1、Designation:D283910Standard 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 revi
2、sion.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 D1505.The samp
3、le 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 purport to addres
4、s 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.NOTE1There is no known ISO equivalent to this standard.NOTE2Th
5、e 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 Density-Gradient Techn
6、iqueD4703 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.Significance and Use4.1 This prac
7、tice 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 neces-sarily recommended for re
8、sin 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 samplepreparation differs from that obt
9、ained 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 combination thereof,covered in thematerial
10、s 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-mL low form,graduated,with watch-glassco
11、vers.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 plate after cutting off.When Procedure B of Te
12、st 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.NOTE3It has been shown that the measured density of an extrudedstrand can be significantly affected by changes in the localized air velocity1This pract
13、ice 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.Last previous edition approved in 2005 as D2839-05.DOI:1
14、0.1520/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 ASTM website.*A Summary of Changes section appears at the end o
15、f this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 due to external drafts,location in relation to HVAC outlets,and so forth.It is advisable to minimize any external airflow and to recognize this whenrelocating instruments or w
16、hen 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 this so thatthe amount of water can be maintained at 200 mLfor the wholeperiod without interrupting the boiling.Let the strand conditionin the boiling water for 30 min.NOTE4A time interval of five days at room temperature betweenextrusion of the strand and dropping
