Polyurethane composite material for new energy automobile battery pack and preparation method thereof

Abstract

The invention provides a polyurethane composite material for a new energy automobile battery pack and a preparation method thereof, and the preparation method comprises the following steps: heating a polycarbonate polyol component to 60-70 DEG C, adding a heat-resistant filler, and stirring at a stirring speed of 500-700 rpm for 20-30 min to obtain a mixed slurry; aromatic modified isocyanate is added into the mixed slurry, the stirring speed is adjusted to 200-300 rpm, the real-time temperature is kept at 60-70 DEG C, stirring is conducted for 30-60 min, defoaming is conducted after stirring is completed, and a polyurethane prepolymer is obtained; and heating the polyurethane prepolymer to 80-90 DEG C, preserving heat for 1-2 hours, then heating to 120-130 DEG C, preserving heat for 3-4 hours, and cooling to obtain the polyurethane composite material for the new energy automobile battery pack. The material can automatically repair microcracks, prevent crack propagation and prolong the service life of the material. Therefore, a heat-resistant skeleton is formed, and the molecular movement of the soft segment is not excessively limited, so that the polyurethane composite material has excellent elasticity.

Description

Technical Field

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

[0002] During use, the battery pack of new energy vehicles needs to deal with various external factors such as vibration, collision, temperature changes, etc., which places high demands on the safety and stability of the battery. Polyurethane materials can fill the gaps in the battery pack, so that each battery cell is tightly combined to prevent the battery from loosening or being damaged due to vehicle vibration or collision. Its excellent elasticity and energy absorption characteristics can effectively alleviate external shocks. During the battery charging and discharging process, the local temperature may rise significantly. Heat-resistant polyurethane materials can ensure that they still maintain sufficient mechanical strength, elasticity and energy absorption capacity at high temperatures, and will not lose the fixation and protection of the battery cells due to thermal softening or deformation.

[0003] In the related technology, the heat resistance of polyurethane materials is improved by filling them with heat-resistant materials. However, the high hardness of heat-resistant materials will cause the elasticity of polyurethane materials to decrease. When polyurethane materials are subjected to vehicle vibrations, road bumps or collision impacts, the energy absorption effect is weakened and the external impact force cannot be effectively dispersed, causing the battery cells to be subjected to local excessive stress, increasing the risk of damage. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a polyurethane composite material for a new energy vehicle battery pack and a preparation method thereof, aiming to solve the problem that the heat resistance and elasticity of the polyurethane material cannot be balanced.

[0005] In order to solve the above problems, the present invention proposes a method for preparing a polyurethane composite material for a new energy vehicle battery pack, the steps comprising: S1. Heat the polycarbonate polyol component to 60-70° C., add a heat-resistant filler and stir at a stirring speed of 500-700 rpm for 20-30 min to obtain a mixed slurry; S2, adding aromatic modified isocyanate to the mixed slurry, adjusting the stirring speed to 200-300 rpm, maintaining the real-time temperature at 60-70° C., stirring for 30-60 min, and degassing after the stirring is completed to obtain a polyurethane prepolymer; S3. Raise the temperature of the polyurethane prepolymer to 80-90° C., keep the temperature for 1-2 hours, then raise the temperature to 120-130° C., keep the temperature for 3-4 hours, and obtain a polyurethane composite material for a new energy vehicle battery pack after cooling.

[0006] In some embodiments of the present invention, step S1 comprises: S1. Heat the polycarbonate polyol component to 60-70°C, add the chain extender and stir at a stirring speed of 200-300 rpm for 10 min; S1.2, add the catalyst and antioxidant, maintain the speed and temperature, and stir for 20 minutes; S1.3, place the heat-resistant raw material in the modifier, heat to 40-50°C, stir for 30 minutes, and dry at 80-100°C for 1-2 hours to obtain a heat-resistant filler; S1.4, add the heat-resistant filler, increase the rotation speed to 500-700 rpm, stir for 20-30 minutes, and obtain a mixed slurry after stirring.

