Glycidyl methacrylate grafted ethylene propylene diene rubber, thermal insulation layer and preparation method and application thereof

Abstract

The application provides a glycidyl methacrylate grafted ethylene-propylene-diene rubber, a thermal insulation layer and a preparation method and application thereof, and the structure of the glycidyl methacrylate grafted ethylene-propylene-diene rubber is shown as formula (I). The glycidyl methacrylate grafted ethylene-propylene-diene rubber is added into the ethylene-propylene-diene rubber thermal insulation material as a compatilizer, the compatibility of the ethylene-propylene-diene rubber and a polar polymer is improved, the dispersion of a fiber filler in the ethylene-propylene-diene rubber matrix is improved, the fiber amount is increased while the uniform dispersion is ensured. By cooperating with other functional additives and fillers, an ablation-resistant ethylene-propylene-diene rubber thermal insulation layer with excellent mechanical properties for a solid rocket engine is obtained. The ablation resistance and the erosion resistance of the thermal insulation material are improved, and the performance requirements of the ablation resistance and the erosion resistance of the thermal insulation layer under the engine overload are met. (I)

Description

Technical Field

[0001] This invention relates to the field of solid rocket motor insulation technology, specifically to a glycidyl methacrylate-grafted EPDM rubber, an insulation layer, its preparation method, and its application. Background Technology

[0002] Ethylene propylene diene monomer (EPDM) rubber insulation material is widely used internationally in the internal insulation layer of solid rocket motors due to its advantages such as low density, good weather resistance, aging resistance, and high thermal insulation performance. As an important component of solid rocket motors, EPDM insulation material should possess good mechanical properties, ablation resistance, and adhesion properties.

[0003] To meet the various performance requirements of solid rocket motors for insulation materials, multiple fillers are typically added, mainly including fibers, reinforcing fillers, flame retardants, vulcanizing agents, and functional additives. Among these, fiber fillers can maintain their original stable form or melt into a viscous liquid during engine operation, improving the strength of the carbon layer and solidifying the bond between the carbon layer and the bulk material. This is one of the effective ways to improve the ablation resistance of the insulation layer. However, during the mixing and sheeting process of insulation materials, fibers undergo orientation along the calendering direction under the shear force of the rollers, causing the insulation layer to exhibit anisotropic effects, particularly in tensile mechanical behavior, which shows significant anisotropy. This manifests as a low elongation at break parallel to the sheeting direction, failing to meet overall design specifications. Furthermore, the EPDM rubber molecule's main chain structure is in a saturated state, with only a small number of unsaturated double bonds on the third monomer of the side chains. Therefore, it is inherently a weakly polar material, exhibiting poor compatibility with polar fiber fillers. Fiber dispersion directly affects the mechanical properties of thermal insulation materials. Increasing fiber filler can reduce the ablation rate of thermal insulation materials, but it further leads to uneven fiber dispersion in the matrix, causing a decline in the mechanical properties of thermal insulation materials.

[0004] Therefore, ensuring uniform dispersion of fiber fillers at high filler levels is essential. Fibers are typically subjected to physical or chemical modification (ultrasonic treatment, surface grafting, coupling agent treatment) to improve their dispersion with the matrix. However, physical modification requires high-precision equipment, has limited surface control, and results in uneven modification. Chemical modification often involves the use of hazardous chemicals, leading to environmental pollution and increased costs associated with subsequent waste treatment and cleaning. Summary of the Invention

[0005] This invention provides a glycidyl methacrylate-grafted EPDM rubber, an insulation layer, its preparation method, and its application. Glycidyl methacrylate-grafted EPDM rubber is added as a compatibilizer to EPDM rubber insulation materials, solving the problem of poor compatibility of fiber fillers and the direct impact of fiber dispersion on the mechanical properties of insulation materials.

[0006] To solve the above-mentioned technical problems, the present invention provides a glycidyl methacrylate-grafted EPDM rubber, the structural formula of which is shown in formula (I): .

