1、Designation: D 991 89 (Reapproved 2005)Standard Test Method forRubber PropertyVolume Resistivity Of ElectricallyConductive and Antistatic Products1This standard is issued under the fixed designation D 991; the number immediately following the designation indicates the year oforiginal adoption or, in
2、 the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 T
3、his test method covers the determination of volumeresistivity of rubbers used in electrically conductive andantistatic products.1.2 This test method assumes that the surface conductivityis negligible compared with the conductivity through thespecimen.1.3 The values stated in SI units are to be regar
4、ded as thestandard. The values given in parentheses are for informationonly.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 determi
5、ne the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 3182 Practice for RubberMaterials, Equipment, andProcedures for Mixing Standard Compounds and Prepar-ing Standard Vulcanized SheetsD 4483 Practice for Evaluating Precision for Test MethodStandar
6、ds in the Rubber and Carbon Black ManufacturingIndustries3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 rubber product, antistatica rubber product suffi-ciently conductive to prevent a build-up of an electrical chargeon the surface and sufficiently insulating to prevent an el
7、ectri-cal hazard.3.1.1.1 DiscussionGenerally, antistatic rubber productsare considered to have a resistance of 104to 108V.3.1.2 rubber product, conductivea rubber product havingan electrical conductivity of sufficient magnitude that might beconsidered an electrical or thermal hazard.3.1.2.1 Discussi
8、onGenerally, conductive rubber productsare considered to have a resistance of less than 104V at 120 V.3.1.3 volume resistivitythe ratio of the electric potentialgradient to the current density when the gradient is parallel tothe current in the material.4. Significance and Use4.1 The electrical behav
9、ior of rubber products used inparticular applications is important for a variety of reasonssuch as safety, static changes, current transmission, etc. Thistest method is useful in predicting the behavior of such rubberproducts.5. Apparatus5.1 Electrode AssemblyThe electrode assembly (Fig. 1)shall con
10、sist of a rigid base made from an electrically insulat-ing material having a resistivity greater than 10 TVm (forexample, hard rubber, polyethylene, polystyrene, etc.) to whicha pair of current electrodes and a pair of potential electrodes arefastened in such a manner that the four electrodes are pa
11、ralleland their top surfaces are in the same horizontal plane.Anotherpair of current electrodes identical with the first pair shall befastened to a second piece of insulating material so that theycan be superimposed on the specimen directly above the firstpair. The current electrodes shall have a le
12、ngth at least 10 mm(0.4 in.) greater than the specimen width, a width between 5and 8 mm (0.2 and 0.3 in.), and a height uniform within 0.05mm (0.002 in.) between 10 and 15 mm (0.4 and 0.6 in.). Thepotential electrodes shall have a length and height equal to thecurrent electrodes and shall be tapered
13、 to an edge having aradius of 0.5 mm (0.02 in.) maximum at the top surface. Thedistance between the potential electrodes shall not be less than10 mm (0.4 in.) nor more than 66 mm (2.6 in.) and shall beknown within 62 %. The current electrodes shall be equidis-tant outside the potential electrodes an
14、d separated from themby at least 20 mm (0.8 in.). The electrodes shall be made from1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.10 on Physical Testing.Current edition approved May 1, 2005. Published May 2005. Original
15、lyapproved in 1948. Last previous edition approved in 2000 as D 991 89 (2000).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 on
16、the ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.a corrosion-resistant metal such as brass, nickel, stainless steel,etc. Insulation resistance between electrodes shall be greaterthan 1 TV.5.2 Resistance-Measuring Devi
17、ceResistance may bemeasured by any electrical circuit that enables the currentthrough the current electrodes and the potential across thepotential electrodes to be measured within 2 %. Suitabledevices for measuring current are: (1) a precision milliamme-ter,or(2) potential measurement across a refer
18、ence resistor(resistance value known within 2 % in series with the currentelectrodes. Suitable devices for measuring potential are: (1)agalvanometer having a sensitivity of 1 A or less per scaledivision in a null-voltage circuit; (2) an electrostatic voltmeterhaving a d-c resistance greater than 19
