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

Abstract

The present invention relates to the field of radiation protection technology, and specifically to a tungsten-containing lead-free rubber with radiation shielding function and a preparation method thereof. The present invention overcomes the problems of poor shielding performance and poor mechanical properties of current tungsten-containing lead-free rubber. The present invention first performs maleic anhydride grafting modification on EPDM rubber, and performs silane coupling agent treatment and polydopamine coating on the composite tungsten filler; then, the modified rubber, composite fiber and other components are sequentially put into an internal mixer for coarse mixing and fine mixing, and then the tungsten-containing lead-free rubber is obtained through open mixing and vulcanization treatment. The synergistic effect between the various materials and processes enables the rubber to have both excellent radiation shielding performance and mechanical properties, and can replace traditional lead rubber materials, with good application prospects.

Description

Technical Field

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

[0002] In the field of radiation protection, traditional radiation shielding materials, such as lead rubber, have good shielding properties, but lead is toxic and poses potential hazards to the environment and human health. Furthermore, it is bulky and inconvenient to use in certain applications. With people's increasing emphasis on health and environmental protection, and the widespread application of nuclear technology in medicine, industry, energy, and other fields, the demand for environmentally friendly, efficient, and lightweight radiation shielding materials is becoming increasingly urgent. This is where tungsten-containing lead-free rubber comes in.

[0003] Existing technology utilizes tungsten's high density and atomic number, which provide excellent shielding capabilities against X-rays, gamma rays, and other radiation-shielding materials. By adding tungsten to a rubber matrix in a suitable form, this material can be prepared. Furthermore, based on the specific characteristics of different rubber matrices, such as natural rubber, nitrile rubber, and silicone rubber, various additives and fillers are added to modify the rubber matrix, thereby improving the material's mechanical properties, processing characteristics, and aging resistance to suit different application scenarios.

[0004] Although existing technologies have achieved the preliminary preparation and performance optimization of tungsten-containing lead-free rubber, technical problems still exist in actual research and development and application. For example, how to accurately control the dispersion of tungsten in the rubber matrix to avoid agglomeration to ensure the uniformity of the material's shielding performance; how to further improve the interfacial bonding between the rubber matrix and tungsten so that the material's mechanical and shielding properties remain stable during long-term use are both difficult problems that need to be solved urgently. In summary, today's tungsten-containing lead-free rubber has problems with poor shielding performance and poor mechanical properties, which cannot meet market demand.

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

[0006] The present invention aims to design a tungsten-containing, lead-free rubber with radiation shielding properties and its preparation method. This method first involves grafting maleic anhydride onto EPDM rubber, treating the composite tungsten filler with a silane coupling agent, and coating it with a polydopamine coating. The modified rubber, composite fiber, and other components are then sequentially placed in an internal mixer for coarse and fine mixing. The resulting product undergoes open mixing and vulcanization to produce the tungsten-containing, lead-free rubber. The synergistic effects of these materials and processes result in a rubber with both excellent radiation shielding and mechanical properties, making it a viable alternative to traditional lead rubber materials and promising for future applications.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] In one aspect, the present invention provides a method for preparing tungsten-containing lead-free rubber with radiation shielding function, the preparation method comprising the following steps:

[0009] EPDM rubber is grafted with maleic anhydride and then cut into small pieces to obtain modified rubber;

[0010] The composite tungsten filler is treated with a silane coupling agent and coated with a polydopamine coating to obtain a modified composite tungsten filler;

[0011] In an internal mixer, modified rubber, composite fiber, zinc oxide, stearic acid and composite antioxidant are sequentially added, followed by the addition of modified composite tungsten filler, carbon black and liquid paraffin, and rough mixing is performed to obtain a coarse mixture; zinc borate and boron nitride are added to the coarse mixture, and fine mixing is performed to obtain a masterbatch;

[0012] A composite accelerator and sulfur are added to the masterbatch for refining and vulcanization to obtain tungsten-containing lead-free rubber.

