ASTM D2756-07(2017)

Standard Test Method for Weight Loss of Electrical Insulating Varnishes

SIGNIFICANCE AND USE
5.1 Weight loss is useful for indicating:  
5.1.1 A form of degradation at elevated temperatures in air, and  
5.1.2 Evolution of volatiles that have the potential to affect other components.
SCOPE
1.1 This test method covers the measurement of the loss in weight of cured electrical insulating varnishes on exposure to elevated temperature in air.  
1.2 The values stated in SI units are the standard.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific precaution statements, see Section 7.
Note 1: IEC 60216 Part 2 is technically equivalent to this standard.  
1.4 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-2017
• ICS: 29.035.60 - Varnished fabrics
• Technical Committee: D09 - Electrical and Electronic Insulating Materials
• Drafting Committee: D09.01 - Electrical Insulating Products

Relations

• Replaces: ASTM D2756-07(2012) - Standard Test Method for Weight Loss of Electrical Insulating Varnishes
• Effective Date: 01-Nov-2017
• Refers: ASTM D1711-24 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Mar-2024
• Refers: ASTM D115-17(2024) - Standard Test Methods for Testing Solvent Containing Varnishes Used for Electrical Insulation
• Effective Date: 01-Mar-2024
• Refers: ASTM D1932-19 - Standard Test Method for Thermal Endurance of Flexible Electrical Insulating Varnishes
• Effective Date: 01-Nov-2019
• Refers: ASTM D1932-18 - Standard Test Method for Thermal Endurance of Flexible Electrical Insulating Varnishes
• Effective Date: 01-Nov-2018
• Refers: ASTM D115-17 - Standard Test Methods for Testing Solvent Containing Varnishes Used for Electrical Insulation
• Effective Date: 01-Nov-2017
• Refers: ASTM D1711-15 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2015
• Refers: ASTM D115-14 - Standard Test Methods for Testing Solvent Containing Varnishes Used for Electrical Insulation
• Effective Date: 01-Nov-2014
• 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 D1932-13 - Standard Test Method for Thermal Endurance of Flexible Electrical Insulating Varnishes
• Effective Date: 01-Apr-2013
• Refers: ASTM D115-07(2012) - Standard Test Methods for Testing Solvent Containing Varnishes Used for Electrical Insulation
• Effective Date: 01-Apr-2012
• Refers: ASTM D1711-11a - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Aug-2011
• Refers: ASTM D1932-04(2009) - Standard Test Method for Thermal Endurance of Flexible Electrical Insulating Varnishes
• Effective Date: 01-Oct-2009

Overview

ASTM D2756-07(2017) - Standard Test Method for Weight Loss of Electrical Insulating Varnishes establishes a uniform procedure for measuring the loss in weight of cured electrical insulating varnishes when they are exposed to elevated temperatures in air. Developed by ASTM International, this standard provides valuable guidance for evaluating the thermal stability and volatile release characteristics of insulating varnishes used in electrical insulation systems. The method is recognized internationally and aligns with the principles outlined by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

Key Topics

• Purpose of Weight Loss Testing
  • Assesses degradation of electrical insulating varnishes under high temperature conditions.
  • Measures evolution of volatiles that might impact surrounding materials or components in electrical assemblies.
• Test Scope
  • Applicable to cured electrical insulating varnishes subjected to specific air temperatures.
  • Utilizes standardized procedures and apparatus for reproducible results.
  • All measurements are performed in SI units to ensure global consistency.
• Safety and Compliance
  • Emphasizes user responsibility for safety, health, and environmental practices.
  • References specific safety instructions regarding the handling of varnishes and solvents.
• Test Procedure Highlights
  • Preparation involves coating and curing specimens, weighing to high precision, and exposing samples to controlled high-temperature environments.
  • Analysis includes comparing initial and final weights to determine varnish loss as a percentage.
  • Offers guidelines on sample sizes, oven settings, and recommended time intervals.

Applications

• Electrical Equipment Manufacturers
  • Assists in qualifying varnishes for insulation systems in motors, transformers, and other electrical apparatus.
  • Enables prediction and monitoring of thermal endurance for more reliable product performance.
• Quality Control
  • Provides a standardized, repeatable method for verifying the thermal resistance of varnish products during production and batch testing.
• Material Development and Selection
  • Supports R&D teams in assessing new varnish formulations for improved thermal stability and lower volatile emissions.
• Component Reliability Analysis
  • Offers insights into potential risks from volatiles in electrical assemblies, helping to prevent component failures and improve system longevity.
• Regulatory and Standards Compliance
  • Facilitates alignment with international standards, supporting export and market access for electrical components.

