Pael composites for robotic wear-resistant joints and methods of making and using the same

Abstract

The present application relates to PAEK composite material for robot wear-resistant joint and its preparation method and application, belong to polymer composite material technical field. The technical problem solved by the present application is to provide PAEK composite material for robot wear-resistant joint. The material is formed by melt blending the following components with mass percentage: liquid crystal polymer 0.5-3%; glass microspheres 20-40%; auxiliary agent 0-3%; the rest is PAEK matrix resin powder. The present application solves the problems of uneven dispersion of added graphene and weak interface bonding by forming graphene sheet in situ on the surface of PAEK powder; the introduction of a small amount of LCP realizes the triple functions of flow enhancement, micro-fiber self-reinforcement and surface lubrication; through the spherical bearing effect and hardness improvement effect of glass microspheres, the balance of hardness and fluidity is realized. The material has good wear resistance, low friction coefficient, significantly improved thermal conductivity, excellent processing fluidity, balanced mechanical properties, and meets the bearing requirements of robot joint. And its preparation process is simple and environment-friendly.

Description

Technical Field

[0001] This invention relates to PAEK composite materials for wear-resistant joints in robots, their preparation methods, and applications, belonging to the field of polymer composite materials technology. Background Technology

[0002] With the rapid development of humanoid robots, collaborative robots, and industrial robots, robot joints, as core components for motion execution, face stringent comprehensive performance requirements for their materials. During service, components such as joint bushings and bearing liners must withstand continuous friction and wear caused by high-frequency reciprocating motion, while also facing the following unique operational challenges:

[0003] (1) Wear resistance and self-lubrication: The robot joints frequently start and stop and operate at low speed and heavy load. It is difficult for lubricating grease to form a stable oil film on the friction surface. The material itself must have a low coefficient of friction and high wear resistance. (2) Thermal conductivity: The joint generates a lot of frictional heat during continuous friction. If it cannot be dissipated in time, it will cause the polymer matrix to soften thermally and accelerate wear failure. (3) Lightweight: The robot is extremely sensitive to its own weight. The joint material must be as lightweight as possible while ensuring mechanical properties. (4) Isotropic: The joint movement direction is varied. The material must have uniform mechanical and tribological properties in all directions.

[0004] Polyaryl ether ketone (PAEK) resins, especially polyether ether ketone (PEEK), are valued for their excellent high-temperature resistance (T...). g Approximately 143℃, T m With a temperature of approximately 343°C, good mechanical strength, outstanding chemical resistance, and biocompatibility, PAEK has become an important candidate material for robot joints. However, pure PAEK has a high coefficient of friction (approximately 0.30–0.40 for dry friction against steel) and insufficient wear resistance, making it unable to directly meet the long-term service requirements of robot joints.

[0005] In existing technologies, PAEK wear-resistant composite materials mainly adopt the following technical approaches:

[0006] (1) PTFE + Graphite + Carbon Fiber (CF) Standard System: Represented by Victrex 150FC30, this system adds polytetrafluoroethylene (PTFE) as a solid lubricant, graphite as an auxiliary lubricant and thermally conductive filler, and carbon fiber as a reinforcing phase. The friction coefficient of this system can be reduced to 0.08-0.15, but it has the following shortcomings: ① PTFE is prone to softening and loss under high temperature (>260℃) and continuous frictional heat, resulting in a decrease in lubrication performance; ② Graphite, as an external filler, has weak interfacial bonding with the PAEK matrix, poor dispersion uniformity, and is prone to agglomeration to form defect sources; ③ Carbon fiber has obvious anisotropy, resulting in significant differences in the mechanical properties and wear behavior of the material in different directions, which is not conducive to joint components subjected to multi-directional loads.

[0007] (2) Added graphene / graphene oxide system: Graphene is considered an ideal wear-resistant functional filler due to its excellent mechanical properties (theoretical strength 130 GPa), ultra-high thermal conductivity (approximately 5000 W / m·K per single layer) and self-lubricating properties. However, added graphene suffers from severe agglomeration problems in the PAEK matrix: the strong van der Waals forces between graphene sheets make it difficult to disperse uniformly in the polymer, and conventional methods such as ultrasonication and mechanical stirring can only achieve limited deagglomeration. Agglomerated graphene not only fails to exert its intrinsic properties but also becomes a stress concentration point, reducing the mechanical properties of the composite material. In addition, the interfacial bonding force between added graphene and the PAEK matrix is ​​weak (relying only on van der Waals forces or weak hydrogen bonds), and it is easy to be pulled out of the matrix during friction rather than forming an effective transfer film.

[0008] (3) Glass microsphere reinforced PAEK: There are existing commercial products (such as Victrex's glass microsphere reinforced PEEK), which are mainly used to improve dimensional stability and reduce the coefficient of thermal expansion, but have not systematically solved the problems of wear resistance and self-lubrication.

[0009] In recent years, laser-induced graphene (LIG) technology has attracted widespread attention. This technology utilizes the photothermal effect of lasers to carbonize and rearrange the surface of carbon-containing precursors (such as polyimide (PI) and wood) to form sp. 2 Hybridized graphene structures. Previous studies have shown that LIG can form porous graphene layers on the surface of PEEK films / sheets for surface functionalization in sensors, electronic devices, and bio-implants (e.g., Qian et al. from Soochow University, ACS paper 2025; USC Vandervelde et al., Small Science paper 2025). However, existing LIG technologies all target solid surfaces (films or sheets) for the fabrication of conductive / sensing elements or surface functionalization coatings, with laser parameters and process design all serving this goal. Applying LIG technology to PEEK powder particles to form a thin layer of graphene in situ on the surface of each powder particle to impart wear resistance and thermal conductivity to the composite material has not yet been reported.

[0010] Furthermore, patent CN113789033A discloses a method for 3D printing three-dimensional graphene structures, using a CO2 laser to carbonize polymer powders such as PI / PEEK layer by layer to form a graphene framework, followed by resin filling. However, this patent constructs a macroscopic three-dimensional graphene framework, rather than forming a nanoscale thin layer of graphene on the surface of a single powder particle. Patent CN202511394457A discloses a laser carbonization functionalization preparation of graphene composite coatings, using a PI / PPS / PEI / PEEK solution as a carbon source to induce the formation of a LIG coating. However, this is a coating process involving solution film formation and surface carbonization, which is fundamentally different from the powder processing route.

