ASTM_D_2756_-_07_2012.pdf

Designation:D275607(Reapproved 2012)Standard Test Method forWeight Loss of Electrical Insulating Varnishes1This standard is issued under the fixed designation D2756;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This test method covers the measurement of the loss inweight of cured electrical insulating varnishes on exposure toelevated 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 thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.For specificprecaution statements,see Section 7.NOTE1IEC 60216 Part 2 is technically equivalent to this standard.2.Referenced Documents2.1 ASTM Standards:2D115 Test Methods for Testing Solvent Containing Var-nishes Used for Electrical InsulationD1711 Terminology Relating to Electrical InsulationD1932 Test Method for Thermal Endurance of FlexibleElectrical Insulating VarnishesD2518 Specification for Woven Glass Fabrics for ElectricalInsulation(Withdrawn 2013)3D5423 Specification for Forced-Convection Laboratory Ov-ens for Evaluation of Electrical Insulation2.2IEC Standards:IEC 60216 Guide for the determination of thermal endur-ance properties of electrical insulating materialsPart 2:Choice of test criteria43.Terminology3.1 Definitions:For definitions of terms used in this testmethod,refer to Terminology D1711.4.Summary of Test Method4.1 Specimens are prepared by coating glass cloth withvarnish to be tested.The specimens are aged at elevatedtemperatures and the loss in weight is determined after aspecific time.5.Significance and Use5.1 Weight loss is useful for indicating:5.1.1 A form of degradation at elevated temperatures in air,and5.1.2 Evolution of volatiles that have the potential to affectother components.6.Apparatus6.1 Air-Circulating Oven,capable of meeting the require-ments of Specification D5423,Type II.6.2 Glass Cloth,heat-cleaned,Style No.116,as described inSpecification D2518.6.3 Balance,capable of weighing to nearest 0.001 g.6.4 Desiccator Jar,with a suitable desiccant.7.Safety Precautions7.1 Do not use varnish at temperatures above the flash pointwhen inadequate ventilation and the possibility of flames orsparks exist.Store all varnishes,reagents and solvents in sealedcontainers.Apply these precautions to the handling of thecalled for reagents and solvents.8.Sampling8.1 Sample the varnish in accordance with Test MethodsD115.9.Test Specimens9.1 Prepare the test specimens as described in Test MethodD1932.Make one panel for each test temperature.Use anaverage of ten readings to determine the thickness of thepanels.1This test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.01 on Electrical Insulating Varnishes,Powders and Encapsulat-ing Compounds.Current edition approved April 1,2012.Published April 2012.Originallyapproved in 1968.Last previous edition approved in 2007 as D2756 07.DOI:10.1520/D2756-07R12.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from International Electrotechnical Commission(IEC),3 rue deVaremb,Case postale 131,CH-1211,Geneva 20,Switzerland,http:/www.iec.ch.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 9.2 Cure the varnish in accordance with manufacturersrequirements.9.3 Cut two specimens,100 by 125 mm(4 by 5 in.)fromeach panel to be used for the tests.9.4 Cut an uncoated piece of cloth,100 by 125 mm(4 by 5in.)10.Procedure10.1 Dry two cured specimens for each test temperature andone uncoated specimen for 2 h at 110C(230F).Place them ina desiccator and allow them to cool to room temperature.Weigh each specimen to the nearest 0.001 g.The weight of thecoated specimen will be the initial weight.10.2 Subtract the weight of the uncoated specimen from theweight of each coated specimen.This is the initial weight of thevarnish solids on which the percent weight loss is based.10.3 Select at least four temperatures between 150C(300F)and 250C(480F)for weight loss aging.Suggestedtemperatures are:150C(300F),200C(390F),220C(430F),and 250C(480F).10.4 Hang the cured specimens in the aging ovens,takingthe necessary precautions to assure good air flow parall