Flame-retardant lead-boron modified polyethylene composite shielding material and preparation method thereof

Abstract

The invention discloses a flame-retardant lead-boron modified polyethylene composite shielding material and a preparation method thereof. The flame-retardant lead-boron modified polyethylene composite shielding material is prepared from the following components in percentage by weight: 14 to 16 percent of ultrahigh molecular weight polyethylene powder, 0.5 to 3 percent of boron carbide powder, 70 to 80 percent of lead powder of which the purity is greater than or equal to 99.5 percent, 5 to 10 percent of modified aluminum diethylphosphinate, 0.1 to 0.2 percent of antioxidant and 0.1 to 0.2 percent of lubricant, wherein the lead powder comprises 200-mesh granular lead powder and 300-500-mesh spherical lead powder, the mass ratio of the 200-mesh granular lead powder to the 300-500-mesh spherical lead powder is 1: 1, and the modified aluminum diethyl phosphinate is silane coupling agent modified aluminum diethyl phosphinate. The shielding performance of the prepared flame-retardant lead-boron modified polyethylene composite shielding material is equivalent to that of a conventional lead-boron polyethylene material, and the flame-retardant lead-boron modified polyethylene composite shielding material has excellent flame retardance and physical and chemical properties, the oxygen index of the flame-retardant lead-boron modified polyethylene composite shielding material is greater than or equal to 32, and the vertical combustion method reaches V0 level.

Description

Technical Field

[0001] This invention relates to the field of shielding materials technology. Specifically, it relates to a flame-retardant lead-boron modified polyethylene composite shielding material and its preparation method. Background Technology

[0002] Lead-boron polyethylene (PPE) is a composite shielding material prepared by adding lead powder, boron carbide powder, and processing aids to polyethylene. PPE has a high hydrogen content, and hydrogen has a good attenuation ability for fast neutrons; boron carbide has a high boron content, and boron has a large thermal neutron absorption cross-section; lead has a good shielding effect against gamma radiation. Therefore, PPE simultaneously possesses excellent shielding effects against fast neutrons, thermal neutrons, and gamma radiation. Compared with traditional metallic materials, PPE helps simplify the shielding structure, reduce the weight and volume of the shield, and has been widely used in the shielding protection design of nuclear technology devices.

[0003] However, polyethylene, the base material of lead-boron polyethylene, is a flammable material, and its oxygen index is only 18, posing a safety hazard in engineering applications. Therefore, without reducing the shielding performance, flame-retardant modification of lead-boron polyethylene is a solution to improve its safety. However, the addition of a large amount of lead powder to lead-boron polyethylene significantly increases the difficulty of the process, and the improvement in flame-retardant performance is very limited. For example, invention patent CN200510116946.5, "A lead-boron polyethylene composite shielding material and its preparation method," mentions that adding 2 parts by weight of flame retardant, including magnesium hydroxide, aluminum hydroxide, and phosphorus pentoxide, achieves an oxygen index of 22, while the oxygen index of the material without flame retardant is only 19. Invention patent CN101033313A, "A Flame-Retardant Lead-Boron Polyethylene Composite Material," mentions the use of 2.8-3.8 parts by weight of a composite flame retardant, consisting of 10-20% zinc borate, 60-70% microencapsulated red phosphorus, and 10-20% phenolic resin. The flame-retardant performance meets the FV-1 requirement of GB4609-84. Invention patent CN118006018A, "A Novel High Flame-Retardant Polyethylene-Based Shielding Material," proposes adding lead powder, boron carbide powder, cerium oxide, and benzoyl peroxide to an ultra-high molecular weight polyethylene substrate, followed by twin-screw extrusion granulation. The oxygen index of the product reaches a maximum of 31, but no performance data on vertical combustion is provided. Furthermore, cerium oxide is a rare earth material, relatively expensive, and difficult to widely apply.

