Polyimide-silicon carbide high-adhesion damp-heat-resistant ink and preparation process thereof

Abstract

The invention relates to the field of preparation of novel ink, in particular to polyimide-silicon carbide high-adhesion damp-heat-resistant ink and a preparation process thereof. The invention provides polyimide-silicon carbide high-adhesion damp-heat-resistant ink and a preparation process thereof, which are mainly characterized in that siloxane-modified polyimide and surface-modified silicon carbide nanoparticles are subjected to multi-stage dispersion blending treatment to form a stable ink dispersion system, and the ink has high adhesion and also has high temperature resistance and damp-heat resistance.

Description

Technical Field

[0001] The present invention relates to the field of preparation of novel inks, and specifically to polyimide-silicon carbide high-adhesion moisture and heat resistant ink and its preparation process. Background Art

[0002] Due to its excellent thermal stability and mechanical properties, polyimide (PI) resin has become the core matrix of high-temperature protection materials and is widely used in fields such as aerospace electronic packaging and automotive sensor coatings. However, the existing technology still faces significant challenges in the coupled environment of high humidity and high temperature, specifically manifested as the following technical bottlenecks:

[0003] Traditional polyimide inks often improve adhesion by physically blending silane coupling agents (as described in patent CN116948520A) or inorganic fillers. However, high humidity (>85% RH) can cause hydrolysis at the resin-filler interface, and the adhesion drops from the initial 4B level to below 2B. For example, patent CN116948520A modifies PI with a crosslinking agent. Although the adhesion is improved to a tape test peeling area of <1%, its upper temperature limit for heat resistance is only 350°C, far from meeting the requirements above 600°C. In addition, the direct introduction of silicon carbide (SiC) nano-fillers is prone to microcracks due to the mismatch of interfacial thermal stress.

[0004] The high surface energy of silicon carbide (SiC) nanoparticles (200 nm) leads to agglomeration. After conventional mechanical dispersion, the particle size distribution broadens to more than 500 nm, and significant sedimentation and stratification occur after long-term storage. Literature research shows that unmodified SiC and the PI matrix are only combined by van der Waals forces, and the interfacial binding energy is as low as 0.7 J / m 2 at high temperature, resulting in insufficient thermal stability. Existing technologies such as patent CN117866216B use water-dispersed light-cured PI resin, which improves environmental friendliness but does not solve the problem of chemical bonding between the filler and the matrix.

[0005] Traditional hydrophobic modification schemes mostly physically incorporate fluorocarbon resins (such as PTFE) or silicone oils. However, their compatibility with PI is poor, phase separation occurs at high temperature (contact angle <100°), and the thermal decomposition temperature is as low as 280°C. For example, the water-dispersed light-cured PI patent of Sumitomo Technology reduces the use of organic solvents but does not involve the design of a high-temperature hydrophobic synergistic mechanism. In addition, the Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, improves the interfacial bonding by modifying PI fibers with carbon nanotubes, but does not optimize for the humid and hot environment, and the wear resistance only increases by 34.5% at 300°C.

[0006] Based on the above limitations, it is urgent to develop a novel polyimide-silicon carbide composite ink, and its core innovation needs to solve:

[0007] (1) Construct a covalent interface between the resin and the filler through siloxane chemical bonding to overcome the problem of adhesion decline in the humid and hot environment;

[0008] (2) Realize in-situ grafting and stable dispersion of SiC nanoparticles;

[0009] (3) Design a multi-scale hydrophobic network that still has moisture resistance at high temperatures.

[0010] The technology of the present invention focuses on solving the above problems and invents a polyimide-silicon carbide high-adhesion moisture and heat-resistant ink, and improves its preparation process. The prepared ink can be used in a variety of scenarios, including surface coating, marking, etc. of special environmental carriers such as ships, airplanes, high-speed rails, and ocean engineering. Summary of the Invention

[0011] Based on the problems summarized above, the present invention provides a polyimide-silicon carbide high-adhesion moisture and heat-resistant ink and its preparation process. Its main feature is to perform multi-stage dispersion and blending treatment on polyimide modified by siloxane and surface-modified silicon carbide nanoparticles to form a stable ink dispersion system, which has high adhesion and is also resistant to high temperature, moisture and heat. The specific technical solutions are as follows:

[0012] The polyimide-silicon carbide high-adhesion moisture and heat-resistant ink contains the following components in parts by mass: 40-60 parts of siloxane-modified polyimide, 5-15 parts of surface-modified silicon carbide nanoparticles, 5-10 parts of hydrophobic fluorinated polymer, 20-40 parts of mixed solvent, 0.5 part of dispersant, and 0.5 part of defoamer.

[0013] Further, the siloxane-modified polyimide is prepared by co-condensation of 4,4'-diaminodiphenyl ether-3,3'-bis(trifluoromethyl) and a siloxane prepolymer, and the siloxane prepolymer is prepared from amino-terminated polydimethylsiloxane and pyromellitic dianhydride.

[0014] Further, the surface-modified silicon carbide nanoparticles are modified by γ-glycidoxypropyltrimethoxysilane.

[0015] Further, the hydrophobic fluorinated polymer is polytetrafluoroethylene;

[0016] The mixed solvent is a mixture of N-methylpyrrolidone and γ-butyrolactone in a volume ratio of 7:3;

[0017] The dispersant is BYK-dispersant, and the defoamer is BYK-066N.

