Flame-retardant nuclear shielding material as well as preparation method and application thereof

Abstract

The invention provides a flame-retardant nuclear shielding material as well as a preparation method and application thereof, and belongs to the field of functional composite materials. According to the invention, a high-hydrogen-content polymer ultra-high molecular weight polyethylene is taken as a research object, and under the conditions that the content of nuclear radiation shielding key elements in the nuclear shielding material is not obviously reduced and the nuclear shielding effect is good, flame retardants with different characteristics are compounded; a physical / chemical composite multi-layer synergistic compound efficient flame-retardant system based on lamellar barrier, free radical capture and catalytic char forming mechanisms is constructed, the flame-retardant nuclear shielding composite material with excellent nuclear shielding performance, flame retardance and mechanical performance is prepared, and the composite material has good application prospects in the field of high-temperature nuclear radiation protection.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials, specifically relating to a flame-retardant nuclear shielding material, its preparation method, and its applications. Background Technology

[0002] Nuclear energy, as a clean energy source, is widely used in many fields. However, the alpha, beta, gamma, and X-rays, as well as neutrons emitted by reactors, pose safety hazards to workers and equipment, thus requiring effective protection against nuclear radiation. In terms of radiation shielding, traditional radiation shielding materials (such as water, concrete, and heavy metal Pb) are insufficient to meet the construction and usage requirements in some specialized areas. Organic shielding materials, due to their advantages of being lightweight, inexpensive, easy to mold, diverse in type, and with a wide range of adjustable properties, are increasingly widely used in nuclear radiation protection. However, their flammability limits their further application. A typical example is polyethylene (PE), which has a high hydrogen content and is widely used in neutron shielding. Its limiting oxygen index (LOI) is only 17.4%, making it highly flammable, burning rapidly, producing large amounts of smoke, and easily dripping during combustion, which can lead to the spread and expansion of fires, posing a significant threat to life and property.

[0003] To overcome the flammability of polyethylene and improve its flame-retardant properties, researchers both domestically and internationally have conducted extensive studies in recent years. Adding flame retardants, specifically those containing flame-retardant elements such as P, N, B, and Si, to polymers like polyethylene to exert a flame-retardant effect, offers advantages such as simple processing, low cost, and ease of large-scale industrial production, making it the most widely used method in practice.

[0004] Traditional flame retardants mainly include halogenated flame retardants, inorganic flame retardants, and phosphorus-nitrogen flame retardants. Halogenated flame retardants produce a large amount of toxic and harmful gases during combustion; inorganic flame retardants, when added in large quantities, will significantly deteriorate the mechanical properties of the material. For example, in the literature "Surface Modification of Magnesium Hydroxide and Its Application in High-Density Polyethylene" (Zhang Hongxia, Su Guixian, Zhang Ning, et al. Engineering Plastics Application, 2018, 46(7): 117-121.), when the amount of modified magnesium hydroxide added was 30%, the limiting oxygen index of HDPE / magnesium hydroxide composite material only increased to 24.6%, and the flame retardant performance was only slightly improved; phosphorus-nitrogen flame retardants, as a high-efficiency, smokeless, low-toxic, and pollution-free flame retardant, have the advantages of good compatibility with the matrix resin and excellent flame retardant performance, and have attracted much attention from researchers. However, the flame retardant effect of a single flame retardant system is poor, and a large amount needs to be added, which reduces the overall performance of the material.

[0005] Furthermore, although researchers both domestically and internationally have conducted extensive research on improving the flame retardant properties of polyethylene materials, finding that the use of metal hydroxides, phosphorus-based, nitrogen-based, and intumescent flame retardants can effectively improve the flame retardant properties of polyethylene materials and broaden the application areas of polyethylene composites, existing research mainly focuses on conventional fields such as wires and cables and packaging plastics, lacking research on the flame retardant properties of organic shielding materials for nuclear protection. For example, the literature "Recent Advances in Halogen-Free Flame Retardants for Polyolefin Cable Sheath Materials" (Li,Y.;Qi,L.;Liu,Y.;Qiao,J.;Wang,M.;Liu,X.;Li,S.Polymers,2022,14(14),2876.) reviews approximately 240 articles on flame retardant work in the field of polyolefins, with research focusing on cable sheaths, building materials, consumer electronics, and transportation materials, and few reports on the flame retardant properties of polyolefin materials for nuclear shielding.

[0006] In the field of nuclear shielding, to achieve better nuclear shielding effects, it is usually necessary to introduce a large number of shielding particles. For example, in the literature "Fabricating UHMWPE-based Shielding Materials with Excellent High-temperature Mechanical Properties and Irradiation Endurance Properties via Controlling Crosslinked and Crystalline Structures" (Xu,R.; Zhou,C.; Sun,X.; Yang,J.; Wu,Y.; Pan,X.; Chen,Y.; Heng,Z.; Zou,H. Polymers for Advanced Techs,2024,35(1),e6204.), 800 phr of lead (Pb) was introduced into 100 phr of ultra-high molecular weight polyethylene to improve its shielding performance. However, the large amount of shielding particles will limit the amount of flame retardant added, thus affecting the flame retardant effect. In the context of nuclear shielding applications, how to effectively improve the flame retardant performance of composite materials while ensuring a high content of shielding particles has become a key challenge. Therefore, research on flame retardant technology for PE-based and other organic nuclear shielding materials is of great significance in order to further increase their applicability and safety. Summary of the Invention

[0007] The purpose of this invention is to provide a flame-retardant nuclear shielding material, its preparation method, and its applications.

