A high-performance porous polymer / silica aerogel composite foam material and a preparation method thereof

Abstract

The application discloses a kind of high-performance porous polymer / silica aerogel composite foam materials and preparation method thereof, the preparation method is: polymer is formed into composite sheet by blending with PEO;Sol is prepared using silicon source and ethanol;Composite sheet is completely immersed in sol until a large number of pores appear in and outside composite sheet, and sol presents completely transparent state;After being transferred to airtight container and standing aging, it is immersed in the mixed solution of n-hexane and hydrophobic modifier to age, to obtain hydrophobic composite sheet, then placed in foaming kettle to obtain composite foam material.The beneficial effects of the present application are: not only ensure that the material has the characteristics of light weight and low thermal conductivity, but also significantly improve the flexibility and strength of the material, and the anti-powdering, anti-humidity and dimensional stability are better;At the same time, the process is simplified, the cost is reduced, it is easy to scale, and the key performance can be controlled as needed.

Description

Technical Field

[0001] This invention relates to the field of composite materials, and in particular to a high-performance porous polymer / silica aerogel composite foam material for use in construction, transportation and other fields, and its preparation method. Background Technology

[0002] Against the backdrop of rapid development in green building and intelligent transportation, the demand for high-efficiency materials that combine energy saving, thermal insulation, and fire safety is increasingly urgent. Porous polymer materials, with their lightweight and high specific surface area, have become ideal candidates for building insulation and transportation fire protection. However, traditional porous polymers generally face technical bottlenecks such as insufficient mechanical strength and difficulty in synergistically optimizing thermal insulation and flame retardant properties, severely restricting their application in high-value-added scenarios such as new energy vehicle battery packs and high-rise building curtain walls. Aerogel, as a nanoporous material with ultra-high porosity and extremely low thermal conductivity, has broad application prospects in the field of thermal insulation. However, aerogel itself has poor mechanical properties and is brittle, limiting its large-scale application.

[0003] In existing technologies, the performance limitations of traditional materials can be effectively overcome by synergistically utilizing the flexibility of polymers and the excellent thermal insulation properties of aerogels. Currently, conventional preparation methods for porous polymer / aerogel composites mainly involve mixing aerogel powder with a polymer matrix and then molding it using processes such as hot pressing and injection molding. Although these methods can obtain high-strength porous composites, they generally suffer from problems such as uneven aerogel dispersion and weak interfacial bonding, leading to powder shedding and severely restricting the full realization of the thermal insulation advantages of aerogels. Therefore, it is necessary to develop a novel preparation method that combines multiple strategies, is simple in process, and has outstanding efficiency, to obtain porous polymer / aerogel composites with high mechanical strength, excellent thermal insulation properties, and flame retardant properties. This would effectively address the core requirement of integrated "strength-insulation-flame retardancy" materials in current green building systems and new energy transportation vehicles under extreme environments. Summary of the Invention

[0004] To address the challenges of high thermal conductivity, difficulty in balancing mechanical properties and thermal insulation in traditional polymer foams, brittleness and powder shedding of silica aerogels, poor interfacial bonding with the polymer matrix, and complex process dispersion, this invention provides a porous polymer / silica aerogel composite foam material and its preparation method, comprising four major technological breakthroughs: 1) An innovative one-step molding method, simplifying the preparation process through in-situ PEO washing technology, simultaneously forming an open-cell structure and composite aerogel, significantly improving production efficiency and reducing costs; 2) Utilizing the reinforcing effect of PEO, its combination with silica aerogel greatly enhances the material's flexibility and mechanical strength, effectively mitigating powder shedding; 3) Employing supercritical drying technology to achieve both thorough material drying and polymer foaming, further reducing the composite material's thermal conductivity and significantly improving its thermal insulation performance; 4) By optimizing the ratio of polymer matrix, PEO, and silica, as well as supercritical process parameters, precise control of material properties is achieved, meeting diverse application requirements. These technological innovations provide new ideas for the industrial production of high-performance thermal insulation materials.

