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Jutz F.,Imperial College London | Buchard A.,Imperial College London | Kember M.R.,Imperial College London | Fredriksen S.B.,Norner AS | Williams C.K.,Imperial College London
Journal of the American Chemical Society | Year: 2011

The reaction kinetics of the copolymerization of carbon dioxide and cyclohexene oxide to produce poly(cyclohexene carbonate), catalyzed by a dizinc acetate complex, is studied by in situ attenuated total reflectance infrared (ATR-IR) and proton nuclear magnetic resonance ( 1H NMR) spectroscopy. A parameter study, including reactant and catalyst concentration and carbon dioxide pressure, reveals zero reaction order in carbon dioxide concentration, for pressures between 1 and 40 bar and temperatures up to 80 °C, and a first-order dependence on catalyst concentration and concentration of cyclohexene oxide. The activation energies for the formation of poly(cyclohexene carbonate) and the cyclic side product cyclohexene carbonate are calculated, by determining the rate coefficients over a temperature range between 65 and 90 °C and using Arrhenius plots, to be 96.8 ± 1.6 kJ mol -1 (23.1 kcal mol -1) and 137.5 ± 6.4 kJ mol -1 (32.9 kcal mol -1), respectively. Gel permeation chromatography (GPC), 1H NMR spectroscopy, and matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry are employed to study the poly(cyclohexene carbonate) produced, and reveal bimodal molecular weight distributions, with narrow polydispersity indices (≤1.2). In all cases, two molecular weight distributions are observed, the higher value being approximately double the molecular weight of the lower value; this finding is seemingly independent of copolymerization conversion or reaction parameters. The copolymer characterization data and additional experiments in which chain transfer agents are added to copolymerization experiments indicate that rapid chain transfer reactions occur and allow an explanation for the observed bimodal molecular weight distributions. The spectroscopic and kinetic analyses enable a mechanism to be proposed for both the copolymerization reaction and possible side reactions; a dinuclear copolymerization active site is implicated. © 2011 American Chemical Society. Source


Fredriksen S.B.,Norner AS | Jens K.-J.,Telemark Technological R and D Institute | Jens K.-J.,Telemark University College
Energy Procedia | Year: 2013

Alkanolamine based post-combustion capture processes (PCC) are currently the most attractive technologies for CO2 capture. Solvents are degraded in this service by flue gas components, for example oxygen. Solvent degradation can be classified into two reaction types: 1) amine oxidative degradation through a) autoxidation pathways, b) oxidation in the presence of metal ions and 2) thermal degradation including reactions in the presence of CO2. This study represents a literature survey of oxidative degradation (reaction type 1a) of 2-Amino-1-ethanol (MEA), 2-Amino-2-methyl-1- propanol (AMP), N,N-Bis(2-hydroxyethyl)methyl-amine (MDEA), and Piperazine (Pz). Thermal degradation products (reaction type 2) are included where appropriate in order to contribute to a more complete degradation overview of these compounds. Source


Barreto C.,University of Oslo | Barreto C.,Norner AS | Hansen E.,University of Oslo | Fredriksen S.,Norner AS
Polymer Degradation and Stability | Year: 2012

Poly(propylene carbonate), PPC, is produced via a catalytic copolymerization of CO 2 and propylene oxide. The common side product propylene carbonate and catalyst residues are detrimental to the thermal and mechanical properties of the resulting PPC. Thus, efficient purification procedures are needed. PPC produced using zinc glutarate (ZnGA) catalyst was purified by a novel solid-liquid extraction using aqueous maleic acid. The resulting PPC exhibited a dramatically increased thermal stability as the onset of the degradation was increased by 85°C compared to that of a crude PPC reference sample. It is suggested that metal-ion coordination between some in situ produced zinc species and the carbonyl moieties in the PPC backbone may explain this. The stiffness of the PPC increased by 75% when plasticizer side products were removed by the solid-liquid extraction. This novel purification method provides a sustainable alternative because only water and no organic solvent is used, and the method allows for the tailoring of the metal residues from the catalyst in the final polymer. The novel solid-liquid extraction procedure renders the PPC thermally stable at 200°C for ca 60 min, thus expanding the processing window for PPC. © 2012 Elsevier Ltd. All rights reserved. Source


Barreto C.,University of Oslo | Barreto C.,Norner AS | Altskar A.,Swedish Institute for Food and Biotechnology | Fredriksen S.,Norner AS | And 2 more authors.
European Polymer Journal | Year: 2013

The focus of this report concerns the preparation nanocomposites from poly(propylene carbonate) (PPC) and multiwall carbon nanotubes (MWNTs). A solvent route using tetrahydrofuran, ethoxylated non- ionic surfactants combined with sonication was found to be successful in deagglomerating and dispersing the nanotubes. Transmission electron microscopy revealed highly disentangled and dispersed nanotubes and was supported by the qualitative stability evaluations. The morphology and molecular mobility of the prepared nanocomposites (0.5, 3.0 and 5.0 wt% of nanotubes) were characterized by rheology, microscopy, low-field solid-state nuclear magnetic resonance, and electrical conductivity. The networking of nanotubes was highest with a stearyl alcohol ethoxylate surfactant, and was found to improve with the sonication time. Nanotube percolation was established, both rheologically and electrically, from a filler content of approximately 0.5 wt%. A higher tendency toward particle agglomeration was observed at higher MWNT loadings. Only minor changes in the glass transition temperature were measured presumably due to the presence of solvent and surfactant residues. The thermal stability was marginally improved by increasing the loading and dispersion of the nanotubes, and appeared to be modified by solvent and surfactant residues. © 2013 Elsevier Ltd. All rights reserved. Source


Intawiwat N.,Nofima AS | Intawiwat N.,Norwegian University of Life Sciences | Myhre E.,Norner AS | Oysaaed H.,Norner AS | And 2 more authors.
Polymer Engineering and Science | Year: 2012

Packaging material with optimal light barrier properties can prevent food quality deterioration. For dairy products, wavelength in the visible region between 400-450 nm and 600-650 nm should be blocked out due to the content of chlorophyll in dairy products. Six low density polyethylene blown films were formulated with the combination of four different pigments and additives: green, yellow, silver additive, and optical brightener, in addition to four reference samples. All films were transparent. Optical properties and light transmission were measured for each film, and microscopy analyses were used to investigate the surface topography. The sample containing high concentration of both green and yellow pigments had the lowest value in gloss and transmittance. This film blocked the light below 450 nm and transmitted 10% at 600-650 nm. Optical brightener had an effect only on visual appearance but not on light transmission properties. Samples containing silver additive were more intense green and gave a higher light transmission in blue region (380-500 nm) and lower in red region (600-700 nm) compared with samples without silver additive. These developed films can be applied in dairy products and other food products in the future. POLYM. ENG. SCI., 52:2015-2024, 2012. © 2012 Society of Plastics Engineers Copyright © 2012 Society of Plastics Engineers. Source

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