[0007] Based on the same inventive concept, the present invention also provides a method for preparing glycidyl methacrylate-grafted EPDM rubber, comprising the following steps: S1: Add EPDM rubber, glycidyl methacrylate, and dicumyl peroxide to the torque rheometer for melt grafting; S2: After the reaction is complete, the material is discharged and cooled to room temperature. Then, it is passed through a two-roll mill three times to obtain glycidyl methacrylate-grafted EPDM rubber.

[0008] Preferably, in S1, the mass ratio of EPDM rubber, glycidyl methacrylate, and dicumyl peroxide is 200:16:3; the reaction temperature is 160 °C, and the reaction time is 10 min.

[0009] The present invention also provides an ablation-resistant EPDM insulation layer, which is prepared from the following raw materials in parts by weight: 70-90 parts of EPDM rubber; 10-30 parts of glycidyl methacrylate-grafted EPDM rubber as described in claim 1; 5-25 parts of reinforcing agent; 5-20 parts of reinforcing fiber; 10-25 parts of flame retardant; 10-20 parts of ablation-resistant filler; 2-5 parts of tackifying resin; 5-10 parts of plasticizer; 3-7 parts of vulcanizing agent; and 5-10 parts of vulcanization accelerator.

[0010] Preferably, the reinforcing agent is fumed silica; the reinforcing fiber is one or more of the following: pulp-like or long-fiber poly(p-phenylene terephthalamide) fiber, polyimide fiber, and phenolic fiber.

[0011] Preferably, the flame retardant is a combination of two or more of ammonium polyphosphate, melamine polyphosphate, magnesium hydroxide, and aluminum hydroxide; the ablation-resistant filler is phenolic resin or modified phenolic resin.

[0012] Preferably, the tackifying resin is a terpene resin or a phenolic resin; the plasticizer is a cycloalkane oil or a paraffin oil.

[0013] Preferably, the vulcanizing agent is dicumyl peroxide or di-tert-butyl peroxide and N'-m-phenylenebismaleimide, triallyl isocyanurate or sulfur; the mass ratio of dicumyl peroxide or di-tert-butyl peroxide and N'-m-phenylenebismaleimide, triallyl isocyanurate or sulfur is 1:1-2.

[0014] Preferably, the vulcanization accelerator is zinc oxide and stearic acid; the mass ratio of zinc oxide to stearic acid is 5-10:1.

[0015] Based on the same inventive concept, the present invention also provides a method for preparing an ablation-resistant EPDM insulation layer, comprising the following steps: S1: Place EPDM rubber and glycidyl methacrylate-grafted EPDM rubber into an internal mixer and mix them. S2: Reinforcing fibers, reinforcing agents, plasticizers, tackifying resins, ablation-resistant fillers, flame retardants, and vulcanization accelerators are added sequentially to S1 and mixed multiple times in stages. S3, add vulcanizing agent to the compounded rubber in S2, then mix and discharge the material; S4 involves pressing the S3 rubber compound through a two-roll mill, and then extruding it into sheets after 5-8 passes. S5. The sheet obtained in S4 is placed for more than 12 hours and then vulcanized and formed by a flat vulcanizing machine to obtain an ablation-resistant EPDM insulation layer.

[0016] Preferably, in S1, the mixing temperature is 30-80℃ and the time is 5-10 minutes; in S2, the mixing temperature is 80-130℃ and the time is not less than 20 minutes; in S3, the mixing temperature is 40℃-65℃ and the time is not less than 5 minutes; in S4, when the open mill passes through the mill, the roll temperature is controlled at 40℃-60℃ and the roll gap is not greater than 0.5mm; in S5, the vulcanization molding temperature is 150℃-160℃, the vulcanization time is 40-100 minutes, and the vulcanization pressure is 2MPa-6MPa.

