Radiation shielding ethylene propylene rubber material and method of making same

Abstract

The application provides an ethylene-propylene rubber material for radiation shielding and a preparation method thereof, relates to the technical field of materials, and comprises an ethylene-propylene rubber base and tungsten-functionalized zirconium metal organic framework nanoparticles dispersed in the ethylene-propylene rubber base; in the tungsten-functionalized zirconium metal organic framework nanoparticles, tungsten is introduced into the zirconium metal organic framework in a chemical bonding or doping manner and is anchored on the metal cluster node of the zirconium metal organic framework. The material solves the common technical problems in the prior art, such as poor compatibility of tungsten fillers with the ethylene-propylene rubber base, uneven dispersion, and difficulty in simultaneously considering the radiation shielding efficiency and mechanical properties, simultaneously fills the technical gap of MOF materials in the application field of ethylene-propylene rubber-based cable sheath radiation shielding, and has important engineering application value and academic research significance.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a radiation shielding ethylene propylene rubber material and its preparation method. Background Technology

[0002] As the core carrier of power transmission and signal control, cables are widely used in special radiation environments such as nuclear power, aerospace, medical irradiation, and high-energy physics experiments. In these high-radiation applications, the cable outer sheath not only needs to possess conventional properties such as high temperature resistance, impact resistance, and halogen-free low smoke, but also must have sufficient radiation shielding capabilities to effectively attenuate high-energy ionizing radiation such as X-rays and gamma rays present in the environment, preventing radiation from penetrating the outer sheath and causing radiation damage to the internal insulation layer of the cable, while reducing radiation hazards to surrounding equipment and personnel.

[0003] Ethylene propylene rubber (EPR), including binary ethylene propylene rubber (EPM) and ternary ethylene propylene rubber (EPDM), possesses excellent heat aging resistance, ozone resistance, weather resistance, and electrical insulation properties due to its molecular chain being predominantly composed of saturated C-C bonds. Furthermore, it is halogen-free, making it widely used in cable insulation layers and outer sheaths. EPR has a continuous operating temperature range of -50℃ to +150℃ and exhibits excellent weathering resistance and light stability, making it particularly suitable for applications requiring flame retardancy and halogen-free, low-smoke performance. However, pure ethylene propylene rubber matrix materials have a low mass attenuation coefficient for high-energy ionizing radiation, offering almost no effective radiation shielding capability. In high-radiation environments such as nuclear power plants and irradiation devices, high-energy rays easily penetrate the rubber outer sheath, causing cumulative radiation damage to the internal insulation layer and conductor of the cable, significantly shortening its service life. Studies have shown that existing ethylene propylene rubber often exhibits rapid hardening, embrittlement, and significant strength degradation in high-energy radiation environments, resulting in a marked decrease in mechanical stability and severely reducing the reliability and safety of cables.

[0004] Therefore, this invention is proposed. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a radiation-shielding ethylene propylene rubber material and its preparation method. This invention develops an ethylene propylene rubber-based cable outer sheath material that combines excellent radiation shielding performance, good mechanical properties, high-temperature resistance, and halogen-free, low-smoke, and environmentally friendly characteristics. This solves the common technical problems in existing technologies, such as poor compatibility and uneven dispersion of tungsten-based fillers with the ethylene propylene rubber matrix, and the difficulty in simultaneously achieving both radiation shielding effectiveness and mechanical properties. Furthermore, it fills the technical gap in the application of MOF materials in the radiation shielding field of ethylene propylene rubber-based cable sheaths, possessing significant engineering application value and academic research significance.

[0006] In order to achieve the objective of this invention, the following technical solution is adopted: The present invention provides a radiation shielding ethylene propylene rubber material comprising an ethylene propylene rubber matrix and tungsten-functionalized zirconium-based metal-organic framework nanoparticles dispersed in the ethylene propylene rubber matrix; In the tungsten-functionalized zirconium-based metal-organic framework nanoparticles, tungsten is introduced into the zirconium-based metal-organic framework (Zr-MOF) through chemical bonding or doping and anchored to the metal cluster nodes of the zirconium-based metal-organic framework.

[0007] Furthermore, the ethylene propylene rubber matrix is ​​binary ethylene propylene rubber or ternary ethylene propylene rubber.

