ASTM D7895/D7895M-19

Standard Test Method for Thermal Endurance of Coating Powders Used for Powder Coating Insulation Systems

SIGNIFICANCE AND USE
5.1 A major factor affecting the life of insulating materials is thermal degradation. It is possible that other factors, such as moisture and vibration, will cause failures after the material has been weakened by thermal degradation.  
5.2 Electrical insulation is effective in electrical equipment only as long as it retains its physical and electrical integrity. The following are potential indicators of thermal degradation: weight change, porosity, crazing, and generally a reduction in flexibility. Thermal degradation is usually accompanied by an ultimate reduction in dielectric breakdown.  
5.3 This test method is useful in determining the thermal endurance of coating powders applied over a steel substrate material.
SCOPE
1.1 This test method provides a procedure for evaluating thermal endurance of coating powders by determining the length of aging time at selected elevated temperatures required to achieve dielectric breakdown at room temperature at a pre-determined proof voltage. Thermal endurance is expressed in terms of a temperature index.  
1.2 This test method is applicable to insulating powders used over a substrate material of steel.  
1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems is likely to result in non-conformance with the standard.  
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. Specific precautionary statements are given in Section 7.  
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

• Status: Published
• Publication Date: 31-Oct-2019
• ICS: 29.060.10 - Wires
• ICS: 29.080.01 - Electrical insulation in general
• ICS: 87.040 - Paints and varnishes
• Technical Committee: D09 - Electrical and Electronic Insulating Materials
• Drafting Committee: D09.01 - Electrical Insulating Products

Relations

• Replaces: ASTM D7895/D7895M-14(2018) - Standard Test Method for Thermal Endurance of Coating Powders Used for Powder Coating Insulation Systems
• Effective Date: 01-Nov-2019
• Refers: ASTM D1711-24 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Mar-2024
• Refers: ASTM D149-20 - Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies
• Effective Date: 01-Jan-2020
• Refers: ASTM D1711-15 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2015
• Refers: ASTM D1711-14a - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2014
• Refers: ASTM D1711-14 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-May-2014
• Refers: ASTM D1711-13 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2013
• Refers: ASTM D1711-11a - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Aug-2011
• Refers: ASTM D1711-08 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-May-2008
• Refers: ASTM D5423-93(2005) - Standard Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation (Withdrawn 2014)
• Effective Date: 01-Sep-2005
• Refers: ASTM D149-97a(2004) - Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies
• Effective Date: 01-Mar-2004
• Refers: ASTM D1711-02 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 10-Mar-2002
• Refers: ASTM D1711-99 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 10-Oct-1999
• Refers: ASTM D5423-93(1999) - Standard Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation
• Effective Date: 10-Mar-1999
• Refers: ASTM D149-97a - Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies
• Effective Date: 01-Jan-1997

Overview

ASTM D7895/D7895M-19 is the internationally recognized standard test method for assessing the thermal endurance of coating powders used in powder coating insulation systems, specifically over steel substrates. Published by ASTM International, this standard defines procedures to determine how long insulating coating powders maintain their electrical integrity when subjected to elevated temperatures. This is crucial for estimating product lifespan and ensuring reliable electrical insulation in various industrial applications.

Thermal degradation severely impacts the effectiveness of electrical insulation materials. ASTM D7895/D7895M-19 helps identify when thermal damage compromises the insulation, signaling end-of-life for a coating. The standard provides a framework for manufacturers, quality control professionals, and materials engineers to evaluate and compare insulating powders used in bus bars, electrical panels, and other systems requiring durable thermal insulation.

Key Topics

• Thermal Endurance Assessment: The standard outlines a method to evaluate how long an insulating powder withstands high temperatures before its dielectric breakdown voltage diminishes below a defined threshold.
• Temperature Index Calculation: The method results in a temperature index, representing the highest temperature at which a coating can maintain its properties over a predefined period.
• Testing Procedure:
  • Specimens coated over steel substrates are aged at three or more elevated temperatures.
  • Periodic dielectric strength tests at room temperature indicate the onset of breakdown.
  • Testing includes cycles of high temperature, cold exposure, mechanical vibration, and high humidity to simulate real-world stress.
• Indicators of Degradation: Weight change, porosity, cracking (crazing), flexibility reduction, and loss of dielectric strength are monitored.
• Specimen Preparation: Requires at least 50 coated steel specimens, with consistent geometry suited for practical use cases.
• Safety Considerations: Addresses hazards associated with high-voltage testing and appropriate safety practices.

