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Standard Test Methods for Absorbance of Polyethylene Due to Methyl Groups at 1378 cm?1
NORMA vydaná dňa 1.9.2022
Označenie normy: ASTM D2238-22
Dátum vydania normy: 1.9.2022
Kód tovaru: NS-1084176
Počet strán: 7
Približná hmotnosť: 21 g (0.05 libier)
Krajina: Americká technická norma
Kategória: Technické normy ASTM
Keywords:
Fourier transform spectroscopy, infrared spectroscopy, methyl groups, polyethylene, quantitative analysis,
Significance and Use | ||||||||||||||||
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
?m).
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. |
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1. Scope | ||||||||||||||||
1.1?These test methods cover measurement by infrared absorption spectrophotometry of the 1378 cm?1 (7.25 ?m) band in polyethylene due to methyl groups. (1, 2, 3-6)2 Two test methods are covered: 1.1.1?Test Method A?uses compensation with a standard sample film of known methyl content. 1.1.2?Test Method B?uses compensation with a wedge of polymethylene or a polyethylene of known low methyl content. 1.2?These test methods are applicable to polyethylenes of Types I (density 0.910 to 0.925 g/cm3), II (density 0.926 to 0.940 g/cm3), and III (density 0.941 to 0.965 g/cm3). Note 1:?For determination of density, see Specifications
D1505.
Note 2:?In cases of Type III polyethylene with densities
greater than 0.950 g/cm3, different results are obtained
with the two test methods.
1.3?The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.4?This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Note 3:?There is no known ISO equivalent to this standard. 1.5?This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. |
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2. Referenced Documents | ||||||||||||||||
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