Polyphenylene sulfide flame-retardant material for new energy automobile battery pack shell and preparation method of polyphenylene sulfide flame-retardant material

Abstract

The invention relates to the field of high polymer materials, and particularly discloses a polyphenylene sulfide flame-retardant material for a new energy automobile battery pack shell and a preparation method of the polyphenylene sulfide flame-retardant material. The invention discloses a polyphenylene sulfide flame-retardant material for a new energy automobile battery pack shell. The polyphenylene sulfide flame-retardant material comprises the following raw materials in parts by weight: 50-70 parts of polyphenylene sulfide resin, 1-3 parts of a plasticizer, 2-6 parts of a flexibilizer, 2-3 parts of a flame retardant, 0.1-1 part of an antioxidant and 30-50 parts of modified composite fibers, the modified composite fiber comprises polydopamine modified carbon fiber and silicon dioxide modified aramid fiber in a mass ratio of 1: (0.8-1). The polyphenylene sulfide flame-retardant material provided by the invention has the advantages of low brittleness, strong toughness, good tensile and impact-resistant effects and thermal oxidation resistance, and can prevent polyphenylene sulfide from embrittlement and cracking due to thermal oxidation.

Description

Technical Field

[0001] This application relates to the technical field of polymer materials, and more specifically, it relates to a polyphenylene sulfide flame-retardant material for a new energy vehicle battery pack housing and a preparation method thereof. Background Art

[0002] The core of new energy vehicles is the three-electric system, including electric drive, battery, and electronic control. The power battery is an important power source for current electric vehicles. The battery pack housing is mainly used to protect the power battery from being damaged when it is subjected to external collisions and squeezes. As the carrier of the battery module, the battery housing plays a key role in the safe operation and protection of the battery module.

[0003] In the power battery system, the battery housing accounts for 20-30% of the total system weight and is a main structural component. Therefore, on the premise of ensuring the functional safety of the battery system and the overall safety of the vehicle, the lightweight of the battery housing has become one of the main improvement goals of the battery system. Polyphenylene sulfide is a thermoplastic crystalline polymer with excellent comprehensive properties, having good molding processability, chemical resistance, flame retardancy, rigidity, and modulus. It has high dimensional stability, excellent electrical properties, high fatigue strength, good creep resistance, easy molding, and characteristics such as aging resistance, radiation resistance, and non-toxicity. Moreover, it has excellent heat resistance: its melting point exceeds 280°C, the heat distortion temperature exceeds 260°C, the long-term use temperature is 220-240°C, it degrades at 700°C in air, and still retains 40% of its mass in an inert gas at 1000°C. The flame retardancy can reach UL94V-0 level, and the oxygen index (LOI) > 57%, having good flame-retardant properties. Therefore, it can be used as a lightweight flame-retardant material for the battery housing.

[0004] However, due to its molecular structure in which benzene rings are alternately connected to sulfur atoms at the para position, the molecular chain of polyphenylene sulfide has great rigidity and regularity. Thus, polyphenylene sulfide is a crystalline polymer with a maximum crystallinity of 70%-80%. Although polyphenylene sulfide has high rigidity, it is brittle and has poor toughness. In the prior art, polyphenylene sulfide and glass fiber are often blended to improve the mechanical properties of the blended material with the high strength of glass fiber. However, the affinity between glass fiber and the resin matrix is poor, and the interfacial adhesion is low. When the polyphenylene sulfide composite material is actually applied to the battery pack housing, there are still problems such as easy fragmentation. Summary of the Invention

[0005] In order to reduce the brittleness of the polyphenylene sulfide material, improve its toughness, and improve the protection of the new energy vehicle battery housing for the battery module, this application provides a polyphenylene sulfide flame-retardant material for a new energy vehicle battery pack housing and a preparation method thereof.

[0006] In the first aspect, this application provides a polyphenylene sulfide flame-retardant material for a new energy vehicle battery pack housing, adopting the following technical solution: A polyphenylene sulfide flame retardant material for a new energy vehicle battery pack housing, comprising the following raw materials in parts by weight: 50-70 parts of polyphenylene sulfide resin, 1-3 parts of plasticizer, 2-6 parts of toughening agent, 2-3 parts of flame retardant, 0.1-1 part of antioxidant, and 30-50 parts of modified composite fiber; The modified composite fiber comprises polydopamine-modified carbon fiber and silica-modified aramid fiber with a mass ratio of 1:0.8-1.

[0007] By adopting the above technical solution, in the blend based on polyphenylene sulfide resin, a toughening agent and a plasticizer are added to improve its flexibility and impact resistance. And polydopamine-modified carbon fiber and silica-modified aramid fiber are used as composite fibers. The carbon fiber has very high mechanical strength and can be bent in multiple directions with excellent bending resistance. Moreover, it has excellent high-temperature resistance in an oxidizing atmosphere. Because polydopamine is similar in composition structure to mussel adhesion protein, it has strong adhesiveness, thus enhancing the surface roughness of the carbon fiber, improving the wettability of polyphenylene sulfide on the carbon fiber surface, making the carbon fiber disperse evenly in the polyphenylene sulfide, and improving the mechanical strength and thermal oxidation resistance of the polyphenylene sulfide composite material; Aramid is a linear polymer composed of aromatic groups and amide groups, and the main chain structure has a high degree of regularity, and the macromolecules exist in a very extended state. This structure makes aramid fiber have characteristics such as ultra-high strength, high modulus, and low elongation at break, so its mechanical properties are particularly prominent, and its thermal oxidation resistance is also very excellent. Because its molecular chain contains a strong benzene ring bond structure, aramid fiber can exist stably in a high-temperature environment. Silica is loaded on the surface of the aramid fiber to increase the surface roughness of the aramid fiber, increase the wettability of polyphenylene sulfide on the aramid fiber, and enhance the dispersibility of the aramid fiber, thereby improving the bending resistance and impact resistance of the polyphenylene sulfide, enhancing the toughness of the battery pack housing, and improving its tensile resistance and impact resistance.

