A new energy vehicle electric control upper cover PA66 composite material and a preparation method thereof

Abstract

This invention provides a PA66 composite material for the electronic control cover of new energy vehicles and its preparation method. The composite material consists of 25-35% PPO, 15-25% PA66, 5-10% MXD6, 2-4% DZ570 synergistic flame retardant, 2-5% microencapsulated red phosphorus, 0.5-2% MCA, 0.3-1% phosphorus-nitrogen synergist, 18-25% matte alkali-free glass fiber, 4-8% spherical silica powder, 1-4% nickel-plated carbon fiber, 0.5-1.5% infrared-transparent black inorganic pigment, 0.2-0.5% dispersing wax, 0.1-0.5% nucleating agent, 0.1-0.5% low-shrinkage agent, 0.2-0.6% antioxidant, 0.3-0.8% weathering agent, and 0.1-0.5% fluorine-based internal lubricant. Through resin drying, graded premixing, low-shear twin-screw granulation, and high-temperature injection molding, the products, with a thickness of 1.5mm, meet UL94 V0, CTI≥600V, shielding≥35dB, shrinkage≤0.3%, anisotropy≤0.1%, protection IP67 / IP6K9K, salt spray resistance≥960h, and no cracking after 500 cycles at -40℃~125℃. They fully meet the requirements of national standards such as GB 18488, achieving integrated insulation, flame retardancy, shielding, and sealing, with a yield rate≥99%.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and in particular to a PA66 composite material for the electronic control cover of new energy vehicles and its preparation method. Background Technology

[0002] The cover of the electronic control unit (VCU / MCU / OBU) in new energy vehicles must simultaneously meet five core requirements: high-voltage insulation, flame retardant safety, dimensional accuracy, electromagnetic shielding, and environmental durability. However, existing materials generally have defects: conventional PA66 / glass fiber systems have high water absorption and large warping, making the sealing surface prone to failure and failing to meet IP67 / IP6K9K protection levels; ordinary flame-retardant systems have a lower tracking index (CTI) (<400V) compared to conventional systems, failing to meet the high-voltage safety requirements of vehicles; conductive fillers added to improve electromagnetic shielding can easily reduce insulation and CTI, making it difficult to balance electromagnetic compatibility (EMC) and electrical safety. In addition, materials are prone to cracking, precipitation, and yellowing under high temperature and humidity cycling, failing to meet automotive-grade durability standards.

[0003] Current technical solutions mostly focus on optimizing a single performance aspect, such as only improving the flame retardancy rating or only reducing warpage, without forming a standardized process across the entire chain from formulation design, pretreatment, twin-screw granulation to injection molding. Therefore, existing materials cannot simultaneously meet multiple national standards and automotive specifications, including GB 18488, GB / T 4208, UL94 V0, CTI≥600V, and salt spray ≥960h. There is an urgent need for a composite material and its preparation method that can achieve integrated insulation, flame retardancy, electromagnetic shielding, and dimensional sealing. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a PA66 composite material that meets the requirements of the electronic control cover of new energy vehicles, so as to solve the technical problem that the electronic control cover material in the prior art cannot simultaneously meet multiple national standards and automotive-grade requirements such as UL94 V0 flame retardancy, CTI≥600V, electromagnetic shielding≥35dB, and low warpage; at the same time, this invention will also provide a method for preparing the PA66 composite material that meets the requirements of the electronic control cover of new energy vehicles.

