Premium
Polymer ferroelectret based on polypropylene foam: Piezoelectric properties improvement using post‐processing thermomechanical treatment
Author(s) -
Mohebbi Abolfazl,
Mighri Frej,
Ajji Abdellah,
Rodrigue Denis
Publication year - 2017
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.44577
Subject(s) - materials science , composite material , piezoelectricity , polypropylene , polymer , piezoelectric coefficient , ultimate tensile strength , dynamic mechanical analysis , anisotropy , optics , physics
ABSTRACT In this work, the effect of post‐processing parameters (time, temperature, and pressure) on the morphology as well as mechanical and piezoelectric properties of foamed polypropylene (PP) films were studied. Two different post‐processing methods, based on the saturation of a foamed film with supercritical nitrogen (N 2 ), were used to obtain an optimized eye‐like cellular structure with a high cell aspect ratio ( AR ). The results showed that, when the PP‐foamed films were exposed to a gradual temperature and pressure increase, an appropriate cellular structure with high AR value (about 6.6) was obtained. This structure led to a high quasi‐static piezoelectric d 33 coefficient of 800 pC/N (45% higher than for untreated ones) indicating the importance of the post‐processing treatment on the piezoelectric behavior of these films. On the other hand, when the treatment was performed in steps, cell morphology changed from an eye‐like to a less elongated shape, resulting in lower d 33 values. The tensile characterization showed that higher cell aspect ratio led to lower Young's modulus, which is suitable to achieve higher piezoelectric properties. Finally, dynamic mechanical analysis (DMA) was used as a simple method to correlate mechanical and piezoelectric properties of cellular PP. This was done via the ratio of the storage moduli in the longitudinal and transverse directions, which is directly related to film anisotropy ( AR value) and thus to the piezoelectric behavior. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44577.