Thermoplastic-coated glass fiber reinforced plastic composite pipe and preparation method thereof

Abstract

The invention relates to a thermoplastic plastic coated glass fiber reinforced plastic composite pipe and a preparation method thereof. The composite pipe comprises the following raw materials: modified polyethylene, nano aluminum oxide, styrene, dihydroxydiphenylmethane, a benzotriazole compound, dioctyl phthalate and the like, wherein the modified polyethylene is synergistically modified by introducing a double-dynamic cross-linked structure and a multifunctional copolymer; the self-repairing function, the high temperature resistance, the ultraviolet resistance and the intelligent response characteristic are realized. The preparation method of the modified polyethylene comprises the steps of melt blending, cross-linking reaction, copolymerization reaction and toughening treatment, and the mechanical property and durability of the thermoplastic plastic coated glass fiber reinforced plastic composite pipe can be remarkably improved. Through an extrusion molding process, the finally obtained composite pipe has excellent ultraviolet resistance, high temperature resistance, wear resistance and self-repairing performance, and is suitable for pipeline protection in a severe environment.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic composite materials, and in particular to a thermoplastic-coated fiberglass composite pipe and its preparation method. Background Technology

[0002] Fiberglass composite pipes are widely used in chemical, petroleum, power, and environmental protection fields due to their excellent mechanical properties, corrosion resistance, and lightweight nature, especially in highly corrosive and high-temperature environments. However, the surface of existing fiberglass composite pipes often lacks sufficient wear resistance, UV resistance, and long-term weather resistance, making them prone to aging, deterioration, or surface damage during long-term use, thus affecting their service life and reliability.

[0003] To overcome this problem, traditional modification methods include coating or covering the surface of fiberglass pipes, but these methods often suffer from drawbacks such as poor coating adhesion and durability. Therefore, researchers and engineers have proposed using thermoplastics to cover fiberglass composite pipes, leveraging the excellent processability, weather resistance, and UV resistance of thermoplastics to enhance the surface properties of the composite pipes.

[0004] While existing thermoplastic coating technologies have made progress in some aspects, they still face several challenges. For example, existing thermoplastic materials are prone to aging under high temperatures and ultraviolet radiation, lack effective self-healing capabilities, and often fail to fully leverage the synergistic effects of composite materials. Therefore, there is an urgent need for new and innovative coating materials and methods that can further improve the UV resistance, high-temperature resistance, and self-healing functions of composite pipes while ensuring their durability and reliability, thereby extending their service life and expanding their application range. Summary of the Invention

[0005] To overcome the shortcomings of existing fiberglass composite pipes in terms of weather resistance, UV resistance, and high-temperature resistance, this invention aims to provide a novel thermoplastic-coated fiberglass composite pipe and its preparation method. This composite pipe, through the use of modified polyethylene material and the synergistic modification of a dual dynamic cross-linking structure and multifunctional copolymers, endows it with self-healing capabilities, excellent high-temperature resistance, UV resistance, and intelligent response characteristics, thereby significantly improving the durability and performance of the fiberglass composite pipe. This invention mixes modified polyethylene with materials such as nano-alumina and styrene, and modifies it through processes such as melt blending, cross-linking, and copolymerization to obtain a high-performance polyethylene material. This modified polyethylene material is then coated onto the surface of the fiberglass composite pipe to form a thermoplastic coating layer, thereby enhancing the surface properties and overall durability of the composite pipe. This invention, through innovative synergistic modification of modified polyethylene, improves the weather resistance, high-temperature resistance, and self-healing ability of the thermoplastic-coated fiberglass composite pipe, significantly extending the service life of the composite pipe and enhancing its reliability in harsh environments.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A thermoplastic-coated fiberglass composite pipe, comprising the following raw materials in parts by weight: 90-95 parts modified polyethylene; 5-10 parts nano-alumina; 5-10 parts styrene; 0.5-2 parts dihydroxydiphenylmethane; 0.5-2 parts benzotriazole compounds; and 1-3 parts dioctyl phthalate; wherein the modified polyethylene is synergistically modified by introducing a bidynamic crosslinking structure and a multifunctional copolymer, giving it self-healing function, high temperature resistance, UV resistance, and intelligent response characteristics.

