Basalt fiber composite material and preparation method and application thereof

Abstract

This invention relates to the field of composite materials and their preparation technology, and particularly to a basalt fiber composite material, its preparation method, and its applications. This invention significantly reduces the internal porosity of the basalt fiber composite material through graded densification, improving its heat resistance and the stability of its flame-retardant reaction. Through interface treatment and modification, this invention enhances the interfacial bonding strength and thermal shock resistance between the basalt fiber and the resin matrix. Furthermore, by constructing a flame-retardant coating, this invention further enhances the flame-retardant barrier properties and durability of the basalt fiber composite material. The preparation method provided by this invention can address multi-scale porous structures, achieving step-by-step matrix filling through controllable graded densification, and combined with high-adhesion surface flame-retardant coating treatment, to construct a denser, more stable basalt fiber composite material with excellent flame-retardant properties.

Description

Technical Field

[0001] This invention relates to the field of fiber composite materials and their preparation technology, and in particular to a basalt fiber composite material, its preparation method and application. Background Technology

[0002] Basalt fiber, a continuous inorganic fiber prepared from natural basalt ore, possesses excellent mechanical properties, heat resistance, and chemical stability, and has gained widespread attention in recent years in fields such as transportation, building fire protection, special protection, and structural reinforcement. Compared to glass fiber, basalt fiber has advantages in temperature resistance, dielectric stability, and environmental friendliness; compared to carbon fiber, basalt fiber has a lower cost and better flame retardant and high-temperature resistance properties. Therefore, basalt fiber composites are considered important candidate materials for achieving highly flame-retardant and highly reliable structural components.

[0003] However, existing basalt fiber composites still have significant shortcomings in terms of flame retardancy, density, and interfacial bonding performance. Firstly, due to the low surface chemical activity of basalt fibers, the interfacial bonding ability between basalt fibers and the resin matrix is ​​limited, resulting in insufficient interlayer strength in basalt fiber composites. This, in turn, affects the adhesion of flame-retardant coatings and the overall durability of the basalt fiber composites. Secondly, in the preparation process of conventional resin-based or inorganic-based composites, it is difficult to completely eliminate micropores and residual channels within the material. The porous structure accelerates the thermal decomposition process, reduces flame-retardant efficiency, and affects mechanical stability. Furthermore, the method of directly applying flame-retardant coatings to improve flame retardancy generally suffers from insufficient adhesion, poor thermal shock resistance, and easy detachment, failing to meet the long-term use requirements under complex loads and thermal environments.

[0004] In summary, existing basalt fiber composite materials suffer from defects such as difficulty in effectively eliminating internal pores, insufficient interfacial bonding strength, and poor durability of flame-retardant coatings. Overcoming the technical bottlenecks of weak interfacial bonding, high porosity, and unstable flame-retardant effect of basalt fiber composite materials is an urgent problem to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides a basalt fiber composite material, its preparation method and application. The basalt fiber composite material provided by the present invention has a dense structure, stable interface and excellent flame retardant properties.

[0006] This invention provides a method for preparing basalt fiber composite materials, comprising the following steps: 1) Basalt fibers are sequentially laid up and shaped to obtain basalt fiber preforms; 2) The basalt fiber preform is subjected to interface treatment, interface modification, graded densification, impregnation with functionalized flame-retardant resin, curing, and coating with flame-retardant coating in sequence to obtain the basalt fiber composite material; the graded densification includes a first densification, which includes the following steps: impregnating the interface-modified basalt fiber preform in resin and then sequentially venting, pressure impregnation, and curing; the resin includes one or more of epoxy resin and phenolic resin; the viscosity of the resin at 25°C is 150~300 mPa·s.

[0007] Preferably, the fiber arrangement of the layup is an orthogonal layup or a quasi-isotropic layup; the areal density of a single layer of fiber in the layup is 300~500 g / m³. 2 The thickness of the basalt fiber preform is 4-6 mm; the fiber volume fraction of the basalt fiber preform is 20-25%.

[0008] Preferably, the interface treatment is plasma activation; the plasma activation uses a mixed gas of Ar and O2; the volume ratio of Ar to O2 is 4~9:1; the power of plasma activation is 180~260W, and the plasma activation time is 8~15 minutes.

[0009] Preferably, the interface modification includes the following steps: mixing an inorganic precursor, a silane coupling agent and a solvent to obtain a sol, impregnating the interface-treated basalt fiber preform in the sol and then drying it to form an inorganic nano-interface layer.

[0010] Preferably, after the first densification, the product is further densified or pressed into shape; the second densification is resin impregnation pyrolysis or polymer impregnation pyrolysis (PIP); the resin impregnation pyrolysis includes the following steps: impregnating the first densified basalt fiber preform in resin and then drying and pyrolyzing it in sequence, wherein the resin is the same as the resin used in the first densification.

