Polyamide compound as well as preparation method and application thereof

Abstract

The invention provides a polyamide compound as well as a preparation method and application thereof, and relates to the technical field of high polymer materials. The polyamide compound comprises the following components in parts by weight: 60-75 parts of a polyamide matrix which comprises PAMXD6, PA10T, PA12I and PA66; the reinforcing auxiliary material comprises basalt fibers and hollow glass beads subjected to hydrophobic pretreatment, and the ratio of the basalt fibers to the hollow glass beads is (3-5): 1; 1-5 parts of a hydrophobic modification aid; the nucleating agent is formed by compounding sodium diphenyl phosphate and 1, 3: 2, 4-dibenzylidene sorbitol according to the mass ratio of (2 to 4): 1; 0.4 to 0.8 part of an antioxidant; 0.1 to 0.5 part of a lubricant; the polyamide compound provided by the invention has the comprehensive advantages of high strength, light weight and easiness in processing, is far better than a traditional polyamide material, and can meet the requirements of unmanned aerial vehicle paddles and other scenes with strict performance requirements.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, and in particular to a polyamide composite, its preparation method and application. Background Technology

[0002] Polyamide (PA, commonly known as nylon), as a class of high-performance engineering plastics, has been widely used in high-end fields such as electronics, automotive manufacturing, aerospace, and drones due to its good mechanical strength, chemical corrosion resistance, and processing flowability. Among these, drone propellers, as the core power components of drones, place stringent demands on the comprehensive performance of materials—they must not only possess high strength (to withstand centrifugal force and airflow impact during high-speed rotation) and lightweight (to reduce motor load and improve endurance), but also excellent resistance to damp heat (to resist corrosion in humid outdoor environments), aging resistance (to adapt to long-term outdoor use), and molding precision (to ensure stable aerodynamic performance). However, traditional polyamide materials and existing modification technologies are unable to simultaneously meet these requirements, gradually becoming a key bottleneck restricting the performance upgrade of drone propellers.

[0003] First, while traditional single polyamides are low-cost and easy to process, they have significant performance limitations. For example, PA66 has high mechanical strength but insufficient high-temperature resistance (its heat distortion temperature is usually below 220℃), making it prone to thermal softening under the localized high temperatures generated by the high-speed rotation of drone propellers, leading to a decline in mechanical properties. Existing technologies have attempted to improve performance by blending two polyamides, but lack synergistic design for multi-component polyamides (such as high-temperature resistant, water-resistant, and easy-to-process types), often only improving a single property and failing to achieve a comprehensive balance of "high-temperature resistance, high strength, water resistance, and easy processing." Second, traditional reinforcing materials are mainly glass fiber and carbon fiber: while glass fiber is low-cost, its high density (approximately 2.5 g / cm³) makes it difficult to achieve the lightweight target required for drone propellers. Furthermore, its strong hydrophilicity results in weak interfacial bonding with the polyamide matrix, making it susceptible to interfacial delamination due to moisture intrusion, affecting long-term mechanical stability. While carbon fiber can achieve a synergistic effect of "reinforcement and weight reduction," its high cost makes it unsuitable. Furthermore, the preparation of existing polyamide composites mostly adopts the "one-time mixing-melt extrusion" mode. For single polyamides, this method can be well adapted, but for multi-component polyamides, how to reasonably control the preparation parameters between multiple components is one of the current difficulties in multi-component polyamides. Summary of the Invention

[0004] The purpose of this application is to provide a polyamide composite, its preparation method, and its application, in order to solve at least one of the above-mentioned technical problems.

[0005] To achieve the above-mentioned technical objectives, this application provides a polyamide composite, its preparation method, and its application. In a first aspect, this application provides a polyamide composite comprising the following components: Polyamide matrix, 60-75 parts, including PAMXD6, PA10T, PA12I and PA66; Reinforcing additives, 30-40 parts, including basalt fiber and hydrophobically pretreated hollow glass microspheres, wherein the ratio of basalt fiber to hollow glass microspheres is (3-5):1; Hydrophobic modifying agent, 1-5 parts; Nucleating agent, 0.5-2 parts, is a compound of sodium diphenyl phosphate and 1,3:2,4-dibenzyl sorbitol in a mass ratio of (2-4):1; Antioxidant, 0.4-0.8 parts; Lubricant, 0.1-0.5 parts.

[0006] Preferably, the weight ratio of PAMXD6, PA10T, PA12I and PA66 is (10-15):(6-8):(1-2):(6-8).

[0007] Preferably, the diameter of the basalt fiber is 8-12 μm; and the particle size of the hollow glass microspheres is 30-50 μm.

[0008] Preferably, the basalt fiber is surface-treated with γ-aminopropyltriethoxysilane, and the silane grafting rate on the fiber surface after treatment is 3-5%. The hollow glass microspheres have a wall thickness of 15-25 μm and a bulk density of 0.4-0.6 g / cm³. 3 Furthermore, the surface is pretreated with methyltrimethoxysilane for hydrophobicity.

[0009] Preferably, the hydrophobic pretreatment of the hollow glass microspheres involves soaking them in 5-8 wt% methyltrimethoxysilane for 30-60 minutes, followed by drying at 110-120°C.

[0010] Preferably, the hydrophobic modifying agent is silane-modified nano-silica; the silane-modified nano-silica is prepared by grafting nano-silica with γ-methacryloxypropyltrimethoxysilane, wherein the particle size of the nano-silica is 10-50 nm, and the grafting rate of the γ-methacryloxypropyltrimethoxysilane is 5-10%.

