COMPUTATION OF THE MORPHOLOGICAL-CHANGES OF A POLYMER BLEND ALONG A TWIN-SCREW EXTRUDER

The control of the morphology of an immiscible polymer melt is of vita l importance for the mastering of the final properties of the product. As polymer blends are produced using corotating twin-screw extruders, understanding and modeling the changes experienced by the blend durin g this process is of great interest. In the present study, starting fr om Ludovic software, developed for computing flow parameters in the tw in-screw extrusion process, we present a computation of the droplet mo rphology development, based on the basic mechanisms of break-up and co alescence. Depending on the value of a local capillary number and on l ocal flow conditions, different changes may occur: affine deformation, drop splitting, break-up by capillary instability, and coalescence. I t is thus possible to follow, all along the screws, the changes in mor phology, either for a single particle or for a particle distribution. Examples of these different computations are presented and compared wi th experimental results. Generally speaking, orders of magnitude of dr oplet size and tendencies when modifying processing conditions are cor rectly described, but the model still suffers from the abscence of des cription of the melting process.