Polypropylene flame-retardant composite material and preparation method thereof

Abstract

The invention belongs to the field of high polymer materials, and particularly relates to a polypropylene flame-retardant composite material and a preparation method thereof. Epoxy functionalization is realized by grafting the ethylene-octylene copolymer, triazine ring is introduced through combination of an epoxy group and hydroxyl to obtain the modified ethylene-octylene copolymer, and the modified ethylene-octylene copolymer and zinc oxide and other components are used together to prepare the polypropylene flame-retardant composite material, so that the flame-retardant performance of the polypropylene composite material is improved while good flame-retardant performance is ensured. The material hardness is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and particularly relates to a polypropylene flame-retardant composite material and a preparation method thereof. Background Art

[0002] As one of the five general-purpose plastics, polypropylene has the advantages of light weight, corrosion resistance, excellent insulation performance, etc., so polypropylene is widely used in the fields of the automotive industry, product packaging, etc. However, polypropylene plastics also have their own disadvantages such as low mechanical properties, flammability, and poor thermal conductivity, which greatly limit their use in high-end products with special performance requirements. As a typical olefin-based high polymer, the combustion of polypropylene is accompanied by not only physical softening but also chemical processes such as molecular chain breakage and thermal degradation. The occurrence of the combustion process is first due to the absorption of heat, which causes the breakage of small molecular chains, and the volatilization of volatile combustible small molecular gases and free radicals. Then, after the combustible gas is mixed with air, the temperature is higher than the ignition point, and combustion occurs.

[0003] Chinese Patent (Publication No. CN116082754B) discloses a modified graphene oxide / hydrotalcite composite material, a preparation method thereof, and an application in a flame-retardant reinforced polypropylene composite material. The invention uses p-aminobenzenesulfonic acid diazonium salt to compound graphene oxide and hydrotalcite, avoiding the agglomeration phenomenon when used alone as a reinforcing agent. At the same time, ethylene-octene copolymer and naphthenic oil are added to the matrix, and the fluidity of the matrix is improved under their synergistic effect, so that the filler is well dispersed in the PP matrix. The prepared flame-retardant reinforced PP composite material has enhanced flame retardancy, better mechanical properties, and expanded application range compared with ordinary PP composite materials. This patented technology requires the addition of a reinforcing agent to achieve better effects. However, there is still a lack of in-depth research on how to improve the hardness of polypropylene composite materials and obtain good flame retardant properties without adding modified graphene oxide / hydrotalcite composite materials in the prior art.

[0004] Therefore, there is an urgent need for a polypropylene composite material that does not add modified graphene oxide / hydrotalcite as a reinforcing agent, but improves the flame retardancy and obtains better hardness through the modification treatment of the components of the composite material and the joint action of multiple components. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a polypropylene flame-retardant composite material and a preparation method thereof; in the present invention, the ethylene-octene copolymer is grafted to achieve epoxy functionalization, and then a triazine ring is introduced through the combination of epoxy groups and hydroxyl groups to obtain a modified ethylene-octene copolymer. By cooperating with the common use of zinc oxide and other components, a polypropylene flame-retardant composite material is prepared, which effectively improves the hardness of the material while ensuring good flame retardant performance.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows: In the first aspect of the present invention, a polypropylene flame-retardant composite material is provided, which includes the following components in parts by weight: 50 - 60 parts of polypropylene, 10 - 20 parts of modified ethylene-octene copolymer, 4 - 8 parts of zinc oxide, 2 - 4 parts of antioxidant, 2 - 4 parts of naphthenic oil, 1.4 - 1.8 parts of zinc stearate, and 1.2 - 1.6 parts of stearic acid.

[0007] As a preferred solution, the weight parts of the polypropylene in the present invention can be 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, etc.

[0008] As a preferred solution, the weight parts of the modified ethylene-octene copolymer in the present invention can be 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, etc.

[0009] As a preferred solution, the weight parts of the zinc oxide in the present invention can be 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, etc.

