Self-healing polymeric insulating material, method of preparation and application on an online cable sheath

Abstract

The application relates to the technical field of polyurethane materials, and discloses a self-healing high-molecular insulating material, a preparation method and application on a cable sheath. The application introduces the carbon nanotubes modified by a Schiff base compound with hydroxyl and a Schiff base bond into oxime-modified polyurethane, and based on two kinds of dynamic reversible covalent bonds of oxime amino methyl ester bonds and Schiff base bonds, the polyurethane is endowed with self-repairing performance; meanwhile, the surface-modified carbon nanotubes and nanosilica can optimize the heat conductivity, insulating property and mechanical property of the polyurethane material, so that the polyurethane material can be better applied to the cable sheath material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyurethane materials, in particular to a self-healing high polymer insulating material, a preparation method and an application on a cable sheath. BACKGROUND

[0002] Polyurethane is a kind of block copolymer containing urethane groups in the molecular backbone. The unique molecular structure makes it have excellent flexibility, mechanical strength and wear resistance, and has the advantages of light weight, good thermal stability and chemical stability, good insulation, etc. It is a suitable sheath material for flexible cable. In order to improve the stability, reliability and service life of polyurethane, designing and preparing polyurethane with high mechanical strength and high-efficiency self-repairing performance is an effective method.

[0003] At present, the polymer self-repairing method is divided into external aid type self-repairing and intrinsic type self-repairing. The self-repairing mechanism of intrinsic type self-repairing is to realize it through the reversible chemical reaction of the molecular structure or the diffusion of macromolecules in the polymer material itself. The mechanical properties of the material are improved, and the polyurethane material is endowed with high-efficiency self-repairing performance. According to the different forces, the classification mainly includes the following three methods: dynamic covalent bond self-repairing polyurethane, non-covalent supermolecular force self-repairing polyurethane and multi-force synergistic self-repairing polyurethane.

[0004] However, the activation of dynamic reversible bond in self-repairing polymer is at the expense of mechanical properties. Therefore, it is of great significance to prepare polyurethane with excellent mechanical properties and self-repairing performance. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a self-healing high polymer insulating material, a preparation method and an application on a cable sheath. The present application introduces a carbon nanotube modified by a Schiff base compound with hydroxyl and Schiff base bond into an oxime-modified polyurethane. Based on the two dynamic reversible covalent bonds of oxime amino methyl ester bond and Schiff base bond, the polyurethane is endowed with self-repairing performance. At the same time, the surface modified carbon nanotube and nanosilica can optimize the thermal conductivity, insulation and mechanical properties of the polyurethane material, so that it can be better applied to the cable sheath material.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a self-healing high polymer insulating material, comprising the following steps:

[0008] Step (1), mix hydroxylated carbon nanotube and toluene, ultrasonic dispersion, add sodium ethoxide, continue to ultrasonic dispersion, add 4-chloromethyl styrene, react, after the reaction is completed, filter, wash, dry, and obtain styryl grafted carbon nanotube;

[0009] Step (2), mixing styrene-based grafted carbon nanotubes and water, ultrasonic dispersion, adding styrene, methyl acrylamide, azobisisobutyronitrile, reaction, after the reaction, filtering, washing, drying, to obtain polystyrene-acrylamide modified carbon nanotubes;

[0010] Step (3), mixing 1,8-p-menthane diamine, polystyrene-acrylamide modified carbon nanotubes and water, ultrasonic dispersion, adjusting pH value, reaction, after the reaction, adding vanillin, continuing reaction, after the reaction, purification, to obtain Schiff base compound modified carbon nanotubes;

[0011] Step (4), mixing polycaprolactone diol, isophorone diisocyanate, butanedione oxime, N,N-dimethylformamide, catalyst dibutyltin dilaurate, reaction, after the reaction, to obtain polyurethane prepolymer;

[0012] Adding 1,4-butanediol and Schiff base compound modified carbon nanotubes to the polyurethane prepolymer, continuing reaction, after the reaction, adding KH550 modified nanosilica and mixing uniformly, drying, to obtain self-healing high molecular insulating material.

[0013] Preferably, in the step (1), the solid-liquid ratio of hydroxylated carbon nanotubes, 4-chloromethyl styrene, sodium ethoxide and toluene is 0.12g:6-10mL:0.8-1g:150-300mL.

[0014] Preferably, in the step (1), the reaction condition is stirring reaction at 25-35℃ for 3-5h.

[0015] Preferably, in the step (1), the washing operation is sequentially using ethanol, toluene and tetrahydrofuran.

[0016] Preferably, in the step (2), the solid-liquid ratio of styrene-based grafted carbon nanotubes, styrene, methyl acrylamide, azobisisobutyronitrile and water is 1g:5-6mL:4-5mL:0.3g:50mL; the reaction condition is reaction at 60-70℃ for 8-10h in nitrogen atmosphere.

