Injection molding die for graphite polypropylene high-thermal-conductivity composite material and preparation method thereof

Abstract

The injection molding mold of the graphite polypropylene high-thermal-conductivity composite material comprises a fixed mold block, a core mold block and a movable mold block, the core mold block is fixed in a core groove on the top of the movable mold block, and the fixed mold block is closed with the top of the movable mold block; the core mold block comprises a core mold block main body, a cavity, a main runner, a trapezoidal runner, a gate and an overflow groove, two cavities are arranged on the two sides of the core mold block main body, the main runner is arranged between the two cavities, the two ends of the main runner are respectively communicated with branch runners, the two branch runners are respectively connected with the trapezoidal runner, the trapezoidal runner is respectively communicated with one end of the cavity through the gate with different heights, and the other end of the two cavities is respectively provided with the overflow groove.The composite material prepared by the application has different degrees of orientation in the horizontal direction and the vertical direction of graphite, the vertical direction orientation is particularly prominent, and the axial thermal conductivity is as high as 24.1 W·m ‑1 ·K ‑1 .

Description

Technical Field

[0001] This invention relates to an injection molding die for a graphite-polypropylene high thermal conductivity composite material and its preparation method, belonging to the field of polymer composite materials. Background Technology

[0002] Seawater desalination technology is developing rapidly worldwide. The horizontal tube falling film evaporator, composed of four main components—a liquid distributor, horizontal evaporation tubes, a reflux system, and an exhaust channel—is a core component of multi-effect distillation seawater desalination technology. During operation, the liquid distributor above the evaporator sprays seawater onto the horizontal evaporation tubes below, where it exchanges heat with the steam inside. Therefore, the evaporation tubes need high thermal conductivity to ensure high utilization efficiency. Most commonly used heat exchange tubes are made of metal. While metals have excellent thermal conductivity, they are easily corroded and scaled by seawater during use, significantly reducing their lifespan and increasing cleaning and maintenance costs, thus leading to excessively high prices for desalinated water. Unlike metal materials, high thermal conductivity polypropylene composite materials have extremely strong corrosion resistance and scale inhibition properties, which can greatly extend their service life and reduce usage and maintenance costs. However, the overall performance of graphite-polypropylene thermally conductive composite materials is currently not high, with a thermal conductivity of approximately 3.0 to -3.3 W·m. -1 ·K -1 The main reason why these composite materials cannot meet the requirements for heat exchange tubes is that during the processing and molding of the composite material, graphite easily forms a single planar (radial) orientation, resulting in a generally high radial thermal conductivity and a generally low axial (perpendicular) thermal conductivity. This increases the anisotropy of thermal conductivity in the composite material, limiting its application in heat exchange technology. Therefore, improving the axial orientation of graphite in the thermally conductive composite material and increasing its axial thermal conductivity and thermal efficiency is key to enhancing the application value of this type of composite material.

