A method of modifying a PAI material to reduce its moisture absorption

Abstract

The application discloses a modification method for reducing the hygroscopicity of PAI material, and comprises the following steps: (1) fluorination pretreatment of inorganic nanoparticles by using a fluorine-containing coupling agent to obtain pre-fluorinated inorganic nanoparticles; (2) gradient plasma fluorination modification of the pre-fluorinated inorganic nanoparticles to obtain fluorinated inorganic nanoparticles; and (3) mixing of PAI powder and the fluorinated inorganic nanoparticles and injection molding to obtain the PAI material. The inorganic nanoparticles are modified by plasma fluorination, and then the PAI powder and the fluorinated inorganic nanoparticles are mixed and injection molded to obtain the PAI material, so that the agglomeration of the inorganic nano-material is greatly reduced, the prepared PAI material has extremely low water absorption under the premise of ensuring that the mechanical properties of the material are not affected, the moisture resistance of the polyamide-imide material is improved, and the application of the polyamide-imide material in harsh working conditions such as high wear resistance and high humidity is expanded.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and particularly relates to a method for modifying PAI materials. Background Technology

[0002] Polyamide-imide (PAI) sits at the top of the materials performance pyramid. It is an advanced, high-performance material containing both amide and imide structures in its molecular backbone, capable of withstanding complex service environments involving high temperatures, corrosion, and fatigue. It is a key guarantee for high-end manufacturing. Its flexible amide structure endows the material with excellent wear resistance, self-lubrication, and processability, while the rigid imide units give it significant advantages over conventional engineering plastics used in transmission systems in terms of temperature resistance, load-bearing capacity, creep resistance, and corrosion resistance. However, PAI materials also have some drawbacks. The introduction of amide bonds leads to high water absorption, affecting the material's dimensional stability. This high water absorption limit its application in harsh conditions such as high humidity. Therefore, reducing the hygroscopicity of PAI materials has become a key research hotspot for technological breakthroughs.

[0003] Inorganic nanomaterials have been widely used due to their simple preparation and significantly improved water absorption properties. However, due to their high surface energy, nanomaterials are prone to aggregation and lack polar organic functional groups on their surface, making them unable to bond with most polymer materials. This results in weak bonding strength between the inorganic filler particles and the polymer matrix, affecting their functional properties and even introducing inhomogeneous phases and interfacial defects into the composite material, causing a decline in its original properties. Therefore, surface activation or functionalization is necessary before use to avoid these defects. Currently, coupling agents are mostly used to modify nanomaterials in practical applications, but these methods still suffer from drawbacks such as low fluorination rates and insufficient bonding strength. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above and to provide a modification method for reducing the hygroscopicity of PAI materials.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0006] A method for modifying PAI materials to reduce hygroscopicity includes the following steps: (1) Fluorine-containing coupling agents are used to pre-fluorinate inorganic nanoparticles to obtain pre-fluorinated inorganic nanoparticles; (2) The prefluorinated inorganic nanoparticles are modified by gradient plasma fluorination to obtain fluorinated inorganic nanoparticles; the gradient plasma fluorination modification includes deep etching and activation with NF3 / He gas source, deep fluorocarbon implantation in C4F8 / Ar gas source, and high-density fluorination modification on the surface with CF4 / N2 gas source. (3) PAI powder and the fluorinated inorganic nanoparticles are mixed and injection molded to obtain PAI material.

[0007] In the above modification method, preferably, the inorganic nanoparticles are subjected to surface modification treatment before fluorination pretreatment using a fluorinated coupling agent. When the inorganic nanoparticles are nano-SiO2, the surface modification treatment is to use an alkaline solution to etch the surface of the nano-SiO2; when the inorganic nanoparticles are nano-TiO2, the surface modification treatment is to use an anodic oxidation method to generate TiO2 nanotubes on the surface.

[0008] In the above modification method, preferably, the alkaline solution is a KOH solution with a concentration of 0.1-0.2M, the etching temperature is 50-60℃, and the etching time is 6-10min; during the anodic oxidation process, the voltage is controlled at 26-32V, and the reaction time is 3-6min.

