Environmentally friendly polypropylene-based composite material, preparation method thereof, and application thereof

Abstract

The present invention provides an environmentally friendly polypropylene-based composite material, a preparation method thereof, and an application thereof, belonging to the technical field of polypropylene materials. Polypropylene is modified by introducing maleic anhydride and triallyl isocyanurate to improve its polarity and interfacial bonding strength, while enhancing thermal stability and mechanical properties. Graphene oxide is modified by biomimetic lipid bilayers and silanization to improve its dispersibility and interfacial compatibility, and further endowed with intelligent response capabilities by grafting thermosensitive polymers. Carbon nanotubes are activated by plasma and deposited with magnesium hydroxide to construct a core-shell structure, enhancing their interfacial bonding strength and flame retardancy. Octylphosphite modification further forms a synergistic flame retardant system. The metal coordination modifier significantly improves the flame retardant efficiency and thermal stability of the material by promoting carbonization and releasing non-flammable gases. A composite material with excellent mechanical properties, thermal stability, and flame retardancy is prepared.

Description

Technical Field

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

[0002] In modern materials science, polypropylene, as an important thermoplastic, has been widely used in various fields, such as power pipelines, packaging materials, automotive parts, and household appliance casings, thanks to its excellent mechanical properties, chemical stability, and easy processing. Its advantages, including low density, high tensile strength, and excellent corrosion resistance, have given it a key position in various industrial fields. However, despite its many advantages in everyday applications, polypropylene still has certain deficiencies in mechanical properties and flame retardancy, which limit its performance and safety in some specialized applications.

[0003] First, although polypropylene has good toughness and impact resistance, it often exhibits low strength and rigidity under high temperature or high load conditions, especially when subjected to large mechanical stresses. This makes polypropylene prone to deformation or cracking in some application scenarios, especially in complex working environments such as high temperature, large impact or long-term load conditions, which can significantly affect its structural stability and durability.

[0004] Secondly, polypropylene's relatively weak flame retardancy, especially in high-temperature environments, can increase the risk of fire. When exposed to a fire source, polypropylene is prone to spontaneous combustion and rapid fire spread, potentially releasing toxic and hazardous gases such as carbon monoxide, carbon dioxide, and certain volatile organic compounds, posing a potential threat to human health and environmental safety. In applications with stringent safety requirements, polypropylene's insufficient flame retardancy can significantly increase the risk of 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 and introduces maleic anhydride and triallyl isocyanurate to improve the polarity and interfacial bonding strength of the matrix, while enhancing its thermal stability and mechanical properties. The dispersibility and interfacial compatibility of graphene oxide are improved by biomimetic lipid bilayer and silanization modification, and it is further endowed with intelligent response capability by grafting thermosensitive polymers. Carbon nanotubes are constructed into a core-shell structure through plasma activation and magnesium hydroxide deposition, which enhances their interfacial bonding strength and flame retardant properties. The modification of n-octyl phosphite further forms a synergistic flame retardant system, 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. Finally, through the multiple synergistic effects of functional fillers and modification strategies, a composite material with excellent mechanical properties, thermal stability and flame retardant properties is prepared.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing an environmentally friendly polypropylene-based composite material, the method comprising:

[0008] S11: A lipid film was prepared by rotary evaporation using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine; graphene oxide was dispersed and then composited with the lipid film and surface modified with 3-glycidylpropyltrimethoxysilane to obtain a biomimetic layer-modified graphene oxide;

[0009] S12: dispersing the biomimetic layer modified graphene oxide in water, adding N-isopropylacrylamide monomer, and performing active polymerization in a cuprous bromide / pentamethyldiethylenetriamine catalytic system, followed by adding sodium ascorbate to terminate the reaction, thereby obtaining a double modified graphene oxide;

[0010] 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-layered flame-retardant modified carbon nanotube;

[0011] S21: Hexafluorocyclotriphosphazene is reacted with 4-aminophenol in the presence of triethylamine, followed by the introduction of silane coupling agent KH560 and tetrabutylammonium bromide, and metal coordination modification is performed with acrylic acid in the presence of zinc chloride catalysis to obtain a metal coordination modifier;

[0012] S22: preactivating polypropylene with dicumyl 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;

[0013] S23: The modified polypropylene is melt-blended and extruded with the double-modified graphene oxide, the multi-layered flame-retardant modified carbon nanotubes and the dispersant through a twin-screw extruder to obtain an environmentally friendly polypropylene-based composite material.

[0014] 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 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;

[0015] 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, and stirring to react after deoxygenation; adding sodium ascorbate, centrifuging, washing, and vacuum drying to obtain a dual-modified graphene oxide;

[0016] 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, adding a sodium hydroxide solution dropwise 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, adding a tetrahydrofuran solution of n-octyl phosphite dropwise to obtain a reaction solution H, filtering, washing, and drying after the reaction to obtain a multi-layered flame-retardant modified carbon nanotube;

[0017] 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; stirring the mixture at room temperature under nitrogen protection, adding a silane coupling agent KH560 solution and tetrabutylammonium bromide to obtain a reaction solution J; and adding acrylic acid and zinc chloride to obtain a mixed solution after constant temperature reaction, stirring the mixture at room temperature, concentrating under reduced pressure, recrystallizing, and drying in vacuo to obtain a metal coordination modifier;

[0018] S22: premixing polypropylene, dicumyl peroxide, an antioxidant, and zinc stearate under nitrogen to obtain preactivated polypropylene; adding a metal coordination modifier, maleic anhydride, and triallyl isocyanurate to the preactivated polypropylene, melt-grafting under vacuum, cooling, and pelletizing to obtain modified polypropylene;

[0019] S23: Modified polypropylene, double-modified graphene oxide and dispersant are premixed in a high-speed mixer, and then multi-layer flame-retardant modified carbon nanotubes are added and mixed evenly. Subsequently, the mixture is extruded using a twin-screw extruder and pelletized with water cooling to obtain an environmentally friendly polypropylene-based composite material.

