A composite thermal barrier coating based on stable covalently cross-linked bonding phase induced by ethanol evaporation and a preparation method thereof

Abstract

This invention belongs to the field of thermal insulation materials technology and discloses a composite thermal insulation coating based on an ethanol evaporation-induced stable covalent crosslinked adhesive phase and its preparation method. The composite thermal insulation coating includes a crosslinked adhesive phase and hollow glass microspheres dispersed and fixed within the crosslinked adhesive phase. The crosslinked adhesive phase is obtained by ethanol evaporation-induced crosslinking of a reactive precursor formed by the reaction of thioctic acid and amino-functionalized polydimethylsiloxane. During the drying process of the precursor, ethanol evaporation gradually forms an adhesive network containing polydimethylsiloxane segments and a covalently crosslinked structure derived from thioctic acid. The preparation method includes reactive precursor preparation, slurry compounding, and drying and curing steps, requiring no additional crosslinking agent or high-temperature curing, and can complete crosslinking and film formation at room temperature or under moderate heating conditions. The thermal conductivity of the composite thermal insulation coating can be as low as 0.025–0.030 W / (m·K), and it possesses good adhesion, waterproof and moisture-proof properties, mechanical stability, and environmental durability.

Description

Technical Field

[0001] This invention belongs to the field of thermal insulation materials technology, specifically relating to a composite thermal insulation coating based on the formation of a stable covalent crosslinked adhesive phase induced by ethanol volatilization and its preparation method. Background Technology

[0002] Thermal insulation coatings, due to their convenient construction, wide range of applicable substrates, and ease of surface integration, have broad application prospects in fields such as building energy conservation, thermal protection of industrial equipment, thermal management of electronic devices, and thermal safety of new energy systems. Existing thermal insulation coatings typically achieve thermal barrier properties by combining a resin matrix with lightweight thermal insulation fillers, but there are still challenges in balancing curing processes, interface stability, and long-term service performance in these systems.

[0003] From the perspective of the preparation process, some existing systems rely on additional crosslinking agents, catalysts, or high-temperature curing conditions, resulting in a large number of components, relatively complex processes, and high energy consumption, which is not conducive to simple construction and large-scale application. For thermal insulation coatings, if the binder phase can be constructed under milder conditions and the dependence on external curing components is minimized, it will be more conducive to improving the feasibility of the process and its application value.

[0004] From a service performance perspective, existing thermal insulation coatings often struggle to simultaneously achieve thermal insulation performance, interfacial bonding stability, waterproofing and moisture resistance, and environmental durability during long-term use. Especially under conditions of humidity or mechanical friction, some systems are prone to interfacial instability, filler detachment, decreased structural integrity, or reduced thermal insulation effectiveness. This indicates that the performance of composite thermal insulation coatings depends not only on the thermal insulation capacity of the filler itself, but also closely on the crosslinking stability of the binder phase, the fixation effect of the filler in the matrix, and the interfacial bonding state.

[0005] Furthermore, the interfacial interaction between the filler and the binder phase has a significant impact on the structural stability and overall performance of the composite coating. Hollow glass microspheres are a type of lightweight, heat-insulating functional filler; however, if they are fixed in the binder phase solely through physical dispersion or weak interfacial interactions, problems such as filler detachment, interfacial instability, or attenuation of heat insulation performance can easily occur during humid conditions, friction, or long-term service. Therefore, it is necessary to develop a composite heat-insulating coating system that is easy to construct, requires no additional crosslinking agents or high-temperature curing, and can form a stable covalently crosslinked binder phase at room temperature or during moderate heating and drying, in order to achieve a synergistic improvement in heat insulation performance, adhesion performance, waterproof and moisture-proof performance, mechanical stability, and environmental durability. For example, the inorganic heat-insulating coating reported in patent CN114456659A uses glass microspheres as a functional filler, which has relatively excellent heat insulation performance, but suffers from problems such as high hygroscopicity and poor weather resistance during long-term use. Therefore, it is necessary to develop a composite thermal insulation coating system that is easy to construct, requires no additional crosslinking agent, can form a stable crosslinked structure under relatively mild conditions, and can form a good interfacial bond with hollow glass microspheres, so as to achieve a synergistic improvement in thermal insulation performance, adhesion performance, waterproof and moisture-proof performance, mechanical stability and environmental durability. Summary of the Invention

