Preparation Method of Basalt Fiber Reinforced Fireproof and Flame Retardant Polymer Matrix Composite Material

Abstract

The invention discloses a preparation method of a basalt fiber reinforced fireproof and flame-retardant polymer matrix composite material. Firstly, a resin prepolymer is mixed with a flame-retardant modifier and a promoter to obtain a copolymerized resin prepolymer; then the copolymerized resin prepolymer is dissolved in a mixed solvent of methyl ethyl ketone and N,N-dimethylformamide to obtain a resin sizing solution; then the resin sizing solution is impregnated on the surface of basalt fibers, and after airing for 2 h, drying treatment is carried out to obtain basalt fiber prepregs; then the basalt fiber prepregs are placed in a flat die, and after hot pressing, a basalt fiber reinforced fireproof and flame-retardant polymer matrix composite material is obtained. The process method provided by the invention is simple and efficient, and the composite material has outstanding flame retardancy and structural properties, and is applicable to the field of lightweight and high-strength composite materials with fireproof and flame-retardant requirements such as aerospace, machinery and ships.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer matrix composite preparation, and more specifically to a preparation method of basalt fiber reinforced fireproof and flame-retardant polymer matrix. Background Art

[0002] With the continuous development of modern society, polymer materials have been widely used in various fields. However, due to their own structural characteristics, polymer materials are extremely flammable and are important hidden dangers in production safety prevention. Therefore, it is extremely important to improve the fireproof and flame-retardant properties of polymer materials. Currently, the best choice to improve the flame retardancy of polymers is to add flame retardants to the matrix. However, with the development of flame retardant technology, higher requirements have been put forward for flame-retardant polymer composites. In addition to meeting the requirements of flame retardancy, it is also necessary to avoid causing great damage to the mechanical properties of the base material due to the addition of flame retardants.

[0003] Achieving the flame retardancy of polymer materials by adding flame retardants to polymer materials is currently the main technical method for polymer flame retardant modification. Traditional flame retardants are mainly halogen-based flame retardants. Halogen-based flame retardants have good flame retardant effects and low prices, but due to their poor thermal stability, they are only suitable for products processed below 200°C. At the same time, a large number of studies have found that after the flame-retardant polymer materials containing halogen-based flame retardants are burned in a fire, they will produce a large amount of thick smoke and toxic substances, leading to asphyxiation of personnel and causing secondary injuries. In addition, when the waste of these materials is recycled at high temperatures, it is easy to generate carcinogenic substances such as dioxins, causing environmental pollution. Although phosphorus-based and organic-inorganic hybrid flame retardants can reduce the harm to the human body and environmental damage during thermal decomposition, a high dosage is required to achieve the flame retardant effect, which will increase the material cost. Moreover, when phosphorus-based flame retardants and organic-inorganic compound flame retardants are used in polymer molding processing, there are usually problems such as high melting temperatures and difficult uniform dispersion control, resulting in a great contradiction between their melt molding processing technology with the polymer matrix and the mechanical properties of polymer matrix 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 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 lead to cumbersome processing of polymer composites. The use of a large amount of flame retardants will lead to 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 used. 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 the current modification research of flame-retardant polymers mainly focusing on the fields of composite materials with low temperature resistance such as modified epoxy resins, modified polypropylene, and modified polyethylene, 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 needs of aerospace, machinery, ships and other fields for high-performance fire-retardant materials.

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

[0006] A Chinese invention patent (CN113248634B) discloses a Chitosan-Schiff / DOPO flame retardant and a preparation method thereof, as well as research on flame retardant modification of epoxy resin. First, chitosan is used as the main raw material to prepare Chitosan-Schiff and Chitosan-Schiff / DOPO flame retardants, respectively. Then, the flame retardant and curing agent are synergistically modified to modify the epoxy resin, and the flame retardant polymer is obtained by room temperature curing and step-by-step temperature curing. If the curing time of the flame retardant polymer is too long during the preparation process, it will lead to low production efficiency and increase production costs. In addition, phosphorus-based flame retardants generally have a high water absorption rate, which will seriously limit the application of modified epoxy resin polymers in the field of electronic materials.

