1、Designation: D7486 08 (Reapproved 2013)1D7486 14Standard 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
2、the case 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.1 NOTEReapproved with editorial changes to Section 3 in November 2013.1. Scope Scope*1.1 This te
3、st method measures the amount of fine particles adhered on plastic pellets or granules in which they are commonlyproduced and supplied. The lower limit of this test method is restricted only by the porosity of the filter disc used to capture theparticle size being quantified.1.2 The wet analysis tec
4、hnique allows for separation and collection of statically charged particles by liquid wash and filtrationmethods. 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
5、 the quality of plastics once the production cycle is terminated andto evaluate the performance of pellet cleaning systems or of the special pneumatic conveying systems for the distinct size fractionsbelow 500 micron only.1.5 This standard does not purport to address all of the safety concerns, if a
6、ny, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM Standar
7、ds:2D883 Terminology Relating to PlasticsD1921 Test Methods for Particle Size (Sieve Analysis) of Plastic MaterialsE11 Specification for Woven Wire Test Sieve Cloth and Test Sieves2.2 FEM Standards:3FEM 2482 Test Method to Determine Content of Fines and Streamers in Plastic Pellets.3. Terminology3.1
8、 DefinitionsFor definitions of terms associated with plastic materials, see Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 finesfines (Dust) are small particles of plastic which have been torn away from the original pellet by contact with a rough1 This test method is under
9、 the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.70 on Analytical Methods.Current edition approved Nov. 1, 2013Aug. 1, 2014. Published December 2013September 2014. Originally approved in 2008. Last previous edition approved in 20082013as D7486
10、- 08.08(2013)1 DOI:10.1520/D7486-08R13 DOI:10.1520/D7486-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3
11、 Available from European Federation of Materials Handling, Diamant Building, 80 Boulevard Auguste Reyers B, 1030 Brussels, Belgium, http:/www.fem-.TABLE 1 Comparison of Typical Particle Sizes MeasuredType Lower Limit Upper Limit Test MethodD1921 500 m 2000 m dryD7486 1.6 mA 500 m wetAThe lower limit
12、 is set by the porosity of the filter disk.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. Becauseit may not be technically possible to adequately depict all changes accurately, A
13、STM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, P
14、O Box C700, West Conshohocken, PA 19428-2959. United States1surface and friction at high conveying velocities. They are defined as the particle fraction with a particle size up to 2000 m.3.2.2 streamersstrings of plastics of various lengths that are created when the resin travels through pneumatic c
15、onveying linesat high velocity. Streamers are also known as angel hair, foil, floss, film or snake skin.4. Summary of Test Method4.1 Fines or streamers, or both, are generated in polymer resins during pneumatic conveying. Fines and streamers are knownto cause problems in plastic producing and proces
16、sing plants by clogging the transporting and procession lines. On finishedproducts, fines cause the formation of gel, contamination, surface imperfection and weak spots.4.2 The streamer content for a particle size considerably larger than the pellet diameter are determined by dry screeningaccording
17、to Test Method D1921.4.3 The fundamental principle used in this document is based upon the condition that statically charged fines normally adheringto plastic pellets be removed by rinsing the test sample with a washing liquid, causing fines in the sample to wash away into acontainer. These particle
18、s are then poured into a filter funnel to separate the fines from the washing liquid. The weight of the filterpaper is accurately measured before and after the collection process, and used to calculate the PPM level for that sample.4.4 Wet analysis quantifies the amounts of dust with particle sizes
19、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 producers try toremove the dust and streamers with dust removal systems prior to packaging and loading. How to accurately measure
20、dust andstreamer content in plastic pellets is an important quality control issue.5.2 Particle size analysis is used to determine a percentage of particle size distribution from a representative sample of thewhole. In terms of size analysis concerning plastic pellets, sieving is used to determine th
21、e dust content in the range of 500 to 2000micron. Test Method D1921, Test Method B, is used to determine this type of particle sizing.5.3 After dry sieve analysis, particles smaller than 500 microns need to be analyzed by wet method. A fresh sample shall beused for wet analysis. This test method all
22、ows washing down the fines attached to the pellets by electrostatic forces.5.4 The wet analysis provides accurate quantification of small to large amounts of fines, negating static effects, and eliminatingdetrimental effects of mechanical agitation. A wet analysis must be employed to accurately quan
23、tify lower PPM dust levels inplastic pellets.6. Interferences6.1 Filtration paper has to be made of glass microfiber material. Paper filter fibers swell, reducing filtration speed and increasingfiltration time.6.2 Glass microfiber filters are fragile. Care must be taken when handling the wet filter
24、to keep tears from being produced.6.3 Some plastics contain certain additives that dissolve in washing liquids. This creates a particulate cloud of the washingliquid, clogs the filter paper, and gives inaccurate weight results.6.4 When analyzing material that reacts with heat (low melting temperatur
25、e), 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 pellets deep.6.6 Replace the water and clean supply hoses on a regular basis. Algae or slime can develop and skew test results.6.7 Discard sieves if t
26、he wire-cloth is damaged or no longer taut, as they no longer conform to Specification E11.6.8 Use a non-stick, high temperature surface for the oven racks. The glass microfiber filter discs stick to the metal oven rackduring the drying process.7. Apparatus7.1 The function of the apparatus (see Fig.
