Long carbon chain modified PA66 composite material and preparation method thereof

Abstract

The application provides a long carbon chain modified PA66 composite material and a preparation method thereof, and belongs to the field of polymer material modification. The long carbon chain molecule containing both quaternary ammonium salt cation groups and siloxane groups is combined with functional nanoparticles, and is co-grafted and modified on the surface of the PA66 molecule pre-grafted with amino acids to prepare a PA66 composite film with super-hydrophobic function and antistatic performance, so as to solve the problems that the existing PA66 material has strong hygroscopicity, weak antistatic capacity and cannot be applied in the high-end electronic and semiconductor fields. The long carbon chain modified PA66 composite material prepared by the application has excellent super-hydrophobicity and antistatic performance, and can maintain stable surface conductivity in different humidity environments, and still maintains stability after physical friction and solution erosion, and the preparation process is simple, suitable for large-scale production and application, and shows high development potential.

Description

Technical Field

[0001] This invention relates to the field of polymer material modification, specifically to a long-carbon-chain modified PA66 composite material and its preparation method. Background Technology

[0002] Nylon 66 (PA66) is an industrial plastic with excellent abrasion resistance, electrical insulation, heat resistance, and high mechanical strength, often making it a preferred material in applications requiring high strength, heat resistance, and abrasion resistance, where plastics can replace steel. However, PA66 also exhibits strong hygroscopicity; the amide groups in its molecular chain readily form hydrogen bonds with water molecules, resulting in high water absorption and poor dimensional stability, severely limiting its application in high-end electronics and semiconductor fields. Furthermore, due to its excellent insulation properties, PA66 is prone to static electricity buildup during use, which can cause electrostatic discharge during precision electronics and semiconductor manufacturing processes, leading to irreversible damage to electronic components.

[0003] To improve the insulation and antistatic properties of PA66, surface treatment is required. CN119800549A discloses a PA66 fiber with flame retardant and superhydrophobic effects. This is achieved by melt-blending a flame retardant with PA66, followed by high-temperature mixing in a reactor and extrusion spinning to obtain flame-retardant PA66 fibers. Subsequently, solutions of nano-silica and polydimethylsiloxane, as well as a water-based epoxy resin solution, are prepared. The PA66 fibers are sequentially immersed in these three solutions, a curing agent is added, and the fibers are stirred, removed, and dried. This process coats the PA66 surface with a superhydrophobic coating. However, this process requires three solutions and multiple sequential coating steps, making the preparation complex and intolerant of errors. Furthermore, while the three-layer hydrophobic coating achieves good hydrophobicity, the interfacial bonding between layers and the adhesion between the coating and the fiber matrix weaken over time, leading to the hydrophobic coating peeling off after long-term use and the material losing its hydrophobicity again. CN120424332A discloses an antibacterial and antistatic nylon material. First, a block copolymer with antibacterial and antistatic properties is synthesized. Then, this copolymer is used as a functional additive and melt-blended with a PA66 matrix to obtain an antibacterial and antistatic nylon composite material. This preparation process is complex, requires stringent reaction conditions, and is difficult to control in terms of production costs and operational complexity, thus making it unsuitable for large-scale production.

[0004] The above studies show that both antistatic and superhydrophobic modifications of PA66 require complex processes. Even with a superhydrophobic coating, PA66 still exhibits electrostatic hazards, and PA66 with added antistatic agents retains strong hygroscopicity, thus affecting its antistatic effect. Furthermore, the melt blending of modified materials with the PA66 matrix often alters the original mechanical properties or durability of PA66. Therefore, the key technology for achieving the application requirements of PA66 composite materials in high-end electronics and semiconductor fields lies in developing a PA66 composite material that possesses both superhydrophobicity and antistatic capabilities without affecting the mechanical properties of the matrix itself, while ensuring a robust and environmentally stable modified layer. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a long-chain modified PA66 composite material and its preparation method. This invention pre-grafts long-chain amino acid molecules onto the surface of PA66, using long carbon chains containing quaternary ammonium salt cationic groups and siloxane groups as a covalently grafted modification layer. Functional nanoparticles are introduced to form a micro / nano structure. The amino acid molecules connect the PA66 matrix, the modification layer, and the functional nanoparticles, giving PA66 superhydrophobicity and stable antistatic properties. Simultaneously, due to the anchoring effect of the amino acid molecules, the functional modification layer is firmly bonded together. This solves the problems of strong hygroscopicity and poor antistatic properties of existing PA66 matrix, and the easy detachment of the modification layer in modified PA66 composite materials, thus meeting the needs of PA66 composite materials for use in high-end electronics and semiconductor fields.

