High density power composite pipe and method of making same

Abstract

This application relates to a high-density power composite pipe and its preparation method. The high-density power composite pipe includes a polypropylene layer and a polyolefin composite layer. The polyolefin composite layer comprises the following components by weight: 107-140 parts of polypropylene-polyethylene mixture, 42-52 parts of epoxy resin composite material, 12-18 parts of silica, 20-26 parts of styrene-butadiene rubber, 7-9 parts of plasticizer, and 4-6 parts of dispersant. The polypropylene-polyethylene mixture includes polypropylene, high-density polyethylene, boron nitride, and polypropylene grafted with maleic anhydride. This application has the effect of improving the impact resistance and tensile strength of the composite pipe.

Description

Technical Field

[0001] This application relates to the field of composite pipes, and in particular to a high-density power composite pipe and its preparation method. Background Technology

[0002] Pipes are building materials used for transportation. Composite pipes are pipes based on thermoplastic composite structures, with inner linings of non-metallic materials such as polypropylene, polyethylene, or outer welded cross-linked polyethylene. They are widely used in the power industry.

[0003] Polypropylene possesses advantages such as good heat resistance, mechanical properties, electrical insulation, low cost, ease of processing, and, as a thermoplastic polymer, is easy to recycle and reuse, making it suitable as a matrix for composite thermally conductive polymer materials. However, its low impact strength limits its widespread application in engineering plastics. Summary of the Invention

[0004] To further improve the overall performance of composite pipes, this application provides a high-density power composite pipe and its preparation method.

[0005] This application provides a high-density power composite pipe and its preparation method, which adopts the following technical solution:

[0006] Firstly, this application provides a high-density power composite pipe, which adopts the following technical solution:

[0007] A high-density power composite pipe includes a polypropylene layer and a polyolefin composite layer, wherein the polyolefin composite layer comprises the following components by weight:

[0008] 107-140 parts of polypropylene-polyethylene blend, 42-52 parts of epoxy resin composite, 12-18 parts of silica, 20-26 parts of styrene-butadiene rubber, 7-9 parts of plasticizer, and 4-6 parts of dispersant;

[0009] The polypropylene-polyethylene blend includes polypropylene, high-density polyethylene, boron nitride, and polypropylene grafted with maleic anhydride.

[0010] By adopting the above technical solution, a polypropylene-polyethylene composite material is prepared by mixing polypropylene, high-density polyethylene, boron nitride, and polypropylene grafted with maleic anhydride. Polypropylene, as the base material of the composite pipe, has good heat resistance and mechanical properties and is easy to process. However, the impact strength of polypropylene is relatively weak. The addition of high-density polyethylene can effectively improve the overall impact resistance of the system. Boron nitride has good thermal conductivity, oxidation resistance, corrosion resistance, and chemical stability. Its addition can effectively improve the thermal conductivity at the interface of the base material, thereby improving the overall thermal stability of the pipe. The grafting of maleic anhydride onto polypropylene enhances the compatibility between polypropylene and boron nitride in the composite material, allowing more particles to enter the polypropylene and promoting the nucleation effect of boron nitride in polypropylene, further improving the stability of the system. Epoxy resin composite material is also added to the pipe, which has good bonding performance, improving the bonding performance of the materials in the pipe and further enhancing the mechanical properties of the pipe.

[0011] Preferably, the mass ratio of polypropylene, high-density polyethylene, boron nitride and polypropylene grafted with maleic anhydride is 64:16:15:(5.3-5.7).

[0012] By adopting the above technical solution, the mass ratio of polypropylene, high-density polyethylene, boron nitride and polypropylene grafted maleic anhydride is preferably within the above range. The boron nitride is dispersed in the matrix in a manner similar to a sea-island structure, which can further improve the comprehensive performance of polypropylene-polyethylene blends.

[0013] Preferably, the epoxy resin composite material includes modified carboxyl carbon nanotubes, composite aramid fibers, epoxy resin, and tannic acid.

