A method for recycling discarded bulletproof helmets

Abstract

This invention relates to a method for recycling discarded bulletproof helmets. The method includes the following steps: Step 1, disassembling the discarded bulletproof helmet to obtain the helmet body; Step 2, treating the polyurea coating on the helmet body; Step 3, primary degradation of the helmet body; Step 4, secondary degradation of the helmet body; Step 5, drying the recycled fiber cloth. The recycling method of this invention first treats the polyurea coating on the surface of the bulletproof helmet. Treating the polyurea coating on the surface of the bulletproof helmet facilitates the diffusion of the degradation liquid inside the helmet, which can greatly improve the degradation efficiency of the bulletproof helmet. This method does not require cutting the discarded bulletproof helmet, reducing the difficulty of processing the bulletproof helmet, and can effectively recover aramid fibers or polyethylene fibers from the bulletproof helmet. The recovered fibers have minimal damage, high mechanical property retention rate, and high recycling value.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a method for recycling discarded bulletproof helmets. Background Technology

[0002] Aramid fiber is a high-performance fiber material spun from aromatic polyamide resin, possessing advantages such as high strength and modulus, high temperature resistance, corrosion resistance, good insulation, and low specific gravity. Ultra-high molecular weight polyethylene fiber, abbreviated as UHMWPE fiber, also known as high-strength, high-modulus polyethylene fiber, is an unbranched linear polyethylene with a molecular weight of over 1.5 million. It boasts excellent comprehensive properties, including low specific gravity, high strength and modulus, aging resistance, and good chemical stability. Aramid fiber and ultra-high molecular weight polyethylene fiber are currently the most widely used high-performance bulletproof materials both domestically and internationally.

[0003] Bulletproof products made from ultra-high molecular weight polyethylene (UHMWPE) and aramid fibers can effectively protect the lives of police officers. However, precisely because of their material properties, the disposal of obsolete bulletproof products is quite difficult. Currently, the main methods for disposing of obsolete bulletproof products in my country include open-air incineration, underground landfill, and open-air or warehouse storage. These methods have significant drawbacks: on the one hand, incineration and landfill pollute the environment, and storage occupies a large amount of land resources and storage space; on the other hand, none of these methods can recover the still usable fibers from obsolete bulletproof products, resulting in a serious waste of resources.

[0004] Patent CN108219190A discloses a method for preparing aramid pulp from discarded bulletproof helmets. The method involves separating fibers and resin through steps such as cutting and crushing, solvent soaking, ball milling, and centrifugation, and then using the recovered fibers to prepare aramid pulp. While this method can recover aramid fibers from retired bulletproof helmets, it also has drawbacks: First, aramid fibers have extremely high strength and modulus, while bulletproof helmets are made of many layers of aramid fiber woven fabric stacked and cured with resin, making cutting very difficult; second, the surface of bulletproof helmets generally has a dense polyurea coating, which, without removing, makes it difficult for solvents to penetrate the helmet's interior. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention is proposed. This invention provides a method for recycling obsolete bulletproof helmets, solving the technical problem in the prior art where the dense polyurea coating on the surface of bulletproof helmets makes it difficult for solvents to penetrate the helmet during recycling, thus causing significant challenges in the recycling process.

[0006] This invention provides a method for recycling obsolete bulletproof helmets, comprising the following steps: Step 1, disassembling the obsolete bulletproof helmet to obtain the helmet body, head support structure, screws, metal clips, and surface protective fabric; Step 2, treating the polyurea coating on the helmet body by placing the disassembled helmet body obtained in Step 1 into an oven for baking at a temperature of 70-140℃ for 2-6 hours, then removing the helmet body from the oven and peeling off the polyurea coating on the helmet surface; Step 3, primary degradation of the helmet body by placing the treated helmet body from Step 2 into a reaction vessel for primary degradation by adding degradation solution to the reaction vessel and then heating the reaction vessel at a temperature of 70-160℃. The time is 8-24 hours; then the degradation solution in the reactor is cooled to below 60°C, the helmet body is removed, and the fiber cloth constituting the helmet body is peeled off layer by layer to obtain sheet-like fiber cloth; Step 4, secondary degradation of the helmet body, the sheet-like fiber cloth obtained in step 3 is put back into the degradation solution in step 3 for heating, the heating temperature is 70-160°C, and the heating time is 4-12 hours; then the degradation solution in the reactor is cooled to room temperature, filtered, and the recovered fiber cloth and the recovered degradation solution are obtained; Step 5, drying treatment of the recovered fiber cloth, the recovered fiber cloth obtained in step 4 is washed with water, filtered, and then placed in an oven for baking, the oven temperature is 80-130°C, and dried for 2-6 hours to obtain dried fiber cloth.

