Biologic intrinsic type self-repairing flame-retardant polyurethane composite material and preparation method thereof

Abstract

The invention discloses a bio-based intrinsic type self-repairing flame-retardant polyurethane composite material and a preparation method thereof. The bio-based intrinsic type self-repairing flame-retardant polyurethane composite material is prepared from bio-based polyethylene glycol, fluorine-containing diisocyanate, dihydric alcohol containing dynamic covalent bonds, a dyhydroxyl flame-retardant monomer, aromatic ring-containing dianhydride and a catalyst through a one-step polymerization reaction. The fluorine-containing diisocyanate is introduced to a polyurethane main chain, the fluorine-containing diisocyanate enhances CO2 affinity and regulates and controls phase separation, the performance of polyurethane in supercritical CO2 foaming is remarkably improved, the polyurethane is endowed with multiple functionalization, and the prepared bio-based intrinsic type self-repairing flame-retardant polyurethane foam has more excellent flame-retardant performance and can be used as a flame-retardant polyurethane foam material. The material has good self-repairing performance, mechanical performance and processability, and high yield and molecular weight.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a self-healing flame-retardant polyurethane composite material with biological basic characteristics and its preparation method. Background Technology

[0002] Polyurethane (PU) is a general term for macromolecular compounds containing urethane (-NHCOO-) groups in their main chain, formed by the addition polymerization of organic diisocyanates or polyisocyanates with dihydroxy or polyhydroxy compounds. PU is widely used in fibers, plastics, elastomers, and biomaterials due to its excellent wear resistance, high toughness, and chemical resistance. However, during use, PU is susceptible to surface cracking or internal cracking due to external stimuli such as force and light. These cracks reduce the overall dimensional stability, mechanical properties, and service life of the material. Furthermore, the highly reactive urethane groups and abundant C, H, and O elements in PU make it extremely flammable, limiting its practical applications in many fields. Therefore, endowing PU with self-healing capabilities, remodeling properties, and environmental adaptability through reversible breaking and recombination of dynamic bonds, and performing flame-retardant treatment to improve its fire safety, is crucial for expanding its application range. Furthermore, most of the monomers used in the synthesis of PU, such as polyisocyanates and polyols, are derived from petrochemical derivatives. Since petroleum is a non-renewable resource, this limits the sustainable development of the PU industry. Therefore, given the shortcomings of traditional PU, it is of great significance to utilize renewable resources (such as vegetable oils, lignin, natural carbohydrates, and carbon dioxide (CO2)) to prepare bio-based self-healing flame-retardant PU with excellent comprehensive performance.

[0003] Bio-based polyethylene glycol (Bio-PEG) is a linear polymer composed of multiple ethylene glycol units linked by ether bonds, exhibiting good water solubility, biocompatibility, and chemical stability. The unique physicochemical properties of fluorine atoms can improve the performance of PU. Due to its extremely high electronegativity, small atomic radius, and high bond energy of the CF bond, fluorine can significantly enhance the weather resistance, chemical stability, and thermal stability of PU while maintaining its original excellent properties. Furthermore, fluorine has low thermal conductivity and high chemical stability, enabling it to form a dense char layer structure at high temperatures, effectively isolating oxygen and heat and inhibiting the combustion process. Therefore, introducing fluorine into the molecular structure can significantly improve the flame retardant properties of polyurethane materials. Although flame-retardant PU materials with different molecular structures have been prepared by reacting different dihydroxy compounds with fluorinated diisocyanates, research on the preparation of bio-based self-healing flame-retardant PU is relatively limited.

[0004] Chinese invention patent application No. 202410721866.5 discloses a microporous foamed thermoplastic polyurethane substrate, its preparation method, and its application. The microporous foamed thermoplastic polyurethane substrate obtained by this invention possesses suitable mechanical properties and hardness; however, its preparation steps are cumbersome, and the yield and molecular weight are relatively low. Chinese invention patent application No. 202211712591.6 discloses a flame-retardant polyurethane material and its preparation method. The flame-retardant polyurethane material prepared by this invention exhibits significantly improved flame-retardant performance, effectively solving the problems of high dosage and low flame-retardant efficiency of traditional additive flame retardants. However, it lacks self-healing properties, resulting in a short material lifespan. Therefore, developing a self-healing flame-retardant polyurethane foam based on biomass raw materials is of great significance and is an urgent technical problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a bio-based self-healing flame-retardant polyurethane composite material and its preparation method. Fluorinated diisocyanate is introduced into the polyurethane backbone. By enhancing CO2 affinity and regulating phase separation, the fluorinated diisocyanate significantly improves the performance of polyurethane in supercritical CO2 foaming, thus endowing it with multifunctionality.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A bio-based self-healing flame-retardant polyurethane composite material, with the following structural formula:

