Mechanical properties of wood/plastic composites formed using wood flour produced by wet ball-milling under various milling times and drying methods

The objective of this study was to investigate the mechanical properties of wood/plastic composites (WPCs) produced using wood flour (WF) prepared by wet ball-milling under various milling times (0–120 min) and drying methods (freeze- or heat drying). The drying method did not affect the particle size distribution, shape, or specific surface area of WF at milling times shorter than 40 min. At milling ≥ 40 min, freeze-dried ball-milled WF (FDWF) had smaller particle sizes and higher specific surface area than heat-dried ball-milled WF (HDWF). The highest tensile strength and modulus of rupture (MOR) were observed in WPCs made from freeze- and heat-dried WF at a milling time of 30 min. At milling time of 30 min, the amount of 100–300 µm FDWF and HDWF was 37% and 36%, respectively. The impact strength of WPCs increased, as the milling time increased. The amount of small freeze- and heat-dried WF particles increased due to an increase in the amount of 17 µm particles and specific surface area with increased milling time. Thus, impact strength of WPCs increased as particle size decreased. At milling times ≤ 60 min, there were no significant differences in mechanical properties between WPCs containing freeze- and heat-dried WF under the condition of this study.