Flame-retardant coating for PC (polycarbonate) base material and preparation method of flame-retardant coating

Abstract

The invention relates to the field of coatings, in particular to a flame-retardant coating for a PC base material and a preparation method thereof.The flame-retardant coating is prepared through the following steps that 1, ferrite-plated microbeads are prepared by weight; (2) preparing a compatible base material; and (3) mixing and preparing: adding ferrite-plated microbeads into the compatible base material in the step (2), uniformly stirring, adding silane pre-modified carbon nanotubes and hydrophobic silicon dioxide, dispersing, adding an organic tin catalyst, defoaming, and filtering to obtain the flame-retardant coating for the PC base material. According to the scheme, through coordination and complementation among the components and process control, each component has the characteristic of multiple functions, and the waterproof, fireproof, stealth and heat insulation effects are simultaneously realized by using one coating.

Description

Technical Field

[0001] The present invention relates to the field of coatings, and in particular to a flame retardant coating for a PC substrate and a preparation method thereof. Background Art

[0002] Currently, there is a demand for multifunctional coatings on polycarbonate (PC) substrates. While conventional flame-retardant coatings (such as intumescent acrylic systems) can achieve V-0 flame retardancy by forming an intumescent carbon layer with ammonium polyphosphate (APP), they struggle to balance electromagnetic shielding effectiveness with thermal insulation. Existing solutions often employ a functional stacking strategy—for example, first applying a ferrite-containing absorbing layer followed by an intumescent flame-retardant layer—resulting in a total coating thickness exceeding 500μm. This not only reduces the light transmittance and mechanical flexibility of the PC substrate but also causes delamination failure due to poor interlayer compatibility. Furthermore, while lightweight fillers can improve thermal insulation, their surface inertness can lead to weak resin interfacial bonding, making them susceptible to water seepage and peeling in hot and humid environments. Currently, most coatings for PC are developed for a single function. For example, CN117417658A describes a flame-retardant coating for mobile phone PC substrates that includes the following components: adhesive component A, adhesive component B, acrylic basecoat, curing agent, diluent, prefabricated flame-retardant slurry, flame-retardant midcoat, flame-retardant topcoat, and UV-curable coating. The flame-retardant coating for mobile phone casings made with this invention passes the GB-T5169.5 needle flame test. This means that after a 120-second flame exposure, no holes are formed in the PC casing of the mobile phone coated with the flame-retardant coating, significantly improving the safety and service life of the mobile phone. Therefore, developing a single-coat, low-temperature curing system that combines high flame retardancy, broadband electromagnetic shielding, low thermal conductivity, and strong water resistance has become a key path to breaking through the bottleneck of multifunctional protection technology for PC substrates. Summary of the Invention

[0003] In order to achieve the above-mentioned purpose, the present invention discloses a flame retardant coating for PC substrates. Through the coordination and complementarity between components and process control, each component realizes multiple functional characteristics, and a single coating simultaneously achieves the effects of waterproofing, fireproofing, stealth, and thermal insulation.

[0004] This solution specifically adopts the following technical solutions:

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

[0006] By weight,

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

[0008] Step (2) preparing a compatible base material: stirring and dispersing 45-50 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate (APP), and 10 parts by mass of aluminum hypophosphite to obtain a compatible base material;

[0009] Step (3) is mixed and prepared as follows: 30-35 parts by mass of ferrite-plated microbeads are added to the compatible base material of step (2), and after stirring evenly, 2.5-3 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.5-5 parts by mass of hydrophobic silica are added, the mixture is heated to 50±2°C and dispersed, and then 5-7 parts by mass of an organic tin catalyst (dibutyltin dilaurate) is added, and degassing is carried out for 40 minutes with biaxial stirring (revolution 20 rpm / rotation 800 rpm) under a vacuum of -0.1 MPa, and filtering is performed to obtain a flame retardant coating for a PC substrate.

