High-strength lead-boron polyvinyl shielding material and preparation method thereof

Abstract

The invention discloses a high-strength lead-boron polyvinyl shielding material and a preparation method thereof, and the high-strength lead-boron polyvinyl shielding material is composed of the following components: 8-25 wt% of ultra-high molecular weight polyethylene powder, 0.5-8.0 wt% of boron carbide powder, 70-90 wt% of lead powder, 0.1-0.2 wt% of an antioxidant and 0.5-2.0 wt% of a lubricant. The production efficiency of the lead-boron polyethylene plate is improved on the basis of ensuring the mixing uniformity, the compatibility of the ultra-high molecular weight polyethylene and the lead powder can be remarkably improved by adding the proper surface compatilizer and matching with the corresponding technological process, the mechanical strength is remarkably improved, chips made of lead-boron materials are mainly formed during processing, and the production efficiency of the lead-boron polyethylene plate is greatly improved. And the lead powder flying dust is greatly reduced, and the environmental safety is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of shielding materials, in particular to a high-strength lead-boron polyethylene-based shielding material and a preparation method thereof. Background Art

[0002] Lead-boron polyethylene is a composite shielding material prepared by adding lead powder, boron carbide powder and processing aids to polyethylene. The polyethylene in the lead-boron polyethylene material has a high hydrogen content, and the hydrogen element has a good weakening ability for fast neutrons; the boron content in boron carbide is high, and the boron element has a large cross-section for absorbing thermal neutrons; the lead element has a good shielding effect on gamma radiation; therefore, lead-boron polyethylene has excellent fast neutron, thermal neutron and gamma radiation shielding effects at the same time. Compared with traditional metal materials, lead-boron polyethylene helps to simplify the shielding structure, reduce the weight of the shielding body, and reduce the volume of the shielding body. It has been widely used in the shielding protection design of nuclear technology devices.

[0003] Invention patent CN 104610637 A "A processing method for a boron-containing ultra-high molecular weight polyethylene sheet" mentions using alcohol to dilute the coupling agent and spray it into the powder mixed with ultra-high molecular weight polyethylene and boron carbide. After the alcohol evaporates, it is directly heated to 270°C in the press for molding, and the shielding performance data of the sheet is given, but the mechanical performance data is not given. The method of spraying the coupling agent with alcohol only sandblasts the coupling agent on the surface of the material, and the interface improvement effect is limited. At the same time, the molding time is too long, and polyethylene is easily degraded at high temperature for a long time. In addition, the production efficiency is low, which has an adverse effect on the comprehensive performance of the material. Invention patent CN 112961423A "A lead-boron polyethylene sheet and size control method" mentions mixing boron carbide powder, lead powder and ultra-high polyethylene powder, putting them into the mold, gradually heating and pressurizing them to 170°C to 200°C, and then putting them into the cold press to cool them to room temperature for demolding. The patent does not mention the addition of a surface treatment agent, and the gradual heating process takes a long time.

[0004] At present, the lead-boron polyethylene material based on high-density ultra-high molecular weight polyethylene has low surface polarity, high melt index, poor compatibility with inorganic additives, and poor bonding effect with high-filling lead powder and boron carbide powder, resulting in low strength. In addition, lead powder dust is easily generated during processing, which not only pollutes the environment, but also poses serious hidden dangers to the physical health of workers. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to provide a high-strength lead-boron polyethylene-based shielding material and a preparation method thereof, to improve the production efficiency of lead-boron polyethylene sheets on the basis of ensuring mixing uniformity, and to significantly improve the compatibility of ultra-high molecular weight polyethylene with lead powder by adding a suitable surface compatibilizer and coordinating the corresponding process flow, and to significantly improve the mechanical strength. During processing, mainly lead-boron material debris is formed, which greatly reduces the generation of lead powder dust and significantly improves environmental safety.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A high-strength lead-boron polyethylene-based shielding material consists of the following components: 8-25wt% ultra-high molecular weight polyethylene powder, 0.5-8.0wt% boron carbide powder, 70-90wt% lead powder, 0.1-0.2wt% antioxidant and 0.5-2.0wt% lubricant.

[0008] The high-strength lead-boron polyethylene-based shielding material has a boron carbide powder particle size less than or equal to 100 μm.

[0009] The high-strength lead-boron polyethylene-based shielding material has a lead powder particle size of 80 to 500 meshes and a lead powder purity greater than or equal to 99.5wt%.

