A fire-retardant coating for PC substrates and a method for preparing the same

Abstract

This invention relates to the field of coatings, specifically to a flame-retardant coating for PC substrates and its preparation method, which is obtained through the following steps: by weight, step (1) preparation of ferrite microspheres; step (2) preparation of a compatible base material; step (3) mixing: ferrite microspheres are added to the compatible base material in step (2), stirred evenly, and then silane pre-modified carbon nanotubes and hydrophobic silica are added, dispersed, an organotin catalyst is added, degassing is performed, and filtration is carried out to obtain a flame-retardant coating for PC substrates. This solution achieves multiple functional characteristics for each component through the synergistic complementarity between components and the control of the process, simultaneously achieving waterproof, fireproof, stealth, and heat insulation effects with a single coating.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coatings, in particular to a flame-retardant coating for PC substrates and a preparation method thereof. BACKGROUND

[0002] There is a demand for multifunctionalization of current polycarbonate (PC) substrate surface functionalization coating technology. Traditional flame-retardant coatings (such as intumescent acrylic systems) can achieve V-0 level flame retardation by forming an intumescent carbon layer with ammonium polyphosphate (APP), but it is difficult to balance electromagnetic shielding effectiveness and thermal insulation. Existing solutions mostly use a functional superposition strategy - for example, first coating an iron oxide-containing wave-absorbing layer, and then covering an intumescent flame-retardant layer - resulting in a total coating thickness of more than 500 μm, which not only reduces the light transmittance and mechanical flexibility of the PC substrate, but also causes peeling failure due to poor interlayer compatibility. In addition, lightweight fillers can improve thermal insulation, but their surface inertness easily leads to weak resin interface bonding, which can easily cause water penetration and peeling in a humid environment. At present, most coatings for PC are developed for single function, for example, CN117417658A, a flame-retardant coating applied to a PC substrate of a mobile phone, includes the following components: an adhesion agent A component, an adhesion agent B component, an acrylic base paint, a curing agent, a diluent, a pre-prepared flame-retardant slurry, a flame-retardant mid-coat paint, a flame-retardant topcoat paint, and an ultraviolet light curing coating. The flame-retardant coating prepared by the present application for the PC substrate of the mobile phone shell passes the GB-T5169.5 needle flame test, that is, after applying a flame to the mobile phone PC shell coated with the flame-retardant coating for 120 seconds, no holes are generated on the mobile phone PC shell, greatly improving the safety and service life of the mobile phone. Therefore, developing a single-coat low-temperature curing system that integrates high flame retardation, wideband electromagnetic shielding, low thermal conductivity, and strong waterproofness is a key path to breaking through the bottleneck of multifunctional protection technology for PC substrates. SUMMARY

[0003] To achieve the above-mentioned purpose, the present application discloses a flame-retardant coating for PC substrates, which realizes multiple functional characteristics of each component through coordination and complementation between components and process control, and simultaneously realizes the effects of waterproofing, fireproofing, stealth, and thermal insulation with one coating.

[0004] The present application specifically adopts the following technical solutions:

[0005] A flame-retardant coating for PC substrates is prepared by the following steps:

[0006] by weight parts,

[0007] Step (1) ferrite microbead plating preparation: 100 parts by mass of hollow glass microbeads (particle size 20-50 μm) were placed in a fluidized bed, and argon plasma (power 150 W, flow rate 25 L / min) was introduced for 5-10 minutes for activation; then 10-15 parts by mass of nano-magnetic iron oxide, 2-2.5 parts by mass of silane coupling agent KH-550, and 0.5-1 part by mass of stearic acid were added to an ethanol aqueous solution, and ultrasonic dispersion (25 kHz, 30 minutes) was performed to obtain a modified slurry; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.3 MPa, and fluidized treatment was performed at 80±2°C for 30-40 minutes to obtain ferrite microbeads;

[0008] Step (2) compatibility base preparation: 45-50 parts by mass of phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate (APP), and 10 parts by mass of aluminum hypophosphite were stirred and dispersed to obtain a compatibility base;

[0009] Step (3) mixing: 30-35 parts by mass of ferrite microbeads were added to the compatibility base of step (2), and after uniform stirring, 2.5-3 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.5-5 parts by mass of hydrophobic silica were added, and the temperature was raised to 50±2°C for dispersion; then 5-7 parts by mass of organotin catalyst (dibutyltin dilaurate) was added, and vacuum degassing was performed at -0.1 MPa under biaxial stirring (revolution 20 rpm / rotation 800 rpm) for 40 minutes, and filtration was performed to obtain a flame-retardant coating for PC substrates.

[0010] The flame-retardant coating for PC substrates provided by the present scheme has multiple composite effects:

[0011] 1. Flame-retardant effect: The core flame-retardant effect of the present scheme mainly relies on the classic combination of ammonium polyphosphate (APP) and aluminum hypophosphite. When encountering high temperatures or flames, APP rapidly decomposes to produce polyphosphoric acid that can catalyze the dehydration and carbonization of the resin and itself, while releasing a large amount of non-combustible gas. These gases cause the molten coating to expand, forming a fluffy, oxygen- and heat-insulating foam carbon layer. Aluminum hypophosphite plays the role of a synergist, absorbing a large amount of heat when it decomposes, effectively reducing the temperature in the combustion area, and releasing phosphorus-containing free radicals that can capture active free radicals in the flame that sustain combustion, breaking the combustion chain reaction. Furthermore, the nano-magnetic iron oxide uniformly coated on the surface of the hollow glass microbeads not only catalyzes the formation of a carbon layer at high temperatures, making it more dense and more resistant to ablation, but also has a certain heat absorption and physical barrier effect. Finally, the phenyl-modified epoxy resin used has a rigid benzene ring structure, which has higher heat resistance and carbonization rate than ordinary epoxy resins, providing a more stable framework for the entire flame-retardant system.

