1、Designation: D 5155 07Standard Test Methods forPolyurethane Raw Materials: Determination of theIsocyanate Content of Aromatic Isocyanates1This standard is issued under the fixed designation D 5155; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 These test methods measure the isocyanate content ofaromatic isocyanates used as polyuret
3、hane raw materials.1.1.1 Test Method AUnheated toluene-dibutylamine de-termines the amount of toluene diisocyanate in refined toluene-2,4-diisocyanate and toluene-2,6-diisocyanate, or mixtures ofthe two. Other isomers, if present, will be included in thedetermination. This test method may also be ap
4、plied to otherisocyanates of suitable reactivity and solubility.1.1.2 Test Method BHeated toluene-dibutylamine deter-mines the amine equivalent of crude or modified isocyanatesderived from toluene diisocyanate, methylenebis-(4-phenylisocyanate), and polymethylene polyphenylisocyanate.1.1.3 Test Meth
5、od CUnheated trichlorobenzene-toluene-dibutylamine determines the isocyanate content of crude ormodified isocyanates derived from toluene diisocyanate,methylene-bis-(4-phenylisocyanate), and polymethylenepolyphenylisocyanate. This test method can also be used toassay isomer mixtures of toluene diiso
6、cyanate and methylene-bis-(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 regula
7、tory limitations prior to use. For specificwarning and precautionary statements, see Note 2.NOTE 1Method C of this test method is equivalent to Method B ofISO 14896.2. Referenced Documents2.1 ASTM Standards:2D 883 Terminology Relating to PlasticsD 1193 Specification for Reagent WaterE 180 Practice f
8、or Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals2.2 ISO Standard:ISO 14896 Polyurethane Raw Materials-Determination ofIsocyanate Content3. Terminology3.1 Definitions:3.1.1 polyurethanea polymer prepared by the reaction ofan organic diisocyan
9、ate or polyisocyanate with compoundscontaining hydroxyl groups.3.1.1.1 DiscussionPolyurethanes or urethanes, as they aresometimes called, may be thermosetting, thermoplastic, rigidor soft and flexible, or cellular or solid (see TerminologyD 883).3.2 Definitions of Terms Specific to This Standard:3.2
10、.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 weight percent of theNCO groups present in the sample.4. Summary of Test Methods4.1 Al
11、l three test methods react the isocyanate sample withan excess of dibutylamine to form the corresponding urea. TheNCO content is determined from the amount of dibutylamineconsumed in the reaction. Each test method varies solvent orheating times to yield accurate assays of the sample inquestion.4.1.1
12、 Test Method AThe sample is added to an excess ofdibutylamine in toluene and allowed to stand at room tempera-ture for 15 min. The reaction mixture is diluted with isopropylalcohol, and the excess dibutylamine is back-titrated withhydrochloric acid.4.1.2 Test Method BThe sample is added to an excess
13、 ofdibutylamine in toluene and stirred for 20 min. The resultingsolution is then heated rapidly to 100C, removed from theheat, and allowed to stand for 30 min. The reaction mixture isdiluted with isopropyl alcohol, and the excess dibutylamine isback-titrated with hydrochloric acid.1These test method
14、s are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.22 on CellularMaterials - Plastics and Elastomers. These test methods were recommended toASTM by the Society of the Plastics Industry Polyurethane Raw MaterialsAnalysisCommittee.Curren
15、t edition approved April 1, 2007. Published April 2007. Originallyapproved in 1991. Last previous edition approved in 2001 as D 5155 - 01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
16、information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.1.3 Test Method CThe sample is added to
17、a solution ofdibutylamine in toluene and trichlorobenzene. The resultingsolution 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
18、 forquality 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
19、 that 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, i
20、t is 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.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its
21、 use 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 D 1193.8. Sampling8.1 Since organic isocyanates react with atmospheric mois-ture to for
22、m ureas, take special precautions in sampling (seeNote 2). Usual sampling methods (for example, sampling anopen drum with a thief), even when conducted rapidly, cancause contamination of the sample with insoluble urea. There-fore, blanket the sample with dry air or nitrogen at all times.NOTE 2Warnin
23、g: Organic isocyanates are toxic when absorbedthrough the skin, or when the vapors are breathed. Precaution: Provideadequate ventilation and wear protective gloves and eyeglasses.9. Test Conditions9.1 Since isocyanates react with moisture, keep the labora-tory humidity low, preferably below 50 % rel
24、ative 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 ice and water.10.3 Pipet capable of reproducibly delivering 50 6 .05 mL.11. Re
25、agents11.1 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, stirringvigorously until the amount of insoluble residue remainsconstant. Decant the aqueous portion into a 100-mLvolumetricflask
