ASTM D7409-15(2020)

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: D7409 − 15 (Reapproved 2020)
Standard Test Method for
Carboxyl End Group Content of Polyethylene Terephthalate
(PET) Yarns
This standard is issued under the fixed designation D7409; 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 3.1.1 automatic titration, n—a titration method in which a
machine is used that automatically dispenses small volumes of
1.1 This test procedure is based significantly on the GRI
the titrant and monitors the pH or the electrochemical potential
GG7 test procedure, Carboxyl End Group Content of Polyeth-
of the solution.
ylene Terephthalate (PET) Yarns.
3.1.2 carboxyl end groups (CEG), n—non-reacted carbox-
1.2 This test method is used to determine the concentration,
ylic acid groups of terephthalic acid located at either end of a
in mmol/kg, of carboxyl end groups (CEG) found in poly(eth-
polymer chain.
ylene terephthalate) (PET) yarns by titration.
3.1.3 colorimetric titration, n—atitrationmethodthatmoni-
1.3 This test is applicable to geogrid yarns that are made
torsthechangeincolorofthesolutionasthetitrationproceeds.
from PET resin.
A chemical indicator sensitive to pH is added to create the
NOTE 1—This test is also applicable to high-strength geotextile yarns
color change.
that are made from PET and are used in reinforcement applications.
3.1.4 fibers, n—a generic term for any one of the various
1.4 The values stated in SI units are to be regarded as
types of material that form the basic structure of a geogrid (or
standard. No other units of measurement are included in this
geotextile), which are characterized by having a length at least
standard.
100 times its diameter.
1.5 This standard does not purport to address all of the
3.1.5 filaments, n—a continuous fiber of extremely long
safety concerns, if any, associated with its use. It is the
length.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
3.1.6 potentiometric titration, n—a titration method that
mine the applicability of regulatory limitations prior to use.
monitors the change in electrochemical potential, expressed as
1.6 This international standard was developed in accor-
mV, of the solution as the titration proceeds.
dance with internationally recognized principles on standard-
3.1.7 titration, n—titration is a standard laboratory method
ization established in the Decision on Principles for the
of quantitative chemical analysis which can be used to deter-
Development of International Standards, Guides and Recom-
mine the concentration of a known reactant. Typically, the
mendations issued by the World Trade Organization Technical
reactionisaneutralizationreactionbetweenanacidandabase.
Barriers to Trade (TBT) Committee.
3.1.8 yarns, n—a generic term for a continuous strand of
2. Referenced Documents
fibers, filaments, or material in a form suitable for knitting,
2.1 ASTM Standards:
weaving, or otherwise intertwining to form a textile related
D123 Terminology Relating to Textiles
geogrid (or geotextile).
3. Terminology
4. Summary of Test Method
3.1 Definitions:
4.1 This method defines a specific procedure for the deter-
mination of carboxyl end groups (CEG) of PETby a titrimetric
This test method is under the jurisdiction of ASTM Committee D35 on
method.
Geosynthetics and is the direct responsibility of Subcommittee D35.02 on Endur-
ance Properties.
4.2 PET yarns are dissolved in o-cresol at 80 °C. The
Current edition approved Dec. 1, 2020. Published December 2020. Originally
solution is diluted with dichloro methane, and titrated against
approved in 2007. Last previous edition approved in 2015 as D7409 – 15. DOI:
10.1520/D7409-15R20.
KOH dissolved in methanol, by either a potentiometric or
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
colorimetric method. The amount of potassium hydroxide
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
required to complete the titration with the PET solution is
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. measured and used to calculate to the concentration of CEGs.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7409 − 15 (2020)
5. Significance and Use 8.3 Methanol—It is moderately toxic and flammable.Avoid
inhalation and skin contact. Methanol may be absorbed
5.1 This test method can be used for manufacturing quality
through the skin. Wear the appropriate safety clothing that is
control or manufacturing quality assurance purposes to deter-
required for the chemical laboratory when handling. If contact
mine the CEG concentration of PET yarns used in either
is made, wash the affected area with water for at least 15 or
geogrids or geotextiles.
20 min, get medical treatment immediately. Keep solvent away
5.2 The CEG content of the PET yarns may have an
from sparks and flames.
influence on the properties of the geosynthetic, such as its
8.4 Dichloro Methane—It is toxic and flammable. Avoid
hydrolysis resistance. The lower the value, the higher the
breathing vapors and skin contact. If contact is made, wash the
hydrolysis resistance of the yarns.
affectedareawithwaterfor15to20min.Getmedicalattention
5.3 This test does not set the limiting (maximum) value for
immediately.
various engineering applications. Such a specification is a
decision of the design engineer, owner, and/or regulator.
9. Sample Preparation
6. Apparatus
9.1 Collect a representative sample of yarns (3 to 4 g) from
the longitudinal direction of the geogrid (or geotextile) to
6.1 An automatic titrator is the preferred equipment for this
perform three (3) replicate CEG determinations.
test method. However, acceptable results can be achieved
NOTE 2—The coating on geogrid yarns must be completely removed.
manually with the use of a micro burette, with 10 mL capacity
The recommended solvent for removal of PVC coatings is methyl ethyl
and accurate to 0.
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