[0008] Optionally, the preparation method of the silica-modified aramid fiber is as follows: Mix silane coupling agent KH550, ethanol and deionized water, adjust the pH to 5-5.5, add nano-silica, impregnate and modify at 30-40 °C for 1-2 h, and vacuum dry to obtain modified nano-silica; Dissolve polyvinylidene fluoride to form a base solution with a concentration of 10 wt%. Add the modified nano-silica to the base solution, mix well and spray it on the aramid fiber, and vacuum dry at 70-80 °C. The mass ratio of aramid fiber, modified nano-silica and polyvinylidene fluoride is 10:1-1.5:0.1-0.15.

[0009] The sulfur atoms in polyphenylene sulfide are not saturated, and the benzene rings and sulfur atoms on the molecular chain form a conjugated structure, making the sulfur ether bonds in the polyphenylene sulfide macromolecules extremely easy to be oxidized into sulfoxide groups and sulfone groups. The benzene rings and adjacent macromolecules crosslink due to oxidation to form oxygen bridges, and even the main chain breaks. The oxidation and fracture mode of polyphenylene sulfide is mainly thermal oxidation and photooxidation. When used for the battery pack housing, during the driving of the vehicle, the battery module generates heat, causing thermal oxidation to the battery pack housing, thus making the molecular chain of the battery pack housing prone to breakage, the toughness deteriorates, and it is extremely easy to become brittle and crack; by adopting the above technical solution, the silica is modified with the silane coupling agent KH550. When the silane coupling agent KH550 encounters water, it will undergo a hydrolysis reaction to generate silanol groups, and some of the hydroxyl groups undergo dehydration and polycondensation reactions by themselves to form an oligomeric siloxane containing silanol groups. The silanol groups on the oligomeric siloxane form hydrogen bonds with the hydroxyl groups on the surface of the nano-silica, and the two combine to form a hydrophobic film on the surface of the silica; the C-F in the polyvinylidene fluoride molecular chain has a strong bond energy, making it have a high stability on the surface when facing an oxidation environment. Moreover, polyvinylidene fluoride has a high crystallinity, which can reduce the penetration probability of oxygen and has good thermal oxidation resistance. After it is dissolved, a base liquid with a certain viscosity is obtained, and then the modified silica is adhered to the aramid fiber by using the base liquid. The polar amino group at the other end of the molecular chain of the silane coupling agent KH550 bound to the nano-silica can interact with the polar F atoms in the polyvinylidene fluoride to form a structure similar to a molecular bridge, coupling the nano-silica and the polyvinylidene fluoride. After vacuum drying, the hydrogen bond between the nano-silica and the oligomeric siloxane turns into water and separates, and a covalent bond is formed between the two, tightly binding them. Moreover, the surface of the nano-silica changes from hydrophilic to lipophilic, slowing down the agglomeration of the nano-silica, effectively improving the dispersibility of the nano-silica in the polyvinylidene fluoride base liquid, so that the modified silica particles sprayed on the surface of the aramid fiber are more evenly distributed. Under the adhesion of the polyvinylidene fluoride, the modified nano-silica is evenly adhered to the aramid fiber, increasing the surface roughness of the aramid fiber, enhancing the bonding area between the aramid fiber and the polyphenylene sulfide resin, making it easier for the two to combine. Moreover, the modified nano-silica can act as a heterogeneous nucleating agent in the polyphenylene sulfide resin, increasing the crystallinity of the polyphenylene sulfide resin, having a plasticizing effect on the polyphenylene sulfide resin, and improving the flexural strength and impact strength of the composite material; and the modified nano-silica can effectively hinder the thermal oxidation crosslinking of the polyphenylene sulfide, reducing the thermal degradation reaction. The aramid fiber has strong heat resistance and antioxidant ability, and together with the polyvinylidene fluoride with strong thermal oxidation resistance, it can enhance the thermal oxidation resistance effect of the polyphenylene sulfide composite material and extend the service life.

[0010] Optionally, molybdenum disulfide is further added to the base liquid, and the mass ratio of molybdenum disulfide to the aramid fiber is 0.5-1:10.

[0011] By adopting the above technical solution, molybdenum disulfide is a transition metal chalcogenide with a hexagonal crystal system structure and unique physical and chemical properties. When molybdenum disulfide is added to the base fluid, it adheres to the surface of aramid fibers by utilizing the adhesion of polyvinylidene fluoride. When the aramid fibers are blended with polyphenylene sulfide resin, due to the introduction of molybdenum-oxygen bonds in molybdenum disulfide, the antioxidant ability of polyphenylene sulfide at high temperatures is enhanced. Moreover, the bond energy of the molybdenum-oxygen bond is higher, which can better resist the impact of heat flow and form a film-like substance to further protect polyphenylene sulfide. In addition, molybdenum disulfide has a high thermal conductivity, which can increase the heat conduction ability of aramid fibers, enhance the heat absorption and dissipation effects of the polyphenylene sulfide battery pack housing, accelerate the dissipation of heat, and reduce the thermal oxidation of polyphenylene sulfide.