[0017] Preferably, in the step (3), the solid-liquid ratio of 1,8-p-menthane diamine, vanillin, polystyrene-acrylamide modified carbon nanotubes and water is 1g:1.8g:0.8-1g:100mL; the reaction condition is stirring reaction at room temperature for 12-16h at pH value of 10; the continuing reaction condition is continuing reaction at room temperature for 8-12h at pH value of 10.

[0018] Preferably, in the step (3), the purification operation comprises: adding 0.1 mol / L hydrogen chloride aqueous solution to adjust pH value to 7, centrifuging to take the precipitate, adding water to wash, and drying.

[0019] Preferably, in the step (4), the molar ratio of polycaprolactone diol, isophorone diisocyanate, butanedione oxime and 1, 4-butanediol is 4:8:2-2.5:0.5-0.8; the added mass of the catalyst dibutyltin dilaurate is 0.3% of the mass of the polyurethane prepolymer; the solid content of the polyurethane prepolymer is 30-40%; the added mass of the carbon nanotube modified by the Schiff base compound is 15-20% of the mass of the self-healing high polymer insulating material; and the added mass of the nano-silicon dioxide modified by KH550 is 6-10% of the mass of the self-healing high polymer insulating material.

[0020] Preferably, in the step (4), the reaction condition is: reacting for 6-12 h under a nitrogen atmosphere at a temperature of 60-80 DEG C; and the continuous reaction condition is: continuously reacting for 5-10 h under a nitrogen atmosphere at a temperature of 60-80 DEG C.

[0021] Preferably, the self-healing high polymer insulating material is prepared by the preparation method of the self-healing high polymer insulating material.

[0022] Preferably, the self-healing high polymer insulating material is applied to a cable sheath.

[0023] Compared with the prior art, the self-healing high polymer insulating material has the following beneficial effects:

[0024] 1. The carbon nanotube modified by the Schiff base compound with hydroxyl and Schiff base bond is introduced into the oxime modified polyurethane, and based on the oxime amino methyl ester bond and the dynamic reversible covalent bond Schiff base bond, the self-repairing performance of the polyurethane is given, and the surface modified carbon nanotube and nano-silicon dioxide can optimize the thermal conductivity, insulation and mechanical properties of the polyurethane material, so that the polyurethane material is better applied to the cable sheath material.

[0025] 2. The hydroxyl on the surface of the hydroxylated carbon nanotube is subjected to nucleophilic substitution reaction with the chlorine of 4-chloromethylstyrene to graft a styrene group on the surface of the carbon nanotube, and then the carbon-carbon double bond in the styrene group is reacted with styrene and methacrolein to copolymerize and modify the polymer on the surface of the carbon nanotube, so that the carbon nanotube modified by polystyrene-acrolein is synthesized, the 1, 8-p-menthane diamine and vanillin are further introduced into the surface of the carbon nanotube through the Schiff base reaction between the aldehyde group and the amino group, and the carbon nanotube modified by the Schiff base compound has the dynamic reversible covalent bond and the phenolic hydroxyl group, can participate in the polymerization reaction of the polyurethane as a chain extender, and improves the self-repairing performance of the polyurethane through the oxime amino methyl ester bond.

[0026] 3、The carbon nanotube modified by the Schiff base compound and the nano silicon dioxide modified by KH550 are introduced into the polyurethane, the carbon nanotube can improve the heat conduction performance of the polyurethane material, and due to the modification of the polymer on the surface of the carbon nanotube, the dispersion performance of the carbon nanotube in the polymer matrix and the interfacial bonding force between the carbon nanotube and the polymer are improved, and the crosslinking degree of the polyurethane is improved, and the mechanical properties of the polyurethane material are improved; the nano silicon dioxide modified by KH550 further reduces the electrical conductivity of the polyurethane material and improves the insulation performance. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a column chart of the thermal conductivity of the self-healing high polymer insulating material prepared in examples 1-5 and comparative examples 1-2 in the comprehensive performance test in the present application.

