A polypropylene flame-retardant composite material and a preparation method thereof

Abstract

The application belongs to the field of high polymer materials, and particularly relates to a polypropylene flame-retardant composite material and a preparation method thereof. The modified ethylene-octene copolymer is prepared by grafting ethylene-octene copolymer to realize epoxy functionalization, introducing a triazine ring through the combination of an epoxy group and a hydroxyl group, and using zinc oxide and other components together, so that the polypropylene flame-retardant composite material is prepared, and the material hardness is effectively improved while good flame-retardant performance is ensured.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a flame-retardant polypropylene composite material and its preparation method. Background Technology

[0002] Polypropylene, one of the five major general-purpose plastics, boasts advantages such as light weight, corrosion resistance, and excellent insulation properties, making it widely used in the automotive industry and product packaging. However, polypropylene also has drawbacks, including relatively low mechanical properties, flammability, and poor thermal conductivity, significantly limiting its use in high-end products with specific performance requirements. As a typical olefin polymer, polypropylene combustion involves not only physical softening but also chemical processes such as molecular chain breakage and thermal degradation. The combustion process begins with the absorption of heat, leading to the breakage of small molecular chains and the release of volatile, flammable small-molecule gases and free radicals. The flammable gases then mix with air at a temperature exceeding their ignition point, resulting in combustion.

[0003] Chinese patent (publication number CN116082754B) discloses a modified graphene oxide / hydrotalcite composite material, its preparation method, and its application in flame-retardant and reinforcing polypropylene composites. This invention utilizes diazonium salt of p-aminobenzenesulfonic acid to composite graphene oxide with hydrotalcite, avoiding the agglomeration phenomenon that occurs when graphene oxide is used alone as a reinforcing agent. Simultaneously, ethylene-octene copolymer and naphthenic oil are added to the matrix, which synergistically improve the fluidity of the matrix, resulting in good dispersion of the filler in the PP matrix. Compared with ordinary PP composites, the resulting flame-retardant and reinforcing PP composite material exhibits enhanced flame retardancy, better mechanical properties, and expands the material's application range. This patented technology requires the addition of a reinforcing agent to achieve good results. However, existing technologies lack in-depth research on how to improve the hardness of polypropylene composites and obtain good flame retardant properties without adding modified graphene oxide / hydrotalcite composite materials.

[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 instead improves flame retardancy and achieves better hardness by modifying the components of the composite material and leveraging the synergistic effect between multiple components. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a polypropylene flame-retardant composite material and its preparation method. The present invention achieves epoxy functionalization by grafting ethylene-octene copolymer, and then introduces a triazine ring through the combination of epoxy groups and hydroxyl groups to obtain a modified ethylene-octene copolymer. Combined with zinc oxide and other components, a polypropylene flame-retardant composite material is prepared, effectively improving material hardness while ensuring good flame-retardant properties.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] A first aspect of the present invention provides a polypropylene flame-retardant composite material, comprising, by weight, the following components:

[0008] 50-60 parts polypropylene, 10-20 parts modified ethylene-octene copolymer, 4-8 parts zinc oxide, 2-4 parts antioxidant, 2-4 parts naphthenic oil, 1.4-1.8 parts zinc stearate and 1.2-1.6 parts stearic acid.

[0009] As a preferred embodiment, the polypropylene in this invention can be in the following weight proportions: 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, or 60 parts, etc.

[0010] As a preferred embodiment, the modified ethylene-octene copolymer of the present invention may be in the following weight proportions: 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, or 20 parts, etc.

[0011] As a preferred embodiment, the zinc oxide in this invention can be in the form of 4, 5, 6, 7, or 8 parts by weight.

[0012] As a preferred embodiment, the antioxidant in this invention can be expressed in parts by weight of 2, 2.5, 3, 3.5, or 4 parts, etc.

[0013] As a preferred embodiment, the naphthenic oil in this invention can be in the following weight proportions: 2 parts, 2.5 parts, 3 parts, 3.5 parts, or 4 parts, etc.

[0014] As a preferred embodiment, the weight parts of zinc stearate in this invention may be 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, or 1.8 parts, etc.

[0015] As a preferred embodiment, the weight parts of stearic acid in this invention may be 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, or 1.6 parts, etc.

[0016] As a preferred embodiment, the method for preparing the modified ethylene-octene copolymer includes: grafting a commercially available ethylene-octene copolymer and glycidyl methacrylate to obtain an epoxide-octene copolymer; and then blending the epoxide-octene copolymer with 1,3,5-tris(2-hydroxyethyl)cyanuric acid to obtain the modified ethylene-octene copolymer.