[0008] Furthermore, the mass ratio of the tungsten-functionalized zirconium-based metal-organic framework nanoparticles to the ethylene propylene rubber matrix is ​​(5~50):100.

[0009] The present invention also provides a method for preparing the radiation shielding ethylene propylene rubber material, comprising the following steps: S1. Tungsten is doped into zirconium-based metal-organic frameworks to obtain functionalized zirconium-based metal-organic framework nanoparticles. S2. Functionalized zirconium-based metal-organic framework nanoparticles are incorporated into the ethylene propylene rubber matrix.

[0010] Furthermore, S1 specifically includes: S101. Dissolve ZrCl4, terephthalic acid, and a tungsten-containing modifier in an organic solvent to obtain a mixture; S102. The mixture is sealed and heated to 120°C and reacted for 20-28 hours to obtain functionalized zirconium-based metal-organic framework nanoparticles.

[0011] Furthermore, S2 specifically includes: S201. Plasticize and soften the ethylene propylene rubber matrix to obtain a softened ethylene propylene rubber matrix; S202. Add activator and antioxidant to the softened ethylene propylene rubber matrix; S203. Functionalized zirconium-based metal-organic framework nanoparticles are added to the product in S202 in batches and slowly to ensure uniform dispersion and obtain intermediate products. S204. Add vulcanizing agent and accelerator to the intermediate product and mix until the color is uniform to obtain compound rubber. S205. After the compounded rubber is thinly passed through, it is wrapped in a triangular package, sheeted out, placed at room temperature for 10-20 hours, vulcanized, and demolded to obtain radiation shielding ethylene propylene rubber material.

[0012] Furthermore, the regulator for the tungsten-containing component is an H2WO4 formic acid solution, wherein the concentration of H2WO4 is 0.067 mol / L. The molar ratio of ZrCl4 to terephthalic acid to H2WO4 is 1:1.0:0.2, and the amount of solvent N,N-dimethylformamide used is 25 mL of N,N-dimethylformamide (DMF) for every 1 mmol of ZrCl4.

[0013] Furthermore, the activator is selected from at least one of zinc oxide, stearic acid, and polyethylene glycol; The antioxidant is selected from at least one of the following: 2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD), N-isopropyl-N'-phenyl-p-phenylenediamine (4010NA), and 2-mercaptobenzimidazole (MB); The vulcanizing agent is selected from at least one of: dicumyl peroxide (DCP), sulfur, and bis-tert-butyl peroxide (BIPB); The accelerator is selected from at least one of tetramethylthiuram disulfide (TMTD), dibenzothiazole disulfide (DM), and N-cyclohexyl-2-benzothiazole sulfenamide (CZ).

[0014] The present invention also provides the above-mentioned cable outer sheath, which uses the above-mentioned radiation shielding ethylene propylene rubber material.

[0015] This invention also provides the application of the above-mentioned radiation shielding ethylene propylene rubber material in the preparation of radiation protection products.

[0016] The present invention has the following technical effects: (1) The Zr-based tungsten-doped MOF material prepared by this method has a linear decay coefficient of approximately 2.6 cm at an energy of 80.99 keV. -1 At an energy of 661.64 keV, the linear decay coefficient is approximately 0.1702 cm⁻¹. -1 Compared to EPDM matrix with added tungsten powder, its linear attenuation coefficient for gamma rays is increased by about 50%, and the transmitted radiation dose can be reduced by about 33% under the same shielding thickness.

[0017] (2) This method addresses the problem of uneven dispersion and easy agglomeration of tungsten elements in the polymer matrix, which leads to the deterioration of mechanical properties. By forming Zr-OW chemical bonds in the MOF skeleton, tungsten atoms are anchored in the nanocage structure, which effectively inhibits the agglomeration of tungsten particles, thereby improving the tensile strength of tungsten-doped MOF / EPDM composites compared to pure EPDM.

