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    ASTM D4733 - 17

    Standard Test Methods for Solventless Electrical Insulating Varnishes

    Active Standard ASTM D4733 | Developed by Subcommittee: D09.01

    Book of Standards Volume: 10.02

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    Significance and Use

    4.1 The test methods referenced in these test methods are useful for control purposes during the manufacture and use of solventless varnishes.

    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 other certain pressure), spraying, or brushing for the purpose of impregnating or sealing electrical equipment. The following test methods are included:

              Property Tests (Uncured):




                   Flash Point


                   Gel Time


                   Monomer Content


                   Rheological Properties (Non-Newtonian)


                   Rotational Viscosity


                   Performance Property Tests (cured):


                   Bond Strength


                   Coating Thickness


                   Dielectric Strength


                   Dielectric Strength-Using Metal Panels


                   Permittivity and Dissipation Factor




    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, health, and environmental 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.

    Note 1: This test method is related to IEC 60455. Since both methods contain multiple test procedures, many procedures are technically equivalent while others differ significantly.

    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 (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D93 Test Methods for Flash Point by Pensky-Martens Closed Cup Tester

    D115 Test Methods for Testing Solvent Containing Varnishes Used for Electrical Insulation

    D149 Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies

    D150 Test Methods for AC Loss Characteristics and Permittivity (Dielectric Constant) of Solid Electrical Insulation

    D374 Test Methods for Thickness of Solid Electrical Insulation (Metric) D0374_D0374M

    D923 Practices for Sampling Electrical Insulating Liquids

    D1475 Test Method for Density of Liquid Coatings, Inks, and Related Products

    D1711 Terminology Relating to Electrical Insulation

    D2196 Test Methods for Rheological Properties of Non-Newtonian Materials by Rotational Viscometer

    D2519 Test Method for Bond Strength of Electrical Insulating Varnishes by the Helical Coil Test

    D3056 Test Method for Gel Time of Solventless Varnishes

    D3278 Test Methods for Flash Point of Liquids by Small Scale Closed-Cup Apparatus

    D3312 Test Method for Percent Reactive Monomer in Solventless Varnishes

    D3487 Specification for Mineral Insulating Oil Used in Electrical Apparatus

    D3636 Practice for Sampling and Judging Quality of Solid Electrical Insulating Materials

    D6054 Practice for Conditioning Electrical Insulating Materials for Testing

    E176 Terminology of Fire Standards

    IEC Standards

    IEC 60455 Resin Based Reactive Compounds Used for Electrical Insulation

    ICS Code

    ICS Number Code 29.035.60 (Varnished fabrics)

    Referencing This Standard
    Link Here
    Link to Active (This link will always route to the current Active version of the standard.)

    DOI: 10.1520/D4733-17

    Citation Format

    ASTM D4733-17, Standard Test Methods for Solventless Electrical Insulating Varnishes, ASTM International, West Conshohocken, PA, 2017, www.astm.org

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