Nano-modified antistatic sheet and preparation method thereof

Abstract

The invention relates to the technical field of plastic plates, and particularly discloses a nano-modified antistatic thin plate and a preparation method thereof. The invention discloses a nano-modified antistatic thin plate and a preparation method thereof. The nano-modified antistatic thin plate comprises the following components in parts by weight: 100-120 parts of linear low density polyethylene, 10-15 parts of modified fibers, 5-10 parts of carbon nanotubes, 1-3 parts of a processing aid and 0.5-1 part of an antioxidant, and the modified fibers are prepared by performing silicon dioxide deposition on a carbon fiber matrix. The nano-modified antistatic thin plate prepared by the invention has the advantages of good mechanical property and good antistatic property.

Description

Technical Field

[0001] The present application relates to the technical field of plastic sheets, and more specifically, to a nano-modified antistatic sheet and a preparation method thereof. Background Art

[0002] Linear low-density polyethylene has demonstrated significant advantages in many fields. Due to its good flexibility, impact resistance and processing performance, it is widely used in the manufacture of thin sheets in the packaging, electronics, medical and other industries.

[0003] However, the inherent high insulation properties of linear low-density polyethylene (LLDPE) make it extremely susceptible to static charge accumulation during use. This problem causes numerous practical problems, most notably the tendency of LLDPE sheets to attract dust, affecting the product's appearance and user experience. More seriously, in flammable and explosive environments, the accumulation of static charge can cause electric shock, leading to serious safety accidents. For example, when LLDPE containers are used at gas stations, static discharge can cause fires or explosions.

[0004] Traditional antistatic measures for linear low-density polyethylene (LLDPE) primarily involve adding small molecule antistatic agents and conductive fillers. However, these methods have significant drawbacks. Small molecule antistatic agents rely on migrating to the material surface to exert their antistatic effect. However, their antistatic performance is not stable and is easily lost when the material surface is wiped or washed. Fluctuations in ambient humidity can also interfere with their migration, resulting in a lack of sustained antistatic performance. While adding conductive fillers can improve material conductivity, achieving optimal antistatic performance often requires a filler content exceeding 20%. Such a high filler content not only significantly increases material density and cost but also severely compromises the mechanical properties of LLDPE, such as reduced tensile strength, which can lead to product breakage. Furthermore, the material's processing fluidity is compromised, making it difficult to uniformly fill the mold during plastic sheet molding, failing to meet sheet molding process requirements. This significantly limits the further application and development of LLDPE in related fields.

[0005] A Chinese patent application, publication number CN110492122A, discloses a conductive plastic plate for a composite bipolar plate and its preparation method and equipment. This invention discloses a conductive plastic plate suitable for composite bipolar plates, comprising the following components by weight: 35%-55% base resin, 10%-20% superconductive carbon black, 20%-50% conductive graphite, 5%-15% carbon nanotubes, 0.5%-10% compatibilizer, and 3%-30% toughening agent. This document describes the addition of large amounts of conductive fillers, compatibilizers, and toughening agents to improve the conductive and mechanical properties of the conductive plastic plate. This increases production costs, but relying solely on the compatibilizer and toughening agent makes it difficult to significantly improve the mechanical properties of the conductive plastic plate. Summary of the Invention

[0006] In order to further improve the mechanical properties and antistatic properties of plastic sheets, the present application provides a nano-modified antistatic sheet and a preparation method thereof.

[0007] In a first aspect, the present application provides a nano-modified antistatic sheet, which adopts the following technical solution: A nano-modified antistatic sheet comprises the following components in parts by weight: 100-120 parts of linear low-density polyethylene, 10-15 parts of modified fibers, 3-6 parts of carbon nanotubes, 1-3 parts of processing aids, and 0.5-1 part of antioxidants; the modified fibers consist of a carbon fiber matrix and a silicon dioxide layer wrapped on the surface thereof.

