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  • 1
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 7 (1982), S. 489-495 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Autooxidation of low density polyethylene has been studied in melt and in 1,2,4-trichlorobenzene solution. The kinetics of oxygen-absorption, concentrations of hydroperoxides, carboxyl, and other oxo groups and average number of scissions have been investigated. It has been found that the main features of the oxidative processes in solution and in melt do not differ significantly. However, the concentration of hydroperoxides as a function of conversion and the dependence of the maximum concentration of hydroperoxides on temperature make exception. There is a very good agreement between average number of chain scissions and carboxyl groups and this is independent of phase, concentration, temperature, and conversion. From one mole consumed oxygen approximately 0.6 ÷ 0.7 mole remains in the polymer backbone in the form of oxygen-containing functional groups. The ratio of average chain scissions to the formed carbonyl groups is 1∶5, i.e., functional groups form both at the chain ends, in consecutive reactions after the scission, and along the polymer chain.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary This work proposes a description of the kinetics of polyethylene autoxidation in melt. The model takes into consideration the effect of neighbouring groups on the hydroperoxide decomposition. Using the proposed model, reliable constants can be calculated for the autoxidation of polyethylene.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This paper accumulates the mechanism and kinetics of oxidation and the inhibition mechanism of oxidation processes using preventive antioxidants, chain-breaking antioxidants and deviations from the simple inhibition mechanism.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 150 (1987), S. 89-111 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Abbau eines handelsüblichen Polyethylens niedriger Dichte wurde unter dynamischen Verhältnissen untersucht, die den Verarbeitungsprozeß simulierten. Sowohl die dynamische Oxidation über 140°C als auch die statische Oxidation bei niedrigem Sauerstoffdruck sind stark diffusionskontrolliert. Während des Prozesses konkurrieren Kettenspaltung und Vernetzung (hauptsächlich C - C Bindungen) miteinander. In der Anfangsphase des Abbaus überwiegen die Hydroperoxidgruppen. Während ihr Anteil aber schnell abnimmt, nimmt der der Oxygruppen zu und wird dominant.Unter 140°C ist der Prozeß ähnlich der statischen Oxidation bei höherem Sauerstoffdruck, die Diffusionskontrolle spielt aber noch immer eine Rolle. Eine geringe änderung des Molekulargewichts ist zu beobachten. Während des Prozesses dominieren die Hydroperoxide. Während des Knetens ist ihr Anteil unter den gebildeten funktionellen Gruppen nahezu konstant. Der Einfluß der mechanischen Beanspruchung ist unbedeutend.Die Steigerung der Knetgeschwindigkeit beschleunigt die Abbauprozesse. Je höher die totale in das LDPE eingebaute Menge des Sauerstoffes ist, desto niedriger ist die restliche Oxidationsstabilität.
    Notes: The degradation of commercial LDPE was studied under dynamic conditions which simulate the processing. Dynamic oxidation above 140°C is similar to static oxidation under low oxygen pressure both having strong diffusion control. Fragmentation and crosslinking (mainly C—C bonds) compete in the process. The hydroperoxides predominate at the beginning of the mixing. Their quantity rapidly decreases while that of oxo groups increases and becomes predominant.Below 140°C, the conditions are resembling to static oxidation performed under higher oxygen pressure but the process is still somewhat diffusion controlled. The change in the molecular mass is not considerable in the process. The hydroperoxides predominate among the functional groups formed. Their ratio is constant during mixing. The effect of mechanical stress is not considerable.An increase in the mixing speed resulted in an increase in the rate of the processes studied above.The higher the total amount of oxygen incorporated in the PE, the smaller is the remaining oxidative stability.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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