[0020] As a preferred technical solution of the present invention, in step S11, the mass ratio of the 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, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] In some optional 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0022] In some optional embodiments, the pH of the sodium hydroxide solution is adjusted to 7-7.5, for example, 7.00, 7.05, 7.10, 7.15, 7.20, 7.25, 7.30, 7.35, 7.40, 7.45 or 7.50, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] In some optional embodiments, the mass ratio of the 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0024] In some optional embodiments, the mass fraction of the ethanol solution of 3-glycidylpropyltrimethoxysilane 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.%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0025] In some optional embodiments, the mass ratio of 3-glycidylpropyltrimethoxysilane to 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0026] In some optional embodiments, the temperature of the stirring reaction of the reaction liquid 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0027] In some optional embodiments, the rotation speed of the stirring reaction of the reaction liquid 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0028] In some optional embodiments, the stirring reaction time of the reaction liquid C is 2-3h, for example, it can be 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] As a preferred technical solution of the present invention, in step S12, the mass ratio of the bionic 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0030] In some optional embodiments, the concentration of N-isopropylacrylamide in the reaction solution E is 30-35 mg / mL, for example, 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, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] In some optional embodiments, the mass ratio of cuprous bromide to N-isopropylacrylamide is 1-1.5:100, for example, 1.0:100, 1.1:100, 1.2:100, 1.3:100, 1.4:100 or 1.5:100, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0032] In some optional embodiments, the mass ratio of pentamethyldiethylenetriamine to N-isopropylacrylamide is 1.5-2:100, for example, 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 this numerical range are also applicable.

[0033] In some optional embodiments, the temperature of the stirring reaction of the reaction liquid E after deoxygenation 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0034] In some optional embodiments, the stirring reaction time of the reaction liquid E after deoxygenation is 8-10 hours, for example, it can be 8.0 hours, 8.2 hours, 8.4 hours, 8.6 hours, 8.8 hours, 9.0 hours, 9.2 hours, 9.4 hours, 9.6 hours, 9.8 hours or 10.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] In some optional embodiments, the mass ratio of sodium ascorbate to N-isopropylacrylamide is 5-6:100, for example, 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0036] 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0037] In some optional embodiments, the concentration of the magnesium sulfate solution is 0.1-0.2M, for example, it can be 0.10M, 0.11M, 0.12M, 0.13M, 0.14M, 0.15M, 0.16M, 0.17M, 0.18M, ​​0.19M or 0.20M, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0038] In some optional 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0039] In some optional 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, 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 temperature of the stirring reaction of the reaction liquid 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0041] In some optional embodiments, the stirring reaction time of the reaction liquid G is 4-5h, for example, it can be 4.0h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, 4.6h, 4.7h, 4.8h, 4.9h or 5.0h, 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 concentration of the carbon nanotube / magnesium hydroxide core-shell material dispersed in anhydrous 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0043] In some optional 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.%, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0044] In some optional embodiments, the mass ratio of n-octyl phosphite to magnesium sulfate is 1:3-4, for example, 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, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] In some optional embodiments, the reaction temperature of the reaction liquid 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0046] In some optional embodiments, the reaction time of the reaction liquid H is 6-7h, for example, it can be 6.0h, 6.1h, 6.2h, 6.3h, 6.4h, 6.5h, 6.6h, 6.7h, 6.8h, 6.9h or 7.0h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] As a preferred technical solution of the present invention, in step S21, the mass ratio of the hexafluorocyclotriphosphazene in the tetrahydrofuran solution 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, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] In some optional embodiments, the concentration of the tetrahydrofuran solution of 4-aminophenol is 20-25 mg / mL, for example, 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0049] In some optional embodiments, the mass ratio of 4-aminophenol to hexafluorocyclotriphosphazene is 1.5-2:1, for example, 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, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0050] 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 this numerical range are also applicable.

[0051] In some optional embodiments, the reaction solution I is stirred at room temperature under nitrogen protection for 12-15 hours, for example, 12.0 hours, 12.3 hours, 12.6 hours, 12.9 hours, 13.2 hours, 13.5 hours, 13.8 hours, 14.1 hours, 14.4 hours, 14.7 hours or 15.0 hours, 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 molar ratio of the silane coupling agent KH560 to deionized water in the silane coupling agent KH560 solution is 1:1-4, for example, 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.

[0053] In some optional embodiments, the molar ratio of the silane coupling agent KH560 to hexafluorocyclotriphosphazene is 5-6:1, for example, 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 values ​​not listed within the numerical range are also applicable.

[0054] 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.

[0055] 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 is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0056] In some optional embodiments, the mixture is stirred at room temperature for 2-3 hours, for example, 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours, or 3.0 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0057] 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 this numerical range are also applicable.

[0058] 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 this numerical range are also applicable.

[0059] 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 this numerical range are also applicable.

[0060] 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.

[0061] 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.

[0062] 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 this numerical range are also applicable.

[0063] 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 this numerical range are also applicable.

[0064] 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 this numerical range are also applicable.

[0065] 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 this numerical range are also applicable.

[0066] 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.

[0067] 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).

[0068] 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 values ​​not listed within this numerical range are also applicable.

[0069] In some optional embodiments, the premixing time of the modified polypropylene, the double-modified graphene oxide and the 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.

[0070] 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 this numerical range are also applicable.

[0071] In some optional embodiments, the operating speed of the twin-screw extruder is 160-180 rpm, for example, it can be 160 rpm, 162 rpm, 164 rpm, 166 rpm, 168 rpm, 170 rpm, 172 rpm, 174 rpm, 176 rpm, 178 rpm or 180 rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0072] In a second aspect, the present invention provides an environmentally friendly polypropylene-based composite material prepared by the above-mentioned preparation method.

[0073] 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 power pipelines.

[0074] Polypropylene is selected as the substrate in the present invention. Polypropylene is a semicrystalline thermoplastic compound whose backbone consists of non-polar carbon-carbon bonds, resulting in its chemical inertness and hydrophobicity. Polypropylene also has extremely low electrical conductivity, making it suitable for use as an insulation layer in power pipelines. However, due to its non-polar nature, it lacks intermolecular interaction with polar nanofillers, resulting in poor interfacial compatibility. Therefore, it is necessary to introduce polar groups through chemical modification to improve the interfacial bonding between polypropylene and the filler.

[0075] First, polypropylene is activated using dicumyl peroxide. Dicumyl peroxide is a highly efficient free radical initiator that decomposes at high temperatures to produce free radicals. These free radicals abstract hydrogen atoms from the side chains of the polypropylene molecules, generating polypropylene free radicals. These free radicals then undergo free radical addition reactions with the double bonds in maleic anhydride and triallyl isocyanurate molecules, resulting in grafting onto the polypropylene chains. The anhydride groups introduced by maleic anhydride provide polar groups that bind to polar fillers through hydrogen bonds or chemical reactions, enhancing interfacial compatibility. The isocyanurate groups introduced by triallyl isocyanurate further increase the polarity of the polypropylene while providing potential crosslinking capabilities, enhancing the thermal stability and mechanical properties of the composite.

