ASTM D7191-10
(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
This test method is intended for use as a control, acceptance, and assessment test.
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.
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 and health practices and determine the applicability of regulatory limitations prior to use.
Note 1—There is no known ISO equivalent to this standard.
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Designation: D7191 − 10
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 3. Terminology
1.1 This test method covers the quantitative determination 3.1 Definitions—The definitions used in this test method are
in accordance with Terminology D883.
of water down to 20 ppm in plastics using a relative humidity
sensor.
4. Summary of Test Method
1.2 Values stated in SI units are to be regarded as standard.
4.1 Asample is loaded into a septum-capped glass vial that
1.3 Specimenstestedinthistestmethodcanreachorexceed
is moved into a heater to evolve the volatiles from the sample
250°C, use caution when handling them after testing has into the headspace.Acoaxial needle, or two needle set, pierces
completed. 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
1.4 This standard does not purport to address all of the
headspace into the sensor manifold. In the sensor manifold, the
safety concerns, if any, associated with its use. It is the
carriergasiscooledtoallowhigh-boilingvolatilestocondense
responsibility of the user of this standard to establish appro-
on a hydrophobic filter. The filter’s hydrophobic properties
priate safety and health practices and determine the applica-
allow the moisture in the carrier gas to pass through and then
bility of regulatory limitations prior to use.
be measured as an increase in potential at the relative humidity
NOTE 1—There is no known ISO equivalent to this standard.
sensor. This sensor signal is integrated over time to provide a
measurementofthetotalmassofwaterinthesample.Thetotal
2. Referenced Documents
moisture is then divided by sample mass to yield moisture
2
2.1 ASTM Standards:
content.
D1193 Specification for Reagent Water
4.2 This test method utilizes a sealed, airtight flow system
D883 Terminology Relating to Plastics
that prevents contamination of the analyzer from water present
D1600 TerminologyforAbbreviatedTermsRelatingtoPlas-
in the atmosphere.
tics
5. Significance and Use
D6869 Test Method for Coulometric and Volumetric Deter-
mination of Moisture in Plastics Using the Karl Fischer
5.1 This test method is intended for use as a control,
Reaction (the Reaction of Iodine with Water)
acceptance, and assessment test.
E177 Practice for Use of the Terms Precision and Bias in
5.2 Moisture can seriously affect the processability of plas-
ASTM Test Methods
tics. It is possible that high moisture content will cause surface
E691 Practice for Conducting an Interlaboratory Study to
imperfections (that is, splay or bubbling) or degradation by
Determine the Precision of a Test Method
hydrolysis. Low moisture (with high temperature) has been
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 April 1, 2010. Published June 2010. Originally
6. Interferences
approved in 2005. Last previous edition approved in 2005 as D7191 - 05.
DOI:10.1520/D7191-10.
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 − 10
7. Apparatus 9.2 Duetothehygroscopicnatureofmanyplastics,samples
3 shall be stored in airtight containers made of glass or other
7.1 Moisture Analyzer , an apparatus that consists of:
qualified or suitable material.
7.1.1 Flow Regulator, capable of maintaining the carrier gas
flow rate within the manufacturer’s specified conditions. 9.3 Samples that have been heated to remove moisture prior
7.1.2 Flow Meter, capable of measuring the carrier gas flow to processing and testing shall be allowed to cool to room
rate in accordance with the manufacturer’s specified condi- temperature in a se
...
This document is not anASTM standard and is intended only to provide the user of anASTM 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:D7191–05 Designation:D7191–10
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 and health practices and determine the applicability of regulatory
limitations prior to use.
NOTE1—There is no similar or equivalent ISO standard. 1—There is no known ISO equivalent to this standard.
2. Referenced Documents
2
2.1 ASTM Standards:
D1193 Specification for Reagent Water
D883 Terminology Relating to Plastics D1600
D1600 Terminology for Abbreviated Terms Relating to Plastics
D6869 TestMethodforCoulometricandVolumetricDeterminationofMoistureinPlasticsUsingtheKarlFischerReaction(the
Reaction of Iodine with Water) 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 Asample is loaded into a septum-capped glass vial that is moved into a heater to evolve the volatiles from the sample into
the headspace.Acoaxial needle, or two needle set, pierces the septum of the vial as it enters the heater.Adry 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
inthecarriergastopassthroughandthenbemeasuredasanincreaseinpotentialattherelativehumiditysensor.Thissensorsignal
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.
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
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 November 1, 2005. Published November 2005. DOI: 10.1520/D7191-05.
CurrenteditionapprovedApril1,2010.PublishedJune2010.Originallyapprovedin2005.Lastpreviouseditionapprovedin2005asD7191 - 05.DOI:10.1520/D7191-10.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM 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 ----------------------
D7191–10
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 Elevatedconcentrationsofsomecommonsolventssuchasmethanol,ethanolandacetonewillgivebiasedhighreadingsdue
to their polar characteristics and ability to permeate the thermoset polymer layers of the relative humidity sensor.
7. Apparatus
3
7.1 Moisture Analyzer , an apparatus that
...
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