Polylactide/montmorillonite nanocomposites: Structure, dielectric, viscoelastic and thermal properties

Polylactide-based systems composed of an organoclay (Cloisite® 30B) and/or a compatibilizer (Exxelor VA1803) prepared by melt blending were investigated. Two types of not compatibilized nanocomposites containing 3 wt% or 10 wt% of the organoclay were studied to reveal the effect of the filler concentration on the nanostructure and physical properties of such systems. The 3 wt%-nanocomposite was also additionally compatibilized in order to improve the nanoclay dispersion. Neat polylactide and polylactide with the compatibilizer processed in similar conditions were used as reference samples. The X-ray investigations showed the presence of exfoliated nanostructure in 3 wt%-nanocomposite. Compatibilization of such system noticeably enhanced the degree of exfoliation of the organoclay. Viscoelastic spectra (DMTA) showed an increase of the storage and loss moduli with the increase of the organoclay content and dispersion. Dielectric properties of the nanocomposites show a weak influence of the nanoclay on segmental (αS) and local (β)-relaxations in PLA, except for the highest nanoclay content. Above Tg a strong increase of dc conductivity related to ionic species in the clay is observed. It gives rise also to the Maxwell–Wagner–Sillars interfacial polarization and both real and imaginary parts of ε strongly increase. In the temperature dependence of low frequency dielectric constant and mechanical moduli (at 1 Hz) an additional maximum around 80–90 °C is observed due to cold crystallization of PLA.