Tungsten-containing lead-free rubber with radiation shielding function and preparation method thereof

Abstract

The invention relates to the technical field of radiation protection, in particular to tungsten-containing lead-free rubber with a radiation shielding function and a preparation method of the tungsten-containing lead-free rubber. The tungsten-containing lead-free rubber overcomes the problems of poor shielding performance and poor mechanical performance of the existing tungsten-containing lead-free rubber. The preparation method comprises the following steps: firstly, carrying out maleic anhydride grafting modification on ethylene propylene diene monomer, and carrying out silane coupling agent treatment and polydopamine coating coating on a composite tungsten filler; then, multiple components such as the modified rubber and the composite fibers are sequentially put into an internal mixer to be subjected to rough mixing and refined mixing, and then the tungsten-containing lead-free rubber is obtained through open mixing and vulcanization treatment. All the materials and the process have a synergistic effect, so that the rubber has excellent radiation shielding performance and mechanical performance, can replace a traditional lead rubber material, and has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of radiation protection, and specifically to a tungsten-containing lead-free rubber with radiation shielding function and its preparation method. Background Art

[0002] In the field of radiation protection, traditional radiation protection materials such as lead rubber have good shielding performance, but lead is toxic and poses potential hazards to the environment and human health, and is relatively bulky and inconvenient to use in some application scenarios. With the increasing attention to health and environmental protection, and the wide application of nuclear technology in fields such as medicine, industry, and energy, the demand for environmentally friendly, efficient, and lightweight radiation shielding materials is becoming increasingly urgent, and tungsten-containing lead-free rubber has thus emerged.

[0003] In the prior art, taking advantage of the characteristics of tungsten with high density and high atomic number and having good shielding ability for X-rays, γ-rays, etc., it is added to the rubber matrix in a suitable form to prepare a material with radiation shielding function. At the same time, aiming at the respective characteristics of different rubber matrices such as natural rubber, nitrile rubber, silicone rubber, etc., various additives and fillers are added to modify the rubber matrix, so as to improve the mechanical properties, processing properties, and aging resistance of the material to adapt to different application scenarios.

[0004] Although the prior art has achieved the preliminary preparation and performance optimization of tungsten-containing lead-free rubber, there are still technical problems in actual research and development and application. For example, how to accurately control the dispersion of tungsten in the rubber matrix and avoid agglomeration to ensure the uniformity of the shielding performance of the material; how to further improve the interfacial bonding force between the rubber matrix and tungsten so that the mechanical properties and shielding performance of the material remain stable during long-term use are all difficult problems to be solved. To sum up, the existing tungsten-containing lead-free rubber has problems of poor shielding performance and poor mechanical properties, and cannot meet the market demand.

[0005] Therefore, a tungsten-containing lead-free rubber with radiation shielding function and its preparation method are proposed. Summary of the Invention

[0006] The purpose of the present invention is to design a tungsten-containing lead-free rubber with radiation shielding function and its preparation method. The present invention first conducts maleic anhydride graft modification on ethylene-propylene-diene monomer rubber, and conducts silane coupling agent treatment and polydopamine coating on the composite tungsten filler; then the modified rubber, composite fiber and other multi-components are sequentially put into a mixer for rough mixing and refined mixing, and then open milled and vulcanized to obtain tungsten-containing lead-free rubber. Each material and process play a synergistic role, making the rubber have excellent radiation shielding performance and mechanical properties, and can replace traditional lead rubber materials, having good application prospects.

[0007] To achieve the above object, the present invention provides the following technical solutions: On the one hand, the present invention provides a preparation method of a tungsten-containing lead-free rubber with radiation shielding function, and the preparation method includes the following steps: The ethylene propylene diene monomer rubber is subjected to graft modification treatment with maleic anhydride, and then cut into small pieces to obtain modified rubber; The composite tungsten filler is treated with a silane coupling agent and coated with a polydopamine coating to obtain a modified composite tungsten filler; The modified rubber, composite fiber, zinc oxide, stearic acid and composite antioxidant are sequentially added into an internal mixer, and then the modified composite tungsten filler, carbon black and liquid paraffin are added. After rough mixing treatment, a rough mixture is obtained; Zinc borate and boron nitride are added to the rough mixture, and after refined mixing, a masterbatch is obtained; A composite accelerator and sulfur are added to the masterbatch for open milling and vulcanization treatment to obtain tungsten-containing lead-free rubber.

[0008] Preferably, by weight, the specific process of the graft modification treatment is as follows: 95-105 parts of ethylene propylene diene monomer rubber are put into an internal mixer, the temperature is controlled at 70 °C, and after kneading for 8 min, pretreated rubber is obtained; The pretreated rubber, 5-10 parts of maleic anhydride, 1 part of diisopropylbenzene peroxide and 0.5 part of 2,6-di-tert-butyl-4-methylphenol are added to the internal mixer for mixing, and mixed at 90 °C for 5-15 min to obtain a mixed material; The mixed material is put into a twin-screw extruder, the screw temperature is set at 180 °C, the screw speed is 200 rpm, and after staying for 3 min, the extruded material is cut into small pieces, washed with ethanol and dried to obtain modified rubber.

