1、Designation: D1505 10Standard Test Method forDensity of Plastics by the Density-Gradient Technique1This standard is issued under the fixed designation D1505; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision
2、. 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 Department of Defense.1. Scope*1.1 This test method covers the determination of the
3、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 1This test method is equivalent to ISO 1183-2.1.3 The values stated in SI units are to be reg
4、arded 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-priate safety and health practices and determine the applica-bility of regulatory limitations prior t
5、o use.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD2839 Practice for Use of a Melt Index Strand for Deter-mining Density of PolyethyleneD4703 Practice for Compression Molding ThermoplasticMaterials into Test Specimens, Plaques, or SheetsE691 Practice for Conductin
6、g an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:ISO 1183-2 Methods for Determining the Density and Rela-tive Density of Noncellular Plastics33. Terminology3.1 Refer to Terminology D883 for definitions of otherterms relating to this test method.3.2 Definitions:3.
7、2.1 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 volume of the material to that of an equalvolume of water at a stated temperature.4. Signific
8、ance 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 means of identification.4.2 This test method is designed to yield results accurate tobetter t
9、han 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 sensitivity of thecolumn is then 0.0001 g/cm3mm. Where less accuracy is needed, thegradient tub
10、e 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 liquid in the tube at 23 6 0.1C. Athermostatted water jacket around the tube is a satisfacto
11、ry 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, for use in determining the densities of thestandard floats.1This test method is under the
12、jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.70 on Analytical Methods(Section D20.70.01).Current edition approved July 1, 2010. Published September 2010. Originallyapproved in 1957. Last previous edition approved in 2003 as D1505 - 03. DOI:10.152
13、0/D1505-10.2For 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.3Available from American National Standards Instit
14、ute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.4Tubes similar to those described 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,
15、 PA 19428-2959, United States.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 tubeexert a solvent or chemical effect upon the test specimens during the timeof specimen immersion.5.6 HydrometersA set of suitabl
16、e hydrometers coveringthe range of densities to be measured. These hydrometers shallhave 0.001 density graduations.5.7 Analytical Balance, with a sensitivity of 0.0001 g orbetter.5.8 Siphon or Pipet Arrangement, for filling the gradienttube. This piece of equipment shall be constructed so that thera
17、te 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 shall be cut to any shape convenient foreasy identification, but shall have dimensions that permit themost accurate position measurement of the c
18、enter of volume ofthe suspended specimen (Note 5). Care shall be taken in cuttingspecimens to avoid change in density resulting from compres-sive stress.NOTE 5The equilibrium positions of film specimens in the thicknessrange from 0.025 to 0.051 mm (0.001 to 0.002 in.) may be affected byinterfacial t
19、ension. If this effect is suspected, films not less than 0.127 mm(0.005 in.) in thickness shall 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. Preparation of Density-Gradient Columns7.1
20、 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 specimens. Prepare a solution (400 to600 mL)
21、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 discard those that sink very fast, or save th
22、em 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 otherappropriate abrasive. Progress shall be fo
23、llowed 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. Fill the cylinder about two thirdsfull with a solution
24、of two suitable liquids selected from Table1, the density of which can be varied over the desired range bythe addition of either liquid to the mixture. After the cylinderand solution have attained temperature equilibrium, place thefloat in the solution, and if it sinks, add the denser liquid bysuita
25、ble means with good stirring until the float reversesdirection of movement. If the float rises, add the less denseliquid by suitable means with good stirring until the floatreverses direction of movement.7.2.2 When reversal of movement has been observed, re-duce the amount of the liquid additions to
26、 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 must be coveredwhenever it is being observed for
27、 balance, and the liquidsurface must be below the surface of the liquid in theconstant-temperature bath. After vigorous stirring, the liquidwill continue to move for a considerable length of time; makesure that the observed movement of the float is not due to liquidmotion by waiting at least 15 min
