CNT / CaCO3 composite material and application thereof in electromagnetic shielding

Abstract

The invention discloses a CNT / CaCO3 composite material and application thereof in electromagnetic shielding, the CNT / CaCO3 composite material is prepared by growing co-activated and modified nano calcium carbonate on the surface of CNT in situ, the material and PVC are prepared into a PVC / CNT / CaCO3 electromagnetic shielding film, the dispersity of the CNT / CaCO3 composite material is improved while the dispersity of the nano calcium carbonate is improved, and the electromagnetic shielding performance of the CNT / CaCO3 composite material is improved. Therefore, the dispersity of the CNT / CaCOs composite material in a PVC matrix is synergistically improved, and the electromagnetic shielding property and mechanical property of the PVC composite material are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of composite conductive material preparation, and in particular to a CNT / CaCO3 composite material and its application in electromagnetic shielding. Background Art

[0002] With the rapid development of wearable flexible devices, flexible conductive materials, as key functional components, have a significant impact on their reliability and application range. Traditional metal electrode materials, due to their lack of flexibility and susceptibility to fracture, struggle to meet the stretchability and durability requirements of wearable devices. Polymer-based flexible conductive materials have become a research hotspot due to their lightweight, processability, and tunable conductivity. Composite conductive polymers, which incorporate conductive fillers (such as carbon nanotubes (CNTs)) dispersed within a polymer matrix, offer significant advantages. However, existing technologies often favor oxidation of intrinsically conductive polymers and unstable conductivity, while filler dispersion issues within composite conductive materials (such as the aggregation of CNTs and the dielectric filler nano-calcium carbonate (CaCO3)) severely restrict their performance. In particular, in the field of electromagnetic shielding, a single conductive network struggles to achieve the synergistic effects of multiple loss mechanisms (conductance, dielectric, and magnetic losses), limiting the material's broadband and efficient absorption capabilities. While in situ growth of CaCO3 on the surface of CNTs can partially address this dispersion issue, the subsequent modification steps are complex and the process is costly.

[0003] For example, Chinese patent application number 202510215959.5 discloses a method for preparing a water-based conductive super-hydrophobic composite coating. The method describes steps A1: Mix one part CNT, 0.15 part Ca(OH)2, and 100 parts distilled water, by weight, to an initial pH of 11. A2: Heat the mixture in a water bath until the system temperature reaches 60°C, then introduce carbon dioxide until the pH drops to 7. The mixture is then aerated, filtered, washed, and dried to obtain a CNT / CaCO3 nanopowder. The CaCO3 in this patent is not activated, resulting in poor dispersibility, which severely limits its performance, particularly in electromagnetic shielding applications, where it significantly restricts the material's broadband, high-efficiency absorption capacity.

[0004] Therefore, there is an urgent need to develop an efficient and simple CNT / CaCO3 composite material to improve its dispersion in the polymer matrix and optimize the electromagnetic shielding performance. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the main purpose of the present invention is to provide a CNT / CaCO3 composite material to solve the dispersion problem of fillers in composite conductive materials.

[0006] Another object of the present invention is to provide a CNT / CaCO3 composite material, thereby applying the composite material in the field of electromagnetic shielding.

[0007] The CNT / CaCO3 composite material provided by the present invention is prepared by in-situ growing of activated and modified nano-calcium carbonate on the surface of CNTs.

[0008] The CNT referred to in the present invention is carbon nanotube; the CaCO3 referred to in the present invention is nano calcium carbonate;

[0009] The present invention provides a CNT / CaCO3 composite material, the preparation method of which is as follows, and based on the second purpose, an electromagnetic shielding film is prepared, which solves the dispersion problem in the matrix and significantly improves the shielding performance and mechanical properties;

[0010] (1) Preparation of carbon nanotube / nano-calcium carbonate materials:

[0011] 1) Preparing a composite slurry: uniformly mixing CNTs, calcium hydroxide slurry, and a nucleating agent, and stirring at high speed under ultrasound to obtain a composite slurry; the concentration of the calcium hydroxide slurry is 5 wt% to 10 wt%, and the molar ratio of CNTs to calcium ions is 1:2 to 1:10;

[0012] 2) Preparation of modified slurry: Continuously introduce mixed gas into the composite slurry to perform carbonization reaction. When the slurry begins to gel and become viscous, a surface modifier is added to the reaction system to obtain a modified slurry.

