Effects of in-situ poling and process parameters on fused filament fabrication printed PVDF sheet mechanical and electrical properties

Polyvinylidene fluoride (PVDF) is a polymer prized for its unique material properties, including a high resistance to corrosive acids such as HCL and HF and its piezoelectric potential based on the proper microstructure arrangement. In this work, the effects of fused filament fabrication (FFF) routine parameters on printed PVDF film properties were investigated using a variety of experimental methods. The influence of in-fill angle (0 degrees, 45 degrees, and 90 degrees) on the effective Young's Modulus, Poisson's ratio, and yield strength were evaluated using tensile testing and a digital image correlation (DIC) analysis. The phase content, in particular the beta-phase amount, within the semi-crystalline PVDF films was determined as a function of processing parameters using the FTIR method. Considered parameters included the extrusion temperature, horizontal speed, in-situ applied hot end voltage, and bed material. Results showed that higher beta-phase content was associated with lower extrusion temperatures, faster extrusion rates, and higher hot end voltages. While all "as printed" films demonstrated little to no measurable piezoelectricity, PVDF films printed with a high beta-phase content and subjected to a post-printing corona poling procedure showed a small, but consistent piezoelectric response. Based on a static deflection cantilever beam experiment, the d(31) coefficient of the poled specimens was estimated at 1.19 pm/V. (C) 2016 Elsevier B.V. All rights reserved.