[0010] The flame retardant coating for PC substrate proposed in this scheme has multiple composite effects:

[0011] 1. Flame Retardancy: The core flame retardancy of this solution relies on the classic combination of ammonium polyphosphate (APP) and aluminum hypophosphite. When exposed to high temperatures or flames, APP rapidly decomposes, producing polyphosphoric acid that catalyzes the dehydration and carbonization of the resin and itself, while simultaneously releasing large amounts of non-flammable gases. These gases cause the molten coating to expand, forming a fluffy, oxygen- and heat-isolating foamy carbon layer. Aluminum hypophosphite acts as a synergist, absorbing significant heat during decomposition, effectively lowering the temperature in the combustion zone. The released phosphorus-containing free radicals capture the active free radicals in the flame that sustain combustion, interrupting the combustion chain reaction. Furthermore, the nano-ferroferric oxide uniformly coated on the surface of the hollow glass microspheres not only catalyzes the formation of the carbon layer at high temperatures, making it denser and more resistant to ablation, but also provides a certain degree of heat absorption and physical barrier properties. Finally, the phenyl-modified epoxy resin, due to its rigid benzene ring structure, inherently exhibits higher heat resistance and charring efficiency than standard epoxy resins, providing a more stable framework for the entire flame retardant system.

[0012] 2. Stealth Effect: This stealth effect is achieved primarily through a cleverly constructed magnetic-dielectric dual-loss synergistic absorption mechanism. The core functional material is ferrite-coated microspheres: The solution securely coats nano-iron tetroxide, which exhibits strong magnetic loss, onto the surface of hollow glass microspheres, which exhibit dielectric loss properties. When incident radar waves encounter the coating, they are largely absorbed by the magnetic ferroferric oxide through mechanisms such as natural resonance and eddy current loss. Furthermore, the dielectric properties and unique hollow structure of the hollow glass microspheres effectively adjust the electromagnetic parameters of the coating, improving impedance matching and allowing more electromagnetic waves to enter the coating rather than being reflected. The hollow structure of the microspheres also scatters and attenuates electromagnetic waves. The pre-dispersed carbon nanotubes added in the synergistic coating are excellent dielectric loss materials. Their large surface area and conductive network effectively absorb and convert electromagnetic wave energy. Pre-modification with a silane coupling agent not only improves their dispersion in the resin matrix, preventing agglomeration, but also strengthens their interfacial bonding with the matrix, ensuring full absorption efficiency. The synergistic effect of magnetic ferrite microbeads and dielectric carbon nanotubes is expected to broaden the coating's effective absorption bandwidth. Finally, while hydrophobic silica's primary functions are waterproofing and thermal insulation, its nanoscale and hydrophobic properties can subtly influence the coating's dielectric constant distribution, helping to optimize overall impedance matching and indirectly improving absorption efficiency.

[0013] 3. Thermal Insulation: Thermal insulation performance lies in effectively blocking the three pathways of heat transfer (conduction, convection, and radiation). Even when coated with ferroferric oxide, the hollow glass microspheres, protected by a coating, maintain a hollow, sealed structure. The thin gas (or near-vacuum) within them is an extremely poor thermal conductor, significantly hindering heat conduction. Furthermore, the tiny particle size (20-50 μm) greatly limits convection within the air. Hydrophobic nanosilica, a key filler, possesses an extremely high specific surface area and extremely fine particle size, capable of filling the gaps between the microspheres. This not only reduces its own thermal conductivity but, more importantly, renders the heat transfer path extremely tortuous and lengthy. Its enormous surface energy also enhances phonon scattering, further inhibiting solid-state thermal conduction. The hydrophobic nature ensures that even in high humidity environments, the thermal conductivity of the microspheres, both internally and on the surface, does not increase significantly due to water absorption. Finally, the low-thermal-conductivity epoxy resin matrix provides a continuous, low-thermal-conductivity phase for the entire insulation system.