[0006] This invention discloses a long-carbon-chain modified PA66 composite material, the specific technical solution of which is as follows:

[0007] A long-chain modified PA66 composite material exhibiting both superhydrophobicity and antistatic properties comprises the following components: a PA66 matrix, a pre-grafting agent, a bifunctional grafting agent, and functional nanoparticles. The pre-grafting agent is one or more of 8-aminooctanoic acid, 11-aminoundecanoic acid, N-ε-lauroyl-L-lysine, and O-lauroyl-L-serine; the bifunctional grafting agent is a long-chain silane coupling agent with quaternary ammonium salt cationic groups and siloxane groups, including one or more of octadecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride, hexadecyltrimethyl(3-triethoxysilylpropyl)ammonium chloride, and dodecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride; the functional nanoparticles include one or more of hydrophobic fumed silica, hydrophobic precipitated silica, carbon nanotubes, and nano-titanium dioxide.

[0008] This invention also discloses a method for preparing long-chain modified PA66 composite material, the specific technical solution of which is as follows:

[0009] Step 1: The surface of the PA66 film is activated and pretreated to create more active sites for grafting reaction on the surface of PA66 molecules. At the same time, amino acids are dissolved in dimethylformamide, and N-hydroxysuccinimide and carbodiimide are added to the solution in sequence. After stirring, the solution is used as a pre-grafting solution. The surface-activated PA66 matrix is ​​immersed in the pre-grafting solution and heated to react. The sample is then taken out and ultrasonically cleaned in dimethylformamide, anhydrous ethanol, and deionized water, respectively, and dried to obtain the pre-grafted PA66 matrix.

[0010] Step 2: Add the bifunctional grafting agent to the ethanol-water solution and stir to disperse it. Then add the functional nanoparticles and stir to hydrolyze the silane to generate silanol. The nanoparticles are fully dispersed to form a stable grafting solution.

[0011] Step 3: Immerse the surface-activated PA66 matrix in the grafting solution and heat it to cause the silanol generated by the hydrolysis of silane to undergo a dehydration condensation reaction with the carboxyl and amino groups on the PA66 surface to form strong Si-OC or Si-ON covalent bonds. At the same time, the nanoparticles are also fixed on the PA66 surface. Then, the immersed sample is taken out, cleaned with anhydrous ethanol and dried and cured to obtain a long carbon chain modified PA66 composite material with both superhydrophobicity and antistatic ability.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] 1. The material surface is constructed with micro-nano structures and chemically modified with low surface energy to achieve a superhydrophobic effect. The static contact angle of water droplets on the surface of this invention is greater than 150°, almost spherical, and rolls off immediately upon contact. The sliding angle is extremely small. During the rolling process, the water droplets can automatically carry away dust particles and dirt, exhibiting a typical "lotus leaf effect". This superhydrophobic self-cleaning ability makes the material surface difficult to wet and contaminate, greatly reducing the need for cleaning and maintenance, avoiding the accumulation of dust and water stains on the surface of sensitive devices, and helping to maintain the reliable and stable operation of electronic products for a long time.

