A flame-retardant aerogel / resin-based composite material and a preparation method and application thereof

Abstract

The present application relates to a kind of flame-retardant aerogel / resin-based composite material and its preparation method and application, belong to new energy automobile battery safety protection technical field.Flame-retardant aerogel / resin-based composite material includes at least one layer of ceramicizable resin composite material structure layer and at least one layer of aerogel heat insulation layer;Ceramicizable resin composite material structure layer includes reinforcing fiber and ceramicizable modified resin matrix;Ceramicizable modified resin matrix includes resin matrix, ceramicizable component and synergistic flame retardant;Ceramicizable component includes ceramic filler, reinforcing filler and sintering aid with mass ratio of (0.5~1) : (0.3~0.5) :1;Aerogel heat insulation layer is modified by silane coupling agent surface;Ceramicizable resin composite material structure layer and aerogel heat insulation layer are compounded by interface coupling effect.The present application flame-retardant aerogel / resin-based composite material can be used for battery package shell, and has light weight high strength, high efficiency flame-retardant, excellent heat insulation and high temperature ablation resistance performance.

Description

Technical Field

[0001] This invention belongs to the field of new energy vehicle battery safety protection technology, and particularly relates to a flame-retardant gel / resin-based composite material, its preparation method and application. Background Technology

[0002] With the urgent need for lightweighting in new energy vehicles, traditional metal battery pack casings are gradually being replaced by thermosetting / thermoplastic composites reinforced with glass fiber (GF) and carbon fiber (CF). However, the flammability of the polymer matrix itself poses a significant safety hazard.

[0003] Currently, the mainstream technical approaches to improving the fire resistance of polymers and composite materials can generally be divided into the following routes: First, the ceramicizable flame retardant route includes (1) flame retardant filler modification: widely using halogen, phosphorus, nitrogen and inorganic hydroxides (such as aluminum hydroxide, magnesium hydroxide, etc.). These flame retardants achieve flame retardancy by endothermic decomposition, diluting oxygen or generating heat-insulating carbon layers when heated. However, halogens have environmental problems, and the amount of inorganic fillers usually needs to be very high (>60wt%) to be effective, which will seriously deteriorate the processing fluidity and mechanical properties of composite materials, and their flame retardant efficiency will rapidly decay at extreme high temperatures (>600℃), and cannot provide long-term structural support. (2) Intrinsic flame retardant resins: such as phenolic resins, polyimides, etc., which have high flame retardant ratings. However, these resins often have problems such as high brittleness, difficult processing and high cost, which limit their widespread application in large battery pack shells. (3) Ceramizable polymers: The principle is to add ceramizable components (such as silicates, borates, montmorillonite, etc.) to the polymer matrix. During normal processing at room temperature, under high-temperature flame ablation, the matrix decomposes while the filler sinters and reacts to generate a continuous porous ceramic body. This ceramic body can maintain its original structural shape, thus preserving structural integrity during a fire. Existing technologies are mostly concentrated on cable sheaths or building fireproof materials, and their application in complex structural components such as battery pack casings has not yet been observed. In particular, the integrated molding technology with thermal insulation materials remains a blank.

[0004] Second, the fireproof and heat-insulating route of aerogel: SiO2 aerogel is known as the "ultimate heat insulation material" due to its extremely low thermal conductivity (<0.013W / (m·K)) and has shown great potential in the field of high temperature protection. At present, the main attempts to combine it with composite materials are: (1) Sandwich structure: aerogel felt or board is used as core material and bonded to the composite material panel with adhesive. This method has weak interfacial bonding force and is prone to delamination failure under vibration, impact or high temperature, and increases the thickness and weight of the structure. (2) Powder filling: aerogel is ground into micro-nano powder and directly dispersed into the resin matrix. Although this method can improve the heat insulation of the matrix to a certain extent, it will seriously damage the mechanical properties and processing viscosity of the resin. More importantly, aerogel powder is very easy to agglomerate under high filling amount, forming defects, and the powder cannot form a continuous and dense heat insulation layer in the matrix, greatly reducing the heat insulation effect. (3) In-situ generation: aerogel is prepared in the interior of the composite material by sol-gel method. This process is complex, time-consuming, and has a large shrinkage rate. It also requires extremely high control over the wettability of the composite fiber skeleton, making it difficult to achieve large-scale industrial production.

[0005] In summary, existing flame-retardant technologies for composite material battery pack casings mostly focus on "delaying ignition" or "self-extinguishing upon removal of flame," lacking a systematic solution that can efficiently insulate against heat while maintaining structural integrity to "enclose the flame" in the face of continuous, extreme high-temperature environments such as "thermal runaway" of the battery.

[0006] Therefore, it is essential to provide a flame-retardant gel / resin-based composite material, its preparation method, and its application. Summary of the Invention

[0007] To address one or more technical problems existing in the prior art, this invention provides a flame-retardant gel / resin-based composite material, its preparation method, and its application. The flame-retardant gel / resin-based composite material of this invention is a battery pack shell composite material that combines lightweight, high strength, high efficiency in flame retardancy, excellent thermal insulation, and resistance to high-temperature ablation.

[0008] The present invention provides a flame-retardant gel / resin-based composite material in a first aspect, the flame-retardant gel / resin-based composite material comprising at least one ceramizable resin composite structural layer and at least one aerogel insulation layer; the ceramizable resin composite structural layer comprises reinforcing fibers and a ceramizable modified resin matrix; the ceramizable modified resin matrix comprises a resin matrix, a ceramizable component, and a synergistic flame retardant; the ceramizable component comprises a ceramic-forming filler, a reinforcing filler, and a sintering aid in a mass ratio of (0.5~1):(0.3~0.5):1, wherein the ceramic-forming filler is selected from one or more of wollastonite, mica powder, and kaolin, the reinforcing filler is silica powder and / or diatomaceous earth, and the sintering aid is fusible glass powder; the aerogel insulation layer is surface-modified with a silane coupling agent; the ceramizable resin composite structural layer and the aerogel insulation layer are composited together through interfacial coupling.

[0009] Preferably, in the ceramizable modified resin matrix, the proportion of the ceramizable component is 10-60% of the mass of the resin matrix.

[0010] Preferably, the reinforcing fiber is glass fiber and / or carbon fiber; and / or the resin matrix is ​​one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, phenolic epoxy resin, and vinyl ester resin.

[0011] Preferably, the synergistic flame retardant is a phosphorus-nitrogen-based flame retardant.

[0012] Preferably, the phosphorus-nitrogen flame retardant is ammonium polyphosphate and / or an NP-cage-type macromolecular intumescent flame retardant.

[0013] Preferably, the aerogel insulation layer is a SiO2 aerogel insulation layer; and / or the silane coupling agent is γ-glycidoxypropyltrimethoxysilane and / or γ-aminopropyltriethoxysilane.

[0014] Preferably, the raw materials for preparing the ceramizable resin composite structural layer include the following components in parts by mass: 50-200 parts of reinforcing fiber, 100 parts of resin matrix, 10-60 parts of ceramizable component, and 5-15 parts of synergistic flame retardant.

[0015] The present invention provides, in a second aspect, a method for preparing a flame-retardant gel / resin-based composite material according to the first aspect of the present invention, the method comprising the following steps: (1) Prepare sheet molding compound or prepreg of ceramizable resin composite material; (2) The surface of the aerogel was modified with a silane coupling agent to obtain an aerogel with a silane coupling agent surface modified. (3) Lay up a ceramicizable resin composite sheet molding compound or a ceramicizable resin composite prepreg with a silane coupling agent-modified aerogel to obtain a composite; (4) The assembly is placed in a mold for molding and heating curing, and then demolded to obtain a flame-retardant gel / resin-based composite material.

[0016] Preferably, the pressure for molding and heating curing is 1~15MPa, the temperature is 80~180℃, and the time is 1~40min.

[0017] Preferably, step (2) includes: preparing a silane coupling agent solution with a concentration of 1-5 wt% using an aqueous ethanol solution, adjusting the pH of the silane coupling agent solution to 4-10 and performing pre-hydrolysis for 20-60 min to obtain a pre-hydrolyzed silane coupling agent solution, then impregnating or spraying the aerogel with the pre-hydrolyzed silane coupling agent solution, and then heat-treating it to obtain an aerogel with silane coupling agent surface modification.

[0018] Preferably, in step (2): the silane coupling agent is γ-glycidoxypropyltrimethoxysilane and / or γ-aminopropyltriethoxysilane; the aerogel is SiO2 aerogel felt or SiO2 aerogel plate; the ethanol aqueous solution is prepared by mixing anhydrous ethanol and water in a volume ratio of (8~10):1; the heat treatment temperature is 80~120℃ and the time is 0.5~2h.

