This study aimed to investigate and compare the qualitative and quantitative anatomical characteristics of Acacia mangium and Acacia hybrid in plantation forests in Vietnam. The qualitative and quantitative anatomical characteristics were evaluated according to the International Association of Wood Anatomists list of microscopic features for hardwood identification. In terms of qualitative features, A. mangium had a rough, hard, and fissured bark surface with a golden brown to dark brown color, whereas A. hybrid had a smooth and slightly scaly bark surface with greenish brown to greyish brown color, and yellowish white to pale white spots. Moreover, the heartwood–sapwood color and microscopic features of both species were identical. In terms of quantitative features, A. mangium had higher values in the tangential diameter of vessel lumina, vessel per square millimeter, ray number per millimeter, fiber length, and fiber wall thickness than A. hybrid, whereas A. hybrid had a higher ray height and lumen diameter than A. mangium. Thus, it is suggested that bark morphology and some quantitative anatomical characteristics can be used for identification and evaluation of wood quality between A. mangium and A. hybrid growing in Vietnam.

As petrochemical products (including plastics) contribute to the destruction of the natural environment, the use of such products must be reduced. Plastics account for 90% of the insulation materials used in Korea, including extruded polystyrene (EPS), expanded polystyrene (XPS), and urethane foam. Wood-fiber insulation board (WIB) is a promising natural alternative to petrochemical insulation. This study aimed to determine the optimal amount of adhesive resin required for manufacturing WIB. Fire-resistant WIB was prepared with a melamine-urea-formaldehyde (MUF) resin (ranging from 20% to 35%), and the physicochemical and fire-resistant properties were determined. Higher resin content led to improved physical properties, while the thermal conductivity was unaffected. With the exception of 35% resin content in the WIB, the formaldehyde emissions of the WIB samples complied with the Korean Industrial Standards requirements for Super E0 grade (less than 0.3 mg per L). The physicochemical properties of the WIB samples were sufficient for use as an insulating material, even at 20% resin content. A perpendicular flame test revealed that all samples formed a carbonized layer to prevent flame penetration, except for the specimen with 20% of the resin content. The cone calorimeter testing indicated that the MUF adhesives acted as an effective fire retardant at resin contents above 25%.

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, wood-fiber 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 eco-friendliness and inexpensiveness, these fiberboards offer themselves as efficient and effective alternative sound-absorbing materials.

Fire-retardant performance was imparted to the existing wood-fiber insulation boards (WIB) via internal and external treatment with silica- and phosphorus-based fire-retardants. The combustion and smoke characteristics were investigated using a cone calorimeter. Based on combustion for 600 s, the weight loss and shrinkage of WIBs decreased due to fire-retardant treatment. The time to ignition was delayed to more than 400 s on the WIBs treated internal and external fire- retardant (WIB-IEs), whereas that of WIB with only internal treatment (WIB-I) was 5 s. The overall heat release rate (HRR), HRRpeak, and total heat release (THR) of WIB-IE specimens decreased, and the fire resistance standard Class II was satisfied. The WIB-IE2 showed higher fire resistance performance, with a HRRmean level of 6.7 kW/m2 and a THR of 1.3 MJ/m2. The WIB-I showed extremely low total smoke release (TSR) compared to the external fire-retardant treated specimen. However, the externally treated WIB-IEs had an increased TSR of 165 to 256 m2/m2 due to the increase in incomplete combustion caused by the fire-retardant. After fire-retardant treatment, CO2 generation decreased because the rate of complete combustion decreased, but CO emission increased slightly. Therefore, silica- and phosphorus-based fire-retardants by internal and external treatments were suitable for WIBs.