Applications

ASTM D7895/D7895M-19 is vital for industries relying on powder-coated electrical insulation systems. Key application areas include:

• Electrical Equipment Manufacturing: For validating insulation coatings on bus bars, switchgear, and motor windings used in industrial, commercial, and utility-scale power systems.
• Quality Assurance: Manufacturers use this test to benchmark and certify the thermal endurance of their powder coatings, ensuring compliance with safety and reliability requirements.
• Materials Development: R&D teams apply the standard when developing new insulating powders or improving existing formulations to withstand higher operating temperatures.
• Regulatory Compliance: Facilitates adherence to both domestic and international regulations regarding insulation materials and end-use safety standards.

Using ASTM D7895/D7895M-19 provides a quantifiable measure-the temperature index-for purchasing and specifying powder coatings in critical electrical insulation applications.

Related Standards

Understanding and applying ASTM D7895/D7895M-19 often involves referencing additional standards, including:

• ASTM D149: Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies.
• ASTM D1711: Terminology Relating to Electrical Insulation-ensures consistent definitions across tests.
• ASTM D5423: Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation-guides oven requirements for thermal aging.
• IEEE 101A: Simplified Method for Calculation of the Regression Line-used in data analysis for calculating the temperature index.

Adhering to these related standards and ASTM D7895/D7895M-19 ensures robust and consistent evaluation of powder coating insulation systems, supporting both product reliability and customer safety.

Keywords: ASTM D7895, powder coating insulation, thermal endurance, dielectric breakdown, temperature index, electrical insulating materials, steel substrate, insulation system testing

