Fluorescence Marker based Measurement of the Residence Time Distribution and its Statistical Moments

One of the key parameters in the quality assurance of the polymer extrusion process is the retention or residence time defined as the first statistical moment of the residence time distribution (RTD). The shape of the residence time distribution depends on the combined effect of the flow pattern developed, the mixing mechanisms and the reaction and heat transfer processes. By studying the shape of the RTD one might be able to infer otherwise hidden properties of the extrusion process. We report on a highly sensitive fluorescence marker based system that allows us to characterize the RTD function to fluorescence levels close to baseline thus enabling to better determine the standard deviation and skewness of the RTD which are thought to also convey important information.