1、Designation: D4660 18Standard Test Methods forPolyurethane Raw Materials: Determination of the IsomerContent of Toluenediisocyanate1This standard is issued under the fixed designation D4660; the number immediately following the designation indicates the year oforiginal adoption or, in the case of re
2、vision, 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*1.1 These test methods measure the amount of toluene-2,6-diisocyanate (2,6-TDI) isomer or toluene2,4d
3、iisocyanate(2,4-TDI) isomer in mixtures of the 2,4- and 2,6-isomers oftoluenediisocyanate (TDI). Two different test methods areprovided to give accurate results over the broad range ofisomer concentrations possible.1.1.1 Test Method AApplicable to TDI samples containing5 to 95 % of 2,6-TDI isomer (5
4、 to 95 % 2,4-TDI isomer).1.1.2 Test Method BApplicable toTDI samples containing0 to 5 % of 2,6-TDI isomer (95 to 100 % 2,4-TDI isomer).NOTE 1These test methods are equivalent to ISO 15064.1.2 The values stated in SI units are to be regarded asstandard.1.3 This standard does not purport to address al
5、l of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed i
6、n accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2
7、.1 ASTM Standards:2D883 Terminology Relating to PlasticsE180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals (Withdrawn 2009)32.2 ISO Standard:4ISO 15064 PlasticsAromatic Isocyanates for Use in theProduction of PolyurethanesDeterm
8、ination of the Iso-mer Ratio in Toluenediisocyanate3. Terminology3.1 Terminology in these test methods is in accordance withTerminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 isomera compound having the same molecular for-mula (percentage composition and molecular weight) as a
9、n-other compound but differs in chemical or physical properties.3.2.2 isomer contentthe amount of an isomer expressed asa percentage of total 2,4 and 2,6-TDI isomer amount.4. Summary of Test Methods4.1 Both test methods are based on the quantitative mea-surement of absorption bands arising from out-
10、of-plane C-Hdeformation vibrations of the aromatic ring.4.2 In Test Method A, the infrared spectrum of a cyclo-hexane solution of the sample is recorded in the 770 to840-cm1region. The absorbance ratio of the 805 cm1to the782 cm1band is measured and converted to percent 2,6-TDI,or percent 2,4-TDI, o
11、r both, from a previously establishedcalibration curve.4.3 In Test Method B, the absorbance of the 782-cm1bandis measured from an infrared spectrum of an undiluted sampleand then converted to percent 2,6-TDI from a previouslyestablished calibration curve.5. Significance and Use5.1 These test methods
12、 are suitable for research or forquality control to determine the isomer content of toluenediisocyanates.1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.22 on CellularMaterials - Plastics and Elastomers.Current edi
13、tion approved April 1, 2018. Published April 2018. Originallyapproved in 1959. Last previous edition approved in 2012 as D4660 - 12. DOI:10.1520/D4660-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMS
14、tandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.
15、org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization
16、established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.15.2 The isomer content of a toluene diisocyanate relates toits reactivity.6. Apparatus6.1 Spectropho
17、tometerAny single- or double-beam re-cording infrared spectrophotometer accurate to 0.2 % transmis-sion and capable of resolving the two peaks of the 2,4-TDIisomer doublet at 805-815 cm1(see Fig. 1).6.2 Cells, sealed sodium chloride (NaCl) liquid absorptioncells with 0.2-mm (Test Method A) and 0.1-m
18、m (Test MethodB) path lengths. The actual thicknesses of the cells are to beknown to 60.002 mm.6.3 Glassware, 25-mL, glass-stoppered, volumetric flasks,10-mL, glass-stoppered, flasks, 0.80-mL volumetric pipet, andan all-glass syringe.7. Reagents and Materials7.1 Purity of ReagentsUse reagent grade c
19、hemicals in alltests. Unless otherwise noted, all reagents conform to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Society where such specifications areavailable.5Other grades are acceptable, provided it is ascer-tained that the reagent is of sufficiently high pu
20、rity to permit itsuse without lessening the accuracy of the determination.7.2 Cyclohexane, anhydrous, stored over molecular sieve.7.3 Diisocyanate StandardsPure samples of 2,4-TDI and2,6-TDI are required for calibration. The following criteria canbe used to judge purity:Pure Isomer Freezing point Re