[0014] 2. A covalent grafting technique was used to simultaneously construct an ionic conductive network and a nanoparticle electronic conductive network on the substrate surface. Quaternary ammonium salt cation groups on the substrate surface can adsorb a thin layer of water molecules from the air, forming an ionic conductive network. The nanoparticles, in contact with each other, constitute physical electronic conduction pathways. This dual-pathway conductivity mechanism allows the material surface to maintain a certain level of conductivity regardless of whether the environment is dry or humid, keeping the surface resistivity within an ideal antistatic range. When the ambient humidity is high, the ionic conductive network on the material surface plays a primary role; when the ambient humidity is low, the physical electronic conduction pathways between the nanoparticles still provide a release route for static electricity. The synergy of these two conductivity mechanisms ensures that the antistatic capability is not dependent on a single condition, giving the material strong adaptability to different environments.

[0015] 3. An amino acid molecule is pre-filled between the covalently bonded modified layer formed by the bifunctional grafting agent and the PA66 matrix. The active groups at both ends of the amino acid molecule chain covalently bond with the modified layer and the matrix, resulting in a stronger bond between the modified layer and the matrix. At the same time, due to the flexibility of the long carbon chain of amino acid molecules, this flexible interface layer can absorb and dissipate energy through slight deformation when the material is subjected to external force, making the modified layer less likely to fall off due to external force, and greatly improving the wear resistance and durability of the modified layer.

[0016] 4. The covalently bonded modified layer formed by the bifunctional grafting agent and the superhydrophobic barrier it constitutes improve the environmental tolerance of the PA66 matrix. The superhydrophobic barrier significantly reduces the contact between moisture or corrosive media and the PA66 matrix, inhibiting hydrolysis and chemical corrosion. At the same time, the siloxane network and nanoparticles in the modified layer have a certain reflective and shielding effect on ultraviolet light, effectively slowing down the aging rate of PA66 in the environment.

[0017] 5. In the modification method proposed in this invention, all modification reactions occur within the nanoscale range of the PA66 surface layer, without affecting the internal structure and content of the matrix. This ensures that PA66's key advantages, such as high strength, high rigidity, wear resistance, and heat resistance, are fully preserved. Simultaneously, the superhydrophobic surface effectively prevents icing, fogging, and bioadhesion, giving the composite material advantages such as waterproofing, dustproofing, icing prevention, fogging prevention, and antistatic properties, thus achieving multifunctional modification of PA66. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the preparation process of the long-carbon-chain modified PA66 composite material of the present invention.

[0019] Figure 2 The water contact angle test results for each experimental group of samples are shown in the diagram.

[0020] Figure 3 The graph shows the water contact angle test results for each experimental group sample after 24 hours. Detailed Implementation

[0021] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0022] This invention proposes a long-chain modified PA66 composite material, which is composed of PA66 matrix, pre-grafting agent, bifunctional grafting agent and functional nanoparticles, and has superhydrophobic and antistatic properties.

[0023] This invention also proposes a method for preparing long-chain modified PA66 composite materials, the specific technical solution of which is as follows:

[0024] 1. Surface activation treatment

[0025] The PA66 matrix was immersed in a dilute NaOH solution for a period of time, then removed and washed with anhydrous ethanol until neutral, and subsequently dried for later use. The slight etching effect of the alkali solution on the PA66 surface also hydrolyzes the amide bonds in the PA66 molecules, exposing more carboxyl and amino groups, thus providing more active sites for subsequent silane reactions.

[0026] 2. Surface pre-grafting treatment

[0027] Amino acids are dissolved in dimethylformamide, followed by the sequential addition of activators N-hydroxysuccinimide and carbodiimide, and the mixture is stirred until homogeneous. The surface-activated PA66 is then immersed in the solution, heated and stirred, and subsequently removed, washed, and dried to obtain the pre-grafted PA66 material. Amino acid molecules contain amino and carboxyl groups. The carboxyl group reacts with the activator to form a highly reactive N-hydroxysuccinimide ester, which readily reacts with the amino groups on the pretreated PA66 surface to form strong amide bonds, allowing the amino acid molecules to tightly bind to the PA66 matrix.