[0009] Preferably, by weight, the specific preparation method of the modified composite tungsten filler is as follows: 0.5-1.5 parts of silane coupling agent KH-550 are dissolved in 100 parts of absolute ethanol to obtain a silane coupling agent solution; 40-50 parts of composite tungsten filler are added to the silane coupling agent solution, and ultrasonically dispersed for 15 min to obtain a mixed filler; The mixed filler is subjected to water bath heating at 60 °C, and continuously stirred and reacted for 3 h. After the reaction is completed, it is washed and vacuum dried to obtain a pretreated composite tungsten filler; 1.5 parts of dopamine are added to Tris-HCl buffer solution to prepare a dopamine solution; The pretreated composite tungsten filler is added to the dopamine solution, stirred for 20-24 h, and after the reaction is completed, it is washed and vacuum dried to obtain a modified composite tungsten filler; The composite tungsten filler includes nano tungsten powder and bismuth tungstate, and the weight ratio of nano tungsten powder to bismuth tungstate is 5-7:3.

[0010] Preferably, the composite fiber includes carbon fiber and glass fiber, and the weight ratio of carbon fiber to glass fiber is 2-4:1.

[0011] Preferably, the composite antioxidant includes antioxidant 4020 and antioxidant DDA, and the weight ratio of antioxidant 4020 to antioxidant DDA is 1-3:1.

[0012] Preferably, by weight parts, the specific process of the rough mixing treatment is as follows: After preheating the internal mixer, put in the modified rubber, and obtain softened rubber after plasticizing; then successively add 11-15 parts of composite fiber, 3-5 parts of zinc oxide, 1-3 parts of stearic acid and 1-5 parts of composite antioxidant, and continue mixing for 3 min - 5 min to obtain a premix; subsequently add modified composite tungsten filler, 25-35 parts of carbon black and 10 parts of liquid paraffin, increase the rotational speed of the internal mixer to 60 rpm - 80 rpm, control the temperature at 110°C - 130°C, mix for 8 min - 12 min, and obtain a rough mix after discharging and cooling.

[0013] Preferably, by weight parts, the specific process of the refined mixing is as follows: Put the rough mix into an internal mixer preheated to 70°C - 80°C, mix for 3 min - 5 min to obtain a softened rough mix; then add 2-4 parts of zinc borate and 1-3 parts of boron nitride, and continue mixing for 5 min - 9 min. After mixing is completed, discharge the colloid and cool and store it for 10 h to obtain a masterbatch.

[0014] Preferably, the specific process of open mill mixing and vulcanization treatment is as follows: Set the roll temperature of the open mill to 45°C, put the masterbatch into the open mill, thin pass 3-5 times to obtain a treated masterbatch; then add 1-2 parts of composite accelerator and 1-3 parts of sulfur, adjust the roll gap for re-mixing, and the mixing time is 11 min - 15 min. After mixing is completed, take off the sheet to obtain a rubber sheet; vulcanize the rubber sheet, the vulcanization temperature is 160°C - 170°C, the vulcanization pressure is 15 MPa, and the vulcanization time is 20 min - 30 min. After completion, cool to obtain tungsten-containing lead-free rubber; the composite accelerator includes accelerator MBT and accelerator TMTD, and the weight ratio of accelerator MBT to accelerator TMTD is 3:1 - 3.

[0015] On the other hand, the present invention provides a tungsten-containing lead-free rubber with radiation shielding function. The tungsten-containing lead-free rubber includes modified rubber, composite fiber, zinc oxide, stearic acid, composite antioxidant, modified composite tungsten filler, carbon black, liquid paraffin, zinc borate, boron nitride, composite accelerator and sulfur; the modified rubber includes ethylene propylene diene monomer rubber and maleic anhydride; the modified composite tungsten filler includes composite tungsten filler, silane coupling agent KH-550 and dopamine.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The dispersion synergy of modified rubber and modified composite tungsten filler in the rough mixing step ensures that the modified composite tungsten filler is evenly distributed in the rubber matrix. The EPDM rubber is grafted with maleic anhydride to enhance polarity and compatibility, optimize the molecular chain structure and provide active sites, which improves the dispersion with modified composite tungsten filler; the composite tungsten filler is treated with silane coupling agent and coated with polydopamine coating to improve the surface activity, dispersion and bonding with rubber. The tungsten element can give full play to the shielding ability of X-rays, gamma rays, etc., solving the problem of poor shielding effect of rubber. The modified composite tungsten filler absorbs scattered rays, and the modified rubber stabilizes the network to assist in dispersing energy, which significantly improves the protective effectiveness of rubber in the field of radiation protection.

