Investigation of cellulose acetate viscoelastic properties in different solvents and microstructure

This paper deals with the effect of solvent on the viscoelastic properties and microstructure of cellulose acetate (CA) by means of rheological measurements, dynamic-mechanical analysis and scanning electron microscopy. Acetone, acetic acid, dimethylacetamide (DMAc) and dimethylformamide (DMF) were used as good solvents and water as a non-solvent. The addition of water in the cellulose acetate/solvent mixture led to the development of an intense shear thinning behavior, as it caused the formation of CA agglomerates which were disrupted in a steady shearing condition. Apart from this, a three-dimensional elastic gel behavior in the CA/DMF/water and CA/DMAc/water solutions was observed during dynamical rheological analysis. The formation of CA agglomerates was controlled by the solvent type and resulted in microstructure changes, going from a dense structure to a porous one, and also influenced the CA chain rigidity and consequently the glass transition temperatures of the CA films.