[0012] Optionally, the preparation method of the polydopamine-modified carbon fiber is as follows: Adjust the pH of the dopamine hydrochloride solution to 8 - 8.5 with Tris-HCl buffer solution, add boron carbide and carbon aerogel to obtain a treatment solution; immerse the carbon fiber in the treatment solution at room temperature for 22 - 24 h, wash and dry it. The mass ratio of carbon fiber, boron carbide, and carbon aerogel is 1:0.1 - 0.15:0.1 - 0.3.

[0013] By adopting the above technical solution, dopamine hydrochloride undergoes a self-polymerization reaction in an alkaline environment to form polydopamine. After adding boron carbide and carbon aerogel and being adhered by polydopamine, they are loaded on the carbon fiber. Boron carbide has a special chemical structure, which can effectively inhibit the spread of flames at high temperatures and produce less harmful gases. In addition, it also has good antioxidant properties, excellent properties such as high hardness, high melting point, chemical resistance, and low density, and can form a stable oxide film at high temperatures to play an antioxidant role. The molecular structure of boron carbide is relatively special, and the chemical reaction between boron carbide and the oxidant is relatively slow, which makes boron carbide not easily eroded by oxygen; boron carbide also has excellent thermal conductivity, which can enable heat to be quickly conducted to the material surface, dissipate heat faster, and improve the flame retardancy effect and thermal oxidation resistance of polyphenylene sulfide; carbon aerogel is an ultra-light solid material with a special three-dimensional network structure, with excellent mechanical properties such as high load-bearing capacity and compression resilience, which can effectively avoid structural damage caused by local stress concentration and improve the tensile resistance of carbon fibers; due to its special carbon structure and stable chemical bonds, carbon aerogel has extremely high heat resistance and can maintain structural stability at extremely high temperatures, and can improve the thermal oxidation resistance of polymer materials through high thermal stability and chemical stability Optionally, the preparation method of the carbon aerogel is as follows: Disperse nanocellulose in deionized water and ultrasonicate to obtain a cellulose sol. After pre-freezing, freeze-drying, and carbonizing at 550 - 650 °C for 2 - 3 h under nitrogen protection, then crush it to obtain a basic carbon aerogel with a particle size of 1 - 4 mm; Mix sodium sulfate decahydrate and disodium hydrogen phosphate dodecahydrate in a mass ratio of 1:3 - 4, heat up to 50 - 55 °C, and perform ultrasonic treatment to obtain an impregnating solution. Place the basic carbon aerogel in the impregnating solution and perform vacuum impregnation at 50 - 60 °C for 3 - 4 h.

[0014] By adopting the above technical solution, under the action of ultrasonic waves, nanocellulose is dispersed in deionized water, and hydrogen bonds are formed between molecular chains to obtain a stable cellulose skeleton. A fixed three-dimensional network structure is formed during pre-freezing, and vacuum drying further strengthens the three-dimensional structure of the cellulose aerogel. The nitrogen protection and appropriate carbonization temperature during the carbonization process enable the cellulose to be uniformly carbonized, ultimately forming a basic carbon aerogel with a three-dimensional network structure and a rough surface. Moreover, after carbonization, the unsaturated carbon structure increases, and the hydrophilic groups of the original cellulose molecules basically disappear, improving the hydrophobicity of the carbon aerogel to a certain extent; both sodium sulfate decahydrate and disodium hydrogen phosphate dodecahydrate are inorganic phase change materials. The phase change temperature of sodium sulfate decahydrate is 32.4 °C, and the phase change temperature of disodium hydrogen phosphate dodecahydrate is 35.1 °C, with a phase change latent heat of 265 kJ / kg. It is a good low-temperature energy storage material. By mixing two different phase change materials in a specific ratio, a eutectic phase change energy storage material is obtained, making its phase change temperature closer to the heating temperature of the battery pack shell, thereby absorbing the heat of the battery pack shell through phase change, reducing the heating temperature of the battery pack shell, and reducing the thermal oxidation of the polyphenylene sulfide battery pack shell.

[0015] Optionally, nanozinc oxide is further added to the impregnating solution, and the mass ratio of nanozinc oxide to sodium sulfate decahydrate is 0.2 - 0.4:1.

[0016] By adopting the above technical solution, nanozinc oxide has an extremely high specific surface area and activity. By impregnating it in the carbon aerogel, it can increase the thermal conductivity of the cellulose carbon aerogel, increase the heat exchange rate between the phase change material and the external environment, shorten the time required for temperature rise and fall, and can also act synergistically with other flame retardant components to absorb a large amount of heat at high temperatures, reduce the surface temperature of the material, and increase the flame retardant effect and thermal oxidation resistance.

[0017] Optionally, the toughening agent is selected from one or more of methyl methacrylate - butadiene - styrene random copolymer, ethylene - methyl acrylate - glycidyl methacrylate random copolymer, and maleic anhydride grafted ethylene - octene copolymer.

[0018] By adopting the above technical solution, the toughening agent is a copolymer of a plastic phase and a rubber phase. The plastic phase plays a role in being compatible with the polymer matrix, and the rubber phase plays a role in absorbing and buffering external impact forces, showing a good toughening effect on polyphenylene sulfide.

[0019] Optionally, the plasticizer is selected from one or more of trioctyl trimellitate, diethyl phthalate, methyl methacrylate and dioctyl phthalate.

[0020] By adopting the above technical solution, the plasticizer can improve the flexibility and plasticity of polyphenylene sulfide, so that the plasticity of the manufactured battery pack shell is increased, and the impact resistance and crack resistance are enhanced.

