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Jean-luc Gardette - One of the best experts on this subject based on the ideXlab platform.
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Photooxidative behaviour of polyethylene/polyamide-6 blends
Polymer Degradation and Stability, 2010Co-Authors: S. Therias, Jean-luc Gardette, N. Tzankova Dintcheva, F. La MantiaAbstract:The photochemical behaviour of several polyethylene/polyamide-6 blends was studied under conditions of artificial accelerated weathering. Particular attention was paid to five different compositions ranging from pure polyethylene to pure polyamide with blends of PE/PA-6 of various compositions: 75/25, 50/50 and 25/75 wt/wt%. Analysis by infrared spectroscopy of the chemical modifications caused by Photooxidation showed that exposing the polyethylene/polyamide-6 blends to UV-light irradiation led to the formation of oxidation photoproducts in both polymer phases. In agreement with both the mechanical and spectroscopic analyses, the Photooxidation rate of the blends was observed to be much higher than that of the homopolymers. The results given in this paper suggest that Photooxidation of the PE/PA blends starts in the polyamide phase and that the subsequent Photooxidation of the polyethylene phase may be initiated by the radicals coming from the oxidation of PA.
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Photochemical behaviour of fire-retarded polymers
Polymer Degradation and Stability, 2010Co-Authors: D. Chantegraille, Sandrine Morlat-therias, Jean-luc GardetteAbstract:The influence of a non-halogenated intumescent fire retardant on the Photooxidation of polypropylene is reported. The Photooxidation of polypropylene stabilised with a phenolic antioxidant and two redox antioxidants (HALS), without and with the flame retardant has been studied. The chemical modifications resulting from UV-light exposure with wavelengths above 300 nm in the presence of oxygen were followed by IR and UV-visible spectroscopies. Special attention was given to the influence of each component on the rate of oxidation of the polymeric matrix. The Photooxidation of the fire-retarded polymer can be described by two independent phenomena: the Photooxidation of the intumescent agent and the Photooxidation of the polymer. The results obtained offer new insight in the formulation of stabilised fire-retarded PP for outdoors applications.
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Polymer/carbon nanotube nanocomposites: Influence of carbon nanotubes on EVA photodegradation
Polymer Degradation and Stability, 2007Co-Authors: Sandrine Morlat-therias, Sophie Peeterbroeck, Elisabeth Fanton, Jean-luc Gardette, Michael Alexandre, Philippe DuboisAbstract:The influence of carbon nanotubes on the photodegradation of EVA/carbon nanotube nanocomposites was studied by irradiation under photooxidative conditions (at λ > 300 nm, at 60 °C and in the presence of oxygen). The influence of the nanotubes on both the Photooxidation mechanism of EVA and the rates of oxidation of the matrix was characterized on the basis of infrared analysis. On one hand, it was shown that the carbon nanotubes act as inner filters and antioxidants, which contribute to reduction in the rate of Photooxidation of the polymeric matrix. On the other hand, it was shown that light absorption could provoke an increase in the local temperature and then induce the Photooxidation of the polymer. The competition between these three effects determines the global rate of Photooxidation of the polymeric matrix. Several factors are involved, the concentration of the carbon nanotubes, the morphology of the nanotubes and the functionalization of the nanotube surface.
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phototransformation of water soluble polymers i photo and thermooxidation of poly ethylene oxide in solid state
Polymer, 2001Co-Authors: Sandrine Morlat, Jean-luc GardetteAbstract:Abstract The Photooxidation of two poly(ethylene oxide) samples (PEOlw M=105 and PEOhw M=4×106) has been studied under irradiation at long wavelengths (λ≥300 nm, 35°C) and in the presence of oxygen. Thermooxidation experiments, at 50°C, of PEO samples are also reported and compared to Photooxidation results. Differences in the ratio ester/formates are observed. Thermooxidation produces equal amounts of esters and formates whereas Photooxidation generates formates in a ratio of 5/1 against chain esters. The oxidation kinetic curves were plotted for films of thickness less than 40 μm to avoid heterogeneous degradation. In order to identify the oxidation products, photo- and thermooxidised films have been submitted to chemical treatments. A mechanism accounting for the main routes of oxidation is proposed. The differences between thermooxidation and Photooxidation are explained on the basis of different evolutions of the macroperoxyradicals POO . The formation of hydroperoxides is favoured in thermooxidation whereas recombination of the peroxyradicals is more likely to occur in Photooxidation.
