Phosphorus-containing flame-retardant nano fluid as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of flame retardance of polymer composite materials, and particularly discloses a preparation method of a phosphorus-containing flame-retardant nano fluid, which comprises the following steps: uniformly mixing a neck-shaped layer coupling agent and a coronal layer flexible polymer chain according to a ratio, vacuumizing, introducing nitrogen, removing water and oxygen for multiple times, and preparing a phosphorus-containing flame-retardant nano fluid; bonding an organic functional group of the coupling agent with a terminal functional group of the flexible polymer chain to finish a primary grafting reaction, so as to obtain a solvent-free grafted polymer intermediate; carrying out surface functionalization treatment on the flame-retardant nano core to obtain a functionalized flame-retardant nano core; uniformly dispersing the functionalized flame-retardant nano core in hydrolysate prepared from alcohol and water in proportion, adding dilute acid to adjust pH to obtain dispersion liquid, adding the dispersion liquid into the solvent-free graft polymer intermediate, and reacting to obtain a phosphorus-containing flame-retardant nano fluid crude product; carrying out dialysis purification on the obtained phosphorus-containing flame-retardant nano fluid crude product; and filtering the dialyzed and purified reaction liquid, and performing rotary evaporation, concentration and drying to obtain the phosphorus-containing flame-retardant nano fluid.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant technology of polymer composite materials, specifically relating to a phosphorus-containing flame retardant nanofluid, its preparation method, and its application. Background Technology

[0002] Epoxy resin (EP), as an important class of thermosetting polymer materials, has been widely used in key fields such as aerospace, automotive manufacturing, electronics, and construction engineering due to its excellent mechanical strength, chemical resistance, and electrical insulation properties. However, the inherently low thermal decomposition temperature of epoxy resin makes it prone to combustion in high-temperature environments, accompanied by the release of large amounts of smoke during combustion. This problem severely restricts its application expansion in high-end flame-retardant applications. Therefore, developing efficient and environmentally friendly flame-retardant modification technologies has become one of the core directions in the research field of epoxy resin functionalization modification.

[0003] Nanoparticles, possessing unique surface, volume, quantum size, and macroscopic quantum tunneling effects, can modulate the properties of polymer matrices through physical or chemical interactions, enabling nanoparticle / polymer composites to exhibit excellent mechanical, photoelectric, thermal stability, and flame-retardant properties, laying a solid foundation for their application in high-end fields. However, in practical applications, inorganic nanoparticles face two major bottlenecks: first, they are difficult to uniformly disperse in polymer matrices, easily agglomerating into micron-sized aggregates, thus losing their unique nano-effects; second, the interfacial bonding between nanoparticles and the polymer matrix is ​​weak, exhibiting significant interfacial incompatibility, leading to a significant decrease in the toughness of the composite material. These defects greatly limit the application potential of nanoparticle / polymer composites, thus necessitating the development of novel modification technologies to overcome this application dilemma.

[0004] Nanofluids, as a novel type of organic-inorganic hybrid material, possess a typical core-shell binary structure: typically, inorganic nanoparticles form the core, silane coupling agents or similar media serve as the core-shell interface, and the coronal layer is composed of flexible organic long chains. This unique core-shell structure allows the inorganic nanocore to be uniformly coated by an organic shell, effectively weakening van der Waals forces between nanoparticles and significantly alleviating their aggregation. Simultaneously, it preserves the inherent physicochemical properties of the nanoparticles, providing high-quality raw materials for the preparation of functional composite materials, and possessing significant academic research value and broad industrial application prospects. Currently, there are related explorations into phosphorus-containing flame-retardant nanofluids and their preparation methods, but existing preparation processes have many drawbacks: poor dispersibility and coating effects, easily leading to nanoparticle aggregation and loss of nano-effects; demanding preparation conditions and environmental unfriendliness, making industrial mass production difficult; difficulty in achieving synergy between flame retardancy and mechanical properties, and complex and costly processes that cannot meet the needs of high-end applications.

[0005] Therefore, it is essential to develop a new method for preparing phosphorus-containing flame-retardant nanofluids. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the existing technology and provide a phosphorus-containing flame-retardant nanofluid, its preparation method and application. By using organic molecular chains to modify the surface of nano-flame-retardant materials, a core-shell structure phosphorus-containing flame-retardant nanofluid is constructed, which improves the dispersion uniformity of nano-flame-retardant materials in epoxy resin matrix, solves the interfacial compatibility problem of composite materials, and realizes the controllable preparation of multifunctional epoxy resin composite materials with high flame retardant efficiency, excellent mechanical strength and high transparency.