[0076] The hexafluorocyclotriphosphazene structure in the metal coordination modifier contains abundant phosphorus-nitrogen bonds, which decompose at high temperatures, slowly releasing compounds such as inorganic phosphoric acid and nitrogen oxides. These decomposition products promote carbonization on the substrate surface, forming a thermally stable expanded carbon layer that acts as a heat and oxygen barrier. Furthermore, the released non-combustible gas dilutes the concentration of combustible gases in the combustion zone, significantly improving the material's flame retardancy. Furthermore, the formation of the expanded carbon layer enhances the material's structural integrity, preventing mechanical property loss at high temperatures.

[0077] Further introducing 4-aminophenol and acrylic acid into the molecular structure of the metal coordination modifier significantly improves flame retardancy and thermal stability. 4-Aminophenol introduces phenolic hydroxyl and amino groups through reaction with hexafluorocyclotriphosphazene. The phenolic hydroxyl groups help promote the carbonization reaction of the material at high temperatures, while the amino groups increase the nitrogen source, providing more non-flammable gas for the flame retardant process. The carboxyl groups in the acrylic acid molecules can chemically bond with the substrate or filler, further increasing 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.

[0078] Zinc chloride plays a crucial role in carbonization catalysis in this system. As a highly efficient carbonization catalyst, zinc chloride accelerates the substrate's dehydration and carbonization process at high temperatures, reducing the activation energy of the carbonization reaction and significantly improving carbonization efficiency. Furthermore, zinc chloride forms a coordination structure with oxygen- or nitrogen-containing groups in the modifier. This coordination further enhances the efficiency of the carbonization catalysis process and improves the flame retardant properties of the composite material.

[0079] To enhance the interfacial bonding ability of the metal coordination modifier, the silane coupling agent KH560 was introduced. The silane groups in the KH560 molecule can form stable chemical bonds with the surface of the inorganic filler, while its epoxy moiety can chemically react with the active groups in the polymer matrix. This bifunctional structure gives KH560 a bridging effect at the "organic-inorganic" interface, significantly improving the chemical bonding and stability of the interface. In addition, the carboxyl groups in acrylic acid can also form complexes with inorganic fillers or other modifiers, further enhancing interfacial bonding. This multiple interaction enables the metal coordination modifier to simultaneously form a stable bond with the polymer matrix and the inorganic filler, thereby effectively improving the mechanical properties, thermal stability, and flame retardant efficiency of the composite material.

[0080] The present invention introduces graphene oxide as a filler. Graphene oxide is a two-dimensional nanomaterial with a large number of oxygen-containing functional groups on its surface and edges. These functional groups give it strong polarity, a high specific surface area, and good chemical reactivity, allowing it to be further functionalized through chemical modification. Graphene oxide's lamellar structure has high strength, and its high specific surface area enables it to form a large interfacial contact area with a polypropylene matrix, thereby effectively transferring stress, preventing microcracks from expanding, and significantly improving the mechanical properties of polypropylene. Furthermore, graphene oxide has good thermal conductivity, and its introduction can form a heat conduction path in the matrix, improving the thermal stability of the composite material.

[0081] The lamellar structure of graphene oxide forms a dense, expanded carbonized layer during combustion, effectively preventing heat and oxygen from transferring into the interior of the substrate, thereby enhancing the material's flame retardancy. Furthermore, the gases produced by graphene oxide's decomposition at high temperatures also help dilute combustible gases in the combustion zone. 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 graphene oxide surface impart a strong hydrophilicity, making it incompatible with the hydrophobic polypropylene matrix, leading to aggregation and insufficient interfacial bonding within the matrix. Therefore, further modification is necessary.

[0082] 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 graphene oxide surface, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine self-assembles to form a biomimetic lipid bilayer structure: the hydrophilic head interacts with hydroxyl or carboxyl groups on the graphene oxide surface through electrostatic interactions and hydrogen bonds, while the hydrophobic tails align with each other through van der Waals forces, forming a stable bilayer structure. This bilayer structure effectively reduces the surface energy of the graphene oxide, making its surface both hydrophilic and hydrophobic, thereby significantly improving the dispersion of the graphene oxide in the polypropylene matrix.

[0083] 3-glycidylpropyltrimethoxysilane was then introduced for further modification. The epoxy groups of 3-glycidylpropyltrimethoxysilane chemically bonded with hydroxyl or carboxyl groups on the graphene oxide surface through a ring-opening reaction, forming stable chemical bonds. Simultaneously, the trimethoxysilane moiety of 3-glycidylpropyltrimethoxysilane hydrolyzed under the influence of humidity or moisture to generate silanols, which further condensed with each other or with groups on the graphene oxide surface to form Si-O-Si cross-linked structures. This process not only significantly enhanced the chemical and thermal stability of graphene oxide but also stabilized the lipid bilayer structure, further enhancing the modification effect.

[0084] Secondly, N-isopropylacrylamide was grafted onto the surface of the biomimetic layer-modified graphene oxide via atom transfer radical polymerization (ATRP), forming thermoresponsive polymer poly(N-isopropylacrylamide) segments, thereby constructing a "core-shell-brush" three-layer structure. This structure is formed and functions in the following ways: the core layer, with graphene oxide as its core, provides high strength, high thermal conductivity, and two-dimensional support; a lipid bilayer formed by biomimetic assembly coats the graphene oxide surface to form a shell layer, improving the dispersibility and interfacial compatibility of graphene oxide while providing a stable substrate for subsequent polymerization reactions; and poly(N-isopropylacrylamide) segments grafted onto the surface via atom transfer radical polymerization form an outer brush-like structure, endowing the graphene oxide with intelligent responsiveness. The poly(N-isopropylacrylamide) segments are thermoresponsive polymers, and this thermoresponsive characteristic provides the composite material with intelligent control capabilities, enabling it to form an adaptive conductive network structure. When the temperature rises, the poly(N-isopropylacrylamide) chain segments shrink, reducing the distance between graphene oxide sheets, thereby optimizing the conductive path and effectively improving electrical conductivity. This chain segment shrinkage also helps limit local overheating, thereby providing thermal management and protection. Conversely, when the temperature drops, the chain segment swelling behavior resumes, allowing the conductive network structure to expand, maintaining the material's excellent performance at lower temperatures.

