Flame-retardant composite shielding material, method for preparing same, and use thereof

Abstract

The application provides a flame-retardant composite shielding material and a preparation method and application thereof, and belongs to the technical field of nuclear radiation shielding materials. The flame-retardant composite shielding material comprises the following components in parts by mass: 10-20 parts of high-density polyethylene, 68-81 parts of lead, 0.5-4 parts of boron carbide and 9-20 parts of a flame retardant. By adopting high-density polyethylene, lead, boron carbide and a flame retardant and controlling the mass fraction of each component, the heat resistance, flame retardance and shielding performance of the flame-retardant composite shielding material can be improved.

Description

Technical Field

[0001] This application relates to the field of nuclear radiation shielding materials technology, and in particular to flame-retardant composite shielding materials, their preparation methods, and applications. Background Technology

[0002] Common types of nuclear radiation include X-rays, gamma rays, and neutron radiation. These radiations not only endanger the safety and health of workers but also affect the reliability and safety of equipment. Therefore, effective protection against nuclear radiation is necessary to ensure the safe use of nuclear energy in various fields.

[0003] Traditional shielding materials have good attenuation capabilities against different types of radiation. However, under long-term exposure to high-intensity radiation, shielding materials (such as polyethylene) are at risk of thermal degradation, molecular chain breakage, or even combustion due to internal heat accumulation, which seriously affects the safe operation of nuclear facilities.

[0004] Therefore, optimizing the composition of shielding materials to improve their heat resistance, flame retardancy, and shielding performance has become an urgent technical problem to be solved. Summary of the Invention

[0005] Based on this, the main objective of this application is to provide flame-retardant composite shielding materials, their preparation methods, and applications, so as to improve the heat resistance, flame retardancy, and shielding performance of flame-retardant composite shielding materials.

[0006] The first aspect of this application provides a flame-retardant composite shielding material, comprising the following components in parts by weight:

[0007] 10-20 parts high-density polyethylene, 68-81 parts lead, 0.5-4 parts boron carbide and 9-20 parts flame retardant.

[0008] In some embodiments, the flame-retardant composite shielding material further includes an ethylene-vinyl acetate copolymer.

[0009] In some embodiments, the mass ratio of the high-density polyethylene to the ethylene-vinyl acetate copolymer is 1:(0.01-0.2); and / or,

[0010] In the ethylene-vinyl acetate copolymer, the mass fraction of vinyl acetate is 15%-20%; and / or,

[0011] The melt index of the ethylene-vinyl acetate copolymer is 1-5 g / 10min.

[0012] In some embodiments, the flame retardant includes at least one of magnesium hydroxide and aluminum hydroxide; and / or,

[0013] The mass ratio of the flame retardant to the high-density polyethylene is (0.60-1.3):1; and / or,

[0014] The high-density polyethylene meets the following condition: density ≥ 0.95 g / cm³. 3 Melt index of 0.5-10 g / 10min; and / or,

[0015] The theoretical density of the flame-retardant composite shielding material is 3.60-3.80 g / cm³. 3 .

[0016] In some embodiments, the flame-retardant composite shielding material further includes a compatibilizer and a dispersant.

[0017] In some embodiments, the compatibilizer in the flame-retardant composite shielding material is 1-5 parts by mass; and / or,

[0018] The compatibilizer includes maleic anhydride graft copolymer; and / or

[0019] In the flame-retardant composite shielding material, the dispersant comprises 1-3 parts by mass; and / or,

[0020] The dispersant includes at least one of polyethylene wax and oxidized polyethylene wax.

[0021] In some embodiments, the maleic anhydride graft copolymer includes at least one of maleic anhydride grafted polyethylene and maleic anhydride grafted polypropylene.

[0022] A second aspect of this application provides a method for preparing the flame-retardant composite shielding material described in the first aspect, comprising the following steps:

[0023] The components are mixed and pressed to prepare the flame-retardant composite shielding material.