[0017] The present invention also provides an application of an ablation-resistant EPDM insulation layer, wherein the ablation-resistant EPDM insulation layer is used as an insulation layer for the combustion chamber of a solid rocket motor.

[0018] The above-described one or more technical solutions of the present invention have at least one or more of the following technical effects: 1. The glycidyl methacrylate-grafted EPDM rubber synthesized in this invention is simple to prepare and can be mass-produced. While maintaining a series of important physicochemical properties of EPDM itself without significant changes, it improves polarity and enhances the orientation and dispersibility of fiber fillers in the EPDM matrix.

[0019] 2. The thermal insulation material obtained by this invention, through optimizing the amount of fiber and glycidyl methacrylate grafted EPDM rubber, can still be uniformly dispersed even with a high fiber filling amount. The thermal insulation material has high elongation in both parallel and perpendicular directions with a small difference between the two, ensuring the performance reliability of the thermal insulation layer in different directions and meeting the special requirements of engines for the mechanical properties of the thermal insulation layer.

[0020] 3. The thermal insulation material obtained by the present invention improves the ablation resistance and erosion resistance of the thermal insulation material by optimizing the type and / or amount of fiber, flame retardant and ablation resistant resin, thus meeting the performance requirements of the thermal insulation layer for ablation resistance and erosion resistance under engine overload.

[0021] 4. The thermal insulation material obtained by the present invention, by introducing the compatibilizer glycidyl methacrylate grafted onto EPDM rubber, increases the polarity of EPDM rubber, improves fiber dispersion, and further enhances the interfacial adhesion performance between the thermal insulation material and steel. Attached Figure Description

[0022] Figure 1 Infrared spectra of glycidyl methacrylate grafted onto EPDM rubber, EPDM rubber and glycidyl methacrylate. Figure 2 Relative difference graphs of elongation at break in the vertical and parallel directions for Examples 1-5 and Comparative Examples 1-4. Detailed Implementation

[0023] This invention provides a glycidyl methacrylate-grafted EPDM rubber, the structural formula of which is shown in formula (I): .

[0024] Based on the same inventive concept, this invention also provides a method for preparing glycidyl methacrylate-grafted EPDM rubber, the reaction process of which is as follows:

[0025] Includes the following steps: S1: Add EPDM rubber, glycidyl methacrylate, and dicumyl peroxide to the torque rheometer for melt grafting; S2: After the reaction is complete, the material is discharged and cooled to room temperature. Then, it is passed through a two-roll mill three times to obtain glycidyl methacrylate-grafted EPDM rubber.

[0026] In S1, the mass ratio of EPDM rubber, glycidyl methacrylate, and dicumyl peroxide is 200:16:3.

[0027] In S1, the reaction temperature is 160 ℃ and the reaction time is 10 min.

[0028] This invention also provides an ablation-resistant EPDM insulation layer, which is prepared from the following raw materials in parts by weight: 70-90 parts of EPDM rubber; 10-30 parts of glycidyl methacrylate-grafted EPDM rubber as described in claim 1; 5-25 parts of reinforcing agent; 5-20 parts of reinforcing fiber; 10-25 parts of flame retardant; 10-20 parts of ablation-resistant filler; 2-5 parts of tackifying resin; 5-10 parts of plasticizer; 3-7 parts of vulcanizing agent; and 5-10 parts of vulcanization accelerator.

[0029] The EPDM rubber is 4045 raw rubber; the reinforcing agent is fumed silica, which not only produces a reinforcing effect, but also melts and absorbs a large amount of heat at high temperatures. The molten silica fills the pores of the carbon layer, which plays a role in consolidating the carbon layer and also improves the ablation performance of the material.

[0030] The reinforcing fiber is one or more of the following: pulp-like or long-fiber poly(p-phenylene terephthalamide) fiber, polyimide fiber, and phenolic fiber. During engine operation, the fiber can maintain its original shape or melt to form a viscous liquid, thereby improving the strength of the carbon layer and solidifying the bond between the carbon layer and the engine body. Preferably, the fiber is 2mm-5mm long-fiber poly(p-phenylene terephthalamide) fiber (PA) and polyimide fiber (PI).