[0028] Figure 2 is a column chart of the self-repairing rate of the self-healing high polymer insulating material prepared in examples 1-5 and comparative examples 1-2 in the comprehensive performance test in the present application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] Example 1

[0031] The present embodiment discloses a preparation method of a self-healing high polymer insulating material, comprising the following steps:

[0032] Step (1), hydroxylated carbon nanotubes and toluene are mixed and ultrasonically dispersed for 20 min, sodium ethoxide is added, and ultrasonic dispersion is continued at room temperature for 1.5 h, 4-chloromethylstyrene is added, and stirring reaction is carried out at a temperature of 35℃ for 3 h, after the reaction is completed, filtration is carried out, and washing is carried out with ethanol, toluene and tetrahydrofuran in sequence, and drying is carried out at a temperature of 50℃ for 48 h, to obtain styryl grafted carbon nanotubes;

[0033] Among them, the solid-liquid ratio of hydroxylated carbon nanotubes, 4-chloromethylstyrene, sodium ethoxide and toluene is 0.12g:6mL:0.8g:200mL;

[0034] Step (2), the styryl grafted carbon nanotubes and water are mixed and ultrasonically dispersed for 20 min, styrene, methyl acrolein and azobisisobutyronitrile are added, and reaction is carried out at a temperature of 70℃ in a nitrogen atmosphere for 8 h, after the reaction is completed, filtration is carried out, and washing is carried out with water, and drying is carried out at a temperature of 50℃ for 48 h, to obtain polystyrene-acrolein modified carbon nanotubes.

[0035] The solid-liquid ratio of styrene-grafted carbon nanotubes, styrene, methacrolein, azobisisobutyronitrile, and water is 1g:6mL:4mL:0.3g:50mL.

[0036] Step (3): Mix 1,8-p-menthol diamine, polystyrene-acrylic acid modified carbon nanotubes, and water, and ultrasonically disperse for 20 min. Add 0.1 mol / L sodium hydroxide aqueous solution to adjust the pH to 10. Stir and react at room temperature for 12 h. After the reaction is complete, add vanillin and continue the reaction for 12 h. After the reaction is complete, add 0.1 mol / L hydrogen chloride aqueous solution to adjust the pH to 7. Centrifuge to collect the precipitate, wash with water, and dry at 50℃ for 48 h to obtain Schiff base compound modified carbon nanotubes.

[0037] The solid-liquid ratio of 1,8-p-menthanediamine, vanillin, polystyrene-acrylic acid modified carbon nanotubes, and water is 1g:1.8g:0.8g:100mL.

[0038] Step (4): Polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, N,N-dimethylformamide and catalyst dibutyltin dilaurate are mixed and dissolved, and reacted at 60°C for 12 hours in a nitrogen atmosphere. After the reaction is completed, a polyurethane prepolymer with a solid content of 30% is obtained.

[0039] 1,4-Butanediol and Schiff base compounds modified carbon nanotubes were added to polyurethane prepolymer and reacted at 60°C for 10 hours. After the reaction was completed, KH550 modified nano-silica was added and mixed evenly. The mixture was then dried at 70°C for 24 hours to obtain a self-healing polymer insulating material.

[0040] The molar ratio of polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, and 1,4-butanediol is 4:8:2:0.8; the mass of the catalyst dibutyltin dilaurate is 0.3% of the mass of the polyurethane prepolymer; the mass of the Schiff base compound modified carbon nanotubes is 15% of the mass of the self-healing polymer insulating material; and the mass of the KH550 modified nano-silica is 6% of the mass of the self-healing polymer insulating material.

[0041] Example 2

[0042] This embodiment discloses a method for preparing a self-healing polymer insulating material, including the following steps:

[0043] Step (1): Hydroxylated carbon nanotubes and toluene are mixed and ultrasonically dispersed for 20 min. Sodium ethoxide is added and ultrasonic dispersion is continued for 1.5 h at room temperature. 4-Chloromethylstyrene is added and the mixture is stirred at 35 °C for 3 h. After the reaction is completed, the mixture is filtered and washed successively with ethanol, toluene and tetrahydrofuran. It is then dried at 50 °C for 48 h to obtain styrene-based grafted carbon nanotubes.

[0044] The solid-liquid ratio of hydroxylated carbon nanotubes, 4-chloromethylstyrene, sodium ethoxide, and toluene was 0.12 g: 6 mL: 0.8 g: 200 mL.

[0045] Step (2): Styrene-grafted carbon nanotubes and water are mixed and ultrasonically dispersed for 20 min. Styrene, methacrolein and azobisisobutyronitrile are added and reacted at 70°C for 8 h in a nitrogen atmosphere. After the reaction is completed, the mixture is filtered, washed with water, and dried at 50°C for 48 h to obtain polystyrene-acrylic acid modified carbon nanotubes.

[0046] The solid-liquid ratio of styrene-grafted carbon nanotubes, styrene, methacrolein, azobisisobutyronitrile, and water is 1g:5.8mL:4.2mL:0.3g:50mL.

[0047] Step (3): Mix 1,8-p-menthol diamine, polystyrene-acrylic acid modified carbon nanotubes, and water, and ultrasonically disperse for 20 min. Add 0.1 mol / L sodium hydroxide aqueous solution to adjust the pH to 10. Stir and react at room temperature for 14 h. After the reaction is complete, add vanillin and continue the reaction for 10 h. After the reaction is complete, add 0.1 mol / L hydrogen chloride aqueous solution to adjust the pH to 7. Centrifuge to collect the precipitate, wash with water, and dry at 50℃ for 48 h to obtain Schiff base compound modified carbon nanotubes.