[0007] To achieve the above objectives, one of the technical solutions of the present invention is: a method for preparing phosphorus-containing flame-retardant nanofluids, comprising the following steps:

[0008] (1) Mix the neck layer coupling agent and the coronal layer flexible polymer chain in proportion, evacuate and purge with nitrogen multiple times to remove water and oxygen, and perform grafting reaction at 60~110℃ for 3~24 h to bond the organic functional groups of the coupling agent with the terminal functional groups (such as amino and hydroxyl groups) of the flexible polymer chain, complete the preliminary grafting reaction, and obtain solvent-free grafted polymer intermediate;

[0009] (2) Surface functionalization treatment of phosphorus-containing flame-retardant nanonuclei was carried out to obtain functionalized phosphorus-containing flame-retardant nanonuclei; the hydroxyl active sites on the surface of the nanonuclei were increased to facilitate strong chemical bonding with the neck layer coupling agent in subsequent steps;

[0010] (3) The functionalized phosphorus-containing flame-retardant nanonuclei obtained in step (2) are uniformly dispersed in a mixed solvent of alcohol and water in proportion. After adjusting the pH with dilute acid, a dispersion is obtained and then added to the solvent-free grafted polymer intermediate obtained in step (1). The reaction is carried out to obtain a crude product of phosphorus-containing flame-retardant nanofluid.

[0011] (4) The crude product of phosphorus-containing flame-retardant nanofluid obtained in step (3) is purified by dialysis for 48-96 h.

[0012] (5) The reaction solution purified by dialysis in step (4) is filtered, concentrated by rotary evaporation and dried to obtain phosphorus-containing flame-retardant nano-fluid. The rotary evaporation concentration and drying temperature is 40~70℃ and the time is 0.5~5 h.

[0013] In this invention, the neck layer coupling agent refers to a molecule that chemically bonds to the surface of the nanonucleus and acts as a linker; the coronal layer flexible polymer chain refers to a flexible organic long chain grafted onto the outside of the neck layer to provide fluidity and interfacial compatibility.

[0014] In a preferred embodiment of the present invention, in step (1), the neck layer coupling agent is one of an epoxy-containing silane coupling agent, an amino-containing silane coupling agent, a quaternary ammonium salt type silane coupling agent, and a sulfonic acid silane coupling agent, and the coronal layer flexible polymer chain is one of polyetheramine, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, nonylphenol polyoxyethylene ether sulfate sodium (NPES), polyphosphite, polyalkyl (C1~C6) phosphonate, polyaryl phosphonate, poly2-carboxyethylphenyl phosphonate, polyalkyl (C1~C6) borate, and polyaryl borate.

[0015] In a preferred embodiment of the present invention, the molar ratio of the neck layer coupling agent and the coronal layer flexible polymer chain in step (1) is (0.2~1.5):1, preferably (0.5~1.5):1, further preferably (0.6~1.3):1, more preferably (0.7~1.1):1, and most preferably (0.8~1.0):1.

[0016] In a preferred embodiment of the present invention, the temperature for the initial grafting reaction in step (1) to remove water and oxygen is 70~110℃, preferably 80~110℃, and more preferably 90~100℃; the reaction time is 3~12 h, preferably 3~9 h, more preferably 3~8 h, and more preferably 3~6 h.

[0017] In a preferred embodiment of the present invention, the phosphorus-containing flame-retardant nanonucleus in step (2) is one of aluminum phosphinate, zinc phosphinate, calcium phosphinate, magnesium phosphinate, aluminum diethyl phosphinate, calcium diethyl phosphinate, magnesium diethyl phosphinate, zinc diethyl phosphinate, aluminum diethylphenyl phosphinate, aluminum dipropyl phosphinate, aluminum isobutyl phosphinate, aluminum methyl ethyl phosphinate, zinc methyl butyl phosphinate, zinc methylphenyl phosphinate, iron methyl phosphinate, aluminum phenyl phosphinate, ammonium polyphosphate, aluminum phosphate, zinc phosphate, iron phosphate, copper phosphate, and cobalt phosphate.

[0018] In a preferred embodiment of the present invention, the surface functionalization treatment in step (2) is one of the following: hydrogen peroxide oxidation, alkaline piranha solution oxidation, hydrogen peroxide reflux, ultraviolet light excitation, and plasma treatment.

[0019] In a preferred embodiment of the present invention, the volume ratio of alcohol to water in the mixed solvent in step (3) is (8~10):1, and the alcohol is one of isopropanol, ethylene glycol, methanol and ethanol.

[0020] In a preferred embodiment of the present invention, the pH in step (3) is 3 to 6, and the pH is adjusted by one of acetic acid, dilute hydrochloric acid and dilute sulfuric acid.

[0021] In a preferred embodiment of the present invention, in step (3), the mass ratio of functionalized phosphorus-containing flame-retardant nanonuclei to mixed solvent is 1:(50~150), and the mass ratio of dispersion to solvent-free grafted polymer intermediate is (1~2):1.