[0007] Chinese invention patent (CN116200018A) discloses a preparation method of hyperbranched triazine macromolecule modified bentonite and its research on modifying polymers as an inorganic flame retardant. By using a triazine compound and a phosphorus chloride compound to carry out a polymerization reaction between the layers of bentonite to generate a hyperbranched macromolecule flame retardant, and then exfoliating and modifying the bentonite, while achieving efficient flame retardancy, it improves the dispersibility of the inorganic filler bentonite in the polymer. The prepared flame retardant polymer has good fire resistance and mechanical properties. However, the preparation process of the modified bentonite involves multiple chemical synthesis and purification processes, which not only easily causes environmental pollution but also significantly increases production costs.

[0008] Therefore, providing a simple and efficient preparation method for fire-retardant polymer-based composites is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0009] In view of this, the present invention provides a preparation method of a basalt fiber-reinforced fire-retardant polymer-based composite, which can solve the problems of complicated steps, large pollution, high cost, etc. in the synthesis of existing external flame retardants, simplifies the molding process of the polymer-based composite, improves production efficiency, and at the same time provides a new type of high-performance composite material for the field of high-performance fiber-reinforced polymer-based composites.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A resin prepolymer, the structural formula is:

[0012]

[0013] Preferably, the preparation method of the resin prepolymer is: adding phenolphthalin, aminophenoxyphthalonitrile and paraformaldehyde into a mixed solvent of xylene and absolute ethanol in a molar ratio of 1:(2 - 2.05):(3.9 - 4.05) in sequence. The mass ratio of xylene to absolute ethanol is 1:(1.4 - 1.6), and the mass ratio of the three solid raw materials of phenolphthalin, aminophenoxyphthalonitrile and paraformaldehyde to the mixed solvent is 1:(0.85 - 1.15). After adding the materials, a dark brown mixed solution is obtained. Then, continue to heat up to 70 - 85 °C and react for 3 - 6 h, and then heat up to 90 - 110 °C to remove the solvent, thus obtaining the above resin prepolymer.

[0014] The synthesis route is:

[0015]

[0016] Preferably, the resin prepolymer contains both phenolphthalin groups, benzoxazine rings and nitrile groups.

[0017] 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 main chain of the resin molecule, ensuring that the polymer material exhibits strong structural characteristics; 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 the promoter, thereby ensuring the effective conduct of the copolymerization reaction.

[0018] A method for preparing a basalt fiber reinforced fire-retardant polymer-based composite material containing the resin prepolymer comprises the following steps:

[0019] (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;

[0020] (2) dissolving the copolymer resin prepolymer in a mixed solvent of butanone and N,N-dimethylformamide to prepare a resin glue solution;

[0021] (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;

[0022] (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.

[0023] The beneficial effect of the above technical solution is that the present invention improves the compatibility of the components of the system by preferably selecting resin prepolymers and flame retardant modifiers of 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.

[0024] Preferably, the flame retardant modifier in step (1) contains a nitrile group and has the structural formula:

[0025]

[0026] 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 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO solid raw materials 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, the reaction is continued for 3-5 hours, a brown-yellow turbid mixed solution is obtained, and after separation and washing, it is dried in a vacuum drying oven at 80°C for 8-12 hours to obtain the flame retardant modifier.

[0027] The synthetic route is:

[0028]

[0029] Preferably, the accelerator in step (1) is a tetraglycidylamine type epoxy resin; the melt prepolymerization temperature is 80 to 120° C., and the prepolymerization time is 30 to 60 minutes.

[0030] The beneficial effects of the above technical solution are: selecting tetraglycidylamine type epoxy resin, because the epoxy resin has high reactivity and 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.

[0031] The melt prepolymerization temperature is selected. When it is higher than this temperature, it is easy to cause 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 large, 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.

[0032] 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 copolymer resin prepolymer to mixed solvent is 1:(0.5-0.9).

[0033] The beneficial effects of the above technical solutions are as follows: Regarding the proportion selection of the blended solvent, when it is higher than this proportion, the resin prepolymer with strong polarity and the flame retardant modifier are difficult to be fully dissolved, resulting in insufficient impregnation of the fiber cloth subsequently; when it is lower than this proportion, the amount of the high-boiling solvent is too high, leading to high energy consumption and large pollution during the subsequent drying to remove the solvent. Regarding the proportion selection of the resin prepolymer and the mixed solvent, when it is higher than this proportion, the concentration of the resin sizing is relatively large, resulting in insufficient impregnation of the fiber cloth and affecting the mechanical properties of the composite material; when it is lower than this proportion, the amount of the solvent is large, and the subsequent drying process has high energy consumption and great environmental pollution.