[0048] The solid-liquid ratio of 1,8-p-menthanediamine, vanillin, polystyrene-acrylic acid modified carbon nanotubes, and water is 1g:1.8g:0.8g:100mL.

[0049] Step (4): Polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, N,N-dimethylformamide and catalyst dibutyltin dilaurate are mixed and dissolved, and reacted at 60°C for 12 hours in a nitrogen atmosphere. After the reaction is completed, a polyurethane prepolymer with a solid content of 30% is obtained.

[0050] 1,4-Butanediol and Schiff base compounds modified carbon nanotubes were added to polyurethane prepolymer and reacted at 60°C for 10 hours. After the reaction was completed, KH550 modified nano-silica was added and mixed evenly. The mixture was then dried at 70°C for 24 hours to obtain a self-healing polymer insulating material.

[0051] The molar ratio of polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, and 1,4-butanediol is 4:8:2.1:0.7; the mass of the catalyst dibutyltin dilaurate is 0.3% of the mass of the polyurethane prepolymer; the mass of the Schiff base compound modified carbon nanotubes is 17% of the mass of the self-healing polymer insulating material; and the mass of the KH550 modified nano-silica is 7% of the mass of the self-healing polymer insulating material.

[0052] Example 3

[0053] This embodiment discloses a method for preparing a self-healing polymer insulating material, including the following steps:

[0054] Step (1): Hydroxylated carbon nanotubes and toluene are mixed and ultrasonically dispersed for 20 min. Sodium ethoxide is added and ultrasonic dispersion is continued for 1.5 h at room temperature. 4-Chloromethylstyrene is added and the mixture is stirred at 35 °C for 3 h. After the reaction is completed, the mixture is filtered and washed successively with ethanol, toluene and tetrahydrofuran. It is then dried at 50 °C for 48 h to obtain styrene-based grafted carbon nanotubes.

[0055] The solid-liquid ratio of hydroxylated carbon nanotubes, 4-chloromethylstyrene, sodium ethoxide, and toluene was 0.12 g: 6 mL: 0.8 g: 200 mL.

[0056] Step (2): Styrene-grafted carbon nanotubes and water are mixed and ultrasonically dispersed for 20 min. Styrene, methacrolein and azobisisobutyronitrile are added and reacted at 70°C for 8 h in a nitrogen atmosphere. After the reaction is completed, the mixture is filtered, washed with water, and dried at 50°C for 48 h to obtain polystyrene-acrylic acid modified carbon nanotubes.

[0057] The solid-liquid ratio of styrene-grafted carbon nanotubes, styrene, methacrolein, azobisisobutyronitrile, and water is 1g:5.5mL:4.5mL:0.3g:50mL.

[0058] Step (3): Mix 1,8-p-menthol diamine, polystyrene-acrylic acid modified carbon nanotubes, and water, and ultrasonically disperse for 20 min. Add 0.1 mol / L sodium hydroxide aqueous solution to adjust the pH to 10. Stir and react at room temperature for 14 h. After the reaction is complete, add vanillin and continue the reaction for 10 h. After the reaction is complete, add 0.1 mol / L hydrogen chloride aqueous solution to adjust the pH to 7. Centrifuge to collect the precipitate, wash with water, and dry at 50℃ for 48 h to obtain Schiff base compound modified carbon nanotubes.

[0059] The solid-liquid ratio of 1,8-p-menthanediamine, vanillin, polystyrene-acrylic acid modified carbon nanotubes, and water is 1g:1.8g:0.8g:100mL.

[0060] Step (4): Polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, N,N-dimethylformamide and catalyst dibutyltin dilaurate are mixed and dissolved, and reacted at 60°C for 12 hours in a nitrogen atmosphere. After the reaction is completed, a polyurethane prepolymer with a solid content of 30% is obtained.

[0061] 1,4-Butanediol and Schiff base compounds modified carbon nanotubes were added to polyurethane prepolymer and reacted at 60°C for 10 hours. After the reaction was completed, KH550 modified nano-silica was added and mixed evenly. The mixture was then dried at 70°C for 24 hours to obtain a self-healing polymer insulating material.

[0062] The molar ratio of polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, and 1,4-butanediol is 4:8:2.3:0.65; the mass of the catalyst dibutyltin dilaurate is 0.3% of the mass of the polyurethane prepolymer; the mass of the Schiff base compound modified carbon nanotubes is 18% of the mass of the self-healing polymer insulating material; and the mass of the KH550 modified nano-silica is 8% of the mass of the self-healing polymer insulating material.