[0008] By adopting the above technical solution, the porous silica layer on the surface of the modified fiber forms a good intercalation effect with the plastic matrix, thereby improving the interface bonding strength and avoiding interface peeling between the spiral carbon fiber and the plastic matrix, thereby maintaining the stability and integrity of the conductive network. At the same time, the anchoring effect of the pores on the molecular chains of the plastic matrix can effectively transmit stress, further improving the mechanical properties of the thin plate.

[0009] Preferably, the modified fiber is obtained by mixing and reacting a carbon fiber matrix and silica gel.

[0010] By adopting the above technical solution, a porous layer of silica is deposited on the surface of the carbon fiber matrix. The porous structure increases the contact area between silica and the plastic matrix. When the molecular chains in the plastic matrix approach the silica layer, they can enter the gaps and form a mechanical interlocking structure, thereby improving the bonding force, avoiding displacement of the spiral carbon fibers when subjected to force, and maintaining the stability of the conductive network and stress dispersion path.

[0011] Preferably, the carbon fiber matrix is ​​obtained by dispersing helical carbon fibers in a tris(hydroxymethyl)aminomethane hydrochloride aqueous solution and reacting the resultant with dopamine hydrochloride.

[0012] By adopting the above technical solution, a layer of polydopamine is coated on the surface of the spiral carbon fiber. Polydopamine serves as a flexible transition layer, which absorbs and disperses stress, relieves the local stress concentration of the spiral carbon fiber during deformation, improves the fracture toughness of the fiber, and thus improves the mechanical properties of the thin plate; at the same time, the amino group and the silanol group of polydopamine enhance the bonding force between the silica layer and the carbon fiber matrix through coordination, effectively inhibits the peeling of the silica layer when subjected to stress, and thus improves the stability of the thin plate.

[0013] Preferably, the method for preparing the spiral carbon fiber comprises the following steps: soaking the plant fiber in an alkaline solution and an acid solution in sequence, drying the plant fiber, and then immersing the plant fiber in a urea aqueous solution, and then carbonizing the plant fiber to obtain the spiral carbon fiber.

[0014] By adopting the above technical solution, nitrogen is doped into the spiral carbon fiber. The nitrogen enters the lattice structure of the spiral carbon fiber during the carbonization process to form nitrogen doping. Nitrogen atoms have one more electron than carbon atoms. After doping, additional electrons are introduced into the spiral carbon fiber. These electrons can participate in conduction as carriers, thereby increasing the carrier concentration and improving the conductivity of the spiral carbon fiber, thereby improving the antistatic performance of the thin plate.

[0015] Preferably, the preparation of the silica gel comprises the following steps: mixing an organic silicon source and an inorganic silicon source, and adjusting the pH with an alkaline solution to obtain the silica gel.

[0016] By adopting the above technical solution, the organic silicon source and the inorganic silicon source work synergistically to make the porous silica layer deposited on the surface of the carbon fiber matrix have higher stability. At the same time, the addition of the inorganic silicon source enhances the pore wall strength of the porous silica layer, preventing it from breaking due to shear stress, maintaining the stability of the porous silica layer, and thereby enhancing the bonding force between the modified fiber and the plastic matrix, making the construction of the conductive network more stable and complete.

[0017] Preferably, the organic silicon source consists of tetraethyl orthosilicate, ethanol, hydrochloric acid and deionized water; and the inorganic silicon source consists of sodium silicate, hydrochloric acid and deionized water.

[0018] Preferably, the thickness of the silicon dioxide layer is ≤120 nm.

[0019] Preferably, the plant fiber is tea leaves or bamboo leaves.

[0020] Preferably, the mass ratio of the helical carbon fiber, tris(hydroxymethyl)aminomethane hydrochloric acid aqueous solution and dopamine hydrochloride is 1:(180-200):(0.4-0.6).

[0021] Preferably, the preparation method of the tris(hydroxymethyl)aminomethane hydrochloric acid aqueous solution is: uniformly mixing tris(hydroxymethyl)aminomethane base and water in a mass ratio of 1:(800-820), and then adjusting the pH to 7.5-8.5 with hydrochloric acid.

[0022] Preferably, the processing aid is one of stearic acid, zinc stearate and polyethylene wax.

