Enhanced Multifunctional Properties of Polypropylene/Bi ₂ O ₃ Nanocomposites for Energy Storage and Packaging Applications

ABSTRACT This study reports the development of multifunctional polypropylene (PP) nanocomposites reinforced with Bi 2 O 3 nanoparticles synthesized via the solvothermal method. Structural characterization of Bi 2 O 3 was carried out by XRD, TEM, and FTIR. Nanocomposites containing 0.5–5 wt% Bi 2 O 3 were fabricated using extrusion and hot‐pressing, and their optical, morphological, electrical, and mechanical properties were systematically investigated. UV–Vis analyses revealed a reduction in band gap and an increase in refractive index, extinction coefficient, and optical conductivity with increasing Bi 2 O 3 content. Electrical measurements indicated improved energy storage capability, particularly at 5 wt% Bi 2 O 3 loading, while maintaining low dielectric loss. Mechanical tensile tests showed that 5 wt% Bi 2 O 3 increased Young's modulus by 49.5% compared to pure PP, improving stiffness and rigidity, whereas 0.5 wt% Bi 2 O 3 enhanced stress at break and strain at break, indicating improved toughness and ductility. Wettability measurements revealed a hydrophobic transition at 0.5 wt% and a return to hydrophilic behavior at higher loadings, consistent with surface roughness trends. Overall, the results demonstrate that Bi 2 O 3 nanoparticle‐reinforced PP nanocomposites exhibit synergistic improvements in optical, dielectric, and mechanical performance, making them promising candidates for lightweight structural components, durable flexible packaging, and advanced dielectric energy storage devices.