1、Designation: D5155 10Standard Test Methods forPolyurethane Raw Materials: Determination of theIsocyanate Content of Aromatic Isocyanates1This standard is issued under the fixed designation D5155; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、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. Scope1.1 These test methods measure the isocyanate content ofaromatic isocyanates used as polyurethane
3、 raw materials.1.1.1 Test Method AUnheated toluene-dibutylamine de-termines the toluene diisocyanate content, the amine equivalentand the isocyanate content of refined toluene-2,4-diisocyanateand toluene-2,6-diisocyanate, or mixtures of the two. Otherisomers, if present, will be included in the dete
4、rmination. Thistest method may also be applied to other isocyanates of suitablereactivity and solubility.1.1.2 Test Method BHeated toluene-dibutylamine deter-mines the amine equivalent and the isocyanate content of crudeor modified isocyanates derived from toluene diisocyanate,methylene di-(4-phenyl
5、isocyanate) and polymeric (methylenephenylisocyanate).1.1.3 Test Method CUnheated trichlorobenzene-toluene-dibutylamine determines the amine equivalent and the isocy-anate content of crude or modified isocyanates derived fromtoluene diisocyanate, methylene-di-(4-phenylisocyanate) andpolymeric (methy
6、lene phenylisocyanate).1.2 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
7、 to use.NOTE 1Method C of this test method is equivalent to Method B ofISO 14896.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsD1193 Specification for Reagent WaterE180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and
8、Spe-cialty Chemicals3E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standard:ISO 14896 Polyurethane Raw Materials-Determination ofIsocyanate Content3. Terminology3.1 DefinitionsFor definitions of terms that appear in thistest method, refer to
9、Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 amine equivalentthe weight of sample that willcombine with 1.0-g equivalent weight of dibutylamine.3.2.2 assaythe percent by weight of toluene diisocyanatepresent in the sample.3.2.3 isocyanate (NCO) contentthe percent by weig
10、ht ofNCO groups present in the sample.4. Summary of Test Methods4.1 All three test methods react the isocyanate sample withan excess amount of dibutylamine to form the correspondingurea. The NCO content is determined from the amount ofdibutylamine consumed in the reaction. The test methods differin
11、the reaction conditions, or solvents used, or both.4.1.1 Test Method AThe sample is added to an excessamount of dibutylamine in toluene and allowed to stand atroom temperature for 15 min. The reaction mixture is dilutedwith isopropyl alcohol, and the excess dibutylamine is back-titrated with hydroch
12、loric acid.4.1.2 Test Method BThe sample is added to an excessamount of dibutylamine in toluene and stirred for 20 min. Theresulting solution is then heated rapidly to 100C, removedfrom the heat, and allowed to stand for 30 min. The reactionmixture is diluted with isopropyl alcohol, and the excessdi
13、butylamine is back-titrated with hydrochloric acid.4.1.3 Test Method CThe sample is added to an excessamount of dibutylamine in toluene and trichlorobenzene. The1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.22 on
14、 CellularMaterials - Plastics and Elastomers.Current edition approved April 1, 2010. Published June 2010. Originallyapproved in 1991. Last previous edition approved in 2007 as D5155 - 07. DOI:10.1520/D5155-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custom
15、er Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO
16、Box C700, West Conshohocken, PA 19428-2959, United States.resulting solution is allowed to stand until it has cooled to roomtemperature. The reaction mixture is diluted with methanol andback-titrated with hydrochloric acid.5. Significance and Use5.1 These test methods can be used for research or for
17、quality control to characterize isocyanates used in polyurethaneproducts.6. Interferences6.1 Phosgene, the carbamyl chloride of the isocyanate,hydrogen chloride, and any other acidic or basic compoundswill interfere. In refined isocyanates, these impurities areusually present in such low amounts tha
18、t they do not affect thedetermination. While some crude or modified isocyanatescontain acidities of up to approximately 0.05 %, the NCOcontent is not normally corrected.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is
19、 intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use
20、 without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Types I through IV of Specification D1193.8. Sampling8.1 Since organic isocyanates react with atmospheric mois-ture, take speci
21、al 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. (WarningManydiisocyanates are known or suspected sensitizers. Over-exposure to diisocyanates