[0008]

[0009] in,

[0010]

[0011]

[0012] The preparation method of the above-mentioned bio-based self-healing flame-retardant polyurethane composite material includes the following specific steps:

[0013] S1. Heat the oil bath to a certain temperature, add a certain amount of bio-based polyethylene glycol to the three-necked flask, set a certain stirring speed, and after it is completely melted, evacuate to a certain negative pressure and maintain it for a period of time.

[0014] S2. Set a certain oil bath temperature. After the oil bath temperature reaches the set temperature, introduce a protective gas, add fluorinated diisocyanate, aromatic dianhydride and catalyst, and react at a constant temperature for a period of time.

[0015] S3. Then, cool the oil bath to a certain temperature, add a diol containing dynamic covalent bonds and a dihydroxy flame-retardant monomer, and react at a constant temperature for a period of time.

[0016] S4. After the reaction is complete, the product is poured onto a PTFE plate and cooled at room temperature for a certain period of time. Then, the PTFE plate is placed in an oven at a certain temperature for a certain period of time to obtain a bio-based self-healing flame-retardant polyurethane.

[0017] S5. Then, the obtained bio-based self-healing flame-retardant polyurethane is placed in a high-temperature and high-pressure foaming autoclave with an inert gas as the foaming agent. Under certain foaming temperature and pressure conditions, after a certain swelling time, the pressure inside the autoclave is quickly released to prepare the bio-based self-healing flame-retardant polyurethane foam material.

[0018] Preferably, in step S1, the oil bath temperature is 100-130°C, the stirring speed is 200-400 r / min, the negative pressure is -0.06--0.1 MPa, and the negative pressure extraction time is 50-80 min.

[0019] Preferably, in step S2, the oil bath temperature is 70–100°C, the constant temperature reaction temperature is 70–100°C, the reaction time is 1–3 hours, and the protective gas is one of nitrogen, helium, argon, or neon.

[0020] Preferably, in step S2, the fluorinated diisocyanate is at least one of 1,2,3,5-tetrafluoro-4,6-diisocyanate, 1,2,4,5-tetrafluoro-3,6-diisocyanate, 2,2',3,3',5,5',6,6'-octafluoro-4,4'-diisocyanate-1,1'-biphenyl, 3-nitro-azapentane-1,5-diisocyanate, and bis(1,1-dihydroperfluorodiisocyanate propyl ether); the aromatic dianhydride is at least one of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, and 1,4,5,8-naphthalenetetracarboxylic acid dianhydride; and the catalyst is at least one of dibutyltin dilaurate, didodecylthiodioctyltin, stannous octoate, dibutyltin oxide, and dibutyltin dichloro.

[0021] Preferably, in step S3, the oil bath temperature is 50–90°C and the reaction time is 1–3 hours.

[0022] Preferably, in step S3, the diol containing dynamic covalent bonds is a mixture of fluorinated dihydroxy disulfide and 1,3-dihydroxymethylurea, and the dihydroxy flame retardant monomer is a diphenol derivative of DOPO.

[0023] Preferably, in step S4 above, the cooling temperature is room temperature, the cooling time is 6 to 10 hours, the oven temperature is 100 to 120°C, and the oven treatment time is 5 to 7 hours.

[0024] Preferably, in step S5, the foaming temperature is 80–120°C, the foaming pressure is 10–16 MPa, and the swelling time is 50–100 min.

[0025] Preferably, the molar ratio of the aforementioned bio-based polyethylene glycol, fluorinated diisocyanate, catalyst, aromatic dianhydride, fluorinated dihydroxy disulfide, 1,3-dihydroxymethylurea, and DOPO diphenol derivative is 2-5:10-15:0.01-0.04:3-6:1-3:2-4:3-6.

