A composite flame retardant, a fire-retardant coating material for magnesium alloys or aluminum alloys, and its preparation method.

Abstract

This invention relates to a composite flame retardant composed of the following raw materials in the indicated mass ratios: 10-15 parts melamine polyphosphate, 10-15 parts melamine cyanurate, 2-5 parts chitosan, and 2-5 parts kaolin. This invention also provides a fire-retardant coating material for magnesium or aluminum alloys. This invention uses alkyd-modified phenolic resin as the matrix material, and based on a highly efficient and synergistic compounded flame retardant, adds chitosan, kaolin, and hollow glass microspheres to prepare the fire-retardant coating material. This allows for the rapid formation of a carbon network structure, and the hollow layer reduces heat transfer, improving the coating's fire resistance and effectively protecting magnesium and aluminum alloys. It also significantly reduces the coating's weight. The matrix material has good peelability, reducing smoke release and protecting the matrix, while simultaneously reducing the coating's weight, providing a foundation for aircraft maintainability, weight reduction, and widespread adoption.

Description

Technical Field

[0001] This invention relates to a composite flame retardant, a fire-retardant coating material for magnesium alloys or aluminum alloys, and a method for preparing the same. Background Technology

[0002] The successful commercial operation of large aircraft such as the C919 has injected new momentum into the development of subsequent aircraft models. Lightweighting and economic efficiency in aircraft have received increasing attention, making the use of lightweight materials the preferred choice for aircraft designers. Magnesium alloys have a specific gravity similar to plastics, strength and rigidity comparable to aluminum alloys, and excellent properties such as strong shock resistance, electromagnetic induction, thermal conductivity, and electrical conductivity, making them a promising candidate for aircraft applications. However, the flammability, poor heat resistance, high reactivity, and lack of stability of magnesium alloys limit their widespread use in aircraft with extremely high fire protection requirements. New aerospace aluminum alloys also face significant fire resistance challenges. Currently, the aviation industry tends to use fire-retardant coatings to improve the fire resistance of magnesium and aluminum alloys.

[0003] Aircraft operate in complex environments with limited space, and high expansion ratio fire-retardant coatings can restrict aircraft functionality. During operation, significant vibrations cause low-strength coatings to easily peel off, failing to meet fire resistance requirements. Furthermore, aircraft maintainability necessitates excellent removability of the fire-retardant coating. Currently, real-time monitoring of the strength performance of materials and components under high flame impact conditions is not possible to assess their fire resistance and fire protection, thereby demonstrating their airworthiness compliance. Therefore, based on the requirements for lightweight aircraft and materials, there is an urgent need for a fire-retardant coating material with low thickness, low expansion ratio, high thermal insulation, moderate adhesion and hardness, and removability.

[0004] CN202310322757 (An Intumescent Ceramicized Fire-Retardant Coating Material for Magnesium Alloys, Its Preparation Method and Application) discloses an intumescent fire-retardant coating for magnesium alloys. Using raw materials such as epoxy film-forming agents, organic rubber, zirconia ceramics, expanded graphite, ammonium polyphosphate, aluminum hydroxide, curing agents, and organic solvents, the intumescent fire-retardant coating is prepared by mixing, filtering, and sieving, and then spraying it onto the sandblasted magnesium alloy surface. This coating can withstand flame impact at 1100℃ for 15 minutes. However, this coating uses a large amount of raw materials; the film-forming agents, such as rubber, have low material strength and are easily damaged; it has a high expansion ratio, which is unfavorable for aviation operations; to meet the fire protection requirements of aviation regulations (CCAR25.853 and CCAR 33.17), the coating thickness often needs to be increased, resulting in increased weight; and it lacks rapid repair and removability. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a fire-retardant coating material for magnesium alloys and aluminum alloys with high temperature resistance, high strength, low thickness, and repairability and peelability that meets the fire protection requirements of civil aviation CCAR25.853, CCAR 33.17 and AC 20-135, as well as a preparation method thereof.

