Morphological and ferroelectric characterizations of porous poly (ethylene‐co‐vinyl acetate) copolymer films prepared by coextrusion and pressing methods for pseudo‐piezoelectric effect

Abstract

A piezoelectric porous film is designed to convert daily human activities and acoustic vibrations into usable electrical energy. Copolymers are one of the materials used for harvesting this wasted energy by creating the pseudo piezoelectric effect. One of the important steps to obtain a good piezoelectric response is to produce a homogeneous dispersion of the cells/voids with a good distribution. Several production methods were used. In this work, the effect of porosity-processing on the morphology as well as piezoelectric properties of Porous Poly (ethylene-co-vinyl acetate) Copolymer were studied. Two different foam-processing methods, coextrusion process and multilayer hot-pressing method were used. The morphologic characterization was obtained using SEM. Coextrusion process gives a good dispersion of the cells/voids withinthe EVA matrix rather than multilayer hot-pressing, irregular cells/voids were obtained with a random distribution. The 160–320 μm film thicknesses ranging elaborated by coextrusion using 1% and 2% chemical foaming agent lead to a porous thin films with a porosity of 37% and 65% respectively. The porosity percentage effect on our EVA thin films produced by coextrusion process on piezoelectric coefficient d33 and remanent polarization Pr were studied too. The results showed that d33 and Pr increases with increasing the porosity of our films reaching 4.7 pC/N and 2.21 C/cm2 respectively for a 65% EVA film.