ASTM D4672-12
(Test Method)Standard Test Method for Polyurethane Raw Materials: Determination of Water Content of Polyols
Standard Test Method for Polyurethane Raw Materials: Determination of Water Content of Polyols
SIGNIFICANCE AND USE
5.1 This test method is suitable for quality control, as a specification test, and for research. The water content of a polyol is important since isocyanates react with water.
SCOPE
1.1 This test method measures water content of polyols and many other organic compounds.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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.Note 1—This test method is equivalent to ISO 14897.
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Designation: D4672 − 12
Standard Test Method for
Polyurethane Raw Materials: Determination of Water
1
Content of Polyols
This standard is issued under the fixed designation D4672; 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.
1. Scope* 4. Summary of Test Methods
1.1 This test method measures water content of polyols and 4.1 This method is based essentially on volumetric or
many other organic compounds. coulometric titrations that follow the reduction of iodine by
sulfur dioxide in the presence of water. This reaction proceeds
1.2 The values stated in SI units are to be regarded as the
quantitatively when methanol or another alcohol (ROH) and
standard. The values given in parentheses are for information
pyridine (C H N) or a similar amine (R'N) are present to react
5 5
only.
withthesulfurtrioxide(SO )andhydriodicacid(HI)produced
3
1.3 This standard does not purport to address all of the
according to the following reactions:
safety concerns, if any, associated with its use. It is the
ROH+SO + R'N→ [R'NH]SO R
2 3
responsibility of the user of this standard to establish appro-
HO+I + [R'NH]SO R + 2R'N→ [R'NH]SO R + 2[R'NH]I
2 2 3 4
priate safety and health practices and determine the applica-
4.2 To determine water, Karl Fischer reagent (a solution of
bility of regulatory limitations prior to use.
iodine, sulfur dioxide, imidazole, and pyridine or a pyridine
NOTE 1—This test method is equivalent to ISO 14897.
substitute) is added to a solution of the sample in methanol or
other alcohol until all the water present has been consumed.
2. Referenced Documents
The titrant is either added by buret (volumetry) or generated
2
2.1 ASTM Standards: electrochemically in the titration cell (coulometry). Coulomet-
D1193 Specification for Reagent Water
ric titrations eliminate the need for standardizing the reagent.
D883 Terminology Relating to Plastics
E180 Practice for Determining the Precision of ASTM
5. Significance and Use
Methods for Analysis and Testing of Industrial and Spe-
5.1 This test method is suitable for quality control, as a
3
cialty Chemicals (Withdrawn 2009)
specification test, and for research. The water content of a
polyol is important since isocyanates react with water.
3. Terminology
3.1 Definitions: 6. Apparatus
3.1.1 polyurethane, n—a polymer prepared by the reaction
6.1 Several commercial Karl Fischer autotitrators are avail-
of an organic diisocyanate with compounds containing hy- 4
able that employ volumetric or coulometric titrations. These
droxyl groups.
instruments consist of an automated buret assembly, a sealed
3.1.1.1 Discussion—Polyurethanes,orurethanes,astheyare
titration vessel with appropriate electrodes and sensing
sometimes called, may be thermosetting, thermoplastic, rigid
circuitry, and a vacuum system for removal of solution after
or soft and flexible, cellular or solid. (See Terminology D883.)
analysis. These automated systems provide several advantages
and conveniences.Atmospheric moisture contamination can be
more closely controlled; calibration is simplified; and the
1
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
preneutralization step is automatic. Titrations are rapid, and
and are the direct responsibility of Subcommittee D20.22 on Cellular Materials -
reagent consumption is low. Autotitrators automatically calcu-
Plastics and Elastomers.
late and display or print the water concentration.
Current edition approved Aug. 1, 2012. Published August 2012. Originally
ε1
approved in 1991. Last previous edition approved in 2000 as D4672 - 00(2006) .