[0026] The advantages of this invention are as follows: This invention introduces fluorinated diisocyanate into the polyurethane backbone. By enhancing CO2 affinity and regulating phase separation, the fluorinated diisocyanate significantly improves the performance of polyurethane in supercritical CO2 foaming, giving it multifunctionality. Furthermore, by introducing flame-retardant monomers, the flame-retardant properties of the polyurethane elastomer can be significantly improved. The resulting bio-based self-healing flame-retardant polyurethane composite ester exhibits superior flame-retardant and self-healing properties, good mechanical and processing properties, high yield and molecular weight, and is environmentally friendly. Attached Figure Description

[0027] Figure 1 The FT-IR curve of PUD-2 prepared in Example 2 of this invention;

[0028] Figure 2 Scanning electron microscope images of PUD-2 prepared in Example 2 of the present invention ((a) Optical microscope image of the material before self-healing; (b) Optical microscope image of the material after self-healing). Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] A method for preparing a bio-based self-healing flame-retardant polyurethane composite material includes the following specific steps:

[0032] Heat the oil bath to 120°C, introduce nitrogen gas into the three-necked flask, add 24.1g of polyethylene glycol, and after it melts, apply a negative pressure of -0.09MPa to remove water for 60 minutes, setting the stirring speed to 200r / min. Once the oil bath temperature drops to 90°C, add 11.4g of 1,2,3,5-tetrafluoro-4,6-diisocyanate benzene, 7.3g of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, and 50μL of dibutyltin dilaurate. React at a constant temperature of 90°C for 1 hour. The oil bath was then cooled to 60°C, and 1.1g of fluorinated dihydroxy disulfide, 0.9g of 1,3-dihydroxymethylurea, and 1.3g of a bisphenol derivative of the flame-retardant monomer DOPO were added (molar ratio: polyethylene glycol: benzene 1,2,3,5-tetrafluoro-4,6-diisocyanate: dibutyltin dilaurate: 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride: fluorinated dihydroxy disulfide: 1,3-dihydroxymethylurea: DOPO bisphenol derivative = 3:12:0.02:4:1:2:2). The chain extension reaction was carried out for 2 hours. The product was then cooled at room temperature for 10 hours and treated in an oven at 110°C for 6 hours to obtain a bio-based self-healing flame-retardant polyurethane (PUD-1). Then, PUD-1 was placed in a high-temperature and high-pressure foaming autoclave with carbon dioxide as the foaming agent. Under the conditions of 90°C and 12MPa, the pressure inside the autoclave was rapidly released after the swelling time reached 80 minutes to prepare a bio-based self-healing flame-retardant polyurethane foam material (FPUD-1).

[0033] Example 2

[0034] The preparation steps in this embodiment are the same as in Example 1, except that the amount of flame retardant monomer used is different: the amount of DOPO bisphenol derivative added is 3.4g (molar ratio, polyethylene glycol: benzene 1,2,3,5-tetrafluoro-4,6-diisocyanate: dibutyltin dilaurate: 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride: fluorinated dihydroxy disulfide: 1,3-dihydroxymethylurea: DOPO bisphenol derivative = 3:12:0.02:4:1:2:5), thus preparing a bio-basic self-healing flame retardant polyurethane foam material (FPUD-2).

[0035] Example 3

[0036] The preparation steps in this embodiment are the same as in Example 1, except that the amount of flame retardant monomer used is different: the amount of DOPO bisphenol derivative added is 5.4g (molar ratio, polyethylene glycol: benzene 1,2,3,5-tetrafluoro-4,6-diisocyanate: dibutyltin dilaurate: 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride: fluorinated dihydroxy disulfide: 1,3-dihydroxymethylurea: DOPO bisphenol derivative = 3:12:0.02:4:1:2:8), thus preparing a bio-basic self-healing flame retardant polyurethane foam material (FPUD-3).