[0011] To improve the flowability of highly filled PAEK composites, existing technologies mainly rely on adding processing aids (such as low molecular weight waxes) or adjusting processing parameters, but this sacrifices mechanical properties. A study on the PEEK / CF / LCP system published by Song et al. in RSC Advances found that 5 wt% LCP reduced the equilibrium torque of the PEEK / CF system by 18.17%. However, in this system, LCP is partially compatible with PEEK through π-π interactions, and the presence of carbon fibers alters the dispersion morphology and mechanism of action of LCP.

[0012] Therefore, there is an urgent need for a PAEK composite material and its preparation method that can solve the problem of graphene dispersion uniformity while taking into account wear resistance, thermal conductivity, flowability and mechanical properties. Summary of the Invention

[0013] To address the above deficiencies, the first technical problem solved by this invention is to provide a PAEK composite material for wear-resistant joints in robots.

[0014] The present invention relates to a PAEK composite material for wear-resistant joints of robots, which is melt-blended from the following components in the indicated mass percentages: liquid crystal polymer (LCP) 0.5-3%; glass microspheres 20-40%; additives 0-3%; and the remainder being PAEK matrix resin powder. The PAEK matrix resin powder is treated with laser irradiation to form graphene sheets in situ on the powder surface, and the graphene sheets are covalently bonded to the PAEK matrix.

[0015] In one specific embodiment, the PAEK matrix resin is selected from one or more of polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketone (PEK), and polyetheretherketoneketone (PEEKK); the additives are selected from one or more of antioxidants, heat stabilizers, and silane coupling agents; the glass microspheres are solid glass microspheres with an average particle size of 10-50 μm and a density of 2.2-2.5 g / cm³; and the surface of the glass microspheres is treated with a silane coupling agent.

[0016] In one specific embodiment, the particle size of the PAEK matrix resin powder is 50–500 μm, preferably 100–300 μm.

[0017] In one specific embodiment, the graphene sheet thickness is 50–500 nm, and the number of graphene sheets is 3–20.

[0018] In one specific embodiment, the parameters for laser irradiation are: laser power of 10–100 W, irradiation time of 0.5–5 s, and laser wavelength of 975–1070 nm near-infrared laser or 10.6 μm CO2 laser.

[0019] In one specific embodiment, the melting temperature of the liquid crystal polymer is 20–80°C lower than that of the PAEK matrix resin. The liquid crystal polymer is dispersed in the PAEK matrix in the form of microfibers in the composite material. The aspect ratio of the microfibers is 5–30:1, and the diameter of the microfibers is 0.2–2 μm.

[0020] In one specific embodiment, by weight percentage, the liquid crystal polymer is 0.5-3%; the glass microspheres are 20-40%; the additives are 0.5-3%; and the remainder is PAEK matrix resin powder. Preferably, by weight percentage, the liquid crystal polymer is 1.5-2.5%; the glass microspheres are 25-35%; the additives are 0.5-2%; and the remainder is PAEK matrix resin powder.

[0021] In one specific embodiment, the graphene sheets on the surface of the PAEK powder exhibit characteristic D peaks (~1350 cm⁻¹) and G peaks (~1580 cm⁻¹) in Raman spectroscopy, with an I_D / I_G ratio of 0.1 to 0.8. The graphene sheets are connected to the PAEK matrix by C-C covalent bonds and / or COC ether bonds, wherein the covalent bonds originate from the chemical bonding between the incompletely carbonized aromatic rings and the PAEK molecular chains during laser irradiation.

[0022] The second technical problem solved by the present invention is to provide a method for preparing the PAEK composite material for wear-resistant joints of robots as described in the present invention.

[0023] The present invention relates to a method for preparing PAEK composite material for wear-resistant joints of robots, comprising the following steps:

[0024] S1. Laser irradiation: PAEK matrix resin powder is placed in a rotatable irradiation container. Under a protective atmosphere, the PAEK matrix resin powder is irradiated with a laser to form graphene sheets in situ on the surface of the PAEK matrix resin powder. During the irradiation process, the container is continuously rotated to ensure that the powder is irradiated evenly.

[0025] S2. Premixing: PAEK matrix resin powder treated by laser irradiation is premixed with liquid crystal polymer powder, glass microspheres and additives to obtain a premix;

[0026] S3. Melt blending extrusion: The premixed material is added to a twin-screw extruder and melt blended and extruded at a temperature 20-50°C above the melting temperature of the PAEK matrix resin, and then granulated to obtain composite material granules.

[0027] In some specific embodiments, in step S1, the protective atmosphere is nitrogen or argon, and the oxygen content is controlled below 0.5%; the laser spot diameter is 5-30 mm, and the cumulative irradiation time for each powder particle is controlled between 0.5 and 5 s; in step S3, the screw speed of the twin-screw extruder is 150-350 rpm, the extrusion temperature is 370-410℃, and the L / D ratio is 30-40:1.

[0028] The present invention also provides the application of the PAEK composite material for wear-resistant robot joints described herein in wear-resistant robot joints.

[0029] The present invention relates to a PAEK composite material for wear-resistant robot joints, which can be used in wear-resistant robot joints, including one or more of joint bushings, joint bearing liners, and harmonic reducer flex wheel pads.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. Significantly improved graphene dispersion uniformity. Graphene sheets are formed in situ on the surface of each PAEK powder particle using laser technology. The graphene is uniformly distributed within the matrix as the powder melts, fundamentally solving the problem of uneven dispersion and agglomeration of externally added graphene. Compared to Comparative Example 2 (externally added graphene), the wear rate of Example 1 of this invention is reduced by more than 60%, demonstrating that the wear resistance of in-situ graphene is significantly superior to that of externally added graphene.

[0032] 2. Significantly enhanced interfacial bonding. The in-situ formed graphene sheets are covalently bonded to the PAEK matrix, and the interfacial shear strength is much higher than that of the physically adsorbed interface of the added graphene. Raman spectroscopy and XPS analysis confirmed the existence of CC and COC chemical bonds between the graphene sheets and PAEK.