[0006] The purpose of this invention is to solve the aforementioned technical problems and provide a composite thermal insulation coating based on an ethanol volatilization-induced stable covalent crosslinked binder phase and its preparation method. The resulting composite thermal insulation coating has a thermal conductivity as low as 0.025–0.030 W / (m·K) and possesses excellent adhesion, thermal insulation, waterproof and moisture-proof properties, mechanical stability, and environmental stability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a composite thermal insulation coating based on an ethanol volatilization-induced stable covalent crosslinked binder phase. The composite thermal insulation coating includes a crosslinked binder phase and hollow glass microspheres fixed in the crosslinked binder phase. The crosslinked binder phase is formed by crosslinking a reactive precursor containing thioctic acid structural units and polydimethylsiloxane segments through ethanol volatilization-induced crosslinking. The reactive precursor is obtained by reacting thioctic acid with amino-functionalized polydimethylsiloxane.

[0008] Preferably, the amino-functionalized polydimethylsiloxane has the following general structural formula: Its average molecular weight is approximately 1500–2400, m is 11–16, and n is 1–4.

[0009] More preferably, the amino-functionalized polydimethylsiloxane has an average molecular weight of 2000, m=13, n=1, and the model number is DY-N323.

[0010] Preferably, the reactive precursor contains polydimethylsiloxane segments, amide linkages, and disulfide structural units derived from thioctic acid.

[0011] Preferably, the reactive precursor is formed by reacting lipoic acid with amino-functionalized polydimethylsiloxane.

[0012] Preferably, the molar ratio of the carboxyl group in the thioctic acid to the amino group in the amino-functionalized polydimethylsiloxane is 1 to 4:1.

[0013] More preferably, the molar ratio is 2 to 4:1.

[0014] More preferably, the molar ratio is 3:1.

[0015] Preferably, the true density of the hollow glass microspheres is 0.18–0.34 g / cm³. 3 .

[0016] Preferably, the median particle size D50 of the hollow glass microspheres is 45–65 µm.

[0017] Preferably, the hollow glass microspheres are selected from one or more of HL20, HL25, HL30 and HL32.

[0018] More preferably, the hollow glass microspheres are HL20.

[0019] Preferably, the dry basis mass ratio of the binder phase to the hollow glass microspheres (the mass ratio of the pure solid effective components after deducting the solvent) is 0.5:1 to 4:1.

[0020] More preferably, the dry mass ratio of the binder phase to the hollow glass microspheres is 1:1.

[0021] Preferably, the hydroxyl groups on the surface of the hollow glass microspheres can form an interface with the polar groups in the binder phase.

[0022] More preferably, the interfacial interaction includes hydrogen bonding between the hydroxyl groups on the surface of the hollow glass microspheres and the amide groups in the binder phase.

[0023] Preferably, the amide group is derived from the reaction between the carboxyl group of thioctic acid and the amino group in amino-functionalized polydimethylsiloxane.

[0024] Preferably, the composite heat insulation coating, while maintaining heat insulation performance, also has good adhesion, waterproof and moisture-proof performance and environmental stability.

[0025] The present invention also provides a method for preparing any of the above-mentioned composite heat-insulating coatings based on an ethanol volatilization-induced stable covalent crosslinking binder phase, comprising the following steps: (1) Preparation of precursor ethanol solution: The reactive precursor is added to ethanol to form a binder phase precursor ethanol solution; (2) Slurry composite: Hollow glass microspheres are added to the ethanol solution of the binder phase precursor and dispersed to obtain a composite construction slurry; (3) Construction and curing: The composite construction slurry is applied to the surface of the substrate and / or placed in a mold. During the construction and / or drying process, it is dried and cured at room temperature or under mild heating conditions, so that the ethanol evaporates and induces the reactive precursor to form a stable covalent cross-linked adhesive phase, thereby fixing the hollow glass microspheres in the cross-linked adhesive phase to obtain a composite heat insulation coating.

[0026] Preferably, in step (1), the reactive precursor is formed by reacting thioctic acid with amino-functionalized polydimethylsiloxane in ethanol.

[0027] More preferably, the reaction temperature of the thioctic acid and the amino-functionalized polydimethylsiloxane in ethanol is 40–100 °C, and the reaction time is 2–5 h.

[0028] More preferably, the reaction temperature is 60 °C and the reaction time is 3 h.

[0029] More preferably, the stirring speed during the reaction process is 300 to 800 r / min.

[0030] More preferably, the stirring speed is 600 r / min.

[0031] Preferably, the dispersion process in step (2) is ultrasonic dispersion.

[0032] More preferably, the ultrasonic output power is 300-500 W, the ultrasonic working frequency is 40 kHz, and the ultrasonic time is 10-15 min.

