A nitrogen-containing heterocyclic cross-linked polyphosphazene and its hybrid derivatives, flame-retardant polyurea elastomer and epoxy resin

Abstract

The present invention discloses a nitrogen-containing heterocyclic cross-linked phosphazene and its hybrid derivatives, a flame-retardant polyurea elastomer and an epoxy resin, belonging to the technical field of flame-retardant polymer materials. A nitrogen-containing heterocyclic cross-linked polyphosphazene is prepared by a cross-linking reaction between hexachlorocyclotriphosphazene and 3,5-diamino-1,2,4-triazole; further, melamine cyanuric acid is introduced in situ through hydrogen bonding to prepare a nitrogen-containing heterocyclic cross-linked phosphazene hybrid derivative HTDA@MCA; metal ions are introduced to prepare a nitrogen-containing heterocyclic cross-linked phosphazene hybrid derivative HTDA-M through the metal coordination of the azole structure. The nitrogen-containing heterocyclic cross-linked polyphosphazene and its hybrid derivatives proposed by the present invention can be used to prepare flame-retardant and aging-resistant polyurea elastomers and epoxy resins, which not only have efficient flame retardant and smoke suppression effects, but also can maintain or improve the mechanical properties of the base material.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardant polymer materials, and specifically provides a nitrogen-containing heterocyclic cross-linked polyphosphazene and its hybrid derivatives, a flame retardant polyurea elastomer and an epoxy resin, as well as a preparation method and application thereof. Background Art

[0002] Polyurea is an elastomeric material, which can be generally divided into aromatic polyurea, aliphatic polyurea and aspartic acid polyurea according to its composition. Aromatic polyurea has excellent mechanical properties, chemical corrosion resistance, aging resistance, and waterproof and wear resistance. At the same time, it can be formed by solvent-free spraying or brushing by adjusting the reaction speed of the system. As a protective coating, it is widely used in building waterproofing, pipeline anti-corrosion, coastal defense and hull protection, and battery box protection.

[0003] Epoxy resins are high-performance thermosetting polymers with excellent mechanical strength and chemical stability. These resins, primarily including bisphenol A epoxy resins, are widely used in coatings, adhesives, and electronic packaging. Cured epoxy resins not only exhibit excellent temperature and corrosion resistance but can also be modified to meet specific flame retardancy and thermal conductivity requirements. Consequently, they are widely used in industries such as aviation, automotive, and construction.

[0004] However, polyurea is inherently flammable, producing numerous flaming droplets. After curing, epoxy resins, thanks to their cross-linked network, confine the droplets, making them difficult to extinguish. Unflame-retardant polyurea and epoxy resins have a limiting oxygen index (LOI) of only 21%-22%, and both emit significant amounts of toxic fumes upon combustion. Their flammability poses a potential fire hazard in their applications.

[0005] Due to the reaction characteristics of polyurea and epoxy resins, existing technologies for improving their flame retardancy primarily employ reactive and additive methods. Reactive flame retardancy involves modifying the molecular structure of the polyurea or epoxy resin, introducing flame-retardant units through the use of reactive monomers and curing agents containing flame-retardant elements. However, this often alters the existing curing process for the polyurea or epoxy resin, increasing costs and hindering industrial production.

[0006] Additive flame retardants, which are inert or low-reactivity flame retardants added to polyurea or epoxy resin curing formulas, can be used to prepare flame-retardant polyurea or epoxy resins without substantially changing the reaction conditions. This method offers excellent practicality and cost-effectiveness, making it a common method in industry. However, current flame retardant systems for polyurea and epoxy resins suffer from low flame retardancy and, at high addition levels, deteriorate the mechanical, thermal, and aging properties of the substrates, hindering their application. Summary of the Invention

[0007] In order to overcome the deficiencies of the prior art and obtain a flame retardant system that can take into account both the flame retardancy and mechanical properties of polyurea elastomers and epoxy resins, the present invention provides a nitrogen-containing heterocyclic cross-linked polyphosphazene and its hybrid derivatives, a flame retardant and aging-resistant polyurea elastomer and epoxy resin, and a preparation method thereof.