[0006] This invention provides a composite flame retardant, which is composed of raw materials in the following mass ratio:

[0007] 10-15 parts melamine polyphosphate, 10-15 parts melamine cyanurate, 2-5 parts chitosan, and 2-5 parts kaolin.

[0008] More preferably, it is composed of raw materials in the following mass ratio:

[0009] 12 parts melamine polyphosphate, 12 parts melamine cyanurate, 3 parts chitosan, and 3 parts kaolin.

[0010] The present invention also provides the application of the aforementioned composite flame retardant in the preparation of fire-retardant coating materials for magnesium alloys or aluminum alloys.

[0011] This invention provides a fire-retardant coating material for magnesium alloys or aluminum alloys, which is prepared from alkyd-modified phenolic resin, the aforementioned composite flame retardant, hollow glass microspheres, and basalt fiber, with the following mass ratio:

[0012] 15-25 parts of alkyd modified phenolic resin, 24-40 parts of composite flame retardant, 5-15 parts of hollow glass microspheres, and 2-5 parts of basalt fiber.

[0013] More preferably, the mass ratio of the alkyd-modified phenolic resin, composite flame retardant, hollow glass microspheres, and basalt fiber is as follows:

[0014] 20 parts of alkyd modified phenolic resin, 30 parts of composite flame retardant, 15 parts of hollow glass microspheres, and 5 parts of basalt fiber.

[0015] The hollow glass microspheres have a particle size of 10-50 micrometers and a density of 0.2-0.4 g / ml; the basalt fibers have a diameter of 20-40 micrometers and an aspect ratio of 5:1-10:1.

[0016] This invention provides a method for preparing the fire-retardant coating material for magnesium alloys or aluminum alloys, characterized in that:

[0017] a. Weigh the raw materials according to the specified mass ratio;

[0018] b. Add the raw materials to an organic solvent and mix for 1-3 hours under stirring at 1000-1500 rpm. Then grind the mixture for 0.5-2 hours. Finally, brush or spray the mixture onto the surface of an aluminum or magnesium alloy and dry it for 3-9 days to obtain the fireproof coating material.

[0019] The organic solvents mentioned are xylene, toluene, and cyclohexanone.

[0020] More preferably, the mixture is stirred at 1300 rpm for 2 hours; ground in a grinder for 1 hour; and dried for 7 days.

[0021] The present invention also provides the application of the fire-retardant coating material for magnesium alloys or aluminum alloys in fire-retardant coatings for aircraft.

[0022] Compared with existing technologies, the present invention has the following advantages:

[0023] (1) A fire-retardant coating material was prepared using alkyd-modified phenolic resin as the matrix material and a highly efficient and synergistic compounded flame retardant as the base material, with the addition of chitosan, kaolin, and hollow glass microspheres. This material can rapidly form a carbon layer network structure, and the hollow layer reduces heat transfer, improving the fire resistance of the coating and effectively protecting magnesium and aluminum alloys. Furthermore, it significantly reduces the weight of the coating, and the matrix material has good removability, providing a foundation for aircraft maintainability and weight reduction.

[0024] (2) Based on melamine polyphosphate and melamine cyanurate high-efficiency flame retardants, this invention adds chitosan and kaolin, which themselves have excellent high-temperature resistance and form a continuous, complete, and dense multi-layered structure of carbon layers and intercalation structures after heating. This achieves the goal of isolating heat sources, inhibiting heat transfer, and improving the ultimate fire-resistant function of the coating. At the same time, it reduces smoke emission, which is also an important indicator required by aircraft fire protection regulations.