[0014] By adopting the above technical solution, the addition of epoxy resin to the pipe can effectively improve the bonding performance between the various components of the pipe. Modified carboxylated carbon nanotubes and composite aramid fibers are added to the epoxy resin, which can fill the gaps between the materials, increasing the surface area per unit volume and thus improving the interfacial bonding force. Carbon nanotubes have excellent mechanical, thermal, and electrical properties, and a high specific surface area. When added to the system, they can better transfer stress to the material and improve the overall heat resistance of the system. However, strong van der Waals forces and π-π bonds... Under the interaction of various factors, carbon nanotubes have high cohesive force. Modified carbon nanotubes can improve their aggregation phenomenon and enhance their dispersion performance, thereby improving the stability of the prepared epoxy resin composite material. Aramid fibers can enhance the connection relationship between various components in the system, making the connection between the various components in the system tighter. Tannic acid, as a renewable resource, can be introduced into the system to modify the epoxy resin, thereby further improving the crosslinking and bonding performance of the epoxy resin, thus improving the overall performance of the prepared epoxy resin composite material.

[0015] Preferably, the modified carboxyl-based carbon nanotubes are prepared by the following method:

[0016] Polyethyleneimine was mixed with water to obtain an aqueous solution of polyethyleneimine. Carboxylated multi-walled carbon nanotubes were added to the aqueous solution of polyethyleneimine, refluxed, vacuum filtered, washed, and freeze-dried to obtain modified carboxylated carbon nanotubes.

[0017] By adopting the above technical solution, polyethyleneimine is grafted onto the surface of carboxylated multi-walled carbon nanotubes through an amidation reaction. The high-molecular-weight polyethyleneimine grafted onto the surface of carbon nanotubes can effectively improve the dispersion effect of carbon nanotubes in epoxy resin, and can also participate in some of the subsequent curing and crosslinking reactions of epoxy resin, thereby improving the interfacial bonding between carbon nanotubes and epoxy resin matrix, and thus improving the comprehensive performance of epoxy resin composite materials.

[0018] Preferably, the mass ratio of the carboxyl carbon nanotubes to polyethyleneimine is (0.08-0.12):1.

[0019] By adopting the above technical solution, and preferably having the mass ratio of carboxylated carbon nanotubes to polyethyleneimine within the above range, the overall performance of the prepared modified carboxylated carbon nanotubes can be effectively improved.

[0020] Preferably, the composite aramid fiber is prepared by the following method:

[0021] Glycidyl polyhedral silsesquioxane, polyamic acid and tetrahydrofuran were mixed to obtain a mixed solution; aramid fibers were added to the mixed solution, impregnated and then placed in a supercritical CO2 reactor for treatment. After treatment, the aramid fibers were removed and then heated to obtain composite aramid fibers.

[0022] By adopting the above technical solution, using supercritical CO2 to assist in modifying aramid fibers with small molecule glycidyl polyhedral silsesquioxane and macromolecular polyamic acid, the bonding performance between aramid fibers and other components can be effectively improved. At the same time, the interfacial twisting property of styrene-butadiene rubber can also be further enhanced, thereby improving the overall mechanical properties of the composite material.

[0023] Preferably, the mass concentration of glycidyl polyhedral silsesquioxane and the concentration of polyamic acid in the mixed solution are 4-6%.

[0024] By adopting the above technical solution, and preferably having the concentrations of glycidyl polyhedral silsesquioxane and polyamic acid in the mixed solution within the above range, the overall performance of the prepared composite aramid fiber can be further improved.

[0025] Preferably, the epoxy resin composite material is prepared by the following method:

[0026] Tetraglycidyl-4,4'-diaminodiphenylmethane was mixed with acetone, and tannic acid was added. The solvent was evaporated by heating and stirring. Then m-phenylenediamine was added to obtain a mixture. The mixture was vacuumed to remove bubbles to obtain a modified epoxy resin. The modified epoxy resin, composite aramid fiber and modified carboxylated carbon nanotubes were mixed and stirred to obtain an epoxy resin composite material.

[0027] By adopting the above technical solution, tannic acid is used to toughen and modify epoxy resin. Tannic acid has a special highly branched spherical structure and a large number of active phenolic hydroxyl groups, which can act as physical-chemical crosslinking points, promote the curing and crosslinking reaction of epoxy resin, improve the interfacial interaction of the matrix, and improve the crosslinking density. This further enhances the overall tensile strength and elongation at break of the epoxy resin composite material, thereby improving the comprehensive performance of the prepared composite pipe.

[0028] Preferably, the mass ratio of the modified carboxylated carbon nanotubes, aramid fibers and modified epoxy resin is (0.05-0.09):1:5.6.

