A polytetrafluoroethylene insulated cable and its preparation process

Abstract

The present invention relates to the technical field of cables, and specifically to a polytetrafluoroethylene insulated cable and its preparation process. In the present invention, a cobalt source is used to irradiate a polytetrafluoroethylene film and glycidyl methacrylate is grafted on its surface; allylamine and 1,1,3,3-tetramethyldisiloxane are used as raw materials, and terminal amino group-containing tetramethyldisiloxane is obtained through a hydrosilylation reaction. The product is reacted with biphenyltetracarboxylic dianhydride, and then trimellitic anhydride is added for end-capping to obtain terminal carboxyl group-containing silicon-containing polyimide; the terminal carboxyl group-containing silicon-containing polyimide, epoxy resin, curing agent, nano silicon carbide, silane coupling agent, and antioxidant are mixed to obtain an epoxy resin adhesive solution; a polytetrafluoroethylene film is coated on the surface of a silver-plated copper conductor core and the epoxy resin adhesive solution is applied, and then cured to obtain an insulating layer; a silver film is attached to the surface of the insulating layer to form a shielding layer; a PFA sheath is coated on the surface of the shielding layer to obtain the product. The polytetrafluoroethylene insulated cable prepared by the present invention has good waterproof, wear-resistant, and corrosion-resistant properties.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, and specifically to a polytetrafluoroethylene insulated cable and its preparation process. Background Art

[0002] A cable is a medium for electric energy and information transmission, and has a large number of applications in fields such as electrical communication, transportation, and industrial production, and its types are various. With the rapid development of technology, the demand for cable materials in various industries is increasing day by day, and at the same time, the requirements for cable materials are also getting higher and higher.

[0003] In order to avoid cable equipment failures and eliminate potential safety hazards, it is usually necessary to set a waterproof layer to prevent moisture from penetrating into the interior, so as to achieve the effects of waterproofing and moisture-proofing and extend the service life of the cable. Polytetrafluoroethylene is a high molecular polymer prepared by polymerizing tetrafluoroethylene as a monomer, which has good hydrophobic and water-resistant properties. In addition, it also has outstanding heat resistance, cold resistance, acid and alkali resistance, so it is called the "king of plastics". However, polytetrafluoroethylene has problems such as low strength and poor wear resistance, which limits its application in cables. Summary of the Invention

[0004] The purpose of the present invention is to provide a polytetrafluoroethylene insulated cable and its preparation process to solve the problems raised in the above background art.

[0005] To solve the above technical problems, the present invention provides the following technical solutions: A polytetrafluoroethylene insulated cable and its preparation process, including the following steps:

[0006] Coat a polytetrafluoroethylene film on the surface of a silver-plated copper conductor core and apply an epoxy resin glue solution with a coating thickness of 50 - 80 μm, and cure at 100 - 120 °C to obtain an insulating layer; attach a silver film on the surface of the insulating layer to form a shielding layer; coat a PFA sheath on the surface of the shielding layer to obtain the product.

[0007] Further, the preparation method of the polytetrafluoroethylene film includes the following steps:

[0008] S1: Mix polytetrafluoroethylene resin and auxiliary oil, let it stand and ripen, and then make a blank; extrude the blank into a strip-shaped material, and after calendering and stretching, shape it to obtain a polytetrafluoroethylene film with a thickness of 0.2 - 0.3 mm;

[0009] S2: Put the polytetrafluoroethylene film into 60Pre-irradiation is carried out in a Co cobalt source. After reaching an absorbed dose of 8 - 15 kGy, it is taken out. A solution of glycidyl methacrylate / chlorobenzene with a mass concentration of 35 - 40% is prepared. After purging with nitrogen for 30 min, using benzoyl peroxide as an initiator, the polytetrafluoroethylene membrane is immersed in the glycidyl methacrylate / chlorobenzene solution, and the temperature is raised to 80 - 90 °C for reaction for 4 - 6 h; it is washed with acetone and dried.

[0010] Further, in S1, by weight, 100 parts of polytetrafluoroethylene resin and 15 - 20 parts of auxiliary oil are mixed.

