ASTM D4470-18

Standard Test Method for Static Electrification

SIGNIFICANCE AND USE
4.1 Whenever two dissimilar materials are contacted and separated, excess electrostatic charge (triboelectric charge) will be found on these materials if at least one of the materials is a good insulator. This excess charge gives rise to electric fields which can exert forces on other objects. If these fields exceed the breakdown strength of the surrounding gas, a disruptive discharge (spark) can occur. The heat from this discharge can ignite explosive atmospheres, the light can fog photosensitized materials, and the current flowing in a static discharge can cause catastrophic failure of solid state devices. Electric forces can be used beneficially, as in electrostatic copying, spray painting and beneficiation of ores. They can be detrimental as when they attract dirt to a surface or when they cause sheets to stick together. Since most plastic materials in use today have very good insulating qualities, it is difficult to avoid generation of static electricity. Since it depends on many parameters, it is difficult to generate static electricity reliably and reproducibly.
SCOPE
1.1 This test method covers the generation of electrostatic charge, the measurement of this charge and its associated electric field, and the test conditions which must be controlled in order to obtain reproducible results. This test method is applicable to both solids and liquids. This test method is not applicable to gases, since a transfer of a gas with no solid impurities in it does not generate an electrostatic charge. This test method also does not cover the beneficial uses of static electrification, its associated problems or hazards, or the elimination or reduction of unwanted electrostatic charge.2  
1.2 The values stated in SI units are to be regarded as the standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Mar-2018
• ICS: 17.220.01 - Electricity. Magnetism. General aspects
• Technical Committee: D09 - Electrical and Electronic Insulating Materials
• Drafting Committee: D09.12 - Electrical Tests

Relations

• Replaces: ASTM D4470-97(2010) - Standard Test Method for Static Electrification
• Effective Date: 01-Apr-2018
• Refers: ASTM D1711-24 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Mar-2024
• Refers: ASTM D5032-19 - Standard Practice for Maintaining Constant Relative Humidity by Means of Aqueous Glycerin Solutions
• Effective Date: 01-Mar-2019
• Refers: ASTM D1711-15 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2015
• Refers: ASTM D1711-14a - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2014
• Refers: ASTM D1711-14 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-May-2014
• Refers: ASTM D1711-13 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Nov-2013
• Refers: ASTM E104-02(2012) - Standard Practice for Maintaining Constant Relative Humidity by Means of Aqueous Solutions
• Effective Date: 01-Apr-2012
• Refers: ASTM D5032-11 - Standard Practice for Maintaining Constant Relative Humidity by Means of Aqueous Glycerin Solutions
• Effective Date: 01-Aug-2011
• Refers: ASTM D1711-11a - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-Aug-2011
• Refers: ASTM D618-08 - Standard Practice for Conditioning Plastics for Testing
• Effective Date: 01-Nov-2008
• Refers: ASTM D1711-08 - Standard Terminology Relating to Electrical Insulation
• Effective Date: 01-May-2008
• Refers: ASTM E104-02(2007) - Standard Practice for Maintaining Constant Relative Humidity by Means of Aqueous Solutions
• Effective Date: 01-Oct-2007
• Refers: ASTM D618-05 - Standard Practice for Conditioning Plastics for Testing
• Effective Date: 01-Nov-2005
• Refers: ASTM D5032-97(2003) - Standard Practice for Maintaining Constant Relative Humidity by Means of Aqueous Glycerin Solutions
• Effective Date: 10-Mar-2003

Overview

ASTM D4470-18 – Standard Test Method for Static Electrification provides a comprehensive method for generating, measuring, and analyzing electrostatic charges and their associated electric fields in both solid and liquid materials. Developed by ASTM International, this standard is essential for industries where understanding static electricity is crucial for product safety, quality control, and process efficiency. The standard excludes gases as generation of static charge typically does not occur without solid impurities, and it also does not address the beneficial or hazardous effects of electrostatic charges, focusing solely on their reliable and reproducible measurement.

Key Topics

• Static Electricity Generation: Explains how triboelectric charges are produced when dissimilar materials, especially insulators, come into contact and are subsequently separated.
• Electrostatic Charge Measurement: Details the use of devices such as the Faraday cage, electrometers, and fieldmeters for quantifying static charges and electric fields.
• Controlled Test Conditions: Emphasizes the importance of maintaining specific parameters like specimen cleanliness, area and time of contact, separation speed, and ambient electric fields during testing to ensure reproducibility.
• Specimen Preparation and Conditioning: Discusses specimen selection, preparation, and environmental conditioning (temperature and humidity) for standardized results.
• Calibration Procedures: Outlines steps for calibrating measurement instruments to ensure precision and accuracy.

Applications

The standardized method from ASTM D4470-18 is applicable across various industries and research settings, where understanding and controlling static electricity is critical. Typical uses include:

• Quality Control in Manufacturing: Ensuring materials such as plastics, films, powders, and liquids do not accumulate unsafe static charges during processing, packaging, and transport.
• Workplace Safety: Minimizing static discharge risks that could ignite flammable atmospheres or damage sensitive electronic equipment.
• Product Testing and R&D: Evaluating the electrostatic properties of new materials for use in electronics, coatings, textiles, and packaging.
• Process Optimization: Identifying process parameters that influence static build-up during handling of materials such as powders or web-based products.

