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  • 51. Fateh-Alavi, K.
    et al.
    Nunez, M. E.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    The effect of stabilizer concentration on the air-plasma-induced surface oxidation of crosslinked polydimethylsiloxane2002In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 78, no 1, p. 17-25Article in journal (Refereed)
    Abstract [en]

    The concentrations of three stabilizers-a hindered phenol (Irganox 1076), a hindered amine light stabilizer (Tinuvin 770) and a bifunctional stabilizer with chain-breaking hindered phenol and secondary amine and hydroperoxide-decomposing sulphide moieties (Irganox 565)-in crosslinked polydimethylsiloxane were varied using swelling solutions of the stabilizers at different concentrations. The concentration of the stabilizer in the rubber was assessed by UV-Vis spectroscopy of Soxhlet and microwave assisted extracts. Irganox 1076 and Tinuvin 770 were soluble in polydimethylsiloxane to at least 0.2-0.3 wt.%, whereas the solubility of Irganox 565 was considerably lower. The samples were exposed to GHz air plasma and the surface structures of the exposed samples were studied by X-ray photoelectron spectroscopy, and by optical and scanning electron microscopy after uniaxial stretching. The plasma exposure time required for the formation of an oxidised glassy layer increased in a linear fashion with increasing stabilizer concentration, suggesting that the consumption rate was constant in time during the plasma exposure. Tinuvin 770 showed the strongest overall protecting effect whereas Irganox 565 showed the strongest protecting effect per mass fraction of stabilizer. Irganox 1076 was of moderate efficiency. The results suggest that efficient protection towards air plasma is achieved with hindered amine stabilizers or with stabilizers combining chain-breaking and hydroperoxide-decomposing functions. Differential scanning calorimetry showed that Tinuvin 770 and Irganox 565 protected polydimethylsiloxane against thermal oxidation at elevated temperatures. The chemical consumption of these stabilizers followed basically the classical scheme with zero-order kinetics and a rate constant obeying the Arrhenius law.

  • 52.
    Fateh-Alavi, Kamyar
    KTH, Superseded Departments, Polymer Technology.
    The effects of stabilizers on the air-plasma-induced surface oxidation of polydimethylsiloxane2001Licentiate thesis, comprehensive summary (Other scientific)
  • 53.
    Fateh-Alavi, Kamyar
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Effect of stabilizers on surface oxidation of silicone rubber by corona discharge2004In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 84, no 3, p. 469-474Article in journal (Refereed)
    Abstract [en]

    Crosslinked polydimethylsiloxane (PDMS) containing Irganox(R) 1076, Tinuvin(R) 770 or lrganox(R) 565, prepared by swelling PDMS in a solution of one of these stabilizers in n-hexane, was exposed to a corona discharge and the corona exposure time (tau(crit)) to form a brittle, silica-like layer was determined by optical microscopy. The critical corona exposure time showed a linear increase with increasing stabilizer concentration; Tinuvin 770 showed the highest efficiency and Irganox 1076 the lowest. The increase in tau(crit) on corona exposure of the stabilized samples with reference to the value for unstabilized PDMS was similar to that reported earlier for air plasma exposed samples. The efficiency of the stabilizers towards corona-induced surface oxidation of PDMS was also confirmed by X-ray photoelectron spectroscopy.

  • 54.
    Fateh-Alavi, Kamyar
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    A rapid microwave-assisted solvent extraction method for assessment of stabilizer concentration in crosslinked polydimethylsiloxane2004In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 93, no 5, p. 2185-2192Article in journal (Refereed)
    Abstract [en]

    Crosslinked polyclimethylsiloxanes were prepared containing 0.05 to 0.2 wt % of either a phenolic antioxidant (Irganox(R) 1010) or a hindered amine stabilizer (Tinuvin(R) 144). The stabilizer concentration was assessed by HPLC and UV-Vis spectroscopy of Soxhlet and microwave-assisted solvent extracts. Almost complete recovery of stabilizer was achieved with Soxhlet extraction. High stabilizer recovery was achieved when acetone was used as the solvent in the microwave-assisted extraction. HPLC was shown to be an efficient method for determining the concentration of Irganox 1010. For Tinuvin 144 the selectivity of both UV-Vis spectroscopy and HPLC was poor, leading to imprecise evaluation of the antioxidant concentration. The loss of stabilizer by migration from polymer to hot water (75 and 95degreesC) was monitored for the systems stabilized with Irganox 1010 and the diffusion coefficient of the antioxidant in the polymer was determined.

  • 55. Fazio, V. S. U.
    et al.
    Lagerwall, S. T.
    Busson, P.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Motschmann, H.
    Phase-matched second-harmonic generation in a ferroelectric liquid crystal waveguide2000In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 77, no 3, p. 319-321Article in journal (Refereed)
    Abstract [en]

    True phase-matched second-harmonic generation in a waveguide of crosslinkable ferroelectric liquid crystals is demonstrated. These materials allow the formation of macroscopically polar structures whose order can be frozen by photopolymerization. Homeotropic alignment was chosen which offers decisive advantages compared to other geometries. All parameters contributing to the conversion efficiency are maximized by deliberately controlling the supramolecular arrangement. The system has the potential to achieve practical level of performances as a frequency doubler for low power laser-diodes.

  • 56. Fazio, V. S. U.
    et al.
    Lagerwall, S. T.
    Zauls, V.
    Schrader, S.
    Busson, P.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Motschmann, H.
    Nonlinear optical properties of a channel waveguide produced with crosslinkable ferroelectric liquid crystals2000In: The European Physical Journal E Soft matter, ISSN 1292-8941, E-ISSN 1292-895X, Vol. 3, no 3, p. 245-251Article in journal (Refereed)
    Abstract [en]

    A binary mixture of ferroelectric liquid crystals (FLCs) was used for the design of a channel waveguide. The FLCs possess two important functionalities: a chromophore with a high hyperpolarizability beta and photoreactive groups. The smectic liquid crystal is aligned in layers parallel to the glass plates in a sandwich geometry. This alignment offers several advantages, such as that moderate electric fields are sufficient to achieve a high degree of polar order. The arrangement was then permanently fixed by photopolymerization which yielded a polar network possessing a high thermal and mechanical stability which did not show any sign of degradation within the monitored period of several months. The linear and nonlinear optical properties have been measured and all four independent components of the nonlinear susceptibility tensor (d) over bar have been determined. The off-resonant d-coefficients are remarkably high and comparable to those of the best known inorganic materials. The alignment led to an inherent channel waveguide for p-polarized light without additional preparation steps. The photopolymerization did not induce scattering sites in the waveguide and the normalized losses were less than 2 dB/cm. The material offers a great potential for the design of nonlinear optical devices such as frequency doublers of low-power laser diodes.

  • 57. Fazio, V. S. U.
    et al.
    Zauls, V.
    Schrader, S.
    Busson, P.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Lagerwall, S. T.
    Motschmann, H.
    Enhanced phase-matched second-harmonic generation in a ferroelectric liquid crystal waveguide2001In: Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, ISSN 1058-725X, Vol. 368, p. 4061-4070Article in journal (Refereed)
    Abstract [en]

    A binary mixture of crosslinkable ferroelectric liquid crystals (FLCs) was used for the design of a channel waveguide. The liquid crystal was aligned in layers parallel to the glass plates (homeotropic) in a sandwich geometry and then the arrangement was permanently fixed by photopolymerization which yielded a polar network possessing a high thermal and mechanical stability. The linear and nonlinear optical properties have been measured and all four independent components of the nonlinear susceptibility tensor d have been determined. The off-resonant d-coefficients are remarkably high and comparable to those of the best known inorganic materials. Phase-matching was achieved by taking advantage of the modal dispersion of the waveguide. A reversal of sign of chi ((2)) at the nodal plane of the electric field distribution of the first-order mode was needed to maximize the overlap. integral between the fundamental and the second-harmonic (SH) light. In samples with chi ((2)) inversion the SH Signal was 1000 larger that in samples without chi ((2)) inversion.