[0011] Further, in S2, the curing time is 24 - 30 h; the billet-making pressure is 2 - 3 Mpa; the shaping temperature is 300 - 400 °C.

[0012] Further, in S2, the polytetrafluoroethylene membrane is immersed in the glycidyl methacrylate / chlorobenzene solution according to a bath ratio of 1:(10 - 15).

[0013] Further, the preparation method of the epoxy resin adhesive is as follows: by weight percentage, 10 - 18% of carboxyl-terminated polyimide containing silicon and 82 - 90% of epoxy resin are mixed to obtain a modified epoxy resin; by weight fraction, 100 parts of the modified epoxy resin, 46 - 57 parts of a curing agent, 18 - 25 parts of nano silicon carbide, 10 - 12 parts of a silane coupling agent, and 3 - 5 parts of an antioxidant are mixed to obtain the epoxy resin adhesive.

[0014] Further, the preparation method of the carboxyl-terminated polyimide containing silicon includes the following steps:

[0015] a. Allylamine is dispersed in tetrahydrofuran. Using an isopropanol solution of chloroplatinic acid as a catalyst, in a nitrogen environment, 1,1,3,3-tetramethyldisiloxane is added, and the temperature is raised to 60 - 70 °C for reaction for 5 - 8 h; after distilling off the solvent under reduced pressure, it is washed with methanol and dried to obtain amino-terminated tetramethyldisiloxane;

[0016] b. The amino-terminated tetramethyldisiloxane and biphenyltetracarboxylic dianhydride are dispersed in N-methylpyrrolidone. After reacting for 6 - 8 h in a nitrogen environment, the temperature is raised to 70 - 80 °C, and trimellitic anhydride is added for end-capping reaction for 2 - 3 h to obtain the carboxyl-terminated polyimide containing silicon.

[0017] Further, in step a, the molar ratio of allylamine to 1,1,3,3-tetramethyldisiloxane is 1:1.

[0018] Further, in step b, the amino-terminated tetramethyldisiloxane and biphenyltetracarboxylic dianhydride are dispersed in N-methylpyrrolidone according to a molar ratio of (1.2 - 1.5):1.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention provides a polytetrafluoroethylene insulated cable. Polytetrafluoroethylene has good corrosion resistance and hydrophobic properties. As an insulating material for coating the cable, it can effectively improve the service life and safety performance of the cable.

[0020] In order to prevent the polytetrafluoroethylene on the surface of the cable from being scratched and damaged by external forces during use, the present invention coats the surface of the polytetrafluoroethylene insulated cable with epoxy resin glue for protection. Epoxy resin itself has good wear resistance. The present invention also adds nano silicon carbide to further improve the wear resistance of the epoxy resin coating. Since the molecular chain of polytetrafluoroethylene is composed of carbon (C) and fluorine (F) atoms, and each carbon atom is connected to two fluorine atoms, the surface of polytetrafluoroethylene is almost completely covered by fluorine atoms. And the electronegativity of fluorine atoms is very strong, forming a very stable chemical barrier, so its surface shows extremely strong non-stickiness. Therefore, the present invention irradiates the polytetrafluoroethylene film with a cobalt source and graft-modifies the irradiated polytetrafluoroethylene with glycidyl methacrylate to introduce epoxy groups on its surface. The epoxy group-modified polytetrafluoroethylene can form stable chemical bonds through reactions during the curing process of epoxy resin, improving the bonding strength between the two, avoiding sliding friction caused by poor adhesion effect during the friction process and resulting in wear on the surface of polytetrafluoroethylene, and thus playing a role in protecting the cable.

