Temperature-resistant modified MPP composition for power cable protection pipes and its preparation method

Abstract

This invention relates to the field of polymer materials and discloses a temperature-resistant modified MPP composition for power cable protection pipes and its preparation method. The temperature-resistant modified MPP composition includes: polypropylene resin, modified MXene nanosheets, functionally modified layered nano-zirconium phosphate, ammonium polyphosphate, and additives. The modified MXene nanosheets are prepared by grafting a triphenylamine-based modifier, prepared by a nucleophilic substitution reaction of 4-bromotriphenylamine and 8-bromo-1-octene, onto thiolized MXene nanosheets. The functionally modified layered nano-zirconium phosphate is prepared by grafting a polymer formed by copolymerizing a double-bond modified hindered phenol monomer prepared by reacting 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid with N-(2-hydroxyethyl)acrylamide, a double-bond modified phosphorus-containing monomer prepared by reacting diethyl hydroxymethylphosphonate with acryloyl chloride, and maleic anhydride onto amino-modified layered nano-zirconium phosphate. The composition prepared by this invention has good mechanical properties, UV aging resistance, high-temperature thermo-oxidative aging resistance, and flame retardancy.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a temperature-resistant modified MPP composition for power cable protection pipes and its preparation method. Background Technology

[0002] MPP cable protection pipes are widely used in power, telecommunications, and other fields. They are primarily used to protect cables and other facilities from damage caused by external environmental factors (such as soil corrosion and mechanical damage). MPP cable protection pipes use modified polypropylene as the main raw material and possess electrical insulation and external pressure resistance. However, MPP cable protection pipes have poor flame retardancy, which can easily cause fire hazards. For example, in cable laying projects in the power and telecommunications industries, the flame retardancy of MPP cable protection pipes is subject to certain limitations.

[0003] Inorganic nanoparticles, such as carbon nanomaterials, metal oxides, and inorganic minerals, exhibit unique functional properties such as flame retardancy, UV protection, and energy storage due to the nanosize effect. However, nanoparticles with high specific surface area inevitably cause agglomeration in polymers and weak interfacial bonding due to poor compatibility between inorganic and polymer matrices. Furthermore, single inorganic nanoparticles have low flame retardancy efficiency and limited UV protection capabilities. In addition, polypropylene molecular chains contain tertiary hydrogen atoms that are easily removed under high temperature or UV irradiation conditions, which can easily generate unstable free radicals during use, leading to material aging. Currently used small-molecule anti-aging agents have key problems such as easy precipitation and difficulty in dispersion, resulting in generally poor stability of the performance of the products obtained. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a temperature-resistant modified MPP composition for power cable protection pipes and its preparation method. By adding modified MXene nanosheets and functionally modified layered nano-zirconium phosphate, the composition is endowed with good mechanical properties, UV aging resistance, high-temperature thermo-oxidative aging resistance, and flame retardant properties.

[0005] The objective of this invention can be achieved through the following technical solutions: A temperature-resistant modified MPP composition for power cable protection pipes comprises the following components in parts by weight: 60-85 parts polypropylene resin, 2-5 parts modified MXene nanosheets, 1-3 parts functional modified layered nano-zirconium phosphate, 3-6 parts ammonium polyphosphate, 0.5-2.5 parts compatibilizer, 0.1-1 part plasticizer, and 0.1-1 part lubricant. The modified MXene nanosheets were prepared by grafting KH590 onto MXene nanosheets to prepare thiolized MXene nanosheets, followed by a thiol-alkene click reaction between the thiolized MXene nanosheets and a triphenylamine modifier; the triphenylamine modifier was prepared by reacting 4-bromotriphenylamine with tert-butyllithium in a lithium-halogen exchange reaction, followed by a nucleophilic substitution reaction with 8-bromo-1-octene. The functionally modified layered zirconium phosphate nanoparticles are prepared by esterification of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and N-(2-hydroxyethyl)acrylamide to form a double-bond modified hindered phenol monomer, by nucleophilic substitution of diethyl hydroxymethylphosphonate and acryloyl chloride to form a double-bond modified phosphorus-containing monomer, and by free radical copolymerization of maleic anhydride to form a polymer solution. Then, amino-modified layered zirconium phosphate nanoparticles are reacted with the polymer solution to undergo a ring-opening addition reaction. The amino-modified layered zirconium phosphate nanoparticles are prepared by modifying zirconium phosphate nanoparticles with intercalating agents tetrabutylammonium hydroxide and KH550.

