1、Designation: D2572 97 (Reapproved 2010)Standard Test Method forIsocyanate Groups in Urethane Materials or Prepolymers1This standard is issued under the fixed designation D2572; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method covers the det
3、ermination of the isocy-anate group (NCO) content of a urethane intermediate orprepolymer.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, assoc
4、iated 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 to use. For specific hazardstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2D841 Specifi
5、cation for Nitration Grade Toluene3. Summary of Test Method3.1 The 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 1Solvent
6、s other than toluene may be needed in some cases, forexample, anhydrous 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,
7、the carbamyl chloride of isocyanate, hydro-gen chloride, or any other 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)
8、covered with alumi-num foil to fit 250-mL Erlenmeyer flasks.6.2 Magnetic 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
9、. Unless otherwiseindicated, it is intended that all reagents shall 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 suff
10、iciently high purity topermit its use without lessening the accuracy 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
11、-butylamine Solution, 0.1 N in dry toluene. Notstandardized.7.4 Hydrochloric Acid Solution, 0.1 N standardized usingbromphenol blue indicator solution.7.5 Isopropyl Alcohol.7.6 Toluene, anhydrous, conforming to Specification D841or equivalent dried with molecular sieve pellets.1This test method is u
12、nder the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.33 on Polymers and Resins.Current edition approved Dec. 1, 2010. Published December 2010. Originallyapproved in 1967. Last previous edition approv
13、ed in 2003 as D2572 97 (2003)1.DOI: 10.1520/D2572-97R10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Bure
14、ts and pipets shall conform to National Institute of Standards andTechnology tolerances.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards
15、for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, 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.8. Hazards8.1
16、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 ofwater
17、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 Erl
18、enmeyerflask.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 Usi
19、ng 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 including
20、all reagents above butomitting the specimen.10. Calculations10.1 Calculate the NCO content as follows:NCO,%5B 2 V! 3 N 3 0.0420W3 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 of
21、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 morethan
22、 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 dicyclohexylmethane-
23、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 diisocyanateAST
24、M 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 en
25、tirely 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 standardsa
26、nd 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 Committee
27、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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D2572 97 (2010)2