[0037] The structural formulas of the bio-basic self-healing flame-retardant polyurethane foam materials prepared in Examples 1-3 are shown below:

[0038]

[0039] in,

[0040]

[0041]

[0042] Example 4

[0043] The preparation steps in this embodiment are the same as in Example 2, except that the amount of fluorinated dihydroxy disulfide is different: the amount of fluorinated dihydroxy disulfide added is 0.88g (molar ratio, polyethylene glycol: benzene 1,2,3,5-tetrafluoro-4,6-diisocyanate: dibutyltin dilaurate: 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride: fluorinated dihydroxy disulfide: 1,3-dihydroxymethylurea: DOPO diphenol derivative = 3:12:0.02:4:0.8:2:5).

[0044] Example 5

[0045] The preparation steps in this embodiment are the same as in Example 2, except that the amount of fluorinated dihydroxy disulfide is different: the amount of fluorinated dihydroxy disulfide added is 1.32g (molar ratio, polyethylene glycol: benzene 1,2,3,5-tetrafluoro-4,6-diisocyanate: dibutyltin dilaurate: 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride: fluorinated dihydroxy disulfide: 1,3-dihydroxymethylurea: DOPO diphenol derivative = 3:12:0.02:4:1.2:2:5).

[0046] Comparative Example 1

[0047] The preparation steps in this embodiment are the same as in Example 2, except that: no bisphenol derivative of the flame-retardant monomer DOPO was added, and polyurethane foam material (FPU-1) was prepared.

[0048] Comparative Example 2

[0049] The preparation steps in this embodiment are the same as in Example 2, except that no fluorinated dihydroxy disulfide is added, and polyurethane foam material (FPU-2) is prepared.

[0050] Comparative Example 3

[0051] The preparation steps in this embodiment are the same as in Example 2, except that 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride was not added, and polyurethane foam material (FPU-3) was prepared.

[0052] Performance testing

[0053] (1) According to Figure 1 It can be seen that at 1737cm -1 and 1249cm -1 The characteristic absorption peak at 2939 cm⁻¹ is due to the stretching vibrations of the C=O and COC groups. -1 and 789cm -1 Corresponding to the stretching and bending vibrations of the CH bond, respectively; 3386cm -1 and 1524cm -1 These are stretching vibrations and in-plane bending vibrations of the NH bond in the urea group (-NHCOO-); 2240–2280 cm⁻¹ -1 The disappearance of the characteristic absorption peak of -NCO indicates that the -NCO group in the isocyanate has completely reacted. In summary, infrared spectroscopy analysis shows that the target product was obtained.

[0054] (2) According to Figure 2 (a) and Figure 2 As can be seen from (b), the surface scratches basically disappeared after the material was repaired at 60℃ for 2 hours.

[0055] (3) The flame retardant properties of the foamed materials in Examples 1-5 and Comparative Examples 1-3 were tested. The test method was GB / T2408-2008. The specific results are shown in Table 1.

[0056] Table 1. Flame retardant performance test results of Comparative Examples 1-3 and Examples 1-5

[0057] Sample code sample Flame retardant monomer content LOI (%) Flame retardant rating Does the molten droplet ignite upon dripping? Comparative Example 1 FPU-1 0％ 17 Flammable dripping, igniting Comparative Example 2 FPU-2 5％ 29 V-2 dripping, igniting Comparative Example 3 FPU-3 5％ 31 V-1 It drips but does not ignite. Example 1 FPUD-1 2％ 28 V-2 dripping, igniting Example 2 FPUD-2 5％ 34 V-1 It drips but does not ignite. Example 3 FPUD-3 8％ 37 V-0 No dripping Example 4 FPUD-4 5％ 30 V-1 It drips but does not ignite. Example 5 FPUD-5 5％ 36 V-1 It drips but does not ignite.

[0058] As shown in Table 1, when the flame retardant monomer content increased from 2% to 8% (FPUD-3), the LOI value increased from 28% to 37% and achieved UL94 V-0 rating with no dripping. The principle is that the phosphorus-phenanthrene structure of DOPO catalyzes dehydration to form char during combustion, while the CF bonds in the fluorinated diisocyanate and hexafluoropropane dianhydride form a dense fluorinated carbon layer at high temperature, creating a double barrier to isolate oxygen and heat. Although Comparative Example 2 (FPU-2) contains 5% flame retardant monomer, the lack of dynamic sulfur bonds (-SS-) of fluorinated dihydroxy disulfide leads to the inability of internal microcracks to self-repair. During combustion, the cracks accelerate oxygen diffusion, resulting in an LOI of only 29% and dripping ignition, confirming the contribution of dynamic covalent bonds to flame retardant durability. In contrast, Comparative Example 3 (FPU-3) lacks aromatic dianhydride, and although the LOI reaches 31%, the dripping does not ignite (V-1 rating), highlighting the irreplaceable role of fluorinated dianhydride in carbon layer densification.