[0013] Preferably, the specific process of the graft modification treatment is as follows, by weight: 95-105 parts of EPDM rubber are placed in an internal mixer, the temperature is controlled at 70°C, and the internal mixer is kneaded for 8 minutes to obtain a pretreated rubber; the pretreated rubber, 5-10 parts of maleic anhydride, 1 part of dicumyl peroxide and 0.5 part of 2,6-di-tert-butyl-4-methylphenol are added to the internal mixer for mixing, and the mixture is mixed at 90°C for 5-15 minutes to obtain a mixture; the mixture is placed in a twin-screw extruder, the screw temperature is set to 180°C, the screw speed is 200 rpm, and after staying for 3 minutes, the extruded material is cut into small pieces, washed with ethanol and dried to obtain a modified rubber.

[0014] Preferably, the specific preparation method of the modified composite tungsten filler is as follows, in parts by weight: dissolving 0.5-1.5 parts of a silane coupling agent KH-550 in 100 parts of anhydrous ethanol to obtain a silane coupling agent solution; adding 40-50 parts of a composite tungsten filler to the silane coupling agent solution, and ultrasonically dispersing for 15 minutes to obtain a mixed filler; heating the mixed filler in a water bath at 60° C., stirring continuously for a reaction of 3 hours, and washing and vacuum drying after the reaction to obtain a pretreated composite tungsten filler; adding 1.5 parts of dopamine to a Tris-HCl buffer to prepare a dopamine solution; adding the pretreated composite tungsten filler to the dopamine solution, stirring for 20 hours to 24 hours, and washing and vacuum drying after the reaction to obtain a modified composite tungsten filler; the composite tungsten filler includes nano tungsten powder and bismuth tungstate, and the weight ratio of the nano tungsten powder to the bismuth tungstate is 5-7:3.

[0015] Preferably, the composite fiber comprises carbon fiber and glass fiber, and the weight ratio of carbon fiber to glass fiber is 2-4:1.

[0016] Preferably, the composite antioxidant includes antioxidant 4020 and antioxidant DDA, and the weight ratio of antioxidant 4020 to antioxidant DDA is 1-3:1.

[0017] Preferably, the specific process of the rough mixing treatment is as follows, by weight: the modified rubber is added after preheating the internal mixer, and the softened rubber is obtained after plasticizing; then 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 are added in sequence, and mixing is continued for 3min-5min to obtain a premix; then modified composite tungsten filler, 25-35 parts of carbon black and 10 parts of liquid paraffin are added, the speed of the internal mixer is increased to 60rpm-80rpm, the temperature is controlled at 110℃-130℃, mixing is carried out for 8min-12min, and the rough mixture is obtained after the glue is discharged and cooled.

[0018] Preferably, the specific process of fine mixing is as follows, based on parts by weight: the coarse mix is ​​put into an internal mixer preheated to 70°C-80°C, and mixed for 3-5 minutes to obtain a softened coarse mix; then 2-4 parts of zinc borate and 1-3 parts of boron nitride are added, and mixing is continued for 5-9 minutes. After the mixing is completed, the colloid is discharged and cooled and allowed to stand for 10 hours to obtain a masterbatch.

[0019] Preferably, the specific process of the open mill and vulcanization treatment is: setting the roller temperature of the open mill to 45°C, putting the masterbatch into the open mill, and thinning it 3-5 times to obtain the treated masterbatch; then adding 1-2 parts of the composite accelerator and 1-3 parts of sulfur, adjusting the roller spacing for refining, the mixing time is 11min-15min, and after the mixing is completed, the sheet is removed to obtain a film; the film is vulcanized at a vulcanization temperature of 160°C-170°C, a vulcanization pressure of 15MPa, and a vulcanization time of 20min-30min. After the end, it is cooled to obtain a 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.

[0020] 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, a composite antioxidant, a modified composite tungsten filler, carbon black, liquid paraffin, zinc borate, boron nitride, a composite accelerator and sulfur; the modified rubber includes EPDM rubber and maleic anhydride; the modified composite tungsten filler includes a composite tungsten filler, a silane coupling agent KH-550 and dopamine.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The synergistic dispersion of the modified rubber and modified composite tungsten filler during the rough mixing step ensures the modified composite tungsten filler is evenly distributed within the rubber matrix. Maleic anhydride grafting modification of EPDM rubber enhances polarity and compatibility, optimizes the molecular chain structure, and provides active sites, improving its dispersibility with the modified composite tungsten filler. Treatment of the composite tungsten filler with a silane coupling agent and coating with a polydopamine coating enhances its surface activity, dispersibility, and adhesion to the rubber. The tungsten element can fully demonstrate its shielding capabilities against X-rays, gamma rays, and other radiation, resolving the issue of poor rubber shielding effectiveness. The modified composite tungsten filler absorbs scattered radiation, while the modified rubber stabilizes the network and assists in dispersing energy, significantly enhancing the protective effectiveness of rubber in the field of radiation protection.