[0013] 3) Crystal form guidance: When the pH of the modified slurry is 10±0.5, add the crystal form guidance agent and stir until the pH reaches 6.5±0.5, then stop aeration;

[0014] 4) Preparation of modified CNT / CaCO3 powder: Directly drying the crystal-guided solution to obtain modified carbon nanotubes / nano-calcium carbonate.

[0015] (2) Preparation of PVC / CNT / CaCO3 electromagnetic shielding film: According to the mass percentage, 15-25% PVC, 2-20% modified carbon nanotube / nano-calcium carbonate powder, 2-6% porogen, and 46-81% solvent are placed in a 250 ml three-necked flask, heated and stirred at 70°C to dissolve and mix, and the casting liquid is obtained after sufficient degassing; at room temperature, the casting liquid is scraped on the surface of the non-woven fabric at a speed of 0.1-5.0 m / s to form a flat film, and after air cooling, it is solidified in room temperature water and soaked for 1-24 hours to remove the solvent and porogen; taken out and drained to obtain the polymer-based electromagnetic shielding film with a film thickness of 100-400 μm.

[0016] Furthermore, the nucleating agent is zinc chloride, and the content of the zinc chloride is 0.1 wt% to 5 wt% of the total amount of the calcium hydroxide slurry.

[0017] Furthermore, the carbonization reaction temperature is 0°C to 50°C.

[0018] Furthermore, in steps 1) to 3), the mixed gas is continuously introduced during the reaction and high-speed stirring is continued.

[0019] Furthermore, the mixed gas is a mixture of carbon dioxide and inert gas, and the flow rate ratio of carbon dioxide to inert gas in the mixed gas is 1:3.

[0020] Furthermore, the surface modifier is a composite modifier of copolymer salt and sodium stearate saponified solution;

[0021] Furthermore, the mass ratio of the copolymer salt to sodium stearate is 5~1:5~1;

[0022] Furthermore, the copolymer salt is one of a polystyrene-carboxylic anhydride functional group copolymer, a polystyrene-N-phenylmaleimide-carboxylic anhydride functional group terpolymer, a polyacrylonitrile-styrene-butadiene rubber-carboxylic anhydride functional group terpolymer, and a polybutadiene-acrylonitrile-styrene-carboxylic anhydride functional group tetrapolymer, and the salt is obtained by ring-opening under alkaline conditions;

[0023] Furthermore, the alkali solution is sodium hydroxide solution.

[0024] Furthermore, the sodium stearate saponification solution is a product obtained by saponifying stearic acid in a sodium hydroxide solution at a molar ratio of 1:1.

[0025] Furthermore, the amount of the surface modifier is 0.1 wt% to 2 wt% of the total amount of the calcium hydroxide solution.

[0026] Furthermore, the crystal directing agent is sulfuric acid, and the molar ratio of sulfuric acid to calcium ions is 0.01:1 to 0.001:1.

[0027] Furthermore, the high-speed stirring has a rotation speed of 800 rpm to 1200 rpm.

[0028] Furthermore, the drying temperature is 50-80° C., and the drying time is 24-48 hours.

[0029] Furthermore, the porogen in step (2) is polyethylene glycol, and the molecular weight is one of 200 g / mol, 400 g / mol, 600 g / mol, 800 g / mol, and 1000 g / mol;

[0030] Furthermore, the solvent is one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide;

[0031] Furthermore, the nonwoven fabric is polyethylene terephthalate or polyamide nonwoven fabric, and its thickness is 50 to 150 μm.