[0018] (3) This invention employs an atomic-level tungsten doping strategy to uniformly distribute tungsten elements in the MOF framework as single-atom sites, rather than physically filling it as micron-sized particles. This atomic-level dispersion significantly increases the probability of interaction between a unit mass of tungsten elements and incident photons, resulting in a significant improvement in shielding efficiency. This allows the invention to achieve the same or even better radiation shielding effect with a lower tungsten content, realizing the technical effect of low filling and high shielding, while maintaining excellent processing performance while reducing material density and cost. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 SEM image of unfunctionalized UiO-66 sample; Figure 2 SEM images of UiO-66 samples after tungsten functionalization; Figure 3 : Tungsten-modified UiO-66 powder sample; Figure 4 Comparison of shielding efficiency of ethylene propylene rubber with different mass ratios of fillers; Figure 5 Comparison of tensile strength of ethylene propylene rubber with different mass ratios of fillers; Figure 6 Comparison of elongation at break of ethylene propylene rubber with different mass ratios of fillers; Figure 7 Comparison of hardness of ethylene propylene rubber with different mass ratios of fillers; Figure 8 Process flow diagram. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] Firstly, to address the insufficient radiation shielding capability of ethylene propylene rubber outer sheaths, existing technologies primarily employ a scheme of adding high-density, high-atomic-number radiation shielding functional fillers to the rubber matrix. Commonly used radiation shielding functional fillers include lead and its compounds, tungsten and its compounds, bismuth and its compounds, and rare earth element compounds, which are then blended with the matrix material using rubber processing techniques to prepare radiation shielding composite materials.

[0023] Among the aforementioned functional metal fillers, tungsten, due to its high density and high atomic number, exhibits a significantly superior mass attenuation coefficient for X-rays and gamma rays compared to traditional lead-based materials. Furthermore, tungsten and its compounds are non-toxic and environmentally friendly, overcoming the toxicity and secondary pollution problems associated with lead materials. Therefore, it is considered an ideal choice for next-generation radiation shielding fillers. Tungsten-based composite materials can significantly reduce material thickness and weight while achieving the same shielding effect, with shielding efficiency approximately 30% higher than lead.

[0024] However, in practical applications, directly adding tungsten powder or tungsten oxide as a functional filler to the ethylene propylene rubber matrix presents the following technical challenges: First, tungsten-based fillers have poor compatibility and weak interfacial bonding with the organic polymer matrix, easily leading to filler agglomeration and uneven dispersion within the matrix. This creates stress concentration points and "weak zones" in radiation shielding within the composite material, reducing both the material's mechanical properties and the overall uniformity of radiation shielding. Second, to achieve effective radiation shielding, the amount of tungsten-based filler added is usually large, but a high filler content significantly increases the density and hardness of the composite material, sacrificing the flexibility and elasticity required for the ethylene propylene rubber outer sheath, while also exacerbating the filler agglomeration problem. Third, the surface of tungsten powder or tungsten oxide particles lacks functional groups that strongly interact with the rubber matrix, making it impossible to form effective interfacial bonding and stress transfer in the rubber vulcanization crosslinking network. Consequently, the overall mechanical properties of the composite material are insufficient to meet the impact resistance and flexibility requirements of cable outer sheaths.

[0025] The purpose of this invention is to improve the radiation shielding performance and overall service reliability of cable sheaths based on ethylene propylene diene monomer (EPDM) rubber. As mentioned above, existing EPDM-based cable sheaths face a fundamental contradiction between "high shielding effectiveness" and "good mechanical properties" when introducing tungsten-based radiation shielding fillers. Because traditional inorganic fillers such as tungsten powder or tungsten oxide have significant polarity differences and poor interfacial compatibility with the EPDM rubber matrix, increasing the filler content to achieve effective radiation attenuation inevitably leads to severe agglomeration and uneven dispersion of the filler in the matrix, resulting in a sharp deterioration in the material's impact strength and elongation at break. Conversely, if the filler content is controlled to ensure the sheath's flexibility and formability, the radiation shielding effect cannot meet the stringent environmental requirements of nuclear power plants. Furthermore, tungsten-based fillers lack effective chemical bonding with rubber molecular chains, failing to form a stable stress transfer interface in the vulcanization network. This makes the material prone to interfacial debonding and performance degradation under the long-term coupling of high-energy radiation and mechanical forces. The above contradictions are the main reasons why there is currently a lack of ethylene propylene rubber cable outer sheath materials that combine high radiation shielding efficiency, excellent impact resistance, halogen-free low smoke, and high temperature resistance.

