ASTM D7252-06(2011)e1
(Test Method)Standard Test Method for Polyurethane Raw Materials: Determination of Monomer and Isomers in Isocyanates
Standard Test Method for Polyurethane Raw Materials: Determination of Monomer and Isomers in Isocyanates
SIGNIFICANCE AND USE
This test method can be used for research or for quality control to characterize isocyanates used in polyurethane products.
SCOPE
1.1 This test method determines the percent by weight of monomeric isomers and total monomer in crude or modified isocyanates. The test method is applicable to methylene di(phenylisocyanate) (MDI) and polymeric (meththylene phenylisocyanate) (PMDI). (See Note 1.)
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Note 1—There is no known ISO equivalent to this standard.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D7252 − 06 (Reapproved 2011)
Standard Test Method for
Polyurethane Raw Materials: Determination of Monomer and
Isomers in Isocyanates
This standard is issued under the fixed designation D7252; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Reapproved with editorial changes in September 2011.
1. Scope chromatography (HPLC). The separated, derivatized isomers
are quantified through the use of an internal standard.
1.1 This test method determines the percent by weight of
monomeric isomers and total monomer in crude or modified
5. Significance and Use
isocyanates.Thetestmethodisapplicabletomethylenedi(phe-
nylisocyanate) (MDI) and polymeric (meththylene phenyliso- 5.1 This test method can be used for research or for quality
cyanate) (PMDI). (See Note 1.)
control to characterize isocyanates used in polyurethane prod-
ucts.
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
6. Apparatus
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
6.1 High Performance Liquid Chromatograph, consisting
bility of regulatory limitations prior to use.
of:
6.1.1 Binary (or greater) solvent pump, capable of main-
NOTE 1—There is no known ISO equivalent to this standard.
taining a pulse-free flow rate of 1-3 millilitres per minute
6.1.2 Sample injector, automatic or manual, capable of
2. Referenced Documents
reproducibly injecting a 2 microlitre volume
2.1 ASTM Standards:
6.1.3 Column heater, capable of maintaining a temperature
D883 Terminology Relating to Plastics
of 30 6 0.2°C
E682 Practice for Liquid Chromatography Terms and Rela-
6.1.4 UV detector, capable of measurements at 235 nm.
tionships
6.1.5 Chart recorder or Data system, capable of peak area
E691 Practice for Conducting an Interlaboratory Study to
integration.
Determine the Precision of a Test Method
6.2 HPLC analytical column, 250 mm by 4.6 mm by 5 µm
3. Terminology cyano stationary phase
3.1 For definitions of terms used in these test methods see NOTE 2—Other chromatographic columns can be used provided it is
ascertained that similar chromatographic performance is obtained.
Terminology D883.
6.3 Magnetic Stirring Hotplate.
4. Summary of Test Method
7. Reagents and Materials
4.1 The sample is reacted (derivatized) with methanol to
form a mixture of methyl urethanes. The urethanes mixture is
7.1 Purity of Reagents—Reagent-grade chemicals are to be
then separated by normal phase high performance liquid
used in all tests. Unless otherwise indicated, it is intended that
all reagents conform to the specifications of the Committee on
Analytical Reagents of theAmerican Chemical Society, where
This test method is under the jurisdiction ofASTM Committee D20 on Plastics such specifications are available. Other grades can be used,
and is the direct responsibility of Subcommittee D20.22 on Cellular Materials -
provided it is first ascertained that the reagent is of sufficiently
Plastics and Elastomers.
high purity to permit its use without lessening the accuracy of
Current edition approved Sept. 1, 2011. Published October 2011. Originally
the determination.
approved in 2006. Last previous edition approved in 2006 as D7252 - 06.
DOI:10.1520/D7252-06R11E01.
