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Internal finishing materials for large auditoriums or public facilities are regulated in South Korea to ensure their flame-retardant performance. Flame-retardant treatment of low-density fiberboard (LDF), an eco-friendly material, was performed to expand its use as a sound absorber by improving its fire safety. In this study, an LDF with a target density of 0.15 g/cm3 was prepared from radiata pine wood fibers and melamine–urea–formaldehyde resin, and recommended amounts of commercially available flame retardants (liquid type) were applied immediately after hot pressing. A powder-type flame retardant was blended with the resin used in LDF manufacture. The surface color and material changed partially depending on the flame-retardant type. The external application method slightly increased the moisture content and density, but it did not affect the physical properties of the LDF. The flame-retardant treatment reduced the emission of formaldehyde, as a scavenger. After treatment, the char area and char length of the LDFs decreased significantly to 9.42–23.64%, and 6.11–11.91%, respectively. The sound absorption performance of the flame-retardant-treated LDFs improved 4.08–9.11%, while their thermal-insulation performance remained unaffected. The flame-retardant-treated LDFs satisfy the regulation of flame retardancy, while maintaining sound absorption and thermal insulation functions.

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]