Development of Sustainable Radiation-Shielding Blend Using Natural Rubber/NBR, and Bismuth Filler

: This research entailed the production of composite materials through the combination of natural rubber and acrylonitrile butadiene rubber, along with nano-silica-loaded bismuth (III) oxide, in varying concentrations ranging from 0 to 45 parts per hundred parts of rubber (phr). The gamma attenuation properties of the composites at different concentrations of Bi 2 O 3 were measured. Additionally, the mechanical properties of the resulting composites, including hardness, tensile strength, and elongation, were tested. The composites with a concentration of 20 phr exhibited the highest tensile strength and elongation at break, followed by a subsequent decrease as the concentration of Bi 2 O 3 increased. The gamma mass-attenuation coefﬁcient of the composites increased as the Bi 2 O 3 concentration increased from 0 to 45 phr, with values ranging from 0.083 to 0.090 cm 2 /g at 0.662 MeV. Moreover, the fast neutron mass removal cross-sections ranged from 0.092 to 0.072 cm 2 /g, corresponding to the variation of Bi 2 O 3 concentration from 0–45 phr are also determined. Various parameters related to gamma-ray shielding, including the half-value layer, exposure build-up factor (EBF) up to 40 mean free path (mfp) penetration depth, and effective atomic number (Z eff ) are also included. The radiation-induced aging of the prepared blend is tested by measuring the effect of radiation exposure on its shielding capability via its porosity change. The obtained results indicated that the prepared composites could be used for several radiation-protection applications.


Introduction
Nuclear radiation has various useful applications in different fields such as industries, agriculture, food irradiation, defects detection in metal casting, nuclear reactors, medical diagnostic, imaging and therapy, nuclear power plants, aerospace, and radiation chemistry of polymers [1]. Nevertheless, exposure to ionizing radiation can result in radiation sickness, organ damage, cell mutation, cancer, component failure, and other negative effects, depending on the amount of radiation absorbed. Therefore, it is essential to use shielding to protect individuals from these harmful effects.
Radiation shielding is essential for protecting people and equipment from the harmful effects of ionizing radiation. Ionizing radiation can cause damage to living tissue and DNA, leading to an increased risk of cancer, radiation sickness, and other health problems. It can also damage electronic equipment and sensitive instruments, causing malfunctions or complete failure [2]. Radiation shielding works by absorbing or scattering the radiation, reducing its intensity and protecting the people and equipment behind the shield. Shielding materials can vary depending on the type and energy of the radiation being shielded. For example, bismuth and lead are commonly used for shielding against gamma and X-rays [3], while concrete or water can be used for shielding against neutron radiation [4,5].

Preparation of Composites
The rubber blends were created using a two-roll mill that had a diameter of 470 mm and a working distance of 300 mm. The slow roller was set to rotate at 24 revolutions per minute, with a gear ratio of 1:1.4. The mixing process followed ASTM D3182 guidelines, with close attention paid to controlling temperature, nip gap, and the order of adding ingredients.
The vulcanization process was conducted using an electrically heated hydraulic press, which was equipped with an automatic control system. The temperature was maintained at 152 ± 1 • C, while the pressure was set at approximately 4 MPa. Standard methods were used to test the compounded rubber and vulcanizates, including ASTM D2084-11(2012) for determining rheometric characteristics using a Monsanto Rheometer model and an oscillating disc rheometer R-100 (MDR one moving Die Rheometer, TA instruments, New Castle, DE, USA).

