1、Designation: D4883 08Standard Test Method forDensity of Polyethylene by the Ultrasound Technique1This standard is issued under the fixed designation D4883; 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.1. Scope*1.1 This test method covers the determination of the densityof polyethylene through the utilization of ultrasound equip-ment.1.2 This te
3、st method is based on the distinct behaviors of theamorphous and crystalline phases of polyethylene in responseto ultrasound. Polyethylene shall be viewed as a compositestructure where high-density crystalline regions are connectedby lower-density amorphous material. The ratio of crystallineto amorp
4、hous material determines the final density of thematerial. The amorphous and crystalline phases exhibit verydistinct behaviors with regard to the propagation of soundwaves. The propagation characteristics in the composite willdepend on the relative amount of the two phases (the degree ofcrystallinit
5、y).1.3 Inorganic materials increase density as measured by TestMethods D792 and D1505, but they have little or no effect onultrasonic density. The ultrasonic measurement is basically abase resin density.1.4 The values stated in SI units are to be regarded as thestandard. The values given in parenthe
6、ses are for informationonly.1.5 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
7、prior to use.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD792 Test Methods for Density and Specific Gravity (Rela-tive Density) of Plastics by DisplacementD883 Terminology Relating to PlasticsD1
8、248 Specification for Polyethylene Plastics ExtrusionMaterials for Wire and CableD1505 Test Method for Density of Plastics by the Density-Gradient TechniqueD3350 Specification for Polyethylene Plastics Pipe and Fit-tings MaterialsD4703 Practice for Compression Molding ThermoplasticMaterials into Tes
9、t Specimens, Plaques, or SheetsD4976 Specification for Polyethylene Plastics Molding andExtrusion MaterialsE494 Practice for Measuring Ultrasonic Velocity in Materi-alsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 DefinitionsThe def
10、initions given in TerminologyD883, as well as in Test Methods D792 and D1505, areapplicable to this test method.4. Significance and Use4.1 The density of polyethylene is a conveniently measur-able property which is frequently useful as a means offollowing physical changes in a sample, as an indicati
11、on ofuniformity among samples, and as a means of identification.4.2 This test method is designed to yield results with aprecision of 60.08 % or better.5. Apparatus5.1 Use an instrument which utilizes a sonic technique toevaluate the density of polyethylene. The DS 500 instrument3utilizes a sonic sen
12、sing head (transducer) which measures thevelocity of sound in a molded specimen. Because sonicvelocity is positively correlated to density in polyethylene, ameasurement of this velocity is used to determine specimen1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is t
13、he direct responsibility of Subcommittee D20.70 on Analytical Methods.Current edition approved Nov. 1, 2008. Published November 2008. Originallyapproved in 1989. Last previous edition approved in 2003 as D4883 03. DOI:10.1520/D4883-08.2For referenced ASTM standards, visit the ASTM website, www.astm.
14、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.3The sole source of supply of the DS 500 instrument known to the committee atthis time is Deguise Technologies, Inc., 11755 Ru
15、e de Guise, Quebec City (PQ),Canada, G2A 3K6; Phone: (418) 845-9064; (email:jraymondb2b2c.ca). If you areaware of alternative suppliers, please provide this information to ASTM Interna-tional Headquarters. Your comments will receive careful consideration at a meetingof the responsible technical comm
16、ittee,1which you may attend.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesNOTICE: This standard has either been superseded and replaced by a new version or withdrawn.Co
17、ntact ASTM International (www.astm.org) for the latest information1density. The information from this transducer then must beelectronically evaluated; in the DS 500 instance this is donewith a computer, and the result is reported either through adisplay or printout.5.2 Equipment specified in Test Me
18、thod D1505.5.3 Equipment specified in Test Methods D792.5.4 Equipment specified in Practice D618.5.5 Equipment specified in Practice D4703, Annex 1.NOTE 2The equipment specified in 5.2 or 5.3 is required for the initialcalibration of the sonic equipment. Once the equipment is calibrated, thisadditio
