Preparation method of CF-PEEK particles with high strength and high thermal conductivity

Abstract

The invention is applied to the technical field of special engineering plastic modification, and discloses a preparation method of high-strength high-thermal-conductivity CF-PEEK particles, which comprises the following steps: S1, carbon fiber surface treatment; s2, chopping the carbon fibers; s3, pretreating the PEEK resin; s4, pretreating the nano material; s5, mixing the nano material with PEEK; s6, mixing the carbon fibers with the resin; and S7, performing granulation. According to the preparation method of the high-strength and high-thermal-conductivity CF-PEEK particles, aiming at the key pain point that an existing chopped CF / PEEK composite material cannot meet high rigidity (low deformation) and high thermal conductivity (heat dissipation) at the same time, through accurate introduction of carbon nanotubes (CNT) and optimization of technological parameters, cooperative improvement of performance is successfully achieved, the problem of heat accumulation in high-speed rotation and friction scenes is effectively solved, and the high-strength and high-thermal-conductivity CF-PEEK particles are obtained. And high-end application requirements of humanoid robot joints, transmission parts and the like are completely met.

Description

Technical Field

[0001] This invention relates to the field of special engineering plastic modification technology, specifically a method for preparing high-strength, high-thermal-conductivity CF-PEEK particles. Background Technology

[0002] In the field of high-performance composite materials, carbon fiber reinforced polymer matrix composites are widely used in aerospace, automotive industry, sporting goods and many other fields due to their excellent properties, such as high specific strength, high specific modulus and fatigue resistance. Among them, PEEK (polyether ether ketone) resin, as a high-performance thermoplastic resin matrix, has outstanding high temperature resistance, chemical corrosion resistance, good mechanical properties and processability, making it one of the ideal matrix choices for carbon fiber reinforced composite materials. The important application of chopped carbon fiber reinforced PEEK composites is in the joints and transmission parts of humanoid robots. The chopped CF / PEEK composites used in robots not only require high stiffness to meet the low deformation capacity under stress, but also good thermal conductivity (heat dissipation) to avoid heat accumulation caused by high-speed rotation and friction. Therefore, chopped CF / PEEK composites are required to have both high stiffness and high thermal conductivity. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing high-strength, high-thermal-conductivity CF-PEEK particles, so as to solve the problem mentioned in the background art that existing short-cut CF / PEEK composite materials cannot simultaneously achieve high stiffness and high thermal conductivity.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing high-strength, high-thermal-conductivity CF-PEEK particles, comprising the following steps: S1. Carbon fiber surface treatment: The carbon fiber is surface treated with a sizing agent; S2, Carbon fiber stub cutting: The carbon fibers treated in step S1 are stubbed at 15-25℃, and the stub length is controlled to be 2.5-4.0mm; S3, PEEK resin pretreatment: PEEK coarse powder is ground by one of mechanical grinding, liquid nitrogen cooling grinding or air jet grinding, with a grinding mesh of 300-800 mesh; S4. Nanomaterial pretreatment: Select one or a mixture of two types of single-walled carbon nanotubes and multi-walled carbon nanotubes for grinding. S5. Mixing nanomaterials with PEEK: Mix the PEEK powder from step S3 with the nanomaterials from step S4 at a mass ratio of CNT:PEEK = 0.5%-5%, with a stirring paddle speed of 10-50 m / min and a mixing time of 10-20 min. S6. Mixing carbon fiber and resin: Mix the short-cut carbon fiber from step S2 with the mixture from step S5 at a mass ratio of 3:7-5.5:4.5; S7. Granulation: The mixture from step S6 is fed into a twin-screw extruder for granulation. The die temperature is 350-400℃ to obtain CF-PEEK particles.

[0005] Preferably, in step S1, the sizing agent treatment method is impregnation, and after treatment, the carbon fiber is placed in an oven at 60-80℃ and dried for 1-2 hours.

[0006] By adopting the above technical solution, the sizing agent can be uniformly coated on the surface of carbon fiber to form a stable interface layer. At the same time, through precise temperature and time drying treatment, residual moisture and impurities on the surface of carbon fiber can be effectively removed, significantly improving the interfacial bonding force between carbon fiber and PEEK resin, and laying the foundation for enhancing the overall mechanical properties of composite materials.

