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The demand for noise control in residential environments is steadily increasing, but the currently available noise-reducing materials used in walls and floors are unsustainable and expensive. As an alternative, woodfiber could be a good resource to manufacture eco-friendly acoustic materials. In this study, fiberboards were prepared by mixing wood-fibers (Pinus densiflora) with melamine-urea-formaldehyde resin adhesive, obtaining specimens with different final densities and resin contents. The acoustic, physical, and morphological properties of the fiberboards were investigated. The sound absorption was greatly influenced by the density of the fiberboard: lower densities showed higher sound absorption performances. Furthermore, the low-frequency absorption coefficient was higher for lower resin contents. The materials met all the criteria required by the Korean standards for fiberboards. As the density increased, the dimensional stability and the bending strength increased; in contrast, the physical properties were not affected by the resin content. Microscopy observations confirmed that specimens with different densities and resin contents had different porosities; the porosity was assumed to be the main property that governs the noise-reducing ability. Due to their ecofriendliness and inexpensiveness, these fiberboards offer themselves as efficient and effective alternative sound-absorbing materials. [ABSTRACT FROM AUTHOR]

As the demand increases for low energy green buildings, such as passive housing, the development of new insulation systems based on natural materials is underway. In this study, 20-mm-thick wood fiber insulation board (WIB) samples of different densities were prepared using melamineformaldehyde-urea (MFU) resin adhesives. The resin contents were fixed at 35% and the target densities were 0.10 g/cm³, 0.15 g/cm3, 0.20 g/cm³, and 0.25 g/cm³. The thermal conductivities of the WIBs gradually increased as the density increased. The formaldehyde (HCHO) emissions of all the WIBs indicated that they were of "Super E0" (SE0) grade, but the quantity of the HCHO emissions slightly increased as the density increased. The thickness swelling of all the WIBs was stable at less than 3%, and the bending strength linearly increased as the WIB density increased. A notable decrease in the water absorption rate was observed between the lower and higher density WIB samples. Based on the results of the cone calorimeter tests, the carbonization depth ratio and the weight loss rate remarkably decreased as the density increased. Therefore, the optimum WIB density was in the range of 0.15 g/cm³ to 0.20 g/cm³ to provide adequate insulation performance as well as human and structural safety. [ABSTRACT FROM AUTHOR]