Preparation method and application of PEEK composite material

Abstract

The invention relates to the technical field of composite material manufacturing, in particular to a preparation method and application of a PEEK composite material. The preparation method of the PEEK composite material comprises the following steps: carrying out high-temperature oxidation and silane coupling agent impregnation pretreatment on short carbon fibers, and meanwhile, carrying out dry premixing on polyimide microspheres and nano silicon dioxide; feeding and stirring step by step according to the proportion to form a premix with uniformly distributed components; carbon fibers are supplemented in a lateral feeding mode, and melt blending and granulation are completed in cooperation with precise temperature control; and finally, drying the composite material particles, and carrying out injection molding or compression molding to obtain a finished product. The prepared PEEK composite material has excellent comprehensive performance: the material density is extremely low, and the specific strength is excellent; a multi-scale enhanced network is constructed in the composite material, high rigidity and high toughness are both considered, and the composite material has excellent impact resistance; the composite material has a self-lubricating property and outstanding wear resistance and fatigue resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite material manufacturing, in particular to a PEEK composite material preparation method and application thereof. BACKGROUND

[0002] The commercialization of humanoid robots is becoming one of the core development directions in the field of intelligent manufacturing, but its large-scale application is still limited by the key challenges of insufficient endurance, poor motion flexibility, substandard performance of core components, and high overall cost, and lightweight is the core technical path to simultaneously solve the above problems.

[0003] Traditional robot joints, skeletons, and transmission systems and other core structural components are mostly made of metal materials such as aluminum alloys. Although such materials have high mechanical strength, their density is generally high, which leads to a large weight of the robot, seriously restricting the workability of humanoid robots in complex scenarios.

[0004] As a high-performance engineering plastic, polyether ether ketone (PEEK) has become an ideal alternative material due to its extremely low density, extremely high specific strength, excellent heat resistance, and chemical stability. However, the mechanical properties of pure PEEK resin have obvious shortcomings, and it cannot simultaneously meet the comprehensive requirements of high rigidity, high wear resistance, and impact toughness in robot joints such as harmonic reducer rigid wheels and bearing rings under high dynamic load and high frequency motion.

[0005] To improve the performance of pure PEEK, the industry generally uses carbon fiber reinforcement modification technology, which can effectively improve the strength and modulus of the material, but also brings a series of new problems: the toughness of the material decreases significantly, and brittle fracture easily occurs under transient overload conditions; the anisotropy of carbon fiber leads to significant differences in mechanical properties in different directions of the component, affecting the transmission accuracy; and the processing difficulty of the reinforced material increases, increasing the production cost. In addition, in the long-term high-frequency friction motion of robot joints, the wear resistance and fatigue resistance of traditional carbon fiber reinforced PEEK still have a lot of room for optimization, and it is difficult to match the stringent standards of service life and operation stability of precision transmission components such as harmonic reducers.

[0006] In recent years, researchers have tried to modify PEEK by using fiber fillers such as carbon fiber and glass fiber, and have also explored step-by-step preparation of master batches to improve the dispersion uniformity of fillers in the matrix. However, these technical solutions focus on improving a single performance dimension, lack a systematic and collaborative optimization of the overall solution for material specific strength, wear resistance, fatigue resistance, and dimensional stability, and cannot simultaneously meet the comprehensive performance requirements of lightweight, high precision, and long life of robot core components.

[0007] Therefore, it is urgent for technical personnel to solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing PEEK composite materials, which aims to solve the problems of insufficient mechanical properties of pure PEEK in existing designs, poor toughness and wear resistance of single carbon fiber reinforced PEEK, and difficulty in meeting the requirements of high rigidity, fatigue resistance and dimensional stability of robot joints.