[0021] Optionally, the flame retardant is selected from one or more of melamine, melamine cyanurate, melamine phosphate, etc.

[0022] By adopting the above technical scheme, melamine can provide an inert gas source, dilute the density of combustible gases generated by oxygen and polymer decomposition, and take away part of the heat through gas generation and heat convection, so as to achieve a flame retardant effect. In addition, melamine and polyphenylene sulfide resin have good compatibility, so that the toughening agent can be evenly dispersed in the polyphenylene sulfide matrix, thereby improving the overall flame retardant effect of the material, and helping to maintain the mechanical properties and processing properties of the material. It can also work in conjunction with melamine phosphate. Melamine phosphate can form a stable carbon layer when burning to prevent the transfer of heat and oxygen, thereby achieving a good flame retardant effect. It also has the characteristics of low smoke and non-toxicity, and will not have a significant impact on the color and transparency of the material.

[0023] In the second aspect, the present application provides a method for preparing a polyphenylene sulfide flame retardant material for a new energy vehicle battery pack shell, using the following technical solution: A method for preparing a polyphenylene sulfide flame retardant material for a new energy vehicle battery pack shell comprises the following steps: The polydopamine modified carbon fiber and the silica modified aramid fiber are mixed to obtain a modified composite fiber, and then the polyphenylene sulfide resin, a plasticizer, a toughening agent, a flame retardant, an antioxidant and the modified composite fiber are mixed to obtain a premix; The premix is ​​extruded, cooled, solidified and pelletized to obtain the polyphenylene sulfide flame retardant material.

[0024] By adopting the above technical solution, the raw materials are mixed evenly before extrusion, thereby avoiding the undesirable phenomena such as uneven melting and fiber floating on the outer surface of the material when the inorganic filler is added from the side feeding port.

[0025] In summary, this application has the following beneficial effects: 1. Since this application uses a combination of polydopamine-modified carbon fiber and silica-modified aramid fiber as the modified composite fiber, after modification with polydopamine, the wettability of the carbon fiber and the polyphenylene sulfide resin matrix is improved, and the silica-modified aramid fiber also increases the compatibility between the aramid fiber and the polyphenylene sulfide resin, so that the carbon fiber and the aramid fiber are uniformly dispersed in the polyphenylene sulfide resin matrix, reducing its brittleness, increasing flexibility, and improving the impact resistance and bending resistance.

[0026] 2. In this application, it is preferably to use a silane coupling agent KH550 to modify the dispersion of silica in polyvinylidene fluoride, and then utilize the adhesion of polyvinylidene fluoride to load the modified silica on the aramid fiber, increasing the surface roughness of the aramid fiber and improving the wettability of polyphenylene sulfide to it. In addition, silica and polyvinylidene fluoride can further improve the thermal oxidation resistance of polyphenylene sulfide, extend the service life of the battery pack housing, and reduce the possibility of its thermal oxidation and embrittlement.

[0027] 3. In this application, it is preferably to use polydopamine to load boron carbide and carbon aerogel on the surface of carbon fiber, increasing the compatibility of carbon fiber in polyphenylene sulfide. In addition, boron carbide and carbon aerogel also further improve the heat-resistant oxidation effect of polyphenylene sulfide, preventing the polyphenylene sulfide battery pack housing from being embrittled by thermal oxidation. Specific Embodiments

[0028] The following examples further illustrate this application in detail.

[0029] Preparation Examples 1-6 of Silica-Modified Aramid Fiber Preparation Example 1: Disperse 15 g of silica in 15 g of deionized water, mix evenly, spray it on 100 g of aramid fiber, and vacuum dry it at 80 °C. The particle size of the nano-silica is 50 ± 5 nm. The aramid fiber is selected from Hubei Tengdi New Materials, with the product number TD240730 and a length of 6 mm.

[0030] Preparation Example 2: (1) Mix 2 g of silane coupling agent KH550, ethanol, and deionized water according to a mass ratio of 2:78:20, adjust the pH to 5 with glacial acetic acid, add nano-silica, impregnate and modify it at 30 °C for 1 h, and vacuum dry it at 70 °C for 24 h to obtain modified nano-silica with a particle size of 50 ± 5 nm; (2) Dissolve 1.5 g of polyvinylidene fluoride in DMF to obtain a base solution with a concentration of 10 wt%, add 15 g of modified nano-silica, mix evenly, spray it on 100 g of aramid fiber, and vacuum dry it at 80 °C for 6 h. The polyvinylidene fluoride model is FR904, Mn = 4.5×10 5g / mol, crystallinity 32.13%, selected from Shanghai 3F Materials, aramid fiber selected from Hubei Tengdi New Materials, product number TD240730, length 6 mm.

[0031] Preparation Example 3: (1) Mix 2 g of silane coupling agent KH550, ethanol, and deionized water in a mass ratio of 2:78:20, adjust the pH to 5.5 with glacial acetic acid, add nano-silica, impregnate and modify at 40 °C for 2 h, and vacuum dry at 70 °C for 24 h to obtain modified nano-silica with a nano-silica particle size of 50 ± 5 nm; (2) Dissolve 1 g of polyvinylidene fluoride in DMF to obtain a base solution with a concentration of 10 wt%, add 10 g of modified nano-silica, mix evenly and spray on 100 g of aramid fiber, and vacuum dry at 70 °C for 8 h. The polyvinylidene fluoride model is FR904, Mn = 4.5 × 10 5 g / mol, crystallinity 32.13%, selected from Shanghai 3F Materials, aramid fiber selected from Hubei Tengdi New Materials, product number TD240730, length 6 mm.