[0011] Secondly, this application provides a method for preparing polyamide composites as described above, the method comprising the following steps: S1. Premixing: Add the polyamide matrix, hydrophobic modifier, and nucleating agent to a high-speed mixer and premix for 5-8 minutes at 80-100℃ and a stirring speed of 800-1000 rpm. At the same time, introduce ultrasonic-assisted dispersion with a power of 300-500W to obtain the premixed material. S2, Stepwise Melt Blending: The premix obtained in step S1 is added from the main feed port of the twin-screw extruder and melted and plasticized at a temperature of 250-260℃ in zone one and 280-290℃ in zone two; then basalt fibers are added from the first side feed port of the twin-screw extruder and mixed at a temperature of 300-310℃ in zone three; then hollow glass microspheres are added from the second side feed port and blended further at a temperature of 310-320℃ in zone four and 300-310℃ in zone five; the first side corresponds to the screw anti-meshing section, and the second side corresponds to the screw homogenization section; S3. Extrusion granulation: The blend obtained in step S2 is passed through the transition section of a twin-screw extruder, where the temperature of the transition section is 305-315℃, and then conveyed to the die head for extrusion, where the temperature of the die head is 300-310℃. During the extrusion process, the screw speed is maintained at 300-400 rpm and the vacuum degree is -0.09- (-0.08) MPa. Subsequently, the mixture is water-cooled, stretched, and granulated to obtain the polyamide composite.

[0012] Preferably, in step S2, the length-to-diameter ratio of the twin-screw extruder is (40-48):1.

[0013] Thirdly, this application provides an application of a polyamide composite in the preparation of drone propeller blades, wherein the polyamide composite is prepared by the preparation method described above; The method of application includes the following steps: S4. The masterbatch of the polyamide composite is vacuum dried at 110-120℃ for 4-6 hours and then added to an injection molding machine. The injection mold adopts a gradient temperature control mold, wherein the mold temperature at the root of the blade is 130-140℃, the mold temperature at the edge of the blade is 90-100℃, the injection pressure is 80-100MPa, the holding pressure is 60-70MPa, the holding time is 15-20s, and the cooling time is 30-40s to form the initial product of the drone blade. S5. Place the initial blade sample in a constant temperature oven at 120-140℃ for low-temperature annealing for 2-3 hours, and then immediately transfer it to an ultrasonic cleaner. Use an ultrasonic cleaner with a frequency of 40-50kHz and a power of 200-300W. Ultrasonically treat it in anhydrous ethanol medium for 15-20 minutes, and finally dry it at 80-90℃ for 1-2 hours to obtain the finished UAV blade.

[0014] Compared with the prior art, the technical solution provided in this application has the following advantages: The polyamide composite material prepared in this application, through component synergistic design and process optimization, significantly overcomes the technical bottleneck of simultaneously achieving "high strength, lightweight, and easy processing." Specifically: (1) This application uses a four-component compound of PAMXD6, PA10T, PA12I and PA66 (optimal ratio 10-15:6-8:1-2:6-8) to form a functionally complementary system: PAMXD6 and PA10T synergistically improve thermal stability (to cope with local high temperature during high speed rotation of the blade), PA66 ensures processing fluidity and basic mechanical strength, and PA12I significantly reduces water absorption (water absorption rate as low as 0.17% at 23℃ / 24h, far better than Comparative Example 3 (0.36%) without PA12I), ultimately achieving a balance of "temperature resistance-strength-water resistance-processability" in the matrix, providing a stable foundation for subsequent reinforcement.

[0015] (2) In this application, basalt fiber and hydrophobically pretreated hollow glass microspheres are compounded in a ratio of (3-5):1: Basalt fiber (diameter 8-12μm, grafting rate 3-5% after silane treatment) has high specific strength and excellent corrosion resistance, which can significantly improve the mechanical properties of the composite (the bending strength of Example 2 is 274MPa and the tensile strength is 250MPa, which is better than the untreated fiber in Comparative Example 5 (bending strength 236MPa)); the hollow glass microspheres have low density (which achieves both lightweighting and reduces interface defects through hydrophobic modification (the water absorption rate of the untreated Comparative Example 7 increased to 0.29%)). The ratio of the two is designed to avoid "excessive microspheres leading to a decrease in strength and excessive fiber leading to an increase in density", thus achieving a "strengthening-weight reduction" synergy.

[0016] (3) In this application, the nucleating agent is sodium diphenyl phosphate and 1,3:2,4-dibenzyl sorbitol in a ratio of 2-4:1 to refine the polyamide grains and improve the uniformity of crystallization.

[0017] (4) This application adopts the “premix + step-by-step melt blending” process. The premixing stage (80-100℃, 800-1000rpm + 300-500W ultrasound) achieves micro-dispersion of nano-auxiliaries. The step-by-step blending is achieved by using different feeding ports of the twin screw (premixed material is added at the main feeding port, fibers are added at the counter-meshing section, and microspheres are added at the homogenization section) and temperature control (250-260℃ in zone 1 to 300-310℃ in zone 5). This ensures uniform dispersion of fibers and avoids high shear damage to the microsphere structure in the homogenization section. The combination of (40-48):1 aspect ratio (the comparative example 9 with insufficient aspect ratio has uneven mixing and the bending strength drops to 249MPa) ensures uniform dispersion of components, no bubble defects, and stable particle quality of the final composite.

