Flame-retardant composite material for new energy automobile and preparation method of flame-retardant composite material

Abstract

The invention provides a flame-retardant composite material for a new energy automobile and a preparation method thereof.The preparation method comprises the steps that a biochar source is placed in an inert atmosphere for high-temperature activation, then nano silicon compound particles are added for mixing, and a flame-retardant synergistic body is obtained; melting the modified plastic matrix, adding the flame-retardant synergy body and nano copper sulfate particles, uniformly mixing, and extruding and pelletizing after mixing, so as to obtain flame-retardant master batch; and carrying out hot-pressing processing on the flame-retardant master batch according to a preset mold to obtain a molded part, spraying a high-temperature-resistant coating on the surface of the molded part, heating to 80-90 DEG C, and carrying out heat preservation for 2-4 hours to obtain the flame-retardant composite material for the new energy automobile. The flame-retardant composite material for the new energy automobile can quickly form a physical heat-insulating layer and a chemical flame-retardant layer at high temperature through dual protection of an internal flame-retardant synergistic effect and an external high-temperature-resistant coating, heat transfer is effectively blocked, and the characteristics of low toxicity and environmental protection meet the requirements of the new energy automobile industry on greenness, safety and sustainable development.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardant materials, and in particular relates to a flame retardant composite material for new energy vehicles and a preparation method thereof. Background Art

[0002] New energy vehicles have very strict safety requirements. New energy vehicles generally use high-energy-density lithium-ion batteries, which have the risk of thermal runaway and short circuit. Flame retardant materials can effectively delay the spread of fire and reduce the threat of fire accidents to the safety of vehicles and passengers. In key components such as battery packs and electronic control units, flame retardant materials can form an insulating layer at the beginning of a fire to prevent high temperature and flames from further invading other components. As an important part of the battery system of new energy vehicles, flame retardant materials are used in battery casings, isolation plates, heat dissipation structures, etc., which can effectively prevent battery packs from triggering chain reactions when failure occurs.

[0003] In order to improve the flame retardant effect, the flame retardants in the related art include halogen flame retardants, phosphorus flame retardants and metal-containing flame retardants, etc. Although they have a certain flame retardant effect, when thermal runaway or fire occurs, the temperature exceeds 300-400°C, and these flame retardants will produce highly toxic byproducts such as hydrogen halides, phosphoric acid fumes, and metal compounds, which pose a toxic risk. If inhaled by the driver in the car, it will cause secondary damage and lead to serious consequences. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a flame retardant composite material for new energy vehicles and a preparation method thereof, aiming to solve the problem of toxicity hazards of flame retardant materials at high temperatures.

[0005] In order to solve the above technical problems, the present invention is implemented as follows: a method for preparing a flame retardant composite material for new energy vehicles is proposed, and the steps include: S1, placing the biochar source in an inert atmosphere, performing high temperature activation, and then adding nano silicon compound particles to mix to obtain a flame retardant synergist; S2, melting the modified plastic matrix, adding the flame retardant synergist and the nano copper sulfate particles and mixing them evenly, extruding and pelletizing them after the mixing is completed to obtain a flame retardant masterbatch, wherein the modified plastic matrix includes active functional groups grafted on the molecular chain, and the active functional groups include at least one of carboxyl, hydroxyl, and epoxy groups; S3. Hot-pressing the flame-retardant masterbatch according to a preset mold to obtain a molded part, spraying a high-temperature resistant coating on the surface of the molded part, heating it to 80-90° C., and keeping it warm for 2-4 hours to obtain a flame-retardant composite material for new energy vehicles, wherein the high-temperature resistant coating includes at least one of a silicone resin coating, a polyimide coating, and a modified epoxy resin coating.

[0006] In some embodiments of the present invention, in step S1, the biochar source includes at least one of rice husks, wood chips, and peanut shells, the nano-silicon compound particles include at least one of colloidal silica, fused silica, and mesoporous silica, and the inert atmosphere is high-purity nitrogen or argon.

[0007] In some embodiments of the present invention, calculated according to the mass ratio, the biochar source: the nano-silicon compound particles = (3-5): 1.