[0012] 2. Stealth effect: The stealth effect is mainly achieved by cleverly constructing a magnetic-dielectric dual loss synergistic absorption mechanism. The core functional substance is iron oxide microbeads: The scheme firmly coats the nanometer magnetite with strong magnetic loss ability on the surface of hollow glass microbeads with dielectric loss characteristics. When the incident radar wave encounters the coating, on the one hand, it will be consumed in large quantities by the magnetic magnetite through natural resonance, eddy current loss and other mechanisms; on the other hand, the dielectric properties of the hollow glass microbead and its special hollow structure can effectively adjust the electromagnetic parameters of the coating, improve the impedance matching, and let more electromagnetic waves enter the coating instead of being reflected. The hollow structure of the microbead itself can also scatter and attenuate electromagnetic waves. The pre-dispersed carbon nanotubes added synergistically are excellent dielectric loss materials, which have a large specific surface area and a conductive network that can effectively absorb and convert electromagnetic wave energy. Using a silane coupling agent for pre-modification not only improves its dispersibility in the resin matrix, avoiding agglomeration, but also enhances its interface bonding with the matrix, ensuring that its wave-absorbing efficiency is fully utilized. The synergistic effect of magnetic iron oxide microbeads and dielectric carbon nanotubes is expected to broaden the effective wave-absorbing frequency band of the coating. Finally, although the main function of hydrophobic silica is waterproofing and thermal insulation, its nanoscale and hydrophobic properties can also subtly affect the dielectric constant distribution of the coating, assisting in optimizing the overall impedance matching and indirectly improving the wave-absorbing efficiency.

[0013] 3. Thermal insulation: Thermal insulation is based on efficiently blocking the three ways of heat transfer (conduction, convection, and radiation). The coated hollow glass microbeads, even if coated with magnetite, still maintain a hollow and sealed structure inside. The thin gas (or near vacuum) inside is a very poor thermal conductor, significantly hindering heat conduction. At the same time, the small particle size (20-50 μm) greatly limits the internal air convection. Hydrophobic nanosilica, as a key filler, has a very high specific surface area and a very fine particle size, which can fill the gaps between the microbeads. Not only is its thermal conductivity low, but more importantly, it makes the heat transfer path extremely tortuous and long. Its large surface energy also enhances phonon scattering, further suppressing solid heat conduction. Hydrophobicity ensures that even in high humidity environments, its interior and surface will not cause a significant increase in thermal conductivity due to water absorption. Finally, the low thermal conductivity of the epoxy resin matrix provides a continuous low thermal conductivity phase for the entire thermal insulation system.

[0014] 4. Waterproof: waterproof performance is realized by double lines of hydrophobic barrier and dense structure. The hydrophobic silica is specially selected, which has hydrophobicity after surface treatment, can effectively reduce the wettability of the coating surface, make it difficult for water droplets to spread and penetrate, and the surface of nano-magnetic iron oxide and carbon nanotubes is modified by silane coupling agent, which also exists in the base material. The hydrophobic alkyl chain produced by the hydrolysis of silane coupling agent covers the surface of the filler and the interface between the filler and the resin, blocks the invasion path of water molecules, and enhances the interfacial bonding force, reduces water penetration caused by interfacial defects, thus constructing a hydrophobic barrier. Strong dispersion (high speed, gradient mixing) ensures that all components are evenly distributed, and weak points caused by agglomeration are avoided; fine vacuum degassing (stages of high vacuum and high shear stirring) completely eliminates air and micro-bubbles generated by solvent evaporation during stirring, which are potential water penetration channels. The staged operation ensures the efficiency and thoroughness of degassing; strict filtration removes coarse particles or gels that may affect the continuity and density of the coating; effective low-temperature curing (organic tin catalyst) also ensures that the resin is fully cross-linked to form a solid, complete and low-porosity coating film body.

[0015] As preferred, the solid content of the slurry in step (1) is 40±2wt%.

[0016] As preferred, the phenyl-modified epoxy resin is prepared by copolymerization of bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.5-3:1.

[0017] As preferred, the organic tin catalyst is a compound of dibutyltin dilaurate and stannous octoate at a mass ratio of 1.8-2:1.

[0018] As preferred, the carbon nanotube modification method in step (1) is: immerse the carbon nanotube in 5wt% KH-550 ethanol aqueous solution, stir at 60℃ for 60 minutes, and then dry. The volume fraction of ethanol in the ethanol aqueous solution is 60-80%.

[0019] As preferred, the hydrophobic silica is fumed silica with BET 200±10m 2 / g.

[0020] As preferred, the vacuum degassing in step (3) is divided into two stages:

[0021] First stage: -0.06MPa, 15-20 minutes, 600rpm self-rotation;

[0022] Second stage: -0.10MPa, 20-30 minutes, 1000rpm self-rotation.

[0023] As preferred, the pressure during filtration is ≤0.15MPa, and the filter screen aperture is 45μm.

[0024] The scheme also provides a preparation method of the fire-retardant coating for PC substrates.