[0018] Further, it is characterized by including the following steps:

[0019] S1: After preheating, dissolve the raw materials for preparing the silicone-modified polyimide in a solvent according to a certain molar ratio, control the solid content range, gradually raise the temperature to a certain temperature for reaction to generate a polyamic acid intermediate containing silicone, then under nitrogen protection, raise the temperature to a certain temperature for heat preservation, and then raise the temperature to a certain temperature for reaction for a period of time. Finally, perform vacuum treatment to form the silicone-modified polyimide.

[0020] S2: Disperse the first raw material for preparing the surface-modified silicon carbide nanoparticles in a solvent according to a ratio, stir magnetically, then add the second raw material, perform ultrasonic treatment, and then perform vacuum drying to obtain the surface-modified silicon carbide nanoparticles.

[0021] S3: Gradually add the silicone-modified polyimide to the mixed solvent, stir at a certain temperature until completely dissolved, then sequentially add the surface-modified silicon carbide nanoparticles and the hydrophobic fluoropolymer to form a premixed slurry. Add a dispersant and an antifoaming agent to the premixed slurry, stir, and use a multi-stage dispersion and blending process to obtain the polyimide-silicon carbide high-adhesion and moisture-resistant and heat-resistant ink.

[0022] Further, for the preheating described in S1, the temperature reached by preheating is set to 80 °C.

[0023] The "certain molar ratio" described in S1 is a 1:1 molar ratio.

[0024] For the "control of the solid content range" described in S1, the range is controlled at 20-25%.

[0025] After the "gradually raising the temperature to a certain temperature for reaction" described in S1, it is set to gradually raise the temperature to 150 °C and then react for 2 hours.

[0026] After the "raising the temperature to a certain temperature for heat preservation under nitrogen protection" described in S1, it is set to raise the temperature to 280 °C under nitrogen protection for constant temperature heat preservation for 1 hour.

[0027] For the "raising the temperature to a certain temperature for reaction for a period of time" described in S1, it is set to raise the temperature to 320 °C and react for 2 hours.

[0028] Further, the "disperse in ethanol according to a ratio" described in S2 is set to disperse in the solvent at a solid-liquid ratio of 1:20.

[0029] For the "magnetic stirring" described in S2, the parameters are set to stir at a speed of 500 rpm for 30 minutes.

[0030] For the "adding the second raw material" described in S2, the added amount is calculated according to 3% of the first raw material.

[0031] For the "ultrasonic treatment" described in S2, the parameters are set to an ultrasonic frequency of 40 kHz, a treatment time of 1 hour, and an ultrasonic power density of 0.5 W / cm 3 ;

[0032] For the vacuum drying described in S2, the parameter settings are a drying temperature of 80 °C, a pressure of < 10 kPa during drying, and a drying time of 12 hours.

[0033] Furthermore, for the stirring until complete dissolution at a certain temperature described in S3, the temperature is controlled at 45 - 55 °C;

[0034] For the stirring described in S3, the parameter settings are a stirring rate of 500 rpm and a stirring time of 10 minutes.

[0035] Furthermore, the multi - stage dispersion and blending process described in S3 includes pre - mixing and dispersion using a high - speed shear disperser, three - roll grinding, high - pressure micro - jetting, and ultrasonic treatment in sequence.

[0036] Furthermore, for the pre - mixing and dispersion using the high - speed shear disperser, the set rotational speed is 3000 rpm and the treatment time is 30 minutes;

[0037] For the three - roll grinding, the set gap is 10 μm and the cycle is 3 times;

[0038] For the high - pressure micro - jetting, the set pressure is 200 MPa and the cycle is 5 times;

[0039] For the ultrasonic treatment, the set frequency is 40 kHz and the power density is 1 W / cm 3 , and the treatment time is 30 minutes.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) Through the copolymerization modification of the silicone flexible segment (Si - O - Si) and the rigid polyimide backbone in the present invention, the high - temperature resistance of the ink is significantly improved. And by surface grafting of silicon carbide (SiC) nanoparticles with KH560 silane coupling agent to form Si - O - C covalent bonds, the interfacial strength is enhanced. At the same time, the introduction of fluorinated polymers constructs a low - surface - energy hydrophobic layer to inhibit water molecule penetration.

[0042] (2) Through the molecular design of the silicone - PI copolymer in the present invention, the short - term temperature resistance reaches 650 °C. In addition, the three - roll grinding and high - pressure micro - jetting synergistic dispersion technology of silicon carbide nanoparticles forms a dense cross - linked network to improve the ink performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is the process flow chart of the preparation of the polyimide - silicon carbide high - adhesion and moisture - resistant ink of the present invention;

[0044] Figure 2 It is the Fourier transform infrared spectroscopy test result chart of the silicone - modified polyimide of the present invention;

[0045] Figure 3This is a comparison chart of the damp heat resistance test results of the samples made from the ink of the present invention. Detailed Embodiments

[0046] The following embodiments further explain and illustrate the technical solutions of the present invention. It should be specifically noted that each detailed embodiment is a specific implementation and explanation of the technical solution, and should not be regarded as a limitation on the protection scope of the present invention. Those of ordinary skill 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. Such modifications or substitutions do not change the essence of the corresponding technical solutions and do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention.

