Bearing and heat-insulating integrated foam prepared by pouring forming method and preparation method of bearing and heat-insulating integrated foam

Abstract

The invention discloses load-bearing and heat-insulating integrated foam prepared by adopting a pouring molding method and a preparation method thereof, and relates to the technical field of carrier rockets, silicon dioxide aerogel with a three-dimensional nano-porous structure is added, a one-step method is adopted for pouring molding from bottom to top, the preparation process is greatly simplified, the production cycle is shortened, and the production efficiency is improved. Meanwhile, the problem of attachment of the foam layer and the metal shell is effectively solved. The integrated foam organically combines a bearing function and a heat insulation function, is not easy to deform or damage when bearing an external load, and can be directly used as a structural component.

Description

Technical Field

[0001] This invention relates to the field of launch vehicle technology, specifically to a load-bearing and heat-insulating integrated foam prepared by a casting molding method and its preparation method. Background Technology

[0002] Polyurethane foam is widely used in construction, refrigeration, and other fields due to its lightweight, high elasticity, and good thermal and sound insulation properties. Its excellent flexibility allows it to adapt to complex shape filling requirements, and its relatively low cost makes it an ideal material for industrial production. However, with the expansion of application scenarios, defects such as the high thermal conductivity of polyurethane foam and the decline in mechanical properties at high temperatures have gradually become apparent, making it difficult to meet the requirements for use in extreme environments.

[0003] To overcome these shortcomings, researchers have turned their attention to silica aerogel, a material with ultra-low thermal conductivity, attempting to add it to polyurethane foam to construct a highly efficient thermal insulation network. For example, Chinese invention patent application CN110003527A proposes modifying aerogel with acrylic resin and then mixing it with a polyether polyol system for foaming. This chemical modification improves the compatibility of the aerogel with the organic matrix and reduces agglomeration. However, the process is complex, and the dispersion of the modified aerogel by the polyether polyol system still relies on a high-pressure foaming agent, requiring sophisticated equipment. Another example is Chinese invention patent application CN109575355A, which uses a coating to isolate the aerogel from the foam matrix, achieving flame retardancy and thermal insulation through physical coating. However, the coating has weak interfacial adhesion with the foam and is prone to peeling off after long-term use.

[0004] In the field of launch vehicle technology, the performance requirements for structural materials are extremely stringent. During launch and flight, rockets must withstand complex and extreme mechanical and thermal environments, which prompts researchers to continuously explore and develop high-performance materials to meet the rocket's needs in terms of reliability, safety, and efficiency.

[0005] Traditional material systems have gradually revealed numerous limitations when dealing with these extreme conditions. For example, commonly used single-function materials often focus only on one aspect of performance, such as simple load-bearing or thermal insulation, making it difficult to achieve the synergistic integration of multiple key functions. In practical applications, this necessitates the use of multiple independent components in rocket structural design to achieve different functions, thus increasing structural complexity and weight. Regarding thermal insulation materials, while traditional materials can block heat transfer to some extent, they are prone to deformation or even damage under large external loads, failing to provide reliable support and protection for the rocket structure. When a rocket passes through the atmosphere, external aerodynamic heating causes a rapid increase in the surface temperature of the rocket body. If the load-bearing capacity of the thermal insulation material is insufficient, the insulation layer may fail, endangering the safety of the precision instruments and equipment inside the rocket.

[0006] Regarding load-bearing materials, while common metals possess high strength and rigidity, enabling them to withstand significant mechanical loads, their thermal insulation performance is relatively poor. During rocket flight, heat can easily be rapidly conducted to the interior through the metal structure, affecting the normal operation of equipment and potentially even causing thermal failure.

[0007] Traditional material preparation methods also have many drawbacks in terms of manufacturing processes. Taking traditional PMI foam preparation as an example, the process is cumbersome, involving multiple complex steps. This not only results in a long production cycle but also numerous intermediate steps, which increases production costs and reduces production efficiency. For instance, the spraying process involves spraying layer by layer, leading to low construction efficiency. Furthermore, sanding is required, and the resulting surface has open structures that need to be sealed before repainting for protection. Additionally, bonding the foam layer to the metal outer shell presents significant technical challenges, which to some extent limits the widespread application of the material in rocket structures.

