## 3 Results
### Characterization of the Structural and Morphological Properties of Tungsten-Reinforced Polyisoprene
#### 3.1.2 Structural Properties of Tungsten-Reinforced Polyisoprene Characterized by X-Ray Diffraction
The results of the XCOM-based computational analysis confirm that WO\({}_{3}\)-reinforced NR exhibits good radiation attenuation that approaches the performance of PbO\({}_{2}\). 2.2 Computational Assessment of Tungsten-Reinforced Polyisoprene for Radiation Shielding Applications Using Phy-X/PSD Simulations  
The Phy-X/PSD software shielding values are presented in Figure 9, at 140 keV, corresponding to the primary photon energy of Tc-99m [40]. The mass attenuation coefficient (MAC) is an essential metric that explains how photons interact with matter, specifically the potential of photon absorption or scattering per unit mass. MAC is a key component in many applications, including radiation shielding. Figure 9A shows that the low-energy region of 10\({}^{-4}\) to 1 MeV presents a significant variation because of the photoelectric effect dominance, which is dependent on the atomic number (Z) of the material, PbO\({}_{2}\) high atomic number (Z = 82), exhibiting the highest MAC, followed by the 100% WO\({}_{3}\) composite, which contains tungsten (Z = 74). The fluctuations at low-energy photon energies, for high-Z materials, correspond to the K-edge absorption of WO\({}_{3}\) and PbO\({}_{2}\). The intermediate-energy area (10\({}^{-2}\) to 10 MeV) shows a significant drop in MAC, indicating a shift from photoelectric absorption to Compton scattering as the primary interaction mechanism. Although the attenuation behavior of various materials converges, PbO\({}_{2}\) and high-WO\({}_{3}\) compositions still provide better shielding capacities. At the high-energy region, the MAC values stabilize at a lower level, suggesting dominance of pair production at high energies. PbO\({}_{2}\) is the most effective material for photon attenuation and the WO\({}_{3}\)-based composites exhibit promising shielding properties, particularly at high concentrations (\(\geq\)75% WO\({}_{3}\)). Figure 9: Phy-X/PSD-based simulation of radiation shielding materials for Tc-99m applications. The graphs depict key radiation-shielding parameters as a function of photon energy for various shielding materials, including lead oxide (PbO\({}_{2}\)), natural rubber (NR), and tungsten-reinforced polyisoprene (WO\({}_{3}\)-reinforced NR) composites with 25%, 50%, 75%, 90%, and 100% tungsten oxide (WO\({}_{3}\)). The evaluated shielding parameters include (**A**) mass attenuation coefficient (MAC), (**B**) linear attenuation coefficient (LAC), (**C**) half-value layer (HVL), and (**D**) tenth-value layer (TVL). The insets in each plot provide parameter values at 140 keV, corresponding to the primary photon energy of Tc-99m, facilitating a comparative assessment of shielding efficiency across the materials. Figure 9B indicates that increasing photon energy results in a declining trend in the linear attenuation coefficient (LAC) values. This result is compatible with the typical photon interaction models, in which pair formation at extremely high energies (>1 MeV) dominates, photoelectric absorption dominates at lower energies, and Compton scattering becomes prominent at intermediate levels. The sharp peaks at lower photon energies (<10\({}^{-2}\) MeV) correspond to the K-edge binding energy of K-shell electrons, beyond which incident X-ray photons have enough energy to eject them from the atom of the high-Z elements (lead 88.0 keV, tungsten 69.5 keV), where photoelectric absorption dominates. Given Tc-99m gamma emission energy of 140 keV, the most suitable shielding material should have a high LAC value in this energy range. The inset graph shows that PbO\({}_{2}\) and high-percentage WO\({}_{3}\) composites (\(\geq\)75% WO\({}_{3}\)) have better attenuation at 140 keV. The LAC data confirms that tungsten-reinforced NR composites display increased radiation shielding performance with increasing WO\({}_{3}\) concentration. The half-value layer (HVL) refers to the thickness of a material needed to reduce incoming radiation intensity to 50% of its initial level.