Preparation method for basalt fiber-reinforced fireproof and flame-retardant polymer-based composite material

Abstract

Disclosed in the present invention are a preparation method for a basalt fiber-reinforced fireproof and flame-retardant polymer-based composite material. The preparation method comprises: firstly, mixing a resin prepolymer with a flame retardant modifier and an accelerator to obtain a copolymerized resin prepolymer; dissolving the copolymerized resin prepolymer in the mixed solvent of butanone and N,N-dimethylformamide to obtain a resin glue solution; then, impregnating the resin glue solution on the surface of a basalt fiber, airing same for 2 h and drying same to obtain a basalt fiber prepreg; and finally, the basalt fiber prepreg is placed in a flat mould, and hot-pressed to obtain the basalt fiber-reinforced fireproof and flame-retardant polymer-based composite material. The process method provided by the present invention is simple, and high in terms of efficiency, and the composite material has outstanding flame retardancy and structural performance, and is suitable for the fields of lightweight and high-strength composite materials with fireproof and flame-retardant requirements such as aerospace, mechanical ships, etc.

Description

Preparation method of basalt fiber reinforced fire-retardant polymer-based composite material Technical Field

[0001] The present invention relates to the technical field of polymer-based composite material preparation, and more particularly to a method for preparing a basalt fiber-reinforced fire-retardant polymer-based material. Background Art

[0002] With the continuous development of modern society, polymer materials have been widely used in various fields. However, due to their inherent structural characteristics, polymer materials are highly flammable, posing a significant safety hazard in production. Therefore, improving the fire retardancy of polymer materials is extremely important. Currently, the best option for improving the flame retardancy of polymers is to add flame retardants to the matrix. However, with the development of flame retardant technology, people have put forward higher requirements for flame-retardant polymer composites. In addition to meeting the flame retardant performance requirements, it is also necessary to avoid significant damage to the mechanical properties of the substrate caused by the addition of flame retardants.

[0003] Currently, the primary method for flame-retardant modification of polymers is to add flame retardants. Traditional flame retardants are primarily halogenated, offering excellent flame retardancy and low cost. However, due to their poor thermal stability, they are only suitable for processing products below 200°C. Furthermore, numerous studies have shown that flame-retardant polymers containing halogenated flame retardants produce large amounts of smoke and toxic substances when exposed to fire, leading to suffocation and secondary injuries. Furthermore, waste from these materials can easily generate carcinogens such as dioxins during high-temperature recycling, causing environmental pollution. While phosphorus-based and organic-inorganic hybrid flame retardants can reduce harm to the human body and the environment during thermal decomposition, they require high dosages to achieve flame retardancy, increasing material costs. Furthermore, phosphorus-based and organic-inorganic hybrid flame retardants often suffer from high melting temperatures and difficulty in uniformly dispersing during polymer molding. This creates significant conflicts with the melt molding process of the polymer matrix and the mechanical properties of polymer-based composites.

[0004] The existing flame-retardant polymer composite materials are mainly prepared by adding flame retardants. After the polymer matrix is ​​formed and polymerized, the flame retardant mechanism such as solid-phase flame retardancy / gas-phase flame retardancy of the flame retardant is used to inhibit the combustion and degradation of the matrix polymer, thereby achieving the purpose of fire prevention and flame retardancy. However, the following problems still exist: 1) The halogen-free flame retardants currently used include phosphorus-containing, nitrogen-containing, silicon-containing, and metal-containing flame retardants. Such flame retardants have the disadvantages of high water absorption, poor flame retardant effect when used alone, and large usage. The high water absorption will make polymer composites unable to be used in the field of fine electronic materials. The poor flame retardant effect when used alone requires compounding and regulation, which will make the processing of polymer composites cumbersome. The use of a large amount of flame retardants will lead to the deterioration of the structural strength of the composites, thereby limiting their application in the field of structural materials; 2) When flame retardant polymers are prepared in the form of added flame retardants, melt blending or solution blending is usually adopted. The preparation process has problems such as high energy consumption, high risk, and easy environmental pollution; 3) The low decomposition temperature of existing flame retardants results in low processing and use temperatures, resulting in current research on the modification of flame retardant polymers mainly focusing on the fields of modified epoxy resins, modified polypropylene, modified polyethylene and other composite materials with low temperature resistance, which seriously limits the development and application of fire retardant properties of high-performance polymer-based composites. In summary, the existing flame retardants and flame retardant polymers have problems such as complicated synthesis process, high pollution, and the need to improve polymer performance. They cannot meet the demand for high-performance fire-retardant materials in aerospace, machinery and shipbuilding fields.

[0005] In recent years, the research focus of scholars has been to improve the structural characteristics of flame retardants to make them compatible with polymer matrices or to improve the dispersion of inorganic flame retardants in polymer matrices to achieve flame retardant effects.