[0017] As a preferred embodiment, the grafting process includes: mixing 90-100 parts by weight of commercially available ethylene-octene copolymer, 4-6 parts by weight of glycidyl methacrylate and 0.4-0.6 parts by weight of dicumyl peroxide, and then transferring the mixture to a twin-screw extruder for melt grafting.

[0018] As a preferred embodiment, the temperature of the fusion grafting is 170~180℃, and the screw speed is 50~60r / min.

[0019] As a preferred embodiment, the blending process includes: 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.

[0020] The modified ethylene-octene copolymer of this invention is first grafted with glycidyl methacrylate to achieve epoxy functionalization of the ethylene-octene copolymer. Then, by combining the epoxy groups with the hydroxyl groups in 1,3,5-tris(2-hydroxyethyl)cyanuric acid, a triazine ring is introduced into the ethylene-octene copolymer, thus preparing a modified ethylene-octene copolymer containing a triazine ring. When the material burns, the triazine ring structure rapidly generates a continuous and dense char layer in the condensed phase, slowing down mass and heat transfer between the inside and outside of the char layer. Simultaneously, the thermal decomposition of the triazine ring structure releases nitrogen-containing inert gas, diluting the oxygen around the burning material in the gas phase and carrying away the heat generated during combustion. The triazine ring structure in the modified ethylene-octene copolymer can endow the material with rigidity to resist external forces, while 1,3,5-tris(2-hydroxyethyl)cyanuric acid can act as a curing agent for the epoxy groups, forming a cured cross-linked network, further improving the hardness of the composite material.

[0021] As a preferred embodiment, the zinc oxide is a zinc oxide composite material;

[0022] The method for preparing the zinc oxide composite material includes: surface-treating nano zinc oxide with vinyltrimethoxysilane to obtain surface-double-bonded zinc oxide; pre-treating hydroxylated carbon nanotubes to obtain pre-treated carbon nanotubes, and then performing a composite reaction with surface-double-bonded zinc oxide to obtain the zinc oxide composite material.

[0023] As a preferred embodiment, the particle size of the nano zinc oxide is 20~50nm.

[0024] As a preferred embodiment, the surface treatment steps include: adding 2-4 parts by weight of nano zinc oxide to a mixture of 120-130 parts by weight of anhydrous ethanol and 20-30 parts by weight of deionized water, stirring at 800-1000 r / min for 30-40 min, heating to 70-80℃, adding 0.2-0.8 parts by weight of vinyltrimethoxysilane, stirring for 100-120 min, centrifuging, washing with anhydrous ethanol, and vacuum drying.

[0025] As a preferred embodiment, the pretreatment step includes: adding 1-3 parts by weight of hydroxylated carbon nanotubes to 400-500 parts of N,N-dimethylformamide and dispersing them evenly by ultrasonication; adding 3-5 parts of 4-cyano-4-(phenylthiocarbamoylthio)valerate 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 precipitate.

[0026] As a preferred embodiment, the steps of the composite reaction include: mixing 12-20 parts by weight of surface-double-bonded zinc oxide, 2-4 parts by weight of pretreated carbon nanotubes and 0.02-0.04 parts by weight of 4,4'-azobis(4-cyanopentanoic acid), then adding 40-50 parts by weight of 0.1 mol / L acetate-sodium acetate buffer solution, placing the mixture under a nitrogen atmosphere, heating to 50-60°C and stirring for 18-20 h, washing with water, and lyophilizing.

[0027] The vinyltrimethoxysilane of the present invention undergoes hydrolysis in a mixture of anhydrous ethanol and deionized water to generate silanol groups, which then undergo dehydration condensation with hydroxyl groups on the surface of nano zinc oxide, thereby introducing active double bonds on the surface of zinc oxide. The hydroxylated carbon nanotubes are first pretreated to graft RAFT chain transfer agent onto the surface of the carbon nanotubes, and then composited with the surface double-bonded zinc oxide through RAFT polymerization via carbon-carbon double bonds to form a carbon nanotube-zinc oxide composite material.