27、 1) is to separate all fines below 500 micron from the pellets of the product sampleto be tested. The apparatus runs with a washing liquid in recirculation mode.7.2 The apparatus consists of a wash beaker with spray hose and nozzle, a filter funnel, a water tank reservoir with drain, a pumpwith thro
28、ttle valve and flow meter, and connecting piping. The entire set-up consists of the following equipment.47.2.1 Balance, with a capacity of 500 g or higher, sensitive to 0.1 mg.4 The apparatus uses standard laboratory equipment. However, the apparatus is also available commercially. The sole source o
29、f supply of the apparaturs, FineAnalyzer,known to the committee at this time is by Pelletron Corporation, 499 Running Pump Rd., Lancaster, PA17601, http:/. If you are aware of alternativesuppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful
30、 consideration at a meeting of the responsible technicalcommittee,1 which you may attend.D7486 1427.2.2 Scale, with a capacity of 1200 g or higher, sensitive to 0.1 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, conforming to the req
31、uirements 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 micron, 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
32、Flask, 1000-mL, borosilicate glass, to connect to filter funnel.7.2.8 Beaker, 1500-mL, borosilicate glass, to hold washed test sample.7.2.9 Funnel, 260-mm. top O.D., to hold sieve during test sample washing.7.2.10 Nozzle, flat fan spray, for washing test sample at line pressures below 2.8 Bar.7.2.11
33、 Tweezers or Forceps, blunt nose, for handling filtration disc.7.2.12 Plastic Sheet, non-stick surface, polytetrafluoroethylene (PTFE), 1-mm thick, to keep filtration discs from sticking tooven rack during drying process.7.2.13 Aspirator, to allow flushing of sample and support return flow of water
34、back to the storage tank.7.2.14 Water Storage Tank, with drain valve and bottom outlet for recirculation loop. All inlet and outlet openings must be ofsufficient size to enable the necessary liquid flow rates to be achieved.7.2.15 Wash Bottle, with safety label, to rinse 1500-mL beaker and filter fu
35、nnel assembly.FIG. 1 Test Equipment for Determining Fines Content in Plastic PelletsD7486 1438. Test Specimen8.1 Three test specimens of 100 g each have to be taken from a sample size of approximately 50 litres.NOTE 2The preferred sample size is 100 g but can be up to 200 g if the fines are low.8.2
36、For samples taken during any part of the conveyance process, a larger sample size (test unit) can be obtained in order tocollect 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, fun
37、nel and sieve on the scale, pour the desired amount of material into thesieve. Any contaminate that remains inside the cup, or on the inner surfaces of the scoop, has to be brushed into the sieve pan,because it belongs to the test specimen.8.3 For samples taken from the end process (packaged or cont
38、ainerized material), use the following procedure.8.4 Measure out specimen into a small, resealable, plastic bag. Any contaminate that remains inside the cup, or on the innersurfaces of the scoop, has to be brushed into the bag, because it belongs to the test specimen.8.5 For large containers of mate
39、rial, take test specimens at various levels of the container to measure the contaminatedistribution.9. Calibration9.1 Calibrate instruments using procedures recommended by the equipment manufacturer.9.2 Standard lab practices have to be observed. Balances and scales have to be periodically calibrate
40、d to maintain consistentresults.9.3 Sieves have to be periodically tested or verified for accuracy or replaced as necessary in order to maintain accurate results.10. Procedure10.1 The selection of a suitable washing liquid is dependent on the characteristics of the test product. Unless otherwiseindi
41、cated, use filtered, deionized, demineralized, or distilled water. In the case that water interacts with the plastic to be tested, useother washing solution instead. In case another washing liquid is used, it has to be ensured that the chosen liquid does not leaveany residue after drying the filters
42、, nor change the characteristics of the product, by decomposing or dissolving. Known problemsconcerning this point are the combination of waxy products or XLDPE with ethanol as a solvent. The washing liquid must notaffect any parts of the measuring device with which it is in contact. The use of any
43、other liquids, as a substitute for water, has tobe thoroughly researched to define associated hazards. Modifications to the equipment, to allow the use of a different medium, mustmeet applicable Occupational Safety and Health Administration (OSHA) safety requirements.10.2 Fill the water tank with cl
44、ean water. If not previously done, clean the tank so that NO particle remains. Ensure allcomponents are properly connected. Assemble the filter funnel assembly. For initial use of the apparatus, flush the system bycirculating water through the system with a filter in place. To complete this, positio
45、n the rinse tube over the filter collection unitand turn the pump on. Adjust the level control so that the water level in the filter collection sleeve is maintained at approximatelyhalf full and circulate water for 10 to 20 minutes at a flow rate of 250 6 50 mL/min.After this initial flush, discard
46、all of the waterand the filter and refill the system. Turn on the oven and obtain a stable inside temperature of about 100C.10.3 Weigh a dry disc on the balance. Place the filter in the filter funnel assembly.10.4 Place the sieve into the funnel, and place this assembly on top of the 1500-mL beaker.
47、 Add the test specimen to the sieve,ensuring all the fines in the specimen container are rinsed into the sieve.10.5 Rinse the sample with a strong spray of liquid at 500 6 50 mL/min. Make sure to evenly agitate and wash all the pellets.When the beaker is almost filled, pour the liquid into the filte
48、r funnel to start the filtration process.10.6 Using another beaker, continue the washing process one-quarter beaker at a time. Check each quarter beaker for visiblefines or particles. When no more are observed, the rinse process is complete. When emptying the beaker contents, rinse the beakerinto th
49、e filter funnel to ensure capture of all fines. When all the liquid has been filtered, rinse the sides of the filter funnel to ensureall are on the filter disc. To remove the filter from the filter funnel, remove the clamps and the reservoir. If any fines are on thereservoir body, use the wash bottle to rinse the fines onto the filter disc, ensuring no over spillage. Use the blunt nose forceps tocarefully fold the filter disc in half, and then in half again. Place the removed filter disc into the oven and dry the disc for at leastone h