[0019] In a third aspect, the present invention provides a battery pack housing, wherein the raw materials for preparing the battery pack housing include the flame-retardant gel / resin-based composite material described in the first aspect of the present invention or the flame-retardant gel / resin-based composite material prepared by the preparation method described in the second aspect of the present invention; the battery pack housing is a battery pack housing for new energy vehicles.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention breaks through the traditional single material or simple sandwich structure approach. This invention creatively proposes a battery pack shell composite material (flame-retardant gel / resin-based composite material) with a thickness gradient architecture design of "aerogel insulation layer + ceramizable resin composite material structural layer". This design enables the material to achieve temporal and spatial synergy of functions when subjected to thermal attack. The aerogel insulation layer is responsible for dealing with instantaneous high heat flux, and the ceramizable resin composite material structural layer is responsible for maintaining structural integrity under continuous high temperature. This is an important upgrade to the existing battery pack protection concept. Specifically, the flame-retardant gel / resin-based composite material integrates the ceramizable resin composite material structural layer, which is oriented towards medium and high temperature ceramization, and the aerogel insulation layer, which has been surface modified by silane coupling agent, through a molding process. In the event of battery thermal runaway, the aerogel insulation layer acts as the first line of defense, providing instantaneous and efficient heat insulation and preventing heat from being transferred inward. In particular, it solves the key problem of weak interface bonding between aerogel and resin matrix. The ceramizable resin composite material structural layer acts as the second line of defense, transforming into a structural ceramic body at high temperature, providing long-term structural support and blocking flames. This invention provides a novel material solution for addressing battery pack safety issues through a synergistic "heat insulation-structure" protection mechanism.

[0021] (2) In response to the industry technical problem of poor interfacial compatibility between aerogel and resin, this invention proposes a targeted chemical modification method for aerogel surface. By using silane coupling agents containing epoxy groups and / or amino groups to modify the surface of aerogel, active functional groups that can covalently crosslink with resin (e.g., epoxy resin) are introduced on its surface, realizing the leap from physical anchoring to chemical bonding, significantly improving the interfacial strength and durability of the laminated structure, and ensuring that it does not delaminate under harsh working conditions.

[0022] (3) This invention develops a ceramicizable resin (epoxy resin-based) composite material system suitable for compression molding of automotive parts. By optimizing the types and ratios of ceramicizable components and synergistic flame retardants, effective ceramicization is achieved within a wide temperature range of 400~900℃. Simultaneously, the method of this invention prepares the material into SMC and / or prepreg form, and molds it in one step with a silane coupling agent-modified aerogel insulation layer through a compression molding process. This establishes a complete and industrializable technical path from "SMC / prepreg preparation - aerogel surface modification - lay-up - compression molding and curing," solving the compatibility problem between high-performance materials and large-scale manufacturing processes. This invention, through an integrated material structure design with functional gradient synergy between "aerogel insulation" and "ceramizable structure" in the thickness direction, integrates the ceramicizable resin composite material structure with a silane coupling agent-modified aerogel, providing a new material and molding process for preparing battery pack shells for new energy vehicles. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention and are only used to more clearly illustrate the technical solutions of the embodiments of the present invention, so they should not be regarded as a limitation of the scope. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings of the present invention are provided for illustrative purposes only, and the proportions, sizes, and quantities of the parts in the drawings may not be consistent with the actual product.

[0024] Figure 1 These are schematic diagrams of the structure of the flame-retardant gel / resin-based composite material in some specific embodiments of the present invention; Figure 2 This is a flowchart illustrating the preparation process of the flame-retardant gel / resin-based composite material in some specific embodiments of the present invention; Figure 3 These are experimental results of the flame-retardant gel / resin-based composite material prepared in Example 3 of this invention under high-temperature flame conditions; Figure 3 In the image, (a) shows the high-temperature ablation test result; (b) shows the ablation result on the front side; and (c) shows the ablation result on the back side. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments thereof. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] This invention provides an integrated material structure that achieves gradient synergy between the functions of "aerogel thermal insulation" and "ceramizable structure" in the thickness direction. It also solves the technical problem of weak interlayer bonding between aerogel and resin-based composite materials, and provides a stable and reliable method for preparing flame-retardant aerogel / resin-based composite materials that is compatible with large-scale production in the automotive industry.

[0027] The present invention provides a flame-retardant gel / resin-based composite material in a first aspect, the flame-retardant gel / resin-based composite material comprising at least one ceramizable resin composite structural layer and at least one aerogel insulation layer; preferably, the number of ceramizable resin composite structural layers is n layers, the number of aerogel insulation layers is n-1 layers, n≥2 and is a positive integer, and the ceramizable resin composite structural layers and the aerogel insulation layers are alternately arranged, for example, as... Figure 1As shown; in some other preferred embodiments, multiple layers (e.g., two or more) of ceramizable resin composite material structural layers are first laid as a load-bearing layer, and then aerogel insulation layers and ceramizable resin composite material structural layers are alternately laid on the load-bearing layer, wherein the number of ceramizable resin composite material structural layers is at least two more than that of the aerogel insulation layer; the ceramizable resin composite material structural layer includes reinforcing fibers and a ceramizable modified resin matrix; the ceramizable modified resin matrix includes a resin matrix and ceramizable components. The ceramizable component comprises a ceramic-forming filler, reinforcing filler, and sintering aid in a mass ratio of (0.5~1):(0.3~0.5):1. The ceramic-forming filler is selected from one or more of wollastonite, mica powder, and kaolin. The reinforcing filler is silica powder (SiO2 powder) and / or diatomaceous earth. The sintering aid is fusible glass powder. Under high-temperature environments (e.g., 400~900℃ and above), the resin matrix in the ceramizable modified resin matrix undergoes pyrolysis and carbonization. This process forms a loose and porous residual carbon skeleton. Simultaneously, the fusible glass powder in the ceramizable component flows and spreads after reaching the melting temperature, wetting the ceramic filler, reinforcing filler, and residual carbon surface. The fusible glass powder binds the ceramic filler and reinforcing filler, and the ceramic filler undergoes sintering and chemical reaction to generate a continuous, porous ceramic body with a certain strength, mainly composed of Si-O-Si or Si-O-Al network structure. The reinforcing filler, as a supporting skeleton, is bonded and fixed in the ceramic network by the fusible glass powder. The residual carbon and the ceramic body are nested and composited. Under high temperature, the resin and ceramizable components in the ceramizable modified resin matrix undergo a synergistic transformation process of pyrolysis-carbonization-ceramization, and are retained and function in the final structure in the form of residual carbon and ceramic phase, forming a structurally complete ceramic protective layer that combines the high-temperature stability of ceramics with the thermal insulation performance of residual carbon. The aerogel thermal insulation layer is surface modified with a silane coupling agent. The ceramizable resin composite material structural layer and the aerogel thermal insulation layer are composited together through interfacial coupling (e.g., covalent bonding).

[0028] In this invention, at least one ceramizable resin composite structural layer and at least one aerogel insulation layer are integrally molded through a molding process to obtain the laminated structure of the flame-retardant gas gel / resin-based composite material. This flame-retardant gas gel / resin-based composite material is a thickness-gradient flame-retardant gas gel / resin-based composite material that can be used for battery pack housings, and can also be referred to as a battery pack housing composite material. When this flame-retardant gas gel / resin-based composite material is used for a battery pack housing, during normal battery pack service, the flame-retardant gas gel / resin-based composite material housing provides the required mechanical strength and stiffness due to the characteristics of fiber-reinforced composite materials. When the battery experiences thermal runaway, the local... When the temperature rises sharply to hundreds or even thousands of degrees Celsius, the aerogel insulation layer, with its nanoporous structure, rapidly exerts its superior heat insulation effect, greatly blocking the transfer of heat to the battery pack interior and other parts of the vehicle body. This buys valuable time (tens of seconds to several minutes) for occupant escape and system response, forming the first line of defense (instantaneous heat insulation) of the material and structure of this invention during a fire. When the sustained heat raises the temperature of the ceramizable resin composite material structural layer to approximately 400°C, the resin matrix begins to decompose, while the ceramizable components melt and sinter at high temperatures, reacting with the decomposition products of the synergistic flame retardant to generate a hard, porous ceramic protective layer in situ. This ceramic protective layer can firmly adhere to the undecomposed composite material skeleton, maintaining the overall structural shape of the battery pack shell, preventing the battery pack shell from softening, melting, or cracking at high temperatures, and ensuring that flames and high-temperature particles are effectively contained inside the battery pack, preventing leakage and endangering occupant safety. This forms the second line of defense (structural ceramization) of the material and structure of this invention during a fire. Through this dual "gradient" division of labor mechanism based on thickness and temperature, optimal protective performance is achieved under different temperature ranges and heat fluxes.