[0047] The present invention provides a polyimide-silicon carbide high adhesion damp heat resistant ink and its preparation process. The ink composition includes: 40-60 parts of siloxane-modified polyimide, 5-15 parts of surface-modified silicon carbide nanoparticles, 5-10 parts of hydrophobic fluorinated polymer, 20-40 parts of mixed solvent, 0.5 part of dispersant, and 0.5 part of defoamer; as shown in the Figure 1 following, its detailed preparation steps include:

[0048] 1. Synthesis of siloxane-modified polyimide:

[0049] 1.1 Selection of monomers and preparation of prepolymer

[0050] - Pretreatment of raw materials

[0051] The raw material monomers used in the synthesis of siloxane-modified polyimide include fluorinated diamine monomers. The fluorinated diamine monomer is selected as 4,4'-diaminodiphenyl ether-3,3'-bis(trifluoromethyl) (TFMB). The -CF3 group in its molecule can improve the hydrophobicity and solvent resistance of the resin; another raw material monomer is selected as a siloxane prepolymer (PDMS-PAA). The prepolymer is synthesized by mixing terminal amino poly(dimethylsiloxane) (PDMS, Mn = 2000-5000) and pyromellitic dianhydride (PMDA) at a molar ratio of 1:0.8-1:1.2, and stirring and reacting at 80°C for 4 hours under nitrogen protection to form a polyamic acid (PAA) solution. The viscosity of the reaction system is controlled at 500-1000 mPa·s, and the viscosity is measured using a Brookfield viscometer.

[0052] It should be noted that the addition ratio of PMDA should be in an excess of 10%-20%. In addition to ensuring the full reaction of the terminal amino group of PDMS, it can also avoid the residual of unreacted PDMS chain segments; on the other hand, by adjusting the molar ratio of PDMS and PMDA, it can also play a role in controlling the uniformity of the distribution of siloxane segments in the copolymer.

[0053] 1.2 Copolycondensation reaction

[0054] In the co-condensation polymerization stage, the reactions at different temperature stages are controlled. In the low-temperature condensation stage, it is preheated to 80°C, and the PDMS-PAA prepolymer and TFMB monomer are dissolved in N-methylpyrrolidone (NMP) at a molar ratio of 1:1, with the solid content controlled at 20-25%. Then it is gradually heated to 150°C and reacted for 2 hours to form a polyamic acid containing siloxane (Si-PAA) intermediate; in the high-temperature imidization stage, under nitrogen protection, it is first heated to 280°C at a rate of 5°C / min and kept at a constant temperature for 1 hour, and then heated to 320°C at a rate of 2°C / min and reacted for 2 hours. Through the thermal imidization reaction, Si-PAA dehydrates to form an imide ring, and at the same time, the siloxane chain segment forms a chemical bond with the polyimide main chain.

[0055] When under nitrogen protection, it is necessary to ensure that the oxygen content is <50 ppm to prevent the oxidation degradation of the polyimide main chain at high temperatures; vacuum treatment should be carried out in the later stage of the reaction, and the vacuum degree is controlled below 10-3 MPa to facilitate the removal of residual NMP and avoid bubble defects.

[0056] In the above steps, the introduction of siloxane is mainly based on its ability to increase the flexibility of the overall structure and enhance the high-temperature resistance of the product through the coordination effect. Specifically, based on the basic properties of the Si-O-Si bond in PDMS, which is different from the C-C bond, it can endow the chain segment with higher free volume and rotational freedom. The microphase separation structure of the siloxane chain segment and the polyimide main chain can also reduce the internal stress to about one-fifth of the pure polyimide structure; in addition, the siloxane chain segment has the characteristic of being easily enriched on the material surface, which can improve the adhesion to the material.

[0057] In terms of improving the high-temperature resistance, the PDMS chain segment will oxidize to form a dense SiO2 layer above 400°C, which plays a role in blocking the diffusion of oxygen to the inside; it can assist the polyimide aromatic ring structure to maintain the integrity of the skeleton under the impact of short-term high heat (>550°C); on the other hand, the strong electronegativity of the fluorine-containing group (-CF3) will inhibit the movement of the molecular chain and can improve the glass transition temperature of the material to a certain extent.

[0058] As shown in the Figure 2 attachment, the figure shows the Fourier transform infrared spectroscopy test results (after removing the solvent) of the siloxane-modified polyimide. 1710 cm -1 is the asymmetric stretching vibration of C=O in the imide ring, and 1258 m -1 is the symmetric bending vibration of Si-CH3 in PDMS. The coexistence of the two proves the formation of the copolymer structure; in addition, the peak in the range of 1775-1785 cm -1 is also caused by the stretching vibration of the carbonyl group. Compared with the empirical spectrum of pure polyimide, the peak position shifts to a higher wavenumber, indicating that the siloxane chain segment changes the local electron cloud density; 1710 cm -1 and 1258 m-1 The peak intensity ratio also roughly meets the added ratio.

[0059] 2. Silicon carbide surface modification

[0060] 2.1 Pretreatment and coupling agent selection

[0061] - Raw material preparation

[0062] Silicon carbide particle selection: Use β-SiC nanoparticles with a particle size of 30 to 50 nm and a large specific surface area (>50m 2 / g), the surface hydroxyl group (Si-OH) density is high (about 3 ~ 5OH / nm 2 );

[0063] Solvent selection: Ethanol (purity > 99.9%) is used as the dispersion medium. It has moderate polarity and can promote the hydrolysis of the coupling agent while preventing the oxidation of SiC particles.

[0064] Coupling agent selection: Silane coupling agent KH560 (γ-glycidyloxypropyltrimethoxysilane), whose molecular structure contains siloxane groups (bonded with SiC) and epoxy groups (reacting with resin), achieving dual-functional interface bridging.

[0065] —Dispersing and coupling agent addition

[0066] SiC nanoparticles were dispersed in ethanol at a solid-liquid ratio of 1:20 (w / v) and magnetically stirred (500 rpm) for 30 min to initially break up soft agglomerates;

[0067] 3% KH560 (based on the mass of SiC) was added. This concentration was optimized to cover approximately 80% of the active sites on the SiC surface and avoid self-aggregation of excess coupling agent.

