ASTM D352-97(2008)e1

Standard Test Methods for Pasted Mica Used in Electrical Insulation

SIGNIFICANCE AND USE
This test determines the compressive creep under laboratory conditions or under conditions that may be encountered during manufacture of electrical equipment. It has special significance if the material to be tested is applied as commutator segment insulation. It serves as a measure under specified conditions of the ability of the material to resist deformation while under compressive load, during exposure to elevated temperature for a specified time. This test is suitable for acceptance tests and for manufacturing control.
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 Creep4-10  Dielectric Strength38-41  Mica or Binder Content19  Molding Test31-36  Organic Binder20-24  Resistivity42-46   Silicone Binder25-30   Stability Under Heat and Pressure11-18  
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 40.1 and 45.1 for specific hazard statements.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

General Information

• Status: Historical
• Publication Date: 30-Apr-2008
• ICS: 29.035.50 - Mica based materials
• Technical Committee: D09 - Electrical and Electronic Insulating Materials

Relations

• Replaces: ASTM D352-97(2003) - Standard Test Methods for Pasted Mica Used in Electrical Insulation
• Effective Date: 01-May-2008

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
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Designation: D352 − 97(Reapproved 2008)
Standard Test Methods for
Pasted Mica Used in Electrical Insulation
This standard is issued under the fixed designation D352; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—The units statement in subsection 1.4 was corrected editorially in July 2008.
1. Scope D1711Terminology Relating to Electrical Insulation
1.1 These test methods cover the testing of bonded mica
3. Terminology
splittings and bonded mica paper to be used for commutator
insulation, hot molding, heater plates, and other similar insu-
3.1 Definitions:
lating purposes.
3.1.1 For definitions of terms relating to electrical
insulation, refer to Terminology D1711.
1.2 These test methods appear in the following sections:
3.2 Definitions of Terms Specific to This Standard:
Test Sections
Compressive Creep 4–10 3.2.1 binder content, n, (of pasted mica)—the percent by
Dielectric Strength 38–41
weight of binder relative to the original weight of a specimen
Mica or Binder Content 19
as determined by procedures specified herein.
Molding Test 31–36
Organic Binder 20–24 3.2.1.1 Discussion—Binder content includes any residual
Resistivity 42–46
solvent.Pastedmicamaterialsnotfullycured(suchasmolding
Silicone Binder 25–30
and flexible plates) may contain appreciable quantities of
Stability Under Heat and Pressure 11–18
solvent in the binder. This solvent is usually later removed
1.3 The values stated in inch-pound units are to be regarded
when the material is cured in the manufacture of electrical
as standard. The values given in parentheses are mathematical
equipment. In such cases, the binder content after cure is less
conversions to SI units that are provided for information only
(by the amount of solvent removed) than would be determined
and are not considered standard.
by this method. To determine the binder content after cure of
1.4 This standard does not purport to address all of the
materialsthatarenotfullycured,butsubsequentlywillbe,itis
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-
specimenforatimeandatatemperaturethatdependsuponthe
priate safety and health practices and determine the applica-
material from which the specimen is prepared.
bility of regulatory limitations prior to use. See 40.1 and 45.1
3.2.2 compressive creep, n—the change in thickness of a
for specific hazard statements.
bondedmicaceousmaterialresultingfromexposuretoelevated
temperature for a specified time while a specimen is under a
2. Referenced Documents
specified compressive load.
2.1 ASTM Standards:
3.2.3 mica content, n, (of pasted mica)—the percent by
D149Test Method for Dielectric Breakdown Voltage and
weight of mica relative to the original weight equal to 100%
DielectricStrengthofSolidElectricalInsulatingMaterials
minusthebindercontentasdeterminedbyproceduresspecified
at Commercial Power Frequencies
herein.
D257Test Methods for DC Resistance or Conductance of
Insulating Materials
COMPRESSIVE CREEP
4. Significance and Use
These test methods are under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and are the direct responsibility of
4.1 This test determines the compressive creep under labo-
Subcommittee D09.19 on Dielectric Sheet and Roll Products.
ratory conditions or under conditions that may be encountered
CurrenteditionapprovedMay1,2008.PublishedJuly2008.Originallyapproved
during manufacture of electrical equipment. It has special
in 1932. Last previous edition approved in 2003 as D352–97(2003). DOI:
10.1520/D0352-97R08E01.
significance if the material to be tested is applied as commu-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
tatorsegmentinsulation.Itservesasameasureunderspecified
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
conditions of the ability of the material to resist deformation