19、nal equipment is no longer required. It is recommended that thestandards used for the initial calibration be retained for any additionalcalibration when needed. It is also recommended that one or more of thecalibration standards be evaluated on a routine basis for calibrationverification. The absolu
20、te accuracy of data produced will not be better thanthis initial calibration and continued verification. Samples for initialcalibration are available from various sources (such as the NationalInstitute of Standards and Technology (NIST), resin manufacturers, and soforth).6. Test Specimens and Materi
21、als6.1 Test plaques shall be prepared in accordance to themolding procedure specified in Practice D4703, Annex 1,Procedure C.6.2 The test specimen shall consist of a piece of the materialunder test. Mold or cut the sample specimen to the specifieddimensions. When a sample piece is cut from a molded
22、plaque,care must be taken to avoid change in density resulting fromcompressive stress.Specimen Dimensions, mm (in.)LengthWidthThickness8010035451.53(3.153.94)(1.381.77)(0.060.12)NOTE 3Aminimum thickness of 1.5 mm is required to provide properspecimen stiffness and for the instrument to distinguish s
23、ignal from echo.A maximum thickness of 3.0 mm is the thickness which the instrumentsample holder allows.NOTE 4A sample thickness of 1.9 6 0.2 mm shall be used in order tobe in compliance with Specifications D1248, D3350 and D4976 forPolyethylene Plastics.6.3 Use the same plaque thickness for calibra
24、tion samplesand testing samples.6.4 The specimen shall be free of foreign matter and voidsand shall have no surface marks or other surface flaws.6.5 Use demineralized water for the testing equipmentswater bath.7. Conditioning7.1 ConditioningCondition the test specimens at23 6 2C (73.4 6 3.6F) for no
25、t less than 40 h prior to test inaccordance with Procedure A of Practice D618, for those testswhere conditioning is required. In cases of disagreement,specimens shall be conditioned at 23 6 1C and 50 6 5%relative humidity.7.2 Test ConditionsConduct tests in instruments waterbath at a temperature of
26、23 6 2C (73.4 6 3.6F) unlessotherwise specified. In cases of disagreement, the tolerancesshall be 61C (1.8F).NOTE 5Testing in normal plant operations frequently calls for testingbefore the sample has become fully conditioned. It will be necessary toestablish a correlation between the conditioning ti
27、me and measureddensity and to apply the correlation to obtain the predicted density. If thespecimens have not reached a level of stability that assures the densityaccuracy, the density determination shall be tested under test conditions inaccordance with the test method listed in the applicable ASTM
28、 specifi-cation.8. Calibration8.1 Refer to instruments operating manual for details onoperating the instrument.NOTE 6The cleanliness of the demineralized water used in the waterbath shall be monitored and the water be replaced on a regular basis toavoid erroneous testing results.8.2 Resins to be uti
29、lized for calibration shall be molded intoplaques in accordance with Practice D4703 Annex 1, Proce-dure C and be conditioned in accordance with Practice D618.Specimens to be used for calibration shall undergo full condi-tioning.NOTE 7One method of ensuring full conditioning is by aging at 70Cfor 24
30、h.8.3 Determine the density value of the specimen in accor-dance with Test Methods D792 or D1505. Conduct thedeterminations as specified by the test methods, that is, twodeterminations for D792 or three determinations for D1505.Calculate a mean density value for the sample plaque.8.4 Evaluate each p
31、laque on ultrasound instrument and usethe mean density obtained in 8.3 for calibration. Use either thesame sample plaque used in Section 8.3 or different plaques.This is considered as one data point. Six data points arerecommended per resin sample. Ensure that the moldedsamples acquired for Test Met
32、hods D792 or D1505 accuratelyrepresent the molded samples utilized for the ultrasonic cali-bration.8.5 The absolute accuracy of the data acquired is directlycorrelated to the accuracy of the calibration curve. This curveshall be made up of as many data points as possible and coverthe entire density
33、range of interest. A minimum of 30 datapoints per calibration curve is required. More data points arerecommended if a broad density range is to be measured. Thesedata points shall be evenly spread throughout the density range.NOTE 8Numerous product attributes such as product family, reactorgeometry,
34、 catalyst, comonomer, additives and fillers, have been known toinfluence instrument calibration. Use different calibration curves fordifferent products when needed. Verify the calibration curve when anychange of this nature is made to the product.NOTE 9Because this test method is based on electronic
