ASTM D4274-99

Standard Test Methods for Testing Polyurethane Raw Materials Determination of Hydroxyl Numbers of Polyols

SCOPE
1.1 These test methods measure the hydroxyl groups in polyester and polyether polyols. They also apply to many other hydroxyl-containing substances.  
1.1.1 Test Method A-Acetic Anhydride Pressure Bottle, recommended for polyesters.  
1.1.2 Test Method B-Phthalic Anhydride Pressure Bottle, recommended for polyethers and polyesters.  
1.1.3 Test Method C-Phthalic Anhydride Reflux, recommended for polyethers and polyesters.  
1.1.4 Test Method D-Imidazole-Catalyzed Phthalic Anhydride Pressure Bottle, recommended for polyethers, polyesters, polymer polyols, and amine-initiated polyols.
1.1.5 Test Method E  - Imidazole-Catalyzed Pyromellitic Dianhydride Esterification , recommended for polyols used for flexible and rigid polyurethane foams and urethane elastomers. It is recommended for polyester polyols, polyether polyols, amine-started polyols, and polymer polyols (polyacrylonitrile/copolystyrene-based).  
1.2 Other ASTM test methods for measuring hydroxyl groups are Test Methods D1957, E222, E326, and E335 (see Note 1). Note 1-Test Method C is essentially similar to ISO 6796-1981, but there are some differences in the concentrations used and some procedural details. There are currently no data available for comparing the results of Test Method C to those of ISO 6796-1981.
1.3 The values stated in SI units are to be regarded as the standard.  
1.4 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.

General Information

• Status: Historical
• Publication Date: 09-Nov-1999
• ICS: 83.080.20 - Thermoplastic materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.22 - Cellular Materials - Plastics and Elastomers

Relations

• Replaced By: ASTM D4274-05 - Standard Test Methods for Testing Polyurethane Raw Materials: Determination of Hydroxyl Numbers of Polyols
• Effective Date: 01-Jul-2005
• Referred By: ASTM E1899-23 - Standard Test Method for Hydroxyl Groups Using Reaction with <emph type="ital">p</emph >-Toluenesulfonyl Isocyanate (TSI) and Potentiometric Titration with Tetrabutylammonium Hydroxide
• Effective Date: 10-Nov-1999
• Referred By: ASTM D6342-22 - Standard Practice for Polyurethane Raw Materials: Determining Hydroxyl Number of Polyols by Near Infrared (NIR) Spectroscopy
• Effective Date: 10-Nov-1999