[0006] A Chinese invention patent (CN113248634B) discloses a Chitosan-Schiff / DOPO flame retardant and its preparation method, as well as research on flame-retardant modification of epoxy resin. Chitosan is first used as the main raw material to prepare Chitosan-Schiff and Chitosan-Schiff / DOPO flame retardants, respectively. The flame retardant and curing agent are then used to synergistically modify the epoxy resin, and the flame-retardant polymer is obtained by room temperature curing and step-by-step temperature curing. The flame-retardant polymer has a long curing time during the preparation process, resulting in low production efficiency and increased production costs. Furthermore, phosphorus-based flame retardants generally have a high water absorption rate, which severely limits the application of modified epoxy resin polymers in the field of electronic materials.

[0007] A Chinese invention patent (CN116200018A) discloses a method for preparing a hyperbranched triazine macromolecular modified bentonite and its use as an inorganic flame retardant in modified polymers. Triazine compounds and chlorinated phosphorus compounds undergo a polymerization reaction between bentonite layers to produce a hyperbranched macromolecular flame retardant, which is then exfoliated from the modified bentonite. This achieves high flame retardancy while also improving the dispersibility of the inorganic filler bentonite in the polymer. The resulting flame-retardant polymer exhibits excellent flame retardancy and mechanical properties. However, the preparation of the modified bentonite involves multiple chemical synthesis and purification steps, which can cause environmental pollution and significantly increase production costs.

[0008] Therefore, providing a simple and efficient method for preparing a fire-retardant polymer-based composite material is an urgent problem to be solved by those skilled in the art.

[0009] Summary of the Invention

[0010] In view of this, the present invention provides a method for preparing a basalt fiber-reinforced fire-retardant polymer-based composite material, which can solve the problems of complicated steps, high pollution and high cost in the synthesis process of existing external flame retardants, simplify the molding process of polymer-based composite materials, improve production efficiency, and at the same time provide a new type of high-performance composite material for the field of high-performance fiber-reinforced polymer-based composite materials.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] A resin prepolymer with the structural formula:

[0013] Preferably, the preparation method of the resin prepolymer is: phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde are added to a mixed solvent of xylene and anhydrous ethanol in a molar ratio of 1: (2 to 2.05): (3.9 to 4.05), the mass ratio of xylene to anhydrous ethanol is 1: (1.4 to 1.6), and the mass ratio of the three solid raw materials of phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde to the mixed solvent is 1: (0.85 to 1.15). After the addition is completed, a dark brown mixed solution is obtained, which is further heated to 70 to 85°C, reacted for 3 to 6 hours, and then heated to 90 to 110°C to remove the solvent to obtain the above-mentioned resin prepolymer.

[0014] The synthetic route is:

[0015] Preferably, the resin prepolymer contains a phenolphthalein group, a benzoxazine ring and a nitrile group.

[0016] The beneficial effects of the above technical solution are: by introducing phenolphthalein and benzoxazine rings, at least the following effects can be achieved: 1) the cyclization polymerization of nitrile groups is efficiently promoted, thereby obtaining a highly heat-resistant polymer material; 2) the presence of phenolphthalein groups and benzoxazine rings can improve the flexibility of the resin molecule main chain, ensuring that the polymer material exhibits strong and tough structural properties; 3) the presence of active functional groups can provide more reaction sites for the subsequent copolymerization reaction between the prepolymer and the flame retardant modifier and accelerator, ensuring the effective conduct of the copolymerization reaction.

[0017] A method for preparing a basalt fiber-reinforced fire-retardant polymer-based composite material containing the resin prepolymer comprises the following steps:

[0018] (1) mixing the resin prepolymer with a flame retardant modifier and an accelerator in a mass ratio of 1: (0.05-0.15): (0.1-0.25) and then melt-prepolymerizing to obtain a copolymerized resin prepolymer;

[0019] (2) dissolving the copolymerized resin prepolymer in a mixed solvent of butanone and N,N-dimethylformamide to prepare a resin glue solution;

[0020] (3) impregnating the resin glue on the surface of the basalt fiber cloth, and after the fiber cloth is evenly impregnated, leaving it at room temperature for 2 hours and then transferring it to a high-temperature drying oven for drying to obtain a basalt fiber prepreg;

[0021] (4) After the basalt fiber prepregs are stacked, they are placed in a flat mold and pressed into a laminated plate by a hot pressing process to obtain a basalt fiber reinforced fire-retardant polymer-based composite material.

[0022] The beneficial effect of the above technical solution is that: the present invention improves the compatibility of the components of the system by optimizing resin prepolymers and flame retardant modifiers with specific structures through copolymerization reactions between active functional groups, thereby overcoming the problems of uneven mixing and phase separation in the polymer system caused by the addition of flame retardants.

[0023] Preferably, the flame retardant modifier in step (1) contains a nitrile group and has the structural formula:

[0024] Preferably, the preparation method of the flame retardant modifier is as follows: 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO are dissolved in a tetrahydrofuran solvent in a molar ratio of 1:(2-2.06):(2-2.1), wherein the mass ratio of the solid raw materials of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO to tetrahydrofuran is 1:(0.6-0.8); an acid binder ethylenediamine is added, and the amount of the acid binder is 0.5% to 1% of the mass of 2,6-(p-aminophenoxy)benzonitrile. The solution system temperature is maintained at 60-75°C, and the reaction is continued for 3-5 hours to obtain a brown-yellow turbid mixed solution. After separation and washing, the mixed solution is dried in a vacuum drying oven at 80°C for 8-12 hours to obtain the flame retardant modifier.