[0033] 3. Significantly reduced coefficient of friction. The synergistic effect of the graphene transfer film and the surface lubrication of LCP microfibers reduces the coefficient of friction of the composite material to 0.10-0.15 (dry friction against steel), which is close to the level of standard wear-resistant PEEK containing PTFE, but without the problem of PTFE loss at high temperatures.

[0034] 4. Significantly improved thermal conductivity. The in-situ graphene sheets construct a highly efficient heat conduction network with a thermal conductivity of 0.8–1.2 W / m·K, which is 2–3 times that of pure PEEK, effectively preventing thermal softening at friction hotspots.

[0035] 5. Excellent processing fluidity. The flow-enhancing effect of LCP and the bearing effect of glass microspheres work synergistically to ensure that the MFR of the high-filled (30% glass microspheres) composite material still reaches 8-12 g / 10min, which meets the requirements of injection molding.

[0036] 6. Balanced mechanical properties. Tensile strength reaches 120-130 MPa and isotropic, meeting the load-bearing requirements of robot joints.

[0037] 7. The process is green and efficient. The laser irradiation process does not require the addition of external graphene raw materials. It utilizes the aromatic structure of PAEK for in-situ conversion, making the process simple and environmentally friendly. Attached Figure Description

[0038] Figure 1 This is a flowchart illustrating the preparation process of the PAEK composite material in this embodiment of the invention.

[0039] Figure 2 The image shows a comparison of the Raman spectra of PAEK powder before and after laser irradiation in Example 1 of the present invention, where (a) is untreated PAEK powder and (b) is PAEK powder treated by laser irradiation.

[0040] Figure 3 This is a graph showing the variation of the I_D / I_G ratio and the number of graphene layers on the surface of PAEK powder under different laser powers in Example 7 of the present invention.

[0041] Figure 4 This is a bar chart comparing the friction coefficients of Example 1 and Comparative Examples 1 to 4 of the present invention.

[0042] Figure 5 This is a bar chart comparing the wear rates of Example 1 and Comparative Examples 1-4 of the present invention.

[0043] Figure 6 This is a bar chart comparing the thermal conductivity of Embodiment 1 and Comparative Examples 1 to 4 of the present invention. Detailed Implementation

[0044] The present invention relates to a PAEK composite material for wear-resistant joints of robots, which is melt-blended from the following components in the indicated mass percentages: liquid crystal polymer (LCP) 0.5-3%; glass microspheres 20-40%; additives 0-3%; and the remainder being PAEK matrix resin powder. The PAEK matrix resin powder is treated with laser irradiation to form graphene sheets in situ on the powder surface, and the graphene sheets are covalently bonded to the PAEK matrix.

[0045] This invention relates to a PAEK composite material for wear-resistant robot joints. By forming graphene sheets in situ on the surface of PAEK powder, the problems of uneven dispersion and weak interfacial bonding of added graphene are solved. By introducing a small amount of liquid crystal polymer (LCP), the thermodynamic incompatibility between LCP and PAEK is utilized to achieve the triple functions of flow enhancement, microfiber self-reinforcement, and surface lubrication. Through the spherical bearing effect and hardness enhancement effect of glass microspheres, a balance between hardness and flowability is achieved.

[0046] In one specific embodiment, the PAEK matrix resin is selected from one or more of polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetherketone (PEK), and polyetheretherketoneketone (PEEKK).

[0047] In one specific embodiment, the particle size of the PAEK matrix resin powder is 50–500 μm, preferably 100–300 μm.

[0048] PAEK matrix resin powder is treated with laser irradiation to form graphene sheets in situ on the powder surface. In one specific embodiment, the laser irradiation parameters are: laser power of 10-100 W, irradiation time of 0.5-5 s, and laser wavelength of 975-1070 nm near-infrared laser or 10.6 μm CO2 laser.

[0049] In this invention, the graphene sheets form a transfer film on the grinding surface during the friction process and dissipate frictional heat. In one specific embodiment, the graphene sheet thickness is 50–500 nm, and the number of graphene sheets is 3–20.

[0050] In one specific embodiment, the graphene sheets on the surface of PAEK powder exhibit characteristic D peaks (~1350 cm⁻¹) and G peaks (~1580 cm⁻¹) in Raman spectroscopy, with an I_D / I_G ratio of 0.1 to 0.8.

[0051] In one specific embodiment, the graphene sheets are connected to the PAEK matrix via C-C covalent bonds and / or COC ether bonds, wherein the covalent bonds originate from the chemical bonding between the aromatic rings that are not fully carbonized during laser irradiation and the PAEK molecular chains.

[0052] In one specific embodiment, the additive is selected from one or more of antioxidants, heat stabilizers, and silane coupling agents.

[0053] In one specific embodiment, the glass microspheres are solid glass microspheres with an average particle size of 10–50 μm and a density of 2.2–2.5 g / cm³; and the surface of the glass microspheres is treated with a silane coupling agent.

[0054] LCP and PAEK are thermodynamically incompatible. During melt processing, LCP disperses in independent micro-regions and orients under shear force to form a microfiber structure. After the microfibers are exposed on the friction surface, they form a lubricating phase. In one specific embodiment, the liquid crystal polymer (LCP) is a thermotropic liquid crystal polymer selected from aromatic polyester liquid crystal polymers, including one or more of liquid crystal polyesters (LCP-I type) and liquid crystal polyesteramides (LCP-II type).

[0055] In one specific embodiment, the melting temperature of the liquid crystal polymer is 20–80°C lower than that of the PAEK matrix resin. The liquid crystal polymer is dispersed in the PAEK matrix in the form of microfibers in the composite material. The aspect ratio of the microfibers is 5–30:1, and the diameter of the microfibers is 0.2–2 μm.

[0056] In one specific embodiment, by weight percentage, the liquid crystal polymer is 0.5-3%; the glass microspheres are 20-40%; the additives are 0.5-3%; and the remainder is PAEK matrix resin powder. Preferably, by weight percentage, the liquid crystal polymer is 1.5-2.5%; the glass microspheres are 25-35%; the additives are 0.5-2%; and the remainder is PAEK matrix resin powder.

