The addition of MoO$_3$ or SiO$_2$ nano-/microfillers thermally stabilized and mechanically reinforce the PVDF-HFP/PVP polymer composite thin films

The properties of thin polymer films are influenced by the size of the fillers, their morphology, the surface properties and their distribution/interaction in the polymer matrix. In this work, thin polymer composite films with MoO$_3$ or SiO$_2$ nano and micro fillers in PVDF-HFP/PVP polymer matrix were successfully fabricated using the solvent casting method. The effects of different types, sizes and morphologies of the inorganic fillers on the crystallization of the PVDF-HFP polymer were investigated, as well as the effects on the thermal and mechanical properties of the composites. Scanning electron microscopy, ATR-FTIR spectroscopy, differential scanning calorimetry, nanoindentation and uniaxial mechanical tests were used for characterization. The results showed that MoO$_3$ nanowires thermally stabilized the polymer matrix, induced crystallization of the PVDF-HFP polymer in all three polymorphs (α-, β-, γ-phase) and formed a geometrical network in the polymer matrix, resulting in the highest elastic moduli, hardness and Young’s modulus.