[0025] The synthetic route is:

[0026] Preferably, the accelerator in step (1) is a tetraglycidylamine type epoxy resin; the melt prepolymerization temperature is 80-120° C., and the prepolymerization time is 30-60 min.

[0027] The beneficial effects of the above technical solution are: selecting a tetraglycidylamine type epoxy resin, because the epoxy resin has high reactivity and a high epoxy value, and can provide abundant active hydroxyl groups due to the opening of the epoxy ring during the thermal polymerization process, and the active hydroxyl groups are the key catalysts for the cross-linking polymerization reaction of the resin prepolymer and the flame retardant modifier in the present invention; at the same time, the epoxy resin has a low melting point and strong adhesion, and can produce a strong bonding effect with the fibers during the preparation of the composite material, thereby improving the structural strength of the composite material.

[0028] The melt prepolymerization temperature is selected. When it is higher than this temperature, it is easy to trigger a rapid reaction of the resin system, which is not conducive to the slow and uniform growth of the molecular weight of the resin prepolymer, and it is difficult to control the degree of prepolymerization. At the same time, the energy consumption is high. When it is lower than this temperature, the melt viscosity of the resin prepolymer is too high, and it is difficult to achieve uniform mixing between the components. At the same time, the reaction rate of the system is slow, which reduces the processing efficiency of the resin.

[0029] Preferably, in step (2), the mass ratio of butanone to N,N-dimethylformamide solvent is 1:(0.3-0.7), and the mass ratio of copolymerized resin prepolymer to mixed solvent is 1:(0.5-0.9).

[0030] The beneficial effects of the above technical solution are as follows: When the ratio of the co-solvent is selected, if it is higher than this, the highly polar resin prepolymer and flame retardant modifier are difficult to fully dissolve, resulting in inadequate subsequent impregnation of the fiber cloth; if it is lower than this, the amount of high-boiling-point solvent used is too high, resulting in high energy consumption and pollution during the subsequent drying and solvent removal. When the ratio of the resin prepolymer to the mixed solvent is selected, if it is higher than this, the concentration of the resin glue is high, resulting in insufficient impregnation of the fiber cloth and affecting the mechanical properties of the composite material; if it is lower than this, the amount of solvent used is high, resulting in high energy consumption and severe environmental pollution during the subsequent drying process.

[0031] Preferably, the mass ratio of the resin glue to the basalt fiber in step (3) is (0.35-0.92):1, the drying oven temperature is set to 150-160° C., and the drying time is 5-15 minutes.

[0032] The beneficial effects of the above technical solution are as follows: The mass ratio of resin glue to basalt fiber is selected. Since resin acts as an adhesive in composite materials and is more expensive than fiber, if the ratio is higher than this, the resin content in the composite material is too high, the strengthening and toughening effect of the fiber material is not obvious, and the cost is high. If the ratio is lower than this, the resin content is too low to fully impregnate the fiber cloth, and sufficient adhesion between the fiber cloth layers cannot be guaranteed. The drying oven temperature and drying time are selected. If the temperature is higher than this and the drying time is longer than this, the resin system solidifies on the surface of the fiber cloth, loses its adhesiveness, and subsequent lamination procedures cannot be carried out. If the temperature is lower than this and the drying time is shorter than this, the solvent in the prepreg cannot be fully removed. During the subsequent lamination process to prepare the laminate, micro-defects will appear within the composite material due to solvent leakage, which will damage the structural strength of the system.

[0033] Preferably, the number of basalt fiber prepreg layers in step (4) is 6 to 10, and the hot pressing process is: the pressure is maintained at 15-20 MPa, the program temperature is 200°C for 2 to 4 hours, 220 to 240°C for 2 to 4 hours, and 260 to 280°C for 2 to 4 hours.

[0034] The beneficial effects of the above technical solution are as follows: The selection of a hot pressing pressure above this pressure can easily lead to a large loss of resin glue, resulting in insufficient bonding of the composite material; below this pressure, insufficient contact between the prepreg layers and incomplete gas discharge can easily lead to numerous defects within the composite material, affecting the composite material's structural performance. The selection of a hot pressing temperature program and time above this temperature or for a time longer than this temperature imposes stringent requirements on the equipment, increases energy consumption, and reduces production efficiency; below this temperature or for a time shorter than this temperature, the polymer cross-linking reaction is incomplete, affecting the flame retardancy and structural strength of the composite material, and failing to obtain a high-performance composite material.

[0035] It can be seen from the above technical solution that, compared with the prior art, the present invention discloses a method for preparing a basalt fiber reinforced fire-retardant polymer-based composite material, which has the following beneficial effects:

[0036] (1) By optimizing the resin prepolymer and flame retardant modifier with a specific structure, the compatibility of the components of the system is improved through the copolymerization reaction between the active functional groups, thereby overcoming the problems of uneven mixing and phase separation in the polymer system caused by the addition of flame retardants;

[0037] (2) The nitrile groups in the resin prepolymer and the flame retardant modifier structure are used to generate a nitrogen-containing aromatic heterocyclic structure under thermal catalysis conditions, and the compounding with the phosphorus-containing flame retardant is realized in situ to achieve high-efficiency flame retardant properties of the composite material, thereby overcoming the problem of poor flame retardant effect of the existing single flame retardant;

[0038] (3) By utilizing the structure and polymerization reaction characteristics of the resin matrix, a polymer material with excellent flame retardancy and structural strength is obtained without the need to introduce various modifiers and additives, which simplifies the production process and reduces production costs.