22、 can lead to adverse health effects,which include the development of occupational asthma andother respiratory, skin, and eye effects. Engineering controlsand/or personal protective equipment, including respiratory,skin, and eye protection, are to be used when there is apotential for over-exposure to
23、 diisocyanates. The productsuppliers Material Data Safety Sheet (MSDS) provides moredetailed information about potential adverse health effects andother important safety and handling information. Alwaysfollow the specific instructions provided on the MSDS.)9. Test Conditions9.1 Since isocyanates rea
24、ct with moisture, keep the labora-tory humidity low, preferably below 50 % relative humidity.TEST METHOD AUNHEATED TOLUENE-DIBUTYLAMINE10. Apparatus10.1 Any weighing device that can weigh a liquid bydifference to the nearest 0.001 g.10.2 Cooling BathAny container approximately 50 mmdeep filled with
25、ice and water.10.3 Pipet capable of reproducibly delivering 50 6 .05 mL.10.4 Buret capable of dispensing 0.05 mL at a time.11. Reagents11.1 Bromcresol Green Indicator SolutionUsing 1.5 mLof 0.1 N sodium hydroxide, extract the bromcresol green from0.100 g of bromcresol green indicator-grade powder, s
26、tirringvigorously until the amount of insoluble residue remainsconstant. Decant the aqueous portion into a 100-mLvolumetricflask and dilute to the mark with water.11.2 Dibutylamine Solution (260 g/L)Dilute 260 g of drydibutylamine to 1 L with dry toluene. Dry the solution with adrying agent.511.3 Hy
27、drochloric Acid (1 N)Prepare 1 N HCl (hydro-chloric acid) and standardize frequently enough to detectchanges of 0.001 N.11.4 Isopropyl Alcohol.11.5 Toluene, dry with a drying agent.512. Procedure12.1 Run sample and blank determinations side by side.Run the blank determination exactly as described in
28、 12.2-12.4,but without adding the sample.12.2 Add a magnetic stirring bar and 40 mL of dry tolueneto a 500-mLErlenmeyer flask that has been rinsed successivelywith water, alcohol, and high-purity acetone, dried at 100C,and allowed to cool in a desiccator.Accurately add, by pipet orburet,650 mL of di
29、butylamine solution and mix carefully.12.3 While stirring the contents of the flask, slowly add 6.5to 7.0 g of the sample weighed to the nearest 0.001 g (Note 2).Wash down the sides of the flask with 10 mL of dry toluene,then stopper the flask loosely and allow it to stand at roomtemperature for 15
30、min.NOTE 2If spattering is anticipated, cool the flask and contents in thecooling bath before adding the sample and continue to cool until the heatof reaction is dissipated. Add 10 mL of dry toluene, stopper the flaskloosely, and allow the contents to come to room temperature.12.4 Add 225 mL of isop
31、ropyl alcohol and 0.8 mL ofbromcresol green indicator solution. Titrate with 1 N HClsolution in a 50 or 100-mL buret7while stirring the flask4Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted b
32、y the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5The 4A Molecular Sieve, or its equivalent, has been found suitable. The 4A
33、Molecular Sieve is available from VWR International,Inc., 1310 Goshen Parkway,West Chester, PA 19380.6Pipets and burets shall conform to National Institute of Standards andTechnology tolerances, as given in Peffer, E. L., and Mulligan, G. C., “Testing ofGlass Volumetric Apparatus,” NIST Circular C43
34、4, 1941, available from theSuperintendent of Documents, U.S. Government Printing Office, Washington, DC20025.7If an isocyanate monomer other than TDI is used, substitute the equivalentweight of the material being analyzed. The calculated assay result will be percent byweight of the monomer used.D515
35、5 102contents with the magnetic stirring bar. Near the end point,slowly add the HCl dropwise. The end point is reached whenthe blue color disappears and a yellow color appears thatpersists for at least 15 s (Note 3).NOTE 3Alternatively, the end point may be determined using apotentiometer and electr
36、odes. When using this apparatus, it may benecessary to transfer the solution to a 600-mL beaker prior to titration.After transfer, rinse the Erlenmeyer flask with 25 mL of isopropyl alcoholand add the rinse to the 600-mL beaker. To titrate, immerse the calomeland glass electrodes or a combination el
37、ectrode of the pH meter(standardized with pH 4.0 and pH 7.0 standard buffers) and titrate thesample to the break that occurs at approximately pH 4.2 to 4.5 with 1.0 NHCl while stirring the solution with a stirring bar.13. Calculation13.1 Calculate the assay as follows:%TDI 5B 2 S!N!87.08!100!1000W!(
38、1)When constants are combined, this equation reduces to:%TDI 5B 2 S!N!87.08!W!(2)13.2 Calculate the amine equivalent as follows:Amine Equivalent 51000W!NB S!(3)13.3 Calculate the percent NCO as follows:%NCO 542.02B S!N!100!1000W!(4)When contants are combined, this equation reduces to:%NCO 54.202B S!
