1、Designation: D 5897 96 (Reapproved 2007)Standard Test Method forDetermination of Percent Hydroxyl on Cellulose Esters byPotentiometric TitrationAlternative Method1This standard is issued under the fixed designation D 5897; the number immediately following the designation indicates the year oforigina
2、l adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure for determining thepercent hy
3、droxyl 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 thesa
4、fety 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:2D 817 Test Methods of Testing
5、Cellulose Acetate Propi-onate and Cellulose Acetate ButyrateD 871 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-m
6、ethylimidazole.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.
7、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 D 817 and D 871.4.2 The hydroxyl content is an important indicator ofsolubilit
8、y 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-dens
9、er 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,3equipped with Glass Electrode, or equivalent.6.2 Heating/Stirring Module,
10、six-place.6.3 Heating/Stirring Block, cut from polished-finish alumi-num block to fit stirrer in 7.2 (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, cap
11、able 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 ofSubcomm
12、ittee D01.36 on Cellulose and Cellulose Derivatives.Current edition approved June 1, 2007. Published August 2007. Originallyapproved in 1996. Last previous edition approved in 2001 as D 5897 -96 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Serv
13、ice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Titrator and instruction manual such as Mettler DL77 equipped with DG-115-SC glass electrode available from Mettler Toledo Inc., 69 Princeton-Hightestown, P.O
14、. Box 71, Hightestown, NJ 08520 has been found suitable for thispurpose.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.10 Analytical Balance, capable of weighing 1000 g to thesecond decimal place.7. Reagents and Materials7.1 Purit
15、y of ReagentsAmerican Chemical Society4re-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-
16、life of this solution is 5 days.7.5 Dimethylformamide.7.6 Deionized Water, purified to 18.3 MV resistance.7.7 Hydrolyzing SolutionMix 600 mL dimethylforma-mide, 300 mL pyridine, and 100 mL water in a 1-L bottleequipped with a bottle top dispenser capable of dosing 35 mL.Stir for at least 10 min prio
17、r to use. The shelf-life of thissolution 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).7.12 Methanol.7.13 Sodium Hydroxide, 0.5 N
18、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),5M, weigh 37.3 g(60.3000 g) of KCl into a 100-mL volumetric flask. Dilute tothe mark with purified water. Shake into
19、 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 capand 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 pr
20、ocedure for cali-bration of the electrode.8.1.2 Add about 50 mL of pH 4 buffer into a titration cupand lower the electrode into it.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the Ameri
21、can 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. 1 Heating/Stirring Block DimensionsFIG. 2 Flask and Air Condensor DimensionsD 589
22、7 96 (2007)28.1.3 Run the procedure for the titrator to read the correctpH.8.1.4 Repeat process 9.1.1-9.1.3 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 suspected.8.2 Standardization of Metha
23、nolic 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 Normality is calculated as follows
24、:N 5W 3 1000mL 3 204.23(1)where:W = weight of KHP in g,mL = volume of titrant used for titration, and204.23 = formula weight of KHP.9. Procedure5,69.1 Blank DeterminationThis has to be done every timenew reagents are used.9.1.1 Flush burettes delivering the reagent, clearing tubingof air bubbles.9.1
25、.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 the air condenser afteraddition of
26、 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 the ground-glassjoint with the h
27、ydrolyzing 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 sucrosecontrol sample is run on a regular s
28、chedule, 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 into a weighingpan, and then tare
29、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 the sucrose solution stir at 115 6
30、 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 in the flask and let stir for at l
31、east 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 electrode into the flask andtitrate the
32、 solution.9.2.7 The percent hydroxyl is calculated as follows:mL blank 2 mL sample!3N 3 17grams sample 3 10003 100 % (2)where:N = normality of KOH (;0.5),17 = molecular weight hydroxyl group, and1000 = conversion of mL to L.9.2.8 Plot the sucrose percent hydroxyl on a control chartwith the following
33、 parameters: Average: 39.85 %, Upper con-trol limit: 41.00 %, and lower control limit: 38.70 %. Follownormal solid phase extraction (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 fromthe oven, cap, and allow to cool for
34、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 balance with the weighing pan and sampl
35、e 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 a heating block at 115 6 5C.9.3.4 Let
36、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 solution. Replace theair condenser in the fla
37、sk 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 fromeach flask, and rinse them including the ground-glass joint withthe hydrolyzing solution.9.3.7 Lower the buret tip and electrode into t
38、he flask andtitrate the solution.9.3.8 The percent hydroxyl is calculated in the same way asfor the sucrose control.5Siggia, S. and Hanna, J. G., “Quantitative Organic Analysis via FunctionalGroups,” Wiley-Interscience Publication , New York, 1979.6Conners, K. A. and Pandit, N. K., “N-methylimidazol
39、e as a Catalyst forAnalytical Acetylations of Hydroxy Compounds,” Analytical Chemistry, Vol 50,No. 11, 1978.D 5897 96 (2007)310. Report10.1 Report the percent hydroxyl to two decimal places.11. Precision and Bias11.1 PrecisionThe precision data is based on 30 pairs ofcellulose acetate samples. The d
40、ata 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.12. Keywords12.1 cellulose e
41、sters; percent hydroxyl; potentiometrictitrationASTM 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 validity of any such patent rights,
42、 and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for rev
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44、 shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 5897 96 (2007)4
