A composite coating based on FPEEK, and a preparation method and application thereof

Abstract

The application provides a FPEEK-based composite coating, a preparation method and application thereof, and relates to the technical field of polymer composites.The preparation method comprises the following steps: adding polyaspartic acid ester (a polyurea precursor) into a FPEEK solution and uniformly dispersing, introducing h-BN and TiO2 inorganic fillers, and finally adding isocyanate to initiate curing.In this process, the molecular chains of the in-situ generated polyaspartic acid ester are interpenetrated and entangled with the FPEEK, forming a "double-resin" continuous phase matrix with strong interface bonding, which greatly enhances the cohesive strength of the coating and the adhesion to the substrate.Meanwhile, the composite matrix can effectively stabilize and disperse the h-BN and TiO2 nanofillers, prevent their agglomeration, and make them uniformly distributed in the coating, thereby synergistically endowing the coating with high solar reflectivity and high mid-infrared radiation characteristics.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and in particular to a composite coating based on FPEEK, its preparation method and application. Background Technology

[0002] In the building and industrial sectors, space cooling is a major energy consumption area, accounting for a significant portion of global electricity consumption and placing immense pressure on the power grid during peak summer periods. Traditional active cooling technologies not only consume large amounts of electricity, but their waste heat emissions further exacerbate the urban heat island effect. Therefore, developing passive cooling technologies that require no external energy input has become a key direction for overcoming the current predicament.

[0003] Radiative cooling technology is a highly promising passive cooling method. Its physical basis lies in the "atmospheric transparency window" in the mid-infrared band (8-13 μm) of Earth's atmosphere, allowing surface heat radiation to directly penetrate the atmosphere and dissipate into the cold outer space. By designing materials to have high infrared emissivity in this band and high reflectivity in the main energy range of the solar spectrum (0.3-2.5 μm), spontaneous cooling of objects under sunlight can be achieved. Radiative cooling coatings developed based on this principle are considered one of the ideal solutions for achieving large-scale building energy conservation and outdoor equipment thermal management due to their advantages such as direct application to existing building and equipment surfaces, convenient construction, and relatively low cost.

[0004] However, the current radiation cooling coating still faces a series of key technical challenges in moving from the laboratory to actual large-scale and long-term applications. Some organic polymer materials with intrinsic high emissivity in the mid-infrared band (such as polyether ether ketone, PEEK) are ideal functional matrices, but these high-performance polymers generally have problems such as poor solubility, high processing temperature, and weak adhesion to the substrate, making it difficult to make coatings suitable for large-scale construction (such as spraying and brushing) and obtain strong and durable coatings.

[0005] In view of this, it is necessary to design an improved FPEEK-based composite coating, its preparation method and application, in order to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a composite coating based on FPEEK, its preparation method and application.

[0007] To achieve the above-mentioned objective, in a first aspect, the present invention provides a method for preparing a composite coating for preparing a composite coating, comprising the following steps:

[0008] A polyurea precursor was added to a fluorinated polyether ether ketone solution and dispersed evenly. Then, an inorganic filler was added and ultrasonically dispersed to obtain a suspension. Diphenylmethane diisocyanate was added to the suspension and a curing reaction was carried out to obtain a composite coating.

[0009] The polyurea precursor is polyaspartic acid ester, and the inorganic filler is hexagonal boron nitride and TiO2, with a mass ratio of 1:1.

[0010] The mass ratio of fluorinated polyether ether ketone to polyaspartic acid ester in the fluorinated polyether ether ketone solution is (5-7):(3-5).

[0011] Preferably, the concentration of the fluorinated polyether ether ketone solution is 0.32 mg / mL, and the dispersion time of the polyaspartic ester in the fluorinated polyether ether ketone solution is 0.5-1.5 h.

[0012] Preferably, the mass ratio of fluorinated polyether ether ketone to polyaspartic acid ester in the fluorinated polyether ether ketone solution is 7:3.