[0018] (5) When preparing UAV propeller blades, gradient temperature control molds are used (130-140℃ at the root to promote crystallization and ensure strength, and 90-100℃ at the edge to quickly set shape and ensure aerodynamic accuracy) to solve the problem of dimensional stability; low temperature annealing at 120-140℃ (2-3h) eliminates internal stress, and ultrasonic cleaning with anhydrous ethanol (40-50kHz) removes surface impurities. The final product has excellent mechanical consistency and strong resistance to damp heat, which can meet the core requirements of UAV propeller blades: "high-speed rotation to resist centrifugal force, outdoor resistance to rain erosion, and lightweight to improve endurance". Detailed Implementation

[0019] To make the objectives, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention are described in detail below with reference to examples. Several embodiments of the present invention are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be more thorough and complete: This application provides a polyamide composite, comprising the following components by weight: Polyamide matrix, 60-75 parts, including PAMXD6, PA10T, PA12I and PA66; Reinforcing additives, 30-40 parts, including basalt fiber and hydrophobically pretreated hollow glass microspheres, wherein the ratio of basalt fiber to hollow glass microspheres is (3-5):1; Hydrophobic modifying agent, 1-5 parts; Nucleating agent, 0.5-2 parts, is a compound of sodium diphenyl phosphate and 1,3:2,4-dibenzyl sorbitol in a mass ratio of (2-4):1; Antioxidant, 0.4-0.8 parts; Lubricant, 0.1-0.5 parts; In this design, PAMXD6 and PA10T, as high-temperature resistant polyamides, impart excellent thermal stability to the composite, enabling it to withstand high-temperature environments during processing and outdoor use. PA66 possesses high strength and good processing flowability, balancing mechanical properties with ease of molding. PA12I reduces overall water absorption and improves the composite's water resistance. This blend of four matrices overcomes the limitations of single polyamides, forming a balanced matrix system that combines high temperature resistance, high strength, water resistance, and ease of processing. The reinforcing additives consist of a combination of basalt fiber and hydrophobically pretreated hollow glass microspheres (3-5:1). Basalt fiber, with its high specific strength and corrosion resistance, significantly improves the tensile strength and flexural modulus of the composite, while the hollow structure of the hollow glass microspheres effectively reduces density (achieving lightweighting). Furthermore, the hydrophobic pretreatment reduces interfacial defects between the microspheres and the matrix. The optimized ratio avoids both strength reduction due to excessive microspheres and density increase due to excessive fiber, achieving a synergistic effect of reinforcement and weight reduction. Hydrophobic modifiers (1-5 parts) can fill the tiny gaps between the matrix and reinforcing additives, further improving overall hydrophobicity and resisting corrosion in humid outdoor environments; specific compound nucleating agents (sodium diphenyl phosphate and 1,3:2,4-dibenzyl sorbitol 2-4:1) can refine polyamide grains, improve crystallization uniformity, solve the problem of slow crystallization speed or coarse grains of single nucleating agents, make the mechanical properties of the composite more stable, and avoid the risk of cracking caused by local stress concentration; antioxidants (0.4-0.8 parts) can inhibit oxidative degradation during processing and use, and extend service life; lubricants (0.1-0.5 parts) improve the fluidity of the molten composite, avoid the phenomenon of sticking to the wall during extrusion granulation, and improve production stability. The overall weight ratio (60-75 parts polyamide matrix and 30-40 parts reinforcing additives) ensures the continuity of the matrix and the effective dispersion of the reinforcing additives. This not only guarantees the structural integrity of the composite but also fully utilizes the functions of each component. Ultimately, the composite possesses the comprehensive advantages of high strength, lightweight, and easy processing, far exceeding traditional polyamide materials. It can meet the demanding performance requirements of scenarios such as drone propellers.

[0020] In some implementations, the weight ratio of PAMXD6, PA10T, PA12I and PA66 is (10-15):(6-8):(1-2):(6-8). In this scheme, by limiting the specific weight ratio of the four polyamide matrices (10-15:6-8:1-2:6-8), the synergistic effect of the matrix system is further optimized, making the composite performance more precisely suited to the needs of high-end applications. Among them, PAMXD6 has the highest proportion (10-15 parts). As the core component of the matrix, the aromatic ring in its molecular structure endows it with excellent mechanical strength and thermal stability. It can maintain the stability of the molecular chain under the conditions of twin-screw extrusion (300-320℃) and high-speed rotation of UAV propellers, avoiding performance degradation caused by high temperature or stress, and becoming the "main support" for the strength and temperature resistance of the composite. PA10T (6-8 parts) is an auxiliary high-temperature resistant component. Its aliphatic and aromatic structure can not only synergistically improve the overall heat distortion temperature with PAMXD6, but also enhance the chemical corrosion resistance of the composite, resisting the erosion of trace chemicals (such as rainwater residue) in the outdoor environment, and making up for the lack of chemical resistance of PAMXD6. Although PA12I (1-2 parts) has the lowest proportion, it plays a crucial role. Its low water absorption significantly reduces the overall water absorption rate of the composite, solving the problem of decreased mechanical properties caused by the easy water absorption of traditional polyamides. Moreover, adding a small amount can avoid the overall cost surge caused by the high cost of PA12I, achieving a balance between "performance improvement and cost control". PA66 (6-8 parts), with its good processing fluidity and cost-effectiveness, improves the melt flowability of the mixed matrix, allowing the matrix to more fully encapsulate basalt fibers and hollow glass microspheres during subsequent twin-screw extrusion, reducing interfacial voids. At the same time, its high strength properties can help PAMXD6 improve the overall mechanical properties, avoiding the increased processing difficulty caused by the addition of other high-temperature resistant components. This proportional design enables the four matrices to form a "functionally complementary and synergistic" system. Compared to other proportions (where an excessively high proportion of PAMXD6 leads to processing difficulties, and insufficient PA12I leads to increased water absorption), it can more accurately match the performance requirements of reinforcing additives, ensuring that the composite achieves the optimal balance in terms of strength, temperature resistance, water resistance, processability, and cost. This lays a more stable matrix foundation for subsequent integration with reinforcing additives and auxiliaries, resulting in a final product with better dimensional stability and mechanical consistency. It is especially suitable for components such as UAV propellers, which have extremely high requirements for performance uniformity.

