1、Designation: D6980 12Standard Test Method forDetermination of Moisture in Plastics by Loss in Weight1This standard is issued under the fixed designation D6980; 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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the quantitative determinationof moisture by means of loss in weight technology down to 50mg/kg as it app
3、lies to most plastics.1.2 The values stated in SI units are to be regarded as thestandard.1.3 Specimens tested by this method will be hot, use cautionwhen handling them after testing has been completed.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with i
4、ts 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 this standard.2. Referenced Documents2.1 ASTM Standards:2D883 Terminolo
5、gy Relating to PlasticsD1600 Terminology for Abbreviated Terms Relating toPlasticsD6869 Test Method for Coulometric and Volumetric Deter-mination of Moisture in Plastics Using the Karl FischerReaction (the Reaction of Iodine with Water)E691 Practice for Conducting an Interlaboratory Study toDetermin
6、e the Precision of a Test Method3. Terminology3.1 DefinitionsThe definitions used in this test method arein accordance with Terminologies D883 and D1600.3.2 Symbols:3.2.1 liftthe result of convection currents created duringthe heating of the specimen raising the sample pan off of itssupport falsely
7、indicating a moisture loss.3.2.1.1 DiscussionThe effects of lift are compensated forin different ways by different manufacturers.3.2.2 temperinga process that re-defines the molecularstructure of a metal to enhance its performance.4. Summary of Test Method4.1 The specimen is spread onto a sample pan
8、 that issupported on a balance in a heating chamber that has beenpreheated and equilibrated to the specified idle temperature. Itis then heated to vaporize the moisture. The analysis iscompleted when the indicated weight loss falls below a ratespecified in the test conditions. The total loss of weig
9、ht isintegrated and displayed as the percent of moisture. Both theanalyzers balance and heater are calibrated to NIST standardsto achieve precise and accurate results.4.2 Through adjustment of the analyzers parameter set-tings, a set of conditions is developed to measure moisture.5. Significance and
10、 Use5.1 This test method is intended for use as a control,acceptance, and assessment test.5.2 Moisture will affect the processability of some materi-als. For these materials, defects will occur if they are processedwith a moisture content outside of the recommended range.5.3 The physical properties
11、of some plastics are greatlyaffected by the moisture content.6. Interferences6.1 When testing plastic materials for moisture by a loss inweight technique, the possibility exists for volatiles other thanmoisture to be evolved and cause a biased high result if thematerial has not been dried to remove
12、excess moisture and lowboiling volatiles. It is important to have a working knowledgeof the material that is being tested and to remain below anymelting or decomposition temperatures that would unnecessar-ily cause the emission of volatiles which can be harmful.7. Apparatus7.1 Moisture Analyzer, con
13、taining:7.1.1 The capability of the oven shall be selected basedupon the specific material being tested. Suggested test tem-peratures for specific plastics are shown in Tables A1.1 andA2.1.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility o
14、f Subcommittee D20.70 on Analytical Methods.Current edition approved Feb. 1, 2012. Published March 2012. Originallyapproved in 2004. Last previous edition approved in 2009 as D6980 - 09. DOI:10.1520/D6980-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custome
15、r Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.NOTE 2It will be necessary to contact
16、the analyzer manufacturer forsuggested test temperatures for materials not listed in Tables A1.1 andA2.1.7.1.2 A balance capable of measuring to 0.0001 g.7.1.3 An electronic or mechanical means of compensatingfor lift caused by convection currents created during testing.7.1.4 A processor that is cap
17、able of converting the loss ofweight to digital data.7.1.5 Digital display for presenting the digital data aspercent moisture.7.1.6 Sample Pans, made from “0” temper, Aluminum 3003or other nonreactive material.8. Test Specimen and Sample8.1 Due to the small specimen size, exercise care to ensurethat
18、 the specimen is representative of the sample.8.2 Due to the hygroscopic nature of many plastics, samplesshall be stored in airtight containers made of glass or otherqualified or suitable material.8.3 Samples that have been heated to remove moisture priorto processing and testing shall be allowed to
