A gradient density thermal protection material and preparation method thereof

Abstract

The present invention relates to a gradient density thermal protection material and a preparation method thereof, wherein the gradient density thermal protection material comprises a low-density thermal insulation layer, a medium-density thermal protection layer and a high-density ablation layer in sequence; the low-density thermal insulation layer comprises a lightweight filler and a resin; the medium-density thermal protection layer comprises a lightweight filler, a thermal protection filler, chopped fibers and a resin; the high-density ablation layer comprises a high-temperature resistant ceramic filler and a resin; the lightweight filler is a hollow glass microsphere and / or a thermal expansion microsphere; the thermal protection filler is one or more of aluminum oxide, silicon oxide, zirconium oxide, silicon carbide, silicon boride and boron nitride. The material of the present invention gradually transitions from ablation resistance and heat protection to thermal insulation, and has the functional characteristics of heat protection, heat insulation and dimensional integration; the gradient layers have good interfacial adhesion, and based on the material gradient design, the structure and composition of the composite material can change continuously in space, thereby better leveraging the different advantages of the various components and realizing low-cost and controllable preparation of gradient density thermal protection materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal protection materials, and in particular relates to a gradient density thermal protection material and a preparation method thereof. Background Art

[0002] A thermal protection system (TPS) covers the exterior of an aircraft, protecting the fuselage and internal structures from external aerodynamic thermal loads. As a key sub-technology for aircraft, advanced TPMS materials are essential for achieving high flight speeds. The development of TPMS materials faces a persistent conflict between improving thermal protection efficiency, reducing material weight, and withstanding the harsh aerodynamic thermal environment.

[0003] Future new aerospace vehicles require thermal protection materials with functions such as high-temperature non-ablative, high-efficiency thermal insulation, light weight and reliability. Therefore, new functional gradient composite materials have gradually emerged. This material realizes the above-mentioned different functions through structural zoning design, and uses different materials / structures in different temperature zones to form a thermal protection material with a gradient density structure. However, the thermal responses between different materials are different, and debonding is prone to occur at the interface. Moreover, there are few related studies on functional gradient composite materials at present. Most of them use fiber mixed woven gradient density preform structures to achieve gradient functional thermal protection. The structural design of the preform is complex, the preparation cycle is long, and the price is high, which brings difficult problems to the mass production of the product. Therefore, it is of great significance to develop a new low-cost gradient density thermal protection material that has heat protection, heat insulation, and dimensional integration. Summary of the Invention

[0004] In order to solve one or more technical problems existing in the prior art, the present invention provides a gradient density thermal protection material and a preparation method thereof.

[0005] In a first aspect, the present invention provides a gradient density thermal protection material, which comprises a low-density thermal insulation layer, a medium-density thermal protection layer and a high-density ablation layer in sequence; the low-density thermal insulation layer contains lightweight filler and resin; the medium-density thermal protection layer contains lightweight filler, thermal protection filler, chopped fiber and resin; the high-density ablation layer contains high-temperature resistant ceramic filler and resin; the lightweight filler is hollow glass microspheres and / or thermal expansion microspheres; the thermal protection filler is one or more of aluminum oxide, silicon oxide, zirconium oxide, silicon carbide, silicon boride and boron nitride.

[0006] Preferably, the resin is one or more of phenolic resin, modified phenolic resin, epoxy resin, and bismaleimide resin; the chopped fiber is one or more of quartz fiber, high silica fiber, phenolic fiber, carbon fiber, and aramid fiber; and / or the high-temperature resistant ceramic filler is one or more of metal oxide ceramic filler, nitride ceramic filler, carbide ceramic filler, boride ceramic filler, and silicide ceramic filler.

[0007] Preferably, the high temperature resistant ceramic filler is one or more of alumina ceramic filler, zirconia ceramic filler, titanium oxide ceramic filler, chromium oxide ceramic filler, boron nitride ceramic filler, silicon carbide ceramic filler, boron carbide ceramic filler, zirconium boride ceramic filler, and molybdenum disilicide ceramic filler.

[0008] Preferably, in the low-density thermal insulation layer, the mass ratio of the lightweight filler to the resin is (40-80): (50-100); in the medium-density thermal insulation layer, the mass ratio of the lightweight filler, the thermal insulation filler, the chopped fiber and the resin is (40-80): (1-5): (1-10): (50-100); and / or in the high-density ablation layer, the mass ratio of the high-temperature resistant ceramic filler to the resin is (10-50): (50-100).

[0009] Preferably, the resin contained in the low-density heat-insulating layer, the medium-density heat-protective layer and the high-density ablation layer is the same.

[0010] Preferably, the lightweight filler is composed of hollow glass microspheres and heat-expandable microspheres in a mass ratio of 1:(0.2-0.4); preferably, the heat-expandable microspheres are modified heat-expandable microspheres.