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Long-term behavior of oil-based varnishes and paints. Photo- and thermooxidation of cured linseed oil
Journal of the American Oil Chemists' Society, 2000Co-Authors: J. Mallégol, Jean-luc Gardette, Jacques LemaireAbstract:Thermooxidation at 100°C and Photooxidation at wavelengths above 300 nm of dried oil films were evaluated. The chemical modifications of the networks were determined by infrared analysis coupled with gaseous treatments (NO, SF_4, and NH_3). The dried films are rather stable in thermooxidation, whereas in Photooxidation, important degradation of the network occurs with many chain scissions. This photoinstability results from the presence of crosslinks that are sensitive to radical attack because of the lability of the hydrogen atom on the tertiary carbons. The Photooxidation reactions are fully described in this paper. Yellowing of the cured samples, observed with ultraviolet-visible and fluorescence spectrometries, rapidly is decreased by irradiation because the oil contaminants that are mainly responsible for the yellowness are photooxidized. On the contrary, yellowing slowly but continuously increases during thermooxidation at 100°C.
Sandrine Morlat-therias - One of the best experts on this subject based on the ideXlab platform.
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Photochemical behaviour of fire-retarded polymers
Polymer Degradation and Stability, 2010Co-Authors: D. Chantegraille, Sandrine Morlat-therias, Jean-luc GardetteAbstract:The influence of a non-halogenated intumescent fire retardant on the Photooxidation of polypropylene is reported. The Photooxidation of polypropylene stabilised with a phenolic antioxidant and two redox antioxidants (HALS), without and with the flame retardant has been studied. The chemical modifications resulting from UV-light exposure with wavelengths above 300 nm in the presence of oxygen were followed by IR and UV-visible spectroscopies. Special attention was given to the influence of each component on the rate of oxidation of the polymeric matrix. The Photooxidation of the fire-retarded polymer can be described by two independent phenomena: the Photooxidation of the intumescent agent and the Photooxidation of the polymer. The results obtained offer new insight in the formulation of stabilised fire-retarded PP for outdoors applications.
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Polymer/carbon nanotube nanocomposites: Influence of carbon nanotubes on EVA photodegradation
Polymer Degradation and Stability, 2007Co-Authors: Sandrine Morlat-therias, Sophie Peeterbroeck, Elisabeth Fanton, Jean-luc Gardette, Michael Alexandre, Philippe DuboisAbstract:The influence of carbon nanotubes on the photodegradation of EVA/carbon nanotube nanocomposites was studied by irradiation under photooxidative conditions (at λ > 300 nm, at 60 °C and in the presence of oxygen). The influence of the nanotubes on both the Photooxidation mechanism of EVA and the rates of oxidation of the matrix was characterized on the basis of infrared analysis. On one hand, it was shown that the carbon nanotubes act as inner filters and antioxidants, which contribute to reduction in the rate of Photooxidation of the polymeric matrix. On the other hand, it was shown that light absorption could provoke an increase in the local temperature and then induce the Photooxidation of the polymer. The competition between these three effects determines the global rate of Photooxidation of the polymeric matrix. Several factors are involved, the concentration of the carbon nanotubes, the morphology of the nanotubes and the functionalization of the nanotube surface.
Philippe Dubois - One of the best experts on this subject based on the ideXlab platform.