[0009] This invention relates to a method for preparing PEEK composite materials, comprising the following steps: S1. Short-cut carbon fibers are oxidized at high temperature, then impregnated in an ethanol solution containing silane coupling agent, and dried for later use; polyimide microspheres and nano-silica are placed in a high-speed mixer for dry premixing to obtain an inorganic-organic particle premix. S2. By weight, take 100 parts of PEEK resin and put it into a high-speed mixer. While stirring, add 11 to 24 parts of pretreated short-cut carbon fiber, 4 to 13 parts of inorganic-organic particle premix, 2 to 6 parts of composite lubricant and 0.5 to 1.5 parts of antioxidant in sequence. Mix evenly to obtain the premix. S3. The premixed material is fed into the twin-screw extruder through the main feed port, and 4-6 parts of pretreated short-cut carbon fibers are added to the rear of the extruder's melting section via a side feeder; the temperature of each section of the twin-screw extruder is controlled as follows: Zone 1: 320-340℃, Zone 2: 350-370℃, Zone 3: 360-380℃, Zone 4: 360-380℃, and the die head: 360-380℃; the material is melt-extruded, water-cooled, and pelletized to obtain PEEK composite material particles; S4. Dry the composite material particles at 150°C, and then obtain PEEK composite material products through injection molding or compression molding processes.

[0010] As a further improvement to the technical solution disclosed in this invention, the inorganic-organic particle premix is ​​composed of 3 to 8 parts by weight of polyimide microspheres and 1 to 5 parts by weight of nano-silica; the composite lubricant is a mixture of polytetrafluoroethylene and molybdenum disulfide.

[0011] As a further improvement to the technical solution disclosed in this invention, in step S3, the screw speed of the twin-screw extruder is 200-400 rpm; in step S4, the drying time of the composite material particles is 4-6 h.

[0012] As a further improvement to the technical solution disclosed in this invention, in step S1, the high-temperature oxidation treatment temperature of the short-cut carbon fiber is 400-500℃, and the treatment time is 1-2h; the mass concentration of the silane coupling agent in the ethanol solution is 1-3%, the impregnation time is 0.5-1h, the drying temperature is 80-100℃, and the drying time is 2-3h.

[0013] As a further improvement to the technical solution disclosed in this invention, in step S1, the high-temperature oxidation treatment adopts a gradient heating mode, first heating to 300°C at a rate of 5°C / min and holding for 30 min, then heating to 450-500°C at a rate of 3°C / min and holding for 1-2 h, and the oxidation treatment atmosphere is an air atmosphere containing 5-8 vol% ozone.

[0014] As a further improvement to the technical solution disclosed in this invention, 0.2 to 0.5 wt% of titanate coupling agent is added to the ethanol solution containing silane coupling agent, and the impregnation process is accompanied by ultrasonic vibration. After impregnation, the solution is first pre-dried in a vacuum environment at 60°C, and then heated to dry.

[0015] As a further improvement to the technical solution disclosed in this invention, the frequency of ultrasonic vibration is 20-30kHz, the power is 100-150W, the pre-drying time in a vacuum environment at 60℃ is 1h, and the subsequent heating and drying temperature is 80-100℃, and the drying time is 2-3h.

[0016] As a further improvement to the technical solution disclosed in this invention, in step S3, the chopped carbon fibers added by the side feeder account for 20-30% of the total amount of chopped carbon fibers; the middle and rear part of the melting section of the twin-screw extruder is the third zone, the length of the chopped carbon fibers is 3mm, and the antioxidant is antioxidant 1010.

[0017] As a further improvement to the technical solution disclosed in this invention, in step S3, the screw of the twin-screw extruder adopts a variable pitch combination structure, the pitch of the melt section gradually changes from 40mm to 25mm, and an airflow buffer chamber is provided at the side feed port, and inert gas is introduced into the buffer chamber to protect the added short-cut carbon fibers.

[0018] In addition, the present invention also discloses specific applications of PEEK composite materials, applying PEEK composite material products prepared by the above preparation method to the joints, skeletons and transmission system components of robots.

