Research Articles

This study aimed to determine the amount of flame retardant for semi-combustible performance required to comply with the Ministry of Land, Infrastructure, and Transport Notice 2023-24 for hinoki cypress (Chamaecyparis obtusa) plywood, which is commonly used as a building material. A cone calorimeter was used to observe the changes in the total heat release (THR) depending on the solid content of the flame-retardant impregnation (SCFI). The relationship between the SCFI and THR was expressed as an exponential function. The solid content of the flame-retardant impregnation required to meet the prescribed standard of 8.0 MJ/m² was 108 kg/m³ (semi-combustible performance standards) for hinoki cypress plywood.

Climate change has increasingly disrupted the growth and development of many fruit crops. Among the associated challenges, sunburn caused by excessive light and solar radiation is a major physiological disorder affecting citrus and other fruit species. This study evaluated the potential of kaolin (KL), calcium oxide (CaO), and boric acid (B₂O₃) to mitigate sunburn and improve fruit set, yield, and quality in Murcott mandarin. Foliar sprays were applied at concentrations of 2000, 3000, and 4000 ppm KL, either alone or in combination with CaO and B₂O₃ at 0 CaO + 0 B₂O₃, 500 ppm CaO + 50 ppm B₂O₃, and 1000 ppm CaO + 100 ppm B₂O₃. Applications were performed four times during each season (mid-March, early July, early August, and early September) in 2023 and 2024. The results demonstrated that foliar application of KL, CaO, and B₂O₃ significantly increased fruit set, yield, and both physical and chemical quality attributes by reducing sunburn incidence across both study seasons. The most effective treatments were 4000 ppm KL + 500 ppm CaO + 50 ppm B₂O₃ and 4000 ppm KL + 1000 ppm CaO + 100 ppm B₂O₃.

Bamboo, despite its environmental advantages, often suffers from poor coating adhesion because of its natural surface characteristics, thereby limiting its application as an exterior material. This study aimed to improve the performance of coatings applied to moso bamboo (Phyllostachys edulis) by introducing surface sanding as a pretreatment. Sanding was performed using #100 sandpaper with stroke counts of 10, 20, 30, and 40; the resulting changes in the epidermal and fibrous layers and their influence on the coating adhesion were evaluated. The 40-stroke treatment exposed the fibrous layer and enhanced the surface wettability. According to the ISO 2409 (2020) cross-cut test, the sanded specimens exhibited excellent adhesion (Grade 1), in contrast to untreated specimens, for which coating delamination was evident. Furthermore, under accelerated-aging tests, coating adhesion was maintained for the sanded samples, whereas pronounced delamination was observed for the untreated samples. These findings demonstrated the effectiveness of surface sanding. In conclusion, surface pretreatment is essential for improving the durability and coating quality of moso bamboo, and the results of this study can serve as fundamental data for the practical application and broader utilization of bamboo materials.

Microfibrillated cellulose (MFC) is a promising bio-based material owing to its excellent mechanical, optical, and barrier properties. However, its inherent hydrophilicity limits its applicability in moisture-sensitive environments. In this study, the surface hydrophobicity of MFC films was enhanced by incorporating an alkyl ketene dimer (AKD) and thermal curing. MFC was prepared from hardwood bleached kraft pulp via high-pressure homogenization to fabricate AKD-modified MFC films using vacuum filtration. The water contact angles of the AKD-modified MFC films were measured after thermal curing to determine the optimum manufacturing conditions for MFC film hydrophobicity. The presence of the AKD in the MFC matrix was confirmed by the appearance of alkyl chain C–H stretching bands in the Fourier transform infrared spectroscopy spectra. The water contact angle measurements showed that the addition of AKD alone improved the hydrophobicity but did not yield contact angles greater than 90°. However, with subsequent thermal curing at 105 °C, the contact angles increased significantly, reaching 104° under optimal conditions. The highest hydrophilicities were achieved with 2% AKD and 30 min curing and with 3% AKD and 10 min curing. These findings demonstrated that thermal curing was essential for activating the hydrophobic potential of AKD and achieving uniform, water-repellent MFC films.

The organosolv method, using water and n-butanol with acid catalysts, separates biomass into three phases: n-butanol, aqueous, and solid, which primarily contain lignin, hemicellulose, and cellulose, respectively. In this study, maleic acid was applied as a catalyst in the water/n-butanol method to avoid using inorganic acids. Comparable or better component separation was achieved relative to using sulfuric acid as a catalyst. Furthermore, by using a high concentration of maleic acid, instead of a catalytic amount, lignin was extracted from softwood with a high yield (more than 97 wt.% lignin extracted) under the condition at 180 °C for 1 hour with approximately 10 wt% maleic acid. Additionally, the reaction temperature and time were varied to achieve better lignin fractionation and functionalization. The highest total fractionation extent and well-carboxylated lignin were obtained at 150 °C. The chemical properties of lignin were also analyzed, and their structure and molecular weight were investigated.