  • 58.
    Finne, Anna
    KTH, Superseded Departments, Polymer Technology.
    Novel Possibilities for Advanced Molecular Structure Design for Polymers and Networks2003Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Synthetic and degradable polymers are an attractive choicein many areas, since it is possible to control the way in whichthey are manufactured; more specifically, pathways tomanipulate the architecture, the mechanical properties and thedegradation times have been identified. In this work,L-lactide, 1,5-dioxepan-2-one and ε-caprolactone were usedas monomers to synthesize polymers with different architecturesby ring-opening polymerization. By using novel initiators,triblock copolymers, functionalized linear macromonomers andstar-shaped aliphatic polyesters with well-defined structureshave been synthesized. To synthesize triblock copolymers,cyclic germanium initiators were studied. The polymerizationproceeded in a controlled manner although the reaction rateswere low. To introduce functionality into the polymer backbone,functionalized cyclic tin alkoxides were prepared and used asinitiators. During the insertion-coordination polymerization,the initiator fragment consisting mainly of a double bond wasincorporated into the polymer backbone. The double bond wasalso successfully epoxidized and this gave unique possibilitiesof synthesizing graft polymers with precise spacing. Themacromonomer technique is a very effective method for producingwell-defined graft polymers. Spirocyclic tin initiators weresynthesized and used to construct star-shaped polymers. Thestar-shaped polymers were subsequently crosslinked in apolycondensation reaction. These crosslinked structures swelledin water, and swelling tests showed that by changing thestructure of the hydrogel network, the degree of swelling canbe altered. A first evaluation of the surface characteristicsof the linear triblock copolymers was also performed. AFManalysis of the heat-treated surfaces revealed nanometer-scalefibers and tests showed that keratinocytes were able to growand proliferate on these surfaces.

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  • 59.
    Finne, Anna
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Controlled synthesis of star-shaped L-lactide polymers using new spirocyclic tin initiators2002In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 3, no 4, p. 684-690Article in journal (Refereed)
    Abstract [en]

    The reaction between pentaerythritol ethoxylate compounds and dibutyltin oxide was developed as a route to synthesize two new spirocyclic tin initiators. The initiators were successfully synthesized and they were characterized by H-1 NMR and differential scanning calorimetry (DSC). The H-1 NMR spectra showed the characteristic signals for the methylene protons in the ether chains. Furthermore, the usefulness of the new initiators was examined in ring-opening polymerizations of L-lactide in chloroform at 60 degreesC. L-Lactide was polymerized at monomer-to-initiator ([M]/[I]) ratios between 20 and 500. The results indicated that the initiation was instantaneous and that the molecular weight distribution was very narrow, <1.13, The number average molecular weight could be controlled by the [M]/[I] ratio, and the yield was very high. H-1 NMR, size exclusion chromatography, and DSC were used to clarify the architecture, The expected results were obtained. The star-shaped polymers had a smaller hydrodynamic volume, and the melting point was lower than that obtained for the corresponding linear poly(L-lactide).

  • 60.
    Finne, Anna
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    New functionalized polyesters to achieve controlled architectures2004In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 42, no 3, p. 444-452Article in journal (Refereed)
    Abstract [en]

    Following our continued interest in the production of bioerodible and biodegradable functional polymers for biomedical applications, we synthesized and characterized new unsaturated polyesters. The presence of functional groups in the polymer backbone provided sites for chemical modification, and through a variation in the structure, the physical properties, such as the hydrophilicity and solubility, could be affected. With 1,1-di-n-butyl-stanna-2,7-dioxacyclo-4-heptene as the initiator in the ring-opening polymerization of polyesters, a new set of functionalized polyesters was created. The polymerization of epsilon-caprolactone resulted in poly(epsilon-caprolactone) with a double bond incorporated into the structure. The polymers were obtained in a controlled manner with low molecular dispersities. The double bond was previously incorporated into L-lactide polymers, and the two reactions were compared in this study. The conversion of E-caprolactone, with a degree of polymerization of 50, was completed within 140 min, whereas for L-lactide, only a 45% conversion took place in the same period of time. The dispersities were somewhat higher with E-caprolactone because of the higher reaction rate and, therefore, lower selectivity. The incorporated C-C double bond in the polyesters provided a variety of opportunities for further modifications. In this case, the double bond of the L-lactide macromonomers was oxidized into epoxides. Epoxidation was carried out with m-chloroperoxybenzoic acid as a chemical reagent. The conversion of the double bonds into epoxides was completed, and the obtained yields were good (>95%). As a result of the mild reaction conditions, the epoxidation of the double bond was carried out quantitatively without any side reactions.

  • 61.
    Finne, Anna
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Polyester hydrogels with swelling properties controlled by the polymer architecture, molecular weight, and crosslinking agent2003In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 41, no 9, p. 1296-1305Article in journal (Refereed)
    Abstract [en]

    Hydrogels of poly(1,5-dioxepan-2-one) and hydrogels of block copolymers of poly(1,5-dioxepan-2-one) and poly(L-lactide) were synthesized. Both star-shaped polymers and linear polymers were polymerized with ring-opening polymerization and crosslinked in situ with a tetrafunctional acid chloride (1,2,3,4-cyclopentane tetracarboxylic acid chloride) or a difunctional acid chloride (succinyl chloride). Different network architectures were synthesized in this way. The initial monomer concentrations and the molecular weights of the macromonomers were also altered. The networks were characterized with H-1 NMR and differential scanning calorimetry, and the swelling abilities of the different hydrogels were investigated in water and dichloromethane. The ratio of the monomer to the crosslinking agent was assessed by the quantification of the signal intensities in the H-1 NMR spectra of the swelled network and agreed with the theoretical crosslinking density. Both the homopolymers of 1,5-dioxepan-2-one and the copolymers of 1,5-dioxepan-2-one and L-lactide swelled to a high degree in water. The swelling properties of the materials could be varied over a broad range by changes in the architecture, molecular weight, and content of the precursor in the network. Star-shaped poly(1,5-dioxepan-2-one) crosslinked with a difunctional acid chloride had the highest degree of swelling among the different homopolymer hydrogels. This network also had the lowest glass-transition temperature because of the flexible units in the structure. The same trends found for the homopolymer hydrogels were also seen in the hydrogels with block copolymers. The hydrogels swelled enormously in dichloromethane, and as in water, the star-shaped copolymer crosslinked with a difunctional acid chloride had the highest degree of swelling.

  • 62.
    Finne, Anna
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Andronova, Natalia
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Well-organized phase-separated nanostructured surfaces of hydrophilic/hydrophobic ABA triblock copolymers2003In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 4, no 5, p. 1451-1456Article in journal (Refereed)
  • 63.
    Finne, Anna
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Reema,
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Use of germanium initiators in ring-opening polymerization of L-lactide2003In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 41, no 19, p. 3074-3082Article in journal (Refereed)
    Abstract [en]

    Three different, new germanium initiators were used for ring-opening polymerization Of L-lactide. Chlorobenzene and 120 degreesC was a usable polymerization system for solution polymerization, and the results from the polymerizations depended on the initiator structure and bulkiness around the insertion site. The average molecular weights as measured by size exclusion chromatography increased linearly with the monomer conversion, and the molecular weight dispersity was around 1.2 for initiators 1 and 2, whereas it was around 1.4 for initiator 3. The average molecular weight of poly(L-lactide) could be controlled with all three initiators by adding different ratios of monomer and initiator. The reaction rate for the solution polymerization was, however, overall extremely slow. With an initial monomer concentration of 1 M and a monomer-to-initiator ratio of 50, the conversion was 93% after 161 h for the fastest initiator. In bulk polymerization, 160 degreesC, the conversion was 90% after 10 h.

