Nitrogen-containing heterocyclic cross-linked polyphosphazene and hybrid derivative thereof, flame-retardant polyurea elastomer and epoxy resin

Abstract

The invention discloses nitrogen-containing heterocyclic cross-linked phosphazene, a hybrid derivative of nitrogen-containing heterocyclic cross-linked phosphazene, a flame-retardant polyurea elastomer and epoxy resin, and belongs to the technical field of flame-retardant high polymer materials. The preparation method comprises the following steps: carrying out a cross-linking reaction on phosphonitrilic chloride trimer and 3, 5-diamino-1, 2, 4-triazole to prepare nitrogen heterocyclic ring cross-linked polyphosphazene; melamine cyanuric acid is further introduced in situ through hydrogen-bond interaction, and a nitrogen-containing heterocyclic ring cross-linked phosphazene hybrid derivative HTDA (at) MCA is prepared; metal ions are introduced, and the nitrogen-containing heterocyclic ring cross-linked phosphazene hybrid derivative HTDA-M is prepared through the metal coordination effect of an azole structure. The nitrogen-containing heterocyclic cross-linked polyphosphazene and the hybrid derivative thereof provided by the invention can be used for preparing flame-retardant anti-aging polyurea elastomer and epoxy resin, not only have efficient flame-retardant and smoke-suppression effects, but also can maintain or improve the mechanical properties of a matrix material.

Description

Technical field:

[0001] The invention belongs to the technical field of flame retardant polymer materials, and specifically provides a nitrogen-containing heterocyclic cross-linked phosphazene and a hybrid derivative thereof, a flame retardant polyurea elastomer and an epoxy resin, and a preparation method and application thereof. Background technology:

[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, waterproofness and wear resistance. At the same time, it can be formed by solvent-free spraying or brushing process by adjusting the reaction speed of the system. As a protective coating, it is widely used in the fields of building waterproofing, pipeline anti-corrosion, coastal defense and hull protection, and battery box protection.

[0003] Epoxy resin is a high-performance thermosetting polymer with excellent mechanical strength and chemical stability. This type of resin mainly includes bisphenol A epoxy resin, which is widely used in coatings, adhesives and electronic packaging. Its cured products not only have excellent temperature and corrosion resistance, but can also be modified to meet specific flame retardant and thermal conductivity requirements. Therefore, they are widely used in industries such as aviation, automobiles and construction.

[0004] However, polyurea itself is very flammable, and it is accompanied by a large number of flaming droplets when burning. After epoxy resin is cured, the droplets are limited due to the cross-linked network, but it is difficult to extinguish. The limiting oxygen index (LOI) of polyurea and epoxy resin is only 21%-22% when they are not flame retardant, and they are accompanied by a large amount of toxic smoke when burning. The flammability brings potential fire hazards to the application of polyurea and epoxy resin.

[0005] According to the reaction characteristics of polyurea and epoxy resin, the existing technology mainly improves the flame retardancy of polyurea and epoxy resin by reactive flame retardant and additive flame retardant. Reactive flame retardant means changing the molecular structure of polyurea or epoxy resin and introducing flame retardant units by using reactive monomers and curing agents containing flame retardant elements. However, it often changes the original curing process of polyurea or epoxy, and at the same time causes an increase in cost. It is not conducive to industrial production.

[0006] Additive flame retardants are added to the curing formula of polyurea or epoxy resin. Flame-retardant polyurea or epoxy resin is prepared without changing the reaction conditions. It has good practicality and economy and is a commonly used method in industry. However, the flame retardant system currently used for polyurea or epoxy resin has problems such as low flame retardant efficiency and deterioration of mechanical properties, thermal properties and aging resistance of the substrate due to large addition amount, which affects the application of flame-retardant polyurea and epoxy resin. Summary of the invention:

[0007] In order to solve 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 elastomer and epoxy resin, the present invention provides a nitrogen-containing heterocyclic cross-linked phosphazene 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 object, the nitrogen-containing heterocyclic cross-linked phosphazene of the present invention has the following structural formula:

[0009]