[0025] (3) This invention not only uses a compounded high-efficiency composite flame retardant, but also uses hollow glass microspheres to physically block heat transfer, reduce the heat transfer of the fireproof coating by the high temperature and high heat flow flame specified in AC20-135, protect the substrate, and reduce the weight of the coating. Attached Figure Description

[0026] Figure 1 The temperature curve of the back of the specimen obtained in Example 1;

[0027] Figure 2 The temperature curve of the back of the specimen obtained in Example 2. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0029] Example 1: Preparation of the fire-retardant coating material for magnesium alloys or aluminum alloys according to the present invention

[0030] 200g of alkyd-modified phenolic resin, 120g of melamine polyphosphate, 120g of melamine cyanurate, 30g of chitosan, 30g of kaolin, 150g of hollow glass microspheres, and 50g of basalt fiber were added to 300g of xylene solvent and stirred at 1300rpm for 2 hours. The mixture was then transferred to a grinder and ground for 1 hour. A fire-retardant coating was applied to a 600mm x 600mm ZM5 magnesium alloy surface using a brush and allowed to dry at room temperature for 1 day. This process was repeated twice more, and after drying for 7 days, a 0.6mm thick fire-retardant coating was formed.

[0031] Example 2: Preparation of the fire-retardant coating material for magnesium alloys or aluminum alloys according to the present invention.

[0032] 150g of alkyd-modified phenolic resin, 150g of melamine polyphosphate, 150g of melamine cyanurate, 50g of chitosan, 50g of kaolin, 150g of hollow glass microspheres, and 50g of basalt fiber were added to 250g of xylene solvent and stirred at 1300rpm for 2 hours. The mixture was then transferred to a grinder and ground for 1 hour. A fire-retardant coating was applied to a 600mm x 600mm 2024-T42 aluminum alloy surface using a brush and allowed to dry at room temperature for 1 day. This process was repeated twice more, and after drying for 7 days, a 0.6mm thick fire-retardant coating was formed.

[0033] Example 3: Preparation of the fire-retardant coating material for magnesium alloys or aluminum alloys according to the present invention.

[0034] 150g of alkyd-modified phenolic resin, 150g of melamine polyphosphate, 150g of melamine cyanurate, 50g of chitosan, 50g of kaolin, 150g of hollow glass microspheres, and 50g of basalt fiber were added to 250g of xylene solvent and stirred at 1000rpm for 1 hour. The mixture was then transferred to a grinder and ground for 0.5 hours. A fire-retardant coating was applied to a 600mm x 600mm 2024-T42 aluminum alloy surface using a brush and allowed to dry at room temperature for 1 day. This process was repeated twice more, and after drying for 3 days, a 0.6mm thick fire-retardant coating was formed.

[0035] Comparative Example 1

[0036] 150g of alkyd-modified phenolic resin, 150g of melamine polyphosphate, and 150g of melamine cyanurate were added to 250g of xylene solvent and stirred at 1300rpm for 2 hours. The mixture was then transferred to a grinder and ground for 1 hour. A fire-retardant coating was applied to a 600mm x 600mm ZM5 magnesium alloy surface using a brush and allowed to dry at room temperature for 1 day. This process was repeated twice more, resulting in a 0.6mm thick fire-retardant coating after 7 days of drying.

[0037] Comparative Example 2

[0038] 150g of alkyd-modified phenolic resin, 150g of melamine polyphosphate, and 150g of melamine cyanurate were added to 250g of xylene solvent and stirred at 1300rpm for 2 hours. The mixture was then transferred to a grinder and ground for 1 hour. A fire-retardant coating was applied to a 600mm x 600mm 2024-T42 aluminum alloy surface using a brush and allowed to dry at room temperature for 1 day. This process was repeated twice more, resulting in a 0.6mm thick fire-retardant coating after 7 days of drying.

[0039] According to aviation regulations CCAR25.853 and CCAR 33.17 and procedure AC20-135, the flame test was conducted using No. 3 aviation kerosene, which has a large flow rate, high temperature, large heat flux, and strong flame impact force, causing significant impact damage to materials. It is difficult to achieve effective fire prevention using a simple composite flame retardant, so a multi-component flame retardant is required.