[0022] In a preferred embodiment of the present invention, the dialysis purification time in step (4) is 48~90 h, preferably 48~86 h, more preferably 48~80 h, and most preferably 48~72 h; the rotary evaporation concentration and drying temperature is 40~70℃, preferably 40~65℃, more preferably 45~65℃, more preferably 45~60℃, and most preferably 50~60℃; the rotary evaporation concentration and drying time is 0.5~5 h, preferably 0.5~4.5 h, more preferably 0.5~4.0 h, more preferably 0.5~3.5 h, and most preferably 0.5~3.0 h.

[0023] To achieve the above objectives, the second technical solution of the present invention is: a method for preparing phosphorus-containing flame-retardant nanofluids.

[0024] To achieve the above objectives, the third technical solution of the present invention is: the application of a phosphorus-containing flame-retardant nanofluid.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The phosphorus-containing flame-retardant nanofluid prepared by this invention is in a fluid-like state. The flame retardant nanoparticles do not agglomerate and can retain their inherent physicochemical properties, significantly improving the processing and application performance of the flame retardant. By controlling the flexible polymer chain structure of the coronal layer, nanofluids with diverse properties can be flexibly prepared.

[0027] 2. The phosphorus-containing flame-retardant nanofluid prepared by this invention has both plasticizer and toughening agent functions, and can be used in combination with a variety of matrix materials. While significantly improving the flame-retardant properties of the matrix materials, it also effectively improves their mechanical strength.

[0028] 3. The phosphorus-containing flame-retardant nanofluid prepared by this invention can maintain the high transparency of the composite material, achieving a balance of high flame-retardant efficiency, excellent mechanical properties and high transparency, which greatly expands the application field of the modified composite material. Attached Figure Description

[0029] Figure 1 The images and structural diagrams are of the solvent-free aluminum diethylphosphinate nanofluid in Example 3 of this invention.

[0030] Figure 2 The image shows the FTIR spectrum of the solvent-free aluminum diethylphosphinate nanofluid in Example 3 of this invention.

[0031] Figure 3 The TG curve of the solvent-free aluminum diethylphosphinate nanofluid / epoxy resin composite material in Example 7 of the present invention;

[0032] Figure 4 The limiting oxygen index diagram of the solvent-free aluminum diethylphosphinate nanofluid / epoxy resin composite material in Example 7 of the present invention;

[0033] Figure 5 The mechanical properties of the solvent-free aluminum diethylphosphinate nanofluid / epoxy resin composite material in Example 7 of this invention are shown in the figure.

[0034] Figure 6 This is a SEM image of the solvent-free aluminum diethylphosphinate nanofluid / epoxy resin composite material in Example 7 of the present invention.

[0035] Figure 7 This is a cross-sectional elemental distribution diagram of the solvent-free aluminum diethylphosphinate nanofluid / epoxy resin composite material in Example 7 of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0037] A method for preparing a phosphorus-containing flame-retardant nanofluid includes the following steps:

[0038] (1) Mix the neck layer coupling agent and the coronal layer flexible polymer chain in proportion, evacuate and purge with nitrogen multiple times to remove water and oxygen, and perform grafting reaction at 60~110℃ for 3~24 h to bond the organic functional groups of the coupling agent with the terminal functional groups (such as amino and hydroxyl groups) of the flexible polymer chain, complete the preliminary grafting reaction, and obtain solvent-free grafted polymer intermediate;

[0039] (2) Surface functionalization treatment of phosphorus-containing flame-retardant nanonuclei was carried out to obtain functionalized phosphorus-containing flame-retardant nanonuclei; the hydroxyl active sites on the surface of the nanonuclei were increased to facilitate strong chemical bonding with the neck layer coupling agent in subsequent steps;

[0040] (3) The functionalized phosphorus-containing flame-retardant nanonuclei obtained in step (2) are uniformly dispersed in a mixed solvent of alcohol and water in proportion. After adjusting the pH with dilute acid, a dispersion is obtained and then added to the solvent-free grafted polymer intermediate obtained in step (1). The reaction is carried out to obtain a crude product of phosphorus-containing flame-retardant nanofluid.

[0041] (4) The crude product of phosphorus-containing flame-retardant nanofluid obtained in step (3) is purified by dialysis for 48-96 h.

[0042] (5) The reaction solution purified by dialysis in step (4) is filtered, concentrated by rotary evaporation and dried to obtain phosphorus-containing flame-retardant nano-fluid. The rotary evaporation concentration and drying temperature is 40~70℃ and the time is 0.5~5 h.

[0043] In this invention, the neck layer coupling agent refers to a molecule that chemically bonds to the surface of the nanonucleus and acts as a linker; the coronal layer flexible polymer chain refers to a flexible organic long chain grafted onto the outside of the neck layer to provide fluidity and interfacial compatibility.

