An electrospinning strategy was used to manufacture composite mats consisting of nontoxic tungsten powder with a content up to 500 wt% and inexpensive polyurethane (PU) nanofibers for X-ray shielding applications. The electrospun composite mats have X-ray mass attenuation coefficients comparable to conventional sheets prepared by a wet-casting method, but their gas permeability and flexibility are almost two and five times higher, respectively, than those of conventional mats. The successful incorporation of tungsten powder into the electrospun PU nanofibers well beyond their typical limits can allow for the development of nontoxic shielding materials with controlled structural and physical properties. More information can be found in the Full Paper by Hongsik Byun, Sung-Yul Kim et al.