, L.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Olsson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Superparamagnetic [sic] nanofibers by electrospinning2016Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, nr 26, s. 21413-21422Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The preparation of superparamagnetic thin fibers by electrospinning dispersions of nanosized magnetite (Fe3O4, SPIO/USPIO) in a PMMA/PEO polymer solution is reported. The saturation magnetization and coercivity were not affected by the concentration (0, 1, 10, 20 wt%) or fiber orientation, showing hysteresis loops with high magnetization (64 A m(2) kg(-1) @ 500 kA m(-1)) and record low coercivity (20 A m(-1)). AC susceptibility measurements vs. temperature at frequencies from 60 to 2 kHz confirmed superparamagnetism. The mechanical properties were only slightly dependent on the particle concentration because the nanoparticles were separately encapsulated by the polymer. A uniform fibre fracture cross section was found at all the investigated particle contents, which suggests a strong interaction at the polymer/particle interface. A theoretical value of the magnetic low field susceptibility was calculated from the Langevin function and compared with measured values. The results show a distinct but concentration-independent anisotropy, favoring magnetization along the fiber orientation with no sign of exchange interaction, explained by complete nanoparticle separation. Superparamagnetism cannot be inferred from particle size alone, so a relevant interpretation and criterion for superparamagnetism is presented, in accordance with Neel's original definition. From the measurements, it can be concluded that magnetic characterization can be used to elucidate the material morphology beyond the resolution of available microscopy techniques (TEM and SEM).

  • 6.
    Andersson, Richard L.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Martinez-Abad, Antonio
    Lagaron, Jose M.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Mallon, Peter E.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Antibacterial Properties of Tough and Strong Electrospun PMMA/PEO Fiber Mats Filled with Lanasol-A Naturally Occurring Brominated Substance2014Ingår i: International Journal of Molecular Sciences, ISSN 1422-0067, E-ISSN 1422-0067, Vol. 15, nr 9, s. 15912-15923Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new type of antimicrobial, biocompatible and toughness enhanced ultra-thin fiber mats for biomedical applications is presented. The tough and porous fiber mats were obtained by electrospinning solution-blended poly (methyl methacrylate) (PMMA) and polyethylene oxide (PEO), filled with up to 25 wt % of Lanasol-a naturally occurring brominated cyclic compound that can be extracted from red sea algae. Antibacterial effectiveness was tested following the industrial Standard JIS L 1902 and under agitated medium (ASTM E2149). Even at the lowest concentrations of Lanasol, 4 wt %, a significant bactericidal effect was seen with a 4-log (99.99%) reduction in bacterial viability against S. aureus, which is one of the leading causes of hospital-acquired (nosocomial) infections in the world. The mechanical fiber toughness was insignificantly altered up to the maximum Lanasol concentration tested, and was for all fiber mats orders of magnitudes higher than electrospun fibers based on solely PMMA. This antimicrobial fiber system, relying on a dissolved antimicrobial agent (demonstrated by X-ray diffraction and Infrared (IR)-spectroscopy) rather than a dispersed and "mixed-in" solid antibacterial particle phase, presents a new concept which opens the door to tougher, stronger and more ductile antimicrobial fibers.

  • 7.
    Andersson, Richard L.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Mallon, Peter E.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Micromechanics of ultra-toughened electrospun PMMA/PEO fibres as revealed by in-situ tensile testing in an electron microscope2014Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, s. 6335-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A missing cornerstone in the development of tough micro/nano fibre systems is an understanding of the fibre failure mechanisms, which stems from the limitation in observing the fracture of objects with dimensions one hundredth of the width of a hair strand. Tensile testing in the electron microscope is herein adopted to reveal the fracture behaviour of a novel type of toughened electrospun poly(methyl methacrylate)/poly(ethylene oxide) fibre mats for biomedical applications. These fibres showed a toughness more than two orders of magnitude greater than that of pristine PMMA fibres. The in-situ microscopy revealed that the toughness were not only dependent on the initial molecular alignment after spinning, but also on the polymer formulation that could promote further molecular orientation during the formation of micro/nano-necking. The true fibre strength was greater than 150 MPa, which was considerably higher than that of the unmodified PMMA (17 MPa). This necking phenomenon was prohibited by high aspect ratio cellulose nanocrystal fillers in the ultra-tough fibres, leading to a decrease in toughness by more than one order of magnitude. The reported necking mechanism may have broad implications also within more traditional melt-spinning research.

  • 8.
    Antonio, Capezza
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Andersson, Richard L.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Wu, Qiong
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer.
    Sacchi, Benedetta
    Univ Milan, Dept Chem, Via Golgi 19, I-20133 Milan, Italy.
    Farris, Stefano
    Univ Milan, DeFENS, Dept Food Environm & Nutr Sci, Packaging Div, Via Celoria 2, I-20133 Milan, Italy.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Olsson, Richard T.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Preparation and Comparison of Reduced Graphene Oxide and Carbon Nanotubes as Fillers in Conductive Natural Rubber for Flexible Electronics2019Ingår i: Omega, ISSN 0030-2228, E-ISSN 1541-3764, Vol. 4, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Conductive natural rubber (NR) nanocomposites were prepared by solvent-casting suspensions of reduced graphene oxide(rGO) or carbon nanotubes (CNTs), followed by vulcanization of the rubber composites. Both rGO and CNT were compatible as fillers in the NR as well as having sufficient intrinsic electrical conductivity for functional applications. Physical (thermal) and chemical reduction of GO were investigated, and the results of the reductions were monitored by X-ray photoelectron spectroscopy for establishing a reduction protocol that was useful for the rGO nanocomposite preparation. Field-emission scanning electron microscopy showed that both nanofillers were adequately dispersed in the main NR phase. The CNT composite displays a marked mechanical hysteresis and higher elongation at break, in comparison to the rGO composites for an equal fraction of the carbon phase. Moreover, the composite conductivity was always ca. 3-4 orders of magnitude higher for the CNT composite than for the rGO composites, the former reaching a maximum conductivity of ca. 10.5 S/m, which was explained by the more favorable geometry of the CNT versus the rGO sheets. For low current density applications though, both composites achieved the necessary percolation and showed the electrical conductivity needed for being applied as flexible conductors for a light-emitting diode. 

  • 9.
    Blomfeldt, Thomas O. J.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Menon, Mohan
    Plackett, David
    Johansson, Eva
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Novel Foams Based on Freeze-Dried Renewable Vital Wheat Gluten2010Ingår i: Macromolecular materials and engineering (Print), ISSN 1438-7492, E-ISSN 1439-2054, Vol. 295, nr 9, s. 796-801Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new way of producing rigid or semi-rigid foams from vital wheat gluten using a freeze-drying process is reported. Water/gluten-based mixtures were frozen and freeze-dried. Different foam structures were obtained by varying the mixing process and wheat gluten concentration, or by adding glycerol or bacterial cellulose nanofibers. MIP revealed that the foams had mainly an open porosity peaking at 93%. The average pore diameter ranged between 20 and 73 mm; the sample with the highest wheat gluten concentration and no plasticizer had the smallest pores. Immersion tests with limonene revealed that the foams rapidly soaked up the liquid. An especially interesting feature of the low-wheat-concentration foams was the "in situ'' created soft-top-rigid-bottom foams.

