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  • 51. Johansson, E. E.
    et al.
    Lind, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    The general link between random scissions in linear polymers, changes in average chain length and the Mark-Houwink equation2005In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 88, no 2, p. 159-167Article in journal (Refereed)
    Abstract [en]

    Theories for random scission degradation of polymers are motivated from the basic scientific interest in reaction kinetics and yields of process. There is a tradition to derive scission-measures (bond consumption or cleavage) from the number average of chain length in a molecular weight distribution. It is understood by many that the validity of these derivations will be conditional and many attempts are made to extend the accuracy of the models. This article presents a mass-based derivation for changes in chain length that offers scission-values not only from number averages but also from the mass and viscosity averages, independent of molecular weight distribution profile. The derivation shows the interdependence between the Mark-Houwink equation and scission calculus. The exponent in the Mark-Houwink equation is proposed to originate from the process of varying polymer chain lengths for calibration and the initial content of polymer chain ends in the sample as well as the earlier proposed effects from chain curl. Calculation of the number of random scission hence demands the Mark-Houwink parameters to be calibrated by varying polymer chain lengths using random scission generation.

  • 52.
    Kaali, Peter
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Czel, Gyoergy
    Department of Polymer Engineering, University of Miskolc.
    Momcilovic, Dane
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Antimicrobial properties of Ag+ loaded zeolite polyester polyurethane and silicone rubber and long-term properties after exposure to in-vitro ageing2010In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, no 9, p. 1456-1465Article in journal (Refereed)
    Abstract [en]

    In biomedical applications, tubes (e.g. catheters etc.) are commonly produced from polyurethane (PU) and silicone rubber which are known to be biocompatible materials. Several studies have shown that tubes, which are connected to the body (invasive) (especially urinary, tracheotomy and central venous catheters) are associated with infections. The present study reports the development of a new method aiming at obtaining antibacterial properties for PU and silicone rubber by mixing respective material with a natural antibacterial agent (Ag+ loaded zeolite) in different weight fractions. The influence of the zeolite content on the antimicrobial properties were analysed by exposure to bacteria (ISO 22196) and mixtures of fungi (ISO 846). The materials were also subject to artificial body fluids (Artificial Lysosomal Fluid (ALF) and Gamble's solution) for periods up to three months and the subsequent changes in the chemical properties after in-vitro exposure were determined by Matrix Assisted Laser Deposition/Ionization Time Of Flight Mass Spectrometry (MALDI-TOF MS) and Attenuated Total Reflection Fourier Transform Infra Red spectroscopy (ATR-FTIR). It was established that the antimicrobial effect of the materials increased with the increase of the zeolite content. The wettability of the materials was found to decrease significantly during the in-vitro exposure, but this could not be correlated to the zeolite content. In the PU samples, the formation of free carbonyl and -OH groups was observed, which corresponds to oxidative degradation. In case of the silicone rubber the ratio of cyclic PDMS to linear PDMS (H, CH3 and dimethyl terminated) decreased, which indicates a change in the concentration of the compounds. The formation and increase of the O-H bond during the exposure was also confirmed by the infrared spectra of the material which corresponds to hydrolysis of the silicone rubber.

  • 53.
    Kallio, Kai J.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Ageing properties of polyamide-12 pipes exposed to fuels with and without ethanol2008In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 93, no 10, p. 1846-1854Article in journal (Refereed)
    Abstract [en]

    The chemical and physical properties of polyamide-12 (PA12) fuel pipes/lines, aged for <= 2400 h at 110 degrees C, have been investigated. The pipes, containing fuel with or without ethanol, were either of a single PA12 layer, or of two PA12 layers surrounding a poly(vinylidene fluoride) barrier layer. The molar mass of the inner surface region obtained by size-exclusion chromatography was reduced during ageing. and optical microscopy revealed a surface that was partly dissolved in the presence of ethanol. Infrared spectroscopy revealed a rapid loss of plasticiser, especially in the presence of ethanol, and the fuel contained plasticiser and other polymer related components. Immersion tests at 60 degrees C showed that the swelling of the pipe and the amount of dissolved material were greatest for the fuels with intermediate ethanol content (50 vol.%). Aged samples experienced an increase in melting point, presumably, to a large extent, due to the loss of plasticiser and/or PA12-related components. In addition, for several samples, the crystallinity seemed to increase with ageing. (C) 2008 Elsevier Ltd. All rights reserved.

  • 54.
    Kallio, Kai J.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Degradation of Polyamide-12 pipes aged in fuelIn: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321Article in journal (Other academic)
    Abstract [en]

    In this work properties of polyamide-12 (PA12) fuel lines, exposed for ≤2400 h at 110°C and ≤26000 h at 50°C, containing fuels with different ethanol contents, were investigated. Dynamic mechanical thermal analysis indicated a sizeable loss of plasticiser during ageing. Viscosity measurements suggested that chain scission was an important mechanism of degradation at the higher temperature and size exclusion chromatography suggested that this was probably the case also at 50°C after long ageing times. The molar mass and polydispersity data indicated that the most degraded samples were those exposed to high ethanol contents at 110°C. Thermogravimetry showed that the onset temperature of the main degradation stage was 340-410°C (depending on heating rate). X-ray fluorescence spectroscopy and high performance liquid chromatography indicated migration of stabiliser and in the three-layered pipe, having two PA12 layers divided by a poly(vinylidene fluoride) barrier layer, the migration occurred preferentially from the inner pipe layer into the fuel.

  • 55.
    Karlsson, S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Ljungquist, O.
    Albertsson, A-C.
    Biodegradation of polyethylene and the influence of surfactants1988In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 21, no 3, p. 237-250Article in journal (Refereed)
  • 56. Khabbaz, Farideh
    et al.
    Albertsson, Ann-Christine
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Trapping of volatile low molecular weight photoproducts in inert and enhanced degradable LDPE1998In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 61, no 2, p. 329-342Article in journal (Refereed)
  • 57. Kirchhain, A.
    et al.
    Yu, Wenbin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Engman, L.
    Organochalcogen stabilizers efficiently protect model polyolefins exposed to chlorinated media2015In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 118, p. 82-87Article in journal (Refereed)
    Abstract [en]

    The small amounts of chlorine dioxide that are routinely supplemented to drinking water as a disinfectant also cause a degradation of the polyolefin pipes that are used for distribution of the water. Commonly used phenolic antioxidants can extend the service life of the polymer but the expected lifetime is still much shorter than desired (50 years) due to depletion of the antioxidant in the surface zone exposed to the aqueous solution. In search for better stabilizers for the pipes, we have tested an organotellurium compound, 4-(N,N-dimethylamino)phenyl 3-phenoxypropyl telluride (1), as well as its corresponding selenium and sulphur analogues and a series of organotellurium compounds where the electron density at the heteroatom was varied. Stabilizers were dissolved in squalane, which is a liquid hydrocarbon that could serve as a model for a polyolefin. The oxidation induction time (OIT), determined after exposure of the squalane solution to an aqueous solution of 10 ppm of chlorine dioxide for various times was determined by DSC to indicate the loss of antioxidant protection. Whereas Irganox 1010 was only effective as a stabilizer for a few hours, many of the organochalcogen compounds were considerably more resistant (>91 h for compound 1) towards chlorine dioxide. Thermogravimetric analyses of antioxidants indicated insignificant decomposition below 200 degrees C and increasing stability for the lighter chalcogen compounds (telluride < selenide < sulfide). Among organotelluriums, stability increases with increasing electron density at the heteroatom. Oxidation potentials of stabilizers as determined by cyclic voltammetry correlated fairly well with their protective effect in squalane (OIT-values). We therefore hypothesize that these compounds act primarily as electron donors towards peroxyl radicals. As determined by Te-125 NMR-spectroscopy, organotellurium compound 1 in the presence of an excess of chlorine dioxide failed to produce an oxidation product. This may be the clue to its long-lasting protective effect in the squalane-assay.