[0057] The technical solution of this invention is based on the following three core logic chains:

[0058] (1) "Laser-guided in-situ graphene" - solving the problems of uneven dispersion and weak interfacial bonding of added graphene

[0059] PAEK resin possesses abundant aromatic ring structures and is a natural high-carbon content precursor. When a laser irradiates the surface of PAEK powder, the photothermal effect of the laser instantly heats the powder surface to 2000–3000°C. At this temperature, the non-aromatic structures (ether bonds, ketone bonds) in the PAEK molecular chain break, while the aromatic ring structures undergo sp... 2 Hybrid rearrangement forms graphene sheets. The key to this process lies in: ① Precise control of laser parameters ensures that the carbonization depth is limited to the powder surface (50–500 nm), preventing the entire powder from being completely graphitized, thus preserving the mechanical properties of the PAEK matrix; ② The graphene sheets are covalently bonded to the uncarbonized PAEK matrix within the matrix via C-C bonds and / or C-C ether bonds. This chemical bonding originates from the connection between the incompletely decomposed aromatic rings in the carbonization transition layer and the PAEK molecular chains, resulting in a much stronger interfacial bonding force than the physical adsorption of externally added graphene; ③ Since graphene sheets are formed on the surface of each powder particle, the graphene is uniformly distributed within the matrix during subsequent melt blending as the powder melts, resulting in naturally superior dispersion uniformity compared to external methods.

[0060] The resulting graphene sheets play a dual role in the service life of the composite material: ① Wear resistance and self-lubrication – The graphene sheets form a transfer film on the friction surface, reducing the coefficient of friction; simultaneously, the high hardness of the graphene sheets (Mohs hardness 1-2 but extremely low interlaminar shear strength) enables them to act as solid lubricants during friction. ② Thermal conductivity – The high thermal conductivity of the graphene sheets (approximately 1000–3000 W / m·K, depending on the number of layers) constructs an efficient heat conduction network, promptly dissipating heat generated by friction hotspots and preventing accelerated wear caused by localized thermal softening.

[0061] (2) "LCP incompatibility booster + microfiber self-reinforcement + surface lubrication" - solving the dual needs of poor flowability and wear resistance of high filler.

[0062] LCP (aromatic polyester liquid crystal polymer) and PAEK (aromatic polyetherketone) have fundamentally different chemical structures: the main chain of LCP contains ester bonds (-COO-) and rigid mesocrystalline units, while the main chain of PAEK contains ether bonds (-O-) and ketone bonds (-CO-). They are thermodynamically incompatible (Flory-Huggins interaction parameter χ>0.05), and during melt blending, LCP is dispersed in the PAEK matrix as independent microregions. This incompatibility is creatively utilized in this invention, producing three beneficial effects:

[0063] ① Flow-enhancing effect: The melting temperature of LCP is 20-80℃ lower than that of the PAEK matrix. At the PAEK melt processing temperature, LCP is already in a low-viscosity liquid crystal state. The LCP microregions act as "lubricating microregions" in the PAEK melt, significantly reducing the melt viscosity of the composite system. Unlike conventional processing aids, LCP forms rigid microfibers rather than flexible segments after cooling, without sacrificing the mechanical properties of the material.

[0064] ② Microfiber self-reinforcement: Under the high shear force of a twin-screw extruder, the LCP microregions undergo orientation deformation, forming a microfiber structure with an aspect ratio of 5:1 to 30:1. These microfibers, like "micro-fibers," play a role in load-bearing and crack deflection within the PAEK matrix, enhancing the tensile strength and impact toughness of the composite material. This self-reinforcing effect eliminates the need for additional fiber reinforcement, avoiding the anisotropy problems associated with fiber reinforcement.

[0065] ③ Surface lubrication: During friction, LCP microfibers are exposed on the friction surface as the PAEK matrix gradually wears down. The exposed LCP microfibers have low surface energy, forming a lubricating phase on the friction surface, further reducing the coefficient of friction. This adaptive lubrication mechanism of "wear-exposure-lubrication," in synergy with the graphene transfer film, achieves stable low friction over a wide speed and load range.

[0066] The amount of LCP added must be strictly controlled within the range of 0.5% to 3%. When it is below 0.5%, the number of LCP microregions is insufficient, and the flow-increasing and microfiber reinforcement effects are not obvious; when it is above 3%, the excessive LCP microregions will merge and grow due to thermodynamic incompatibility, forming macroscopic incompatible regions, which become stress concentration points and defect sources, leading to the deterioration of mechanical properties.

[0067] (3) "Glass microsphere spherical bearing effect" - solving the balance between hardness and fluidity

[0068] Glass microspheres, as spherical rigid fillers, play multiple roles in this invention: ① improving material hardness and compressive strength, enhancing the load-bearing capacity of joint components; ② the "bearing effect" of spherical morphology—spherical particles roll in the melt, reducing melt viscosity and improving fluidity, which is the opposite of the behavior of irregularly shaped fillers (such as carbon fiber and wollastonite) that increase melt viscosity; ③ isotropic—the reinforcing effect of spherical fillers is consistent in all directions, eliminating the anisotropy caused by fiber reinforcement and ensuring the uniformity of joint component performance under multi-directional loading; ④ reducing the coefficient of thermal expansion (CTE) and improving dimensional stability.

[0069] The present invention relates to a method for preparing PAEK composite material for wear-resistant joints of robots, comprising the following steps:

[0070] S1. Laser irradiation: PAEK matrix resin powder is placed in a rotatable irradiation container. Under a protective atmosphere, the PAEK matrix resin powder is irradiated with a laser to form graphene sheets in situ on the surface of the PAEK matrix resin powder. During the irradiation process, the container is continuously rotated to ensure that the powder is irradiated evenly.

[0071] S2. Premixing: PAEK matrix resin powder treated by laser irradiation is premixed with liquid crystal polymer powder, glass microspheres and additives to obtain a premix;

[0072] S3. Melt blending extrusion: The premixed material is added to a twin-screw extruder and melt blended and extruded at a temperature 20-50°C above the melting temperature of the PAEK matrix resin, and then granulated to obtain composite material granules.

[0073] S4. Injection molding: The composite material granules are injection molded into the desired products.

[0074] In step S1, the protective atmosphere is an atmosphere that does not participate in the reaction. In some specific embodiments, in step S1, the protective atmosphere is nitrogen or argon, and the oxygen content is controlled below 0.5%.

[0075] In some specific embodiments, in step S1, the diameter of the laser spot is 5 to 30 mm, and the laser scanning speed is matched with the rotation speed of the container, so that the cumulative irradiation time of each powder is controlled within the range of 0.5 to 5 seconds.