[0005] To achieve the above-mentioned objectives, this invention provides a high-performance porous polymer / silica aerogel composite foam material, the preparation method of which includes the following steps: Step S1: 100-150 parts by weight of polymer and 40-100 parts by weight of PEO are blended in the molten state and then molded to obtain PEO / polymer composite sheet; Step S2: Mix silicon source and ethanol at a molar ratio of 1:3-9 and stir until homogeneous. Add deionized water and acidic catalyst in sequence, and adjust the pH to 2.0±0.2 using an alkaline neutralizing agent to obtain a sol system. The preferred molar ratio of silicon source to ethanol is 1:6. Step S3: Immerse the PEO / polymer composite sheet vertically into the sol system. After complete immersion, place it in a constant temperature water bath and stir until a large number of pores appear on the surface and inside of the PEO / polymer composite sheet, and the sol system becomes completely transparent. Step S4: Transfer to a sealed container and allow to stand for aging, so that the sol-gel reaction can be fully carried out in the pores of the PEO / polymer composite sheet to form a three-dimensional cross-linked PEO / silica wet gel network, thus obtaining the PEO / silica wet gel / polymer composite sheet. Step S5: Immerse the PEO / silica wet gel / polymer composite sheet in a mixture of n-hexane and hydrophobic modifier at room temperature, centrifuge and filter, and then age it in the hydrophobic modifier to replace the surface hydroxyl groups with hydrophobic methyl groups, thereby obtaining the hydrophobic composite sheet. Step S6: Place the hydrophobic composite sheet in a high-pressure foaming autoclave and seal it. Inject foaming gas, rinse and remove air and moisture, then inject CO2 to 15-20 MPa. Maintain the temperature and pressure at 60-160℃ until the gas reaches equilibrium in the hydrophobic composite sheet. Then depressurize to 7.5-10 MPa, then pressurize again to 15-20 MPa and maintain the temperature and pressure until equilibrium is reached. Repeat this cycle of pressurization, depressurization, and maintaining the temperature and pressure until equilibrium is reached 4-5 times until saturation is achieved. Then depressurize, open the high-pressure foaming autoclave and quickly remove the material to obtain porous PEO / silica aerogel / polymer composite foam.

[0006] Preferably, in step S1, The polymer is one or more of the following: rubber, polycarbonate (PC), acrylonitrile-styrene-acrylate copolymer (ASA), acrylonitrile-butadiene-styrene copolymer (ABS), polyphenylene oxide (PPO), polystyrene (PS), thermoplastic polyurethane (TPU), and polymethyl methacrylate (PMMA); the rubber is preferably butadiene rubber (BR), ethylene propylene rubber (EPDM), silicone rubber (MVQ), or fluororubber (FKM). The molecular weight of the PEO is 100-5000 g / mol; The polymer and the PEO are melt-blended in an internal mixer to obtain a homogeneous mixture. The speed of the internal mixer is 50-100 rpm, the temperature is 90-200℃, and the mixing time is 2-3 h. After melt blending, the uniform mixture is injected into a mold with a thickness of 1-10mm and placed in a hot press for hot pressing. The pressure of the hot press is 5-20MPa, the temperature is 100-250℃, and the time is 5-10min.

[0007] In step S2 The silicon source is one or more of the following: tetraethoxysilane (TEOS), methyltrimethoxysilane (MTMS), dimethyldimethoxysilane (DMDMS), methyl orthosilicate (TMOS), polyhydromethylsiloxane (PHMS), sodium silicate, and silicon-containing biomass (preferably rice husk ash). The acidic catalyst is hydrochloric acid; the alkaline neutralizing agent is ammonia. The silicon source and ethanol are stirred to homogeneity using a magnetic stirrer at a speed of 100-500 rpm.

[0008] In step S3 The temperature of the constant temperature water bath is 40-80℃, the stirring speed is 100-500rpm, and the time is 15-80min.

[0009] In step S4 The aging temperature is 50-70℃, and the aging time is 24-60h.

[0010] In step S5 The hydrophobic modifier is one or a combination of two or more of trimethylchlorosilane (TMCS), hexamethyldisilazane (HMDS), methyltrimethoxysilane (MTMS), and methyltriethoxysilane (MTES). The volume ratio of n-hexane to the hydrophobic modifier is 6-12:1, preferably 8:1; The soaking time at room temperature is 3-6 hours; the aging time in the hydrophobic modified solution is 15-30 hours.

[0011] In step S6 The heat preservation and pressure holding are carried out under oil bath temperature of 60-160℃, the pressure holding time is 3-4 hours, and the final saturation time is 8-10 hours.