[0032] Preparation Example 4: The difference from Preparation Example 2 is that an equal amount of deionized water is used to replace the base solution.

[0033] Preparation Example 5: The difference from Preparation Example 2 is that 10 g of molybdenum disulfide is further added to the base solution, and the mass ratio of molybdenum disulfide to aramid fiber is 1:10.

[0034] Preparation Example 6: The difference from Preparation Example 2 is that 5 g of molybdenum disulfide is further added to the base solution, and the mass ratio of molybdenum disulfide to aramid fiber is 0.5:10.

[0035] Preparation Examples 7-14 of Polydopamine-Modified Carbon Fiber Preparation Example 7: (1) Adjust the pH of 1000 g of a hydrochloric acid dopamine solution with a concentration of 2 g / l to 8.5 with a 0.01 mol / l Trsi-HCl buffer solution to obtain a treatment solution; (2) Immerse 100 carbon fibers in the treatment solution at room temperature for 24 h, wash with distilled water, and dry at 50 °C for 24 h. The carbon fiber length is 3 mm.

[0036] Preparation Example 8: (1) Adjust the pH of 1000 g of a dopamine hydrochloride solution with a concentration of 2 g / l to 8.5 using a 0.01 mol / l Trsi-HCl buffer solution, add 15 g of boron carbide and 30 g of carbon aerogel to obtain a treatment solution. The carbon aerogel is prepared by the following method: Disperse 1 g of nanocellulose in 100 ml of deionized water, sonicate for 30 min at a power of 350 W to obtain a cellulose sol, pre-freeze at -20°C for 24 h, then freeze-dry at -30°C for 48 h. Under nitrogen protection, heat to 600°C at a rate of 5°C / min and carbonize for 2 h, then pulverize to obtain a carbon aerogel with a particle size of 4 mm. The boron carbide is selected from Anhui Nanhao Electronic Technology, with a model of B4C; (2) Immerse 100 g of carbon fiber in the treatment solution at room temperature for 24 h, wash with distilled water, and dry at 50°C for 24 h. The length of the carbon fiber is 3 mm.

[0037] Preparation Example 9: (1) Adjust the pH of 1000 g of a dopamine hydrochloride solution with a concentration of 2 g / l to 8.5 using a 0.01 mol / l Trsi-HCl buffer solution, add 10 g of boron carbide and 10 g of carbon aerogel to obtain a treatment solution. The carbon aerogel is prepared by the following method: Disperse 1 g of nanocellulose in 100 ml of deionized water, sonicate for 30 min at a power of 350 W to obtain a cellulose sol, pre-freeze at -20°C for 24 h, then freeze-dry at -30°C for 48 h. Under nitrogen protection, heat to 550°C at a rate of 5°C / min and carbonize for 3 h, then pulverize to obtain a carbon aerogel with a particle size of 1 mm. The boron carbide is selected from Anhui Nanhao Electronic Technology, with a model of B4C; (2) Immerse 100 g of carbon fiber in the treatment solution at room temperature for 22 h, wash with distilled water, and dry at 50°C for 24 h. The length of the carbon fiber is 3 mm.

[0038] Preparation Example 10: The difference from Preparation Example 8 is that boron carbide is not added.

[0039] Preparation Example 11: The difference from Preparation Example 8 is that carbon aerogel is not added.

[0040] Preparation Example 12: The difference from Preparation Example 8 is that the carbon aerogel is prepared by the following method: The carbon aerogel is prepared by the following method: Disperse 1 g of nanocellulose in 100 ml of deionized water, sonicate for 30 min at a power of 350 W to obtain a cellulose sol, pre-freeze at -20°C for 24 h, then freeze-dry at -30°C for 48 h. Under nitrogen protection, heat to 600°C at a rate of 5°C / min and carbonize for 2 h, then pulverize to obtain a basic carbon aerogel with a particle size of 4 mm; Mix sodium sulfate decahydrate, disodium hydrogen phosphate dodecahydrate, and zinc oxide nanoparticles in a mass ratio of 1:3:0.4, heat to 55°C, and sonicate for 30 min to obtain an impregnation solution; Place the base carbon aerogel in the impregnating solution and impregnate it under vacuum at 50 °C for 4 h.

[0041] Preparation Example 13: The difference from Preparation Example 8 is that the carbon aerogel is prepared by the following method: The carbon aerogel is prepared by the following method: Disperse 1 g of nanocellulose in 100 ml of deionized water, ultrasonicate it at a power of 350 W for 30 min to obtain a cellulose sol, pre-freeze it at -20 °C for 24 h, then freeze-dry it at -30 °C for 48 h, and under nitrogen protection, heat it to 550 °C at a rate of 5 °C / min and carbonize it for 3 h, and then crush it to obtain a base carbon aerogel with a particle size of 4 mm; Mix sodium sulfate decahydrate, disodium hydrogen phosphate dodecahydrate and zinc oxide nanoparticles in a mass ratio of 1:4:0.2, heat it up to 50 °C and ultrasonicate it for 30 min to obtain an impregnating solution; Place the base carbon aerogel in the impregnating solution and impregnate it under vacuum at 60 °C for 4 h.

