A castable ablation-resistant coating material and its preparation method

Abstract

This invention provides a castable ablation-resistant coating material and its preparation method. The material is composed of unsaturated polyester resin, cobalt naphthenate, cyclohexanone peroxide, trichloroethyl phosphate, boron phenolic resin, silicon carbide, and hexa(4-aldehyde phenoxy)cyclotriphosphazene. Through optimized compounding design of the coating material, this invention achieves a castable ablation-resistant coating material with an ablation rate as low as 0.11 mm / s and a viscosity as low as 5900 mPa·s. This material possesses both excellent ablation resistance and casting process performance, and has broad application prospects in the casting and coating of solid rocket motor propellants.

Description

Technical Field

[0001] This invention belongs to the field of energetic material coating technology, and relates to unsaturated polyester resin coating materials, specifically to a castable ablation-resistant coating material and its preparation method. Background Technology

[0002] The coating layer is an important component of the propellant in a solid rocket engine. It is mostly made of polymer materials and is usually wrapped around the propellant to limit combustion and provide heat insulation, so that the propellant burns according to a predetermined pattern.

[0003] The main coating forming processes include injection molding, winding, encapsulation, patching, pressure injection, and casting. Among these, casting is the most adaptable and is an important component of existing propellant production lines such as screw casting, composite casting, granulation casting, and casting. It is widely used in rockets, tactical missiles, and various catapult weapon systems.

[0004] Unsaturated polyester resin is generally a linear polymer compound formed by the condensation polymerization of unsaturated or saturated diacids and unsaturated diols. It is diluted with crosslinking monomers or active solvents to form a resin solution with a certain viscosity. Due to its low viscosity, it is a natural coating material suitable for casting processes and is currently used in various fields such as missiles, engines, and rockets.

[0005] Due to technological advancements, propellant energies are increasing, leading to severe ablation and erosion of the coating layer during rocket ignition. Unsaturated polyester resin, with its aliphatic molecular structure, exhibits poor ablation resistance and typically fails to meet the requirements for propellant flame retardancy and heat insulation to protect the engine. Therefore, improving the ablation resistance of unsaturated polyester resin coatings has been a key research focus for scientists.

[0006] Currently, the simplest and most effective way to improve the ablation resistance of unsaturated polyester resin coatings is through filler compounding. For example, the article "Influence and Analysis of Phosphazene Flame Retardants on the Performance of Unsaturated Polyester Resin Coatings" shows that the addition of hexa(4-hydroxymethylphenoxy)cyclotriphosphazene flame retardant can improve the thermal stability and ablation resistance of unsaturated polyester resin coatings, reducing the linear ablation rate from 0.75 mm / s to 0.36 mm / s. However, when the phosphazene flame retardant content increases from 0 to 40 parts, the viscosity of the blank resin is 400 MPa·s; when the phosphazene flame retardant content is 8 parts, the viscosity of the mixed slurry rises to 41000 MPa·s; and when the phosphazene flame retardant content is 40 parts, the viscosity has risen to 98000 MPa·s, seriously affecting the process performance.

[0007] The article "Study on the Influence of OPS Compound on the Properties of Unsaturated Polyester Resin Coatings" shows that when the OPS content is 7.4%, the ablation rate of the unsaturated polyester resin coating decreases from approximately 0.75 mm / s in the blank resin to 0.63 mm / s. Under the condition of OPS content of 7.4%, the viscosity of the coating reaches 6252 MPa·s. When the OPS content is increased to 17.0%, the viscosity of the coating increases sharply to 34800 MPa·s, which leads to the deterioration of the processing performance of the coating compound and has an adverse effect on the casting process.

[0008] Based on the above analysis of existing technologies, it can be seen that with the development of charge technology, the requirements for the ablation resistance of the coating layer are becoming increasingly higher, and at the same time, higher requirements are also being placed on its process performance. Although the ablation resistance of the unsaturated polyester resin coating layer can be improved by compounding fillers, it often deteriorates the process performance of the unsaturated polyester resin coating layer, resulting in defects such as pores during the casting process, which leads to a significant decrease in the yield of the product. Summary of the Invention

[0009] In view of the defects and deficiencies of the existing technology, the purpose of this invention is to provide a castable ablation-resistant coating material and its preparation method, thereby solving the technical problem that the unsaturated polyester resin coating materials prepared by the existing technology are difficult to have both excellent ablation resistance and casting process performance.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0011] A castable ablation-resistant coating material is composed of unsaturated polyester resin, cobalt naphthenate, cyclohexanone peroxide, trichloroethyl phosphate, boron phenolic resin, silicon carbide, and hexa(4-aldehyde phenoxy)cyclotriphosphazene.

