1、Designation: D1921 12D1921 18Standard Test Methods forParticle Size (Sieve Analysis) of Plastic Materials1This standard is issued under the fixed designation D1921; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r
2、evision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope*1.1 These test methods cover the measurem
3、ent of the particle size of plastic materials in the powdered, granular, or pelletedforms in which they are commonly supplied. As these test methods utilize dry sieving, the lower limit of measurement isconsidered to be about 38 m (No. 400 sieve). For smaller particle sizes, sedimentation test metho
4、ds are recommended.1.2 Two test methods are described:1.2.1 Test Method AThis test method uses multiple sieves selected to span the particle size of the material. This method is usedto determine the mean particle diameter and particle size distribution.1.2.2 Test Method BThis test method is an abbre
5、viated version of Test Method A conducted with a few specific sieves. Thistest method determines “percent passing” or “percent retained” on a given sieve. Test Method B is applicable to materials whichdo not have a normal particle size distribution such as pellets and cubes.1.3 The values stated in
6、SI units shall be considered are to be regarded as standard for dimensions of the wire cloth openingsand the diameter of the wires used in the wire cloth. The values stated in inch-pound units shall be considered standard with regardto the sieve frames.1.4 This standard does not purport to address a
7、ll of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.NOTE 1There is no known ISO equival
8、ent for this test method.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization
9、 Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E11 Specification for Woven Wire Test Sieve Cloth and Test SievesE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method3. Summary of Test Methods3.1 Adry mass of plastic
10、 material is placed on a series of sieves arranged in order of increasing fineness and the mass is dividedinto fractions corresponding to the sieve opening.4. Significance and Use4.1 These test methods are used to determine particle size distribution and therefore are useful for determining lot-to-l
11、otuniformity.4.2 The particle sizes of plastic materials affect the handling characteristics and sometimes will affect the processingcharacteristics of some polymers.1 These test methods are under the jurisdiction of ASTM Committee D20 on Plastics and are the direct responsibility of Subcommittee D2
12、0.70 on Analytical Methods(Section D20.70.01).Current edition approved Aug. 1, 2012April 1, 2018. Published September 2012April 2018. Originally approved in 1961. Last previous edition approved in 20062012 asD1921 - 06D1921 - 12.1. DOI: 10.1520/D1921-12.10.1520/D1921-18.2 For referencedASTM standard
13、s, 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.This document is not an ASTM standard and is intended only to provide the user of an ASTM
14、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, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by
15、 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, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Interferences5.1 Some materials develop a static charge during sieving
16、. This charge interferes with the sieving process and results in a coarsebias. Use of an antistat is necessary to obtain meaningful results.5.2 The choice of antistat (or slip agent) has been known to affect the coarse bias. Some materials are more effective in aidingthe fines to separate from the m
17、ass.5.3 Too much material on a sieve causes mass blinding and results in a coarse bias. The sieve selection and charge weight mustbe chosen to avoid overloading any sieve.5.4 Wavy, improperly stretched wire-cloth potentially allows wires to separate without being visually damaged. Sieves withwavy or
18、 torn wires shall not be used, as they no longer conform to Specification E11.6. Apparatus6.1 Balance, 500-g minimum capacity with the capability of reading to the nearest 0.1 g.6.2 Mechanical Sieving Device and Time SwitchA mechanical sieve-shaking device equipped with an automatic time switch.This
19、 device shall be capable of imparting uniform rotary motion and a tapping action at a rate of 150 6 10 taps/min.6.3 Wire Cloth Sieves, woven wire cloth conforming to Specification E11, as shown in Table 1, mounted in 8-in.203-mm(203-mm) frames. The number of sieves and the choice of sizes shall be s