[0012] The weight proportions of each component in the preparation method are as follows: 100-150 parts polymer, 40-100 parts PEO, 50-90 parts silicon source, 0.5-5 parts acidic catalyst, 0.5-5 parts alkaline neutralizer, 300-420 parts ethanol, 200-400 parts deionized water, 150-200 parts n-hexane, and 19-25 parts hydrophobic modifier. The hydrophobic modifier needs to be divided into two equal parts because step S6 involves two separate applications.

[0013] The present invention also includes composite foam materials obtained by the preparation method described above.

[0014] The beneficial effects of this invention are: the materials prepared by the method of this invention not only ensure that the materials have the characteristics of being lightweight and having low thermal conductivity, but also significantly improve the flexibility and strength of the materials, and have better resistance to pulverization, resistance to damp heat, and dimensional stability; at the same time, the process is simplified, the cost is reduced, it is easy to scale up, and the key properties can be controlled as needed. Specifically: 1. One-step molding method: This method employs an in-situ PEO washing strategy, simplifying the preparation process. It eliminates the need for complex post-processing, significantly streamlining the production flow, reducing production costs, and offering excellent processability with common equipment, making it highly suitable for industrial production. This method can simultaneously form open-pore structures and PEO-silica aerogel, improving preparation efficiency.

[0015] 2. Reinforcing effect of PEO: The combination of PEO eluted in situ with silica aerogel improves the flexibility and mechanical strength of the silica aerogel. PEO acts as a reinforcing and adhesive agent in the composite aerogel, improving its mechanical properties and reducing dust shedding. Through the reinforcing effect of PEO, the mechanical strength of the composite material is significantly improved, making it more reliable in practical applications.

[0016] 3. Supercritical technology: Supercritical technology allows PEO silica aerogel to be fully dried while the polymer foams, further reducing the thermal conductivity of the composite material. This effectively reduces heat transfer, giving it a greater advantage in the field of thermal insulation. It also makes the composite material lighter overall, making it easier to install and transport.

[0017] 4. Multifunctionality control: By adjusting the ratio of polymer matrix, PEO and silica aerogel and supercritical process, the performance of composite materials can be optimized as needed to meet the requirements of different application fields. Attached Figure Description

[0018] Figure 1 This is a test image of the hydrophobic angle of the sample surface obtained in Example 1 of the present invention.

[0019] Figure 2 This is a SEM image of silica aerogel in the sample obtained in Example 1 of the present invention.

[0020] Figure 3 This is a photograph of the flame impact test of the sample obtained in Example 2 of the present invention.

[0021] Figure 4 This is a microscopic image of the surface of sample 2 in the comparative experiment of this invention.

[0022] Figure 5 The images show infrared thermal images of Example 1 and Comparative Example 1 on a heating stage at 100°C in the comparative test of this invention. Detailed Implementation

[0023] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0024] Example 1 This invention provides a method for preparing a high-performance porous polymer / silica aerogel composite foam material, specifically: (1) Raw material preparation: 120 parts of polymer (ABS), 40 parts of PEO with a molecular weight of 1500 g / mol, 50 parts of silicon source (PHMS), 1.5 parts of acidic catalyst (hydrochloric acid), 1.5 parts of alkaline neutralizer (ammonia water), 360 parts of ethanol, 380 parts of deionized water, 180 parts of n-hexane and 20 parts of hydrophobic modifier (MTES); (2) Add ABS and PEO to a mixer preheated to 160°C and melt-blend at 80 rpm for 2 hours. After the mixture is homogeneous, inject it into a 3 mm thick mold and then place it in a hot press. Press it for 7 minutes at 8 MPa pressure and 170°C to finally obtain PEO / ABS composite sheet.

[0025] (3) In a 1000 mL beaker, PHMS and ethanol were mixed and placed on a magnetic stirrer and stirred at 100 rpm until homogeneous. Then, 380 parts of deionized water and 1.5 parts of hydrochloric acid catalyst were added to the mixture in sequence, and the pH was adjusted to 2.0±0.2 with 1.5 parts of ammonia. The prepared PEO / ABS composite sheet was vertically immersed into the sol system. After ensuring complete immersion, it was transferred to a constant temperature water bath and stirred at 150 rpm for 50 minutes at 70°C until a large number of pores appeared on the surface and inside of the ABS composite sheet and the system became a completely transparent sol state. (4) Transfer the sol and PEO / ABS composite sheet to a sealed container and let it stand for 45 hours at 60°C to allow the sol-gel reaction to occur fully in the pores inside the sheet, and finally form a three-dimensional cross-linked PEO-silica wet gel network. (5) PEO-silica wet gel / ABS is immersed in a mixture of 10 parts hydrophobic modifier MTES and 180 parts n-hexane. After soaking at room temperature for 5 hours, it is centrifuged and filtered, and then aged in 10 parts modifier solution for 20 hours. The hydrophobic modification is completed through the substitution reaction of surface hydroxyl groups and hydrophobic methyl groups.

