ASTM D6869-03(2011)
(Test Method)Standard Test Method for Coulometric and Volumetric Determination of Moisture in Plastics Using the Karl Fischer Reaction (the Reaction of Iodine with Water)
Standard Test Method for Coulometric and Volumetric Determination of Moisture in Plastics Using the Karl Fischer Reaction (the Reaction of Iodine with Water)
SIGNIFICANCE AND USE
Moisture will affect the processability of some plastics. High moisture content causes surface imperfections (that is, splay or bubbling) or degradation by hydrolysis. Low moisture (with high temperature) causes polymerization.
The physical properties of some plastics are affected by the moisture content.
SCOPE
1.1 This method uses the reaction of Iodine (I2) with water (Karl Fischer Reaction) to determine the amount of moisture in a polymer sample.
1.2 This test method is intended to be used for the determination of moisture in most plastics. Plastics containing volatile components such as residual monomers and plasticizers are capable of releasing components that will interfere with the I2/water reaction.
1.3 This method is suitable for measuring moisture over the range of 0.005 to 100 %. Sample size shall be adjusted to obtain an accurate moisture measurement.
1.4 The values stated in SI units are regarded as the standard.
Note 1—This standard is technically equivalent to ISO 15512 Method B.
1.5 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: D6869 − 03 (Reapproved 2011)
Standard Test Method for
Coulometric and Volumetric Determination of Moisture in
Plastics Using the Karl Fischer Reaction (the Reaction of
1
Iodine with Water)
This standard is issued under the fixed designation D6869; 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 collected in the solution within the titration cell is determined
using the reaction of water with I .
2
1.1 This method uses the reaction of Iodine (I ) with water
2
(Karl Fischer Reaction) to determine the amount of moisture in 3.2 Endpoint detection is made by instrumented methods.
2
a polymer sample. Determination of the moisture present is made using the
reaction of I with water.
2
1.2 This test method is intended to be used for the determi-
nation of moisture in most plastics. Plastics containing volatile 3.3 Coulometric instruments use Faraday’s law to measure
components such as residual monomers and plasticizers are the moisture present with 10.71 Coulombs (C) of generating
- -
capable of releasing components that will interfere with the current corresponding to 1 mg of water (2I → I +2e ).
2
I /water reaction. Volumetric instruments measure the volume of solution con-
2
taining I that is required to keep the current constant.
2
1.3 This method is suitable for measuring moisture over the
range of 0.005 to 100 %. Sample size shall be adjusted to
4. Significance and Use
obtain an accurate moisture measurement.
4.1 Moisture will affect the processability of some plastics.
1.4 The values stated in SI units are regarded as the
High moisture content causes surface imperfections (that is,
standard.
splay or bubbling) or degradation by hydrolysis. Low moisture
NOTE 1—This standard is technically equivalent to ISO 15512 Method
(with high temperature) causes polymerization.
B.
1.5 This standard does not purport to address all of the 4.2 The physical properties of some plastics are affected by
safety concerns, if any, associated with its use. It is the the moisture content.
responsibility of the user of this standard to establish appro-
5. Interferences
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
5.1 Some compounds, such as aldehydes and ketones,
interfere in the determination of moisture content using this
2. Referenced Documents
method.
2.1 ISO Document:
6. Apparatus
3
ISO 15512 Plastics—Determination of Water Content
6.1 Heating Unit, consisting of an oven capable of heating
2
the sample to approximately 300°C, a furnace tube, a tempera-
3. Summary of Test Method
turecontrolunit,acarriergasflowmeter,anddesiccatingtubes
3.1 Samples are heated to vaporize water that is transported
for the carrier gas.
by a nitrogen carrier gas to the titration cell. The moisture
6.2 SamplePan(Boat),normallyaglasssampleboatorboat
manufactured of a suitable material to transfer the oven heat to
the sample. It is permitted to use aluminum foil as a disposable
1
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
liner for the sample pan.
and is the direct responsibility of Subcommittee D20.70 on Analytical Methods.
Current edition approved Sept. 1, 2011. Published October 2011. Originally
6.3 Titration Unit, consisting of a control unit, titration cell
approved in 2003. Last previous edition approved in 2003 as D6869 - 03.
with a solution cathode, platinum electrode, and solution
DOI:10.1520/D6869-03R11.
2
See Appendix X1, History of Reagents Associated With the Karl Fischer
stirring capability.This apparatus has the capability to generate
Reaction, for an explanation of coulometric and volumetric techniques as well as an
or deliver iodine to react stoiciometrically with the moisture
explanation of the Karl Fischer Reaction and Karl Fischer Reagents.
3
present in the titration cell. The current or volume required to
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. generate the iodine converts to micrograms of water present.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D6869 − 03 (2011)
The percent moisture in the sample is then calculated based on 10. Preparation of Apparatus
the sample weight used and is given as a direct digital readout.
10.1 Assemble the apparatus according to the manufactur-
er’s instructions. Molecular sieve or suitable desiccant must be
6.4 Analytical Balance, capable of weighing 0.1 mg (four
d
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