[0014] 4. Waterproof: Waterproof performance is achieved through a double line of defense of hydrophobic barrier and dense structure. The hydrophobic silica specially selected for this solution has a surface treated to be hydrophobic, which can effectively reduce the wettability of the coating surface and make it difficult for water droplets to spread and penetrate. The silane coupling agent modifies the surface of nano-ferroferric oxide and the surface of carbon nanotubes, and is also present in the base material. The hydrophobic alkyl chains produced after the hydrolysis of the silane coupling agent cover the surface of the filler and the interface between the filler and the resin, blocking the invasion path of water molecules, and enhancing the interfacial bonding force, reducing water seepage caused by interface defects, thereby constructing a hydrophobic barrier. Strong dispersion (high speed, gradient mixing) ensures that all components are evenly distributed without weak points caused by agglomeration; fine vacuum degassing (staged high vacuum, high shear stirring) completely eliminates the air entrapped during the stirring process and the microbubbles generated by the volatilization of the solvent. These bubbles are potential water seepage channels. The phased 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; and effective low-temperature curing (organotin catalyst) also ensures that the resin is fully cross-linked to form a strong, complete, low-porosity coating body.

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

[0016] Preferably, the phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 2.5-3:1.

[0017] Preferably, the organotin catalyst is a mixture of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.8-2:1.

[0018] Preferably, the carbon nanotube modification method in step (1) is: immersing the carbon nanotubes in a 5 wt% KH-550 ethanol aqueous solution, stirring at 60° C. for 60 minutes and then drying, wherein the volume proportion of ethanol in the ethanol aqueous solution is 60-80%.

[0019] Preferably, the hydrophobic silica is BET200±10m 2 / g of fumed silica.

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

[0021] Stage 1: -0.06 MPa, 15-20 minutes, rotation 600 rpm;

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

[0023] Preferably, the filtration process pressure is ≤0.15 MPa and the filter mesh pore size is 45 μm.

[0024] This proposal also proposes a method for preparing the flame retardant coating for PC substrates.

[0025] Compared with existing technologies, the advantages of this solution are:

[0026] 1. Use one coating to achieve the effects of waterproofing, fireproofing, stealth, and thermal insulation;

[0027] 2. Through the coordination and complementarity between components and process control, each component has achieved multiple functional characteristics. In particular, after the ferrite-plated microbeads are mixed with the carbon nanotubes pre-modified with silane coupling agent, while ensuring the electromagnetic shielding and thermal insulation effects of the ferrite-plated microbeads themselves, the describing properties of the ferrite-plated microbeads in the matrix are also improved. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] Overall embodiment

[0030] A flame retardant coating for PC substrate is prepared by the following steps:

[0031] By weight,

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

[0033] Step (2) preparing a compatible base material: stirring and dispersing 45-50 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate (APP), and 10 parts by mass of aluminum hypophosphite to obtain a compatible base material; the phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 2.5-3:1 to obtain a compatible base material;

[0034] Step (3) is mixed and prepared by adding 30-35 parts by mass of ferrite-plated microbeads to the compatible base material of step (2), stirring evenly, and then adding 2.5-3 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.5-5 parts by mass of BET200±10m 2 / g of fumed silica, heated to 50±2°C and dispersed, then added with 5-7 parts by mass of an organic tin catalyst (dibutyltin dilaurate and stannous octoate in a mass ratio of 1.8-2:1), degassed with biaxial stirring under vacuum for 40 minutes, filtered at a pressure of ≤0.15MPa and a filter mesh aperture of 45μm to obtain a flame retardant coating for a PC substrate; the carbon nanotube modification method 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, wherein the volume proportion of ethanol in the ethanol aqueous solution is 60-80%.

