A modified polypropylene material and its application in HPPM double-wall corrugated pipes

Abstract

This invention relates to the field of polymer materials and discloses a modified polypropylene material and its application in HPPM double-wall corrugated pipes. The modified polypropylene material comprises: polypropylene resin, modified graphitic carbon nitride, modified multi-walled carbon nanotubes, and additives. The modified graphitic carbon nitride is prepared by grafting a hindered amine-type bromine-substituted intermediate with amino-modified graphitic carbon nitride. The hindered amine-type bromine-substituted intermediate is prepared by reacting ethyl 2-amino-4-methylthiazolium-5-carboxylate with 1,4-dibromobutane and then undergoing transesterification with 2,2,6,6-tetramethyl-4-piperidinol. The modified multi-walled carbon nanotubes are prepared by grafting acyl chloride multi-walled carbon nanotubes with a cyclotriphosphazene derivative. The cyclotriphosphazene derivative is prepared by reacting 4-imidazolium formaldehyde with p-phenylenediamine, then undergoing substitution with hexachlorocyclotriphosphazene and further addition with DOPO. The modified polypropylene material prepared by this invention possesses good mechanical properties, UV aging resistance, flame retardancy, and antibacterial properties.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a modified polypropylene material and its application in HPPM double-wall corrugated pipes. Background Technology

[0002] Polypropylene, as a general-purpose plastic, is widely used in HPPM double-wall corrugated pipes due to its excellent physical properties, ease of molding and processing, and low density. Furthermore, polypropylene is playing an increasingly important role in the plastics industry because of its lightweight, high strength, good weldability, long service life, and low manufacturing and installation costs. However, polypropylene also has some inherent weaknesses, such as poor flame retardancy, low notched impact strength, and susceptibility to photo-oxidation under ultraviolet light, leading to a reduced service life. In addition, with the improvement of living standards, people are paying more and more attention to the quality of drinking water, and the requirements are becoming increasingly stringent. Therefore, the development and use of antibacterial pipes to improve water quality and pipeline hygiene, and reduce the adhesion and growth of bacteria and microorganisms, has great development potential. Currently, the most widely used antibacterial agents are those made using the bactericidal and bacteriostatic properties of metals such as silver and zinc and their ions. However, these antibacterial agents are physically mixed with polypropylene pipes, resulting in poor long-lasting antibacterial performance. The silver and zinc metals are also prone to migration, affecting the performance of the pipes. Summary of the Invention

[0003] To address the shortcomings mentioned in the background art, the present invention aims to provide a modified polypropylene material and its application in HPPM double-wall corrugated pipes. By adding modified graphitic carbon nitride and modified multi-wall carbon nanotubes, the prepared modified polypropylene material has high tensile strength, is not easy to break, has good impact resistance, and also has good UV aging resistance, flame retardant properties, and antibacterial properties.

[0004] The objective of this invention can be achieved through the following technical solutions: A modified polypropylene material includes: modified graphitic carbon nitride prepared by grafting a hindered amine-type bromine-substituted intermediate with amino-modified graphitic carbon nitride using a chemical reaction; modified multi-walled carbon nanotubes prepared by oxidizing multi-walled carbon nanotubes with nitric acid and performing acyl chlorination treatment, and then grafting them with cyclotriphosphazene derivatives; polypropylene resin; compatibilizer; lubricant; and antioxidant. By weight, the polypropylene resin comprises 85-100 parts, modified graphitic carbon nitride comprises 4-9 parts, modified multi-walled carbon nanotubes comprises 1-5 parts, compatibilizer comprises 1-3 parts, lubricant comprises 1-3 parts, and antioxidant comprises 0.5-2 parts. The hindered amine-type bromine-substituted intermediate is a reaction product of the bromine-substituted intermediate obtained by reacting ethyl 2-amino-4-methylthiazol-5-carboxylate with 1,4-dibromobutane and 2,2,6,6-tetramethyl-4-piperidinol; the amino-modified graphitic carbon nitride is a reaction product of graphitic carbon nitride prepared by calcining melamine precursor and ethylenediamine solution. The cyclotriphosphazene derivative is the product of a nucleophilic addition reaction between a cyclotriphosphazene substituted product prepared by reacting a Schiff base product with hexachlorocyclotriphosphazene and DOPO; wherein the Schiff base product is the product of a Schiff base reaction between 4-imidazolium carboxaldehyde and p-phenylenediamine.