[0011] Preferably, the impregnation of the functionalized flame retardant resin includes the following steps: mixing resin and flame retardant particles to obtain a functionalized flame retardant resin, and then impregnating the graded and densified basalt fiber preform in the functionalized flame retardant resin, wherein the resin is the same as the resin used for the first densification.

[0012] Preferably, the impregnation in the functionalized flame-retardant resin includes sequential initial impregnation and subsequent impregnation, or direct impregnation; the impregnation solution used for the initial impregnation is a functionalized flame-retardant resin containing phosphorus-based flame-retardant particles; the content of phosphorus-based flame-retardant particles in the impregnation solution used for the initial impregnation is 10-12 wt%; the impregnation solution used for the subsequent impregnation is a functionalized flame-retardant resin containing silicon-based flame-retardant particles; the content of silicon-based flame-retardant particles in the impregnation solution used for the subsequent impregnation is 8-10 wt%.

[0013] Preferably, the flame-retardant coating comprises one of a high-temperature resistant inorganic ceramic coating and a silicon-phosphorus composite coating; the silicon-phosphorus composite coating is an intumescent silicon-phosphorus flame-retardant coating; the coating of the intumescent silicon-phosphorus flame-retardant coating comprises the following components in parts by weight: 40 parts of water-based silicone-acrylic emulsion, 30 parts of ammonium polyphosphate, 15 parts of pentaerythritol (PER), 10 parts of melamine (MEL), 5 parts of nano-silica, and deionized water; the amount of deionized water added is based on the viscosity of the intumescent silicon-phosphorus flame-retardant coating being 25-26 s.

[0014] The present invention also provides a basalt fiber composite material obtained by the preparation method described above, comprising a basalt fiber reinforcement, a functionalized flame-retardant resin coated on the surface of the basalt fiber reinforcement, and a flame-retardant coating coated on the surface of the functionalized flame-retardant resin; wherein the basalt fiber reinforcement comprises a basalt fiber matrix and a fiber reinforcing phase distributed in the basalt fiber matrix.

[0015] The present invention also provides the application of the basalt fiber composite material described above in the fields of flame retardancy, structural reinforcement, or special protection.

[0016] This invention provides a method for preparing basalt fiber composite materials. The invention significantly reduces the internal porosity of the basalt fiber composite material (≤3%) through graded densification, improving heat resistance and the stability of the flame-retardant reaction. Through interfacial chemical strengthening (interfacial treatment) and inorganic nanolayer deposition (interfacial modification), the invention enhances the interfacial bonding strength between basalt fibers and the resin matrix (interlayer shear strength increased by more than 40%) and thermal shock resistance. Furthermore, by constructing a high-temperature resistant surface coating (flame-retardant coating), the invention further enhances the flame-retardant barrier properties and durability of the basalt fiber composite material. The preparation method provided by this invention can address multi-scale porous structures, achieving stepwise matrix filling through controllable graded densification, and combined with high-adhesion surface flame-retardant coating treatment, to construct a denser, more stable basalt fiber composite material with excellent flame-retardant properties.

[0017] Furthermore, traditional methods for preparing basalt fiber composites rely on empirical parameter tuning. This invention, based on graded densification and surface coating treatment, achieves a unified approach to high flame retardancy, high stability, and engineerable preparation of basalt fiber composites through a multi-stage densification strategy, interfacial chemical reinforcement, and a high heat-resistant and flame-retardant coating.

[0018] This invention also provides a basalt fiber composite material obtained by the preparation method described above. The basalt fiber composite material provided by this invention has a limiting oxygen index (LOI) ≥38%, a vertical burning rating of V-0, and a coating adhesion rating of 0 in the cross-cut adhesion test.

[0019] This invention also provides applications of the basalt fiber composite material described above in flame retardancy, structural reinforcement, or special protection fields. The basalt fiber composite material provided by this invention achieves a synergistic improvement in low porosity, excellent flame retardancy, and good mechanical properties. It is suitable for load-bearing components with high flame retardancy and structural reliability requirements, and has broad application prospects in the transportation and construction industries, such as for fireproof and heat-insulating structures, flame-retardant panels, fireproof building partitions, and protective components for transportation equipment. It has significant engineering application value and promising prospects for widespread application. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of this invention, the accompanying drawings used in the embodiments of this invention or in the prior art are briefly described below. For those skilled in the art, other drawings can be derived from the following drawings without creative effort, and all such drawings are within the protection scope of this invention.