[0085] This invention introduces carbon nanotubes as functional fillers. Carbon nanotubes are hollow, tubular nanostructures formed by sp² hybridization of carbon atoms. Their high thermal conductivity stems from the efficient transfer of electrons and phonons within their one-dimensional tubular structure. In composite materials, carbon nanotubes can form thermal paths through the dispersion and connection of fillers, significantly improving the overall thermal conductivity of the material. This improved thermal conductivity helps achieve more efficient heat transfer during use, preventing localized overheating.

[0086] Secondly, carbon nanotubes exhibit good thermal stability and resistance to decomposition at high temperatures, forming a physical barrier during combustion, preventing the diffusion of heat and combustible gases and thus inhibiting the spread of flames. Furthermore, carbon nanotubes can synergize with other flame-retardant fillers to further enhance the flame retardancy of composite materials by increasing the density and thermal stability of the carbonized layer.

[0087] Carbon nanotubes have excellent conductive properties. After introducing carbon nanotubes into the polymer matrix, they can significantly improve its antistatic properties and electromagnetic shielding properties 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.

[0088] 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 and limiting their reinforcing effect in composite materials. Therefore, it is necessary to surface activate or chemically modify carbon nanotubes to enhance their interfacial bonding.

[0089] First, the carbon nanotube surface is activated through plasma treatment. Plasma treatment bombards the carbon nanotube surface with high-energy particles, destroying the inert carbon-carbon bond structure and introducing polar active functional groups such as hydroxyl and carboxyl groups onto the carbon nanotube surface. The introduction of these functional groups significantly increases the polarity of the carbon nanotubes, improving their dispersibility and interfacial bonding in polar matrices. Furthermore, the presence of hydroxyl and carboxyl groups provides active sites for subsequent chemical modification, laying the foundation for the construction of multifunctional composite structures.

[0090] Magnesium hydroxide is deposited on the surface of activated carbon nanotubes via chemical precipitation, forming a core-shell structure. Specifically, during the chemical precipitation process, the surface functional groups of the activated carbon nanotubes complex with Mg²⁺, promoting uniform deposition of magnesium hydroxide. The resulting structure is a "carbon nanotube@magnesium hydroxide" composite structure, with the carbon nanotubes as the "core" and magnesium hydroxide as the "shell." Magnesium hydroxide is an inorganic flame retardant. During heating, it undergoes endothermic decomposition, releasing water, which lowers the temperature in the combustion zone, inhibiting flame propagation. It also dilutes the concentration of combustible gases in the combustion zone, further suppressing the combustion reaction.

[0091] To further enhance the flame retardancy, the magnesium hydroxide surface was functionalized with n-octyl phosphite. The phosphate groups in n-octyl phosphite react or coordinate with the hydroxyl groups on the magnesium hydroxide surface, introducing phosphorus-containing groups into the composite structure. This results in a ternary synergistic flame retardant system of "carbon nanotubes + magnesium hydroxide + phosphate." During combustion, the magnesium hydroxide decomposes through endothermic decomposition, releasing water and cooling the combustion zone, acting as a physical flame retardant. The decomposed magnesium oxide residue has high thermal stability and forms a dense thermal barrier, further preventing heat transfer and flame spread. The phosphate groups in n-octyl phosphite decompose at high temperatures to produce active phosphorylated products. These products catalyze char formation on the polymer matrix surface. This char layer acts as a heat and oxygen barrier, significantly reducing the material's combustion rate. Furthermore, the phosphorus-containing groups capture free radicals generated during combustion, inhibiting flame spread and further enhancing the flame retardancy. The carbon nanotubes, as the core support structure, not only enhance the mechanical properties of the composite but also, through their high thermal conductivity, facilitate efficient heat transfer and diffusion, thereby preventing localized overheating.

[0092] Within the composite system, significant synergy exists between graphene oxide and carbon nanotubes. The geometrical complementarity between graphene oxide's two-dimensional lamellar structure and carbon nanotubes' one-dimensional rod-like morphology enables them to construct a three-dimensional network within the matrix, significantly enhancing the composite's mechanical properties. Graphene oxide's high aspect ratio and lamellar structure provide rigid support within the matrix, limiting its plastic deformation. The carbon nanotubes, with their high aspect ratio and flexibility, further serve as a bridge between the lamellar layers, imparting enhanced structural integrity and stress transfer efficiency. Furthermore, the oxygen-containing functional groups on the graphene oxide surface and the active groups on the activated carbon nanotubes form a stable interfacial bond through hydrogen bonding, further strengthening the interaction between the two. Furthermore, π-π stacking between graphene oxide and carbon nanotubes provides additional bonding, further enhancing the composite's interfacial strength. Because this three-dimensional network effectively prevents the propagation of microcracks within the matrix, the composite's mechanical properties are enhanced.

[0093] In terms of flame retardancy, the synergistic effect between graphene oxide and carbon nanotubes significantly enhances the composite's fire resistance by creating a multi-layered flame-retardant barrier. The magnesium hydroxide deposited on the carbon nanotube surface is an effective inorganic flame retardant. Its endothermic decomposition at high temperatures releases water, lowering the temperature in the combustion zone and diluting the concentration of combustible gases, acting as a physical flame retardant. The decomposed magnesium oxide residue further forms a dense thermal barrier, preventing the spread of heat and flames. Simultaneously, the two-dimensional lamellae of graphene oxide stack during combustion, forming a dense carbonized layer that isolates heat and oxygen, thereby slowing the combustion process. This lamellae barrier, combined with the longitudinal flame-retardant effect of the carbon nanotubes, creates a multi-scale flame-retardant system. Furthermore, the oxygen-containing functional groups on the graphene oxide surface react with the magnesium hydroxide surface, further strengthening interfacial bonding, making this multifunctional filler more stable during combustion and achieving a more pronounced flame retardant effect. Ultimately, the synergistic effect of carbon nanotubes and graphene oxide effectively improved the flame retardancy and thermal stability of the composite material through the combination of physical flame retardancy and chemical flame retardancy.

[0094] Compared with the prior art, the present invention has the following beneficial effects:

[0095] This invention uses polypropylene as the matrix material, whose chemical inertness and hydrophobicity result in poor interfacial compatibility with polar fillers. Maleic anhydride and triallyl isocyanurate are grafted onto the polypropylene chain via a free radical reaction initiated by dicumyl peroxide, introducing polar groups to enhance interfacial bonding with the filler while also improving the material's thermal stability and mechanical properties.

