Flame-retardant cross-linked aromatic polyamide, reinforced composite material of flame-retardant cross-linked aromatic polyamide, and preparation method and application of reinforced composite material
Through the water-catalyzed imine bond exchange technology of phosphorus-containing amino-terminated aromatic polyamide and hexavanillin-terminated cyclotriphosphazene, the flame retardancy and recyclability problems of high-performance fiber-reinforced composites were solved, and efficient flame retardancy and closed-loop recycling were achieved.
Patent Information
- Application Number
- CN202510866710.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-26
- Publication Date
- 2025-10-03
AI Technical Summary
Existing high-performance fiber-reinforced composite materials have low flame retardancy and are difficult to recycle in a closed-loop, resulting in waste of resources and safety hazards.
Phosphorus-containing amino-terminated aromatic polyamide and hexavanillin-terminated cyclotriphosphazene were used as the main raw materials. The degradation and recovery of the cross-linked materials were achieved through water-catalyzed imine bond exchange to prepare flame-retardant cross-linked aromatic polyamide.
The prepared flame-retardant cross-linked aromatic polyamide has excellent flame retardant properties and recyclability, with a limiting oxygen index of 39.8%, a tensile strength of 380.6 MPa, and a modulus of 3.5 GPa, realizing efficient closed-loop recycling of composite materials.
Smart Images
Figure CN120737331A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of polymer materials, and in particular relates to a flame-retardant cross-linked aromatic polyamide, a reinforced composite material thereof, and a preparation method and application thereof. Background Art
[0002] Fiber-reinforced composites (FRPs) typically use high-performance fibers (glass, carbon, and aramid fibers) as reinforcements and epoxy resins, rubber, and inorganic materials as matrices. They offer advantages such as high strength, high modulus, corrosion resistance, and dimensional stability, and are widely used in military, aerospace, vehicle and shipbuilding, sports, and construction applications. However, traditional epoxy resin-based composites are difficult to degrade after curing, preventing the expensive fibers from being recycled. Furthermore, epoxy resins are flammable, creating numerous economic, resource, environmental, and safety challenges.
[0003] CN116023761A discloses a recyclable flame-retardant carbon fiber / epoxy resin composite material and its preparation method. The composite material uses an aldehyde-containing epoxy compound and an amino-containing cyclotriphosphazene compound as curing agents. The two are combined to form an epoxy resin containing a Schiff base structure, achieving both flame retardant and biodegradable properties. However, after acid degradation of the matrix, only the fiber can be recovered, thus failing to achieve closed-loop recycling of the composite material. In addition, although para-aramid is a flame-retardant fiber with a limiting oxygen index of approximately 30%, para-aramid composite materials typically use traditional epoxy resin as a matrix, and epoxy resin is generally flammable, so the flame retardancy of the composite material will be significantly reduced. However, there are currently no reports on improving the flame retardancy of high-strength aramid fiber-reinforced composite materials or on closed-loop recycling of the fiber and matrix. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a flame-retardant cross-linked aromatic polyamide, its reinforced composite material, and its preparation method and application, so as to overcome the defects of high-performance fiber-reinforced composite materials in the prior art, such as low flame retardancy and difficulty in closed-loop recycling.
[0005] The present invention provides a cross-linked aromatic polyamide, the structural formula of the polyamide is
[0006]
[0007] Where R is Wherein m=20-100; n=2-20;
[0008] Wherein Ar1 and Ar2 are aromatic groups.
[0009] Furthermore, Ar1 and Ar2 are both selected from
[0010] One or more of the .
[0011] The present invention provides a method for preparing a cross-linked aromatic polyamide, comprising:
[0012] Phosphorus-containing amino-terminated aromatic polyamide, hexavanillin-terminated cyclotriphosphazene and a solvent are mixed and reacted to obtain a cross-linked aromatic polyamide.