19、TV;or(3) an electrom-eter such as a multirange voltmeter having an input d-cimpedance greater than 0.1 TV (Note 1). In any case, thecurrent through the potential electrodes during measurementmust be less than 1 % of that through the current electrodes. Astable source of d-c potential shall be provid
20、ed that can beadjusted to limit the power dissipated in the specimen betweenpotential electrodes to approximately 0.1 W. Because of thelarge range of resistances covered by conductive and antistaticrubbers, separate equipment for measuring resistances aboveand below approximately 50 000 V is general
21、ly desirable.NOTE 1Schematic diagrams of a typical apparatus that have beenfound to be satisfactory are shown in Figs. X1.1 and X1.2.5.3 Electrode ContactsMasses shall be provided to pro-duce a uniform contacting force across the width of thespecimen of approximately 300 N/m (4.5 kg (10 lb) on thest
22、andard sheet, 150 mm (6 in.) wide, by the current electrodesand 60 N/m (0.9 kg (2 lb) on the standard sheet, 150 mm (6in.) wide, by the potential electrodes.6. Specimens6.1 SizeThe width of the specimen shall be between 10and 150 mm (0.4 and 6 in.) and the length shall be between 70and 150 mm (2.8 a
23、nd 6 in.). The width shall be uniform within61 %. The thickness of cut specimens is specified in 6.3.Molded specimens are specially prepared as described in 6.2and therefore have a thickness of 2.0 6 0.2 mm (0.08 6 0.008in.).6.2 Molded SpecimenStandard sheets prepared in accor-dance with Practice D
24、3182 may be used, provided the surfaceof the uncured rubber is kept free of soapstone or othercontamination, and the surface of the vulcanized sheet is notcontaminated with mold lubricant. To avoid surface contami-nation and minimize distortion of specimen prior to test, sheetsmay be molded between
25、sheets of moisture-sensitive cello-phane, which can be readily removed after brief immersion inwarm water. After removing the cellophane, the surface of thesheet should be patted dry, taking care not to bend or stretch thesheet.6.3 Cut SpecimenThe specimen shall be cut from aproduct that has not bee
26、n buffed or abraded. Surfaces of thespecimen shall be cleaned if necessary by rubbing with Fullersearth and water, washing with distilled water, and drying in air.The specimen shall be uniform in thickness within 65 %, notmore than 6.6 mm (0.26 in.), and if possible, not less than 2mm (0.08 in.) thi
27、ck. Care shall be taken to avoid distortion ofthe specimen during preparation.7. Conditioning7.1 The time between vulcanization and testing shall be notless than 16 h nor more than 4 weeks for molded specimens.Products shall be tested within 2 months after receipt by thecustomer.7.2 Specimens cut fr
28、om products or molded specimens thathave been inadvertently distorted shall be annealed in air for 3hat236 2C (73.4 6 3.6F) to remove strains or other effectsof handling.7.3 Specimens shall be conditioned for at least 16 h andtested at a temperature of 23 6 2C (73.4 6 3.6F) and aA Mass for applying
29、contact force between current electrodes and specimen(300 N/m times specimen width in meters) (Note 1)B Mass for applying contact force between potential electrodes and specimen(60 N/m times specimen width in meters) (Note 2)C SpecimenF Distance between current and potential electrodes (20 mm minimu
30、m)G Distance between potential electrodes (see Note 2in Section 9)depends on specimen size.H Width of current electrode, 5 to 8 mm (0.2 to 0.3 in.)X InsulationD Current ElectrodesE Potential ElectrodesNOTE 1For a specimen 150 mm (6 in.) wide, mass is approximately 4.5 kg (10 lb).NOTE 2For a specimen
31、 150 mm (6 in.) wide, mass is approximately 0.9 kg (2 lb).FIG. 1 Electrode AssemblyD 991 89 (2005)2maximum relative humidity of 65 %. Molded specimens can beconditioned in a desiccator. Specimens annealed at roomtemperature may be stored in a closed container during theconditioning period.8. Procedu
32、re8.1 After conditioning, place the specimen in the electrodeassembly, taking care to avoid flexing or distortion. Theidentification portion of standard sheets shall be normal to thecalender grain and shall not be in contact with, nor lie between,the current electrodes.8.2 Adjust the current through
33、 the specimen after connec-tion to the d-c source so that the power dissipation in thespecimen between potential electrodes is approximately 0.1 W.The following values should not be exceeded for the maximumcurrent in the specimen for various potentials across thepotential electrodes:Potential Curren
34、t, mA35062510 1530 575 2150 1300 0.58.3 As soon as the current has stabilized, in a maximumtime of 5 s, measure the potential difference across thepotential electrodes and the current through the current elec-trodes to the nearest 1 % of the respective values.8.4 Measure the thickness and width of t
