Flexible,lead-free,gamma-shielding materials based on natural rubber/metal oxide composites

Properties such as gamma shielding, cure characteristics, and mechanical properties of natural rubber (NR) system with addition of oxides such as: iron (II, III) oxide (Fe₃O₄), tungsten (III) oxide (W₂O₃), or bismuth (III) oxide (Bi₂O₃) were studied for potential replacement of flexible lead (Pb), and introduced as gamma-shielding materials, to minimize risks caused by Pb. The results showed that increase in the content of oxides such as Fe₃O₄, W₂O₃, or Bi₂O₃ from 0 to 100, 300, and 500 parts/100 parts of rubber by weight (phr) increased the gamma attenuation coefficients, tensile modulus at 100% elongation, and hardness (Shore A), though they reduced the tensile strength and elongation-at-break. The composites also underwent thermal aging tests at 70 °C for 96 h. The results indicated slight reduction in the overall tensile properties. Specifically, for NR composites with 300 or 500 phr of Bi₂O₃, the mass attenuation coefficients (μ _m) of these composites were the highest among other composites and even higher than lead sheets that were measured using the same set-up. The outcome of the results imply great possibilities of replacing hazardous lead-containing gamma-shielding materials with the investigated composites, while still providing safe and efficient gamma-shielding properties for the users.