Radiation refrigeration coating and preparation method thereof

Abstract

The invention discloses a radiation refrigeration coating and a preparation method thereof. The radiation refrigeration coating comprises the following raw materials in parts by weight: 18-21 parts of epoxy resin, 8-9 parts of a reactive diluent, 22-23 parts of an anhydride curing agent, 25-30 parts of hollow silicon dioxide microspheres, 15-20 parts of high-refractive-index filler, 1.1-1.5 parts of a dispersing agent, 0.2-0.3 part of a flatting agent, 0.3-0.5 part of a curing accelerator and 15-30 parts of a solvent. The high-refractive-index filler is one or more of titanium dioxide, zirconium oxide, zinc oxide and barium sulfate. The hollow silicon dioxide microspheres and the high-refractive-index filler are compounded, and meanwhile, backward scattering and surface scattering are combined, so that the scattering efficiency of the filler is greatly improved, the proportion of the filler can be reduced, and the thickness of the coating can also be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of functional materials, and particularly relates to a radiative cooling coating and a preparation method thereof. Background Art

[0002] In recent years, due to the increasingly severe problems of global warming and extreme climate, the energy consumption and greenhouse gas emissions brought about by refrigeration have reached unprecedented levels. As a zero-consumption and environmentally friendly refrigeration means, radiative cooling technology has great application potential.

[0003] Radiative cooling achieves zero-consumption all-weather cooling by reflecting solar radiation and increasing infrared emission. On the one hand, an object with a temperature will release energy in the form of thermal radiation, and through the atmospheric window band of 8 - 13 μm, the surface object can directly release thermal radiation energy to the cold universe in the form of electromagnetic waves. On the other hand, the surface object will absorb the radiation energy from the sun and reflect sunlight as much as possible within the solar spectrum range to reduce the absorbed energy. Even during the day, the heat loss caused by releasing energy into the universe is greater than the energy absorbed from the sun, so that the temperature of the object is lower than the ambient temperature, realizing refrigeration. Researchers have developed and designed various structures and forms of materials, such as metamaterials, metal reflective layers, double-layer coatings, fabrics, etc. to achieve radiative cooling. However, most of these materials and means have problems such as high price, complex production, inability to be used in large areas, and poor practicability. In contrast, radiative cooling coatings have received extensive attention from researchers due to their low price, simple production, and wide application scenarios, especially in the field of building surface cooling.

[0004] The current radiative cooling coatings have problems such as excessive proportion of spectral fillers, large thickness, and high cost. For example, Chinese Patent Application CN114656851A discloses a radiative cooling coating with complementary spectral bands, and its disadvantage is that hydrophobic materials such as polytetrafluoroethylene and fluorinated polyethylene are used, resulting in high costs. CN117567894A discloses a high-emissivity rare-earth-based radiative cooling coating, and its disadvantages are excessive proportion of spectral fillers and only 80% reflectivity in the visible light band, resulting in poor refrigeration effect. CN115851126A discloses a radiative cooling coating, and its disadvantages are that cage-type polyhedral oligomeric silsesquioxane is used as an additive, resulting in high costs and complex preparation processes.

[0005] For radiative cooling coatings, an excessive proportion of fillers will greatly affect the basic performance of the coating. In order to improve the optical performance of the coating, a large amount of fillers are often added and the thickness of the coating is increased, which not only increases the cost of the coating but also is not conducive to construction and long-term use.

[0006] In summary, it is crucial to develop a radiative cooling coating with a suitable filler proportion, low cost, convenient production, and good refrigeration effect. Summary of the Invention

[0007] This invention application solves the problems in the prior art. When using fillers with a single scattering mechanism, such as when using high refractive index fillers alone, as the proportion of the filler increases, due to optical congestion caused by near-field coupling, the scattering efficiency of the filler is greatly reduced, thus greatly increasing the demand for the filler. When using hollow silica microspheres alone, due to their low refractive index, a higher filler proportion and a larger thickness are required to meet the spectral requirements.

[0008] In view of the above problems existing in the prior art, this invention provides a radiative cooling coating with a dual scattering mechanism and its preparation method. By compounding hollow silica microspheres with high refractive index fillers and combining backscattering and surface scattering, the scattering efficiency of the filler is greatly improved, which can not only reduce the proportion of the filler but also reduce the thickness of the coating, providing a feasible solution for the use of radiative cooling coatings.

