1、Designation: D6980 12D6980 17Standard 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 las
2、t revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This test method covers the quantitative determination of moisture by means of loss in weight technology down to 5
3、0 mg/kg(50 ppm) as it applies to most plastics.1.2 The values stated in SI units are to be regarded as the standard.1.3 Specimens tested by this method will be hot, use caution when handling them after testing has been completed.1.4 This standard does not purport to address all of the safety concern
4、s, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.NOTE 1There is no known ISO equivalent to this standard.1.5 This international standard
5、was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Reference
6、d Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD1600 Terminology for Abbreviated Terms Relating to PlasticsD6869 Test Method for Coulometric and Volumetric Determination of Moisture in Plastics Using the Karl Fischer Reaction (theReaction of Iodine with Water)E691 Practice for C
7、onducting an Interlaboratory Study to Determine the Precision of a Test MethodE2935 Practice for Conducting Equivalence Testing in Laboratory Applications3. Terminology3.1 DefinitionsThe definitions used in this test method are in accordance with Terminologies D883 and D1600.3.2 Symbols:3.2.1 liftth
8、e result of convection currents created during the heating of the specimen raising the sample pan off of its supportfalsely indicating a moisture loss.3.2.1.1 DiscussionThe effects of lift are compensated for in different ways by different manufacturers.3.2.2 temperinga process that re-defines the m
9、olecular structure of a metal to enhance its performance.1 This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.70 on Analytical Methods.Current edition approved Feb. 1, 2012June 15, 2017. Published March 2012August 2017. O
10、riginally approved in 2004. Last previous edition approved in 20092012 asD6980 - 09.D6980 - 12. DOI: 10.1520/D6980-12.10.1520/D6980-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume info
11、rmation, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately d
12、epict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM Internat
13、ional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Method4.1 The specimen is spread onto a sample pan that is supported on a balance in a heating chamber that has been preheated andequilibrated to the specified idle temperature. It is then h
14、eated to vaporize the moisture. The analysis is completed when theindicated weight loss falls below a rate specified in the test conditions. The total loss of weight is integrated and displayed as thepercent of moisture. Both the analyzers balance and heater are calibrated to NISTstandards to achiev
15、e precise and accurate results.4.2 Through adjustment of the analyzers parameter settings, 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 Moisture will affect the processability of
16、 some materials. For these materials, defects will occur if they are processed witha moisture content outside of the recommended range.5.3 The physical properties of some plastics are greatly affected by the moisture content.6. Interferences6.1 When testing plastic materials for moisture by a loss i
17、n weight technique, the possibility exists for volatiles other thanmoisture to be evolved and cause a biased high result if the material has not been dried to remove excess moisture and low boilingvolatiles. It is important to have a working knowledge of the material that is being tested and to rema
18、in below any melting ordecomposition temperatures that would unnecessarily cause the emission of volatiles which can be harmful.7. Apparatus7.1 Moisture Analyzer, containing:7.1.1 The capability of the oven shall be selected based upon the specific material being tested. Suggested test temperatures
19、forspecific plastics are shown in Tables A1.1 and A1.1-A2.1A3.1.NOTE 2It will be necessary to contact the analyzer manufacturer for suggested test temperatures for materials not listed in Tables A1.1 andA1.1-A2.1A3.1.7.1.2 A balance capable of measuring to 0.0001 g.7.1.3 An electronic or mechanical
