Colorless and transparent composites with flexibility for enhanced X-ray shielding using glycerol and starch as matrix

Pb glasses that are transparent and exhibit X-ray shielding behavior have been studied in previous works, as have flexible, X-ray-shielding composites composed of a matrix and nanometal particles. However, the development of X-ray shielding materials that are colorless, transparent, flexible, and exhibit X-ray shielding behavior remains a challenge. In this work, we report X-ray shielding composites consisting of glycerol and tapioca starch, focusing on solvated metal ions in glycerol. The X-ray shielding properties of composites containing BaBr 2 dissolved in glycerol are compared with those of composites containing BaSO 4 dispersed in glycerol, where the composites contain the same number of Ba atoms. The visible-light transparency of the composites prepared using BaBr 2 dissolved as metal ions was greater than 90 % under all of the investigated visible-light wavelengths. Ionized Ba 2 + and Br − were found to exist in the composite as ions, without recrystallizing into BaBr 2 . In addition, the X-ray shielding properties were better than those of the composites prepared using BaSO 4 because of good dispersion of the Ba 2+ ions and Br − as counter ions. The Ba 2+ ions form clusters, and the clusters improve the mechanical properties of the resultant composites by artificially cross-linking. The composite material with starch based on BaBr 2 dissolved in glycerol is expected to be used in medical and nuclear applications as an alternative to Pb glass. • Colorless and transparent composites were developed using glycerol, starch, and BaBr 2 . • BaBr 2 XRD peaks were confirmed to be absent after formation of the composite. • BaBr 2 ionized in the composite was more effective for X-ray shielding. • Glycerol-BaBr 2 /Modified-TS composites exhibit superior mechanical properties. • The proposed composite combines transparency, X-ray shielding, and flexibility.