[0009] The technical solution of this invention is as follows:

[0010] The first object of this invention is to provide a radiative cooling coating, and the raw materials and their weight parts are as follows:

[0011]

[0012] The high refractive index filler is one or more of titanium dioxide, zirconia, zinc oxide, and barium sulfate.

[0013] In one embodiment of this invention, the refractive index of the high refractive index filler is 1.6 - 2.7.

[0014] In one embodiment of this invention, the particle size of the high refractive index filler is 500 - 600 nm.

[0015] In one embodiment of this invention, the model of titanium dioxide is R216.

[0016] In one embodiment of this invention, the hollow silica microspheres are prepared by the hard template method, and their particle size is 300 - 1000 nm.

[0017] In one embodiment of this invention, the epoxy resin is one or more of E51, E20, and E12.

[0018] In one embodiment of this invention, the epoxy resin is E51.

[0019] In one embodiment of this invention, the reactive diluent is one or more of allyl glycidyl ether, n-butyl glycidyl ether, methyl methacrylate glycidyl ether, and ethylene glycol diglycidyl ether.

[0020] In one embodiment of the present invention, the acid anhydride curing agent is one or more of methylhexahydrophthalic anhydride, maleic anhydride, trimellitic anhydride, and pyromellitic dianhydride.

[0021] In one embodiment of the present invention, the dispersant is one or more of BYK-9077, BYK-1165, BYK-W 903, and BYK-151.

[0022] Preferably, the dispersant is BYK-151.

[0023] In one embodiment of the present invention, the leveling agent is one or more of BYK-347, BYK-333, and QM-3300.

[0024] Preferably, the leveling agent is QM-3300.

[0025] In one embodiment of the present invention, the curing accelerator is 1,8-diazabicyclo[5,4,0]undec-7-ene.

[0026] In one embodiment of the present invention, the solvent is one or more of absolute ethanol, ethyl acetate, and propylene glycol monomethyl ether.

[0027] Preferably, the solvent is absolute ethanol.

[0028] In one embodiment of the present invention, the molar ratio of epoxy groups to acid anhydride in the coating formulation is 1:0.8 - 1.2.

[0029] The second object of the present invention is to provide a preparation method of the above-mentioned radiative cooling coating, including the following steps: the raw materials are in parts by weight;

[0030] S1. Mix 0.2 - 0.3 parts of leveling agent, 1.1 - 1.5 parts of dispersant, 15 - 20 parts of high refractive index filler, 25 - 30 parts of hollow silica microspheres, and 15 - 30 parts of solvent, and stir evenly to obtain a mixed solution;

[0031] S2. Add 18 - 21 parts of epoxy resin, 8 - 9 parts of reactive diluent, 22 - 23 parts of acid anhydride curing agent, and 0.3 - 0.5 parts of curing accelerator to the mixed solution obtained in step S1, and stir evenly to obtain the radiative cooling coating.

[0032] The third object of the present invention is to provide a coating prepared from the above-mentioned radiative cooling coating. By means of roller coating, brushing, or spraying, the radiative cooling coating is evenly coated on the construction working surface. After drying or air-drying the solvent, heat curing is carried out to obtain the coating.

[0033] In one embodiment of the present invention, the conditions for thermal curing are: curing at 75 - 85 °C for 1 - 3 h, curing at 95 - 105 °C for 1 - 3 h, curing at 115 - 125 °C for 1 - 3 h, and curing at 155 - 165 °C for 1 - 3 h.

[0034] In one embodiment of the present invention, the conditions for thermal curing are: curing at 80 °C for 2 h, curing at 100 °C for 2 h, curing at 120 °C for 2 h, and curing at 160 °C for 2 h.

[0035] The beneficial technical effects of the present invention are as follows:

[0036] The present invention application uses hollow silica microspheres in combination with high refractive index fillers. The hollow structure of the hollow silica microspheres enables strong backscattering, and the high refractive index fillers enable strong surface scattering of the coating. The two mechanisms work synergistically, greatly improving the scattering efficiency of the fillers, reducing both the filler loading and the coating thickness, thus reducing costs. At the same time, it also has excellent spectral properties; the average reflectivity of the prepared radiative cooling coating can reach 93.7%, and the average emissivity can reach 98.1%.