[0029] By adopting the above technical solution, and preferably within the above-mentioned range the mass ratio of modified carboxylated carbon nanotubes, aramid fibers and modified epoxy resin, the overall performance of the prepared epoxy composite material can be further improved.

[0030] Secondly, this application provides a method for preparing high-density power composite pipes, employing the following technical solution:

[0031] The preparation method of high-strength power composite pipe includes the following steps:

[0032] A polypropylene-polyethylene blend, silica, styrene-butadiene rubber, plasticizer, and dispersant are added to a Banbury mixer and mixed. The mixed material is then combined with an epoxy resin composite material and fed into a twin-screw extruder to form a polyolefin composite layer. This layer is then co-extruded with the polypropylene layer produced in the twin-screw extruder to obtain an electrical composite pipe. In summary, this application includes at least one of the following beneficial technical effects:

[0033] The composite pipe prepared in this application contains a polypropylene-polyethylene composite prepared by grafting maleic anhydride onto polypropylene, high-density polyethylene, boron nitride, and polypropylene. After mixing polypropylene and high-density polyethylene, the overall impact resistance of the system is improved. Boron nitride has good thermal conductivity, oxidation resistance, corrosion resistance, and chemical stability. Its addition to the system can effectively improve the thermal conductivity at the interface of the substrate, thereby improving the thermal stability of the composite pipe. Grafting maleic anhydride onto polypropylene enhances the compatibility between polypropylene and boron nitride, allowing more particles to enter the polypropylene and promoting the nucleation effect of boron nitride in polypropylene, thus further improving the stability of the system. The pipe also contains epoxy resin composite material, silica, and styrene-butadiene rubber, which can effectively improve the mechanical properties of the composite pipe.

[0034] The epoxy resin composite material is prepared by modifying carboxylated carbon nanotubes, composite aramid fibers, epoxy resin and tannic acid. The modified carboxylated carbon nanotubes and composite aramid fibers can fill the gaps between epoxy resin materials to improve the bonding force between interfaces, thereby improving the mechanical properties of epoxy resin. The introduction of tannic acid into the system modifies the epoxy resin, further improving the crosslinking performance and adhesion of epoxy resin, so as to improve the overall performance of epoxy resin composite material.

[0035] Using supercritical CO2 to modify aramid fibers with small-molecule glycidyl polyhedral silsesquioxane and macromolecular polyamic acid can effectively improve the bonding performance between aramid fibers and other components. At the same time, it can also further enhance the interfacial adhesion of styrene-butadiene rubber, thereby improving the overall mechanical properties of the composite material. Detailed Implementation

[0036] The present application will be further described in detail below with reference to the embodiments:

[0037] Raw material description: All raw materials used in the examples are commercially available; Example 1

[0038] Preparation of polypropylene-polyethylene blends:

[0039] 127.62g of polypropylene, 31.9g of high-density polyethylene, 29.91g of boron nitride, and 10.57g of polypropylene grafted with maleic anhydride were dried in an oven at 50℃ for 6 hours. The dried raw materials were then mixed in a mixer for 3 minutes. The mixture was then melted, blended, and extruded through a screw extruder to obtain a polypropylene-polyethylene blend. The four temperature zones of the screw extruder were 160℃, 175℃, 185℃, and 170℃, and the screw speed was 15 r / min.

[0040] Preparation of modified carboxyl carbon nanotubes:

[0041] 0.37 g of polyethyleneimine was added to 100 mL of deionized water to obtain a polyethyleneimine aqueous solution. 4.63 g of carboxylated multi-walled carbon nanotubes were added to the polyethyleneimine aqueous solution. The mixture was refluxed at 120 °C for 12 h, vacuum filtered, and then washed repeatedly with deionized water 5 times. The mixture was then freeze-dried in a hollow fiber freezer at -20 °C for 12 h to obtain modified carboxylated carbon nanotubes.

[0042] Preparation of composite aramid fibers:

[0043] Glycidyl polyhedral silsesquioxane, polyamic acid, and tetrahydrofuran were mixed to obtain a 200 mL mixed solution. The mass concentration of glycidyl polyhedral silsesquioxane in the mixed solution was 4%, and the mass concentration of polyamic acid was 6%. 20 g of aramid fiber with a length of 2 mm was added to the above mixed solution and immersed for 10 min. Then, the aramid fiber was taken out and placed in a supercritical CO2 reactor and treated at 50 °C and 10 MPa for 30 min. Then, the aramid fiber was taken out and heated to 250 °C for 2 h to obtain composite aramid fiber.