[0033] More preferably, the drying and curing temperature in step (3) is 15 to 60 °C.

[0034] More preferably, the drying and curing can be carried out at room temperature; if it is necessary to shorten the drying time, it can also be carried out at 50-60 °C.

[0035] Preferably, the drying and curing time in step (3) is 8 to 24 hours.

[0036] More preferably, the drying and curing time is 12 h.

[0037] Preferably, the preparation method of the present invention does not require an additional crosslinking agent.

[0038] More preferably, the preparation method of the present invention has the advantages of fewer process steps, milder curing conditions, and ease of continuous implementation.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The present invention uses a reactive precursor soluble in ethanol as the source of the binder phase, and relies on the evaporation of ethanol to induce the formation of a stable covalent cross-linked structure during construction and drying. No additional cross-linking agent or high temperature curing is required. Cross-linking film can be completed at room temperature or under moderate heating conditions, which helps to simplify the preparation process and reduce the complexity of the process.

[0040] (2) The present invention combines the ethanol volatilization-induced covalent crosslinking binder with hollow glass microsphere thermal insulation filler, and controls the parameters and composite ratio of hollow glass microspheres, which helps to obtain better thermal insulation performance while maintaining the film-forming properties and interface stability of the coating.

[0041] (3) Since the binder phase forms a relatively stable covalent cross-linked network structure, the resulting composite thermal insulation coating has good adhesion performance, mechanical stability and environmental stability, which is beneficial to improving the structure retention ability of the coating during long-term service.

[0042] (4) The binder phase contains polydimethylsiloxane segments, and the molecular chain is rich in methyl groups, which helps to reduce surface energy and improve the waterproof and moisture-proof performance of the coating, thereby improving its performance retention ability in humid environments.

[0043] (5) Hydrogen bonds can be formed between the hydroxyl groups on the surface of the hollow glass microspheres and the amide groups in the cross-linked matrix, which is beneficial to enhance the interfacial bonding between the filler and the matrix, thereby improving the mechanical stability and structural integrity of the composite heat insulation coating.

[0044] (6) The composite heat insulation coating obtained by the present invention has good wear resistance, damp heat stability and environmental durability, and can be used in coating protection material systems that require heat insulation, moisture protection and structural stability. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the reaction process for the formation of the binder phase described in this invention; Figure 2 The nuclear magnetic resonance spectrum of the binder phase described in this invention; Figure 3 This is the ultraviolet absorption spectrum of the binder phase described in this invention; Figure 4 This is a quantitative test diagram of the swelling behavior of the adhesive phase described in this invention; Figure 5The bonding strength of the adhesive on different substrates under different ratios of lipoic acid:PDMS-NH2 in Examples 1-4 (LA:PDMS=1:1, 2:1, 3:1, 4:1, abbreviated as LP-1, LP-2, LP-3, LP-4 in the figure, respectively); Figure 6 Temperature control curves of samples prepared with the optimal binder ratio (lipoic acid:PDMS-NH2=3:1) and different sizes of glass microspheres (HL20, HL25, HL30, HL32) (referred to as HLP-1, HLP-25, HLP-30, and HLP-32 respectively in the figure); Figure 7 The temperature control curves of 2 mm samples at 200 °C in Examples 5, 1, 6, 7, and 8 (referred to as HLP-0.5, HLP-1, HLP-2, HLP-3, and HLP-4 in the figure, respectively) are shown. Figure 8 Temperature control curves of thermal insulation coatings of different thicknesses (2 mm, 4 mm, 6 mm, 8 mm) at 200 °C for the optimal proportion Example 1; Figure 9 Temperature control curves of the 2 mm heat insulation coating in Example 1 (Optimal Ratio) at 100 °C, 200 °C, and 300 °C; Figure 10 Image showing the water contact angle test results of the sample in Example 1 (the optimal proportion). Figure 11 The water contact angle of the samples in Examples 5, 1, 6, 7, and 8 with different dry mass ratios of the binder phase to the hollow glass microspheres, i.e., 0.5:1, 1:1, 2:1, 3:1, and 4:1, was tested. Figure 12 Water contact angle tests were conducted on the optimal proportion of Sample 1 and Comparative Samples 2 and 3. Figure 13 The 2 mm sample of the optimal ratio Example 1 was placed in an outdoor environment, and the change of the temperature control curve at a temperature of 200 °C was tested (1 day, 4 days, 7 days, 10 days, 14 days). Figure 14 The water contact angle of the 2 mm sample of the optimal ratio example 1 was tested after being rubbed with a 200 g weight for different numbers of times (0 / 300 / 600 / 900 / 1200 / 1500 times); Figure 15 Temperature control curves were tested after the 2 mm sample of the optimal ratio example 1 was rubbed with a 200 g weight for different numbers of times (0 / 300 / 600 / 1500 times); Figure 16 Infrared camera image of a 2 mm sample from the optimal scale example 1 during testing on a heating table. Detailed Implementation

[0046] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0047] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, instruments, and equipment used in the embodiments, unless otherwise specified, are all conventional substances or equipment known to those skilled in the art and can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention's content can all achieve the stated reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention.