Material Characterizations
The Zwick tensile testing machine (model Z010, Ulm, Germany) was utilized to determine the tensile strength and elongation at break. Compressed sheets were first cut into dumbbell-shaped specimens with appropriate punching dies, which had a width of 4 mm, a neck length of 15 mm, and a thickness of 1-1.5 mm, in accordance with ASTM D412 standards [24]. Mechanical property testing was carried out using a crosshead speed of 500 mm/min and a load cell of 10-20, as per the ASTM guidelines. Hardness measurements were obtained using a Shore A durometer (Bareiss, Oberdischingen, Germany), following ASTM D2240. The test specimens were at least 6 mm thick.
Mass density was measured at 25 • C using a standard Archimedes procedure, which was based on a given equation. where W a is the sample's weight in air, W b is the sample's weight in Toluene, and ρ b is Toluene density of (ρ b = 0.87 g/cm 3 ). Furthermore, the evaluation of porosity was conducted using the boiling water technique outlined in ASTM C 20-00 [25]. Porosity refers to the ratio between the volume of voids and the total volume of a given specimen. Employing Archimedes' saturation technique (C20-00, 2015), the water displacement method was used, wherein the mass of porous specimens was measured both when dry and when submerged in water. The apparent porosity (P) can be calculated using the following equation: where W represents the saturated mass of the specimen in grams, D is the dry mass of the specimen in grams, and V denotes the exterior volume of the specimen in cubic centimeters.
To attain a constant dry mass, the specimens were placed in an oven at 105-110 • C for 48 h. Subsequently, the dry specimens were immersed in boiling water for 2 h to obtain the saturated mass. A Bruker Alpha II spectrometer with KBr pellet technique was used to measure attenuated total reflectance Fourier transform infrared (ATR-FTIR) values at spectral range 400-4000 cm −1 .
The gamma-ray-shielding properties of the created rubber matrix were assessed by measuring the parameters at 0.662 MeV gamma photons, which were emitted from a Cs-137-point source and were placed under appropriate geometrical conditions. A NaI (Tl) scintillation detector (Teledyne Isotopes "2 × 2" NaI (Tl) Scintillation Detector, Alabama, USA) was utilized to conduct the measurements, and it possessed an energy resolution of 8% at 662 keV.

Theoretical Background
The modified Lambert-Beer Law was employed to compute the linear attenuation coefficients in the following manner [26]: where the initial photon intensity (I 0 ) and the transmitted photon intensity (I) are related to the linear attenuation coefficient (µ) in units of cm −1 , while the buildup factor (B) is dependent on the thickness (x) of the material used and the energy (E) of the incident photon. To calculate the mass attenuation coefficient (µ m ), one can use the linear attenuation coefficient and the mass density (ρ) values with the following equation [27]: In the case of a compound or mixture, the following formula can be used to determine µ m [28]: where (µ m ) i is the mass attenuation coefficient of the examined mixture's ith element and w i stands for its weight percentage. The half-value layer (HVL) and the mean free path (MFP) of the prepared composites can be calculated by using the following formulas, respectively [29][30][31]: In order to determine the mass attenuation coefficients of the prepared samples across a wide range of energies from 0.015 to 15 MeV, the National Institute of Standard and Tech-Sustainability 2023, 15, 9679 5 of 18 nology (NIST) developed a photon cross-sections database named XCOM, which includes the attenuation coefficients of all elements in the periodic table at different energies [32].
The ratio of an object's electronic cross-section (σ a ) to its effective atomic cross-section (σ e ) is used to define the effective atomic number of a material (Z eff ). The obtained data for the mass attenuation coefficient (µ m ) of the produced prepared samples can be utilized with the following formula to estimate the values of Z eff [33]: where A i is the atomic weight, Z i is the atomic number, (µ m ) i is the mass attenuation coefficient for the ith element, and f i represents ith element fractional abundance concerning the number of atoms. In order to determine the buildup factor, we need to obtain the Compton partial attenuation coefficient ((µ m ) comp ) and the total attenuation coefficient ((µ m ) total ) values for the constituent elements and compounds present in the prepared samples being analyzed within the energy range of 0.015-15.0 MeV. Using these values, we can then calculate the equivalent atomic number (Z eq ) for the produced prepared samples by comparing the ratio (µ m ) comp /(µ m ) total at a specific energy with comparable ratios of elements at the same energy. The interpolation of the equivalent atomic number was determined through a logarithmic interpolation algorithm [34], where the ratio (µ m ) comp /(µ m ) total falls between two consecutive ratios of elements.
The values of Z 1 and Z 2 are the atomic numbers of the pure elements that correspond to the ratios R 1 and R 2 , respectively. R is the ratio for the prepared samples being studied at certain energy [35]. The exposure buildup factor EBF for the prepared samples was calculated using the general progressive (G-P) interpolation in the energy range of 0.015-15 MeV up to 40 mfp, with the help of the equations provided in Harima et al. (1993) [36][37][38]: These formulas involve several variables such as photon energy (E), separation (X) between detector and source, exposure buildup factor (EBF) value at 1 mean free path (MFP) denoted by B, dosage multiplicative factor (K), and several fitting parameters (b, c, a, X K , and d) that are dependent on the attenuating medium and source energy. The fitting parameters for the prepared samples, namely b, c, a, X K , and d, can be estimated for the energy range of gamma rays from 0.015 MeV to 15 MeV, up to a distance of 40 MFP, using logarithmic interpolation with the help of the following equation-like method [39,40].
The values of the G-P fitting parameters at specific energy for atomic numbers Z 1 and Z 2 are denoted by P 1 and P 2 , respectively. The criteria for the G-P fit for the elements, as established by the American Nuclear Society study, were applied [41].

