Open-cell P(VDF-TrFE)/MWCNT nanocomposite foams with local piezoelectric and conductive effects for passive airborne sound absorption

Abstract

Open-cell nanocomposite foams of poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)] and multi-walled carbon nanotubes (MWCNTs) were investigated for airborne sound absorption. When MWCNTs were well dispersed in the P(VDF-TrFE) matrix, the degree of crystallinity of the polar phase of the polymer was enhanced, and hence, the local piezoelectric effect and the electrical conductivity varied by nearly seven orders of magnitude dependent on the amount of MWCNT loading. The measurements in a standard acoustic tube showed that introduction of an appropriate amount of MWCNTs significantly enhanced the airborne sound absorption coefficient of P(VDF-TrFE) foam without poling, particularly in the lower and intermediate frequency range (below 2 kHz), which is attributed to the local piezoelectric effect in the polar polymer matrix and charge dissipation through the conductive MWCNT interfacing the polar phase. The experimental results and data analysis indicate that the open-cell nanocomposite foam with an optimal combination of local piezoelectric effect and electrical conductivity is promising for noise mitigation applications with enhanced passive airborne sound absorption.