[0005] Preferably, the method for preparing the modified graphitic carbon nitride includes the following steps: A. Take ethyl 2-amino-4-methylthiazo-5-carboxylate, 1,4-dibromobutane, N,N-dimethylformamide and potassium carbonate in a reactor and react them at 85~90℃ for 10~12h. After the reaction is completed, the intermediate is prepared by filtration, rotary evaporation and column chromatography. B. Take the bromine-substituted intermediate, 2,2,6,6-tetramethyl-4-piperidinol, dibutyltin oxide and xylene in a reactor and react them at 155~160℃ for 3~4h. After the reaction is complete, add xylene to dissolve it, then cool to room temperature and add methanol. After filtration, drying and recrystallization of xylene, the hindered amine type bromine-substituted intermediate is prepared. C. Take amino-modified graphitic carbon nitride, hindered amine-type bromine-substituted intermediate, potassium carbonate and dimethyl sulfoxide into a reactor, and react at 85~90℃ for 12~18h. After the reaction is completed, centrifuge, wash and dry to prepare modified graphitic carbon nitride.

[0006] Preferably, the method for preparing amino-modified graphitic carbon nitride includes the following steps: C1. After thoroughly grinding melamine, transfer it to a corundum crucible and compact it. Then, calcine it in a muffle furnace at a heating rate of 3-5℃ / min to 520-550℃ for 2-6 hours. After natural cooling, graphitic carbon nitride is obtained. C2. Place graphitic carbon nitride into the inner liner of the reactor, add ethylenediamine solution and magnetically stir at room temperature for 25-30 minutes. After stirring, remove the magnetic stir bar, place it in the reactor, and heat it in an oven at 115-125℃ for 7-9 hours. After cooling to room temperature, wash, dry and grind to prepare amino-modified graphitic carbon nitride.

[0007] Preferably, the concentration of the ethylenediamine solution is 2.1~8.5 mol / L.

[0008] Preferably, the method for preparing the modified multi-walled carbon nanotubes includes the following steps: (1) Take 4-imidazolium formaldehyde, p-phenylenediamine and anhydrous ethanol into a reactor and stir at 80~85℃ for 6~8h. After the reaction is completed, the Schiff base product is prepared by filtration, rotary evaporation and column chromatography. (2) Hexachlorocyclotriphosphazene and acetonitrile were placed in a reactor, heated to 45-55°C, and a mixed solution of Schiff base product and acetonitrile was added. Then sodium hydroxide solid was added and the reaction was refluxed for 5-7 hours. After the reaction was completed, the product was filtered, rotary evaporated and dried to prepare the cyclotriphosphazene substituted product. (3) Take the cyclic triphosphazene substituted product, DOPO and anhydrous ethanol into a reactor, stir and react at 80~85℃ for 10~12h, and after the reaction is completed, filter, wash and dry to prepare the cyclic triphosphazene derivative; (4) Take multi-walled carbon nanotubes in a reactor, add nitric acid with a mass fraction of 65~68%, and stir at 105~110℃ for 6~8h. After the reaction is completed, filter, wash and dry to prepare carboxylated multi-walled carbon nanotubes. (5) Carboxylated multi-walled carbon nanotubes were added to thionyl chloride solvent and N,N-dimethylformamide, and then refluxed at 65~70℃ for 20~24h. After the reaction was completed, the solvent was removed by rotary evaporation, and the product was dried under vacuum at room temperature. Then, cyclotriphosphazene derivative, N,N-dimethylformamide and pyridine were added, and the mixture was stirred at 75~80℃ for 20~24h. After the reaction was completed, the modified multi-walled carbon nanotubes were prepared by filtration, washing and drying.

[0009] Preferably, the molar ratio of 4-imidazolium formaldehyde and p-phenylenediamine in step (1) is 1:1.