[0005] To achieve the above objectives and other related objectives,

[0006] A method for preparing PA66 composite material for the electronic control cover of new energy vehicles includes the following steps: S1, mixing PPO resin, PA66 resin and MXD6 resin to form a mixed resin, and drying it at 110-120℃ until the moisture content is ≤0.06%; S2, independently premixing the flame retardant premix, filler and shielding premix, and pigment premix, wherein the premixing speed of the flame retardant premix is ​​400-600 r / min and the time is 3-8 min; the premixing speed of the filler and shielding premix is ​​1500-2500 r / min and the time is 10-20 min; the premixing speed of the pigment premix is ​​1000-2000 r / min and the time is 5-15 min; S3, combining the dried mixed resin from S1, the flame retardant premix, the filler and shielding premix, the pigment premix, as well as matte alkali-free glass fiber and DZ570 synergistic flame retardant. Nucleating agent, low-shrinkage agent, antioxidant, weathering agent, and fluorine-based internal lubricant are added to a twin-screw extruder. The screw length-to-diameter ratio is controlled to be ≥40:1, the rotation speed is 180-260 r / min, and the processing temperature gradient is set as follows: feed port 230-240℃, melting section 245-255℃, shearing section 255-265℃, homogenization section 260-270℃, die head 255-265℃, and vacuum degree -0.07 to -0.10 MPa. After melting, mixing, degassing, extrusion, pelletizing, and drying, composite material particles are obtained. The pellets are cylinders with a length of 2-3 mm. After pelletizing, they are cooled and shaped in a circulating cooling water tank at 20-30℃. After drying, the moisture content of the particles is ≤0.05%. S4, the composite material particles are injection molded at a mold temperature of 85-105℃, using a staged injection and holding pressure process, with a cooling time of 30-50 seconds, to obtain the electronic control cover product.

[0007] Furthermore, the matte alkali-free glass fiber in S3 is added by side feeding, and the diameter of the matte alkali-free glass fiber is 10-13μm; the total length of the kneading block element in the screw assembly of the twin-screw extruder accounts for ≤30% of the total screw length.

[0008] Furthermore, the injection molding described in S4 uses a 300-500T injection molding machine with a mold temperature of 90-100℃; the process parameters for the staged injection are: first stage injection pressure 80-100MPa, injection speed 30-50mm / s, second stage injection pressure 60-80MPa, injection speed 50-70mm / s, third stage injection pressure 40-60MPa, injection speed 20-30mm / s; holding pressure 40-60MPa, holding time 15-20 seconds.

[0009] Furthermore, after the composite material particles described in S3 are pelletized, they are further dried at 80-90℃ for 2-3 hours to control the moisture content to ≤0.05%.

[0010] Furthermore, the flame retardant composition is composed of microencapsulated red phosphorus, MCA, and phosphorus-nitrogen synergist. The flame retardant composition is premixed with the partially dried mixed resin in S1 at a mass ratio of 1:10 to form a flame retardant premix. The filler and shielding premix is ​​composed of spherical silica powder, nickel-plated carbon fiber, and dispersion wax. The pigment premix is ​​composed of infrared-transparent black inorganic pigment and dispersion wax, and the mass ratio of infrared-transparent black inorganic pigment to dispersion wax is 1:0.3.

[0011] Further, the mass percentage of each component in the composite material is as follows: PPO resin 25-35%, PA66 resin 15-25%, MXD6 resin 5-10%, DZ570 synergistic flame retardant 2-4%, microencapsulated red phosphorus 2-5%, MCA 0.5-2%, phosphorus-nitrogen synergist 0.3-1%, matte alkali-free glass fiber 18-25%, spherical silica powder 4-8%, nickel-plated carbon fiber 1-4%, infrared-transparent black inorganic pigment 0.5-1.5%, dispersion wax 0.2-0.5%, nucleating agent 0.1-0.5%, low shrinkage agent 0.1-0.5%, antioxidant 0.2-0.6%, weathering agent 0.3-0.8%, and fluorine-based internal lubricant 0.1-0.5%.

[0012] In another real-world example of the present invention, a PA66 composite material prepared by the method is provided. The composite material achieves a UL94 V0 flame retardant rating at a thickness of 1.5 mm, with a tracking index (CTI) ≥ 600 V, electromagnetic shielding effectiveness ≥ 35 dB, molding shrinkage ≤ 0.3%, anisotropy ≤ 0.1%, protection rating of IP67 / IP6K9K, salt spray resistance ≥ 960 h, and no cracking after 500 temperature cycles from -40°C to 125°C.

[0013] Furthermore, the composite material has a CTI ≥ 650V, electromagnetic shielding effectiveness ≥ 38dB, molding shrinkage ≤ 0.22%, dimensional tolerance of ± 0.03mm, passes 1000 hours of salt spray test, and passes 500 temperature cycles without cracking.

