Experimental Investigation of the Acoustic Attenuation by Monolithic Polyurea Aerogels

Aerogels are lightweight, porous nanostructured materials with exceptional thermal insulation properties. the most widely studied aerogel variety is based on silica; however, recent advances in all-polymer aerogels have resolved fragility issues and render them viable alternatives. in particular, polyurea aerogels can be synthesized in a single environmentally friendly step from inexpensive triisocyanates and water over a wide range of densities. Reasoning that the nanoporous characteristics of polyurea aerogels could be accompanied by high, structure-dependent acoustic attenuation, this work investigates the acoustic properties of polyurea aerogels with emphasis on their acoustic attenuation. Conventional materials with high acoustic damping capabilities typically have relatively high densities or are bulky. in applications where weight and volume are at a premium, polyurea aerogels may potentially provide a solution where traditional materials fail. Using a three-microphone impedance tube method, this work experimentally investigates the propagation coefficient of several monolithic polyurea aerogels at different densities. in contrast to traditional porous materials, polyurea aerogels demonstrate very high acoustic attenuation and therefore show promise for a wide range of applications. This paper discusses experimental results and addresses challenges in the measurement of acoustic properties with high attenuation materials.