Charged closed-cell polypropylene polymer foams are highly sensitive and broadband piezoelectric materials with a quasistatic piezoelectric d33 coefficient about 250 pC/N and a dynamic d33 coefficient of 140 pC/N at 600 kHz. The piezoelectric coefficient is much larger than that of ferroelectric polymers, like polyvinylidene fluoride, and compares favorably with ferroelectric ceramics, such as lead zirconate titanate. The pyroelectric coefficient p3=0.25 μC/m2 K is small in comparison to ferroelectric polymers and ferroelectric ceramics. The low density, small pyroelectric coefficient and high piezoelectric sensitivity make charged polymer foams attractive for a wide range of sensor and transducer applications in acoustics, air-borne ultrasound, medical diagnostics, and nondestructive testing.
Neaugschwandtner, G., Schwödiauer, R., Bauer-Gogonea, S., Bauer, S., Paajanen, M., & Lekkala, J. (2001). Piezo- and pyroelectricity of a polymer-foam space-charge electret. Journal of Applied Physics, 89(8), 4503-4511. https://doi.org/10.1063/1.1355719