[0017] 2. While the modified composite tungsten filler, composite fiber, and carbon black each play their own role, there is also a synergistic relationship between the three. After the modified composite tungsten filler enhances the rigidity of the rubber matrix, it provides a more stable supporting environment for the composite fiber and carbon black, so that the skeleton structure of the composite fiber and the reinforcing effect of carbon black can be better exerted; the reinforcing network constructed by the composite fiber and carbon black assists the modified composite tungsten filler to be more evenly dispersed, avoiding the stress concentration problem caused by filler agglomeration. This multi-component, multi-step synergistic effect optimizes the molecular structure and filler distribution of the rubber, and significantly enhances the mechanical properties of the rubber.

[0018] 3. The composite antioxidant, zinc borate, and boron nitride work together with the refinement and mixing steps. The composite antioxidant effectively inhibits rubber oxidation, prevents molecular chain breakage, maintains the structural integrity of the rubber matrix, and avoids strength loss due to aging. Zinc borate forms a glassy protective film at high temperatures, which enhances the thermal stability of the rubber, reduces the thermal degradation of the molecular chain under high temperature conditions, and enables the rubber to maintain good tensile strength when used at high temperatures. Boron nitride, with its high thermal conductivity, quickly and evenly disperses heat to avoid local overheating that causes rubber performance degradation. At the same time, its special structure can enhance the stress transfer efficiency inside the rubber. The three are evenly dispersed during refinement and mixing, and work together to significantly improve the stability of the mechanical properties of the rubber.

[0019] 4. Zinc oxide, stearic acid, composite accelerator, sulfur and vulcanization steps work together. Zinc oxide reacts with stearic acid to form an activator, which reduces the activation energy of the vulcanization reaction, accelerates the vulcanization speed, and promotes the full cross-linking of the rubber molecular chains to form a dense three-dimensional network structure and improve the hardness of the rubber. The composite accelerator and sulfur constitute the core of the vulcanization system, regulate the cross-linking reaction process, optimize the cross-linking density and network uniformity, and give the rubber good tensile strength. The synergy of each component makes the vulcanization reaction more complete and controllable, reduces the phenomenon of under-sulfurization or over-sulfurization, enhances the interaction between molecular chains, and effectively improves the mechanical properties of rubber such as wear resistance and tear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is the preparation flow chart of the tungsten-containing lead-free rubber of the present invention. Specific Embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] Specifically refer to Figure 1 , the present invention provides a tungsten-containing lead-free rubber with radiation shielding function and its preparation method. The technical solutions are as follows: Example 1 Put 100 parts of ethylene propylene diene monomer rubber into a mixer, control the temperature at 70 °C, and obtain pretreated rubber after mixing for 8 minutes; add the pretreated rubber, 7 parts of maleic anhydride, 1 part of dicumyl peroxide and 0.5 part of 2,6-di-tert-butyl-4-methylphenol into the mixer for mixing, and mix at 90 °C for 10 minutes to obtain a mixed material; put the mixed material into a twin-screw extruder, set the screw temperature at 180 °C, the screw speed at 200 rpm, cut the extruded material into small pieces after staying for 3 minutes, wash with ethanol and dry to obtain modified rubber.

[0023] Dissolve 1 part of silane coupling agent KH-550 in 100 parts of absolute ethanol to obtain a silane coupling agent solution; add 45 parts of composite tungsten filler into the silane coupling agent solution, and ultrasonically disperse for 15 minutes to obtain a mixed filler; heat the mixed material in a water bath at 60 °C, continuously stir and react for 3 hours, wash and vacuum dry after the reaction to obtain pretreated composite tungsten filler; add 1.5 parts of dopamine into Tris-HCl buffer solution to prepare a dopamine solution; add the pretreated composite tungsten filler into the dopamine solution, stir for 22 hours, wash and vacuum dry after the reaction to obtain modified composite tungsten filler; the composite tungsten filler includes nano tungsten powder and bismuth tungstate, and the weight ratio of nano tungsten powder to bismuth tungstate is 6:3.

[0024] The composite fiber includes carbon fiber and glass fiber, and the weight ratio of carbon fiber to glass fiber is 3:1; the composite antioxidant includes antioxidant 4020 and antioxidant DDA, and the weight ratio of antioxidant 4020 to antioxidant DDA is 2:1.