[0034] Preferably, in step (3), the mass ratio of the resin sizing to the basalt fiber 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 min.

[0035] The beneficial effects of the above technical solutions are as follows: Regarding the mass ratio selection of the resin sizing and the basalt fiber, since the resin plays the role of an adhesive in the composite material and its cost is higher than that of the fiber, when it is higher than this proportion, the resin content in the composite material is too high, and the reinforcing and toughening effects of the fiber material are not obvious, and the cost is high; when it is lower than this proportion, the resin content is too low to fully impregnate the fiber cloth and cannot ensure sufficient adhesion between layers of the fiber cloth. Regarding the selection of the temperature and drying time of the drying oven, when it is higher than this temperature and longer than this time, the resin system cures on the surface of the fiber cloth, losing its adhesiveness and unable to carry out the subsequent pressing process; when it is lower than this temperature and shorter than this time, the solvent in the prepreg cannot be fully removed, and microdefects will appear inside the composite material due to the escape of the solvent during the subsequent pressing to prepare the laminate, damaging the structural strength of the system.

[0036] Preferably, in step (4), the number of layers of the basalt fiber prepreg is 6 - 10 layers, and the hot pressing process is: the pressure is maintained at 15 - 20 MPa, the program temperature is 200 °C for heat preservation and pressure holding for 2 - 4 h, 220 - 240 °C for heat preservation and pressure holding for 2 - 4 h, and 260 - 280 °C for heat preservation and pressure holding for 2 - 4 h.

[0037] The beneficial effects of the above technical solutions are as follows: Regarding the selection of the hot pressing pressure, when it is higher than this pressure, it is easy to cause a large amount of loss of the resin sizing, and then the adhesion of the composite material is insufficient; when it is lower than this pressure, the contact between layers of the prepreg is insufficient, and the gas cannot be discharged thoroughly, easily resulting in a large number of defects inside the composite material and affecting the structural performance of the composite material. Regarding the selection of the hot pressing temperature program and time, when it is higher than this temperature or longer than this time, it is demanding on the equipment, increases energy consumption, and reduces production efficiency; when it is lower than this temperature or shorter than this time, the cross-linking reaction of the polymer is insufficient, affecting the flame retardancy and structural strength of the composite material, and a high-performance composite material cannot be obtained.

[0038] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a method for preparing a basalt fiber-reinforced fireproof and flame-retardant polymer matrix composite material, and the beneficial effects are as follows:

[0039] (1) By preferably selecting a resin prepolymer and a flame retardant modifier with a specific structure, the compatibility of each component in the system is improved through the copolymerization reaction between active functional groups, overcoming problems such as uneven mixing and phase separation in the polymer system caused by the addition of external flame retardants;

[0040] (2) Using the nitrile groups in the structures of the resin prepolymer and the flame retardant modifier to generate a nitrogen-containing aromatic heterocyclic structure under thermal catalytic conditions, in-situ realizing the compounding with a phosphorus-containing flame retardant, and achieving the high-efficiency flame retardant characteristics of the composite material, overcoming the problem of poor flame retardant effect of existing single flame retardants;

[0041] (3) Utilizing the structure and polymerization reaction characteristics of the resin matrix, a polymer material with excellent flame retardant properties and structural strength is obtained, without the need to introduce various modifiers and additives, simplifying the production process and flow, and reducing the production cost.

[0042] In summary, the process method provided by the present invention is simple and efficient, the flame retardant and structural properties of the composite material are outstanding, and it is applicable to the field of lightweight and high-strength composite materials with fireproof and flame retardant requirements such as aerospace, machinery, and ships. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0044] Figure 1 It is the test results of the mechanical properties of the composite materials prepared in Examples 1-5 and Comparative Examples 1-4 provided by the present invention; among them, the numbers 1-9 respectively correspond to the composite materials prepared in Examples 1-5 and Comparative Examples 1-4, and Comparative Example 3 cannot be tested. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0046] An embodiment of the present invention provides a method for preparing a basalt fiber-reinforced fireproof and flame-retardant polymer matrix composite material, comprising the following steps:

[0047] A resin prepolymer, the structural formula of which is:

[0048]

[0049] The preparation method of the resin prepolymer is as follows: phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde are sequentially added into a mixed solvent of xylene and absolute ethanol according to a molar ratio of 1:(2-2.05):(3.9-4.05). The mass ratio of xylene to absolute ethanol is 1:(1.4-1.6). The mass ratio of the three solid raw materials of phenolphthalein, aminophenoxyphthalonitrile and paraformaldehyde to the mixed solvent is 1:(0.85-1.15). After the feeding is completed, a dark brown mixed solution is obtained. Then, the temperature is raised to 70-85 °C and reacted for 3-6 h, and then the temperature is raised to 90-110 °C to remove the solvent, thus obtaining the above resin prepolymer.