DOI: 10.1520/D4672-12.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Instruments similar to and including the following types have been found
Standards volume information, refer to the standard’s Document Summary page on suitable for determining water content of polyols, based on round-robin studies:
the ASTM website. Metrohm models 633, 652, 658, 665, 684, 701, 720, 737, and 758 (available from
3
The last approved version of this historical standard is referenced on Brinkmann Instruments, Inc. at www.brinkmann.com) and Mettler Toledo models
www.astm.org. DL 18, 31, 37, and 38 (www.mt.com).
*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
1
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D4672 − 12
A
TABLE 1 Volumetric Titration
7. Reagents
% Water Expected Sugges
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D4672 − 00 (Reapproved 2006) D4672 − 12
Standard Test MethodsMethod for
Polyurethane Raw Materials: Determination of Water
1
Content of Polyols
This standard is issued under the fixed designation D4672; 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.
1
´ NOTE—Removed non-mandatory language throughout in March 2006.
1. Scope*
1.1 TheseThis test methods measuremethod measures water content of polyols and many other organic compounds.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
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.
NOTE 1—TheseThis test methods aremethod is equivalent to ISO 14897.
2. Referenced Documents
2
2.1 ASTM Standards:
D1193 Specification for Reagent Water
D883 Terminology Relating to Plastics
E180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals
3
(Withdrawn 2009)
3. Terminology
3.1 Definitions:
3.1.1 polyurethane, n—a polymer prepared by the reaction of an organic diisocyanate with compounds containing hydroxyl
groups.
1
These test methods are under the jurisdiction of ASTM Committee D20 on Plastics and are the direct responsibility of Subcommittee D20.22 on Cellular Materials -
Plastics and Elastomers.
Current edition approved March 15, 2006. Published June 2006. Originally approved in 1991. Last previous edition approved in 2000 as D4672 - 00. DOI:
10.1520/D4672-00R06E01.
2
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 the ASTM website.
3
The last approved version of this historical standard is referenced on www.astm.org.
3.1.1.1 Discussion—
Polyurethanes, or urethanes, as they are sometimes called, may be thermosetting, thermoplastic, rigid or soft and flexible, cellular
or solid. (See Terminology D883.)
4. Summary of Test Methods
4.1 Test Methods A and B are This method is based essentially on volumetric or coulometric titrations that follow the reduction
of iodine by sulfur dioxide in the presence of water. This reaction proceeds quantitatively when methanol or another alcohol (ROH)
and pyridine (C H N) or a similar amine (R8N) are present to react with the sulfur trioxide (SO ) and hydriodic acid (HI) produced
5 5 3
according to the following reactions:
ROH + SO + R8N → [R8NH]SO R
2 3
H O + I + [R8NH]SO R + 2R8N → [R8NH]SO R + 2[R8NH]I
2 2 3 4
*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
1
---------------------- Page: 1 ----------------------
D4672 − 12
4.2 To determine water, Karl Fischer reagent (a solution of iodine, sulfur dioxide, imidazole, and pyridine or a pyridine
substitute) is added to a solution of the sample in methanol or other alcohol until all the water present has been consumed. The
titrant is either added by buret (volumetry) or generated electrochemically in the titration cell (coulometry). Coulometric titrations
eliminate the need for standardizing the reagent.
5. Significance and Use
5.1 TheseThis test methods aremethod is suitable for quality control, as a specification test, and for research. The water content
of a polyol is important since isocyanates react with water.
TEST METHOD A: MANUAL PROCEDURE
NOTE 2—Commercially available automated Karl Fischer titrators are used extensively.
5.2 The description of the manual systems presented below is for reference purposes and has been included in order to better
define the principles of the Karl Fischer measurement.
6. Apparatus
6.1 Titration Vessel—A vessel of approximately 300-mL capacity, such as a tall-form, lipless beaker, provided with a tight-fitting
closure to protect the reaction mixture from atmospheric moisture. The vessel shall also be fitted with a nitrogen inlet tube, a 10-mL
buret, a stirrer (preferably magnetic),
...
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