Designation: D 6980 – 04
Standard Test Method for
Determination of Moisture in Plastics by Loss in Weight 1 This standard is issued under the fixed designation D 6980; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript supers cript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Sco Scope pe
3.1.2 tempering—a proc process ess that re-defines re-defines the mole molecula cularr structure of a metal to enhance its performance.
1.1 This test meth method od cover coverss the quan quantita titative tive determinati determination on of moisture by means of loss in weight technology down to 50 ppm as it applies to most plastics. 1.2 The values values stated stated in SI units are to be reg regard arded ed as the standard. 1.3 Spe Specim cimens ens tested tested in thi thiss met method hod can rea reach ch or exc exceed eed 250°C,, use caution when handl 250°C handling ing them after testing testing has been completed. 1.4 This sta standa ndard rd does not purport purport to add addre ress ss all of the safe sa fety ty co conc ncer erns ns,, if an anyy, as asso soci ciat ated ed wi with th it itss us use. e. It is th thee responsibility of the user of this standard to establish appro priate safety and health practices and determine the applicability of regulatory limitations prior to use.
4. Summ Summary ary of Test Test Method 4.1 4. 1 The sp spec ecim imen en is sp spre read ad on onto to a sa samp mple le pa pan n th that at is supported suppor ted on a bal balanc ancee in a hea heatin ting g cha chambe mberr tha thatt has been preheated and equilibrated to the specified idle temperature. It is th then en he heat ated ed to va vapo pori rize ze th thee mo mois istu ture re.. Th Thee an anal alys ysis is is completed when the indicated weight loss falls below a rate specifi spe cified ed in the test con condit dition ions. s. The tot total al los losss of wei weight ght is integrated and displayed as the percent of moisture. Both the analyzer’s balance and heater are calibrated to NIST standards to achieve precise and accurate results. 4.2 Through adjus adjustmen tmentt of the analyzer’s analyzer’s para paramete meterr settings, a set of conditions is developed to measure moisture.
NOTE 1—There is no similar or equivalent ISO standard.
5. Signi Significanc ficancee and Use
2. Referenced Documents
5.1 This te 5.1 test st me meth thod od is in inte tend nded ed fo forr us usee as a co cont ntro rol, l, acceptance, and assessment test. 5.2 Moisture can seriously affect affect the processability processability of plastics. It is possible that high moisture content will cause surface imperfec impe rfection tionss (tha (thatt is, spla splay y or bubbl bubbling) ing) or degr degradati adation on by hydrolysi hydr olysis. s. Low mois moisture ture (with high temperature) temperature) has been known to cause solid phase polymerization. 5.3 The phy physic sical al pro proper pertie tiess of som somee pla plasti stics cs are gre greatl atly y affected by the moisture content.
2.1 ASTM Standards: 2 D 883 Termi erminolog nology y Relat Relating ing to Plast Plastics ics D 1600 Terminolo Terminology gy for Abbre Abbreviate viated d Terms Rela Relating ting to Plastics D 6869 6869 Test Meth Method od for Coulo Coulometr metric ic and Volum Volumetri etricc Determination of Moisture in Plastics Using the Karl Fischer Reaction (the Reaction of Iodine with Water) 3. Terminology 3.1 Definitions— The The definitions used in this test method are in accordance with Terminologies D 883 and D 1600. 3.1.1 lift —the —the result of convection currents created during the heating of the specimen raising the sample pan off of its support falsely indicating a moisture loss. 3.1.1.1 Discussion—The effects of lift are compensated for in different ways by different manufacturers.
6. Interference Interferencess 6.1 When testing testing plastic material materialss for mois moisture ture by a loss in weight technique, the possibility exists for volatiles other than wate wa terr to be ev evol olve ved d an and d ca caus usee a bi bias ased ed hi high gh re resu sult lt if th thee material has not been dried to remove excess moisture and low boiling volatiles. It is important to have a working knowledge of the material that is being tested and to remain below any melting or decomposition temperatures that would unnecessarily cause the emission of volatiles which can be harmful.