[0006] Preferably, the compatibilizer is one or more combinations of maleic anhydride-grafted polypropylene, ethylene-vinyl acetate copolymer, maleic anhydride-grafted polyethylene, and ethylene-octene copolymer.

[0007] Preferably, the plasticizer is one or a combination of dioctyl adipate, dimethyl phthalate, dioctyl phthalate, and diisodecyl phthalate.

[0008] Preferably, the lubricant is one or more of stearic acid, polyethylene wax, and oxidized polyethylene wax.

[0009] Preferably, the method for preparing the modified MXene nanosheets includes the following steps: Ⅰ. Take MXene nanosheets and ultrasonically disperse them in a mixed solution of ethanol and deionized water. Adjust the pH of the system to 4 using hydrochloric acid. After stirring and mixing, add KH590 and stir at 55~70℃ for 12~16h. After the reaction is completed, centrifuge, wash and dry to prepare thiolized MXene nanosheets. II. Add 4-bromotriphenylamine, potassium tert-butoxide, and tetrahydrofuran to the reactor, stir to dissolve, and then transfer to a low-temperature tank at -78°C. Slowly add tert-butyllithium solution, stir and react for 30 min, then raise the temperature to 0°C and continue the reaction for 3 h. Subsequently, add 8-bromo-1-octene and continue stirring and reacting for 12 h. After the reaction is complete, slowly add the reaction solution to a saturated ammonium chloride solution to quench the reaction, extract and separate the liquids, combine the organic phases, evaporate by rotary evaporation, and dry with anhydrous magnesium sulfate. Then filter, perform chromatography, and distill under reduced pressure to prepare the triphenylamine-based modifier. III. Add mercapto-modified MXene nanosheets, triphenylamine modifier and toluene to the reactor, disperse evenly by ultrasonication, then add azobisisobutyronitrile, and react at 45~55℃ for 20~24h. After the reaction is completed, filter, wash and dry to prepare modified MXene nanosheets.

[0010] Preferably, the mass ratio of the thiolized MXene nanosheets to the triphenylamine modifier is 1:0.4~0.6.

[0011] Preferably, the preparation method of the functionally modified layered zirconium phosphate nanoparticles includes the following steps: A. Disperse nano-zirconium phosphate in deionized water using ultrasound, slowly add a mixed solution of tetrabutylammonium hydroxide and deionized water, and stir with ultrasound at room temperature for 7-8 hours. Then, slowly add phosphoric acid for acidification treatment and stir with ultrasound for 2-3 hours. After the reaction is complete, centrifuge to collect the bottom precipitate. Wash the precipitate with deionized water until the pH value is 6-7 to prepare layered nano-zirconium phosphate. B. The layered zirconium phosphate nanoparticles were ultrasonically dispersed in a mixed solution of ethanol and deionized water. KH550 was then added and the mixture was stirred at 85-90℃ for 6-7 hours. After filtration, washing, and drying, amino-modified layered zirconium phosphate nanoparticles were obtained. The amino-modified layered zirconium phosphate nanoparticles were then ultrasonically dispersed in a polymer solution and stirred at room temperature for 4-7 hours. After the reaction was completed, the mixture was filtered, washed, and dried to prepare functionally modified layered zirconium phosphate nanoparticles.