[0028] In zinc oxide composites, nano-zinc oxide, together with carbon nanotubes, forms a network-like barrier. When the material burns upon contact with an external heat source, this barrier effectively hinders flame propagation and heat conduction, thereby reducing the combustion rate and the likelihood of flame spread. Simultaneously, nano-zinc oxide reacts with carbon monoxide and nitrogen oxides, lowering the flame temperature and the concentration of gaseous combustion products, thus reducing flue gas emissions. Carbon nanotubes promote the formation of a continuous thermally conductive network, delaying thermal decomposition and providing a catalytic surface to facilitate char formation. Through the synergistic effect of zinc oxide and carbon nanotubes, the flame retardancy of the composite material is significantly improved. Furthermore, the high modulus and nanoscale size of nano-zinc oxide act as rigid support points, restricting the movement of polymer chain segments, while the high strength and high aspect ratio of carbon nanotubes effectively disperse stress and reduce plastic deformation of the matrix. The combined effect of these two elements forms a network structure, significantly improving the hardness of the composite material.

[0029] As a preferred embodiment, the antioxidant is selected from 2,6-di-tert-butyl-p-cresol or tris(2,4-di-tert-butylphenyl) phosphite.

[0030] As a preferred embodiment, the naphthenic oil is selected from Karamay KN4010 or Karamay KN4006.

[0031] A second aspect of the present invention provides a method for preparing a polypropylene flame-retardant composite material as described in the first aspect.

[0032] Includes the following steps:

[0033] By weight, 50-60 parts of polypropylene were added to a torque rheometer for mixing, followed by 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 for further mixing. After cooling to room temperature, the mixture was pressed into shape and then extruded and granulated using a twin-screw extruder to obtain a flame-retardant polypropylene composite material.

[0034] As a preferred embodiment, the mixing temperature is 190~200℃ and the time is 30~40min.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The modified ethylene-octene copolymer of the present invention introduces epoxy groups through grafting, while 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 reaction with the epoxy functional groups, thereby constructing a high-density structure in the material and reinforcing the polypropylene matrix. At the same time, zinc oxide, carbon nanotubes and other rigid nodes will also restrict the slippage of polypropylene molecular chain segments, thereby improving the overall hardness of the composite material.

[0037] (2) The triazine ring of the modified ethylene-octene copolymer of the present invention will rapidly generate a carbon layer when the material is burned, and promote the carbonization reaction through the catalytic surface provided by carbon nanotubes, thereby improving the density of the carbon layer and effectively slowing down the mass and heat transfer between the inside and outside of the carbon layer; the thermal decomposition of the triazine ring structure releases nitrogen-containing inert gas to dilute the oxygen around the burning material, while nano zinc oxide reacts with carbon monoxide, nitrogen oxides, etc., to synergistically reduce the concentration of gaseous combustion products; through the synergistic effect of triazine ring-zinc oxide-carbon nanotubes, the flame retardant performance of the composite material is effectively improved. Detailed Implementation

[0038] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0039] The sources of some components in the examples and comparative examples are as follows:

[0040] Commercially available ethylene-octene copolymer, grade POE 8200, purchased from DuPont, USA;

[0041] Glycidyl methacrylate, CAS No. 106-91-2, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0042] Dicumyl peroxide, CAS No. 80-43-3, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0043] 1,3,5-Tris(2-hydroxyethyl)cyanuric acid, CAS No. 839-90-7, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0044] Nano zinc oxide I, product number Z112847, with a particle size of 30nm, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0045] Nano zinc oxide II, product number Z431819, with a particle size of 3μm, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0046] Vinyltrimethoxysilane, CAS No. 2768-02-7, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0047] Hydroxylated carbon nanotubes, product number XFM32, were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0048] N,N-Dimethylformamide, CAS No. 68-12-2, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0049] 4-Cyano-4-(phenylthiocarbamoylthio)valerate, CAS No. 201611-92-9, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0050] 4-Dimethylaminopyridine, CAS No. 1122-58-3, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0051] N,N'-Dicyclohexylcarbodiimide, CAS No. 538-75-0, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0052] 4,4'-Azobis(4-cyanopentanoic acid), CAS No. 2638-94-0, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0053] Polypropylene, model EP548R, purchased from CNOOC Shell Petrochemicals Co., Ltd.

