Preparation method of chopped carbon fiber reinforced PEEK particles

Abstract

The invention is applied to the technical field of engineering plastic processing, and discloses a preparation method of chopped carbon fiber reinforced PEEK particles, and the preparation method comprises the following steps: S1, refining treatment of PEEK resin; s2, cationizing the surface of the resin; and S3, blending and granulating the carbon fiber / PEEK. According to the preparation method of the short carbon fiber reinforced PEEK particles, PEEK resin powder is subjected to surface treatment by using a cationic surfactant, so that the surface of the PEEK resin powder is positively charged, and the positively charged resin and carbon fiber can form electrostatic adsorption, so that the resin and the carbon fiber are uniformly dispersed in a physical mixing stage, and a uniform solid-solid mixture is formed; in the subsequent resin melt blending process, the uniformity is maintained, the problem of non-uniform weight distribution of the material is effectively solved, and the material uniformity of the chopped carbon fiber reinforced PEEK particles is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of engineering plastic processing, in particular to a method for preparing chopped carbon fiber reinforced PEEK particles. Background Art

[0002] Chopped carbon fiber reinforced PEEK particles are important intermediates of chopped carbon fiber composite materials, which can be processed into rods, plates and various parts downstream. The fiber content (weight) of the currently commercialized chopped carbon fiber reinforced PEEK particles is up to 30%, and there is also serious material inhomogeneity. The main reason is that the carbon fiber is unevenly distributed in the PEEK resin, which is manifested in uneven material weight distribution. The preparation method of chopped carbon fiber reinforced PEEK particles generally adopts the method of melt blending PEEK resin with chopped carbon fiber in a screw extruder. The process method is to add solid resin powder and carbon fiber to the hopper of the screw extruder for feeding. However, in the existing screw extruder melt blending process, Since PEEK resin itself has a high melting point, it requires a higher temperature to melt in the screw extruder, which not only consumes a lot of energy, but also easily causes PEEK resin degradation due to local excessive temperature, affecting product performance. Moreover, traditional processes make it difficult to accurately control the degree of dispersion of carbon fiber in PEEK resin, and the interfacial bonding force between carbon fiber and PEEK resin is weak, which greatly reduces the mechanical properties of the material. At the same time, the existing preparation method is highly dependent on equipment, and the equipment is severely worn, resulting in high production costs. In addition, the conventional preparation process is complicated and the production efficiency is low, which makes it difficult to meet the growing market demand. Therefore, an innovative preparation method for chopped carbon fiber reinforced PEEK particles is urgently needed to solve these problems. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing chopped carbon fiber reinforced PEEK particles to solve the problems of high energy consumption, easy impact on product performance, poor material uniformity, high production cost and low production efficiency in the existing screw extruder melt blending process proposed in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a method for preparing chopped carbon fiber reinforced PEEK particles, the preparation method comprising the following steps: S1. Refining of PEEK resin: A combination of a jaw crusher, a roller mill and a jet mill is used to pulverize and refine the commercial PEEK resin particles. The PEEK resin particles are first crushed to a particle size of 2-5 cm by a jaw crusher, and then further ground to a particle size of 0.1-0.5 cm by a roller mill. Finally, the jet mill is used to refine the particles to a particle diameter of 100 nm-1 um. S2. Resin surface cationization: (1) Prepare the solution: dissolve the cationic surfactant hexadecyltrimethylammonium bromide in water or ethanol to prepare a solution with a concentration of 0.1%-1%; (2) Mixing treatment: add the refined resin powder to the above solution at a resin to solvent ratio of 1:1 to 1:10, stir at a speed of 200-500 rpm and disperse at an ultrasonic frequency of 20-40 kHz for 1-12 hours; (3) Separation and drying: Separate the resin by centrifugation or filtration, and then dry it at 60-80°C for 2-4 hours; S3, carbon fiber / PEEK blending and granulation: a high-speed mixer is used to physically mix the chopped carbon fiber and the PEEK resin with surface cationization treatment. The mixing time of the high-speed mixer is 10-30 minutes, and the mixing speed is 800-1200rpm. The resin is coated on the fiber surface by electrostatic adsorption. Then, the generated fiber resin blend is added to the hopper of a twin-screw extruder for plastic particle granulation. The screw speed of the twin-screw extruder is 150-300rpm, and the extrusion temperature is 380℃-420℃. Preferably, the jaw plate spacing of the jaw crusher in S1 is adjusted to 1-3 cm, and the roller spacing of the roller grinder is adjusted to 0.05-0.2 cm; Preferably, when the air flow mill in S1 is working, the air inlet pressure is controlled at 0.6-0.8 MPa, so as to stably and efficiently refine the resin to the required particle size range of 100 nm-1 um; Preferably, the stirring speed in S2 is 300 rpm and the ultrasonic frequency is 30 kHz; Preferably, the mixing time of the high-speed mixer in S3 is 20 min, the mixing speed is 1000 rpm, the screw speed of the twin-screw extruder is 200 rpm, and the extrusion temperature is 400° C.; Preferably, when the cationic surfactant hexadecyltrimethylammonium bromide solution in S2 is prepared using ethanol as a solvent, the purity of the ethanol must be controlled to be no less than 95% to ensure the stability of the solution performance and the effectiveness of the cationization treatment of the resin surface; Preferably, in the resin separation step in S2, the rotation speed of the centrifuge is controlled at 3000-5000 rpm to achieve rapid and thorough separation of the resin and the solution; Preferably, the chopped carbon fiber in S3 needs to be subjected to plasma treatment for 5-10 minutes before being mixed with the PEEK resin subjected to surface cationization treatment, so as to improve the roughness and activity of the carbon fiber surface and enhance its bonding force with the resin; Preferably, the aspect ratio of the twin-screw extruder in S3 is 30-40 to ensure that the fiber resin blend can be fully plasticized and mixed during the extrusion process, thereby improving the quality uniformity of the particles; Preferably, in said S3, before the fiber resin blend is added into the hopper of the twin-screw extruder, the hopper is preheated at a temperature of 100-120° C. to prevent the blend from condensing and agglomerating in the hopper, thereby ensuring a smooth extrusion process.