[0013] Preferably, the ultrasonic dispersion time is 2 hours.

[0014] Preferably, the mass ratio of diphenylmethane diisocyanate to polyaspartic acid ester is 1:1.

[0015] Secondly, the present invention provides a composite coating based on FPEEK, which is obtained by curing a composite coating and has a thickness of 140-280 μm.

[0016] Thirdly, the present invention provides a method for preparing a composite coating based on FPEEK, comprising the following steps:

[0017] The composite coating is obtained by applying the composite coating to the surface of the substrate and curing it.

[0018] Fourthly, the present invention provides an application of composite coatings in the preparation of radiation cooling materials.

[0019] Fifthly, the present invention provides an application of a composite coating in the preparation of radiation cooling materials.

[0020] The beneficial effects of this invention are:

[0021] 1. The composite coating provided by this invention for preparing composite coatings uses FPEEK, polyaspartic acid ester, h-BN, and TiO2 as raw materials, and simultaneously synthesizes polyaspartic acid ester polyurea during the preparation process to obtain a composite coating with high infrared radiation and high solar reflectance. In the above scheme, in-situ polymerization allows the newly generated polyaspartic acid ester polymer chains and FPEEK molecular chains to interpenetrate and entangle with each other at the nanoscale, greatly strengthening the two-phase interface and avoiding phase separation that may occur with simple blending, thereby forming a continuous, dense, and tough resin matrix network inside the coating; secondly, the FPEEK solution and the newly generated polyaspartic acid ester together constitute a continuous two-resin phase, which can effectively wet and encapsulate h-BN and TiO2, preventing their aggregation and sedimentation through steric hindrance effect, thereby achieving the uniformity and stability of the two in the coating.

[0022] 2. The composite coating preparation method provided by this invention uses FPEEK as the functional matrix, introduces h-BN and TiO2 as functional fillers, and simultaneously employs in-situ synthesis of polyaspartic acid ester, significantly improving the coating's cohesive strength and substrate adhesion, ensuring the coating's durability. The introduction of h-BN and TiO2 synergistically enhances the coating's high reflectivity in the solar spectral region. This one-step composite process achieves the organic integration and synergistic enhancement of three major functions: efficient mid-infrared radiation, high solar reflectivity, and strong interfacial adhesion, providing a feasible technical path for developing weather-resistant radiation cooling coatings with both excellent optical performance and long-term environmental stability. Attached Figure Description

[0023] Figure 1 The results show the radiation cooling performance of the pure coatings obtained in Examples 1 to 3 of this invention.

[0024] Figure 2 The optical performance results of the composite coatings obtained in Examples 1 to 3 of this invention are shown.

[0025] Figure 3 The results show the spectral performance characterization of the composite coatings obtained in Examples 1 and 4 to 6 of this invention.

[0026] Figure 4 The results of micro-area composition and morphology analysis of the composite coatings obtained in Examples 1 and 4 to 6 of this invention;

[0027] Figure 5 The results represent the comprehensive characterization and verification of the performance of the radiation-cooled coating of the composite coating in Example 5 of this invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0030] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0031] On the one hand, the present invention provides a method for preparing a composite coating based on FPEEK, comprising the following steps:

[0032] A polyurea precursor is added to a fluorinated polyether ether ketone (FPEEK) solution and dispersed evenly. Then, an inorganic filler is added and ultrasonically dispersed to obtain a suspension. Diphenylmethane diisocyanate is added to the suspension and the mixture is stirred rapidly for 5-10 minutes to induce a curing reaction, thus obtaining a composite coating. The composite coating is then applied to the surface of a substrate and cured to obtain a composite coating layer.

[0033] In some embodiments, the inorganic filler is specifically hexagonal boron nitride (h-BN) and TiO2, with a mass ratio of 1:1, and the mass ratio of the inorganic filler to the fluorinated polyether ether ketone solution is 3.5:2.14.

