Hierarchical-pore flexible aerogel thermal insulation coating capable of long-term service in 1100 °c environment

Abstract

The application discloses a kind of hierarchical pore flexible aerogel heat insulation coating capable of long-term service in 1100 ℃ environment, belongs to heat insulation coating technical field, each component in aerogel coating is by aluminum dihydrogen phosphate 10-30 parts, water 10-35 parts, gamma-glycidyl ether oxypropyltrimethoxysilane 10-30 parts, alpha-aluminum oxide 5-17 parts, emulsifier 1-3 parts, defoaming agent 1-3 parts, aerogel nanofiber 1-6 parts, aerogel powder 3-5 parts by mass fraction.The 2-3mm thick aerogel coating prepared in the application can control the back temperature below 300 ℃ under the condition of heating the front side to 1050-1100 ℃, meets the heat insulation requirement of steel structure and other metals, and has excellent fireproof performance.The coating preparation process is simple, the production cost is low, the heat insulation and fireproof performance is excellent, and has wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation coating technology, specifically relating to a graded pore size flexible aerogel thermal insulation coating that can serve for a long time at 1100℃. Background Technology

[0002] Traditional thermal insulation and fireproofing materials use organic resins as binders, which greatly limits their upper service temperature range. They also suffer from drawbacks such as containing volatile organic compounds and being prone to aging and failure. Aerogel, as a super-insulating material, is often limited to specific engineering environments due to its high cost. With continuous technological advancements, silica aerogel has now achieved industrial-scale mass production, offering low cost and quality that fully meets the needs of building engineering. However, aerogel felts and aerogel composite felts are more commonly used in current engineering projects, but they suffer from high brittleness and poor mechanical properties. Summary of the Invention

[0003] Based on the shortcomings of the aforementioned background technology, the purpose of this invention is to provide a graded pore size flexible aerogel thermal insulation coating that can be used for a long time in an environment of 1100℃. This solves the problems of stable preservation of aerogel molecules in the coating and the inability of inorganic coatings to achieve complete deformation due to their brittleness. It retains the porous thermal insulation properties of aerogel while improving the workability and flexibility of aerogel powder, thereby enabling long-term service in high-temperature environments.

[0004] The technical solution adopted in this invention is as follows: A graded pore size flexible aerogel thermal insulation coating that can be used for a long time in an environment of 1100℃, wherein the components are formulated in the following proportions by mass: 10-30 parts aluminum dihydrogen phosphate, 10-35 parts water, 10-30 parts γ-glycidyl etheroxypropyltrimethoxysilane, 5-17 parts α-alumina, 1-3 parts emulsifier, 1-3 parts defoamer, 1-6 parts aerogel nanofibers, and 3-5 parts aerogel powder.

[0005] Furthermore, the optimized proportions of each component by mass are as follows: 30 parts aluminum dihydrogen phosphate, 33 parts water, 30 parts γ-glycidyl etheroxypropyltrimethoxysilane, 8 parts α-alumina, 1 part emulsifier, 1 part defoamer, 1-3 parts aerogel nanofibers, and 5 parts aerogel powder.

[0006] Furthermore, in the aerogel thermal insulation coating described above, the α-alumina has a particle size of 0.5 micrometers to 20 micrometers, the defoamer is a tripolyphosphate or an organosilicon defoamer, the emulsifier is hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide or benzalkonium chloride, the aerogel nanofibers are mullite fibers or zirconium silicate fibers with a diameter of 500 nanometers to 1.5 micrometers and a length distribution of 40 micrometers to 200 micrometers, and the aerogel powder is hydrophobic silica aerogel or hydrophobic silica-alumina aerogel with a particle size of 1 micrometer to 20 micrometers.

[0007] Furthermore, as described above, the aerogel thermal insulation coating has micron-sized pores on its surface after curing. Its internal structure is composed of an interpenetrating PO-Si-Al mesh skeleton and a nanofiber skeleton. The tough phase (transformed from a dispersed phase to a continuous phase) and the brittle phase (transformed from a continuous phase to a dispersed phase) undergo an inversion, thereby improving the mechanical properties of the coating.