[0003] To address the aforementioned technical issues, domestic scholars have conducted extensive research. For example, patent CN202010777399.X discloses a high-filler, high-thermal-conductivity polypropylene composite material and its preparation method. This polypropylene composite material is a blend of polypropylene, layered carbon-based fillers, and spherical fillers. The layered carbon-based fillers and spherical fillers account for 30wt% to 70wt% of the total filler content of the polypropylene composite material, and the spherical fillers account for 2.5wt% to 10wt% of the mass content of the polypropylene composite material. The layered carbon-based fillers are one or two of flake graphite and graphene, and the spherical fillers are specifically one or more of alumina, calcium carbonate, and magnesium oxide. After melt mixing, the composite material obtained by melt pressing reaches a vertical thermal conductivity of 1.84 W·m. -1 ·K -1Patent CN201910414513.X discloses a polypropylene composite material with high vertical thermal conductivity and excellent mechanical properties, and its preparation method. This polypropylene composite material is a blend of polypropylene, maleic anhydride-grafted polypropylene, and various carbon-based fillers. The carbon-based fillers contain at least two-dimensional and zero-dimensional carbon structures, with the carbon-based fillers accounting for 5%–80% of the total mass of polypropylene and carbon-based fillers. The mass ratio of maleic anhydride-grafted polypropylene to the total mass of polypropylene and carbon-based fillers is 0.01%–10%:100%. After melt mixing, the composite material obtained by sheet molding reaches a vertical thermal conductivity of 3.15 W·m. -1 ·K -1 Patent CN202011426337.0 discloses a thermally conductive and insulating polypropylene composite material, its preparation method, and its application. This thermally conductive and insulating polypropylene composite material comprises, by weight, 10-70 parts polypropylene, 5-20 parts component A, 20-55 parts component B, 5-20 parts component C, 0.2-2 parts antioxidant, and 0... The following components are prepared by weight: 1.2-2 parts lubricant; 2. Component A is prepared by weight of 80-95 parts polypropylene, 5-20 parts inorganic nanoparticles, 0.2-2 parts silane coupling agent, and 0.1-1 parts nucleating agent; 3. Component B is prepared by weight of 50-80 parts hexagonal boron nitride, 20-50 parts thermally conductive filler, 1-10 parts intercalating agent, 1-10 parts polymethylsilane, and 0.2-5 parts silane coupling agent; 4. Component C is prepared by weight of 50-80 parts graft-modified resin and 20-50 parts titanate coupling agent modified inorganic whiskers. The above components are weighed, mixed, and extruded to obtain a thermally conductive and insulating polypropylene composite material with a vertical thermal conductivity of 0.8-1.2 W·m. -1 ·K -1 The planar thermal conductivity is 1.5–3.4 W·m. -1 ·K -1 In existing technologies, the radial thermal conductivity of graphite-polypropylene composite materials is generally higher than that of the axial (vertical) thermal conductivity, exhibiting significant anisotropy in thermal conductivity. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides an injection molding die for graphite-polypropylene high thermal conductivity composite materials and its preparation method. The invention utilizes a coupling agent to treat the graphite surface and controls the extruder granulation process, resulting in more uniform dispersion of high-content graphite within the composite material, increasing the complete thermal conductivity pathways within the material. Simultaneously, using a special injection molding die, and through precise control of the injection rate and pressure of the injection molding machine, the molten masterbatch flows uniformly through a trapezoidal runner and a narrow gate. Under shear force, it fills the cavity in a wave-like pattern, constructing a more uniform and complete three-dimensional thermal conductivity pathway for the composite material. The graphite within the material exhibits different degrees of orientation in the horizontal and vertical directions, with the vertical orientation being particularly prominent, thereby improving the average thermal conductivity and axial thermal conductivity of the composite material.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] An injection molding mold for graphite-polypropylene high thermal conductivity composite material, the injection molding mold comprising a fixed module, a core module, and a moving module, the core module being fixed in a core groove at the top of the moving module, the fixed module and the top of the moving module being closed; the core module comprising a core module body, cavities, a main runner, a trapezoidal runner, a gate, and an overflow groove, two cavities being provided, respectively disposed on both sides of the core module body, the main runner being disposed between the two cavities, the two ends of the main runner being respectively connected to branch runners, the two branch runners being respectively connected to the trapezoidal runners, the trapezoidal runners being respectively connected to one end of the cavities through gates of different heights, and the other ends of the two cavities being respectively provided with overflow grooves.

[0007] The injection molding die for the above-mentioned graphite polypropylene high thermal conductivity composite material includes a fixed template, a fixed mold base plate, an injection port, and positioning holes. The fixed template is fixed on the fixed mold base plate, the positioning holes are located at the four corners of the fixed template, the injection port passes through the center of the fixed template and the fixed mold base plate, and the fixed mold base plate is connected to the injection molding machine.

[0008] The moving module includes a moving template, a core groove, a pad, and a moving mold base plate. The core groove is located at the top center of the moving template, and its size matches the main body of the core module. The main body of the core module is embedded in the core groove and is flush with the top of the core groove wall. The lower end of the moving template is connected to the moving mold base plate through the pad. Four positioning posts are provided at the four corners of the upper end of the moving template. The fixed template aligns with the moving template to form a mold. The positioning posts pass through the positioning holes. The moving mold base plate is connected to the injection molding machine.

[0009] The injection molding mold for the above-mentioned graphite polypropylene high thermal conductivity composite material has a trapezoidal flow channel with an upper base of 23mm, a lower base of 40mm, and a length of 15mm.

