Standard Test Method for Vinylidene Unsaturation in Polyethylene by Infrared Spectrophotometry

Importancia y uso:

5.1 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.

5.2 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.

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

5.4 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).

Subcomité:

D20.70

Referida por:

D6645-18, D5576-00R21E01, D6248-21

Volúmen:

08.01

Número ICS:

83.080.20 (Thermoplastic materials)

Palabras clave:

FTIR; infrared spectrophotometry; polyethylene; vinylidene unsaturation;