Radiation-resistant vulcanized rubber as well as preparation method and application thereof

Abstract

The invention discloses irradiation-resistant vulcanized rubber as well as a preparation method and application thereof, and belongs to the technical field of rubber preparation. The vulcanized rubber is prepared from the following raw materials in parts by mass: 50-150 parts of rubber, 1-30 parts of an active agent, 10-60 parts of a reinforcing agent, 0.05-10 parts of a vulcanization accelerator and 0.05-10 parts of a vulcanizing agent. The vulcanized rubber disclosed by the invention has excellent radiation resistance, provides a new idea for improving the radiation resistance of natural rubber and long-term safe use of nuclear equipment, and has a wide application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber preparation, and in particular relates to a radiation-resistant vulcanized rubber and a preparation method and application thereof. Background Art

[0002] Natural rubber (NR), as a bio-derived elastomer, has been widely used in aerospace, transportation, and medical fields due to its excellent comprehensive properties, including high elasticity, wear resistance, tear resistance, and fatigue resistance. In the nuclear industry, NR is also used as an important elastic material in shock absorption and sealing applications. However, these NR materials are inevitably exposed to nuclear radiation, such as gamma rays, during the application process. Due to the high energy and strong penetrating power of gamma rays, they can cause serious damage to the microscopic network structure of NR materials. Long-term exposure to gamma rays usually leads to a serious degradation of NR performance or even material failure, posing a threat to the safe operation of nuclear-related equipment.

[0003] Therefore, to maximize the application value of natural rubber, its network structure must be improved through the vulcanization process to enhance its performance. The vulcanized network of rubber refers to the three-dimensional cross-linked network structure formed during the vulcanization reaction. This process is a key step in rubber processing, endowing the rubber material with excellent mechanical properties, elasticity, and durability.

[0004] Crosslinking and irradiation are inextricably linked, but little research has been conducted on the changes in the vulcanization network of natural rubber during irradiation. To ensure the safety and stability of NR devices exposed to nuclear radiation, further research is needed to develop radiation-resistant NR materials. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the object of the present invention is to provide a radiation-resistant vulcanized rubber and a preparation method and use thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The invention provides a vulcanized rubber, which is prepared from the following raw materials in parts by mass: 50-150 parts of rubber, 1-30 parts of an activator, 10-60 parts of a reinforcing agent, 0.05-10 parts of a vulcanization accelerator, and 0.05-10 parts of a vulcanizing agent.

[0008] Furthermore, the rubber is natural rubber, the activator is at least one of zinc oxide and stearic acid, the reinforcing agent is carbon black, the vulcanization accelerator is at least one of N-cyclohexyl-2-benzothiazolesulfonamide, 2-mercaptobenzothiazole, dibenzothiazole disulfide, N-tert-butyl-2-benzothiazolesulfenamide, N-oxydiethylene-2-benzothiazolesulfenamide, N,N'-dicyclohexyl-2-benzothiazolesulfenamide, tetramethylthiuram disulfide, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, pentamethylenethiuram hexasulfide, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc dimethyldithiocarbamate, and diphenylguanidine, and the vulcanizing agent is sulfur.

[0009] Furthermore, the active agent is zinc oxide and stearic acid, and the vulcanization accelerator is N-cyclohexyl-2-benzothiazole sulfonamide.

[0010] Furthermore, the mass ratio of the zinc oxide to stearic acid is 1:(0.1-5).

[0011] Furthermore, the mass ratio of the zinc oxide to stearic acid is 1:0.75.

[0012] Furthermore, the vulcanized rubber is prepared from the following raw materials in parts by mass: 80-120 parts of rubber, 3-15 parts of activator, 25-45 parts of reinforcing agent, 0.6-2.6 parts of vulcanization accelerator, and 0.5-2.5 parts of vulcanizing agent.

[0013] Furthermore, the vulcanized rubber is prepared from the following raw materials in parts by mass: 100 parts of rubber, 7 parts of activator, 35 parts of reinforcing agent, 0.6 parts of vulcanization accelerator, and 1.5-2 parts of vulcanizing agent.