  • 10.
    Capezza, Antonio Jose
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Glad, David
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Ozeren, Husamettin Deniz
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Newson, William R.
    SLU Swedish Univ Agr Sci, Fac Landscape Planning Hort & Crop Prod Sci, Dept Plant Breeding, Sundsvagen 10, S-23053 Alnarp, Sweden..
    Olsson, Richard
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Johansson, Eva
    SLU Swedish Univ Agr Sci, Fac Landscape Planning Hort & Crop Prod Sci, Dept Plant Breeding, Sundsvagen 10, S-23053 Alnarp, Sweden..
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Novel Sustainable Superabsorbents: A One-Pot Method for Functionalization of Side-Stream Potato Proteins2019Ingår i: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 7, nr 21, s. 17845-17854Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The functionalization of inexpensive potato protein concentrate (PPC) is presented as a simple and easily scalable method to produce bio-based superabsorbent powders. Five nontoxic acylating agents were evaluated at different reaction temperatures for solvent-free acylation of the protein. The best results were obtained for succinic anhydride (SA) and a reaction temperature of 140 degrees C. These conditions resulted in efficient functionalization that provided formation of a useful network, which allowed high uptake of fluids and little material disintegration during the uptake, that is, due to protein hydrolysis during the functionalization. The SA-acylated PPC showed increased water and saline swelling capacities of 600 and 60%, respectively, as compared to untreated PPC. The acylated potato protein also showed a saline liquid holding capacity of approximately 50% after centrifugation at 1230 rpm for 3 min, as well as a significant blood swelling capacity of 530%. This blood swelling represents more than 50% of that of a commercial fossil-based superabsorbent (SAP) used for blood absorption in sanitary health products. The swelling properties of these inexpensive protein-based acylated materials highlight their potential as sustainable SAP materials (from industrial side-streams) in applications such as daily care products that are currently dominated by fossil-based SAPs.

  • 11. Castro-Mayorga, J. L.
    et al.
    Fabra, M. J.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Lagaron, J. M.
    The impact of zinc oxide particle morphology as an antimicrobial and when incorporated in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) films for food packaging and food contact surfaces applications2017Ingår i: Food and Bioproducts Processing, ISSN 0960-3085, E-ISSN 1744-3571, Vol. 101, s. 32-44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, zinc oxide (ZnO) micron and nano sized-particles with different morphologies were synthesized by aqueous precipitation and evaluated as antimicrobial agents against foodborne pathogens. The most effective bactericide system was selected to prepare active poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films by three different methods (i) direct melt-mixing, (ii) melt-mixing of preincorporated ZnO into PHBV18 (18 mol% valerate content) fiber mats made by electrospinning, and, (iii) as a coating of the annealed electrospun PHBV18/ZnO fiber mats over compression molded PHBV. Results showed that ZnO successfully improved the thermal stability of the PHBV18, being the preincorporation method the most efficient in mitigating the negative impact that the PHBV18 had on the thermal stability, barrier and optical properties of the PHBV films. Similar behavior was found for the coating structure although this film showed effective and prolonged antibacterial activity against Listeria monocytogenes. This study highlights the suitability of the PHBV/ZnO nanostructures for active food packaging and food contact surface applications.

  • 12.
    Chen, Fei
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Gällstedt, M.
    Olsson, Rickard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    A novel chitosan/wheat gluten biofoam fabricated by spontaneous mixing and vacuum-drying2015Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, nr 114, s. 94191-94200Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new type of chitosan and wheat gluten biofoam is presented. The pore structure achieved relied solely on the specific mixing and phase distribution when a film was cast from an aqueous mixture of chitosan/wheat gluten solution, in the absence of any chemical blowing agent, porogen or expanding gas. The foam was obtained when the liquid phase was removed by vacuum drying, without the need for the traditional freeze-drying that is frequently used for pore formation. Soft foam samples could be prepared with stiffnesses from 0.3 to 1.2 MPa and a high rebound resilience (64 and 94% at compressive strains of 80 and 20%, respectively). The foams were relatively ductile and did not require any plasticiser to allow for in-plane deformation (20% compression) and smaller bending. Only open pores with sizes of the order of 70-80 μm were observed by microscopy. The density of all the foams was ∼50 kg m-3, due to the high porosity (96% air). The foams showed a rapid and large uptake of both non-polar (limonene) and polar (water) liquids. When immersed in these liquids for 1 second, the maximum uptake recorded was 40 times the initial mass of the foam for limonene and 8 times for water.

  • 13.
    Chen, Fei
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Gällstedt, Mikael
    Olsson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    A Novel Chitosan/Wheat Gluten Biofoam Fabricated by Mixing and Vacuum-dryingManuskript (preprint) (Övrigt vetenskapligt)
  • 14.
    Chen, Fei
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Gällstedt, Mikael
    Olsson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Unusual Effects of Monocarboxylic Acids on The Structure and on The Transport and Mechanical Properties of Chitosan Films2015Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 132, s. 419-429Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this study was to study the transport of monocarboxylic acids in chitosan films, since this is important for understanding and predicting the drying kinetics of chitosan from aqueous solutions. Despite the wealth of data on chitosan films prepared from aqueous monocarboxylic acid solutions, this transport has not been reported. Chitosan films were exposed to formic, acetic, propionic and butyric acid vapours, it was found that the rate of uptake decreased with increasing molecular size. The equilibration time was unexpectedly long, especially for propionic and butyric acid, nine months. A clear two-stage uptake curve was observed for propionic acid. Evidently, the rate of uptake was determined by acid-induced changes in the material. X-ray diffraction and infrared spectroscopy indicated that the structure of the chitosan acetate and buffered chitosan films changed during exposure to acid and during the subsequent drying. The dried films previously exposed to the acid showed less crystalline features than the original material and a novel repeating structure possibly involving acid molecules. The molar mass of the chitosan decreased on exposure to acid but tensile tests revealed that the films were always ductile. The films exposed to acid vapour (propionic and butyric acid) for the longest period of time were insoluble in the size-exclusion chromatography eluent, and they were also the most ductile/extensible of all samples studied.

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

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

  • 16.
    Das, Oisik
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Johansson, E.
    Olsson, Richard
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Loho, T. A.
    Capezza, Antonio J.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Singh Raman, R. K.
    Holder, Shima
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    An all-gluten biocomposite: Comparisons with carbon black and pine char composites2019Ingår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 120, s. 42-48Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 17.
    Fang, Mei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Belova, Lyubov
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Rao, K. Venkat
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Particle size and magnetic properties dependence on growth temperature for rapid mixed co-precipitated magnetite nanoparticles2012Ingår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, nr 14, s. 145601-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnetite nanoparticles have been prepared by co-precipitation using a custom-designed jet mixer to achieve rapid mixing (RM) of reactants in a timescale of milliseconds. The quick and stable nucleation obtained allows control of the particle size and size distribution via a more defined growth process. Nanoparticles of different sizes were prepared by controlling the processing temperature in the first few seconds post-mixing. The average size of the nanoparticles investigated using a Tecnai transmission electron microscope is found to increase with the temperature from 3.8 nm at 1 +/- 1 degrees C to 10.9 nm for particles grown at 95 +/- 1 degrees C. The temperature dependence of the size distribution follows the same trend and is explained in terms of Ostwald ripening of the magnetite nanoparticles during the co-precipitation of Fe2+ and Fe3+. The magnetic properties were studied by monitoring the blocking temperature via both DC and AC techniques. Strikingly, the obtained RM particles maintain the high magnetization (as high as similar to 88 A m(2) kg(-1) at 500 kA m(-1)) while the coercivity is as low as similar to 12 A m(-1) with the expected temperature dependence. Besides, by adding a drop of tetramethylammonium hydroxide, aqueous ferrofluids with long term stability are obtained, suggesting their suitability for applications in ferrofluid technology and biomedicine.

