ASTM D4273-99
(Test Method)Standard Test Methods for Polyurethane Raw Materials Determination of Primary Hydroxyl Content of Polyether Polyols
Standard Test Methods for Polyurethane Raw Materials Determination of Primary Hydroxyl Content of Polyether Polyols
SCOPE
1.1 Test Method A-Fluorine-19 Nuclear Magnetic Resonance Spectroscopy (fluorine-19 NMR), measures the primary hydroxyl content in ethylene oxide-propylene oxide polyethers used in flexible urethane foams. It is suitable for polyethers with hydroxyl numbers of 24 to 300 and primary hydroxyl percentages of 2 to 98.
1.2 Test Method B-Carbon-13 Nuclear Magnetic Resonance Spectroscopy (carbon-13 NMR), measures the primary hydroxyl content of ethylene-oxide-propylene oxide polyethers used in preparing flexible foams. It is suitable for polyethers with hydroxyl numbers of 24 to 109 and primary hydroxyl contents of 10 to 90% (see Note 1). Note 1-There are no equivalent ISO standards.
1.3 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.
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Designation:D4273–99
Standard Test Methods for
Polyurethane Raw Materials: Determination of Primary
Hydroxyl Content of Polyether Polyols
This standard is issued under the fixed designation D 4273; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope * 3. Terminology
1.1 Test Method A—Fluorine-19 Nuclear Magnetic Reso- 3.1 Definitions: The terminology in these test methods
nance Spectroscopy (fluorine-19 NMR), measures the primary follows the standard terminology defined in Terminology
hydroxyl content in ethylene oxide-propylene oxide polyethers D 883.
used in flexible urethane foams. It is suitable for polyethers 3.2 Acronym Specific to This Standard:
with hydroxyl numbers of 24 to 300 and primary hydroxyl 3.2.1 RCF, n—relative centrifugal force, expressed as a
percentages of 2 to 98. multiple of gravitational force.
1.2 Test Method B—Carbon-13 Nuclear Magnetic Reso-
4. Summary of Test Methods
nance Spectroscopy (carbon-13 NMR), measures the primary
hydroxyl content of ethylene oxide-propylene oxide polyethers 4.1 Test Method A—Hydroxyl-terminated polyethers are
reacted with trifluoroacetic anhydride, converting them quan-
used in preparing flexible foams. It is suitable for polyethers
with hydroxyl numbers of 24 to 109 and primary hydroxyl titatively to trifluoroacetate esters. High-resolution fluorine-19
NMR spectra of the esters have well-resolved resonance peaks
contents of 10 to 90 % (see Note 2).
fortheestersofprimaryandsecondaryalcohols.Areasofthese
NOTE 1—There are no equivalent ISO standards.
peaks are measured by the spectrometer’s integration system,
1.3 This standard does not purport to address all of the
and the relative primary hydroxyl content is calculated from
safety concerns, if any, associated with its use. It is the
the ratio of the areas of the primary hydroxyl peaks to the total
responsibility of the user of this standard to establish appro-
area of primary and secondary hydroxyl peaks.
priate safety and health practices and determine the applica-
4.1.1 Mixtures of polyethers may be analyzed provided
bility of regulatory limitations prior to use.
none of the trifluoroacetylation derivatives extract preferen-
tially into aqueous bicarbonate solution. Extractable polyethers
2. Referenced Documents
are polyethylene glycols of molecular weight greater than 300.
2.1 ASTM Standards:
2 NOTE 2—Ablendofpolypropyleneglycol(hydroxylnumberequals60)
D 883 Terminology Relating to Plastics
and polyethylene glycol (hydroxyl number equals 75) had a calculated
E 180 Practice for Determining the Precision of ASTM
primary hydroxyl of 49.7 % and an observed value by the fluorine-19
Methods forAnalysis and Testing of Industrial Chemicals
NMR derivatization method of 39.9 %. This example is extreme since
E 691 Practice for Conducting an Interlaboratory Study to
these components are incompatible. Nevertheless, a test is described in
Determine the Precision of a Test Method
Section 12 to determine the test method’s applicability to a particular
blend.
