Balancing photon attenuation and neutron absorption in BaSO4/B(OH)3-reinforced natural rubber composites apply for medical radiation shielding.

This study investigates BaSO4/B(OH)3 hybrid natural rubber composites designed for the combined attenuation of photon and neutron radiation in medical region energies. Peroxide-crosslinked natural rubber was incorporated with a fixed total loading of 150 phr, while the BaSO4/B(OH)3 ratio was systematically varied to elucidate the composition-property correlations influencing radiation shielding efficacy. Shore A hardness was evaluated to determine the impact of the hybrid fillers on resistance to localized indentation. Photon attenuation was experimentally assessed at 60, 122, and 342 keV with 241Am, 57Co, and 133Ba sources, respectively, with 342 keV regarded as the effective energy corresponding to the nominal 356 keV emission of 133Ba. The linear and mass attenuation coefficients were compared with WinXCOM and Phy-X/PSD calculations, while the photon interaction characteristics were further analyzed using the half-value layer (HVL), mean free path (MFP), effective atomic number, effective electron density, buildup factors, and photon kerma coefficient. Neutron attenuation was evaluated utilizing a paraffin-moderated 241Am/Be source and a 3He proportional counter, employing bare and cadmium-covered observations to estimate the effective thermal and non-thermal neutron components. The enhancement of the BaSO4 content improved composite density, Shore A hardness, and photon attenuation, especially at 60 keV, due to the significant influence of photoelectric absorption from high-Z barium. The elevated photon energies, the distinctions among the formulations diminished as Compton scattering increasingly dominated the interaction response. Conversely, increasing the B(OH)3 concentration enhanced effective thermal-neutron attenuation due to boron-assisted capture subsequent to moderation by the hydrogen-rich rubber matrix. The findings indicate a distinct compositional equilibrium between photon attenuation, thermal-neutron attenuation, and hardness, underscoring BaSO4/B(OH)3 filled natural rubber as a potential material for mixed-radiation shielding applications in medical filled.