[0025] Preheat the internal mixer and then charge the modified rubber. After plasticizing, softened rubber is obtained. Then, 13 parts of composite fiber, 4 parts of zinc oxide, 2 parts of stearic acid, and 3 parts of composite antioxidant are added in sequence, and mixing is continued for 4 min to obtain a premix. Subsequently, modified composite tungsten filler, 30 parts of carbon black, and 10 parts of liquid paraffin are added. The rotation speed of the internal mixer is increased to 70 rpm, the temperature is controlled at 120 °C, and mixing is carried out for 10 min. After discharging and cooling, a rough mix is obtained. Charge the rough mix into an internal mixer preheated to 75 °C and mix for 4 min to obtain a softened rough mix. Then, 3 parts of zinc borate and 2 parts of boron nitride are added, and mixing is continued for 7 min. After the mixing is completed, the colloid is discharged and cooled and parked for 10 h to obtain mother rubber. Set the roll temperature of the open mill to 45 °C, charge the mother rubber into the open mill, and thin pass 4 times to obtain treated mother rubber. Then, 1.5 parts of composite accelerator and 2 parts of sulfur are added, the roll gap is adjusted for re-mixing, the mixing time is 13 min, and after the mixing is completed, the sheet is taken off to obtain a rubber sheet. The rubber sheet is vulcanized at a vulcanization temperature of 165 °C, a vulcanization pressure of 15 MPa, and a vulcanization time of 25 min. After cooling, tungsten-containing lead-free rubber is obtained. The composite accelerator includes accelerator MBT and accelerator TMTD, and the weight ratio of accelerator MBT to accelerator TMTD is 3:2.

[0026] Examples 1-3 Refer to the parameter conditions in Example 1, and the specific differences are shown in Table 1.

[0027] The parameter conditions of Example 1, Example 4, Example 7, and Example 10 are the same.

[0028] Table 1 Parameter conditions of Examples 1-3

[0029] Comparative Example 1 Refer to the parameter conditions in Example 1, the difference is that the ethylene propylene diene monomer rubber is not subjected to graft modification.

[0030] Comparative Example 2 Refer to the parameter conditions in Example 1, the difference is that composite tungsten filler is added to replace the modified composite tungsten filler.

[0031] Comparative Example 3 Refer to the parameter conditions in Example 1, the difference is that only the composite tungsten filler is treated with a silane coupling agent.

[0032] Comparative Example 4 Refer to the parameter conditions in Example 1, the difference is that only the composite tungsten filler is coated with a polydopamine coating.

[0033] Experimental Example 1 Shielding performance test Prepare tungsten-containing lead-free rubber gloves from Examples 1-3 and Comparative Examples 1-4, and test the shielding performance of Examples 1-3 and Comparative Examples 1-4 according to the standard of GBZ / T 147-2002. The obtained results are shown in Table 2.

[0034] Table 2 Shielding Performance of Examples 1-3 and Comparative Examples 1-4

[0035] It can be found from Table 2 that in Comparative Example 1, the ethylene propylene diene monomer (EPDM) rubber was not graft-modified, and the rubber had low polarity and poor compatibility with the composite tungsten filler. During the mixing process, the composite tungsten filler was prone to agglomeration and could not be uniformly dispersed in the rubber matrix, resulting in a reduction in the effective area of shielding rays and unable to meet the requirements of radiation protection for material uniformity. In Comparative Example 2, the composite tungsten filler was used to replace the modified composite tungsten filler. The binding force between the surface of the untreated filler and the rubber matrix was weak, and the interfacial compatibility was poor. After the rubber was vulcanized, there were many voids and defects between the filler and the rubber, and the rays were easily penetrated from these weak points, resulting in a significant reduction in the shielding performance. In Comparative Example 3, only the composite tungsten filler was treated with a silane coupling agent. Although the partial interfacial binding force between the filler and the rubber was improved, the lack of further modification of the polydopamine coating, which can endow the filler with more active groups and enhance the interaction with the rubber, led to insufficient dispersion stability of the filler in the rubber, uneven distribution of the filler in some areas, and the lead equivalent uniformity could not meet the qualified standard. In Comparative Example 4, only the polydopamine coating was used for coating, and a stable organic layer was not formed on the filler surface through the treatment with a silane coupling agent. The binding between the polydopamine coating and the filler was not strong enough, and the coating was prone to falling off or shifting during the mixing and vulcanization processes, affecting the filler dispersion and shielding effect, resulting in a reduction in the lead equivalent uniformity and making it difficult to achieve uniform and efficient radiation shielding.

[0036] In summary, due to the enhanced polarity and compatibility, the modified rubber has a strong interaction with the surface-modified composite tungsten filler, promoting the uniform dispersion of the modified composite tungsten filler in the rubber matrix at the nanoscale, forming a stable dispersion system, and avoiding the decrease in shielding performance caused by filler agglomeration. When the rays are incident, the modified composite tungsten filler can preferentially absorb and scatter the rays, while the modified rubber ensures the stable distribution of the filler through a stable network structure and assists in dispersing the energy generated by the rays, preventing local energy concentration from leading to shielding failure. The two work together to greatly improve the radiation shielding performance of the rubber and effectively solve the problem of poor shielding performance of existing tungsten-containing lead-free rubber.

[0037] Examples 4-6 Referring to the parameter conditions in Example 4, the specific differences are shown in Table 3.

[0038] Table 3 Parameter Conditions of Examples 4-6

[0039] Comparative Example 5 Referring to the parameter conditions in Example 4, the difference is that no composite fiber is added.

