Reinforced and toughened CM square electric corrugated pipe and preparation method thereof

Abstract

The invention discloses a reinforced and toughened CM square electric power corrugated pipe and a preparation method thereof, belongs to the technical field of electric power pipe preparation, and aims to solve the technical problem that the impact resistance and flame retardance of a square electric power corrugated pipe in the prior art need to be further improved. According to the invention, PI-Si hybrid resin, a modified aramid fiber reinforcement and a P-N-Si modified flaky core-shell mica structure are prepared in sequence, a multi-scale synergistic interface system consisting of a matrix phase, a reinforcement phase and an inorganic lamellar layer is constructed, and the system realizes synergistic regulation and control of chain segment movement, interface bonding and lamellar barrier behaviors in a forming process; according to the square electric power corrugated pipe, stress transmission is more continuous, energy dissipation paths are more graded, interface polarization and local heat accumulation are remarkably reduced, and therefore the mechanical property, abrasion resistance, thermal size stability, flame retardance, insulating property and the like of the obtained square electric power corrugated pipe are structurally improved.

Description

Technical Field

[0001] This invention relates to the field of power pipe manufacturing technology, specifically to a reinforced and toughened CM square power corrugated pipe and its manufacturing method. Background Technology

[0002] Square power cable corrugated pipes are mainly used for the protection and laying of power cables. The material system is usually composed of thermoplastic resin, reinforcing fiber or inorganic filler, and flame retardant and modified components. In order to meet the requirements of bending adaptability, mechanical load and wear resistance in power engineering, polyolefin, polyamide or polyester resin is often used as the matrix, and glass fiber, aramid fiber and sheet inorganic materials are added to improve structural strength and stability. In the long-term operating environment, cable protection materials also need to have good thermal dimensional stability and insulation performance. Therefore, flame retardants, inorganic sheet materials or polarity modifiers are generally added to improve heat resistance, flame retardancy and dielectric properties.

[0003] However, current square power corrugated pipe technology still has significant shortcomings in terms of the synergistic effect of multiple properties such as mechanics, thermal response and electrical insulation. Traditional systems mostly rely on a simple combination of resin, reinforcement and flame-retardant filler. Its interface structure lacks hierarchical control, which makes it difficult to effectively transfer and disperse stress under external force, and cracks are easy to propagate rapidly. It is difficult to improve the impact resistance and wear resistance of the material at the same time. In thermal environments, conventional flame retardant and heat-resistant measures mainly rely on additives or inorganic fillers, but the barrier structure formed by them is discontinuous. At high temperatures, chain segment relaxation, volume shrinkage and thermal deformation still easily occur, resulting in insufficient dimensional stability.

[0004] Meanwhile, under electric field conditions, existing insulating fillers mostly provide macroscopic dielectric barriers, while the interface region between the resin and the reinforcement is still prone to dipole response and local electric field concentration, resulting in short carrier migration paths and obvious interface polarization, thus affecting the overall insulation uniformity and long-term electrical stability of the system.

[0005] The aforementioned technical deficiencies make it difficult for traditional materials to achieve a comprehensive performance that combines mechanical, flame-retardant, and insulating properties in complex service environments. Therefore, a solution is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a reinforced and toughened CM square power corrugated pipe and its preparation method, which solves the technical problem that the impact resistance and flame retardant properties of square power corrugated pipes in the prior art need to be further improved.

[0007] The objective of this invention can be achieved through the following technical solution: a reinforced and toughened CM square power corrugated pipe, comprising the following raw material components by weight: 100 parts polypropylene resin, 25-35 parts PI-Si hybrid resin, 10-15 parts modified aramid reinforcement, 20-25 parts PN-Si modified lamellar core-shell mica, 0.1-0.2 parts antioxidant 1010, 0.1-0.2 parts antioxidant 168, and 0.2-0.4 parts calcium stearate; The PI-Si hybrid resin was prepared by the following method: A1. Add the polyamic acid prepolymer dispersion to a reactor and stir. Then add glacial acetic acid and deionized water in sequence. After mixing evenly, add 3-(2,3-epoxypropoxy)propyltrimethoxysilane. Then heat the reactor to 40-50℃ and stir for 2-3 hours to obtain siloxane-modified polyamic acid dispersion. A2. Add the siloxane-modified polyamic acid dispersion and the modified liquid to the reactor and stir. After the mixture is uniform, heat the reactor to 120-140℃ and keep it at that temperature for 1-2 hours. Then heat it to 170-190℃ and keep it at that temperature for 2-4 hours. The post-treatment yields the PI-Si hybrid resin.

[0008] The reaction principle for preparing PI-Si hybrid resin is as follows: The trimethoxysilane group of 3-(2,3-epoxypropoxy)propyltrimethoxysilane first hydrolyzes in the presence of water to generate silanol, and then forms Si-O-Si bonds through the condensation reaction between silanols, thereby constructing a siloxane network structure. At the same time, the epoxy group on the 3-(2,3-epoxypropoxy)propyltrimethoxysilane molecule undergoes a nucleophilic ring-opening reaction with the amino group on the polyamic acid chain, introducing a hydroxyl-containing β-amino alcohol structure and achieving covalent bonding with the polyamic acid chain. Subsequently, under the action of the acetic anhydride / pyridine system, the amic acid structure inside the polyamic acid undergoes ring closure and is transformed into an imide ring, thereby preparing the PI-Si hybrid resin.