[0048] In this invention, thioctic acid was purchased from Shanghai Titan Technology Co., Ltd., amino-functionalized polydimethylsiloxane (PDMS-NH2) was purchased from Shandong Dayi Chemical Co., Ltd., commercial waterborne resin was purchased from Anhui Feimiao Chemical Co., Ltd., and HL20 and other types of hollow glass microspheres were purchased from Henan Jieyang New Materials Co., Ltd. In this invention, room temperature refers to 15–35 °C, preferably 20–30 °C; moderate heating refers to drying heating conditions not exceeding 60 °C, used to promote ethanol evaporation and shorten drying and curing time. Unless otherwise stated, drying and curing can be carried out at room temperature or under moderate heating conditions.

[0049] Example 1 1 g of amino-functionalized polydimethylsiloxane (PDMS-NH2) and 0.5715 g of lipoic acid (LA) were dissolved in 3 mL of ethanol (EtOH). The mixture was then transferred to a 50 mL three-necked round-bottom flask equipped with a reflux condenser. The reaction was carried out at 60 °C with continuous magnetic stirring (600 r / min) under a nitrogen atmosphere for 3 h (nitrogen was first introduced into the three-necked flask, one port connected to a condenser, and the other two ports connected to rubber stoppers, with a needle inserted into one of the rubber stopper ports to connect a nitrogen-containing balloon). After completion, the synthesized LA-PDMS ethanol solution was poured into an Erlenmeyer flask and stored, and used as needed, to obtain a precursor solution of binder (LP-3) with a lipoic acid:PDMS-NH2 molar ratio of 3:1, which is the reactive precursor of this invention.

[0050] Then, 2 mL of LP-3 ethanol solution with a solid content of about 0.5 g / mL was mixed with 6 mL of ethanol to form a binder phase precursor ethanol solution. Subsequently, 1 g of HL20 hollow glass microspheres (HGM) was added to make the dry basis mass ratio of the binder phase to the hollow glass microspheres about 1:1, and the mixture was ultrasonically dispersed at 40 kHz for 10 min to make the two evenly mixed, thus obtaining the composite construction slurry, denoted as HLP-1.

[0051] The slurry was then placed in a mold and cured in a 60 °C forced-air oven for 12 h. The average thermal conductivity of the prepared sample was 0.0283 W / (m·K). The sample dimensions were 3 cm in length, 1.5 cm in width, and 2 mm in thickness.

[0052] The following section explores the effect of varying adhesive component ratios on bonding performance.

[0053] Example 2 Based on Example 1, only the binder was prepared without adding heat-insulating filler. 1 g of amino-functionalized polydimethylsiloxane (PDMS-NH2) and 0.1905 g of lipoic acid (LA) were dissolved in 3 ml of ethanol (EtOH). The mixture was then transferred to a 50 mL three-necked round-bottom flask equipped with a reflux condenser. The reaction was carried out at 60 °C with continuous magnetic stirring (600 r / min) under a nitrogen atmosphere for 3 h (nitrogen was first introduced into the three-necked flask, one port connected to a condenser, and the other two ports connected to rubber stoppers; a needle was inserted into one of the rubber stopper ports to connect a nitrogen-containing balloon). After completion, the synthesized LA-PDMS ethanol solution was poured into an Erlenmeyer flask and stored, to be used as needed, yielding a binder (LP-1) with a lipoic acid:PDMS-NH2 molar ratio of 1:1.