[0011] In a second aspect, the present invention provides a method for preparing the gradient density heat protection material according to the first aspect of the present invention, the method comprising the following steps:

[0012] (1) adding a lightweight filler to a resin and kneading the mixture uniformly to obtain a wet pellet A, and then drying the wet pellet A to obtain a composition A;

[0013] (2) mixing the lightweight filler, the heat-resistant filler, and the chopped fibers uniformly, adding the mixture to the resin, and kneading the mixture uniformly to obtain a wet pellet B, and then drying the wet pellet B to obtain a composition B;

[0014] (3) adding a high-temperature resistant ceramic filler to the resin and kneading the mixture uniformly to obtain a wet pellet C, and then drying the wet pellet C to obtain a composition C;

[0015] (4) Composition A, composition B and composition C are sequentially applied and then compression molded to obtain a gradient density thermal protection material.

[0016] Preferably, in step (1), step (2) and / or step (3), the kneading time is 10 to 30 minutes; in step (2), the mixing time is 5 to 10 minutes; and / or in step (1), step (2) and / or step (3), the wet embryo dough is spread out and then dried at 50 to 80° C. for 20 to 60 minutes.

[0017] Preferably, the density of the composition A is 0.3-0.5 g / cm 3 The density of the composition B is 0.4-0.6 g / cm 3 The density of the composition C is 0.8-1.2 g / cm 3 .

[0018] In a third aspect, the present invention provides a gradient density thermal protection material prepared by the preparation method described in the second aspect of the present invention.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] The gradient density thermal protection material in the present invention includes three gradient functional layers: a high-density ablation-resistant layer, a medium-density heat-protection layer, and a low-density heat-insulating layer. The material function gradually transitions from ablation resistance and heat protection to heat insulation from the outer layer to the inner layer, and has the functional characteristics of heat protection, heat insulation, and dimensional integration; each gradient layer material uses the same resin base material as an adhesive, which can organically combine the gradient layers into a whole, so that the gradient layers have good interface adhesion; at the same time, through the compression molding process (hot pressing and curing molding), instead of the complex and expensive mixed fiber preform, based on the material gradient design, the structure and composition of the composite material can be continuously changed in space, so that the different advantages of multiple components can be better brought into play, and the low-cost and controllable preparation of gradient density thermal protection materials can be achieved. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] In a first aspect, the present invention provides a gradient density thermal protection material, which comprises a low-density thermal insulation layer, a medium-density thermal protection layer and a high-density ablation layer in sequence; the low-density thermal insulation layer contains a lightweight filler and a resin; specifically, for example, the low-density thermal insulation layer is formed by composition A, and the composition A contains a lightweight filler and a resin; the medium-density thermal protection layer contains a lightweight filler, a thermal protection filler, a chopped fiber and a resin; specifically, for example, the medium-density thermal protection layer is formed by composition B, and the composition B contains a lightweight filler, a thermal protection filler, a chopped fiber and a resin; the high-density ablation layer contains a high-temperature resistant ceramic filler and a resin; specifically, for example, the high-density ablation layer is formed by composition C, and the composition C contains a high-temperature resistant ceramic filler and a resin; in the low-density thermal insulation layer and the medium-density thermal protection layer, the lightweight filler is hollow glass microspheres and / or thermal expansion microspheres; in the medium-density thermal protection layer, the thermal protection filler is one or more of aluminum oxide, silicon oxide, zirconium oxide, silicon carbide, silicon boride and boron nitride.

[0023] The gradient density thermal protection material in the present invention includes three gradient functional layers: a high-density ablation-resistant layer, a medium-density heat-protection layer, and a low-density heat-insulating layer. The material function gradually transitions from ablation resistance and heat protection to heat insulation from the outer layer to the inner layer, and has the functional characteristics of heat protection, heat insulation, and dimensional integration; each gradient layer material uses the same resin base material as an adhesive, which can organically combine the gradient layers into a whole, so that the gradient layers have good interface adhesion; at the same time, when preparing the gradient density thermal protection material, the molding process (hot pressing curing molding) can be used to replace the complex and expensive mixed fiber preform. Based on the material gradient design, the structure and composition of the composite material can be continuously changed in space, so that the different advantages of multiple components can be better brought into play, and the low-cost and controllable preparation of gradient density thermal protection materials can be achieved.

[0024] According to some preferred embodiments, the resin is one or more of phenolic resin, modified phenolic resin, epoxy resin, and bismaleimide resin; the chopped fibers are one or more of quartz fibers (also recorded as quartz chopped fibers or chopped quartz fibers), high silica fibers (also recorded as high silica chopped fibers or chopped high silica fibers), phenolic fibers (also recorded as phenolic chopped fibers or chopped phenolic fibers), carbon fibers (also recorded as carbon chopped fibers or chopped carbon fibers), and aramid fibers (also recorded as chopped aramid fibers or aramid chopped fibers); preferably, the chopped fibers are composed of quartz chopped fibers, phenolic chopped fibers, and aramid chopped fibers in a mass ratio of 6: (3-4): (1-2); in the present invention, it is preferred that the chopped fibers are composed of quartz fibers, phenolic chopped fibers, and aramid chopped fibers in a mass ratio of 6: (3-4): (1-2). According to the mass ratio of 6: (3-4): (1-2), the present invention found that compared with the use of a certain type of chopped fiber alone or chopped fibers at other compounding ratios, the preferred chopped fiber composition in the present invention can make up for each other's shortcomings and be relatively evenly distributed in the medium-density heat-proof layer, which helps to achieve the uniformity and consistency of the material, reduces the hot spots and fragile areas that may be caused by unevenness, and can form more interfaces and staggered layers in the medium-density heat-proof layer, thereby increasing the strength and stability of the heat-proof layer, which helps to improve the overall performance of the gradient density thermal protection material, making it more resistant to high temperatures and heat shocks; and / or the high-temperature resistant ceramic filler is one or more of metal oxide ceramic fillers, nitride ceramic fillers, carbide ceramic fillers, boride ceramic fillers, and silicide ceramic fillers.