[0007] In some embodiments of the present invention, in step S1, the polycarbonate polyol component includes at least one of carbon dioxide-based polycarbonate polyol, polyethylene glycol carbonate, poly (1,4-butylene glycol) carbonate, and poly (cyclohexanedimethanol) carbonate, the chain extender includes at least one of 1,4-butylene glycol, hexanediol, and diphenylmethane diisocyanate, the catalyst includes at least one of trifluorotin chloride, cobalt dichloride, and an organic metal salt-quaternary ammonium salt, the antioxidant includes 2,6-di-tert-butyl-4-methylphenol, tetrakis (β-(3,5-di-tert-butyl-4-hydroxyphenyl) ) propionic acid) pentaerythritol ester, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), the heat-resistant filler includes at least one of aluminum hydroxide, ammonium polyphosphate, melamine polyphosphate, melamine cyanurate, and expanded graphite, the modifier includes an organic silane reagent or a low-molecular hydroxyl reagent, the organic silane reagent includes at least one of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, and vinyl silane, and the low-molecular hydroxyl reagent includes at least one of diethanolamine, pentaerythritol, citric acid, polypropylene glycol, and polyethylene glycol.

[0008] In some embodiments of the present invention, in step S1, calculated by mass ratio, the polycarbonate polyol component: the chain extender: the catalyst: the antioxidant: the heat-resistant filler = 100:6:1:0.5:30.

[0009] In some embodiments of the present invention, step S2 includes: S2.1, adding an aromatic modified isocyanate having an isocyanate group content of 25-30% to the mixed slurry in batches, adjusting the stirring speed to 200-300 rpm, maintaining the temperature at 60-70°C, and stirring for 30-60 min; S2.2. After stirring, evacuate to -0.05MPa, maintain for 2 minutes, and then restore to normal pressure for 1 minute. Repeat several times until the degassing time is 5~10min. During the degassing stage, maintain the stirring speed at 5~10rpm. After stirring, the polyurethane prepolymer is obtained.

[0010] In some embodiments of the present invention, step S2 includes: The aromatic modified isocyanate includes at least one of carbodiimide modified diphenylmethane diisocyanate, urea polymer modified diphenylmethane diisocyanate, and toluene diisocyanate-based prepolymer. The toluene diisocyanate-based prepolymer includes toluene diisocyanate and polyether or polyester polyol. Calculated by mass ratio, the mixed slurry: the aromatic modified isocyanate = 20: (4~7).

[0011] In some embodiments of the present invention, step S3 includes: S3.1, heating the polyurethane prepolymer to 80-90°C and keeping warm for 1-2 hours; S3.2. Raise the temperature to 120-130°C at a rate of 2-4°C / min, keep warm for 1-2 hours, cool down to 100°C for a short time, then raise the temperature back to 120-130°C, keep warm for another 1-2 hours, and after cooling, obtain a polyurethane composite material for new energy vehicle battery packs.

[0012] The present invention provides a polyurethane composite material for a new energy vehicle battery pack, characterized in that it is prepared by the preparation method of the polyurethane composite material for a new energy vehicle battery pack according to any one of claims 1 to 9, and the polyurethane composite material for a new energy vehicle battery pack comprises: a polycarbonate polyol component, a heat-resistant filler and an aromatic modified isocyanate; wherein, The polycarbonate polyol component is used to improve the heat resistance of the polyurethane composite material; The heat-resistant filler is used to enhance the thermal stability of the polyurethane composite material; The aromatic modified isocyanate is used to form a cross-linked skeleton with the polycarbonate polyol component.

