Environment-friendly polypropylene-based composite material as well as preparation method and application thereof

Abstract

The invention provides an environment-friendly polypropylene-based composite material as well as a preparation method and application thereof, and belongs to the technical field of polypropylene materials. Maleic anhydride and triallyl isocyanurate are introduced to modify polypropylene, so that the polarity and the interface bonding force of the polypropylene are improved, and meanwhile, the thermal stability and the mechanical property are enhanced; the dispersibility and interfacial compatibility of the graphene oxide are improved through bionic lipid bilayer and silanization modification, and the graphene oxide is further endowed with intelligent response capability through grafting a thermo-sensitive polymer; the carbon nanotubes are subjected to plasma activation and magnesium hydroxide deposition to construct a core-shell structure, the interface bonding force and flame retardance of the carbon nanotubes are enhanced, and a synergistic flame-retardant system is further formed through n-octyl phosphite modification; and the metal coordination modifier significantly improves the flame retardant efficiency and thermal stability of the material by promoting carbonization and releasing non-combustible gas. The composite material with excellent mechanical property, thermal stability and flame retardant property is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of polypropylene materials, and relates to an environmentally friendly polypropylene-based composite material, a preparation method thereof, and an application thereof. Background Art

[0002] In modern materials science, polypropylene, as an important thermoplastic, has been widely used in many fields, such as power pipes, packaging materials, automotive parts, and household appliance casings, due to its excellent mechanical properties, chemical stability, and processing convenience. Its advantages include a relatively low density, high tensile strength, and excellent corrosion resistance, which have enabled it to occupy an important position in many industrial fields. However, despite the many advantages of polypropylene in daily applications, there are still certain deficiencies in its mechanical properties and flame retardancy, which limit its performance and safety in some special applications.

[0003] Firstly, although polypropylene has good toughness and impact resistance, under high-temperature or high-load conditions, especially when subjected to large mechanical stresses, it often exhibits low strength and rigidity. This makes polypropylene prone to deformation or rupture in some application scenarios, especially in complex working environments, such as under high temperature, large impact, or long-term load conditions, where the structural stability and durability of polypropylene will be significantly affected.

[0004] Secondly, the flame retardancy of polypropylene is relatively weak. Especially in a high-temperature environment, its flammable characteristics may lead to an increased fire risk. When polypropylene encounters a fire source, it is prone to spontaneous combustion and rapid spread of the fire, and may also release toxic and harmful gases, such as carbon monoxide, carbon dioxide, and certain volatile organic compounds, which pose a potential threat to human health and environmental safety. Especially in application scenarios with high safety requirements, the insufficient flame retardancy of polypropylene will greatly increase the danger during a fire. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to provide an environmentally friendly polypropylene-based composite material, its preparation method and application. The present invention chemically modifies the polypropylene matrix, introduces maleic anhydride and triallyl isocyanurate to enhance the polarity and interfacial bonding force of the matrix, and at the same time enhances its thermal stability and mechanical properties. Graphene oxide improves its dispersibility and interfacial compatibility through biomimetic lipid bilayer and silanization modification, and further endows it with intelligent response ability by grafting thermosensitive polymers. Carbon nanotubes are constructed with a core-shell structure through plasma activation and magnesium hydroxide deposition, enhancing their interfacial bonding force and flame retardancy. The modification of n-octyl phosphite further forms a synergistic flame retardant system, and the metal coordination modifier significantly improves the flame retardancy efficiency and thermal stability of the material by promoting carbonization and releasing non-combustible gases. Finally, through the multiple synergistic effects and modification strategies of functional fillers, a composite material with excellent mechanical properties, thermal stability and flame retardancy is prepared.

[0006] To achieve this purpose, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a preparation method of an environmentally friendly polypropylene-based composite material, and the preparation method of the environmentally friendly polypropylene-based composite material includes: S11: Use 1,2-dipalmitoyl-sn-glycero-3-phosphocholine to prepare a lipid film by rotary evaporation; disperse graphene oxide and then compound it with the lipid film, and add 3-glycidylpropyltrimethoxysilane for surface modification to obtain biomimetic layer-modified graphene oxide; S12: Disperse the biomimetic layer-modified graphene oxide in an aqueous phase, add N-isopropylacrylamide monomer, and carry out living polymerization in a copper bromide / pentamethyldiethylenetriamine catalytic system, and then add sodium ascorbate to terminate the reaction to obtain doubly modified graphene oxide; S13: After plasma activation of carbon nanotubes, use magnesium sulfate for modification to obtain carbon nanotube / magnesium hydroxide core-shell material; then introduce n-octyl phosphite for surface modification to obtain multi-level flame retardant modified carbon nanotubes; S21: React hexafluorocyclotriphosphazene with 4-aminophenol in the presence of triethylamine, and then introduce silane coupling agent KH560 and tetrabutylammonium bromide, and carry out metal coordination modification with acrylic acid under the catalysis of zinc chloride to obtain a metal coordination modifier; S22: Pre-activate polypropylene with dicumyl peroxide to obtain pre-activated polypropylene, and carry out melt grafting with the metal coordination modifier, maleic anhydride and triallyl isocyanurate to obtain modified polypropylene; S23: Melt-blend and extrude the modified polypropylene, doubly modified graphene oxide, multi-level flame retardant modified carbon nanotubes and a dispersant through a twin-screw extruder to obtain an environmentally friendly polypropylene-based composite material.

[0007] Specifically, S11: dispersing 1,2-dipalmitoyl-sn-glycero-3-phosphocholine in ethyl acetate, and rotary evaporating to obtain a lipid film; dispersing graphene oxide in deionized water, and adjusting the pH with a sodium hydroxide solution to obtain a dispersion A; adding the dispersion A to the lipid film to obtain a mixed solution B; adding an ethanol solution of 3-glycidylpropyltrimethoxysilane to the mixed solution B to obtain a reaction solution C, stirring the reaction, centrifuging, washing, and vacuum drying to obtain a biomimetic layer-modified graphene oxide; S12: dispersing the biomimetic layer modified graphene oxide in deionized water to obtain a dispersion D, adding N-isopropylacrylamide, cuprous bromide, and pentamethyldiethylenetriamine to obtain a reaction solution E, stirring and reacting after deoxygenation; adding sodium ascorbate, centrifuging, washing, and vacuum drying to obtain a double modified graphene oxide; S13: Plasma-treating carbon nanotubes to obtain surface-activated carbon nanotubes; dispersing the surface-activated carbon nanotubes in deionized water to obtain a surface-activated carbon nanotube dispersion, adding the dispersion to a magnesium sulfate solution and stirring to obtain a reaction solution F, dropping a sodium hydroxide solution to obtain a reaction solution G, stirring and reacting, centrifuging, washing, and drying to obtain a carbon nanotube / magnesium hydroxide core-shell material; dispersing the carbon nanotube / magnesium hydroxide core-shell material in anhydrous ethanol, dropping a tetrahydrofuran solution of n-octyl phosphite to obtain a reaction solution H, filtering, washing, and drying after the reaction to obtain a multi-layer flame-retardant modified carbon nanotube; S21: adding a tetrahydrofuran solution of 4-aminophenol and triethylamine dropwise to a tetrahydrofuran solution of hexafluorocyclotriphosphazene in an ice bath to obtain a reaction solution I; adding a silane coupling agent KH560 solution and tetrabutylammonium bromide to the mixture under nitrogen protection at room temperature to obtain a reaction solution J; adding acrylic acid and zinc chloride to obtain a mixed solution after constant temperature reaction; stirring at room temperature, concentrating under reduced pressure, recrystallizing, and drying under vacuum to obtain a metal coordination modifier; S22: premixing polypropylene, dicumyl peroxide, an antioxidant and zinc stearate under nitrogen protection to obtain preactivated polypropylene; adding a metal coordination modifier, maleic anhydride and triallyl isocyanurate to the preactivated polypropylene, melt grafting under a vacuum environment, cooling, and pelletizing to obtain modified polypropylene; S23: premixing modified polypropylene, double modified graphene oxide and dispersant in a high-speed mixer, then adding multi-layer flame retardant modified carbon nanotubes and mixing evenly, then extruding with a twin-screw extruder and water-cooling pelletizing to obtain an environmentally friendly polypropylene-based composite material.

