ASTM D7191-18
(Test Method)Standard Test Method for Determination of Moisture in Plastics by Relative Humidity Sensor
Standard Test Method for Determination of Moisture in Plastics by Relative Humidity Sensor
SIGNIFICANCE AND USE
5.1 This test method is intended for use as a control, acceptance, and assessment test.
5.2 Moisture can seriously affect the processability of plastics. It is possible that high moisture content will cause surface imperfections (that is, splay or bubbling) or degradation by hydrolysis. Low moisture (with high temperature) has been known to cause solid phase polymerization.
5.3 The physical properties of some plastics are greatly affected by the moisture content.
SCOPE
1.1 This test method covers the quantitative determination of water down to 20 ppm in plastics using a relative humidity sensor.
1.2 Values stated in SI units are to be regarded as standard.
1.3 Specimens tested in this test method can reach or exceed 250°C, use caution when handling them after testing has completed.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
Note 1: There is no known ISO equivalent to this standard.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7191 − 18
Standard Test Method for
Determination of Moisture in Plastics by Relative Humidity
1
Sensor
This standard is issued under the fixed designation D7191; 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 E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 This test method covers the quantitative determination
of water down to 20 ppm in plastics using a relative humidity
3. Terminology
sensor.
3.1 Definitions—The definitions used in this test method are
1.2 Values stated in SI units are to be regarded as standard.
in accordance with Terminology D883.
1.3 Specimenstestedinthistestmethodcanreachorexceed
4. Summary of Test Method
250°C, use caution when handling them after testing has
4.1 Asample is loaded into a septum-capped glass vial that
completed.
is moved into a heater to evolve the volatiles from the sample
1.4 This standard does not purport to address all of the
into the headspace.Acoaxial needle, or two needle set, pierces
safety concerns, if any, associated with its use. It is the
the septum of the vial as it enters the heater. A dry carrier gas
responsibility of the user of this standard to establish appro-
then flows into the vial and carries the evolved volatiles in the
priate safety, health, and environmental practices and deter-
headspace into the sensor manifold. In the sensor manifold, the
mine the applicability of regulatory limitations prior to use.
carriergasiscooledtoallowhigh-boilingvolatilestocondense
NOTE 1—There is no known ISO equivalent to this standard.
on a hydrophobic filter. The filter’s hydrophobic properties
1.5 This international standard was developed in accor- allow the moisture in the carrier gas to pass through and then
dance with internationally recognized principles on standard- be measured as an increase in potential at the relative humidity
ization established in the Decision on Principles for the sensor. This sensor signal is integrated over time to provide a
Development of International Standards, Guides and Recom- measurementofthetotalmassofwaterinthesample.Thetotal
mendations issued by the World Trade Organization Technical moisture is then divided by sample mass to yield moisture
Barriers to Trade (TBT) Committee. content.
4.2 This test method utilizes a sealed, airtight flow system
2. Referenced Documents
that prevents contamination of the analyzer from water present
2
2.1 ASTM Standards:
in the atmosphere.
D1193 Specification for Reagent Water
5. Significance and Use
D883 Terminology Relating to Plastics
D1600 TerminologyforAbbreviatedTermsRelatingtoPlas-
5.1 This test method is intended for use as a control,
tics
acceptance, and assessment test.
D6869 Test Method for Coulometric and Volumetric Deter-
5.2 Moisture can seriously affect the processability of plas-
mination of Moisture in Plastics Using the Karl Fischer
tics. It is possible that high moisture content will cause surface
Reaction (the Reaction of Iodine with Water)
imperfections (that is, splay or bubbling) or degradation by
E177 Practice for Use of the Terms Precision and Bias in
hydrolysis. Low moisture (with high temperature) has been
ASTM Test Methods
known to cause solid phase polymerization.
5.3 The physical properties of some plastics are greatly
1
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
affected by the moisture content.
and is the direct responsibility of Subcommittee D20.70 on Analytical Methods.
Current edition approved Dec. 1, 2018. Published December 2018. Originally
6. Interferences
approved in 2005. Last previous edition approved in 2010 as D7191 - 10.
DOI:10.1520/D7191-18.
6.1 Elevated concentrations of some common solvents such
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
as methanol, ethanol and acetone will give biased high read-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ings due to their polar characteristics and ability to permeate
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. the thermoset polymer layers of the relative humidity sensor.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
D7191 − 18
7. Apparatus 9.2 Duetothehygroscopicnatureofmanyplastics,samples
3 shall be stored
...
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.
Designation: D7191 − 10 D7191 − 18
Standard Test Method for
Determination of Moisture in Plastics by Relative Humidity
1
Sensor
This standard is issued under the fixed designation D7191; 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
1.1 This test method covers the quantitative determination of water down to 20 ppm in plastics using a relative humidity sensor.
1.2 Values stated in SI units are to be regarded as standard.
1.3 Specimens tested in this test method can reach or exceed 250°C, use caution when handling them after testing has
completed.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
NOTE 1—There is no known ISO equivalent to this standard.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
D1193 Specification for Reagent Water
D883 Terminology Relating to Plastics
D1600 Terminology for Abbreviated Terms Relating to Plastics
D6869 Test Method for Coulometric and Volumetric Determination of Moisture in Plastics Using the Karl Fischer Reaction (the
Reaction of Iodine with Water)
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions—The definitions used in this test method are in accordance with Terminology D883.
4. Summary of Test Method
4.1 A sample is loaded into a septum-capped glass vial that is moved into a heater to evolve the volatiles from the sample into
the headspace. A coaxial needle, or two needle set, pierces the septum of the vial as it enters the heater. A dry carrier gas then flows
into the vial and carries the evolved volatiles in the headspace into the sensor manifold. In the sensor manifold, the carrier gas is
cooled to allow high-boiling volatiles to condense on a hydrophobic filter. The filter’s hydrophobic properties allow the moisture
in the carrier gas to pass through and then be measured as an increase in potential at the relative humidity sensor. This sensor signal
is integrated over time to provide a measurement of the total mass of water in the sample. The total moisture is then divided by
sample mass to yield moisture content.
4.2 This test method utilizes a sealed, airtight flow system that prevents contamination of the analyzer from water present in
the atmosphere.
1
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.70 on Analytical Methods.
Current edition approved April 1, 2010Dec. 1, 2018. Published June 2010December 2018. Originally approved in 2005. Last previous edition approved in 20052010 as
D7191 - 05.D7191 - 10. DOI:10.1520/D7191-10.DOI:10.1520/D7191-18.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
D7191 − 18
5. Significance and Use
5.1 This test method is intended for use as a control, acceptance, and assessment test.
5.2 Moisture can seriously affect the processability of plastics. It is possible that high moisture content will cause surface
imperfections (that is, splay or bubbling) or degradation by hydrolysis. Low moisture (with high temperature) has been known to
cause solid phase polymerization.
5.3 The physical properties of some plastics are greatly affected by the moisture content.
6. Interferences
6.1 Elevated concentrations of some common solvents such as methanol, ethanol and acetone will give
...
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