[0008] In some embodiments of the present invention, step S1 comprises: S1.1, after drying the biochar source in air, crush it to a particle size within the range of 1 to 3 mm, place it in an inert atmosphere reactor, heat it to 700 to 900 ° C, the heating rate is 10 ° C / min, keep it warm for 1 to 2 hours, and obtain activated biochar powder after cooling; S1.2, immersing the nano-silicon compound particles in an organic silane solution, controlling the reaction temperature at 60 to 80°C, the reaction time at 30 to 60 minutes, and then washing with isopropanol and drying to obtain modified nano-silicon compound particles; S1.3, the activated biochar powder and the modified nano-silicon compound particles are ball-milled for 1 to 2 hours at a rotation speed of 200 to 400 rpm to obtain a flame retardant synergist.

[0009] In some embodiments of the present invention, in step S2, the modified plastic matrix includes at least one of modified polypropylene, modified polyamide, and modified polycarbonate.

[0010] In some embodiments of the present invention, calculated by weight percentage, the modified plastic matrix accounts for 70-90wt%, the flame retardant synergist accounts for 5-25wt%, and the nano copper sulfate particles account for 2-10wt%.

[0011] In some embodiments of the present invention, step S2 comprises: S2.1, heating the modified plastic matrix to 80-100°C and drying for 4-6 hours, and then heating to 21-250°C, maintaining the rotation speed at 150-250 rpm, to obtain a molten modified plastic matrix; S2.2, adding sodium hydroxide solution dropwise to the copper sulfate solution, and continuing to dropwise add methanol, while maintaining stirring during the dropping process, with a rotation speed of 200-400 rpm, after the dropping is completed, washing the precipitate by high-speed centrifugation, immersing it in an organic acid solution and drying it to obtain nano copper sulfate particles; S2.3, adding the nano copper sulfate particles and the flame retardant synergist to the molten modified plastic matrix, maintaining the temperature at 210-250°C, the rotation speed at 150-250rpm, and performing vacuum degassing at the same time, the stirring time is 1-2 hours, and after mixing, extrusion and pelletizing are performed to obtain flame retardant masterbatch.

[0012] In some embodiments of the present invention, step S3 includes: S3.1, preheating the flame retardant masterbatch to 210-250°C, hot pressing pressure of 5-10 MPa, hot pressing holding time of 3-5 minutes, to obtain a molded part; S3.2. Perform plasma or chemical surface treatment on the surface of the molded part, then spray a high-temperature resistant coating, control the coating thickness to be between 20 and 50 microns, heat to 80-90°C, and control the insulation time to be within 2 to 4 hours to obtain a flame-retardant composite material for new energy vehicles.

[0013] The flame retardant composite material for new energy vehicles of the present invention is prepared by the preparation method of the flame retardant composite material for new energy vehicles as described above. The flame retardant composite material for new energy vehicles comprises a biochar source, nano silicon compound particles, a modified plastic matrix and nano copper sulfate particles; wherein: The biochar source is used to provide a thermal physical insulation layer; The nano silicon compound particles are used to cooperate with the biochar source to form a silicon-carbon composite protective layer; The modified plastic matrix is ​​used to provide mechanical and structural properties; The nano copper sulfate particles are used as a catalyst and a cross-linking accelerator.

[0014] Compared with the prior art, the method for preparing a flame-retardant composite material for new energy vehicles in the present invention has the following beneficial effects: When the biochar source is activated at high temperature, high-purity nitrogen or argon is used as an inert atmosphere. The lack of oxygen under such conditions avoids oxidation reactions, ensuring that the biochar mainly undergoes devolatilization and carbonization processes without generating toxic oxidation byproducts that would be produced under traditional combustion conditions. The flame-retardant synergist obtained by ball milling the biochar source and nano-silicon compound particles can quickly form a dense, continuous insulation layer at the beginning of combustion, reducing the flame spread rate. In addition, nano-copper sulfate particles can catalyze cross-linking reactions at high temperatures, further promoting the formation of carbon layers and forming multiple flame-retardant protections. The grafted active functional groups in the modified plastic matrix not only enhance the interface bonding with the flame retardant additives, but also ensure the uniformity of the material in the molten state, ensuring that the final product has excellent mechanical strength and heat resistance. The high-temperature resistant coating forms a dense protective film after low-temperature curing, further reducing the risk of toxic smoke release.