  • 18.
    Fang, Mei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Belova, Lyubov
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Rao, K. Venkat
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Rapid mixing: A route to synthesize magnetite nanoparticles with high moment2011Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, nr 22, s. 222501-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate the impact of rapid mixing of the precursors in a time scale of milliseconds on the reaction rate and magnetic properties of co-precipitated magnetite with a custom-made mixer. The mixed volume is directed into a desk-top AC susceptometer to monitor the magnetic response from the growing particles in real-time. These measurements indicate that the reaction is mostly completed within a minute. The obtained superparamagnetic nanoparticles exhibit a narrow size distribution and large magnetization (87 Am(2) kg(-1)). Transmission electron micrographs suggest that rapid mixing is the key for better crystallinity and a more uniform morphology leading to the observed magnetization values.

  • 19.
    Galland, Sylvain
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Andersson, Richard L.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Olsson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
    Strong and Moldable Cellulose Magnets with High Ferrite Nanoparticle Content2014Ingår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, nr 22, s. 20524-20534Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major limitation in the development of highly functional hybrid nanocomposites is brittleness and low tensile strength at high inorganic nanoparticle content. Herein, cellulose nanofibers were extracted from wood and individually decorated with cobalt-ferrite nanoparticles and then for the first time molded at low temperature (<120 degrees C) into magnetic nanocomposites with up to 93 wt % inorganic content. The material structure was characterized by TEM and FE-SEM and mechanically tested as compression molded samples. The obtained porous magnetic sheets were further impregnated with a thermosetting epoxy resin, which improved the load-bearing functions of ferrite and cellulose material. A nanocomposite with 70 wt % ferrite, 20 wt % cellulose nanofibers, and 10 wt % epoxy showed a modulus of 12.6 GPa, a tensile strength of 97 MPa, and a strain at failure of ca. 4%. Magnetic characterization was performed in a vibrating sample magnetometer, which showed that the coercivity was unaffected and that the saturation magnetization was in proportion with the ferrite content. The used ferrite, CoFe2O4 is a magnetically hard material, demonstrated by that the composite material behaved as a traditional permanent magnet. The presented processing route is easily adaptable to prepare millimeter-thick and moldable magnetic objects. This suggests that the processing method has the potential to be scaled-up for industrial use for the preparation of a new subcategory of magnetic, low-cost, and moldable objects based on cellulose nanofibers.

  • 20.
    Galland, Sylvain
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Andersson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Salajkova, Michaela
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Olsson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Cellulose nanofibers decorated with magnetic nanoparticles: synthesis, structure and use in magnetized high toughness membranes for a prototype loudspeaker2013Ingår i: Journal of Materials Chemistry C, ISSN 2050-7526, Vol. 1, nr 47, s. 7963-7972Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnetic nanoparticles are the functional component for magnetic membranes, but they are difficult to disperse and process into tough membranes. Here, cellulose nanofibers are decorated with magnetic ferrite nanoparticles formed in situ which ensures a uniform particle distribution, thereby avoiding the traditional mixing stage with the potential risk of particle agglomeration. The attachment of the particles to the nanofibrils is achieved via aqueous in situ hydrolysis of metal precursors onto the fibrils at temperatures below 100 °C. Metal adsorption and precursor quantification were carried out using Induction Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). FE-SEM was used for high resolution characterization of the decorated nanofibers and hybrid membranes, and TEM was used for nanoparticle size distribution studies. The decorated nanofibers form a hydrocolloid. Large (200 mm diameter) hybrid cellulose/ferrite membranes were prepared by simple filtration and drying of the colloidal suspension. The low-density, flexible and permanently magnetized membranes contain as much as 60 wt% uniformly dispersed nanoparticles (thermogravimetric analysis data). Hysteresis magnetization was measured by a Vibrating Sample Magnetometer; the inorganic phase was characterized by XRD. Membrane mechanical properties were measured in uniaxial tension. An ultrathin prototype loudspeaker was made and its acoustic performance in terms of output sound pressure was characterized. A full spectrum of audible frequencies was resolved.

  • 21. Ghaani, M.
    et al.
    Rovera, C.
    Pucillo, F.
    Ghaani, M. R.
    Olsson, Richard T.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Scampicchio, M.
    Farris, S.
    Determination of 2,4-diaminotoluene by a bionanocomposite modified glassy carbon electrode2018Ingår i: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 277, s. 477-483Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work describes the development of a modified glassy carbon electrode (GCE) for the selective determination of 2,4-diaminotoluene (TDA), a primary aromatic amines (PAAs) that can be formed in food packaging materials including aromatic polyurethane (PU) adhesives. The electrode's surface was modified with multi-walled carbon nanotubes (MWCNTs), MWCNTs in chitosan (CS), and gold nanoparticles (AuNPs). The highest current response was achieved with AuNPs/MWCNTs-CS/GC electrodes, which exhibited an oxidation peak of 9.87 μA by cyclic voltammetry (CV), compared with 1.39 μA of the bare GCE. A detection limit of 35 nM was estimated by amperometry experiments. The oxidation of TDA was strongly dependent on the pH of the medium, having maximum sensitivity at pH ∼ 7. From a mechanistic point of view, the diffusion coefficient of TDA (D = 6.47 × 10−4 cm2 s−1) and the number of electrons (n ≈ 2) involved in the catalytic oxidation of TDA at the surface of the AuNPs/MWCNTs-CS/GCE were determined. The practical utility of this nanocomposite modified electrode was demonstrated by migration studies from conventional food packaging materials. 

  • 22.
    Ghaani, Masoud
    et al.
    Univ Milan, Dept Food Environm & Nutr Sci, DeFENS, Food Packaging Lab, Via Celoria 2, I-20133 Milan, Italy..
    Pucillo, Flavia
    Univ Milan, Dept Food Environm & Nutr Sci, DeFENS, Food Packaging Lab, Via Celoria 2, I-20133 Milan, Italy..
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Scampicchio, Matteo
    Free Univ Bolzano, Piazza Univ 1, I-39100 Bolzano, Italy..
    Farris, Stefano
    Univ Milan, Dept Food Environm & Nutr Sci, DeFENS, Food Packaging Lab, Via Celoria 2, I-20133 Milan, Italy.;Univ Milan, Natl Consortium Mat Sci & Technol, INSTM, Local Unit, Via Celoria 2, I-20133 Milan, Italy..
    A bionanocomposite- modified glassy carbon electrode for the determination of 4,4 0-methylene diphenyl diamine2018Ingår i: Analytical Methods, ISSN 1759-9660, E-ISSN 1759-9679, Vol. 10, nr 34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A nanosensor based on a glassy carbon electrode modified with the biopolymer chitosan, multi-wall carbon nanotubes, and gold nanoparticles (MWCNTs-CS-AuNPs/GCE) was developed for the determination of 4,4-diaminodiphenyl diamine (MDA). Cyclic voltammetry (CV) was used to investigate the electrochemical behavior of the sensor in the presence of MDA. MDA displayed a well-expressed oxidation peak at 0.54 V (versus Ag/AgCl) in Britton-Robinson (B-R) universal buffer solution (pH = 10). The transfer coefficient, , and the overall number of electrons (n) involved in the catalytic oxidation of MDA at the MWCNTs-CS-AuNPs/GCE surface were also determined by CV. The reactivity of spiked MDA was strongly dependent on the pH of the supporting electrolyte, with the pH dependence of the MDA oxidation quantified as 27.576 mV pH(-1). Through chronoamperometry, the diffusion coefficient (D) of MDA was calculated to be 9.49 x 10(-5) cm(2) s(-1). The limit of detection of MDA was estimated to be approximate to 20 nM through amperometry experiments, while three linear ranges were found for MDA, i.e., 0.49-10.14 M, 10.14-94.9 M, and 94.9-261.18 M. Real sample tests enabled us to emphasize the potential of this nanocomposite-modified electrode as a new analytical tool for the determination of MDA.