4.1.2 The hydroxyl contribution of chain extenders in poly-
ethers may be determined provided that (1) their trifluoroac-
These test methods are under the jurisdiction of ASTM Committee D-20 on
Plastics and are the direct responsibility of Subcommittee D20.22 on Cellular
etate derivatives are not volatile under the derivatization
Plastics. These test methods were recommended to ASTM by the Society of the
conditions, (2) their derivatives do not extract into aqueous
Plastics Industry Polyurethane Raw Materials Analysis Committee.
bicarbonate, and (3) their fluorine-19 NMR peaks are well-
Current edition approved Nov. 10, 1999. Published February 2000. Originally
published as D 4273 – 83. Last previous edition D 4273 – 94. resolved.
Annual Book of ASTM Standards, Vol 08.01.
NOTE 3—Atest of the test method’s applicability to samples containing
Annual Book of ASTM Standards, Vol 15.05.
Annual Book of ASTM Standards, Vol 14.02. chain extenders is given in Section 12.
*A Summary of Changes section appears at the end of this standard.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959, United States.
D4273–99
4.2 Test Method B—The resonance bands of the primary
Hydroxyl Number Volume Anhydride,
of Polyol mL
and secondary hydroxyl carbons of the polyethers used in
24 to 75 1.0
flexible urethane foams are well-resolved in high-resolution
76 to 150 2.0
carbon-13 NMR spectra. The band areas are measured by the 151 to 225 3.0
226 to 300 4.0
spectrometer’s integration system, and the relative primary
hydroxyl content is determined from the ratio of the primary
9.1.1 Heat the uncapped vial or tube on a hot plate or steam
hydroxyl area to the total area of the primary and secondary
bath in an exhaust hood for about 10 min or until the excess
hydroxyl bands.
methylene chloride and trifluoroacetic anhydride have boiled
off. Cool the concentrate (about 2 mL) to ambient temperature.
5. Significance and Use
Add 0.54 mL of chloroform-d and 2 mL of saturated aqueous
5.1 Measurements of primary hydroxyl content are used in
bicarbonate solution (Note 5). Cap the vial or tube and shake
research to estimate the reactivities of polyols.
vigorously with venting. Decant into a 10-mL centrifuge tube
and centrifuge at an RCF of about 800. Transfer the organic
TEST METHOD A—FLUORINE-19 NMR
layer(bottom)toa1-dramvialcontainingabout0.3gofdrying
agent.After 5 min, filter the trifluoroacetylated polyol solution
6. Equipment
into an NMR tube.
6.1 NMR Spectrometer, with a fluorine-19 resonance fre-
quency of 75 MHz or higher.
NOTE 5—Trifluoroacetate derivatives are hydrolytically unstable. The
analysis should not be interrupted once water is added.
NOTE 4—There was only a small loss in precision when this test
method was used with 56-MHz spectrometers. Although this test method
10. Instrument Preparation
is written for continuous-wave instruments, fourier-transform NMR has
been used with comparable precision.
10.1 The instrument settings given here are for a Varian
6.2 NMR Sample Tubes, having an outside diameter of at
EM-390 spectrometer. Instrument preparation may vary with
least 5 mm.
the spectrometer. For a description of a particular spectrometer
6.3 Centrifuge, bench-top type that can provide a relative
and details of its operation, refer to the manufacturer’s oper-
centrifugal force (RCF) of about 800.
ating manual.
10.2 Typical EM-390 console settings are as follows:
7. Reagents and Materials
Lock −30 ppm (fluorotrichloromethane)
7.1 All reagents should be ACS certified or reagent grade
Offset + 46.3 ppm
Sweep width 1 ppm
unless otherwise specified and should be reasonably free of
Sweep time 2 min
paramagnetic materials (less than 100 ppm iron, for example).
