Viscoelastic behaviour of cellulose acetate/triacetin blends by rheology in the melt state.

The viscoelastic behaviour of cellulose acetate with a degree of substitution (DS) of 245 plasticized by triacetin was studied at short times by dynamic oscillatory measurements. Two distinct regimes and unexpected scaling behaviour according to plasticizer content were highlighted. The dynamics of chains and their structural organization are not modified up to 35 wt% of triacetin. The rheological behaviour is led by a constant correlation length corresponding to the distance between strong intermolecular interactions subsisting in the melt state at high temperature even in the presence of plasticizer. This particular structure involves the apparition of strain hardening effects during uniaxial extensional flow tests and an important elasticity corresponding to the apparition of a Weissenberg effect at really low shear rates during shear sweeps. Intramolecular hydrogen bonds are responsible of the high rigidity of cellulose acetate chains. Plasticized cellulose acetate in the melt state belongs to the class of associating polymers and its rheological behaviour is mainly led by stickers.