26、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.411.3 Hydrochloric Acid (1 N)Prepare 1 N HCl (hydro-chloric acid) and standardize frequently enough to detectchanges of 0.001 N.11.4 Isop
27、ropyl Alcohol.11.5 Toluene, dry with a drying agent.412. Procedure12.1 Run sample and blank determinations side by side.Run the blank determination exactly as described as follows,but without adding the sample.12.2 Add a magnetic stirring bar and 40 mL of dry tolueneto a 500-mLErlenmeyer flask that
28、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,550 mL of dibutylamine solution and mix carefully.12.3 While stirring the contents of the flask, slowly add 6.5to 7.0 g of the sample weighed t
29、o the nearest 0.001 g (Note 3).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 3If spattering is anticipated, cool the flask and contents in thecooling bath before adding the sample and continue to coo
30、l 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 ofbromcresol green indicator solution. Titrate with 1 N HClsolution in a 50 or 100-mL buret6while stirring
31、 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 4).NOTE 4Alternatively, the end point may be determined using apotentiometer and e
32、lectrodes. When using this apparatus, it may benecessary to transfer the solution to a 600-mL beaker prior to titration.3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemic
33、al 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.4The 4A Molecular Sieve, or its equivalent, has been found suitable. The 4AMolecular Sieve is av
34、ailable from VWR International,Inc., 1310 Goshen Parkway,West Chester, PA 19380.5Pipets 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 C 434 , 1941, available
35、from theSuperintendent of Documents, U.S. Government Printing Office, Washington, DC20025.6If an isocyanate other than TDI is used, substitute the equivalent weight of thematerial being analyzed.D5155072After transfer, rinse the Erlenmeyer flask with 25 mL of isopropyl alcoholand add the rinse to th
36、e 600-mL beaker. To titrate, immerse the calomeland glass electrodes of the pH meter (standardized with pH 4.0 and pH 7.0standard buffers) and titrate the sample to the break that occurs atapproximately pH 4.2 to 4.5 with 1.0 N HCl while stirring the solutionwith a stirring bar.13. Calculation13.1 C
37、alculate the assay, %, as follows:Assay 5 B 2 S!N!87.08!100!/1000 W (1)When constants are combined, this equation reduces toAssay 5 8.708 B 2 S!N/W (2)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 us
38、ed, g,87.08 = equivalent weight of TDI, mg/meq,101000 = conversion from g to mg, and100 = conversion to percent.14. Precision and Bias714.1 Attempts to develop a precision and bias statement forthis test method have not been successful due to the limitednumber of laboratories participating in round-
39、robin tests. Dataon precision and bias cannot be given for this reason. Anyonewishing 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 wa
40、s 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 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
41、standards by which to esti-mate the bias of this test method.TEST METHOD BHEATED 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 differen
42、ce to the nearest 0.001 g.15.5 Magnetic Stirrer.15.6 Thermometer, from 10 to 100C range.15.7 Pipet capable of reproducibly delivering 25 6 .025mL.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 hydrochlorica
43、cid (HCl) and standardize frequently enough to detect changesof 0.001 N.16.3 Isopropyl Alcohol, 99 % minimum purity.16.4 Toluene, dry, dried with a drying agent.417. Procedure17.1 Add 50 mL of dry toluene to a dry 600-mL beaker.Pipet 255mL of the dibutylamine solution into the beaker.Swirl the beake
44、r 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 sampleneeded can be calculated from the following equation:weight of sample g! 5 105/expected % NCO (3)Start the magnetic stirrer carefully and rinse the sides of the
45、beaker 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 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
46、 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 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 ap
47、parent pH approximately 4.2 to 4.5 (for manualtitration see Note 5, below).17.6 Prepare and titrate a blank exactly as described in17.1-17.5, but without adding the sample.18. Calculation18.1 Calculate the amine equivalent as follows:amine equivalent 51000W!NB 2 S!(4)18.2 Calculate the percent NCO a
48、s follows:% NCO 5 42.02 B 2 S! N! 100! / 1000 W! (5)When constants are combined, this equation reduces to:% NCO 5 4.202 B 2 S! N / W (6)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, and7Supporting data are av
49、ailable from ASTM Headquarters. Request RR:D20-1089.D51550734.202 = constant combining the equivalent weight of NCO(42.02) mg/meq, conversion of g to 1000 mg, andconversion to 100%19. Precision and Bias819.1 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 cannot be given for this reason. Anyonewishing to participate in the development of precision and biasdata are to contact the Chairman,
