Study of the effects of processing parameters on the sound absorption of open-cell microcellular polymeric foams

Various researchers have investigated microcellular polymeric foams extensively over the last twenty years or so; however, little work has been conducted on the acoustic performance of these foams when their microstructural components are modified by controlling the manufacturing process parameters. The studies discussed in this paper represent an initial stage in the development of open cell foams that exhibit optimized acoustic performance as a result of controlling processing parameters. This study was focused to understand and control certain parameters that dictate the material's microstructure, such as cell size, and link them to the main macroscopic parameters, such as the airflow resistivity and porosity, which govern the overall sound absorption of an open cell material. In this paper, we investigate a new processing technology to manufacture open-cell sound absorbing PMMA (Poly Methyl Methacrylate) materials using a gas foaming/particulate leaching method. An acoustic parametric study is conducted by altering the main processing parameters such as foaming temperature, particle size, and percentage of foaming agent, which affect the cell morphologies and thus control the macroscopic properties. As such, we explore the effects of the adjusted processing parameters on the acoustic performance of the manufactured PMMA samples. The correlations between the resulting cell morphologies and the sound absorption properties indicate that understanding and controlling the porous material's inner structure is crucial for developing any type of open-cell porous material with optimal acoustical efficiency. (C) 2010 Institute of Noise Control Engineering.