[0014] Furthermore, the vulcanized rubber is prepared from the following raw materials in parts by mass: 100 parts of rubber, 7 parts of activator, 35 parts of reinforcing agent, 2.6 parts of vulcanization accelerator, and 0.5 parts of vulcanizing agent.

[0015] The present invention also provides a method for preparing the vulcanized rubber, which comprises the steps of uniformly mixing the rubber, an active agent, a reinforcing agent, a vulcanization accelerator and a vulcanizing agent, allowing the mixture to stand, and vulcanizing the mixture to obtain the vulcanized rubber.

[0016] Furthermore, the parking time is 8 to 24 hours, and the vulcanization time is 10 to 60 minutes.

[0017] Furthermore, the parking time is 8 to 12 hours, and the vulcanization time is 25 minutes.

[0018] Furthermore, the vulcanization process is hot press vulcanization, the temperature of the hot press vulcanization is 130-150° C., and the pressure of the hot press vulcanization is 10-15 MPa.

[0019] Furthermore, the temperature of the hot pressing vulcanization is 143° C., and the pressure of the hot pressing vulcanization is 10 MPa.

[0020] The present invention also provides use of the vulcanized rubber in preparing radiation-resistant products.

[0021] Furthermore, the product is a medical device or a nuclear device.

[0022] The present invention has achieved the following beneficial effects:

[0023] The present invention prepares vulcanized natural rubber samples with different sulfur contents. Experiments show that after irradiation, the tensile strength of the vulcanized natural rubber first increases and then decreases with increasing sulfur content. Among them, the vulcanized natural rubber with a sulfur content of 2 phr has the highest tensile strength under a high-energy irradiation environment.

[0024] The present invention also compares the effects of different vulcanization systems on the radiation resistance of natural rubber and finds that the effective vulcanization system (EV) sample has the best stability to radiation.

[0025] The present invention provides a method for regulating the radiation resistance of natural rubber and a network design scheme for radiation-resistant natural rubber, which provides new ideas for improving the radiation resistance of natural rubber and the long-term safe use of nuclear equipment and has broad application prospects.

[0026] Obviously, based on the above contents of the present invention, according to common technical knowledge and customary means in this field, without departing from the above basic technical ideas of the present invention, other various forms of modifications, replacements or changes can be made.

[0027] The following further describes the above content of the present invention in detail through specific embodiments in the form of examples. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention fall within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The preparation process of vulcanized natural rubber samples.

[0029] Figure 2 Vulcanization curves of (a) natural rubber with different sulfur contents and (b) natural rubber with different vulcanization systems.

[0030] Figure 3 (a) Stress-strain curves and (b) tensile strength of natural rubber with different sulfur contents before and after irradiation.

[0031] Figure 4Cyclic tensile curves of natural rubber with different sulfur contents before (a), (b), (c) and after (d), (e), and (f) irradiation at different strains.

[0032] Figure 5 Energy dissipation rate of natural rubber with different sulfur contents under different strains (a) before irradiation and (b) after irradiation.

[0033] Figure 6 This is a graph showing the toughness of natural rubber with different sulfur contents before and after irradiation.

[0034] Figure 7 (a) Loss factor; (b) storage modulus of natural rubber with different sulfur content before irradiation; (c) loss factor; (d) storage modulus after irradiation.

[0035] Figure 8 (a) Crosslinking density and (b) hardness of natural rubber with different sulfur contents before and after irradiation.

[0036] Figure 9 MR fitting curves of different sulfur contents (a) before irradiation; (b) after irradiation, and (c) Ge value before and after irradiation; (d) Gc value.

[0037] Figure 10 (a) Stress-strain curves of different vulcanization systems before and after irradiation; (b) tensile strength; (c) elongation at break; (d) retention of tensile strength and elongation at break.