  • 64.
    Finne Wistrand, Anna
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Ryner, M.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Degradable polymers: Design, synthesis and testing2003In: Macromolecular Symposia, ISSN 1022-1360, E-ISSN 1521-3900, Vol. 195, p. 241-246Article in journal (Refereed)
    Abstract [en]

    The object for our research is to mimic Nature's perfectly designed resorbable materials to obtain important materials, which are biocompatible and degradable. We have therefore synthesized different architectures and copolymers of aliphatic polyesters with ring-opening polymerization. The first studies of these materials properties show that properties like hydrophilicity and tensile properties can be controlled.

  • 65. Flodberg, G.
    et al.
    Axelson-Larsson, L.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Liquid Crystalline Polymer Pouches for Local Anaesthetic Emulsion2001In: Packaging technology & science, ISSN 0894-3214, E-ISSN 1099-1522, Vol. 14, no 4, p. 159-170Article in journal (Refereed)
    Abstract [en]

    In order to enhance the long-term properties of a high-pH local anaesthetic drug, emulsion tests were conducted where the emulsion was stored in pouches made of a compression moulded high-barrier liquid-crystalline polymer, Vectra A950. The oxygen permeability of the pouch materia I was too low to be detected at 23 degreesC and 0% relative humidity with the instrument used. The water vapour transmission rate was 0.135 (g.mm/m(2).day) at 38 degreesC and 100% relative humidity. The emulsion, containing prilocain and lidocain as active substances, was stored in pouches which were sealed by the thermal impulse technique at 260 degreesC for 1.08 s. It was possible to obtain good quality films and good quality seals by optimization of the compression moulding and sealing operations. The concentrations of prilocain and lidocain in the emulsion were studied for 14 weeks at two different temperatures, 40 degreesC and 60 degreesC, and at 100% relative humidity. The decrease in concentration was higher for prilocain (5.4-8.3%) than for lidocain (3.4-3.6%). The loss of the substances from the emulsion was due mainly to adsorption onto the polar surface of the liquid crystalline polymer.

  • 66. Flodberg, G.
    et al.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Barrier properties of injection molded blends of liquid crystalline polyesters (Vectra) and high-density polyethylene2003In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 43, no 5, p. 1044-1057Article in journal (Refereed)
    Abstract [en]

    Blends of an extrusion-grade high-density polyethylene and two liquid crystalline copolyesters (LCP; Vectra A950 and Vectra RD501) were prepared by melt mixing and injection molding, and the. morphologies and oxygen permeabilities of the blends were assessed. Scanning electron microscopy revealed that the LCP was present in the blends as mixed oriented bands and small spheres at low LCP contents (4-9 vol%), Whereas blends with more than 18 vol% LCP showed LCP lamellae of macroscopic lateral size (mm). Scanning electron microscopy revealed a two-dimensional continuity of the LCP domains in the disc plane due to radial shear deformation and circumferential stretching of the melt leaving the central gate of the disc-shaped cavity. The oxygen permeability, diffusivity and solubility decreased with increasing LCP content of the blends. The decrease in permeability with respect to polyethylene was significant (46%-55%) already at 9 vol% LCP. At 27 vol% LCP, the decrease with respect to polyethylene, was 92% for the Vectra A950 blend and 98% for the Vectra RD501 blend. These blends showed a greater decrease in diffusivity (86%-92%) than in solubility (39%-76%) with respect to polyethylene, which showed the very pronounced effect of the LCP lamellae on the geometrical impedance factor. Microvoids were present in all the blends despite the use of a very high injection pressure (180 MPa) but their impact on the oxygen permeability was negligible for the Vectra. RD501 blends and relatively small for the Vectra A950 blends.

  • 67. Flodberg, G.
    et al.
    Hellman, A.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Sadiku, E. R.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Barrier properties of blends based on liquid crystalline polymers and polyethylene2000In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 40, no 9, p. 1969-1978Article in journal (Refereed)
    Abstract [en]

    Blends of an extrusion-grade polyethylene and two different liquid crystalline polymers of Vectra type were prepared by melt mixing using poly(ethylene-co-methacrylic acid) as compatibilizer. Oxygen and water vapor permeability, transparency and welding strength of compression molded and film blown specimens were studied. The compression molded blends showed gas permeabilities conforming to the Maxwell equation assuming low permeability liquid crystalline polymer spheres in a high permeability polyethylene matrix One of the liquid crystalline polymers with suitable rheological properties formed a more continuous phase in the film blown blends and a substantial decrease in oxygen and water vapor permeability was observed in these blends. The compression molded blends with 50% liquid crystalline polymer and some of blow molded blends showed very high gas permeabilities. It is believed that voids forming continuous paths through the structure were present in these samples. The blends showed significantly higher opacity than pure polyethylene.

  • 68. Flodberg, G.
    et al.
    Hojvall, L.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Migration of monomers from liquid crystalline poly(p-hydroxybenzoic acid-co-2-hydroxy-6-naphthoic acid)2002In: Food Additives and Contaminants, ISSN 0265-203X, E-ISSN 1464-5122, Vol. 19, no 5, p. 492-501Article in journal (Refereed)
    Abstract [en]

    Liquid-crystalline co-polyesters (e.g. a random co-polyester based on p-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA) known as Vectra A950) offer good barrier properties, but for food-contact use require overall and specific migration testing. For Vectra A950 films, the highest overall migration level obtained was 2.3 mg kg(-1) in olive oil (10 days at 40degrees C) well below the EC limit of 60 mg kg(-1). The highest specific migration for p-hydroxybenzoic acid was 15.2 mug dm(-2) in olive oil (2 h at 175degreesC). For 2-hydroxy-6-naphthoic acid, the highest value obtained was 4.3 mug dm(-2) in 10% ethanol (4 h at 100degrees C), although it was not on the EC positive and cannot yet be used for food-contact materials. At conditions considered as severe, the estimated daily intake for p-hydroxybenzoic acid was calculated as 11.9 mug/person day(-1) and for 2-hydroxy-6-naphthoic acid it was 5.3 mug/person day(-1). The results exceed the threshold of regulation of 1.5 mug/person day(-1).