[0068] 2.2 Ultrasonic dispersion and drying

[0069] - Ultrasonic treatment

[0070] The dispersed solution was treated with a 40kHz ultrasonic cleaner for 1 hour at a power density of 0.5W / cm 3 ;Use the ultrasonic cavitation effect to generate local high temperature and high pressure, and mechanical shear force to destroy SiC hard agglomerates, while promoting the migration and adsorption of KH560 molecules to the particle surface.

[0071] - Vacuum drying

[0072] The mixture was dried under vacuum at 80°C (pressure <10 kPa) for 12 h to completely remove residual ethanol and hydrolysis by-products. A gradient temperature increase (25°C → 80°C / h) was used to avoid local overheating that could lead to decomposition of the coupling agent.

[0073] In the above steps, KH560 promotes the hydrolysis of methoxy (-OCH3) through hydrolysis reaction to generate silanol (-SiOH), which improves the activity and facilitates the condensation with the hydroxyl groups on the SiC surface. As a result, the hydroxyl groups (Si-OH) on the SiC surface and the silanol (Si-OH) of KH560 undergo dehydration condensation to form Si-O-Si covalent bonds, with tight adsorption, which is beneficial to subsequent reactions. In addition, the Zeta potential on the surface of modified SiC increases, and the combined action with the thick steric hindrance layer provided by the long chain (C3H6-O-) of KH560 can effectively inhibit agglomeration.

[0074] To verify the effect of dispersion stability, a long-term dispersion stability comparison was carried out for the modified and unmodified SiC dispersions. The specific test methods and conditions are as follows:

[0075] —Sample preparation

[0076] Take the surface-modified SiC nanoparticles (modified with KH560) and disperse them in deionized water (pH = 7) at a mass fraction of 1%, and stir magnetically (300 rpm) for 30 minutes to ensure uniform initial dispersion.

[0077] The unmodified SiC nanoparticles were dispersed under the same conditions as the control group.

[0078] —Instrument settings

[0079] The test equipment used is Malvern Zetasizer Nano ZS, which has a dynamic light scattering DLS mode and is equipped with a He-Ne laser.

[0080] —Test parameters

[0081] Temperature control: 25.0 ± 0.1 °C;

[0082] Sample cell: disposable polystyrene cuvette with an optical path of 10 mm;

[0083] Detection time: Each sample was measured 3 times repeatedly, and the acquisition time for each measurement was 60 seconds.

[0084] —Long-term monitoring process

[0085] Time node: Starting from the completion of dispersion, samples were taken and detected at a fixed time every day for 25 days;

[0086] Sample storage: The dispersion was stored in a sealed container in a constant temperature and light-proof environment at 25 °C to avoid external contamination or evaporation;

[0087] Data recording: Record the D90 (the particle size of 90% of the particles is less than this value) and the polydispersity index (PDI) for each measurement.

[0088] —Sedimentation observation

[0089] Visual method: Inject the dispersion liquid into a transparent glass tube. After standing still, record the height from the liquid surface to the precipitation layer with a digital camera.

[0090] Centrifugation method: Take 10 mL of the dispersion liquid, centrifuge it at 3000 rpm for 15 minutes, weigh the mass of the precipitate at the bottom of the centrifuge tube, and calculate the sedimentation rate: precipitate mass / initial mass × 100%.

[0091] The test results are shown in Table 1. The change rate of D90 of the modified SiC dispersion liquid is <5%, the PDI is always <0.25, and there is no precipitation layer in the direct apparent properties. Compared with the unmodified SiC dispersion liquid, its dispersion stability has been significantly improved.

[0092] Table 1 Comparison table of dispersion stability test between the modified group and the control group of SiC nanoparticles

[0093]

[0094] 3. Ink blending and dispersion

[0095] 3.1 Solvent system construction

[0096] — Solvent ratio optimization

[0097] Mix NMP and γ-butyrolactone (GBL) in a volume ratio of 7:3 to form a composite solvent system; gradually add 40 - 60 wt% of silicone-modified polyimide, stir until completely dissolved, and control the temperature at 50 ± 5 °C; then sequentially add 5 - 15 wt% of modified silicon carbide (SiC) nanoparticles and 5 - 10 wt% of polytetrafluoroethylene (PTFE) micro-powder to form a premixed slurry.

[0098] — Functional additive addition

[0099] Add 0.5 wt% of BYK-dispersant (polyurethane polymer) and 0.5 wt% of defoamer (BYK-066N) to the premixed slurry to improve dispersion stability and eliminate bubbles; then stir, set the stirring rate at 500 rpm, and set the stirring time at 10 minutes to ensure that the additives are evenly adsorbed on the particle surface.

[0100] In the above solvent system, the high polarity of NMP can effectively dissolve the polyimide resin to form a continuous phase; while the low viscosity of GBL can reduce the system viscosity, improve the fluidity of the slurry, and at the same time inhibit solvent volatilization, and the two solvents form a synergistic effect.

[0101] 3.2 Multi-stage dispersion and blending

[0102] — Premixed dispersion

[0103] Pre - mixing and dispersion were carried out using a high - speed shear disperser. The rotation speed was set at 3000 rpm, and the treatment time was 30 minutes. The soft aggregates of SiC and PTFE were broken by pre - mixing and dispersion to form a uniform slurry.