[0007] Furthermore, a 100L explosion-proof double-layered glass reactor was selected. The reactor is equipped with a high-temperature circulating oil bath and a low-temperature coolant circulating pump. The reactor is not completely sealed and has a connection port to a condenser. During the degradation reaction, the organic vapor is condensed and refluxed through the condenser, and the gas produced by the reaction is harmlessly discharged after being absorbed by the tail gas.

[0008] Preferably, the helmet body is made of either aramid fiber or ultra-high molecular weight polyethylene fiber.

[0009] Preferably, the degradation solution is one or more of methanol, ethanol, n-pentanol, formic acid, acetic acid, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, and N,N-dimethylformamide.

[0010] Preferably, the degradation solution recovered in step 4 is treated by vacuum distillation and recycled as the degradation solution in step 3.

[0011] Preferably, in step 2, the oven temperature is 80-130℃.

[0012] Preferably, in step 3, the heating temperature of the reaction vessel is 80-150℃.

[0013] Preferably, in step 4, the heating temperature of the reaction vessel is 80-150℃.

[0014] In the reactor, organic vapors are condensed and refluxed through a condenser, and the gases produced by the reaction are absorbed by the tail gas and then discharged harmlessly.

[0015] Preferably, the materials of the scrapped bulletproof helmet include ultra-high molecular weight polyethylene fiber and aramid fiber.

[0016] Furthermore, the ultra-high molecular weight polyethylene (UHMWPE) fiber unidirectional fabric, made from bulletproof helmets, can be used in civilian protection to manufacture safety slings, soft handcuffs, safety ropes, cut-resistant gloves, cut-resistant work clothes, stab-resistant vests, etc.; in the marine industry, it can be made into mooring cables, trawl cables, cables for marine aquaculture, cables for seabed harvesting operations, etc.

[0017] Furthermore, aramid fiber woven fabric, made from bulletproof helmets made of aramid fibers, can be used in personal protective equipment such as brake pads, clutch plates, and asbestos substitutes for gaskets. It can also be used as a material in the manufacture of fire suits, fire masks, fire blankets, escape ropes, flame-retardant curtains, and cut-resistant gloves.

[0018] This invention provides a method for recycling discarded bulletproof helmets. The method includes the following steps: Step 1, disassembling the discarded bulletproof helmet to obtain the helmet body; Step 2, treating the polyurea coating on the helmet body; Step 3, primary degradation of the helmet body; Step 4, secondary degradation of the helmet body; Step 5, drying the recycled fiber cloth. The recycling method of this invention first treats the polyurea coating on the surface of the bulletproof helmet. Since the polyurea coating on the surface of the bulletproof helmet makes it difficult for solvents to penetrate into the helmet during recycling, increasing the difficulty of recycling, treating the polyurea coating facilitates the diffusion of the degradation liquid inside the helmet, greatly improving the degradation efficiency. Furthermore, this method does not require cutting the discarded bulletproof helmet, reducing the difficulty of processing it. It can effectively recover aramid or polyethylene fibers from the bulletproof helmet, with minimal damage to the recovered fibers, high retention of mechanical properties, and high recycling value. The recycling method of this invention uses mild reaction conditions, simple equipment, high process safety, and generates less waste, facilitating large-scale production. The degradation liquid is easy to recover and can be reused, which helps reduce processing costs. Attached Figure Description

[0019] The above and other objects, features, and advantages of the present invention will become more apparent from the more detailed description of the embodiments of the invention in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same parts or steps.

