Cable shielding layer preparation method based on nanometer material

Abstract

The invention provides a cable shielding layer preparation method based on a nanometer material, and belongs to the technical field of organic polymers. The conductive composite material comprises the following components: conductive filler, a polymer matrix material, a silane coupling agent and fiber filler, wherein the conductive filler is prepared by blending silica sol-coated titanium carbide, multi-walled carbon nanotubes and aramid nanofibers and then carrying out hot pressing. According to the invention, multi-walled carbon nanotubes and titanium carbide are used as electric conductors; by combining an optimized dispersion process and interface design, full-band electromagnetic shielding is realized; and by adding the aramid fiber, high mechanical strength and environmental stability are realized. In addition, a silane coupling agent is used for bridging an inorganic material and a polymer matrix, interface defects are reduced, and electric signal loss is inhibited.

Description

Technical Field

[0001] The invention belongs to the technical field of organic polymers, and in particular relates to a method for preparing a cable shielding layer based on nanomaterials. Background Art

[0002] The basic structure of an electrical wire mainly includes several parts: conductor, insulation layer, shielding layer and protective layer; the shielding layer can effectively shield the electromagnetic field inside the cable, reducing electromagnetic interference to surrounding equipment or people.

[0003] The performance requirements for cable shielding are as follows:

[0004] 1. Shielding effectiveness (core indicator); requires good shielding capabilities against low-frequency magnetic fields, high-frequency magnetic fields and transient surges.

[0005] 2. Electrical and mechanical reliability; the shielding layer needs to have good conductive continuity, transition resistance, as well as mechanical flexibility and extrusion resistance.

[0006] 3. Material and environmental adaptability: In some special areas, such as high temperature, high humidity and seaside locations, good weather resistance is required.

[0007] 4. Grounding compatibility: The grounding system provides comprehensive performance in terms of safety protection, signal integrity, and interference immunity within a specific electromagnetic environment. Its core goal is to ensure that devices can operate safely in complex electromagnetic environments without interfering with other devices or being interfered with. Summary of the Invention

[0008] The object of the present invention is to provide a cable shielding layer comprising the following components in parts by mass:

[0009]

[0010]

[0011] The conductive filler is made by hot pressing titanium carbide coated with silica sol, multi-walled carbon nanotubes and aramid nanofibers;

[0012] In the conductive filler, the mass ratio of titanium carbide to silica sol in the silica sol-coated titanium carbide is 92-96:3-4.5;

[0013] The mass ratio of the silica sol-coated titanium carbide and the multi-walled carbon nanotubes in the conductive filler is 1:0.3-2; the amount of the aramid nanofiber added is 10-18% of the total mass of the silica sol-coated titanium carbide and the multi-walled carbon nanotubes;

[0014] The preparation method of the cable shielding layer comprises the steps of mixing various raw materials, mixing, extruding and granulating.

[0015] Preferably, the preparation method of the conductive filler comprises the following steps:

[0016] Titanium carbide coating: titanium carbide powder is mixed with silica sol and sodium polyacrylate and dissolved in water, and then spray-dried to obtain silica sol-coated titanium carbide; the amount of sodium polyacrylate added is 1.0-1.8wt% of the titanium carbide;

[0017] Surface modification of multi-walled carbon nanotubes: reflux the multi-walled carbon nanotubes in a mixed solution of concentrated sulfuric acid and nitric acid, then centrifuge, wash and dry;

[0018] Preparation of aramid nanofibers: immerse aramid in a dissociation solution and then perform plasma activation treatment;

[0019] Conductive filler blending: adding a carbon nanotube water dispersant to a solvent; then adding silica sol-coated titanium carbide, multi-walled carbon nanotubes and aramid nanofibers, ultrasonically dispersing, centrifugally purifying, and filtering to obtain a mixed slurry; the amount of the carbon nanotube water dispersant added is at least 0.2 times the mass of the multi-walled carbon nanotubes; the solvent is a mixed solvent of ethanol and water; the mass proportion of ethanol is 60-70wt%.

[0020] Drying: Dry the mixed slurry to obtain powdered conductive filler.

[0021] Preferably, in the multi-walled carbon nanotube surface modification step, the multi-walled carbon nanotubes are refluxed in a mixed solution of concentrated sulfuric acid and nitric acid at 80-100° C. for at least 6 hours, and then centrifuged, washed and dried.

[0022] Preferably, in the preparation of the aramid nanofibers: the dissociation solution contains potassium hydroxide, dimethyl sulfoxide and an alcohol intercalant; and the plasma activation treatment is a plasma treatment in an air atmosphere.