[0014] As described above, the complete PA66 composite material for the electronic control cover of new energy vehicles and its preparation method of the present invention have the following beneficial effects: The present invention provides a preparation method and the obtained material of PPO / PA66 composite material that meets the national standard requirements for electronic control covers of new energy vehicles, which have the following beneficial effects: First, by using the synergistic low water absorption and low warpage of the PPO / PA66 / MXD6 ternary resin matrix, combined with the compounding of the halogen-free flame retardant system and the DZ570 synergistic flame retardant, and the 1:10 premixing process of the flame retardant and resin, a CTI ≥ 600V (preferably up to 680V) under the UL94 V0 flame retardant rating is achieved, while the electromagnetic shielding effectiveness is ≥ 35dB (preferably 38dB), successfully solving the industry problem of mutual constraint between shielding and insulation. Secondly, the invention employs a low-shear twin-screw extruder (kneading block ratio ≤30%), side-feeding glass fiber, and gradient temperature control, achieving a glass fiber length retention rate of 60%-75%. The resulting product has a molding shrinkage rate ≤0.3%, anisotropy ≤0.1%, dimensional tolerance ±0.03mm, and sealing surface flatness ≤0.1mm, meeting IP67 / IP6K9K protection requirements. Thirdly, a standardized process throughout the entire process (resin drying moisture ≤0.06%, granule secondary drying moisture ≤0.05%, high mold temperature graded injection molding) ensures stable granule quality, a yield ≥99%, salt spray resistance ≥1000h, and 500 temperature cycles from -40℃ to 125℃ without cracking, fully complying with national standards such as GB 18488 and GB / T 4208, as well as automotive standards. Finally, the composite material of this invention is more than 40% lighter than metal, with a cost reduction of approximately 30%, and is halogen-free and environmentally friendly. It can be mass-produced stably, providing a high-safety, high-reliability, and lightweight engineering plastic solution for new energy vehicle electronic control units. Attached Figure Description

[0015] Figure 1 The diagram shown is a flowchart of the method of the present invention. Detailed Implementation

[0016] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0017] Example 1

[0018] like Figure 1As shown, this invention provides a method for preparing PA66 composite material for the electronic control cover of new energy vehicles, comprising the following steps: S1, mixing PPO resin, PA66 resin and MXD6 resin to form a mixed resin, and drying at 110-120℃ until the moisture content is ≤0.06%; S2, independently premixing the flame retardant premix, filler and shielding premix, and pigment premix, wherein the flame retardant premix is ​​premixed at a speed of 400-600 r / min for 3-8 min; the filler and shielding premix is ​​premixed at a speed of 1500-2500 r / min for 10-20 min; and the pigment premix is ​​premixed at a speed of 1000-2000 r / min for 5-15 min; S3, combining the dried mixed resin from S1, the flame retardant premix, filler and shielding premix, pigment premix, and matte alkali-free glass fiber, DZ570 co-processing agent... Effective flame retardants, nucleating agents, low-shrinkage agents, antioxidants, weathering agents, and fluorine-based internal lubricants are added to a twin-screw extruder. The screw length-to-diameter ratio is controlled to be ≥40:1, the rotation speed is 180-260 r / min, and the processing temperature gradient is set as follows: feed port 230-240℃, melting section 245-255℃, shearing section 255-265℃, homogenization section 260-270℃, die head 255-265℃, and vacuum degree -0.07 to -0.10 MPa. After melting, mixing, degassing, extrusion, pelletizing, and drying, composite material particles are obtained. The pellets are cylinders with a length of 2-3 mm. After pelletizing, they are cooled and shaped in a circulating cooling water bath at 20-30℃. After drying, the moisture content of the particles is ≤0.05%. S4, the composite material particles are injection molded at a mold temperature of 85-105℃, using a staged injection and holding pressure process, with a cooling time of 30-50 seconds, to obtain the electronic control cover product.

[0019] This invention employs a process called S1, in which PPO, PA66, and MXD6 resins are mixed and dried. The synergistic effect of these ternary resins reduces water absorption and warpage. In S2, the flame-retardant premix, filler and shielding premix, and pigment premix are premixed independently. The filler and shielding premix are premixed at a high speed of 1500-2500 r / min to ensure thorough dispersion of the spherical silica powder and nickel-plated carbon fibers, laying the foundation for the subsequent formation of a three-dimensional conductive network and interfacial insulation distribution. In S3, a low-shear twin-screw extruder (length-to-diameter ratio ≥40:1, speed 180-260 r / min, kneading block ratio ≤30%) is used in conjunction with side-feeding matting alkali-free glass fiber and a precise five-stage temperature gradient (230-270℃) to effectively maintain the glass fiber length. Simultaneously, vacuum degassing removes small-molecule volatiles, resulting in water-cooled pellets with a moisture content ≤0.05%. The S4 uses a high mold temperature (85-105℃) and a staged injection and pressure holding process to ensure uniform melt filling, low internal stress, and to obtain a dimensionally stable and flat-sealed electronic control cover product after cooling and shaping.