[0020] Figure 1 This is a schematic diagram of a recycling process for a scrapped bulletproof helmet provided in an embodiment of the present invention;

[0021] Figure 2 This is a flowchart illustrating the recycling process of a scrapped bulletproof helmet according to an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the recycled ultra-high molecular weight polyethylene fiber unidirectional fabric provided in Embodiment 1 of the present invention;

[0023] Figure 4 This is a schematic diagram of the recycled aramid fiber woven fabric provided in Embodiment 2 of the present invention. Detailed Implementation

[0024] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0025] Example 1

[0026] A scrapped bulletproof helmet (made of ultra-high molecular weight polyethylene fiber) was disassembled. The disassembled helmet body was placed in an oven and baked at 80°C for 5 hours. After that, the polyurea coating on the helmet body was peeled off. The helmet body with the polyurea coating removed was placed in a 100L explosion-proof double-layered glass reactor (Zhengzhou Kerry Instrument Equipment Co., Ltd.). The reactor was equipped with a high-temperature circulating oil bath and a low-temperature coolant circulating pump. Acetic acid was added to the reactor until the helmet body was completely submerged. The reactor was heated to 120°C using the high-temperature circulating oil bath for primary degradation of the helmet body. After 20 hours of degradation, heating was stopped, and the degradation solution in the reactor was cooled to 60°C using the low-temperature coolant circulating pump. The helmet body was then removed, and the unidirectional fiber fabric of the helmet body was peeled off layer by layer to obtain sheet-like unidirectional fiber fabric. The sheet-like unidirectional fiber fabric was then placed in the degradation solution and heated to 120°C for secondary degradation. After 10 hours of secondary degradation, heating was stopped, and the degradation solution was cooled to room temperature. Vacuum filtration was performed using a Buchner funnel and a filter bottle to obtain the recovered unidirectional fiber fabric and the recovered degradation solution. After washing the recycled unidirectional fiber fabric with water, it is placed in a 110℃ oven and dried for 4 hours to obtain dried ultra-high molecular weight polyethylene fiber unidirectional fabric. The dried ultra-high molecular weight polyethylene fiber unidirectional fabric is as follows: Figure 3 As shown. The recovered degradation solution, after vacuum distillation, can be used for the next batch of degradation.

[0027] Figure 3 This is a schematic diagram of the recycled ultra-high molecular weight polyethylene fiber unidirectional fabric provided in Embodiment 1 of the present invention; Figure Figure 3 As shown, the recovered ultra-high molecular weight polyethylene fibers were subjected to monofilament tensile testing using a WDW-100H (0.5 grade) microcomputer-controlled electronic universal testing machine (Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd.). The breaking strength was 25.96 cN / dtex, which, compared with the original fiber's 28.5 cN / dtex, showed a strength retention rate of 91.09%. The resin residue rate of the recovered fibers was determined to be 0.94% using a thermogravimetric analyzer HTG-1 (Beijing Hengjiu Experimental Equipment Co., Ltd.).

[0028] Example 2

[0029] A discarded bulletproof helmet (made of aramid fiber) was disassembled. The helmet body was placed in a 100℃ oven for 3 hours, then removed, and the polyurea coating was peeled off. The helmet body, now without the polyurea coating, was placed in a 100L explosion-proof double-layered glass reactor (Zhengzhou Kerry Instrument Equipment Co., Ltd.). This reactor was equipped with a high-temperature circulating oil bath and a low-temperature coolant circulation pump. Xylene, a degradation solution, was added to the reactor until the helmet body was completely submerged. The reactor was heated to 150℃ for primary degradation. After 12 hours of degradation, heating was stopped, and the degradation solution in the reactor was cooled to 60℃ using the low-temperature coolant circulation pump. The helmet body was then removed, and the fiber woven fabric was peeled off layer by layer to obtain sheet-like fiber woven fabric. This sheet-like fiber woven fabric was then placed in the degradation solution and heated to 150℃ for secondary degradation. After 6 hours of secondary degradation, heating was stopped, the degradation solution was cooled to room temperature, filtered, and the recovered fiber woven fabric and recovered degradation solution were obtained. The recovered woven fabric is washed with water and then placed in a 120℃ oven for 4 hours to dry, yielding dried aramid fiber woven fabric. The recovered degradation solution is distilled under reduced pressure and can be used for the next batch of degradation.

[0030] Figure 4 This is a schematic diagram of the recycled aramid fiber woven fabric provided in Embodiment 2 of the present invention, as shown below. Figure 4 As shown, the recovered aramid fibers were subjected to monofilament tensile testing using a WDW-100H (0.5 grade) microcomputer-controlled electronic universal testing machine (Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd.). The breaking strength was 20.47 cN / dtex, which, compared to the original fiber's 22.4 cN / dtex, showed a strength retention rate of 91.38%. The resin residue rate of the recovered fibers was determined to be 0.64% using a thermogravimetric analyzer HTG-1 (Beijing Hengjiu Experimental Equipment Co., Ltd.).

