A study of rheological properties of cellulose diacetate in acetone solution at low and high shear rates

The rheological properties of cellulose diacetate (CDA) with different intrinsic viscosity (IV) and different concentration in acetone solutions were studied at low and high shear rates. The zero-shear viscosity increased and the structural index increased, when the IV of CDA was increased or the acetone solution concentration was increased. Evidence suggested that a sulfate structure may be forming. It is shown that the increase of hemicellulose and sulfur content is associated with an increase of chain entanglements between CDA molecules and the abnormal increase of solution zero-shear viscosity. At a high shear rate, the correlation curve between inlet pressure drop and solution concentration obtained by Bagley method analysis shows an inflection point, which appears to be the critical concentration at which the cellulose diacetate molecular chains in the solution form a long range entangled elastic network. After the concentration exceeds a certain range of above critical points, the entanglement of the molecular chains in the solution is significantly enhanced. The zero shear viscosity inflection point concentration calculated by the rheological curve with low shear velocity and the inlet pressure drop inflection point concentration calculated by the capillary rheological calculation have good consistency.