[0028] 3. Co-grafting modification

[0029] Bifunctional grafting agents and functional nanoparticles were sequentially added to an ethanol-water solution, heated and stirred to disperse them, forming a stable grafting solution. Pre-grafted PA66 was then placed in the grafting solution, and the mixture was heated and kept at a constant temperature for reaction. During this process, the siloxane in the bifunctional grafting agent molecule undergoes hydrolysis to generate silanol, which then undergoes a dehydration condensation reaction with the amino group in the amino acid molecule to form strong Si-OC or Si-ON covalent bonds. Simultaneously, the silanol also reacts with the hydroxyl groups on the nanoparticle surface, covalently fixing the nanoparticles to the PA66 surface. Furthermore, condensation reactions also occur between silanols, forming a siloxane network structure on the surface, further enhancing the stability of the functional layer.

[0030] 4. Curing treatment

[0031] The samples, after being immersed in the grafting agent solution, are removed and rinsed with anhydrous ethanol and deionized water to remove unreacted substances adsorbed by physical adsorption. The samples are then dried in an oven, allowing the grafting agent on the sample surface to cross-link and solidify, promoting further condensation of residual silanol and forming a more complete and stable cross-linked network structure in the functional layer, thus improving its wear resistance and durability. After curing, the modified layer firmly adheres to the PA66 surface, making it less susceptible to erosion or peeling by the subsequent usage environment. This creates a composite layer on the PA66 surface with a micro-nano rough structure, low surface energy, and conductive pathways, giving the PA66 material both superhydrophobicity and antistatic properties.

[0032] The following are some specific embodiments of the present invention:

[0033] Example 1

[0034] S1: Select a PA66 film with a thickness of 100μm, rinse it with anhydrous ethanol and deionized water, dry it in an oven at 80℃, then immerse it in a 1mol / L NaOH solution and treat it in a constant temperature water bath at 50℃ for 10min. Then take it out and rinse it with deionized water until neutral, and dry it in an oven at 70℃ for 1h to obtain a surface-activated PA66 film.

[0035] S2: Weigh 0.4g of 8-aminooctanoic acid and dissolve it in 20g of dimethylformamide. Then, add 0.6g of N-hydroxysuccinimide and 0.8g of carbodiimide to the solution in sequence. Stir at room temperature for 30min. Then, immerse the surface-activated PA66 film obtained in S1 into the solution and stir at 60℃ for 2.5h. Take out the PA66 film and ultrasonically clean it with dimethylformamide, anhydrous ethanol and deionized water in sequence for 15min. Then, put it in a vacuum drying oven at 60℃ and dry it for 4h to obtain a PA66 film with amino acid pre-grafted on the surface.

[0036] S3: Take 180 mL of anhydrous ethanol and 20 mL of deionized water, mix them evenly as a solvent, weigh 3 g of octadecyl dimethyl (3-trimethoxysilylpropyl) ammonium chloride, add it to the solvent and stir until completely dissolved, then add 1.5 g of hydrophobic fumed silica nanoparticles to the solution, stir at 35 °C for 60 min to obtain a uniformly dispersed bifunctional graft solution;

[0037] S4: The PA66 film with amino acid pre-grafted surface obtained in S3 was immersed in the bifunctional grafting solution obtained in S2 and reacted at 60℃ for 3h. Then the film was taken out, rinsed three times each with anhydrous ethanol and deionized water, dried at 70℃ for 30min, and then cured in an oven at 90℃ for 2h to obtain a long carbon chain modified PA66 composite film.

[0038] Example 2

[0039] The experimental method is the same as in Example 1, except that:

[0040] S2: The amino acid selected is 11-aminoundecanoic acid. The surface-activated PA66 film is immersed in the solution and stirred at 50°C for 2 hours.

[0041] S3: Weigh 1g of hexadecyltrimethyl(3-triethoxysilylpropyl)ammonium chloride, add it to the solvent and stir until completely dissolved, then add 0.2g of hydrophobic precipitated silica to the solution;

[0042] S4: Immerse the film in the bifunctional grafting solution, react at 50°C for 0.5 h, clean and dry, and then cure in an oven at 80°C for 0.5 h. The remaining steps are the same.

