ASTM D2519-96

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
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Designation: D 2519 – 96 An American National Standard
Standard Test Method for
Bond Strength of Electrical Insulating Varnishes by the
Helical Coil Test
This standard is issued under the fixed designation D 2519; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope recording device to react to change in stress on a specimen
under test.
1.1 This test method covers determination of the bond
strength of an electrical insulating varnish when applied to a
4. Summary of Test Method
helical coil. The helical coil can be made from bare aluminum
4.1 Flexural strength tests are made on varnish-treated
or copper wire or from film or fiber-insulated magnet wire.
helical coils to determine the force required to break the coil
Helical coils made from bare aluminum or bare copper wire
under specified conditions.
will yield values of bond strength for the varnish when applied
to bare metal conductors. The use of film or fiber-insulated
5. Significance and Use
magnet wire will show values for that particular combination
5.1 Values obtained by flexural tests can provide informa-
of insulation and varnish.
tion with regard to the bond strength of the particular varnish,
1.2 The values stated in SI units are to be regarded as the
in combination with a particular wire, when measured under
standard. The values given in parentheses are for information
conditions described in this test method.
only.
1.3 This standard does not purport to address all of the
6. Apparatus
safety concerns, if any, associated with its use. It is the
6.1 Tensile Testing Machine—An adjustable-speed drive
responsibility of the user of this standard to establish appro-
and a suitable instrument for measuring force should be used in
priate safety and health practices and determine the applica-
breaking the specimen. This may be in the form of one of the
bility of regulatory limitations prior to use. See Section 7.
generally available tensile testing machines, or may be simply
an accurate spring gage and a separate adjustable-speed drive.
2. Referenced Documents
To cover the range of load strength values which are commonly
2.1 ASTM Standards:
encountered it is recommended that a multirange tester be
D 115 Test Methods for Testing Solvent Containing Var-
2 used.
nishes Used for Electrical Insulation
6.1.1 It has been found that gages rated 5, 25, 150, and
D 618 Practice for Conditioning Plastics and Electrical
3 500 N or (1, 5, 30, and 100 lbf) are adequate to cover the range
Insulating Materials for Testing
of varnishes.
6.2 Test Fixture—The test fixture shall consist essentially of
3. Terminology
two rollers, attached to a common frame, to be pulled in one
3.1 Definitions:
direction, and a 90° V-block to be pulled in the opposite
3.1.1 bond strength—a measure of the force required to
direction. There shall be no friction contact which will affect
separate surfaces which have been bonded together.
this movement. The general shape and the relative position of
3.2 Definitions of Terms Specific to This Standard:
these parts is shown in Fig. 1. The rollers shall have a diameter
3.2.1 event time—the time between initial application of a
of 9.5 mm (0.375 in.) at the center and shall be parallel having
physical or electrical stress and failure of the specimen under
a center-to-center distance of 44.5 mm (1.75 in.). The 90°
test.
V-block shall have a radius at the apex of 0.8 mm (0.03 in.).
3.2.2 response time—the time required for an indicating or
6.3 Test Fixture Enclosure—For tests at other than room
temperature, an insulated heat-resistant enclosure, designed to
This test method is under the jurisdiction of ASTM Committee D-9 on fit around the test fixture and into the tension testing machine,
Electrical and Electronic Insulating Materials and is the direct responsibility of
should be used. This enclosure should permit a frictionless
Subcommittee D09.01 on Electrical Insulating Varnishes, Powders, and Encapsu-
lating Compounds.
Current edition approved March 10, 1996. Published May 1996. Originally
published as D 2519 – 66 T. Last previous edition D 2519 – 91. Spring gages from John Chattilon and Sons, 83-30 Kew Gardens Road, Kew
Annual Book of ASTM Standards, Vol 10.01. Gardens, NY 11415 or from Hunter Spring Co., One Spring Avenue, Hatfield, PA
Annual Book of ASTM Standards, Vol 08.01. 19440, or its equivalent, have been found satisfactory for this purpose.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 2519
8.1.4 Fiber-insulated magnet wire.
NOTE 1—A practical method of winding a tight helical coil is to guide
the wire from the rotating reel between folds of a clean cloth onto the
rotating mandrel using moderate hand tension. A trailing angle of 1 to 5°
from a perpendicular to the mandrel should be maintained. When the wire
is cut, the coil must be restrained to avoid rapid spring back.
8.2 The type of wire should be mutually agreed upon
between the supplier and the user.
8.3 Prepare six or more specimens for each condition to be
investigated.
8.4 Adjust the viscosity of the varnish to be tested, by trial,
to produce a dry film build of 0.043 to 0.053 mm (0.0017 to
0.0021 in.) on a double coated aluminum panel coated in
accordance with Test Methods D 115.
8.5 Coils made from bare wire shall be immersed in a
solvent of 50 % toluene and 50 % denatured alcohol by weight
for 30 min, removed and dried for 15 min a
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