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D4274–99
Standard Test Methods for Testing
Polyurethane Raw Materials: Determination of Hydroxyl
Numbers of Polyols
This standard is issued under the fixed designation D4274; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope * 2. Referenced Documents
1.1 These test methods measure the hydroxyl groups in 2.1 ASTM Standards:
polyester and polyether polyols containing primary and sec- D883 Terminology Relating to Plastics
ondary hydroxyl groups. They also apply to many other D1193 Specification for Reagent Water
hydroxyl-containing substances. D1957 Test Method for Hydroxyl Value of Fatty Oils and
1.1.1 Test Method A—Acetic Anhydride Pressure Bottle, Acids
recommended for polyesters. E180 Practice for Determining the Precision of ASTM
1.1.2 Test Method B—Phthalic Anhydride Pressure Bottle, Methods forAnalysis andTesting of Industrial Chemicals
recommended for polyethers and polyesters. E200 Practice for Preparation, Standardization, and Stor-
1.1.3 Test Method C—Phthalic Anhydride Reflux, recom- age of Standard and Reagent Solutions for Chemical
mended for polyethers and polyesters. Analysis
1.1.4 Test Method D—Imidazole–Catalyzed Phthalic Anhy- E203 Test Method for Water Using Karl Fischer Reagent
dride Pressure Bottle,recommendedforpolyethers,polyesters, E222 Test Methods for Hydroxyl Groups byAceticAnhy-
polymer polyols, and amine-initiated polyols. dride Acetylation
1.1.5 Test Method E —Imidazole-Catalyzed Pyromellitic E326 Test Method for Hydroxyl Groups by PhthalicAnhy-
Dianhydride Esterification, recommended for polyols used for dride Esterification
flexibleandrigidpolyurethanefoamsandurethaneelastomers. E335 Test Method for Hydroxyl Groups by Pyromellitic
It is recommended for polyester polyols, polyether polyols, Dianhydride Esterification
amine-started polyols, and polymer polyols (polyacrylonitrile/ E691 Practice for Conducting an Interlaboratory Study to
copolystyrene-based). Determine the Precision of a Test Method
1.2 Other ASTM test methods for measuring hydroxyl 2.2 ISO Standard:
groupsareTestMethodsD1957,E222,E326,andE335(see ISO 6791-1981 Polyglycols for Industrial Use—
Note 1). Determination of Hydroxyl Number—PhthalicAnhydride
Esterification Method
NOTE 1—Test Method C is essentially similar to ISO 6796-1981, but
therearesomedifferencesintheconcentrationsusedandsomeprocedural
3. Terminology
details. There are currently no data available for comparing the results of
3.1 Definitions—The terminology in these test methods
Test Method C to those of ISO 6796-1981.
follows the standard terminology defined in Terminology
1.3 The values stated in SI units are to be regarded as the
D883.
standard.
3.2 Definitions of Terms Specific to This Standard—There
1.4 This standard does not purport to address all of the
are no terms in these test methods that require new or other
safety concerns, if any, associated with its use. It is the
than dictionary definitions.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
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 Annual Book of ASTM Standards, Vol 08.01.
Plastics. These test methods were recommended to ASTM by the Society of the Annual Book of ASTM Standards, Vol 06.03.
Plastics Industry Polyurethane Raw Material Analysis Committee. Annual Book of ASTM Standards, Vol 15.05.
Current edition approved Nov. 10, 1999. Published February 2000. Originally Annual Book of ASTM Standards, Vols 06.03, 08.03, and 14.02.
published as D4274–88. Last previous edition D4274–94. Available from American National Standards Institute, 11 W. 42nd St., 13th
Annual Book of ASTM Standards, Vol 11.01. Floor, New York, NY 10036.
*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.
D4274
4. Summary of Test Methods material is a finely-ground solid it is necessary to melt (using
no higher temperature than necessary) and mix the resin well
4.1 Test Method A—The sample is acetylated with a solu-
before removing a sample for analysis. Many polyols are
tion of acetic anhydride (Caution: see Note 2) in pyridine in a
hygroscopic, and care should be taken to provide minimum
pressure bottle at 98°C. The excess reagent is hydrolyzed with
exposure to atmospheric moisture during the sampling.
water and the acetic acid is titrated with standard sodium
hydroxide solution. The hydroxyl content is calculated from
TEST METHOD A—ACETYLATION
the difference in titration of the blank and sample solutions.
8. Interferences
NOTE 2—Caution:Acetic anhydride and pyridine are toxic and flam-
mable. In addition, acetic anhydride is corrosive. Proper precautions
8.1 Dry the sample if it contains more than 0.2% water.
should be taken in handling these reagents.