[0021] Figure 1 This is a process flow diagram for preparing basalt fiber composite materials according to the present invention. Detailed Implementation

[0022] This invention provides a method for preparing basalt fiber composite materials, comprising the following steps: 1) Basalt fibers are sequentially laid up and shaped to obtain basalt fiber preforms; 2) The basalt fiber preform is subjected to interface treatment, interface modification, graded densification, impregnation with functional flame-retardant resin, curing and coating with flame-retardant coating in sequence to obtain the basalt fiber composite material.

[0023] The process flow for preparing basalt fiber composite materials according to this invention is as follows: Figure 1 As shown. This invention involves sequentially laying and molding basalt fibers to obtain a basalt fiber preform. In this invention, the basalt fibers are preferably basalt fiber felt or continuous basalt fiber yarn; the basalt fiber felt is preferably chopped basalt fiber felt; the monofilament diameter of the continuous basalt fiber yarn is preferably 10-15 micrometers, more preferably 12-13 micrometers.

[0024] In this invention, the fiber arrangement of the layup is preferably orthogonal layup or quasi-isotropic layup; the areal density of the single-layer fiber of the layup is preferably 300~500 g / m³. 2 More preferably 400g / m 2 The number of layers is preferably 8 to 12, more preferably 10.

[0025] This invention regulates the internal multi-scale pore structure of basalt fiber preforms by adjusting the layup density, number of layers, and fiber arrangement. The pore size is distributed in the range of micrometers to sub-millimeters, constructing a fiber skeleton with controllable multi-scale pores. This provides controllable channels and mechanical support for resin penetration in the subsequent impregnation process, and provides a structural basis for graded densification and interface treatment.

[0026] In this invention, the forming method is preferably needle punching or weaving; the weaving is preferably two-dimensional weaving or three-dimensional weaving.

[0027] In this invention, the needle punching preferably includes the following steps: layering and mechanically reinforcing basalt fiber felt in sequence.

[0028] In this invention, the weaving preferably includes the following steps: using a two-dimensional plain weave fabric or a three-dimensional Z-axis weave fabric as the base fabric, and weaving continuous basalt fiber yarns.

[0029] In this invention, the thickness of the basalt fiber preform is preferably 4 to 6 mm, more preferably 5 mm.

[0030] In this invention, the fiber volume fraction of the basalt fiber preform is preferably 20-25%, more preferably 22-24%.

[0031] After obtaining the basalt fiber preform, the present invention sequentially performs interface treatment, interface modification, graded densification, impregnation with functionalized flame-retardant resin, curing (referred to as the first curing), and coating with a flame-retardant coating to obtain the basalt fiber composite material. In the present invention, the interface treatment preferably includes pretreatment of the basalt fiber preform; the pretreatment includes sequential cleaning and drying (referred to as the first drying).

[0032] In this invention, the cleaning reagent is preferably one or more of acetone and isopropanol; the cleaning is preferably ultrasonic cleaning; the ultrasonic cleaning power is preferably 200~300W, more preferably 240~270W; the cleaning time is preferably 8~12 minutes, more preferably 10 minutes.

[0033] In this invention, the temperature of the first drying is preferably 75-85 degrees Celsius, more preferably 80 degrees Celsius, and the heat preservation time is preferably 1.5-2.5 hours, more preferably 2 hours.

[0034] In this invention, the interface treatment is preferably plasma activation. By using interface treatment during the fiber reinforcement phase preparation stage, this invention effectively enhances the surface energy and chemical reactivity (wettability) of basalt fibers, thereby strengthening the interfacial bonding strength between the resin matrix and the subsequent functionalized flame-retardant coating and the basalt fibers.

[0035] In this invention, the plasma activation preferably uses a mixed gas of Ar and O2; the volume ratio of Ar to O2 is preferably 4~9:1, more preferably 5~8:1, and even more preferably 6~7:1; the plasma activation power is preferably 180~260W, more preferably 220~230W, and the plasma activation time is preferably 8~15 minutes, more preferably 10~13 minutes. This invention introduces oxygen-containing polar groups (e.g., hydroxyl, carbonyl groups) onto the surface of basalt fibers through interface treatment, increasing the surface energy to ≥70mN / m, which is beneficial for the subsequent deposition and wetting of the interface modification layer.

[0036] In this invention, the interface modification preferably includes the following steps: mixing an inorganic precursor, a silane coupling agent, and a solvent (denoted as the first mixture) to obtain a sol; impregnating the interface-treated basalt fiber preform in the sol (denoted as the first impregnation) and then drying it (denoted as the second drying) to form an inorganic nano-interface layer. The interface modification described above in this invention is a sol-gel interface modification, which involves uniformly dispersing silicon-based or aluminum-based nanoparticles in an alcohol solution containing a silane coupling agent, followed by impregnation and drying to form an inorganic nano-interface layer, thereby significantly improving the bonding strength and thermal stability of the basalt fiber and resin matrix interface.