[0023] Preferably, the particle size of the titanium carbide is required to be ≤500 nm.

[0024] Preferably, the width of the multi-walled carbon nanotube is ≤20 nm; and the length is ≤15 μm.

[0025] Preferably, the polymer matrix material includes at least one of polyethylene, polyvinyl chloride, polypropylene, ethylene-butyl acrylate copolymer, and thermoplastic elastomer.

[0026] Preferably, the fiber filler is at least one of carbon fiber, basalt fiber, and natural plant fiber.

[0027] Preferably, it further comprises granular filler, wherein the granular filler is 3-5 parts; the granular filler comprises at least one of talc, calcium carbonate and wollastonite.

[0028] Preferably, a processing aid is also included.

[0029] The conductive filler in the present invention is mainly responsible for constructing a conductive network to achieve electromagnetic shielding (absorption / reflection of electromagnetic waves); it includes three components, among which the high conductivity of silica sol-coated titanium carbide serves as the main conductive medium; and silica sol coating is used to improve oxidation resistance and dispersibility to prevent filler agglomeration. The surface of the multi-walled carbon nanotubes modified by acid treatment enhances interfacial bonding, forming a three-dimensional interpenetrating conductive network, lowering the percolation threshold; and the high aspect ratio improves charge transfer efficiency and enhances high-frequency shielding effectiveness. The difference in conductivity between the two can also be used to form a hierarchical conductive gradient, further improving shielding efficiency. Aramid nanofibers mainly provide mechanical reinforcement, improve and compensate for the brittle defects of nanofillers, and enhance flexibility. In addition, aramid nanofibers also have a positive effect on electromagnetic shielding performance. The polar groups on the surface of ANF are rich in dielectric constants, which are different from those of silica sol-coated titanium carbide and multi-walled carbon nanotubes, which can enhance interfacial polarization relaxation. Aramid nanofibers have a high aspect ratio and excellent mechanical strength, and can form a three-dimensional mesh scaffold in the polymer matrix. This structure can effectively bridge the conductive fillers, reduce filler agglomeration, and promote the continuity of the electron migration path, thereby improving the conductive loss.

[0030] The polymer matrix material serves as an insulating support and molding carrier, which determines the material's processability and environmental adaptability; different matrix materials are selected according to different usage environments.

[0031] Silane coupling agent acts as an interface modifier to improve the compatibility between inorganic materials and polymer matrices; it can also inhibit interface micropores and reduce the risk of partial discharge.

[0032] Fiber fillers and particle fillers are used for cost control, mechanical reinforcement, processing assistance and heat resistance improvement; different fillers can be selected or not added according to different usage environments.

[0033] In the present invention, the aramid nanofibers and multi-walled carbon nanotubes are surface treated before mixing in order to introduce active groups such as carboxyl (-COOH) and hydroxyl (-OH) on the surface, thereby significantly improving dispersibility and compatibility with polymers and preventing agglomeration.

[0034] The size of multi-walled carbon nanotubes (MWCNTs) and titanium carbide (TiC) has a clear impact on their conductivity. The smaller the diameter (width) of MWCNTs, the better their conductivity. The conductivity improves until the aspect ratio reaches a certain peak, but this peak is uncertain and depends on the surface structure, width and length, and whether there is doping. Generally speaking, the conductivity of titanium carbide decreases with smaller grains, while the larger the specific surface area (microscopic shape), the better its conductivity. At the same time, defects (such as dislocations and impurities) increase electron scattering, thereby reducing conductivity.

[0035] The present invention sets a maximum size requirement for multi-walled carbon nanotubes (MWCNT) and titanium carbide (TiC) based on the conductivity requirements of the cable shielding layer; the present invention finds that the conductivity of related materials exceeding this limit is difficult to support the realization of their functions.

[0036] The beneficial technical effects of the present invention are at least as follows:

[0037] The present invention uses multi-walled carbon nanotubes and titanium carbide as conductors; combines optimized dispersion technology and interface design to achieve full-band electromagnetic shielding; and achieves high mechanical strength through the addition of aramid.

[0038] In addition, silane coupling agents are used to bridge inorganic materials and polymer matrices to reduce interface defects and inhibit electrical signal loss. DETAILED DESCRIPTION

[0039] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0040] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the specified features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0041] In the description of the present invention, the term "for example" is used to mean "used as an example, illustration or illustration". Any embodiment of the present invention described as "for example" is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is given to enable any person skilled in the art to implement and use the present invention. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present invention can be implemented without using these specific details. In other examples, well-known structures and processes are not elaborated in detail to avoid obscuring the description of the present invention with unnecessary details. Therefore, the present invention is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed herein.