[0005] Compared with the prior art, the invention has the following beneficial effects: the method for preparing chopped carbon fiber reinforced PEEK particles: 1. The present invention uses a cationic surfactant to perform surface treatment on PEEK resin powder so that its surface carries a positive charge. Since the carbon fiber contains anionic groups such as carboxyl and carbonyl groups on its surface after anodization during the production process, the positively charged resin and the carbon fiber can form electrostatic adsorption, thereby promoting the uniform dispersion of the two in the physical mixing stage, thereby forming a uniform solid-solid mixture. In the subsequent resin melt blending process, this uniformity is maintained, effectively solving the problem of uneven material weight distribution, greatly improving the material uniformity of chopped carbon fiber reinforced PEEK particles, and providing a more stable quality intermediate for downstream processing into rods, plates and various parts; 2. The existing screw extruder melt blending process consumes a lot of energy to heat up the molten resin due to the high melting point of PEEK resin. However, the present invention first prepares a uniform solid-solid mixture. During the subsequent melt blending, due to the better dispersion of carbon fiber and resin, there is no need to raise the temperature to an excessively high level to achieve the initial mixing of the two as in the traditional process, thereby effectively reducing energy consumption and reducing the energy expenditure part of the production cost; 3. With the help of electrostatic adsorption, the surface cationized PEEK resin is tightly combined with the carbon fiber, which greatly enhances the interfacial bonding force between the two. This makes the short carbon fiber reinforced PEEK particles more excellent in mechanical properties. Compared with the products prepared by traditional processes, the rods, plates and various parts made of it are not easy to debond between the carbon fiber and the PEEK resin when subjected to external forces. They can better coordinate the load bearing, significantly improve the overall mechanical properties of the material, and expand its application range in fields with high requirements for mechanical properties; 4. The traditional process is highly dependent on equipment such as screw extruders, and due to problems such as uneven mixing and excessively high local temperatures, the equipment is severely worn. The present invention optimizes the preparation process. Through effective physical mixing and electrostatic adsorption in the early stage, the material has better fluidity and uniformity when the screw extruder is melt blended, and the pressure and friction of each component inside the equipment are more uniform, thereby significantly reducing the wear of the equipment, extending the service life of the equipment, and reducing the cost of equipment maintenance and replacement; 5. The present invention simplifies the conventional preparation process and reduces the time for complex mixing in the screw extruder through a unique surface treatment and mixing method. From the initial raw material processing to the final production of chopped carbon fiber reinforced PEEK particles, the entire process is more efficient and can produce more products per unit time. DETAILED DESCRIPTION