[0010] As a preferred solution, the weight parts of the antioxidant in the present invention can be 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, etc.

[0011] As a preferred solution, the weight parts of the naphthenic oil in the present invention can be 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, etc.

[0012] As a preferred solution, the weight parts of the zinc stearate in the present invention can be 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, etc.

[0013] As a preferred solution, the weight parts of the stearic acid in the present invention can be 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, etc.

[0014] As a preferred solution, the preparation method of the modified ethylene-octene copolymer includes: mixing a commercially available ethylene-octene copolymer and glycidyl methacrylate for grafting treatment to obtain an epoxidized ethylene-octene copolymer; then blending the epoxidized ethylene-octene copolymer and 1,3,5-tris(2-hydroxyethyl) cyanuric acid to obtain a modified ethylene-octene copolymer.

[0015] As a preferred solution, the steps of the grafting treatment include: mixing 90 - 100 parts of a commercially available ethylene-octene copolymer, 4 - 6 parts of glycidyl methacrylate, and 0.4 - 0.6 parts of diisopropyl peroxide in parts by weight, and transferring the mixture to a twin-screw extruder for melt grafting.

[0016] As a preferred solution, the temperature of the melt grafting is 170-180° C., and the screw speed is 50-60 r / min.

[0017] As a preferred solution, the blending step comprises: mixing 90-100 parts of ethylene oxide-octene copolymer and 1-3 parts of 1,3,5-tris(2-hydroxyethyl)cyanuric acid, and melt blending at 150-160° C. for 40-60 minutes.

[0018] The modified ethylene-octene copolymer of the present invention is first grafted with glycidyl methacrylate to achieve epoxy functionalization of the ethylene-octene copolymer, and then the triazine ring is introduced into the ethylene-octene copolymer by combining the epoxy group with the hydroxyl group in 1,3,5-tris(2-hydroxyethyl)cyanuric acid to prepare a modified ethylene-octene copolymer containing a triazine ring. When the material burns, the triazine ring structure will quickly produce a continuous and dense carbon layer in the condensed phase, slowing down the mass transfer and heat transfer between the inside and outside of the carbon layer. At the same time, the triazine ring structure is thermally cracked to release nitrogen-containing inert gas, which dilutes the oxygen around the burning material in the gas phase and takes away the heat generated during the combustion process. The triazine ring structure in the modified ethylene-octene copolymer can give the material rigidity to resist external forces, and at the same time, 1,3,5-tris(2-hydroxyethyl)cyanuric acid can be used as a curing agent for the epoxy group to form a cured cross-linked network, further improving the hardness of the composite material.

[0019] As a preferred solution, the zinc oxide is a zinc oxide composite material; The preparation method of the zinc oxide composite material comprises: using vinyltrimethoxysilane to perform surface treatment on nano zinc oxide to obtain surface double-bonded zinc oxide; pre-treating hydroxylated carbon nanotubes to obtain pre-treated carbon nanotubes, and then performing composite reaction with surface double-bonded zinc oxide to obtain the zinc oxide composite material.

[0020] As a preferred solution, the particle size of the nano zinc oxide is 20-50 nm.

[0021] As a preferred solution, the surface treatment step includes: adding 2 to 4 parts of nano zinc oxide to a mixture of 120 to 130 parts of anhydrous ethanol and 20 to 30 parts of deionized water by weight, stirring at a speed of 800 to 1000 r / min for 30 to 40 minutes, heating to 70 to 80° C., adding 0.2 to 0.8 parts of vinyl trimethoxy silane and stirring for 100 to 120 minutes, centrifuging, washing with anhydrous ethanol, and vacuum drying.

[0022] As a preferred embodiment, the steps of the pretreatment include: by weight, adding 1 to 3 parts of hydroxylated carbon nanotubes into 400 to 500 parts of N,N-dimethylformamide, ultrasonically dispersing uniformly, adding 3 to 5 parts of 4-cyano-4-(phenylthiocarbonothioylthio) pentanoic acid and 0.6 to 0.8 parts of 4-dimethylaminopyridine, stirring for 4 to 8 min, then adding 2 to 4 parts of N,N'-dicyclohexylcarbodiimide and stirring for 40 to 48 h, centrifuging, and vacuum-drying the lower-layer precipitate.

