1、Designation: D5897 13Standard 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 th
2、e 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 e
3、sters 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
4、, 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 Prop
5、ionateand 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
6、 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 T
7、his 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. Interfe
8、rences5.1 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 in
9、to 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
10、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,
11、 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 De
12、rivatives.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.
13、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 States16.10 Analytical Balance, capable of weighing 1000 g to thesecond deci
14、mal 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 need
15、s 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 Hydrolyzing SolutionMix 600 mLdimethylformamide, 300 mL pyridine, and 100 mL water in a1-L bottle equipped with a bottle top dispenser capable ofdo
16、sing 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 for1hat105C (65C).7.
17、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 volumetric flask. Dilute
18、 tothe mark with purified water. Shake into solution.7.16 1,2-Dichloroethane.8. Calibration and Standardization8.1 Calibration of the Electrode:NOTE 1If the electrode is new, perforate the nipple on the rubber cap3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society,
19、 Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG.
20、 1 Heating/Stirring Block DimensionsFIG. 2 Flask and Air Condenser DimensionsD5897 132and soak the electrode in 5 M potassium chloride for 1 h. Store in pH 4buffer until use.8.1.1 Select from the titrator menu the procedure for cali-bration of the electrode.8.1.2 Add about 50 mL of pH 4 buffer into
21、a titration cupand lower the electrode into it.8.1.3 Run the procedure for the titrator to read the correctpH.8.1.4 Repeat process 8.1.1-8.1.3 for buffer pH 7.8.1.5 Make sure that the calibration is done when a newelectrode is put into use and then check once/month thereafteror when a problem is sus
22、pected.8.2 Standardization of Methanolic 0.5 N Sodium Hydroxide:8.2.1 Weigh approximately 1.5 6 0.1000 g of KHP into atitration cup and record the weight. Add about 35 mL ofpurified water and allow to dissolve.8.2.2 Ensure that the burette is flushed with the 0.5 NNaOH.8.2.3 Titrate the sample.8.2.4
23、 Normality is calculated as follows:N 5W 31000mL 3204.23(1)where:W = weight of KHP in g,mL = volume of titrant used for titration, and204.23 = formula weight of KHP.9. Procedure4,59.1 Blank DeterminationThis has to be done every timenew reagents are used.9.1.1 Flush burettes delivering the reagent,
24、clearing tubingof air bubbles.9.1.2 Dispense 1.0 mL 1-methylimidazole and 20 mL acety-lating solution into three flasks.9.1.3 Immediately place air condenser in the flask, anddispense 35 mL of the hydrolyzing solution into the flaskthrough the air condenser.NOTE 2Dispense 35 mL immediately through t
25、he air condenser afteraddition of the acetylation solution, one sample at the time.9.1.4 Let the three blanks stir for at least 20 min at roomtemperature, then dose 50 mL of 1,2-dichloroethane into theflask through the air condenser. Remove the air condensersfrom each flask, and rinse them including
26、 the ground-glassjoint with the hydrolyzing solution.9.1.5 Titrate the solutions. The average of the three blankswill be used for this test if their relative standard deviation0.3 %.9.2 Control Percent Hydroxyl DeterminationSucrose isused as a statistical control sample for this test. The sucrosecon
27、trol sample is run on a regular schedule, and when thereagents or equipment has changed.9.2.1 Dispense 1.0 mL 1-methylimidazole and 20 mL acety-lating solution into the flask containing a spin-type stirring bar.Set the flask into a heating block at 115 6 5C.9.2.2 Weigh 0.25 g 6 0.0100 g of sucrose i
28、nto a weighingpan, and then tare the balance. Remove the condenser from theflask and add the sample into the solution while it is stillstirring. Immediately replace the condenser and set the weigh-ing pan back on the balance. Record the weight from thebalance as the weight of the sucrose.9.2.3 Let t
29、he sucrose solution stir at 115 6 5C for 30 min.9.2.4 Dispense 35 mL of the hydrolyzing solution into theflask through the air condenser. Remove the air condensersfrom each flask, and rinse them, including the ground-glassjoint into the flask with the hydrolyzing solution. Replace theair condenser i
30、n the flask and let stir for at least 20 min at roomtemperature.9.2.5 Dose 50 mL of 1,2-dichloroethane into the flaskthrough the air condenser. Remove the air condensers fromeach flask, and rinse them, including the ground-glass jointwith the hydrolyzing solution.9.2.6 Lower the buret tip and electr
31、ode into the flask andtitrate the solution.9.2.7 The percent hydroxyl is calculated as follows:mL blank 2 mL sample! 3 N 317#grams sample 310003100% (2)where:N = normality of NaOH (;0.5),17 = molecular weight hydroxyl group, and1000 = conversion of mL to L.9.2.8 Plot the sucrose percent hydroxyl on
32、a control chartwith the following parameters: Average: 39.85 %, Upper con-trol limit: 41.00 %, and lower control limit: 38.70 %. Follownormal statistical process control (SPC) procedures.9.3 Cellulose Esters Samples Percent Hydroxyl Determina-tion:9.3.1 Dry the sample at 105 6 5C for 1 h. Remove fro
33、mthe oven, cap, and allow to cool for 15 min in a desiccator.9.3.2 Dispense 1.0 mL of 1-methylimidazole and 20.0 mLof acetylating solution into the flask containing a stirring bar inthe same way as the preparation for the blanks.9.3.3 Weigh 1.5 6 0.1000 g of the sample into a weighingpan. Tare the b
34、alance with the weighing pan and sample on it.Remove the condenser from the flask and add the sample intothe flask containing the solution. Immediately replace thecondenser and set the weighing pan back on the balance.Record the weight from the balance as the weight of thesample. Set the flask into
35、a heating block at 115 6 5C.9.3.4 Let the sample stir at 115 6 5C for 30 min.9.3.5 Dispense 35 mL of the hydrolyzing solution into theflask through the air condenser. Remove the air condensersfrom each flask, and rinse them, including the ground-glassjoint into the flask with the hydrolyzing solutio
36、n. Replace theair condenser in the flask and let stir for at least 20 min at roomtemperature.9.3.6 Dose 50 mL of 1,2-dichloroethane into the flaskthrough the air condenser. Remove the air condensers from4Siggia, S. and Hanna, J. G., “Quantitative Organic Analysis via FunctionalGroups,” Wiley-Intersc
37、ience Publication, New York, 1979.5Conners, K. A. and Pandit, N. K., “N-methylimidazole as a Catalyst forAnalytical Acetylations of Hydroxy Compounds,” Analytical Chemistry, Vol 50,No. 11, 1978.D5897 133each flask, and rinse them including the ground-glass joint withthe hydrolyzing solution.9.3.7 Lo
38、wer the buret tip and electrode into the flask andtitrate the solution.9.3.8 The percent hydroxyl is calculated in the same way asfor the sucrose control.10. Report10.1 Report the percent hydroxyl to two decimal places.11. Precision and Bias11.1 PrecisionThe precision data is based on 30 pairs ofcel
39、lulose acetate samples. The data was gathered over a periodof three months by two analysts. At the 95 % confidenceinterval the percent hydroxy at a level of 3.65 % should differno more than 0.06 % absolute for duplicate analysis.11.2 BiasNo suitable reference material is available todetermine a bias
40、.12. Keywords12.1 cellulose esters; percent hydroxyl; potentiometric titra-tionASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the vali
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