[0020] The composite material prepared by the above method can achieve a UL94 V0 flame retardant rating at a thickness of 1.5 mm. Compared to a tracking index (CTI) ≥ 600V, electromagnetic shielding effectiveness ≥ 35dB, molding shrinkage ≤ 0.3% and anisotropy ≤ 0.1%, it meets IP67 / IP6K9K protection requirements, has salt spray resistance ≥ 960h, and exhibits no cracking after 500 temperature cycles from -40℃ to 125℃. It fully complies with national standards such as GB18488 and GB / T 4208, as well as automotive standards. Furthermore, the entire process is standardized, particle moisture and dispersibility are controllable, and the yield rate can reach over 99%. It is suitable for the large-scale stable production of new energy vehicle electronic control covers, achieving integrated insulation, flame retardancy, electromagnetic shielding, and dimensional sealing.

[0021] The matte alkali-free glass fiber in S3 is added by side feeding, and the diameter of the matte alkali-free glass fiber is 10-13μm; the total length of the kneading block element in the screw assembly of the twin-screw extruder accounts for ≤30% of the total screw length.

[0022] The matte, alkali-free glass fiber is added via side feeding, with a diameter of 10-13 μm. In the twin-screw extruder, the total length of the kneading block element accounts for ≤30% of the total screw length. Side feeding ensures the glass fiber is added after the melt enters the shearing section, preventing it from being subjected to severe shearing at the feed inlet and thus preserving a longer original length (≥60% retention rate). The 10-13 μm diameter ensures effective interfacial bonding between the glass fiber and the resin matrix while avoiding the breakage of excessively fine glass fibers. A kneading block length of ≤30% represents a low-shear screw configuration, which, combined with the low speed of the main extruder (180-260 r / min), minimizes mechanical damage to the glass fiber and flame retardant particles during melt mixing and dispersion. This helps maintain the integrity of the spherical silica powder morphology and the conductive network structure of the nickel-plated carbon fiber, and reduces localized overheating and decomposition of the flame retardant caused by high shear.

[0023] By limiting the fiber length as described above, the fiberglass retention rate can be stabilized at 60%-75%, thus endowing the composite material with higher flexural strength and impact toughness, meeting the mechanical durability requirements of the electronically controlled cover. Simultaneously, the reduced number of long fiberglass ends lowers the probability of tracking under an electric field. Combined with low shear protection of the flame retardant structure, this allows the material to achieve a CTI ≥ 600V (preferably ≥ 650V) at the UL94 V0 flame retardancy rating. Furthermore, the low proportion of kneading blocks combined with side feeding significantly reduces torque and energy consumption during melt processing, improves the operational stability of the twin-screw extruder, and results in high batch-to-batch consistency of particle quality, facilitating continuous industrial production.

[0024] The injection molding described in S4 uses a 300-500T injection molding machine with a mold temperature of 90-100℃. The process parameters for the staged injection are as follows: first stage injection pressure 80-100MPa, injection speed 30-50mm / s; second stage injection pressure 60-80MPa, injection speed 50-70mm / s; third stage injection pressure 40-60MPa, injection speed 20-30mm / s; holding pressure 40-60MPa, holding time 15-20 seconds.

[0025] Injection molding uses a 300-500T injection molding machine, with mold temperature controlled at 90-100℃. The staged injection process is a three-stage process: the first stage uses high pressure and high speed (80-100MPa, 30-50mm / s) to quickly fill the mold cavity with melt; the second stage uses medium pressure and medium speed (60-80MPa, 50-70mm / s) to ensure uniform filling; and the third stage uses low pressure and low speed (40-60MPa, 20-30mm / s) to reduce internal stress. Holding pressure of 40-60MPa is maintained for 15-20 seconds to compensate for cooling shrinkage. The mold temperature of 90-100℃ is within the crystallization temperature range of PA66 material, which promotes uniform crystallization and reduces internal stress and warpage in the product. Staged injection effectively avoids melt jetting and trapped air, ensuring no weld lines or air pockets on the sealing surface. Combined with holding pressure and shrinkage compensation, this results in precise product dimensions and a smooth sealing surface.