[0025] Compared with the prior art, the scheme has the advantages of:

[0026] 1. The coating can achieve the effects of waterproofing, fireproofing, stealth, and thermal insulation at the same time;

[0027] 2. Through coordination and complementation between components and process control, each component achieves multiple functional characteristics, and in particular, after the mixture of the plated ferrite microbeads and the silane coupling agent pre-modified carbon nanotubes, the electrical shielding and thermal insulation effects of the plated ferrite microbeads are ensured, and the shape of the plated ferrite microbeads in the matrix is also improved. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0029] OVERALL EMBODIMENT

[0030] A fire-retardant coating for PC substrates is prepared by the following steps:

[0031] by weight parts,

[0032] Step (1) Preparation of plated ferrite microbeads: 100 parts by mass of hollow glass microbeads with a particle size of 20-50 μm are placed in a fluidized bed, argon plasma is introduced, the power is 150 W, the flow rate is 25 L / min, and the activation time is 5-10 minutes; then 10-15 parts by mass of nano-ferroferric oxide, 2-2.5 parts by mass of silane coupling agent KH-550, and 0.5-1 part by mass of stearic acid are added to an ethanol aqueous solution (the volume fraction of ethanol is 80%), ultrasonic dispersion is performed at 25 kHz for 30 minutes to obtain a modified slurry with a solid content of 40±2 wt%; the modified slurry is atomized and sprayed into the fluidized bed at a pressure of 0.3-0.4 MPa, and fluidized treatment is performed at 80±2℃ for 30-40 minutes to obtain plated ferrite microbeads;

[0033] Step (2) Preparation of compatible base: 45-50 parts by mass of phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate (APP), and 10 parts by mass of aluminum hypophosphite are stirred and dispersed to obtain a compatible base; the phenyl-modified epoxy resin is prepared by copolymerization of bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.5-3:1 to obtain a compatible base;

[0034] Step (3) mixing: 32 parts by mass of plated ferrite microbeads were added to the compatible base material of step (2), and after uniform stirring, 2.8 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by mass of BET 205 ± 10 m 2 / g fumed silica were added, heated to 50 ± 2°C, dispersed, and then 5-7 parts by mass of organotin catalyst (a mixture of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.8-2:1) was added. The mixture was degassed under vacuum for 40 minutes with double shaft stirring, filtered under the conditions of pressure ≤0.15 MPa and filter screen aperture 45 μm to obtain a flame-retardant coating for PC substrate; the carbon nanotube modification method was as follows: the carbon nanotubes were immersed in a 5 wt% KH-550 ethanol aqueous solution, stirred at 60°C for 60 minutes, and then dried; the volume fraction of ethanol in the ethanol aqueous solution was 60-80%.

[0035] Example 1

[0036] A flame-retardant coating for PC substrate was prepared by the following steps:

[0037] Step (1) preparation of plated ferrite microbeads: 100 parts by mass of hollow glass microbeads were placed in a fluidized bed and activated by argon plasma with a power of 150 W and a flow rate of 25 L / min for 7 minutes; 12 parts by mass of nano-magnetic iron oxide, 2.2 parts by mass of silane coupling agent KH-550 and 0.7 parts by mass of stearic acid were added to an ethanol aqueous solution with a volume fraction of ethanol of 80%, and ultrasonic dispersion was performed at 25 kHz for 30 minutes to obtain a modified slurry with a solid content of 40 wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.35 MPa, and fluidized treatment was performed at 80°C for 35 minutes to obtain plated ferrite microspheres;

[0038] Step (2) preparation of compatible base material: 47 parts by mass of phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate and 10 parts by mass of aluminum hypophosphite were stirred and dispersed; the phenyl-modified epoxy resin was prepared by copolymerization of bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 2.7:1 to obtain a compatible base material;

[0039] Step (3) mixing: 32 parts by mass of plated ferrite microbeads were added to the compatible base material of step (2), and after uniform stirring, 2.8 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by mass of BET 205 ± 10 m 2fumed silica, heated to 50℃ for dispersion, 6 parts by mass of organotin catalyst was added, and under vacuum, double shaft stirring revolution 20 rpm / rotation 800 rpm, defoaming for 40 minutes, filtering under the condition of pressure 0.12 MPa, filter screen aperture 45 μm, to obtain the flame-retardant coating for PC substrate; the method for pre-modifying carbon nanotubes with silane coupling agent was as follows: the carbon nanotubes were immersed in 5wt% KH-550 ethanol aqueous solution, the volume fraction of ethanol was 70%, and after stirring at 60℃ for 60 minutes, drying; the organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate with a mass ratio of 1.9:1.

[0040] Example 2

[0041] A flame-retardant coating for PC substrate was prepared by the following steps:

[0042] Step (1) ferrite microbead plating preparation: 100 parts by mass of hollow glass microbeads were placed in a fluidized bed, and argon plasma power 150 W, flow rate 25 L / min was introduced for activation for 5 minutes; 10 parts by mass of nano-magnetic iron oxide, 2.0 parts by mass of silane coupling agent KH-550, and 0.5 parts by mass of stearic acid were added to an ethanol aqueous solution with a volume fraction of ethanol of 80%, and ultrasonic dispersion was performed at 25 kHz for 30 minutes to obtain a modified slurry with a solid content of 40wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.30 MPa, and fluidized treatment was performed at 80℃ for 30 minutes to obtain ferrite microbead plating;

[0043] Step (2) compatibility base preparation: 45 parts by mass of phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite were stirred and dispersed; the phenyl-modified epoxy resin was prepared by copolymerization of bisphenol A epoxy resin and phenyl glycidyl ether with a mass ratio of 2.5:1 to obtain a compatibility base;

[0044] Step (3) mixing: 30 parts by mass of ferrite microbead plating was added, and after uniform stirring, 2.5 parts by mass of pre-modified carbon nanotubes with silane coupling agent and 4.5 parts by mass of BET195m 2 fumed silica, heated to 50℃ for dispersion, 6 parts by mass of organotin catalyst was added, and under vacuum, double shaft stirring revolution 20 rpm / rotation 800 rpm, defoaming for 40 minutes, filtering under the condition of pressure 0.12 MPa, filter screen aperture 45 μm, to obtain the flame-retardant coating for PC substrate; the method for pre-modifying carbon nanotubes with silane coupling agent was as follows: the carbon nanotubes were immersed in 5wt% KH-550 ethanol aqueous solution, the volume fraction of ethanol was 70%, and after stirring at 60℃ for 60 minutes, drying; the organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate with a mass ratio of 1.9:1.