[0043] Example 3

[0044] The experimental method is the same as in Example 1, except that:

[0045] S2: The amino acid selected is N-ε-lauroyl-L-lysine. The surface-activated PA66 film is immersed in the solution and stirred at 70°C for 4 hours.

[0046] S3: Weigh 10g of dodecyl dimethyl (3-trimethoxysilylpropyl)ammonium chloride, add it to the solvent and stir until completely dissolved, then add 4g of carbon nanotubes to the solution;

[0047] S4: Immerse the film in the bifunctional grafting solution, react at 80°C for 4 hours, clean and dry, and then cure in an oven at 120°C for 4 hours. The remaining steps are the same.

[0048] Example 4

[0049] The experimental method is the same as in Example 1, except that:

[0050] S2: The amino acid selected is O-lauroyl-L-serine. The surface-activated PA66 film is immersed in the solution and stirred at 65°C for 3 hours.

[0051] S3: Weigh 5g of octadecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride, add it to the solvent and stir until completely dissolved, then add 3g of nano titanium dioxide to the solution;

[0052] S4: Immerse the film in the bifunctional grafting solution, react at 70°C for 1 hour, clean and dry, and then cure in an oven at 100°C for 3 hours. The remaining steps are the same.

[0053] Comparative Example 1

[0054] The experimental method is the same as in Example 1, except that:

[0055] S3: Weigh 3g of octadecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride, add it to 100mL of toluene and stir until completely dissolved. Then add 1.5g of hydrophobic fumed silica to the solution and sonicate for 30min to form a uniform suspension.

[0056] S4: Use a spray gun to uniformly spray the suspension obtained in S2 onto the surface of the PA66 film after surface activation treatment. Then dry the sprayed film at 60°C for 1 hour to allow the solution to evaporate. No high-temperature curing treatment is performed. All other steps are the same.

[0057] This comparative preparation modifies the PA66 composite material by forming a physically adsorbed functional coating on the film surface, rather than by utilizing covalently bonded PA66 composites.

[0058] Comparative Example 2

[0059] The experimental method is the same as in Example 1, except that:

[0060] S3: Weigh 3g of cetyltrimethylammonium bromide, add it to an ethanol-water solution and stir until completely dissolved. Then add 1.5g of hydrophobic fumed silica and ultrasonically disperse for 30min to form a uniformly dispersed graft solution.

[0061] S4: Immerse the surface-activated PA66 film in the grafting solution at 60°C for 1 hour, then remove it and wash it three times each with anhydrous ethanol and deionized water, and dry it at 60°C. Do not perform high-temperature curing treatment. All other steps are the same.

[0062] This comparative example prepared a long-chain modified PA66 composite material with the surface of PA66 molecules modified by long-chain molecules containing only quaternary ammonium salt cationic groups, and the hydrophobicity was achieved solely by the addition of functional nanoparticles.

[0063] Comparative Example 3

[0064] S1: Place PA66 matrix, 8-aminooctanoic acid, octadecyl dimethyl (3-trimethoxysilylpropyl)ammonium chloride, and hydrophobic fumed silica nanoparticles in an oven and dry at 80°C for 12 hours to ensure that there is no moisture.

[0065] S2: Weigh 48g of dried PA66 matrix, 0.4g of 8-aminooctanoic acid, 1g of octadecyl dimethyl (3-trimethoxysilylpropyl)ammonium chloride, and 1g of hydrophobic fumed silica nanoparticles. Mix them evenly and pour them into a twin-screw extruder for melt blending. Set the barrel temperature to 240~260℃ and the screw speed to 200rpm. Extrude and pelletize for later use.

[0066] S3: The pellets obtained in S2 are fed into a casting molding machine with a barrel temperature of 255~265℃ to prepare PA66 composite film.