More than that will interfere by destroying the esterification
4.2 Test Method B—The hydroxyl group is esterified with a
reagents.
solution of phthalic anhydride in pyridine in a pressure bottle
8.2 Primary and secondary amines and long-chain fatty
at 98°C. The excess reagent is titrated with standard sodium
acids react with the reagent to form stable compounds that
hydroxide solution.
would be included in the analysis.
4.3 Test Method C—The hydroxyl group is esterified with a
solution of phthalic anhydride in pyridine under reflux condi- 9. Apparatus
tions at 115°C. The excess reagent is titrated with standard 9
9.1 Bottle, pressure, heat-resistant, approximately 350 mL.
sodium hydroxide solution.
9.2 Bag, heavy fabric with draw string to hold bottle. As
4.4 Test Method D—The hydroxyl group is esterified by
an alternative, a stainless steel mesh jacket fitted to cover the
reaction with phthalic anhydride in a pyridine medium at
bottle may be used.
approximately 100°C. The esterification reaction is catalyzed
9.3 Buret,100-mLtotalcapacity,rangeofgraduatedportion
by imidazole. The excess anhydride is hydrolyzed with water,
50 mL, 0.1-mL graduations.
and the phthalic acid formed is titrated to the phenolphthalein
NOTE 3—As a substitute, if the 100-mL buret is not available, the first
end point with standard sodium hydroxide solution. The
50 mL of titrant may be added by pipet (uniform drainage time for all
hydroxylcontentiscalculatedfromthedifferenceintitrationof
aliquots) and the titration completed with a 50-mL buret.
the blank and the sample solution.
9.4 Water Bath,9862°C,containingenoughwatertocover
4.5 Test Method E—The hydroxyl group is esterified with a
the liquid in the sample bottles. The water level must be as
solution of imidazole (IMDA) and pyromellitic dianhydride
prescribed, and the temperature must be within the prescribed
(PMDA) in dimethylformamide in an iodine flask at 70 to
range and uniform throughout the bath.
80°C. The excess reagent is titrated with standard sodium
hydroxide solution.
10. Reagents
5. Significance and Use
10.1 Acetic Anhydride.
10.2 Acetylation Reagent—Mix127mLofaceticanhydride
5.1 These test methods are suitable for research and as
with 1000 mL of pyridine (10.5). Prepare the reagent fresh
quality control and specification tests. It is necessary to know
daily and keep it in a dark bottle. Do not use it if it is darker
the hydroxyl contents of polyols in order to formulate poly-
than pale yellow.
urethane systems.
10.3 Hydrochloric Acid, Standard (0.5 N)—Prepare and
6. Reagents
standardize in accordance with Sections 20 to 24 of Practice
E200. Determine and record the temperature at which the
6.1 Purity of Reagents—Use reagent-grade chemicals in all
standardization was performed. The concentration of the solu-
tests. Unless otherwise indicated, all reagents must conform to
tion shall be corrected to the temperature at which the
the specifications of the Committee onAnalytical Reagents of
determinationisperformedasdescribedin10.6.Thefactorfor
theAmerican Chemical Society, where such specifications are
thethermalexpansionofthissolutionis0.00014.Thissolution
available. Other grades may be used, provided they are pure
isrequiredonlyifacorrectionistobeappliedforthepresence
enough to be used without lowering accuracy.
of strong base in the sample being analyzed.
6.2 Purity of Water—Unless otherwise indicated, use Type
10.4 Phenolphthalein Indicator Solution—Dissolve1gof
II water conforming to Specification D1193.
phenolphthalein in 100 mL of pyridine.
7. Sampling
10.5 Pyridine, containing from 0.30 to 0.45% water. Deter-
mine the water content of the pyridine using Test Method
7.1 Polyesters and polyethers usually contain molecules
E203.Addtherequiredamountofwater.Thevolumeofwater
covering an appreciable range of molecular weights. These
to add, mL, per litre of pyridine may be calculated as follows:
have a tendency to fractionate during solidification. Unless the
8 9
“ReagentChemicals,AmericanChemicalSocietySpecifications,”Am.Chemi- AsuitablebottleisavailablefromB.PreiserCo.,Inc.,Charleston,WV,Catalog
cal Soc., Washington, DC. For suggestions on the testing of reagents not listed by No. 10-5485; Chemical Rubber Co., Cleveland, OH, Catalog No. 33052A; and
theAmericanChemicalSociety,see“ReagentChemicalsandStandards,”byJoseph Scientific Glass Co., Bloomfield, NJ, Catalog No. B-5317.
Rosin, D. Van Nostrand Co., Inc., New York, NY, and the “United States Available from Flaherty Filter Media, Inc., 16 Passaic Ave., P.O. Box 357,
Pharmacopeia.” Spring Lake, NJ 07762.
D4274
Watertoadd 54.0 29A (1)
Add to the flask 75 mL of redistilled pyridine, 75 mL of
distilled water, and 0.5 mL of phenolphthalein indicator solu-