[0008] In order to achieve the above-mentioned object, the nitrogen-containing heterocyclic cross-linked polyphosphazene of the present invention has the following structural formula:

[0009]

[0010] Among them, the R1 structure is: .

[0011] As an implementation method, the nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative is a nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid, and its structural formula is:

[0012]

[0013] As another implementation method, the nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative is a nitrogen-containing heterocyclic cross-linked polyphosphazene-metal complex, and its structural formula is:

[0014]

[0015] Among them, the M structure is Zn 2+ 、Fe 2+ 、Cu 2+ 、Ni 2+ Any of .

[0016] The preparation method of the nitrogen-containing heterocyclic cross-linked polyphosphazene of the present invention comprises dissolving 3,5-diamino-1,2,4-triazole and hexachlorocyclotriphosphazene in an organic solvent and reacting them in the presence of an acid-binding agent to produce the nitrogen-containing heterocyclic cross-linked polyphosphazene. The molar ratio of 3,5-diamino-1,2,4-triazole:triethylamine:hexachlorocyclotriphosphazene is 3.1-3.5:3.3-3.8:1, preferably 3.2:3.3:1.

[0017] The acid binding agent is one or more of triethylamine, potassium carbonate, pyridine, ethylenediamine, N,N-diisopropylethylamine, etc., and the organic solvent is one or more of dichloromethane, tetrahydrofuran, acetonitrile, acetone, ethyl acetate, N,N-dimethylformamide.

[0018] The nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid preparation method of the present invention comprises: adding melamine to deionized water, heating it to 90°C until completely dissolved, then adding the nitrogen-containing heterocyclic cross-linked polyphosphazene and cyanuric acid, and reacting them. After the reaction is complete, the product is collected, washed, and dried. The molar ratio of melamine:cyanuric acid:nitrogen-containing heterocyclic cross-linked polyphosphazene is 1-1.2:1:1-1.4, preferably 1:1:1.

[0019] The preparation method of the nitrogen-containing heterocyclic cross-linked polyphosphazene-metal complex of the present invention comprises the following steps: uniformly dispersing the nitrogen-containing heterocyclic cross-linked polyphosphazene in deionized water, then dropwise adding the deionized water solution containing a metal salt, reacting at room temperature, and collecting, washing, and drying the product after the reaction is completed. The metal salt is a Zn salt, an Fe salt, a Cu salt, or a Ni salt.

[0020] The metal salts include but are not limited to zinc nitrate heptahydrate, zinc sulfate heptahydrate, ferric nitrate hexahydrate, cupric chloride dihydrate, nickel nitrate hexahydrate and the like.

[0021] The nitrogen-containing heterocyclic cross-linked polyphosphazene and its hybrid derivatives are used as flame retardants.

[0022] The nitrogen-containing heterocyclic cross-linked polyphosphazene and its hybrid derivatives are used as flame retardants in polymer materials such as epoxy resins, polyureas, polyurethanes, polyolefins, polyamides, and polycarbonates. The polyurea elastomer can be used as a protective coating in building waterproofing, pipeline corrosion protection, coastal defense, ship hull protection, and battery box protection. The flame-retardant epoxy resin can be used in fiber-reinforced composites and electronic packaging materials.