[0007] Preferably, in step S2, a dedicated carbon fiber short cutting machine is used to cut the carbon fiber to ensure that the cut is flat.

[0008] By adopting the above technical solution, problems such as splitting, fuzzing or uneven length of carbon fibers during the short cutting process can be avoided, ensuring that the carbon fibers are evenly dispersed in the subsequent mixing and molding process, reducing stress concentration caused by fiber damage, and further improving the mechanical property stability of CF-PEEK particles.

[0009] Preferably, in step S3, mechanical grinding is used for batch processing; Liquid nitrogen cooling grinding uses low temperatures to embrittle PEEK resin and obtain fine powder; Air jet milling uses high-speed airflow to achieve particle collision and grinding, resulting in a uniform particle size distribution of the ground powder.

[0010] By adopting the above technical solution, the appropriate grinding method can be flexibly selected according to the production scale and product precision requirements. It can meet the efficiency requirements of mass production through mechanical grinding, obtain finer PEEK powder through liquid nitrogen cooling grinding, or ensure the consistency of powder particle size through air jet grinding. The grinding precision of 300-800 mesh can ensure the maximum contact area between PEEK and nanomaterials and carbon fibers, and improve the mixing compatibility.

[0011] Preferably, in step S4, if a mixture of single-walled carbon nanotubes and multi-walled carbon nanotubes is used, the mixing ratio of the two can be adjusted according to the target thermal conductivity requirements.

[0012] By adopting the above technical solution, the high thermal conductivity of single-walled carbon nanotubes and the cost-controllable and highly dispersible characteristics of multi-walled carbon nanotubes can be combined with the proportion adjustment to achieve precise control of thermal conductivity. This can meet the stringent requirements of high thermal conductivity in high-end scenarios as well as the cost-effectiveness requirements of ordinary scenarios, thus broadening the application range of the product.

[0013] Preferably, the carbon fiber in step S2 is a common modulus carbon fiber with a modulus of 235-250 GPa.

[0014] By adopting the above technical solution, carbon fibers in this modulus range have both excellent mechanical strength and good processing adaptability. Compared with high modulus carbon fibers, they have a cost advantage and can form a good synergistic effect with PEEK resin. While ensuring the high stiffness of CF-PEEK particles, it avoids the processing brittleness problem caused by excessively high carbon fiber modulus, thus balancing performance and practicality.

[0015] Preferably, the grinding parameters for the nanomaterials in step S4 are: grinding time 5-15 min, grinding speed 1000-2000 rpm.

[0016] By adopting the above technical solution and precisely controlling the grinding time and speed, the initial agglomerates of carbon nanotubes can be effectively broken, and well-dispersed nanoparticles can be obtained. This avoids the agglomeration caused by insufficient grinding affecting the formation of thermal conductivity pathways, and also prevents the destruction of carbon nanotube structure caused by excessive grinding, thus ensuring that its thermal conductivity enhancement effect is fully exerted.

[0017] Preferably, in step S5, a high-efficiency mechanical mixing device is used for mixing, which is a high-speed mixer or a plow-type mixer.

[0018] Using the above technical solutions, both the high-speed mixer and the plow-type mixer have strong shearing and high dispersion capabilities. Combined with a stirring paddle linear speed of 10-50 m / min and a mixing time of 10-20 min, the nanomaterials can be uniformly dispersed in the PEEK grinding powder, avoiding local nanomaterial aggregation and ensuring the uniformity of the thermal conductivity and mechanical properties of the subsequent composite materials.

[0019] Preferably, in step S6, a mechanical stirring device is used for mixing. In the initial stage of stirring, a low speed is used to avoid material splashing. After preliminary mixing, the speed is increased to enhance the mixing effect.

[0020] Using the above technical solution, the segmented stirring strategy takes into account both material loss control and mixing effect: the low speed stage can prevent the mixture of chopped carbon fibers and PEEK nanomaterials from splashing and wasting due to high-speed impact, while the high speed stage can enhance the shearing and penetration between materials, ensuring that the chopped carbon fibers are evenly distributed in the resin matrix and improving the structural integrity of the composite material.

[0021] Preferably, in step S7, the extrusion speed of the twin-screw extruder is 5-20 m / min, and the diameter of the obtained CF-PEEK particles is 1-3 mm.