[0039] In summary, the process provided by the present invention is simple and efficient, and the flame retardant and structural properties of the composite material are outstanding. It is suitable for the field of lightweight and high-strength composite materials with fire retardant requirements in aerospace, machinery and ships, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0041] FIG1 shows the mechanical property test results of the composite materials prepared in Examples 1-5 and Comparative Examples 1-4 provided by the present invention; wherein, numbers 1-9 correspond to the composite materials prepared in Examples 1-5 and Comparative Examples 1-4, respectively, and Comparative Example 3 could not be tested. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] The embodiment of the present invention provides a method for preparing a basalt fiber reinforced fire-retardant polymer-based composite material, comprising the following steps:

[0044] A resin prepolymer with the structural formula:

[0045] The preparation method of the resin prepolymer comprises the following steps: adding phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde in a molar ratio of 1:(2-2.05):(3.9-4.05) to a mixed solvent of xylene and anhydrous ethanol in sequence, wherein the mass ratio of xylene to anhydrous ethanol is 1:(1.4-1.6), and the mass ratio of the three solid raw materials, phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde to the mixed solvent is 1:(0.85-1.15). After the addition is completed, a dark brown mixed solution is obtained, which is further heated to 70-85°C, reacted for 3-6 hours, and then heated to 90-110°C to remove the solvent, thereby obtaining the above resin prepolymer.

[0046] In order to further optimize the above technical solution, the resin prepolymer contains phenolphthalein groups, benzoxazine rings and nitrile groups at the same time.

[0047] The method for preparing a basalt fiber reinforced fire-retardant polymer-based composite material using the resin prepolymer comprises the following steps:

[0048] (1) mixing the above resin prepolymer with a flame retardant modifier and an accelerator in a mass ratio of 1: (0.05-0.15): (0.1-0.25) and then melt-prepolymerizing to obtain a copolymerized resin prepolymer;

[0049] (2) dissolving the copolymer resin prepolymer in a mixed solvent of butanone and N,N-dimethylformamide to prepare a resin glue solution;

[0050] (3) impregnating the surface of the basalt fiber cloth with the resin glue, and after the fiber cloth is evenly impregnated, leaving it at room temperature for 2 hours and then transferring it to a high-temperature drying oven for drying to obtain a basalt fiber prepreg;

[0051] (4) After the basalt fiber prepregs are stacked, they are placed in a flat mold and pressed into a laminated sheet through a hot pressing process to obtain a basalt fiber reinforced fire-retardant polymer-based composite material.

[0052] In order to further optimize the above technical solution, the flame retardant modifier in step (1) contains a nitrile group, and the structural formula is:

[0053] To further optimize the above technical solution, a flame retardant modifier is prepared by dissolving 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde, and DOPO in a molar ratio of 1:(2-2.06):(2-2.1) in tetrahydrofuran solvent, wherein the mass ratio of the solid raw materials of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde, and DOPO to tetrahydrofuran is 1:(0.6-0.8); adding an acid binder, ethylenediamine, in an amount of 0.5% to 1% of the mass of 2,6-(p-aminophenoxy)benzonitrile, maintaining the solution system temperature at 60-75°C, and continuing the reaction for 3-5 hours to obtain a brown-yellow turbid mixed solution, separating and washing, and then drying in a vacuum drying oven at 80°C for 8-12 hours to obtain the flame retardant modifier.

[0054] In order to further optimize the above technical solution, the accelerator in step (1) is a tetraglycidylamine type epoxy resin; the melt prepolymerization temperature is 80-120° C., and the prepolymerization time is 30-60 min.

[0055] In order to further optimize the above technical solution, in step (2), the mass ratio of butanone to N,N-dimethylformamide solvent is 1:(0.3-0.7), and the mass ratio of copolymerized resin prepolymer to mixed solvent is 1:(0.5-0.9).

[0056] In order to further optimize the above technical solution, the mass ratio of the resin glue to the basalt fiber in step (3) is (0.35-0.92):1, the drying oven temperature is set to 150-160°C, and the drying time is 5-15 minutes.

[0057] In order to further optimize the above technical solution, the number of basalt fiber prepreg layers in step (4) is 10, and the hot pressing process is: the pressure is maintained at 15-20 MPa, the program temperature is 200°C for 2 to 4 hours, 220 to 240°C for 2 to 4 hours, and 260 to 280°C for 2 to 4 hours.

[0058] The following examples and comparative examples were prepared according to the above-mentioned relevant preparation methods.

[0059] The raw material dosages and process parameters of Examples 1-5 and Comparative Documents 1-4 are as follows.

[0060] Example 1

[0061] 10 g of resin prepolymer, 0.5 g of flame retardant modifier and 1.5 g of accelerator were melt-prepolymerized to obtain 12 g of copolymerized resin prepolymer; butanone and N,N-dimethylformamide were mixed in a mass ratio of 5 g:2 g to obtain 7 g of mixed solvent.

