ASTM D115-14
(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 and health 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.
General Information
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D115 − 14
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* D93 Test Methods for Flash Point by Pensky-Martens
Closed Cup Tester
1.1 These test methods cover tests for solvent containing
D149 Test Method for Dielectric Breakdown Voltage and
varnishes primarily intended to provide electrical, mechanical,
DielectricStrengthofSolidElectricalInsulatingMaterials
and chemical protection for electrical equipment. These test
at Commercial Power Frequencies
methods include tests for control and performance as follows:
D202 Test Methods for Sampling and Testing Untreated
Procedure Section
Paper Used for Electrical Insulation
Build 38–42
D287 Test Method for API Gravity of Crude Petroleum and
Dielectric Strength 43–48
Drainage 26–32
Petroleum Products (Hydrometer Method)
Flash Point 18–20
D295 Test Methods for Varnished Cotton Fabrics Used for
Nonvolatile Matter 21–25
Oil Resistance 54–56 Electrical Insulation
Preparation of Test Specimens 7
D374 Test Methods for Thickness of Solid Electrical Insu-
Specific Gravity 9–12
lation (Withdrawn 2013)
Temperature Index 49 – 50
Time of Drying 33–37 D580 Specification for Greige Woven Glass Tapes and
Varnish Compatibility 51–53
Webbings
Viscosity 13–17
D1475 Test Method For Density of Liquid Coatings, Inks,
1.2 Wheretheentiretestmethodisincludedinthisstandard,
and Related Products
the precision and bias are not known unless given in the stated
D1932 Test Method for Thermal Endurance of Flexible
method.
Electrical Insulating Varnishes
1.3 The values stated in SI units are to be regarded as D2518 Specification for Woven Glass Fabrics for Electrical
standard. The values given in parentheses are for information Insulation (Withdrawn 2013)
only. D2519 Test Method for Bond Strength of Electrical Insulat-
ing Varnishes by the Helical Coil Test
1.4 This standard does not purport to address all of the
D3145 Test Method for Thermal Endurance of Electrical
safety concerns, if any, associated with its use. It is the
Insulating Varnishes by the Helical Coil Method
responsibility of the user of this standard to establish appro-
D3251 Test Method for Thermal Endurance Characteristics
priate safety and health practices and determine the applica-
of Electrical Insulating Varnishes Applied Over Film-
bility of regulatory limitations prior to use. For specific hazard
Insulated Magnet Wire
statements, see Section 5.
D3278 Test Methods for Flash Point of Liquids by Small
NOTE 1—There is no equivalent IEC standard.
Scale Closed-Cup Apparatus
D3487 Specification for Mineral Insulating Oil Used in
2. Referenced Documents
Electrical Apparatus
2.1 ASTM Standards:
D5032 Practice for Maintaining Constant Relative Humidity
D56 Test Method for Flash Point by Tag Closed Cup Tester
by Means of Aqueous Glycerin Solutions
D5423 Specification for Forced-Convection Laboratory Ov-
ens for Evaluation of Electrical Insulation
These test methods are under the jurisdiction of ASTM Committee D09 on
E104 Practice for Maintaining Constant Relative Humidity
Electrical and Electronic Insulating Materials and are the direct responsibility of
Subcommittee D09.01 on Electrical Insulating Varnishes, Powders and Encapsulat- by Means of Aqueous Solutions
ing Compounds.
Current edition approved Nov. 1, 2014. Published November 2014. Originally
3. Terminology
approved in 1941. Last previous edition approved in 2012 as D115 – 07 (2012).
3.1 Definitions:
DOI: 10.1520/D0115-14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D115 − 14
3.1.1 dielectric strength, n—the voltage gradient at which 4.2 Performance—The following tests are useful for deter-
dielectric failure of the insulating material occurs under spe- mining the performance of varnishes during application and
cific conditions of test. use:
4.2.1 Drainage,
3.1.2 drainage, n—of an insulating varnish, a measure of
4.2.2 Time of drying,
the variation in thickness from top to bottom of a varnish film
4.2.3 Build,
obtained on the surface of a vertically dip-coated panel after a
4.2.4 Dielectric strength,
specified time and temperature.