[0067] This comparative preparation involves melt blending a PA66 matrix and a modifier to prepare a long-chain modified PA66 composite material, rather than using surface covalent grafting modification.

[0068] Experimental Example 1

[0069] The samples prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to water contact angle tests and antistatic performance tests.

[0070] Static water contact angle test:

[0071] According to ASTM D5946, "Standard Method for Testing Corona-Treated Polymer Films by Water Contact Angle Measurement", the test liquid is ultrapure water. At room temperature, 5 μL of ultrapure water is slowly and gently added to the sample surface at a rate of 0.5~1 μL / s. After waiting for 10 seconds for the liquid to stabilize, the water contact angle is measured at 5 different points on the sample. The sample is then placed at room temperature for 24 hours and the contact angle is tested again to observe the hydrophobic stability of the sample.

[0072] Dynamic roll angle test:

[0073] At room temperature, 10 μL of ultrapure water is slowly and gently added to the sample surface at a rate of 0.5~1 μL / s. The sample stage is adjusted to tilt slowly at a rate of 1° / s. The angle of the platform when the droplet on the sample surface begins to roll continuously is observed, which is the dynamic roll angle. The corresponding roll angles are measured at 5 different points on the sample.

[0074] Antistatic test:

[0075] According to ASTM D257 "Test Standard for DC Resistance or Conductivity of Insulating Materials", the surface resistivity of the sample was measured using a concentric ring three-electrode system. The test voltage was set to 100V and the charging time to 60s. The sample was tested at ambient humidity of 15%RH and 55%RH. The surface resistivity was measured at three different points on the sample surface. The sample was placed at room temperature of 15%RH for 24h and the surface resistivity was measured again to observe the antistatic stability of the sample.

[0076] The test results are shown in Table 1.

[0077] Table 1 Comparison of superhydrophobicity and antistatic properties of the experimental group samples

[0078]

[0079] From Table 1 and Figure 2As can be seen, the static contact angle of the sample in the examples is greater than 150° and the dynamic roll-off angle is less than 10°, exhibiting standard superhydrophobic properties. The surface resistivity is also within 10^10 in environments with relative humidity of 15%RH and 55%RH, and the change in surface resistivity with humidity is small, indicating that the sample in the examples has a certain antistatic ability, and the antistatic ability is not greatly affected in environments with different humidity. In contrast, Comparative Example 1 sample only used a spraying method to coat the modified layer onto the PA66 film surface. Since there were no chemical bonds between the modified layer and the substrate, and its existence relied on physical adsorption, the coating's adhesion was weak. Although it initially possessed some hydrophobicity, after a period of time, the coating cracked and powdered due to internal stress, and the nanoparticles detached, rendering the quaternary ammonium salt completely ineffective, resulting in a significant reduction in hydrophobicity and antistatic properties. Comparative Example 2 sample relied on physical adsorption and mixing to fix the modified material onto the PA66 surface. The long-chain molecules and nanoparticles containing the quaternary ammonium salt were not evenly distributed on the PA66 surface, and the modification affected the material's hydrophobicity and antistatic properties. Since the materials are not a single unit, the two modified materials will interfere with each other during use. After a period of time, the modified coating on the material surface will continuously migrate and be lost, leading to a rapid decline in hydrophobicity and antistatic properties. In Comparative Example 3, the modifier and PA66 matrix were melt-blended. The groups and particles that play the role of superhydrophobicity and antistaticity were sealed inside PA66. Therefore, the material could not achieve stable hydrophobicity and antistatic properties. The surface resistivity was also greatly affected under different humidity environments. This indicates that the surface resistivity of the sample prepared by this method depends on the water molecules adsorbed on the sample surface in the environment. The modified material cannot perform its due function.

[0080] Experimental Example 2

[0081] The samples prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to abrasion resistance and solvent resistance tests.