  • 23. González-Ausejo, J.
    et al.
    Sanchez-Safont, E.
    Lagaron, J. M.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gamez-Perez, J.
    Cabedo, L.
    Assessing the thermoformability of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/poly(acid lactic) blends compatibilized with diisocyanates2017Ingår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 62, s. 235-245Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a renewable alternative to conventional barrier packaging polymers due to its thermoplastic properties, biodegradability and gas barrier performance but its potential industrial applications are limited by its high price and difficult processability. A thorough study concerning the thermoforming ability of PHBV, and blends with poly(lactic acid) (PLA) incorporating three different diisocyanates as compatibilizers (hexamethylene diisocyanate, poly(hexamethylene) diisocyanate and 1,4-phenylene diisocyanate) is herein presented after component melt blending. A straightforward universal qualitative method is proposed to assess the thermoformability, based on a visual inspection of a thermoformed specimen and the ability to reproduce the mold shape, and the thermoforming window of the material. The results reveal a significant improvement in the thermoforming capacity and a widening of the thermoforming windows as the correct amounts of diisocyanates are incorporated. The barrier properties and the biodisintegrability of the blends was also studied, confirming a predictable slight decrease of the barrier performance when PLA is added, but without negatively affecting the disintegrability under composting conditions with respect to pristine PHBV.

  • 24.
    Guex, Leonard Gaston
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Sacchi, B.
    Peuvot, Kevin F.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Andersson, Richard L.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Farris, S.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Experimental review: chemical reduction of graphene oxide (GO) to reduced graphene oxide (rGO) by aqueous chemistry2017Ingår i: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, nr 27, s. 9562-9571Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The electrical conductivity of reduced graphene oxide (rGO) obtained from graphene oxide (GO) using sodium borohydride (NaBH4) as a reducing agent has been investigated as a function of time (2 min to 24 h) and temperature (20 degrees C to 80 degrees C). Using a 300 mM aqueous NaBH4 solution at 80 degrees C, reduction of GO occurred to a large extent during the first 10 min, which yielded a conductivity increase of 5 orders of magnitude to 10 S m(-1). During the residual 1400 min of reaction, the reduction rate decreased significantly, eventually resulting in a rGO conductivity of 1500 S m(-1). High resolution XPS measurements showed that C/O increased from 2.2 for the GO to 6.9 for the rGO at the longest reaction times, due to the elimination of oxygen. The steep increase in conductivity recorded during the first 8-12 min of reaction was mainly due to the reduction of C-O (e.g., hydroxyl and epoxy) groups, suggesting the preferential attack of the reducing agent on C-O rather than C=O groups. In addition, the specular variation of the percentage content of C-O bond functionalities with the sum of Csp(2) and Csp(3) indicated that the reduction of epoxy or hydroxyl groups had a greater impact on the restoration of the conductive nature of the graphite structure in rGO. These findings were reflected in the dramatic change in the structural stability of the rGO nanofoams produced by freeze-drying. The reduction protocol in this study allowed to achieve the highest conductivity values reported so far for the aqueous reduction of graphene oxide mediated by sodium borohydride. The 4-probe sheet resistivity approach used to measure the electrical conductivity is also, for the first time, presented in detail for filtrate sheet assemblies' of stacked GO/rGO sheets.

  • 25. Jänis, A.
    et al.
    Olsson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Savage, S. J.
    Klement, U.
    Microwave absorbing properties of structural nanocomposites with surface treated Co ferrite nanoparticles as filler2010Ingår i: Behavior And Mechanics Of Multifunctional Materials And Composites 2010, SPIE - International Society for Optical Engineering, 2010, s. 76441E-Konferensbidrag (Refereegranskat)
    Abstract [en]

    An analysis of the microwave absorbing properties of several polymer-(epoxy) based nanocomposites is presented. The nanoparticles of interest for this study were cobalt ferrite nanoparticles. For better dispersion of the nanoparticles in the polymer matrix surface treatment of the nanoparticles with silane compounds was performed. The nanoparticles were surface-treated with 3-glycidoxypropyl- (GPTMS), aminopropyl- (APTMS) or methyl-silsesquioxane (MTMS). The nanoparticles with GPTMS-coating dispersed well in epoxy without sedimentation while the other nanoparticles formed agglomerates in epoxy. The GPTMS-based composites showed higher fracture toughness than the MTMS-based composites. The microwave properties, permittivity and permeability, of GPTMS-based composites were measured in the frequency range between 3.95 GHz and 18 GHz and showed no influence of surface treatment on permeability.

  • 26. Jänis, A.
    et al.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Savage, S. J.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Klement, U.
    Microwave absorbing properties of ferrite-based nanocomposites2007Ingår i: Behavior and Mechanics of Multifunctional and Composite Materials 2007, SPIE - International Society for Optical Engineering, 2007, s. 65261P-Konferensbidrag (Refereegranskat)
    Abstract [en]

    A study of the microwave absorbing properties of polymer (epoxy) based nanocomposites is presented. The ferrite nanoparticles employed as filler materials were produced by a co-precipitation method, which was designed for production of large amounts at low cost. The absorbing properties of different kinds of ferrite nanoparticles, soft (manganese) and hard (cobalt) magnetic nanoparticles, are compared. In addition, the impact of high and low densities of the respective ferrite type has been investigated. Our analysis of the microwave absorbing properties is made over a wide frequency band including both MHz and GHz regions, which is of high interest for a number of different applications both military and civilian.

  • 27.
    Karlsson, Mattias E.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Mamie, Yann C.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Calamida, Andrea
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Gardner, James M.
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Olsson, Richard
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Synthesis of Zinc Oxide Nanorods via the Formation of Sea Urchin Structures and Their Photoluminescence after Heat Treatment2018Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 17, s. 5079-5087Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A protocol for the aqueous synthesis of ca. 1-mu m-long zinc oxide (ZnO) nanorods and their growth at intermediate reaction progression is presented, together with photoluminescence (PL) characteristics after heat treatment at temperatures of up to 1000 degrees C. The existence of solitary rods after the complete reaction (60 min) was traced back to the development of sea urchin structures during the first 5 s of the precipitation. The rods primarily formed in later stages during the reaction due to fracture, which was supported by the frequently observed broken rod ends with sharp edges in the final material, in addition to tapered uniform rod ends consistent with their natural growth direction. The more dominant rod growth in the c direction (extending the length of the rods), together with the appearance of faceted surfaces on the sides of the rods, occurred at longer reaction times (>5 min) and generated zinc-terminated particles that were more resistant to alkaline dissolution. A heat treatment for 1 h at 600 or 800 degrees C resulted in a smoothing of the rod surfaces, and PL measurements displayed a decreased defect emission at ca. 600 nm, which was related to the disappearance of lattice imperfections formed during the synthesis. A heat treatment at 1000 degrees C resulted in significant crystal growth reflected as an increase in luminescence at shorter wavelengths (ca. 510 nm). Electron microscopy revealed that the faceted rod structure was lost for ZnO rods exposed to temperatures above 600 degrees C, whereas even higher temperatures resulted in particle sintering and/or mass redistribution along the initially long and slender ZnO rods. The synthesized ZnO rods were a more stable Wurtzite crystal structure than previously reported ball-shaped ZnO consisting of merging sheets, which was supported by the shifts in PL spectra occurring at ca. 200 degrees C higher annealing temperature, in combination with a smaller thermogravimetric mass loss occurring upon heating the rods to 800 degrees C.