[0008] This invention provides a flame-retardant nuclear shielding material, which is prepared from the following raw materials in the indicated mass percentages: 5-70% polyethylene or modified polyethylene, 0.1-10% grafted or modified polymer, 5-30% polybasic acid or its salt, 1-10% polyhydroxy compound, 0-1% hindered amine light stabilizer, 0-10% layered inorganic compound or its derivative, 0-90% high-density heavy metal or its alloy, and 0-5% boride or its complex.

[0009] Furthermore,

[0010] The polyethylene or modified polyethylene is ultra-high molecular weight polyethylene;

[0011] And / or, the grafted or modified polymer is polyethylene grafted with maleic anhydride;

[0012] And / or, the polybasic acid or its salt is ammonium polyphosphate;

[0013] And / or, the polyhydroxy compound bispentaerythritol;

[0014] And / or, the hindered amine light stabilizer is an N-alkoxy hindered amine;

[0015] And / or, the layered inorganic compound or its derivative is zirconium phosphate;

[0016] And / or, the high-density heavy metal or its alloy is lead or tungsten;

[0017] And / or, the boride or its complex is boron carbide.

[0018] Furthermore, the aforementioned flame-retardant nuclear shielding material is prepared from the following raw materials in the indicated mass percentages: 65% ultra-high molecular weight polyethylene, 5% polyethylene grafted maleic anhydride, 16-24% ammonium polyphosphate, 4-6% dipentaerythritol, 0-0.8% N-alkoxy hindered amine, and 0-10% zirconium phosphate.

[0019] Alternatively, it is prepared from the following raw materials in the indicated mass percentages: 8% ultra-high molecular weight polyethylene, 0.62% polyethylene grafted maleic anhydride, 7-14% ammonium polyphosphate, 1-4% dipentaerythritol, 0.1-0.3% N-alkoxy hindered amine, 0.8-1.6% zirconium phosphate, 70-85% lead, and 1.4% boron carbide powder.

[0020] Furthermore, the aforementioned flame-retardant nuclear shielding material is prepared from the following raw materials in the indicated mass percentages: 8% ultra-high molecular weight polyethylene, 0.62% polyethylene grafted maleic anhydride, 13.65% ammonium polyphosphate, 3.41% dipentaerythritol, 0.25% N-alkoxy hindered amine, 1.57% zirconium phosphate, 71.1% lead, and 1.4% boron carbide powder.

[0021] Furthermore, the molecular weight of the ultra-high molecular weight polyethylene is 2 million to 4 million.

[0022] The present invention also provides a method for preparing the aforementioned flame-retardant nuclear shielding material, which includes the following steps: weighing each raw material according to the mass percentage, and preparing it by hot pressing, extrusion molding or injection molding.

[0023] Furthermore, the aforementioned method includes the following steps:

[0024] (1) Weigh each raw material according to its mass percentage;

[0025] (2) Melt and blend all raw materials evenly;

[0026] (3) The material that was mixed evenly in step (2) is subjected to plasticizing, degassing, hot pressing and cold pressing in sequence to obtain the final product.

[0027] Furthermore,

[0028] In step (3), the plasticizing temperature is 180-220℃ and the plasticizing time is 5-20 min;

[0029] And / or, in step (3), the hot pressing temperature is 180-220°C, the pressure is 10-20 MPa, and the time is 10-30 min;

[0030] And / or, in step (3), the pressure of the cold pressing is 10-20 MPa and the time is 5-20 min.

[0031] The present invention also provides the use of the aforementioned flame-retardant nuclear shielding material in the preparation of nuclear radiation shielding materials.

[0032] Furthermore, the nuclear radiation shielding material is a nuclear radiation shielding flame-retardant material suitable for high-temperature scenarios.

[0033] This invention studies the influence of different flame-retardant systems and synergistic compounding systems on the comprehensive properties of polyethylene, including flame retardancy and nuclear shielding performance. Ultimately, it achieves improved flame retardancy of polyethylene while maintaining the content of key nuclear shielding elements above 70 wt%, resulting in a polyethylene composite material with a limiting oxygen index of 40%. Simultaneously, the composite material exhibits a shear strength greater than 1.5 MPa, meeting the application requirements.