[0013] Preferably, the phosphorus-containing amino-terminated aromatic polyamide has the structural formula
[0014]
[0015] Wherein Ar1 and Ar2 are aromatic groups; wherein m=20-100; and n=2-20.
[0016] Preferably, the structural formula of the hexavanillin-terminated cyclotriphosphazene is:
[0017]
[0018] Preferably, the molar ratio of the phosphorus-containing amino-terminated aromatic polyamide to the hexavanillin-terminated cyclotriphosphazene is 3:1 to 3, more preferably 3:2.
[0019] The solvent includes one or more of dimethylacetamide DMAC, N-methylpyrrolidone NMP, and N,N-dimethylformamide DMF; preferably DMAC.
[0020] Preferably, the reaction is carried out at 20-30° C. for 18-24 hours.
[0021] The preparation of the phosphorus-containing amino-terminated aromatic polyamide comprises: mixing a phosphorus-containing diamine monomer, a diamine monomer and a solvent, adding a diacyl chloride monomer for reaction, stirring for reaction, and neutralizing to obtain the phosphorus-containing amino-terminated aromatic polyamide.
[0022] Furthermore, the molar ratio of the phosphorus-containing diamine monomer, the diamine monomer and the diacyl chloride monomer is 5:110:100.
[0023] Furthermore, the structural formula of the phosphorus-containing diamine monomer is
[0024] Wherein Ar1 is an aromatic group;
[0025] The diamine monomer includes one or more of 1,3-phenylenediamine, 1,4-phenylenediamine, 3,3'-diaminobiphenyl, 4,4'-diaminobiphenyl, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl sulfone.
[0026] The diacyl chloride monomer includes one or more of 1,4-phthaloyl chloride, 1,3-phthaloyl chloride, 4,4'-biphenyl diacetyl chloride, and 4,4'-diphenyl ether diacetyl chloride.
[0027] The solvent includes one or more of DMAC, NMP, and DMF, preferably DMAC.
[0028] The reaction in the preparation of the phosphorus-containing amino-terminated aromatic polyamide includes three stages. In the first stage, the starting temperature is -15 to -10°C, and the diacyl chloride monomer is added dropwise, and the temperature is controlled at 10 to 20°C, and the reaction is carried out for 0.5 to 1 hour. In the second stage, stirring is performed at room temperature, the reaction temperature is 20 to 30°C, and the reaction time is 1 to 2 hours. The third stage is a calcium hydroxide neutralization reaction, the reaction temperature is 60 to 80°C, and the reaction time is 1 to 2 hours.
[0029] The preparation of the phosphorus-containing amino-terminated aromatic polyamide comprises: mixing vanillin, potassium carbonate and a solvent, adding hexachlorocyclotriphosphazene for reaction, and continuing the reaction to obtain hexachlorovanillin-terminated cyclotriphosphazene.
[0030] The molar ratio of vanillin to hexachlorocyclotriphosphazene is 6:1 to 12:1
[0031] In the preparation of phosphorus-containing amino-terminated aromatic polyamide, the solvent includes one or more of acetonitrile and tetrahydrofuran, preferably tetrahydrofuran.
[0032] In the preparation of the phosphorus-containing amino-terminated aromatic polyamide, the reaction includes two stages. The first stage is the dropwise addition of hexachlorocyclotriphosphazene, the reaction temperature is 20-30°C, and the reaction time is 2-3 hours. The second stage is the synthesis of hexavanillin-terminated cyclotriphosphazene, and the reaction temperature is continued at 60-80°C and the reaction time is 24-48 hours.
[0033] The preparation of the phosphorus-containing diamine monomer comprises: dissolving the diamine monomer in a solvent, adding an organic base, adding a phenylphosphonyl dichloride solution for reaction, heating and continuing the reaction, purifying after the reaction is completed, and drying to obtain the phosphorus-containing diamine monomer.
[0034] The molar ratio of phenylphosphonic dichloride to diamine monomer is 1:2 to 4, for example 1:2, 1:3 or 1:4, preferably 1:3.
