Preparation method of compressed aerogel heat insulation core material

Abstract

The invention discloses a preparation method of a compressed aerogel heat insulation core material. Relates to the technical field of aerogel heat insulation core materials, a basic framework is provided for the material through double-network construction, mechanical properties are improved through fiber reinforcement, structural integrity is guaranteed through graded replacement and safe drying, and performance optimization is achieved through compression activation. The prepared aerogel heat insulation core material is remarkably improved in the aspects of heat insulation performance, mechanical strength, durability and the like, and can be widely applied to the field of new energy automobiles, building external wall heat insulation materials, industrial pipeline and equipment heat insulation and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aerogel thermal insulation core material, and particularly relates to a preparation method of compressed aerogel thermal insulation core material. BACKGROUND

[0002] Aerogel material is known as "the lightest solid in the world" due to its nano-porous structure, extremely low thermal conductivity and light weight characteristics, and has shown broad application prospects in building energy saving, industrial insulation, new energy vehicles and other fields. In particular, silica aerogel has become a representative of the new generation of high-performance thermal insulation materials due to its excellent thermal stability, low density and excellent thermal insulation performance, and has attracted widespread attention under the background of increasingly stringent energy saving and emission reduction requirements.

[0003] However, the traditional aerogel material still faces many technical bottlenecks in the process of actual popularization and application: first, its inherent brittleness and poor mechanical properties limit its application in load-bearing structures and vibration environments. Conventional aerogels are prone to fracture at a strain of 0.5% to 1.0%, which is difficult to meet the requirements of mechanical strength in engineering applications. Second, the aerogels prepared by traditional normal pressure drying process have problems such as uneven pore size distribution and serious structure shrinkage, which leads to unstable thermal insulation performance. Although the supercritical drying process can improve the structural integrity, it requires large equipment investment and high energy consumption, and the rapid pressure reduction in the drying process is easy to cause micro-cracks, affecting the product qualification rate. In addition, the existing aerogel material is prone to structural aging and performance degradation during long-term use, especially in high temperature and high humidity environments, and the lack of durability restricts its service life.

[0004] In view of the above technical defects, a solution is proposed. SUMMARY

[0005] The purpose of the present application is to provide a basic framework for the material through the construction of a double network, to improve the mechanical properties through fiber reinforcement, to ensure the structural integrity through graded replacement and safe drying, and to optimize the performance through compression activation. The prepared aerogel thermal insulation core material is significantly improved in terms of thermal insulation performance, mechanical strength and durability.

[0006] In order to achieve the above purpose, the present application adopts the following technical scheme: A preparation method of compressed aerogel thermal insulation core material, comprising the following steps: Step S1, constructing a flexible polymer cross-linked network: adding polyvinyl alcohol powder into preheated deionized water, continuously stirring until completely dissolved to obtain a PVA aqueous solution, and cooling for standby use; Step S2, constructing a rigid SiO2 aerogel network: Anhydrous ethanol, deionized water and hydrochloric acid are mixed as solvents, and tetraethyl orthosilicate is slowly added dropwise under continuous stirring. The mixture is stirred in a constant temperature water bath to obtain a pre-hydrolyzed transparent silica sol. The PVA solution from S1 is mixed with the silica sol in a volume ratio and stirred. The mixture is then transferred to a sealed container, and the gel transformation is completed by gas-phase ammonia catalysis to obtain a double-network wet gel. Step S3, Preparation and pretreatment of ceramic fiber preform: Ceramic fiber cotton is pulped with deionized water to form a uniform slurry, which is then vacuum filtered and dehydrated to form a wet fiber felt. After drying, it is heat-treated at high temperature to obtain a pretreated ceramic fiber preform. Step S4, Vacuum Impregnation Composite and Network Reinforcement: The fiber preform is placed in a vacuum impregnation tank, and after the negative pressure is maintained, a double network wet gel is introduced. After the vacuum is released, impregnation continues. After impregnation, the composite is immersed in a crosslinking solution to carry out a crosslinking reaction. After rinsing, it is soaked in an aging solution to strengthen the SiO2 network. Step S5, Solvent replacement and atmospheric pressure drying: The water is replaced by soaking in organic solvent in sequence, and gradient temperature drying is performed to obtain the initial aerogel block; Step S6, Compression Activation and Shaping: The initial aerogel block is unidirectionally compressed to the set strain, and after holding the pressure, it is slowly depressurized and allowed to stand and solidify under standard conditions.

