1、Designation: D5155 141Standard 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.1NOTEEditorially corrected Eq 2 in January 2016.1. Scope*1.1 These test methods measure the isocyanate c
3、ontent ofaromatic isocyanates used as polyurethane raw materials.1.1.1 Test Method AUnheated toluene-dibutylamine deter-mines 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. Othe
4、risomers, if present, will be included in the determination. Thistest method is also applicable 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
5、 from toluene diisocyanate,methylene di-(4-phenylisocyanate) and polymeric (methylenephenylisocyanate).1.1.3 Test Method CUnheated trichlorobenzene-toluene-dibutylamine determines the amine equivalent and the isocya-nate content of crude or modified isocyanates derived fromtoluene diisocyanate, meth
6、ylene-di-(4-phenylisocyanate) andpolymeric (methylene phenylisocyanate).1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use
7、. 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.NOTE 1Method C of this test method is equivalent to Method B ofISO 14896.2. Referenced Documents2.1 ASTM Standards:2D88
8、3 Terminology Relating to PlasticsD1193 Specification for Reagent WaterE180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals (Withdrawn 2009)3E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test
9、 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 Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 amine equivalentthe weight of sample
10、 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 weight ofNCO groups present in the sample.4. Summary of Test Methods4.1 All three test methods react the isocyanat
11、e 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 the reaction conditions, or solvents used, or both.4.1.1 Test Method AThe sample is added to an excessamount o
12、f dibutylamine in toluene and allowed to stand atroom temperature for 15 min. The reaction mixture is diluted1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.22 on CellularMaterials - Plastics and Elastomers.Current
13、 edition approved Nov. 1, 2014. Published November 2014. Originallyapproved in 1991. Last previous edition approved in 2010 as D5155 - 10. DOI:10.1520/D5155-14.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of
14、 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive,
15、 PO Box C700, West Conshohocken, PA 19428-2959. United States1with isopropyl alcohol, and the excess dibutylamine is back-titrated with hydrochloric 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
16、rapidly to 100C, removedfrom the heat, and allowed to stand for 30 min. The reactionmixture is diluted with isopropyl alcohol, and the excessdibutylamine is back-titrated with hydrochloric acid.4.1.3 Test Method CThe sample is added to an excessamount of dibutylamine in toluene and trichlorobenzene.
17、 Theresulting 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 are to be used for research or forquality control to characterize isocyanates used in
18、 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 that they do not affect thedetermination. While some c
19、rude 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 intended thatall reagents shall conform to the spe
20、cifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades areallowed, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination
21、.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 atmosphericmoisture, take special precautions in sampling. Usual samplingmethods, ev
22、en 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
23、 can cause skin and respiratory sensitization(asthma) in some people. Once sensitized, further exposure todiisocyanates should be eliminated. A combination of engi-neering controls and personal protective equipment, includingrespiratory, skin and eye protection, may be used to preventover-exposure t
24、o diisocyanates. Consult the product suppliersSafety Data Sheet (SDS) for more detailed information aboutpotential health effects and other specific safety and handlinginstructions for the product.)9. Test Conditions9.1 Since isocyanates react with moisture, keep the labora-tory humidity low, prefer
25、ably below 50 % relative humidity.TEST METHOD AUNHEATED TOLUENE-DIBUTYLAMINE10. Apparatus10.1 Any weighing device that weighs a liquid by differenceto the nearest 0.001 g.10.2 Cooling BathAny container approximately 50 mmdeep filled with ice and water.10.3 Pipet capable of reproducibly delivering 50
26、 6 .05 mL.10.4 Buret capable of dispensing 0.05 mL at a time.11. Reagents11.1 Bromocresol Green Indicator SolutionUsing 1.5 mLof 0.1 N sodium hydroxide, extract the bromocresol green from0.100 g of bromocresol green indicator-grade powder, stirringvigorously until the amount of insoluble residue rem
27、ainsconstant. 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 Hydrochloric Acid (1 N)Prepare 1 N HCl (hydro-chloric acid) a
28、nd 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 12.2 12.4, but without adding the sample.12.2 Add a magnet
29、ic 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 dibutylamine solution and mix carefully.4Reagent Chemicals,
30、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 Formu
31、lary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.5The 4A Molecular Sieve, or its equivalent, has been found suitable. The 4AMolecular Sieve is available from VWR International,Inc., 1310 Goshen Parkway,West Chester, PA 19380.6Pipets and burets shall conform to National Institute of Sta
32、ndards andTechnology tolerances, as given in Peffer, E. L., and Mulligan, G. C., “Testing ofGlass Volumetric Apparatus,” NIST Circular C434, 1941, available from theSuperintendent of Documents, U.S. Government Printing Office, Washington, DC20025.D5155 141212.3 While stirring the contents of the fla
33、sk, 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 min.NOTE 2If spattering is anticipated, cool the flask and contents in thecooling
34、 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 isopropyl alcohol and 0.8 mL ofbromocresol green indicator solution. Titrate with 1 N
35、 HClsolution in a 50 or 100-mL buret7while stirring the flaskcontents 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
36、 point is determined using a potentiom-eter and electrodes.When using this apparatus, it occasionally is necessaryto transfer the solution to a 600-mLbeaker prior to titration.After transfer,rinse the Erlenmeyer flask with 25 mL of isopropyl alcohol and add therinse to the 600-mL beaker. To titrate,
37、 immerse the calomel and glasselectrodes or a combination electrode of the pH meter (standardized withpH 4.0 and pH 7.0 standard buffers) and titrate the sample to the break thatoccurs at approximately pH 4.2 to 4.5 with 1.0 N HCl while stirring thesolution with a stirring bar.13. Calculation13.1 Ca
38、lculate the assay as follows:%TDI 5B 2 S!N!87.08!100!1000W!(1)When constants are combined, this equation reduces to:%TDI 5B 2 S!N!8.708!W!(2)13.2 Calculate the amine equivalent as follows:Amine Equivalent 51000W!NB 2 S!(3)13.3 Calculate the percent NCO as follows:%NCO 542.02B 2 S!N!100!1000W!(4)When
39、 constants are combined, this equation reduces to:%NCO 54.202B 2 S!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,1000 = conversion from g to mg
40、, and100 = conversion to percent.14. Precision and Bias814.1 Attempts 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 are not given for this reason. Anyonewis
41、hing to participate in the development of precision and biasdata 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 analys
42、t are to be considered suspect if they differ by0.4 % TDI.14.2.2 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
43、TOLUENE-DIBUTYLAMINE15. Apparatus15.1 Potentiometric Titrator, or 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
44、 range.15.7 Pipet or buret capable of reproducibly delivering 25 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.
45、16.3 Isopropyl Alcohol, 99 % minimum purity.16.4 Toluene, dry, dried 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 equivalen
46、ts of thesample weighed to the nearest 0.001 g. The amount of sampleneeded is calculated from the following equation:weight of sample g! 5105expected% NCO(6)7If an isocyanate monomer other than TDI is used, substitute the equivalentweight of the material being analyzed. The calculated assay result w
47、ill be percent byweight of the monomer used.8Supporting data are available from ASTM Headquarters. Request RR:D20-1089.D5155 1413Start 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
48、.17.3 Place the beaker on a hot 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 a
49、llowit to stand for 30 min.17.4 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 in 17.1 17.5, but without adding the sample.18. Calculation18.1 Calculate the amine equivalent as follows:Amine Equivalent 51000W!NB 2 S!(7)18.2 Calculate the percent NCO as follows:% NCO 542.02B 2 S!N!