[0008] As a preferred technical solution of the present invention, in step S11, the mass ratio of graphene oxide dispersed in deionized water is 1:200 - 250. For example, it can be 1:200.0, 1:205.0, 1:210.0, 1:215.0, 1:220.0, 1:225.0, 1:230.0, 1:235.0, 1:240.0, 1:245.0 or 1:250.0. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0009] In some alternative embodiments, the concentration of the sodium hydroxide solution is 0.1 - 0.2 mol / L. For example, it can be 0.10 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, 0.15 mol / L, 0.16 mol / L, 0.17 mol / L, 0.18 mol / L, 0.19 mol / L or 0.20 mol / L. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0010] In some alternative embodiments, the sodium hydroxide solution adjusts the pH to 7 - 7.5. For example, it can be 7.00, 7.05, 7.10, 7.15, 7.20, 7.25, 7.30, 7.35, 7.40, 7.45 or 7.50. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0011] In some alternative embodiments, the mass ratio of graphene oxide to the lipid film is 1:5 - 8. For example, it can be 1:5.0, 1:5.3, 1:5.6, 1:5.9, 1:6.2, 1:6.5, 1:6.8, 1:7.1, 1:7.4, 1:7.7 or 1:8.0. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0012] In some alternative embodiments, the mass fraction of the ethanol solution of 3 - glycidoxypropyltrimethoxysilane is 2 - 3 wt.%. For example, it can be 2.0 wt.%, 2.1 wt.%, 2.2 wt.%, 2.3 wt.%, 2.4 wt.%, 2.5 wt.%, 2.6 wt.%, 2.7 wt.%, 2.8 wt.%, 2.9 wt.% or 3.0 wt.%. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0013] In some alternative embodiments, the mass ratio of the 3-glycidylpropyltrimethoxysilane to the graphene oxide is 4-6:1. For example, it can be 4.0:1, 4.2:1, 4.4:1, 4.6:1, 4.8:1, 5.0:1, 5.2:1, 5.4:1, 5.6:1, 5.8:1, or 6.0:1. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0014] In some alternative embodiments, the temperature for the stirring reaction of the reaction solution C is 55-60 °C. For example, it can be 55.0 °C, 55.5 °C, 56.0 °C, 56.5 °C, 57.0 °C, 57.5 °C, 58.0 °C, 58.5 °C, 59.0 °C, 59.5 °C, or 60.0 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0015] In some alternative embodiments, the rotation speed for the stirring reaction of the reaction solution C is 400-500 rpm. For example, it can be 400 rpm, 410 rpm, 420 rpm, 430 rpm, 440 rpm, 450 rpm, 460 rpm, 470 rpm, 480 rpm, 490 rpm, or 500 rpm. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0016] In some alternative embodiments, the time for the stirring reaction of the reaction solution C is 2-3 h. For example, it can be 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h, or 3.0 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0017] As a preferred technical solution of the present invention, in step S12, the mass ratio of the biomimetic layer-modified graphene oxide to deionized water is 1:100-150. For example, it can be 1:100, 1:105, 1:110, 1:115, 1:120, 1:125, 1:130, 1:135, 1:140, 1:145, or 1:150. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0018] In some alternative embodiments, the concentration of N-isopropylacrylamide in reaction solution E is 30-35 mg / mL. For example, it can be 30.0 mg / mL, 30.5 mg / mL, 31.0 mg / mL, 31.5 mg / mL, 32.0 mg / mL, 32.5 mg / mL, 33.0 mg / mL, 33.5 mg / mL, 34.0 mg / mL, 34.5 mg / mL or 35.0 mg / mL. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0019] In some alternative embodiments, the mass ratio of cuprous bromide to N-isopropylacrylamide is 1-1.5:100. For example, it can be 1.0:100, 1.1:100, 1.2:100, 1.3:100, 1.4:100 or 1.5:100. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0020] In some alternative embodiments, the mass ratio of pentamethyldiethylenetriamine to N-isopropylacrylamide is 1.5-2:100. For example, it can be 1.5:100, 1.6:100, 1.7:100, 1.8:100, 1.9:100 or 2.0:100. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0021] In some alternative embodiments, the temperature of the stirred reaction after deoxygenating reaction solution E is 40-45 °C. For example, it can be 40.0 °C, 40.5 °C, 41.0 °C, 41.5 °C, 42.0 °C, 42.5 °C, 43.0 °C, 43.5 °C, 44.0 °C, 44.5 °C or 45.0 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0022] In some alternative embodiments, the time of the stirred reaction after deoxygenating reaction solution E is 8-10 h. For example, it can be 8.0 h, 8.2 h, 8.4 h, 8.6 h, 8.8 h, 9.0 h, 9.2 h, 9.4 h, 9.6 h, 9.8 h or 10.0 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0023] In some alternative embodiments, the mass ratio of sodium ascorbate to N-isopropylacrylamide is 5-6:100. For example, it can be 5.0:100, 5.1:100, 5.2:100, 5.3:100, 5.4:100, 5.5:100, 5.6:100, 5.7:100, 5.8:100, 5.9:100 or 6.0:100. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0024] As a preferred technical solution of the present invention, in step S13, the concentration of the surface-activated carbon nanotube dispersion is 1-2 mg / mL. For example, it can be 1.0 mg / mL, 1.1 mg / mL, 1.2 mg / mL, 1.3 mg / mL, 1.4 mg / mL, 1.5 mg / mL, 1.6 mg / mL, 1.7 mg / mL, 1.8 mg / mL, 1.9 mg / mL or 2.0 mg / mL. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0025] In some alternative embodiments, the concentration of the magnesium sulfate solution is 0.1-0.2 M. For example, it can be 0.10 M, 0.11 M, 0.12 M, 0.13 M, 0.14 M, 0.15 M, 0.16 M, 0.17 M, 0.18 M, 0.19 M or 0.20 M. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0026] In some alternative embodiments, the mass ratio of the surface-activated carbon nanotubes to magnesium sulfate is 1:6-7. For example, it can be 1:6.0, 1:6.1, 1:6.2, 1:6.3, 1:6.4, 1:6.5, 1:6.6, 1:6.7, 1:6.8, 1:6.9 or 1:7.0. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0027] In some alternative embodiments, the sodium hydroxide solution adjusts the pH of the reaction solution F to 10-11. For example, it can be 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9 or 11.0. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0028] In some alternative embodiments, the temperature of the stirring reaction of the reaction solution G is 50 - 60 °C, for example, it can be 50.0 °C, 51.0 °C, 52.0 °C, 53.0 °C, 54.0 °C, 55.0 °C, 56.0 °C, 57.0 °C, 58.0 °C, 59.0 °C or 60.0 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0029] In some alternative embodiments, the time of the stirring reaction of the reaction solution G is 4 - 5 h, for example, it can be 4.0 h, 4.1 h, 4.2 h, 4.3 h, 4.4 h, 4.5 h, 4.6 h, 4.7 h, 4.8 h, 4.9 h or 5.0 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0030] In some alternative embodiments, the concentration of the carbon nanotube / magnesium hydroxide core - shell material dispersed in absolute ethanol is 2 - 3 mg / mL, for example, it can be 2.0 mg / mL, 2.1 mg / mL, 2.2 mg / mL, 2.3 mg / mL, 2.4 mg / mL, 2.5 mg / mL, 2.6 mg / mL, 2.7 mg / mL, 2.8 mg / mL, 2.9 mg / mL or 3.0 mg / mL. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0031] In some alternative embodiments, the mass fraction of the tetrahydrofuran solution of n - octyl phosphite is 5 - 6 wt.%, for example, it can be 5.0 wt.%, 5.1 wt.%, 5.2 wt.%, 5.3 wt.%, 5.4 wt.%, 5.5 wt.%, 5.6 wt.%, 5.7 wt.%, 5.8 wt.%, 5.9 wt.% or 6.0 wt.%. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0032] In some alternative embodiments, the mass ratio of n - octyl phosphite to magnesium sulfate is 1:3 - 4, for example, it can be 1:3.0, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9 or 1:4.0. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0033] In some alternative embodiments, the temperature for the reaction of the reaction solution H is 50 - 60 °C. For example, it can be 50.0 °C, 51.0 °C, 52.0 °C, 53.0 °C, 54.0 °C, 55.0 °C, 56.0 °C, 57.0 °C, 58.0 °C, 59.0 °C or 60.0 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0034] In some alternative embodiments, the reaction time of the reaction solution H is 6 - 7 h. For example, it can be 6.0 h, 6.1 h, 6.2 h, 6.3 h, 6.4 h, 6.5 h, 6.6 h, 6.7 h, 6.8 h, 6.9 h or 7.0 h. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0035] As a preferred technical solution of the present invention, in step S21, the mass ratio in the tetrahydrofuran solution of hexachlorocyclotriphosphazene is 1:40 - 50. For example, it can be 1:40.0, 1:41.0, 1:42.0, 1:43.0, 1:44.0, 1:45.0, 1:46.0, 1:47.0, 1:48.0, 1:49.0 or 1:50.0. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0036] In some alternative embodiments, the concentration of the 4 - aminophenol tetrahydrofuran solution is 20 - 25 mg / mL. For example, it can be 20.0 mg / mL, 20.5 mg / mL, 21.0 mg / mL, 21.5 mg / mL, 22.0 mg / mL, 22.5 mg / mL, 23.0 mg / mL, 23.5 mg / mL, 24.0 mg / mL, 24.5 mg / mL or 25.0 mg / mL. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0037] In some alternative embodiments, the mass ratio of 4 - aminophenol to hexachlorocyclotriphosphazene is 1.5 - 2:1. For example, it can be 1.5:1.0, 1.55:1.0, 1.60:1.0, 1.65:1.0, 1.70:1.0, 1.75:1.0, 1.80:1.0, 1.85:1.0, 1.90:1.0, 1.95:1.0 or 2.0:1.0. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0038] In some optional embodiments, the molar ratio of triethylamine to 4-aminophenol is 1-1.5:1, for example, it can be 1.0:1.0, 1.05:1.0, 1.10:1.0, 1.15:1.0, 1.20:1.0, 1.25:1.0, 1.30:1.0, 1.35:1.0, 1.40:1.0, 1.45:1.0 or 1.50:1.0, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] In some optional embodiments, the reaction solution I is stirred at room temperature under nitrogen protection for 12-15 hours, for example, it can be 12.0h, 12.3h, 12.6h, 12.9h, 13.2h, 13.5h, 13.8h, 14.1h, 14.4h, 14.7h or 15.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In some optional embodiments, the molar ratio of silane coupling agent KH560 to deionized water in the silane coupling agent KH560 solution is 1:1-4, for example, it can be 1:1, 1:13, 1:16, 1:19, 1:2.2, 1:2.5, 1:2.8, 1:3.1, 1:3.4, 1:3.7 or 1:4, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0041] In some optional embodiments, the molar ratio of the silane coupling agent KH560 to hexafluorocyclotriphosphazene is 5-6:1, for example, it can be 5.0:1.0, 5.1:1.0, 5.2:1.0, 5.3:1.0, 5.4:1.0, 5.5:1.0, 5.6:1.0, 5.7:1.0, 5.8:1.0, 5.9:1.0 or 6.0:1.0, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] In some optional embodiments, the mass ratio of tetrabutylammonium bromide to silane coupling agent KH560 is 0.5-1:100, for example, it can be 0.5:100, 0.55:100, 0.6:100, 0.65:100, 0.7:100, 0.75:100, 0.8:100, 0.85:100, 0.9:100, 0.95:100 or 1:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In some optional embodiments, the molar ratio of zinc chloride to acrylic acid is 0.8-1.2:2, for example, it can be 0.8:2.0, 0.84:2.0, 0.88:2.0, 0.92:2.0, 0.96:2.0, 1.00:2.0, 1.04:2.0, 1.08:2.0, 1.12:2.0, 1.16:2.0, 1.20:2.0, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In some optional embodiments, the mixed liquid is stirred at room temperature for 2-3 h, for example, 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h, 3.0 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] As a preferred technical solution of the present invention, in step S22, the mass ratio of dicumyl peroxide to polypropylene is 0.1-0.2:100, for example, it can be 0.10:100, 0.11:100, 0.12:100, 0.13:100, 0.14:100, 0.15:100, 0.16:100, 0.17:100, 0.18:100, 0.19:100 or 0.20:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In some optional embodiments, the mass ratio of the antioxidant to polypropylene is 0.5-0.6:100, for example, it can be 0.50:100, 0.51:100, 0.52:100, 0.53:100, 0.54:100, 0.55:100, 0.56:100, 0.57:100, 0.58:100, 0.59:100 or 0.60:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] In some optional embodiments, the mass ratio of zinc stearate to polypropylene is 0.5-1:100, for example, it can be 0.50:100, 0.55:100, 0.60:100, 0.65:100, 0.70:100, 0.75:100, 0.80:100, 0.85:100, 0.90:100, 0.95:100 or 1.00:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0048] In some optional embodiments, the premix temperature is 175-180°C, for example, it can be 175.0°C, 175.5°C, 176.0°C, 176.5°C, 177.0°C, 177.5°C, 178.0°C, 178.5°C, 179.0°C, 179.5°C or 180.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] In some optional embodiments, the premixing time is 5-8 min, for example, it can be 5.0 min, 5.3 min, 5.6 min, 5.9 min, 6.2 min, 6.5 min, 6.8 min, 7.1 min, 7.4 min, 7.7 min or 8.0 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] In some optional embodiments, the mass ratio of the metal coordination modifier to preactivated polypropylene is 3-5:100, for example, it can be 3.0:100, 3.2:100, 3.4:100, 3.6:100, 3.8:100, 4.0:100, 4.2:100, 4.4:100, 4.6:100, 4.8:100 or 5.0:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] In some optional embodiments, the mass ratio of maleic anhydride to preactivated polypropylene is 1-2:100, for example, it can be 1.0:100, 1.1:100, 1.2:100, 1.3:100, 1.4:100, 1.5:100, 1.6:100, 1.7:100, 1.8:100, 1.9:100 or 2.0:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] In some optional embodiments, the mass ratio of triallyl isocyanurate to preactivated polypropylene is 1-1.5:100, for example, it can be 1:100, 1.05:100, 1.1:100, 1.15:100, 1.2:100, 1.25:100, 1.3:100, 1.35:100, 1.4:100, 1.45:100 or 1.5:100, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0053] In some optional embodiments, the temperature of the melt grafting is 180-185°C, for example, it can be 180°C, 180.5°C, 181°C, 181.5°C, 182°C, 182.5°C, 183°C, 183.5°C, 184°C, 184.5°C or 185°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0054] In some optional embodiments, the melt grafting time is 6-8 min, for example, it can be 6.0 min, 6.2 min, 6.4 min, 6.6 min, 6.8 min, 7.0 min, 7.2 min, 7.4 min, 7.6 min, 7.8 min or 8.0 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] As a preferred technical solution of the present invention, in step S23, the mass ratio of the modified polypropylene, the double modified graphene oxide, the multi-level flame retardant modified carbon nanotubes and the dispersant is 100: (1-3): (1-3): (0.2-0.4).