[0009] Furthermore, in step A1, the ratio of the polyamic acid prepolymer dispersion, glacial acetic acid, deionized water and 3-(2,3-epoxypropoxy)propyltrimethoxysilane is 80mL:1.5mL:2-3mL:3-4mL. Further, in step A2, the ratio of the siloxane-modified polyamic acid dispersion to the modifying liquid is 80 mL: 40-45 mL. The modifying liquid is obtained by mixing acetic anhydride and pyridine in a ratio of 40-50 mL: 2-3 mL. The post-treatment includes: after the reaction is completed, the reaction vessel is cooled to 80-90°C, and the reaction liquid is slowly poured into a mixture of five times its volume of 50 wt% ethanol aqueous solution. After the precipitation is complete, the filter cake is collected by vacuum filtration, washed until neutral, and then transferred to an oven at 80°C for vacuum drying to constant weight to obtain PI-Si hybrid resin.

[0010] Furthermore, the preparation method of the polyamic acid prepolymer dispersion is as follows: 4,4'-oxodiphenylamine and N-methyl-2-pyrrolidone are added to a reaction vessel and stirred. After the mixture is uniform, the reaction vessel is cooled to 0-5°C, and the calculated amount of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is added in ten batches with an interval of 10-15 minutes between additions. After the addition is completed, the reaction vessel is heated to 20-30°C and kept at this temperature for 3-4 hours with stirring. After stirring is completed, the obtained material is collected to obtain the polyamic acid prepolymer dispersion.

[0011] The reaction principle for preparing polyamic acid prepolymer dispersions is as follows: The dianhydride structure of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride undergoes stepwise ring-opening with the amino group of 4,4'-oxodiphenylamine in a polar solvent to generate polyamic acid segments containing amide bonds and carboxylic acid groups. These segments then grow in a linear stepwise condensation manner under low temperature conditions, thereby forming a prepolymer dispersion system with the amic acid structure as the repeating unit, and finally preparing the polyamic acid prepolymer dispersion.

[0012] Furthermore, the ratio of 4,4'-oxodiphenylamine to N-methyl-2-pyrrolidone is 10-12 g: 100 mL, wherein the amount of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride added is 0.40-0.45 times the molar amount of amino group in the reaction system.

[0013] Furthermore, the modified aramid reinforcement is prepared by the following method: B1. After cooling the reactor to 0-5℃, add p-phenylenediamine, lithium chloride, calcium chloride and N-methyl-2-pyrrolidone to the reactor and stir. After mixing evenly, continue to add the calculated amount of 4,4'-biphenylacetyl chloride and anhydrous sodium carbonate in ten batches with an interval of 10-12 minutes between additions. After the addition is completed, heat the reactor to 20-30℃ and keep it at the temperature and stir for 3-4 hours to obtain an aramid prepolymer resin dispersion. B2. Add 4-hydroxy-4'-cyanobiphenyl, N,N'-dicyclohexylcarbodiimide, 4-dimethylaminopyridine and N-methyl-2-pyrrolidone to a reaction vessel and stir. After mixing evenly, add aramid prepolymer resin dispersion and stir at room temperature for 2-3 hours. Then heat the reaction vessel to 60-80℃ and stir for 2-4 hours. Post-treatment yields modified aramid reinforcement.

[0014] The reaction principle for preparing modified aramid reinforcement is as follows: First, p-phenylenediamine and 4,4'-biphenylacetyl chloride undergo acyl chloride-amine condensation under alkaline conditions to form an aromatic amide prepolymer segment with p-phenylene and biphenyl structures as repeating units. Simultaneously, the byproduct hydrogen chloride is neutralized by anhydrous sodium carbonate. Lithium chloride and calcium chloride in the system act as solvators and complexing agents to promote the formation of a stable dispersed phase of the prepolymer in N-methyl-2-pyrrolidone. Subsequently, under the promotion of carbodiimide condensing agent and 4-dimethylaminopyridine, the hydroxyl groups of 4-hydroxy-4'-cyanobiphenyl are esterified or acylated to the carboxyl groups at the end or side groups of the prepolymer segment. The carbodiimide promotes this condensation process via an O-acylurea intermediate. Thus, the aramid prepolymer segment and the hydroxy-cyanobiphenyl monomer are further connected by covalent bonds to form a cocondensation structure containing amide and ester bonds, thereby preparing a modified aramid reinforcement.

[0015] Furthermore, in step B1, the ratio of p-phenylenediamine, lithium chloride and calcium chloride, N-methyl-2-pyrrolidone and anhydrous sodium carbonate is 8-10 mL: 3-4 g: 2-3 g: 100 mL: 2 g, wherein the amount of 4,4'-biphenylacetyl chloride added is 0.55-0.60 times the molar amount of amino in the reaction system; Further, in step B2, the ratio of the amount of 4-hydroxy-4'-cyanobiphenyl, N,N'-dicyclohexylcarbodiimide, 4-dimethylaminopyridine, N-methyl-2-pyrrolidone and aramid prepolymer resin dispersion is 5-6g:6-7g:0.5-0.6g:30-40mL:100mL. The post-treatment includes: after the reaction is completed, the reaction vessel is cooled to room temperature, and the reaction solution is slowly poured into a mixture of five times its volume of 50wt% ethanol aqueous solution. After the precipitation is complete, the filter cake is collected by vacuum filtration, washed until neutral, and then transferred to an oven at 80°C for vacuum drying to constant weight to obtain the modified aramid reinforcement.

[0016] Furthermore, the preparation method of the PN-Si modified sheet-like core-shell mica is as follows: Phlogopite and anhydrous ethanol are added to a reaction vessel and stirred. After being evenly dispersed, hexachlorocyclotriphosphazene and 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide are added sequentially. Then, 3-aminopropyltriethoxysilane and deionized water are added. Triethylamine is then added to adjust the pH of the reaction system to 8-9. The reaction vessel is heated to 60-80℃ and stirred for 4-6 hours. After post-treatment, PN-Si modified sheet-like core-shell mica is obtained.