[0029] To address the industry-wide technical challenge of poor interfacial compatibility between aerogels and resins, this invention proposes a targeted chemical modification method for aerogel surfaces. By using silane coupling agents containing epoxy groups and / or amino groups to modify the surface of aerogels, active functional groups capable of covalently cross-linking with resins (such as epoxy resins) are introduced onto the surface, achieving a leap from physical anchoring to chemical bonding. This significantly improves the interfacial strength and durability of the laminated structure, ensuring that it does not delaminate under harsh working conditions.

[0030] According to some specific embodiments, the flame-retardant gel / resin-based composite material is a functionally graded laminate structure integrally formed by molding at least one layer of ceramizable resin composite structural layer and at least one layer of aerogel insulation layer. The interlayer interfaces are composited through interfacial cross-linking, resulting in a strong interfacial bond. The present invention does not limit the thickness of the ceramizable resin composite structural layer and the aerogel insulation layer. Those skilled in the art can conventionally select the thicknesses, for example, the thickness of each ceramizable resin composite structural layer is independently 0.5~2mm, and the thickness of each aerogel insulation layer is independently 1~3mm.

[0031] According to some preferred embodiments, the fusible glass powder is borosilicate glass powder and / or phosphate glass powder. The present invention does not particularly limit the borosilicate glass powder and / or phosphate glass powder, but preferably uses borosilicate glass powder and / or phosphate glass powder with a softening point of 400~750℃, more preferably 400~650℃. In some specific embodiments, the borosilicate glass powder can be, for example, borosilicate glass powder B-3033 or D245.

[0032] According to some preferred embodiments, in the ceramizable modified resin matrix, the proportion of the ceramizable component is 10-60% (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%) of the mass of the resin matrix, preferably 30-60% (e.g., 30%, 35%, 40%, 45%, 50%, 55% or 60%).

[0033] According to some preferred embodiments, the ceramizable component is composed of micron-sized SiO2 powder, nano-sized SiO2 powder, wollastonite, mica powder, and borosilicate glass powder in a mass ratio of (0.8~1.4):(0.4~0.7):(1.5~2.5):(0.8~1.2):(4~6). This invention has obtained the optimal ceramizable component compound formula through numerous creative experiments. This invention has found that when the mass ratio of micron-sized SiO2 powder to nano-sized SiO2 powder is too low, the ceramic skeleton is not sufficiently supported; when it is too high, it affects high-temperature fluidity. When the borosilicate glass powder content is too low, the liquid phase is insufficient, failing to effectively bind the filler; when it is too high, it leads to excessive liquid phase, excessive shrinkage of the ceramic body, or even flow, reducing refractory performance. When the mica powder is within the above range, under the promoting effect of the borosilicate glass powder, Al... 3+The release rate matches the ceramization process. This invention reveals that the ceramizable components in this compound formulation exhibit superior synergistic ceramization behavior during thermal exposure at 400–900°C. This may be because a suitable amount of borosilicate glass powder softens at 400–750°C, forming a B-Si-O amorphous network liquid phase that effectively encapsulates other inorganic components, accelerates ion diffusion, and lowers the sintering temperature, thus promoting ceramization. Suitable amounts of nano-SiO2 powder and micron-SiO2 powder serve as structural supports. Nano-SiO2 powder, with its high specific surface area and uniform dispersion in the glass phase, enhances the initial density of the framework, while micron-SiO2 powder provides rigid framework support. Together, they suppress excessive flow and deformation of the material at high temperatures, maintaining the integrity of the porous structure. Wollastonite forms an interwoven framework at high temperatures, further enhancing the toughness of the ceramic body. Mica powder, promoted by the borosilicate glass powder, releases Al at high temperatures. 3+ The process involves constructing a three-dimensional network structure with Si-O-Al bonds, which can improve the refractory properties and high-temperature residual strength of the ceramic body. Ultimately, it is beneficial to form a continuous, dense, and crack-free Si-O-Si and / or Si-O-Al ceramic body. The synergistic effect of multi-scale particles also optimizes the interfacial compatibility with the resin matrix, reduces pyrolysis porosity, and ensures that the ceramic layer and fiber skeleton are tightly bonded after ablation. The flexural strength retention rate is high, and a high degree of unity between structural integrity and fireproof and heat insulation performance under extreme high temperature conditions is achieved, which is significantly better than ceramicizable components made by mixing other components in arbitrary proportions. This invention is not a simple superposition of components, but rather achieves a phased evolution mechanism of "early skeleton formation - mid-term densification promotion - late-term structural stabilization" in the ceramicization process through multi-scale particle size matching, morphological synergy, and liquid-solid phase synergistic regulation.

[0034] According to some preferred embodiments, the particle size of the micron-sized SiO2 powder is 1~10μm, the particle size of the nano-sized SiO2 powder is 20~50nm, the particle size of the wollastonite is 10~50μm, the particle size of the mica powder is 5~30μm, and the particle size of the borosilicate glass powder is 5~30μm.

[0035] According to some preferred embodiments, the reinforcing fiber is glass fiber and / or carbon fiber; in this invention, the reinforcing fiber may be, for example, continuous or chopped glass fiber, carbon fiber or a blend of the above-mentioned fibers, fiber mat or unidirectional tape.

[0036] According to some preferred embodiments, the resin matrix is ​​one or more of bisphenol A type epoxy resin (e.g., E51 epoxy resin), bisphenol F type epoxy resin, phenolic epoxy resin, and vinyl ester resin (e.g., phenolic epoxy vinyl ester resin) to ensure excellent mechanical properties and processability; the present invention does not limit the specific type of these epoxy resins, and those skilled in the art can conventionally select them.

[0037] According to some preferred embodiments, the synergistic flame retardant is a phosphorus-nitrogen-based flame retardant.

[0038] According to some preferred embodiments, the phosphorus-nitrogen flame retardant is ammonium polyphosphate and / or an NP-cage-type macromolecular intumescent flame retardant; preferably, in the ceramizable modified resin matrix, the proportion of the synergistic flame retardant is 5-15% of the mass of the resin matrix; in this invention, preferably, the synergistic flame retardant is a phosphorus-nitrogen flame retardant. This invention has found that, compared with flame retardants such as aluminum hydroxide and magnesium hydroxide, this phosphorus-nitrogen flame retardant can synergistically work with ceramizable components, promoting char formation in the low-temperature region and participating in the ceramization reaction in the high-temperature region, thereby improving the strength of the ceramic layer.

[0039] According to some preferred embodiments, the aerogel insulation layer is a SiO2 aerogel insulation layer; and / or the silane coupling agent is γ-glycidoxypropyltrimethoxysilane (KH-560) and / or γ-aminopropyltriethoxysilane (KH-550). In this invention, it is preferred to impregnate or spray the aerogel with a silane coupling agent solution containing epoxy groups and / or amino groups, followed by heat treatment at a certain temperature (e.g., 80~120°C) to form a reactive molecular bridge on the surface of the aerogel particles; after modification, the epoxy groups and / or amino groups on the surface of the aerogel can covalently bond with the resin matrix (e.g., epoxy resin) in the ceramicizable resin composite structural layer, greatly enhancing the interlayer bonding strength.

[0040] According to some specific embodiments, the aerogel insulation layer is a SiO2 aerogel felt or a SiO2 aerogel board, and its surface is chemically modified with a silane coupling agent containing epoxy groups and / or amino groups. The SiO2 aerogel felt is a composite material composed of silica aerogel as the matrix and fiber as the reinforcing phase. The SiO2 aerogel felt as a whole combines the ultra-low thermal conductivity of aerogel with the good flexibility, tensile strength and bendability of the fiber reinforcing phase, and its macroscopic shape is a rollable and cuttable felt. The present invention does not specifically limit the SiO2 aerogel felt or SiO2 aerogel board, and can use directly purchased products or products prepared by existing methods.

