1、Designation: D7486 08 (Reapproved 2013)1Standard Test Method forMeasurement of Fines and Dust Particles on Plastic Pelletsby Wet Analysis1This standard is issued under the fixed designation D7486; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 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.1NOTEReapproved with editorial changes to Section 3 in November 2013.1. Scope1.1 This test method measur
3、es the amount of fine particlesadhered on plastic pellets or granules in which they arecommonly produced and supplied. The lower limit of this testmethod is restricted only by the porosity of the filter disc usedto capture the particle size being quantified.1.2 The wet analysis technique allows for
4、separation andcollection of statically charged particles by liquid wash andfiltration methods. This must be performed under standardlaboratory conditions.1.3 The values stated in SI units are to be regarded asstandard.1.4 This test method describes an essential practice to checkthe quality of plasti
5、cs once the production cycle is terminatedand to evaluate the performance of pellet cleaning systems orof the special pneumatic conveying systems for the distinct sizefractions below 500 micron only.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its
6、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.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology
7、Relating to PlasticsD1921 Test Methods for Particle Size (Sieve Analysis) ofPlastic MaterialsE11 Specification for Woven Wire Test Sieve Cloth and TestSieves2.2 FEM Standards:3FEM 2482 Test Method to Determine Content of Fines andStreamers in Plastic Pellets.3. Terminology3.1 DefinitionsFor definiti
8、ons of terms associated withplastic materials, see Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 finesfines (Dust) are small particles of plastic whichhave been torn away from the original pellet by contact with arough surface and friction at high conveying velocities. Th
9、eyare defined as the particle fraction with a particle size up to2000 m.3.2.2 streamersstrings of plastics of various lengths thatare created when the resin travels through pneumatic convey-ing lines at high velocity. Streamers are also known as angelhair, foil, floss, film or snake skin.4. Summary
10、of Test Method4.1 Fines or streamers, or both, are generated in polymerresins during pneumatic conveying. Fines and streamers areknown to cause problems in plastic producing and processingplants by clogging the transporting and procession lines. Onfinished products, fines cause the formation of gel,
11、contamination, surface imperfection and weak spots.4.2 The streamer content for a particle size considerablylarger than the pellet diameter are determined by dry screeningaccording to Test Method D1921.4.3 The fundamental principle used in this document isbased upon the condition that statically cha
12、rged fines normallyadhering to plastic pellets be removed by rinsing the testsample with a washing liquid, causing fines in the sample towash away into a container. These particles are then pouredinto a filter funnel to separate the fines from the washing liquid.1This test method is under the jurisd
13、iction ofASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.70 on Analytical Methods.Current edition approved Nov. 1, 2013. Published December 2013. Originallyapproved in 2008. Last previous edition approved in 2008 as D7486 - 08.DOI:10.1520/D7486-08R13.2For reference
14、d 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 Document Summary page onthe ASTM website.3Available from European Federation of Materials Handling, Diamant Building
15、,80 BoulevardAuguste Reyers B, 1030 Brussels, Belgium, http:/www.fem-.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1The weight of the filter paper is accurately measured beforeand after the collection process, and used to calculate
16、the PPMlevel for that sample.4.4 Wet analysis quantifies the amounts of dust with particlesizes typically from 1.6 to 500 microns.5. Significance and Use5.1 Molding and extruding plastic pellets require dust free,dry pellets to prevent processing problems. Plastic producerstry to remove the dust and
17、 streamers with dust removal systemsprior to packaging and loading. How to accurately measuredust and streamer content in plastic pellets is an importantquality control issue.5.2 Particle size analysis is used to determine a percentageof particle size distribution from a representative sample of the
18、whole. In terms of size analysis concerning plastic pellets,sieving is used to determine the dust content in the range of 500to 2000 micron. Test Method D1921, Test Method B, is used todetermine this type of particle sizing.5.3 After dry sieve analysis, particles smaller than 500microns need to be a