[0015] In summary, flame-retardant composite materials for new energy vehicles can quickly form a physical insulation layer and a chemical flame-retardant layer when exposed to high temperatures through the internal flame-retardant synergistic effect and the external high-temperature resistant coating, effectively blocking the transfer of heat. At the same time, the low-toxic and environmentally friendly characteristics meet the requirements of the new energy vehicle industry for green, safe and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic flow chart of a method for preparing a flame retardant composite material for new energy vehicles in one embodiment of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] Please refer to Figure 1 The present invention provides a method for preparing a flame retardant composite material for new energy vehicles, the steps comprising: S1. Place the biochar source in an inert atmosphere for high-temperature activation, and then add nano-silicon compound particles for mixing to obtain a flame retardant synergist. In step S1, the biochar source includes at least one of rice husks, sawdust, and peanut shells, and the nano-silicon compound particles include at least one of colloidal silica, fused silica, and mesoporous silica. The inert atmosphere is high-purity nitrogen or argon. Calculated by mass ratio, biochar source: nano-silicon compound particles = (3-5): 1.

[0019] In step S1, highly reactive biochar is obtained through high-temperature activation, and then combined with modified and uniformly dispersed nano-silicon compound particles to form a flame retardant synergist, which can quickly generate a dense insulating carbon layer and a "silicon-carbon" composite protective structure during combustion, thereby reducing heat transfer and the release of toxic smoke.

[0020] Step S1 includes: S1.1. After air-drying the biochar source, crush it to a particle size within the range of 1 to 3 mm, place it in an inert atmosphere reactor, heat it to 700 to 900°C at a heating rate of 10°C / min, keep it warm for 1 to 2 hours, and obtain activated biochar powder after cooling.

[0021] After air drying, crushing and high temperature activation at 700-900℃, biochar sources such as rice husks, sawdust or peanut shells can be devolatile to form porous activated biochar powder with rich active functional groups on the surface. This activated biochar has a high carbon residue rate and a stable carbon skeleton. It can quickly form a dense carbon layer under fire conditions, providing effective heat insulation and flame retardant protection. Activation in a high-purity nitrogen or argon environment can avoid oxidation, maintain carbon content, and ensure carbonization quality.

[0022] S1.2, immersing the nano silicon compound particles in an organic silane solution, controlling the reaction temperature at 60-80°C, the reaction time at 30-60 minutes, and then washing with isopropanol and drying to obtain modified nano silicon compound particles.

[0023] After the colloidal silica, fused silica or mesoporous silica is immersed in an organic silane solution, its surface functional groups are modified, which is conducive to the formation of chemical adsorption or weak bond with the activated biochar powder. After modification, the dispersibility of the nano-silicon compound particles is significantly improved, avoiding agglomeration in subsequent mixing and ensuring uniform distribution in the flame retardant synergist. The reaction is carried out at 60 to 80 ° C and the treatment time is within 30 to 60 minutes, so that the modification is sufficient and gentle, without destroying the structure and function of the nanoparticles themselves.

[0024] S1.3, the activated biochar powder and the modified nano-silicon compound particles are ball-milled for 1 to 2 hours at a rotation speed of 200 to 400 rpm to obtain a flame retardant synergist.

[0025] The activated biochar powder and modified nano-silicon compound particles are fully mixed in a mass ratio of (3-5):1 by ball milling to form a uniformly dispersed flame retardant synergist. The biochar provides an excellent carbonization basis, while the modified nano-silicon compound particles synergize with the carbonization products during combustion to form a "silicon-carbon" composite insulation layer, thereby greatly improving the overall flame retardant effect. The ball milling process helps to control the particle size and improve the mixing uniformity, providing an ideal additive dispersion state for subsequent blending with the modified plastic matrix.

[0026] S2, melt the modified plastic matrix, add the flame retardant synergist and the nano copper sulfate particles and mix them evenly, extrude and pelletize them after mixing to obtain a flame retardant masterbatch, wherein the modified plastic matrix includes active functional groups grafted on the molecular chain, and the active functional groups include at least one of carboxyl, hydroxyl, and epoxy. In step S2, the modified plastic matrix includes at least one of modified polypropylene, modified polyamide, and modified polycarbonate, and calculated by weight percentage, the modified plastic matrix accounts for 70-90wt%, the flame retardant synergist accounts for 5-25wt%, and the nano copper sulfate particles account for 2-10wt%.

[0027] Step S2 includes: S2.1. Heat the modified plastic matrix to 80-100° C. and dry for 4-6 hours, then heat to 21-250° C., maintain the rotation speed at 150-250 rpm, and obtain a molten modified plastic matrix.