[0019] In practical applications, the PEEK composite material preparation method disclosed in this invention can achieve at least the following beneficial technical effects, specifically: 1) Steps S1 to S4 work synergistically to achieve a dual leap in filler dispersion uniformity and interfacial bonding strength, laying a solid foundation for the excellent comprehensive performance of PEEK composite materials. Specifically, in S1, the short-cut carbon fibers undergo high-temperature oxidation and silane coupling agent impregnation pretreatment to construct active functional groups on the carbon fiber surface, significantly enhancing its interfacial compatibility with the PEEK resin matrix. Furthermore, the dry premixing of polyimide microspheres and nano-silica effectively avoids the agglomeration drawbacks of adding the two particles individually, achieving preliminary uniform dispersion of inorganic-organic particles. The stepwise feeding and mixing mode in S2 allows the pretreated carbon fibers, premixed particles, composite lubricant, and antioxidant to gradually coat the surface of the PEEK resin particles, forming a uniformly distributed premix and eliminating the problem of localized filler enrichment or deficiency from the source. The S3 side-feed carbon fiber addition process can reduce the breakage of carbon fibers under the strong shearing action of the screw without damaging the premixed system, fully retain its aspect ratio, and ensure that the reinforcing phase forms a continuously distributed network structure in the matrix. 2) The pretreatment in S1 and the initial mixing in S2 provide a high-quality premixed system with uniform components and interfacial compatibility for the subsequent melt blending stage. S3, through precise temperature control of each section of the extruder, ensures that the PEEK resin is fully melted while avoiding resin degradation and lubricant failure caused by high temperatures. Crucially, the side-fed carbon fibers form a gradient distribution with the previously added carbon fibers, and together with the premixed inorganic-organic particles, they can construct a multi-scale reinforcing network, ultimately achieving a synergistic performance of high specific strength, high toughness, and low wear rate in the finished PEEK composite material. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a process flow diagram of the PEEK composite material preparation method disclosed in this invention. Detailed Implementation

[0022] The technical solution disclosed in this invention will be further described in detail below with reference to specific embodiments. PEEK composite materials achieve uniform dispersion of fillers and construction of a multi-scale reinforcing network through multi-step process synergistic control. Specific embodiments are as follows: Example 1 The specific steps involved in preparing PEEK composite materials are as follows: S1. Short carbon fibers with a length of 3 mm were placed in a heat treatment furnace and subjected to high-temperature oxidation treatment using a gradient heating mode. The temperature was first increased to 300℃ at a rate of 5℃ / min and held for 30 min, and then increased to 450℃ at a rate of 3℃ / min and held for 1 h. The oxidation atmosphere was air containing 5 vol% ozone. Subsequently, the carbon fibers were impregnated in a 1% silane coupling agent ethanol solution and 0.2 wt% titanate coupling agent was added. The impregnation process was accompanied by ultrasonic vibration at 20 kHz. After impregnation for 0.5 h, the carbon fibers were pre-dried in a vacuum environment at 60℃ for 1 h, and then heated to 80℃ for drying for 2 h. In addition, 3 parts by weight of polyimide microspheres and 1 part by weight of nano-silica were placed in a high-speed mixer for dry premixing to obtain an inorganic-organic particle premix.

[0023] S2. By weight, take 100 parts of PEEK resin and put it into a high-speed mixer. While stirring, add 11 parts of pretreated short-cut carbon fiber, 4 parts of inorganic-organic particle premix, 2 parts of composite lubricant of polytetrafluoroethylene and molybdenum disulfide mixture and 0.5 parts of antioxidant 1010 in sequence. After mixing evenly, the premix is ​​obtained.