28、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. Determine the density of the solution bynormal
29、 methods and make “in vacuo” corrections for allweighings. Record this as the density of the float. Repeat theprocedure for each float.7.3 Gradient Tube Preparation (see Annex A1 for details):7.3.1 Method AStepwise addition.7.3.2 Method BContinuous filling (liquid entering gradi-ent tube becomes pro
30、gressively 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 conditioningis greater than the accuracy required of the density determina-tion shall be conditioned before testing i
31、n accordance with themethod listed in the applicable ASTM material specification.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 tube and specimens to reach equilibrium,which will require 10 min
32、 or more. Thin films of 1 to 2 mils inthickness require approximately 112 h to settle, and recheckingafter several hours is advisable (Note 4).5Manufactured certified glass floats may be purchased.TABLE 1 Liquid Systems for Density-Gradient TubesSystemDensity Range,g/cm3Methanol-benzyl alcohol 0.80
33、to 0.92Isopropanol-water 0.79 to 1.00Isopropanol-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 dib
34、romide-ethylene bromide 1.99 to 2.18Ethylene bromide-bromoform 2.18 to 2.89D1505 1029.2 Read the height of each float and each specimen by aline through the individual center of volume and averaging thethree values. When a cathetometer is used, measure the heightof the floats and specimens from an a
35、rbitrary level using a linethrough their center of volume. If equilibrium is not obtained,the specimen may be imbibing the liquid.9.3 Remove old samples without destroying the gradient byslowly withdrawing a wire screen basket attached to a longwire (Note 6), which is conveniently done by means of a
36、 clockmotor. Withdraw the basket from the bottom of the tube and,after cleaning, return it to the bottom of the tube. It is essentialthat this procedure be performed at a slow enough rate(approximately 30 min/300-mm length of column) so that thedensity gradient is not disturbed.NOTE 6Whenever it is
37、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 samples may be determinedgraphically or by calculation from the levels to which thesamples settle by either of the following methods:10.1.1 Grap
38、hical CalculationPlot float position versusfloat density on a chart large enough to be read accurately to61 mm and the desired precision of density. A minimumcorrelation factor of 0.995 shall be obtained to show thecolumn is acceptable. Plot the positions of the unknownspecimens on the chart and rea
39、d their corresponding 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 standards, a and b, respec-tively, bracketing the unknown measur
40、ed 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 speci-mens,11.1.2 Number of specimens tested if different th
41、an 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 Tested inSeveral LaboratoriesAn interlaboratory test was ru
42、n 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 E691, and the results are given inTable 2.12.2 Specimens Molded and Tested in Several L
43、aboratories:12.2.1 Samples Prepared Using Practice D4703 in EachLaboratoryTable 3 is based on a round robin6conducted in1994 in accordance with Practice E691, involving sevenmaterials tested by 7 to 11 laboratories. For each material, allof the samples were prepared by each laboratory, molded inacco
44、rdance with Procedure C of Annex A1 of Practice D4703,and tested using this test method. The data are for comparisonwith the data of the same samples tested by Practice D2839.Each test result is an individual determination. Each laboratoryobtained six test results for each material.12.2.2 Samples Pr
45、epared Using Practice D2839 in EachLaboratoryTable 4 is based on a round robin6conducted in1994 in accordance with Practice E691, involving sevenmaterials tested by 10 to 15 laboratories. For each material, allof the samples were prepared by each laboratory in accordancewith Practice D2839. Each tes
46、t result is an individual determi-nation. 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 considering the approximate precision ofthis test method. The data i
47、n Tables 2-4 shall not be rigorouslyapplied to acceptance or rejection of material, as those data arespecific to the round robin and cannot be representative ofother lots, conditions, materials, or laboratories. Users of thistest method shall apply the principles outlined in Practice E691to generate
48、 data specific to their laboratory and materials, orbetween specific laboratories. The principles of 12.3-12.3.3will then be valid for each data.If Srand SRhave been calculated from a large enough bodyof data, and for test results that were averages from testing onespecimen:12.3.1 Repeatability Limi
49、t, 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 is obtained by pooling the within-laboratory standard deviations of
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