Temperature Dependent Rheology of Plasticized Polymer Suspensions Filled with Ceramic Nanoparticles

Abstract

The temperature has a significant influence on the character of flow of polymer suspensions filled with BaTiO3 nanoparticles, changing its viscosity and rheology. The viscous flow of suspensions at lower temperature from 5 to 25°C began at higher activation energy ΔEa1 and the systems were thixotropic, characterized with shear thickening at the initial stage of shearing after breaking of structural bonds between the polymer molecules. Herewith, increased shear stresses caused the enlargement of structural elements through additional flocculation by polymer bridging because of adsorption-desorption of EthCell molecule on BaTiO3 nanoparticles surface. At higher temperatures of 30 – 45 °C the viscous flow of suspensions began at the lower values of ΔEa2 indicating decreasing of leisure EthCell chains sufficient to form transient polymer network. Elevation of the temperature stipulated the predominant contribution of thermal Brownian motion to the character of flow. The mobility of macromolecules segments increased, BaTiO3 nanoparticles became to rotate, making impossible the additional structuring. Hence, the effective hydrodynamic radii of floccules remained constant. Moreover, being thixotropic at lower temperatures, the suspensions were characterized by the increasing of effective radii of floccules throughout the shear thickening region. In turn, rheopexic-thixotropic type of flow was characterized by the constant size of floccules along up-flow curves due to the dominant contribution of rotational Brownian motion. Thus, it is very important to control the temperature regime of processing method when exploitation of polymer suspensions.

Keywords

• polymer suspensions
• nanoparticles
• rheology
• thixotropy
• rheopexy