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ASTM D6248-21

Current Revision

Standard Test Method for Vinyl and Trans Unsaturation in Polyethylene by Infrared Spectrophotometry (Withdrawn 2021)

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1.1 This test method covers most types of polyethylene, those ethylene plastics consisting of ethylene and α-olefin comonomers 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific hazards statements are given in Section 8.

Note 1: There is no known ISO equivalent for this standard.

1.4 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.


5.1 There are three types of olefinic groups present in sufficient concentrations to warrant consideration, one or more of that can normally be found in any polyethylene. The three types are trans-vinylene, R-CH=CH-R, sometimes referred to as trans-internal unsaturation; vinylidene or pendent methylene, RRC-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 can also be used to characterize or identify unknown resins or blends of resins.

5.3 Additives can interfere with unsaturation measurements. The use is cautioned to determine which additives are present and if there any absorbance bands caused by additive presence that overlap or interfere with unsaturation absorbance bands used in this test method in the range of 1050 to 850 cm–1. If overlapping bands occur, the method is not applicable.

5.4 Interference fringes resulting from smooth sample surfaces can cause measurement errors. This test method requires the use of aluminum foil in the compression molding of samples to provide an adequately rough surface to minimize interference fringes.

SDO ASTM: ASTM International
Document Number D6248
Publication Date Nov. 15, 2021
Language en - English
Page Count 3
Revision Level 21
Supercedes
Committee D20.70
Publish Date Document Id Type View
Nov. 15, 2021 D6248-21 Revision
May 1, 2012 D6248-98R12E01 Revision
April 10, 1998 D6248-98 Revision
July 1, 2004 D6248-98R04 Reaffirmation