Related Standards

• IEC 60216-2
  • Internationally recognized equivalent standard for determining the thermal endurance properties of electrical insulating materials.
• ASTM D115
  • Test methods for solvent-containing varnishes used for electrical insulation.
• ASTM D1932
  • Method for evaluating the thermal endurance of flexible electrical insulating varnishes.
• ASTM D1711
  • Terminology relating to electrical insulation, ensuring consistent definitions across standards.
• ASTM D5423
  • Specification for forced-convection laboratory ovens used in insulation material testing.

Practical Value

The ASTM D2756-07(2017) standard is essential for ensuring quality, performance, and compliance in the production and application of electrical insulating varnishes. By providing a consistent test method to measure weight loss under thermal stress, organizations can better predict product lifespan, prevent volatile-related failures, and meet precise industry requirements in electrical insulation systems. This standard plays a crucial role in quality assurance, product development, and international regulatory acceptance.

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: D2756 − 07 (Reapproved 2017)
Standard Test Method for
Weight Loss of Electrical Insulating Varnishes
This standard is issued under the fixed designation D2756; 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* 2.2 IEC Standards:
IEC 60216 Guide for the determination of thermal endur-
1.1 This test method covers the measurement of the loss in
ance properties of electrical insulating materials—Part 2:
weight of cured electrical insulating varnishes on exposure to
Choice of test criteria
elevated temperature in air.
3. Terminology
1.2 The values stated in SI units are the standard.
3.1 Definitions: For definitions of terms used in this test
1.3 This standard does not purport to address all of the
method, refer to Terminology D1711.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Summary of Test Method
priate safety, health, and environmental practices and deter-
4.1 Specimens are prepared by coating glass cloth with
mine the applicability of regulatory limitations prior to use.
varnish to be tested. The specimens are aged at elevated
For specific precaution statements, see Section 7.
temperatures and the loss in weight is determined after a
NOTE 1—IEC 60216 Part 2 is technically equivalent to this standard.
specific time.
1.4 This international standard was developed in accor-
5. Significance and Use
dance with internationally recognized principles on standard-
5.1 Weight loss is useful for indicating:
ization established in the Decision on Principles for the
5.1.1 Aform of degradation at elevated temperatures in air,
Development of International Standards, Guides and Recom-
and
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. 5.1.2 Evolution of volatiles that have the potential to affect
other components.
2. Referenced Documents
6. Apparatus
2.1 ASTM Standards:
6.1 Air-Circulating Oven, capable of meeting the require-
D115 Test Methods for Testing Solvent Containing Var-
ments of Specification D5423, Type II.
nishes Used for Electrical Insulation
6.2 Glass Cloth,heat-cleaned,StyleNo.116,asdescribedin
D1711 Terminology Relating to Electrical Insulation
Specification D2518.
D1932 Test Method for Thermal Endurance of Flexible
Electrical Insulating Varnishes
6.3 Balance, capable of weighing to nearest 0.001 g.
D2518 Specification for Woven Glass Fabrics for Electrical
6.4 Desiccator Jar, with a suitable desiccant.
Insulation (Withdrawn 2013)
D5423 Specification for Forced-Convection Laboratory Ov- 7. Safety Precautions
ens for Evaluation of Electrical Insulation
7.1 Do not use varnish at temperatures above the flash point
when inadequate ventilation and the possibility of flames or
sparksexist.Storeallvarnishes,reagentsandsolventsinsealed
This test method is under the jurisdiction of ASTM Committee D09 on containers. Apply these precautions to the handling of the
Electrical and Electronic Insulating Materials and is the direct responsibility of
called for reagents and solvents.
Subcommittee D09.01 on Electrical Insulating Products.
Current edition approved Nov. 1, 2017. Published November 2017. Originally
8. Sampling
approved in 1968. Last previous edition approved in 2012 as D2756 – 07 (2012).
DOI: 10.1520/D2756-07R17. 8.1 Sample the varnish in accordance with Test Methods
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
D115.
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 International Electrotechnical Commission (IEC), 3 rue de
The last approved version of this historical standard is referenced on Varembé, Case postale 131, CH-1211, Geneva 20, Switzerland, http://www.iec.ch.
www.astm.org.
*A Summary of Changes section appears at the end of this standard
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D2756 − 07 (2017)
TABLE 1 Round-Robin Test Results
9. Test Specimens
Interlaboratory Standard
9.1 Prepare the test specimens as described in Test Method Hours at 200 °C Avg.
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