ASTM D7409-07

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Designation:D7409–07
Standard Test Method for
Carboxyl End Group Content of Polyethylene Terephthalate
(PET) Yarns
This standard is issued under the fixed designation D 7409; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.3 potentiometric titration, n—a titration method that
monitors the change in electrochemical potential, expressed as
1.1 This test procedure is based significantly on the GRI
mV, of the solution as the titration proceeds.
GG7 test procedure, Carboxyl End Group Content of Polyeth-
3.1.4 colorimetric titration, n—a titration method that
ylene Terephthalate (PET) Yarns.
monitors the change in color of the solution as the titration
1.2 This test method is used to determine the concentration,
proceeds. A chemical indicator sensitive to pH is added to
in mmol/Kg, of carboxyl end groups (CEG) found in poly(eth-
create the color change.
ylene terephthalate) (PET) yarns by titration.
3.1.5 automatic titration, n—a titration method in which a
1.3 This test is applicable to geogrid yarns that are made
machine is used that automatically dispenses small volumes of
from PET resin.
the titrant and monitors the pH or the electrochemical potential
NOTE 1—This test is also applicable to high strength geotextile yarns
of the solution.
that are made from PET and are used in reinforcement applications.
3.1.6 fibers, n—a generic term for any one of the various
1.4 This standard does not purport to address all of the
types of material that form the basic structure of a geogrid (or
safety concerns, if any, associated with its use. It is the
geotextile), which are characterized by having a length at least
responsibility of the user of this standard to establish appro-
100 times its diameter.
priate safety and health practices and determine the applica-
3.1.7 filaments, n—a continuous fiber of extremely long
bility of regulatory limitations prior to use.
length.
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
D 123 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-
3.1.1 Carboxyl End Groups (CEG), n— non-reacted car-
mination of carboxyl end groups (CEG) of PETby a titrimetric
boxylic acid groups of terephthalic acid located at either end of
method.
a polymer chain.
4.2 PET yarns are dissolved in o-cresol at 80°C. The
3.1.2 titration, n—titration is a standard laboratory method
solution is diluted with dichloro methane, and titrated against
of quantitative chemical analysis which can be used to deter-
KOH dissolved in methanol, by either a potentiometric or
mine the concentration of a known reactant. Typically, the
colorimetric method. The amount of potassium hydroxide
reactionisaneutralizationreactionbetweenanacidandabase.
required to complete the titration with the PET solution is
measured and used to calculate to the concentration of CEGs.
This test method is under the jurisdiction of ASTM Committee D35 on
5. Significance and Use
Geosynthetics and is the direct responsibility of Subcommittee D35.02 on Endur-
ance Properties. 5.1 This test method can be used for manufacturing quality
Current edition approved Dec. 1, 2007. Published March 2008.
control or manufacturing quality assurance purposes to deter-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
mine the CEG concentration of PET yarns used in either
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
geogrids or geotextiles.
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.
D7409–07
5.2 The CEG content of the PET yarns may have an 9. Sample Preparation
influence on the properties of the geosynthetic, such as its
9.1 Collectarepresentativesampleofyarns(3-4g)fromthe
hydrolysis resistance. The lower the value, the higher the
longitudinal direction of the geogrid (or geotextile) to perform
hydrolysis resistance of the yarns.
three (3) replicate CEG determinations.
5.3 This test does not set the limiting (maximum) value for
NOTE 2—The coating on geogrid yarns must be completely removed.
various engineering applications. Such a specification is a
The recommended solvent for removal of PVC coatings is methyl ethyl
decision of the design engineer, owner, and/or regulator.
ketone. Other coatings may require different solvents.
NOTE 3—If the test is being performed on high strength geotextiles,
6. Apparatus
collect a representative sample from the warp direction fibers, filaments or
yarns to perform three (3) replicate CEG determinations.
6.1 An automatic titratoristhepreferredequipmentforthis
test method. However, acceptable results can be achieved
9.2 The fibers, filaments or yarns are cut into small pieces,
manually with the use of a micro burette, with 10 ml capacity
2-5mmin length.
and accurate to 0.02 ml.
9.3 The fibers, filaments or yarns should be washed in ethyl
6.2 A potentiometric titration assembly is required for a
ether to remove sizing agents, and subsequently dried over-
potentiometric titration. The assembly consists of an automatic
night at 50°C.
titra
...