[0082] Abrasion resistance test:

[0083] According to ASTM D4060, "Standard Test Method for Determining the Abrasion Resistance of Organic Coatings Using the Taber Abrasion Tester", the abrasion resistance of the samples was tested using a Taber abrasion tester. The film was fixed on the sample stage with a central hole, and a CS-10 rubber wheel was selected with a load of 250g and a rotation speed of 60rpm. The number of rotations was set to 5000. The sample was removed after every 100 rotations and the contact angle and surface resistivity were tested. When the contact angle dropped below 130° or the surface resistivity increased above 10^2Ω / □, the sample was considered to have failed.

[0084] Solvent resistance test:

[0085] The sample surface was wiped unidirectionally with a non-woven cloth soaked in ethanol. The contact angle and surface resistivity of the sample were tested every 10 wipes. When the contact angle dropped below 130° or the surface resistivity rose above 10^2Ω / □, the sample was deemed to have failed. The number of times the sample was wiped at this time was recorded.

[0086] Immerse the sample in an ethanol solution at room temperature for 24 hours, then remove it and air dry it at room temperature. Observe whether there are any discoloration, peeling, or wrinkling phenomena on the sample surface.

[0087] The test results are shown in Table 2.

[0088] Table 2 Comparison of wear resistance and solvent resistance of experimental group samples

[0089]

[0090] As shown in Table 2, the sample examples all exhibited excellent wear resistance and solvent resistance, indicating that the amino acid molecules link the modified layer composed of the bifunctional modifier and inorganic nanoparticles to the matrix, resulting in a strong bond and strong surface stability for the PA66 composite material. In Comparative Examples 1 and 2, the surface modified layer relies solely on physical adsorption with the PA66 matrix. Therefore, after friction and solvent erosion, the interfacial forces weaken, and the functional coating peels off, leading to a rapid loss of hydrophobicity and antistatic properties. In Example 3, the functional component also lacks a strong chemical bond with the PA66 matrix. After solvent immersion, the solvent penetrates into the interface between the filler and the matrix, forming numerous voids and defects, causing the sample to turn white. Simultaneously, the solvent causes the internally encapsulated gas or molecules to precipitate, resulting in blistering or wrinkling of the sample surface. Because the functional long-chain carbon molecules and nanoparticles are dispersed or detached by the solvent, the sample loses its original hydrophobicity and antistatic properties after a period of time.

Claims

1. A method for preparing a long-chain modified PA66 composite material, characterized in that, Includes the following steps: S1. Select a PA66 film with a thickness of 100 μm, rinse it with anhydrous ethanol and deionized water, and dry it at 80 °C; immerse the PA66 film in a 1 mol / L NaOH solution, treat it in a constant temperature water bath at 50 °C for 10 min, take it out, rinse it with deionized water until neutral, and dry it at 70 °C for 1 h to obtain a surface-activated PA66 film. S2. Dissolve 0.4g of 8-aminooctanoic acid in 20g of dimethylformamide, then add 0.6g of N-hydroxysuccinimide and 0.8g of carbodiimide sequentially, and stir at room temperature for 30min. Immerse the surface-activated PA66 film obtained in S1 into the obtained pre-grafting solution and react at 60℃ for 2.5h. After removal, ultrasonically clean with dimethylformamide, anhydrous ethanol and deionized water for 15min each, and vacuum dry at 60℃ for 4h to obtain a PA66 film with 8-aminooctanoic acid pre-grafted on the surface. S3. Mix 180 mL of anhydrous ethanol and 20 mL of deionized water, add 3 g of octadecyl dimethyl (3-trimethoxysilylpropyl) ammonium chloride and stir until dissolved, then add 1.5 g of hydrophobic fumed silica nanoparticles and stir at 35 °C for 60 min to obtain a bifunctional graft solution. S4. The PA66 film with 8-aminooctanoic acid pre-grafted on the surface obtained in S2 is immersed in the bifunctional grafting solution obtained in S3 and reacted at 60℃ for 3h. After being taken out, it is rinsed three times each with anhydrous ethanol and deionized water, dried at 70℃ for 30min, and then cured at 90℃ for 2h to obtain a long carbon chain modified PA66 composite film.

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