[0024] In some embodiments, the step of mixing the components specifically includes: mixing high-density polyethylene and ethylene-vinyl acetate resin at a mixing speed of 10-40 r / min, a mixing temperature of 150-165°C, and a mixing time of 10-15 min; sequentially adding additives and boron carbide, and continuing mixing for 5-10 min; adding flame retardant, and continuing mixing for 10-20 min; adding lead, and continuing mixing for 5-10 min; and / or,

[0025] The pressing process specifically includes: pre-pressing at 3-5 MPa and 150℃ for 5-10 minutes, then pressing at 10 MPa and 150-160℃ for 5-10 minutes, followed by pressing at 15-20 MPa and 150-160℃ for 10-20 minutes; finally, cooling to 50-60℃ at 18-20 MPa to complete the pressing; and / or,

[0026] After pressing, there is also a settling step, which requires a settling time of more than 24 hours.

[0027] The third aspect of this application provides the application of a flame-retardant composite shielding material prepared by the preparation method of the flame-retardant composite shielding material described in the first aspect or the second aspect in flame-retardant radiation shielding equipment.

[0028] Compared with traditional technologies, this application has at least the following beneficial effects:

[0029] The flame-retardant composite shielding material of this application improves its heat resistance, flame retardancy and shielding performance by using high-density polyethylene, lead, boron carbide and flame retardant, and controlling the mass fraction of each component, resulting in excellent overall performance. Attached Figure Description

[0030] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0031] Figure 1 This is a schematic diagram showing the neutron shielding performance and gamma-ray shielding performance results of the flame-retardant composite shielding materials in Examples 1-6;

[0032] Figure 2 This is a schematic diagram showing the neutron shielding performance and gamma-ray shielding performance results of the flame-retardant composite shielding materials in Examples 7-14;

[0033] Figure 3 The diagram shows the neutron shielding performance and gamma-ray shielding performance of the flame-retardant composite shielding materials in Examples 15-22 and Comparative Examples 1-5. Detailed Implementation

[0034] The present application will be further described in detail below with reference to the embodiments and examples. These embodiments and examples are for illustrative purposes only and are not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to enable a more thorough and comprehensive understanding of the disclosure of the present application. It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. Furthermore, numerous specific details are set forth in the following description to provide a fuller understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] To address the issue that existing shielding materials cannot simultaneously achieve high heat resistance, high flame retardancy, and high shielding performance, this application improves these properties by using high-density polyethylene, lead, boron carbide, and flame retardants, and by controlling the mass fraction of each component. This results in superior overall performance.

[0037] The first aspect of this application provides a flame-retardant composite shielding material, comprising the following components in parts by weight:

[0038] 10-20 parts high-density polyethylene, 68-81 parts lead, 0.5-4 parts boron carbide and 9-20 parts flame retardant.

[0039] This application improves the heat resistance, flame retardancy, and shielding performance of flame-retardant composite shielding materials by using high-density polyethylene, lead, boron carbide, and flame retardants, and by controlling the mass fraction of each component.

[0040] In some embodiments, the high-density polyethylene is in the range of 10 to 20 parts by weight, and can be 10, 10.4, 11, 11.7, 12, 12.07, 12.5, 12.57, 12.91, 13, 13.08, 13.23, 13.32, 13.44, 13.56, 13.57, 13.63, 13.68, 13.8, 13.92, 14, 14.04, 14.16, 14.21, 14.28, 14.67, 14.82, 15, 15.08, 15.52, 16, 17, 18, 19, or 20 parts by weight.

[0041] In some embodiments, the mass fraction of lead is 68-81 parts, and can be 68 parts, 68.8 parts, 68.86 parts, 69 parts, 69.37 parts, 69.39 parts, 69.63 parts, 69.89 parts, 70 parts, 70.01 parts, 70.08 parts, 70.15 parts, 70.41 parts, 70.67 parts, 70.93 parts, 71 parts, 71.19 parts, 71.24 parts, 71.36 parts, 72 parts, 72.09 parts, 72.34 parts, 72.86 parts, 73 parts, 73.37 parts, 73.67 parts, 74 parts, 74.36 parts, 75 parts, 76 parts, 77 parts, 78 parts, 79 parts, 80 parts, or 81 parts.

[0042] In some embodiments, the boron carbide is in the range of 0.5 to 4 parts by mass, and can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5 or 4 parts.

