Thermo-rheological effects of plasticizer types and concentrations on cellulose diacetate with varying molar masses

The thermo-rheological effects of adding different types and amounts of plasticizer to cellulose diacetate were studied using Dynamic Mechanical Thermal Analysis (DMTA) and Oscillation shear rheology (SAOS). Depending on the plasticizer type and concentration the zero shear viscosity, i.e. the first Newtonian plateau, can be adjusted before shear-thinning behavior occurs. The control of the viscoelastic performance is of special interest for extrusion foam processes (comparable to XPS-processes), where low shear rates between 1 and 30 s-1 arise. In this study, the effects of the type of plasticizer and its concentration as well as the molar mass of cellulose diacetate on the entanglement density and the viscoelastic properties of the material are examined. Three different plasticizers have been used in the cellulose acetate blends in concentrations between 15 to 40 wt.-%. The plasticizer concentration and temperature affect the viscosity more pronouncedly than the plasticizer type used does. Furthermore, the plasticizer significantly influences the apparent measured entanglement density of cellulose acetate.