[0045] Example 3

[0046] A flame-retardant coating for PC substrate was prepared by the following steps:

[0047] Step (1) Ferrite microbead plating preparation: 100 parts by mass of hollow glass microbeads were placed in a fluidized bed, and argon plasma power of 150 W and flow rate of 25 L / min were introduced for 10 minutes; 15 parts by mass of nano-magnetic iron oxide, 2.5 parts by mass of silane coupling agent KH-550, and 1.0 part by mass of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80%, and ultrasonic dispersion was performed at 25 kHz for 30 minutes to obtain a modified slurry with a solid content of 40 wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.40 MPa, and fluidized treatment was performed at 80°C for 40 minutes to obtain ferrite microbeads;

[0048] Step (2) Compatibility base preparation: 50 parts by mass of phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite were stirred and dispersed; the phenyl-modified epoxy resin was prepared by copolymerization of bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 3.0:1 to obtain a compatibility base;

[0049] Step (3) Mixing: 35 parts by mass of ferrite microbeads were added to the compatibility base of step (2), and after uniform stirring, 3.0 parts by mass of silane coupling agent pre-modified carbon nanotubes and 5.0 parts by mass of BET 210 m 2 / g fumed silica were added, and the temperature was raised to 50°C for dispersion; 7 parts by mass of organic tin catalyst was added, and the double-shaft stirring was performed under vacuum to degas in two stages:

[0050] revolution 20 rpm,

[0051] First stage: -0.06 MPa, 20 minutes, rotation speed 600 rpm;

[0052] Second stage: -0.10 MPa, 30 minutes, rotation speed 1000 rpm;

[0053] The pressure was 0.15 MPa, and the filter screen aperture was 45 μm to obtain a flame-retardant coating for PC substrate; the method for pre-modifying the carbon nanotubes with silane coupling agent was as follows: the carbon nanotubes were immersed in a 5 wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 80%, and stirring was performed at 60°C for 60 minutes, followed by drying; the organic tin catalyst was a compound of dibutyltin dilaurate and stannous octoate at a mass ratio of 2.0:1.

[0054] Example 4

[0055] A flame-retardant coating for PC substrate was prepared by the following steps:

[0056] Step (1) ferrite microbead plating preparation: 100 parts by mass of hollow glass microbeads were placed in a fluidized bed, and argon plasma power 150 W, flow rate 25 L / min was introduced for 6 minutes; 11 parts by mass of nano-magnetic iron oxide, 2.1 parts by mass of silane coupling agent KH-550, and 0.6 parts by mass of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80%, and ultrasonic dispersion was performed at 25 kHz for 30 minutes to obtain a modified slurry with a solid content of 40 wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.32 MPa, and fluidized treatment was performed at 80°C for 32 minutes to obtain ferrite microbeads;

[0057] Step (2) compatibility base preparation: 48 parts by mass of phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite were stirred and dispersed; the phenyl-modified epoxy resin was prepared by copolymerization of bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.6:1 to obtain a compatibility base;

[0058] Step (3) mixing: 31 parts by mass of ferrite microbeads were added to the compatibility base of step (2), and after uniform stirring, 2.6 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.6 parts by mass of BET 198 m 2 / g fumed silica were added, and the mixture was dispersed at a temperature of 50°C, 5.5 parts by mass of organic tin catalyst was added, and the mixture was degassed under vacuum at a double-shaft stirring revolution speed of 20 rpm / rotation speed of 800 rpm for 40 minutes, and then filtered under a pressure of 0.11 MPa and a filter screen aperture of 45 μm to obtain a flame-retardant coating for PC substrates; the method for pre-modifying the carbon nanotubes with the silane coupling agent was as follows: the carbon nanotubes were immersed in a 5 wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 65%, and then stirred at 60°C for 60 minutes and dried; the organic tin catalyst was a mixture of dibutyltin dilaurate and stannous octoate at a mass ratio of 1.85:1.

[0059] Example 5

[0060] A flame-retardant coating for PC substrates was prepared by the following steps:

[0061] Step (1) ferrite microbead plating preparation: 100 parts by mass of hollow glass microbeads were placed in a fluidized bed, and argon plasma power 150 W, flow rate 25 L / min was introduced for 6 minutes; 11 parts by mass of nano-magnetic iron oxide, 2.1 parts by mass of silane coupling agent KH-550, and 0.6 parts by mass of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80%, and ultrasonic dispersion was performed at 25 kHz for 30 minutes to obtain a modified slurry with a solid content of 40 wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.32 MPa, and fluidized treatment was performed at 80°C for 32 minutes to obtain ferrite microbeads;

[0062] Step (2) Preparation of compatibility base material: 49 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite are stirred and dispersed; the phenyl modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.9:1 to obtain the compatibility base material.

[0063] Step (3) Mixing preparation: Add 34 parts by weight of ferrite microspheres to the compatibility base material in step (2), stir evenly, then add 2.9 parts by weight of silane coupling agent pre-modified carbon nanotubes and 4.9 parts by weight of BET202m 2 / g of fumed silica was dispersed at 50℃, and 6.5 parts by mass of organotin catalyst were added. The mixture was degassed for 40 minutes under vacuum by biaxial stirring at 20 rpm revolution / 800 rpm rotation. The mixture was then filtered at a pressure of 0.14 MPa and a filter screen pore size of 45 μm to obtain a flame-retardant coating for PC substrates. The method for pre-modifying carbon nanotubes with silane coupling agent was as follows: carbon nanotubes were impregnated in a 5wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 75%, stirred at 60℃ for 60 minutes, and then dried. The organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate at a mass ratio of 1.95:1.