[0004] The three patents mentioned above achieve a certain degree of flame retardancy by adding a small amount of flame retardant, but their flame retardancy still cannot meet the needs of actual engineering. For example, engineering fields require materials to reach a flame-retardant level, with an oxygen index greater than 30, and a vertical burning performance of V0. The materials mentioned in the three inventions cannot meet these requirements; they either only specify an oxygen index or only specify a vertical burning performance. For flame-retardant materials, simultaneously meeting both the oxygen index and vertical burning performance requirements is quite difficult to implement. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to provide a flame-retardant lead-boron modified polyethylene composite shielding material and its preparation method. Its shielding performance is comparable to that of conventional lead-boron polyethylene materials, while also having excellent flame-retardant properties and physicochemical properties. Its oxygen index is ≥32, and it reaches V0 level in the vertical burning method.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A flame-retardant lead-boron modified polyethylene composite shielding material is composed of the following components: 14-16 wt% ultra-high molecular weight polyethylene powder, 0.5-3 wt% boron carbide powder, 70-80 wt% lead powder with a purity greater than or equal to 99.5%, 5-10 wt% modified aluminum diethylphosphinate, 0.1-0.2 wt% antioxidant, and 0.1-0.2 wt% lubricant; wherein the lead powder includes 200-mesh granular lead powder and 300-500-mesh spherical lead powder, with a mass ratio of 200-mesh granular lead powder to 300-500-mesh spherical lead powder of 1:1, and the modified aluminum diethylphosphinate is silane coupling agent modified aluminum diethylphosphinate.

[0008] The aforementioned flame-retardant lead-boron modified polyethylene composite shielding material is composed of 300-500 mesh spherical lead powder and 400-500 mesh spherical lead powder mixed in a mass ratio of 1:(3-5).

[0009] The aforementioned flame-retardant lead-boron modified polyethylene composite shielding material has a boron carbide powder particle size of 50–100 μm.

[0010] The above-mentioned flame-retardant lead-boron modified polyethylene composite shielding material has an ultra-high molecular weight polyethylene powder viscosity of 1000-3000 ml / g.

[0011] The aforementioned flame-retardant lead-boron modified polyethylene composite shielding material uses one or more of antioxidants 1010, 7910, FD958, and FD658, with an antioxidant particle size of 200 mesh.

[0012] The aforementioned flame-retardant lead-boron modified polyethylene composite shielding material has a modified aluminum diethylphosphinate particle size of 200–1000 mesh.

[0013] The aforementioned flame-retardant lead-boron modified polyethylene composite shielding material has a density of 3.0–5.0 g / cm³. 3 .

[0014] The above-mentioned flame-retardant lead-boron modified polyethylene composite shielding material uses liquid polyethylene wax and / or paraffin oil as a lubricant.

[0015] The preparation method of the above-mentioned flame-retardant lead-boron modified polyethylene composite shielding material includes the following steps:

[0016] Step 1) Prepare the mixed powder, the specific steps are as follows:

[0017] Step 1-1) Material preparation: Weigh and prepare the materials according to the following formula: 14-16 wt% ultra-high molecular weight polyethylene powder, 0.5-3 wt% boron carbide powder, 70-80 wt% lead powder, 5-10 wt% modified aluminum diethylphosphinate, 0.1-0.2 wt% antioxidant and 0.1-0.2 wt% lubricant; wherein, the lead powder includes 200-mesh granular lead powder and 300-500-mesh spherical lead powder, and the mass ratio of 200-mesh granular lead powder to 300-500-mesh spherical lead powder is 1:1;

[0018] Step 1-2) Preparation of mixed additives: Modified aluminum diethylphosphinate, antioxidant and boron carbide powder are stirred and mixed for 30-60 min at a stirring speed of 600-1000 r / min;

[0019] Steps 1-3) Preparation of the mixed base material: First, take 30-40% by weight of ultra-high molecular weight polyethylene powder and mix it with all the granular lead powder for 5-10 minutes at a stirring speed of 100-400 r / min to obtain the first base material; then, take 20-30% by weight of ultra-high molecular weight polyethylene powder and mix it with all the spherical lead powder for 5-10 minutes at a stirring speed of 100-400 r / min to obtain the second base material; finally, mix the first base material, the second base material, and the remaining ultra-high molecular weight polyethylene powder for 5-10 minutes at a stirring speed of 100-400 r / min to obtain the mixed base material.

