On-line measurement of the PVT properties of polymer/carbon dioxide solutions using a gear pump

This study presents an innovative dilatometer that can accurately measure the pressure-volume-temperature (PVT) properties of polymer/CO2 solutions. The density (or equivalently, the specific volume) of a polymer/CO 2 solution is determined by measuring the mass and volume flow rates of the solution. A positive-displacement gear pump mounted on an extruder is used to measure the volume flow rate of the solution. The positive-displacement volume of the gear pump was determined in calibration experiments with water and oil with the aid of a syringe pump. The gear pump was mounted on a tandem extrusion line. The temperature of melt was precisely controlled and homogenized by using the second extruder and a heat exchanger, which included a static mixer. The pressure was controlled by the rotational speed of the screw in the second extruder. In order to reduce leakage across the gear pump, the difference between the upstream and downstream pressures was minimized using a variable resistance die attached to the downstream outlet of the gear pump. A critical set of experiments was carried out to measure the specific volumes of various pure polymers. (Abstract shortened by UMI.)...