[0017] The reaction principle for preparing PN-Si modified sheet-like core-shell mica is as follows: In an alcoholic medium, hexachlorocyclotriphosphazene can undergo partial chlorination, forming phosphorus-oxygen or phosphorus-nitrogen bonds with the hydroxyl groups and active sites of phosphorus-phenanthrene oxide on the mica surface. Simultaneously, 3-aminopropyltriethoxysilane hydrolyzes to silanol in the presence of water, and undergoes condensation on the mica surface to form silicon-oxygen bonds. Triethylamine provides an alkaline environment to promote the above substitution and condensation reactions, so that the phosphazene structure, the phosphorus-containing aromatic heterocyclic structure and the silicon-oxygen network are covalently fixed on the mica sheet surface, thereby constructing a PN-Si ternary interface layer, and thus preparing PN-Si modified sheet-like core-shell mica.

[0018] Furthermore, in the preparation of PN-Si modified sheet-like core-shell mica, the ratio of phlogopite, anhydrous ethanol, hexachlorocyclotriphosphazene, 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide, 3-aminopropyltriethoxysilane, and deionized water is 15-18 g:100 mL:4-5 g:6 g:8-10 mL:4-6 mL. The post-treatment includes: after the reaction is completed, the filter cake is collected by vacuum filtration, washed three times with deionized water and anhydrous ethanol, transferred to an oven at 120°C and vacuum dried to constant weight, and then milled through a 200-mesh sieve to obtain PN-Si modified sheet-like core-shell mica.

[0019] The present invention also discloses a method for preparing a reinforced and toughened CM square power corrugated pipe, comprising the following steps: S1. Polypropylene resin, PI-Si hybrid resin, modified aramid reinforcement, PN-Si modified flake core-shell mica, antioxidant 1010, antioxidant 168 and calcium stearate are added to a stirred tank and mixed evenly to obtain a mixture. S2. The mixture is added to a twin-screw extruder, melt-extruded and shaped, and then cooled and drawn to obtain a square electric corrugated pipe.

[0020] Furthermore, in step S2, the preparation method of the square power corrugated pipe is as follows: the mixture is added to a twin-screw extruder, the temperature of each temperature zone of the twin-screw extruder is set to 180-220℃, the die head temperature is set to 220-230℃, the screw speed is 200-300r / min, the molten material is formed by the CM square corrugated mold and the forming module, the formed square corrugated pipe is cooled to room temperature in a 20℃ water bath, and then cut to a predetermined length by a traction device to obtain the square power corrugated pipe.

[0021] The present invention has the following beneficial effects: In this system, the prepared PI-Si hybrid resin constitutes the main channel for the transmission and attenuation of impact loads. Its internal silicon-oxygen cross-linked structure exhibits controllable elastic deformation under external force, which can effectively disperse stress concentration and thus delay the formation of initial cracks. When the cracks further propagate, the aramid reinforcement, with its high-modulus chain segments, alters the crack propagation path at the microscopic level, causing it to deflect or bifurcate, significantly improving the material's impact resistance. At the same time, the lamellar structure of PN-Si modified sheet-like core-shell mica introduces interfacial friction and microscale slip mechanisms, forming an interfacial region that hinders material peeling under wear conditions, reducing the cutting wear rate. The mechanical contributions of the three components at different scales jointly construct a multi-level energy dissipation system, enabling a synergistic improvement in impact resistance and wear resistance, rather than the superposition effect of a single material.

[0022] The PN-Si modified sheet-like core-shell mica prepared by this invention can rapidly form a continuous solid-phase barrier layer under thermal action through the phosphazene-silica composite structure constructed on the surface, effectively reducing the heat release rate of the matrix. On this basis, the imide ring structure of the PI-Si hybrid resin endows the material with a high thermal deformation critical temperature, enabling the material to maintain chain segment stability in the high-temperature range, thereby significantly inhibiting longitudinal thermal shrinkage. The aramid reinforcement further restricts the free volume growth of the resin in the high-temperature softening stage through its oriented chain segments, so that the dimensional stability can be maintained in a higher temperature range. The three together constitute a multi-layer thermal response system of gas phase inhibition, solid phase shielding and chain segment stability, so that the flame retardant performance and high-temperature shrinkage resistance exhibit a structured synergistic improvement effect.

[0023] The square power corrugated tube prepared by this invention, under the action of an electric field, is first affected by the orientation structure of the aramid reinforcement. Its regular chain segments form an effective resistance path extension at the microscale, suppressing the migration of charge carriers over short distances. At the same time, the PI-Si hybrid resin fills the structural gaps with its low polarity distribution, further reducing the dipole response at the interface and reducing the overall dielectric loss of the system. Moreover, the sheet structure of PN-Si modified lamellar core-shell mica provides a barrier structure with high dielectric stability on a larger scale. By blocking the local electric field concentration, it weakens the interface polarization phenomenon and avoids the formation of local breakdown channels. The three materials, arranged in spatial arrangements at different scales, jointly construct a hierarchical insulation network, making the improvement of volume resistivity continuous and stable. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the square power corrugated pipe prepared according to the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In this application, antioxidant 168 was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number T822863; antioxidant 1010 was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number P750268; polypropylene resin was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number P875063; calcium stearate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number C805417; and phlogopite was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with item number P875301.