[0025] According to some preferred embodiments, the high temperature resistant ceramic filler is one or more of alumina ceramic filler, zirconia ceramic filler, titanium oxide ceramic filler, chromium oxide ceramic filler, boron nitride ceramic filler, silicon carbide ceramic filler, boron carbide ceramic filler, zirconium boride ceramic filler, and molybdenum disilicide ceramic filler.

[0026] According to some preferred embodiments, in the low-density heat-insulating layer, the mass ratio of the lightweight filler to the resin is (40-80): (50-100), preferably (0.4-1.6): 1 (e.g., 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1 or 1.6:1), more preferably (0.4-0.6): 1 (e.g., 0.4:1, 0.5:1 or 0.6:1); in the medium-density heat-insulating layer, the mass ratio of the lightweight filler, the heat-insulating filler, the chopped fiber and the resin is (40-80): (1-5): (1-10) : (50-100), preferably (0.4-0.8): (0.01-0.05): (0.01-0.1): 1, more preferably (0.4-0.5): (0.03-0.05): (0.04-0.06): 1; and / or in the high-density ablation layer, the mass ratio of the high-temperature resistant ceramic filler to the resin is (10-50): (50-100), preferably (0.1-1): 1 (for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1), more preferably (0.6-0.8): 1 (for example, 0.6:1, 0.7:1 or 0.8:1).

[0027] After a large number of creative experiments, the present invention has obtained the optimal ratio of the components of the low-density thermal insulation layer, the medium-density thermal protection layer and the high-density ablation layer, that is, in the low-density thermal insulation layer, the mass ratio of the lightweight filler to the resin is (0.4-0.6):1, in the medium-density thermal protection layer, the mass ratio of the lightweight filler, the thermal protection filler, the chopped fiber and the resin is (0.4-0.5): (0.03-0.05): (0.04-0.06):1; in the high-density ablation layer, the mass ratio of the high-temperature resistant ceramic filler to the resin is (0.6-0.8):1. The present invention has found that the selection of these component ratios helps to establish a better relationship between different layers. Good bonding ensures that each layer can be tightly combined, which helps to improve the overall stability and performance of the material, and provide better interface bonding. The reasonable mass ratio of each component can improve the thermal insulation performance of the low-density thermal insulation layer, the thermal insulation performance of the medium-density thermal insulation layer and the anti-ablation performance of the high-density ablation layer, so that the thermal insulation filler and chopped fiber in the medium-density thermal insulation layer, and the high-temperature resistant ceramic filler in the high-density ablation layer can provide better anti-ablation protection and reduce material damage. The present invention found that if the ratio of each layer is not appropriate, the bonding between the layers will become relatively weak, which may cause the material to delaminate or peel, and at the same time affect the uniform distribution of the components in the material, the anti-ablation performance and thermal insulation performance, etc.

[0028] According to some preferred embodiments, the resins contained in the low-density heat-insulating layer, the medium-density heat-protective layer, and the high-density ablative layer are the same.

[0029] According to some preferred embodiments, the lightweight filler is composed of hollow glass microspheres and thermal expansion microspheres in a mass ratio of 1: (0.2 to 0.4) (for example, 1: 0.2, 1: 0.3 or 1: 0.4); preferably, the thermal expansion microspheres are modified thermal expansion microspheres, and more preferably, the thermal expansion microspheres are zirconia-modified thermal expansion microspheres. The present invention is preferably in the low-density thermal insulation layer and the medium-density heat-proof layer, so that the lightweight filler is composed of hollow glass microspheres and zirconia-modified thermal expansion microspheres in a mass ratio of 1: (0.2 to 0.4), that is, preferably, a suitable amount of zirconia-modified thermal expansion microspheres is introduced into the lightweight filler. The present invention finds that zirconia-modified thermal expansion microspheres have better high-temperature stability while maintaining thermal expansion properties. They expand at high temperatures and have better thermal expansion matching with materials than ordinary thermal expansion microspheres. They can effectively fill gaps and better bond with resins, which helps to improve the material. The interfacial adhesion of the material is improved, the risk of delamination or peeling between layers is reduced, thereby improving the stability and overall mechanical properties of the overall material. In addition, the introduction of zirconium oxide modified thermal expansion microspheres can improve the thermal insulation performance of the material and help reduce heat conduction. The introduction of zirconium oxide modified thermal expansion microspheres can also improve the thermal insulation performance of the medium-density heat-proof layer. The zirconium oxide modified thermal expansion microspheres can fill the gaps between the resin and other materials, increase the stability of the heat-proof layer, which helps to improve the material's anti-ablation and high-temperature resistance, and help to achieve better thermal protection performance. In addition, the present invention finds that the amount of zirconium oxide modified thermal expansion microspheres introduced should not be too much. Too much zirconium oxide modified thermal expansion microspheres will lead to a weakened structure of the material. During the molding process, the relative pressure inside the material is high, the extrusion amount of the material is too large, and the open pores increase, which will reduce the thermal insulation performance of the material. If the amount of zirconium oxide modified thermal expansion microspheres introduced is too small, it will not have an effective improvement effect.