  • 58.
    Krämer, Roland
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    On the intumescence of ethylene-acrylate copolymers blended with chalk and silicone2007In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 92, p. 1899-1910Article in journal (Refereed)
    Abstract [en]

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

  • 59.
    Krämer, Roland
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Heat release and structural collapse of flexible polyurethane foam2010In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, no 6, p. 1115-1122Article in journal (Refereed)
    Abstract [en]

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

  • 60.
    Krämer, Roland
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Raza, Mohsin Ali
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf W
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Degradation of poly (ethylene-co-methacrylic acid)-calcium carbonate nanocomposites2007In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 92, no 10, p. 1795-1802Article in journal (Refereed)
    Abstract [en]

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

  • 61.
    Linde, Erik
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Plasticizer migration from PVC cable insulation - The challenges of extrapolation methods2014In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 101, no 1, p. 24-31Article in journal (Refereed)
    Abstract [en]

    A single strand PVC-P insulation including an internal metal conductor removed from the jacketed assemblies of a signal cable showed brittleness after 30 years service at 25 +/- 3 degrees C in air. The PVC compound contained diisodecyl phthalate (DIDP), di(2-ethylhexyl) phthalate (DEHP) and a sizeable fraction of filler. Single strand insulation samples with internal metal conductor were aged in air at elevated temperatures for different periods of time after which the strain at break, the Young's modulus and the plasticizer content were assessed by tensile testing and liquid chromatography. Isothermal evaporation rates from pristine DIDP and DEHP and solutions of the two plasticizers were obtained by thermogravimetry. Data for Young's modulus, strain at break and plasticizer contents were extrapolated to service temperature using two different extrapolation methods, Arrhenius extrapolation (constant activation energy) and a method based on models by Langmuir, Clausius-Clapeyron and Kirchhoff. These methods assume that evaporation of plasticizers to the surrounding gas phase is the dominant deterioration mechanism. Both methods predicted only a minor decrease in plasticizer content after 30 years of ageing at 28 degrees C and thus a material with adequate mechanical properties. Liquid chromatography showed that the single strand cable samples contained a very low DIDP content (4 wt.%) and an anomalously high DEHP content; a finding that cannot be explained by the expected evaporative loss mechanism. It is suggested that DIDP was efficiently extracted by contact with a DEHP-rich interface at the insulation surface, a process which is active during plant operation, but could not be simulated by controlled laboratory accelerated ageing studies.

  • 62.
    Lindström, Annika
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Quantitative determination of degradation products an effective means to study early stages of degradation in linear and branched poly(butylene adipate) and poly(butylene succinate)2004In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 83, no 3, p. 487-493Article in journal (Refereed)
    Abstract [en]

    Low molecular weight products migrating from linear and branched poly(butylene adipate) (PBA) and poly(butylene succinate) (M) during hydrolysis were extracted, identified and quantified by solid phase extraction (SPE) and GC-MS. The combination of SPE and GC-MS proved to be a sensitive tool, able to detect small differences in the degradation rate during early stages of hydrolysis before any significant differences were observed by weight loss and molecular weight measurements. The detected low molecular weight products included monomers i.e. adipic acid and 1,4-butanediol for the PBA polymers and succinic acid and 1,4-butanediol for PBS. Several dimers and trimers i.e. hydroxybutyl adipate, hydroxybutyl succinate, di(hydroxybutyl) adipate, di(hydroxybutyl) succinate and hydroxybutyl disuccinate were also detected. Comparison of measured weight loss and the amount of monomeric products showed that weight loss during early stages of hydrolysis was mainly caused by the release of water-soluble oligomers. On prolonged ageing these oligomers continued to hydrolyse to monomeric species.

  • 63.
    Liu, Dongming
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pallon, Love K. H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Sanchez, Carmen Cobo
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Fogelström, Linda
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Interactions between a phenolic antioxidant, moisture, peroxide and crosslinking by-products with metal oxide nanoparticles in branched polyethylene2016In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 125, p. 21-32Article in journal (Refereed)
    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.

  • 64.
    Lokander, Mattias
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Reitberger, Torbjörn
    KTH, Superseded Departments, Chemistry.
    Stenberg, Bengt
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Oxidation of Natural Rubber based Magnetorheological Elastomers2004In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 86, no 3, p. 467-471Article in journal (Refereed)
    Abstract [en]

    The Theological properties of magnetorheological (MR) materials can be changed continuously, rapidly and reversibly by an applied magnetic field. Solid MR materials consist of magnetically polarisable particles, generally iron, in an elastomer matrix. The high iron concentrations required (about 30% by volume) in order to get a substantial magnetorheological effect should influence the long-term stability of the materials. In this paper, the oxidative stability of natural rubber-based magnetorheological elastomers has been studied by chemiluminescence and oven ageing. The results show that the oxidative stability of natural rubber decreases dramatically when large amounts of iron particles are incorporated in the matrix. This is probably due to the large amounts of oxygen on the surface of the particles. Conventional antioxidants can be used to prolong the lifetime of magnetorheological elastomers, but in order to get acceptable lifetime of the materials a careful selection of the antioxidant system has to be made.

  • 65.
    Lundbäck, Marie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Polybutene-1 pipes exposed to pressurized chlorinated water: lifetime and antioxidant consumption2006In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 91, no 4, p. 842-847Article in journal (Refereed)
    Abstract [en]

    Pipes of isotactic polybutene-1 were pressure-tested in chlorinated water at a controlled pH (6.5 ± 0.1), and the lifetime was assessed as a function of temperature (95-115°C) and chlorine content (≤3 ppm). These data were compared with data from pressure testing in hot water (0 ppm chlorine). The lifetime shortening in chlorinated water was significant even at relatively low chlorine contents, 0.5 ppm. A further increase in chlorine content led only to a moderate shortening of the lifetime. The temperature dependence of the lifetime data obeyed the Arrhenius law. The activation energy obtained for failure data in chlorinated water was ∼140 kJ mol-1, which was greater than the value of 108 kJ mol-1 earlier reported for failure data from hot-water pressure testing. A 0.5-mm thick layer of material at the inner wall in the fractured pipes showed depletion of the antioxidant system and the inner wall displayed a large number of surface cracks, confirming that there was a pronounced chemical degradation of the inner wall material. The decrease in the antioxidant concentration was independent of the chlorine concentration in the range 0.5-1.5 ppm. The time to reach depletion of the antioxidant system could be predicted by linear extrapolation in an oxidation induction time (log scale)-exposure time (linear scale) diagram.