[0038] Figure 11 (a) Loss factor; (b) storage modulus of rubber samples with different vulcanization systems before irradiation; (c) loss factor; (d) storage modulus after irradiation.

[0039] Figure 12 SEM images of different vulcanization systems before and after irradiation (a)(b)(c) before irradiation; (d)(e)(f) after irradiation.

[0040] Figure 13 (a) Total crosslinking density (b) Single sulfur bond density (c) Polysulfide bond density (d) Hardness of different vulcanization systems before and after irradiation.

[0041] Figure 14 MR fitting curves of different sulfurization systems (a) before irradiation; (b) after irradiation, and (c) Ge value before and after irradiation; (d) Gc value.

[0042] Figure 15 Schematic diagram of the irradiation mechanism of vulcanized natural rubber. DETAILED DESCRIPTION

[0043] The raw materials and equipment used in the present invention are all known products and are obtained by purchasing commercially available products.

[0044] The parts in the embodiments of the present invention are all parts by mass.

[0045] The natural rubber used in the specific embodiment of the present invention is provided by Guangdong Guangken Rubber Group Co., Ltd., with the brand name TSR20. The carbon black (CB) has a specific surface area of ​​75 to 120 m 2 / g carbon black N330. Sulfur (S), zinc oxide (ZnO), stearic acid (SA), and N-cyclohexyl-2-benzothiazolesulfonamide (CZ) were provided by Sichuan Haida Rubber Group Co., Ltd. Hexyl mercaptan and isopropyl mercaptan were purchased from Adamas Reagent Co., Ltd.

[0046] Example 1: Effects of different vulcanization recipes on vulcanized natural rubber

[0047] The preparation process of vulcanized natural rubber samples is as follows: Figure 1 As shown in Table 1, natural rubber (NR) and various vulcanizing agents were mixed evenly on a two-roll mill and left overnight. Figure 2 The vulcanization curve shown was hot-pressed and vulcanized on a flat vulcanizer at 143°C and 10 MPa for 25 minutes, and finally the sheet samples were obtained and named NR0.5, NR1, NR1.5, NR2, NR2.5, CV, SEV, and EV respectively.

[0048] Table 1 Vulcanization formula of vulcanized natural rubber samples (phr)

[0049]

[0050] Note: phr stands for parts, which refers to how many grams of the substance are added per 100g of rubber.

[0051] The beneficial effects of the present invention are demonstrated by experimental examples below.

[0052] Experimental Example 1. Structural Characterization and Performance Testing of Vulcanized Natural Rubber

[0053] 1. Determination of cross-linking bonds

[0054] In the sulfur vulcanization system, the main types of cross-linking bonds in natural rubber are monosulfide bonds, disulfide bonds and polysulfide bonds. Since different sulfur bonds have different reactivity to different reagents, such as isopropyl mercaptan can react with polysulfide bonds to form disulfide bonds and monosulfide bonds, and n-hexyl mercaptan can react with polysulfide bonds and disulfide bonds to form monosulfide bonds, the vulcanized natural rubber samples can be reacted with n-hexyl mercaptan and ethylpropyl mercaptan respectively to finally obtain different sulfur bond densities.

[0055] 2. Determination of polysulfide bonds

[0056] The crosslink density (V1) of the rubber sample was measured by the swelling method. The total crosslink density of the sample was measured. The sample with V1 was dried and immersed in n-heptane solvent for 12 hours. Then, isopropyl mercaptan and piperidine were added to make the concentration reach 0.4 mol·L -1 The reaction was allowed to proceed for 2 hours. After the reaction, the mixture was extracted in acetone for 12 hours and finally vacuum dried to constant weight. The crosslink density (V2) was then measured using the equilibrium swelling method and dried for later use. The crosslink density at this point is the sum of the monosulfide and disulfide bond densities, so the polysulfide bond density can be expressed as V1-V2.