[0042] Unless otherwise specified, the experimental methods used in the specific embodiments are all conventional methods, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0043] In the present invention, unless otherwise specified, “%” represents mass percentage; the raw materials, reagents, etc. used are all conventional commercially available products.

[0044] Example 1

[0045] In this embodiment, the particle size of titanium carbide is ≤500 nm, and the microscopic surface is irregular in shape;

[0046] The diameter of multi-walled carbon nanotubes is 10-20nm; the length is 5-15um.

[0047] The preparation of the conductive filler comprises the following steps:

[0048] S1 Titanium carbide coating: Mix titanium carbide powder with silica sol and sodium polyacrylate, dissolve in water, and dilute to a solute concentration of 30%; stir and mix until uniform; then spray dry at 90°C to obtain silica sol-coated titanium carbide;

[0049] The mass ratio of titanium carbide powder to silica sol and sodium polyacrylate is 92:3:0.9;

[0050] The silicon content in the silica sol is 30%;

[0051] S2 MWCNT surface modification: Reflux the MWCNTs in mixed acid at 80-100°C for 6 h, then centrifuge, wash with water until neutral, and dry;

[0052] The volume ratio of concentrated sulfuric acid to nitric acid in the mixed acid is (3:1), and the mass fraction of concentrated sulfuric acid is ≥70%. The amount of the mixed acid used is 20 ml for every 1 g of multi-walled carbon nanotubes.

[0053] Preparation of S3 aramid nanofibers: Soak aramid in an aqueous solution of potassium hydroxide for 20 seconds, then add dimethyl sulfoxide and isopropanol and stir for 4 minutes; then vacuum filter and concentrate;

[0054] After filtration, hot air drying was carried out, and then 100W air plasma treatment was performed for 5 minutes;

[0055] The molar concentration of potassium hydroxide in the aqueous solution of potassium hydroxide is 2 mol / L; the dosage is 0.5 ml for 1 g of aramid;

[0056] The molar ratio of dimethyl sulfoxide to isopropyl alcohol is 5:1; the amount of dimethyl sulfoxide used is 500 ml for 1 g of aramid; the amount of isopropyl alcohol used is 66 ml for 1 g of aramid.

[0057] S4 conductive filler blending: Add carbon nanotube water dispersant to the solvent; then add silica sol-coated titanium carbide, multi-walled carbon nanotubes and aramid nanofibers; the overall solid content is 15%;

[0058] After ultrasonic dispersion, centrifugal purification and filtration are performed to obtain a mixed slurry; the mixed slurry is spray-dried to obtain microsphere powder, which is sealed for later use.

[0059] The solvent is a mixed solvent of ethanol and water; the mass proportion of ethanol is 60 wt%.

[0060] The amount of the carbon nanotube water dispersant used is 0.2 times the mass of the multi-walled carbon nanotubes.

[0061] The mass ratio of silica sol-coated titanium carbide to multi-walled carbon nanotubes and aramid nanofibers is 1:0.3:0.13.

[0062] Example 2

[0063] In this embodiment, the particle size of titanium carbide is ≤300 nm, and the microscopic surface is irregular in shape;

[0064] The diameter of multi-walled carbon nanotubes is 8-15nm; the length is 20-50um.

[0065] The preparation of the conductive filler comprises the following steps:

[0066] S1 Titanium carbide coating: Mix titanium carbide powder with silica sol and sodium polyacrylate, dissolve in water, and dilute to a solute concentration of 30%; stir and mix until uniform; then spray dry at 90°C to obtain silica sol-coated titanium carbide;

[0067] The mass ratio of titanium carbide powder to silica sol and sodium polyacrylate is 96:4.5:1.73;

[0068] The silicon content in the silica sol is 30%;

[0069] S2 MWCNT surface modification: Reflux the MWCNTs in mixed acid at 80-100°C for 6 h, then centrifuge, wash with water until neutral, and dry;

[0070] The volume ratio of concentrated sulfuric acid to nitric acid in the mixed acid is (3:1), and the mass fraction of concentrated sulfuric acid is ≥70%. The amount of the mixed acid used is 20 ml for every 1 g of multi-walled carbon nanotubes.