[0023] As a preferred embodiment, the steps of the composite reaction include: by weight, mixing 12 to 20 parts of surface double-bonded zinc oxide, 2 to 4 parts of pretreated carbon nanotubes, and 0.02 to 0.04 parts of 4,4'-azobis(4-cyanopentanoic acid), then adding 40 to 50 parts of 0.1 mol / L acetic acid-sodium acetate buffer solution, placing it in a nitrogen atmosphere, heating to 50 to 60 °C, stirring for 18 to 20 h, washing with water, and freeze-drying.

[0024] Vinyltrimethoxysilane of the present invention will hydrolyze to generate silanol groups in a mixed solution of absolute ethanol and deionized water, and undergo dehydration condensation with the surface hydroxyl groups of nano-zinc oxide, thereby introducing active double bonds on the surface of zinc oxide; hydroxylated carbon nanotubes first graft the RAFT chain transfer agent onto the surface of the carbon nanotubes through pretreatment, and then undergo RAFT polymerization with surface double-bonded zinc oxide through carbon-carbon double bonds to achieve composite, forming a carbon nanotube-zinc oxide composite material.

[0025] The nano-zinc oxide in the zinc oxide composite material can jointly form a barrier similar to a network structure with the carbon nanotubes. When the material encounters an external heat source and burns, this barrier can effectively hinder flame propagation and heat conduction, thereby reducing the combustion rate and the possibility of flame spread. At the same time, nano-zinc oxide can react with carbon monoxide, nitrogen oxides, etc., reducing the temperature of the flame and the concentration of gaseous combustion products, and thus achieving a reduction in flue gas emissions; carbon nanotubes promote the formation of a continuous heat conduction network to delay thermal decomposition and provide a catalytic surface to promote the charring reaction; through the synergistic effect of zinc oxide and carbon nanotubes, the flame retardancy of the composite material is significantly improved. In addition, the high modulus and nano-scale size of nano-zinc oxide can serve as rigid support points to limit the movement of polymer chain segments, while the high strength and high aspect ratio of carbon nanotubes can effectively disperse stress and reduce the plastic deformation of the matrix. The two are combined to form a network structure, significantly improving the hardness of the composite material.

[0026] As a preferred embodiment, the antioxidant is selected from 2,6-di-tert-butyl-p-cresol or tris(2,4-di-tert-butylphenyl) phosphite.

[0027] As a preferred embodiment, the naphthenic oil is selected from Karamay KN4010 or Karamay KN4006.

[0028] In a second aspect of the present invention, there is provided a method for preparing the polypropylene flame-retardant composite material as described in the first aspect, which comprises the following steps: By weight, 50 - 60 parts of polypropylene are added to a torque rheometer for mixing, and then 10 - 20 parts of modified ethylene-octene copolymer, 4 - 8 parts of zinc oxide, 2 - 4 parts of antioxidant, 2 - 4 parts of naphthenic oil, 1.4 - 1.8 parts of zinc stearate and 1.2 - 1.6 parts of stearic acid are added for mixing. After cooling to room temperature, it is press-molded, and then extruded and pelletized using a twin-screw extruder to obtain the polypropylene flame-retardant composite material.

[0029] As a preferred scheme, the temperature of the mixing is 190 - 200 °C and the time is 30 - 40 min.

[0030] Compared with the prior art, the present invention has the following beneficial effects: (1) In the modified ethylene-octene copolymer of the present invention, epoxy groups are introduced by grafting, and the zinc oxide composite material contains hydroxylated carbon nanotubes. During the melt processing of the polypropylene composite material, the hydroxyl groups can undergo ring-opening addition reactions with the epoxy functional groups, thereby constructing a high-density structure in the material and strengthening the polypropylene matrix. At the same time, zinc oxide, carbon nanotubes, etc. act as rigid nodes and also limit the slippage of polypropylene molecular chains, thereby improving the overall hardness of the composite material.