[0007] Furthermore, in step S1, the polyvinyl alcohol is PVA-1788, the amount is 4.5-6.0g, the amount of deionized water is 94.0-95.5g, the dissolution temperature is 92-98℃, and the stirring time is 110-130 minutes.

[0008] Furthermore, in step S2, the amount of tetraethyl orthosilicate used is 38-45 mL, the amount of ethanol used is 95-110 mL, the amount of deionized water used is 18-25 mL, and the amount of hydrochloric acid used is 4-6 mL of 0.1 M hydrochloric acid.

[0009] Furthermore, in step S6, the compressive strain is 55%–60%, the compression rate is 1.0–1.2 mm / min, and the holding time is 30–35 seconds.

[0010] Furthermore, step S5 is replaced with solvent replacement and SCCO2 drying: the water is replaced sequentially with organic solvent in stages, and the gel is transferred to an SCCO2 drying kettle for supercritical CO2 drying. A five-stage intrinsically safe venting system is adopted, including a two-stage venting structure, a cyclone-coalescing gas-liquid separator, a platform-type multi-stage pressure reduction strategy, real-time acoustic emission monitoring, and SIL2-level safety interlock.

[0011] Furthermore, the two-stage venting structure includes a small-orifice throttle valve and a main safety valve connected in series. The orifice diameter of the small-orifice throttle valve is adjustable from 0.5 to 2 mm, and the main safety valve has a DN25 diameter.

[0012] Furthermore, the platform-based multi-stage pressure reduction strategy involves setting up seven pressure reduction platforms, each holding pressure for 15–30 minutes.

[0013] Furthermore, the real-time acoustic emission monitoring uses an AE sensor with a frequency range of 50-400kHz and a threshold set to >50dB.

[0014] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: This invention achieves a significant improvement in the overall performance of compressed aerogel insulation core materials through the organic combination of multiple processes. The various process steps cooperate and work synergistically to form a complete preparation technology system, the specific implementation methods and mechanisms of action of which are as follows: (1) The dual-network synergistic construction process adopts stepwise hydrolysis and gas-phase catalytic gel technology to realize the molecular-level composite of flexible polymer network and rigid inorganic network. The flexible network provides elasticity through the elastic deformation of long molecular chains, while the rigid network provides mechanical support through the three-dimensional skeleton structure. The two interpenetrate to form a dual continuous phase, which effectively prevents crack propagation and significantly improves the deformation recovery ability of the material.

[0015] (2) The fiber reinforcement and interface strengthening process combines vacuum impregnation with chemical crosslinking to establish a strong interfacial bond between the fiber and the matrix. The precisely controlled impregnation process ensures that the aerogel precursor fully penetrates into the gaps between the fiber network, and then covalent bonds are constructed at the interface through crosslinking agents to form a strong mechanical interlock and chemical bond, which significantly improves the compressive strength and structural stability of the material.

[0016] (3) The staged solvent replacement and supercritical drying process gradually reduces the surface tension of the solvent through a carefully designed solvent replacement sequence, effectively alleviating the damage of capillary stress to the nanoporous structure. Subsequently, a multi-stage pressure reduction platform is used to control the supercritical drying process to achieve gentle drying, fully preserve the three-dimensional nanoporous structure of the aerogel, and ensure that the material has excellent thermal insulation performance.

[0017] (4) Compression activation process: Through precise controlled directional compression, the aerogel skeleton is induced to undergo orderly rearrangement. The material is compressed at a specific strain rate to optimize the pore size distribution and pore orientation. While moderately increasing the material density, its mechanical properties are significantly enhanced, achieving the best balance between thermal insulation performance and mechanical strength.