[0010] A method for preparing a graphite-polypropylene high thermal conductivity composite material, wherein the graphite-polypropylene high thermal conductivity composite material comprises the following components in parts by weight: 50-85 parts graphite, 15-50 parts polypropylene, 0.5-2 parts coupling agent, 0.1-2 parts antioxidant, 0.5-2 parts flow agent, and 0.2-1 parts lubricant. The preparation method is injection molding using the injection molding mold according to any one of claims 1 to 3, comprising the following steps:

[0011] a. Add the coupling agent of the formula amount to anhydrous ethanol, sonicate for 20-40 minutes, then mix it with the graphite of the formula amount at high speed until uniform, and dry it at 110-120℃ under vacuum for 1-2 hours to obtain the premix.

[0012] b. Mix the treated graphite, polypropylene, antioxidant, flow agent and lubricant at high speed, and then extrude and granulate using an extruder to obtain a uniformly mixed masterbatch.

[0013] c. The masterbatch is loaded into the injection molding machine for injection molding. The molten masterbatch passes through the 0.4-0.8mm high gate at a uniform speed along the trapezoidal runner, and fills the cavity of the molding device in a wave-like manner to form a graphite polypropylene high thermal conductivity composite material.

[0014] The above-mentioned method for preparing graphite-polypropylene high thermal conductivity composite material, wherein the graphite is in flake form, has a carbon content ≥95%, and a particle size of 10-400 μm.

[0015] In the preparation method of the above-mentioned graphite polypropylene high thermal conductivity composite material, in step b, the extruder is a twin-screw extruder, and the temperatures of each section of the extruder during extrusion granulation are 180±5℃, 195±5℃, 195±5℃, 205±5℃, 195±5℃, and 185±5℃ respectively; the main screw speed of the extruder is 80~120 rpm, the feed screw speed is 5~15 rpm, and after extrusion granulation, it is repeated 3~4 times. After each granulation, it is vacuum dried in an oven at 120℃ for 1 h.

[0016] In the preparation method of the above-mentioned graphite polypropylene high thermal conductivity composite material, in step c, the masterbatch is added to an injection molding machine for injection molding. The temperatures of each section of the injection molding machine screw are 190±5℃, 210±5℃, 220±5℃, 210±5℃, and 180±5℃ respectively; the mold temperature is 170±5℃; the injection rate of the injection molding machine is 10~100 g / s, the injection pressure is 15~25MPa, and the holding pressure is 5~15 s.

[0017] The preparation method of the above-mentioned graphite polypropylene high thermal conductivity composite material is characterized in that: the coupling agent is one or more of the following: titanate coupling agents NDZ-101, NDZ-201 and silane coupling agents KH-550, KH-560 and KH-570.

[0018] In the above-mentioned method for preparing graphite-polypropylene high thermal conductivity composite material, the polypropylene is one or more of homopolymer polypropylene, random copolymer polypropylene, and block copolymer polypropylene with a melt index ≥1g / 10min.

[0019] In the preparation method of the above-mentioned graphite polypropylene high thermal conductivity composite material, the antioxidant is one or more of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 944 and antioxidant DSTDP; the lubricant is one or more of calcium stearate, zinc stearate, stearamide, stearic acid, high boiling point paraffin wax and microcrystalline wax.

[0020] The beneficial effects of this invention are:

[0021] This invention utilizes injection molding to prepare graphite-polypropylene high thermal conductivity composite materials. During the injection molding process, the invention employs a unique injection mold and precise control of the injection rate and pressure of the injection molding machine. This allows the molten masterbatch to pass uniformly through a trapezoidal runner and a narrow gate. Under shear force, the masterbatch fills the cavity in a wavy pattern, creating a more uniform and complete three-dimensional thermal conductivity pathway for the composite material. The graphite within the composite material exhibits varying degrees of orientation in both the horizontal and vertical directions. The resulting composite material boasts an axial thermal conductivity as high as 24.1 W·m. -1 ·K -1 . Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the assembly structure of the core module and the moving module of the present invention;

[0023] Figure 2 This is a schematic diagram of the core module structure;

[0024] Figure 3 This is a schematic diagram of the modular structure;

[0025] Figure 4 This is a schematic diagram of the dynamic module structure.

[0026] In the diagram: 1. Fixed module; 1-1. Fixed template; 1-2. Fixed mold base plate; 1-3. Injection port; 1-4. Positioning hole; 2. Core module; 2-1. Core module body; 2-2. Cavity; 2-3. Main runner; 2-4. Trapezoidal runner; 2-5. Gate; 2-6. Overflow groove; 2-7. Sub-runner; 3. Moving module; 3-1. Moving template; 3-2. Core groove; 3-3. Spacer block; 3-4. Moving mold base plate; 3-5. Positioning post. Implementation

[0027] The present invention will be further described below with reference to the embodiments.

