Lead-free polymer nanocomposites reinforced with high-Z fillers: Comparative study of natural (chitosan) and synthetic (PAN-II) matrices for multifunctional radiation shielding

This study reports the development of eight lead-free polymer nanocomposites based on natural chitosan and synthetic polyacrylonitrile (PAN-I, PAN-II) reinforced with high-Z fillers (Ni-MOFs, ZnO, Fe₃O₄). The composites were prepared via co-precipitation and mechanical blending and characterized by XRD, FTIR, TGA, and SEM/EDX, confirming successful filler incorporation and enhanced structural stability. Successful incorporation of fillers and matrix-filler interactions were confirmed by XRD and FTIR analyses. TGA results evidenced an increase in thermal stability with residual masses ranging from 28 to 52 wt%, depending on filler loading. SEM/EDX mapping showed uniform filler distribution, particularly for the Z4 and Z8 systems. Gamma attenuation was assessed using Cs-137 (0.662 MeV) and Ho-166 (0.184–0.810 MeV), while theoretical calculations provided fast-neutron removal cross-sections (Σ_R) and charged-particle stopping powers. Results revealed that Z8 (PAN-II + ZnO) exhibited the highest gamma shielding efficiency, whereas Z4 (chitosan + Fe₃O₄) showed the best performance among chitosan composites, LAC values 27–35 % higher than its corresponding pristine matrices (LAC: 0.304–0.346 cm−1) and up to 42 % reduced HVL values. In the case of neutrons, removal cross-sections and alpha-particle stopping ranges also increased proportionally with Z3 (chitosan + Ni-MOFs) reaching the highest Σ_R value of 0.172 cm−1. This is due to an increase in the effective atomic number and optimization of filler dispersion.The developed nanocomposites are lightweight, nontoxic, and environmentally sustainable; thus, this represents a promising alternative to conventional lead-based shields. This work presents one of the first comprehensive comparisons of natural versus synthetic polymer matrices for multifunctional radiation protection and highlights a pathway toward next-generation green shielding materials and sustainable alternatives to lead for radiation protection in medical and industrial applications.