[0040] Comparative Example 6 Referring to the parameter conditions in Example 4, the difference is that carbon black is not added.

[0041] Comparative Example 7 Referring to the parameter conditions in Example 4, the difference is that in the primary mixing process, the modified rubber, composite fiber, zinc oxide, stearic acid, and composite antioxidant are all added and mixed, and the subsequent treatment steps remain unchanged.

[0042] Comparative Example 8 Referring to the parameter conditions in Example 4, the difference is that only carbon fiber is added to replace the composite fiber.

[0043] Comparative Example 9 Referring to the parameter conditions in Example 4, the difference is that the modified composite tungsten filler is not added.

[0044] Experimental Example 2 Mechanical Property Test The tungsten-free lead rubber gloves were prepared from Examples 4-6 and Comparative Examples 5-9, and the mechanical properties of Examples 4-6 and Comparative Examples 5-9 were tested according to the GB 24541-2022 standard. The results are shown in Table 4.

[0045] Table 4 Mechanical Properties of Examples 4-6 and Comparative Examples 5-9

[0046] It can be found from Table 4 that the composite fiber plays a role in supporting the skeleton in the rubber, constructing a high-strength network structure. After the composite fiber is lacking in Comparative Example 5, there is a lack of effective support between the rubber molecular chains. When subjected to friction or tearing, the molecular chains are prone to relative sliding and breaking, resulting in a significant decrease in wear resistance and tear resistance. As an important reinforcing agent, carbon black can tightly bind to the rubber molecular chains with its high specific surface area and active groups, enhancing the interaction between the molecular chains. When carbon black is not added in Comparative Example 6, the force between the rubber molecular chains weakens, and the overall strength of the material decreases. During the wear and tear process, the molecular chains are difficult to resist the external force synergistically, resulting in a decrease in both wear resistance and tear resistance. In Comparative Example 7, all the materials were added at one time during the rough mixing, resulting in insufficient dispersion of each component. The modified rubber was mixed with other materials without sufficient plasticization, affecting the dispersion effect of the subsequent fillers and unable to form a uniform and stable reinforcement system. The uneven dispersion state causes stress concentration points inside the rubber. In the mechanical property test, the mechanical properties are significantly deteriorated. The composite fiber is composed of carbon fiber and glass fiber. The surface of the carbon fiber is relatively smooth and prone to agglomeration during dispersion in the rubber matrix, affecting the reinforcement effect; while there are a large number of hydroxyl groups on the surface of the glass fiber, which has better compatibility and dispersibility with the rubber matrix; the two complement each other in performance and jointly enhance the mechanical properties of the rubber. In Comparative Example 8, only carbon fiber is used. Although it has high-strength characteristics, it lacks the advantages of glass fiber in terms of toughness and dispersibility, resulting in a single internal reinforcement structure in the rubber. When resisting wear and tear, it is unable to effectively disperse the stress, and the wear resistance is unqualified. In Comparative Example 9, the modified composite tungsten filler is not added, resulting in a significant decrease in the mechanical properties of the rubber. After being treated with a silane coupling agent and coated with a polydopamine coating, the modified composite tungsten filler has good interfacial bonding force with the rubber matrix. In the rubber system, it can not only play a radiation shielding role but also enhance the rubber as a rigid particle. When this filler is not added, the rubber loses this important reinforcement source, lacks rigid support points inside, and is unable to effectively disperse and transfer the stress.

[0047] Therefore, the addition of modified composite tungsten filler, composite fiber, carbon black, and the reasonable mixing and feeding sequence are crucial for improving the mechanical properties of tungsten-containing lead-free rubber. After special treatment, the modified composite tungsten filler is uniformly dispersed in the rubber matrix as rigid particles and becomes the key nodes of stress transfer by virtue of its good interfacial bonding force with the rubber; the carbon fiber and glass fiber in the composite fiber complement each other in performance. The former provides high-strength rigid support, and the latter absorbs impact energy with good toughness. The two are uniformly dispersed in the rubber matrix to form a stable reinforcement framework; carbon black fills the gaps between rubber molecular chains with its high specific surface area and active groups, enhances the interaction between molecular chains, and jointly constructs a three-dimensional reinforcement network with the composite fiber. And the reasonable mixing and feeding sequence is the key to exerting the synergistic effect of the two. First, the modified rubber is plastically refined to create good conditions for the dispersion of subsequent components, and then the composite fiber, carbon black, etc. are added in turn. Under the shearing and stirring of the internal mixer, it is ensured that each component is fully dispersed and cooperates with each other. The synergistic effect of several components effectively disperses stress, enhances the bonding force between molecular chains, and significantly improves the mechanical properties such as wear resistance and tear resistance of the rubber.

[0048] Examples 7 - 9 Refer to the parameter conditions in Example 7, and the specific differences are shown in Table 5.