[0023] 2. While the modified composite tungsten filler, composite fiber, and carbon black each play their own role, a synergistic relationship exists among them. The modified composite tungsten filler enhances the rigidity of the rubber matrix, providing a more stable support environment for the composite fiber and carbon black, enabling the composite fiber's skeletal structure and carbon black's reinforcing effects to be better utilized. The reinforcing network created by the composite fiber and carbon black helps the modified composite tungsten filler to disperse more evenly, avoiding stress concentration caused by filler agglomeration. This multi-component, multi-step synergistic effect optimizes the rubber's molecular structure and filler distribution, significantly enhancing the rubber's mechanical properties.

[0024] 3. The composite antioxidant, zinc borate, and boron nitride work synergistically 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, enhancing the rubber's thermal stability and reducing thermal degradation of molecular chains in high-temperature environments, allowing the rubber to maintain good tensile strength even during high-temperature use. Boron nitride, with its high thermal conductivity, quickly and evenly disperses heat, preventing localized overheating that can degrade rubber properties. Its unique structure also enhances the efficiency of stress transfer within the rubber. All three are evenly dispersed during refinement and mixing, working together to significantly improve the mechanical stability of the rubber.

[0025] 4. Zinc oxide, stearic acid, a composite accelerator, and sulfur work synergistically with the vulcanization process. Zinc oxide reacts with stearic acid to form an activator, which reduces the activation energy of the vulcanization reaction, accelerates the vulcanization process, and promotes full crosslinking of the rubber molecular chains, forming a dense three-dimensional network structure and improving rubber hardness. The composite accelerator and sulfur form the core of the vulcanization system, regulating the crosslinking reaction process, optimizing crosslink density and network uniformity, and imparting excellent tensile strength to the rubber. These components work together to ensure a more complete and controllable vulcanization reaction, reduce under- or over-vulcanization, enhance inter-chain interactions, and effectively improve the rubber's mechanical properties, such as wear resistance and tear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1The figure is a flow chart for preparing the tungsten-containing lead-free rubber of the present invention. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] Specific reference Figure 1 The present invention provides a tungsten-containing lead-free rubber with radiation shielding function and a preparation method thereof. The technical solution is as follows:

[0029] Example 1

[0030] 100 parts of EPDM rubber were placed in an internal mixer, the temperature was controlled at 70°C, and the mixing was carried out for 8 minutes to obtain a pretreated rubber; the pretreated rubber, 7 parts of maleic anhydride, 1 part of dicumyl peroxide and 0.5 parts of 2,6-di-tert-butyl-4-methylphenol were added to the internal mixer and mixed, and the mixing was carried out at 90°C for 10 minutes to obtain a mixture; the mixture was placed in a twin-screw extruder, the screw temperature was set to 180°C, the screw speed was set to 200 rpm, and after staying for 3 minutes, the extruded material was cut into small pieces, washed with ethanol and dried to obtain a modified rubber.

[0031] 1 part of silane coupling agent KH-550 is dissolved in 100 parts of anhydrous ethanol to obtain a silane coupling agent solution; 45 parts of composite tungsten filler are added to the silane coupling agent solution and ultrasonically dispersed for 15 minutes to obtain a mixed filler; the mixture is heated in a water bath at 60°C, continuously stirred and reacted for 3 hours, and 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 to prepare a dopamine solution; the pretreated composite tungsten filler is added to the dopamine solution, stirred for 22 hours, 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 the nano tungsten powder to the bismuth tungstate is 6:3.

[0032] 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.