  • 28.
    Liu, Dongming
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hoang, A. T.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pallon, Love K. H.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Nilsson, Fritjof
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gubanski, S. M.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Influence of Nanoparticle Surface Coating on Electrical Conductivity of LDPE/Al2O3 Nanocomposites for HVDC Cable Insulations2017Ingår i: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 24, nr 3, s. 1396-1404Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    LDPE/metal oxide nanocomposites are promising materials for future high-voltage DC cable insulation. This paper presents data on the influence of the structure of the nanoparticle coating on the electrical conductivity of LDPE/Al2O3 nanocomposites. Al2O3 nanoparticles, 50 nm in size, were coated with a series of silanes with terminal alkyl groups of different lengths (methyl, n-octyl and n-octadecyl groups). The density of the coatings in vacuum was between 200 and 515 kg m(-3,) indicating substantial porosity in the coating. The dispersion of the nanoparticles in the LDPE matrix was assessed based on statistics for the nearest-neighbor particle distance. The electrical conductivity of the nanocomposites was determined at both 40 and 60 degrees C. The results show that an appropriate surface coating on the nanoparticles allowed uniform particle dispersion up to a filler loading of 10 wt.%, with a maximum reduction in the electrical conductivity by a factor of 35. The composites based on the most porous octyl-coated nanoparticles showed the greatest reduction in electrical conductivity and the lowest temperature coefficient of electrical conductivity of the composites studied.

  • 29.
    Liu, Dongming
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hoang, A.T
    Chalmers University of Technology.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Pallon, Love
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gubanski, Stanislaw
    Chalmers University of Technology.
    Ohlsson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Influence of nanoparticle surface coating on electrical conductivity of polyethylene/aluminium oxide nanocomposites for HVDC cable insulations2016Ingår i: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135Artikel i tidskrift (Refereegranskat)
  • 30.
    Liu, Dongming
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pallon, Love K. H.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Zhang, P.
    Diaz, A.
    Holler, M.
    Schneider, K.
    Olsson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Yu, Shun
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gedde, Ulf W
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Cavitation in strained polyethylene/aluminium oxide nanocomposites2017Ingår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 87, s. 255-265Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The incorporation of metal oxide (e.g. Al2O3) nanoparticles has a pronounced positive effect on low-density polyethylene (LDPE) as an insulating material for high-voltage direct-current (HVDC) cables, the electrical conductivity being decreased by one to two orders of magnitude and charge species being trapped by the nanoparticles. The risk of debonding between the nanoparticles and the polymer matrix leading to electrical treeing via electrical discharges in the formed cavities was the motivation for this study. Scanning electron microscope (SEM), small-angle X-ray scattering (SAXS) and X-ray ptychographic tomography were used to study a series of LDPE nanocomposites which contained Al2O3 nanoparticles treated with silanes having terminal alkyl groups of different lengths (methyl, octyl and octadecyl). When specimens were subjected to a tensile strain (a typical specimen stretched beyond the onset of necking consisted of three zones according to SEM of specimens that were studied after removal of the external force: an essentially cavitation-free zone with low local plastic strain, a transitional zone in which local plastic strain showed a marked increase and the revealed concentration of permanent cavities increased with increasing plastic strain and a highly strained zone with extensive cavitation), the cavitation occurred mainly at the polymer-nanoparticle interface according to SEM and X-ray ptychographic tomography and according to SEM progressed with increasing plastic strain through an initial phase with no detectable formation of permanent cavities to a period of very fast cavitation and finally almost an order of magnitude slower cavitation. The polymer/nanoparticle interface was fractal before deformation, as revealed by the profile of the Porod region in SAXS, presumably due to the existence of bound polymers at the nanoparticle surface. A pronounced decrease in the interface fractal dimension was observed when the strain exceeded a critical value; a phenomenon attributed to the stress-induced de-bonding of nanoparticles. The strain-dependence of the interface fractal dimension value at low strain levels between composites containing differently treated nanoparticles seems to be an indicator of the strength of the nanoparticle-polymer interface.

  • 31.
    Liu, Dongming
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pallon, Love
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Zhang, Peng
    Deutsches Elektronen-Synchrotron (DESY).
    Diaz, Ana
    Paul Scherrer Institut.
    Holler, Mirko
    Paul Scherrer Institut.
    Schneider, Konrad
    Leibniz Institut für Polymerforschung Dresden.
    Olsson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Yu, Shun
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Cavitation in strained polyethylene/aluminium oxide nanocomposites2016Ingår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945Artikel i tidskrift (Refereegranskat)
  • 32.
    Liu, Dongming
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Influence of nanoparticle surface treatment on particle dispersion and interfacial adhesion in low-density polyethylene/aluminium oxide nanocomposites2015Ingår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 66, s. 67-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of silsesquioxane coating of aluminium oxide nanoparticles on their dispersion and on the interfacial strength between nanoparticles and polymer matrix in low-density polyethylene composites was studied. The surface chemistry of the nanoparticles was tailored from hydroxyl groups to alkyl groups with different lengths by reacting methyltrimethoxysilane (C1), octyltriethoxysilane (C8) or octadecyltrimethoxysilane (C18) with aluminium oxide nanoparticles. The core–shell structure of the coated nanoparticles was assessed by transmission electron microscopy, infrared spectroscopy and thermogravimetry. The inter-particle distance of the nanocomposite based on C8-coated nanoparticles showed only a small deviation from the ideal value, indicating a very good particle dispersion in the polymer. The interfacial adhesion between nanoparticles and matrix was determined by stretching nanocomposite specimens in a tensile testing machine to strains well beyond the yield point. A drop in the stress–strain curve indicated the onset of cavitation and necking in the nanocomposites. Samples stretched to different strain levels were studied by scanning electron microscopy and the cavitation was found to be confined to particle interfaces. The composite based on C18-coated nanoparticles showed the highest strain at cavitation/necking suggesting a high interfacial adhesion between nanoparticles and polymer.

  • 33.
    Liu, Dongming
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Pallon, Love K. H.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Andersson, Richard L.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Morphology and properties of silica-based coatings with different functionalities for Fe3O4, ZnO and Al2O3 nanoparticles2015Ingår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, nr 59, s. 48094-48103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A facile single-step method for obtaining 2–3 nm thick silsesquioxane coatings on metal oxide nanoparticles using different carbon-functional silane precursors is presented. Iron oxide nanoparticles 8.5 nm in diameter were used as a model to evaluate the possibilities of forming different uniform carbon-functional coatings, ranging from hydrophobic to hydrophilic in character. Electron microscopy showed that all the coated nanoparticles could be described as core-shell nanoparticles with single Fe3O4 cores and carbon-functional silsesquioxane shells, without any core-free silicone oxide phase. Steric factors strongly influenced the deposited silicon oxide precursors with octyl-, methyl- or aminopropyl functionalities, resulting in coating densities ranging from 260 to 560 kg/m3. The methyl-functional coatings required several layers of silsesquioxane, 3–4, to build up the 2 nm structures, whereas only 1-2 layers were required for silsesquioxane with octyl groups. Pure silica coatings from tetraethoxysilanes were however considerably thicker due to the absence of steric hindrance during deposition, allowing the formation of 5–7 nm coatings of ca. 10 layers. The coating method developed for the iron oxide nanoparticles was generic and successfully transferred and up–scaled 30 and 325 times (by volume) to be applicable to 25 nm ZnO and 45 nm Al2O3 nanoparticles.