[0018] (5) The supercritical drying safety system achieves precise control of the drying process through a multi-level protection mechanism. The coordinated control of small-aperture throttling and main safety valve, combined with efficient gas-liquid separation and real-time acoustic emission monitoring, effectively suppresses the generation of microcracks during the drying process, ensures the integrity of the product's microstructure and batch-to-batch stability, and significantly improves the product's durability.

[0019] By constructing a dual-network structure to provide the basic framework for the material, fiber reinforcement to enhance mechanical properties, graded replacement and safe drying to ensure structural integrity, and compression activation to optimize performance, the prepared aerogel insulation core material exhibits significantly improved thermal insulation performance, mechanical strength, and durability. It can be widely applied in new energy vehicles, building exterior wall insulation materials, and industrial pipeline and equipment insulation. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: This embodiment provides a method for preparing a compressible aerogel thermal insulation core material, including the following steps: Step S1, constructing a flexible polymer crosslinking network: Weigh 5.0g of polyvinyl alcohol (PVA-1788) powder and slowly add it to 95.0g of deionized water preheated to 95℃ under mechanical stirring. Continue stirring for 120 minutes until completely dissolved to obtain a 5wt% PVA aqueous solution. Cool the solution to 50℃ for later use.

[0022] Step S2, Construction of rigid SiO2 aerogel network and gel complex formation: Measure 100 mL of anhydrous ethanol, 20 mL of deionized water, and 5 mL of 0.1 M hydrochloric acid and mix them as a solvent. Slowly add 40 mL of tetraethyl orthosilicate (TEOS) dropwise while continuously stirring. Continue stirring in a 40 °C water bath for 60 minutes to obtain a pre-hydrolyzed transparent silica sol. Mix the PVA solution of S1 with the silica sol at a volume ratio of 1:1 and stir at 500 rpm for 30 minutes. Transfer the mixture to a 5 L sealed container. Place a small beaker containing 10 mL of concentrated ammonia solution 5 cm above the liquid surface, controlling the ammonia concentration in the gas phase to 200-300 ppm. Let it stand at room temperature for 120 minutes to complete the gel transition, obtaining a double-network wet gel.

[0023] Step S3, Preparation and pretreatment of ceramic fiber preform: 15.0g of ceramic fiber cotton with an average diameter of 5μm was weighed and mixed with 500mL of deionized water, and pulped at 2000rpm for 10 minutes to form a uniform slurry. The slurry was then dehydrated and shaped using a vacuum filtration device (-0.08MPa) to obtain a 10mm thick wet-process fiber felt. After drying at 105℃ for 120 minutes, the felt was transferred to a muffle furnace and heated to 600℃ at a rate of 3℃ / min, and held for 60 minutes to obtain a pretreated ceramic fiber preform.

[0024] Step S4, Vacuum impregnation lamination and network reinforcement: The fiber preform was placed in a vacuum impregnation tank and maintained at a negative pressure of 0.09 MPa for 15 minutes. Then, a double-network wet gel was introduced, and after releasing the vacuum, impregnation continued for 60 minutes. Following impregnation, the composite was immersed in a crosslinking solution (pH = 2.5-3.0) containing 1.0 wt% glutaraldehyde and 0.5 wt% hydrochloric acid, and crosslinked in a 50°C water bath for 90 minutes. FTIR analysis showed the characteristic peak of the aldehyde group (1720 cm⁻¹). -1 Conversion rate ≥85%. After rinsing three times with deionized water, it is immersed in a 1:1 volume ratio mixture of anhydrous ethanol and ammonia and aged at 40°C for 24 hours to strengthen the SiO2 network.

[0025] Step S5, solvent replacement and drying at atmospheric pressure: The water was replaced by immersion in anhydrous ethanol three times (each time ≥8 hours) to replace the water, and then replaced with tert-butanol three times in the same way. After replacement, a gradient temperature drying was performed: 35℃ / 6h → 60℃ / 6h → 85℃ / 12h, and the initial aerogel block was obtained by furnace cooling.