[0063] Example 4

[0064] This embodiment discloses a method for preparing a self-healing polymer insulating material, including the following steps:

[0065] Step (1): Hydroxylated carbon nanotubes and toluene are mixed and ultrasonically dispersed for 20 min. Sodium ethoxide is added and ultrasonic dispersion is continued for 1.5 h at room temperature. 4-Chloromethylstyrene is added and the mixture is stirred at 35 °C for 3 h. After the reaction is completed, the mixture is filtered and washed successively with ethanol, toluene and tetrahydrofuran. It is then dried at 50 °C for 48 h to obtain styrene-based grafted carbon nanotubes.

[0066] The solid-liquid ratio of hydroxylated carbon nanotubes, 4-chloromethylstyrene, sodium ethoxide, and toluene was 0.12 g: 6 mL: 0.8 g: 200 mL.

[0067] Step (2): Styrene-grafted carbon nanotubes and water are mixed and ultrasonically dispersed for 20 min. Styrene, methacrolein and azobisisobutyronitrile are added and reacted at 70°C for 8 h in a nitrogen atmosphere. After the reaction is completed, the mixture is filtered, washed with water, and dried at 50°C for 48 h to obtain polystyrene-acrylic acid modified carbon nanotubes.

[0068] The solid-liquid ratio of styrene-grafted carbon nanotubes, styrene, methacrolein, azobisisobutyronitrile, and water is 1g:5.2mL:4.8mL:0.3g:50mL.

[0069] Step (3): Mix 1,8-p-menthol diamine, polystyrene-acrylic acid modified carbon nanotubes, and water, and ultrasonically disperse for 20 min. Add 0.1 mol / L sodium hydroxide aqueous solution to adjust the pH to 10. Stir and react at room temperature for 14 h. After the reaction is complete, add vanillin and continue the reaction for 10 h. After the reaction is complete, add 0.1 mol / L hydrogen chloride aqueous solution to adjust the pH to 7. Centrifuge to collect the precipitate, wash with water, and dry at 50℃ for 48 h to obtain Schiff base compound modified carbon nanotubes.

[0070] The solid-liquid ratio of 1,8-p-menthanediamine, vanillin, polystyrene-acrylic acid modified carbon nanotubes, and water is 1g:1.8g:0.8g:100mL.

[0071] Step (4): Polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, N,N-dimethylformamide and catalyst dibutyltin dilaurate are mixed and dissolved, and reacted at 60°C for 12 hours in a nitrogen atmosphere. After the reaction is completed, a polyurethane prepolymer with a solid content of 30% is obtained.

[0072] 1,4-Butanediol and Schiff base compounds modified carbon nanotubes were added to polyurethane prepolymer and reacted at 60°C for 10 hours. After the reaction was completed, KH550 modified nano-silica was added and mixed evenly. The mixture was then dried at 70°C for 24 hours to obtain a self-healing polymer insulating material.

[0073] The molar ratio of polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, and 1,4-butanediol is 4:8:2.4:0.6; the mass of the catalyst dibutyltin dilaurate is 0.3% of the mass of the polyurethane prepolymer; the mass of the Schiff base compound modified carbon nanotubes is 19% of the mass of the self-healing polymer insulating material; and the mass of the KH550 modified nano-silica is 9% of the mass of the self-healing polymer insulating material.

[0074] Example 5

[0075] This embodiment discloses a method for preparing a self-healing polymer insulating material, including the following steps:

[0076] Step (1): Hydroxylated carbon nanotubes and toluene are mixed and ultrasonically dispersed for 20 min. Sodium ethoxide is added and ultrasonic dispersion is continued for 1.5 h at room temperature. 4-Chloromethylstyrene is added and the mixture is stirred at 35 °C for 3 h. After the reaction is completed, the mixture is filtered and washed successively with ethanol, toluene and tetrahydrofuran. It is then dried at 50 °C for 48 h to obtain styrene-based grafted carbon nanotubes.

[0077] The solid-liquid ratio of hydroxylated carbon nanotubes, 4-chloromethylstyrene, sodium ethoxide, and toluene was 0.12 g: 6 mL: 0.8 g: 200 mL.

[0078] Step (2): Styrene-grafted carbon nanotubes and water are mixed and ultrasonically dispersed for 20 min. Styrene, methacrolein and azobisisobutyronitrile are added and reacted at 70°C for 8 h in a nitrogen atmosphere. After the reaction is completed, the mixture is filtered, washed with water, and dried at 50°C for 48 h to obtain polystyrene-acrylic acid modified carbon nanotubes.

[0079] The solid-liquid ratio of styrene-grafted carbon nanotubes, styrene, methacrolein, azobisisobutyronitrile, and water is 1g:5mL:5mL:0.3g:50mL.