[0030] According to some preferred embodiments, the zirconium oxide modified thermally expandable microspheres are prepared as follows:

[0031] (a) mixing heat-expandable microspheres and a nonionic dispersant (e.g., Tween 80) with water to obtain a mixed solution, then ultrasonically dispersing the mixed solution, filtering, and drying to obtain first modified heat-expandable microspheres. For example, after the ultrasonic dispersion, the mixture is filtered with deionized water, and then dried to obtain the first modified heat-expandable microspheres. The mass ratio of the water, the heat-expandable microspheres, and the nonionic dispersant is 50:(0.4-0.6):(0.4-0.6). The heat-expandable microspheres are spherical powder particles with an outer shell of a thermoplastic acrylate polymer formed by butyl acrylate, methyl methacrylate, and glycidyl methacrylate, and an inner core composed of an alkane gas. The heat-expandable microspheres can be, for example, F-48 heat-expandable microspheres produced by Matsumoto Oil & Pharmaceutical Co., Ltd. of Japan.

[0032] (b) placing the first modified heat-expandable microspheres in a sodium hydroxide aqueous solution and stirring for 3 to 5 hours, then washing and filtering until neutral, and then drying to obtain second modified heat-expandable microspheres; the mass fraction of sodium hydroxide in the sodium hydroxide aqueous solution is 8 to 12%, and the mass ratio of the sodium hydroxide aqueous solution to the heat-expandable microspheres used in step (a) is 40:(0.4 to 0.6);

[0033] (c) dispersing the second modified heat-expandable microspheres in the first portion of water, then adding a polyacrylic acid surfactant (e.g., polyacrylic acid) and stirring for 20 to 40 minutes, and centrifuging at 3000 to 4000 rpm for 15 to 30 minutes after the stirring is completed; dispersing the obtained microspheres in the second portion of water and stirring for 10 to 20 minutes, stirring evenly, and then centrifuging, repeating the process of dispersing the microspheres in water and centrifuging after the dispersion in water twice to obtain third modified heat-expandable microspheres; in step (c), the mass ratio of the first portion of water to the heat-expandable microspheres in step (a) is 50:(0.4 to 0.6), and the mass ratio of the second portion of water to the heat-expandable microspheres in step (a) is 40:(0.4 to 0.6);

[0034] (d) dispersing the third modified thermally expandable microspheres in water, adjusting the pH value to 9-11, stirring for 20-40 minutes, and then ultrasonically dispersing to obtain a microsphere dispersion; dispersing zirconium oxide powder in water by ultrasonic means to obtain a zirconium oxide dispersion, and then stirring the zirconium oxide dispersion and the microsphere dispersion for 20-40 minutes to mix them evenly, filtering with deionized water after the stirring is completed, and drying after the filtration to obtain zirconium oxide modified thermally expandable microspheres; the zirconium oxide dispersion contains 30-45% by mass of zirconium oxide; in step (d), the zirconium oxide powder is used to disperse the third modified thermally expandable microspheres; The mass ratio of the water of the expanded microspheres to the heat-expandable microspheres in step (a) is 25: (0.4-0.6); the mass ratio of the zirconium oxide dispersion to the microsphere dispersion is (0.8-1.2): 1; in steps (a), (b) and (d) of the present invention, the drying conditions can be conventionally selected by those skilled in the art, for example, drying at 40-60° C. for 4-10 hours; in steps (b) to (d), the stirring speed can be conventionally selected by those skilled in the art, for example, 100-800 r / min.

[0035] In a second aspect, the present invention provides a method for preparing the gradient density heat protection material according to the first aspect of the present invention, the method comprising the following steps:

[0036] (1) adding a lightweight filler to a resin and kneading the mixture uniformly to obtain a wet pellet A, and then drying the wet pellet A to obtain a composition A;

[0037] (2) mixing the lightweight filler, the heat-resistant filler, and the chopped fibers uniformly, adding the mixture to the resin, and kneading the mixture uniformly to obtain a wet pellet B, and then drying the wet pellet B to obtain a composition B;

[0038] (3) adding a high-temperature resistant ceramic filler to the resin and kneading the mixture uniformly to obtain a wet pellet C, and then drying the wet pellet C to obtain a composition C;

[0039] (4) Composition A, composition B and composition C are sequentially laid, and then compression molded to obtain a gradient density thermal protection material; in the present invention, the composition A is compression molded to form a low-density thermal insulation layer, the composition B is compression molded to form a medium-density thermal protection layer, and the composition C is compression molded to form a high-density ablation layer; the present invention does not specifically limit the process conditions of compression molding, which is a conventional technology in the field, and those skilled in the art can conventionally select, the compression molding pressure can be, for example, 1 to 10 MPa, the compression molding time can be, for example, 1 to 5 hours, and the compression molding temperature can be, for example, 90 to 200°C. In some specific embodiments of the present invention, the compression molding adopts a gradient temperature rising compression molding procedure, for example, first compression molding at 90°C for 0.5 to 1 hour, then compression molding at 120°C for 0.5 to 1 hour, then compression molding at 150°C for 0.5 to 1 hour, and finally compression molding at 180 to 200°C for 1 to 2 hours. At each temperature stage, the compression molding pressure is more preferably 3 to 6 MPa.