[0012] Preferably, the method for preparing the polymer solution in step B includes the following steps: B1. Add 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, N-(2-hydroxyethyl)acrylamide and dichloromethane to the reactor, stir at 0-5℃ for 20-30 min, then slowly add a mixed solution of N,N'-dicyclohexylcarbodiimide and dichloromethane dropwise over 15-30 min, followed by the addition of 4-dimethylaminopyridine, stirring and heating to 20-25℃, reacting for 20-24 h. The crude product obtained is purified, evaporated under reduced pressure and dried to prepare the double bond modified hindered phenol monomer. B2. Add diethyl hydroxymethylphosphonate, dichloromethane, and triethylamine to the reactor and stir in an ice-salt bath at -5°C for 25-40 min. Then, slowly add a mixed solution of acryloyl chloride and dichloromethane dropwise. After the addition is complete, maintain the system temperature at -5°C and stir for 1-1.5 h. Then, raise the temperature to 30-40°C and continue the reaction for 10-12 h. After the reaction is complete, wash with water, rotary evaporate, and purify to prepare a phosphorus-containing monomer with double bond modification. B3. Add maleic anhydride, double-bond modified hindered phenolic monomer, double-bond modified phosphorus-containing monomer and N,N-dimethylformamide to the reactor, heat to 60~65℃, and then slowly add a mixed solution of azobisisobutyronitrile and N,N-dimethylformamide. After the addition is complete, stir the reaction at 60~65℃ for 10~12h to prepare a polymer solution.

[0013] Preferably, the mass ratio of maleic anhydride, double-bond modified hindered phenolic monomer, and double-bond modified phosphorus-containing monomer is 3.5~4.3:2.7~3.2:6.8~7.5.

[0014] The preparation method of the temperature-resistant modified MPP composition for power cable protection pipes as described above includes the following steps: weighing each component according to the weight parts, stirring and mixing polypropylene resin, modified MXene nanosheets, functional modified layered nano zirconium phosphate, ammonium polyphosphate, compatibilizer, plasticizer and lubricant evenly, and then melt-extruding, granulating and molding at 180~220℃ using a twin-screw extruder to prepare the temperature-resistant modified MPP composition for power cable protection pipes.

[0015] The beneficial effects of this invention are: This invention utilizes the silane coupling agent KH590 to undergo a dehydration condensation reaction with MXene nanosheets to prepare thiolized MXene nanosheets. Simultaneously, this invention utilizes 4-bromotriphenylamine to undergo a lithium-halogen exchange reaction with tert-butyllithium, followed by a nucleophilic substitution reaction with 8-bromo-1-octene to prepare a triphenylamine modifier containing double bonds. Then, thiolized MXene nanosheets are reacted with the triphenylamine modifier via a thiol-alkene click reaction to prepare modified MXene nanosheets. The unique two-dimensional layered structure and electronic properties of the MXene nanosheets exhibit strong adsorption in ultraviolet shielding. It has the ability to absorb and reflect light, and it also has certain advantages such as fire resistance, catalytic char formation and environmental protection and low toxicity. The grafting of triphenylamine-based modifier promotes the relatively uniform dispersion of MXene nanosheets in the MPP substrate, so that its comprehensive performance can be fully utilized. Moreover, the introduced triphenylamine-based modifier has rigid groups with large conjugated structures, which have excellent thermal stability and light stability. Introducing it into the MPP substrate is beneficial to improving the thermal stability and light stability of the MPP substrate, effectively inhibiting the aging of the MPP substrate, and ensuring that the thermal properties and chain structure of the MPP substrate are well maintained during the aging process.

[0016] This invention utilizes the intercalating agent tetrabutylammonium hydroxide and the silane coupling agent KH550 to prepare amino-modified layered zirconium phosphate nanoparticles. Furthermore, this invention utilizes the esterification reaction of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid with N-(2-hydroxyethyl)acrylamide to prepare a double-bond modified hindered phenolic monomer. Simultaneously, it utilizes the nucleophilic substitution reaction of diethyl hydroxymethylphosphonate with acryloyl chloride to prepare a double-bond modified phosphorus-containing monomer. Then, the double-bond modified hindered phenolic monomer and the double-bond modified phosphorus-containing monomer undergo a free radical copolymerization reaction with maleic anhydride to prepare a polymer solution. The amino groups in the amino-modified layered zirconium phosphate nanoparticles are then integrated with the five-membered ring structure introduced into the polymer solution. A ring-opening addition reaction was conducted to prepare functionally modified layered zirconium phosphate nanoparticles. These nanoparticles exhibit good dispersion and strong interfacial bonding in MPP substrates, resulting in improved mechanical properties. The introduced flame-retardant phosphorus element endows the MPP substrate with excellent flame-retardant properties. Simultaneously, the layered zirconium phosphate nanoparticles have catalytic char formation and layer-blocking effects, promoting rapid char formation and improving the char layer, thus blocking the transfer of heat and oxygen and inhibiting the combustion of the MPP substrate. In addition, the increase in antioxidant hindered phenolic units in the polymer solution, i.e., the increase in hydrogen-donating functional groups, enhances the ability to capture free radicals, giving the MPP substrate excellent resistance to high-temperature thermo-oxidative aging. Detailed Implementation