[0034] The present invention has achieved the following beneficial effects:

[0035] This invention focuses on ultra-high molecular weight polyethylene (UHMWPE), a high-hydrogen polymer. While maintaining the content of key nuclear radiation shielding elements in the nuclear shielding material at 70 wt% or higher and ensuring good nuclear shielding performance, a highly efficient flame-retardant system based on a multi-level synergistic physical / chemical composite mechanism involving layered barrier, free radical capture, and catalytic char formation is constructed through the design and compounding of flame retardants with different properties. This results in a highly flame-retardant nuclear shielding composite material with excellent nuclear shielding performance, flame retardant properties, and mechanical properties, showing promising application prospects in the field of high-temperature nuclear radiation protection.

[0036] Obviously, based on the above description of the present invention, and according to common technical knowledge and conventional methods in the field, various other modifications, substitutions or alterations can be made without departing from the basic technical concept of the present invention.

[0037] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following embodiments. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Detailed Implementation

[0038] The raw materials and equipment used in this invention are all known products, obtained by purchasing commercially available products.

[0039] Ultra-high molecular weight polyethylene (UHMWPE), brand: L3000, Mitsui Chemicals, molecular weight approximately 3 million. Polyethylene grafted with maleic anhydride (MAPE), BYNEL. TM 4288, maleic anhydride grafting rate 0.2%-0.5% (by weight). Lead powder (Pb), 400 mesh, Nangong Xindun Alloy Welding Material Spraying Co., Ltd. Boron carbide powder (B4C), 50μm, Zhuyu New Material Technology (Yangzhou) Co., Ltd. Ammonium polyphosphate (APP), degree of polymerization 1500, Shanghai Yi'en Chemical Technology Co., Ltd. Dipentaerythritol (DPER), Shanghai Yi'en Chemical Technology Co., Ltd. N-alkoxy hindered amine (NOR116), BASF, purchased from Suzhou Jixin Trading Co., Ltd. Zirconium phosphate (ZrP), 1.6μm, Sichuan Muxin New Material Co., Ltd.

[0040] The sample naming principle of this invention is as follows: A represents APP; D represents DPER; N represents NOR116; ZrP represents zirconium phosphate; Pb represents lead powder.

[0041] Example 1: Preparation of two-component flame retardant materials

[0042] Example 1 is a flame-retardant material prepared using a two-component flame-retardant system formulation of intumescent flame retardant (APP+DPER) and free radical capture (NOR116). The specific formulation is shown in Table 1.

[0043] Table 1. Formulation of two-component flame retardant system with intumescent flame retardant and free radical scavenging

[0044] sample UHMWPE / wt% MAPE / wt% APP / wt% DPER / wt% NOR116 / wt% ADN-1 65 5 23.84 5.96 0.2 ADN-2 65 5 23.68 5.92 0.4 ADN-3 65 5 23.52 5.88 0.6 ADN-4 65 5 23.36 5.84 0.8

[0045] The specific preparation methods are divided into internal mixing and hot pressing processes:

[0046] 1. Internal mixing process:

[0047] (1) Start the internal mixer, set the temperature to 200℃ and the speed to 60r / min.

[0048] (2) Add UHMWPE and MAPE in batches within 5 minutes until the torque gradually stabilizes.

[0049] (3) Then add APP, NOR116 and DPER in sequence, paying attention to controlling torque fluctuations, and complete the feeding within 15 minutes.

[0050] (4) After the raw materials are added, continue to knead for 10 minutes. During this stage, the torque will first remain constant and then gradually decrease.

[0051] (5) Stop the internal mixing and obtain the internally mixed material.

[0052] 2. Hot pressing process:

[0053] (1) Start the hot press and set the temperature of both the upper and lower plates to 200℃.

[0054] (2) Spread the kneaded material evenly in the mold and place it in the hot press for 5 minutes to plasticize.

[0055] (3) Repeat the pressurization (10MPa) and depressurization (0MPa) exhaust process 5 times to remove gas.

[0056] (4) Hold the pressure at 200℃ and 10MPa for 10 minutes.

[0057] (5) Transfer the mold to the cold press and cold press at 10MPa for 5 minutes to fix the shape. Take out the sample strip to obtain the final product.

[0058] Example 2: Preparation of two-component flame retardant materials

[0059] Example 2 is a flame-retardant material prepared using a two-component flame-retardant system formulation of intumescent flame retardant (APP+DPER) and sheet barrier (ZrP). The specific formulation is shown in Table 2.

[0060] Table 2. Formulation of a two-component flame retardant system combining intumescent flame retardant and lamellar barrier

[0061] sample UHMWPE / wt% MAPE / wt% APP / wt% DPER / wt% ZrP / wt% ADZrP-1 65 5 22 5.5 2.5 ADZrP-2 65 5 20 5 5 ADZrP-3 65 5 18 4.5 7.5 ADZrP-4 65 5 16 4 10

[0062] The specific preparation methods are divided into internal mixing and hot pressing processes:

[0063] 1. Internal mixing process:

[0064] (1) Start the internal mixer, set the temperature to 200℃ and the speed to 60r / min.

[0065] (2) Add UHMWPE and MAPE in batches within 5 minutes until the torque gradually stabilizes.

[0066] (3) Then ZrP is added in batches over 5 minutes. The torque shows an upward trend and then gradually stabilizes.

