Measuring the extent of exfoliation in polymer/clay nanocomposites using real-time process monitoring methods

Abstract

Dielectric and optical transmission measurements obtained during processing of polymer/clay composites yielded quantitative information about the extent of clay exfoliation in the polymer matrix. Measurements were made using an instrumented slit die that was situated at the exit of a twin screw extruder. Nylon 6, 11 and 12 resins were compounded with several organo modified montmorillonite clays. Dielectric and optical data were correlated with off-line transmission electron microscopy. Dielectric observations revealed a large Maxwell–Wagner (MW) relaxation whose characteristic frequency reflects an RC time constant associated with the conduction of ions and the polarization of the resin/clay interface. Optical transmission measurements showed that transmission increased with increasing extent of exfoliation because light scattering due to aggregate clay particles is reduced as the particles exfoliate nanosize silicate flakes. Extent of exfoliation models, based on MW relaxation time and its relationship to interfacial polarization, and based on optical transmission measurements, are developed.