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

[0011] As an implementation method, the nitrogen-containing heterocyclic cross-linked phosphazene 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 phosphazene 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 is as follows: 3,5-diamino-1,2,4-triazole and hexachlorocyclotriphosphazene are dissolved in an organic solvent, and reacted under the action of an acid binding agent to generate 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 preparation method of the nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid of the present invention is: adding melamine to deionized water, heating to 90°C until completely dissolved, then adding the nitrogen-containing heterocyclic cross-linked polyphosphazene and cyanuric acid, reacting, and collecting, washing, and drying the product after the reaction is completed. 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 after the reaction is completed, collecting, washing and drying the product, wherein 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, iron 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 the fields of building waterproofing, pipeline anticorrosion, coastal defense, hull protection, and battery box protection; the flame-retardant epoxy resin can be used in the fields of fiber-reinforced composite materials 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, the flame retardant is divided into a single flame retardant and a composite flame retardant, the component A is a semi-prepolymer obtained by reacting diphenylmethane diisocyanate with polyether polyol, the mass ratio of diphenylmethane diisocyanate to polyether polyol is 44:60; the component B comprises polyetheramine and amine expansion The chain agent is a polyether diamine with a molecular weight of 2000 and a polyether triamine with a molecular weight of 5000. The amine chain extender is any one or any two of dimethylthiotoluenediamine, dimethylthiotoluenediamine, diethyltoluenediamine, and 4,4-bis-sec-butylaminodiphenylmethane, wherein the mass ratio of polyether diamine, polyether triamine, dimethylthiotoluenediamine, and 4,4-bis-sec-butylaminodiphenylmethane is 30:3:20:10. The single flame retardant includes 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 includes 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, wherein the mass ratio of the epoxy resin, the curing agent and the flame retardant is 20:5.37:1.34-4.48, the epoxy resin comprises but is not limited to bisphenol A diglycidyl ether epoxy resin, bisphenol S diglycidyl ether epoxy resin, bisphenol A novolac epoxy resin, etc., the curing agent comprises 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, polyimide, 2-methylimidazole, etc. The 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.

[0025] The nitrogen-containing heterocyclic cross-linked polyphosphazene and its hybrid derivatives of the present invention have the following beneficial effects compared with the prior art: the nitrogen-containing heterocyclic cross-linked polyphosphazene and its hybrid derivatives provided by the present invention have simple preparation process, high phosphorus and nitrogen content, and the nitrogen-containing heterocyclic structure, phosphazene ring structure, triazine structure and metal ions improve the flame retardant and smoke suppression performance of polyurea and epoxy resin through phosphorus and nitrogen synergy, carbonization, catalysis and other effects, and at the same time maintain or improve the mechanical properties of the matrix material through intermolecular forces such as hydrogen bonds, π-π conjugation and the special physical morphology of the flame retardant. Adding a single flame retardant or forming a composite flame retardant can make the polyurea elastomer pass the UL-94 V-0 grade at an addition amount of 15-20%, and the LOI reaches more than 27%; when the addition amount is 5% to 15%, the epoxy resin can pass the vertical combustion V-1 or V-0 grade, and the toxic smoke release is greatly reduced, which has a high flame retardant and smoke suppression effect. 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 the 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] Fig. 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] Fig.10 This is the SEM of the nitrogen-containing heterocyclic cross-linked polyphosphazene and its derivatives prepared in Example 1-2 of the present invention. Specific implementation method:

[0036] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0037] Example 1

[0038] Preparation method of nitrogen-containing heterocyclic cross-linked polyphosphazene:

[0039] 3,5-diamino-1,2,4-triazole HCCP (9.0g, 90.9mmol) and triethylamine TEA (9.6g, 95.1mmol) were evenly dispersed in 250mL dichloromethane DCM, and the system temperature was raised to 60°C. Then hexachlorocyclotriphosphazene TDA (10g, 28.8mmol) was dissolved in dichloromethane DCM (50mL) and slowly added dropwise to the above solution for 48 hours. After collecting the obtained crude product by vacuum filtration, it was washed three times with dichloromethane, deionized water and ethanol respectively, and finally vacuum dried at 80°C for 24 hours to obtain nitrogen-containing heterocyclic cross-linked polyphosphazene HTDA (yield, 81%). (3,5-diamino-1,2,4-triazole: triethylamine: hexachlorocyclotriphosphazene molar ratio is 3.2:3.3:1)

[0040] To further illustrate, Figure 1-4 The infrared spectrum and NMR data are given. 1 The absorption peak is attributed to the stretching vibration of N—H, 1651cm- 1 The peak at 1401 cm- 1The peak at represents the stretching vibration of C—N, and the characteristic absorption peak of the phosphazene ring appears at 1173 cm- 1 and 873cm- 1 , respectively, belonging to P=N and P—N, located at 594cm- 1 The P—Cl absorption peak is missing in the spectrum of nitrogen-containing heterocyclic cross-linked polyphosphazene. 1 In the solid state nuclear magnetic resonance carbon spectrum ( 13 In the solid-state NMR spectrum (C-NMR), the peak at 153.6 ppm clearly shows that the carbon has only one unique chemical environment in this cross-linked structure. 31 In the P-NMR spectrum, the signal at 0.49 ppm indicates that phosphorus is present in a single chemical environment. These results confirm the successful synthesis of high-purity flame retardants. Therefore, the target structural formula can be determined as:

