ASTM D7486-08
(Test Method)Standard Test Method for Measurement of Fines and Dust Particles on Plastic Pellets by Wet Analysis
Standard Test Method for Measurement of Fines and Dust Particles on Plastic Pellets by Wet Analysis
SIGNIFICANCE AND USE
Molding and extruding plastic pellets require dust free, dry pellets to prevent processing problems. Plastic producers try to remove the dust and streamers with dust removal systems prior to packaging and loading. How to accurately measure dust and streamer content in plastic pellets is an important quality control issue.
Particle size analysis is used to determine a percentage of particle size distribution from a representative sample of the whole. In terms of size analysis concerning plastic pellets, sieving is used to determine the dust content in the range of 500 to 2000 micron. Test Method D 1921, Test Method B, is used to determine this type of particle sizing.
After dry sieve analysis, particles smaller than 500 microns need to be analyzed by wet method. A fresh sample shall be used for wet analysis. This test method allows washing down the fines attached to the pellets by electrostatic forces.
The wet analysis provides accurate quantification of small to large amounts of fines, negating static effects, and eliminating detrimental effects of mechanical agitation. A wet analysis must be employed to accurately quantify lower PPM dust levels in plastic pellets.
SCOPE
1.1 This test method measures the amount of fine particles adhered on plastic pellets or granules in which they are commonly produced and supplied. The lower limit of this test method is restricted only by the porosity of the filter disc used to capture the particle size being quantified.
1.2 The wet analysis technique allows for separation and collection of statically charged particles by liquid wash and filtration methods. This must be performed under standard laboratory conditions.
1.3 The values stated in SI units are to be regarded as standard.
1.4 This test method describes an essential practice to check the quality of plastics once the production cycle is terminated and to evaluate the performance of pellet cleaning systems or of the special pneumatic conveying systems for the distinct size fractions below 500 micron only.
1.5 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.
Note 1—There is no known ISO equivalent to this standard.
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Standards Content (Sample)
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Designation: D7486 − 08
StandardTest Method for
Measurement of Fines and Dust Particles on Plastic Pellets
by Wet Analysis
This standard is issued under the fixed designation D7486; 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 2.2 FEM Standards:
FEM2482Test Method to Determine Content of Fines and
1.1 This test method measures the amount of fine particles
Streamers in Plastic Pellets.
adhered on plastic pellets or granules in which they are
commonly produced and supplied. The lower limit of this test
3. Terminology
method is restricted only by the porosity of the filter disc used
3.1 Definitions of Terms Specific to This Standard:
to capture the particle size being quantified.
3.1.1 fines—fines (Dust) are small particles of plastic which
1.2 The wet analysis technique allows for separation and have been torn away from the original pellet by contact with a
collection of statically charged particles by liquid wash and rough surface and friction at high conveying velocities. They
filtration methods. This must be performed under standard are defined as the particle fraction with a particle size up to
laboratory conditions. 2000 µm.
3.1.2 streamers—strings of plastics of various lengths that
1.3 The values stated in SI units are to be regarded as
are created when the resin travels through pneumatic convey-
standard.
ing lines at high velocity. Streamers are also known as angel
1.4 Thistestmethoddescribesanessentialpracticetocheck
hair, foil, floss, film or snake skin.
the quality of plastics once the production cycle is terminated
4. Summary of Test Method
and to evaluate the performance of pellet cleaning systems or
ofthespecialpneumaticconveyingsystemsforthedistinctsize
4.1 Fines or streamers, or both, are generated in polymer
fractions below 500 micron only.
resins during pneumatic conveying. Fines and streamers are
known to cause problems in plastic producing and processing
1.5 This standard does not purport to address all of the
plants by clogging the transporting and procession lines. On
safety concerns, if any, associated with its use. It is the
finished products, fines cause the formation of gel,
responsibility of the user of this standard to establish appro-
contamination, surface imperfection and weak spots.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
4.2 The streamer content for a particle size considerably
largerthanthepelletdiameteraredeterminedbydryscreening
NOTE 1—There is no known ISO equivalent to this standard.
according to Test Method D1921.
4.3 The fundamental principle used in this document is
2. Referenced Documents
based upon the condition that statically charged fines normally
2.1 ASTM Standards:
adhering to plastic pellets be removed by rinsing the test
D1921Test Methods for Particle Size (Sieve Analysis) of
sample with a washing liquid, causing fines in the sample to
Plastic Materials
wash away into a container. These particles are then poured
E11Specification forWovenWireTest Sieve Cloth andTest
intoafilterfunneltoseparatethefinesfromthewashingliquid.
Sieves
The weight of the filter paper is accurately measured before
and after the collection process, and used to calculate the PPM
level for that sample.
ThistestmethodisunderthejurisdictionofASTMCommitteeD20onPlastics
4.4 Wetanalysisquantifiestheamountsofdustwithparticle
and is the direct responsibility of Subcommittee D20.70 on Analytical Methods.
sizes typically from 1.6 to 500 microns.
