High performance durable fire resistant coating for cables and method of making same

Abstract

This application relates to the field of coating technology, specifically disclosing a high-performance, durable fire-retardant coating for cables and its preparation method. The high-performance, durable fire-retardant coating for cables comprises the following raw materials: polyacrylic acid emulsion, polydopamine-montmorillonite-coated ammonium polyphosphate, pentaerythritol, melamine, silane-grafted modified nano-alumina, hydroxypropyl methylcellulose ether, sodium polycarboxylate dispersant, silicone defoamer, and deionized water. The fire-retardant coating of this application is a functional coating for cable surface protection, exhibiting excellent fire-retardant properties and durable fire resistance.

Description

Technical Field

[0001] This application relates to the field of coating technology, and more specifically, to a high-performance, durable fire-retardant coating for cables and a method for preparing the same. Background Technology

[0002] Fire-retardant coatings for cables are a type of functional coating specifically designed for the protection of cable surfaces. They are primarily applied to the cable surface via brushing, rolling, or spraying, and are widely used in buildings, power rooms, chemical industrial parks, and rail transportation systems. They are particularly suitable for cable penetrations through floors, walls, and other critical fire-resistant zones. Their working mechanism involves forming a dense protective film at room temperature, providing basic corrosion and moisture protection for the cable. In the event of a fire, the coating rapidly undergoes a foaming and carbonization reaction, forming a continuous, expanding, heat-insulating carbon layer that blocks the transmission of flames and high temperatures into the cable, delaying the melting and failure of the insulation layer. This buys time for emergency response, personnel evacuation, and fire rescue operations, playing a crucial role in ensuring power system stability and reducing fire losses.

[0003] Various fire-retardant coatings for cables have been disclosed in the prior art. For example, patent CN107556830A discloses a fire-retardant coating for cables. This coating uses acrylic emulsion as the film-forming base material, combined with ammonium polyphosphate, pentaerythritol, and melamine to form an intumescent flame-retardant system, supplemented with pigments and fillers such as titanium dioxide and talc, as well as additives such as dispersants and thickeners. It is prepared through processes such as mixing, stirring, grinding, and dispersing. By optimizing the flame-retardant component ratio, it improves the coating's intumescent charring performance, while also possessing certain adhesion and weather resistance. It can meet the basic fire protection requirements of cables under normal conditions and has been applied to some extent in the protection of ordinary cable lines.

[0004] However, when applying existing fire-retardant coatings for cables to areas where cables pass through floors, there are still two major drawbacks: insufficient flame retardant performance and poor flame retardant durability. From the perspective of flame retardant performance itself, cables are often densely laid in floor areas. The expanded carbon layer of existing coatings is prone to localized collapse in high-temperature fires due to its loose structure, failing to form a continuous and effective heat insulation barrier and making it difficult to resist the long-term erosion of high-intensity flames. From the perspective of durability, floor areas are subject to environmental temperature and humidity fluctuations, slight vibrations, and deformations. The film-forming base material of existing coatings is not sufficiently compatible with the cable substrate and the floor interface, and the flame-retardant components are prone to migration and precipitation under long-term environmental conditions, leading to gradual cracking and peeling of the coating. This results in a significant decrease in flame retardant performance over time, failing to meet the long-term protection requirements of this critical fire-resistant zone. Summary of the Invention

[0005] To enhance the fire resistance and durability of fire-retardant coatings for cables, this application provides a high-performance, durable fire-retardant coating for cables and a method for preparing the same.

[0006] The high-performance, durable fire-retardant coating for cables provided in this application adopts the following technical solution: A high-performance, durable fire-retardant coating for cables, comprising the following raw materials in parts by weight: 20-30 parts of polyacrylic acid emulsion; 20-40 parts of polydopamine-montmorillonite-coated ammonium polyphosphate; Pentaerythritol 12-20 parts; 10-15 parts of melamine; 3-8 parts of silane-grafted modified nano-alumina; 1-3 parts of hydroxypropyl methylcellulose ether; Sodium polycarboxylate dispersant: 0.5-1.5 parts; 0.5-1.5 parts of silicone defoamer; 20-30 parts deionized water.