[0054] 2,6-Di-tert-butyl-p-cresol, CAS No. 128-37-0, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0055] Tris(2,4-di-tert-butylphenyl) phosphite, CAS No. 31570-04-4, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0056] Naphthenic oils: Karamay KN4010, Karamay KN4006;

[0057] Zinc stearate, CAS No. 557-05-1, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0058] Stearic acid, CAS No. 57-11-4, purchased from Sinopharm Chemical Reagent Co., Ltd. Example 1

[0059] This embodiment provides a method for preparing a flame-retardant polypropylene composite material, including the following steps:

[0060] By weight, 60 parts of polypropylene were added to a torque rheometer for mixing, followed by 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 (at 200℃ for 30 min). After cooling to room temperature, the mixture was pressed into shape and then extruded and granulated using a twin-screw extruder to obtain the polypropylene flame-retardant composite material.

[0061] Preparation of the modified ethylene-octene copolymer: By weight, 100 parts of commercially available ethylene-octene copolymer, 6 parts of glycidyl methacrylate and 0.6 parts of dicumyl peroxide are mixed evenly and transferred to a twin-screw extruder for melt grafting (temperature 180℃, screw speed 60r / min) to obtain epoxidized ethylene-octene copolymer; 100 parts of epoxidized ethylene-octene copolymer and 3 parts of 1,3,5-tris(2-hydroxyethyl)cyanuric acid are mixed and melt-blended at 160℃ for 40min to obtain modified ethylene-octene copolymer.

[0062] Preparation of the zinc oxide composite material: By weight, 4 parts of nano-zinc oxide I (item number Z112847, particle size 30 nm) were added to a mixture of 130 parts anhydrous ethanol and 20 parts deionized water. The mixture was stirred at 1000 r / min for 30 min, heated to 80℃, and then 0.8 parts of vinyltrimethoxysilane were added and stirred for 120 min. The mixture was centrifuged, washed with anhydrous ethanol, and vacuum dried to obtain surface-double-bonded zinc oxide. 3 parts of hydroxylated carbon nanotubes were added to 500 parts of N,N-dimethylformamide and ultrasonically dispersed until uniformly dispersed. 5 parts of 4- Cyano-4-(phenylthiocarbamoylthio)valerate and 0.8 parts of 4-dimethylaminopyridine were stirred for 8 min, and then 4 parts of N,N'-dicyclohexylcarbodiimide were added and stirred for 48 h. After centrifugation, the lower precipitate was vacuum dried to obtain pretreated carbon nanotubes. 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) were mixed, and then 50 parts of 0.1 mol / L acetate-sodium acetate buffer were added. The mixture was placed under a nitrogen atmosphere, heated to 60 °C and stirred for 18 h, washed with water and freeze-dried to obtain the zinc oxide composite material. Example 2

[0063] This embodiment provides a method for preparing a flame-retardant polypropylene composite material, including the following steps:

[0064] By weight, 50 parts of polypropylene were added to a torque rheometer for mixing, followed by 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 (at 190°C for 40 min). After cooling to room temperature, the mixture was pressed into shape and then extruded and granulated using a twin-screw extruder to obtain the polypropylene flame-retardant composite material.

[0065] Preparation of the modified ethylene-octene copolymer: By weight, 90 parts of commercially available ethylene-octene copolymer, 4 parts of glycidyl methacrylate and 0.4 parts of dicumyl peroxide are mixed evenly and transferred to a twin-screw extruder for melt grafting (temperature 170℃, screw speed 50r / min) to obtain epoxidized ethylene-octene copolymer; 90 parts of epoxidized ethylene-octene copolymer and 1 part of 1,3,5-tris(2-hydroxyethyl)cyanuric acid are mixed and melt-blended at 150℃ for 60min to obtain modified ethylene-octene copolymer.

[0066] Preparation of the zinc oxide composite material: By weight, 2 parts of nano zinc oxide I (item number Z112847, particle size 30 nm) were added to a mixture of 120 parts anhydrous ethanol and 30 parts deionized water. The mixture was stirred at 800 r / min for 40 min, heated to 70 °C, and then 0.8 parts of vinyltrimethoxysilane were added and stirred for 120 min. The mixture was centrifuged, washed with anhydrous ethanol, and vacuum dried to obtain surface-double-bonded zinc oxide. 1 part of hydroxylated carbon nanotubes was added to 400 parts of N,N-dimethylformamide and ultrasonically dispersed until uniformly dispersed. 3 parts of 4-cyanocyanate were then added. 4-(phenylthiocarbamoylthio)valerate and 0.6 parts of 4-dimethylaminopyridine were stirred for 4 min, and then 2 parts of N,N'-dicyclohexylcarbodiimide were added and stirred for 40 h. After centrifugation, the lower precipitate was vacuum dried to obtain pretreated carbon nanotubes. 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) were mixed, and then 40 parts of 0.1 mol / L acetate-sodium acetate buffer were added. The mixture was placed under a nitrogen atmosphere, heated to 50 °C and stirred for 20 h. After washing with water and freeze-drying, zinc oxide composite material was obtained. Example 3