[0062] In the preparation of the resin prepolymer, the ratio of phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde is 1:2.01:4.05, the ratio of xylene and anhydrous ethanol is 1:1.5, and the ratio of phenolphthalein, aminophenoxyphthalonitrile, paraformaldehyde and the mixed solvent of xylene and anhydrous ethanol is 1:0.9.

[0063] In the preparation of the flame retardant modifier, the ratio of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO is 1:2:2, the dosage ratio of DOPO to tetrahydrofuran is 1:0.6, and the dosage of the acid-binding agent ethylenediamine is 0.6% of the mass of 2,6-(p-aminophenoxy)benzonitrile.

[0064] The melt prepolymerization reaction temperature is 80°C and the reaction time is 60 minutes; the mass ratio of resin glue to basalt fiber cloth is 35wt%; the drying temperature of the prepreg is 155°C and the drying time is 10 minutes. The hot pressing process pressure is 15MPa, and the program temperature is 200°C for 2 hours, 240°C for 2 hours, and 280°C for 2 hours.

[0065] Example 2

[0066] 10 g of resin prepolymer, 0.75 g of flame retardant modifier and 1 g of accelerator were melt-prepolymerized to obtain 11.75 g of copolymerized resin prepolymer; butanone and N,N-dimethylformamide were mixed in a mass ratio of 5 g:3 g to obtain 8 g of mixed solvent.

[0067] In the preparation of the resin prepolymer, the ratio of phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde is 1:2.01:4.0, the ratio of xylene and anhydrous ethanol is 1:1.45, and the ratio of phenolphthalein, aminophenoxyphthalonitrile, paraformaldehyde and the mixed solvent of xylene and anhydrous ethanol is 1:1.

[0068] In the preparation of the flame retardant modifier, the ratio of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO is: 1:2.05:2.1, the dosage ratio of the tetrahydrofuran agent is: 1:0.8, and the dosage of the acid-binding agent ethylenediamine is: 0.8% of the mass of 2,6-(p-aminophenoxy)benzonitrile.

[0069] The melt prepolymerization reaction temperature is 100°C and the reaction time is 45 minutes; the mass ratio of resin glue to basalt fiber cloth is 66wt%; the drying temperature of the prepreg is 160°C and the drying time is 10 minutes. The hot pressing process pressure is 20MPa, and the program temperature is 200°C for 2 hours, 230°C for 3 hours, and 280°C for 3 hours.

[0070] Example 3

[0071] 10 g of resin prepolymer, 1 g of flame retardant modifier and 1.5 g of accelerator were melt-prepolymerized to obtain 12.5 g of copolymerized resin prepolymer; butanone and N,N-dimethylformamide were mixed in a mass ratio of 5 g:2 g to obtain 7 g of mixed solvent.

[0072] In the preparation of the resin prepolymer, the ratio of phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde is 1:2.02:3.9, the ratio of xylene and anhydrous ethanol is 1:1.6, and the ratio of phenolphthalein, aminophenoxyphthalonitrile, paraformaldehyde and the mixed solvent of xylene and anhydrous ethanol is 1:1.1.

[0073] In the preparation of the flame retardant modifier, the ratio of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO is: 1:2.03:2.05, the dosage ratio of the tetrahydrofuran agent is: 1:0.8, and the dosage of the acid-binding agent ethylenediamine is: 0.6% of the mass of 2,6-(p-aminophenoxy)benzonitrile.

[0074] The melt prepolymerization reaction temperature is 120°C, and the reaction time is 30 minutes; the mass ratio of resin glue to basalt fiber cloth is 92wt%; the drying temperature of the prepreg is 150°C, the drying time is 10 minutes, the hot pressing process pressing pressure is 20MPa, and the program temperature is 200°C for 4 hours, 240°C for 2 hours, and 280°C for 2 hours.

[0075] Example 4

[0076] 10 g of resin prepolymer, 1 g of flame retardant modifier and 2 g of accelerator were melt-prepolymerized to obtain 13 g of copolymerized resin prepolymer; butanone and N,N-dimethylformamide were mixed in a mass ratio of 4 g:2.5 g to obtain 6.5 g of mixed solvent.

[0077] In the preparation of the resin prepolymer, the ratio of phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde is 1:2.01:4.05, the ratio of xylene and anhydrous ethanol is 1:1.5, and the ratio of phenolphthalein, aminophenoxyphthalonitrile, paraformaldehyde and the mixed solvent of xylene and anhydrous ethanol is 1:1.15.

[0078] In the preparation of the flame retardant modifier, the ratio of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO is: 1:2.06:2.1, the dosage ratio of the tetrahydrofuran agent is: 1:0.6, and the dosage of the acid-binding agent ethylenediamine is: 0.5% of the mass of 2,6-(p-aminophenoxy)benzonitrile.

[0079] The melt prepolymerization reaction temperature is 90°C and the reaction time is 50 minutes; the mass ratio of resin glue to basalt fiber cloth is 58wt%; the drying temperature of the prepreg is 155°C and the drying time is 15 minutes. The hot pressing process pressure is 20MPa, and the program temperature is 200°C for 4 hours, 220°C for 4 hours, and 260°C for 4 hours.

