Multi-scale reactive extrusion modelling approaches to design polymer synthesis, modification and mechanical recycling

Reactive extrusion (REX) is an important processing and production technique with applications in the field of polymer synthesis, modification and recycling. A full REX design demands a multi-scale approach recognizing at the molecular scale a wide spectrum of elementary reactions, at the micro-scale viscosity variations influencing the observed kinetics, at the meso-scale multiphase and morphological variations, and at the macro-scale various screw configurations and designs. In the present contribution, an overview is given of the multi-scale modeling tools currently available to fundamentally understand REX processes, targeting a (average) chain length increase, preservation or decrease. Emphasis is on computational fluid dynamics, in general, flow oriented approaches, and classical chemical reaction engineering approaches, addressing both deterministic and stochastic solvers. To highlight the potential of the discussed modeling tools five case studies are included, considering functionalization of (bio)polymers, polymer recycling and circularity.