[0041]

[0042] Among them, the structure of R1 is:

[0043] Example 2

[0044] Preparation method of nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid (HTDA@MCA) hybrid flame retardant:

[0045] Melamine ME and deionized water DIW were mixed and heated to 90°C until completely dissolved, and then equal amounts of nitrogen-containing heterocyclic cross-linked polyphosphazene HTDA and cyanuric acid CA were added to the above solution and the reaction was allowed to proceed 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 @ melamine cyanuric acid hybrid flame retardant (yield, 75%). (The molar ratio of melamine: cyanuric acid: nitrogen-containing heterocyclic cross-linked polyphosphazene is 1:1:1)

[0046] To further illustrate, Figure 6 Infrared spectrum data are given. In the spectrum of melamine cyanuric acid, 3390cm- 1 and 3230cm- 1 The peaks at 1740cm- 1 The peak at 1740 cm-1 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 increases from 1740 cm-1 to 1760 cm-1.1 Move to 1730cm- 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:

[0047]

[0048] Example 3

[0049] Preparation method of nitrogen-containing heterocyclic cross-linked polyphosphazene-Zn complex (HTDA-Zn):

[0050] The nitrogen-containing heterocyclic cross-linked polyphosphazene HTDA is uniformly dispersed in deionized water DIW, and a deionized water solution containing a hydrated metal salt is added dropwise to the mixture, and the mixture is allowed to react at room temperature RT for 2 hours. After the reaction is completed, it is allowed to stand at room temperature for 8 hours. Subsequently, the obtained product is collected by centrifugation or vacuum filtration, and washed three times with deionized water and anhydrous ethanol. Finally, the product is 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: nitrogen-containing heterocyclic cross-linked polyphosphazene is 1.2:1). The hydrated metal salt includes but is not limited to zinc nitrate heptahydrate, zinc sulfate heptahydrate, iron nitrate hexahydrate, cupric chloride dihydrate, nickel nitrate hexahydrate, and the like.

[0051] 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 3125cm- 1 The absorption peak is attributed to the stretching vibration of N—H. For metal complexes, 3250cm- 1 The absorption peak near 1651cm- 1 The C=N stretching vibration absorption peak at the metal complex red-shifts to 1634 cm- 1 , indicating that coordination occurred, located at 423cm- 1 The absorption peak at 1173 cm- 1 and 873cm- 1 From 1173cm- 1 Red shifted to 1141cm- 1 and from 873cm- 1 Red shifted to 846cm- 1 , confirming the coordination effect between the two. Therefore, the target structural formula can be determined as:

[0052]

[0053] Among them, the M structure is Zn 2+ , Fe 2+ , Cu 2+ 、Ni 2+ Any of .

[0054] Example 4

[0055] A flame retardant polyurea elastomer, comprising component 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%;

[0056] The component A is a semi-prepolymer obtained by reacting diphenylmethane diisocyanate with polyether polyol; the component B includes polyetheramine and amine chain extender. The flame retardant is divided into a single flame retardant or a composite flame retardant, wherein the single flame retardant includes 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 flame retardant described in Example 3. The composite flame retardant includes any one of the above single flame retardants and any one of aluminum hypophosphite, zinc hypophosphite, and piperazine pyrophosphate.

[0057] The A component described in Example 4 adopts the following preparation 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, and diphenylmethane diisocyanate is added to the three-necked flask mixed with polypropylene glycol, and the reaction is carried out in a nitrogen environment. During this period, the NCO% content is measured every 1 hour by 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 for storage. The mass ratio of diphenylmethane diisocyanate to polypropylene glycol is 44:60.

[0058] The B component of Example 4 is prepared by the following process: first, polyether diamine with a molecular weight of 2000 and polyether triamine with a molecular weight of 5000 are added to a three-necked flask and stirred; after stirring evenly, an amine chain extender is added. The whole system is stirred at 120°C until it is uniform. The amine chain extender is dimethylthiotoluene diamine and 4,4-bis-sec-butylaminodiphenylmethane. The mass ratio of polyether diamine, polyether triamine, dimethylthiotoluene diamine and 4,4-bis-sec-butylaminodiphenylmethane is 30:3:20:10.

