A laminated structure thermal insulation layer, preparation method and application

Abstract

The present invention provides a laminated structure thermal insulation layer, a preparation method, and an application. The laminated structure thermal insulation layer is formed by combining and compressing at least one rubber-based thermal insulation layer and at least one resin-based aerogel layer, wherein the resin-based aerogel layer has a compression strength ≥20MPa, a compression modulus ≥70MPa, and a thermal conductivity of 0.03W / m·K to 0.04W / m·K. The laminated structure thermal insulation layer has both good thermal insulation (ablation resistance, erosion resistance) and thermal insulation (low thermal conductivity) properties. Compared with existing thermal insulation layers, while maintaining the original thermal insulation properties, it further obtains more excellent thermal insulation properties, reducing the thermal conductivity of the existing thermal insulation layer from 0.15W / m·K to 0.25W / m·K to 0.03W / m·K to 0.04W / m·K, which can meet the high performance and lightweight development trend of the next generation of solid rocket engines.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal insulation of solid rocket engines, and in particular relates to a laminated thermal insulation layer, a preparation method and an application thereof. Background Art

[0002] The thermal insulation layer protecting the casing of a solid rocket motor is typically a flexible layer made of rubber with fibers and other ablative-resistant components. Alternatively, a rigid layer can be made of a resin matrix with fibers and other ablative-resistant components. Alternatively, a multilayer composite layer can be constructed by sandwiching a rigid layer of phenolic fiber cloth or carbon fiber felt between two flexible layers. All of these layers offer excellent thermal insulation (ablation and erosion resistance) and heat-isolating properties, ensuring the motor can operate reliably and for extended periods under high temperatures and pressures, despite high-temperature gas ablation and high-temperature particle erosion. However, with the development and application of high-charge and high-specific-impulse solid rocket motor technology in modern warfare, the thickness of the thermal insulation layer must be continuously increased to ensure reliable engine operation. This, in turn, results in a negative impact on the continued increase in the negative mass of the engine. Therefore, there is an urgent need to further improve the thermal insulation (ablation and erosion resistance) and heat-isolating properties of the thermal insulation layer to adapt it to the trend toward higher performance and lighter weight for solid rocket motors. Summary of the Invention

[0003] The technical problem solved by the present invention is: in order to further improve the thermal insulation and heat insulating performance of the solid rocket engine insulation layer, the present invention proposes a rubber-based insulation layer and a resin-based aerogel laminated structure insulation layer, which has both good thermal insulation and heat insulating properties.

[0004] The technical solutions provided by the present invention are as follows:

[0005] In a first aspect, a laminated structure thermal insulation layer is formed by combining and compressing at least one rubber-based thermal insulation layer and at least one resin-based aerogel layer, wherein the resin-based aerogel layer has a compression strength ≥20 MPa, a compression modulus ≥70 MPa, and a thermal conductivity of 0.03 W / m·K to 0.04 W / m·K.

[0006] In a second aspect, a method for preparing a laminated structure thermal insulation layer comprises the following steps:

[0007] The rubber-based insulation layer raw material and the resin-based aerogel layer are placed in a forming mold according to the required stacking structure and thickness, and are pressed into shape by mold pressing, airbag inflation pressing or high-pressure gas pressing.

[0008] In the third aspect, the laminated structure insulation layer described in the first aspect is used as a thermal protection insulation material in the combustion chamber of a solid rocket engine.

[0009] The laminated structure thermal insulation layer, preparation method and application provided by the present invention have the following beneficial effects:

[0010] The present invention provides a laminated structure thermal insulation layer and a preparation method thereof. Compared with the existing thermal insulation layer, while maintaining the original thermal insulation performance, it can further obtain more excellent thermal insulation performance, reducing the thermal conductivity of the existing thermal insulation layer from 0.15W / m·K to 0.25W / m·K to 0.03W / m·K to 0.04W / m·K, which can meet the high performance and lightweight development trend of the next generation of solid rocket engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a photo of the rubber-based thermal insulation layer of the present invention;

[0012] Figure 2 This is a photo of the resin-based aerogel described in the present invention;

[0013] Figure 3 This is a photo of the laminated structure insulation layer of Example 1 of the present invention;

[0014] Figure 4 This is a schematic diagram of a laminated structure thermal insulation layer according to Example 2 of the present invention;

[0015] Figure 5 This is a schematic diagram of the laminated structure insulation layer of Comparative Example 1 described in the present invention. DETAILED DESCRIPTION

[0016] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0017] The word "exemplary" is used exclusively herein to mean "serving as an example, example, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0018] The present invention provides a laminated structure heat insulation layer, comprising at least one rubber-based heat insulation layer ( Figure 1 ) and at least one resin-based aerogel layer ( Figure 2 ) combined with compression molding. The resin-based aerogel layer has a compressive strength of ≥20 MPa, a compression modulus of ≥70 MPa, and a thermal conductivity of 0.03 W / m·K to 0.04 W / m·K.