[0071] Preparation of S3 aramid nanofibers: Soak aramid in an aqueous solution of potassium hydroxide for 20 seconds, then add dimethyl sulfoxide and isopropanol and stir for 4 minutes; then vacuum filter and concentrate;

[0072] After filtration, hot air drying was carried out, and then 100W air plasma treatment was performed for 5 minutes;

[0073] The molar concentration of potassium hydroxide in the aqueous solution of potassium hydroxide is 2 mol / L; the dosage is 0.5 ml for 1 g of aramid;

[0074] The molar ratio of dimethyl sulfoxide to isopropyl alcohol is 5:1; the amount of dimethyl sulfoxide used is 500 ml for 1 g of aramid; the amount of isopropyl alcohol used is 66 ml for 1 g of aramid.

[0075] S4 conductive filler blending: Add carbon nanotube water dispersant to the solvent; then add silica sol-coated titanium carbide, multi-walled carbon nanotubes and aramid nanofibers; the overall solid content is 15%;

[0076] After ultrasonic dispersion, centrifugal purification and filtration are performed to obtain a mixed slurry; the mixed slurry is spray-dried to obtain microsphere powder, which is sealed for later use.

[0077] The solvent is a mixed solvent of ethanol and water; the mass proportion of ethanol is 70 wt%.

[0078] The amount of the carbon nanotube water dispersant used is 0.2 times the mass of the multi-walled carbon nanotubes.

[0079] The mass ratio of silica sol-coated titanium carbide to multi-walled carbon nanotubes and aramid nanofibers is 1:1:0.36.

[0080] Example 3

[0081] The difference from Example 1 is that:

[0082] In this embodiment,

[0083] The diameter of walled carbon nanotubes is 8-15nm; the length is 20-50um.

[0084] Example 4

[0085] The difference from Example 1 is that:

[0086] In this embodiment, the particle size of titanium carbide is ≤300 nm, and the microscopic surface is irregular in shape.

[0087] Example 5

[0088] The difference from Example 1 is that:

[0089] In this embodiment, the particle size of titanium carbide is 800 nm, and the microscopic surface is irregular in shape;

[0090] Example 6

[0091] The difference from Example 1 is that:

[0092] The diameter of multi-walled carbon nanotubes is 15-30nm; the length is 10-30um.

[0093] Example 7

[0094] The difference from Example 1 is that:

[0095] In step S4 of blending the conductive filler, the mass ratio of silica sol-coated titanium carbide to multi-walled carbon nanotubes and aramid nanofibers is 1:0.3:0.39.

[0096] Example 8

[0097] The difference from Example 1 is that:

[0098] In step S4 of blending the conductive filler, the mass ratio of silica sol-coated titanium carbide to multi-walled carbon nanotubes and aramid nanofibers is 1:2:0.30.

[0099] Example 9

[0100] The difference from Example 1 is that step S1 of coating titanium carbide is not performed.

[0101] Example 10

[0102] The difference from Example 1 is that step S3 of preparing aramid nanofibers is not performed; and step S4 of blending the conductive filler is not added with aramid.

[0103] Some key parameters of Examples 1 to 11 are shown in Table 1 below.

[0104] Table 1

[0105]

[0106] Example 11

[0107] The preparation of the cable shielding layer includes the following steps:

[0108] S1 Weighing: Weigh each raw material according to the mass parts recorded in Table 2

[0109] S2 Mixing and granulation: After the raw materials are mixed, they are mixed, extruded and granulated.

[0110] Table 2

[0111]

[0112] Table 2 (continued)

[0113]

[0114] In Table 2, KH-550 refers to silane coupling agent KH-550. The antioxidant is a 1:1 mixture of antioxidant 1010 and antioxidant 168. The lubricant is a 1:1 mixture of stearic acid and zinc oxide.

[0115] The shielding effectiveness of planar electromagnetic shielding materials is measured according to GB / T 30142-2013 Measurement method of shielding effectiveness of planar electromagnetic shielding materials; the flange coaxial device method is used for measurement.

[0116] The results are shown in Table 3.

[0117] Table 3

[0118]

[0119] As shown in Table 3, a comparison of the data for No. 11 (corresponding to Example 1) with Nos. 15 (corresponding to Example 5), 16 (corresponding to Example 6), and 17 (corresponding to Example 7) reveals a significant decline in performance when the sizes of the titanium carbide and multi-walled carbon nanotubes exceed a certain range. A comparison with the experiments for Nos. 12 (corresponding to Example 2), 13 (corresponding to Example 3), 14 (corresponding to Example 4), and 18 (corresponding to Example 8) reveals that smaller titanium carbide particle sizes and higher aspect ratios of the multi-walled carbon nanotubes improve electromagnetic shielding performance.