[0021] Considering the poor toughness of epoxy resin, the coating may crack due to external bending during the actual use of the cable. The present invention uses carboxyl-terminated silicon-containing polyimide to modify epoxy resin. When preparing the silicon-containing polyimide, allylamine reacts with 1,1,3,3-tetramethyldisiloxane to obtain amino-terminated tetramethyldisiloxane; then the amino-terminated tetramethyldisiloxane and biphenyltetracarboxylic dianhydride react, and are capped with trimellitic anhydride to obtain carboxyl-terminated silicon-containing polyimide. The carboxyl groups of the carboxyl-terminated silicon-containing polyimide can undergo esterification reactions with the epoxy groups on the epoxy resin, thereby introducing silicon-containing polyimide molecular chain segments into the crosslinked network of the epoxy resin, improving the toughness and hydrophobicity of the epoxy resin coating. It should be added that when the dosage of carboxyl-terminated silicon-containing polyimide is too high, its compatibility with epoxy resin decreases, and the modification effect will be greatly reduced. After repeated attempts, it is found that when 10-18% of carboxyl-terminated silicon-containing polyimide and 82-90% of epoxy resin are mixed by weight percentage, the performance of the modified epoxy resin is the best.

[0022] It should be added that when the conventional technology in this field uses polytetrafluoroethylene as the insulating layer, due to the strong non-stickiness of the polytetrafluoroethylene surface, it is impossible to effectively combine the shielding layer and the insulating layer by spraying or attaching. Therefore, most of the methods are to first make a silver wire woven mesh and then use the silver wire woven mesh to coat the polytetrafluoroethylene insulating layer to form a silver shielding layer. However, limited by technology and operating processes, the thickness of the silver wire woven mesh is usually between 0.1 and 0.15 mm. In this invention, an epoxy resin coating is covered on the surface of polytetrafluoroethylene. Therefore, a silver shielding layer with a thickness of less than 10 μm can be coated on the surface of the insulating layer by directly coating silver paste or adhering a silver film. The thickness of the silver shielding layer is only 10% of the existing technology, and the weight is reduced to 1%, which is beneficial to realizing the lightweight of the cable. Detailed implementation mode

[0023] Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] The materials and sources used in the present invention: The silver film (10 μm) comes from Jiangsu Namida Optoelectronic Technology Co., Ltd.; the polytetrafluoroethylene resin (model JF-4DE10) comes from Hangzhou Jufu New Materials Technology Co., Ltd.; the auxiliary oil is petroleum ether 60-90, which comes from Suzhou Jiading Chemical Technology Co., Ltd.; the epoxy resin (E51) comes from Hebei Linyuan Fine Chemical Co., Ltd.; the curing agent is triethylenetetramine; the nano-silicon carbide (particle size 40 nm) comes from Beijing Decodaojin Technology Co., Ltd.; the silane coupling agent is KH550; the antioxidant is antioxidant 1076; the PFA sheath material (model FC-103) comes from Hangzhou Jingfu Technology Co., Ltd.

[0025] Example 1: A polytetrafluoroethylene insulated cable and its preparation process, including the following steps:

[0026] Step 1: Prepare a polytetrafluoroethylene film:

[0027] S11: Mix 100 g of polytetrafluoroethylene resin and 18 g of auxiliary oil, let it stand and cure for 24 h, and make a blank under 2 MPa; extrude the blank into a strip-shaped material, and after calendering and stretching, shape it at 300 °C to obtain a polytetrafluoroethylene film with a thickness of 0.3 mm;

[0028] S12: Put the polytetrafluoroethylene film into 60Pre-irradiate in a Co cobalt source, take it out after reaching an absorption dose of 8 kGy; prepare a glycidyl methacrylate / chlorobenzene solution with a mass concentration of 35%, pass nitrogen for 30 min, use benzoyl peroxide as an initiator, and immerse the polytetrafluoroethylene membrane in the glycidyl methacrylate / chlorobenzene solution at a bath ratio of 1:10, heat to 80 °C and react for 4 h; wash with acetone and dry;

[0029] Step 2:

[0030] S21: Disperse allylamine in tetrahydrofuran, use an isopropanol solution of chloroplatinic acid as a catalyst, add 1,1,3,3-tetramethyldisiloxane under a nitrogen atmosphere, heat to 60 °C and react for 5 h; after distilling off the solvent under reduced pressure, wash with methanol and dry to obtain amino-terminated tetramethyldisiloxane; the molar ratio of allyl to 1,1,3,3-tetramethyldisiloxane is 1:1;

