1、Designation: D4672 12D4672 18Standard Test Method forPolyurethane Raw Materials: Determination of WaterContent of Polyols 1This standard is issued under the fixed designation D4672; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he year of last 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*1.1 This test method measures water content of polyols and many other organic compounds.1.2 The values stated
3、in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety saf
4、ety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.NOTE 1This test method is equivalent to ISO 14897.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished
5、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. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD883 Terminology Relating to Plas
6、ticsE203 Test Method for Water Using Volumetric Karl Fischer TitrationE180E691 Practice for Determining Conducting an Interlaboratory Study to Determine the Precision of ASTM Methods forAnalysis and Testing of Industrial and Specialty Chemicalsa Test Method (Withdrawn 2009)2.2 ISO Standards:3ISO 148
7、97 PlasticsPolyols for use in the production of polyurethaneDetermination of water content3. Terminology3.1 Definitions:3.1.1 polyurethane, na polymer prepared by the reaction of an organic diisocyanate with compounds containing hydroxylgroups.3.1.1.1 DiscussionPolyurethanes, or urethanes, as they a
8、re sometimes called, maycan be thermosetting, thermoplastic, rigid or soft and flexible,cellular or solid. (See Terminology D883.)1 This test method is under the jurisdiction ofASTM Committee D20 on Plastics and are the direct responsibility of Subcommittee D20.22 on Cellular Materials - Plasticsand
9、 Elastomers.Current edition approved Aug. 1, 2012April 1, 2018. Published August 2012April 2018. Originally approved in 1991. Last previous edition approved in 20002012 asD4672 - 00D4672 - 12.(2006)1. DOI: 10.1520/D4672-12.10.1520/D4672-18.2 For referencedASTM standards, visit theASTM website, www.a
10、stm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.Available from American National St
11、andards Institute (ANSI), 25 W. 43rd St., 4thFloor, New York, NY 10036, http:/www.ansi.org.4 Instruments similar to and including the following types have been found suitable for determining water content of polyols, based on round-robin studies: Metrohmmodels 633, 652, 658, 665, 684, 701, 720, 737,
12、 and 758 (available from Brinkmann Instruments, Inc. at ) and Mettler Toledo models DL 18, 31, 37,and 38 ().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 te
13、chnically possible to adequately depict 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 th
14、is standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Methods4.1 This method is based essentially on volumetric or coulometric titrations that follow the reduction of iodine by sulfur dioxidein the presence of
15、water. This reaction proceeds quantitatively when methanol or another alcohol (ROH) and pyridine (C5H5N) ora similar amine (RN) are present to react with the sulfur trioxide (SO3) and hydriodic acid (HI) produced according to thefollowing reactions:ROH + SO2 + RN RNHSO3RH2O + I2 + RNHSO3R + 2RN RNHS
16、O4R + 2RNHI4.2 To determine water, Karl Fischer reagent (a solution of iodine, sulfur dioxide, imidazole, and pyridine or a pyridinesubstitute) is added to a solution of the sample in methanol or other alcohol until all of the water present has been consumed. Thetitrant is either added by buret (vol
17、umetry) or generated electrochemically in the titration cell (coulometry). Coulometric titrationseliminate the need for standardizing the reagent. Pyridine is less commonly used recently due to its toxicity. If pyridine is to beused, refer to the SDS for proper precautions.4.3 This method provides d
18、etails specific to water determinations in polyols. General guidance to the use of Karl-Fischeranalysis, including a list of interferences, can be found in Test Method E203.5. Significance and Use5.1 This test method is suitable for quality control, as a specification test, and for research. The wat
19、er content of a polyol isimportant since isocyanates react with water.6. Apparatus6.1 Several commercial Karl Fischer autotitrators are available that employ volumetric or coulometric titrations. Theseinstruments consist of an automated buret assembly, a sealed titration vessel with appropriate elec
20、trodes and sensing circuitry, anda vacuum system for removal of solution after analysis. These automated systems provide several advantages and conveniences.Atmospheric moisture contamination can be more closely controlled; calibration is simplified; and the preneutralization step isautomatic. Titra
21、tions are rapid, and reagent consumption is low.Autotitrators automatically calculate and display or print the waterconcentration.7. Reagents7.1 Commercial reagents and reagent systems of various types are available for use with autotitrators for water determination.Pyridine-free reagents have impro
22、ved stability and less objectionable odor than the conventional Karl Fischer reagent. Reagentscan be purchased are available in split or composite forms in different concentrations to fit various ranges of water content. Acomposite reagent contains all the components required for a Karl Fischer titr
23、ation in a single solution. Split implies separatesolutions of the solvent and titrant.8. Sampling8.1 Sampling is conveniently accomplished by use of a tared syringe. The material is drawn into the syringe, weighed, anddelivered through the sample port of the autotitrator vessel. The syringe is then
24、 reweighed to obtain the sample weight bydifference.8.1.1 It is essential to avoid changes in the water content of the material during sampling operations. Many polyols are quitehygroscopic and errors from this source are particularly significant in the determination of the small amount of water usu
25、allypresent. Use almost-filled, tightly capped containers and limit as much as possible contact of the sample with air when transferringthe sample to the titration vessel.Avoid intermediate sample containers, if possible. If several different analyses are to be performedon the same sample, determine