35、he specimen.8.5 Make the measurements on three specimens.9. Calculation9.1 Calculate the volume resistivity as follows for eachspecimen:r5Vwdk/Il (1)where:r = volume resistivity, Vm,V = potential difference, V, across potential electrodes,I = current, A, through the current electrodes,w = width of s
36、pecimen,d = thickness of specimen,l = distance between potential electrodes,k = factor depending on units in which, w, d, and l aremeasured; that is, k is 0.001 if w, d, and l are inmillimetres and 0.0254 if they are in inches.NOTE 2If l is made 64.5 mm (2.54 in.) and w and d are measured ininches,
37、the equation becomes:r50.01 Vwd/I (2)9.2 Report the median value for the three specimens as thevolume resistivity.10. Report10.1 Report the following information:10.1.1 Temperature during conditioning and test,10.1.2 Relative humidity during conditioning and testing,10.1.3 Size of specimen,10.1.4 Cu
38、rrent through specimen in amperes,10.1.5 Voltage across potential electrodes, and10.1.6 Volume resistivity in ohm-metres, kilohm-metres, ormegohm-metres.11. Precision and Bias311.1 These precision and bias statements have been pre-pared in accordance with Practice D 4483. Refer to PracticeD 4483 for
39、 terminology and other testing and statistical con-cepts.11.2 Because of the special nature of this test and its lack ofwidespread use in the industry, a limited interlaboratory Type 1test program was used to assess precision. Two materials(rubber compositions) of different volume resistivity in the
40、form of cured sheets were prepared in one laboratory and sentto the other participating laboratory. Both laboratories wereexperienced in this testing.11.3 In each laboratory the cured rubber sheets were mea-sured for volume resistivity on two days, on each day by twodifferent operators. The within l
41、aboratory variation, therefore,contains an “operator” and “day” component of variation.11.4 A test result is the median value of three measurementsof volume resistivity.11.4.1 Table 1 gives the precision results. Due to the widerange of volume resistivity values that are possible (101000fold variati
42、on) the analysis was conducted using the (base 10)logarithms of the (test result) volume resistivity, r.11.4.2 The rather large between laboratory variation indi-cates the difficulty frequently experienced with this measure-ment by experienced laboratories and operators.11.4.3 BiasIn test method sta
43、tistical terminology, bias isthe difference between an average test value and the referenceor true test property value. Reference values do not exist forthis test method since the value or level of the test property isexclusively defined by the test method. Bias, therefore, cannotbe determined.3Supp
44、orting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D11-1030.TABLE 1 Type 1 Precision for Log(r)NOTE 1Only two laboratories participated in the program for theseresults.MaterialMeanLevelWithin LaboratoryABetween LaboratoryASrr (r) SRR (
45、R)123.392B4.8550.0650.1320.1840.3745.47.70.3290.5770.9311.6327.433.6ASr= within laboratory standard deviation.r = repeatability (in measurement units).(r) = repeatability (in percent).SR= between laboratory standard deviation.R = reproducibility (in measurement units).(R) = reproducibility (in perce
46、nt).BTabulated values (as used for analysis), log10(r).D 991 89 (2005)3APPENDIX(Nonmandatory Information)X1. CIRCUIT DIAGRAMS AND EXPLANATORY MATERIALX1.1 With switch Sw1closed and the milliammeter set at015 mA, turn the rotary switch Sw2to develop current withmaximum values as follows:Switch Contac
47、ts Maximum Current, mA14 1556 379 1Fine adjustment of current can be accomplished by resis-tances R1, R2, and R3.X1.2 With switch Sw3closed and rotary switch Sw4swungto approximate position, or one or two contacts less than Sw2,close switch Sw7, set R7for minimum resistance (least sensitiveposition
48、for galvanometer), and then close switch Sw5. For nullbalance (zero reading on galvanometer), adjust R4, R5, and R6and increase the sensitivity of the galvanometer by increasingR7, eventually opening switch Sw7to eliminate R7altogether.Close switch Sw6to read voltage. It is desirable to limit thewat
49、tage dissipated in the sample to 0.1 W between voltageelectrodes. This condition is satisfied by the product of voltstimes milliamperes being not greater than 100.A and A8Current electrodes.B and B8Voltage electrodes.Sw1, Sw3, Sw6, and Sw7On-off toggle switches.Sw2and Sw4Single-pole, 11-contact radio type rotary selector switches.Sw5Normally open momentary contact switch.Source of VoltageTwo banks of dry cells each consisting of four 112-V cells,and four 45-V “B” batteriesone connected at 2212 V.MMilliammeter, Weston D-C
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