[0024] S3. The premixed material is fed into the twin-screw extruder through the main feed port. The twin screw adopts a variable pitch combination structure in the melting section, where the pitch gradually changes from 40mm to 25mm. At the same time, nitrogen gas is introduced into the airflow buffer chamber in the third zone (middle and rear of the melting section) through the side feeder for protection. Four parts of pretreated short-cut carbon fiber are added (the amount added is 20% of the total amount). The temperature of each section of the twin-screw extruder is controlled as follows: Zone 1 320℃, Zone 2 350℃, Zone 3 360℃, Zone 4 360℃, and Die head 360℃. The screw speed is 200rpm. The material is melt-extruded, water-cooled, and pelletized to obtain PEEK composite material particles.

[0025] S4. Dry the composite material particles at 150°C for 4 hours, and then use injection molding to obtain standard test strips.

[0026] Example 2 The specific steps involved in preparing PEEK composite materials are as follows: S1. Short carbon fibers with a length of 3 mm were placed in a heat treatment furnace and subjected to high-temperature oxidation treatment using a gradient heating mode. First, the temperature was increased to 300℃ at a rate of 5℃ / min and held for 30 min, then increased to 480℃ at a rate of 3℃ / min and held for 1.5 h. The oxidation atmosphere was air containing 6 vol% ozone. Subsequently, the carbon fibers were impregnated in a 2% silane coupling agent ethanol solution and 0.35 wt% titanate coupling agent was added. The impregnation process was accompanied by ultrasonic vibration at 25 kHz and 125 W. After impregnation for 0.75 h, the carbon fibers were pre-dried in a vacuum environment at 60℃ for 1 h, and then heated to 90℃ for drying for 2.5 h. At the same time, 5 parts by weight of polyimide microspheres and 3 parts by weight of nano-silica were placed in a high-speed mixer for dry premixing to obtain an inorganic-organic particle premix.

[0027] S2. By weight, take 100 parts of PEEK resin and put it into a high-speed mixer. While stirring, add 17 parts of pretreated short-cut carbon fiber, 8 parts of inorganic-organic particle premix, 4 parts of composite lubricant of polytetrafluoroethylene and molybdenum disulfide mixture and 1.0 part of antioxidant 1010 in sequence. After mixing evenly, the premix is ​​obtained.

[0028] S3. The premixed material is fed into the twin-screw extruder from the main feed port. The twin screw adopts a variable pitch combination structure in the melting section, where the pitch gradually changes from 40mm to 25mm. At the same time, argon gas is introduced into the airflow buffer chamber in the third zone (middle and rear of the melting section) through the side feeder for protection, and 5 parts of pretreated short-cut carbon fiber are added (the amount added is 25% of the total amount). The temperature of each section of the twin-screw extruder is controlled as follows: Zone 1 330℃, Zone 2 360℃, Zone 3 370℃, Zone 4 370℃, and Die head 370℃, and the screw speed is 300rpm. The material is melt-extruded, water-cooled, and pelletized to obtain PEEK composite material particles.

[0029] S4. Dry the composite material particles at 150°C for 5 hours, and then use a molding process to obtain standard test strips.

[0030] Example 3 The specific steps involved in preparing PEEK composite materials are as follows: S1. Short carbon fibers with a length of 3 mm were placed in a heat treatment furnace and subjected to high-temperature oxidation treatment using a gradient heating mode. First, the temperature was increased to 300℃ at a rate of 5℃ / min and held for 30 min, then increased to 500℃ at a rate of 3℃ / min and held for 2 h. The oxidation atmosphere was air containing 8 vol% ozone. Subsequently, the carbon fibers were impregnated in a 3% silane coupling agent ethanol solution and 0.5 wt% titanate coupling agent was added. The impregnation process was accompanied by ultrasonic vibration at 30 kHz and 150 W. After impregnation for 1 h, the carbon fibers were pre-dried in a vacuum environment at 60℃ for 1 h, and then heated to 100℃ for drying for 3 h. At the same time, 8 parts by weight of polyimide microspheres and 5 parts by weight of nano-silica were placed in a high-speed mixer for dry premixing to obtain an inorganic-organic particle premix.