39、N!W!(5)where:B = HCl required for titration of the blank, mL,S = HCl required for titration of the sample, mL,N = normality of the HCl, meq/mL,W = sample used, g,87.08 = equivalent weight of TDI, mg/meq,61000 = conversion from g to mg, and100 = conversion to percent.14. Precision and Bias814.1 Attem
40、pts to develop a precision and bias statement forthis test method have not been successful due to the limitednumber of laboratories participating in round-robin tests. Dataon precision and bias cannot be given for this reason. Anyonewishing to participate in the development of precision and biasdata
41、 are to contact the Chairman, Subcommittee D20.22(Section D20.22.01), ASTM, 100 Barr Harbor Drive, WestConshohocken, PA 19428.14.2 A limited round robin was conducted.14.2.1 It has been estimated that duplicate results by thesame analyst are to be considered suspect if they differ by0.4 % TDI.14.2.2
42、 It has been estimated that results reported by differentlaboratories are to be considered suspect if they differ by 0.8 %TDI.14.3 There are no recognized standards by which to esti-mate the bias of this test method.TEST METHOD BHEATED TOLUENE-DIBUTYLAMINE15. Apparatus15.1 Potentiometric Titrator, o
43、r pH meter.15.2 Calomel Electrode or a combination electrode.15.3 Glass Electrode.15.4 Any weighing device suitable for weighing a liquidsample by difference to the nearest 0.001 g.15.5 Magnetic Stirrer.15.6 Thermometer, from 10 to 100C range.15.7 Pipet or buret capable of reproducibly delivering 25
44、 6.025 mL.16. Reagents16.1 Dibutylamine Solution (260 g/L)Dilute 260 g drydibutylamine to 1 L with dry toluene.16.2 Hydrochloric Acid (1 N)Prepare 1 N hydrochloricacid (HCl) and standardize frequently enough to detect changesof 0.001 N.16.3 Isopropyl Alcohol, 99 % minimum purity.16.4 Toluene, dry, d
45、ried with a drying agent.517. Procedure17.1 Add 50 mL of dry toluene to a dry 600-mL beaker.Pipet 256mL of the dibutylamine solution into the beaker.Swirl the beaker to mix the contents.17.2 Transfer to the beaker 0.02 to 0.03 equivalents of thesample weighed to the nearest 0.001 g. The amount of sa
46、mpleneeded can be calculated from the following equation:weight of sample g! 5105expected % NCO(6)Start the magnetic stirrer carefully and rinse the sides of thebeaker with an additional 10 mL of dry toluene. Cover thebeaker and continue mixing for an additional 20 min.17.3 Place the beaker on a hot
47、 plate with the 10 to 100Cthermometer in the sample. Heat the sample mixture rapidlywith stirring, so that the solution reaches a temperature of 95 to100C in 312 to 412 min. Do not overheat. Quickly remove thebeaker from the hot plate, cover it with a watchglass, and allowit to stand for 30 min.17.4
48、 Cool the beaker and contents to room temperature andadd 225 mL of isopropyl alcohol.17.5 Titrate potentiometrically with 1.0 N HCl to the breakthat occurs at apparent pH approximately 4.2 to 4.5 (for manualtitration see Note 4, below).17.6 Prepare and titrate a blank exactly as described in17.1-17.
49、5, but without adding the sample.18. Calculation18.1 Calculate the amine equivalent as follows:Amine Equivalent 51000W!NB 2 S!(7)8Supporting data are available from ASTM Headquarters. Request RR:D20-1089.D5155 10318.2 Calculate the percent NCO as follows:% NCO 542.02 B 2 S! N! 100!1000W!(8)When constants are combined, this equation reduces to:% NCO 54.202 B 2 S! NW!(9)B = HCl required for titration of blank, mL,S = HCl required for titration of sample, mL,N = normality of HCl, meq/mL,W = sample used, g, and4.202 =