[0035] The molar ratio of phenylphosphonyl dichloride to the organic base is 1:2 to 4, for example 1:2, 1:3 or 1:4, preferably 1:3.
[0036] The diamine monomer includes one or more of 1,3-phenylenediamine, 1,4-phenylenediamine, 3,3'-diaminobiphenyl, 4,4'-diaminobiphenyl, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl sulfone.
[0037] The solvent and the solvent of the phenylphosphonic dichloride solution both include one or more of acetonitrile and tetrahydrofuran, preferably acetonitrile.
[0038] The organic base includes one or more of triethylamine, tripropylamine and tributylamine, preferably triethylamine.
[0039] The reaction in the preparation of the phosphorus-containing diamine monomer includes two stages. The first stage is the dropwise addition of phenylphosphonic dichloride, the reaction temperature is -10 to 0°C, and the reaction time is 2 to 3 hours. The second stage is the synthesis of the phosphorus-containing diamine monomer, and the reaction temperature is continued at 25 to 40°C and the reaction time is 12 to 24 hours.
[0040] The purification includes filtering out by-product salt after the reaction is completed, pouring the filtrate into ice water for precipitation, and repeatedly washing with deionized water for multiple times.
[0041] The present invention provides a composite material, which comprises the cross-linked aromatic polyamide, fiber or fabric.
[0042] The present invention provides a method for preparing a composite material, comprising: impregnating fibers or fabrics with the cross-linked aromatic polyamide solution, and drying (ie, drying the solvent) to obtain the composite material.
[0043] The fibers include one or more of aramid, carbon fiber, and glass fiber; and the fabric includes a fabric obtained from one or more of aramid, carbon fiber, and glass fiber.
[0044] The drying procedures include: drying at 80°C for 0.5 to 2 hours, drying at 100°C for 0.5 to 2 hours, drying at 120°C for 0.5 to 2 hours, drying at 140°C for 0.5 to 2 hours, drying at 160°C for 0.5 to 2 hours, and drying at 180°C for 0.5 to 2 hours.
[0045] The present invention provides a recycling method, comprising: soaking the composite material in a solvent, performing degradation treatment, and separating to obtain a solution portion and a solid portion;
[0046] The solution portion is filtered and then dried to obtain a cross-linked aromatic polyamide film;
[0047] The solid part is washed and dried to obtain recycled fibers or fabrics.
[0048] The recycled fibers or fabrics can be used to prepare composite materials.
[0049] In the recovery method, the solvent is a DMAC / H2O mixed solution, wherein the volume ratio of DMAC to H2O is 95:5.
[0050] The degradation treatment temperature is 60-100° C. and the time is 1-30 minutes.
[0051] The drying procedure is as follows: drying at 80° C. for 0.5 to 2 h, drying at 100° C. for 0.5 to 2 h, drying at 120° C. for 0.5 to 2 h, drying at 140° C. for 0.5 to 2 h, drying at 160° C. for 0.5 to 2 h, and drying at 180° C. for 0.5 to 2 h.
[0052] The washing is performed by washing with DMAC and ethanol.
[0053] The present invention provides an application of the cross-linked aromatic polyamide or the composite material in the fields of aerospace, military protection, automobile manufacturing, building materials, etc.
[0054] The flame-retardant cross-linked aromatic polyamide of the present invention can be used as a membrane material or a composite material matrix, and the degradation and recycling of the cross-linked material can be achieved through water-catalyzed imine bond exchange.
[0055] The phosphorus-containing diamine monomer in the present invention contains high-valent phosphorus elements, and the hexavanillin-terminated cyclotriphosphazene has abundant PN bonds, which has a PN synergistic flame retardant effect. Therefore, the prepared flame-retardant cross-linked aromatic polyamide has high flame retardant properties.
