Sustainable magnetite reinforced PLA/Mater-Bi starch/PANi nanocomposites: toward flexible, magnetic, and radiation-protective materials

Abstract With the rising demand for sustainable materials in advanced electronics, biomedical devices, and protective systems, there is an increasing necessity for biodegradable nanocomposites that offer a balance between mechanical strength and electromagnetic shielding performance. This study investigates the synergistic effects of dual fillers, polyaniline (PANi) and magnetite (Fe₃O₄), at low concentrations on PLA/Mater-Bi starch composites. The hybrid nanocomposites were fabricated using twin-screw extrusion followed by hot/cold pressing. PANi enhanced the interfacial interaction between PLA and starch, creating a more homogeneous morphology. At 0.3 wt%, PANi improved tensile strength by 22% and increased elongation at break by 233% (from 5.4% to 18.0%). The incorporation of 0.6 wt% Fe 3 O 4 further increased the tensile strength to 47.8 MPa while maintaining flexibility. All nanocomposites exhibited soft magnetic behavior with low coercivity, and saturation magnetization increased with higher Fe₃O₄ content. Radiation shielding properties including mass and linear attenuation coefficients (59% increase in LAC, 37% reduction in HVL at 0.03 MeV), effective atomic number, and fast neutron removal cross-section, were significantly enhanced with increasing Fe₃O₄ loading. The nanocomposite containing 1.0 wt% Fe₃O₄ demonstrated shielding performance comparable to conventional materials like water and concrete, while offering advantages in reduced density and flexibility. A preliminary LCA showed that these composites have a lower environmental footprint, with up to 78% less fossil resource use and 39% lower carbon emission compared to polyethylene. These findings suggest the potential of PANi/Fe₃O₄-reinforced PLA-based nanocomposites as sustainable, multifunctional materials for lightweight radiation shielding applications.