[0022] By adopting the above technical solution, the extrusion speed of 5-20m / min is matched with the mold temperature of 350-400℃, which can ensure that the material is fully melted and plasticized, and avoid material degradation caused by uneven mixing due to excessive speed or material degradation caused by excessively slow speed. The particle diameter of 1-3mm facilitates subsequent processing (such as injection molding and extrusion molding), and the particle structure is dense and has no internal pores, which further ensures the mechanical properties and thermal conductivity of the final product.

[0023] Compared with the prior art, the beneficial effects of the present invention are: the preparation method of the high-strength, high-thermal-conductivity CF-PEEK particles: 1. Addressing the critical challenge that existing short-cut CF / PEEK composite materials cannot simultaneously meet the requirements of high stiffness (low deformation) and high thermal conductivity (heat dissipation), this method achieves a synergistic performance improvement through the precise introduction of carbon nanotubes (CNTs) and optimization of process parameters. Test data shows that the prepared CF-PEEK particles have a tensile modulus of 40 GPa, a tensile fracture strength of 260 MPa, and a flexural strength of up to 452 MPa, ensuring low deformation under stress. At the same time, the thermal conductivity is increased to 2-3.5 W / (m・K), effectively solving the problem of heat accumulation in high-speed rotation and friction scenarios, and fully adapting to the high-end application requirements of humanoid robot joints, transmission parts, etc. 2. Optimization of multiple processes ensures internal bonding strength and structural uniformity of the material: Carbon fiber is impregnated with a sizing agent and dried to enhance the interfacial bonding strength with PEEK resin and reduce stress concentration. A dedicated short-cutting machine controls the short-cut length of 2.5-4.0mm to ensure a smooth cut and minimal fiber damage. A twin-screw extruder precisely controls the die temperature (350-400℃) and extrusion speed (5-20m / min) to avoid insufficient melting or degradation of the material, ensuring a dense particle structure. The final product has a tensile strength of up to 325MPa and a flexural strength of up to 452MPa, with mechanical properties superior to existing similar products and parameter deviation groups. 3. Innovatively, single-walled / multi-walled carbon nanotubes are introduced as a thermal conductivity enhancement phase. By controlling the mass ratio of 0.5%-5% and adjusting the mixing ratio, the thermal conductivity can be flexibly adjusted according to the target scenario to adapt to different heat dissipation requirements. The carbon nanotubes are ground and pretreated to break up agglomerates. Combined with the uniform dispersion of the high-efficiency mixing equipment, the continuous and complete thermal conductivity path is ensured. 4. Key parameters are designed with a wide adjustment range: carbon fiber to resin mass ratio 3:7-5.5:4.5, PEEK grinding mesh 300-800 mesh, fiber weight content 30-55%. It can be flexibly adjusted according to the performance requirements of different fields such as aerospace, automotive industry, and sporting goods, adapting to diverse scenarios, providing multiple PEEK grinding methods, balancing production efficiency and product precision, and reducing the application threshold for different production capacity scenarios. 5. The entire preparation process is scientifically and rigorously designed, with parameters matched to each step: key control indicators are clearly defined for carbon fiber surface treatment, stub cutting, mixing, granulation, and other steps to avoid process fluctuations affecting product quality. At the same time, a segmented stirring strategy of "initial low speed to prevent splashing + subsequent high speed for strong mixing" is adopted in the mixing stage. In the extrusion granulation stage, the precise matching of mold temperature and extrusion speed ensures product consistency. The stability and repeatability of the process can meet the needs of industrial mass production. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the preparation process of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Please see Figure 1 The present invention provides a technical solution: a method for preparing high-strength, high-thermal-conductivity CF-PEEK particles.