[0021] In some embodiments, the basalt fibers have a diameter of 8-12 μm; the hollow glass microspheres have a particle size of 30-50 μm. In this design, a diameter of 8-12 μm is crucial for achieving efficient reinforcement of basalt fibers. If the diameter is too small, the fiber's specific surface area is too large, making it prone to agglomeration due to excessive surface energy. This results in uneven dispersion within the molten matrix, leading to localized stress concentration and ultimately reducing the composite's strength. Conversely, if the diameter is too large, the contact area between the fiber and the matrix decreases, weakening the interfacial bonding. Under stress, the fiber is easily pulled out of the matrix, failing to effectively transfer stress and significantly reducing the reinforcement effect. A diameter of 8-12 μm ensures that the fiber has sufficient specific surface area to fully bond with the matrix, enhancing interfacial adhesion, while also allowing for uniform dispersion under the shearing action of twin-screw extrusion, preventing agglomeration. This results in a continuous and stable improvement in the composite's tensile strength, flexural strength, and impact toughness, meeting the centrifugal force and airflow impact requirements of high-speed UAV propeller blade rotation. For hollow glass microspheres, a particle size design of 20-50μm is optimally matched with the diameter of basalt fibers: microspheres larger than fibers allow for a "fiber-microsphere filling" spatial structure within the composite, preventing uneven packing caused by mutual encroachment. If the particle size is too small, microspheres easily embed themselves in the fiber gaps, increasing composite density and negating the lightweight advantage; furthermore, small-diameter microspheres have high surface energy, increasing the risk of agglomeration. Conversely, if the particle size is too large, the microspheres' embedding within the matrix deteriorates, making them prone to breakage under stress due to insufficient structural integrity, becoming mechanical defects. A particle size of 20-50μm ensures the stability of the hollow microsphere structure, preventing breakage during extrusion and injection molding, thus maintaining weight reduction, while also complementing the basalt fibers, filling the gaps between fibers and improving composite density. Furthermore, this particle size combination improves the flowability of the molten composite, allowing for sufficient filling of thin-walled areas such as mold edges during injection molding of drone propellers, preventing material shortages or air bubbles, improving molding accuracy, and ensuring the propeller's aerodynamic performance meets standards.

[0022] In some embodiments, the basalt fibers are surface-treated with γ-aminopropyltriethoxysilane, resulting in a silane grafting rate of 3-5% on the fiber surface. The hollow glass microspheres have a wall thickness of 15-25 μm and a bulk density of 0.4-0.6 g / cm³. 3 Furthermore, the surface is pretreated with methyltrimethoxysilane for hydrophobicity.

[0023] In this approach, basalt fibers treated with γ-aminopropyltriethoxysilane with a grafting rate controlled at 3-5% exhibit significantly improved compatibility with the polyamide matrix. The ethoxy groups of the silane molecules react chemically with the hydroxyl groups on the fiber surface to form stable chemical bonds, while the amino groups form hydrogen bonds with the amide bonds of the polyamide, constructing a strong interfacial bonding system of "fiber-silane-matrix". A grafting rate of 3-5% is a critical threshold – below 3%, the fiber surface modification is insufficient, the interfacial bonding strength is only slightly improved, and fiber pull-out is still likely under stress; above 5%, the silane forms an excessively thick coating on the fiber surface, reducing the fiber's inherent strength and potentially causing fiber agglomeration, thus negatively impacting dispersion. This treatment increases the interfacial shear strength between the fiber and matrix by more than 25%, effectively transferring stress and avoiding mechanical property fluctuations caused by interfacial voids. Simultaneously, the modified fibers are more easily dispersed in the molten matrix, reducing defects caused by localized agglomeration. For hollow glass microspheres, a wall thickness of 15-25 μm balances structural strength and lightweight design: If the wall thickness is too low, the microspheres are prone to breakage under the shear force of twin-screw extrusion and the pressure of injection molding, losing their hollow structure, failing to reduce weight, and generating fragmentation defects; if the wall thickness is too high, the microsphere density increases, weakening the lightweight effect, and overly rigid microspheres reduce the toughness of the composite. A wall thickness of 15-25 μm ensures that the microspheres maintain structural integrity during processing, continuously reducing the composite density, while also possessing a certain degree of elasticity to prevent the composite from becoming too brittle. A bulk density of 0.4-0.6 g / cm³ matches the polyamide matrix (approximately 1.1-1.2 g / cm³), preventing microspheres from floating / sinking due to excessive density differences, ensuring uniform dispersion, and preventing differences in mechanical properties caused by localized density unevenness. In addition, the microspheres are pretreated with methyltrimethoxysilane for hydrophobicity, forming a "double hydrophobic" system with hydrophobic modifiers. This effectively resists outdoor rainwater erosion, avoids water-induced interface aging (such as interface peeling caused by hydrolysis), and extends the service life of the composite. It is especially suitable for scenarios where drone propellers are used outdoors for a long time.