[0037] In this invention, the inorganic precursor preferably includes tetraethyl orthosilicate (TEOS) or aluminum isopropoxide (AIP).

[0038] In this invention, the concentration of the inorganic precursor in the sol is preferably 1-5 wt%, more preferably 2-4 wt%, and even more preferably 3 wt%.

[0039] In this invention, the silane coupling agent is preferably γ-aminopropyltriethoxysilane (KH-550).

[0040] In this invention, the concentration of the silane coupling agent in the sol is preferably 0.5 to 2 wt%, more preferably 1 to 1.5 wt%.

[0041] In this invention, the solvent of the silane coupling agent solution is preferably ethanol, specifically anhydrous ethanol.

[0042] In this invention, the first mixing is preferably stirring; the stirring temperature is preferably room temperature (20~35 degrees Celsius), and the stirring time is preferably 0.8~1.2 hours, more preferably 1 hour. Through the above mixing, this invention obtains a uniform and transparent sol.

[0043] In this invention, the temperature of the first impregnation is preferably room temperature (20~35 degrees Celsius), and the impregnation time is preferably 10~20 minutes, more preferably 15 minutes.

[0044] In this invention, the temperature of the second drying is preferably 60-80 degrees Celsius, more preferably 70 degrees Celsius, and the heat preservation time is preferably 1.5-2.5 hours, more preferably 2 hours.

[0045] In this invention, the inorganic nano-interface layer contains SiO2 or Al2O3; the thickness of the inorganic nano-interface layer is preferably 300-600 nanometers, more preferably 400-500 nanometers.

[0046] The fiber-reinforced body constructed in this invention can be shaped in a mold, and edge dimensions or opening positions can be reserved according to structural installation requirements to ensure the structural compatibility and dimensional accuracy of the product.

[0047] In this invention, the graded densification preferably includes a first densification. This invention employs a strategy of "low-viscosity pre-impregnation, vacuum-assisted degassing, pressure impregnation, and curing" to achieve the stepwise filling of multi-scale pores within the reinforcement.

[0048] In this invention, the first densification preferably includes the following steps: impregnating the interface-modified basalt fiber preform in resin (referred to as the second impregnation), followed by sequential degassing, pressure impregnation, and curing (referred to as the second curing). This invention, through the first densification, fills the micropores of the basalt fiber preform.

[0049] In this invention, the resin preferably includes one or more of epoxy resin and phenolic resin; the epoxy resin is preferably E-51 type bisphenol A epoxy resin; and the phenolic resin is preferably 2123 type phenolic resin.

[0050] In this invention, the viscosity (25°C) of the resin is preferably 150~300 mPa·s, more preferably 200~250 mPa·s.

[0051] In this invention, the resin preferably further includes a curing agent; the curing agent preferably includes methyltetrahydrophthalic anhydride; the mass ratio of the resin to the curing agent is preferably 100:15~25, more preferably 100:20.

[0052] In this invention, the temperature of the second immersion is preferably 25-40 degrees Celsius, more preferably 30-35 degrees Celsius, and the immersion time is preferably 10-20 minutes, more preferably 15 minutes.

[0053] In this invention, the venting is preferably carried out in a vacuum chamber; the vacuum degree of the venting is preferably not less than -0.095 MPa, more preferably -0.096 to -0.095 MPa, and the venting time is preferably 10 to 15 minutes, more preferably 12 minutes. This invention removes residual gases and volatiles from the interior through venting.

[0054] In this invention, the pressure for pressure impregnation is preferably 0.2~0.4 MPa, more preferably 0.3 MPa, and the holding time is preferably 15~30 minutes, more preferably 20~25 minutes. This invention, through pressure impregnation, promotes the resin to penetrate deeper into larger pore areas, completing the filling of mesoscale pores.

[0055] In this invention, the second curing temperature is preferably 140-160 degrees Celsius, more preferably 150 degrees Celsius, and the holding time is preferably 20-40 minutes, more preferably 30 minutes. Through the second curing process, this invention enables the overall structure to form a stable and dense cured network.

[0056] In this invention, the first densification preferably further includes a second densification or compression molding of the resulting product; the second densification is preferably performed at least once, more preferably 1 to 2 times. Through the second densification, this invention can further improve the density of the product. Through the second densification or compression molding, this invention can achieve macroscopic closure of the basalt fiber preform.

[0057] In this invention, the second densification is preferably resin impregnation pyrolysis or polymer impregnation pyrolysis; the resin impregnation pyrolysis preferably includes the following steps: impregnating the first densified basalt fiber preform in resin (referred to as the third impregnation) and then drying (referred to as the third drying) and pyrolyzing in sequence.

[0058] In this invention, the resin is preferably the same as the resin used in the first densification process, and will not be described again here.