4.2.5 Thermal endurance,
3.1.3 flash point, n—the lowest temperature of the
4.2.6 Varnish compatibility,
specimen, corrected to a pressure of 760 mm Hg (101.3 kPa),
4.2.7 Salt water proofness, and
at which application of an ignition source causes any vapor
4.2.8 Oil resistance.
from the specimen to ignite under specified conditions of test.
5. Hazards
3.1.4 nonvolatile matter, n—in insulating varnish, that por-
5.1 Warning—Do not use varnish at temperatures above
tion of a varnish which is not volatilized when exposed to
the flash point when inadequate ventilation and the possibility
specifiedconditions;thevalueobtainedisnotnecessarilyequal
of flames or sparks exist. Store varnish in sealed containers.
to the calculated solids incorporated during compounding.
The precautions shall also apply to the handling of the reagents
3.1.4.1 Discussion—For example, the theoretical chemical
and solvents called for herein.
solids are often assumed to be the solid phase materials
incorporated in the varnish at the time of compounding. Many
6. Sampling
of these solid phase intermediate materials will lose volatile
6.1 For all tests the sample shall be taken from a represen-
fractions due to the specified conditions of the nonvolatile
tative lot of the varnish under study. To avoid skin formation
matter procedure. An example is phenolic resin.
and escape of solvents, protect the sample by keeping it at
3.1.5 oil resistance, n—of insulating varnish, a measure of
room temperature in a nearly filled, tightly sealed container.
the retention of properties after exposure to a specified oil
under specified conditions of test.
7. Preparation of Test Specimens
3.1.6 time of drying, n—of insulating varnish, the time
7.1 Selection of Substrate—The selection of the substrate is
required for a film of varnish to dry to a tackfree state under
determined in part by application and in part by thermal class.
specified conditions.
Two types of substrates may be used: copper strip or glass
cloth. Copper strip is generally not used for applications over
3.2 Definitions of Terms Specific to This Standard:
180°C (356°F), due to oxidation.
3.2.1 build, n—of an insulating varnish on copper, the
average thickness of varnish film on one side of a copper panel
7.2 Copper Base—For tests that are to be performed upon
that has received a single coat of the varnish applied and
the varnish as a film on a copper base, copper strips 38 mm
measured under specified conditions.
(1 ⁄2 in.) in width, 200 mm (8 in.) in length, and 0.127 6
0.08 mm (0.005 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
3.2.3 tack-free, adj—condition when a varnish has reached
metal particles with the solvent and a lint-free cloth. If the
the point that the surface can be touched lightly without a
strips are not to be used immediately, they should be kept
sensation of stickiness.
stored in a noncorrosive varnish solvent.
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
forms a dry, tack-free coating, without the application of heat,
suitable cleaning solvents.V.M.&.P. naphtha is a suitable solvent in which
either through evaporation of solvent or by reaction with
to store the strips.
atmospheric oxygen.
7.2.1 Prepare all varnish films for tests at 23 6 1°C (73.5 6
3.2.5 varnish, baking, n—a liquid resin system that forms a 2°F) and 50 6 5 % relative humidity. The air of the room shall
be relatively free of dust by some satisfactory method of
dry, tack-free coating when exposed to elevated temperatures.
filtering.
7.2.2 After the strips have been wiped clean and dry,
4. Significance and Use
prepare the test specimens by dipping them into a tank of the
4.1 Control—The following tests are useful for control
varnish that has been adjusted to a proper consistency and
purposes during the manufacture and use of varnishes, and for
allowed to stand covered until free of bubbles (not to exceed
determining the uniformity of batches:
1 h). Trial testing may be required to establish the proper
4.1.1 Specific gravity,
consistency. Proper consistency has been reached when the
4.1.2 Viscosity,
strips are dipped in the varnish at a temperature of 23 6 1°C
4.1.3 Flash point, and
(73.5 6 2°F) and are withdrawn slowly and uniformly at the
4.1.4 Nonvolatile matter by weight. rate of 100 mm (4 in.)/min., the average thickness of the film
D115 − 14
remaining on each side of a strip when dry shall be 0.025 6 coat. Bake the second coat in accordance with the manufac-
0.005 mm (0.0010 6 0.0002 in.). turer’s recommended schedule for a final coat.