[0028] Example 1 This embodiment provides a method for preparing a PI-Si hybrid resin, including the following steps: Step I: Preparation of polyamic acid prepolymer dispersion Weigh 10.0g of 4,4'-oxodiphenylamine and 100.0mL of N-methyl-2-pyrrolidone and add them to the reaction vessel. Stir until the mixture is homogeneous. Then, cool the reaction vessel to 0℃ and add 3,3',4,4'-biphenyltetracarboxylic acid dianhydride in ten batches, with an interval of 10min between additions. After the addition is complete, heat the reaction vessel to 20℃ and keep it at this temperature for 3h. After stirring, collect the obtained material to obtain the polyamic acid prepolymer dispersion.

[0029] Step II: Preparation of siloxane-modified polyamic acid dispersion Weigh out 80.0 mL of polyamic acid prepolymer dispersion and add it to the reaction vessel. Stir and add 1.5 mL of glacial acetic acid and 2.0 mL of deionized water in sequence. After mixing evenly, add 3.0 mL of 3-(2,3-epoxypropoxy)propyltrimethoxysilane. Then heat the reaction vessel to 40 °C and keep it at that temperature for 2 h to obtain siloxane-modified polyamic acid dispersion.

[0030] Step III: Preparation of PI-Si hybrid resin Weigh out 40.0 mL of acetic anhydride and 2.0 mL of pyridine and mix them to obtain the modified solution; Weigh out 80.0 mL of siloxane-modified polyamic acid dispersion and 40.0 mL of modified liquid and add them to the reaction vessel. Stir until the mixture is homogeneous, then heat the reaction vessel to 120°C and keep it at that temperature for 1 hour. Then heat it to 170°C and keep it at that temperature for 2 hours. After the reaction is complete, let the reaction vessel cool to 80°C and slowly pour the reaction solution into a mixture of five times its volume of 50 wt% ethanol aqueous solution. After the precipitation is complete, filter the filter cake and wash it until it is neutral. Then transfer the filter cake to an oven at 80°C and vacuum dry it to constant weight to obtain PI-Si hybrid resin.

[0031] Example 2 This embodiment provides a method for preparing a PI-Si hybrid resin, including the following steps: Step I: Preparation of polyamic acid prepolymer dispersion Weigh 12.0 g of 4,4'-oxodiphenylamine and 100.0 mL of N-methyl-2-pyrrolidone and add them to the reaction vessel. Stir until the mixture is homogeneous. Then, cool the reaction vessel to 5°C and add 3,3',4,4'-biphenyltetracarboxylic acid dianhydride in ten batches, with an interval of 15 min between additions. After the additions are complete, heat the reaction vessel to 30°C and keep it at this temperature for 4 hours. After stirring, collect the resulting material to obtain the polyamic acid prepolymer dispersion.

[0032] Step II: Preparation of siloxane-modified polyamic acid dispersion Weigh out 80.0 mL of polyamic acid prepolymer dispersion and add it to the reaction vessel. Stir and add 1.5 mL of glacial acetic acid and 3.0 mL of deionized water in sequence. After mixing evenly, add 4.0 mL of 3-(2,3-epoxypropoxy)propyltrimethoxysilane. Then heat the reaction vessel to 50 °C and keep it at that temperature for 3 h to obtain siloxane-modified polyamic acid dispersion.

[0033] Step III: Preparation of PI-Si hybrid resin Weigh out 50.0 mL of acetic anhydride and 3.0 mL of pyridine and mix them to obtain the modified solution; Weigh out 80.0 mL of siloxane-modified polyamic acid dispersion and 45.0 mL of modified liquid and add them to the reaction vessel. Stir until the mixture is homogeneous, then heat the reaction vessel to 140°C and keep it at that temperature for 2 hours. Then heat it to 190°C and keep it at that temperature for 4 hours. After the reaction is complete, let the reaction vessel cool to 90°C and slowly pour the reaction solution into a mixture of five times its volume of 50 wt% ethanol aqueous solution. After the precipitation is complete, filter the filter cake and wash it until it is neutral. Then transfer the filter cake to an oven at 80°C and vacuum dry it to constant weight to obtain PI-Si hybrid resin.

[0034] Example 3 This embodiment provides a method for preparing a PI-Si hybrid resin, including the following steps: Step I: Preparation of polyamic acid prepolymer dispersion Weigh 11.0 g of 4,4'-oxodiphenylamine and 100.0 mL of N-methyl-2-pyrrolidone and add them to the reaction vessel. Stir until the mixture is homogeneous. Then, cool the reaction vessel to 3°C and add 3,3',4,4'-biphenyltetracarboxylic acid dianhydride in ten batches, with an interval of 12 min between additions. After the additions are complete, heat the reaction vessel to 25°C and keep it at this temperature for 4 hours. After stirring, collect the resulting material to obtain the polyamic acid prepolymer dispersion.

[0035] Step II: Preparation of siloxane-modified polyamic acid dispersion Weigh 80.0 mL of polyamic acid prepolymer dispersion and add it to the reaction vessel. Stir and add 1.5 mL of glacial acetic acid and 2.5 mL of deionized water in sequence. After mixing evenly, add 3.5 mL of 3-(2,3-epoxypropoxy)propyltrimethoxysilane. Then heat the reaction vessel to 45 °C and keep it at that temperature for 3 h to obtain siloxane-modified polyamic acid dispersion.