[0026] Step S6, Compression Activation and Shaping: The initial aerogel mass was placed in a universal testing machine and unidirectionally compressed to 40% of its original thickness (60% strain, pressure 1.2 MPa) at a speed of 1 mm / min. After holding the pressure for 30 seconds, the pressure was slowly released, and the material was allowed to stand under standard conditions (23℃, 50% RH) for 48 hours. The material stabilized at 50% ± 2% of its original thickness, and the density decreased from 0.18 g / cm³. 3 Increased to 0.36 g / cm³ 3 .

[0027] Step S7, Performance Characterization and Finished Product Processing: The thermal conductivity at 25℃ was measured to be 0.028 W / (m·K) using a HotDisk thermal constant analyzer (ISO22007-2 standard). After 7 days of environmental treatment at 85% RH and 60℃, the thermal conductivity retention rate was >90%. The compressive strength at 50% compressive strain was 1.58 MPa, and the deformation recovery rate was >95%. BET data showed that the pore size was optimized from 15-35 nm to 8-25 nm after compression. After passing inspection, the product was cut into 500 mm × 500 mm specifications and vacuum-sealed to obtain the final product.

[0028] Example 2 The difference between this embodiment and Embodiment 1 lies in the following parameter optimizations: Step S1: Weigh 6.0g of PVA-1788 and add it to 94.0g of deionized water. Dissolve at 98℃ for 130 minutes to obtain a 6wt% PVA solution. Cool to 55℃ for later use.

[0029] Step S2: Silica sol was prepared by mixing 110 mL of ethanol, 25 mL of water, and 6 mL of 0.1 M hydrochloric acid, with 45 mL of LTEOS added dropwise. Hydrolysis was carried out at 45°C for 70 minutes. The volume ratio of PVA to silica sol was 1.2:1. The mixture was transferred to an 8 L sealed container, with an 8 cm gap between the ammonia solution and the gas phase ammonia concentration of 150-250 ppm. The mixture was allowed to stand for 130 minutes to complete gelation.

[0030] Step S4: The crosslinking solution pH is 2.8-3.2, and FTIR shows that the aldehyde conversion rate is ≥88%.

[0031] Step S6: After compression, the material is left to stand for 72 hours under standard conditions, stabilizing at 55% ± 2% of its original thickness, with the density decreasing from 0.20 g / cm³. 3 Increased to 0.40 g / cm 3 .

[0032] Step S7: Thermal conductivity 0.026 W / (m·K), compressive strength at 50% strain 1.75 MPa, recovery rate >96%. Scanning electron microscopy showed that the fiber-aerogel interface was tightly bonded without cracks.

[0033] Example 3 The difference between this embodiment and Embodiment 1 lies in the following parameter optimizations: Step S1: Weigh 4.5g of PVA-1788 and add it to 95.5g of deionized water. Dissolve at 92℃ for 110 minutes to obtain a 4.5wt% PVA solution. Cool to 48℃ for later use.

[0034] Step S2: Silica sol was prepared using 95 mL ethanol, 18 mL water, and 4 mL 0.1 M hydrochloric acid. 38 mL of LTEOS was added dropwise, and the mixture was hydrolyzed at 38°C for 55 minutes. The volume ratio of PVA to silica sol was 0.9:1. The mixture was transferred to a 3 L sealed container, with ammonia water spaced 3 cm apart. The ammonia concentration in the gas phase was 280-350 ppm. The mixture was allowed to stand for 110 minutes to complete gelation.

[0035] Step S4: The crosslinking solution pH is 2.3-2.8, and FTIR shows an aldehyde conversion rate of ≥82%. The aging conditions are adjusted to 38℃ for 22 hours.

[0036] Step S6: After compression, the material is left to stand under standard conditions for 36 hours, stabilizing at 48% ± 3% of its original thickness, with the density decreasing from 0.16 g / cm³. 3 Increased to 0.33 g / cm³ 3 .