[0010] Preferably, in step (2), the molar ratio of hexachlorocyclotriphosphazene to the Schiff base product is 1:6; in step (3), the molar ratio of the cyclotriphosphazene substituted product to DOPO is 1:6.

[0011] Preferably, the preparation method of the modified polypropylene material includes the following steps: weighing each component according to the weight parts, stirring and mixing polypropylene resin, modified graphitic carbon nitride, modified multi-walled carbon nanotubes, compatibilizer, lubricant and antioxidant evenly, and then melting and extruding through a twin-screw extruder to prepare the modified polypropylene material.

[0012] Preferably, the compatibilizer is one or a combination of maleic anhydride-grafted polypropylene, maleic anhydride-grafted polyethylene, and ethylene-vinyl acetate copolymer; the lubricant is one or a combination of stearic acid, polyethylene wax, and oxidized polyethylene wax; and the antioxidant is one or a combination of antioxidant 1024, antioxidant 1010, antioxidant 168, and antioxidant 1076.

[0013] The application of the modified polypropylene material described above in HPPM double-wall corrugated pipes.

[0014] The beneficial effects of this invention are: This invention utilizes a nucleophilic substitution reaction between the amino group in ethyl 2-amino-4-methylthiazol-5-carboxylate and the terminal bromine atom of 1,4-dibromobutane to prepare a bromine-substituted intermediate. Then, a transesterification reaction is performed between 2,2,6,6-tetramethyl-4-piperidinol and the bromine-substituted intermediate to prepare a hindered amine-type bromine-substituted intermediate. Simultaneously, this invention first prepares graphitic carbon nitride by calcining the precursor melamine, then heats it with ethylenediamine to synthesize amino-modified graphitic carbon nitride. Finally, the ungrafted bromine atom in the hindered amine-type bromine-substituted intermediate is used to react with the amino-modified graphitic carbon. Modified graphitic carbon nitride is prepared by grafting carbon nitride. Graphitic carbon nitride is a typical non-metallic photocatalytic bactericidal material. This invention modifies graphitic carbon nitride through chemical means by introducing thiazole groups with antibacterial activity and hindered amine functional groups with ultraviolet absorption into its molecular skeleton, thereby enhancing the photocatalytic antibacterial ability and UV aging resistance of graphitic carbon nitride. At the same time, the modification of the hindered amine bromine-substituted intermediate promotes more uniform dispersion of graphitic carbon nitride in the matrix material, realizing nano-reinforcement and functionalization.

[0015] This invention utilizes the Schiff base reaction between 4-imidazolium formaldehyde and p-phenylenediamine to prepare a Schiff base product. Then, the -NH group in the imidazolium ring structure of the Schiff base product undergoes a nucleophilic substitution reaction with hexachlorocyclotriphosphazene to prepare a substituted cyclotriphosphazene. Subsequently, the Schiff base group formed in the substituted cyclotriphosphazene undergoes a nucleophilic addition reaction with DOPO to prepare a cyclotriphosphazene derivative. Simultaneously, this invention utilizes nitric acid oxidation of multi-walled carbon nanotubes to enrich the surface of the multi-walled carbon nanotubes with carboxyl groups. Then, the multi-walled carbon nanotubes are chlorinated with thionyl chloride, followed by a grafting reaction with the ungrafted amino groups in the cyclotriphosphazene derivative. Modified multi-walled carbon nanotubes were prepared. These multi-walled carbon nanotubes possess a unique nanoscale tubular structure and a large aspect ratio, exhibiting excellent mechanical properties. Furthermore, the continuous and independent protective layer formed after combustion can act as a barrier to block oxygen and heat. By using a chemical reaction, cyclotriphosphazene derivatives were firmly bonded to the surface of the multi-walled carbon nanotubes, thereby simultaneously introducing multiple flame-retardant elements, phosphorus and nitrogen, significantly improving the flame-retardant efficiency. The introduced imidazole groups also possess certain antibacterial activity. In addition, the grafting reaction improved the compatibility between the multi-walled carbon nanotubes and the matrix material, preventing the agglomeration of nanoparticles that would lead to a decline in mechanical properties. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1 A method for preparing amino-modified graphitic carbon nitride includes the following steps: C1. Take 5g of melamine, grind it thoroughly, transfer it to a corundum crucible and compact it. Then, heat it to 550℃ in a muffle furnace at a heating rate of 5℃ / min and calcine it for 4 hours. After natural cooling, graphitic carbon nitride is obtained. C2. Take 2g of graphitic carbon nitride and put it into the inner liner of the reaction vessel. Add ethylenediamine solution with a concentration of 4.19mol / L and stir magnetically for 30min at room temperature. After stirring, remove the magnetic stir bar and put it into the reaction vessel. Place it in an oven at 120℃ and heat for 8h. After cooling to room temperature, wash, dry and grind to prepare amino-modified graphitic carbon nitride.