[0104] — Nano - scale fine crushing

[0105] First, three - roll grinding was carried out. The gap was set at 10 μm, and it was circulated 3 times. The shear rate reached 10 4 s -1 ; Then, high - pressure micro - jet was carried out. The pressure was set at 200 MPa and it was circulated 5 times. During the above - mentioned treatment process, first, the hard aggregates were crushed by the high shear force in the slit between the rolls. In the laminar shear field of three - roll grinding, the shear stress received by the particles can be expressed as: τ = η·γ, where η is the viscosity of the slurry and γ is the shear rate. The ultra - high shear rate can make the aggregates fully depolymerize in a short time; Then, the high - speed jet and the cavitation effect of the collision chamber were used to further refine the particles. The high - pressure micro - jet breaks finer particles through the dual action of turbulent kinetic energy (ε = ΔP / ρ, ρ is the density of the slurry) and cavitation shock wave.

[0106] — Ultrasonic - assisted homogenization

[0107] Finally, ultrasonic treatment was used to form local high temperature and high pressure due to the rupture of cavitation bubbles, further dispersing the residual aggregates. The ultrasonic frequency was set at 40 kHz, and the ultrasonic power density was 1 W / cm 3 , and the treatment time was 30 minutes.

[0108] Through multi - stage dispersion and blending, a functional ink system with high solid content, stable dispersion, and low viscosity was obtained. Its performance was further verified by testing its particle size distribution and centrifugal stability; The method for testing the particle size distribution refers to the relevant testing method in "2.2 Ultrasonic Dispersion and Drying" above. The centrifugal stability test is to centrifuge the prepared ink at a rotation speed of 3000 rpm for 30 minutes and observe whether there is obvious stratification. The test results are shown in Table 2:

[0109] Table 2 Ink performance test table after multi - stage dispersion and blending

[0110]

[0111] Example 1

[0112] The polyimide - silicon carbide high - adhesion and moisture - resistant ink and its preparation process are as follows:

[0113] The ink composition includes: 50 parts of siloxane - modified polyimide, 10 parts of surface - modified silicon carbide nanoparticles, 9 parts of hydrophobic fluorinated polymer, 30 parts of mixed solvent, 0.5 part of dispersant, and 0.5 part of defoamer.

[0114] The preparation process includes:

[0115] S1: First, preheat the reaction environment to 80 °C. Dissolve the PDMS-PAA prepolymer and TFMB monomer in NMP at a molar ratio of 1:1, and control the solid content at 20 - 25%. Gradually raise the temperature to 150 °C and react for another 2 hours to generate the Si-PAA intermediate. Under nitrogen protection, raise the temperature to 280 °C and keep it constant for 1 hour, then raise the temperature to 320 °C and react for 2 hours. Finally, perform vacuum treatment to form the silicone-modified polyimide.

[0116] S2: Disperse the SiC nanoparticles in ethanol at a solid-liquid ratio of 1:20 (w / v), stir magnetically (500 rpm) for 30 minutes, then add 3% KH560 (based on the mass of SiC). Use a 40 kHz ultrasonic cleaner to treat the dispersion solution for 1 hour, with a power density of 0.5 W / cm 3 , and then vacuum dry (pressure < 10 kPa) at 80 °C for 12 hours to obtain the surface-modified silicon carbide nanoparticles.

[0117] S3: Use a composite solvent system made by mixing NMP and γ-butyrolactone (GBL) at a volume ratio of 7:3. Gradually add the silicone-modified polyimide and stir until completely dissolved, with the temperature controlled at 50 ± 5 °C. Then, sequentially add the surface-modified silicon carbide nanoparticles and PTFE micro-powder to form a premixed slurry. Add a dispersant and an antifoaming agent to the premixed slurry and stir. Set the stirring rate to 500 rpm and the stirring time to 10 minutes. Then, use a high-speed shear disperser for premixed dispersion, set the rotation speed to 3000 rpm, and the treatment time to 30 minutes. Then, perform three-roll grinding, set the gap to 10 μm, and cycle 3 times. Then, perform high-pressure microfluidization, set the pressure to 200 MPa, and cycle 5 times. Finally, perform ultrasonic treatment, set the frequency to 40 kHz, and the power density to 1 W / cm 3 , and the treatment time is 30 minutes.

[0118] Example 2

[0119] The polyimide-silicon carbide high-adhesion and moisture-resistant and heat-resistant ink and its preparation process are as follows:

[0120] The ink composition includes: 40 parts of silicone-modified polyimide, 10 parts of surface-modified silicon carbide nanoparticles, 9 parts of hydrophobic fluorinated polymer, 40 parts of mixed solvent, 0.5 part of dispersant, and 0.5 part of antifoaming agent.

[0121] The preparation process includes:

[0122] S1: First, preheat the reaction environment to 80 °C. Dissolve the PDMS-PAA prepolymer and TFMB monomer in NMP at a molar ratio of 1:1, and control the solid content at 20 - 25%. Gradually raise the temperature to 150 °C and react for another 2 hours to form the Si-PAA intermediate. Under nitrogen protection, raise the temperature to 280 °C and keep it constant for 1 hour, then raise the temperature to 320 °C and react for 2 hours. Finally, perform vacuum treatment to form the silicone-modified polyimide.

[0123] S2: Disperse the SiC nanoparticles in ethanol at a solid-liquid ratio of 1:20 (w / v), stir magnetically (500 rpm) for 30 minutes, then add 3% KH560 (based on the mass of SiC). Use a 40 kHz ultrasonic cleaner to treat the dispersion solution for 1 hour, with a power density of 0.5 W / cm 3 , and then vacuum dry (pressure < 10 kPa) at 80 °C for 12 hours to obtain the surface-modified silicon carbide nanoparticles.