[0056] As a preferred technical solution of the present invention, in step S23, the speed of premixing the modified polypropylene, the double modified graphene oxide and the dispersant in the high-speed mixer is 2000-2500 rpm, for example, it can be 2000 rpm, 2050 rpm, 2100 rpm, 2150 rpm, 2200 rpm, 2250 rpm, 2300 rpm, 2350 rpm, 2400 rpm, 2450 rpm or 2500 rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] In some optional embodiments, the premixing time of the modified polypropylene, double modified graphene oxide and dispersant in the high-speed mixer is 5-8 min, for example, it can be 5.0 min, 5.3 min, 5.6 min, 5.9 min, 6.2 min, 6.5 min, 6.8 min, 7.1 min, 7.4 min, 7.7 min or 8.0 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] In some optional embodiments, the operating temperature of the twin-screw extruder is 170-180°C, for example, it can be 170.0°C, 171.0°C, 172.0°C, 173.0°C, 174.0°C, 175.0°C, 176.0°C, 177.0°C, 178.0°C, 179.0°C or 180.0°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0059] In some optional embodiments, the operating speed of the twin-screw extruder is 160-180rpm, for example, it can be 160rpm, 162rpm, 164rpm, 166rpm, 168rpm, 170rpm, 172rpm, 174rpm, 176rpm, 178rpm or 180rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0060] In a second aspect, the present invention provides an environmentally friendly polypropylene-based composite material prepared by the above-mentioned preparation method.

[0061] In a third aspect, the present invention provides an application of an environmentally friendly polypropylene-based composite material prepared by the above-mentioned preparation method in a power pipeline.

[0062] In the present invention, polypropylene is selected as the substrate. Polypropylene is a semi-crystalline thermoplastic compound whose main chain is composed of non-polar carbon-carbon bonds, which makes it chemically inert and hydrophobic. At the same time, polypropylene has extremely low electrical conductivity and is suitable for the insulating layer of power pipelines. However, due to its non-polar properties, it lacks intermolecular interaction with polar nanofillers and has poor interfacial compatibility. Therefore, it is necessary to introduce polar groups through chemical modification to improve the interfacial bonding force between polypropylene and fillers.

[0063] First, polypropylene is activated using diisopropylbenzene peroxide, which is a highly efficient free radical initiator that can decompose at high temperatures to generate free radicals. The generated free radicals extract hydrogen atoms from the side chains of polypropylene molecules to generate polypropylene free radicals. Next, the polypropylene free radicals react with the double bonds in maleic anhydride and triallyl isocyanurate molecules to form free radical addition reactions, which graft them onto the polypropylene chain. The anhydride groups introduced by maleic anhydride provide polar groups, which combine with polar fillers through hydrogen bonds or chemical reactions, thereby enhancing interfacial compatibility. The isocyanurate groups introduced by triallyl isocyanurate further enhance the polarity of polypropylene, while providing potential cross-linking capabilities, thereby enhancing the thermal stability and mechanical properties of the composite material.

[0064] The hexafluorocyclotriphosphazene structure in the metal coordination modifier contains abundant phosphorus-nitrogen bonds, which can decompose at high temperatures and slowly release inorganic phosphoric acid, nitrogen oxides and other compounds. On the one hand, these decomposition products can promote the carbonization of the substrate surface to generate a thermally stable expanded carbon layer, which plays a role in heat insulation and oxygen isolation; on the other hand, the released non-combustible gas can dilute the concentration of combustible gas in the combustion area, thereby significantly improving the flame retardant efficiency of the material. In addition, the construction of the expanded carbon layer can also enhance the structural integrity of the material and prevent the loss of mechanical properties at high temperatures.

[0065] Further introduction of 4-aminophenol and acrylic acid into the molecular structure of the metal coordination modifier can significantly improve the flame retardancy and thermal stability. 4-aminophenol introduces phenolic hydroxyl and amino groups through the reaction with hexafluorocyclotriphosphazene. The phenolic hydroxyl group helps to promote the carbonization reaction of the material at high temperature, while the amino group can increase the nitrogen source and provide more non-flammable gas for the flame retardant process. The carboxyl group in the acrylic acid molecule can chemically bond with the substrate or filler, further improving the polarity of the modifier and providing active sites for subsequent cross-linking reactions, thereby enhancing the thermal stability and interfacial adhesion of the composite material.

[0066] Zinc chloride plays an important role in carbonization catalysis in this system. As an efficient carbonization catalyst, zinc chloride can accelerate the dehydration carbonization process of the substrate at high temperature, reduce the activation energy of the carbonization reaction, and significantly improve the carbonization efficiency. At the same time, zinc chloride can also form a coordination structure with the oxygen-containing or nitrogen-containing groups in the modifier. This coordination effect further enhances the efficiency of the carbonization catalysis process and improves the flame retardant properties of the composite material.

[0067] In order to improve the interfacial bonding ability of the metal coordination modifier, the silane coupling agent KH560 was introduced. The silane group in the KH560 molecule can form a stable chemical bond with the surface of the inorganic filler, while its epoxy group can react chemically with the active groups in the polymer matrix. This bifunctional structure gives KH560 a bridge effect in the "organic-inorganic" interface, significantly improving the chemical bonding and stability of the interface. In addition, the carboxyl group in acrylic acid can also complex with inorganic fillers or other modifiers to further enhance the interfacial bonding. This multiple effect enables the metal coordination modifier to form a stable bond with the polymer matrix and inorganic filler at the same time, thereby effectively improving the mechanical properties, thermal stability and flame retardant efficiency of the composite material.

[0068] Graphene oxide is introduced as a filler in the present invention. Graphene oxide is a two-dimensional nanomaterial containing a large number of oxygen-containing functional groups on the surface and edges, which give it strong polarity, high specific surface area and good chemical reactivity, and can be further functionalized by chemical modification. The lamellar structure of graphene oxide has high strength, and its high specific surface area enables it to form a large interface contact area with a polypropylene matrix, thereby effectively transmitting stress, preventing microcracks from expanding, and significantly improving the mechanical properties of polypropylene. In addition, graphene oxide has good thermal conductivity, and its introduction can form a heat conduction path in the matrix, thereby improving the thermal stability of the composite material.

[0069] The lamellar structure of graphene oxide can form a dense expanded carbonized layer during the combustion process, effectively preventing heat and oxygen from transferring into the interior of the substrate, thereby improving the flame retardant properties of the material. At the same time, the gas produced by the decomposition of graphene oxide at high temperatures also has a certain effect on diluting the combustible gas in the combustion area. When used in conjunction with other flame retardants, graphene oxide can further enhance the physical strength and structural stability of the carbonized layer. However, the oxygen-containing groups on the surface of graphene oxide give it a strong hydrophilicity, which is incompatible with the hydrophobic polypropylene matrix, and easily leads to agglomeration in the matrix and insufficient interfacial bonding. Therefore, further modification is required.

[0070] First, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine was introduced. 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is a typical phospholipid molecule with a hydrophilic phosphate head and a hydrophobic fatty acid tail. On the surface of graphene oxide, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine forms a biomimetic lipid bilayer structure through self-assembly: the hydrophilic head interacts with the hydroxyl or carboxyl groups on the graphene oxide surface through electrostatic interaction and hydrogen bonding, while the hydrophobic tails are arranged with each other through van der Waals forces to form a stable bilayer structure. This bilayer structure effectively reduces the surface energy of graphene oxide, making its surface both hydrophilic and hydrophobic, thereby significantly improving the dispersibility of graphene oxide in the polypropylene matrix.