[0033] After preheating the internal mixer, the modified rubber was added and plasticized to obtain a softened rubber; then 13 parts of composite fiber, 4 parts of zinc oxide, 2 parts of stearic acid and 3 parts of composite antioxidant were added in sequence and mixed for 4 minutes to obtain a premix; then the modified composite tungsten filler, 30 parts of carbon black and 10 parts of liquid paraffin were added, the speed of the internal mixer was increased to 70 rpm, the temperature was controlled at 120°C, and mixing was carried out for 10 minutes. After the rubber was discharged and cooled, a coarse mixture was obtained;

[0034] The coarse mixture was placed in an internal mixer preheated to 75°C and mixed for 4 minutes to obtain a softened coarse mixture; then 3 parts of zinc borate and 2 parts of boron nitride were added and mixed for another 7 minutes. After the mixing was completed, the colloid was discharged and cooled for 10 hours to obtain a masterbatch;

[0035] The roller temperature of the mixing mill was set to 45°C, and the masterbatch was put into the mixing mill and thinned 4 times to obtain the processed masterbatch; then 1.5 parts of the composite accelerator and 2 parts of sulfur were added, and the roller spacing was adjusted for refining. The mixing time was 13 minutes. After the mixing was completed, the sheet was removed to obtain a film; the film was vulcanized at a vulcanization temperature of 165°C, a vulcanization pressure of 15 MPa, and a vulcanization time of 25 minutes. After the end, the film was cooled to obtain a tungsten-containing lead-free rubber; the composite accelerator included accelerator MBT and accelerator TMTD, and the weight ratio of accelerator MBT to accelerator TMTD was 3:2.

[0036] Examples 1-3 Referring to the parameter conditions in Example 1, the specific differences are shown in Table 1.

[0037] The parameter conditions of Example 1, Example 4, Example 7 and Example 10 are all the same.

[0038] Table 1 Parameter conditions of Examples 1-3

[0039]

[0040] Comparative Example 1 The parameters and conditions in Example 1 are referred to, except that the EPDM rubber is not graft-modified.

[0041] Comparative Example 2 The parameters and conditions in Example 1 are referred to, except that a composite tungsten filler is added instead of the modified composite tungsten filler.

[0042] Comparative Example 3 The parameters and conditions in Example 1 were used with the exception that only the composite tungsten filler was treated with the silane coupling agent.

[0043] Comparative Example 4 The parameters and conditions in Example 1 are referred to, except that only the composite tungsten filler is coated with the polydopamine coating.

[0044] Experimental Example 1 Shielding Performance Test

[0045] Examples 1-3 and Comparative Examples 1-4 were prepared into tungsten-containing lead-free rubber gloves. The shielding properties of Examples 1-3 and Comparative Examples 1-4 were tested according to GBZ / T 147-2002. The results are shown in Table 2.

[0046] Table 2 Shielding performance of Examples 1-3 and Comparative Examples 1-4

[0047]

[0048] Table 2 shows that in Comparative Example 1, the EPDM rubber was not graft-modified. The rubber has low polarity and poor compatibility with the composite tungsten filler. During mixing, the composite tungsten filler easily agglomerated and could not be evenly dispersed in the rubber matrix, resulting in a reduction in the effective radiation shielding area and failing to meet the material uniformity requirements for radiation protection. In Comparative Example 2, the composite tungsten filler was used instead of the modified composite tungsten filler. The untreated filler surface had weak adhesion to the rubber matrix and poor interfacial compatibility. After vulcanization, numerous gaps and defects existed between the filler and the rubber, allowing radiation to easily penetrate through these weak points, significantly reducing shielding performance. In Comparative Example 3, the composite tungsten filler was treated only with a silane coupling agent. While this improved some of the interfacial adhesion between the filler and the rubber, it lacked the further modification of a polydopamine coating, which imparts more reactive groups to the filler and enhances its interaction with the rubber. This lack of a polydopamine coating resulted in insufficient filler dispersion stability in the rubber, uneven filler distribution in some areas, and failure to meet the qualified lead equivalent uniformity standards. In Comparative Example 4, only polydopamine coating was performed, and no silane coupling agent treatment was performed to form a stable organic layer on the filler surface. The bond between the polydopamine coating and the filler was not strong enough. During the mixing and vulcanization process, the coating was easy to fall off or shift, affecting the dispersion and shielding effect of the filler, reducing the uniformity of the lead equivalent, and making it difficult to achieve uniform and efficient radiation shielding.

