ASTM_D_2304_-_10.pdf

Designation:D230410Standard Test Method forThermal Endurance of Rigid Electrical Insulating Materials1This standard is issued under the fixed designation D2304;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.Scope1.1 This test method2provides procedures for evaluating thethermal endurance of rigid electrical insulating materials.Dielectric strength,flexural strength,or water absorption aredetermined at room temperature after aging for increasingperiods of time in air at selected-elevated temperatures.Athermal-endurance graph is plotted using a selected end pointat each aging temperature.A means is described for determin-ing a temperature index by extrapolation of the thermalendurance graph to a selected time.1.2 This test method is most applicable to rigid electricalinsulation such as supports,spacers,voltage barriers,coilforms,terminal boards,circuit boards and enclosures for manytypes of application where retention of the selected propertyafter heat aging is important.1.3 When dielectric strength is used as the aging criterion,itis 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 thosematerials which must retain a degree of flexibility in use.1.4 This test method is not applicable to ceramics,glass,orsimilar inorganic materials.1.5 The values stated in metric units are to be regarded asstandard.Other units(in parentheses)are provided for infor-mation.1.6 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.A specific warningstatement is given in 10.3.4.2.Referenced Documents2.1 ASTM Standards:3D149 Test Method for Dielectric Breakdown Voltage andDielectric Strength of Solid Electrical Insulating Materialsat Commercial Power FrequenciesD229 Test Methods for Rigid Sheet and Plate MaterialsUsed for Electrical InsulationD570 Test Method for Water Absorption of PlasticsD790 Test Methods for Flexural Properties of Unreinforcedand Reinforced Plastics and Electrical Insulating Materi-alsD1830 Test Method for Thermal Endurance of FlexibleSheet Materials Used for Electrical Insulation by theCurved Electrode MethodD5423 Specification for Forced-Convection Laboratory Ov-ens for Evaluation of Electrical Insulation2.2 IEEE:4No.1 General Principles Upon Which Temperature LimitsAre Based in the Rating of Electric EquipmentNo.98 Guide for the Preparation of Test Procedures for theThermal Evaluation of Electrical Insulating MaterialsNo.101 Guide for the Statistical Analysis of Test Data3.Terminology3.1 Definitions:3.1.1 Arrhenius plot,na graph of the logarithm of thermallife as a function of the reciprocal of absolute temperature.3.1.1.1 DiscussionThis is normally depicted as the beststraight line fit,determined by least squares,of end pointsobtained at aging temperatures.It is important that the slope,which is the activation energy of the degradation reaction,beapproximately constant within the selected temperature rangeto ensure a valid extrapolation.3.1.2 temperature index,na number which permits com-parison of the temperature/time characteristics of an electricalinsulating material,or a simple combination of materials,basedon the temperature in degrees Celsius which is obtained by1This test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.07 on Flexible and Rigid Insulating Materials.Current edition approved Oct.1,2010.Published October 2010.Originallyissued as D2304 64 T.Last previous edition approved in 2002 as D2304 97R02.DOI:10.1520/D2304-10.2This test method is a revision of a procedure written by the Working Group onRigid Electrical Insulating Materials of the Subcommittee on Thermal Evaluation,IEEE Electrical Insulation Committee,which was presented as CP 59-113 at theIEEE Winter General Meeting Feb.16,1959.See references at end of this testmethod.3For 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.4Available from the Institute of Electrical and Electronics Engineers,445 HoesLn.,P.O.Box 1331,Piscataway,NJ 08854-1331.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 extrapolating the Arrhenius plot of life versus temperature to aspecified time,usually 20 000 h.3.1.3 thermal life,nthe time