[0009] In this invention, nano-SiO2 is surface-etched using an alkaline solution, and nano-TiO2 is treated with anodic oxidation to form TiO2 nanotubes on its surface. This process has the following advantages: it increases the specific surface area of ​​each nanoparticle, providing more fluorination sites. Simultaneously, the anodic oxidation treatment of nano-TiO2 creates nanostructure tips that enhance the local electric field, promoting plasma penetration and facilitating subsequent plasma fluorination modification. When surface-etching nano-SiO2 with an alkaline solution, the etching time should not be too long, otherwise it will cause over-reaction on the nano-SiO2 surface. Similarly, when treating nano-TiO2 with anodic oxidation, the reaction time should not be too long, otherwise the tubular structure on the TiO2 surface will break down and transform into a sponge-like porous layer, which is detrimental to subsequent plasma fluorination modification.

[0010] In the above modification method, preferably, the fluorinated coupling agent includes tridecafluorodecyltrimethoxysilane or heptadecafluorodecyltrimethoxysilane. During the fluorination pretreatment, the reaction temperature is 40-70℃, the stirring rate is 3000-4000 r / min, and the stirring time is 15-30 min. Too short a fluorination pretreatment time will reduce the surface fluorination rate, which is detrimental to subsequent plasma fluorination modification. Meanwhile, the fluorinated coupling agent used in this invention, compared to commonly used aminosilane coupling agents, can pre-graft to form fluorocarbon chains, reducing the activation energy of CF bond formation, thus facilitating subsequent plasma fluorination grafting. Furthermore, the long-chain fluorocarbon groups have strong hydrophobic repulsion, stabilizing the particle spacing at >20 nm, reducing the aggregation index, thereby improving the efficiency of subsequent plasma fluorination and avoiding excessive consumption of fluorine free radicals.

[0011] In the above modification method, preferably, during the NF3 / He gas source deep etching activation, the voltage and frequency are controlled at 2.6-4.1kV and 8-11kHz, respectively, the gas pressure is controlled at 3.5-5.5kPa, the volume ratio of NF3 to He is 1:5-6, and the processing time is controlled at 2-3min.

[0012] In the above modification method, preferably, when deep fluorocarbon implantation is performed in the C4F8 / Ar gas source, the voltage and frequency are controlled at 4.8-7.3kV and 18-22kHz, respectively, the gas pressure is controlled at 7-9kPa, the volume ratio of C4F8 to Ar is 1:2-3, and the processing time is controlled at 4-7min.

[0013] In the above modification method, preferably, during the high-density fluorination modification of the CF4 / N2 gas source surface, the voltage and frequency are controlled at 7-9kV and 15-35kHz, respectively, the gas pressure is controlled at 15-20kPa, the volume ratio of CF4 to N2 is 1:7-9, and the processing time is controlled at 4-7min.

[0014] In this invention, during the deep etching activation process using an NF3 / He gas source, He, as a metastable particle, can mechanically strip the organic matter and water film adsorbed on the inorganic nanoparticles, creating vacancy defects on the subsurface (3-5 nm depth) of the particle surface after pretreatment (etching or anodizing). Simultaneously, it excites NF3 dissociation, generating highly reactive F radicals and forming strong Ti-F / Si-F bonds. Deep fluorocarbon implantation within the C4F8 / Ar gas source forms CF2. CF2 CF2 CF2 linear fluorocarbon radicals bypass Ti-F / Si-F bonds via chemical diffusion, reacting only at defect sites with an interaction depth of approximately 5-8 nm, ensuring sufficient fluorocarbon chain growth without excessive cross-linking. High-density fluorination modification of the surface layer using a CF4 / N2 gas source under high pressure increases radical density, achieving dense surface fluorination. During deep etching activation using an NF3 / He gas source, the control of the above process parameters avoids over-etching; the generated high-energy F radicals can etch 3-5 nm of the particle surface and remove surface contaminants, facilitating subsequent steps. During deep fluorocarbon implantation using a C4F8 / Ar gas source, the generation of CF2 can be achieved through process parameter control. CF2 CF2 CF2 linear fluorocarbon radicals can be embedded deep (5-8 nm) to form a hydrophobic framework, while avoiding the activation sites of deep etching using the NF3 / He gas source. Finally, a low surface energy surface layer is constructed by controlling the process parameters of high-density fluorination modification using the CF4 / N2 gas source. Surface pretreatment and fluorination pretreatment create conditions for gradient plasma fluorination modification. Combined with the deep etching activation using the NF3 / He gas source, deep fluorocarbon implantation using the C4F8 / Ar gas source, and high-density fluorination modification using the CF4 / N2 gas source, each acting on different sites, the synergistic effect of these steps is beneficial for improving the fluorination grafting rate.