[0124] S3: Use a composite solvent system made by mixing NMP and γ-butyrolactone (GBL) at a volume ratio of 7:3. Gradually add the silicone-modified polyimide and stir until completely dissolved, controlling the temperature at 50 ± 5 °C. Then, sequentially add the surface-modified silicon carbide nanoparticles and PTFE micro-powder to form a premixed slurry. Add a dispersant and an antifoaming agent to the premixed slurry and stir. Set the stirring rate to 500 rpm and the stirring time to 10 minutes. Then, use a high-speed shear disperser for premixed dispersion, set the rotation speed to 3000 rpm, and the treatment time to 30 minutes. Then, perform three-roll grinding, set the gap to 10 μm, and cycle 3 times. Then, perform high-pressure microfluidization, set the pressure to 200 MPa, and cycle 5 times. Finally, perform ultrasonic treatment, set the frequency to 40 kHz, and the power density to 1 W / cm 3 , and the treatment time is 30 minutes.

[0125] Example 3

[0126] The polyimide-silicon carbide high-adhesion and moisture-resistant and heat-resistant ink and its preparation process are as follows:

[0127] The ink composition includes: 60 parts of silicone-modified polyimide, 10 parts of surface-modified silicon carbide nanoparticles, 9 parts of hydrophobic fluorinated polymer, 20 parts of mixed solvent, 0.5 part of dispersant, and 0.5 part of antifoaming agent.

[0128] The preparation process includes:

[0129] S1: First, preheat the reaction environment to 80 °C. Dissolve the PDMS-PAA prepolymer and TFMB monomer in NMP at a molar ratio of 1:1, and control the solid content at 20-25%. Gradually raise the temperature to 150 °C and react for another 2 hours to generate the Si-PAA intermediate. Under nitrogen protection, raise the temperature to 280 °C and keep it at a constant temperature for 1 hour, then raise the temperature to 320 °C and react for 2 hours. Finally, perform vacuum treatment to form the silicone-modified polyimide.

[0130] S2: Disperse the SiC nanoparticles in ethanol at a solid-liquid ratio of 1:20 (w / v), stir magnetically (500 rpm) for 30 minutes, then add 3% KH560 (calculated based on the mass of SiC). Use a 40 kHz ultrasonic cleaner to treat the dispersion solution for 1 hour, with a power density of 0.5 W / cm 3 , and then vacuum dry (pressure < 10 kPa) at 80 °C for 12 hours to obtain the surface-modified silicon carbide nanoparticles.

[0131] S3: Use a composite solvent system made by mixing NMP and γ-butyrolactone (GBL) at a volume ratio of 7:3. Gradually add the silicone-modified polyimide and stir until completely dissolved, controlling the temperature at 50 ± 5 °C. Then, sequentially add the surface-modified silicon carbide nanoparticles and PTFE micro-powder to form a premixed slurry. Add a dispersant and an antifoaming agent to the premixed slurry and stir. Set the stirring rate to 500 rpm and the stirring time to 10 minutes. Then, use a high-speed shear disperser for premixed dispersion, set the rotation speed to 3000 rpm, and the treatment time to 30 minutes. Then, perform three-roll grinding, set the gap to 10 μm, and cycle 3 times. Then, perform high-pressure microfluidization, set the pressure to 200 MPa, and cycle 5 times. Finally, perform ultrasonic treatment, set the frequency to 40 kHz, and the power density to 1 W / cm 3 , and the treatment time is 30 minutes.

[0132] Example 4

[0133] A polyimide-silicon carbide high-adhesion and moisture-resistant and heat-resistant ink and its preparation process are as follows:

[0134] The ink composition includes: 50 parts of silicone-modified polyimide, 15 parts of surface-modified silicon carbide nanoparticles, 4 parts of hydrophobic fluoropolymer, 30 parts of mixed solvent, 0.5 part of dispersant, and 0.5 part of antifoaming agent.

[0135] The preparation process includes:

[0136] S1: First, preheat the reaction environment to 80 °C. Dissolve the PDMS-PAA prepolymer and TFMB monomer in NMP at a molar ratio of 1:1, and control the solid content at 20 - 25%. Gradually raise the temperature to 150 °C and react for another 2 hours to generate the Si-PAA intermediate. Under nitrogen protection, raise the temperature to 280 °C and keep it constant for 1 hour, then raise the temperature to 320 °C and react for 2 hours. Finally, perform vacuum treatment to form the silicone-modified polyimide.

[0137] S2: Disperse the SiC nanoparticles in ethanol at a solid-liquid ratio of 1:20 (w / v), stir magnetically (500 rpm) for 30 minutes, then add 3% KH560 (calculated based on the mass of SiC). Use a 40 kHz ultrasonic cleaner to treat the dispersion solution for 1 hour, with a power density of 0.5 W / cm 3 , and then vacuum dry (pressure < 10 kPa) at 80 °C for 12 hours to obtain the surface-modified silicon carbide nanoparticles.