[0032] Since the present invention adopts the above technical solution, it has the following beneficial effects:

[0033] Compared with the related art, the present invention mixes CNTs with calcium hydroxide solution, and in the process of preparing calcium carbonate through carbonization reaction of calcium hydroxide solution, nano-calcium carbonate modified with copolymer salt and sodium stearate is in situ grown on the surface of CNT. While improving the dispersibility of nano-calcium carbonate, the dispersibility of CNT / CaCO3 composite material is also improved, thereby synergistically improving the dispersibility of CNT / CaCO3 composite material in PVC matrix. In addition, this technology directly uses copolymer salt and sodium stearate for dispersion modification during the in-situ growth of CaCO3 composite material, which can not only improve the interaction force between CNT / CaCO3 composite material and polymer, but also solve the problem of easy falling off of CNT / CaCO3 composite material in polymer matrix; by using copolymer salt and sodium stearate to modify the surface of CaCO3, CNT / CaCO3 composite material is obtained, so that the CNT / CaCO3 composite material has good dispersibility. In the process of preparing PVC composite film, the entanglement between PVC chains and the modifier on the surface of CaCO3 composite material after film formation is utilized to further improve the dispersibility of CNT / CaCO3 composite material in polymer matrix, thereby enhancing the electromagnetic shielding performance and mechanical properties of PVC composite material.

[0034] This invention provides an innovative method for preparing CNT / CaCO3 composite materials, offering significant advantages over existing technologies. Specifically, this method combines carbon nanotubes (CNTs) with a calcium hydroxide solution. During the carbonization reaction of the calcium hydroxide to produce calcium carbonate, CaCO3 modified with a copolymer salt and sodium stearate is grown in situ on the CNT surface. This process design offers the following significant advantages:

[0035] 1. Dispersion-enhancing mechanism: Through an in-situ growth process, a nano-calcium carbonate layer doubly modified with copolymer salt and sodium stearate is constructed on the CNT surface. This not only significantly improves the dispersibility of the nano-calcium carbonate itself, but also achieves a synergistic dispersion effect for the CNT / CaCO3 composite material. In addition, the modifier on the surface of the composite material forms an entanglement with the PVC molecular chains, further enhancing its dispersion stability in the polymer matrix.

[0036] 2. Interface bonding enhancement: The innovative surface modification of the CNT / CaCO3 composite material by the simultaneous introduction of copolymer salt and sodium stearate during the in-situ growth of calcium carbonate effectively enhances the interfacial interaction between the CNT / CaCO3 composite material and the PVC matrix. This method fundamentally solves the problem of easy filler shedding in traditional processes and significantly improves the interfacial bonding strength of the composite material.

[0037] 3. Performance improvement: Thanks to its excellent dispersibility and interfacial bonding, the prepared PVC composite film exhibits significant performance improvement; electromagnetic shielding performance is significantly enhanced, while mechanical properties are also improved simultaneously.

[0038] The technical approach of this invention boasts simple processes and significant results, providing a new approach and method for preparing high-performance polymer-based composites. Through the synergistic effect of in-situ modification and interface regulation, it achieves simultaneous optimization of filler dispersibility and interfacial bonding strength, possessing significant application value in the field of functional composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Attachment Figure 1 This is a TEM image of the carbon nanotube / calcium carbonate composite material of the present invention;

[0040] Attachment Figure 2 This is a TEM image of the PVC / carbon nanotube / calcium carbonate composite film of the present invention. DETAILED DESCRIPTION

[0041] The following describes the technical solutions in the embodiments of the present invention in detail with reference to several embodiments and accompanying drawings. It is apparent that the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are considered to fall within the scope of protection of the present invention.

[0042] Example 1

[0043] (1) Preparation of composite slurry: 1 wt% of CNT, calcium hydroxide slurry, and 0.1 wt% of zinc chloride were uniformly mixed and stirred at 800 rpm to obtain a composite slurry; the concentration of the calcium hydroxide slurry was 5 wt%; the mixed gas was continuously introduced and stirred at high speed.