[0007] By adopting the above technical solution, the formula uses polydopamine-montmorillonite-coated ammonium polyphosphate as the core flame retardant component, replacing the traditional unmodified ammonium polyphosphate. Combined with silane-grafted modified nano-alumina, it forms an integrated system that takes into account both flame retardant enhancement and structural stability. This not only does not affect the original basic properties of the coating, such as workability and corrosion resistance, but also precisely solves the core technical problems.

[0008] Regarding the improvement of fire resistance, this formula effectively addresses the problem of loose and easily disintegrating expanded char layer in existing coatings through synergistic optimization of components. Polydopamine-montmorillonite-coated ammonium polyphosphate can form a composite char layer structure of "char film skeleton + dense foaming" in a fire. Combined with the foaming and char-forming reaction of pentaerythritol and melamine, it significantly improves the high-temperature impact resistance and structural integrity of the char layer, preventing localized disintegration at high temperatures and forming a continuous and effective heat insulation barrier. This can resist the long-term erosion of high-intensity flames in scenarios with dense cable laying, greatly enhancing the fire protection capability of the coating.

[0009] In terms of improving fire resistance and durability, the two core modified components in the formula play a crucial role. The polydopamine-montmorillonite coating structure forms a physical barrier layer, inhibiting the migration and precipitation of ammonium polyphosphate under long-term temperature and humidity fluctuations and floor vibration conditions, thus maintaining the stability of the flame-retardant system. The silane-grafted modified nano-alumina strengthens the internal structure and interfacial bonding of the coating, reducing cracking and peeling caused by changes in working conditions, ensuring that the fire resistance performance does not significantly decrease over time, and meeting the long-term protection needs of the floor slab as a key fire-resistant zone.

[0010] In addition, this formula uses acrylic emulsion as the base material, combined with hydroxypropyl methylcellulose ether, sodium polycarboxylate dispersant and other additives. While ensuring the improvement of core performance, it also takes into account the film density, dispersion uniformity and construction adaptability of the coating. It can be applied by conventional methods such as brushing and rolling. The resulting coating can not only form a good bond with cable substrate and floor slab, but also has a certain degree of flexibility and deformation resistance, which can meet the protection needs under complex working conditions.

[0011] Optionally, the polydopamine-montmorillonite-coated ammonium polyphosphate is prepared by the following method: Ammonium polyphosphate was dispersed in deionized water, the pH was adjusted to 8.8-9.2, dopamine hydrochloride was added, and the mixture was stirred at a constant temperature of 32-36℃ for 5-7 hours. Then organomontmorillonite was added, and the mixture was stirred for another 2-4 hours. After filtration, the mixture was dried at 80-85℃ to constant weight to obtain polydopamine-montmorillonite coated ammonium polyphosphate.

[0012] By adopting the above technical solution, the preparation process of polydopamine-montmorillonite-coated ammonium polyphosphate was clarified. Precise control of the reaction environment and process ensures the uniformity and integrity of the composite coating, providing a process guarantee for improving the fire resistance and durability of the coating. This preparation process induces dopamine self-polymerization in a weakly alkaline environment, allowing polydopamine to tightly adsorb onto the surface of ammonium polyphosphate to form an initial coating layer. Then, organomontmorillonite is introduced to construct a composite shell layer, avoiding the problems of loose structure and insufficient barrier properties of a single coating layer. This ensures the effective formation of the char layer skeleton during a fire and enhances the inhibition of flame-retardant component migration, fully leveraging the synergistic flame-retardant efficacy and stability of the coated ammonium polyphosphate.

[0013] Optionally, the amount of dopamine hydrochloride added is 5%-10% of the mass of ammonium polyphosphate.

[0014] Optionally, the amount of organomontmorillonite added is 4%-8% of the mass of ammonium polyphosphate.

[0015] Optionally, the silane-grafted modified nano-alumina is prepared by the following method: Nano-alumina was dispersed in a mixed solvent of anhydrous ethanol and deionized water, and KH570 silane coupling agent was added. The mixture was refluxed at 75-85℃ for 3-4 hours. After centrifugation, the mixture was dried at 100-110℃ to obtain silane-grafted modified nano-alumina.