21、fractive Index 20C n20DDensity 20C/4C2,4-TDI 22.0C 1.56781 1.21862,6-TDI 18.2C 1.57111 1.22708. Sampling8.1 Since organic isocyanates react with atmosphericmoisture, take special precautions in sampling. Usual samplingmethods, even when conducted rapidly, can cause contamina-tion of the sample with
22、insoluble urea. Therefore, blanket thesample with dry air or nitrogen at all times. WarningDiisocyanates are eye, skin and respiratory irritants at concen-trations above the occupational exposure limit (TLV or PEL).Diisocyanates can cause skin and respiratory sensitization(asthma) in some people. On
23、ce sensitized, it is essential to limitfurther exposure to diisocyanates. Use a combination ofengineering controls and personal protective equipment, in-cluding respiratory, skin and eye protection, to prevent over-exposure to diisocyanates. Consult the product suppliersSafety Data Sheet (SDS) for m
24、ore detailed information aboutpotential health effects and other specific safety and handlinginstructions for the product.9. Test Conditions9.1 Since isocyanates react with moisture, keep laboratoryhumidity low, preferably around 50 % relative humidity.TEST METHOD ASAMPLES CONTAINING 5 TO95 % 2,6-TD
25、I10. Calibration10.1 Weigh amounts of pure 2,4-TDI and 2,6-TDI into dry,10-mL, glass-stoppered flasks (Note 2) to obtain the weightratios given in 10.1.1 or 10.1.2. Carefully shake the mixtures.From the weights of pure 2,4-TDI and 2,6-TDI, calculate theweight ratios (2,4-TDI to 2,6-TDI), or the weig
26、ht percentcomposition of the mixtures, or both, expressed to foursignificant figures.NOTE 2Carefully dry all glassware since the diisocyanates reactreadily with moisture.10.1.1 Approximate standard mixtures for wide-range cali-bration are given in Table 1 (5-95 % 2,6-TDI).10.1.2 Approximate standard
27、 mixtures for narrow-rangecalibrations (see Note 3) are given in Table 2 (15-25 %2,6-TDI) and Table 3 (30-40 % 2,6-TDI).5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemica
28、l Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 IR Scan of TDI Showing 2,4-TDI Isomer Doublet at 810 cm1and 2,6 TDI Isomer at 782 cm1D4660
29、 182NOTE 3Calibration over a narrow range covering the expected isomerratio gives more accurate results than a wide-range calibration.10.2 Preparation of Standard Solutions Using a pipet,transfer 0.80 mL(0.98 g) of standard mixture into a dry, 25-mLglass-stoppered, volumetric flask. Dilute to volume
30、 with cy-clohexane and mix thoroughly.10.3 Fill two 0.2-mm sealed, liquid absorption cells (one fora single-beam instrument) with cyclohexane and record itsspectrum from 770 to 840 cm1. Refill the sample cell with astandard solution from 10.2 and record the spectrum superim-posing it over the previo
31、usly recorded solvent spectrum. Theinstrument controls must remain unchanged between the blankand the standards of a given series. Repeat the process for eachstandard solution from 10.2.10.4 Using the solvent spectrum as the baseline, measurethe absorbance of each standard solution sample at 805 cm1
32、(2,4-TDI) and 782 cm1(2,6-TDI) and calculate the 805/782-cm1absorbance ratio. Construct a calibration curve (see Fig.2) by plotting absorbance ratio (ordinate) versus weight ratio of2,4-TDI to 2,6-TDI (abscissa).10.5 For convenience in short-range calibrations, the absor-bance ratio may be plotted a
33、gainst the concentration, expressedin weight percent, of each isomer (see Figs. 3 and 2). Thisallows direct determination of composition without equations,however, the relationship is not linear and the shape of thecalibration curve must be carefully determined.11. Procedure11.1 Using a dry pipet, t
34、ransfer 0.8 mL (0.98 g) of sampleinto a dry, 25-mL, glass-stoppered, volumetric flask. Dilute tovolume with anhydrous cyclohexane and mix thoroughly. Fillthe 0.2-mm cell with the cyclohexane and record the blanksolvent spectrum from 770 to 840 cm1. Without changinginstrument settings, refill the sam
35、ple cell with the samplesolution and record its spectrum superimposed on the blanksolvent spectrum.NOTE 4All scans of the solvent, standards, and samples should beratioed against an open beam background.12. Calculation12.1 Using the solvent spectrum as the baseline, measurethe absorbance of the samp