[0012] The present invention also has the following technical features:

[0013] Preferably, the material is composed of the following raw materials by mass: 40%–80% unsaturated polyester resin, 0.05%–1% cobalt naphthenate, 0.05%–10.0% cyclohexanone peroxide, 1%–15% trichloroethyl phosphate, 1%–20% boron phenolic resin, 1%–20% silicon carbide, and 1%–25% hexa(4-aldehyde phenoxy)cyclotriphosphazene, and the sum of the mass parts of the raw materials is 100%.

[0014] More preferably, the material is composed of the following raw materials by mass: 50%–70% unsaturated polyester resin, 0.1%–0.4% cobalt naphthenate, 1.0%–5.0% cyclohexanone peroxide, 3%–8% trichloroethyl phosphate, 5%–15% boron phenolic resin, 5%–15% silicon carbide, and 5%–20% hexa(4-aldehyde phenoxy)cyclotriphosphazene, with the sum of the mass parts of the raw materials being 100%.

[0015] Most preferably, the material is composed of the following raw materials by mass: 58.2%–66.94% unsaturated polyester resin, 0.22%–0.26% cobalt naphthenate, 2.7%–3.0% cyclohexanone peroxide, 4.7%–6.1% trichloroethyl phosphate, 7%–10% boron phenolic resin, 7.4%–9% silicon carbide, and 10%–15.95% hexa(4-aldehyde phenoxy)cyclotriphosphazene, with the sum of the mass parts of the raw materials being 100%.

[0016] Specifically, the material has a linear ablation rate as low as 0.11 mm / s and a viscosity as low as 5900 mPa·s.

[0017] This invention also protects a method for preparing the castable ablation-resistant coating material as described above, the method specifically comprising the following steps:

[0018] Step 1: Pre-dry silicon carbide and hexa(4-aldehyde phenoxy)cyclotriphosphazene to remove moisture, then dry and cool to room temperature;

[0019] Step 2: Add boron phenolic resin, hexa(4-aldehyde phenoxy)cyclotriphosphazene and silicon carbide to unsaturated polyester resin according to the specified ratio, and stir until uniform to obtain a premixed adhesive.

[0020] Step 3: Add the premixed rubber compound obtained in Step 2 to a three-roll mill for grinding and then feed it out. Repeat the above process several times until the rubber compound is uniform, and then discharge it to obtain the ground rubber compound.

[0021] Step 4: Add the weighed trichloroethyl phosphate and cyclohexanone peroxide to the grinding compound obtained in step 3, and stir until uniform; then add the weighed cobalt naphthenate, and stir until uniform to obtain the coating compound.

[0022] Step 5: Pour the coating material obtained in step 4 into the mold and then vacuum it.

[0023] Step 6: Place the mold with the coating material into an oven for curing. After curing, remove the mold to obtain a castable ablation-resistant coating material.

[0024] Specifically, in step one, the temperature for pre-drying and dehydration is 80–150 ℃, and the pre-drying and dehydration time is 1–3 hours.

[0025] Specifically, in step three, the grinding time is 5 to 30 minutes.

[0026] Specifically, in step five, the emptying time is 5 to 30 minutes.

[0027] Specifically, in step six, the curing temperature is 20–60 ℃, and the curing time is 8–24 hours.

[0028] The beneficial technical effects of this invention compared to the prior art are as follows:

[0029] (I) This invention optimizes the design of the coating material to achieve a castable ablation-resistant coating material with an ablation rate as low as 0.11 mm / s and a viscosity as low as 5900 mPa·s. This material has both excellent ablation resistance and casting process performance, and has broad application prospects in the casting and coating of solid rocket engine propellants.

[0030] (II) In the preparation of the coating material, the present invention controls the temperature, time and other conditions of each step to ensure the stability of the final coating material.

