Preparation method of directional arrangement of high thermal conductivity graphite-based conductive shielding material for bus trunking

Abstract

The application relates to the technical field of electrical material preparation, and discloses a bus duct high-thermal-conductivity graphite-based conductive shielding material directional arrangement preparation method. The method comprises the following steps: graphene / carbon nanotube composite powder and a coupling agent modified resin matrix are dynamically and cyclically sheared and dispersed under the assistance of an asymmetric alternating electric field to form an anisotropic conductive slurry; the slurry is injected into a limited flow channel mold with a parallel staggered flow guide structure, a pulse magnetic field perpendicular to the flow direction is applied to deflect and orient the filler; the oriented structure is frozen by segmental temperature control phase separation treatment to form a pre-oriented film; the pre-oriented film is transferred to the surface of a heated printing substrate, and is gradually compressed and densified under a constant pressure hot roller and a temperature gradient; finally, programmed temperature solidification is carried out, and the pre-oriented film sequentially undergoes low-temperature pre-solidification, medium-temperature crosslinking and high-temperature post-solidification. Through the synergistic orientation of the electric field and the magnetic field, the physical freezing of phase separation and the segmented solidification, the graphite-based filler is highly and directionally arranged in the resin matrix and is stably maintained.

Description

Technical Field

[0001] This invention relates to the field of electrical material preparation technology, specifically a method for the directional arrangement of high thermal conductivity graphite-based conductive shielding material for busbar trunking. Background Technology

[0002] Busbar trunking, as a key power distribution device in power transmission systems, is widely used in power transmission and distribution lines in high-rise buildings, large factories, data centers, and rail transit systems. With the continuous increase in electricity load and the increasing trend towards miniaturization of electrical equipment, busbar trunking systems place higher demands on the comprehensive performance of conductive materials: on the one hand, they need excellent conductivity to reduce line losses; on the other hand, they need high thermal conductivity to dissipate Joule heat in a timely manner, preventing excessive temperature rise that could lead to insulation aging or a decrease in current carrying capacity. Simultaneously, the electromagnetic radiation generated during busbar trunking operation may interfere with nearby sensitive equipment; therefore, the conductive shielding material must also possess electromagnetic interference shielding capabilities.

[0003] Existing busbar conductive materials mostly use copper or aluminum busbars coated with an insulating layer. While these metal conductors have good electrical conductivity, their thermal conductivity is limited by the inherent thermal conductivity of the metals themselves (approximately 400 W / (m·K) for copper and 237 W / (m·K) for aluminum). Furthermore, their high density and cost make them unsuitable for lightweight design and efficient heat dissipation. In recent years, graphite-based composite materials have been considered a promising alternative due to their extremely high in-plane thermal conductivity (theoretically up to 5300 W / (m·K) for single-layer graphene) and good electrical conductivity, while maintaining a much lower density than metals. However, the random dispersion of graphite-based fillers in the resin matrix severely restricts the material's performance—only when anisotropic fillers such as graphene and carbon nanotubes are arranged in an ordered manner along specific directions can their excellent in-plane thermoelectric transport properties be fully utilized.

[0004] Currently, methods for achieving directional packing mainly include external field-assisted orientation, mechanical stretching, and template induction. Mechanical stretching is simple to operate, but it has poor control over film thickness uniformity and is prone to defects during the stretching process. Template induction can achieve high orientation, but the process is complex, inefficient, and difficult to scale up for continuous production. In external field-assisted orientation, the driving force for deflecting high aspect ratio packing is limited when an electric or magnetic field acts alone, especially when the slurry viscosity is high, resulting in high packing rotation resistance and unsatisfactory orientation. Furthermore, most existing processes separate dispersion, orientation, and curing steps, lacking synergy between these stages. This leads to easy relaxation and rearrangement of the packing during subsequent processing, resulting in a significant decrease in orientation.

[0005] Regarding the selection of resin matrices, epoxy resins are widely used due to their excellent adhesion, heat resistance, and processing adaptability. However, unmodified epoxy resins have weak interfacial bonding with graphite-based fillers, and the internal stress generated by curing shrinkage can disrupt the established filler arrangement structure. Although there are reports on modifying resins with coupling agents, conventional modification methods struggle to achieve interfacial chemical bonding simultaneously during filler dispersion, resulting in low modification efficiency. In terms of curing regimes, traditional isothermal curing methods allow sufficient time for fillers to undergo Brownian motion or sedimentation before gelation, leading to the destruction of the orientation structure. Even with staged curing, existing technologies primarily focus on controlling the crosslinking reaction, rather than integrating the temperature control process with the filler orientation freezing in a unified design. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking by directional arrangement, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides a method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking by directional arrangement, the method comprising: Step 1: The graphene / carbon nanotube composite powder and the coupling agent modified resin matrix are dynamically cyclically sheared and dispersed in a closed cavity under the assistance of an asymmetric alternating electric field to form an anisotropic conductive slurry. Step 2: Inject the anisotropic conductive slurry into a confined flow channel mold with a parallel interlaced flow guiding structure, and apply a pulsed magnetic field perpendicular to the flow direction to cause the graphite-based filler to deflect and orient itself along a preset direction. Step 3: Perform segmented temperature-controlled phase separation treatment on the deflected and oriented slurry to promote micro-region crystallization of the resin matrix, freeze and solidify the oriented arrangement structure of the graphite-based filler, and form a conductive shielding pre-oriented film with in-plane preferred orientation. Step 4: Transfer the conductive shielding pre-oriented film to the surface of the heated substrate and perform a stepwise compression densification process under constant pressure hot roller rolling, while maintaining a temperature gradient to maintain the orientation of the filler. Step 5: Place the densified film in a programmed temperature rise oven and sequentially undergo three stages: low-temperature pre-curing, medium-temperature cross-linking, and high-temperature post-curing to obtain the high thermal conductivity graphite-based conductive shielding material for the busbar.