[0008] In existing technologies, the first is the non-metallic honeycomb sandwich aluminum alloy shell with a common bottom structure, represented by the CZ-3B three-stage tank. This structure achieves thermal insulation through vacuuming. While the vacuum layer provides good insulation and has low thermal conductivity, the common bottom structure is complex, places high demands on the insulation layer, and requires vacuuming before testing and use, resulting in high efficiency, low cost, and a long preparation time before launch. Secondly, the variable-thickness polymethacrylimide (PMI) foam sandwich aluminum alloy panel common bottom tank structure, represented by the CZ-6 two-stage tank, is relatively simpler than the vacuum common bottom structure and does not require vacuuming before testing and use, shortening the preparation time before launch. However, PMI foam raw materials are expensive, and the upper and lower panels use a complex interlocking welding process, resulting in large panel size and positional tolerances. The bonding of the foam layer to the metal shell is difficult, requiring VARI technology for adhesive bonding. Furthermore, the connection structure between the two common bottom panels is complex, leading to high processing costs and low efficiency. In addition, the common bottom configuration of a single metal panel layer and a non-metallic insulation layer, represented by Chinese invention patent CN115750142A, is simple in structure and processing, and easy to manufacture. However, during operation, the lower surface of the non-metallic insulation layer directly contacts the propellant, while the non-metallic layer contacts the cryogenic propellant, which poses a risk of cracking or even falling off.

[0009] In recent years, with the rapid development of aerospace technology, the performance requirements for launch vehicles have become increasingly stringent. Higher carrying capacity, more precise orbit control, and safer and more reliable flight have all posed unprecedented challenges to the structural materials of rockets. Against this backdrop, the development of a new type of foam material that can integrate load-bearing and heat insulation functions and has a simple and efficient manufacturing process has become a research hotspot and urgent need in this field. Summary of the Invention

[0010] Therefore, the purpose of this invention is to provide a load-bearing and heat-insulating integrated foam prepared by casting molding method and the preparation method thereof.

[0011] The objective of this invention is achieved through the following technical solution: <First Aspect> This invention provides a method for preparing an integrated foam using a casting molding method, comprising the following steps: The mold with the top opening is placed at the bottom of the part to be foamed and in close contact. Material A and material B are injected into the mold through a high-flow pipe and foamed.

[0012] As one implementation scheme, the mass ratio of material A to material B is 100:80~100.

[0013] As one implementation scheme, material A is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0014] In one embodiment, component B comprises silica aerogel and hydroxyl-terminated polyether polyol. In another embodiment, component B further comprises polyester polyol, catalyst, and foaming agent; component B is composed of polyester polyol, silica aerogel, hydroxyl-terminated polyether polyol, catalyst, and foaming agent in a mass ratio of 100~105 : 4~8 : 8~15 : 0.6~1.0 : 20~40.

[0015] As one embodiment, material A is a blend of toluene diisocyanate and isophorone diisocyanate in a mass ratio of 3 to 7: 5.

[0016] In some embodiments, the mass ratio of toluene diisocyanate to isophorone diisocyanate in material A is 3~5:5.

[0017] As one implementation, the mass ratio of silica aerogel to hydroxyl-terminated polyether polyol in material B is 6~8:10~15.

[0018] As one implementation, the mass ratio of polyester polyol, silica aerogel, hydroxyl-terminated polyether polyol, catalyst and foaming agent in material B is 100~105 : 6~8 : 10~15 : 0.6~1.0 : 30.

[0019] In some embodiments, the mass ratio of polyester polyol, silica aerogel, hydroxyl-terminated polyether polyol, catalyst and foaming agent in material B is 100 : 6~8 : 10~15 : 0.6 : 30.

[0020] In some embodiments, the mass ratio of material A to material B is 100:80.

[0021] In some embodiments, the hydroxyl-terminated polyether polyol comprises a difunctional hydroxyl-terminated polyether polyol. Preferably, the difunctional hydroxyl-terminated polyether polyol is a hydroxyl-terminated polyether polyol with propylene glycol as an initiator, such as WANOL® C2020 from Wanhua Chemical.

[0022] As one embodiment, the catalyst is selected from one or more of triethylenediamine, dimethylcyclohexylamine, dibutyltin dilaurate, and stannous octoate.

[0023] In some embodiments, the catalyst is triethylenediamine.

[0024] As one implementation, the foaming agent is selected from trifluoroiodomethane and / or cyclopentane.

[0025] In some embodiments, the foaming agent is trifluoroiodomethane.

[0026] As one implementation method, the pouring is carried out by bottom pouring.

[0027] As one implementation, the foaming treatment temperature is 20~40℃, and the foaming time is 2~24h.