20、means of compensating for lift caused by convection currents created during testing.7.1.4 A processor that is capable of converting the loss of weight to digital data.7.1.5 Digital display for presenting the digital data as percent moisture.7.1.6 Sample Pans, made from “0” temper, Aluminum 3003 or o
21、ther nonreactive material.8. Test Specimen and Sample8.1 Due to the small specimen size, exercise care to ensure that the specimen is representative of the sample.8.2 Due to the hygroscopic nature of many plastics, samples shall be stored in airtight containers made of glass or other qualifiedor sui
22、table material.8.3 Samples that have been heated to remove moisture prior to 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, or ground material.9. Calibration and Standardization9.1 To
23、 maintain the integrity of the test results the balance and heater shall both be calibrated using NIST-traceable weights andan NIST-traceable temperature calibration interface.a traceable standard.9.2 The calibration is verified using sodium tartrate dihydrate exhibiting a known crystal water conten
24、t of 15.66 % with anacceptable result range of 15.61 to 15.71 %. Other materials with verifiable theoretical water content are acceptable for validation.9.3 Prepare the analyzer for use and perform the analysis as described in 10.1.9.4 If the result is not within the acceptable range, return to 9.3
25、for re-analysis.9.5 If results are still not within the acceptable range, first perform a temperature calibration and then a balance calibration toensure analyzer performance. Retest with sodium tartrate dihydrate. If results still are not within the acceptable range, the causeof the nonconformance
26、must be determined and corrected before proceeding with testing.10. Procedure10.1 Sample Analysis:10.1.1 Prepare analyzer as suggested by instrument manufacturer.10.1.2 Program the analyzer with the suggested test conditions listed in Annex A1, Annex A2, or Annex A3.D6980 172NOTE 3If test conditions
27、 for a specific material are not listed in Annex A1, Annex A2, or Annex A3, they will have to be determined experimentallyor by contacting the analyzer manufacturer.10.1.3 Begin the program and follow the prompts for placing the sample on the sample pan.10.1.4 At the end of the test allow the analyz
28、er to cool (if standby heating is not enabled) and remove 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 allow equilibration prior to beginning subsequent tests.10.2 Determination of Optimal Test Conditions:NOTE 4When dete
29、rmining the optimal test conditions for a material, it is useful to have a Karl Fischer apparatus available and test in accordancewith Test Method D6869 or contact the analyzer manufacturer who in some cases will provide this service for you.10.2.1 Program the analyzer in accordance with the conditi
30、ons listed in Annex A1, Annex A2or , or Annex A2A3.10.2.2 To determine the optimum test temperature for a material, run a single test which includes several consecutive programsthat have been linked together. Each program is identical in its parameters except the temperature is increased 5.5C.NOTE 5
31、When increasing the test temperature, do not exceed a temperature where the potential exists for the emission of harmful fumes.NOTE 6Ensure that the program selected to run first is the lowest temperature.10.2.3 After the tests have completed, plot the result versus temperature to make a curve as in
32、 Fig. 1.10.2.3.1 Most of the moisture is vaporized in temperature range from points 1 to 3.10.2.3.2 Between points 3 and 5 the moisture result is very low and constant. Choose a temperature in this range as the optimumtest temperature.10.2.3.3 Above point 5 the moisture result begins to increase. Th
33、is 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 be above the melting point of the selected plastic due to the distance between theresistive thermal device and the sample pan.11
34、. Calculation11.1 Result is reported in percent moisture to three decimal places so no further calculations are necessary.11.2 If conversion to mg/kg is desired, calculate as follows:mg/kg5Moisture content %!310000 (1)12. Report12.1 Report the following information:12.1.1 Complete identification of
35、the sample tested, including type of material, source, manufacturers code, form, and previoushistory,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 Bias3,413.1 The precisionrepeatability