[0042] Preparation Example 14: The difference from Preparation Example 12 is that zinc oxide nanoparticles are not added. Examples

[0043] Example 1: A polyphenylene sulfide flame retardant material for a new energy vehicle battery pack housing, the raw material dosages are shown in Table 1, wherein the polyphenylene sulfide resin is selected from Toray of Japan, model A900, the plasticizer is trioctyl trimellitate, selected from Shandong Yousuo Chemical Technology, model TOTM, the toughening agent is methyl methacrylate-butadiene-styrene random copolymer (MBS), selected from Ningbo Jiuli New Materials, model EM500, product number 1037, the flame retardant is melamine, the antioxidant is antioxidant 1010, and the modified composite fiber includes poly-dopamine modified carbon fiber and silica modified aramid fiber with a mass ratio of 1:1. The silica modified aramid fiber is made from Preparation Example 1, and the poly-dopamine modified carbon fiber is made from Preparation Example 7.

[0044] The preparation method of the above-mentioned polyphenylene sulfide flame retardant material for a new energy vehicle battery pack housing includes the following steps: S1. Mix the poly-dopamine modified carbon fiber and the silica modified aramid fiber to obtain a modified composite fiber, and then stir and mix the polyphenylene sulfide resin, plasticizer, toughening agent, flame retardant, antioxidant and modified composite fiber at a speed of 100 rpm for 3 h to obtain a premix; S2. Extrude, cool and solidify, and pelletize the premix to obtain a polyphenylene sulfide flame retardant material. The extrusion temperature is 290 °C and the screw speed is 300 rpm.

[0045] Table 1 Raw material ratio of polyphenylene sulfide flame retardant material for new energy vehicle battery pack housing Example 2: A polyphenylene sulfide flame retardant material for a new energy vehicle battery pack housing. The raw material dosages are shown in Table 1. The polyphenylene sulfide resin is selected from Toray of Japan, with the model A900. The plasticizer is diethyl phthalate. The toughening agent is ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMA), selected from Arkema, with the model AX8900. The flame retardant is melamine cyanurate, selected from Jiangsu Xinsu New Materials, with the model MAC. The antioxidant is antioxidant 1010. The modified composite fiber includes poly-dopamine modified carbon fiber and silica modified aramid fiber with a mass ratio of 1:0.8. The silica modified aramid fiber is made from Preparation Example 1, and the poly-dopamine modified carbon fiber is made from Preparation Example 7.

[0046] The preparation method of the above-mentioned polyphenylene sulfide flame retardant material for a new energy vehicle battery pack housing includes the following steps: S1. Mix the polyphenylene sulfide resin, plasticizer, toughening agent, flame retardant, antioxidant and modified composite fiber to obtain a premix; S2. Extrude, cool and solidify, and pelletize the premix to obtain the polyphenylene sulfide flame retardant material. The extrusion temperature is 300 °C, and the screw speed is 300 rpm.

[0047] Example 3: A polyphenylene sulfide flame retardant material for a new energy vehicle battery pack housing. The raw material dosages are shown in Table 1. The polyphenylene sulfide resin is selected from Toray of Japan, with the model A900. The plasticizer is methyl methacrylate. The toughening agent is maleic anhydride grafted ethylene-octene copolymer (POE-g-MAH), selected from Dow of the United States, with the model M2265. The flame retardant is a mixture of melamine and melamine cyanurate with a mass ratio of 1:1. The melamine cyanurate is selected from Jiangsu Xinsu New Materials, with the model MAC. The antioxidant is antioxidant 1010. The modified composite fiber includes poly-dopamine modified carbon fiber and silica modified aramid fiber with a mass ratio of 1:1. The silica modified aramid fiber is made from Preparation Example 1, and the poly-dopamine modified carbon fiber is made from Preparation Example 7.

[0048] The preparation method of the above-mentioned polyphenylene sulfide flame retardant material for a new energy vehicle battery pack housing includes the following steps: S1. Mix the polyphenylene sulfide resin, plasticizer, toughening agent, flame retardant, antioxidant and modified composite fiber to obtain a premix; S2. Extrude, cool and solidify, and pelletize the premix to obtain the polyphenylene sulfide flame retardant material. The extrusion temperature is 300 °C, and the screw speed is 300 rpm.

[0049] Examples 4-8: A polyphenylene sulfide flame retardant material for a new energy vehicle battery pack housing, which is different from Example 1 in that the preparation examples of the silica modified aramid fiber are selected as shown in Table 2.

[0050] Examples 9 - 15: A polyphenylene sulfide flame - retardant material for a new - energy vehicle battery pack housing, which is different from Example 4 in that the preparation examples of the polydopamine - modified carbon fiber are selected as shown in Table 2.

[0051] Table 2 Selection of silica - modified aramid fiber and polydopamine - modified carbon fiber in Examples 5 - 15 Example Silica-modified aramid fiber Polydopamine-modified carbon fiber Example 4 Preparation Example 2 Preparation Example 7 Example 5 Preparation Example 3 Preparation Example 7 Example 6 Preparation Example 4 Preparation Example 7 Example 7 Preparation Example 5 Preparation Example 7 Example 8 Preparation Example 6 Preparation Example 7 Example 9 Preparation Example 2 Preparation Example 8 Example 10 Preparation Example 2 Preparation Example 9 Example 11 Preparation Example 2 Preparation Example 10 Example 12 Preparation Example 2 Preparation Example 11 Example 13 Preparation Example 2 Preparation Example 12 Example 14 Preparation Example 2 Preparation Example 13 Example 15 Preparation Example 2 Preparation Example 14 Comparative Examples Comparative Example 1: A polyphenylene sulfide flame - retardant material for a new - energy vehicle battery pack housing, which is different from Example 1 in that an equal amount of polydopamine - modified carbon fiber is used to replace the silica - modified aramid fiber.