[0054] Example 3 Based on Example 1, only the binder was prepared without adding heat-insulating filler. 1 g of amino-functionalized polydimethylsiloxane (PDMS-NH2) and 0.381 g of lipoic acid (LA) were dissolved in 3 ml of ethanol (EtOH). The mixture was then transferred to a 50 mL three-necked round-bottom flask equipped with a reflux condenser. The reaction was carried out at 60 °C with continuous magnetic stirring (600 r / min) under a nitrogen atmosphere for 3 h (nitrogen was first introduced into the three-necked flask, one neck connected to a condenser, and the other two necks connected to rubber stoppers; a needle was inserted into one of the rubber stopper necks to connect to a nitrogen-filled balloon). After completion, the synthesized LA-PDMS ethanol solution was poured into an Erlenmeyer flask and stored, to be used as needed, yielding a binder (LP-2) with a lipoic acid:PDMS-NH2 molar ratio of 2:1.

[0055] Example 4 Based on Example 1, only the binder was prepared without adding heat-insulating filler. 1 g of amino-functionalized polydimethylsiloxane (PDMS-NH2) and 0.762 g of lipoic acid (LA) were dissolved in 3 ml of ethanol (EtOH). The mixture was then transferred to a 50 mL three-necked round-bottom flask equipped with a reflux condenser. The reaction was carried out at 60 °C with continuous magnetic stirring (600 r / min) under a nitrogen atmosphere for 3 h (nitrogen was first introduced into the three-necked flask, one neck connected to a condenser, and the other two necks connected to rubber stoppers; a needle was inserted into one of the rubber stopper necks to connect to a nitrogen-filled balloon). After completion, the synthesized LA-PDMS ethanol solution was poured into an Erlenmeyer flask and stored, to be used as needed, yielding a binder (LP-4) with a lipoic acid:PDMS-NH2 molar ratio of 4:1.

[0056] In Examples 2-4, the molar ratio of thioctic acid and PDMS in the adhesive was varied to demonstrate the effect of different thioctic acid-PDMS ratios on bond strength. Specifically, thioctic acid and PDMS were mixed at different molar ratios, and the bond strength of the mixed adhesives was tested and compared with that of the adhesive in Example 1. The test method involved preparing the adhesive on a substrate and measuring it using a computerized tensile and compressive strength testing machine. The results were the average of three tests. Specific results are shown in Table 1 below. Figure 5 As shown, Figure 5 The bonding strength of the adhesive on different substrates under different molar ratios of thioctic acid and PDMS-NH2.

[0057] Table 1

[0058] The experimental results show that when the molar ratio of lipoic acid to PDMS-NH2 is 3:1 and 4:1, the differences in the key properties of the composite material are minimal, with performance fluctuations of less than 5%. Further increasing the amount of lipoic acid does not result in significant performance gains. Considering the controllability of the reaction, the utilization rate of raw materials, and the overall performance of the system, the optimal reaction ratio is 3:1 for lipoic acid to PDMS-NH2.

[0059] The following explores the effect of the binder to filler ratio on thermal insulation performance.

[0060] Example 5 Take 1 mL of LP-3 ethanol solution with a solid content of about 0.5 g / mL and mix it with 7 mL of ethanol to form a binder phase precursor ethanol solution; then add 1 g of HL20 hollow glass microspheres (HGM) to make the dry basis mass ratio of the binder phase to the hollow glass microspheres about 0.5:1, and ultrasonically disperse at 40 kHz for 10 min to make the two mix evenly, and obtain the composite construction slurry, denoted as HLP-0.5.

[0061] The slurry was then placed in a mold and cured in a 60 ℃ forced-air oven for 12 h. The average thermal conductivity of the prepared sample was 0.0252 W / (m·K).

[0062] Example 6 Take 4 mL of LP-3 ethanol solution with a solid content of about 0.5 g / mL and mix it with 4 mL of ethanol to form a binder phase precursor ethanol solution; then add 1 g of HL20 hollow glass microspheres (HGM) to make the dry basis mass ratio of binder phase to hollow glass microspheres about 2:1, and ultrasonically disperse at 40 kHz for 10 min to make the two mix evenly, and obtain the composite construction slurry, denoted as HLP-2.

[0063] The slurry was then placed in a mold and cured in a 60 ℃ forced-air oven for 12 hours. The average thermal conductivity of the prepared sample was 0.0325 W / (m·K).

[0064] Example 7 Take 6 mL of LP-3 ethanol solution with a solid content of about 0.5 g / mL and mix it with 2 mL of ethanol to form a binder phase precursor ethanol solution; then add 1 g of HL20 hollow glass microspheres (HGM) to make the dry basis mass ratio of binder phase to hollow glass microspheres about 3:1, and ultrasonically disperse at 40 kHz for 10 min to make the two mix evenly, and obtain the composite construction slurry, denoted as HLP-3.