[0037] The hollow silica microspheres used in the present invention are synthesized by the hard template method, and the particle size is controlled within 300 - 1000 nm; the particle sizes of titanium dioxide, zirconia, zinc oxide, or barium sulfate are 500 - 600 nm. The particle sizes of the two fillers are comparable to the wavelengths of the solar spectrum, generating strong Mie scattering and having a high reflectivity in the visible and near-infrared bands.

[0038] The coating prepared by the present invention does not require external energy input and directly releases heat in the form of electromagnetic waves into space. It can not only meet the cooling demand in the form of carbon neutrality but also meet the sustainable development requirements of carbon peak. It is a green and environmentally friendly cooling method and has high practical application value. Description of the Drawings

[0039] Figure 1 Spectral performance diagram of the radiative cooling coating prepared in Example 1.

[0040] Figure 2 Spectral performance diagrams of the radiative cooling coatings prepared in Example 2 and Comparative Examples 1 - 3.

[0041] Figure 3 Spectral performance diagrams of the radiative cooling coatings with different thicknesses prepared in Example 1.

[0042] Figure 4 Color difference change diagram during the ultraviolet aging test of the radiative cooling coating prepared in Example 1.

[0043] Figure 5 Outdoor cooling test diagram of the radiative cooling coating prepared in Example 1.

[0044] Figure 6 It is the actual application cooling test diagram of the radiation cooling coating prepared in Example 1. Specific implementation mode

[0045] The present invention will be specifically described below in conjunction with the accompanying drawings and embodiments.

[0046] In the following embodiments, the curing accelerator is 1,8-diazabicyclo[5,4,0]undec-7-ene.

[0047] Example 1

[0048] A preparation method of a radiation cooling coating, comprising the following steps:

[0049] S1. Mix 0.2 part of a leveling agent (QM-3300), 1.3 parts of a dispersant (BYK-151), 15 parts of titanium dioxide (R216) with an average particle size of 500 nm, 30 parts of hollow silica microspheres with an average particle size of 300 nm, and 20 parts of absolute ethanol, and stir evenly to obtain a mixed solution.

[0050] S2. Add 18 parts of an epoxy resin (E51), 8 parts of an active diluent allyl glycidyl ether, 0.5 part of a curing accelerator, and 22 parts of an acid anhydride curing agent methyl hexahydrophthalic anhydride to the mixed solution obtained in S1, and stir evenly to obtain a coating.

[0051] The coating obtained in S2 is evenly coated on an iron plate by brushing, and after drying, it is thermally cured. After curing at 80°C for 2 h, the temperature is slowly raised to 100°C and cured for 2 h, then slowly raised to 120°C and cured for 2 h, and finally slowly raised to 160°C and cured for 2 h. The thickness of the coating after curing is 400 μm.

[0052] Example 2

[0053] A preparation method of a radiation cooling coating, comprising the following steps:

[0054] S1. Mix 0.3 part of a leveling agent (QM-3300), 1.2 parts of a dispersant (BYK-151), 20 parts of titanium dioxide (R216) with an average particle size of 500 nm, 25 parts of hollow silica microspheres with an average particle size of 500 nm, and 20 parts of absolute ethanol, and stir evenly to obtain a mixed solution.

[0055] S2. Add 18 parts of an epoxy resin (E51), 8 parts of an active diluent allyl glycidyl ether, 0.5 part of a curing accelerator, and 22 parts of an acid anhydride curing agent methyl hexahydrophthalic anhydride to the mixed solution obtained in S1, and stir evenly to obtain a coating.

[0056] By brushing, the coating obtained in S2 was evenly coated on an iron plate. After drying, it was thermally cured. After curing at 80 °C for 2 h, the temperature was slowly raised to 100 °C and cured for 2 h, then slowly raised to 120 °C and cured for 2 h, and finally slowly raised to 160 °C and cured for 2 h. The thickness of the coating after curing was 400 μm.

[0057] Example 3

[0058] A preparation method of a radiative cooling coating, comprising the following steps:

[0059] S1. Mix 0.3 parts of a leveling agent (QM-3300), 1.2 parts of a dispersant (BYK-151), 15 parts of barium sulfate (ZT-NB97) with an average particle size of 600 nm, 30 parts of hollow silica microspheres with an average particle size of 500 nm, and 20 parts of absolute ethanol, and stir evenly to obtain a mixed solution.