[0035] Example 1

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

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

[0038] Step (2) preparing a compatible base material: stirring and dispersing 47 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite; the phenyl-modified epoxy resin is prepared by copolymerizing 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) is mixed and prepared by adding 32 parts by mass of ferrite-plated microbeads to the compatible base material of step (2), stirring evenly, and then adding 2.8 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by mass of BET205m 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 is: 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 is: 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) Preparation of ferrite-plated microspheres: 100 parts by mass of hollow glass microspheres are placed in a fluidized bed, and an argon plasma power of 150 W and a flow rate of 25 L / min is introduced for activation for 6 minutes; 11 parts by mass of nano-ferrosoferric oxide, 2.1 parts by mass of silane coupling agent KH-550, and 0.6 parts by mass of stearic acid are added to an ethanol aqueous solution with an ethanol volume ratio of 80%, and ultrasonic dispersion is performed at 25 kHz for 30 minutes to obtain a modified slurry with a solid content of 40 wt%; the slurry is atomized and sprayed into the fluidized bed at a pressure of 0.32 MPa, and fluidized at 80° C. for 32 minutes to obtain ferrite-plated microspheres;

[0057] Step (2) preparing a compatible base material: stirring and dispersing 48 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite; the phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 2.6:1 to obtain a compatible base material;

[0058] Step (3) is mixed and prepared by adding 31 parts by mass of ferrite-coated microbeads to the compatible base material of step (2), stirring evenly, and then adding 2.6 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.6 parts by mass of BET198m 2 / g of fumed silica, heated to 50°C for dispersion, added with 5.5 parts by mass of an organic tin catalyst, degassed under vacuum with a biaxial stirring rotation of 20 rpm / 800 rpm for 40 minutes, filtered under a pressure of 0.11 MPa and a filter mesh aperture of 45 μm to obtain a flame retardant coating for a PC substrate; a method for pre-modifying carbon nanotubes with a silane coupling agent is as follows: immersing the carbon nanotubes in a 5 wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 65%, stirring at 60°C for 60 minutes and then drying; the organic tin catalyst is a compound of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.85:1.

[0059] Example 5

[0060] A flame retardant coating for PC substrate is prepared by the following steps:

[0061] Step (1) Preparation of ferrite-plated microspheres: 100 parts by mass of hollow glass microspheres are placed in a fluidized bed, and an argon plasma power of 150 W and a flow rate of 25 L / min is introduced for activation for 9 minutes; 14 parts by mass of nano-ferrosoferric oxide, 2.4 parts by mass of silane coupling agent KH-550, and 0.9 parts by mass of stearic acid are added to an ethanol aqueous solution with an ethanol volume ratio of 80%, and ultrasonic dispersion is performed at 25 kHz for 30 minutes to obtain a modified slurry with a solid content of 40 wt%; the slurry is atomized and sprayed into the fluidized bed at a pressure of 0.38 MPa, and fluidized at 80° C. for 38 minutes to obtain ferrite-plated microspheres;

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

[0063] Step (3) is mixed and prepared by adding 34 parts by mass of ferrite-plated microbeads to the compatible base material of step (2), stirring evenly, and then adding 2.9 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.9 parts by mass of BET202m 2 / g of fumed silica, heated to 50°C for dispersion, added with 6.5 parts by mass of an organic tin catalyst, degassed under vacuum with a biaxial stirring rotation of 20 rpm / 800 rpm for 40 minutes, filtered under a pressure of 0.14 MPa and a filter mesh aperture of 45 μm to obtain a flame retardant coating for a PC substrate; a method for pre-modifying carbon nanotubes with a silane coupling agent is as follows: immersing the carbon nanotubes in a 5 wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 75%, stirring at 60°C for 60 minutes and then drying; the organic tin catalyst is a compound of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.95:1.