[0065] The slurry was then placed in a mold and cured in a 60 ℃ forced-air oven for 12 hours. The average thermal conductivity of the prepared sample was 0.0350 W / (m·K).

[0066] Example 8 Take 8 mL of LP-3 ethanol solution with a solid content of about 0.5 g / mL, then add 1 g of HL20 hollow glass microspheres (HGM) to make the dry mass ratio of the binder phase to the hollow glass microspheres about 2:1, and ultrasonically disperse at 40 kHz for 10 min to mix the two evenly, and obtain the composite construction slurry, denoted as HLP-4.

[0067] The slurry was then placed in a mold and cured in a 60 ℃ forced-air oven for 12 h. The average thermal conductivity of the prepared sample was 0.0388 W / (m·K).

[0068] In Examples 1, 5, 6, 7, and 8, the proportion of binder in the thermal insulation coating was varied to demonstrate its impact on thermal insulation performance. Specifically, different volumes of LP-3 were mixed with the same mass of glass microspheres, and the thermal insulation performance of the mixed thermal insulation samples was tested and compared with that of Example 1. Details are shown in Table 2 below. Figure 7 As shown, Figure 7 The temperature control curves for Examples 5, 1, 6, 7, and 8 are shown when the heating table temperature is controlled at 200 °C.

[0069] Table 2

[0070] Generally, an excessively high proportion of binder phase weakens the lightweight and thermal insulation properties of the composite system. While a dry-to-basic mass ratio of 0.5:1 results in a lower apparent thermal conductivity and temperature rise, the low binder phase content leads to insufficient fixation of the hollow glass microspheres. This results in powder shedding and localized damage during demolding, edge cutting, or friction, making it difficult to meet the requirements for actual coating formation and use. Considering film integrity, structural stability, and thermal insulation performance, a dry-to-basic mass ratio of 1:1 was ultimately determined to be the optimal ratio.

[0071] Example 9 Take 2 ml of LP-3 and mix it with 6 ml of ethanol to form a binder phase precursor ethanol solution; then add 1 g of HL25 hollow glass microspheres (HGM) to it, and sonicate at 40 kHz for 10 min to mix the two evenly to obtain the product, which is a composite construction slurry.

[0072] The above slurry was then placed in a mold and cured in a 60 ℃ forced-air oven for 12 h. The prepared sample had a length of 3 cm, a width of 1.5 cm, and a thickness of 2 mm, and was designated as HLP-25.

[0073] Example 10 Take 2 ml of LP-3 and mix it with 6 ml of ethanol to form a binder phase precursor ethanol solution; then add 1 g of HL30 hollow glass microspheres (HGM) to it, and sonicate at 40 kHz for 10 min to mix the two evenly to obtain the product, which is a composite construction slurry.

[0074] The above slurry was then placed in a mold and cured in a 60 ℃ forced-air oven for 12 h. The prepared sample had a length of 3 cm, a width of 1.5 cm, and a thickness of 2 mm, and was designated as HLP-30.

[0075] Example 11 Take 2 ml of LP-3 and mix it with 6 ml of ethanol to form a binder phase precursor ethanol solution; then add 1 g of HL32 hollow glass microspheres (HGM) to it, and sonicate at 40 kHz for 10 min to mix the two evenly to obtain the product, which is a composite construction slurry.

[0076] The above slurry was then placed in a mold and cured in a 60 ℃ forced-air oven for 12 h. The prepared sample had a length of 3 cm, a width of 1.5 cm, and a thickness of 2 mm, and was designated as HLP-32.

[0077] Example 12 Take the heat insulation coating sample prepared in Example 1, and use a dust-free degreased cotton ball dipped in a small amount of anhydrous ethanol to gently wipe the surface of the coating test area and the bottom of the sample to thoroughly remove surface dust, oil stains, floating dust and loose coating particles. After wiping, let it air dry naturally until the surface is dry and there are no residual traces.

[0078] The operator holds the top of a 200g weight, ensuring its flat bottom is vertically and stably placed against the marked friction area of ​​the heat-insulating coating. Throughout the process, the weight's own weight is the sole point of contact with the coating; the operator only controls the direction of movement, without applying additional downward pressure, lifting it off the coating surface, or tilting the weight. A slow, uniform reciprocating motion is used for horizontal linear friction. Each reciprocating motion has a consistent rhythm, speed, and stroke, maintaining the bottom of the weight in flat contact with the coating surface throughout. The friction status is observed continuously during the process. If a small amount of wear debris appears, it does not need to be removed. The friction motion is continued until all 0 / 300 / 600 / 900 / 1200 / 1500 standard reciprocating friction cycles are completed. During operation, sudden pulling or pushing, localized pressure, tilting, or other improper actions are strictly prohibited to ensure completely uniform friction conditions for each sample group.