where A=percent of water in pyridine.
tion.
10.6 Sodium Hydroxide, Standard Solution (0.5 N)—
11.8 Acidity Correction—If the solution is colorless, titrate
Prepare and standardize in accordance with Sections 14 to 19
with standard 0.1 N NaOH to a pink end point that persists for
of Practice E200. Determine and record the temperature at
at least 15 s. Make a blank titration on the reagent mixture
which the standardization was performed. The factor for
described in 11.7, omitting the sample. The acidity correction,
thermal expansion of this solution is 0.00014. For calculation
mg KOH/g, is calculated as follows:
of the hydroxyl content, the normality of the solution shall be
corrected to the temperature at which the determination is
Aciditycorrection 5 @~A 2 B!N 356.1#/W (4)
performed by the following:
where:
Nt 5 Nt 1 ~t 2 t !~F! (2)
2 1 1 2
A = NaOHsolutionrequiredfortitrationoftheblank,mL,
B = NaOHsolutionrequiredfortitrationoftheblank,mL,
where:
N = normality of the NaOH solution, and
Nt = normality when standardized,
W = sample used, g.
Nt = normality during analysis of samples,
11.9 Alkalinity Correction—If the solution in 11.7 is pink,
t = temperature of solution during standardization,° C,
titrate to the disappearance of the pink color with 0.1 N HCl,
t = temperature of solution during analysis of samples,
and then add 1.0 mL excess. Back-titrate with standard 0.1 N
°C, and
NaOH to a pink end point that persists for at least 15 s.Titrate
F = factor to correct for thermal expansion of the
withstandard0.1 NNaOHablankcontainingexactlythesame
solution (see each solution for appropriate factor).
amount of added 0.1 N HCl and the reagent mixture described
in 11.7 omitting the sample. The alkalinity correction, mg
11. Procedure
KOH/g, is calculated as follows:
11.1 Pipet 20.0 mL of the acetylation reagent to each
Alkalinitycorrection 5 B 2 A!N 356.1 /W (5)
pressure bottle for the blank and sample determinations (in @~ #
duplicate). Use the same drainage time for each aliquot.
where the terms are as defined as in 11.8.
11.2 Reservetwoofthebottlesfortheblankdeterminations;
weigh samples to the nearest 0.1 mg into the other bottles.
12. Calculation
Determine the sample weight, g, as follows:
12.1 Calculate the hydroxyl number, mg KOH/g, of sample
Sampleweight
as follows:
Hydroxylnumber 5 @~B 2 A!N 356.1#/W (6)
5 ~561 30.98!/approximatehydroxylnumber (3)
Since the calculated weight will be near the maximum where:
A = NaOH required for titration of the sample, mL,
permitted by the test method, adhere closely to the indicated
B = NaOH required for titration of the blank, mL,
weight.
N = normality of the NaOH, and
11.3 Stopper the bottle and swirl it until the sample is
W = sample used, g.
completely dissolved. Enclose each bottle in a fabric bag and
12.2 If the sample contains free acidity or alkalinity as
place all bottles as close together as possible in the water bath
measured in 11.7-11.9, the result in 12.1 must be corrected as
at98 62°Cfor2h.Keepenoughwaterinthebathtocoverthe
follows:
level of liquid in the bottles.
11.4 Remove the bottles from the bath and allow them to Hydroxylnumber ~corrected!
cool to room temperature. Untie the bags, uncap the bottles to
5hydroxylnumber 1acidity,or
release any pressure, and then remove the bags.
(7)
11.5 Carefullyrinseanyliquidonthestopperintothebottle
Hydroxylnumber ~corrected!
and rinse the walls of the flask with 20 to 30 mLof water.Add
clean crushed ice to each of the bottles until about half full.
5hydroxylnumber 2alkalinity
11.6 Add 1 mL of the phenolphthalein indicator solution
(8)
and titrate immediately with the 0.5 N NaOH solution to the
first faint pink end point that persists for 15 s. The solution
13. Report
shouldbeswirledduringthetitration,withvigorousswirlingas
13.1 Report the corrected hydroxyl number to the nearest
the end point is reached. Record the volume of titrant to 0.02
0.1.
mL (Note 4). Record the temperature of the NaOH solution.
14. Precision and Bias
NOTE 4—Ifthevolumeof0.5 NNaOHsolutionrequiredforthesample
is less than 80% of that required for the blank, the sample was too large
14.1 Precision—Attempts to develop a precision and bias
and the analysis must be repeated with a smaller sample.
statement for this test method have not been successful. For
11.7 Acidity or Alkalinity Correction—If the sample con-
tains significant acidity or alkalinity, correct the result as
follows. Weigh into a 400-mL Erlenmeyer flask the same
Supporting data are available from ASTM Headquarters. Request RR: D20-
amount of sample used before for the hydroxyl determination. 1089.
D4274
thisreason,dataonprecisiona
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