[0071] Subsequently, 3-glycidylpropyltrimethoxysilane was introduced for further modification. The epoxy group of 3-glycidylpropyltrimethoxysilane chemically combines with the hydroxyl or carboxyl groups on the surface of graphene oxide through a ring-opening reaction to form a stable chemical bond; at the same time, the trimethoxysilane part of 3-glycidylpropyltrimethoxysilane is hydrolyzed under the action of humidity or water to generate silanols, which further condense with each other or with the groups on the surface of graphene oxide to form a Si-O-Si cross-linked structure. This process not only significantly enhances the chemical and thermal stability of graphene oxide, but also fixes the lipid bilayer structure, further improving the modification effect.

[0072] Secondly, N-isopropylacrylamide was grafted onto the surface of biomimetic layer-modified graphene oxide by atom transfer radical polymerization to form thermosensitive polymer poly N-isopropylacrylamide segments, thus constructing a "core-shell-brush" three-layer structure. This structure is formed and functions in the following ways: the core layer is based on graphene oxide, providing high strength, high thermal conductivity and two-dimensional support; the lipid bilayer formed by biomimetic assembly is coated on the surface of graphene oxide to form a shell layer, which improves the dispersibility and interfacial compatibility of graphene oxide and provides a stable substrate for subsequent polymerization reactions; the poly N-isopropylacrylamide segments grafted on the surface by atom transfer radical polymerization form an outer brush-like structure, giving graphene oxide intelligent response capabilities. The poly N-isopropylacrylamide segments are thermosensitive polymers. This thermosensitive response characteristic provides intelligent regulation capabilities for composite materials, allowing them to form an adaptive conductive network structure. When the temperature rises, the poly(N-isopropylacrylamide) chain segments shrink, causing the distance between graphene oxide sheets to decrease, thereby optimizing the conductive path and effectively improving the conductive performance; at the same time, this chain segment shrinkage behavior also helps to limit the occurrence of local overheating, thereby playing a role in thermal management and protection. Conversely, when the temperature drops, the swelling behavior of the chain segments is restored, and the structure of the conductive network is expanded, maintaining the excellent performance of the material at lower temperatures.

[0073] The present invention introduces carbon nanotubes as functional fillers. Carbon nanotubes are hollow tubular nanostructures formed by carbon atoms through sp² hybridization. The high thermal conductivity of carbon nanotubes comes from the efficient transfer of electrons and phonons in their one-dimensional tubular structure. In composite materials, carbon nanotubes can form heat conduction paths through the dispersion and connection of fillers, thereby significantly improving the overall thermal conductivity of the material. This improvement in thermal conductivity helps the material achieve more efficient heat transfer during use and avoid local overheating; Secondly, carbon nanotubes show good thermal stability and resistance to decomposition at high temperatures, and can form a physical barrier during the combustion process to prevent the diffusion of heat and combustible gases, thereby inhibiting the spread of flames. In addition, carbon nanotubes can also work synergistically with other flame retardant fillers to further improve the flame retardant properties of composite materials by improving the density and thermal stability of the carbonized layer; Carbon nanotubes have excellent conductive properties. After introducing carbon nanotubes into a polymer matrix, their antistatic and electromagnetic shielding properties can be significantly improved by forming a conductive network inside the material. The high mechanical strength and high aspect ratio of carbon nanotubes enable them to be effectively used as a reinforcing phase material. By dispersing in the polymer matrix and forming a continuous reinforcing network, carbon nanotubes can significantly improve the tensile strength, modulus and impact resistance of the composite material.

[0074] However, due to the lack of active functional groups on the surface of carbon nanotubes, their interfacial bonding with the polymer matrix is ​​weak, resulting in insufficient stress transfer efficiency, which limits their reinforcement effect in composite materials. Therefore, it is necessary to surface activate or chemically modify carbon nanotubes to enhance their interfacial bonding.

[0075] First, the surface of carbon nanotubes is activated by plasma treatment. Plasma treatment bombards the surface of carbon nanotubes with high-energy particles, destroying the inert carbon-carbon bond structure on the surface and introducing polar active functional groups such as hydroxyl and carboxyl groups on the surface of carbon nanotubes. The introduction of these functional groups significantly enhances the polarity of carbon nanotubes, improves their dispersibility and interfacial bonding in polar matrices. In addition, the presence of hydroxyl and carboxyl groups provides active sites for subsequent chemical modifications, laying the foundation for further construction of multifunctional composite structures.

[0076] Magnesium hydroxide is deposited on the surface of activated carbon nanotubes by chemical precipitation to form a core-shell structure. Specifically, during the chemical precipitation process, the surface functional groups of the activated carbon nanotubes react with Mg²⁺ to promote the uniform deposition of magnesium hydroxide. Finally, a composite structure of "carbon nanotubes@magnesium hydroxide" is formed with carbon nanotubes as the "core" and magnesium hydroxide as the "shell". Magnesium hydroxide is an inorganic flame retardant. During the heating process, magnesium hydroxide undergoes endothermic decomposition and releases water, thereby reducing the temperature of the combustion area, inhibiting the spread of flames, and diluting the concentration of combustible gases in the combustion area, further inhibiting the combustion reaction.

[0077] In order to further enhance the flame retardant effect, the surface of magnesium hydroxide was functionalized by n-octyl phosphite. The phosphate groups in n-octyl phosphite can react or coordinate with the hydroxyl groups on the surface of magnesium hydroxide, thereby introducing phosphorus-containing groups into the composite structure. Finally, a ternary synergistic flame retardant system of "carbon nanotubes + magnesium hydroxide + phosphate" was formed: during the combustion process, magnesium hydroxide releases water by endothermic decomposition, cools the combustion area, and plays a physical flame retardant role; the decomposed magnesium oxide residue has high thermal stability and can form a dense thermal insulation barrier to further prevent heat transfer and flame expansion. The phosphate groups in n-octyl phosphite decompose at high temperatures to generate active phosphorylated products, which can catalyze the carbonization reaction on the surface of the polymer matrix. The carbonization layer acts as a heat-insulating and oxygen-isolating barrier, significantly reducing the combustion rate of the material. At the same time, the phosphorus-containing groups can capture the free radicals generated during the combustion process, inhibit the spread of flames, and further enhance the flame retardant effect. Carbon nanotubes, as the core supporting structure, not only improve the mechanical properties of the composite material, but also promote the efficient transfer and diffusion of combustion heat through their high thermal conductivity, thereby avoiding local overheating.

[0078] In the entire composite material system, there is a significant synergistic effect between graphene oxide and carbon nanotubes. The two-dimensional sheet structure of graphene oxide and the one-dimensional rod-like morphology of carbon nanotubes are complementary in geometry, which enables the two to jointly construct a three-dimensional network structure in the matrix, thereby significantly improving the mechanical properties of the composite material. The high aspect ratio and sheet structure of graphene oxide provide rigid support in the matrix, limiting the plastic deformation of the matrix, while carbon nanotubes, with their high aspect ratio and flexibility, further act as a connecting bridge between the sheets, giving the system higher structural integrity and stress transfer efficiency. In addition, the oxygen-containing functional groups on the surface of graphene oxide and the active groups on the surface of activated carbon nanotubes can form a stable interface bond through hydrogen bonding, further enhancing the interaction between the two. At the same time, the π-π stacking effect between graphene oxide and carbon nanotubes provides additional bonding force, further improving the interface strength of the composite material. Since this three-dimensional network can effectively prevent the propagation of microcracks inside the matrix, the mechanical properties of the composite material are enhanced.

[0079] In terms of flame retardant properties, the synergistic effect between graphene oxide and carbon nanotubes significantly improves the fire resistance of composite materials by constructing a multi-layer flame retardant barrier. Magnesium hydroxide deposited on the surface of carbon nanotubes is an effective inorganic flame retardant. It releases water through its endothermic decomposition at high temperature, which can reduce the temperature of the combustion area and dilute the concentration of combustible gases, playing a role of physical flame retardant. The decomposed magnesium oxide residue further forms a dense thermal insulation barrier to prevent the spread of heat and flames. At the same time, the two-dimensional sheet structure of graphene oxide forms a dense carbonized layer by stacking during the combustion process, which can isolate the transfer of heat and oxygen, thereby delaying the combustion process. This sheet barrier effect is combined with the longitudinal flame retardant effect of carbon nanotubes to construct a multi-scale flame retardant system. In addition, the oxygen-containing functional groups on the surface of graphene oxide can react with the surface of magnesium hydroxide, further enhancing the interface bonding, making this multifunctional filler more stable during the combustion process and more flame retardant. Ultimately, the synergistic effect of carbon nanotubes and graphene oxide effectively improved the flame retardant properties and thermal stability of the composite material through the combination of physical flame retardancy and chemical flame retardancy.

[0080] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses polypropylene as the matrix material, and its chemical inertness and hydrophobicity lead to poor interfacial compatibility with polar fillers. Maleic anhydride and triallyl isocyanurate are grafted onto the polypropylene chain by initiating a free radical reaction with diisopropylbenzene peroxide, and polar groups are introduced to enhance the interfacial bonding force with the filler, while improving the thermal stability and mechanical properties of the material.

[0081] The metal coordination modifier provides abundant phosphorus-nitrogen bonds through the hexafluorocyclotriphosphazene in its molecular structure, which decomposes at high temperature to generate inorganic phosphoric acid and nitrogen oxides, which not only promotes the carbonization of the matrix and forms a thermally stable expanded carbon layer to insulate heat and oxygen, but also dilutes the concentration of combustible gas in the combustion area by releasing non-combustible gas, significantly improving the flame retardant performance. The function of the modifier is further enhanced by the introduction of 4-aminophenol and acrylic acid, which respectively improves the thermal stability and flame retardant efficiency of the composite material by promoting carbonization and enhancing interfacial adhesion. In addition, zinc chloride as a carbonization catalyst significantly reduces the activation energy of the carbonization reaction and improves the carbonization efficiency, while further enhancing the flame retardant effect through coordination with the modifier. The silane coupling agent KH560 enhances the chemical bonding between the inorganic filler and the matrix through its dual-functional structure.

