Detailed evaluation of X-ray shielding performance of boron-filled bio-based rigid polyurethane foam composites: Experimental measurement and theoretical modeling

This study aims to comprehensively investigate the X-ray shielding performance of bio-based rigid polyurethane foam (bPUF) composites incorporated with amorphous boron, using both experimental measurements and theoretical modeling approaches. A series of foam samples with different boron content (0–20 wt%) were fabricated via one-shut free-rise method and, the variation in X-ray attenuation capabilities of the produced foams depending on boron content were analyzed meticulously. The key parameters such as linear and mass attenuation coefficients (LAC, MAC), half-value layer (HVL), tenth-value layer (TVL), mean free path (MFP), effective atomic number (Z eff ), and radiation protection efficiency (RPE) were evaluated. The findings showed that the inclusion of boron led to slightly improvement in X-ray radiation shielding, particularly at low photon energies, primarily attributed to both the increment in the foam density and presence of boron having relatively higher atomic number in the foam matrices. The best-performing composite (with 20% boron) demonstrated slight enhancements in LAC, Z eff , and stopping power performance for charged particles. The addition of boron also increased the electrical conductivity (C eff ) of the foams, as boron particles acted as a semiconductive bridge promoting conduction. Although low atomic number of boron limited its direct interaction with high-energy X-rays, its contribution to foam densification supported secondary interaction mechanisms to shield radiation. All in all, these findings highlighted the boron-filled bPUFs could be used as environmentally friendly, lightweight, and moderately effective X-ray shielding materials.