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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 3669-3688 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The radiation crosslinking of poly(vinyl chloride), PVC, with trimethylolpropane trimethacrylate, TMPTMA, has been examined. The polyfunctional TMPTMA undergoes rapid polymerization incorporating the PVC into a three-dimensional network. The kinetics and mechanism of these crosslinking reactions were studied with particular reference to dose dependence and thermal treatment. The gel was rapidly formed with a TMPTMA polymerization rate greater than that of the PVC grafting reaction. Only 30-40% of the available bonds were used in the initial polymerization. The remaining 60-70% of the double bonds predominantly react in the final stages of crosslinking (80-100% gelation). The macroscopic properties (e.g., solubility, glass transition temperatures, mechanical characteristics, etc.) of the PVC-TMPTMA blend are discussed in terms of the molecular crosslinking mechanism. The effect of thermal treatment, during and after irradiation, on the reaction rates and mechanism is examined.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 2001-2013 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The compatibility of mixtures of poly(2,3-dichloro-1-propyl acrylate) and poly(glycidyl methacrylate-co-ethyl acrylate) has been investigated by measurement of the following properties: density, light transmission, glass transition temperature, vapor absorption, and NMR relaxation times. To varying degrees, all results provided evidence supporting the contention that these mixtures are compatible.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 9 (1971), S. 829-839 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mobilities of polymer chain segments in mixtures of rubber and carbon black were investigated by nuclear magnetic resonance. Spin-spin relaxation time (T2) measurements on cis-polybutadiene and ethylene-propylene-diene rubber (EPDM) bound rubbers detected at least two relaxing regions: an immobile region and a relatively free region. The molecular motions in the relatively free region are still constrained compared to those of the pure gum.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 18 (1980), S. 2337-2345 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Homogeneous films comprised of mixtures of polystyrene and poly(vinyl methyl ether) can be obtained by evaporation from a ternary solution containing toluene as the solvent. Heterogeneous films result when the solvent is trichloroethylene. The possibility that a heterogeneous film cast from trichloroethylene can be transformed to a homogeneous one by physical means is a logical expectation when the polymer-polymer interaction is favorable, though as yet no comprehensive report has appeared in the literature. We have accomplished the transformation by increasing the temperature. Optical microscopy and glass transition experiments were employed to observe the effects.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2019-07-18
    Description: Aircraft measurements of ozone, its key precursors, and a variety of chemical tracers were made in the troposphere of the western and central Pacific in October 1991. These data are presented and analyzed to examine the occurrence of low ozone concentrations in the remote marine boundary layer of the tropical and equatorial Pacific Ocean. The data from these flights out of Guam, covering an area extending from the equator to 20 N and from south of the Philippines to Hawaii, show average O3 concentrations as low as 8-9 ppb (ppb=10(exp-9)v/v) at altitudes of 0.3-0.5 km in the boundary layer. Individual measurements as low as 2-5 ppb were recorded. Low O3 concentrations do not always persist in space and time. High O3, generally associated with the transport of upper tropospheric air, was also encountered in the boundary layer. In practically all cases, O3 increased to values as large as 25-30 ppb within 2 km above the boundary layer top. Steady state model computations are used to suggest that these low O3 concentrations are a result of net photochemical O3 destruction in a low NO environment, sea-surface deposition, and extremely low net entrainment rates (1-2 mm per second) from the free troposphere. Day/night measurements of ethane, propane, gaseous and aerosol Cl suggest that daytime (morning) Cl atom concentrations in the vicinity of 10(exp 5) molecules per cubic centimeter may be present in the marine boundary layer. This Cl atom abundance can be rationalized only if sea salt aerosols can release free chlorine (Cl2) to the gas phase in the presence of sun light (and possibly O3). These Cl atom concentrations, however, are still insufficient and Cl (or Br) chemistry is not likely to be an important cause of the observed low O3.
    Keywords: Environment Pollution
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  • 6
    Publication Date: 2019-07-13
    Description: A major observation recorded during NASA's western Pacific Exploratory Mission (PEM-West B) was the large shift in tropical NO levels as a function of geographical location. High-altitude NO levels exceeding 100 pptv were observed during portions of tropical flights 5-8, while values almost never exceeded 20 pptv during tropical flights 9 and 10. The geographical regions encompassing these two flight groupings are here labeled "high" and "low" NOx regimes. A comparison of these two regimes, based on back trajectories and chemical tracers, suggests that air parcels in both were strongly influenced by deep convection. The low NO(x) regime appears to have been predominantly impacted by marine convection, whereas the high NO(x) regime shows evidence of having been more influenced by deep convection over a continental land mass. DMSP satellite observations point strongly toward lightning as the major source of NOx in the latter regime. Photochemical ozone formation in the high NOx regime exceeded that for low NO(x) by factors of 2 to 6, whereas O3 destruction in the low NO(x)regime exceeded that for high NOx by factors of up to 3. Taking the tropopause height to be 17 km, estimates of the net photochemical effect on the O3 column revealed that the high NO(x) regime led to a small net production. By contrast, the low NOx regime was shown to destroy O3 at the rate of 3.4 % per day. One proposed mechanism for off-setting this projected large deficit would involve the transport of 03 rich midlatitude air into the tropics. Alternatively, it is suggested that O3 within the tropics may be overall near self-sustaining with respect to photochemical activity. This scenario would require that some tropical regions, unsampled at the time of PEM-B, display significant net column O3 production, leading to an overall balanced budget for the "greater" tropical Pacific basin. Details concerning the chemical nature of such regimes are discussed.
    Keywords: Environment Pollution
    Type: Paper-97JD00011 , Journal of Geophysical Research (ISSN 0148-0227); 102; D23; 28,447-28,468
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  • 7
    Publication Date: 2019-07-13
    Description: The impact of ship emissions on marine boundary layer (MBL) NO(x) and SO2 levels over the Pacific Ocean has been explored by comparing predictions (with and without ships) from a global chemical transport model (GCTM) against compiled airborne observations of MBL NO(x) and SO2. For latitudes above 15 N, which define that part of the Pacific having the heaviest shipping, this analysis revealed significant model over prediction for NOx and a modest under prediction for SO2 when ship emissions were considered. Possible reasons for the difference in NO(x) and SO2 were explored using a full-chemistry box model. These results revealed that for an actual plume setting the NO(x) lifetime could be greatly shortened by chemical processes promoted by ship plume emissions themselves. Similar chemical behavior was not found for SO2.
    Keywords: Environment Pollution
    Type: Paper-2000GL012013 , Geophysical Research Letters (ISSN 0094-8276); 28; 2; 235-238
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