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. while under compressive load, during exposure to elevated
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D352 − 97 (2008)
temperature for a specified time. This test is suitable for specimen to remain at the specified temperature for 2 h after
acceptance tests and for manufacturing control. reaching that temperature, and at the same time maintain the
1000-psi pressure.
5. Apparatus
7.3 Remove the thermal insulation and, while maintaining
the pressure, allow the specimen to cool until the temperature
5.1 Hydraulic Press—Ahydraulic press having temperature
is 5°C above the temperature (room ambient) at which the
controlled, electrically heated platens, or a press with other
original thickness was measured. Control the rate of cooling
provisions for heating the specimen and controlling the tem-
such that it does not exceed the rate at which the temperature
perature. The platens shall be at least 4 by 4 in. (102 by 102
was raised. Then determine the thickness of the stack while
mm) in size. The press shall be capable of exerting a force of
under 1000-psi compressive load.
at least 4000 lb (18 kN). The apparatus shall be capable of
maintaining a specimen temperature of at least 200 6 5°C. It
NOTE1—Experiencehasshownthatinordertocoolthespecimentothe
ispreferablethattheapparatushaveplatenswithwaterductsor
specified temperature within a reasonable time, forced-cooling means
must be employed. It is suggested that a fan be initially utilized to force
other provisions for cooling the specimen. (See Note 1 in 7.3.)
air across the specimen for the first 5 min, after which cooling water may
5.2 Pressure Gage—Apressuregagecapableofdetermining
be allowed to circulate in ducts provided in the platens. The rate of water
the pressure on the specimen with an accuracy of 65%. flow, if used, should be adjusted to give a cooling rate no greater than the
rate at which the specimen was initially heated.
5.3 Thickness Gage—A thickness gage capable of measur-
ingthethicknessofthespecimentothenearest0.001in.(0.025
8. Calculation
mm).
8.1 Calculate the percentage compressive creep, C, as fol-
5.4 Potentiometer—Temperature measuring instrument and
lows:
a No. 30AWG or smaller thermocouple with overall accuracy
C,% 5 T 2 T' /T 3100 (1)
@~ ! #
of 62°C for measurement of specimen temperature.
where:
5.5 Steel Plates—Two 4 by 4-in. (102 by 102-mm) or larger
1 T = thickness of the stack at 1000 psi (7 MPa) before
polished steel plates of at least ⁄16-in. (1.6-mm) thickness,
heating, and
surface ground so that the top and bottom surfaces of each
T' = thickness of the stack at 1000 psi after heating.
piece are parallel, one plate each for the top and bottom of the
test specimen.
9. Report
6. Test Specimen 9.1 Report the following information:
9.1.1 The identity of the material,
6.1 Thetestspecimenshallconsistofasufficientnumberof
9.1.2 The nominal thickness of the pasted mica,
pieces of bonded micaceous plate, 2 by 2 in. (51 by 51 mm) in
9.1.3 The observed values of T and T',
size, to form a stack approximately but not greater than 1.000
9.1.4 The percentage compressive creep, and
in. (25.40 mm) in thickness. The pieces shall be selected so as
9.1.5 The specimen temperature.
toberepresentativeoftheentiresheet.Atleastthreespecimens
shall be tested for each lot of material.
10. Precision and Bias
7. Procedure
10.1 This method has been in use for many years but no
statement for precision has been made and no activity is
7.1 Centerthestackedspecimenbetweenthe4by4-in.(102
planned to develop such a statement.
by 102-mm) steel plates and then center this assembly in the
10.2 A statement of bias is not possible due to a lack of a
press. Place the thermocouple between pieces near the middle
standard reference material.
of the stack. Carefully align the stack to form a right parallel-
epiped.Apply a pressure of 1000 psi (7 MPa) to the specimen
STABILITY UNDER HEAT AND PRESSURE
surfaces, and carefully determine the average thickness of the
stack by means of the gage. Where inside gages are used,
11. Scope
measurethethicknessateachofthefourcornersasclosetothe
specimen as possible. Measurements shall be made within 5
11.1 The test for stability under heat and pressure deter-
min.
minesmicaorbinderdisplacement,orboth,underthespecified
conditions of test.
7.2 Pack approximately 2 in. (51 mm) of thermal insulation
material around the specimen without disturbing it. Heat the
12. Significance and Use
specimen to 160 6 5°C or 200 6 5°C as specified. The time
required to reach the specified temperature should be not less 12.1 This test serves as a measure of the ability of bonded
than 30 min nor more than 75 min. The platen temperature micaceous materials to maintain their physical integrity under
shall not exceed the specified temperature by more than the exposuretoheatandpressure.Ithasspecialsignificancewhere
specified tolerance. If the specimen is heated by other means, the material to be tested is employed as commutator segment
the surrounding medium shall not exceed the specified tem- insulation. This test is suitable for acceptance tests and for