NR/NBR Blend
Five blends of NR/NBR are prepared according to the compounding formulations for NR and NBR blends with peroxide for optimum blend ratio as shown in Table 2. Rheometric characteristics of these blends are investigated, and the blend of the best mechanical properties will be used to be loaded with bismuth oxide to enhance the blend's radiation-shielding characteristics. The rheometric characteristics of the prepared NR/NBR blends cured with 3phr peroxide are shown in Table 3.  The obtained data regarding the mechanical properties of the five NR/NBR prepared blends are shown in Figure 1, where N4 (75/25 phr) showed the highest tensile strength and elongation. These results can be attributed to the nature of the blend which has a highly interconnected two-phase morphology.

NR/NBR/Bi 2 O 3 Matrix (Composites)
Accordingly, the blend ratio 75/25 NR/NBR was chosen to be incorporated with different concentrations of Bi 2 O 3 (0-45 phr) to test the shielding blend properties in the rubber composite formulations.
The mass density of NR/NBR/Bi 2 O 3 blend increases proportionally with increasing bismuth ratio as shown in Table 4. The vulcanization of NR/NBR/Bi 2 O 3 was carried out using peroxide as a curing agent. The rheometric characteristics blends were determined at 152 • C and listed in Table 5. As illustrated in Table 5, the maximum torque (M H ) initially increased with bismuth concentration due to the crosslinking that occurred while the subsequence decrease refers to the degradation that happened in the blend composites. The observed decrease in scorch time with the increase in bismuth concentration indicates how quickly the material begins to vulcanize with adding bismuth. Following the addition of bismuth, the vulcanization of the NR/NBR mix is accelerated as a result of the interaction between bismuth and the vulcanization system. By encouraging the cross-linking of rubber molecules and accelerating the vulcanization process, bismuth increases the effectiveness of curing in general. As a result, the mix vulcanizes more quickly and completely, giving the vulcanized product more strength, stability, and other desirable qualities [42].

Total Reflectance Fourier Transform Infrared (ATR-FTIR)
The absorbance spectra of NR/NBR/ Bi 2 O 3 with different concentrations of bismuth oxide are shown in Figure 2. The peak positions and their assignment vibrational modes are shown in Table 6.  begins to vulcanize with adding bismuth. Following the addition of bismuth, the vulc ization of the NR/NBR mix is accelerated as a result of the interaction between bism and the vulcanization system. By encouraging the cross-linking of rubber molecules a accelerating the vulcanization process, bismuth increases the effectiveness of curing general. As a result, the mix vulcanizes more quickly and completely, giving the vulc ized product more strength, stability, and other desirable qualities [42].

Total Reflectance Fourier Transform Infrared (ATR-FTIR)
The absorbance spectra of NR/NBR/ Bi2O3 with different concentrations of bism oxide are shown in Figure 2. The peak positions and their assignment vibrational mo are shown in Table 6.

Mechanical Properties of NR/NBR/Bi 2 O 3 Composites
The impact of the presence of bismuth filler on the mechanical characteristics of the NR/NBR/Bi 2 O 3 composites was evaluated, and the results are depicted in Figures 3-5. The outcomes revealed that the incorporation of bismuth led to an enhancement in tensile strength, elongation, and hardness. The tensile strength and elongation of the base material increased as the filler loading increased up to 20 phr, after which they slightly decreased as the bismuth concentration rose. The impact of the presence of bismuth filler on the mechanical characteristics of the NR/NBR/Bi2O3 composites was evaluated, and the results are depicted in Figures 3-5. The outcomes revealed that the incorporation of bismuth led to an enhancement in tensile strength, elongation, and hardness. The tensile strength and elongation of the base material increased as the filler loading increased up to 20 phr, after which they slightly decreased as the bismuth concentration rose.