[0020] Steps 1-4) Mix the mixing additives, mixing base materials and lubricants for 3-5 minutes at a stirring speed of 100-400 r / min to obtain the mixed powder.

[0021] Step 2) Mixing: Add the mixed powder obtained in step 1) into the rheometer chamber of the internal mixer and heat and stir for 10-300s to obtain the mixed material. The temperature of the internal mixer is 150-190℃ and the speed is 10-40r / min.

[0022] Step 3) Molding: After weighing the mixture obtained in Step 2), place it into a mold for pressing to obtain a flame-retardant lead-boron modified polyethylene composite shielding material; the specific pressing operation is as follows:

[0023] Step 3-1) Pre-compress for 15-30 minutes, with a pre-compressing pressure of 18-20 MPa and a pre-compressing temperature of 150-160℃;

[0024] Step 3-2) Formal pressing: Pressing time is 60-90 min, pressure is 18-20 MPa, and temperature is 180-220℃;

[0025] Step 3-3) Cool the water to 50-60℃ and maintain the pressure at 18-20MPa.

[0026] In the above preparation method, in steps 1-4), the lubricant is added by spraying for 1-2 minutes.

[0027] The technical solution of the present invention achieves the following beneficial technical effects:

[0028] 1. It has good flame retardant properties, with an oxygen index reaching the flame-retardant level and a vertical burning V0 rating, which is significantly improved compared to traditional lead-boron polyethylene materials.

[0029] 2. Through the combined use of coupling agents, lubricants, and flame retardants, as well as reasonable preparation process flow and control parameters, the polyethylene substrate and the large amount of added lead powder additives are tightly bonded, which significantly reduces dust pollution during cutting and processing, greatly reduces the generation of lead dust, protects the physiological health of operators, and improves the environmental safety of the production environment.

[0030] 3. By mixing different lead powders with ultra-high molecular weight polyethylene powder separately and then mixing them together, the present invention can make spherical lead powder and granular lead powder uniformly dispersed in the ultra-high molecular weight polyethylene substrate, thereby achieving a better shielding effect. Attached Figure Description

[0031] Figure 1 Electron micrograph of a flame-retardant lead-boron modified polyethylene composite shielding material. Detailed Implementation

[0032] Example 1

[0033] The flame-retardant lead-boron modified polyethylene composite shielding material in this embodiment is composed of 15 parts by weight of ultra-high molecular weight polyethylene powder with a molecular weight of 1.5 million, 77.4 parts by weight of lead powder with a purity greater than or equal to 99.5 wt%, 1.4 parts by weight of boron carbide powder with a particle size of 200 mesh, 15 parts by weight of modified aluminum diethylphosphinate, 0.1 parts by weight of antioxidant 1010, and 0.1 parts by weight of paraffin oil. The modified aluminum diethylphosphinate is aluminum diethylphosphinate modified with a silane coupling agent.

[0034] In this embodiment, the lead powder includes 38.7 parts by weight of granular lead powder with a particle size of 200 mesh and 38.7 parts by weight of spherical lead powder with a particle size of 300-500 mesh. The granular lead powder is lead powder particles with an irregular morphology obtained by mechanical grinding, and the spherical lead powder is spherical or near-spherical lead powder particles obtained by atomization.