[0049] Table 5 Parameter Conditions of Examples 7 - 9

[0050] Comparative Example 10 Refer to the parameter conditions in Example 7, except that the composite antioxidant is not added.

[0051] Comparative Example 11 Refer to the parameter conditions in Example 7, except that zinc borate is not added.

[0052] Comparative Example 12 Refer to the parameter conditions in Example 7, except that boron nitride is not added.

[0053] Comparative Example 13 Refer to the parameter conditions in Example 7, except that zinc borate and boron nitride are not added.

[0054] Comparative Example 14 Refer to the parameter conditions in Example 7, except that only antioxidant 4020 is added to replace the composite antioxidant.

[0055] Comparative Example 15 Refer to the parameter conditions in Example 7, except that in the refined mixing, all the crude mixture, zinc borate, and boron nitride are added for mixing, and the subsequent treatment steps remain unchanged.

[0056] Experimental Example 3 Mechanical Property Test Put the gloves prepared in Experimental Examples 7 - 9 and Comparative Examples 10 - 15 into a photothermal aging oven for 48 h, and conduct tests according to the test method in Experimental Example 2. The obtained results are shown in Table 6.

[0057] Table 6 Mechanical Properties of Examples 7-9 and Comparative Examples 10-15

[0058] It can be found from Table 6 that the compound antioxidant can effectively inhibit the oxidative aging of rubber. After the compound antioxidant was missing in Comparative Example 10, during the processing and use of rubber, it was susceptible to factors such as oxygen and ultraviolet rays, resulting in the breakage and cross-linking of molecular chains, leading to the embrittlement of the rubber structure and a decrease in hardness. Zinc borate decomposes at high temperatures to form a vitreous protective layer, which plays a role in heat insulation and combustion inhibition. In Comparative Example 11, without the addition of zinc borate, heat easily invaded the interior of the rubber in a high-temperature environment, accelerating the degradation of molecular chains and destroying the stable structure of the rubber. Boron nitride can evenly disperse heat due to its high thermal conductivity, avoiding local overheating of the rubber. When boron nitride was missing in Comparative Example 12, during the process of the rubber being stressed or the environmental temperature changing, local heat accumulation occurred, triggering the deterioration of the properties of molecular chains. In Comparative Example 13, both zinc borate and boron nitride were missing. The rubber lacked both a heat-insulating protective layer and the ability to dissipate heat effectively. The destructive effect of high temperature on the rubber was significantly enhanced, the internal structure of the rubber was severely damaged, and the mechanical properties decreased significantly. Antioxidants 4020 and DDA in the compound antioxidant act synergistically to more comprehensively inhibit the aging of rubber. In Comparative Example 14, only antioxidant 4020 was used, which could not completely block all links of the oxidation reaction, resulting in insufficient anti-aging ability of the rubber and a decrease in mechanical properties. In Comparative Example 15, when the crude mixture, zinc borate, and boron nitride were all added during fine mixing, it would cause insufficient dispersion of zinc borate and boron nitride. The uneven dispersion prevented the formation of an effective thermal protection and stable structure inside the rubber. During wear and tear, the stress could not be evenly distributed, resulting in a decrease in mechanical properties.

[0059] In summary, antioxidants 4020 and DDA in the compound antioxidant cooperate with each other to capture free radicals and block the oxidative chain reaction, inhibiting the breakage and cross-linking of rubber molecular chains at the source and maintaining the structural integrity of the rubber matrix; zinc borate decomposes into an expansive vitreous protective film at high temperatures, isolating oxygen and heat and reducing the damage of thermo-oxidative aging to the rubber; boron nitride, due to its high thermal conductivity, quickly and evenly dissipates the heat generated inside the rubber, avoiding molecular chain degradation caused by local overheating. And the reasonable fine mixing steps are like a precise formulator, ensuring that the three are evenly dispersed in the rubber matrix at the nanoscale level at specific temperatures and rotation speeds of the internal mixer, forming a "anti-oxidation - heat insulation - heat dissipation" trinity protection system. The close cooperation of each component and process not only reduces the performance attenuation of rubber caused by aging and heat, but also synergistically disperses stress when stressed, significantly enhancing the mechanical properties such as wear resistance and tear resistance of the rubber.

[0060] Examples 10-12 Refer to the parameter conditions in Example 10, and the specific differences are shown in Table 7.

[0061] Table 7 Parameter Conditions of Examples 10-12

[0062] Comparative Example 16 Refer to the parameter conditions in Example 10, the difference is that no compound accelerator is added.

[0063] Comparative Example 17 Refer to the parameter conditions in Example 10, the difference is that accelerator MBT is added to replace the compound accelerator.

[0064] Comparative Example 18 Refer to the parameter conditions in Example 10, the difference is that no zinc oxide is added.

[0065] Comparative Example 19 Refer to the parameter conditions in Example 10, the difference is that no stearic acid is added.

[0066] Comparative Example 20 Refer to the parameter conditions in Example 10, the difference is that no sulfur is added.

