Fabrication of medical radiation shielding sheets using reactive densification–based tungsten/PE porous composite materials

X-ray shielding materials used in medical institutions are applied in various forms, including garments, sheets, films, and membranes, and recent studies have actively focused on the adoption of environmentally friendly materials and processing technologies. In this study, lead-free radiation shielding sheets were designed and fabricated by introducing an HDPE/W/ADCA-based foaming-calendering process as an alternative to conventional lead-based X-ray shields. The correlation between microstructural characteristics and shielding performance was quantitatively analyzed using a reactive densification model. HDPE/W/ADCA composites were first prepared as foamable preforms with thicknesses of 1.0-2.0 mm through twin-screw compounding followed by single-screw sheet extrusion. Subsequently, multi-stage calendering was applied at temperatures ranging from 100 to 140 °C to produce final shielding sheets with a thickness of 0.3 mm. FESEM analysis revealed that tungsten particles were uniformly distributed throughout the cross-section of the sheets, while residual pores were present only in fine, localized forms. The shielding efficiency evaluated under medical X-ray conditions (60-120 kVp) ranged from 92.63% to 78.80%, which is approximately 5% points lower than that of lead sheets of the same thickness (97.67-84.86%), corresponding to about 95% of the relative shielding performance of lead. According to the reactive densification model, the enhanced flowability of the polymer matrix contributed to the effective dispersion of metal particles and a localized increase in effective density, indicating that a thickness increase of only approximately 0.02-0.05 mm would be sufficient to achieve shielding performance comparable to that of lead. These results suggest that controlling local density and particle dispersion is a critical design parameter in the development of lightweight and flexible lead-free radiation shielding materials.