[0052] Comparative Example 2: A polyphenylene sulfide flame - retardant material for a new - energy vehicle battery pack housing, which is different from Example 1 in that the aramid fiber is not treated with silica modification.

[0053] Comparative Example 3: A polyphenylene sulfide flame - retardant material for a new - energy vehicle battery pack housing, which is different from Example 1 in that the silica - modified aramid fiber is not added.

[0054] Comparative Example 4: A polyphenylene sulfide flame - retardant material for a new - energy vehicle battery pack housing, which is different from Example 1 in that an equal amount of glass fiber is used to replace the modified composite fiber.

[0055] Performance Detection Test Prepare the polyphenylene sulfide flame - retardant material according to the methods in the examples and comparative examples, and conduct performance detection with reference to the following methods. Record the detection results in Table 3.

[0056] 1. Tensile property: Test according to the "Standard Test Method for Tensile Properties of Plastics" GB / T1040 - 2006.

[0057] 2. Impact property: Test according to the "Test Method for Izod Impact Strength of Rigid Plastics" GB / T1043 - 1993.

[0058] 3. Bending strength: Test according to the "Determination of Flexural Properties of Plastics" GB / T9341 - 2008.

[0059] 3. Flame - retardant property: Test according to the "Standard Test Method for Oxygen Index of Plastics" GB / T2406 - 1993.

[0060] 4. Thermal oxidation resistance: Let the prepared polyphenylene sulfide material stand at 200 °C for 72 h, then detect the tensile strength and calculate the strength retention rate.

[0061] Table 3 Performance Detection Results of the Polyphenylene Sulfide Flame - Retardant Material As can be seen from Examples 1-3 and the data in Table 3, by using specific amounts of polydopamine-modified carbon fibers and silica-modified aramid fibers, the prepared polyphenylene sulfide composite materials have strong flexural strength and impact resistance, good toughness, are not prone to fragmentation, and have a high oxygen index and good flame retardancy.

[0062] In Example 4 and Example 5, the silica-modified aramid fibers prepared in Preparation Example 2 and Preparation Example 3 were used respectively. In Example 6, the silica-modified aramid fibers prepared in Preparation Example 4 were used. Compared with Example 4, the basic liquid made of polyvinylidene fluoride was not used as a binder. The data in Table 3 show that the thermal oxidation ability of the polyphenylene sulfide flame retardant material decreased, and the flexural strength and impact strength decreased slightly, indicating that polyvinylidene fluoride can increase the interfacial adhesion strength on the surface of silica and aramid fibers, thereby increasing the surface roughness of aramid fibers and improving their degree of intercalation with the polyphenylene sulfide matrix resin, thus improving the improvement effect of aramid fibers on mechanical strength.

[0063] Compared with Example 4, in Example 7 and Example 8, the silica-modified aramid fibers prepared in Preparation Example 5 and Preparation Example 6 were used respectively. The data in Table 3 show that after high-temperature oxidation, the strength retention rate of the polyphenylene sulfide flame retardant material increased, and the impact resistance was high, and the flame retardant effect was slightly improved.

[0064] In Example 9 and Example 10, the silica-modified aramid fibers prepared in Preparation Example 2 were used, and the polydopamine-modified carbon fibers prepared in Preparation Example 8 and Preparation Example 9 were used respectively. Compared with Preparation Example 7, boron carbide and carbon aerogel were also used in Preparation Example 8 and Preparation Example 9. The data in Table 3 show that compared with Example 4, the oxygen index of the polyphenylene sulfide flame retardant materials prepared in Example 9 and Example 10 increased, the strength retention increased, and the flexural and impact resistance were further improved.

[0065] In Example 11 and Example 12, the polydopamine-modified carbon fibers prepared in Preparation Example 10 and Preparation Example 11 were used respectively. Compared with Preparation Example 8, boron carbide and carbon aerogel were not added in Preparation Example 10 and Preparation Example 11 respectively. The data in Table 3 show that compared with Example 9, the decrease in tensile strength, flexural strength and impact strength in Example 11 was not very obvious, but the oxygen index and strength retention rate decreased significantly, indicating that boron carbide can improve the heat resistance of the material. In Example 12, the oxygen index changed little, but the mechanical properties such as tensile strength and the strength retention rate decreased significantly, indicating that carbon aerogel can significantly improve the mechanical properties and thermal oxidation resistance of the polyphenylene sulfide composite material.

[0066] In Example 13 and Example 14, the polydopamine-modified carbon fibers prepared in Preparation Example 12 and Preparation Example 13 were used respectively. As shown in Table 3, the thermal oxidation resistance of the polyphenylene sulfide flame retardant materials prepared in Example 13 and Example 14 was enhanced, indicating that the addition of sodium sulfate decahydrate and disodium hydrogen phosphate dodecahydrate could improve the endothermic effect of the carbon aerogel and reduce the heat.

[0067] In Preparation Example 15, the polydopamine-modified carbon fiber prepared in Preparation Example 14 was used. Compared with Preparation Example 12, nano-zinc oxide was not added. As shown in Table 3, the thermal oxidation resistance of the polyphenylene sulfide flame retardant material prepared in Example 15 was weakened, and the other properties were not much different from those in Example 13.

