ASTM D2304-23

Standard Test Method for Thermal Endurance of Rigid Electrical Insulating Materials

SIGNIFICANCE AND USE
6.1 Thermal degradation is often a major factor affecting the life of insulating materials and the equipment in which they are used. The temperature index provides a means for comparing the thermal capability of different materials in respect to the degradation of a selected property (the aging criterion). This property needs to directly or indirectly represent functional needs in application. For example, it is possible that a change in dielectric strength will be of direct, functional importance. However, more often it is possible that a decrease in dielectric strength will indirectly indicate the development of undesirable cracking (embrittlement). A decrease in flexural strength has the potential to be of direct importance in some applications, but also has the potential to indirectly indicate a susceptibility to failure in vibration. Often, it is necessary that two or more criteria of failure be used; for example, dielectric strength and flexural strength.  
6.2 Other factors, such as vibration, moisture and contaminants, have the potential to cause failure after thermal degradation takes place. In this test method, water absorption provides one means to evaluate such considerations.  
6.3 For some applications, the aging criteria in this test method will not be the most suitable. Other criteria, such as elongation at tensile or flexural failure, or resistivity after exposure to high humidity or weight loss, have the potential to serve better. The procedures in this test method have the potential to be used with such aging criteria. It is important to consider both the nature of the material and its application. For example, it is possible that tensile strength will be a poor choice for glass-fiber reinforced laminates, because it is possible that the glass fiber will maintain the tensile strength even when the associated resin is badly deteriorated. In this case, flexural strength is a better criterion of thermal aging.  
6.4 When dictated by the needs of t...
SCOPE
1.1 This test method2 provides procedures for evaluating the thermal endurance of rigid electrical insulating materials. Dielectric strength, flexural strength, or water absorption are determined at room temperature after aging for increasing periods of time in air at selected-elevated temperatures. A thermal-endurance graph is plotted using a selected end point at each aging temperature. A means is described for determining a temperature index by extrapolation of the thermal endurance graph to a selected time.  
1.2 This test method is most applicable to rigid electrical insulation such as supports, spacers, voltage barriers, coil forms, terminal boards, circuit boards and enclosures for many types of application where retention of the selected property after heat aging is important.  
1.3 When dielectric strength is used as the aging criterion, it is also acceptable to use this test method for some thin sheet (flexible) materials, which become rigid with thermal aging, but is not intended to replace Test Method D1830 for those materials which must retain a degree of flexibility in use.  
1.4 This test method is not applicable to ceramics, glass, or similar inorganic materials.  
1.5 The values stated in metric units are to be regarded as standard. Other units (in parentheses) are provided for information.  
1.6 When determining the thermal endurance of rigid EIM, the basic concepts in this standard follow IEEE 1, IEEE 98, and IEEE 101.  
1.7 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. A specific warning statement is given in 11.3.4.  
1.8 This international standard was developed in accordance with internationally recognized principles on standardization establis...

General Information

• Status: Published
• Publication Date: 30-Apr-2023
• ICS: 29.035.01 - Insulating materials in general
• Technical Committee: D09 - Electrical and Electronic Insulating Materials
• Drafting Committee: D09.07 - Electrical Insulating Materials