19、 cool to roomtemperature in a sealed container prior to determination.8.4 Test specimens in the form of powders, pellets, orground material.9. Calibration and Standardization9.1 To maintain the integrity of the test results the balanceand heater shall both be calibrated using NIST-traceableweights a
20、nd an NIST-traceable temperature calibration inter-face.9.2 The calibration is verified using sodium tartrate dihy-drate3exhibiting a known crystal water content of 15.66 %with an acceptable result range of 15.61 to 15.71 %. Othermaterials with verifiable theoretical water content are accept-able fo
21、r validation.9.3 Prepare the analyzer for use and perform the analysis asdescribed in 10.1.9.4 If the result is not within the acceptable range, return to9.3 for re-analysis.9.5 If results are still not within the acceptable range, firstperform a temperature calibration and then a balance calibra-ti
22、on to ensure analyzer performance. Retest with sodiumtartrate dihydrate. If results still are not within the acceptablerange, the cause of the nonconformance must be determinedand corrected before proceeding with testing.10. Procedure10.1 Sample Analysis:10.1.1 Prepare analyzer as suggested by instr
23、ument manu-facturer.10.1.2 Program the analyzer with the suggested test condi-tions listed in Annex A1, Annex A2,orAnnex A3.NOTE 3If test conditions for a specific material are not listed inAnnexA1, Annex A2,orAnnex A3, they will have to be determined experimen-tally or by contacting the analyzer ma
24、nufacturer.10.1.3 Begin the program and follow the prompts forplacing the sample on the sample pan.10.1.4 At the end of the test allow the analyzer to cool andremove the sample pan.10.1.5 Record the result as displayed in percent moisture.10.1.6 Place a clean sample pan in the analyzer and allowequi
25、libration prior to beginning subsequent tests.10.2 Determination of Optimal Test Conditions:NOTE 4When determining the optimal test conditions for a material,it is useful to have a Karl Fischer apparatus available and test inaccordance with Test Method D6869 or contact the analyzer manufacturerwho i
26、n some cases will provide this service for you.10.2.1 Program the analyzer in accordance with the condi-tions listed in Annex A1 or Annex A2.10.2.2 To determine the optimum test temperature for amaterial, run a single test which includes several consecutiveprograms that have been linked together. Ea
27、ch program isidentical in its parameters except the temperature is increased5.NOTE 5When increasing the test temperature, do not exceed atemperature where the potential exists for the emission of harmful fumes.NOTE 6Ensure that the program selected to run first is the lowesttemperature.10.2.3 After
28、the tests have completed, plot the result versustemperature to make a curve as in Fig. 1.10.2.3.1 Most of the moisture is vaporized in temperaturerange from points 1 to 3.10.2.3.2 Between points 3 and 5 the moisture result is verylow and constant. Choose a temperature in this range as theoptimum tes
29、t temperature.10.2.3.3 Above point 5 the moisture result begins to in-crease. This is likely caused by the generation of water due todecomposition or solid phase polymerization of the sample.NOTE 7It is not uncommon for the optimal test temperature to beabove the melting point of the selected plasti
30、c due to the distance betweenthe resistive thermal device and the sample pan.11. Calculation11.1 Result is reported in percent moisture to three decimalplaces so no further calculations are necessary.11.2 If conversion to mg/kg is desired, calculate as follows:mg/kg 5 Moisture content %! 3 10000 (1)
31、12. Report12.1 Report the following information:3Sodium tartrate dihydrate may be sourced from the analyzer manufacturer orfrom GFS Chemicals, P.O. Box 245, Powell, Ohio, 43065.FIG. 1 Optimum Test Temperature SelectionD6980 12212.1.1 Complete identification of the sample tested, includ-ing type of m
32、aterial, source, manufacturers code, form, andprevious history,12.1.2 Date of test,12.1.3 Individual specimen size,12.1.4 Individual specimen moisture, and12.1.5 Average moisture if multiple tests are run.13. Precision and Bias413.1 The precision of this test method is based on aninterlaboratory stu
33、dy conducted in 2007. Eight laboratoriesanalyzed eight different plastic materials for moisture content.Every “test result” represents an individual determination. Thelaboratories reported two to four replicate results for eachanalysis in order to estimate the repeatability and reproducibil-ity limi
34、ts of the standard. Practice E691 was followed for thedesign and analysis of the data.13.1.1 Repeatability Limit (r)Two test results obtainedwithin one laboratory shall be judged not equivalent if theydiffer by more than the r value for that material; r is the intervalrepresenting the critical diffe