[0008] Optionally, the modified polyethylene comprises the following raw materials in parts by weight: 90-95 parts polyethylene; 5-10 parts nano-alumina; 0.5-2 parts sulfide crosslinking agent; 1-3 parts epoxy group comonomer; 1-3 parts polyether toughening agent; and 0.5-2 parts polyethylene light stabilizer; wherein the sulfide crosslinking agent is a disulfide; the epoxy group comonomer is ethylene oxide; the polyether toughening agent is polyether glycol; and the polyethylene light stabilizer is dibenzotriazole.

[0009] Optionally, the method for preparing modified polyethylene includes the following steps:

[0010] (1) Mix polyethylene and nano-alumina by melt blending at high temperature to ensure that nano-alumina is uniformly dispersed in the polyethylene matrix to obtain a mixture;

[0011] (2) Add sulfide crosslinking agent to the mixture and carry out crosslinking reaction under high temperature conditions to crosslink the polyethylene molecular chain, thereby enhancing its thermal stability and anti-aging properties;

[0012] (3) Add epoxy-based comonomers to the reaction products to carry out copolymerization reaction, forming a multifunctional copolymer structure, which improves the UV resistance, high temperature resistance and self-healing ability of polyethylene.

[0013] (4) Add polyether toughening agents to the reaction products and mix them to improve the flexibility and impact resistance of polyethylene;

[0014] (5) Cool to room temperature and obtain modified polyethylene material by extrusion molding.

[0015] Optionally, the melt blending conditions in step (1) are a temperature of 170–220°C, a rotation speed of 100–300 rpm, and a mixing time of 5–15 minutes; the crosslinking reaction conditions in step (2) are a temperature of 160–220°C and a reaction time of 30–60 minutes.

[0016] Optionally, the copolymerization reaction conditions in step (3) are a temperature of 180–220°C, a pressure of 0.5–2 MPa, and a reaction time of 20–40 minutes.

[0017] Optionally, the mixing conditions in step (4) are a mixing temperature of 100-150°C and a reaction time of 10-20 minutes; the extrusion molding conditions in step (5) are an extrusion temperature of 180-220°C, a screw speed of 50-150 rpm, an extrusion pressure of 5-15 MPa, a molding die temperature of 20-60°C, and an extrusion speed of 1-5 m / min.

[0018] Optionally, the benzotriazole compound is 2-hydroxybenzotriazole.

[0019] Optionally, a method for preparing a thermoplastic-coated fiberglass composite pipe includes the following steps:

[0020] S1, Modified polyethylene, nano-alumina, styrene, dihydroxydiphenylmethane, benzotriazole compounds, and dioctyl phthalate are mixed to obtain a modified polyethylene mixture;

[0021] S2, the modified polyethylene mixture is coated on the outer surface of the fiberglass composite pipe to ensure uniform coating, and the coating is formed by extrusion molding to obtain a thermoplastic-coated fiberglass composite pipe.

[0022] Optionally, the extrusion molding conditions in step S2 are: extrusion temperature 180–220°C, screw speed 50–150 rpm, extrusion pressure 5–15 MPa, molding die temperature 20–60°C, and extrusion speed 1–5 m / min.

[0023] The beneficial effects of this invention are:

[0024] This invention, through the synergistic modification of a dual dynamic crosslinking structure and multifunctional copolymers, endows thermoplastic-coated fiberglass composite pipes with self-healing capabilities, intelligent responsiveness, and significantly improved UV resistance and high-temperature resistance. These innovative modifications effectively extend the service life of the composite pipe in harsh environments, particularly under conditions of high temperature, UV radiation, and long-term aging, thereby enhancing the overall performance and durability of the composite pipe. Attached Figure Description

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] Figure 1 This is a comparison chart of the wear resistance test results for samples with different formulation ratios. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Equivalent adjustments made without departing from the spirit and essence of the present invention should also be considered to fall within the protection scope of the present invention.

[0028] Example 1

[0029] The purpose of this embodiment is to obtain a modified polyethylene material with excellent weather resistance, UV resistance, and high temperature resistance by using a higher proportion of modified components, which can be used to coat fiberglass composite pipes with thermoplastic plastics, thereby improving their service life in harsh environments.

[0030] Formula: 95 parts modified polyethylene; 10 parts nano alumina; 10 parts styrene; 2 parts dihydroxydiphenylmethane; 2 parts benzotriazole compounds; 3 parts dioctyl phthalate;

[0031] S1, Preparation method of modified polyethylene:

[0032] (1) Mix 95 parts of polyethylene with 10 parts of nano alumina by melt blending at 220°C, 300 rpm and 10 minutes to obtain a mixture.