[0044] In step (1), the neck layer coupling agent is one of epoxy-containing silane coupling agents, amino-containing silane coupling agents, quaternary ammonium salt type silane coupling agents, and sulfonic acid silane coupling agents. The flexible polymer chain of the coronal layer is one of polyetheramine, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, nonylphenol polyoxyethylene ether sulfate sodium (NPES), polyphosphite, polyalkyl (C1~C6) phosphonate, polyaryl phosphonate, poly2-carboxyethylphenyl phosphonate, polyalkyl (C1~C6) borate, and polyaryl borate.

[0045] In step (1), the molar ratio of the neck coupling agent to the coronal flexible polymer chain is (0.2~1.5):1, preferably (0.5~1.5):1, further preferably (0.6~1.3):1, more preferably (0.7~1.1):1, and most preferably (0.8~1.0):1.

[0046] In step (1), the temperature for the initial grafting reaction to remove water and oxygen is 70~110℃, preferably 80~110℃, and more preferably 90~100℃; the reaction time is 3~12 h, preferably 3~9 h, more preferably 3~8 h, and more preferably 3~6 h.

[0047] In step (2), the phosphorus-containing flame-retardant nanonucleus is one of the following: aluminum phosphinate, zinc phosphinate, calcium phosphinate, magnesium phosphinate, aluminum diethyl phosphinate, calcium diethyl phosphinate, magnesium diethyl phosphinate, zinc diethyl phosphinate, aluminum diethylphenyl phosphinate, aluminum dipropyl phosphinate, aluminum isobutyl phosphinate, aluminum methyl ethyl phosphinate, zinc methyl butyl phosphinate, zinc methylphenyl phosphinate, iron methyl phosphinate, aluminum phenyl phosphinate, ammonium polyphosphate, aluminum phosphate, zinc phosphate, iron phosphate, copper phosphate, and cobalt phosphate.

[0048] The surface functionalization treatment in step (2) is one of the following: hydrogen peroxide oxidation, alkaline piranha solution oxidation, hydrogen peroxide reflux, ultraviolet light excitation, and plasma treatment.

[0049] In step (3), the volume ratio of alcohol to water in the mixed solvent is (8~10):1, and the alcohol is one of isopropanol, ethylene glycol, methanol and ethanol.

[0050] In step (3), the pH is 3 to 6, and the pH is adjusted by one of acetic acid, dilute hydrochloric acid, and dilute sulfuric acid.

[0051] In step (3), the mass ratio of functionalized phosphorus-containing flame-retardant nanonuclei to mixed solvent is 1:(50~150), and the mass ratio of dispersion to solvent-free grafted polymer intermediate is (1~2):1.

[0052] In step (4), the dialysis purification time is 48-90 h, preferably 48-86 h, more preferably 48-80 h, and most preferably 48-72 h; the rotary evaporation concentration and drying temperature is 40-70℃, preferably 40-65℃, more preferably 45-65℃, more preferably 45-60℃, and most preferably 50-60℃; the rotary evaporation concentration and drying time is 0.5-5 h, preferably 0.5-4.5 h, more preferably 0.5-4.0 h, more preferably 0.5-3.5 h, and most preferably 0.5-3.0 h.

[0053] A method for preparing phosphorus-containing flame-retardant nanofluids.

[0054] Application of a phosphorus-containing flame-retardant nanofluid.

[0055] The present invention does not impose any special limitations on the specific method of application of the phosphorus-containing flame-retardant nanofluid in flame-retardant epoxy materials, which can be determined based on the technical common sense of those skilled in the art.

[0056] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0057] The sources and specifications of reagents used in the following examples are as follows:

[0058] SIT8378.3: 3-(trihydroxysilyl)-propanesulfonic acid, CAS (70942-24-4), aqueous solution, effective content 30-35 wt%, 100g, Shanghai Mairui Biochemical Technology Co., Ltd.;

[0059] NPES: Sodium nonylphenol polyoxyethylene ether sulfate, analytical grade AR60.0%, 100g, Guangdong Wengjiang Chemical Reagent Co., Ltd.

[0060] Example 1

[0061] A phosphorus-containing flame-retardant nanofluid is prepared by the following method, including the following steps:

[0062] (1) Preliminary grafting reaction: The neck layer coupling agent SIT8378.3 and the coronal layer flexible polymer chain NPES were mixed at a molar ratio of 0.8:1 and stirred evenly. The system was evacuated and purged with nitrogen three times to remove water and oxygen. The reaction was carried out at 60°C for 6 h to allow the organic functional groups (epoxy groups) in the coupling agent to bond with the active functional groups (hydroxyl groups) at the end of the NPES to complete the preliminary grafting reaction and obtain a solvent-free grafted polymer intermediate.

[0063] (2) Surface functionalization of inorganic flame retardant: The hydrogen peroxide method was adopted. 1 g of aluminum diethylphosphonate was mixed with 50 mL of 30% hydrogen peroxide aqueous solution and refluxed at 90℃ for 3 h to oxidize and activate the hydroxyl groups on the surface of aluminum diethylphosphonate, generating functionalized aluminum diethylphosphonate rich in active oxygen groups.