7.3.4 Measuring Specimen Thickness—Measure specimen
7.2.3 Calculate the average thickness by averaging at least
thickness using a dead-weight dial-type micrometer in accor-
six measurements taken along the length of the strip and over
dance with Test Methods D374, Method C, except that the
3mm( ⁄8 in.) from either edge. Thickness measurements shall
weight on the specimen shall be limited to 567 6 7 g (20 6
be made in accordance with Test Methods D374.
0.25 oz.) and the anvil surface upon which the specimen rests
7.2.4 Itisrecognizedthatthethicknessofthefilmcannotbe
shall be 51 mm (2 in.) in diameter. Allow the presser foot to
measured with the precision stated, but a close control of the
remain on the specimens about 2 s before taking a reading.
thickness of the varnish film is desired. With the method
Where thickness measurements along a line or in an area are
specified, the actual average thickness should be within
nonuniform,repeatthemeasurements,takingcaretoavoidfilm
60.005 mm (60.0002 in.) of the measured thickness.
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
8.1 Condition the specimens as described in the individual
air for such times and at such temperatures as the user and the
test procedures.
supplier agree are suitable. If necessary, readjust the consis-
tency of the varnish and dip the specimen in the reverse
SPECIFIC GRAVITY
direction to the first and air dry.
9. Terminology
7.2.6 Withbakingvarnishes,allowthespecimenstodrainat
a temperature of 23 6 1°C (73.5 6 2°F), then bake for such
9.1 Definitions:
times and at such temperatures as the user and the supplier
9.1.1 specific gravity—the ratio of the weight of a unit
agree are suitable. If necessary, readjust the consistency of the
volume of sample as compared with the weight of the same
varnishanddipthespecimeninthereversedirectiontothefirst
unit volume of distilled water at 23 6 1°C (73.5 6 2°F).
and bake.
10. Significance and Use
7.3 Glass Cloth Base:
10.1 Specific gravity indicates the relative weight per unit
7.3.1 For tests that are to be performed on the varnish as a
volume of a varnish. It is a useful test for control purposes.
combination with glass cloth, use a glass strip instead of a
copper strip. Prepare the strip from specimens 38 mm (1.5 in.)
11. Procedure
wide by approximately 250 mm (10 in.) long from heat-
11.1 Determine the specific gravity of the varnish by using
cleaned woven glass fabric (Note 3). The length shall be in the
a wide-mouth pycnometer (25-mLminimum capacity) at 23 6
direction of the warp threads.The fabric shall be Style No. 116
1°C (73.5 6 2°F). Refer toTest Method D1475. Determine the
aslistedinTable1ofSpecificationD2518.Thevolatilecontent
specific gravity by dividing the weight of an equal volume of
oftheheat-cleanedfabricshallnotexceed0.1 %asdetermined
distilled water at the same temperature.
in accordance with the organic content test of Specification
D580 (Note 4). The strip form specimens shall be kept in a
11.2 A hydrometer is another method for determining this
Standard Laboratory Atmosphere (see 7.2.1).
property, in accordance with Test Method D287.
7.3.2 Condition the heat-cleaned glass strips1hat 105°C
12. Report
(221°F) and cool in a Standard LaboratoryAtmosphere before
coating.
12.1 Report the following information:
12.1.1 Identification of the varnish used, and
NOTE 3—The strip form specimens may be stamped out of the woven
12.1.2 The specific gravity at 23 6 1°C (73.5 6 2°F),
glass fabric by means of die and clicker.This technique causes the ends of
the fibers to bind together and prevents the unraveling of the yarn. reported to the third decimal place.
NOTE 4—Commercially heat-cleaned fiberglass fabric meeting this
VISCOSITY
volatile content is available.