[0018] Example 2 A method for preparing modified graphitic carbon nitride includes the following steps: A. Take 9.3g of ethyl 2-amino-4-methylthiazolyl-5-carboxylate, 23.7g of 1,4-dibromobutane, 120mL of N,N-dimethylformamide and 17.3g of potassium carbonate in a reactor and react at 85℃ for 12h. After the reaction is completed, the intermediate is prepared by filtration, rotary evaporation and column chromatography. B. Take 12.8 g of the bromine-substituted intermediate, 8.2 g of 2,2,6,6-tetramethyl-4-piperidinol, 0.8 g of dibutyltin oxide and 120 mL of xylene in a reactor and react at 160 °C for 4 h. After the reaction is complete, add xylene to dissolve it, then cool to room temperature and add methanol. After filtration, drying and recrystallization from xylene, the hindered amine type bromine-substituted intermediate is prepared. C. Take 2g of amino-modified graphitic carbon nitride prepared in Example 1, 2.6g of hindered amine-type bromine-substituted intermediate, 2.1g of potassium carbonate and 150mL of dimethyl sulfoxide into a reactor and react at 90℃ for 16h. After the reaction is completed, the modified graphitic carbon nitride is prepared by centrifugation, washing and drying.

[0019] Example 3 A method for preparing modified multi-walled carbon nanotubes includes the following steps: (1) Take 4.8g of 4-imidazolium formaldehyde, 5.5g of p-phenylenediamine and 100mL of anhydrous ethanol into a reactor, stir at 80℃ for 6h, and after the reaction is completed, purify by filtration, rotary evaporation and column chromatography to prepare Schiff base product; (2) Take 3.5g of hexachlorocyclotriphosphazene and 50mL of acetonitrile in a reactor, heat to 50℃, add 11.2g of Schiff base product and 50mL of acetonitrile mixed solution, then add 2.4g of sodium hydroxide solid, reflux for 6h, after the reaction is completed, filter, rotary evaporate and dry to prepare cyclotriphosphazene substituted product; (3) Take 6.2g of cyclotriphosphazene substituted product, 6.5g of DOPO and 100mL of anhydrous ethanol into a reactor, stir at 80℃ for 12h, and after the reaction is completed, filter, wash and dry to prepare cyclotriphosphazene derivative; (4) Take 0.5g of multi-walled carbon nanotubes into a reactor, add 100mL of 66% nitric acid, stir at 110℃ for 7h, and after the reaction is completed, filter, wash and dry to prepare carboxylated multi-walled carbon nanotubes. (5) Take 0.5g of carboxylated multi-walled carbon nanotubes, add 100mL of thionyl chloride solvent and 2mL of N,N-dimethylformamide, and then reflux at 70℃ for 24h. After the reaction is completed, remove the solvent by rotary evaporation. Dry the product under vacuum at room temperature. Then add 0.8g of cyclotriphosphazene derivative, 100mL of N,N-dimethylformamide and 0.15mL of pyridine, and stir at 80℃ for 24h. After the reaction is completed, filter, wash and dry to prepare modified multi-walled carbon nanotubes.

