ASTM D4671-99
(Test Method)Standard Test Method for Polyurethane Raw Materials Determination of Unsaturation of Polyols
Standard Test Method for Polyurethane Raw Materials Determination of Unsaturation of Polyols
SCOPE
1.1 This test method measures unsaturation in polyether polyols. (See Note.)
1.2 This standard does not purport to address all of the safety problems, 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-There is no equivalent ISO standard.
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Designation:D4671–99
Standard Test Methods for
Polyurethane Raw Materials: Determination of Unsaturation
of Polyols
This standard is issued under the fixed designation D 4671; 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* 4. Summary of Test Method
1.1 These test methods measure unsaturation in polyether 4.1 Carbon-to-carbon unsaturated compounds in the sample
polyols. (See Note 1.) are reacted with mercuric acetate and methanol in a methanolic
1.1.1 Test Method A, High-Volume Reagent Method—Uses solution to produce acetoxymercuricmethoxy compounds and
about50mLof0.1 Mmercuricacetatereagentinmethanoland acetic acid. The amount of acetic acid released in this
15 g or more of sample. This test method uses an indicator for equimolar reaction, which is determined by titration with
colorimetric determination of an end point. It is recommended standard alcoholic potassium hydroxide, is a measure of the
for polyols with low values (below 0.01 millequivalents per unsaturation originally present. Because the acid cannot be
gram (meq/g)) of unsaturation where large sample sizes are titrated in the presence of excess mercuric acetate, due to the
required. formation of insoluble mercuric oxide, sodium bromide is
1.1.2 Test Method B, Low-Volume Reagent Method—Uses 2 added to convert the mercuric acetate to the bromide, which
mL of ca. 0.05 M mercuric acetate reagent in methanol and does not interfere. Inasmuch as this test method is based on an
about1gof sample or less. This test method uses a potentio- acidimetrictitration,asuitablecorrectionmustbeappliedifthe
metric determination of an end point. sample is not neutral to phenolphthalein indicator. Take care to
1.2 This standard does not purport to address all of the exclude carbon dioxide, which titrates as an acid and gives
safety concerns, if any, associated with its use. It is the erroneous results.
responsibility of the user of this standard to establish appro-
5. Significance and Use
priate safety and health practices and determine the applica-
5.1 These test methods are suitable for quality control, as
bility of regulatory limitations prior to use.
specification tests, and for research.
NOTE 1—There is no equivalent ISO standard.
5.2 Side reactions that form unsaturated compounds in
polypropylene oxides produce small amounts of polymers with
2. Referenced Documents
only one hydroxyl group per chain. These unsaturated poly-
2.1 ASTM Standards:
mers lower functionality and molecular weight, while broad-
D 883 Terminology Relating to Plastics
ening the overall molecular-weight distribution.
E 180 Practice for Determining the Precision of ASTM
Methods for Analysis and Testing of Industrial Chemicals
6. Interferences
6.1 These test methods do not apply to compounds in which
3. Terminology
the unsaturation is conjugated with carbonyl, carboxyl, or
3.1 Definitions—For definitions of terms used in these test
nitrile groups. Because water presumably hydrolyzes the reac-
methods, see Terminology D 883.
tion products to form basic mercuric salts, quantitative results
are obtained only when the system is essentially anhydrous.
Acetone in low concentrations does not interfere significantly,
These test methods are under the jurisdiction of ASTM Committee D-20 on
Plastics and is the direct responsibility of Subcommittee D20.22 on Cellular
although its presence may be detrimental to the end point.
Plastics. Test Method A was recommended to ASTM by the Society of the Plastics
Inorganic salts, especially halides, must be absent from the
Industry Polyurethane Raw Materials Analysis Committee.
Current edition approved Nov. 10, 1999. Published February 2000. Originally
published as D 4671 – 87. Last previous edition D 4671 – 93.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Sigia, S. and Hanna, J.G., “Quantitative Organic Analysis via Functional
the ASTM website. Groups,” John Wiley and Sons, New York, 1979.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4671–99
sample because even small amounts of salts may nullify the that persists for at least 15 s. Record the volume of titrant used
reaction of the mercuric acetate with the unsaturated com- for the samples as D and that used for the blank as E. The
pound. sample titration should not exceed 50 mL of 0.1 N alcoholic
KOH solution.