[0068] Compared with Example 1, in Comparative Example 1, polydopamine-modified carbon fiber was used to replace silica-modified aramid fiber. The data in Table 3 showed that although the polyphenylene sulfide flame retardant material prepared in Comparative Example 1 had good flame retardant performance, its tensile resistance, bending resistance, impact resistance and thermal oxidation resistance decreased.

[0069] In Comparative Example 2, polydopamine-modified carbon fiber and aramid fiber were used, and the aramid fiber was not treated with silica modification. As shown in Table 3, compared with Example 1, the thermal oxidation resistance of the polyphenylene sulfide material prepared in Comparative Example 2 decreased, and the impact resistance and bending resistance weakened, and the heat-resistant oxidation performance weakened.

[0070] In Comparative Example 3, silica-modified aramid fiber was not added, and the amount of modified composite fiber was reduced. Compared with Example 1, all the properties of the polyphenylene sulfide material prepared in Comparative Example 3 decreased. In Comparative Example 4, glass fiber was used to replace the modified composite fiber. Although it had good flame retardant effect, its bending resistance and impact resistance decreased significantly.

[0071] This specific embodiment is only an explanation of the present application, and it does not limit the present application. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A polyphenylene sulfide flame retardant material for a new energy vehicle battery pack shell, characterized in that: The invention comprises the following raw materials in parts by weight: 50-70 parts of polyphenylene sulfide resin, 1-3 parts of plasticizer, 2-6 parts of toughening agent, 2-3 parts of flame retardant, 0.1-1 parts of antioxidant and 30-50 parts of modified composite fiber; The modified composite fiber comprises polydopamine modified carbon fiber and silica modified aramid fiber in a mass ratio of 1:0.8-1.

2. The polyphenylene sulfide flame retardant material for new energy vehicle battery pack shell according to claim 1, characterized in that: The preparation method of the silica-modified aramid fiber is as follows: Mix silane coupling agent KH550, ethanol and deionized water, adjust the pH to 5-5.5, add nano-silica, immerse and modify at 30-40°C for 1-2h, and vacuum dry to obtain modified nano-silica; Dissolve polyvinylidene fluoride to form a base liquid with a concentration of 10wt%, add modified nano-silica to the base liquid, mix well and spray on aramid fiber, and vacuum dry at 70-80°C. The mass ratio of aramid fiber, modified nano-silica and polyvinylidene fluoride is 10:1-1.5:0.1-0.

15.

3. The polyphenylene sulfide flame retardant material for the battery pack shell of new energy vehicles according to claim 2, characterized in that: Molybdenum disulfide is also added to the base liquid, and the mass ratio of molybdenum disulfide to aramid fiber is 0.5-1:

10.

4. The polyphenylene sulfide flame retardant material for new energy vehicle battery pack shell according to claim 1, characterized in that: The preparation method of the polydopamine modified carbon fiber is as follows: The dopamine hydrochloride solution is adjusted to pH 8-8.5 with Tris-HCl buffer, and boron carbide and carbon aerogel are added to prepare a treatment solution; The carbon fiber is immersed in the treatment solution at room temperature for 22-24 hours, washed and dried, and the mass ratio of the carbon fiber, boron carbide and carbon aerogel is 1:0.1-0.15:0.1-0.

3.

5. The polyphenylene sulfide flame retardant material for new energy vehicle battery pack shell according to claim 4, characterized in that: The preparation method of the carbon aerogel is as follows: The nanocellulose is dispersed in deionized water, ultrasonicated to obtain a cellulose sol, which is pre-frozen, freeze-dried, carbonized at 550-650°C for 2-3 hours under nitrogen protection, and then crushed to obtain a basic carbon aerogel with a particle size of 1-4 mm; Sodium sulfate decahydrate and disodium hydrogen phosphate dodecahydrate are mixed in a mass ratio of 1:3-4, heated to 50-55° C., and ultrasonicated to prepare an impregnation solution; The basic carbon aerogel was placed in the impregnation solution and vacuum impregnated at 50-60°C for 3-4 hours.

6. The polyphenylene sulfide flame retardant material for the battery pack shell of new energy vehicles according to claim 5, characterized in that: Nano zinc oxide is also added to the impregnation solution, and the mass ratio of nano zinc oxide to sodium sulfate decahydrate is 0.2-0.4:

1.

7. The polyphenylene sulfide flame retardant material for new energy vehicle battery pack shell according to claim 1, characterized in that: The toughening agent is selected from one or more of methyl methacrylate-butadiene-styrene terpolymer, ethylene-methyl acrylate-glycidyl methacrylate terpolymer, and maleic anhydride grafted ethylene-octene copolymer.

8. The polyphenylene sulfide flame retardant material for new energy vehicle battery pack shell according to claim 1, characterized in that: The plasticizer is selected from one or more of trioctyl trimellitate, diethyl phthalate, methyl methacrylate and dioctyl phthalate.

9. The polyphenylene sulfide flame retardant material for new energy vehicle battery pack shell according to claim 1, characterized in that: The flame retardant is selected from one or more of melamine, melamine cyanurate, melamine phosphate and the like.

10. The method for preparing the polyphenylene sulfide flame retardant material for the battery pack shell of new energy vehicles according to any one of claims 1 to 9, characterized in that: The following steps are involved: The polydopamine modified carbon fiber and the silica modified aramid fiber are mixed to obtain a modified composite fiber, and then the polyphenylene sulfide resin, a plasticizer, a toughening agent, a flame retardant, an antioxidant and the modified composite fiber are mixed to obtain a premix; The premix is ​​extruded, cooled, solidified and pelletized to obtain the polyphenylene sulfide flame retardant material.

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