[0006] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0007] The invention provides a technical solution: a method for preparing chopped carbon fiber reinforced PEEK particles.

[0008] Embodiment 1: preparation process 1. Refinement of PEEK resin: When selecting a combination of a jaw crusher, a roller mill and an air flow mill for refining, the differences in the characteristics of different batches of commercial PEEK resin particle blocks need to be considered. For batches with higher hardness, the feed rate of the jaw crusher can be appropriately reduced from the conventional 50kg / h to 30kg / h to avoid excessive wear of the equipment. At the same time, the jaw plate spacing of the jaw crusher is adjusted to 1cm, and the roller spacing of the roller mill is adjusted to 0.05cm. The PEEK resin particle blocks of this batch are first crushed to a particle size of 2cm by a jaw crusher, and then further ground to a particle size of 0.1cm by a roller mill. Finally, an air flow mill is used to refine them to a particle diameter of 100nm at an intake pressure of 0.6MPa. The effects of parameters such as the feed rate after this adjustment on the final particle performance are recorded. It has been tested that this adjustment increases the tensile strength of the final particles by 15% compared with the unadjusted state.

[0009] 2. Resin surface cationization: Preparation of solution: Dissolve the cationic surfactant hexadecyltrimethylammonium bromide in 95% pure ethanol to prepare a solution with a concentration of 0.1%; Mixing treatment: according to the ratio of resin to solvent of 1:1, add the refined resin powder into the above solution, stir at a speed of 200 rpm and disperse at an ultrasonic frequency of 20 kHz for 1 hour; Separation and drying: Use a centrifuge with the speed controlled at 3000 rpm for separation, and then dry at 60°C for 2 hours; 3. Carbon fiber / PEEK blending and granulation: The chopped carbon fiber was first treated with plasma for 5 minutes, and then physically mixed with the surface cationized PEEK resin using a high-speed mixer. Before mixing, the length distribution of the chopped carbon fiber was detected using microscope imaging technology combined with image analysis software, and the proportion of carbon fibers of different lengths in the blend was counted. After testing, the proportion of carbon fibers with a length of 0.51 mm was 60%, 12 mm was 30%, and 2 mm and above was 10%. The mixing time of the high-speed mixer was 10 minutes, the mixing speed was 800 rpm, and the resin was coated on the fiber surface by electrostatic adsorption. The hopper of the twin-screw extruder was preheated to 100 ° C, and the resulting fiber resin blend was added to the hopper of a twin-screw extruder with an aspect ratio of 30 for plastic particle granulation. The screw speed of the twin-screw extruder was 150 rpm and the extrusion temperature was 380 ° C. The study found that the higher the proportion of carbon fibers with a length of 0.51 mm, the better the bending strength of the particles.

[0010] Detection methods and monitoring data 1. Material uniformity test: Randomly select 10 groups of prepared short carbon fiber reinforced PEEK particles, each group is 10g, use a high-precision electronic balance to measure the weight of each group of particles, and calculate the standard deviation of the weight of each group of particles. The smaller the standard deviation, the better the material uniformity. After measurement, the standard deviation of the weight of these 10 groups of particles is 0.05g, indicating that the material uniformity is good.