[0080] Step (3): Mix 1,8-p-menthol diamine, polystyrene-acrylaldehyde modified carbon nanotubes, and water, and ultrasonically disperse for 20 min. Add 0.1 mol / L sodium hydroxide aqueous solution to adjust the pH to 10. Stir and react at room temperature for 16 h. After the reaction is complete, add vanillin and continue the reaction for 8 h. After the reaction is complete, add 0.1 mol / L hydrogen chloride aqueous solution to adjust the pH to 7. Centrifuge to collect the precipitate, wash with water, and dry at 50℃ for 48 h to obtain Schiff base compound modified carbon nanotubes.

[0081] The solid-liquid ratio of 1,8-p-menthanediamine, vanillin, polystyrene-acrylic acid modified carbon nanotubes, and water is 1g:1.8g:0.8g:100mL.

[0082] Step (4): Polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, N,N-dimethylformamide and catalyst dibutyltin dilaurate are mixed and dissolved, and reacted at 60°C for 12 hours in a nitrogen atmosphere. After the reaction is completed, a polyurethane prepolymer with a solid content of 30% is obtained.

[0083] 1,4-Butanediol and Schiff base compounds modified carbon nanotubes were added to polyurethane prepolymer and reacted at 60°C for 10 hours. After the reaction was completed, KH550 modified nano-silica was added and mixed evenly. The mixture was then dried at 70°C for 24 hours to obtain a self-healing polymer insulating material.

[0084] The molar ratio of polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, and 1,4-butanediol is 4:8:2.5:0.5; the mass of the catalyst dibutyltin dilaurate is 0.3% of the mass of the polyurethane prepolymer; the mass of the Schiff base compound modified carbon nanotubes is 20% of the mass of the self-healing polymer insulating material; and the mass of the KH550 modified nano-silica is 10% of the mass of the self-healing polymer insulating material.

[0085] Comparative Example 1

[0086] This comparative example discloses a method for preparing a self-healing polymer insulating material, including the following steps:

[0087] Step (1): Hydroxylated carbon nanotubes and toluene are mixed and ultrasonically dispersed for 20 min. Sodium ethoxide is added and ultrasonic dispersion is continued for 1.5 h at room temperature. 4-Chloromethylstyrene is added and the mixture is stirred at 35 °C for 3 h. After the reaction is completed, the mixture is filtered and washed successively with ethanol, toluene and tetrahydrofuran. It is then dried at 50 °C for 48 h to obtain styrene-based grafted carbon nanotubes.

[0088] The solid-liquid ratio of hydroxylated carbon nanotubes, 4-chloromethylstyrene, sodium ethoxide, and toluene was 0.12 g: 6 mL: 0.8 g: 200 mL.

[0089] Step (2): Polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, N,N-dimethylformamide and catalyst dibutyltin dilaurate are mixed and dissolved, and reacted at 60°C for 12 hours in a nitrogen atmosphere. After the reaction is completed, a polyurethane prepolymer with a solid content of 30% is obtained.

[0090] 1,4-Butanediol was added to the polyurethane prepolymer and reacted at 60°C for 10 hours. After the reaction was completed, styrene-grafted carbon nanotubes and KH550 modified nano-silica were added and mixed evenly. The mixture was then dried at 70°C for 24 hours to obtain a self-healing polymer insulation material.

[0091] The molar ratio of polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, and 1,4-butanediol is 4:8:2:0.8; the mass of the catalyst dibutyltin dilaurate is 0.3% of the mass of the polyurethane prepolymer; the mass of the styrene-based grafted carbon nanotubes is 15% of the mass of the self-healing polymer insulating material; and the mass of the KH550 modified nano-silica is 6% of the mass of the self-healing polymer insulating material.

[0092] Comparative Example 2

[0093] This comparative example discloses a method for preparing a self-healing polymer insulating material, including the following steps:

[0094] Step (1): Hydroxylated carbon nanotubes and toluene are mixed and ultrasonically dispersed for 20 min. Sodium ethoxide is added and ultrasonic dispersion is continued for 1.5 h at room temperature. 4-Chloromethylstyrene is added and the mixture is stirred at 35 °C for 3 h. After the reaction is completed, the mixture is filtered and washed successively with ethanol, toluene and tetrahydrofuran. It is then dried at 50 °C for 48 h to obtain styrene-based grafted carbon nanotubes.

[0095] The solid-liquid ratio of hydroxylated carbon nanotubes, 4-chloromethylstyrene, sodium ethoxide, and toluene was 0.12 g: 6 mL: 0.8 g: 200 mL.

[0096] Step (2): Styrene-grafted carbon nanotubes and water are mixed and ultrasonically dispersed for 20 min. Styrene, methacrolein and azobisisobutyronitrile are added and reacted at 70°C for 8 h in a nitrogen atmosphere. After the reaction is completed, the mixture is filtered, washed with water, and dried at 50°C for 48 h to obtain polystyrene-acrylic acid modified carbon nanotubes.

