ASTM D2765-16(2024)
(Test Method)Standard Test Methods for Determination of Gel Content and Swell Ratio of Crosslinked Ethylene Plastics
Standard Test Methods for Determination of Gel Content and Swell Ratio of Crosslinked Ethylene Plastics
SIGNIFICANCE AND USE
5.1 Many important properties of crosslinked ethylene plastics vary with the gel content. Hence, determination of the gel content provides a means of both controlling the process and rating the quality of finished products.
5.2 Extraction tests permit verification of the proper gel content of any given crosslinked ethylene plastic and they also permit comparison between different crosslinked ethylene plastics, including those containing fillers, provided that, for the latter, the following conditions are met:
5.2.1 The filler is not soluble in either decahydronaphthalene or xylenes at the extraction temperature.
5.2.2 The amount of filler present in the compound either is known or will be determined by other means.
5.2.3 Sufficient crosslinking has been achieved to prevent migration of filler during the extraction. Usually it has been found that, at extraction levels up to 50 %, the extractant remains clear and free of filler.
5.3 A suitable antioxidant is added to the extractant to inhibit possible oxidative degradation at the extraction temperatures.
5.4 Before proceeding with this test method, reference shall be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters, or a combination thereof, covered in the materials specification shall take precedence over those mentioned in this test method. If there are no material specifications, then the default conditions apply.
SCOPE
1.1 The gel content (insoluble fraction) produced in ethylene plastics by crosslinking is determined by extracting with solvents such as decahydronaphthalene or xylenes. The methods described herein are applicable to crosslinked ethylene plastics of all densities, including those containing fillers, and all provide corrections for the inert fillers present in some of those compounds.
1.2 Test Method A, which permits most complete extraction in least time, is to be used for referee tests, but two alternative nonreferee Test Methods B and C are also described. Test Method B differs from the referee test method only in sample preparation; that is, it requires use of shavings taken at selected points in cable insulation, for example, rather than the ground sample required by the referee test method. Because the shaved particles are larger, less total surface per sample is exposed to the extractant, so this test method ordinarily yields extraction values about 1 to 2 % lower than the referee method. Test Method C requires that a specimen in one piece be extracted in xylenes at a constant temperature of 110°C. At this temperature and with a one-piece specimen, even less extraction occurs (from 3 to 9 % less than the referee test method), this method permits swell ratio (a measure of the degree of crosslinking in the gel phase) be determined.
1.3 Extraction tests are made on articles of any shape. They have been particularly useful for electrical insulations since specimens can be selected from those portions of the insulation most susceptible to insufficient crosslinking.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.
Note 1: This test method is equivalent to ISO 10147, Method B. It is not equivalent to ISO 10147 in any other measurement or section.
1.5 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 precautionary statements are given in Sections 6, 9, and 24.
1.6 This int...
General Information
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Standards Content (Sample)
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.
Designation: D2765 − 16 (Reapproved 2024)
Standard Test Methods for
Determination of Gel Content and Swell Ratio of
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Crosslinked Ethylene Plastics
This standard is issued under the fixed designation D2765; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
not equivalent to ISO 10147 in any other measurement or section.
1. Scope*
1.5 This standard does not purport to address all of the
1.1 The gel content (insoluble fraction) produced in ethyl-
safety concerns, if any, associated with its use. It is the
ene plastics by crosslinking is determined by extracting with
responsibility of the user of this standard to establish appro-
solvents such as decahydronaphthalene or xylenes. The meth-
priate safety, health, and environmental practices and deter-
ods described herein are applicable to crosslinked ethylene
mine the applicability of regulatory limitations prior to use.
plastics of all densities, including those containing fillers, and
Specific precautionary statements are given in Sections 6, 9,
all provide corrections for the inert fillers present in some of
and 24.
those compounds.
1.6 This international standard was developed in accor-
1.2 Test Method A, which permits most complete extraction
dance with internationally recognized principles on standard-
in least time, is to be used for referee tests, but two alternative
ization established in the Decision on Principles for the
nonreferee Test Methods B and C are also described. Test
Development of International Standards, Guides and Recom-
Method B differs from the referee test method only in sample
mendations issued by the World Trade Organization Technical
preparation; that is, it requires use of shavings taken at selected
Barriers to Trade (TBT) Committee.
points in cable insulation, for example, rather than the ground
sample required by the referee test method. Because the shaved
2. Referenced Documents
particles are larger, less total surface per sample is exposed to
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2.1 ASTM Standards:
the extractant, so this test method ordinarily yields extraction
D297 Test Methods for Rubber Products—Chemical Analy-
values about 1 to 2 % lower than the referee method. Test
sis
Method C requires that a specimen in one piece be extracted in
D618 Practice for Conditioning Plastics for Testing
xylenes at a constant temperature of 110°C. At this temperature
D883 Terminology Relating to Plastics
and with a one-piece specimen, even less extraction occurs
D1603 Test Method for Carbon Black Content in Olefin
(from 3 to 9 % less than the referee test method), this method
Plastics
permits swell ratio (a measure of the degree of crosslinking in
D1998 Specification for Polyethylene Upright Storage Tanks
the gel phase) be determined.
D3351 Test Method for Gel Count of Plastic Film (With-
1.3 Extraction tests are made on articles of any shape. They 3
drawn 2000)
have been particularly useful for electrical insulations since
E691 Practice for Conducting an Interlaboratory Study to
specimens can be selected from those portions of the insulation
Determine the Precision of a Test Method
most susceptible to insufficient crosslinking.
2.2 ISO Standard:
1.4 The values stated in either SI units or inch-pound units
ISO 10147 Pipes and Fittings Made of Crosslinked Poly-
are to be regarded separately as standard. The values stated in
ethylene (Pe-X)—Estimation of the Degree of Crosslink-
each system are not necessarily exact equivalents; therefore, to
ing by Determination of the Gel Content
ensure conformance with the standard, each system shall be
used independently of the other, and values from the two
3. Terminology
systems shall not be combined.
3.1 Definitions of Terms Specific to This Standard:
NOTE 1—This test method is equivalent to ISO 10147, Method B. It is
1 2
These test methods are under the jurisdiction of ASTM Committee D20 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Plastics and are the direct responsibility of Subcommittee D20.15 on Thermoplastic contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Materials. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Feb. 1, 2024. Published February 2024. Originally the ASTM website.
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approved in 1968. Last previous edition approved in 2016 as D2765 – 16. DOI: The last approved version of this historical standard is referenced on
10.1520/D2765-16R24. www.astm.org.
*A Sum
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