ASTM E2980-14
(Test Method)Standard Test Methods for Estimating Average Particle Size of Powders Using Air Permeability
Standard Test Methods for Estimating Average Particle Size of Powders Using Air Permeability
SIGNIFICANCE AND USE
4.1 These test methods provide procedures for determining the envelope-specific surface area of powders, from which is calculated an “average” particle diameter, assuming the particles are monosize, smooth surface, nonporous, spherical particles. For this reason, values obtained by these test methods will be reported as an average particle size. The degree of correlation between the results of these test methods and the quality of powders in use will vary with each particular application and has not been fully determined.
4.2 These test methods are generally applicable to all powders, including metals (see Test Methods B330 for specific metal powder requirements), ceramics, and organic materials, for particles having diameters between 0.2 and 75 µm. They should not be used for powders composed of particles whose shape is too far from equiaxed - that is, flakes or fibers. In these cases, it is permissible to use the test methods described only by agreement between the parties concerned. These test methods shall not be used for mixtures of different powders, nor for powders containing binders or lubricants. When the powder contains agglomerates, the measured surface area may be affected by the degree of agglomeration. Methods of de-agglomeration such as that specified in Practice B859 may be used if agreed upon between the parties concerned.
4.3 When an “average” particle size of powders is determined by these methods, it should be clearly kept in mind that this average size is derived from the determination of the specific surface area of the powder using a relationship that is true only for powders of uniform size and spherical shape. Thus, the results of these methods are only estimates of average particle size.
4.4 Reported particle size measurement is a function of both the actual dimension and shape factor as well as the particular physical or chemical properties of the particle being measured. Caution is required when comparing data from instruments op...
SCOPE
1.1 These test methods use air permeability to determine an envelope-specific surface area and its associated average equivalent spherical diameter (from 0.2 to 75 µm) of powders. Two test methods are described: One test method for inorganic materials (Test Method 1), and another test method for organic materials (Test Method 2). The values obtained are not intended to be absolute but are generally useful on a relative basis for control purposes.
1.2 Units—With the exception of the values for density and the mass used to determine density, for which the use of the gram per cubic centimetre (g/cm3) and gram (g) units is the longstanding industry practice; and the units for pressure, cm H2O—also long-standing practice; the values in SI units are to be regarded as 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 and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E2980 − 14
StandardTest Methods for
Estimating Average Particle Size of Powders Using Air
Permeability
This standard is issued under the fixed designation E2980; 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 E2589 Terminology Relating to Nonsieving Methods of
Powder Characterization
1.1 These test methods use air permeability to determine an
2.2 ISO Documents:
envelope-specific surface area and its associated average
ISO 10070 Metallic Powders: Determinations of Envelope-
equivalent spherical diameter (from 0.2 to 75 µm) of powders.
Specific Surface Area from Measurements of the Perme-
Two test methods are described: One test method for inorganic
ability to Air of a Powder Bed Under Steady-State Flow
materials (Test Method 1), and another test method for organic
Conditions
materials (Test Method 2). The values obtained are not
intended to be absolute but are generally useful on a relative
3. Terminology
basis for control purposes.
3.1 Definitions—Many terms used in this test method are
1.2 Units—With the exception of the values for density and
defined in Terminologies E1638 and E2589.
the mass used to determine density, for which the use of the
3.2 Definitions of Terms Specific to This Standard:
gram per cubic centimetre (g/cm ) and gram (g) units is the
3.2.1 air permeability, n—measurement of air pressure drop
longstanding industry practice; and the units for pressure, cm
across a packed bed of powder.
H O—also long-standing practice; the values in SI units are to
3.2.2 average particle size, n—for the purposes of these test
be regarded as standard.
methods only, an estimate of the equivalent average spherical
1.3 This standard does not purport to address all of the
particle diameter, calculated from the measured envelope-
safety concerns, if any, associated with its use. It is the
specific surface area, assuming that all the powder particles are
responsibility of the user of this standard to establish appro-
spherical and that all are exactly the same size.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. 3.2.3 de-agglomeration, n—process used to break up ag-
glomerates of particles.
2. Referenced Documents
3.2.4 envelope-specific surface area, n—specific surface
2.1 ASTM Standards:
area of a powder as determined by gas permeametry in
B330 Test Methods for Estimating Average Particle Size of
accordance with ISO 10070.
Metal Powders and Related Compounds Using Air Per-
3.2.5 HEL Sub-Sieve AutoSizer (HEL SAS), n—a commer-
meability
cially available permeability instrument for measuring
B859 Practice for De-Agglomeration of Refractory Metal
envelope-specific surface area and estimating average particle
Powders and Their Compounds Prior to Particle Size
size from 0.2 to 75 µm.
Analysis
3.2.6 porosity of a bed of powder, n—ratio of the volume of
E29 Practice for Using Significant Digits in Test Data to
the void space in the powder bed to that of the overall volume
Determine Conformance with Specifications
of the powder bed.