[0031] (2) The triazine ring of the modified ethylene-octene copolymer of the present invention will rapidly generate a carbon layer during material combustion, and promote the carbonization reaction through the catalytic surface provided by the carbon nanotubes, improving the density of the carbon layer and effectively slowing down the mass transfer and heat transfer between the inside and outside of the carbon layer; the triazine ring structure thermally decomposes to release nitrogen-containing inert gases to dilute the oxygen around the combustible material, and the nano-zinc oxide reacts with carbon monoxide, nitrogen oxides, etc., synergistically reducing the concentration of gaseous combustibles; through the synergistic effect of the triazine ring - zinc oxide - carbon nanotubes, the flame-retardant performance of the composite material is effectively improved. Specific Embodiments

[0032] To facilitate the understanding of the present invention, the following examples are listed for the present invention. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0033] The sources of some components in the examples and comparative examples are as follows: Commercially available ethylene-octene copolymer, grade POE 8200, purchased from DuPont, USA; Glycidyl methacrylate, CAS No. 106 - 91 - 2, purchased from Sinopharm Chemical Reagent Co., Ltd.; Dicumyl peroxide, CAS No. 80 - 43 - 3, purchased from Sinopharm Chemical Reagent Co., Ltd.; 1,3,5-Tris(2-hydroxyethyl) cyanuric acid, CAS No. 839-90-7, purchased from Shanghai Macklin Biochemical Co., Ltd.; Nano-zinc oxide Ⅰ, product number Z112847, particle size 30 nm, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Nano-zinc oxide Ⅱ, product number Z431819, particle size 3 μm, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; Vinyltrimethoxysilane, CAS No. 2768-02-7, purchased from Sinopharm Chemical Reagent Co., Ltd.; Hydroxylated carbon nanotubes, product number XFM32, purchased from Jiangsu Xianfeng Nano Materials Technology Co., Ltd.; N,N-Dimethylformamide, CAS No. 68-12-2, purchased from Sinopharm Chemical Reagent Co., Ltd.; 4-Cyano-4-(phenylthiocarbonothioylthio) pentanoic acid, CAS No. 201611-92-9, purchased from Shanghai Macklin Biochemical Co., Ltd.; 4-Dimethylaminopyridine, CAS No. 1122-58-3, purchased from Sinopharm Chemical Reagent Co., Ltd.; N,N'-Dicyclohexylcarbodiimide, CAS No. 538-75-0, purchased from Shanghai Macklin Biochemical Co., Ltd.; 4,4'-Azobis(4-cyanovaleric acid), CAS No. 2638-94-0, purchased from Shanghai Macklin Biochemical Co., Ltd.; Polypropylene, model EP548R, purchased from CNOOC and Shell Petrochemical Co., Ltd.; 2,6-Di-tert-butyl-p-cresol, CAS No. 128-37-0, purchased from Shanghai Macklin Biochemical Co., Ltd.; Tris(2,4-di-tert-butylphenyl) phosphite, CAS No. 31570-04-4, purchased from Shanghai Macklin Biochemical Co., Ltd.; Naphthenic oil: Karamay KN4010, Karamay KN4006; Zinc stearate, CAS No. 557-05-1, purchased from Shanghai Macklin Biochemical Co., Ltd.; Stearic acid, CAS No. 57-11-4, purchased from Sinopharm Chemical Reagent Co., Ltd. Example 1

[0034] This example provides a preparation method of a polypropylene flame retardant composite material, including the following steps: Add 60 parts by weight of polypropylene into a torque rheometer for mixing, then add 20 parts of modified ethylene-octene copolymer, 8 parts of zinc oxide composite material, 4 parts of antioxidant 2,6-di-tert-butyl-p-cresol, 4 parts of naphthenic oil Karamay KN4010, 1.8 parts of zinc stearate and 1.6 parts of stearic acid for mixing (temperature is 200 °C, time is 30 min). After cooling to room temperature, press and form, and then use a twin-screw extruder for extrusion granulation to obtain a polypropylene flame-retardant composite material.