[0031] Example 3

[0032] A discarded bulletproof helmet (made of aramid fiber) was disassembled. The helmet body was placed in a 120℃ oven for 2 hours, then removed, and the polyurea coating was peeled off. The helmet body without the polyurea coating was then placed in a 100L explosion-proof double-layered glass reactor (Zhengzhou Kerry Instrument Equipment Co., Ltd.). This reactor was equipped with a high-temperature circulating oil bath and a low-temperature coolant circulation pump. N,N-dimethylformamide degradation solution was added to the reactor until the helmet body was completely submerged. The reactor was heated to 140℃ for primary degradation. After 12 hours of degradation, heating was stopped, and the degradation solution was cooled to 60℃. The helmet body was then removed, and the fiber woven fabric was peeled off layer by layer to obtain sheet-like fiber woven fabric. This sheet-like fabric was then placed in the degradation solution and heated to 140℃ for secondary degradation. After 6 hours of degradation, heating was stopped, and the degradation solution in the reactor was cooled to room temperature using a low-temperature coolant circulation pump. The solution was then filtered, yielding recovered fiber woven fabric and recovered degradation solution. The recovered woven fabric is washed with water and then placed in a 130℃ oven for 4 hours to dry, yielding dried aramid fiber woven fabric. The recovered degradation solution is distilled under reduced pressure and can be used for the next batch of degradation.

[0033] The recovered aramid fibers were subjected to monofilament tensile testing using a WDW-100H (0.5 grade) microcomputer-controlled electronic universal testing machine (Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd.). The breaking strength was 20.76 cN / dtex, which, compared to the original fiber's 22.4 cN / dtex, showed a strength retention rate of 92.68%. The residual resin rate of the recovered resin was determined to be 0.82% using a thermogravimetric analyzer HTG-1 (Beijing Hengjiu Experimental Equipment Co., Ltd.).

[0034] Example 4

[0035] A discarded bulletproof helmet (made of ultra-high molecular weight polyethylene fiber) was disassembled. The helmet body was placed in a 90℃ oven for 4 hours, then removed, and the polyurea coating was peeled off. The helmet body without the polyurea coating was then placed in a 100L explosion-proof double-layered glass reactor (Zhengzhou Kerry Instrument Equipment Co., Ltd.). This reactor was equipped with a high-temperature circulating oil bath and a low-temperature coolant circulation pump. Ethanol was added to the reactor until the helmet body was completely submerged, and the temperature was raised to 80℃ for primary degradation. After 20 hours of degradation, heating was stopped, and the degradation solution in the reactor was cooled to 60℃ using the low-temperature coolant circulation pump. The helmet body was then removed, and the unidirectional fiber fabric was peeled off layer by layer to obtain sheet-like unidirectional fiber fabric. The unidirectional fiber fabric was then placed in the degradation solution and heated to 80℃ for secondary degradation. After 10 hours of degradation, heating was stopped, the degradation solution was cooled to room temperature, filtered, and the recovered unidirectional fiber fabric and recovered degradation solution were obtained. The recovered unidirectional fiber fabric is washed with water and then placed in a 100℃ oven for 4 hours to dry, yielding dried ultra-high molecular weight polyethylene fiber unidirectional fabric. The recovered degradation solution is distilled under reduced pressure and can be used for the next batch of degradation.

[0036] The recovered ultra-high molecular weight polyethylene (UHMWPE) fibers were subjected to monofilament tensile testing using a WDW-100H (0.5 grade) microcomputer-controlled electronic universal testing machine (Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd.). The breaking strength was 26.56 cN / dtex, which, compared to the original fiber's 28.5 cN / dtex, showed a strength retention rate of 93.19%. The resin residue rate of the recovered fibers was determined to be 2.57% using a thermogravimetric analyzer HTG-1 (Beijing Hengjiu Experimental Equipment Co., Ltd.).