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This test method is under the jurisdiction jurisdiction of ASTM Committee Committee D20 on Plastics and is the direct respon responsibility sibility of Subco Subcommittee mmittee D20.70 on Analytical Methods. Current edition approved July 1, 2004. Published August 2004. 2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@
[email protected] astm.org. g. For For Annual Annual Book of ASTM volume information, refer to the standard’s Document Summary page on Standards volume Standards the ASTM website website..
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D 6980 – 04 7. Apparatus
10. Procedure
7.1 Moisture Analyzer, 3 containing: 7.1.1 The capability of the oven shall be selected based upon the specific material being tested. Suggested test temperatures for specific plastics are shown in Tables A1.1 and A2.1.
10.1 Sample Analysis: 10.1.1 Place the analyzer on a flat, level surface. 10.1.2 Turn the analyzer on and allow equilibration at the programmed idle temperature for 15 min. 10.1.3 Program the analyzer with the suggested test conditions listed in Annex A1 or Annex A2.
NOTE 2—It will be necessary to contact the analyzer manufacturer for suggested test temperatures for materials not listed in Tables A1.1 and A2.1.
NOTE 3—If test conditions for a specific material are not listed in Annex A1 or Annex A2, they will have to be determined experimentally or by contacting the analyzer manufacturer.
7.1.2 A balance capable of measuring to 0.0001 g. 7.1.3 An electronic or mechanical 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 other nonreactive material.
10.1.4 Begin the program and follow the prompts for placing the sample on the sample pan. 10.1.5 At the end of the test allow the analyzer to cool and remove 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 allow equilibration prior to beginning subsequent tests. 10.2 Determination of Optimal Test Conditions : NOTE 4—When determining the optimal test conditions for a material, it is useful to have a Karl Fischer apparatus available and test in accordance with Test Method D 6869 or contact the analyzer manufacturer who in some cases will provide this service for you.
8. Test Specimen and Sample 8.1 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 qualified or suitable material. 8.3 Samples that have been heated to remove moisture prior to processing and testing shall be allowed to cool to room temperature in a sealed container prior to determination. 8.4 Test specimens in the form of powders, pellets, or ground material.
10.2.1 Program the analyzer in accordance with the conditions listed in Annex A1 or Annex A2. 10.2.2 To determine the optimum test temperature for a material, run a single test which includes several consecutive programs that have been linked together. Each program is identical in its parameters except the temperature is increased 5°. NOTE 5—When increasing the test temperature, do not exceed a temperature where the potential exists for the emission of harmful fumes. NOTE 6—Ensure that the program selected to run first is the lowest temperature.
9. Calibration and Standardization 9.1 To maintain the integrity of the test results the balance and heater shall both be calibrated using NIST-traceable weights and an NIST-traceable temperature calibration interface. 9.2 The calibration is validated by way of using sodium tartrate dihydrate 4 exhibiting a theoretical crystal water content of 15.66 % with an acceptable result range of 15.61 to 15.71 %. Other materials with known 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 for re-analysis. 9.5 If results are still not within the acceptable range, first perform a temperature calibration and then a balance calibration to ensure analyzer performance. Retest with sodium tartrate dihydrate. If results still are not within the acceptable range, contact analyzer manufacturer.
10.2.3 After the tests have completed, plot the result versus temperature to make a curve as in 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 optimum test temperature. 10.2.3.3 Above point 5 the moisture result begins to increase. This is likely caused by the generation of water due to decomposition or solid phase polymerization of the sample. NOTE 7—It is not uncommon for the optimal test temperature to be
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The model Computrac MAX 2000XL Moisture Analyzer, available from Arizona Instrument, LLC, 1912 West 4th Street, Tempe, Arizona, 85281, and the Mark 2HP Moisture Analyzer, available from Omnimark Instrument Corporation, 1320 South Priest Drive, Tempe, Arizona, 85281 have been found satisfactory for this purpose, or equivalent. 4 Sodium tartrate dihydrate may be sourced from the analyzer manufacturer or from GFS Chemicals, P.O. Box 245, Powell, Ohio, 43065.