[0035] Preparation of the modified ethylene-octene copolymer: Mix 100 parts by weight of commercially available ethylene-octene copolymer, 6 parts of glycidyl methacrylate and 0.6 parts of diisopropylbenzene peroxide evenly, transfer to a twin-screw extruder for melt grafting (temperature is 180 °C, screw speed is 60 r / min) to obtain an epoxidized ethylene-octene copolymer; Mix 100 parts of epoxidized ethylene-octene copolymer and 3 parts of 1,3,5-tris(2-hydroxyethyl) cyanuric acid, and carry out melt blending at 160 °C for 40 min to obtain a modified ethylene-octene copolymer.

[0036] Preparation of the zinc oxide composite material: Add 4 parts by weight of nano-zinc oxide I (product number Z112847, particle size is 30 nm) into a mixed solution of 130 parts of absolute ethanol and 20 parts of deionized water, stir at a speed of 1000 r / min for 30 min, heat up to 80 °C and then add 0.8 parts of vinyltrimethoxysilane and stir for 120 min, centrifuge, wash with absolute ethanol, and vacuum dry to obtain surface double-bonded zinc oxide; Add 3 parts of hydroxylated carbon nanotubes into 500 parts of N,N-dimethylformamide, ultrasonically disperse evenly, add 5 parts of 4-cyano-4-(phenylthiocarbamoylthio) pentanoic acid and 0.8 parts of 4-dimethylaminopyridine and stir for 8 min, then add 4 parts of N,N'-dicyclohexylcarbodiimide and stir for 48 h, centrifuge, and vacuum dry the lower layer precipitate to obtain pretreated carbon nanotubes; Mix 20 parts of surface double-bonded zinc oxide, 4 parts of pretreated carbon nanotubes and 0.04 parts of 4,4'-azobis(4-cyanopentanoic acid), then add 50 parts of 0.1 mol / L acetic acid-sodium acetate buffer solution, place in a nitrogen atmosphere, heat up to 60 °C and stir for 18 h, wash with water, and freeze-dry to obtain a zinc oxide composite material. Example 2

[0037] This example provides a preparation method of a polypropylene flame-retardant composite material, including the following steps: Add 50 parts by weight of polypropylene into a torque rheometer for mixing, then add 10 parts of modified ethylene-octene copolymer, 4 parts of zinc oxide composite material, 2 parts of antioxidant tris(2,4-di-tert-butylphenyl) phosphite, 2 parts of naphthenic oil Karamay KN4006, 1.4 parts of zinc stearate and 1.2 parts of stearic acid for mixing (temperature is 190 °C, time is 40 min). After cooling to room temperature, press and mold, and then use a twin-screw extruder for extrusion granulation to obtain a polypropylene flame-retardant composite material.

[0038] Preparation of the modified ethylene-octene copolymer: Mix 90 parts by weight of commercially available ethylene-octene copolymer, 4 parts of glycidyl methacrylate and 0.4 parts of diisopropylbenzene peroxide evenly, transfer to a twin-screw extruder for melt grafting (temperature is 170 °C, screw speed is 50 r / min) to obtain an epoxidized ethylene-octene copolymer; Mix 90 parts of epoxidized ethylene-octene copolymer and 1 part of 1,3,5-tris(2-hydroxyethyl) cyanuric acid, and carry out melt blending at 150 °C for 60 min to obtain a modified ethylene-octene copolymer.

