Study on the Morphological Characteristics and Formation Mechanism of Thermally Modified Bamboo Milling Dust

The hazards of dust are receiving increasing attention with the application of bamboo industrialization. This study focuses on the morphological characteristics and formation mechanisms of milling dust from raw bamboo (RB), dried bamboo (DB), and thermally modified bamboo (TMB) treated at temperatures of 160°C, 190°C, and 220°C. The bamboo milling particle size distribution, area-equivalent diameter, minimum Feret diameter, aspect ratio, roundness, and convexity were investigated by using sieving and flatbed scanning image methods to analyze their morphological characteristics. Furthermore, Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD) were employed to investigate the chemical composition changes with the dust. The formation mechanism of bamboo milling dust was explained by the finite element simulation. The research shows that bamboo thermal modification has a significant impact on the particle size distribution, and generates the excessive inhalation of dust. Thermal treatment temperature influences dust morphology and distribution and adds similar features to dust. The thermal treatment has a notable influence on the convexity of milling dust and reduces the surface dispersion of dust, and the stability of dust morphology has been improved. Moreover, thermal modification caused the degradation of hemicellulose and increased crystallinity which affected bamboo's transverse mechanical properties. The bamboo milling deformation and chip formation are investigated through finite element simulation, and three kinds of chip morphologies larger than 200 μm and four kinds smaller than 200 μm were analyzed. The study contributes to understanding the characteristics of thermally modified bamboo milling dust and provides basic data for cleaner production and health protection.