[0020] Example 4 A modified polypropylene material, comprising the following components in parts by weight: 88 parts of polypropylene resin, 4.5 parts of modified graphitic carbon nitride prepared in Example 2, 1.2 parts of modified multi-walled carbon nanotubes prepared in Example 3, 1.2 parts of maleic anhydride-grafted polypropylene compatibilizer, 1.1 parts of oxidized polyethylene wax lubricant, and 0.6 parts of antioxidant 1024.

[0021] The preparation method of the above-mentioned modified polypropylene material includes the following steps: weigh each component according to the weight parts, stir and mix polypropylene resin, modified graphitic carbon nitride, modified multi-walled carbon nanotubes, compatibilizer, lubricant and antioxidant evenly, and then melt extrude through a twin-screw extruder to prepare the modified polypropylene material.

[0022] Example 5 A modified polypropylene material, comprising the following components in parts by weight: 94 parts of polypropylene resin, 6.1 parts of modified graphitic carbon nitride prepared in Example 2, 3.2 parts of modified multi-walled carbon nanotubes prepared in Example 3, 2.1 parts of maleic anhydride-grafted polypropylene compatibilizer, 1.7 parts of oxidized polyethylene wax lubricant, and 1.1 parts of antioxidant 1024.

[0023] The preparation method of the modified polypropylene material is the same as in Example 4.

[0024] Example 6 A modified polypropylene material, comprising the following components in parts by weight: 99 parts of polypropylene resin, 8.6 parts of modified graphitic carbon nitride prepared in Example 2, 4.7 parts of modified multi-walled carbon nanotubes prepared in Example 3, 2.7 parts of maleic anhydride-grafted polypropylene compatibilizer, 2.5 parts of oxidized polyethylene wax lubricant, and 1.6 parts of antioxidant 1024.

[0025] The preparation method of the modified polypropylene material is the same as in Example 4.

[0026] Comparative Example 1: A method for preparing modified graphitic carbon nitride includes the following steps: A. Take 9.3g of ethyl 2-amino-4-methylthiazolyl-5-carboxylate, 23.7g of 1,4-dibromobutane, 120mL of N,N-dimethylformamide and 17.3g of potassium carbonate in a reactor and react at 85℃ for 12h. After the reaction is completed, the intermediate is prepared by filtration, rotary evaporation and column chromatography. B. Take 2g of amino-modified graphitic carbon nitride prepared in Example 1, 1.9g of bromine-substituted intermediate, 2.1g of potassium carbonate and 150mL of dimethyl sulfoxide into a reactor and react at 90℃ for 16h. After the reaction is completed, the modified graphitic carbon nitride is prepared by centrifugation, washing and drying.

[0027] Comparative Example 2: A method for preparing modified multi-walled carbon nanotubes includes the following steps: (1) Take 4.8g of 4-imidazolium formaldehyde, 5.5g of p-phenylenediamine and 100mL of anhydrous ethanol into a reactor, stir at 80℃ for 6h, and after the reaction is completed, purify by filtration, rotary evaporation and column chromatography to prepare Schiff base product; (2) Take 3.5g of hexachlorocyclotriphosphazene and 50mL of acetonitrile in a reactor, heat to 50℃, add 11.2g of Schiff base product and 50mL of acetonitrile mixed solution, then add 2.4g of sodium hydroxide solid, reflux for 6h, after the reaction is completed, filter, rotary evaporate and dry to prepare cyclotriphosphazene substituted product; (3) Take 0.5g of multi-walled carbon nanotubes into a reactor, add 100mL of 66% nitric acid, stir at 110℃ for 7h, and after the reaction is completed, filter, wash and dry to prepare carboxylated multi-walled carbon nanotubes. (4) Take 0.5g of carboxylated multi-walled carbon nanotubes, add 100mL of thionyl chloride solvent and 2mL of N,N-dimethylformamide, and then reflux at 70℃ for 24h. After the reaction is completed, remove the solvent by rotary evaporation. Dry the product under vacuum at room temperature. Then add 0.8g of cyclotriphosphazene substituted product, 100mL of N,N-dimethylformamide and 0.15mL of pyridine, and stir at 80℃ for 24h. After the reaction is completed, filter, wash and dry to prepare modified multi-walled carbon nanotubes.