[0080] Example 5

[0081] 10 g of resin prepolymer, 1.5 g of flame retardant modifier and 2.5 g of accelerator were melt-prepolymerized to obtain 14 g of copolymerized resin prepolymer; butanone and N,N-dimethylformamide were mixed in a mass ratio of 9 g:3.5 g to obtain 12.5 g of mixed solvent.

[0082] In the preparation of the resin prepolymer, the ratio of phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde is 1:2.03:3.9, the ratio of xylene and anhydrous ethanol is 1:1.5, and the ratio of phenolphthalein, aminophenoxyphthalonitrile, paraformaldehyde and the mixed solvent of xylene and anhydrous ethanol is 1:1.05.

[0083] In the preparation of the flame retardant modifier, the ratio of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO is: 1:2.05:2.1, the dosage ratio of the tetrahydrofuran agent is: 1:0.8, and the dosage of the acid-binding agent ethylenediamine is: 0.6% of the mass of 2,6-(p-aminophenoxy)benzonitrile.

[0084] The melt prepolymerization reaction temperature is 110°C, and the reaction time is 60 minutes; the mass ratio of resin glue to basalt fiber cloth is 60wt%; the drying temperature of the prepreg is 160°C, the drying time is 5 minutes, the hot pressing process pressing pressure is 15MPa, and the program temperature is 200°C for 2 hours, 240°C for 2 hours, and 280°C for 2 hours.

[0085] Comparative Example 1

[0086] 10 g of resin prepolymer and 2.5 g of accelerator were melt-prepolymerized to obtain 12.5 g of copolymerized resin prepolymer; butanone and N,N-dimethylformamide were mixed in a mass ratio of 4.5 g:2.5 g to obtain 7 g of mixed solvent.

[0087] In the preparation of the resin prepolymer, the ratio of phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde is 1:2.05:4.0, the ratio of xylene and anhydrous ethanol is 1:1.5, and the ratio of phenolphthalein, aminophenoxyphthalonitrile, paraformaldehyde and the mixed solvent of xylene and anhydrous ethanol is 1:1.05.

[0088] The melt prepolymerization reaction temperature is 120°C, and the reaction time is 40 minutes; the mass ratio of resin glue to basalt fiber cloth is 60wt%; the drying temperature of the prepreg is 160°C, the drying time is 5 minutes, the hot pressing process pressing pressure is 20MPa, and the program temperature is 200°C for 2 hours, 240°C for 2 hours, and 280°C for 2 hours.

[0089] Comparative Example 2

[0090] 10 g of resin prepolymer and 1.5 g of flame retardant modifier were melt-prepolymerized to obtain 11.5 g of copolymerized resin prepolymer; butanone and N,N-dimethylformamide were mixed in a mass ratio of 5.5 g:2.5 g to obtain 8 g of mixed solvent.

[0091] In the preparation of the resin prepolymer, the ratio of phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde is 1:2.01:4.0, the ratio of xylene and anhydrous ethanol is 1:1.5, and the ratio of phenolphthalein, aminophenoxyphthalonitrile, paraformaldehyde and the mixed solvent of xylene and anhydrous ethanol is 1:1.1.

[0092] In the preparation of the flame retardant modifier, the ratio of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO is: 1:2.01:2.1, the dosage ratio of the tetrahydrofuran agent is: 1:0.6, and the dosage of the acid-binding agent ethylenediamine is: 0.6% of the mass of 2,6-(p-aminophenoxy)benzonitrile.

[0093] The melt prepolymerization reaction temperature is 120°C, and the reaction time is 50 minutes; the mass ratio of resin glue to basalt fiber cloth is 60wt%; the drying temperature of the prepreg is 160°C, the drying time is 15 minutes, the hot pressing process pressing pressure is 20MPa, and the program temperature is 200°C for 2 hours, 240°C for 2 hours, and 280°C for 2 hours.

[0094] Comparative Example 3

[0095] 10 g of resin prepolymer, 1.5 g of flame retardant modifier and 2.5 g of accelerator were melt-prepolymerized to obtain 14 g of copolymerized resin prepolymer; butanone and N,N-dimethylformamide were mixed in a mass ratio of 6 g:2 g to obtain 8 g of mixed solvent.

[0096] In the preparation of the resin prepolymer, the ratio of phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde is 1:2.05:4.01, the ratio of xylene and anhydrous ethanol is 1:1.6, and the ratio of phenolphthalein, aminophenoxyphthalonitrile, paraformaldehyde and the mixed solvent of xylene and anhydrous ethanol is 1:1.15.

[0097] In the preparation of the flame retardant modifier, the ratio of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO is: 1:2.01:2.1, the dosage ratio of the tetrahydrofuran agent is: 1:0.6, and the dosage of the acid-binding agent ethylenediamine is: 0.6% of the mass of 2,6-(p-aminophenoxy)benzonitrile.

