ASTM D1505-2003 Standard Test Method for Density of Plastics by the Density-Gradient Technique《用密度梯度法测定塑料密度的标准试验方法》.pdf

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1、Designation: D 1505 03Standard Test Method forDensity of Plastics by the Density-Gradient Technique1This standard is issued under the fixed designation D 1505; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi

2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This test method covers the determination of t

3、he densityof solid plastics.1.2 This test method is based on observing the level towhich a test specimen sinks in a liquid column exhibiting adensity gradient, in comparison with standards of knowndensity.NOTE 1The comparable ISO document is ISO 11832. There has notbeen any data generated to date co

4、mparing the results of the ISO methodwith this method.1.3 The values stated in SI units are to be regarded as thestandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-

5、priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 941 Test Method for Density and Relative Density (Spe-cific Gravity) of Liquids by Lipkin Bicapillary PycnometerD 2839 Practice for Use of a Melt In

6、dex Strand for Deter-mining Density of PolyethyleneD 4703 Practice for Compression Molding ThermoplasticMaterials into Test Specimens, Plaques, or SheetsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:ISO 1183-2 Methods for Determinin

7、g the Density and Rela-tive Density of Noncellular Plastics33. Terminology3.1 Definition:3.1.1 density of plasticsthe weight per unit volume ofmaterial at 23C, expressed as follows:D23C, g/cm3(1)NOTE 2Density is to be distinguished from specific gravity, which isthe ratio of the weight of a given vo

8、lume of the material to that of an equalvolume of water at a stated temperature.4. Significance and Use4.1 The density of a solid is a conveniently measurableproperty which is frequently useful as a means of followingphysical changes in a sample, as an indication of uniformityamong samples, and a me

9、ans of identification.4.2 This test method is designed to yield results accurate tobetter than 0.05 %.NOTE 3Where accuracy of 0.05 % or better is desired, the gradienttube shall be constructed so that vertical distances of 1 mm shall representdensity differences no greater than 0.0001 g/cm.3The sens

10、itivity of thecolumn is then 0.0001 g/cm3mm. Where less accuracy is needed, thegradient tube shall be constructed to any required sensitivity.5. Apparatus5.1 Density-Gradient TubeA suitable graduate withground-glass stopper.45.2 Constant-Temperature BathA means of controllingthe temperature of the l

11、iquid in the tube at 23 6 0.1C. Athermostatted water jacket around the tube is a satisfactory andconvenient method of achieving this.5.3 Glass FloatsA number of calibrated glass floats cov-ering the density range to be studied and approximately evenlydistributed throughout this range.5.4 Pycnometer,

12、 for use in determining the densities of thestandard floats.5.5 Liquids, suitable for the preparation of a density gradi-ent (Table 1).NOTE 4It is very important that none of the liquids used in the tube1This test method is under the jurisdiction of ASTM Committee D20 on Plasticand is the direct res

13、ponsibility of Subcommittee D20.70 on Analytical Methods(Section D20.70.01).Current edition approved November 1, 2003. Published January 2004. Originallyapproved in 1957. Last previous edition approved in 1998 as D 1505 - 98.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcon

14、tact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.4Tubes similar to those descr

15、ibed in Refs (6) and (12) may also be used.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.exert a solvent or chemical effect upon the test specimens during the timeof

16、 specimen immersion.5.6 HydrometersA set of suitable hydrometers coveringthe range of densities to be measured. These hydrometersshould have 0.001 density graduations.5.7 Analytical Balance, with a sensitivity of 0.001 g.5.8 Siphon or Pipet Arrangement, for filling the gradienttube. This piece of eq

17、uipment should be constructed so that therate of flow of liquid may be regulated to 10 6 5 mL/min.6. Test Specimen6.1 The test specimen shall consist of a piece of the materialunder test. The piece may be cut to any shape convenient foreasy identification, but should have dimensions that permit them

18、ost accurate position measurement of the center of volume ofthe suspended specimen (Note 5). Care should be taken incutting specimens to avoid change in density resulting fromcompressive stress.NOTE 5The equilibrium positions of film specimens in the thicknessrange from 0.025 to 0.051 mm (0.001 to 0

19、.002 in.) may be affected byinterfacial tension. If this affect is suspected, films not less than 0.127 mm(0.005 in.) in thickness should be tested.6.2 The specimen shall be free of foreign matter and voidsand shall have no cavities or surface characteristics that willcause entrapment of bubbles.7.