[0024] In some embodiments, the hydrophobic pretreatment of the hollow glass microspheres involves soaking them in 5-8 wt% methyltrimethoxysilane for 30-60 min and then drying them at 110-120°C. In this scheme, when the concentration of methyltrimethoxysilane is too low, the silane molecules do not cover the surface of the microspheres sufficiently, the number of hydrophobic groups (methyl groups) is insufficient, and the microspheres are still easy to combine with water molecules, resulting in limited improvement in hydrophobicity. When the concentration is too high, excess silane will form multilayer accumulation on the surface of the microspheres. Unreacted silane cannot be completely removed by subsequent drying. Residual silane is easy to precipitate during twin-screw extrusion, which will not only affect the interfacial bonding between the matrix and the microspheres, but may also cause defects such as spots and pinholes on the surface of the final product (such as drone propellers), reducing appearance and mechanical properties.

[0025] In some embodiments, the hydrophobic modifying agent is silane-modified nano-silica; the silane-modified nano-silica is prepared by grafting nano-silica with γ-methacryloxypropyltrimethoxysilane, wherein the particle size of the nano-silica is 10-50 nm, and the grafting rate of the γ-methacryloxypropyltrimethoxysilane is 5-10%. In this scheme, silane-modified nano-silica is chosen instead of traditional organic hydrophobic additives (such as organic waxes and fluorides), which combines the advantages of nano-effects and interfacial compatibility: the 10-50nm particle size of nano-silica can form an extremely high specific surface area, creating a large number of "nanoscale hydrophobic points" in the matrix, hindering the penetration of water molecules; at the same time, silane modification (γ-methacryloyloxypropyltrimethoxysilane) upgrades the combination of additives and polyamide matrix from "physical mixing" to "chemical / physical dual combination" - acryloyloxy can entangle with polyamide molecular chains, and the silane part can interact with the amide bonds of the matrix, avoiding nanoparticle aggregation, which is impossible for traditional organic additives; in addition, when the particle size is too small, the particle surface energy is extremely high, and even after silane modification, it is still easy to aggregate, and the formed aggregates become defect points; when the particle size is too large, the nano-effect weakens, the interfacial interaction area with the matrix decreases, and the hydrophobic and reinforcing effects decrease simultaneously. When the grafting rate is too low, there are insufficient modified groups, and the nanoparticles are still prone to agglomeration, resulting in limited improvement in hydrophobicity. When the grafting rate is too high, the excessively dense modified groups will generate steric hindrance, hindering the flow of particles in the matrix, affecting the uniformity of dispersion, and may also increase costs. In addition, nano-silica can also assist in reinforcement: its high hardness can improve the surface hardness and wear resistance of the composite, avoiding surface damage to drone propellers caused by slight friction during use. Uniformly dispersed nanoparticles can also improve the flowability of the molten composite, making it easier to fill the fine structure of the mold (such as the propeller connection hole) during injection molding, thus improving molding accuracy.

[0026] In some embodiments, the antioxidant is a mixture of antioxidant 3114 and antioxidant 168; In this solution, antioxidant 3114 (hindered phenol) serves as the primary antioxidant, which can terminate the free radical chain reaction by providing hydrogen atom capture complexes during processing (such as twin-screw extrusion at 300-320℃) and use (outdoor high-temperature exposure), thereby inhibiting oxidative degradation from the source. Antioxidant 168 (phosphite) serves as the secondary antioxidant, which can decompose hydroperoxides (oxidation intermediates) generated during oxidation and convert them into stable compounds. At the same time, it can react with the oxidation products of the primary antioxidant, regenerating the primary antioxidant and extending its service life. The two form a dual protection of "free radical capture - hydroperoxide decomposition", which solves the performance shortcomings of single antioxidants.

[0027] This application also provides a method for preparing any of the above-described polyamide composites, the method comprising the following steps: S1. Premixing: Add the polyamide matrix, hydrophobic modifier, and nucleating agent to a high-speed mixer and premix for 5-8 minutes at 80-100℃ and a stirring speed of 800-1000 rpm, while simultaneously introducing ultrasonic-assisted dispersion with a power of 300-500W to obtain the premixed material. S2, Stepwise Melt Blending: The premix obtained in step S1 is added from the main feed port of the twin-screw extruder and melted and plasticized at a temperature of 250-260℃ in zone one and 280-290℃ in zone two; then basalt fibers are added from the first side feed port of the twin-screw extruder and mixed at a temperature of 300-310℃ in zone three; then hollow glass microspheres are added from the second side feed port and blended further at a temperature of 310-320℃ in zone four and 300-310℃ in zone five; the first side corresponds to the screw anti-meshing section, and the second side corresponds to the screw homogenization section; S3. Extrusion granulation: The blend obtained in step S2 is passed through the transition section of a twin-screw extruder at a temperature of 305-315°C, and then conveyed to the die head for extrusion at a temperature of 300-310°C. During the extrusion process, the screw speed is maintained at 300-400 rpm and the vacuum degree is -0.09-0.08 MPa. Subsequently, the product is water-cooled, stretched, and granulated to obtain the polyamide composite.

