Monitoring the relaxation behavior of nylon/clay nanocomposites in the melt with an online dielectric sensor

Abstract

Dielectric spectrometry was used to correlate microstructure of the filler with relaxation behavior of the polymer matrix in nylon/clay nanocomposites. Agglomerated, intercalated, and exfoliated composites were fabricated by extruding nylon 6 and nylon 12 with montmorillonite clays treated by two types of amino surfactants. A new on-line dielectric slit die sensor was used to examine the melt state properties during extrusion compounding in a frequency range from 50 to 106 Hz. Using non-linear regression methods, the experimental data were fit with the Cole-Cole dielectric relaxation functions corrected for electrode polarization and d.c. conductivity. Characteristic frequency, relaxation strength, relaxation time distribution, as well as d.c. conductivities were extracted from curves with overlapping relaxation modes. Only one dielectric dispersion was found in the neat nylon, which was identified as α relaxation associated with molecular segmental motion. Two dielectric relaxations, α relaxation and Maxwell-Wagner-Sillars interfacial polarization (MWS), were observed in the composite melt. MWS is ascribed to conducting ions in a polymer/filler mixture and has relaxation properties that are dependent upon the microstructure of the filler.