[0039] Preparation of the zinc oxide composite material: Add 2 parts by weight of nano-zinc oxide I (product number Z112847, particle size is 30 nm) into a mixed solution of 120 parts of absolute ethanol and 30 parts of deionized water, stir at a speed of 800 r / min for 40 min, raise the temperature to 70 °C, then add 0.8 parts of vinyltrimethoxysilane and stir for 120 min, centrifuge, wash with absolute ethanol, and vacuum dry to obtain surface double-bonded zinc oxide; Add 1 part of hydroxylated carbon nanotubes into 400 parts of N,N-dimethylformamide and disperse evenly by ultrasonic treatment, add 3 parts of 4-cyano-4-(phenylthiocarbamoylthio) pentanoic acid and 0.6 parts of 4-dimethylaminopyridine and stir for 4 min, then add 2 parts of N,N'-dicyclohexylcarbodiimide and stir for 40 h, centrifuge, and vacuum dry the lower layer precipitate to obtain pretreated carbon nanotubes; Mix 12 parts of surface double-bonded zinc oxide, 2 parts of pretreated carbon nanotubes and 0.02 parts of 4,4'-azobis(4-cyanopentanoic acid), then add 40 parts of 0.1 mol / L acetic acid-sodium acetate buffer solution, place in a nitrogen atmosphere, raise the temperature to 50 °C and stir for 20 h, wash with water, and freeze-dry to obtain a zinc oxide composite material. Example 3

[0040] This example provides a preparation method of a polypropylene flame-retardant composite material, including the following steps: 55 parts by weight of polypropylene was added to a torque rheometer for mixing, and then 15 parts of a modified ethylene-octene copolymer, 6 parts of a zinc oxide composite material, 3 parts of an antioxidant (2,6-di-tert-butyl-p-cresol or tris(2,4-di-tert-butylphenyl) phosphite), 3 parts of naphthenic oil (Karamay KN4010 or Karamay KN4006), 1.6 parts of zinc stearate and 1.4 parts of stearic acid were added for mixing (temperature: 195 °C, time: 35 min). After cooling to room temperature, it was compression molded, and then extruded and pelletized using a twin-screw extruder to obtain a flame-retardant polypropylene composite material.

[0041] Preparation of the modified ethylene-octene copolymer: 95 parts by weight of a commercially available ethylene-octene copolymer, 5 parts of glycidyl methacrylate and 0.5 parts of diisopropyl peroxide were mixed evenly, transferred to a twin-screw extruder for melt grafting (temperature: 175 °C, screw speed: 55 r / min) to obtain an epoxidized ethylene-octene copolymer; 95 parts of the epoxidized ethylene-octene copolymer and 2 parts of 1,3,5-tris(2-hydroxyethyl) cyanuric acid were mixed and melt-blended at 155 °C for 50 min to obtain the modified ethylene-octene copolymer.

[0042] Preparation of the zinc oxide composite material: 3 parts of nano-zinc oxide I (product number Z112847, particle size: 30 nm) was added to a mixed solution of 125 parts of absolute ethanol and 25 parts of deionized water, stirred at a speed of 900 r / min for 35 min, heated to 75 °C, then 0.6 parts of vinyltrimethoxysilane was added and stirred for 110 min, centrifuged, washed with absolute ethanol, and vacuum dried to obtain surface double-bonded zinc oxide; 2 parts of hydroxylated carbon nanotubes were added to 450 parts of N,N-dimethylformamide and ultrasonically dispersed evenly, 4 parts of 4-cyano-4-(phenylthiocarbamoylthio) pentanoic acid and 0.7 parts of 4-dimethylaminopyridine were added and stirred for 6 min, then 3 parts of N,N'-dicyclohexylcarbodiimide was added and stirred for 44 h, centrifuged, and the lower layer precipitate was vacuum dried to obtain pretreated carbon nanotubes; 16 parts of surface double-bonded zinc oxide, 3 parts of pretreated carbon nanotubes and 0.03 parts of 4,4'-azobis(4-cyanopentanoic acid) were mixed, then 45 parts of 0.1 mol / L acetic acid-sodium acetate buffer solution was added, placed in a nitrogen atmosphere, heated to 55 °C and stirred for 19 h, washed with water, and freeze-dried to obtain the zinc oxide composite material. Example 4

[0043] The difference between this example and Example 1 is that nano-zinc oxide I (product number Z112847) was used to replace the zinc oxide composite material.