7.3.3 Dipping and Curing—Condition the varnish to be
13. Significance and Use
tested for a minimum of4hat Standard Laboratory Tempera-
13.1 Theviscositymeasurementmaybeusedtoindicatethe
ture before coating the strips. Immerse specimens in the
flowing characteristics of a varnish.
varnish until bubbling stops. Withdraw at 100 mm (4 in.)/min.
13.2 Viscosity is also useful for control purposes during the
and drain in a dipping and draining chamber in the same
manufacture and use of a varnish.
position as dipped for 30 min., or as agreed between the user
and supplier. In order to facilitate dipping and curing and to
14. Apparatus
obtain smoother specimens, the fiberglass strips may be se-
cured at the ends to rectangular wire frames about 240 by 14.1 Rotational Viscometer (Note 5)—The essential instru-
70 mm(9.5by2.75 in.).Bakespecimensforthetimeandatthe mentation
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D115 − 07 (Reapproved 2012) D115 − 14
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*
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 37 – 41
Build 38 – 42
Dielectric Strength 42 – 47
Dielectric Strength 43 – 48
Drainage 25 – 31
Drainage 26 – 32
Flash Point 17 – 19
Flash Point 18 – 20
Nonvolatile Matter 20 – 24
Nonvolatile Matter 21 – 25
Oil Resistance 53 – 55
Oil Resistance 54 – 56
Preparation of Test Specimens 7
Preparation of Test Specimens 7
Specific Gravity 9 – 12
Temperature Index 48-49
Temperature Index 49 – 50
Time of Drying 32 – 36
Time of Drying 33 – 37
Varnish Compatibility 50 – 52
Varnish Compatibility 51 – 53
Viscosity 13 – 16
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 the 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 and health 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.
2. Referenced Documents
2.1 ASTM Standards:
D56 Test Method for Flash Point by Tag Closed Cup Tester
D93 Test Methods for Flash Point by Pensky-Martens Closed Cup Tester
D149 Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at
Commercial Power Frequencies
D202 Test Methods for Sampling and Testing Untreated Paper Used for Electrical Insulation
D287 Test Method for API Gravity of Crude Petroleum and Petroleum Products (Hydrometer Method)
These test methods are under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and are the direct responsibility of Subcommittee
D09.01 on Electrical Insulating Varnishes, Powders and Encapsulating Compounds.
Current edition approved April 1, 2012Nov. 1, 2014. Published April 2012November 2014. Originally approved in 1941. Last previous edition approved in 20072012 as
D115 – 07.D115 – 07 (2012). DOI: 10.1520/D0115-07R12.10.1520/D0115-14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D115 − 14
D295 Test Methods for Varnished Cotton Fabrics Used for Electrical Insulation
D374 Test Methods for Thickness of Solid Electrical Insulation (Withdrawn 2013)
D580 Specification for Greige Woven Glass Tapes and Webbings
D1475 Test Method For Density of Liquid Coatings, Inks, and Related Products
D1638 Method of Testing Urethane Foam Isocyanate Raw Materials
D1932 Test Method for Thermal Endurance of Flexible Electrical Insulating Varnishes
D2518 Specification for Woven Glass Fabrics for Electrical Insulation (Withdrawn 2013)
D2519 Test Method for Bond Strength of Electrical Insulating Varnishes by the Helical Coil Test
D3145 Test Method for Thermal Endurance of Electrical Insulating Varnishes by the Helical Coil Method
D3251 Test Method for Thermal Endurance Characteristics of Electrical Insulating Varnishes Applied Over Film-Insulated
Magnet Wire
D3278 Test Methods for Flash Point of Liquids by Small Scale Closed-Cup Apparatus
D3487 Specification for Mineral Insulating Oil Used in Electrical Apparatus
D5032 Practice for Maintaining Constant Relative Humidity by Means of Aqueous Glycerin Solutions
D5423 Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation
E104 Practice for Maintaining Constant Relative Humidity by Means of Aqueous Solutions
3. Terminology
3.1 Definitions:
3.1.1 dielectric strength—strength, n—the voltage gradient at which dielectric failure of the insulating material occurs under
specific conditions of test.