[0016] By adopting the above technical solution, the preparation process of silane-grafted modified nano-alumina was clarified. Through control of the solvent system and reaction conditions, the effective grafting of KH570 silane coupling agent onto the surface of nano-alumina was ensured. This process enables the formation of organic functional groups on the surface of nano-alumina, overcoming the tendency of its inorganic particles to aggregate. Simultaneously, it enhances compatibility with polyacrylic acid emulsions, providing a structural basis for coating interface strengthening and internal toughening. This effectively solves the problem of poor compatibility between the coating and cable substrates / floor slabs, reduces the risk of coating cracking and peeling, and ensures the long-term stability of fire resistance performance.

[0017] Optionally, the mass ratio of anhydrous ethanol to deionized water in the mixed solvent is (3-5):1; the mass ratio of nano-alumina to the mixed solvent is 1:(8-12).

[0018] Optionally, the amount of KH570 silane coupling agent added is 10%-14% of the mass of nano-alumina.

[0019] Secondly, this application provides a method for preparing a high-performance, durable fire-retardant coating for cables, employing the following technical solution: A method for preparing a substance includes the following steps: S1. Add deionized water, sodium polycarboxylate dispersant, and organosilicon defoamer to a mixing tank and stir at 800-1000 r / min for 10-15 min. Then add hydroxypropyl methylcellulose ether and silane-grafted modified nano-alumina in sequence. Heat to 40-45℃ and stir at 1200-1500 r / min for 25-35 min to obtain a pre-dispersion. S2. Add core-shell structured polydopamine-montmorillonite coated ammonium polyphosphate, pentaerythritol, and melamine to the pre-dispersion liquid. Adjust the rotation speed to 2000-2800 r / min and disperse for 50-70 min. Cool to 25-30℃, add polyacrylic acid emulsion, and stir at 1500-1800 r / min for 20-30 min to obtain a high-performance and durable fire-retardant coating for cables.

[0020] By employing the above-mentioned technical solution, through stepwise dispersion, temperature-controlled stirring, and speed adjustment, uniform mixing of all components is ensured, preventing local component agglomeration from affecting coating performance. This method first pre-disperses the additives and modified nano-alumina to improve the uniformity of the coating's internal structure; then, high-speed dispersion and cooling stirring ensure full integration of the flame-retardant system and the film-forming base material, guaranteeing both the synergistic effect of the composite flame-retardant system and enhancing the coating's density. A rational preparation process allows the functions of each component in the coating to be fully utilized, further improving fire resistance and structural stability, ensuring the coating's protective effect under complex working conditions.

[0021] In summary, this application has the following beneficial effects: 1. This application effectively improves the core fire-retardant performance of cable fire-retardant coatings through core component modification and synergistic combination, solving the technical problem of loose and easily disintegrating expanded char layer in existing coatings. By replacing traditional unmodified polyphosphate with polydopamine-montmorillonite-coated ammonium polyphosphate, a composite char layer structure of "char film skeleton + dense foaming" can be formed in the event of a fire. Combined with the synergistic effect of the foamed char components, this significantly enhances the high-temperature impact resistance and structural integrity of the char layer, preventing localized disintegration at high temperatures. It can form a continuous and effective heat insulation barrier in scenarios with dense cable laying, resisting the long-term erosion of high-intensity flames, greatly improving the fire protection capability of the coating, and meeting the fire protection requirements of key fire-resistant zones in floor slabs.

[0022] 2. This application, through targeted component structure design, significantly improves the flame retardant performance and durability of fire-retardant coatings, solving the problems of flame retardant component migration and coating cracking and peeling under long-term working conditions. The polydopamine-montmorillonite composite coating structure can form an effective physical barrier layer, inhibiting the migration and precipitation of flame retardant components under conditions such as temperature and humidity fluctuations and floor vibration, maintaining the long-term stability of the flame retardant system; the silane-grafted modified nano-alumina strengthens the internal structure and interfacial bonding of the coating, improves the coating's resistance to deformation and cracking, avoids the degradation of flame retardant performance due to coating damage, and ensures that the coating can maintain excellent fire resistance after long-term use, meeting the long-term protection needs of critical parts.