[0044] Preparation of epoxy resin composite materials:

[0045] 80g of tetraglycidyl-4,4'-diaminodiphenylmethane was mixed with 500g of acetone, and then 2.4g of tannic acid was added. The mixture was heated to 80℃ and stirred to evaporate the solvent. Then, 110g of m-phenylenediamine was added, and the mixture was heated at 80℃ until all components were dissolved. The mixture was then vacuum-dried in a vacuum drying oven to remove air bubbles, resulting in modified epoxy resin. 66.96g of modified epoxy resin, 11.96g of composite aramid fiber, and 1.08g of modified carboxylated carbon nanotubes were mixed and stirred at 200r / min for 20min to obtain epoxy resin composite material.

[0046] Preparation of power composite pipes:

[0047] 107g of polypropylene-polyethylene blend, 12g of silica, 20g of styrene-butadiene rubber, 7g of plasticizer, and 4g of dispersant were mixed to obtain a mixture. The mixture was then added to a mixer and mixed at 170℃ for 20 minutes. Subsequently, the mixed material and 42g of epoxy resin composite material were added to a twin-screw extruder. The temperature of each zone of the twin-screw extruder was 200℃, and the screw speed was 170r / min. The mixture was co-extruded with the polypropylene material in the twin-screw extruder to obtain a power composite pipe with a polypropylene layer and a polyolefin composite layer. Example 2

[0048] Preparation of polypropylene-polyethylene blends:

[0049] 127.11g of polypropylene, 31.78g of high-density polyethylene, 29.79g of boron nitride, and 11.32g of polypropylene grafted with maleic anhydride were dried in an oven at 50℃ for 6 hours. The dried raw materials were then mixed in a mixer for 3 minutes. The mixture was then melted, blended, and extruded through a screw extruder to obtain a polypropylene-polyethylene blend. The four temperature zones of the screw extruder were 160℃, 175℃, 185℃, and 170℃, and the screw speed was 15 r / min.

[0050] Preparation of modified carboxyl carbon nanotubes:

[0051] 0.54 g of polyethyleneimine was added to 100 mL of deionized water to obtain a polyethyleneimine aqueous solution. 4.46 g of carboxylated multi-walled carbon nanotubes were added to the polyethyleneimine aqueous solution. The mixture was refluxed at 120 °C for 12 h, vacuum filtered, and then washed repeatedly with deionized water 5 times. The mixture was then freeze-dried in a hollow fiber freezer at -20 °C for 12 h to obtain modified carboxylated carbon nanotubes.

[0052] Preparation of composite aramid fibers:

[0053] Glycidyl polyhedral silsesquioxane, polyamic acid, and tetrahydrofuran were mixed to obtain a 200 mL mixed solution. The mass concentration of glycidyl polyhedral silsesquioxane in the mixed solution was 6%, and the mass concentration of polyamic acid was 4%. 20 g of aramid fiber with a length of 2 mm was added to the above mixed solution and immersed for 10 min. Then, the aramid fiber was removed and placed in a supercritical CO2 reactor and treated at 50 °C and 10 MPa for 30 min. The aramid fiber was then removed and heated to 250 °C for 2 h to obtain composite aramid fiber.

[0054] Preparation of epoxy resin composite materials:

[0055] 80g of tetraglycidyl-4,4'-diaminodiphenylmethane was mixed with 500g of acetone, and then 2.4g of tannic acid was added. The mixture was heated to 80℃ and stirred to evaporate the solvent. Then, 110g of m-phenylenediamine was added, and the mixture was heated at 80℃ until all components were dissolved. The mixture was then vacuum-dried in a vacuum drying oven to remove air bubbles, resulting in modified epoxy resin. 66.77g of modified epoxy resin, 11.92g of composite aramid fiber, and 1.31g of modified carboxylated carbon nanotubes were mixed and stirred at 200r / min for 20min to obtain epoxy resin composite material.

