Development of Macroporous Silicone Rubber for Acoustic Applications

This work reports a comprehensive and scalable acoustic material preparation by a medium internal phase emulsion-templating technique from a single part room temperature vulcanizable silicone rubber and pore generator (water and mineral oil mixture). By optimization of the mixing conditions, the pore-generator volume and cure-schedule macroporous sound-absorbing silicone rubber was developed. By optical and scanning electron microscopy, the pore size, their interconnectivity, and heterogeneity were analyzed. For an optimized sample (0,5 volume-ratio water and 3.67 volume % mineral oil, porosity similar to 83%, thickness similar to 12.5 +/- 1 mm) the average sound absorption coefficient and transmission loss measured by an impedance tube technique in 50-6400 Hz were similar to 0.45 and 6.7-42 dB, respectively. Insertion loss measurements in 125-6300 Hz with the material as cladding inside (100%) and outside (85%) of an acoustical enclosure demonstrated minimum/maximum noise reduction of 2.31 dB at 630 Hz/20.9 dB at 4000 Hz and 3.55 dB at 400 Hz/13.71 dB at 2000 Hz, respectively.