ASTM_D_4672_-_18.pdf

Designation:D467218Standard Test Method forPolyurethane Raw Materials:Determination of WaterContent of Polyols1This 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,the 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 andmany other organic compounds.1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.3 This 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.NOTE1This test method is equivalent to ISO 14897.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD883 Terminology Relating to PlasticsE203 Test Method for Water Using Volumetric Karl FischerTitrationE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standards:3ISO 14897 PlasticsPolyols for use in the production ofpolyurethaneDetermination of water content3.Terminology3.1 Definitions:3.1.1 polyurethane,na polymer prepared by the reactionof an organic diisocyanate with compounds containing hy-droxyl groups.3.1.1.1 DiscussionPolyurethanes,or urethanes,as they aresometimes called,can be thermosetting,thermoplastic,rigid orsoft and flexible,cellular or solid.(See Terminology D883.)4.Summary of Test Methods4.1 This method is based essentially on volumetric orcoulometric titrations that follow the reduction of iodine bysulfur dioxide in the presence of water.This reaction proceedsquantitatively when methanol or another alcohol(ROH)andpyridine(C5H5N)or a similar amine(RN)are present to reactwith the sulfur trioxide(SO3)and hydriodic acid(HI)producedaccording to the following reactions:ROH+SO2+RN RNHSO3RH2O+I2+RNHSO3R+2RN RNHSO4R+2RNHI4.2 To determine water,Karl Fischer reagent(a solution ofiodine,sulfur dioxide,imidazole,and pyridine or a pyridinesubstitute)is added to a solution of the sample in methanol orother alcohol until all of the water present has been consumed.The titrant is either added by buret(volumetry)or generatedelectrochemically in the titration cell(coulometry).Coulomet-ric titrations eliminate the need for standardizing the reagent.Pyridine is less commonly used recently due to its toxicity.Ifpyridine is to be used,refer to the SDS for proper precautions.4.3 This method provides details specific to water determi-nations in polyols.General guidance to the use of Karl-Fischeranalysis,including a list of interferences,can be found in TestMethod E203.5.Significance and Use5.1 This test method is suitable for quality control,as aspecification test,and for research.The water content of apolyol is important since isocyanates react with water.6.Apparatus6.1 Several commercial Karl Fischer autotitrators are avail-able that employ volumetric or coulometric titrations.These1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand are the direct responsibility of Subcommittee D20.22 on Cellular Materials-Plastics and Elastomers.Current edition approved April 1,2018.Published April 2018.Originallyapproved in 1991.Last previous edition approved in 2012 as D4672-12.DOI:10.1520/D4672-18.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 instruments consist of an automated buret assembly,a sealedtitration vessel with appropriate electrodes and sensingcircuitry,and a vacuum system for removal of solution afteranalysis.These automated systems provide several adv