Stress-impact-resistant thermal insulation material and preparation method thereof

Abstract

The invention relates to the technical field of thermal insulation materials, and particularly discloses a stress-impact-resistant thermal insulation material and a preparation method thereof.The thermal insulation material comprises nitrile rubber, a plasticizer, a reinforcing filler, an ablation-resistant filler, a fiber filler, a flame retardant, 4-12 parts of an active agent, a vulcanizing agent, a vulcanization accelerator and a tackifier; the tackifier is an organic silicon epoxy and polyether block copolymer. By introducing a strong-polarity high-flexibility polyether structure and a weak-polarity polysiloxane chain segment, self-aggregation can be carried out to generate microphase separation to form a sea-island structure, and the structure can reduce cohesion of a polymer body and is beneficial to creep deformation to adapt to stress caused by external impact; and huge impact force generated by rapid ignition pressure buildup of the solid engine is absorbed. The thermal insulation material has excellent mechanical property and ablation resistance, and especially can fully resist a large amount of external stress when being used as an artificial debonding layer, so that the working safety of a solid rocket engine is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of thermal insulation and ablation-resistant materials for solid rocket engines, and in particular to a stress-impact-resistant thermal insulation material and a preparation method thereof. Background Art

[0002] The artificial debonding layer is an important component of the solid rocket engine. Its purpose is to resist the large amount of stress caused by the shrinkage during the curing and storage of the propellant and prevent the failure of the bonding between the propellant and the insulation layer. At present, the artificial debonding layer material of the solid engine is mainly ordinary insulation layer material, which is usually consistent with the insulation layer material. However, during long-term storage and transportation, due to the aging of materials such as propellants and insulation layers, debonding and damage of the bonding interface may occur. During the curing process of the propellant or the rapid pressure building after the engine is ignited, due to the impact and vibration loads, a stress concentration area appears at the root of the artificial debonding layer structure. If the strength of the artificial debonding layer cannot fully resist a large amount of external stress, it is very likely that the root will tear or debond due to excessive positive stress on the interface, causing air to enter the gap between the propellant and the insulation layer, causing the insulation layer to face the risk of burning in advance, which may lead to uncontrolled combustion of the engine. Therefore, in order to ensure the safety of the operation of the solid rocket engine, it is necessary to improve the ability of the artificial debonding layer material to resist external stress.

[0003] CN114953519A discloses a single-side crack enhancement simulation part of an artificial debonding structure of a solid rocket engine and a molding method. The end of the artificial debonding layer is structurally changed to a smooth arc to reduce the stress concentration caused by the existence of the corner. However, this method has certain limitations on the engine structure. In addition, high-elastic nylon cloth and rubber rope are introduced into the insulation layer, which has the risk of reduced ablation resistance and interface bonding performance of the insulation layer. Summary of the invention

[0004] The invention provides a stress impact resistant heat insulating material and a preparation method thereof. The material has both excellent stress release capability and good interface bonding performance and can be used as an artificial debonding layer.

[0005] The technical solution of the present invention is to provide a stress impact resistant insulation material, comprising the following raw materials in parts by mass: 90-120 parts of nitrile rubber, 8-30 parts of plasticizer, 10-30 parts of reinforcing filler, 10-30 parts of ablation resistant filler, 8-30 parts of fiber filler, 5-15 parts of flame retardant, 4-12 parts of activator, 0.25-2 parts of vulcanizer, 0.25-2 parts of vulcanization accelerator, and 46-92 parts of tackifier; the tackifier is a silicone epoxy and polyether block copolymer.

[0006] Optionally, the plasticizer is one or a combination of liquid paraffin, chlorinated paraffin, dibutyl phthalate or high aromatic oil.

[0007] Optionally, the reinforcing filler is carbon black and / or white carbon black; the ablation-resistant filler is one or more of phenolic resin, boron phenolic resin, polyimide resin, and furfural resin; the fiber filler is one or more of chopped or pulp-like polyimide fibers, phenolic fibers, poly(p-phenylene terephthalamide) fibers, and aramid fibers.

[0008] Optionally, the flame retardant is one or more of ammonium polyphosphate, magnesium hydroxide, and aluminum hydroxide.

[0009] Optionally, the active agent is one or both of zinc oxide and stearic acid.

