1、Designation: D7252 06 (Reapproved 2011)1D7252 17Standard 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
2、, in the 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 NOTEReapproved with editorial changes in September 2011.1. Scope1.1 This test method dete
3、rmines the percent by weight of monomeric isomers and total monomer in crude or modifiedisocyanates. The test method is applicable to methylene di(phenylisocyanate) (MDI) and polymeric (meththylene(methylenephenylisocyanate) (PMDI). (See Note 1.)1.2 UnitsThe values stated in SI units are to be regar
4、ded as standard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determi
5、ne the applicability of regulatorylimitations prior to use.NOTE 1There is no known ISO equivalent to this standard.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of
6、 International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to PlasticsE682 Practice for Liquid Chromatography Terms and RelationshipsE691 Practice for Cond
7、ucting an Interlaboratory Study to Determine the Precision of a Test Method3. Terminology3.1 For definitions of terms used in these test methods see Terminology D883.4. Summary of Test Method4.1 The sample is reacted (derivatized) with methanol to form a mixture of methyl urethanes. The urethanes mi
8、xture is thenseparated by normal phase high performance liquid chromatography (HPLC). The separated, derivatized isomers are quantifiedthrough the use of an internal standard.5. Significance and Use5.1 This test method can be is used for research or for quality control to characterize isocyanates us
9、ed in polyurethane products.6. Apparatus6.1 High Performance Liquid Chromatograph, consisting of:6.1.1 Binary (or greater) solvent pump, capable of maintaining a pulse-free flow rate of 1-3 millilitresmilliliters per minute1 This test method is under the jurisdiction of ASTM Committee D20 on Plastic
10、s and is the direct responsibility of Subcommittee D20.22 on Cellular Materials - Plasticsand Elastomers.Current edition approved Sept. 1, 2011April 15, 2017. Published October 2011May 2017. Originally approved in 2006. Last previous edition approved in 20062011 asD7252 - 06.D7252 - 06(2011)1 DOI:10
11、.1520/D7252-06R11E01. . DOI:10.1520/D7252-17.2 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.This document is
12、 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 accurately, ASTM recommends that users consult prior editions as appropr
13、iate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16.1.2 Sample injector, automatic or manual, capable of reproduci
14、bly injecting a 2 microlitremicroliter volume6.1.3 Column heater, capable of maintaining a temperature of 30 6 0.2C6.1.4 UV detector, capable of measurements at 235 nm.6.1.5 Chart recorder or Data system, capable of peak area integration.6.2 HPLC analytical column, 250 mm by 4.6 mm by 5 m cyano stat
15、ionary phasephase.NOTE 2Other chromatographic columns can be are used provided it is ascertained that similar chromatographic performance is obtained.6.3 Magnetic Stirring Hotplate.7. Reagents and Materials7.1 Purity of ReagentsReagent-grade chemicals are to be used in all tests. Unless otherwise in
16、dicated, it is intended that allreagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where suchspecifications are available. Other grades can be are used, provided it is first ascertained that the reagent is of sufficiently highpurity to pe
17、rmit its use without lessening the accuracy of the determination.7.1.1 Acetanilide, 99.9 % purity, to be used as an internal standard.7.1.2 Acetonitrile, dry. Dry this and reagents below over molecular sieve for twenty-four hours.7.1.3 Ethanol, dry. Use of ethanol denatured with methanol (such as SD
18、A-30) can be is 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 dry methanol and ethanol.7.1.7 Derivatization Internal Standard and derivatization solution, Dissolve 0.20 g of acetanilide in 1 L of dry methanol.8. Sampling8.1 Since org
19、anic 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 urea. Therefore, blanket the sample with dryair or nitrogen at all times. (WarningMany diisocyanates are kn
20、own or suspected sensitizers. Over-exposure to diisocyanatescan lead to adverse health effects which include the development of occupational asthma and other respiratory, skin and eye effects.Engineering controls and/or Diisocyanates are eye, skin and respiratory irritants at concentrations above th
21、e occupational exposurelimit (TLV or PEL). Diisocyanates can cause skin and respiratory sensitization (asthma) in some people. Once sensitized, it isessential to limit further exposure to diisocyanates. Use a combination of engineering controls and personal protective equipment,including respiratory
22、, skin and eye protection, are to be used when there is a potential for to prevent over-exposure to diisocyanates.The Consult the product suppliers Material Safety Data Sheet (MSDS) provides(SDS) for more detailed information aboutpotential adverse health effects and other importantspecific safety a
23、nd handling information.Always follow the specific instructionsprovided on the MSDS.instructions for the product)9. Instrument Preparation9.1 The instrument settings here are to be used as a guide for laboratory specific instrument-column combinations, which areto be adjusted to provide adequate sep
24、aration and sensitivity as described 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 = 2 LColumn Temperature = 30CStop Time
25、 = 25 minutesPost Run Time = 10 minutes9.1.4 Solvent Program9.1.4.1 After the components of interest have eluted, it is desirable to flush the remainder of the material from the column toavoid interference with subsequent analyses. A solvent program such as the one below can be is used for analysis
26、and cleanup:(1) InitialEluent A = 90 %Eluent B = 10 %Hold for 15 minutes.D7252 172(2) Column FlushEluent A = 0 %Eluent B = 100 %Hold for 10 minutes.(3) ReequilibrationRe-equilibrationEluent A = 90 %Eluent B = 10 %Hold for 2.5 minutes10. Calibration and Standardization10.1 The primary standard consis
