Silicone foams for sound absorption: on the link between elaboration parameters and acoustic performances
Invited paper
FEMTO-ST Applied Mechanics
Tuesday 2 june, 2015, 17:00 - 17:20
0.7 Lisbon (47)
Abstract:
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.