[0015] Without the aforementioned surface pretreatment and fluorination pretreatment, the subsequent gradient plasma fluorination modification effect will be affected, which is not conducive to improving the fluorination grafting rate and the fluorination modification effect will be poor. After the aforementioned specific surface pretreatment and fluorination pretreatment, the gradient fluorination process of this invention can solve the problem of low fluorination rate in conventional DBD process, so that the surface fluorination rate of the prepared nanoparticles is higher than that of commonly used fluorination modification methods, and has better hydrophobic properties. The fluorinated modified nanoparticles prepared by the gradient fluorination process have lower surface energy and a surface fluorination rate of more than 31%. At the same time, a large number of fluorine-containing polar groups are bonded to the surface of the modified nanoparticles, which greatly improves the binding and dispersion ability of nanoparticles with resin materials without affecting the mechanical properties of the materials.

[0016] In the above modification method, preferably, after switching gases between the steps of deep etching and activation with NF3 / He gas source, deep fluorocarbon implantation with C4F8 / Ar gas source, and high-density fluorination modification on the surface with CF4 / N2 gas source, the discharge is restarted after stabilizing for 20-40 seconds. This setting avoids mutual interference between the steps and can better ensure the fluorination effect.

[0017] In the above modification method, preferably, the PAI powder molecular structure contains fluorine and ether structural groups, and the molecular structural formula is as follows: ; Where Ar1 and Ar2 are any one of the following formulas 1, 2 and 3, x is 7-9 and y is 1-3; .

[0018] The above-mentioned PAI powder contains fluorine and ether structural groups in its molecular structure. The polyamide-imide structure is a fluorine-ether synergistic structure, which can enable the polyamide-imide material to form F·F pseudo-halogen bonds (bond energy 8-12 kJ / mol) with the fluorinated modified nanomaterials, and reduce the nanoparticle-resin interface energy by 35%, which is more conducive to the uniform co-mixing of PAI powder and fluorinated nano SiO2 or TiO2 particles.

[0019] In the above modification method, preferably, the particle size of the inorganic nanoparticles is 20-50 nm; the amount of fluorinated inorganic nanoparticles added does not exceed 20 wt% of the mass of the PAI powder.

[0020] More specifically, in this invention, the process of obtaining fluorinated nano-SiO2 / TiO2 particles by fluorination modification of nano-SiO2 / TiO2 particles using gradient plasma includes the following steps: S1. Pretreatment of nano-SiO2 / TiO2: Take an appropriate amount of nano-SiO2 and perform surface etching treatment with KOH solution; treat nano-TiO2 by anodic oxidation to generate TiO2 nanotubes on its surface.

[0021] S2. Fluorination pretreatment using nano-SiO2 / TiO2 coupling agent: Weigh the nanoparticles treated in step S1, add them to a beaker with deionized water at an appropriate mass ratio, add an appropriate amount of alcohol, and stir with ultrasound (the optimal mass ratio of nanomaterial powder to deionized water is 1:2, and the optimal stirring temperature is 50℃); after stirring, add a suitable fluorinated coupling agent to the mixture, add an appropriate amount of alcohol, stir and react under the same conditions, and finally dry, grind, and seal for later use.

[0022] S3. Plasma Fluorination Modification of Nano-SiO2 / TiO2: A DBD-structured plasma fluorination modification platform is used to perform plasma fluorination modification on pre-fluorinated nano-SiO2 / TiO2 using a gradient fluorination method. The process includes deep etching and activation with an NF3 / He gas source, deep fluorocarbon implantation with a C4F8 / Ar gas source, and high-density surface fluorination modification with a CF4 / N2 gas source. After switching gases between each step, the system is stabilized for 20-40 seconds before starting the discharge.