[0064] Comparative Example 1

[0065] The difference from Example 1 is that iron(III) oxide was not prepared on the surface of the hollow glass microspheres:

[0066] A flame-retardant coating for PC substrates is prepared by the following steps:

[0067] Step (1) Preparation of ferrite microspheres: 100 parts by weight of hollow glass microspheres were placed in a fluidized bed and activated for 7 minutes by argon plasma with a power of 150W and a flow rate of 25L / min; 2.2 parts by weight of silane coupling agent KH-550 and 0.7 parts by weight of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80% and ultrasonically dispersed at 25kHz for 30 minutes to obtain a modified slurry with a solid content of 40wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.35MPa and fluidized at 80℃ for 35 minutes to obtain modified microspheres;

[0068] Step (2) Preparation of compatibility base material: 47 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite are stirred and dispersed; the phenyl modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.7:1 to obtain the compatibility base material.

[0069] Step (3) Mixing preparation: Add 32 parts by weight of modified microspheres to the compatibility base material in step (2), stir evenly, then add 2.8 parts by weight of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by weight of BET205m 2 / g of fumed silica was dispersed at 50℃, and 6 parts by mass of organotin catalyst were added. The mixture was degassed for 40 minutes under vacuum by biaxial stirring at 20 rpm revolution / 800 rpm rotation. The mixture was then filtered at a pressure of 0.12 MPa and a filter screen pore size of 45 μm to obtain a flame-retardant coating for PC substrates. The method for pre-modifying carbon nanotubes with silane coupling agent was as follows: carbon nanotubes were impregnated in a 5wt% KH-550 ethanol aqueous solution (ethanol volume ratio 70%), stirred at 60℃ for 60 minutes, and then dried. The organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate at a mass ratio of 1.9:1.

[0070] Comparative Example 2

[0071] The difference from Example 1 is that hollow glass microspheres were not used:

[0072] A flame-retardant coating for PC substrates is prepared by the following steps:

[0073] Step (1) Preparation of ferrite microspheres: 12 parts by mass of nano-iron oxide, 2.2 parts by mass of silane coupling agent KH-550 and 0.7 parts by mass of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80%. The mixture was ultrasonically dispersed at 25 kHz for 30 minutes to obtain a modified slurry with a solid content of 40 wt%. The slurry was dried at 80 ℃ to obtain modified nano-iron oxide.

[0074] Step (2) Preparation of compatibility base material: 47 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite are stirred and dispersed; the phenyl modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.7:1 to obtain the compatibility base material.

[0075] Step (3) Mixing preparation: Add 32 parts by weight of modified nano-Fe3O4 to the compatibility base material in step (2), stir evenly, then add 2.8 parts by weight of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by weight of BET205m 2 / g of fumed silica was dispersed at 50℃, and 6 parts by mass of organotin catalyst were added. The mixture was degassed for 40 minutes under vacuum by biaxial stirring at 20 rpm revolution / 800 rpm rotation. The mixture was then filtered at a pressure of 0.12 MPa and a filter screen pore size of 45 μm to obtain a flame-retardant coating for PC substrates. The method for pre-modifying carbon nanotubes with silane coupling agent was as follows: carbon nanotubes were impregnated in a 5wt% KH-550 ethanol aqueous solution (ethanol volume ratio 70%), stirred at 60℃ for 60 minutes, and then dried. The organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate at a mass ratio of 1.9:1.

[0076] Comparative Example 3

[0077] The difference from Example 1 is that the hollow glass microspheres were not plasma activated:

[0078] A flame-retardant coating for PC substrates is prepared by the following steps:

[0079] Step (1) Preparation of ferrite-coated microspheres: 100 parts by weight of hollow glass microspheres were placed in a fluidized bed; 12 parts by weight of nano-iron oxide, 2.2 parts by weight of silane coupling agent KH-550, and 0.7 parts by weight of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80%, and ultrasonically dispersed at 25 kHz for 30 minutes to obtain a modified slurry with a solid content of 40 wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.35 MPa, and fluidized at 80 ℃ for 35 minutes to obtain ferrite-coated microspheres;

[0080] Step (2) Preparation of compatibility base material: 47 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite are stirred and dispersed; the phenyl modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.7:1 to obtain the compatibility base material.

[0081] Step (3) Mixing preparation: Add 32 parts by weight of ferrite microspheres to the compatibility base material in step (2), stir evenly, then add 2.8 parts by weight of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by weight of BET205m 2 / g of fumed silica was dispersed at 50℃, and 6 parts by mass of organotin catalyst were added. The mixture was degassed for 40 minutes under vacuum by biaxial stirring at 20 rpm revolution / 800 rpm rotation. The mixture was then filtered at a pressure of 0.12 MPa and a filter screen pore size of 45 μm to obtain a flame-retardant coating for PC substrates. The method for pre-modifying carbon nanotubes with silane coupling agent was as follows: carbon nanotubes were impregnated in a 5wt% KH-550 ethanol aqueous solution (ethanol volume ratio 70%), stirred at 60℃ for 60 minutes, and then dried. The organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate at a mass ratio of 1.9:1.

[0082] Comparative Example 4

[0083] The difference from Example 1 is that the modified slurry has a solid content of 45%.

[0084] A flame-retardant coating for PC substrates is prepared by the following steps:

[0085] Step (1) Preparation of ferrite-coated microspheres: 100 parts by mass of hollow glass microspheres were placed in a fluidized bed and activated for 7 minutes by argon plasma with a power of 150W and a flow rate of 25L / min; 12 parts by mass of nano-iron oxide, 2.2 parts by mass of silane coupling agent KH-550, and 0.7 parts by mass of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80% and ultrasonically dispersed at 25kHz for 30 minutes to obtain a modified slurry with a solid content of 45wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.35MPa and fluidized at 80℃ for 35 minutes to obtain ferrite-coated microspheres;

[0086] Step (2) Preparation of compatibility base material: 47 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite are stirred and dispersed; the phenyl modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.7:1 to obtain the compatibility base material.