[0017] 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.

[0018] Example 1: A method for preparing modified MXene nanosheets includes the following steps: Ⅰ. Take 1g of MXene nanosheets and ultrasonically disperse them in a mixed solution of 90mL ethanol and 20mL deionized water. Adjust the pH of the system to 4 using hydrochloric acid. After stirring and mixing, add 1.5mL KH590 and stir at 60℃ for 14h. After the reaction is completed, centrifuge, wash and dry to prepare thiolized MXene nanosheets. II. Add 12.9 g of 4-bromotriphenylamine, 0.54 g of potassium tert-butoxide, and 120 mL of tetrahydrofuran to the reactor. After stirring and dissolving, transfer the mixture to a low-temperature bath at -78 °C. Slowly add 75 mL of tert-butyllithium solution and stir for 30 min. Then raise the temperature to 0 °C and continue the reaction for 3 h. Subsequently, add 8 g of 8-bromo-1-octene and continue stirring for 12 h. After the reaction is complete, slowly add the reaction solution to a saturated ammonium chloride solution to quench the reaction. Extract and separate the liquids. Extract with diethyl ether. Combine the organic phases and evaporate by rotary evaporation. Dry with anhydrous magnesium sulfate. Then filter, perform silica gel column chromatography with n-hexane as the developing solvent, and distill under reduced pressure to prepare the triphenylamine-based modifier. III. Add 1g of thiolized MXene nanosheets, 0.5g of triphenylamine modifier and 100mL of toluene to the reactor, disperse evenly by ultrasonication, then add 0.05g of azobisisobutyronitrile, and react at 50℃ for 24h. After the reaction is completed, filter, wash and dry to prepare modified MXene nanosheets.

[0019] Example 2 A method for preparing functionally modified layered zirconium phosphate nanoparticles includes the following steps: A. Take 6g of nano-zirconium phosphate and disperse it ultrasonically in 600mL of deionized water. Slowly add a mixed solution of 20.68g of tetrabutylammonium hydroxide and 178mL of deionized water. Stir ultrasonically at room temperature for 8h. Then slowly add 180mL of phosphoric acid acidification treatment and stir ultrasonically for 2h. After the reaction is complete, centrifuge and take the bottom precipitate. Wash the precipitate with deionized water until the pH value is 7 to prepare layered nano-zirconium phosphate. B. Take 2g of layered zirconium phosphate nanoparticles and ultrasonically disperse them in a mixed solution of 90mL ethanol and 10mL deionized water. Then add 2.2g KH550 and stir at 90℃ for 6h. After filtration, washing and drying, amino-modified layered zirconium phosphate nanoparticles are obtained. Then, 2g of amino-modified layered zirconium phosphate nanoparticles are ultrasonically dispersed in 85mL polymer solution and stirred at room temperature for 6h. After the reaction is completed, filter, wash and dry to prepare functional modified layered zirconium phosphate nanoparticles.