[0010] The antioxidant of the high-strength lead-boron polyethylene-based shielding material is one or more of antioxidant 1010, antioxidant 7910, antioxidant FD958 and antioxidant FD658.

[0011] The above-mentioned high-strength lead-boron polyethylene-based shielding material has an antioxidant particle size of 200 meshes.

[0012] The lubricant of the high-strength lead-boron polyethylene-based shielding material is polyethylene wax or oxidized polyethylene wax, and the melting point of the polyethylene wax is ≥132°C.

[0013] The above-mentioned high-strength lead-boron polyethylene-based shielding material, the ultra-high molecular weight polyethylene powder is made of ultra-high molecular weight polyethylene with a viscosity coefficient of 1000-4500 ml / g.

[0014] The high-strength lead-boron polyethylene-based shielding material has a density of 3.0 to 5.0 g / cm 3 .

[0015] The preparation method of the above-mentioned high-strength lead-boron polyethylene-based shielding material comprises the following steps:

[0016] Step 1) Mixing: weighing ultra-molecular weight polyethylene powder, boron carbide powder, lead powder, flame retardant, antioxidant powder, coupling agent and lubricant and mixing them in a dry powder mixer to obtain a mixed powder, with a rotation speed of 20 to 60 r / min and a mixing time of 2 to 120 min;

[0017] Step 2) Mixing: Add the mixed powder obtained in step 1) into the rheometer chamber of an internal mixer and heat and stir for 10 to 300 seconds to obtain a mixed material. The temperature of the internal mixer is 160 to 190° C. and the speed is 10 to 40 r / min.

[0018] Step 3) Molding: The mixed material obtained in step 2) is weighed and placed in a mold for pressing to obtain a high-strength lead-boron polyethylene-based shielding material. The mold temperature is 150-190° C., the pressing pressure is 10-20 MPa, and the pressing time is 20-40 min.

[0019] In the above preparation method, in step 3), the specific operation of the pressing process is:

[0020] Step 3-1) pre-pressing for 5 to 10 minutes, the pre-pressing pressure is 3 to 5 MPa, and the pre-pressing temperature is 130 to 150°C;

[0021] Step 3-2) two-stage formal pressing: the first stage of formal pressing has a pressing time of 5 to 10 minutes, a pressure of 10 MPa, and a temperature of 150 to 170° C.; the second stage of formal pressing has a pressing time of 10 to 20 minutes, a pressure of 15 to 20 MPa, and a temperature of 170 to 190° C.;

[0022] Step 3-3) Cool the mixture to 50-60°C with cooling water and maintain the pressure at 18-20 MPa.

[0023] The technical solution of the present invention achieves the following beneficial technical effects:

[0024] 1. When the high-strength lead-boron polyethylene-based shielding material preparation method of the present invention is used to prepare the high-strength lead-boron polyethylene-based shielding material, the heating molding time is only 1 to 2 hours and the material can be cooled in the cold press, which significantly improves the production efficiency.

[0025] 2. The high-strength lead-boron polyethylene-based shielding material of the present invention significantly improves the tensile strength and bending strength, and the radiation resistance is also significantly improved, thereby increasing the application range and service life of the material.

[0026] 3. The lead powder in the high-strength lead-boron polyethylene-based shielding material of the present invention is tightly attached to the polyethylene woven structure, forming a high-strength polyethylene-lead microstructure, which significantly reduces the generation of lead dust mist during cutting and processing, protects the health of operators, and reduces environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a ×500 electron microscope photograph of the high-strength lead-boron polyethylene-based shielding material prepared in Example 4. DETAILED DESCRIPTION

[0028] Example 1

[0029] In this embodiment, the high-strength lead-boron polyethylene-based shielding material is composed of 25 parts by weight of ultra-high molecular weight polyethylene powder MI with a molecular weight of 1.5 million, 70 parts by weight of lead powder with a particle size of 200 mesh and a purity greater than or equal to 99.5wt%, 3 parts by weight of boron carbide powder with a particle size of 200 mesh, 0.1 parts by weight of antioxidant 1010 and 1.9 parts by weight of polyethylene wax 0A9.

