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Standard Test Method for Determination of …

Designation: D 6980 – 04 Standard Test Method for Determination of Moisture in Plastics by Loss in Weight1 This standard is issued under the fixed designation D ...

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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 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or This test method covers the quantitative determinationof moisture by means of loss in weight technology down to 50ppm as it applies to most The values stated in SI units are to be regarded as Specimens tested in this method can reach or exceed250 C, use caution when handling them after testing has standard does not purport to address all of thesafety concerns, if any, associated 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 There is no similar or equivalent ISO Referenced Standards:2D 883 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. The definitions used in this test method arein accordance with Terminologies D 883 and D the result of convection currents created duringthe heating of the specimen raising the sample pan off of itssupport falsely indicating a moisture The effects of lift are compensated forin different ways by different a process that re-defines the molecularstructure of a metal to enhance its Summary of Test The specimen is spread onto a sample pan 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 weight isintegrated and displayed as the percent of moisture. Both theanalyzer s balance and heater are calibrated to NIST standardsto achieve precise and accurate Through adjustment of the analyzer s parameter set-tings, a set of conditions is developed to measure Significance and This test method is intended for use as a control,acceptance, and assessment 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 The physical properties of some plastics are greatlyaffected by the moisture 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 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 test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee on Analytical edition approved July 1, 2004. Published August referenced ASTM standards, visit the ASTM website, , orcontact ASTM Customer Service at ForAnnual Book of ASTMStandardsvolume information, refer to the standard s Document Summary page onthe ASTM ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United Analyzer,3 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 It will be necessary to contact the analyzer manufacturer forsuggested test temperatures for materials not listed in Tables A balance capable of measuring to An electronic or mechanical means of compensatingfor lift caused by convection currents created during A processor that is capable of converting the loss ofweight to digital Digital display for presenting the digital data aspercent Pans, made from 0 temper, Aluminum 3003or other nonreactive Test Specimen and Due to the small specimen size, exercise care to ensurethat the specimen is representative of the Due to the hygroscopic nature of many plastics, samplesshall be stored in airtight containers made of glass or otherqualified or suitable 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 Test specimens in the form of powders, pellets, orground Calibration and To maintain the integrity of the test results the balanceand heater shall both be calibrated using NIST-traceableweights and an NIST-traceable temperature calibration The calibration is validated by way of using sodiumtartrate dihydrate4exhibiting a theoretical crystal water contentof % with an acceptable result range of to %.Other materials with known theoretical water content areacceptable for Prepare the analyzer for use and perform the analysis asdescribed in If the result is not within the acceptable range, return for 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 still are not within the acceptablerange, contact analyzer Place the analyzer on a flat, level Turn the analyzer on and allow equilibration at theprogrammed idle temperature for 15 Program the analyzer with the suggested test condi-tions listed in Annex A1 or Annex If 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 Begin the program and follow the prompts forplacing the sample on the sample At the end of the test allow the analyzer to cool andremove the sample Record the result as displayed in percent Place a clean sample pan in the analyzer and allowequilibration prior to beginning subsequent of Optimal Test Conditions:NOTE4 When 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 Program the analyzer in accordance with the condi-tions listed in Annex A1 or Annex 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 .NOTE5 When increasing the test temperature, do not exceed atemperature where the potential exists for the emission of harmful Ensure that the program