PhD defence Prashanth Thirunavukkarasu

Analysis of the interfacial flow behavior of polymers along the walls of an internal mixer

 

 

Prashanth Thirunavukkarasu completed his thesis within the CFL team, under the supervision of Edith Peuvrel-Disdier and Rudy Valette. His PhD work was funded by Michelin.

 

Abstract:

 

The internal mixing process is crucial to the manufacturing of rubber compounds as it is instrumental to the final properties of the product. Understanding the interfacial phenomena during mixing is crucial to the evaluation of the process, determination of process parameters and numerical prediction of the same. These phenomena include wall slip, adhesion and movement of free surfaces. The evolution of wall slip velocities was characterized with classical indirect rheological techniques. An eccentric counter-rotating Couette cell was designed and developed during this PhD to observe the free surfaces of viscous fluids under shear flow in steady-state conditions. A small volume of silicone fluid was used to study the flow behavior and observe the free surfaces in counter-rotating conditions. Steady state conditions were investigated for different conditions of cylinder velocities, volumes of fluid, surface roughness and nature of cylinder surfaces. The contribution of the adhesion energy to the stabilization velocities appears to be negligible. Finally, the influence of shear flow on the movement and shape of free surfaces was explored with the help of finite element method. Numerical simulations with the integration of an adhesion boundary condition show a clear effect of the adhesion energy on the free surface shape and movement. But the level of adhesion energy necessary in the case of viscous fluids was found to be far too high to be observed experimentally.

 

Keywords: Internal mixing, Rubber, Wall slip, Movement of free surfaces, Adhesion