1、Designation: D295 12Standard Test Methods forVarnished Cotton Fabrics Used for Electrical Insulation1This standard is issued under the fixed designation D295; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio
2、n. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 These test methods cover procedures for the
3、testing ofvarnished cotton fabrics and varnished cotton fabric tapes(Note 1) to be used as electrical insulation and are directlyapplicable to both “straight-cut” and “bias-cut” materials,unless otherwise stated in the test method.NOTE 1Methods of testing varnished glass fabrics and tapes are giveni
4、n Test Methods D902.1.2 The procedures appear in the following order:Procedures SectionsASTM TestMethodsBreaking Strength 20 to 27 .ConditioningDielectric Breakdown Voltage543 to 46.D149Dielectric Breakdown Voltage Under Elongation 47 to 53 D149Dissipation Factor and Permittivity 54 to 60 D150Elonga
5、tionResistance to Oil35 to 4268 to 73.D92Selection of Test Specimens 4 .Tear Resistance 28 to 34 D689Thickness 6 to 10 D374Thread Count 15 to 19 .Volume Resistance 61 to 67 D257Weight 11 to 14 .1.3 The values stated in inch-pound units are to be regardedas the standard. The metric equivalents of inc
6、h-pound unitsmay be approximate.1.4 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 limitati
7、ons prior to use. For specificprecautionary statements, see 44.4, 51.1, 58.1, and 65.1.NOTE 2This standard resembles IEC 603942 in title only. Thecontent is significantly different.2. Referenced Documents2.1 ASTM Standards:2D92 Test Method for Flash and Fire Points by ClevelandOpen Cup TesterD149 Te
8、st Method for Dielectric Breakdown Voltage andDielectric Strength of Solid Electrical Insulating Materialsat Commercial Power FrequenciesD150 Test Methods for AC Loss Characteristics and Permit-tivity (Dielectric Constant) of Solid Electrical InsulationD257 Test Methods for DC Resistance or Conducta
9、nce ofInsulating MaterialsD374 Test Methods for Thickness of Solid Electrical Insu-lation (Metric) D0374_D0374MD689 Test Method for Internal Tearing Resistance of Paper(Withdrawn 2009)3D902 Test Methods for Flexible Resin-Coated Glass Fabricsand Glass Fabric Tapes Used for Electrical InsulationD1711
10、 Terminology Relating to Electrical Insulation2.2 IEC Standard:IEC 603942 Varnished Fabrics for Electrical Purposes Part 2: Methods of Test43. Terminology3.1 DefinitionsFor definitions of terms used in these testmethods refer to Terminology D1711.3.2 Definitions of Terms Specific to This Standard:3.
11、2.1 weightof varnished cloth and varnished cloth tapes,the weight per unit area as determined in accordance with thistest method. It is usually expressed in pound per square yardfor a specified nominal thickness.3.2.2 threads per inchof varnished cloths, the count of thenumber of warp and filling ya
12、rns present in the base cloth perlinear inch of width or length, respectively.1These test methods are under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and are the direct responsibility ofSubcommittee D09.07 on Electrical Insulating Materials.Current editi
13、on approved Jan. 15, 2012. Published February 2012. Originallyapproved in 1928. Last previous edition approved in 2004 as D295 99 (2004)which was withdrawn in October 2009 and reinstated in January 2012. DOI:10.1520/D0295-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcon
14、tact 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 American National Standards Institut
15、e, 11 W 42nd St.,NewYork, NY 10036.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Pri
16、nciples for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.2.3 elongationthe amount of strain observed in a givenlength of varnished cloth or tape when subjected to prescribedloading conditio
17、ns at prescribed atmospheric conditions. It isexpressed as a percentage of the initial length.3.2.4 oil resistanceof varnished cloth or tape, the abilityof the varnish film to withstand the attack of oil withoutexcessive impairment of its physical and electrical character-istics when the varnished c
18、loth or tape is immersed in aspecified oil for a prescribed period of time at a giventemperature.4. Selection of Test Specimens4.1 Select specimens for test from portions of material freefrom defects.4.2 In the case of rolls of material other than those packedin oil, remove the outer two layers of c
19、loth or the outer sixlayers of tape and prepare test specimens from the remainingmaterial. In the case of oil-packed tape, remove the outer layerfrom each roll to be tested. In the case of sheets and tape strips,remove the outer six layers of material and prepare testspecimens from that remaining.NO
