High‐Loaded Bismuth Oxide/Copper Silicone Rubber Composites and Their Application as Shielding Collar for I‐ <b>131</b> Treated Thyroid Cancer Patients

ABSTRACT The development of flexible, non‐lead radiation‐shielding materials remains a critical challenge, particularly for I‐131 protection, where no effective options currently exist. In this study, silicone rubber composites incorporating up to 80 wt% of bismuth oxide or copper were fabricated via room‐temperature vulcanization technique. The composites were systematically evaluated to optimize radiation attenuation, flexibility, and mechanical durability. The most effective formulation, providing shielding performance equivalent to 2 mm of lead, was fabricated into an I‐131 thyroid‐shielding scarf and tested in patients undergoing I‐131 therapy. The scarf reduced I‐131 radioactivity by up to 40% with a thickness of 1 cm, demonstrating the potential of high–filler‐content silicone composites as practical, flexible alternatives to conventional lead‐based shielding materials.