[0033] (2) Add 2 parts of disulfide crosslinking agent to the mixture and carry out crosslinking reaction at a temperature of 220°C and a reaction time of 60 minutes to enhance its thermal stability and anti-aging properties;

[0034] (3) Add 3 parts of ethylene oxide to the reaction product and carry out copolymerization reaction. The reaction conditions are temperature 220°C, pressure 1.5MPa, reaction time 30 minutes to form a multifunctional copolymer structure, which improves the UV resistance, high temperature resistance and self-healing ability of polyethylene.

[0035] (4) Add 3 parts of polyether glycol to the reaction product and mix to improve the flexibility and impact resistance of polyethylene. The mixing temperature is 150°C and the reaction time is 15 minutes.

[0036] S2, the modified polyethylene mixture is cooled to room temperature and coated by extrusion molding process. The extrusion temperature is 220°C, the screw speed is 150rpm, the extrusion pressure is 15MPa, the molding die temperature is 60°C, and the extrusion speed is 5m / min to obtain thermoplastic plastic coated fiberglass composite pipe.

[0037] Example 2

[0038] The purpose of this embodiment is to obtain a thermoplastic-coated fiberglass composite pipe with good comprehensive performance by using a moderate proportion of modified components, which is suitable for applications under different environmental conditions.

[0039] Formula: 92 parts modified polyethylene; 7 parts nano alumina; 7 parts styrene; 1.5 parts dihydroxydiphenylmethane; 1.5 parts benzotriazole compounds; 2 parts dioctyl phthalate;

[0040] S1, Preparation method of modified polyethylene:

[0041] (1) Mix 92 parts of polyethylene with 7 parts of nano alumina by melt blending at 200°C, 250 rpm and 10 minutes to obtain a mixture.

[0042] (2) Add 1.5 parts of disulfide crosslinking agent to the mixture and carry out crosslinking reaction at a temperature of 200°C and a reaction time of 45 minutes to enhance its thermal stability and anti-aging properties;

[0043] (3) Add 2.5 parts of ethylene oxide to the reaction product and carry out copolymerization reaction. The reaction conditions are temperature 200°C, pressure 1MPa, and reaction time 25 minutes to form a multifunctional copolymer structure, which improves the UV resistance, high temperature resistance and self-healing ability of polyethylene.

[0044] (4) Add 2.5 parts of polyether glycol to the reaction product and mix to improve the flexibility and impact resistance of polyethylene. The mixing temperature is 130°C and the reaction time is 15 minutes.

[0045] S2, the modified polyethylene mixture is cooled to room temperature and coated by extrusion molding process. The extrusion temperature is 200°C, the screw speed is 100rpm, the extrusion pressure is 10MPa, the molding die temperature is 50°C, and the extrusion speed is 3m / min to obtain thermoplastic plastic coated fiberglass composite pipe.

[0046] Example 3

[0047] The purpose of this embodiment is to optimize the balance between cost and performance by using a lower proportion of modified components, making it suitable for low-cost application environments.

[0048] Formula: 90 parts modified polyethylene; 5 parts nano alumina; 5 parts styrene; 1 part dihydroxydiphenylmethane; 1 part benzotriazole compound; 1 part dioctyl phthalate;

[0049] S1, Preparation method of modified polyethylene:

[0050] (1) Mix 90 parts of polyethylene with 5 parts of nano alumina by melt blending at a temperature of 170°C, a rotation speed of 200 rpm and a mixing time of 8 minutes to obtain a mixture.

[0051] (2) Add 1 part of disulfide crosslinking agent to the mixture and carry out crosslinking reaction at a temperature of 180°C and a reaction time of 40 minutes to enhance its thermal stability and anti-aging properties;

[0052] (3) Add 2 parts of ethylene oxide to the reaction product and carry out copolymerization reaction. The reaction conditions are temperature 180°C, pressure 0.8MPa, and reaction time 30 minutes to form a multifunctional copolymer structure, which improves the UV resistance, high temperature resistance and self-healing ability of polyethylene.

[0053] (4) Add 2 parts of polyether glycol to the reaction product and mix to improve the flexibility and impact resistance of polyethylene. The mixing temperature is 120°C and the reaction time is 12 minutes.

[0054] S2, the modified polyethylene mixture is cooled to room temperature and coated by extrusion molding process. The extrusion temperature is 180°C, the screw speed is 80rpm, the extrusion pressure is 8MPa, the molding die temperature is 30°C, and the extrusion speed is 2m / min to obtain thermoplastic plastic coated fiberglass composite pipe.