  • 69.
    Flodberg, Göran
    KTH, Superseded Departments (pre-2005), Polymer Technology.
    Barrier Properties of Liquid Crystalline Polymers and their Blends with PE and PETP2002Doctoral thesis, comprehensive summary (Other scientific)
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  • 70.
    Fogelström, Linda
    et al.
    KTH, Superseded Departments (pre-2005), Fibre and Polymer Technology.
    Antoni, P
    KTH.
    Malmström, Eva
    KTH, Superseded Departments (pre-2005), Polymer Technology.
    Hult, Anders
    KTH, Superseded Departments (pre-2005), Polymer Technology.
    UV-curable nanocomposite coatings.2005In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 229, p. U986-U986Article in journal (Other academic)
  • 71.
    Forss, Tomas
    KTH, Superseded Departments, Polymer Technology.
    Design for recycling using hot melt adhesive joints1999Licentiate thesis, comprehensive summary (Other scientific)
  • 72.
    Forsström, Dan
    KTH, Superseded Departments, Polymer Technology.
    Novel techniques for characterisation of the oxidative stability of polyamides1999Doctoral thesis, comprehensive summary (Other scientific)
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  • 73. Gallet, G.
    et al.
    Carroccio, S.
    Rizzarelli, P.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Thermal degradation of poly(ethylene oxide-propylene oxide-ethylene oxide) triblock copolymer: comparative study by SEC/NMR, SEC/MALDI-TOF-MS and SPME/GC-MS2002In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 43, no 4, p. 1081-1094Article in journal (Refereed)
    Abstract [en]

    By comparing size exclusion chromatography/matrix assisted laser desorption ionisation (SEC/MALDI) and SEC/NMR spectra from virgin poly(ethylene oxide-propylene oxide-ethylene oxide) triblock copolymer, we were able to understand the bimodal distribution observed in poloxamer 407. Propylene oxide, isomerised to allyl alcohol during polymerisation, eventually forms a Poly(ethylene oxide-propylene oxide) diblock copolymer when EO is added to the feed. The oxidative thermal degradation of poloxamer 407 at 80 degreesC in air was studied. We found by MALDI that degradation starts after 21 days in the PPO block of the copolymer. This result was confirmed by solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS): The first volatile degradation product to appear is 1,2-propanediol,1-acetate,2-formate. The structure of this molecule suggests that a six-ring intramolecular decomposition reaction of the PPO chain occurs at the very beginning of the polymer breakdown. Thus, the secondary hydroperoxide formed on the PPO chain plays a major role on the thermoxidation of poloxamer materials.

  • 74. Gallet, G.
    et al.
    Erlandsson, B.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Thermal oxidation of poly(ethylene oxide-propylene oxide-ethylene oxide) triblock copolymer: focus on low molecular weight degradation products2002In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 77, no 1, p. 55-66Article in journal (Refereed)
    Abstract [en]

    The oxidative thermal degradation of poloxamer 407, a poly(ethylene oxide-propylene oxide-ethylene oxide) triblock copolymer, at 50 and 80 degreesC in air was studied by solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS). At 80 degreesC, we found that degradation was initiated on the PPO block of the copolymer by three mechanisms involving hydroperoxyl formation and depropagation. 1,2-propanediol,1-acetate; 1,2-propanediol,2-formate; 1, 2-propanediol,1-acetate, 2-formate and 2-propanone,1-hydroxy were the first degradation products produced. Random chain scissions and a sharp decrease in the molecular weight of the material followed the initiation period. Formic acid and acetic acid, formed upon degradation, participated in esterification reactions leading to the formation of the formate and acetate forms of 1,2-propanediol and ethanediol. Though degradation at 50 degreesC was much slower, the oxidative mechanisms leading to low molecular weight formates and acetates were the same as those observed at 80 degreesC.

  • 75. Gallet, G.
    et al.
    Lempiainen, R.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Characterisation by solid phase microextraction-gas chromatography-mass spectrometry of matrix changes of poly(L-lactide) exposed to outdoor soil environment2000In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 71, no 1, p. 147-151Article in journal (Refereed)
    Abstract [en]

    Films of poly(L-lactide), PLLA, were buried in outdoor environment in south Finland during two years. The changes in polylactide matrix were characterised by size exclusion chromatography and differential scanning calorimetry, and formation of volatile oligomers was monitored by solid phase microextraction (SPME)-gas chromatography-mass spectrometry. SPME sample preparation was found suitable for analysing small volatile compounds in solid PLLA samples. The oligomers in polylactide were readily extracted with polar CW/DVB fibre. The oligomers were analysed without any complicated sample handling procedure and no solvent was needed. Lactic acid, lactide and lactoyl lactic acid were extracted from the unaged and aged films. Lactide was observed in all films and its content did not change during the two years of soil burial. No lactic acid was observed in any of the polylactide films during the first year. After 20 months lactic acid and lactoyl lactic acid appeared as a result of hydrolysis. After 24 months the amount of lactoyl lactic acid decreased due to biotic hydrolysis of the film. The molecular weight M-n of polylactide increased and the polydispersity decreased during the first year. A slow chemical hydrolysis combined with the migration of small oligomers in soil caused the molecular weight changes for this period. During the second year of soil burial both M-n, and M-w decreased and the polydispersity decreased towards 2. This indicates that a faster hydrolysis took place in the film. It was confirmed by the differential scanning calorimetry analysis of PLLA, which showed that during the second year in soil the thermal properties of the films (T-g and T-m) were affected. PLLA was thus degraded by a combination of hydrolysis and biotic activity. In a first stage, after an induction period of 1 year, the film of PLLA undergoes hydrolysis. In a second stage microorganisms assimilate the small products of degradation while hydrolysis takes place.

  • 76.
    Gallet, Guillaume
    KTH, Superseded Departments, Polymer Technology.
    From Fast to Slow Degradation: Different Strategies to Characterise Polymer Degradation by Chromatographic Techniques2001Doctoral thesis, comprehensive summary (Other scientific)
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  • 77. Gallstedt, M.
    et al.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Oxygen and water barrier properties of coated whey protein and chitosan films2002In: Journal of polymers and the environment, ISSN 1064-7546, E-ISSN 1572-8900, Vol. 10, no 02-jan, p. 1-4Article in journal (Refereed)
    Abstract [en]

    Films of whey protein and chitosan acetic acid salt have lower oxygen permeability than, for example, ethylene-co-vinylalcohol under dry conditions, but water and water vapor seriously impair the gas barrier properties. To reduce the oxygen permeability at 90% relative humidity and the water-vapor transmission rate at 100% relative humidity, the films were coated with an alkyd, a beeswax compound, or a nitrocellulose lacquer. Permeability and transmission rate measurements were performed in accordance with standard methods and showed that the beeswax compound and the nitrocellulose were appropriate as water-vapor barriers. Overall migration to water was measured after 10 days exposure time, with the coated surface exposed to the water, showing that the alkyd-coated and the nitrocellulose-coated films were both below the safety limit for food contact. Water absorbency tests, performed by the Cobb method, showed that the films coated with the beeswax compound or with nitrocellulose lacquer exhibit lower absorbency than the alkyd-coated films.

  • 78. Gallstedt, M.
    et al.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Packaging-related properties of alkyd-coated, wax-coated, and buffered chitosan and whey protein films2004In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 91, no 1, p. 60-67Article in journal (Refereed)
    Abstract [en]

    Packaging-related properties of coated films of chitosan-acetic acid salt and whey protein concentrate (WPC) were studied. Chitosan (84.7% degree of deacetylation) and WPC (65-67% protein) were solution cast to films. These films are potential oxygen barriers for use in packaging. Coatings of wax or alkyds were used to enhance the water-barrier properties. The packaging-related properties of chitosan films treated in a buffering solution, with a pH of 7.8, were also investigated. The coated films were characterized with respect to Cobb absorbency, overall migration to water, water vapor transmission rate, and oxygen permeability. The creasability and bending toughness were determined. The wax was a more efficient barrier to liquid water and 90-95% relative humidity than the alkyd. However, the alkyd-coated material had superior packaging-converting properties. The alkyd-coated WPC and chitosan-salt films were readily folded through 180degrees without any visible cracks or delamination. The overall migration from the alkyd-coated materials was below the safety limit, provided the coat weight was higher than 7.5 mg/cm(2) on WPC and 2.1 mg/cm(2) on chitosan-salt. The barrier properties of chitosan film under moist conditions were improved by the buffer treatment. However, the buffering also resulted in shrinkage of the film.