Correct application of this standard helps in mitigating static-related issues, such as unwanted particle attraction, damage to electronic components, and risks of fires or explosions due to electrostatic discharge.

Related Standards

Several ASTM standards are referenced and complement ASTM D4470-18 for static electrification testing and material conditioning:

• ASTM D618: Practice for Conditioning Plastics for Testing
• ASTM D1711: Terminology Relating to Electrical Insulation
• ASTM D5032: Practice for Maintaining Constant Relative Humidity by Means of Aqueous Glycerin Solutions
• ASTM E104: Practice for Maintaining Constant Relative Humidity by Means of Aqueous Solutions

These related standards ensure consistent specimen preparation and clear terminology, helping achieve reliable and comparable static electrification measurements.

---

Keywords: ASTM D4470, static electrification, electrostatic charge measurement, triboelectric charge, Faraday cage, fieldmeter, static electricity testing, material conditioning, antistatic testing, static discharge control, plastic insulation, charge density, electrostatic field strength, quality control, workplace safety.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D4470 −18
Standard Test Method for
Static Electrification
This standard is issued under the fixed designation D4470; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope by Means of Aqueous Glycerin Solutions
E104Practice for Maintaining Constant Relative Humidity
1.1 This test method covers the generation of electrostatic
by Means of Aqueous Solutions
charge, the measurement of this charge and its associated
electric field, and the test conditions which must be controlled
3. Terminology
in order to obtain reproducible results. This test method is
applicable to both solids and liquids. This test method is not
3.1 Definitions:
applicable to gases, since a transfer of a gas with no solid
3.1.1 Fordefinitionsoftermsusedinthisspecification,refer
impurities in it does not generate an electrostatic charge. This
to Terminology D1711.
test method also does not cover the beneficial uses of static
3.1.2 conductingmaterial(conductor),n—amaterialwithin
electrification, its associated problems or hazards, or the
which an electric current is produced by application of a
elimination or reduction of unwanted electrostatic charge.
voltage between points on or within the material.
3.1.2.1 Discussion—The term “conducting material” is usu-
1.2 The values stated in SI units are to be regarded as the
ally applied only to those materials in which a relatively small
standard.
potentialdifferenceresultsinarelativelylargecurrentsinceall
1.3 This standard does not purport to address all of the
materials appear to permit some conduction current. Metals
safety concerns, if any, associated with its use. It is the
and strong electrolytes are examples of conducting materials.
responsibility of the user of this standard to establish appro-
3.1.3 electric field strength, n—the magnitude of the vector
priate safety, health, and environmental practices and deter-
force on a point charge of unit value and positive polarity.
mine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accor- 3.1.4 excess electrostatic charge, n—the algebraic sum of
dance with internationally recognized principles on standard-
all positive and negative electric charges on the surface of, or
ization established in the Decision on Principles for the in, a specific volume.
Development of International Standards, Guides and Recom-
3.1.5 insulatingmaterial(insulator),n—amaterialinwhich
mendations issued by the World Trade Organization Technical
a voltage applied between two points on or within the material
Barriers to Trade (TBT) Committee.
produces a small and sometimes negligible current.
3.1.6 resistivity, surface, n—the surface resistance multi-
2. Referenced Documents
plied by that ratio of specimen surface dimensions (width of
2.1 ASTM Standards:
electrodes defining the current path divided by the distance
D618Practice for Conditioning Plastics for Testing
between electrodes) which transforms the measured resistance
D1711Terminology Relating to Electrical Insulation
to that obtained if the electrodes formed the opposite sides of
D5032PracticeforMaintainingConstantRelativeHumidity
a square.
3.1.6.1 Discussion—Surface resistivity is expressed in
ohms.Itispopularlyexpressedalsoasohms/square(thesizeof
This test method is under the jurisdiction of ASTM Committee D09 on
thesquareisimmaterial).Surfaceresistivityisthereciprocalof
Electrical and Electronic Insulating Materials and is the direct responsibility of
surface conductivity.
Subcommittee D09.12 on Electrical Tests.
Current edition approved April 1, 2018. Published April 2018. Originally
3.2 Definitions of Terms Specific to This Standard:
approved in 1985. Last previous edition approved in 2010 as D4470–97(2010).
DOI: 10.1520/D4470-18. 3.2.1 apparent contact area, n—the area of contact between
Vosteen, R. E., and Bartnikas, R., Chapter 5, “Electrostatic Charge
two flat bodies.
Measurements,” Engineering Dielectrics, Vol. IIB, Electrical Properties of Solid
3.2.1.1 Discussion—It is the area one would calculate by
Insulating Materials, Measurement Techniques, R. Bartnikas, Editor, ASTM STP
measuringthelengthandwidthoftherectangularmacroscopic
926, ASTM, Philadelphia, 1987.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact region.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3.2.2 dissipative material, n—a material with a volume
Standards volume information, refer to the standard’s Document Summary page on
4 12
the ASTM website. resistivitygreaterthan10 ohm-cmandlessthan10 ohm-cm,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4470−18
a resistivity range between conductive and insulating material fieldmeter, or the charge on the web can be measured with a
as defined in this test method. cylindrical Faraday cage if the width of the web is not too
large.
3.2.3 real contact area, n—the regions of contact between
5.1.3 Transport of Insulating or Partially Insulating Sheet
two bodies through which mechanical actions or reactions are
Material—Sheet materials are able to be transported on air
transferred.
layers, by sliding down chutes, by vacuum platens, and by