  • 66.
    Lundbäck, Marie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Mattozzi, Allesandro
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Migration of phenolic antioxidants from linear and branched polyethylene2006In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 91, no 7, p. 1571-1580Article in journal (Refereed)
    Abstract [en]

    Plaques of linear polyethylene (LPE) and branched polyethylene (BPE) were exposed to oxygen-free media (nitrogen or water) at 75, 90 and 95 degrees C. The polymers were stabilized with one of the following three bifunctional phenolic antioxidants: Santonox R, Irganox 1081 or Lowinox 22M46. The initial concentration of antioxidant in the plaques was similar to 0.09 wt.%. After ageing, the oxidation induction time profiles obtained by differential scanning calorimetry often became very flat, which indicated that migration was controlled by the boundary loss process. The unexpected higher migration rate from LPE than from BPE was due to the dominance of the boundary loss process. It is proposed that the low boundary loss rate in BPE was due to the presence of a thin liquid-like (oligomeric) surface layer which developed during ageing of this polymer. A qualitative relationship was found between the boundary loss rate to water and the polarity of the antioxidant. The antioxidant diffusivities in LPE and BPE were approximately equal, a finding which, in view of the morphological analysis estimating the geometrical impedance factor, indicated that the constraining effect of the crystals on the non-crystalline fraction was not sensed by the antioxidant molecules. It is suggested that the large molecular size and the low segmental flexibility of the antioxidant molecules inhibited their ability to penetrate the interfacial component.

  • 67.
    Lundbäck, Marie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Strandberg, Clara
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Loss of stability by migration and chemical reaction of Santonox R in branched polyethylene under anaerobic and aerobic conditions2006In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 91, no 5, p. 1071-1078Article in journal (Refereed)
    Abstract [en]

    Plaques of branched polyethylene stabilized with 0.1 wt.% 4,4′-thiobis(6-tert-butyl-3-methylphenol) [Santonox® R] were aged at different temperatures between 75 and 95°C in anaerobic (nitrogen or water) and aerobic (air or water saturated with air) media. Antioxidant concentration profiles were obtained by oxidation induction time (OIT) measurements using differential scanning calorimetry. Results obtained by high performance liquid chromatography of extracts confirmed that the gradual decrease in OIT with increasing ageing time was due to migration of antioxidant to the surrounding medium. The antioxidant concentration profiles along the plaque thickness direction were flat in the plaques aged in the non-aqueous media indicating that the migration of antioxidant to the surrounding medium was controlled by the low evaporation rate at the material boundary. Crystals of antioxidant were detected by optical microscopy on the samples exposed to nitrogen. The similarity of the antioxidant concentration profiles obtained after ageing in nitrogen and in air suggested that the fraction of the antioxidant oxidized is negligible in comparison with the loss of antioxidant by migration to the surrounding media. The antioxidant concentration profiles along the plaque thickness direction obtained after ageing in water were less flat, suggesting faster dissolution in the water phase than evaporation in the case of non-aqueous ageing. The antioxidant diffusivity could be determined from the aqueous experiments and was in reasonable agreement with data reported by Moisan. For the samples exposed to water, the loss of antioxidant was faster from the samples exposed to water saturated with air. This difference is attributed to a faster degradation of the antioxidant in the oxygen-containing water phase increasing the mass transport from the polymer phase boundary to the water phase.

  • 68.
    Nawaz, Sohail
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hillberg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Migration of a phenolic antioxidant from aluminium oxide-poly(ethylene-co- butyl acrylate) nanocomposites in aqueous media2013In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 98, no 2, p. 475-480Article in journal (Refereed)
    Abstract [en]

    The migration of a phenolic antioxidant (Irganox 1010) from nanocomposites based on aluminium oxide (2-12 wt.%; uncoated or coated with aminopropyltriethoxysilane or octyltriethoxysilane) and poly(ethylene-co-butyl acrylate) (EBA) with 13 wt.% butyl acrylate nanocomposites in aqueous media (liquid water or air with 100%RH) at 90°C was studied. The concentration of effective antioxidant in the composites was assessed by the oxidation induction time (OIT) measured by DSC. The flat OIT-profiles through the materials showed that the migration was controlled by the boundary conditions. The boundary antioxidant loss rates to the different media were (in relative units): 1 (dry air; data reported earlier), 1.5-3 (humid air) and 4-10 (liquid water). OIT-profiles for two-layer sandwich samples (a pristine EBA layer and a nanocomposite layer containing 0.2 wt.% Irganox 1010) showed that the antioxidant diffusivity was lowest in the composites containing uncoated nanoparticles (which had the highest surface concentration of hydroxyl groups of all the studied nanoparticles). The presence of water in the composites had only a small effect on the diffusivity; it was 10-50% greater than in the dry systems.

  • 69.
    Nawaz, Sohail
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Nordell, Patricia
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Azhdar, Bruska
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hillberg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Stabilizer activity in Al2O3/ poly(ethylene-co-butylacrylate) nanocompositesIn: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321Article in journal (Other academic)
    Abstract [en]

    The stabilizer activity of polymer nanocomposites based on poly(ethylene-co-butylacrylate) and 0.5 - 3 vol. % of two different types of Al2O3 nanoparticles was investigated. The nanoparticles were either functionalized using octyl- or amino-terminated silanes, or used as received. The nanocomposites also contained 0.2 wt. % of Irganox 1010, a hindered phenolic stabilizer. The activity of the stabilizer in the samples was analyzed by Differential Scanning Calorimetry (assessment of Oxidation Induction Time (OIT)), and compared those obtained for the pristine polymers. The stabilizer was adsorbed to the untreated Al2O3 nanoparticles resulting in a significant reduction in OIT. The reduction increased with increasing total surface area of the particles. Surface silanization of the nanoparticles resulted in an increase in OIT, compared to the untreated particles. The activity of the stabilizer was evaluated by OIT after thermal ageing of the nanocomposites in hot-air oven at 90C up to 30 days. No surface oxidation was observed on any of the samples using reflection infrared spectroscopy. The ageing showed that the stabilizer was not irreversibly adsorbed to the particle surfaces, resulting in a gradual release with the ageing time. This resulted in a slower reduction in OIT as function of aging time for the nanocomposites, compared to the pristine polymer. In order for the nanocomposites to exhibit similar or higher OIT values after thermal ageing, compared to unfilled EBA, > 0.5 mg of stabilizer per m2 of octyl- or amine-coated Al2O3 nanoparticles was needed. The loss of stabilizer was controlled by the evaporation rate of the stabilizer from the surface of the samples to the surrounding air.

