1、Designation: D7252 06 (Reapproved 2011)1Standard Test Method forPolyurethane Raw Materials: Determination of Monomer andIsomers in Isocyanates1This standard is issued under the fixed designation D7252; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 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.1NOTEReapproved with editorial changes in September 2011.1. Scope1.1 This test method determines th
3、e percent by weight ofmonomeric isomers and total monomer in crude or modifiedisocyanates. The test method is applicable to methylene di(phe-nylisocyanate) (MDI) and polymeric (meththylene phenyliso-cyanate) (PMDI). (See Note 1.)1.2 This standard does not purport to address all of thesafety concerns
4、, 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 regulatory limitations prior to use.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1 AST
5、M Standards:2D883 Terminology Relating to PlasticsE682 Practice for Liquid Chromatography Terms and Rela-tionshipsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 For definitions of terms used in these test methods seeTerminology D883.
6、4. Summary of Test Method4.1 The sample is reacted (derivatized) with methanol toform a mixture of methyl urethanes. The urethanes mixture isthen separated by normal phase high performance liquidchromatography (HPLC). The separated, derivatized isomersare quantified through the use of an internal st
7、andard.5. Significance and Use5.1 This test method can be used for research or for qualitycontrol to characterize isocyanates used in polyurethane prod-ucts.6. Apparatus6.1 High Performance Liquid Chromatograph, consistingof:6.1.1 Binary (or greater) solvent pump, capable of main-taining a pulse-fre
8、e flow rate of 1-3 millilitres per minute6.1.2 Sample injector, automatic or manual, capable ofreproducibly injecting a 2 microlitre volume6.1.3 Column heater, capable of maintaining a temperatureof 30 6 0.2C6.1.4 UV detector, capable of measurements at 235 nm.6.1.5 Chart recorder or Data system, ca
9、pable of peak areaintegration.6.2 HPLC analytical column, 250 mm by 4.6 mm by 5 mcyano stationary phaseNOTE 2Other chromatographic columns can be used provided it isascertained that similar chromatographic performance is obtained.6.3 Magnetic Stirring Hotplate.7. Reagents and Materials7.1 Purity of
10、ReagentsReagent-grade chemicals are to beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society, wheresuch specifications are available. Other grades can be used,provided it
11、is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.7.1.1 Acetanilide, 99.9 % purity, to be used as an internalstandard.7.1.2 Acetonitrile, dry. Dry this and reagents below overmolecular sieve for twenty-four hours.
12、1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.22 on Cellular Materials -Plastics and Elastomers.Current edition approved Sept. 1, 2011. Published October 2011. Originallyapproved in 2006. Last previous edition approv
13、ed in 2006 as D7252 - 06.DOI:10.1520/D7252-06R11E01.2For 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.1Copyrigh
14、t ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7.1.3 Ethanol, dry. Use of ethanol denatured with methanol(such as SDA-30) can be used if more readily available.7.1.4 Hexane, dry.7.1.5 Methanol, dry.7.1.6 Eluent solution, Mix 1:1 by volume of
15、 dry methanoland ethanol.7.1.7 Derivatization solution, Dissolve 0.20 g of acetanilidein 1 L of dry methanol.8. Sampling8.1 Since organic isocyanates react with atmospheric mois-ture, take special precautions in sampling. Usual samplingmethods, even when conducted rapidly, can cause contamina-tion o
16、f the sample with insoluble urea. Therefore, blanket thesample with dry air or nitrogen at all times. (WarningManydiisocyanates are known or suspected sensitizers. Over-exposure to diisocyanates can lead to adverse health effectswhich include the development of occupational asthma andother respirato
17、ry, skin and eye effects. Engineering controlsand/or personal protective equipment, including respiratory,skin and eye protection, are to be used when there is a potentialfor over-exposure to diisocyanates. The product suppliersMaterial Safety Data Sheet (MSDS) provides more detailedinformation abou
18、t potential adverse health effects and otherimportant safety and handling information. Always follow thespecific instructions provided on the MSDS.)9. Instrument Preparation9.1 The instrument settings here are to be used as a guide forlaboratory specific instrument-column combinations, which areto b