[0034] In some embodiments, the FPEEK solution is obtained by dissolving FPEEK in an organic solvent, preferably N-methylpyrrolidone, and the concentration of the FPEEK solution is 0.32 mg / mL. It should be noted that FPEEK can be prepared according to existing methods, and therefore will not be described in detail here.

[0035] In some embodiments, the polyurea precursor is specifically polyaspartic acid ester, with a mass ratio (g) of ester to fluorinated polyetheretherketone (PEEK) of 3.5:1.58, and the dispersion time of the polyurea precursor in the FPEEK solution is 1 h. The introduction of polyaspartic acid ester increases the uniform dispersion of inorganic fillers in the matrix, and the uniform distribution of boron nitride and titanium dioxide in the matrix is ​​beneficial for constructing a uniform multiple light scattering network and infrared radiation interface within the film layer. On the one hand, the uniformly dispersed TiO2 and h-BN can effectively enhance multiple scattering and reflection in the solar light band and reduce solar heat absorption; on the other hand, the rich and uniform filler-matrix interface helps to improve the thermal radiation emission capability in the mid-infrared band, especially the atmospheric window band.

[0036] In some embodiments, the ultrasonic dispersion time is 2 hours and the power is 150 W.

[0037] In some embodiments, the mass ratio of diphenylmethane diisocyanate to polyaspartic acid ester is 1:1.

[0038] In some embodiments, the substrate is one or more of wood materials, metal materials, polymer materials, and inorganic non-metallic materials, and the coating method is spraying, scraping, or other methods.

[0039] The following specific embodiments further illustrate the FPEEK-based composite coating, its preparation method, and its applications provided by the present invention:

[0040] Example 1

[0041] This embodiment provides a method for preparing a composite coating based on FPEEK, including the following steps:

[0042] 3.5 g of FPEEK was dissolved in 11 mL of NMP (99% purity), and stirred for 1 h. Then, 0.79 g of polyaspartic acid ester was added, and stirring continued for 30 min until uniformly dispersed. Next, 1.07 g each of h-BN and TiO2 were added, and the mixture was ultrasonically dispersed for 2 h to obtain a suspension. 0.79 g of diphenylmethane diisocyanate was added to the suspension, and the mixture was stirred at 500 r / min for 5 min. The polyaspartic acid ester and diphenylmethane diisocyanate reacted to form polyaspartic acid ester polyurea, yielding a white composite coating. This coating was then applied to the surface of a wooden board and cured at room temperature to obtain a composite coating with a thickness of 140 μm. It should be noted that, unless otherwise specified, all reagents and raw materials used in the embodiments of this invention can be obtained commercially.

[0043] Examples 2 to 3

[0044] The only difference between Examples 2 and 3 and Example 1 is that the mass ratio of FPEEK to polyaspartic acid ester is different. All other experimental parameters are the same as those in Example 1, and will not be repeated here.

[0045] The mass ratios of FPEEK and polyaspartic acid ester in Examples 1 to 3 are shown in Table 1. The radiation cooling performance of the pure coating obtained after direct curing of the composite coating under the corresponding conditions is shown in Table 1. Figure 1 As shown, Figure 1 Figure (a) shows the solar reflectance results for the pure coating. Figure 1Figure (b) shows the solar emissivity results of the pure coatings. Figure (a) shows that the reflectivity of the three coatings is very high (>80%) and flat across the entire solar spectrum. The solar-weighted average reflectivity of the pure coatings in Examples 1 to 3 is 94.28%, 94.69%, and 93.98%, respectively. This result indicates that the coatings can reflect most of the solar heat irradiated onto them, thereby greatly reducing heat absorption at the source. Figure (b) shows that the three coatings exhibit extremely high infrared emissivity (>93%) in the 8-13 μm band, indicating that the composite coating can continuously dissipate heat outward through radiation.