  • 70.
    Nawaz, Sohail
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Nordell, Patricia
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hillborg, Henrik
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Antioxidant activity in aluminium oxide - Poly(ethylene-co-butyl acrylate) nanocomposites2012In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 6, p. 1017-1025Article in journal (Refereed)
    Abstract [en]

    The antioxidant activity of Irganox 1010 (0.2 wt%) in aluminium oxide (2-12 wt%) - poly(ethylene-co-butyl acrylate) nanocomposites was studied. The aluminium oxide nanoparticles were in three different forms: uncoated and coated with either octyltriethoxysilane or aminopropyltriethoxysilane. The activity of the stabilizer in the nanocomposites was assessed by determining the oxidation induction time (OIT) using DSC. Composites with untreated aluminium oxide nanoparticles showed a much shorter OIT than the pristine polymer with the same overall antioxidant concentration indicating adsorption of the antioxidant onto the nanoparticle surfaces. The adsorption of antioxidant onto both uncoated and coated nanoparticles was confirmed by X-ray photoelectron spectroscopy. Composites containing coated nanoparticle fillers showed a significantly smaller depression of the OIT, indicating that the replacement of hydroxyl groups with organic silane tails decreased the concentration of available adsorption sites on the particle surfaces. Composites with a filler coated with a silane having terminal aliphatic amine groups showed an increased OIT with respect to that of the pristine polymer suggesting a synergistic on the stability effect between the antioxidant and the amine groups. The long-term activity of the stabilizer was assessed by measuring the OIT on samples after ageing in air at 90°C for 720 h. The decrease in OIT with increasing ageing time of the nanocomposites was slower than for the unfilled polymer. A possible interpretation of these data is that the antioxidant was slowly released from the adsorption sites on extended ageing.

  • 71.
    Olsson, Sara
    et al.
    SP Technical Research Institute of Sweden.
    Johansson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Westin, Mats
    SP Technical Research Institute of Sweden.
    Östmark, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Grafting of 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone and epoxidized soybean oil to wood: Reaction conditions and effects on the color stability of Scots pine2012In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 9, p. 1779-1786Article in journal (Refereed)
    Abstract [en]

    This study investigates the photostabilizing effect of the reactive UV-absorber 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone (HEPBP) when used as a primer for wood. The present work further includes a study on the effect of HEPBP used in combination with an epoxy functionalized vegetable oil as a primer system. The study is based on reactions performed on pine veneers using 3-pentanone as a solvent and 4-(dimethylamino)pyridine (DMAP) as a catalyst, varying the reaction time and temperature. Results from FTIR and SEC measurements indicate that a desired reaction between HEPBP and wood does occur and that there are synergetic effects when HEPBP and oil are combined. Color measurements also indicate that the use of HEPBP and epoxidized soybean oil as pretreatment for wood results in a lower color change after 400 h of artificial weathering. We conclude that using HEPBP in combination with epoxy functionalized soybean oil does improve photostability of wood exposed to artificial weathering.

  • 72.
    Olsson, Sara
    et al.
    SP Technical Research Institute of Sweden, Wood Technology, Sweden.
    Johansson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Westin, Mats
    Östmark, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology. SP Technical Research Institute of Sweden, Wood Technology, Sweden.
    Reactive UV-absorber and epoxy functionalized soybean oil for enhanced UV-protection of clear coated wood2014In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 110, p. 405-414Article in journal (Refereed)
    Abstract [en]

    The present work investigates the photostabilising effect of a pretreatment consisting of 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone (HEPBP) and epoxy functionalized soybean oil (ESBO), reacted on to Scots pine veneers coated with two different acrylic top coats. Two different pretreatment procedures were used, varying in reaction time and temperature. Results from FTIR and SEC analysis indicate that a large amount of reactant was present on the veneers after treatment with either of the two reaction procedures. Furthermore, coating of the pretreated surfaces was possible and the pretreatment does not seem to affect the adhesion between the coating and the wood substrate. Both accelerated ageing and natural exposure was used to study the resistance to photodegradation, and the results were analysed using colour measurements, FTIR and SEM. These analyses all show that 1400 h of accelerated ageing degrades neither the wood nor the coating to any larger extent. However, after 4000 h of UV exposure some signs of degradation are visible but to a lesser extent for pretreated samples. For the samples exposed to natural weathering during 14 months the performance was good in terms of photostabilisation, however all samples suffer from mould to different extents. Pretreated samples show smaller and more evenly distributed areas of mould compared to the references, which show slightly more mould. The combined coating/pretreatment system is thus assumed to have an effect in terms of photostabilization of the coated wood.

  • 73.
    Olsson, Sara
    et al.
    SP Technical Research Institute of Sweden, Wood Technology, Sweden.
    Matsunaga, H.
    Kataoka, Y.
    Johansson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Matsumura, J.
    Westin, Mats
    Östmark, Emma
    SP Technical Research Institute of Sweden.
    A SEM study on the use of epoxy functional vegetable oil and reactive UV-absorber as UV-protecting pretreatment for wood2015In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 113, no SI, p. 40-45Article in journal (Refereed)
    Abstract [en]

    The present study investigates the ageing performance of a UV protective system for wood, comprising the reactive UV absorber 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone (HEPBP) and epoxy functional vegetable oils (linseed and soybean oil). Scots pine samples of radial or cross-sectional surfaces were treated using a combination of the two components, or using only one of the oils. The treated samples were then aged in a Weather-Ometer for 2 x 60 h and analysed using VPSEM to follow the degradation of the wood substrate in the exact same spot before, during and after ageing. The results of the radial surfaces show slightly less degradation of samples treated with a combination of HEPBP and oil, and for the cross-sectional surfaces an even stronger protective effect is visible. For samples treated with only one of the two oils, no improvement was detectable. The radial surfaces were also analysed using FTIR where the results indicate presence of the protective treatment even after 120 h of exposure. Overall the combined pretreatment of HEPBP and epoxy functional linseed oil was concluded to have a photo-stabilising effect of the wood substrate.

  • 74.
    Pourmand, Payam
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Lisa
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Pourrahimi, Amir Masoud
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Reitberger, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Effect of gamma radiation on carbon-black-filled EPDM seals in water and air2017In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 146, p. 184-191Article in journal (Refereed)
    Abstract [en]

    The effects of gamma radiation in air and water on a highly filled carbon-black-containing EPDM seal, used in transportation valves for old-fuel rods, were investigated. Samples were irradiated at a dose rate of 7 kGy h(-1) until total doses of 0.35, 1.4, 2.1 and 3.5 MGy were reached. The doses were chosen to correspond to 1, 4, 6 and 10 years of service. Infrared spectroscopy, mechanical indenter and NMR relaxation time (T-2) measurements indicated an oxidative crosslinking of the seal, which increased monotonically with the dose. The effects were larger in air than in water, and in air, diffusion-limited oxidation was observed. The compression set increased with increasing dose of radiation and was the highest for seals irradiated in air. The water uptake into the rubber, which was always lower than 1 wt.%, increased with the dose, showing the effect of increased polarity by the oxidation of the rubber.