[0079] Comparative Example 1 Dissolve 2 g of amino-functionalized polydimethylsiloxane (PDMS-NH2) in 6 ml of ethanol (EtOH). Stir continuously with a magnetic force (600 r / min) for ten minutes until completely dissolved. This yields a PDMS-NH2 ethanol solution.

[0080] Then take 8 mL of the above solution, add 1 g of HL20 hollow glass microspheres (HGM) to it, and ultrasonically disperse at 40 kHz for 10 min to mix the two evenly, thus obtaining the composite construction slurry.

[0081] The slurry was then placed in a mold and cured in a 60°C forced-air oven for 12 hours. However, the final curing effect was very poor, with only partial curing.

[0082] Comparative Example 2 Dissolve 1 g of lipoic acid (LA) in 8 ml of ethanol (EtOH). Stir continuously with a magnetic force (600 r / min) for 10 minutes until completely dissolved. This yields a lipoic acid-ethanol solution.

[0083] Then take 8 mL of the above solution, add 1 g of HL20 hollow glass microspheres (HGM) to it, and ultrasonically disperse at 40 kHz for 10 min to mix the two evenly, thus obtaining the composite construction slurry.

[0084] The above slurry is then placed in a mold and cured in a 60 ℃ forced-air oven for 12 hours. The final cured and shaped product is designated as HL-1.

[0085] Comparative Example 3 Dissolve 1 g of commercial aqueous resin in 8 ml of water. Stir continuously with a magnetic force (600 r / min) for ten minutes until completely dissolved. The resulting aqueous resin solution is obtained.

[0086] Then take 8 mL of the above solution, add 1 g of HL20 hollow glass microspheres (HGM) to it, and ultrasonically disperse at 40 kHz for 10 min to mix the two evenly, thus obtaining the composite construction slurry.

[0087] The above slurry is then placed in a mold and cured in a 60 ℃ forced-air oven for 12 hours. The final cured and molded product is designated as HS-1.

[0088] The detection methods involved are as follows: First, swelling rate test: The LP-3 sample was vacuum dried at 40℃ to constant weight, ensuring no residual solvent. It was cut into regular shapes and the initial mass m0 was recorded. The dried sample was completely immersed in different organic solvents and allowed to stand at room temperature for 24 hours. Sufficient solvent was ensured, and the sample was completely covered, without exposure, folding, or adhesion. After 24 hours, the sample was carefully removed with tweezers. Excess solvent on the surface was quickly blotted with filter paper, avoiding compression of the sample. The wet weight was immediately recorded as m1. The swollen sample was placed in a 40℃ vacuum drying oven and dried to constant weight. The dry weight m2 was recorded. Each sample group was tested at least three times. The swelling rate was calculated using the formula W (swelling rate) = (m1 - m0) / m1 × 100%, and the average value was taken as the final result. The test results are as follows: Figure 4 As shown; The results showed that the dried binder phase could not be redissolved into the initial homogeneous flow solution, but instead maintained its overall morphology or only underwent limited swelling, indicating that the system formed a stable cross-linked structure after the ethanol evaporated.

[0089] Second, temperature control curve test: The prepared coating sample (2 mm thick) was placed on a heating stage set to a specific temperature (e.g., 100 ℃, 200 ℃, 300 ℃). A thermocouple was used to record the temperature change at the center point of the sample's upper surface over time (e.g., 0-5 minutes). The ambient temperature was 25±2 ℃. The test results are as follows: Figure 6 , 7As shown in 8, 9, 13, and 15.

[0090] Third, durability testing: After placing the sample in a specific environment for a specified time, the above-mentioned temperature control test was performed. The test results are as follows: Figure 13 As shown.

[0091] The results showed that after being placed outdoors for two weeks, the heat insulation performance remained excellent, and there was no significant difference from the original sample.

[0092] Fourth, hydrophobicity test: The prepared coating sample was wiped with anhydrous ethanol, and then gently wiped with lint-free paper to remove dust and oil. It was then allowed to air dry at room temperature. An optical contact angle meter was used for testing, with ultrapure water as the test liquid and a droplet volume of 4 μL. The sample was horizontally fixed on the instrument stage, and the optical path and focus were adjusted to ensure a clear interface image. A water droplet was slowly added to the smooth surface of the coating. After the droplet stabilized for 10 seconds, a contour image was acquired. The static water contact angle was calculated using the circular fitting method in software. Five different locations were randomly selected for testing in each sample group, with a minimum distance of 5 mm between each test point. The average of the five test data sets was taken as the water contact angle result for the coating. The test results are shown in Table 3 below. Figure 11 , 12 As shown.

