Energy absorption capacity of ferroelectrets based on porous polypropylene

Ferroelectret materials are special group of piezoelectric materials obtained from the cellular structure of nonpolar polymers. They are under investigation for a variety of applications such as actuators, vibration control, speakers, microphones, sensors, as well as healthcare monitoring systems. In this work, the effect of morphological and mechanical properties of ferroelectret films on their capacitance and stored energy capacity was studied. Different eye-like cellular structure of porous polypropylene films with different cell aspect ratio (AR) and mechanical properties were used. The optimized sample was obtained with AR=6.6 using nitrogen (N-2) as the ionizing gas to give a quasi-static piezoelectric coefficient (d(33)) of about 800 pC/N, an electrode charge density of about 2.10 mC/m(2), a maximum capacitance of about 465 pF, as well as a maximum stored energy capacity of about 1,824 pJ. It was observed that replacing air with N-2 as the ionizing gas led to an increase in charge/voltage output. Moreover, by replacing air with N-2 as the ionizing gas, the capacitance and stored energy of the samples were improved by about 20% and 80%, respectively. Hence, it can be concluded that the capacitance was mostly related to the cellular morphology of the samples while the stored energy was also function of the ionizing gas used. POLYM. ENG. SCI., 58:300-309, 2018. (c) 2017 Society of Plastics Engineers