ASTM D4733-98 - 10.11.1998
 
1. Scope

1.1 These test methods cover solventless varnishes used primarily as electrical, mechanical, and environmental protection for electrical equipment.

1.2 These test methods are used on solventless varnishes that are applied by dipping (at atmospheric pressure conditions or under vacuum or pressure), spraying, or brushing for the purpose of impregnating or sealing electrical equipment. The following test methods are included:

Property Tests (Uncured): Section Density 7 Flash Point 8 Gel Time 9 Monomer Content 10 Rheological Properties (Non-Newtonian) 11 Brookfield Viscosity 12 Performance Property Tests (cured):Bond Strength 13 Coating Thickness 14 Dielectric Strength 15 and 16 Permittivity and Dissipation Factor 17

1.3 The values stated in inch-pound units are to be regarded as the standard. The values in parentheses are for information only.

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 and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in 8.3, 15.5.1, and 15.5.2.

 
2. Referenced Documents

D923-15(2023)

Standard Practices for Sampling Electrical Insulating Liquids

D1475-13(2025)

Standard Test Method for Density of Liquid Coatings, Inks, and Related Products

D1711-26

Standard Terminology Relating to Electrical Insulation

D2196-20(2026)

Standard Test Methods for Rheological Properties of Non-Newtonian Materials by Rotational Viscometer

D2519-19a(2025)

Standard Test Method for Bond Strength of Electrical Insulating Varnishes by the Helical Coil Test (Includes all amendments and changes 12/23/2025).

D3056-23

Standard Test Method for Gel Time of Solventless Varnishes

D3278-21

Standard Test Methods for Flash Point of Liquids by Small Scale Closed-Cup Apparatus

D3312-25

Standard Test Method for Percent Reactive Monomer in Solventless Varnishes

D3487-25

Standard Specification for Mineral Insulating Liquid Used in Electrical Apparatus

D3636-24

Standard Practice for Sampling and Judging Quality of Solid Electrical Insulating Materials

D6054-97

Standard Practice for Conditioning Electrical Insulating Materials for Testing

E176-24a

Standard Terminology of Fire Standards (Includes all amendments and changes 12/9/2024).

IEC 60455

Resin Based Reactive Compunds Used for Electrical Insulation

D374-99

Standard Test Methods for Thickness of Solid Electrical Insulation

D93-26

Standard Test Methods for Flash Point by Pensky-Martens Closed Cup Tester

D115-17(2024)

Standard Test Methods for Testing Solvent Containing Varnishes Used for Electrical Insulation

D149-25

Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies

D150-22

Standard Test Methods for AC Loss Characteristics and Permittivity (Dielectric Constant) of Solid Electrical Insulation

D168-94(2000)

Standard Test Method for Coke Residue of Creosote (Withdrawn 2006)