[0028] By drying at 80-100°C for 4-6 hours, the moisture in the modified plastic matrix can be effectively removed to prevent the generation of water vapor or bubbles during the melting process, ensure the uniformity of the melt and avoid thermal degradation. When the moisture melts at high temperature, it may cause local gasification and decomposition, resulting in a decrease in material performance. Pre-drying can improve the stability of the material, ensure that the molecular chains are fully in contact during subsequent processing, and facilitate the active functional groups to play a role. Heating to 210-250°C and maintaining a speed of 150-250rpm ensures that the modified plastic matrix is ​​completely melted and has moderate fluidity, providing a good reaction and dispersion environment. In the molten state, the grafted active functional groups (such as carboxyl, hydroxyl, and epoxy groups) in the matrix can be exposed, providing reaction sites for subsequent chemical or physical crosslinking with the flame retardant synergist and nano copper sulfate particles, and enhancing interface bonding.

[0029] S2.2. Add the sodium hydroxide solution dropwise into the copper sulfate solution, and continue to add methanol dropwise. Keep stirring during the addition process at a speed of 200-400 rpm. After the addition is completed, wash the precipitate by high-speed centrifugation, immerse it in an organic acid solution, and then dry it to obtain nano copper sulfate particles.

[0030] By dropping sodium hydroxide solution into copper sulfate solution and continuing to drop methanol, uniform nucleation is achieved while maintaining stirring at 200-400rpm, ensuring that the generated copper sulfate precipitate has a nanometer particle size. Slow and uniform dropping and high-speed stirring prevent local oversaturation and rapid growth of particles, so that the initial nucleus is quickly generated and the particle size distribution is narrow; the addition of methanol improves the polarity of the reaction medium and further inhibits particle growth. The precipitate is separated by high-speed centrifugation, washed, and immersed in an organic acid solution and then dried to remove by-products and impurities, thereby obtaining nano copper sulfate particles with good dispersibility and high purity. The centrifugation and washing steps ensure that there are no excess ions or solvent residues on the surface of the particles, and the immersion in organic acid helps to stabilize the surface, prevent the particles from agglomerating during the subsequent high-temperature blending process, and ensure that they are evenly dispersed in the composite material.

[0031] The reaction is carried out at room temperature (generally maintained at 20-25°C) to avoid rapid growth of particles at high temperatures. Low temperature helps to quickly form a large number of primary nuclei, while subsequent growth is inhibited, thereby ensuring that the particle size is in the nanometer range. Precise control of the reaction kinetics is achieved by stabilizing the low temperature environment, ensuring that the generated precipitated particles are uniform at the primary nucleus stage.

[0032] When adding NaOH solution to copper sulfate solution, a slow and uniform drop rate is used. This can minimize the local concentration fluctuation of the reaction and promote the uniform generation of a large number of small nuclei without local oversaturation causing the particles to grow too fast. Magnetic stirring or mechanical stirring equipment is used to maintain high-speed uniform stirring during the reaction to ensure that the reaction is fully mixed, further prevent agglomeration and local concentration gradient formation, thereby limiting particle growth. A proper amount of methanol is added to the reaction system, and its main function is to promote the dehydration reaction and accelerate the conversion from intermediate products to copper sulfate. Methanol can change the polarity of the reaction system and reduce the surface tension of the solvent medium, thereby promoting the formation of primary nuclei and hindering the excessive growth of particles. In addition, the lower boiling point and volatility of methanol help to quickly remove it during post-treatment, prevent the particles from continuing to grow in the solution, and ensure that the generated nanoparticles have a high specific surface area and uniformity. After the reaction is completed, high-speed centrifugation is used to separate the generated precipitate from the mother liquor. High-speed centrifugation helps to quickly fix the particle size, while removing impurities and excess ions through repeated washing to prevent the particles from secondary growth or agglomeration due to changes in the solution environment. Vacuum drying or low-temperature drying (eg, 40-60°C) is used to avoid particle aggregation or grain growth under high temperature conditions, thereby maintaining the nanometer size.

[0033] S2.3. Add nano copper sulfate particles and flame retardant synergists to the molten modified plastic matrix, maintain the temperature at 210-250°C, maintain the rotation speed at 150-250rpm, and perform vacuum degassing at the same time. The stirring time is 1-2 hours. After mixing, extrude and pelletize to obtain flame retardant masterbatch.