[0008] Another object of the present invention is to provide a method for preparing a graded pore size flexible aerogel thermal insulation coating capable of long-term service at 1100°C, as described above, comprising the following steps:

[0009] Step 1: Mix aluminum dihydrogen phosphate powder with water according to the formula ratio until completely dissolved, add γ-glycidyl etheroxypropyltrimethoxysilane and emulsifier, shake, and let stand until the bubbles completely disappear to obtain a preliminary coating solution;

[0010] Step 2: Add the aerogel powder to the preliminary coating solution described in Step 1 in three portions according to the weight ratio. After each addition of aerogel powder, shake to ensure that it is fully and evenly dispersed to obtain a coating emulsion. The volume of the added aerogel powder is 1 to 4 times the volume of the preliminary coating solution.

[0011] Step 3: Place the aerogel nanofibers in water, fully shear and disperse them, centrifuge the dispersed nanofibers and pour off the excess water, dry them, and add them to the coating emulsion described in Step 2 according to the weight proportions. Then add α-alumina powder and shake to obtain a paste-like aerogel coating.

[0012] Step 4: Add the defoamer to the paste-like aerogel coating described in Step 3 according to the weight ratio, stir, and let stand for 24 hours to obtain the heat-insulating and fire-retardant aerogel coating.

[0013] Furthermore, in step 1 of the method described above, the oscillation frequency is 100-300 rpm, the amplitude is 4 mm or 8 mm, and the oscillation time is 6-12 hours.

[0014] Furthermore, in step 2 of the method described above, the oscillation frequency is 300-400 rpm, the amplitude is 20 mm, and the oscillation time is 2 hours.

[0015] Furthermore, in step 3 of the method described above, the shearing speed is 3000-8000 r / min, the shearing time is 1-5 min, the centrifugation speed is 12000 r / min, the centrifugation time is 20 min, the drying temperature is 105℃, the drying time is 1 hour, the oscillation frequency is 400 rpm, the amplitude is 20 mm, and the oscillation time is 3 hours.

[0016] Furthermore, the method described above is characterized in that the stirring rate in step 4 is 300-500 r / min, and the stirring time is 30-60 min.

[0017] The principle of this invention: This invention uses an emulsifier to form emulsion molecules from aerogel powder, thereby preserving the pore size of the aerogel during the preparation process. Simultaneously, an antifoaming agent that slowly interacts with the emulsifier molecules causes the emulsion molecules to slowly break down during coating and curing, ensuring the complete preservation and effective performance of the aerogel's thermal insulation properties. The emulsion's slow-release effect allows for the retention of more micron-sized pores during the coating's curing process, achieving the design and realization of graded pore sizes in the coating. Furthermore, addressing the issue of high brittleness in aluminum dihydrogen phosphate coatings, this invention proposes using a silane coupling agent as a modifier to pre-crosslink the aluminum dihydrogen phosphate solution. Under the action of the curing agent α-alumina, the PO-Al, Si-O-Al, and PO-Si-Al network structures continuously intertwine, enabling the coating to cure at room temperature. Simultaneously, the originally brittle bulk phase transforms into a dispersed phase, utilizing the principle of brittle-ductile phase reversal to achieve high bending deformation capability in the brittle coating.

[0018] Advantages and benefits of the present invention:

[0019] 1. The raw materials of this invention are inexpensive, the production process is simple, the production energy consumption is low, and large-scale mass production can be easily achieved. It can be widely used in steel structure protection for bridges, airports, stations and other places, and has broad market prospects.

[0020] 2. The heat-insulating coating of this invention can cure at room temperature, and the cured product mainly exists in an amorphous form. Simultaneously, flexible ceramic nanofibers form an interpenetrating network structure, transforming the brittle phase from a continuous phase to a dispersed phase and the tough phase from a dispersed phase to a bulk phase. This significantly improves the coating's flexibility, giving it excellent deformation capabilities. It can be bent, twisted, and withstand more complex loads. Compared to other inorganic coatings, it not only significantly improves deformation capabilities but also substantially enhances bonding strength, exhibiting superior mechanical properties.