[0056] Preparation of power composite pipes:

[0057] 140g of polypropylene-polyethylene blend, 18g of silica, 26g of styrene-butadiene rubber, 9g of plasticizer, and 6g of dispersant were mixed to obtain a mixture. The mixture was then added to an internal mixer and mixed at 170℃ for 20 minutes. Subsequently, the mixed material and 52g of epoxy resin composite material were added to a twin-screw extruder. The temperature of each zone of the twin-screw extruder was 200℃, and the screw speed was 170r / min. The mixture was co-extruded with the polypropylene material in the twin-screw extruder to obtain a power composite pipe with a polypropylene layer and a polyolefin composite layer. Example 3

[0058] Preparation of polypropylene-polyethylene blends:

[0059] 127.36g of polypropylene, 31.84g of high-density polyethylene, 29.85g of boron nitride, and 10.95g of polypropylene grafted with maleic anhydride were dried in an oven at 50℃ for 6 hours. The dried raw materials were then mixed in a mixer for 3 minutes. The mixture was then melted, blended, and extruded through a screw extruder to obtain a polypropylene-polyethylene blend. The four temperature zones of the screw extruder were 160℃, 175℃, 185℃, and 170℃, and the screw speed was 15 r / min.

[0060] Preparation of modified carboxyl carbon nanotubes:

[0061] 0.45 g of polyethyleneimine was added to 100 mL of deionized water to obtain a polyethyleneimine aqueous solution. 4.55 g of carboxylated multi-walled carbon nanotubes were added to the polyethyleneimine aqueous solution. The mixture was refluxed at 120 °C for 12 h, vacuum filtered, and then washed repeatedly with deionized water 5 times. The mixture was then freeze-dried in a hollow fiber freezer at -20 °C for 12 h to obtain modified carboxylated carbon nanotubes.

[0062] Preparation of composite aramid fibers:

[0063] Glycidyl polyhedral silsesquioxane, polyamic acid, and tetrahydrofuran were mixed to obtain a 200 mL mixed solution. The mass concentration of glycidyl polyhedral silsesquioxane and polyamic acid in the mixed solution was 5%. 20 g of aramid fiber with a length of 2 mm was added to the above mixed solution and immersed for 10 min. Then, the aramid fiber was taken out and placed in a supercritical CO2 reactor and treated at 50 °C and 10 MPa for 30 min. Then, the aramid fiber was taken out and heated to 250 °C for 2 h to obtain composite aramid fiber.

[0064] Preparation of epoxy resin composite materials:

[0065] 80g of tetraglycidyl-4,4'-diaminodiphenylmethane was mixed with 500g of acetone, and then 2.4g of tannic acid was added. The mixture was heated to 80℃ and stirred to evaporate the solvent. Then, 110g of m-phenylenediamine was added, and the mixture was heated at 80℃ until all components were dissolved. The mixture was then vacuum-dried in a vacuum drying oven to remove air bubbles, resulting in modified epoxy resin. 66.87g of modified epoxy resin, 11.94g of composite aramid fiber, and 1.19g of modified carboxylated carbon nanotubes were mixed and stirred at 200r / min for 20min to obtain epoxy resin composite material.

[0066] Preparation of power composite pipes:

[0067] 123g of polypropylene-polyethylene blend, 15g of silica, 23g of styrene-butadiene rubber, 8g of plasticizer, and 5g of dispersant were mixed to obtain a mixture. The mixture was then added to a mixer and mixed at 170°C for 20 minutes. Subsequently, the mixed material and 15g of epoxy resin composite material were added to a twin-screw extruder. The temperature of each zone of the twin-screw extruder was 200°C, and the screw speed was 170r / min. The mixture was then co-extruded with the polypropylene material in the twin-screw extruder to obtain a power composite pipe with a polypropylene layer and a polyolefin composite layer. Example 4

[0068] Example 4 is based on Example 3. The difference between Example 4 and Example 3 is that when preparing composite aramid fibers, the mass concentration of glycidyl polyhedral silsesquioxane in the mixed solution is 3% and the mass concentration of polyamic acid is 8%. Example 5

[0069] Example 5 is based on Example 3. The difference between Example 5 and Example 3 is that, in the preparation of composite aramid fibers, the mass concentration of glycidyl polyhedral silsesquioxane in the mixed solution is 8%, and the mass concentration of polyamic acid is 3%. Example 6

[0070] Example 6 is based on Example 3. The difference between Example 6 and Example 5 is that only glycidyl polyhedral silsesquioxane is used to modify aramid fibers. Example 7