[0037] Step S7: Thermal conductivity 0.030 W / (m·K), compressive strength at 50% strain 1.42 MPa, recovery rate >94%. BET data shows the most probable pore size decreased from 28 nm to 15 nm. The recovery rate remained at 90% after thermal shock testing (-20℃ to 60℃).

[0038] Example 4 This embodiment provides a method for preparing a fiber-reinforced dual-network structure compressible aerogel thermal insulation core material. The core of this method lies in achieving a synergistic improvement in the integrity of the aerogel microstructure and its thermal insulation performance through meticulous control of the entire process and an intrinsically safe SCCO2 drying system. The specific steps are as follows: Step S1, constructing a flexible polymer crosslinking network: Weigh 5.5g of polyvinyl alcohol (PVA-1788) powder and slowly add it to 94.5g of deionized water preheated to 96℃ under mechanical stirring. Stir continuously at 200rpm for 125 minutes with a frame-type stirrer until completely dissolved, obtaining a clear and transparent 5.5wt% PVA aqueous solution. Cool the solution to 52℃ for later use; its viscosity is 320±20mPa·s (Brookfield DV2T, 25℃).

[0039] Step S2, Construction of rigid SiO2 aerogel network and gel complex formation: Measure 105 mL of anhydrous ethanol, 22 mL of deionized water, and 5.5 mL of 0.1 M hydrochloric acid to prepare the solvent system. Add 42 mL of tetraethyl orthosilicate (TEOS) dropwise at a rate of 2 mL / min using a constant flow pump while continuously stirring. Continue stirring in a 42°C water bath for 65 minutes to obtain a pre-hydrolyzed transparent silica sol (pH=2.1). Mix the PVA solution of S1 with the silica sol at a volume ratio of 1.1:1 and stir at 600 rpm for 35 minutes using a high-speed disperser. Transfer the mixture to a 6 L sealed container. Place a small beaker containing 12 mL of concentrated ammonia (28 wt%) 6 cm above the liquid surface, controlling the ammonia concentration in the gas phase to 220-280 ppm. Allow the mixture to stand at room temperature for 125 minutes to complete the gel transition. The gelation time is preset to 105 ± 5 min, resulting in a double-network wet gel.

[0040] Step S3, Preparation and pretreatment of ceramic fiber preform: 16.0g of ceramic fiber cotton with an average diameter of 5μm and an aspect ratio >500 was weighed and mixed with 550mL of deionized water. The mixture was pulped at 2200rpm for 12 minutes using a pulper to form a homogeneous slurry. The slurry was then dehydrated and shaped using a vacuum filtration device (-0.08MPa) to obtain a 12mm thick wet-process fiber felt (28% solid content). After drying at 110℃ for 130 minutes, the felt was transferred to a muffle furnace and heated to 650℃ at a rate of 4℃ / min, holding for 70 minutes to obtain a pretreated ceramic fiber preform (92% porosity, average pore size 45μm).

[0041] Step S4, Vacuum impregnation lamination and network reinforcement: The fiber preform was placed in a vacuum impregnation tank and maintained at a negative pressure of 0.09 MPa for 18 minutes. Then, a double-network wet gel was introduced, and after releasing the vacuum, impregnation continued for 70 minutes (impregnation efficiency >95%). After impregnation, the composite was immersed in a crosslinking solution (pH = 2.6-2.9) containing 1.2 wt% glutaraldehyde and 0.6 wt% hydrochloric acid, and crosslinked in a water bath at 52℃ for 95 minutes. FTIR analysis showed the characteristic peak of the aldehyde group (1720 cm⁻¹). -1 Conversion rate ≥87%, COC characteristic peak (1110cm) -1 The strength increased by 35%. After rinsing three times with deionized water, it was soaked in a 1:1 volume ratio mixture of anhydrous ethanol and ammonia and aged at 42°C for 26 hours to strengthen the SiO2 network (linear shrinkage rate <3%).