[0057] 3. Determination of single sulfide bonds

[0058] The sample with measured V2 was dried and placed in a mixed solvent of n-hexyl mercaptan and piperidine (7 ml n-hexyl mercaptan: 43 ml piperidine) for reaction at room temperature for 48 hours, followed by extraction with acetone for 12 hours. After drying, the cross-linking density (V3) was measured. The cross-linking density at this time was the single sulfide bond density (V3).

[0059] 4. Characterization test

[0060] (1) Vulcanization performance

[0061] The vulcanization characteristics of the rubber samples were tested using a rubber processing analyzer (model RPA-8000) from High Speed ​​Rail Testing Instruments (Dongguan) Co., Ltd., with a vulcanization temperature of 143°C.

[0062] (2) Mechanical properties

[0063] The mechanical properties of the samples were tested using a universal testing machine (Instron 3367) at a tensile rate of 100 mm min -1 The sample was dumbbell-shaped (25 mm × 4 mm × 1 mm), and the average value of three parallel measurements was taken.

[0064] (3) Rubber hardness

[0065] The hardness of different nanofiller composite materials was tested using an LX-A Shore hardness tester. The samples were cylindrical with a bottom diameter of d = 15 mm and a height of h = 16 mm. Each sample was measured at least three times to obtain the average value.

[0066] (4) Irradiation test

[0067] The gamma ray irradiation in this study was provided by the Institute of Biotechnology and Nuclear Technology, Sichuan Academy of Agricultural Sciences, using a 60Co radiation source with a dose rate of 7.42 KGy / h and a total dose of 1000 KGy.

[0068] (5) Dynamic Mechanical Testing (DMA)

[0069] Dynamic mechanical properties of the prepared nanocomposites were tested using a TA Q850 dynamic mechanical analyzer (DMA, TA Instrument, USA). The tensile mode was used with a frequency of 1 Hz, an amplitude of 15 μm, a heating rate of 3°C / min, and a test temperature range of -80°C to 60°C. The effective portion of the specimen had dimensions of 15 × 5 × 1 mm.

[0070] (6) Scanning electron microscopy (SEM)

[0071] Scanning electron microscopy (SEM, JEOL JSM-5900LV) was used to analyze the microstructure of the sample after liquid nitrogen fracture. The test acceleration voltage was 20 kV.

[0072] (7) Crosslink density

[0073] The crosslink density of vulcanized natural rubber was determined using the equilibrium swelling method. First, 0.2 g of vulcanized natural rubber was placed in n-hexane and soaked at room temperature for 72 hours. The surface solvent was then quickly wiped off with filter paper and weighed. The crosslink density was calculated using the Flory-Rehner equation.

[0074]

[0075]

[0076] Where Ve is the crosslink density per unit volume of degraded rubber; Vr is the volume fraction of the sample; Vs is the molar volume of the solvent (106.4 cm 3 / mol), m r is the mass of the sample; m s is the mass of toluene in the swollen sample; ρ r is the sample density, tested with a density meter; ρ s is the density of heptane (0.71 g / cm3); χ is the interaction parameter between NR and heptane (χ = 0.43).

[0077] 5. Experimental results

[0078] 5.1 Analysis of radiation resistance of NR with different sulfur contents

[0079] (1) The results are as follows Figure 3 As shown in the figure, in the unirradiated state, the tensile strength of natural rubber increases significantly with the increase of sulfur content. This is mainly attributed to the fact that sulfur, as a cross-linking agent, effectively promotes the cross-linking reaction between natural rubber molecular chains, thereby enhancing the network structure strength and mechanical properties of the material.

[0080] However, after irradiation, the mechanical behavior of the material showed a significant dependence on sulfur content: at low sulfur contents (0.5 and 1 phr), the tensile strength slightly increased; however, above 1 phr, the tensile strength began to decline, and particularly at 2.5 phr, the strength dropped sharply. These results indicate that crosslink density has a dual effect on the irradiation properties of natural rubber: moderate crosslink density enhances the material's irradiation stability, while excessive crosslink density exacerbates embrittlement and performance degradation.