[0049] In summary, the modified rubber, thanks to its enhanced polarity and compatibility, interacts strongly with the surface-modified composite tungsten filler, causing the modified composite tungsten filler to be evenly dispersed at the nanoscale within the rubber matrix, forming a stable dispersion system and preventing filler agglomeration from causing a decrease in shielding performance. When radiation is incident, the modified composite tungsten filler preferentially absorbs and scatters the radiation. The modified rubber, through its stable network structure, ensures a stable distribution of the filler and assists in dispersing the energy generated by the radiation, preventing localized energy concentration from leading to shielding failure. The synergistic effect of these two factors significantly enhances the rubber's radiation shielding performance, effectively resolving the poor shielding performance of existing tungsten-containing, lead-free rubbers.

[0050] Example 4-6 Referring to the parameter conditions in Example 4, the specific differences are shown in Table 3.

[0051] Table 3 Parameter conditions of Examples 4-6

[0052]

[0053] Comparative Example 5 The parameters and conditions in Example 4 were referred to, except that no composite fiber was added.

[0054] Comparative Example 6 The parameters and conditions in Example 4 were referred to, except that no carbon black was added.

[0055] Comparative Example 7 The parameters and conditions in Example 4 are referred to, except that the modified rubber, composite fiber, zinc oxide, stearic acid and composite antioxidant are all added and mixed in the rough mixing process, and the subsequent processing steps remain unchanged.

[0056] Comparative Example 8 The parameters and conditions in Example 4 are referred to, except that only carbon fibers are added instead of composite fibers.

[0057] Comparative Example 9 The parameters and conditions in Example 4 were referred to, except that the modified composite tungsten filler was not added.

[0058] Experimental Example 2 Mechanical Properties Test

[0059] Examples 4-6 and Comparative Examples 5-9 were prepared into tungsten-containing lead-free rubber gloves. The mechanical properties of Examples 4-6 and Comparative Examples 5-9 were tested according to GB 24541-2022. The results are shown in Table 4.

[0060] Table 4 Mechanical properties of Examples 4-6 and Comparative Examples 5-9

[0061]

[0062] It can be seen from Table 4 that the composite fiber plays a skeletal supporting role in the rubber, constructing a high-strength network structure. In Comparative Example 5, the lack of composite fibers results in 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. Carbon black, as an important reinforcing agent, has a high specific surface area and active groups that can tightly bind to the rubber molecular chains, enhancing the interaction between the molecular chains. When no carbon black was added in Comparative Example 6, the interaction between the rubber molecular chains was weakened, and the overall strength of the material was reduced. During the wear and tear process, the molecular chains found it difficult to cooperate to resist external forces, resulting in a decrease in both wear resistance and tear resistance. In Comparative Example 7, all materials were added at once during rough mixing, resulting in the inability to fully disperse the components. The modified rubber was mixed with other materials before being fully plasticized, affecting the subsequent dispersion effect of the filler, and it was impossible to form a uniform and stable reinforcement system. The uneven dispersion state caused stress concentration points to exist inside the rubber, and in the mechanical property test, the mechanical properties were significantly deteriorated. Composite fibers are composed of carbon fibers and glass fibers. The surface of carbon fibers is relatively smooth and tends to agglomerate when dispersed in the rubber matrix, affecting the reinforcement effect. Glass fibers, on the other hand, have a large number of hydroxyl groups on their surface, which improves compatibility with the rubber matrix and allows for better dispersion. The two complement each other and together enhance the mechanical properties of the rubber. Comparative Example 8 uses only carbon fibers. Although it has high strength properties, it lacks the toughness and dispersibility advantages of glass fibers. This results in a single internal reinforcement structure for the rubber, which is unable to effectively disperse stress when resisting wear and tear, and its wear resistance is unqualified. Comparative Example 9 does not add modified composite tungsten filler, 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 with the rubber matrix. In the rubber system, it not only plays a radiation shielding role but also acts as a rigid particle to reinforce the rubber. Without this filler, the rubber loses this important source of reinforcement, lacks rigid support points internally, and is unable to effectively disperse and transmit stress.