20、TE 3In the case of bias-cut materials, exclude seams and jointedselvage from test areas.NOTE 4If it is desired to test seams and jointed selvages for breakingstrength, prepare additional test specimens so that the seams or joints arein the center of the specimens.5. Conditioning5.1 Significance and
21、UseBecause the physical and elec-trical properties of most fabrics change with variation of theirmoisture content, it is necessary to control this property at thetime of testing in order to attain reasonably good reproducibil-ity of test values. For example, when cotton fabric absorbsmoisture it ten
22、ds to swell and increase in dimensions. Also, theflexibility, elongation, and tensile strength of the materialnormally increase with increased relative humidity, whereas,conversely, the electrical properties are depreciated when thematerial is subjected to these conditions. The time of exposureto th
23、e conditioned atmosphere must be long enough to permitthe moisture content of the test specimen to reach a relativelystable value. If the fabric is untreated, a few hours exposure issufficient. Treated fabrics like varnished cloth require appre-ciably longer time.5.2 Where it is desired to test in a
24、 controlled atmosphere,condition the test specimens for 48 h in the Standard Labora-tory Atmosphere of 50 6 2 % relative humidity at 23 6 1C(73.4 6 1.8 F). If a conditioning cabinet or chamber is used,subject the specimens to test immediately upon withdrawalfrom the cabinet or chamber, unless otherw
25、ise specified.5.3 If it is desired to test the material in the condition asreceived by the purchaser, allow the packages containing therolls of material from which the specimens are to be taken toreach room temperature before opening. Open the packages,remove the roll and immediately prepare such te
26、st specimensas required, unless otherwise specified.5.4 In the case of dispute, the procedure described in 5.2shall be the referee method.TEST METHOD A: THICKNESS6. Significance and Use6.1 The thickness test is necessary to determine whether thematerial meets specified tolerances for thickness. In a
27、ddition,thickness values are essential because of the importance ofspace factor in designing electrical equipment.7. Test Specimens7.1 In the case of cloths or sheets, cut test specimens 1 in.(25.4 mm) wide across the entire width. In the case of bias-cutcloth, exclude seams or jointed selvages from
28、 the area of test.7.2 In the case of tapes or strips, remove specimens 36 in.(910 mm) long from the sample of material selected inaccordance with Section 4.8. Procedure8.1 Measure the thickness in accordance with Test MethodsD374, with the following modifications:8.1.1 Either Method B or Method C ma
29、y be used butMethod C is to be used unless otherwise specified. Method Ashall not be used.8.1.2 In making thickness measurements, use only one layerof material.8.1.3 In the case of cloths, take ten measurements equallyspaced across the width of the specimen. The thickness of thecloth shall be the av
30、erage of the ten measurements.8.1.4 In the case of tapes, unless otherwise specified, taketen measurements equally spaced along the length of eachspecimen. The thickness of the tape shall be the average of tenmeasurements.9. Report9.1 Report the average, maximum, and minimum thicknessin inches (or c
31、entimetres).10. Precision and Bias10.1 This test method has been in use for many years, but noinformation has been presented to ASTM upon which to basea statement of precision. No activity has been planned todevelop such information.10.2 This test method has no bias because the value forthickness is
32、 determined solely in terms of this test methoditself.TEST METHOD B: WEIGHT11. Significance and Use11.1 Weight values are useful for estimating weight indesigning electrical equipment containing a constituent part ofvarnished cloth or tape.12. Procedure12.1 Prepare either square or rectangular speci
33、mens ofsufficient size to weigh not less than 0.18 oz (5 g). Accuratelyweigh on an analytical balance. Measure the length and widthdimensions with sufficient precision to be able to compute thearea within 0.3 %. Compute the weight per unit area.D295 12213. Report13.1 Report a description of the mate
34、rial and the weight inpounds per square yard or kilograms per square metre.14. Precision and Bias14.1 This test method has been in use for many years, but noinformation has been presented to ASTM upon which to basea statement of precision. No activity has been planned todevelop such information.14.2