[0056] In the present invention, water and temperature have a promoting effect on imine bond exchange, so under the condition of sufficient swelling, the imine bond-containing material can be rapidly degraded, thereby realizing the recovery of the cross-linked material.
[0057] Beneficial effects
[0058] The flame-retardant cross-linked aromatic polyamide prepared by the present invention has excellent mechanical properties, flame retardant properties and recyclability. It can be efficiently degraded through water-catalyzed imine bond exchange. This process is short in time, low in energy consumption, and can be recycled in a closed loop. After being compounded with high-performance fibers or their fabrics, the flame retardant properties of the composite material can be improved, and the fibers and matrix materials can be efficiently recycled.
[0059] The flame-retardant cross-linked aromatic polyamide-based composite material obtained by the present invention has excellent flame retardant properties, a limiting oxygen index of 39.8%, a flame retardant grade of UL-94V0, a tensile strength of 380.6MPa, and a modulus of 3.5GPa. The composite material can be degraded and recycled through water-catalyzed imine bond exchange and imine bond metathesis. The recycling process is characterized by short time consumption, low energy consumption, non-destructive fiber recovery, and closed-loop recycling. BRIEF DESCRIPTION OF THE DRAWINGS
[0060] Figure 1 Schematic diagram of closed-loop recycling of flame-retardant cross-linked aromatic polyamide-based composite materials;
[0061] Figure 2 This is the H NMR spectrum of the phosphorus-containing diamine monomer;
[0062] Figure 3 This is the H NMR spectrum of hexavanillin-terminated cyclotriphosphazene;
[0063] Figure 4 This is the H-NMR spectrum of phosphorus-containing amino-terminated aromatic polyamide;
[0064] Figure 5 Photos of hexavanillin-terminated cyclotriphosphazene and phosphorus-containing amino-terminated aromatic polyamide before and after cross-linking reaction, as well as photos of the cross-linked film;
[0065] Figure 6 This is a photo of the vertical combustion test of the fiber-reinforced composite material in Example 5;
[0066] Figure 7 Scanning electron micrographs of the surface of flame-retardant cross-linked aromatic polyamide-based para-aramid composite materials before and after fiber recycling;
[0067] Figure 8 This is a photo of the vertical combustion test of the fiber-reinforced composite material in Comparative Example 1. DETAILED DESCRIPTION
[0068] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.
[0069] Related tests:
[0070] UL-94 vertical burning rating test standard: GB / T2408-2008;
[0071] Limiting oxygen index test standard: GBT 2406.2-2009;
[0072] Tensile properties test standard: ASTM D3039 / D3039M-17.
[0073] Example 1
[0074] 150 mmol (16.221 g) of m-phenylenediamine and 150 mmol (15.179 g) of triethylamine were dissolved in 100 mL of acetonitrile, and the temperature of the reaction system was lowered to 0°C. 50 mmol (9.749 g) of phenylphosphonic dichloride was dissolved in 40 mL of acetonitrile and slowly added dropwise to the reaction system. The reaction was carried out at this temperature for 2 h. The temperature was raised to 25°C and the reaction was continued for 12 h. After the reaction was completed, the by-product salt was filtered out, the filtrate was precipitated in ice water and washed three times with deionized water, and dried at 80°C for 12 h to obtain a light yellow solid product with a yield of 67.9%. The product H NMR spectrum was as follows: Figure 2 As shown, the structure was consistent with the theory after analysis, and the phosphorus-containing diamine monomer was successfully synthesized.
[0075] Example 2
[0076] 430 mmol (65.425 g) of vanillin and 430 mmol (59.429 g) of potassium carbonate were dissolved and mixed in 1 L of tetrahydrofuran, and 48 mmol (16.688 g) of hexachlorocyclotriphosphazene was dissolved in 50 mL of tetrahydrofuran. The mixture was slowly added dropwise to the vanillin solution at a temperature of 20-30°C. The reaction time was 2 h, the temperature was raised to 60°C, and the reaction was continued for 48 h. After the reaction was completed, the precipitate was filtered and washed repeatedly with ethanol and deionized water for 3 times, and dried at 80°C for 12 h to obtain a white powder product with a yield of 79.8%. The product had a hydrogen nuclear magnetic spectrum as shown in FIG. Figure 3 As shown, the structure analysis was consistent with the theory, and hexavanillin-terminated cyclotriphosphazene was successfully synthesized.
