1、Designation: D 6980 09Standard Test Method forDetermination of Moisture in Plastics by Loss in Weight1This standard is issued under the fixed designation D 6980; 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. Scope1.1 This test method covers the quantitative determinationof moisture by means of loss in weight technology down to 50ppm 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 in this method can reach or exceed250C, use caution when handling them after testing has beencompleted.1.4 This standard does not purport to address all of thesafety concerns, if any, assoc
4、iated 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.NOTE 1There is no similar or equivalent ISO standard.2. Referenced Documents2.1 ASTM Standards:2D 883
5、 Terminology Relating to PlasticsD 1600 Terminology for Abbreviated Terms Relating toPlasticsD 6869 Test Method for Coulometric and Volumetric De-termination of Moisture in Plastics Using the Karl FischerReaction (the Reaction of Iodine with Water)E 177 Practice for Use of the Terms Precision and Bi
6、as inASTM Test Methods3. Terminology3.1 DefinitionsThe definitions used in this test method arein accordance with Terminologies D 883 and D 1600.3.1.1 liftthe result of convection currents created duringthe heating of the specimen raising the sample pan off of itssupport falsely indicating a moistur
7、e loss.3.1.1.1 DiscussionThe effects of lift are compensated forin different ways by different manufacturers.3.1.2 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 that issupported on
8、 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 weight isintegrated and
9、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 Use5.1 This test me
10、thod is intended for use as a control,acceptance, and assessment test.5.2 Moisture can seriously affect the processability of plas-tics. It is possible that high moisture content will cause surfaceimperfections (that is, splay or bubbling) or degradation byhydrolysis. Low moisture (with high tempera
11、ture) has beenknown to cause solid phase polymerization.5.3 The physical properties 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 thanwater to be ev
12、olved and cause a biased high result if thematerial has not been dried to remove 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
13、emission of volatiles which can be harmful.1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.70 on Analytical Methods.Current edition approved Feb. 1, 2009. Published March 2009. Originallyapproved in 2004. Last previous
14、 edition approved in 2004 as D 6980 - 04.2For 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.1Copyright ASTM Inte
15、rnational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Apparatus7.1 Moisture Analyzer,3containing: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 i
16、n Tables A1.1 andA2.1.NOTE 2It will be necessary to contact 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 c
17、urrents created during testing.7.1.4 A processor that is capable 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
18、 Due to the small specimen size, exercise care to ensurethat 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
19、 moisture priorto processing and testing shall be allowed to 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 h
20、eater shall both be calibrated using NIST-traceableweights and an NIST-traceable temperature calibration inter-face.9.2 The calibration is validated by way of using sodiumtartrate dihydrate4exhibiting a theoretical crystal water contentof 15.66 % with an acceptable result range of 15.61 to 15.71 %.O
21、ther materials with known theoretical water content areacceptable for 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,
22、firstperform a temperature calibration and then a balance calibra-tion to ensure analyzer performance. Retest with sodiumtartrate dihydrate. If results still are not within the acceptablerange, contact analyzer manufacturer.10. Procedure10.1 Sample Analysis:10.1.1 Place the analyzer on a flat, level
23、 surface.10.1.2 Turn the analyzer on and allow equilibration at theprogrammed idle temperature for 15 min.10.1.3 Program the analyzer with the suggested test condi-tions listed in Annex A1 or Annex A2.NOTE 3If test conditions for a specific material are not listed inAnnexA1 or Annex A2, they will ha
24、ve to be determined experimentally or bycontacting the analyzer manufacturer.10.1.4 Begin the program and follow the prompts forplacing the sample on the sample pan.10.1.5 At the end of the test allow the analyzer to cool andremove the sample pan.10.1.6 Record the result as displayed in percent mois
25、ture.10.1.7 Place a clean sample pan in the analyzer and allowequilibration 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 inaccordanc
26、e with Test Method D 6869 or contact the analyzer manufacturerwho in 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 incl