[0023] Preferably, the antioxidant is one of antioxidant 1010, antioxidant 168 and antioxidant 1076.

[0024] In the second aspect, the present application provides a method for preparing a nano-modified antistatic thin plate, comprising the following steps: linear low-density polyethylene, modified fibers, carbon nanotubes, processing aids and antioxidants are mixed and added to a twin-screw extruder for melt blending, and then extruded and formed to obtain a nano-modified antistatic thin plate.

[0025] Preferably, the process parameters of the melt blending are: screw speed of 300-400 r / min, temperature of the feeding section of 160-180°C, and temperature of the extruder head of 200-220°C.

[0026] In summary, this application has the following beneficial effects: 1. When the material is impacted by external force, the spiral structure of the spiral carbon fiber reduces the influence of stress on the nano-modified antistatic sheet through its own deformation and energy dissipation, thereby improving the toughness and impact resistance of the sheet; at the same time, polydopamine forms a flexible interface phase after being coated on the surface of the spiral carbon fiber, which effectively absorbs impact energy through its viscoelastic behavior, and dissipates stress through the extension and fracture of the molecular chain when cracks are generated and expand, thereby inhibiting the rapid propagation of cracks and further enhancing the toughness of the sheet.

[0027] 2. A porous silica layer is deposited on the surface of the carbon fiber matrix. The rich pore structure on its surface increases the contact area between the plastic matrix and the modified fiber. When the plastic melt penetrates into the porous network of silica during processing, this part of the plastic matrix is ​​fixed by the pores between the silica during cooling and solidification, thereby improving the interfacial bonding strength, reducing the movement of the modified fiber when impacted, better bearing external forces, and effectively transmitting stress, thereby improving the strength, toughness and fatigue resistance of the nano-modified antistatic sheet. At the same time, the amino groups in the polydopamine molecules interact with each other through hydrogen bonds, producing adsorption and bonding with the surface of the silica particles, enhancing the bonding strength between the silica and the carbon fiber matrix, preventing the silica from falling off due to external forces on the sheet, and improving the stability of the sheet.

[0028] 3. Nitrogen is introduced during the preparation process of spiral carbon fibers. Nitrogen doping increases the carrier concentration in the spiral carbon fibers, making the migration of electrons inside the material more frequent, conducting charges in a timely manner, effectively reducing the resistance of the spiral carbon fibers, and improving their electrical conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the tensile properties and impact resistance of the nano-modified antistatic sheets of Examples 1-3 and Comparative Examples 1-2 of the present application.

[0030] Figure 2 Schematic diagram of the surface resistance of the nano-modified antistatic sheets of Examples 1-3 and Comparative Examples 1-2 of the present application.

[0031] Figure 3 is a scanning electron microscope image of the modified helical fiber of Example 2 of the present application. DETAILED DESCRIPTION

[0032] The present application is further described in detail below with reference to the embodiments.

[0033] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0034] Example 1: The nano-modified antistatic sheet of this example is composed of the following components: 100 g of linear low-density polyethylene, 10 g of modified fiber, 3 g of carbon nanotubes, 1 g of stearic acid, and 0.5 g of antioxidant 1010.

[0035] The preparation method of the modified fiber of this embodiment is as follows: 1) Mix 10g of tetraethyl orthosilicate, 8g of ethanol, and 15g of deionized water, and adjust the pH to 4 with hydrochloric acid to obtain an organic silicon source; mix 10g of sodium silicate and 50g of deionized water, and adjust the pH to 5 with hydrochloric acid to obtain an inorganic silicon source; add the inorganic silicon source to the organic silicon source, mix evenly, and add ammonia water to adjust the pH to 6.5 to obtain silica gel; 2) 0.5 g of tris(hydroxymethylaminomethane) base and 400 g of deionized water were mixed evenly, and hydrochloric acid was added to adjust the pH to 7.5 to obtain a tris(hydroxymethylaminomethane) hydrochloric acid aqueous solution; 1 g of helical carbon fiber was dispersed in 180 g of the tris(hydroxymethylaminomethane) hydrochloric acid aqueous solution, and ultrasonicated for 30 min. 0.4 g of dopamine hydrochloride was added, and the mixture was reacted at room temperature in the dark for 10 h. The mixture was then centrifuged, washed, and dried to obtain a carbon fiber matrix; 3) 5 g of carbon fiber matrix and 150 g of ethanol were mixed evenly, and ultrasonically dispersed for 20 min. The dispersed carbon fiber suspension was mixed evenly with 350 g of silica gel, and ammonia water was added to adjust the pH to 9. The mixture was heated to 60°C, reacted for 3 h, allowed to stand for 8 h, centrifuged, washed, dried, crushed and ground to obtain modified fibers. The average thickness of the silica deposition layer on the surface of the modified fibers was about 100 nm.

