## 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 characteristic photoelectric absorption edges correspond to absorption edges of lead and tungsten, where photon interactions increase sharply. For high-WO\({}_{3}\) composites, Zeq stabilizes in the intermediate energy range (10\({}^{-2}\) to 100 MeV), therefore suggesting a shift from photoelectric absorption dominance to Compton scattering. Though the variance closes as energy rises, PbO\({}_{2}\) maintains higher Zeq values than WO\({}_{3}\)-reinforced composites. NR shows negligible changes in Zeq, indicating it provides negligible shielding. In the high-energy region (>100 MeV), the Zeq values for all materials converge, indicating that at elevated photon energies, Compton scattering prevails, diminishing the influence of atomic number on attenuation. The PbO\({}_{2}\) and WO\({}_{3}\)-reinforced NR composites demonstrate similar shielding performance, while NR continues to be less effective. In summary, the Phy-X/PSD shielding analysis indicates that PbO\({}_{2}\) demonstrates exceptional shielding capabilities, with WO\({}_{3}\)-reinforced NR composites following closely, contingent upon their WO\({}_{3}\) content. Natural rubber, in isolation, proves inadequate as a means of radiation shielding. At 140 keV (Tc-99m energy), WO\({}_{3}\)-reinforced NR composites exhibit improved shielding capabilities, positioning them as promising substitutes for lead-based materials. 2.3 Experimental Evaluation of the Gamma Radiation-Shielding Efficiency of Tungsten-Reinforced Polyisoprene for Tc-99m  
The experimental data presented in Figure 12 compares the shallow-dose equivalent (Hp(0.07)) for different shielding materials at two activity levels: 185 MBq (5 mCi) and 740 MBq (20 mCi). The shielding materials include WO\({}_{3}\)-reinforced NR composites with varying tungsten content (25%, 50%, 75%, 90%). In addition, a lead shield of 0.5 mm thickness is commonly used as a reference standard in gamma radiation shielding, providing a baseline for comparing the attenuation effectiveness of alternative materials under equivalent radiation conditions. The shallow-dose equivalent results (Figure 12A,D) indicate overall material thicknesses, with the lead (0.5 mm) routinely exhibiting the lowest Hp(0.07). At lower activity, the shielding performance of WO\({}_{3}\)-reinforced NR composites is comparable, with no significant advantage of higher tungsten concentrations. Lead outperforms polymer-based composites at 1 mm thickness, but differences diminish at 3 mm and 6 mm. Increasing material thickness (1 mm \(\rightarrow\) 3 mm \(\rightarrow\) 6 mm) lowers the dose equivalents. Lead shield and 25% WO\({}_{3}\)-reinforced NR at 1 mm thickness exhibit a notable difference (\(p\) < 0.05) according to statistical analysis. There are no statistically significant variations (ns) across compositions of WO\({}_{3}\)-reinforced NR. The eye lens dose equivalent (185 MBq, 5 mCi) in Figure 12B indicates a declining trend with increasing material thickness across all compositions. At a thickness of 1 mm, NR-WO\({}_{3}\) compositions provide somewhat reduced dose equivalents compared to lead, while statistical significance is noted only for certain compositions (\(p\) < 0.05). At a thickness of 3 mm, the same trends are seen, with the shielding efficacy of WO\({}_{3}\)-reinforced NR nearing that of lead. At a thickness of 6 mm, all WO\({}_{3}\)-reinforced NR compositions provide equivalent shielding, exhibiting no statistically significant differences from lead. The eye lens dose equivalent at high activity (Figure 12E) is generally elevated under these conditions. At a thickness of 1 mm, WO\({}_{3}\)-reinforced NR compositions exhibit comparable shielding efficacy to lead, with no statistically significant differences. At 3 mm thickness, a marginal decrease in dose is noted with increasing WO\({}_{3}\)-reinforced NR concentration, though statistical differences are minimal.