Pour 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 ot polymerization.
About 2000 grams starting material of each sample of cellulose acetate
were needed to obtain approximately 50 grams or sharp fraction ror
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 ot refractionations, a sharp traction of each ot 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 ot 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.
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