[0010] Optionally, the vulcanizing agent is any one or more of dicumyl peroxide, benzoyl peroxide, (1,4)-di-tert-butyl dicumyl peroxide or sulfur; the vulcanization accelerator is one or more of accelerator TMTD, accelerator DM, accelerator CZ or accelerator M.

[0011] Optionally, the tackifier includes a silicone epoxy and polyether block copolymer component A and a curing agent component B, and the mass ratio of the two is 20~40: 26~52.

[0012] Optionally, when preparing component A of the silicone epoxy and polyether block copolymer, first mix the terminal hydroxy silicone monomer, water and epoxy silicone monomer, add a catalyst and heat up to 60-80°C to obtain terminal epoxy silicone oil; mix the polyether monomer and water at 0-5°C, then add epichlorohydrin and powdered alkali and heat up to 60-80°C to obtain monoepoxy-terminated polyether; finally, react the terminal epoxy silicone oil with the monoepoxy-terminated polyether and a solid catalyst at 60-80°C to obtain component A.

[0013] The present invention also relates to a method for preparing the stress impact resistant thermal insulation material, comprising the following steps: S1. Add nitrile rubber and plasticizer on the open mill for three-stage plasticizing. The rubber material is left for more than 24 hours after each stage of plasticizing. S2, adding the plasticized rubber, reinforcing filler, fiber filler, ablation-resistant filler, flame retardant and activator to the internal mixer in proportion, and mixing until uniformly mixed; S3. Put the rubber material obtained in S2 into an open mixing mill, add vulcanizing agent, vulcanization accelerator and tackifier in proportion to mix, then thin pass 8-10 times, and thin pass evenly to produce sheets; vulcanize and form.

[0014] Optionally, the roller distance of the mixing mill in S1 is 0.25-0.75 mm, and the roller temperature is controlled at 40-70° C.; the temperature of the vulcanization molding in S3 is 140-160° C., and the time is 60-160 min.

[0015] The thermal insulation material provided by the invention can be used as an artificial debonding layer of a solid rocket engine.

[0016] The present invention has the following beneficial effects: (1) The present invention introduces silicone epoxy and polyether block thickeners into the nitrile rubber insulation material. The weakly polar polysiloxane chain segments have weak intermolecular forces, which is conducive to the relative slippage of the polymer segments to absorb the energy brought by the impact, and better play the role of stress release materials. The highly polar and highly flexible polyether structure and the weakly polar polysiloxane chain segments in the thickener can undergo phase separation under certain conditions to form microspheres similar to "island structures". This structure can further reduce the cohesive force of the material body, which is conducive to creep adaptation to the stress brought by external impact, and is used for the insulation layer or artificial debonding layer of solid rocket engines to absorb the huge impact force generated by the rapid pressure buildup of the engine ignition.

[0017] (2) The stress-impact resistant internal insulation material of the present invention can further absorb a large amount of energy released during the combustion of the propellant, since the introduced organic silicon material itself has excellent anti-ablation performance, and can meet the engine's requirements for the ablation resistance of the internal insulation material; especially when used as an artificial debonding layer, it can fully resist a large amount of external stress and ensure the safety of the solid rocket engine.

[0018] (3) In the thermal insulation layer of the present invention, the highly polar and highly flexible polyether structure and epoxy curing point can match the strong polarity of the nitrile rubber to generate a strong interaction force, thereby ensuring good interface bonding performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a SEM picture of the stress impact resistant insulation material prepared in Example 1 when subjected to external stress.

[0020] Figure 2 This is the tensile diagram of the stress impact resistant insulation material prepared in Example 1. DETAILED DESCRIPTION

[0021] The experimental methods in the following examples are conventional methods unless otherwise specified. The raw materials, reagents, etc. used in the following examples are commercially available products unless otherwise specified.

[0022] The tackifier used in the following examples is a mixture of a silicone epoxy and polyether block copolymer component A and a curing agent component B in a mass ratio of 25:32.5.

[0023] When preparing the silicone epoxy and polyether block copolymer component A, first mix 200g of terminal hydroxyl polydimethylsiloxane, 80g of water and 96g of epoxy polydimethylsilane, add 40g of catalyst and heat to 60-80°C to obtain terminal epoxy silicone oil; mix 96g of polyethylene glycol 400 and 3g of water at 0-5°C, then add 48g of epichlorohydrin and 20g of powdered sodium hydroxide and heat to 60-80°C to obtain monoepoxy terminated polyether; finally, react the terminal epoxy silicone oil with the monoepoxy terminated polyether at a mass ratio of 1:1 at 60-80°C to obtain component A.