Mechanical Properties of NR/NBR/Bi2O3 Composites
The impact of the presence of bismuth filler on the mechanical characteristics of the NR/NBR/Bi2O3 composites was evaluated, and the results are depicted in Figures 3-5. The outcomes revealed that the incorporation of bismuth led to an enhancement in tensile strength, elongation, and hardness. The tensile strength and elongation of the base material increased as the filler loading increased up to 20 phr, after which they slightly decreased as the bismuth concentration rose.   Adding Bi2O3 to the rubber blend (NR/NBR) can improve mechanical properties such as tensile strength, hardness, and maximum elongation. This is due to the following reasons: Bismuth is a high-density material (9.78 g/cm 3 ), which increases the overall density of the rubber blend. As a result, the intermolecular forces between the polymer chains and the filler particles become stronger, leading to an increase in the tensile strength of the Adding Bi 2 O 3 to the rubber blend (NR/NBR) can improve mechanical properties such as tensile strength, hardness, and maximum elongation. This is due to the following reasons: Bismuth is a high-density material (9.78 g/cm 3 ), which increases the overall density of the rubber blend. As a result, the intermolecular forces between the polymer chains and the filler particles become stronger, leading to an increase in the tensile strength of the blend [53,54]. Bismuth also has a relatively high modulus of elasticity compared to other fillers, which can increase the stiffness and hardness of the rubber blend. This can be particularly useful in radiation-shielding applications where the material needs to be rigid and maintain its shape under exposure to high radiation doses. Bismuth has a low coefficient of thermal expansion, which means that it does not expand or contract much with changes in temperature. This property can prevent the filler particles from separating from the polymer matrix, which can improve the maximum elongation of the blend.
While adding Bi 2 O 3 to the natural rubber/nitrile butadiene rubber (NR/NBR) blend can improve the mechanical properties, increasing the concentration of Bi 2 O 3 beyond a 20 phr can lead to a decrease in these properties. This can be explained as follows: At high concentrations, Bi particles can agglomerate, causing the formation of clusters that reduce the intermolecular forces between the polymer chains and the filler particles. This reduces the strength of the polymer-filler interface, leading to a decrease in the tensile strength of the blend [11]. Moreover, Bi 2 O 3 is a relatively brittle material, and increasing its concentration can make the blend more prone to cracking and fracture. This can reduce the maximum elongation and toughness of the blend, making it less suitable for applications where flexibility and impact resistance are required.
Therefore, it is essential to carefully control the concentration of Bi 2 O 3 in the NR/NBR blend and optimize the processing conditions to achieve the desired mechanical properties. Figures 6 and 7 show the results of Z eff and µ m of the prepared rubber matrix at the energy range 0.015-15 MeV, respectively. The variation profile of Z eff with energy for different Bi 2 O 3 concentrations was almost the same but shifted to higher values. As previously reported [55], photoelectric interaction is proportional to Z 4−5 for attenuation, while Compton interaction and pair production are proportional to Z and Z 2 , respectively. This could cause a realized increase in the effective atomic numbers with the Bi 2 O 3 concentration (phr) increment. Moreover, during the vulcanization process, the rubber mixture is heated, and the bismuth compounds decompose, releasing bismuth ions (Bi 3+ ). These ions can then react with the rubber molecules and form chemical bonds, which help to strengthen the rubber network. The bismuth ions can also react with other elements in the mixture, such as sulfur and zinc oxide, to form crosslinks that further reinforce the rubber network and cause a distinct increase in both Z eff and µ m . heated, and the bismuth compounds decompose, releasing bismuth ions (Bi 3+ ). These ions can then react with the rubber molecules and form chemical bonds, which help to strengthen the rubber network. The bismuth ions can also react with other elements in the mixture, such as sulfur and zinc oxide, to form crosslinks that further reinforce the rubber network and cause a distinct increase in both Zeff and µm. Figure 6. Effective atomic numbers for NR/NBR/Bi2O3 rubber matrix.   When the incident photon energy is in the low-energy range of about 0.1 MeV, w the photoelectric interaction dominates, Zeff increases in all samples. The highest val Zeff is observed at about 0.091 MeV due to the K-edge of Bi2O3 absorption [56]. How as photoelectric absorption decreases and Compton scattering becomes more domina the energy range of 0.1-1 MeV, there is a sharp decrease in Zeff. Pair production intera is the most dominant from 1-15 MeV, and the interaction probability is directly pro tional to the energy. These findings are consistent with the fundamental concep gamma photon interaction probability, which is directly proportional to the effe atomic number of the matrix and inversely proportional to photon energy. The effe increasing Bi2O3 (phr) and energy on Zeff variation is similar to that on µm. Figures 6 a depict this relationship. Figure 8 shows that the half-value layer (HVL) increases with energy NR/NBR/Bi2O3 rubber composites. The change in Zeff with Bi2O3 concentration and ph energy is consistent with the results obtained for µm and the corresponding HVL.        The energy buildup factor (EBF) results were obtained by considering the concentration of Bi2O3, photon energy, and penetration depth as factors that influence EBF. Figure  10a-j indicate that the EBF has the lowest values in the low-and high-energy regions where complete absorption of a photon occurs during photoelectric interactions at low energy and pair production interactions at high energy. Conversely, the intermediate energy region is characterized by Compton scattering interactions, resulting in higher EBF values [57]. The energy buildup factor (EBF) results were obtained by considering the concentration of Bi 2 O 3 , photon energy, and penetration depth as factors that influence EBF. Figure 10a-j indicate that the EBF has the lowest values in the low-and high-energy regions where complete absorption of a photon occurs during photoelectric interactions at low energy and pair production interactions at high energy. Conversely, the intermediate energy region is characterized by Compton scattering interactions, resulting in higher EBF values [57].