  • 34.
    Liu, Dongming
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pourrahimi, Amir Masoud
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pallon, Love K. H.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Sanchez, Carmen Cobo
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Fogelström, Linda
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Interactions between a phenolic antioxidant, moisture, peroxide and crosslinking by-products with metal oxide nanoparticles in branched polyethylene2016Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 125, s. 21-32Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyethylene composites based on metal oxide nanoparticles are emerging materials for use in the insulation of extruded HVDC cables. The short-term electrical performance of these materials is adequate, but their stability for extended service needs to be assessed. This study is focussed on the capacity of the nanoparticles to adsorb polar species (water, dicumyl peroxide and byproducts from peroxide-vulcanisation, acetophenone and cumyl alcohol) that have an impact on the electrical conductivity of nanocomposites, the oxidative stability by adsorption of phenolic antioxidants on the nanoparticles and the potential transfer of catalytic impurities from the nanoparticles to the polymer. The adsorption of water, dicumyl peroxide, acetophenone, cumyl alcohol and Irganox 1076 (phenolic antioxidant) on pristine and coated (hydrophobic silanes and poly(lauryl methacrylate)) Al2O3, MgO and ZnO particles ranging from 25 nm to 2 gm was assessed. Composites based on low-density polyethylene and the particles mentioned (<= 12 wt.%) were prepared, the degree of adsorption of Irganox 1076 onto the particles was assessed by OIT measurements, and the release of volatile species at elevated temperature was assessed by TG. The concentration of moisture adsorbed on the particles at 25 degrees C increased linearly with both increasing hydroxyl group concentration on the particle surfaces and increasing relative humidity. Dicumyl peroxide showed no adsorption on any of the nanoparticles. Acetophenone and cumyl alcohol showed a linear increase in adsorption with increasing concentration of hydroxyl groups, but the quantities were much smaller than those of water. Irganox 1076 adsorbed only onto the uncoated nanoparticles. Uncoated ZnO nanoparticles that contained ionic species promoted radical formation and a lowering of the OIT. This study showed that carefully coated pure metal oxide nano particles are not likely to adsorb phenolic antioxidants or dicumyl peroxide, but that they have the capacity to adsorb moisture and polar byproducts from peroxide vulcanisation, and that they will not introduce destabilizing ionic species into the polymer matrix. Low contents of dry, equiaxed ZnO and MgO particles strongly retarded the release of volatile species at temperatures above 300 degrees C.

  • 35.
    Liu, Dongming
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wu, Qiong
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Andersson, Richard L.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Farris, Stefano
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Cellulose nanofibril core-shell silica coatings and their conversion into thermally stable nanotube aerogels2015Ingår i: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, nr 30, s. 15745-15754Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A facile water-based one-pot reaction protocol for obtaining 20 nm thick uniform silica coatings on cellulose nanofibrils (CNFs) is herein presented for the first time. The fully covering silica shells result in the thermal stability of the CNFs improved by ca. 70 degrees C and 50 degrees C under nitrogen and oxygen atmospheres, respectively. Heating of the core-shell hybrid fibres to 400 degrees C results in complete degradation/removal of the CNF cores, and demonstrates an inexpensive route to large-scale preparation of silica nanotubes with the CNFs used as templates. The key to a uniform condensation of silica (from tetraethyl orthosilicate) to cellulose is a reaction medium that permits in situ nucleation and growth of the silica phase on the fibrils, while simultaneously matching the quantity of the condensed silica with the specific surface area of the CNFs. Most coatings were applied to bundles of 2-3 associated CNFs, which could be discerned from their negative imprint that remained inside the silica nanotubes. Finally, it is demonstrated that the coated nanofibrils can be freeze-dried into highly porous silica/cellulose aerogels with a density of 0.005 g cm(-3) and how these hybrid aerogels preserve their shape when extensively exposed to 400 degrees C in air (>6 h). The resulting material is the first reported silica nanotube aerogel obtained by using cellulose nanofibrils as templates.

  • 36.
    Lo Re, Giada
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer.
    Engström, Joakim
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Wu, Qiong
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer.
    Malmström, Eva
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Gedde, Ulf W.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Olsson, Richard
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymera material.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Ytbehandlingsteknik.
    Improved Cellulose Nanofibril Dispersion in Melt-Processed Polycaprolactone Nanocomposites by a Latex-Mediated Interphase and Wet Feeding as LDPE Alternative2018Ingår i: ACS Applied Nano Materials, ISSN 2574-0970, Vol. 1, nr 6, s. 2669-2677Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work reports the development of a sustainable and green one-step wet-feeding method to prepare tougher and stronger nanocomposites from biodegradable cellulose nanofibrils (CNF)/polycaprolactone (PCL) constituents, compatibilized with reversible addition fragmentation chain transfer-mediated surfactant-free poly(methyl methacrylate) (PMMA) latex nanoparticles. When a PMMA latex is used, a favorable electrostatic interaction between CNF and the latex is obtained, which facilitates mixing of the constituents and hinders CNF agglomeration. The improved dispersion is manifested in significant improvement of mechanical properties compared with the reference material. The tensile tests show much higher modulus (620 MPa) and strength (23 MPa) at 10 wt % CNF content (compared to the neat PCL reference modulus of 240 and 16 MPa strength), while maintaining high level of work to fracture the matrix (7 times higher than the reference nanocomposite without the latex compatibilizer). Rheological analysis showed a strongly increased viscosity as the PMMA latex was added, that is, from a well-dispersed and strongly interacting CNF network in the PCL.

  • 37. Martinez-Sanz, Marta
    et al.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Lopez-Rubio, Amparo
    Lagaron, Jose M.
    Development of bacterial cellulose nanowhiskers reinforced EVOH composites by electrospinning2012Ingår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 124, nr 2, s. 1398-1408Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the current study, hybrid electrospun ethylene vinyl alcohol (EVOH) fibers reinforced with bacterial cellulose nanowhiskers (BCNW) were developed and characterized. Additionally, electrospinning was suggested as a method for the incorporation of well-dispersed BCNW into an EVOH matrix by melt compounding. With the aim of maximizing the BCNW's loading in the electrospun fibers, an optimized method was applied for generating fibers from solutions containing up to 40 wt % BCNW. As demonstrated by FTIR spectroscopy, it was possible to incorporate BCNW concentrations up to similar to 24 wt %, although a complete incorporation of the nanofiller into the fibers was only achieved with solutions containing up to 20 wt % of the filler, DSC analyses suggested that the incorporation of the nanofiller reduced the crystallinity of the as-obtained EVOH fibers and produced an increase in the glass transition temperature of these during the second heating run. Thermogravimetric analyses showed that even though EVOH protects the nanowhiskers from thermal degradation, the electrospun hybrid fibers present a relatively lower thermal stability than the pure EVOH fibers. FTIR analyses of the samples subjected to different thermal treatments confirmed that the stiffening effect observed by DSC only occurs after melting of the EVOH phase and is cooperative with a partial acid chemical development in the BCNW, which promotes strong chemical interactions between the polymeric matrix and the nanofiller. Finally, the hybrid electrospun fibers were incorporated into pure EVOH by melt compounding to produce composite films. This methodology showed higher stability and dispersion of the BCNW than direct addition of the freeze-dried nanofiller to EVOH.