[0046] Table 1. Mass ratio settings of FPEEK and polyaspartic acid ester in Examples 1 to 3

[0047]

[0048] The optical properties of the composite coatings formed after applying the composite coatings of Examples 1 to 3 to the wood surface are as follows: Figure 2 As shown, where, Figure 2 Figure (a) shows the solar reflectivity of the composite coating. Figure 2 Figure (b) shows the mid-infrared emissivity of the composite coating. Figure (a) shows that the solar reflectivity of the composite coatings obtained in Examples 1 to 3 are 93.31%, 90.74%, and 92.99%, respectively, indicating that the composite coating can directly reflect most of the incident solar radiation back, greatly reducing heat absorption at the source. Compared with the uncoated wood (reflectivity of only 57.32%), the reflectivity improvement effect is extremely obvious. Figure (b) shows that the infrared emissivity of the three composite coatings is higher than 92% in the key atmospheric transparency window band (8-13μm). Secondly, the high emissivity band of the composite coating highly overlaps with the high transmittance window of the atmosphere (light yellow shaded area), which means that the infrared radiation emitted by the composite coating can penetrate the Earth's atmosphere almost unimpeded and escape into the cold outer space, thereby achieving effective radiative cooling.

[0049] Examples 4 to 6

[0050] The only difference between Examples 4 to 6 and Example 1 is that the thickness of the composite coating formed after applying the composite coating to the wood is different from that in Example 1. All other experimental parameters are the same as those in Example 1, and will not be repeated here.

[0051] The thicknesses of the composite coatings in Examples 1 and 4 to 6 are shown in Table 2, and the spectral performance characterization results of the composite coatings under the corresponding conditions are as follows: Figure 3 As shown, Figure 3 Figure (a) shows the solar reflectivity of composite coatings with different thicknesses. Figure 3Figure (b) shows the mid-infrared emissivity of composite coatings with different thicknesses. Figure (a) shows that when the thickness of the composite coating increases from 70 μm to 280 μm, its average solar reflectance increases from 91.03% to 93.96%. This is because the increase in thickness can more effectively cover the substrate and form a more complete optical structure, thereby reducing the absorption of solar heat. However, from 140 μm to 280 μm, the reflectance of the composite coating increases only slightly from 93.31% to 93.96%. Considering cost factors, 140 μm can be selected as the optimal thickness for the composite coating.

[0052] Table 2. Composite coating thickness settings for Examples 1 and 4 to 6

[0053]

[0054] Micro-area composition and morphology analysis of different composite coatings, such as Figure 4 As shown, where Figure 4 Figures (a)-(d) are SEM images of the composite coatings of Examples 1 and 4 to 6. Figure 4 Figure (e) shows the cross-sectional EDS-mapping diagram of the composite coating in Example 5. The results show that when the composite coating is thin, it may form an uneven texture due to surface tension, i.e., the "orange peel phenomenon", as shown in Figure (a). At the same time, when the coating is thin, the inorganic filler will be directly exposed on the surface due to insufficient liquid encapsulation and sinking space, forming particle agglomerates, as shown in Figure (b). Only when the thickness of the composite coating is moderate, its liquid surface tension will drive the liquid flow, forming a smooth and flat surface as shown in Figure (c). When the thickness of the composite coating reaches 280 μm, the curing rate and solvent evaporation rate of the coating interior and surface are inconsistent. The solvent on the surface will evaporate rapidly and form a "skin", which will hinder the escape of the lower solvent layer. The tiny bubbles generated by the vapor pressure of the internal solvent are trapped in the coating, and after curing, they will form small particles again, affecting the uniformity of the coating. Figure (e) shows that C and O elements are uniformly distributed in the overall material, while F, B, and Ti elements are concentrated in the coating, showing a clear layered structure.