[0040] According to some preferred embodiments, in step (1), step (2) and / or step (3), the kneading time is 10 to 30 min (e.g., 10, 15, 20, 25 or 30 min); in step (2), the mixing time is 5 to 10 min (e.g., 5, 8 or 10 min); and / or in step (1), step (2) and / or step (3), the wet embryo dough is spread out and then dried at 50 to 80° C. (e.g., 50° C., 60° C., 70° C. or 80° C.) for 20 to 60 min (e.g., 20, 30, 40, 50 or 60 min).

[0041] According to some preferred embodiments, the density of the composition A is 0.3-0.5 g / cm 3 The density of the composition B is 0.4-0.6 g / cm 3 The density of the composition C is 0.8-1.2 g / cm 3 .

[0042] In the present invention, it is preferred that the density of the composition A is 0.3-0.5 g / cm 3 The density of the composition B is 0.4-0.6 g / cm 3 The density of the composition C is 0.8-1.2 g / cm 3The present invention can achieve more effective thermal protection by combining layered materials of different densities. The high-density ablation layer has a higher heat capacity and thermal resistance, which makes it have excellent anti-ablation performance; the high-density ablation layer formed by the high-density composition C can resist the ablation effect under high temperature, extend the life of the material, and provide strong thermal protection, while the low-density thermal insulation layer provides excellent thermal insulation; the medium-density thermal protection layer provides a balance between the two to ensure good performance, and the present invention can achieve better dimensional integration function through the adjustment of the density gradient. The layered materials of different densities can compensate each other, thereby reducing the deformation and stress of the material in a high temperature environment, improving the dimensional integration capability, and realizing gradual performance changes between different density layers, ensuring that the gradient density thermal protection material has excellent comprehensive performance of thermal insulation, heat protection and anti-ablation performance; the gradient density thermal protection material obtained by the present invention is significantly different from the existing gradient density thermal protection material. The realization of the existing gradient density thermal protection material relies on the reinforcement of the gradient density fiber preform, but this method has a complex preparation process and high price, while the method of the present invention prepares a gradient density thermal protection material that is simple to prepare and low in cost.

[0043] According to some specific embodiments, the gradient density heat protection material is prepared as follows:

[0044] 1. Preparation of a Low-Density Insulation Layer: Lightweight fillers are added to the resin, kneaded uniformly, and then dried in a forced air drying oven to remove most of the solvent from the wet billet A, thereby obtaining composition A. In the present invention, the liquid resin used for molding is purchased directly from the market, such as liquid phenolic resin, which generally contains some solvent. Therefore, after kneading uniformly, it needs to be dried.

[0045] 2. Preparation of medium-density heat-proof layer: Mix the lightweight filler, heat-proof filler and chopped fibers evenly and add them to the resin. After kneading evenly, place them in a blast drying oven for drying to remove most of the solvent in the wet embryo B to obtain composition B.

[0046] 3. Preparation of a high-density ablation layer: Add a high-temperature resistant ceramic filler to the resin, knead the mixture evenly, and then place it in a blast drying oven for drying to remove most of the solvent in the wet embryo C to obtain a composition C; in the present invention, the wet embryo A, wet embryo B, and wet embryo C can be collectively referred to as wet embryos.

[0047] 4. Preparation of low-cost gradient density thermal protection material: In a mold, composition A, composition B, and composition C are sequentially laid from bottom to top, and then compression molding is performed to obtain a low-cost gradient density thermal protection material; the composition A, composition B, and composition C are made of the same resin material.

[0048] In a third aspect, the present invention provides a gradient density thermal protection material produced by the preparation method described in the second aspect of the present invention.

[0049] The present invention will be further described below by way of examples, but the protection scope of the present invention is not limited to these examples.

[0050] Example 1

[0051] 1. Preparation of low-density thermal insulation layer: hollow glass microspheres were added to liquid phenolic resin and kneaded for 20 minutes to obtain wet embryo A. The wet embryo A was then spread on a tray and placed in a blast drying oven at 60°C for 40 minutes to obtain a density of 0.4 g / cm 3 The mass ratio of the hollow glass microspheres to the liquid phenolic resin is 0.5:1.

[0052] Preparation of medium-density heat-resistant layer: hollow glass microspheres, zirconium oxide powder and quartz fiber were mixed for 10 minutes and then added to liquid phenolic resin. After kneading for 20 minutes, wet embryo B was obtained. The wet embryo B was spread on a tray and placed in a blast drying oven at 60°C for 40 minutes to obtain a density of 0.54 g / cm 3 The mass ratio of hollow glass microspheres, zirconium oxide powder, quartz fiber and liquid phenolic resin is 0.5:0.03:0.06:1.