[0028] Comparative Example 3: A modified polypropylene material comprising the following components in parts by weight: 99 parts of polypropylene resin, 8.6 parts of modified graphitic carbon nitride prepared in Comparative Example 1, 4.7 parts of modified multi-walled carbon nanotubes prepared in Example 3, 2.7 parts of maleic anhydride-grafted polypropylene compatibilizer, 2.5 parts of oxidized polyethylene wax lubricant, and 1.6 parts of antioxidant 1024.

[0029] The preparation method of the modified polypropylene material is the same as in Example 4.

[0030] Comparative Example 4: A modified polypropylene material comprising the following components in parts by weight: 99 parts of polypropylene resin, 8.6 parts of amino-modified graphitic carbon nitride prepared in Example 1, 4.7 parts of modified multi-walled carbon nanotubes prepared in Example 3, 2.7 parts of maleic anhydride-grafted polypropylene compatibilizer, 2.5 parts of oxidized polyethylene wax lubricant, and 1.6 parts of antioxidant 1024.

[0031] The preparation method of the modified polypropylene material is the same as in Example 4.

[0032] Comparative Example 5: A modified polypropylene material comprising the following components in parts by weight: 99 parts of polypropylene resin, 8.6 parts of modified graphitic carbon nitride prepared in Example 2, 4.7 parts of modified multi-walled carbon nanotubes prepared in Comparative Example 2, 2.7 parts of maleic anhydride-grafted polypropylene compatibilizer, 2.5 parts of oxidized polyethylene wax lubricant, and 1.6 parts of antioxidant 1024.

[0033] The preparation method of the modified polypropylene material is the same as in Example 4.

[0034] Comparative Example 6: A modified polypropylene material comprising the following components in parts by weight: 99 parts of polypropylene resin, 8.6 parts of modified graphitic carbon nitride prepared in Example 2, 4.7 parts of multi-walled carbon nanotubes, 2.7 parts of maleic anhydride-grafted polypropylene compatibilizer, 2.5 parts of oxidized polyethylene wax lubricant, and 1.6 parts of antioxidant 1024.

[0035] The preparation method of the modified polypropylene material is the same as in Example 4.

[0036] Performance testing The modified polypropylene materials prepared in Examples 4-6 and Comparative Examples 3-6 were subjected to performance testing: (1) Mechanical properties and UV aging resistance test: The tensile properties were tested using a universal testing machine according to GB / T 1040.2-2022. The tensile specimen size was 100mm×5mm×3.5mm. The impact strength was tested according to GB / T 1843-2008. The specimen size was 80mm×10mm×4mm. The sample was irradiated with a 40W UV lamp at 60℃ for a total of 72h. The sample was turned over 36h to ensure uniform irradiation. Then the change rate of tensile strength and elongation at break was tested. The distance between the sample and the lamp tube was 254mm. The UV aging resistance of the sample was evaluated. The data results are shown in Table 1.

[0037] (2) Flame retardant performance test: The limiting oxygen index and vertical burning rating of the samples were tested in accordance with GB / T 2408-2021 to evaluate the flame retardant performance of the samples. The data results are shown in Table 1.

[0038] (3) Antibacterial performance test: The antibacterial rate of the samples was tested in accordance with GB / T 21866-2008. The test species were Staphylococcus aureus and Escherichia coli. The data results are shown in Table 1.