[0035] The flame-retardant lead-boron modified polyethylene composite shielding material in this embodiment is prepared through the following steps:

[0036] Step 1) Prepare the mixed powder, the specific steps are as follows:

[0037] Step 1-1) Material preparation: Weigh and prepare the materials according to the following formula: 14-16 wt% ultra-high molecular weight polyethylene powder, 0.5-3 wt% boron carbide powder, 70-80 wt% lead powder, 5-10 wt% modified aluminum diethylphosphinate, 0.1-0.2 wt% antioxidant and 0.1-0.2 wt% lubricant; wherein, the lead powder includes 200-mesh granular lead powder and 300-500-mesh spherical lead powder, and the mass ratio of 200-mesh granular lead powder to 300-500-mesh spherical lead powder is 1:1;

[0038] Step 1-2) Preparation of mixed additives: Modified aluminum diethylphosphinate, antioxidant and boron carbide powder are stirred and mixed for 30-60 min at a stirring speed of 600-1000 r / min;

[0039] Steps 1-3) Preparation of the mixed base material: First, take 30% by weight of ultra-high molecular weight polyethylene powder and mix it with all the granular lead powder for 5-10 minutes at a stirring speed of 100-400 r / min to obtain the first base material; then take 20% by weight of ultra-high molecular weight polyethylene powder and mix it with all the spherical lead powder for 5-10 minutes at a stirring speed of 100-400 r / min to obtain the second base material; finally, mix the first base material, the second base material, and the remaining ultra-high molecular weight polyethylene powder for 5-10 minutes at a stirring speed of 100-400 r / min to obtain the mixed base material.

[0040] Steps 1-4) Mix the mixing additives, mixing base material and lubricant for 3-5 minutes at a stirring speed of 100-400 r / min to obtain the mixed powder; wherein, the lubricant is added by spraying for 1-2 minutes.

[0041] Step 2) Mixing: Add the mixed powder obtained in step 1) into the rheometer chamber of the internal mixer and heat and stir for 10-300s to obtain the mixed material. The temperature of the internal mixer is 150-190℃ and the speed is 10-40r / min.

[0042] Step 3) Molding: After weighing the mixture obtained in Step 2), place it into a mold for pressing to obtain a flame-retardant lead-boron modified polyethylene composite shielding material; the specific pressing operation is as follows:

[0043] Step 3-1) Pre-compress for 15-30 minutes, with a pre-compressing pressure of 18-20 MPa and a pre-compressing temperature of 150-160℃;

[0044] Step 3-2) Formal pressing: Pressing time is 60-90 min, pressure is 18-20 MPa, and temperature is 180-220℃;

[0045] Step 3-3) Cool the water to 50-60℃ and maintain the pressure at 18-20MPa.

[0046] Example 2

[0047] The difference between the flame-retardant lead-boron modified polyethylene composite shielding material in this embodiment and the flame-retardant lead-boron modified polyethylene composite shielding material in Example 1 is that the spherical lead powder in this embodiment is made by mixing 300-mesh spherical lead powder and 400-500-mesh spherical lead powder in a mass ratio of 1:3.

[0048] Example 3

[0049] The difference between the flame-retardant lead-boron modified polyethylene composite shielding material in this embodiment and the flame-retardant lead-boron modified polyethylene composite shielding material in Example 1 is that the spherical lead powder in this embodiment is made by mixing 300-mesh spherical lead powder and 400-500-mesh spherical lead powder in a mass ratio of 1:4.

[0050] Example 4

[0051] The difference between the flame-retardant lead-boron modified polyethylene composite shielding material in this embodiment and the flame-retardant lead-boron modified polyethylene composite shielding material in Example 1 is that the spherical lead powder in this embodiment is made by mixing 300-mesh spherical lead powder and 400-500-mesh spherical lead powder in a mass ratio of 1:5.

[0052] Example 5

[0053] The difference between the flame-retardant lead-boron modified polyethylene composite shielding material in this embodiment and the flame-retardant lead-boron modified polyethylene composite shielding material in Example 1 is that the spherical lead powder in this embodiment is made by mixing 300-mesh spherical lead powder and 400-500-mesh spherical lead powder in a mass ratio of 1:4.5.

