ASTM D6645

This method determines the number of branches (that is, comonomer content) in copolymers of ethylene with 1-butene, 1-hexene or 1-octene. This information can be correlated with physical properties such as melting point, density, and stiffness, all of which depend on the degree of crystallinity of the polymer. Differences in the comonomer content thus may have a significant effect on the final properties of products made from these resins.

1. Scope

1.1 This test method covers the determination of methyl groups (that is, comonomer content) in polyethylenes by infrared spectrophotometry. The test method is applicable to copolymers of ethylene with 1-butene, 1-hexene, or 1-octene having densities above 900 kg/m³. High-pressure low-density polyethylenes (LDPE) and terpolymers are excluded.

1.2 The values stated in SI units, based on IEEE/ASTM S1-10, are to be regarded as the standard.

1.3 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 and health practices and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents

ASTM Standards
D1505 Test Method for Density of Plastics by the Density-Gradient Technique
D1898 Practice for Sampling of Plastics
D2238 Test Method for Absorbance of Polyethylene Due to methyl Groups at 1378 cm-1
D3124 Test Method for Vinylidene Unsaturation in Polyethylene by Infrared Spectrophotometry
D5576 Practice for Determination of Structural Features in Polyolefins and Polyolefin Copolymers by Infrared Spectroscopy
D792 Test Method for Density and Specific Gravity (Relative Density) of Plastics by Displacement
E131 Terminology Relating to Molecular Spectroscopy
E1421 Practice for Describing and Measuring Performance of Fourier Transform Infrared (FT-IR) Spectrometers: Level Zero and Level One Tests
E168 Practice for General Techniques of Infrared Quantitative Analysis
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E932 Practice for Describing and Measuring Performance of Dispersive Infrared Spectrophotometers
IEEE/ASTMSI-10 Standard for Use of the International System of Units (SI): The Modern System (Replaces ASTM E 380 and ANSI/IEEE Standard 268-1992)

Index Terms

branching; comonomer; FTIR; infrared spectrophotometry; polyethylene; ICS Number Code 19.100 (Non-destructive testing); 83.080.20 (Thermoplastic materials)

Citing ASTM Standards

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