Sound absorption characteristics of nanocomposite polyurethane foams infused with carbon nanotubes

Flexible, open-cell polymeric foams are among the most commonly used and effective materials for passively dissipating noise and vibration. Their unique cellular structure results in materials which are lightweight but still highly absorptive, making them particularly useful for weight-sensitive applications, such as aircraft cabin noise reduction. "Nanocomposite" polymeric foams, which are synthesized from polymeric materials containing nanoscale fillers (e.g. carbon nanotubes and silicate nanoclays), have altered morphological and mechanical properties in comparison to conventional counterparts. Many of these same properties intrinsically control the sound absorption characteristics of polymeric foams. Thus, by utilizing nanoscale fillers to control relevant morphological and mechanical properties, polymeric foams with enhanced sound absorption properties could potentially be created. In this study, various composites of polyurethane foam and multi-walled carbon nanotubes were synthesized and then experimentally characterized to observe the effects of the nanofiller infusion on sound absorption in terms of the normal incidence sound absorption coefficient. Additionally, a number of related material parameters were measured including porosity, flow resistivity, elastic modulus, loss factor, and density, and connections were made between the effects of the carbon nanotubes on these properties and the observed changes to sound absorption. Results indicated that polymeric foams infused with multi-walled carbon nanotubes exhibited an increased ratio of sound absorption to density, depending on the weight fraction of carbon nanotubes dispersed within the foam. (C) 2015 Institute of Noise Control Engineering.