[0082] Graphene oxide is used as a functional filler. By introducing 1,2-dipalmitoyl-sn-glycero-3-phosphocholine to form a bionic lipid bilayer, the dispersibility and interfacial bonding strength are improved. Subsequently, the chemical stability and thermal stability of graphene oxide are further enhanced by chemical modification with 3-glycidylpropyltrimethoxysilane, and it is endowed with thermosensitive intelligent response ability by grafting with poly (N-isopropylacrylamide), thereby optimizing the conductivity and thermal management performance.

[0083] Carbon nanotubes, as another filler, need to be treated with plasma to introduce polar functional groups to enhance interfacial bonding; magnesium hydroxide is then deposited on its surface by chemical precipitation to form a core-shell structure, constructing a physical flame retardant barrier for endothermic decomposition and gas dilution. n-octyl phosphite is further introduced for modification to form a ternary synergistic flame retardant system based on magnesium hydroxide, which significantly improves the flame retardant performance and carbonization ability.

[0084] In the whole system, the two-dimensional sheet structure of graphene oxide and the one-dimensional rod structure of carbon nanotubes complement each other in geometric morphology, constructing a stable three-dimensional network structure and significantly improving the mechanical properties of the composite material. The two also show synergistic effects in flame retardancy: the sheet barrier effect of graphene oxide and the endothermic decomposition of magnesium hydroxide on the surface of carbon nanotubes jointly construct a multi-layer flame retardant barrier, further enhancing the thermal stability and fire resistance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 A high-resolution transmission electron microscopy image of the bionic layer modified graphene oxide provided in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the carbon nanotube / magnesium hydroxide core-shell material provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0086] The technical solution of the present invention is described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limitations on the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments recorded herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments recorded herein.

[0087] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products without further purification or treatment.

[0088] Example 1 like Figure 1 As shown, this embodiment provides an environmentally friendly polypropylene-based composite material and a preparation method thereof, and the preparation method specifically comprises the following steps: S11: using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine to prepare a lipid film by rotary evaporation; dispersing graphene oxide and compounding it with the lipid film and adding 3-glycidylpropyltrimethoxysilane for surface modification to obtain a biomimetic layer-modified graphene oxide; Specifically, S11: 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine is dispersed in ethyl acetate, and a lipid film is obtained by rotary evaporation; graphene oxide is dispersed in deionized water at a mass ratio of 1:200, and the pH is adjusted to 7.3 with a sodium hydroxide solution having a concentration of 0.12 mol / L to obtain a dispersion A; the dispersion A is added to the lipid film, wherein the mass ratio of graphene oxide to the lipid film is 1:7 to obtain a mixed solution B; an ethanol solution of 3-glycidylpropyltrimethoxysilane with a mass fraction of 2.3 wt.% is added to the mixed solution B to obtain a reaction solution C, wherein the mass ratio of 3-glycidylpropyltrimethoxysilane to graphene oxide is 4.6:1, and the mixture is stirred at 55°C at a speed of 400 rpm for 2.6 hours, and then centrifuged, washed, and vacuum dried to obtain a biomimetic layer-modified graphene oxide; Figure 1 From its high-resolution transmission electron microscope image, it can be observed that the graphene oxide flakes are relatively clear, and due to the presence of the lipid thin layer, the edges of the flakes show a shallow local contrast.

[0089] S12: dispersing the biomimetic layer modified graphene oxide in water phase, adding N-isopropylacrylamide monomer, performing active polymerization in a cuprous bromide / pentamethyldiethylenetriamine catalytic system, and then adding sodium ascorbate to terminate the reaction, thereby obtaining double modified graphene oxide; Specifically, S12: dispersing the bionic layer modified graphene oxide in deionized water to obtain a dispersion D, wherein the mass ratio of the bionic layer modified graphene oxide to deionized water in the dispersion D is 1:100, adding N-isopropylacrylamide, cuprous bromide, and pentamethyldiethylenetriamine to obtain a reaction solution E, wherein the concentration of N-isopropylacrylamide in the reaction solution E is 32 mg / mL, the mass ratio of cuprous bromide to N-isopropylacrylamide is 1:100, the mass ratio of pentamethyldiethylenetriamine to N-isopropylacrylamide is 1.5:100, and stirring and reacting at 40° C. for 8.8 hours after deoxygenation; adding sodium ascorbate in a mass ratio of 5.6:100 to N-isopropylacrylamide, centrifuging, washing, and vacuum drying to obtain double modified graphene oxide; S13: After plasma activation of the carbon nanotubes, the carbon nanotubes are modified with magnesium sulfate to obtain a carbon nanotube / magnesium hydroxide core-shell material; then n-octyl phosphite is introduced for surface modification to obtain a multi-layer flame retardant modified carbon nanotube; Specifically, S13: plasma-treating carbon nanotubes to obtain surface-activated carbon nanotubes; dispersing the surface-activated carbon nanotubes in deionized water to obtain a surface-activated carbon nanotube dispersion with a concentration of 1.2 mg / mL, adding the dispersion to a 0.1 M magnesium sulfate solution and stirring to obtain a reaction solution F, wherein the mass ratio of carbon nanotubes to magnesium sulfate is 1:6, dropping a sodium hydroxide solution until the pH of the reaction solution F reaches 10 to obtain a reaction solution G, stirring and reacting at 50°C for 4.5 hours, centrifuging, washing, and drying to obtain a carbon nanotube / magnesium hydroxide core-shell material; dispersing the carbon nanotube / magnesium hydroxide core-shell material in anhydrous ethanol at a concentration of 2 mg / mL, dropping a tetrahydrofuran solution of n-octyl phosphite with a mass fraction of 5 wt.% to obtain a reaction solution H, wherein the mass ratio of n-octyl phosphite to magnesium sulfate is 1:3, reacting at 52°C for 6.8 hours, filtering, washing, and drying to obtain a multi-layer flame-retardant modified carbon nanotube; Figure 2 This is a scanning electron microscope image of the carbon nanotube / magnesium hydroxide core-shell material. It can be observed that there is a relatively uniform deposition structure of sodium hydroxide particles on the surface of the carbon nanotube.

[0090] S21: using hexafluorocyclotriphosphazene to react with 4-aminophenol in the presence of triethylamine, then introducing silane coupling agent KH560 and tetrabutylammonium bromide, and performing metal coordination modification with acrylic acid under the catalysis of zinc chloride to obtain a metal coordination modifier; Specifically, S21: under an ice bath, a tetrahydrofuran solution of 4-aminophenol with a concentration of 20 mg / mL and triethylamine were added dropwise to a tetrahydrofuran solution of hexafluorocyclotriphosphazene with a mass ratio of 1:45 to obtain a reaction solution I, wherein the mass ratio of 4-aminophenol to hexafluorocyclotriphosphazene is 1.5:1, and the molar ratio of triethylamine to 4-aminophenol is 1:1. After stirring at room temperature for 12 hours under nitrogen protection, a silane coupling agent KH560 solution with a molar ratio of 5:1 to hexafluorocyclotriphosphazene and a silane coupling agent KH560 solution with a molar ratio of 5:1 to hexafluorocyclotriphosphazene were added. The reaction mixture was added with tetrabutylammonium bromide in a mass ratio of 0.5:100 of tetrabutylammonium bromide and 560 to obtain a reaction solution J, wherein the molar ratio of the silane coupling agent KH560 to deionized water in the silane coupling agent KH560 solution was 1:2, and acrylic acid and zinc chloride were added after reacting at a constant temperature of 63°C for 4.6 hours to obtain a mixed solution, wherein the molar ratio of acrylic acid to the silane coupling agent KH560 was 1:1, and the molar ratio of zinc chloride to acrylic acid was 0.8:2, and the mixture was stirred at room temperature for 3 hours, concentrated under reduced pressure, recrystallized, and dried in vacuo to obtain a metal coordination modifier; S22: preactivating polypropylene with diisopropylbenzene oxide to obtain preactivated polypropylene, and melt-grafting the preactivated polypropylene with a metal coordination modifier, maleic anhydride and triallyl isocyanurate to obtain modified polypropylene; Specifically, S22: premixing polypropylene, diisopropylbenzene peroxide, antioxidant 1010 and zinc stearate at 175° C. for 5 minutes under nitrogen protection to obtain preactivated polypropylene, wherein the mass ratio of diisopropylbenzene peroxide to polypropylene is 0.15:100, the mass ratio of antioxidant 1010 to polypropylene is 0.5:100, and the mass ratio of zinc stearate to polypropylene is 0.5:100; adding a metal coordination modifier, maleic anhydride and triallyl isocyanurate to the preactivated polypropylene, wherein the mass ratio of the metal coordination modifier to the preactivated polypropylene is 3:100, the mass ratio of maleic anhydride to the preactivated polypropylene is 1:100, and the mass ratio of triallyl isocyanurate to the preactivated polypropylene is 1.3:100; melt grafting is performed at 182° C. under a vacuum environment for 7 minutes, followed by cooling, and pelletizing to obtain modified polypropylene; S23: The modified polypropylene, double-modified graphene oxide and multi-layer flame-retardant modified carbon nanotubes are melt-blended and extruded through a twin-screw extruder to obtain an environmentally friendly polypropylene-based composite material.

[0091] Specifically, S23: modified polypropylene, double modified graphene oxide and BYK-9077 are premixed in a high-speed mixer at a speed of 2000 rpm for 6 minutes, and then multi-layer flame retardant modified carbon nanotubes are added and mixed evenly, wherein the mass ratio of modified polypropylene, double modified graphene oxide, multi-layer flame retardant modified carbon nanotubes and dispersant is 100:1:3:0.2, and then extruded using a twin-screw extruder, wherein the operating temperature of the twin-screw extruder is 170°C, the operating speed is 170 rpm, and water-cooled pelletizing is used to obtain an environmentally friendly polypropylene-based composite material.