[0008] Preferably, in step one: The frequency of the asymmetric alternating electric field is 50Hz to 500Hz, the field strength is 0.5kV / m to 5kV / m, and the angle between the electric field direction and the horizontal direction is 15° to 75°. The shear rate of the dynamic cyclic shear dispersion is 1000s⁻¹~8000s⁻¹, the shearing time is 30min~90min, and the shearing temperature is controlled at 25°C~45°C; The vacuum level inside the sealed cavity is -0.08 MPa to -0.1 MPa.

[0009] Preferably, in step one: The mass ratio of the graphene / carbon nanotube composite powder to the coupling agent modified resin matrix is ​​1:(3-8). In the graphene / carbon nanotube composite powder, the graphene sheet diameter is 5μm to 25μm, the carbon nanotube outer diameter is 10nm to 30nm, the carbon nanotube length is 1μm to 10μm, and the mass ratio of graphene to carbon nanotube is 1:(0.2 to 1.5). The coupling agent modified resin matrix is ​​prepared by reacting bisphenol A type epoxy resin and γ-glycidoxypropyltrimethoxysilane at a mass ratio of 10:(0.5-2) at 60°C-80°C for 1-3 hours.

[0010] Preferably, in step two: The parallel staggered flow guiding structure consists of multiple sets of strip-shaped flow guiding ridges with a spacing of 0.5mm to 3mm. The extension directions of two adjacent sets of ridges are parallel to each other and staggered, with a stagger distance of 0.5 to 2 times the width of the ridge. The flow channel thickness of the confined flow channel mold is 100μm to 500μm, the flow channel width is 50mm to 200mm, and the flow channel length is 200mm to 800mm. The magnetic induction intensity of the pulsed magnetic field is 0.2T to 1.5T, the pulse frequency is 1Hz to 20Hz, the duty cycle is 30% to 70%, and the angle between the magnetic field direction and the flow channel length direction is 0° to 30°. The injection flow rate of the anisotropic conductive slurry is 0.5 mL / min to 5 mL / min.

[0011] Preferably, in step two: During the process of injecting the anisotropic conductive slurry into the confined flow channel mold, ultrasonic vibration is applied simultaneously to assist dispersion. The ultrasonic frequency is 20kHz to 60kHz, the ultrasonic power is 100W to 500W, and the ultrasonic action direction is perpendicular to the slurry flow direction. The synergistic effect of the pulsed magnetic field and the ultrasonic vibration lasts for 5 to 20 minutes.

[0012] Preferably, in step three: The segmented temperature-controlled phase separation process includes sequential processing of a first temperature zone, a second temperature zone, and a third temperature zone. The first temperature zone has a processing temperature of 50°C to 70°C and a processing time of 1 min to 5 min; The second temperature zone has a processing temperature of 20°C to 35°C and a processing time of 10 min to 30 min. The third temperature zone has a processing temperature of -5°C to 5°C and a processing time of 2 min to 10 min. The rate of temperature change between adjacent temperature zones is 0.5°C / s to 2°C / s.

[0013] Preferably, in step four: The transfer temperature of the conductive shielding pre-oriented film to the heated substrate surface is 40°C to 60°C, and the transfer pressure is 0.1MPa to 0.5MPa. The constant pressure hot roll rolling is a two-stage rolling process. The rolling temperature of the first stage is 55°C to 65°C, the rolling pressure is 1MPa to 3MPa, and the rolling speed is 0.5m / min to 2m / min. The second stage rolling temperature is 70°C to 85°C, the rolling pressure is 3MPa to 6MPa, and the rolling speed is 0.2m / min to 1m / min; The temperature gradient is a linear increase of 5°C to 15°C along the rolling direction from the feed end to the discharge end.

[0014] Preferably, in step four: During the constant pressure hot roll rolling process, a laser online thickness gauge is used to monitor the film thickness in real time, and the rolling pressure is dynamically adjusted according to the thickness deviation. The adjustment response time is 0.5s to 2s, the thickness control target is 50μm to 200μm, and the allowable thickness deviation range is ±5μm. After rolling, the film is cooled to 25°C to 35°C at a cooling rate of 0.5°C / min to 2°C / min.

[0015] Preferably, in step five: The low-temperature pre-curing stage is a treatment at 80°C to 100°C for 15 to 30 minutes. The intermediate-temperature crosslinking stage is a treatment at 120°C to 150°C for 10 to 20 minutes. The high-temperature post-curing stage involves processing at a temperature of 170°C to 200°C for 5 to 15 minutes. The heating rate between adjacent stages is 1°C / min to 5°C / min; The atmosphere inside the programmed heating oven is a nitrogen atmosphere or an argon atmosphere, and the gas flow rate is 0.5L / min to 3L / min.

[0016] Preferably, in step five: The programmed heating oven has a first heating zone, a second heating zone, and a third heating zone arranged sequentially along the direction of film material travel, with the length ratio of each zone being 1:(0.8~1.2):(0.6~1.0). The traveling speed of the membrane material within the programmed temperature drying tunnel is 0.1 m / min to 0.5 m / min; After the high-temperature post-curing stage is completed, the film material is cooled to room temperature at a cooling rate of 2°C / min to 8°C / min and left to stand at room temperature for 12h to 24h.

[0017] Compared with the prior art, the beneficial effects of the present invention are: In step one, an asymmetric alternating electric field-assisted dynamic cyclic shear dispersion is employed. The electric field direction forms a certain angle with the horizontal direction, allowing the graphene / carbon nanotube composite powder to achieve efficient deagglomeration of aggregates under the combined action of the shear flow field and electric force. Furthermore, this process enables the filler to acquire an initial orientation tendency in the early stages of dispersion. The coupling agent-modified resin matrix maintains full contact with the filler within a sealed cavity, and the vacuum environment effectively eliminates air bubbles, preventing the formation of porosity defects during subsequent molding. The appropriate combination of shear rate and time ensures uniform dispersion of the composite powder without damaging the filler structure. Simultaneously, the active groups of the coupling agent chemically react with the defect sites on the filler surface, forming a strong interfacial bond, providing chemical anchoring points for maintaining the subsequent orientation structure.