[0044] (2) Preparation of modified slurry: continuously introduce mixed gas into the composite slurry, carry out carbonization reaction at 0°C, and when the slurry begins to gel and become viscous, add 0.1wt% of the total amount of calcium hydroxide solution as a surface modifier into the reaction system to obtain a modified slurry; continuously introduce mixed gas and continue stirring at high speed;

[0045] Preparation method of a surface modifier: a. Ring-opening a polystyrene-carboxylic anhydride functional group copolymer under sodium hydroxide conditions; b. Saponifying stearic acid in a sodium hydroxide solution at a molar ratio of 1:1; c. Mixing the products of step a and step b at a ratio of 1:5 to prepare a surface modifier;

[0046] (3) Crystal guidance: Continue to introduce mixed gas and stir at high speed. When the pH of the modified slurry reaches 9.5, add sulfuric acid with a molar ratio of sulfuric acid to calcium ion of 0.01:1. Stir until the pH reaches 6 and stop aeration.

[0047] The mixed gas is a mixture of carbon dioxide and argon gases, and the flow rate ratio of the carbon dioxide to the argon gases in the mixed gas is 1:3.

[0048] (4) Preparation of modified carbon nanotube / nano-calcium carbonate powder: The crystal-guided solution was dried at 50 °C for 24 h to obtain modified carbon nanotube / nano-calcium carbonate powder.

[0049] (5) 15% PVC, 20% carbon nanotube / nano-calcium carbonate composite material, 2% polyethylene glycol with a molecular weight of 200 g / mol, and 62% N,N-dimethylformamide were placed in a 250 ml three-necked flask, heated and stirred at 70 °C to dissolve and mix, and the polymer solution was obtained after sufficient degassing; at room temperature, the casting liquid was scraped on the surface of polyethylene terephthalate non-woven fabric at a speed of 0.1 m / s to form a flat film, and after air cooling, it was solidified in room temperature water and soaked for 24 hours to remove N,N-dimethylformamide and polyethylene glycol, and then taken out and drained to obtain a multi-component composite flexible conductive film with a film thickness of 220 μm.

[0050] Example 2

[0051] (1) Preparation of composite slurry: CNT (5 wt% of the total amount of calcium hydroxide slurry), calcium hydroxide slurry, and zinc chloride (5 wt% of the total amount of calcium hydroxide slurry) were uniformly mixed and stirred at 1200 rpm to obtain a composite slurry; the concentration of the calcium hydroxide slurry was 10 wt%; the mixed gas was continuously introduced and stirred at high speed.

[0052] (2) Preparation of modified slurry: continuously introduce mixed gas into the composite slurry, and carry out carbonization reaction at 50 °C. When the slurry begins to gel and become viscous, add 2 wt% of the total amount of calcium hydroxide solution as a surface modifier into the reaction system to obtain a modified slurry; continuously introduce mixed gas and continue stirring at high speed;

[0053] Preparation method of a surface modifier: a. Ring-opening a polybutadiene-acrylonitrile-styrene-carboxylic anhydride functional group quaternary copolymer under sodium hydroxide conditions; b. Saponifying stearic acid in a sodium hydroxide solution at a molar ratio of 1:1; c. Mixing the products of step a and step b at a ratio of 5:1 to prepare a surface modifier;

[0054] (3) Crystal guidance: Continue to introduce mixed gas and stir at high speed until the pH of the modified slurry reaches 10.5, then add sulfuric acid with a molar ratio of sulfuric acid to calcium ion of 0.001:1, stir until the pH reaches 7, and then stop aeration;

[0055] The mixed gas is a mixture of carbon dioxide and helium, and the flow rate ratio of the carbon dioxide to helium in the mixed gas is 1:3.

[0056] (4) Preparation of modified carbon nanotube / nano-calcium carbonate powder: The crystal-guided solution was dried at 50 °C for 24 h to obtain modified carbon nanotube / nano-calcium carbonate powder.

[0057] (5) 18% PVC, 10% carbon nanotube / nano-calcium carbonate composite material, 3% polyethylene glycol with a molecular weight of 600 g / mol, and 69% N-methylpyrrolidone were placed in a 250 ml three-necked flask, heated and stirred at 70 °C to dissolve and mix, and the polymer solution was obtained after sufficient degassing; at 20 °C, the casting liquid was scraped on the surface of polyethylene terephthalate non-woven fabric at a speed of 3 m / s to form a flat film, and after air cooling, it was solidified in room temperature water and soaked for 18 hours to remove N-methylpyrrolidone and polyethylene glycol, taken out and drained to obtain a multi-component composite flexible conductive film with a film thickness of 250 μm.