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Polymer/carbon nanotube nanocomposites: Influence of carbon nanotubes on EVA photodegradation
Polymer Degradation and Stability, 2007Co-Authors: Sandrine Morlat-therias, Sophie Peeterbroeck, Elisabeth Fanton, Jean-luc Gardette, Michael Alexandre, Philippe DuboisAbstract:The influence of carbon nanotubes on the photodegradation of EVA/carbon nanotube nanocomposites was studied by irradiation under photooxidative conditions (at λ > 300 nm, at 60 °C and in the presence of oxygen). The influence of the nanotubes on both the Photooxidation mechanism of EVA and the rates of oxidation of the matrix was characterized on the basis of infrared analysis. On one hand, it was shown that the carbon nanotubes act as inner filters and antioxidants, which contribute to reduction in the rate of Photooxidation of the polymeric matrix. On the other hand, it was shown that light absorption could provoke an increase in the local temperature and then induce the Photooxidation of the polymer. The competition between these three effects determines the global rate of Photooxidation of the polymeric matrix. Several factors are involved, the concentration of the carbon nanotubes, the morphology of the nanotubes and the functionalization of the nanotube surface.
Jr John T Yates - One of the best experts on this subject based on the ideXlab platform.
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absence of platinum enhancement of a photoreaction on tio2 co Photooxidation on pt tio2 110
Journal of the American Chemical Society, 1996Co-Authors: Amy Linsebigler, And Camelia Rusu, Jr John T YatesAbstract:The influence of deposited Pt metal clusters on the CO Photooxidation reaction on the TiO2(110) surface was investigated. An enhancement in the CO Photooxidation reaction rate or yield is not observed in the presence of Pt metal clusters on the TiO2(110) surface. These results indicate that kinetic models involving Schottky-barrier electron trapping in metal deposits leading to enhanced electron-hole pair lifetimes are not applicable in the case of CO Photooxidation on Pt/TiO2(110).
John H. Seinfeld - One of the best experts on this subject based on the ideXlab platform.
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the effect of water on gas particle partitioning of secondary organic aerosol ii m xylene and 1 3 5 trimethylbenzene Photooxidation systems
Atmospheric Environment, 2001Co-Authors: David R Cocker, Brian T Mader, Markus Kalberer, Richard C Flagan, John H. SeinfeldAbstract:An investigation of the effect of relative humidity on aerosol formation from m-xylene and 1,3,5-trimethylbenzene Photooxidation is reported. Experiments were performed in the presence and absence of ammonium sulfate seed particles (both aqueous and dry) to ascertain the effect of partitioning of oxidation products into a strong electrolytic solution or onto dry crystalline seed particles. In marked contrast to the α-pinene/ozone system, the final measured secondary organic aerosol yield was unaffected by the presence of gas-phase or liquid-phase water at relative humidities (RH) up to 50%. The hygroscopic nature of the aerosol generated upon Photooxidation of m-xylene and 1,3,5-trimethylbenzene was examined; the hygroscopicity of the aerosol at 85% RH for both parent organics increased with the extent of the reaction, indicating that the first-generation oxidation products undergo further oxidation. Limited identification of the gas- and aerosol-phase products of m-xylene and 1,3,5-trimethylbenzene Photooxidation is reported. It is evident that a more complete molecular identification of aromatic Photooxidation aerosol awaits analytical techniques not yet brought to bear on this problem.
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Aerosol formation in the Photooxidation of isoprene and β-pinene
Atmospheric Environment. Part A. General Topics, 1991Co-Authors: Spyros N. Pandis, John H. Seinfeld, Suzanne E. Paulson, Richard C FlaganAbstract:Isoprene and β-pinene, at concentration levels ranging from a few ppb to a few ppm, were reacted photochemically with NO_x in the Caltech outdoor smog chamber facility. Aerosol formation from the isoprene Photooxidation is found to be negligible even under extreme ambient conditions due to the relatively high vapor pressure of its products. Aerosol carbon yield from the β-pinene Photooxidation is as high as 8% and depends strongly on the initial HC/NO_x ratio. The average vapor pressure of the β-pinene aerosol is estimated to be 37±24 ppt at 31 °C. Monoterpene Photooxidation can be a significant source of secondary aerosol in rural environments and in urban areas with extended natural vegetation.