[0064] Comparative Example 1

[0065] The difference from Example 1 is that ferrosoferric oxide is not prepared on the surface of the hollow glass microspheres:

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

[0067] Step (1) Preparation of ferrite-plated microspheres: 100 parts by mass of hollow glass microspheres were placed in a fluidized bed, and activated by introducing argon plasma with a power of 150 W and a flow rate of 25 L / min for 7 minutes; 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 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 at 80° C. for 35 minutes to obtain modified microspheres;

[0068] Step (2) preparing a compatible base material: stirring and dispersing 47 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite; the phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 2.7:1 to obtain a compatible base material;

[0069] Step (3) is mixed and prepared by adding 32 parts by mass of modified microbeads to the compatible base material of step (2), stirring evenly, and then adding 2.8 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by mass of BET205m 2 / g fumed silica, heated to 50℃ and dispersed, 6 parts by mass of organotin catalyst was added, and under vacuum, double shaft stirring revolution 20 rpm / rotation 800 rpm was used to defoam for 40 minutes, filtered under the conditions of pressure 0.12 MPa, filter screen aperture 45 μm, to obtain a flame-retardant coating for a PC substrate; the method for pre-modifying carbon nanotubes with a silane coupling agent was as follows: the carbon nanotubes were immersed in a 5wt% KH-550 ethanol aqueous solution, the ethanol volume ratio was 70%, and after stirring at 60℃ for 60 minutes, drying was performed; the organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.9:1.

[0070] Comparative Example 2

[0071] The difference from Example 1 was that hollow glass microbeads were not used:

[0072] A flame-retardant coating for a PC substrate was prepared by the following steps:

[0073] Step (1) ferrite microbead plating preparation: 12 parts by mass of nanometer ferroferric 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, the ethanol volume ratio was 80%, and ultrasonic dispersion was performed at 25 kHz for 30 minutes to obtain modified nanometer ferroferric oxide with a solid content of 40wt%; drying was performed at 80℃;

[0074] Step (2) compatibility base preparation: 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 compatibility base;

[0075] Step (3) mixing: 32 parts by mass of modified nanometer ferroferric oxide was added to the compatibility base of Step (2), and after uniform stirring, 2.8 parts by mass of pre-modified carbon nanotubes with a silane coupling agent and 4.8 parts by mass of BET 205m 2 / g fumed silica, heated to 50℃ and dispersed, 6 parts by mass of organotin catalyst was added, and under vacuum, double shaft stirring revolution 20 rpm / rotation 800 rpm was used to defoam for 40 minutes, filtered under the conditions of pressure 0.12 MPa, filter screen aperture 45 μm, to obtain a flame-retardant coating for a PC substrate; the method for pre-modifying carbon nanotubes with a silane coupling agent was as follows: the carbon nanotubes were immersed in a 5wt% KH-550 ethanol aqueous solution, the ethanol volume ratio was 70%, and after stirring at 60℃ for 60 minutes, drying was performed; the organotin catalyst was a compound of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.9:1.

[0076] Comparative Example 3

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

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

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

[0080] Step (2) preparing a compatible base material: stirring and dispersing 47 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite; the phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 2.7:1 to obtain a compatible base material;

[0081] Step (3) is mixed and prepared by adding 32 parts by mass of ferrite-plated microbeads to the compatible base material of step (2), stirring evenly, and then adding 2.8 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by mass of BET205m 2 / g of fumed silica, heated to 50°C for dispersion, added 6 parts by mass of an organic tin catalyst, degassed under vacuum with a biaxial stirring rotation of 20 rpm / 800 rpm for 40 minutes, filtered under a pressure of 0.12 MPa and a filter mesh aperture of 45 μm to obtain a flame retardant coating for a PC substrate; a method for pre-modifying carbon nanotubes with a silane coupling agent is as follows: immersing the carbon nanotubes in a 5wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 70%, stirring at 60°C for 60 minutes, and then drying; the organic tin catalyst is a compound of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.9:1.

[0082] Comparative Example 4

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

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

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

[0086] Step (2) preparing a compatible base material: stirring and dispersing 47 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite; the phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 2.7:1 to obtain a compatible base material;

[0087] Step (3) is mixed and prepared by adding 32 parts by mass of ferrite-plated microbeads to the compatible base material of step (2), stirring evenly, and then adding 2.8 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by mass of BET205m 2 / g of fumed silica, heated to 50°C for dispersion, added 6 parts by mass of an organic tin catalyst, degassed under vacuum with a biaxial stirring rotation of 20 rpm / 800 rpm for 40 minutes, filtered under a pressure of 0.12 MPa and a filter mesh aperture of 45 μm to obtain a flame retardant coating for a PC substrate; a method for pre-modifying carbon nanotubes with a silane coupling agent is as follows: immersing the carbon nanotubes in a 5wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 70%, stirring at 60°C for 60 minutes, and then drying; the organic tin catalyst is a compound of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.9:1.

