ASTM D352-97

Standard Test Methods for Pasted Mica Used in Electrical Insulation

SCOPE
1.1 These test methods cover the testing of bonded mica splittings and bonded mica paper to be used for commutator insulation, hot molding, heater plates, and other similar insulating purposes.  
1.2 These test methods appear in the following sections:  Test Sections Compressive Creep 4 to 10 Dielectric Strength 38 to 41 Mica or Binder Content 19 Molding Test 31 to 37 Organic Binder 20 to 24 Resistivity 42 to 46 Silicone Binder 25 to 30 Stability Under Heat and Pressure 11 to 18
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. See Notes 3 and 5 and 38.1 and 43.1 for specific hazard statements.
1.4 The values stated in inch-pound units are to be regarded as the standard.

General Information

• Status: Historical
• Publication Date: 09-Sep-1997
• Technical Committee: D09 - Electrical and Electronic Insulating Materials

Relations

• Replaced By: ASTM D352-97(2003) - Standard Test Methods for Pasted Mica Used in Electrical Insulation
• Effective Date: 10-Mar-2003

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
An American National Standard
Designation: D 352 – 97
Standard Test Methods for
Pasted Mica Used in Electrical Insulation
This standard is issued under the fixed designation D 352; 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 3.2.1 compressive creep, n—the change in thickness of a
bonded micaceous material resulting from exposure to elevated
1.1 These test methods cover the testing of bonded mica
temperature for a specified time while a specimen is under a
splittings and bonded mica paper to be used for commutator
specified compressive load.
insulation, hot molding, heater plates, and other similar insu-
3.2.2 binder content, n, (of pasted mica)—the percent by
lating purposes.
weight of binder relative to the original weight of a specimen
1.2 These test methods appear in the following sections:
as determined by procedures specified herein.
Test Sections
3.2.2.1 Discussion—Binder content includes any residual
Compressive Creep 4-10
solvent. Pasted mica materials not fully cured (such as molding
Dielectric Strength 38-41
Mica or Binder Content 19 and flexible plates) may contain appreciable quantities of
Molding Test 31-36
solvent in the binder. This solvent is usually later removed
Organic Binder 20-24
when the material is cured in the manufacture of electrical
Resistivity 42-46
equipment. In such cases, the binder content after cure is less
Silicone Binder 25-30
(by the amount of solvent removed) than would be determined
Stability Under Heat and Pressure 11-18
by this method. To determine the binder content after cure of
1.3 This standard does not purport to address all of the
materials that are not fully cured, but subsequently will be, it is
safety concerns, if any, associated with its use. It is the
necessary, before initially weighing the specimen, to heat the
responsibility of the user of this standard to establish appro-
specimen for a time and at a temperature that depends upon the
priate safety and health practices and determine the applica-
material from which the specimen is prepared.
bility of regulatory limitations prior to use. See Note 3 and
3.2.3 mica content, n, (of pasted mica)—the percent by
Note 5 and 38.1 and 43.1 for specific hazard statements.
weight of mica relative to the original weight equal to 100 %
1.4 The values stated in inch-pound units are to be regarded
minus the binder content as determined by procedures specified
as the standard.
herein.
2. Referenced Documents
COMPRESSIVE CREEP
2.1 ASTM Standards:
4. Significance and Use
D 149 Test Method for Dielectric Breakdown Voltage and
Dielectric Strength of Solid Electrical Insulating Materials 4.1 This test determines the compressive creep under labo-
at Commercial Power Frequencies ratory conditions or under conditions that may be encountered
D 257 Test Methods for D-C Resistance or Conductance of during manufacture of electrical equipment. It has special
Insulating Materials significance if the material to be tested is applied as commu-
D 1711 Terminology Relating to Electrical Insulation tator segment insulation. It serves as a measure under specified
conditions of the ability of the material to resist deformation
3. Terminology
while under compressive load, during exposure to elevated
3.1 Definitions:
temperature for a specified time. This test is suitable for
3.1.1 For definitions of terms relating to electrical insula- acceptance tests and for manufacturing control.
tion, refer to Terminology D 1711.
5. Apparatus
3.2 Definitions of Terms Specific to This Standard:
5.1 Hydraulic Press—A hydraulic press having temperature
controlled, electrically heated platens, or a press with other
These test methods are under the jurisdiction of ASTM Committee D-9 on
provisions for heating the specimen and controlling the tem-
Electrical and Electronic Insulating Materials and are the direct responsibility of
perature. The platens shall be at least 4 by 4 in. (102 by 102
Subcommittee D09.19 on Dielectric Sheet and Roll Products.