36、le at 805 cm1(2,4-TDI) and 782cm1(2,6-TDI) and calculate the 805/782-cm1absorbanceratio. From the appropriate standard curve, obtain the percent-age composition (Figs. 3 and 2), or isomer weight ratio (R),(Fig. 4), or both, that corresponds to the measured absorbanceratio.12.2 When using the isomer
37、weight ratio, (R), calculate thepercentage of each isomer as follows:Percent 2,6 2 TDI 5100R11!(1)andPercent 2,4 2 TDI 5 100 2 percent 2,6 2 TDI (2)12.3 Express the result to one decimal place.13. Precision and Bias13.1 PrecisionTable 4 is based on a round robin con-ducted in 1994 involving two samp
38、les tested by eight labora-tories. For each material, all the samples were prepared at onesource, but the individual specimens were prepared at thelaboratories that tested them. Each laboratory obtained ten testresults for each material on a given day. Narrow-range cali-brations were used.13.1.1 The
39、 following explanations of r and R (13.1.2 13.1.5) are only intended to present a meaningful way ofconsidering the approximate precision of this test method. Thedata in Table 4 are not to be rigorously applied to theacceptance or rejection of material, as these data apply only tothe materials tested
40、 in the round robin and are unlikely to berigorously representative of other lots, conditions, materialsand laboratories. Users of this test method should apply theprinciples outlined in Practice E180 to generate data specific toTABLE 1 Approximate Standard Mixtures for Wide-RangeCalibration, 595 %
41、2,6-TDIWeight Ratio%, 2,4-TDI %, 2,6-TDI 2,4-/2,6-TDI5.0 95.0 0.0510.0 90.0 0.1120.0 80.0 0.2530.0 70.0 0.4340.0 60.0 0.6750.0 50.0 1.0060.0 40.0 1.5070.0 30.0 2.3380.0 20.0 4.0090.0 10.0 9.0095.0 5.0 19.00TABLE 2 Approximate Standard Mixtures for Narrow-RangeCalibration, 1525 % 2,6-TDIWeight Ratio%
42、, 2,4-TDI %, 2,6-TDI 2,4-/2,6-TDI75.0 25.0 3.0078.5 21.5 3.6579.0 21.0 3.7679.5 20.5 3.8880.0 20.0 4.0080.5 19.5 4.1381.0 19.0 4.2681.5 18.5 4.4085.0 15.0 5.67TABLE 3 Approximate Standard Mixtures for Narrow-RangeCalibration, 3040 % 2,6-TDIWeight Ratio%, 2,4-TDI %, 2,6-TDI 2,4-/2,6-TDI60.0 40.0 1.50
43、63.5 36.5 1.7464.0 36.0 1.7764.5 35.5 1.8265.0 35.0 1.8665.5 34.5 1.9066.0 34.0 1.9466.5 33.5 1.9870.0 30.0 2.33D4660 183their laboratory and materials, or between specific laboratories.The principles of 13.1.2 13.1.5 would then be valid for suchdata.13.1.2 RepeatabilityPrecision under repeatability
44、 condi-tions.13.1.3 ReproducibilityPrecision under reproducibilityconditions.13.1.4 Repeatability LimitThe value below which theabsolute difference between two individual test results obtainedunder repeatability conditions may be expected to occur with aprobability of approximately 0.95 (95 %). For
45、the data gener-ated above, the maximum expected difference between two testresults for the same material, obtained by the same operatorusing the same equipment on the same day in the samelaboratory due solely to the method is 0.21 % for TD-80 and0.26 % for TD-65.13.1.5 Reproducibility LimitThe value
46、 below which theabsolute difference between two individual test results obtainedunder reproducibility conditions may be expected to occur witha probability of approximately 0.95 (95 %). For the datagenerated above, the maximum expected difference betweentwo test results for the same material, obtain
47、ed by differentFIG. 2 Calibration Curve Toluene Diisocyanate 65:35 (2,4-TDI : 2,6-TDI)FIG. 3 Calibration Curve Toluene Diisocyanate 80:20 (2,4-TDI : 2,6-TDI)D4660 184operators using different equipment in different laboratoriesdue solely to the method is 0.45 % for TD-80 and 0.31 % forTD65.13.2 Bias
48、There are no recognized standards by which toestimate the bias of this test method.TEST METHOD BSAMPLES CONTAINING0 TO 5 % 2,6-TDI14. Calibration14.1 Using pure 2,4- and 2,6-TDI and dry, 10-mL, glass-stoppered flasks, prepare a series of calibration mixtures asgiven in Table 5.14.2 From the weights
49、of pure 2,4- and 2,6-TDI, calculatethe concentration of 2,6-TDI in each of the mixtures, expressedto four significant figures.14.3 Using a 0.1-mm sealed liquid absorption cell, recordthe spectrum of each of the calibration mixtures from 770 to840 cm1.14.4 For each of the calibration mixtures, measure theabsorbance of the 2,6-TDI isomer band at 782 cm1from abaseline-drawn tangent to the band shoulders.14.5 Construct a calibration curve by plotting the absor-bance (ordinate) versus the concentration of 2,6-TDI (abscissa)expresse