[0054] Example 6

[0055] The difference between the flame-retardant lead-boron modified polyethylene composite shielding material in this embodiment and the flame-retardant lead-boron modified polyethylene composite shielding material in Example 5 is that: in steps 1-3, the ultra-high molecular weight polyethylene powder mixed with all the granular lead powder accounts for 40% of the total amount of ultra-high molecular weight polyethylene powder, and the ultra-high molecular weight polyethylene powder mixed with all the spherical lead powder accounts for 30% of the total amount of ultra-high molecular weight polyethylene powder.

[0056] The ×500 electron microscope image of the flame-retardant lead-boron modified polyethylene composite shielding material prepared in Example 6 of this invention is shown below. Figure 1 As shown. By Figure 1 As shown in the diagram, the smaller spherical lead powder particles fill the spaces between the larger granular lead powder particles. Combined with the addition of other components, this results in an internal structure in the flame-retardant lead-boron modified polyethylene composite shielding material sample prepared in Example 6 that is unsuitable for neutrons and... 60 Coγ achieves a good shielding effect through its irregularly shaped mating structure, which is refracted or reflected. This irregular mating structure refers to the irregularly shaped, three-dimensional contact surfaces between different particles.

[0057] The performance of the flame-retardant lead-boron modified polyethylene composite shielding materials in Examples 1 to 6 and the lead-boron polyethylene PB202 mentioned in the literature "High-efficiency shielding material lead-boron polyethylene" were tested, and the test results are shown in Table 1.

[0058] Table 1. Performance test results of flame-retardant lead-boron modified polyethylene composite shielding material and PB202.

[0059] Among them, Samples 1 to 6 are samples prepared from the flame-retardant lead-boron modified polyethylene composite shielding materials obtained in Examples 1 to 6, respectively. Compared with lead-boron polyethylene PB202 mentioned in the literature "High-Efficiency Shielding Material Lead-Boron Polyethylene", under similar density conditions, the oxygen index of the flame-retardant lead-boron modified polyethylene composite shielding material of this invention is significantly improved, reaching the flame-retardant level, and the vertical burning performance reaches the V0 level, while the mechanical strength is significantly improved.

[0060] As shown in Table 1, when the amount of 400-500 mesh spherical lead powder increases to a certain extent, the tensile strength, flexural strength, oxygen index, neutron shielding coefficient, and other properties of the resulting flame-retardant lead-boron modified polyethylene composite shielding material also increase. 60 The Coγ shielding coefficient decreases with the increase of the amount of 400-500 mesh spherical lead powder. This is because when the amount of 400-500 mesh spherical lead powder is large, the excess 400-500 mesh spherical lead powder will be outside the stable gradation system when it is graded with 300 mesh spherical lead powder and 200 mesh granular lead powder, which will have a negative impact on the performance of the product.

[0061] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A flame-retardant lead-boron modified polyethylene composite shielding material, characterized in that, It is composed of the following components: 14-16 wt% ultra-high molecular weight polyethylene powder, 0.5-3 wt% boron carbide powder, 70-80 wt% lead powder with a purity greater than or equal to 99.5%, 5-10 wt% modified aluminum diethylphosphinate, 0.1-0.2 wt% antioxidant, and 0.1-0.2 wt% lubricant; wherein the lead powder includes 200-mesh granular lead powder and 300-500-mesh spherical lead powder, with a mass ratio of 200-mesh granular lead powder to 300-500-mesh spherical lead powder of 1:1, and the modified aluminum diethylphosphinate is silane coupling agent modified aluminum diethylphosphinate.

2. The flame-retardant lead-boron modified polyethylene composite shielding material according to claim 1, characterized in that, 300-500 mesh spherical lead powder is made by mixing 300 mesh spherical lead powder and 400-500 mesh spherical lead powder in a mass ratio of 1:(3-5).