  • 75.
    Pourmand, Payam
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Radiochemical ageing of highly filled EPDM seals as revealed by accelerated ageing and ageing in-service for 21 years2017In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 144, p. 473-484Article in journal (Refereed)
    Abstract [en]

    Highly filled EPDM rubber used in cable transit seals in nuclear power plants were exposed to gamma radiation at a high dose rate at 23 degrees C in media with different oxygen partial pressures (1-21.2 kPa). The motivation of this study was threefold: highly filled polymers are replacing halogen-containing polymers and these materials have rendered less attention in the literature; there is a need to find efficient tools to make possible condition monitoring and extrapolation. Several profiling methods were used: IR microscopy, micro-indentation, micro-sample extraction/gravimetry and non-invasive NMR spectroscopy, and three different deterioration processes were identified: polymer oxidation, migration of low molar mass species, and anaerobic changes in the polymer network. IR microscopy, micro-indentation profiling and the portable NMR method confirmed diffusion-limited oxidation in samples irradiated in air. The inner non-oxidized part of the blocks showed a pronounced change in the indenter modulus by migration of primarily glyceryl tristearate migration was accelerated by the presence of oxygen in the surface layer and anaerobic changes in the polymer network. For extrapolation or for condition monitoring, it is best to use the data obtained by indenter modulus profiling and to use the correlation between indenter modulus and strain-at-break to quantify the sample status. Non-invasive NMR profiling provided useful data but was less precise than the indenter modulus data to predict the strain-at-break.

  • 76.
    Regnell Andersson, Sofia
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Long-term properties and migration of low molecular mass compounds from modified PLLA materials during accelerated ageing2012In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 6, p. 914-920Article in journal (Refereed)
    Abstract [en]

    The durability of polylactide during accelerated ageing and the entire degradation process were significantly altered by different low molecular mass additives and stereocomplexation. The samples were aged in air at 60°C and 90°C and the degradation process was followed by monitoring mass loss, molar mass, presence and formation of low molecular mass compounds, changes in surface structure and thermal properties. Stereocomplexation increased the long-term durability of polylactide materials. Mass loss and molar mass changes also indicated that addition of TiO 2 nanoparticles had a stabilizing effect at higher temperature and during longer exposure times. Interestingly addition of linear lactic acid oligomers resulted in lower mass loss compared to materials containing cyclic lactide oligomers. This is interpreted as a result of stronger interactions between the linear oligomers and PLLA chains, resulting in slower migration rate, which was also shown by ESI-MS analysis. However, the linear oligomer additives accelerated the molar mass decrease, probably due to the catalytic effect of the end groups. The stereocomplex displayed the greatest resistance towards degradation, a consequence of strong secondary interactions.

  • 77. Renstad, Rasmus
    et al.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    Influence of processing parameters on the molecular weight and mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)1997In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 57, no 3, p. 331-338Article in journal (Refereed)
  • 78. Renstad, Rasmus
    et al.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    The influence of processing induced differences in molecular structure on the biological and non-biological degradation of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate), P(3-HB-co-3-HV)1999In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 63, no 2, p. 201-211Article in journal (Refereed)
  • 79. Roy, P. K.
    et al.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nanoclay effects on the degradation process and product patterns of polylactide2012In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 8, p. 1254-1260Article in journal (Refereed)
    Abstract [en]

    The addition of montmorillonite (MMT) nanoclays shifted the degradation product patterns of polylactide towards shorter lactic acid oligomers as compared to the product patterns of plain polylactide and halloysite modified polylactide hydrolysed under same conditions. The addition of the two MMT sheet type nanoclays led to substantial improvement in the barrier properties of polylactide, which was attributed to the inherent restriction offered by the inorganic filler towards the movement of gases through the film. This could be connected to the observed change in the degradation product patterns as the formed degradation products, especially the longer oligomers, could be partially trapped inside the films leading to catalytic effect, higher mass loss at later stages of hydrolysis as well as release of shorter lactic acid oligomers into the ageing water. The nanocomposites generally exhibited higher contact angles indicating increased hydrophobicity. However, hyperbranched polyesters additives were found to be preferentially present at the surface of the films which led to increased surface hydrophilicity for these materials. The hydrolytic degradation was performed at 60 °C for up to 12 weeks and the process was monitored by mass loss measurements, molar mass changes and calorimetric studies. The water-soluble degradation products were examined by electrospray ionization-mass spectrometry (ESI-MS).

  • 80. Sandelin, M. J.
    et al.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Long-term performance of cables based on chlorosulphonated polyethylene2004In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 86, no 2, p. 331-338Article in journal (Refereed)
    Abstract [en]

    Cables based on chlorosulphonated polyethylene were aged at different temperatures between 120 and 200 degreesC and their conditions were assessed by mechanical methods: micro-indenter and tensile testing. Some of the cables were not aged prior to the oven ageing whereas other cables had been exposed to almost 25 years of service at controlled temperatures (30-54 degreesC) and atmospheres (nitrogen and air). An indenter modulus twice that of the initial value was used as a lifetime criterion; the criterion is based on earlier reported data on similar cables from LOCA tests simulating nuclear power plant failure. The remaining lifetime of the cables exposed to almost 25 years of service was determined by a second-stage ageing at 155 and 170 degreesC and a comparison with lifetime data obtained for unexposed cable samples. The lifetime data, covering a very broad range of temperatures (40-200 degreesC), obeyed the Arrhenius law with the following values for the activation energy depending on the surrounding atmosphere: I I I +/- 5 (nitrogen) and 96 +/- 5 U mol(-1) (air). Air was found to be a more degrading environment than nitrogen at all the temperatures studied.

  • 81.
    Vilaplana, Francisco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ribes-Greus, Amparo
    Instituto de Tecnología de Materiales (ITM), Universidad Politécnica de Valencia.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Chromatographic pattern in recycled high-impact polystyrene (HIPS): Occurrence of low molecular weight compounds during the life cycle2010In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, no 2, p. 172-186Article in journal (Refereed)
    Abstract [en]

    The analysis of the chromatographic pattern of virgin, reprocessed, thermo-oxidised, and recycled high-impact polystyrene (HIPS) proves to be a suitable and sensitive tool to assess the degree of degradation of HIPS during its first life and subsequent recycling. Different low molecular weight compounds, such as residues of polymerisation, degradation products, and additives have been identified and relatively quantified in HIPS, using microwave-assisted extraction and further analysis by gas chromatography-mass spectrometry (GC-MS). The release of residues of polymerisation has been proven to occur during reprocessing, thermo-oxidation, and in recycled samples, which may show the emissions of volatile and semi-volatile organic compounds during the life cycle of HIPS. A wide range of oxidised degradation products are formed during reprocessing and thermo-oxidation; these products can be identified as oxidised fragments of polystyrene (PS), oxidised fragments from polybutadiene (PB) phase, and oxidised fragments from the grafting points between the PS and PB phase. Real recycled HIPS samples may also contain contaminations and fragments from additives included in their original formulations; the presence of brominated fragments from flame retardants in electronic waste is here observed.