[0030] The high-strength lead-boron polyethylene-based shielding material in this embodiment is prepared by the following steps:

[0031] Step 1) After weighing the ultra-high molecular weight polyethylene powder, boron carbide powder, lead powder, antioxidant 1010 and polyethylene wax, put them into a closed container, start the powder mixing equipment, rotate at 40r / min, mix for 30min, and obtain a mixed powder;

[0032] Step 2) The temperature of the internal mixer is set to 160-190° C. and the speed is 25 r / min. The mixed powder obtained in step 1) is poured into the internal mixer and internally mixed for 3 minutes to obtain a mixed material. During the internal mixing process, the temperature is controlled to prevent the material from agglomerating due to excessive temperature.

[0033] Step 3) The mixed material obtained in step 2) is weighed and put into a mold while hot, the mold temperature is set to 170°C, the pre-pressure is 3-5MPa, the time is 5min, and the temperature is 130°C; the pressure is increased to 10MPa, the time is 10min, and the temperature is 150°C; the pressure is increased to 20MPa, the pressure is maintained for 30min, and the temperature is 170°C; cooling water is passed to cool down, and the pressure is maintained at 18-20MPa;

[0034] Step 4) After hot pressing for 30 minutes, move to the cold press to maintain a pressure of 18-20 MPa and demold at 70°C.

[0035] Example 2

[0036] In this embodiment, the high-strength lead-boron polyethylene-based shielding material is composed of 20.9 parts by weight of ultra-high molecular weight polyethylene powder MII I with a molecular weight of 3 million, 70 parts by weight of lead powder with a particle size of 200 mesh and a purity greater than or equal to 99.5wt%, 8 parts by weight of boron carbide powder with a particle size range of 0 to 44μm, 0.1 parts by weight of antioxidant 1010 and 1 part by weight of oxidized polyethylene wax G-15.

[0037] The high-strength lead-boron polyethylene-based shielding material in this embodiment is prepared by the following steps:

[0038] Step 1) After weighing the ultra-high molecular weight polyethylene powder, boron carbide powder, lead powder, antioxidant 1010 and oxidized polyethylene wax, put them into a closed container, start the powder mixing equipment, rotate at 30r / min, mix for 40min, and obtain a mixed powder;

[0039] Step 2) The temperature of the internal mixer is set to 180° C. and the speed is set to 25 r / min. The mixed powder obtained in step 1) is poured into the internal mixer and mixed for 2.5 min to obtain a mixed material. During the internal mixing process, the temperature is controlled to prevent the material from agglomerating due to excessive temperature.

[0040] Step 3) The mixed material obtained in step 2) is weighed and put into a mold while hot, the mold temperature is set to 180°C, the pre-pressure is 3-5MPa, the time is 5min, and the temperature is 140°C; the pressure is increased to 10MPa, the time is 10min, and the temperature is 160°C; the pressure is increased to 20MPa, the pressure is maintained for 30min, and the temperature is 180°C; cooling water is passed to cool down, and the pressure is maintained at 18-20MPa;

[0041] Step 4) After hot pressing for 40 minutes, move to a cold press to maintain a pressure of 18-20 MPa and demold at 70°C.

[0042] Example 3

[0043] In this embodiment, the high-strength lead-boron polyethylene-based shielding material is composed of 18 parts by weight of ultra-high molecular weight polyethylene powder MI with a molecular weight of 1.5 million, 80 parts by weight of lead powder with a particle size of 260 mesh and a purity greater than or equal to 99.5wt%, 1 part by weight of boron carbide powder with a particle size of 0 to 35μm, 0.1 parts by weight of antioxidant 1010 and 1 part by weight of polyethylene wax TW-F0054H.

[0044] The high-strength lead-boron polyethylene-based shielding material in this embodiment is prepared by the following steps:

[0045] Step 1) After weighing the ultra-high molecular weight polyethylene powder, boron carbide powder, lead powder, antioxidant 1010 and polyethylene wax, put them into a closed container, start the powder mixing equipment, rotate at 50r / min, mix for 15min, and obtain a mixed powder;

[0046] Step 2) The temperature of the internal mixer is set to 190° C. and the speed is set to 20 r / min. The mixed powder obtained in step 1) is poured into the internal mixer and internally mixed for 2 minutes to obtain a mixed material. During the internal mixing process, the temperature is controlled to prevent the material from agglomerating due to excessive temperature.