[0138] S3: Use a composite solvent system made by mixing NMP and γ-butyrolactone (GBL) at a volume ratio of 7:3. Gradually add the silicone-modified polyimide and stir until completely dissolved, with the temperature controlled at 50 ± 5 °C. Then, sequentially add the surface-modified silicon carbide nanoparticles and PTFE micropowder to form a premixed slurry. Add a dispersant and an antifoaming agent to the premixed slurry and stir. Set the stirring rate to 500 rpm and the stirring time to 10 minutes. Then, use a high-speed shear disperser for premixed dispersion, set the rotation speed to 3000 rpm, and the treatment time to 30 minutes. Then, perform three-roll grinding with a gap set at 10 μm and cycle 3 times. Then, perform high-pressure microfluidization, set the pressure to 200 MPa, and cycle 5 times. Finally, perform ultrasonic treatment, set the frequency to 40 kHz, and the power density to 1 W / cm 3 , and the treatment time is 30 minutes.

[0139] Example 5

[0140] A polyimide-silicon carbide high-adhesion and moisture-resistant ink and its preparation process are as follows:

[0141] The ink composition includes: 50 parts of silicone-modified polyimide, 5 parts of surface-modified silicon carbide nanoparticles, 9 parts of hydrophobic fluoropolymer, 35 parts of mixed solvent, 0.5 part of dispersant, and 0.5 part of antifoaming agent.

[0142] The preparation process includes:

[0143] S1: First, preheat the reaction environment to 80 °C. Dissolve the PDMS-PAA prepolymer and TFMB monomer in NMP at a molar ratio of 1:1, and control the solid content at 20-25%. Gradually raise the temperature to 150 °C and react for another 2 hours to generate the Si-PAA intermediate. Under nitrogen protection, raise the temperature to 280 °C and keep it at a constant temperature for 1 hour, then raise the temperature to 320 °C and react for 2 hours. Finally, perform vacuum treatment to form the silicone-modified polyimide.

[0144] S2: Disperse the SiC nanoparticles in ethanol at a solid-liquid ratio of 1:20 (w / v), stir magnetically (500 rpm) for 30 minutes, then add 3% KH560 (calculated based on the mass of SiC). Use a 40 kHz ultrasonic cleaner to treat the dispersion solution for 1 hour, with a power density of 0.5 W / cm 3 , and then vacuum dry (pressure < 10 kPa) at 80 °C for 12 hours to obtain the surface-modified silicon carbide nanoparticles.

[0145] S3: Prepare a composite solvent system by mixing NMP and γ-butyrolactone (GBL) at a volume ratio of 7:3. Gradually add the silicone-modified polyimide and stir until completely dissolved, controlling the temperature at 50 ± 5 °C. Then, sequentially add the surface-modified silicon carbide nanoparticles and PTFE micropowder to form a premixed slurry. Add a dispersant and an antifoaming agent to the premixed slurry and stir. Set the stirring rate to 500 rpm and the stirring time to 10 minutes. Then, use a high-speed shear disperser for premixed dispersion, set the rotation speed to 3000 rpm, and the treatment time to 30 minutes. Then, perform three-roll grinding, set the gap to 10 μm, and cycle 3 times. Then, perform high-pressure microfluidization, set the pressure to 200 MPa, and cycle 5 times. Finally, perform ultrasonic treatment, set the frequency to 40 kHz, and the power density to 1 W / cm 3 , and the treatment time is 30 minutes.

[0146] Comparative Example 1

[0147] Polyimide-silicon carbide high-adhesion and moisture- and heat-resistant ink and its preparation process are as follows:

[0148] Refer to the preparation steps of Example 1, except that in step S1, TFMB and pyromellitic dianhydride (PMDA) are used for reaction to generate polyimide, which is polyimide without silicone modification.

[0149] Comparative Example 2

[0150] Polyimide-silicon carbide high-adhesion and moisture- and heat-resistant ink and its preparation process are as follows:

[0151] Refer to the preparation steps of Example 1, except that the modification of SiC nanoparticles in step S2 is cancelled, and directly proceed to step S3.

[0152] Experimental Example 1

[0153] Samples of the inks obtained in Examples 1-5 and Comparative Examples 1-2 were taken and test samples were prepared. The temperature resistance of the samples was determined with reference to the national standard "GBT 1735-2009 Determination of Heat Resistance of Paints and Varnishes"; the damp heat resistance of the samples was determined with reference to the national standard "GB / T 2423.3-2016 Damp Heat, Steady State Test Method"; the adhesion of the samples was tested with reference to the standard "ASTM D3359 Adhesion of Organic Coatings by Scratch Test", and the adherend substrate used was 316L stainless steel substrate.

[0154] Through the comparative experiment of Experimental Example 1, the results are statistically as follows:

[0155] Table 3 Comparison table of experimental results of Examples 1-5 and Comparative Examples 1-2

[0156]

[0157] Combined with the attached Figure 3 , it can be seen from the above comparison results that in Comparative Example 1, the polyimide was not copolymer-modified with siloxane, and the Si-O-Si bond was not introduced into the system, resulting in insufficient chain segment flexibility in the system. Under high-temperature impact, due to the lack of the dense SiO2 layer that siloxane could originally form on the surface, the heat-blocking layer was not achieved, resulting in a decrease in the resistance of the prepared ink system to high temperature. Also, due to the lack of the structure in which siloxane segments were enriched on the material surface, the adhesion of the system was also decreased; in Comparative Example 2, SiC nanoparticles were not modified, which made it impossible to achieve good dispersion of SiC nanoparticles in the subsequent addition to polyimide, affecting the overall performance of the prepared ink system, especially in terms of adhesion and resistance to damp heat. It was unable to construct a better hydrophobic layer on the surface of the system, and the improvement of the mutual adsorption ability between the ink and the printing carrier interface was also limited.