[0120] The experimental results of No. 19 (corresponding to Example 9) show that the uncoated titanium carbide nanosheets have high surface energy and are easily agglomerated in the polymer matrix, hindering the formation of a continuous conductive path; and are extremely easy to oxidize, resulting in a long-term decline in shielding performance. However, since they were not stored for a long time during the experiment, the decline in shielding effectiveness did not show an order of magnitude change.

[0121] The conductive filler of No. 20 (corresponding to Example 10) does not contain aramid, and its shielding effectiveness is somewhat reduced, which is consistent with the previous conclusion.

[0122] In addition, the comparison of serial numbers 11, 21, and 22 shows that the selection of different polymer matrix materials and fillers has basically no significant effect on the shielding effectiveness, and as the content of conductive fillers increases, the shielding effectiveness increases accordingly.

[0123] The above detailed description is a specific description of one feasible embodiment of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A cable shielding layer, characterized in that: The following components are included in parts by mass: The conductive filler is made by hot pressing titanium carbide coated with silica sol, multi-walled carbon nanotubes and aramid nanofibers; In the conductive filler, the mass ratio of titanium carbide to silica sol in the silica sol-coated titanium carbide is 92-96:3-4.5; The mass ratio of the silica sol-coated titanium carbide and the multi-walled carbon nanotubes in the conductive filler is 1:0.3-2; the amount of the aramid nanofiber added is 10-18% of the total mass of the silica sol-coated titanium carbide and the multi-walled carbon nanotubes; The preparation method of the cable shielding layer comprises the steps of mixing various raw materials, mixing, extruding and granulating.

2. The cable shielding layer according to claim 1, characterized in that The preparation method of the conductive filler comprises the following steps: Titanium carbide coating: titanium carbide powder is mixed with silica sol and sodium polyacrylate and dissolved in water, and then spray-dried to obtain silica sol-coated titanium carbide; the amount of sodium polyacrylate added is 1.0-1.8wt% of the titanium carbide; Surface modification of multi-walled carbon nanotubes: reflux the multi-walled carbon nanotubes in a mixed solution of concentrated sulfuric acid and nitric acid, then centrifuge, wash and dry; Preparation of aramid nanofibers: immerse aramid in a dissociation solution and then perform plasma activation treatment; Conductive filler blending: adding a carbon nanotube aqueous dispersant to a solvent; then adding silica sol-coated titanium carbide, multi-walled carbon nanotubes, and aramid nanofibers, ultrasonically dispersing, centrifugally purifying, and filtering to obtain a mixed slurry; the amount of the carbon nanotube aqueous dispersant added is at least 0.2 times the mass of the multi-walled carbon nanotubes; the solvent is a mixed solvent of ethanol and water, with the mass proportion of ethanol being 60-70wt%; Drying: Dry the mixed slurry to obtain powdered conductive filler.

3. The cable shielding layer according to claim 2, characterized in that In the multi-walled carbon nanotube surface modification step, the multi-walled carbon nanotubes are refluxed in a mixed solution of concentrated sulfuric acid and nitric acid at 80-100° C. for at least 6 hours, and then centrifuged, washed and dried.

4. The cable shielding layer according to claim 2, characterized in that In the preparation of the aramid nanofibers: the dissociation solution contains potassium hydroxide, dimethyl sulfoxide and an alcohol intercalant; and the plasma activation treatment is a plasma treatment in an air atmosphere.

5. The cable shielding layer according to claim 1, characterized in that The particle size of the titanium carbide is required to be ≤500nm.

6. The cable shielding layer according to claim 1, characterized in that The multi-walled carbon nanotube has a width of ≤20 nm and a length of ≤15 μm.

7. The cable shielding layer according to claim 1, characterized in that The polymer matrix material includes at least one of polyethylene, polyvinyl chloride, polypropylene, ethylene-butyl acrylate copolymer, and thermoplastic elastomer.

8. The cable shielding layer according to claim 1, characterized in that The fiber filler is at least one of carbon fiber, basalt fiber, and natural plant fiber.

9. The cable shielding layer according to claim 1, characterized in that It also includes 3-5 parts of granular filler; the granular filler includes at least one of talc, calcium carbonate, and wollastonite.

10. The cable shielding layer according to claim 1, characterized in that Also includes processing aids.

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