[0041] According to some preferred embodiments, the raw materials for preparing the ceramizable resin composite structural layer comprise the following components in parts by mass: The raw materials for preparing the ceramizable resin composite structural layer include 50-200 parts of reinforcing fiber, 100 parts of resin matrix, 10-60 parts of ceramizable component, and 5-15 parts of synergistic flame retardant. In some specific embodiments, the raw materials for preparing the ceramizable resin composite structural layer may also include 0-8 parts of other fillers, and / or the raw materials for preparing the ceramizable resin composite structural layer may also include curing agent, accelerator, and / or flow aid. This invention does not specifically limit the type and amount of curing agent, accelerator, and / or flow aid; those skilled in the art can conventionally select and add them according to the needs of the selected resin matrix. In some specific embodiments, when the resin matrix is ​​E51 epoxy resin, the raw materials for preparing the ceramizable resin composite structural layer also include methylhexahydrophthalic anhydride (MHHPA) curing agent, N,N-dimethylbenzylamine (BDMA) accelerator, and BYK-333 flow aid (i.e., BYK-333 leveling agent). The mass ratio of the resin matrix to the curing agent is, for example, 100:(50). ~90), the mass ratio of the resin matrix to the accelerator is, for example, 100:(0.5~1), and the mass ratio of the resin matrix to the flow aid is, for example, 100:(0.2~0.5). Specifically, 100 parts of E51 epoxy resin are placed in a constant temperature stirring tank at 60~65℃ and preheated for 30 minutes to stabilize the resin flowability; MHHPA curing agent (50~90 parts) is added in sequence, and stirred at 600 rpm for 15 minutes; 0.5~1 parts of BDMA accelerator are added to improve the curing reaction rate, and stirring is continued for 5 minutes; 0.2~0.5 parts of BYK-333 flow aid are added, and stirred for 8~10 minutes to improve flowability; when the resin matrix is ​​phenolic epoxy resin, the raw materials for preparing the ceramicizable resin composite material structural layer also include dicyandiamide curing agent and urea accelerator; when the resin matrix is ​​vinyl ester resin, the raw materials for preparing the ceramicizable resin composite material structural layer also include initiator and accelerator. In this invention, "parts" refers to parts by mass. In specific embodiments and comparative examples, the unit of parts by mass can be uniformly "g" or "kg" or other weight units.

[0042] According to some preferred embodiments, the ceramizable modified resin matrix further comprises modified boronene nanosheets (filler). Preferably, the modified boronene nanosheets account for 0.5-3% of the mass of the resin matrix in the ceramizable modified resin matrix. In this invention, it is preferable to add modified boronene nanosheets to the ceramizable modified resin matrix and control their amount to 0.5-3% of the resin matrix mass. This can significantly improve the comprehensive performance of the flame-retardant gel / resin-based composite material. The possible reason is that the modified boronene nanosheets have a high specific surface area and excellent layered barrier effect. After being uniformly dispersed in the resin matrix, they can effectively improve the interfacial bonding and mechanical properties of the resin matrix, thereby enhancing the structural strength, thermal shock resistance, and dimensional stability of the flame-retardant gel / resin-based composite material. The aerogel insulation layers modified with silane coupling agents exhibit good interfacial compatibility, which is beneficial for achieving stable material composites. Under high-temperature conditions, modified boronene nanosheets can act as char-forming promoters, working synergistically with synergistic flame retardants to promote the formation of a dense char layer and inhibit heat transfer and oxygen permeation. This invention found that when the amount of modified boronene nanosheets added is too small, it is difficult to fully exert the mechanical reinforcement and char-forming promotion effects, and the improvement effect on the overall performance is not significant. On the other hand, when the amount of modified boronene nanosheets added is too large, it will lead to an increase in internal defects in the resin matrix, resulting in a decrease in interfacial bonding force. This will not only reduce the mechanical properties and processing fluidity of the material, but also weaken the density and integrity of the char layer and ceramic layer, thus adversely affecting the thermal insulation and structural stability of the flame-retardant aerogel / resin-based composite material.

[0043] According to some preferred embodiments, the preparation of the modified boronene nanosheets includes the following steps: (a) Add a silane coupling agent to an ethanol-water solution and stir until homogeneous to obtain an ethanol-water solution of the silane coupling agent. Then adjust the pH of the ethanol-water solution of the silane coupling agent to 4-10 and perform pre-hydrolysis for 20-60 min to obtain an ethanol-water solution of the pre-hydrolyzed silane coupling agent. In step (a), the silane coupling agent is γ-glycidoxypropyltrimethoxysilane (KH-560) and / or γ-aminopropyltriethoxysilane (KH-550). The ethanol-water solution is prepared by mixing anhydrous ethanol and water in a volume ratio of (8-10):1. In step (a) of this invention, acetic acid or ammonia is used to adjust the pH of the ethanol-water solution of the silane coupling agent to 4-10. 4~10. When the silane coupling agent used is γ-glycidoxypropyltrimethoxysilane (KH-560), for example, acetic acid can be used to adjust the pH of the ethanol aqueous solution of the silane coupling agent to 4~5. The present invention does not specify the amount of acetic acid used, as long as the pH of the ethanol aqueous solution of the silane coupling agent is adjusted to the target range. When the silane coupling agent used is γ-aminopropyltriethoxysilane (KH-550), for example, ammonia can be used to adjust the pH of the ethanol aqueous solution of the silane coupling agent to 9~10. The present invention does not specify the concentration and amount of ammonia, as long as the pH of the ethanol aqueous solution of the silane coupling agent is adjusted to the target range. (b) Add boronene nanosheets to an ethanol-water solution of a pre-hydrolyzed silane coupling agent and sonicate under an inert gas (such as nitrogen or argon) to obtain a boronene nanosheet suspension; the sonication temperature is 30-40°C, the sonication power is 300-500W, and the sonication time is 60-90min. (c) The boronene nanosheet suspension is stirred at 50-60°C for 2-3 hours under inert gas (such as nitrogen or argon) protection, and then separated, washed and dried to obtain modified boronene nanosheets; In this invention, for example, the suspension system obtained after stirring for 2-3 hours is centrifuged at 6000-10000 rpm for 10-20 minutes under inert gas (such as nitrogen or argon) protection, the supernatant is discarded, the precipitate is collected, anhydrous ethanol is added to the precipitate and centrifuged and washed 3 times under inert gas (such as nitrogen or argon) protection, and finally the washed precipitate is placed in a vacuum drying oven and vacuum dried at 50°C to constant weight to obtain the modified boronene nanosheets.

[0044] In this invention, the modified boronene nanosheets are prepared using raw materials comprising boronene nanosheets, a silane coupling agent, and an ethanol aqueous solution in a mass ratio of 1:(0.5~1):(50~80). A specific preparation method is as follows: silane coupling agent (KH-560) is added to the ethanol aqueous solution and stirred until homogeneous to obtain an ethanol aqueous solution of the silane coupling agent. Then, acetic acid is added to the ethanol aqueous solution of the silane coupling agent to adjust the pH to 4~5, and pre-hydrolyzing is performed for 20 minutes under stirring (300~400 rpm). After 60 min, an ethanol-water solution of the pre-hydrolyzed silane coupling agent was obtained. Boronene nanosheets were then added to the ethanol-water solution of the pre-hydrolyzed silane coupling agent, and the mixture was ultrasonically treated at 30-40°C and 300-500 W for 60-90 min under argon protection to obtain a uniform suspension of boronene nanosheets. The boronene nanosheet suspension was then stirred at 50-60°C (300-400 rpm) under argon protection for 2-3 h. The resulting suspension system after 2-3 h of stirring was then... Centrifuge at 6000-10000 rpm for 10-20 min under argon protection, discard the supernatant, collect the precipitate, add anhydrous ethanol to the precipitate and centrifuge and wash three times under argon protection. Finally, place the washed precipitate in a vacuum drying oven and vacuum dry at 50°C to constant weight to obtain the modified boronene nanosheets. Compared with unmodified boronene nanosheets, modified boronene nanosheets are more uniformly dispersed in the resin matrix and have stronger interfacial bonding, which can significantly improve the comprehensive performance of flame-retardant gel / resin-based composite materials. This invention does not specifically limit the boronene nanosheets used in the preparation of modified boronene nanosheets; commercially available products or products prepared by existing methods can be used. In this invention, the boronene nanosheets can be prepared, for example, by referring to the method in Chinese Patent CN112758950B. The average sheet diameter of the boronene nanosheets is, for example, 0.05-10 μm, preferably 1-5 μm, and the average thickness is, for example, 0.8-20 nm, preferably 4-13 nm.