[0028] As one implementation, during the pouring process, the flow rate of material A is 10~30 mL / s, and the flow rate of material B is 8~24 mL / s.

[0029] In some embodiments, during the pouring process, the flow rate of material A is 10~20 mL / s, and the flow rate of material B is 8~16 mL / s.

[0030] <Second aspect> This invention provides an integrated foam prepared by a casting molding method, which is prepared by the above-mentioned method.

[0031] As one embodiment, the foam has a compressive strength of 0.79~0.97 MPa and a thermal conductivity of 0.021~0.027 W·(m·K). -1 Its density is 55~67 kg / m³ 3 .

[0032] As one embodiment, the foam has a compressive strength of 0.90~0.97 MPa and a thermal conductivity of 0.021~0.024 W·(m·K). -1 Its density is 55~58 kg / m³ 3 .

[0033] Compared with the prior art, the present invention has the following beneficial effects: 1) The method for preparing integrated load-bearing / insulating foam using the casting molding method provided by this invention greatly simplifies the preparation process compared to the cumbersome multi-step process of traditional PMI foam preparation, reduces intermediate steps, effectively shortens the production cycle, and improves production efficiency. Furthermore, the bottom-up foam casting method, which is a one-step molding process, solves the problem of difficult bonding between the foam layer and the metal shell. At the same time, the finished product after casting does not require grinding, has a skin on the surface, and has no open-cell structure. Compared to traditional single-function materials, the integrated foam provided by this invention is not easily deformed or damaged under external loads, achieving an organic combination of load-bearing and insulation functions, and can be used directly as a structural component.

[0034] 2) Due to the three-dimensional nanoporous network of silica aerogel, which is dispersed in the foam matrix in the form of nanoparticles, its nanoscale pores significantly inhibit heat conduction, mainly in the following ways: ① The framework is a fine nanoscale network, which greatly reduces the solid contact area and blocks the heat conduction path by the porous structure; ② The aerogel is uniformly dispersed in the foam matrix, forming a two-scale thermal insulation network with the pore structure of the foam itself: the nanoscale silica channels inhibit gas heat conduction, and the micron-scale foam pores weaken heat convection. The combination of the two greatly reduces the heat conduction capacity; ③ The aerogel particles have high surface roughness, which has the effect of nucleating agents. Moreover, the dispersed aerogel particles are adsorbed on the bubble walls, forming a physical barrier that hinders the merging and rupture of bubbles during the rising process, making the foam pore size more uniform and reducing large pore defects.

[0035] 3) The long-chain structure of hydroxyl-terminated polyether polyol interweaves with the rigid network of polyester polyol, relieving stress concentration and improving the impact resistance of foam; in addition, the hydroxyl groups of hydroxyl-terminated polyether polyol form hydrogen bonds with the silanol groups on the surface of aerogel, enhancing the interfacial bonding between aerogel and polyurethane matrix, reducing interfacial thermal resistance, and forming a steric hindrance layer on the surface of aerogel, preventing aerogel particles from agglomerating, and significantly improving the dispersion uniformity of aerogel in polyurethane foam.

[0036] 4) This invention proposes to prepare polyurethane foam by using a high-flow-rate casting method. The high flow rate generates strong shear force in the pipe, which cuts off the interaction between aerogel nanoparticles like "scissors". In addition, the high-frequency collision between particles in the turbulent state helps to break up the agglomerates and improve the uniformity of dispersion. Detailed Implementation

[0037] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0038] To facilitate understanding, the abbreviations or nouns mentioned below will be explained first: The toluene diisocyanate, isophorone diisocyanate, and polyester polyol used in this invention were purchased from Shanghai Kaiyin Chemical Co., Ltd. Toluene diisocyanate, model TDI-80, was selected. The isophorone diisocyanate selected is WANNATE® IPDI; The hydroxyl value of the polyester polyol is 300~450 mg KOH / g, and the molecular weight is 1000~4000 g / mol; The hydroxyl-terminated polyether polyol selected is WANOL®C2020 from Wanhua Chemical. Polyether polyol, selected from Dawson POL204; The catalyst used is triethylenediamine; The foaming agent used is trifluoroiodomethane; Silica aerogel was purchased from Kramar, item number 1308121314.

[0039] Example 1 This embodiment provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method, the steps of which are as follows: The mold with the top opening is placed at the bottom of the storage tank and in close contact with it, and the inner cavity of the mold is set to the desired shape; By mass fraction, 100 parts of material A and 80 parts of material B are poured into the mold at the bottom of the storage tank through high-flow pipes. The flow rate of material A is 20 mL / s and the flow rate of material B is 16 mL / s. They are mixed at the bottom of the mold at room temperature (25℃). After pouring, the mixture is allowed to stand for 24 hours to react. The mold is then removed to obtain a one-step heat insulation foam.