[0060] S2. Add 18 parts of epoxy resin (E51), 8 parts of an active diluent allyl glycidyl ether, 0.5 part of a curing accelerator, and 22 parts of an acid anhydride curing agent methylhexahydrophthalic anhydride to the mixed solution obtained in S1, and stir evenly to obtain a coating.

[0061] By brushing, the coating obtained in S2 was evenly coated on an iron plate. After drying, it was thermally cured. After curing at 80 °C for 2 h, the temperature was slowly raised to 100 °C and cured for 2 h, then slowly raised to 120 °C and cured for 2 h, and finally slowly raised to 160 °C and cured for 2 h. The thickness of the coating after curing was 400 μm.

[0062] Example 4

[0063] A preparation method of a radiative cooling coating, comprising the following steps:

[0064] S1. Mix 0.3 parts of a leveling agent (QM-3300), 1.2 parts of a dispersant (BYK-151), 20 parts of barium sulfate (ZT-NB97) with an average particle size of 500 nm, 25 parts of hollow silica microspheres with an average particle size of 600 nm, and 20 parts of absolute ethanol, and stir evenly to obtain a mixed solution.

[0065] S2. Add 18 parts of epoxy resin (E51), 8 parts of an active diluent allyl glycidyl ether, 0.5 part of a curing accelerator, and 22 parts of an acid anhydride curing agent methylhexahydrophthalic anhydride to the mixed solution obtained in S1, and stir evenly to obtain a coating.

[0066] By brushing, the coating obtained in S2 was evenly coated on an iron plate. After drying, it was thermally cured. After curing at 80 °C for 2 h, the temperature was slowly raised to 100 °C and cured for 2 h, then slowly raised to 120 °C and cured for 2 h, and finally slowly raised to 160 °C and cured for 2 h. The thickness of the coating after curing was 400 μm.

[0067] Comparative Example 1

[0068] A preparation method of a radiative cooling coating includes the following steps:

[0069] S1. Mix 0.3 part of a leveling agent (QM-3300), 1.2 parts of a dispersant (BYK-151), 45 parts of hollow silica microspheres with an average particle size of 500 nm, and 20 parts of absolute ethanol, and stir evenly to obtain a mixed solution.

[0070] S2. Add 18 parts of an epoxy resin (E51), 8 parts of an active diluent allyl glycidyl ether, 0.5 part of a curing accelerator, and 22 parts of an acid anhydride curing agent methyl hexahydrophthalic anhydride to the mixed solution obtained in S1, and stir evenly to obtain a coating.

[0071] By brushing, the coating obtained in S2 was evenly coated on an iron plate. After drying, it was thermally cured. After curing at 80 °C for 2 h, the temperature was slowly raised to 100 °C and cured for 2 h, then slowly raised to 120 °C and cured for 2 h, and finally slowly raised to 160 °C and cured for 2 h. The thickness of the coating after curing was 400 μm.

[0072] Comparative Example 2

[0073] A preparation method of a radiative cooling coating includes the following steps:

[0074] S1. Mix 0.3 part of a leveling agent (QM-3300), 1.2 parts of a dispersant (BYK-151), 35 parts of titanium dioxide (R216) with an average particle size of 550 nm, 10 parts of hollow silica microspheres with an average particle size of 700 nm, and 25 parts of ethanol, and stir evenly to obtain a mixed solution.

[0075] S2. Add 18 parts of an epoxy resin (E51), 8 parts of an active diluent allyl glycidyl ether, 0.5 part of a curing accelerator, and 22 parts of an acid anhydride curing agent methyl hexahydrophthalic anhydride to the mixed solution obtained in S1, and stir evenly to obtain a coating.

[0076] By brushing, the coating obtained in S2 was evenly coated on an iron plate. After drying, it was thermally cured. After curing at 80 °C for 2 h, the temperature was slowly raised to 100 °C and cured for 2 h, then slowly raised to 120 °C and cured for 2 h, and finally slowly raised to 160 °C and cured for 2 h. The thickness of the coating after curing was 400 μm.

