Effects of Ionic Liquid Content on the Electrical Properties of PVDF Films by Fused Deposition Modeling

In this study, polyvinylidene fluoride (PVDF) composite films were prepared by fused deposition modeling, and the effects of ionic liquid (IL) content on the printability, crystallization behavior, and electrical properties of melted PVDF were systematically investigated. The results show that the addition of IL increased the temperature sensitivity of melted PVDF and decreased its viscosity, while IL acted as a plasticizer to lower the melting point of PVDF and improve its FDM printability. The imidazole cations in IL had electrostatic interactions with the -CF₂- groups in PVDF, which promoted the transformation of the nonpolar phase to the polar phase in PVDF; thus, the addition of IL was beneficial to the increase in the polar β phase. The PVDF with 20 wt.% IL contained the highest proportion of β phase content (32.59%). Moreover, the increase in polar β-phase content also increased the polarization strength of PVDF and improved its ferroelectric properties. PVDF with 10 wt.% IL had the highest residual polarization strength (16.87 μC/m²).