[0013] Compared with the prior art, the method for preparing a polyurethane composite material for a new energy vehicle battery pack in the present invention has the following beneficial effects: The molecular chain of polycarbonate polyol has a long and compliant flexible chain segment, and the carbonate bond contained in it not only provides high thermal stability, but also has good elasticity. These long chain segments constitute continuous soft areas in polyurethane, which are responsible for energy absorption and buffering, so that the material can quickly return to its original state when subjected to external force, and constitute the soft segment of polyurethane composite materials. The hard segment generated by aromatic modified isocyanate after reaction with polyol has high rigidity and glass transition temperature. These rigid fragments interact through hydrogen bonds and other interactions to form tiny hard domains in polyurethane, giving the material good heat resistance and mechanical strength, while also enhancing flame retardant properties, and forming the hard segment of polyurethane composite materials. Adding heat-resistant fillers can further improve the heat resistance of the material on the one hand, and on the other hand, the evenly dispersed heat-resistant fillers form a good interface with the polymerization system, which will not significantly interfere with the flexibility of the soft segment. By maintaining a mild reaction at 60-70°C in the S1 and S2 stages, the soft segment and the hard segment react initially without crosslinking too quickly, ensuring the fluidity and flexibility of the soft segment; in the S3 stage, the temperature is raised in stages and an appropriate holding time is set to allow the hard segment to fully react and crosslink, while making the microphase separation structure more obvious. This staged heating process allows the hard domain to be evenly distributed in the soft phase, forming a heat-resistant skeleton without excessively restricting the molecular movement of the soft segment, thus giving the polyurethane composite material excellent elasticity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a schematic diagram of a method for preparing a polyurethane composite material for a new energy vehicle battery pack in one embodiment of the present invention. DETAILED DESCRIPTION

[0015] 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.

[0016] Please refer to Figure 1 The present invention provides a method for preparing a polyurethane composite material for a new energy vehicle battery pack, the steps comprising: S1. Heat the polycarbonate polyol component to 60-70°C, add a heat-resistant filler and stir at a stirring speed of 500-700 rpm for 20-30 min to obtain a mixed slurry.

[0017] Step S1 includes: S1. Heat the polycarbonate polyol component to 60-70°C, add the chain extender and stir at a speed of 200-300 rpm for 10 min.

[0018] The polycarbonate polyol component is heated to 60-70°C to reduce viscosity and facilitate the uniform dispersion of the chain extender in a relatively low-viscosity system. In this step, the catalyst is not added to avoid the chain extension from releasing a large amount of heat too quickly. The two are fully mixed within 10 minutes by stirring at a medium speed (200-300 rpm). Adding a chain extender can regulate the hard segment content in the subsequent polyurethane composite material, so that the material has stronger mechanical properties (such as tensile strength and elastic modulus).

[0019] S1.2. Add the catalyst and antioxidant, maintain the speed and temperature, and stir for 20 minutes.

[0020] The polycarbonate polyol component includes at least one of carbon dioxide-based polycarbonate polyol, polyethylene glycol carbonate, poly(1,4-butylene glycol) carbonate, and poly(cyclohexanedimethanol) carbonate; the chain extender includes at least one of 1,4-butylene glycol, hexanediol, and diphenylmethane diisocyanate; the catalyst includes at least one of tin trifluorochloride, cobalt dichloride, and an organic metal salt-quaternary ammonium salt; and the antioxidant includes at least one of 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, and 2,2'-methylenebis(4-methyl-6-tert-butylphenol).

[0021] When the chain extender is diphenylmethane diisocyanate, the catalyst enters the system to initiate or accelerate the reaction of isocyanate groups and hydroxyl groups, which is carried out in a mild environment of 60-70°C to avoid instantaneous temperature surges that lead to scorching. The addition of antioxidants can inhibit the free radical oxidation process in subsequent higher temperature processing or service, ensuring the long-term thermal stability of the material. Continue stirring at a medium speed for 20 minutes to ensure that the catalyst and antioxidant are evenly dispersed in the system, so that the reaction is more controllable and the oxidation inhibition effect is better.

[0022] When the chain extender does not contain diphenylmethane diisocyanate, if the catalyst is added at the same time as the isocyanate at a later stage, there will be over-catalysis in some areas, and the temperature will rise instantly, resulting in scorching. Dispersing in a relatively low viscosity system in advance can reduce such risks. When the aromatic modified isocyanate is actually added to S2, the catalyst is evenly distributed, and as long as the appropriate temperature is maintained, the reaction will proceed relatively smoothly and evenly.

[0023] Although the S1 temperature is only 60~70℃, the system has begun to slowly heat up or react in a small range (such as a weak side reaction between the chain extender and the carbonate end group). Adding antioxidants in advance can reduce the early signs of color change or molecular chain breakage. Like catalysts, antioxidants are added at a stage with low viscosity and not too high temperature, which makes it easier to evenly distribute to each component in the system, thereby continuing to play a protective role in the subsequent high-temperature curing (S3) and use environment.

