ASTM D4470-1997(2004) Standard Test Method for Static Electrification《静电起电的标准试验方法》.pdf
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1、Designation: D 4470 97 (Reapproved 2004)An American National StandardStandard Test Method forStatic Electrification1This standard is issued under the fixed designation D 4470; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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.1. Scope1.1 This test method covers the generation of electrostaticcharge, the measurement of this charge and its associated
3、electric field, and the test conditions which must be controlledin order to obtain reproducible results. This test method isapplicable to both solids and liquids. This test method is notapplicable to gases, since a transfer of a gas with no solidimpurities in it does not generate an electrostatic ch
4、arge. Thistest method also does not cover the beneficial uses of staticelectrification, its associated problems or hazards, or theelimination or reduction of unwanted electrostatic charge.21.2 The values stated in SI units are to be regarded as thestandard.1.3 This standard does not purport to addre
5、ss 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.2. Referenced Documents2.1 ASTM Standards:3D 618 Practice
6、for Conditioning Plastics for TestingD 5032 Practice for Maintaining Constant Relative Humid-ity by Means of Aqueous Glycerin SolutionsE 104 Practice for Maintaining Constant Relative Humidityby Means of Aqueous Solutions3. Terminology3.1 Definitions:3.1.1 conducting material (conductor), na materia
7、l withinwhich an electric current is produced by application of avoltage between points on or within the material.3.1.1.1 DiscussionThe term “conducting material” is usu-ally applied only to those materials in which a relatively smallpotential difference results in a relatively large current since a
8、llmaterials appear to permit some conduction current. Metalsand strong electrolytes are examples of conducting materials.3.1.2 electric field strength, nthe magnitude of the vectorforce on a point charge of unit value and positive polarity.3.1.3 excess electrostatic charge, nthe algebraic sum ofall
9、positive and negative electric charges on the surface of, orin, a specific volume.3.1.4 insulating material (insulator), na material in whicha voltage applied between two points on or within the materialproduces a small and sometimes negligible current.3.1.5 resistivity, surfacethe surface resistanc
10、e multipliedby that ratio of specimen surface dimensions (width of elec-trodes defining the current path divided by the distancebetween electrodes) which transforms the measured resistanceto that obtained if the electrodes formed the opposite sides ofa square.3.1.5.1 DiscussionSurface resistivity is
11、 expressed inohms. It is popularly expressed also as ohms/square (the size ofthe square is immaterial). Surface resistivity is the reciprocal ofsurface conductivity.3.2 Definitions of Terms Specific to This Standard:3.2.1 apparent contact area, nthe area of contact betweentwo flat bodies.3.2.1.1 Dis
12、cussionIt is the area one would calculate bymeasuring the length and width of the rectangular macroscopiccontact region.3.2.2 dissipative material, na material with a volumeresistivity greater than 104ohm-cm and less than 1012ohm-cm,a resistivity range between conductive and insulating materialas de
13、fined in this test method.3.2.3 real contact area, nthe regions of contact betweentwo bodies through which mechanical actions or reactions aretransferred.1This test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibilit
14、y ofSubcommittee D09.12 on Electrical Tests.Current edition approved March 1, 2004. Published March 2004. Originallyapproved in 1985. Last previous edition approved in 1997 as D 4470 97.2Vosteen, R. E., and Bartnikas, R., Chapter 5, “Electrostatic Charge Measure-ments,” Engineering Dielectrics, Vol.
15、 IIB, Electrical Properties of Solid InsulatingMaterials, Measurement Techniques , R. Bartnikas, Editor, ASTM STP 926, ASTM,Philadelphia, 1987.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards vo
16、lume information, refer to the standards Document Summary page onthe ASTM website.4Annual Book of ASTM Standards, Vol 11.03.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.3.1 DiscussionSince real bodies are never perfectlysmooth
17、, at least on a microscopic scale, the real contact area ofapparently flat materials is always less than the apparentcontact area.3.2.4 triboelectric charge generationthe formation, withor without rubbing, of electrostatic charges by separation ofcontacting materials.54. Significance and Use4.1 When
18、ever two dissimilar materials are contacted andseparated, excess electrostatic charge (triboelectric charge) willbe found on these materials if at least one of the materials is agood insulator. This excess charge gives rise to electric fieldswhich can exert forces on other objects. If these fields e
19、xceedthe breakdown strength of the surrounding gas, a disruptivedischarge (spark) may occur. The heat from this discharge mayignite explosive atmospheres, the light may fog photosensi-tized materials, and the current flowing in a static dischargemay cause catastrophic failure of solid state devices.
20、 Electricforces may be used beneficially, as in electrostatic copying,spray painting and beneficiation of ores. They may be detri-mental as when they attract dirt to a surface or when they causesheets to stick together. Since most plastic materials in usetoday have very good insulating qualities, it
21、 is difficult to avoidgeneration of static electricity. Since it depends on manyparameters, it is difficult to generate static electricity reliablyand reproducibly.5. Apparatus5.1 Charging MechanismsThe charging mechanisms canbe constructed in a variety of ways, and should preferably bemade as anala
22、gous to the particular application as possible.Some examples of charging mechanisms are described in 5.1.1,5.1.2, and 5.1.3.5.1.1 Powder or Liquids Transported Through Tubes orDown TroughsContact between the specimen and wall of thetube will charge the specimen or the tube, or both. Either thespecim
23、en or the tube must be insulating, or partially insulating.When the specimen is separated from the tube, electrostaticcharge will be generated. This charge may be measured bycatching a known amount of the specimen in a Faraday cage,or the charge remaining on the tube may be measured.Atroughmay be su
24、bstituted for the tube and gravity used to effect themovement of the specimen along the trough.5.1.2 Webs Transported Over RollersContact between theweb and the roller surface will charge the web if it is aninsulator or partial insulator. If the rollers are insulators orpartial insulators they will
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