[0036] The preparation method of the spiral carbon fiber of the present embodiment is as follows: 10g bamboo leaves, 7g sodium hydroxide, 8g sodium sulfate and 100g deionized water are mixed uniformly, heated to 50°C, reacted for 2h, filtered, washed, and then immersed in 150g of sulfuric acid aqueous solution with a mass percentage concentration of 30%, ultrasonicated for 1h, filtered, washed, and dried. The mixture is sequentially immersed in a potassium hydroxide aqueous solution with a mass percentage concentration of 0.34%, a potassium carbonate aqueous solution with a mass percentage concentration of 0.83% and a zinc chloride aqueous solution with a soaking time of 3h, 3h and 4h respectively. After drying, it is immersed in 150g of urea aqueous solution with a mass percentage concentration of 1.2%, shaken for 2.5h, filtered, washed, and placed in a tubular furnace after drying. Under a nitrogen atmosphere, the temperature is increased to 800°C at a heating rate of 3°C / min, kept warm for 2h, washed to neutrality, and dried to obtain a spiral carbon fiber.

[0037] The preparation method of the nano-modified antistatic sheet of this embodiment is as follows: 100g of linear low-density polyethylene, 10g of modified fiber, 3g of carbon nanotubes, 1g of stearic acid and 0.5g of antioxidant 1010 are mixed and added to a twin-screw extruder for melt blending, the screw speed is adjusted to 300r / min, the temperature of the feeding section is 160°C, and the temperature of the extruder head is 200°C. After extrusion and molding, a nano-modified antistatic sheet is obtained.

[0038] Example 2: The nano-modified antistatic sheet of this example is composed of the following components: 120 g of linear low-density polyethylene, 15 g of modified fiber, 6 g of carbon nanotubes, 3 g of zinc stearate, and 1 g of antioxidant 168.

[0039] The preparation method of the modified fiber of this embodiment is as follows: 1) Mix 10g of tetraethyl orthosilicate, 25g of ethanol, and 5g of deionized water, and adjust the pH to 6 with hydrochloric acid to obtain an organic silicon source; mix 10g of sodium silicate and 100g of deionized water, and adjust the pH to 6 with hydrochloric acid to obtain an inorganic silicon source; add the inorganic silicon source to the organic silicon source, mix evenly, and add ammonia water to adjust the pH to 7.5 to obtain silica gel; 2) 0.5 g of tris(hydroxymethylaminomethane) base and 410 g of deionized water were mixed evenly, and hydrochloric acid was added to adjust the pH to 8.5 to obtain a tris(hydroxymethylaminomethane) hydrochloric acid aqueous solution; 1 g of helical carbon fiber was dispersed in 200 g of the tris(hydroxymethylaminomethane) hydrochloric acid aqueous solution, ultrasonically treated for 40 min, 0.6 g of dopamine hydrochloride was added, and the mixture was reacted at room temperature in the dark for 8 h, centrifuged, washed, and dried to obtain a carbon fiber matrix; 3) 5 g of carbon fiber matrix and 200 g of ethanol were mixed evenly, and ultrasonically dispersed for 40 min. The dispersed carbon fiber suspension was mixed evenly with 360 g of silica gel, and ammonia water was added to adjust the pH to 10. The mixture was heated to 60°C, reacted for 5 h, allowed to stand for 6 h, centrifuged, washed, dried, crushed and ground to obtain modified fibers. The average thickness of the silica deposition layer on the surface of the modified fibers was about 120 nm.