[0024] S1.3, place the heat-resistant raw material in the modifier, heat to 40~50℃, stir for 30min, dry at 80~100℃ for 1~2h to obtain a heat-resistant filler. The modifier includes an organic silane reagent or a low molecular weight hydroxyl reagent, the organic silane reagent includes at least one of γ-aminopropyl triethoxysilane, γ-glycidyl ether oxypropyl trimethoxysilane, and vinyl silane, and the low molecular weight hydroxyl reagent includes at least one of diethanolamine, pentaerythritol, citric acid, polypropylene glycol, and polyethylene glycol. The heat-resistant filler includes at least one of aluminum hydroxide, ammonium polyphosphate, melamine polyphosphate, melamine cyanurate, and expanded graphite. Calculated by mass ratio, polycarbonate polyol component: chain extender: catalyst: antioxidant: heat-resistant filler = 100:6:1:0.5:30.

[0025] The heat-resistant raw materials are impregnated, adsorbed or surface condensed with organic silane reagents or low molecular weight hydroxyl reagents. After surface modification, the surface of the heat-resistant filler has functional groups (amino, hydroxyl, epoxy, etc.) that are compatible with the soft segment / hard segment of the polyurethane composite material to form a transition layer. Stir at 40~50℃ for 30min to make the modifier evenly coat the powder particles, and then dry at 80~100℃ to fix or condense the modifier and the surface of the heat-resistant filler, reduce the agglomeration of the heat-resistant filler and enhance its embedding force in the polyurethane matrix. Not only does it retain the heat resistance and heat resistance of the heat-resistant filler, but it can also form a more flexible transition zone in the polyurethane composite material to avoid brittle fracture.

[0026] S1.4, add heat-resistant filler, increase the speed to 500~700rpm, stir for 20~30min, and obtain a mixed slurry after stirring. The modified and fully dried heat-resistant filler is fully mixed with the previously prepared catalytic system at a medium-high stirring rate (500~700rpm) to refine and disperse the particles and reduce local hardening caused by filler agglomeration; the heat-resistant filler not only enhances the heat resistance of the material, but also achieves good synergy with the soft segment of the polyurethane composite material through its surface flexibility, retaining the elasticity of the material, and stirring for 20~30min to ensure that the viscosity of the mixed system is stable and there is no obvious deposition, laying a good foundation for subsequent steps.

[0027] S2. Add aromatic modified isocyanate to the mixed slurry, adjust the stirring speed to 200-300 rpm, maintain the real-time temperature at 60-70°C, stir for 30-60 minutes, and degas after stirring to obtain a polyurethane prepolymer. The aromatic modified isocyanate includes at least one of carbodiimide modified diphenylmethane diisocyanate, urea polymer modified diphenylmethane diisocyanate, and toluene diisocyanate-based prepolymer. The toluene diisocyanate-based prepolymer includes toluene diisocyanate and polyether or polyester polyol. According to the mass ratio, the mixed slurry: aromatic modified isocyanate = 20: (4-7). Within the range of 20: (4-7), by changing the amount of isocyanate added, the hard segment content and crosslinking density of the final polyurethane network can be adjusted to meet different requirements for mechanical properties (elasticity, strength) and heat resistance, avoid large-scale polymerization exothermic runaway, and reduce the risk of scorch or material defects.

[0028] Various modification methods (carbodiimidization, urea polymerization, etc.) can improve the stability of isocyanates at high temperatures, reduce side reactions and provide the material with a higher glass transition temperature. Modified isocyanates tend to have lower viscosity and moderate activity, which helps to achieve controllable reactions at medium temperatures (60~70°C) without violent heat release.

[0029] Step S2 includes: S2.1. Add aromatic modified isocyanate with an isocyanate group content of 25-30% to the mixed slurry in batches, adjust the stirring speed to 200-300 rpm, maintain the temperature at 60-70°C, and stir for 30-60 minutes.