[0067] (4) Add APP and DPER in sequence, paying attention to controlling torque fluctuations, and complete the feeding within 15 minutes.

[0068] (5) After the raw materials are added, continue to knead for 10 minutes. During this stage, the torque will first remain constant and then gradually decrease.

[0069] (6) Stop the internal mixing process and obtain the internally mixed material.

[0070] 2. Hot pressing process:

[0071] (1) Start the hot press and set the temperature of both the upper and lower plates to 200℃.

[0072] (2) Spread the kneaded material evenly in the mold and place it in the hot press for 5 minutes to plasticize.

[0073] (3) Repeat the pressurization (10MPa) and depressurization (0MPa) exhaust process 5 times to remove gas.

[0074] (4) Hold the pressure at 200℃ and 10MPa for 10 minutes.

[0075] (5) Transfer the mold to the cold press and cold press at 10MPa for 5 minutes to fix the shape. Take out the sample strip to obtain the final product.

[0076] In the two-component flame retardant systems of Examples 1 and 2, the total mass percentage of the flame retardant was set at 30 wt%, and the mass ratio of APP to DPER was 4:1. Studies showed that the optimal mass percentage of NOR116 was 0.4 wt%, and the optimal mass percentage of ZrP was 2.5 wt%.

[0077] Example 3: Preparation of three-component flame retardant materials

[0078] Example 3 is a flame-retardant material prepared using a three-component flame-retardant system formulation consisting of an intumescent flame retardant (APP+DPER), a free radical capture (NOR116), and a layer barrier (ZrP). The specific formulation is shown in Table 3.

[0079] Table 3. Formulation of three-component flame retardant system with intumescent flame retardant, free radical capture, and lamellar barrier

[0080] sample UHMWPE / wt% MAPE / wt% APP / wt% DPER / wt% NOR116 / wt% ZrP / wt% ADNZrP-1 65 5 21.68 5.42 0.4 2.5 ADNZrP-2 65 5 19.68 4.92 0.4 5 ADNZrP-3 65 5 21.36 5.34 0.8 2.5 ADNZrP-4 65 5 19.36 4.84 0.8 5

[0081] The specific preparation methods are divided into internal mixing and hot pressing processes:

[0082] 1. Internal mixing process:

[0083] (1) Start the internal mixer, set the temperature to 200℃ and the speed to 60r / min.

[0084] (2) Add UHMWPE and MAPE in batches within 5 minutes until the torque gradually stabilizes.

[0085] (3) Then ZrP is added in batches over 5 minutes. The torque shows an upward trend and then gradually stabilizes.

[0086] (4) Add APP, NOR116 and DPER in sequence, paying attention to controlling the fluctuation of torque, and complete the feeding within 15 minutes.

[0087] (5) After the raw materials are added, continue to knead for 10 minutes. During this stage, the torque will first remain constant and then gradually decrease.

[0088] (6) Stop the internal mixing process and obtain the internally mixed material.

[0089] 2. Hot pressing process:

[0090] (1) Start the hot press and set the temperature of both the upper and lower plates to 200℃.

[0091] (2) Spread the kneaded material evenly in the mold and place it in the hot press for 5 minutes to plasticize.

[0092] (3) Repeat the pressurization (10MPa) and depressurization (0MPa) exhaust process 5 times to remove gas.

[0093] (4) Hold the pressure at 200℃ and 10MPa for 10 minutes.

[0094] (5) Transfer the mold to the cold press and cold press at 10MPa for 5 minutes to fix the shape. Take out the sample strip to obtain the final product.

[0095] Based on the research on two-component flame retardant systems, with a total flame retardant mass percentage of 30%, an APP to DPER mass ratio of 4:1, NOR116 mass percentages of 0.4wt% and 0.8wt%, and ZrP mass percentages of 2.5wt% and 5wt%, the optimal ratio of a three-component flame retardant system was explored. The study showed that the ADNZrP-1 sample (NOR116 mass percentage of 0.4wt% and ZrP mass percentage of 2.5wt%) had the best performance.

[0096] Taking a total flame retardant content of 30 wt% as an example, the APP content is 21.68 wt%, DPER content is 5.42 wt%, NOR116 content is 0.4 wt%, and ZrP content is 2.5 wt%. In subsequent studies, shielding particles Pb powder and B4C were introduced, and the content of each flame retardant was determined according to the above-mentioned mass percentages, based on the total flame retardant content after their introduction.

[0097] Example 4: Formulation of a flame-retardant system for lead-boron-polyethylene nuclear shielding samples

[0098] Example 4 shows a flame-retardant nuclear shielding material prepared using a lead-boron-polyethylene nuclear shielding sample flame-retardant system formulation, as detailed in Table 4.

[0099] Table 4. Flame retardant system formulation for lead-boron-polyethylene nuclear shielding samples

[0100]

[0101] The specific preparation methods are divided into internal mixing and hot pressing processes:

[0102] 1. Internal mixing process:

[0103] (1) Start the internal mixer, set the temperature to 200℃ and the speed to 60r / min.

[0104] (2) Add UHMWPE and MAPE in batches within 5 minutes until the torque gradually stabilizes.

