ASTM D3377-96
(Test Method)Standard Test Method for Weight Loss of Solventless Varnishes
Standard Test Method for Weight Loss of Solventless Varnishes
SCOPE
1.1 This test method covers the determination of the percent weight loss of cured solventless electrical varnishes when exposed to elevated temperatures for prescribed periods of time.
1.2 Results of this test method are based on 6-mm (1/4-in.) thick specimens and may not be applicable to specimens appreciably thinner or thicker than 6 mm.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 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.
Note 1--This standard resembles IEC 60216-2 (1990-06) "Guide for the determination of thermal endurance properties of electrical insulating materials. Part 2: Choice of test criteria" in a number of ways, but is not consistently similar throughout. The data obtained using either standard may be technically equivalent.
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NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: D 3377 – 96 An American National Standard
Standard Test Method for
Weight Loss of Solventless Varnishes
This standard is issued under the fixed designation D 3377; 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 4.1.2 Cause cracking of insulation due to pressure, buildup
in thick cross sections, or
1.1 This test method covers the determination of the percent
4.1.3 Corrode other parts in the assembly.
weight loss of cured solventless electrical varnishes when
4.2 Amount and rate of weight loss may affect the thermal
exposed to elevated temperatures for prescribed periods of
rating of a varnish.
time.
1.2 Results of this test method are based on 6.4-mm ( ⁄4-in.)
5. Apparatus
thick specimens and may not be applicable to specimens
5.1 Metal Mold, consisting of two flat sheets 305 by 305 by
appreciably thinner or thicker than 6.4 mm.
1 1
6.4 mm (12 by 12 by ⁄4 in.) separated by 6.4-mm ( ⁄4-in.) thick
1.3 The values stated in SI units are to be regarded as the
spacers along three sides. The spacers also seal the edges of the
standard.
mold and the assembly is held together with “C” clamps or
1.4 This standard does not purport to address all of the
bolts. Aluminum or polished steel plates can be used.
safety concerns, if any, associated with its use. It is the
5.2 Laboratory Balance, with accuracy of 61 mg.
responsibility of the user of this standard to establish appro-
5.3 Forced-Convection Laboratory Oven, meeting require-
priate safety and health practices and determine the applica-
ments of Specification D 5423, Type II for each test tempera-
bility of regulatory limitations prior to use.
ture.
2. Referenced Documents 5.4 Screening Platform, 6.4-mm ( ⁄4-in.) mesh, with 51-mm
(2-in.) legs.
2.1 ASTM Standards:
5.5 Mold Release.
D 5423 Specification for Forced-Convection Laboratory
Ovens for Evaluation of Electrical Insulation
NOTE 1—Fluorocarbon-type release agents are satisfactory.
5.6 Desiccator.
3. Terminology
3.1 Definition:
6. Procedure
3.1.1 varnish, n—electrical insulating, a liquid resin system
6.1 Apply a thin, uniform coating of release agent to the
that is applied to and cured on electrical components providing
contact surfaces of the mold.
electrical, mechanical, and environmental protection.
6.2 Assemble the mold, taking precautionary measures to
3.1.1.1 Discussion—There are two types of electrical insu-
avoid leaks.
lating varnish: solvent-containing and solventless. The solvent-
6.3 Pour the sample into the open edge of the mold, using
containing varnish is a solution, dispersion, or emulsion of a
care to avoid bubbles.
polymer or mixture of polymers in a volatile, nonreactable
NOTE 2—In some cases, it may be necessary to prevacuum the sample
liquid. The solventless type is a liquid resin system free of
before pouring.
volatile, nonreactable solvents.
6.4 Cure the sample using the recommended cure cycle.
4. Significance and Use
6.5 After curing, remove the mold and contents from the
4.1 The amount and composition of by-products produced
oven and allow to cool to room temperature.
by exposure of insulating varnishes to elevated temperatures
6.6 Carefully disassemble the mold and remove the cast
can possibly:
sheet.
4.1.1 Deteriorate other insulations in the system,
6.7 From the cast sheet, cut at least three specimens
approximately 51 by 51 mm (2 by 2 in.) for each test
temperature.
This test method is under the jurisdiction of ASTM Committee D-9 on
Electrical and Electronic Insulating Materials and is direct responsibility of 6.8 Dry
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