3. The flame-retardant lead-boron modified polyethylene composite shielding material according to claim 1, characterized in that, The boron carbide powder has a particle size of 50–100 μm.

4. The flame-retardant lead-boron modified polyethylene composite shielding material according to claim 1, characterized in that, The viscosity of ultra-high molecular weight polyethylene powder is 1000-3000 ml / g.

5. The flame-retardant lead-boron modified polyethylene composite shielding material according to claim 1, characterized in that, The antioxidant is one or more of antioxidant 1010, antioxidant 7910, antioxidant FD958 and antioxidant FD658, and the antioxidant particle size is 200 mesh.

6. The flame-retardant lead-boron modified polyethylene composite shielding material according to claim 1, characterized in that, The particle size of the modified aluminum diethylphosphonate is 200-1000 mesh.

7. The flame-retardant lead-boron modified polyethylene composite shielding material according to claim 1, characterized in that, The obtained flame-retardant lead-boron modified polyethylene composite shielding material has a density of 3.0–5.0 g / cm³. 3 .

8. The flame-retardant lead-boron modified polyethylene composite shielding material according to claim 1, characterized in that, The lubricant is liquid polyethylene wax and / or paraffin oil.

9. The preparation method of the flame-retardant lead-boron modified polyethylene composite shielding material according to claim 1, characterized in that, Includes the following steps: Step 1) Prepare the mixed powder, the specific steps are as follows: Step 1-1) Material preparation: Weigh and prepare the materials according to the following formula: 14-16 wt% ultra-high molecular weight polyethylene powder, 0.5-3 wt% boron carbide powder, 70-80 wt% lead powder, 5-10 wt% modified aluminum diethylphosphinate, 0.1-0.2 wt% antioxidant and 0.1-0.2 wt% lubricant; wherein, the lead powder includes 200-mesh granular lead powder and 300-500-mesh spherical lead powder, and the mass ratio of 200-mesh granular lead powder to 300-500-mesh spherical lead powder is 1:1; Step 1-2) Preparation of mixed additives: Modified aluminum diethylphosphinate, antioxidant and boron carbide powder are stirred and mixed for 30-60 min at a stirring speed of 600-1000 r / min; Steps 1-3) Preparation of the mixed base material: First, take 30-40% by weight of ultra-high molecular weight polyethylene powder and mix it with all the granular lead powder for 5-10 minutes at a stirring speed of 100-400 r / min to obtain the first base material; then, take 20-30% by weight of ultra-high molecular weight polyethylene powder and mix it with all the spherical lead powder for 5-10 minutes at a stirring speed of 100-400 r / min to obtain the second base material; finally, mix the first base material, the second base material, and the remaining ultra-high molecular weight polyethylene powder for 5-10 minutes at a stirring speed of 100-400 r / min to obtain the mixed base material. Steps 1-4) Mix the mixing additives, mixing base materials and lubricants for 3-5 minutes at a stirring speed of 100-400 r / min to obtain the mixed powder. Step 2) Mixing: Add the mixed powder obtained in step 1) into the rheometer chamber of the internal mixer and heat and stir for 10-300s to obtain the mixed material. The temperature of the internal mixer is 150-190℃ and the speed is 10-40r / min. Step 3) Molding: After weighing the mixture obtained in Step 2), place it into a mold for pressing to obtain a flame-retardant lead-boron modified polyethylene composite shielding material; the specific pressing operation is as follows: Step 3-1) Pre-compress for 15-30 minutes, with a pre-compressing pressure of 18-20 MPa and a pre-compressing temperature of 150-160℃; Step 3-2) Formal pressing: Pressing time is 60-90 min, pressure is 18-20 MPa, and temperature is 180-220℃; Step 3-3) Cool the water to 50-60℃ and maintain the pressure at 18-20MPa.

10. The preparation method according to claim 9, characterized in that, In steps 1-4), the lubricant is added by spraying for 1-2 minutes.

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