1、Designation: D5155 10D5155 14Standard 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 t
2、he 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 Scope*1.1 These test methods measure the isocyanate content of aromatic isocyanates used
3、 as polyurethane raw materials.1.1.1 Test Method AUnheated toluene-dibutylamine determines the toluene diisocyanate content, the amine equivalent and theisocyanate content of refined toluene-2,4-diisocyanate and toluene-2,6-diisocyanate, or mixtures of the two. Other isomers, ifpresent, will be incl
4、uded in the determination. This test method mayis also be applied applicable to other isocyanates of suitablereactivity and solubility.1.1.2 Test Method BHeated toluene-dibutylamine determines the amine equivalent and the isocyanate content of crude ormodified isocyanates derived from toluene diisoc
5、yanate, methylene di-(4-phenylisocyanate) and polymeric (methylene phenyli-socyanate).1.1.3 Test Method CUnheated trichlorobenzene-toluene-dibutylamine determines the amine equivalent and the isocyanatecontent of crude or modified isocyanates derived from toluene diisocyanate, methylene-di-(4-phenyl
6、isocyanate) and polymeric(methylene phenylisocyanate).1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the res
7、ponsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.NOTE 1Method C of this test method is equivalent to Method B of ISO 14896.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Rel
8、ating to PlasticsD1193 Specification for Reagent WaterE180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals(Withdrawn 2009)3E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method2.2 ISO St
9、andard:ISO 14896 Polyurethane Raw Materials-Determination of Isocyanate Content3. Terminology3.1 DefinitionsFor definitions of terms that appear in this test method, refer to Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 amine equivalentthe weight of sample that will comb
10、ine with 1.0-g equivalent weight of dibutylamine.3.2.2 assaythe percent by weight of toluene diisocyanate present in the sample.3.2.3 isocyanate (NCO) contentthe percent by weight of NCO groups present in the sample.1 These test methods are under the jurisdiction of ASTM Committee D20 on Plastics an
11、d are the direct responsibility of Subcommittee D20.22 on Cellular Materials -Plastics and Elastomers.Current edition approved April 1, 2010Nov. 1, 2014. Published June 2010November 2014. Originally approved in 1991. Last previous edition approved in 20072010 asD5155 - 07.D5155 - 10. DOI: 10.1520/D5
12、155-10.10.1520/D5155-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this h
13、istorical standard is referenced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurat
14、ely, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Dr
15、ive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Summary of Test Methods4.1 All three test methods react the isocyanate sample with an excess amount of dibutylamine to form the corresponding urea.The NCO content is determined from the amount of dibutylamine consumed in the reacti
16、on. The test methods differ in the reactionconditions, or solvents used, or both.4.1.1 Test Method AThe sample is added to an excess amount of dibutylamine in toluene and allowed to stand at roomtemperature for 15 min. The reaction mixture is diluted with isopropyl alcohol, and the excess dibutylami
17、ne is back-titrated withhydrochloric acid.4.1.2 Test Method BThe sample is added to an excess amount of dibutylamine in toluene and stirred for 20 min. The resultingsolution is then heated rapidly to 100C, removed from the heat, and allowed to stand for 30 min. The reaction mixture is dilutedwith is
18、opropyl alcohol, and the excess dibutylamine is back-titrated with hydrochloric acid.4.1.3 Test Method CThe sample is added to an excess amount of dibutylamine in toluene and trichlorobenzene. The resultingsolution is allowed to stand until it has cooled to room temperature. The reaction mixture is
19、diluted with methanol and back-titratedwith hydrochloric acid.5. Significance and Use5.1 These test methods can are to be used for research or for quality control to characterize isocyanates used in polyurethaneproducts.6. Interferences6.1 Phosgene, the carbamyl chloride of the isocyanate, hydrogen
20、chloride, and any other acidic or basic compounds willinterfere. In refined isocyanates, these impurities are usually present in such low amounts that they do not affect the determination.While some crude or modified isocyanates contain acidities of up to approximately 0.05 %, the NCO content is not
21、 normallycorrected.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, wheresuch sp
22、ecifications are available.4 Other grades may be used, are allowed, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening the accuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, references to water shall be unders
23、tood to mean reagent water as defined byTypes I through IV of Specification D1193.8. Sampling8.1 Since organic isocyanates react with atmospheric moisture, take special precautions in sampling. Usual sampling methods,even when conducted rapidly, can cause contamination of the sample with insoluble u
24、rea. Therefore, blanket the sample with dryair or nitrogen at all times. (WarningMany diisocyanates are known or suspected sensitizers. Over-exposure to diisocyanatescan lead to adverse health effects, which include the development of occupational asthma and other respiratory, skin, and eyeeffects.