[0067] Comparative Example 21 Refer to the parameter conditions in Example 10, the difference is that no kneading treatment is carried out.

[0068] Experimental Example 4 Mechanical Property Test Test Examples 10 - 12 and Comparative Examples 16 - 21 were tested with reference to the test method of Experimental Example 2, and the results are shown in Table 8.

[0069] Table 8 Mechanical Properties of Examples 10 - 12 and Comparative Examples 16 - 21

[0070] It can be found from Table 8 that the compound accelerator plays a key catalytic role in the vulcanization process, which can reduce the activation energy of the vulcanization reaction and accelerate the rubber cross-linking speed. When the compound accelerator is missing in Comparative Example 16, the rubber molecular chains are difficult to cross-link sufficiently, and the degree of vulcanization is insufficient. The formed three-dimensional network structure is loose and incomplete, which makes the weak network structure unable to effectively resist external forces in the wear resistance test and tear resistance test. The compound accelerator is composed of accelerator MBT and accelerator TMTD in a specific ratio, and their synergistic effect can optimize the vulcanization reaction process. In Comparative Example 17, only accelerator MBT is used, and the ideal vulcanization effect cannot be achieved. The speed and degree of the cross-linking reaction are limited, the cross-linking density of the rubber molecular chains is insufficient, the wear resistance is poor, and the mechanical properties of the rubber decline. Zinc oxide acts as an activator in the vulcanization system and reacts with stearic acid to form zinc soap, which can enhance the activity of the accelerator, improve the vulcanization efficiency and cross-linking density. In Comparative Examples 18-19, when zinc oxide or stearic acid is not added, the vulcanization reaction cannot proceed fully, the rubber cross-linking network structure is unstable, the binding force between molecular chains is weakened, and the ability of the rubber to resist wear and tear decreases in the mechanical property test. Sulfur is the key cross-linking agent for rubber vulcanization. The rubber molecular chains form sulfur bridges through reaction with sulfur to achieve cross-linking. In Comparative Example 20, sulfur is not added, and the rubber cannot form an effective three-dimensional network structure. Essentially, it is still a polymer with linear molecular chains, and its strength and toughness are extremely poor. The open mill treatment can make the masterbatch, compound accelerator and sulfur mix evenly, promote the dispersion of the vulcanizing agent in the rubber, and ensure the uniform progress of the vulcanization reaction. In Comparative Example 21, the open mill step is skipped, and the vulcanizing agent is unevenly distributed, resulting in inconsistent vulcanization degree in the rubber locally, over-cross-linking in some areas and under-cross-linking in some areas. This uneven structure greatly weakens the mechanical properties of the rubber.

[0071] In summary, the compound accelerator, zinc oxide, stearic acid, sulfur and the open mill process are closely coordinated to form an efficient and orderly system. The compound accelerator accelerates the rubber cross-linking reaction by reducing the activation energy of the vulcanization reaction; zinc oxide reacts with stearic acid to form zinc soap, which, as a "catalyst enhancer", further activates the activity of the accelerator and improves the vulcanization efficiency; sulfur, as the "cross-linking core", with the assistance of the accelerator and zinc soap, precisely constructs sulfur bridges between rubber molecular chains to form a dense three-dimensional network structure. The open mill process, relying on the shearing and mixing effects of the rollers, ensures the uniform dispersion of each component, allows the vulcanizing agent to fully penetrate the rubber matrix, and guarantees the uniform and full progress of the vulcanization reaction. Each component and process are closely linked and work together, not only enabling the rubber to achieve efficient vulcanization, but also effectively dispersing stress by virtue of the stable cross-linking network when stressed, significantly enhancing the wear resistance and tear resistance of the rubber.

[0072] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of tungsten-containing lead-free rubber with radiation shielding function, characterized in that: The preparation method comprises the following steps: The ethylene-propylene-diene monomer (EPDM) rubber is subjected to graft modification with maleic anhydride, and then cut into small pieces to obtain the modified rubber. The composite tungsten filler is treated with a silane coupling agent and coated with a polydopamine coating to obtain the modified composite tungsten filler. The modified rubber, composite fiber, zinc oxide, stearic acid, and composite antioxidant are sequentially added into a mixer. Then, the modified composite tungsten filler, carbon black, and liquid paraffin are added, and after rough mixing, a rough mixture is obtained. Zinc borate and boron nitride are added to the rough mixture, and after fine mixing, the masterbatch is obtained. A composite accelerator and sulfur are added to the masterbatch, and after open mixing and vulcanization, the tungsten-containing lead-free rubber is obtained.

