ASTM D115-17(2024)
(Test Method)Standard Test Methods for Testing Solvent Containing Varnishes Used for Electrical Insulation
Standard Test Methods for Testing Solvent Containing Varnishes Used for Electrical Insulation
SIGNIFICANCE AND USE
4.1 Control—The following tests are useful for control purposes during the manufacture and use of varnishes, and for determining the uniformity of batches:
4.1.1 Specific gravity,
4.1.2 Viscosity,
4.1.3 Flash point, and
4.1.4 Nonvolatile matter by weight.
4.2 Performance—The following tests are useful for determining the performance of varnishes during application and use:
4.2.1 Drainage,
4.2.2 Time of drying,
4.2.3 Build,
4.2.4 Dielectric strength,
4.2.5 Thermal endurance,
4.2.6 Varnish compatibility,
4.2.7 Salt water proofness, and
4.2.8 Oil resistance.
SCOPE
1.1 These test methods cover tests for solvent containing varnishes primarily intended to provide electrical, mechanical, and chemical protection for electrical equipment. These test methods include tests for control and performance as follows:
Procedure
Section
Build
38 – 42
Dielectric Strength
43 – 48
Drainage
26 – 32
Flash Point
18 – 20
Nonvolatile Matter
21 – 25
Oil Resistance
54 – 56
Preparation of Test Specimens
7
Specific Gravity
9 – 12
Temperature Index
49 – 50
Time of Drying
33 – 37
Varnish Compatibility
51 – 53
Viscosity
13 – 17
1.2 Where the entire test method is included in this standard, the precision and bias are not known unless given in the stated method.
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 5.
Note 1: There is no equivalent IEC standard.
1.5 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.
General Information
Relations
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: D115 − 17 (Reapproved 2024)
Standard Test Methods for Testing
Solvent Containing Varnishes Used for Electrical Insulation
This standard is issued under the fixed designation D115; 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.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 These test methods cover tests for solvent containing
D56 Test Method for Flash Point by Tag Closed Cup Tester
varnishes primarily intended to provide electrical, mechanical,
D93 Test Methods for Flash Point by Pensky-Martens
and chemical protection for electrical equipment. These test
Closed Cup Tester
methods include tests for control and performance as follows:
D149 Test Method for Dielectric Breakdown Voltage and
Procedure Section
Dielectric Strength of Solid Electrical Insulating Materials
Build 38 – 42
Dielectric Strength 43 – 48
at Commercial Power Frequencies
Drainage 26 – 32
D202 Test Methods for Sampling and Testing Untreated
Flash Point 18 – 20
Paper Used for Electrical Insulation
Nonvolatile Matter 21 – 25
Oil Resistance 54 – 56
D287 Test Method for API Gravity of Crude Petroleum and
Preparation of Test Specimens 7
Petroleum Products (Hydrometer/Method)
Specific Gravity 9 – 12
D295 Test Methods for Varnished Cotton Fabrics Used for
Temperature Index 49 – 50
Time of Drying 33 – 37
Electrical Insulation (Withdrawn 2020)
Varnish Compatibility 51 – 53
D374/D374M Test Methods for Thickness of Solid Electri-
Viscosity 13 – 17
cal Insulation
1.2 Where the entire test method is included in this standard,
D580/D580M Practice for Greige Woven Glass Tapes and
the precision and bias are not known unless given in the stated
Webbings
method.
D1475 Test Method for Density of Liquid Coatings, Inks,
and Related Products
1.3 The values stated in SI units are to be regarded as
D1932 Test Method for Thermal Endurance of Flexible
standard. The values given in parentheses are for information
Electrical Insulating Varnishes
only.
D2518 Specification for Woven Glass Fabrics for Electrical
1.4 This standard does not purport to address all of the
Insulation (Withdrawn 2013)
safety concerns, if any, associated with its use. It is the
D2519 Test Method for Bond Strength of Electrical Insulat-
responsibility of the user of this standard to establish appro-
ing Varnishes by the Helical Coil Test
priate safety, health, and environmental practices and deter-
D3145 Test Method for Thermal Endurance of Electrical
mine the applicability of regulatory limitations prior to use.
Insulating Varnishes by Helical Coil Method
For specific hazard statements, see Section 5.
D3251 Test Method for Thermal Endurance Characteristics
of Electrical Insulating Varnishes Applied Over Film-
NOTE 1—There is no equivalent IEC standard.