35、 This test method has no bias because the value forweight per unit area is determined solely in terms of this testmethod itself.TEST METHOD C: THREAD COUNT15. Terminology15.1 Definitions of Terms Specific to This Standard:15.1.1 threads per inchof varnished cloths, the count ofthe number of warp and
36、 filling yarns present in the base clothper linear inch of width or length, respectively.16. Significance and Use16.1 Thread count, together with the weight and width ofthe cloth, is accepted as the common means for designating andidentifying cloth constructions.16.2 Certain of the physical and elec
37、trical properties ofwoven fabrics are dependent on thread count. That is, assumingthe same size of yarn, an increase in thread count increases theweight, breaking strength, and density of the cloth. Also, thedielectric breakdown voltage and the dissipation factor of thevarnished fabric may be change
38、d by altering the thread countof the cloth.17. Procedure17.1 Determine separately the warp and filling threads perinch of cloth by counting in a space of not less than 1 in. (25.4mm) in at least five different places on the specimen. Theaverage of the five determinations shall be the thread count.18
39、. Report18.1 Report the warp count and the filling count separatelyas threads per inch (or millimetre).NOTE 5The warp threads in straight-cut materials are the threads thatare parallel with the length or machine-direction dimension, while inbias-cut materials the warp threads are parallel with the s
40、eams or jointedselvages.NOTE 6Before counting black varnished materials it will be necessaryto remove the varnish film with a knife blade or other suitable instrument.Liquid varnish removers are unsuitable for this purpose as they may causea swelling of the fibers and a shrinkage of cloth with a con
41、sequent increasein threads per inch count; therefore, the films must be removed mechani-cally.19. Precision and Bias19.1 This test method has been in use for many years, but noinformation has been presented to ASTM upon which to basea statement of precision. No activity has been planned todevelop su
42、ch information.19.2 This test method has no bias because the value forthread count is determined solely in terms of this test methoditself.TEST METHOD D: BREAKING STRENGTH20. Significance and Use20.1 The breaking strength of finished cloth and tape is ofimportance as a measure of its ability to with
43、stand reasonablepulling without failure while being applied.21. Apparatus21.1 Testing machines of the dead-weight pendulum or ofthe constant-rate-of-elongation types shall be used, the latterbeing preferred.21.2 The machine shall be graduated to read 0.5 kg or 1 lb,or less per scale division for tes
44、ting specimens breaking at 50lb (22.7 kg) or over, and to 0.25 kg, or 0.5 lb, or less for testingspecimens breaking under 50 lb.22. Test Specimens22.1 Cut test specimens 1 in. (25.4 mm) in width and notless than 12 in. (305 mm) in length from full-width cloth orfrom tapes over 1 in. (25.4 mm) in wid
45、th. In the case of tapeshaving a nominal width of 1 in. (25.4 mm) or less, prepare testspecimens not less than 12 in. (305 mm) long using the originalwidth.NOTE 7If it is desired to test the seams or jointed selvages of bias-cutmaterials for breaking strength, mount specimens obtained as described i
46、nNote 4,(4.2) in the testing machine so that the seams or jointed selvagesare midway between the two jaws.23. Number of Specimens23.1 In the case of straight-cut cloths, cut five specimens inthe direction of the warp threads and five in the direction of thefilling threads from samples selected in ac
47、cordance with 4.1and 4.2.23.2 In the case of bias-cut cloths, cut five specimens in thedirection of the length from samples selected in accordancewith 4.1 and 4.2.23.3 In the case of tapes, cut five specimens from each rollselected in accordance with 4.1 and 4.2.24. Conditioning24.1 Condition specim
48、ens in accordance with Section 5.25. Procedure25.1 Adjust the clearance distance between jaws to be 6 in.(150 mm).25.2 Select the rate of travel of the movable jaw to beconstant and preferably 12 in. (305 mm)/min, but it may bewithin the limits of 11 and 13 in. (280 and 330 mm)/min,provided it is co
49、nstant.25.3 Reject all readings obtained when the specimens breakat or in the jaws.26. Report26.1 Report the following information:D295 12326.1.1 The average, maximum, and minimum breakingloads in kilograms or pounds, together with the width of thespecimens and the nominal thickness, and26.1.2 The relative humidity and temperature during theconditioning period, and at the time of the test.26.2 In the case of straight-cut cloths, report the breakingstrength of the warp threads and the filling threads separately.27. Precision and Bias27.1 This test method has been
