In-line optical techniques to characterize the polymer extrusion

In the past 15 years our research group has been creating new optical devices to characterize in real time the extrusion process. These detectors are made of a slit‐die fitted at the extruder exit from where the molten polymer flows, with a pair of transparent windows that allows a light beam to pass orthogonally through the molten flow. Following the reduction of the transmitted light intensity one is able to quantify the turbidity, which is a function of the type, concentration and particle size and shape of the second phase present in the flow. By evaluating the scattering pattern of a laser beam (LALLS) it is possible to get information upon the morphology of the molten polymeric system in real time during the extrusion. With the interposition of a pair of crossed polarizers in the optical beam, rheo‐polarimetry, it is possible to evaluate quantitatively the flow birefringence, which is a function of the degree of the polymer matrix orientation. POLYM. ENG. SCI., 54:386–395, 2014. © 2013 Society of Plastics Engineers