ASTM_D_4667_-_93.pdf

Designation:D 4667 93An American National StandardStandard Test Method forPolyurethane Raw Materials:Determination of Acidity InToluene Diisocyanate1This standard is issued under the fixed designation D 4667;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 reapproval.1.Scope1.1 This test method determines the acidity of toluene-2,4-diisocyanate and toluene-2,6-diisocyanate or mixtures of thetwo.(See Note 1.)1.2 This standard does not purport to address all of thesafety problems,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.Specific hazardsstatements are given in Note 2.NOTE1There is no equivalent ISO standard.2.Referenced Documents2.1 ASTM Standards:D 883 Terminology Relating to Plastics2D 1193 Specification for Reagent Water33.Terminology3.1 Definitions:For definitions of terms used in this testmethod see Terminology D 883.4.Summary of Test Method4.1 The isocyanates react with excess n-propanol to formurethanes.The acidic components released are titrated poten-tiometrically with methanolic potassium hydroxide.5.Significance and Use5.1 This test method can be used for research or for qualitycontrol to characterize toluene diisocyanates(TDI).Aciditycorrelates with performance in some polyurethane systems.6.Apparatus6.1 Potentiometric Titrator,or pH meter.6.2 Calomel Electrode.6.3 Glass Electrode.6.4 Buret,10-mL,graduated in 0.05-mL divisions.6.5 Volumetric Pipets,10-mL and 100-mL.6.6 Magnetic Stirrer and Stirring Bar.7.Reagents and Materials7.1 Purity of ReagentsUse reagent grade chemicals in alltests.Unless otherwise indicated,it is intended that all reagentsconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society where suchspecifications are available.4Other grade may be used,pro-vided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.7.2 Purity of WaterUnless otherwise indicated,referencesto water shall be understood to mean reagent water as definedby Type I of Specification D 1193.7.3 Hydrochloric Acid(HCl),(0.01 N)Standardize fre-quently enough to detect changes of 0.0005 N.7.4 n-propanol.57.5 Potassium Hydroxide(KOH),Methanolic Solution(0.01N)Standardize frequently enough to detect changes of0.0005 N.8.Sampling8.1 Since organic isocyanates react with atmospheric mois-ture,take special precautions in sampling(Warning:PrecautionNote 2).Usual sampling methods(for example,sampling an open drum with a thief),even when carried outrapidly,can cause contamination of the sample with insolubleurea.Therefore,blanket the sample with dry air or nitrogen atall times.NOTE2Warning:Organic isocyanates are toxic when they are ab-sorbed through the skin,or when the vapors are breathed.PrecautionProvide adequate ventilation and wear protective gloves and eyeglasses.9.Test Conditions9.1 Since isocyanates react with moisture,keep laboratoryhumidity low,preferably around 50%relative humidity.1This test method is under the jurisdiction of ASTM Committee D20 onPlastics and is the direct responsibility of Subcommittee D 20.22 on CellularPlastics.Current edition approved June 15,1993.Published August 1993.Originallypublished as D 4667 87.Last previous edition D 4667 87e1.2Annual Book of ASTM Standards,Vol 08.01.3Annual Book of ASTM Standards,Vol 11.01.4Reagent Chemicals,American Chemical Society Specifications,AmericanChemical Society,Washington,DC.For suggestions on the testing of reagents notlisted by the American Chemical Society,see Analar Standards for LaboratoryChemicals,BDH Ltd.,Poole,Dorset,U.K.,and the United States Pharmacopeiaand National Formulary,U.S.Pharmaceutical Convention,Inc.(USPC),Rockville,MD.5Kodak Chemicals No.848 or its equivalent are satisfactory for this purpose.Kodak Chemicals No.848 are available from Kodak Laboratory and ResearchProducts,Eastman Kodak Company,343 State Street,Rochester,NY 14650.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTMNOTICE:This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM International(www.astm.org)for the latest information.10.Procedure10.1 Pipet 100 mL of n-propanol into clean 250-mL beakercontaining a stirring bar.With stirring,add by pipet 10 mL ofTDI sample(Note 3).Cover the beaker with a watch glass andstir for exactly 10 min.NOTE3If the acidity of the sample is less than 0.005%HCl,use a20-mL sample and 200 mL of npropanol.10.2 Titrate the solution potentiometrically with 0.01 Nmethanolic KOH sol