3.2.3.1 Discussion—Since real bodies are never perfectly
pinch rollers. Of these types of transport, pinch rollers and
smooth,atleastonamicroscopicscale,therealcontactareaof
sliding down chutes generate the largest amount of charge.
apparently flat materials is always less than the apparent
Generally, the better the contact (larger real contact area), the
contact area.
greater will be the charge generated. Pinch rollers are usually
3.2.4 triboelectric charge generation—theformation,with
a high pressure, small apparent area of contact, leading to a
or without rubbing, of electrostatic charges by separation of
relatively large real area of contact between the sheet and
contacting materials.
rollers. Sliding serves to multiply the real area of contact over
that which would be obtained with a contact without sliding.
4. Significance and Use
5.2 Electrostatic Charge Measurements—Fig. 1 shows a
4.1 Whenever two dissimilar materials are contacted and
block diagram of the typical components necessary for this
separated,excesselectrostaticcharge(triboelectriccharge)will
measurement while Fig. 2 shows a schematic diagram.
be found on these materials if at least one of the materials is a
5.2.1 Faraday Cage—The Faraday cage consists of two
good insulator. This excess charge gives rise to electric fields
conducting enclosures, one enclosed and insulated from the
which can exert forces on other objects. If these fields exceed
other.Theinnerenclosureiselectricallyconnectedtotheshunt
the breakdown strength of the surrounding gas, a disruptive
capacitors and the electrometer input. It is insulated from the
discharge (spark) can occur. The heat from this discharge can
outerenclosurebyrigid,veryhighresistance,insulatorswhich
ignite explosive atmospheres, the light can fog photosensitized
haveresistancepracticallyindependentofrelativehumidity(an
materials, and the current flowing in a static discharge can
example is polytetrafluoroethylene (PFTE). The inner enclo-
cause catastrophic failure of solid state devices. Electric forces
sureshallbeofsuchconstructionthatthetestspecimencanbe
can be used beneficially, as in electrostatic copying, spray
substantially surrounded by it. The outer enclosure is con-
painting and beneficiation of ores. They can be detrimental as
nected to ground and serves to shield the inner enclosure from
when they attract dirt to a surface or when they cause sheets to
external fields which could affect the measurement.
stick together. Since most plastic materials in use today have
5.2.2 Shunt Capacitors—It is possible shunt capacitors will
verygoodinsulatingqualities,itisdifficulttoavoidgeneration
be be necessary to reduce the measured voltage to a range
of static electricity. Since it depends on many parameters, it is
whereitcanbereadbytheelectrometer.Suchshuntcapacitors
difficult to generate static electricity reliably and reproducibly.
must have very low leakage insulation relatively unaffected by
relative humidity changes (for example, polystyrene). Keep
5. Apparatus
them short-circuited when not in use and protected from high
5.1 Charging Mechanisms—The charging mechanisms can
relative humidity.
be constructed in a variety of ways; preferably it will be made
5.2.3 Electrometer—The electrometer voltmeter measures
as analogous to the particular application as possible. Some
the voltage developed on the Faraday cage and shunt capaci-
examplesofchargingmechanismsaredescribedin5.1.1,5.1.2,
tors. The electrometer must have a high impedance (such as
and 5.1.3.
100TΩorhigher)andalowdriftrateconcordantwiththetime
5.1.1 Powder or Liquids Transported Through Tubes or
of measurement. Electrometers are available with built-in
DownTroughs—Contactbetweenthespecimenandwallofthe
shunt capacitors selected by a range switch. Electrometers are
tube will charge the specimen or the tube, or both. Either the
also available with negative feedback circuits which minimize
specimenorthetubemustbeinsulating,orpartiallyinsulating.
the effect of input capacity. These circuits reduce the input
When the specimen is separated from the tube, electrostatic
voltagedroptonearlyzerominimizingtheeffectsofleakageof
charge will be generated. This charge can be measured by
charge to ground and polarization of insulators.
catching a known amount of the specimen in a Faraday cage,
5.2.4 Display Unit—The display unit indicates the voltage
ormeasuringthechargeremainingonthetube.Itispermissible
developed on the electrometer. If the input capacitance is
for trough to be substituted for the tube and gravity used to
known and does not vary, or if negative feedback is used, the
affect the movement of the specimen along the trough.
5.1.2 Webs Transported Over Rollers—Contact between the
web and the roller surface will charge the web if it is an
insulator or partial insulator. If the rollers are insulators or
partial insulators they will become charged thus lowering, or
eliminating, the charge transfer to the web after a period of
time. The electric field on the web can be measured with a
Shashoua, V. E., “Static Electricity in Polymers: Theory and Measurement,” FIG. 1 Block Diagram of Apparatus for Measurement of Electro-
Journal of Polymer Science, Vol XXXIII, 1958, pp 65–85. static Charge
D4470−18
vane is opposite the sensor, the induced charge in the sensor is
a maximum. Thus the rotating vane produces a periodically
varying electrical signal on the sensor plate. This signal is
amplified,processed,andreadonasuitabledisplayunit.These
fieldmeters can be made polarity-sensitive by inducing a
charge of known polarity on the sensor with an internal source
or by phase detection circuitry. Efforts must be made to
adequately shield the sensor and associated circuits from noise
generated by the motor driving the rotating vane.
FIG. 2 Schematic Diagram 5.3.2 Vibrating Plate Fieldmeter—In Fig. 2 a vibrating
sensor plate is enclosed in a sensing unit. A charged material
placed in front of the sensing unit induces a charge in the face
display unit can be calibrated to measure the charge on the
plate and in the sensor. As the sensor moves away from the
Faraday cage directly. The unit can be a meter showing the
charged material, less charge is induced on the sensor. As it
instantaneous value or be a more complicated equipment, such