7.1.1 Acetanilide, 99.9 % purity, to be used as an internal
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
standard.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
7.1.2 Acetonitrile, dry. Dry this and reagents below over
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. molecular sieve for twenty-four hours.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D7252 − 06 (2011)
7.1.3 Ethanol, dry. Use of ethanol denatured with methanol (3)Reequilibration
(such as SDA-30) can be used if more readily available. Eluent A = 90 %
7.1.4 Hexane, dry.
Eluent B = 10 %
7.1.5 Methanol, dry. Hold for 2.5 minutes
7.1.6 Eluent solution, Mix 1:1 by volume of dry methanol
and ethanol.
10. Calibration and Standardization
7.1.7 Derivatization solution, Dissolve 0.20 g of acetanilide
10.1 The primary standard consists of monomeric material
in 1 L of dry methanol.
of sufficient purity and containing all isomers of interest. The
concentrations of the isomers in the standard are to be in the
8. Sampling
same ranges as those expected in samples to be analyzed.
8.1 Since organic isocyanates react with atmospheric
Becauseofthedifficultyinobtainingprimarystandardsforthis
moisture, take special precautions in sampling. Usual sampling
test, agreement on the standard material to be used in testing
methods, even when conducted rapidly, can cause contamina-
must be obtained between the testing laboratory and the
tion of the sample with insoluble urea. Therefore, blanket the
recipient of the final test results. Several strategies in obtaining
sample with dry air or nitrogen at all times. (Warning—Many
suitable standard material have been used.
diisocyanates are known or suspected sensitizers. Over-
10.1.1 Several isomers of suitable purity are commercially
exposure to diisocyanates can lead to adverse health effects
available, such as those from Sigma/Aldrich (2,4’-MDI
which include the development of occupational asthma and
#51881-6; 4,4’-MDI #25643-9). These individual isomers are
other respiratory, skin and eye effects. Engineering controls
combined to produce a primary standard with isomers in the
and/or personal protective equipment, including respiratory,
same range as the samples.
skin and eye protection, are to be used when there is a potential
10.1.2 Alternatively, monomer of suitable purity consisting
for over-exposure to diisocyanates. The product suppliers’
of unknown quantities of the isomers of interest can be
Material Safety Data Sheet (MSDS) provides more detailed
analyzed by gas chromatography with a flame ionization
information about potential adverse health effects and other
detector. An area percent technique is employed to determine
important safety and handling information. Always follow the
the isomer content. Again, agreement between the testing
specific instructions provided on the MSDS.)
laboratory and the recipient of the final test results must be
obtained for the specific conditions of the gas chromatographic
9. Instrument Preparation
determination.
9.1 Theinstrumentsettingsherearetobeusedasaguidefor
laboratoryspecificinstrument-columncombinations,whichare
10.2 Regardless of which of the strategies above is used, the
to be adjusted to provide adequate separation and sensitivity as
primary standard is prepared and analyzed as described in the
described in Practice E682.
following sections.
9.1.1 Pump
Flow = 1.5 mL/min
11. Procedure
Eluent A (hexane) = 90 %
11.1 Sample Preparation
Eluent B (1:1 by volume ethanol:methanol) = 10 %
11.1.1 Weigh the sample to be analyzed in a 250 mLbeaker.
9.1.2 Detector
Use the formula below to determine the correct weight. Record
Wavelength = 235 nm
actual weight to the nearest 0.1 milligram.
Output Range = 2.000 au full scale
9.1.3 Additional Settings
Weightofsample ~milligrams! 5
Injection volume=2µL
Expectedwt% monomerinsample
Column Temperature = 30°C
(1)
Stop Time = 25 minutes
Post Run Time = 10 minutes
11.1.2 Dissolve the sample in 20 mL of dry acetonitrile and
9.1.4 Solvent Program add exactly 100 mL of the derivatization solution. Add a
9.1.4.1 After the components of interest have eluted, it is
stirring bar, cover with watch glass and heat on hotplate/stirrer
desirable to flush the remainder of the material from the for fifteen minutes. The hotplate temperature must be set such
column to avoid interference with subsequent analyses. A
that the sample solution begins to boil in 7-10 minutes.
solvent program such as the one below can be used for analysis
11.1.3 Remove the sample solution from heat and allow t
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