[0023] 3. This application optimizes core performance while also considering the practicality and compatibility of the coating, achieving a synergistic unity between performance improvement and construction application. The formula uses polyacrylic acid emulsion as the film-forming base material, combined with suitable additives, which does not affect the original anti-corrosion and construction properties of the coating, while improving the film density and flexibility. The supporting preparation process, through step-by-step dispersion, temperature-controlled stirring and other operations, ensures that the components are fully integrated and avoids agglomeration that affects performance. The coating can be applied using conventional methods, can form good adhesion with cable substrates and floor slabs, and is suitable for construction and protection needs under complex working conditions, possessing strong practical application value. Detailed Implementation

[0024] The present application will be further described in detail below with reference to the embodiments.

[0025] Preparation example of polydopamine-montmorillonite coated ammonium polyphosphate Preparation Example 1 Polydopamine-montmorillonite coated ammonium polyphosphate was prepared by the following method: 10 kg of ammonium polyphosphate was dispersed in 50 kg of deionized water. The pH of the system was adjusted to 8.8 with a 5% sodium hydroxide solution. 0.5 kg of dopamine hydrochloride was added, and the mixture was stirred at 32 °C for 5 h. Then 0.4 kg of organomontmorillonite was added, and the mixture was stirred for another 2 h. After filtration, the mixture was dried at 80 °C to constant weight to obtain polydopamine-montmorillonite coated ammonium polyphosphate.

[0026] Preparation Example 2 Polydopamine-montmorillonite coated ammonium polyphosphate was prepared by the following method: 10 kg of ammonium polyphosphate was dispersed in 50 kg of deionized water. The pH of the system was adjusted to 9.0 with a 5% sodium hydroxide solution. 0.75 kg of dopamine hydrochloride was added, and the mixture was stirred at 34 °C for 6 h. Then 0.6 kg of organomontmorillonite was added, and the mixture was stirred for another 3 h. After filtration, the mixture was dried at 82 °C to constant weight to obtain polydopamine-montmorillonite coated ammonium polyphosphate.

[0027] Preparation Example 3 Polydopamine-montmorillonite coated ammonium polyphosphate was prepared by the following method: 10 kg of ammonium polyphosphate was dispersed in 50 kg of deionized water. The pH of the system was adjusted to 9.2 with a 5% sodium hydroxide solution. 0.1 kg of dopamine hydrochloride was added, and the mixture was stirred at 36 °C for 7 h. Then 0.8 kg of organomontmorillonite was added, and the mixture was stirred for another 4 h. After filtration, the mixture was dried at 85 °C to constant weight to obtain polydopamine-montmorillonite coated ammonium polyphosphate.

[0028] Preparation Example 4 Polydopamine-coated ammonium polyphosphate was prepared using the following method: 10 kg of ammonium polyphosphate was dispersed in 50 kg of deionized water. The pH of the system was adjusted to 9.2 with a 5% sodium hydroxide solution. 0.1 kg of dopamine hydrochloride was added, and the mixture was stirred at 36 °C for 7 h. After filtration, the mixture was dried at 85 °C to constant weight to obtain polydopamine-coated ammonium polyphosphate.

[0029] Preparation example of silane-grafted modified nano-alumina Preparation Example 5 Silane-grafted modified nano-alumina was prepared using the following method: 1 kg of nano-alumina was dispersed in 8 kg of a mixed solvent, which was anhydrous ethanol and deionized water in a mass ratio of 3:1. 0.1 kg of KH570 silane coupling agent was added, and the mixture was refluxed at 75 °C for 3 h. After centrifugation, the mixture was dried at 100 °C to obtain silane-grafted modified nano-alumina.

[0030] Preparation Example 6 1 kg of nano-alumina was dispersed in 10 kg of a mixed solvent, which was anhydrous ethanol and deionized water in a mass ratio of 4:1. 0.12 kg of KH570 silane coupling agent was added, and the mixture was refluxed at 80 °C for 3.5 h. After centrifugation, the mixture was dried at 105 °C to obtain silane-grafted modified nano-alumina.