[0031] S22: Disperse amino-terminated tetramethyldisiloxane and biphenyltetracarboxylic dianhydride in N-methylpyrrolidone at a molar ratio of 1.2:1, react for 6 h under a nitrogen atmosphere, then heat to 70 °C, add trimellitic anhydride for end-capping reaction for 2 h to obtain carboxyl-terminated silicon-containing polyimide;

[0032] S23: Mix 10% carboxyl-terminated silicon-containing polyimide and 90% epoxy resin by weight percentage to obtain a modified epoxy resin; mix 100 g of the modified epoxy resin, 53 g of a curing agent, 25 g of nano silicon carbide, 11 g of a silane coupling agent, and 3.8 g of an antioxidant to obtain an epoxy resin adhesive;

[0033] Step 3:

[0034] Coat the polytetrafluoroethylene membrane in S12 on the surface of the silver-plated copper conductor core and coat the epoxy resin adhesive, with a coating thickness of 80 μm, and cure at 100 °C to obtain an insulating layer; attach a silver film on the surface of the insulating layer to form a shielding layer; coat a PFA sheath on the surface of the shielding layer to obtain the product.

[0035] Example 2: A polytetrafluoroethylene insulated cable and its preparation process, including the following steps:

[0036] Step 1: Prepare a polytetrafluoroethylene membrane:

[0037] S11: Mix 100 g of polytetrafluoroethylene resin and 18 g of auxiliary oil, let it stand and cure for 27 h, and carry out blanking at 2.5 MPa; extrude the blank into a strip-shaped material, and after calendering and stretching, shape it at 350 °C to obtain a polytetrafluoroethylene membrane with a thickness of 0.3 mm;

[0038] S12: Put the polytetrafluoroethylene membrane under aerobic conditions into 60Pre-irradiate in a Co cobalt source, take it out after reaching an absorbed dose of 12 kGy; prepare a glycidyl methacrylate / chlorobenzene solution with a mass concentration of 35%, pass nitrogen for 30 min, use benzoyl peroxide as an initiator, and soak the polytetrafluoroethylene membrane in the glycidyl methacrylate / chlorobenzene solution according to a bath ratio of 1:12, heat up to 85 °C and react for 5 h; wash with acetone and dry;

[0039] Step 2:

[0040] S21: Disperse allylamine in tetrahydrofuran, use an isopropanol solution of chloroplatinic acid as a catalyst, add 1,1,3,3-tetramethyldisiloxane under a nitrogen atmosphere, heat up to 65 °C and react for 6 h; after distilling off the solvent under reduced pressure, wash with methanol and dry to obtain amino-terminated tetramethyldisiloxane; the molar ratio of allyl to 1,1,3,3-tetramethyldisiloxane is 1:1;

[0041] S22: Disperse amino-terminated tetramethyldisiloxane and biphenyltetracarboxylic dianhydride in N-methylpyrrolidone according to a molar ratio of 1.2:1, react for 7 h under a nitrogen atmosphere, then heat up to 75 °C, add trimellitic anhydride for end-capping reaction for 2.5 h to obtain carboxyl-terminated silicon-containing polyimide;

[0042] S23: Mix 15% carboxyl-terminated silicon-containing polyimide and 85% epoxy resin by weight percentage to obtain a modified epoxy resin; mix 100 g of the modified epoxy resin, 53 g of a curing agent, 25 g of nano silicon carbide, 11 g of a silane coupling agent, and 3.8 g of an antioxidant to obtain an epoxy resin adhesive;

[0043] Step 3:

[0044] Coat the polytetrafluoroethylene membrane in S12 on the surface of a silver-plated copper conductor core and coat the epoxy resin adhesive, with a coating thickness of 80 μm, and cure at 100 °C to obtain an insulating layer; attach a silver film on the surface of the insulating layer to form a shielding layer; coat a PFA sheath on the surface of the shielding layer to obtain the product.