19、e adjusted to provide adequate separation and sensitivity asdescribed in Practice E682.9.1.1 PumpFlow = 1.5 mL/minEluent A (hexane) = 90 %Eluent B (1:1 by volume ethanol:methanol) = 10 %9.1.2 DetectorWavelength = 235 nmOutput Range = 2.000 au full scale9.1.3 Additional SettingsInjection volume=2LCol
20、umn Temperature = 30CStop Time = 25 minutesPost Run Time = 10 minutes9.1.4 Solvent Program9.1.4.1 After the components of interest have eluted, it isdesirable to flush the remainder of the material from thecolumn to avoid interference with subsequent analyses. Asolvent program such as the one below
21、can be used for analysisand cleanup:(1) InitialEluent A = 90 %Eluent B = 10 %Hold for 15 minutes.(2) Column FlushEluent A=0%Eluent B = 100 %Hold for 10 minutes.(3) ReequilibrationEluent A = 90 %Eluent B = 10 %Hold for 2.5 minutes10. Calibration and Standardization10.1 The primary standard consists o
22、f monomeric materialof sufficient purity and containing all isomers of interest. Theconcentrations of the isomers in the standard are to be in thesame ranges as those expected in samples to be analyzed.Because of the difficulty in obtaining primary standards for thistest, agreement on the standard m
23、aterial to be used in testingmust be obtained between the testing laboratory and therecipient of the final test results. Several strategies in obtainingsuitable standard material have been used.10.1.1 Several isomers of suitable purity are commerciallyavailable, such as those from Sigma/Aldrich (2,4
24、-MDI#51881-6; 4,4-MDI #25643-9). These individual isomers arecombined to produce a primary standard with isomers in thesame range as the samples.10.1.2 Alternatively, monomer of suitable purity consistingof unknown quantities of the isomers of interest can beanalyzed by gas chromatography with a fla
25、me ionizationdetector. An area percent technique is employed to determinethe isomer content. Again, agreement between the testinglaboratory and the recipient of the final test results must beobtained for the specific conditions of the gas chromatographicdetermination.10.2 Regardless of which of the
26、strategies above is used, theprimary standard is prepared and analyzed as described in thefollowing sections.11. Procedure11.1 Sample Preparation11.1.1 Weigh the sample to be analyzed in a 250 mL beaker.Use the formula below to determine the correct weight. Recordactual weight to the nearest 0.1 mil
27、ligram.Weight of sample milligrams! 55000Expected wt % monomer in sample(1)11.1.2 Dissolve the sample in 20 mL of dry acetonitrile andadd exactly 100 mL of the derivatization solution. Add astirring bar, cover with watch glass and heat on hotplate/stirrerfor fifteen minutes. The hotplate temperature
28、 must be set suchthat the sample solution begins to boil in 7-10 minutes.11.1.3 Remove the sample solution from heat and allow tocool to room temperature.11.2 Analysis11.2.1 Prior to injecting any sample, allow the chromato-graphic system to equilibrate by pumping the initial eluentthrough the colum
29、n for at least 20-30 minutes. When a stablebaseline is observed, analyze an aliquot of the derivatizedsample solution. After all isomers of interest have eluted, flushthe column as specified by the solvent program above.D7252 06 (2011)1212. Calculation12.1 Calculate the weight percent of isomer “i”
30、as follows:Isomer i,%5AisampleAISstdWistd100AistdAISsampleWsample(2)Aisample= the area of the “i” isomer peak in the samplechromatogram (see Fig. 1)AISstd= the area of the internal standard peak in thestandard chromatogram (see Fig. 2)Aistd= the area of the “i” isomer peak in the standardchromatogra
31、mAISsample= the area of the internal standard peak in thesample chromatogramWistd= the weight of the “i” isomer in the standardsolution in milligramsWsample= the weight of the sample in milligrams12.2 Calculate the percent monomer in the sample by:Monomer, % = Sum of all isomers, %.13. Report13.1 Re
32、port the weight percent of each isomer and of themonomer to the nearest 0.1%.14. Precision and Bias314.1 PrecisionAttempts to develop a precision and biasstatement for this test method have not been successful. Forthis reason, only estimates of data on precision and bias can begiven. Because this te