[0076] In some specific embodiments, in step S3, the screw speed of the twin-screw extruder is 150-350 rpm, the extrusion temperature is 370-410℃, and the L / D ratio is 30-40:1.

[0077] The present invention relates to a PAEK composite material for wear-resistant robot joints, which can be used in wear-resistant robot joints, including one or more of joint bushings, joint bearing liners, and harmonic reducer flex wheel pads.

[0078] The specific embodiments of the present invention will be further described below with reference to examples, but the invention is not limited to the scope of the described embodiments. Raw materials used in the examples:

[0079] PAEK resin: PEEK resin (JUTPEEK 550P or Victrex 450G), melt temperature 343℃; PEKK resin (Arkem Kepstan 7000 series), melt temperature 338℃.

[0080] Liquid crystal polymers (LCPs): LCP-I type (Vectra A950, p-hydroxybenzoic acid / 6-hydroxy-2-naphthoic acid copolymer, melt temperature 280℃); LCP-II type (Vectra B950, HBA / HNA / AP copolyesteramide, melt temperature 275℃).

[0081] Glass microspheres: Solid borosilicate glass microspheres (3M iM30K, average particle size 20μm, density 2.3 g / cm³, compressive strength >30000 psi), with surface treated with γ-aminopropyltriethoxysilane coupling agent.

[0082] Laser equipment: near-infrared fiber laser (wavelength 1070 nm, maximum power 100 W, spot diameter adjustable from 5 to 30 mm) or CO2 laser (wavelength 10.6 μm).

[0083] The preparation process of the PAEK composite material in the examples is as follows: Figure 1 As shown, the process includes five steps: S1 matrix resin pulverization → S2 laser irradiation → S3 mixing and premixing → S4 melt blending and extrusion → S5 injection molding. Specifically:

[0084] S1. Matrix Resin Pulverization: PAEK resin particles are pulverized using a mechanical pulverizer under liquid nitrogen cooling conditions, and then sieved to obtain PAEK powder of the target particle size. Liquid nitrogen cooling can prevent PAEK from sticking and thermal degradation caused by frictional heat during the pulverization process.

[0085] S2. Laser Irradiation: PAEK powder is placed in a rotatable cylindrical irradiation container with a light-transmitting window in the container wall. Under a nitrogen atmosphere (oxygen content <0.5%), the powder is irradiated through the window with a laser of set power and time. The container rotates continuously at 10–30 rpm, causing the powder to tumble and ensuring uniform irradiation of each powder particle. During laser irradiation, the surface of the PAEK powder heats up instantaneously under the laser photothermal effect, causing non-aromatic structures (ether bonds, ketone bonds) to break and aromatic ring structures to rearrange through sp² hybridization, forming graphene sheets. By precisely controlling the laser power and irradiation time, the carbonization depth is limited to the powder surface within the range of 50–500 nm, preventing the entire powder particle from being completely graphitized.

[0086] S3. Premixing: PAEK powder treated by laser irradiation, LCP powder (particle size 50-100μm), glass microspheres treated with silane coupling agent, and additives are premixed in a high-speed mixer at 1500 rpm for 5-10 minutes to obtain a uniform premix.

[0087] S4. Melt Blending Extrusion: The premixed material is added to a co-rotating twin-screw extruder (L / D = 36:1), and melt blending is performed under set temperature and screw speed. The resulting composite material granules are then water-cooled and granulated. The extrusion temperature gradually increases from the feeding section to the die: 360℃ in the feeding section, 375℃ in the compression section, 385℃ in the metering section, and 390℃ in the die. The screw speed is 200–300 rpm. During extrusion, LCP melts into a liquid crystal state in the PAEK melt and orients to form a microfiber structure under the high shear force of the twin screw. Graphene sheets are uniformly dispersed in the matrix along with the melting of the PAEK powder.

[0088] S5. Injection Molding: After drying the composite material granules at 120°C for 4 hours, they are injection molded into standard test strips or joint parts in an injection molding machine (barrel temperature 380~400°C, mold temperature 160~180°C).

[0089] Performance testing methods:

[0090] Friction coefficient: Refer to standard GB / T 3960-2016, dry friction, for GCr15 steel, load 2 MPa, speed 0.5 m / s, test distance 1000 m.

[0091] Wear rate refers to standard GB / T 3960-2016, thermal conductivity refers to standard GB / T 3399-1982, tensile strength refers to standard GB / T 1040.2-2022, flexural strength refers to standard GB / T 9341-2008, and MFR refers to standard GB / T3682.1-2018.

[0092] Example 1 (PEEK matrix, optimized formulation)

[0093] PAEK composite material formulation (by weight): PEEK powder (particle size 150–250 μm) 66%, LCP-I type (Vectra A950) 2%, glass microspheres (3M iM30K, average particle size 20 μm) 30%, antioxidant (Irganox 1010) 1%, silane coupling agent (pre-coated on the surface of glass microspheres) 1%.

[0094] Preparation parameters:

[0095] Laser irradiation parameters: near-infrared fiber laser, power 50 W, wavelength 1070 nm, spot diameter 15 mm, irradiation time 1.5 s, nitrogen atmosphere (oxygen content <0.3%), container rotation speed 20 rpm.

[0096] After laser irradiation, a graphene sheet approximately 200 nm thick forms on the surface of the PEEK powder, and the Raman spectrum shows a D peak (1352 cm⁻¹). -1 ) and G peak (1583 cm) -1 I_D / I_G=0.35, corresponding to approximately 8 graphene layers.

[0097] Extrusion parameters: screw speed 250 rpm, extrusion temperature (feeding section → die head) 360→390℃.

[0098] Performance test results: coefficient of friction 0.12 (dry friction, for GCr15 steel, load 2 MPa, speed 0.5 m / s, test distance 1000 m), wear rate 2.1×10 -6 mm 3 / N·m, thermal conductivity 1.05 W / m·K, tensile strength 126 MPa, flexural strength 185 MPa, MFR 10.2 g / 10min (400℃, 5 kg).

[0099] Example 2 (Low Filler)

[0100] PAEK composite material formulation (by weight): PEEK powder (particle size 150-250μm) 73%, LCP-I type 1%, glass microspheres 25%, antioxidant 0.5%, silane coupling agent 0.5%.

