Accelerated α Relaxation Dynamics in the Exfoliated Nylon-11/Clay Nanocomposite Observed in the Melt and Semicrystalline State by Dielectric Spectroscopy

Melt state properties of nylon-11 and its exfoliated silicate nanocomposite were monitored during extrusion compounding using an on-line dielectric slit die sensor, and solid-state properties were probed off-line below the melting temperature by a dielectric spectrometer. A comprehensive relaxation master map for nylon-11 and its exfoliated clay nanocomposite featuring six relaxation modes in both melt and semicrystalline states revealed changes in molecular dynamics upon the addition of nanofillers. α relaxation was observed in the neat resin as well as the composite, and a Maxwell−Wagner−Sillars (MWS) relaxation was detected in the composite melt yet absent from the neat molten nylon. The MWS relaxation mode, which exhibited a broader relaxation time distribution and a much greater dielectric intensity compared to the α relaxation, resulted from polarization at the filler/polymer interfaces. MWS can be used to distinguish the neat polymer from the composite during real-time processing. The presence of exfoliated clay particles accelerated the α relaxation dynamics in the semicrystalline state as delaminated silicate platelets diminished the intermolecular cooperativity of the amorphous chains. Randomization of molecular dipoles upon increasing temperature was only observed in the neat nylon. Hindered molecular dipole orientation due to the rigid silicate fillers in the nanocomposite was observed.