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: D2304 − 23
Standard Test Method for
1
Thermal Endurance of Rigid Electrical Insulating Materials
This standard is issued under the fixed designation D2304; 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* priate safety, health, and environmental practices and deter-
2
mine the applicability of regulatory limitations prior to use. A
1.1 This test method provides procedures for evaluating the
specific warning statement is given in 11.3.4.
thermal endurance of rigid electrical insulating materials.
1.8 This international standard was developed in accor-
Dielectric strength, flexural strength, or water absorption are
dance with internationally recognized principles on standard-
determined at room temperature after aging for increasing
ization established in the Decision on Principles for the
periods of time in air at selected-elevated temperatures. A
Development of International Standards, Guides and Recom-
thermal-endurance graph is plotted using a selected end point
mendations issued by the World Trade Organization Technical
at each aging temperature. A means is described for determin-
Barriers to Trade (TBT) Committee.
ing a temperature index by extrapolation of the thermal
endurance graph to a selected time.
2. Referenced Documents
1.2 This test method is most applicable to rigid electrical
3
2.1 ASTM Standards:
insulation such as supports, spacers, voltage barriers, coil
D149 Test Method for Dielectric Breakdown Voltage and
forms, terminal boards, circuit boards and enclosures for many
Dielectric Strength of Solid Electrical Insulating Materials
types of application where retention of the selected property
at Commercial Power Frequencies
after heat aging is important.
D229 Test Methods for Rigid Sheet and Plate Materials
1.3 When dielectric strength is used as the aging criterion, it
Used for Electrical Insulation
is also acceptable to use this test method for some thin sheet
D570 Test Method for Water Absorption of Plastics
(flexible) materials, which become rigid with thermal aging,
D790 Test Methods for Flexural Properties of Unreinforced
but is not intended to replace Test Method D1830 for those
and Reinforced Plastics and Electrical Insulating Materi-
materials which must retain a degree of flexibility in use.
als
D1830 Test Method for Thermal Endurance of Flexible
1.4 This test method is not applicable to ceramics, glass, or
Sheet Materials Used for Electrical Insulation by the
similar inorganic materials.
Curved Electrode Method
1.5 The values stated in metric units are to be regarded as
D5423 Specification for Forced-Convection Laboratory Ov-
standard. Other units (in parentheses) are provided for infor-
ens for Evaluation of Electrical Insulation
mation.
4
2.2 IEEE:
1.6 When determining the thermal endurance of rigid EIM,
No. 1 General Principles Upon Which Temperature Limits
the basic concepts in this standard follow IEEE 1, IEEE 98, and
Are Based in the Rating of Electric Equipment
IEEE 101.
No. 98 Guide for the Preparation of Test Procedures for the
1.7 This standard does not purport to address all of the Thermal Evaluation of Electrical Insulating Materials
safety concerns, if any, associated with its use. It is the No. 101 Guide for the Statistical Analysis of Test Data
responsibility of the user of this standard to establish appro-
3. Terminology
3.1 Definitions:
1
This test method is under the jurisdiction of ASTM Committee D09 on
3.1.1 Arrhenius plot, n—a graph of the logarithm of thermal
Electrical and Electronic Insulating Materials and is the direct responsibility of
life as a function of the reciprocal of absolute temperature.
Subcommittee D09.07 on Electrical Insulating Materials.
Current edition approved May 1, 2023. Published June 2023. Originally issued
as D2304 – 64 T. Last previous edition approved in 2018 as D2304 – 18. DOI:
3
10.1520/D2304-23. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
2
This test method is a revision of a procedure written by the Working Group on contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Rigid Electrical Insulating Materials of the Subcommittee on Thermal Evaluation, Standards volume information, refer to the standard’s Document Summary page on
IEEE Electrical Insulation Committee, which was presented as CP 59-113 at the the ASTM website.
4
IEEE Winter General Meeting Feb. 1–6, 1959. See references at end of this test Av
...

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: D2304 − 18 D2304 − 23
Standard Test Method for
1
Thermal Endurance of Rigid Electrical Insulating Materials
This standard is issued under the fixed designation D2304; 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*
2
1.1 This test method provides procedures for evaluating the thermal endurance of rigid electrical insulating materials. Dielectric
strength, flexural strength, or water absorption are determined at room temperature after aging for increasing periods of time in
air at selected-elevated temperatures. A thermal-endurance graph is plotted using a selected end point at each aging temperature.
A means is described for determining a temperature index by extrapolation of the thermal endurance graph to a selected time.
1.2 This test method is most applicable to rigid electrical insulation such as supports, spacers, voltage barriers, coil forms, terminal
boards, circuit boards and enclosures for many types of application where retention of the selected property after heat aging is
important.
1.3 When dielectric strength is used as the aging criterion, it is also acceptable to use this test method for some thin sheet (flexible)
materials, which become rigid with thermal aging, but is not intended to replace Test Method D1830 for those materials which must
retain a degree of flexibility in use.
1.4 This test method is not applicable to ceramics, glass, or similar inorganic materials.
1.5 The values stated in metric units are to be regarded as standard. Other units (in parentheses) are provided for information.
1.6 When determining the thermal endurance of rigid EIM, the basic concepts in this standard follow IEEE 1, IEEE 98, and IEEE
101.
1.7 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. A specific warning statement is given in 11.3.4.
1.8 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.
1
This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of Subcommittee
D09.07 on Electrical Insulating Materials.
Current edition approved May 1, 2018May 1, 2023. Published May 2018June 2023. Originally issued as D2304 – 64 T. Last previous edition approved in 20102018 as
D2304 – 10.D2304 – 18. DOI: 10.1520/D2304-18.10.1520/D2304-23.
2
This test method is a revision of a procedure written by the Working Group on Rigid Electrical Insulating Materials of the Subcommittee on Thermal Evaluation, IEEE
Electrical Insulation Committee, which was presented as CP 59-113 at the IEEE Winter General Meeting Feb. 1–6, 1959. See references at end of this test method.
*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
1

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D2304 − 23
2. Referenced Documents
3
2.1 ASTM Standards:
D149 Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at
Commercial Power Frequencies
D229 Test Methods for Rigid Sheet and Plate Materials Used for Electrical Insulation
D570 Test Method for Water Absorption of Plastics
D790 Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials
D1830 Test Method for Thermal Endurance of Flexible Sheet Materials Used for Electrical Insulation by the Curved Electrode
Method
D5423 Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation
4
2.2 IEEE:
No. 1 General Principles Upon Which Temperature Limits Are Based in the Rating of Electric Equipment
No. 98 Guide for the Preparation of Test Procedures for the Thermal Evaluation of Electrical Insulating Materials
No. 101 Guide for the Statistica
...