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  • Chemical Engineering  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 13 (1973), S. 429-434 
    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: Differential thermal analysis offers a convenient and rapid way of determining stabilization levels in polyolefin compositions. Since it is normally used at temperatures in the fabrication range, it provides a direct readout of processing stability. At the same time, because the chemistry of the polymer system at these temperatures may be quite different from that at normal use temperatures, judgment must be exercised in attempting to extrapolate high temperature data. New factors can come in at either end of the temperature range which are inoperative at the other extreme.The experimental procedures used are described, and the special precautions necessary for operation down to the 140-150°C range indicated. Problems arising from sample inhomogeneities are discussed, and the critical importance of stabilizer migration in the solid state pointed out, including invalidation of extrapolation down to normal temperatures of data taken above the melting range.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 6 (1966), S. 217-226 
    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: Renewed interest in the development of a quantitative optical technique for assessing the quality of carbon dispersion in weather-resistant polyethylene compositions has given fresh significance to the findings of a study conducted earlier by a task group of ATSM Committee D-20 but not previously reported in the literature. This group evolved and refined a spectrophotometric procedure which was shown to be capable of good interlaboratory reproducibility when the same film was measured by each of the participants in turn. When each laboratory prepared its own film specimen from a standard lot of pellets, however, this reproducibility dropped to a very unsatisfactory level. It was concluded that fine-grained inhomogeneities even in compounds considered to have excellent dispersion quality preclude reproducible test results when sample weights of only a few milligrams are involved. The problem is aggravated by the difficulty of preparing thin, uniform films and complicated by a nonlinear dependence of transmission on film thickness.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 5 (1965), S. 125-129 
    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: Possible applicability of Griffith's theory to stress-cracking in microcrystalline organic polymers is considered. Although the time-dependent nature of the phenomenon and the plastico-elastico-viscous character of the medium make such application debatable, it is found that this approach in combination with the contributions of others notably Rebinder and his associates, can provide rationalization for many of the empirical facts. The observed “case-hardening” action of surfactants on specimens under stress suggests that the mobility of polymer chain segments in surface layers may in fact be restricted under these conditions as theorized, facilitating local concentration of stresses to a level exceeding the strength of the material.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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