moves toward the charged material, more charge is induced on
as a strip chart recorder giving a reading as a function of time.
the sensor. This produces a periodically varying electrical
The electrometer and display unit can be combined in one
signal on the sensor plate. This signal is amplified, processed,
instrument.
and read on a suitable display unit. Charge polarity is deter-
5.2.5 Electrical Connnections:
mined by phase detection circuits. Again, the sensor and
5.2.5.1 Connections to Faraday Cage—Connections from
associated circuits must be adequately shielded from noise
the inner enclosure of the Faraday cage to the shunt capacitors
generated by the driving mechanism.
andtheelectrometermustbehighlyinsulatedandwellshielded
5.3.3 Display Unit—The display unit can contain the power
from external electric fields. They will preferably be stable in
switch, circuits to process the signal (amplifiers, rectifiers,
timeandinthedifferentambientconditionsinwhichmeasure-
phase detectors, and the like), and a meter showing the
ments are made. Preferably, they will be rigid, although it is
instantaneous value of the electric field. Alternatively, a strip
permissibleforshieldedcabletobeusedifitislownoisecable
chart recorder giving a reading as a function of time is
where flexing will not lead to the generation of static charge
permissible.
between the shield and the insulation of the cable.When using
cable or rigid connections, the capacitance of these must be
6. Test Conditions
considered when calculating or measuring the capacitance of
the input system, unless using an electrometer with negative
6.1 Staticelectrificationdependsuponmanyparameters.To
feedback.
obtain reproducible results apparatus must be constructed to
5.2.5.2 Connections to Display Unit—No special connect-
control all the measurable parameters and to keep all the
ing wires are normally necessary between the electrometer
unmeasurable parameters constant. The known parameters are
output and the display unit. Manufacturer’s recommendations
as follows:
shall be followed when connecting an external display unit to
6.1.1 Cleanliness of Material Surfaces—Static electrifica-
the electrometer output.
tionofcontactingmaterialsisasurfacephenomenon.Thus,the
5.3 Electric Field Strength Measurements—The diagram of surfaces must be kept in an uncontaminated state. Since
Fig. 3 illustrates the major parts of a commercially available contaminationisverydifficulttomeasure,effortsshallbemade
rotating vane fieldmeter. A commercially available vibrating to keep the surfaces clean. Storing samples under constant
plate fieldmeter is illustrated in Fig. 4. The setup required for ambient conditions, such as temperature and relative humidity,
calibration of a fieldmeter is shown in Fig. 5. isamust.Introductionofdifferentgasesintotheairwherethey
5.3.1 Rotating Vane Fieldmeter—In Fig. 1 an electrostati- can be adsorbed on the surfaces has been known to change the
cally charged material placed at a known distance from the resultsofanelectrificationtest.Dirtparticlessettlingononeor
sensing unit will induce electrostatic charge in the face of the more surfaces can alter the results. Even contact to another
sensing unit, the rotating vane, and the fixed sensor plate. surface during a test can alter a surface and give nonreproduc-
When the rotating vane covers the sensor plate, the induced ible results in subsequent tests. Sometimes, it is better to use
charge in the sensor is small.When the opening in the rotating newsamplesfromasufficientlyuniformmaterialthantore-use
FIG. 3 Rotating Vane Fieldmeter
D4470−18
FIG. 4 Vibrating Sensor Fieldmeter
FIG. 5 Calibration Fixture
samples. “Cleaning” of a surface with solvents rarely cleans Electricfieldscanexistbecauseofotherchargedobjectsinthe
the surface. However, it produces a uniform, reproducible, vicinity of the test. They also exist by virtue of any excess
stateofcontamination.Thus,cleaningwithsolventsisameans charge on a contacting surface before a test contact is made.
of obtaining reproducibility in a test. Elimination of external fields can be accomplished by remov-
6.1.2 Real Area of Contact—Charge is transferred only at ing all insulators from the region of the test or by shielding the
the points of real contact. Any test parameter that affects the test area from external fields (remember that a person can
realareaofcontactbetweensurfaces,suchaspressure,mustbe become charged and produce external fields). Eliminating the
controlled. Slip between surfaces during the making or break- effects of excess charge are not easy. Radioactive and corona
ing of contact must be minimized or measured so it can be dischargers can be used to get rid of most of the charge but
made reproducible. Roughness of surfaces can alter the real rarely eliminate all of it.Also, it is possible that elimination of
contact area and hence the charge transfer, so one must be excess charge on a sheet with these dischargers will not
carefultotestsurfacesofapproximatelythesameroughnessor neutralize the charge, but instead lead to “polar” charge. Polar
underconditions(suchashighpressureorlongtimeofcontact) charge exists when one side of the sheet has excess charge of
where surface roughness has less affect. one polarity and the other side has an equal excess charge of
6.1.3 Time of Contact—Electrostatic charge is transferred the opposite polarity. Very high charge densities can exist in a
almost instantaneously at the points of real contact. As time polar configuration with little measurable external field. Usu-
goes on, charge can flow from the contact areas to the ally polar charges can be detected by placing the sheet on a
noncontactareasandintothebulkofthespecimen.Also,some grounded metal plate and bringing an insulated metal plate
materials undergo plastic deformation under pressure which connected to an ungrounded electrometer into contact with the
can produce a time dependent increase in real contact area. other side of the sheet. An electrostatic field measuring or
Plastic deformation often depends upon temperature and ad- noncontacting voltage measuring instrument of sufficient sen-
sorbed water, which is another reason for controlling these sitivity can also be used.
parameters.
NOTE 1—One must also be aware of contact potential differences