FIG. 1 Optimum Test Temperature Selection
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D 6980 – 04 TABLE 1 Repeatability and Correlation for Computrac MAX 2000XL versus KF
Material POM ABS ABS + PC Acrylic PA 6 PA 6/6 PBT PC PEI PET PPS PS PVC TPE TPU
Computrac Mean
Standard Deviation
Coefficient of Variation
Karl Fischer Mean
Standard Deviation
Coefficient of Variation
0.086 0.027 0.027 0.006 0.132 0.181 0.013 0.014 0.012 0.109 0.026 0.019 0.076 0.036 0.007
0.0007 0.0016 0.0024 0.0007 0.0018 0.0030 0.0005 0.0006 0.0012 0.0018 0.0010 0.0010 0.0011 0.0010 0.0005
0.77 5.91 8.86 10.57 1.33 0.39 3.67 4.14 9.54 1.68 3.37 5.25 1.46 3.74 6.98
0.0875 0.0262 0.0260 0.0068 0.1350 0.1820 0.0136 0.0134 0.0130 0.1118 0.0247 0.0187 0.0743 0.0358 0.0076
0.0004 0.0011 0.0025 0.0010 0.0048 0.0060 0.0001 0.0011 0.0015 0.0022 0.0032 0.0009 0.0062 0.0004 0.0007
0.46 4.09 9.75 14.11 3.58 3.20 0.27 7.91 11.91 2.00 13.05 5.05 8.40 1.16 9.45
12.1.2 12.1.3 12.1.4 12.1.5
above the melting point of the selected plastic due to the distance between the resistive thermal device and the sample pan.
11. Calculation 11.1 Result is reported in percent moisture to three decimal places 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
Date of test, Individual specimen size, Individual specimen moisture, and Average moisture.
13. Precision and Bias 13.1 Precision and bias statements will be established following completion of round robin analyses per ASTM requirements. See Table 1 for information on repeatability of this test method.
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12. Report 12.1 Report the following information: 12.1.1 Complete identification of the sample tested, including type of material, source, manufacturer’s code, form, and previous history,
14. Keywords 14.1 moisture determination; plastics; volatile content
ANNEXES (Mandatory Information) A1. COMPUTRAC MAX 2000XL MOISTURE ANALYZER
A1.1 The test conditions for sodium tartrate dihydrate are pre-programmed into the MAX 2000XL as a method labeled TARTRATE.
Temperatures
Ending Crit eria Sample Size Tare O ptions
A1.2 Suggested test conditions for selected plastics are given in Table A1.1.
Lift Compensation
Test—Set to 30°C below melt point Hi Sta rt—25°C Idle—100°C End on Rate—0.005 %/min 30 6 2 g sample window Pan Tare—Ultra Low Moisture Sample Tare—8 s 100 %
A1.3.2 For materials with an expected moisture content above 0.10 % program the instrument as follows and then perform procedure in 10.2 to determine the optimal test temperature:
A1.3 Use the following guidelines for determining test conditions for a material not listed in Table A1.1. A1.3.1 For materials with an expected moisture content below 0.10 % program the instrument as follows and then perform procedure in 10.2 to determine the optimal test temperature:
Temperatures
Ending Crit eria Sample Size Tare O ptions Lift Compensation
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Test—Set to 30°C below melt point Hi Sta rt—25°C Idle—100°C End on Rate—0.010 %/min 20 6 2 g sample window Pan Tare—Ultra Low Moisture Sample Tare—8 s 100 %
D 6980 – 04 TABLE A1.1 Suggested Test Conditions for Selected Plastics Material
Test Temp. (°C)
Idle Temp.