  • 38. Martinez-Sanz, Marta
    et al.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lopez-Rubio, Amparo
    Lagaron, Jose M.
    Development of electrospun EVOH fibres reinforced with bacterial cellulose nanowhiskers. Part I: Characterization and method optimization2011Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 18, nr 2, s. 335-347Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present study, hybrid electrospun EVOH fibres reinforced with bacterial cellulose nanowhiskers (BCNW) were developed and characterized. The nanowhiskers, obtained by sulphuric acid digestion of native bacterial cellulose mats generated by Gluconacetobacter xylinum, were morphologically characterized by SEM and optical microscopy with polarized light and revealed a highly crystalline structure of nanofibrils aggregates. XRD analyses suggested a crystalline structure corresponding to the cellulose I allomorph. It was also confirmed by means of FT-IR spectroscopy that amorphous regions were preferentially digested by the acid treatment, whereas TGA analyses showed a decrease in the thermal stability of the nanowhiskers most likely due to incorporation of sulphate groups and the inherent acidity remaining in the filler even after extensive washing cycles. A method was developed for improving the incorporation of BCNW within the EVOH electrospun fibres, consisting on the addition of the BCNW in the form of a centrifuged precipitate, versus the most conventionally employed freeze-dried nanowhiskers. DSC analyses showed a significant increase in the glass transition temperature of the composites during the second heating run, which may be related to the acidic character of the nanofiller. Finally, sonication was seen to enhance interfacial interaction but to reduce the incorporation of the filler in the matrix in the case of the centrifuged material.

  • 39.
    Medhi, Pangkhi
    et al.
    Loughborough Univ Technol, Dept Chem Engn, Loughborough, Leics, England..
    Olatunji, Ololade
    Univ Lagos, Dept Chem Engn, Lagos, Nigeria..
    Nayak, Atul
    Loughborough Univ Technol, Dept Chem Engn, Loughborough, Leics, England..
    Uppuluri, Chandra Teja
    KVSR Siddhartha Coll Pharmaceut Sci, Pinnamaneni Polyclin Rd, Vijayawada, Andhra Pradesh, India..
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Nalluri, Buchi N.
    KVSR Siddhartha Coll Pharmaceut Sci, Pinnamaneni Polyclin Rd, Vijayawada, Andhra Pradesh, India..
    Das, Diganta B.
    Loughborough Univ Technol, Dept Chem Engn, Loughborough, Leics, England..
    Lidocaine-loaded fish scale-nanocellulose biopolymer composite microneedles2017Ingår i: AAPS PharmSciTech, ISSN 1530-9932, E-ISSN 1530-9932, Vol. 18, nr 5, s. 1488-1494Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microneedle (MN) technology has emerged as an effective drug delivery system, and it has tremendous potential as a patient friendly substitute for conventional methods for transdermal drug delivery (TDD). In this paper, we report on the preparation of lidocaine-loaded biodegradable microneedles, which are manufactured from fish scale-derived collagen. Lidocaine, a common tissue numbing anaesthetic, is loaded in these microneedles with an aim of delivering the drug with controlled skin permeation. Evaluation of lidocaine permeation in porcine skin has been successfully performed using Franz diffusion cell (FDC) which has shown that the drug permeation rate increases from 2.5 to 7.5% w/w after 36 h and pseudo steady state profile is observed from 5.0 to 10.0% w/w lidocaine-loaded microneedle. Swelling experiments have suggested that the microneedles have negligible swellability which implies that the patch would stick to the tissue when inserted. The experiments on MN dissolution have depicted that the lidocaine loaded in the patch is lower than the theoretical loading, which is expected as there can be losses of the drug during initial process manufacture.

  • 40.
    Nordenström, Malin
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Riazanova, Anastasia
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Järn, Mikael
    RISE Res Inst Sweden, Div Biosci & Mat, SE-11428 Stockholm, Sweden..
    Paulraj, Thomas
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Turner, Charlotta
    Lund Univ, Dept Chem, SE-22100 Lund, Sweden..
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Olsson, Richard
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Svagan, Anna
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Superamphiphobic coatings based on liquid-core microcapsules with engineered capsule walls and functionality2018Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, artikel-id 3647Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microcapsules with specific functional properties, related to the capsule wall and core, are highly desired in a number of applications. In this study, hybrid cellulose microcapsules (1.2 +/- 0.4 mu m in diameter) were prepared by nanoengineering the outer walls of precursor capsules. Depending on the preparation route, capsules with different surface roughness (raspberry or broccoli-like), and thereby different wetting properties, could be obtained. The tunable surface roughness was achieved as a result of the chemical and structural properties of the outer wall of a precursor capsule, which combined with a new processing route allowed in-situ formation of silica nanoparticles (30-40 nm or 70 nm in diameter). By coating glass slides with "broccoli-like" microcapsules (30-40 nm silica nanoparticles), static contact angles above 150 degrees and roll-off angles below 6 degrees were obtained for both water and low surface-tension oil (hexadecane), rendering the substrate superamphiphobic. As a comparison, coatings from raspberry-like capsules were only strongly oleophobic and hydrophobic. The liquid-core of the capsules opens great opportunities to incorporate different functionalities and here hydrophobic superparamagnetic nanoparticles (SPIONs) were encapsulated. As a result, magnetic broccoli-like microcapsules formed an excellent superamphiphobic coating-layer on a curved geometry by simply applying an external magnetic field.

  • 41. Olatunji, O.
    et al.
    Olsson, Richard
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymera material.
    Processing and characterization of natural polymers2015Ingår i: Natural Polymers: Industry Techniques and Applications, Springer, 2015, s. 19-61Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    This chapter covers recent techniques applied in processing and characterization of natural polymers. This includes techniques in processing natural polymers from their natural forms into modified forms for more varied application and functionality. It also looks at techniques for processing modified and unmodified natural polymers for various purposes such as film formation for transdermal patches, composite and blends production to form films with improved mechanical properties, magnetic decoration for production of tough membranes with magnetic properties. The characterization methods covered in this chapter include X-ray diffraction, microscopy, and Fourier transform infrared spectrometry. We look at recent reported processing and characterization techniques which are applicable to the major industries today for natural polymer-based materials.

  • 42. Olatunji, O.
    et al.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Microneedles from fishscale-nanocellulose blends using low temperature mechanical press method2015Ingår i: Pharmaceutics, ISSN 1999-4923, E-ISSN 1999-4923, Vol. 7, nr 4, s. 363-378Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fish scale biopolymer blended with nanocellulose crystals is used for production of microneedles applying mechanical press microfabrication and the effect of nanocellulose on microfabrication, water absorption, moisture stability and mechanical properties of the microneedles is reported. The results show that microneedles produced from the nanocellulose loaded fish scale biopolymer requires higher temperature for micromolding (80 ± 5 °C) than microneedles from only fish scale biopolymer, which were moldable at 50 ± 5 °C. The mechanical properties of the fish scale biopolymer-nanocellulose (FSBP-NC) films showed that the addition of nanocellulose (NC) resulted in lower elongation and higher tensile stress compared to fish scale biopolymer (FSBP) films. The nanocellulose also prevented dissolution of the needles and absorbed up to 300% and 234% its own weight in water (8% and 12% w/w NC/FSBP), whereas FSBP films dissolved completely within 1 min, Indicating that the FSBP-NC films can be used to produce microneedles with prolonged dissolution rate. FTIR spectrometry of the FSBP films was compared with the FSBP-NC films and the NC gels. The FTIR showed typical peaks for fish scale polymer and nanocellulose with evidence of interactions. SEM micrographs showed relatively good dispersion of NC in FSBP at both NC contents corresponding to 8% and 12% w/w NC/FSBP respectively.