6.1.4 Rapidity of Separation—As two contacting materials
between metals that affect charge transfer. If one uses a thin insulating
are separated, transferred charge can tunnel back to its origin.
sheet mounted on metal, and uses a different metal to contact the surface
ofthesheet,thecontact-potentialdifferencebetweenthemetalscanaffect
This process occurs rapidly up until a certain separation
the charge transfer between the metal and insulator.
distance between two points is achieved. This separation
distance is unmeasurable and probably does not change much
7. Test Specimens
with speed of separation. However, if the surfaces or volumes
are partial insulators, charge can flow from a broken contact 7.1 The form and size of test specimens is largely deter-
point to an unbroken point and hence back to its origin. This mined by the end use of the material or other practical
means that for partially insulating materials, such as some considerations. Since this test method has a wide range of
websbeingtransportedoverrollers,thechargeonthewebwill applicability (solids in various forms and liquids), specimen
be a function of the web resistivity and the web velocity as it preparation guidelines are, of necessity, general. Depending
leaves a roller. upon the mode of charging, use specimens of equal sizes for
6.1.5 Electric Fields—Since charge transfer is a movement comparison.Testfivespecimensofeachcomposition.Keepthe
of charged particles, electric fields can affect the movement. specimens free of contamination. When using specimens for
D4470−18
repeatedcontacts,recognizeandconsidertheprobabilityofthe specified test condition before conditioning. Equally condition
results being affected by contamination. When cleaned with specimens for at least 24 h at the specified relative humidity
solvents, recondition the specimens after cleaning and before before testing. Make the measurements at the end of the
further testing. conditioning time in the conditioning environment.
8. Calibration and Standardization
10. Procedure
8.1 Calibration of Charge Measuring Apparatus:
10.1 Electrostatic Charging—Because of the wide variety
8.1.1 Calibrate the electrometer and associated readout
of material shapes and charging mechanisms, the procedure
equipment to the desired accuracy by applying a precision
shall be determined by the experimenter. Maintain careful
voltage source to the electrometer input.Accomplish this with
notes of the procedure and include them in the report.
the cage and shunt capacitors disconnected, if possible, to
10.2 Measurement of Electrostatic Charge:
avoid polarization of the insulators of these components.
10.2.1 Small Specimens—Measure electrostatic charge on
8.1.2 The capacitance, C, of the system consists of the
small specimens by dropping them into a Faraday cage in the
parallel combination of the capacitance of the cage, the shunt,
formoftwocupswithasmallopeningontopoftheinnercup,
theconnectinglines,andtheelectrometer,infarads,asfollows:
and a lid which can be closed on the top of the outer cup. The
C 5 C 1C 1C 1C (1)
c s l e
inner cup shall be of sufficient depth so that the depth is large
whencomparedwiththeopeninginthecupandwiththeheight
where:
of the specimen (or specimens) from the bottom of the cup.
C = capacitance of the cage,
e
10.2.2 Large Specimens—Measure electrostatic charge on
C = capacitance of the shunt,
s
portions of large specimens which cannot be totally enclosed
C = capacitance of the connecting lines, and
l
byaFaradaycage(suchaslongwebs)byusingtwoconcentric
C = capacitance of the electrometer.
e
cylinders enclosing the portion of the specimen to be mea-
With standard audio frequency bridges, C +C +C c
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4470 − 97 (Reapproved 2010) D4470 − 18
Standard Test Method for
Static Electrification
This standard is issued under the fixed designation D4470; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the generation of electrostatic charge, the measurement of this charge and its associated electric
field, and the test conditions which must be controlled in order to obtain reproducible results. This test method is applicable to both
solids and liquids. This test method is not applicable to gases, since a transfer of a gas with no solid impurities in it does not
generate an electrostatic charge. This test method also does not cover the beneficial uses of static electrification, its associated
problems or hazards, or the elimination or reduction of unwanted electrostatic charge.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D618 Practice for Conditioning Plastics for Testing
D1711 Terminology Relating to Electrical Insulation
D5032 Practice for Maintaining Constant Relative Humidity by Means of Aqueous Glycerin Solutions
E104 Practice for Maintaining Constant Relative Humidity by Means of Aqueous Solutions
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this specification, refer to Terminology D1711.
3.1.2 conducting material (conductor), n—a material within which an electric current is produced by application of a voltage
between points on or within the material.
3.1.2.1 Discussion—
The term “conducting material” is usually applied only to those materials in which a relatively small potential difference results
in a relatively large current since all materials appear to permit some conduction current. Metals and strong electrolytes are
examples of conducting materials.
3.1.3 electric field strength, n—the magnitude of the vector force on a point charge of unit value and positive polarity.
3.1.4 excess electrostatic charge, n—the algebraic sum of all positive and negative electric charges on the surface of, or in, a
specific volume.
This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of Subcommittee
D09.12 on Electrical Tests.
Current edition approved Oct. 1, 2010April 1, 2018. Published October 2010April 2018. Originally approved in 1985. Last previous edition approved in 20042010 as
D4470 – 97 (2010).(2004). DOI: 10.1520/D4470-97R10.10.1520/D4470-18.
Vosteen, R. E., and Bartnikas, R., Chapter 5, “Electrostatic Charge Measurements,” Engineering Dielectrics, Vol. IIB, Electrical Properties of Solid Insulating Materials,