[0098] The melt prepolymerization reaction temperature is 130°C, and the reaction time is 50 minutes; the mass ratio of resin glue to basalt fiber cloth is 60wt%; the drying temperature of the prepreg is 155°C, the drying time is 15 minutes, the hot pressing process pressing pressure is 20MPa, and the program temperature is 200°C for 2 hours, 240°C for 2 hours, and 280°C for 2 hours.

[0099] Comparative Example 4

[0100] 10 g of resin prepolymer, 1.5 g of flame retardant modifier and 2.5 g of accelerator were melt-prepolymerized to obtain 14 g of copolymerized resin prepolymer; butanone and N,N-dimethylformamide were mixed in a mass ratio of 5 g:3 g to obtain 8 g of mixed solvent.

[0101] In the preparation of the resin prepolymer, the ratio of phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde is 1:2.05:4.0, the ratio of xylene and anhydrous ethanol is 1:1.5, and the ratio of phenolphthalein, aminophenoxyphthalonitrile, paraformaldehyde and the mixed solvent of xylene and anhydrous ethanol is 1:1.1.

[0102] In the preparation of the flame retardant modifier, the ratio of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO is: 1:2.01:2.1, the dosage ratio of the tetrahydrofuran agent is: 1:0.6, and the dosage of the acid-binding agent ethylenediamine is: 0.6% of the mass of 2,6-(p-aminophenoxy)benzonitrile.

[0103] The melt prepolymerization reaction temperature is 120°C, and the reaction time is 50 minutes; the mass ratio of resin glue to basalt fiber cloth is 30wt%; the drying temperature of the prepreg is 155°C, the drying time is 15 minutes, the hot pressing process pressing pressure is 20MPa, and the program temperature is 200°C for 2 hours, 240°C for 2 hours, and 280°C for 2 hours.

[0104] Comparative Examples 1-4 were compared and verified from four aspects: the mass of the flame retardant modifier, the mass of the accelerator, the prepolymerization temperature and the mass ratio of the resin to the fiber.

[0105] In order to investigate the flame retardancy and mechanical properties of the products prepared in the above examples and comparative examples, the samples obtained in Examples 1-5 and Comparative Examples 1-4 were tested.

[0106] The specific test methods are as follows:

[0107] According to the GBT2406.2-2009 test standard, the material was cut into 100×10×3 specimens for testing. The test stipulates that if the specimen fails to meet any of the following conditions under a certain oxygen content (volume percentage): (1) extinguished within 3 minutes, (2) does not burn to 5 cm below the lower end of the specimen where it is ignited, this critical oxygen content value is defined as the limiting oxygen index (LOI) of the specimen. When the oxygen index (LOI) is less than 22%, the material is considered flammable; when the oxygen index (LOI) is between 22% and 27%, the material is considered combustible; when the oxygen index (LOI) is greater than 27%, the material is considered to be flame retardant.

[0108] The material was tested for vertical combustion (UL-94) according to ASTM D3801. The sample size was 100×12×3mm. 3 The flame retardant properties of the obtained flame retardant polymer were tested by limiting oxygen index (LOI) experiment, and the results are shown in Table 1.

[0109] Table 1 Flame retardant performance test results of composite materials prepared in Examples 1-5 and Comparative Examples 1-4

[0110] Note: In Comparative Example 3, the resin gelled due to the high prepolymerization temperature during the prepolymerization process and could not be further dissolved in the solvent and impregnated on the fiber surface. Therefore, a composite material that met the test requirements could not be obtained.

[0111] The mechanical properties of the resulting flame-retardant polymer-based composites were tested using an electronic universal testing machine in accordance with the GB / T 1040-2006 standard. The tensile rate was 10 mm / min, and each sample was tested five times to obtain the average value. The results are shown in Figure 1.

[0112] The thermal stability of the resulting flame-retardant polymer was tested using a thermogravimetric analyzer (TAQ50) in accordance with the GB / T 2951.41-2008 standard. Approximately 10 mg of the resin polymer was scraped from the surface of the fiber-reinforced polymer-based composite material and placed in a crucible. The temperature was then increased from 40°C to 800°C at a rate of 20°C / min under an oxygen atmosphere with a nitrogen flow rate of 50 mL / min. The results are shown in Table 2.

[0113] Table 2 Thermal stability test parameters of the composite materials prepared in Examples 1-5 and Comparative Examples 1-4

[0114] As can be seen from Figure 1 and Table 1-2, the prepared basalt fiber reinforced flame retardant polymer matrix composite material has the following advantages:

[0115] ① Excellent flame retardancy, with a limiting oxygen index exceeding 27%, meeting the standards for flame-retardant materials. The flame retardant modifier and accelerator play a significant role in improving flame retardancy. With the addition of the flame retardant modifier, the limiting oxygen index of the composite system reaches 40%, demonstrating excellent flame retardancy. The addition of the accelerator can, to a certain extent, promote the ring-opening reaction of the benzoxazine ring in the resin prepolymer, thereby initiating cyclization polymerization between the prepolymer and the nitrile group in the flame retardant modifier, forming a nitrogen-containing aromatic heterocyclic structure, thereby improving the flame retardancy of the system from the perspective of the polymer molecular structure.