[0064] (3) Hydrolysis and dispersion: 1g of functionalized aluminum diethylphosphinate obtained in step (2) was uniformly dispersed in a mixed solvent of 100 mL of ethanol and water, wherein the volume ratio of ethanol to water was 10:1. The pH of the mixture was adjusted to 4.0 using 0.1mol / L dilute hydrochloric acid to obtain a dispersion. Then, the dispersion was added to 50g of grafted polymer intermediate obtained in step (1), and stirred continuously at 60℃ for 4 h to allow the functionalized aluminum diethylphosphinate to undergo interfacial condensation with the active groups on the grafted polymer chain through surface hydroxyl groups, forming a solvent-free nano-fluid crude product.

[0065] (4) Dialysis purification: The crude product obtained in step (3) is placed in the dialysis bag of Mv3500, placed in deionized water, and dialyzed at room temperature for 72 h to remove unreacted monomers, small molecule by-products and inorganic salts.

[0066] (5) Concentration and drying: After dialysis, the reaction solution was filtered and concentrated by rotary evaporation at 45°C for 3 hours to obtain solvent-free aluminum diethylphosphinate nanofluid.

[0067] Example 2

[0068] A phosphorus-containing flame-retardant nanofluid is prepared by the following method, including the following steps:

[0069] (1) Preliminary grafting reaction: The neck layer coupling agent SIT8378.3 and the coronal layer flexible polymer chain polyphosphite were mixed at a molar ratio of 1:1 and stirred evenly; the system was evacuated and purged with nitrogen three times to remove moisture and oxygen, and reacted at 70°C for 12 h to allow the epoxy groups of the coupling agent to bond with the hydroxyl groups at the end of the polyphosphite, thus completing the preliminary grafting reaction and obtaining a solvent-free grafted polymer intermediate;

[0070] (2) Surface functionalization of inorganic flame retardant: The hydrogen peroxide method was adopted. 1 g of aluminum hypophosphite was mixed with 50 mL of 30% hydrogen peroxide aqueous solution and refluxed at 90℃ for 3 h to oxidize the phosphate groups on the HAP surface and form highly active hydroxyl and peroxy groups to obtain functionalized aluminum hypophosphite.

[0071] (3) Hydrolysis and dispersion: The functionalized aluminum hypophosphite obtained in step (2) is uniformly dispersed in a mixed solvent of ethylene glycol and water, wherein the volume ratio of ethylene glycol to water is 8:1. The pH of the mixture is adjusted to 3.5 using acetic acid to obtain a dispersion. Then, the dispersion is slowly added to the grafted polymer intermediate obtained in step (1), and stirred continuously at 70°C for 5 h to promote the functionalized aluminum hypophosphite and the polymer chain to achieve interfacial bonding through hydrogen bonding and condensation reaction, forming a solvent-free nano-fluid crude product.

[0072] (4) Dialysis purification: The crude product obtained in step (3) was placed in the dialysis bag of Mv3500 and placed in deionized water for dialysis at room temperature for 60 h;

[0073] (5) Concentration and drying: After dialysis, the reaction solution was filtered and concentrated by rotary evaporation at 60°C for 4 h to obtain solvent-free aluminum hypophosphite flame-retardant nanofluid.

[0074] Example 3

[0075] A phosphorus-containing flame-retardant nanofluid is prepared by the following method, including the following steps:

[0076] (1) Preliminary grafting reaction: The neck layer coupling agent KH560 (γ-glycidyl etheroxypropyltrimethoxysilane) and the coronal layer flexible polymer chain M2070 (polyether siloxane) were mixed at a molar ratio of 0.6:1 and stirred evenly; the system was evacuated and purged with nitrogen three times to remove water and oxygen, and reacted at 80℃ for 6 h to allow the epoxy group of KH560 to bond with the terminal hydroxyl group of M2070 to complete the preliminary grafting reaction and obtain a solvent-free grafted polymer intermediate;

[0077] (2) Surface functionalization of inorganic flame retardant: The alkaline piranha solution oxidation method was adopted. 1 g of aluminum diethylphosphinate (DEAL) was mixed with 10 mL of alkaline piranha solution (NaOH:H2O2 = 3:1, volume ratio) and reacted at 60℃ for 3 h. The surface organic impurities were removed and the inorganic surface was activated by strong oxidation to generate functionalized aluminum diethylphosphinate rich in active oxygen and hydroxyl groups.

[0078] (3) Hydrolysis and dispersion: The functionalized aluminum diethylphosphinate obtained in step (2) is uniformly dispersed in an ethanol-water mixed solvent, wherein the volume ratio of ethanol to water is 9:1. The pH is adjusted to 4.0 using dilute hydrochloric acid to obtain a dispersion. Then, the dispersion is slowly added to the grafted polymer intermediate obtained in step (1), and stirred continuously at 60°C for 4 h to allow the functionalized aluminum diethylphosphinate to undergo a condensation reaction with the siloxane groups on the polymer chain through the surface hydroxyl groups, forming a stable solvent-free nano-fluid crude product.

