Study of flow-induced crystallization in polyvinylidene fluoride 3D printing

This study explores how additive manufacturing processes, specifically fused filament fabrication (FFF) parameters, affect the β-crystallization of polyvinylidene fluoride (PVDF). A key focus is to ascertain if flow-induced crystallization during FFF improves the overall crystallinity, as the polymer melt is subjected to high shear forces during printing, which reduces kinetic barriers to crystallization and influences the resulting morphology. Using a design-of-experiments approach, the effects of extrusion temperature and printing speed were systematically evaluated to assess their impact on crystallinity, characterized through differential scanning calorimetry, Fourier-transform infrared spectroscopy, and polarized optical microscopy. Statistical analysis identified extrusion temperature as the most significant parameter for promoting β-phase formation, with the highest crystallinity observed at an extrusion temperature of 235 °C. In contrast, printing speed appeared to have a limited influence on crystalline phase distribution, indicating that higher production rates may be achievable without adversely affecting material properties. Nevertheless, rheological investigations underscored the role of both extrusion temperature and printing speed in facilitating shear-induced crystallization. These findings provide valuable insights into the optimization of FFF parameters for PVDF-based functional devices, advancing the development of improved piezoelectric and energy harvesting applications while reducing the cost and complexity associated with conventional manufacturing techniques.