Flow-induced structures in isotropic and anisotropic cellulose derivative blends
Résumé
The shear flow behavior of cellulose derivative-based incompatible blends has been studied using rheological and rheo-optical (polarizing microscopy) methods. Two types of model systems were used, one with a high interfacial tension (hydroxypropylcellulose in water/polydimethylsiloxane) and one with a low interfacial tension (two cellulose derivatives in a common solvent). This study shows the importance of coupling rheological investigations with morphological observations in order to understand the behavior during flow: positive deviation of the viscosity from the ideal mixing law when the morphology is globular, and negative deviation of the viscosity with a fibrillar morphology. This final morphology clearly results from the competition between the interfacial and viscous forces (globular when the interfacial tension dominates, fibrillar for dominating viscous forces). Almost no effect is observed when changing the minor component from an isotropic to a liquid crystalline (anisotropic) phase.