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: D7895/D7895M − 19
Standard Test Method for
Thermal Endurance of Coating Powders Used for Powder
Coating Insulation Systems
This standard is issued under the fixed designation D7895/D7895M; 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 at Commercial Power Frequencies
D1711 Terminology Relating to Electrical Insulation
1.1 This test method provides a procedure for evaluating
D5423 Specification for Forced-Convection Laboratory Ov-
thermal endurance of coating powders by determining the
ens for Evaluation of Electrical Insulation
length of aging time at selected elevated temperatures required
2.2 IEEE Document
to achieve dielectric breakdown at room temperature at a
IEEE 101A Simplified Method for Calculation of the Re-
pre-determined proof voltage. Thermal endurance is expressed
gression Line
in terms of a temperature index.
1.2 This test method is applicable to insulating powders
3. Terminology
used over a substrate material of steel.
3.1 Definitions:
1.3 Units—The values stated in either SI units or inch-
3.1.1 For definitions of terms used in this test method refer
pound units are to be regarded separately as standard. The
to Terminology D1711.
values stated in each system are not necessarily exact equiva-
3.2 Definitions of Terms Specific to This Standard:
lents; therefore, each system shall be used independently of the
3.2.1 thermal endurance, n—an expression for the stability
other. Combining values from the two systems is likely to
of an electrical insulating material, or a simple combination of
result in non-conformance with the standard.
materials, when maintained at elevated temperatures for ex-
tended periods of time.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.3 Definitions—For definitions of terms used in this test
responsibility of the user of this standard to establish appro-
method refer to Terminology D1711.
priate safety, health, and environmental practices and deter-
4. Summary of Test Method
mine the applicability of regulatory limitations prior to use.
Specific precautionary statements are given in Section 7.
4.1 Specimens are aged in air at a minimum of three
1.5 This international standard was developed in accor-
temperatures above the expected use temperature of the mate-
dance with internationally recognized principles on standard-
rial. Exposure to ambient stress conditions, followed by
ization established in the Decision on Principles for the
dielectric proof voltage tests in an electrically conductive
Development of International Standards, Guides and Recom-
solution, are periodically conducted to determine the time of
mendations issued by the World Trade Organization Technical
aging at each elevated temperature required to reduce the
Barriers to Trade (TBT) Committee.
breakdown voltage to a preselected percentage of the original
breakdown value. These thermal life values are used to
2. Referenced Documents
construct a thermal endurance graph by means of which it is
2.1 ASTM Standards:
possible to estimate a temperature index, corresponding to a
D149 Test Method for Dielectric Breakdown Voltage and
thermal life as specified in the material specification or as
Dielectric Strength of Solid Electrical Insulating Materials
agreed upon between the user and the supplier. It is possible
that a material will have multiple indices, each corresponding
to a different thermal life as required by a given application.
This test method is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of
5. Significance and Use
Subcommittee D09.01 on Electrical Insulating Products.
Current edition approved Nov. 1, 2019. Published November 2019. Originally
5.1 Amajorfactoraffectingthelifeofinsulatingmaterialsis
approved in 2014. Last previous edition approved in 2018 as D7895/
thermal degradation. It is possible that other factors, such as
D7895M – 14 (2018). DOI: 10.1520/D7895_D7895M-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE),
the ASTM website. 445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331, http://www.ieee.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7895/D7895M − 19
moisture and vibration, will cause failures after the material apparatus, and all associated equipment electrically connected
has been weakened by thermal degradation. to it, be properly designed and installed for safe operation.
Solidly ground all electrically conductive parts which are
5.2 Electrical insulation is effective in electrical equipment
possible for a person to contact during the test. Provide means
only as long as it retains its physical and electrical integrity.
for use at the completion of any test to ground any parts which
The following are potential indicators of thermal degradation:
were at high voltage during the test, or have the potential for
weight change, porosity, crazing, and generally a reduction in