[0021] 3. The heat insulation coating of the present invention has excellent self-leveling properties, fast surface drying speed, and convenient construction, which greatly shortens the coating construction process. At the same time, the coating thickness can be flexibly controlled to meet the needs of different engineering environments, which greatly improves production efficiency.

[0022] 4. The heat insulation coating of the present invention, when sprayed into a 3mm thick heat insulation coating, can maintain the back temperature at around 220℃ within 30 minutes when the front heating temperature is 1100℃ and the back temperature is continuously heated, thus achieving heat insulation and fire prevention. This meets the engineering requirement that the steel structure should be kept below 300℃ for a long time when exposed to fire. This performance is significantly better than other heat insulation materials such as aerogel felt.

[0023] 5. Compared with existing aerogel thermal insulation coatings, the service temperature of the aerogel coating of the present invention can be increased to 1000-1300℃, and it has excellent low-temperature crack resistance, which can adapt to more complex engineering environments. Attached Figure Description

[0024] Figure 1 The preparation process described in this invention;

[0025] Figure 2 This is a sample image after the paint has been applied.

[0026] Figure 3 The back temperature curve results are for a 3mm thick coating.

[0027] Figure 4 The bending morphology of a 2mm thick coating;

[0028] Figure 5 This is a diagram showing the hierarchical pore size microstructure of the coating.

[0029] Figure 6 The image shows the microstructure of the coating during the complete cycle test and the test area.

[0030] Figure 7 The back temperature curve results are for a sample subjected to 10,000 bending cycles. Detailed Implementation

[0031] The technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on this invention are within the scope of protection of this invention. Unless otherwise specified in the specific circumstances, the numerical ranges listed herein include upper and lower limits, as well as all integers and fractions within that range, but are not limited to the specific values ​​listed when the range is defined.

[0032] Example 1: This example provides a graded pore size flexible aerogel thermal insulation coating that can be used for a long time at 1100℃. The formulation consists of 150g aluminum dihydrogen phosphate, 300g water, 100g γ-glycidyl etheroxypropyltrimethoxysilane, 80g α-alumina, 10g benzalkonium chloride, 10g tripolyphosphate, 10g mullite aerogel nanofibers, and 51g silica aerogel powder, with a solution volume fraction of 200%.

[0033] Example 1 of the present invention describes a method for preparing an aerogel coating, which includes the following steps:

[0034] 1) Mix aluminum dihydrogen phosphate powder with water according to the stated weight proportions until completely dissolved, add γ-glycidyl etheroxypropyltrimethoxysilane and emulsifier, and shake at a shaking frequency of 200 rpm and an amplitude of 4 mm for 6 hours. Let stand until the bubbles completely disappear to obtain a preliminary coating solution.

[0035] 2) Add the aerogel powder to the preliminary coating solution described in step 1 in three parts by weight. After each addition of aerogel powder, shake at a frequency of 400 rpm and an amplitude of 20 mm for 2 hours to ensure that the aerogel powder is fully and evenly dispersed, thereby obtaining the coating emulsion.

[0036] 3) Place the aerogel fibers in water and shear them at 5000 r / min for 3 min using a high-speed shearing machine. The diameter of the dispersed fibers is 500 nm to 1.5 μm and the length distribution is 40 μm to 200 μm. Centrifuge the dispersed nanofibers at 12000 r / min for 20 min, drain off the excess water, and dry them at 105 °C for 1 hour. Add them to the coating emulsion described in step 2 according to the weight ratio, and then add α-alumina powder. Vibrate at a frequency of 400 rpm and an amplitude of 20 mm for 3 hours to obtain a paste-like aerogel coating.

[0037] 4) Add the defoamer to the coating emulsion described in step 3 according to the weight ratio, stir at 400 r / min for 30 min, and let stand for 24 hours to obtain the heat-insulating and fire-retardant aerogel coating.

[0038] Example 2: The only difference between Example 2 and Example 1 is the composition of the raw materials and proportions of the aerogel as follows: each component is composed of 200g aluminum dihydrogen phosphate, 200g water, 200g γ-glycidyl etheroxypropyltrimethoxysilane, 130g α-alumina, 10g benzalkonium chloride, 10g organosilicon defoamer, 2g zirconium silicate aerogel nanofibers, and 60g silica aerogel powder, with a solution volume fraction of 300%.