[0058] Example 3

[0059] (1) Preparing a composite slurry: uniformly mixing 3 wt% of CNTs, calcium hydroxide slurry, and 3 wt% of zinc chloride based on the total amount of calcium hydroxide slurry, and stirring at 1000 rpm to obtain a composite slurry; the concentration of the calcium hydroxide slurry is 8 wt%; continuously introducing the mixed gas and continuously stirring at high speed;

[0060] (2) Preparation of modified slurry: continuously introduce mixed gas into the composite slurry, and carry out carbonization reaction at 25°C. When the slurry begins to gel and become viscous, add a surface modifier of 1 wt% of the total amount of calcium hydroxide solution into the reaction system to obtain a modified slurry; continuously introduce mixed gas and continue stirring at high speed;

[0061] Preparation method of a surface modifier: a. Ring-opening a polystyrene-N-phenylmaleimide-carboxylic anhydride functional group terpolymer under sodium hydroxide conditions; b. Saponifying stearic acid in a sodium hydroxide solution at a molar ratio of 1:1; c. Mixing the products of step a and step b at a ratio of 2:1 to prepare a surface modifier;

[0062] (3) Crystal guidance: Continue to introduce mixed gas and stir at high speed until the pH of the modified slurry reaches 10, then add sulfuric acid with a molar ratio of sulfuric acid to calcium ion of 0.005:1, stir until the pH reaches 6.5, and then stop aeration;

[0063] The mixed gas is a mixture of carbon dioxide and helium, and the flow rate ratio of carbon dioxide to helium in the mixed gas is 1:3.

[0064] (4) Preparation of modified carbon nanotube / nano-calcium carbonate powder: The crystal-guided solution was dried at 50 °C for 24 h to obtain modified carbon nanotube / nano-calcium carbonate powder.

[0065] (5) 25% PVC, 5% carbon nanotube / nano-calcium carbonate composite material, 6% polyethylene glycol with a molecular weight of 1000 g / mol, and 64% dimethyl sulfoxide were placed in a 250 ml three-necked flask, heated and stirred at 70 ° C to dissolve and mix, and the polymer solution was obtained after sufficient degassing; at room temperature, the casting liquid was scraped on the surface of polyethylene terephthalate non-woven fabric at a speed of 5 m / s to form a flat film, and after air cooling, it was solidified in room temperature water and soaked for 18 hours to remove dimethyl sulfoxide and polyethylene glycol, taken out and drained to obtain a multi-component composite flexible conductive film with a film thickness of 250 μm.

[0066] Example 4

[0067] (1) Preparing a composite slurry: 5 wt% of CNTs, calcium hydroxide slurry, and 0.1 wt% of zinc chloride based on the total amount of calcium hydroxide slurry were uniformly mixed, and stirred at 1200 rpm to obtain a composite slurry; the concentration of the calcium hydroxide slurry was 5 wt%; the mixed gas was continuously introduced and stirred at a high speed;

[0068] (2) Preparation of modified slurry: continuously introduce mixed gas into the composite slurry, and carry out carbonization reaction at 0°C. When the slurry begins to gel and become viscous, add a surface modifier of 2 wt% of the total amount of calcium hydroxide solution into the reaction system to obtain a modified slurry; continuously introduce mixed gas and continue stirring at high speed;

[0069] Preparation method of a surface modifier: a. Ring-opening a polystyrene-N-phenylmaleimide-carboxylic anhydride functional group terpolymer under sodium hydroxide conditions; b. Saponifying stearic acid in a sodium hydroxide solution at a molar ratio of 1:1; c. Mixing the products of step a and step b at a ratio of 1:5 to prepare a surface modifier;

[0070] (3) Crystal guidance: Continue to introduce mixed gas and stir at high speed until the pH of the modified slurry reaches 9.5, then add sulfuric acid with a molar ratio of sulfuric acid to calcium ion of 0.005:1, stir until the pH reaches 6, and then stop aeration;

[0071] The mixed gas is a mixture of carbon dioxide and helium, and the flow rate ratio of carbon dioxide to helium in the mixed gas is 1:3.