27、ts of monomeric material of sufficient purity and containing all isomers of interest. Theconcentrations of the isomers in the standard are to be in the same ranges as those expected in samples to be analyzed. Becauseof the difficulty in obtaining primary standards for this test, agreement on the sta
28、ndard material to be used in testing must beobtained between the testing laboratory and the recipient of the final test results. Several strategies in obtaining suitable standardmaterial have been used.10.1.1 Several isomers isomer blends of suitable purity are commercially available, such as those
29、from Sigma/Aldrich(2,4-MDI #51881-6; 4,4-MDI #25643-9). These individual isomers available from several isocyanate manufacturers. Theseblends are combined to produce a primary standard with isomers in the same range as the samples.10.1.2 Alternatively, monomer of suitable purity consisting of unknow
30、n quantities of the isomers of interest can be is analyzedby gas chromatography with a flame ionization detector. An area percent technique is employed to determine the isomer content.Again, agreement between the testing laboratory and the recipient of the final test results must be obtained for the
31、 specificconditions of the gas chromatographic determination.10.2 Regardless of which of the strategies above is used, the primary 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. Us
32、e the formula below to determine the correct weight. Recordactual weight to the nearest 0.1 milligram.Weight of sample milligrams! 5 5000Expected wt%monomer in sample (1)11.1.2 Dissolve the sample in 20 mL of dry acetonitrile and add exactly 100 mL of the derivatization (Internal Standard andderivat
33、ization) solution. Add a stirring bar, cover with watch glass and heat on hotplate/stirrer for fifteen minutes. The hotplatetemperature must be set such that the sample solution begins to boil in 7-10 minutes.11.1.3 Remove the sample solution from heat and allow to cool to room temperature.11.2 Anal
34、ysis11.2.1 Prior to injecting any sample, allow the chromatographic system to equilibrate by pumping the initial eluent through thecolumn for at least 20-30 minutes. When a stable baseline is observed, analyze an aliquot of the derivatized sample solution.Afterall isomers of interest have eluted, fl
35、ush the column as specified by the solvent program above.12. Calculation12.1 Calculate the weight percent of isomer “i” as follows:Isomer i,%5Aisample AISstd Wistd 100Aistd AISsample Wsample (2)Aisample = the area of the “i” isomer peak in the sample chromatogram (see Fig. 1)AISstd = the area of the
36、 internal standard peak in the standard chromatogram (see Fig. 2 )Aistd = the area of the “i” isomer peak in the standard chromatogramAISsample = the area of the internal standard peak in the sample chromatogramWistd = the weight of the “i” isomer in the standard solution in milligramsWsample = the
37、weight of the sample in milligrams12.2 Calculate the percent monomer in the sample by:Monomer, % = Sum of all isomers, %.13. Report13.1 Report the weight percent of each isomer and of the monomer to the nearest 0.1%.D7252 173FIG. 1 Example of a Standard Solution ChromatogramFIG. 2 Example of a Sampl
38、e Solution ChromatogramD7252 17414. Precision and Bias314.1 PrecisionAttempts to develop a precision and bias statement for this test method have not been successful. For thisreason, only estimates of data on precision and bias can be are given. Because this test method does not contain an acceptabl
39、enumerical precision and bias statement, it shall not be used as a referee test method in case of dispute. Anyone wishing toparticipate in the development of precision and bias data is to contact the Chairman, Subcommittee D20.22 (Section D20.22.01),ASTM, 100 Barr Harbor Drive, West Conshohocken, PA
40、 19428.14.1.1 A limited round robin was performed with three laboratories. Tables 1-4 are based on a round robin conducted in 2004in general accordance with Practice E691, involving six materials tested by three laboratories. Each test result was the average oftwo individual determinations. Each lab
41、oratory made duplicate determinations on each material on each of two days.(WarningThe following explanations of r and R (14.1.2-14.1.3) are only intended to present a meaningful way of consideringthe approximate precision of this test method. The data in Tables 1-4 must not be rigorously applied to
42、 the acceptance or rejectionof material, as those data are specific to the limited round robin and will not be representative of other lots, conditions, materials,and laboratories. Users of this test method must apply the principles outlined in Practice E691 to generate data specific to theirlaborat
43、ory and materials, or between specific laboratories. The principles of 14.1.2-14.1.3 would then be valid for such data.)14.1.2 Repeatability, r(Comparing two replicates for the same material, obtained by the same operator using the sameequipment on the same day.) It is estimated that the two replica
44、te results will be judged not equivalent if they differ by more thanthe r value for that material.14.1.3 Reproducibility, R(Comparing two results, each the mean of duplicates, for the same material, obtained by differentoperators using different equipment in different laboratories on different days.
45、) It is estimated that the two results will be judgednot equivalent if they differ by more than the R value for that material.14.1.4 Any judgment in accordance with 14.1.2 and 14.1.3 has an approximate 95 % (0.95) probability of being correct.14.2 BiasThe bias of this test method has not yet been de
46、termined.15. Keywords15.1 chromatography; diisocyanate; HPLC; isocyanate; isomers; monomer; polymeric MDI; polyurethane raw materials; pureMDI3 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D20-1243.TABLE 1 Estimated Precision
47、 for 2,2- IsomerWeight % 2,2- MDIMaterial Average SrA SRB rC RD nE1 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 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 standar
48、d 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.D7252 175ASTM International takes
49、 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 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 ad