[0031] Preparation Example 7 1 kg of nano-alumina was dispersed in 12 kg of a mixed solvent, which was anhydrous ethanol and deionized water in a mass ratio of 5:1. 0.14 kg of KH570 silane coupling agent was added, and the mixture was refluxed at 85 °C for 4 h. After centrifugation, the mixture was dried at 110 °C to obtain silane-grafted modified nano-alumina.

[0032] Example 1

[0033] A high-performance, durable fire-retardant coating for cables, the raw material composition and dosage of which are shown in Table 1, wherein the solid content of the polyacrylic acid emulsion is 35%; the polydopamine-montmorillonite coated ammonium polyphosphate is selected from the polydopamine-montmorillonite coated ammonium polyphosphate prepared in Preparation Example 1; and the silane grafted modified nano alumina is selected from the silane grafted modified nano alumina prepared in Preparation Example 5.

[0034] A method for preparing a high-performance, durable fire-retardant coating for cables includes the following steps: S1. Add deionized water, sodium polycarboxylate dispersant, and organosilicon defoamer to a mixing tank and stir at 800 r / min for 10 min. Then add hydroxypropyl methylcellulose ether and silane-grafted modified nano-alumina in sequence. Heat to 40℃ and stir at 1200 r / min for 25 min to obtain a pre-dispersion. S2. Add core-shell structured polydopamine-montmorillonite coated ammonium polyphosphate, pentaerythritol, and melamine to the pre-dispersion liquid. Adjust the rotation speed to 2000 r / min, disperse for 50 min, cool to 25℃, add polyacrylic acid emulsion, and stir at 1500 r / min for 20 min to obtain a high-performance and durable fireproof coating for cables.

[0035] Example 2

[0036] A high-performance, durable fire-retardant coating for cables, the raw material composition and dosage of which are shown in Table 1, wherein the solid content of the polyacrylic acid emulsion is 38%; the polydopamine-montmorillonite coated ammonium polyphosphate is selected from the polydopamine-montmorillonite coated ammonium polyphosphate prepared in Preparation Example 2; and the silane grafted modified nano-alumina is selected from the silane grafted modified nano-alumina prepared in Preparation Example 6.

[0037] A method for preparing a high-performance, durable fire-retardant coating for cables includes the following steps: S1. Add deionized water, sodium polycarboxylate dispersant, and organosilicon defoamer to a mixing tank and stir at 900 r / min for 12 min. Then add hydroxypropyl methylcellulose ether and silane-grafted modified nano-alumina in sequence. Heat to 43℃ and stir at 1350 r / min for 30 min to obtain a pre-dispersion. S2. Add core-shell structured polydopamine-montmorillonite coated ammonium polyphosphate, pentaerythritol, and melamine to the pre-dispersion liquid. Adjust the rotation speed to 2400 r / min, disperse for 60 min, cool to 28℃, add polyacrylic acid emulsion, and stir at 1600 r / min for 25 min to obtain a high-performance and durable fireproof coating for cables.

[0038] Example 3

[0039] A high-performance, durable fire-retardant coating for cables, the raw material composition and dosage of which are shown in Table 1, wherein the solid content of the polyacrylic acid emulsion is 40%; the polydopamine-montmorillonite coated ammonium polyphosphate is selected from the polydopamine-montmorillonite coated ammonium polyphosphate prepared in Preparation Example 3; and the silane grafted modified nano-alumina is selected from the silane grafted modified nano-alumina prepared in Preparation Example 7.

[0040] A method for preparing a high-performance, durable fire-retardant coating for cables includes the following steps: S1. Add deionized water, sodium polycarboxylate dispersant, and organosilicon defoamer to a mixing tank and stir at 1000 r / min for 15 min. Then add hydroxypropyl methylcellulose ether and silane-grafted modified nano-alumina in sequence. Heat to 45℃ and stir at 1500 r / min for 35 min to obtain a pre-dispersion. S2. Add core-shell structured polydopamine-montmorillonite coated ammonium polyphosphate, pentaerythritol, and melamine to the pre-dispersion liquid. Adjust the rotation speed to 2800 r / min, disperse for 70 min, cool to 30℃, add polyacrylic acid emulsion, and stir at 1800 r / min for 30 min to obtain a high-performance and durable fireproof coating for cables.