Rate
Sample Size (grams)
Pan Tare
Sample Tare (seconds)
Lift Compensation
ABS ABS + PC POM Acrylic PA 6 PA 6/6 PBT PC PEI PET PPS PS PVC TPE TPU
140 155 160 150 175 210 175 170 170 160 170 165 105 140 155
100 100 100 100 100 100 100 100 100 100 100 100 100 100 100
0.010 0.005 0.005 0.007 0.015 0.015 0.005 0.005 0.005 0.005 0.005 0.005 0.010 0.005 0.010
18 to 22 28 to 32 18 to 22 28 to 32 18 to 22 18 to 22 28 to 32 28 to 32 28 to 32 28 to 32 28 to 32 28 to 32 18 to 22 28 to 32 18 to 22
Ultra-Low Ultra-Low Ultra-Low Ultra-Low Ultra-Low Ultra-Low Ultra-Low Ultra-Low Ultra-Low Ultra-Low Ultra-Low Ultra-Low Ultra-Low Ultra-Low Ultra-Low
8 8 8 8 8 8 8 8 8 8 8 8 8 8 8
100 100 100 100 100 100 100 100 100 100 100 100 100 100 100
NOTE 1—If you notice degradation of material including more than moderate discoloration, melting, or smoke, lower the test temperature by 10°C per test until no discoloration appears and the pellets retain their shape. NOTE 2—Lift compensation accounts for the difference in heat absorption properties between resins. In essence, it adjusts for the stronger air currents present in the test chamber when testing opaque resins. NOTE 3—These suggested conditions were determined through extensive tests that have been completed on these common plastics. It is not intended to be inclusive of every grade of every plastic and it will potentially be necessary to contact the analyzer manufacturer for assistance with determining the best test conditions for your specific material.
A2. MARK 2HP MOISTURE ANALYZER
A2.1 Test conditions for sodium tartrate dihydrate: Temperatures
Times Ideal Weight Start Delay Win
Times
Temp 1—150°C Temp 2—Off Stdby—100°C Time 1—Off Time 2—Off 10 g 0 Window—2.0 min % IW—0.020 %
Win
A2.2 Suggested test conditions for selected plastics are given in Table A2.1. A2.3 Use the following guidelines for determining test conditions for a material not listed in Table A2.1 and then perform procedure in 10.2 to determine the optimal test temperature: Temperatures
Ideal Weight
Temp 1—Set to 30°C below melt temperature Temp 2—Off
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Stdby—Set equal to Temp 1 Time 1—Typically set at 4 to 5 min for materials such as Polyamides and TPU that evolve moisture slowly. Used to prevent early termination of the test before sample has been thoroughly heated. Set to OFF if not necessary. Time 2—Off Window—Set to 1.5 to 3.0 min % IW—For mold spec between 0.010 % and 0.050 %, set to 0.005 to 0.010 % For mold spec between 0.050 % and 0.250 % set to 0.010 to 0.020 % Endpt—Actual For mold spec between 0.005 % and 0.020 % set to 50 to 80 g For mold spec between 0.020 % and 0.150 % set to 30 to 50 g For mold spec greater than 0.150 % set to 20 to 35 g Start Delay—9
D 6980 – 04 TABLE A2.1 Suggested Test Conditions for Selected Plastics Material
Test Temp (Celsius)
Time (min)
Standby Temp (Celsius)
Endpoint Slope (%/min)
Sample Size (grams)
Sample Delay (seconds)
ABS ABS + PC POM Acrylic PA 6 PA 6/6 PBT PC PEI PET PPS PS PVC TPE TPU
130 130 140 150 160 160 140 140 140 150 160 120 100 140 150
Off Off Off 4 5 5 Off 4 Off Off 4 Off 4 8 5
130 130 130 140 140 150 140 140 140 150 150 120 100 140 140
0.020 / 2.0 0.005 / 2.0 0.010 / 2.0 0.010 / 2.0 0.015 / 2.0 0.015 / 2.0 0.005 / 2.0 0.010 / 2.0 0.010 / 2.0 0.005 / 2.0 0.010 / 2.0 0.010 / 3.0 0.010 / 1.5 0.010 / 2.0 0.020 / 2.0
40 50 40 50 30 25 60 70 50 70 70 50 40 30 40
9 9 9 9 9 9 9 9 9 9 9 9 9 9 9
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