[0059] Example 4 The following typical preparation process is used to prepare polyurea elastomers (samples 1#-7#): The polyurea B component and the flame retardant are blended and stirred at room temperature until the flame retardant is evenly mixed in the polyurea B component, the polyurea B component or the mixture of the polyurea B component and the flame retardant is quickly added to the polyurea A component, mechanically stirred for 30s to 60s, and poured into a polytetrafluoroethylene mold for pressure curing after the system becomes hot and sticky. After room temperature curing for 2 hours, the mold is demoulded, placed in a constant temperature and humidity chamber at 25°C and 50% rh for 24 hours, and finally placed in an 80°C oven for further curing for 48 hours to obtain a flame-retardant polyurea sample. The obtained flame-retardant polyurea sample can be placed in a constant temperature and humidity chamber at 25°C and 50% rh for storage and then tested. The vertical combustion grade and limiting oxygen index of the material are tested using a vertical combustion instrument and a critical digital oxygen index analyzer. The results are shown in Table 1.

[0060] Table 1

[0061]

[0062]

[0063] Example 5

[0064] A flame retardant epoxy resin comprises an epoxy resin, a curing agent and a flame retardant, wherein the mass ratio of the epoxy resin, the curing agent and the 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 type 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.

[0065] Example 12 The following typical preparation process was used to prepare epoxy resin thermosetting materials (samples 8#-16#): bisphenol A diglycidyl ether epoxy resin and flame retardant (no addition to sample 8#) were blended and stirred at 110°C until the flame retardant was evenly mixed in the epoxy resin. After cooling to 90°C, the curing agent 4,4-diaminodiphenylmethane was added to the mixed solution, mechanically stirred until completely dissolved in the epoxy resin, and then the mixed solution was placed in a 60°C vacuum oven for defoaming, and finally the mixed solution 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. When the mold was cooled to room temperature and demolded, a flame-retardant epoxy resin sample was obtained, and the vertical combustion grade, limiting oxygen index and mechanical properties of the material 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.

[0066] Table 2

[0067]

[0068]

[0069] It can be seen from Table 1 and Table 2 that the flame retardant effect of HTDA@MCA is better than that of HTDA. On the one hand, the physical morphology has changed significantly, and after hybridization, it has become a lamellar structure, which helps to hinder the spread of flames and smoke and has better flame retardant properties. On the other hand, the lamellar structure shares stress and improves mechanical properties. In addition, the peripheral MCA itself is a good nitrogen-containing flame retardant. During the combustion process, it releases nitrogen, ammonia and other combustible gases and oxygen in the diluent gas phase, which can also promote the expansion (blowing) of the carbon layer. The flame retardant effect of HTDA-Zn is better than that of HTDA, which is attributed to the catalytic carbonization and smoke suppression effect of the introduction of metal ions.

Claims

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

2. The nitrogen-containing heterocyclic cross-linked polyphosphazene according to claim 1, characterized in that: The preparation method is as follows: 3,5-diamino-1,2,4-triazole and hexachlorocyclotriphosphazene are dissolved in an organic solvent, and reacted under the action of an acid-binding agent to generate a nitrogen-containing heterocyclic cross-linked polyphosphazene.

3. A nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative, characterized in that: The structural diagram is as follows:

4. The nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative according to claim 3, characterized in that: The cross-linked polyphosphazene containing nitrogen heterocyclics as claimed in claim 1 and melamine and cyanuric acid are prepared by in-situ self-assembly in water phase, and have a multi-hydrogen bond hybrid structure.

5. A nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative, characterized in that: The structural formula is: Where M is Zn 2+ , Fe 2+ , Cu 2+ 、Ni 2+ Any of .

6. The nitrogen-containing heterocyclic cross-linked polyphosphazene hybrid derivative according to claim 5, characterized in that: Prepared by coordination of the nitrogen-containing heterocyclic cross-linked polyphosphazene according to claim 1 and metal ions, 7. Use of the nitrogen-containing heterocyclic cross-linked polyphosphazene according to claim 1 and the hybrid derivative according to claim 2 or 4 as flame retardants.

8. Use of the nitrogen-containing heterocyclic cross-linked polyphosphazene according to claim 1 and the hybrid derivative according to claim 2 or 4 as flame retardants in epoxy resins, polyureas, polyurethanes, polyolefins, polyamides and polycarbonates.

9. 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 obtained by reacting diphenylmethane diisocyanate with a polyether polyol, the component B comprises a polyetheramine and an amine chain extender, 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 described in claim 1, the nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid described in claim 2, and the nitrogen-containing heterocyclic cross-linked polyphosphazene-metal complex described in claim 3, and the composite flame retardant comprises any one of the single flame retardant and any one of aluminum hypophosphite, zinc hypophosphite, and piperazine pyrophosphate.

10. A flame retardant epoxy resin, characterized in that: The invention comprises epoxy resin, curing agent and 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 described in claim 1, the nitrogen-containing heterocyclic cross-linked polyphosphazene@melamine cyanuric acid described in claim 2, and the nitrogen-containing heterocyclic cross-linked polyphosphazene-metal complex described in claim 3.

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