[0042] Step S5, solvent replacement and SCCO2 drying: The gel was soaked three times in anhydrous ethanol to displace water, each time for at least 10 hours. Then, it was sequentially displaced twice each in isopropanol and n-hexane, each time for at least 8 hours, with strict control over the solvent surface tension as it gradually decreased from 72.8 mN / m (water) to 18.4 mN / m (n-hexane). After displacement, the gel was transferred to an SCCO2 drying autoclave and dried using supercritical CO2 at 35°C and 10 MPa, employing a five-stage intrinsically safe venting system. Two-stage relief structure: a small orifice throttle valve (orifice diameter adjustable from 0.5 to 2 mm) and a main safety valve (DN25) are connected in series to achieve both precise pressure control and emergency relief functions; Cyclone-coalescing gas-liquid separator: separation efficiency ≥98%, dry ice particle removal rate >95%; Platform-type multi-stage pressure reduction: Seven pressure reduction platforms are set according to 12→10→8→6→4→2→0.1MPa, and each platform holds pressure for 15 to 30 minutes; Real-time acoustic emission monitoring: AE sensor (frequency range 50-400kHz) monitors microcracks in real time, with a threshold set to >50dB; SIL2 level safety interlock: Automatically switches to safety mode when P>12.5MPa or AE surges.

[0043] After drying, an initial aerogel mass was obtained with an apparent density of 0.19 g / cm³. 3 No visible cracks were found.

[0044] Step S6, Compression Activation and Shaping: The initial aerogel mass was placed in a universal testing machine (Instron 5967) and unidirectionally compressed to 45% of its original thickness (55% strain, pressure 1.3 MPa) at a speed of 1.2 mm / min. After holding the pressure for 35 seconds, the pressure was slowly released at 0.5 mm / min. The material was then allowed to stand for 60 hours under standard conditions (23°C, 50% RH). The material stabilized at 52% ± 2% of its original thickness, and the density decreased from 0.19 g / cm³. 3 Increased to 0.38 g / cm³ 3 Volumetric rebound rate <5%.

[0045] Step S7, Performance Characterization and Finished Product Processing: The thermal conductivity at 25℃ was measured using a HotDisk thermal constant analyzer according to ISO 22007-2 standards: 0.027 W / (m·K), increasing to 0.035 W / (m·K) at 200℃. After 7 days of environmental treatment at 85% RH and 60℃, the thermal conductivity retention rate was >92%, and it remained at 88% after damp heat aging. The compressive strength at 50% compressive strain was 1.68 MPa, and the deformation recovery rate was >96% (after 100 cycles). BET data showed that the most probable pore size decreased from 18 nm to 9 nm after compression, with a pore volume of 0.85 cm³. 3 / g. Scanning electron microscopy showed that the fiber and aerogel interface were tightly bonded with no debonding. After undergoing thermal shock testing (-40℃ to 80℃, 50 cycles), the structure remained intact, with a thermal conductivity change of <3%. After passing the test, the fiber was cut into 500mm×500mm×10mm dimensions and vacuum-sealed to obtain the final product.

[0046] Examples 1-3 are under conventional drying conditions, while Example 4 is under special SCCO2 drying process and safety system conditions.

[0047] Comparative Example 1 The difference between this comparative example and Example 1 lies in step S1, which involves constructing a rigid SiO2 aerogel network: 100 mL of anhydrous ethanol, 20 mL of deionized water, and 5 mL of 0.1 M hydrochloric acid are mixed as a solvent. 40 mL of tetraethyl orthosilicate (TEOS) is slowly added dropwise under continuous stirring, and the mixture is stirred for 60 minutes in a 40°C water bath to obtain a pre-hydrolyzed transparent silica sol. The silica sol is transferred to a 5 L sealed container, and a small beaker containing 10 mL of concentrated ammonia is placed 5 cm above the liquid surface. The ammonia concentration in the gas phase is controlled at 200-300 ppm. The mixture is allowed to stand at room temperature for 120 minutes to complete the gel transformation, yielding a wet gel.

[0048] The other steps S2-S6 are the same as in Example 1.