[0059] In this invention, the parameters of the third impregnation are preferably the same as those of the second impregnation, and will not be repeated here.

[0060] In this invention, the temperature of the third drying is preferably 70-90 degrees Celsius, more preferably 80 degrees Celsius, and the heat preservation time is preferably 1.5-2.5 hours, more preferably 2 hours.

[0061] In this invention, the pyrolysis temperature is preferably 200-300 degrees Celsius, more preferably 240-270 degrees Celsius, and the holding time is preferably 0.8-1.2 hours, more preferably 1 hour.

[0062] In this invention, the pressing is preferably hot pressing or isostatic pressing.

[0063] In this invention, the preferred temperature for hot pressing is 140-160 degrees Celsius, more preferably 150 degrees Celsius; the preferred pressure is 0.5-1 MPa, more preferably 0.8 MPa; and the preferred holding time is 20-40 minutes, more preferably 30 minutes. This invention achieves final densification through hot pressing, reducing the porosity of the basalt fiber composite material to below 3%.

[0064] In this invention, the impregnation of functionalized flame retardant resin preferably includes the following steps: mixing resin and flame retardant particles (referred to as the second mixing) to obtain functionalized flame retardant resin, and then impregnating the graded and densified basalt fiber preform in the functionalized flame retardant resin (referred to as the fourth impregnation).

[0065] In this invention, the resin is preferably the same as the resin used in the first densification process, and will not be described again here.

[0066] In this invention, the flame-retardant particles preferably include one or more of phosphorus-based flame-retardant particles, boron-based flame-retardant particles, and silicon-based flame-retardant particles; the phosphorus-based flame-retardant particles preferably include ammonium polyphosphate (APP); the boron-based flame-retardant particles preferably include zinc borate (ZnB2O4); and the silicon-based flame-retardant particles preferably include nano-silica (SiO2).

[0067] In this invention, the particle size of the flame-retardant particles is preferably 50-300 nanometers, more preferably 100-250 nanometers, and even more preferably 150-200 nanometers.

[0068] In this invention, the mass ratio of the flame-retardant particles to the resin is preferably 5~15:100, more preferably 8~13:100, and even more preferably 10:100.

[0069] In this invention, the second mixing is preferably stirring; the stirring speed is preferably 800-1200 rpm, more preferably 1000 rpm; the second mixing time is preferably 1-2 hours, more preferably 1.5 hours. This invention obtains a uniform and stable flame-retardant system by controlling the mixing rate and the viscosity of the resin, ensuring no agglomeration.

[0070] In this invention, the fourth impregnation preferably includes sequential initial impregnation and subsequent impregnation, or direct impregnation; the impregnation solution used for the initial impregnation is preferably a functionalized flame-retardant resin containing phosphorus-based flame-retardant particles; the content of phosphorus-based flame-retardant particles in the impregnation solution used for the initial impregnation is preferably 10-12 wt%, more preferably 11 wt%; the initial impregnation time is preferably 18-22 minutes, more preferably 20 minutes; the impregnation solution used for the subsequent impregnation is preferably a functionalized flame-retardant resin containing silicon-based flame-retardant particles; the content of silicon-based flame-retardant particles in the impregnation solution used for the subsequent impregnation is preferably 8-10 wt%, more preferably 9 wt%; the subsequent impregnation time is preferably 10-14 minutes, more preferably 12 minutes.

[0071] In this invention, the direct immersion time is preferably 22 to 27 minutes, more preferably 25 minutes.

[0072] This invention utilizes segmented impregnation with functionalized flame-retardant resins in different proportions. The initial impregnation is rich in phosphorus-based flame-retardant particles to promote internal charring, while the subsequent impregnation is rich in silicon-based flame-retardant particles to enhance the surface oxidation barrier. This allows the flame-retardant components to form a gradient distribution within the material, thereby improving internal charring efficiency and enhancing surface oxidation barrier, thus significantly improving overall flame-retardant performance and flame stability.

[0073] In this invention, the first curing temperature is preferably 155-165 degrees Celsius, more preferably 160 degrees Celsius, and the heat preservation time is preferably 35-45 minutes, more preferably 40 minutes.

[0074] In this invention, the flame-retardant coating preferably includes one of a high-temperature resistant inorganic ceramic coating and a silicon-phosphorus composite coating; the silicon-phosphorus composite coating is preferably an intumescent silicon-phosphorus flame-retardant coating; the coating material of the intumescent silicon-phosphorus flame-retardant coating preferably includes the following components in parts by weight: 40 parts of water-based silicone-acrylic emulsion, 30 parts of ammonium polyphosphate, 15 parts of pentaerythritol, 10 parts of melamine, 5 parts of nano-silica, and deionized water; the amount of deionized water added is based on the coating material of the intumescent silicon-phosphorus flame-retardant coating reaching the application viscosity; the application viscosity is preferably 25~26s, more preferably 25s.