[0023] A flame retardant polyurea elastomer comprises component A, component B and a flame retardant, wherein the mass ratio of component A, component B and the flame retardant is 100:63:29-54, and the flame retardant is divided into a single flame retardant and a composite flame retardant, wherein the component A is a semi-prepolymer prepared by reacting diphenylmethane diisocyanate and polyether polyol, and the mass ratio of diphenylmethane diisocyanate to polyether polyol is 44:60; the component B comprises polyetheramine and amine expansion The chain agent is selected from the group consisting of polyether diamine with a molecular weight of 2000 and polyether triamine with a molecular weight of 5000. The amine chain extender is selected from the group consisting of dimethylthiotoluenediamine, dimethylthiotoluenediamine, diethyltoluenediamine, and 4,4-bis-sec-butylaminodiphenylmethane. The mass ratio of polyether diamine, polyether triamine, dimethylthiotoluenediamine, and 4,4-bis-sec-butylaminodiphenylmethane is 30:3:20:10. The single flame retardant comprises any one of nitrogen-containing heterocyclic cross-linked polyphosphazene, nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid, and nitrogen-containing heterocyclic cross-linked polyphosphazene-metal complex. The composite flame retardant comprises any one of the above single flame retardants and any one of aluminum hypophosphite, zinc hypophosphite, and piperazine pyrophosphate.

[0024] A flame-retardant epoxy resin comprises an epoxy resin, a curing agent, and a flame retardant. The mass ratio of the epoxy resin, curing agent, and flame retardant is 20:5.37:1.34-4.48. The epoxy resin includes, but is not limited to, bisphenol A diglycidyl ether epoxy resin, bisphenol S diglycidyl ether epoxy resin, bisphenol A novolac epoxy resin, and the like. The curing agent is 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, polyimide, 2-methylimidazole, and the like. The flame retardant comprises any one of a nitrogen-containing heterocyclic cross-linked polyphosphazene, a nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid, and a nitrogen-containing heterocyclic cross-linked polyphosphazene-metal complex.

[0025] The nitrogen-containing heterocyclic cross-linked polyphosphazenes and their hybrid derivatives disclosed herein offer the following advantages over existing technologies: They feature a simple preparation process and high phosphorus and nitrogen content. The nitrogen-containing heterocyclic structures, phosphazene rings, triazine structures, and metal ions enhance the flame retardancy and smoke suppression properties of polyureas and epoxy resins through phosphorus-nitrogen synergy, carbonization, and catalysis. Furthermore, the flame retardants maintain or enhance the mechanical properties of the substrate material through intermolecular forces such as hydrogen bonding and π-π conjugation, as well as their unique physical morphology. When added alone or in combination with a flame retardant, polyurea elastomers can pass the UL-94 V-0 rating and achieve a LOI exceeding 27% at a 15-20% addition rate. At a 5-15% addition rate, epoxy resins can pass vertical combustion V-1 or V-0 ratings, significantly reducing toxic smoke emissions and demonstrating highly effective flame retardancy and smoke suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the infrared spectrum of the nitrogen-containing heterocyclic cross-linked polyphosphazene prepared in Example 1 of the present invention.

[0027] Figure 2 This is a hydrogen nuclear magnetic resonance spectrum of the nitrogen-containing heterocyclic cross-linked polyphosphazene prepared in Example 1 of the present invention.

[0028] Figure 3 This is the carbon nuclear magnetic resonance spectrum of the nitrogen-containing heterocyclic cross-linked polyphosphazene prepared in Example 1 of the present invention.

[0029] Figure 4 This is the nuclear magnetic resonance phosphorus spectrum of the nitrogen-containing heterocyclic cross-linked polyphosphazene prepared in Example 1 of the present invention.

[0030] Figure 5 This is an X-ray photoelectron spectrum of the nitrogen-containing heterocyclic cross-linked polyphosphazene prepared in Example 1 of the present invention.

[0031] Figure 6 This is the infrared spectrum of the nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid hybrid flame retardant prepared in Example 2 of the present invention.

[0032] Figure 7 This is an X-ray photoelectron spectrum of the nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid hybrid flame retardant prepared in Example 2 of the present invention.

[0033] Figure 8 This is the infrared spectrum of the nitrogen-containing heterocyclic cross-linked polyphosphazene-Zn complex prepared in Example 3 of the present invention.