36、of this test method is based on an interlaboratory study conducted in 2007. Eight laboratoriesanalyzed eight different plastic materials for moisture content. Every “test result” represents an individual determination. The3 Supporting data have been filed at ASTM International Headquarters and may b
37、e obtained by requesting Research Report RR:D20-1250.4 Equivalence testing in ASTM standards are covered by Practice E2935.FIG. 1 Optimum Test Temperature SelectionD6980 173laboratories reported two to four replicate results for each analysis in order to estimate the repeatability and reproducibilit
38、y limitsof the standard. Practice E691 was followed for the design and analysis of the data.13.1.1 Repeatability Limit (r)Two test results obtained within one laboratory shall be judged not equivalent if they differ bymore than the The rvalue for that material; below which r is the interval represen
39、ting the critical the absolute difference betweentwo individual test results for the same material, obtained by the same operator using the same equipment on the same day in thesame laboratory.obtained under repeatability conditions may be expected to occur with a probability of approximately 0.95 (
40、95 %).13.1.1.1 Repeatability limits are listed in Table 1.13.1.2 Reproducibility Limit (R)Two test results shall be judged not equivalent if they differ by more than the The Rvalue forthat material; below which R is the interval representing the critical the absolute difference between two individua
41、l test results forthe same material, obtained by different operators using different equipment in different laboratories.obtained under reproducibilityconditions may be expected to occur with a probability of approximately 0.95 (95 %).13.1.2.1 Reproducibility limits are listed in Table 1.13.1.3 Any
42、judgment in accordance with statements 13.1.1 and 13.1.2 would have an approximate 95 % probability of beingcorrect.13.2 BiasAt the time of the study, the test specimens chosen for analysis were not accepted reference materials suitable fordetermining the bias for this test method, therefore no stat
43、ement on bias is being made.13.3 The precisionrepeatability statement was determined through statistical examination of 162 data points, from eightlaboratories, on eight materials. These eight materials were described as the following:Material A: Nylon 6/6 (not dried)Material B: PET (dried)Material
44、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: PET (not-dried)13.4 To judge the equivalency of two test results, it is recommended to choose the material closest in characteristics to the testmaterial.14. K
45、eywords14.1 moisture determination; plastics; volatile contentTABLE 1 Moisture (%)MaterialAverageA StandardDeviation ofLab AveragesRepeatabilityStandardDeviationReproducibilityStandardDeviationRepeatabilityLimitReproducibilityLimitx Sx sr sR r Rx S sr sR r RA (Nylon 6/6) 0.4954 0.0131 0.0086 0.0151
46、0.0242 0.0423B (PET) 0.0292 0.0084 0.0047 0.0094 0.0133 0.0263C (TPE) 0.0107 0.0070 0.0026 0.0073 0.0072 0.0204D (PC) 0.0748 0.0040 0.0061 0.0067 0.0171 0.0187E (Nylon 6/6) 0.1390 0.0302 0.0241 0.0367 0.0674 0.1027F (TPE) 0.0406 0.0329 0.0024 0.0330 0.0068 0.0924G (PC) 0.0181 0.0085 0.0030 0.0088 0.
47、0083 0.0247H (PET) 0.1053 0.0109 0.0049 0.0117 0.0138 0.0327AThe average of the laboratories calculated averages.D6980 174ANNEXES(Mandatory Information)A1. MOISTURE ANALYZER WITH ELECTRONIC LIFT COMPENSATIONA1.1 Suggested test conditions for sodium tartrate dihydrate and selected plastics are given
48、in Table A1.1.A1.2 Use the following guidelines for determining test conditions for a material not listed in Table A1.1, and then performprocedure in 10.2 to determine the optimal test temperature:Materials with anexpected moisturecontent below 0.10 %Materials with anexpected moisturecontent below 0
49、.10 %Materials with anexpected moisturecontent below 0.10 %Materials with anexpected moisturecontent above 0.10 %Temperatures TestSet to 30Cbelow melt pointTestSet to 30Cbelow melt pointHi Start25C Hi Start25CIdle100C Idle100CEndingCriteriaEnd on Rate0.005 % minEnd on Rate0.010 % minSampleSize30 2 gsample window20 2 gsample windowTareOptionsPan TareUltraLow MoisturePan TareUltraLow MoistureSample Tare8 s Sample Tare8 sLiftCompensation100 % 100 %TABLE A1.1 Suggested Test Conditions for Selected PlasticsMaterial Test Temp.(C) Idle T
