1、Designation: D2839 16Standard Practice forUse of a Melt Index Strand for Determining Density ofPolyethylene1This standard is issued under the fixed designation D2839; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice covers the preparation of a sample forpolyethylene density determination in accordance with TestMethod D150
3、5. The sample consists of a strand produced byextrusion of the polyethylene in accordance with Test MethodD1238, Condition 190/2.16 (Melt Index).1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not pur
4、port to address all of thesafety concerns, if any, associated with its 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 thi
5、s standard.NOTE 2The precision data on densities measured using this samplepreparation practice is listed in Test Method D1505.2. Referenced Documents2.1 ASTM Standards:2D1238 Test Method for Melt Flow Rates of Thermoplasticsby Extrusion PlastometerD1505 Test Method for Density of Plastics by the De
6、nsity-Gradient TechniqueD4703 Practice for Compression Molding ThermoplasticMaterials into Test Specimens, Plaques, or Sheets3. Terminology3.1 Definitions:3.1.1 melt index strandthe extrudate produced when poly-ethylene is extruded in accordance with Test Method D1238,Condition 190/2.16.4. Significa
7、nce and Use4.1 This practice has been found to be very useful forpreparing polyethylene samples suitable for determination ofdensity by Test Method D1505, for quality control purposes,especially in a resin manufacturing facility where fast,reproducible, comparative results are needed. It is not nece
8、s-sarily recommended for resin specifications that are part of asales contract between the buyer and the seller.4.2 The density of a polyethylene sample is highly depen-dent on the preparation and thermal history of the specimens.The level of density results obtained by this practice of sampleprepar
9、ation differs from that obtained by other methods asdescribed in Practice D4703, Annex A1.4.3 Before proceeding with this practice, reference shall bemade to the specification of the material being tested. Any testspecimen preparation, conditioning, dimensions, or testingparameters, or some combinat
10、ion thereof, covered in thematerials specification shall take precedence over those men-tioned in this practice. If there are no material specifications,the default conditions apply.5. Apparatus5.1 Extrusion Plastometer, as described in Test MethodD1238.5.2 Hot Plate, to boil water.5.3 Beakers, 250-
11、mL low form, graduated, with watch-glasscovers.6. Sample6.1 Polyethylene, in any form suitable for test in accordancewith Test Method D1238.7. Procedure7.1 Prepare a Melt Index Strand by extruding the sample inaccordance with Test Method D1238, Condition 190/2.16,dropping the strand on a cool metal
12、plate after cutting off.When Procedure B of Test Method D1238 is used, cut off theextrudate at about the time the timer is actuated and discard.Save the portion extruded during the timed interval.NOTE 3It has been shown that the measured density of an extruded1This practice is under the jurisdiction
13、 ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.15 on Thermoplastic Materials(D20.15.01).Current edition approved Oct. 1, 2016. Published October 2016. Originallyapproved in 1969. Last previous edition approved in 2010 as D2839 - 10. DOI:10.1520/D2839-16.2For re
14、ferenced 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.*A Summary of Changes section appears at the end of this standardCop
15、yright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1strand is significantly affected by changes in the localized air velocity dueto external drafts, location in relation to HVAC outlets, and so forth. It isadvisable to minimize any external
16、airflow and to recognize this whenrelocating instruments or when comparing results from instruments indifferent locations.7.2 Drop the strand into a 250-mL beaker containing at least200 mL of briskly boiling water, and cover with a watch-glass.Keep a large beaker full of water boiling along with thi
17、s so thatthe amount of water can be maintained at 200 mL for the wholeperiod without interrupting the boiling. Let the strand conditionin the boiling water for 30 min.NOTE 4A time interval of five days at room temperature betweenextrusion of the strand and dropping into boiling water has not been fo
18、undcritical.7.3 At the end of the boiling time, remove the beaker fromthe hot plate, making sure the water level is at approximately200 mL, and allow to stand on the bench at standard laboratorytemperature for 1 h.NOTE 5It is acceptable to quench cool the melt strand by omittingprocedures 7.2 and 7.
19、3. In such case, after a 10-min cooling period, cut offthe density specimen as described in 7.4 and determine the density inaccordance with Test Method D1505. This quick approach gives adifferent result than following 7.2 and 7.3 and shall be reported.7.4 Remove the strand from the water and cut off
20、 a 5-mm(14-in.) length from the thicker end of the strand. Discard thisportion, and, from the next 10 mm (12 in.) of strand, cut at leastthree short pieces of convenient size for density determination.Cut the strand with a very sharp blade; and cut the strand veryslowly to avoid whitening on the sam
21、ple. Cutting under waterwill avoid whitening. This whitening appears to affect sampledensity and shall be avoided. Discard any specimens withbubbles. Discard samples that display visible roughness.7.5 Determine the density of the specimen in accordancewith Test Method D1505 within 24 h of the condit
22、ioningdescribed in 7.2 and 7.3.8. Report8.1 Report the following information:8.1.1 Any deviations from the procedure, including omis-sion of the conditioning (subsections 7.2 and 7.3).8.1.2 The density according to the Report Section of TestMethod D1505.9. Keywords9.1 density; melt index strand; PE;
23、 polyethyleneSUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue (D2839 - 10)that may impact the use of this standard. (October 1, 2016)(1) Removed permissive language in Note 3 and Note 5. (2) Revised 7.4.ASTM International takes no
24、position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsi
25、bility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to
26、 ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the addr
27、ess shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 162