[0023] More specifically, in this invention, mixing PAI powder and the fluorinated nano-SiO2 / TiO2 particles, and then injection molding the resulting PAI material comprises the following steps: S1. Weigh appropriate amounts of PAI powder, colorant, and fluorinated nano-SiO2 / TiO2 particles into a high-speed mixer, set appropriate speed and mixing time parameters, and mix. The colorant can be talc, zinc oxide, or carbon black, etc.; using a high-speed mixer is beneficial for improving dispersibility.

[0024] S2. Place the well-mixed powder into a vacuum oven to dry and remove moisture.

[0025] S3. After the above-mentioned dried powder is granulated, it is prepared into the required sample by injection molding and its performance is tested.

[0026] In this invention, fluorinated nano-SiO2 or TiO2 particles can be added to PAI resin in proportions of 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, and 20wt%, and the sample is prepared by granulation and injection molding processes.

[0027] Plasma fluorination, as an emerging surface treatment technology, provides excellent reaction conditions for the surface state modulation of inorganic nanoparticles. This invention uses low-pressure plasma to fluorinate and modify nano-SiO2 or TiO2, which has low cost and excellent hydrophobic properties, significantly improving the waterproof performance of the material and making it perform well in humid environments. Specifically, this invention uses a surface pretreatment-coupling agent modification-gradient plasma fluorination process to precisely control the surface activation energy and fluorination rate of the modified nanoparticles. The prepared fluorinated modified nano-SiO2 or TiO2 has high fluorine content, excellent dispersibility and hydrophobicity, thereby improving the dispersion ability of nanoparticles and reducing the possibility of agglomeration during use. At the same time, the introduction of polar groups into the inorganic nanoparticles makes the fluorinated modified nanomaterial compatible with other resin materials to reduce the water absorption rate of the material. Furthermore, fluorinated nano-SiO2 or TiO2 has a similar structure to PAI powder containing fluorine and ether structural groups, making it easy to form chemical bonds. The two have a stronger bonding ability, which greatly improves the bonding strength between nano-SiO2 or TiO2 particles and PAI matrix. This can reduce the water absorption rate of PAI material to ≤0.16%. Moreover, using fluorinated nano-SiO2 or TiO2 to modify the PAI matrix has the advantages of simple process and equipment, readily available modified raw materials, and no need for subsequent modification or other treatments, making it suitable for mass production.

[0028] Compared with the prior art, the advantages of the present invention are as follows: The present invention provides a modification method for reducing the hygroscopicity of PAI materials. This method involves plasma fluorination modification of inorganic nanoparticles, followed by mixing PAI powder and fluorinated inorganic nanoparticles, and injection molding to obtain PAI materials. This method significantly reduces the agglomeration of inorganic nanoparticles and ensures that the prepared PAI materials have extremely low water absorption rates while maintaining the mechanical properties of the materials. This improves the moisture resistance of polyamide-imide materials and expands their application in harsh working conditions such as high wear resistance and high humidity. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the DBD structure modification device used in this invention.

[0031] Figure 2 These are SEM images of the nano-silica before and after fluorination modification according to the present invention.

[0032] Figure 3 This is a comparison of the morphology of the nano-SiO2 particles before and after prefluorination in this invention.

[0033] Figure 4 This is a graph showing the water absorption rate of PAI materials under different proportions of fluorinated modified nano-silica according to the present invention. Detailed Implementation

[0034] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] Example 1: A method for modifying PAI materials to reduce hygroscopicity includes the following steps: (1) Weigh an appropriate amount of 40-50 nm SiO2 powder, mix it with 0.1 M KOH at 60 °C and stir thoroughly for 10 min. After the reaction is complete, rinse with water and dry.

[0038] (2) At 50°C, the nanoparticles treated in step (1) above are mixed with deionized water at a mass ratio of 1:2, and then an appropriate amount of alcohol is added. The mixture is stirred at 4000 r / min for 20 min with ultrasonic waves. After stirring, tridecylfluorodecyltrimethoxysilane is added to the mixture, and then an appropriate amount of alcohol is added. The mixture is stirred for 30 min under the same conditions. Finally, it is dried, ground, and sealed for later use.