19、nalyzed by wet method. A fresh sampleshall be used for wet analysis. This test method allows washingdown the fines attached to the pellets by electrostatic forces.5.4 The wet analysis provides accurate quantification ofsmall to large amounts of fines, negating static effects, andeliminating detrimen
20、tal effects of mechanical agitation. A wetanalysis must be employed to accurately quantify lower PPMdust levels in plastic pellets.6. Interferences6.1 Filtration paper has to be made of glass microfibermaterial. Paper filter fibers swell, reducing filtration speed andincreasing filtration time.6.2 G
21、lass microfiber filters are fragile. Care must be takenwhen handling the wet filter to keep tears from being produced.6.3 Some plastics contain certain additives that dissolve inwashing liquids. This creates a particulate cloud of the washingliquid, clogs the filter paper, and gives inaccurate weigh
22、tresults.6.4 When analyzing material that reacts with heat (lowmelting temperature), a lower drying temperature is required.6.5 Too much material on a sieve causes mass blinding.Pellet bed depth has to be kept to no more than two pelletsdeep.6.6 Replace the water and clean supply hoses on a regularb
23、asis. Algae or slime can develop and skew test results.6.7 Discard sieves if the wire-cloth is damaged or no longertaut, as they no longer conform to Specification E11.6.8 Use a non-stick, high temperature surface for the ovenracks. The glass microfiber filter discs stick to the metal ovenrack durin
24、g the drying process.7. Apparatus7.1 The function of the apparatus (see Fig. 1) is to separateall fines below 500 micron from the pellets of the productsample to be tested. The apparatus runs with a washing liquidin recirculation mode.7.2 The apparatus consists of a wash beaker with spray hoseand no
25、zzle, a filter funnel, a water tank reservoir with drain, apump with throttle valve and flow meter, and connectingpiping. The entire set-up consists of the following equipment.47.2.1 Balance, with a capacity of 500 g or higher, sensitiveto 0.1 mg.7.2.2 Scale, with a capacity of 1200 g or higher, sen
26、sitive to0.1 g.7.2.3 Oven, gravity convection, controlled up to 100 6 5C.7.2.4 Wire-Cloth Sieve, 8-in. or 200-mm, full height, con-forming to the requirements of Specification E11, 500 micron.7.2.5 Filtration Disc, glass microfiber, diameter 90 mm,porosity 0.7 to 2.7 micron, thickness , 260 to 420 m
27、icron,tensile range, 5.5 to 8.9 N/15 mm.7.2.6 Filter Funnel Assembly, 3-piece, borosilicate glass,able to hold a 90-mm filter disc.7.2.7 Filtering Flask, 1000-mL, borosilicate glass, to con-nect to filter funnel.7.2.8 Beaker, 1500-mL, borosilicate glass, to hold washedtest sample.7.2.9 Funnel, 260-m
28、m. top O.D., to hold sieve during testsample washing.7.2.10 Nozzle, flat fan spray, for washing test sample at linepressures below 2.8 Bar.7.2.11 Tweezers or Forceps, blunt nose, for handling filtra-tion disc.7.2.12 Plastic Sheet, non-stick surface, polytetrafluoroeth-ylene (PTFE), 1-mm thick, to ke
29、ep filtration discs fromsticking to oven rack during drying process.7.2.13 Aspirator, to allow flushing of sample and supportreturn flow of water back to the storage tank.7.2.14 Water Storage Tank, with drain valve and bottomoutlet for recirculation loop. All inlet and outlet openings mustbe of suff
30、icient size to enable the necessary liquid flow rates tobe achieved.7.2.15 Wash Bottle, with safety label, to rinse 1500-mLbeaker and filter funnel assembly.8. Test Specimen8.1 Three test specimens of 100 g each have to be takenfrom a sample size of approximately 50 litres.4The apparatus uses standa
31、rd laboratory equipment. However, the apparatus isalso available commercially. The sole source of supply of the apparaturs,FineAnalyzer, known to the committee at this time is by Pelletron Corporation, 499Running Pump Rd., Lancaster, PA 17601, http:/. If you areaware of alternative suppliers, please
32、 provide this information to ASTM Interna-tional Headquarters. Your comments will receive careful consideration at a meetingof the responsible technical committee,1which you may attend.TABLE 1 Comparison of Typical Particle Sizes MeasuredType Lower Limit Upper Limit Test MethodD1921 500 m 2000 m dry
33、D7486 1.6 mA500 m wetAThe lower limit is set by the porosity of the filter disk.D7486 08 (2013)12NOTE 2The preferred sample size is 100 g but can be up to 200 g ifthe fines are low.8.2 For samples taken during any part of the conveyanceprocess, a larger sample size (test unit) can be obtained in ord
34、erto collect the test specimen. When ready to perform the test,use a small scoop or cup to retrieve the test specimen from theapproximate center of the test unit. With the beaker, funnel andsieve on the scale, pour the desired amount of material into thesieve. Any contaminate that remains inside the