[0096] The metal coordination modifier provides abundant phosphorus-nitrogen bonds through the hexafluorocyclotriphosphazene in its molecular structure, which decomposes at high temperatures to form inorganic phosphoric acid and nitrogen oxides. This not only promotes the carbonization of the matrix, forming a thermally stable expanded carbon layer to insulate heat and oxygen, but also significantly improves the flame retardant properties by releasing non-combustible gases to dilute the concentration of combustible gases in the combustion area. The function of the modifier is further enhanced by the introduction of 4-aminophenol and acrylic acid, which respectively improve 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, improves the carbonization efficiency, and further enhances the flame retardant effect through coordination with the modifier. The silane coupling agent KH560, through its dual-functional structure, strengthens the chemical bonding between the inorganic filler and the matrix.

[0097] Graphene oxide is used as a functional filler, and a biomimetic lipid bilayer is formed by introducing 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, thereby improving the dispersibility and interfacial bonding strength. Subsequently, the chemical stability and thermal stability of graphene oxide are further enhanced through chemical modification with 3-glycidylpropyltrimethoxysilane, and it is given thermosensitive intelligent response capabilities through poly (N-isopropylacrylamide) grafting, thereby optimizing the conductivity and thermal management performance.

[0098] Carbon nanotubes, another filler, are treated with plasma to introduce polar functional groups to enhance interfacial bonding. Magnesium hydroxide is then deposited on their surface via chemical precipitation to form a core-shell structure, creating a physical flame-retardant barrier that allows for endothermic decomposition and gas dilution. Further modification with n-octyl phosphite creates a ternary synergistic flame-retardant system based on magnesium hydroxide, significantly improving both flame retardancy and char-forming capacity.

[0099] Within the entire system, the two-dimensional sheet structure of graphene oxide and the one-dimensional rod-like structure of carbon nanotubes complement each other in terms of geometric morphology, forming a stable three-dimensional network structure that significantly improves the mechanical properties of the composite material. The two also exhibit a synergistic effect in terms of flame retardancy: the barrier effect of the graphene oxide sheets and the endothermic decomposition of magnesium hydroxide on the surface of the carbon nanotubes jointly construct a multi-layered flame retardant barrier, further enhancing the thermal stability and fire resistance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0100] Figure 1 A high-resolution transmission electron microscopy image of the biomimetic layer-modified graphene oxide provided in Example 1 of the present invention;

[0101] 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

[0102] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments described herein are specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be understood as limiting the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments described 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 described herein.

[0103] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products without further purification or treatment.

[0104] Example 1

[0105] 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 includes the following steps:

[0106] S11: A lipid film was prepared by rotary evaporation using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine; graphene oxide was dispersed and then composited with the lipid film and surface modified with 3-glycidylpropyltrimethoxysilane to obtain a biomimetic layer-modified graphene oxide;

[0107] Specifically, S11: 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is dispersed in ethyl acetate, and rotary evaporated to obtain a lipid film; 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 and 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.

[0108] S12: dispersing the biomimetic layer modified graphene oxide in water, adding N-isopropylacrylamide monomer, and performing active polymerization in a cuprous bromide / pentamethyldiethylenetriamine catalytic system, followed by adding sodium ascorbate to terminate the reaction, thereby obtaining a double modified graphene oxide;

[0109] Specifically, S12: dispersing the biomimetic layer modified graphene oxide in deionized water to obtain a dispersion D, wherein the mass ratio of the biomimetic 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, and the mass ratio of pentamethyldiethylenetriamine to N-isopropylacrylamide is 1.5:100, and after deoxygenation, stirring and reacting at 40° C. for 8.8 hours; adding sodium ascorbate at a mass ratio of 5.6:100 to N-isopropylacrylamide, centrifuging, washing, and vacuum drying to obtain a double-modified graphene oxide;

[0110] 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-layered flame-retardant modified carbon nanotube;

[0111] 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 surface-activated carbon nanotube 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, adding 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, adding 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. A relatively uniform sodium hydroxide particle deposition structure can be observed on the surface of the carbon nanotube.

[0112] S21: Hexafluorocyclotriphosphazene is reacted with 4-aminophenol in the presence of triethylamine, followed by the introduction of silane coupling agent KH560 and tetrabutylammonium bromide, and metal coordination modification is performed with acrylic acid in the presence of zinc chloride catalysis to obtain a metal coordination modifier;

[0113] 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 under nitrogen protection for 12 hours, 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 stirred at room temperature for 3 hours, and then concentrated under reduced pressure, recrystallized, and dried in vacuo to obtain a metal coordination modifier.

[0114] S22: preactivating polypropylene with dicumyl 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;

[0115] Specifically, S22: premixing polypropylene, dicumyl peroxide, antioxidant 1010 and zinc stearate under nitrogen protection at 175° C. for 5 minutes to obtain preactivated polypropylene, wherein the mass ratio of dicumyl 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 at 182° C. under a vacuum environment for 7 minutes, cooling, and pelletizing to obtain modified polypropylene;

[0116] S23: The modified polypropylene is melt-blended and extruded with the double-modified graphene oxide and the multi-layered flame-retardant modified carbon nanotubes through a twin-screw extruder to obtain an environmentally friendly polypropylene-based composite material.

[0117] 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 performed to obtain an environmentally friendly polypropylene-based composite material.

[0118] Example 2

[0119] This embodiment provides an environmentally friendly polypropylene-based composite material and a preparation method thereof, wherein the preparation method specifically comprises the following steps:

[0120] S11: A lipid film was prepared by rotary evaporation using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine; graphene oxide was dispersed and then composited with the lipid film and surface modified with 3-glycidylpropyltrimethoxysilane to obtain a biomimetic layer-modified graphene oxide;

[0121] Specifically, S11: 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is dispersed in ethyl acetate and rotary evaporated to obtain a lipid film; 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 h, followed by centrifugation, washing, and vacuum drying to obtain a biomimetic layer-modified graphene oxide;

[0122] S12: dispersing the biomimetic layer modified graphene oxide in water, adding N-isopropylacrylamide monomer, and performing active polymerization in a cuprous bromide / pentamethyldiethylenetriamine catalytic system, followed by adding sodium ascorbate to terminate the reaction, thereby obtaining a double modified graphene oxide;

[0123] Specifically, S12: dispersing the biomimetic layer modified graphene oxide in deionized water to obtain a dispersion D, wherein the mass ratio of the biomimetic 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, and the mass ratio of pentamethyldiethylenetriamine to N-isopropylacrylamide is 2:100, and after deoxygenation, stirring and reacting at 45° C. for 10 hours; adding sodium ascorbate at a mass ratio of 6:100 to N-isopropylacrylamide, centrifuging, washing, and vacuum drying to obtain a double-modified graphene oxide;

[0124] 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-layered flame-retardant modified carbon nanotube;

[0125] 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, adding 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, adding 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;

[0126] S21: Hexafluorocyclotriphosphazene is reacted with 4-aminophenol in the presence of triethylamine, followed by the introduction of silane coupling agent KH560 and tetrabutylammonium bromide, and metal coordination modification is performed with acrylic acid in the presence of zinc chloride catalysis to obtain a metal coordination modifier;

[0127] 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 under nitrogen protection for 15 hours, 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. The reaction mixture was stirred at room temperature for 2.3 hours, and then concentrated under reduced pressure, recrystallized, and dried in vacuo to obtain a metal coordination modifier.