[0079] (4) Dialysis purification: The crude product was placed in the dialysis bag of Mv3500 and dialyzed in deionized water at room temperature for 72 h;

[0080] (5) Concentration and drying: After dialysis, the reaction solution was filtered and concentrated by rotary evaporation at 50°C for 3 h to remove residual solvent and obtain solvent-free aluminum diethylphosphinate flame retardant nanofluid.

[0081] The macroscopic morphology of the solvent-free aluminum diethylphosphinate nanofluid prepared in this embodiment is shown in the figure below. Figure 1 As shown in the figure, the solvent-free aluminum diethylphosphinate nanofluid is a viscous, pale yellow liquid that flows at room temperature. Figure 2 The images show the infrared spectra of the solvent-free aluminum diethylphosphine nanofluid and aluminum diethylphosphine powder prepared in this embodiment. As can be seen from the figures, the solvent-free aluminum diethylphosphine nanofluid retains the peak of aluminum diethylphosphine in the fingerprint region, and the peak is observed at 1100 cm⁻¹. -1 Si-O absorption peaks and 700 cm⁻¹ were observed. -1 The Si-C absorption peak at the point of origin confirms the successful synthesis of solvent-free aluminum diethylphosphinate nanofluids.

[0082] Example 4

[0083] A phosphorus-containing flame-retardant nanofluid is prepared by the following method, including the following steps:

[0084] (1) Preliminary grafting reaction: The neck layer coupling agent KH560 and the coronal layer flexible polymer chain polyarylphosphonate were mixed at a molar ratio of 0.8:1 and stirred evenly; the system was evacuated and purged with nitrogen three times to remove moisture and oxygen, and reacted at 70°C for 8 h to allow the epoxy groups of KH560 to bond with the hydroxyl groups at the end of the polyarylphosphonate, thus completing the preliminary grafting reaction and obtaining a solvent-free grafted polymer intermediate;

[0085] (2) Surface functionalization of inorganic flame retardant: Using plasma treatment, 1 g of aluminum phosphate (AlPO4) was placed in a plasma cleaner, the working power was set to 150 W, high-purity oxygen was introduced, and the treatment was carried out for 10 min. A large number of hydroxyl groups and oxygen-containing active groups were generated on the surface by oxygen plasma bombardment, and functionalized aluminum phosphate was obtained.

[0086] (3) Hydrolysis and dispersion: The functionalized aluminum phosphate obtained in step (2) is uniformly dispersed in an ethanol-water mixed solvent, wherein the volume ratio of ethanol to water is 9:1. The pH is adjusted to 5.0 using acetic acid to obtain a dispersion. Then, the dispersion is slowly added to the grafted polymer intermediate obtained in step (1), and stirred continuously at 70°C for 5 h, so that the functionalized aluminum phosphate undergoes a condensation reaction with the siloxane groups on the polymer chain through the surface hydroxyl groups to form a stable solvent-free nano-fluid crude product.

[0087] (4) Dialysis purification: The crude product was placed in the dialysis bag of Mv3500 and dialyzed in deionized water at room temperature for 72 h;

[0088] (5) Concentration and drying: After dialysis, the reaction solution was filtered and concentrated by rotary evaporation at 60°C for 2 h to remove the solvent and obtain solvent-free aluminum phosphate flame-retardant nanofluid.

[0089] Example 5

[0090] A phosphorus-containing flame-retardant nanofluid is prepared by the following method, including the following steps:

[0091] (1) Preliminary grafting reaction: The neck layer coupling agent KH560 and the coronal layer flexible polymer chain M1000 (polyether siloxane) were mixed in a molar ratio of 1:1 and stirred evenly; the system was evacuated and purged with nitrogen three times to remove moisture and oxygen, and the reaction was carried out at 90°C for 6 hours to bond the epoxy groups of KH560 with the hydroxyl groups at the end of M1000, thus completing the preliminary grafting reaction and obtaining a solvent-free grafted polymer intermediate;

[0092] (2) Surface functionalization of inorganic flame retardant: Using plasma treatment, 1 g of aluminum diethylphenylphosphine (DEPPA) was placed in a plasma cleaner, the working power was set to 150 W, high-purity oxygen was introduced, and the treatment was carried out for 10 min. The surface was activated by oxygen plasma to generate active sites rich in hydroxyl and carboxyl groups, thus obtaining functionalized aluminum diethylphenylphosphine.