[0041] Table 1. Raw material components and dosage (kg) of fire-retardant coatings in Examples 1-3 polyacrylic emulsion 20 25 30 Polydopamine-montmorillonite coated ammonium polyphosphate 20 30 40 Pentaerythritol 12 16 20 melamine 10 12 15 Silane-grafted modified nano-alumina 3 5 8 Hydroxypropyl methylcellulose ether 1 2 3 Sodium polycarboxylate dispersant 0.5 1 1.5 silicone defoamer 0.5 1 1.5 Deionized water 20 25 30 Example 4

[0042] A high-performance, durable fire-retardant coating for cables, which differs from Example 2 in that the polydopamine-montmorillonite coated ammonium polyphosphate in this example is the polydopamine-montmorillonite coated ammonium polyphosphate prepared in Preparation Example 1.

[0043] Example 5

[0044] A high-performance, durable fire-retardant coating for cables, which differs from Example 2 in that the polydopamine-montmorillonite coated ammonium polyphosphate in this example is the polydopamine-montmorillonite coated ammonium polyphosphate prepared in Preparation Example 3.

[0045] Example 6

[0046] A high-performance, durable fire-retardant coating for cables, differing from Example 2 in that the polyacrylic acid emulsion in this example has a solid content of 20%.

[0047] Comparative Example Comparative Example 1 A fire-retardant coating was prepared according to Example 1 in the patent application document CN118652591A, entitled "A Water-based Intumescent Cable Fire-retardant Coating and Its Preparation Method".

[0048] Comparative Example 2 A high-performance, durable fire-retardant coating for cables, which differs from Example 2 in that polydopamine-montmorillonite coated ammonium polyphosphate was not added in this comparative example.

[0049] Comparative Example 3 A high-performance, durable fire-retardant coating for cables, which differs from Example 2 in that no silane-grafted modified nano-alumina is added in this comparative example.

[0050] Comparative Example 4 A high-performance, durable fire-retardant coating for cables, which differs from Example 2 in that the polydopamine-montmorillonite coated ammonium polyphosphate in this comparative example is the polydopamine-montmorillonite coated ammonium polyphosphate prepared in Preparation Example 4.

[0051] Performance testing

[0052] 1. Flame penetration time (min) The coating was brushed onto the surface of a standard cable sample (20 mm in diameter and 300 mm in length), with a dry film thickness of 1.5 mm. After curing for 7 days, the sample was fixed to a fireproof test frame to simulate a floor slab penetration scenario and fill with fireproof sealing material. An alcohol torch (outer flame temperature 1000℃) was used to continuously burn the sample, and the time from flame penetration of the coating to melting and breaking of the cable insulation layer was recorded. Each group was tested in parallel for 3 times and the average value was taken. The test results are shown in Table 2. 2. Migration and release rate of flame retardant components (%) The coating was brushed onto the surface of a 100mm×100mm×3mm steel plate (dry film thickness 1.5mm), cured for 7 days, and the total mass was weighed. It was then placed in a simulated working condition test chamber (-10℃~60℃ every 8 hours, humidity 60%~90%, 5Hz / 0.5mm vibration) for 30 days. The precipitate was removed, rinsed, and dried to constant weight. The amount of precipitate was determined by ion chromatography, and the precipitate rate was calculated as (mass of precipitated ammonium polyphosphate / total mass of ammonium polyphosphate in the coating) × 100%. The test results are shown in Table 2. 3. Flame penetration time retention rate after long-term operation (%) Samples were prepared according to the above-mentioned "flame penetration time" method and the initial time (t1) was measured. Another identical sample was treated under simulated working conditions for 30 days, and the flame penetration time (t2) was measured again. The retention rate was calculated as (t2 / t1)×100%. The degree of performance degradation was comprehensively evaluated. The test results are shown in Table 2.