[0040] Material A is a blend of toluene diisocyanate and isophorone diisocyanate in a mass ratio of 5:5, which is stirred and mixed evenly at room temperature. Material B is a polyol blend, which is obtained by mixing polyester polyol, silica aerogel, hydroxyl-terminated polyether polyol, catalyst, and foaming agent in a mass ratio of 100:6:10:0.6:30 at room temperature.

[0041] In this embodiment, during the mixing process of component B, polyester polyol is first added to a stirring container, and stirring is started at 300 r / min. Then, hydroxyl-terminated polyether polyol is slowly added, and stirring is continued for 15 min to ensure that the two are fully mixed. Next, silica aerogel is added and stirred for 30 min to ensure that the aerogel is uniformly dispersed in the slurry system. Finally, catalyst and foaming agent are added, and stirring is continued for 5 min to obtain the polyol composition of component B.

[0042] Example 2 This embodiment provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method, the steps of which are as follows: By mass fraction, 100 parts of material A and 80 parts of material B are poured into the mold at the bottom of the storage tank through high-flow pipes. The flow rate of material A is 20 mL / s and the flow rate of material B is 16 mL / s. They are mixed at the bottom of the mold at room temperature (25℃). After pouring, the mixture is allowed to stand for 24 hours to react. The mold is then removed to obtain a one-step heat insulation foam.

[0043] Material A is a blend of toluene diisocyanate and isophorone diisocyanate in a mass ratio of 7:5, which is stirred and mixed evenly at room temperature. Material B is a polyol blend, which is obtained by mixing polyester polyol, silica aerogel, hydroxyl-terminated polyether polyol, catalyst, and foaming agent in a mass ratio of 100:4:8:0.6:30 at room temperature. The mixing steps are as described in Example 1.

[0044] Example 3 This embodiment provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method, the steps of which are as follows: By mass fraction, 100 parts of material A and 80 parts of material B are poured into the mold at the bottom of the storage tank through high-flow pipes. The flow rate of material A is 20 mL / s and the flow rate of material B is 16 mL / s. They are mixed at the bottom of the mold at room temperature (25℃). After pouring, the mixture is allowed to stand for 24 hours to react. The mold is then removed to obtain a one-step heat insulation foam.

[0045] Material A is a blend of toluene diisocyanate and isophorone diisocyanate in a mass ratio of 3:5, which is stirred and mixed evenly at room temperature. Material B is a polyol blend, which is obtained by mixing polyester polyol, silica aerogel, hydroxyl-terminated polyether polyol, catalyst, and foaming agent in a mass ratio of 100:8:15:0.6:30 at room temperature. The mixing steps are as described in Example 1.

[0046] Example 4 This embodiment provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method, the steps of which are as follows: By mass fraction, 100 parts of material A and 120 parts of material B are poured into the mold at the bottom of the storage tank through high-flow pipes. The flow rate of material A is 20 mL / s and the flow rate of material B is 24 mL / s. They are mixed at the bottom of the mold at room temperature (25℃). After pouring, the mixture is allowed to stand for 24 hours to react. The mold is then removed to obtain a one-step heat-insulating foam.

[0047] Material A is a blend of toluene diisocyanate and isophorone diisocyanate in a mass ratio of 5:5, which is stirred and mixed evenly at room temperature. Material B is a polyol blend, which is obtained by mixing polyester polyol, silica aerogel, hydroxyl-terminated polyether polyol, catalyst, and foaming agent in a mass ratio of 100:6:10:0.6:30 at room temperature. The mixing steps are as described in Example 1.

[0048] Example 5 This embodiment provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method. The steps are basically the same as in Embodiment 1, with the difference being: The mass fraction of silica aerogel in material B is 2%, while other parameters remain unchanged.

[0049] Example 6 This embodiment provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method. The steps are basically the same as in Embodiment 1, with the difference being: The mass fraction of silica aerogel in material B is 6.5%, while other parameters remain unchanged.

[0050] Example 7 This embodiment provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method. The steps are basically the same as in Embodiment 1, with the difference being: During pouring, the flow rate of material A is 10 mL / s, the flow rate of material B is 8 mL / s, and other parameters remain unchanged.