33、st method does not contain an acceptablenumerical precision and bias statement, it shall not be used asa referee test method in case of dispute. Anyone wishing toparticipate in the development of precision and bias data is tocontact the Chairman, Subcommittee D20.22 (SectionD20.22.01), ASTM, 100 Bar
34、r Harbor Drive, West Consho-hocken, PA 19428.14.1.1 A limited round robin was performed with threelaboratories. Tables 1-4 are based on a round robin conductedin 2004 in general accordance with Practice E691, involvingsix materials tested by three laboratories. Each test result wasthe average of two
35、 individual determinations. Each laboratorymade duplicate determinations on each material on each of twodays. (WarningThe following explanations of r and R(14.1.2-14.1.3) are only intended to present a meaningful wayof considering the approximate precision of this test method.The data in Tables 1-4
36、must not be rigorously applied to theacceptance or rejection of material, as those data are specific tothe limited round robin and will not be representative of otherlots, conditions, materials, and laboratories. Users of this testmethod must apply the principles outlined in Practice E691 togenerate
37、 data specific to their laboratory and materials, orbetween specific laboratories. The principles of 14.1.2-14.1.3would then be valid for such data.)14.1.2 Repeatability, r(Comparing two replicates for thesame material, obtained by the same operator using the sameequipment on the same day.) It is es
38、timated that the tworeplicate results will be judged not equivalent if they differ bymore than the r value for that material.14.1.3 Reproducibility, R(Comparing two results, eachthe mean of duplicates, for the same material, obtained by3Supporting data have been filed at ASTM International Headquart
39、ers and maybe obtained by requesting Research Report RR:D20-1243.FIG. 1 Example of a Sample Solution ChromatogramD7252 06 (2011)13different operators using different equipment in different labo-ratories on different days.) It is estimated that the two resultswill be judged not equivalent if they dif
40、fer by more than the Rvalue for that material.14.1.4 Any judgment in accordance with 14.1.2 and 14.1.3has an approximate 95 % (0.95) probability of being correct.14.2 BiasThe bias of this test method has not yet beendetermined.15. Keywords15.1 chromatography; diisocyanate; HPLC; isocyanate; iso-mers
41、; monomer; polymeric MDI; polyurethane raw materials;pure MDIFIG. 2 Example of a Standard Solution ChromatogramTABLE 1 Estimated Precision for 2,2- IsomerWeight % 2,2- MDIMaterial Average SrASRBrCRDnE1 3.05 0.08 0.09 0.21 0.26 32 0.13 0.01 0.12 0.02 0.33 33 0.00 0.00 0.00 0.00 0.00 34 0.13 0.02 0.11
42、 0.06 0.31 35 0.77 0.03 0.03 0.09 0.10 26 1.33 0.04 0.05 0.11 0.15Pooled data 0.04 0.08 0.11 0.23 . . .ASr= within-laboratory standard deviation of the replicates.BSR= between-laboratory standard deviation of the averages.Cr = within-laboratory repeatability limit = 2.8*Sr.DR = between-laboratory re
43、producibility limit = 2.8*SR.En = number of laboratories contributing valid data for this material.D7252 06 (2011)14ASTM 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 a
44、dvised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are 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, eith
45、er reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend.
46、 If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee 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. Indi
47、vidual 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
48、from the ASTM website (www.astm.org/COPYRIGHT/).TABLE 2 Estimated Precision for 2,4- IsomerEstimated Precision for 2,4- Isomer Weight % 2,4- MDIMaterial Average SrASRBrCRDnE1 50.47 0.89 0.89 2.49 2.49 32 4.16 0.08 0.08 0.22 0.22 33 1.24 0.02 0.02 0.07 0.07 34 2.84 0.06 0.06 0.15 0.15 35 13.36 0.38 0
49、.38 1.06 1.06 36 22.67 0.31 0.31 0.86 0.86 2Pooled data 0.42 0.42 1.19 1.19ASr= within-laboratory standard deviation of the replicates.BSR= between-laboratory standard deviation of the averages.Cr = within-laboratory repeatability limit = 2.8*Sr.DR = between-laboratory reproducibility limit = 2.8*SR.En = number of laboratories contributing valid data for this material.TABLE 3 Estimated Precision for 4,4- IsomerEstimated Precision for 4,4- Isomer Weight % 4,4- MDIMaterial Average SrASRBrCRDnE1 49.24 0.82 1.44 2.30 4.04 32 37.83 0.72 1.01 2.02 2.83 33