Measurement Techniques, R. Bartnikas, Editor, ASTM STP 926, ASTM, Philadelphia, 1987.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
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3.1.5 insulating material (insulator), n—a material in which a voltage applied between two points on or within the material
produces a small and sometimes negligible current.
3.1.6 resistivity, surface—surface, n—the surface resistance multiplied by that ratio of specimen surface dimensions (width of
electrodes defining the current path divided by the distance between electrodes) which transforms the measured resistance to that
obtained if the electrodes formed the opposite sides of a square.
3.1.6.1 Discussion—
Surface resistivity is expressed in ohms. It is popularly expressed also as ohms/square (the size of the square is immaterial). Surface
resistivity is the reciprocal of surface conductivity.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 apparent contact area, n—the area of contact between two flat bodies.
3.2.1.1 Discussion—
It is the area one would calculate by measuring the length and width of the rectangular macroscopic contact region.
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3.2.2 dissipative material, n—a material with a volume resistivity greater than 10 ohm-cm ohm-cm and less than 10 ohm-cm,
ohm-cm, a resistivity range between conductive and insulating material as defined in this test method.
3.2.3 real contact area, n—the regions of contact between two bodies through which mechanical actions or reactions are
transferred.
3.2.3.1 Discussion—
Since real bodies are never perfectly smooth, at least on a microscopic scale, the real contact area of apparently flat materials is
always less than the apparent contact area.
3.2.4 triboelectric charge generation—the formation, with or without rubbing, of electrostatic charges by separation of
contacting materials.
4. Significance and Use
4.1 Whenever two dissimilar materials are contacted and separated, excess electrostatic charge (triboelectric charge) will be
found on these materials if at least one of the materials is a good insulator. This excess charge gives rise to electric fields which
can exert forces on other objects. If these fields exceed the breakdown strength of the surrounding gas, a disruptive discharge
(spark) maycan occur. The heat from this discharge maycan ignite explosive atmospheres, the light maycan fog photosensitized
materials, and the current flowing in a static discharge maycan cause catastrophic failure of solid state devices. Electric forces
maycan be used beneficially, as in electrostatic copying, spray painting and beneficiation of ores. They maycan be detrimental as
when they attract dirt to a surface or when they cause sheets to stick together. Since most plastic materials in use today have very
good insulating qualities, it is difficult to avoid generation of static electricity. Since it depends on many parameters, it is difficult
to generate static electricity reliably and reproducibly.
5. Apparatus
5.1 Charging Mechanisms—The charging mechanisms can be constructed in a variety of ways, and should preferablyways;
preferably it will be made as analagousanalogous 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 or Down Troughs—Contact between the specimen and wall of the tube will
charge the specimen or the tube, or both. Either the specimen or the tube must be insulating, or partially insulating. When the
specimen is separated from the tube, electrostatic charge will be generated. This charge maycan be measured by catching a known
amount of the specimen in a Faraday cage, or measuring the charge remaining on the tube may be measured. A trough maytube.
It is permissible for trough to be substituted for the tube and gravity used to effectaffect the movement of the specimen along the
trough.
5.1.2 Webs Transported Over Rollers—Contact between the web and the roller surface will charge the web if it is an insulator
or partial insulator. If the rollers are insulators or partial insulators they will become charged thus lowering, or eliminating, the
charge transfer to the web after a period of time. The electric field on the web maycan be measured with a fieldmeter, or the charge
on the web can be measured with a cylindrical Faraday cage if the width of the web is not too large.
Shashoua, V. E., “Static Electricity in Polymers: Theory and Measurement,” Journal of Polymer Science, Vol XXXIII, 1958, pp 65–85.
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5.1.3 Transport of Insulating or Partially Insulating Sheet Material—Sheet materials may are able to be transported on air
layers, by sliding down chutes, by vacuum platens, and by pinch rollers. Of these types of transport, pinch rollers and sliding down
chutes generate the largest amount of charge. Generally, the better the contact (larger real contact area), the greater will be the
charge generated. Pinch rollers are usually a high pressure, small apparent area of contact, leading to a relatively large real area
of contact between the sheet and rollers. Sliding serves to multiply the real area of contact over that which would be obtained with
a contact without sliding.
5.2 Electrostatic Charge Measurements—Fig. 1 shows a block diagram of the typical components necessary for this
measurement while Fig. 2 shows a schematic diagram.
5.2.1 Faraday Cage—The Faraday cage consists of two conducting enclosures, one enclosed and insulated from the other. The
inner enclosure is electrically connected to the shunt capacitors and the electrometer input. It is insulated from the outer enclosure
by rigid, very high resistance, insulators which have resistance practically independent of relative humidity (an example is
polytetrafluoroethylene (PFTE). The inner enclosure shouldshall be of such construction that the test specimen can be substantially
surrounded by it. The outer enclosure is connected to ground and serves to shield the inner enclosure from external fields which
could affect the measurement.
5.2.2 Shunt Capacitors—Shunt capacitors may be It is possible shunt capacitors will be be necessary to reduce the measured
voltage to a range where it can be read by the electrometer. Such shunt capacitors must have very low leakage insulation relatively