[0045] Example 3: A polytetrafluoroethylene insulated cable and its preparation process, including the following steps:

[0046] Step 1: Prepare a polytetrafluoroethylene membrane:

[0047] S11: Mix 100 g of polytetrafluoroethylene resin and 18 g of auxiliary oil, let it stand and cure for 30 h, and carry out blanking at 3 MPa; extrude the blank into a strip-shaped material, and after calendering and stretching, shape it at 400 °C to obtain a polytetrafluoroethylene membrane with a thickness of 0.3 mm;

[0048] S12: Put the polytetrafluoroethylene membrane under aerobic conditions into 60Pre-irradiate in a Co cobalt source, take it out after reaching an absorbed dose of 15 kGy; prepare a glycidyl methacrylate / chlorobenzene solution with a mass concentration of 35%, pass nitrogen for 30 min, use benzoyl peroxide as an initiator, and immerse the polytetrafluoroethylene membrane in the glycidyl methacrylate / chlorobenzene solution at a bath ratio of 1:15, heat to 90 °C and react for 6 h; wash with acetone and dry;

[0049] Step 2:

[0050] S21: Disperse allylamine in tetrahydrofuran, use an isopropanol solution of chloroplatinic acid as a catalyst, add 1,1,3,3-tetramethyldisiloxane under a nitrogen atmosphere, heat to 70 °C and react for 8 h; after evaporating the solvent under reduced pressure, wash with methanol and dry to obtain amino-terminated tetramethyldisiloxane; the molar ratio of allyl to 1,1,3,3-tetramethyldisiloxane is 1:1;

[0051] S22: Disperse amino-terminated tetramethyldisiloxane and biphenyltetracarboxylic dianhydride in N-methylpyrrolidone at a molar ratio of 1.2:1, react for 8 h under a nitrogen atmosphere, then heat to 80 °C, add trimellitic anhydride for end-capping reaction for 3 h to obtain silicon-containing polyimide with carboxyl end groups;

[0052] S23: Mix 18% silicon-containing polyimide with carboxyl end groups and 82% epoxy resin by weight percentage to obtain a modified epoxy resin; mix 100 g of the modified epoxy resin, 53 g of a curing agent, 25 g of nano silicon carbide, 11 g of a silane coupling agent, and 3.8 g of an antioxidant to obtain an epoxy resin adhesive;

[0053] Step 3:

[0054] Coat the polytetrafluoroethylene membrane in S12 on the surface of the silver-plated copper conductor core and coat the epoxy resin adhesive, with a coating thickness of 80 μm, cure at 100 °C to obtain an insulating layer; attach a silver film on the surface of the insulating layer to form a shielding layer; coat a PFA sheath on the surface of the shielding layer to obtain the product.

[0055] Comparative Example 1: Do not graft epoxy groups on the polytetrafluoroethylene membrane, and the other parameters are the same as in Example 1.

[0056] Step 1: Prepare a polytetrafluoroethylene membrane:

[0057] Mix 100 g of polytetrafluoroethylene resin and 18 g of auxiliary oil, let it stand and cure for 24 h, and form a blank at 2 MPa; extrude the blank into a strip-shaped material, and after calendering and stretching, shape it at 300 °C to obtain a polytetrafluoroethylene membrane with a thickness of 0.3 mm;

[0058] Step 2:

[0059] S21: Disperse allylamine in tetrahydrofuran, use an isopropanol solution of chloroplatinic acid as a catalyst, add 1,1,3,3-tetramethyldisiloxane under a nitrogen atmosphere, and raise the temperature to 60 °C for reaction for 5 h; after distilling off the solvent under reduced pressure, wash with methanol and dry to obtain amino-terminated tetramethyldisiloxane; the molar ratio of allylamine to 1,1,3,3-tetramethyldisiloxane is 1:1;

[0060] S22: Disperse amino-terminated tetramethyldisiloxane and biphenyltetracarboxylic dianhydride in N-methylpyrrolidone according to a molar ratio of 1.2:1, react for 6 h under a nitrogen atmosphere, then raise the temperature to 70 °C, add trimellitic anhydride for end-capping reaction for 2 h to obtain carboxyl-terminated silicon-containing polyimide;

