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  • Wiley-Blackwell  (4)
  • 2020-2024
  • 1980-1984  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Antioxidant mechanisms of hindered amine light stabilizersHindered amine light stabilizers are frequently referred to simply as HALS.Issued as NRCC # 23446. (1984)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 8 (1984), S. 79-88 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Secondary and tertiary hindered amines of the piperidyl type and many other piperidyl compounds can protect various polymers against oxidations initiated by light, heat and ionizing radiation. These amines stabilize by being converted to a series of products which can scavenge with high stoichiometry the main radicals responsible for the oxidative chain. This high stoichiometry results from the cyclical regeneration of the scavenging piperidyl species. The efficiency of the hindered amines as antioxidants in polyolefins is enhanced by their ability to associate with the unstable oxidized domains in which photo- and thermal oxidations will eventually reinitiate. Secondary amines can also slowly decompose intramolecularly hydrogen bonded hydroperoxide groups of the type found in polypropylene. This process may destroy the unstable oxidation product before the hydroperoxide can re-initiate oxidation and also generates another powerful antioxidant, a hydroxylamine. Despite the cyclical regeneration of active piperidyl radical scavengers, side reactions can produce non-scavenging products or even photo-initiators which will progressively accumulate and strangle the antioxidant activities.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1984.020081984107
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  • 2
    Electronic Resource
    Electronic Resource
    Submicron patterns in substituted polystyrene resists by focused-ion-beam lithography (1983)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 23 (1983), S. 941-946 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Submicron lines in negative working, substituted polystyrene resists by focused-ion-beam lithography were demonstrated. These features were transferred into an underlying molybdenum layer by plasma etching using the resist as an etch mask, with the minimum continuous line having a width of 0.20 μm.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760231705
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  • 3
    Electronic Resource
    Electronic Resource
    Photochemical degradation of blends of polystyrene and poly(2,6 -dimethyl-1,4-phenylene oxide) (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 2737-2746 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Blends of polystyrene and poly(2,6-dimethyl-1,4-phenylene oxide) that cover the entire compositional range have been subjected to the action of singlet oxygen from microwave discharge, dye-sensitized reaction, and photochemical oxidation. With the applied analytical technique, which consisted of infrared (IR) analysis, including ATR technique and a spectroscopic method combined with chemical analysis for hydroperoxide groups, it was not possible to detect any effect of the singlet oxygen treatment. For that reason singlet oxygen does not appear to be important to the initiation of the photooxidation of these blends. In connection with photochemical oxidation the interaction observed between the two components probably involves energy transfer from PS to PPO. This interaction results in the enhancement of reactions in PPO that lead to greater carbonyl group formation and crosslinking. Simultaneously, the probability of chain scission in the PS is lowered with increased PPO content, found by determining the changes in the molecular weights.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170180830
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  • 4
    Electronic Resource
    Electronic Resource
    Energy transfer in connection with the photo-oxidation of polystyrene and its blends with poly(2,6-dimethyl-1,4-phenylene oxide) (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 2765-2771 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By fluorescence spectroscopy it is possible to investigate some of the photophysical processes, particularly the energy transfer, that occur during the photo-oxidative degradation of polystyrene (PS), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), and homogeneous blends of these. In connection with the irradiation, a part of the absorbed energy is transferred from excited phenyl groups in PS to PPO. The decrease in PS excimer fluorescence at 319 nm by admixture of PPO is greater than expected from the absorption of PPO at the excitation wavelength. A radiative energy transfer is suggested from PS to PPO which absorbs at 319 nm. Energy transfer also occurs to groups formed during photo-oxidation. The quenching of PS excimer fluorescence during the process has been studied for both the homopolymer and the blends, and in all cases the reactions occurring during photo-oxidation result in marked quenching at 319 nm.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.170191112
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