[0072] (4) Preparation of modified carbon nanotube / nano-calcium carbonate powder: The crystal-guided solution was dried at 50 °C for 48 h to obtain modified carbon nanotube / nano-calcium carbonate powder.

[0073] (5) 15% PVC, 20% carbon nanotube / nano-calcium carbonate composite material, 2% polyethylene glycol with a molecular weight of 1000 g / mol, and 46% dimethyl sulfoxide were placed in a 250 ml three-necked flask, heated and stirred at 70 ° C to dissolve and mix, and the polymer solution was obtained after sufficient degassing; at room temperature, the casting liquid was scraped on the surface of polyethylene terephthalate non-woven fabric at a speed of 0.1 m / s to form a flat film, and after air cooling, it was solidified in room temperature water and soaked for 1 hour to remove dimethyl sulfoxide and polyethylene glycol, and then taken out and drained to obtain a multi-component composite flexible conductive film with a film thickness of 100 μm.

[0074] Example 5

[0075] (1) Preparing a composite slurry: uniformly mixing 3 wt% of CNTs, calcium hydroxide slurry, and 5 wt% of zinc chloride, based on the total amount of calcium hydroxide slurry, and stirring at 800 rpm to obtain a composite slurry; the concentration of the calcium hydroxide slurry is 5 wt%; continuously introducing the mixed gas and continuously stirring at high speed;

[0076] (2) Preparation of modified slurry: continuously introduce mixed gas into the composite slurry, and carry out carbonization reaction at 50 °C. When the slurry begins to gel and become viscous, add 0.1 wt% of the total amount of calcium hydroxide solution as a surface modifier into the reaction system to obtain a modified slurry; continuously introduce mixed gas and continue stirring at high speed;

[0077] Preparation method of a surface modifier: a. Ring-opening a polystyrene-N-phenylmaleimide-carboxylic anhydride functional group terpolymer under sodium hydroxide conditions; b. Saponifying stearic acid in a sodium hydroxide solution at a molar ratio of 1:1; c. Mixing the products of step a and step b at a ratio of 5:1 to prepare a surface modifier;

[0078] (3) Crystal guidance: Continue to introduce mixed gas and stir at high speed until the pH of the modified slurry reaches 10.5, then add sulfuric acid with a molar ratio of sulfuric acid to calcium ion of 0.005:1, stir until the pH reaches 7, and then stop aeration;

[0079] The mixed gas is a mixture of carbon dioxide and helium, and the flow rate ratio of carbon dioxide to helium in the mixed gas is 1:3.

[0080] (4) Preparation of modified carbon nanotube / nano-calcium carbonate powder: The crystal-guided solution was dried at 80 °C for 24 h to obtain modified carbon nanotube / nano-calcium carbonate powder.

[0081] (5) 25% PVC, 2% carbon nanotube / nano-calcium carbonate composite material, 6% polyethylene glycol with a molecular weight of 1000 g / mol, and 81% dimethyl sulfoxide were placed in a 250 ml three-necked flask, heated and stirred at 70 ° C to dissolve and mix, and the polymer solution was obtained after sufficient degassing; at room temperature, the casting liquid was scraped on the surface of polyethylene terephthalate non-woven fabric at a speed of 0.1 m / s to form a flat film, and after air cooling, it was solidified in room temperature water and soaked for 24 hours to remove dimethyl sulfoxide and polyethylene glycol, taken out and drained to obtain a multi-component composite flexible conductive film with a film thickness of 400 μm.

[0082] Comparative Example 1

[0083] (1) Preparing a composite slurry: uniformly mixing 1 wt% of CNTs, calcium hydroxide slurry, and 0.1 wt% of zinc chloride based on the total amount of calcium hydroxide slurry, and stirring at 1200 rpm to obtain a composite slurry; the concentration of the calcium hydroxide slurry is 7 wt%; continuously introducing the mixed gas and continuously stirring at high speed;

[0084] (2) Preparation of modified slurry: continuously introduce mixed gas into the composite slurry and carry out carbonization reaction at 30 °C until carbonization is completed;

[0085] (3) Crystal guidance: Continue to introduce mixed gas and stir at high speed. When the pH of the modified slurry reaches 9.5, add sulfuric acid with a molar ratio of sulfuric acid to calcium ion of 0.01:1. Stir until the pH reaches 6 and stop aeration.

