Effect of the inflation strategy on the piezoelectric response of cellular poly(vinylidene fluoride) ferroelectret

Cellular poly(vinylidene fluoride) (PVDF)-montmorillonite (MMT)-calcium carbonate (CaCO3) based piezoelectret films were produced using uniaxial stretching and various gas diffusion expansion (GDE) treatments followed by corona charging. The cross section micrographs revealed that a cellular structure was developed at the interface between the solid CaCO3 particles and the polymer matrix. Sample characterization showed that the piezoelectric coefficient (d(33)) was a function of the external gas pressure and treatment temperature, as well as the way they were applied. The results also showed that the maximum d(33) was obtained when the inflation pressure was increased stepwise from 3 to 5 MPa at a constant treatment temperature of 130 degrees C for a certain period of time. Finally, the overall electromechanical performance of the cellular PVDF piezoelectrets is discussed in terms of the GDE procedure and the developed microstructures. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47540.