[0018] In step two, the parallel, staggered flow-guiding structure within the confined flow channel mold causes the slurry to undergo repeated contraction-expansion rheological processes during flow, generating localized stretching flow and further promoting the pre-alignment of the filler along the flow direction. Based on this, a pulsed magnetic field perpendicular to the flow direction is applied. Due to the significant in-plane diamagnetic anisotropy of carbon nanotubes and graphene sheets, the pulsed magnetic field generates a deflection torque, causing the normals of the filler sheets to gradually turn perpendicular to the magnetic field direction, i.e., the sheet surfaces tend to be parallel to the film surface. Compared to a steady magnetic field, the pulsed magnetic field can generate a periodic micro-vibration effect, effectively overcoming the static frictional resistance during filler rotation. Especially for high aspect ratio carbon nanotubes, the pulsed magnetic field can excite their micro-oscillations, helping them overcome the orientation energy barrier and achieve a higher in-plane orientation. The synchronous introduction of ultrasonic vibration not only assists the slurry flow and filling but also disrupts localized ordered stacking at the microscale, preventing flocculation and sedimentation of the filler during orientation and ensuring the uniformity of spatial distribution after orientation.

[0019] Step three, segmented temperature-controlled phase separation, is one of the key design features of this invention. In traditional curing processes, the viscosity of the resin matrix gradually decreases during heating, making it easy for oriented fillers to undergo rotational relaxation. This invention employs a first short-term treatment in a first temperature zone (50°C–70°C) to moderately thicken the slurry and restrict large-angle rotation of the filler; then, it enters a second temperature zone (20°C–35°C) to induce micro-crystallization of the resin matrix, forming physical cross-linking network points. These microcrystalline regions act as "anchor points," fixing the relative positions of adjacent filler layers, ensuring that the overall orientation of the filler remains intact even with subsequent temperature changes; finally, a low-temperature treatment in a third temperature zone (–5°C–5°C) brings the resin matrix into a glassy state, freezing the molecular chain segment movement and thus completely "locking in" the oriented structure of the filler. A moderate temperature change rate is used between the three temperature zones to avoid internal stress caused by thermal shock while ensuring the kinetic conditions for microcrystal nucleation and growth. This approach of freezing orientation through physical phase separation rather than chemical reaction ensures that the filler arrangement structure is already in a stable state before entering high-temperature crosslinking, and the subsequent curing process will not have a significant impact on the degree of orientation.

[0020] Step four, the constant-pressure hot-roll rolling process, achieves progressive compression and densification of the film layer. The two-stage rolling design fully considers the presence of trace amounts of solvent or oligomers in the film layer at the initial stage. The first stage rolling uses lower temperatures and pressures to slowly compact the film layer and expel entrained gases. The second stage rolling is conducted at higher temperatures and pressures, promoting further flow of the resin matrix to fill the filler gaps. Simultaneously, the oriented filler sheets are moderately compressed in the thickness direction, reducing the interlayer distance and increasing the number of contact points, thereby significantly improving the density of in-plane thermal and electrical conduction pathways. The temperature gradient design along the rolling direction results in different rheological responses in different sections of the film layer. The lower temperature at the feed end prevents excessive softening of the film layer, which could lead to orientation disorder, while the higher temperature at the discharge end helps eliminate residual stress generated during rolling, ultimately obtaining a dense film layer with uniform thickness and a smooth surface. The closed-loop control system, consisting of laser online thickness measurement and pressure feedback adjustment, can compensate in real time for thickness deviations caused by fluctuations in slurry solid content or die wear, ensuring batch-to-batch product consistency. Attached Figure Description

[0021] Figure 1 This diagram illustrates the operational steps of the method for preparing the high thermal conductivity graphite-based conductive shielding material for busbar trunking according to the present invention. Detailed Implementation

[0022] This invention discloses a method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking with directional arrangement. The core process utilizes a synergistic approach involving asymmetric alternating electric field shear dispersion, pulsed magnetic field-assisted ultrasonic orientation, segmented temperature-controlled phase separation and shaping, gradient hot roller densification, and segmented inert atmosphere curing. This achieves precise directional arrangement of graphene / carbon nanotube composite fillers within a resin matrix, significantly improving the material's thermal conductivity, electrical conductivity, and electromagnetic shielding performance, thus meeting the stringent operating requirements of busbar trunking. The superiority of this invention's process is demonstrated in detail below through four examples and three comparative examples, combined with specific process parameters and performance test data.

[0023] Example 1 See appendix Figure 1 This embodiment provides a method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking by directional arrangement, including the following specific steps: Step 1: Preparation of anisotropic conductive paste. First, a coupling agent-modified resin matrix is ​​prepared. Bisphenol A type epoxy resin and γ-glycidyl etheroxypropyltrimethoxysilane are added to a reaction vessel at a mass ratio of 10:1 and reacted at 70℃ with stirring for 2 hours to obtain the modified resin matrix. Then, graphene / carbon nanotube composite powder is mixed with the above modified resin matrix at a mass ratio of 1:5, wherein the mass ratio of graphene to carbon nanotubes in the composite powder is 1:0.8, the graphene sheet diameter is 15 μm, and the carbon nanotube outer diameter is 20 nm and the length is 5 μm. The mixture was placed into a closed shearing chamber, the vacuum degree of the chamber was adjusted to -0.09MPa, the shearing temperature was controlled at 35℃, an asymmetric alternating electric field with a frequency of 200Hz, a field strength of 2kV / m and an angle of 45° with the horizontal direction was applied, the dynamic cyclic shearing rate was set to 4000s⁻¹, and shearing was continued for 60min to complete the uniform dispersion and preliminary anisotropic control of the filler, and an anisotropic conductive slurry was obtained.