[0051] Example 8 This embodiment provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method. The steps are basically the same as in Embodiment 1, with the difference being: During pouring, the flow rate of material A is 30 mL / s, the flow rate of material B is 24 mL / s, and other parameters remain unchanged.

[0052] Example 9 This embodiment provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method. The steps are basically the same as in Embodiment 1, with the difference being: During pouring, the flow rate of material A is 40 mL / s, the flow rate of material B is 32 mL / s, and other parameters remain unchanged.

[0053] Example 10 This embodiment provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method. The steps are basically the same as in Embodiment 1, with the difference being: During pouring, the flow rate of material A is 50 mL / s, the flow rate of material B is 40 mL / s, and other parameters remain unchanged.

[0054] Comparative Example 1 This comparative example provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method. The steps are basically the same as in Example 1, except that: Material B does not contain hydroxyl-terminated polyether polyols, and other parameters remain unchanged.

[0055] Comparative Example 2 This comparative example provides a method for preparing a load-bearing / thermal insulation integrated foam using a casting molding method. The steps are basically the same as in Example 1, except that: In component B, the hydroxyl-terminated polyether polyol is replaced with a polyether polyol, while other parameters remain unchanged.

[0056] Performance testing: The performance of the foam prepared in the above embodiments was tested, including foam density, compressive strength, and thermal conductivity, as shown in Table 1.

[0057] Table 1

[0058] It can be seen that by flexibly adjusting parameters such as silica aerogel, hydroxyl-terminated polyether polyol, and high-throughput casting, the various properties of the foam can be precisely controlled, mainly in the following aspects: As the silica aerogel content increases, the thermal conductivity of the foam shows an overall trend of gradually decreasing (with local fluctuations), while the compressive strength shows an overall trend of gradually increasing (with local fluctuations). According to Examples 1, 3, and 7, when the ratio of aerogel to hydroxyl-terminated polyether polyol is preferably controlled at 6-8:10-15, the mass ratio of toluene diisocyanate to isophorone diisocyanate in component A is 3-5:5, and the high-throughput flow rate is controlled at 10-20 mL / s for component A and 8-16 mL / s for component B, the density of the prepared sample is lower (55-58 kg / m³). 3It has higher compressive strength (0.9~0.97 MPa) and lower thermal conductivity (0.021~0.024 W·(m·K)). -1 ).

[0059] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing an integrated foam using a casting molding method, characterized in that, Includes the following steps: The mold with the top opening is placed at the bottom of the part to be poured with foam and in close contact. Material A and material B are injected into the mold through a high-flow pipe and foamed. Material A is selected from one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, and polymethylene polyphenyl polyisocyanate. Material B includes silica aerogel and hydroxyl-terminated polyether polyol; The mass ratio of material A to material B is 100:80~100.

2. The method according to claim 1, characterized in that, Material A is a blend of toluene diisocyanate and isophorone diisocyanate in a mass ratio of 3~7:

5.

3. The method according to claim 1, characterized in that, The mass ratio of silica aerogel to hydroxyl-terminated polyether polyol in material B is 6~8:10~15.

4. The method according to claim 1, characterized in that, The B component further includes polyester polyol, catalyst, and foaming agent; in the B component, the mass ratio of polyester polyol, silica aerogel, hydroxyl-terminated polyether polyol, catalyst, and foaming agent is 100~105 : 4~8 : 8~15 : 0.6~1.0 : 20~40.

5. The method according to claim 4, characterized in that, The catalyst is selected from one or more of triethylenediamine, dimethylcyclohexylamine, dibutyltin dilaurate, and stannous octoate.

6. The method according to claim 4, characterized in that, The foaming agent is selected from trifluoroiodomethane and / or cyclopentane.

7. The method according to claim 1, characterized in that, The flow rate of material A is 10~30L / min, and the flow rate of material B is 8~24L / min; the foaming treatment temperature is 20~40℃, and the foaming time is 2~24h.

8. The method according to claim 1, characterized in that, The pouring is carried out using the bottom pouring method.

9. An integrated foam prepared according to any one of claims 1 to 8, characterized in that, The integrated foam has a compressive strength of 0.79~0.97 MPa and a thermal conductivity of 0.021~0.027 W·(m·K). -1 Its density is 55~67 kg / m³ 3 .

10. The integrated foam according to claim 9, characterized in that, The integrated foam has a compressive strength of 0.90~0.97 MPa and a thermal conductivity of 0.021~0.024 W·(m·K). -1 Its density is 55~58 kg / m³ 3 .

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