Synergistic Enhancement of Wood Fiber‐Reinforced Polypropylene Composites Using Nano‐Zinc Oxide and Olefin Block Copolymer

ABSTRACT This work aims to broaden the use of wood fiber‐reinforced polypropylene composites in automotive lightweighting by developing a synergistic modification system incorporating nano‐zinc oxide (nano‐ZnO) and olefin block copolymer (OBC). Alkali‐acid‐treated wood fibers (WFs) and maleic anhydride‐grafted polypropylene (MAPP) were used to improve interfacial compatibility. The effects of nano‐ZnO and OBC were evaluated relative to an unmodified system. Nano‐ZnO, functioning as a rigid nanofiller, increased stiffness, hardness, and thermal resistance, whereas OBC improved toughness by promoting energy dissipation through controlled matrix deformation. Microscopy revealed that nano‐ZnO anchors at the fiber–matrix interface while OBC forms dispersed elastomeric domains, together strengthening interfacial adhesion and enabling a cooperative reinforcement–toughening mechanism. Thermal analysis showed that this dual‐modifier system stabilizes the polymer structure during heating and promotes more uniform crystallization. A formulation combining moderate nano‐ZnO loading with low OBC content achieved the best balance of mechanical performance and thermal reliability, supporting its selection as the optimal composition. By partially replacing petroleum‐based polymers with renewable wood fibers and enabling lightweight, recyclable automotive components, this approach offers an effective and environmentally favorable route for developing high‐performance natural fiber composites.