[0053] 3. Preparation of high-density ablation layer: Molybdenum disilicide powder was added to liquid phenolic resin and kneaded for 20 minutes to obtain wet embryo C. The wet embryo C was spread on a tray and placed in a blast drying oven at 60°C for 40 minutes to obtain a density of 1g / cm 3 composition C; the mass ratio of the molybdenum disilicide powder to the liquid phenolic resin is 0.7:1; the composition A, composition B, and composition C use the same liquid phenolic resin.

[0054] 4. Preparation of gradient density heat protection material: In a mold, composition A, composition B, and composition C are sequentially laid from bottom to top, and then compression molding is performed to obtain a gradient density heat protection material.

[0055] Example 2

[0056] Example 2 is basically the same as Example 1, except that:

[0057] 2. Preparation of medium-density heat-resistant layer: hollow glass microspheres, zirconium oxide powder and chopped fibers were mixed for 10 minutes and then added to liquid phenolic resin. After kneading for 20 minutes, wet embryo B was obtained. The wet embryo B was spread on a tray and placed in a blast drying oven at 60°C for 40 minutes to obtain a density of 0.53 g / cm 3Composition B; the mass ratio of hollow glass microspheres, zirconia powder, chopped fibers and liquid phenolic resin is 0.5:0.03:0.06:1; the chopped fibers are composed of quartz chopped fibers, phenolic chopped fibers and aramid chopped fibers in a mass ratio of 6:3:1.5.

[0058] Example 3

[0059] Example 3 is basically the same as Example 1, except that:

[0060] 1. Preparation of a low-density thermal insulation layer: Hollow glass microspheres were added to liquid phenolic resin and kneaded for 20 minutes to obtain a wet mass A. The wet mass A was then spread flat on a tray and dried in a forced air drying oven at 60°C for 40 minutes to obtain a composition A. The mass ratio of the hollow glass microspheres to the liquid phenolic resin was 0.3:1.

[0061] 2. Preparation of a medium-density heat-resistant layer: hollow glass microspheres, zirconia powder, and quartz fiber were mixed for 10 minutes, then added to liquid phenolic resin and kneaded for 20 minutes to obtain a wet ball B. The wet ball B was spread flat on a tray and placed in a blast drying oven at 60°C for 40 minutes to obtain a composition B. The mass ratio of hollow glass microspheres, zirconia powder, quartz fiber, and liquid phenolic resin was 0.3:0.02:0.03:1.

[0062] 3. Preparation of a high-density ablation layer: Molybdenum disilicide powder was added to a liquid phenolic resin and kneaded for 20 minutes to obtain a wet dough C. The wet dough C was spread on a tray and dried in a forced air drying oven at 60°C for 40 minutes to obtain a composition C. The mass ratio of the molybdenum disilicide powder to the liquid phenolic resin was 0.4:1. The same liquid phenolic resin was used for compositions A, B, and C.

[0063] Example 4

[0064] Example 4 is basically the same as Example 1, except that:

[0065] 1. Preparation of a low-density thermal insulation layer: Hollow glass microspheres were added to liquid phenolic resin and kneaded for 20 minutes to obtain a wet mass A. The wet mass A was then spread flat on a tray and dried in a forced air drying oven at 60°C for 40 minutes to obtain a composition A. The mass ratio of the hollow glass microspheres to the liquid phenolic resin was 1.5:1.

[0066] 2. Preparation of a medium-density heat-resistant layer: hollow glass microspheres, zirconia powder, and quartz fiber were mixed for 10 minutes, then added to liquid phenolic resin and kneaded for 20 minutes to obtain a wet ball B. The wet ball B was spread flat on a tray and placed in a forced air drying oven at 60°C for 40 minutes to obtain a composition B. The mass ratio of hollow glass microspheres, zirconia powder, quartz fiber, and liquid phenolic resin was 0.6:0.06:0.07:1.

[0067] 3. Preparation of a high-density ablation layer: Molybdenum disilicide powder was added to a liquid phenolic resin and kneaded for 20 minutes to obtain a wet dough C. The wet dough C was spread flat on a tray and placed in a forced air drying oven at 60°C for 40 minutes to obtain a composition C. The mass ratio of the molybdenum disilicide powder to the liquid phenolic resin was 1:1. The same liquid phenolic resin was used for compositions A, B, and C.

[0068] Example 5

[0069] Example 5 is basically the same as Example 1, except that:

[0070] 1. Preparation of low-density insulation layer: Lightweight filler was added to liquid phenolic resin and kneaded for 20 minutes to obtain wet dough A. The wet dough A was then spread on a tray and placed in a blast drying oven at 60°C for 40 minutes to obtain a low-density insulation layer with a density of 0.44 g / cm 3 The invention relates to a composition A comprising: a lightweight filler and a liquid phenolic resin in a mass ratio of 0.5:1; the lightweight filler is composed of hollow glass microspheres and heat-expandable microspheres in a mass ratio of 1:0.3; the heat-expandable microspheres are spherical powder particles having an outer shell of a thermoplastic acrylate polymer formed by butyl acrylate, methyl methacrylate and glycidyl methacrylate, and an inner core composed of an alkane gas; the heat-expandable microspheres are F-48 heat-expandable microspheres produced by Matsumoto Oil & Fat Pharmaceutical Co., Ltd. of Japan.