[0037] Example 5

[0038] A discarded bulletproof helmet (made of ultra-high molecular weight polyethylene fiber) was disassembled. The helmet body was placed in a 110℃ oven for 3 hours, then removed, and the polyurea coating was peeled off. The helmet body without the polyurea coating was then placed in a 100L explosion-proof double-layered glass reactor (Zhengzhou Kerry Instrument Equipment Co., Ltd.). This reactor was equipped with a high-temperature circulating oil bath and a low-temperature coolant circulating pump. Butanone (MEK) was added to the reactor until the helmet body was completely submerged, and the temperature was raised to 80℃ for primary degradation. After 24 hours of degradation, heating was stopped, and the degradation solution was cooled to 60℃. The helmet body was then removed, and the unidirectional fiber fabric was peeled off layer by layer to obtain sheet-like unidirectional fiber fabric. The unidirectional fiber fabric was then placed in the degradation solution and heated to 80℃ for secondary degradation. After 12 hours of degradation, heating was stopped, the degradation solution was cooled to room temperature, filtered, and the recovered unidirectional fiber fabric and recovered degradation solution were obtained. The recovered unidirectional fiber fabric is washed with water and then placed in a 100℃ oven for 4 hours to dry, yielding dried ultra-high molecular weight polyethylene fiber unidirectional fabric. The recovered degradation solution is distilled under reduced pressure and can be used for the next batch of degradation.

[0039] The recovered ultra-high molecular weight polyethylene fibers were subjected to monofilament tensile testing using a WDW-100H (0.5 grade) microcomputer-controlled electronic universal testing machine (Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd.). The breaking strength was 26.33 cN / dtex, which, compared with the original fiber's 28.5 cN / dtex, showed a strength retention rate of 92.39%. The resin residue rate of the recovered fibers was determined to be 2.32% using a thermogravimetric analyzer HTG-1 (Beijing Hengjiu Experimental Equipment Co., Ltd.).

[0040] Example 6

[0041] A discarded bulletproof helmet (made of aramid fiber) was disassembled. The helmet body was placed in a 130℃ oven for 2 hours, then removed, and the polyurea coating was peeled off. The helmet body without the polyurea coating was then placed in a 100L explosion-proof double-layered glass reactor (Zhengzhou Kerry Instrument Equipment Co., Ltd.). This reactor is equipped with a high-temperature circulating oil bath and a low-temperature coolant circulation pump. Toluene degradation solution was added to the reactor until the helmet body was completely submerged, and the temperature was raised to 110℃ for primary degradation. After 16 hours of degradation, heating was stopped, and the degradation solution was cooled to 60℃. The helmet body was then removed, and the fiber woven fabric was peeled off layer by layer to obtain sheet-like fiber woven fabric. The fiber woven fabric was then placed in the degradation solution and heated to 110℃ for secondary degradation. After 8 hours of secondary degradation, heating was stopped, and the degradation solution was cooled to room temperature and filtered to obtain the recovered fiber woven fabric and the recovered degradation solution. The recovered woven fabric is washed with water and then placed in a 120℃ oven for 4 hours to dry, yielding dried aramid fiber woven fabric. The recovered degradation solution is distilled under reduced pressure and can be used for the next batch of degradation.

[0042] The recovered aramid fibers were subjected to monofilament tensile testing using a WDW-100H (0.5 grade) microcomputer-controlled electronic universal testing machine (Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd.). The breaking strength was 20.97 cN / dtex, which, compared to the original fiber's 22.4 cN / dtex, showed a strength retention rate of 93.62%. The residual resin rate of the recovered resin was determined to be 2.34% using a thermogravimetric analyzer HTG-1 (Beijing Hengjiu Experimental Equipment Co., Ltd.).

[0043] Example 7

[0044] A discarded bulletproof helmet (made of aramid fiber) was disassembled. The disassembled helmet body was placed in an 80℃ oven for 6 hours, then removed, and the polyurea coating was peeled off. The helmet body without the polyurea coating was then placed in a 100L explosion-proof double-layered glass reactor (Zhengzhou Kerry Instrument Equipment Co., Ltd.). This reactor is equipped with a high-temperature circulating oil bath and a low-temperature coolant circulation pump. Pentyl alcohol was added to the reactor until the helmet body was completely submerged, and the temperature was raised to 140℃ for primary degradation. After 12 hours of degradation, heating was stopped, and the degradation solution in the reactor was cooled to 60℃ using the low-temperature coolant circulation pump. The helmet body was then removed, and the fiber woven fabric was peeled off layer by layer to obtain sheet-like fiber woven fabric. The fiber woven fabric was then placed in the degradation solution and heated to 140℃ for secondary degradation. After 6 hours of secondary degradation, heating was stopped, the degradation solution was cooled to room temperature, filtered, and the recovered fiber woven fabric and recovered degradation solution were obtained. The recovered woven fabric is washed with water and then placed in a 130℃ oven for 4 hours to dry, yielding dried aramid fiber woven fabric. The recovered degradation solution is distilled under reduced pressure and can be used for the next batch of degradation.