[0050] To further optimize the above technical solution, the resin prepolymer contains a phenolphthalein group, a benzoxazine ring and a nitrile group.

[0051] A method for preparing a basalt fiber-reinforced fireproof and flame-retardant polymer matrix composite material by using the above resin prepolymer, comprising the following steps:

[0052] (1) Mix the above resin prepolymer with a flame retardant modifier and a promoter according to a mass ratio of 1:(0.05-0.15):(0.1-0.25), and perform melt pre-polymerization to obtain a copolymerized resin prepolymer;

[0053] (2) Dissolve the copolymerized resin prepolymer in a mixed solvent of butanone and N,N-dimethylformamide to prepare a resin glue solution;

[0054] (3) Immerse the resin glue solution on the surface of basalt fiber cloth. After the fiber cloth is evenly impregnated, leave it to dry at room temperature for 2 h and then transfer it to a high-temperature drying oven for drying treatment to obtain a basalt fiber prepreg;

[0055] (4) Stack the basalt fiber prepregs and place them in a flat mold, and press laminated plates through a hot pressing process to obtain a basalt fiber-reinforced fireproof and flame-retardant polymer matrix composite material.

[0056] To further optimize the above technical solution, the flame retardant modifier in step (1) contains a nitrile group, and the structural formula is:

[0057]

[0058] In order to further optimize the above technical scheme, 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 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO solid raw materials to tetrahydrofuran is 1:(0.6-0.8); an acid binding agent ethylenediamine is added, and the amount of the acid binding agent is 0.5% to 1% of the mass of 2,6-(p-aminophenoxy)benzonitrile, the temperature of the solution system is maintained at 60-75° C., the reaction is continued for 3-5 hours, a brown-yellow turbid mixed solution is obtained, and after separation and washing, the mixed solution is dried in a vacuum drying oven at 80° C. for 8-12 hours to obtain the above flame retardant modifier;

[0059] 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 to 120° C., and the prepolymerization time is 30 to 60 minutes.

[0060] 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 copolymer resin prepolymer to mixed solvent is 1:(0.5-0.9).

[0061] 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.

[0062] In order to further optimize the above technical solution, in step (4), the number of basalt fiber prepreg stacking layers 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.

[0063] The following examples and comparative examples were prepared according to the above-mentioned relevant preparation methods.

[0064] The raw material dosage and process parameters of Examples 1-5 and Comparative Documents 1-4 are as follows.

[0065] Example 1

[0066] Take 10g of resin prepolymer, 0.5g of flame retardant modifier and 1.5g of accelerator for melt prepolymerization to obtain 12g of copolymerized resin prepolymer; mix butanone and N,N-dimethylformamide in a mass ratio of 5g:2g to obtain 7g of mixed solvent.

[0067] In the preparation of the resin prepolymer, the proportion values of phenolphthalin, aminophenoxyl phthalonitrile and paraformaldehyde are: 1:2.01:4.05, the proportion value of xylene and absolute ethanol is: 1:1.5, and the proportion value of phenolphthalin, aminophenoxyl phthalonitrile, paraformaldehyde and the mixed solvent of xylene and absolute ethanol is: 1:0.9.

[0068] In the preparation of the flame retardant modifier, the proportion values of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO are: 1:2:2, the dosage ratio with 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.

[0069] The melting prepolymerization reaction temperature is 80 °C, and the reaction time is 60 min; the mass ratio of the resin sizing agent to the basalt fiber cloth is 35 wt%; the drying temperature of the prepreg is 155 °C, the drying time is 10 min, the pressing pressure of the hot pressing process is 15 MPa, the program temperature is 200 °C for heat preservation and pressure holding for 2 h, 240 °C for heat preservation and pressure holding for 2 h, and 280 °C for heat preservation and pressure holding for 2 h.