mm) in size. The press shall be capable of exerting a force of
Current edition approved Sept. 10, 1997. Published December 1997. Originally
published as D 352 – 32 T. Last previous edition D 352 – 92.
at least 4000 lb (18 kN). The apparatus shall be capable of
Annual Book of ASTM Standards,Vol 10.01.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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D352–97
be allowed to circulate in ducts provided in the platens. The rate of water
maintaining a specimen temperature of at least 200 6 5°C. It
flow, if used, should be adjusted to give a cooling rate no greater than the
is preferable that the apparatus have platens with water ducts or
rate at which the specimen was initially heated.
other provisions for cooling the specimen. (See Note 1 in 7.3.)
5.2 Pressure Gage—A pressure gage capable of determin-
8. Calculation
ing the pressure on the specimen with an accuracy of 65%.
8.1 Calculate the percentage compressive creep, C, as fol-
5.3 Thickness Gage—A thickness gage capable of measur-
lows:
ing the thickness of the specimen to the nearest 0.001 in. (0.025
C,% 5 @~T 2 T8!/T# 3 100 (1)
mm).
5.4 Potentiometer—Temperature measuring instrument and
where:
a No. 30 AWG or smaller thermocouple with overall accuracy
T = thickness of the stack at 1000 psi (7 MPa) before
of 62°C for measurement of specimen temperature.
heating, and
5.5 Steel Plates—Two 4 by 4-in. (102 by 102-mm) or larger
T8 = thickness of the stack at 1000 psi after heating.
polished steel plates of at least ⁄16-in. (1.6-mm) thickness,
surface ground so that the top and bottom surfaces of each
9. Report
piece are parallel, one plate each for the top and bottom of the
9.1 Report the following information:
test specimen.
9.1.1 The identity of the material,
9.1.2 The nominal thickness of the pasted mica,
6. Test Specimen
9.1.3 The observed values of T and T8,
6.1 The test specimen shall consist of a sufficient number of
9.1.4 The percentage compressive creep, and
pieces of bonded micaceous plate, 2 by 2 in. (51 by 51 mm) in
9.1.5 The specimen temperature.
size, to form a stack approximately but not greater than 1.000
in. (25.40 mm) in thickness. The pieces shall be selected so as
10. Precision and Bias
to be representative of the entire sheet. At least three specimens
10.1 This method has been in use for many years but no
shall be tested for each lot of material.
statement for precision has been made and no activity is
7. Procedure planned to develop such a statement.
10.2 A statement of bias is not possible due to a lack of a
7.1 Center the stacked specimen between the 4 by 4-in. (102
standard reference material.
by 102-mm) steel plates and then center this assembly in the
press. Place the thermocouple between pieces near the middle
STABILITY UNDER HEAT AND PRESSURE
of the stack. Carefully align the stack to form a right parallel-
epiped. Apply a pressure of 1000 psi (7 MPa) to the specimen
11. Scope
surfaces, and carefully determine the average thickness of the
11.1 The test for stability under heat and pressure deter-
stack by means of the gage. Where inside gages are used,
mines mica or binder displacement, or both, under the specified
measure the thickness at each of the four corners as close to the
conditions of test.
specimen as possible. Measurements shall be made within 5
min.
12. Significance and Use
7.2 Pack approximately 2 in. (51 mm) of thermal insulation
12.1 This test serves as a measure of the ability of bonded
material around the specimen without disturbing it. Heat the
micaceous materials to maintain their physical integrity under
specimen to 1606 5°C or 200 6 5°C as specified. The time
exposure to heat and pressure. It has special significance where
required to reach the specified temperature should be not less
the material to be tested is employed as commutator segment
than 30 min nor more than 75 min. The platen temperature
insulation. This test is suitable for acceptance tests and for
shall not exceed the specified temperature by more than the
manufacturing control.
specified tolerance. If the specimen is heated by other means,
the surrounding medium shall not exceed the specified tem-
13. Nature of Test
perature by more than the specified tolerance. Allow the
13.1 This test method utilizes the application of a shearing
specimen to remain at the specified temperature for 2 h after
force as well as a compressive force, which is accomplished by
reaching that temperature, and at the same time maintain the
placing the specimens between specified wedges, thereby
1000-psi pressure.
causing the applied force to resolve into compression and shear
7.3 Remove the thermal insulation and, while maintaining
components. This test is particularly useful for material used in
the pressure, allow the specimen to cool until the temperature
commutator assemblies where shearing as well as compressive
is 5°C above the temperature (room ambient) at which the
forces are encountered. Test results are expressed quantita-
original thickness was measured. Control the rate of cooling