[0045] The recovered aramid fibers were subjected to monofilament tensile testing using a WDW-100H (0.5 grade) microcomputer-controlled electronic universal testing machine (Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd.). The breaking strength was 20.56 cN / dtex, which, compared to the original fiber's 22.4 cN / dtex, showed a strength retention rate of 91.79%. The residual resin rate of the recovered resin was determined to be 1.13% using a thermogravimetric analyzer HTG-1 (Beijing Hengjiu Experimental Equipment Co., Ltd.).

[0046] Example 8

[0047] A discarded bulletproof helmet (made of ultra-high molecular weight polyethylene fiber) was disassembled. The disassembled helmet body was placed in a 120℃ oven for 3 hours, then removed, and the polyurea coating on the helmet body was peeled off. The helmet body without the polyurea coating was then placed in a 100L explosion-proof double-layered glass reactor (Zhengzhou Kerry Instrument Equipment Co., Ltd.). This reactor is equipped with a high-temperature circulating oil bath and a low-temperature coolant circulating pump. Methyl isobutyl ketone (Methyl isobutyl ketone) degradation solution was added to the reactor until the helmet body was completely submerged, and the temperature was raised to 120℃ for primary degradation. After 24 hours of degradation, heating was stopped, and the degradation solution was cooled to 60℃. The helmet body was then removed, and the unidirectional fiber fabric of the helmet body was peeled off layer by layer to obtain sheet-like unidirectional fiber fabric. The unidirectional fiber fabric was then placed in the degradation solution and heated to 120℃ for secondary degradation. After 12 hours of degradation, heating was stopped, the degradation solution was cooled to room temperature, filtered, and the recovered unidirectional fiber fabric and recovered degradation solution were obtained. The recovered unidirectional fiber fabric is washed with water and then placed in a 120℃ oven for 4 hours to dry, yielding dried ultra-high molecular weight polyethylene fiber unidirectional fabric. The recovered degradation solution is distilled under reduced pressure and can be used for the next batch of degradation.

[0048] The recovered ultra-high molecular weight polyethylene fibers were subjected to monofilament tensile testing using a WDW-100H (0.5 grade) microcomputer-controlled electronic universal testing machine (Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd.). The breaking strength was 25.89 cN / dtex, which, compared to the original fiber's 28.5 cN / dtex, showed a strength retention rate of 90.84%. The resin residue rate of the recovered fibers was determined to be 1.35% using a thermogravimetric analyzer HTG-1 (Beijing Hengjiu Experimental Equipment Co., Ltd.).

[0049] Example 9

[0050] A scrapped bulletproof helmet (made of ultra-high molecular weight polyethylene fiber) was disassembled. The disassembled helmet body was placed in an oven and baked at 80°C for 5 hours. After that, the polyurea coating on the helmet body was peeled off. The helmet body, with the polyurea coating removed, was immersed in a 100L explosion-proof double-layered glass reactor (Zhengzhou Kerry Instrument Equipment Co., Ltd.). This reactor was equipped with a high-temperature circulating oil bath and a low-temperature cooling liquid circulation pump. Acetic acid was added to the reactor until the helmet body was completely submerged. The reactor was heated to 120°C using the high-temperature circulating oil bath for primary degradation of the helmet body. After 16 hours of degradation, heating was stopped, and the degradation solution in the reactor was cooled to 60°C using the low-temperature cooling liquid circulation pump. The helmet body was then removed, and the unidirectional fiber fabric was peeled off layer by layer to obtain sheet-like unidirectional fiber fabric. This sheet-like unidirectional fiber fabric was then immersed in the degradation solution and heated to 120°C for secondary degradation. After 8 hours of secondary degradation, heating was stopped, and the degradation solution was cooled to room temperature. Vacuum filtration was performed using a Buchner funnel and a filter bottle to obtain the recovered unidirectional fiber fabric and the recovered degradation solution. The recovered unidirectional fiber fabric was washed with water and then placed in a 110°C oven for 4 hours of drying to obtain dried ultra-high molecular weight polyethylene fiber unidirectional fabric. The recovered degradation solution, after vacuum distillation, can be used for the next batch of degradation.

