Correlation between the acoustic and porous cell morphology of polyurethane foam: Effect of interconnected porosity

Interconnected pore cell in appropriately chosen porous media can help to enhance their sound absorption performance. Acoustic absorbing foam materials were produced from polyurethane (PU) with addition of water as a blowing agent and OR-501 as open pore cell agent. The pore sizes of the foams were varied from 0.35 to 1.05 mm in diameter and the pore cells were interconnected with open porosity in the range from 16.0% to 88.6%. The compressive strength of the foams decreased with increase of interconnected cell ratios. There was a decrease of the strength lower than 92.6% compared to the closed cell sample when interconnected cell ratio was 88.6%. The acoustical efficiencies of PU foams were studied, and the results showed that the porous cell size and interconnected porosity of PU foams had significant influence on the acoustical efficiencies. Significant enhancements of the absorption properties could be obtained over a low frequency band by increasing the interconnected porous cell. The absorption coefficient of the interconnected cell foam was 0.66 at low frequency of 250–600 Hz with an increase of 100% compared to the closed-cell ones. The internal transmission path and loss mechanism of noise in the porous polyurethane materials were also analyzed in the present work.