This work experimentally determined the X-ray shielding and morphological, density, and tensile properties of sulfur-vulcanized natural rubber latex (SVNRL) nanocomposites containing varying content of nano-Bi2O3 or nano-BaSO4 from 0 to 200 phr in 100 phr increments, with modified procedures in sample preparation to overcome the insufficient strength of the samples found in other reports. The experimental X-ray shielding results, which were numerically verified using a web-based software package (XCOM), indicated that the overall X-ray attenuation abilities of the SVNRL nanocomposites generally increased with increasing filler content, with the 0.25-mm-thick SVNRL films containing 200 phr of the filler providing the highest overall X-ray shielding properties, as evidenced by the highest values of lead equivalence (Pbeq) of 0.0371 mmPb and 0.0326 mmPb in Bi2O3/SVNRL nanocomposites, and 0.0326 mmPb and 0.0257 mmPb in BaSO4/SVNRL nanocomposites, for 60 kV and 100 kV X-rays, respectively. The results also revealed that the addition of either filler increased the tensile modulus at 300% elongation (M300) and density but decreased the tensile strength and the elongation at break of the Bi2O3/SVNRL and BaSO4/SVNRL nanocomposites. In addition, the modified procedures introduced in this work enabled the developed nanocomposites to acquire sufficient mechanical and X-ray shielding properties for potential use as medical X-ray protective gloves, with the recommended content of Bi2O3 and BaSO4 being in the range of 95–140 phr and 105–120 phr, respectively (in accordance with the requirements outlined in ASTM D3578-19 and the value of Pbeq being greater than 0.02 mmPb). Consequently, based on the overall outcomes of this work, the developed Bi2O3/SVNRL and BaSO4/SVNRL nanocomposites show great potential for effective application in medical X-ray protective gloves, while the modified procedures could possibly be adopted for large-scale production.

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This work theoretically determined the high-energy photon shielding properties of high-density polyethylene (HDPE) composites containing rare-earth oxides, namely samarium oxide (Sm2O3), europium oxide (Eu2O3), and gadolinium oxide (Gd2O3), for potential use as lead-free X-ray-shielding and gamma-shielding materials using the XCOM software package. The considered properties were the mass attenuation coefficient (µm), linear attenuation coefficient (µ), half value layer (HVL), and lead equivalence (Pbeq) that were investigated at varying photon energies (0.001–5 MeV) and filler contents (0–60 wt.%). The results were in good agreement (less than 2% differences) with other available programs (Phy-X/PSD) and Monte Carlo particle transport simulation code, namely PHITS, which showed that the overall high-energy photon shielding abilities of the composites considerably increased with increasing rare-earth oxide contents but reduced with increasing photon energies. In particular, the Gd2O3/HDPE composites had the highest µm values at photon energies of 0.1, 0.5, and 5 MeV, due to having the highest atomic number (Z). Furthermore, the Pbeq determination of the composites within the X-ray energy ranges indicated that the 10 mm thick samples with filler contents of 40 wt.% and 50 wt.% had Pbeq values greater than the minimum requirements for shielding materials used in general diagnostic X-ray rooms and computerized tomography rooms, which required Pbeq values of at least 1.0 and 1.5 mmPb, respectively. In addition, the comparisons of µm, µ, and HVL among the rare-earth oxide/HDPE composites investigated in this work and other lead-free X-ray shielding composites revealed that the materials developed in this work exhibited comparable X-ray shielding properties in comparison with that of the latter, implying great potential to be used as effective X-ray shielding materials in actual applications.

The neutron- and X-ray-shielding, morphological, physical, mechanical, and self-healing properties were investigated for natural rubber (NR) composites containing varying gadolinium oxide (Gd2O3) contents (0, 25, 50, 75, and 100 parts per hundred parts of rubber; phr) to investigate their potential uses as self-healing and flexible neutron- and X-ray-shielding materials. Gd2O3 was selected as a radiation protective filler in this work due to its preferable properties of having relatively high neutron absorption cross-section (σabs), atomic number (Z), and density (ρ) that could potentially enhance interaction probabilities with incident radiation. The results indicated that the overall neutron-shielding and X-ray-shielding properties of the NR composites were enhanced with the addition of Gd2O3, as evidenced by considerable reductions in the half-value layer (HVL) values of the samples containing 100 phr Gd2O3 to just 1.9 mm and 1.3 mm for thermal neutrons and 60 kV X-rays, respectively. Furthermore, the results revealed that, with the increase in Gd2O3 content, the mean values (± standard deviations) of the tensile strength and elongation at break of the NR composites decreased, whereas the hardness (Shore A) increased, for which extreme values were found in the sample with 100 phr Gd2O3 (3.34 ± 0.26 MPa, 411 ± 9%, and 50 ± 1, respectively). In order to determine the self-healing properties of the NR composites, the surfaces of the cut samples were gently pressed together, and they remained in contact for 60 min; then, the self-healing properties (the recoverable strength and the %Recovery) of the self-healed samples were measured, which were in the ranges of 0.30–0.40 MPa and 3.7–9.4%, respectively, for all the samples. These findings confirmed the ability to autonomously self-heal damaged surfaces through the generation of a reversible ionic supramolecular network. In summary, the outcomes from this work suggested that the developed Gd2O3/NR composites have great potential to be utilized as effective shielding materials, with additional dual shielding and self-healing capabilities that could prolong the lifetime of the materials, reduce the associated costs of repairing or replacing damaged equipment, and enhance the safety of all users and the public.

This work theoretically compared the X-ray attenuation capabilities in natural rubber (NR) composites containing bismuth oxide (Bi2O3) by determining the effects of multi-layered structures on the shielding properties of the composites using two different software packages (XCOM and PHITS). The shielding properties of the single-layered and multi-layered Bi2O3/NR composites investigated consisted of the transmission factor (I/I0), effective linear attenuation coefficient (µeff), effective mass attenuation coefficient (µm,eff), and effective half-value layer (HVLeff). The results, with good agreement between those obtained from XCOM and PHITS (with less than 5% differences), indicated that the three-layered NR composites (sample#4), with the layer arrangement of pristine NR (layer#1)-Bi2O3/NR (layer#2)-pristine NR (layer#3), had relatively higher X-ray shielding properties than either a single-layer or the other multi-layered structures for all X-ray energies investigated (50, 100, 150, and 200 keV) due to its relatively larger effective percentage by weight of Bi2O3 in the composites. Furthermore, by varying the Bi2O3 contents in the middle layer (layer#2) of sample#4 from 10 to 90 wt.%, the results revealed that the overall X-ray shielding properties of the NR composites were further enhanced with additional filler, as evidenced by the highest values of µeff and µm,eff and the lowest values of I/I0 and HVLeff observed in the 90 wt.% Bi2O3/NR composites. In addition, the recommended Bi2O3 contents for the actual production of three-layered Bi2O3/NR composites (the same layer structure as sample#4) were determined by finding the least Bi2O3 content that enabled the sample to attenuate incident X-rays with equal efficiency to that of a 0.5-mm lead sheet (with an effective lead equivalence of 0.5 mmPb). The results suggested that the recommended Bi2O3 contents in layer#2 were 82, 72, and 64 wt.% for the combined 6 mm, 9 mm, and 12 mm samples, respectively.