[0063] Therefore, the addition of modified composite tungsten fillers, composite fibers, and carbon black, along with the appropriate mixing and adding sequence, is crucial for enhancing the mechanical properties of tungsten-containing, lead-free rubber. After special processing, the modified composite tungsten filler is uniformly dispersed within the rubber matrix as rigid particles. Thanks to its excellent interfacial bonding with the rubber, it serves as a key node for stress transfer. The carbon fibers and glass fibers in the composite fibers complement each other: the former provides high-strength rigid support, while the latter absorbs impact energy with its excellent toughness. Together, they form a stable, reinforcing framework, uniformly dispersed within the rubber matrix. Carbon black, with its high surface area and active groups, fills the gaps between the rubber molecular chains, enhancing interchain interactions and, together with the composite fibers, forming a three-dimensional reinforcement network. The optimal mixing and adding sequence is crucial for unleashing the synergistic effects of these two components. The modified rubber is first plasticized to create optimal conditions for the subsequent dispersion of the components. The composite fibers, carbon black, and other components are then added sequentially. The shear and agitation of the internal mixer ensures that the components are fully dispersed and interact with each other. The synergistic effect effectively disperses stress, strengthens interchain bonding, and significantly enhances the rubber's mechanical properties, such as wear and tear resistance.

[0064] Examples 7-9 refer to the parameter conditions in Example 7, with specific differences as shown in Table 5.

[0065] Table 5 Parameter conditions of Examples 7-9

[0066]

[0067] Comparative Example 10 The parameters and conditions in Example 7 were referred to, except that no composite antioxidant was added.

[0068] Comparative Example 11 The parameters and conditions in Example 7 were referred to, except that zinc borate was not added.

[0069] Comparative Example 12 The parameters and conditions in Example 7 were referred to, except that no boron nitride was added.

[0070] Comparative Example 13 The parameters and conditions in Example 7 were referred to, except that zinc borate and boron nitride were not added.

[0071] Comparative Example 14 The parameters and conditions in Example 7 are referred to, except that only antioxidant 4020 is added instead of the composite antioxidant.

[0072] Comparative Example 15 The parameters and conditions in Example 7 are referred to, except that the coarse mixture, zinc borate and boron nitride are all added and mixed during the fine mixing, and the subsequent processing steps remain unchanged.

[0073] Experimental Example 3 Mechanical Properties Test

[0074] The gloves prepared in Experimental Examples 7-9 and Comparative Examples 10-15 were placed in a light-heat aging chamber for 48 hours and tested according to the test method of Experimental Example 2. The results are shown in Table 6.

[0075] Table 6 Mechanical properties of Examples 7-9 and Comparative Examples 10-15

[0076]

[0077] Table 6 shows that the composite antioxidant can effectively inhibit the oxidative aging of rubber. In Comparative Example 10, the composite antioxidant is missing. During processing and use, the rubber is susceptible to factors such as oxygen and ultraviolet rays, causing molecular chain breakage and crosslinking, resulting in brittle rubber structure and reduced hardness. Zinc borate decomposes at high temperatures to form a glassy protective layer, which provides insulation and inhibits combustion. In Comparative Example 11, zinc borate is not added. Heat easily penetrates the rubber under high temperature conditions, accelerating molecular chain degradation and destroying the rubber's stable structure. Boron nitride, with its high thermal conductivity, evenly distributes heat, preventing local overheating of the rubber. In Comparative Example 12, the lack of boron nitride causes localized heat accumulation in the rubber when subjected to stress or changes in ambient temperature, leading to degradation of the molecular chain performance. In Comparative Example 13, both zinc borate and boron nitride are missing. The rubber lacks a thermal insulation protective layer and cannot effectively dissipate heat. The destructive effects of high temperatures on the rubber are significantly enhanced, severely damaging the rubber's internal structure and significantly reducing its mechanical properties. The antioxidant 4020 and antioxidant DDA in the composite antioxidant work synergistically to more comprehensively inhibit rubber aging. Comparative Example 14, which used only antioxidant 4020, failed to completely block all stages of the oxidation reaction, resulting in insufficient rubber anti-aging and reduced mechanical properties. Comparative Example 15, in which the coarse mix, zinc borate, and boron nitride were all added during fine mixing, prevented the zinc borate and boron nitride from being fully dispersed. This uneven dispersion prevented effective thermal protection and a stable structure from forming within the rubber. Consequently, stress was not evenly distributed during wear and tear, resulting in reduced mechanical properties.