[0059] (4) The self-healing performance, mechanical properties and thermal properties of the foamed materials in Examples 1-5 and Comparative Examples 1-3 were tested respectively. The test methods were as follows: the scratch self-healing experiment was conducted under a scanning electron microscope. The sample surface was scratched with a blade and kept at a constant temperature of 60°C under a heating device for self-healing. The self-healing of the scratch was then observed. The mechanical properties were tested according to standard GB / T 1040-2006. The thermal properties were tested according to standard GB / T 33047.1-2016. The specific results are shown in Table 2.

[0060] Table 2 shows the self-healing performance test results of Comparative Examples 1-3 and Examples 1-5.

[0061]

[0062] Table 2 shows that FPUD-2 achieves a self-healing efficiency of 92%, primarily due to the reversible breaking / recombining ability of the -SS- bonds in the fluorinated dihydroxy disulfide. With increasing fluorinated dihydroxy disulfide content, FPUD-5 achieves a self-healing efficiency of 95%, while Comparative Example 2 (FPU-2) suffers from zero self-healing efficiency due to the absence of this component. The improved mechanical properties of the foamed material are attributed to the rigid aromatic ring structure of hexafluoropropane dianhydride and the strong electronegativity of fluorine atoms, which enhances the dipole-dipole interactions between molecular chains, resulting in a 49% increase in the tensile strength (61 MPa) of FPUD-2 compared to FPU-1 (41 MPa). The improved thermal stability (T...) of FPUD-2... d5％ The high temperature (reaching 292℃) is due to the high bond energy of the CF bond inhibiting the thermal motion of chain segments, and the presence of fluorinated dianhydrides promoting the formation of cross-linked networks. In contrast, comparative example 3 (FPU-3) exhibits loose molecular chain stacking when lacking dianhydrides. d5％The temperature dropped to 284.2℃. Notably, FPUD-3's repair efficiency (89%) and strength (59MPa) were slightly lower than FPUD-2 due to the large phosphaphenanthrene groups of the excessive DOPO derivative (8%) slightly hindering chain movement, proving that 5% is the optimal percentage of flame-retardant monomers.

[0063] (4) The yield and molecular weight of flame-retardant polyurethane in Examples 1-5 and Comparative Examples 1-3 were calculated respectively, and the specific results are shown in Table 3.

[0064] Table 3. Yield and molecular weight test results of Comparative Examples 1-3 and Examples 1-5

[0065] Sample code sample Flame retardant monomer content Yield (%) Molecular weight (Mn) Comparative Example 1 PU-1 0％ 95.9 60000 Comparative Example 2 PU-2 5％ 96.2 64000 Comparative Example 3 PU-3 5％ 95.0 63000 Example 1 PUD-1 2％ 97.3 67000 Example 2 PUD-2 5％ 99.1 69000 Example 3 PUD-3 8％ 98.7 66000 Example 4 PUD-4 5％ 97.9 65000 Example 5 PUD-5 5％ 98.6 68000

[0066] As shown in Table 3, PUD-2 has a high molecular weight of 69,000, a 15% increase compared to the basic formulation (PU-1, 60,000). This is attributed to the strong electron-withdrawing effect of fluorine atoms in the fluorinated diisocyanate, which reduces the electron cloud density of the -NCO group and enhances its reactivity with the -OH group of bio-based polyethylene glycol. The 99.1% yield is due to the high selectivity of the dibutyltin dilaurate catalyst for the -NCO / -OH reaction, and the flexible thioether bond (-S-) of the fluorinated dihydroxy disulfide can alleviate polymerization stress and inhibit side reactions. The molecular weight of FPUD-3 drops to 66,000 because the steric hindrance effect of the excess DOPO derivative hinders chain growth, confirming that the flame retardant monomer content needs to be controlled below 5% to achieve a balance between polymerization efficiency and performance.