[0128] S22: preactivating polypropylene with dicumyl 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;

[0129] Specifically, S22: premixing polypropylene, dicumyl peroxide, antioxidant 168 and zinc stearate under nitrogen protection at 176° C. for 8 minutes to obtain preactivated polypropylene, wherein the mass ratio of dicumyl 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 at 183° C. under a vacuum environment for 7.8 minutes, cooling, and pelletizing to obtain modified polypropylene;

[0130] S23: The modified polypropylene is melt-blended and extruded with the double-modified graphene oxide and the multi-layered flame-retardant modified carbon nanotubes through a twin-screw extruder to obtain an environmentally friendly polypropylene-based composite material.

[0131] 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 performed to obtain an environmentally friendly polypropylene-based composite material.

[0132] Example 3

[0133] This embodiment provides an environmentally friendly polypropylene-based composite material and a preparation method thereof, wherein the preparation method specifically comprises the following steps:

[0134] S11: A lipid film was prepared by rotary evaporation using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine; graphene oxide was dispersed and then composited with the lipid film and surface modified with 3-glycidylpropyltrimethoxysilane to obtain a biomimetic layer-modified graphene oxide;

[0135] Specifically, S11: 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is dispersed in ethyl acetate, and rotary evaporated to obtain a lipid film; graphene oxide is dispersed in deionized water at a mass ratio of 1:220, and the pH is adjusted to 7.0 with a sodium hydroxide solution having a concentration of 0.1 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 1:5 to obtain a mixed solution B; an ethanol solution of 3-glycidylpropyltrimethoxysilane with a mass fraction of 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 5:1, and the mixture is stirred at 57°C and a speed of 460 rpm for 3 hours, followed by centrifugation, washing, and vacuum drying to obtain a biomimetic layer-modified graphene oxide;

[0136] S12: dispersing the biomimetic layer modified graphene oxide in water, adding N-isopropylacrylamide monomer, and performing active polymerization in a cuprous bromide / pentamethyldiethylenetriamine catalytic system, followed by adding sodium ascorbate to terminate the reaction, thereby obtaining a double modified graphene oxide;

[0137] Specifically, S12: dispersing the biomimetic layer modified graphene oxide in deionized water to obtain a dispersion D, wherein the mass ratio of the biomimetic layer modified graphene oxide to deionized water in the dispersion D is 1:135, 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 30 mg / mL, the mass ratio of cuprous bromide to N-isopropylacrylamide is 1.2:100, and the mass ratio of pentamethyldiethylenetriamine to N-isopropylacrylamide is 1.8:100, and after deoxygenation, stirring and reacting at 42° C. for 9.8 hours; adding sodium ascorbate at a mass ratio of 5.8:100 to N-isopropylacrylamide, centrifuging, washing, and vacuum drying to obtain a double-modified graphene oxide;

[0138] 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-layered flame-retardant modified carbon nanotube;

[0139] 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 1.6 mg / mL, adding the surface-activated carbon nanotube dispersion to a 0.16 M magnesium sulfate solution and stirring to obtain a reaction solution F, wherein the mass ratio of carbon nanotubes to magnesium sulfate is 1:6.6, adding sodium hydroxide solution until the pH of the reaction solution F reaches 10.5 to obtain a reaction solution G, stirring and reacting at 55°C for 4.8 hours, then 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 2.5 mg / mL, and adding a tetrahydrofuran solution of n-octyl phosphite with a mass fraction of 5.3 wt.% to obtain a reaction solution H, wherein the mass ratio of n-octyl phosphite to magnesium sulfate is 1:3.7, reacting at 50°C for 6 hours, filtering, washing, and drying to obtain a multi-layer flame retardant modified carbon nanotube;

[0140] S21: Hexafluorocyclotriphosphazene is reacted with 4-aminophenol in the presence of triethylamine, followed by the introduction of silane coupling agent KH560 and tetrabutylammonium bromide, and metal coordination modification is performed with acrylic acid in the presence of zinc chloride catalysis to obtain a metal coordination modifier;

[0141] Specifically, S21: under an ice bath, a tetrahydrofuran solution of 4-aminophenol with a concentration of 22 mg / mL and triethylamine were added dropwise to a tetrahydrofuran solution of hexafluorocyclotriphosphazene with a mass ratio of 1:48 to obtain a reaction solution I, wherein the mass ratio of 4-aminophenol to hexafluorocyclotriphosphazene is 1.8:1, and the molar ratio of triethylamine to 4-aminophenol is 1:1.2. After stirring at room temperature under nitrogen protection for 13 hours, a silane coupling agent KH560 solution with a molar ratio of 5.5:1 to hexafluorocyclotriphosphazene and a silane coupling agent KH560 solution with a molar ratio of 5.5:1 to hexafluorocyclotriphosphazene were added. a mixture of tetrabutylammonium bromide and KH560 at a mass ratio of 0.75:100 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 is 1:4, and the mixture is reacted at a constant temperature of 60° C. for 4 hours, and then acrylic acid and zinc chloride are added to obtain a mixed solution, wherein the molar ratio of acrylic acid to the silane coupling agent KH560 is 1.4:1, and the molar ratio of zinc chloride to acrylic acid is 1:2. The mixture is stirred at room temperature for 2.7 hours, concentrated under reduced pressure, recrystallized, and dried in vacuo to obtain a metal coordination modifier;

[0142] S22: preactivating polypropylene with dicumyl 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;

[0143] Specifically, S22: premixing polypropylene, dicumyl peroxide, antioxidant 168 and zinc stearate under nitrogen protection at 178° C. for 6 minutes to obtain preactivated polypropylene, wherein 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; 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 4:100, the mass ratio of maleic anhydride to the preactivated polypropylene is 1.8:100, and the mass ratio of triallyl isocyanurate to the preactivated polypropylene is 1:100, melt grafting is carried out at 180° C. under a vacuum environment for 6 minutes, and then cooling is carried out, and pelletizing is obtained to obtain modified polypropylene;

[0144] S23: The modified polypropylene is melt-blended and extruded with the double-modified graphene oxide and the multi-layered flame-retardant modified carbon nanotubes through a twin-screw extruder to obtain an environmentally friendly polypropylene-based composite material.