[0031] The flame retardant is a combination of two or more of the following: ammonium polyphosphate, melamine polyphosphate, magnesium hydroxide, and aluminum hydroxide. The metal hydroxide flame retardant decomposes into metal oxides and water at high temperatures. The evaporation of water absorbs heat and dilutes the density of the combustible gas. The decomposed metal oxides can then react with polyphosphate to form polyphosphate, thus synergistically improving the flame retardancy of the system. Preferably, the flame retardant has a mass ratio of ammonium polyphosphate to magnesium hydroxide of 2:1.

[0032] The ablation-resistant filler is phenolic resin or modified phenolic resin. Phenolic resin itself has a high char residue rate, and after modification, it can also fix the free radicals generated by the thermal decomposition of the insulation material, making it a commonly used and excellent ablation-resistant filler in EPDM insulation materials.

[0033] The tackifying resin is either a terpene resin or a phenolic resin. For EPDM rubber, its self-adhesive properties are poor, requiring the use of a tackifier to increase the material's self-adhesion and mutual adhesion. Preferably, a terpene resin is chosen as the tackifier.

[0034] The plasticizer is a cycloalkane oil or paraffin oil. Its main function is to adjust the viscosity of the rubber, wet the filler to facilitate its dispersion in the matrix, increase the flexibility of the product, and lower the embrittlement temperature. Preferably, paraffin oil is chosen as the plasticizer.

[0035] The vulcanizing agent is dicumyl peroxide or di-tert-butyl peroxide and N'-m-phenylenebismaleimide, triallyl isocyanurate, or sulfur; the mass ratio of dicumyl peroxide or di-tert-butyl peroxide and N'-m-phenylenebismaleimide, triallyl isocyanurate, or sulfur is 1:1-2. Preferably, the vulcanizing agent is dicumyl peroxide, and the co-vulcanizing agent is triallyl isocyanurate and sulfur.

[0036] The vulcanization accelerator is zinc oxide and stearic acid; the mass ratio of zinc oxide to stearic acid is 5-10:1.

[0037] This invention also provides a method for preparing an ablation-resistant EPDM insulation layer, comprising the following steps: S1: Place EPDM rubber and glycidyl methacrylate-grafted EPDM rubber into an internal mixer and mix them. S2: Reinforcing fibers, reinforcing agents, plasticizers, tackifying resins, ablation-resistant fillers, flame retardants, and vulcanization accelerators are added sequentially to S1 and mixed multiple times in stages. S3, add vulcanizing agent to the compounded rubber in S2, then mix and discharge the material; S4 involves pressing the S3 rubber compound through a two-roll mill, and then extruding it into sheets after 5-8 passes. S5. The sheet obtained in S4 is placed for more than 12 hours and then vulcanized and formed by a flat vulcanizing machine to obtain an ablation-resistant EPDM insulation layer.

[0038] In S1, the mixing temperature is 30-80℃ and the time is 5-10 minutes; in S2, the mixing temperature is 80-130℃ and the time is not less than 20 minutes; in S3, the mixing temperature is 40℃-65℃ and the time is not less than 5 minutes; in S4, when the open mill passes through the mill, the roll temperature is controlled at 40℃-60℃ and the roll gap is not greater than 0.5mm; in S5, the vulcanization molding temperature is 150℃-160℃, the vulcanization time is 40-100 minutes, and the vulcanization pressure is 2MPa-6MPa.

[0039] This invention also provides an application of an ablation-resistant EPDM insulation layer, which is used as an insulation layer for the combustion chamber of a solid rocket engine.