perature by more than the specified tolerance. Allow the manufacturing control.
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D352 − 97 (2008)
13. Nature of Test 16.2 Pack approximately 2 in. (51 mm) of thermal insulat-
ing material, such as glass or other inorganic fiber mat, around
13.1 This test method utilizes the application of a shearing
the specimen without disturbing either the specimen or dial
forceaswellasacompressiveforce,whichisaccomplishedby
gages. Heat the specimen to 160 6 5°C or 200 6 5°C, as
placing the specimens between specified wedges, thereby
specified, and allow to remain at the specified temperature for
causingtheappliedforcetoresolveintocompressionandshear
5+1,−0 min. Do not allow the platen temperature to exceed
components.Thistestisparticularlyusefulformaterialusedin
the specimen temperature by more than 10°C.
commutator assemblies where shearing as well as compressive
forces are encountered. Test results are expressed quantita- 16.3 Adjust both gages to read zero. Apply and hold a
tively as units of linear deflection. pressureof4400psi(30MPa)within5sonthetopandbottom
assembly surfaces and maintain for 15 min at the specified
14. Apparatus
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
14.1 Hydraulic Press, Pressure Gage, and Thermocoupleas
beginning with the instant that the 4400 psi pressure is
described in Section 5, except that the hydraulic press shall be
obtained.
capable of producing a force of 26400 lb (118 kN) on the
specimen,
17. Report
14.2 Steel Wedges—Two steel wedges of the same size as
17.1 Report the following information:
the specimen by approximately ⁄4 in. (19 mm) thick, with one
17.1.1 The identity of the material,
face tapered at an angle of 3° with the horizontal and a center
17.1.2 The dimensions of the specimen used,
wedge as shown in Fig. 1. They shall be hardened and surface
17.1.3 The temperature used, and
ground top and bottom.
17.1.4 Theaveragedeflectionateachofthetimeintervalsin
14.3 Dial Gages—Two dial gages having 0.001-in. (0.02-
accordance with 16.3.
mm) graduations and a range of at least ⁄2-in. (13-mm),
designed to be accurate at the specified test temperature, and 18. Precision and Bias
suitably mounted on the steel wedges described in 14.2.
18.1 See 10.1.
NOTE 2—Where the dial gages are mounted through nonmetallic
18.2 See 10.2.
bushings,orifsomeothersuitablemethodisusedtointerruptthemetallic
thermal path, it shall not be necessary to utilize gages designed to be
MICA OR BINDER CONTENT
accurate at the test temperature.
19. Significance and Use
15. Test Specimen
19.1 Physical (such as the ability to hot mold, flexibility)
15.1 Thespecimenshallconsistoftworectangularpiecesof
andelectrical(suchasdielectricstrength,resistivity)properties
bonded micaceous plate between 4 and 6 in. (2580 and 3870
of bonded micaceous materials are affected, among other
mm ) in area, the shorter side being not less than 1 ⁄2 in. (38
things,bytheproportionalcontentsofthebinderandmica.The
mm).
methods for mica or binder content are suitable for acceptance
tests and manufacturing control.
16. Procedure
ORGANIC BINDER
16.1 Insert the specimen between the wedges, as shown in
Fig. 1. Center the assembly in the press and carefully align,
20. Apparatus
usingjustenoughpressuretoholdtheassemblytogether.Insert
the thermocouple and fit it tightly in the hole provided in the
20.1 Burner—Bunsen burner or muffle furnace.
center wedge. Cement the thermocouple into the hole.Apply a
20.2 Dishes—Platinum or porcelain dishes or crucibles.
pressureof100 610psi(690 670kPa)onthetopandbottom
assembly surfaces.
21. Test Specimen
21.1 Specimens from Plates—From a plate, cut a sufficient
numberofindividualpiecesinaccordancewithFig.2toobtain
a composite specimen weighing 5 to 10 g.
21.2 Specimens From Fabricated Parts—From a lot, take a
representative test specimen weighing 5 to 10 g.
22. Procedure
22.1 Warning—Thistestmethodinvolvestheuseofheatto
remove organic material which in a gaseous state may be
hazardous. Conduct this test under a hood equipped with
adequate ventilation. Alternatively, a muffle furnace with an
Minimum size of sheet: A = 3 in.; B=18in.
adequateexhaustsystemmaybeusedtoburnoffthemicauntil
FIG. 1 Apparatus for Stability Test Under Heat and Pressure, An-
gular Method it is carbon free.
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D352 − 97 (2008)
NOTE 3—It is not necessary to use the glass fiber mat of 25.1 if a test
specimen contains bonded mica splittings.
26. Reagents
26.1 Butyl Alcohol, normal, cp grade.
26.2 Toluol, cp grade.
26.3 Alkaline Solvent—Dissolve about5gof potassium
hydroxide (KOH) (ACS grade) in 100-mL normal butyl
alcohol and add 400 mL of toluol.
26.4 Ethyl Alcohol, cp grade.
FIG. 2 Pattern for Location of Test Pieces for Determination of
27. Test Specimen
Mica of Binder Content
27.1 Refer to Fig. 2. Cut sufficient material into pieces
approximately ⁄4 in. (6 mm) size to obtain a specimen of 1 to
22.2 Weigh each specimen to the nearest 0.001 g in a tared
1.5 g.
dish or crucible.
28. Procedure
22.3 Place the dish with the specimen over a bunsen burner
28.1 Warning—This test method involves the use of
or in a muffle furnace and heat at a lo
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