[0055] The comprehensive performance characterization and verification of the radiation-cooled composite coating in Example 5 are as follows: Figure 5 As shown, where Figure 5 Figure (a) in the figure is a schematic diagram of the principle of radiation cooling. Figure 5 Figure (b) shows the emissivity spectrum of the composite coating in Example 5. Figure 5 Figures (c)-(e) in the figure show the temperature changes over time for wood with composite coating, pure wood, and ambient air in Example 5. Figure 5 Figure (f) in the figure shows the temperature difference between the wood with the composite coating and the pure wood in Example 5. Figure 5 Figure (g) in the figure is a temperature difference diagram of the wood with composite coating in Example 5 relative to ambient air. Figure 5 Figure (h) shows the temperature difference between the composite coating and the commercial white coating. Figure (a) shows that the composite coating achieves radiative cooling by reflecting sunlight and emitting infrared thermal radiation. It significantly reduces heat input by highly reflecting sunlight (especially in the visible and near-infrared bands), while simultaneously emitting high infrared radiation in the atmospheric window band (8-13 μm), directly dissipating the object's heat into the cold space, thus achieving passive cooling and even lowering the object's temperature below the ambient temperature. Figure (b) shows that the composite coating has high reflectivity in the 0.3-2.5 μm solar spectrum range, meaning that the coating can effectively resist solar heating. The average reflectivity of 96% indicates that it can reflect 96% of sunlight, which is a prerequisite for daytime cooling. High infrared emissivity (which should be shown in the figure as very high emissivity in the 8-13 μm atmospheric window): This means that the coating can efficiently radiate heat away. The average emissivity of 0.97 is also extremely high, close to that of an ideal blackbody, indicating a strong radiative heat dissipation capability. Figure (c) shows that the temperature of the wood coated with the composite coating is significantly lower than that of the uncoated wood and also lower than the ambient air temperature. This result directly proves the effectiveness of the coating on the actual application (wooden roof), achieving "sub-ambient cooling" below the ambient temperature. Figure (e) shows that the temperature of the pure composite coating (i.e., the coating formed by direct curing of the composite coating) is lower than that of the coating obtained by curing commercial white paint (acrylic polyurethane). Figure (f) shows that during the test period (10:00-14:00), the average temperature difference between the wood with the composite coating and the pure wood was 2.91°C, which directly proves the application effect of the composite coating itself. During the midday period when solar radiation is strongest (around 12:00), the temperature difference ΔT also remained close to the peak, indicating that even under the strongest heating conditions, the high solar reflectivity of the composite coating remains effective. Figure (g) shows that the surface temperature of the composite coating is on average 6.69°C lower than the ambient air temperature. This value is greater than the temperature difference in Figure (f). During the afternoon when solar radiation is extremely strong (test period 12:45-15:00), the surface temperature of the composite coating is always lower than the air temperature. This conclusion verifies the "active cooling" capability of the composite coating. In addition to reflecting sunlight, it can also radiate heat outward through atmospheric windows, and its heat dissipation power exceeds the heating power of the sun.

[0056] Comparative Example 1

[0057] The only difference between this comparative example and Example 1 is that, in the process of preparing the composite coating, the polyaspartic acid ester in Example 1 was replaced with an equal amount of ketimine-type latent amine curing agent. The other experimental parameters are the same as those in Example 1, and will not be repeated here.

[0058] Comparative Example 2

[0059] The only difference between this comparative example and Example 1 is that the polyaspartic acid ester in Example 1 is omitted in the preparation of the composite coating. The other experimental parameters are the same as in Example 1, and will not be repeated here.

[0060] Table 3 shows a comparison of the performance of the composite coatings formed on the wood surface by the composite coatings obtained in Example 1 and Comparative Examples 1-2. The results show that the performance of the composite coating in Example 1 is significantly better than that in Comparative Examples 1-2. This is because polyaspartic acid ester has a polyamine structure, which can quickly form a strong and highly cross-linked polyurea matrix network with isocyanate. This network is not only dense itself, but can also effectively encapsulate and stabilize TiO2 and h-BN fillers through interfacial interactions, thereby achieving dual optimization of matrix reinforcement and uniform filler dispersion. In contrast, the ketimine latent curing agent used in Comparative Example 1 has an incomplete curing network and weak wetting and anchoring ability for fillers due to the delayed hydrolysis reaction, which affects the reflectivity and emissivity of the coating. After omitting polyaspartic acid ester in Comparative Example 2, although it retains a certain emissivity, its reflectivity (81.65%) is significantly lower than that of Example 1 (93.69%) due to the severe lack of filler dispersion. Therefore, polyaspartic acid ester is a key structural component that simultaneously improves the matrix performance and filler dispersion morphology, rather than a simple curing agent.