acquiring an induced charge during the test, or retaining a
flexibility. Thermal degradation is usually accompanied by an
charge even after disconnection of the voltage source. Thor-
ultimate reduction in dielectric breakdown.
oughly instruct all operators as to the correct procedures for
5.3 This test method is useful in determining the thermal
performing tests safely. When making high voltage tests,
endurance of coating powders applied over a steel substrate
particularly in compressed gas or in oil, it is possible for the
material.
energy released at breakdown to be sufficient to result in fire,
explosion, or rupture of the test chamber. Design test
6. Apparatus
equipment,testchambers,andtestspecimenssoastominimize
6.1 Dielectric Breakdown Test Set—The set shall meet the
the possibility of such occurrences and to eliminate the
requirements of Test Method D149.
possibility of personal injury. If the potential for fire exists,
have fire suppression equipment available.
6.2 Ovens—Ovens shall meet the requirements of Specifi-
cation D5423, Type I.
8. Test Specimens
6.3 Electrically Conductive Solution:
8.1 The substrate material to be used for evaluating integral
6.3.1 An appropriate container shall be selected for the
bus-bar insulation systems shall be steel. It is preferred that the
electrically conductive solution.
configuration of the substrate material be representative of the
6.3.2 Prepare a solution having a conductivity of at least
end application. One configuration that has been found to be
2.5 mS (millisiemens).
useful is shown in Fig. 1. Alternative configurations are
NOTE 1—A solution comprised of tap water and a solute such as NaCl
acceptable if agreed to by all interested parties.
orNH Clhasbeenfoundtobeacceptable.Sincethewatersolutionisused
8.2 The substrate shall be coated with the powder and cured
to detect (not cause) material decomposition/breakdown, the solution is
acceptable for use as long as it meets the minimum conductivity
using the manufacturer’s standard process. One end of the
requirements. It is recommended to change the solution when it becomes
specimens shall be left uncoated for making an electrical
difficult to observe breakdown due to cloudiness or other contamination.
connection during the dielectric strength tests.
6.3.3 During testing, the conductive solution is at ground
potential. The ground connection, using an immersed 9. Number of Test Specimens
electrode, is made using Nichrome, stainless steel, or other
9.1 A set of specimens for thermal aging shall consist of at
non-corrosive metal.
least ten specimens. Prepare one set for each aging temperature
6.3.4 Fit the container with a cover to prevent evaporation
chosen.
of the solution when not in use.
9.2 The initial value (unaged) set shall consist of at least
7. Hazards twenty specimens.
7.1 Warning—Lethal voltages are a potential hazard during 9.3 The minimum number of test specimens is 50. It is
the performance of this test. It is essential that the test recommended to prepare extra specimens for situations such as
FIG. 1 Example Specimen Dimensions
D7895/D7895M − 19
the need to add additional aging temperatures, or to have 12.4 Make one measurement on each specimen and com-
replacement specimens available for any specimens that are pute the average dielectric breakdown voltage for the set.
found during the screening test to be unsuitable for use in Record this as the initial value.
thermal aging.
13. Screening Test
10. Calibration and Standardization
13.1 Prior to thermal aging, all specimens shall be subjected
10.1 Expose the test material to at least three aging tem-
to a screening test in order to remove defective units. Any
peratures. The preferred number of aging temperatures is four.
specimen that cannot pass the screening test shall be discarded
and a replacement specimen selected for thermal aging.
10.2 Minimum thermal life target values for the high and
low temperatures shall be selected based on application.
13.2 Selectascreeningtestvoltagelevelthatisapercentage
of the average initial value.
10.3 Aging temperatures shall differ by at least 10 °C.
13.3 Selectascreeningtestperiodoftimethatisexpectedto
NOTE 2—Experience has shown that the suggested target thermal life
values listed in Table 1 are generally satisfactory. causefailureinweakspecimenswithoutcausingdamagetothe
remaining specimens.
11. Selection of Aging Cycles
NOTE 4—Experience has shown that a screening test voltage level of
11.1 To provide approximately equal exposures to the other
75 % of the initial value for a period of 10 s is generally satisfactory.
conditionings, and to more accurately determine the property
13.4 Suspend each specimen in the electrically conductive
endpoint, the heat aging time per cycle shall be shorter for the
solution in the same manner as described for the initial value
h
...