[0019] The rubber-based insulation layer can be any of a homogeneous insulation layer made of rubber (such as EPDM, silicone rubber, and nitrile rubber) with fibers or other ablation-resistant components added, a composite insulation layer made of rubber combined with epoxy resin or phenolic resin with fibers or other ablation-resistant components added, or a combined insulation layer made of one or more layers of rigid phenolic fiber cloth or carbon fiber felt sandwiched between two homogeneous insulation layers. The elongation of the homogeneous insulation layer, composite insulation layer, and combined insulation layer decreases in order. The thermal conductivity of the rubber-based insulation layer is 0.15W / m·K to 0.25W / m·K, and the linear ablation rate is 0.03mm / s to 0.25mm / s.

[0020] In a preferred embodiment, the resin-based aerogel layer is a benzoxazole aerogel or a benzimidazole aerogel having a continuous open-pore structure formed by stacking irregular particles.

[0021] Aerogels are a type of nanoporous material that possesses both ultra-low density and ultra-low thermal conductivity in terms of physical and chemical properties, making them an ideal lightweight thermal insulation material. Currently, silica aerogels, as well as novel cellulose aerogels, carbon aerogels, graphene and graphene oxide aerogels, chalcogenide aerogels, novel nanotube aerogels, nanometal aerogels, and supramolecular aerogels, are widely used. However, these high-porosity structures, primarily constructed from inorganic materials such as nanoscale silica, suffer from high brittleness, poor compressive strength, and poor thermal insulation properties, limiting their application in thermal insulation within solid rocket engines. The inventors have conducted extensive research and determined that benzoxazole aerogels and benzimidazole aerogels, both of which have high compressive strength, can be used as thermal insulation materials. These materials, when pressed together with a rubber-based insulation layer, yield lightweight thermal insulation materials with both excellent thermal and insulation properties.

[0022] The resin-based aerogel layer is prepared by a sol-gel method to obtain a wet gel, and then the aerogel is obtained by a supercritical fluid drying method or the like.

[0023] In a preferred embodiment, the laminated insulation layer is a combination of one or more rubber-based insulation layers and resin-based aerogel layers, combining the thermal insulation properties of both the rubber-based insulation layer and the resin-based aerogel layer. Specifically, the laminated insulation layer includes the following forms: ① an AB structure consisting of at least one rubber-based insulation layer A and at least one resin-based aerogel layer B; ② an ABA sandwich structure consisting of at least one rubber-based insulation layer A, at least one resin-based aerogel layer B, and at least one rubber-based insulation layer A; ③ an insulation layer C consisting of at least one rubber-based insulation layer A, at least one rubber-based insulation layer A, and at least one resin-based aerogel layer B stacked randomly, and at least one rubber-based insulation layer A sandwich structure.

[0024] When the laminated insulation layer is an AB structure, the rubber-based insulation layer is placed on the side of the engine casing close to the combustion chamber, which can resist the erosion of high-speed airflow and high-temperature particles of the solid propellant; the resin-based aerogel layer is placed on the side of the engine casing close to the metal casing, which can isolate the heat from the combustion chamber from being transferred toward the casing.

[0025] In a preferred embodiment, the compression molding method is any one of mold compression, airbag inflation compression, or high-pressure gas compression. Specifically, the rubber-based thermal insulation layer raw material and the resin-based aerogel layer are placed into a molding mold according to the desired layered structure and thickness, and compression molding is performed under specific temperature, time, and pressure conditions. After demolding, the laminated thermal insulation layer is obtained. The temperature and pressure during compression molding meet the vulcanization conditions of the rubber-based thermal insulation layer.

[0026] Example

[0027] Example 1

[0028] A 10mm thick laminated structure thermal insulation layer, comprising an upper layer of an EPDM flexible thermal insulation layer of approximately 2mm thickness (thermal conductivity 0.20W / m·K to 0.25W / m·K, linear ablation rate 0.12mm / s to 0.15mm / s), an intermediate layer of an oxadiazole aerogel layer of approximately 6mm thickness (compression strength 29MPa, compression modulus 84.6MPa, thermal conductivity 0.04W / m·K), and a lower layer of an EPDM flexible thermal insulation layer of approximately 2mm thickness (thermal conductivity 0.20W / m·K to 0.25W / m·K, linear ablation rate 0.12mm / s to 0.15mm / s). The specific preparation process comprises the following steps:

[0029] Step 1: Place a 2mm EPDM flexible insulation layer green sheet, a 6mm benzoxazole aerogel, and a 2mm EPDM flexible insulation layer green sheet in the molding mold in the order of top, middle, and bottom.