[0047] Step 3) The mixed material obtained in step 2) is weighed and put into a mold while hot, the mold temperature is set to 170°C, the pre-pressure is 3-5MPa, the time is 5min, and the temperature is 135°C; the pressure is increased to 10MPa, the time is 10min, and the temperature is 155°C; the pressure is increased to 20MPa, the pressure is maintained for 30min, and the temperature is 170°C; cooling water is passed to cool down, and the pressure is maintained at 18-20MPa.

[0048] Step 4) After hot pressing for 40 minutes, move to a cold press to maintain a pressure of 18-20 MPa and demold at 70°C.

[0049] Example 4

[0050] In this embodiment, the high-strength lead-boron polyethylene-based shielding material is composed of 12.9 parts by weight of ultra-high molecular weight polyethylene powder MII with a molecular weight of 2.5 million, 85 parts by weight of lead powder with a particle size of 200 mesh and a purity greater than or equal to 99.5wt%, 2 parts by weight of boron carbide powder with a particle size of 0 to 35μm, 0.1 parts by weight of antioxidant 7910 and 1 part by weight of oxidized polyethylene wax S3816.

[0051] The high-strength lead-boron polyethylene-based shielding material in this embodiment is prepared by the following steps:

[0052] Step 1) After weighing ultra-high molecular weight polyethylene powder, boron carbide powder, lead powder, antioxidant 7910 and oxidized polyethylene wax powder, put them into a closed container, start the powder mixing equipment, rotate at 50r / min, mix for 20min, and obtain a mixed powder;

[0053] Step 2) The temperature of the internal mixer is set to 190° C. and the speed is 30 r / min. The mixed powder obtained in step 1) is poured into the internal mixer and internally mixed for 1.5 min to obtain a mixed material. During the internal mixing process, the temperature is controlled to prevent the material from agglomerating due to excessive temperature.

[0054] Step 3) The mixed material obtained in step 2) is weighed and put into a mold while hot, the mold temperature is set to 180°C, the pre-pressure is 3-5MPa, the time is 5min, and the temperature is 140°C; the pressure is increased to 10MPa, the time is 10min, and the temperature is 160°C; the pressure is increased to 20MPa, the pressure is maintained for 30min, and the temperature is 180°C; cooling water is passed to cool down, and the pressure is maintained at 18-20MPa;

[0055] Step 4) After hot pressing for 40 minutes, move to a cold press to maintain a pressure of 18-20 MPa and demold at 70°C.

[0056] Example 5

[0057] In this embodiment, the high-strength lead-boron polyethylene-based shielding material is composed of 8.9 parts by weight of ultra-high molecular weight polyethylene powder MI with a molecular weight of 1.5 million, 90 parts by weight of lead powder with a particle size of 200 mesh and a purity greater than or equal to 99.5wt%, 0.51 parts by weight of boron carbide powder with a particle size of 0 to 35μm, 0.1 parts by weight of antioxidant 1010 and 0.5 parts by weight of polyethylene wax TW-F0062.

[0058] The high-strength lead-boron polyethylene-based shielding material in this embodiment is prepared by the following steps:

[0059] 1) After weighing ultra-high molecular weight polyethylene powder, boron carbide powder, lead powder, antioxidant 1010 and polyethylene wax, put them into a closed container, start the powder mixing equipment, rotate at 30r / min, mix for 35min, and obtain a mixed powder;

[0060] 2) The temperature of the internal mixer is set to 180° C. and the speed is set to 30 r / min. The mixed powder obtained in step 1) is poured into the internal mixer and mixed for 2 minutes to obtain a mixed material. During the internal mixing process, the temperature is controlled to prevent the material from agglomerating due to excessive temperature.

[0061] Step 3) The mixed material obtained in step 2) is weighed and put into a mold while hot, the mold temperature is set to 185°C, the pre-pressure is 3-5MPa, the time is 5min, and the temperature is 150°C; the pressure is increased to 10MPa, the time is 10min, and the temperature is 170°C; the pressure is increased to 20MPa, the pressure is maintained for 30min, and the temperature is 185°C; cooling water is passed to cool down, and the pressure is maintained at 18-20MPa;

[0062] Step 4) After hot pressing for 40 minutes, move to a cold press to maintain a pressure of 18-20 MPa and demold at 70°C.

[0063] Comparative Example

[0064] The high-strength lead-boron polyethylene-based shielding material in this embodiment is composed of the following components: 80%wt lead powder, 1.5%wt boron carbide powder and 18.5%wt ultra-high polyethylene powder. In addition, the preparation method of the high-strength lead-boron polyethylene-based shielding material in this embodiment is the same as the preparation method in Example 4.