[0055] Comparative Example 1

[0056] The purpose of this comparative study is to investigate the effect of modified polyethylene on the performance of thermoplastic-coated fiberglass composite pipes without the addition of sulfide crosslinking agents.

[0057] Formula: 92 parts modified polyethylene; 7 parts nano alumina; 7 parts styrene; 1.5 parts dihydroxydiphenylmethane; 1.5 parts benzotriazole compounds; 2 parts dioctyl phthalate;

[0058] S1, Preparation method of modified polyethylene:

[0059] (1) Mix 92 parts of polyethylene with 7 parts of nano alumina by melt blending at 200°C, 250 rpm and 10 minutes to obtain a mixture.

[0060] (2) Copolymerize the mixture without adding a sulfide crosslinking agent, while retaining the other steps;

[0061] (3) Add 2.5 parts of ethylene oxide to the reaction product and carry out copolymerization reaction. The reaction conditions are temperature 200°C, pressure 1MPa, and reaction time 25 minutes to form a multifunctional copolymer structure, which improves the UV resistance, high temperature resistance and self-healing ability of polyethylene.

[0062] (4) Add 2.5 parts of polyether glycol to the reaction product and mix to improve the flexibility and impact resistance of polyethylene. The mixing temperature is 130°C and the reaction time is 15 minutes.

[0063] S2, the modified polyethylene mixture was cooled to room temperature and coated by extrusion molding process. The extrusion temperature was 200°C, the screw speed was 100 rpm, the extrusion pressure was 10 MPa, the molding die temperature was 50°C, and the extrusion speed was 3 m / min, to obtain the comparative example 1 sample.

[0064] Comparative Example 2

[0065] The purpose of this comparative study is to investigate the effect of modified polyethylene on the performance of thermoplastic-coated fiberglass composite pipes without the addition of styrene.

[0066] Formula: 92 parts modified polyethylene; 7 parts nano alumina; 1.5 parts dihydroxydiphenylmethane; 1.5 parts benzotriazole compound; 2 parts dioctyl phthalate;

[0067] S1, Preparation method of modified polyethylene:

[0068] (1) Mix 92 parts of polyethylene with 7 parts of nano alumina by melt blending at 200°C, 250 rpm and 10 minutes to obtain a mixture.

[0069] (2) Add 1.5 parts of disulfide crosslinking agent to the mixture and carry out crosslinking reaction at a temperature of 200°C and a reaction time of 45 minutes to enhance its thermal stability and anti-aging properties;

[0070] (3) Instead of adding styrene to the reaction product, a copolymerization reaction is carried out directly, with 2.5 parts of ethylene oxide added. The reaction conditions are 200°C, 1 MPa, and 25 minutes to form a multifunctional copolymer structure, which improves the UV resistance, high temperature resistance and self-healing ability of polyethylene.

[0071] (4) Add 2.5 parts of polyether glycol to the reaction product and mix to improve the flexibility and impact resistance of polyethylene. The mixing temperature is 130°C and the reaction time is 15 minutes.

[0072] S2, the modified polyethylene mixture was cooled to room temperature and coated by extrusion molding process. The extrusion temperature was 200°C, the screw speed was 100 rpm, the extrusion pressure was 10 MPa, the molding die temperature was 50°C, and the extrusion speed was 3 m / min, to obtain the comparative example 2 sample.

[0073] Comparative Example 3

[0074] The purpose of this comparative study is to investigate the effect of modified polyethylene on the performance of thermoplastic-coated fiberglass composite pipes without the addition of benzotriazole compounds.

[0075] Formula: 92 parts modified polyethylene; 7 parts nano alumina; 7 parts styrene; 1.5 parts dihydroxydiphenylmethane; 2 parts dioctyl phthalate;

[0076] S1, Preparation method of modified polyethylene:

[0077] (1) Mix 92 parts of polyethylene with 7 parts of nano alumina by melt blending at 200°C, 250 rpm and 10 minutes to obtain a mixture.

[0078] (2) Add 1.5 parts of disulfide crosslinking agent to the mixture and carry out crosslinking reaction at a temperature of 200°C and a reaction time of 45 minutes to enhance its thermal stability and anti-aging properties;

[0079] (3) Add 2.5 parts of ethylene oxide to the reaction product and carry out copolymerization reaction. The reaction conditions are temperature 200°C, pressure 1MPa, and reaction time 25 minutes to form a multifunctional copolymer structure, which improves the UV resistance, high temperature resistance and self-healing ability of polyethylene.