unaffected by relative humidity changes (for example, polystyrene). They should be kept Keep them short-circuited when not in
use and should be protected from high relative humidity.
5.2.3 Electrometer—The electrometer voltmeter measures the voltage developed on the Faraday cage and shunt capacitors. The
electrometer must have a high impedenceimpedance (such as 100 TΩ or higher) and a low drift rate concordant with the time of
measurement. Electrometers are available with built-in shunt capacitors selected by a range switch. Electrometers are also available
with negative feedback circuits which minimize the effect of input capacity. These circuits reduce the input voltage drop to nearly
zero minimizing the effects of leakage of charge to ground and polarization of insulators.
5.2.4 Display Unit—The display unit indicates the voltage developed on the electrometer. If the input capacitance is known and
does not vary, or if negative feedback is used, the display unit maycan be calibrated to measure the charge on the Faraday cage
directly. The unit maycan be a meter showing the instantaneous value or it may be a more complicated equipment, such as a strip
chart recorder giving a reading as a function of time. The electrometer and display unit maycan be combined in one instrument.
5.2.5 Electrical Connnections:
5.2.5.1 Connections to Faraday Cage—Connections from the inner enclosure of the Faraday cage to the shunt capacitors and
the electrometer must be highly insulated and well shielded from external electric fields. They should will preferably be stable in
time and in the different ambient conditions in which measurements are made. Preferably, they shouldwill be rigid, although it is
permissible for shielded cable mayto be used if it is low noise cable where flexing will not lead to the generation of static charge
between the shield and the insulation of the cable. When using cable or rigid connections, the capacitance of these must be taken
into account considered when calculating or measuring the capacitance of the input system, unless using an electrometer with
negative feedback.
5.2.5.2 Connections to Display Unit—No special connecting wires are normally necessary between the electrometer output and
the display unit. Manufacturer’s recommendations shouldshall be followed when connecting an external display unit to the
electrometer output.
5.3 Electric Field Strength Measurements—The diagram of Fig. 3 illustrates the major parts of a commercially available rotating
vane fieldmeter. A commercially available vibrating plate fieldmeter is illustrated in Fig. 4. The setup required for calibration of
a fieldmeter is shown in Fig. 5.
5.3.1 Rotating Vane Fieldmeter—In Fig. 1 an electrostatically charged material placed at a known distance from the sensing unit
will induce electrostatic charge in the face of the sensing unit, the rotating vane, and the fixed sensor plate. When the rotating vane
covers the sensor plate, the induced charge in the sensor is small. When the opening in the rotating vane is opposite the sensor,
the induced charge in the sensor is a maximum. Thus the rotating vane produces a periodically varying electrical signal on the
sensor plate. This signal is amplified, processed, and read on a suitable display unit. These fieldmeters can be made
polarity-sensitive by inducing a charge of known polarity on the sensor with an internal source or by phase detection circuitry.
Efforts must be made to adequately shield the sensor and associated circuits from noise generated by the motor driving the rotating
vane.
FIG. 1 Block Diagram of Apparatus for Measurement of Electrostatic Charge
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FIG. 2 Schematic Diagram
5.3.2 Vibrating Plate Fieldmeter—In Fig. 2 a vibrating sensor plate is enclosed in a sensing unit. A charged material placed in
front of the sensing unit induces a charge in the face plate and in the sensor. As the sensor moves away from the charged material,
less charge is induced on the sensor. As it moves toward the charged material, more charge is induced on the sensor. This produces
a periodically varying electrical signal on the sensor plate. This signal is amplified, processed, and read on a suitable display unit.
Charge polarity is determined by phase detection circuits. Again, the sensor and associated circuits must be adequately shielded
from noise generated by the driving mechanism.
5.3.3 Display Unit—The display unit maycan contain the power switch, circuits to process the signal (amplifiers, rectifiers,
phase detectors, and the like), and a meter showing the instantaneous value of the electric field. Alternatively, a strip chart recorder
giving a reading as a function of time may be used.is permissible.
6. Test Conditions
6.1 Static electrification depends upon many parameters. To obtain reproducible results apparatus must be constructed to control
all the measurable parameters and to keep all the unmeasurable parameters constant. The known parameters are as follows:
6.1.1 Cleanliness of Material Surfaces—Static electrification of contacting materials is a surface phenomenon. Thus, the
surfaces must be kept in an uncontaminated state. Since contamination is very difficult to measure, efforts shouldshall be made to
keep the surfaces clean. Storing samples under constant ambient conditions, such as temperature and relative humidity, is a must.
Introduction of different gases into the air where they can be adsorbed on the surfaces has been known to change the results of
an electrification test. Dirt particles settling on one or more surfaces can alter the results. Even contact to another surface during
a test can alter a surface and give nonreproducible results in subsequent tests. Sometimes, it is better to use new samples from a
sufficiently uniform material than to re-use samples. “Cleaning” of a surface with solvents rarely cleans the surface. It
probablyHowever, it produces a uniform, reproducible, state of contamination, however. contamination. Thus, cleaning with
solvents should be considered as is a means of obtaining reproducibility in a test.
6.1.2 Real Area of Contact—Charge is transferred only at the points of real contact. Any test parameter that affects the real area