[0034] The prefabricated nano copper sulfate particles and flame retardant synergists are added to the melted modified plastic matrix at the same time. At 210-250°C, the speed is maintained at 150-250rpm, and vacuum degassing is performed to ensure that the components are fully and evenly dispersed without bubbles. The molten state at high temperature provides a reaction site for the active functional groups, so that the nano copper sulfate and flame retardant synergists can be chemically cross-linked or physically adsorbed with the matrix; vacuum degassing removes bubbles to prevent the mechanical properties of the finished product and the density of the flame retardant layer from being affected. The uniformly mixed molten material is extruded through a die using a twin-screw extruder, and pelletized after water cooling or air cooling to obtain a flame retardant masterbatch with uniform particle size. Precise temperature control, speed and online exhaust ensure the uniformity and stability of the internal structure of the masterbatch, providing a high-quality raw material basis for subsequent molding processes (such as hot pressing and high-temperature resistant coating treatment).

[0035] S3. Hot-press the flame-retardant masterbatch according to a preset mold to obtain a molded part, spray a high-temperature resistant coating on the surface of the molded part, heat it to 80-90°C, and keep it warm for 2-4 hours to obtain a flame-retardant composite material for new energy vehicles, wherein the high-temperature resistant coating includes at least one of a silicone resin coating, a polyimide coating, and a modified epoxy resin coating.

[0036] Step S3 includes: S3.1. Preheat the flame retardant masterbatch to 210-250°C, set the hot pressing pressure to 5-10 MPa, and hold the hot pressing time to 3-5 minutes to obtain a molded part.

[0037] After preheating the flame retardant masterbatch to 210-250℃, hot pressing is performed at a pressure of 5-10MPa, and the pressure is maintained for 3-5 minutes, so that the material can fully melt, flow and fill the mold, and realize a molded part with precise size and smooth surface. Under high temperature and high pressure conditions, the modified plastic matrix is ​​completely melted, and the active functional groups contained therein can undergo further chemical crosslinking or physical combination with the flame retardant synergist and nano copper sulfate particles to form a dense and uniform structure. By fully discharging the bubbles and voids in the mold, the overall mechanical properties and flame retardant properties of the molded part are ultimately improved. During the hot pressing process, the good contact and fusion between the matrix and the additives help the subsequent high temperature resistant coating to form a continuous and dense insulation layer on the surface of the molded part, providing the first protective barrier for the flame retardant material. The uniformity and stability of the internal structure of the molded part provide a good base for the subsequent sprayed high temperature resistant coating, so that the overall flame retardant composite material can quickly form a carbonized layer when encountering a fire source, reducing the heat transfer rate and the generation of toxic smoke.

[0038] S3.2. Perform plasma or chemical surface treatment on the surface of the molded part, then spray a high-temperature resistant coating, control the coating thickness between 20 and 50 microns, heat to 80-90°C, and control the insulation time within 2 to 4 hours to obtain a flame-retardant composite material for new energy vehicles.

[0039] By plasma or chemical surface treatment of the molded parts, surface oil, oxides and other impurities can be effectively removed, surface activity can be increased, and a stronger chemical or physical bond can be formed between the high temperature resistant coating (at least one of silicone resin coating, polyimide coating, and modified epoxy resin coating) and the molded parts. After surface treatment, the surface energy of the molded parts increases and the micro-roughness is improved, which is conducive to the uniform spreading and full penetration of the coating material into the micropores of the substrate, ensuring that the coating is uniform and does not fall off during the subsequent curing process. The coating thickness is controlled between 20 and 50 microns, and after spraying, it is heated to 80-90°C and kept warm for 2-4 hours to fully cross-link and cure the coating material to form a dense and continuous high temperature resistant protective layer. Under low temperature curing conditions of 80-90°C, the active functional groups in the high temperature resistant coating continue to undergo cross-linking reactions and are converted into a stable solid network structure. This dense coating not only has excellent heat insulation and flame retardant effects, but also effectively prevents the spread of flames, heat and toxic fumes, further improving the safety and stability of the composite material.