[0026] Furthermore, improving the radiation shielding performance of materials must be done while also considering the adaptability of the cable outer sheath extrusion molding process. In wire and cable manufacturing, the continuous extrusion and vulcanization molding of thin-walled outer sheaths are extremely sensitive to the rheological properties and dispersion uniformity of the rubber compound. On the one hand, to improve the mass attenuation coefficient of the material against X-rays and gamma rays, the atomic number and amount of functional fillers should be as high as possible; on the other hand, to ensure the surface quality, dimensional accuracy, and production efficiency of the extruded sheath, large particle agglomerates must not exist in the rubber compound, otherwise it will lead to extrusion pressure fluctuations, rough sheath surface, or even holes. There is a contradiction between these two aspects. Especially for the outer sheaths of mobile nuclear cables that require high shielding effectiveness and have limited wall thickness, balancing radiation shielding effectiveness and molding performance is particularly difficult.

[0027] This invention utilizes highly stable Zr metal clusters as a structural framework, introducing tungsten, an element with high radiation shielding capability, into the Zr-MOF framework through chemical bonding or doping to construct tungsten-functionalized Zr-MOF nanoparticles that combine structural stability and functional compositeness. Through the strong interaction between the organic ligands in this tungsten-functionalized Zr-MOF and the ethylene propylene rubber molecular chains, the problems of poor compatibility and uneven dispersion of tungsten-based functional fillers in the ethylene propylene rubber matrix are fundamentally solved. This achieves highly efficient radiation shielding with low filler content, while simultaneously inhibiting the degradation of the rubber matrix and filler interface failure under irradiation. Ultimately, a composite material meeting the comprehensive performance requirements of cable outer sheaths—impact resistance, high temperature resistance, halogen-free low smoke, and radiation shielding—is obtained. Another objective of this invention is to provide a preparation method adapted to existing continuous extrusion molding processes for cables, ensuring the feasibility of large-scale production of high-shield cable outer sheaths.

[0028] The present invention provides a radiation shielding ethylene propylene rubber material comprising an ethylene propylene rubber matrix and tungsten-functionalized zirconium-based metal-organic framework nanoparticles dispersed in the ethylene propylene rubber matrix; In the tungsten-functionalized zirconium-based metal-organic framework nanoparticles, tungsten is introduced into the zirconium-based metal-organic framework through chemical bonding or doping and anchored to the metal cluster nodes of the zirconium-based metal-organic framework.

[0029] The mechanism of introducing tungsten components into Zr-MOFs demonstrates that Zr-based MOFs exhibit excellent performance, maintaining high stability even under high-dose irradiation (85 MGy He ions). An ultrastable MOF, UiO-66, with Zr metal clusters as nodes, was synthesized. The framework itself does not contain tungsten but possesses regularly arranged nanopores. Each metal cluster node in UiO-66 can connect to 12 organic ligands, which extend and connect in three-dimensional space, constructing a three-dimensional network formed by alternating arrangements of two different sizes and shapes of pores.

[0030] Taking advantage of the empty framework of UiO-66, tungsten is introduced through chemical means to form tungsten-modified Zr-UiO-66. Tungsten does not exist independently, but rather is stably bonded to the defect sites of the Zr6O4(OH)4 metal cluster nodes in the form of single-atom sites by forming Zr-OW covalent bonds.

[0031] In some embodiments, the ethylene propylene rubber matrix is ​​binary ethylene propylene rubber or ternary ethylene propylene rubber.

[0032] In some embodiments, the mass ratio of the tungsten-functionalized zirconium-based metal-organic framework nanoparticles to the ethylene propylene rubber matrix is ​​(5~50):100.

[0033] Secondly, the present invention provides a method for preparing a radiation-shielding ethylene propylene rubber material, comprising the following steps: S1. Tungsten is doped into zirconium-based metal-organic frameworks to obtain functionalized zirconium-based metal-organic framework nanoparticles. S2. Functionalized zirconium-based metal-organic framework nanoparticles are incorporated into the ethylene propylene rubber matrix.

[0034] In some embodiments, S101, ZrCl4, terephthalic acid, and a tungsten-containing modifier are dissolved in an organic solvent to obtain a mixture; S102. The mixture is sealed and heated to 120°C and reacted for 20-28 hours to obtain functionalized zirconium-based metal-organic framework nanoparticles.