[0145] Specifically, S23: modified polypropylene, doubly modified graphene oxide and BYK-2150 are premixed in a high-speed mixer at a speed of 2300 rpm for 5 minutes, and then multi-layer flame retardant modified carbon nanotubes are added and mixed evenly, wherein the mass ratio of modified polypropylene, doubly modified graphene oxide, multi-layer flame retardant modified carbon nanotubes and dispersant is 100:2:2:0.3, and then extruded using a twin-screw extruder, wherein the operating temperature of the twin-screw extruder is 175°C, the operating speed is 160 rpm, and water-cooled pelletizing is used to obtain an environmentally friendly polypropylene-based composite material.

[0146] Example 4

[0147] This embodiment provides an environmentally friendly polypropylene-based composite material and a preparation method thereof, wherein the preparation method specifically comprises the following steps:

[0148] S11: A lipid film was prepared by rotary evaporation using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine; graphene oxide was dispersed and then composited with the lipid film and surface modified with 3-glycidylpropyltrimethoxysilane to obtain a biomimetic layer-modified graphene oxide;

[0149] Specifically, S11: 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is dispersed in ethyl acetate, and rotary evaporated to obtain a lipid film; graphene oxide is dispersed in deionized water at a mass ratio of 1:240, and the pH is adjusted to 7.4 with a sodium hydroxide solution having a concentration of 0.2 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 1:6 to obtain a mixed solution B; an ethanol solution of 3-glycidylpropyltrimethoxysilane with a mass fraction of 2 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 6:1, and the mixture is stirred at 59° C. and a speed of 480 rpm for 2.3 h, followed by centrifugation, washing, and vacuum drying to obtain a biomimetic layer-modified graphene oxide;

[0150] S12: dispersing the biomimetic layer modified graphene oxide in water, adding N-isopropylacrylamide monomer, and performing active polymerization in a cuprous bromide / pentamethyldiethylenetriamine catalytic system, followed by adding sodium ascorbate to terminate the reaction, thereby obtaining a double modified graphene oxide;

[0151] Specifically, S12: dispersing the biomimetic layer modified graphene oxide in deionized water to obtain a dispersion D, wherein the mass ratio of the biomimetic layer modified graphene oxide to deionized water in the dispersion D is 1:145, 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 35 mg / mL, the mass ratio of cuprous bromide to N-isopropylacrylamide is 1.4:100, and the mass ratio of pentamethyldiethylenetriamine to N-isopropylacrylamide is 1.7:100, and after deoxygenation, stirring and reacting at 43° C. for 8 hours; adding sodium ascorbate at a mass ratio of 5:100 to N-isopropylacrylamide, centrifuging, washing, and vacuum drying to obtain a double-modified graphene oxide;

[0152] 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-layered flame-retardant modified carbon nanotube;

[0153] 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 mg / mL, adding the dispersion to a 0.12M magnesium sulfate solution and stirring to obtain a reaction solution F, wherein the mass ratio of carbon nanotubes to magnesium sulfate is 1:6.8, adding sodium hydroxide solution until the pH of the reaction solution F reaches 10.7 to obtain a reaction solution G, stirring and reacting at 56°C for 4 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 2.3 mg / mL, adding a tetrahydrofuran solution of n-octyl phosphite with a mass fraction of 5.6 wt.% to obtain a reaction solution H, wherein the mass ratio of n-octyl phosphite to magnesium sulfate is 1:3.4, reacting at 60°C for 7 hours, filtering, washing, and drying to obtain a multi-layer flame retardant modified carbon nanotube;

[0154] S21: Hexafluorocyclotriphosphazene is reacted with 4-aminophenol in the presence of triethylamine, followed by the introduction of silane coupling agent KH560 and tetrabutylammonium bromide, and metal coordination modification is performed with acrylic acid in the presence of zinc chloride catalysis to obtain a metal coordination modifier;

[0155] Specifically, S21: under an ice bath, a tetrahydrofuran solution of 4-aminophenol with a concentration of 23 mg / mL and triethylamine were added dropwise to a tetrahydrofuran solution of hexafluorocyclotriphosphazene with a mass ratio of 1:50 to obtain a reaction solution I, wherein the mass ratio of 4-aminophenol to hexafluorocyclotriphosphazene was 1.7:1, and the molar ratio of triethylamine to 4-aminophenol was 1.3:1. After stirring at room temperature under nitrogen protection for 14 hours, a silane coupling agent KH560 solution with a molar ratio of 5.6:1 to hexafluorocyclotriphosphazene and a silane coupling agent KH560 solution with a molar ratio of 5.6:1 to hexafluorocyclotriphosphazene were added. a mixture of tetrabutylammonium bromide and KH560 at a mass ratio of 0.88:100 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 is 1:1, the mixture is reacted at a constant temperature of 65° C. for 6 hours, and then acrylic acid and zinc chloride are added to obtain a mixed solution, wherein the molar ratio of acrylic acid to the silane coupling agent KH560 is 1.2:1, and the molar ratio of zinc chloride to acrylic acid is 1.1:2. The mixture is stirred at room temperature for 2 hours, concentrated under reduced pressure, recrystallized, and dried in vacuo to obtain a metal coordination modifier;

[0156] S22: preactivating polypropylene with dicumyl 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;

[0157] Specifically, S22: premixing polypropylene, dicumyl peroxide, antioxidant 1010 and zinc stearate under nitrogen protection at 180° C. for 7 minutes to obtain preactivated polypropylene, wherein 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; 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 5:100, the mass ratio of maleic anhydride to the preactivated polypropylene is 2:100, and the mass ratio of triallyl isocyanurate to the preactivated polypropylene is 1.2:100, melt grafting at 185° C. under a vacuum environment for 8 minutes, cooling, and pelletizing to obtain modified polypropylene;

[0158] S23: The modified polypropylene is melt-blended and extruded with the double-modified graphene oxide and the multi-layered flame-retardant modified carbon nanotubes through a twin-screw extruder to obtain an environmentally friendly polypropylene-based composite material.