[0065] The performance tests were conducted on the high-strength lead-boron polyethylene-based shielding materials obtained in Examples 1 to 5 and the comparative examples. The test results are shown in Table 1.

[0066] Table 1 Performance test results of high-strength lead-boron polyethylene-based shielding materials

[0067]

[0068]

[0069] Among them, samples 1 to 5 are samples of high-strength lead-boron polyethylene-based shielding materials prepared in Examples 1 to 5, respectively, and the comparative sample is a sample of high-strength lead-boron polyethylene-based shielding materials prepared in the comparative example. The ×500 electron microscope photo of the high-strength lead-boron polyethylene-based shielding material prepared in Example 4 of the present invention is as follows Figure 1 As shown in Table 1, the lead powder and boron carbide powder are evenly dispersed in the polyethylene substrate and form a close bond with the polyethylene substrate, thereby improving the mechanical strength of the material. From the data recorded in Table 1, it can be clearly seen that the tensile strength and bending strength of the high-strength lead-boron polyethylene-based shielding material of the present invention have been significantly improved. 252 The shielding effect of Cf neutrons has not been weakened.

[0070] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A high-strength lead-boron polyethylene-based shielding material, characterized in that: The invention is composed of the following components: 8-25wt% of ultra-high molecular weight polyethylene powder, 0.5-8.0wt% of boron carbide powder, 70-90wt% of lead powder, 0.1-0.2wt% of antioxidant and 0.5-2.0wt% of lubricant.

2. The high-strength lead-boron polyethylene-based shielding material according to claim 1, characterized in that: The particle size of the boron carbide powder is less than or equal to 100 μm.

3. The high-strength lead-boron polyethylene-based shielding material according to claim 1, characterized in that: The lead powder has a particle size of 80 to 500 meshes, and the lead powder has a purity greater than or equal to 99.5wt%.

4. The high-strength lead-boron polyethylene-based 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.

5. The high-strength lead-boron polyethylene-based shielding material according to claim 1, characterized in that: The particle size of the antioxidant is 200 mesh.

6. The high-strength lead-boron polyethylene-based shielding material according to claim 1, characterized in that: The lubricant is polyethylene wax or oxidized polyethylene wax.

7. The high-strength lead-boron polyethylene-based shielding material according to claim 1, characterized in that: The ultra-high molecular weight polyethylene powder is made of ultra-high molecular weight polyethylene with a viscosity coefficient of 1000 to 4500 ml / g.

8. The high-strength lead-boron polyethylene-based shielding material according to claim 1, characterized in that: The density of high-strength lead-boron polyethylene-based shielding material is 3.0-5.0g / cm 3 .

9. The method for preparing the high-strength lead-boron polyethylene-based shielding material according to claim 1, characterized in that: The steps include: Step 1) Mixing: weighing ultra-molecular weight polyethylene powder, boron carbide powder, lead powder, flame retardant, antioxidant powder, coupling agent and lubricant and mixing them in a dry powder mixer to obtain a mixed powder, with a rotation speed of 20 to 60 r / min and a mixing time of 2 to 120 min; Step 2) Mixing: Add the mixed powder obtained in step 1) into the rheometer chamber of an internal mixer and heat and stir for 10 to 300 seconds to obtain a mixed material. The temperature of the internal mixer is 160 to 190° C. and the speed is 10 to 40 r / min. Step 3) Molding: The mixed material obtained in step 2) is weighed and placed in a mold for pressing to obtain a high-strength lead-boron polyethylene-based shielding material. The mold temperature is 150-190° C., the pressing pressure is 10-20 MPa, and the pressing time is 20-40 min.

10. The preparation method according to claim 9, characterized in that: In step 3), the specific operation of the pressing process is: Step 3-1) pre-pressing for 5 to 10 minutes, the pre-pressing pressure is 3 to 5 MPa, and the pre-pressing temperature is 130 to 150°C; Step 3-2) two-stage formal pressing: the first stage of formal pressing has a pressing time of 5 to 10 minutes, a pressure of 10 MPa, and a temperature of 150 to 170° C.; the second stage of formal pressing has a pressing time of 10 to 20 minutes, a pressure of 15 to 20 MPa, and a temperature of 170 to 190° C.; Step 3-3) Cool the water to 50-60°C and maintain the pressure at 18-20 MPa.

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