Influences of post-processing treatments on mechanical properties and beta-phase content in material extrusion additively manufactured polyvinylidene fluoride structures

Three-dimensional (3D) printing of polymer smart materials offers great potential in terms of design of applications either requiring inherent electromechanical sensing or vibration-based energy production capabilities. Currently, the piezoelectric response of homopolymer 3D printed polyvinylidene fluoride (PVDF) lags the properties offered using the costly alternative feedstock PVDF-TrFE or the geometrically limited sheets of homopolymer PVDF produced commercially via mechanical stretching. This work focuses on the influences of using post-printing processing techniques for producing material extrusion additive manufactured (MEAM) PVDF components with mechanical and electromechanical properties comparable to their more expensive counterparts. In particular, this research describes the effects of using post-fabrication thermal cycles and electrical poling on the development of microstructures favorable to piezoelectricity and on the mechanical properties. The dynamic electromechanical response is demonstrated for the highest beta-phase case of each in a simplistic energy harvesting application. Results from characterization tests showed that higher beta-phase content and greater Young’s modulus and ultimate tensile strength were affiliated with longer annealing process times. Structures annealed at temperature 85 °C for 5 h exhibited greater beta-phase crystallinity than other annealing conditions. In addition, applying electrical field was led to increasing the piezoelectric response within the 3D printed PVDF parts.