[0086] (4) Preparation of modified carbon nanotube / nano-calcium carbonate powder: The crystal-guided solution was dried at 50 °C for 24 h to obtain modified carbon nanotube / nano-calcium carbonate powder.

[0087] (5) 15% PVC, 20% carbon nanotube / nano-calcium carbonate composite material, 2% polyethylene glycol with a molecular weight of 200 g / mol, and 62% N,N-dimethylformamide were placed in a 250 ml three-necked flask, heated and stirred at 70 °C to dissolve and mix, and the polymer solution was obtained after sufficient degassing; at room temperature, the casting liquid was scraped on the surface of polyethylene terephthalate non-woven fabric at a speed of 0.1 m / s to form a flat film, and after air cooling, it was solidified in room temperature water and soaked for 24 hours to remove N,N-dimethylformamide and polyethylene glycol, and then taken out and drained to obtain a multi-component composite flexible conductive film with a film thickness of 220 μm.

[0088] Comparative Example 2

[0089] (1) Preparation of composite slurry: 1 wt% of CNT, calcium hydroxide slurry, and 0.1 wt% of zinc chloride in the total amount of calcium hydroxide slurry were uniformly mixed, and then 0.1 wt% of the total amount of calcium hydroxide solution of surface modifier was added, and stirred at 800 rpm to obtain composite slurry; the concentration of the calcium hydroxide slurry was 5 wt%; the mixed gas was continuously introduced and stirred at high speed.

[0090] (2) Preparation of modified slurry: continuously introduce mixed gas into the composite slurry and perform carbonization reaction at 50°C until carbonization is completed;

[0091] Preparation method of a surface modifier: a. Ring-opening a polybutadiene-acrylonitrile-styrene-carboxylic anhydride functional group quaternary copolymer under sodium hydroxide conditions; b. Saponifying stearic acid in a sodium hydroxide solution at a molar ratio of 1:1; c. Mixing the products of step a and step b at a ratio of 1:5 to prepare a surface modifier;

[0092] (3) Crystal guidance: Continue to introduce mixed gas and stir at high speed. When the pH of the modified slurry reaches 9.5, add sulfuric acid with a molar ratio of sulfuric acid to calcium ion of 0.01:1. Stir until the pH reaches 6 and stop aeration.

[0093] The mixed gas is a mixture of carbon dioxide and argon gases, and the flow rate ratio of the carbon dioxide to the argon gases in the mixed gas is 1:3.

[0094] (4) Preparation of modified carbon nanotube / nano-calcium carbonate powder: The crystal-guided solution was dried at 50 °C for 24 h to obtain modified carbon nanotube / nano-calcium carbonate powder.

[0095] (5) 15% PVC, 20% carbon nanotube / nano-calcium carbonate composite material, 2% polyethylene glycol with a molecular weight of 200 g / mol, and 62% N,N-dimethylformamide were placed in a 250 ml three-necked flask, heated and stirred at 70 °C to dissolve and mix, and the polymer solution was obtained after sufficient degassing; at room temperature, the casting liquid was scraped on the surface of polyethylene terephthalate non-woven fabric at a speed of 0.1 m / s to form a flat film, and after air cooling, it was solidified in room temperature water and soaked for 24 hours to remove N,N-dimethylformamide and polyethylene glycol, and then taken out and drained to obtain a multi-component composite flexible conductive film with a film thickness of 220 μm.

[0096] The composite films prepared in Examples 1-5 and the composite films prepared in Comparative Examples 1-2 were subjected to performance tests respectively. The test process was carried out in accordance with the corresponding national standards. The electromagnetic shielding performance, tensile strength, elongation at break, and toughness were measured and are shown in the following table.