[0105] (3) Then Pb powder, B4C and ZrP are added in batches within 5 minutes. The torque shows an upward trend and then gradually stabilizes.

[0106] (4) Add APP, NOR116 and DPER in sequence, paying attention to controlling torque fluctuations, and complete the feeding within 15 minutes.

[0107] (5) After the raw materials are added, continue to knead for 10 minutes. During this stage, the torque will first remain constant and then gradually decrease.

[0108] (6) Stop the internal mixing process and obtain the internally mixed material.

[0109] (7) The intensively mixed material is intensively mixed again 2-3 times (each intensive mixing condition is 200℃, 10min) to obtain a uniformly melt-blended composite material.

[0110] 2. Hot pressing process:

[0111] (1) Start the hot press and set the temperature of both the upper and lower plates to 200℃.

[0112] (2) Spread the kneaded material evenly in the mold and place it in the hot press for 5 minutes to plasticize.

[0113] (3) Repeat the pressurization (10MPa) and depressurization (0MPa) exhaust process 5 times to remove gas.

[0114] (4) Hold the pressure at 200℃ and 10MPa for 10 minutes.

[0115] (5) Transfer the mold to the cold press and cold press at 10MPa for 5 minutes to fix the shape. Take out the sample strip to obtain the final product.

[0116] The following experimental examples demonstrate the beneficial effects of the present invention.

[0117] Example 1: Performance Analysis of the Two-Component Flame Retardant System of the Present Invention

[0118] I. Experimental Methods

[0119] The samples prepared in Examples 1 and 2 (ADN-1, ADN-2, ADN-3, ADN-4, ADZrP-1, ADZrP-2, ADZrP-3 and ADZrP-4) were characterized as follows.

[0120] 1. Oxygen Index Test: The test standard is GB / T 2406.2-2009, the sample size is 80*10*4mm, and the oxygen index of the material is tested using an oxygen index meter JF-3.

[0121] 2. Vertical burning test: The test standard is GB / T 2408-2021, the sample size is 125*13*4mm, and the vertical burning performance of the material is tested using a horizontal and vertical burning tester.

[0122] II. Experimental Results

[0123] 1. Oxygen Index Analysis

[0124] Table 5. Limiting Oxygen Index and Vertical Combustion Test Results of the Two-Component Flame Retardant System

[0125]

[0126] The limiting oxygen index (LOI) is the minimum oxygen concentration required to sustain combustion; a higher LOI value indicates better flame retardancy. UL-94 vertical flammability ratings are divided into: No Rating (NR), V2, V1, and V0, with flame retardancy improving from left to right. Oxygen index testing (Table 5) revealed that the LOI of the ADN system gradually decreased with increasing NOR116 content. This trend was also observed in the ADZrP system. This may be because the increased NOR116 and ZrP content led to a decrease in APP content. APP, as a major acid source component in intumescent flame retardants, is crucial for char formation during combustion, indicating that the absolute APP content is essential for improving the LOI of the composite material. The results showed that the LOIs of the ADN and ADZrP systems reached a maximum of 28.7% and 29.5%, respectively, representing a significant improvement compared to pure UHMWPE (19%).

[0127] 2. Vertical Combustion Analysis

[0128] In the vertical burning test, a flame is applied to the sample for 10 seconds, and the duration of the first combustion (t1) is recorded. After the flame extinguishes, a flame is immediately applied again for 10 seconds, and the afterflame time of the second combustion (t2) is recorded. After the flame extinguishes, the afterglow time (t3) is recorded again. Additionally, the dripping of the sample is recorded during the test. Table 5 uses Y / N (Yes / No) in the Dripping section to indicate whether dripping occurred during the sample's combustion. The UL-94 vertical burning rating of the sample is evaluated based on t1, t2, t3, the presence or absence of dripping, and whether the dripping ignites the absorbent cotton below. Afterflame refers to the continuous flame of the material after the ignition source is removed under specified conditions; afterglow refers to the continuous glow of the material after the flame terminates when the ignition source is removed under specified conditions, or when no flame is produced.

[0129] Through vertical burning tests (Table 5), this invention found that although the ADN-1 sample could self-extinguish during combustion, the time required was relatively long, especially after the second ignition, when combustion lasted for 21 seconds. Furthermore, molten drippings were produced during combustion, which ignited the absorbent cotton below, resulting in a UL-94 flame retardancy rating of only V2. Increasing the NOR116 content to 0.4 wt% (ADN-2 sample), although its oxygen index decreased slightly (28.7 >> 28.1), directly improved the flame retardancy rating from V2 to V0. This indicates that the flame retardant effect of the NOR116 free radical flame retardant mainly occurs in the initial stage of combustion, effectively improving the extinguishing and melting dripping conditions, and effectively improving the flame retardancy rating of the composite material. However, when the NOR116 content was further increased, the flame retardancy rating first decreased and then increased, indicating that its improvement in vertical burning requires a suitable content but not excessive amounts. That is, a NOR116 content of 0.4 wt% is preferable.

