Relaxation in poly-(ethylene terephthalate glycol)/montmorillonite nanocomposites studied by dielectric methods

Samples of polyethylene-1,4-cyclohexylenedimethylene terephthalate glycol (PETG) with different filler contents were prepared by a master batch process. The dispersion state of montmorillonite was characterized using X-ray diffraction. The influence of nanofiller on molecular mobility at the glass transition was studied by dielectric relaxation spectroscopy and thermo stimulated depolarization currents. The use of these two techniques allowed us to determine the fragility index m. For this parameter, we observed a maximum for a 1 wt% montmorillonite content. For higher contents, no significant modification of the fragility index was observed. This behavior has been attributed to nanofiller agglomeration.