[0024] Step 2: Slurry Orientation Treatment. The conductive slurry prepared in Step 1 was injected into a confined flow channel mold with a parallel staggered flow guide structure at a constant flow rate of 2 mL / min. The flow channel of the mold was 300 μm thick, 120 mm wide, and 500 mm long. The flow guide structure consisted of strip-shaped flow guide ridges spaced 1.5 mm apart, with the misalignment distance between adjacent ridges being 1 times the width of the ridge. During the slurry injection process, ultrasonic vibration perpendicular to the flow direction was applied simultaneously at a frequency of 40 kHz and a power of 300 W. Simultaneously, a pulsed magnetic field with a magnetic induction intensity of 0.8 T, a pulse frequency of 10 Hz, a duty cycle of 50%, and an angle of 15° with the length of the flow channel was applied. The ultrasonic and magnetic fields worked synergistically for 12 minutes to fully deflect and orient the graphite-based filler along the predetermined direction.

[0025] Step 3: Segmented Temperature-Controlled Phase Separation and Shaping. The oriented slurry is fed into a segmented temperature-controlled chamber for three-stage temperature-controlled phase separation. The first temperature zone is 60℃ for 3 minutes; the second temperature zone is 28℃ for 20 minutes; and the third temperature zone is 0℃ for 5 minutes. The temperature change rate between adjacent temperature zones is controlled at 1℃ / s. This gradient temperature control promotes micro-crystallization of the resin matrix, freezes and solidifies the oriented filler structure, and produces a conductive shielding pre-oriented film with preferred in-plane orientation.

[0026] Step 4: Gradient Hot Roll Densification Treatment. The pre-oriented film is transferred to the surface of a heated substrate under process conditions of 50℃ and 0.3MPa, and densification is performed using a two-stage constant-pressure hot roll rolling process. The first stage rolling temperature is 60℃, rolling pressure is 2MPa, and rolling speed is 1m / min; the second stage rolling temperature is 75℃, rolling pressure is 4MPa, and rolling speed is 0.6m / min. A linear temperature gradient of 5℃ is set along the rolling direction to maintain the orientation stability of the filler. During the rolling process, a laser online thickness gauge is used to monitor the film thickness in real time, dynamically adjust the rolling pressure, with a response time of 1s, and control the target film thickness to 100μm, with the thickness deviation controlled within ±5μm. After rolling, the film is cooled to 30℃ at a cooling rate of 1℃ / min.

[0027] Step 5: Segmented Inert Atmosphere Curing Treatment. The densified film layer is placed in a nitrogen-filled programmed temperature drying tunnel with a gas flow rate of 1.5 L / min. The tunnel is divided into three heating zones along the film's travel direction, with a length ratio of 1:1:0.8. The film travel speed is 0.3 m / min. Three stages of curing are performed sequentially: low-temperature pre-curing at 90℃ for 20 min; medium-temperature cross-linking at 135℃ for 15 min; and high-temperature post-curing at 185℃ for 10 min. The heating rate between adjacent stages is 3℃ / min. After curing, the film is cooled to room temperature at a rate of 5℃ / min and allowed to stand for 18 hours, ultimately yielding a high thermal conductivity graphite-based conductive shielding material for busbar trunking.

[0028] Example 2 This embodiment provides a method for directional arrangement of a high thermal conductivity graphite-based conductive shielding material for busbar trunking, including the following specific steps: Step 1: Preparation of anisotropic conductive paste. A coupling agent-modified resin matrix was prepared by adding bisphenol A epoxy resin and γ-glycidyl etheroxypropyltrimethoxysilane at a mass ratio of 10:0.8 to a reactor and reacting at 65℃ for 2.5 h to obtain the modified resin matrix. Graphene / carbon nanotube composite powder was mixed with the modified resin matrix at a mass ratio of 1:4. The mass ratio of graphene to carbon nanotubes in the composite powder was 1:0.5, with graphene sheet diameter of 10 μm and carbon nanotube outer diameter of 15 nm and length of 3 μm. The mixture was placed in a sealed cavity under a vacuum of -0.085 MPa, a shear temperature of 30℃, and an asymmetric alternating electric field with a frequency of 150 Hz, a field strength of 1.5 kV / m, and an angle of 30°. The shear rate was 3000 s⁻¹, and the shear time was 45 min, resulting in the anisotropic conductive paste.

[0029] Step 2: Orientation of the slurry. Conductive slurry is injected into a confined flow channel mold at a flow rate of 1 mL / min. The mold flow channel is 200 μm thick, 100 mm wide, and 400 mm long, with a 1 mm spacing between the guiding ridges and a misalignment distance of 0.8 times the ridge width between adjacent ridges. Simultaneously, ultrasonic vibration (30 kHz frequency, 200 W power) and a pulsed magnetic field (0.5 T magnetic induction, 8 Hz frequency, 40% duty cycle, 10° angle) are applied for 8 minutes to achieve directional deflection and orientation of the filler.

[0030] Step 3: Segmented temperature-controlled phase separation and shaping. Three temperature-controlled treatments are performed sequentially: first temperature zone 55℃, treatment for 2 min; second temperature zone 25℃, treatment for 15 min; third temperature zone -2℃, treatment for 3 min; the temperature change rate between the temperature zones is 0.8℃ / s. The filler orientation structure is fixed by resin micro-region crystallization to obtain a conductive shielding pre-oriented film.

[0031] Step 4: Gradient hot rolling densification treatment. The pre-oriented film transfer temperature is 45℃, and the transfer pressure is 0.2MPa; the first stage rolling temperature is 58℃, the pressure is 1.5MPa, and the speed is 0.8m / min; the second stage rolling temperature is 72℃, the pressure is 3.5MPa, and the speed is 0.4m / min; the temperature gradient along the rolling direction is 8℃. Laser thickness measurement is used to adjust the film thickness in real time to 80μm, with a thickness deviation of ±5μm and a pressure adjustment response time of 0.8s. After rolling, the film is cooled to 28℃ at a rate of 0.8℃ / min.