[0045] In a second aspect, the present invention provides a method for preparing the flame-retardant gel / resin-based composite material according to the first aspect of the present invention, the preparation flowchart of which is shown below. Figure 2 As shown, the preparation method includes the following steps: (1) Preparation of sheet molding compound (SMC) or prepreg of ceramizable resin composite material; In this invention, the sheet molding compound or prepreg of ceramizable resin composite material is used to form a ceramizable resin composite material structural layer. The ceramizable resin composite material structural layer material is prepared in the form of sheet molding compound (SMC) or prepreg to facilitate compression molding; This invention does not specifically limit the preparation of SMC or prepreg. Those skilled in the art can make conventional choices. For example, the preparation process of the sheet molding compound (SMC) of ceramizable resin composite material is as follows: impregnate chopped fiber felt with resin paste containing resin matrix, ceramizable component and synergistic flame retardant, and then roll it up and cure it; (2) The aerogel is surface modified with a silane coupling agent to obtain an aerogel with a silane coupling agent surface modified; in this invention, the surface modification is impregnation or spraying treatment; the aerogel with a silane coupling agent surface modified forms an aerogel insulation layer; in this invention, the aerogel is an aerogel felt or aerogel board. (3) Laying (stacking) a ceramicizable resin composite sheet molding compound or a ceramicizable resin composite prepreg with a silane coupling agent-modified aerogel to obtain an assembly; In this invention, for example, a ceramicizable resin composite sheet molding compound or a ceramicizable resin composite prepreg with a silane coupling agent-modified aerogel is laid in a designed order to obtain an assembly. (4) The assembly is placed in a mold for molding and heating curing (molding), and then demolded to obtain a flame-retardant gel / resin-based composite material; In this invention, for example, the assembly is placed in a preheated mold for molding and heating curing. The molding and heating curing pressure is 1~15MPa, the molding and heating curing temperature is 80~180℃, and the molding and heating curing time is 1~40min, so that the resin is fully cured and a flame-retardant gel / resin-based composite material with a gradient of fire-retardant function in the thickness direction is prepared; In this invention, for example, after demolding the product in step (4), the product is further trimmed and polished.

[0046] According to some preferred embodiments, the pressure of the molding heat curing is 1~15MPa, the temperature is 80~180℃, and the time is 1~40min, preferably 1~30min; the heating rate of the molding heat curing can be, for example, 2~3℃ / min.

[0047] According to some preferred embodiments, step (2) includes: preparing a silane coupling agent solution with a concentration of 1~5wt% using an aqueous ethanol solution, then adjusting the pH of the silane coupling agent solution to 4~10 and performing pre-hydrolysis for 20~60 min to obtain a pre-hydrolyzed silane coupling agent solution, then impregnating or spraying the aerogel with the pre-hydrolyzed silane coupling agent solution, and then performing heat treatment to obtain an aerogel with silane coupling agent surface modification.

[0048] According to some preferred embodiments, in step (2): the silane coupling agent is γ-glycidoxypropyltrimethoxysilane (KH-560) and / or γ-aminopropyltriethoxysilane (KH-550); the aerogel is SiO2 aerogel felt or SiO2 aerogel board; the ethanol aqueous solution is prepared by mixing anhydrous ethanol and water in a volume ratio of (8~10):1; the heat treatment temperature is 80~120℃ and the time is 0.5~2h; the impregnation time is, for example, 5~20min; when spraying, the spraying amount of the pre-hydrolyzed silane coupling agent solution is 10~30g / m 2 In step (2) of this invention, acetic acid or ammonia is used to adjust the pH of the silane coupling agent solution to 4-10. When the silane coupling agent used is γ-glycidoxypropyltrimethoxysilane (KH-560), for example, acetic acid can be used to adjust the pH of the silane coupling agent solution to 4-5. This invention does not make specific limitations on the amount of acetic acid used, as long as the pH of the silane coupling agent solution is adjusted to the target range. When the silane coupling agent used is γ-aminopropyltriethoxysilane (KH-550), for example, ammonia can be used to adjust the pH of the silane coupling agent solution to 9-10. This invention does not make specific limitations on the concentration and amount of ammonia, as long as the pH of the silane coupling agent solution is adjusted to the target range.

[0049] In a third aspect, the present invention provides a battery pack housing, wherein the raw materials for preparing the battery pack housing include the flame-retardant gel / resin-based composite material described in the first aspect of the present invention or the flame-retardant gel / resin-based composite material prepared by the preparation method described in the second aspect of the present invention; the battery pack housing is a battery pack housing for new energy vehicles.

[0050] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments. The present invention may have many other embodiments, and those skilled in the art can make various corresponding changes and modifications based on the present invention without departing from its spirit and essence. However, all such corresponding changes and modifications should fall within the scope of protection of the appended claims. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials, reagents, etc., used in the following embodiments can be obtained commercially or by existing methods.

[0051] Example 1 (1) Preparation of ceramicizable resin composite sheet molding compound (SMC): a. Place 100 parts of E51 epoxy resin (Phoenix 618) in a 65℃ constant temperature stirring tank and preheat for 30 minutes to stabilize the resin flowability; add 60 parts of MHHPA curing agent in sequence and stir at 600 rpm for 15 minutes; add 0.8 parts of BDMA accelerator to improve the curing reaction rate and continue stirring for 5 minutes; add 0.3 parts of BYK-333 flow aid and stir for 10 minutes to improve flowability to obtain E51 epoxy resin mixture.

[0052] b. Using a high-speed disperser at a speed of 1200 rpm, mix 12 parts of micron-sized SiO2 (average particle size 5 μm), 10 parts of wollastonite (average particle size 10 μm), 10 parts of mica powder (average particle size 15 μm), and 24 parts of borosilicate glass powder (D245, average particle size 10 μm) and stir for 10 min until uniformly mixed to obtain a ceramicizable component. Then, add the ceramicizable component in batches (divided into three equal parts) to the E51 epoxy resin mixture obtained in step a and stir at a speed of 600 rpm for 20 min to disperse it evenly. Then, add 10 parts of NP cage-type macromolecular intumescent flame retardant (IFR-101A) and continue stirring at a speed of 600 rpm for 10 min to obtain a ceramicizable modified resin matrix as a resin paste.

[0053] c. Cut the chopped glass fiber mat (EMC600) into 300mm×300mm sheets; take half of the ceramizable modified resin matrix (resin paste) obtained in step b and evenly coat it on the conveyor belt, and scrape it with a scraper to form a resin layer; lay the cut chopped glass fiber mat on the resin layer; then evenly coat the other half of the ceramizable modified resin matrix (resin paste) obtained in step b on the chopped glass fiber mat to form the top resin layer, and press it to obtain the SMC blank; calender the SMC blank through a twin-roll calender, set the roll temperature to 70℃, the calendering pressure to 0.3MPa, and the linear speed to 0.5m / min, and wind it up and cure it to obtain ceramizable resin composite sheet molding compound (SMC); follow the same method as steps a to c above to obtain two ceramizable resin composite sheet molding compounds (SMC) with a thickness of 2mm.

[0054] (2) Aerogel modification: The SiO2 aerogel felt is cut into the required size. Silane coupling agent (KH-560) is added to an ethanol aqueous solution (made by mixing ethanol and water in a volume ratio of 9:1) and mixed evenly to obtain a silane coupling agent solution with a concentration of 2wt%. Then, acetic acid is added to the silane coupling agent solution to adjust the pH of the silane coupling agent solution to 4.5 and pre-hydrolyzes it for 30 min under stirring (speed of 300 rpm) to obtain a pre-hydrolyzed silane coupling agent solution. Subsequently, the SiO2 aerogel felt is immersed in the pre-hydrolyzed silane coupling agent solution for 10 min. After removal, it is heat-treated at 100℃ for 1 h to allow the silane coupling agent to undergo a condensation reaction with the silanol groups on the surface of the SiO2 aerogel felt, forming an active interface modification layer on the surface of the SiO2 aerogel felt, resulting in a SiO2 aerogel felt with a thickness of 3 mm modified by the silane coupling agent.

[0055] (3) Compression molding: Lay out the following layers in the order of “ceramizable resin composite sheet molding compound (2mm) - SiO2 aerogel felt with silane coupling agent surface modification (3mm) - ceramizable resin composite sheet molding compound (2mm)”, and place them in a mold preheated to 150°C for compression molding and curing. The compression molding and curing temperature is 150°C, the pressure is 3MPa, and the time is 20min. After cooling to <60°C and demolding, a flame-retardant gel / resin-based composite material with a total thickness of about 7mm is obtained.

[0056] Comparative Example 1 (1) Preparation of glass fiber epoxy resin composite sheet molding compound (SMC): a. Place 100 parts of E51 epoxy resin (Phoenix 618) in a 65℃ constant temperature stirring tank and preheat for 30 minutes to stabilize the resin flowability; add 60 parts of MHHPA curing agent in sequence and stir at 600 rpm for 15 minutes; add 0.8 parts of BDMA accelerator to improve the curing reaction rate and continue stirring for 5 minutes; add 0.3 parts of BYK-333 flow aid and stir for 10 minutes to improve flowability, and obtain the E51 epoxy resin mixture as resin paste.

[0057] b. Cut the chopped glass fiber mat (EMC600) into 300mm×300mm sheets; take half of the E51 epoxy resin mixture (resin paste) obtained in step a and evenly coat it on the conveyor belt, and use a scraper to form a resin layer; lay the cut chopped glass fiber mat on the resin layer; then evenly coat the other half of the E51 epoxy resin mixture (resin paste) obtained in step a on the chopped glass fiber mat to form the top resin layer, and press it to obtain the SMC blank; calender the SMC blank through a twin-roll calender, set the roll temperature to 70℃, the calendering pressure to 0.3MPa, and the linear speed to 0.5m / min, and then wind and cure it to obtain glass fiber epoxy resin composite sheet molding compound (SMC); according to the same method as steps a to b above, obtain 4 glass fiber epoxy resin composite sheet molding compounds (SMC) with a thickness of 2mm.