[0092] Example 2 This embodiment provides an environmentally friendly polypropylene-based composite material and a preparation method thereof, wherein the preparation method specifically comprises the following steps: S11: using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine to prepare a lipid film by rotary evaporation; dispersing graphene oxide and compounding it with the lipid film and adding 3-glycidylpropyltrimethoxysilane for surface modification to obtain a biomimetic layer-modified graphene oxide; Specifically, S11: 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine is dispersed in ethyl acetate, and a lipid film is obtained by rotary evaporation; graphene oxide is dispersed in deionized water at a mass ratio of 1:250, and the pH is adjusted to 7.5 with a sodium hydroxide solution having a concentration of 0.18 mol / L to obtain a dispersion A; the dispersion A is added to the lipid film, wherein the mass ratio of graphene oxide to the lipid film is 1:8 to obtain a mixed solution B; an ethanol solution of 3-glycidylpropyltrimethoxysilane with a mass fraction of 2.7 wt.% is added to the mixed solution B to obtain a reaction solution C, wherein the mass ratio of 3-glycidylpropyltrimethoxysilane to graphene oxide is 4:1, and the mixture is stirred at 60°C and a speed of 500 rpm for 2 hours, and then centrifuged, washed, and vacuum dried to obtain a biomimetic layer modified graphene oxide; S12: dispersing the biomimetic layer modified graphene oxide in water phase, adding N-isopropylacrylamide monomer, performing active polymerization in a cuprous bromide / pentamethyldiethylenetriamine catalytic system, and then adding sodium ascorbate to terminate the reaction, thereby obtaining double modified graphene oxide; Specifically, S12: dispersing the bionic layer modified graphene oxide in deionized water to obtain a dispersion D, wherein the mass ratio of the bionic layer modified graphene oxide to deionized water in the dispersion D is 1:150, adding N-isopropylacrylamide, cuprous bromide, and pentamethyldiethylenetriamine to obtain a reaction solution E, wherein the concentration of N-isopropylacrylamide in the reaction solution E is 34 mg / mL, the mass ratio of cuprous bromide to N-isopropylacrylamide is 1.5:100, the mass ratio of pentamethyldiethylenetriamine to N-isopropylacrylamide is 2:100, and stirring and reacting at 45° C. for 10 hours after deoxygenation; adding sodium ascorbate in a mass ratio of 6:100 to N-isopropylacrylamide, centrifuging, washing, and vacuum drying to obtain double modified graphene oxide; S13: After plasma activation of the carbon nanotubes, the carbon nanotubes are modified with magnesium sulfate to obtain a carbon nanotube / magnesium hydroxide core-shell material; then n-octyl phosphite is introduced for surface modification to obtain a multi-layer flame retardant modified carbon nanotube; Specifically, S13: plasma-treating carbon nanotubes to obtain surface-activated carbon nanotubes; dispersing the surface-activated carbon nanotubes in deionized water to obtain a surface-activated carbon nanotube dispersion with a concentration of 2 mg / mL, adding the dispersion to a 0.2 M magnesium sulfate solution and stirring to obtain a reaction solution F, wherein the mass ratio of carbon nanotubes to magnesium sulfate is 1:7, dropping a sodium hydroxide solution until the pH of the reaction solution F reaches 11 to obtain a reaction solution G, stirring and reacting at 60°C for 5 hours, centrifuging, washing, and drying to obtain a carbon nanotube / magnesium hydroxide core-shell material; dispersing the carbon nanotube / magnesium hydroxide core-shell material in anhydrous ethanol at a concentration of 3 mg / mL, dropping a tetrahydrofuran solution of n-octyl phosphite with a mass fraction of 6 wt.% to obtain a reaction solution H, wherein the mass ratio of n-octyl phosphite to magnesium sulfate is 1:4, reacting at 59°C for 6.3 hours, filtering, washing, and drying to obtain a multi-layer flame-retardant modified carbon nanotube; S21: using hexafluorocyclotriphosphazene to react with 4-aminophenol in the presence of triethylamine, then introducing silane coupling agent KH560 and tetrabutylammonium bromide, and performing metal coordination modification with acrylic acid under the catalysis of zinc chloride to obtain a metal coordination modifier; Specifically, S21: under an ice bath, a tetrahydrofuran solution of 4-aminophenol with a concentration of 25 mg / mL and triethylamine were added dropwise to a tetrahydrofuran solution of hexafluorocyclotriphosphazene with a mass ratio of 1:40 to obtain a reaction solution I, wherein the mass ratio of 4-aminophenol to hexafluorocyclotriphosphazene is 2:1, and the molar ratio of triethylamine to 4-aminophenol is 1.5:1. After stirring at room temperature for 15 hours under nitrogen protection, a silane coupling agent KH560 solution with a molar ratio of 6:1 to hexafluorocyclotriphosphazene and a silane coupling agent KH560 solution with a molar ratio of 6:1 to hexafluorocyclotriphosphazene were added. 60 with a mass ratio of 1:100 tetrabutylammonium bromide to obtain a reaction solution J, wherein the molar ratio of silane coupling agent KH560 to deionized water in the silane coupling agent KH560 solution is 1:3, and acrylic acid and zinc chloride are added after reacting at a constant temperature of 64°C for 4.8 hours to obtain a mixed solution, wherein the molar ratio of acrylic acid to silane coupling agent KH560 is 1.5:1, and the molar ratio of zinc chloride to acrylic acid is 1.2:2, and after stirring at room temperature for 2.3 hours, it is concentrated under reduced pressure, recrystallized, and vacuum dried to obtain a metal coordination modifier; S22: preactivating polypropylene with diisopropylbenzene oxide to obtain preactivated polypropylene, and melt-grafting the preactivated polypropylene with a metal coordination modifier, maleic anhydride and triallyl isocyanurate to obtain modified polypropylene; Specifically, S22: premixing polypropylene, diisopropylbenzene peroxide, antioxidant 168 and zinc stearate under nitrogen protection at 176° C. for 8 minutes to obtain preactivated polypropylene, wherein the mass ratio of diisopropylbenzene peroxide to polypropylene is 0.17:100, the mass ratio of antioxidant 168 to polypropylene is 0.56:100, and the mass ratio of zinc stearate to polypropylene is 0.6:100; adding a metal coordination modifier, maleic anhydride and triallyl isocyanurate to the preactivated polypropylene, wherein the mass ratio of the metal coordination modifier to the preactivated polypropylene is 4.5:100, the mass ratio of maleic anhydride to the preactivated polypropylene is 1.5:100, and the mass ratio of triallyl isocyanurate to the preactivated polypropylene is 1.5:100; melt grafting is performed at 183° C. under a vacuum environment for 7.8 minutes, then cooled, and pelletized to obtain modified polypropylene; S23: The modified polypropylene, double-modified graphene oxide and multi-layer flame-retardant modified carbon nanotubes are melt-blended and extruded through a twin-screw extruder to obtain an environmentally friendly polypropylene-based composite material.

[0093] Specifically, S23: modified polypropylene, double modified graphene oxide and BYK-2150 are premixed in a high-speed mixer at a speed of 2500 rpm for 7 minutes, and then multi-layer flame retardant modified carbon nanotubes are added and mixed evenly, wherein the mass ratio of modified polypropylene, double modified graphene oxide, multi-layer flame retardant modified carbon nanotubes and dispersant is 100:3:1:0.4, and then extruded using a twin-screw extruder, wherein the operating temperature of the twin-screw extruder is 178°C, the operating speed is 178 rpm, and water-cooled pelletizing is used to obtain an environmentally friendly polypropylene-based composite material.