[0026] Through the above injection molding process, the molding shrinkage of the composite material can be reduced to below 0.22%, anisotropy ≤0.08%, dimensional tolerance to ±0.03mm, and sealing surface flatness ≤0.1mm, thus meeting the stringent sealing requirements of IP67 / IP6K9K. High mold temperature combined with graded pressure holding ensures that the product does not crack after 500 temperature cycles from -40℃ to 125℃ and has salt spray resistance ≥1000h. Furthermore, 300-500T injection molding machines adapted to the graded parameters can stably produce large electronically controlled top covers (projected area ≥0.1m²) with a yield rate ≥99%, while avoiding damage to the conductive network of the nickel-plated carbon fiber due to excessive injection pressure, ensuring electromagnetic shielding effectiveness ≥38dB.

[0027] The composite material granules described in S3 are further dried at 80-90℃ for 2-3 hours after pelletizing to control the moisture content to ≤0.05%. Since both PA66 and MXD6 resins have strong hygroscopicity, the cooling and pelletizing process after conventional granulation (20-30℃ water bath) will cause a small amount of moisture to be adsorbed on the surface of the granules. If directly injected into the mold, the moisture will vaporize at high temperatures, leading to silver streaks on the surface of the product, internal bubbles, or even degradation. Through secondary drying at 80-90℃, above the boiling point of water but below the heat distortion temperature of the resin, hot air convection removes free water and some bound water from the inside and surface of the granules for 2-3 hours, ensuring that moisture diffuses to the center of the granules. The dried granules are then quickly transferred to sealed packaging or directly injected into the mold to prevent further moisture absorption.

[0028] Reducing the moisture content of composite material particles from the conventional 0.10%-0.20% to below 0.05% eliminates defects caused by moisture during injection molding, resulting in a smooth surface and dense internal structure in the electrical control cover, and improving mechanical properties (especially impact strength and elongation at break) by more than 15%. Simultaneously, the low moisture condition significantly reduces the risk of hydrolytic degradation of PA66 at high temperatures, ensuring the long-term thermo-oxidative aging performance and CTI stability of the product, preventing cracking even after 500 temperature cycles from -40℃ to 125℃. Furthermore, this drying parameter, combined with the particle storage time before S4, enables continuous production, avoiding batch-to-batch quality fluctuations due to moisture absorption, and maintaining a yield rate consistently above 99%.

[0029] A flame-retardant composition is formed by microencapsulated red phosphorus, MCA, and a phosphorus-nitrogen synergist. The flame-retardant composition is premixed with a portion of the dried mixed resin in S1 at a mass ratio of 1:10 to form a flame-retardant premix. The filler and shielding premix is ​​composed of spherical silica powder, nickel-plated carbon fiber, and dispersion wax. The pigment premix is ​​composed of infrared-transparent black inorganic pigment and dispersion wax, and the mass ratio of infrared-transparent black inorganic pigment to dispersion wax is 1:0.3.

[0030] A flame-retardant composition consisting of microencapsulated red phosphorus, MCA, and a phosphorus-nitrogen synergist is premixed with partially dried mixed resin from S1 at a mass ratio of 1:10 to form a flame-retardant premix. Premixing ensures the flame retardant is uniformly adsorbed onto the surface of the resin particles, preventing agglomeration of the flame retardant in the subsequent twin-screw extrusion. Simultaneously, the 1:10 ratio ensures that the resin initially dilutes the flame retardant during the premixing stage, reducing localized overheating and decomposition of high-concentration flame retardants and improving flame-retardant efficiency. The filler and shielding premix consists of spherical silica powder, nickel-plated carbon fiber, and dispersion wax. The dispersion wax, at a high rotation speed of 1500-2500 r / min, fully wets and deagglomerates the two powders, allowing the spherical silica powder to uniformly coat the surface of the nickel-plated carbon fiber, forming an "insulating-conductive" composite structure. In the pigment premix, infrared-transmitting black inorganic pigment and dispersing wax are premixed at a ratio of 1:0.3. The dispersing wax acts as a carrier to disperse the pigment at the nanoscale, while meeting the requirement of ≥85% infrared transmittance in the 800-1200nm range, which facilitates subsequent laser marking or welding.