[0032] Step 5: Segmented inert atmosphere curing treatment. The drying tunnel is filled with nitrogen atmosphere at a flow rate of 1 L / min. The length ratio of the three heating zones is 1:0.9:0.7, and the film material travel speed is 0.2 m / min. Low-temperature pre-curing is performed at 85℃ for 25 min; medium-temperature cross-linking at 125℃ for 18 min; and high-temperature post-curing is performed at 175℃ for 12 min. The heating rate is 2℃ / min. After curing, the temperature is lowered to room temperature at 4℃ / min, and the mixture is allowed to stand for 15 h to obtain the target material.

[0033] Example 3 This embodiment provides a method for directional arrangement of a high thermal conductivity graphite-based conductive shielding material for busbar trunking, including the following specific steps: Step 1: Preparation of anisotropic conductive paste. Bisphenol A type epoxy resin and coupling agent were mixed at a mass ratio of 10:1.5 and reacted at 75℃ for 1.5 h to obtain a modified resin matrix. The mass ratio of graphene / carbon nanotube composite powder to the resin matrix was 1:6, with a graphene to carbon nanotube mass ratio of 1:1.2. The graphene sheet diameter was 20 μm, and the carbon nanotube outer diameter was 25 nm and the length was 8 μm. Anisotropic conductive paste was prepared by using a sealed cavity with a vacuum degree of -0.095 MPa, a shear temperature of 40℃, an asymmetric alternating electric field frequency of 350 Hz, a field strength of 3.5 kV / m, an angle of 60°, a shear rate of 6000 s⁻¹, and a shear time of 75 min.

[0034] Step 2: Slurry Orientation Treatment. The slurry injection rate is 3.5 mL / min. The mold channel thickness is 400 μm, width is 150 mm, and length is 600 mm. The spacing between the guide ridges is 2.5 mm, and the misalignment distance is 1.5 times the ridge width. Ultrasonic vibration at a frequency of 50 kHz and a power of 400 W, along with a pulsed magnetic field with a magnetic induction intensity of 1.2 T, a frequency of 15 Hz, a duty cycle of 60%, and an included angle of 25°, are applied synergistically for 18 minutes to complete the filler orientation.

[0035] Step 3: Segmented temperature-controlled phase separation and shaping. First temperature zone: 65℃, 4 min; second temperature zone: 32℃, 25 min; third temperature zone: 3℃, 8 min; temperature change rate of 1.5℃ / s, the resin matrix micro-region crystallizes and solidifies the filler structure to prepare a pre-oriented film.

[0036] Step 4: Gradient hot rolling densification treatment. Transfer temperature 55℃, transfer pressure 0.4MPa; first stage rolling temperature 62℃, pressure 2.5MPa, speed 1.5m / min; second stage rolling temperature 80℃, pressure 5MPa, speed 0.8m / min; rolling temperature gradient 12℃. Laser thickness measurement controls the target film thickness to 150μm, with a thickness deviation of ±5μm and a pressure response time of 1.5s. After rolling, cool to 32℃ at a rate of 1.5℃ / min.

[0037] Step 5: Segmented inert atmosphere curing treatment. The drying tunnel uses an argon atmosphere with a gas flow rate of 2 L / min, a three-zone length ratio of 1:1.1:0.9, and a film material travel speed of 0.4 m / min. Low-temperature pre-curing is performed at 95℃ for 18 min; medium-temperature cross-linking at 145℃ for 12 min; and high-temperature post-curing at 195℃ for 8 min; the heating rate is 4℃ / min. After curing, the temperature is lowered to room temperature at 6℃ / min, and the mixture is allowed to stand for 20 h to obtain the target material.

[0038] Example 4 This embodiment provides a method for directional arrangement of a high thermal conductivity graphite-based conductive shielding material for busbar trunking, including the following specific steps: Step 1: Preparation of anisotropic conductive slurry. A modified resin matrix was prepared by reacting bisphenol A epoxy resin and coupling agent at a mass ratio of 10:2 at 80℃ for 1 hour. A graphene / carbon nanotube composite powder was prepared at a mass ratio of 1:8 to the resin matrix, with a graphene to carbon nanotube mass ratio of 1:1.5. The graphene sheet diameter was 25 μm, and the carbon nanotube outer diameter was 30 nm and the length was 10 μm. Anisotropic conductive slurry was obtained by high-speed shear dispersion under the following conditions: a sealed cavity vacuum of -0.1 MPa, a shear temperature of 45℃, an asymmetric alternating electric field frequency of 500 Hz, a field strength of 5 kV / m, an angle of 75°, a shear rate of 8000 s⁻¹, and a shear time of 90 min.

[0039] Step 2: Slurry Orientation Treatment. The slurry injection rate is 5 mL / min. The mold channel thickness is 500 μm, width is 200 mm, and length is 800 mm. The spacing between the guide ridges is 3 mm, and the misalignment distance is twice the width of the ridge. Ultrasonic vibration is applied at a frequency of 60 kHz and a power of 500 W. A pulsed magnetic field with a magnetic induction intensity of 1.5 T, a frequency of 20 Hz, a duty cycle of 70%, and an included angle of 30° is used for 20 minutes to achieve optimal directional arrangement of the filler.

[0040] Step 3: Segmented temperature-controlled phase separation and shaping. First temperature zone: 70℃, 5 min; second temperature zone: 35℃, 30 min; third temperature zone: 5℃, 10 min; temperature change rate of 2℃ / s, rapid gradient temperature control to complete resin crystallization and filler structure curing.

[0041] Step 4: Gradient hot rolling densification treatment. Transfer temperature 60℃, transfer pressure 0.5MPa; first stage rolling temperature 65℃, pressure 3MPa, speed 2m / min; second stage rolling temperature 85℃, pressure 6MPa, speed 1m / min; rolling temperature gradient 15℃. Laser online thickness measurement adjusts the film thickness to 200μm, with a deviation of ±5μm, and pressure adjustment response time of 2s. After rolling, cool to 35℃ at a rate of 2℃ / min.