[0011] 2. Energy consumption monitoring: The total operation time of the equipment and the power parameters of the equipment were recorded during the preparation process. After calculation, the total energy consumption of this preparation process was 50kW·h. Compared with the energy consumption of preparing the same number of particles by traditional processes (80kW·h), the energy consumption was reduced by 37.5%.

[0012] 3. Mechanical properties test: The prepared particles were injection molded into standard specimens, and tensile strength and flexural strength tests were performed using a universal material testing machine according to standard test methods. The tensile strength test results were 150 MPa, and the flexural strength test results were 200 MPa. The tensile strength of the same specification specimens prepared by the traditional process was 120 MPa, and the flexural strength was 160 MPa. The mechanical properties of the particles prepared in this embodiment are significantly improved.

[0013] 4. Equipment wear monitoring: Before and after the preparation process, use high-precision measuring tools to measure the dimensions of key parts of the twin-screw extruder screw, and evaluate the degree of wear by comparing the dimensional changes. After measurement, the dimensional changes of key parts of the screw are within 0.01mm, and the degree of equipment wear is low.

[0014] 5. Thermal performance test: The melting temperature, crystallization temperature and thermal enthalpy of the chopped carbon fiber reinforced PEEK particles were measured using a differential scanning calorimeter (DSC). The melting temperature was 343°C, the crystallization temperature was 295°C, and the thermal enthalpy was 35 J / g. The thermal stability and crystallization behavior were evaluated to be good. Compared with the particles prepared by the traditional process, the particles prepared in this embodiment have higher thermal stability and better crystallization behavior.

[0015] 6. Rheological properties test: The viscosity of particles at different temperatures and shear rates was measured using a rotational rheometer. -1 When the viscosity is 200Pa·s, the fluidity is good, which provides good data support for subsequent processing technologies such as injection molding and extrusion.

[0016] Comparative experiment Compared with the traditional process: a control group was set up to prepare short carbon fiber reinforced PEEK particles according to the traditional screw extruder melt blending process. Under the same test conditions, the standard deviation of the particle material uniformity prepared by the traditional process was 0.1g, the tensile strength was 120MPa, the bending strength was 160MPa, the energy consumption was 80kW·h, and the dimensional change of the key parts of the twin-screw extruder screw was about 0.05mm. The particles prepared in this embodiment have obvious advantages in terms of material uniformity, mechanical properties, energy consumption, equipment wear, etc.

[0017] Comparison of different surfactants: By changing the type of cationic surfactant, dodecyltrimethylammonium chloride was used instead of hexadecyltrimethylammonium bromide, and other conditions remained unchanged. After testing, the particles prepared with dodecyltrimethylammonium chloride had a tensile strength of 140MPa, a flexural strength of 180MPa, and a material uniformity standard deviation of 0.06g. In comparison, the particles prepared with hexadecyltrimethylammonium bromide had better mechanical properties and better surface treatment effects.

[0018] Embodiment 2: preparation process 1. Refinement of PEEK resin: For a batch of PEEK resin particle blocks with higher toughness, the feed speed of the jaw crusher was increased from the conventional 50kg / h to 60kg / h, and the jaw plate spacing of the jaw crusher was adjusted to 3cm, and the roller spacing of the roller grinder was adjusted to 0.2cm. The batch of PEEK resin particle blocks was initially crushed to a particle size of 5cm by the jaw crusher, and then ground to a particle size of 0.5cm by the roller grinder. Finally, it was refined to a particle diameter of 1μm by a jet mill at an intake pressure of 0.8MPa. The effects of parameters such as the feed speed after this adjustment on the final particle performance were recorded. The impact strength of the final particles was increased by 16% compared with the unadjusted state.

[0019] 2. Resin surface cationization: Preparation of solution: Dissolve the cationic surfactant hexadecyltrimethylammonium bromide in water to prepare a 1% solution.

[0020] Mixing treatment: according to the resin to solvent ratio of 1:10, the refined resin powder is added to the above solution, stirred at a speed of 500 rpm and dispersed at an ultrasonic frequency of 40 kHz for 12 hours.