[0130] The same trend was observed in the ADZrP-1 sample. Introducing a small amount of ZrP into the AD intumescent flame-retardant system improved the flame retardancy rating to V0. This is because the lamellar barrier of zirconium phosphate physically hinders the continued propagation of the flame, thus improving the flame retardancy rating. In other words, the introduction of a small amount of ZrP is beneficial for self-extinguishing during combustion, achieving a UL94-V0 rating for vertical burning. Excessive ZrP leads to persistent burning, possibly due to the reduction in APP content. Therefore, the APP / DPER content needs to be at least 25wt% to maintain a V0 flame retardancy rating.

[0131] Based on the above analysis of oxygen index and vertical combustion, the optimal dosages of NOR116 and ZrP are 0.4 wt% and 2.5 wt%, respectively. Based on these optimal contents, a more rational design of the three-component flame retardant system formulation can be achieved.

[0132] Experimental Example 2: Performance Analysis of a Three-Component Flame-Retardant System and a Lead-Boron Polyethylene Flame-Retardant Nuclear Shielding System

[0133] I. Experimental Methods

[0134] The oxygen index test and vertical combustion test were the same as in Example 1. The test samples were ADNZrP-1, ADNZrP-2, ADNZrP-3, ADNZrP-4, ADNZrP-Pb-1, ADNZrP-Pb-2, and ADNZrP-Pb-3 prepared in Examples 3 and 4.

[0135] TGA analysis: Manufacturer: METTLER TOLEDO, Equipment No.: 2019BE5D, Sample amount: 3-8 mg, Temperature range: 35℃-800℃, Heating rate: 10℃ / min, Air atmosphere.

[0136] Conical calorimetry test: The test standard is GB / T 16172-2007, the sample size is 100*100*4mm, and the heat flux is 35kW / m³. 2 .

[0137] II. Experimental Results

[0138] 1. Oxygen Index Analysis

[0139] Table 6. Oxygen Index Test Results of Three-Component Flame Retardant System and Lead-Boron Polyethylene Flame Retardant Nuclear Shielding System

[0140]

[0141]

[0142] In Table 6, X represents a sample burning time exceeding 3 minutes or a burning length exceeding 50 mm at the current oxygen concentration; O represents a burning time less than 3 minutes and a burning length less than 50 mm. These are the burning results of the samples at various oxygen concentrations, used to derive the Limiting Oxygen Index (LOI).

[0143] The limiting oxygen index (LOI) test results are shown in Table 6 above. The highest LIO index of the ADNZrP three-component flame-retardant system is only 27%, and even after introducing Pb powder, the LIO index remains at 27%, indicating that the introduction of 80 wt% Pb powder has little impact on the flame-retardant performance of the composite material. In the formulation with a Pb content of 71%, with the matrix content remaining consistent with the above, the limiting oxygen index of the flame-retardant shielding formulation reaches 40%, and the shielding performance is still within an acceptable range (Pb, a key element for nuclear radiation shielding, is above 70 wt%). At this point, the total flame retardant content is 17.31 wt%, proving the effectiveness of the three-component flame-retardant mechanism. This demonstrates that the minimum flame retardant content and the optimal flame-retardant formulation for achieving an LIO index of 40% have been determined.

[0144] 2. Vertical Combustion Analysis

[0145] Table 7. Vertical combustion test results of ADNZrP-Pb-3 samples in the lead-boron polyethylene flame-retardant nuclear shielding system.

[0146]

[0147] Vertical burning tests showed that ADNZrP-1 had a flame retardancy rating of V2, ADNZrP-2 had a flame retardancy rating of V0, ADNZrP-3 had a flame retardancy rating of NR, ADNZrP-4 had a flame retardancy rating of V2, ADNZrP-Pb-1 had a flame retardancy rating of NR, ADNZrP-Pb-2 had a flame retardancy rating of V2, and ADNZrP-Pb-3 had a flame retardancy rating of V0. Comparison of vertical burning tests on each sample revealed that increasing the NOR116 content was more beneficial to improving the vertical burning rating of the composite material than introducing ZrP. Specifically, the vertical burning rating of the ADNZrP-2 sample improved from V2 to V0 compared to the ADNZrP-1 sample, which is consistent with the above research results. In the ADNZrP-Pb system, compared to ADNZrP-Pb-1 and ADNZrP-Pb-2, the increased NOR116 content (0.13wt% >> 0.26wt%) improved the flame retardant rating of the Pb-containing flame retardant system from NR to V2. Finally, in ADNZrP-Pb-3, the samples extinguished within approximately 2 seconds after both the first and second ignitions, achieving a flame retardant rating of V0. This indicates that increasing the flame retardant content is highly effective in improving the vertical burning rating, meaning that the optimal amount of flame retardant was determined while maintaining a Pb content (71wt%) greater than 70wt%.