[0071] Example 7 is based on Example 3. The difference between Example 7 and Example 3 is that only polyamic acid is used to modify aramid fibers. Example 8

[0072] Example 8 is based on Example 3. The difference between Example 8 and Example 3 is that the composite aramid fiber in the epoxy resin composite material was not prepared by supercritical CO2. Example 9

[0073] Example 9 uses Example 3 as the base. The difference between Example 9 and Example 3 is that when preparing the modified carboxylated carbon nanotubes, 0.24g of polyethyleneimine and 4.76g of carboxylated carbon nanotubes are used. Example 10

[0074] Example 10 is based on Example 3. The difference between Example 10 and Example 3 is that in the preparation of modified carboxylated carbon nanotubes, 0.65g of polyethyleneimine and 4.35g of carboxylated carbon nanotubes were used. Example 11

[0075] Example 11 is based on Example 3. The difference between Example 11 and Example 3 is that the modified carboxyl carbon nanotubes in the epoxy resin composite material are replaced with ordinary carbon nanotubes. Example 12

[0076] Example 12 is based on Example 3. The difference between Example 12 and Example 3 is that when preparing the epoxy resin composite material, the modified carboxylated carbon nanotubes used are 0.6g, the composite aramid fiber is 12.03g, and the modified epoxy resin is 67.37g. Example 13

[0077] Example 13 is based on Example 3. The difference between Example 13 and Example 3 is that, in the preparation of epoxy resin composite material, 1.78g of modified carboxylated carbon nanotubes, 11.85g of composite aramid fiber, and 66.37g of modified epoxy resin were used. Example 14

[0078] Example 14 is based on Example 3. In Example 14, no modified carboxyl carbon nanotubes were added to the epoxy resin composite material. Instead, the modified carboxyl carbon nanotubes were replaced with an equal mass of composite aramid fibers. Example 15

[0079] Example 15 is based on Example 3. In Example 15, no composite aramid fiber was added to the epoxy resin composite material. Instead, the composite aramid fiber was replaced with an equal mass of modified carboxylated carbon nanotubes. Example 16

[0080] Example 16 is based on Example 3. In Example 16, when preparing the polypropylene-polyethylene mixture, the amount of polypropylene used is 128g, the amount of high-density polyethylene used is 32g, the amount of boron nitride used is 30g, and the amount of polypropylene grafted with maleic anhydride used is 10g. Example 17

[0081] Example 17 is based on Example 3. In Example 17, when preparing the polypropylene-polyethylene mixture, the amount of polypropylene used is 126.73g, the amount of high-density polyethylene used is 31.68g, the amount of boron nitride used is 29.7g, and the amount of polypropylene grafted with maleic anhydride used is 11.89g.

[0082] Comparative Example 1

[0083] In Comparative Example 1, no polypropylene grafted maleic anhydride was added during the preparation of the polypropylene-polyethylene mixture; instead, polypropylene was used as an equal substitute.

[0084] Comparative Example 2

[0085] In Comparative Example 2, boron nitride was not added during the preparation of the polypropylene-polyethylene blend; instead, polypropylene was used as an equal substitute.

[0086] Comparative Example 3

[0087] In Comparative Example 3, the polypropylene-polyethylene blend was prepared by mixing polypropylene with high-density polyethylene, with polypropylene replacing maleic anhydride and boron nitride in equal amounts.

[0088] Performance testing

[0089] The following performance tests were performed on the sample tubes of Examples 1-17 and Comparative Examples 1-3:

[0090] (1) Tensile properties

[0091] Using GB / T 1040-2006 as the testing standard, the tensile properties and elongation at break of the samples were tested using a KJ-1065 high-precision peel force and release force testing machine. Each sample was tested three times, and the average value was taken. The test results were recorded in Table 1.

[0092] (2) Bending performance test

[0093] Using GB / T 9341-2008 as the testing standard, the bending performance of the samples was tested. Each sample was tested 3 times, and the average value was taken. The test results were recorded in Table 1.

[0094] Table 1 Performance test results of Examples 1-17 and Comparative Examples 1-3

[0095]

[0096] As shown in Table 1, the tensile strength of Examples 1-3 is 123 MPa or higher, and the elongation at break is 3% or higher, indicating that the composite pipe prepared in this application has good tensile properties; the bending strength of Examples 1-3 is 130 MPa or higher, indicating that the composite pipe prepared in this application has good bending properties.