[0034] Figure 9 This is an X-ray photoelectron spectrum of the nitrogen-containing heterocyclic cross-linked polyphosphazene-Zn complex prepared in Example 3 of the present invention.

[0035] Figure 10 This is the SEM of the nitrogen-containing heterocyclic cross-linked polyphosphazene and its derivatives prepared in Examples 1-2 of the present invention. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention. Example 1

[0037] Preparation method of nitrogen-containing heterocyclic cross-linked polyphosphazene:

[0038] 3,5-Diamino-1,2,4-triazole (TDA) (9.0 g, 90.9 mmol) and triethylamine (TEA) (9.6 g, 95.1 mmol) were evenly dispersed in 250 mL of dichloromethane (DCM). The system temperature was raised to 60°C. Hexachlorocyclotriphosphazene (HCCP) (10 g, 28.8 mmol) was then dissolved in 50 mL of dichloromethane (DCM) and slowly added dropwise to the solution. The reaction was allowed to proceed for 48 hours. The crude product was collected by vacuum filtration and washed three times with dichloromethane, deionized water, and ethanol, respectively. Finally, it was dried under vacuum at 80°C for 24 hours to obtain nitrogen-containing heterocyclic cross-linked polyphosphazene HTDA (yield, 81%). (The molar ratio of 3,5-diamino-1,2,4-triazole:triethylamine:hexachlorocyclotriphosphazene was 3.2:3.3:1.)

[0039] To further illustrate, Figure 1-4Infrared spectra and nuclear magnetic resonance (NMR) data are presented. The absorption peak at 3125 cm⁻¹ in the nitrogen-containing heterocyclic cross-linked polyphosphazene is attributed to N—H stretching vibration, the peak at 1651 cm⁻¹ corresponds to C=N stretching vibration, and the peak at 1401 cm⁻¹ represents C—N stretching vibration. Characteristic absorption peaks of the phosphazene ring appear at 1173 cm⁻¹ and 873 cm⁻¹, attributed to P=N and P—N, respectively. The P—Cl absorption peak at 594 cm⁻¹ is absent from the spectrum of the nitrogen-containing heterocyclic cross-linked polyphosphazene. In the proton nuclear magnetic resonance (1H-NMR) spectrum, the peak at 5.28 ppm corresponds to the hydrogen in the —P—NH— structure, which originates from the substitution of P—Cl. In the solid-state carbon nuclear magnetic resonance (13C-NMR) spectrum, the peak at 153.6 ppm clearly demonstrates that the carbon in this cross-linked structure has only one unique chemical environment. Similarly, in the solid-state nuclear magnetic resonance phosphorus (31P-NMR) spectrum, the signal at 0.49 ppm indicated that phosphorus was present in a single chemical environment. These results confirmed the successful synthesis of a high-purity flame retardant. Therefore, the target structural formula can be determined as:

[0040]

[0041] Among them, the R1 structure is: . Example 2

[0042] Preparation method of nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid (HTDA@MCA) hybrid flame retardant:

[0043] Melamine (ME) and deionized water (DIW) were mixed and heated to 90°C until completely dissolved. Equal amounts of nitrogen-containing heterocyclic cross-linked polyphosphazene (HTDA) and cyanuric acid (CA) were then added to the solution and allowed to react for 2 hours. The resulting product was collected by vacuum filtration and washed three times with deionized water and anhydrous ethanol. Finally, the product was dried in a vacuum oven at 80°C for 24 hours to obtain a nitrogen-containing heterocyclic cross-linked polyphosphazene and melamine cyanuric acid hybrid flame retardant (yield, 75%). (The molar ratio of melamine:cyanuric acid: nitrogen-containing heterocyclic cross-linked polyphosphazene was 1:1:1.)