[0094] Example 3 This embodiment provides an environmentally friendly polypropylene-based composite material and a preparation method thereof, wherein the preparation method specifically comprises the following steps: S11: using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine to prepare a lipid film by rotary evaporation; dispersing graphene oxide and compounding it with the lipid film and adding 3-glycidylpropyltrimethoxysilane for surface modification to obtain a biomimetic layer-modified graphene oxide; Specifically, S11: 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is dispersed in ethyl acetate, and a lipid film is obtained by rotary evaporation; graphene oxide is dispersed in deionized water at a mass ratio of 1:220, and the pH is adjusted to 7.0 with a 0.1 mol / L sodium hydroxide solution to obtain dispersion A; dispersion A is added to the lipid film, and the mass ratio of graphene oxide to the lipid film is 1:5 to obtain mixture B; an ethanol solution of 3-glycidoxypropyltrimethoxysilane with a mass fraction of 3 wt.% is added to mixture B, where the mass ratio of 3-glycidoxypropyltrimethoxysilane to graphene oxide is 5:1, and the mixture is stirred and reacted at 57 °C at a rotation speed of 460 rpm for 3 h, then centrifuged, washed, and vacuum dried to obtain biomimetic layer modified graphene oxide; S12: The biomimetic layer modified graphene oxide is dispersed in an aqueous phase, N-isopropylacrylamide monomer is added, and living polymerization is carried out in a copper(I) bromide / pentamethyldiethylenetriamine catalytic system, and then sodium ascorbate is added to terminate the reaction to obtain doubly modified graphene oxide; Specifically, S12: The biomimetic layer modified graphene oxide is dispersed in deionized water to obtain dispersion D, where the mass ratio of the biomimetic layer modified graphene oxide to deionized water in dispersion D is 1:135, N-isopropylacrylamide, copper(I) bromide, and pentamethyldiethylenetriamine are added to obtain reaction solution E, where the concentration of N-isopropylacrylamide in reaction solution E is 30 mg / mL, the mass ratio of copper(I) bromide to N-isopropylacrylamide is 1.2:100, the mass ratio of pentamethyldiethylenetriamine to N-isopropylacrylamide is 1.8:100, and after deoxygenation, the mixture is stirred and reacted at 42 °C for 9.8 h; sodium ascorbate with a mass ratio of 5.8:100 to N-isopropylacrylamide is added, centrifuged, washed, and vacuum dried to obtain doubly modified graphene oxide; S13: After the carbon nanotubes are activated by plasma, they are modified with magnesium sulfate to obtain a carbon nanotube / magnesium hydroxide core-shell material; then n-octyl phosphite is introduced for surface modification to obtain multi-level flame retardant modified carbon nanotubes; Specifically, S13: Plasma treat the carbon nanotubes to obtain surface-activated carbon nanotubes; Disperse the surface-activated carbon nanotubes in deionized water to obtain a surface-activated carbon nanotube dispersion with a concentration of 1.6 mg / mL, add it to a magnesium sulfate solution with a concentration of 0.16 M and stir to obtain reaction solution F, where the mass ratio of carbon nanotubes to magnesium sulfate is 1:6.6, add sodium hydroxide solution until the pH of reaction solution F reaches 10.5 to obtain reaction solution G, stir and react at 55 °C for 4.8 h, then centrifuge, wash, and dry to obtain carbon nanotube / magnesium hydroxide core-shell material; Disperse the carbon nanotube / magnesium hydroxide core-shell material in absolute ethanol at a concentration of 2.5 mg / mL, add a tetrahydrofuran solution of n-octyl phosphite with a mass fraction of 5.3 wt.% to obtain reaction solution H, where the mass ratio of n-octyl phosphite to magnesium sulfate is 1:3.7, react at 50 °C for 6 h, then filter, wash, and dry to obtain multi-level flame-retardant modified carbon nanotubes; S21: React hexachlorocyclotriphosphazene with 4-aminophenol in the presence of triethylamine, then introduce silane coupling agent KH560 and tetrabutylammonium bromide, and carry out metal coordination modification with acrylic acid under the catalysis of zinc chloride to obtain a metal coordination modifier; Specifically, S21: Under ice bath, dropwise add a 4-aminophenol tetrahydrofuran solution with a concentration of 22 mg / mL and triethylamine to a tetrahydrofuran solution of hexachlorocyclotriphosphazene with a mass ratio of 1:48 to obtain reaction solution I, where the mass ratio of 4-aminophenol to hexachlorocyclotriphosphazene is 1.8:1 and the molar ratio of triethylamine to 4-aminophenol is 1:1.2. After stirring and reacting at room temperature for 13 h under nitrogen protection, add a silane coupling agent KH560 solution with a molar ratio of 5.5:1 to hexachlorocyclotriphosphazene and tetrabutylammonium bromide with a mass ratio of 0.75:100 to KH560 to obtain reaction solution J, where the molar ratio of silane coupling agent KH560 to deionized water in the silane coupling agent KH560 solution is 1:4. After reacting at a constant temperature of 60 °C for 4 h, add acrylic acid and zinc chloride to obtain a mixed solution, where the molar ratio of acrylic acid to silane coupling agent KH560 is 1.4:1 and the molar ratio of zinc chloride to acrylic acid is 1:2. After stirring at room temperature for 2.7 h, carry out vacuum concentration, recrystallization, and vacuum drying to obtain a metal coordination modifier; S22: Pre-activate polypropylene with diisopropylbenzene peroxide to obtain pre-activated polypropylene, and carry out melt grafting with a metal coordination modifier, maleic anhydride, and triallyl isocyanurate to obtain modified polypropylene; Specifically, in S22: Polypropylene, dicumyl peroxide, antioxidant 168, and zinc stearate are premixed at 178°C for 6 min under nitrogen protection to obtain pre-activated polypropylene. The mass ratio of dicumyl peroxide to polypropylene is 0.18:100, the mass ratio of antioxidant 168 to polypropylene is 0.58:100, and the mass ratio of zinc stearate to polypropylene is 0.7:100. A metal coordination modifier, maleic anhydride, and triallyl isocyanurate are added to the pre-activated polypropylene. The mass ratio of the metal coordination modifier to the pre-activated polypropylene is 4:100, the mass ratio of maleic anhydride to the pre-activated polypropylene is 1.8:100, and the mass ratio of triallyl isocyanurate to the pre-activated polypropylene is 1:100. After melt grafting at 180°C for 6 min in a vacuum environment and then cooling, it is pelletized to obtain modified polypropylene. S23: The modified polypropylene, double-modified graphene oxide, and multi-level flame-retardant modified carbon nanotubes are melt-blended and extruded through a twin-screw extruder to obtain an environmentally friendly polypropylene-based composite material.

[0095] Specifically, in S23: The modified polypropylene, double-modified graphene oxide, and BYK-2150 are premixed in a high-speed mixer at a rotation speed of 2300 rpm for 5 min, and then the multi-level flame-retardant modified carbon nanotubes are added and mixed evenly. The mass ratio of the modified polypropylene, double-modified graphene oxide, multi-level flame-retardant modified carbon nanotubes, and dispersant is 100:2:2:0.3. Subsequently, it is extruded using a twin-screw extruder. The working temperature of the twin-screw extruder is 175°C, the working rotation speed is 160 rpm, and water-cooled pelletization is performed to obtain an environmentally friendly polypropylene-based composite material.

[0096] Example 4 This example provides an environmentally friendly polypropylene-based composite material and a preparation method thereof. The preparation method specifically includes the following steps: S11: Use 1,2-dipalmitoyl-sn-glycero-3-phosphocholine to prepare a lipid film by rotary evaporation; after dispersing graphene oxide, it is compounded with the lipid film and 3-glycidoxypropyltrimethoxysilane is added for surface modification to obtain biomimetic layer-modified graphene oxide. Specifically, S11: 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is dispersed in ethyl acetate, and a lipid film is obtained by rotary evaporation; graphene oxide is dispersed in deionized water at a mass ratio of 1:240, and the pH is adjusted to 7.4 with a 0.2 mol / L sodium hydroxide solution to obtain dispersion A; dispersion A is added to the lipid film, and the mass ratio of graphene oxide to the lipid film is 1:6 to obtain mixture B; an ethanol solution of 3-glycidylpropyltrimethoxysilane with a mass fraction of 2 wt.% is added to mixture B, where the mass ratio of 3-glycidylpropyltrimethoxysilane to graphene oxide is 6:1, and the mixture is stirred and reacted at 59 °C at a rotation speed of 480 rpm for 2.3 h, then centrifuged, washed, and vacuum dried to obtain biomimetic layer-modified graphene oxide; S12: The biomimetic layer-modified graphene oxide is dispersed in an aqueous phase, N-isopropylacrylamide monomer is added, and living polymerization is carried out in a copper(I) bromide / pentamethyldiethylenetriamine catalytic system, and then sodium ascorbate is added to terminate the reaction, and double-modified graphene oxide is obtained after treatment; Specifically, S12: The biomimetic layer-modified graphene oxide is dispersed in deionized water to obtain dispersion D, where the mass ratio of the biomimetic layer-modified graphene oxide to deionized water in dispersion D is 1:145, N-isopropylacrylamide, copper(I) bromide, and pentamethyldiethylenetriamine are added to obtain reaction solution E, where the concentration of N-isopropylacrylamide in reaction solution E is 35 mg / mL, the mass ratio of copper(I) bromide to N-isopropylacrylamide is 1.4:100, the mass ratio of pentamethyldiethylenetriamine to N-isopropylacrylamide is 1.7:100, and after deoxygenation, the mixture is stirred and reacted at 43 °C for 8 h; sodium ascorbate with a mass ratio of 5:100 to N-isopropylacrylamide is added, centrifuged, washed, and vacuum dried to obtain double-modified graphene oxide; S13: After the carbon nanotubes are activated by plasma, they are modified with magnesium sulfate to obtain a carbon nanotube / magnesium hydroxide core-shell material; then n-octyl phosphite is introduced for surface modification to obtain multi-level flame-retardant modified carbon nanotubes; Specifically, S13: The carbon nanotubes are subjected to plasma treatment to obtain surface-activated carbon nanotubes; the surface-activated carbon nanotubes are dispersed in deionized water to obtain a surface-activated carbon nanotube dispersion with a concentration of 1 mg / mL, which is added to a magnesium sulfate solution with a concentration of 0.12 M and stirred to obtain reaction solution F, where the mass ratio of carbon nanotubes to magnesium sulfate is 1:6.8. Sodium hydroxide solution is added dropwise to reaction solution F until the pH reaches 10.7 to obtain reaction solution G, and after stirring and reacting at 56 °C for 4 h, centrifugation, washing, and drying are carried out to obtain carbon nanotube / magnesium hydroxide core-shell material; the carbon nanotube / magnesium hydroxide core-shell material is dispersed in absolute ethanol at a concentration of 2.3 mg / mL, and a tetrahydrofuran solution of n-octyl phosphite with a mass fraction of 5.6 wt.% is added dropwise to obtain reaction solution H, where the mass ratio of n-octyl phosphite to magnesium sulfate is 1:3.4. After reacting at 60 °C for 7 h, filtration, washing, and drying are carried out to obtain multi-level flame-retardant modified carbon nanotubes; S21: Hexafluorocyclotriphosphazene reacts with 4-aminophenol in the presence of triethylamine, and then a silane coupling agent KH560 and tetrabutylammonium bromide are introduced, and metal coordination modification is carried out with acrylic acid under the catalysis of zinc chloride to obtain a metal coordination modifier; Specifically, S21: A 4-aminophenol tetrahydrofuran solution with a concentration of 23 mg / mL and triethylamine are added dropwise to a tetrahydrofuran solution of hexafluorocyclotriphosphazene with a mass ratio of 1:50 in an ice bath to obtain reaction solution I, where the mass ratio of 4-aminophenol to hexafluorocyclotriphosphazene is 1.7:1 and the molar ratio of triethylamine to 4-aminophenol is 1.3:1. After stirring and reacting at room temperature for 14 h under nitrogen protection, a silane coupling agent KH560 solution with a molar ratio of 5.6:1 to hexafluorocyclotriphosphazene and tetrabutylammonium bromide with a mass ratio of 0.88:100 to KH560 are added to obtain reaction solution J, where the molar ratio of silane coupling agent KH560 to deionized water in the silane coupling agent KH560 solution is 1:1. After reacting at a constant temperature of 65 °C for 6 h, acrylic acid and zinc chloride are added to obtain a mixed solution, where the molar ratio of acrylic acid to silane coupling agent KH560 is 1.2:1 and the molar ratio of zinc chloride to acrylic acid is 1.1:2. After stirring at room temperature for 2 h, concentration under reduced pressure, recrystallization, and vacuum drying are carried out to obtain a metal coordination modifier; S22: Polypropylene is pre-activated with dicumyl peroxide to obtain pre-activated polypropylene, which is melt-grafted with a metal coordination modifier, maleic anhydride, and triallyl isocyanurate to obtain modified polypropylene; Specifically, in S22: Polypropylene, dicumyl peroxide, antioxidant 1010, and zinc stearate are premixed under nitrogen protection at 180°C for 7 minutes to obtain pre-activated polypropylene, where the mass ratio of dicumyl peroxide to polypropylene is 0.2:100, the mass ratio of antioxidant 1010 to polypropylene is 0.6:100, and the mass ratio of zinc stearate to polypropylene is 1:100; a metal coordination modifier, maleic anhydride, and triallyl isocyanurate are added to the pre-activated polypropylene, where the mass ratio of the metal coordination modifier to the pre-activated polypropylene is 5:100, the mass ratio of maleic anhydride to the pre-activated polypropylene is 2:100, the mass ratio of triallyl isocyanurate to the pre-activated polypropylene is 1.2:100, and it is melt grafted at 185°C for 8 minutes in a vacuum environment and then cooled, and pelletized to obtain modified polypropylene; S23: The modified polypropylene, double-modified graphene oxide, and multi-level flame-retardant modified carbon nanotubes are melt-blended and extruded through a twin-screw extruder to obtain an environmentally friendly polypropylene-based composite material.

