ASTM D2756-02
(Test Method)Standard Test Method for Weight Loss of Electrical Insulating Varnishes
Standard Test Method for Weight Loss of Electrical Insulating Varnishes
SCOPE
1.1 This test method covers the measurement of the loss in weight of cured electrical insulating varnishes on exposure to elevated temperature in air.
1.2 The values stated in SI units are 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. For specific precaution statements, see Section 7.
Note 1—IEC 60216 Part 2 is technically equivalent to this standard.
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An American National Standard
Designation:D2756–02
Standard Test Method for
1
Weight Loss of Electrical Insulating Varnishes
This standard is issued under the fixed designation D 2756; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Summary of Test Method
1.1 This test method covers the measurement of the loss in 4.1 Specimens are prepared by coating glass cloth with
weight of cured electrical insulating varnishes on exposure to varnish to be tested. The specimens are aged at elevated
elevated temperature in air. temperatures and the loss in weight is determined after a
1.2 The values stated in SI units are the standard. specific time.
1.3 This standard does not purport to address all of the
5. Significance and Use
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 5.1 Weight loss is useful for indicating:
5.1.1 Aform of degradation at elevated temperatures in air,
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For specific and
5.1.2 Evolution of volatiles which may affect other compo-
precaution statements, see Section 7.
nents.
NOTE 1—IEC 60216 Part 2 is technically equivalent to this standard.
6. Apparatus
2. Referenced Documents
6.1 Air-Circulating Oven, capable of meeting the require-
2.1 ASTM Standards:
ments of Specification D 5423, Type II.
D 115 Test Methods for Testing Solvent Containing Var-
6.2 Glass Cloth,heat-cleaned,StyleNo.116,asdescribedin
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nishes Used for Electrical Insulation
Specification D 2518.
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D 1711 Terminology Relating to Electrical Insulation
6.3 Balance, capable of weighing to nearest 0.001 g.
D 1932 Test Method for Thermal Endurance of Flexible
6.4 Desiccator Jar, with a suitable desiccant.
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Electrical Insulating Varnishes
D 2518 SpecificationforWovenGlassFabricsforElectrical
7. Safety Precautions
3
Insulation
7.1 Varnish should not be used at temperatures above the
D 5423 Specification for Forced-Convection Laboratory
flash point when inadequate ventilation and the possibility of
3
Ovens for Evaluation of Electrical Insulation
flames or sparks exist. Varnish should be stored in sealed
2.2 IEC Standards:
containers. The precautions shall also apply to the handling of
IEC 60216 Guide for the determination of thermal endur-
the called for reagents and solvents.
ance properties of electrical insulating materials—Part 2:
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Choice of test criteria
8. Sampling
8.1 Sample the varnish in accordance with Test Methods
3. Terminology
D 115.
3.1 Definitions: For definitions of terms used in this test
method, refer to Terminology D 1711.
9. Test Specimens
9.1 Prepare the test specimens as described in Test Method
1
D 1932. Make one panel for each test temperature. Use an
This test method is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of average of ten readings to determine the thickness of the
Subcommittee D09.01 on Electrical Insulating Varnishes, Powders and Encapsulat-
panels.
ing Compounds.
9.2 Cure the varnish in accordance with manufacturer’s
Current edition approved Sept. 10, 2002. Published October 2002. Originally
requirements.
issued as D 2756 – 68. Last previous edition D 2756 – 85 (1998).
2
Annual Book of ASTM Standards, Vol 10.01.
9.3 Cut two specimens, 100 by 125 mm (4 by 5 in.) from
3
Annual Book of ASTM Standards, Vol 10.02.
each panel to be used for the tests.
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D2756–02
whipping around in the ovens. The use of the foil tabs also prevents the
9.4 Cut an uncoated piece of cloth, 100 by 125 mm (4 by 5
battery clips from picking up any varnish, which could introduce an error
in.)
in the measurement.
NOTE 3—Whenmoreinformationisrequired,itmaybedesirabletouse
10. Procedure
a number of selected time periods (for example: 4, 24, 48, 96 h, and in
10.1 Dry two cured specimens for each test temperature and
somecases,evenlongerperiodsoftime).Acurveofweightlossversusthe
one uncoated specimen for 2 h at 110°C (230°F). Place them in
logarithm of time may then be plotted which shows the instantaneous rate
a desiccator and allow them to cool to room temperature. of the loss. A comparison of the initial rate and subsequent or final rate
may provide valuable information as to the degradative mecha
...
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