[0026] (6) Place the prepared sample in a preheated autoclave and seal it. First, inject about 1 MPa of foaming gas to flush the autoclave three times to fully remove air and moisture. Then, fill the autoclave with 18 MPa of CO2 and maintain the pressure for 4 hours under oil bath conditions at 150°C (actual temperature inside the autoclave is 130°C). Next, repeat the operation of depressurizing to 9 MPa and then repressurizing to 18 MPa four times to ensure that the gas is fully saturated. After a total of 9 hours of saturation treatment, quickly depressurize and open the autoclave to finally obtain porous ABS / PEO-silica aerogel composite foam material.

[0027] The surface hydrophobicity angle of the material in this embodiment was tested, and the results are as follows: Figure 1 As shown, the material in this embodiment exhibits good resistance to damp heat; furthermore, the SEM images of the in-situ generated silica aerogel (such as...) demonstrate this. Figure 2 As shown in the figure, silica aerogel is indeed generated inside the material in this embodiment.

[0028] Example 2 In step (1), the polymer is silicone rubber MVQ, the amount of PEO is 100 parts, PHMS is replaced with TEOS, and the rest of the process is the same as in Example 1. The heat resistance and insulation performance of the sample is... Figure 3 Presented in the middle.

[0029] Example 3 In step (1), the polymer is thermoplastic polyurethane (TPU), the molecular weight of PEO is 3000 g / mol, the amount is 80 parts, PHMS is replaced with MTMS (amount 90 parts), MTES is replaced with HMDS, and the rest are the same as the process flow in Example 1.

[0030] Example 4 In step (1), the polymer is polycarbonate (PC), the molecular weight of PEO is 4000 g / mol, the amount is 100 parts, MTES is replaced with HMDS, and the rest are the same as the process flow in Example 1.

[0031] Example 5 In step (1), the polymer is acrylonitrile-styrene-acrylate copolymer (ASA), the molecular weight of PEO is 3000 g / mol, the amount is 100 parts, MTES is replaced with MTMS, and the rest is the same as the process flow in Example 1.

[0032] Example 6 In step (1), the polymer is polyphenylene ether (PPO), the amount of PEO is 70 parts, the amount of PHMS is 70 parts, and the rest are the same as the process flow in Example 1.

[0033] Example 7 In step (1), the polymer is polymethyl methacrylate (PMMA), and PHMS is replaced with TMOS; the remaining operation steps are the same as the process flow in Example 1.

[0034] Example 8 In step (1), the polymer is polystyrene (PS), the molecular weight of PEO is 3000 g / mol and the amount is 100 parts, PHMS is replaced with TMOS (the amount is 90 parts), and MTES is replaced with MTMS; the remaining operation steps are the same as the process flow in Example 1.

[0035] Example 9 In step (1), the polymer is MVQ, the molecular weight of PEO is 4500 g / mol, PHMS is replaced with DMDMS, MTES is replaced with TMCS, and the rest are the same as the process flow in Example 1.

[0036] Example 10 In step (1), the polymer is TPU, the amount of PHMS is 90 parts, MTES is replaced with TMCS, and the rest are the same as the process flow in Example 1.

[0037] Comparative Example 1 This comparative example provides a method for preparing porous ABS foam material, as detailed below: (1) The raw material composition includes the following components by mass: 120 parts of polymer (ABS); (2) The operation steps are as follows: Add ABS to a mixer preheated to 160°C and melt and blend at 80 rpm for 2 hours; after the blending is completed, inject it into a 3 mm thick mold, and then place it in a hot press and hot press at 8 MPa pressure and 170°C temperature for 7 minutes to finally obtain polymer sheet. (2) The ABS sheet obtained above was placed in a preheated autoclave and sealed. The autoclave was first flushed three times with approximately 1 MPa of foaming gas to thoroughly remove air and moisture. Then, 18 MPa of CO2 was introduced into the autoclave, and the pressure was maintained for 4 hours in an oil bath at 150°C (the actual temperature inside the autoclave was 130°C). Next, the process of depressurizing to 9 MPa and then repressurizing to 18 MPa was repeated four times to ensure complete gas saturation. After a total of 9 hours of saturation treatment, the pressure was quickly released and the autoclave opened, finally yielding porous ABS foam material.