[0148] 3. TGA Testing

[0149] Table 8. Thermogravimetric results of the three-component flame-retardant system and the flame-retardant nuclear shielding system

[0150]

[0151] TGA analysis of the three-component flame retardant system and the flame retardant system containing Pb (Table 8) shows that the TGA of the ADNZrP-2 sample is significantly different. 5％ The temperature was increased by 5°C compared to the ADNZrP-1 sample. Furthermore, after the introduction of Pb powder, the temperature of the composite material increased. 5％ The temperature was increased to 456℃, indicating a significant improvement in the thermal stability of the composite material.

[0152] 4. Cone calorimetry

[0153] Table 9. Conical calorimetric analysis of some samples in the flame retardant system

[0154]

[0155] Cone calorimetry analysis revealed (Table 9): (1) The introduction of ADN and ADZrP flame retardants effectively extended the ignition time to about 200s and reduced the heat release rate during combustion, which proves the synergistic effect of the two-component flame retardant. (2) The ADNZrP-Pb-3 flame retardant system did not burn after heating for 500s, meaning it could not be ignited in the cone calorimetry test, proving the material's excellent heat resistance and flame retardant properties.

[0156] Experimental Example 3: Analysis of the nuclear shielding performance of the flame-retardant nuclear shielding material of the present invention

[0157] In the field of nuclear shielding materials, heavy metals with high atomic numbers, such as lead (Pb) and tungsten (W), can effectively attenuate high-energy radiation such as gamma rays. A good shielding effect usually depends on a high content of heavy metals. For example, in the paper "Preparation and characterization of tungsten / epoxy composites for gamma-rays radiation shielding" (L. Chang, Y. Zhang, Y. Liu, et al. Nucl. Instrum. Meth. B. 356–357 (2015) 88–93), W / epoxy resin (W / EP) composites with different proportions of W powder were prepared. The results showed that the radiation shielding performance increased with increasing W content. Specifically, when the mass fraction of W increased from 0% to 80%, 60 The attenuation coefficient of W / EP under Co source increased from 0.08 to 0.27 cm. -1The literature "Fabricating UHMWPE-based shielding materials with excellent high-temperature mechanical properties and irradiation endurance properties via controlling crosslinked and crystalline structures" (R. Xu, C. Zhou, X. Sun, et al. Polym. Adv. Technol. 35(1)(2024)e6204) prepared a high-temperature resistant shielding composite material composed of UHMWPE and Pb, in which the Pb content in 100 phr UHMWPE was 800 phr. As the thickness of the shielding material increased, both the linear attenuation coefficient and the mass attenuation coefficient decreased slightly. The literature "Preparation and Radiation Attenuation Performances of Metal Oxide Filled Polyethylene Based Composites for Ionizing Electromagnetic Radiation Shielding Applications" (Eren In Belgin, E.; Aycik, GA J Radioanal. Nucl. Chem. 2015, 306(1), 107–117., linear low-density polyethylene-based metal oxide (PbO and WO3) filled composites were prepared and characterized. The results showed that the prepared composites exhibited good radiation attenuation performance, especially under high filling amounts.

[0158] To verify the nuclear shielding effect of the flame-retardant nuclear shielding material of this invention, Geant4 simulation and gamma irradiation experiments were used to verify the nuclear shielding effect of the flame-retardant nuclear shielding material.

[0159] I. Experimental Methods

[0160] 1. Geant4 shielding performance simulation

[0161] Materials: UHMWPE, ADN-1, ADZrP-1, ADNZrP-1, ADNZrP-3 (UHMWPE is the raw material, and other materials are prepared according to the methods of the corresponding examples).

[0162] Material thickness settings: 2, 4, 6, 8, 10 cm.

[0163] The emitted particles are gamma, numbering 1,000,000, with an energy of 1 MeV.

[0164] The penetration coefficient I / I0 of the material is calculated by counting the number of particles before and after the material is incident using the detector, and its linear attenuation coefficient and mass attenuation coefficient are calculated using the following formulas.

[0165] I = I0e (-μ·d) (1)

[0166] μ m =μ / ρ (2)

[0167] In the formula, I is the penetration intensity of the material; I0 is the incident intensity; d is the thickness of the material; μ is the linear attenuation coefficient; μ m ρ is the mass decay coefficient; ρ is the density of the material.

[0168] 2. Gamma irradiation experiment test

[0169] Provided by the China Nuclear Power Research and Design Institute, the average energy is 1250keV ( 60 Co), 662keV 137 The sample was Cs), and the sample was ADNZrP-Pb-3 with a size of 300*300*20mm.