[0035] In some embodiments, S2 specifically includes: S201. Plasticize and soften the ethylene propylene rubber matrix to obtain a softened ethylene propylene rubber matrix; S202. Add activator and antioxidant to the softened ethylene propylene rubber matrix; S203. Functionalized zirconium-based metal-organic framework nanoparticles are added to the product in S202 in batches and slowly to ensure uniform dispersion and obtain intermediate products. S204. Add vulcanizing agent and accelerator to the intermediate product and mix until the color is uniform to obtain compound rubber. S205. After the compounded rubber is thinly passed through, it is wrapped in a triangular package, sheeted out, placed at room temperature for 10-20 hours, vulcanized, and demolded to obtain radiation shielding ethylene propylene rubber material.

[0036] In some embodiments, the modifier for the tungsten-containing component is an H2WO4 formic acid solution; The concentration of H2WO4 was 0.067 mol / L, the molar ratio of ZrCl4 to terephthalic acid to H2WO4 was 1:1.0:0.2, and the amount of solvent N,N-dimethylformamide was 25 mL DMF per 1 mmol ZrCl4.

[0037] In some embodiments, the activator is selected from at least one of zinc oxide, stearic acid, and polyethylene glycol; The antioxidant is selected from at least one of the following: 2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD), N-isopropyl-N'-phenyl-p-phenylenediamine (4010NA), and 2-mercaptobenzimidazole (MB); The vulcanizing agent is selected from at least one of: dicumyl peroxide (DCP), sulfur, and bis-tert-butyl peroxide (BIPB); The accelerator is selected from at least one of tetramethylthiuram disulfide (TMTD), dibenzothiazole disulfide (DM), and N-cyclohexyl-2-benzothiazole sulfenamide (CZ).

[0038] Thirdly, the present invention also provides a cable outer sheath using the aforementioned radiation-shielding ethylene propylene rubber material.

[0039] Fourthly, the present invention also provides the application of the radiation shielding ethylene propylene rubber material in the preparation of radiation protection products.

[0040] The following is a detailed explanation using specific embodiments: Example 1: Preparation of radiation shielding ethylene propylene rubber material Process flow as follows Figure 8 As shown.

[0041] (1) Dissolve the metal salt ZrCl4, terephthalic acid, and tungsten-containing component H2WO4 formic acid adjuster in an organic solvent DMF at a molar ratio of 1:1.0:0.2, wherein the concentration of H2WO4 is 0.067 mol / L, the molar ratio of ZrCl4 to terephthalic acid to H2WO4 is 1:1.0:0.2, and the amount of solvent N,N-dimethylformamide used is 25 mL of DMF for every 1 mmol of ZrCl4.

[0042] (2) Seal the mixed solution in a reaction vessel and heat it to about 120°C for about 24 hours. Formic acid is used to control the crystal growth rate and size.

[0043] (3) After the reaction is completed, the unreacted substances are removed by centrifugation at 8000 rpm and washing twice with DMF and methanol respectively. Finally, the solvent molecules in the pores are removed by vacuum drying or supercritical CO2 drying (supercritical CO2 drying is used in this example), thereby activating the adsorption performance of MOF.

[0044] (4) Plasticize the EPDM raw rubber in a two-roll mill or internal mixer to soften it.

[0045] (5) Add zinc oxide 4 phr, stearic acid 2 phr, and 2,2,4-trimethyl-1,2-dihydroquinoline polymer 2 phr in sequence.

[0046] (6) Add the pretreated MOF nanoparticles in batches and slowly to ensure uniform dispersion.

[0047] (7) Add 1.5 phr of sulfur and 1 phr of tetramethylthiuram disulfide, and continue to mix until the color is uniform.

[0048] (8) After the compound is thinly passed through, it is wrapped in a triangular shape 5-8 times (6 times in this embodiment), and finally sheeted out. It is left at room temperature for at least 16 hours to allow the additives to spread evenly.

[0049] (9) Use a vulcanizer to measure the positive vulcanization time (T90) 35 min and scorch time (ts2) 6 min of the compound at the set vulcanization temperature (usually 150-170°C, the temperature in this embodiment is 150°C) to determine the molding process parameters.