[0044] To further illustrate, Figure 6 Infrared spectrum data are given. In the spectrum of melamine cyanuric acid, 3390 cm⁻ 1 and 3230 cm⁻ 1 The peaks at 1740 cm⁻ correspond to the symmetric and asymmetric stretching vibrations of -NH-. 1The peak at 1740 cm⁻ is attributed to the stretching vibration of C=O. After the introduction of nitrogen-containing heterocyclic cross-linked polyphosphazene, the infrared spectrum of the hybrid flame retardant is roughly similar to that of melamine cyanuric acid. However, due to the formation of hydrogen bonds, the -NH- peak becomes broadened and the C=O peak shifts from 1740 cm⁻ to 1740 cm⁻. 1 Shift to 1730 cm⁻ 1 , indicating a red shift. This shift indicates the formation of hydrogen bonds between the two, further confirming the successful interaction of the two components in the hybrid flame retardant. Therefore, the target structural formula can be determined as:

[0045] Example 3

[0046] Preparation method of nitrogen-containing heterocyclic cross-linked polyphosphazene-Zn complex (HTDA-Zn):

[0047] A nitrogen-containing heterocyclic cross-linked polyphosphazene (HTDA) was uniformly dispersed in deionized water (DIW). A hydrated metal salt solution was added dropwise to the mixture and allowed to react at room temperature for 2 hours. After the reaction, the mixture was allowed to stand at room temperature for 8 hours. The resulting product was then collected by centrifugation or vacuum filtration and washed three times with deionized water and anhydrous ethanol. Finally, the product was dried in a vacuum oven at 80°C for 24 hours to obtain a nitrogen-containing heterocyclic cross-linked polyphosphazene-metal complex (yield, 91%). (The mass ratio of hydrated metal salt to nitrogen-containing heterocyclic cross-linked polyphosphazene was 1.2:1.) The hydrated metal salts include, but are not limited to, zinc nitrate heptahydrate, zinc sulfate heptahydrate, ferric nitrate hexahydrate, cupric chloride dihydrate, and nickel nitrate hexahydrate.

[0048] To further illustrate, Figure 8 The cross-linked polyphosphazene with nitrogen-containing heterocyclic ring and Zn 2+ Infrared spectrum data after coordination. The nitrogen-containing heterocyclic cross-linked polyphosphazene is located at 3125 cm⁻ 1 The absorption peak is attributed to the stretching vibration of N-H. For metal complexes, 3250 cm⁻ 1 The absorption peak near 1651 cm⁻ disappears, proving the deprotonation of -NH- in the triazole ring. 1 The C=N stretching vibration absorption peak at 1634 cm⁻ is red-shifted to 1634 cm⁻ in the metal complex. 1 , indicating that coordination occurred, located at 423 cm⁻ 1 The appearance of the absorption peak at 1173 cm⁻ can be attributed to Zn-N. In addition, the characteristic absorption peak of the phosphazene ring appears at 1173 cm⁻ 1 and 873 cm⁻ 1 From 1173 cm⁻ 1 Redshift to 1141 cm⁻ 1 and from 873 cm⁻ 1Redshift to 846 cm⁻ 1 , confirming the coordination effect between the two. Therefore, the target structural formula can be determined as:

[0049]

[0050] Among them, the M structure is Zn 2+ 、Fe 2+ 、Cu 2+ 、Ni 2+ Any of . Example 4

[0051] A flame retardant polyurea elastomer, comprising a component A, a component B, and a flame retardant, wherein the mass ratio of component A to component B is 100:63, and the mass percentage of the flame retardant is 15%-25%;

[0052] Component A is a semi-prepolymer prepared by reacting diphenylmethane diisocyanate with a polyether polyol; Component B includes a polyetheramine and an amine chain extender. Flame retardants can be either single or composite flame retardants. Single flame retardants include any of the nitrogen-containing heterocyclic cross-linked polyphosphazene flame retardant described in Example 1, the nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid hybrid flame retardant described in Example 2, or the nitrogen-containing heterocyclic cross-linked polyphosphazene-metal complex flame retardant described in Example 3. Composite flame retardants include any of the above single flame retardants combined with aluminum hypophosphite, zinc hypophosphite, or piperazine pyrophosphate.