  • 82.
    Vilaplana, Francisco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ribes-Greus, Amparo
    Instituto de Tecnología de Materiales (ITM), Universidad Politécnica de Valencia.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Degradation of recycled high-impact polystyrene. Simulation by reprocessing and thermo-oxidation2006In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 91, no 9, p. 2163-2170Article in journal (Refereed)
    Abstract [en]

     A simulation of the degradation of high-impact polystyrene (HIPS), occurring during service life and mechanical recycling, was performed by multiple processing and thermo-oxidative ageing. All samples were characterized by differential scanning calorimetry (DSC), melt mass-flow rate (MFR) measurements, tensile testing and infrared spectroscopy (FTIR). Multiple processing and thermo-oxidative ageing clearly alter the oxidative stability and the elongation at break of the materials. These changes observed at a macroscopic scale have been related to chemical alterations in the structure of HIPS. The polybutadiene phase was demonstrated to be the initiation point of the degradative processes induced by processing, service life and mechanical recycling. Thermo-oxidative degradation affects more severely the degree of degradation of the material, so it may be deduced that the changes occurring during service life of HIPS are the part of the life cycle that mostly affects its further recycling possibilities and performance in second-market applications.

  • 83.
    Vilaplana, Francisco
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Strömberg, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Environmental and resource aspects of sustainable biocomposites2010In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, no 11, p. 2147-2161Article in journal (Refereed)
    Abstract [en]

    This review critically discusses the environmental and resource implications for the design of sustainable biocomposites. Sustainable biocomposites should satisfy several requirements: (i) renewable and/or recycled resources should be utilized for their manufacture; (ii) the synthetic, modification, and processing operations should be benign and energy effective; (iii) no hazardous environmental or toxicological effects should arise during any stage of their life cycle; and (iv) their waste management options should be implemented. The future integration of biorefineries and green chemistry will guarantee the availability of a wide range of raw materials for their preparation. The emission of volatile organic compounds and the release of nanoparticles should be evaluated from a toxicological and environmental point of view. Finally, the susceptibility of sustainable biocomposites towards degradation, including abiotic effects (water absorption, thermo- and photo-oxidation) and biofilm formation and biodegradation, must be considered, to guarantee their structural and functional stability during service life, and to ensure their biodegradability and assimilation during composting.

  • 84.
    Wallström, Stina
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Dowling, K.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Development and comparison of test methods for evaluating formation of biofilms on silicones2002In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 78, no 2, p. 257-262Article in journal (Refereed)
    Abstract [en]

    Silicone rubber formulations used for outdoor high voltage insulation are sometimes reported to be colonized by microorganisms. Different formulations show different sensitivity towards biological growth. In this study five rubbers were tested. Two standard practices were used, ASTM G21-90 and IEC 68-2-10. In addition a new method was developed to measure the rate of colonisation of a sample by biological growth. Results showed that the tested rubbers supported fungal growth when an external carbon source was available. Thus none of the silicones can be called bio-resistant. However the materials are not biodegradable either. This was clearly shown when mould spores were added to the samples in clean water, when none of the rubbers was contaminated. Some of the materials did, however, support growth when only nutrient salts, no carbon source, was added. The most bioresistant formulations contained the flame retardant zinc borate, indicating that this additive suppresses fungal growth. Further investigation with the new method supported that theory.

  • 85.
    Wallström, Stina
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    karlsson, Sigbritt
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Biofilms on silicone rubber insulators; microbial composition and diagnostics of removal by use of ESEM/EDS - Composition of biofilms infecting silicone rubber insulators2004In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 85, no 2, p. 841-846Article in journal (Refereed)
    Abstract [en]

    Silicone rubber high voltage insulators are sometimes reported to be colonised by microorganisms. When the hydrophobic polymeric surface is covered by a hydrophilic biofilm, the isolating properties of the insulator are reduced. However, cleaning the surface can restore the function of the insulator. In this study biofilms colonising insulators from Tanzania, Sri Lanka and Sweden were investigated. Results showed that the examined biofilms shared several properties. Small unicellular green algae associated with bacteria and filamentous fungi dominated all samples. Environmental scanning electron microscopy (ESEM) with X-ray energy disperse spectroscopy (EDS) is proposed as a new method to determine if an infected surface can be cleaned.

  • 86.
    Wallström, Stina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Image analysis and laser induced fluorescence combined to determine biological growth on silicone rubber insulators2005In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 88, no 3, p. 394-400Article in journal (Refereed)
    Abstract [en]

    High-voltage outdoor insulators made from silicone rubber are sometimes reported to be colonised by microorganisms. When the hydrophobic polymeric surface is covered by a hydrophilic biofilm, the electrical properties of the insulator are altered. In this work, mixed biofilms, similar to those formed on the surfaces of polymeric insulators in the field, were successfully grown on five types of silicone rubber substrates in the laboratory, using specially designed microenvironment chambers. Photography and digital image analysis were utilized to estimate the areas covered by the growth. It was found that direct UV-light exposure hindered growth of the biofilms. Further, growth was also hindered on samples where zinc borate had been added as flame retardant. In contrast, addition of ATH did not influence the growth. In parallel, LIF spectroscopy was explored as a tool for detection of biofilms on silicon rubber samples. Experiments revealed that even weak traces of growth, not visible to the naked eye, could be detected. Finally, it is believed that LIF spectroscopy in combination with image analysis can be used for field diagnostics of biological growth on insulators in service.

  • 87.
    Wei, Xinfeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Akhlaghi, Shahin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Kallio, K. J.
    Bruder, S.
    Bellander, M.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Long-term performance of polyamide-based multilayer (bio)diesel fuel lines aged under “in-vehicle” conditions2017In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 144, p. 100-109Article in journal (Refereed)
    Abstract [en]

    The behaviour of a polyamide (PA)-based multilayer fuel pipe was investigated in “close to real” conditions using specially-designed ageing equipment with a program designed according to known customer driving modes and conditions (a key life test). The pipe was exposed to petroleum diesel and a combination of petroleum diesel and biodiesel. The fuel exposure pattern, as well as the temperature profile, followed a specified scheme in the key life test. It allowed for the investigation and understanding of complex ageing mechanisms, often observed in multi-layer systems with a variation in the running conditions. The mechanisms involved included migration of plasticizer from the innermost PA6 layer of the pipe to the fuel, and from the PA12 outer layer to the ambient air. At the same time, fuel was absorbed in the inner layer of the pipe. The oxidation of the innermost PA6 layer was promoted by the oxidation products of biodiesel. The diffusion-limited oxidation of the PA6 layer led to the formation of a 30 μm highly oxidized zone at the inner surface of the pipe, resulting in discoloration and oxidative crosslinking of the polymer. The toughness and extensibility of the pipe decreased significantly after prolonged ageing, and the extensibility was only 7% of that of the unaged pipe after 2230 h.