[0040] In order to quantify the flame retardant properties of flame retardant composite materials for new energy vehicles, it is convenient for technicians to intuitively control various parameters in the reaction and summarize the flame retardant properties. The control equation is as follows: in, , is an empirical constant (dimensionless), which is used to quantitatively adjust the coefficient of each parameter's influence on the flame retardant performance. It is obtained by repeatedly conducting synthetic experiments on flame retardant composite materials for new energy vehicles and collating experimental data. , is 0.5~1.5. For example, orthogonal experiments, response surface analysis or full factorial experimental design can be used to control and change key process parameters (such as biochar source activation temperature, holding time, mixing time, hot pressing pressure, etc.), and record the flame retardant performance indicators of each group of composite materials (such as limiting oxygen index, heat release rate, etc.). Use experimental equipment such as thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), limiting oxygen index (LOI) tester, UL-94 combustion test, etc. to measure the flame retardant properties and related thermal properties of samples under different process conditions. Collect the data of each parameter and the corresponding flame retardant performance data at each experimental point. Substitute the collected data into the constructed flame retardant performance model, and use statistical methods such as regression analysis (such as least squares method) and response surface method to fit and adjust the empirical constants and exponential parameters in the model. Through fitting, a set of optimal parameters is determined so that the error between the flame retardant performance predicted by the model and the experimentally measured indicators is minimized. Use part of the experimental data for cross-validation to confirm that the empirical constants obtained by fitting have good prediction accuracy, and then further optimize the experimental scheme and model parameters as needed.

[0041] It is the degree of activation of biochar source (dimensionless), which is obtained by measuring the amount of residual carbon after high temperature by thermogravimetric analysis (TGA) and then normalizing it. is the hot pressing pressure (MPa), is the reference pressure (MPa), is the melting and extrusion temperature (°C), is the reference temperature (°C), is the modification degree of nano-silicon compound particles (dimensionless), which is obtained by normalizing the surface energy change evaluated by contact angle test. are the influence indexes of each parameter (dimensionless), which respectively represent the sensitivity of the activation degree of biochar source, the degree of nano-silicon compound particles and the normalized pressure-temperature ratio to the flame retardant properties, and are obtained by fitting multiple experimental data. Can be 1~1.5, Can be 1~1.2, It can be 0.5~1. is the melt mixing time (h or min), is the reference time (h or min), is the activation energy (J / mol) in the melting process of step S2, obtained by differential scanning calorimetry (DSC) or other thermodynamic test methods. R is the gas constant [8.314 J / (mol·K)].

[0042] From the model point of view, in order to improve the dimensionless flame retardant performance index , can improve , that is, increase the activation temperature and holding time (within the allowable range) to improve the degree of biochar activation. , that is, optimizing the nano-silicon modification conditions, such as extending the immersion time, increasing the concentration of organic silane, etc., to enhance the modification effect. , that is, during the hot pressing process, the pressure is appropriately increased while ensuring the stability of the material. , that is, to ensure that all components are fully mixed and reacted. , that is, maintain it in a temperature range suitable for the stability of the modified plastic matrix and sufficient mixing reaction.

[0043] The present invention provides a flame retardant composite material for new energy vehicles, which is prepared by a method for preparing a flame retardant composite material for new energy vehicles. The flame retardant composite material for new energy vehicles comprises a biochar source, nano silicon compound particles, a modified plastic matrix and nano copper sulfate particles; wherein: Biochar sources are used to provide a physical insulation layer from the heat; Nano silicon compound particles are used to cooperate with the biochar source to form a silicon-carbon composite protective layer; Modified plastic matrices are used to provide mechanical and structural properties; Nano copper sulfate particles are used as catalyst and cross-linking accelerator.

[0044] The high energy density battery pack of new energy vehicles will control the temperature through the cooling system during normal operation, but in the event of thermal runaway or fire, the local temperature may rise sharply to extremely high temperatures. In fires or extreme accidents, the temperature inside the battery module may far exceed other parts of the vehicle body due to chemical reactions and thermal runaway, becoming the hottest area in the entire vehicle body. Using flame-retardant composite materials for new energy vehicles as flame-retardant materials for batteries can minimize safety and toxicity risks.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a flame retardant composite material for new energy vehicles, characterized in that the steps include: S1, placing the biochar source in an inert atmosphere, performing high temperature activation, and then adding nano silicon compound particles to mix to obtain a flame retardant synergist; S2, melting the modified plastic matrix, adding the flame retardant synergist and the nano copper sulfate particles and mixing them evenly, extruding and pelletizing them after the mixing is completed to obtain a flame retardant masterbatch, wherein the modified plastic matrix includes active functional groups grafted on the molecular chain, and the active functional groups include at least one of carboxyl, hydroxyl, and epoxy groups; S3. Hot-pressing the flame-retardant masterbatch according to a preset mold to obtain a molded part, spraying a high-temperature resistant coating on the surface of the molded part, heating it to 80-90° C., and keeping it warm for 2-4 hours to obtain a flame-retardant composite material for new energy vehicles, wherein the high-temperature resistant coating includes at least one of a silicone resin coating, a polyimide coating, and a modified epoxy resin coating.