[0087] Step (3) Mixing preparation: Add 32 parts by weight of ferrite microspheres to the compatibility base material in step (2), stir evenly, then add 2.8 parts by weight of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by weight of BET205m 2 / g of fumed silica was dispersed at 50℃, and 6 parts by mass of organotin catalyst were added. The mixture was degassed for 40 minutes under vacuum by biaxial stirring at 20 rpm revolution / 800 rpm rotation. The mixture was then filtered at a pressure of 0.12 MPa and a filter screen pore size of 45 μm to obtain a flame-retardant coating for PC substrates. The method for pre-modifying carbon nanotubes with silane coupling agent was as follows: carbon nanotubes were impregnated in a 5wt% KH-550 ethanol aqueous solution (ethanol volume ratio 70%), stirred at 60℃ for 60 minutes, and then dried. The organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate at a mass ratio of 1.9:1.

[0088] Comparative Example 5

[0089] The difference from Example 1 is that the phenyl-modified epoxy resin was prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 3.2:1.

[0090] A flame-retardant coating for PC substrates is prepared by the following steps:

[0091] Step (1) Preparation of ferrite-coated microspheres: 100 parts by weight of hollow glass microspheres were placed in a fluidized bed and activated for 7 minutes by argon plasma with a power of 150W and a flow rate of 25L / min; 12 parts by weight of nano-iron oxide, 2.2 parts by weight of silane coupling agent KH-550, and 0.7 parts by weight of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80% and ultrasonically dispersed at 25kHz for 30 minutes to obtain a modified slurry with a solid content of 40wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.35MPa and fluidized at 80℃ for 35 minutes to obtain ferrite-coated microspheres;

[0092] Step (2) Preparation of compatibility base material: 47 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite are stirred and dispersed; the phenyl modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 3.2:1 to obtain the compatibility base material.

[0093] Step (3) Mixing preparation: Add 32 parts by weight of ferrite microspheres to the compatibility base material in step (2), stir evenly, then add 2.8 parts by weight of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by weight of BET205m 2 / g of fumed silica was dispersed at 50℃, and 6 parts by mass of organotin catalyst were added. The mixture was degassed for 40 minutes under vacuum by biaxial stirring at 20 rpm revolution / 800 rpm rotation. The mixture was then filtered at a pressure of 0.12 MPa and a filter screen pore size of 45 μm to obtain a flame-retardant coating for PC substrates. The method for pre-modifying carbon nanotubes with silane coupling agent was as follows: carbon nanotubes were impregnated in a 5wt% KH-550 ethanol aqueous solution (ethanol volume ratio 70%), stirred at 60℃ for 60 minutes, and then dried. The organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate at a mass ratio of 1.9:1.

[0094] Comparative Example 6

[0095] The difference from Example 1 is that no silane coupling agent was added to pre-modify the carbon nanotubes:

[0096] A flame-retardant coating for PC substrates is prepared by the following steps:

[0097] Step (1) Preparation of ferrite-coated microspheres: 100 parts by weight of hollow glass microspheres were placed in a fluidized bed and activated for 7 minutes by argon plasma with a power of 150W and a flow rate of 25L / min; 12 parts by weight of nano-iron oxide, 2.2 parts by weight of silane coupling agent KH-550, and 0.7 parts by weight of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80% and ultrasonically dispersed at 25kHz for 30 minutes to obtain a modified slurry with a solid content of 40wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.35MPa and fluidized at 80℃ for 35 minutes to obtain ferrite-coated microspheres;

[0098] Step (2) Preparation of compatibility base material: 47 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite are stirred and dispersed; the phenyl modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.7:1 to obtain the compatibility base material.

[0099] Step (3) Mixing preparation: Add 32 parts by weight of ferrite microspheres to the compatibility base material in step (2), stir evenly, and then add 4.8 parts by weight of BET205m 2 / g of fumed silica was dispersed at 50℃, and 6 parts by mass of organotin catalyst were added. The mixture was degassed for 40 minutes under vacuum by biaxial stirring at 20 rpm revolution / 800 rpm rotation. The mixture was then filtered at a pressure of 0.12 MPa and a filter screen pore size of 45 μm to obtain a flame-retardant coating for PC substrates. The method for pre-modifying carbon nanotubes with silane coupling agent was as follows: carbon nanotubes were impregnated in a 5wt% KH-550 ethanol aqueous solution (ethanol volume ratio 70%), stirred at 60℃ for 60 minutes, and then dried. The organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate at a mass ratio of 1.9:1.

[0100] Comparative Example 7

[0101] The difference from Example 1 is that fumed silica was not added:

[0102] A flame-retardant coating for PC substrates is prepared by the following steps:

[0103] Step (1) Preparation of ferrite-coated microspheres: 100 parts by weight of hollow glass microspheres were placed in a fluidized bed and activated for 7 minutes by argon plasma with a power of 150W and a flow rate of 25L / min; 12 parts by weight of nano-iron oxide, 2.2 parts by weight of silane coupling agent KH-550, and 0.7 parts by weight of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80% and ultrasonically dispersed at 25kHz for 30 minutes to obtain a modified slurry with a solid content of 40wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.35MPa and fluidized at 80℃ for 35 minutes to obtain ferrite-coated microspheres;

[0104] Step (2) Preparation of compatibility base material: 47 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite are stirred and dispersed; the phenyl modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.7:1 to obtain the compatibility base material.