Claims

1. Polyimide-silicon carbide high adhesion and moisture and heat resistant ink, characterized in that, It contains the following components in parts by mass: 40 - 60 parts of silicone-modified polyimide, 5 - 15 parts of surface-modified silicon carbide nanoparticles, 5 - 10 parts of hydrophobic fluorinated polymer, 20 - 40 parts of mixed solvent, 0.5 part of dispersant, and 0.5 part of defoamer.

2. The polyimide-silicon carbide high-adhesion and moisture and heat resistant ink according to claim 1, wherein The silicone-modified polyimide is prepared by co-condensation polymerization of 4,4'-diaminodiphenyl ether-3,3'-bis(trifluoromethyl) and a silicone prepolymer, and the silicone prepolymer is prepared from amino-terminated polydimethylsiloxane and pyromellitic dianhydride.

3. The polyimide-silicon carbide high-adhesion and moisture and heat resistant ink according to claim 1, wherein The surface-modified silicon carbide nanoparticles are modified with γ-glycidoxypropyltrimethoxysilane.

4. The polyimide-silicon carbide high-adhesion and moisture and heat resistant ink according to claim 1, characterized in that The hydrophobic fluorinated polymer is polytetrafluoroethylene; The mixed solvent is composed of N-methylpyrrolidone and γ-butyrolactone mixed in a volume ratio of 7:3; The dispersant is BYK-dispersant, and the defoamer is BYK-066N.

5. The preparation process of the polyimide-silicon carbide high-adhesion and moisture and heat resistant ink according to any one of claims 1 to 4, characterized in that, It includes the following steps: S1: After preheating, dissolve the raw materials for preparing the silicone-modified polyimide in a solvent according to a certain molar ratio, control the solid content range, gradually raise the temperature to a certain temperature for reaction to form a polyamic acid intermediate containing silicone, then under nitrogen protection, raise the temperature to a certain temperature for heat preservation, and then raise the temperature to a certain temperature for reaction for a period of time, and finally perform vacuum treatment to form the silicone-modified polyimide; S2: Disperse the first raw material for preparing the surface-modified silicon carbide nanoparticles in a solvent according to a ratio, stir magnetically, then add the second raw material, perform ultrasonic treatment, and then perform vacuum drying to obtain the surface-modified silicon carbide nanoparticles; S3: Gradually add the silicone-modified polyimide to the mixed solvent, stir at a certain temperature until completely dissolved, then sequentially add the surface-modified silicon carbide nanoparticles and the hydrophobic fluorinated polymer to form a premixed slurry, add the dispersant and defoamer to the premixed slurry, stir, and use a multi-stage dispersion and blending process to obtain the polyimide-silicon carbide high-adhesion and moisture and heat resistant ink.

6. The preparation process of the polyimide-silicon carbide high-adhesion and moisture and heat resistant ink according to claim 5, characterized in that The preheating in S1 is set to reach a temperature of 80°C; The certain molar ratio in S1 is a 1:1 molar ratio; The control of the solid content range in S1 is controlled within the range of 20 - 25%; After gradually raising the temperature to a certain temperature for reaction in S1, it is set to gradually raise the temperature to 150°C and then react for 2 hours; After raising the temperature to a certain temperature for heat preservation under nitrogen protection in S1, it is set to raise the temperature to 280°C under nitrogen protection for constant temperature heat preservation for 1 hour; Then raising the temperature to a certain temperature for reaction for a period of time in S1 is set to raise the temperature to 320°C and react for 2 hours.

7. The preparation process of the polyimide-silicon carbide high-adhesion and moisture and heat resistant ink according to claim 5, characterized in that The dispersion in ethanol according to a ratio in S2 is set to disperse in a solvent at a solid-liquid ratio of 1:20; The magnetic stirring in S2 has the parameters set to stir at a speed of 500 rpm for 30 minutes; The addition of the second raw material in S2 is calculated according to 3% of the first raw material. The ultrasonic treatment described in S2 has parameters set as an ultrasonic frequency of 40 kHz, a treatment time of 1 hour, and an ultrasonic power density of 0.5 W / cm 3 ; The vacuum drying described in S2 has parameter settings of a drying temperature of 80 °C, a pressure of < 10 kPa during drying, and a drying time of 12 hours.

8. The preparation process of the polyimide-silicon carbide high-adhesion moisture and heat resistant ink according to claim 5, characterized in that Stirring is carried out at a certain temperature until completely dissolved, and the temperature is controlled at 45 - 55 °C; Stirring is carried out as described in S3, with parameter settings of a stirring rate of 500 rpm and a stirring time of 10 minutes.

9. The preparation process of the polyimide-silicon carbide high adhesion and moisture and heat resistant ink according to claim 5, characterized in that, The multi-stage dispersion and blending process described in S3 includes pre-mixing and dispersion, three-roll grinding, high-pressure microfluidization, and ultrasonic treatment in sequence using a high-speed shear disperser.

10. The preparation process of the polyimide-silicon carbide high-adhesion and moisture and heat resistant ink according to claim 9, characterized in that, The parameter settings for the high-speed shear disperser to carry out pre-mixing and dispersion, three-roll grinding, high-pressure microfluidization, and ultrasonic treatment are respectively: When the high-speed shear disperser carries out pre-mixing and dispersion, the set rotation speed is 3000 rpm and the treatment time is 30 minutes; For the three-roll grinding, the gap is set at 10 μm and the cycle is 3 times; For the high-pressure microfluidization, the set pressure is 200 MPa and the cycle is 5 times; The ultrasonic treatment is set at a frequency of 40 kHz, a power density of 1 W / cm 3 , and a treatment time of 30 minutes.

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