[0036] Step III: Preparation of PI-Si hybrid resin Weigh out 45.0 mL of acetic anhydride and 2.0 mL of pyridine and mix them to obtain the modified solution; Weigh out 80.0 mL of siloxane-modified polyamic acid dispersion and 42.0 mL of modified liquid and add them to the reaction vessel. Stir until the mixture is homogeneous, then heat the reaction vessel to 130°C and keep it at that temperature for 2 hours. Then heat it to 180°C and keep it at that temperature for 3 hours. After the reaction is complete, let the reaction vessel cool to 85°C and slowly pour the reaction solution into a mixture of five times the volume of 50 wt% ethanol aqueous solution. After the precipitation is complete, filter the filter cake and wash it until it is neutral. Then transfer the filter cake to an oven at 80°C and vacuum dry it to constant weight to obtain PI-Si hybrid resin.

[0037] Example 4 This embodiment provides a method for preparing a modified aramid reinforcement, including the following steps: Step (1): Preparation of aramid prepolymer resin dispersion After cooling the reactor to 0℃, add 8.0 mL of p-phenylenediamine, 3.0 g of lithium chloride, 2.0 g of calcium chloride, and 100.0 mL of N-methyl-2-pyrrolidone and stir. After mixing evenly, add 0.55 times the molar amount of amino in the reaction system of 4,4'-biphenylacetyl chloride and 2.0 g of anhydrous sodium carbonate in ten batches with an interval of 10 min between additions. After the addition is completed, heat the reactor to 20℃ and keep it at this temperature for 3 h with stirring to obtain an aramid prepolymer resin dispersion.

[0038] Step 2: Preparation of modified aramid reinforcement Weigh out 5.0 g of 4-hydroxy-4'-cyanobiphenyl, 6.0 g of N,N'-dicyclohexylcarbodiimide, 0.5 g of 4-dimethylaminopyridine, and 30.0 mL of N-methyl-2-pyrrolidone and add them to the reaction vessel. Stir until the mixture is homogeneous, then add 100.0 mL of aramid prepolymer resin dispersion and stir at room temperature for 2 h. Then heat the reaction vessel to 60 °C and keep it at that temperature for 2 h. After the reaction is complete, let the reaction vessel cool to room temperature and slowly pour the reaction solution into a mixture of five times its volume of 50 wt% ethanol aqueous solution. After the precipitation is complete, filter and collect the filter cake. Wash until neutral and then transfer the filter cake to an oven at 80 °C and vacuum dry to constant weight to obtain the modified aramid reinforcement.

[0039] Example 5 This embodiment provides a method for preparing a modified aramid reinforcement, including the following steps: Step (1): Preparation of aramid prepolymer resin dispersion After cooling the reactor to 5°C, add 10.0 mL of p-phenylenediamine, 4.0 g of lithium chloride, 3.0 g of calcium chloride, and 100.0 mL of N-methyl-2-pyrrolidone and stir. After mixing evenly, add 0.60 times the molar amount of amino in the reaction system of 4,4'-biphenylacetyl chloride and 2.0 g of anhydrous sodium carbonate in ten batches with an interval of 12 min between additions. After the addition is completed, heat the reactor to 30°C and keep it at this temperature for 4 hours with stirring to obtain an aramid prepolymer resin dispersion.

[0040] Step 2: Preparation of modified aramid reinforcement Weigh out 6.0 g of 4-hydroxy-4'-cyanobiphenyl, 7.0 g of N,N'-dicyclohexylcarbodiimide, 0.6 g of 4-dimethylaminopyridine, and 40.0 mL of N-methyl-2-pyrrolidone and add them to the reaction vessel. Stir until the mixture is homogeneous, then add 100.0 mL of aramid prepolymer resin dispersion and stir at room temperature for 3 h. Then heat the reaction vessel to 80 °C and keep it at that temperature for 4 h. After the reaction is complete, let the reaction vessel cool to room temperature and slowly pour the reaction solution into a mixture of five times the volume of 50 wt% ethanol aqueous solution. After the precipitation is complete, filter and collect the filter cake. Wash until neutral and then transfer the filter cake to an oven at 80 °C and vacuum dry to constant weight to obtain the modified aramid reinforcement.

[0041] Example 6 This embodiment provides a method for preparing a modified aramid reinforcement, including the following steps: Step (1): Preparation of aramid prepolymer resin dispersion After cooling the reactor to 3°C, add 9.0 mL of p-phenylenediamine, 4.0 g of lithium chloride, 2.5 g of calcium chloride, and 100.0 mL of N-methyl-2-pyrrolidone and stir. After mixing evenly, add 0.57 times the molar amount of amino in the reaction system of 4,4'-biphenylacetyl chloride and 2.0 g of anhydrous sodium carbonate in ten batches with an interval of 12 min between additions. After the addition is completed, heat the reactor to 25°C and keep it at this temperature for 4 h with stirring to obtain an aramid prepolymer resin dispersion.

[0042] Step 2: Preparation of modified aramid reinforcement Weigh out 5.5g of 4-hydroxy-4'-cyanobiphenyl, 7.0g of N,N'-dicyclohexylcarbodiimide, 0.6g of 4-dimethylaminopyridine, and 35.0mL of N-methyl-2-pyrrolidone and add them to the reaction vessel. Stir until the mixture is homogeneous, then add 100.0mL of aramid prepolymer resin dispersion and stir at room temperature for 3h. Then heat the reaction vessel to 70℃ and stir for 3h. After the reaction is complete, let the reaction vessel cool to room temperature, then slowly pour the reaction solution into a mixture of five times the volume of 50wt% ethanol aqueous solution. After the precipitation is complete, filter and collect the filter cake. Wash until neutral, then transfer the filter cake to an oven at 80℃ and vacuum dry to constant weight to obtain the modified aramid reinforcement.

