Upcycling Waste Expanded Polystyrene for Development of Bamboo‐Reinforced Sustainable Wood–Plastic Composites

Expanded polystyrene (EPS) is widely used in packaging because of its low density and excellent shock‐absorption and thermal insulation properties. However, its hard‐to‐recycle nature leads to severe environmental pollution. In this study, EPS waste was upcycled to develop lightweight, high‐performance wood–plastic composites (WPCs) using bamboo fibers and pulp. EPS was dissolved in a mixed solvent of ethyl acetate and acetone to form a novel adhesive binder for composite fabrication. Three bamboo‐to‐EPS ratios (40:60, 50:50, and 60:40) were investigated, while a constant bamboo pulp‐to‐fiber ratio of 70:30 was maintained to ensure a compact structure and improved surface finish. The composites were fabricated by compression molding and evaluated through mechanical, physical, screw holding, thermal, and morphological characterizations. WPCs containing 60% EPS exhibited superior properties, with modulus of rupture (MOR) of 28.13 N/mm 2 and a modulus of elasticity (MOE) of 4155.38 N/mm 2 , indicating high strength and stiffness. Additionally, these composites showed reduced water absorption due to the inherent hydrophobicity of EPS, along with improved screw withdrawal resistance (SWR) and greater thermal stability. These results demonstrate that EPS waste can be effectively converted into value‐added WPCs suitable for interior building panels and automotive interior applications.