  • 88.
    Wei, Xin-Feng
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Kallio, K. J.
    Bruder, S.
    Bellander, M.
    Gedde, Ulf W
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Long-term performance of a polyamide-12-based fuel line with a thin poly(ethylene-co-tetrafluoroethylene) (ETFE) inner layer exposed to bio- and petroleum diesel2018In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 156, p. 170-179Article in journal (Refereed)
    Abstract [en]

    The long-term performance of a polyamide-12 (PA12)-based (bio)diesel fuel line/pipe with a thin poly(ethylene-co-tetrafluoroethylene) (ETFE) inner layer was investigated in “close to real” and high-temperature isothermal conditions with fuel on the inside and air on the outside of the pipe. The inner carbon-black-containing ETFE layer resisted fuel attack, as revealed by the small fuel uptake, the very low degree of oxidation, and the unchanged electrical conductivity, glass transition and melting behaviour. The properties of the ETFE layer remained the same after exposure to all the fuel types tested (petroleum diesel, biodiesel and a blend of 80% diesel with 20% biodiesel). Because of the presence of the ETFE layer on the inside, the fuel pipe experienced noticeable changes only in the outer PA12 pipe layer through migration of plasticizer, annealing and slight oxidation. The evaporation of plasticizer was found to be diffusion-controlled and it led to an increase in the glass transition temperature of PA12 by 20 °C. This, together with a small annealing-induced increase in crystallinity, resulted in a stiffer and stronger pipe with an increase in the flexural/tensile modulus and strength. The oxidation of PA12 remained at a low level and did not lead to an embrittled pipe during the simulated lifetime of the vehicle. This study reveals that fluoropolymers have a great potential for use as fuel-contacting materials in “demanding” motor vehicle fuel line systems. 

  • 89.
    Wei, Xin-Feng
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Kallio, Kai
    Bruder, Stefan
    Bellander, Martin
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Plasticizer loss in a complex system (polyamide 12): Kinetics, prediction and its effects on mechanical properties2019In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321Article in journal (Refereed)
  • 90.
    Wei, Xin-Feng
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Kallio, Kai J.
    Volvo Car Corp, Polymer Ctr, SE-40531 Gothenburg, Sweden..
    Bruder, Stefan
    Scania CV AB, Mat Technol, SE-15187 Sodertalje, Sweden..
    Bellander, Martin
    Scania CV AB, Mat Technol, SE-15187 Sodertalje, Sweden..
    Kausch, Hans-Henning
    Swiss Fed Inst Technol Lausanne EPFL, CH-1015 Lausanne, Switzerland..
    Gedde, Ulf W
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Diffusion-limited oxidation of polyamide: Three stages of fracture behavior2018In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 154, p. 73-83Article in journal (Refereed)
    Abstract [en]

    Polyamides (PAs) frequently experience diffusion-limited oxidation (DLO) under elevated temperatures due to their combination of relatively high oxygen barrier properties and high susceptibility to, and rate of, oxidation; under DLO conditions, oxidation is uneven and limited to a thin surface layer. In this study, the reduced extensibility/embrittlement of unstabilized PA6 under DLO conditions was understood by revealing DLO-induced fracture behavior. The DLO was induced by thermally ageing PA6 samples at 180 degrees C; the built-up of the thin oxidized layer by ageing was revealed by infrared microscopy. Notably, the formation of the thin oxidized layer significantly reduced the strain-at-break. Depending on whether the oxidized layer was brittle, two types of surface behavior (voiding and cracking) occurred during the tensile tests, which in turn lead to three types (stages) of tensile fracture behavior. In particular, in the early stage (Stage I) of ageing, the fracture was caused by a long crack formed by the coalescence of adjacent surface voids, leading to a decrease in the strain-at-break from 300% to 30%. In Stage II, multiple surface cracks, which initiated in the oxidized layer, was arrested by the interface between the oxidized and unoxidized material, leading to an almost constant strain-at-break (at or close to the necking strain). Maximum brittleness occurred in Stage III, where a more extensive oxidation of the oxidized layer initiated cracks with high propagation rate, causing the interface to be unable to arrest the cracks. 

  • 91.
    Westberg, Åsa
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Momcilovic, Dane
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Björk, Folke
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Investigation of the emissions from an acrylate and a carpet adhesive in humid and alkaline environments by the micro-scale headspace vial (MHV) method2010In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 95, no 9, p. 1877-1882Article in journal (Refereed)
    Abstract [en]

    In this study, emissions from a carpet adhesive and an acrylate dispersion in simulated humid and alkaline environments were investigated by the micro-scale head space vial (MHV) method. Relative humidity (RH) levels of 75%, 86% and 93% were tested in combination with pH values in the range 10-13. The polymeric materials were exposed at these conditions in sealed 20 mL headspace vials. Chemical analysis of the volatile emission products was performed by headspace solid-phase micro-extraction with subsequent gas chromatography mass spectrometry after three and 36 days. The effect of the RH and pH on the emissions was investigated. It was found that 2-ethyl-1-hexanol was one of the major volatile constituents, and that the emissions of this compound increased dramatically for pH > 12. This can be explained by alkali catalyzed hydrolysis of ester-linked 2-ethylhexyl groups. The other compounds that were detected after exposure of the adhesive were not as strongly dependant on pH and RH as 2-ethyl-1-hexanol. (C) 2010 Elsevier Ltd. All rights reserved.

  • 92.
    Westberg, Åsa
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Momcilovic, Dane
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Björk, Folke
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Quality assessment of building products by the micro-scale headspace vial (MHV) method and HS-SPME for monitoring the emission of hydrolysis products from phthalates2009In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 94, no 6, p. 914-920Article in journal (Refereed)
    Abstract [en]

    2-Ethyl hexanol from hydrolysed di-octyl-phthalate (DOP) may cause a secondary emission from building products such as PVC carpets and/or glues causing indoor air pollution. In the present study, a micro-scale headspace vial (MHV) method, earlier developed by us, was refined to study the degradation of DOP and di-isononyl phthalate (DINP) in humid and alkaline environments. By HS-SPME it was possible to extract the degradation products at low temperature, 35 degrees C, which limits the risks of unwanted degradation during sampling. Three different types of HS-SPME fibres were evaluated. The carbowax-divinyl benzene (CW/DVB) fibre had the highest extraction capacity of 2-ethyl-1-hexanol and 5-nonanol. Although significantly shorter extraction times could be used with the 7 mu m and 30 mu m poly-dimethylsiloxane (PDMS) fibres, the CW/DVB fibre was found to be the most suitable for these alcohols. Furthermore, it was found that pH of the alkaline environment strongly influences the formation of degradation products from DOP and DINP.