[0028] In this scheme, during the premixing stage (80-100℃, 800-1000rpm, 5-8min, 300-500W ultrasound), the temperature of 80-100℃ slightly softens the polyamide matrix, increasing its fluidity and facilitating mixing with hydrophobic modifiers and nucleating agents, while avoiding premature melting or oxidation of the matrix due to high temperature; the stirring rate of 800-1000rpm provides sufficient shear force to initially break up component agglomerates, while the 300-500W ultrasound-assisted dispersion can use high-frequency vibration to break up the micro-agglomerates of nano-scale additives (such as hydrophobic modified nano-silica), achieving dual dispersion of "macro-stirring + micro-ultrasound". Compared with simple stirring, it can effectively improve the dispersion uniformity and lay a good foundation for subsequent melt blending; the 5-8min time ensures sufficient dispersion and avoids matrix degradation caused by excessive stirring.

[0029] It should be noted that the stepwise melt blending method in this scheme achieves good results: the premix is ​​added to the main feed port, and the temperature is gradually increased to melt in Zone 1 (250-260℃) and Zone 2 (280-290℃) to ensure that the matrix is ​​fully plasticized to form a continuous phase; then, basalt fibers are added from the first side feed port (opposite meshing section) in Zone 3 (300-310℃, when the matrix has the best fluidity). The shear force of the opposite meshing section is moderate, which can evenly disperse the fibers into the molten matrix, while avoiding excessive shearing that could cause fiber breakage; finally, hollow glass microspheres are added from the second side feed port (homogenization section) in Zone 4 (310-320℃) and Zone 5 (300-310℃). The low shear force of the homogenization section can protect the hollow structure of the microspheres from cracking, while achieving full mixing of the microspheres with the "matrix-fiber" system. This design solves the contradiction between "fiber dispersion and microsphere protection" - if both are fed at the same time, either the fiber dispersion will be uneven or the microspheres will break.

[0030] It is further important to note that the parameters in the extrusion granulation stage are equally crucial: the temperatures of the transition section (305-315℃) and the die head (300-310℃) must match the melt temperature to ensure stable flowability of the molten composite and avoid uneven extrusion caused by temperature fluctuations; a screw speed of 300-400 rpm provides sufficient conveying force while avoiding excessive shearing due to excessive speed; a high vacuum of -0.09 to -0.08 MPa effectively removes air bubbles (moisture vaporization, residual air) from the molten composite, preventing a decrease in mechanical properties caused by air bubbles; water-cooled strip drawing and pelletizing enable rapid cooling and shaping, preventing uneven crystallization during particle cooling and ensuring consistent particle quality. Through parameter optimization and step-by-step design, the entire process produces polyamide composite particles with uniform composition, no defects, and stable performance, providing high-quality raw materials for subsequent injection molding of drone propellers.

[0031] In some embodiments, the length-to-diameter ratio of the screw in the twin-screw extruder in step S2 is 40-48:1.

[0032] In this scheme, the composite of this application contains a polyamide matrix, basalt fiber, hollow glass microspheres, and various additives. The composition is complex and varies greatly in density and morphology, requiring sufficient residence time and mixing cycles to achieve uniform dispersion. When the aspect ratio is too low, the material residence time in the screw is short, resulting in insufficient mixing and problems such as fiber agglomeration and uneven distribution of microspheres, leading to fluctuations in composite performance. When the aspect ratio is higher than 48:1, the material residence time is too long, which can easily lead to excessive degradation at high temperatures of 300-320℃, causing polyamide molecular chains to break and reducing the tensile strength of the composite, while also increasing equipment energy consumption and production costs. An aspect ratio of (40-48):1 allows for a suitable material residence time, ensuring sufficient mixing of each component while avoiding excessive degradation, thus ensuring stable mechanical properties of the composite.

[0033] This application also provides an application of a polyamide composite in the preparation of drone propeller blades, wherein the polyamide composite is prepared by the above-described preparation method; The application method includes the following steps: S4. Vacuum dry the polyamide composite masterbatch at 110-120℃ for 4-6 hours, and add it to the injection molding machine; the injection mold adopts a gradient temperature control mold, wherein the mold temperature at the blade root is 130-140℃, the mold temperature at the blade edge is 90-100℃, the injection pressure is 80-100MPa, the holding pressure is 60-70MPa, the holding time is 15-20s, and the cooling time is 30-40s to form the initial drone blade; It should be noted that gradient temperature control molds have already been applied in the injection molding field, so there is no difficulty in implementation. This application will not elaborate on its specific mechanism and principle, but it is understood that this will not affect the understanding of the solution as a whole by those skilled in the art.

[0034] S5. Place the initial blade sample in a constant temperature oven at 120-140℃ for low-temperature annealing for 2-3 hours, and then immediately transfer it to an ultrasonic cleaner. Use an ultrasonic cleaner with a frequency of 40-50kHz and a power of 200-300W. Ultrasonically treat it in anhydrous ethanol medium for 15-20 minutes, and finally dry it at 80-90℃ for 1-2 hours to obtain the finished UAV blade.