[0058] (2) Compression molding: Four 2mm thick glass fiber epoxy resin composite sheet molding compounds are laid up and placed in a mold preheated to 150℃ for compression molding and curing. The compression molding and curing temperature is 150℃, the pressure is 3MPa, and the time is 20min. After cooling to <60℃ and demolding, a glass fiber epoxy resin composite material with a total thickness of about 8mm is obtained.

[0059] Comparative Example 2 (1) Same as step (1) in Example 1.

[0060] (2) Compression molding: The layers are laid in the following order: “ceramizable resin composite sheet molding compound (2mm) - SiO2 aerogel felt (3mm) - ceramizable resin composite sheet molding compound (2mm)”. The layers are bonded together with hot melt adhesive. The layers are placed in a mold preheated to 150°C for compression molding and curing. The compression molding and curing temperature is 150°C, the pressure is 3MPa, and the time is 20min. After cooling to <60°C and demolding, an aerogel sandwich resin-based composite material with a total thickness of about 7mm is obtained.

[0061] The properties of the materials finally obtained in Example 1 and Comparative Examples 1-2 were compared in this invention, and the results are shown in Table 1. In this invention, LOI was determined according to GB / T 2406.2 standard; thermal diffusivity was determined according to ASTM E1461 standard; the ablation test was conducted using a propane flame at a temperature of 1300℃ for 30 minutes, with the flame nozzle 50 mm away from the sample surface; and the flexural strength (bending strength) was determined according to GB / T 1449 standard.

[0062] Table 1

[0063] Example 2 (1) Preparation of ceramicizable resin composite prepreg: a. Resin Mixing and Melt Dispersion: Place 100 parts of phenolic epoxy resin (Nanya 638S) in a reactor and heat to 100℃ to completely melt it; add the ceramizable components (10 parts of nano-SiO2 with an average particle size of 30nm, 20 parts of mica powder with an average particle size of 15μm, and 30 parts of borosilicate glass powder D245 with an average particle size of 10μm) and 8 parts of ammonium polyphosphate (degree of polymerization ≥1000) sequentially at 500rpm; increase the speed to 1200rpm for high-shear dispersion for 45min; cool to 80℃, add 35 parts of dicyandiamide curing agent and 3 parts of urea accelerator (N,N-dimethylurea), and continue stirring for 20min, controlling the viscosity of the system at 5×10⁻⁶. 4 ~1×10 5 mPa·s (90℃) yielded a ceramic-modified resin matrix.

[0064] b. Pre-dry the carbon fiber fabric (T700-12K plain weave fabric) in an oven at 120℃ for 2 hours; coat the ceramizable modified resin matrix obtained in step a onto release paper using a hot melt coating method to form a resin film, setting the melt temperature to 100℃ and the coating amount to 40% of the total mass of the resin matrix in the prepreg; composite the carbon fiber fabric and resin film under hot press rollers, setting the roller pressing temperature to 100℃ and the roller pressing speed to 0.5m / min, so that the resin fully impregnates the fiber, and then set it by cooling rollers and wind it up to obtain a ceramizable resin composite prepreg; the amount of carbon fiber fabric used is 150 parts; the prepreg is stored at -18℃ in a dry environment for a storage period of ≥30 days. Following the same method as steps a to b above, two ceramizable resin composite prepregs with a thickness of 1.5mm are prepared.

[0065] (2) Surface modification process of aerogel insulation layer: Add silane coupling agent (KH-550) to ethanol aqueous solution (made by mixing ethanol and water in a volume ratio of 9:1) and mix evenly to obtain a silane coupling agent solution with a concentration of 3wt%. Add ammonia water with a concentration of 28wt% to the silane coupling agent solution to adjust the pH of the silane coupling agent solution to 9.5 and perform pre-hydrolysis for 30 min under stirring (speed of 300 rpm) to obtain a pre-hydrolyzed silane coupling agent solution. Spray the pre-hydrolyzed silane coupling agent solution evenly on both sides of the SiO2 aerogel plate by spraying. Spraying amount: 20 g / m 2 Let stand for 10 minutes; then place in a 120℃ hot air circulating oven for 40 minutes to obtain a 2mm thick SiO2 aerogel plate modified with silane coupling agent; an amino-containing siloxane active layer is formed on the surface of the surface-modified SiO2 aerogel plate.

[0066] (3) Compression molding: The layers are laid in the following order: “ceramizable resin composite prepreg (1.5mm) - SiO2 aerogel sheet modified with silane coupling agent (2.0mm) - ceramizable resin composite prepreg (1.5mm)”. The layers are then placed in a mold preheated to 160°C for compression molding and curing. The compression molding and curing temperature is 160°C, the pressure is 8MPa, and the time is 25min. After cooling to <80°C and demolding, a flame-retardant aerogel / resin-based composite material with a total thickness of about 5mm is obtained.

[0067] Comparative Example 3 (1) Preparation of phenolic epoxy resin prepreg: a. Resin mixing and melt dispersion: 100 parts of phenolic epoxy resin (Nanya 638s) were placed in a reactor and heated to 100°C to completely melt it; the temperature was lowered to 80°C, and 35 parts of dicyandiamide curing agent and 3 parts of urea accelerator (N,N-dimethylurea) were added. The mixture was stirred at 500 rpm for 20 min to obtain a phenolic epoxy resin mixture.

[0068] b. Preparation of prepreg by hot melt impregnation: The carbon fiber fabric (T700-12K plain weave fabric) is pre-dried in an oven at 120℃ for 2 hours; the phenolic epoxy resin mixture obtained in step a is coated onto release paper by hot melt coating to form a resin film, with the melt temperature set at 100℃ and the coating amount being 40% of the total mass of the resin matrix in the prepreg; the carbon fiber fabric and the resin film are compounded under hot press rollers, with the roller pressing temperature set at 100℃ and the roller pressing speed at 0.5m / min, so that the resin fully impregnates the fiber, and after being shaped by cooling rollers, it is wound up to obtain the phenolic epoxy resin prepreg; the amount of carbon fiber fabric used is 150 parts. Following the same method as steps a to b above, four phenolic epoxy resin composite prepregs with a thickness of 1.5mm are prepared.

[0069] (2) Compression molding: Four phenolic epoxy resin prepreg layers with a thickness of 1.5 mm were laid up and placed in a mold preheated to 160°C for compression molding and curing. The compression molding and curing temperature was 160°C, the pressure was 8 MPa, and the time was 25 min. After cooling to <80°C and demolding, a carbon fiber reinforced phenolic epoxy resin composite material with a total thickness of about 6 mm was obtained.

[0070] The properties of the materials finally obtained in Example 2 and Comparative Example 3 were compared in this invention, and the results are shown in Table 2.

[0071] Table 2

[0072] Example 3 (1) Preparation of ceramicizable resin composite prepreg: a. Add 100 parts of phenolic epoxy vinyl ester resin (Shangwei 907) to a planetary mixer. At 300 rpm, sequentially add 12 parts of micron-sized SiO2 (average particle size 5 μm), 10 parts of wollastonite (average particle size 10 μm), 10 parts of mica powder (average particle size 15 μm), and 24 parts of borosilicate glass powder D245 (average particle size 10 μm) and stir for 10 minutes until homogeneous. Then add 10 parts of NP cage-type macromolecular intumescent flame retardant (IFR-101A) and stir for 10 minutes. Mix until homogeneous, then increase the speed to 1000 rpm and stir for 60 min before vacuum degassing (vacuum degree -0.08 MPa, vacuum degassing time 15 min); control the system viscosity to 12000 mPa·s (25℃), then stir at 600 rpm for 10 min, add 1.8 parts of initiator (methyl ethyl ketone peroxide) and 0.4 parts of accelerator (cobalt isooctanoate) and continue stirring at 600 rpm for 5 min to obtain a ceramic-modified resin matrix.

[0073] b. Fiberglass fabric (area density 450 g / m²) 2 Pre-dry in an oven at 120℃ for 2 hours; use a doctor blade to coat glass fiber fabric with the ceramizable modified resin matrix obtained in step a to prepare prepreg, control the linear speed at 0.8 m / min and the resin content at 45% of the total mass of the prepreg, and then roll it up after being shaped by a cooling roller to obtain a ceramizable resin composite prepreg with a single layer thickness of 0.5 mm; prepare multiple ceramizable resin composite prepregs by following the same method as steps a to b above.