[0101] Laser irradiation parameters: near-infrared fiber laser, power 50 W, irradiation time 1.5 s, the rest are the same as in Example 1.

[0102] Performance test results: coefficient of friction 0.14, wear rate 3.5×10⁻⁶ -6 mm 3 / N·m, thermal conductivity 0.82 W / m·K, tensile strength 132 MPa, flexural strength 192 MPa, MFR 14.5 g / 10min.

[0103] Example 3 (High Filler Content)

[0104] PAEK composite material formulation (mass percentage): PEEK powder (particle size 150-250μm) 59%, LCP-I type 3%, glass microspheres 38%, antioxidant 0.5%, silane coupling agent 0.5% (included in the coating amount on the surface of glass microspheres) — Note: Here, the total amount is 59% PEEK + 3% LCP + 38% glass microspheres = 100%, and the additives are included in the pre-coating amount on the surface of glass microspheres.

[0105] Laser irradiation parameters: near-infrared fiber laser, power 50 W, irradiation time 1.5 s, the rest are the same as in Example 1.

[0106] Performance test results: coefficient of friction 0.11, wear rate 1.8×10 -6 mm 3 / N·m, thermal conductivity 1.18 W / m·K, tensile strength 118 MPa, flexural strength 175 MPa, MFR 6.8 g / 10min.

[0107] Example 4 (Impact of LCP Content – ​​Verification that Excessive LCP Leads to Performance Degradation)

[0108] PAEK composite material formulation (by weight): PEEK powder (particle size 150-250 μm) 62%, LCP-I type 5%, glass microspheres 33%.

[0109] The laser irradiation parameters are the same as in Example 1.

[0110] Performance test results: coefficient of friction 0.15, wear rate 4.2×10⁻⁶ -6 mm 3 / N·m, thermal conductivity 0.95 W / m·K, tensile strength 108 MPa, flexural strength 158 MPa, MFR 15.3 g / 10min.

[0111] Analysis: At 5% LCP, the MFR (mesh flow rate) increased significantly (increased fluidity), but the tensile strength decreased markedly (from 126 MPa to 108 MPa). SEM observation showed that LCP microregions merged and grew, forming incompatible regions with a scale >10 μm, becoming mechanically weak points. The wear rate was also higher than in Example 1 because excessive LCP formed a large soft phase region on the friction surface, reducing the continuity and protective effect of the transfer film. This example verifies the necessity of controlling the upper limit of LCP content to 3%.

[0112] Example 5 (PEKK matrix)

[0113] PAEK composite material formulation (mass percentage): PEKK powder (particle size 100-200μm) 66%, LCP-I type 2%, glass microspheres 30%, antioxidant 1%, silane coupling agent 1%.

[0114] Laser irradiation parameters: near-infrared fiber laser, power 45W, irradiation time 1.8s (PEKK has a higher ketone bond density than PEEK, and its carbonization activation energy is slightly lower, so the power is appropriately reduced and the irradiation time is extended to obtain an equivalent carbonization depth), the rest are the same as in Example 1.

[0115] Performance test results: coefficient of friction 0.12, wear rate 2.3×10⁻⁶ -6 mm 3 / N·m, thermal conductivity 1.02 W / m·K, tensile strength 123 MPa, flexural strength 180 MPa, MFR 11.5 g / 10min.

[0116] Example 6 (PEKK High Filler Content)

[0117] PAEK composite material formulation (by weight): PEKK powder (particle size 100-200 μm) 59%, LCP-II type (Vectra B950) 3%, glass microspheres 38%.

[0118] Laser irradiation parameters: near-infrared fiber laser, power 45W, irradiation time 2.0s, the rest are the same as in Example 1.

[0119] Performance test results: coefficient of friction 0.11, wear rate 1.6×10⁻⁶ -6 mm 3 / N·m, thermal conductivity 1.15 W / m·K, tensile strength 115 MPa, flexural strength 170 MPa, MFR 7.2 g / 10min.

[0120] Example 7 (Comparison of the effects of laser power / time)

[0121] Using the same formulation as in Example 1, but with only the laser irradiation parameters changed, the effects of different laser conditions on the graphene sheet characteristics on the PAEK powder surface and the properties of the composite material were investigated, as detailed in Table 1.

[0122] Table 1

[0123] A 15 3.0 0.72 18 85 0.18 5.6 128 B 30 2.0 0.51 12 150 0.14 3.2 127 C 50 1.5 0.35 8 200 0.12 2.1 126 D 70 1.0 0.22 5 310 0.11 2.0 118 E 90 0.5 0.15 4 420 0.12 2.8 108

[0124] Analysis: At low power (15 W, 3.0 s), carbonization was incomplete, resulting in a high I_D / I_G ratio (0.72), numerous graphene defects, and an excessive number of layers (18 layers), limiting the improvement in wear resistance. At high power (90 W, 0.5 s), carbonization was excessive, leading to overly thick graphene sheets (420 nm). Although the crystallinity of graphene increased (I_D / I_G=0.15), the excessively deep carbonized layers weakened the mechanical properties of the PAEK matrix, reducing the tensile strength to 108 MPa and increasing the wear rate. A power of 50 W and a time of 1.5 s are the preferred parameters for this invention, achieving the best balance between graphene quality and matrix performance.

[0125] Reference Figure 3 The I_D / I_G ratio decreases with increasing power under different laser powers, and the number of graphene layers also decreases with increasing power (but too few layers correspond to an excessively thick carbonized layer). Both reach their optimal range in the 50-70 W range.

[0126] Example 8 (Physical Verification of Robot Joint Bushings)

[0127] Using the formulation and process of Example 1, a shoulder joint bushing (inner diameter 25 mm, outer diameter 32 mm, length 20 mm) for a 6-DOF collaborative robot was injection molded to replace the original PTFE+graphite+CF reinforced PEEK bushing. A 1 million cycle reciprocating oscillation life test was conducted (oscillation angle ±60°, frequency 1 Hz, radial load 500 N, no external lubrication).

[0128] Test results: The bushing of this invention exhibits a frictional torque increase of <8% and an inner diameter wear of <15 μm after 1 million cycles. In contrast, the original PTFE+graphite+CF reinforced PEEK bushing shows a sudden increase in frictional torque at approximately 650,000 cycles (PTFE loss at high temperatures leading to lubrication failure), and an inner diameter wear of 45 μm after 1 million cycles. The service life of the bushing of this invention is more than 50% longer than that of existing products.