[0021] Separation and drying: The resin was separated by filtration and then dried at 80°C for 4 h.

[0022] 3. Carbon fiber / PEEK blending and granulation: The chopped carbon fiber was first treated with plasma for 10 minutes. Before mixing, the length distribution of the chopped carbon fiber was also detected using microscope imaging technology combined with image analysis software. After testing, the carbon fiber with a length of 0.51 mm accounted for 50%, 12 mm accounted for 35%, and 2 mm and above accounted for 15%. A high-speed mixer was used to physically mix it with the PEEK resin that had been surface cationized. The mixing time of the high-speed mixer was 30 minutes and the mixing speed was 1200 rpm. The hopper of the twin-screw extruder was preheated to 120°C, and the fiber resin blend was added to the hopper of the twin-screw extruder with an aspect ratio of 40 for plastic particle granulation. The screw speed of the twin-screw extruder was 300 rpm and the extrusion temperature was 420°C. The study found that under this length distribution, the tensile modulus of the particles was improved.

[0023] Detection methods and monitoring data 1. Material uniformity test: Randomly select 10 groups of particles, each group is 10g, measure the weight and calculate the standard deviation. The standard deviation of the weight of the 10 groups of particles is 0.06g, and the material uniformity is good.

[0024] 2. Energy consumption monitoring: The total operating time and power of the equipment were recorded, and the total energy consumption was calculated to be 55 kW h, which is about 31.25% lower than the energy consumption of traditional processes.

[0025] 3. Mechanical properties testing: The particles were injection molded into standard specimens for testing. The tensile strength was 160MPa and the bending strength was 210MPa. The mechanical properties of the specimens prepared by traditional processes were significantly improved.

[0026] 4. Equipment wear monitoring: Comparing the dimensions of key parts of the twin-screw extruder screw before and after preparation, the dimensional change was within 0.02mm, and the degree of equipment wear was low.

[0027] 5. Thermal performance test: Differential scanning calorimeter (DSC) was used to measure parameters such as melting temperature, crystallization temperature and thermal enthalpy of short carbon fiber reinforced PEEK particles. The melting temperature was measured to be 345°C, the crystallization temperature was 297°C, and the thermal enthalpy was 37 J / g. It was evaluated that its thermal stability and crystallization behavior were good. Compared with the particles prepared by traditional processes, its thermal performance is better.

[0028] 6. Rheological properties test: The viscosity of the particles at different temperatures and shear rates was measured using a rotational rheometer. -1 When the viscosity is 180Pa·s, the fluidity is good, which provides good data support for subsequent processing technology.

[0029] Comparative experiment Compared with the traditional process: a control group was set up, and short carbon fiber reinforced PEEK particles were prepared according to the traditional screw extruder melt blending process. Under the same testing conditions, the standard deviation of the uniformity of the particle material prepared by the traditional process was ±1g, the tensile strength was 200MPa, the bending strength was 200MPa, the energy consumption was 80kW·h, and the dimensional change of the key parts of the twin-screw extruder screw was about 0.06mm. The weight accuracy of the particles prepared in this embodiment was ±0.1g, and the tensile strength / modulus was increased by more than 20%.

[0030] Comparison of different surfactants: By changing the type of cationic surfactant, dodecyltrimethylammonium chloride was used instead of hexadecyltrimethylammonium bromide, and other conditions remained unchanged. After testing, the particles prepared with dodecyltrimethylammonium chloride had a tensile strength of 135MPa, a flexural strength of 175MPa, and a material uniformity standard deviation of ±2g. In comparison, the particles prepared with hexadecyltrimethylammonium bromide had better performance.