[0020] The preparation method of the polymer solution in step B includes the following steps: B1. Add 2.09 g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, 0.86 g of N-(2-hydroxyethyl)acrylamide and 20 mL of dichloromethane to a reactor, stir at 0 °C for 20 min, then slowly add a mixed solution of 2.3 g of N,N'-dicyclohexylcarbodiimide and 10 mL of dichloromethane, followed by adding 0.09 g of 4-dimethylaminopyridine, stirring, heating to 20 °C and reacting for 24 h. The crude product obtained is purified by elution with ethyl acetate:cyclohexane in a volume ratio of 1:1, evaporated under reduced pressure, and dried to prepare a double bond modified hindered phenol monomer. B2. Add 16.8g of diethyl hydroxymethylphosphonate, 50mL of dichloromethane and 10.1g of triethylamine to the reactor, place it in an ice-salt bath at -5℃ and stir for 30min. Then slowly add a mixed solution of 9g of acryloyl chloride and 10mL of dichloromethane. After the addition is complete, maintain the system temperature at -5℃ and stir for 1h. Then raise the temperature to 35℃ and continue the reaction for 12h. After the reaction is complete, wash with water and rotary evaporate. Use ethyl acetate as the mobile phase and purify by neutral silica gel column chromatography to prepare the double bond modified phosphorus-containing monomer. B3. Add maleic anhydride, double-bond modified hindered phenolic monomer, double-bond modified phosphorus-containing monomer and 60 mL N,N-dimethylformamide to the reactor in a mass ratio of 3.9:2.9:7.1. Heat to 65℃, and then slowly add a mixture of azobisisobutyronitrile (1% of the monomer mass) and 40 mL N,N-dimethylformamide. After the addition is complete, stir the mixture at 65℃ for 12 h to prepare the polymer solution.

[0021] Example 3: A temperature-resistant modified MPP composition for power cable protection conduits, comprising the following components in parts by weight: 63 parts of polypropylene resin, 2.2 parts of modified MXene nanosheets prepared in Example 1, 1.1 parts of functionally modified layered zirconium phosphate nanosheets prepared in Example 2, 3.3 parts of ammonium polyphosphate, 0.6 parts of maleic anhydride-grafted polypropylene compatibilizer, 0.2 parts of dioctyl adipate plasticizer, and 0.1 parts of stearic acid lubricant.

[0022] The preparation method of the above-mentioned temperature-resistant modified MPP composition for power cable protection pipes includes the following steps: weighing each component according to the weight parts, stirring and mixing polypropylene resin, modified MXene nanosheets, functional modified layered nano zirconium phosphate, ammonium polyphosphate, compatibilizer, plasticizer and lubricant evenly, and then melting and extruding, granulating and molding at 200°C using a twin-screw extruder to prepare the temperature-resistant modified MPP composition for power cable protection pipes.

[0023] Example 4: A temperature-resistant modified MPP composition for power cable protection conduits, comprising the following components in parts by weight: 74 parts of polypropylene resin, 3.4 parts of modified MXene nanosheets prepared in Example 1, 1.8 parts of functionally modified layered nano-zirconium phosphate prepared in Example 2, 4.5 parts of ammonium polyphosphate, 1.3 parts of compatibilizer ethylene-vinyl acetate copolymer, 0.5 parts of plasticizer dimethyl phthalate, and 0.5 parts of lubricant polyethylene wax.

[0024] The preparation method of the above-mentioned temperature-resistant modified MPP composition for power cable protection pipes is the same as in Example 3.

[0025] Example 5: A temperature-resistant modified MPP composition for power cable protection conduits, comprising the following components in parts by weight: 82 parts of polypropylene resin, 4.6 parts of modified MXene nanosheets prepared in Example 1, 2.8 parts of functionally modified layered nano-zirconium phosphate prepared in Example 2, 5.8 parts of ammonium polyphosphate, 2.3 parts of compatibilizer ethylene-octene copolymer, 0.8 parts of plasticizer dioctyl phthalate, and 0.7 parts of lubricant oxidized polyethylene wax.

[0026] The preparation method of the above-mentioned temperature-resistant modified MPP composition for power cable protection pipes is the same as in Example 3.

[0027] Comparative Example 1: A temperature-resistant modified MPP composition for power cable protection conduits, comprising the following components in parts by weight: 82 parts polypropylene resin, 4.6 parts MXene nanosheets, 2.8 parts functional modified layered nano-zirconium phosphate prepared in Example 2, 5.8 parts ammonium polyphosphate, 2.3 parts compatibilizer ethylene-octene copolymer, 0.8 parts plasticizer dioctyl phthalate, and 0.7 parts lubricant oxidized polyethylene wax.