[0040] Example 1 A method for preparing glycidyl methacrylate-grafted EPDM rubber includes the following steps: S1: 200 parts by weight of EPDM rubber, 8 parts by weight of glycidyl methacrylate, and 1.5 parts by weight of dicumyl peroxide were added to a torque rheometer for melt grafting. The reaction temperature was 160 ℃ and the reaction time was 10 min. S2: After the reaction is complete, the material is discharged and cooled to room temperature. Then, it is passed through a two-roll mill three times to obtain glycidyl methacrylate-grafted EPDM rubber.

[0041] like Figure 1 As shown, the characteristic peak of EPDM mainly includes 2930 cm⁻¹. -1 2850cm -1 1460 cm -1 1375 cm -1 and 720cm -1 The peaks at these locations correspond to the absorption peaks of CH asymmetric and symmetric stretching vibrations, CH deformation vibrations, CH deformation vibrations on tertiary carbon, and CH rocking vibrations, respectively. The characteristic absorption peaks of GMA mainly include the peak at 1640 cm⁻¹. -1 1730 cm -1 and 1160 cm -1 At these locations, the absorption peaks correspond to the C=C, C=O, and CO stretching vibrations, respectively.

[0042] Compared to EPDM, the infrared spectrum of GMA-g-EPDM is at 1730 cm⁻¹. -1 A new absorption peak appeared at the point, namely the C=O stretching vibration absorption peak. Therefore, it can be concluded that GMA has been grafted onto EPDM, and glycidyl methacrylate grafted EPDM rubber has been successfully prepared.

[0043] Examples 2-6 The composition of the ablation-resistant EPDM insulation layer in Examples 2-6 is shown in Table 1. The values ​​for each raw material in Table 1 are the parts by weight of that raw material.

[0044] Table 1. Composition of ablation-resistant EPDM insulation layers in Examples 2-6

[0045] Example 2-6 describes a method for preparing an ablation-resistant EPDM insulation layer, comprising the following steps: S1: Prepare raw materials according to the formulas in Examples 2-6 of Table 1; S2: ① Add EPDM raw rubber and glycidyl methacrylate-grafted EPDM rubber to a mixer and mix for 3 min; ② Add poly(p-phenylene terephthalamide) fiber and polyimide fiber and mix for 20 min; ③ Add reinforcing agent fumed silica and plasticizer paraffin oil and mix for 10 min; ④ Add modified phenolic resin, ammonium polyphosphate, magnesium hydroxide, zinc oxide and stearic acid and mix for (5-10) min; ⑤ Add terpene resin and mix for (5-10) min; ⑥ After the temperature drops to 30℃-40℃, add dicumyl peroxide, triallyl isocyanurate and sulfur, and mix for (5-10) min; S3: Adjust the roller gap of the open mill to 0.5mm, and pass the mixed rubber compound through the open mill 6 times to produce sheets; S4: After the sample is placed at room temperature for 12 hours, it is vulcanized by a flat vulcanizing machine. The vulcanization temperature is 150℃, the vulcanization time is 90 minutes, and the vulcanization pressure is 3MPa.

[0046] Comparative Examples 1-4 The composition of the insulation layer in Comparative Examples 1-4 is shown in Table 2. The values ​​for each raw material in Table 2 are the parts by weight of that raw material.

[0047] Table 2 Composition of Insulation Layers in Comparative Examples 1-4

[0048] The preparation methods of the insulation layer in Comparative Examples 1-4 include the following steps: S1: Prepare raw materials according to the formulas of Comparative Examples 1-4 in Table 2.

[0049] S2: ① Add EPDM raw rubber to the internal mixer and mix for 3 min; ② Add reinforcing fiber poly(p-phenylene terephthalamide) fiber and / or polyimide fiber and mix for 20 min; ③ Add reinforcing agent fumed silica and plasticizer paraffin oil and mix for 10 min; ④ Add modified phenolic resin, ammonium polyphosphate, magnesium hydroxide, zinc oxide and stearic acid and mix for (5-10) min; ⑤ Add terpene resin and mix for (5-10) min; ⑥ After the temperature drops to 30℃-40℃, add dicumyl peroxide, triallyl isocyanurate and sulfur, and mix for (5-10) min.

