Effect of Molecular Weight Distribution on the Creep Behavior of Cellulose Acetate

Creep measurements were carried out at 80°C on cellulose acetate fractions characterized as to molecular weight distribution by the equilibrium ultracentrifuge. Stress levels were low enough that linear viscoelastic behavior was observed. Although the effect of molecular weight was not marked, the presence of low molecular weight material in a sample decreased the amount of permanent set and increased the recoverable deformation. In all cases, more than half of the recoverable deformation occurred in less than 10 sec. The results suggest that there was present some sort of a network, although no direct x-ray evidence for crystallinity could be seen.