[0049] Comparative Example 2 The difference between this comparative example and Example 1 is that in step S2, the mixture is directly poured into the mold for gelation. Steps S3-S6 are the same as in Example 1, except that the preparation process of the fiber preform is omitted.

[0050] Comparative Example 3 (conventional drying, no solvent displacement) The difference between this comparative example and Example 1 is that the solvent replacement step is omitted, and the product is directly dried at atmospheric pressure: Step S5, direct atmospheric pressure drying: Place the aged wet gel directly into the drying oven and perform gradient temperature drying: 35℃ / 6h→60℃ / 6h→85℃ / 12h.

[0051] The other steps are the same as in Example 1.

[0052] Comparative Example 4 The difference between this comparative example and Example 1 lies in step S6, which involves direct shaping: the initial aerogel block is left to stand for 48 hours under standard conditions (23°C, 50%RH). Steps S1-S5 are the same as in Example 1.

[0053] Comparative Example 5 The difference between this comparative example and Example 4 is that a safety relief system is not used during the SCCO2 drying process: Step S5, SCCO2 drying without a safety system: The gel is transferred to an SCCO2 drying vessel and dried under supercritical CO2 conditions at 35°C and 10MPa, using conventional linear pressure reduction (from 10MPa directly to 0.1MPa, taking 30 minutes).

[0054] Steps S1-S4 and S6-S7 are the same as in Example 4.

[0055] The detection method is as follows: GB / T 34336-2017 Nanoporous Aerogel Composite Thermal Insulation Products GB / T 32983-2025 Determination of compressive creep properties of thermal insulation products for building use According to the above standards, product quality testing and analysis (compression performance value, damp heat aging resistance value, and thermal stability value) were performed on Examples 1-4 and Comparative Examples 1-5. The specific details of the testing under normal temperature (22℃) and humidity (45%) are as follows (Table 1): Table 1 ; The specific details of the testing at 60℃ and 85% relative humidity are as follows (Table 2): ; As shown in the table above, the compressible aerogel insulation core material prepared in the embodiments of the present invention is significantly superior to the comparative example in terms of thermal conductivity, mechanical properties, and durability. Specifically: The thermal conductivity of the embodiments reached 0.026-0.030 W / (m·K), while the thermal conductivity of Comparative Example 1 was 0.038 W / (m·K), the thermal conductivity of Comparative Example 2 was 0.025 W / (m·K), the thermal conductivity of Comparative Example 3 was 0.045 W / (m·K), the thermal conductivity of Comparative Example 4 was 0.022 W / (m·K), and the thermal conductivity of Comparative Example 5 was 0.034 W / (m·K). The 50% compressive strain compressive strength of the example reached 1.42-1.75 MPa, while the compressive strength of Comparative Example 1 was 0.82 MPa, the compressive strength of Comparative Example 2 was 0.45 MPa, the compressive strength of Comparative Example 3 was 0.95 MPa, the compressive strength of Comparative Example 4 was 0.28 MPa, and the compressive strength of Comparative Example 5 was 1.25 MPa. The deformation recovery rate of the embodiments reached 94% to 96%, while the deformation recovery rate of Comparative Example 1 was 65%, the deformation recovery rate of Comparative Example 2 was 28%, the deformation recovery rate of Comparative Example 3 was 72%, the deformation recovery rate of Comparative Example 4 was 88%, and the deformation recovery rate of Comparative Example 5 was 82%. Regarding resistance to damp heat aging, the thermal conductivity retention rate of the examples reached 89% to 96%, while the retention rate of Comparative Example 1 was 75%, Comparative Example 2 was 82%, Comparative Example 3 was 65%, Comparative Example 4 was 85%, and Comparative Example 5 was 80%.

[0056] In summary, through a series of technological innovations, including constructing a dual-network structure, introducing fiber reinforcement, optimizing the solvent replacement process, employing compression activation, and using an SCCO2 safe drying system, this invention has successfully prepared a compressible aerogel insulation core material with excellent thermal insulation performance, good mechanical strength, and long-term durability. All performance indicators are significantly better than those of the comparative example, demonstrating the technological progress and practical value of this invention.