[0043] In some embodiments, the flame retardant is present in parts by weight of 9 to 20, and may be 9, 9.31, 10, 10.56, 11, 11.74, 12, 12.07, 12.57, 12.86, 13, 13.08, 13.32, 13.44, 13.56, 13.63, 13.68, 13.8, 13.92, 14, 14.04, 14.16, 14.21, 14.82, 14.92, 15, 15.88, 16, 16.79, 17, 18, 19, or 20 parts.

[0044] In some embodiments, the flame-retardant composite shielding material further includes an ethylene-vinyl acetate copolymer.

[0045] In some embodiments, the mass ratio of the high-density polyethylene to the ethylene-vinyl acetate copolymer is 1:(0.01-0.2), and can be 1:0.01, 1:0.02, 1:0.05, 1:0.08, 1:0.1, 1:0.15, or 1:0.2; and / or,

[0046] In the ethylene-vinyl acetate copolymer, the mass fraction of vinyl acetate is 15%-20%; and / or,

[0047] The melt index of the ethylene-vinyl acetate copolymer is 1-5 g / 10min.

[0048] In some embodiments, the ethylene-vinyl acetate copolymer in the flame-retardant composite shielding material is 0.1 to 4 parts by mass, and can be 0.1, 1, 1.3, 2, 2.6, 3 or 4 parts.

[0049] In some embodiments, the theoretical density of the flame-retardant composite shielding material is 3.5-4.0 g / cm³. 3 It can be 3.5g / cm 3 3.6g / cm 3 3.7g / cm 3 3.8g / cm 3 3.9g / cm 3 Or 4.0g / cm 3 .

[0050] In some embodiments, the flame retardant includes at least one of magnesium hydroxide and aluminum hydroxide; and / or,

[0051] The mass ratio of the flame retardant to the high-density polyethylene is (0.60-1.3):1, and can be 0.6:1, 0.67:1, 0.7:1, 0.8:1, 0.86:1, 0.9:1, 1:1, 1.08:1, 1.1:1, 1.12:1, 1.2:1, 1.25:1, or 1.3:1; and / or,

[0052] The high-density polyethylene meets the following condition: density ≥ 0.95 g / cm³. 3 Melt index of 0.5-10 g / 10min; and / or,

[0053] The theoretical density of the flame-retardant composite shielding material is 3.60-3.80 g / cm³. 3 It can be 3.60 g / cm³ 3 3.65g / cm 3 3.70g / cm 3 3.75g / cm 3 Or 3.80g / cm3 .

[0054] In some embodiments, the flame-retardant composite shielding material further includes a compatibilizer and a dispersant.

[0055] In some embodiments, the compatibilizer in the flame-retardant composite shielding material is in the range of 1 to 5 parts by mass, specifically 1, 2, 3, 4, or 5 parts; and / or,

[0056] The compatibilizer includes maleic anhydride graft copolymer; and / or

[0057] In the flame-retardant composite shielding material, the dispersant comprises 1-3 parts by mass, specifically 1 part, 1.5 parts, 2 parts, 2.5 parts, or 3 parts; and / or,

[0058] The dispersant includes at least one of polyethylene wax and oxidized polyethylene wax.

[0059] In some embodiments, the maleic anhydride graft copolymer includes at least one of maleic anhydride grafted polyethylene and maleic anhydride grafted polypropylene.

[0060] A second aspect of this application provides a method for preparing the flame-retardant composite shielding material described in the first aspect, comprising the following steps:

[0061] The components are mixed and pressed to prepare the flame-retardant composite shielding material.

[0062] In some embodiments, the step of mixing the components specifically includes: mixing high-density polyethylene and ethylene-vinyl acetate resin at a mixing speed of 10-40 r / min, a mixing temperature of 150-165°C, and a mixing time of 10-15 min; sequentially adding additives and boron carbide, and continuing mixing for 5-10 min; adding flame retardant, and continuing mixing for 10-20 min; adding lead, and continuing mixing for 5-10 min; and / or,

[0063] The pressing process specifically includes: pre-pressing at 3-5 MPa and 150℃ for 5-10 minutes, then pressing at 10 MPa and 150-160℃ for 5-10 minutes, followed by pressing at 15-20 MPa and 150-160℃ for 10-20 minutes; finally, cooling to 50-60℃ at 18-20 MPa to complete the pressing; and / or,

[0064] After pressing, there is also a settling step, which requires a settling time of more than 24 hours.

