Yu-Hsin Lee

A dielectric slit die for in-line monitoring of polymer compounding

The dielectric slit die is an instrument that is designed to measure electrical, rheological, ultrasonics, optical, and other properties of a flowing liquid. In one application, it is connected to the exit of an extruder, pump or mixing machine that passes liquefied material such as molten plastic, solvents, slurries, colloidal suspensions, and foodstuffs into the sensing region of the slit-shaped die. Dielectric sensing is the primary element of the slit die, but in addition to the dielectric sensor, the die contains other sensing devices such as pressure, optical fiber, and ultrasonic sensors that simultaneously yield an array of materials property data. The slit die has a flexible design that permits interchangeability among sensors and sensor positions. The design also allows for the placement of additional sensors and instrumentation ports that expand the potential data package obtained. To demonstrate sensor operation, we present data from the extrusion and compounding of a polymer/clay nanocomposit...

Monitoring clay exfoliation during polymer/clay compounding using fluorescence spectroscopy

A fluorescent probe molecule, Nile blue perchlorate, was used to monitor the compounding of nylon 11 with clay filler. Prior to compounding, Nile blue was incorporated into the gallery region between silicate layers of the clay by an ion-exchange process. While residing in the gallery, fluorescence from Nile blue was quenched because of fluorescence resorption in a high dye concentration environment. However, when clay is compounded with the nylon, clay exfoliation allowed the dye to escape the gallery region and to become dispersed in the resin matrix. During batch mixing, we observed that fluorescence increased with time indicating that dye molecules were migrating from the gallery. Experiments carried out using a twin-screw extruder to compound resin and clay showed that twin-screw compounding was much more efficient in producing clay exfoliation than was the batch mixer.

In-line monitoring of dielectric and fluorescence spectroscopy during polymer/filler compounding

Abstract A new multipurpose instrument has been used to obtain real-time dielectric and fluorescence spectroscopy from polymer resins compounded with inorganic fillers. The instrument, which is mounted at the exit of an extruder, contains a flow-through slit channel that provides a constant geometry platform for dielectric and fluorescence sensors and for other sensors that can be added as needed. The results of real-time monitoring of Nylon 6 and ethyl vinyl acetate copolymer (EVA) compounded with organo modified montmorillonite clays will be presented. Real-time dielectric data are corrected for electrode and conductivity effects before analysis yields information about dielectric relaxation phenomena. Significant differences in dielectric dispersion parameters were observed for clay nanocomposites in the aggregate, intercalated and exfoliated states. Fluorescent dyes, doped into EVA copolymer, are being used as molecular probes to study the effects of microstructure conformation on their spectra.