[0077] Comparative Example 3

[0078] A preparation method of a radiative cooling coating, comprising the following steps:

[0079] S1. Mix 0.3 part of a leveling agent (QM-3300), 1.2 parts of a dispersant (BYK-151), 15 parts of barium sulfate with an average particle size of 10 μm (ZT-NB97), 30 parts of hollow silica microspheres with an average particle size of 2 μm, and 30 parts of ethanol, and stir evenly to obtain a mixed solution.

[0080] S2. Add 18 parts of an epoxy resin (E51), 8 parts of an active diluent allyl glycidyl ether, 0.5 part of a curing accelerator, and 22 parts of an acid anhydride curing agent methyl hexahydrophthalic anhydride to the mixed solution obtained in S1, and stir evenly to obtain a coating.

[0081] By means of brushing, the coating obtained in S2 is evenly coated on an iron plate, and after drying, it is thermally cured. After curing at 80 °C for 2 h, it is slowly heated to 100 °C and cured for 2 h, then slowly heated to 120 °C and cured for 2 h, and finally slowly heated to 160 °C and cured for 2 h. The thickness of the coating after curing is 400 μm.

[0082] The types and dosages of the raw materials in Comparative Examples 1-3 and Examples 1-4 are shown in Table 1.

[0083] Table 1

[0084]

[0085]

[0086] Test Example:

[0087] (1) Spectral performance

[0088] The spectral performance requirements of the radiative cooling coating mainly include: having a high emissivity in the solar spectrum (0.3-2.5 μm band) to reduce the absorption of solar radiation; maintaining a relatively high emissivity in the atmospheric window spectrum (8-13 μm) to release heat to outer space. The reflectivity and emissivity of the coating are respectively tested by a UV-Vis-NIR spectrometer and a Fourier transform infrared spectrometer with a gold integrating sphere accessory.

[0089] Figure 1 Figure is the spectral performance diagram of the radiative cooling coating prepared in Example 1. As can be seen from the figure, the prepared multi-filler compounded radiative cooling coating has excellent spectral performance. Through calculation, the average reflectivity of the coating can reach 93.7%, and the average emissivity can reach 98.1%. Figure 2 Figure is the solar spectrum characteristic diagram of the radiative cooling coatings of Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0090] Comparative Example 1 used pure hollow silica microspheres with a particle size of 500 nm as the filler, and at the same thickness, the reflectivity was low. This is because it is difficult to completely reflect the energy in the solar band only relying on the backscattering matrix; the filler in Comparative Example 2 was 35 parts of titanium dioxide and 10 parts of hollow silica microspheres, and its spectral performance was lower than that of Example 2. The reason is that at this time, there is too much high-refractive-index filler, which has exceeded the critical value of optical congestion, and there is less backscattering matrix, resulting in poor comprehensive scattering effect; the filler in Comparative Example 3 was 10 μm high-refractive-index filler and hollow silica microspheres with a particle size of 2 μm, and its scattering effect was lower than that of Example 2. This is because the Mie scattering of the 10 μm-sized scatterer is weak in the 0.3-2.5 μm band, while the filler size in Example 2 is 500 nm, which is comparable to the visible light wavelength, and the scattering effect is good.

[0091] Combining Comparative Examples 1-3 and Example 2, it can be seen that by compounding hollow silica microspheres with strong backscattering and high-refractive-index fillers with surface scattering, and at the same time enhancing the Mie scattering efficiency by controlling the filler size within the range comparable to the solar spectral wavelength, a radiative cooling coating with excellent spectral performance can be prepared.

[0092] (2) Basic properties of the coating

[0093] The thickness, adhesion, and environmental stability of the radiative cooling coating were tested. According to the preparation method of Example 1, coatings with a coating thickness of 200-500 nm were prepared, and their spectral properties were tested. The results are as Figure 3 shown. The prepared coatings showed excellent optical properties at 400 μm, avoiding the problem of excessive coating thickness that may be caused by pursuing high optical performance. According to the methods of Example 1, Example 2, and Example 3, coatings with the same thickness were prepared on iron plates, wooden boards, and concrete boards respectively. According to the cross-cut adhesion test standard of GB / T 9286-2021, all coatings reached level 0, indicating that the prepared coatings had excellent adhesion on different substrates. According to the ASTM D4587 test standard, Example 1 was subjected to UV aging test in a QUV ultraviolet aging test chamber. The results are as Figure 4 shown. In the 400-hour UV aging test, the color difference of the coating was small and tended to be stable, indicating good environmental stability.

