Silicone foams for sound absorption: on the link between elaboration parameters and acoustic performances

Invited paper

Morvan Ouisse

FEMTO-ST Applied Mechanics

Tuesday 2 june, 2015, 17:00 - 17:20

0.7 Lisbon (47)

The aim of this study is the investigation of the link between the elaboration process, the microstructure and the acoustic behavior of silicone foams. These ones are obtained using a two-component silicone: Part A is the polymer and Part B the curing agent. When components are thoroughly mixed, the product will expand and cure to a foamed elastomer at room temperature. Different parameters were varied such as the ratio of A/B, the addition of a thinning agent (silicone oil) and the increase of the curing temperature to understand the influence of each parameter in the foam’s absorption efficiency. The microstructure of the foams is analyzed using SEM and the acoustic absorption properties are measured in an impedance tube. Two non-acoustical properties are also investigated, namely the porosity Φ and the flow resistivity σ, both measured on a specific bench. Tests results show that the surface quality (obtained using water jet cutting) of the samples is critical for the correct measurement of the foam characteristics in impedance tube for absorption but also for SEM and non-acoustical properties. It is observed that the pore cell size and interconnected porosity of the silicone foam has a great impact on the acoustical properties. Significant enhancements of the absorption properties could be obtained in the low frequency band by adding a high quantity of agent B and increasing the amount of interconnected porous cell. An improvement in absorption is observed in the higher frequency range when a thinning agent is added to the mixture. High temperature tends to deteriorate the sample’s quality by forming air cavities.

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