1、Designation:D552315Standard Test Method forPolyurethane Raw Materials:Acidity by ArgentometricDetermination of Hydrolyzable Chlorine in Monomeric,Aromatic Isocyanates1This standard is issued under the fixed designation D5523;the number immediately following the designation indicates the year oforigi
2、nal 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 the hydrolyzable chlorinecontent of monomeri
3、c,aromatic isocyanates used as polyure-thane raw materials and expresses it as HCl acidity.The testmethod is applicable to toluene diisocyanate(TDI)and mono-meric methylene di(phenylisocyanate),known as MDI.Themain sources of hydrolyzable chlorine and,therefore,acidity inmonomeric aromatic isocyanat
4、es are carbamyl chlorides,acidchlorides,and dissolved phosgene.All of these compoundsreact with alcohols and water to form hydrochloric acid.1.2 This test method applies only to monomeric isocyanatesin which all of the acidity is derived from species that generateHCl on solvolysis.1.3 The values sta
5、ted in SI units are to be regarded as thestandard.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 regu
6、latory limitations prior to use.NOTE1There is no known ISO equivalent to this standard.2.Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to Plastics3.Terminology3.1 DefinitionsFor definitions of terms used in this testmethod,see Terminology D883.3.2 Definitions of Terms Specific to
7、 This Standard:3.2.1 aciditythe acid strength of a sample expressed asparts per million hydrochloric acid(HCl)present.3.2.2 hydrolyzable chlorinethe amount of chlorine re-leased as chloride ion under the conditions of the test,expressed as parts per million chlorine.4.Summary of Test Method4.1 The s
8、ample reacts with 2-propanol to form urethanesand hydrochloric acid,which is liberated from the labilecarbamyl chlorides,acid chlorides,and dissolved phosgene.The chlorides of the liberated acid are then determinedpotentiometrically using standard methanolic silver nitratesolution and calculated as
9、parts per million HCl.5.Significance and Use5.1 This test method is suitable for research or for qualitycontrol to characterize TDI and MDI.5.2 This test method was developed to overcome problemswith low-level acidity determinations that use glass electrodesin the presence of reagent alcohol solvent
10、s.Reagent alcoholscontain acidic and basic species,which complicate the glasselectrode methods at low levels of acidity.6.Interferences6.1 Acidic species that do not generate chloride ions underthe conditions of this test method will not be determinedbecause acidity is determined indirectly from the
11、 chloride ionconcentration.6.2 Acidic species that do not produce chloride ions areexpected to be negligible at low levels of acidity and for themonomeric isocyanates in this test method.6.3 Care must be taken to avoid chloride contamination ofglassware and sample containers.7.Apparatus7.1 Potentiom
12、etric Titrator.7.2 Combination Silver Billet Electrode(Note 2).7.3 Oven,70C(Note 3).7.4 Magnetic Stirrer.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
13、approved April 1,2015.Published May 2015.Originallyapproved in 1994.Last previous edition approved in 2010 as D5523-10.DOI:10.1520/D5523-15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume in
14、formation,refer to the standards Document Summary page onthe ASTM website.*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 NOTE2The combination silver billet electrode is to
15、be stored in 0.01N methanolic silver nitrate solution in order to keep the electrodeconditioned properly.The use of chloride containing solutions must beavoided during storage and maintenance of the apparatus.NOTE3Monomeric MDI samples can be solid when received in thelaboratory.An oven is to be use
16、d to melt the sample prior to beginning thetest procedure.8.Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.3Other grades can be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the