[0039] (3) Utilize, for example Figure 1 The plasma fluorination modification platform of the DBD structure shown uses a gradient fluorination method to perform plasma fluorination modification on nano-SiO2 and other materials that have undergone fluorination pretreatment in step (2). The process includes deep etching and activation with NF3 / He gas source, deep fluorocarbon implantation in C4F8 / Ar gas source, and high-density fluorination modification on the surface of CF4 / N2 gas source. After switching gases between each step, the system is stabilized for 30 seconds before starting the discharge. For deep etching activation using an NF3 / He gas source, the voltage / frequency was controlled at 3.7 kV / 8.9 kHz, the gas pressure at 3.9 kPa, the NF3 to He ratio at approximately 1:5, and the processing time at 2 min. For deep fluorocarbon implantation using a C4F8 / Ar gas source, the voltage / frequency was controlled at 6.1 kV / 19 kHz, the gas pressure at 7.9 kPa, the C4F8 to Ar ratio at approximately 1:3, and the processing time at 5 min. For high-density fluorination modification of the surface using a CF4 / N2 gas source, the voltage / frequency was controlled at 7.9 kV / 27 kHz, the gas pressure at 18 kPa, the CF4 to N2 ratio at approximately 1:7, and the processing time at 5 min. The prepared fluorinated nanoparticles were sealed and stored using the above gradient fluorination process for later use.

[0040] (4) Weigh 1000g of polyamide-imide resin powder, 4% colorant and fluorinated nano-SiO2 particles prepared in step (3) in proportions of 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, and 20wt% and put them into a high-speed mixer, add them to a ball mill, set the speed to about 2500r / min, mix for 10min, mix for a total of 5 times to obtain a fully mixed powder and transfer it to an oven to dry and remove residual moisture.

[0041] (5) The above-mentioned blended samples are prepared into the required samples by granulation and injection molding processes. The samples are numbered sequentially as sample 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

[0042] like Figure 1As shown, the DBD structure plasma platform mainly consists of a power system, a pneumatic component, a DBD discharge space, and a testing component.

[0043] Figure 2 The images show the SEM morphology of nano-silica before and after gradient plasma fluorination modification. The images clearly show that the nanoparticles are less prone to aggregation and have a rougher surface after fluorination.

[0044] Figure 3 The images show the SEM morphology of prefluorinated inorganic SiO2 particles (right) and unmodified inorganic SiO2 powder (left). The images clearly show that the nano-SiO2 particles after prefluorination have a larger specific surface area and a rougher surface.

[0045] The structural formula of the above polyamide-imide resin powder is as follows: The PAI powder contains fluorine and ether groups in its molecular structure, and its molecular structure is as follows: ; Ar1 and Ar2 are respectively represented by Equation 1 and Equation 2, where x is 9, y is 1, and the molecular weight is approximately 80,000. .

[0046] Example 2: A method for modifying PAI materials to reduce hygroscopicity includes the following steps: (1) Weigh an appropriate amount of 40-50 nanometer TiO2 powder and react it at 30V for 5 minutes using the anodic oxidation method to form TiO2 nanotubes on its surface.

[0047] (2) At 50°C, the nanoparticles treated in step (1) above are mixed with deionized water at a mass ratio of 1:2, and then an appropriate amount of alcohol is added. The mixture is stirred at 4000 r / min for 20 min with ultrasonic waves. After stirring, heptadecafluorodecyltrimethoxysilane is added to the mixture, and then an appropriate amount of alcohol is added. The mixture is stirred for 30 min under the same conditions. Finally, it is dried, ground, and sealed for later use.

[0048] (3) Utilize, for example Figure 1The plasma fluorination modification platform of the DBD structure shown uses a gradient fluorination method to perform plasma fluorination modification on nano-TiO2 and other materials that have undergone fluorination pretreatment in step (2). The process includes deep etching and activation with NF3 / He gas source, deep fluorocarbon implantation in C4F8 / Ar gas source, and high-density fluorination modification on the surface of CF4 / N2 gas source. After switching gases between each step, the system is stabilized for 30 seconds before starting the discharge. For deep etching activation using an NF3 / He gas source, the voltage / frequency was controlled at 3.9 kV / 10.1 kHz, the gas pressure at 5.4 kPa, the NF3 to He ratio at approximately 1:5, and the processing time at 2 min. For deep fluorocarbon implantation using a C4F8 / Ar gas source, the voltage / frequency was controlled at 6.8 kV / 20.8 kHz, the gas pressure at 8 kPa, the C4F8 to Ar ratio at approximately 1:3, and the processing time at 5 min. For high-density fluorination modification of the surface using a CF4 / N2 gas source, the voltage / frequency was controlled at 8.7 kV / 19.9 kHz, the gas pressure at 19 kPa, the CF4 to N2 ratio at approximately 1:7, and the processing time at 5 min. The prepared fluorinated nanoparticles were sealed and stored using the above gradient fluorination process for later use.

