1、Designation: D4496 13Standard Test Method forD-C Resistance or Conductance of Moderately ConductiveMaterials1This standard is issued under the fixed designation D4496; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t 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 method covers the determination of electricalresistance and electrical resistivity of materials that are gener-
3、ally categorized as moderately conductive and are neither goodelectrical insulators nor good conductors.1.2 This test method applies to the materials that exhibitvolume resistivity in the range of 100to 107-cm or surfaceresistivity in the range of 103to 107 (per square).1.3 This test method is desig
4、ned for measurements atstandard conditions of 23C and 50 % relative humidity, but itsprinciples of operation can be applied to specimens measuredat lower or higher temperatures and relative humidities.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with it
5、s 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. Specific precau-tionary statements are given in 8.3.2. Referenced Documents2.1 ASTM Standards:2D257 Test Methods
6、for DC Resistance or Conductance ofInsulating MaterialsD374 Test Methods for Thickness of Solid Electrical Insu-lation (Withdrawn 2013)3D991 Test Method for Rubber PropertyVolume Resistiv-ity Of Electrically Conductive and Antistatic ProductsD1711 Terminology Relating to Electrical InsulationD6054 P
7、ractice for Conditioning Electrical Insulating Mate-rials for Testing (Withdrawn 2012)32.2 ASTM Adjuncts:Carbon black test cell (two drawings)43. Terminology3.1 Definitions:3.1.1 moderately conductivea solid material having vol-ume resistivity between 100and 107cm.3.1.2 For definitions of the terms
8、used, but not defined inthis standard, refer to Terminology D1711.3.2 Definitions of Terms Specific to This Standard:3.2.1 steady statefor the purpose of this test method,steady-state is attained if any rate of change in the observedresistance (or conductance) averages less than 0.25 %s.4. Summary o
9、f Test Method4.1 Specimens of the test material are conditioned at pre-scribed conditions and subjected to direct-voltage stress. Re-sistance or conductance is measured and used with the dimen-sional aspects of the specimen to compute the resistivity of thematerial. The apparatus and techniques used
10、 in this test methodare selected in accordance with the general principles set forthin Test Methods D257.5. Significance and Use5.1 This test method is useful for the comparison ofmaterials, as a quality control test, and for specificationpurposes.5.2 This test method is useful in the selection and
11、use ofmaterials in wires, cables, bushings, high-voltage rotatingmachinery, and other electrical apparatus in which shielding orthe distribution of voltage stress is of value.5.3 Commercially available “moderately conductive” mate-rials frequently are comprised of both conductive and resistivecompon
12、ents (that is, cellulose fibers with colloidal carbonblack particles attached to portions of the surfaces of thosefibers, or discrete conductive particles adhered to the surfacesof electrical insulating polymers). Such commercially availablematerials are often manufactured in a manner that results i
13、n1This test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.12 on Electrical Tests.Current edition approved May 1, 2013. Published July 2013. Originally approvedin 1985. Last previous edition
14、approved in 2004 as D4496 041, which waswithdrawn in January 2013 and reinstated in May 2013. DOI: 10.1520/D4496-13.2For 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
15、the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from ASTM International Headquarters. Order Adjunct No.ADJD4496.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, P
16、A 19428-2959. United States1anisotropy of electrical conduction. Hence, the significance oftests using this test method depends upon the orientation of thespecimen tested to the direction of the electric field and therelationship between this orientation and the orientation of thematerial in the ele
17、ctrical apparatus, which uses these materials.6. Apparatus6.1 Use apparatus conforming to the general requirementsset forth in Test Methods D257.6.2 Power SourceCapable of limiting the magnitude ofthe direct voltage applied to the specimen. (See Appendix X1for discussion of voltage stress and specim
18、en heating.)6.3 Test cells, that have been found to be satisfactory aredepicted in Fig. 1, Fig. 2, and Fig. 3.4NOTE 1Conductive paint is a suitable electrode material for speci-mens of certain materials and testing such specimens does not require testcell assemblies similar to ones shown in Fig. 1,