  • 79. Gallstedt, M.
    et al.
    Mattozzi, Alessandro
    KTH, Superseded Departments, Polymer Technology.
    Johansson, E.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Transport and tensile properties of compression-molded wheat gluten films2004In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 5, no 5, p. 2020-2028Article in journal (Refereed)
    Abstract [en]

    Mechanical and transport properties were assessed on wheat gluten films with a glycerol content of 25-40%, prepared by compression molding for 5-15 min at temperatures between 90 and 130 degreesC. Effects of storing the films up to 24 days, in 0 and 50% relative humidity (RH), were assessed by tensile measurements. The films were analyzed with respect to methanol zero-concentration diffusivity, oxygen permeability (OP), water vapor permeability (WVP), Cobb(60) and sodium dodecyl sulfate (SDS) solubility coupled with sonication. The SDS solubility and methanol diffusivity were lower at the higher molding temperature. Higher glycerol content resulted in higher OP (90-95% RH), WVP, and Cobb(60) values, due to the plasticizing and hygroscopic effects. Higher glycerol contents gave a lower fracture stress, lower Young's modulus, lower fracture strain, and less strain hardening. The mold time had less effect on the mechanical properties than mold temperature and glycerol content. The fracture stress and Young's modulus increased and the fracture strain decreased with decreasing moisture content.

  • 80. Gallstedt, M.
    et al.
    Tornqvist, J.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Properties of nitrocellulose-coated and polyethylene-laminated chitosan and whey films2001In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 39, no 10, p. 985-992Article in journal (Refereed)
    Abstract [en]

    Chitosan (chitosan acetic acid salt) and whey (65% protein) films were coated with a nitrocellulose lacquer or laminated with polyethylene to enhance their water resistance and gas barrier properties in humid environments. The barrier properties were measured by the Cobb,, test and water-vapor (100% relative humidity) transmission and oxygen (90% relative humidity) permeability tests. Mechanical properties were obtained with tensile tests. Packaging properties were studied with crease and folding tests. The Cobb,, test revealed that the coated films were resistant to liquid water, at least for a short exposure time, if the coating thickness was at least 10-17 mum. Water-vapor transmission rates comparable to those of polyethylene-laminated films were obtained for coated chitosan at a coating thickness of 5-7 mum. The coated films possessed low oxygen permeability despite the high humidity. Coated films dried for 3 weeks showed oxygen permeabilities at 90% relative humidity that were similar to values for dry ethylene-co-vinyl alcohol at 0% relative humidity. The lacquer partly penetrated the whey films, and this led to excellent adhesion but poor lacquer toughness. The lacquer coating on chitosan was tougher, and it was possible to fold these films 90 degrees without the coating fracturing if the coating thickness was small. The coated whey films were readily creasable.

  • 81. Glauser, T.
    et al.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Johansson, Mats K. G.
    KTH, Superseded Departments, Polymer Technology.
    Kornmann, X.
    Berglund, Lars A.
    Toughening of electron-beam cured acrylate resins2000In: Macromolecular materials and engineering (Print), ISSN 1438-7492, E-ISSN 1439-2054, Vol. 280, no 08-jul, p. 20-25Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to improve the toughness of EB-cured acrylate thermost resins by using hyperbranched aliphatic polyesters as additives to obtain a liquid-liquid phase-separated resin. The hyperbranched polyester can be considered as a hydroxyl functional scaffold, on which functional groups were reacted by control phase separation and crosslinking. Alkyl chains of different lengths attached to the scaffold controlled phase separation. The amount of crosslinking within the rubbery particle and between the particles and the matrix was set by the percentage of methacrylate groups. A good phase separation was obtained; therefore, T-g decreased only slightly compared to the pure acrylate. The K-IC value of the cured resins was increased by 30%. The phase-separated resins showed stability with time and no significant increase in particle size was noticed after 18 months.

  • 82. Glauser, T.
    et al.
    Johansson, Mats K. G.
    KTH, Superseded Departments, Polymer Technology.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    A comparison of radiation and thermal curing of thick composites2000In: Macromolecular materials and engineering (Print), ISSN 1438-7492, E-ISSN 1439-2054, Vol. 274, no 1, p. 25-30Article in journal (Refereed)
    Abstract [en]

    This work aimed to compare three different techniques to cure thick composite matrices to see the effect of the process on the network and the thermomechanical properties of the polymer matrix. Two different thermoset resins. one acrylate and one methacrylate, have been free-radically cured with high-energy electron beam (EB), ultra-violet light (UV) ol heat (thermal). The differences in curing mechanisms as well as the thermomechanical properties of the cured resins have been investigated. For this type of resins, EB-cured samples showed the highest thermo-mechanical properties and the lowest residual unsaturation. Thermally cured resins showed similar properties, but with drawbacks such as long curing cycles and thermal degradation in the matrix. The cure did not proceed to the same extent in the UV-cured samples. But the simplicity of the curing equipment makes UV-curing an interesting complement to thermal or EB-curing.

  • 83. Glauser, T.
    et al.
    Johansson, Mats K. G.
    KTH, Superseded Departments, Polymer Technology.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Electron-beam curing of thick thermoset composites: Effect of temperature and fiber2000In: Macromolecular materials and engineering (Print), ISSN 1438-7492, E-ISSN 1439-2054, Vol. 274, no 1, p. 20-24Article in journal (Refereed)
    Abstract [en]

    Electron-beam curing of thermoset resins used in fiber-reinforced composites has been investigated. Two resins, a bisphenol-A acrylate and methacrylate, were used as model systems. The temperature was monitored during cure to know the thermal history of the composite during cure. The thermo-mechanical properties were measured on the cured samples. It could be seen that all these values were influenced by the nature (glass or carbon) and amount (0-50 wt.-%) of fiber. A linear correlation was found between the maximum temperature during cure and the glass transition temperature. It was shown that it is possible to compensate for alack of heat during dire in systems with too low exotherms. Some influence on the network homogeneity was also noticed when the thermal energy available during cure was too low.

  • 84.
    Glauser, Thierry
    KTH, Superseded Departments, Polymer Technology.
    Electron-beam curing of thermoset resins for composites1999Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Electron-beams (EB) are an alternative to traditionalthermal curing when manufacturing thick thermoset composites.It is a quick and energetically efficient technique when curinglarge fiber reinforced parts. Most of the published work onEB-curing deals with curing of thin layers of resin or withcrosslinking of polymers.

    In this thesis, the curing of acrylic resins is studied tohighlight the critical parameters and the particularities ofEB-curing. Tgof the thermoset increases with increasingirradiation dose and levels-off at Tg∞, when the resin is fully cured. As inthermal curing, the temperature during cure strongly affectsthe crosslinking of the resin and the thermo-mechanicalproperties of the cured thermoset. Up to Tg∞, a linear relationship between the maximumtemperature during cure and Tgwas found.

    Carbon and glass fiber composites were EB-cured and tested.Adding fibers to the acrylic resins lowered the exotherm, whichclearly confirmed the importance of temperature during cure tofully crosslink the polymer matrix.

    Comparing EB-, UV- and thermal cure showed that the curingmethod was not the factor that most influenced the propertiesof the cured thermoset. The curing technique imposesconstraints, such as starting temperature and curing time, butit does not influence directly the polymerization and thenetwork formation. These properties are inherent to the monomerused.

    An acrylate resin was blended it with a series of alkyl andmethacrylate functionalized hyperbranched polyester. Thephase-separated thermoset exhibited increased toughness.