[0030] Aromatic modified isocyanate is added in batches so that the reaction between isocyanate groups and hydroxyl groups can release heat smoothly, avoiding the risk of rapid temperature rise and scorching caused by all-in-one addition; by monitoring the temperature and viscosity in sections, if the reaction is too fast, the addition can be stopped or the stirring speed can be reduced to keep the system in a safe temperature range (60~70℃). Medium speed can avoid bubble entrainment or local temperature rise caused by too fast stirring, and also ensure that the catalyst and isocyanate are fully in contact with the polyol. 30~60min allows the cross-linking of isocyanate groups and hydroxyl groups in the early stage to form a stable prepolymer structure, and the viscosity gradually increases, but still maintains fluidity, which is convenient for subsequent degassing operations.

[0031] In this temperature range, the polyurethane reaction speed is moderate, which can ensure the production rate and reduce excessive heat release. Too high a temperature may cause self-condensation, scorching, etc., while too low a temperature will cause too slow a reaction, waste energy or extend the process cycle.

[0032] The mixing equipment for the mixed slurry and aromatic modified isocyanate is equipped with a precise temperature control system, such as an electric heating belt or a constant temperature water bath heating system. In order to avoid excessive temperature fluctuations, a circulating hot water heating system can be used to ensure stable temperature. Use real-time temperature sensors (such as thermocouples or infrared temperature sensors) to accurately monitor the temperature of the mixed slurry. The sensors need to be placed at different locations in the reactor (such as the bottom, side and top) to avoid local overheating. At the beginning of the reaction, the reactants can be gradually heated to 60°C by the heating system, and then the temperature can be adjusted by a water cooling cycle or cooling plate during the reaction. If the temperature is too high (such as more than 70°C), the cooling system can be started to quickly control the temperature within the set range. The set temperature is 60~70°C, and the heating power or cooling flow is adjusted by the automated temperature control system to ensure that the temperature remains in a stable range.

[0033] S2.2. After stirring, evacuate to -0.05MPa, maintain for 2 minutes, and then restore to normal pressure for 1 minute. Repeat several times until the degassing time is 5~10min. During the degassing stage, maintain the stirring speed at 5~10rpm. After stirring, the polyurethane prepolymer is obtained.

[0034] Intermittent vacuum plus normal pressure cycle can make the bubbles dissolved or suspended in the slurry expand, burst and escape continuously, effectively reducing the material defects caused by bubbles; if the bubbles inside the prepolymer are not removed in time, they may expand into structural voids or cause local stress concentration during the subsequent high-temperature curing (S3). If high-speed stirring is still used during degassing, new bubbles will be continuously introduced or the bubbles that have floated up will be broken again. Low-speed stirring can slightly stir the slurry to avoid precipitation, while not destroying the vacuum environment and ensuring degassing efficiency. It can then directly enter the S3 high-temperature curing stage to ensure material uniformity. In the degassed and initially cross-linked state, the polyurethane prepolymer has a predictable curing curve and mechanical performance foundation.

[0035] S3. The polyurethane prepolymer is heated to 80-90° C., kept warm for 1-2 hours, then heated to 120-130° C., kept warm for 3-4 hours, and cooled to obtain a polyurethane composite material for a new energy vehicle battery pack.

[0036] Step S3 includes: S3.1. Heat the polyurethane prepolymer to 80-90°C and keep it warm for 1-2 hours.

[0037] Keeping the material in a medium temperature range of 80~90℃ can further promote the formation of the polyurethane network, but the reaction rate does not reach its peak, avoiding excessive heat release or uneven curing in the early stage. The material is initially hardened at this stage, and the supporting force and shape stability are greatly improved, preparing for subsequent deep curing at higher temperatures. Heat treatment at lower viscosity allows the molecular segments to have a certain fluidity, which can eliminate local internal stress and residual bubbles, making the material structure denser and more uniform. This stage can avoid surface curing first, internal delayed delamination or cracks caused by instantaneous temperature rise. In an environment of 80~90℃, side reactions that are prone to occur at high temperatures (such as self-condensation or scorching) will not be triggered, ensuring that the polyurethane cross-linking reaction proceeds smoothly and improving the final quality stability.

[0038] S3.2. Raise the temperature to 120-130°C at a rate of 2-4°C / min, keep warm for 1-2 hours, cool down to 100°C for a short time, then raise the temperature back to 120-130°C, keep warm for another 1-2 hours, and after cooling, obtain a polyurethane composite material for new energy vehicle battery packs.