[0042] Step 5: Segmented inert atmosphere curing treatment. Argon atmosphere drying tunnel, gas flow rate 3L / min, three-zone length ratio 1:1.2:1.0, film material travel speed 0.5m / min. Low-temperature pre-curing 100℃, 15min; medium-temperature cross-linking 150℃, 10min; high-temperature post-curing 200℃, 5min; heating rate 5℃ / min. After curing, cool to room temperature at 8℃ / min, and let stand for 24h to obtain a highly oriented graphite-based conductive shielding material.

[0043] Comparative Example 1 (Electric Field-Free Shear Dispersion Process) The preparation process of this comparative example is basically the same as that of Example 1, except that the asymmetric alternating electric field assistance is eliminated in step one, and only pure mechanical dynamic cyclic shear dispersion is used. The remaining process parameters and operating steps are exactly the same, and the specific steps are as follows: Step 1: Prepare the coupling agent modified resin matrix. Bisphenol A type epoxy resin and γ-glycidyl etheroxypropyltrimethoxysilane are reacted at a mass ratio of 10:1 at 70℃ for 2 hours. Graphene / carbon nanotube composite powder is mixed with the modified resin matrix at a mass ratio of 1:5, with the powder ratio and particle size parameters consistent with Example 1. The mixture is placed in a sealed chamber, and under vacuum of -0.09 MPa and shear temperature of 35℃, it is mechanically sheared at a shear rate of 4000 s⁻¹ for 60 minutes without electric field assistance to obtain a common conductive slurry.

[0044] Steps two through five: All processes, including orientation treatment, phase separation and shaping, hot roller densification, and segmented curing, are exactly the same as those in Example 1, ultimately producing a graphite-based conductive shielding material without electric field-assisted modification.

[0045] Comparative Example 2 (Pulseless Magnetic Field + Ultrasonic Orientation Process) The preparation process of this comparative example is basically the same as that of Example 1, except that the pulsed magnetic field and ultrasonic vibration synergistic orientation process is omitted in step two. After the slurry is injected into the mold, it is naturally oriented by the flow channel structure. The other process parameters and operation steps are exactly the same. The specific steps are as follows: Step 1: Completely replicate the electric field-assisted shear dispersion process of Example 1 to prepare anisotropic conductive slurry.

[0046] Step 2: Inject the conductive slurry into the same confined flow channel mold at a flow rate of 2 mL / min. Do not apply pulsed magnetic field or ultrasonic vibration. The filler is naturally oriented by relying solely on the parallel staggered flow guiding structure. The action time is 12 min.

[0047] Steps 3 to 5: Using the same shaping, densification, and curing processes as in Example 1, a conductive shielding material without external field synergistic orientation is finally obtained.

[0048] Comparative Example 3 (Segmented Temperature-Controlled Phase Separation and Shaping Process) The preparation process of this comparative example is basically the same as that of Example 1, except that the three-stage segmented temperature-controlled phase separation process in step three is omitted, and a single constant-temperature curing method is used for shaping. The other process parameters and operating steps are exactly the same, and the specific steps are as follows: Step 1 and Step 2 are exactly the same as the slurry preparation and external field synergistic orientation process in Example 1, resulting in an oriented slurry system.

[0049] Step 3: The segmented temperature control treatment was cancelled. The orientation slurry was placed directly under a single constant temperature of 28℃ for 28 minutes to complete the resin curing and shaping. Micro-region gradient crystallization and orientation structure freezing were not carried out.

[0050] Steps 4 and 5: Using the same hot roller densification and segmented curing process as in Example 1, a conductive shielding material without segmented temperature control shaping is finally obtained.

[0051] The conductive shielding materials for busbar trunking prepared in each embodiment and comparative example underwent uniform performance testing: the in-plane thermal conductivity was tested using the laser flare method; the volume resistivity was tested using a four-probe analyzer; the electromagnetic shielding effectiveness in the 30MHz–1.5GHz frequency band was tested using a vector network analyzer; and the orientation degree of the filler was observed using scanning electron microscopy, and the regularity of the filler's directional arrangement was statistically analyzed. All samples were uniformly 100mm × 100mm in size, and the testing environment was 25℃ and 50% humidity. Each group was tested three times, and the average value was taken. The final test results are shown in the table below.

[0052] Table 1: Comparison of core performance parameters of materials in each embodiment and comparative example As shown in Table 1, the four sets of sample examples prepared by the present invention through multi-process synergy exhibit significantly better core performance than the three sets of comparative sample examples, demonstrating outstanding process superiority. The in-plane thermal conductivity of all four examples exceeds 168 W / (m·K), the volume resistivity is as low as 0.0071–0.0095 Ω·cm, the average electromagnetic shielding effectiveness exceeds 55 dB, and the filler orientation regularity is higher than 89%, fully meeting the requirements of high thermal conductivity, high electrical conductivity, and high shielding for busbar trunking.

[0053] By comparing the data of the example groups longitudinally, the performance of Examples 2 to 4 was gradually optimized as the filler ratio, electric field strength, magnetic field strength, and curing parameters were gradually increased. Among them, Example 4 adopted the optimal filler ratio and extreme process parameters, and the thermal conductivity, shielding effectiveness, and orientation regularity reached their peak values ​​of 202.4 W / (m·K), 63.5 dB, and 96.2%, respectively. The lowest volume resistivity was 0.0071 Ω·cm, which proves that the process parameters of the present invention have good gradient adaptability and the material performance can be precisely optimized through parameter adjustment.