E1638 Terminology Relating to Sieves, Sieving Methods,
and Screening Media
4. Significance and Use
4.1 These test methods provide procedures for determining
These test methods are under the jurisdiction of ASTM Committee E29 on
the envelope-specific surface area of powders, from which is
Particle and Spray Characterization and is the direct responsibility of Subcommittee
calculated an “average” particle diameter, assuming the par-
E29.02 on Non-Sieving Methods.
ticles are monosize, smooth surface, nonporous, spherical
Current edition approved Dec. 1, 2014. Published January 2015. DOI: 10.1520/
E2980-14. particles.Forthisreason,valuesobtainedbythesetestmethods
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
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E2980 − 14
all plug heights when new plugs are purchased and periodically thereafter
will be reported as an average particle size. The degree of
to make sure all are equal in height.
correlation between the results of these test methods and the
quality of powders in use will vary with each particular
5.2 Powder funnel, stainless steel, with spout outside diam-
application and has not been fully determined.
eter slightly smaller than the sample tube inside diameter.
4.2 These test methods are generally applicable to all
5.3 The manufacturer provides instructions which should be
powders, including metals (seeTest Methods B330 for specific
followed. Particular attention should be given to proper main-
metal powder requirements), ceramics, and organic materials,
tenance of the instrument with special reference to the instruc-
for particles having diameters between 0.2 and 75 µm. They
tions on (1) “homing” the piston when turning on from an
should not be used for powders composed of particles whose
unpowered state, (2) setting the pressure and periodic checking
shapeistoofarfromequiaxed-thatis,flakesorfibers.Inthese
of the pressure, (3) condition of O-rings on the piston and
cases, it is permissible to use the test methods described only
sample spigot, and (4) the sample packing assembly (plugs and
by agreement between the parties concerned. These test meth-
paper disks).
ods shall not be used for mixtures of different powders, nor for
5.4 Balance, having a capacity of at least 50 g and a
powders containing binders or lubricants. When the powder
sensitivity of 0.001 g.
contains agglomerates, the measured surface area may be
affected by the degree of agglomeration. Methods of de-
6. Standardization of Apparatus
agglomeration such as that specified in Practice B859 may be
used if agreed upon between the parties concerned.
6.1 BeforeproceedingwithstandardizationoftheHELSAS
instrument, the following items shall be checked:
4.3 When an “average” particle size of powders is deter-
6.1.1 The sample tube and plugs shall not be worn to the
mined by these methods, it should be clearly kept in mind that
point where results are affected.
this average size is derived from the determination of the
6.1.2 Inspect the O-ring seals for tears and abrasion marks.
specific surface area of the powder using a relationship that is
The O-ring seals shall not be worn to the point where the
true only for powders of uniform size and spherical shape.
sample tube moves easily by hand or the pressure reading
Thus, the results of these methods are only estimates of
varies as the sample tube is moved.
average particle size.
6.1.3 The drying agent shall be in proper condition.
4.4 Reportedparticlesizemeasurementisafunctionofboth
6.2 Whenever the instrument is turned on from an unpow-
the actual dimension and shape factor as well as the particular
ered state, the piston shall be “homed” according to the
physical or chemical properties of the particle being measured.
manufacturer’s instructions. See Note 1 above.
Caution is required when comparing data from instruments
operating on different physical or chemical parameters or with
6.3 Before running the initial sample, the pressure shall be
different particle size measurement ranges. Sample acquisition,
set to 50.0 (+0.1, –0.5) cm H O, using the metering valve; then
handling, and preparation can also affect reported particle size
checked and reset if necessary every few hours, or if the
results.
ambient temperature changes more than 62°C.
5. Apparatus
NOTE 2—The metering valve position should not be adjusted for repeat
runs of the same sample as this will likely lead to a loss of precision even
5.1 HEL Sub-Sieve AutoSizer (HEL SAS), consisting of an
iftheinletpressurereadinghasdriftedalittleoutsidethe50.0(+0.1,–0.5)
air pump, a calibrated gas mass flow controller, a precision-
cm H O range. Further adjustment is not necessary as the pressure is
bore sample tube, a sample tube retaining collar, a spacer tool,
controlled precisely during the particle size measurement.
a gas flow metering valve, two precision pressure transducers
6.4 Standardization is recommended before and after any
(inlet and outlet), a stepper motor controlled ballscrew-
series of determinations or at least every 4 hours of continued
mounted piston, and computer hardware and software for
operation. Warm-up of the instrument is required if it has been
instrument control and calculation and reporting of results.
off for more than 30 minutes.
Included is accessory equipment consisting of a plug manipu-
6.5 Calibration of the pressure transducers is recommended
lator (extraction rod), two porous plugs, and a supply of paper
every 3–6 months, using a traceable external pressure gauge
disks.
per the manufacturer’s instructions.
NOTE 1—When homing the piston, adjust the sample packing assembly
(1) as described in the manufacturer’s directions, with the plugs and paper
7. Procedure
disks stacked together and placed on the fixed anvil spigot, or (2) using a
specially designed baseline (homing
...
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