20、Preparation of Density-Gradient Columns7.1 Preparation of Standard Glass Floats5Prepare glassfloats by any convenient method such that they are fullyannealed, approximately spherical, have a maximum diameterless than one fourth the inside diameter of the column, and donot interfere with the test spe

21、cimens. Prepare a solution (400 to600 mL) of the liquids to be used in the gradient tube such thatthe density of the solution is approximately equal to the desiredlowest density. When the floats are at room temperature, dropthem gently into the solution. Save the floats that sink veryslowly, and dis

22、card those that sink very fast, or save them foranother tube. If necessary to obtain a suitable range of floats,grind selected floats to the desired density by rubbing the headpart of the float on a glass plate on which is spread a thin slurryof 400 or 500-mesh silicon carbide (Carborundum) or other

23、appropriate abrasive. Progress may be followed by droppingthe float in the test solution at intervals and noting its changein rate of sinking.7.2 Calibration of Standard Glass Floats (see AppendixX1):7.2.1 Place a tall cylinder in the constant-temperature bathmaintained at 23 6 0.1C. Then fill the c

24、ylinder about twothirds full with a solution of two suitable liquids selected fromTable 1, the density of which can be varied over the desiredrange by the addition of either liquid to the mixture. After thecylinder and solution have attained temperature equilibrium,place the float in the solution, a

25、nd if it sinks, add the denserliquid by suitable means with good stirring until the floatreverses direction of movement. If the float rises, add the lessdense liquid by suitable means with good stirring until the floatreverses direction of movement.7.2.2 When reversal of movement has been observed,

26、re-duce the amount of the liquid additions to that equivalent to0.0001-g/cm3density. When an addition equivalent to 0.0001-g/cm3density causes a reversal of movement, or when the floatremains completely stationary for at least 15 min, the float andliquid are in satisfactory balance. The cylinder mus

27、t be coveredwhenever it is being observed for balance, and the liquidsurface must be below the surface of the liquid in theconstant-temperature bath. After vigorous stirring, the liquidmay continue to move for a considerable length of time; makesure that the observed movement of the float is not due

28、 to liquidmotion by waiting at least 15 min after stirring has stoppedbefore observing the float.7.2.3 When balance has been obtained, fill a freshly cleanedand dried pycnometer with the solution and place it in the 236 0.1C bath for sufficient time to allow temperature equilib-rium of the glass. De

29、termine the density of the solution bynormal methods (Test Method D 941) and make “in vacuo”corrections for all weighings. Record this as the density of thefloat. Repeat the procedure for each float.7.3 Gradient Tube Preparation (see appendix for details):7.3.1 Method AStepwise addition.7.3.2 Method

30、 BContinuous filling (liquid entering gradi-ent tube becomes progressively less dense).7.3.3 Method CContinuous filling (liquid entering gradi-ent tube becomes progressively more dense).8. Conditioning8.1 Test specimens whose change in density on conditioningmay be greater than the accuracy required

31、 of the densitydetermination shall be conditioned before testing in accordancewith the method listed in the applicable ASTM materialspecification.9. Procedure9.1 Wet three representative test specimens with the lessdense of the two liquids used in the tube and gently place themin the tube. Allow the

32、 tube and specimens to reach equilibrium,which will require 10 min or more. Thin films of 1 to 2 mils inthickness require approximately 112 h to settle, and recheckingafter several hours is advisable (Note 4).9.2 Read the height of each float and each specimen by aline through the individual center

33、of volume and averaging the5Glass floats may be purchased from American Density Materials, 3826Springhill Rd. Staunton, VA 24401, Ph: (540) 887-1217.TABLE 1 Liquid Systems for Density-Gradient TubesSystemDensity Range,g/cm3Methanol-benzyl alcohol 0.80 to 0.92Isopropanol-water 0.79 to 1.00Isopropanol

34、-diethylene glycol 0.79 to 1.11Ethanol-carbon tetrachloride 0.79 to 1.59Toluene-carbon tetrachloride 0.87 to 1.59Water-sodium bromide 1.00 to 1.41Water-calcium nitrate 1.00 to 1.60Carbon tetrachloride-trimethylene dibromide 1.60 to 1.99Trimethylene dibromide-ethylene bromide 1.99 to 2.18Ethylene bro

