1、Designation: D 2572 97 (Reapproved 2003)e1Standard Test Method forIsocyanate Groups in Urethane Materials or Prepolymers1This standard is issued under the fixed designation D 2572; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e 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.This standard has been approved for use by agencies of the Department of Defense.e1NOTEKeywords were added editorially
3、in July 2003.1. Scope1.1 This test method covers the determination of the isocy-anate group (NCO) content of a urethane intermediate orprepolymer.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 stan
4、dard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:D 841 Specification for Nitration Grade Toluene23. Summary of Test Method3.1 The
5、urethane prepolymer is allowed to react with anexcess of di-n-butylamine in toluene (Note 1). After thereaction is complete, the excess of di-n-butylamine is deter-mined by back titration with standard hydrochloric acid.NOTE 1Solvents other than toluene may be needed in some cases, forexample, anhyd
6、rous dimethylformamide (DMF), but the procedure hasnot been evaluated using them.4. Significance and Use4.1 The percent NCO is used to establish unit ratios forstoichiometric reactions with co-reactants.5. Interferences5.1 Phosgene, the carbamyl chloride of isocyanate, hydro-gen chloride, or any oth
7、er acidic or basic impurities ofsufficient strength will interfere. The concentration of thesecompounds is usually sufficiently low that their effect on thedetermination is negligible.6. Apparatus6.1 Polyethylene Stoppers (or corks) covered with alumi-num foil to fit 250-mL Erlenmeyer flasks.6.2 Mag
8、netic Stirrer with PTFE-fluorocarbon-covered stir-ring bar.6.3 Pipet,325-mL.6.4 Buret,350- or 100-mL.6.5 Analytical Balance.7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests unless otherwise specified. Unless otherwiseindicated, it is intended that all reagents shall
9、 conform to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Society, where such specifications areavailable.4Other grades may be used, provided that it is firstascertained that the reagent is of sufficiently high purity topermit its use without lessening the accurac
10、y of the determi-nation.7.2 Bromphenol Blue Indicator, Prepare 0.1 % solution bymixing 0.10 g of acid, nonwater soluble bromphenol blue with1.5 mL of 0.1 N sodium hydroxide solution and diluting to 100mL with distilled water.7.3 Di-n-butylamine Solution, 0.1 N in dry toluene. Notstandardized.7.4 Hyd
11、rochloric Acid Solution, 0.1 N standardized usingbromphenol blue indicator solution.7.5 Isopropyl Alcohol.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.33 on Polymers and
12、 Resins.Current edition approved July 10, 2003. Published July 2003. Originallyapproved in 1967. Last previous edition approved in 1997 as D 2572 97.2Annual Book of ASTM Standards, Vol 06.04.3Burets and pipets shall conform to National Institute of Standards andTechnology tolerances.4Reagent Chemica
13、ls, 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 F
14、ormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7.6 Toluene, anhydrous, conforming to Specification D 841or equivalent dried with molecular sieve pellets.8. Hazards8.
15、1 Diisocyanates are strong skin irritants and sensitizers.They are also hazardous to the lungs. (TLV for toluene 2,4-diisocyanate is 0.005 ppm.) Avoid contact with skin, eyes, andclothing, and avoid breathing these substances. Use withadequate ventilation. In case of contact, wash with plenty ofwate
16、r and flush eyes for 15 min. Call a physician before reuse.See Suppliers Material Safety Data Sheet for additionalinformation.9. Procedure9.1 Weigh to 0.1 g a specimen containing approximately 1.1milliequivalents of NCO (for example, 1.0 g of prepolymercontaining approximately 5 % NCO) in a 250-mL E
17、rlenmeyerflask.9.2 Add 25 mL of dry toluene (Note 2), place a stopper inthe flask, and swirl by hand or on a mechanical agitator todissolve the prepolymer. Solution may be aided by warming ona hot plate.NOTE 2If the polymer is insoluble, add 10 mL of dry, analytical gradeacetone to the toluene.9.3 U
18、sing a pipet, add 25.00 mL of 0.1 N di-n-butylaminesolution and continue swirling for 15 min with stopper in place.9.4 Add 100 mL of isopropyl alcohol and 4 to 6 drops ofbromphenol blue indicator solution. Titrate with 0.1 N hydro-chloric acid to a yellow end point.9.5 Run a blank titration includin
19、g all reagents above butomitting the specimen.10. Calculations10.1 Calculate the NCO content as follows:NCO,%5B 2 V! 3 N 3 0.0420#W3 100 (1)where:B = volume of HCl for titration of the blank, mL,V = volume of HCl for titration of the specimen, mL,N = normality of HCl,0.0420 = milliequivalent weight
20、of the NCO group, andW = grams of specimen weight, g.11. Precision and Bias11.1 The following criteria should be used for judging theacceptability of results at the 95 % confidence level:11.1.1 RepeatabilityTwo results obtained by the sameoperator should be considered suspect if they differ by moret
21、han 0.11 % absolute NCO.11.1.2 ReproducibilityTwo results obtained by operatorsin different laboratories should be considered suspect if theydiffer by more than 0.4 % absolute NCO.11.2 BiasNo bias can be determined for this test methodsince no standard resin exists.12. Keywords12.1 dicyclohexylmetha
22、ne-4,4-diisocyanate (rMDI); hex-amethylene diisocyanate; isophorone diisocyanate (IPDI);polymeric MDI; toluene, 2,4-diisocyanate based intermediate;toluene, 2,4-diisocyanate based prepolymer; urethane interme-diate; urethane prepolymer;2,4-diphenylmethanediisocyanate;4,4-diphenylmethane diisocyanate
23、ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are
24、 entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standar
25、dsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committ
26、ee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 2572 97 (2003)e12