[0057] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for producing a compressed-state aerogel thermal insulation core material, characterized by, The method comprises the following steps: Step S1, constructing a flexible polymer crosslinked network: adding polyvinyl alcohol powder into preheated deionized water, continuously stirring until completely dissolved to obtain a PVA aqueous solution, and cooling for standby; Step S2, constructing a rigid SiO2 aerogel network: mixing anhydrous ethanol, deionized water and hydrochloric acid as a solvent, slowly adding tetraethyl orthosilicate under continuous stirring, continuously stirring in a constant temperature water bath to obtain a pre-hydrolysis transparent silica sol, mixing the PVA solution of S1 with the silica sol according to the volume ratio, stirring, transferring to a sealed container, and completing the gel transition by gas-phase ammonia catalysis to obtain a double-network wet gel; Step S3, preparation and pretreatment of ceramic fiber preform: beating ceramic fiber cotton and deionized water to form a uniform slurry, vacuum filtration dewatering to form a wet fiber mat, drying, and high-temperature heat treatment to obtain a pretreated ceramic fiber preform; Step S4, vacuum impregnation, compounding and network strengthening: placing the fiber preform in a vacuum impregnation tank, introducing the double-network wet gel after maintaining negative pressure, continuing to impregnate after releasing the vacuum, immersing the impregnated body in a crosslinking solution for crosslinking reaction, rinsing, and then soaking in an aging liquid to strengthen the SiO2 network; Step S5, solvent replacement and atmospheric drying: sequentially replacing moisture with organic solvents, and performing gradient temperature drying to obtain an initial aerogel block; Step S6, compression activation and shaping: unidirectionally compressing the initial aerogel block to a set strain, maintaining pressure, slowly releasing pressure, and standing still under standard conditions for shaping.

2. The method of claim 1, wherein the compressed aerogel insulation core material is prepared by the steps of: The polyvinyl alcohol in step S1 is PVA-1788, the amount is 4.5-6.0 g, the amount of deionized water is 94.0-95.5 g, the dissolution temperature is 92-98℃, and the stirring time is 110-130 minutes.

3. The method of claim 1, wherein the compressed aerogel insulation core material is prepared by the steps of: The amount of tetraethyl orthosilicate in step S2 is 38-45 mL, the amount of ethanol is 95-110 mL, the amount of deionized water is 18-25 mL, and the amount of 0.1M hydrochloric acid is 4-6 mL.

4. The method of claim 1, wherein the compressed aerogel insulation core material is prepared by the steps of: The compression strain in step S6 is 55%-60%, the compression speed is 1.0-1.2 mm / min, and the pressure maintaining time is 30-35 seconds.

5. The method of claim 1-4, wherein the compressed aerogel insulation core material is prepared by the steps of: Step S5 is replaced by solvent replacement and SCCO2 drying: sequentially replacing moisture with organic solvents, transferring the gel to a SCCO2 drying oven for supercritical CO2 drying, adopting a five-stage intrinsic safety relief system including two-stage relief structure, cyclone-coalescence gas-liquid separator, platform-type multi-stage pressure reduction strategy, acoustic emission real-time monitoring and SIL2-level safety interlocking.

6. The method of claim 5, wherein the compressed aerogel insulation core material is prepared by the steps of: The two-stage relief structure includes a small orifice throttle valve and a main safety valve in series, the orifice throttle valve has an adjustable aperture of 0.5-2 mm, and the main safety valve has a DN25 aperture.

7. The method of claim 6, wherein the compressed aerogel insulation core material is prepared by the steps of: The platform-type multi-stage pressure reduction strategy sets 7 pressure reduction platforms, each platform maintains pressure for 15-30 min.

8. The method of claim 7, wherein the compressed aerogel insulation core material is prepared by the steps of: The acoustic emission real-time monitoring adopts an AE sensor with a frequency range of 50-400 kHz and a threshold set to >50 dB.