[0065] In some embodiments, the lead is added in 2-3 batches.

[0066] The third aspect of this application provides the application of a flame-retardant composite shielding material prepared by the preparation method of the flame-retardant composite shielding material described in the first aspect or the second aspect in flame-retardant radiation shielding equipment.

[0067] The embodiments of this application will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this application, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0068] As an example, the raw materials used in the embodiments of this application are as follows:

[0069] High-density polyethylene: purchased from Yanshan Petrochemical, model 5000S, density 0.95 g / cm³. 3 The melt flow index is 0.9 g / 10 min (190℃ / 2.16 kg).

[0070] Ethylene-vinyl acetate copolymer (EVA): purchased from Yanshan Petrochemical, model Y2022, wherein the mass fraction of vinyl acetate (VA) is 14% and the melt index is 2 g / 10min (190℃ / 2.16kg).

[0071] Lead: Lead powder, with an average particle size of 300 mesh;

[0072] Boron carbide: Boron carbide powder with an average particle size of 75 μm;

[0073] Polyethylene wax: purchased from BASF, model number BASF Luwax® A.

[0074] In this application, the theoretical density calculation formula for the flame-retardant composite shielding material is as follows:

[0075] ;

[0076] in, Theoretical density; The first in flame-retardant composite shielding materials Mass fraction of the components; The first in flame-retardant composite shielding materials The density of each component.

[0077] Examples 1-6

[0078] Flame-retardant composite shielding material is composed of the following components:

[0079] High-density polyethylene, ethylene-vinyl acetate copolymer, lead, boron carbide, flame retardant (magnesium hydroxide), antioxidant, lubricant and coupling agent;

[0080] The mass fractions of high-density polyethylene, ethylene-vinyl acetate copolymer, lead, boron carbide and flame retardant (magnesium hydroxide) are shown in Table 1. The mass fraction of antioxidant (antioxidant 1010) is 0.2 parts, the mass fraction of lubricant (polyethylene wax) is 0.5 parts, and the mass fraction of coupling agent (KH550) is 0.3 parts.

[0081] Flame-retardant composite shielding materials are prepared by the following methods:

[0082] Step 1) Mixing: High-density polyethylene and ethylene-vinyl acetate resin are placed in a mixing equipment and mixed at a temperature of 160℃ for 12 minutes. After the high-density polyethylene is completely melted, antioxidant, lubricant, coupling agent and boron carbide are added in sequence. After mixing for 6 minutes, flame retardant is added, and after mixing for another 15 minutes, lead is added. Then, mixing is continued for another 5 minutes to obtain a mixture. The lead powder is added in two batches.

[0083] Step 2) Molding: After weighing the mixture obtained in Step 1), place it into a mold for pressing to obtain the flame-retardant lead-boron polyethylene-based shielding material; the specific operation of the pressing process is as follows:

[0084] Pre-compression for 5 minutes, with a pre-compression pressure of 5 MPa and a pre-compression temperature of 135℃;

[0085] Then the pressing time is 25 minutes, the pressure is 15 MPa, and the temperature is 165℃;

[0086] Cool the mold to 55°C with cooling water and maintain the pressure at 20MPa. Once the mold temperature drops to 55°C, place it on a natural horizontal surface for 24 hours to prepare the flame-retardant composite shielding material.

[0087] The performance of each flame-retardant composite shielding material was determined, including Vicat softening point, oxygen index and vertical flammability rating. The results are shown in Table 1.

[0088] Test method for Vicat softening point: The Vicat softening temperature (VST) of thermoplastic plastics shall be determined in accordance with GB / T 1633-2000.

[0089] Oxygen index test method: The test shall be conducted in accordance with GB / T 2406.2-2009 Oxygen index method for plastics - determination of combustion behavior - Part 2: Room temperature test;

[0090] Test method for vertical flammability rating: The test shall be conducted in accordance with GB / T 2408-2008 Determination of flammability of plastics - Horizontal and vertical methods.

