Françoise Berzin

Modelling of flow and chemistry in twin screw extruders

Abstract Reactive extrusion involves the difficulties of mastering the twin screw extrusion process and controlling a chemical reaction under very specific conditions (high viscosity medium, high temperatures, short residence times). Therefore, it is often very difficult to understand all the aspects of the process and the complex interactions between the numerous variables, and then to properly optimise the industrial process. Numerical modelling can be a very efficient tool to overcome these difficulties. However, it is a real challenge, as the information needed is sometimes difficult to obtain with the required accuracy. After a general presentation of the principles of reactive extrusion modelling, different examples of applications are presented to illustrate the interest of the method.

Grafting of maleic anhydride on polypropylene by reactive extrusion: effect of maleic anhydride and peroxide concentrations on reaction yield and products characteristics

Abstract A series of polypropylenes (PPs) grafted with maleic anhydride (MA), prepared by reactive extrusion in a twin screw extruder with different contents of peroxide and MA, was characterized. For each sample, the amount of grafted MA, the molecular weight distribution, the viscoelastic properties in small amplitude oscillatory shear and the transition temperatures and enthalpies were measured. The respective influence of initial MA and peroxide concentrations on these parameters was characterized. In particular, it was shown that the rheological properties are only controlled by the molecular weight, whatever the way it has been obtained, by varying either MA content or peroxide concentration. Moreover, it is clearly shown that the presence of MA tends to enhance the PP degradation due to the peroxide.