PVP incorporation effects on the structural, thermal, electrical, and mechanical properties of PVDF-HFP/PVP blend

Flexible free-standing membranes (thickness ~ 60 µm) of poly (vinylidene fluoride-co-hexafluoropropylene)/polyvinyl pyrrolidone (PVDF-HFP/PVP) blends with various weight fractions of PVP were fabricated by the solution casting technique. The inclusion of PVP enhanced the semi-crystalline polymer PVDF-HFP's amorphous region, as confirmed by X-ray diffraction (XRD). Fourier transform infrared microscopy (FT-IR) investigations of the macromolecular blend membranes revealed interactions between the PVP and PVDF-HFP. The impact of adding PVP to PVDF-HFP on the miscibility of the resulting blends was examined using scanning electron microscopy (SEM). The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) confirmed a complete miscibility of PVDF-HFP with PVP. Additionally, the Coats-Redfern model was used to calculate the activation energies of all samples. The uniform dispersion of PVP significantly boosted the thermal stability of the PVDF-HFP-based blend. The PVDF-HFP: PVP (75:25) blend polymer showed the minimum electrical conductivity (σ_DC) of ~ 1.23 × 10⁻¹⁴ S cm⁻¹. Adding PVP to the polymer causes additional relaxation because of the PVP/PVDF-HFP interface, which increases the blend's dielectric constant ε_r to 9.6 for the sample with 25% PVP. Dynamic mechanical analysis (DMA) showed an improvement in the storage modulus of blended polymer, with the 25% PVP sample exhibiting a storage modulus of ~ 0.23 GPa at ~ 45 °C. These advantageous improvements suggest that the PVDF-HFP/PVP blend is well-suited for insulating applications.