TEST METHOD A—HIGH-VOLUME REAGENT
METHOD
10. Calculation
10.1 Calculate the concentration of unsaturated compounds,
7. Apparatus
meq/g, as follows:
7.1 Pipet, 50-mL capacity.
C 5 ~A 3 N!/W (1)
7.2 Erlenmeyer Flask, 250-mL glass-stoppered.
7.3 Balance, 1000-g capacity, 0.1-g sensitivity.
where:
7.4 Buret, 50-mL capacity.
A = 0.1 N alcoholic KOH solution required to neutralize
the sample, mL,
8. Reagents
N = normality of the alcoholic KOH solution, and
8.1 Purity of Reagents—Use reagent-grade chemicals in all W = sample used, g.
tests. Unless otherwise indicated, it is intended that all reagents
therefore:
shall conform to the specifications of the Committee on
Total unsaturation 5 [~D 2 E!N/W] 2 C (2)
Analytical Reagents of theAmerican Chemical Society, where
such specifications are available. Other grades may be used, where:
provided it is first ascertained that the reagent is of sufficiently D = alcoholic KOH solution required for titration of the
sample, mL
high purity to permit its use without lessening the accuracy of
E = alcoholic KOH solution required for titration of the
the determination.
blank, average mL, and
8.2 Mercuric Acetate, Methanol Solution (40 g/L)—
C = average of results from Eq 1, meq of acidity/g of
Dissolve 40 g of mercuric acetate (Hg(C H O ) in sufficient
2 3 2 2
sample.
methanol to make 1 L of solution and add sufficient glacial
acetic acid to require a blank titration of 1 to 10 mL of 0.1 N
11. Precision and Bias
alcoholicKOHsolution/50mLofreagent.Usually3or4drops
11.1 Precision—Attempts to develop a precision and bias
of acid are sufficient. Prepare the reagent fresh weekly and
statement for this test method have not been successful. For
filter before using.
this reason, data on precision and bias cannot be given.
8.3 Sodium Bromide (NaBr).
Because this test method does not contain a numerical preci-
9. Procedure
sion and bias statement, it shall not be used as a referee test
method in case of dispute.Anyone wishing to participate in the
9.1 Add 50 mL of methanol to a sufficient number of
development of precision and bias data should contact the
250-mL Erlenmeyer flasks to determine the acidity of each
Chairman,SubcommitteeD20.22(SectionD20.22.01),ASTM,
sample in duplicate. Neutralize to a faint pink end point, using
100 Barr Harbor Dr., PO Box C700, West Conshohocken, PA
a few drops of phenolphthalein indicator solution and 0.1 N
19428.
alcoholicKOHsolution.Add30gofthesampleweighedtothe
11.1.1 It is estimated that duplicate results by the same
nearest0.1gtoeachflaskandswirltoeffectcompletesolution.
analystshouldbeconsideredsuspectiftheydifferbymorethan
Titrate with 0.1 N alcoholic KOH solution to a pink end point
0.002.
that persists for at least 15 s and record the volume of titrant as
11.2 Bias—The bias for this test method has not yet been
A.
determined.
9.2 Pipet 50 mLof the Hg(C H O ) solution into each of a
2 3 2 2
sufficient number of 250-mL Erlenmeyer flasks to make all
TEST METHOD B—LOW-VOLUME REAGENT
blank and sample determinations in duplicate. Reserve two of
METHOD
the flasks for the blank determination. Into each of the other
flasks, introduce 30 g of the sample weighed to the nearest 0.1
12. Apparatus
g and swirl to effect complete solution. Allow the samples to
12.1 Pipet, 2-mL capacity.
stand together with the blanks at room temperature for 30 min.
12.2 Autotitrator, capable of determining acidimetric end
Swirl the flasks occasionally.Add 8 to 10 g of NaBr crystals to
points using a 5-mL buret.
each flask and swirl to mix thoroughly. Add approximately 1
12.3 Combination, Glass, pH Electrode, for use with the
mL of phenolphthalein indicator solution and titrate immedi-
autotitrator.
ately with 0.1 N alcoholic KOH solution to a pink end point
12.4 Balance, capable of weighing samples to 0.0001 g.
12.5 Titration Vessels, 50- to 100-mL capacity.
Reagent Chemicals, American Chemical Society Specifications, American
13. Reagents
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
listed by the Am
...
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