[0105] Step (3) Mixing preparation: Add 32 parts by mass of ferrite microspheres to the compatibility base material in step (2), stir evenly, add 2.8 parts by mass of silane coupling agent pre-modified carbon nanotubes, heat to 50℃ for dispersion, add 6 parts by mass of organotin catalyst, degas for 40 minutes under vacuum with biaxial stirring at 20 rpm revolution / 800 rpm rotation, filter under pressure of 0.12 MPa and filter screen pore size of 45 μm to obtain flame retardant coating for PC substrate; The method of silane coupling agent pre-modified carbon nanotubes is as follows: impregnate carbon nanotubes in 5wt% KH-550 ethanol aqueous solution with ethanol volume ratio of 70%, stir at 60℃ for 60 minutes and then dry; The organotin catalyst is a compound of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.9:1.

[0106] Comparative Example 8

[0107] The difference from Example 1 is that vacuum degassing was not performed:

[0108] A flame-retardant coating for PC substrates is prepared by the following steps:

[0109] Step (1) Preparation of ferrite-coated microspheres: 100 parts by weight of hollow glass microspheres were placed in a fluidized bed and activated for 7 minutes by argon plasma with a power of 150W and a flow rate of 25L / min; 12 parts by weight of nano-iron oxide, 2.2 parts by weight of silane coupling agent KH-550, and 0.7 parts by weight of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80% and ultrasonically dispersed at 25kHz for 30 minutes to obtain a modified slurry with a solid content of 40wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.35MPa and fluidized at 80℃ for 35 minutes to obtain ferrite-coated microspheres;

[0110] Step (2) Preparation of compatibility base material: 47 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite are stirred and dispersed; the phenyl modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.7:1 to obtain the compatibility base material.

[0111] Step (3) Mixing preparation: Add 32 parts by weight of ferrite microspheres to the compatibility base material in step (2), stir evenly, then add 2.8 parts by weight of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by weight of BET205m 2 / g of fumed silica was dispersed at 50℃, and 6 parts by mass of organotin catalyst were added. The mixture was degassed for 40 minutes by biaxial stirring at 20 rpm revolution / 800 rpm rotation. The mixture was then filtered under a pressure of 0.12 MPa and a filter screen pore size of 45 μm to obtain a flame-retardant coating for PC substrates. The method for pre-modifying carbon nanotubes with silane coupling agent was as follows: carbon nanotubes were impregnated in a 5wt% KH-550 ethanol aqueous solution (ethanol volume ratio 70%), stirred at 60℃ for 60 minutes, and then dried. The organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate at a mass ratio of 1.9:1.

[0112] Comparative Example 9

[0113] The difference from Example 1 is that it was not filtered:

[0114] A flame-retardant coating for PC substrates is prepared by the following steps:

[0115] Step (1) Preparation of ferrite-coated microspheres: 100 parts by weight of hollow glass microspheres were placed in a fluidized bed and activated for 7 minutes by argon plasma with a power of 150W and a flow rate of 25L / min; 12 parts by weight of nano-iron oxide, 2.2 parts by weight of silane coupling agent KH-550, and 0.7 parts by weight of stearic acid were added to an ethanol aqueous solution with an ethanol volume ratio of 80% and ultrasonically dispersed at 25kHz for 30 minutes to obtain a modified slurry with a solid content of 40wt%; the slurry was atomized and sprayed into the fluidized bed at a pressure of 0.35MPa and fluidized at 80℃ for 35 minutes to obtain ferrite-coated microspheres;

[0116] Step (2) Preparation of compatibility base material: 47 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite are stirred and dispersed; the phenyl modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.7:1 to obtain the compatibility base material.

[0117] Step (3) Mixing preparation: Add 32 parts by weight of ferrite microspheres to the compatibility base material in step (2), stir evenly, then add 2.8 parts by weight of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by weight of BET205m 2 / g of fumed silica was dispersed at 50℃, and 6 parts by mass of organotin catalyst were added. The mixture was then degassed for 40 minutes under vacuum by biaxial stirring at 20 rpm revolution / 800 rpm rotation to obtain a flame-retardant coating for PC substrates. The method for pre-modifying carbon nanotubes with silane coupling agent was as follows: carbon nanotubes were impregnated in a 5wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 70%, stirred at 60℃ for 60 minutes, and then dried. The organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate at a mass ratio of 1.9:1.

[0118] Performance testing should refer to the following standards:

[0119] Flame retardancy: GB / T2408-2021;

[0120] Thermal insulation performance: GB / T3399-2022;

[0121] Electromagnetic shielding performance: GB / T25471-2010;

[0122] Waterproof performance: GB / T4208-2017;

[0123] Tear resistance: ISO 4624;

[0124] The results are shown in Table 1.

[0125] Table 1. Performance Comparison of Examples and Comparative Examples

[0126]

[0127] This solution achieves performance breakthroughs through multi-level synergy between components and precise process control: Ferrite-coated microspheres use hollow glass microspheres as the core, with a nano-ferric oxide coating layer on the surface simultaneously imparting magnetic loss absorption and catalytic carbonization functions, while carbon nanotubes modified with silane coupling agent KH-550 are embedded in the matrix to form a dielectric loss network, constituting a broadband electromagnetic shielding synergy with the magnetic microspheres; Hydrophobic fumed silica fills the gaps between the microspheres, blocking heat conduction paths through the nano-confinement effect, and jointly constructing a molecular-level waterproof barrier with the hydrophobic alkyl chains and KH-550 hydrolysis products; Phenyl-modified epoxy resin balances char formation and toughness with a precise ratio (2.5-3:1) of rigid benzene rings and flexible ether chains, and low-temperature organotin catalytic curing avoids thermal damage to the PC substrate; Plasma activation strengthens the interfacial bonding of the microspheres, and gradient mixing and staged vacuum degassing eliminate filler agglomeration and bubble defects, ultimately forming a dense, multifunctional integrated coating.