[0116] ② Excellent mechanical properties, with a flexural strength greater than 790 MPa and a flexural modulus greater than 28 GPa. The outstanding structural strength is attributed, on the one hand, to the high structural strength of the basalt fiber itself, and on the other hand, to the outstanding structural properties of the polymer matrix, which ultimately comes from the high degree of polymerization and high crosslinking density of the polymer matrix. The reduced flexural strength and modulus in Comparative Example 4 are mainly due to the low resin content during the preparation of the composite material, which results in insufficient bonding between the fiber layers, obvious delamination during testing, and a significant deterioration in structural properties.

[0117] ③ The thermal stability is outstanding, with the material's initial decomposition temperature (T5%) above 380°C and a carbon residue of 65% at 800°C, further demonstrating the high degree of polymerization of the polymer matrix and the high thermal stability of the composite material. Therefore, the flame-retardant polymer-based composite material obtained in the above embodiment can be used in high-performance flame-retardant materials in aerospace, machinery, and ships.

[0118] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0119] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be construed in the widest possible manner consistent with the principles and novel features disclosed herein.

Claims

1. A resin prepolymer, characterized in that: The structural formula is:

2. The resin prepolymer according to claim 1, characterized in that The preparation method of the resin prepolymer is as follows: phenolphthalein, aminophenoxyphthalonitrile and polyformaldehyde are sequentially added into a mixed solvent of xylene and anhydrous ethanol in a molar ratio of 1:(2-2.05):(3.9-4.05), the mass ratio of xylene to anhydrous ethanol is 1:(1.4-1.6), the mass ratio of the three solid raw materials of phenolphthalein, aminophenoxyphthalonitrile and polyformaldehyde to the mixed solvent is 1:(0.85-1.15), after the addition is completed, a dark brown mixed solution is obtained, the temperature is continuously raised to 70-85°C, the reaction is continued for 3-6 hours, and then the temperature is raised to 90-110°C to remove the solvent, so as to obtain the above resin prepolymer.

3. A method for preparing a basalt fiber reinforced fire-retardant polymer-based composite material comprising the resin prepolymer according to claim 1, characterized in that: The following steps are involved: (1) mixing the resin prepolymer with a flame retardant modifier and an accelerator in a mass ratio of 1: (0.05-0.15): (0.1-0.25) and then melt prepolymerizing to obtain a copolymer resin prepolymer; (2) dissolving the copolymer resin prepolymer in a mixed solvent of butanone and N,N-dimethylformamide to prepare a resin glue solution; (3) impregnating the resin glue on the surface of the basalt fiber cloth, and after the fiber cloth is evenly impregnated, leaving it in the air at room temperature for 2 hours and then transferring it to a high-temperature drying oven for drying to obtain a basalt fiber prepreg; (4) After the basalt fiber prepregs are stacked, they are placed in a flat mold and pressed into a laminated board by a hot pressing process to obtain a basalt fiber reinforced fire-retardant polymer-based composite material.

4. The method for preparing the basalt fiber reinforced fire-retardant polymer-based composite material according to claim 3, characterized in that: The flame retardant modifier in step (1) contains a nitrile group and has the structural formula:

5. The method for preparing the basalt fiber reinforced fire-retardant polymer-based composite material according to claim 4, characterized in that: The preparation method of the flame retardant modifier comprises the following steps: dissolving 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO in a molar ratio of 1:(2-2.06):(2-2.1) in a tetrahydrofuran solvent, wherein the mass ratio of the solid raw materials of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO to tetrahydrofuran is 1:(0.6-0.8); adding an acid binding agent ethylenediamine, wherein the amount of the acid binding agent is 0.5%-1% of the mass of 2,6-(p-aminophenoxy)benzonitrile, maintaining the temperature of the solution system at 60-75°C, continuing the reaction for 3-5 hours, obtaining a brown-yellow turbid mixed solution, separating and washing, and drying the mixed solution in a vacuum drying oven at 80°C for 8-12 hours, thereby obtaining the flame retardant modifier.

6. The method for preparing the basalt fiber reinforced fire-retardant polymer-based composite material according to claim 3, characterized in that: The accelerator in step (1) is a tetraglycidylamine type epoxy resin; the melt prepolymerization temperature is 80-120° C., and the prepolymerization time is 30-60 min.

7. The method for preparing the basalt fiber reinforced fire-retardant polymer-based composite material according to claim 3, characterized in that: The mass ratio of butanone to N,N-dimethylformamide solvent in step (2) is 1:(0.3-0.7), and the mass ratio of copolymer resin prepolymer to mixed solvent is 1:(0.5-0.9).

8. The method for preparing the basalt fiber reinforced fire-retardant polymer-based composite material according to claim 3, characterized in that: The mass ratio of the resin glue to the basalt fiber in step (3) is (0.35-0.92):1, the temperature of the drying oven is set at 150-160° C., and the drying time is 5-15 minutes.

9. The method for preparing the basalt fiber reinforced fire-retardant polymer-based composite material according to claim 3, characterized in that: The number of basalt fiber prepreg layers in step (4) is 6 to 10, and the hot pressing process is: the pressure is maintained at 15-20 MPa, the program temperature is 200° C. for 2 to 4 hours, 220 to 240° C. for 2 to 4 hours, and 260 to 280° C. for 2 to 4 hours.

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