[0070] Example 2

[0071] Take 10 g of the resin prepolymer, 0.75 g of the flame retardant modifier, and 1 g of the accelerator for melting prepolymerization to obtain 11.75 g of the copolymer resin prepolymer; mix methyl ethyl ketone and N,N-dimethylformamide according to a mass ratio of 5 g:3 g to obtain 8 g of the mixed solvent.

[0072] In the preparation of the resin prepolymer, the proportion values of phenolphthalin, aminophenoxyl phthalonitrile and paraformaldehyde are: 1:2.01:4.0, the proportion value of xylene and absolute ethanol is: 1:1.45, and the proportion value of phenolphthalin, aminophenoxyl phthalonitrile, paraformaldehyde and the mixed solvent of xylene and absolute ethanol is: 1:1.

[0073] In the preparation of the flame retardant modifier, the proportion values of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO are: 1:2.05:2.1, the dosage ratio with 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.

[0074] The melting prepolymerization reaction temperature is 100 °C, and the reaction time is 45 min; the mass ratio of the resin sizing agent to the basalt fiber cloth is 66 wt%; the drying temperature of the prepreg is 160 °C, the drying time is 10 min, the pressing pressure of the hot pressing process is 20 MPa, the program temperature is 200 °C for heat preservation and pressure holding for 2 h, 230 °C for heat preservation and pressure holding for 3 h, and 280 °C for heat preservation and pressure holding for 3 h.

[0075] Example 3

[0076] Take 10 g of resin prepolymer, 1 g of flame retardant modifier, and 1.5 g of accelerator, and melt and pre-polymerize them to obtain 12.5 g of copolymer resin prepolymer; mix methyl ethyl ketone and N,N-dimethylformamide in a mass ratio of 5 g:2 g to obtain 7 g of mixed solvent.

[0077] In the preparation of the resin prepolymer, the proportion values of phenolphthalin, aminophenoxyphtalocyanine, and paraformaldehyde are: 1:2.02:3.9, the proportion value of xylene and absolute ethanol is: 1:1.6, and the proportion value of phenolphthalin, aminophenoxyphtalocyanine, paraformaldehyde and the mixed solvent of xylene and absolute ethanol is: 1:1.1.

[0078] In the preparation of the flame retardant modifier, the proportion values of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde, and DOPO are: 1:2.03:2.05, the dosage ratio with tetrahydrofuran 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.

[0079] The temperature of the melt pre-polymerization reaction is 120 °C, and the reaction time is 30 min; the mass ratio of the resin glue solution to the basalt fiber cloth is 92 wt%; the drying temperature of the prepreg is 150 °C, the drying time is 10 min, the pressing pressure of the hot pressing process is 20 MPa, the program temperature is 200 °C for heat preservation and pressure holding for 4 h, 240 °C for heat preservation and pressure holding for 2 h, and 280 °C for heat preservation and pressure holding for 2 h.

[0080] Example 4

[0081] Take 10 g of resin prepolymer, 1 g of flame retardant modifier, and 2 g of accelerator, and melt and pre-polymerize them to obtain 13 g of copolymer resin prepolymer; mix methyl ethyl ketone and N,N-dimethylformamide in a mass ratio of 4 g:2.5 g to obtain 6.5 g of mixed solvent.

[0082] In the preparation of the resin prepolymer, the proportion values of phenolphthalin, aminophenoxyphtalocyanine, and paraformaldehyde are: 1:2.01:4.05, the proportion value of xylene and absolute ethanol is: 1:1.5, and the proportion value of phenolphthalin, aminophenoxyphtalocyanine, paraformaldehyde and the mixed solvent of xylene and absolute ethanol is: 1:1.15.

[0083] In the preparation of the flame retardant modifier, the proportion values of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde, and DOPO are: 1:2.06:2.1, the dosage ratio with tetrahydrofuran 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.

[0084] The melting pre-polymerization reaction temperature is 90 °C, and the reaction time is 50 min; the mass ratio of the resin glue solution to the basalt fiber cloth is 58 wt%; the drying temperature of the prepreg is 155 °C, the drying time is 15 min, the pressing pressure of the hot pressing process is 20 MPa, the programmed temperature is 200 °C for heat preservation and pressure holding for 4 h, 220 °C for heat preservation and pressure holding for 4 h, and 260 °C for heat preservation and pressure holding for 4 h.

[0085] Example 5

[0086] Take 10 g of resin prepolymer, 1.5 g of flame retardant modifier, and 2.5 g of accelerator for melting pre-polymerization to obtain 14 g of copolymer resin prepolymer; mix methyl ethyl ketone and N,N-dimethylformamide according to a mass ratio of 9 g:3.5 g to obtain 12.5 g of mixed solvent.