20、elected for the material being tested. A coverand a bottom pan are also required.6.4 Accessories for Cleaning the Screens:6.4.1 Brush3,6.4.2 Vacuum Cleaner, and6.4.3 Air Hose.7. Reagents and Materials7.1 Antistat (or slip) agent suitable to the material being tested.8. Hazards8.1 The sieving operati
21、on and cleaning of the sieves sometimes introduce fine plastic particles and antistat agent into theatmosphere. Take precautions to avoid breathing these particles.9. Sampling9.1 Homogenize the lot where possible before removing the test sample to avoid segregation of particles during handling.10. P
22、reparation of Apparatus10.1 Thorough cleaning and inspection of the sieve are required prior to initiating a test. Carefully clean the sieves with a brushand vacuum cleaner or compressed air, or both. Periodic washing with soap and water or suitable solvent is recommended withsome materials.10.2 Tar
23、e each sieve and the pan. Record tare weights to the nearest 0.1 g.10.3 Assemble sieves so that the sieve openings decrease in size in sequence from the top of the stack. Place the pan at thebottom.10.4 Use full- or half-size screens to accommodate the holder in the shaker.11. Conditioning11.1 The p
24、lastic material must be in a free-flowing condition.11.2 If possible, condition the material to the laboratory temperature and humidity.TEST METHOD A12. Procedure12.1 Select sieves in sufficient number to cover the expected range of particle sizes, and nest them together in order ofdiminishing openi
25、ng with the coarsest sieve on top and the pan on the bottom.3 The sole source of supply of the Type 8577 (W. S. Tyler) Brush known to the committee at this time is W. S. Tyler, Inc., 8750 Tyler Blvd., Mentor, OH 44060. If youare aware of alternative suppliers, please provide this information to ASTM
26、 International Headquarters. Your comments will receive careful consideration at a meeting ofthe responsible technical committee,1 which you may attend.D1921 18212.2 Select sieves in sufficient number to have significant measurable quantities on four or more sieves. Weigh the sieves ona balance read
27、ing to the nearest 0.1 g. Record these sieve masses as their tare masses, respectively.12.3 Weigh 50 g of sample to the nearest 0.1 g and transfer it to the top of the stack. Record the sample weight used. Largesample size causes screen blinding and will skew the results to the coarse particle size.
28、 A screen is considered blinded if it isholding 20 or more g. For repeatable results,grams or more. If screen blinding occurs, use a smaller sample size.NOTE 2For some materials an antistat (or slip agent) is needed. Add 1 % of the antistat (or slip agent) to the sample and mix in with a spatula. Wi
29、thpolyvinyl chloride resins, it has been found that the distribution will skew to either the fine or the coarse particle size depending on the antistat used.Record the antistat (or slip agent) used.12.4 Cover the stack and place it in the mechanical sieve shaker. Start the shaker and run for 10 min.
30、 Run the shaker for a longertime if it is required by the material and the efficiency of the shaker.12.5 After shaking, carefully separate the stack of sieves, beginning at the top, and weigh each sieve with powdermaterial tothe nearest 0.1 g. Determine the net weight of the powdermaterial remaining
31、 in each sieve by subtracting the sieve tare masses fromthe total weight of the sieve and the powdermaterial in that sieve.12.6 If the cumulative total of actual weight is less than 98 %, carefully check the weights and operations and repeat the workif necessary.13. Analysis of Particle Distribution
32、13.1 Calculation of Particle Distribution:13.1.1 Obtain net weight of material retained on each sieve. Calculate percentage by dividing net weight by total sampleweight 100.13.1.2 Repeat for each sieve.13.2 Calculation of Mean Particle Size:13.2.1 Obtain net weight of material retained on each sieve
33、.13.2.2 Determine an average particle size for each sieve. The average particle size is defined as the nominal opening size of thatsieve plus the nominal opening size of the next larger sieve in the stack divided by two.NOTE 3Options are recommended to determine the average mesh size of the top siev
34、e and the pan. On the coarse end, if the particles have alreadybeen through a coarser screen, the screen size of the “through screen” can be used as the upper limit of the top screen (first screen). A commonly usedmethod is to place a set of sieves with openings greater than the desired top sieve. S
35、elect the lowest sieve where there is no particle on or the amountof particles on the sieve is insignificant. Use the opening size of this sieve for calculation. Similar analog can be used to the pan by using smaller openingsieves. A more practical way is to divide the opening size of the sieve abov