[0049] (4) Weigh 1000g of polyamide-imide resin powder, 4% colorant and fluorinated nano-TiO2 particles prepared in step (3) in proportions of 2wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, and 20wt% and put them into a high-speed mixer, add them to a ball mill, set the speed to about 2500r / min, mix for 10min, mix for a total of 5 times to obtain a fully mixed powder and transfer it to an oven to dry and remove residual moisture.

[0050] (5) The above-mentioned blended samples are prepared into the required samples by granulation and injection molding processes. The samples are numbered sequentially as samples 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20.

[0051] The structural formula of the above polyamide-imide resin powder is as follows: The molecular structure is as follows: ; Ar1 and Ar2 are respectively represented by Equation 1 and Equation 2, where x is 9, y is 1, and the molecular weight is approximately 80,000. .

[0052] Comparative Example 1: The main difference between this comparative example and Example 1 is the addition of 12 wt% inorganic nano-SiO2 particles in step (4). These inorganic nano-SiO2 particles were not treated in any way. All other conditions were the same as steps (4) and (5) of Example 1. The sample obtained in this comparative example was numbered 0 and used for subsequent sample comparison.

[0053] Comparative Example 2: The main difference between this comparative example and Example 1 is that it skips steps (1) and (2) and directly uses gradient plasma fluorination in step (3).

[0054] All other conditions were the same as in Example 1. When the amount of fluorinated nano-SiO2 particles added was 12 wt%, the sample obtained in this comparative example was numbered 21 and used for subsequent sample comparison.

[0055] Comparative Example 3: The main difference between this comparative example and Example 1 is that gradient plasma fluorination is not used in step (3), while other conditions are the same as in Example 1. When the amount of fluorinated nano-SiO2 particles added is 12wt%, the sample obtained in this comparative example is numbered 22, which is used for subsequent sample comparison.

[0056] Comparative Example 4: The main difference between this comparative example and Example 2 is that gradient plasma fluorination is not used in step (3), while other conditions are the same as in Example 2. When the amount of fluorinated nano-TiO2 particles added is 12wt%, the sample obtained in this example is numbered 23, which is used for subsequent sample comparison.

[0057] Example 3: Compared with Example 1, the main difference in this embodiment is that the polyamide-imide resin powder used in step (4) is a trifluoromethyl polyamide-imide resin powder, and its specific structural formula is as follows: The molecular weight is controlled by n, which is approximately 80,000.

[0058] All other conditions were the same as in Example 1. When the amount of fluorinated nano-SiO2 particles added was 12wt%, the sample obtained in this example was numbered 24 and used for subsequent sample comparison.

[0059] The polyamide-imide samples prepared in the above examples and comparative examples were subjected to performance tests. The types of tests, test methods, and test standards are as follows: The glass transition temperature testing standard in this embodiment is GB / T 1634-2004 "Determination of Glass Transition Temperature of Plastics".

[0060] The test standard for the moisture absorption performance of the test sample material in this embodiment is GB / T 1034 "Determination of Water Absorption of Plastics".

[0061] The compressive strength test in this embodiment refers to the standard GB / T 1041 "Determination of compressive properties of plastics".

[0062] The shear strength test in this embodiment refers to the standard "ASTM D732 Plastics Shear Strength Test".

[0063] The performance test results of Examples 1-3 and Comparative Examples 1-4 are shown in Table 1 below.