[0044] Comparative Example 1 The difference between this comparative example and Example 1 is that a commercially available ethylene-octene copolymer (grade POE 8200) is used to replace the modified ethylene-octene copolymer, and nano-zinc oxide I (product number Z112847) is used to replace the zinc oxide composite material.

[0045] Comparative Example 2 The difference between this comparative example and Example 1 is that a commercially available ethylene-octene copolymer (grade POE 8200) is used to replace the modified ethylene-octene copolymer.

[0046] Comparative Example 3 The difference between this comparative example and Example 1 is that nano-zinc oxide I (product number Z112847) is used to replace nano-zinc oxide II (product number Z431819) for the preparation of the zinc oxide composite material.

[0047] The properties of the polypropylene composite materials provided in the above examples and comparative examples were tested, and the test methods are as follows: (1) Oxygen index test: The test was carried out with reference to the requirements of "GB / T 2406.2-2009 Plastics - Determination of burning behavior by oxygen index - Part 2: Ambient temperature test".

[0048] (2) Rockwell hardness test: The test was carried out with reference to the requirements of "GB / T 3398.2-2008 Plastics - Determination of hardness - Part 2: Rockwell hardness".

[0049] The above performance test data are shown in Table 1:

[0050] It can be seen from the above that in the present invention, the ethylene-octene copolymer is grafted to achieve epoxy functionalization, and then a triazine ring is introduced by the combination of epoxy groups and hydroxyl groups to obtain a modified ethylene-octene copolymer. The modified ethylene-octene copolymer is used in combination with the zinc oxide composite material to prepare a polypropylene flame-retardant composite material (Examples 1 to 3), whose oxygen index is 26.2 - 26.5%, and the Rockwell hardness is 100.9 - 101.4.

[0051] Compared with Example 1, when using nano-zinc oxide I (product number Z112847) to replace the zinc oxide composite material, the oxygen index decreases and the Rockwell hardness decreases (Example 4); compared with Example 1, when using a commercially available ethylene-octene copolymer (grade POE8200) to replace the modified ethylene-octene copolymer and using nano-zinc oxide I (product number Z112847) to replace the zinc oxide composite material, the oxygen index decreases and the Rockwell hardness decreases (Comparative Example 1); compared with Example 1, when using a commercially available ethylene-octene copolymer (grade POE 8200) to replace the modified ethylene-octene copolymer, the oxygen index decreases and the Rockwell hardness decreases (Comparative Example 2); compared with Example 1, when using nano-zinc oxide I (product number Z112847) to replace nano-zinc oxide II (product number Z431819) for the preparation of the zinc oxide composite material, since the particle size of nano-zinc oxide II is too large and the modification effect is poor, the oxygen index decreases and the Rockwell hardness decreases (Comparative Example 3).

[0052] In summary, the present invention realizes epoxy functionalization by grafting an ethylene-octene copolymer, and then introduces a triazine ring by combining an epoxy group with a hydroxyl group to obtain a modified ethylene-octene copolymer. By jointly using zinc oxide and other components, a polypropylene flame-retardant composite material is prepared, which effectively improves the material hardness while ensuring good flame-retardant performance.

Claims

1. A polypropylene flame-retardant composite material, characterized in that by weight, it comprises the following components: 50 - 60 parts of polypropylene, 10 - 20 parts of modified ethylene-octene copolymer, 4 - 8 parts of zinc oxide, 2 - 4 parts of antioxidant, 2 - 4 parts of naphthenic oil, 1.4 - 1.8 parts of zinc stearate and 1.2 - 1.6 parts of stearic acid; The preparation method of the modified ethylene-octene copolymer includes: mixing a commercially available ethylene-octene copolymer and glycidyl methacrylate for grafting treatment to obtain an epoxidized ethylene-octene copolymer; then blending the epoxidized ethylene-octene copolymer and 1,3,5-tris(2-hydroxyethyl) cyanuric acid to obtain a modified ethylene-octene copolymer.

