Effect of degree of acetylation on mechanical properties of cellulose acetate films

Four samples of cellulose acetates having degrees of combined acetic acid between 50.8 - 55.8% were fractionated to obtain sharp fractions or approximately the same degree of polymerization.

About 2000 grams starting material of each sample of cellulose acetate were needed to obtain approximately 50 grams or sharp fraction for testing the mechanical properties of their films.

Fractionation of the cellulose acetate was from an acetone-water mixture, by addition of n-heptane to precipitate a certain traction. After a series of refractionations, a sharp fraction of each of the four cellulose acetates was obtained. These fractions had different degrees of acetylation but approximately the same degrees of polymerization. These fractions were then dissolved in acetone and cast into films which were conditioned for three days and their mechanical properties were determined in an attempt to determine the effect of degree of acetylation on the mechanical properties.

It was found that the degrees of acetylation of the various sharp tractions of cellulose acetates had no appreciable effect on the mechanical properties of their films.

It was concluded that the degrees of polymerization of the various fractions were so high that the effect of the degree or acetylation on the mechanical properties could not be detected.

The degrees of polymerization of the various samples were determined by the viscosity method using acetone and cupriethylenediamine as the solvents, It was found that the degrees of polymerization of the various samples of cellulose acetates determined by the cupriethylenediamine viscosity method were almost four times greater than the degrees of polymerization of the same samples determined by the acetone viscosity method using constants obtained from the literature.