[0071] 2. Preparation of medium-density heat-resistant layer: Lightweight filler, zirconium oxide powder and quartz fiber were mixed for 10 minutes and then added to liquid phenolic resin. After kneading for 20 minutes, wet embryo B was obtained. The wet embryo B was spread on a tray and placed in a blast drying oven at 60°C for 40 minutes to obtain a density of 0.58g / cm 3Composition B; the mass ratio of lightweight filler, zirconium oxide powder, quartz fiber and liquid phenolic resin is 0.5:0.03:0.06:1; the lightweight filler is composed of hollow glass microspheres and heat-expandable microspheres in a mass ratio of 1:0.3; the heat-expandable microspheres are spherical powder particles with an outer shell of a thermoplastic acrylate polymer formed by butyl acrylate, methyl methacrylate and glycidyl methacrylate, and a core composed of alkane gas. The heat-expandable microspheres are F-48 heat-expandable microspheres produced by Matsumoto Oil and Fat Pharmaceutical Co., Ltd. of Japan.

[0072] Example 6

[0073] Example 6 is basically the same as Example 1, except that:

[0074] 1. Preparation of low-density insulation layer: Lightweight filler was added to liquid phenolic resin and kneaded for 20 minutes to obtain wet dough A. The wet dough A was then spread on a tray and placed in a blast drying oven at 60°C for 40 minutes to obtain a low-density insulation layer with a density of 0.48 g / cm 3 composition A; the mass ratio of the lightweight filler to the liquid phenolic resin is 0.5:1; the lightweight filler consists of hollow glass microspheres and zirconium oxide modified thermal expansion microspheres in a mass ratio of 1:0.3.

[0075] 2. Preparation of medium-density heat-resistant layer: Lightweight filler, zirconium oxide powder and quartz fiber were mixed for 10 minutes and then added to liquid phenolic resin. After kneading for 20 minutes, wet embryo B was obtained. The wet embryo B was spread on a tray and placed in a blast drying oven at 60°C for 40 minutes to obtain a density of 0.6 g / cm 3 Composition B; the mass ratio of lightweight filler, zirconium oxide powder, quartz fiber and liquid phenolic resin is 0.5:0.03:0.06:1; the lightweight filler consists of hollow glass microspheres and zirconium oxide modified thermal expansion microspheres in a mass ratio of 1:0.3.

[0076] In step 1 and step 2, the preparation of the zirconium oxide modified thermal expansion microspheres is as follows:

[0077] (a) Heat-expandable microspheres and Tween 80 are uniformly mixed with water to obtain a mixed solution, and the mixed solution is then ultrasonically dispersed for 2 hours, filtered, and dried to obtain first modified heat-expandable microspheres; the mass ratio of the water, the heat-expandable microspheres, and Tween 80 is 50:0.5:0.5; the heat-expandable microspheres are spherical powder particles with an outer shell of a thermoplastic acrylate polymer formed by butyl acrylate, methyl methacrylate, and glycidyl methacrylate, and an inner core composed of an alkane gas; the heat-expandable microspheres are F-48 heat-expandable microspheres produced by Matsumoto Oil & Fat Pharmaceutical Co., Ltd. of Japan.

[0078] (b) placing the first modified heat-expandable microspheres in a sodium hydroxide aqueous solution and stirring for 4 hours, then washing and filtering until neutral, and then drying to obtain second modified heat-expandable microspheres; the mass fraction of sodium hydroxide contained in the sodium hydroxide aqueous solution is 10%, and the mass ratio of the sodium hydroxide aqueous solution to the heat-expandable microspheres used in step (a) is 40:0.5.

[0079] (c) dispersing the second modified heat-expandable microspheres in the first portion of water, then adding a polyacrylic acid surfactant (polyacrylic acid) and stirring for 30 minutes. After the stirring is completed, centrifugation is performed at 3000 r / min for 20 minutes. After the centrifugation is completed, the obtained microspheres are dispersed in the second portion of water and stirred for another 20 minutes. After stirring, centrifugation is performed. The process of dispersing the microspheres in water and centrifuging after the dispersion in water is repeated twice to obtain third modified heat-expandable microspheres. In step (c), the mass ratio of the first portion of water to the heat-expandable microspheres in step (a) is 50:0.5, and the mass ratio of the second portion of water to the heat-expandable microspheres in step (a) is 40:0.5.

[0080] (d) dispersing the third modified heat-expandable microspheres in water, adjusting the pH value to 10.5, stirring for 30 minutes, and then ultrasonically dispersing for 1.5 hours to obtain a microsphere dispersion; dispersing zirconium oxide powder in water by ultrasonic means to obtain a zirconium oxide dispersion, and then stirring the zirconium oxide dispersion and the microsphere dispersion for 30 minutes to mix evenly, filtering with deionized water after the stirring, and drying after the filtration to obtain zirconium oxide-modified heat-expandable microspheres; the mass fraction of zirconium oxide in the zirconium oxide dispersion is 35%; in step (d), the mass ratio of the water used to disperse the third modified heat-expandable microspheres to the heat-expandable microspheres in step (a) is 25:0.5; the mass ratio of the zirconium oxide dispersion to the microsphere dispersion is 1:1.