[0159] Specifically, S23: modified polypropylene, double modified graphene oxide and BYK-9077 are premixed in a high-speed mixer at a speed of 2400 rpm for 8 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 100:2.3:2.8:0.34, and then extruded using a twin-screw extruder, wherein the operating temperature of the twin-screw extruder is 180°C, the operating speed is 180 rpm, and water-cooled pelletizing is performed to obtain an environmentally friendly polypropylene-based composite material.

[0160] Comparative Example 1

[0161] This comparative example provides an environmentally friendly polypropylene-based composite material, which differs from Example 1 in that, in step S11, the mass ratio of graphene oxide to lipid film is 1:10, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0162] Comparative Example 2

[0163] This comparative example provides an environmentally friendly polypropylene-based composite material, which differs from Example 1 in that, in step S11, the mass ratio of graphene oxide to lipid film is 1:2, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0164] Comparative Example 3

[0165] This comparative example provides an environmentally friendly polypropylene-based composite material, which differs from Example 1 in that, in step S22, the mass ratio of the metal coordination modifier to the preactivated polypropylene is 8:100, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0166] Comparative Example 4

[0167] This comparative example provides an environmentally friendly polypropylene-based composite material, which differs from Example 1 in that, in step S22, the mass ratio of the metal coordination modifier to the preactivated polypropylene is 1:100, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0168] Comparative Example 5

[0169] This comparative example provides an environmentally friendly polypropylene-based composite material, which differs from Example 1 in that, in step S23, the mass ratio of modified polypropylene, double-modified graphene oxide, multi-layer flame-retardant modified carbon nanotubes, and dispersant is 100:1:5:0.2, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0170] Comparative Example 6

[0171] This comparative example provides an environmentally friendly polypropylene-based composite material, which differs from Example 1 in that, in step S23, the mass ratio of modified polypropylene, double-modified graphene oxide, multi-layer flame-retardant modified carbon nanotubes, and dispersant is 100:1:0.5:0.2, and the other operating steps and process parameters are exactly the same as those in Example 1.

[0172] The performance test of the environmentally friendly polypropylene-based composite materials of Examples 1-6 and Comparative Examples 1-6 was carried out, and the specific process is as follows:

[0173] Test the tensile strength and elongation at break of composite materials according to GB / T 1040.2-2022;

[0174] According to GB / T 2408-2021, the vertical burning grade of the test sample is tested;

[0175] The test results are shown in Table 1.

[0176] Table 1: Performance test results of environmentally friendly polypropylene-based composite materials of Examples 1-4 and Comparative Examples 1-6

[0177]

[0178] The test results of Example 1 and Comparative Examples 1 and 2 show that graphene oxide itself forms a dense, expanded carbonized layer through sheet stacking during the combustion process, which acts as a heat and oxygen barrier. 1,2-Dipalmitoyl-sn-glycero-3-phosphorylcholine forms a lipid bilayer structure on the surface of graphene oxide, improving its dispersibility and interfacial bonding in the polypropylene matrix. Excessive 1,2-Dipalmitoyl-sn-glycero-3-phosphorylcholine may lead to a high coverage of the graphene oxide surface, affecting the stacking of its sheets and the formation of thermal conductivity paths, and in turn reducing the mechanical properties and flame retardant properties. If the amount is insufficient, incomplete lipid layer coverage will lead to a decrease in the dispersibility and interfacial bonding of graphene oxide in the polypropylene matrix, significantly weakening the enhancement effect of mechanical properties and reducing flame retardant properties.

[0179] The test results of Example 1 and Comparative Examples 3 and 4 indicate that the hexafluorocyclotriphosphazene in the metal coordination modifier improves interfacial compatibility with the polypropylene matrix through chemical bonding with the silane coupling agent KH560 and acrylic acid. Furthermore, the introduction of components such as 4-aminophenol and zinc chloride promotes crosslinking of the material, enhancing the structural integrity and thermal stability of the composite material. Excessive use of hexafluorocyclotriphosphazene can lead to excessive crosslinking of the polypropylene matrix, reducing its toughness and affecting mechanical properties. Excessive catalytic carbonization can also result in an excessive carbonized layer, compromising the integrity of the material. Insufficient use of hexafluorocyclotriphosphazene can result in insufficient decomposition products to form an effective intumescent carbonized layer, resulting in reduced flame retardancy.

[0180] The test results of Example 1 and Comparative Examples 5 and 6 indicate that the addition of multi-layered flame-retardant modified carbon nanotubes can improve the mechanical and flame retardancy of polypropylene composites through a three-layered structure: "core," "shell," and "brush." ​​Excessive carbon nanotube content can lead to uneven dispersion within the matrix, forming aggregates and reducing stress transfer efficiency and flame retardancy. However, too low a content prevents the formation of a continuous reinforcement network, resulting in limited improvements in mechanical and flame retardancy.

[0181] The above description is only a specific embodiment 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: S11: A lipid film was prepared by rotary evaporation using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine; graphene oxide was dispersed and then composited with the lipid film and surface modified with 3-glycidylpropyltrimethoxysilane to obtain a biomimetic layer-modified graphene oxide; S12: dispersing the biomimetic layer modified graphene oxide in water, adding N-isopropylacrylamide monomer, and performing active polymerization in a cuprous bromide / pentamethyldiethylenetriamine catalytic system, followed by adding sodium ascorbate to terminate the reaction, thereby obtaining a 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-layered flame-retardant modified carbon nanotube; S21: Hexafluorocyclotriphosphazene is reacted with 4-aminophenol in the presence of triethylamine, followed by the introduction of silane coupling agent KH560 and tetrabutylammonium bromide, and metal coordination modification is performed with acrylic acid in the presence of zinc chloride catalysis to obtain a metal coordination modifier; S22: preactivating polypropylene with dicumyl 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 the double-modified graphene oxide, the multi-layered flame-retardant modified carbon nanotubes and the 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: In S11: The mass ratio of the graphene oxide dispersed in deionized water is 1:200-250; The mass ratio of the graphene oxide to the 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 1, characterized in that: In said S12: The mass ratio of the biomimetic 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: In S13: The mass ratio of the surface activated carbon nanotubes to magnesium sulfate is 1:6-7; The mass ratio of the 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 the maleic anhydride to the 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-layered 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. Use 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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