[0053] Table 2 Experimental Results Example 1 52.3 1.8 88.6 Example 2 58.7 1.2 92.3 Example 3 56.2 1.5 90.5 Example 4 49.8 2.3 86.4 Example 5 51.5 2.1 87.8 Example 6 47.6 2.5 84.2 Comparative Example 1 21.4 12.6 45.8 Comparative Example 2 18.6 15.3 38.7 Comparative Example 3 28.3 10.8 52.3 Comparative Example 4 32.5 6.7 65.6 Based on the flame penetration time data, the overall performance of the example group significantly outperformed the comparative group, fully demonstrating the synergistic fire-retardant enhancement effect of the core modified components in this application. The flame penetration times of Examples 1-3 reached 52.3 min, 58.7 min, and 56.2 min, respectively, with Example 2 showing the best performance. This is due to its use of polydopamine-montmorillonite-coated ammonium polyphosphate from Preparation Example 2 and silane-grafted modified nano-alumina from Preparation Example 6, combined with the optimal ratio of raw material components, resulting in the most complete "carbon film skeleton + dense foaming" composite carbon layer structure, which can effectively resist the long-term erosion of a 1000℃ high-temperature flame. Examples 4-5, due to the use of different preparation processes for coated ammonium polyphosphate, showed slightly lower performance than Example 2, but were still significantly better than the comparative group, indicating that the coating process parameters have a controllable impact on the integrity of the carbon layer, and the advantages of the composite coating structure over traditional unmodified ammonium polyphosphate remain prominent. In Example 6, due to the polyacrylic acid emulsion having a solid content of only 20%, the film density was insufficient, resulting in a flame penetration time of 47.6 min, which confirms the auxiliary role of the film-forming base material performance in the construction of fire barriers.

[0054] The data on the migration and leaching rate of flame-retardant components clearly demonstrate the physical barrier value of the polydopamine-montmorillonite composite coating. The leaching rates in all example groups were below 2.5%, with Example 2 achieving optimal stability at a leaching rate of 1.2%. This was attributed to the precise matching of pH value, reaction time, and montmorillonite addition in its coating process, resulting in a uniform and dense composite coating that effectively inhibited the migration and loss of ammonium polyphosphate under fluctuating temperature and humidity conditions and vibration. In Examples 4-5, the leaching rate slightly increased to 2.1%-2.3% due to deviations in the coating agent preparation process parameters from optimal values. In Example 6, the leaching rate reached 2.5% due to increased coating porosity caused by a lower emulsion solid content, but all were significantly lower than the comparative groups. Comparative Example 2, without the coating of ammonium polyphosphate, had a precipitation rate as high as 15.3%; Comparative Example 4, with a single polydopamine coating, had a precipitation rate of 6.7%, indicating that the barrier properties of a single coating layer are insufficient. The introduction of montmorillonite can significantly enhance the stability of the coating structure, which is completely consistent with the design intention of the composite coating structure in the technical solution of this application.

[0055] The flame penetration time retention rate data after long-term operation comprehensively reflects the improved fire resistance and durability of the coating in this application. The retention rates of all example groups exceeded 84%, with Example 2 exhibiting the best long-term stability at a retention rate of 92.3%. This is primarily due to the synergistic effect of the polydopamine-montmorillonite composite coating layer and the silane-grafted modified nano-alumina: the former inhibits the migration of flame-retardant components, while the latter strengthens the internal structure and interfacial bonding of the coating, reducing cracking and peeling. Examples 4-5, affected by the coating process, showed a slight decrease in retention rate to 86.4%-87.8%. Example 6, due to its low emulsion solid content, experienced a slightly more significant performance degradation after coating aging, with a retention rate of 84.2%, but all were significantly better than the comparative examples. Comparative Example 1 (prior technology) had a retention rate of only 45.8%, Comparative Example 2 had a retention rate of 38.7%, and Comparative Example 3, lacking modified nano-alumina, was prone to cracking, resulting in a retention rate of only 52.3%. This clearly demonstrates that prior art cannot simultaneously solve the problems of flame-retardant component migration and coating structural instability, while the component design of this application precisely addresses this durability challenge.