[0077] Example 3
[0078] 2.5mmol (0.846g) of phosphorus-containing diamine monomer and 55mmol (5.948g) of m-phenylenediamine were dissolved in 50mL DMAC, the reaction temperature was lowered to -10°C, 50mmol (10.151g) of isophthaloyl chloride was slowly added, the temperature was controlled at 10-20°C, the reaction was carried out for 0.5h, and then stirred at room temperature, the reaction temperature was 20-30°C, the reaction time was 1h, 50mmol (3.705g) of calcium hydroxide was added and stirred thoroughly, the reaction temperature was 60°C, the reaction time was 1h, and after the reaction was completed, the polymer solution was poured into deionized water for precipitation and washed with water several times, and a white powdery resin was obtained after drying. The product nuclear magnetic hydrogen spectrum is as follows Figure 4 As shown, the structure analysis was consistent with the theory, and phosphorus-containing amino-terminated aromatic polyamide was successfully synthesized.
[0079] The molecular weight was calculated to be 2.0 kDa by the H-NMR spectrum integral ratio.
[0080] Example 4
[0081] 1.5 mmol (2.931 g) of 2.0 kDa phosphorus-containing amino-terminated aromatic polyamide and 1 mmol (1.041 g) of hexavanillin-terminated cyclotriphosphazene were dissolved in 30 mL of DMAC and reacted at 20-30 °C for 24 h to obtain a flame-retardant cross-linked aromatic polyamide. After evaporation of the solvent and high-temperature curing, a cross-linked film (such as Figure 5 As shown), the tensile strength of the composite material was 129.5 MPa when tested by a universal tensile machine (25°C, 65% humidity), and the limiting oxygen index reached 38.4%.
[0082] Example 5
[0083] A 100 mm × 100 mm para-aramid fabric was laid flat in a glass mold, and 13 mL of a flame-retardant cross-linked aromatic polyamide (Example 4) with a concentration of 0.1324 g / mL was poured into it. After vacuum degassing and sufficient infiltration, the fabric was dried at 80° C. for 2 h, 100° C. for 2 h, 120° C. for 2 h, 140° C. for 2 h, 160° C. for 2 h, and 180° C. for 2 h. A fully cured flame-retardant cross-linked aromatic polyamide-based para-aramid composite material with a glue content of 50.6% was obtained. After testing, the flame-retardant cross-linked aromatic polyamide-based para-aramid composite material had a tensile strength of 380.6 MPa, a modulus of 3.5 GPa, a limiting oxygen index of 39.8%, and a vertical combustion flame retardancy rating of V0, which could not be ignited ( Figure 6 ).
[0084] The flame-retardant cross-linked aromatic polyamide-based para-aramid composite material in Example 5 was immersed in a mixed solution of DMAC:H2O=95:5 (volume ratio), heated to 80°C, and slowly stirred for 20 minutes to completely degrade the matrix. The fabric was taken out and washed with DMAC and ethanol and dried. Figure 7 The surface scanning electron microscope images of the fibers before and after recycling show that water-catalyzed degradation recycling has no effect on the fibers.
[0085] The matrix solution after degradation in Example 5 was filtered, as shown in FIG. Figure 1 As shown, not only can the film be recombined with the fabric by evaporating the solvent, but the film can also be directly evaporated and cured at high temperature to obtain a high-strength flame-retardant cross-linked aromatic polyamide film.