[0039] In the range of 120~130℃, the polyurethane network enters the deep crosslinking stage, the residual isocyanate groups and hydroxyl or amino functional groups fully react, the material molecular chains are closely arranged and form a high degree of crosslinking, which significantly improves heat resistance, mechanical strength and dimensional stability. The temperature is prevented from soaring instantly by controlling the heating rate, maintaining the thermal balance of the reaction and reducing cracks or local scorching. After 1~2 hours of high temperature insulation, cooling down first can reduce the temperature difference between the inside and outside of the material, release some internal stress, and then raise it to 120~130℃ again to allow the remaining reaction to be completed thoroughly, avoiding structural embrittlement or over-crosslinking caused by long-term high temperature. Some micropores or microcracks are refilled or melted during the cooling and heating process, further improving the density and appearance quality of the parts. Natural or controlled cooling gradually releases the thermal stress of the parts, maintains good dimensional stability, and reduces warping deformation; the finished product can be subsequently inspected and assembled at room temperature or after slightly accelerated cooling.

[0040] The elasticity of polyurethane composites is related to the content of isocyanate and the filling amount of heat-resistant filler, and the relationship is as follows: in, The tensile elastic modulus (Pa or MPa) characterizes the elasticity level of the material. The larger the value, the more elastic the polyurethane composite material is and the stronger its deformation resistance is. is the isocyanate group content (mass percentage) in the polyurethane composite material, which can be obtained by titration or infrared quantification. Within a certain range, The higher the value, the higher the degree of chemical cross-linking, and the elastic modulus tends to increase. Indicates the threshold value of isocyanate content (mass percentage); when When the value is lower than this, the network structure is not sufficient to form an effective elastic skeleton. The modulus is considered very small or approximately that of a soft material. is the empirical coefficient ((Pa·m³) / (J / mol)), is 1~20, reflecting The slope of the contribution to the crosslink density needs to be combined with the specific chemical system (polycarbonate polyol / aromatic modified isocyanate / ) and the test temperature, and is obtained by fitting multiple sets of test data. is the gas constant, about 8.314 J / (mol·K). is the absolute temperature (K) and refers to the heating temperature of the polyurethane composite material. It is a filler correction function, which is used to describe the contribution or influence of heat-resistant filler on the elastic modulus of polyurethane composites. is the volume fraction of heat-resistant filler.

[0041] Specifically, The form can be in, is the stiffening coefficient ([Pa·m³] or [MPa·m³]), which plays a role in adjusting the degree of reinforcement of the polyurethane composite material by the unit volume fraction of the heat-resistant filler. The larger the k value, the greater the influence of the heat-resistant filler on the hardness of the polyurethane composite material at the same volume fraction, resulting in the hardening of the polyurethane composite material. B is a power term (dimensionless), which characterizes the degree to which the heat-resistant filler improves the modulus of the polyurethane composite material in different filling ranges. B>1, the higher the content of the heat-resistant filler, the faster the reinforcement effect, indicating that there is a synergistic or agglomeration effect between the heat-resistant fillers; B<1, the reinforcement effect of the heat-resistant filler decreases or increases sublinearly, and the heat-resistant filler is poorly dispersed and aggregated too much at a high content. If the heat-resistant filler is a spherical filler, B is 1~2, and if the heat-resistant filler is a nano-scale filler, B is 2~4.

[0042] A is an exponential growth rate coefficient [1 / m³], reflecting the exponential effect of heat-resistant fillers on the performance of polyurethane composites. When the A value is large, When a slight increase in the elastic modulus or hardness of the material leads to a significant increase, when the A value is small, the effect of the heat-resistant filler is mild, close to linear or sublinear growth. Similar to the power law model, through experimental fitting (at least 2~3 different If the heat-resistant filler is a spherical filler, A is 1-3; if the heat-resistant filler is a nano-scale filler, A is 4-10.