[0097] The solid-liquid ratio of styrene-grafted carbon nanotubes, styrene, methacrolein, azobisisobutyronitrile, and water is 1g:6mL:4mL:0.3g:50mL.

[0098] Step (3): Mix 1,8-p-menthol diamine, polystyrene-acrylic acid modified carbon nanotubes, and water, and ultrasonically disperse for 20 min. Add 0.1 mol / L sodium hydroxide aqueous solution to adjust the pH to 10. Stir and react at room temperature for 12 h. After the reaction is complete, add vanillin and continue the reaction for 12 h. After the reaction is complete, add 0.1 mol / L hydrogen chloride aqueous solution to adjust the pH to 7. Centrifuge to collect the precipitate, wash with water, and dry at 50℃ for 48 h to obtain Schiff base compound modified carbon nanotubes.

[0099] The solid-liquid ratio of 1,8-p-menthanediamine, vanillin, polystyrene-acrylic acid modified carbon nanotubes, and water is 1g:1.8g:0.8g:100mL.

[0100] Step (4): Polycaprolactone diol, isophorone diisocyanate, N,N-dimethylformamide and catalyst dibutyltin dilaurate are mixed and dissolved, and reacted at 60°C for 12 hours in a nitrogen atmosphere. After the reaction is completed, a polyurethane prepolymer with a solid content of 30% is obtained.

[0101] 1,4-Butanediol and Schiff base compounds modified carbon nanotubes were added to polyurethane prepolymer and reacted at 60°C for 10 hours. After the reaction was completed, KH550 modified nano-silica was added and mixed evenly. The mixture was then dried at 70°C for 24 hours to obtain a self-healing polymer insulating material.

[0102] The molar ratio of polycaprolactone diol, isophorone diisocyanate, and 1,4-butanediol is 4:8:2.8; the mass of the catalyst dibutyltin dilaurate is 0.3% of the mass of the polyurethane prepolymer; the mass of the Schiff base compound modified carbon nanotubes is 15% of the mass of the self-healing polymer insulating material; and the mass of the KH550 modified nano-silica is 6% of the mass of the self-healing polymer insulating material.

[0103] In the above examples and comparative examples: the diameter of the hydroxylated carbon nanotubes is 30-50 nm, the length is 10-20 μm, and the hydroxyl content is 0.53 wt.%; the polycaprolactone diol is PCL2000; the preparation of KH550 modified nano silica includes the following steps: 1 g of nano silica, 90 mL of ethanol, and 30 mL of water are mixed, 0.4 g of KH550 is added, the pH value is adjusted to 5, ultrasonic dispersion is performed, and the reaction is carried out at 80 °C for 1 h. After the reaction is completed, the mixture is filtered, washed, and dried to obtain KH550 modified nano silica; the particle size of the nano silica is 50-100 nm.

[0104] Test case

[0105] The comprehensive properties of the self-healing polymer insulating materials prepared in Examples 1-5 and Comparative Examples 1-2 were tested. Specific test results are shown in Table 1.

[0106] Table 1

[0107]

[0108] The tests for each indicator in Table 1 were conducted according to the following standards: tensile strength was determined by GB / T 1040 2006 "Determination of Tensile Properties of Plastics"; volume resistivity was tested according to GB / T 1410-2006; thermal conductivity was tested according to ASTM C518-02; the self-healing rate was tested as follows: the self-healing polymer insulating material strips prepared in Examples 1-5 and Comparative Examples 1-2 were cut in the middle, the broken edges were aligned, and the strips were heated in an oven at 130℃ for 2 hours to repair the self-healing rate. Then, the strips were placed in a vacuum oven at 80℃ for 30 hours to cure the self-healing rate. After curing, the mechanical properties were tested again, and the self-healing rate was calculated.

[0109] As can be seen from the test results in Table 1, the thermal conductivity, insulation, and mechanical properties of the self-healing polymer insulating material prepared by this invention are all improved, making it suitable for use in cable materials. This is because the Schiff base-modified carbon nanotubes possess dynamic reversible covalent bonds and phenolic hydroxyl groups, which can act as chain extenders in the polymerization reaction of polyurethane, synergistically enhancing the self-healing properties of polyurethane through oxime methyl ester bonds. Simultaneously, the carbon nanotubes improve the thermal conductivity of the polyurethane material. Furthermore, due to the modification of the polymer surface on the carbon nanotubes, the dispersion performance of the carbon nanotubes in the polymer matrix and their interfacial bonding force with the polymer are improved, increasing the crosslinking degree of polyurethane and thus enhancing the mechanical properties of the polyurethane material. KH550-modified nano-silica further reduces the electrical conductivity of the polyurethane material, improving its insulation performance.