19、Fig. 2, and Fig. 34(seeAnnex A1 for additional information).7. Specimen Preparation and Selection7.1 Take specimens from a sample of material that has beenobtained in a random manner. Take care to protect the sampleand the specimens from any contamination, which will affectthe results of the resista
20、nce or conductance tests. Such con-tamination can include, in particular, salts or moisture fromhuman hands. Be aware of elevated temperatures, extremes ofhigh or low humidity, and the presence of chemical vapors, etc.7.2 Prior to testing, condition all specimens to equilibriumin the standard labora
21、tory atmosphere prescribed in PracticeD6054. For many materials the time of conditioning toequilibrium will require only a few hours (that is, less than 24h). Equilibrium with standard laboratory conditions is declaredattained if two consecutive volume resistance measurements onthe same specimen agr
22、ee within 61 %. The two consecutivemeasurements are to be made at the intervals separated at leastby4h.7.3 Determine the dimensions of the test specimens towithin6 2 % on material in equilibrium with the standardlaboratory atmosphere. Make all thickness measurements inaccordance with Method D of Tes
23、t Methods D374 using theappropriate procedure for the material being tested.7.4 For specimens incorporating conductive paint electrodessee Annex A1.7.5 For anisotropic materials, label and prepare specimensfor testing in each of the principal directions of anisotropy.NOTE 2Moderately conductive pape
24、r exhibits three axes of anisot-ropy. The principal axes in paper are machine direction (MD); cross-machine direction (CMD); and thickness direction (TD). Extruded poly-meric materials frequently show anisotropy with the axis of extrusion(direction of flow) compared to the axis of the material at ri
25、ght angles tothat direction of flow.8. Procedure8.1 Unless otherwise specified, make all measurementsusing an electrification time of less than 1 min. The electrifi-cation time shall be long enough to attain a “steady state” andthe magnitude of the voltage shall not be so great as to causeheating of
26、 the test specimen. See Appendix X1 for discussionof time effects of voltage application and specimen heating.8.2 Do not apply to the test specimen a power inputexceeding 1 W. For very conductive materials it is useful toincrease the size of a specimen or to decrease the test voltageby one or more o
27、rders of magnitude below 500 V in order toavoid the specimen overheating.8.3 Test a minimum of five specimens from each sample ineach of the principal directions of anisotropy. Use caution inhandling the specimens to avoid contaminating the surfaces.8.4 Place the specimen in the test cell or attach
28、the leads tothe painted-on electrodes. If mercury electrodes are used, takespecial care in handling the mercury.8.4.1 WarningMercury metal-vapor poisoning has longbeen recognized as a hazard in the industry. The maximumFIG. 1 Cell For Volume Resistivity 1-in.2Electrode (Mercury)D4496 132exposure lim
29、its are set by the American Conference of Gov-ernmental Industrial Hygienists.5The concentration of mercuryvapor over spills from broken thermometers, barometers, orother instruments using mercury can easily exceed theseexposure limits. Mercury, being a liquid and quite heavy, willdisintegrate into
30、small droplets and seep into cracks andcrevices in the floor. The use of a commercially availableemergency spill kit is recommended whenever a spill occurs.The increased area of exposure adds significantly to themercury vapor concentration in the air. Mercury vapor concen-tration is easily monitored
31、 using commercially available sniff-ers. Spot checks are to be made periodically around operationswhere mercury is exposed to the atmosphere. Thorough checksare to be made after spills.8.5 Measure the conductance, resistance, or voltagecurrentvalues, depending upon the type of apparatus shown in Tes
32、tMethods D257, that is being used. Record each observedmeasurement.8.6 Calculate the resistivity in accordance with Section 9.9. Calculation9.1 If the voltmeter-ammeter method of Test Methods D257is used in 8.5, calculate the resistance for each specimen usingthe equation:R 5 VI (1)where:R = resista
33、nce, ,V = applied direct voltage, V, andI = magnitude of the direct current, A.9.2 If the direct method of resistance of Test Methods D257is used, use the values observed and calculate the resistivity asfollows:5Available from the American Conference of Governmental IndustrialHygienists, Building No
34、. D-7, 6500 Glenway Ave., Cincinnati, OH 45211.AMass for applying contact force between current electrodes and the specimen (300 N/m times the specimen width in metres) (Note 1).BMass for applying contact force between potential electrodes and the specimen (60 N/m times specimen width in metres) (No
