1、Designation: D 6980 04Standard 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 (e) 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 ap
3、plies 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, asso
4、ciated 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 88
5、3 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)3. Terminology3.1 DefinitionsThe definitions used i
6、n 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 moisture loss.3.1.1.1 DiscussionThe effects of lift are compensated forin differ
7、ent 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 a balance in a heating chamber that has beenpreheated and equilibrated t
8、o 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 displayed as the percent of moisture. Both theanalyzers balance and heate
9、r 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 method is intended for use as a control,acceptance, and assessment test.5.2
10、 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 temperature) has beenknown to cause solid phase polymerization.5.3 The physical
11、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 evolved and cause a biased high result if thematerial has not been dried to
12、 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 emission of volatiles which can be harmful.1This test method is under the
13、 jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.70 on Analytical Methods.Current edition approved July 1, 2004. Published August 2004.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceas
14、tm.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.7. Apparatus7.1 Moisture Analyzer,3containing:7.1.1 The capa
15、bility 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.NOTE 2It will be necessary to contact the analyzer manufacturer forsuggested test temperatures for materials not listed in Tables A1.
16、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 capable of converting the loss ofweight to digital data.7.1.5 Digital display for presenting the d
17、igital 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 the specimen is representative of the sample.8.2 Due to the hygroscopic nature of many plastic
18、s, 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 cool to roomtemperature in a sealed container prior to determination.8.4 Test specimens in the
19、 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 and an NIST-traceable temperature calibration inter-face.9.2 The calibration is validated by way
20、 of using sodiumtartrate dihydrate4exhibiting a theoretical crystal water contentof 15.66 % with an acceptable result range of 15.61 to 15.71 %.Other materials with known theoretical water content areacceptable for validation.9.3 Prepare the analyzer for use and perform the analysis asdescribed in 1
21、0.1.9.4 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-tion to ensure analyzer performance. Retest with sodiumtartrate dihydrate. If results sti
22、ll are not within the acceptablerange, contact analyzer manufacturer.10. Procedure10.1 Sample Analysis:10.1.1 Place the analyzer on a flat, level 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 te
23、st condi-tions listed in Annex A1 or Annex A2.NOTE 3If test conditions for a specific material are not listed in AnnexA1 or Annex A2, they will have to be determined experimentally or bycontacting the analyzer manufacturer.10.1.4 Begin the program and follow the prompts forplacing the sample on the
24、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 moisture.10.1.7 Place a clean sample pan in the analyzer and allowequilibration prior to beginning subsequent tests.10.2 Determination of Optimal Test Conditi
25、ons: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 D 6869 or contact the analyzer manufacturerwho in some cases will provide this service for you.10.2.1 Program the analyzer in accordanc
26、e 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. Each program isidentical in its parameters except the temperature is increased5.NOTE 5Whe
27、n 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 the tests have completed, plot the result versustemperature to make a curve as in Fig.