[0028] See Figures 1 to 4 The graphite polypropylene high thermal conductivity composite material of the present invention is injection molded using the injection molding mold of the present invention. The injection molding mold includes a fixed module 1, a core module 2, and a moving module 3. The core module 2 is fixed in the core groove at the top of the moving module 3. The fixed module 1 and the top of the moving module 3 are closed. The core module 2 includes a core module body 2-1, a cavity 2-2, a main runner 2-3, a trapezoidal runner 2-4, a gate 2-5, and an overflow groove 2-6. There are two cavities 2-2, which are respectively located on both sides of the core module body 2-1. The main runner 2-3 is located between the two cavities 2-2. The two ends of the main runner are respectively connected to the branch runners 2-7. The two branch runners are respectively connected to the trapezoidal runners 2-4. The trapezoidal runners are respectively connected to one end of the cavity through the gates 2-5 of different heights. The other ends of the two cavities 2-2 are respectively provided with the overflow grooves 2-6.

[0029] The fixed module 1 includes a fixed template 1-1, a fixed mold base plate 1-2, an injection port 1-3, and a positioning hole 1-4. The fixed template 1-1 is fixed on the fixed mold base plate 1-2. The positioning hole 1-4 is located at the four corners of the fixed template 1-1. The injection port 1-3 passes through the center of the fixed template and the fixed mold base plate. The fixed mold base plate 1-2 is fixedly connected to the injection molding machine.

[0030] The moving module 3 includes a moving template 3-1, a core groove 3-2, a pad 3-3, and a moving mold base plate 3-4. The core groove 3-2 is located at the top center of the moving template 3-1, and its size matches that of the core module body 2-1. The core module body 2-1 is embedded in the core groove 3-2 and is flush with the top of the core groove wall. The lower end of the moving template 3-1 is connected to the moving mold base plate 3-4 through the pad 3-3. Four positioning posts 3-5 are provided at the four corners of the upper end of the moving template 3-1. The fixed template 1-1 aligns with the moving template 3-1 to form the mold. The positioning posts 3-5 pass through the positioning holes 1-4. The moving mold base plate 3-4 is connected to the injection molding machine. Graphite polypropylene high thermal conductivity composite material masterbatch is injected into the injection mold through the injection port 1-3. The masterbatch flows into the cavities on both sides through the main runner. After the cavities are filled, injection stops. During the injection molding process, the masterbatch enters the branch runner from the main runner and then fills the cavity in a wave-like manner through the trapezoidal runner.

[0031] Example 1

[0032] Step 1: Add 0.2 parts by weight of coupling agent KH-550 to 4 parts by weight of anhydrous ethanol, sonicate for 30 minutes, mix evenly with 50 parts by weight of graphite with a particle size of 75μm at high speed, and then dry at 110℃ for 1 hour in a high-temperature forced-air drying oven.

[0033] Step 2: The treated graphite, 25 parts by weight of polypropylene K1035, 25 parts by weight of polypropylene 230, 0.7 parts by weight of antioxidant 1010, 1 part by weight of flow agent, and 0.7 parts by weight of lubricant zinc stearate are mixed at high speed. The mixture is then added to a twin-screw extruder for extrusion granulation. The temperatures of each section of the extruder are 185℃, 195℃, 195℃, 200℃, 195℃, and 185℃, respectively. The main screw speed is 100 rpm, and the feed screw speed is 20 rpm. The extrusion granulation is performed 3 times. After each granulation, the mixture is vacuum dried in a 120℃ oven for 1 hour to obtain the masterbatch.

[0034] Step 3: Add the masterbatch to the injection molding machine for injection molding. The molten masterbatch passes through two gates with heights of 0.5 mm and 0.75 mm at a uniform speed along the trapezoidal runner. The temperatures of each section of the injection molding machine screw are 190℃, 210℃, 220℃, 210℃, and 180℃ respectively. The injection mold temperature is 170℃, the injection rate is 70 g / s, the injection pressure is 15 MPa, and the holding pressure is 8 s. After demolding, a graphite polypropylene high thermal conductivity composite material is obtained. Example 2

[0035] Step 1: 55 parts by weight of graphite with a particle size of 75 μm, KH-560 as the coupling agent, and the other conditions are the same as in Example 1. The amount of materials used is shown in Table 1 below.

