ASTM D3124

There are three types of olefinic groups present in sufficient concentrations to warrant consideration, one or more of which can normally be found in any polyethylene (4). The three types are: trans-vinylene, R - CH = CH - R′, sometimes referred to as transinternal unsaturation; vinylidene or pendent methylene, RR′C = CH₂; and vinyl unsaturation, R - CH = CH₂, also referred to as terminal unsaturation.

The type and quantity of these groups can influence the chemical and physical properties of the resin. Information concerning their presence may also be used to characterize or identify unknown resins or blends of resins.

Vinylidene unsaturation represents the major portion of the unsaturation present in most low-density polyethylenes.

Infrared spectroscopy can be used for the determination of unsaturation in polyethylene (1, 3, 5). The values determined by infrared agree with those determined by IC1 uptake (5).

1. Scope

1.1 This test method is applicable to all types of polyethylenes, those ethylene plastics consisting of ethylene and -olefin copolymers longer than propylene, and blends of the above in any ratio.

1.2 The values stated in SI units 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. Specific hazards statements are given in Section 8.

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

2. Referenced Documents

ASTM Standards
Proposed Methods for Evaluation of Spectrophotometers
D1505 Test Method for Density of Plastics by the Density-Gradient Technique
D1898 Practice for Sampling of Plastics
D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement
E131 Terminology Relating to Molecular Spectroscopy
E168 Practices for General Techniques of Infrared Quantitative Analysis
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E275 Practice for Describing and Measuring Performance of Ultraviolet, Visible, and Near Infrared Spectrophotometers
IEEE/ASTMSI10 Standard for Use of the International System of Units (the Modernized Metric System)

Index Terms

FTIR; infrared spectrophotometry; polyethylene; vinylidene unsaturation; ICS Number Code 83.080.20 (Thermoplastic materials)

Citing ASTM Standards

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