25、Engineering controls and/orDiisocyanates are eye, skin and respiratory irritants at concentrations above the occupationalexposure limit (TLV or PEL). Diisocyanates can cause skin and respiratory sensitization (asthma) in some people. Once sensitized,further exposure to diisocyanates should be elimin
26、ated.Acombination of engineering controls and personal protective equipment,including respiratory, skin,skin and eye protection, are to be used when there is a potential for may be used to preventover-exposure to diisocyanates. The product suppliers Material Data Safety Sheet (MSDS) providesConsult
27、the product suppliersSafety Data Sheet (SDS) for more detailed information about potential adverse health effects and other importantspecific safetyand handling information. Always follow the specific instructions provided on the MSDS.instructions for the product.)9. Test Conditions9.1 Since isocyan
28、ates react with moisture, keep the laboratory humidity low, preferably below 50 % relative humidity.TEST METHOD AUNHEATED TOLUENE-DIBUTYLAMINE10. Apparatus10.1 Any weighing device that can weigh weighs a liquid by difference to the nearest 0.001 g.10.2 Cooling BathAny container approximately 50 mm d
29、eep filled with ice and water.4 Reagent Chemicals, American Chemical Society Specifications, , American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K
30、., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.D5155 14210.3 Pipet capable of reproducibly delivering 50 6 .05 mL.10.4 Buret capable of dispensing 0.05 mL at a time.11. Reagents11.1 BromcresolBromocresol Green Indicator Solution
31、Using 1.5 mL of 0.1 N sodium hydroxide, extract the bromcresolbro-mocresol green from 0.100 g of bromcresolbromocresol green indicator-grade powder, stirring vigorously until the amount ofinsoluble residue remains constant. Decant the aqueous portion into a 100-mL volumetric flask and dilute to the
32、mark with water.11.2 Dibutylamine Solution (260 g/L)Dilute 260 g of dry dibutylamine to 1 Lwith dry toluene. Dry the solution with a dryingagent.511.3 Hydrochloric Acid (1 N)Prepare 1 N HCl (hydrochloric acid) and standardize frequently enough to detect changes of0.001 N.11.4 Isopropyl Alcohol.11.5
33、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, butwithout adding the sample.12.2 Add a magnetic stirring bar and 40 mL of dry toluene to a 500-mL Erlenmeyer flask that has been rinse
34、d successively withwater, alcohol, and high-purity acetone, dried at 100C, and allowed to cool in a desiccator. Accurately add, by pipet or buret,650 mL of dibutylamine solution and mix carefully.12.3 While stirring the contents of the flask, slowly add 6.5 to 7.0 g of the sample weighed to the near
35、est 0.001 g (Note 2). Washdown the sides of the flask with 10 mL of dry toluene, then stopper the flask loosely and allow it to stand at room temperaturefor 15 min.NOTE 2If spattering is anticipated, cool the flask and contents in the cooling bath before adding the sample and continue to cool until
36、the heat ofreaction is dissipated. Add 10 mL of dry toluene, stopper the flask loosely, and allow the contents to come to room temperature.12.4 Add 225 mL of isopropyl alcohol and 0.8 mL of bromcresolbromocresol green indicator solution. Titrate with 1 N HClsolution in a 50 or 100-mL buret7 while st
37、irring the flask contents with the magnetic stirring bar. Near the end point, slowly addthe HCl dropwise. The end point is reached when the blue color disappears and a yellow color appears that persists for at least15 s (Note 3).NOTE 3Alternatively, the end point may be is determined using a potenti
38、ometer and electrodes. When using this apparatus, it may beoccasionallyis necessary to transfer the solution to a 600-mL beaker prior to titration. After transfer, rinse the Erlenmeyer flask with 25 mL of isopropyl alcohol andadd the rinse to the 600-mL beaker. To titrate, immerse the calomel and gl
39、ass electrodes 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 that occurs at approximately pH 4.2 to 4.5 with 1.0 N HCl while stirring the solutionwith a stirring bar.13. Calculation13.1 Calculate the assay as foll
40、ows:%TDI5B 2S!N!87.08!100!1000W! (1)When constants are combined, this equation reduces to:%TDI5B 2S!N!87.08!W! (2)13.2 Calculate the amine equivalent as follows:Amine Equivalent5 1000W!NB2S! (3)13.3 Calculate the percent NCO as follows:5 The 4A Molecular Sieve, or its equivalent, has been found suit
41、able. The 4A Molecular Sieve is available from VWR International,Inc., 1310 Goshen Parkway, WestChester, PA 19380.6 Pipets and burets shall conform to National Institute of Standards and Technology tolerances, as given in Peffer, E. L., and Mulligan, G. C., “Testing of Glass VolumetricApparatus,” NI
42、ST Circular C434, 1941, available from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20025.7 If an isocyanate monomer other than TDI is used, substitute the equivalent weight of the material being analyzed. The calculated assay result will be percent by weightof th
43、e monomer used.D5155 143%NCO542.02B 2S!N!100!1000W! (4)When contantsconstants are combined, this equation reduces to:%NCO54.202B 2S!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
44、 = equivalent weight of TDI, mg/meq,687.08 = equivalent weight of TDI, mg/meq,1000 = conversion from g to mg, and100 = conversion to percent.14. Precision and Bias814.1 Attempts to develop a precision and bias statement for this test method have not been successful due to the limited numberof labora
45、tories participating in round-robin tests. Data on precision and bias cannot beare not given for this reason.Anyone wishingto participate in the development of precision and bias data are to contact the Chairman, Subcommittee D20.22 (SectionD20.22.01), ASTM, 100 Barr Harbor Drive, West Conshohocken,
46、 PA 19428.14.2 A limited round robin was conducted.14.2.1 It has been estimated that duplicate results by the same analyst are to be considered suspect if they differ by 0.4 % TDI.14.2.2 It has been estimated that results reported by different laboratories are to be considered suspect if they differ
47、 by 0.8 %TDI.14.3 There are no recognized standards by which to estimate 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 suitabl
48、e for weighing a liquid sample 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 6 .025 mL.16. Reagents16.1 Dibutylamine Solution (260 g/L)Dilute 260 g dry dibutylamine to 1 L with dry toluene.
49、16.2 Hydrochloric Acid (1 N)Prepare 1 N hydrochloric acid (HCl) and standardize frequently enough to detect changes of0.001 N.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 256 mL of the dibutylamine solution into the beaker. Swirl thebeaker to mix the contents.17.2 Transfer to the beaker 0.02 to 0.03 equivalents of the sample weighed to the nearest 0.001 g. The amount of sample neededcan be is calculated from the fo