[0081] The above results show that the mechanical properties of sample NR2 are optimal when the sulfur content is 2 phr.

[0082] (2) The tensile cycle curves of natural rubber before and after irradiation are as follows Figure 4 The pre-irradiation curves show the mechanical behavior at 100%, 300%, and 500% strain, respectively. As the sulfur content increases, the tensile stress during loading gradually increases, and the residual strain after unloading also increases. However, the post-irradiation curves show that samples with different sulfur contents exhibit roughly the same residual strain, indicating that the permanent deformation of the materials after irradiation tends to be consistent.

[0083] (3) Energy dissipation rate of natural rubber with different sulfur contents under different strains Figure 5 As shown. Figure 5 (a) As can be seen, the energy dissipation efficiency gradually decreases with increasing sulfur content, and the variation pattern is similar at 100%, 300%, and 500% strain. This phenomenon indicates that the increase in sulfur content significantly strengthens the material's crosslinking network, restricting the mobility of the molecular chains and thus inhibiting the rubber material's energy dissipation capacity. While increasing the crosslink density enhances the material's rigidity and strength, it also reduces its dynamic response and energy dissipation efficiency.

[0084] Figure 5 (b) shows that despite the different sulfur contents, the energy dissipation rate shows an upward trend with increasing strain before and after irradiation, indicating that larger strains are more conducive to energy dissipation. This phenomenon may be related to the slippage and disentanglement of molecular chains and the destruction of the filler-matrix interface under high strain, which together contribute to higher energy dissipation. However, when the sulfur content reaches 2.5 parts, the maximum strain of the material can only reach 250%, so only the energy dissipation rate at 100% strain can be measured, at which point its performance is similar to that of other samples. This result further indicates that excessive cross-linking will significantly reduce the ductility and toughness of the material, limiting its energy dissipation capacity under high strain.

[0085] At 300% and 500% strain, the other samples showed roughly the same energy dissipation rate, further confirming the rubber material's excellent high toughness properties under high strain. This high toughness is mainly attributed to the moderate crosslinking density and flexibility of the molecular chain, which enables the material to effectively absorb and dissipate energy under high strain through molecular chain rearrangement and energy dissipation mechanisms (such as molecular chain slippage and filler-matrix interface debonding). These results not only reveal the significant effect of sulfur content on the energy dissipation behavior of rubber materials, but also provide important guidance for the design of high-performance rubber materials: by optimizing the crosslinking density and molecular chain structure, the energy dissipation capacity and toughness of the material can be significantly improved while maintaining its strength.

[0086] (4) Changes in toughness of natural rubber samples with different sulfur contents before and after irradiation Figure 6 In the unirradiated state, the toughness of the low sulfur content samples (NR0.5, NR1) is low. When the sulfur content increases to 1.5 parts, the toughness is significantly improved, with the increase nearly doubling.

[0087] After irradiation, the toughness of all samples decreased significantly, indicating that irradiation caused varying degrees of damage to the rubber material's structure. The sample with a sulfur content of 2.5 parts per million (NR2.5) showed the greatest decrease in toughness, indicating the most severe irradiation damage.

[0088] In contrast, the NR1.5 and NR2 samples maintained high toughness levels before and after irradiation, indicating that the rubber materials at these two sulfur contents have good resistance to irradiation. Among them, the NR2 sample has the best resistance to irradiation.

[0089] (5) In order to explore the effect of different sulfur contents on the radiation resistance of natural rubber, the dynamic mechanical properties of the samples were further tested. Figure 7 The loss factor and storage modulus curves of each sample before irradiation are shown. Figure 7 (a) It can be seen that with the increase of sulfur content, the glass transition temperature (Tg) gradually increases, and the storage modulus also shows an upward trend ( Figure 7 (b)). After irradiation, Figure 7 As shown in (c), the variation pattern of Tg with the increase of sulfur content remains unchanged, and the Tg of all samples is significantly increased compared with that before irradiation. In addition, Figure 7 (d) shows that the storage modulus of the sample after irradiation is significantly increased compared with that before irradiation.