[0028] The preparation method of the above-mentioned temperature-resistant modified MPP composition for power cable protection pipes is the same as in Example 3.

[0029] Comparative Example 2: A temperature-resistant modified MPP composition for power cable protection conduits, comprising the following components in parts by weight: 82 parts of polypropylene resin, 4.6 parts of modified MXene nanosheets prepared in Example 1, 2.8 parts of amino-modified layered nano-zirconium phosphate prepared in Example 2, 5.8 parts of ammonium polyphosphate, 2.3 parts of ethylene-octene copolymer as compatibilizer, 0.8 parts of dioctyl phthalate as plasticizer, and 0.7 parts of oxidized polyethylene wax as lubricant.

[0030] The preparation method of the above-mentioned temperature-resistant modified MPP composition for power cable protection pipes is the same as in Example 3.

[0031] Comparative Example 3: A temperature-resistant modified MPP composition for power cable protection conduits, comprising the following components in parts by weight: The mixture contained 82 parts of polypropylene resin, 4.6 parts of modified MXene nanosheets prepared in Example 1, 2.8 parts of nano-zirconium phosphate, 5.8 parts of ammonium polyphosphate, 2.3 parts of ethylene-octene copolymer as a compatibilizer, 0.8 parts of dioctyl phthalate as a plasticizer, and 0.7 parts of oxidized polyethylene wax as a lubricant.

[0032] The preparation method of the above-mentioned temperature-resistant modified MPP composition for power cable protection pipes is the same as in Example 3.

[0033] Performance testing The modified MPP compositions prepared in Examples 3-5 and Comparative Examples 1-3 were subjected to performance testing: (1) Mechanical property testing: Tensile properties were tested using a universal mechanical testing machine in accordance with GB / T 1040.2-2022. The tensile specimen size was 100mm×5mm×3.5mm. The data results are shown in Table 1.

[0034] (2) UV aging resistance test: The test was conducted in a UV aging test chamber. The aging process was divided into a light stage and a dark stage. The light stage lasted for 8 hours and the dark stage lasted for 4 hours. The two stages were repeated to simulate the natural aging process of the sample. The illumination conditions were as follows: ultraviolet wavelength: 300-340 nm; temperature: 60±3℃; irradiance: 0.89 kW / m². 2 The samples were dried; the dark stage conditions were: no ultraviolet light irradiation; temperature: 50±3℃, condensation; the sample aging treatment time was 72h and 120h. The anti-ultraviolet aging performance was evaluated by the change rate of tensile strength and the change rate of elongation at break. The data results are shown in Table 1.

[0035] (3) Flame retardant performance test: Referring to GB / T 2406.2-2009 standard, the limiting oxygen index of the sample was tested to evaluate the flame retardant performance of the sample. The data results are shown in Table 1.

[0036] (4) High temperature thermo-oxidative aging performance test: The samples were placed in the HJ881 type air heat aging test chamber for high temperature thermo-oxidative aging at 100℃. The aging cycle was divided into four test cycles of 3, 6, 12 and 24 days. Five samples were taken in each cycle. The oxidation induction time of each sample was tested to evaluate the high temperature thermo-oxidative aging performance of the samples. The data results are shown in Table 2.

[0037] Table 1. Test results of mechanical properties, UV aging resistance and flame retardant properties of the samples. Table 2. Test results of high-temperature thermo-oxidative aging resistance of samples As can be seen from the data in Tables 1-2, the modified MPP compositions prepared in Examples 3-5 of this invention possess good mechanical properties, UV aging resistance, high-temperature thermo-oxidative aging resistance, and flame retardant properties. In Comparative Example 1, where MXene nanosheets were not modified, the measured tensile strength and elongation at break were lower than in Examples 3-5. This is because the modification and grafting of MXene nanosheets promotes good dispersion and strong interfacial bonding in the MPP substrate, enhancing mechanical properties. Simultaneously, the measured changes in tensile strength and elongation at break were significantly different from those in Examples 3-5, and the oxidation induction time was shorter. This indicates that the addition of modified MXene nanosheets is beneficial for improving the UV aging resistance and high-temperature thermo-oxidative aging resistance of the MPP substrate. In Example 2, functionally modified layered zirconium phosphate nanoparticles were replaced with amino-modified layered zirconium phosphate nanoparticles in equal amounts. In Comparative Example 3, functionally modified layered zirconium phosphate nanoparticles were replaced with nano-zirconium phosphate in equal amounts. The oxidation induction time and limiting oxygen index in Comparative Examples 2-3 were shorter and lower than those in Examples 3-5, respectively. The limiting oxygen index was the most significantly reduced in Comparative Example 3. At the same time, the tensile strength and elongation at break in Comparative Example 3 were lower than those in Examples 3-5. This indicates that the addition of functionally modified layered zirconium phosphate nanoparticles is beneficial to improving the mechanical properties, high-temperature thermo-oxidative aging resistance, and flame retardant properties of MPP substrates.