[0056] The comparative data between the examples and the comparative examples further highlight the indispensability of the core modified components. Comparative Example 3, without the addition of silane-grafted modified nano-alumina, showed significantly worse flame penetration time (28.3 min), precipitation rate (10.8%), and retention rate (52.3%) compared to the example group. This demonstrates the crucial role of modified nano-alumina in strengthening the coating structure and improving interfacial adhesion, effectively reducing coating damage caused by changes in operating conditions and indirectly ensuring the stability of the flame-retardant system. Comparative Example 4, using a single polydopamine coating, showed better performance than other comparative examples but weaker than the example group, indicating that the introduction of montmorillonite optimizes the coating structure, improves the strength and barrier properties of the char layer skeleton, and verifies the technical advantages of the composite coating design of this application compared to single modification. Comparative Example 1 (prior art) lagged behind in all indicators, confirming its inherent defects in char layer stability and flame-retardant component retention. In contrast, this application, through core component modification and synergistic combination, achieves simultaneous improvement in fire resistance and durability.

[0057] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-performance, durable fire-retardant coating for cables, characterized in that, The raw materials include the following parts by weight: 20-30 parts of polyacrylic acid emulsion; 20-40 parts of polydopamine-montmorillonite-coated ammonium polyphosphate; Pentaerythritol 12-20 parts; 10-15 parts of melamine; 3-8 parts of silane-grafted modified nano-alumina; 1-3 parts of hydroxypropyl methylcellulose ether; Sodium polycarboxylate dispersant: 0.5-1.5 parts; 0.5-1.5 parts of silicone defoamer; 20-30 parts deionized water.

2. The high-performance, durable fire-retardant coating for cables according to claim 1, characterized in that, The polydopamine-montmorillonite-coated ammonium polyphosphate was prepared by the following method: Ammonium polyphosphate was dispersed in deionized water, the pH was adjusted to 8.8-9.2, dopamine hydrochloride was added, and the mixture was stirred at a constant temperature of 32-36℃ for 5-7 hours. Then organomontmorillonite was added, and the mixture was stirred for another 2-4 hours. After filtration, the mixture was dried at 80-85℃ to constant weight to obtain polydopamine-montmorillonite coated ammonium polyphosphate.

3. The high-performance, durable fire-retardant coating for cables according to claim 2, characterized in that: The amount of dopamine hydrochloride added is 5%-10% of the mass of ammonium polyphosphate.

4. The high-performance, durable fire-retardant coating for cables according to claim 2, characterized in that: The amount of organomontmorillonite added is 4%-8% of the mass of ammonium polyphosphate.

5. The high-performance, durable fire-retardant coating for cables according to claim 2, characterized in that, The silane-grafted modified nano-alumina was prepared using the following method: Nano-alumina was dispersed in a mixed solvent of anhydrous ethanol and deionized water, and KH570 silane coupling agent was added. The mixture was refluxed at 75-85℃ for 3-4 hours. After centrifugation, the mixture was dried at 100-110℃ to obtain silane-grafted modified nano-alumina.

6. The high-performance, durable fire-retardant coating for cables according to claim 5, characterized in that: The mass ratio of anhydrous ethanol to deionized water in the mixed solvent is (3-5):1; the mass ratio of nano-alumina to the mixed solvent is 1:(8-12).

7. A high-performance, durable fire-retardant coating for cables according to claim 5, characterized in that: The amount of KH570 silane coupling agent added is 10%-14% of the mass of nano-alumina.

8. A method for preparing a high-performance, durable fire-retardant coating for cables according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Add deionized water, sodium polycarboxylate dispersant, and organosilicon defoamer to a mixing tank and stir at 800-1000 r / min for 10-15 min. Then add hydroxypropyl methylcellulose ether and silane-grafted modified nano-alumina in sequence. Heat to 40-45℃ and stir at 1200-1500 r / min for 25-35 min to obtain a pre-dispersion. S2. Add core-shell structured polydopamine-montmorillonite coated ammonium polyphosphate, pentaerythritol, and melamine to the pre-dispersion liquid. Adjust the rotation speed to 2000-2800 r / min and disperse for 50-70 min. Cool to 25-30℃, add polyacrylic acid emulsion, and stir at 1500-1800 r / min for 20-30 min to obtain a high-performance and durable fire-retardant coating for cables.