Fluorescence based temperature measurements and applications to real-time polymer processing

We have used temperature sensitive fluorescent dyes, doped into polymer resins, to monitor the true resin temperature during extrusion processing. Two types of temperature sensitive fluorescent dyes were used: mobility dyes and fluorescence band definition dyes. When mixed with the resin at dopant concentrations, the fluorescent dye resides in a molecular neighborhood composed of resin molecules. Under these circumstances, its fluorescence spectrum reflects the resin temperature in its neighborhood. We apply this measurement concept to extrusion processing by using an optical sensor that accesses the machine at standard instrumentation ports. We show that, under processing conditions, the true resin temperature is significantly different from the machine temperature. Two examples of real-time process monitoring are presented: first, the effects of shear heating during extrusion were measured, and second, the effects of poor temperature control during extrusion were observed. The effects due to pressure on the fluorescence temperature measurements are examined. The fluorescence temperature measurements are compared to melt temperature thermocouple measurements.