[0050] (10) Place the stored rubber compound into a preheated flat vulcanizing mold and perform compression vulcanization at a pressure of 10-15 MPa and a vulcanization temperature for a time of T90 to prepare a 2 mm thick sheet.

[0051] (11) After vulcanization, demold quickly, cool naturally to room temperature, remove burrs and flash, and obtain tungsten-functionalized MOF / EPDM composite sheet or product.

[0052] Experimental Example 1: Characterization Results Unfunctionalized UiO-66 samples exhibit typical spherical nanoparticle morphology, such as... Figure 1 As shown, the particle size distribution is relatively uniform, with an average particle size of approximately 2 μm. The particle surfaces are smooth with clear boundaries. Although there is some soft agglomeration between particles, no obvious melting or distortion phenomena were observed. This morphology indicates that UiO-66 prepared by the solvothermal method has high crystallinity and good structural integrity, making it an ideal precursor for subsequent tungsten functionalization.

[0053] After tungsten functionalization, the overall morphology of UiO-66 nanoparticles is as follows: Figure 2 As shown, there were no significant changes compared to the unfunctionalized sample; the octahedral / quasi-spherical characteristics were still maintained, with a slight increase in particle size. This is attributed to the chemical anchoring of tungsten species on the surface of the metal cluster nodes, along with a small amount of pore filling. High-magnification SEM revealed a slightly rougher particle surface, but no free tungsten oxide aggregates or heterogeneous precipitates were observed, indicating that the tungsten component is uniformly distributed in the MOF framework at the atomic or sub-nanometer scale without disrupting the original crystal morphology. These results demonstrate that tungsten was successfully introduced into the UiO-66 structure using the precursor in-situ doping method, and that the functionalization process did not cause significant phase separation or structural collapse.

[0054] Tungsten-modified UiO-66 powder samples, such as Figure 3 As shown, from Figure 3 As can be seen, the UiO-66 powder is uniformly grayish-white. The material maintains the typical microporous crystal morphology of UiO-66. The powder is fine, and tungsten is highly dispersed in zirconium clusters or framework channels in the form of isolated tungsten oxide species, polytungstate ions or a small amount of tungsten oxide clusters. The overall appearance is uniform and there is no obvious agglomeration.

[0055] Experiment Example 2: Shielding Performance Test The shielding performance was tested using an 80 keV gamma-ray source, and the results are shown in Table 1. Table 1: Comparison of shielding efficiency of ethylene propylene rubber with different mass ratios of filler Experimental results are as follows Figure 4As shown, the shielding performance of tungsten-functionalized UiO-66 / EPDM composite materials was tested using a 1 cm thick sample under an 80 keV gamma-ray source. The results show that the shielding efficiency of the composite material against 80 keV gamma rays increases non-linearly with increasing tungsten-functionalized UiO-66 filling content. When the filler-to-EPDM mass ratio is 10:100, the shielding efficiency reaches 10.43%; when the mass ratio is increased to 50:100, the shielding efficiency reaches 38.62%. It is worth emphasizing that even with a total tungsten content of only 4.00 wt% (50 phr) in the composite material, its shielding efficiency is close to 40%, significantly better than that of traditional tungsten powder / EPDM composite materials with the same tungsten content. This is attributed to the atomically dispersed tungsten anchoring to Zr-MOF metal cluster nodes, forming highly uniform nanoscale absorption sites, avoiding the "dead zone" effect caused by tungsten particle agglomeration, thus achieving efficient radiation attenuation even with low tungsten content. Furthermore, the shielding efficiency did not plateau or decrease with increasing filler content, indicating that the tungsten-functionalized UiO-66 was uniformly dispersed in the EPDM matrix, with good interfacial bonding, and no significant agglomeration or filler precipitation occurred. In summary, the tungsten-functionalized zirconium-based metal-organic framework / ethylene propylene rubber composite material provided by this invention possesses excellent low-energy gamma-ray shielding capability even with low tungsten content, and also features lightweight, flexibility, and processing safety, making it suitable for applications such as nuclear protection, medical shielding, and aerospace cable sheathing.

[0056] Experiment Example 3: Mechanical Property Testing Mechanical properties were tested according to GB / T 528-2009, using a thickness of 2 mm and a tensile speed of 500 mm / min. The results are shown in Table 2.