[0091] Table 1. Theoretical density and performance of flame-retardant composite shielding materials in Examples 1-6

[0092]

[0093] Note: " / " indicates that it has not been added.

[0094] In Table 1, Examples 1-6 obtained flame-retardant composite shielding materials with different theoretical densities by adjusting the amount of lead powder and controlling the mass ratio of flame retardant magnesium hydroxide and high-density polyethylene to 1:1.

[0095] The theoretical density of lead-boron polyethylene material with grade PB10 is 3.57 g / cm³. 3 It is composed of the following components in parts by weight: 80 parts lead, 1.5 parts boron carbide, 18.5 parts ultra-high molecular weight polyethylene, 0.2 parts antioxidant 1010, 0.5 parts lubricant (polyethylene wax), and 0.3 parts coupling agent (KH550). The ultra-high molecular weight polyethylene was purchased from Yanshan Petrochemical, model MⅡ, with a molecular weight of 2.5 million; the lead powder has an average particle size of 200 mesh and a purity of 99.9%; the boron carbide has a particle size of 180 μm.

[0096] The dose equivalent changes of lead-boron polyethylene material (grade PB10) and flame-retardant composite shielding materials of different theoretical densities from Examples 1-6 were compared using simulation programs after shielding against neutrons and gamma rays, respectively. The neutron dose equivalent ratio and gamma ray dose equivalent ratio were calculated, and the results are as follows: Figure 1 As shown.

[0097] Neutron dose equivalent ratio = neutron dose after shielding with flame-retardant composite shielding material / neutron dose after shielding with PB10 shielding material of the same thickness;

[0098] Gamma-ray dose equivalent ratio = gamma-ray dose after shielding with flame-retardant composite shielding material / gamma-ray dose after shielding with PB10 shielding material of the same thickness.

[0099] Depend on Figure 1 It is known that as the theoretical density of flame-retardant composite shielding materials increases, their neutron shielding performance gradually decreases, while their gamma-ray shielding performance rapidly improves. This is because as the theoretical density of flame-retardant composite shielding materials increases, the lead content gradually increases, thus enhancing the shielding effect against gamma rays, while the hydrogen content gradually decreases, leading to a reduction in its neutron shielding effect.

[0100] Among them, the theoretical density of flame-retardant composite shielding materials is 3.60-3.80 g / cm³. 3Within this range, the lead content is 70-73 parts, which is no more than 2 parts higher than the theoretical density of lead-boron polyethylene material of grade PB10. However, the maximum lead content can be reduced by about 10 parts, while the overall shielding performance is not reduced. Further increasing the theoretical density of the flame-retardant composite shielding material to greater than 3.80 g / cm³... 3 While its shielding performance against gamma rays can be further improved, the increased theoretical density of flame-retardant composite shielding materials poses risks such as affecting the processability and durability of the materials.

[0101] Examples 7-14

[0102] The preparation methods of the flame-retardant composite shielding materials in Examples 7-14 are basically the same as those in Example 1, except that the mass fractions of high-density polyethylene, ethylene-vinyl acetate copolymer, lead, boron carbide and flame retardant (magnesium hydroxide) are shown in Table 2; the flame-retardant composite shielding materials are prepared according to the method of Example 1.

[0103] Table 2 Theoretical density and performance of flame-retardant composite shielding materials in Examples 7-14

[0104]

[0105] Note: " / " indicates that it has not been added.

[0106] In Table 2, the theoretical density of the flame-retardant composite shielding material in Examples 7-14 is 3.65 g / cm³. 3 The amounts of boron carbide and lead powder were adjusted, and the mass ratio of flame retardant magnesium hydroxide to high-density polyethylene was controlled to be 1:1.

[0107] Following the method described in Example 1, the differences in dose equivalent changes after shielding neutrons and gamma rays with the flame-retardant composite shielding materials of Examples 7-14 were compared. The neutron dose equivalent ratio and the gamma ray dose equivalent ratio were calculated, and the results are as follows: Figure 2 As shown.