[0128] In this scheme, a break in the coordination between components and processes leads to systemic failure: Comparative Example 1, due to the absence of the iron oxide coating, not only disrupted the magnetic loss-catalytic carbonization dual-function coupling of the hollow microspheres, but also caused the flame retardant system to lose the catalytic enhancement effect of metal ions; Comparative Example 2, after removing the hollow microspheres, the collapse of the insulation skeleton and density imbalance disrupted the filler gradient distribution, resulting in bubble channels in the waterproof barrier; Comparative Example 3, omitting plasma activation, resulted in weak interfacial bonding between iron oxide and hollow glass microspheres, and local breakage of the electromagnetic synergistic network; Comparative Example 4, the high solids content slurry caused microsphere agglomeration, disrupting the interstitial filling rhythm of the hydrophobic silica, leading to uneven performance distribution and a decline in overall performance; Comparative Example 5, the excess benzene... The base resin disrupts the rigid-flexible balance, causing a mismatch in the stress transmission between the matrix and filler, reducing coordination, and resulting in a decline in overall performance. Comparative Example 6 lacks pre-modified carbon nanotubes, leading to an isolated dielectric network that cannot form a broadband loss resonance with the magnetic microspheres. Comparative Example 7 did not add fumed silica, resulting in the failure to cut off the thermal bridges between microspheres. At the same time, the nanopores disrupted the densification process formed by degassing, disrupting the uniform distribution of the dielectric constant of the coating. Comparative Example 8 eliminated vacuum degassing, allowing bubbles to penetrate the coating and severing the continuous hydrophobic interface constructed by KH-550. In Comparative Example 9, the unfiltered agglomerates not only hindered electromagnetic impedance matching but also induced microcracks during the curing process, resulting in a slight decrease in overall performance, but still slightly better performance compared to the other comparative examples.

Claims

1. A flame-retardant coating for PC substrates, characterized in that, It is prepared through the following steps: By weight, Step (1) Preparation of ferrite-coated microspheres: 100 parts by mass of hollow glass microspheres with a particle size of 20-50 μm were placed in a fluidized bed and activated by argon plasma for 5-10 minutes; then 10-15 parts by mass of nano-iron oxide, 2-2.5 parts by mass of silane coupling agent and 0.5-1 parts by mass of stearic acid were added to an ethanol aqueous solution, ultrasonically dispersed to obtain a modified slurry, and fluidized to obtain ferrite-coated microspheres; Step (2) Preparation of compatible base material: Stir and disperse 45-50 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite to obtain a compatible base material; Step (3) Mixing preparation: Add 30-35 parts by weight of ferrite microspheres to the compatibility base material in step (2), stir evenly, then add 2.5-3 parts by weight of silane coupling agent pre-modified carbon nanotubes and 4.5-5 parts by weight of hydrophobic silica, heat to 50±2℃, disperse, then add 5-7 parts by weight of organotin catalyst, stir and degas under -0.1MPa vacuum for 40 minutes, filter, and obtain flame retardant coating for PC substrate.

2. The flame-retardant coating for PC substrates according to claim 1, characterized in that, In step (1), the slurry solid content is 40±2wt%.

3. The flame-retardant coating for PC substrates according to claim 1, characterized in that, The phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether at a mass ratio of 2.5-3:

1.

4. The flame-retardant coating for PC substrates according to claim 1, characterized in that, The organotin catalyst is a mixture of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.8-2:

1.

5. The flame-retardant coating for PC substrates according to claim 1, characterized in that, In step (3), the modification method of the silane coupling agent pre-modified carbon nanotubes is as follows: the carbon nanotubes are immersed in a 5wt% KH-550 ethanol aqueous solution, stirred at 60°C for 60 minutes, and then dried.

6. The flame-retardant coating for PC substrates according to claim 1, characterized in that, The hydrophobic silica is BET200±10m. 2 / g of fumed silica.

7. The flame-retardant coating for PC substrates according to claim 1, characterized in that, Step (3) Vacuum stirring and degassing is divided into two stages: First stage: -0.06MPa, 15-20 minutes, rotation 600rpm; Second stage: -0.10MPa, 20-30 minutes, rotation at 1000rpm.

8. The flame-retardant coating for PC substrates according to claim 1, characterized in that, The filtration process pressure is ≤0.15MPa, and the filter screen pore size is 45μm.

9. The flame-retardant coating for PC substrates according to claim 1, characterized in that, In step (1), the fluidization process is as follows: the modified slurry is atomized and sprayed into the fluidized bed at a pressure of 0.3 MPa, and fluidized at 80±2℃ for 30-40 minutes.

10. A method for preparing a flame-retardant coating for a PC substrate as described in any one of claims 1-9, characterized in that, Includes the following steps: By weight, Step (1) Preparation of ferrite-coated microspheres: 100 parts by mass of hollow glass microspheres with a particle size of 20-50 μm were placed in a fluidized bed and activated by argon plasma for 5-10 minutes; then 10-15 parts by mass of nano-iron oxide, 2-2.5 parts by mass of silane coupling agent and 0.5-1 parts by mass of stearic acid were added to an ethanol aqueous solution, ultrasonically dispersed to obtain a modified slurry, and fluidized to obtain ferrite-coated microspheres; Step (2) Preparation of compatible base material: Stir and disperse 45-50 parts by weight of phenyl modified epoxy resin, 20 parts by weight of ammonium polyphosphate and 10 parts by weight of aluminum hypophosphite to obtain a compatible base material; Step (3) Mixing preparation: Add 30-35 parts by weight of ferrite microspheres to the compatibility base material in step (2), stir evenly, then add 2.5-3 parts by weight of silane coupling agent pre-modified carbon nanotubes and 4.5-5 parts by weight of hydrophobic silica, heat to 50±2℃, disperse, then add 5-7 parts by weight of organotin catalyst, stir and degas under -0.1MPa vacuum for 40 minutes, filter, and obtain flame retardant coating for PC substrate.

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