[0061] S23: Mix 10% carboxyl-terminated silicon-containing polyimide and 90% epoxy resin by weight percentage to obtain a modified epoxy resin; mix 100 g of the modified epoxy resin, 53 g of a curing agent, 25 g of nano silicon carbide, 11 g of a silane coupling agent, and 3.8 g of an antioxidant to obtain an epoxy resin adhesive;

[0062] Step 3:

[0063] Coat the surface of the silver-plated copper conductor wire core with the polytetrafluoroethylene film in S12 and coat with the epoxy resin adhesive, with a coating thickness of 80 μm, and cure at 100 °C to obtain an insulating layer; attach a silver film on the surface of the insulating layer to form a shielding layer; coat a PFA sheath on the surface of the shielding layer to obtain the product.

[0064] Comparative Example 2: Do not add carboxyl-terminated silicon-containing polyimide, and the other parameters are the same as those in Example 2.

[0065] Step 1: Prepare a polytetrafluoroethylene film:

[0066] S11: Mix 100 g of polytetrafluoroethylene resin and 18 g of an auxiliary oil, let it stand and cure for 27 h, and perform blanking at 2.5 MPa; extrude the blank into a strip-shaped blank, and after calendering and stretching, shape it at 350 °C to obtain a polytetrafluoroethylene film with a thickness of 0.3 mm;

[0067] S12: Put the polytetrafluoroethylene film into 60 a Co cobalt source under aerobic conditions for pre-irradiation, take it out after reaching an absorbed dose of 12 kGy; prepare a methyl methacrylate glycidyl ester / chlorobenzene solution with a mass concentration of 35%, pass nitrogen for 30 min, use benzoyl peroxide as an initiator, and soak the polytetrafluoroethylene film in the methyl methacrylate glycidyl ester / chlorobenzene solution according to a bath ratio of 1:12, raise the temperature to 85 °C and react for 5 h; wash with acetone and dry;

[0068] Step 2:

[0069] Mix 100 g of modified epoxy resin, 53 g of curing agent, 25 g of nano silicon carbide, 11 g of silane coupling agent, and 3.8 g of antioxidant to obtain an epoxy resin adhesive solution;

[0070] Step 3:

[0071] Coat the surface of the silver-plated copper conductor core with a polytetrafluoroethylene film in S12 and coat it with the epoxy resin adhesive solution. The coating thickness is 80 μm, and cure it at 100 °C to obtain an insulating layer; attach a silver film to the surface of the insulating layer to form a shielding layer; coat a PFA sheath on the surface of the shielding layer to obtain the product.

[0072] Comparative Example 3: Increase the dosage of silicon-containing polyimide with terminal carboxyl groups in the modified epoxy resin, and the other parameters are the same as those in Example 3.

[0073] Step 1: Prepare a polytetrafluoroethylene film:

[0074] S11: Mix 100 g of polytetrafluoroethylene resin and 18 g of auxiliary oil, let it stand and cure for 30 h, and perform blanking at 3 MPa; extrude the blank into a strip-shaped blank, and after calendering and stretching, shape it at 400 °C to obtain a polytetrafluoroethylene film with a thickness of 0.3 mm;

[0075] S12: Put the polytetrafluoroethylene film into 60 a Co cobalt source under aerobic conditions for pre-irradiation, take it out after reaching an absorbed dose of 15 kGy; prepare a 35% mass concentration of glycidyl methacrylate / chlorobenzene solution, pass nitrogen for 30 min, use benzoyl peroxide as an initiator, and soak the polytetrafluoroethylene film in the glycidyl methacrylate / chlorobenzene solution at a bath ratio of 1:15, heat it to 90 °C and react for 6 h; wash it with acetone and dry it;

[0076] Step 2:

[0077] S21: Disperse allylamine in tetrahydrofuran, use an isopropanol solution of chloroplatinic acid as a catalyst, add 1,1,3,3-tetramethyldisiloxane under a nitrogen atmosphere, and heat it to 70 °C and react for 8 h; after evaporating the solvent under reduced pressure, wash it with methanol and dry it to obtain amino-terminated tetramethyldisiloxane; the molar ratio of allyl to 1,1,3,3-tetramethyldisiloxane is 1:1;