36、e the pan by two and use it as the average particle size of the pan.13.2.3 For materials that have a normal distribution, calculate the mean particle size asDm 5(Pi 3Di!Dm 5(Pi 3Di!100where:Dm = mean particle diameter, m,Pi = material retained on sieve (or pan), %, andDi = average particle size of m
37、aterial on sieve, m.14. Report14.1 Report the following information:14.1.1 Percentage of material retained on each sieve, with its corresponding sieve size,14.1.2 Sample weight,14.1.3 Antistat (or slip agent) used, and14.1.4 Mean particle size and method used for calculation.TEST METHOD B15. Procedu
38、re15.1 Choose the sieve(s) to be used and weigh each of them to the nearest 0.1 g. Record these sieve masses as their tare masses,respectively. If a single sieve is being used, stack it on the pan and transfer a sample weighing 100 6 0.1 g to that sieve. If twosieves are to be used in the analysis o
39、f the sample, stack the coarse sieve over the fine sieve and transfer the weighed sample tothe coarse sieve. For those finely divided powders which tend to clog the sieves, add 1.0 % of an antistat (see Note 2).15.2 Cover the stack and place it in the mechanical sieve shaker. Start the shaker and ru
40、n for 10 min 6 15 s.D1921 18315.3 After shaking, carefully separate the stack of sieves, beginning at the top, and weigh each sieve with powder to the nearestone tenth of a gram.16. Report16.1 Report the following information:16.1.1 Percentage of material retained on each sieve, with its correspondi
41、ng sieve size,16.1.2 Sample weight, and16.1.3 Antistat (or slip agent) used.17. Precision and Bias417.1 PrecisionTable 21 and Table 32 are based on a round robin conducted in 1985 in accordance with Practice E691, usingD1921 89, involving four materials tested by three laboratories. For each materia
42、l, all the samples were prepared at one source,but the individual specimens were prepared at the laboratories that tested them. Each test result was the result of one individualdetermination. Each laboratory obtained two test results for each material. (WarningThe explanations of r and R (17.2 17.2.
43、2)are only intended to present a meaningful way of considering the approximate precision of this test method. The data in Table 21and Table 32 are not applied for the acceptance or rejection of materials, as these data apply only to the materials tested in the roundrobin and are unlikely to be rigor
44、ously representative of other lots, formulations, conditions, materials, or laboratories. Users ofthis test method are encouraged to apply the principles outlined in Practice E691 to generate data specific to their materials andlaboratory (or between specific laboratories). The principles of 17.2 17
45、.2.2 would then be valid for such data.)17.2 Concept of r and R in Table 32If Sr and SR had been calculated from a large enough body of data, and for test resultsthat were averages from testing seven specimens for each test result, then the following would apply:4 Supporting data have been filed at
46、ASTM International Headquarters and may be obtained by requesting Research Report RR:D20-1139.TABLE 21 Percent Retained on Each Sieve of Screen PackMaterial USA SieveNumberValues in Units of PercentMean Retainedon Sieve SrA SRB IrC IRDAcrylic powder 40 13.5 0.1 1.2 0.3 3.460 15.0 0.2 1.4 0.6 4.080 9
47、.3 0 0.4 0 1.1100 6.6 0.1 0.7 0.3 2.0200 22.9 0.1 1.2 0.3 3.4325 16.2 0.2 1.6 0.6 4.5PAN 16.5 0.1 3.6 0.3 10.2Polyethylene powder 40 11.4 0.6 2.6 1.7 7.4608047.818.00.60.12.90.81.70.37.62.3100 7.5 0.1 0.7 0.3 2.0PAN 15.3 0.1 1.3 0.3 3.7Polyvinyl chloride powder with carbon black antistat 40 0 . . .
48、.60 0.1 0.1 0.1 0.3 0.380 5.4 0.9 0.9 2.5 2.5100 28.4 2.1 2.2 5.9 6.2140 53.7 1.3 1.6 3.7 4.5200 11.4 1.7 1.5 4.8 4.2PAN 0.9 0.3 6.3 0.9 0.9Polyvinyl chloride powder with hi-sil antistat 40 0 . . . .60 0 . . . .80 4.2 0.7 0.6 2.0 1.7100 30.3 2.9 2.9 8.2 8.2140 52.6 2.0 2.2 5.7 6.2200 11.3 1.3 1.3 3.
49、7 3.7PAN 1.5 0.3 0.3 0.9 6.9Polystyrene cubes 20 99.9 . . . .PAN 0.06 . 0.04 . 0.1A Sr = within-laboratory standard deviation of the average (median/other function),B SR = between-laboratories standard deviation of the average median,C Ir = 2.83 Sr, andD IR = 2.83 SR.D1921 18417.2.1 RepeatabilityTwo test results obtained within one laboratory shall be judged not equivalent if they differ by more thanthe r value for that material; r is the interval representing the critical difference between two test results for the same materialobtained by the same ope
