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

Abstract

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.

Dielectric properties of polyamide 6-montmorillonite nanocomposites

“…This relaxation is assigned to more co-operative motions of CH 2 sequences involving water molecules H-bonded to the free NH groups [8,13,1518,[22][23][24][25][26].…”

“…It is associated to the glass-rubber transition of PA6 plasticized with water. The variation of the humidity content causes large changes in the shape and dynamics of this relaxation [8,16,17,24].…”

Dielectric properties of nylon 6/clay nanocomposites from on-line process monitoring and off-line measurements

“…The relaxation dispersion map that emerges from both on-line and off-line measurements shows distinct differences in the dielectric relaxation dynamics between well-exfoliated and poorly exfoliated samples. In another paper from our laboratory, we described results from dielectric measurements on nylon 11 and its clay composite [6]. The impact of clay exfoliation on the molecular dynamics in nylon 6 and nylon 11 is similar.…”

Depercolation of aggregates upon polymer grafting in simplified industrial nanocomposites studied with dielectric spectroscopy

“…Polymer in contact with NP surfaces may form immobilized, sometimes referred to as "glassy", layers which are mainly detected by NMR [13,23]. On larger scales, at high temperature (above the glass transition), the occurrence of a Maxwell-Wagner-Sillars (MWS) process has been reported in several composite systems using broadband dielectric spectroscopy (BDS) [21,[24][25][26]. MWS processes are related to polarization effects due to charge carrier diffusion through the different phases of the nanocomposites.…”