[0088] Comparative Example 5

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

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

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

[0092] Step (2) preparing a 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 are stirred and dispersed; the phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 3.2:1 to obtain a compatible base material;

[0093] Step (3) is mixed and prepared by adding 32 parts by mass of ferrite-plated microbeads to the compatible base material of step (2), stirring evenly, and then adding 2.8 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by mass of BET205m 2 / g of fumed silica, heated to 50°C for dispersion, added 6 parts by mass of an organic tin catalyst, degassed under vacuum with a biaxial stirring rotation of 20 rpm / 800 rpm for 40 minutes, filtered under a pressure of 0.12 MPa and a filter mesh aperture of 45 μm to obtain a flame retardant coating for a PC substrate; a method for pre-modifying carbon nanotubes with a silane coupling agent is as follows: immersing the carbon nanotubes in a 5wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 70%, stirring at 60°C for 60 minutes, and then drying; the organic tin catalyst is a compound of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.9:1.

[0094] Comparative Example 6

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

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

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

[0098] Step (2) preparing a compatible base material: stirring and dispersing 47 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite; the phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 2.7:1 to obtain a compatible base material;

[0099] Step (3) is mixed and prepared by adding 32 parts by mass of ferrite-plated microbeads to the compatible base material of step (2), stirring evenly and then adding 4.8 parts by mass of BET205m 2 / g of fumed silica, heated to 50°C for dispersion, added 6 parts by mass of an organic tin catalyst, degassed under vacuum with a biaxial stirring rotation of 20 rpm / 800 rpm for 40 minutes, filtered under a pressure of 0.12 MPa and a filter mesh aperture of 45 μm to obtain a flame retardant coating for a PC substrate; a method for pre-modifying carbon nanotubes with a silane coupling agent is as follows: immersing the carbon nanotubes in a 5wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 70%, stirring at 60°C for 60 minutes, and then drying; the organic tin catalyst is a compound of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.9:1.

[0100] Comparative Example 7

[0101] The difference from Example 1 is that no fumed silica is added:

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

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

[0104] Step (2) preparing a compatible base material: stirring and dispersing 47 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite; the phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 2.7:1 to obtain a compatible base material;

[0105] Step (3) is mixed and prepared as follows: 32 parts by mass of ferrite-plated microbeads are added to the compatible base material of step (2), and after stirring evenly, 2.8 parts by mass of silane coupling agent pre-modified carbon nanotubes are added, the temperature is raised to 50°C for dispersion, 6 parts by mass of organic tin catalyst are added, and degassing is carried out for 40 minutes with biaxial stirring at 20 rpm and 800 rpm under vacuum, and filtering is carried out under the conditions of pressure of 0.12 MPa and filter mesh aperture of 45 μm to obtain a flame retardant coating for PC substrate; the method for pre-modifying the carbon nanotubes with a silane coupling agent is as follows: the carbon nanotubes are immersed in a 5wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 70%, stirred at 60°C for 60 minutes, and then dried; the organic tin 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 no vacuum degassing is performed:

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

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

[0110] Step (2) preparing a compatible base material: stirring and dispersing 47 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite; the phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 2.7:1 to obtain a compatible base material;

[0111] Step (3) is mixed and prepared by adding 32 parts by mass of ferrite-plated microbeads to the compatible base material of step (2), stirring evenly, and then adding 2.8 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by mass of BET205m 2 / g of fumed silica, heated to 50°C for dispersion, added 6 parts by mass of an organic tin catalyst, degassed for 40 minutes with a biaxial stirring system of 20 rpm orbital rotation and 800 rpm rotation, and filtered under a pressure of 0.12 MPa and a filter mesh aperture of 45 μm to obtain a flame retardant coating for a PC substrate; a method for pre-modifying carbon nanotubes with a silane coupling agent is as follows: immersing the carbon nanotubes in a 5 wt% KH-550 ethanol aqueous solution with an ethanol volume ratio of 70%, stirring at 60°C for 60 minutes, and then drying; the organic tin catalyst is a compound of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.9:1.