[0035] In this solution, the masterbatch is vacuum-dried at 110-120℃ for 4-6 hours. It's understandable that polyamide is hygroscopic; if moisture is not removed, it will vaporize during injection molding, forming bubbles and causing porosity in the impeller blades, reducing mechanical strength and aerodynamic performance. Vacuum drying removes moisture more thoroughly than hot air drying, while also avoiding high-temperature oxidation, ensuring stable masterbatch performance. The innovative design of the gradient temperature-controlled mold (130-140℃ at the root, 90-100℃ at the edge) is well-suited to the structural characteristics of the impeller blades. The blade root needs to withstand motor torque, requiring high strength and high crystallinity. The high temperature of 130-140℃ promotes full crystallization of polyamide, improving the tensile strength and flexural modulus at the root. The edge has a thin-walled structure, requiring dimensional accuracy and aerodynamic shape. The low temperature of 90-100℃ allows for rapid cooling and shaping, preventing edge shrinkage and deformation, thus resolving the contradiction of "insufficient crystallization at the root" or "edge deformation" in constant-temperature molds. The design of injection pressure (80-100MPa) and holding pressure parameters (60-70MPa, 15-20s) ensures that the molten composite fully fills the mold cavity, avoiding material shortage. The holding pressure stage compensates for cooling shrinkage, reduces shrinkage cavities and depressions, ensures a smooth blade surface, and improves aerodynamic performance. A cooling time of 30-40s ensures both shaping and production efficiency. Post-treatment processes further enhance blade performance: low-temperature annealing at 120-140℃ for 2-3 hours effectively eliminates internal stress generated during injection molding. Ultrasonic cleaning (40-50kHz, 200-300W) in anhydrous ethanol efficiently removes mold release agent residue, oil, and other impurities from the blade surface. Anhydrous ethanol evaporates quickly and leaves no residue, preventing impurities from affecting the blade's hydrophobicity or subsequent coating treatment. Drying at 80-90℃ quickly removes ethanol and prevents moisture residue. The blades prepared by this solution can meet the core requirements of drones: lightweight design reduces motor load and effectively improves battery life; high strength withstands centrifugal force and airflow impact from high-speed rotation; hydrophobicity resists rainwater erosion; and aging resistance adapts to outdoor environments.

[0036] The following are some specific examples. When %, it refers to a percentage by weight. It should be noted that the following examples do not exhaustively list all possible scenarios, and unless otherwise specified, the materials used in the following examples are commercially available.

[0037] The main raw materials used in this invention are as follows: PAMXD6: Solvay IXEF1022 (USA); PA10T: Swiss EMS XE 4120 BK; PA12I: Wanhua Chemical Co., Ltd., Yantai, Shandong; PA66: DuPont FR50 (USA); Basalt fiber: Haining Anjie Composite Materials Co., Ltd.; Hollow glass microspheres: Zhejiang Haiyue New Materials Co., Ltd.; γ-aminopropyltriethoxysilane: Commercially available; Methyltrimethoxysilane: Commercially available; γ-Methacryloxypropyltrimethoxysilane: Commercially available; Antioxidant 3114: BASF Irganox 3114 FF; Antioxidant 168: BASF Irgafos 168; Nucleating agent: Commercially available; Lubricant: Commercially available.

[0038] In Examples 1 and 1 Comparative, the polyamide composites were prepared according to the following method: S1. Premixing: Add the polyamide matrix, hydrophobic modifier, and nucleating agent to a high-speed mixer and premix for 7 minutes at 90°C and a stirring speed of 900 rpm. At the same time, introduce ultrasonic dispersion with a power of 400W to obtain the premixed material. S2, Stepwise Melt Blending: The premix obtained in step S1 is added from the main feed port of the twin-screw extruder and melted and plasticized at a temperature of 255°C in zone one and 285°C in zone two; then basalt fibers are added from the first side feed port of the twin-screw extruder and mixed at a temperature of 305°C in zone three; then hollow glass microspheres are added from the second side feed port and blended further at a temperature of 315°C in zones four and five; the first side corresponds to the screw anti-meshing section, and the second side corresponds to the screw homogenization section; S3. Extrusion granulation: The blend obtained in step S2 is passed through the transition section of a twin-screw extruder at a temperature of 310°C, and then conveyed to the die head for extrusion at a temperature of 305°C. During the extrusion process, the screw speed is maintained at 350 rpm and the vacuum degree is -0.08 MPa. Subsequently, the mixture is water-cooled, stretched, and granulated to obtain a polyamide composite. In step S2, the length-to-diameter ratio of the twin-screw extruder is 44:1.

[0039] Table 1 Comparative Example 7 This comparative example is basically the same as Example 2, except that: this comparative example does not perform hydrophobic pretreatment on the hollow glass microspheres.

[0040] Comparative Example 8 This comparative example is basically the same as Example 2, except that the antioxidant used in this comparative example is a single antioxidant 3114.

[0041] Comparative Example 9 This comparative example is basically the same as Example 2, except that the length-to-diameter ratio of the screw in this comparative example is 35:1.

[0042] Comparative Example 10 This comparative example is basically the same as Example 2, except that the premixed ultrasonic power in step S1 of this comparative example is 150W.

[0043] Example 6 This embodiment provides an application of a polyamide composite in the preparation of drone propeller blades, wherein the polyamide composite uses the formulation shown in Example 2; the application method includes the following steps: S4. Vacuum dry the polyamide composite masterbatch at 115℃ for 5 hours and add it to the injection molding machine. The injection mold adopts a gradient temperature control mold, wherein the mold temperature at the root of the blade is 135℃, the mold temperature at the edge of the blade is 95℃, the injection pressure is 90MPa, the holding pressure is 65MPa, the holding time is 15-20s, and the cooling time is 30-40s to form the initial product of the drone blade. S5. Place the initial blade sample in a constant temperature oven at 130℃ for low-temperature annealing for 2.5 hours, and then immediately transfer it to an ultrasonic cleaner. Use an ultrasonic cleaner with a frequency of 45kHz and a power of 250W. Ultrasonically treat it in anhydrous ethanol medium for 18 minutes, and finally dry it at 85℃ for 1.5 hours to obtain the finished UAV blade.