[0024] Component B is tetraethylenediamine.

[0025] The viscosity enhancer is prepared by mixing components A and B before preparing the thermal insulation material. The mixture is ready for use and the storage time is controlled within 30 minutes.

[0026] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0027] Embodiment 1~5: The composition of the raw materials of the thermal insulation materials used in Examples 1 to 5 is shown in Table 1.

[0028] Table 1

[0029] The material preparation in the above embodiment includes the following steps: (1) Plastication: Weigh nitrile rubber and dibutyl phthalate in proportion and plasticize them in three stages on an open mill. The rubber material should be left for more than 24 hours after each stage of plasticization. The roller gap of the open mill should be 0.25-0.50 mm and the roller temperature should be controlled at 40-60 °C.

[0030] (2) Mixing: Weigh the plasticized rubber, aramid fiber pulp, white carbon black, stearic acid, ammonium polyphosphate and zinc oxide in proportion, put them into an internal mixer for internal mixing, pour them into an open mixer after mixing evenly, add sulfur, accelerator DM and tackifier in proportion and mix them, then pass them through thinly 8 times, and then produce sheets after the thinning is evenly performed.

[0031] During the mixing process of rubber compound, the temperature of internal mixer should be lower than 110℃, and the temperature of open mixer should be lower than 70℃, so as to avoid the rubber compound being scorched by excessive temperature and affecting the performance of thermal insulation material. The mixed rubber compound should be stored away from light.

[0032] (3) Sample preparation: Prepare 2.5 mm thick sheets to test mechanical properties and density; 5 Φ30 mm × 10 mm ablation samples to test oxyacetylene ablation rate; 5 Φ40 mm × 3 mm bonding specimens to test interfacial bonding performance; the vulcanization conditions of the rubber are: 150°C × 80 min × 5 MPa.

[0033] (4) Performance test: The various properties of the insulation materials are tested in accordance with the relevant standards and specifications. The specific results are shown in Table 3.

[0034] Depend on Figure 1 It can be seen that when the insulation material containing the tackifier is subjected to the energy brought by the external stress impact, the silicone spheres with better toughness can help the nitrile chain segments to disperse the stress and enhance the material's ability to cope with the external stress. Macroscopically, the silicone spheres are transformed from relatively regular spheres to relatively flat ellipsoids. When the crack approaches the silicone sphere, the crack deflection occurs, protecting the propellant from the impact force and further enhancing the ability of the artificial debonding layer to resist external stress.

[0035] Figure 2 It can be seen that the impact-resistant insulation material has high elongation and flexibility, which can not only effectively absorb external stress, but also meet the mechanical performance requirements of the artificial debonding layer.

[0036] Comparative Example 1 Based on Example 1, the only difference is that no tackifier is added to the nitrile rubber formulation.

[0037] Comparative Example 2 Based on Example 1, the only difference is that the tackifier in the nitrile rubber formula is resorcinol.

[0038] Comparative Example 3 Based on Example 1, the only difference is that the tackifier is epoxy-terminated silicone oil.

[0039] The preparation methods of the materials provided in the above comparative examples are the same as those in Examples 1 to 5.

[0040] The yields obtained in the above-mentioned embodiments and comparative examples were subjected to performance tests.

[0041] The mechanical properties were tested by the American Instron 5967, and the tensile strength and elongation at break were tested according to the "GB / T528-2009 Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber" standard, with a test temperature of 23°C and a tensile rate of 500mm / min. The density was tested according to the "QJ 917A-1997 Density determination method for composite solid propellants, linings, and insulation materials" standard, with a test temperature of 23°C. The oxygen-acetylene line ablation rate was determined according to the provisions of the national military standard "GJB323B-2018 Ablation Test Method for Ablative Materials", and the test conditions were: nozzle diameter 2mm, ablation distance 10mm, oxygen pressure 0.4MPa, acetylene pressure 0.095MPa, oxygen flow rate 1512L / h, acetylene flow rate 1116L / h, oxygen-acetylene mixing ratio 1.35, and ablation time 20s. The interface bonding performance is tested according to the D-type specimen specified in "Q / QJB 349-2020 Test Method for Interface Bonding Strength of Solid Rocket Engine Combustion Chamber", with a test temperature of 23°C and a tensile rate of 50 mm / min.