  • 43.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Alternative Routes to Highly Dispersed Cobalt Ferrite Nanocomposites2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 44.
    Olsson, Richard T.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Synthesis and characterization of ferrite based nanocomposites for microwave absorbing applications2005Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 45.
    Olsson, Richard T.
    et al.
    KTH, Tidigare Institutioner, Fiber- och polymerteknologi.
    Bair, H E
    Kuck, V
    Hale, A
    Acceleration of the cationic polymerization of an epoxy with hexanediol2004Ingår i: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926, Vol. 76, nr 2, s. 367-377Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin films of 3,4-epoxycyclohexyhnethyl 3',4'-epoxycyclohexane carboxylate were UV irradiated (1.1 J cm(-2)) under isothermal conditions ranging from 0 to 50degreesC. Under these conditions the polymerization advanced quickly but only to a conversion level of less than 10% before the reaction rate slowed by more than an order of magnitude. This drop off in rate was not caused by the glass transition temperature, T-g, reaching or exceeding the reaction temperature, T-rxn, since the epoxide's T-g remained at least 40degreesC below T-rxn. Raising the sample temperature above 60degreesC caused a sharp increase in the conversion level. At 100degreesC conversion exceeds 80% and the ultimate T-g approaches 190degreesC. The addition of 10 mass% 1,6-hexanediol, HD, to the epoxy caused the conversion at room temperature to quintuple over the level obtained without the alcohol present. The heat liberated from this alcohol epoxy blend during cure on a UV conveyor belt system caused the sample's temperature to increase by about 100degreesC above ambient whereas the epoxy alone under these conditions only experienced a modest temperature rise of about 26degreesC. If the amount of HD in the blend is increased above 10% the heat of reaction at 23degreesC decreases due to HD being trapped in a nonreactive crystalline phase. Boosting reaction temperatures above 50degreesC melts the HD crystals and yields significantly improved conversion ratios. As the level of alcohol blended with the epoxy is raised its ultimate T-g is lowered and when the concentration of alcohol in the blend nears 30 mass% T-g drops below room temperature.

  • 46.
    Olsson, Richard T.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Fogelström, Linda
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Martínez-Sanz, M.
    Henriksson, Marielle
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Cellulose nanofillers for food packaging2011Ingår i: Multifunctional and Nanoreinforced Polymers for Food Packaging, Cambridge: Woodhead Publishing Limited, 2011, s. 86-107Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    This chapter presents a review of methods for the extraction of cellulose nanofillers, as well as the most important characteristic features related to the exploration of these nanofillers in composite applications. Various methods for the extraction and surface modification of cellulose crystals are presented for the adaption of cellulose crystals in composite applications. A brief review of the different morphological characteristics as well as mechanical properties of different cellulose nanofillers are also presented.

  • 47.
    Olsson, Richard T.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hedenqvist, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gedde, Ulf
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Salazar-Alvarez, German
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Muhammed, M.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Synthesis and characterization of cubic cobalt ferrite nanoparticles2005Ingår i: Ninth International Conference on Ferrites (ICF-9) / [ed] Soohoo, RF, 2005, s. 835-840Konferensbidrag (Refereegranskat)
    Abstract [en]

    The preparation of approximately 20 g cubic cobalt ferrite nanoparticles (edge length 30-60 nm) with composition CoxFe3-xO4 (0.85 center dot x center dot 1.00 +/- 0.02) using the co-precipitation method in a batch type reactor has been investigated. The morphology, composition, size and size distribution of the synthesized particles were characterized by transmission electron microscopy, X-ray diffraction and the BET method. The majority of the particles were cubic although spherical particles were also observed. Aging of the suspensions resulted in a narrowing of the initial size distribution with no effect on the morphology and composition of the particles.

  • 48.
    Olsson, Richard T.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Deng, Jinglan
    Neway, Bereket
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Savage, Steven J.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Characterization of particle dispersion and mechanical properties of nanocomposites based on cobalt ferrite nanoparticles with functional silesquioxane coatings.Manuskript (preprint) (Övrigt vetenskapligt)
  • 49.
    Olsson, Richard T.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Deng, J.
    Savage, S. J.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Core-Shell Structured Ferrite-Silsesquioxane-Epoxy Nanocomposites: Composite Homogeneity and Mechanical and Magnetic Properties2011Ingår i: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 51, nr 5, s. 862-874Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Epoxy-based composites of ferrite nanoparticles (50 nm) with 3-glycidoxypropyl- (GPTMS), aminopropyl(APTMS), or methyl-silsesquioxane (MTMS) coatings are reported. The GPTMS coatings (30-nm thick) allowed uniform particle dispersion in the epoxy and prevented sedimentation of the nanoparticles, whereas the APTMS-coated particles formed agglomerates, leading to particle sedimentation. The particles with the thinnest coating (MTMS - 3 nm) agglomerated in the composites without sedimentation. The composites based on GPTMS-coated particles showed higher fracture toughness than the composites based on MTMS-coated particles. The uniformity and thickness of the coatings were related to alcohol composition of the coating media. Coating removal by a novel ultrasonic etching allowed precise determination of the effective ferrite content in the coated nanoparticles. A markedly lower coercivity for nanoparticles without coatings as compared with the nanoparticles with thicker coatings was observed. The saturation magnetization and the coercivity of the composites were independent of coating and casting procedures.

  • 50.
    Olsson, Richard T.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Ström, Valter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Deng, Jinglan
    School of Science, Wuhan University of Technology.
    Savage, Stephen J.
    Swedish Defence Research Agency (FOI), Linköping.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Core-shell nanostructured cobalt ferrite-sisesquioxane-epoxy composites: nanofiller surface treatment, particle dispersion, mechanical and magnetic propertiesIngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, s. 1-44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Magnetic core-shell cobalt ferrite-silsesquioxane-epoxy nanocomposites have been prepared with uniform nanoparticle distribution. The nanoparticles were surface-treated with methyl- (MTMS), aminopropyl- (APTMS), glycidoxypropyl- (GPTMS) trimethoxy-silane. The optimum coating process was performed in a water/merthanol solution on the particles directly after their synthesis without prior drying. The GPTMS-coatings were 30 nm thick and the nanoparticles dispersed well in epoxy without sedimentation. The MTMS-coated nanoparticles (3 nm coating) formed weak agglomerates in epoxy but showed no sedimentation. The APTMS-coated particles formed stronger agglomerates, which led to sedimentation of the aorticles during molding. The GPTMS-based composites showed higher fracture toughness than the MTMS-based composites. This was attributed to the presence of large agglomerates in the latter systems and to the stronger interface between coating and epoxy in the former systems. Ultrasonic alkaline etching allowed precis determination of the ferrite content of the core-shell nanoparticles. Magnetometry showe a markedly lower coercivity for nanoparticles with thin coatings (MTMS) than for the nanoparticles with thicker coatings (GPTMS) suggesting the occurrence of magnetic exchange interaction in the former systems. The nanocomposites showed no influence of surface coating on coercivity or saturation magnetization suggesting that the inter-particle distances were greater than 0.5 nm.

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