[0080] (4) Add 2.5 parts of polyether glycol to the reaction product and mix to improve the flexibility and impact resistance of polyethylene. The mixing temperature is 130°C and the reaction time is 15 minutes.

[0081] S2, the modified polyethylene mixture was cooled to room temperature and coated by extrusion molding process. The extrusion temperature was 200°C, the screw speed was 100 rpm, the extrusion pressure was 10 MPa, the molding die temperature was 50°C, and the extrusion speed was 3 m / min, to obtain the comparative example 3 sample.

[0082] Performance testing

[0083] 1. UV resistance test

[0084] This test was used to evaluate the anti-aging and UV resistance of thermoplastic-coated fiberglass composite pipes under prolonged ultraviolet (UV) irradiation. The test method involved exposing the samples to an accelerated UV aging apparatus at a temperature of 50°C and a UV radiation intensity of 0.89 W / m² for 1000 hours. After the test, changes in appearance, physical properties, and color were measured to assess the durability of the composite pipe under UV irradiation.

[0085] 2. High-temperature heat resistance test

[0086] This test is used to evaluate the thermal stability and performance changes of thermoplastic-coated fiberglass composite pipes under high-temperature environments. The test method involves placing the sample in a high-temperature environment and subjecting it to 24 hours of static heating and isothermal conditions. After the test, the mechanical properties of the sample are measured, including tensile strength, elastic modulus, and elongation at break, to analyze whether the composite pipe exhibits thermal deformation, cracking, or performance degradation.

[0087] 3. Wear resistance test

[0088] This test evaluates the wear resistance of thermoplastic-coated fiberglass composite pipes. The test method involves placing the composite pipe sample in a test environment with the grinding wheel in contact with the sample using a standard wear testing machine, and setting it to 500 cycles. After the test, the wear resistance of the composite pipe is evaluated by measuring the degree of surface wear and changes in mechanical properties.

[0089] 4. Self-healing performance test

[0090] The self-healing performance test is used to evaluate the repair capability of thermoplastic-coated fiberglass composite pipes after external damage. The test method involves artificially cutting or scratching the surface of the composite pipe to create a damaged area. The sample is then heated to a set temperature, and its self-healing process is observed under simulated environmental conditions. During the test, the cracks or scratches on the composite pipe surface are periodically checked to see if they heal spontaneously until the damaged area is completely or partially repaired. The repair time and effect are recorded, and the self-healing capability is ultimately evaluated.

[0091] Table 1 Performance Test Results

[0092] Sample number UV resistance High temperature heat resistance wear resistance Self-healing performance Example 1 minute surface changes No obvious deformation 0.12mm³ Self-repair is slow. Example 2 No significant changes No deformation 0.05mm³ Good self-repairing effect Example 3 Slight fading Micro deformation 0.18mm³ Self-repair is slow. Comparative Example 1 Noticeable fading Obvious deformation 0.25mm³ No repair Comparative Example 2 Significant fading Severe deformation 0.30mm³ No repair Comparative Example 3 Cracking, fading Brittle 0.40mm³ No repair

[0093] Based on the test results, Example 2 performed the best, outperforming all other examples and comparative examples in all test items. Firstly, regarding UV resistance, Example 2 showed almost no surface change after 1000 hours of UV irradiation and exhibited minimal tensile strength loss, indicating excellent UV resistance. Examples 1 and 3 performed well after UV irradiation, but still showed some fading and tensile strength loss, indicating relatively weaker UV resistance. The comparative examples performed poorly, especially Comparative Example 3, whose surface not only faded severely but also cracked.

[0094] Regarding high-temperature heat resistance, Example 2 showed no deformation after being heated at 180°C for 24 hours, maintaining excellent high-temperature resistance. Examples 1 and 3 performed well at high temperatures; although slight deformation occurred, their overall performance remained acceptable. In contrast, the comparative examples exhibited poor high-temperature resistance, especially Comparative Example 3, which cracked under high-temperature conditions, showing significant performance degradation.

[0095] Regarding wear resistance, Figure 1 Example 2 exhibited the least wear, at only 0.05 mm³, and showed the least change in tensile strength, indicating strong wear resistance. Examples 1 and 3 also demonstrated good wear resistance; although the wear was slightly higher, they still maintained good wear resistance. In contrast, the comparative examples showed poor wear resistance, especially Comparative Example 3, which exhibited the most severe changes in wear and tensile strength, indicating insufficient wear resistance.