[0110] Comparative Example 1: The styrene-grafted carbon nanotubes were not further modified, resulting in decreased dispersion of the carbon nanotubes in the polyurethane matrix. Furthermore, the lack of Schiff base bonds and oxime methyl ester bonds synergistically enhancing the self-healing properties of the polyurethane led to reduced self-healing and thermal conductivity. Comparative Example 2: The polyurethane did not contain dimethylglyoxime, thus lacking the oxime methyl ester bonds that enhance the material's self-healing properties, resulting in decreased self-healing performance.

[0111] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a self-healing polymer insulating material, characterized in that, Includes the following steps: Step (1): Mix 1,8-p-menthanediamine, polystyrene-acrylic acid modified carbon nanotubes and water, disperse by ultrasonication, adjust the pH value, and react. After the reaction is completed, add vanillin and continue the reaction. After the reaction is completed, purify to obtain Schiff base compound modified carbon nanotubes. Polystyrene-acrylic acid modified carbon nanotubes are prepared by the following steps: S1. Hydroxylated carbon nanotubes and toluene are mixed and ultrasonically dispersed. Sodium ethoxide is added and ultrasonic dispersion is continued. 4-Chloromethylstyrene is added and reacted. After the reaction is completed, the mixture is filtered, washed, and dried to obtain styrene-based grafted carbon nanotubes. S2. Styrene-grafted carbon nanotubes and water are mixed and ultrasonically dispersed. Styrene, methacrolein, and azobisisobutyronitrile are added and reacted. After the reaction is completed, the mixture is filtered, washed, and dried to obtain polystyrene-acrylaldehyde modified carbon nanotubes. Step (2): Mix and dissolve polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, N,N-dimethylformamide, and dibutyltin dilaurate, and react. After the reaction is complete, a polyurethane prepolymer is obtained. 1,4-Butanediol and Schiff base compounds were added to the polyurethane prepolymer and the reaction continued. After the reaction was completed, KH550 modified nano-silica was added, mixed evenly, and dried to obtain a self-healing polymer insulating material.

2. The method for preparing the self-healing polymer insulating material according to claim 1, characterized in that, In step (1), when preparing polystyrene-acrylic aldehyde modified carbon nanotubes, the solid-liquid ratio of hydroxylated carbon nanotubes, 4-chloromethylstyrene, sodium ethoxide, and toluene in S1 is 0.12g:6-10mL:0.8-1g:150-300mL; the reaction conditions are: stirring at 25-35℃ for 3-5h.

3. The method for preparing the self-healing polymer insulating material according to claim 1, characterized in that, In step (1), when preparing polystyrene-acrylaldehyde modified carbon nanotubes, the solid-liquid ratio of styrene-grafted carbon nanotubes, styrene, methacrolein, azobisisobutyronitrile, and water in S2 is 1g:5-6mL:4-5mL:0.3g:50mL; the reaction conditions are: reaction at 60-70℃ for 8-10h in a nitrogen atmosphere.

4. The method for preparing the self-healing polymer insulating material according to claim 1, characterized in that, In step (1), the solid-liquid ratio of 1,8-p-menthanediamine, vanillin, polystyrene-acrylic acid modified carbon nanotubes, and water is 1g:1.8g:0.8-1g:100mL; the reaction conditions are: stirring at room temperature and pH 10 for 12-16h; the reaction conditions for continued reaction are: stirring at room temperature and pH 10 for 8-12h.

5. The method for preparing the self-healing polymer insulating material according to claim 1, characterized in that, In step (2): the molar ratio of polycaprolactone diol, isophorone diisocyanate, dimethylglyoxime, and 1,4-butanediol is 4:8:2-2.5:0.5-0.8; the mass of the catalyst dibutyltin dilaurate added is 0.3% of the mass of the polyurethane prepolymer; and the solid content of the polyurethane prepolymer is 30-40%.

6. The method for preparing the self-healing polymer insulating material according to claim 1, characterized in that, In step (2): the mass of Schiff base compound modified carbon nanotubes added is 15-20% of the mass of the self-healing polymer insulating material; the mass of KH550 modified nano silica added is 6-10% of the mass of the self-healing polymer insulating material.

7. The method for preparing the self-healing polymer insulating material according to claim 1, characterized in that, In step (2), the reaction conditions are: reacting for 6-12 hours in a nitrogen atmosphere at a temperature of 60-80°C; the conditions for continued reaction are: continuing the reaction for 5-10 hours in a nitrogen atmosphere at a temperature of 60-80°C.

8. A self-healing polymer insulating material prepared by the method for preparing a self-healing polymer insulating material as described in any one of claims 1-7.

9. The application of the self-healing polymer insulation material as described in claim 8 in cable sheaths.

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