[0081] Example 7

[0082] Example 7 is basically the same as Example 6, except that:

[0083] In step 1, the lightweight filler is composed of hollow glass microspheres and zirconium oxide modified thermal expansion microspheres in a mass ratio of 1:0.1.

[0084] In step 2, the lightweight filler is composed of hollow glass microspheres and zirconium oxide modified thermal expansion microspheres in a mass ratio of 1:0.1.

[0085] Example 8

[0086] Example 8 is basically the same as Example 6, except that:

[0087] In step 1, the lightweight filler is composed of hollow glass microspheres and zirconium oxide modified thermal expansion microspheres in a mass ratio of 1:0.6.

[0088] In step 2, the lightweight filler is composed of hollow glass microspheres and zirconium oxide modified thermal expansion microspheres in a mass ratio of 1:0.6.

[0089] The present invention conducted a bending strength test on the gradient density thermal protection material prepared in each embodiment, and the test results are shown in Table 1. The damage of the material was tested by a four-point bending test, and the results are shown in Table 1.

[0090] Table 1

[0091]

[0092] The parts of the present invention not described in detail are well known to those skilled in the art. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments or replace some of the technical features therein with equivalents. However, such modifications or replacements do not deviate from the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gradient density thermal protection material, characterized by: The gradient density heat protection material comprises a low-density heat insulation layer, a medium-density heat protection layer and a high-density ablation layer in sequence; The low-density thermal insulation layer is formed by composition A, which contains a lightweight filler and a resin. In the low-density thermal insulation layer, the mass ratio of the lightweight filler to the resin is (40-80): (50-100); The medium-density heat-proof layer is formed by composition B, which contains a lightweight filler, a heat-proof filler, chopped fibers, and a resin. In the medium-density heat-proof layer, the mass ratio of the lightweight filler, the heat-proof filler, the chopped fibers, and the resin is (40-80): (1-5): (1-10): (50-100); The high-density ablation layer is formed of a composition C, which contains a high-temperature resistant ceramic filler and a resin. In the high-density ablation layer, the mass ratio of the high-temperature resistant ceramic filler to the resin is (10-50): (50-100); The density of the composition A is 0.3-0.5 g / cm 3 The density of the composition B is 0.4-0.6 g / cm 3 The density of the composition C is 0.8-1.2 g / cm 3 , and the densities of the composition A, the composition B, and the composition C increase in sequence; The lightweight filler is hollow glass microspheres and / or thermal expansion microspheres; The heat-resistant filler is one or more of aluminum oxide, silicon oxide, zirconium oxide, silicon carbide, silicon boride, and boron nitride.

2. The gradient density thermal protection material according to claim 1, characterized in that: The resin is one or more of phenolic resin, modified phenolic resin, epoxy resin, and bismaleimide resin; The chopped fibers are one or more of quartz fibers, high silica fibers, phenolic fibers, carbon fibers, and aramid fibers; and / or The high temperature resistant ceramic filler is one or more of metal oxide ceramic fillers, nitride ceramic fillers, carbide ceramic fillers, boride ceramic fillers, and silicide ceramic fillers.

3. The gradient density heat protection material according to claim 2, characterized in that: The high temperature resistant ceramic filler is one or more of alumina ceramic filler, zirconia ceramic filler, titanium oxide ceramic filler, chromium oxide ceramic filler, boron nitride ceramic filler, silicon carbide ceramic filler, boron carbide ceramic filler, zirconium boride ceramic filler, and molybdenum disilicide ceramic filler.

4. The gradient density heat protection material according to claim 1, characterized in that: The resin contained in the low-density heat-insulating layer, the medium-density heat-protective layer and the high-density ablative layer is the same.

5. The gradient density heat protection material according to any one of claims 1 to 4, characterized in that: The lightweight filler is composed of hollow glass microspheres and thermal expansion microspheres in a mass ratio of 1: (0.2-0.4).

6. The gradient density heat protection material according to claim 5, characterized in that: The heat-expandable microspheres are modified heat-expandable microspheres.

7. The method for preparing a gradient density heat protection material according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: (1) adding a lightweight filler to a resin and kneading the mixture uniformly to obtain a wet pellet A, and then drying the wet pellet A to obtain a composition A; (2) mixing the lightweight filler, the heat-resistant filler and the chopped fibers uniformly, adding the mixture to the resin and kneading the mixture uniformly to obtain a wet pellet B, and then drying the wet pellet B to obtain a composition B; (3) adding a high-temperature resistant ceramic filler to the resin and kneading the mixture uniformly to obtain a wet ball C, and then drying the wet ball C to obtain a composition C; (4) Composition A, composition B and composition C are sequentially applied and then compression molded to obtain a gradient density thermal protection material.

8. The preparation method according to claim 7, characterized in that: In step (1), step (2) and / or step (3), the kneading time is 10 to 30 minutes; In step (2), the mixing time is 5 to 10 minutes; and / or In step (1), step (2) and / or step (3), the wet embryo mass is spread out and then dried at 50-80° C. for 20-60 minutes.

9. A gradient density thermal protection material prepared by the preparation method according to claim 7 or 8.

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