[0078] In summary, antioxidants 4020 and DDA in the composite antioxidant work together to capture free radicals and block oxidative chain reactions, fundamentally inhibiting rubber chain breakage and crosslinking, thereby maintaining the structural integrity of the rubber matrix. Zinc borate decomposes into an expandable glassy protective film at high temperatures, isolating oxygen and heat, reducing the damage to the rubber caused by thermal oxidative aging. Boron nitride, with its high thermal conductivity, quickly and evenly dissipates heat generated within the rubber, preventing localized overheating and molecular chain degradation. The carefully selected mixing steps act like a precise blender, ensuring that all three ingredients are uniformly dispersed at the nanometer scale within the rubber matrix at the specified internal mixer temperature and speed, forming a trinity of "antioxidant, thermal insulation, and heat dissipation" protection. The close coordination of these components and the process not only reduces the performance degradation of the rubber due to aging and thermal effects, but also synergistically distributes stress when subjected to stress, significantly enhancing the rubber's mechanical properties, such as wear and tear resistance.

[0079] Examples 10-12 Referring to the parameter conditions in Example 10, the specific differences are shown in Table 7.

[0080] Table 7 Parameter conditions of Examples 10-12

[0081]

[0082] Comparative Example 16 The parameters and conditions in Example 10 were used with the exception that no composite accelerator was added.

[0083] Comparative Example 17 The parameters and conditions in Example 10 are referred to, except that the accelerator MBT is added instead of the composite accelerator.

[0084] Comparative Example 18 The parameters and conditions in Example 10 were the same, except that zinc oxide was not added.

[0085] Comparative Example 19 The parameters and conditions in Example 10 were the same, except that stearic acid was not added.

[0086] Comparative Example 20 The parameters and conditions in Example 10 were the same, except that sulfur was not added.

[0087] Comparative Example 21 The parameters and conditions in Example 10 were referred to, except that no open milling treatment was performed.

[0088] Experimental Example 4 Mechanical Properties Test

[0089] 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.

[0090] Table 8 Mechanical properties of Examples 10-12 and Comparative Examples 16-21

[0091]

[0092] As can be seen from Table 8, the composite accelerator plays a key catalytic role in the vulcanization process, which can reduce the activation energy of the vulcanization reaction and accelerate the crosslinking speed of the rubber. When the composite accelerator is missing in Comparative Example 16, the rubber molecular chains are difficult to fully crosslink, the degree of vulcanization is insufficient, and the three-dimensional network structure formed is loose and incomplete. This makes the rubber's weak network structure unable to effectively resist external forces in the wear resistance test and tear resistance test. The composite accelerator is composed of accelerator MBT and accelerator TMTD in a specific ratio. The synergistic effect of the two can optimize the vulcanization reaction process. Comparative Example 17 uses only accelerator MBT, which cannot achieve the ideal vulcanization effect. The speed and degree of the crosslinking reaction are limited, the crosslinking density of the rubber molecular chains is insufficient, the wear resistance is poor, and the mechanical properties of the rubber are reduced. Zinc oxide acts as an active agent in the vulcanization system and reacts with stearic acid to form zinc soap, which can enhance the activity of the accelerator and improve the vulcanization efficiency and crosslinking density. In Comparative Examples 18-19, no zinc oxide or stearic acid was added, and the vulcanization reaction could not proceed fully, the cross-linked network structure of the rubber was unstable, the bonding force between the molecular chains was weakened, and in the mechanical property test, the ability of the rubber to resist wear and tear was reduced. Sulfur is a key cross-linking agent for rubber vulcanization. The rubber molecular chains form sulfur bridges by reacting with sulfur to achieve cross-linking. In Comparative Example 20, no sulfur was added, and the rubber could not form an effective three-dimensional network structure. In essence, it was still a polymer of linear molecular chains with extremely poor strength and toughness. The open milling process can fully mix the masterbatch with the composite accelerator and sulfur, promote the dispersion of the vulcanizing agent in the rubber, and ensure that the vulcanization reaction proceeds evenly. Comparative Example 21 skipped the open milling step, and the vulcanizing agent was unevenly distributed, resulting in inconsistent local vulcanization degrees of the rubber, excessive cross-linking in some areas, and insufficient cross-linking in some areas. This uneven structure greatly weakened the mechanical properties of the rubber.

