1、Designation: D991 89 (Reapproved 2010)Standard Test Method forRubber PropertyVolume Resistivity Of ElectricallyConductive and Antistatic Products1This standard is issued under the fixed designation D991; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This
3、 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 regarded
4、 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 determine
5、the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D3182 Practice for RubberMaterials, Equipment, andProcedures for Mixing Standard Compounds and Prepar-ing Standard Vulcanized SheetsD4483 Practice for Evaluating Precision for Test MethodStandards in
6、 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 electri
7、-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 DiscussionGen
8、erally, 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 behavior o
9、f 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 consist
10、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 paralle
11、land 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 length
12、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 to a
13、n 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 and sep
14、arated 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 Jan. 1, 2010. Published April 2010. Originally
15、approved in 1948. Last previous edition approved in 2005 as D991 89 (2005).DOI: 10.1520/D0991-89R10.2For 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 Do
16、cument Summary page onthe 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 Res
17、istance-Measuring DeviceResistance 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 meas
18、urement across a reference 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 resis
19、tance greater than 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 pot
20、ential shall be provided 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 approximate
21、ly 50 000 V is generally 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
22、.5 kg (10 lb) on thestandard 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 betwe
23、en 70and 150 mm (2.8 and 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-
24、dance with Practice D3182 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, sheetsm
25、ay be molded between 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 apro
26、duct that has not been 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 th
27、an 2mm (0.08 in.) thick. 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
28、.7.2 Specimens cut from 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
29、aA Mass for applying 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 ele
30、ctrodes (20 mm minimum)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)
31、.NOTE 2For a specimen 150 mm (6 in.) wide, mass is approximately 0.9 kg (2 lb).FIG. 1 Electrode AssemblyD991 89 (2010)2maximum relative humidity of 65 %. Molded specimens can beconditioned in a desiccator. Specimens annealed at roomtemperature may be stored in a closed container during theconditioni
32、ng period.8. Procedure8.1 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
33、 the current through 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 electro
34、des:Potential Current, 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 thic
35、kness and width of the 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 elect
36、rodes,w = width of specimen,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
37、 measured ininches, 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 o
38、f specimen,10.1.4 Current 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 D4483. Refer to
39、 PracticeD4483 for 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
40、resistivity in theform 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 opera
41、tors. The within laboratory 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 (
42、101000fold variation) 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 Bias
43、In test method statistical 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, cannotb
44、e determined.3Supporting 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 Laborat
45、oryASrr (r) SRR (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) = reproduc
46、ibility (in percent).BTabulated values (as used for analysis), log10(r).D991 89 (2010)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 follo
47、ws:Switch Contacts 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 se
48、nsitiveposition 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
49、 to limit thewattage 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.MMilliam