35、 cup, or on theinner surfaces of the scoop, has to be brushed into the sievepan, because it belongs to the test specimen.8.3 For samples taken from the end process (packaged orcontainerized material), use the following procedure.8.4 Measure out specimen into a small, resealable, plasticbag. Any cont
36、aminate that remains inside the cup, or on theinner surfaces of the scoop, has to be brushed into the bag,because it belongs to the test specimen.8.5 For large containers of material, take test specimens atvarious levels of the container to measure the contaminatedistribution.9. Calibration9.1 Calib
37、rate instruments using procedures recommendedby the equipment manufacturer.9.2 Standard lab practices have to be observed. Balancesand scales have to be periodically calibrated to maintainconsistent results.9.3 Sieves have to be periodically tested or verified foraccuracy or replaced as necessary in
38、 order to maintain accurateresults.10. Procedure10.1 The selection of a suitable washing liquid is dependenton the characteristics of the test product. Unless otherwiseindicated, use filtered, deionized, demineralized, or distilledwater. In the case that water interacts with the plastic to betested,
39、 use other washing solution instead. In case anotherwashing liquid is used, it has to be ensured that the chosenliquid does not leave any residue after drying the filters, norchange the characteristics of the product, by decomposing ordissolving. Known problems concerning this point are theFIG. 1 Te
40、st Equipment for Determining Fines Content in Plastic PelletsD7486 08 (2013)13combination of waxy products or XLDPE with ethanol as asolvent. The washing liquid must not affect any parts of themeasuring device with which it is in contact. The use of anyother liquids, as a substitute for water, has t
41、o be thoroughlyresearched to define associated hazards. Modifications to theequipment, to allow the use of a different medium, must meetapplicable Occupational Safety and Health Administration(OSHA) safety requirements.10.2 Fill the water tank with clean water. If not previouslydone, clean the tank
42、so that NO particle remains. Ensure allcomponents are properly connected. Assemble the filter funnelassembly. For initial use of the apparatus, flush the system bycirculating water through the system with a filter in place. Tocomplete this, position the rinse tube over the filter collectionunit and
43、turn the pump on. Adjust the level control so that thewater level in the filter collection sleeve is maintained atapproximately half full and circulate water for 10 to 20 minutesat a flow rate of 250 6 50 mL/min. After this initial flush,discard all of the water and the filter and refill the system.
44、 Turnon the oven and obtain a stable inside temperature of about100C.10.3 Weigh a dry disc on the balance. Place the filter in thefilter funnel assembly.10.4 Place the sieve into the funnel, and place this assemblyon top of the 1500-mL beaker. Add the test specimen to thesieve, ensuring all the fine
45、s in the specimen container arerinsed into the sieve.10.5 Rinse the sample with a strong spray of liquid at 500 650 mL/min. Make sure to evenly agitate and wash all thepellets. When the beaker is almost filled, pour the liquid intothe filter funnel to start the filtration process.10.6 Using another
46、beaker, continue the washing processone-quarter beaker at a time. Check each quarter beaker forvisible fines or particles. When no more are observed, the rinseprocess is complete. When emptying the beaker contents, rinsethe beaker into the filter funnel to ensure capture of all fines.When all the li
47、quid has been filtered, rinse the sides of the filterfunnel to ensure all are on the filter disc. To remove the filterfrom the filter funnel, remove the clamps and the reservoir. Ifany fines are on the reservoir body, use the wash bottle to rinsethe fines onto the filter disc, ensuring no over spill
48、age. Use theblunt nose forceps to carefully fold the filter disc in half, andthen in half again. Place the removed filter disc into the ovenand dry the disc for at least one hour. After one hour, removethe filter disc from the oven and place on the balance for weightcalculation. Allow the balance to
49、 stabilize and record theweight.NOTE 3One hour has been found adequate for most samples. Useother time if necessary.11. Calculation or Interpretation of Results11.1 Calculate the weight of the collected fines on the filterdisc(s) by subtracting the tare weight from the final filterweight. Divide the contaminate weight by the test specimenweight.11.2 Multiply the calculated number by 1,000,000 to obtainthe PPM of the sample. For Example: Test Specimen is 100.0g, and Fine Weight is 0.0045 g. Calculation: (0.0045 g/100.0 g) 1,000,000 = 4
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