[0027] Example 1: This example provides a method for preparing high-strength, high-thermal-conductivity CF-PEEK particles. The specific steps are as follows: S1. Carbon fiber surface treatment: Ordinary modulus carbon fiber with a modulus of 240 GPa is selected. Epoxy sizing agent is used for surface treatment by impregnation method to ensure that the carbon fiber surface is uniformly coated with sizing agent. After treatment, it is placed in a 70℃ oven to dry for 1.5h. S2. Carbon fiber stub cutting: The carbon fiber treated in step S1 is stubbed at room temperature of 20℃ using a special carbon fiber stub cutting machine, and the stub length is controlled to be 3.0mm to ensure that the cut is flat and there is no obvious fiber damage. S3, PEEK resin pretreatment: PEEK coarse powder is ground using liquid nitrogen cooling grinding method. The low temperature of liquid nitrogen makes PEEK resin brittle, improves grinding efficiency, and finally obtains 500 mesh PEEK grinding powder. S4. Nanomaterial pretreatment: Multi-walled carbon nanotubes were selected as nanomaterials and ground at 1500 rpm for 10 minutes to break up the initial agglomerates of carbon nanotubes. S5. Mixing nanomaterials with PEEK: Mix the PEEK grinding powder from step S3 with the multi-walled carbon nanotubes from step S4 at a mass ratio of CNT:PEEK=2%. Use a high-speed mixer to mix the nanomaterials, setting the stirring paddle linear speed to 30m / min and the mixing time to 15min to ensure uniform dispersion of the nanomaterials. S6. Mixing carbon fiber and resin: Mix the short carbon fiber from step S2 with the mixture from step S5 at a mass ratio of 4:6. Use a mechanical stirring device to mix. In the initial stage, stir at a low speed of 50 rpm for 5 minutes to avoid material splashing. Then, increase the speed to 200 rpm for 10 minutes to enhance the mixing effect. S7. Granulation: The mixture from step S6 is fed into a twin-screw extruder for granulation. The die temperature is set to 380℃ and the extrusion speed is 12m / min to obtain CF-PEEK particles with a diameter of 2mm.

[0028] Comparative Example 1 (nanomaterials omitted); The only difference between this comparative example and Example 1 is that step S4, nanomaterial pretreatment, and step S5, nanomaterial and PEEK mixing process are omitted. The PEEK grinding powder from step S3 and the short-cut carbon fiber from step S2 are directly mixed at a mass ratio of 6:4. The remaining steps and parameters are completely consistent with Example 1 to obtain CF-PEEK particles.

[0029] Comparative Example 2 (deviation of carbon fiber stub length); The only difference between this comparative example and Example 1 is that the carbon fiber stub length is controlled to 1.0 mm in step S2. The remaining steps and parameters are completely consistent with those in Example 1, and CF-PEEK particles are obtained.

[0030] Comparative Example 3 (deviation in carbon fiber to resin ratio); The only difference between this comparative example and Example 1 is that the mass ratio of short-cut carbon fiber to the mixture in step S5 is 2:8 in step S6. The remaining steps and parameters are completely consistent with those in Example 1, and CF-PEEK particles are obtained.

[0031] Comparative Example 4 (Mold Temperature Deviation); The only difference between this comparative example and Example 1 is that the die temperature of the twin-screw extruder in step S7 is set to 330°C. The remaining steps and parameters are completely consistent with those of Example 1, and CF-PEEK particles are obtained.

[0032] Performance testing and results analysis The CF-PEEK particles prepared in Example 1 and Comparative Examples 1-4 were subjected to performance tests. The test items included tensile strength (according to GB / T1040.2-2006), flexural strength (according to GB / T9341-2008), and thermal conductivity (according to GB / T10297-1998). The test results are shown in Table 1 below.

[0033] Meanwhile, to clearly demonstrate the superiority of the technical solution of this invention, the core performance of the CF-PEEK particles prepared by this invention is compared with that of ordinary CF-PEEK particles, and the results are shown in Table 2 below.

[0034] Table 1. Performance test results of the examples and comparative examples. Table 2. Performance comparison of the present invention with ordinary CF-PEEK particles. Combining the data in Tables 1 and 2, it can be seen that the CF-PEEK particles prepared in Example 1 not only performed best in the internal comparison, but also had significant advantages compared with ordinary CF-PEEK particles. Table 2 shows that the fiber weight content of the particles of the present invention has a wider range of adjustment and can adapt to different scenario requirements. The tensile modulus increased from 25.9 GPa to 40 GPa, and the tensile breaking strength increased from 249 MPa to 260 MPa, resulting in a significant enhancement of mechanical properties. The thermal conductivity increased from 0.9-1.5 W / (mK) to 2-3.5 W / (mK), effectively doubling the thermal conductivity. In contrast, Comparative Example 1, due to the omission of nanomaterials, experienced a sharp drop in thermal conductivity to 1.2 W / (mK), approaching the level of ordinary materials, demonstrating that carbon nanotubes are the key to improving thermal conductivity. Comparative Examples 2-4, due to key parameters deviating from the optimized range, all showed a significant decrease in mechanical properties, further verifying the scientific validity and necessity of parameter matching in each step of this invention. This technical solution, through precise process design, successfully prepared CF-PEEK particles that combine high strength and high thermal conductivity, exhibiting outstanding performance advantages.