[0087] In the preparation of the resin prepolymer, the proportion values of phenolphthalin, aminophenoxyphtalocyanine, and paraformaldehyde are: 1:2.03:3.9, the proportion value of xylene and absolute ethanol is: 1:1.5, and the proportion value of phenolphthalin, aminophenoxyphtalocyanine, paraformaldehyde and the mixed solvent of xylene and absolute ethanol is: 1:1.05.

[0088] In the preparation of the flame retardant modifier, the proportion values of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde, and DOPO are: 1:2.05:2.1, the dosage ratio to tetrahydrofuran 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.

[0089] The melting pre-polymerization reaction temperature is 110 °C, and the reaction time is 60 min; the mass ratio of the resin glue solution to the basalt fiber cloth is 60 wt%; the drying temperature of the prepreg is 160 °C, the drying time is 5 min, the pressing pressure of the hot pressing process is 15 MPa, the programmed temperature is 200 °C for heat preservation and pressure holding for 2 h, 240 °C for heat preservation and pressure holding for 2 h, and 280 °C for heat preservation and pressure holding for 2 h.

[0090] Comparative Example 1

[0091] Take 10 g of resin prepolymer and 2.5 g of accelerator for melting pre-polymerization to obtain 12.5 g of copolymer resin prepolymer; mix methyl ethyl ketone and N,N-dimethylformamide according to a mass ratio of 4.5 g:2.5 g to obtain 7 g of mixed solvent.

[0092] In the preparation of the resin prepolymer, the proportion values of phenolphthalin, aminophenoxyphtalocyanine, and paraformaldehyde are: 1:2.05:4.0, the proportion value of xylene and absolute ethanol is: 1:1.5, and the proportion value of phenolphthalin, aminophenoxyphtalocyanine, paraformaldehyde and the mixed solvent of xylene and absolute ethanol is: 1:1.05.

[0093] The melting pre-polymerization reaction temperature is 120 °C, and the reaction time is 40 min; the mass ratio of the resin glue solution to the basalt fiber cloth is 60 wt%; the drying temperature of the prepreg is 160 °C, the drying time is 5 min, the pressing pressure of the hot pressing process is 20 MPa, the programmed temperature is 200 °C for heat preservation and pressure holding for 2 h, 240 °C for heat preservation and pressure holding for 2 h, and 280 °C for heat preservation and pressure holding for 2 h.

[0094] Comparative Example 2

[0095] Take 10 g of the resin prepolymer and 1.5 g of the flame retardant modifier for melting pre-polymerization to obtain 11.5 g of the copolymer resin prepolymer; mix methyl ethyl ketone and N,N-dimethylformamide in a mass ratio of 5.5 g:2.5 g to obtain 8 g of the mixed solvent.

[0096] In the preparation of the resin prepolymer, the proportion values of phenolphthalin, aminophenoxyl phthalonitrile and paraformaldehyde are: 1:2.01:4.0, the proportion value of xylene and absolute ethanol is: 1:1.5, and the proportion value of phenolphthalin, aminophenoxyl phthalonitrile, paraformaldehyde and the mixed solvent of xylene and absolute ethanol is: 1:1.1.

[0097] In the preparation of the flame retardant modifier, the proportion values of 2,6-(p-aminophenoxy)benzonitrile, benzaldehyde and DOPO are: 1:2.01:2.1, the dosage ratio 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.

[0098] The melting pre-polymerization reaction temperature is 120 °C, and the reaction time is 50 min; the mass ratio of the resin glue solution to the basalt fiber cloth is 60 wt%; the drying temperature of the prepreg is 160 °C, the drying time is 15 min, the pressing pressure of the hot pressing process is 20 MPa, the programmed temperature is 200 °C for heat preservation and pressure holding for 2 h, 240 °C for heat preservation and pressure holding for 2 h, and 280 °C for heat preservation and pressure holding for 2 h.

[0099] Comparative Example 3

[0100] Take 10 g of the resin prepolymer, 1.5 g of the flame retardant modifier and 2.5 g of the accelerator for melting pre-polymerization to obtain 14 g of the copolymer resin prepolymer; mix methyl ethyl ketone and N,N-dimethylformamide in a mass ratio of 6 g:2 g to obtain 8 g of the mixed solvent.