[0043] Example 7 This embodiment provides a method for preparing a reinforced and toughened CM square power corrugated pipe, including the following steps: Step 1: Preparation of PN-Si modified sheet-like core-shell mica Weigh 15.0g of phlogopite and 100.0mL of anhydrous ethanol and add them to the reaction vessel. Stir until the mixture is evenly dispersed. Then add 4.0g of hexachlorocyclotriphosphazene and 6.0g of 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide in sequence. Then add 8.0mL of 3-aminopropyltriethoxysilane and 4.0mL of deionized water. Add triethylamine to adjust the pH of the reaction system to 8. Heat the reaction vessel to 60℃ and stir for 4 hours. After the reaction is complete, filter the cake and wash it three times with deionized water and anhydrous ethanol. Then transfer it to an oven at 120℃ and vacuum dry it to constant weight. Grind it through a 200-mesh sieve to obtain PN-Si modified sheet-like core-shell mica.

[0044] Step 2: Preparation of the mixture By weight, weigh out 100 parts of polypropylene resin, 25 parts of PI-Si hybrid resin prepared in Example 1, 10 parts of modified aramid reinforcement prepared in Example 4, 20 parts of PN-Si modified lamellar core-shell mica, 0.1 parts of antioxidant 1010, 0.1 parts of antioxidant 168 and 0.2 parts of calcium stearate, add them to a stirring tank and mix evenly to obtain a mixture.

[0045] Step 3: Fabrication of a square power corrugated pipe The mixture is added to a twin-screw extruder. The temperature of each zone of the twin-screw extruder is set to 180℃, the die head temperature is set to 220℃, and the screw speed is 200r / min. The molten material is formed by the CM square corrugated die and the forming module. The formed square corrugated pipe is cooled to room temperature in a 20℃ water bath. After being drawn to a predetermined length by the traction device, it is cut to a predetermined length to obtain a square electric corrugated pipe.

[0046] Example 8 This embodiment provides a method for preparing a reinforced and toughened CM square power corrugated pipe, including the following steps: Step 1: Preparation of PN-Si modified sheet-like core-shell mica Weigh 18.0 g of phlogopite and 100.0 mL of anhydrous ethanol and add them to the reaction vessel. Stir until the mixture is evenly dispersed. Then add 5.0 g of hexachlorocyclotriphosphazene and 6.0 g of 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide in sequence. Then add 10.0 mL of 3-aminopropyltriethoxysilane and 6.0 mL of deionized water. Add triethylamine to adjust the pH of the reaction system to 9. Heat the reaction vessel to 80 °C and stir for 6 h. After the reaction is complete, filter and collect the filter cake. Wash the cake three times with deionized water and anhydrous ethanol and then transfer it to an oven at 120 °C and vacuum dry it to constant weight. Grind the cake through a 200-mesh sieve to obtain PN-Si modified sheet-like core-shell mica.

[0047] Step 2: Preparation of the mixture By weight, weigh out 100 parts of polypropylene resin, 35 parts of PI-Si hybrid resin prepared in Example 2, 15 parts of modified aramid reinforcement prepared in Example 6, 25 parts of PN-Si modified lamellar core-shell mica, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168 and 0.4 parts of calcium stearate, add them to a stirring tank and mix evenly to obtain a mixture.

[0048] Step 3: Fabrication of a square power corrugated pipe The mixture is added to a twin-screw extruder. The temperature of each zone of the twin-screw extruder is set to 220℃, the die head temperature is set to 230℃, and the screw speed is 300r / min. The molten material is formed by the CM square corrugated die and the forming module. The formed square corrugated pipe is cooled to room temperature in a 20℃ water bath. After being drawn to a predetermined length by the traction device, it is cut to obtain a square electric corrugated pipe.

[0049] Example 9 This embodiment provides a method for preparing a reinforced and toughened CM square power corrugated pipe, including the following steps: Step 1: Preparation of PN-Si modified sheet-like core-shell mica Weigh 16.0 g of phlogopite and 100.0 mL of anhydrous ethanol and add them to the reaction vessel. Stir until the mixture is evenly dispersed. Then add 5.0 g of hexachlorocyclotriphosphazene and 6.0 g of 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide in sequence. Then add 9.0 mL of 3-aminopropyltriethoxysilane and 5.0 mL of deionized water. Add triethylamine to adjust the pH of the reaction system to 9. Heat the reaction vessel to 70 °C and stir for 5 h. After the reaction is complete, filter and collect the filter cake. Wash the cake three times with deionized water and anhydrous ethanol and then transfer it to an oven at 120 °C and vacuum dry it to constant weight. Grind the cake through a 200-mesh sieve to obtain PN-Si modified sheet-like core-shell mica.

[0050] Step 2: Preparation of the mixture By weight, weigh out 100 parts of polypropylene resin, 30 parts of PI-Si hybrid resin prepared in Example 3, 12 parts of modified aramid reinforcement prepared in Example 6, 21 parts of PN-Si modified lamellar core-shell mica, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168 and 0.3 parts of calcium stearate, add them to a stirring tank and mix evenly to obtain a mixture.

[0051] Step 3: Fabrication of a square power corrugated pipe The mixture is added to a twin-screw extruder. The temperature of each zone of the twin-screw extruder is set to 200℃, the die head temperature is set to 230℃, and the screw speed is 250r / min. The molten material is formed by the CM square corrugated die and the forming module. The formed square corrugated pipe is cooled to room temperature in a 20℃ water bath. After being drawn to a predetermined length by the traction device, it is cut to obtain a square electric corrugated pipe.

[0052] Comparative Example 1 The difference between this comparative example and Example 9 is that step II is omitted in the preparation process of the PI-Si hybrid resin used in step II.

[0053] Comparative Example 2 The difference between this comparative example and Example 9 is that step (2) is omitted during the preparation of the modified aramid reinforcement used in step two.