[0036] Step 2: 25 parts by weight of polypropylene S2040, 20 parts by weight of polypropylene 1937, antioxidant 1076, and calcium stearate as lubricant. The remaining conditions are the same as in Example 1.

[0037] Step 3: Same as in Example 1.

[0038] Detailed specifications are shown in Table 1 below:

[0039] Table 1 Formulation of graphite-polypropylene high thermal conductivity composite material

[0040] Example 3

[0041] Step 1: 60 parts by weight of graphite with a particle size of 15 μm, the coupling agent is NDZ-102, and the other conditions are the same as in Example 1. The amount of materials used is shown in Table 2 below.

[0042] Step 2: 20 parts by weight of polypropylene 1940 and 20 parts by weight of polypropylene 230, antioxidants are antioxidant 1076 and antioxidant 168, the temperatures of each section of the extruder are 190℃, 197℃, 197℃, 202℃, 197℃ and 190℃ respectively, the main screw speed is 90 rpm, and the other conditions are the same as in Example 1.

[0043] Step 3: The temperatures of each section of the injection molding machine screw are 195℃, 210℃, 220℃, 210℃, and 185℃ respectively; the injection rate is 40 g / s, the injection pressure is 20 MPa, the holding pressure is 10 s, and the other conditions are the same as in Example 1.

[0044] Detailed specifications are shown in Table 2 below:

[0045] Table 2 Formulation of graphite-polypropylene high thermal conductivity composite material

[0046] Example 4

[0047] Step 1: The coupling agent is NDZ-201, and the mass fraction is 65 parts of graphite with a particle size of 15μm. The other conditions are the same as in Example 3, and the material amounts are shown in Table 3 below.

[0048] Step 2: 20 parts by weight of polypropylene J940, 15 parts by weight of polypropylene M2600, antioxidants are antioxidant 1010 and antioxidant 168, and the remaining conditions are the same as in Example 3.

[0049] Step 3: Same as in Example 3.

[0050] Detailed specifications are shown in Table 3 below:

[0051] Table 3 Formulation of graphite-polypropylene high thermal conductivity composite material

[0052] Example 5

[0053] Step 1: The coupling agent is NDZ-201, and the mass fraction is 70 parts of graphite with a particle size of 35μm. The other conditions are the same as in Example 1. The material amounts are shown in Table 4 below.

[0054] Step 2: 15 parts by weight of polypropylene K4038 and 15 parts by weight of polypropylene 3805, antioxidants 1010 and 168, extruder temperatures of each section are 190℃, 200℃, 200℃, 205℃, 200℃ and 190℃ respectively, main screw speed is 90 rpm, feed screw speed is 15 rpm, extrusion granulation is performed 4 times, and other conditions are the same as in Example 1.

[0055] Step 3: The temperatures of each section of the injection molding machine screw are 195℃, 215℃, 225℃, 215℃, and 190℃ respectively; the injection rate is 30 g / s, the mold temperature is 175℃, the injection pressure is 25 MPa, the holding pressure is 10 s, and the other conditions are the same as in Example 1.

[0056] Detailed specifications are shown in Table 4 below:

[0057] Table 4 Formulation of graphite-polypropylene high thermal conductivity composite material

[0058] Example 6

[0059] Step 1: The coupling agent is NDZ-201, the flake graphite particle size is 35μm, and the other conditions are the same as in Example 5. The amount of materials used is shown in Table 5 below.

[0060] Step 2: 12 parts by weight of polypropylene K4038, 13 parts by weight of polypropylene 1937, antioxidants 1076 and 168, and other conditions are the same as in Example 5.

[0061] Step 3: Same as step 5 in Example 5.

[0062] Detailed specifications are shown in Table 5 below:

[0063] Table 5 Formulation of graphite-polypropylene high thermal conductivity composite material

[0064] Comparative Example 1

[0065] Step 1 is the same as in Example 5.