2. The preparation method of a tungsten-containing lead-free rubber with radiation shielding function according to claim 1, characterized in that: By weight, the specific process of the graft modification is as follows: 95-105 parts of the EPDM rubber are put into a mixer, and after mixing for 8 min, the pretreated rubber is obtained. The pretreated rubber, 5-10 parts of maleic anhydride, 1 part of diisopropylbenzene peroxide, and 0.5 part of 2,6-di-tert-butyl-4-methylphenol are added to the mixer for mixing. The mixture is mixed at 90 °C for 5-15 min to obtain a mixed material. The mixed material is put into a twin-screw extruder, and after staying for 3 min, the extruded material is cut into small pieces, washed, and dried to obtain the modified rubber.

3. The preparation method of a tungsten-containing lead-free rubber with radiation shielding function according to claim 1, characterized in that: By weight, the specific preparation method of the modified composite tungsten filler is as follows: 0.5-1.5 parts of silane coupling agent KH-550 are dissolved in 100 parts of absolute ethanol to obtain a silane coupling agent solution. 40-50 parts of the composite tungsten filler are added to the silane coupling agent solution, and ultrasonic dispersion is carried out to obtain a mixed filler. The mixed filler is heated in a water bath at 60 °C, and continuously stirred and reacted for 3 h. After the reaction is completed, it is washed and vacuum dried to obtain the pretreated composite tungsten filler. 1.5 parts of dopamine are added to a Tris-HCl buffer solution to prepare a dopamine solution. The pretreated composite tungsten filler is added to the dopamine solution, and stirred for 20-24 h. After the reaction is completed, it is washed and vacuum dried to obtain the modified composite tungsten filler. The composite tungsten filler comprises nano tungsten powder and bismuth tungstate, and the weight ratio of the nano tungsten powder to the bismuth tungstate is 5-7:

3.

4. The preparation method of a tungsten-containing lead-free rubber with radiation shielding function according to claim 1, characterized in that: The composite fiber comprises carbon fiber and glass fiber, and the weight ratio of the carbon fiber to the glass fiber is 2-4:

1.

5. The preparation method of a tungsten-containing lead-free rubber with radiation shielding function according to claim 1, characterized in that: The composite antioxidant comprises antioxidant 4020 and antioxidant DDA, and the weight ratio of the antioxidant 4020 to the antioxidant DDA is 1-3:

1.

6. The preparation method of a tungsten-containing lead-free rubber with radiation shielding function according to claim 1, characterized in that: By weight parts, the specific process of the rough mixing treatment is as follows: After preheating the internal mixer, put the modified rubber into it, and obtain softened rubber after plasticizing; then successively add 11 - 15 parts of the composite fiber, 3 - 5 parts of the zinc oxide, 1 - 3 parts of the stearic acid and 1 - 5 parts of the composite antioxidant, and continue mixing for 3 min - 5 min to obtain a premix; subsequently add the modified composite tungsten filler, 25 - 35 parts of the carbon black and the liquid paraffin, increase the rotational speed of the internal mixer to 60 rpm - 80 rpm, control the temperature at 110°C - 130°C, mix for 8 min - 12 min, and obtain the rough mix after discharging the rubber and cooling.

7. The preparation method of a tungsten-containing lead-free rubber with radiation shielding function according to claim 1, characterized in that: By weight parts, the specific process of the refining mixing is as follows: Put the rough mix into an internal mixer preheated to 70°C - 80°C, mix for 3 min - 5 min to obtain a softened rough mix; then add 2 - 4 parts of the zinc borate and 1 - 3 parts of the boron nitride, and continue mixing for 5 min - 9 min. After the mixing is completed, discharge the colloid, cool and store it to obtain the masterbatch.

8. The preparation method of a tungsten-containing lead-free rubber with radiation shielding function according to claim 1, characterized in that: By weight parts, the specific process of the open mill and vulcanization treatment is as follows: Set the roll temperature of the open mill to 45°C, put the masterbatch into the open mill, and thin pass 3 - 5 times to obtain a treated masterbatch; then add 1 - 2 parts of the composite accelerator and 1 - 3 parts of the sulfur, adjust the roll gap for re - mixing, and the mixing time is 11 min - 15 min. After the mixing is completed, take off the sheet to obtain a rubber sheet; vulcanize the rubber sheet, the vulcanization temperature is 160°C - 170°C, the vulcanization pressure is 15 MPa, and the vulcanization time is 20 min - 30 min. After cooling, obtain the tungsten - containing lead - free rubber; the composite accelerator includes accelerator MBT and accelerator TMTD, and the weight ratio of accelerator MBT to accelerator TMTD is 3:1 - 3.

9. A tungsten-containing lead-free rubber with radiation shielding function, characterized in that: The tungsten - containing lead - free rubber is prepared by the preparation method according to any one of claims 1 - 8; the tungsten - containing lead - free rubber includes modified rubber, composite fiber, zinc oxide, stearic acid, composite antioxidant, modified composite tungsten filler, carbon black, liquid paraffin, zinc borate, boron nitride, composite accelerator and sulfur; the modified rubber includes ethylene - propylene - diene monomer rubber and maleic anhydride; the modified composite tungsten filler includes composite tungsten filler, silane coupling agent KH - 550 and dopamine.

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