[0057] Table 2: Comparison of mechanical properties of ethylene propylene rubber with different mass ratios of fillers Comparison of tensile strength of ethylene propylene rubber with different mass ratios of fillers, for example Figure 5 As shown, the tensile strength is 6.2 MPa when unfilled (0 phr). The tensile strength gradually increases with increasing filler content, reaching a maximum of 8.1 MPa at 20 phr, an increase of approximately 30.6% compared to the unfilled value. Beyond 20 phr, the strength begins to decrease, dropping to 6.4 MPa at 40 phr and further to 5.2 MPa at 50 phr (lower than the unfilled value). In summary, an appropriate amount of filler (~20 phr) can effectively strengthen the EPDM matrix, but excessive filler can lead to filler agglomeration or weakened interfacial bonding, which is detrimental to strength.

[0058] Comparison of elongation at break of ethylene propylene rubber with different mass ratios of fillers, for example Figure 6As shown, the elongation at break is 519% when unfilled. As the filler content increases, the elongation at break decreases monotonically: the addition of filler restricts the movement of rubber molecular chains, making the material brittle and reducing its ductility. Moreover, the greater the amount of filler added, the more obvious the loss of toughness.

[0059] The hardness of ethylene propylene rubber with different mass ratios of fillers, for example Figure 7 As shown, the unfilled hardness is 59, and the hardness increases continuously with the increase of filler. Tungsten-functionalized UiO-66, as a rigid particle, significantly improves the surface hardness and deformation resistance of EPDM, and enhances the overall rigidity of the material.

[0060] In summary, when the tungsten-based MOF / EPDM mass ratio is 20:100, the composite material achieves the best overall performance: tensile strength of 8.1 MPa, elongation at break of 415%, and Shore A hardness of 71. Compared with pure EPDM, the tensile strength is increased by 30%, and the hardness is increased by 12 degrees. When the filler content is increased to 50:100, the tensile strength is still greater than 5 MPa, and the elongation at break is greater than 250%, indicating that the material still has good flexibility under high shielding requirements.

[0061] Experiment Example 4: Compatibility Test The Flory-Huggins interaction parameters of tungsten-functionalized UiO-66-doped ethylene propylene rubber samples were determined using the equilibrium swelling method. Vulcanized rubber with a known crosslinking density was immersed in toluene, a good solvent, and after swelling equilibrium was reached, the mass or volume before and after swelling was measured. The χ² value was calculated using the Flory-Rehner equation, as follows: Where v r This represents the volume fraction of the vulcanized rubber in the swollen gel.

[0062] The χ² value of ethylene propylene rubber doped with tungsten-functionalized UiO-66 was 0.6. This result indicates that the filler and the rubber matrix exhibit thermodynamic compatibility. Surface modification effectively reduces the interfacial free energy and enhances the dispersion stability of inorganic particles in ethylene propylene rubber, thereby improving the mechanical properties and uniformity of the composite material. This demonstrates that the tungsten-functionalized UiO-66 nanoparticles have good compatibility with ethylene propylene rubber.

[0063] Tg is the characteristic temperature at which the amorphous chain segments of EPDM transition from the glassy state to the rubbery state. Good filler compatibility and adsorption of rubber molecular chains on the filler surface, which restricts chain segment movement, lead to an increase in Tg. Tg increases monotonically with increasing tungsten-functionalized UiO-66 filling amount, as shown in Table 3 below. Table 3: DSC glass transition temperature of ethylene propylene rubber with different mass ratios of fillers As the mass ratio of tungsten-functionalized UiO-66 filler to EPDM increased from 0 phr to 50 phr, the glass transition temperature (Tg) of the composite material monotonically increased from -48.2 °C to -42.3 °C, with a total increase of 5.9 °C. Specifically, in the low filler content (≤20 phr) stage, Tg increased rapidly, by 3.3 °C; when the filler content exceeded 20 phr, the rate of Tg increase gradually slowed down, increasing by 3.6 °C at 30 phr and 5.9 °C at 50 phr. This indicates a good interfacial interaction between the filler and the EPDM matrix, effectively restricting the movement of rubber molecular chain segments. Furthermore, all samples exhibited only a single Tg value, without bimodal or shoulder peaks, indicating good compatibility and no macroscopic phase separation. The gradual increase in Tg also reflects the gradual approach of saturation of adsorbed segments on the filler surface.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A radiation-shielding ethylene propylene rubber material, characterized in that, The invention comprises an ethylene propylene rubber matrix and tungsten-functionalized zirconium-based metal-organic framework nanoparticles dispersed in the ethylene propylene rubber matrix. In the tungsten-functionalized zirconium-based metal-organic framework nanoparticles, tungsten is introduced into the zirconium-based metal-organic framework through chemical bonding or doping and anchored to the metal cluster nodes of the zirconium-based metal-organic framework. The zirconium-based metal-organic framework is UiO-66.