[0112] Comparative Example 9

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

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

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

[0116] Step (2) preparing a compatible base material: stirring and dispersing 47 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite; the phenyl-modified epoxy resin is prepared by copolymerizing bisphenol A epoxy resin and phenyl glycidyl ether in a mass ratio of 2.7:1 to obtain a compatible base material;

[0117] Step (3) is mixed and prepared by adding 32 parts by mass of ferrite-plated microbeads to the compatible base material of step (2), stirring evenly, and then adding 2.8 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.8 parts by mass of BET205m 2 / g of fumed silica, heated to 50°C for dispersion, added 6 parts by mass of an organic tin catalyst, and degassed for 40 minutes with a biaxial stirring system at 20 rpm and 800 rpm under vacuum to obtain a flame retardant coating for a PC substrate; a method for pre-modifying carbon nanotubes with a silane coupling agent comprises: immersing the carbon nanotubes in a 5wt% KH-550 ethanol aqueous solution (70% by volume of ethanol), stirring at 60°C for 60 minutes, and then drying; the organic tin catalyst is a compound of dibutyltin dilaurate and stannous octoate in a mass ratio of 1.9:1.

[0118] Performance testing refers to the following standards:

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

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

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

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

[0123] Tear strength: ISO4624;

[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: the ferrite-plated microbeads are composed of hollow glass microbeads as their core, and the surface nano-iron tetroxide coating simultaneously imparts magnetic loss absorption and catalytic carbonization functions. Carbon nanotubes modified with the silane coupling agent KH-550 are embedded in the matrix to form a dielectric loss network, forming a broadband electromagnetic shielding synergist with the magnetic microbeads. Hydrophobic fumed silica fills the gaps between the microbeads, blocking the heat conduction path 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 carbonization and toughness with a precise ratio of rigid benzene rings to flexible ether chains (2.5-3:1), and is combined with low-temperature organotin catalytic curing to avoid thermal damage to the PC substrate. Plasma activation strengthens the interface bonding of the microbeads, while gradient mixing and staged vacuum degassing eliminate filler agglomeration and bubble defects, ultimately forming a dense, multifunctional integrated coating.

[0128] Once the coordination relationship between the components and the process in this solution is broken, it will cause systemic failure: Comparative Example 1 lacks the ferroferric oxide coating, which not only destroys the magnetic loss-catalytic carbonization dual-functional coupling of the hollow microspheres, but also causes the flame retardant system to lose the metal ion catalytic enhancement; After the hollow microspheres are removed in Comparative Example 2, the collapse of the insulation skeleton and the imbalance of density destroy the filler gradient distribution, resulting in bubble channels in the waterproof barrier; Comparative Example 3 omits plasma activation, resulting in weak interface bonding between ferroferric oxide and hollow glass microspheres, and local rupture of the electromagnetic cooperative network; the high solid content slurry in Comparative Example 4 causes microspheres to agglomerate, breaking the gap filling rhythm of hydrophobic silica, resulting in uneven performance distribution and a decrease in overall performance; the excessive benzene in Comparative Example 5 The base resin destroys the balance between rigidity and flexibility, causing the matrix-filler stress transfer to be out of tune, the coordination to decrease, and the overall performance to decline; the lack of pre-modified carbon nanotubes in comparative example 6 leads to the isolation of the dielectric network, which cannot form a broadband loss resonance with the magnetic microbeads; the lack of addition of fumed silica in comparative example 7 means that the thermal bridges between the microbeads are not cut off, and the nanopores destroy the densification process formed by degassing, thereby destroying the uniform distribution of the dielectric constant of the coating; the cancellation of vacuum degassing in comparative example 8 allows bubbles to penetrate the coating and cut the continuous hydrophobic interface constructed by KH-550; the unfiltered agglomerates introduced in comparative example 9 not only hinder the electromagnetic wave impedance matching, but also induce microcracks during the curing process, resulting in a slight decline in overall performance, but the performance is slightly better than that of the other comparative examples.