[0097] Specifically, in S23: The modified polypropylene, double-modified graphene oxide, and BYK-9077 are premixed in a high-speed mixer at a rotation speed of 2400 rpm for 8 minutes, and then the multi-level flame-retardant modified carbon nanotubes are added and mixed evenly, where the mass ratio of the modified polypropylene, double-modified graphene oxide, multi-level flame-retardant modified carbon nanotubes, and dispersant is 100:2.3:2.8:0.34, and then it is extruded using a twin-screw extruder, where the operating temperature of the twin-screw extruder is 180°C, the operating rotation speed is 180 rpm, and water-cooled pelletization is performed to obtain an environmentally friendly polypropylene-based composite material.

[0098] Comparative Example 1 This comparative example provides an environmentally friendly polypropylene-based composite material. The difference from Example 1 is that in step S11, the mass ratio of graphene oxide to the lipid film is 1:10, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0099] Comparative Example 2 This comparative example provides an environmentally friendly polypropylene-based composite material. The difference from Example 1 is that in step S11, the mass ratio of graphene oxide to the lipid film is 1:2, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0100] Comparative Example 3 This comparative example provides an environmentally friendly polypropylene-based composite material. The difference from Example 1 is that in step S22, the mass ratio of the metal coordination modifier to the pre-activated polypropylene is 8:100, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0101] Comparative Example 4 This comparative example provides an environmentally friendly polypropylene-based composite material. The difference from Example 1 is that in step S22, the mass ratio of the metal coordination modifier to the pre-activated polypropylene is 1:100, and the other operation steps and process parameters are exactly the same as those in Example 1.

[0102] Comparative Example 5 This comparative example provides an environmentally friendly polypropylene-based composite material. The difference from Example 1 is that in step S23, the mass ratio of the modified polypropylene, doubly modified graphene oxide, multi-level flame-retardant modified carbon nanotubes, and dispersant is 100:1:5:0.2, and the other operation steps and process parameters are exactly the same as those in Example 1.

[0103] Comparative Example 6 This comparative example provides an environmentally friendly polypropylene-based composite material. The difference from Example 1 is that in step S23, the mass ratio of the modified polypropylene, doubly modified graphene oxide, multi-level flame-retardant modified carbon nanotubes, and dispersant is 100:1:0.5:0.2, and the other operation steps and process parameters are exactly the same as those in Example 1.

[0104] Perform performance tests on the environmentally friendly polypropylene-based composite materials of the above Examples 1-6 and Comparative Examples 1-6. The specific process is as follows: Test the tensile strength and elongation at break of the composite material according to GB / T 1040.2-2022; Test the vertical burning rating of the sample according to GB / T 2408-2021; The test results are shown in Table 1.

[0105] Table 1: Performance test results of the environmentally friendly polypropylene-based composite materials of Examples 1-4 and Comparative Examples 1-6

[0106] From the test results of Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that graphene oxide itself forms a dense expanded carbonized layer through lamellar stacking during combustion, playing a role in heat insulation and oxygen isolation. 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine forms a lipid bilayer structure on the surface of graphene oxide, enhancing its dispersibility and interfacial binding force in the polypropylene matrix. Excessive 1,2-dipalmitoyl-sn-glycero-3-phosphocholine may cause high coverage on the surface of graphene oxide, affecting the stacking of its lamellae and the formation of the heat conduction path, thereby reducing the mechanical properties and flame retardancy; if the amount is insufficient, incomplete coverage of the lipid layer will lead to a decrease in the dispersibility and interfacial binding force of graphene oxide in the polypropylene matrix, significantly weakening the enhancement effect of the mechanical properties and reducing the flame retardancy.

[0107] From the test results of Example 1 and Comparative Example 3 and Comparative Example 4, it can be seen that hexafluorocyclotriphosphazene in the metal coordination modifier enhances the interfacial compatibility with the polypropylene matrix through chemical bonding with silane coupling agent KH560 and acrylic acid. At the same time, components such as 4-aminophenol and zinc chloride are introduced to promote the cross-linking behavior of the material, enhance the structural integrity and thermal stability of the composite material. Excessive use of it will cause excessive cross-linking of the polypropylene matrix, reduce its toughness, and affect the mechanical properties. At the same time, excessive catalytic charring may lead to too much char layer, affecting the integrity of the material; if the amount used is insufficient, the decomposition products are not enough to form an effective expanded char layer, and the flame retardant performance will decline.

[0108] From the test results of Example 1 and Comparative Example 5 and Comparative Example 6, it can be seen that the addition of multi-level flame retardant modified carbon nanotubes can improve the mechanical properties and flame retardant properties of polypropylene composites through the three-level structures of "core", "shell" and "brush". When its content is too high, it will cause uneven dispersion in the matrix, form aggregates, and reduce the stress transfer efficiency and flame retardant properties; when its content is too low, a continuous reinforcement network cannot be formed, and the improvement of mechanical properties and flame retardant properties is limited.

[0109] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing an environmentally friendly polypropylene-based composite material, characterized in that: The preparation method comprises: S21: using hexafluorocyclotriphosphazene to react with 4-aminophenol in the presence of triethylamine, then introducing silane coupling agent KH560 and tetrabutylammonium bromide, and performing metal coordination modification with acrylic acid under the catalysis of zinc chloride to obtain a metal coordination modifier; S22: preactivating polypropylene with diisopropylbenzene oxide to obtain preactivated polypropylene, and melt-grafting the preactivated polypropylene with a metal coordination modifier, maleic anhydride and triallyl isocyanurate to obtain modified polypropylene; S23: The modified polypropylene is melt-blended and extruded with double-modified graphene oxide, multi-layer flame-retardant modified carbon nanotubes and a dispersant through a twin-screw extruder to obtain an environmentally friendly polypropylene-based composite material.

2. The method for preparing an environmentally friendly polypropylene-based composite material according to claim 1, characterized in that: The preparation method of the double-modified graphene oxide is: S11: using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine to prepare a lipid film by rotary evaporation; dispersing graphene oxide and compounding it with the lipid film and adding 3-glycidylpropyltrimethoxysilane for surface modification to obtain a biomimetic layer-modified graphene oxide; S12: dispersing the biomimetic layer modified graphene oxide in water phase, adding N-isopropylacrylamide monomer, performing active polymerization in a cuprous bromide / pentamethyldiethylenetriamine catalytic system, and then adding sodium ascorbate to terminate the reaction, thereby obtaining double modified graphene oxide; The mass ratio of the graphene oxide dispersed in deionized water is 1:200-250; The mass ratio of graphene oxide to lipid film is 1:5-8; The mass ratio of the 3-glycidylpropyltrimethoxysilane to graphene oxide is 4-6:

1.

3. The method for preparing an environmentally friendly polypropylene-based composite material according to claim 2, characterized in that: In S12: The mass ratio of the bionic layer modified graphene oxide to deionized water is 1:100-150; The mass ratio of cuprous bromide to N-isopropylacrylamide is 1-1.5:100; The mass ratio of pentamethyldiethylenetriamine to N-isopropylacrylamide is 1.5-2:100; The mass ratio of the sodium ascorbate to N-isopropylacrylamide is 5-6:

100.

4. The method for preparing an environmentally friendly polypropylene-based composite material according to claim 1, characterized in that: The preparation method of the multi-layer flame retardant modified carbon nanotubes is: S13: after plasma activation of the carbon nanotubes, modification with magnesium sulfate is performed to obtain a carbon nanotube / magnesium hydroxide core-shell material; Then, n-octyl phosphite was introduced for surface modification to obtain multi-layer flame-retardant modified carbon nanotubes; The mass ratio of the surface activated carbon nanotubes to magnesium sulfate is 1:6-7; The mass ratio of n-octyl phosphite to magnesium sulfate is 1:3-4.

5. The method for preparing an environmentally friendly polypropylene-based composite material according to claim 1, characterized in that: In S21: The mass ratio of 4-aminophenol to hexafluorocyclotriphosphazene is 1.5-2:1; The molar ratio of the triethylamine to 4-aminophenol is 1-1.5:

1.

6. The method for preparing an environmentally friendly polypropylene-based composite material according to claim 1, characterized in that: In S21: The molar ratio of the silane coupling agent KH560 to hexafluorocyclotriphosphazene is 5-6:1; The mass ratio of tetrabutylammonium bromide to silane coupling agent KH560 is 0.5-1:100; The molar ratio of zinc chloride to acrylic acid is 0.8-1.2:

2.

7. The method for preparing an environmentally friendly polypropylene-based composite material according to claim 1, characterized in that: In S22: The mass ratio of dicumyl peroxide to polypropylene is 0.1-0.2:100; The mass ratio of the metal coordination modifier to the preactivated polypropylene is 3-5:100; The mass ratio of maleic anhydride to preactivated polypropylene is 1-2:100; The mass ratio of triallyl isocyanurate to preactivated polypropylene is 1-1.5:100; The temperature of the melt grafting is 180-185°C; The time of the melt grafting is 6-8 minutes.

8. The method for preparing an environmentally friendly polypropylene-based composite material according to claim 1, characterized in that: In S23: The mass ratio of the modified polypropylene, the double modified graphene oxide, the multi-level flame retardant modified carbon nanotubes and the dispersant is 100:(1-3):(1-3):(0.2-0.4); The dispersant is BYK-9077 or BYK-2105; The operating temperature of the twin-screw extruder is 170-180°C; The operating speed of the twin-screw extruder is 160-180 rpm.

9. An environmentally friendly polypropylene-based composite material prepared by the preparation method according to any one of claims 1 to 8.

10. Application of an environmentally friendly polypropylene-based composite material prepared by the preparation method according to any one of claims 1 to 8 in power pipelines.

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