selected to run first is the After the tests have completed, plot the result versustemperature to make a curve as in Fig. Most of the moisture is vaporized in temperaturerange from points 1 to Between points 3 and 5 the moisture result is verylow and constant. Choose a temperature in this range as theoptimum test 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 It 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, and theMark 2HP Moisture Analyzer, available from Omnimark Instrument Corporation,1320 South Priest Drive, Tempe, Arizona, 85281 have been found satisfactory forthis purpose, or tartrate dihydrate may be sourced from the analyzer manufacturer orfrom GFS Chemicals, Box 245, Powell, Ohio, 1 Optimum Test Temperature SelectionD6980 042above the melting point of the selected plastic due to the distance betweenthe resistive thermal device and the sample Result is reported in percent moisture to three decimalplaces so no further calculations are If conversion to parts per million (PPM) is desired,calculate as follows:PPM5Moisture content~%!310000(1)12. Report the following Complete identification of the sample tested, includ-ing type of material, source, manufacturer s code, form, andprevious history, Date of test, Individual specimen size, Individual specimen moisture, Average Precision and Precision and bias statements will be established fol-lowing completion of round robin analyses per ASTM require-ments. See Table 1 for information on repeatability of this moisture determination; plastics; volatile contentANNEXES(Mandatory Information)A1. COMPUTRAC MAX 2000XL MOISTURE The test conditions for sodium tartrate dihydrate arepre-programmed into the MAX 2000XL as a method test conditions for selected plastics aregiven in Table the following guidelines for determining testconditions for a material not listed in Table For materials with an expected moisture contentbelow % program the instrument as follows and thenperform procedure in to determine the optimal testtemperature:TemperaturesTest Set to 30 C below melt pointHi Start 25 CIdle 100 CEnding CriteriaEnd on Rate %/minSample Size3062 g sample windowTare OptionsPan Tare Ultra Low MoistureSample Tare 8 sLift Compensation100 % For materials with an expected moisture contentabove % program the instrument as follows and thenperform procedure in to determine the optimal testtemperature:TemperaturesTest Set to 30 C below melt pointHi Start 25 CIdle 100 CEnding CriteriaEnd on Rate %/minSample Size2062 g sample windowTare OptionsPan Tare Ultra Low MoistureSample Tare 8 sLift Compensation100 %TABLE 1 Repeatability and Correlation for Computrac MAX 2000XL versus KFMaterialComputracMeanStandardDeviation Coefficientof VariationKarl FischerMeanStandardDeviationCoefficiento f + 6 043A2. MARK 2HP MOISTURE Test conditions for sodium tartrate dihydrate:TemperaturesTemp 1 150 CTemp 2 OffStdby 100 CTimesTime 1 OffTime 2 OffIdeal Weight10 gStart Delay0WinWindow min% IW % test conditions for selected plastics aregiven in Table the following guidelines for determining testconditions for a material not listed in Table and thenperform procedure in to determine the optimal testtemperature:TemperaturesTemp 1 Set to 30 C below melt temperatureTemp 2 OffStdby Set equal to Temp 1TimesTime 1 Typically set at 4 to 5 min formaterials such as Polyamides and TPUthat evolve moisture slowly. Used toprevent early termination of the testbefore sample has been to OFF if not 2 OffWinWindow Set to to min% IW For mold spec between % %, set to to %For mold spec between % % set to to %Endpt ActualIdeal WeightFor mold spec between % % set to 50 to 80 gFor mold spec between % % set to 30 to 50 gFor mold spec greater than %set to 20 to 35 gStart Delay 9TABLE Suggested Test Conditions for Selected PlasticsMaterialTest Temp.( C)Idle Size(grams)Pan TareSample Tare(seconds) to 22Ultra-Low8100ABS + to to to 32Ultra-Low8100PA to 22Ultra-Low8100PA 6 to to to to to to to to to to 22Ultra-Low8100NOTE1 If you notice degradation of material including more than moderate discoloration, melting, or smoke, lower the test temperature by 10 C pertest until no discoloration appears and the pellets retain their Lift 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 These 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 contact the analyzer manufacturer for assistance with determiningthe best test conditions for your specific 044ASTM 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 rights, and the riskof infringement of such rights, are entirely their own standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or (e-mail); or through the ASTM website( ).TABLE Suggested Test Conditions for Selected PlasticsMaterialTest Temp(Celsius)Time(min)Standby Temp(Celsius)Endpoint Slope(%/min)Sample Size(grams)Sample Delay(seconds) / + / / / / 6 / / / / / / / / / / 045

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