[0074] (2) Aerogel modification: The SiO2 aerogel felt is cut into the required size. Silane coupling agent (KH-560) is added to an ethanol aqueous solution (made by mixing ethanol and water in a volume ratio of 9:1) and mixed evenly to obtain a silane coupling agent solution with a concentration of 2wt%. Then, acetic acid is added to the silane coupling agent solution to adjust the pH of the silane coupling agent solution to 4.5 and pre-hydrolyzes it for 30 min under stirring (speed of 300 rpm) to obtain a pre-hydrolyzed silane coupling agent solution. Subsequently, the SiO2 aerogel felt is immersed in the pre-hydrolyzed silane coupling agent solution for 10 min. After removal, it is heat-treated at 100℃ for 1 h to allow the silane coupling agent to undergo a condensation reaction with the silanol groups on the surface of the SiO2 aerogel felt, forming an active interface modification layer on the surface of the SiO2 aerogel felt, resulting in a SiO2 aerogel felt with a thickness of 1 mm modified by the silane coupling agent.

[0075] (3) The layup sequence is as follows: the total thickness of the layup is 5.5 mm, and the layup sequence (from the fire source to the unfired side) is as follows: 0.5 mm ceramicizable resin composite prepreg; 1.0 mm SiO2 aerogel felt modified with silane coupling agent; 0.5 mm ceramicizable resin composite prepreg; 1.0 mm SiO2 aerogel felt modified with silane coupling agent; 0.5 mm ceramicizable resin composite prepreg; 1.0 mm SiO2 aerogel felt modified with silane coupling agent; 0.5 mm ceramicizable resin composite prepreg; 0.5 mm ceramicizable resin composite prepreg (unfired bearing layer); after layup in this sequence, the composite is obtained.

[0076] (4) Compression molding: The assembly is placed in a mold preheated to 150°C for compression molding and curing. The compression molding and curing temperature is 150°C, the pressure is 3MPa, and the time is 30min. After cooling to <60°C and demolding, a flame-retardant gel / resin-based composite material with a total thickness of about 5.5mm is obtained.

[0077] This embodiment improves the weight (lightweighting) and cost by increasing the number of functional layers in the thickness direction, while ensuring the overall protective performance. In the propane ablation test, the structure remained intact after ablation with a 1300°C propane flame for 30 minutes, without burn-through or change in shape, and a hard ceramic layer was formed on the surface.

[0078] Comparative Example 4 (1) Same as step (1) in Example 3.

[0079] (2) Eleven 0.5 mm thick ceramicizable resin composite prepregs were laid up (stacked) and placed in a mold preheated to 150 °C for molding and curing. The molding and curing temperature was 150 °C, the pressure was 3 MPa, and the time was 30 min. After cooling to <60 °C and demolding, a flame-retardant resin-based composite material with a total thickness of about 5.5 mm was obtained.

[0080] Comparative Example 5 Comparative Example 5 is basically the same as Example 3, except that: a. Add 100 parts of phenolic epoxy vinyl ester resin (Shangwei 907) to a planetary stirred tank. Add 11.2 parts of silicon carbide powder (average particle size 15 μm) and 44.8 parts of zirconium diboride powder sequentially at 300 rpm and stir for 10 min until uniformly mixed. Then add 10 parts of NP cage-type macromolecular intumescent flame retardant (IFR-101A) and stir for 10 min until uniformly mixed. Then increase the speed to 1000 rpm and stir for 60 min to disperse. Perform vacuum degassing (vacuum degree -0.08 MPa, vacuum degassing time 15 min). Then stir at 600 rpm for 10 min. Add 1.8 parts of initiator (methyl ethyl ketone peroxide) and 0.4 parts of accelerator (cobalt isooctanoate) and continue stirring at 600 rpm for 5 min to obtain the modified resin matrix. Use this modified resin matrix to replace the ceramicizable modified resin matrix in Example 3 for subsequent experimental steps.

[0081] The properties of the materials finally obtained in Example 3 and Comparative Examples 4-5 were compared in this invention, and the results are shown in Table 3.

[0082] Table 3 In Table 3, the symbol "-" indicates that the performance item was not tested.

[0083] Example 4 Example 4 is basically the same as Example 3, except that: In step a, 100 parts of phenolic epoxy vinyl ester resin (Shangwei 907) were added to a planetary mixer. At 300 rpm, 8 parts of micron-sized SiO2 (average particle size 5 μm), 4 parts of nano-sized SiO2 (average particle size 30 nm), 13.33 parts of wollastonite (average particle size 10 μm), 6.67 parts of mica powder (average particle size 15 μm), and 24 parts of borosilicate glass powder D245 (average particle size 10 μm) were added sequentially and stirred for 10 minutes until homogeneous. Then, NP-cage-type macromolecules were added. Ten parts of intumescent flame retardant (IFR-101A) were mixed and stirred for 10 minutes until homogeneous. Then, the stirring speed was increased to 1000 rpm and the mixture was dispersed for 60 minutes. Vacuum degassing was then performed (vacuum degree -0.08 MPa, vacuum degassing time 15 minutes). The mixture was then stirred at 600 rpm for 10 minutes. Then, 1.8 parts of initiator (methyl ethyl ketone peroxide) and 0.4 parts of accelerator (cobalt isooctanoate) were added and the mixture was stirred at 600 rpm for 5 minutes to obtain a ceramic-modified resin matrix.

[0084] Example 5 The difference between Example 5 and Example 3 is that: In step a, 100 parts of phenolic epoxy vinyl ester resin (Shangwei 907) were added to a planetary stirred tank. At 300 rpm, 12 parts of micron-sized SiO2 (average particle size 5 μm), 10 parts of wollastonite (average particle size 10 μm), 10 parts of mica powder (average particle size 15 μm), and 24 parts of borosilicate glass powder D245 (average particle size 10 μm) were added sequentially and stirred for 10 min until uniformly mixed. Then, 10 parts of aluminum hydroxide flame retardant were added and stirred for 10 min until uniformly mixed. The stirring speed was then increased to 1000 rpm and stirred for 60 min. Vacuum degassing was then performed (vacuum degree -0.08 MPa, vacuum degassing time 15 min). Then, the stirring speed was increased to 600 rpm and stirred for 10 min. Then, 1.8 parts of initiator (methyl ethyl ketone peroxide) and 0.4 parts of accelerator (cobalt isooctanoate) were added and stirred for 5 min at 600 rpm to obtain a ceramic-modified resin matrix.

[0085] Example 6 Example 6 is basically the same as Example 3, except that: In step a, 100 parts of phenolic epoxy vinyl ester resin (Shangwei 907) are added to a planetary mixer. At 300 rpm, 12 parts of micron-sized SiO2 (average particle size 5 μm), 10 parts of wollastonite (average particle size 10 μm), 10 parts of mica powder (average particle size 15 μm), and 24 parts of borosilicate glass powder D245 (average particle size 10 μm) are added sequentially and stirred for 10 minutes until homogeneous. Then, a halogenated flame retardant (composed of decabromodiphenyl ethane (DBDPE) and antimony trioxide) is added. Ten parts of a mixture (3:1 by mass) were stirred for 10 minutes until homogeneous. Then, the stirring speed was increased to 1000 rpm and the mixture was dispersed for 60 minutes. Vacuum degassing was then performed (vacuum degree -0.08 MPa, vacuum degassing time 15 minutes). The mixture was then stirred at 600 rpm for 10 minutes. Then, 1.8 parts of initiator (methyl ethyl ketone peroxide) and 0.4 parts of accelerator (cobalt isooctanoate) were added and the mixture was stirred at 600 rpm for 5 minutes to obtain a ceramic-modified resin matrix.