[0093] (3) Hydrolysis and dispersion: The functionalized aluminum diethylphenylphosphinate obtained in step (2) is uniformly dispersed in a methanol-water mixed solvent, wherein the volume ratio of methanol to water is 10:1. The pH is adjusted to 4.5 using acetic acid to obtain a dispersion. Then, the dispersion is slowly added dropwise to the grafted polymer intermediate obtained in step (1), and stirred continuously at 80°C for 5 h to allow the functionalized aluminum diethylphenylphosphinate to chemically bond with the polymer chain through surface active groups, forming a solvent-free nano-fluid crude product.

[0094] (4) Dialysis purification: The crude product was placed in the dialysis bag of Mv3500 and dialyzed in deionized water at room temperature for 84 hours;

[0095] (5) Concentration and drying: After dialysis, the reaction solution was filtered and concentrated by rotary evaporation at 70°C for 3 hours to remove the solvent and obtain solvent-free aluminum diethylphenylphosphinate flame retardant nanofluid.

[0096] Example 6

[0097] A phosphorus-containing flame-retardant nanofluid is prepared by the following method, including the following steps:

[0098] (1) Preliminary grafting reaction: The neck layer coupling agent DC5700 (a vinyl-containing siloxane) and the crown layer flexible polymer chain NPES were mixed at a molar ratio of 1:1 and stirred evenly. The system was evacuated and purged with nitrogen three times to remove moisture and oxygen. The reaction was carried out at 90°C for 10 h to allow the vinyl groups of DC5700 to undergo addition or condensation reactions with the thiol groups at the ends of NPES, thus obtaining a solvent-free grafted polymer intermediate.

[0099] (2) Surface functionalization of inorganic flame retardant: 1 g of zinc methylphenylphosphine (MPPZn) was placed in a plasma cleaner, the working power was set to 150 W, high-purity oxygen was introduced, and the treatment was carried out for 10 min. The surface was activated by oxygen plasma to generate abundant hydroxyl groups and oxygen-containing functional groups, thus obtaining functionalized zinc methylphenylphosphine.

[0100] (3) Hydrolysis and dispersion: The functionalized zinc methylphenylphosphinate obtained in step (2) is uniformly dispersed in a methanol-water mixed solvent, wherein the volume ratio of methanol to water is 9:1. The pH is adjusted to 4.0 using dilute hydrochloric acid to obtain a dispersion. Then, the dispersion is slowly added dropwise to the grafted polymer intermediate obtained in step (1), and stirred continuously at 80°C for 5 h to allow the functionalized zinc methylphenylphosphinate to chemically bond with the polymer chain through surface active groups, forming a solvent-free nano-fluid crude product.

[0101] (4) Dialysis purification: The crude product was placed in a dialysis bag with a molecular weight cutoff of Mv3500 and dialyzed in deionized water at room temperature (25±2℃) for 80 h. The dialysate was changed every 6 h to ensure the purity of the product.

[0102] (5) Concentration and drying: After dialysis, the reaction solution was filtered through a 0.22 μm microporous membrane, concentrated and dried by rotary evaporation at 60℃ for 3.5 h to remove residual solvent and obtain a viscous solvent-free phosphorus-containing flame-retardant nanofluid.

[0103] Example 7

[0104] Application of a phosphorus-containing flame-retardant nanofluid in composite materials.

[0105] Solvent-free aluminum diethylphosphinate nanofluidic / epoxy resin composite material was obtained using the solvent-free aluminum diethylphosphinate nanofluidic system described in Example 3. Its TG curve is shown below. Figure 3 As shown in the figure, it can be seen that with the increase of the content of solvent-free aluminum diethylphosphinate nanofluid, the initial decomposition temperature of the composite material decreases slightly, but the maximum decomposition temperature continuously increases, and the char residue at 800°C continuously increases. The limiting oxygen index of the solvent-free aluminum diethylphosphinate nanofluid / epoxy resin composite material in this embodiment is shown in the figure below. Figure 4 As shown in the figure, it can be seen that the solvent-free aluminum diethylphosphinate nanofluid does not improve the limiting oxygen index of the composite material at low content. However, with the increase of the addition amount, the oxygen index of the composite material increases rapidly. When the content is 12 wt.%, the limiting oxygen index reaches 29.5, which greatly improves the flame retardant performance of the composite material.

[0106] Figure 5 The graph shows the mechanical properties of the solvent-free aluminum diethylphosphinate nanofluid / epoxy resin composite material in this embodiment. As can be seen from the graph, the overall mechanical properties of the composite material show a trend of first increasing and then decreasing with the change in the amount of solvent-free aluminum diethylphosphinate nanofluid added. Figure 6 The pattern of the interface cracks is consistent. Figure 6The image shows a SEM image of the solvent-free aluminum diethylphosphinate nanofluid / epoxy resin composite material from the example. The image shows no nanoparticle aggregation, indicating good compatibility between the solvent-free aluminum diethylphosphinate nanofluid and the epoxy resin, enabling uniform dispersion. Figure 5 This provides strong evidence of the laws governing the improvement of mechanical properties. Figure 7 The figure shows the cross-sectional elemental distribution of the solvent-free aluminum diethylphosphinate nanofluid / epoxy resin composite material of this embodiment. As can be seen from the figure, the solvent-free aluminum diethylphosphinate nanofluid is uniformly dispersed in the composite material and no agglomeration occurs.