[0097] Example Electromagnetic shielding performance (dB) tensile strength Elongation at break (%) Toughness (MJ / m3) Example 1 22.4 45.36 55.18 63.17 Example 2 21.7 43.38 52.75 57.61 Example 3 20.6 44.36 53.18 62.17 Example 4 25.3 56.13 57.92 64.68 Example 5 16.8 44.18 51.54 56.96 Comparative Example 1 9.3 40.45 45.19 51.75 Comparative Example 2 7.8 39.45 43.92 50.51

Claims

1. A CNT / CaCO3 composite material, characterized in that: It is made of nano-calcium carbonate that is in situ grown on the surface of CNT and then activated and modified.

2. The CNT / CaCO3 composite material according to claim 1, wherein The method comprises the following preparation steps: 1) Preparing a composite slurry: uniformly mixing CNTs, calcium hydroxide slurry, and a nucleating agent, and stirring at high speed under ultrasound to obtain a composite slurry; the concentration of the calcium hydroxide slurry is 5 wt% to 10 wt%, and the molar ratio of CNTs to calcium ions is 1:2 to 1:10; 2) Preparation of modified slurry: Continuously introduce mixed gas into the composite slurry to perform carbonization reaction. When the slurry begins to gel and become viscous, a surface modifier is added to the reaction system to obtain a modified slurry. 3) Crystal form guidance: When the pH of the modified slurry is 10±0.5, add the crystal form guidance agent and stir until the pH reaches 6.5±0.5, then stop aeration; 4) Preparation of modified CNT / CaCO3 powder: The crystal-guided solution is directly dried to obtain a CNT / CaCO3 composite material.

3. The CNT / CaCO3 composite material according to claim 1, wherein The activated and modified nano-calcium carbonate is achieved by modification with a surfactant; the amount of the surface modifier used is 0.1 wt% to 2 wt% of the total amount of the calcium hydroxide solution.

4. The CNT / CaCO3 composite material according to claim 2 or 3, characterized in that The surfactant is a composite modifier prepared by mixing copolymer salt and sodium stearate saponified solution in a mass ratio of 5-1:5-1; The copolymer salt is one of a polystyrene-carboxylic anhydride functional group copolymer, a polystyrene-N-phenylmaleimide-carboxylic anhydride functional group terpolymer, a polyacrylonitrile-styrene-butadiene rubber-carboxylic anhydride functional group terpolymer, and a polybutadiene-acrylonitrile-styrene-carboxylic anhydride functional group tetrapolymer, and the salt is obtained by ring-opening under alkaline solution conditions.

5. The CNT / CaCO3 composite material according to claim 4, characterized in that The sodium stearate saponification solution is a product obtained by saponifying stearic acid in a sodium hydroxide solution at a molar ratio of 1:

1.

6. The CNT / CaCO3 composite material according to claim 2, wherein: The nucleating agent is zinc chloride, and the content of the zinc chloride is 0.1 wt% to 5 wt% of the total amount of the calcium hydroxide slurry.

7. The CNT / CaCO3 composite material according to claim 2, wherein: The crystal directing agent is sulfuric acid, and the molar ratio of sulfuric acid to calcium ion is 0.01:1 to 0.001:

1.

8. Application of a CNT / CaCO3 composite material in the field of electromagnetic shielding.

9. The use according to claim 8, characterized in that Preparation of PVC / CNT / CaCO3 electromagnetic shielding film: (1) by mass percentage, 15-25% PVC, 2-20% PVC / CNT / CaCO3 powder, 2-6% porogen, and 46-81% solvent are placed in a 250 ml three-necked flask, heated at 70°C with stirring to dissolve and mix, and fully degassed to obtain a casting solution; (2) At room temperature, the casting liquid is scraped onto the surface of the nonwoven fabric at a speed of 0.1-5.0 m / s to form a flat film. After air cooling, the film is solidified in room temperature water and soaked for 1-24 hours to remove the solvent and porogen. (3) Taking out and drying to obtain the polymer-based electromagnetic shielding film.

10. The use according to claim 9, characterized in that The polymer-based electromagnetic shielding film has a thickness of 100-400 μm.

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