[0044] The polyamide materials prepared in each embodiment and comparative example were subjected to performance tests. The test items and methods are as follows, and the results are shown in Table 2: Bending strength: ASTM D790; Flexural modulus: ASTM D790; Notched impact strength: ASTM D256; Tensile strength: ASTM D638; Water absorption rate: ISO 62.

[0045] As can be seen from the above embodiments, the polyurethane composite provided by this application has excellent performance indicators. In Example 2, its water absorption rate is as low as 0.17% at 23°C for 24 hours. At the same time, its flexural strength can reach 274 MPa, flexural modulus can reach 18000 MPa, tensile strength can reach 250 MPa, and notched impact strength can reach 135 J / m.

[0046] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0047] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application shall fall within the scope of the technical solution of this application.

Claims

1. A polyamide compound, characterized by: By weight parts, including the following components: Polyamide matrix, 60-75 parts, including PAMXD6, PA10T, PA12I and PA66; Reinforcing accessories, 30-40 parts, including basalt fiber and hydrophobic pretreated hollow glass beads, the ratio of basalt fiber to hollow glass beads is (3-5):1; Hydrophobic modification aid, 1-5 parts; Nucleating agent, 0.5-2 parts, compounded by sodium diphenyl phosphate and 1,3:2,4-dibenzyl sorbitol in a mass ratio of (2-4):1; Antioxidant, 0.4-0.8 parts; Lubricant, 0.1-0.5 parts.

2. The polyamide compound according to claim 1, characterized in that: The weight ratio of PAMXD6, PA10T, PA12I and PA66 is (10-15):(6-8):(1-2):(6-8).

3. The polyamide compound according to claim 1, characterized in that: The diameter of basalt fiber is 8-12 μm; the particle size of hollow glass beads is 30-50 μm.

4. The polyamide compound according to claim 3, characterized in that: The basalt fiber is treated by γ-aminopropyl triethoxysilane, and the silane grafting rate on the fiber surface after treatment is 3-5%; The hollow glass microsphere has a wall thickness of 15-25 μm, a bulk density of 0.4-0.6 g / cm 3 and a surface pre-treated with methyltrimethoxysilane for hydrophobicity.

5. The polyamide compound according to claim 1, characterized in that: The hydrophobic pretreatment of hollow glass beads is to immerse in 5-8wt% methyltrimethoxysilane for 30-60min, and then dry at 110-120℃.

6. The polyamide compound according to claim 1, characterized in that: The hydrophobic modification aid is silane modified nano silica; the silane modified nano silica is prepared by grafting modification of nano silica with γ-methacryloxypropyltrimethoxysilane, wherein the particle size of nano silica is 10-50nm, and the grafting rate of γ-methacryloxypropyltrimethoxysilane is 5-10%.

7. The polyamide compound according to claim 1, characterized in that: The antioxidant is a mixture of antioxidant 3114 and antioxidant 168.

8. A process for the preparation of the polyamide composite according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: S1, premixing: adding polyamide matrix, hydrophobic modification aid, nucleating agent into a high-speed mixer, premixing at 80-100℃, stirring rate 800-1000rpm for 5-8min, while introducing ultrasonic auxiliary dispersion with power of 300-500W, to obtain premixing material; S2, stepwise melt blending: adding the premixing material obtained in step S1 from the main feeding port of the twin screw extruder, melting and plasticizing at zone 1 temperature 250-260℃ and zone 2 temperature 280-290℃; then adding basalt fiber from the first side feeding port of the twin screw extruder, mixing at zone 3 temperature 300-310℃; then adding hollow glass beads from the second side feeding port, continuing to blend at zone 4 temperature 310-320℃ and zone 5 temperature 300-310℃; the first side corresponds to the counter-rotating meshing section of the screw, and the second side corresponds to the homogenizing section of the screw; S3, extrusion granulation: the blend obtained in step S2 passes through the transition section of the twin screw extruder, the transition section temperature is 305-315℃, then it is conveyed to the die head for extrusion, the die head temperature is 300-310℃, the screw rotation speed is maintained at 300-400rpm and the vacuum degree is -0.09--0.08MPa during the extrusion process, then water cooling, drawing and granulating to obtain polyamide composite.

9. The method of claim 8, wherein: The screw length-diameter ratio of the twin screw extruder in step S2 is (40-48):

1.

10. Use of a polyamide composite for the production of a drone blade, characterized in that: The polyamide composite is prepared by the preparation method of any one of claims 8 or 9; The application method comprises the following steps: S4, vacuum drying the polyamide composite master batch 110-120℃ for 4-6h, and adding into an injection molding machine; a gradient temperature control mold is used for the injection mold, wherein the blade root mold temperature is 130-140℃, the blade edge mold temperature is 90-100℃, the injection pressure is 80-100MPa, the holding pressure is 60-70MPa, the holding time is 15-20s, the cooling time is 30-40s, and the unmanned aerial vehicle blade preliminary product is formed; S5, placing the blade preliminary product in a constant temperature box at 120-140℃ for low temperature annealing for 2-3h, then immediately transferring into an ultrasonic cleaning machine, and performing ultrasonic treatment in anhydrous ethanol medium for 15-20min at an ultrasonic cleaning agent frequency of 40-50kHz and a power of 200-300W, and finally drying at 80-90℃ for 1-2h to obtain the unmanned aerial vehicle blade finished product.

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