[0031] The technical solution of the present invention will be further described below with reference to the embodiments. Detailed Implementation

[0032] It should be noted that, unless otherwise specified, all raw materials and testing methods used in this invention are those known in the art, such as:

[0033] The unsaturated polyester resin used is a conventional unsaturated polyester resin known in the prior art, preferably an unsaturated polyester resin compound of grade 79Ⅲ produced by Changzhou Huake Polymer Co., Ltd.

[0034] Cyclohexanone peroxide is a conventional cyclohexanone peroxide product known in the prior art.

[0035] Cobalt naphthenate is a cobalt naphthenate product known in the prior art.

[0036] The trichloroethyl phosphate used is a product of trichloroethyl phosphate known in the prior art.

[0037] The boron phenolic resin used is a conventional boron phenolic resin product known in the prior art, preferably with a particle size of 150 mesh.

[0038] The hexa(4-aldehyde phenoxy)cyclotriphosphazene is a known hexa(4-aldehyde phenoxy)cyclotriphosphazene product with a purity ≥98.5%.

[0039] The silicon carbide used is a conventional silicon carbide product known in the existing technology, with a purity of ≥99%.

[0040] Viscosity testing was performed in accordance with the method of GB / T24148.4-2009, the National Standard of the People's Republic of China.

[0041] The oxyacetylene line ablation rate was tested according to the method of the National Standard of the People's Republic of China GJB323A-1996.

[0042] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0043] Example 1:

[0044] This embodiment provides a castable ablation-resistant coating material, which is composed of the following raw materials in parts by weight: 66.94% unsaturated polyester resin, 0.26% cobalt naphthenate, 2.7% cyclohexanone peroxide, 4.7% trichloroethyl phosphate, 8% boron phenolic resin, 7.4% silicon carbide, and 10% hexa(4-aldehyde phenoxy)cyclotriphosphazene.

[0045] Example 2:

[0046] This embodiment provides a castable ablation-resistant coating material, which is composed of the following raw materials in parts by weight: 58.2% unsaturated polyester resin, 0.22% cobalt naphthenate, 2.9% cyclohexanone peroxide, 6.1% trichloroethyl phosphate, 10% boron phenolic resin, 9% silicon carbide, and 13.58% hexa(4-aldehyde phenoxy)cyclotriphosphazene.

[0047] Example 3:

[0048] This embodiment provides a castable ablation-resistant coating material, which is composed of the following raw materials in parts by weight: 60.4% unsaturated polyester resin, 0.25% cobalt naphthenate, 3.0% cyclohexanone peroxide, 6% trichloroethyl phosphate, 7% boron phenolic resin, 7.4% silicon carbide, and 15.95% hexa(4-aldehyde phenoxy)cyclotriphosphazene.

[0049] Example 4:

[0050] This embodiment provides a method for preparing the castable ablation-resistant coating material as described in Embodiments 1 to 3. The method specifically includes the following steps:

[0051] Step 1: Pre-dry silicon carbide and hexa(4-aldehyde phenoxy)cyclotriphosphazene at 120 °C for 2 hours to remove moisture, then dry and cool to room temperature.

[0052] Step 2: Add boron phenolic resin, hexa(4-aldehyde phenoxy)cyclotriphosphazene and silicon carbide to the unsaturated polyester resin according to the specified ratio, and stir manually until uniform to obtain a premixed adhesive.

[0053] Step 3: Add the premixed rubber compound obtained in Step 2 to a three-roll mill and grind for 10 minutes. Then discharge the material. Repeat the above process three times until the rubber compound is uniform. Then discharge the material to obtain the ground rubber compound.

[0054] Step 4: Add the weighed trichloroethyl phosphate and cyclohexanone peroxide to the grinding compound obtained in step 3, and stir by hand until uniform; then add the weighed cobalt naphthenate, and stir by hand until uniform to obtain the coating compound.

[0055] Step 5: Pour the coating material obtained in Step 4 into the mold and evacuate for 10 minutes to remove the gas from the material.

[0056] Step 6: Place the mold with the coating material into an oven and cure it at 40°C for 12 hours. After curing, remove the mold to obtain a castable ablation-resistant coating material.

[0057] Performance testing:

[0058] In this embodiment, after step five is completed, a sample is taken and a viscosity test is performed. The test results are shown in Table 1.

[0059] In this embodiment, after step six, the cured coating layer is machined into a sample with a diameter of 30 mm and a height of 10 mm, and then the ablation rate is tested. The test results are shown in Table 1.