[0093] In summary, the composite accelerator, zinc oxide, stearic acid, sulfur, and the open mill process work closely together to form an efficient and orderly system. The composite 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 acts as a "catalyst enhancer" to further activate the accelerator activity and improve vulcanization efficiency; sulfur, as the "cross-linking core," with the assistance of the accelerator and zinc soap, accurately constructs sulfur bridges between rubber molecular chains, forming a dense three-dimensional network structure. The open mill process, relying on the shearing and mixing action of the rollers, ensures that all components are evenly dispersed, allowing the vulcanizer to fully penetrate the rubber matrix and ensure that the vulcanization reaction proceeds uniformly and fully. The various components and processes are closely linked and work together to not only achieve efficient vulcanization of the rubber, but also effectively disperse stress when subjected to stress through a stable cross-linked network, significantly enhancing the rubber's wear and tear resistance.

[0094] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing tungsten-containing lead-free rubber with radiation shielding function, characterized by: The preparation method comprises the following steps in parts by weight: 95-105 parts of ethylene propylene diene monomer (EPDM) rubber are placed in an internal mixer and kneaded for 8 minutes to obtain a pretreated rubber; the pretreated rubber, 5-10 parts of maleic anhydride, 1 part of dicumyl peroxide, and 0.5 parts of 2,6-di-tert-butyl-4-methylphenol are added to the internal mixer and mixed at 90° C. for 5-15 minutes to obtain a mixture; the mixture is placed in a twin-screw extruder, left for 3 minutes, and then the extruded material is cut into small pieces, washed, and dried to obtain a modified rubber; Dissolving 0.5-1.5 parts of a silane coupling agent KH-550 in 100 parts of anhydrous ethanol to obtain a silane coupling agent solution; adding 40-50 parts of a composite tungsten filler to the silane coupling agent solution, and ultrasonically dispersing to obtain a mixed filler; heating the mixed filler in a water bath at 60° C., stirring continuously for a reaction of 3 hours, and washing and vacuum drying after the reaction to obtain a pretreated composite tungsten filler; adding 1.5 parts of dopamine to a Tris-HCl buffer to prepare a dopamine solution; adding the pretreated composite tungsten filler to the dopamine solution, stirring for 20 hours to 24 hours, and washing and vacuum drying after the reaction to obtain a 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; After preheating the internal mixer, the modified rubber is added and plasticized to obtain a softened rubber; then 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 are added in sequence and the mixing is continued for 3-5 minutes to obtain a premix; then the modified composite tungsten filler, 25-35 parts of carbon black and liquid paraffin are added, the speed of the internal mixer is increased to 60-80 rpm, the temperature is controlled at 110-130°C, the mixing is carried out for 8-12 minutes, and the rubber is discharged and cooled to obtain a rough mix; the rough mix is ​​added to the internal mixer which has been preheated to 70-80°C and mixed for 3-5 minutes to obtain a softened rough mix; then 2-4 parts of zinc borate and 1-3 parts of boron nitride are added and the mixing is continued for 5-9 minutes. After the mixing is completed, the colloid is discharged and cooled to obtain a masterbatch; The roller temperature of the open mill is set to 45° C., the masterbatch is put into the open mill, and thinned 3-5 times to obtain a processed masterbatch; then 1-2 parts of a composite accelerator and 1-3 parts of sulfur are added, and the roller spacing is adjusted to perform refining for 11 minutes to 15 minutes. After the mixing is completed, the sheet is removed to obtain a film; the film is vulcanized at a vulcanization temperature of 160° C. to 170° C., a vulcanization pressure of 15 MPa, and a vulcanization time of 20 minutes to 30 minutes. After completion, the film is cooled to obtain the tungsten-containing lead-free rubber. The composite fiber includes carbon fiber and glass fiber, and the weight ratio of the carbon fiber to the glass fiber is 2-4:1; the composite antioxidant includes antioxidant 4020 and antioxidant DDA, and the weight ratio of the antioxidant 4020 to the antioxidant DDA is 1-3:1; the composite accelerator includes accelerator MBT and accelerator TMTD, and the weight ratio of the accelerator MBT to the accelerator TMTD is 3:1-3.

2. A tungsten-containing lead-free rubber with radiation shielding function, characterized by: The tungsten-containing lead-free rubber is prepared by the preparation method according to claim 1; the tungsten-containing lead-free rubber includes modified rubber, composite fiber, zinc oxide, stearic acid, a composite antioxidant, a modified composite tungsten filler, carbon black, liquid paraffin, zinc borate, boron nitride, a composite accelerator and sulfur; the modified rubber includes EPDM rubber and maleic anhydride; the modified composite tungsten filler includes a composite tungsten filler, a silane coupling agent KH-550 and dopamine.

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