3.1.2 drainage—drainage, n—of an insulating varnish, a measure of the variation in thickness from top to bottom of a varnish
film obtained on the surface of a vertically dip coated dip-coated panel after a specified time and temperature.
3.1.3 flash point—point, n—the lowest temperature of the specimen, corrected to a pressure of 760 mm Hg (101.3 kPa), at which
application of an ignition source causes any vapor from the specimen to ignite under specified conditions of test.
3.1.4 nonvolatile matter—matter, n—in insulating varnish, that portion of a varnish which is not volatilized when exposed to
specified conditions; the value obtained is not necessarily equal to the calculated solids incorporated during compounding.
The last approved version of this historical standard is referenced on www.astm.org.
3.1.4.1 Discussion—
For example, the theoretical chemical solids are often assumed to be the solid phase materials incorporated in the varnish at the
time of compounding. Many of these solid phase intermediate materials will lose volatile fractions due to the specified conditions
of the nonvolatile matter procedure. An example is phenolic resin.
3.1.5 oil resistance—resistance, n—of insulating varnish, a measure of the retention of properties after exposure to a specified
oil under specified conditions of test.
3.1.6 time of drying—drying, n—of insulating varnish, the time required for a film of varnish to dry to a tackfree state under
specified conditions.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 build, n—of an insulating varnish on copper, the average thickness of varnish film on one side of a copper panel that has
received a single coat of the varnish applied and measured under specified conditions.
3.2.2 build, n—of an insulating varnish on glass cloth, the average overall thickness of strips of glass cloth that have received
two dips of the varnish applied and measured under specified conditions.
3.2.3 tack free, tack-free, adj—condition when a varnish has reached the point that the surface can be touched lightly without
a sensation of stickiness.
3.2.4 varnish, air-drying, n—a liquid resin system that forms a dry, tack free tack-free coating, without the application of heat,
either through evaporation of solvent or by reaction with atmospheric oxygen.
3.2.5 varnish, baking, n—a liquid resin system that forms a dry, tack free tack-free coating when exposed to elevated
temperatures.
4. 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,
D115 − 14
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.
5. Hazards
5.1 Warning—Do not use varnish at temperatures above the flash point when inadequate ventilation,ventilation and the
possibility of flames or sparks exist. Store varnish in sealed containers. The precautions shall also apply to the handling of the
reagents and solvents called for herein.
6. Sampling
6.1 For all tests the sample shall be taken from a representative lot of the varnish under study. To avoid skin formation and
escape of solvents, protect the sample by keeping it at room temperature in a nearly filled, tightly sealed container.
7. Preparation of Test Specimens
7.1 Selection of Substrate—The selection of the substrate is determined in part by application and in part by thermal class. Two
types of substrates may be used: copper strip or glass cloth. Copper strip is generally not used for applications over 180°C
(356°F)(356°F), due to oxidation.
7.2 Copper Base: Base—
7.2.1 For tests that are to be performed upon the varnish as a film on a copper base, copper strips 38 mm (1 ⁄2 in.) in width,
200 mm (8 in.) in length, and 0.127 6 0.08 mm (0.005 6 0.0003 in.) in thickness shall be used, unless otherwise specified.
Measure the thickness of these strips to the nearest 0.002 mm (0.0001 in.). Clean the strips with a suitable solvent (Note 2), then
polish thoroughly with No. 000 steel wool. Wipe the strips free of any fingerprints or metal particles with the solvent and a lint-free
cloth. If the strips are not to be used immediately, they should be kept stored in a noncorrosive varnish solvent.
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 to store
the strips.For tests that are to be performed upon the varnish as a film on a copper base, copper strips 38 mm (1 ⁄2 in.) in width, 200
mm (8 in.) in length, and 0.127 6 0.08 mm (0.005 6 0.0003 in.) in thickness shall be used, unless otherwise specified. Measure
the thickness of these strips to the nearest 0.002 mm (0.0001 in.). Clean the strips with a suitable solvent (Note 2), then polish
thoroughly with No. 000 steel wool. Wipe the strips free of any fingerprints or metal particles with the solvent and a lint-free cloth.