27、udes several consecutiveprograms that have been linked together. Each 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 p
28、rogram selected to run first is the lowesttemperature.10.2.3 After 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
29、 and constant. Choose a temperature in this range as theoptimum test 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 t
30、est temperature to be3The model Computrac MAX 2000XL Moisture Analyzer, available fromArizona Instrument, LLC, 1912 West 4th Street, Tempe, Arizona, 85281, and theMark 2HP Moisture Analyzer, available from Omnimark Instrument Corporation,1320 South Priest Drive, Tempe, Arizona, 85281 have been found
31、 satisfactory forthis purpose, or equivalent.4Sodium tartrate dihydrate may be sourced from the analyzer manufacturer orfrom GFS Chemicals, P.O. Box 245, Powell, Ohio, 43065.FIG. 1 Optimum Test Temperature SelectionD6980092above the melting point of the selected plastic due to the distance betweenth
32、e 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 parts per million (PPM) is desired,calculate as follows:PPM 5 Moisture content %! 3 10000 (1)12. Report12.1 R
33、eport the following information:12.1.1 Complete identification of the sample tested, includ-ing type of material, 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.13. Precision an
34、d Bias513.1 The precision of this test method is based on aninterlaboratory study 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 fo
35、r eachanalysis in order to estimate the repeatability and reproducibil-ity limits of the standard. Practice E 691 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
36、 the r value for that material; r is the intervalrepresenting the critical difference 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
37、 Limit (R)Two test results shall bejudged not equivalent if they differ by more 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.1
38、3.1.2.1 Reproducibility limits are listed in Table 1.13.1.3 The above terms (repeatability limit and reproduc-ibility limit) are used as specified in Practice E 177.13.1.4 Any judgment in accordance with statements 13.1.1and 13.1.2 would have an approximate 95 % probability ofbeing correct.13.2 Bias
39、At 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 being made.13.3 The precision statement was determined through sta-tistical examination of 162 data points, fr
40、om 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: Polycarbonate (not dried)Material E: Nylon 6/6 (dried)Material F: TPE (not dried)Material G: PC (dried)Material H:
41、 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 determination; plastics; volatile content5Supporting data have been filed at ASTM International Headquarters and maybe o
42、btained by requesting Research Report RR: D201250.TABLE 1 Moisture (%)MaterialAverageAStandardDeviation ofLab AveragesRepeatabilityStandardDeviationReproducibilityStandardDeviationRepeatabilityLimitReproducibilityLimitxS xsrsRrRA 0.4954 0.0131 0.0086 0.0151 0.0242 0.0423B 0.0292 0.0084 0.0047 0.0094
43、 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 0.0181 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 laborato
44、ries calculated averages.D6980093ANNEXES(Mandatory Information)A1. COMPUTRAC MAX 2000XL MOISTURE ANALYZERA1.1 The test conditions for sodium tartrate dihydrate arepre-programmed into the MAX 2000XL as a method labeledTARTRATE.A1.2 Suggested test conditions for selected plastics aregiven in Table A1.
45、1.A1.3 Use the following guidelines for determining testconditions for a material not listed in Table A1.1.A1.3.1 For materials with an expected moisture contentbelow 0.10 % program the instrument as follows and thenperform procedure in 10.2 to determine the optimal testtemperature:Temperatures Test
46、Set to 30C below melt pointHi Start25CIdle100CEnding Criteria End on Rate0.005 %/minSample Size 30 6 2 g sample windowTare Options Pan TareUltra Low MoistureSample Tare8 sLift Compensation 100 %A1.3.2 For materials with an expected moisture contentabove 0.10 % program the instrument as follows and t
47、henperform procedure in 10.2 to determine the optimal testtemperature:Temperatures TestSet to 30C below melt pointHi Start25CIdle100CEnding Criteria End on Rate0.010 %/minSample Size 20 6 2 g sample windowTare Options Pan TareUltra Low MoistureSample Tare8 sLift Compensation 100 %A2. MARK 2HP MOISTU
48、RE ANALYZERA2.1 Test conditions for sodium tartrate dihydrate:Temperatures Temp 1150CTemp 2OffStdby100CTimes Time 1OffTime 2OffIdeal Weight 10 gStart Delay 0Win Window2.0min% IW0.020 %A2.2 Suggested test conditions for selected plastics aregiven in Table A2.1.TABLE A1.1 Suggested Test Conditions for
49、 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-Low 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-Low 8 100PET 160 100 0.005 28 to 32 Ultra-