[0090] (6) The crosslinking density of natural rubber with different sulfur contents was determined by the swelling method. The results are as follows: Figure 8As shown in (a). With the increase of sulfur content, the crosslinking density of the samples before and after irradiation showed a trend of gradual increase, and the crosslinking density of all samples increased significantly after irradiation. This further confirmed that irradiation can induce the crosslinking reaction of natural rubber, resulting in an increase in the material modulus and the characteristics of embrittlement and hardening, as shown in Figure 2. Figure 8 (b) shown.

[0091] (7) In order to more intuitively analyze the changes in the cross-linked structure of each sample before and after irradiation, the stress-strain curves were fitted by MR based on the pipeline model. The results are shown in Figure 2. Figure 9 shown. Figure 9 (a) and (b) show the changes in the reduced stress of samples with different sulfur contents before and after irradiation: before irradiation, the reduced stress gradually increases with the increase of sulfur content; after irradiation, the reduced stress of NR2.5 is significantly higher than that of other samples, indicating that it has undergone significant structural changes during the irradiation process. Figure 9 (c) and (d) show the variation of physical crosslinking (Ge) and chemical crosslinking (Gc), respectively: Before irradiation, the degree of physical crosslinking of each sample is roughly the same ( Figure 9 (c)), but after irradiation, the overall trend is downward, and the higher the sulfur content, the greater the degree of damage to the physical entanglement; in terms of chemical cross-linking ( Figure 9 (d) From NR0.5 to NR2.5, the values ​​show an upward trend before and after irradiation, with the increase in NR2.5 being particularly significant. This indicates that the increase in sulfur content promotes the chemical crosslinking of rubber molecular chains. Furthermore, chemical crosslinking significantly increased in all samples after irradiation, further confirming the irradiation-promoting effect of chemical crosslinking.

[0092] These results demonstrate that natural rubber's radiation resistance is not simply positively correlated with the degree of crosslinking; rather, there exists a critical crosslinking level at which the material exhibits optimal radiation stability. Among the natural rubber samples with different sulfur contents presented in this study, the NR2 sample maintained excellent performance both before and after irradiation, demonstrating the best radiation stability.

[0093] 5.2 Analysis of radiation resistance of NR with different curing systems

[0094] (1) Analysis of radiation resistance of NR with different curing systems

[0095] like Figure 10 As shown in (a), the stress-strain curves of CV (conventional vulcanization), SEV (semi-effective vulcanization) and EV (effective vulcanization) systems before irradiation are almost completely overlapped, indicating that their crosslinking density and network structure are similar. However, after irradiation, the stress-strain curves of the three systems are clearly separated, indicating that there are significant differences in their tolerance to irradiation. Figure 10(b) and (c) show that the tensile strength and elongation at break of CV, SEV and EV systems decreased significantly after irradiation, but the EV system always maintained the highest strength and elongation at break before and after irradiation. Figure 10 (d) It was further confirmed that the EV system had better retention of strength and elongation at break after irradiation than the other systems. These results indicate that the effective vulcanization system (EV) has the best resistance to gamma rays.

[0096] (2) The dynamic mechanical properties analysis results of different vulcanization systems are as follows Figure 11 As shown. Among them, Figure 11 (a) and (c) show the temperature-dependent change curves of the loss factor before and after irradiation, respectively. The analysis results show that irradiation significantly increases the glass transition temperature (Tg) of each system, and the CV, SEV, and EV systems all show the same change pattern before and after irradiation. Figure 11 In (b) and (d), the modulus of the CV system shows a significant downward trend from a maximum to a minimum value with increasing temperature before and after irradiation, indicating relatively poor thermal stability. In contrast, the modulus of the SEV and EV systems exhibits greater stability in response to temperature and irradiation, with no significant fluctuations, indicating that these two systems have superior radiation resistance and thermal stability.

