ASTM D5897-13(R2021) pdf free download

ASTM D5897-13(R2021) pdf free download.Standard Test Method for Determination of Percent Hydroxyl on Cellulose Esters by Potentiometric Titration—Alternative Method
1. Scope
1.1 This test method covers a procedure for determining the percent hydroxyl on cellulose esters by potentiometric titration. The typical range of percent hydroxyl measured is 0.7 to 10.0 %. 1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Summary of Test Method
3.1 The cellulose ester is dissolved in pyridine and the hydroxyl sites on the cellulose ester are acetylated with acetic anhydride in the presence ofbasic catalyst, 1-methylimidazole. The excess acetic anhydride is hydrolyzed and the resulting acetic acid is titrated with sodium hydroxide. An automatic titrator dispenses the titrant, potentiometrically determines the endpoint, and calculates the percent hydroxyl on the cellulose ester based on a blank determination.
4. Significance and Use
4.1 This test method provides a simpler means for the determination of the hydroxyl content of cellulose esters than the preparation and measurement of the carbanilate derivative described in Test Methods D817 and D871. 4.2 The hydroxyl content is an important indicator of solubility and reactivity.
5. Interferences
5.1 Undissolved ester may accumulate on the sides of the flask and on top of the stirring-star during dissolution, leading to low results. Gently swirling the solution during titration can reduce this problem. 5.2 The ground glass joints of the flask and the air con- denser must always be rinsed into the flask with hydrolyzing solution at the point ofhydrolysis and before titration. This will prevent erroneous results from material that may have refluxed into the joint.
7. Reagents and Materials
7.1 Purity of Reagents—American Chemical Society 3 re- agent grade chemicals shall be used throughout this test unless otherwise indicated. 7.2 Pyridine. 7.3 Acetic Anhydride. 7.4 Acetylating Solution—115 6 0.50 g of acetic anhydride per litre of pyridine. The container needs to be equipped with 20-mL buret. The shelf-life of this solution is 5 days. 7.5 Dimethylformamide. 7.6 Deionized Water, purified to 18.3 MΩ resistance. 7.7 Hydrolyzing Solution—Mix 600 mL dimethylformamide, 300 mL pyridine, and 100 mL water in a 1-L bottle equipped with a bottle top dispenser capable of dosing 35 mL. Stir for at least 10 min prior to use. The shelf-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 of Standards and Technology primary standard grade. Store in desiccator, after drying for 1 h at 105°C (65°C). 7.12 Methanol. 7.13 Sodium Hydroxide, 0.5 N in methanol. This solution has a shelf life of 2 weeks. 7.14 Traceable Buffers, pH 4 and pH 7, available from National 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 to the mark with purified water. Shake into solution. 7.16 1,2-Dichloroethane.
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 a titration cup and lower the electrode into it. 8.1.3 Run the procedure for the titrator to read the correct pH. 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 new electrode is put into use and then check once/month thereafter or when a problem is suspected. 8.2 Standardization ofMethanolic 0.5 NSodium Hydroxide: 8.2.1 Weigh approximately 1.5 6 0.1000 g of KHP into a titration cup and record the weight. Add about 35 mL of purified water and allow to dissolve. 8.2.2 Ensure that the burette is flushed with the 0.5 N NaOH.