[0038] Comparative Example 2 This comparative example provides a method for preparing an ABS / silica aerogel composite foam material, specifically: (1) The raw materials include the following components in parts by mass: 120 parts of polymer (ABS), 50 parts of silicon source (PHMS), 1.5 parts of acidic catalyst (hydrochloric acid), 1.5 parts of alkaline neutralizer (ammonia), 360 parts of ethanol, 380 parts of deionized water, 180 parts of n-hexane, and 20 parts of hydrophobic modifier (MTES). (2) In a 1000 mL beaker, 50 parts of PHMS and 360 parts of ethanol were placed on a magnetic stirrer and stirred at 100 rpm until homogeneous. Then, deionized water and hydrochloric acid catalyst were added to the mixture in sequence, and the pH was adjusted to 2.0±0.2 with ammonia. Under constant temperature of 70℃, the mixture was stirred continuously at 150 rpm for 50 min until the solution was observed to become a completely transparent sol. (3) The sol was allowed to stand at 60°C for 45 hours to age, eventually forming a three-dimensional cross-linked silica wet gel network; (4) Immerse the silica wet gel in a mixture of hydrophobic modifier MTES and n-hexane, soak at room temperature for 5 hours, centrifuge and filter, and then age in the modifier solution for 20 hours to complete the hydrophobic modification through the substitution reaction of surface hydroxyl groups and hydrophobic methyl groups. (5) Place the prepared sample in a preheated autoclave and seal it. First, inject about 1 MPa of foaming gas to flush the autoclave three times to fully remove air and moisture. Then, fill the autoclave with 18 MPa of CO2 and maintain the pressure for 4 hours under an oil bath at 150°C (the actual temperature inside the autoclave is 130°C). Next, repeat the operation of depressurizing to 9 MPa and then repressurizing to 18 MPa four times to ensure that the gas is fully saturated. After a total of 9 hours of saturation treatment, quickly depressurize and open the autoclave to finally obtain dry silica aerogel powder material. (6) Add ABS and the dry silica aerogel powder obtained in step (5) into a mixer preheated to 160°C and melt-blend at 80 rpm for 2 hours. After the blending is completed, inject it into a 3 mm thick mold and then place it in a hot press. Press it for 7 minutes at 8 MPa pressure and 170°C to finally obtain ABS / silica aerogel sheet. (7) Place the ABS / silica aerogel sheet prepared in step (6) into a preheated autoclave and seal it. First, inject about 1 MPa of foaming gas to flush the autoclave three times to fully remove air and moisture. Then, fill the autoclave with 18 MPa of CO2 and maintain the pressure for 4 hours under an oil bath at 150°C (the actual temperature inside the autoclave is 130°C). Next, repeat the operation of depressurizing to 9 MPa and then repressurizing to 18 MPa four times to ensure that the gas is fully saturated. After a total of 9 hours of saturation treatment, quickly depressurize and open the autoclave to finally obtain the ABS / silica aerogel composite foam material.

[0039] Comparative Example 3 In step (1), the polymer is MVQ, PHMS is replaced with DMDMS, MTES is replaced with TMCS, and the rest are the same as the process flow in Comparative Example 2.

[0040] Comparative experiment: Four performance indicators were tested on Examples 1-10 and Comparative Examples 1-3: oxygen index (flame retardancy), thermal conductivity (insulation), pendulum rebound (resilience), and hardness (rigidity). The test data are shown in Table 1. Table 1. Comparison of performance indicators of each embodiment and comparative example.

[0041] Analysis of the data in Table 1 shows that: The oxygen indices of the various embodiments of the present invention range from 29% to 38%, with Examples 2 (36%) and 9 (38%) showing significantly higher oxygen indices than Comparative Examples 1 (16%), 2 (20%), and 3 (25%), demonstrating superior flame-retardant properties. This is due to the internal structure of the material and the synergistic effect between its components, which requires a higher oxygen concentration to sustain combustion. The relatively low oxygen indices of the comparative examples further demonstrate the advantages of the material of the present invention in terms of flame-retardant performance.