[0039] Example 3: The only difference between Example 3 and Example 1 is the raw materials and composition of the aerogel as follows: each component is composed of 300g aluminum dihydrogen phosphate, 300g water, 250g γ-glycidyl etheroxypropyltrimethoxysilane, 170g α-alumina, 10g octadecyltrimethylammonium bromide, 10g tripolyphosphate, 30g mullite aerogel nanofibers, and 81g silica-alumina aerogel powder, with a solution volume fraction of 400%.

[0040] Example 4: The only difference between Example 4 and Example 1 is the raw materials and composition of the aerogel as follows: each component is composed of 300g aluminum dihydrogen phosphate, 330g water, 300g γ-glycidyl etheroxypropyltrimethoxysilane, 80g α-alumina, 10g hexadecyltrimethylammonium bromide, 10g tripolyphosphate, 30g mullite aerogel nanofibers, and 90g silica-alumina aerogel powder, with a solution volume fraction of 300%.

[0041] Comparative Example 1: Based on Example 1, but with adjustments, except that no emulsifier was added, and the aerogel emulsified itself to form a Pickering emulsion. The amounts of other raw materials and the preparation method were the same as in Example 1.

[0042] Comparative Example 2: The only difference between Comparative Example 2 and Example 1 is that the raw materials and proportions of the aerogel are as follows: 300g aluminum dihydrogen phosphate, 300g water, 100g γ-glycidyl etheroxypropyltrimethoxysilane, 80g α-alumina, 10g benzalkonium chloride, 10g tripolyphosphate, and 60g silica aerogel powder, which is 200% by volume.

[0043] Comparative Example 3: The only difference between Comparative Example 3 and Example 1 is that the raw materials and composition of the aerogel are as follows: 300g aluminum dihydrogen phosphate, 300g water, 80g α-alumina, 10g benzalkonium chloride, 10g tripolyphosphate, 30g zirconium silicate aerogel nanofibers, and 45g silica aerogel powder, which is 200% by volume fraction.

[0044] Testing and Experiment

[0045] Experiment 1: Examples 1-4 and Comparative Examples 1-3 were coated with a thickness of 2-3 mm and cured at room temperature for 7 days. The application performance, surface morphology after drying and curing, and cracking were tested. The test results are shown in Table 1.

[0046] Table 1 Curing and Cracking of the Coating

[0047] Example 1 Excellent liquidity No cracks Example 2 Good liquidity No cracks Example 3 Poor fluidity, viscous No cracks Example 4 Good liquidity No cracks Comparative Example 1 Construction is not possible No cracks Comparative Example 2 Excellent liquidity cracking Comparative Example 3 Good liquidity cracking

[0048] The results showed that no cracks appeared on the surface of Examples 1-4 after drying and curing. On the one hand, the flexible nanofibers, aluminum phosphate coating skeleton and aerogel powder formed a stable three-dimensional interpenetrating network structure, which played a good skeletal support role for the coating and endowed the coating with greater deformation ability. On the other hand, γ-glycidyl etheroxypropyltrimethoxysilane hydrolyzed and reacted in acidic aluminum dihydrogen phosphate solution to form a more complex network structure of -Al-O-Si- and -Al-(O)P(O)-Si-, the inorganic polymer chains were further extended, the tough phase changed from the dispersed phase to the continuous phase, and the brittle phase changed from the continuous phase to the dispersed phase, which improved the overall flexibility and crosslinking degree of the coating and effectively solved the cracking problem of aerogel coating. The workability test results of Examples 1-3 and Comparative Examples 1 and 2 show that the fluidity of the coating is directly related to the amount of aerogel powder. When the aerogel powder content is 400%, the coating cannot self-level after application, making construction difficult. The coating sample without emulsifier, which allows the aerogel powder to self-emulsify to form a Pickering emulsion, exhibits a non-Newtonian fluid state and cannot be applied.