[0051] The recovered ultra-high molecular weight polyethylene fibers were subjected to monofilament tensile testing using a WDW-100H (0.5 grade) microcomputer-controlled electronic universal testing machine (Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd.). The breaking strength was 26.12 cN / dtex, which, compared to the original fiber's 28.5 cN / dtex, showed a strength retention rate of 91.65%. The resin residue rate of the recovered fibers was determined to be 1.21% using a thermogravimetric analyzer HTG-1 (Beijing Hengjiu Experimental Equipment Co., Ltd.).

[0052] Example 10

[0053] A discarded bulletproof helmet (made of aramid fiber) was disassembled. The helmet body was placed in a 100℃ oven for 3 hours, then removed, and the polyurea coating was peeled off. The helmet body, now without the polyurea coating, was placed in a 100L explosion-proof double-layered glass reactor (Zhengzhou Kerry Instrument Equipment Co., Ltd.). This reactor was equipped with a high-temperature circulating oil bath and a low-temperature coolant circulation pump. Xylene, a degradation solution, was added to the reactor until the helmet body was completely submerged. The reactor was heated to 140℃ for primary degradation. After 12 hours of degradation, heating was stopped, and the degradation solution in the reactor was cooled to 60℃ using the low-temperature coolant circulation pump. The helmet body was then removed, and the fiber woven fabric was peeled off layer by layer to obtain sheet-like fiber woven fabric. This sheet-like fiber woven fabric was then placed in the degradation solution and heated to 140℃ for secondary degradation. After 6 hours of secondary degradation, heating was stopped, the degradation solution was cooled to room temperature, filtered, and the recovered fiber woven fabric and recovered degradation solution were obtained. The recovered woven fabric is washed with water and then placed in a 120℃ oven for 4 hours to dry, yielding dried aramid fiber woven fabric. The recovered degradation solution is distilled under reduced pressure and can be used for the next batch of degradation.

[0054] The recovered aramid fibers were subjected to monofilament tensile testing using a WDW-100H (0.5 grade) microcomputer-controlled electronic universal testing machine (Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd.). The breaking strength was 20.64 cN / dtex, which, compared to the original fiber's 22.4 cN / dtex, showed a strength retention rate of 92.14%. The resin residue rate of the recovered fibers was determined to be 0.88% using a thermogravimetric analyzer HTG-1 (Beijing Hengjiu Experimental Equipment Co., Ltd.).

[0055] Table 1. Test results of fibers recovered in Examples 1-10

[0056]

[0057]

[0058] 1. As shown in Table 1, Examples 1, 4, 5, 8, and 9 all used discarded bulletproof helmets made of UHMWPE material for recycling. Examples 4 and 5 had the lowest degradation temperatures, both at 80℃. Examples 4 and 5 also had the highest mechanical properties, with breaking strengths of 26.56 cN / dtex and 26.33 cN / dtex, respectively. Therefore, the lower the degradation temperature, the better the mechanical properties of the recycled fibers.

[0059] 2. Examples 2, 3, 6, 7, and 10 all used discarded bulletproof helmets made of aramid material for recycling. Examples 3, 7, and 10 had the same degradation temperature of 140℃ and the same total degradation time of 18 hours. The degradation solutions were DMF, n-pentanol, and xylene, respectively. The strength retention rates of the recycled aramid fibers were 92.68%, 91.79%, and 92.14%, respectively, and the resin residue rates were 0.82%, 1.13%, and 0.88%, respectively. The type of degradation solution affects the mechanical properties and degradation effect of the recycled fibers. DMF and xylene, as degradation solutions, resulted in high retention rates of mechanical properties and low resin residue rates in the recycled aramid fibers, demonstrating excellent degradation effects.

[0060] 3. The degradation temperature in Examples 1 and 9 was 120°C, the degradation solution was the same (acetic acid), and the total degradation time was 30 h and 24 h, respectively. The mechanical strength retention rates of the recovered ultra-high molecular weight polyethylene fibers were 91.09% and 91.65%, respectively, and the resin residue rates were 0.94% and 1.21%, respectively. The longer the degradation time, the lower the resin residue rate and the better the degradation effect.