[0129] Comparative Example 1 (without laser treatment)

[0130] The formulation is exactly the same as in Example 1, but the PAEK powder is not treated with laser irradiation and is directly mixed with LCP and glass microspheres and extruded.

[0131] Performance test results: coefficient of friction 0.32, wear rate 16.5×10 -6 mm 3 / N·m, thermal conductivity 0.35 W / m·K, tensile strength 128 MPa, MFR 10.8 g / 10min.

[0132] Analysis: The PAEK powder without laser treatment lacks graphene sheets on its surface, resulting in a composite material that lacks a transfer film lubrication mechanism and a thermally conductive reinforcement network. Consequently, its coefficient of friction and wear rate are significantly higher than in Example 1. The tensile strength is similar to that of Example 1, indicating that laser irradiation has minimal impact on the matrix's mechanical properties. The mean surface roughness (MFR) is also similar, suggesting that laser treatment does not affect processing flowability.

[0133] Comparative Example 2 (Added graphene instead of laser-induced in-situ graphene)

[0134] Formula: 64.3% PEEK powder (untreated by laser), 1.7% commercially available multilayer graphene powder (5-10 layers, 5-15μm diameter), 2% LCP-I type, 30% glass microspheres, 1% antioxidant, and 1% silane coupling agent.

[0135] The 1.7% added graphene content is calculated based on the mass fraction of graphene sheets on the surface of PEEK powder after laser irradiation in Example 1, ensuring that the total graphene content is comparable to that in Example 1.

[0136] Mixing method: First, premix the graphene powder and PEEK powder in a high-speed mixer at 2000 rpm for 10 minutes, then mix them with LCP and glass microspheres. The extrusion process is the same as in Example 1.

[0137] Performance test results: coefficient of friction 0.21, wear rate 7.8×10⁻⁶ -6 mm 3 / N·m, thermal conductivity 0.68 W / m·K, tensile strength 112 MPa, MFR 9.5 g / 10min.

[0138] Analysis: Although the added graphene content was comparable to that of Example 1, its dispersion uniformity was far inferior to that of the in-situ method. SEM observation revealed significant graphene agglomeration (agglomerate size 5-50 μm), with these agglomerated areas becoming stress concentration points and wear initiation points. The thermal conductivity was only 65% ​​of that of Example 1, indicating that the added graphene failed to form an effective heat conduction network. The tensile strength was lower than that of Example 1 (112 vs 126 MPa), demonstrating the negative impact of agglomerated graphene. This comparative example strongly demonstrates the significant advantages of in-situ graphene compared to added graphene.

[0139] Comparative Example 3 (without LCP)

[0140] Formulation: 67% PEEK powder (laser irradiated, parameters same as in Example 1), 30% glass microspheres, 1.5% antioxidant, and 1.5% silane coupling agent.

[0141] Performance test results: coefficient of friction 0.16, wear rate 4.5×10⁻⁶. -6 mm 3 / N·m, thermal conductivity 1.02 W / m·K, tensile strength 122 MPa, MFR 5.2 g / 10min.

[0142] Analysis: Without LCP, the composite material lacks the surface lubrication contribution of LCP microfibers, resulting in a higher coefficient of friction than in Example 1 (0.16 vs 0.12). More importantly, the MFR drops sharply from 10.2 to 5.2 g / 10min, indicating severely insufficient flowability and making the high-filler system difficult to process. The thermal conductivity is close to that of Example 1, suggesting that LCP has little impact on thermal conductivity, with the thermal conductivity mainly contributed by the graphene sheets.

[0143] Comparative Example 4 (Laser treatment of glass microspheres instead of PAEK powder)

[0144] The formulation was the same as in Example 1, but the laser irradiation target was changed to glass microspheres (instead of PAEK powder), and the PAEK powder was not laser-treated. The laser parameters were the same as in Example 1.

[0145] Performance test results: coefficient of friction 0.30, wear rate 15.2×10⁻⁶ -6 mm 3 / N·m, thermal conductivity 0.38 W / m·K, tensile strength 125 MPa, MFR 10.5 g / 10min.

[0146] Analysis: Laser treatment of glass microspheres may cause micro-roughening of the microsphere surface, but it will not form graphene (inorganic silicates do not possess the conditions for sp² carbonization). This comparative example confirms that the formation of graphene in this invention depends on the aromatic carbon framework of PAEK, rather than simply originating from the laser irradiation itself. The tribological properties are close to those of Comparative Example 1 (without laser treatment), further demonstrating that in-situ graphene on the surface of PAEK powder is the core of improved wear resistance.

[0147] Reference Figures 4-6 The key performance comparison between Example 1 and Comparative Examples 1-4 is shown in Table 2 below.

[0148] Table 2

[0149] Example 1 0.12 2.1 1.05 126 10.2 Comparative Example 1 0.32 16.5 0.35 128 10.8 Comparative Example 2 0.21 7.8 0.68 112 9.5 Comparative Example 3 0.16 4.5 1.02 122 5.2 Comparative Example 4 0.30 15.2 0.38 125 10.5

[0150] As can be seen from the table above: (1) Comparison Example 1 with Example 1 demonstrates the decisive contribution of laser-induced in-situ graphene to wear resistance and thermal conductivity (friction coefficient reduced by 62.5%, wear rate reduced by 87.3%, and thermal conductivity increased by 200%). (2) Comparison Example 2 with Example 1 demonstrates the significant advantages of in-situ graphene over externally added graphene in terms of dispersion uniformity and interfacial bonding (wear rate further reduced by 73.1%). (3) Comparison Example 3 with Example 1 demonstrates the indispensable role of LCP in flow enhancement and surface lubrication (MFR increased by 96.2%, and friction coefficient reduced by 25%). (4) Comparison Example 4 with Example 1 demonstrates that the formation of graphene must use the aromatic structure of PAEK as the carbon source, and laser irradiation of glass microspheres cannot produce an equivalent effect.