[0042] The thermal conductivity of Examples 1-10 is relatively low, ranging from 0.02 to 0.051 W / (m·K), lower than that of Comparative Example 1 (0.071 W / (m·K)), Comparative Example 2 (0.06 W / (m·K)), and Comparative Example 3 (0.059 W / (m·K)). In particular, the thermal conductivity of Example 9 is as low as 0.02 W / (m·K), indicating that the porous polymer / PEO silica aerogel composite foam material prepared by the method of this invention has excellent thermal insulation performance. This is due to the combined effects of in-situ generated silica aerogel and polymer foaming, as well as the optimization of the internal structure of the material, which significantly hinders heat transfer.

[0043] The pendulum rebound rates of Examples 1 (49%), 2 (80%), and 9 (78%) were significantly higher than those of Comparative Examples 1 (14%), 2 (20%), and 3 (39%). Meanwhile, Examples 7 (88°C) and 8 (90°C) exhibited excellent hardness, demonstrating the optimization of the material's mechanical properties. The mechanism lies in the combination of PEO and silica aerogel: PEO acts as a reinforcing agent, improving both the material's flexibility (pendulum rebound) and the brittleness and powder shedding issues of silica aerogel, while also strengthening the interfacial bonding with the polymer matrix, collectively enhancing mechanical strength. Furthermore, the comparison between the other examples and the comparative examples demonstrates the adjustability of mechanical properties, proving that performance can be controlled by optimizing the ratio of polymer matrix, PEO, and silica. This proves that the present invention can precisely control material properties through formulation adjustments to meet diverse application needs.

[0044] Furthermore, the one-step molding method of this invention exhibits significant advantages in both preparation efficiency and material properties. From the perspective of the preparation process, Comparative Examples 2 and 3 employ a step-by-step method of "first preparing aerogel powder, then blending it with the polymer," which is cumbersome. In contrast, the embodiments of this invention achieve in-situ integration of sol-gel, hydrophobic modification, and foaming in a one-step process, significantly improving preparation efficiency. Specifically, from a performance perspective: Comparing Example 1 (one-step method) with Comparative Example 2 (step-by-step method): In terms of flame retardancy, the oxygen index of Example 1 is 34%, which is higher than that of Comparative Example 2 (20%); in terms of thermal insulation, the thermal conductivity of Example 1 is 0.033 W / (m·K), which is better than that of Comparative Example 2 (0.06 W / (m·K); in terms of mechanical properties, the pendulum rebound of Example 1 is 49% and the hardness is 78C, both of which are higher than those of Comparative Example 2 (20% and 55C respectively). Comparing Example 9 (one-step method) with Comparative Example 3 (step-by-step method): In terms of flame retardancy, the oxygen index of Example 9 is 38%, which is higher than that of Comparative Example 3 (25%); in terms of thermal insulation, the thermal conductivity of Example 9 is 0.02 W / (m·K), which is better than that of Comparative Example 3 (0.059 W / (m·K); in terms of mechanical properties, the pendulum rebound of Example 9 is 78% and the hardness is 49C, both of which are higher than those of Comparative Example 3 (39% and 35C).

[0045] This demonstrates that the one-step method is superior in all aspects, including flame retardancy, heat insulation, resilience, and hardness. The reason lies in the fact that in the one-step method, silica aerogel grows in situ within the polymer / PEO porous system, resulting in a tighter bond with the matrix interface. This avoids the defects of physical mixing between aerogel powder and polymer in the stepwise method (e.g., ...). Figure 4 (As shown). This structure allows the mechanical strength (synergistic enhancement of hardness and resilience with polymer and PEO) and functional properties (uniform dispersion optimizes flame retardancy and thermal insulation) of the aerogel to be fully utilized. A comparison of Comparative Example 1 (pure ABS foam) and the composite system of the examples also demonstrates that the one-step method achieves a comprehensive performance leap through the synergy of "polymer / PEO / silica aerogel". The improvement in thermal insulation performance is particularly outstanding, with the insulation temperature increasing by 16.7℃ compared to single-component materials (e.g., ...). Figure 5 (As shown).

