Fiber length shortening and fluorescence spectroscopy as characterization method for distributive and dispersive mixing in a co-rotating twin screw extruder

Mixing is a key step in almost every polymer processing operation. In compounding processes there are two mechanisms of mixing that need to be considered: distributive mixing and dispersive mixing. A fiber shortening method and CFD numerical simulations have been used to investigate the mixing performance in co-rotating twin screw extruders. Thereby, we described the influence of the shear forces on fiber length reduction under different operating conditions, employing polypropylene with carbon fibers as the model system. We compare the cumulative frequency function of fiber length to the shear force distribution over the entire length of the kneading blocks implemented in the screw configuration as obtained from the CFD mixing simulation. For measuring the fiber length values, a FASEP system was employed.