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Polyvinyl Alcohol
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(C2H4O)n

Ethenol, homopolymer.
Vinyl alcohol polymer [9002-89-5].
» Polyvinyl Alcohol is a water-soluble synthetic resin, represented by the formula:
(C2H4O)n,
in which the average value of n lies between 500 and 5000. It is prepared by 85 percent to 89 percent hydrolysis of polyvinyl acetate. The apparent viscosity, in centipoises, at 20, of a solution containing 4 g of Polyvinyl Alcohol in each 100 g is not less than 85.0 percent and not more than 115.0 percent of that stated on the label.
Packaging and storage— Preserve in well-closed containers.
Viscosity— After determining the Loss on drying, weigh a quantity of undried Polyvinyl Alcohol, equivalent to 6.00 g on the dried basis. Over a period of seconds, transfer the test specimen with continuous slow stirring to about 140 mL of water contained in a suitable tared flask. When the specimen is well-wetted, increase the rate of stirring, avoiding mixing in excess air. Heat the mixture to 90, and maintain the temperature at 90 for about 5 minutes. Discontinue heating, and continue stirring for 1 hour. Add water to make the mixture weigh 150 g. Resume stirring to obtain a homogenous solution. Filter the solution through a tared 100-mesh screen into a 250-mL conical flask, cool to about 15, mix, and proceed as directed under Viscosity 911.
pH 791: between 5.0 and 8.0, in a solution (1 in 25).
Loss on drying 731— Dry it at 110 to constant weight: it loses not more than 5.0% of its weight.
Residue on ignition 281: not more than 2.0%.
Water-insoluble substances— Wash the tared 100-mesh screen used in the test for Viscosity with two 25-mL portions of water, and dry at 110 for 1 hour: not more than 6.4 mg of water-insoluble substances is found (0.1%).
Organic volatile impurities, Method I 467: meets the requirements.
Degree of hydrolysis—
Procedure— Transfer about 1 g of Polyvinyl Alcohol, previously dried at 110 to constant weight and accurately weighed, to a wide-mouth, 250-mL conical flask fitted by means of a suitable glass joint to a reflux condenser. Add 35 mL of dilute methanol (3 in 5), and mix gently to assure complete wetting of the solid. Add 3 drops of phenolphthalein TS, and add 0.2 N hydrochloric acid or 0.2 N sodium hydroxide, if necessary, to neutralize. Add 25.0 mL of 0.2 N sodium hydroxide VS, and reflux gently on a hot plate for 1 hour. Wash the condenser with 10 mL of water, collecting the washings in the flask, cool, and titrate with 0.2 N hydrochloric acid VS. Concomitantly perform a blank determination in the same manner, using the same quantity of 0.2 N sodium hydroxide VS.
Calculation of saponification value— Calculate the saponification value by the formula:
[(B A)N56.11] / W,
in which B and A are the volumes, in mL, of 0.2 N hydrochloric acid VS consumed in the titration of the blank and the test preparation, respectively, N is the exact normality of the hydrochloric acid solution, W is the weight, in g, of the portion of Polyvinyl Alcohol taken, and 56.11 is the molecular weight of potassium hydroxide.
Calculation of degree of hydrolysis— Calculate the degree of hydrolysis, expressed as percentage of hydrolysis of polyvinyl acetate, by the formula:
100 [7.84S / (100 0.075S)],
in which S is the saponification value of the Polyvinyl Alcohol taken: between 85% and 89% is found.
Residual solvents 467: meets the requirements.
(Official January 1, 2007)
Auxiliary Information— Staff Liaison : Hong Wang, Ph.D. , Senior Scientific Associate
Expert Committee : (EM205) Excipient Monographs 2
USP29–NF24 Page 1753
Phone Number : 1-301-816-8351