[0086] Comparative Example 1
[0087] Bisphenol A epoxy resin E51 and polyetheramine D230 purchased from the market were uniformly mixed in a weight ratio of 100:30. A 100mm×100mm para-aramid fabric was flattened in a silicone mold, and the calculated amount of E51 / D230 curing system was poured into it. After vacuum degassing and sufficient infiltration, the mixture was cured at 80℃ for 2h, 120℃ for 2h, and 150℃ for 2h to obtain a fully cured epoxy resin-based para-aramid composite material with a glue content of 51.8%. After testing, the epoxy resin-based para-aramid composite material had a tensile strength of 351.2MPa, a modulus of 4.2GPa, a limiting oxygen index of 20.2%, and no flame retardant grade in vertical combustion, and was completely burned ( Figure 8 ), and cannot be degraded and recycled.
Claims
1. A cross-linked aromatic polyamide, characterized in that: The structural formula of the polyamide Where R is Wherein m=20-100; n=2-20; Wherein Ar1 and Ar2 are aromatic groups.
2. The cross-linked aromatic polyamide according to claim 1, characterized in that: Said Ar1 and Ar2 are selected from One or more of the .
3. A method for preparing a cross-linked aromatic polyamide, comprising: Phosphorus-containing amino-terminated aromatic polyamide, hexavanillin-terminated cyclotriphosphazene and a solvent are mixed and reacted to obtain a cross-linked aromatic polyamide.
4. The preparation method according to claim 3, characterized in that The phosphorus-containing amino-terminated aromatic polyamide structural formula is wherein Ar1 and Ar2 are aromatic groups; wherein m=20 to 100; n=2 to 20; The structural formula of the hexavanillin-terminated cyclotriphosphazene is: The molar ratio of the phosphorus-containing amino-terminated aromatic polyamide and the hexavanillin-terminated cyclotriphosphazene is 3:1-3; The solvent includes one or more of dimethylacetamide DMAC, NMP, and DMF; The reaction is carried out at 20-30° C. for 18-24 hours.
5. The preparation method according to claim 3, characterized in that: The preparation of the phosphorus-containing amino-terminated aromatic polyamide comprises: mixing a phosphorus-containing diamine monomer, a diamine monomer and a solvent, adding a diacyl chloride monomer to react, stirring the reaction, and neutralizing the reaction to obtain the phosphorus-containing amino-terminated aromatic polyamide; The preparation of the phosphorus-containing amino-terminated aromatic polyamide comprises: mixing vanillin, potassium carbonate and a solvent, adding hexachlorocyclotriphosphazene for reaction, and continuing the reaction to obtain hexachlorovanillin-terminated cyclotriphosphazene.
6. A composite material, characterized in that The composite material comprises the cross-linked aromatic polyamide, fiber or fabric according to claim 1.
7. A method for preparing a composite material, comprising: The fiber or fabric is impregnated with the cross-linked aromatic polyamide solution according to claim 1 and dried to obtain a composite material.
8. The preparation method according to claim 7, characterized in that: The fibers include one or more of aramid, carbon fiber, and glass fiber; the fabric includes a fabric obtained from one or more of aramid, carbon fiber, and glass fiber; The drying procedures include: drying at 80°C for 0.5 to 2 hours, drying at 100°C for 0.5 to 2 hours, drying at 120°C for 0.5 to 2 hours, drying at 140°C for 0.5 to 2 hours, drying at 160°C for 0.5 to 2 hours, and drying at 180°C for 0.5 to 2 hours.
9. A recycling method comprising: soaking the composite material according to claim 6 in a solvent, subjecting it to degradation treatment, and separating it to obtain a solution portion and a solid portion; The solution portion is filtered and then dried to obtain a cross-linked aromatic polyamide film; The solid part is washed and dried to obtain recycled fibers or fabrics.
10. Use of the cross-linked aromatic polyamide according to claim 1 or the composite material according to claim 6 in the fields of aerospace, military protection, automobile manufacturing, and building materials.