2. The method for preparing a flame-retardant composite material for new energy vehicles according to claim 1, characterized in that: In step S1, the biochar source includes at least one of rice husks, wood chips, and peanut shells, the nano-silicon compound particles include at least one of colloidal silica, fused silica, and mesoporous silica, and the inert atmosphere is high-purity nitrogen or argon.

3. The method for preparing a flame-retardant composite material for new energy vehicles according to claim 2, characterized in that: Calculated according to the mass ratio, the biochar source: the nano silicon compound particles = (3-5):

1.

4. The method for preparing a flame-retardant composite material for new energy vehicles according to claim 1 or 2, characterized in that: Step S1 includes: S1.1, after drying the biochar source in air, crush it to a particle size within the range of 1 to 3 mm, place it in an inert atmosphere reactor, heat it to 700 to 900 ° C, the heating rate is 10 ° C / min, keep it warm for 1 to 2 hours, and obtain activated biochar powder after cooling; S1.2, immersing the nano-silicon compound particles in an organic silane solution, controlling the reaction temperature at 60 to 80°C, the reaction time at 30 to 60 minutes, and then washing with isopropanol and drying to obtain modified nano-silicon compound particles; S1.3, the activated biochar powder and the modified nano-silicon compound particles are ball-milled for 1 to 2 hours at a rotation speed of 200 to 400 rpm to obtain a flame retardant synergist.

5. The method for preparing a flame-retardant composite material for new energy vehicles according to claim 1, characterized in that: In step S2, the modified plastic matrix includes at least one of modified polypropylene, modified polyamide, and modified polycarbonate.

6. The method for preparing a flame-retardant composite material for new energy vehicles according to claim 5, characterized in that: Calculated by weight percentage, the modified plastic matrix accounts for 70-90wt%, the flame retardant synergist accounts for 5-25wt%, and the nano copper sulfate particles account for 2-10wt%.

7. The method for preparing a flame-retardant composite material for new energy vehicles according to claim 1 or 5, characterized in that: Step S2 includes: S2.1, heating the modified plastic matrix to 80-100°C and drying for 4-6 hours, and then heating to 21-250°C, maintaining the rotation speed at 150-250 rpm, to obtain a molten modified plastic matrix; S2.2, adding sodium hydroxide solution dropwise to the copper sulfate solution, and continuing to dropwise add methanol, while maintaining stirring during the dropping process, with a rotation speed of 200-400 rpm, after the dropping is completed, washing the precipitate by high-speed centrifugation, immersing it in an organic acid solution and drying it to obtain nano copper sulfate particles; S2.3, adding the nano copper sulfate particles and the flame retardant synergist to the molten modified plastic matrix, maintaining the temperature at 210-250°C, the rotation speed at 150-250rpm, and performing vacuum degassing at the same time, the stirring time is 1-2 hours, and after mixing, extrusion and pelletizing are performed to obtain flame retardant masterbatch.

8. The method for preparing a flame-retardant composite material for new energy vehicles according to claim 1, characterized in that: Step S3 includes: S3.1, preheating the flame retardant masterbatch to 210-250°C, hot pressing pressure of 5-10 MPa, hot pressing holding time of 3-5 minutes, to obtain a molded part; S3.

2. Perform plasma or chemical surface treatment on the surface of the molded part, then spray a high-temperature resistant coating, control the coating thickness to be between 20 and 50 microns, heat to 80-90°C, and control the insulation time to be within 2 to 4 hours to obtain a flame-retardant composite material for new energy vehicles.

9. A flame retardant composite material for new energy vehicles, characterized in that: The flame retardant composite material for new energy vehicles is prepared by the preparation method of any one of claims 1 to 8, wherein the flame retardant composite material for new energy vehicles comprises a biochar source, nano silicon compound particles, a modified plastic matrix and nano copper sulfate particles; wherein: The biochar source is used to provide a thermal physical insulation layer; The nano silicon compound particles are used to cooperate with the biochar source to form a silicon-carbon composite protective layer; The modified plastic matrix is ​​used to provide mechanical and structural properties; The nano copper sulfate particles are used as a catalyst and a cross-linking accelerator.

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