Integration time 1 min
7.2 Trifluoroacetic Anhydride—Aldrich Gold Label or the
Spectrum amplitude 1000 to 3000
Filter time constant 0.05 s
equivalent.
RF power 0.15 mG
7.3 Methylene Chloride—Alcohol-free.
Lock gain 3 to 4
7.4 Chloroform-d -alcohol-free—Deuterated chloroform is Lock power 0.006 mG
Mode Autoshim
used because non-deuterated chloroform usually contains etha-
nol.
11. NMR Analysis
7.5 Sodium Bicarbonate Solution—Prepare a saturated so-
lution by adding 10 g of sodium bicarbonate to 100 mL of
11.1 Addsufficientchloroform-d orfluorotrichloromethane
water.
to the NMR tube containing the sample to obtain a stable lock
7.6 Anhydrous Magnesium Sulfate, or other drying agent.
signal. Optimize the field homogeneity and scan the trifluoro-
7.7 Fluorotrichloromethane — Stabilized grade.
acetate region (75 to 76 ppm downfield from fluorotrichlo-
romethane, see Fig. 1). Integrate the spectrum six times at a
8. Standards
power level below that which causes saturation.
8.1 This test method does not require standards.To evaluate
11.2 Derivatization Check—Add 10 µL of trifluoroacetic
this test method, standards may be prepared from commer-
anhydride to the NMR tube and rescan the spectrum. If
cially available poly(oxypropylene oxide) and poly(ethylene
hydrolysis has occurred or if not enough reagent was used, the
oxide) of known hydroxyl numbers. Polyethylene glycol of
measured primary hydroxyl content will change by 3 % or
molecular weight less than 300 is preferred since the trifluo-
more. If this happens, add 10-µLincrements of anhydride until
roacetate derivatives of higher-molecular-weight polyethylene
the percent primary hydroxyl remains constant or the anhy-
glycols may partially extract into aqueous bicarbonate solution
dride peak appears (see Fig. 2).
(see Note 2).
NOTE 6—Hydrolysis or insufficient reagent is rarely a problem if the
9. Preparation of Sample
procedure is followed closely. Accelerated hydrolysis has been observed
in polyethers containing tertiary amines. Trifluoroacetylated esters of
9.1 Add about1gof sample, the appropriate trifluoroacetic
primary alcohols hydrolyze faster than those of secondary alcohols.
anhydride volume as follows, and 4 mL of methylene chloride
NOTE 7—You can eliminate the trifluoroacetic anhydride peak by
to a 4-mm vial or test tube. Mix well.
adding 10 µL of water. Add water only after the anhydride peak has
Trifluoroacetic Anhydride Volume
appeared in the spectrum.
D4273–99
FIG. 1 6500 MW Triol (72.0% Primary)
12.2 Prepare a 30 % solution of polyether in chloroform-d
or fluorotrichloromethane. Transfer about 0.5 mL to an NMR
tube. Proceed as in 11.2 using 25-µL aliquots of trifluoroacetic
anhydride (Note 8). Minimize interferences from the spinning
sidebandsoftrifluoroaceticacidbychangingthespinningrate.
After complete derivatization, compare the relative areas of
primary and secondary peaks with those obtained by deriva-
tizing according to Section 9 (Note 9). The test method
described in Section 9 is applicable if the relative areas agree
to within 65 %. Peak shapes and chemical shifts may vary
slightly since they are dependent on trifluoroacetic acid con-
centration (see Fig. 3).
NOTE 8—NMR sample sizes and anhydride aliquots were chosen based
on a 5-mm NMR tube and a polyol having a hydroxyl number of 28. If
different diameter NMR tubes are used or if the polyol has a higher
hydroxyl number, adjust volumes accordingly. Complete deri
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