[0054] Comparing the data from the comparative examples, in Comparative Example 1, after eliminating the electric field shear dispersion process, the thermal conductivity decreased by 39.6%, the volume resistivity increased by 125.6%, the shielding effectiveness decreased by 27%, and the orientation regularity decreased by 28.7% compared to Example 1. This indicates that asymmetric alternating electric field-assisted shearing can effectively solve the problem of filler agglomeration, achieving initial uniform dispersion and anisotropic control of the filler, which is a core prerequisite for ensuring the basic performance of the material. In Comparative Example 2, after eliminating the magnetic field ultrasonic synergistic orientation process, the performance decline was the second largest, proving that external field synergistic orientation can precisely control the filler arrangement direction and construct a continuous and regular thermal and electrical conductive network. In Comparative Example 3, after eliminating the segmented temperature-controlled shaping process, the filler orientation structure was prone to rebound disorder and could not solidify the orderly arrangement structure, resulting in a significant performance degradation, verifying the key shaping role of the segmented temperature-controlled phase separation process.

[0055] Table 2: Comparison of the impact of process omissions on microstructure between Example 1 and each comparative example. After a complete set of processing steps, the sample in Example 1 showed a filler agglomeration rate of only 3.2%, with the filler arrangement tilt angle deviation controlled within ±2.1°. The resin crystals were uniform and dense, and the film porosity was as low as 1.8%, with a regular and orderly microstructure, providing structural support for excellent macroscopic performance. In Comparative Example 1, without electric field shearing assistance, simple mechanical shearing could not completely break up the graphene and carbon nanotube agglomerates, resulting in a significant increase in filler agglomeration rate to 18.5%. The large amount of agglomerated filler led to uneven slurry dispersion, and subsequent orientation and shaping processes could not compensate for the initial dispersion defects. The filler arrangement tilt angle deviation increased significantly, the film porosity increased, and microstructural defects increased, directly blocking thermal and electrical conduction pathways, causing a significant decrease in macroscopic performance.

[0056] Comparative Example 2 lacks external field-assisted orientation and relies solely on the passive orientation of the mold flow channel structure. The filler cannot achieve precise deflection, with an arrangement tilt angle deviation of ±6.3°. Some fillers are randomly distributed, disrupting the continuity of the network structure. Although the filler agglomeration is relatively mild, the orientation regularity is insufficient, resulting in a significant decrease in thermal conductivity, electrical conductivity, and shielding performance.

[0057] Comparative Example 3 uses a single isothermal setting process without segmented gradient temperature control phase separation. The resin matrix cannot achieve micro-regional gradual crystallization, the crystallization rate is too fast and the distribution is uneven, the matrix structure is loose, and the filler orientation structure cannot be effectively frozen. During the subsequent hot roll rolling process, the filler is prone to displacement and rebound, resulting in disordered arrangement, significantly increased porosity and agglomeration rate, greatly reduced microstructural integrity, and poor material stability and performance consistency.

[0058] Table 3: Comparison of material stability tests under various operating conditions for each embodiment (1000h aging test) The service stability of the material prepared by this invention can be effectively verified through a 1000-hour long-term aging test, making it suitable for the long-term continuous operation requirements of busbar trunking. Test data shows that the performance degradation of the four sample examples after aging is minimal, demonstrating excellent stability. Sample example 4 exhibits the best stability, with a thermal conductivity retention rate of 98.1%, a resistivity increase of only 2.1%, a shielding effectiveness decrease of 0.7 dB, and a film flatness change of only 1.2 μm, showing no obvious deformation, cracking, or performance degradation.

[0059] Overall, as the orientation regularity of the filler and the density of the microstructure are improved, the anti-aging performance of the material is gradually optimized. The segmented temperature-controlled shaping, gradient hot roller densification, and segmented inert atmosphere curing processes can effectively improve the crosslinking density of the resin matrix and the bonding strength of the filler, reduce internal defects in the film layer, and inhibit filler slippage and matrix aging failure under long-term high temperature and electric field conditions. Compared with conventional process materials, the material prepared by this invention exhibits significantly improved long-term service stability, effectively avoiding safety issues such as thermal conductivity failure, shielding degradation, and localized overheating that occur during long-term operation of busbar trunking, demonstrating excellent engineering application value.

[0060] This invention addresses the industry pain points of traditional graphite-based shielding materials, such as filler agglomeration, disordered orientation, structural springback, and insufficient density. Asymmetric alternating electric field-assisted dynamic shearing weakens van der Waals forces between fillers through electric field polarization, achieving uniform dispersion of graphene and carbon nanotubes and constructing a preliminary anisotropic slurry system. The synergistic effect of pulsed magnetic field and ultrasonic vibration drives precise deflection of two-dimensional graphene sheets and one-dimensional carbon nanotubes along a preset direction, forming a continuous in-plane thermal and electrical conductive network. Segmented temperature-controlled phase separation achieves gradual crystallization of resin micro-regions through gradient temperature differences, freezing the orderly arrangement of fillers at the microscopic level and completely solving the orientation springback problem. Two-stage gradient hot rolling combined with online thickness control improves film density and optimizes interfacial bonding without damaging filler orientation. Segmented inert atmosphere curing enables gradual cross-linking and curing of the resin, avoiding internal stress and porosity defects caused by rapid curing, ultimately producing a busbar-specific shielding material with high thermal conductivity, high electrical conductivity, high shielding power, and high stability.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking by directional arrangement, characterized in that, Includes the following steps: Step 1: The graphene / carbon nanotube composite powder and the coupling agent modified resin matrix are dynamically cyclically sheared and dispersed in a closed cavity under the assistance of an asymmetric alternating electric field to form an anisotropic conductive slurry. Step 2: Inject the anisotropic conductive slurry into a confined flow channel mold with a parallel interlaced flow guiding structure, and apply a pulsed magnetic field perpendicular to the flow direction to cause the graphite-based filler to deflect and orient itself along a preset direction. Step 3: Perform segmented temperature-controlled phase separation treatment on the deflected and oriented slurry to promote micro-region crystallization of the resin matrix, freeze and solidify the oriented arrangement structure of the graphite-based filler, and form a conductive shielding pre-oriented film with in-plane preferred orientation. Step 4: Transfer the conductive shielding pre-oriented film to the surface of the heated substrate and perform a stepwise compression densification process under constant pressure hot roller rolling, while maintaining a temperature gradient to maintain the orientation of the filler. Step 5: Place the densified film in a programmed temperature rise oven and sequentially undergo three stages: low-temperature pre-curing, medium-temperature cross-linking, and high-temperature post-curing to obtain the high thermal conductivity graphite-based conductive shielding material for the busbar.