Insulated Magnet Wire
1.5 This international standard was developed in accor-
D3278 Test Methods for Flash Point of Liquids by Small
dance with internationally recognized principles on standard-
Scale Closed-Cup Apparatus
ization established in the Decision on Principles for the
D3487 Specification for Mineral Insulating Oil Used in
Development of International Standards, Guides and Recom-
Electrical Apparatus
mendations issued by the World Trade Organization Technical
D5032 Practice for Maintaining Constant Relative Humidity
Barriers to Trade (TBT) Committee.
by Means of Aqueous Glycerin Solutions
1 2
These test methods are under the jurisdiction of ASTM Committee D09 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Electrical and Electronic Insulating Materials and are the direct responsibility of contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Subcommittee D09.01 on Electrical Insulating Products. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved March 1, 2024. Published March 2024. Originally the ASTM website.
approved in 1941. Last previous edition approved in 2017 as D115 – 17. DOI: The last approved version of this historical standard is referenced on
10.1520/D0115-17R24. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D115 − 17 (2024)
D5423 Specification for Forced-Convection Laboratory Ov- 4.1.1 Specific gravity,
ens for Evaluation of Electrical Insulation 4.1.2 Viscosity,
E104 Practice for Maintaining Constant Relative Humidity 4.1.3 Flash point, and
by Means of Aqueous Solutions 4.1.4 Nonvolatile matter by weight.
4.2 Performance—The following tests are useful for deter-
3. Terminology
mining the performance of varnishes during application and
3.1 Definitions:
use:
3.1.1 dielectric strength, n—the voltage gradient at which
4.2.1 Drainage,
dielectric failure of the insulating material occurs under spe-
4.2.2 Time of drying,
cific conditions of test.
4.2.3 Build,
3.1.2 drainage, n—of an insulating varnish, a measure of
4.2.4 Dielectric strength,
the variation in thickness from top to bottom of a varnish film
4.2.5 Thermal endurance,
obtained on the surface of a vertically dip-coated panel after a
4.2.6 Varnish compatibility,
specified time and temperature.
4.2.7 Salt water proofness, and
3.1.3 flash point, n—the lowest temperature of the
4.2.8 Oil resistance.
specimen, corrected to a pressure of 760 mm Hg (101.3 kPa),
at which application of an ignition source causes any vapor 5. Hazards
from the specimen to ignite under specified conditions of test.
5.1 Warning—Do not use varnish at temperatures above
3.1.4 nonvolatile matter, n—in insulating varnish, that por-
the flash point when inadequate ventilation and the possibility
tion of a varnish which is not volatilized when exposed to
of flames or sparks exist. Store varnish in sealed containers.
specified conditions; the value obtained is not necessarily equal
The precautions shall also apply to the handling of the reagents
to the calculated solids incorporated during compounding.
and solvents called for herein.
3.1.4.1 Discussion—For example, the theoretical chemical
solids are often assumed to be the solid phase materials 6. Sampling
incorporated in the varnish at the time of compounding. Many
6.1 For all tests the sample shall be taken from a represen-
of these solid phase intermediate materials will lose volatile
tative lot of the varnish under study. To avoid skin formation
fractions due to the specified conditions of the nonvolatile
and escape of solvents, protect the sample by keeping it at
matter procedure. An example is phenolic resin.
room temperature in a nearly filled, tightly sealed container.
3.1.5 oil resistance, n—of insulating varnish, a measure of
the retention of properties after exposure to a specified oil
7. Preparation of Test Specimens
under specified conditions of test.
7.1 Selection of Substrate—The selection of the substrate is
3.1.6 time of drying, n—of insulating varnish, the time
determined in part by application and in part by thermal class.
required for a film of varnish to dry to a tackfree state under
Two types of substrates are suitable for use: copper strip or
specified conditions.
glass cloth. Copper strip is generally not used for applications
over 180 °C (356 °F), due to oxidation.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 build, n—of an insulating varnish on copper, the
7.2 Copper Base—For tests that are to be performed upon
average thickness of varnish film on one side of a copper panel
the varnish as a film on a copper base, copper strips 38 mm
that has received a single coat of the varnish applied and 1
(1 ⁄2 in.) in width, 200 mm (8 in.) in length, and 0.127 mm 6
measured under specified conditions.
0.08 mm (0.005 in. 6 0.0003 in.) in thickness shall be used,
3.2.2 build, n—of an insulating varnish on glass cloth, the unless otherwise specified. Measure the thickness of these
average overall thickness of strips of glass cloth that have strips to the nearest 0.002 mm (0.0001 in.). Clean the strips
received two dips of the varnish applied and measured under with a suitable solvent (Note 2), then polish thoroughly with
specified conditions. No. 000 steel wool. Wipe the strips free of any fingerprints or
metal particles with the solvent and a lint-free cloth. If the
3.2.3 tack-free, adj—condition when a varnish has reached
strips are not to be used immediately, store in a noncorrosive
the point that the surface can be touched lightly without a
varnish solvent.
sensation of stickiness.
3.2.4 varnish, air-drying, n—a liquid resin system that NOTE 2—Xylene and denatured alcohol (1:1) have been found to be
suitable cleaning solvents. V.M.&.P. naphtha is a suitable solvent in which
forms a dry, tack-free coating, without the application of heat,
to store the strips.
either through evaporation of solvent or by reaction with
atmospheric oxygen. 7.2.1 Prepare all varnish films for tests at 23 °C 6 1 °C
(73.5 °F 6 2 °F) and 50 % 6 5 % relative humidity. The air of
3.2.5 varnish, baking, n—a liquid resin system that forms a
the room shall be relatively free of dust by some satisfactory
dry, tack-free coating when exposed to elevated temperatures.
method of filtering.