[0060] Table 1. Performance test results of material samples in Examples 1, 2 and 3

[0061]

[0062] As can be seen from the above results, the ablation rate of the castable ablation-resistant coating material prepared by the present invention is as low as 0.11 mm / s, and the viscosity can reach as low as 5900 mPa·s. Both the ablation rate and viscosity are lower than those of the unsaturated polyester resin coating material in the prior art, indicating that the castable ablation-resistant coating material prepared by the present invention not only has excellent ablation resistance, but also excellent casting process performance.

Claims

1. A castable ablation-resistant coating material, characterized in that, The material is composed of unsaturated polyester resin, cobalt naphthenate, cyclohexanone peroxide, trichloroethyl phosphate, boron phenolic resin, silicon carbide, and hexa(4-aldehyde phenoxy)cyclotriphosphazene; The material, by mass, is composed of the following raw materials: 40%–80% unsaturated polyester resin, 0.05%–1% cobalt naphthenate, 0.05%–10.0% cyclohexanone peroxide, 1%–15% trichloroethyl phosphate, 1%–20% boron phenolic resin, 1%–20% silicon carbide, and 1%–25% hexa(4-aldehyde phenoxy)cyclotriphosphazene, with the sum of the mass parts of the raw materials being 100%.

2. The castable ablation-resistant coating material as described in claim 1, characterized in that, The material, by mass, is composed of the following raw materials: 50%–70% unsaturated polyester resin, 0.1%–0.4% cobalt naphthenate, 1.0%–5.0% cyclohexanone peroxide, 3%–8% trichloroethyl phosphate, 5%–15% boron phenolic resin, 5%–15% silicon carbide, and 5%–20% hexa(4-aldehyde phenoxy)cyclotriphosphazene, with the sum of the mass parts of the raw materials being 100%.

3. The castable ablation-resistant coating material as described in claim 2, characterized in that, The material, by mass, is composed of the following raw materials: 58.2%–66.94% unsaturated polyester resin, 0.22%–0.26% cobalt naphthenate, 2.7%–3.0% cyclohexanone peroxide, 4.7%–6.1% trichloroethyl phosphate, 7%–10% boron phenolic resin, 7.4%–9% silicon carbide, and 10%–15.95% hexa(4-aldehyde phenoxy)cyclotriphosphazene, with the sum of the mass parts of the raw materials being 100%.

4. The castable ablation-resistant coating material as described in claim 2, characterized in that, The material has a linear ablation rate as low as 0.11 mm / s and a viscosity as low as 5900 mPa·s.

5. A method for preparing a castable ablation-resistant coating material as described in any one of claims 1 to 4, characterized in that, The method specifically includes the following steps: Step 1: Pre-dry silicon carbide and hexa(4-aldehyde phenoxy)cyclotriphosphazene to remove moisture, then dry and cool to room temperature; Step 2: Add boron phenolic resin, hexa(4-aldehyde phenoxy)cyclotriphosphazene and silicon carbide to unsaturated polyester resin according to the specified ratio, and stir until uniform to obtain a premixed adhesive. Step 3: Add the premixed rubber compound obtained in Step 2 to a three-roll mill for grinding and then feed it out. Repeat the above process several times until the rubber compound is uniform, and then discharge it to obtain the ground rubber compound. Step 4: Add the weighed trichloroethyl phosphate and cyclohexanone peroxide to the grinding compound obtained in step 3, and stir until uniform; then add the weighed cobalt naphthenate, and stir until uniform to obtain the coating compound. Step 5: Pour the coating material obtained in step 4 into the mold and then vacuum it. Step 6: Place the mold with the coating material into an oven for curing. After curing, remove the mold to obtain a castable ablation-resistant coating material.

6. The method for preparing the castable ablation-resistant coating material as described in claim 5, characterized in that, In step one, the temperature for pre-drying and dehydration is 80–150 °C, and the pre-drying and dehydration time is 1–3 hours.

7. The method for preparing the castable ablation-resistant coating material as described in claim 5, characterized in that, In step three, the grinding time is 5 to 30 minutes.

8. The method for preparing the castable ablation-resistant coating material as described in claim 5, characterized in that, In step five, the emptying time is 5 to 30 minutes.

9. The method for preparing the castable ablation-resistant coating material as described in claim 5, characterized in that, In step six, the curing temperature is 20–60 °C, and the curing time is 8–24 hours.

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