ASTM D2238 - 92(2012)e1

    Стандартные методы испытаний для определения поглощения полиэтиленом, обусловленного метиловыми группами1 на 1378 см-1

    Active Standard ASTM D2238 Developed by Subcommittee: D20.70

    Book of Standards Volume: 08.01


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    Significance and Use

    4.1 When interpreted with the aid of appropriate calibration data, either test method can be used to compare the total methyl contents of polyethylenes made by similar processes. Such information can be interpreted in terms of specific alkyl groups with the aid of data on infrared absorption at certain other wavelengths (3).

    Note 4The bias of determination of the concentration of total alkyl groups depends on knowing the concentrations of methyl and ethyl branches present, since these branches have anomalously high absorptivities per group at 1378 cm−1 (7.25 μm).

    4.2 Knowledge of total methyl groups in polyethylene, when combined with data on molecular weight and on reactive end groups such as vinyl, can lead to assignment of end-group structures and can shed light upon polymerization mechanisms.

    4.3 Data on total methyl groups in polyethylene can be correlated qualitatively with certain polymer properties such as melting point, density, stiffness, and other mechanical properties that are closely dependent on the degree of crystallinity of the polymer.

    4.4 These test methods are especially suitable for research. They have not been tested for use in manufacturing control.