[0038] 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.

[0039] 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 temperature-resistant modified MPP composition for power cable protection pipes, characterized in that, The composition by weight includes: 2-5 parts of modified MXene nanosheets prepared by a mercapto-olefin click reaction of mercapto-modified MXene nanosheets and triphenylamine modifier; 1-3 parts of functionally modified layered zirconium phosphate nanosheets prepared by a ring-opening addition reaction of a polymer formed by a free radical copolymerization reaction of a double-bond modified hindered phenol monomer, a double-bond modified phosphorus-containing monomer and maleic anhydride and an amino-modified layered zirconium phosphate nanosheets; 3-6 parts of ammonium polyphosphate; 0.5-2.5 parts of compatibilizer; 0.1-1 parts of plasticizer; 0.1-1 parts of lubricant; and 60-85 parts of polypropylene resin.

2. The temperature-resistant modified MPP composition for power cable protection pipes according to claim 1, characterized in that, The compatibilizer is one or more combinations of maleic anhydride-grafted polypropylene, ethylene-vinyl acetate copolymer, maleic anhydride-grafted polyethylene, and ethylene-octene copolymer.

3. The temperature-resistant modified MPP composition for power cable protection pipes according to claim 1, characterized in that, The plasticizer is one or more of dioctyl adipate, dimethyl phthalate, dioctyl phthalate, and diisodecyl phthalate.

4. The temperature-resistant modified MPP composition for power cable protection pipes according to claim 1, characterized in that, The lubricant is one or more of stearic acid, polyethylene wax, and oxidized polyethylene wax.

5. The temperature-resistant modified MPP composition for power cable protection pipes according to claim 1, characterized in that, The mass ratio of the thiolized MXene nanosheets to the triphenylamine modifier is 1:0.4~0.

6.

6. The temperature-resistant modified MPP composition for power cable protection pipes according to claim 1, characterized in that, The triphenylamine-based modifier is prepared by reacting 4-bromotriphenylamine with tert-butyllithium via a lithium-halogen exchange reaction, followed by a nucleophilic substitution reaction with 8-bromo-1-octene.

7. The temperature-resistant modified MPP composition for power cable protection pipes according to claim 1, characterized in that, The double-bond modified hindered phenolic monomer is prepared by esterification of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid with N-(2-hydroxyethyl)acrylamide; the double-bond modified phosphorus-containing monomer is prepared by nucleophilic substitution of diethyl hydroxymethylphosphonate with acryloyl chloride.

8. The temperature-resistant modified MPP composition for power cable protection pipes according to claim 1, characterized in that, The mass ratio of maleic anhydride, double-bond modified hindered phenolic monomer, and double-bond modified phosphorus-containing monomer is 3.5~4.3:2.7~3.2:6.8~7.

5.

9. A method for preparing a temperature-resistant modified MPP composition for power cable protection pipes according to any one of claims 1 to 8, characterized in that, Includes the following steps: Weigh each component according to the weight parts, and stir and mix the polypropylene resin, modified MXene nanosheets, functional modified layered nano zirconium phosphate, ammonium polyphosphate, compatibilizer, plasticizer and lubricant evenly. Then, melt extrusion, granulation and molding are carried out by twin-screw extruder at 180~220℃ to prepare a temperature-resistant modified MPP composition for power cable protection pipe.

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