[0097] In Examples 4 and 5, during the preparation of composite aramid fibers, the concentrations of glycidyl polyhedral silsesquioxane and polyamic acid in the mixed solution were not within the ranges specified in this application. When the concentration of glycidyl polyhedral silsesquioxane was too low, it was difficult to promote the modification of aramid fibers, making it difficult to further improve the bonding performance between aramid fibers and epoxy resin. At the same time, it was difficult to form a stable crosslinking network with styrene-butadiene rubber, affecting the overall performance of the system. When the concentration of glycidyl polyhedral silsesquioxane was too high, it self-polymerized on the surface of aramid fibers under the assisted permeation of supercritical CO2, improving the rigidity of the fibers. However, the crosslinking density decreased, which also affected the performance of the system. When the concentration of polyamic acid was too low, it was difficult to further promote the crosslinking performance of aramid fibers, and the compatibility of aramid fibers in the system was difficult to further improve. When the concentration of polyamic acid was too high, it had a certain negative impact on the stability of the system. Therefore, the performance of Examples 4 and 5 was reduced.

[0098] In both Examples 6 and 7, only aramid fibers were modified individually. It is difficult for aramid fibers modified individually to synergistically promote the compatibility and cross-linking properties of aramid fibers. Therefore, the performance of Examples 6 and 7 was reduced.

[0099] In Example 8, without the assistance of supercritical CO2, the interfacial bonding performance was difficult to improve further, which made it difficult to improve the crosslinking performance of the aramid fiber. Therefore, the performance in Example 8 was reduced.

[0100] In Examples 9 and 10, the mass ratio between polyethyleneimine and carboxylated carbon nanotubes during the preparation of modified carboxylated carbon nanotubes was not within the range specified in this application. When the content of polyethyleneimine was too low, it was difficult to further disrupt the aggregation effect on the surface of the carboxylated carbon nanotubes, and it was also difficult to form hydrogen bonds with other amino groups, making it difficult to form stronger interfacial interactions, thus affecting the performance of the system. When the content of polyethyleneimine was too high, it was difficult for the carboxylated carbon nanotubes to be further modified, and it also affected the overall stability of the system. Therefore, the performance of Examples 9 and 10 both decreased.

[0101] In Example 11, the epoxy resin composite material replaced the modified carboxylated carbon nanotubes with ordinary carboxylated carbon nanotubes. The dispersibility of the unmodified carboxylated carbon nanotubes was difficult to improve further. At the same time, the compatibility of the carboxylated carbon nanotubes in the system was also difficult to improve, which affected the overall stability of the system. Therefore, the performance of Example 11 decreased.

[0102] In Examples 12 and 13, the mass ratios of modified carboxylated carbon nanotubes, composite aramid fibers, and modified epoxy resin in the preparation of epoxy resin composites were not within the range specified in this application. When the amount of modified carboxylated carbon nanotubes used was too small, it was difficult to form a stable structure between sufficient nanoparticles and the epoxy resin matrix. The effect of covalently connecting the three-dimensional network structure after the system was cured was weakened, making it difficult to improve the buffering effect. Therefore, the mechanical properties of the system were difficult to further improve. When the content of modified carboxylated carbon nanotubes was too large, due to the high viscosity of the epoxy resin system, too many modified carboxylated carbon nanotubes agglomerated. Under the action of external force, the performance of the composite material decreased due to stress concentration. Therefore, the performance of Examples 12 and 13 was reduced.

[0103] In Example 14, no modified carboxyl carbon nanotubes were added to the epoxy resin composite material. Without the addition of modified carboxyl nanotubes, the interfacial area of ​​the epoxy resin matrix could not be further increased, and the performance of the system decreased. Therefore, the performance of Example 14 decreased.

[0104] In Example 15, no composite aramid fiber was added to the epoxy resin composite material. Without the addition of composite aramid fiber, it is difficult to further bind the various components in the system and form an interlocking effect. The interfacial bonding force between the systems is difficult to further improve. Therefore, the performance of Example 15 is reduced.