If the strips are not to be used immediately, they should be kept stored in a noncorrosive varnish solvent.
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 to store
the strips.
7.2.1 Prepare all varnish films for tests at 23 6 1°C (73.5 6 2°F) and 50 6 5 % relative humidity. The air of the room shall
be relatively free of dust by some satisfactory method of filtering.
7.2.2 After the strips have been wiped clean and dry, prepare the test specimens by dipping them into a tank of the varnish that
has been adjusted to a proper consistency and allowed to stand covered until free of bubbles (not to exceed 1 h). 1 h). Trial testing
may be required to establish the proper consistency. Proper consistency has been reached when the strips are dipped in the varnish
at a temperature of 23 6 1°C (73.5 6 2°F) and are withdrawn slowly and uniformly at the rate of 100 mm (4 in.)/min., the average
thickness of the film remaining on each side of a strip when dry shall be 0.025 6 0.005 mm (0.0010 6 0.0002 in.).
7.2.3 Calculate the average thickness by averaging at least six measurements taken along the length of the strip and over 3 mm
( ⁄8 in.) from either edge. Thickness measurements shall be made in accordance with Test Methods D374.
7.2.4 It is recognized that the thickness of the film cannot be measured with the precision stated, but a close control of the
thickness of the varnish film is desired. With the method specified, the actual average thickness should be within 60.005 mm
(60.0002 in.) of the measured thickness.
7.2.5 With air dry varnishes, except where time of drying is the property being measured, following each dip, suspend the
specimens vertically in a dipping position and dry in dust-free air for such times and at such temperatures as the user and the
supplier agree are suitable. If necessary, readjust the consistency of the varnish and dip the specimen in the reverse direction to
the first and air dry.
D115 − 14
7.2.6 With baking varnishes, allow the specimens to drain at a temperature of 23 6 1°C (73.5 6 2°F)2°F), then bake for such
times and at such temperatures as the user and the supplier agree are suitable. If necessary, readjust the consistency of the varnish
and dip the specimen in the reverse direction to the first and bake.
7.3 Glass Cloth Base:
7.3.1 For tests that are to be performed on the varnish as a combination with glass cloth, use a glass strip instead of a copper
strip. Prepare the strip from specimens 38 mm (1.5 in.) wide by approximately 250 mm (10 in.) long from heat-cleaned woven
glass fabric (Note 3). The length shall be in the direction of the warp threads. The fabric shall be Style No. 116 as listed in Table
number 1 of Specification D2518. The volatile content of the heat-cleaned fabric shall not exceed 0.1 % as determined in
accordance with the organic content test of Specification D580 (Note 4). The strip form specimens shall be kept in a Standard
Laboratory Atmosphere (see 7.2.27.2.1).
7.3.2 Condition the heat-cleaned glass strips 1 h at 105°C (221°F) and cool in a Standard Laboratory Atmosphere before
coating.
NOTE 3—The strip form specimens may be stamped out of the woven glass fabric by means of die and clicker. This technique causes the ends of the
fibers to bind together and prevents the unraveling of the yarn.
NOTE 4—Commercially heat-cleaned fiberglass fabric meeting this volatile content is available.
7.3.3 Dipping and Curing—Condition the varnish to be tested for a minimum of 4 h at Standard Laboratory Temperature before
coating the strips. Immerse specimens in the varnish until bubbling stops. Withdraw at 100 mm (4 in.)/min. and drain in a dipping
and draining chamber in the same position as dipped for 30 min., or as agreed between the user and supplier. In order to facilitate
dipping and curing and to obtain smoother specimens, the fiberglass strips may be secured at the ends to rectangular wire frames
about 240 by 70 mm 70 mm (9.5 by 2.75 in.). 2.75 in.). Bake specimens for the time and at the temperature specified by the
manufacturer for the first coat. Apply the next coat by reverse dipping, except,except withdraw specimens as soon as immersed
and drain as for the previous coat.
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