[0040] The preparation method of the spiral carbon fiber of this embodiment is as follows: 10g of tea, 7g of sodium hydroxide, 7.5g of sodium sulfate and 100g of deionized water are mixed uniformly, heated to 50°C, reacted for 2h, filtered, washed, and then immersed in 150g of sulfuric acid aqueous solution with a mass percentage concentration of 30%, ultrasonicated for 1h, filtered, washed, and dried, and soaked in potassium hydroxide aqueous solution with a mass percentage concentration of 0.34%, potassium carbonate aqueous solution with a mass percentage concentration of 0.83% and zinc chloride aqueous solution with a soaking time of 3h, 3h and 4h respectively. After drying, immersed in 150g of urea aqueous solution with a mass percentage concentration of 1.2%, vibrated for 2h, filtered, washed, and placed in a tubular furnace after drying. Under a nitrogen atmosphere, the temperature was raised to 800°C at a heating rate of 3°C / min, kept warm for 2h, washed to neutrality, and dried to obtain spiral carbon fiber.

[0041] The preparation method of the nano-modified antistatic sheet of this embodiment is as follows: 120g of linear low-density polyethylene, 15g of modified fiber, 6g of carbon nanotubes, 3g of zinc stearate and 1g of antioxidant 168 are mixed and added to a twin-screw extruder for melt blending, the screw speed is adjusted to 400r / min, the temperature of the feeding section is 180°C, and the temperature of the extruder head is 220°C. After extrusion and molding, a nano-modified antistatic sheet is obtained.

[0042] Example 3: The nano-modified antistatic sheet of this example is composed of the following components: 110 g of linear low-density polyethylene, 12 g of modified fiber, 5 g of carbon nanotubes, 2 g of polyethylene wax, and 0.8 g of antioxidant 1076.

[0043] The preparation method of the modified fiber of this embodiment is as follows: 1) Mix 10 g of tetraethyl orthosilicate, 20 g of ethanol, and 10 g of deionized water, and adjust the pH to 5 with hydrochloric acid to obtain an organic silicon source; mix 10 g of sodium silicate and 70 g of deionized water, and adjust the pH to 5.5 with hydrochloric acid to obtain an inorganic silicon source; add the inorganic silicon source to the organic silicon source, mix evenly, and add ammonia water to adjust the pH to 7 to obtain silica gel; 2) 0.5 g of tris(hydroxymethylaminomethane) base and 405 g of deionized water were mixed evenly, and hydrochloric acid was added to adjust the pH to 8 to obtain a tris(hydroxymethylaminomethane) hydrochloric acid aqueous solution; 1 g of helical carbon fiber was dispersed in 190 g of the tris(hydroxymethylaminomethane) hydrochloric acid aqueous solution, and ultrasonicated for 30 min. 0.5 g of dopamine hydrochloride was added, and the mixture was reacted at room temperature in the dark for 6 h. The mixture was centrifuged, washed, and dried to obtain a carbon fiber matrix; 3) 5 g of carbon fiber matrix and 160 g of ethanol were mixed evenly, and ultrasonically dispersed for 30 min. The dispersed carbon fiber suspension was mixed evenly with 350 g of silica gel, and ammonia water was added to adjust the pH to 9.5. The mixture was heated to 60°C, reacted for 4 h, allowed to stand for 6 h, centrifuged, washed, dried, crushed and ground to obtain modified fibers. The average thickness of the silica deposition layer on the surface of the modified fibers was about 105 nm.