26、 the water first and do not open the sample prior to the actual analysis.8.1.2 In particularly humid environments, the autotitrator can be set up in a dry air or nitrogen purge box so that sample handlingand the titration can be carried out in a low humidity environment.9. Standardization of Reagent
27、9.1 Since different autotitrators may vary in standardization procedures, consult the operating manual for the autotitrator in use.Water is an excellent primary standard. In addition, stable, prepackaged, primary standards are also available for establishing thestandardization factor.10. Procedure10
28、.1 Refer to the operating manual for the autotitrator in use. Basically, after preneutralization of the reagent in the titratorvessel, the sample is introduced, and the volumetric titration (or coulometric generation of titrant) proceeds automatically to theend point.NOTE 2In choosing the appropriat
29、e sample size for use with specific autotitrators, use the manufacturers recommendations. If no instructions areavailable, use the guidelines listed in Table 1 and Table 2.D4672 18211. Calculation11.1 Following each titration, the autotitrator automatically calculates and displays the water content,
30、 based on the stored valuesof sample weight, standardization factor, and titrant volume consumed.12. Precision and Bias4,512.1 PrecisionThe following data should be used for judging the acceptability of results (95 % confidence limits):12.1.1 RepeatabilityDuplicate results obtained by the same analy
31、st are to be considered suspect if they differ by more thanthe percent relative listed in Table 3 for the water level which most closely matches the sample being analyzed.12.1.2 ReproducibilityThe average result of duplicates obtained in one laboratory are to be considered suspect if they differfrom
32、 that of another laboratory by more than the relative percentage given in Table 4 for the water levels listed.12.1 Table 3The, Table 4precision statements above, and Table 5 are based on a 2000 interlaboratory study of three polyolsamples with water contents of approximately 0.03, 0.42, and 1.6 %. O
33、ne analyst in each of nine to twelve laboratories performedduplicate determinations and repeated them on a second day. The samples were analyzed by both volumetric and coulometricmethodologies. Practice E180 was used to develop the precision estimates listed in Table 5. Table 5. Values are listed in
34、 weightpercent of water.12.2 CautionThe explanation of the repeatability (r) and reproducibility (R) is only intended to present a meaningful way ofconsidering the approximate precision of this test method. Do not apply the data in Tables 3-5 to acceptance or rejection ofmaterials, as these data app
35、ly only to the materials tested in the round robin and are unlikely to be rigorously representative of otherlots, formulations, conditions, materials, or laboratories. Users of this test method need to apply the principles outlined in PracticeE691 to generate data specific to their materials and lab
36、oratory (or between specific laboratories). The principles would then bevalid for such data12.3 RepeatabilityPrecision under repeatability conditions.12.4 ReproducibilityPrecision under reproducibility conditions.12.5 Repeatability Limit, rThe value below which the absolute difference between two in
37、dividual test results obtained underrepeatability conditions may be expected to occur with a probability of approximately 0.95 (95 %). For the data generated above,the maximum expected differences between two test results for the same material, obtained by the same operator using the sameequipment o
38、n the same day in the same laboratory due solely to the method are listed in Table 3 for different water levels.12.6 Reproducibility Limit, RThe value below which the absolute difference between two individual test results obtainedunder reproducibility conditions may be expected to occur with a prob
39、ability of approximately 0.95 (95 %). For the data generatedabove, the maximum expected differences between two test results for the same material, obtained by different operators usingdifferent equipment in different laboratories due solely to the method are listed in Table 4 for different water le
40、vels.4 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D20-1068.5 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D20-1209.TABLE 1 Volumetric TitrationA% Wa
41、ter Expected Suggested Sample Size, gBelow 0.5 5100.51.0 1Above 1.0 0.5AFor titrant concentration equivalent to 5 mg H2 O per mL.TABLE 2 Coulometric Titration% Water Expected Suggested Sample Size, gBelow 0.1 50.10.5 10.51.0 0.1TABLE 3 Repeatability StatisticsWater% Water Level Volumetric(relative %
42、)Coulometric(relative %)0.03 8.2 2.80.42 1.6 3.11.6 1.1 3.1D4672 18312.7 BiasThe bias of these test methods have not been determined.There are no recognized standards by which to estimatebias of this method.13. Keywords13.1 Karl Fischer; polyols; polyurethane; raw materials; water contentSUMMARY OF
43、CHANGESCommittee D20 has identified the location of selected changes to this standard since the last issue,D4672 - 00D4672 - 12(06)1, that may impact the use of this standard. (August(April 1, 2012)2018)(1) Removed Test Method ADetermination of Water in Polyols by Manual Karl Fischer Titration since
44、 it is no longer usedtoday.Editorial changes to remove unclear language.(2) Various editorial changes as a result of the change referenced above.Added references to E203 and E691.(3) Added a precautionary statement on the use of pyridine to 4.2.(4) Added 4.3 referring the reader to E203.(5) Removed
45、references to suppliers of titrators and reagents.(6) Added 8.1.2 suggesting that the titrators can be operated in a dry purge box.(7) Updated Precision and Bias section to comply with D4968.ASTM International takes no position respecting the validity of any patent rights asserted in connection with
46、 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 responsibility.This standard is subject to revision at any time by the responsible techni
47、cal 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
48、 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 below.This standard is copyrighted by ASTM International, 100 Barr Harbo
49、r 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 serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ Reagents for Karl F