[0105] In Examples 16 and 17, the mass ratios of polypropylene, high-density polyethylene, boron nitride, and polypropylene grafted maleic anhydride during the preparation of the polypropylene-polyethylene composite material were not within the range specified in this application. When the content of polypropylene grafted maleic anhydride was too low, it was difficult to further improve the overall thermal conductivity of the system, thus making it difficult to improve the interfacial compatibility of the composite material and further improve the stability of the system, thereby affecting the performance of the system. When the content of polypropylene grafted maleic anhydride was too high, it affected the crystallinity of polypropylene and also affected the overall stability of the system. Therefore, the performance of Examples 16 and 17 was reduced.

[0106] In Comparative Example 1, the absence of polypropylene grafted with maleic anhydride made it difficult to improve the compatibility between boron nitride and substrates such as polypropylene and high-density polyethylene, thus affecting the overall performance of the system.

[0107] In Comparative Example 2, no boron nitride was added, making it difficult to further fill the gaps between the materials, which made it difficult to further improve the bonding performance between the substrates and affected the performance of the system.

[0108] In Comparative Example 3, only polypropylene and high-density polyethylene were mixed to prepare a polypropylene-polyethylene composite material. It was difficult to further improve the interfacial compatibility and thermal stability, which affected the overall performance of the system. Therefore, the performance of Comparative Example 3 decreased.

[0109] This specific embodiment is merely an explanation of this application and is not intended to limit it. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. A high-density power composite pipe, characterized in that: It includes a polypropylene layer and a polyolefin composite layer, wherein the polyolefin composite layer comprises the following components in parts by weight: 107-140 parts of polypropylene-polyethylene mixture, 42-52 parts of epoxy resin composite material, 12-18 parts of silica, 20-26 parts of styrene-butadiene rubber, 7-9 parts of plasticizer, and 4-6 parts of dispersant. The polypropylene-polyethylene blend material includes polypropylene, high-density polyethylene, boron nitride, and polypropylene grafted with maleic anhydride. The epoxy resin composite material is prepared by the following method: Tetraglycidyl-4,4'-diaminodiphenylmethane is mixed with acetone, then tannic acid is added, the solvent is evaporated by heating and stirring, and then m-phenylenediamine is added to obtain a mixture. The mixture is then vacuumed to remove bubbles to obtain a modified epoxy resin. The modified epoxy resin, composite aramid fiber and modified carboxyl carbon nanotubes are mixed and stirred to obtain the epoxy resin composite material. The modified carboxylated carbon nanotubes were prepared by the following method: Polyethyleneimine was mixed with water to obtain a polyethyleneimine aqueous solution, carboxylated multi-walled carbon nanotubes were added to the polyethyleneimine aqueous solution, refluxed, vacuum filtered, washed, and freeze-dried to obtain the modified carboxylated carbon nanotubes.

2. The high-density power composite pipe according to claim 1, characterized in that: The mass ratio of polypropylene, high-density polyethylene, boron nitride and polypropylene grafted with maleic anhydride is 64:16:15:(5.3-5.7).

3. The high-density power composite pipe according to claim 1, characterized in that: The mass ratio of the carboxylated multi-walled carbon nanotubes to polyethyleneimine is 1:(0.08-0.12).

4. The high-density power composite pipe according to claim 1, characterized in that: The composite aramid fiber is prepared by the following method: Glycidyl polyhedral silsesquioxane, polyamic acid and tetrahydrofuran were mixed to obtain a mixed solution; aramid fibers were added to the mixed solution, impregnated and then placed in a supercritical CO2 reactor for treatment. After treatment, the aramid fibers were removed and then heated to obtain composite aramid fibers.

5. The high-density power composite pipe according to claim 4, characterized in that: The mass concentration of glycidyl polyhedral silsesquioxane and polyamic acid in the mixed solution is 4-6%.

6. The high-density power composite pipe according to claim 1, characterized in that: The mass ratio of the modified carboxylated carbon nanotubes, composite aramid fibers, and modified epoxy resin is (0.05-0.09):1:5.

6.

7. A method for preparing the high-density power composite pipe according to any one of claims 1-6, characterized in that: Includes the following steps: Polypropylene-polyethylene mixture, silica, styrene-butadiene rubber, plasticizer, and dispersant are added to a mixer and mixed. The mixed material and epoxy resin composite material are then added to a twin-screw extruder to form a polyolefin composite layer. This layer is then co-extruded with the polypropylene layer produced by the twin-screw extruder to obtain the power composite pipe.

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