[0093] Table 3

[0094] The results showed that the presence of polydimethylsiloxane segments in the binder phase, with methyl groups on the molecular chain, helps to reduce surface energy and improve the waterproof and moisture-proof properties of the coating, thereby improving its performance retention in humid environments.

[0095] Fifth, thermal conductivity test: A thermal conductivity meter of model HNB-DRS2 is used. The HNB-DRS2 is a thermal conductivity meter developed using transient planar heat source technology, suitable for testing the thermal conductivity of various types of materials. The specific operation involves taking two prepared coated solid samples (approximately 30 mm in diameter and 50 mm in thickness), clamping a planar probe between the two samples, ensuring the probe is completely covered and not exposed, placing it in the sample holder, and gently tightening it to ensure there are no air gaps between the probe and the sample, no slippage, no cracking of the sample, and no bending of the probe. Select probe number 2, click "Probe Test," and perform 3–5 consecutive tests. Confirm the result after the resistance stabilizes. Set the test time to 160 seconds, the test power to 0.2–0.3 W, and the test reference to 0.02–0.03 V. Start the test; the instrument will automatically heat, collect the temperature curve, and calculate the thermal conductivity. Each sample group is tested five times, and the average value is taken as the final result.

[0096] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A composite thermal insulation coating based on an ethanol volatilization-induced stable covalent crosslinked adhesive phase, characterized in that, The composite heat insulation coating includes a crosslinked adhesive phase and hollow glass microspheres dispersed and fixed in the crosslinked adhesive phase; the crosslinked adhesive phase is formed by crosslinking of a reactive precursor containing thioctic acid structural units and polydimethylsiloxane segments induced by ethanol volatilization; the reactive precursor is obtained by reacting thioctic acid with amino-functionalized polydimethylsiloxane.

2. The composite heat-insulating coating according to claim 1, characterized in that, The reactive precursor contains polydimethylsiloxane segments, amide linkages, and disulfide structural units derived from thioctic acid.

3. The composite heat-insulating coating according to claim 1, characterized in that, The molar ratio of the carboxyl group in the lipoic acid to the amino group in the amino-functionalized polydimethylsiloxane is 1 to 4:

1.

4. The composite heat-insulating coating according to claim 3, characterized in that, The molar ratio is 2 to 4:

1.

5. The composite heat-insulating coating according to claim 4, characterized in that, The molar ratio is 3:

1.

6. The composite heat-insulating coating according to claim 1, characterized in that, The true density of the hollow glass microspheres is 0.18–0.34 g / cm³. 3 The median particle size D50 is 45–65 μm.

7. The composite heat-insulating coating according to claim 1, characterized in that, The dry mass ratio of the adhesive phase to the hollow glass microspheres is 0.5 to 4:

1.

8. A method for preparing a composite thermal insulation coating based on an ethanol volatilization-induced stable covalent crosslinked adhesive phase as described in any one of claims 1-7, characterized in that, Includes the following steps: (1) Preparation of precursor ethanol solution: The reactive precursor is added to ethanol to form a binder phase precursor ethanol solution; (2) Slurry composite: Hollow glass microspheres are added to the ethanol solution of the binder phase precursor and dispersed to obtain a composite construction slurry; (3) Curing: The composite construction slurry is applied to the surface of the substrate and / or placed in a mold, and dried and cured at room temperature or under mild heating conditions, so that the ethanol evaporates and induces the reactive precursor to form a stable covalent crosslinked adhesive phase, thereby obtaining a composite heat insulation coating.

9. The preparation method according to claim 8, characterized in that, In step (1), the reactive precursor is formed by reacting lipoic acid with amino-functionalized polydimethylsiloxane in ethanol; And / or, the dispersion process in step (2) is ultrasonic dispersion, wherein the ultrasonic output power is 300-500 W, the ultrasonic working frequency is 40 KHz, and the ultrasonic time is 10-15 min; And / or, the drying and curing temperature in step (3) is 15 to 60 °C and the curing time is 8 to 24 h.

10. The preparation method according to claim 9, characterized in that, The reaction temperature of the lipoic acid and the amino-functionalized polydimethylsiloxane in ethanol is 40–100 °C, and the reaction time is 2–5 h.

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