35、mide-bromoform 2.18 to 2.89D1505032three values. When a cathetometer is used, measure the heightof the floats and specimens from an arbitrary level using a linethrough their center of volume. If equilibrium is not obtained,the specimen may be imbibing the liquid.9.3 Old samples can be removed withou

36、t destroying thegradient by slowly withdrawing a wire screen basket attachedto a long wire (Note 6). This can be conveniently done bymeans of a clock motor. Withdraw the basket from the bottomof the tube and, after cleaning, return it to the bottom of thetube. It is essential that this procedure be

37、performed at a slowenough rate (approximately 30 min/300-mm length of column)so that the density gradient is not disturbed.NOTE 6Whenever it is observed that air bubbles are collecting onsamples in the column, a vacuum applied to the column will correct this.10. Calculation10.1 The densities of the

38、samples may be determinedgraphically or by calculation from the levels to which thesamples settle by either of the following methods:10.1.1 Graphical CalculationPlot float position versusfloat density on a chart large enough to be read accurately to61 mm and the desired precision of density. Plot th

39、e positionsof the unknown specimens on the chart and read their corre-sponding densities.10.1.2 Numerical CalculationCalculate the density byinterpolation as follows:Density at x 5 a 1 x 2 y!b 2 a!/z 2 y!# (2)where:a and b = densities of the two standard floats,y and z = distances of the two standar

40、ds, a and b, respec-tively, bracketing the unknown measured froman arbitrary level, andx = distance of unknown above the same arbitrarylevel.11. Report11.1 Report the following information:11.1.1 Density reported as D23C, in grams per cubiccentimetre, as the average for three representative test spe

41、ci-mens,11.1.2 Number of specimens tested if different than three,11.1.3 Sensitivity of density gradient in grams per cubiccentimetre per millimetre,11.1.4 Complete identification of the material tested, and11.1.5 Date of the test.12. Precision and Bias612.1 Specimens Molded in One Laboratory and Te

42、sted inSeveral LaboratoriesAn interlaboratory test was run in 1981in which randomized density plaques were supplied to 22laboratories. Four polyethylene samples of nominal densitiesof 0.92 to 0.96 g/cm3were molded in one laboratory. The datawere analyzed using Practice E 691, and the results are giv

43、enin Table 2.12.2 Specimens Molded and Tested in Several Laboratories:12.2.1 Samples Prepared Using Practice D 4703 in EachLaboratoryTable 3 is based on a round robin9conducted in1994 in accordance with Practice E 691, involving sevenmaterials tested by 7 to 11 laboratories. For each material, allof

44、 the samples were prepared by each laboratory, molded inaccordance with Procedure C of Annex A1 of Practice D 4703,and tested using this test method. The data are for comparisonwith the data of the same samples tested by Practice D 2839.Each test result is an individual determination. Each laborator

45、yobtained six test results for each material.12.2.2 Samples Prepared Using Practice D 2839 in EachLaboratoryTable 4 is based on a round robin9conducted in1994 in accordance with Practice E 691, involving sevenmaterials tested by 10 to 15 laboratories. For each material, allof the samples were prepar

46、ed by each laboratory in accordancewith Practice D 2839. Each test result is an individual deter-mination. Each laboratory obtained six test results for eachmaterial.12.3 Concept of r and RWarningThe following expla-nations of r and R (12.3-12.3.3) are only intended to present ameaningful way of con

47、sidering the approximate precision ofthis test method. The data in Table 1 should not be rigorouslyapplied to acceptance or rejection of material, as those data arespecific to the round robin and may not be representative ofother lots, conditions, materials, or laboratories. Users of thistest method

48、 should apply the principles outlined in PracticeE 691 to generate data specific to their laboratory and materi-als, or between specific laboratories. The principles of 12.3-12.3.3 would then be valid for each data.If Srand SRhave been calculated from a large enough bodyof data, and for test results

49、 that were averages from testing onespecimen:12.3.1 Repeatability Limit, r (Comparing two test resultsfor the same material, obtained by the same operator using the6Supporting data are available from ASTM Headquarters. Request RR:D20-1123.TABLE 2 Precision Data SummaryPolyethylene DensityMaterial Average Density, g/cm3SrASRBrCRD1 0.9196 0.00029 0.00106 0.00082 0.00452 0.9319 0.00012 0.00080 0.00034 0.00233 0.9527 0.00033 0.00116 0.00093 0.00334 0.9623 0.00062 0.00114 0.00180 0.0033ASr= within-laboratory standard deviation for the indicated material. It