[0042] The specific performance test results are shown in Table 2.

[0043] Table 2

[0044] It can be seen from the data in Table 3 that the introduction of a tackifier into the material can greatly improve the tensile strength, elongation at break and interfacial bonding strength of the thermal insulation material with the metal shell, effectively reduce the density of the thermal insulation layer, and do not affect the ablation resistance of the thermal insulation material. It can not only ensure good bonding performance between the thermal insulation layer and the shell, but also absorb various impact forces transmitted by the medicine block under various working conditions, and realize the function of stress release.

[0045] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A stress impact resistant thermal insulation material, characterized in that: The invention comprises the following raw materials in parts by mass: 90-120 parts of nitrile rubber, 8-30 parts of plasticizer, 10-30 parts of reinforcing filler, 10-30 parts of ablation-resistant filler, 8-30 parts of fiber filler, 5-15 parts of flame retardant, 4-12 parts of activator, 0.25-2 parts of vulcanizer, 0.25-2 parts of vulcanization accelerator and 46-92 parts of tackifier; the tackifier is a silicone epoxy and polyether block copolymer.

2. The material according to claim 1, characterized in that: The plasticizer is one or a combination of liquid paraffin, chlorinated paraffin, dibutyl phthalate or high aromatic oil.

3. The material according to claim 1, characterized in that: The reinforcing filler is carbon black and / or white carbon black; the ablation-resistant filler is one or more of phenolic resin, boron phenolic resin, polyimide resin, and furfural resin; the fiber filler is one or more of chopped or pulp-like polyimide fibers, phenolic fibers, poly(p-phenylene terephthalamide) fibers, and aramid fibers.

4. The material according to claim 3, characterized in that: The flame retardant is one or more of ammonium polyphosphate, magnesium hydroxide and aluminum hydroxide.

5. The material according to claim 1, characterized in that: The active agent is one or both of zinc oxide and stearic acid.

6. The material according to claim 1, characterized in that: The vulcanizing agent is any one or more of diisopropylbenzene peroxide, benzoyl peroxide, (1,4)-di-tert-butyl diisopropylbenzene peroxide or sulfur; the vulcanization accelerator is one or more of accelerator TMTD, accelerator DM, accelerator CZ or accelerator M.

7. The material according to any one of claims 1 to 6, characterized in that: The tackifier comprises a silicone epoxy and polyether block copolymer component A and a curing agent component B, wherein the curing agent of the component B is a fatty amine substance; the mass ratio of the two is 20-40:26-52; the mixture is mixed before use and the mixture can be used immediately.

8. The material according to claim 7, characterized in that: When preparing component A of the silicone epoxy and polyether block copolymer, firstly, the terminal hydroxy silicone monomer, water and epoxy silicone monomer are mixed, and a catalyst is added and the temperature is raised to 60-80°C to obtain the terminal epoxy silicone oil; the polyether monomer and water are mixed at 0-5°C, and then epichlorohydrin and powdered alkali are added and the temperature is raised to 60-80°C to obtain the monoepoxy terminated polyether; finally, the terminal epoxy silicone oil is reacted with the monoepoxy terminated polyether and the solid catalyst at 60-80°C to obtain component A.

9. The method for preparing the stress-shock resistant solid rocket engine internal insulation material according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Add nitrile rubber and plasticizer on the open mill for three-stage plasticizing. The rubber material is left for more than 24 hours after each stage of plasticizing. S2, adding the plasticized rubber, reinforcing filler, fiber filler, ablation-resistant filler, flame retardant and activator to the internal mixer in proportion, and mixing until uniformly mixed; S3. Put the rubber material obtained in S2 into an open mixing mill, add vulcanizing agent, vulcanization accelerator and tackifier in proportion to mix, then thin pass 8-10 times, and thin pass evenly to produce sheets; vulcanize and form.

10. The preparation method according to claim 9, characterized in that: In S1, the roller distance of the mixing mill is 0.25~0.75mm, and the roller temperature is controlled at 40~70℃; in S3, the temperature of vulcanization molding is 140~160℃, and the time is 60~160min.

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