[0061] 4. Place the disassembled bulletproof helmet body into an oven for baking. Polyurea will fail and soften at high temperatures (70-140℃), and its adhesion to the helmet body will decrease. Through high-temperature treatment, the polyurea coating attached to the helmet body can be easily peeled off. This can solve the technical problem that the dense polyurea coating on the surface of the bulletproof helmet makes it difficult for solvents to enter the helmet during the recycling process, which makes the recycling of bulletproof helmets difficult.

[0062] 5. Because the polyurea coating on the helmet body was treated first, the chemical stability of the resin in the helmet body decreased under high temperature conditions. Under the action of the degradation solution, the molecular bonds broke and dissolved in the degradation solution, thus completing the separation of resin and fiber.

[0063] 6. Since the fiber cloth of the helmet body is usually compressed very tightly, there is residual resin on the fiber cloth obtained through primary degradation, which requires secondary degradation. Peeling the fiber cloth layer by layer before secondary degradation can increase the reaction area and improve the degradation efficiency.

[0064] 7. The degradation method of the present invention is carried out at a temperature below 150°C and under normal pressure, which is highly safe and does not require a pressure vessel; while conventional degradation methods require high temperature (>200°C) and high pressure conditions, and pressure vessels pose a risk of explosion and liquid spraying.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications or equivalent substitutions made within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of recycling a retired ballistic helmet, the method comprising: The method comprises the following steps: Step 1, disassembly of the retired bulletproof helmet The retired bulletproof helmet is disassembled to obtain a helmet body, a head support structure, screws, metal clamps and surface protective fabric; Step 2, treatment of the polyurea coating of the helmet body The helmet body disassembled in step 1 is placed in an oven for baking, the oven temperature is 70-140 DEG C, after baking for 2-6 hours, the helmet body is taken out of the oven, and the polyurea coating on the surface of the helmet body is torn off; Step 3, first degradation of the helmet body The helmet body treated in step 2 is put into a reaction kettle for first degradation, a degradation solution is added to the reaction kettle, and then the reaction kettle is heated, the heating temperature is 70-160 DEG C, and the heating time is 8-24 hours; then the degradation solution in the reaction kettle is cooled to below 60 DEG C, the helmet body is taken out, the fiber cloth constituting the helmet body is peeled off layer by layer, and a sheet-shaped fiber cloth is obtained; Step 4, second degradation of the helmet body The sheet-shaped fiber cloth obtained in step 3 is again put into the degradation solution in step 3 for heating, the heating temperature is 70-160 DEG C, and the heating time is 4-12 hours; then the degradation solution in the reaction kettle is cooled to room temperature, and after filtration, the recovered fiber cloth and the recovered degradation solution are obtained; Step 5, drying treatment of the recovered fiber cloth The recovered fiber cloth obtained in step 4 is washed with water, filtered, and then baked in an oven, the oven temperature is 80-130 DEG C, and after drying for 2-6 hours, dry fiber cloth is obtained.

2. A method of recycling a retired ballistic helmet according to claim 1, wherein, The material of the helmet body is one of aramid fiber or ultra-high molecular weight polyethylene fiber.

3. The method for recycling the retired bulletproof helmet according to claim 2, characterized in that, The degradation solution is one or more of methanol, ethanol, n-pentanol, formic acid, acetic acid, toluene, xylene, butanone, methyl isobutyl ketone and N,N-dimethylformamide.

4. The method of recycling a retired ballistic helmet of claim 1, wherein, The recovered degradation solution in step 4 is treated by reduced pressure distillation and recycled as the degradation solution in step 3.

5. The method of recycling a retired ballistic helmet of claim 1, wherein, In step 2, the oven temperature is 80-130 DEG C.

6. The method of recycling a retired ballistic helmet of claim 1, wherein, In step 3, the heating temperature of the reaction kettle is 80-150 DEG C.

7. The method of recycling a retired ballistic helmet of claim 1, wherein, In step 4, the heating temperature of the reaction kettle is 80-150 DEG C.

8. The method of recycling a retired ballistic helmet of claim 1, wherein, The material of the retired bulletproof helmet includes ultra-high molecular weight polyethylene fiber material and aramid fiber material.

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