[0039] Table 1 Sample performance test results

[0040] As can be seen from the data in Table 1, the modified polypropylene materials prepared in Examples 4-6 of this invention have high tensile strength, are not easily broken, have good impact resistance, and also possess good UV aging resistance, flame retardant properties, and antibacterial properties. In Comparative Example 3, the modified graphitic carbon nitride was not grafted with 2,2,6,6-tetramethyl-4-piperidinol. In Comparative Example 4, the modified graphitic carbon nitride was replaced with an equal amount of amino-modified graphitic carbon nitride. The measured changes in tensile strength and elongation at break in Comparative Examples 3-4 were significantly different from those in Examples 4-6. This is because the hindered amine functional groups with UV absorption were not introduced, leading to a decrease in UV aging resistance. Furthermore, the measured mechanical properties and antibacterial properties in Comparative Example 4 were lower than those in Examples 4-6. This is because the modification with the hindered amine-type bromine-substituted intermediate promoted a more uniform distribution of the graphitic carbon nitride. Dispersed in the matrix material, nano-reinforcement is achieved. At the same time, the introduction of thiazole groups improves the antibacterial properties of the material to a certain extent. The modified multi-walled carbon nanotubes added in Comparative Example 5 were not grafted with DOPO, and the multi-walled carbon nanotubes in Comparative Example 6 were not modified. The flame retardant properties of Comparative Examples 5-6 were found to be lower than those of Examples 4-6, and the decrease was more significant in Comparative Example 6. In addition, the mechanical properties and antibacterial properties of Comparative Example 6 were found to be lower than those of Examples 4-6. The possible reason is that the multi-walled carbon nanotubes agglomerate, which leads to a decrease in mechanical properties. This also indicates that the introduced imidazole groups have certain antibacterial activity.

[0041] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0042] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A modified polypropylene material, characterized in that, include: Modified graphitic carbon nitride prepared by grafting hindered amine-type bromine-substituted intermediates with amino-modified graphitic carbon nitride using chemical reaction; modified multi-walled carbon nanotubes prepared by oxidizing multi-walled carbon nanotubes with nitric acid and then performing acyl chlorination treatment, followed by grafting with cyclotriphosphazene derivatives; polypropylene resin; compatibilizer; lubricant; and antioxidant. By weight, the polypropylene resin comprises 85-100 parts, modified graphitic carbon nitride comprises 4-9 parts, modified multi-walled carbon nanotubes comprises 1-5 parts, compatibilizer comprises 1-3 parts, lubricant comprises 1-3 parts, and antioxidant comprises 0.5-2 parts. The hindered amine-type bromine-substituted intermediate is a reaction product of the bromine-substituted intermediate obtained by reacting ethyl 2-amino-4-methylthiazol-5-carboxylate with 1,4-dibromobutane and 2,2,6,6-tetramethyl-4-piperidinol; the amino-modified graphitic carbon nitride is a reaction product of graphitic carbon nitride prepared by calcining melamine precursor and ethylenediamine solution. The cyclotriphosphazene derivative is the product of a nucleophilic addition reaction between a cyclotriphosphazene substituted product prepared by reacting a Schiff base product with hexachlorocyclotriphosphazene and DOPO; wherein the Schiff base product is the product of a Schiff base reaction between 4-imidazolium carboxaldehyde and p-phenylenediamine.

2. The modified polypropylene material according to claim 1, characterized in that, The concentration of the ethylenediamine solution is 2.1~8.5 mol / L.

3. The modified polypropylene material according to claim 1, characterized in that, The molar ratio of 4-imidazolium formaldehyde to p-phenylenediamine is 1:

1.

4. The modified polypropylene material according to claim 1, characterized in that, The molar ratio of the hexachlorocyclotriphosphazene and the Schiff base product is 1:

6.

5. The modified polypropylene material according to claim 1, characterized in that, The molar ratio of the cyclotriphosphazene substituted product to DOPO is 1:

6.

6. The modified polypropylene material according to claim 1, characterized in that, The preparation method of the modified polypropylene material includes the following steps: weighing each component according to the weight parts, stirring and mixing polypropylene resin, modified graphitic carbon nitride, modified multi-walled carbon nanotubes, compatibilizer, lubricant and antioxidant evenly, and then melting and extruding through a twin-screw extruder to prepare the modified polypropylene material.

7. The modified polypropylene material according to claim 1, characterized in that, The compatibilizer is one or a combination of maleic anhydride-grafted polypropylene, maleic anhydride-grafted polyethylene, and ethylene-vinyl acetate copolymer; the lubricant is one or a combination of stearic acid, polyethylene wax, and oxidized polyethylene wax; the antioxidant is one or a combination of antioxidant 1024, antioxidant 1010, antioxidant 168, and antioxidant 1076.

8. The application of the modified polypropylene material according to any one of claims 1 to 7 in HPPM double-wall corrugated pipes.

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