Gamma-Ray-Shielding Properties of NR/NBR/Bi 2 O 3 Composites
The presence of a peak at 0.08 MeV followed by a valley at 0.1 MeV for Bi 2 O 3 doped samples can be explained by the absorption K-edge of Bi 2 O 3 , which is around 0.1 MeV (0.091 MeV). An increase in Bi 2 O 3 concentration raises the mass attenuation coefficient, thereby reducing the penetration depth. When penetration depth is large, multiple scattering events occur, leading to an increase in the thickness of the interacting substance, and resulting in more scattering events and higher EBF values. Therefore, EBF is directly proportional to penetration depth and inversely proportional to Bi 2 O 3 concentration.

Neutron Attenuation
The fast neutron removal cross-section, also called the "macroscopic cross-section", measures the likelihood that a fast or fission energy neutron will be removed from a group of uncollided neutrons due to its first collision [58]. In Figure 11, the calculated mass removal cross-sections (ΣR) of the prepared samples for fast neutrons are displayed. As the concentration of Bi 2 O 3 increases, the mass removal cross-section of the samples decreases continuously, which can be attributed to the reduction in the weight fraction of hydrogen content. The mass removal cross-section values obtained ranged from 0.092-0.072 cm 2 /g, corresponding to the variation of Bi 2 O 3 concentration from 0-45 phr. In comparison to the commonly utilized B4C with a neutron mass removal cross-section of 0.0559 cm 2 /g, the prepared blend exhibits potential for diverse neutron-shielding applications and is, therefore, a recommended choice.
(0.091 MeV). An increase in Bi2O3 concentration raises the mass attenuation coefficient, thereby reducing the penetration depth. When penetration depth is large, multiple scattering events occur, leading to an increase in the thickness of the interacting substance, and resulting in more scattering events and higher EBF values. Therefore, EBF is directly proportional to penetration depth and inversely proportional to Bi2O3 concentration.

