1、Designation:D609918Standard 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 c
2、ase 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 i
3、socyanate 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.1.2 This international standard was developed in accor-dance wit
4、h 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:2D8
5、83 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Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals(Withdrawn 2009)3E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standards:ISO 14898 Pl
6、asticsAromatic 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 inpp
7、m 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
8、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
9、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-
10、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
11、.32 g KOH pellets(85%KOH)/1000 mL methanol,standardized with potassium hydro-gen phthalate(KHP).1This 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
12、Aug.1,2018.Published August 2018.Originallyapproved in 1997.Last previous edition approved in 2013 as D6099-13.DOI:10.1520/D6099-18.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume informatio
13、n,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
14、 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 Princip
15、les for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 7.2 Toluene or 1,2,4Trichlorobenzene(TCB),dried for 24 hover molecular sieves.7.3 Anhydrous Methanol.8.Sampling8.1 Since organic isocyanates
16、 react with atmosphericmoisture,take special precautions in sampling.Usual samplingmethods,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.(WarningDiisocyanates are eye,skin and respiratory irritants at concen-trations above the occupational exposure limit(TLV or PEL).Diisocyanates can cause skin and respiratory sensitization(asthma)in some people.Once sensitized,it is essential to limitfurth