[0050] S3: Adjust the roller gap of the open mill to 0.5mm, and pass the mixed rubber compound through the open mill 6 times to produce sheets.

[0051] S4: After the sample is placed at room temperature for 12 hours, it is vulcanized by a flat vulcanizing machine. The vulcanization temperature is 150℃, the vulcanization time is 90 minutes, and the vulcanization pressure is 3MPa.

[0052] Performance testing: The vulcanized rubbers of Examples 2-6 and Comparative Examples 1-4 were tested for tensile strength and elongation at break according to GB / T 528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber", the rubber line ablation rate was tested according to GJB323B-2018 "Test Method for Ablation of Ablation Materials", and the shear strength of the rubber-steel interface was tested according to GB / T 13936-2014 "Test Method for Tensile Shear Strength of Adhesion Between Vulcanized Rubber and Metal". The test results are shown in Table 3. Figure 2 As shown: Table 3 Properties of vulcanized rubber in Examples 2-6 and Comparative Examples 1-4

[0053] As shown in Table 3: (1) The mechanical properties of the insulation materials in Comparative Examples 1-4 are significantly anisotropic. The elongation at break in the parallel direction of the insulation materials is low. The anisotropy of the insulation materials is related to the type of fiber. The anisotropy of the insulation materials filled with poly(p-phenylene terephthalamide) fiber is higher than that of polyimide fiber.

[0054] (2) Comparative Examples 1-3 used single fiber fillers, resulting in poor ablation resistance of the insulation material. Furthermore, with the increase in the amount of poly(p-phenylene terephthalamide) fiber, the reduction in the linear ablation rate of the insulation material was limited, failing to meet the technical requirements. Using a combination of poly(p-phenylene terephthalamide) fiber and polyimide fiber can effectively reduce the linear ablation rate of the insulation material.

[0055] (3) Compared with Comparative Examples 1-4, the addition of glycidyl methacrylate grafted EPDM rubber in Examples 2-6 can effectively improve the anisotropy of the mechanical properties of fiber-filled insulation materials. The elongation at break of the insulation material in the parallel calendering direction is significantly improved. With the optimization of the amount of fiber and compatibilizer, the insulation material maintains good mechanical properties while its ablation resistance is further improved, meeting the various performance requirements of the engine for insulation materials.

[0056] (4) Compared with Comparative Examples 1-4, the addition of glycidyl methacrylate grafted EPDM rubber slightly improved the bonding strength between the insulation material and the steel interface, which is beneficial to improving the bonding performance of EPDM rubber insulation material.

[0057] like Figure 2 As shown, the relative difference in elongation at break = (elongation at break in the vertical direction - elongation at break in the parallel direction) / elongation at break in the vertical direction × 100%. In Examples 2-6, the relative difference in elongation at break was 16.83%~26.32%, while in the comparative examples it was 57.49%~77.94%. The addition of glycidyl methacrylate-grafted EPDM rubber can effectively improve the anisotropy of the mechanical properties of fiber-filled insulation materials.

Claims

1. A glycidyl methacrylate-grafted EPDM rubber, characterized in that, The structural formula of the glycidyl methacrylate-grafted EPDM rubber is shown in formula (Ⅰ): 。 2. The method for preparing glycidyl methacrylate-grafted EPDM rubber according to claim 1, characterized in that, Includes the following steps: S1: Add EPDM rubber, glycidyl methacrylate, and dicumyl peroxide to the torque rheometer for melt grafting; S2: After the reaction is complete, the material is discharged and cooled to room temperature. Then, it is passed through a two-roll mill three times to obtain glycidyl methacrylate-grafted EPDM rubber.

