ASTM_D_4671_-_16.pdf

Designation:D467116Standard Test Method forPolyurethane Raw Materials:Determination of Unsaturationof Polyols1This standard is issued under the fixed designation D4671;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 unsaturation in polyetherpolyols.(See Note 1.)It uses 2 mL of ca.0.05 M mercuricacetate reagent in methanol and about 1 g of sample or less.This test method uses a potentiometric determination of an endpoint.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 Mercury has been designated by many regulatory agen-cies as a hazardous substance that can cause serious medicalissues.Mercury,or its vapor,has been demonstrated to behazardous to health and corrosive to materials.Caution shouldbe taken when handling mercury and mercury containingproducts.See the applicable product Safety Data Sheet(SDS)for additional information.Users should be aware that sellingmercury and/or mercury containing products into your state orcountry may be prohibited by law.1.4 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 and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE1This standard is equivalent to ISO 17710.2.Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsE180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals(Withdrawn 2009)32.2 ISO Standards:ISO 17710 PlasticsPolyols for Use in the Production ofPolyurethaneDetermination of Degree of Unsaturationby Microtitration43.Terminology3.1 DefinitionsFor definitions of terms used in these testmethods,see Terminology D883.4.Summary of Test Method4.1 Carbon-to-carbon unsaturated compounds in the sampleare reacted with mercuric acetate and methanol in a methanolicsolution to produce acetoxymercuricmethoxy compounds andacetic acid.5The amount of acetic acid released in thisequimolar reaction,which is determined by titration withstandard alcoholic potassium hydroxide,is a measure of theunsaturation originally present.Because the acid cannot betitrated in the presence of excess mercuric acetate,due to theformation of insoluble mercuric oxide,sodium bromide isadded to convert the mercuric acetate to the bromide,whichdoes not interfere.Inasmuch as these test methods are based onan acidimetric titration,a suitable correction must be applied ifthe sample is not neutral to phenolphthalein indicator.Takecare to exclude carbon dioxide,which titrates as an acid andgives erroneous results.5.Significance and Use5.1 This test method is suitable for quality control,asspecification tests,and for research.5.2 Side reactions that form unsaturated compounds inpolypropylene oxides produce small amounts of polymers withonly one hydroxyl group per chain.These unsaturated poly-mers lower functionality and molecular weight,while broad-ening the overall molecular-weight distribution.1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.22 on CellularMaterials-Plastics and Elastomers.Current edition approved April 1,2016.Published April 2016.Originallyapproved in 1987.Last previous edition approved in 2010 as D4671-05(2010)1.DOI:10.1520/D4671-16.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.5Sigia,S.and Hanna,J.G.,“Quantitative Organic Analysis via FunctionalGroups,”John Wiley and Sons,New York,1979.*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 States1 6.Interferences6.1 This test method does not apply to compounds in whichthe unsaturation is conjugated with carbonyl,carboxyl,ornitrile groups.Because water presumably hydrolyzes the reac-tion products to form basic mercuric salts,quantitative resultsare obtained only when the system is essentially anhydrous.Acetone in low concentrations does not interfere significantly,although its presence can be detrimental to the end point.Inorganic salts,especially halides,must be absent from thesample because even small amounts of salts can nullify thereactio