[0094] (3) Cooling test

[0095] The radiative cooling coating realizes cooling by reflecting solar radiation and releasing radiative energy through the atmospheric window. After having excellent spectral properties, Example 1 was brushed on a concrete board and compared with the uncoated concrete board in an outdoor environment. Outdoor environment: sunny and hot. Figure 3Outdoor cooling test diagram for Example 1. As shown in the figure, the temperature of the concrete slab without the coating is always higher than the air temperature, while the temperature of the concrete slab coated with Example 1 is always 3-4 °C lower than the surrounding air temperature. Even in a very hot summer, the coating shows excellent radiative cooling effect.

[0096] Furthermore, Example 1 was applied to the actual situation. Specifically, Example 1 was sprayed on an iron can, and the iron can with and without spraying were placed in the same environment for temperature testing. Outdoor environment: sunny and hot. The results are as Figure 4 shown. The temperature of the unsprayed iron can is always higher than the ambient temperature, while the temperature of the iron can sprayed with Example 1 is always about 5 °C lower than the ambient temperature, achieving radiative cooling.

[0097] The radiative cooling coating with multi-filler compounding provided by this invention application has the characteristics of low cost, easy production and good cooling effect, and has great application potential.

[0098] The embodiments provided above are not intended to limit the scope covered by this invention, and the described steps are not intended to limit their execution order. Obvious improvements made by those skilled in the art to this invention in combination with the existing common general knowledge also fall within the protection scope defined by the claims of this invention.

Claims

1. A radiant cooling coating, characterized in that: The raw materials and the weight proportions of each raw material are as follows: The high refractive index filler is one or more of titanium dioxide, zirconium oxide, zinc oxide and barium sulfate.

2. The radiant cooling coating according to claim 1, characterized in that: The refractive index of the high refractive index filler is 1.6-2.

7.

3. The radiant cooling coating according to claim 1, characterized in that: The particle size of the high refractive index filler is 500-600nm.

4. The radiant cooling coating according to claim 1, characterized in that: Hollow silica microspheres are prepared by a hard template method and have a particle size of 300-1000 nm.

5. The radiant cooling coating according to claim 1, characterized in that: The epoxy resin is one or more of E51, E20, and E12; the active diluent is one or more of allyl glycidyl ether, n-butyl glycidyl ether, methacrylate glycidyl ether, and ethylene glycol diglycidyl ether; and the acid anhydride curing agent is one or more of methylhexahydrophthalic anhydride, maleic anhydride, trimellitic anhydride, and pyromellitic dianhydride.

6. The radiation cooling coating according to claim 1, characterized in that: The dispersant is one or more of BYK-9077, BYK-1165, BYK-W 903, and BYK-151; the leveling agent is one or more of BYK-347, BYK-333, and QM-3300; the curing accelerator is 1,8-diazabicyclo[5,4,0]undec-7-ene; and the solvent is one or more of anhydrous ethanol, ethyl acetate, and propylene glycol methyl ether.

7. The radiant cooling coating according to claim 1, characterized in that: The molar ratio of epoxy group to anhydride in the coating formula is 1:0.8-1.

2.

8. A method for preparing the radiant cooling coating according to claim 1, characterized in that: The method comprises the following steps: each raw material is measured by weight; S1, 0.2-0.3 parts of a leveling agent, 1.1-1.5 parts of a dispersant, 15-20 parts of a high refractive index filler, 25-30 parts of hollow silica microspheres and 15-30 parts of a solvent are mixed and stirred to obtain a mixed solution; S2. Add 18-21 parts of epoxy resin, 8-9 parts of reactive diluent, 22-23 parts of acid anhydride curing agent, and 0.3-0.5 parts of curing accelerator to the mixed solution obtained in step S1, and stir evenly to obtain the radiant cooling coating.

9. A coating prepared by the radiant cooling coating according to claim 1, characterized in that: The radiation cooling coating is evenly applied to the construction surface by rolling, brushing or spraying, and after drying or airing the solvent, heat curing is performed to obtain the coating.

10. The coating according to claim 9, characterized in that The conditions for thermal curing are: curing at 75-85°C for 1-3h, curing at 95-105°C for 1-3h, curing at 115-125°C for 1-3h, and curing at 155-165°C for 1-3h.

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