3. The method for preparing glycidyl methacrylate-grafted EPDM rubber according to claim 2, characterized in that: In S1, the mass ratio of EPDM rubber, glycidyl methacrylate, and dicumyl peroxide is 200:16:3; the reaction temperature is 160 ℃, and the reaction time is 10 min.

4. An ablation-resistant EPDM insulation layer, characterized in that, The ablation-resistant EPDM insulation layer is prepared from the following raw materials in parts by weight: 70-90 parts of EPDM rubber; 10-30 parts of glycidyl methacrylate-grafted EPDM rubber as described in claim 1; 5-25 parts of reinforcing agent; 5-20 parts of reinforcing fiber; 10-25 parts of flame retardant; 10-20 parts of ablation-resistant filler; 2-5 parts of tackifying resin; 5-10 parts of plasticizer; 3-7 parts of vulcanizing agent; and 5-10 parts of vulcanization accelerator.

5. The ablation-resistant EPDM insulation layer according to claim 4, characterized in that: The reinforcing agent is fumed silica; the reinforcing fiber is one or more of the following: pulp-like or long-fiber poly(p-phenylene terephthalamide) fiber, polyimide fiber, and phenolic fiber.

6. The ablation-resistant EPDM insulation layer according to claim 4, characterized in that: The flame retardant is a combination of two or more of the following: ammonium polyphosphate, melamine polyphosphate, magnesium hydroxide, and aluminum hydroxide; the ablation-resistant filler is phenolic resin or modified phenolic resin.

7. The ablation-resistant EPDM insulation layer according to claim 4, characterized in that: The tackifying resin is a terpene resin or a phenolic resin; the plasticizer is a cycloalkane oil or a paraffin oil.

8. The ablation-resistant EPDM insulation layer according to claim 4, characterized in that: The vulcanizing agent is dicumyl peroxide or di-tert-butyl peroxide and N'-m-phenylenebismaleimide, triallyl isocyanurate or sulfur; the mass ratio of dicumyl peroxide or di-tert-butyl peroxide and N'-m-phenylenebismaleimide, triallyl isocyanurate or sulfur is 1:1-2.

9. The ablation-resistant EPDM insulation layer according to claim 4, characterized in that: The vulcanization accelerator is zinc oxide and stearic acid; the mass ratio of zinc oxide to stearic acid is 5-10:

1.

10. A method for preparing an ablation-resistant EPDM insulation layer as described in any one of claims 4-9, characterized in that, Includes the following steps: S1: Place EPDM rubber and glycidyl methacrylate-grafted EPDM rubber into an internal mixer and mix them. S2: Reinforcing fibers, reinforcing agents, plasticizers, tackifying resins, ablation-resistant fillers, flame retardants, and vulcanization accelerators are added sequentially to S1 and mixed multiple times in stages. S3, add vulcanizing agent to the compounded rubber in S2, then mix and discharge the material; S4 involves pressing the S3 rubber compound through a two-roll mill, and then extruding it into sheets after 5 to 8 passes. S5. The sheet obtained in S4 is placed for more than 12 hours and then vulcanized and formed by a flat vulcanizing machine to obtain an ablation-resistant EPDM insulation layer.

11. The method for preparing the ablation-resistant EPDM insulation layer according to claim 10, characterized in that: In S1, the mixing temperature is 30-80℃ and the time is 5-10 minutes; in S2, the mixing temperature is 80-130℃ and the time is not less than 20 minutes; in S3, the mixing temperature is 40℃-65℃ and the time is not less than 5 minutes; in S4, when the open mill passes through thin sections, the roll temperature is controlled at 40℃-60℃ and the roll gap is not greater than 0.5mm; in S5, the vulcanization molding temperature is 150℃-160℃, the vulcanization time is 40-100 minutes, and the vulcanization pressure is 2MPa-6MPa.

12. An application of the ablation-resistant EPDM insulation layer as described in any one of claims 4-9, characterized in that, The ablation-resistant EPDM insulation layer is used as the insulation layer for the combustion chamber of a solid rocket engine.

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