[0151] Mechanism verification

[0152] (1) Raman spectroscopy verification: refer to Figure 2 Untreated PEEK powder at 1000–2000 cm⁻¹ -1 The region exhibits only a weak fluorescent background, with no D or G peaks; the PEEK powder after laser irradiation shows fluorescence at 1352 cm⁻¹. -1 and 1583 cm -1 Distinct D and G peaks appear at 2705 cm⁻¹, with the 2D peak appearing at 2705 cm⁻¹. -1 This confirms that sp 2 The formation of hybrid graphene structures. I_D / I_G=0.35 indicates that graphene has a certain degree of defect (originating from the rapid non-equilibrium characteristics of the laser carbonization process), but the defect density is within a controllable range.

[0153] (2) XPS verification: In the C1s spectrum of the PEEK powder surface after laser irradiation, sp 2 The area fraction of the CC peak (284.5 eV) increased from approximately 35% in the original PEEK to approximately 65%, while the area fractions of the CO peak (286.5 eV) and C=O peak (287.8 eV) decreased accordingly, confirming the removal of oxygen-containing functional groups and the formation of sp² carbon networks during carbonization. The COC signal was still retained in the transition layer, confirming the chemical bonding between the graphene sheets and the PEEK matrix.

[0154] (3) SEM morphology verification: After laser irradiation, the surface of PEEK powder exhibited a typical porous and wrinkled graphene morphology with a sheet thickness of approximately 200 nm (FIB cross-section observation). After melt blending, the graphene sheets were uniformly distributed in the PEEK matrix without obvious agglomeration. LCP formed a microfiber structure with a diameter of 0.5–1.2 μm and an aspect ratio of 8–15 in the matrix, and was uniformly dispersed.

[0155] (4) Verification of the friction transfer film: Raman mapping of the surface of the steel ball showed that in Example 1, a continuous graphene transfer film was formed on the surface of the steel ball after friction, with a coverage of more than 85%; the surface of the steel ball in Comparative Example 1 had almost no carbon transfer film; the transfer film coverage of Comparative Example 2 was only about 40%, and the distribution was uneven, corresponding to the graphene agglomeration area.

[0156] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A PAEK composite material for use in a robot wear joint, characterized in that: It is a melt blend of the following components in weight percentage: 0.5-3% liquid crystal polymer; 20-40% glass microspheres; 0-3% additives; the remainder is PAEK matrix resin powder; The PAEK matrix resin powder is treated with laser irradiation to form graphene sheets in situ on the powder surface, and the graphene sheets are covalently bonded to the PAEK matrix.

2. The PAEK composite for a robot wear joint of claim 1, wherein: The PAEK matrix resin is selected from one or more of polyetheretherketone, polyetherketoneketone, polyetherketone, and polyetheretherketoneketone. The additives are selected from one or more of antioxidants, heat stabilizers, and silane coupling agents; The glass microspheres are solid glass microspheres with an average particle size of 10–50 μm and a density of 2.2–2.5 g / cm³; and the surface of the glass microspheres is treated with a silane coupling agent.

3. The PAEK composite for a robot wear joint of claim 1, wherein: The particle size of the PAEK matrix resin powder is 50–500 μm, preferably 100–300 μm; the thickness of the graphene sheets is 50–500 nm, and the number of graphene sheets is 3–20.

4. The PAEK composite material for wear-resistant robot joints according to claim 1, characterized in that: The parameters for laser irradiation treatment are: laser power 10-100 W, irradiation time 0.5-5 s, and laser wavelength of 975-1070 nm near-infrared laser or 10.6 μm CO2 laser.

5. The PAEK composite material for wear-resistant robot joints according to claim 1, characterized in that: The melting temperature of the liquid crystal polymer is 20–80°C lower than that of the PAEK matrix resin. The liquid crystal polymer is dispersed in the PAEK matrix in the form of microfibers in the composite material. The aspect ratio of the microfibers is 5–30:1 and the diameter of the microfibers is 0.2–2 μm.

6. The PAEK composite material for wear-resistant robot joints according to claim 1, characterized in that: By weight percentage, the liquid crystal polymer is 0.5-3%; glass microspheres are 20-40%; additives are 0.5-3%; and the remainder is PAEK matrix resin powder. Preferably, by weight percentage, the liquid crystal polymer is 1.5-2.5%; glass microspheres are 25-35%; additives are 0.5-2%; and the remainder is PAEK matrix resin powder.

7. The PAEK composite material for wear-resistant robot joints according to claim 1, characterized in that: Graphene sheets exhibit characteristic D and G peaks in Raman spectroscopy, with an I_D / I_G ratio of 0.1–0.

8. The graphene sheets are connected to the PAEK matrix by C-C covalent bonds and / or COC ether bonds. The covalent bonds originate from the chemical bonding between the aromatic rings that are not fully carbonized during laser irradiation and the PAEK molecular chains.

8. The method for preparing the PAEK composite material for wear-resistant robot joints according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Laser irradiation: PAEK matrix resin powder is placed in a rotatable irradiation container. Under a protective atmosphere, the PAEK matrix resin powder is irradiated with a laser to form graphene sheets in situ on the surface of the PAEK matrix resin powder. During the irradiation process, the container is continuously rotated to ensure that the powder is irradiated evenly. S2. Premixing: PAEK matrix resin powder treated by laser irradiation is premixed with liquid crystal polymer powder, glass microspheres and additives to obtain a premix; S3. Melt blending extrusion: The premixed material is added to a twin-screw extruder and melt blended and extruded at a temperature 20-50°C above the melting temperature of the PAEK matrix resin, and then granulated to obtain composite material granules. S4. Injection molding: The composite material granules are injection molded into the desired products.

9. The method for preparing PAEK composite material for wear-resistant robot joints according to claim 8, characterized in that: In step S1, the protective atmosphere is nitrogen or argon, and the oxygen content is controlled below 0.5%; the laser spot diameter is 5-30 mm, and the cumulative irradiation time for each powder particle is controlled between 0.5 and 5 s; in step S3, the screw speed of the twin-screw extruder is 150-350 rpm, the extrusion temperature is 370-410℃, and the L / D ratio is 30-40:

1.

10. The application of the PAEK composite material for wear-resistant robot joints according to any one of claims 1 to 7 in wear-resistant robot joints, wherein the wear-resistant robot joint comprises one or more of joint bushings, joint bearing liners, and harmonic reducer flex wheel pads.

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