[0108] Figure 2 This indicates that, while maintaining the theoretical density of the flame-retardant composite shielding material, the gamma-ray shielding performance continuously decreases with increasing boron carbide content, which is due to the reduction in lead content. A significant increase in neutron shielding performance occurs when the mass fraction of boron carbide increases from 0.5 parts to 1.0 parts, but no significant increase occurs when the mass fraction of boron carbide increases from 1.0 parts to 4.0 parts. Therefore, with a theoretical density of 3.65 g / cm³ for the flame-retardant composite shielding material... 3 Under certain conditions, boron carbide with a mass fraction of 0.5 wt% to 1 wt% exhibits better overall shielding performance.

[0109] Examples 15-22 and Comparative Examples 1-5

[0110] The preparation methods of flame-retardant composite shielding materials in Examples 15-22, Comparative Examples 1-5 and Example 1 are basically the same, except that the mass fractions of high-density polyethylene, ethylene-vinyl acetate copolymer, lead, boron carbide and flame retardant (magnesium hydroxide) are shown in Table 3; the flame-retardant composite shielding materials are prepared according to the method of Example 1.

[0111] Table 3. Theoretical density and performance of flame-retardant composite shielding materials of Examples 15-22 and Comparative Examples 1-5

[0112]

[0113]

[0114] Note: " / " indicates that it was not added or not tested.

[0115] In Table 3, the theoretical density of the flame-retardant composite shielding material in Examples 15-22 and Comparative Examples 1-5 is 3.65 g / cm³. 3 The mass fraction of boron carbide was 1.5 parts, and the mass ratio of flame retardant magnesium hydroxide and high-density polyethylene was adjusted.

[0116] Using the neutron dose equivalent ratio (n) and gamma-ray dose equivalent ratio (γ) of lead-boron polyethylene material (grade PB10) as benchmarks, the differences in dose equivalent changes after neutron and gamma-ray shielding by the flame-retardant composite shielding materials of Examples 15-22 and Comparative Examples 1-5 were compared according to the method of Example 1. The neutron dose equivalent ratio and gamma-ray dose equivalent ratio were calculated, and the influence of the mass ratio of magnesium hydroxide to high-density polyethylene on the neutron and gamma-ray shielding performance of the composite flame-retardant shielding material was compared. The results are as follows: Figure 3 As shown.

[0117] Figure 3 The results show that, while maintaining the theoretical density of the flame-retardant composite shielding material at 3.65 g / cm³, 3 With a boron carbide mass fraction of 1.5 parts, as the magnesium hydroxide mass fraction increased, the neutron shielding performance of the flame-retardant composite shielding material initially remained unchanged and then decreased, while the gamma-ray shielding performance steadily declined. Therefore, while ensuring the flame-retardant performance of the material meets the requirements, the lower the ratio of magnesium hydroxide to high-density polyethylene, the better the overall shielding performance.

[0118] Examples 23-27 and Comparative Examples 6-8

[0119] The preparation methods of flame-retardant composite shielding materials in Examples 23-27, Comparative Examples 6-8 and Example 1 are basically the same, except that the mass fractions of high-density polyethylene, ethylene-vinyl acetate copolymer, lead, boron carbide and flame retardant (magnesium hydroxide) are shown in Table 4; the flame-retardant composite shielding materials are prepared according to the method of Example 1.

[0120] Table 4 Performance of flame-retardant composite shielding materials in Examples 23-27 and Comparative Examples 6-8

[0121]

[0122] Note: " / " indicates that it has not been added.

[0123] In Table 4, the amount of flame retardant magnesium hydroxide was adjusted in Examples 23-27 and Comparative Examples 6-8.

[0124] The results in Table 4 show that, compared with Comparative Examples 6-8, Examples 23-27, by adjusting the ratio of flame retardant magnesium hydroxide to high-density polyethylene within the range of 0.6-1.12, ensured that the oxygen index of the flame-retardant composite shielding material was greater than 28 parts, thus achieving the flame-retardant rating.

[0125] Examples 28-31 and Comparative Examples 9-15

[0126] The preparation methods of flame-retardant composite shielding materials in Examples 28-31, Comparative Examples 9-15 and Example 1 are basically the same, except that the mass fractions of high-density polyethylene, ethylene-vinyl acetate copolymer, lead, boron carbide and flame retardant (magnesium hydroxide) are shown in Table 5; the flame-retardant composite shielding materials are prepared according to the method of Example 1.