[0097] (3) Figure 12 Scanning electron microscope (SEM) images of different vulcanization systems before and after irradiation are shown. Figure 12 (a)-(c)), the cross sections of CV, SEV and EV systems all showed obvious uneven features. The cross section roughness of CV system was significantly higher than that of SEV and EV systems. This phenomenon was closely related to its higher cross-linking density. Figure 12 As shown in Figures (d)-(f), the cross-sectional roughness of all three systems shows a trend of further increase, directly reflecting the significant impact of radiation-induced cross-linking on the material's micromorphology. However, a comparative analysis reveals that the cross-sectional surface of the EV system consistently exhibits smoother characteristics than the other systems, both before and after irradiation. This indicates a relatively low cross-linking density and a denser surface structure. This denser structure may provide the material with improved radiation resistance.

[0098] (4) Figure 13(a) shows the change of total crosslink density of CV, SEV and EV systems before and after irradiation: before irradiation, the total crosslink density of the three systems is basically the same; after irradiation, the total crosslink density shows a significant increase trend, among which the increase of CV system is the most significant, while the increase of EV system is the smallest. This phenomenon shows that under the condition of similar initial crosslink density, the lower the sulfur content, the stronger the material's tolerance to gamma rays. Further analysis of the change of sulfur bond density, Figure 13 (b) and (c) respectively show the evolution of the density of single sulfur bonds and polysulfide bonds. The change trend of the single sulfur bond density is basically consistent with the total crosslinking density. Both increase significantly after irradiation, but the increase in the EV system is relatively slow; while the polysulfide bond density generally decreases after irradiation, among which the CV system decreases the most and the EV system decreases the least. Comprehensive analysis shows that the change in crosslinking density of the EV system before and after irradiation is the most stable, showing the best irradiation stability; the stability of the SEV system is second; and the CV system is the most sensitive to irradiation. These experimental results confirm that the main reaction mechanism of natural rubber during irradiation is the conversion of polysulfide bonds to single sulfur bonds, and the EV system exhibits the best gamma ray resistance due to the low degree of sulfur bond conversion. In addition, the hardness of the three systems showed a consistent trend of change before and after irradiation, such as Figure 13 (d) shown.

[0099] (5) Figure 14 As shown in the figure, before irradiation, the fitting curves of the SEV and EV systems are highly consistent, indicating that their physical and chemical crosslinking levels are similar; the CV system, on the other hand, exhibits significantly higher chemical crosslinking and relatively lower physical crosslinking. After irradiation, the fitting curves of the three systems show significant differences, with the CV system having the highest chemical crosslinking density and the EV system having the lowest chemical crosslinking density. Figure 14 Figures (c) and (d) further quantify the specific trends in physical and chemical crosslinking in different vulcanization systems before and after irradiation: After irradiation, physical crosslinking in all systems decreased significantly, while chemical crosslinking increased significantly, directly confirming the mechanism of transformation from physical entanglement to permanent chemical crosslinking during irradiation. Notably, the CV system consistently maintained the lowest physical crosslinking and the highest chemical crosslinking density before and after irradiation; in contrast, the EV system exhibited the highest physical crosslinking and the lowest chemical crosslinking density. This characteristic indicates that the chemical crosslinking reaction in the EV system under irradiation is relatively limited, thus giving the material greater structural stability and excellent gamma ray resistance.

[0100] (6) Figure 15As shown in the figure, when vulcanized natural rubber is irradiated with gamma rays, its vulcanization network will be significantly damaged. Due to the low bond energy of polysulfide bonds, they are more likely to break, resulting in a significant decrease in the mechanical properties of the material after irradiation. Broken polysulfide bonds will ionize to form sulfur radicals. These unstable free radicals recombine to form single sulfur bonds, thereby compensating for the tensile strength of the material to a certain extent. However, the conventional vulcanization system (CV) is more easily destroyed during the irradiation process because it contains more polysulfide bonds, resulting in poor radiation resistance. In contrast, the effective vulcanization system (EV) has fewer polysulfide bonds and the vulcanization network remains more complete during the irradiation process, so it can better maintain its mechanical properties, thereby showing better radiation resistance.

