Cross-linked poly(vinyl alcohol)/boric acid gels for radiation shielding applications

Poly(vinyl alcohol) (PVA) gels are soft materials composed by a hydrophilic polymer matrix cross-linked in water by physical or chemical bonds. These materials can be applied for protective purposes in different fields, including in space environment due to their properties of lightweight and water-richness. Thanks to the high hydrogen content, these gels show significant radiation stopping power, thus less fragmentation of incident particles, suggesting their potential use for radiation shielding. In this work, cross-linked gels based on PVA and boric acid (BA) are fabricated, and their properties are investigated. Fourier transform infrared spectroscopy (FTIR) is used to assess the presence of chemical bonds between BA and PVA macromolecules. The gel thermo-mechanical properties are investigated by dynamic mechanical analysis (DMA) in compression mode. The shielding properties of the gels are evaluated in low Earth orbit (LEO) influenced by galactic cosmic rays (GCRs), trapped protons of solar particle events (SPEs) and thermal neutrons using the deterministic transport codes provided by NASA Langley Research Center. The input data were computed using the water content and density experimentally determined. First, the High charge (Z) and Energy TRaNsport (HZETRN) code is employed to create different cross sections as first output for the selected materials, and then, propagate and transport the ionizing energy inside the slab geometries. Second, the online tool for the assessment of radiation in space (OLTARIS) software, based on HZETRN transport code, is used to evaluate the shielding effectiveness on different Earth orbits in slab geometries and then in inner fabrics of the space suit to substitute the Liquid Cooling and Ventilation Garment (LCVG). Results in terms of chemical, thermo-mechanical properties and simulated shielding behavior show the potential application of PVA/BA gels as protective materials in space environment.