[0066] Step 2: Mix the treated graphite, 15 parts by weight of polypropylene K4038, 15 parts by weight of polypropylene 3805, 0.5 parts by weight of antioxidant 1010, 0.5 parts by weight of antioxidant 168, 2 parts by weight of flow agent, and 0.7 parts by weight of lubricant zinc stearate at high speed, and then mix them using an open mill. The mixing conditions are as follows: the gap adjustment and the number of mixing times are: 8 times for 3 grids, 2 times for 5 grids, 2 times for 7 grids, 2 times for 9 grids, and 2 times for 11 grids. The temperature of the open mill is: 185℃ for the front roller and 180℃ for the rear roller. After mixing, a uniform masterbatch is obtained.

[0067] Step 3: The masterbatch is directly loaded into the mold and pressed into the mold. It is melted at high temperature and molded by compression molding. The molding conditions are: upper mold plate 210℃, lower mold plate 195℃, molding pressure 15MPa, heat holding time 10min, and then cooled to room temperature to demold, thus obtaining graphite polypropylene high thermal conductivity composite material.

[0068] Detailed specifications are shown in Table 6 below:

[0069] Table 6 Formulation of graphite-polypropylene high thermal conductivity composite material

[0070]

[0071] The axial and radial thermal conductivity of the composite materials prepared by wave stacking in the above embodiments were tested and compared with the axial and radial thermal conductivity of the material prepared in Comparative Example 1. The test results are shown in Table 7.

[0072] Table 7 Thermal conductivity of composite materials prepared in the examples

[0073]

[0074] As shown in Table 7, the axial and radial thermal conductivity anisotropy of the graphite-polypropylene high thermal conductivity composite material prepared by the injection molding method of this invention is altered to varying degrees, with the axial thermal conductivity reaching as high as 24.1 W·m. -1 ·K -1 Compared with Comparative Example 1, the composite material prepared in Comparative Example 1 has a higher radial thermal conductivity, reaching 19.0 W·m. -1 ·K -1 The thermal conductivity is much higher than that of the axial thermal conductivity. This is because during the compression molding process, the graphite in the composite material is mainly oriented horizontally, resulting in a more complete horizontal thermal conduction path. The average thermal conductivity and axial thermal conductivity of the composite material prepared in Example 5 are 1.59 times and 18.1 times higher than those in Comparative Example 1, respectively. This is because during the injection molding process of the composite material using the special molding die of this invention, the injection rate and injection pressure can be precisely controlled. The molten masterbatch can pass through the trapezoidal runner and special gate at a uniform speed, and under the action of shear force, it fills the cavity in a wave-like pattern, constructing a more uniform and complete three-dimensional thermal conduction path for the composite material. The graphite in the material has different degrees of orientation in the horizontal and vertical directions, with the vertical orientation being particularly prominent. Table 7 also shows that the average thermal conductivity of the composite materials prepared through two gates with different heights does not change much, while the axial and radial thermal conductivity differ significantly. This is because, under the same graphite content and injection molding process conditions, a larger gate height is more conducive to the vertical orientation of graphite in the composite material, while a smaller gate height is more conducive to the horizontal orientation of graphite in the composite material, but it should not be too large or too small.

Claims

1. An injection mold for a graphite-polypropylene high thermal conductivity composite material, characterized in that: The injection molding mold includes a fixed module (1), a core module (2), and a moving module (3). The core module (2) is fixed in the core groove at the top of the moving module (3). The fixed module (1) and the top of the moving module (3) are closed. The core module (2) includes a core module body (2-1), a cavity (2-2), a main runner (2-3), a trapezoidal runner (2-4), a gate (2-5), and an overflow groove (2-6). There are two cavities (2-2), which are respectively located in the core module body (2-1). On both sides of -1), the main channel (2-3) is set between the two cavities (2-2). The two ends of the main channel are connected to the branch channels (2-7). The two branch channels are connected to the trapezoidal channels (2-4). The trapezoidal channels are connected to one end of the cavity through the gates (2-5) of different heights. The molten masterbatch passes through the trapezoidal channels and the narrow gates at a uniform speed. Under the action of shear force, it fills the cavity in a wave-like manner. The other ends of the two cavities (2-2) are respectively provided with overflow grooves (2-6).

