​​Dielectric and simulated radiation shielding properties of cross-linked PMMA/ZrO₂ and PMMA/CeO₂ nanocomposites

Nanocomposites of modified poly (methyl methacrylate) (C-PMMA) reinforced with zirconium dioxide (ZrO₂) and cerium dioxide (CeO₂) nanoparticles were prepared through in situ polymerization. Their dielectric and radiation shielding properties were also evaluated. We used p-phenylenediamine (p-PDA) to modify the PMMA matrix to make it more rigid and stable at high temperatures. Ceramic nanoparticles were incorporated into the composite at various loadings ranging from 5 to 40 wt%. Structural, morphological, and thermal analyses using FTIR, XRD, SEM-EDX, and TGA all showed strong interfacial adhesion and even distribution of nanoparticles. The composites showed enhanced thermal stability, with residual mass rising to 25-30% and onset degradation temperature increasing to ~ 305 °C compared to 280 °C for pristine C-PMMA. Dielectric analysis at 110 °C shows remarkable improvement in electrical properties. The dielectric constant (ε') increased from ~ 3.0 for pristine C-PMMA to ~ 4.6 for the 5 wt% ZrO₂ composite at 500 kHz, corresponding to an improvement of approximately 53%. Moreover, the AC conductivity improved from ~ 6-7 µS (C-PMMA at 1000 kHz) to ~ 25-26 µS for the 5 wt% ZrO₂ composite, which is almost 3-4 times better. Composites of CeO₂ showed mild yet systematic enhancement, with a conductivity of approximately 8 µS at 40% filler loadings. Radiation attenuation simulated experiments conducted with assistance from the Phy-X/PSD software revealed that both CeO₂- and ZrO₂-filled nanocomposites. The linear attenuation coefficient confirmed the great improvement in low-energy photon-shielding capability at high ceramic loadings at 0.015 MeV, which increased by approximately 37.5 cm^-1 for the C-PMMA/ 40% wt. CeO₂ and 9.95 cm^-1 for C-PMMA/ 40% wt. ZrO₂ than pristine C-PMMA, while the corresponding half-value layer at 8 MeV decreased by approximately 39%. The fabricated composites could be used as promising materials for components such as housings, encapsulation layers, and support structures in electronic modules that operate close to radiation sources, where moderate radiation shielding, electrical insulation, and decreased weight are all needed at the same time. However, further verification of mechanical dependability and experimentally determined shielding efficacy will determine their ultimate usefulness.