2. The radiation shielding ethylene propylene rubber material according to claim 1, characterized in that, The ethylene propylene rubber matrix is ​​binary ethylene propylene rubber or ternary ethylene propylene rubber.

3. The radiation shielding ethylene propylene rubber material according to claim 1, characterized in that, Tungsten atoms are anchored to the defect sites of the zirconium-based metal-organic framework via Zr-OW chemical bonds, and the mass ratio of the tungsten-functionalized zirconium-based metal-organic framework nanoparticles to the ethylene propylene rubber matrix is ​​(5~50):

100.

4. A method for preparing a radiation-shielding ethylene propylene rubber material as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Tungsten is doped into zirconium-based metal-organic frameworks to obtain functionalized zirconium-based metal-organic framework nanoparticles. S2. Functionalized zirconium-based metal-organic framework nanoparticles are incorporated into the ethylene propylene rubber matrix.

5. The method for preparing radiation-shielding ethylene propylene rubber material according to claim 4, characterized in that, S1 specifically includes: S101. Dissolve ZrCl4, terephthalic acid, and a tungsten-containing modifier in an organic solvent to obtain a mixture; S102. The mixture is sealed and heated to 120°C and reacted for 20-28 hours to obtain functionalized zirconium-based metal-organic framework nanoparticles.

6. The method for preparing radiation-shielding ethylene propylene rubber material according to claim 4, characterized in that, S2 specifically includes: S201. Plasticize and soften the ethylene propylene rubber matrix to obtain a softened ethylene propylene rubber matrix; S202. Add activator and antioxidant to the softened ethylene propylene rubber matrix; S203. Functionalized zirconium-based metal-organic framework nanoparticles are added to the product in S202 in batches and slowly to ensure uniform dispersion and obtain intermediate products. S204. Add vulcanizing agent and accelerator to the intermediate product and mix until the color is uniform to obtain compound rubber. S205. After the compounded rubber is thinly passed through, it is wrapped in a triangular package, sheeted out, placed at room temperature for 10-20 hours, vulcanized, and demolded to obtain radiation shielding ethylene propylene rubber material.

7. The method for preparing radiation-shielding ethylene propylene rubber material according to claim 5, characterized in that, The regulator for the tungsten-containing component is an H2WO4 formic acid solution, wherein the concentration of H2WO4 is 0.067 mol / L; The molar ratio of ZrCl4 to terephthalic acid to H2WO4 is 1:1.0:0.2, and the amount of N,N-dimethylformamide used is 25 mL of N,N-dimethylformamide per 1 mmol ZrCl4.

8. The method for preparing radiation-shielding ethylene propylene rubber material according to claim 6, characterized in that, The activator is selected from at least one of zinc oxide, stearic acid, and polyethylene glycol. The antioxidant is selected from at least one of the following: 2,2,4-trimethyl-1,2-dihydroquinoline polymer, N-isopropyl-N'-phenyl-p-phenylenediamine, and 2-mercaptobenzimidazole; The vulcanizing agent is selected from at least one of: dicumyl peroxide, sulfur, and di-tert-butyl peroxide; The accelerator is selected from at least one of tetramethylthiuram disulfide, dibenzothiazole disulfide, and N-cyclohexyl-2-benzothiazole sulfenamide.

9. A cable outer sheath, characterized in that, Use the radiation shielding ethylene propylene rubber material as described in any one of claims 1-3.

10. The application of the radiation shielding ethylene propylene rubber material as described in any one of claims 1-3 in the preparation of radiation protection products.

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