Standard Test Methods for Absorbance of Polyethylene Due to Methyl Groups at 1378 cm⁻¹

Importancia y uso:

4.1 When interpreted with the aid of appropriate calibration data, either test method is acceptable for use to compare the total methyl contents of polyethylenes made by similar processes. Data on infrared absorption at certain other wavelengths is potentially useful for information on certain other wavelengths (7).

Note 4: The 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, is potentially useful so as to lead to assignment of end-group structures and to shed light upon polymerization mechanisms.

4.3 Qualitative correlations are possible between data on total methyl groups in polyethylene 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.

Subcomité:

D20.70

Referida por:

D6645-18, D7399-18, F0755-19, D5576-00R21E01

Volúmen:

08.01

Número ICS:

83.080.20 (Thermoplastic materials)

Palabras clave:

Fourier transform spectroscopy; infrared spectroscopy; methyl groups; polyethylene; quantitative analysis;