[0170] II. Experimental Results

[0171] 1. Simulation results of Geant4 shielding performance

[0172] Table 10. Geant4 simulation data for UHMWPE

[0173]

[0174]

[0175] Table 11. Geant4 simulation data for ADN-1

[0176]

[0177] Table 12. Geant4 simulation data for ADZrP-1

[0178]

[0179] Table 13. Geant4 simulation data for ADNZrP-1

[0180]

[0181] Table 14. Geant4 simulation data for ADNZrP-Pb71

[0182]

[0183]

[0184] As shown in Tables 10-14, the transmittance of gamma rays gradually decreases with increasing material thickness. This is because the increased number of scattering events reduces the transmittance of the rays. Specifically, the transmittance of the UHMWPE sample at a thickness of 10 cm is 79.97%, while the transmittances of ADN-1, ADZrP-1, and ADNZrP-1 samples at 10 cm are 60.78%, 60.02%, and 60.02%, respectively. This indicates that the introduction of elements such as N, P, and Zr in the flame retardants reduces the transmittance of gamma rays to some extent, but the difference in their effects on shielding performance is not significant. The transmittance of the ADNZrP-Pb-3 sample at 10 cm is 43.86%, indicating that the introduction of Pb further effectively reduces the transmittance of gamma rays. Furthermore, in terms of the linear attenuation coefficient and the mass attenuation coefficient, all materials reach their maximum values ​​at 4 cm, indicating that although the transmittance gradually decreases with increasing material thickness, the attenuation coefficient per unit thickness reaches its maximum value at 4 cm and then gradually decreases. At a thickness of 4 cm, the linear attenuation coefficient of the ADNZrP-Pb-3 sample is 0.1052 cm⁻¹. -1 The mass decay coefficient is 0.0408 cm⁻¹. 2 / g, which is 303.01% and 50% higher than that of pure UHMWPE, respectively. Simulation results show that the flame retardant material has better gamma ray shielding performance than the pure sample.

[0185] 2. Results of Gamma Irradiation Experiment

[0186] Table 15. Results of Gamma Irradiation Experiment

[0187] Average energy (keV) Attenuation ratio Equivalent lead weight (mm) <![CDATA[1250( 60 Co)]]> 1.337 4.397 <![CDATA[662( 137 Cs)]]> 1.748 4.594

[0188] In addition, the table shows the actual nuclear shielding performance test results (tests provided by the China Nuclear Power Design Institute). It can be observed that at 1250 keV... 60 Under Co testing conditions, the attenuation ratio of a 2cm thick ADNZrP-Pb-3 sample is 1.337, and the equivalent lead weight is 4.397mm, which meets the shielding performance requirements of radiation protection equipment. Simulation and experimental results both demonstrate that the flame-retardant nuclear shielding material of this invention possesses excellent nuclear shielding performance.

[0189] This experimental example demonstrates that the Pb content of the ADNZrP-Pb-3 sample is above 70 wt%, and the high packing of shielding particles can provide excellent shielding against gamma rays. Furthermore, the matrix used is UHMWPE with a high hydrogen content, where hydrogen can effectively moderate fast neutrons. Additionally, boron has a large neutron absorption cross-section, providing excellent neutron absorption. The introduction of B4C into the composite material and the high H content in the matrix work synergistically to also provide good neutron shielding.

[0190] In summary, this invention provides a flame-retardant nuclear shielding material. Using high-hydrogen-content polymer ultra-high molecular weight polyethylene as the research object, and while maintaining the content of key nuclear radiation shielding elements in the nuclear shielding material without significant reduction (remaining at 70 wt% or higher) and ensuring good nuclear shielding effect, this invention designs and combines flame retardants with different properties to construct a highly efficient flame-retardant system based on a physical / chemical composite multi-level synergistic compound mechanism of layered barrier, free radical capture, and catalytic char formation. This results in a highly flame-retardant nuclear shielding composite material with excellent nuclear shielding performance, flame retardant performance, and mechanical properties, which has promising application prospects in the field of high-temperature nuclear radiation protection.

Claims

1. A flame-retardant nuclear shielding material, characterized by: It is prepared from raw materials in the following mass percentages: polyethylene or modified polyethylene 5-70%, grafted or modified polymer 0.1-10%, polybasic acid or its salt 5-30%, polyhydroxy compound 1-10%, hindered amine light stabilizer 0-1%, layered inorganic compound or its derivative 0-10%, high-density heavy metal or its alloy 0-90%, boride or its composite 0-5%. 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide. 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide. 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide. 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide. 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide. 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide. 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide. 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide. 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide.

3. The burn-resistant nuclear shielding material of claim 2, wherein: 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide. 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide.

4. The burn-resistant nuclear shielding material of claim 3, wherein: 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, the high-density heavy metal or its alloy is lead or tungsten; and / or, the boride or its composite is boron carbide.

5. The flame resistant nuclear shielding material of any of claims 2-4, wherein: 2.The nuclear radiation shielding material of claim 1, wherein: the polyethylene or modified polyethylene is ultra-high molecular weight polyethylene; and / or, the grafted or modified polymer is polyethylene grafted maleic anhydride; and / or, the polybasic acid or its salt is ammonium polyphosphate; and / or, the polyhydroxy compound is dipentaerythritol; and / or, the hindered amine light stabilizer is N-alkoxy hindered amine; and / or, the layered inorganic compound or its derivative is zirconium phosphate; and / or, 6. A method of producing the flame-retardant nuclear shielding material according to any one of claims 1 to 5, characterized by: ​ 7. The method of claim 6, wherein: ​ ​ ​ ​ ​ ​ ​ ​ ​ 10. Use according to claim 9, characterized in that: ​

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