[0031] By using a 1:10 resin premix, the flame-retardant composition achieves submicron-level uniform distribution within the matrix, achieving a CTI of 680V at a UL94 V0 flame-retardant rating, far exceeding the 350V of conventionally added flame retardants. In the filler and shielding premix, spherical silica powder and nickel-plated carbon fiber are blended at high speed, with the silica powder preferentially distributed on the fiber surface and interface. After injection molding, a synergistic structure is formed where "a three-dimensional network of nickel-plated carbon fiber provides shielding (≥35dB) + spherical silica powder provides interfacial insulation to ensure CTI," with neither interfering with the other. The 1:0.3 ratio of the pigment premix allows for precise control of the black pigment content, meeting the color requirements of the electronic control cover while maintaining infrared transmittance, facilitating infrared positioning and welding in automated production lines. This graded premixing process significantly reduces the energy consumption for dispersion of each component in the twin-screw extruder, resulting in high batch stability and a yield of ≥99%.

[0032] The mass percentage of each component in the composite material is as follows: PPO resin 25-35%, PA66 resin 15-25%, MXD6 resin 5-10%, DZ570 synergistic flame retardant 2-4%, microencapsulated red phosphorus 2-5%, MCA 0.5-2%, phosphorus-nitrogen synergist 0.3-1%, matte alkali-free glass fiber 18-25%, spherical silica powder 4-8%, nickel-plated carbon fiber 1-4%, infrared-transparent black inorganic pigment 0.5-1.5%, dispersion wax 0.2-0.5%, nucleating agent 0.1-0.5%, low shrinkage agent 0.1-0.5%, antioxidant 0.2-0.6%, weather resistant agent 0.3-0.8%, and fluorine-based internal lubricant 0.1-0.5%.

[0033] The mass percentage range of each component in the composite material is as follows: PPO 25-35%, PA66 15-25%, MXD6 5-10%, which synergistically construct a matrix with low water absorption and low warpage. DZ570 synergistic flame retardant 2-4%, combined with microencapsulated red phosphorus 2-5%, MCA 0.5-2%, and phosphorus-nitrogen synergist 0.3-1%, forms a halogen-free flame retardant system. Red phosphorus and MCA promote char formation and endothermic cooling respectively during combustion, while phosphorus-nitrogen synergy enhances flame retardant efficiency. Matte alkali-free glass fiber 18-25% provides mechanical support, spherical silica powder 4-8% fills shrinkage and improves CTI, and nickel-plated carbon fiber 1-4% constructs a conductive network to achieve electromagnetic shielding. 0.5-1.5% infrared-transmitting black inorganic pigment imparts color and maintains infrared transmittance; 0.2-0.5% dispersing wax assists powder dispersion; 0.1-0.5% each of nucleating agent and low-shrinkage agent control crystallization and warpage; 0.2-0.6% antioxidant, 0.3-0.8% weather resistant agent, and 0.1-0.5% fluorine-based internal lubricant respectively ensure thermal stability, aging resistance, and mold release properties. These components are synergistically optimized to ensure that each functional component achieves its best effect without inhibiting each other.

[0034] Within the above-mentioned formulation range, the composite material can stably achieve UL94 V0 flame retardancy, CTI ≥ 600V, electromagnetic shielding ≥ 35dB, molding shrinkage ≤ 0.3%, and anisotropy ≤ 0.1% at a thickness of 1.5mm. In a specific embodiment, the measured CTI reached 680V, ​​shielding 38dB, and shrinkage 0.22% at the midpoint ratio of PPO 30%, PA66 21.7%, and MXD6 7%, proving the reasonable range. This formulation covers a comprehensive balance from mechanical, flame retardant, to electrical properties, and all components are halogen-free and environmentally friendly, meeting standards such as GB 18488 and GB / T 4208. Meanwhile, the appropriate addition of dispersing wax and lubricant ensures smooth twin-screw extrusion and controllable particle moisture; antioxidants and weathering agents ensure that the product does not crack after 500 cycles at -40℃ to 125℃ and 960h of salt spray, with a yield ≥ 99%. This range balances performance limits and process window, making it suitable for industrial-scale mass production of electronically controlled top covers.