[0049] Experiment 2: The adhesion and thermal insulation properties of the coating were tested by brushing the coating sample from Example 4. The direct shear viscosity of the coating was tested on different substrates, including stainless steel plate, calcium silicate board, PP board, wood board, glass board, and cardboard. The test results are shown in Table 2. The back surface temperature of the coating sample from Example 4 at different thicknesses was tested during continuous heating for 30 minutes. The test results are shown in Table 3.

[0050] Table 2. Adhesion strength and failure of coatings

[0051] Stainless steel sheet 13.6 Paint cracking Calcium silicate board 3.7 Substrate fracture PP board 0.12 Coating Desorption board 10.8 Substrate interface fracture glass plate 3.9 Substrate fracture cardboard 0.27 Substrate interface fracture

[0052] The results show that the bonding strength of the coating samples in Example 4 is related to the type of substrate. For wettable or penetrable samples, the bonding effect is better, and the bonding strength can reach over 10 MPa. For example, the bonding strength of wood board reaches 10.8 MPa, and the failure mode is the fracture of the bonded interface. This indicates that the coating has high adhesive strength, but the interface is relatively weak, thus failing under load. For stainless steel plates, the coating can penetrate into the steel matrix to a certain depth, strengthening the interface and achieving a bonding strength as high as 13.6 MPa. Upon failure, the coating itself fractures. However, for non-wettable substrates, especially hydrophobic PP boards, the bonding relies only on weak intermolecular forces and hydrogen bonds, thus exhibiting lower bonding strength. Substrates such as calcium silicate boards and glass boards have low tensile strength and fracture under load, while the coating does not show significant changes. Cardboard is composed of multiple layers of mixed cellulose, resulting in low local tensile strength. Therefore, under load, failure also occurs at the interface between the substrate and the coating. The coating in Example 4 demonstrates unique advantages in the bonding protection of steel structures.

[0053] Table 3 Thermal insulation test results of coatings

[0054]

[0055] The results show that, for the coating sample in Example 4, when the front temperature was 1100±20℃, the back temperature decreased continuously with increasing thickness, reaching only 210±3℃ when the thickness was 3mm. This is because the emulsion slow-release effect and the aerogel nanopores together constructed a hierarchical pore structure for the coating, resulting in a porous structure ranging from micrometers to nanometers, which gives the coating excellent thermal insulation performance. This fully meets the requirement that the back temperature of steel structures remain below 300℃ during long-term heating.

[0056] Experiment 3: The long-term service performance of the coating was simulated by brushing the coating sample from Example 4. A 2.5mm thick layer of the coating was subjected to a 90° bending cycle test, with 1000, 5000, and 10000 cycles respectively. The presence of cracks was observed. The test results are shown in the appendix. Figure 6 The samples after 10,000 cycles were then subjected to thermal insulation performance testing. The testing method involved monitoring the back temperature curve of the coating, and the testing time was 3600 seconds. The test results are attached. Figure 7 .

[0057] The results showed that no visible cracks appeared in the coating after multiple bending cycles. Scanning electron microscopy (SEM) of the test area also revealed no obvious cracks, indicating good complete fatigue performance. The mechanical properties did not degrade during simulated long-term service. Long-term butane torch ablation tests were conducted on the cycled samples, and the back temperature curves were found to be similar to those in Experiment 2. During the test, the back temperature of the 2.5 mm thick coating remained at approximately 250℃, and the thermal insulation performance did not degrade. Overall, the coating is considered to have good long-term service performance.

[0058] As can be seen from the above examples and comparative examples, the present invention provides a graded pore size flexible aerogel thermal insulation coating that can be used for extended periods at 1100℃. The entire preparation process is simple in terms of equipment, low in raw material costs, high in production efficiency, and has good thermal insulation performance, making it suitable for large-scale production and widespread application.

[0059] The above description is only a partial embodiment of the present invention and is not intended to limit the present invention. Any equivalent changes and modifications made based on the content of this invention are within the protection scope of this invention.