[0064] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-4

[0065] Table 1 shows that adding different amounts of modified nano-SiO2 or TiO2 has little effect on the glass transition temperature of the material, indicating good stability. The water absorption rate decreases continuously with the addition of modified nano-SiO2 or TiO2, reaching a stable effect when the addition exceeds 10% (e.g., ...). Figure 4 (As shown). Samples 1-20, after surface pretreatment and fluorination pretreatment, exhibit significantly better water absorption and mechanical properties than sample 21, which did not undergo surface pretreatment and fluorination pretreatment. Samples 1-20, after gradient plasma fluorination modification, show significantly better water absorption and mechanical properties than samples 22-23, which did not undergo gradient plasma treatment. A comparison of samples 22, 23, and 1-20 shows that samples without gradient plasma fluorination have significantly higher water absorption rates. A comparison of samples 24 and 1-20 shows that PAI powder containing fluorine and ether structural groups has significantly lower water absorption rates and better glass transition temperature and mechanical properties compared to PAI powder without trifluoromethyl structures.

Claims

1. A modification method for reducing the hygroscopicity of PAI materials, characterized in that, Includes the following steps: (1) Fluorine-containing coupling agents are used to pre-fluorinate inorganic nanoparticles to obtain pre-fluorinated inorganic nanoparticles; (2) The prefluorinated inorganic nanoparticles are modified by gradient plasma fluorination to obtain fluorinated inorganic nanoparticles; the gradient plasma fluorination modification includes deep etching and activation with NF3 / He gas source, deep fluorocarbon implantation in C4F8 / Ar gas source, and high-density fluorination modification on the surface with CF4 / N2 gas source. (3) PAI powder and the fluorinated inorganic nanoparticles are mixed and injection molded to obtain PAI material.

2. The modification method according to claim 1, characterized in that, Before the inorganic nanoparticles are pretreated with a fluorinated coupling agent, the inorganic nanoparticles are also subjected to surface modification treatment. When the inorganic nanoparticles are nano-SiO2, the surface modification treatment is to use an alkaline solution to etch the surface of the nano-SiO2; when the inorganic nanoparticles are nano-TiO2, the surface modification treatment is to use an anodic oxidation method to generate TiO2 nanotubes on the surface.

3. The modification method according to claim 2, characterized in that, The alkaline solution is a 0.1-0.2M KOH solution, the etching temperature is 50-60℃, and the etching time is 6-10min; during the anodic oxidation process, the voltage is controlled at 26-32V, and the reaction time is 3-6min.

4. The modification method according to claim 1, characterized in that, The fluorinated coupling agent includes tridecylfluorodecyltrimethoxysilane or heptadecafluorodecyltrimethoxysilane. During the fluorination pretreatment, the reaction temperature is 40-70℃, the stirring rate is 3000-4000 r / min, and the stirring time is 15-30 min.

5. The modification method according to claim 1, characterized in that, During the deep etching activation of NF3 / He gas source, the voltage and frequency are controlled at 2.6-4.1kV and 8-11kHz, respectively, the gas pressure is controlled at 3.5-5.5kPa, the volume ratio of NF3 to He is 1:5-6, and the processing time is controlled at 2-3min.

6. The modification method according to claim 1, characterized in that, When deep fluorocarbon implantation is performed in a C4F8 / Ar gas source, the voltage and frequency are controlled at 4.8-7.3kV and 18-22kHz, respectively, the gas pressure is controlled at 7-9kPa, the volume ratio of C4F8 to Ar is 1:2-3, and the processing time is controlled at 4-7min.

7. The modification method according to claim 1, characterized in that, When the surface of the CF4 / N2 gas source is subjected to high-density fluorination modification, the voltage and frequency are controlled at 7-9kV and 15-35kHz, respectively, the gas pressure is controlled at 15-20kPa, the volume ratio of CF4 to N2 is 1:7-9, and the processing time is controlled at 4-7min.

8. The modification method according to claim 1, characterized in that, After switching gases between the steps of deep etching and activation with NF3 / He gas source, deep fluorocarbon implantation with C4F8 / Ar gas source, and high-density fluorination modification of the surface with CF4 / N2 gas source, the discharge is restarted after stabilizing for 20-40 seconds.

9. The modification method according to claim 1, characterized in that, The PAI powder contains fluorine and ether groups in its molecular structure, and its molecular structure is as follows: ； Where Ar1 and Ar2 are any one of the following formulas 1, 2 and 3, x is 7-9 and y is 1-3; 。 10. The modification method according to claim 1, characterized in that, The inorganic nanoparticles have a particle size of 20-50 nm; the amount of fluorinated inorganic nanoparticles added does not exceed 20 wt% of the mass of the PAI powder.

Images