[0053] The A component described in Example 4 is prepared by the following process: first, polypropylene glycol with a molecular weight of 2000 is added to a three-necked flask equipped with a reflux condenser and a thermometer, and then the temperature is raised to 120 ° C. and stirred evenly at this temperature; thereafter, vacuum dehydration is performed for 3 hours; then the system temperature is lowered to 80 ° C., diphenylmethane diisocyanate is added to the three-necked flask mixed with polypropylene glycol, and the reaction is carried out under a nitrogen environment. During this period, the NCO% content is measured every 1 hour using the di-n-butylamine method until the reaction is stopped when it is close to the theoretical value of 11.8%, and nitrogen is passed through for storage. The mass ratio of diphenylmethane diisocyanate to polypropylene glycol is 44:60.

[0054] Component B described in Example 4 was prepared using the following process: First, polyether diamine with a molecular weight of 2000 and polyether triamine with a molecular weight of 5000 were added to a three-necked flask and stirred. After stirring until uniform, an amine chain extender was added. The entire system was stirred at 120°C until uniform. The amine chain extender was dimethylthiotoluenediamine and 4,4-bis-sec-butylaminodiphenylmethane. The mass ratio of polyether diamine, polyether triamine, dimethylthiotoluenediamine, and 4,4-bis-sec-butylaminodiphenylmethane was 30:3:20:10.

[0055] Example 4: Polyurea elastomers (Samples 1#-7#) were prepared using the following typical preparation process: Polyurea component B and a flame retardant were blended and stirred at room temperature until the flame retardant was evenly mixed into the polyurea component B. The polyurea component B or a mixture of polyurea component B and flame retardant was then rapidly added to the polyurea component A and mechanically stirred for 30 to 60 seconds. After the system heated and became viscous, it was poured into a polytetrafluoroethylene mold and pressurized for curing. After curing at room temperature for 2 hours, the elastomers were demolded and placed in a constant temperature and humidity chamber at 25°C and 50% RH for 24 hours. Finally, they were further cured in an 80°C oven for 48 hours to obtain flame-retardant polyurea samples. The resulting flame-retardant polyurea samples were stored in a constant temperature and humidity chamber at 25°C and 50% RH before testing. The vertical flammability rating and limiting oxygen index of the materials were tested using a vertical combustion instrument and a critical digital oxygen index analyzer. The results are shown in Table 1.

[0056] Table 1

[0057] Example 5

[0058] A flame-retardant epoxy resin comprises an epoxy resin, a curing agent, and a flame retardant. The mass ratio of the epoxy resin, curing agent, and flame retardant is 20:5.37, and the mass percentage of the flame retardant is 5%-15%. The epoxy resin is a bisphenol A diglycidyl ether epoxy resin, and the curing agent is 4,4'-diaminodiphenylmethane. The flame retardant comprises any one of the nitrogen-containing heterocyclic cross-linked polyphosphazene flame retardant described in Example 1, the nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid hybrid flame retardant described in Example 2, and the nitrogen-containing heterocyclic cross-linked polyphosphazene-metal complex described in Example 3.

[0059] Example 12: Epoxy resin thermoset materials (Samples 8#-16#) were prepared using the following typical preparation process: Bisphenol A diglycidyl ether epoxy resin and a flame retardant (sample 8# was omitted) were blended and stirred at 110°C until the flame retardant was evenly mixed into the epoxy resin. After cooling to 90°C, the curing agent, 4,4-diaminodiphenylmethane, was added to the mixture and mechanically stirred until completely dissolved in the epoxy resin. The mixture was then placed in a 60°C vacuum oven for defoaming. Finally, the mixture was poured into a mold preheated at 90°C and cured at 90°C for 2 hours, 130°C for 2 hours, and 170°C for 1 hour. After the mold cooled to room temperature, it was demolded to obtain flame-retardant epoxy resin samples. The vertical flammability rating, limiting oxygen index, and mechanical properties of the materials were tested using a vertical combustion instrument, a critical digital oxygen index analyzer, and a universal material testing machine. The results are shown in Table 2.