    Keywords:electron-beam, thermoset, acrylic resin,hyperbranched polyester, thermal effect, toughening

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  • 85. Groning, M.
    et al.
    Hakkarainen, Minna
    KTH, Superseded Departments, Polymer Technology.
    Headspace solid-phase microextraction with gas chromatography/mass spectrometry reveals a correlation between the degradation product pattern and changes in the mechanical properties during the thermooxidation of in-plant recycled polyamide 6,62002In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 86, no 13, p. 3396-3407Article in journal (Refereed)
    Abstract [en]

    The increased susceptibility of in-plant recycled polyamide 6,6 toward thermooxidation was shown by headspace solid-phase microextraction with gas chromatography/mass spectrometry (HS-SPME/GC-MS), tensile testing, differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). A correlation between the deterioration in mechanical properties and the formation of degradation products due to thermooxidation was found, and the most prominent decrease in mechanical properties coincided with the largest increase in the abundance of degradation products. The recycled materials had a shorter induction period toward oxidation, and their mechanical properties deteriorated faster than the mechanical properties of virgin material. The same trend was observed with HS-SPME/GC-MS because degradation products were found for recycled materials after oxidation times shorter than those for virgin material. Furthermore, larger amounts of degradation products were formed in the recycled materials. The high sensitivity of HS-SPME/GC-MS as an analytical tool was demonstrated because it was able to detect changes caused by oxidation considerably earlier than the other methods. Unlike DSC and FTIR, it could also show differences between samples recycled for different times. Four groups of degradation products-cyclic imides, pyridines, chain fragments, and cyclopentanones-were identified in thermooxidized polyamide 6,6. After 1200 h of thermooxidation, 1-pentyl-2,5-pyrrolidinedione was the most abundant degradation product. Approximately four times more 1-pentyl-2,5-pyrrolidinedione was formed in polyamide recycled three times than in virgin polyamide. Pyridines and chain fragments behaved toward oxidation and repeated processing like cyclic imides; that is, their amounts increased during oxidation, and larger amounts were formed in recycled materials than in virgin material. The cyclopentanone derivatives were present already in unaged material, and their amounts decreased during oxidation. Cyclopentanones were not formed because of the thermooxidation of polyamide 6,6.

  • 86.
    Groning, Mikael
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, Superseded Departments, Polymer Technology.
    Multiple headspace solid-phase microextraction of 2-cyclopentyl-cyclopentanone in polyamide 6.6: possibilities and limitations in the headspace analysis of solid hydrogen-bonding matrices2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1052, no 02-jan, p. 61-68Article in journal (Refereed)
    Abstract [en]

    The interactions between a polar analyte, 2-cyclopentyl-cyclopentanone, and a solid polar matrix, polyamide 6.6, during multiple headspace solid-phase microextraction (MHS-SPME) were studied. Strong hydrogen bonding between the analyte and the matrix was observed and shown to cause slow migration and adsorption of the analyte. These matrix effects led to erroneous quantitation despite the use of multiple headspace extraction. Addition of water disrupted the hydrogen bonding between the analyte and the matrix and a valid quantitation was achieved. The addition of water also increased the sensitivity and allowed the identification of 2,5-bis(cyclopentyl)-1-cyclopentanone. The amount of 2-cyclopentyl-cyclopentanone in five different polyamide 6.6 samples was measured using the developed multiple headspace solid-phase microextraction method with water-displacer. The measured concentrations were in the range of 1.44-15.61 mug/g. These concentrations were up to 30% higher than the concentrations measured after microwave-assisted extraction (MAE), which indicates incomplete recovery by MAE. The use of water as a displacer eliminated the matrix effects and complete recovery of the analyte was achieved by MHS-SPME.

  • 87. Gröning, M.
    et al.
    Hakkarainen, Minna
    KTH, Superseded Departments, Polymer Technology.
    Headspace solid-phase microextraction - a tool for new insights into the long-term thermo-oxidation mechanism of polyamide 6.62001In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 932, no 02-jan, p. 1-11Article in journal (Refereed)
    Abstract [en]

    Low-molecular-mass products formed. during thermo-oxidation of polyamide 6.6 at 100 degreesC were extracted by headspace solid-phase microextraction and identified by GC-MS. A total of 18 degradation products of polyamide 6.6 were identified. In addition some low-molecular-mass products originating from the lubricants were detected. The identified degradation products were categorized into four groups where compounds within each group contain the same structural feature. In groups A, B and C several new thermo-oxidation products of polyamide 6.6 were identified including cyclic imides, pyridines and structural fragments from the original polyamide chain. 1-Pentyl-2,5-pyrrolidinedione (pentylsuccinimide) showed the largest increase in abundance during oxidation. The cyclopentanones in group D were already present in the un-aged material. Their amounts decreased during ageing and they are thus not formed during thermo-oxidation of polyamide 6.6 at 100 degreesC. The identified thermo-oxidation products can be formed as a result of extensive oxidation of the hexamethylenediamine unit in the polyamide backbone. The degradation products pattern shows that the long-term thermo-oxidative degradation, just like thermal degradation and photo-oxidation of polyamide 6.6, starts at the N-vicinal methylene groups.

  • 88.
    Gröning, Mikael
    KTH, Superseded Departments, Polymer Technology.
    Solid phase microextraction (SPME) applied to studies of polyamide 6.6 long-term thermo-oxidation and In-plant recycling2002Licentiate thesis, comprehensive summary (Other scientific)
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  • 89.
    Gröning, Mikael
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Hakkarainen, Minna
    KTH, Superseded Departments, Polymer Technology.
    Correlation between emitted and total amount of 2-cyclopentyl-cyclopentanone in polyamide 6.6 allows rapid assessment by HS and HS-SPME under non-equilibrium conditions2004In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1052, no 02-jan, p. 151-159Article in journal (Refereed)
    Abstract [en]

    A correlation was found between the emitted and total amount of 2-cyclopentyl-cyclopentanone in polyamide 6.6. The emitted amounts were measured by GC-MS after headspace (HS) or headspace solid-phase microextraction (HS-SPME) and the total content was determined after microwave-assisted extraction (MAE). The correlation was valid also under non-equilibrium conditions, which allows rapid assessment of 2-cyclopentyl-cyclopentanone content in polyamide 6.6 by headspace techniques. The incubation time needed for non-equilibrium headspace analysis could be reduced from 5 h to 45 min if the PA66 granules were milled to powder prior to extraction. However, to reach equilibrium between the analyte in the solid sample and the headspace still required 12 h of incubation at 80degreesC. The long incubation time is explained by slow diffusion rate due to the strong hydrogen bonding between analyte and matrix and the relatively high crystallinity of polyamide 6.6. The headspace extraction profile showed several equilibrium-like patterns that are easily mistaken for the real equilibrium.