[0044] The preparation method of the spiral carbon fiber of the present embodiment is as follows: 10g bamboo leaves, 7g sodium hydroxide, 8g sodium sulfate and 150g deionized water are mixed uniformly, heated to 50°C, reacted for 3h, filtered, washed, and then immersed in 150g of sulfuric acid aqueous solution with a mass percentage concentration of 30%, ultrasonicated for 1h, filtered, washed, and dried. The mixture is sequentially immersed in a potassium hydroxide aqueous solution with a mass percentage concentration of 0.3%, a potassium carbonate aqueous solution with a mass percentage concentration of 0.86%, and a zinc chloride aqueous solution with a soaking time of 4h, 3h and 3h, respectively. After drying, it is immersed in 150g of urea aqueous solution with a mass percentage concentration of 1.2%, shaken for 2h, filtered, washed, and placed in a tubular furnace after drying. Under a nitrogen atmosphere, the temperature is increased to 800°C at a heating rate of 2.5°C / min, kept warm for 2h, washed to neutrality, and dried to obtain a spiral carbon fiber.

[0045] The preparation method of the nano-modified antistatic sheet of this embodiment is as follows: 110g of linear low-density polyethylene, 12g of modified fiber, 5g of carbon nanotubes, 2g of polyethylene wax and 0.8g of antioxidant 1076 are mixed and added to a twin-screw extruder for melt blending, the screw speed is adjusted to 320r / min, the temperature of the feeding section is 170°C, and the temperature of the extruder head is 210°C. After extrusion and molding, a nano-modified antistatic sheet is obtained.

[0046] Comparative Example 1 The nano-modified antistatic sheet of this comparative example is composed of the following components: 120 g of linear low-density polyethylene, 15 g of modified fiber, 6 g of carbon nanotubes, 3 g of zinc stearate, and 1 g of antioxidant 168.

[0047] The preparation method of the modified fiber of this comparative example is as follows: 1) Mix 10g of tetraethyl orthosilicate, 25g of ethanol, and 5g of deionized water, and adjust the pH to 6 with hydrochloric acid to obtain an organic silicon source; mix 10g of sodium silicate and 100g of deionized water, and adjust the pH to 6 with hydrochloric acid to obtain an inorganic silicon source; add the inorganic silicon source to the organic silicon source, mix evenly, and add ammonia water to adjust the pH to 7.5 to obtain silica gel; 2) 0.5 g of tris(hydroxymethylaminomethane) base and 410 g of deionized water were mixed evenly, and hydrochloric acid was added to adjust the pH to 8.5 to obtain a tris(hydroxymethylaminomethane) hydrochloric acid aqueous solution; 5 g of spiral carbon fiber and 200 g of ethanol were mixed evenly, and ultrasonically dispersed for 40 min. The dispersed carbon fiber suspension was mixed evenly with 360 g of silica gel, and ammonia water was added to adjust the pH to 10. The mixture was heated to 60°C, reacted for 5 h, allowed to stand for 6 h, centrifuged, washed, dried, crushed and ground to obtain modified fiber. The average thickness of the silica deposition layer on the surface of the modified fiber was about 120 nm.

[0048] The preparation method of the spiral carbon fiber of this comparative example is as follows: 10g of tea leaves, 7g of sodium hydroxide, 7.5g of sodium sulfate and 100g of deionized water are mixed evenly, heated to 50°C, reacted for 2h, filtered, washed, and then immersed in 150g of sulfuric acid aqueous solution with a mass percentage concentration of 30%, ultrasonicated for 1h, filtered, washed, and dried, and soaked in potassium hydroxide aqueous solution with a mass percentage concentration of 0.34%, potassium carbonate aqueous solution with a mass percentage concentration of 0.83% and zinc chloride aqueous solution with a soaking time of 3h, 3h and 4h respectively. After drying, immersed in 150g of urea aqueous solution with a mass percentage concentration of 1.2%, vibrated for 2h, filtered, washed, and placed in a tubular furnace after drying. Under a nitrogen atmosphere, the temperature was raised to 800°C at a heating rate of 3°C / min, kept warm for 2h, washed to neutral, and dried to obtain spiral carbon fiber.

[0049] The preparation method of the nano-modified antistatic sheet of this comparative example is as follows: 120g of linear low-density polyethylene, 15g of modified fiber, 6g of carbon nanotubes, 3g of zinc stearate and 1g of antioxidant 168 are mixed and added to a twin-screw extruder for melt blending, the screw speed is adjusted to 400r / min, the temperature of the feeding section is 180°C, and the temperature of the extruder head is 220°C. After extrusion and molding, a nano-modified antistatic sheet is obtained.