[0060] Table 2

[0061] .

[0062] Tables 1 and 2 show that HTDA@MCA exhibits superior flame retardancy to HTDA. On the one hand, the physical morphology undergoes significant changes, resulting in a lamellar structure after hybridization, which helps to hinder the propagation of flames and smoke, thereby enhancing flame retardancy. On the other hand, the lamellar structure distributes stress, improving mechanical properties. Furthermore, the surrounding MCA itself is a potent nitrogen-containing flame retardant. During combustion, it releases nitrogen, ammonia, and other combustible gases that dilute the gas phase and oxygen, promoting the expansion (blowing) of the char layer. The superior flame retardancy of HTDA-Zn over HTDA is attributed to the smoke suppression effect of the catalytic charring effect of the metal ions.

Claims

1. A nitrogen-containing heterocyclic cross-linked polyphosphazene, characterized in that The structural formula is: Among them, the R1 structure is:

2. The nitrogen-containing heterocyclic cross-linked polyphosphazene according to claim 1, characterized in that The preparation method comprises the following steps: dissolving 3,5-diamino-1,2,4-triazole and hexachlorocyclotriphosphazene in an organic solvent, reacting them under the action of an acid-binding agent to generate a nitrogen-containing heterocyclic cross-linked polyphosphazene, wherein the molar ratio of 3,5-diamino-1,2,4-triazole to hexachlorocyclotriphosphazene is 3.1-3.5:1; 3. A nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative, characterized in that: The structural diagram is as follows: The nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative is prepared by in-situ self-assembly of the nitrogen-containing heterocyclic cross-linked polyphosphazene according to claim 1, melamine and cyanuric acid in an aqueous phase, and has a multiple hydrogen bond hybrid structure.

4. A nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative, characterized in that: The structural formula is: Among them, M 2+ Zn 2+ 、Fe 2+ 、Cu 2+ 、Ni 2+ Any of The nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative is prepared by coordination of the nitrogen-containing heterocyclic cross-linked polyphosphazene according to claim 1 and metal ions.

5. Use of the nitrogen-containing heterocyclic cross-linked polyphosphazene according to claim 1 and the hybrid derivative according to claim 3 or 4 as a flame retardant.

6. Use of the nitrogen-containing heterocyclic cross-linked polyphosphazene according to claim 1 and the hybrid derivative according to claim 3 or 4 as flame retardants in epoxy resins, polyureas, polyurethanes, polyolefins, polyamides, and polycarbonates.

7. A flame retardant polyurea elastomer, characterized in that: The invention comprises component A, component B and a flame retardant, wherein the mass percentage of the flame retardant is 15%-25%, the component A is a semi-prepolymer prepared by reacting diphenylmethane diisocyanate and polyether polyol, the component B comprises polyetheramine and an amine chain extender, and the flame retardant is divided into a single flame retardant and a composite flame retardant, the single flame retardant comprises any one of the nitrogen-containing heterocyclic cross-linked polyphosphazene according to claim 1, the nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative according to claim 3, and the nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative according to claim 4, and the composite flame retardant comprises any one of the single flame retardants and any one of aluminum hypophosphite, zinc hypophosphite, and piperazine pyrophosphate.

8. A flame retardant epoxy resin, characterized in that The invention comprises an epoxy resin, a curing agent and a flame retardant, wherein the mass percentage of the flame retardant is 5%-15%, and the flame retardant comprises any one of the nitrogen-containing heterocyclic cross-linked polyphosphazene according to claim 1, the nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative according to claim 3, and the nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative according to claim 4.

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