[0096] Finally, regarding self-healing performance, Example 2 showed the best performance, effectively repairing surface damage in a short time, with a repair time of only 8 hours. Examples 1 and 3 had poor self-healing capabilities, but could still partially repair damage under certain conditions. The comparative example had no self-healing ability and no repair effect, indicating that its repair capability after damage was almost zero.

[0097] In summary, Example 2 performed excellently in all performance tests, particularly excelling in UV resistance, high-temperature resistance, abrasion resistance, and self-healing properties, making it suitable for applications requiring high performance and long service life. Other examples also performed well, but the comparative examples showed weaker overall performance, especially in UV resistance and self-healing.

Claims

1. A thermoplastic-coated fiberglass composite pipe, characterized in that, The composite tube comprises the following raw materials in parts by weight: 90-95 parts modified polyethylene; 5-10 parts nano alumina; 5-10 parts styrene; 0.5-2 parts dihydroxydiphenylmethane; 0.5-2 parts benzotriazole compounds; and 1-3 parts dioctyl phthalate; wherein the modified polyethylene is synergistically modified by introducing a dual dynamic crosslinking structure and a multifunctional copolymer.

2. The thermoplastic-coated fiberglass composite pipe according to claim 1, characterized in that, The modified polyethylene comprises the following raw materials in parts by weight: 90-95 parts polyethylene; 5-10 parts nano-alumina; 0.5-2 parts sulfide crosslinking agent; 1-3 parts epoxy group comonomer; 1-3 parts polyether toughening agent; and 0.5-2 parts polyethylene light stabilizer; wherein the sulfide crosslinking agent is a disulfide; the epoxy group comonomer is ethylene oxide; the polyether toughening agent is polyether glycol; and the polyethylene light stabilizer is dibenzotriazole.

3. A thermoplastic-coated fiberglass composite pipe according to any one of claims 1 or 2, characterized in that, The method for preparing the modified polyethylene includes the following steps: (1) Polyethylene and nano-alumina are mixed and uniformly mixed at high temperature by melt blending to obtain a mixture; (2) Add a sulfide crosslinking agent to the mixture and carry out the crosslinking reaction under high temperature conditions; (3) Add epoxy-based comonomers to the reaction products to carry out copolymerization; (4) Add a polyether toughening agent to the reaction product and mix. (5) Cool to room temperature and obtain modified polyethylene material by extrusion molding.

4. The thermoplastic-coated fiberglass composite pipe according to claim 3, characterized in that, The melt blending conditions in step (1) are a temperature of 170–220°C, a rotation speed of 100–300 rpm, and a mixing time of 5–15 minutes; the crosslinking reaction conditions in step (2) are a temperature of 160–220°C and a reaction time of 30–60 minutes.

5. The thermoplastic-coated fiberglass composite pipe according to claim 3, characterized in that, The copolymerization reaction conditions in step (3) are a temperature of 180–220°C, a pressure of 0.5–2 MPa, and a reaction time of 20–40 minutes.

6. The thermoplastic-coated fiberglass composite pipe according to claim 3, characterized in that, The mixing conditions in step (4) are a mixing temperature of 100-150°C and a reaction time of 10-20 minutes; the extrusion molding conditions in step (5) are an extrusion temperature of 180-220°C, a screw speed of 50-150 rpm, an extrusion pressure of 5-15 MPa, a molding die temperature of 20-60°C, and an extrusion speed of 1-5 m / min.

7. The thermoplastic-coated fiberglass composite pipe according to claim 1, characterized in that, The benzotriazole compound is 2-hydroxybenzotriazole.

8. A method for preparing a thermoplastic-coated fiberglass composite pipe, wherein the thermoplastic-coated fiberglass composite pipe is as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1, Modified polyethylene, nano-alumina, styrene, dihydroxydiphenylmethane, benzotriazole compounds, and dioctyl phthalate are mixed to obtain a modified polyethylene mixture; S2, the modified polyethylene mixture is coated on the outer surface of the fiberglass composite pipe to ensure uniform coating, and the coating is formed by extrusion molding to obtain a thermoplastic-coated fiberglass composite pipe.

9. The thermoplastic-coated fiberglass composite pipe according to claim 1, characterized in that, The extrusion molding conditions in step S2 are: extrusion temperature 180-220°C, screw speed 50-150 rpm, extrusion pressure 5-15 MPa, molding die temperature 20-60°C, and extrusion speed 1-5 m / min.

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