ASTM_D_6099_-_13.pdf

Designation:D609913Standard Test Method forPolyurethane Raw Materials:Determination of Acidity inModerate to High Acidity Aromatic Isocyanates1This standard is issued under the fixed designation D6099;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 determines the acidity,expressed asparts per million(ppm)of HCl,in aromatic isocyanate samplesof greater than 100ppm acidity.The test method is applicableto products derived from toluene diisocyanate and methylene-bis-(4phenylisocyanate)(see Note 1).NOTE1This test method is equivalent to ISO 14898,Test Method A.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Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals(Withdrawn 2009)3E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standards:ISO 14898 PlasticsAromatic isocyanates for use in theproduction of polyurethaneDetermination of acidity43.Terminology3.1 DefinitionsTerms used in this test method are inaccordance with Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 acidity,nthe acid strength of a sample expressed inppm HCl.4.Summary of Test Method4.1 The isocyanate is mixed with an excess of methanol anda cosolvent.Additional acid is released into the solvent systemduring urethane formation.The acid is titrated potentiometri-cally with methanolic KOH,and the acidity present in theisocyanate sample is calculated from the titer.5.Significance and Use5.1 This test method can be used for research or for qualitycontrol to characterize aromatic isocyanates and prepolymersof moderate to high acidity.Acidity correlates with perfor-mance in some polyurethane systems.6.Apparatus6.1 250-mL Beakers.6.2 50-mL Pipet or Repipet,Class A volumetric.6.3 100-mL Pipet or Repipet,Class A volumetric.6.4 Automatic Titration Equipment,capable of inflectiondetection and stirring the sample while,titrating,such as:6.4.1 Commerically-availableAutomaticTitrationApparatus,6.4.2 Reference Electrode,with saturated LiCl/ethanol so-lution in both chambers.6.4.3 pH Glass Electrode,(see Note 2).NOTE2A combination pH electrode with internal reference also maybe used.6.5 Magnetic Stirrer.6.6 Stir Bars.6.7 Watch Glasses.6.8 Analytical Balance,capable of weighing to the nearest 1mg.7.Reagents and Materials7.1 0.02 N KOH in Methanol1.32 g KOH pellets(85%KOH)/1000 mL methanol,standardized with potassium hydro-gen phthalate(KHP).7.2 Toluene or 1,2,4Trichlorobenzene(TCB),dried for 24 hover molecular sieves.7.3 Anhydrous Methanol.8.Sampling8.1 Since organic isocyanates react with atmosphericmoisture,take special precautions in sampling.Usual sampling1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.22 on Cellular Materials-Plastics and Elastomers.Current edition approved Sept.1,2013.Published September 2013.Originallyapproved in 1997.Last previous edition approved in 2008 as D6099-08.DOI:10.1520/D6099-13.2For 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.*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 methods,even when conducted rapidly,can cause contamina-tion of the sample with insoluble urea.Therefore,blanket thesample with dry air or nitrogen at all times.NOTE3Many diisocyanates are known or suspected sensitizers.Over-exposure to diisocyanates can lead to adverse health effects whichmay include the development of occupational asthma and otherrespiratory,skin and eye effects.Engineering controls and/or personalprotective equipment,including respiratory,skin and eye protection,are tobe used when there is a potential for over-exposure to diisocyanates.Theproduct suppliers Material Data Safety Sheet(MSDS)provides moredetailed information about potential adverse health effects and otherimportant safety and handling information.Always follow the specificinstructions provided on the MSDS.9.Calibration9.1 Calibrate the electrodes using pH 4 and pH 7 aqueousbuffers.10.Test Conditions10.1 Since isocyanates react with moisture,keep laboratoryhumidity low,preferably around 50%relative humidity.11.Procedure11.1 All samples shall be done