35、te 2).CThe specimen.DCurrent electrodes.EPotential electrodes.FDistance between the current and potential electrodes (20 mm minimum).G Distance between potential electrodes depends on specimen size.HWidth of current electrode, 5 to 8 mm (0.2 to 0.3 in.).XElectrical insulating material (10 tera cm vo
36、lume minimum resistivity).Note 1For a specimen 150 mm (6 in.) wide, mass is approximately 4.5 kg (10 lb).Note 2For a specimen 150 mm (6 in.) wide, mass is approximately 0.9 kg (2 lb).Note 3Fig. 2 is taken from Test Method D991.The electrode assembly (Fig. 2) shall consist of a rigid base made from a
37、n electrical insulating material having a volume resistivity greater than 10 T cm (for example,hard rubber, polyethylene, polystyrene, etc.) to which a pair of potential electrodes are fastened in such a manner that the four electrodes are parallel and their top surfacesare in the same horizontal pl
38、ane. Another pair of current electrodes identical with the first pair shall be fastened to a second piece of insulating material so that they canbe superimposed on the specimen directly above the first pair. The current electrodes shall have a length at least 10 mm (0.4 in.) greater than the specime
39、n width, a widthbetween 5 and 8 mm (0.2 and 0.3 in.), and a height uniform with 0.05 mm (0.002 in.) between 10 and 15 mm (0.4 and 0.6 in.). The potential electrodes shall have a lengthand height equal to the current electrodes, and shall be tapered to an edge having a radius of 0.5 mm (0.02 in.) max
40、imum at the top surface. The distance between thepotential electrodes shall be not less than 10 mm (0.4 in.) nor more than 66 mm (2.6 in.) and shall be known within+2%.Thecurrentelectrodes shall be equidistant outsidethe potential electrodes by at least 20 mm (0.8 in.). The electrodes shall be made
41、from a corrosion-resistant metal such as brass, nickel, stainless steel, etc. Insulationresistance between electrodes shall be greater than 1 T.FIG. 2 Electrode AssemblyFIG. 3 Cell For Surface Resistance Assembly PhotoD4496 1339.2.1 Volume Resistivity = v(in cm)v5 RvAt(2)where:Rv= volume resistance,
42、 ,A = area of the electrodes, cm2, andt = distance between the electrodes, cm.9.2.2 Surface Resistivity in (per square) ss5 RsW/L! (3)where:Rs= surface resistance, L = length of the specimen between electrodes, andW = width of the specimen.NOTE 3The ratio (W/L) is analogous to the (P/g) ratio shown
43、in TestMethods D257.NOTE 4L and W must be measured in the same units of distance. Theunit of surface resistivity is ohms (or megohms). It is common practice torefer to surface resistivity as ohms per square.10. Report10.1 Include in the report:10.1.1 Complete identification of the material tested.10
44、.1.2 Average and the standard deviation of the resistivitiescomputed shall be reported as the resistivity of the sample.10.1.3 Median (or central value) of the resistivities com-puted is often of interest and shall be reported.10.1.4 High and low (or the range of ) resistivities.10.1.5 Average, and
45、the high and low (or the range of)resistivity for each principal direction of anisotropy if aniso-tropic material is tested.10.1.6 Listing of any deviations from the prescribed testconditions.10.1.7 Type of test cell used.10.1.8 Fact that conductive paint was used, if applicable.10.1.9 Voltage appli
46、ed to the test specimen.10.1.10 Thickness of the specimens tested.11. Precision and Bias11.1 The measurements have been done using the test cellshown in Fig. 1 and a voltage stress below 10 direct VDC/mil(400 kVDC/m). The results in a single laboratory by threedifferent operators showed agreement wi
47、thin 6 3 % of theaverage value of volume resistivity.The moderately conductivematerials tested were carbon-black cellulose papers havingvolume resistivities 103to 105cm at 23C and 50 % relativehumidity.11.2 Using the test cell shown in Fig. 2 and a voltage stressof approximately 20 kVDC/m, the surfa
48、ce resistivity showedagreement within 610 % of the average value. The moderatelyconductive carbon-black cellulose paper ranged from 104to106 per square at 23C and 50 % relative humidity. Thesurface resistance using silver paint electrodes was not signifi-cantly different from the resistance using th
49、e test cell of Fig. 2and strips cut 1-in. wide.11.3 The bias of this test method has not been determined.12. Keywords12.1 electrical shielding; moderately conductive; semicom;surface resistivity; volume resistivityANNEX(Mandatory Information)A1. INFORMATION PERTINENT TO MEASUREMENTS OF SPECIMENS WITH ELECTRODES OF CONDUCTIVE PAINTINTRODUCTIONIt has been found practical to make resistance measurements with conductive paint applied to thesurface of a specimen to provide an electrode that has intimate contact with the material.Not al