[0030] Step 2: Turn on the flatbed vulcanizing press and set the preheating temperature to 70°C to 80°C;

[0031] Step 3: Cover the upper mold of the forming mold. After the flat plate vulcanizer reaches the temperature of step 2, place the mold loaded with the prefabricated material into the flat plate vulcanizer and preheat for 15 to 20 minutes.

[0032] Step 4: Control the flat vulcanizing press, pressurize to 2MPa~5MPa for about 10 minutes, then release the pressure, pressurize again to 5MPa~8MPa for about 10 minutes, then release the pressure. Adjust the pressure to 10MPa~12MPa, the temperature to 150℃, the time to 60 minutes, and carry out vulcanization;

[0033] Step 5: Turn off the flat vulcanizing press and allow it to cool naturally;

[0034] Step 6: When the temperature is cooled to 70°C to 80°C, the mold is removed and demoulded to obtain a 10mm thick laminated structure insulation layer. The interior of the laminated structure insulation layer is complete and can be pressed into shape.

[0035] The thermal insulation layer obtained in Example 1 is as follows Figure 3 As shown, after multiple tests, the thermal conductivity is 0.03W / m·K~0.04W / m·K, and the linear ablation rate is 0.12mm / s~0.15mm / s.

[0036] Example 2

[0037] A 5mm thick laminated structure thermal insulation layer, with a thickness of about 4mm on the side close to the engine combustion chamber and a thickness of about 1mm on the side close to the engine metal shell. The benzophenone aerogel layer (compression strength 29MPa, compression modulus 84.6MPa, thermal conductivity 0.04W / m·K) is used. The specific preparation process includes the following steps:

[0038] Step 1: Place 1mm benzoxazole aerogel and 4mm EPDM flexible insulation layer inside the engine casing in order;

[0039] Step 2: Turn on the oven and set the preheat temperature to 70℃~80℃;

[0040] Step 3: Place the airbag inside the engine and cover it with the head and tail covers. After the inside of the engine housing reaches the temperature in step 2, continue preheating for 15 to 20 minutes.

[0041] Step 4: The airbag begins to inflate, pressurizes to 1.0MPa~1.2MPa for about 10 minutes, then deflates, pressurizes again to 1.0MPa~1.2MPa for about 10 minutes, then deflates. The airbag begins to inflate, adjusts the pressure to 2MPa, the temperature to 150℃, and the time to 60 minutes, and then implements vulcanization;

[0042] Step 5: Close the oven and allow it to cool naturally;

[0043] Step 6: When the temperature is cooled to 30°C to 50°C, the airbag is deflated and demoulded to obtain a 5mm thick laminated structure insulation layer. The interior of the laminated structure insulation layer is intact and can be press-formed.

[0044] The thermal insulation layer obtained in Example 2 is as follows Figure 4 As shown, after multiple tests, the thermal conductivity is 0.03W / m·K~0.04W / m·K, and the ablation rate is 0.03mm / s~0.08mm / s.

[0045] Example 3

[0046] A 10mm thick laminated structure thermal insulation layer, wherein the upper layer is about 2mm thick, a layer of rigid phenolic fiber cloth or carbon fiber felt is sandwiched between two flexible thermal insulation layers (thermal conductivity 0.18W / m·K to 0.22W / m·K, linear ablation rate 0.03mm / s to 0.04mm / s), the middle layer is about 6mm thick, and a layer of benzimidazole aerogel (compression strength 20.5MPa, compression modulus 77.5MPa, thermal conductivity 0.03W / m·K) is sandwiched between two flexible thermal insulation layers. The specific preparation process comprises the following steps:

[0047] Step 1: Place a 2mm multi-layer composite insulation layer green sheet, a 6mm benzoimidazole aerogel, and a 2mm multi-layer composite insulation layer green sheet in the molding mold in the order of top, middle, and bottom.

[0048] Step 2: Turn on the flatbed vulcanizing press and set the preheating temperature to 90°C to 100°C;

[0049] Step 3: Cover the upper mold of the forming mold, wait for the flat plate vulcanizer to reach the temperature of step 2, and then place the mold loaded with the prefabricated material into the flat plate vulcanizer for preheating for 25 minutes to 30 minutes;

[0050] Step 4: Control the flat vulcanizing press, pressurize to 5MPa-7MPa for about 10 minutes, then release the pressure, pressurize again to 9MPa-10MPa for about 10 minutes, then release the pressure. Adjust the pressure to 13MPa-16MPa, the temperature to 170℃, the time to 90 minutes, and carry out vulcanization;

[0051] Step 5: Turn off the flat vulcanizing press and allow it to cool naturally;

[0052] Step 6: When the temperature is cooled to 70°C to 80°C, the mold is removed and demoulded to obtain a 10mm thick laminated structure insulation layer. The interior of the laminated structure insulation layer is complete and can be pressed into shape.

