Piezo- and pyroelectricity of a polymer-foam space-charge electret

Charged closed-cell polypropylene polymer foams are highly sensitive and br oadband piezoelectric materials with a quasistatic piezoelectric d(33) coef ficient about 250 pC/N and a dynamic d(33) coefficient of 140 pC/N at 600 k Hz. The piezoelectric coefficient is much larger than that of ferroelectric polymers, like polyvinylidene fluoride, and compares favorably with ferroe lectric ceramics, such as lead zirconate titanate. The pyroelectric coeffic ient p(3)=0.25 muC/m(2) 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 f or a wide range of sensor and transducer applications in acoustics, air-bor ne ultrasound, medical diagnostics, and nondestructive testing. (C) 2001 Am erican Institute of Physics.