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: D7895/D7895M − 14 (Reapproved 2018) D7895/D7895M − 19
Standard Test Method for
Thermal Endurance of Coating Powders Used for Powder
Coating Insulation Systems
This standard is issued under the fixed designation D7895/D7895M; 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 This test method provides a procedure for evaluating thermal endurance of coating powders by determining the length of
aging time at selected elevated temperatures required to achieve dielectric breakdown at room temperature at a pre-determined
proof voltage. Thermal endurance is expressed in terms of a temperature index.
1.2 This test method is applicable to insulating powders used over a substrate material of steel.
1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated
in each system are not necessarily exact equivalents; therefore, each system shall be used independently of the other. Combining
values from the two systems is likely to result in non-conformance with the standard.
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. Specific precautionary statements are given in Section 7.
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.
2. Referenced Documents
2.1 ASTM Standards:
D149 Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at
Commercial Power Frequencies
D1711 Terminology Relating to Electrical Insulation
D5423 Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation
2.2 IEEE Document
IEEE 101A Simplified Method for Calculation of the Regression Line
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method refer to Terminology D1711.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 thermal endurance, n—an expression for the stability of an electrical insulating material, or a simple combination of
materials, when maintained at elevated temperatures for extended periods of time.
3.3 Definitions—For definitions of terms used in this test method refer to Terminology D1711.
4. Summary of Test Method
4.1 Specimens are aged in air at a minimum of three temperatures above the expected use temperature of the material. Exposure
to ambient stress conditions, followed by dielectric proof voltage tests in an electrically conductive solution, are periodically
This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of Subcommittee
D09.01 on Electrical Insulating Products.
Current edition approved Nov. 1, 2018Nov. 1, 2019. Published November 2018November 2019. Originally approved in 2014. Last previous edition approved in 2014 as
D7895/D7895M – 14.D7895/D7895M – 14 (2018). DOI: 10.1520/D7895_D7895M-14R18.10.1520/D7895_D7895M-19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE), 445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331, http://www.ieee.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7895/D7895M − 19
conducted to determine the time of aging at each elevated temperature required to reduce the breakdown voltage to a preselected
percentage of the original breakdown value. These thermal life values are used to construct a thermal endurance graph by means
of which it is possible to estimate a temperature index, corresponding to a thermal life as specified in the material specification
or as agreed upon between the user and the supplier. It is possible that a material will have multiple indices, each corresponding
to a different thermal life as required by a given application.
5. Significance and Use
5.1 A major factor affecting the life of insulating materials is thermal degradation. It is possible that other factors, such as
moisture and vibration, will cause failures after the material has been weakened by thermal degradation.
5.2 Electrical insulation is effective in electrical equipment only as long as it retains its physical and electrical integrity. The
following are potential indicators of thermal degradation: weight change, porosity, crazing, and generally a reduction in flexibility.
Thermal degradation is usually accompanied by an ultimate reduction in dielectric breakdown.
5.3 This test method is useful in determining the thermal endurance of coating powders applied over a steel substrate material.
6. Apparatus
6.1 Dielectric Breakdown Test Set—The set shall meet the requirements of Test Method D149.
6.2 Ovens—Ovens shall meet the requirements of Specification D5423, Type I.
6.3 Electrically Conductive Solution:
6.3.1 An appropriate container shall be selected for the electrically conductive solution.
6.3.2 Prepare a solution having a conductivity of at least 2.5 mS (millisiemens).
NOTE 1—A solution comprised of tap water and a solute such as NaCl or NH Cl has been found to be acceptable. Since the water solution is used
to detect (not cause) material decomposition/breakdown, the solution is acceptable for use as long as it meets the minimum conductivity requirements.
It is recommended to change the solution when it becomes difficult to observe breakdown due to cloudiness or other contamination.
6.3.3 During testing, the conductive solution is at ground potential. The ground connection, using an immersed electrode, is
made using Nichrome, stainless steel, or other non-corrosive metal.
6.3.4 Fit the container with a cover to prevent evaporation of the solution when not in use.
7. Hazards
7.1 Warning—Lethal voltages are a potential hazard during the performance of this test. It is essential that the test apparatus,
and all associated equipment electrically connected to it, be properly designed and installed for safe operation. Solidly ground all
electrically conductive parts which are possible for a person to contact during the test. Provide means for use at the completion
of any test to ground any parts which were at high voltage during the test, or have the potential for acquiring an induced charge
during the test, or retaining a charge even after disconnection of the voltage source. Thoroughly instruct all operators as to the
correct procedures for performing tests safely. When making high voltage tests, particularly in compressed gas or in oil, it is
possible for the energy released at breakdown to be sufficient to result in fire, explosion, or rupture of the test chamber. Design
test equipment, test chambers, and test specimens so as to minimize the possibility of such occurrences and to eliminate the
possibility of personal injury. If the potential for fire exists, have fire suppression equipment available.
8. Test Specimens
8.1 The substrate material to be used for evaluating integral bus-bar insulation systems shall be steel. It is preferred that the
configuration of the substrate material be representative of the end application. One configuration that has been found to be useful
is shown in Fig. 1. Alternative configurations are acceptable if agreed to by all interested parties.
8.2 The substrate shall be coated with the powder and cured using the manufacturer’s standard process. One end of the
specimens shall be left uncoated for making an electrical connection during the dielectric strength tests.
9. Number of Test Specimens
9.1 A set of specimens for thermal aging shall consist of at least ten specimens. Prepare one set for each aging temperature
chosen.
9.2 The initial value (unaged) set shall consist of at least twenty specimens.
9.3 The minimum number of test specimens is 50. It is recommended to prepare extra specimens for situations such as the need
to add additional aging temperatures, or to have replacement specimens available for any specimens that are found during the
screening test to be unsuitable for use in thermal aging.
10. Calibration and Standardization
10.1 Expose the test material to at least three aging temperatures. The preferred number of aging temperatures is four.
10.2 Minimum thermal life target values for the high and low temperatures shall be selected based on application.
D7895/D7895M − 19
FIG. 1 Example Specimen Dimensions
10.3 Aging temperatures shall differ by at least 10°C.10 °C.
NOTE 2—Experience has shown that the suggested target thermal life values listed in Table 1 are generally satisfactory.
11. Selection of Aging Cycles
11.1 To provide approximately equal exposures to the other conditionings, and to more accurately determine the property
endpoint, the heat aging time per cycle shall be shorter for the higher aging temperatures and longer for the lower aging
temperatures.
11.2 Cycle times shall be selected such that each set undergoes an adequate (but not excessive) number of cycles before
completion. In order to obtain an appropriate number of cycles, the following adjustments to the cycle time are recommended:
th
11.2.1 If no specimens in a set fail by the end of the 4 cycle, double the heat aging period of the test cycle.
th
11.2.2 If three or more specimens in a set fail by the end of the 4 cycle, halve the heat aging period of the test cycle.
11.2.3 Use observations in the highest temperature set to select appropriate adjustments to the other temperature sets.
NOTE 3—Experience has shown that the suggested cycle times in Table 1 are generally satisfactory.
12. Initial Value Test
12.1 To determine an initial dielectric s
...