[0031] S2. By weight, take 100 parts of PEEK resin and put it into a high-speed mixer. While stirring, add 24 parts of pretreated short-cut carbon fiber, 13 parts of inorganic-organic particle premix, 6 parts of composite lubricant of polytetrafluoroethylene and molybdenum disulfide mixture and 1.5 parts of antioxidant 1010 in sequence. After mixing evenly, the premix is ​​obtained.

[0032] S3. The premixed material is fed into the twin-screw extruder from the main feed port. The twin screw adopts a variable pitch combination structure in the melting section, where the pitch gradually changes from 40mm to 25mm. At the same time, argon gas is introduced into the airflow buffer chamber in the third zone (middle and rear of the melting section) through the side feeder for protection, and 6 parts of pretreated short-cut carbon fiber are added (the amount added is 30% of the total amount). The temperature of each section of the twin-screw extruder is controlled as follows: Zone 1 340℃, Zone 2 370℃, Zone 3 380℃, Zone 4 380℃, and Die head 380℃, and the screw speed is 400rpm. The material is melt-extruded, water-cooled, and pelletized to obtain PEEK composite material particles.

[0033] S4. Dry the composite material particles at 150°C for 6 hours, and then use injection molding to obtain standard test strips.

[0034] Comparative Example 1 The difference between this comparative example and Example 1 is that the sample was prepared using pure PEEK resin. The specific steps are as follows: PEEK resin (450g) was dried at 150℃ for 4 hours and then the standard test strip was prepared by injection molding. No reinforcing fillers or additives were added during the preparation process.

[0035] Comparative Example 2 The difference between this comparative example and Example 1 is that the carbon fiber pretreatment and side feeding processes are omitted. The specific steps are as follows: S1. Short-cut carbon fibers were not subjected to high-temperature oxidation and coupling agent impregnation treatment. Instead, 3 parts by weight of polyimide microspheres and 1 part by weight of nano-silica were directly dry-mixed to obtain an inorganic-organic particle premix.

[0036] S2. By weight, take 100 parts of PEEK resin, add 15 parts of untreated short-cut carbon fiber, 4 parts of inorganic-organic particle premix, 2 parts of composite lubricant and 0.5 parts of antioxidant 1010 in sequence, and mix evenly to obtain the premix.

[0037] S3. All the premixed material is fed into the twin-screw extruder from the main feed port. No carbon fiber is added by side feeding. The extrusion temperature and speed are the same as in Example 1. The composite material particles are obtained by melt extrusion, water cooling and pelletizing.

[0038] S4. After drying the granules at 150℃ for 4 hours, they are injection molded into standard test strips.

[0039] Performance testing The performance of the standard test strips prepared in Examples 1-3 and Comparative Examples 1 and 2 was tested. The test standards and results are shown in the table below: Test results show that the PEEK composite materials prepared in Examples 1-3 of this invention maintain lightweight properties (density of only 1.57-1.59 g / cm³). 3 Simultaneously, the tensile strength and flexural modulus of the modified carbon fiber resin far exceed those of pure PEEK resin, and it also shows a significant improvement compared to conventional carbon fiber reinforced PEEK. The notched impact strength is over 40% higher than Comparative Example 2, while the coefficient of friction and wear rate are reduced to lower levels. Example 3 exhibits the best overall performance. This trend reflects that the carbon fiber pretreatment process strengthens the interfacial bonding between the filler and the matrix, the lateral feeding process preserves the aspect ratio of the carbon fiber, and the multi-scale reinforcement network achieves a balance between strength and toughness, providing a solid mechanical performance basis for its adaptation to the high-load, high-wear-resistance working conditions of robot joints.