[0050] Comparative Example 2 The nano-modified antistatic sheet of this comparative example is composed of the following components: 120 g of linear low-density polyethylene, 15 g of modified fiber, 6 g of carbon nanotubes, 3 g of zinc stearate, and 1 g of antioxidant 168.

[0051] The preparation method of the modified fiber of this comparative example is as follows: 1) Mix 10 g of tetraethyl orthosilicate, 25 g of ethanol, and 5 g of deionized water, and adjust the pH to 6 with hydrochloric acid to obtain silica gel. 2) 0.5 g of tris(hydroxymethylaminomethane) base and 410 g of deionized water were mixed evenly, and hydrochloric acid was added to adjust the pH to 8.5 to obtain a tris(hydroxymethylaminomethane) hydrochloric acid aqueous solution; 1 g of helical carbon fiber was dispersed in 200 g of the tris(hydroxymethylaminomethane) hydrochloric acid aqueous solution, ultrasonically treated for 40 min, 0.6 g of dopamine hydrochloride was added, and the mixture was reacted at room temperature in the dark for 8 h, centrifuged, washed, and dried to obtain a carbon fiber matrix; 3) 5 g of carbon fiber matrix and 200 g of ethanol were mixed evenly, and ultrasonically dispersed for 40 min. The dispersed carbon fiber suspension was mixed evenly with 360 g of silica gel, and ammonia water was added to adjust the pH to 10. The mixture was heated to 60°C, reacted for 5 h, allowed to stand for 6 h, centrifuged, washed, dried, crushed and ground to obtain modified fibers. The average thickness of the silica deposition layer on the surface of the modified fibers was about 110 nm.

[0052] The preparation method of the spiral carbon fiber of this comparative example is as follows: 10g of tea leaves, 7g of sodium hydroxide, 7.5g of sodium sulfate and 100g of deionized water are mixed evenly, heated to 50°C, reacted for 2h, filtered, washed, and then immersed in 150g of sulfuric acid aqueous solution with a mass percentage concentration of 30%, ultrasonicated for 1h, filtered, washed, and dried, and soaked in potassium hydroxide aqueous solution with a mass percentage concentration of 0.34%, potassium carbonate aqueous solution with a mass percentage concentration of 0.83% and zinc chloride aqueous solution with a soaking time of 3h, 3h and 4h respectively. After drying, immersed in 150g of urea aqueous solution with a mass percentage concentration of 1.2%, vibrated for 2h, filtered, washed, and placed in a tubular furnace after drying. Under a nitrogen atmosphere, the temperature was raised to 800°C at a heating rate of 3°C / min, kept warm for 2h, washed to neutral, and dried to obtain spiral carbon fiber.

[0053] The preparation method of the nano-modified antistatic sheet of this comparative example is as follows: 120g of linear low-density polyethylene, 15g of modified fiber, 6g of carbon nanotubes, 3g of zinc stearate and 1g of antioxidant 168 are mixed and added to a twin-screw extruder for melt blending, the screw speed is adjusted to 400r / min, the temperature of the feeding section is 180°C, and the temperature of the extruder head is 220°C. After extrusion and molding, a nano-modified antistatic sheet is obtained.

[0054] Performance testing 1. Surface resistance test: Refer to the national standard GB / T31838.3-2019, and use a high resistance meter to measure the surface resistance of the nano-modified antistatic sheet at a temperature of 25°C and a relative humidity of 50%. During the test, the test voltage is set to 500V. The test results are as follows: Figure 2 shown.

[0055] 2. Tensile performance test: Referring to the national standard GB / T1040.2-2022, the nano-modified antistatic sheet was made into a dumbbell-shaped spline and tested on a universal electronic testing machine at a test speed of 10 mm / min.