Claims

1. A graded pore size flexible aerogel thermal insulation coating capable of long-term service at 1100℃, characterized in that, The components, by mass parts, are formulated as follows: 10-30 parts aluminum dihydrogen phosphate, 10-35 parts water, 10-30 parts γ-glycidyl etheroxypropyltrimethoxysilane, 5-17 parts α-alumina, 1-3 parts emulsifier, 1-3 parts defoamer, 1-6 parts aerogel nanofibers, and 3-5 parts aerogel powder; the α-alumina has a particle size of 0.5 micrometers to 20 micrometers; the defoamer is tripolyphosphate or an organosilicon defoamer; the emulsifier is hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, or benzalkonium chloride; and the aerogel nanofibers are mullite fibers or zirconium silicate fibers, with the fiber straightness... The aerogel powder has a diameter of 500 nanometers to 1.5 micrometers and a length distribution of 40 micrometers to 200 micrometers. It is a hydrophobic silica aerogel or a hydrophobic silica-alumina aerogel, with a particle size of 1 micrometer to 20 micrometers. The γ-glycidyl etheroxypropyltrimethoxysilane is used as a modifier to pre-crosslink the aluminum dihydrogen phosphate solution. Under the action of α-alumina, a PO-Al, Si-O-Al, and PO-Si-Al network structure is formed and continuously interwoven. After curing, the surface of the heat-insulating coating has micron-sized pores, and its internal structure is formed by the interpenetration and overlap of the PO-Si-Al network skeleton and the nanofiber skeleton.

2. The graded pore size flexible aerogel thermal insulation coating capable of long-term service at 1100℃ according to claim 1, characterized in that, The components are formulated as follows by mass: 30 parts aluminum dihydrogen phosphate, 33 parts water, 30 parts γ-glycidyl etheroxypropyltrimethoxysilane, 8 parts α-alumina, 1 part emulsifier, 1 part defoamer, 1-3 parts aerogel nanofibers, and 5 parts aerogel powder.

3. A method for preparing a graded pore size flexible aerogel thermal insulation coating capable of long-term service at 1100℃ according to claim 1 or 2, characterized in that, The steps are as follows: Step 1: Mix aluminum dihydrogen phosphate powder with water according to the formula ratio until completely dissolved, add γ-glycidyl etheroxypropyltrimethoxysilane and emulsifier, shake, and let stand until the bubbles completely disappear to obtain a preliminary coating solution; Step 2: Add the aerogel powder to the preliminary coating solution described in Step 1 in three portions according to the weight ratio. After each addition of aerogel powder, shake to ensure that it is fully and evenly dispersed to obtain a coating emulsion. The volume of the added aerogel powder is 1 to 4 times the volume of the preliminary coating solution. Step 3: Place the aerogel nanofibers in water, fully shear and disperse them, centrifuge the dispersed nanofibers and pour off the excess water, dry them, and add them to the coating emulsion described in Step 2 according to the weight proportions. Then add α-alumina powder and shake to obtain a paste-like aerogel coating. Step 4: Add the defoamer to the paste-like aerogel coating described in Step 3 according to the weight ratio, stir, and let stand for 24 hours to obtain the heat-insulating and fire-retardant aerogel coating.

4. The method for preparing a graded pore size flexible aerogel thermal insulation coating capable of long-term service at 1100℃ according to claim 3, characterized in that: The oscillation frequency in step 1 is 100~300rpm, the amplitude is 4mm or 8mm, and the oscillation time is 6~12 hours.

5. The method for preparing a graded pore size flexible aerogel thermal insulation coating capable of long-term service at 1100℃ according to claim 3, characterized in that: The oscillation frequency in step 2 is 300~400rpm, the amplitude is 20mm, and the oscillation time is 2 hours.

6. The method for preparing a graded pore size flexible aerogel thermal insulation coating capable of long-term service at 1100℃ according to claim 3, characterized in that: In step 3, the shearing speed is 3000-8000 r / min, the shearing time is 1-5 min, the centrifugation speed is 12000 r / min, the centrifugation time is 20 min, the drying temperature is 105℃, the drying time is 1 hour, the oscillation frequency is 400 rpm, the amplitude is 20 mm, and the oscillation time is 3 hours.

7. The method for preparing a graded pore size flexible aerogel thermal insulation coating capable of long-term service at 1100℃ according to claim 3, characterized in that: In step 4, the stirring rate is 300~500 r / min, and the time is 30min~60min.

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