[0078] S22: Disperse amino-terminated tetramethyldisiloxane and biphenyltetracarboxylic dianhydride in N-methylpyrrolidone at a molar ratio of 1.2:1, react for 8 h under a nitrogen atmosphere, then heat it to 80 °C, add trimellitic anhydride for end-capping reaction for 3 h to obtain silicon-containing polyimide with terminal carboxyl groups;

[0079] S23: Mix 30% of silicon-containing polyimide with terminal carboxyl groups and 70% of epoxy resin by weight percentage to obtain a modified epoxy resin; mix 100 g of the modified epoxy resin, 53 g of a curing agent, 25 g of nano silicon carbide, 11 g of a silane coupling agent, and 3.8 g of an antioxidant to obtain an epoxy resin adhesive solution.

[0080] Step 3:

[0081] Coat the surface of the silver-plated copper conductor core with the polytetrafluoroethylene film in S12 and coat it with the epoxy resin adhesive solution, with a coating thickness of 80 μm, and cure it at 100 °C to obtain an insulating layer; attach a silver film to the surface of the insulating layer to form a shielding layer; coat a PFA sheath on the surface of the shielding layer to obtain the product.

[0082] Experiment: Test the polytetrafluoroethylene insulating layers prepared in Examples 1 to 3 and Comparative Examples 1 to 3. The test methods are as follows.

[0083] Bending test: Wind the conductor with the polytetrafluoroethylene insulating layer on the surface around a bending cylinder with a diameter of 13 mm for 3 turns, take it off the bending cylinder after 1 minute, straighten it and observe whether there are cracks on the surface coating.

[0084] Salt resistance: The test temperature is 25 °C. Immerse the conductor with the polytetrafluoroethylene insulating layer on the surface in a 4 g / L sodium chloride solution for one month, and observe whether there are bubbles or damages on the surface.

[0085] Contact angle test: Use a contact angle measuring instrument for testing, select distilled water as the test liquid, and set the droplet volume to 4 μL.

[0086] Wear resistance experiment: Use a friction testing machine for friction testing. The material of the friction pair is 45# carbon steel (AISI 1045), with a Rockwell hardness of 45, a surface roughness of 0.4, an outer diameter of 40×10 mm, and an inner diameter of 16×10 mm. Before testing, the friction pair needs to be polished with 1000-mesh metallographic sandpaper and then cleaned with absolute ethanol; the friction load mass is 5 kg, the friction speed is 100 rpm / min, and the friction time is 10 min. Calculate the weight loss before and after friction, which is the wear amount.

[0087] The experimental results are shown in Table 1 below.

[0088] Table 1. Test results of various properties of the polytetrafluoroethylene insulating layer

[0089]

[0090] Conclusion: The data of Examples 1 to 3 and Comparative Examples 1 to 3 show that the polytetrafluoroethylene insulated cables prepared by the present invention have good performance. The data of Example 1 and Comparative Example 1 show that the adhesion performance between the polytetrafluoroethylene film and the epoxy resin coating can be effectively improved by surface modification of the polytetrafluoroethylene film, the bonding force between the two is better, and it does not fall off or blister after being soaked in salt water; under external force, the sliding friction occurring between the epoxy resin coating and the polytetrafluoroethylene film layer is relatively smaller, so the wear amount is lower; the data of Example 2 and Comparative Example 2 show that after adding carboxyl-terminated polysiloxane polyimide, the epoxy resin coating has better toughness, improved hydrophobic performance, and improved tolerance to salt ions; the data of Example 3 and Comparative Example 3 show that when the content of carboxyl-terminated polysiloxane polyimide added is too high, its compatibility with epoxy resin decreases, and the performance of the polytetrafluoroethylene insulating layer deteriorates.