Claims

1. A flame retardant coating for PC substrate, characterized in that: Prepared by the following steps: By weight, Step (1) Preparation of ferrite-plated microbeads: 100 parts by mass of hollow glass microbeads with a particle size of 20-50 μm are placed in a fluidized bed and activated by argon plasma for 5-10 minutes; then 10-15 parts by mass of nano-ferrosoferric oxide, 2-2.5 parts by mass of a silane coupling agent, and 0.5-1 parts by mass of stearic acid are added to an ethanol aqueous solution, ultrasonically dispersed to obtain a modified slurry, and vulcanized to obtain ferrite-plated microbeads; Step (2) preparing a compatible base material: stirring and dispersing 45-50 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite to obtain a compatible base material; Step (3) is mixed and prepared as follows: 30-35 parts by mass of ferrite-plated microbeads are added to the compatible base material of step (2), and after stirring evenly, 2.5-3 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.5-5 parts by mass of hydrophobic silica are added, the temperature is raised to 50±2° C., dispersed, and then 5-7 parts by mass of an organic tin catalyst is added, and the mixture is stirred and degassed under a vacuum of -0.1 MPa for 40 minutes, and filtered to obtain a flame retardant coating for a PC substrate.

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

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

1.

4. The flame retardant coating for PC substrate according to claim 1, characterized in that: The organic tin 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 substrate according to claim 1, characterized in that: The carbon nanotube modification method in step (1) is as follows: the carbon nanotubes are immersed in a 5 wt % KH-550 ethanol aqueous solution, stirred at 60° C. for 60 minutes, and then dried.

6. The flame retardant coating for PC substrate 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 substrate according to claim 1, characterized in that: Step (3) degassing under vacuum with stirring is divided into two stages: Stage 1: -0.06 MPa, 15-20 minutes, rotation 600 rpm; The second stage: -0.10MPa, 20-30 minutes, rotation 1000rpm.

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

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

10. A method for preparing a flame retardant coating for a PC substrate according to any one of claims 1 to 9, characterized in that: The following steps are involved: By weight, Step (1) Preparation of ferrite-plated microbeads: 100 parts by mass of hollow glass microbeads with a particle size of 20-50 μm are placed in a fluidized bed and activated by argon plasma for 5-10 minutes; then 10-15 parts by mass of nano-ferrosoferric oxide, 2-2.5 parts by mass of a silane coupling agent, and 0.5-1 parts by mass of stearic acid are added to an ethanol aqueous solution, ultrasonically dispersed to obtain a modified slurry, and vulcanized to obtain ferrite-plated microbeads; Step (2) preparing a compatible base material: stirring and dispersing 45-50 parts by mass of a phenyl-modified epoxy resin, 20 parts by mass of ammonium polyphosphate, and 10 parts by mass of aluminum hypophosphite to obtain a compatible base material; Step (3) is mixed and prepared as follows: 30-35 parts by mass of ferrite-plated microbeads are added to the compatible base material of step (2), and after stirring evenly, 2.5-3 parts by mass of silane coupling agent pre-modified carbon nanotubes and 4.5-5 parts by mass of hydrophobic silica are added, the temperature is raised to 50±2° C., dispersed, and then 5-7 parts by mass of an organic tin catalyst is added, and the mixture is stirred and degassed under a vacuum of -0.1 MPa for 40 minutes, and filtered to obtain a flame retardant coating for a PC substrate.

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