[0067] This embodiment provides a method for preparing a flame-retardant polypropylene composite material, including the following steps:

[0068] By weight, 55 parts of polypropylene were added to a torque rheometer for mixing, followed by 15 parts of modified ethylene-octene copolymer, 6 parts of zinc oxide composite material, 3 parts of 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 for mixing (at 195°C for 35 min). After cooling to room temperature, the mixture was pressed into shape and then extruded and granulated using a twin-screw extruder to obtain the polypropylene flame-retardant composite material.

[0069] Preparation of the modified ethylene-octene copolymer: 95 parts by weight of commercially available ethylene-octene copolymer, 5 parts by weight of glycidyl methacrylate and 0.5 parts by weight of dicumyl peroxide are mixed evenly and transferred to a twin-screw extruder for melt grafting (temperature 175℃, screw speed 55r / min) to obtain epoxide-octene copolymer; 95 parts by weight of epoxide-octene copolymer and 2 parts by weight of 1,3,5-tris(2-hydroxyethyl)cyanuric acid are mixed and melt-blended at 155℃ for 50 min to obtain modified ethylene-octene copolymer.

[0070] Preparation of the zinc oxide composite material: By weight, 3 parts of nano zinc oxide I (item number Z112847, particle size 30 nm) were added to a mixture of 125 parts anhydrous ethanol and 25 parts deionized water. The mixture was stirred at 900 r / min for 35 min, heated to 75℃, and then 0.6 parts of vinyltrimethoxysilane were added and stirred for 110 min. The mixture was centrifuged, washed with anhydrous 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 until uniformly dispersed. 4 parts of 4-cyanocyanate were then added. 4,4'-(phenylthiocarbamoylthio)valerate and 0.7 parts of 4-dimethylaminopyridine were stirred for 6 min, and then 3 parts of N,N'-dicyclohexylcarbodiimide were added and stirred for 44 h. After centrifugation, the lower 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, and then 45 parts of 0.1 mol / L acetate-sodium acetate buffer were added. The mixture was placed under a nitrogen atmosphere, heated to 55 °C and stirred for 19 h. After washing with water and lyophilizing, zinc oxide composite material was obtained. Example 4

[0071] The difference between this embodiment and Embodiment 1 is that nano zinc oxide I (item number Z112847) is used instead of zinc oxide composite material.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 1 is that a commercially available ethylene-octene copolymer (brand name POE 8200) was used instead of the modified ethylene-octene copolymer, and nano zinc oxide I (product number Z112847) was used instead of the zinc oxide composite material.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 1 is that a commercially available ethylene-octene copolymer (brand name POE 8200) was used instead of the modified ethylene-octene copolymer.

[0076] Comparative Example 3

[0077] The difference between this comparative example and Example 1 is that nano zinc oxide I (item number Z112847) was used instead of nano zinc oxide II (item number Z431819) in the preparation of the zinc oxide composite material.

[0078] The properties of the polypropylene composite materials provided in the above embodiments and comparative examples were tested using the following methods:

[0079] (1) Oxygen index test: The test shall be conducted in accordance with the requirements of GB / T 2406.2-2009 Determination of combustion behavior of plastics by oxygen index method - Part 2: Room temperature test.

[0080] (2) Rockwell hardness test: The test shall be conducted in accordance with the requirements of GB / T 3398.2-2008 Plastics hardness determination Part 2: Rockwell hardness.

[0081] The performance test data above are shown in Table 1:

[0082] As can be seen from the above, the present invention achieves epoxy functionalization by grafting ethylene-octene copolymer, and then introduces triazine ring through the combination of epoxy group and hydroxyl group to obtain modified ethylene-octene copolymer. When used together with zinc oxide composite material, polypropylene flame retardant composite material is prepared (Examples 1-3), with an oxygen index of 26.2-26.5% and a Rockwell hardness of 100.9-101.4.