[0035] 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 high-strength, high-thermal-conductivity CF-PEEK particles, characterized in that: Includes the following steps: S1. Carbon fiber surface treatment: The carbon fiber is surface treated with a sizing agent; S2, Carbon fiber stub cutting: The carbon fibers treated in step S1 are stubbed at 15-25℃, and the stub length is controlled to be 2.5-4.0mm; S3, PEEK resin pretreatment: PEEK coarse powder is ground by one of mechanical grinding, liquid nitrogen cooling grinding or air jet grinding, with a grinding mesh of 300-800 mesh; S4. Nanomaterial pretreatment: Select one or a mixture of two types of single-walled carbon nanotubes and multi-walled carbon nanotubes for grinding. S5. Mixing nanomaterials with PEEK: Mix the PEEK powder from step S3 with the nanomaterials from step S4 at a mass ratio of CNT:PEEK = 0.5%-5%, with a stirring paddle speed of 10-50 m / min and a mixing time of 10-20 min. S6. Mixing carbon fiber and resin: Mix the short-cut carbon fiber from step S2 with the mixture from step S5 at a mass ratio of 3:7-5.5:4.5; S7. Granulation: The mixture from step S6 is fed into a twin-screw extruder for granulation. The die temperature is 350-400℃ to obtain CF-PEEK particles.

2. The method for preparing high-strength, high-thermal-conductivity CF-PEEK particles according to claim 1, characterized in that: In step S1, the sizing agent treatment method is impregnation, and after treatment, the carbon fiber is placed in an oven at 60-80℃ to dry for 1-2 hours.

3. The method for preparing high-strength, high-thermal-conductivity CF-PEEK particles according to claim 1, characterized in that: In step S2, a special carbon fiber short cutting machine is used to cut the carbon fiber to ensure that the cut is flat.

4. The method for preparing high-strength, high-thermal-conductivity CF-PEEK particles according to claim 1, characterized in that: In step S3, mechanical grinding is used for batch processing; Liquid nitrogen cooling grinding uses low temperatures to embrittle PEEK resin and obtain fine powder; Air jet milling uses high-speed airflow to achieve particle collision and grinding, resulting in a uniform particle size distribution of the ground powder.

5. The method for preparing high-strength, high-thermal-conductivity CF-PEEK particles according to claim 1, characterized in that: In step S4, if a mixture of single-walled carbon nanotubes and multi-walled carbon nanotubes is selected, the mixing ratio of the two can be adjusted according to the target thermal conductivity requirements.

6. The method for preparing high-strength, high-thermal-conductivity CF-PEEK particles according to claim 1, characterized in that: The carbon fiber mentioned in step S2 is a common modulus carbon fiber with a modulus of 235-250 GPa.

7. The method for preparing high-strength, high-thermal-conductivity CF-PEEK particles according to claim 1, characterized in that: The grinding parameters for the nanomaterials in step S4 are: grinding time 5-15 min, grinding speed 1000-2000 rpm.

8. The method for preparing high-strength, high-thermal-conductivity CF-PEEK particles according to claim 1, characterized in that: In step S5, a high-efficiency mechanical mixing device is used for mixing, which is a high-speed mixer or a plow-type mixer.

9. The method for preparing high-strength, high-thermal-conductivity CF-PEEK particles according to claim 1, characterized in that: In step S6, a mechanical stirring device is used for mixing. In the initial stage of stirring, a low speed is used to avoid material splashing. After initial mixing, the speed is increased to enhance the mixing effect.

10. The method for preparing high-strength, high-thermal-conductivity CF-PEEK particles according to claim 1, characterized in that: In step S7, the extrusion speed of the twin-screw extruder is 5-20 m / min, and the diameter of the CF-PEEK particles obtained is 1-3 mm.

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