[0035] Example 2

[0036] A PA66 composite material prepared by the above method, wherein the composite material achieves UL94 V0 flame retardant rating at a thickness of 1.5 mm, has a tracking index (CTI) ≥ 600 V, electromagnetic shielding effectiveness ≥ 35 dB, molding shrinkage ≤ 0.3%, anisotropy ≤ 0.1%, protection rating of IP67 / IP6K9K, salt spray resistance ≥ 960 h, and exhibits no cracking after 500 temperature cycles from -40℃ to 125℃.

[0037] These properties are achieved through the synergistic effect of the aforementioned end-to-end technical features: the ternary resin matrix (PPO / PA66 / MXD6) has low water absorption and low warpage; the flame retardant composition and resin are premixed at a 1:10 ratio with DZ570 to ensure V0 flame retardancy without reducing CTI; nickel-plated carbon fiber and spherical silica powder work together to achieve shielding and insulation compatibility; low-shear twin-screw extruder and side feeding maintain the length of glass fiber and reduce tracking points; high mold temperature graded injection molding eliminates internal stress and ensures a smooth sealing surface; and the addition of antioxidants and weather-resistant agents ensures long-term thermal and oxygen resistance and weather resistance stability.

[0038] This composite material meets all national and automotive standards for new energy vehicle electronic control unit covers in one go, eliminating the drawbacks of requiring multiple materials or multi-layer structures. Real-world testing shows a CTI of up to 680V, ​​38dB shielding, 0.22% shrinkage, 1000h salt spray test, and 500 temperature cycles without cracking, far exceeding the lower limit of standards. The IP67 / IP6K9K protection rating ensures long-term reliability of the electronic control unit under high-pressure water spray, immersion, and even sand and dust environments, preventing seal failure. Simultaneously, the halogen-free flame-retardant system does not produce toxic fumes during combustion, aligning with environmental trends. The integration of these properties enables the electronic control unit cover to achieve lightweight (more than 40% weight reduction compared to metal), high safety, and long lifespan, significantly reducing the overall vehicle failure rate and demonstrating significant engineering application value.

[0039] The composite material has a CTI ≥ 650V, electromagnetic shielding effectiveness ≥ 38dB, molding shrinkage ≤ 0.22%, dimensional tolerance of ± 0.03mm, passes 1000 hours of salt spray test, and passes 500 temperature cycles without cracking.

[0040] The composite material achieving this optimal performance far exceeds the minimum national standard requirements for electrical safety (CTI≥600V), with a measured value of 680V meeting the insulation requirements of an 800V high-voltage platform electrical control system. Its shielding effectiveness of 38dB is nearly 10% higher than the conventional 35dB, effectively suppressing electromagnetic interference. With a shrinkage rate ≤0.22% and a tolerance of ±0.03mm, it reaches the precision injection molding level, allowing direct integration with automated assembly lines without secondary processing. Salt spray testing for 1000 hours and temperature cycling for 500 cycles validates its reliability in extreme environments, ensuring the electrical control cover remains effective even after long-term use in coastal high-humidity or high-low temperature alternating regions. This performance combination represents the leading level of current automotive-grade electrical control cover materials, providing a mature and reliable engineering solution for high-voltage safety and lightweighting in new energy vehicles.

[0041] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. All equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this invention should still be covered by the claims of this invention.

Claims

1. A method for preparing PA66 composite material for the electronic control cover of new energy vehicles, characterized in that, Includes the following steps: S1, PPO resin, PA66 resin, and MXD6 resin are mixed to form a mixed resin, which is then dried at 110-120℃ until the moisture content is ≤0.06%; S2, the flame retardant premix, filler and shielding premix, and pigment premix are premixed separately, with the flame retardant premix premixing speed at 400-600 r / min for 3-8 min; the filler and shielding premix premixing speed at 1500-2500 r / min for 10-20 min; and the pigment premixing speed at 1000-2000 r / min for 5-15 min; S3, the dried mixed resin from S1, the flame retardant premix, filler and shielding premix, pigment premix from S2, as well as matte alkali-free glass fiber, DZ570 synergistic flame retardant, nucleating agent, low shrinkage agent, antioxidant, and weathering agent are combined. A fluorine-based internal lubricant is added to a twin-screw extruder, controlling the screw length-to-diameter ratio to be ≥40:1, the rotation speed to be 180-260 r / min, and the processing temperature gradient to be: feed inlet 230-240℃, melting section 245-255℃, shearing section 255-265℃, homogenization section 260-270℃, die head 255-265℃, and vacuum degree -0.07 to -0.10 MPa. After melting, mixing, venting, extrusion, pelletizing, and drying, composite material particles are obtained. The pellets are cylinders with a length of 2-3 mm. After pelletizing, they are cooled and shaped in a circulating cooling water bath at 20-30℃. After drying, the moisture content of the particles is ≤0.05%. S4, the composite material particles are injection molded at a mold temperature of 85-105℃, using a staged injection and holding pressure process, with a cooling time of 30-50 seconds, to obtain the electronically controlled top cover product.

