Modeling of reactive systems in twin-screw extrusion: challenges and applications

Reactive extrusion processes involve the difficulties of mastering classical polymer processes, such as twin-screw extrusion for example, and the problems of controlling a chemical reaction in very specific conditions (high-viscosity medium, high temperatures, short residence times). Therefore, it is often very difficult to intuitively understand all the aspects of the process and to clarify the complex interactions between the numerous variables, and then to properly design and optimize the industrial process. Numerical modeling can be a very efficient tool to overcome these difficulties. However, it remains a real challenge, as it necessitates to couple flow simulation in complex geometry, reaction kinetics and evolutionary rheological behavior. Moreover, the information needed is sometimes difficult to obtain with the required accuracy. After a general presentation of the principles of the different reactive extrusion modeling methodologies, we will focus on the models we developed, based on continuum mechanics. Different examples of applications are presented for illustrating the interest of this method. To cite this article: B. Vergnes et al., C. R. Chimie 9 (2006).     

New rheological developments for reactive processing of poly(ε-caprolactone)

This short review aims to show how an integrated activity on reactive processing have been developed these last years in our laboratory. We can say that the originality of this approach is based on combining developments in chemistry, in line instrumentation, and rheology aspects. Our rheological works can be divided into four important contributions: rheo-physics, rheo-chemistry, rheo-mixing and rheo-processing. These different parts are illustrated from the ε-caprolactone polymerisation in bulk and dispersed media. Rheo-physics studies allowed us to calculate the molecular weight distribution and chain structures of in situ polymerised poly(ε-caprolactone) samples. From rheo-chemistry works, we are now able to predict the variation of the complex shear modulus versus the extent of the polymerisation. The developments of new rheological tools such as rheo-mixer enable us to investigate complex mixing situations encountered in reactive polymer blends and formulations. Lastly, a rheo-processing approach based on the in-line measurement of the viscosity in a slit rheometer at the die exit of the extruder allows us to envisage its application to the experimental control of the reactive processing in extruder. To cite this article: P. Cassagnau et al., C. R. Chimie 9 (2006).