Neutron Attenuation
The fast neutron removal cross-section, also called the "macroscopic cross-section," measures the likelihood that a fast or fission energy neutron will be removed from a group of uncollided neutrons due to its first collision [58]. In Figure 11, the calculated mass removal cross-sections (ΣR) of the prepared samples for fast neutrons are displayed. As the concentration of Bi2O3 increases, the mass removal cross-section of the samples decreases continuously, which can be attributed to the reduction in the weight fraction of hydrogen content. The mass removal cross-section values obtained ranged from 0.092-0.072 cm 2 /g, corresponding to the variation of Bi2O3 concentration from 0-45 phr. In comparison to the commonly utilized B4C with a neutron mass removal cross-section of 0.0559 cm 2 /g, the prepared blend exhibits potential for diverse neutron-shielding applications and is, therefore, a recommended choice.    Figure 12 shows the effect of gamma irradiation doses on NR/NBR/20 phr Bi 2 O 3 composite's porosity. The observed increase in the rubber composite porosity with an increase in gamma irradiation dose can be explained by the effects of radiation on the polymer structure. When rubber is exposed to gamma radiation, high-energy photons interact with the polymer chains, causing various chemical and physical changes [59]. One of the primary mechanisms leading to increased porosity is chain scission. Gamma radiation can break the polymer chains, resulting in the formation of free radicals and smaller molecular fragments. As the radiation dose increases, the number of chain scissions also increases. The presence of these broken chains weakens the overall structure of the rubber and creates spaces or voids within the material, leading to increased porosity.  Figure 11. Fast neutron mass removal cross-sections (cm 2 /g) for NR/NBR blend at different conc trations of Bi2O3. Figure 12 shows the effect of gamma irradiation doses on NR/NBR/20 phr Bi2O3 co posite's porosity. The observed increase in the rubber composite porosity with an incre in gamma irradiation dose can be explained by the effects of radiation on the polym structure. When rubber is exposed to gamma radiation, high-energy photons interact w the polymer chains, causing various chemical and physical changes [59]. One of the p mary mechanisms leading to increased porosity is chain scission. Gamma radiation break the polymer chains, resulting in the formation of free radicals and smaller molecu fragments. As the radiation dose increases, the number of chain scissions also increas The presence of these broken chains weakens the overall structure of the rubber and c ates spaces or voids within the material, leading to increased porosity.   Figure 12 shows the effect of gamma irradiation doses on NR/NBR/20 phr Bi2O3 composite's porosity. The observed increase in the rubber composite porosity with an increase in gamma irradiation dose can be explained by the effects of radiation on the polymer structure. When rubber is exposed to gamma radiation, high-energy photons interact with the polymer chains, causing various chemical and physical changes [59]. One of the primary mechanisms leading to increased porosity is chain scission. Gamma radiation can break the polymer chains, resulting in the formation of free radicals and smaller molecular fragments. As the radiation dose increases, the number of chain scissions also increases. The presence of these broken chains weakens the overall structure of the rubber and creates spaces or voids within the material, leading to increased porosity. Moreover, gamma irradiation has an additional impact on rubber known as crosslinking. While chain scission causes the breakdown of polymer chains, crosslinking creates new bonds between these chains [60]. However, when exposed to higher radiation doses, the crosslinking density may initially increase until reaching a maximum, after Moreover, gamma irradiation has an additional impact on rubber known as crosslinking. While chain scission causes the breakdown of polymer chains, crosslinking creates new bonds between these chains [60]. However, when exposed to higher radiation doses, the crosslinking density may initially increase until reaching a maximum, after which it begins to decrease due to recombination reactions and the formation of new free radicals. This decrease in crosslinking density can result in an elevation of rubber porosity. Additionally, the degradation induced by radiation can generate volatile by-products. These by-products have the potential to escape from the rubber matrix, leaving behind voids or pores that contribute to the overall increase in porosity. The obtained results of porosity increase with the radiation exposure indicating that the shielding capabilty of the prepared blend is decreasing with the gamma exposure doses. This means the aging effect of this material could be considered.

Conclusions
This study aimed to develop the optimum NR/NBR blend by adding different concentrations of Bi 2 O 3 for gamma-and neutron-shielding applications. The obtained results showed that the NR/NBR blend of 75/25 phr had the maximum tensile strength and elongation. This blend is considered the optimum NR/NBR blend to be incorporated with different concentrations of Bi 2 O 3 (0-45 phr) for the preparation of radiation shielding composites. The mechanical and shielding properties of the NR/NBR/Bi 2 O 3 composites were investigated. Although the mass attenuation coefficient and other shielding parameters increased with the addition of bismuth, the most recommended composite was that at 20 phr Bi 2 O 3 , where the maximum tensile strength and elongation were obtained. This study analyzed the exposure build-up factors (EBF) of composite materials that were prepared with varying concentrations of Bi 2 O 3 . The analysis was conducted for photon energies ranging from 0.015 to 15 MeV and penetration depths up to 40 mfp. Additionally, this study also evaluated the fast neutron mass removal cross-sections of the prepared composites using the partial density approach to determine their potential for attenuating neutrons. Overall, the addition of bismuth to the rubber blend can improve the mechanical properties and make it more suitable for radiation-shielding applications. However, the optimal amount of bismuth and the processing conditions need to be carefully controlled to achieve the desired properties. Moreover, the age of using the prepared blend should take into account the decrease in the shielding capability due to the effect of gamma exposure on its porosity.