Enhancement of the Dielectric Constant and Thermal Properties of α-Poly(vinylidene fluoride)/Zeolite Nanocomposites

Different commercial Y zeolites derivate from faujasite structure with similar total Si/Al ratio, NaY (Si/Al = 2.83), HY (Si/Al = 2.80), and HUSY (Si/Al = 3.00), but different framework Si/Al ratios were used to prepare alpha-poly(vinylidene fluoride) (alpha-PVDF)/zeolite nanocomposites. Structural and textural characterization of different Y zeolites was obtained by XRD, FTIR, elemental analysis and nitrogen adsorption isotherms. Nanocomposite films were prepared containing 14% (w/w) of zeolite and characterized in terms of the dielectric response and thermal stability. The best dielectric properties were obtained with NaY because of its smaller framework Si/Al ratio, which means a larger number of sodium in the zeolite structure. For this zeolite, the dielectric constant was increased by a factor higher than two, maintaining unaltered the dielectric loss for frequencies higher than 0.5 MHz. The zeolite HUSY, which presents an extended mesoporosity, shows the lowest onset temperature for thermal degradation. To clarify the origin of the dielectric response of the nancomposites, zeolites with different sodium amounts were obtained by ion exchange treatment using NaNO3 for HY and NH4NO3 for NaY. The dielectric constant was enhanced with increasing sodium content in the zeolite framework.