[0056] 3. Impact resistance test: Referring to the national standard GB / T1043.1-2008, the nano-modified antistatic sheet was made into A-type notched specimens with dimensions of 80mm long × 10mm wide × 4mm thick, and tested using a digital pendulum impact tester. Before the test, the sample was placed in an environment with a temperature of 23°C and a relative humidity of 50% for 24 hours to reach a stable state. During the test, an impact head with a pendulum energy of 5.5J was used. The tensile and impact resistance test results are shown in the figure below. Figure 1 shown.

[0057] 4. The modified fiber prepared in Example 2 was observed using a scanning electron microscope. The obtained image is as follows: Figure 3 shown.

[0058] Analyze Examples 1-3 and Comparative Examples 1-2 and combine Figure 1-2 It can be seen that in the preparation process of the modified fiber, the introduction of the polydopamine layer and the use of a mixture of an organic silicon source and an inorganic silicon source when depositing silica result in the modified fiber having good mechanical properties. Compared with the modified fiber lacking the polydopamine layer and the inorganic silicon source, the modified fiber used in the nano-modified antistatic sheet has better tensile properties and impact resistance. In addition, the introduction of nitrogen in the helical carbon fiber reduces the surface resistance of the sheet and improves its antistatic properties; the presence of the polydopamine layer and the porous silica layer improves the dispersion stability of the modified fiber, thereby giving it better conductive properties. The surface resistance of the sheets prepared in Examples 1, 2, and 3 is lower than that in Comparative Examples 1 and 2.

[0059] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A nano-modified antistatic sheet, characterized in that: The invention comprises the following components in parts by weight: 100-120 parts of linear low-density polyethylene, 10-15 parts of modified fiber, 3-6 parts of carbon nanotubes, 1-3 parts of processing aid, and 0.5-1 part of antioxidant; the modified fiber consists of a carbon fiber matrix and a silicon dioxide layer wrapped on the surface of the modified fiber.

2. The nano-modified antistatic sheet according to claim 1, characterized in that: The modified fiber is obtained by mixing and reacting a carbon fiber matrix and silicon dioxide gel.

3. A nano-modified antistatic sheet according to claim 1 or 2, characterized in that: The carbon fiber matrix is ​​obtained by dispersing helical carbon fibers in a tris(hydroxymethyl)aminomethane hydrochloride aqueous solution and reacting the solution with dopamine hydrochloride.

4. The nano-modified antistatic sheet according to claim 3, characterized in that: The method for preparing the spiral carbon fiber comprises the following steps: soaking the plant fiber in an alkaline solution and an acid solution in sequence, drying the plant fiber, and then immersing the plant fiber in a urea aqueous solution, and then carbonizing the plant fiber to obtain the spiral carbon fiber.

5. The nano-modified antistatic sheet according to claim 2, characterized in that: The preparation of the silica gel comprises the following steps: mixing an organic silicon source and an inorganic silicon source, and adjusting the pH with an alkaline solution to obtain the silica gel.

6. The nano-modified antistatic sheet according to claim 5, characterized in that: The organic silicon source consists of tetraethyl orthosilicate, ethanol, hydrochloric acid and deionized water; the inorganic silicon source consists of sodium silicate, hydrochloric acid and deionized water.

7. The nano-modified antistatic sheet according to claim 1, characterized in that: The thickness of the silicon dioxide layer is ≤120 nm.

8. The nano-modified antistatic sheet according to claim 3, characterized in that: The mass ratio of the helical carbon fiber, tris(hydroxymethyl)aminomethane hydrochloric acid aqueous solution and dopamine hydrochloride is 1:(180-200):(0.4-0.6).

9. A method for preparing the nano-modified antistatic sheet according to claim 1, characterized in that: The method comprises the following preparation steps: linear low-density polyethylene, modified fiber, carbon nanotube, processing aid and antioxidant are mixed and added into a twin-screw extruder for melt blending, and then extruded and formed to obtain a nano-modified antistatic sheet.

10. The method for preparing the nano-modified antistatic sheet according to claim 9, characterized in that: The process parameters of the melt blending are: screw speed of 300-400 r / min, temperature of the feeding section of 160-180° C., and temperature of the extruder head of 200-220° C.

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