[0075] In this invention, the method for testing the application viscosity is as follows: using a Forte-4 cup viscometer (standard instrument), at an ambient temperature of 25℃±1℃, the coating of the intumescent silicon-phosphorus flame retardant coating is poured into the cup and the bottom orifice is opened, and the time it takes for the coating of the intumescent silicon-phosphorus flame retardant coating to completely flow out is measured.

[0076] In this invention, the solid content of the aqueous silicone-acrylic emulsion is preferably 38-42%, more preferably 40%, and the pH value is preferably 7-9, more preferably 8. In specific embodiments of this invention, the aqueous silicone-acrylic emulsion preferably includes one or more of the following: Badifu RS-9868 aqueous silicone-acrylic emulsion, Sanmu Chemical 3M-680 aqueous silicone-acrylic emulsion, and BASF Acronal® S 760 aqueous silicone-acrylic emulsion.

[0077] In this invention, the particle size of the nano-silica is preferably 45-55 nanometers, and more preferably 50 nanometers.

[0078] In this invention, the process of applying the flame-retardant coating preferably includes sequentially washing and roughening the resulting product; the washing reagent preferably includes one or more of acetone and isopropanol; the washing is preferably ultrasonic cleaning; and the washing time is preferably 8-12 minutes, more preferably 10 minutes. This invention removes surface impurities through washing.

[0079] In this invention, the roughening is preferably achieved by sanding; the sandpaper used for sanding is preferably 240# sandpaper. This invention increases the adhesion of the flame-retardant coating through roughening.

[0080] In this invention, the preferred method for applying the flame-retardant coating is spraying; the preferred number of spraying applications is 2 to 3; the preferred interval between two consecutive spraying applications is 2 hours; the spraying is preferably carried out with a total dry film thickness of 100 to 120 micrometers, more preferably 110 micrometers. For areas subject to significant thermal shock, a multi-layer coating strategy (e.g., 3 layers) can be used to improve durability.

[0081] In this invention, the process of applying the flame-retardant coating preferably includes curing the resulting product (referred to as the third curing).

[0082] In this invention, the third curing temperature is preferably 180-220 degrees Celsius, more preferably 190-210 degrees Celsius, and even more preferably 200 degrees Celsius. The holding time is preferably 2-4 hours, more preferably 3 hours. Through the above curing process, this invention forms a dense, continuous, highly adhesive flame-retardant protective layer with ceramicization potential.

[0083] Through the above steps, this invention achieves a complete process integration of basalt fiber composite materials, from fiber reinforcement construction, interfacial chemical strengthening, multi-level densification treatment to the construction of high-performance flame-retardant coatings, enabling the basalt fiber composite materials provided by this invention to obtain high flame retardancy, high stability and good consistency in engineering preparation.

[0084] In this invention, the third curing step preferably includes cutting and dimensional trimming of the resulting product.

[0085] The present invention also provides a basalt fiber composite material obtained by the preparation method described above, comprising a basalt fiber reinforcement, a functionalized flame-retardant resin coated on the surface of the basalt fiber reinforcement, and a flame-retardant coating coated on the surface of the functionalized flame-retardant resin; wherein the basalt fiber reinforcement comprises a basalt fiber matrix and a fiber reinforcing phase distributed in the basalt fiber matrix.

[0086] The present invention also provides the application of the basalt fiber composite material described above in the fields of flame retardancy, structural reinforcement, or special protection.

[0087] The basalt fiber composite material provided by this invention achieves a synergistic improvement in low porosity, excellent flame retardancy and good mechanical properties. It is suitable for load-bearing components with high flame retardancy and structural reliability requirements, and has broad application prospects in the transportation or construction industries. For example, it can be used for fireproof and heat-insulating structures, flame-retardant panels, fireproof partitions in buildings, protective components for transportation equipment, etc., and has important engineering application value and promotion prospects.

[0088] To further illustrate the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments.

[0089] Example 1: This embodiment prepares a basalt fiber composite material, and the specific steps are as follows: 1) Basalt fiber preform: 2.5D woven, cross-laid basalt fiber fabric (monofilament diameter 13 micrometers, single-layer fiber areal density 400 g / m²). 2 The fibers are laid up to form a basalt fiber preform with a thickness of 5 mm and a fiber volume fraction of 22%.

[0090] 2) Interface treatment: The prepared basalt fiber preform was ultrasonically cleaned with isopropanol for 10 minutes, dried at 80 degrees Celsius for 2 hours, and then placed in an Ar / O2 (Ar and O2 volume ratio 4:1) plasma device and treated at 220W power for 10 minutes.

