1、Designation: D2839 10Standard 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, repro-ducible, comparative results are needed. It is not ne
8、cessarilyrecommended for resin specifications that are part of a salescontract 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 extrudedstrand can be significantly affected by
13、changes in the localized air velocity1This practice is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.15 on Thermoplastic Materials(D20.15.01).Current edition approved Aug. 1, 2010. Published September 2010. Originallyapproved in 1969. Las
14、t previous edition approved in 2005 as D2839 - 05. DOI:10.1520/D2839-10.2For referenced 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 AS
15、TM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.due to external drafts, location in relation to HVAC outlets, and so forth.It is advisable to minimize any e
16、xternal 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
17、with this 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
18、 been foundcritical.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 5The melt strand can be quench cooled, if desired, by omittingprocedures
19、7.2 and 7.3. 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 a
20、nd cut off 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.If the sample whitens when cutting, use a very sharp razorblade, and cut very slowly. Cut
21、ting under water will avoidwhitening. This whitening appears to affect sample density andshall be avoided. Discard any specimens with bubbles orvisible roughness.7.5 Determine the density of the specimen in accordancewith Test Method D1505 within 24 h of the conditioningdescribed in 7.2 and 7.3.8. R
22、eport8.1 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; polyethyleneSUMMARY OF CHANGESComm
23、ittee D20 has identified the location of selected changes to this standard since the last issue (D2839 - 05)that may impact the use of this standard. (August 1, 2010)(1) Changed ISO statement in Note 1.(2) Delete precision and bias statement.(3) Editorial changes: Removed permissive language anddele
24、ted redundant information.ASTM International takes no 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 infrin
25、gement of such rights, are entirely their own responsibility.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
26、 or for additional standardsand should be addressed to 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
27、 known to the ASTM Committee on Standards, at the address 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 ASTM website (www.astm.org/COPYRIGHT/).D2839 102
