ASTM D6645-01 - 10.3.2001
 
Significance and Use

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.

Note 1--There is no similar or equivalent ISO standard.

 
2. Referenced Documents

E1421-99(2021)

Standard Practice for Describing and Measuring Performance of Fourier Transform Mid-Infrared (FT-MIR) Spectrometers: Level Zero and Level One Tests

E168-16(2023)

Standard Practices for General Techniques of Infrared Quantitative Analysis

D5576-00(2021)e1

Standard Practice for Determination of Structural Features in Polyolefins and Polyolefin Copolymers by Infrared Spectrophotometry (FT-IR) (Includes all amendments and changes 2/10/2021).

E131-10(2023)

Standard Terminology Relating to Molecular Spectroscopy

D3124-98

Standard Test Method for Vinylidene Unsaturation in Polyethylene by Infrared Spectrophotometry

D2238-22

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

D1898-68(1989)

Standard Practice for Sampling of Plastics (Withdrawn 1998)

D1505-25

Standard Test Method for Density of Plastics by the Density-Gradient Technique

D792-20

Standard Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement

E932-89(2021)

Standard Practice for Describing and Measuring Performance of Dispersive Infrared Spectrometers

E177-26a

Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods (Includes all amendments and changes 5/14/2026).

IEEE/ASTM SI-10

Standard for Use of the International System of Units (SI): The Modern System