Steam exploded wood cell walls reveals improved gas permeability and sound absorption capability

Steam explosion is a useful method to soften and dimensionally stabilizing wood. The effects of steam explosion at low pressure (6 bar) on wood cell walls are characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), capillary flow porometry and two-microphone transfer function. The average sound absorption coefficient (SAC) of treated Chinaberry samples on the cross-sectional surface exhibited significant improvement of 79% relative to control specimens over a wide frequency range of 250–6400 Hz. Whereas, a little increment SAC of 5% was observed in the case of Ginkgo wood. Color of steam-exploded woods became black due to chemical reactions in wood cell walls during the steam explosion. The air permeability, SAC and color change are correlated with the results of FTIR and XRD. These results suggest that steam explosion could be used to manufacture wood-based sound absorption board to control the acoustical housing environment.