2. The method for preparing a PA66 composite material for the electronic control cover of a new energy vehicle according to claim 1, characterized in that, The matte alkali-free glass fiber in S3 is added by side feeding, and the diameter of the matte alkali-free glass fiber is 10-13μm; the total length of the kneading block element in the screw assembly of the twin-screw extruder accounts for ≤30% of the total screw length.

3. The method for preparing a PA66 composite material for the electronic control cover of a new energy vehicle according to claim 1, characterized in that, The injection molding described in S4 uses a 300-500T injection molding machine with a mold temperature of 90-100℃. The process parameters for the staged injection are as follows: first stage injection pressure 80-100MPa, injection speed 30-50mm / s; second stage injection pressure 60-80MPa, injection speed 50-70mm / s; third stage injection pressure 40-60MPa, injection speed 20-30mm / s; holding pressure 40-60MPa, holding time 15-20 seconds.

4. The method for preparing a PA66 composite material for the electronic control cover of a new energy vehicle according to claim 1, characterized in that, The composite material particles described in S3 are further dried at 80-90℃ for 2-3 hours after being granulated, with the moisture content controlled to be ≤0.05%.

5. The method for preparing a PA66 composite material for the electronic control cover of a new energy vehicle according to claim 1, characterized in that, A flame-retardant composition is formed by microencapsulated red phosphorus, MCA, and a phosphorus-nitrogen synergist. The flame-retardant composition is premixed with a portion of the dried mixed resin in S1 at a mass ratio of 1:10 to form a flame-retardant premix. The filler and shielding premix is ​​composed of spherical silica powder, nickel-plated carbon fiber, and dispersion wax. The pigment premix is ​​composed of infrared-transparent black inorganic pigment and dispersion wax, and the mass ratio of infrared-transparent black inorganic pigment to dispersion wax is 1:0.

3.

6. The method for preparing a PA66 composite material for the electronic control cover of a new energy vehicle according to claim 1, characterized in that, The mass percentage of each component in the composite material is as follows: PPO resin 25-35%, PA66 resin 15-25%, MXD6 resin 5-10%, DZ570 synergistic flame retardant 2-4%, microencapsulated red phosphorus 2-5%, MCA 0.5-2%, phosphorus-nitrogen synergist 0.3-1%, matte alkali-free glass fiber 18-25%, spherical silica powder 4-8%, nickel-plated carbon fiber 1-4%, infrared-transparent black inorganic pigment 0.5-1.5%, dispersion wax 0.2-0.5%, nucleating agent 0.1-0.5%, low shrinkage agent 0.1-0.5%, antioxidant 0.2-0.6%, weather resistant agent 0.3-0.8%, and fluorine-based internal lubricant 0.1-0.5%.

7. A PA66 composite material prepared by the method according to any one of claims 1-6, characterized in that, The composite material achieves a UL94 V0 flame retardant rating at a thickness of 1.5 mm, with a tracking index (CTI) ≥ 600 V, electromagnetic shielding effectiveness ≥ 35 dB, molding shrinkage ≤ 0.3%, anisotropy ≤ 0.1%, protection rating of IP67 / IP6K9K, salt spray resistance ≥ 960 h, and no cracking after 500 temperature cycles from -40℃ to 125℃.

8. The PA66 composite material according to claim 6, characterized in that, The composite material has a CTI ≥ 650V, electromagnetic shielding effectiveness ≥ 38dB, molding shrinkage ≤ 0.22%, dimensional tolerance of ± 0.03mm, passes 1000 hours of salt spray test, and passes 500 temperature cycles without cracking.

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