[0053] The thermal insulation layer obtained in Example 3 was tested multiple times and had a thermal conductivity of 0.18W / m·K to 0.22W / m·K, a linear ablation rate of 0.03mm / s to 0.04mm / s), and an ablation rate of 0.02mm / s.

[0054] Comparative Example 1

[0055] A 10mm thick laminated structure thermal insulation layer, comprising an upper layer of an EPDM flexible thermal insulation layer of approximately 2mm thickness (thermal conductivity 0.20W / m·K to 0.25W / m·K, linear ablation rate 0.12mm / s to 0.15mm / s), an intermediate layer of an approximately 6mm thick silica aerogel with poor compressive resistance (thermal conductivity 0.03W / m·K to 0.04W / m·K), and a lower layer of an EPDM flexible thermal insulation layer of approximately 2mm thickness (thermal conductivity 0.20W / m·K to 0.25W / m·K, linear ablation rate 0.12mm / s to 0.15mm / s). The specific preparation process comprises the following steps:

[0056] Step 1: Place a 2mm EPDM flexible insulation layer green sheet, a 6mm silica aerogel, and a 2mm EPDM flexible insulation layer green sheet in the molding mold in the order of top, middle, and bottom.

[0057] Step 2: Turn on the flatbed vulcanizing press and set the preheating temperature to 70°C to 80°C;

[0058] Step 3: Cover the upper mold of the forming mold. After the flat plate vulcanizer reaches the temperature of step 2, place the mold loaded with the prefabricated material into the flat plate vulcanizer and preheat for 15 to 20 minutes.

[0059] Step 4: Control the flat vulcanizing press, pressurize to 2MPa~5MPa for about 10 minutes, then release the pressure, pressurize again to 5MPa~8MPa for about 10 minutes, then release the pressure. Adjust the pressure to 10MPa~12MPa, the temperature to 150℃, the time to 60 minutes, and carry out vulcanization;

[0060] Step 5: Turn off the flat vulcanizing press and allow it to cool naturally;

[0061] Step 6: When the temperature is cooled to 70°C to 80°C, the mold is removed and demoulding is performed to obtain a 10 mm thick laminated structure insulation layer.

[0062] The heat-insulating layer obtained in Comparative Example 1 is as follows Figure 5 As shown, since the compression strength and compression modulus of the aerogel failed to meet the use requirements, the laminated structure insulation layer suffered internal damage and could not be pressed into shape.

[0063] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

[0064] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A laminated structure thermal insulation layer, characterized in that: The invention is formed by combining and pressing at least one rubber-based insulation layer and at least one resin-based aerogel layer, wherein the resin-based aerogel layer is a benzoxazole aerogel or a benzimidazole aerogel with a continuous open-pore structure formed by stacking irregular particles; the resin-based aerogel layer has a compression strength of ≥20 MPa, a compression modulus of ≥70 MPa, and a thermal conductivity of 0.03 W / m·K to 0.04 W / m·K.

2. The laminated structure thermal insulation layer according to claim 1, characterized in that: The rubber-based thermal insulation layer is any one of a homogeneous thermal insulation layer made of rubber with an ablation-resistant component, a composite thermal insulation layer made of rubber combined with epoxy resin or phenolic resin with an ablation-resistant component, and a combined thermal insulation layer made of phenolic fiber cloth or carbon fiber felt sandwiched between two homogeneous thermal insulation layers.

3. The laminated structure thermal insulation layer according to claim 1, characterized in that: The rubber-based thermal insulation layer has a thermal conductivity of 0.15 W / m·K to 0.25 W / m·K and a linear ablation rate of 0.03 mm / s to 0.25 mm / s.

4. The laminated structure thermal insulation layer according to claim 1, characterized in that: The laminated structure insulation layer includes the following forms: ① an AB structure consisting of at least one rubber-based insulation layer A and at least one resin-based aerogel layer B; ② an ABA sandwich structure consisting of at least one rubber-based insulation layer A, at least one resin-based aerogel layer B, and at least one rubber-based insulation layer A; ③ an insulation layer C consisting of at least one rubber-based insulation layer A, at least one rubber-based insulation layer A, and at least one resin-based aerogel layer B randomly stacked, and an ACA sandwich structure consisting of at least one rubber-based insulation layer A.

5. The laminated structure thermal insulation layer according to claim 1, characterized in that: The compression molding method is any one of mold compression, airbag inflation compression or high-pressure gas compression.

6. A method for preparing a laminated structure thermal insulation layer according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: placing the rubber-based insulation layer raw material and the resin-based aerogel layer into a forming mold according to the required stacking structure and thickness, and pressing and forming the layer by mold pressing, airbag inflation pressing or high-pressure gas pressing.

7. Use of the laminated structure thermal insulation layer according to any one of claims 1 to 5 as a thermal protection and thermal insulation material in a combustion chamber of a solid rocket engine.

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