[0040] Using a standard burner as specified in regulation AC20-135, employing No. 3 jet aviation kerosene (RP-3), the generator produces a temperature of 1100℃±80℃ with a heat flux of 10.6 W / cm². 2 ~12.6W / cm 2 A standard flame was used to conduct a 15-minute fire resistance test on the specimen at a distance of 102 mm ± 2 mm from the specimen. A thermocouple temperature sensor was used on the back of the specimen to measure the temperature change and observe the burn-through condition and temperature of the specimen.

[0041] The test results are shown in the table below. Figure 1 , Figure 2 :

[0042]

[0043] in, Figure 1 The temperature curve of the back of the specimen obtained in Example 1; Figure 2The table above shows the temperature curves on the back of the specimen obtained in Example 2. As can be seen from the table, the fire-retardant coating material prepared by using alkyd-modified phenolic resin as the matrix material, with a highly efficient and synergistic compound flame retardant as the base, and adding chitosan, kaolin, and hollow glass microspheres, can rapidly form a carbon layer network structure. The hollow layer reduces heat transfer, improves the fire resistance of the coating, and effectively protects magnesium alloys and aluminum alloys. The formulation in Example 1 achieved the best results.

Claims

1. A fire-retardant coating material for magnesium alloys or aluminum alloys, characterized in that: It is made from alkyd-modified phenolic resin, composite flame retardant, hollow glass microspheres, and basalt fiber, with the following mass ratio: Alkyd modified phenolic resin 15-25 parts, composite flame retardant 24-40 parts, hollow glass microspheres 5-15 parts, basalt fiber 2-5 parts. The composite flame retardant is composed of raw materials in the following mass ratio: 10-15 parts melamine polyphosphate, 10-15 parts melamine cyanurate, 2-5 parts chitosan, and 2-5 parts kaolin.

2. The fire-retardant coating material for magnesium alloys or aluminum alloys according to claim 1, characterized in that: The mass ratio of the alkyd modified phenolic resin, composite flame retardant, hollow glass microspheres, and basalt fiber is as follows: 20 parts alkyd modified phenolic resin, 30 parts composite flame retardant, 15 parts hollow glass microspheres, and 5 parts basalt fiber. The composite flame retardant is composed of raw materials in the following mass ratio: 12 parts melamine polyphosphate, 12 parts melamine cyanurate, 3 parts chitosan, and 3 parts kaolin.

3. The fire-retardant coating material for magnesium alloys or aluminum alloys according to claim 1 or 2, characterized in that: The hollow glass microspheres have a particle size of 10-50 micrometers and a density of 0.2-0.4 g / ml; the basalt fibers have a diameter of 20-40 micrometers and an aspect ratio of 5:1-10:

1.

4. A method for preparing a fire-retardant coating material for magnesium alloys or aluminum alloys according to any one of claims 1-3, characterized in that: a. Weigh the raw materials according to the specified mass ratio; b. Add the raw materials to an organic solvent and mix for 1-3 hours under stirring at 1000-1500 rpm. Then grind the mixture for 0.5-2 hours. Finally, brush or spray the mixture onto the surface of an aluminum or magnesium alloy and dry it for 3-9 days to obtain the fireproof coating material.

5. The method for preparing the fire-retardant coating material for magnesium alloys or aluminum alloys according to claim 4, characterized in that: The organic solvents mentioned are xylene, toluene, and cyclohexanone.

6. The method for preparing the fire-retardant coating material for magnesium alloys or aluminum alloys according to claim 4, characterized in that: Mix at 1300 rpm for 2 hours; grind in a grinder for 1 hour; dry for 7 days.

7. The application of the fire-retardant coating material for magnesium alloys or aluminum alloys as described in any one of claims 1-3 in fire-retardant coatings for aircraft.

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