[0061] Table 3 Performance results of the composite coatings in Example 1 and Comparative Examples 1-2

[0062]

[0063] Comparative Example 3

[0064] The only difference between this comparative example and Example 1 is that, in the process of preparing the composite coating, FPEEK, h-BN, TiO2 and polyaspartic acid ester polyurea are directly mixed to prepare the composite coating. The amount of each raw material and the other experimental parameters are the same as in Example 1, and will not be repeated here.

[0065] The results showed that the performance of Comparative Example 3 was inferior to that of Example 1. This is because, in the in-situ polymerization synthesis of polyaspartic acid ester polyurea in Example 1, the newly generated polymer chains interpenetrated and entangled with the FPEEK molecular chains, forming a strong and continuous resin network. This greatly strengthened the interface between the two phases and avoided the phase separation problem that easily occurs with simple blending. At the same time, the dual-resin continuous phase formed in the reaction can effectively wet and encapsulate h-BN and TiO2 particles, preventing their aggregation and sedimentation through steric hindrance, thereby ensuring the uniform dispersion and stable existence of the filler in the coating. However, if the pre-synthesized polyaspartic acid ester polyurea is directly physically blended with FPEEK, the molecular-level entanglement and interface reinforcement effect formed by the above-mentioned in-situ polymerization are lacking, and the synergistic stabilizing effect of the dual resins on the filler cannot be achieved. Ultimately, the structural density, interfacial strength, and filler dispersion of the composite material are all inferior to those of Example 1, resulting in a significant decrease in overall performance.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a composite coating for use in preparing composite coatings, characterized in that, Includes the following steps: A polyurea precursor was added to a fluorinated polyether ether ketone solution and dispersed evenly. Then, an inorganic filler was added and ultrasonically dispersed to obtain a suspension. Diphenylmethane diisocyanate was added to the suspension and a curing reaction was carried out to obtain a composite coating. The polyurea precursor is polyaspartic acid ester, and the inorganic filler is hexagonal boron nitride and TiO2, with a mass ratio of 1:

1. The mass ratio of fluorinated polyether ether ketone to polyaspartic acid ester in the fluorinated polyether ether ketone solution is (5-7):(3-5).

2. The preparation method according to claim 1, characterized in that, The concentration of the fluorinated polyether ether ketone solution is 0.32 mg / mL, and the dispersion time of the polyaspartic ester in the fluorinated polyether ether ketone solution is 0.5-1.5 h.

3. The preparation method according to claim 1, characterized in that, The mass ratio of fluorinated polyether ether ketone to polyaspartic acid ester in the fluorinated polyether ether ketone solution is 7:

3.

4. The preparation method according to claim 1, characterized in that, The ultrasonic dispersion time was 2 hours.

5. The preparation method according to claim 1, characterized in that, The mass ratio of diphenylmethane diisocyanate to polyaspartic acid ester is 1:

1.

6. A composite coating based on FPEEK, characterized in that, The composite coating prepared by any one of claims 1-5 is cured to obtain a thickness of 140-280 μm.

7. A method for preparing an FPEEK-based composite coating as described in claim 6, characterized in that, Includes the following steps: The composite coating prepared by any one of claims 1-5 is applied to the surface of a substrate and cured to obtain a composite coating.

8. The application of a composite coating prepared by any one of claims 1-5 in the preparation of radiation cooling materials.

9. The application of the composite coating prepared by the method of claim 7 in the preparation of radiation cooling materials.

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