35、 techniques ascompared to physical methods, it is imperative that the electronics becalibrated correctly. The electronics shall be re-calibrated when thetransducer or the board is replaced.9. Sample Testing9.1 Place the test specimen in the instruments water bathand allow it to condition for approxi
36、mately 10 minutes prior tomeasurement to allow the specimen to become properly wettedand at the proper temperature.9.2 For the most accurate results, test each sample fourtimes (from different locations on the specimen) and determinethe average. If the density of one determination is equal orgreater
37、 than 60.0004 g/cm3from the average, discard thisD4883 082determination. If two determinations are equal or greater than6 0.0004 g/cm3from the average, make a new plaque. If datahas demonstrated that the resin samples have good uniformity,one determination per sample will be sufficient.NOTE 10In the
38、 case that deviation from the average is caused byinadequate conditioning of the sample in the bath, place the sample backto the bath for an additional five minutes then re-measure the density.10. Report10.1 Report the following information:10.1.1 Complete identification of the material or productte
39、sted, including method of specimen preparation and condi-tioning.10.1.2 Average specific gravity for all specimens from asampling unit, reported as sp gr 23/23C = _, or averagedensity reported as D23C = _ g/cm3.10.1.3 A measure of the degree of variation of specificgravity or density within the samp
40、ling unit such as the standarddeviation and number of determinations.10.1.4 Date of test.11. Precision and Bias411.1 PrecisionTable 1 is based on a round robin con-ducted in 1987 in accordance with Practice E691, involvingfour materials tested by six laboratories. Each material wasmolded, with all s
41、pecimens being prepared in one laboratory.Each material tested was represented by four specimens, andeach specimen was evaluated six times. This procedure yielded24 test results for each material under evaluation from eachlaboratory.11.2 Concept of r and RWarningThe following explanations of r and R
42、 (11.2through 11.2.3) are only intended to present a meaningful wayof considering the approximate precision of this test method.The data in Table 1 shall not be rigorously applied toacceptance or rejection of material, as those data are specific tothe round robin and are not to be considered represe
43、ntative ofother lots, conditions, materials, or laboratories. Users of thistest method shall apply the principles outlined in Practice E691to generate data specific to their laboratory and materials, orbetween specific laboratories. The principles of 11.2 through11.2.3 shall then be valid for such d
44、ata.If Srand SRhave been calculated from a large enough bodyof data, and for test results that were averages from testing onespecimen:11.2.1 Repeatability Limit, r(Comparing two test resultsfor the same material, obtained by the same operator using thesame equipment on the same day)The two test resu
45、lts shallbe judged not equivalent if they differ by more than the r valuefor that material.11.2.2 Reproducibility Limit, R(Comparing two test re-sults for the same material, obtained by different operatorsusing different equipment in different laboratories)The twotest results shall be judged not equ
46、ivalent if they differ by morethan the R value for that material.11.2.3 Any judgment in accordance with 11.2.1 or 11.2.2has an approximate 95 % (0.95) probability of being correct.11.3 BiasThere are no recognized standards by which toestimate the bias of this test method.12. Keywords12.1 amorphous;
47、crystalline; density; molded; plaques;polyethylene; sonic; ultrasonic; ultrasoundSUMMARY OF CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue (D4883 - 03)that may impact the use of this standard. (November 1, 2008)(1) Removed permissive langua
48、ge in 1.2 and in Section 11.(2) Revised wording of ISO statement in Note 1 for consis-tency with the latest standards.(3) Updated the contact information for the sole supplierknown for the instrument in Footnote 3.(4) Added informational verbiage in 9.1 and 9.2 for clarifica-tion.4Supporting data ar
49、e available from ASTM Headquarters. Request RR:D20-1157.TABLE 1 Precision DataMaterial Average SrASRBrCRD1 0.9216 0.00029 0.00128 0.00082 0.003622 0.9187 0.00047 0.00107 0.00133 0.003023 0.9341 0.00073 0.00148 0.00207 0.004194 0.9516 0.00039 0.00127 0.00110 0.00359ASr= within-laboratory standard deviation for the indicated material. It is obtainedby pooling the within-laboratory standard deviations of the test results from all ofthe participating laboratories.BSR= between-laboratories reproducibility, expressed as standard devi