[0101] In the preparation of the resin prepolymer, the proportion values of phenolphthalin, aminophenoxyl phthalonitrile and paraformaldehyde are: 1:2.05:4.01, the proportion value of xylene and absolute ethanol is: 1:1.6, and the proportion value of phenolphthalin, aminophenoxyl phthalonitrile, paraformaldehyde and the mixed solvent of xylene and absolute ethanol is: 1:1.15.

[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, and the dosage ratio to the tetrahydrofuran agent is: 1:0.6. The dosage of the acid-binding agent ethylenediamine is: 0.6% of the mass of 2,6-(p-aminophenoxy)benzonitrile.

[0103] The temperature of the melt prepolymerization reaction is 130 °C, and the reaction time is 50 min; the mass ratio of the resin sizing agent to the basalt fiber cloth is 60 wt%; the drying temperature of the prepreg is 155 °C, the drying time is 15 min, the pressing pressure of the hot pressing process is 20 MPa, the program temperature is 200 °C for heat preservation and pressure holding for 2 h, 240 °C for heat preservation and pressure holding for 2 h, and 280 °C for heat preservation and pressure holding for 2 h.

[0104] Comparative Example 4

[0105] Take 10 g of the resin prepolymer, 1.5 g of the flame retardant modifier, and 2.5 g of the accelerator for melt prepolymerization to obtain 14 g of the copolymer resin prepolymer; mix methyl ethyl ketone and N,N-dimethylformamide according to a mass ratio of 5 g:3 g to obtain 8 g of the mixed solvent.

[0106] In the preparation of the resin prepolymer, the ratio of phenolphthalein, aminophenoxyl phthalonitrile and paraformaldehyde is: 1:2.05:4.0, the ratio of xylene and absolute ethanol is: 1:1.5, and the ratio of phenolphthalein, aminophenoxyl phthalonitrile, paraformaldehyde and the mixed solvent of xylene and absolute ethanol is: 1:1.1.

[0107] 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, and the dosage ratio to the tetrahydrofuran agent is: 1:0.6. The dosage of the acid-binding agent ethylenediamine is: 0.6% of the mass of 2,6-(p-aminophenoxy)benzonitrile.

[0108] The temperature of the melt prepolymerization reaction is 120 °C, and the reaction time is 50 min; the mass ratio of the resin sizing agent to the basalt fiber cloth is 30 wt%; the drying temperature of the prepreg is 155 °C, the drying time is 15 min, the pressing pressure of the hot pressing process is 20 MPa, the program temperature is 200 °C for heat preservation and pressure holding for 2 h, 240 °C for heat preservation and pressure holding for 2 h, and 280 °C for heat preservation and pressure holding for 2 h.

[0109] Comparative Examples 1-4 were respectively compared and verified from four aspects: the mass of the flame retardant modifier, the mass of the accelerator, the prepolymerization reaction temperature, and the mass ratio of the resin to the fiber.

[0110] 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.

[0111] The specific test method is as follows:

[0112] The materials were cut into splines of 100×10×3 for testing according to the GBT2406.2-2009 test standard. The test stipulates that if the spline cannot meet any of the following conditions at a certain oxygen content (volume percentage): (1) extinguish within 3 minutes, (2) not burn to 5 cm below the ignition point of the spline, this critical oxygen content value is defined as the limiting oxygen index (LOI) of the spline. When the oxygen index (LOI) is less than 22%, the material is identified as a flammable material; when the oxygen index (LOI) is between 22% and 27%, the material is identified as a combustible material; when the oxygen index (LOI) is greater than 27%, the material is identified as a flame-retardant material.

[0113] The vertical burning (UL-94) test of the materials was carried out according to the ASTM D3801 standard. The sample size was 100×12×3 mm 3 . The flame retardancy of the flame-retardant polymers obtained by the limiting oxygen index (LOI) experiment test is shown in Table 1.

[0114] Table 1 Flame retardancy test results of the composite materials prepared in Examples 1-5 and Comparative Examples 1-4

[0115]

[0116] Note: In Comparative Example 3, the resin pre-polymerization process was gelled due to too high pre-polymerization temperature, and it could not be further dissolved in the solvent and impregnated on the fiber surface, so the composite material that met the test requirements could not be obtained.

[0117] The mechanical properties of the flame-retardant polymer matrix composites obtained were tested using an electronic universal testing machine with reference to the standard GB / T 1040-2006. The tensile rate was 10 mm / min, and each group of samples was tested 5 times to obtain the average value. The results are as Figure 1 shown.

