ASTM_D_5897_-_13.pdf

Designation:D589713Standard Test Method forDetermination of Percent Hydroxyl on Cellulose Esters byPotentiometric TitrationAlternative Method1This standard is issued under the fixed designation D5897;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.Scope1.1 This test method covers a procedure for determining thepercent hydroxyl on cellulose esters by potentiometric titration.The typical range of percent hydroxyl measured is 0.7 to10.0%.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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 determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D817 Test Methods of Testing Cellulose Acetate Propionateand Cellulose Acetate ButyrateD871 Test Methods of Testing Cellulose Acetate3.Summary of Test Method3.1 The cellulose ester is dissolved in pyridine and thehydroxyl sites on the cellulose ester are acetylated with aceticanhydride in the presence of basic catalyst,1-methylimidazole.The excess acetic anhydride is hydrolyzed and the resultingacetic acid is titrated with sodium hydroxide.An automatictitrator dispenses the titrant,potentiometrically determines theendpoint,and calculates the percent hydroxyl on the celluloseester based on a blank determination.4.Significance and Use4.1 This test method provides a simpler means for thedetermination of the hydroxyl content of cellulose esters thanthe preparation and measurement of the carbanilate derivativedescribed in Test Methods D817 and D871.4.2 The hydroxyl content is an important indicator ofsolubility and reactivity.5.Interferences5.1 Undissolved ester may accumulate on the sides of theflask and on top of the stirring-star during dissolution,leadingto low results.Gently swirling the solution during titration canreduce this problem.5.2 The ground glass joints of the flask and the air con-denser must always be rinsed into the flask with hydrolyzingsolution at the point of hydrolysis and before titration.This willprevent erroneous results from material that may have refluxedinto the joint.6.Apparatus6.1 Titrator,equipped with Glass Electrode.6.2 Heating/Stirring Module,six-place.6.3 Heating/Stirring Block,cut from polished-finish alumi-num block to fit stirrer in 6.2(see Fig.1 for dimensions).6.4 Stirrer,six place.6.5 Magnetic Stirrers,size 25 mm and 50 mm.6.6 Stirring Bar.6.7 Flask and Air Condenser,(see Fig.2 for dimensions).6.8 Bottle-Top Dispensers,capable of dispensing 20 mL,35mL,and 50 mL,or equivalent.6.9 Analytical Balance,capable of weighing 250 g to thefourth decimal place.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.36 on Cellulose and Cellulose Derivatives.Current edition approved June 1,2013.Published June 2013.Originallyapproved in 1996.Last previous edition approved in 2007 as D5897 96(2007).DOI:10.1520/D5897-13.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.10 Analytical Balance,capable of weighing 1000 g to thesecond decimal place.7.Reagents and Materials7.1 Purity of ReagentsAmerican Chemical Society3re-agent grade chemicals shall be used throughout this test unlessotherwise indicated.7.2 Pyridine.7.3 Acetic Anhydride.7.4 Acetylating Solution115 6 0.50 g of acetic anhydrideper litre of pyridine.The container needs to be equipped with20-mL buret.The shelf-life of this solution is 5 days.7.5 Dimethylformamide.7.6 Deionized Water,purified to 18.3 M resistance.7.7 HydrolyzingSolutionMix600mLdimethylformamide,300 mL pyridine,and 100 mL water in a1-L bottle equipped with a bottle top dispenser capable ofdosing 35 mL.Stir for at least 10 min prior to use.Theshelf-life of this solution is 1 month.7.8 1-Methylimidazole.7.9 Sucrose.7.10 Acetone.7.11 Potassium Acid Phthalate(KHP),National Institute ofStandards and Technology primary standard grade.Store indesiccator,after drying for 1 h at 105C(65C).7.12 Methanol.7.13 Sodium Hydroxide,0.5 N in methanol.This solutionhas a shelf life of 2 weeks.7.14 Traceable Buffers,pH 4 and pH 7,available fromNational Institute of Standards and Technology.7.15 Potassium Chloride(KCl),5 M,weigh 37.3 g(60.3000 g)of KCl into a 100-mL vol