ASTM D7131-09

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Designation: D7131 − 09
StandardTest Method for
Determination of Ion Exchange Capacity (IEC) in Grafted
1
Battery Separator
This standard is issued under the fixed designation D7131; 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* D1711 Terminology Relating to Electrical Insulation
E438 Specification for Glasses in Laboratory Apparatus
1.1 Thistestmethodevaluatesanimportantcharacteristicof
E1272 Specification for Laboratory Glass Graduated Cylin-
polyolefin or other fibrous nonwoven sheet material intended
ders
for use in alkaline battery separator applications. The hydro-
philic properties of the material are enhanced by grafting a
3. Terminology
functionalgroupontothepolyolefin,andthistestmethodisthe
primary test method to determine the treatment level, that is,
3.1 Definitions:
levelofmonomergraftedtothebasepolymer.Thistestmethod 3.1.1 For definitions of textile terms, refer to Terminology
can also be used for film or membranes D123.
3.1.2 For definitions of electrical terms, refer to Terminol-
1.2 This test method is intended primarily for testing
ogy D1711.
copolymer-grafted polyolefin materials used as battery
3.2 Definitions of Terms Specific to This Standard:
separators, but could be used for any grafted material. These
3.2.1 grafted battery separator, n—a sheet material whose
separators have radiation-initiated grafting of acrylic acid
fiber surface has been grafted to add a functional group to the
monomer (for example) onto a polyolefin base-web material to
base polymer of the fiber by some form of radiation, whereas
generate hydrophilic sites on the material. This process is a
these grafted sites are hydrophilic, thus increasing the sheet
method for surface modification of polymer materials, and is
material’s hydrophilic properties.
used to make separators hydrophilic. Grafting can be accom-
plished by irradiation on common polymers such as 3.2.2 ion-exchange capacity, n—the number of ionic sites
polyethylene, polypropylene and fluoropolymers with various on the separator fiber surface that can participate in the
formsofenergy,suchasUV,gammarays,electronbeams(EB) exchange process. The exchange capacity is expressed in
or X-rays. milliequivalents per gram.
1.3 The values stated in SI units are to be regarded as
4. Summary of Test Method
standard. No other units of measurement are included in this
standard. 4.1 Apredetermined amount of separator in its acid form is
added to a bottle with a potassium hydroxide (KOH) solution.
1.4 This standard does not purport to address all of the
The specimens are conditioned under a controlled temperature
safety concerns, if any, associated with its use. It is the
for 2 h. After being allowed to cool, the amount of grafted
responsibility of the user of this standard to establish appro-
monomer functionality of the grafted surface in the sample can
priate safety and health practices and to determine the
be determined by titration.
applicability of regulatory limitations prior to use.
4.2 Results are calculated as milliequivalents per gram
2. Referenced Documents
(meq/g) using the appropriate equations.
2
2.1 ASTM Standards:
4.3 Sampling must be determined based on experience with
D123 Terminology Relating to Textiles
the separators uniformity and consistency of the grafting
process.
1
This test method is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of
Subcommittee D09.19 on Dielectric Sheet and Roll Products.
5. Significance and Use
Current edition approved Oct. 1, 2009. Published November 2009. Originally
5.1 Nickel-metal hydride (Ni-MH) cells/batteries have a
approved in 2005. Last previous edition approved in 2005 as D7131 – 05. DOI:
10.1520/D7131-09.
tendency to exhibit high rates of self-discharge that may be
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
caused by contamination within a battery cell. The contamina-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
tion source has been shown to originate from electrode
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. impurities. Grafted separators can trap and hold these
*A Summary of Changes section appears at the end of this standard
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D7131 − 09
impurities, thus reducing self-discharge rates and enhancing 8.4 For each specimen, add 90 6 0.5 mL of distille
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