[0031] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and do not limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims

1. A method for preparing chopped carbon fiber reinforced PEEK particles, characterized in that: The preparation method comprises the following steps: S1. Refining of PEEK resin: A combination of a jaw crusher, a roller mill and a jet mill is used to pulverize and refine the commercial PEEK resin particles. The PEEK resin particles are first crushed to a particle size of 2-5 cm by a jaw crusher, and then further ground to a particle size of 0.1-0.5 cm by a roller mill. Finally, the jet mill is used to refine the particles to a particle diameter of 100 nm-1 um. S2. Resin surface cationization: (1) Prepare the solution: dissolve the cationic surfactant hexadecyltrimethylammonium bromide in water or ethanol to prepare a solution with a concentration of 0.1%-1%; (2) Mixing treatment: add the refined resin powder to the above solution at a resin to solvent ratio of 1:1 to 1:10, stir at a speed of 200-500 rpm and disperse at an ultrasonic frequency of 20-40 kHz for 1-12 hours; (3) Separation and drying: Separate the resin by centrifugation or filtration, and then dry it at 60-80°C for 2-4 hours; S3. Carbon fiber / PEEK blending and granulation: Use a high-speed mixer to physically mix the chopped carbon fiber and the PEEK resin that has been surface cationized. The mixing time of the high-speed mixer is 10-30 minutes, and the mixing speed is 800-1200rpm. The resin is coated on the fiber surface by electrostatic adsorption. Then, the generated fiber resin blend is added to the hopper of a twin-screw extruder for plastic particle granulation. The screw speed of the twin-screw extruder is 150-300rpm, and the extrusion temperature is 380℃-420℃.

2. The method for preparing chopped carbon fiber reinforced PEEK particles according to claim 1, characterized in that: The jaw plate spacing of the jaw crusher in S1 is adjusted to 1-3 cm, and the roller spacing of the roller grinding mill is adjusted to 0.05-0.2 cm.

3. The method for preparing chopped carbon fiber reinforced PEEK particles according to claim 1, characterized in that: When the air flow mill in S1 is working, the air inlet pressure is controlled at 0.6-0.8 MPa to stably and efficiently refine the resin to the required particle size range of 100nm-1um.

4. The method for preparing chopped carbon fiber reinforced PEEK particles according to claim 1, characterized in that: The stirring speed in S2 is 300 rpm and the ultrasonic frequency is 30 kHz.

5. The method for preparing chopped carbon fiber reinforced PEEK particles according to claim 1, characterized in that: The mixing time of the S3 medium-speed mixer is 20 minutes, the mixing speed is 1000 rpm, the screw speed of the twin-screw extruder is 200 rpm, and the extrusion temperature is 400°C.

6. The method for preparing chopped carbon fiber reinforced PEEK particles according to claim 1, characterized in that: When preparing the cationic surfactant hexadecyltrimethylammonium bromide solution in S2, if ethanol is selected as the solvent, the purity of ethanol must be controlled to be no less than 95% to ensure the stability of the solution performance and the effectiveness of the cationization treatment of the resin surface.

7. The method for preparing chopped carbon fiber reinforced PEEK particles according to claim 1, characterized in that: In the resin separation step in S2, the rotation speed of the centrifuge is controlled at 3000-5000 rpm to achieve rapid and thorough separation of the resin and the solution.

8. The method for preparing chopped carbon fiber reinforced PEEK particles according to claim 1, characterized in that: Before being mixed with the PEEK resin subjected to surface cationization treatment, the chopped carbon fibers in S3 need to be subjected to plasma treatment for 5-10 minutes to increase the roughness and activity of the carbon fiber surface and enhance its bonding force with the resin.

9. The method for preparing chopped carbon fiber reinforced PEEK particles according to claim 1, characterized in that: The aspect ratio of the twin-screw extruder in S3 is 30-40 to ensure that the fiber resin blend can be fully plasticized and mixed during the extrusion process, thereby improving the quality uniformity of the particles.

10. The method for preparing chopped carbon fiber reinforced PEEK particles according to claim 1, characterized in that: In S3, before the fiber resin blend is added into the hopper of the twin-screw extruder, the hopper is preheated at a temperature of 100-120° C. to prevent the blend from condensing and agglomerating in the hopper, thereby ensuring a smooth extrusion process.