[0054] Comparative Example 3 The difference between this comparative example and Example 9 is that step one is omitted, and in step two, phlogopite is used to replace PN-Si modified sheet-like core-shell mica in an equal amount.

[0055] Performance testing: The simple beam impact strength of the square power corrugated pipes prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 18743.1-2022 "Determination of simple beam impact strength of thermoplastic pipes - Part 1: General test method". The mass wear of the square electric corrugated pipes prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 5478-2008 "Test Method for Rolling Abrasion of Plastics". The longitudinal shrinkage rate at 100°C of the square power corrugated pipes prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 6671-2001 "Determination of longitudinal shrinkage rate of thermoplastic pipes". The limiting oxygen index of the square electric corrugated pipes prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 26526-2011 "Determination of flammability of plastics by oxygen index method - Part 2: Room temperature test". The volume resistivity of the square power corrugated tubes prepared in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 31838.2-2019 "Dielectric and resistive properties of solid insulating materials - Part 2: Resistive properties (DC method) - Volume resistivity and volume resistivity". The specific data are shown in Table 1. Table 1 - Performance Test Data for Each Sample Data Analysis: A comparative analysis of the data in Table 1 reveals that the simply supported beam impact strength of the square power corrugated pipe prepared by this invention is 621 J·m. -2 The mass wear loss is 9.0 mg, the longitudinal shrinkage rate at 100℃ is 0.83%, the limiting oxygen index is 31.2%, and the volume resistivity is 2.3 × 10⁻⁶. 14 Ω·m, all data are better than the comparative example, indicating: In Comparative Example 1, without the siloxane-induced reaction in step II, the polyamic acid system exhibits a structural evolution pattern dominated by linear segment stacking during imidization, making it difficult to form a hybrid network with a regular spatial configuration. Due to the lack of a flexible adjustment structure across the phase region, the inter-segment forces are highly concentrated, preventing the effective dispersion of local energy during stress transmission and resulting in a lower microcrack initiation threshold within the matrix. Simultaneously, the interfacial polarity difference is not weakened, and the interfacial transition layer formed during the subsequent mixing process is discontinuous, making the multiphase interface a preferred instability region for stress and thermal disturbance. These structural characteristics lead to a transition in the macroscopic mechanical response from hierarchical dissipation to single-channel failure, further affecting the structural stability of the material under thermal and frictional fields, resulting in a systematic decline in composite performance. In Comparative Example 2, without the end-group regulation reaction in step (2), the aramid reinforcement retains its intrinsic high-rigidity segment structure. However, its surface chemical environment lacks functional sites that can form an effective coupling interface with the resin matrix. This makes the interaction between the two phases mainly dependent on weak van der Waals forces. During mixing and molding, the reinforcement is unable to establish a stable orientation structure in the matrix, resulting in a limited stress redistribution mechanism at the microscale and linearizing crack propagation behavior. Furthermore, due to insufficient interfacial bonding, relative slippage occurs in the interfacial region under external loads, significantly shortening the energy dissipation path. Under thermal disturbance conditions, the reinforcement also cannot provide sufficient spatial constraints for the thermal motion of the resin segments, leading to a significant weakening of dimensional stability. This change in interfacial behavior ultimately causes an overall degradation of mechanical and thermal responses. In Comparative Example 3, without the interface construction process in Step 1, the surface of the sheet mica retains its original inorganic properties. Its high polarity and the low interfacial energy matching between the resin matrix result in limited dispersibility during melting and mixing, and it is easy to form local agglomerates. The coupling behavior of the electric field and thermal field at the interface is amplified due to the lack of a functionalized transition layer, resulting in obvious interfacial polarization and local heat accumulation. This makes the medium response inside the system non-uniform, reducing the macroscopic insulation stability. At the same time, the unmodified sheets are difficult to participate in the formation of a continuous barrier network during pyrolysis, and the integrity of the solid-phase shielding structure is damaged, making it easier for heat flow and decomposition products to penetrate the system. The lack of a multi-scale interfacial synergistic mechanism ultimately leads to the overall degradation of flame retardant and insulation performance. Ultimately, it is concluded that the degradation of system performance can be attributed to the synergistic failure caused by the weakening of key links in the construction process of the multiphase interface structure. In Comparative Example 1, the matrix did not form a stable hybrid network, resulting in anisotropic distribution of interactions between chain segments. In Comparative Example 2, the reinforcing phase did not establish an interface constraint structure after end-group regulation, leading to a shift in stress transfer mechanism to unit response dominated by interface slip. In Comparative Example 3, after the inorganic layers failed to construct a core-shell interface, the behavior of the medium and thermal disturbances exhibited an amplification effect in the interface region. Although these three changes involve different components of the system, their common result is: decreased continuity of the interface phase, weakened cross-scale coupling mechanism, and a shift in the energy and load transfer path from hierarchical to localized.