[0127] Table 5 Performance of the flame-retardant composite shielding materials of Examples 28-31 and Comparative Examples 9-15

[0128]

[0129]

[0130] Note: " / " indicates that it was not added or not tested.

[0131] In Table 5, the amount of ethylene-vinyl acetate copolymer was adjusted in Examples 28-31 and Comparative Examples 9-15.

[0132] Table 5 shows that, compared with Comparative Examples 9-15, the flame-retardant composite shielding materials of Examples 28-30, by controlling the mass ratio of ethylene-vinyl acetate copolymer to high-density polyethylene within the range of 0-1:5, have a Vicat softening point greater than 120℃, ensuring excellent heat resistance. Simultaneously, their oxygen index is greater than 32%, indicating excellent flame-retardant properties.

[0133] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0134] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A flame-retardant composite shielding material, characterized in that, The components include the following parts by mass: 10-20 parts high-density polyethylene, 68-81 parts lead, 0.5-4 parts boron carbide and 9-20 parts flame retardant.

2. The flame-retardant composite shielding material according to claim 1, characterized in that, The flame-retardant composite shielding material also includes ethylene-vinyl acetate copolymer.

3. The flame-retardant composite shielding material according to claim 2, characterized in that, The mass ratio of the high-density polyethylene to the ethylene-vinyl acetate copolymer is 1:(0.01-0.2); and / or, In the ethylene-vinyl acetate copolymer, the mass fraction of vinyl acetate is 15%-20%; and / or, The melt index of the ethylene-vinyl acetate copolymer is 1-5 g / 10min.

4. The flame-retardant composite shielding material according to claim 1, characterized in that, The flame retardant includes at least one of magnesium hydroxide and aluminum hydroxide; and / or, The mass ratio of the flame retardant to the high-density polyethylene is (0.6-1.3):1; and / or, The high-density polyethylene meets the following condition: density ≥ 0.95 g / cm³. 3 Melt index of 0.5-10 g / 10min; and / or, The theoretical density of the flame-retardant composite shielding material is 3.60-3.80 g / cm³. 3 .

5. The flame-retardant composite shielding material according to claim 1, characterized in that, The flame-retardant composite shielding material also includes a compatibilizer and a dispersant.

6. The flame-retardant composite shielding material according to claim 5, characterized in that, In the flame-retardant composite shielding material, the compatibilizer comprises 1-5 parts by mass; and / or, The compatibilizer includes maleic anhydride graft copolymer; and / or In the flame-retardant composite shielding material, the dispersant comprises 1-3 parts by mass; and / or, The dispersant includes at least one of polyethylene wax and oxidized polyethylene wax.

7. The flame-retardant composite shielding material according to claim 6, characterized in that, The maleic anhydride graft copolymer includes at least one of maleic anhydride grafted polyethylene and maleic anhydride grafted polypropylene.

8. The method for preparing the flame-retardant composite shielding material according to any one of claims 1-7, characterized in that, Includes the following steps: The components are mixed and pressed to prepare the flame-retardant composite shielding material.

9. The method for preparing the flame-retardant composite shielding material according to claim 8, characterized in that, The specific steps for mixing the components include: mixing high-density polyethylene and ethylene-vinyl acetate resin at a speed of 10-40 r / min, a temperature of 150-165℃, and a mixing time of 10-15 min; adding the additives and boron carbide sequentially, and continuing mixing for 5-10 min; adding the flame retardant and continuing mixing for 10-20 min; adding lead and continuing mixing for 5-10 min; and / or... The pressing process specifically includes: pre-pressing at 3-5 MPa and 150℃ for 5-10 minutes, then pressing at 10 MPa and 150-160℃ for 5-10 minutes, followed by pressing at 15-20 MPa and 150-160℃ for 10-20 minutes; finally, cooling to 50-60℃ at 18-20 MPa to complete the pressing; and / or, After pressing, there is also a settling step, which requires a settling time of more than 24 hours.

10. The application of the flame-retardant composite shielding material as described in any one of claims 1-8 or the flame-retardant composite shielding material prepared by the preparation method of claim 9 in flame-retardant radiation shielding equipment.

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