[0040] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a PEEK composite material, characterized in that, Includes the following steps: S1. Short-cut carbon fibers are oxidized at high temperature, then impregnated in an ethanol solution containing silane coupling agent, and dried for later use; polyimide microspheres and nano-silica are placed in a high-speed mixer for dry premixing to obtain an inorganic-organic particle premix. S2. By weight, take 100 parts of PEEK resin and put it into a high-speed mixer. While stirring, add 11 to 24 parts of pretreated short-cut carbon fiber, 4 to 13 parts of the inorganic-organic particle premix, 2 to 6 parts of composite lubricant and 0.5 to 1.5 parts of antioxidant in sequence. Mix evenly to obtain the premix. S3. The premixed material is fed into the twin-screw extruder through the main feed port, and 4-6 parts of pretreated short-cut carbon fibers are added to the rear of the extruder's melting section via a side feeder; the temperature of each section of the twin-screw extruder is controlled as follows: Zone 1: 320-340℃, Zone 2: 350-370℃, Zone 3: 360-380℃, Zone 4: 360-380℃, and the die head: 360-380℃; the material is melt-extruded, water-cooled, and pelletized to obtain PEEK composite material particles; S4. The composite material particles are dried at 150°C, and then PEEK composite material products are obtained by injection molding or compression molding.

2. The method for preparing PEEK composite material according to claim 1, characterized in that, The inorganic-organic particle premix consists of 3-8 parts by weight of polyimide microspheres and 1-5 parts by weight of nano-silica; the composite lubricant is a mixture of polytetrafluoroethylene and molybdenum disulfide.

3. The method for preparing PEEK composite material according to claim 1, characterized in that, In step S3, the screw speed of the twin-screw extruder is 200-400 rpm; in step S4, the drying time of the composite material particles is 4-6 hours.

4. The method for preparing PEEK composite material according to claim 1, characterized in that, In step S1, the high-temperature oxidation treatment temperature of the short-cut carbon fiber is 400-500℃, and the treatment time is 1-2h; the mass concentration of the silane coupling agent in the ethanol solution is 1-3%, the impregnation time is 0.5-1h, the drying temperature is 80-100℃, and the drying time is 2-3h.

5. The method for preparing PEEK composite material according to claim 4, characterized in that, In step S1, the high-temperature oxidation treatment adopts a gradient heating mode. First, the temperature is raised to 300℃ at a rate of 5℃ / min and held for 30min. Then, the temperature is raised to 450-500℃ at a rate of 3℃ / min and held for 1-2h. The oxidation treatment atmosphere is an air atmosphere containing 5-8 vol% ozone.

6. The method for preparing PEEK composite material according to claim 4, characterized in that, The ethanol solution containing silane coupling agent also contains 0.2-0.5 wt% titanate coupling agent, and the impregnation process is accompanied by ultrasonic vibration. After impregnation, it is first pre-dried in a vacuum environment and then heated to dry.

7. The method for preparing PEEK composite material according to claim 6, characterized in that, The ultrasonic vibration frequency is 20-30kHz, the power is 100-150W, the pre-drying time in a vacuum environment at 60℃ is 1h, and the subsequent heating and drying temperature is 80-100℃, and the drying time is 2-3h.

8. The method for preparing PEEK composite material according to claim 1, characterized in that, In step S3, the chopped carbon fibers added by the side feeder account for 20-30% of the total amount of chopped carbon fibers; the middle and rear part of the melting section of the twin-screw extruder is the third zone; the length of the chopped carbon fibers is 3mm; and the antioxidant is antioxidant 1010.

9. The method for preparing PEEK composite material according to claim 1, characterized in that, In step S3, the screw of the twin-screw extruder adopts a variable pitch combination structure, with the pitch of the melt section gradually changing from 40mm to 25mm, and an airflow buffer chamber is set at the side feed port. Inert gas is introduced into the buffer chamber to protect the added short-cut carbon fibers.

10. Applications of PEEK composite materials, characterized in that, The PEEK composite material products prepared by any of the PEEK composite material preparation methods described in claims 1-9 are applied to the joints, skeletons, and transmission system components of robots.

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