of contact between surfaces, such as pressure, must be controlled. Slip between surfaces during the making or breaking of contact
must be minimized or measured so it can be made reproducible. Roughness of surfaces can alter the real contact area and hence
the charge transfer, so one must be careful to test surfaces of approximately the same roughness or under conditions (such as high
pressure or long time of contact) where surface roughness has less affect.
6.1.3 Time of Contact—Electrostatic charge is transferred almost instantaneously at the points of real contact. As time goes on,
charge can flow from the contact areas to the noncontact areas and into the bulk of the specimen. Also, some materials undergo
plastic deformation under pressure which can produce a time dependent increase in real contact area. Plastic deformation often
depends upon temperature and adsorbed water, which is another reason for controlling these parameters.
6.1.4 Rapidity of Separation—As two contacting materials are separated, transferred charge can tunnel back to its origin. This
process occurs rapidly up until a certain separation distance between two points is achieved. This separation distance is
unmeasurable and probably does not change much with speed of separation. However, if the surfaces or volumes are partial
insulators, charge can flow from a broken contact point to an unbroken point and hence back to its origin. This means that for
partially insulating materials, such as some webs being transported over rollers, the charge on the web will be a function of the
web resistivity and the web velocity as it leaves a roller.
6.1.5 Electric Fields—Since charge transfer is a movement of charged particles, electric fields can affect the movement. Electric
fields can exist because of other charged objects in the vicinity of the test. They also exist by virtue of any excess charge on a
contacting surface before a test contact is made. Elimination of external fields can be accomplished by removing all insulators from
the region of the test or by shielding the test area from external fields (remember that a person maycan become charged and produce
external fields). Eliminating the effects of excess charge mayare not be so easy. Radioactive and corona dischargers can be used
to get rid of most of the charge but rarely eliminate all of it. Also, it is possible that elimination of excess charge on a sheet with
these dischargers maywill not neutralize the charge, but instead may lead to “polar” charge. Polar charge exists when one side of
the sheet has excess charge of one polarity and the other side has an equal excess charge of the opposite polarity. Very high charge
densities can exist in a polar configuration with little measurable external field. Usually polar charges can be detected by placing
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FIG. 3 Rotating Vane Fieldmeter
FIG. 4 Vibrating Sensor Fieldmeter
FIG. 5 Calibration Fixture
the sheet on a grounded metal plate and bringing an insulated metal plate connected to an ungrounded electrometer into contact
with the other side of the sheet. An electrostatic field measuring or noncontacting voltage measuring instrument of sufficient
sensitivity maycan also be used.
NOTE 1—One must also be aware of contact potential differences between metals that affect charge transfer. If one uses a thin insulating sheet mounted
on metal, and uses a different metal to contact the surface of the sheet, the contact-potential difference between the metals maycan affect the charge
transfer between the metal and insulator.
7. Test Specimens
7.1 The form and size of test specimens is largely determined by the end use of the material or other practical considerations.
Since this test method has a wide range of applicability (solids in various forms and liquids), specimen preparation guidelines are,
of necessity, general. Depending upon the mode of charging, use specimens of equal sizes for comparison. Test five specimens of
each composition. Keep the specimens free of contamination. When using specimens for repeated contacts, recognize and take into
account consider the probability of the results being affected by contamination. When cleaned with solvents, recondition the
specimens after cleaning and before further testing.
8. Calibration and Standardization
8.1 Calibration of Charge Measuring Apparatus:
8.1.1 Calibrate the electrometer and associated readout equipment to the desired accuracy by applying a precision voltage
source to the electrometer input. Accomplish this with the cage and shunt capacitors disconnected, if possible, to avoid polarization
of the insulators of these components.
8.1.2 The capacitance, C, of the system consists of the parallel combination of the capacitance of the cage, the shunt, the
connecting lines, and the electrometer, in farads, as follows:
C 5 C 1C 1C 1C (1)
c s l e
where:
C = capacitance of the cage,
e
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C = capacitance of the shunt,
s
C = capacitance of the connecting lines, and
l
C = capacitance of the electrometer.
e
With standard audio frequency bridges, C + + C + C can be readily determined. Some electrometers permit a similar
cc ss ll
measurement of C , otherwise, C must be taken from the instruction manual or special procedures. For example, a charge decay
e e e
rate measurement or a charge sharing measurement must be used for determining C experimentally. Electrometers having
ee
feedback circuits minimize the effects of external capacitance so only the capacitance of the electrometer need be measured. After
calibration, or before using the instrument after turning it on, instrument, the drift rate shouldshall be checked to make certain it
is within manufacturer’s specifications.
8.2 Calibration of Fieldmeters—Calibrate the fieldmeters by placing the sensing unit in a hole in a large grounded plate so that
the surface of the sensing unit is flush with the surface of the plate, as shown in Fig. 5. A second plate to which a voltage can be
applied is placed parallel with and at a known distance from the first plate. The plates shouldshall be large enough to ensure a
uniform field in the region of the sensing unit (usually a plate with dimensions five to ten times the dime
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