  • 90.
    Gröning, Mikael
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Recycling of glass fibre reinforced phenolic prepreg waste. part 1. Recovery and reuse of glass fibres in PP and PA62004In: Polymers & polymer composites, ISSN 0967-3911, E-ISSN 1478-2391, Vol. 12, no 6, p. 491-500Article in journal (Refereed)
    Abstract [en]

    The present paper describes a feasible process to reuse glass fibres separated from phenolic prepreg waste as reinforcing filler in polypropylene (PP) and polyamide 6 (PA6). Prior to compounding, the recovered glass fibres were cut into 50 mm long fibre bundles and surface treated with gamma-aminopropyltriethoxysilane (APS) for increased composite interfacial strength. Electron Spectroscopy for Chemical Analysis (ESCA) and Atomic Force Microscopy (AFM) showed that the silane coupling agent was attached to the surface of the glass fibres but the silane layer was somewhat uneven, probably due to the presence of small amounts of organic contaminants. In addition it was found necessary to clean the glass fibres from organic contaminants by thermal treatment in order to attach silane coupling agent to the surfaces. The tensile strengths obtained for PP and PA6 composites with 30 wt% filler level of surface treated recovered glass fibres were 49 MPa and 101 MPa, respectively. This should be compared to 30 MPa and 75 MPa for composites containing untreated glass fibres and 19 MPa and 52 MPa for pure PP and PA6. Addition of 5 wt% PP-g-MA compatibiliser to the PP composite increased the tensile strength by another 14%, i.e. to 56 MPa. The good interfacial compatibility achieved by APS surface treatment and compatibilisation was verified by Scanning Electron Microscopy (SEM).

  • 91.
    Gröning, Mikael
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Recycling of glass-fibre reinforced phenolic prepreg waste. Part 2. Milled prepreg as functional filler in PP and PA62004In: Polymers & polymer composites, ISSN 0967-3911, E-ISSN 1478-2391, Vol. 12, no 6, p. 501-509Article in journal (Refereed)
    Abstract [en]

    Phenolic resin impregnated glass-fibre prepreg waste was milled and used as reinforcing filler in polypropylene (PP) and polyamide 6 (PA6). Prepreg was particularly suitable to be used as filler in PA6. The fibres were homogeneously distributed during compounding and the addition of 20 wt% prepreg increased the tensile strength of PA6 by 63%, from 52 MPa to 85 MPa. Milled prepreg alone did not significantly increase the tensile strength of PP. However, if compounded together with maleic anhydride grafted polypropylene (PP-g-MA, Epolene G3003) compatibiliser, prepreg can be used as reinforcing filler in PP as well. Addition of 20 wt% prepreg together with 5 wt% Epolene G3003 increased the tensile strength of PP from 26 MPa to 43 MPa. In order to mill the prepreg for compounding with thermoplastics it has to be cured. A 2 kg batch of prepreg had to be cured for at least 2 hours at 200 degreesC to prevent the phenolic resin from falling off the glass-fibres. Milling should be performed using screens with holes larger than 3 mm in diameter to reduce the amount of prepreg fibres shorter than 2 mm, as they jam the hopper when feeding the recyclate to the extruder. The initial prepreg fibre length is of little importance to the composite mechanical properties, as the fibres are shortened to approximately the same length during compounding.

  • 92. Gustavsson, Catrin
    et al.
    Ek, M.
    Kadiric, J.
    Teder, Ants.
    KTH, Superseded Departments, Polymer Technology.
    Formation and dissolution/degradation of hexenuronic acids during kraft pulping of Eucalyptus Globulus2001In: 7th Brazilian Symposium on the Chemistry of Lignins and other Wood ComponentsArticle in journal (Refereed)
  • 93. Gustavsson, T. G.
    et al.
    Gubanski, S. M.
    Hillborg, H.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Aging of silicone rubber under ac or dc voltages in a coastal environment2001In: IEEE transactions on dielectrics and electrical insulation, ISSN 1070-9878, E-ISSN 1558-4135, Vol. 8, no 6, p. 1029-1039Article in journal (Refereed)
    Abstract [en]

    Material samples of silicone rubber with known differences in their composition, i.e. different filler content and extra silicone oil added, have been aged at the Anneberg field station on the west coast of Sweden. ac or dc voltage supplied to cylindrical samples at stress levels of 50 or 100 V/mm. The work includes laboratory examination of material changes together with on-site, visual observations and leakage current measurements. Material samplings for the laboratory tests were made after 18 months of electrical aging, which went on for one more year in order to gather further information on the long-term electrical performance of the material. The dominant aging factor was the level of the applied stress, independent of ac or dc voltage. The dc stressed samples showed a higher leakage current and exhibited larger surface degradation compared with samples exposed to ac voltage. The material parameter, an addition of extra silicone oil, initially lead to an increase in adhesion of pollutants, whereas the overall performance was improved by the higher suppression of the leakage current related to oligomer diffusion. Samples with lower level of alumina trihydrate (ATH) exhibited a delayed onset of degradation, but once damaged they degraded more rapidly than the specimens with a higher ATH content. Infrared spectroscopy showed that the ATH was completely consumed at the eroded surface regions. The aging of the surfaces was further assessed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The low molar mass siloxanes present in the pollution layer were extracted and analyzed by size exclusion chromatography and gas chromatography-mass spectroscopy. The results indicated that the main degradation factor was thermal depolymerization activated by electrical discharges. Oxidative crosslinking of the silicone rubber, usually attributed to surface close corona discharges, appeared to have played a minor role.

  • 94.
    Gällstedt, Mikael
    KTH, Superseded Departments, Polymer Technology.
    Packaging related properties of uncoated, coated and laminated whey protein and chitosan films2001Licentiate thesis, comprehensive summary (Other scientific)
  • 95. Haider, N.
    et al.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Kinetics of migration of antioxidants from polyolefins in natural environments as a basis for bioconversion studies2000In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 1, no 3, p. 481-487Article in journal (Refereed)
    Abstract [en]

    Plastics ending up in soil or landfill environment will eventually be degraded. At the same time a slow migration of additives from the plastics will occur. The additives and the degradation products of these and the polymer are potential compounds for bioconversion. To predict the rate of the migration of antioxidants from polyolefins, a medium-density polyethylene film MDPE containing two commercial antioxidants, Irganox 1010 and Irgafos 168, was exposed to simulated landfill environments, viz. aqueous media at pH 5 and 7, with temperatures of 25, 50, 80, and 105 degreesC and solid-to-liquid ratios of 1:5. The migration process of the antioxidants was studied by an ultrasonic extraction technique using chloroform as extraction solvent to recover the nonmigrated antioxidants from the polymeric matrix, followed by quantitative analysis of the extracted antioxidants by high performance liquid chromatography (HPLC) with acetonitrile as the mobile phase and a wavelength of 280 nm. It was found that the release of both Irganox 1010 and Irgafos 168 increases at higher temperature, longer time, and lower pH. Moreover, the migration of Irgafos 168 proceeds faster than that of Irganox 1010 at lower temperatures while at higher temperatures the opposite behavior was observed. No degradation of the polymeric matrix was detected under the testing time. Migration processes included diffusion of the antioxidants within the polymer and their desorption from the surface of the polymer into the boundary layers of leachate. In general, the kinetic of the migration process was well described by first-order equations while an Arrhenius-type relationship was applicable for the temperature dependence of the constants. The general constants calculated for the migration processes were applied to the prediction of the time required for complete release of the antioxidants under different landfill conditions.