[0067] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A bio-essential profile self-repairing flame-retardant polyurethane composite material, characterized in that, The structural formula is: wherein 2. The process for the preparation of the bio-architectured self-repairing flame- retardant polyurethane composites according to claim 1, characterized in that, It comprises the following specific steps: S1, the oil bath pot is heated, and bio-based polyethylene glycol is added into a three-necked flask, stirred, vacuumized to negative pressure after complete melting, and kept; S2, protective gas is introduced into the three-necked flask, fluorine-containing diisocyanate, aromatic ring-containing dianhydride and catalyst are added, and constant temperature reaction is carried out; S3, cooling, adding dynamic covalent bond-containing dihydric alcohol and dihydroxy flame retardant monomer, constant temperature reaction, obtaining the product; S4, the product is cooled for a certain time and then put into an oven for heating treatment, obtaining bio-based characteristic self-repairing flame-retardant polyurethane; S5, the obtained bio-based characteristic self-repairing flame-retardant polyurethane is put into a foaming kettle for foaming, obtaining bio-based characteristic self-repairing flame-retardant polyurethane foaming material.

3. The process for the preparation of a bio-essential profile self-repairing flame- retardant polyurethane composite according to claim 2, characterized in that, In the step S1, the oil bath temperature is 100-130 DEG C, the stirring speed is 200-400 r / min, the negative pressure is-0.06 to-0.1 MPa, and the negative pressure time is 50-80 min.

4. The process for the preparation of bio-essential profile self-repairing flame retardant polyurethane composites according to claim 2, characterized in that, In the step S2, the oil bath temperature is 70-100 DEG C, the constant temperature reaction temperature is 70-100 DEG C, the reaction time is 1-3 h, and the protective gas is one of nitrogen, helium, argon and neon.

5. The method for preparing the bio-based self-healing flame-retardant polyurethane composite material according to claim 2, characterized in that, In the step S2, the fluorine-containing diisocyanate is at least one of 1,2,3,5-tetrafluoro-4,6-diisocyanate benzene, 1,2,4,5-tetrafluoro-3,6-diisocyanate benzene, 2,2',3,3',5,5',6,6'-octafluoro-4,4'-diisocyanate-1,1'-diphenyl, 3-nitro-azapentane-1,5-diisocyanate and bis(1,1-dihydroperfluorodiisocyanate propyl ether); the aromatic ring-containing dianhydride is 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride and 1,4,5,8-naphthalene tetracarboxylic dianhydride; and the catalyst is at least one of dibutyl tin dilaurate, bis(dodecylthio) dioctyl tin, stannous octoate, dibutyl tin oxide and dichlorodibutyl tin.

6. The process for the preparation of biopattern self-repairing flame retardant polyurethane composites according to claim 2, characterized in that, In the step S3, the oil bath temperature is 50-90 DEG C, and the reaction time is 1-3 h.

7. The process for the preparation of biobased self-repairing flame retardant polyurethane composites according to claim 2, characterized in that, In the step S3, the dynamic covalent bond-containing dihydric alcohol is a mixture of fluorine-containing dihydroxy disulfide and 1,3-bis-hydroxymethyl urea, and the dihydroxy flame retardant monomer is a diphenol derivative of DOPO.

8. The process for the preparation of biopattern self-repairing flame retardant polyurethane composites according to claim 2, characterized in that, In the step S4, the cooling temperature is room temperature, the cooling time is 6-10 h, the oven temperature is 100-120 DEG C, and the oven treatment time is 5-7 h.

9. The process for the preparation of biopattern self-repairing flame retardant polyurethane composites according to claim 2, characterized in that, In the step S5, the foaming temperature is 80-120 DEG C, the foaming pressure is 10-16 MPa, and the swelling time is 50-100 min.

10. The method for preparing the bio-based self-healing flame-retardant polyurethane composite material according to claim 7, characterized in that, The molar ratio of the bio-based polyethylene glycol, fluorine-containing diisocyanate, catalyst, aromatic ring-containing dianhydride, fluorine-containing dihydroxy disulfide, 1,3-bis-hydroxymethyl urea and diphenol derivative of DOPO is 2-5:10-15:0.01-0.04:3-6:1-3:2-4:3-6.

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