2. The injection mold for the graphite-polypropylene high thermal conductivity composite material according to claim 1, characterized in that: The fixed module (1) includes a fixed template (1-1), a fixed mold base plate (1-2), an injection port (1-3), and positioning holes (1-4). The fixed template (1-1) is fixed on the fixed mold base plate (1-2). The positioning holes (1-4) are located at the four corners of the fixed template (1-1). The injection port (1-3) passes through the center of the fixed template and the fixed mold base plate. The fixed mold base plate (1-2) is connected to the injection molding machine. The moving module (3) includes a moving template (3-1), a core groove (3-2), a pad (3-3), and a moving mold base plate (3-4). The core groove (3-2) is located at the top center of the moving template (3-1), and its size matches that of the core module body (2-1). The core module body (2-1) is embedded in the core groove (3-2) and is flush with the top of the core groove wall. The lower end of the moving template (3-1) is connected to the moving mold base plate (3-4) through the pad (3-3). Four positioning posts (3-5) are provided at the four corners of the upper end of the moving template (3-1). The fixed template (1-1) and the moving template (3-1) are aligned to form a mold. The positioning posts (3-5) are inserted into the positioning holes (1-4). The moving mold base plate (3-4) is connected to the injection molding machine.

3. The injection mold for the graphite-polypropylene high thermal conductivity composite material according to claim 1, characterized in that: The trapezoidal flow channel (2-4) has an upper base of 23mm, a lower base of 40mm, and a length of 15mm.

4. A method for preparing a graphite-polypropylene high thermal conductivity composite material, characterized in that: The graphite-polypropylene high thermal conductivity composite material comprises the following components in parts by weight: 50-85 parts graphite, 15-50 parts polypropylene, 0.5-2 parts coupling agent, 0.1-2 parts antioxidant, 0.5-2 parts flow agent, and 0.2-1 parts lubricant. The preparation method is injection molding using the injection mold according to any one of claims 1 to 3, comprising the following steps: a. Add the coupling agent of the formula amount to anhydrous ethanol, sonicate for 20-40 minutes, then mix it with the graphite of the formula amount at high speed until uniform, and dry it at 110-120℃ under vacuum for 1-2 hours to obtain the premix. b. Mix the treated graphite, polypropylene, antioxidant, flow agent and lubricant at high speed, and then extrude and granulate using an extruder to obtain a uniformly mixed masterbatch. c. The masterbatch is loaded into the injection molding machine for injection molding. The molten masterbatch passes through the 0.4-0.8mm high gate at a uniform speed along the trapezoidal runner, and fills the cavity of the molding device in a wave-like manner to form a graphite polypropylene high thermal conductivity composite material.

5. The method for preparing the graphite-polypropylene high thermal conductivity composite material according to claim 4, characterized in that: The graphite is in flake form, with a carbon content ≥95% and a particle size of 10–400 μm.

6. The method for preparing the graphite-polypropylene high thermal conductivity composite material according to claim 5, characterized in that: In step b, the extruder is a twin-screw extruder. During extrusion granulation, the temperatures of each section of the extruder are 180±5℃, 195±5℃, 195±5℃, 205±5℃, 195±5℃, and 185±5℃ respectively. The main screw speed of the extruder is 80~120 rpm, the feed screw speed is 5~15 rpm, and the extrusion granulation is performed 3~4 times. After each granulation, the extruder is vacuum dried in an oven at 120℃ for 1 hour.

7. The method for preparing the graphite-polypropylene high thermal conductivity composite material according to claim 6, characterized in that: In step c, the masterbatch is added to the injection molding machine for injection molding. The temperatures of each section of the injection molding machine screw are 190±5℃, 210±5℃, 220±5℃, 210±5℃, and 180±5℃ respectively; the mold temperature is 170±5℃; the injection rate of the injection molding machine is 10~100g / s, the injection pressure is 15~25 MPa, and the holding pressure is 5~15 s.

8. The method for preparing the graphite-polypropylene high thermal conductivity composite material according to claim 4, characterized in that: The coupling agent is one or more of the following: titanate coupling agents NDZ-101 and NDZ-201, and silane coupling agents KH-550, KH-560, and KH-570.

9. The method for preparing the graphite-polypropylene high thermal conductivity composite material according to claim 4, characterized in that: The polypropylene is one or more of homopolymer polypropylene, random copolymer polypropylene, and block copolymer polypropylene with a melt index ≥1g / 10min.

10. The method for preparing the graphite-polypropylene high thermal conductivity composite material according to claim 4, characterized in that: The antioxidant is one or more of antioxidant 1010, antioxidant 1076, antioxidant 168, antioxidant 944, and antioxidant DSTDP; the lubricant is one or more of calcium stearate, zinc stearate, stearamide, stearic acid, high-boiling-point paraffin wax, and microcrystalline wax.

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