ASTM_D_7131_-_09.pdf

Designation:D713109StandardTest Method forDetermination of Ion Exchange Capacity(IEC)in GraftedBattery Separator1This standard is issued under the fixed designation D7131;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This test method evaluates an important characteristic ofpolyolefin or other fibrous nonwoven sheet material intendedfor use in alkaline battery separator applications.The hydro-philic properties of the material are enhanced by grafting afunctional group onto the polyolefin,and this test method is theprimary test method to determine the treatment level,that is,level of monomer grafted to the base polymer.This test methodcan also be used for film or membranes1.2 This test method is intended primarily for testingcopolymer-grafted polyolefin materials used as batteryseparators,but could be used for any grafted material.Theseseparators have radiation-initiated grafting of acrylic acidmonomer(for example)onto a polyolefin base-web material togenerate hydrophilic sites on the material.This process is amethod for surface modification of polymer materials,and isused to make separators hydrophilic.Grafting can be accom-plished by irradiation on common polymers such aspolyethylene,polypropylene and fluoropolymers with variousforms of energy,such as UV,gamma rays,electron beams(EB)or X-rays.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD1711 Terminology Relating to Electrical InsulationE438 Specification for Glasses in Laboratory ApparatusE1272 Specification for Laboratory Glass Graduated Cylin-ders3.Terminology3.1 Definitions:3.1.1 For definitions of textile terms,refer to TerminologyD123.3.1.2 For definitions of electrical terms,refer to Terminol-ogy D1711.3.2 Definitions of Terms Specific to This Standard:3.2.1 grafted battery separator,na sheet material whosefiber surface has been grafted to add a functional group to thebase polymer of the fiber by some form of radiation,whereasthese grafted sites are hydrophilic,thus increasing the sheetmaterials hydrophilic properties.3.2.2 ion-exchange capacity,nthe number of ionic siteson the separator fiber surface that can participate in theexchange process.The exchange capacity is expressed inmilliequivalents per gram.4.Summary of Test Method4.1 A predetermined amount of separator in its acid form isadded to a bottle with a potassium hydroxide(KOH)solution.The specimens are conditioned under a controlled temperaturefor 2 h.After being allowed to cool,the amount of graftedmonomer functionality of the grafted surface in the sample canbe determined by titration.4.2 Results are calculated as milliequivalents per gram(meq/g)using the appropriate equations.4.3 Sampling must be determined based on experience withthe separators uniformity and consistency of the graftingprocess.5.Significance and Use5.1 Nickel-metal hydride(Ni-MH)cells/batteries have atendency to exhibit high rates of self-discharge that may becaused by contamination within a battery cell.The contamina-tion source has been shown to originate from electrodeimpurities.Grafted separators can trap and hold these1This test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.19 on Dielectric Sheet and Roll Products.Current edition approved Oct.1,2009.Published November 2009.Originallyapproved in 2005.Last previous edition approved in 2005 as D7131 05.DOI:10.1520/D7131-09.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesNOTICE:This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTM International(www.astm.org)for the latest information1impurities,thus reducing self-discharge rates and enhancingbattery quality.This test method determines an ionic exchangecapacity that can be used to quantify the level of grafting of aseparator.5.2 This method is useful for research,quality control,andmaterial specifications.6.Apparatus6.1 Beaker,600 m