2. The polypropylene flame-retardant composite material according to claim 1, characterized in that The steps of the grafting treatment include: by weight, mixing 90 - 100 parts of a commercially available ethylene-octene copolymer, 4 - 6 parts of glycidyl methacrylate and 0.4 - 0.6 parts of diisopropylbenzene peroxide evenly, and transferring them to a twin-screw extruder for melt grafting.

3. The polypropylene flame-retardant composite material according to claim 1, characterized in that The steps of the blending treatment include: mixing 90 - 100 parts of the epoxidized ethylene-octene copolymer and 1 - 3 parts of 1,3,5-tris(2-hydroxyethyl) cyanuric acid, and melt-blending them at 150 - 160 °C for 40 - 60 min.

4. The polypropylene flame-retardant composite material according to claim 1, characterized in that The zinc oxide is a zinc oxide composite material; The preparation method of the zinc oxide composite material includes: surface-treating nano zinc oxide with vinyltrimethoxysilane to obtain surface double-bonded zinc oxide; pretreating hydroxylated carbon nanotubes to obtain pretreated carbon nanotubes, and then carrying out a composite reaction with the surface double-bonded zinc oxide to obtain a zinc oxide composite material.

5. The polypropylene flame-retardant composite material according to claim 4, characterized in that The steps of the surface treatment include: by weight, adding 2 - 4 parts of nano zinc oxide into a mixed solution of 120 - 130 parts of absolute ethanol and 20 - 30 parts of deionized water, stirring at a speed of 800 - 1000 r / min for 30 - 40 min, heating to 70 - 80 °C, then adding 0.2 - 0.8 parts of vinyltrimethoxysilane and stirring for 100 - 120 min, centrifuging, washing with absolute ethanol, and vacuum drying.

6. The polypropylene flame-retardant composite material according to claim 4, characterized in that The steps of the pretreatment include: by weight, adding 1 - 3 parts of hydroxylated carbon nanotubes into 400 - 500 parts of N,N-dimethylformamide, ultrasonically dispersing them evenly, adding 3 - 5 parts of 4-cyano-4-(phenylthioformylthio) pentanoic acid and 0.6 - 0.8 parts of 4-dimethylaminopyridine and stirring for 4 - 8 min, then adding 2 - 4 parts of N,N'-dicyclohexylcarbodiimide and stirring for 40 - 48 h, centrifuging, and vacuum drying the lower-layer precipitate.

7. The polypropylene flame-retardant composite material according to claim 4, characterized in that The steps of the composite reaction include: mixing 12-20 parts by weight of surface double-bonded zinc oxide, 2-4 parts of pretreated carbon nanotubes, and 0.02-0.04 parts of 4,4'-azobis(4-cyanovaleric acid), adding 40-50 parts of 0.1 mol / L acetic acid-sodium acetate buffer solution, placing it in a nitrogen atmosphere, heating to 50-60 °C and stirring for 18-20 h, washing with water, and freeze-drying.

8. The polypropylene flame-retardant composite material according to claim 1, wherein the antioxidant is selected from 2,6-di-tert-butyl-p-cresol or tris(2,4-di-tert-butylphenyl) phosphite.

9. The polypropylene flame-retardant composite material according to claim 1, wherein the naphthenic oil is selected from Karamay KN4010 or Karamay KN4006.

10. A method for preparing a polypropylene flame-retardant composite material according to any one of claims 1-9, wherein including the following steps: 50-60 parts by weight of polypropylene are added to a torque rheometer for mixing, then 10-20 parts of modified ethylene-octene copolymer, 4-8 parts of zinc oxide, 2-4 parts of antioxidant, 2-4 parts of naphthenic oil, 1.4-1.8 parts of zinc stearate, and 1.2-1.6 parts of stearic acid are added for mixing, cooled to room temperature and then compression-molded, and then extruded and pelletized using a twin-screw extruder to obtain the polypropylene flame-retardant composite material.

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