[0083] Compared to Example 1, using nano-zinc oxide I (item number Z112847) instead of zinc oxide composite material resulted in a decrease in oxygen index and Rockwell hardness (Example 4); compared to Example 1, using commercially available ethylene-octene copolymer (item number POE8200) instead of modified ethylene-octene copolymer and using nano-zinc oxide I (item number Z112847) instead of zinc oxide composite material resulted in a decrease in oxygen index and Rockwell hardness (Comparative Example 1); compared to Example 1, using commercially available ethylene-octene copolymer (item number POE 8200) instead of modified ethylene-octene copolymer resulted in a decrease in oxygen index and Rockwell hardness (Comparative Example 2); compared to Example 1, using nano-zinc oxide I (item number Z112847) instead of nano-zinc oxide II (item number Z431819) in the preparation of zinc oxide composite material resulted in a decrease in oxygen index and Rockwell hardness due to the excessively large particle size of nano-zinc oxide II and poor modification effect (Comparative Example 3).

[0084] In summary, this invention achieves epoxy functionalization by grafting ethylene-octene copolymer, and then introduces triazine rings through the combination of epoxy groups and hydroxyl groups to obtain modified ethylene-octene copolymer. With the combined use of zinc oxide and other components, a polypropylene flame-retardant composite material is prepared, which effectively improves the material hardness while ensuring good flame-retardant properties.

Claims

1. A flame-retardant polypropylene composite material, characterized in that, Based on parts by weight, it includes the following components: 50-60 parts polypropylene, 10-20 parts modified ethylene-octene copolymer, 4-8 parts zinc oxide composite material, 2-4 parts antioxidant, 2-4 parts naphthenic oil, 1.4-1.8 parts zinc stearate and 1.2-1.6 parts stearic acid; The method for preparing the modified ethylene-octene copolymer includes: grafting a commercially available ethylene-octene copolymer and glycidyl methacrylate to obtain an epoxidized ethylene-octene copolymer; and then blending the epoxidized ethylene-octene copolymer with 1,3,5-tris(2-hydroxyethyl)cyanuric acid to obtain the modified ethylene-octene copolymer. The preparation method of the zinc oxide composite material includes: surface treatment of nano zinc oxide with vinyltrimethoxysilane to obtain surface double-bonded zinc oxide; hydroxylated carbon nanotubes are first pretreated by grafting RAFT chain transfer agent onto the surface of carbon nanotubes to obtain pretreated carbon nanotubes, and then composited with surface double-bonded zinc oxide through RAFT polymerization via carbon-carbon double bonds to obtain zinc oxide composite material.

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

3. The polypropylene flame-retardant composite material according to claim 1, characterized in that, The blending process includes: 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.

4. The polypropylene flame-retardant composite material according to claim 1, characterized in that, The surface treatment steps include: adding 2-4 parts by weight of nano zinc oxide to a mixture of 120-130 parts by weight of anhydrous ethanol and 20-30 parts by weight of deionized water, stirring at 800-1000 r / min for 30-40 min, heating to 70-80℃, adding 0.2-0.8 parts by weight of vinyltrimethoxysilane, stirring for 100-120 min, centrifuging, washing with anhydrous ethanol, and vacuum drying.

5. The polypropylene flame-retardant composite material according to claim 1, characterized in that, The pretreatment steps include: adding 1-3 parts by weight of hydroxylated carbon nanotubes to 400-500 parts of N,N-dimethylformamide and dispersing them evenly by ultrasonication; adding 3-5 parts of 4-cyano-4-(phenylthiocarbamoylthio)valerate 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 precipitate.

6. The polypropylene flame-retardant composite material according to claim 1, characterized in that, The composite process includes: mixing 12-20 parts by weight of surface-double-bonded zinc oxide, 2-4 parts by weight of pretreated carbon nanotubes and 0.02-0.04 parts by weight of 4,4'-azobis(4-cyanopentanoic acid), then adding 40-50 parts by weight of 0.1 mol / L acetate-sodium acetate buffer solution, placing the mixture under a nitrogen atmosphere, heating to 50-60°C and stirring for 18-20 h, washing with water, and lyophilizing.

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

8. The polypropylene flame-retardant composite material according to claim 1, characterized in that, The naphthenic oil is selected from Karamay KN4010 or Karamay KN4006.

9. A method for preparing a polypropylene flame-retardant composite material as described in any one of claims 1-8, characterized in that, Includes the following steps: By weight, 50-60 parts of polypropylene were added to a torque rheometer for mixing, followed by 10-20 parts of modified ethylene-octene copolymer, 4-8 parts of zinc oxide composite material, 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 for further mixing. After cooling to room temperature, the mixture was pressed into shape and then extruded and granulated using a twin-screw extruder to obtain a flame-retardant polypropylene composite material.

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