[0101] The above results show that among the natural rubber samples with different vulcanization systems of the present invention, the radiation resistance of the effective vulcanization system (EV) sample is the best.

[0102] In summary, the present invention prepared vulcanized natural rubber samples with different sulfur contents. Experiments found that after irradiation, the tensile strength of the vulcanized natural rubber showed a trend of first increasing and then decreasing with the increase of sulfur content. Among them, the vulcanized natural rubber with a sulfur content of 2phr had the highest tensile strength under high-energy irradiation environment. The present invention also compared the effects of different vulcanization systems on the radiation resistance of natural rubber and found that the effective vulcanization system had the best stability to irradiation. The present invention provides a method for regulating the radiation resistance of natural rubber and a network design scheme for radiation-resistant natural rubber, which provides new ideas for improving the radiation resistance of natural rubber and the long-term safe use of nuclear equipment, and has broad application prospects.

Claims

1. A vulcanized rubber, characterized in that: The vulcanized rubber is prepared from the following raw materials in parts by mass: 50-150 parts of rubber, 1-30 parts of activator, 10-60 parts of reinforcing agent, 0.05-10 parts of vulcanization accelerator and 0.05-10 parts of vulcanizing agent.

2. The vulcanized rubber according to claim 1, characterized in that The rubber is natural rubber, the activator is at least one of zinc oxide and stearic acid, the reinforcing agent is carbon black, the vulcanization accelerator is at least one of N-cyclohexyl-2-benzothiazole sulfonamide, 2-mercaptobenzothiazole, tetramethylthiuram disulfide, zinc diethyldithiocarbamate, and diphenylguanidine, and the vulcanizing agent is sulfur; preferably, the activators are zinc oxide and stearic acid, and the vulcanization accelerator is N-cyclohexyl-2-benzothiazole sulfonamide.

3. The vulcanized rubber according to claim 1 or 2, characterized in that The vulcanized rubber is prepared from the following raw materials in parts by mass: 80-120 parts of rubber, 3-15 parts of activator, 25-45 parts of reinforcing agent, 0.6-2.6 parts of vulcanization accelerator and 0.5-2.5 parts of vulcanizing agent.

4. The vulcanized rubber according to claim 3, characterized in that The vulcanized rubber is prepared from the following raw materials in parts by mass: 100 parts of rubber, 7 parts of activator, 35 parts of reinforcing agent, 0.6 parts of vulcanization accelerator and 1.5-2 parts of vulcanizing agent.

5. The vulcanized rubber according to claim 3, characterized in that: The vulcanized rubber is prepared from the following raw materials in parts by mass: 100 parts of rubber, 7 parts of activator, 35 parts of reinforcing agent, 2.6 parts of vulcanization accelerator, and 0.5 parts of vulcanizing agent.

6. A method for preparing the vulcanized rubber according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: uniformly mixing rubber, an active agent, a reinforcing agent, a vulcanization accelerator and a vulcanizing agent, allowing the mixture to stand, and vulcanizing the mixture to obtain the product.

7. The method according to claim 6, characterized in that The parking time is 8 to 24 hours, and the vulcanization time is 10 to 60 minutes; preferably, the parking time is 8 to 12 hours, and the vulcanization time is 25 minutes.

8. The method according to claim 6, characterized in that The vulcanization process is hot press vulcanization, the temperature of the hot press vulcanization is 130-150° C., and the pressure of the hot press vulcanization is 10-15 MPa. Preferably, the temperature of the hot press vulcanization is 143° C., and the pressure of the hot press vulcanization is 10 MPa.

9. Use of the vulcanized rubber according to any one of claims 1 to 5 in the preparation of radiation-resistant products.

10. The use according to claim 9, characterized in that: The product in question is a medical device or a nuclear device.

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