[0091] 3) Interface modification: Prepare an anhydrous ethanol solution of 2wt% tetraethyl orthosilicate and 1wt% γ-aminopropyltriethoxysilane. Immerse the interface-treated basalt fiber preform in the prepared anhydrous ethanol solution for 15 minutes and dry at 70°C for 2 hours.

[0092] 4) Graded densification: The interface-modified basalt fiber preform is impregnated in a mixed resin composed of E-51 type bisphenol A epoxy resin (viscosity 200 mPa·s at 25℃) and methyltetrahydrophthalic anhydride at a mass ratio of 100:20 for 15 minutes at 40 degrees Celsius, then vacuumed at -0.098 MPa for 10 minutes, then impregnated again at 0.3 MPa pressure for 20 minutes, and finally cured at 150 degrees Celsius for 30 minutes.

[0093] 5) Functionalized flame retardant resin: Add 10wt% of ammonium polyphosphate (particle size 150nm) to E-51 type bisphenol A epoxy resin and stir at 1000rpm for 1.5 hours to obtain functionalized flame retardant resin. Then, the graded and densified basalt fiber preform is directly impregnated in the functionalized flame retardant resin for 25 minutes, and then cured at 160 degrees Celsius for 40 minutes.

[0094] 6) Flame-retardant coating: Ultrasonic cleaning with acetone for 10 minutes, roughening with 240# sandpaper, spraying an intumescent silicon-phosphorus flame-retardant coating (coating components are as follows: 40 parts of water-based silicone-acrylic emulsion with 40% solid content (Badfu RS-9868 water-based silicone-acrylic emulsion), 30 parts of ammonium polyphosphate, 15 parts of pentaerythritol, 10 parts of melamine, 5 parts of nano-silica with a particle size of 50 nanometers and deionized water, with the viscosity adjusted to 25s by deionized water) for 2 coats, with an interval of 2 hours between each coat, curing at 200℃ for 3 hours, the total thickness of the dry film is 110 micrometers, and the dimensions are trimmed after cutting to obtain basalt fiber composite material.

[0095] Example 2: The preparation method in this embodiment is the same as that in Example 1, except that: 1) Replace the E-51 type bisphenol A epoxy resin in steps (4) and (5) with 2123 type phenolic resin; 2) Functional flame retardant resin to construct a gradient flame retardant system: Initial impregnation for 20 minutes and subsequent impregnation for 12 minutes were performed sequentially. The impregnation solution used for the initial impregnation contained 12wt% ammonium polyphosphate, and the impregnation solution used for the subsequent impregnation contained 8wt% nano-SiO2 (particle size 50nm). 3) Add a second densification step to the segmented densification process: The basalt fiber preform after the first densification is immersed in 2123 type phenolic resin at 30 degrees Celsius for 15 minutes, then dried at 80 degrees Celsius for 2 hours, and then pyrolyzed at 250 degrees Celsius for 1 hour.

[0096] Example 3: The preparation method in this embodiment is the same as that in Example 1, except that: 1) An anhydrous ethanol solution of 3 wt% aluminum isopropoxide and 1.5 wt% γ-aminopropyltriethoxysilane was prepared for interface modification. 2) Apply three coats of intumescent silicon-phosphorus flame retardant coating, with a total dry film thickness of 115 micrometers.

[0097] Test Example 1: The basalt fiber composite materials prepared in Examples 1-3 were subjected to the following performance tests: 1) Porosity determination: The porosity of basalt fiber composites was determined by Archimedes' drainage method in accordance with the national standard GB / T 33649–2017 "Test method for pore content of fiber reinforced plastics".

[0098] 2) Limiting Oxygen Index (LOI) Test: The limiting oxygen index of basalt fiber composite material at room temperature was determined according to GB / T 2406.2–2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics - Part 2: Room Temperature Test".

[0099] 3) Vertical flammability: The UL-94 vertical flammability rating is determined according to GB / T 2408–2008 "Determination of flammability of plastics - Horizontal and Vertical Methods".

[0100] 4) Coating adhesion test: According to GB / T 9286–2021 "Cross-cut test of paint and varnish film", the adhesion level of flame retardant coating is evaluated by cross-cut test with a 1mm spacing (0 is the best, no peeling).

[0101] 5) Interlaminar shear strength (ILSS): The interlaminar shear strength was determined using the short beam three-point bending method according to GB / T 1450.2-2005 "Test Method for Interlaminar Shear Strength of Fiber Reinforced Plastics" to evaluate the interfacial bonding performance. The test results are shown in Table 1.