2. The method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking according to claim 1, characterized in that, In step one: The frequency of the asymmetric alternating electric field is 50Hz to 500Hz, the field strength is 0.5kV / m to 5kV / m, and the angle between the electric field direction and the horizontal direction is 15° to 75°. The shear rate of the dynamic cyclic shear dispersion is 1000s⁻¹~8000s⁻¹, the shearing time is 30min~90min, and the shearing temperature is controlled at 25°C~45°C; The vacuum level inside the sealed cavity is -0.08 MPa to -0.1 MPa.

3. The method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking according to claim 1, characterized in that, In step one: The mass ratio of the graphene / carbon nanotube composite powder to the coupling agent modified resin matrix is ​​1:(3-8). In the graphene / carbon nanotube composite powder, the graphene sheet diameter is 5μm to 25μm, the carbon nanotube outer diameter is 10nm to 30nm, the carbon nanotube length is 1μm to 10μm, and the mass ratio of graphene to carbon nanotube is 1:(0.2 to 1.5). The coupling agent modified resin matrix is ​​prepared by reacting bisphenol A type epoxy resin and γ-glycidoxypropyltrimethoxysilane at a mass ratio of 10:(0.5-2) at 60°C-80°C for 1-3 hours.

4. The method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking according to claim 1, characterized in that, In step two: The parallel staggered flow guiding structure consists of multiple sets of strip-shaped flow guiding ridges with a spacing of 0.5mm to 3mm. The extension directions of two adjacent sets of ridges are parallel to each other and staggered, with a stagger distance of 0.5 to 2 times the width of the ridge. The flow channel thickness of the confined flow channel mold is 100μm to 500μm, the flow channel width is 50mm to 200mm, and the flow channel length is 200mm to 800mm. The magnetic induction intensity of the pulsed magnetic field is 0.2T to 1.5T, the pulse frequency is 1Hz to 20Hz, the duty cycle is 30% to 70%, and the angle between the magnetic field direction and the flow channel length direction is 0° to 30°. The injection flow rate of the anisotropic conductive slurry is 0.5 mL / min to 5 mL / min.

5. The method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking according to claim 1, characterized in that, In step two: During the process of injecting the anisotropic conductive slurry into the confined flow channel mold, ultrasonic vibration is applied simultaneously to assist dispersion. The ultrasonic frequency is 20kHz to 60kHz, the ultrasonic power is 100W to 500W, and the ultrasonic action direction is perpendicular to the slurry flow direction. The synergistic effect of the pulsed magnetic field and the ultrasonic vibration lasts for 5 to 20 minutes.

6. The method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking according to claim 1, characterized in that, In step three: The segmented temperature-controlled phase separation process includes sequential processing of a first temperature zone, a second temperature zone, and a third temperature zone. The first temperature zone has a processing temperature of 50°C to 70°C and a processing time of 1 min to 5 min; The second temperature zone has a processing temperature of 20°C to 35°C and a processing time of 10 min to 30 min. The third temperature zone has a processing temperature of -5°C to 5°C and a processing time of 2 min to 10 min. The rate of temperature change between adjacent temperature zones is 0.5°C / s to 2°C / s.

7. The method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking according to claim 1, characterized in that, In step four: The transfer temperature of the conductive shielding pre-oriented film to the heated substrate surface is 40°C to 60°C, and the transfer pressure is 0.1MPa to 0.5MPa. The constant pressure hot roll rolling is a two-stage rolling process. The rolling temperature of the first stage is 55°C to 65°C, the rolling pressure is 1MPa to 3MPa, and the rolling speed is 0.5m / min to 2m / min. The second stage rolling temperature is 70°C to 85°C, the rolling pressure is 3MPa to 6MPa, and the rolling speed is 0.2m / min to 1m / min; The temperature gradient is a linear increase of 5°C to 15°C along the rolling direction from the feed end to the discharge end.

8. The method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking according to claim 1, characterized in that, In step four: During the constant pressure hot roll rolling process, a laser online thickness gauge is used to monitor the film thickness in real time, and the rolling pressure is dynamically adjusted according to the thickness deviation. The adjustment response time is 0.5s to 2s, the thickness control target is 50μm to 200μm, and the allowable thickness deviation range is ±5μm. After rolling, the film is cooled to 25°C to 35°C at a cooling rate of 0.5°C / min to 2°C / min.

9. The method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking according to claim 1, characterized in that, In step five: The low-temperature pre-curing stage is a treatment at 80°C to 100°C for 15 to 30 minutes. The intermediate-temperature crosslinking stage is a treatment at 120°C to 150°C for 10 to 20 minutes. The high-temperature post-curing stage involves processing at a temperature of 170°C to 200°C for 5 to 15 minutes. The heating rate between adjacent stages is 1°C / min to 5°C / min; The atmosphere inside the programmed heating oven is a nitrogen atmosphere or an argon atmosphere, and the gas flow rate is 0.5L / min to 3L / min.

10. The method for preparing a high thermal conductivity graphite-based conductive shielding material for busbar trunking according to claim 1, characterized in that, In step five: The programmed heating oven has a first heating zone, a second heating zone, and a third heating zone arranged sequentially along the direction of film material travel, with the length ratio of each zone being 1:(0.8~1.2):(0.6~1.0). The traveling speed of the membrane material within the programmed temperature drying tunnel is 0.1 m / min to 0.5 m / min; After the high-temperature post-curing stage is completed, the film material is cooled to room temperature at a cooling rate of 2°C / min to 8°C / min and left to stand at room temperature for 12h to 24h.

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