4. Significance and Use
7.2.2 After the strips have been wiped clean and dry,
4.1 Control—The following tests are useful for control prepare the test specimens by dipping them into a tank of the
purposes during the manufacture and use of varnishes, and for varnish that has been adjusted to a proper consistency and
determining the uniformity of batches: allowed to stand covered until free of bubbles (not to exceed
D115 − 17 (2024)
1 h). Trial testing is required to establish the proper consis- ends to rectangular wire frames about 240 mm by 70 mm
tency. Proper consistency has been reached when the strips are (9.5 in. by 2.75 in.). Bake specimens for the time and at the
dipped in the varnish at a temperature of 23 °C 6 1 °C (73.5 °F temperature specified by the manufacturer for the first coat.
6 2 °F) and are withdrawn slowly and uniformly at the rate of Apply the next coat by reverse dipping, except withdraw
100 mm (4 in.)/min., the average thickness of the film specimens as soon as immersed and drain as for the previous
remaining on each side of a strip when dry shall be 0.025 mm coat. Bake the second coat in accordance with the manufac-
6 0.005 mm (0.0010 in. 6 0.0002 in.). turer’s recommended schedule for a final coat.
7.2.3 Calculate the average thickness by averaging at least 7.3.4 Measuring Specimen Thickness—Measure specimen
thickness using a dead-weight dial-type micrometer in accor-
six measurements taken along the length of the strip and over
3 mm ( ⁄8 in.) from either edge. Thickness measurements shall dance with Test Methods D374/D374M, Method C, except that
the weight on the specimen shall be limited to 567 g 6 7 g
be made in accordance with Test Methods D374/D374M.
(20 oz 6 0.25 oz) and the anvil surface upon which the
7.2.4 It is recognized that the thickness of the film cannot be
specimen rests shall be 51 mm (2 in.) in diameter. Allow the
measured with the precision stated, but a close control of the
presser foot to remain on the specimens about 2 s before taking
thickness of the varnish film is desired. With the method
a reading. Where thickness measurements along a line or in an
specified, the actual average thickness is within 60.005 mm
area are nonuniform, repeat the measurements, taking care to
(60.0002 in.) of the measured thickness.
avoid film abnormalities.
7.2.5 With air dry varnishes, except where time of drying is
the property being measured, following each dip, suspend the
8. Conditioning
specimens vertically in a dipping position and dry in dust-free
air for such times and at such temperatures as the user and the
8.1 Condition the specimens as described in the individual
supplier agree are suitable. If necessary, readjust the consis-
test procedures.
tency of the varnish and dip the specimen in the reverse
SPECIFIC GRAVITY
direction to the first and air dry.
7.2.6 With baking varnishes, allow the specimens to drain at
9. Terminology
a temperature of 23 °C 6 1 °C (73.5 °F 6 2 °F), then bake for
such times and at such temperatures as the user and the supplier 9.1 Definitions:
agree are suitable. If necessary, readjust the consistency of the 9.1.1 specific gravity—the ratio of the weight of a unit
varnish and dip the specimen in the reverse direction to the first volume of sample as compared with the weight of the same
and bake. unit volume of distilled water at 23 °C 6 1 °C (73.5 °F 6
2 °F).
7.3 Glass Cloth Base:
7.3.1 For tests that are to be performed on the varnish as a
10. Significance and Use
combination with glass cloth, use a glass strip instead of a
10.1 Specific gravity indicates the relative weight per unit
copper strip. Prepare the strip from specimens 38 mm (1.5 in.)
volume of a varnish. It is a useful test for control purposes.
wide by approximately 250 mm (10 in.) long from heat-
cleaned woven glass fabric (Note 3). The length shall be in the
11. Procedure
direction of the warp threads. The fabric shall be Style No. 116
as listed in Table 1 of Specification D2518. The volatile content
11.1 Determine the specific gravity of the varnish by using
of the heat-cleaned fabric shall not exceed 0.1 % as determined
a wide-mouth pycnometer (25 mL minimum capacity) at 23 °C
in accordance with the organic content test of Specification
6 1 °C (73.5 °F 6 2 °F). Refer to Test Method D1475.
D580/D580M (Note 4). The strip form specimens shall be kept
Determine the specific gravity by dividing the weight of an
in a Standard Laboratory Atmosphere (see 7.2.1).
equal volume of distilled water at the same temperature.
7.3.2 Condition the heat-cleaned glass strips 1 h at 105 °C
11.2 A hydrometer is another method for determining this
(221 °F) and cool in a Standard Laboratory Atmosphere before
property, in accordance with Test Method D287.
coating.
12. Report
NOTE 3—One method of creating the strip form specimens is by
stamping out of the woven glass fabric by means of die and clicker. This
12.1 Report the following information:
technique causes the ends of the fibers to bind together and prevents the
12.1.1 Identification of the varnish used, and
unraveling of the yarn.
12.1.2 The specific gravity at 23 °C 6 1 °C (73.5 °F 6
NOTE 4—Commercially heat-cleaned fiberglass fabric meeting this
volatile content is available. 2 °F
...
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