[0107] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a phosphorus-containing flame-retardant nanofluid, characterized in that, Includes the following steps: (1) Mix the neck layer coupling agent and the coronal layer flexible polymer chain in proportion, evacuate and purge with nitrogen to remove water and oxygen multiple times, and perform grafting reaction at 60~110℃ for 3~24 h to bond the organic functional groups of the coupling agent with the terminal functional groups of the flexible polymer chain, complete the preliminary grafting reaction, and obtain solvent-free grafted polymer intermediate. (2) Surface functionalization treatment of phosphorus-containing flame-retardant nanonuclei was carried out to obtain functionalized phosphorus-containing flame-retardant nanonuclei; (3) The functionalized phosphorus-containing flame-retardant nanonuclei obtained in step (2) are uniformly dispersed in a mixed solvent of alcohol and water in proportion. After adjusting the pH with dilute acid, a dispersion is obtained and then added to the solvent-free grafted polymer intermediate obtained in step (1). The reaction is carried out to obtain a crude product of phosphorus-containing flame-retardant nanofluid. (4) The crude product of phosphorus-containing flame-retardant nanofluid obtained in step (3) is purified by dialysis for 48-96 h. (5) The reaction solution purified by dialysis in step (4) is filtered, concentrated by rotary evaporation and dried to obtain phosphorus-containing flame-retardant nano-fluid. The rotary evaporation concentration and drying temperature is 40~70℃ and the time is 0.5~5 h.

2. The preparation method of phosphorus-containing flame-retardant nanofluids as described in claim 1, characterized in that, In step (1), the neck layer coupling agent is one of epoxy-containing silane coupling agents, amino-containing silane coupling agents, quaternary ammonium salt type silane coupling agents, and sulfonic acid silane coupling agents. The flexible polymer chain of the coronal layer is one of polyetheramine, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, nonylphenol polyoxyethylene ether sodium sulfate, polyphosphite, polyalkyl (C1~C6) phosphonate, polyaryl phosphonate, poly2-carboxyethylphenyl phosphonate, polyalkyl (C1~C6) borate, and polyaryl borate.

3. The preparation method of phosphorus-containing flame-retardant nanofluid as described in claim 1, characterized in that, In step (1), the molar ratio of the neck coupling agent to the coronal flexible polymer chain is (0.2~1.5):

1.

4. The preparation method of phosphorus-containing flame-retardant nanofluid as described in claim 1, characterized in that, In step (2), the phosphorus-containing flame-retardant nanonucleus is one of the following: aluminum phosphinate, zinc phosphinate, calcium phosphinate, magnesium phosphinate, aluminum diethyl phosphinate, calcium diethyl phosphinate, magnesium diethyl phosphinate, zinc diethyl phosphinate, aluminum diethylphenyl phosphinate, aluminum dipropyl phosphinate, aluminum isobutyl phosphinate, aluminum methyl ethyl phosphinate, zinc methyl butyl phosphinate, zinc methylphenyl phosphinate, iron methyl phosphinate, aluminum phenyl phosphinate, ammonium polyphosphate, aluminum phosphate, zinc phosphate, iron phosphate, copper phosphate, and cobalt phosphate.

5. The method for preparing phosphorus-containing flame-retardant nanofluids as described in claim 1, characterized in that, The surface functionalization treatment in step (2) is one of the following: hydrogen peroxide oxidation, alkaline piranha solution oxidation, hydrogen peroxide reflux, ultraviolet light excitation, and plasma treatment.

6. The method for preparing phosphorus-containing flame-retardant nanofluids as described in claim 1, characterized in that, In step (3), the volume ratio of alcohol to water in the mixed solvent is (8~10):1, and the alcohol is one of isopropanol, ethylene glycol, methanol and ethanol.

7. The method for preparing phosphorus-containing flame-retardant nanofluids as described in claim 1, characterized in that, In step (3), the pH is 3 to 6, and the pH is adjusted by one of acetic acid, dilute hydrochloric acid, and dilute sulfuric acid.

8. The method for preparing phosphorus-containing flame-retardant nanofluids as described in claim 1, characterized in that, In step (3), the mass ratio of functionalized phosphorus-containing flame-retardant nanonuclei to mixed solvent is 1:(50~150), and the mass ratio of dispersion to solvent-free grafted polymer intermediate is (1~2):

1.

9. A phosphorus-containing flame-retardant nanofluid prepared by the preparation method of the phosphorus-containing flame-retardant nanofluid as described in any one of claims 1-8.

10. An application of the phosphorus-containing flame-retardant nanofluid as described in claim 9.

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