[0102] Table 1. Performance test results of basalt fiber composite materials in Examples 1-3:

[0103] As shown in Table 1, the basalt fiber composite material provided by this invention has an LOI of no less than 38%, a vertical flammability rating of V-0, and a cross-cut adhesion rating of 0. This invention effectively solves the technical problem of balancing high flame retardancy, high density, and high mechanical properties in basalt fiber composite materials through a triple synergistic strategy of "multi-scale structure construction + graded densification + flame-retardant coating." The equipment and methods used are compatible with existing composite material production lines, possessing good repeatability and industrial scale-up potential, and are easily applicable to high flame-retardant engineering fields such as rail transportation, aerospace, and building fire protection.

[0104] The embodiments of the present invention have been described above; however, these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. All other embodiments obtained by those skilled in the art based on the above embodiments of the present invention without inventive effort are within the protection scope of the present invention.

Claims

1. A method for preparing a basalt fiber composite material, characterized in that, Includes the following steps: 1) Basalt fibers are sequentially laid up and shaped to obtain basalt fiber preforms; 2) The basalt fiber preform is subjected to interface treatment, interface modification, graded densification, impregnation with functional flame-retardant resin, curing and coating with flame-retardant coating in sequence to obtain the basalt fiber composite material. The graded densification includes a first densification, which includes the following steps: impregnating the interface-modified basalt fiber preform in resin, followed by sequential degassing, pressure impregnation, and curing. The resin includes one or more of epoxy resin and phenolic resin; The viscosity of the resin at 25°C is 150~300 mPa·s.

2. The preparation method according to claim 1, characterized in that, The fiber arrangement of the layup is either orthogonal layup or quasi-isotropic layup; The areal density of the single-layer fiber in the layup is 300~500 g / m². 2 ; The thickness of the basalt fiber preform is 4-6 mm; The fiber volume fraction of the basalt fiber preform is 20-25%.

3. The preparation method according to claim 1, characterized in that, The interface treatment is plasma activation, which uses a mixed gas of Ar and O2. The volume ratio of Ar to O2 is 4~9:1; The plasma activation power is 180~260W, and the plasma activation time is 8~15 minutes.

4. The preparation method according to claim 1, characterized in that, The interface modification includes the following steps: mixing an inorganic precursor, a silane coupling agent and a solvent to obtain a sol, then impregnating the interface-treated basalt fiber preform in the sol and drying it to form an inorganic nano-interface layer.

5. The preparation method according to claim 1, characterized in that, The first densification process also includes a second densification or compression molding of the resulting product; The second densification is achieved through resin impregnation pyrolysis or polymer impregnation pyrolysis; The resin impregnation pyrolysis includes the following steps: impregnating the first densified basalt fiber preform in resin and then drying and pyrolyzing it in sequence, wherein the resin is the same as the resin used for the first densification.

6. The preparation method according to claim 1, characterized in that, The impregnation of the functionalized flame retardant resin includes the following steps: mixing resin and flame retardant particles to obtain a functionalized flame retardant resin, and then impregnating the graded and densified basalt fiber preform in the functionalized flame retardant resin, wherein the resin is the same as the resin used for the first densification.

7. The preparation method according to claim 1, characterized in that, The impregnation in the functionalized flame retardant resin includes sequential initial impregnation and subsequent impregnation, or direct impregnation; The impregnation solution used in the initial impregnation is a functionalized flame retardant resin containing phosphorus-based flame retardant particles. The content of phosphorus-based flame-retardant particles in the impregnation solution used for the initial impregnation is 10-12 wt%. The impregnation solution used in the later impregnation is a functionalized flame retardant resin containing silicon-based flame retardant particles. The content of silicon-based flame-retardant particles in the impregnation solution used for the subsequent impregnation is 8-10 wt%.

8. The preparation method according to claim 1, characterized in that, The flame-retardant coating includes one of a high-temperature resistant inorganic ceramic coating and a silicon-phosphorus composite coating. The silicon-phosphorus composite coating is an intumescent silicon-phosphorus flame-retardant coating. The intumescent silicon-phosphorus flame retardant coating comprises the following components in parts by weight: 40 parts of water-based silicone-acrylic emulsion, 30 parts of ammonium polyphosphate, 15 parts of pentaerythritol, 10 parts of melamine, 5 parts of nano-silica, and deionized water; the amount of deionized water added is based on the viscosity of the intumescent silicon-phosphorus flame retardant coating being 25-26s.

9. The basalt fiber composite material obtained by the preparation method according to any one of claims 1 to 8, characterized in that, It includes a basalt fiber reinforcement, a functionalized flame-retardant resin coating the surface of the basalt fiber reinforcement, and a flame-retardant coating coating the surface of the functionalized flame-retardant resin. The basalt fiber reinforced body includes a basalt fiber matrix and a fiber reinforcing phase distributed in the basalt fiber matrix.

10. The application of the basalt fiber composite material of claim 9 in the fields of flame retardancy, structural reinforcement, or special protection.

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