[0118] The thermal stability of the flame-retardant polymers obtained was tested using a thermogravimetric analyzer (TGA, TA Q50) with reference to the standard GB / T 2951.41-2008. About 10 mg of resin polymer was scraped from the surface of the fiber-reinforced polymer matrix composite and placed in a crucible. Under an oxygen atmosphere, it was heated from 40 °C to 800 °C at a heating rate of 20 °C / min, and the nitrogen gas flow rate was 50 mL / min. The results are shown in Table 2.

[0119] Table 2 Thermal stability test parameters of the composite materials prepared in Examples 1-5 and Comparative Examples 1-4

[0120] Sample / Test Item <![CDATA[Thermal decomposition temperature (T 5％ )]]> <![CDATA[Thermal decomposition temperature (T 10％ )]]> Residual Carbon Ratio (800 °C) Example 1 385.3 442.1 65.3 Example 2 389.1 448.5 68.1 Example 3 395.7 456.7 70.4 Example 4 389.9 449.1 69.8 Example 5 394.3 458.2 68.7 Comparative Example 1 386.5 447.1 68.0 Comparative Example 2 365.9 436.1 63.7 Comparative Example 3 - - - Comparative Example 4 387.7 451.2 69.0

[0121] Through Figure 1As can be seen from Table 1-2, the prepared basalt fiber-reinforced flame-retardant polymer matrix composite material has the following advantages:

[0122] ① Excellent flame retardancy, with a limiting oxygen index above 27%, meeting the standard of flame-retardant materials. Among them, the flame retardant modifier and promoter play an important role in improving the flame retardancy. With the addition of the flame retardant modifier, the limiting oxygen index of the composite system reaches 40%, showing excellent flame retardant characteristics. The addition of the promoter can, to a certain extent, promote the ring-opening reaction of the benzoxazine ring in the resin prepolymer, and then trigger the ring-forming polymerization of the prepolymer and the nitrile group in the flame retardant modifier, forming a nitrogen-containing aromatic heterocyclic structure, improving the flame retardancy of the system from the polymer molecular structure aspect;

[0123] 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 to the high structural strength of the basalt fiber itself on the one hand and the outstanding structural properties of the polymer matrix on the other hand. Ultimately, it is due to the high degree of polymerization and high crosslinking density of the polymer matrix; In Comparative Example 4, the flexural strength and modulus decreased mainly because the resin content was too low during the preparation of the composite material, resulting in insufficient adhesion between the fiber cloth layers, obvious delamination during the test, and significant deterioration of the structural properties;

[0124] ③ Outstanding thermal stability, with the initial decomposition temperature (T5%) of the material above 380 °C and the char residue at 800 °C as high as 65%, verifying again the high degree of polymerization of the polymer matrix and the high thermal stability of the composite material. Therefore, the flame-retardant polymer matrix composite material obtained through the above examples can be used in high-performance flame-retardant material fields such as aerospace and mechanical ships.

[0125] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same and similar parts among the embodiments, reference can be made to each other.

[0126] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

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

2. A method for preparing a basalt fiber-reinforced fireproof and flame-retardant polymer matrix composite material comprising the resin prepolymer described in 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) stacking the basalt fiber prepregs, placing them in a flat mold, and pressing the laminated plates through a hot pressing process to obtain a basalt fiber reinforced fire-retardant polymer-based composite material; The flame retardant modifier in step (1) contains a nitrile group and has the structural formula: The accelerator in step (1) is a tetraglycidylamine type epoxy resin; the melt prepolymerization temperature is 80 to 120° C., and the prepolymerization time is 30 to 60 minutes; 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); 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.

3. The preparation method of the basalt fiber reinforced fireproof and flame-retardant polymer matrix composite material according to claim 2, 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.

4. The preparation method of the basalt fiber reinforced fireproof and flame-retardant polymer matrix composite material according to claim 2, characterized in that, In step (4), the number of layers of the basalt fiber prepreg is 6 to 10 layers, and the hot pressing process is as follows: the pressure is maintained at 15 - 20 MPa, the programmed temperature is 200 °C for heat preservation and pressure holding for 2 - 4 h, 220 - 240 °C for heat preservation and pressure holding for 2 - 4 h, and 260 - 280 °C for heat preservation and pressure holding for 2 - 4 h.

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