[0043] The isocyanate group concentration (%NCO) and filler volume fraction ( ) can achieve controllable mechanical properties in polyurethane composites, especially in terms of elastic modulus, tensile strength and elongation. According to the equation, the performance of the material is not only directly related to the concentration of %NCO, but also affected by the volume fraction of fillers. Therefore, the material properties can be optimized by adjusting these variables during the production process, thereby achieving material customization for different application requirements, especially under specific requirements for elasticity, strength and heat resistance.

[0044] Optimizing thermal stability and high temperature resistance of high performance composites: In polyurethane composites, temperature is one of the key factors affecting reaction rate and final performance. The temperature factor introduced in the equation It indicates the effect of temperature on the reaction rate of isocyanate groups with the polyurethane matrix, crosslink density and material properties. By controlling the %NCO and filler volume fraction and precisely adjusting the temperature during the reaction, the heat resistance and thermal stability of the material can be optimized, especially in high temperature environments, such as the working environment of new energy vehicle battery packs, where the heat resistance of the material is critical. As the temperature increases, the reaction rate accelerates, the degree of crosslinking increases, and the high temperature resistance of the final product is enhanced.

[0045] Controlling the filler reinforcement effect and nonlinear reinforcement mechanism of the composite material, the performance of the polyurethane composite material is enhanced with the increase of the filler volume fraction, especially when the filler content is high, the reinforcing effect of the filler becomes more significant. By adjusting A and B, the speed of the filler enhancement on the performance of the polyurethane composite material can be further controlled, and the stiffness, strength and elasticity of the composite material can be precisely adjusted. This nonlinear behavior can provide guidance for the design of high-performance composite materials in practical applications, especially in situations where high rigidity or high elasticity materials are required.

[0046] Precisely control the reaction degree and crosslinking density of isocyanate groups: The content of isocyanate groups directly affects the crosslinking density and degree of polymerization of polyurethane. A high concentration of isocyanate groups can promote a higher degree of crosslinking, enhance the hardness and strength of the material, but may also cause brittleness. By adjusting the %NCO, it is possible to avoid excessive crosslinking while maintaining the flexibility of the material. The %NCO adjustment factor in the equation This allows the reaction process to be flexibly adjusted, thereby optimizing the mechanical properties and heat resistance of the material.

[0047] The present invention provides a polyurethane composite material for a new energy vehicle battery pack, which is prepared by a preparation method of a polyurethane composite material for a new energy vehicle battery pack. The polyurethane composite material for a new energy vehicle battery pack comprises: a polycarbonate polyol component, a heat-resistant filler and an aromatic modified isocyanate; wherein: The polycarbonate polyol component is used to improve the heat resistance of polyurethane composites; Heat-resistant fillers are used to enhance the thermal stability of polyurethane composites; The aromatic modified isocyanate is used to form a cross-linking backbone with the polycarbonate polyol component.

[0048] The above are only preferred embodiments of the present invention and are 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 polyurethane composite material for a new energy vehicle battery pack, characterized in that the steps include: S1. Heat the polycarbonate polyol component to 60-70° C., add a heat-resistant filler and stir at a stirring speed of 500-700 rpm for 20-30 min to obtain a mixed slurry; S2, adding aromatic modified isocyanate to the mixed slurry, adjusting the stirring speed to 200-300 rpm, maintaining the real-time temperature at 60-70° C., stirring for 30-60 min, and degassing after the stirring is completed to obtain a polyurethane prepolymer; S3. Raise the temperature of the polyurethane prepolymer to 80-90° C., keep the temperature for 1-2 hours, then raise the temperature to 120-130° C., keep the temperature for 3-4 hours, and obtain a polyurethane composite material for a new energy vehicle battery pack after cooling.

2. The method for preparing the polyurethane composite material for new energy vehicle battery pack according to claim 1, characterized in that: Step S1 includes: S1. Heat the polycarbonate polyol component to 60-70°C, add the chain extender and stir at a stirring speed of 200-300 rpm for 10 min; S1.2, add the catalyst and antioxidant, maintain the speed and temperature, and stir for 20 minutes; S1.3, place the heat-resistant raw material in the modifier, heat to 40-50°C, stir for 30 minutes, and dry at 80-100°C for 1-2 hours to obtain a heat-resistant filler; S1.4, add the heat-resistant filler, increase the rotation speed to 500-700 rpm, stir for 20-30 minutes, and obtain a mixed slurry after the stirring is completed.