[0091] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent substitution on some of the technical features. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a polytetrafluoroethylene insulated cable, characterized in that: It includes the following steps: Coat a polytetrafluoroethylene film on the surface of a silver-plated copper conductor core and apply an epoxy resin adhesive solution with a coating thickness of 50 - 80 μm, and cure it at 100 - 120 °C to obtain an insulating layer; attach a silver film on the surface of the insulating layer to form a shielding layer; coat a PFA sheath on the surface of the shielding layer to obtain the product; The preparation method of the polytetrafluoroethylene film is as follows: S1: Mix polytetrafluoroethylene resin and auxiliary oil, let it stand and cure, and then make a blank; extrude the blank into a strip-shaped material, and after calendering and stretching, shape it to obtain a polytetrafluoroethylene film with a thickness of 0.2 - 0.3 mm; S2: Put the polytetrafluoroethylene membrane into 60 a Co cobalt source under aerobic conditions for pre-irradiation. After the absorbed dose reaches 8-15 kGy, take it out; Prepare a glycidyl methacrylate / chlorobenzene solution with a mass concentration of 35-40%. After introducing nitrogen for 30 min, use benzoyl peroxide as an initiator, immerse the polytetrafluoroethylene membrane in the glycidyl methacrylate / chlorobenzene solution, heat up to 80-90 °C and react for 4-6 h; Wash with acetone and dry; The preparation method of the epoxy resin adhesive solution is: Mix carboxyl-terminated silicon-containing polyimide and epoxy resin to obtain a modified epoxy resin; By weight, mix 100 parts of the modified epoxy resin, 46 - 57 parts of a curing agent, 18 - 25 parts of nano silicon carbide, 10 - 12 parts of a silane coupling agent, and 3 - 5 parts of an antioxidant to obtain the epoxy resin adhesive solution; The preparation method of the carboxyl-terminated silicon-containing polyimide includes the following steps: a. Disperse allylamine in tetrahydrofuran, use an isopropanol solution of chloroplatinic acid as a catalyst, add 1,1,3,3-tetramethyldisiloxane under a nitrogen atmosphere, heat up to 60 - 70 °C and react for 5 - 8 h; after distilling off the solvent under reduced pressure, wash with methanol and dry to obtain amino-terminated tetramethyldisiloxane; b. Disperse amino-terminated tetramethyldisiloxane and biphenyltetracarboxylic dianhydride in N-methylpyrrolidone, react for 6 - 8 h under a nitrogen atmosphere, then heat up to 70 - 80 °C, add trimellitic anhydride for end-capping reaction for 2 - 3 h to obtain carboxyl-terminated silicon-containing polyimide.

2. The preparation method of a polytetrafluoroethylene insulated cable according to claim 1, characterized in that: In S1, by weight, mix 100 parts of polytetrafluoroethylene resin and 15 - 20 parts of auxiliary oil.

3. The preparation method of a polytetrafluoroethylene insulated cable according to claim 1, characterized in that: In S1, the curing time is 24 - 30 h; the blank-making pressure is 2 - 3 Mpa; the shaping temperature is 300 - 400 °C.

4. The preparation method of a polytetrafluoroethylene insulated cable according to claim 1, characterized in that: In S2, soak the polytetrafluoroethylene film in a glycidyl methacrylate / chlorobenzene solution according to a bath ratio of 1:(10 - 15).

5. The preparation method of a polytetrafluoroethylene insulated cable according to claim 1, characterized in that: In the modified epoxy resin, by weight percentage, 10 - 18% carboxyl-terminated silicon-containing polyimide and 82 - 90% epoxy resin.

6. The preparation method of a polytetrafluoroethylene insulated cable according to claim 1, characterized in that: In step a, the molar ratio of allylamine to 1,1,3,3-tetramethyldisiloxane is 1:

1.

7. The preparation method of a polytetrafluoroethylene insulated cable according to claim 1, characterized in that: In step b, the molar ratio of amino-terminated tetramethyldisiloxane to biphenyltetracarboxylic dianhydride is (1.2 - 1.5):

1.

8. A polytetrafluoroethylene insulated cable prepared by the preparation method according to any one of claims 1 - 7.

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