such that it does not exceed the rate at which the temperature tively as units of linear deflection.
was raised. Then determine the thickness of the stack while
14. Apparatus
under 1000-psi compressive load.
14.1 Hydraulic Press, Pressure Gage, and Thermocou-
NOTE 1—Experience has shown that in order to cool the specimen to
ple as described in Section 5, except that the hydraulic press
the specified temperature within a reasonable time, forced-cooling means
shall be capable of producing a force of 26 400 lb (118 kN) on
must be employed. It is suggested that a fan be initially utilized to force
air across the specimen for the first 5 min, after which cooling water may the specimen,
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
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D352–97
14.2 Steel Wedges—Two steel wedges of the same size as 17.1.2 The dimensions of the specimen used,
the specimen by approximately ⁄4 in. (19 mm) thick, with one 17.1.3 The temperature used, and
face tapered at an angle of 3° with the horizontal and a center 17.1.4 The average deflection at each of the time intervals in
wedge as shown in Fig. 1. They shall be hardened and surface accordance with 16.3.
ground top and bottom.
18. Precision and Bias
14.3 Dial Gages—Two dial gages having 0.001-in. (0.02-
mm) graduations and a range of at least ⁄2-in. (13-mm),
18.1 See 10.1.
designed to be accurate at the specified test temperature, and
18.2 See 10.2.
suitably mounted on the steel wedges described in 14.2.
MICA OR BINDER CONTENT
NOTE 2—Where the dial gages are mounted through nonmetallic
bushings, or if some other suitable method is used to interrupt the metallic
19. Significance and Use
thermal path, it shall not be necessary to utilize gages designed to be
19.1 Physical (such as the ability to hot mold, flexibility)
accurate at the test temperature.
and electrical (such as dielectric strength, resistivity) properties
15. Test Specimen
of bonded micaceous materials are affected, among other
15.1 The specimen shall consist of two rectangular pieces of things, by the proportional contents of the binder and mica. The
bonded micaceous plate between 4 and 6 in. (2580 and 3870 methods for mica or binder content are suitable for acceptance
mm ) in area, the shorter side being not less than 1 ⁄2 in. (38 tests and manufacturing control.
mm).
ORGANIC BINDER
16. Procedure
20. Apparatus
16.1 Insert the specimen between the wedges, as shown in
20.1 Burner—Bunsen burner or muffle furnace.
Fig. 1. Center the assembly in the press and carefully align,
20.2 Dishes—Platinum or porcelain dishes or crucibles.
using just enough pressure to hold the assembly together. Insert
the thermocouple and fit it tightly in the hole provided in the
21. Test Specimen
center wedge. Cement the thermocouple into the hole. Apply a
pressure of 100 6 10 psi (690 6 70 kPa) on the top and bottom 21.1 Specimens from Plates—From a plate, cut a sufficient
assembly surfaces. number of individual pieces in accordance with Fig. 2 to obtain
16.2 Pack approximately 2 in. (51 mm) of thermal insulat- a composite specimen weighing 5 to 10 g.
21.2 Specimens From Fabricated Parts— From a lot, take a
ing material, such as glass or other inorganic fiber mat, around
the specimen without disturbing either the specimen or dial representative test specimen weighing 5 to 10 g.
gages. Heat the specimen to 160 6 5°C or 200 6 5°C, as
22. Procedure
specified, and allow to remain at the specified temperature for
5 +1, −0 min. Do not allow the platen temperature to exceed
NOTE 3—Caution: This test method involves the use of heat to remove
the specimen temperature by more than 10°C.
organic material which in a gaseous state may be hazardous. Conduct this
16.3 Adjust both gages to read zero. Apply and hold a test under a hood equipped with adequate ventilation. Alternatively, a
muffle furnace with an adequate exhaust system may be used to burn off
pressure of 4400 psi (30 MPa) within5sonthetopand bottom
the mica until it is carbon free.
assembly surfaces and maintain for 15 min at the specified
22.1 Weigh each specimen to the nearest 0.001 g in a tared
temperature. Record the deflection as determined by the top
and bottom dial gages after 15 s, 30 s, 1, 2, 5, 10, and 15 min dish or crucible.
22.2 Place the dish with the specimen over a bunsen burner
beginning with the instant that the 4400 psi pressure is
obtained. or in a muffle furnace and heat at a low red heat (to avoid the
dehydration of mica) until all the organic material and carbon
17. Report
are burned off. After cooling in a desiccator, determine the
weight of the residue.
17.1 Report the following information:
17.1.1 The identity of the material,
Minimum size of sheet: A = 3 in.; B = 18 in.
FIG. 1 Apparatus for Stability Test Under Heat and Pressure, FIG. 2 Pattern for Location of Test Pieces for Determination of
Angular Method Mica of Binder Content
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D352–97
23. Report solvent to
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