Dielectric properties of polyamide 12-chromium (III) oxide nanocomposites

Broadband dielectric spectroscopy was employed to study polymer nanocomposites based on PA12 filled with different loading ($0.1$ – $10$ wt.%) of nanosized (average grain size of about $1$ – $5$ nm) chromium (III) oxide. The experimental dielectric data were analyzed within the formalisms of complex permittivity and electric modulus. Three relaxation processes and Maxwell–Wagner–Sillars (MWS) interfacial polarizations were observed. It was found that all the relaxations were sensitive to filler contents. The presence of nanosized amphoteric chromium (III) oxide was shown to lead to the softening of the polyamide matrix that manifested in decrease of the activation energy of the $\alpha$ and $\beta$ relaxation processes and glass transition temperatures. The softening of polymer matrix is the reason for the decrease in the mechanical properties of the polymer nanocomposites as compared to that of neat PA12.