  • 96. Haider, N.
    et al.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Loss and transformation products of the aromatic antioxidants in MDPE film under long-term exposure to biotic and abiotic conditions2002In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 85, no 5, p. 974-988Article in journal (Refereed)
    Abstract [en]

    The loss of a primary phenolic antioxidant Irganox 1010 and of a secondary phosphite antioxidant Irgafos 168 from a medium density polyethylene film (MDPE) was investigated after exposure of the film for 4 years to different environments such as aqueous media at pH5 and 7, open air, and compost, with an exposure of exposition of 25degreesC. An ultrasonic extraction technique using chloroform as extraction solvent was applied to recover the residual antioxidants from the polymeric matrix, and this was followed by High-Performance Liquid Chromatography (HPLC) with acetonitrile as mobile phase and a quantitative analysis at a wavelength of 280 run of the extracted antioxidants. The amount of antioxidant lost varied remarkably depending on the testing medium. The fastest loss of antioxidant was found on exposure to open air and sunlight while the slowest loss was observed in compost. Thermo-analytical measurements were made to characterize the residual thermo-oxidative stability of MDPE film in terms of oxidation temperature and oxidation induction time, to provide a greater insight into the underlying mechanisms of ageing in the different environments. Analysis by Gas chromatography-Mass Spectrometry (GC-MS) revealed that degradation of the polymeric matrix resulted in the formation of hydrocarbons and oxygen-containing compounds such as alcohols, carboxylic acids, aldehydes, and esters. The transformation products of the antioxidants formed as result of processing or exposure to the tested media were also identified. The transformation of the phenoxy radical of the Irganox 1010 produced the ester, acid, dealkylated cinnamate, and quinone products, whereas Irgafos 168 yielded oxidation products and the phenolic hydrolysis byproduct 2,4-ditert-butylphenol.

  • 97. Haider, N.
    et al.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Loss of Chimassorb 944 from LDPE and identification of additive degradation products after exposure to water, air and compost2001In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 74, no 1, p. 103-112Article in journal (Refereed)
    Abstract [en]

    A low-density polyethylene (LDPE) film containing a hindered amine light stabiliser (Chimassorb 944) was exposed to a composting mixture, chemical hydrolysis at pH 5 and pH 7 and air, in all cases at room temperature and for a period of 4 years. The structural changes of the LDPE film were investigated by differential scanning calorimetry (DSC) and size exclusion chromatography with viscosity detection (SEC-viscosity) while degradation products of LDPE and Chimassorb 944 were identified by gas chromatography-mass spectrometry (GC-MS). Determination of the amount of remaining stabiliser was performed using an ultrasonic extraction technique followed by LN spectroscopy analysis (250 nm, absorption of 1,3,5-triazine group). The ultrasonic extraction of Chimassorb 944 was carried out at 60 degreesC for a period of 1 h, using chloroform as extracting solvent. Loss of the stabiliser accompanied by structural changes of the polymeric matrix occurred during exposition time and was strongly influenced by exposure conditions. Thus, the fastest loss of the stabiliser was found on exposition to chemical hydrolysis at both pH while the slowest loss was observed during ageing in compost. Different products formed from Chimassorb 944 were found in all the tested environments as a result both of degradation of the stabiliser to smaller fragments and of reactions between these fragments and other additives present in LDPE. Thus, (Z)-9-octadecenamide was found in both unexposed and all the tested samples and was formed already during processing. 2,2,6,6-Tetramethyl-4-aminopiperidine was found in air and compost aged samples while 2,4-di-t-butyl-6-nitro-phenol was found in the samples exposed to air and water environments and [2-cyclohexene-1-dione, 3,5-dimethyl, O-methyloxime] were found exclusively in the samples aged in water at pH 5.

  • 98.
    Haider, Nadejzda
    KTH, Superseded Departments, Polymer Technology.
    Consumption and loss of commercial stabilisers in polyethylene exposed to different natural environments2001Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    A procedure for the extraction and analysis of commercialstabilisers in low density and medium density polyethylene(LDPE and MDPE) films was developed and used to study theconsumption of stabilisers in polymers exposed to differentnatural environments. An ultrasonic technique was applied toextract HALS-3 (Chimassorb 944) from LDPE film and antioxidants(Irganox 1010 and Irgafos 168) from MDPE film. This wasfollowed by a quantitative analysis of Chimassorb 944 by UVspectroscopy at a detection wavelength of 250 nm for theabsorption of the 1,3,5-triazine group and a quantitativeanalysis of the antioxidants by High Performance LiquidChromatography (HPLC) using acetonitrile as mobile phase and adetection wavelength of 280 nm.

    The migration of the stabilisers from the polymeric matrixwas studied when LDPE and MDPE films were exposed to asimulated landfill leachate (aqueous media, pH5) as well asrainfall (aqueous media, pH7) both under accelerated conditionsand in real time (exposure temperatures of 25°C,50°C, 80°C and 105°C) with a solid-to-liquidratio of 1:5 (a ratio of 1:10 was also used in LDPE for thepurpose of comparison). The amount of stabilisers, whichmigrated from the polyethylene matrix, increased continuouslywith time. An increase in temperature as well as a lowersolid-to-liquid ratio accelerated the migration process,whereas a rise in pH retarded it. The kinetics of the migrationwere well described by first order equations, and anArrhenius-type relationship was applicable for thetemperature-dependence of the migration rate constants. Thetime required for the complete release of the stabilisers underdifferent landfill conditions was predicted.

    The consumption and conversion products of the stabilisersas well as the degradation behaviour of the polymeric matriceswere investigated after long-term exposure for a period of 4years to different natural environments such as open air andsunlight, composting mixture and chemical hydrolysis at pH5 and7, in all cases at room temperature. Loss of the stabilisersand structural changes occurred in the polymeric matricesduring this exposure time and were strongly influenced by theexposure conditions.

    The structural changes in the polyethylene films both afteraccelerated exposure to simulated landfill leachate andrainfall and after long-term exposure to natural environmentswere investigated by different methods such as ScanningElectron Microscopy (SEM), Fourier Transform InfraredSpectroscopy (FTIR), Differential Scanning Calorimetry (DSC)and Size Exclusion Chromatography with Viscosity detection(SEC-Viscosity). Degradation of the polymers caused changes incrystallinity, an increase in melting temperature and theformation of crosslinks.

    A variety of degradation and transformation products fromboth the polymeric matrices and the stabilisers were identifiedby Gas Chromatography-Mass Spectrometry (GC-MS). The amounts ofdegradation products were remarkably greater from the LDPE thanfrom the MDPE film, indicating a much higher extent ofdegradation in the LDPE matrix than in the MDPE matrix. Themain degradation products found were linear and branchedalkanes, alkenes, alcohols, carboxylic acids, aldehydes,ketones and esters. Different products formed from Chimassorb944 were found in all the tested environments as a result bothof degradation of the stabiliser to smaller fragments and ofreactions between these fragments and other additives presentin LDPE. The transformation products of the antioxidants formedas result of processing and/or exposure to thetested mediawere also identified. The transformation of the phenoxylradical of the Irganox 1010 led to ester, acid, dealkylatedcinnamate and quinone products, whereas conversion oxidationproducts and the phenolic hydrolysis by-product 2,4-di-tert-butylphenol were formed from Irgafos 168.

    Keywords: LDPE, MDPE, ultrasonic extraction, polymeradditives, stabilisers, antioxidants, HALS, Irganox 1010,Irgafos 168, migration, consumption, GC-MS, additivedegradation products.

  • 99.
    Haider, Nadejzda
    KTH, Superseded Departments, Polymer Technology.
    Extraction and analysis of polyethylene stabilisers and their migration in a simulated landfill environment1998Licentiate thesis, comprehensive summary (Other scientific)
  • 100.
    Hakkarainen, Minna
    KTH, Superseded Departments, Polymer Technology.
    Aliphatic polyesters: Abiotic and biotic degradation and degradation products2002In: Advances in Polymer Science, ISSN 0065-3195, E-ISSN 1436-5030, Vol. 157, p. 113-138Article, review/survey (Refereed)
    Abstract [en]

    This paper reviews the degradation behavior of aliphatic polyesters of current interest, including polylactide, polycaprolactone, poly(3-hydroxybutyrate) and their copolymers. Special focus is given to degradation products formed in different abiotic and biotic environments. The influence of processing and processing additives on the properties and degradation behavior is also briefly discussed.

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