[0056] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A reinforced and toughened CM square power corrugated pipe, comprising polypropylene resin, PI-Si hybrid resin, modified aramid reinforcement, PN-Si modified lamellar core-shell mica, antioxidant 1010, antioxidant 168 and calcium stearate, which are thoroughly mixed and then melt-extruded to obtain the pipe, characterized in that... The process also includes adding a polyamic acid prepolymer dispersion to a reactor and stirring, then adding glacial acetic acid and deionized water sequentially. After the mixture is homogeneous, 3-(2,3-epoxypropoxy)propyltrimethoxysilane is added. The reactor is then heated to 40-50°C and stirred for 2-3 hours to obtain a siloxane-modified polyamic acid dispersion. The siloxane-modified polyamic acid dispersion and the modification solution are then added to the reactor and stirred. After the mixture is homogeneous, the reactor is heated to 120-140°C and held for 1-2 hours. The temperature is then raised to 170-190°C and held for 2-4 hours. The final treatment yields a PI-Si hybrid resin. The process also includes cooling the reactor to 0-5℃, adding p-phenylenediamine, lithium chloride, calcium chloride, and N-methyl-2-pyrrolidone to the reactor and stirring. After the mixture is homogeneous, the calculated amounts of 4,4'-biphenylacetyl chloride and anhydrous sodium carbonate are added in ten batches with an interval of 10-12 minutes between additions. After the addition is complete, the reactor is heated to 20-30℃ and stirred for 3-4 hours to obtain an aramid prepolymer resin dispersion. Then, 4-hydroxy-4'-cyanobiphenyl, N,N'-dicyclohexylcarbodiimide, 4-dimethylaminopyridine, and N-methyl-2-pyrrolidone are added to the reactor and stirred. After the mixture is homogeneous, the aramid prepolymer resin dispersion is added and stirred at room temperature for 2-3 hours. The reactor is then heated to 60-80℃ and stirred for 2-4 hours. The post-treatment yields a modified aramid reinforcement. By weight, the polypropylene resin comprises 100 parts, the PI-Si hybrid resin comprises 25-35 parts, the modified aramid reinforcement comprises 10-15 parts, the PN-Si modified lamellar core-shell mica comprises 20-25 parts, the antioxidant 1010 comprises 0.1-0.2 parts, the antioxidant 168 comprises 0.1-0.2 parts, and the calcium stearate comprises 0.2-0.4 parts. After being thoroughly mixed, the mixture is melt-extruded to obtain the reinforced and toughened CM square power corrugated pipe.

2. The reinforced and toughened CM square power corrugated pipe according to claim 1, characterized in that, The ratio of the polyamic acid prepolymer dispersion, glacial acetic acid, deionized water, and 3-(2,3-epoxypropoxy)propyltrimethoxysilane is 80 mL:1.5 mL:2-3 mL:3-4 mL; the ratio of the siloxane-modified polyamic acid dispersion to the modification solution is 80 mL:40-45 mL, wherein the modification solution is obtained by mixing acetic anhydride and pyridine in a ratio of 40-50 mL:2-3 mL.

3. The reinforced and toughened CM square power corrugated pipe according to claim 2, characterized in that, The preparation method of the polyamic acid prepolymer dispersion is as follows: 4,4'-oxodiphenylamine and N-methyl-2-pyrrolidone are added to a reaction vessel and stirred. After the mixture is uniform, the reaction vessel is cooled to 0-5°C, and the calculated amount of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is added in ten batches with an interval of 10-15 minutes between additions. After the addition is completed, the reaction vessel is heated to 20-30°C and kept at the temperature for stirring for 3-4 hours. After stirring is completed, the obtained material is collected to obtain the polyamic acid prepolymer dispersion.

4. The reinforced and toughened CM square power corrugated pipe according to claim 3, characterized in that, In the preparation of polyamic acid prepolymer dispersion, the ratio of 4,4'-oxodiphenylamine to N-methyl-2-pyrrolidone is 10-12 g:100 mL, wherein the amount of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride added is 0.40-0.45 times the molar amount of amino group in the reaction system.

5. The reinforced and toughened CM square power corrugated pipe according to claim 1, characterized in that, The ratio of p-phenylenediamine, lithium chloride, calcium chloride, N-methyl-2-pyrrolidone, and anhydrous sodium carbonate is 8-10 mL:3-4 g:2-3 g:100 mL:2 g, wherein the amount of 4,4'-biphenylacetyl chloride added is 0.55-0.60 times the molar amount of amino group in the reaction system; the ratio of 4-hydroxy-4'-cyanobiphenyl, N,N'-dicyclohexylcarbodiimide, 4-dimethylaminopyridine, N-methyl-2-pyrrolidone, and aramid prepolymer resin dispersion is 5-6 g:6-7 g:0.5-0.6 g:30-40 mL:100 mL.

6. The reinforced and toughened CM square power corrugated pipe according to claim 1, characterized in that, The preparation method of the PN-Si modified sheet-like core-shell mica is as follows: Phlogopite and anhydrous ethanol are added to a reaction vessel and stirred. After being evenly dispersed, hexachlorocyclotriphosphazene and 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide are added in sequence. Then, 3-aminopropyltriethoxysilane and deionized water are added. Triethylamine is then added to adjust the pH of the reaction system to 8-9. The reaction vessel is heated to 60-80℃ and stirred for 4-6 hours. After post-treatment, PN-Si modified sheet-like core-shell mica is obtained.

7. The reinforced and toughened CM square power corrugated pipe according to claim 6, characterized in that, In the preparation of PN-Si modified sheet-like core-shell mica, the ratio of phlogopite, anhydrous ethanol, hexachlorocyclotriphosphazene, 9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide, 3-aminopropyltriethoxysilane and deionized water is 15-18g:100mL:4-5g:6g:8-10mL:4-6mL.

8. A method for preparing a reinforced and toughened CM square power corrugated pipe as described in any one of claims 1-7, characterized in that, Includes the following steps: First, polypropylene resin, PI-Si hybrid resin, modified aramid reinforcement, PN-Si modified lamellar core-shell mica, antioxidant 1010, antioxidant 168 and calcium stearate are added to a mixing tank and mixed evenly to obtain a mixture. Then, the mixture is added to a twin-screw extruder, melt-extruded and shaped, and then cooled and drawn to obtain a square electric corrugated pipe.

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