[0086] Example 7 Example 7 is basically the same as Example 4, except that: In step a, modified boronene nanosheets are first prepared. The raw materials used include boronene nanosheets in a mass ratio of 1:0.6:70, silane coupling agent (KH-560), and an aqueous ethanol solution (ethanol to water volume ratio of 9:1). The preparation method is as follows: silane coupling agent (KH-560) is added to the aqueous ethanol solution and stirred (350 rpm) until homogeneous to obtain an aqueous ethanol solution of silane coupling agent. Then, acetic acid is added to the aqueous ethanol solution of silane coupling agent to adjust the pH to 4.5, and pre-hydrolyzing is carried out for 30 min under stirring (350 rpm) to obtain pre-hydrolyzed silane coupling agent. The ethanol-water solution of the coupling agent was first prepared, followed by the addition of boronene nanosheets. The mixture was then sonicated at 35°C with an ultrasonic power of 400 W for 80 min under argon protection to obtain a uniform suspension of boronene nanosheets. This suspension was then stirred at 60°C (350 rpm) for 2.5 h under argon protection. The resulting suspension was then centrifuged at 8000 rpm for 15 min under argon protection. The supernatant was discarded, and the precipitate was collected. Anhydrous ethanol was added to the precipitate, and the mixture was centrifuged again under argon protection. The sample was washed three times, and the precipitate was then placed in a vacuum drying oven and dried at 50°C to constant weight to obtain modified boronene nanosheets. The preparation of the ceramicizable modified resin matrix was as follows: 100 parts of phenolic epoxy vinyl ester resin (Shangwei 907) were added to a planetary stirred tank, and 12 parts of micron-sized SiO2 (average particle size 5 μm), 10 parts of wollastonite (average particle size 10 μm), 10 parts of mica powder (average particle size 15 μm), and 24 parts of borosilicate glass powder D245 (average particle size 10 μm) were added sequentially at 300 rpm and stirred for 10 min until homogeneous. Then, 1.5 parts of modified boronene nanosheets and 10 parts of NP cage-type macromolecular intumescent flame retardant (IFR-101A) were added and stirred for 10 minutes until uniformly mixed. Then, the speed was increased to 1000 rpm and stirred for 60 minutes for dispersion, followed by vacuum degassing (vacuum degree -0.08 MPa, vacuum degassing time 15 minutes). Then, the mixture was stirred at 600 rpm for 10 minutes, and 1.8 parts of initiator (methyl ethyl ketone peroxide) and 0.4 parts of accelerator (cobalt isooctanoate) were added and stirred at 600 rpm for 5 minutes to obtain a ceramicizable modified resin matrix.

[0087] Example 8 Example 8 is basically the same as Example 7, except that: In step a, modified boronene nanosheets are first prepared. The raw materials used include boronene nanosheets in a mass ratio of 1:0.6:70, silane coupling agent (KH-560), and an aqueous ethanol solution (ethanol to water volume ratio of 9:1). The preparation method is as follows: silane coupling agent (KH-560) is added to the aqueous ethanol solution and stirred (350 rpm) until homogeneous to obtain an aqueous ethanol solution of silane coupling agent. Then, acetic acid is added to the aqueous ethanol solution of silane coupling agent to adjust the pH to 4.5, and pre-hydrolyzing is carried out for 30 min under stirring (350 rpm) to obtain pre-hydrolyzed silane coupling agent. The ethanol-water solution of the coupling agent was first prepared, and then boronene nanosheets were added to the ethanol-water solution of the pre-hydrolyzed silane coupling agent. The mixture was then sonicated at 35°C with an ultrasonic power of 400W for 80 min under argon protection to obtain a uniform suspension of boronene nanosheets. This suspension was then stirred at 60°C (350 rpm) for 2.5 h under argon protection. After stirring for 2.5 h, the resulting suspension was centrifuged at 8000 rpm for 15 min under argon protection. The supernatant was discarded, and the precipitate was collected. Anhydrous ethanol was added to the precipitate, and the mixture was then subjected to further centrifugation under argon protection. The precipitate was centrifuged and washed three times. The washed precipitate was then placed in a vacuum drying oven and dried at 50°C to constant weight to obtain modified boronene nanosheets. The preparation of the ceramicizable modified resin matrix was as follows: 100 parts of phenolic epoxy vinyl ester resin (Shangwei 907) were added to a planetary stirred tank. At 300 rpm, 12 parts of micron-sized SiO2 (average particle size 5 μm), 10 parts of wollastonite (average particle size 10 μm), 10 parts of mica powder (average particle size 15 μm), and 24 parts of borosilicate glass powder D245 (average particle size 10 μm) were added sequentially and stirred for 10 min until homogeneous. The mixture was stirred until homogeneous. Then, 5 parts of modified boronene nanosheets and 10 parts of NP cage-type macromolecular intumescent flame retardant (IFR-101A) were added and stirred for 10 minutes until homogeneous. The stirring speed was then increased to 1000 rpm and stirred for 60 minutes before vacuum degassing (vacuum degree -0.08 MPa, vacuum degassing time 15 minutes). The mixture was then stirred at 600 rpm for 10 minutes, and then 1.8 parts of initiator (methyl ethyl ketone peroxide) and 0.4 parts of accelerator (cobalt isooctanoate) were added and stirred at 600 rpm for 5 minutes to obtain a ceramicizable modified resin matrix.

[0088] The properties of the materials finally obtained in Examples 4 to 8 were compared in this invention, and the results are shown in Table 4.

[0089] Table 4 The parts of this invention not described in detail are techniques known to those skilled in the art.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A flame-retardant gel / resin-based composite material, characterized in that, The flame-retardant gel / resin-based composite material includes at least one ceramicizable resin composite structural layer and at least one aerogel insulation layer. The ceramizable resin composite structural layer comprises reinforcing fibers and a ceramizable modified resin matrix; The ceramizable modified resin matrix comprises a resin matrix, a ceramizable component, and a synergistic flame retardant; the synergistic flame retardant is a phosphorus-nitrogen based flame retardant. The ceramicizable component comprises ceramic filler, reinforcing filler and sintering aid in a mass ratio of (0.5~1):(0.3~0.5):

1. The ceramic filler is selected from one or more of wollastonite, mica powder and kaolin. The reinforcing filler is silica powder and / or diatomaceous earth. The sintering aid is fusible glass powder. The aerogel insulation layer is surface-modified with a silane coupling agent; The ceramicizable resin composite structural layer and the aerogel insulation layer are bonded together through interfacial coupling.

2. The flame-retardant gel / resin-based composite material according to claim 1, characterized in that: In the ceramizable modified resin matrix, the proportion of the ceramizable component is 10-60% of the mass of the resin matrix.

3. The flame-retardant gel / resin-based composite material according to claim 1, characterized in that: The reinforcing fiber is glass fiber and / or carbon fiber; and / or The resin matrix is ​​one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic epoxy resin, and vinyl ester resin.

4. The flame-retardant gel / resin-based composite material according to claim 1, characterized in that: The phosphorus-nitrogen flame retardant is ammonium polyphosphate and / or an NP-cage-type macromolecular intumescent flame retardant.

5. The flame-retardant gel / resin-based composite material according to claim 1, characterized in that: The aerogel insulation layer is a SiO2 aerogel insulation layer; and / or The silane coupling agent is γ-glycidoxypropyltrimethoxysilane and / or γ-aminopropyltriethoxysilane.

6. The flame-retardant gel / resin-based composite material according to any one of claims 1 to 5, characterized in that, The raw materials for preparing the ceramizable resin composite structural layer include the following components in parts by mass: The composition includes 50-200 parts reinforcing fiber, 100 parts resin matrix, 10-60 parts ceramizable component, and 5-15 parts synergistic flame retardant.

7. The method for preparing the flame-retardant gel / resin-based composite material according to any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: (1) Prepare sheet molding compound or prepreg of ceramizable resin composite material; (2) The surface of the aerogel was modified with a silane coupling agent to obtain an aerogel with a silane coupling agent surface modified. (3) Lay up a ceramicizable resin composite sheet molding compound or a ceramicizable resin composite prepreg with a silane coupling agent-modified aerogel to obtain a composite; (4) The assembly is placed in a mold for molding and heating curing, and then demolded to obtain a flame-retardant gel / resin-based composite material.

8. The preparation method according to claim 7, characterized in that: The pressure for molding and heating curing is 1~15MPa, the temperature is 80~180℃, and the time is 1~40min.

9. The preparation method according to claim 7, characterized in that, Step (2) includes: A silane coupling agent solution with a concentration of 1-5 wt% is prepared using an aqueous ethanol solution. The pH of the silane coupling agent solution is then adjusted to 4-10 and pre-hydrolyzed for 20-60 minutes to obtain a pre-hydrolyzed silane coupling agent solution. The aerogel is then impregnated or sprayed with the pre-hydrolyzed silane coupling agent solution and subjected to heat treatment to obtain an aerogel with a silane coupling agent surface modification.

10. The preparation method according to claim 9, characterized in that, In step (2): The silane coupling agent is γ-glycidoxypropyltrimethoxysilane and / or γ-aminopropyltriethoxysilane; The aerogel is a SiO2 aerogel felt or a SiO2 aerogel plate; The ethanol-water solution is prepared by mixing anhydrous ethanol and water in a volume ratio of (8~10):1; The heat treatment is performed at a temperature of 80~120℃ for a time of 0.5~2h.

11. A battery pack housing, characterized in that, The raw materials for preparing the battery pack housing include the flame-retardant gel / resin-based composite material according to any one of claims 1 to 6 or the flame-retardant gel / resin-based composite material prepared by any one of claims 7 to 10; the battery pack housing is a new energy vehicle battery pack housing.

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