Current edition approved Nov. 1, 2008. Published November 2008. DOI:
10.1520/D7486-08.
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 AvailablefromEuropeanFederationofMaterialsHandling,DiamantBuilding,
Standards volume information, refer to the standard’s Document Summary page on 80BoulevardAugusteReyersB,1030Brussels,Belgium,http://www.fem-eur.com.
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7486 − 08
TABLE 1 Comparison of Typical Particle Sizes Measured
sample to be tested. The apparatus runs with a washing liquid
Type Lower Limit Upper Limit Test Method in recirculation mode.
D1921 500 µm 2000 µm dry
A
7.2 Theapparatusconsistsofawashbeakerwithsprayhose
D7486 1.6 µm 500 µm wet
A and nozzle, a filter funnel, a water tank reservoir with drain, a
The lower limit is set by the porosity of the filter disk.
pump with throttle valve and flow meter, and connecting
piping.The entire set-up consists of the following equipment.
5. Significance and Use
7.2.1 Balance, with a capacity of 500 g or higher, sensitive
to 0.1 mg.
5.1 Molding and extruding plastic pellets require dust free,
7.2.2 Scale,withacapacityof1200gorhigher,sensitiveto
dry pellets to prevent processing problems. Plastic producers
0.1 g.
trytoremovethedustandstreamerswithdustremovalsystems
7.2.3 Oven,gravityconvection,controlledupto100 65°C.
prior to packaging and loading. How to accurately measure
7.2.4 Wire-Cloth Sieve, 8-in. or 200-mm, full height, con-
dust and streamer content in plastic pellets is an important
forming to the requirements of Specification E11, 500 micron.
quality control issue.
7.2.5 Filtration Disc, glass microfiber, diameter 90 mm,
5.2 Particle size analysis is used to determine a percentage
porosity 0.7 to 2.7 micron, thickness , 260 to 420 micron,
ofparticlesizedistributionfromarepresentativesampleofthe
tensile range, 5.5 to 8.9 N/15 mm.
whole. In terms of size analysis concerning plastic pellets,
7.2.6 Filter Funnel Assembly, 3-piece, borosilicate glass,
sievingisusedtodeterminethedustcontentintherangeof500
able to hold a 90-mm filter disc.
to2000micron.TestMethodD1921,TestMethodB,isusedto
7.2.7 Filtering Flask, 1000-mL, borosilicate glass, to con-
determine this type of particle sizing.
nect to filter funnel.
5.3 After dry sieve analysis, particles smaller than 500
7.2.8 Beaker, 1500-mL, borosilicate glass, to hold washed
microns need to be analyzed by wet method. A fresh sample
test sample.
shallbeusedforwetanalysis.Thistestmethodallowswashing
7.2.9 Funnel, 260-mm. top O.D., to hold sieve during test
down the fines attached to the pellets by electrostatic forces.
sample washing.
7.2.10 Nozzle, flat fan spray, for washing test sample at line
5.4 The wet analysis provides accurate quantification of
pressures below 2.8 Bar.
small to large amounts of fines, negating static effects, and
7.2.11 Tweezers or Forceps, blunt nose, for handling filtra-
eliminating detrimental effects of mechanical agitation. A wet
tion disc.
analysis must be employed to accurately quantify lower PPM
7.2.12 Plastic Sheet, non-stick surface, polytetrafluoroeth-
dust levels in plastic pellets.
ylene (PTFE), 1-mm thick, to keep filtration discs from
6. Interferences
sticking to oven rack during drying process.
7.2.13 Aspirator, to allow flushing of sample and support
6.1 Filtration paper has to be made of glass microfiber
return flow of water back to the storage tank.
material. Paper filter fibers swell, reducing filtration speed and
7.2.14 Water Storage Tank, with drain valve and bottom
increasing filtration time.
outlet for recirculation loop.All inlet and outlet openings must
6.2 Glass microfiber filters are fragile. Care must be taken
be of sufficient size to enable the necessary liquid flow rates to
whenhandlingthewetfiltertokeeptearsfrombeingproduced.
be achieved.
6.3 Some plastics contain certain additives that dissolve in
7.2.15 Wash Bottle, with safety label, to rinse 1500-mL
washingliquids.Thiscreatesaparticulatecloudofthewashing
beaker and filter funnel assembly.
liquid, clogs the filter paper, and gives inaccurate weight
results. 8. Test Specimen
6.4 When analyzing material that reacts with heat (low
8.1 Three test specimens of 100 g each have to be taken
melting temperature), a lower drying temperature is required. from a sample size of approximately 50 litres.
6.5 Too much material on a sieve causes mass blinding.
NOTE 2—The preferred sample size is 100 g but can be up to 200 g if
Pellet bed depth has to be kept to no more than two pellets the fines are low.
deep.
8.2 For samples taken during any part of the conveyance
process,alargersample
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