3. The method for preparing the polyurethane composite material for new energy vehicle battery pack according to claim 2, characterized in that: In step S1, the polycarbonate polyol component includes at least one of a carbon dioxide-based polycarbonate polyol, a polyethylene glycol carbonate, a poly(1,4-butylene glycol) carbonate, and a poly(cyclohexanedimethanol) carbonate; the chain extender includes at least one of 1,4-butylene glycol, hexanediol, and diphenylmethane diisocyanate; the catalyst includes at least one of tin trifluorochloride, cobalt dichloride, and an organic metal salt-quaternary ammonium salt; the antioxidant includes 2,6-di-tert-butyl-4-methylphenol, tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid)pentylene glycol, and the like. The invention discloses a novel heat-resistant filler comprising at least one of tetraol ester, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), the heat-resistant filler comprising at least one of aluminum hydroxide, ammonium polyphosphate, melamine polyphosphate, melamine cyanurate, and expanded graphite, the modifier comprising an organic silane reagent or a low molecular weight hydroxyl reagent, the organic silane reagent comprising at least one of γ-aminopropyl triethoxysilane, γ-glycidyloxypropyl trimethoxysilane, and vinyl silane, and the low molecular weight hydroxyl reagent comprising at least one of diethanolamine, pentaerythritol, citric acid, polypropylene glycol, and polyethylene glycol.

4. The method for preparing the polyurethane composite material for new energy vehicle battery pack according to claim 1, characterized in that: In step S1, according to the mass ratio, the polycarbonate polyol component: the chain extender: the catalyst: the antioxidant: the heat-resistant filler = 100:6:1:0.5:

30.

5. The method for preparing the polyurethane composite material for new energy vehicle battery pack according to claim 1, characterized in that: Step S2 includes: S2.1, adding an aromatic modified isocyanate having an isocyanate group content of 25-30% to the mixed slurry in batches, adjusting the stirring speed to 200-300 rpm, maintaining the temperature at 60-70°C, and stirring for 30-60 min; S2.

2. After stirring, evacuate to -0.05MPa, maintain for 2 minutes, and then restore to normal pressure for 1 minute. Repeat several times until the degassing time is 5~10min. During the degassing stage, maintain the stirring speed at 5~10rpm. After stirring, the polyurethane prepolymer is obtained.

6. The method for preparing the polyurethane composite material for new energy vehicle battery pack according to claim 1, characterized in that: Step S2 includes: The aromatic modified isocyanate includes at least one of carbodiimide modified diphenylmethane diisocyanate, urea polymer modified diphenylmethane diisocyanate, and toluene diisocyanate-based prepolymer. The toluene diisocyanate-based prepolymer includes toluene diisocyanate and polyether or polyester polyol. Calculated by mass ratio, the mixed slurry: the aromatic modified isocyanate = 20: (4~7).

7. The method for preparing the polyurethane composite material for new energy vehicle battery pack according to claim 1, characterized in that: Step S3 includes: S3.1, heating the polyurethane prepolymer to 80-90°C and keeping warm for 1-2 hours; S3.

2. Raise the temperature to 120-130°C at a rate of 2-4°C / min, keep warm for 1-2 hours, cool down to 100°C for a short time, then raise the temperature back to 120-130°C, keep warm for another 1-2 hours, and after cooling, obtain a polyurethane composite material for new energy vehicle battery packs.

8. A polyurethane composite material for a new energy vehicle battery pack, characterized in that: The polyurethane composite material for a new energy vehicle battery pack is prepared by the preparation method of the polyurethane composite material for a new energy vehicle battery pack according to any one of claims 1 to 9, wherein the polyurethane composite material for a new energy vehicle battery pack comprises: a polycarbonate polyol component, a heat-resistant filler and an aromatic modified isocyanate; wherein, The polycarbonate polyol component is used to improve the heat resistance of the polyurethane composite material; The heat-resistant filler is used to enhance the thermal stability of the polyurethane composite material; The aromatic modified isocyanate is used to form a cross-linked skeleton with the polycarbonate polyol component.

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