[0046] In summary, the one-step molding method not only simplifies the preparation process and improves efficiency, but also fully utilizes the mechanical strength (bonding with the polymer interface) and functional properties (flame retardancy and heat insulation) of silica aerogel through the structural advantage of "in-situ composite", ultimately obtaining a composite foam material with better performance.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a porous polymer / silica aerogel composite foam material, characterized in that, The preparation method includes the following steps: Step S1: 100-150 parts by weight of polymer and 40-100 parts by weight of PEO are blended in the molten state and then molded to obtain a PEO / polymer composite sheet. The polymer is one or more of the following: rubber, polycarbonate, acrylonitrile-styrene-acrylate copolymer, acrylonitrile-butadiene-styrene copolymer, polyphenylene ether, polystyrene, thermoplastic polyurethane, and polymethyl methacrylate; the rubber is one or more of the following: butadiene rubber, ethylene propylene rubber, silicone rubber, and fluororubber. The molecular weight of the PEO is 100-5000 g / mol; The polymer and the PEO are melt-blended in an internal mixer to obtain a homogeneous mixture. The speed of the internal mixer is 50-100 rpm, the temperature is 90-200℃, and the mixing time is 2-3 h. After melt blending, the uniform mixture is injected into a mold with a thickness of 1-10mm, and then placed in a hot press for hot pressing. The pressure of the hot press is 5-20MPa, the temperature is 100-250℃, and the time is 5-10min. Step S2: Mix silicon source and ethanol at a molar ratio of 1:3-9 and stir until homogeneous. Add deionized water and acidic catalyst in sequence, and adjust the pH to 2.0±0.2 using an alkaline neutralizing agent to obtain a sol system. Step S3: After completely immersing the PEO / polymer composite sheet in the sol system, place it in a constant temperature water bath and stir until a large number of pores appear on the surface and inside of the PEO / polymer composite sheet, and the sol system becomes completely transparent. The temperature of the constant temperature water bath is 40-80℃, the stirring speed is 100-500 rpm, and the time is 15-80 min; Step S4: Transfer to a sealed container and allow to stand for aging, so that the sol-gel reaction can be fully carried out in the pores of the PEO / polymer composite sheet to form a three-dimensional cross-linked PEO / silica wet gel network, thus obtaining the PEO / silica wet gel / polymer composite sheet. Step S5: Immerse the PEO / silica wet gel / polymer composite sheet in a mixture of n-hexane and hydrophobic modifier, soak at room temperature, centrifuge and filter, and then age it in the hydrophobic modifier to obtain the hydrophobic composite sheet. Step S6: Place the hydrophobic composite sheet in a high-pressure foaming kettle and seal it. Inject CO2, rinse and remove air and moisture, then fill with CO2 to 15-20 MPa. Maintain the temperature and pressure until the CO2 reaches equilibrium in the hydrophobic composite sheet. Then depressurize to 7.5-10 MPa, fill with CO2 again to increase the pressure to 15-20 MPa, and maintain the temperature and pressure until equilibrium is reached. Repeat this cycle of increasing pressure, depressurizing, maintaining temperature and pressure until equilibrium is reached 4-5 times until saturation is reached. Then depressurize, open the high-pressure foaming kettle and quickly remove the foam to obtain porous PEO / silica aerogel / polymer composite foam. The heat preservation and pressure holding are carried out under oil bath temperature of 60-160℃, the pressure holding time is 3-4 hours, and the final saturation time is 8-10 hours.

2. The preparation method according to claim 1, characterized in that, In step S2 The silicon source is one or more of the following: tetraethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, methyl orthosilicate, polyhydromethylsiloxane, sodium silicate, and silicon-containing biomass. The acidic catalyst is hydrochloric acid; the alkaline neutralizing agent is ammonia. The silicon source and ethanol are stirred to homogeneity using a magnetic stirrer at a speed of 100-500 rpm.

3. The preparation method according to claim 1, characterized in that, In step S4 The aging temperature is 50-70℃, and the aging time is 24-60h.

4. The preparation method according to claim 1, characterized in that, In step S5 The hydrophobic modifier is one or a combination of two or more of trimethylchlorosilane, hexamethyldisilazane, methyltrimethoxysilane, and methyltriethoxysilane. The volume ratio of n-hexane to the hydrophobic modifier is 6-12:1; The soaking time at room temperature is 3-6 hours; the aging time in the hydrophobic modified solution is 15-30 hours.

5. The preparation method according to claim 1, characterized in that, The weight proportions of each component in the preparation method are as follows: 100-150 parts of polymer, 40-100 parts of PEO, 50-90 parts of silicon source, 0.5-5 parts of acidic catalyst, 0.5-5 parts of alkaline neutralizer, 300-420 parts of ethanol, 200-400 parts of deionized water, 150-200 parts of n-hexane, and 19-25 parts of hydrophobic modifier.

6. The composite foam material prepared by any one of claims 1-5.

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