  • 93. Westphal, C.
    et al.
    Perrot, C.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Py-GC/MS as a means to predict degree of degradation by giving microstructural changes modelled on LDPE and PLA2001In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 73, no 2, p. 281-287Article in journal (Refereed)
    Abstract [en]

    The degree of changes in the patterns and ratio of peaks (oligomers) in pyrograms from pyrolysed polymers exposed to hydrolysis (chemical and/or biological) and oxidation are related the extent of degradation and could be used to predict life-time. PLA and LDPE with enhanced degradability (LDPE with LLDPE, corn starch and pro-oxidant [SBS + manganese stearate (MB)] were used as models for hydrolysable and oxidisable polymers and pyrolysis gas chromatography mass spectrometry (Py-GC/MS) analysed for its versatility show differences in microstructure of polymers. In parallel size exclusion chromatography (SEC), gas chromatography mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FTIR) gave other signs of degradation. Pyrolysed LDPE samples gave fragments constituting a triplet from C-6, to C-30, With a peak maxima at C-10, C-14 and C-18 expect for LDPE with pro-oxidant and starch exposed to thermo-oxidation. This sample instead had a high amount of C-9 fragment which is related to hydrogen abstraction occuring along the chain. FTIR showed that this samples had formed higher amounts of carbonyl compounds at the surface. Thermogravimetry analysis (TGA) gave changes in the constituents of the LDPE with starch, pro-oxidant and starch. By fractionated Py-GC-MS at 400 and 500 degreesC, acetaldehyde, acrylic acid, lactoyl acrylic acid, two lactide isomers and cyclic oligomers up to pentamer were identified in poly(lactide) (PLA). The ratio of meso-lactide to D, L-lactide was lower in the biotically hydrolysed PLA, while the PLA matrices changes of unaged and chemically hydrolysed samples gave quite similar pyrograms. Thus, the most severly thermo-oxidised LDPE-sample had in a large peak at the C-9 fragment opposite to the other LDPE-samples while the most severly hydrolysed PLA (biotically hydrolysed) had a ratio of meso-lactide to D,L-lactide quite different from unaged and chemically hydrolysed sample.

  • 94.
    Yu, Wenbin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Azhdar, Bruska
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Andersson, D.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Reitberger, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry (closed 20110630).
    Hassinen, J.
    Exova AB, Studsvik, Tystberga, Sweden.
    Hjertberg, T.
    Borealis AB, Stenungsund, Sweden.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Deterioration of polyethylene pipes exposed to water containing chlorine dioxide2011In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 96, no 5, p. 790-797Article in journal (Refereed)
    Abstract [en]

    Chlorine species used as disinfectants in tap water have a deteriorating effect on many materials including polyethylene. There are only very few scientific reports on the effect on polyethylene pipes of water containing chlorine dioxide. Medium-density polyethylene pipes stabilized with hindered phenol and phosphite antioxidants were pressure tested with water containing 4 ppm chlorine dioxide at 90 degrees C and pH = 6.8 as internal medium. The stabilizers were rapidly consumed towards the inner pipe wall; the rate of consumption was four times greater than in chlorinated water (4 ppm, pH = 6.8) at the same temperature. The depletion of stabilizer occurred far into the pipe wall. A supplementary study on a polymer analogue (squalane) containing the same stabilizer package showed that the consumption of the phenolic antioxidant was 2.5 times faster when exposed water containing chlorine dioxide than on exposure to chlorinated water. The subsequent polymer degradation was an immediate surface reaction. It was confirmed by differential scanning calorimetry, infrared spectroscopy and size exclusion chromatography that in the surface layer which came into contact with the oxidising medium, the amorphous component of the polymer was heavily oxidized leaving a highly crystalline powder with many carboxylic acid chain ends in extended and once-folded chains. Scanning electron microscopy showed that propagation of cracks through the pipe wall was assisted by polymer degradation.

  • 95.
    Yu, Wenbin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Characterization of degradation products from a phenolic antioxidant in squalane exposed to chlorinated aqueous mediaIn: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321Article in journal (Other academic)
  • 96.
    Yu, Wenbin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Reitberger, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE).
    Hjertberg, T.
    Oderkerk, J.
    Costa, F. R.
    Englund, V.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Chlorine dioxide resistance of different phenolic antioxidants in polyethylene2015In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 111, p. 1-6Article in journal (Refereed)
    Abstract [en]

    A series of polyethylene tape samples containing 8 different phenolic antioxidants (concentration = 0.1 +/- 0.01 wt.%) were exposed to water containing 10 ppm chlorine dioxide buffered to pH = 6.8 at 70 degrees C for different periods of time. The degradation rate and depletion time of the antioxidants in the polyethylene were obtained by oxidation induction time measurements using DSC. The majority of the tape samples (6 out of 8) showed a simple behaviour: the rate of antioxidant loss decreased and the antioxidant depletion time increased in linear fashion with increasing initial molar concentration of phenolic groups in the polymer. The tape that contained Hostanox O3 had a high initial phenolic concentration but it exhibited a short antioxidant depletion time due to the limited solubility of this antioxidant in polyethylene. Tapes containing Irganox 1330 and Cyanox 1790 showed antioxidant depletion times that were almost twice that of the other antioxidants with the same initial molar concentration of phenolic groups.

  • 97.
    Yu, Wenbin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Reitberger, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hjertberg, T.
    Oderkerk, J.
    Costa, F. R.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Antioxidant consumption in squalane and polyethylene exposed to chlorinated aqueous media2012In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 97, no 11, p. 2370-2377Article in journal (Refereed)
    Abstract [en]

    Squalane stabilized with 0.2 wt.% of Irganox 1010 and a medium-density polyethylene containing 0.1 wt.% of the same antioxidant were exposed to two different aqueous media (water solutions containing either 10 ppm Cl-2 or 10 ppm ClO2, both buffered to pH = 6.8) at different temperatures between 30 and 70 degrees C. The squalane phase was characterized by differential scanning calorimetry (oxidation induction time, OIT) and infrared spectroscopy, and the aqueous media were analysed after concentrating the analytes using liquid-liquid extraction by liquid chromatography, mass spectrometry and infrared spectroscopy. OIT measurements were carried out on the polyethylene samples after exposure to the chlorinated aqueous media. Exposure of the squalane systems to water containing ClO2 resulted in discolouration by the formation of quinoid structures and a faster depletion of the antioxidant than exposure to water containing Cl-2. The activation energy for the loss of antioxidant activity on exposure to ClO2-water was very low (<10 kJ mol(-1)) in the squalane test (no diffusion control) and 21 +/- 2 kJ mol(-1) at a depth of 1-2 mm from the surface of polyethylene plaques (diffusion control). Calculation from earlier published OIT data from a HDPE exposed to Cl-2-water yielded an activation energy for the loss antioxidant activity of 68 kJ mol(-1). The antioxidant degradation products obtained from the exposure to the ClO2 aqueous medium were found at a higher concentration, were more polar and exhibited a higher proportion of low molar mass species than those obtained after exposure to the Cl-2 aqueous medium. The important chemical difference between ClO2 and Cl-2 is that the former is a one-electron oxidant whereas the latter preferentially reacts by hydrogen substitution. Possible further reactions, in agreement with the observations made, are proposed.

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