Study the effects of functionality of carbon nanotubes upon acoustic wave absorption coefficient, microstructure, and viscoelastic behavior of polyurethane/CNT nanocomposite foam

In this study, lightweight and flexible polyurethane (PU) foams loaded with multiwalled carbon nanotubes (MWCNTs) are synthesized by the free-rising foaming process. The CNT's surface functionality influences cellular structure and mechanical, acoustic wave absorption characteristics of the nanocomposite foams. Flow resistivity and compressive mechanical properties of the fabricated samples have been studied. The acoustic wave absorbency within a wide range of frequencies (63–6300 Hz) was evaluated for the prepared PU/CNT foamed nanocomposite samples. Results indicated that carbon nanotubes' functionalization enhanced the acoustic absorption coefficient above 1000 Hz frequencies. The unfunctionalized-based PU/CNT nanocomposite foam exhibited better acoustical properties within low frequencies. In addition, by functionalizing MWCNT, the nanocomposite foams' mechanical damping behavior decreases, indicating enhanced interfaces between PU segments and CNT particles via functionalization, which leads to a lower viscous response to the mechanical field.