28、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 test temperature.10.2.3.3 Above point 5 the moisture result begins to in-crease. This is l
29、ikely 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 be3The model Computrac MAX 2000XL Moisture Analyzer, available fromArizona Instrument, LLC, 1912 West 4th Street, Tempe, Arizona, 85281
30、, and theMark 2HP Moisture Analyzer, available from Omnimark Instrument Corporation,1320 South Priest Drive, Tempe, Arizona, 85281 have been found satisfactory forthis purpose, or equivalent.4Sodium tartrate dihydrate may be sourced from the analyzer manufacturer orfrom GFS Chemicals, P.O. Box 245,
31、Powell, Ohio, 43065. FIG. 1 Optimum Test Temperature SelectionD6980042above the melting point of the selected plastic 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 calculation
32、s 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 Report the following information:12.1.1 Complete identification of the sample tested, includ-ing type of material, source, manufacturers code, form, andpr
33、evious 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 and Bias13.1 Precision and bias statements will be established fol-lowing completion of round robin analyses per ASTM require-ments. See Table 1 for inform
34、ation on repeatability of this testmethod.14. Keywords14.1 moisture determination; plastics; volatile contentANNEXES(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 labeledTARTRAT
35、E.A1.2 Suggested test conditions for selected plastics aregiven in Table A1.1.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
36、procedure in 10.2 to determine the optimal testtemperature:Temperatures TestSet 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 e
37、xpected moisture contentabove 0.10 % program the instrument as follows and thenperform 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 Ta
38、reUltra Low MoistureSample Tare8 sLift Compensation 100 %TABLE 1 Repeatability and Correlation for Computrac MAX 2000XL versus KFMaterialComputracMeanStandardDeviationCoefficientof VariationKarl FischerMeanStandardDeviationCoefficientof VariationPOM 0.086 0.0007 0.77 0.0875 0.0004 0.46ABS 0.027 0.00
39、16 5.91 0.0262 0.0011 4.09ABS + PC 0.027 0.0024 8.86 0.0260 0.0025 9.75Acrylic 0.006 0.0007 10.57 0.0068 0.0010 14.11PA 6 0.132 0.0018 1.33 0.1350 0.0048 3.58PA 6/6 0.181 0.0030 0.39 0.1820 0.0060 3.20PBT 0.013 0.0005 3.67 0.0136 0.0001 0.27PC 0.014 0.0006 4.14 0.0134 0.0011 7.91PEI 0.012 0.0012 9.5
40、4 0.0130 0.0015 11.91PET 0.109 0.0018 1.68 0.1118 0.0022 2.00PPS 0.026 0.0010 3.37 0.0247 0.0032 13.05PS 0.019 0.0010 5.25 0.0187 0.0009 5.05PVC 0.076 0.0011 1.46 0.0743 0.0062 8.40TPE 0.036 0.0010 3.74 0.0358 0.0004 1.16TPU 0.007 0.0005 6.98 0.0076 0.0007 9.45D6980043A2. MARK 2HP MOISTURE ANALYZERA
41、2.1 Test conditions for sodium tartrate dihydrate:Temperatures Temp 1150CTemp 2OffStdby100CTimes Time 1OffTime 2OffIdeal Weight 10 gStart Delay 0Win Window2.0 min% IW0.020 %A2.2 Suggested test conditions for selected plastics aregiven in Table A2.1.A2.3 Use the following guidelines for determining t
42、estconditions for a material not listed in Table A2.1 and thenperform procedure in 10.2 to determine the optimal testtemperature:Temperatures Temp 1Set to 30C below melt temperatureTemp 2OffStdbySet equal to Temp 1Times Time 1Typically set at 4 to 5 min formaterials such as Polyamides and TPUthat ev
43、olve moisture slowly. Used toprevent early termination of the testbefore sample has been thoroughlyheated.Set to OFF if not necessary.Time 2OffWin WindowSet to 1.5 to 3.0 min% IWFor mold spec between 0.010 % and0.050 %, set to 0.005 to 0.010 %For mold spec between 0.050 % and0.250 % set to 0.010 to
44、0.020 %EndptActualIdeal Weight For mold spec between 0.005 % and0.020 % set to 50 to 80 gFor mold spec between 0.020 % and0.150 % set to 30 to 50 gFor mold spec greater than 0.150 %set to 20 to 35 gStart Delay9TABLE A1.1 Suggested Test Conditions for Selected PlasticsMaterialTest Temp.(C)Idle Temp.
45、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
46、 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-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 1
47、8 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 material including more than moderate discoloration, melting, or smoke, lower the test temperature by 10C pertest until no discoloration appears and the pelle
48、ts retain their shape.NOTE 2Lift compensation accounts for the difference in heat absorption properties between resins. In essence, it adjusts for the stronger air currentspresent in the test chamber when testing opaque resins.NOTE 3These suggested conditions were determined through extensive tests
49、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 contact the analyzer manufacturer for assistance with determiningthe best test conditions for your specific material.D6980044ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent right