35、rence between two test results forthe same material, obtained by the same operator using thesame equipment on the same day in the same laboratory.13.1.1.1 Repeatability limits are listed in Table 1.13.1.2 Reproducibility Limit (R)Two test results shall bejudged not equivalent if they differ by more
36、than the R valuefor that material; R is the interval representing the criticaldifference between two test results for the same material,obtained by different operators using different equipment indifferent laboratories.13.1.2.1 Reproducibility limits are listed in Table 1.13.1.3 Any judgment in acco
37、rdance with statements 13.1.1and 13.1.2 would have an approximate 95 % probability ofbeing correct.13.2 BiasAt the time of the study, the test specimenschosen for analysis were not accepted reference materialssuitable for determining the bias for this test method, thereforeno statement on bias is be
38、ing made.13.3 The precision statement was determined through sta-tistical examination of 162 data points, from eight laboratories,on eight materials. These eight materials were described as thefollowing:Material A: Nylon 6/6 (not dried)Material B: PET (dried)Material C: TPE (dried)Material D: Polyca
39、rbonate (not dried)Material E: Nylon 6/6 (dried)Material F: TPE (not dried)Material G: PC (dried)Material H: PET (not-dried)13.4 To judge the equivalency of two test results, it isrecommended to choose the material closest in characteristicsto the test material.14. Keywords14.1 moisture determinatio
40、n; plastics; volatile content4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D20-1250.TABLE 1 Moisture (%)MaterialAverageAStandardDeviation ofLab AveragesRepeatabilityStandardDeviationReproducibilityStandardDeviationRepeatabilit
41、yLimitReproducibilityLimitxS xsrsRrRA 0.4954 0.0131 0.0086 0.0151 0.0242 0.0423B 0.0292 0.0084 0.0047 0.0094 0.0133 0.0263C 0.0107 0.0070 0.0026 0.0073 0.0072 0.0204D 0.0748 0.0040 0.0061 0.0067 0.0171 0.0187E 0.1390 0.0302 0.0241 0.0367 0.0674 0.1027F 0.0406 0.0329 0.0024 0.0330 0.0068 0.0924G 0.01
42、81 0.0085 0.0030 0.0088 0.0083 0.0247H 0.1053 0.0109 0.0049 0.0117 0.0138 0.0327AThe average of the laboratories calculated averages.D6980 123ANNEXES(Mandatory Information)A1. MOISTURE ANALYZER WITH ELECTRONIC LIFT COMPENSATIONA1.1 Suggested test conditions for sodium tartrate dihy-drate and selecte
43、d plastics are given in Table A1.1.A1.2 Use the following guidelines for determining testconditions for a material not listed in Table A1.1, and thenperform procedure in 10.2 to determine the optimal testtemperature:Materials with anexpected moisturecontent below 0.10 %Materials with anexpected mois
44、turecontent below 0.10 %Temperatures TestSet to 30Cbelow melt pointTestSet to 30Cbelow melt pointHi Start25C Hi Start25CIdle100C Idle100CEndingCriteriaEnd on Rate0.005 %/minEnd on Rate0.010 %/minSampleSize30 6 2gsample window20 6 2gsample windowTareOptionsPan TareUltraLow MoisturePan TareUltraLow Mo
45、istureSample Tare8 s Sample Tare8 sLiftCompensation100 % 100 %TABLE A1.1 Suggested Test Conditions for Selected PlasticsMaterialTest Temp.(C)Idle Temp. RateSample Size(grams)Pan TareSample Tare(seconds)LiftCompensationABS 140 100 0.010 18 to 22 Ultra-Low 8 100ABS + PC 155 100 0.005 28 to 32 Ultra-Lo
46、w 8 100POM 160 100 0.005 18 to 22 Ultra-Low 8 100Acrylic 150 100 0.007 28 to 32 Ultra-Low 8 100PA 6 175 100 0.015 18 to 22 Ultra-Low 8 100PA 6/6 210 100 0.015 18 to 22 Ultra-Low 8 100PBT 175 100 0.005 28 to 32 Ultra-Low 8 100PC 170 100 0.005 28 to 32 Ultra-Low 8 100PEI 170 100 0.005 28 to 32 Ultra-L
47、ow 8 100PET 160 100 0.005 28 to 32 Ultra-Low 8 100PPS 170 100 0.005 28 to 32 Ultra-Low 8 100PS 165 100 0.005 28 to 32 Ultra-Low 8 100PVC 105 100 0.010 18 to 22 Ultra-Low 8 100TPE 140 100 0.005 28 to 32 Ultra-Low 8 100TPU 155 100 0.010 18 to 22 Ultra-Low 8 100NOTE 1If you notice degradation of materi
48、al including more than moderate discoloration, melting, or smoke, lower the test temperature by 10C pertest until no discoloration appears and the pellets retain their shape.NOTE 2Lift compensation accounts for the difference in heat absorption properties between resins. In essence, it adjusts for t
49、he stronger air currentspresent in the test chamber when testing opaque resins.NOTE 3These suggested conditions were determined through extensive tests that have been completed on these common plastics. It is not intendedto be inclusive of every grade of every plastic and it will potentially be necessary to optimize the conditions for special materials.D6980 124A2. ENHANCED SENSITIVITY MOISTURE ANALYZERA2.1 Suggested test conditions for sodium tartrate dihy-drate and selected plastics are given in Table A2.1.A2.2 Use the following guide
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