Photo-thermal dual-curing wave-absorbing coating as well as preparation method and application thereof

Abstract

The invention discloses a photo-thermal dual-curing wave-absorbing coating as well as a preparation method and application thereof, and particularly relates to the field of coatings. The preparation method comprises the following steps: mixing polyurethane acrylate, epoxy acrylate, isocyanate and a reactive diluent to obtain slurry A; and adding a photoinitiator, an absorbent and an auxiliary agent into the slurry A to obtain the photo-thermal dual-cured wave-absorbing coating. Spraying the photo-thermal dual-cured wave-absorbing coating on the surface of a base material; wherein after the coating with the preset thickness is sprayed every time, ultraviolet curing is conducted on the surface of the coating; and the sprayed base material is heated and cured. Through coordination of the components, combination of two mechanisms of ultraviolet curing and thermocuring is realized, so that a wave-absorbing coating formed by the coating is high in curing speed and good in mechanical property, and emergency repair construction requirements of the wave-absorbing coating can be met.

Description

Technical Field

[0001] The present application relates to the field of coatings, and in particular to a light-thermal dual-curing microwave-absorbing coating and a preparation method and application thereof. Background Art

[0002] With the continuous advancement of modern detection methods, stealth performance has become increasingly important for detection equipment. Absorbing coatings can be applied to the surface of various equipment to absorb and lose incident electromagnetic waves, reducing the probability of detection equipment being discovered, and are therefore widely studied and applied.

[0003] At present, absorbing coatings are generally cured at room temperature or heat-cured. Although the resulting coating has good mechanical properties, the curing speed is slow and it is difficult to meet the needs of emergency repair construction. Photocurable resin is a commonly used fast-curing coating binder. The curing process is triggered by ultraviolet light or visible light, and the curing time can be shortened to a few minutes or even tens of seconds. However, due to the fast curing speed of photocurable resin, the internal stress of the coating cannot be released in time, resulting in the absorbing coating being hard and brittle, and difficult to meet the mechanical performance requirements. Summary of the invention

[0004] The main purpose of the present application is to provide a light-thermal dual-curing absorbing coating and a preparation method and application thereof, aiming to solve the problem that the absorbing coating in the prior art is difficult to simultaneously meet the requirements of rapid curing and strong mechanical properties for emergency repair construction.

[0005] To achieve the above-mentioned purpose, the present application provides a light-heat dual-curing absorbing coating, the raw materials of which include the following components in terms of mass fraction: 10%-14% polyurethane acrylate, 2%-4% epoxy acrylate, 3%-7% isocyanate, 3%-7% photoinitiator, 2%-6% active diluent, 65%-75% absorbent, and 0.5%-1.5% additive.

[0006] Optionally, reactive diluents include β-hydroxyethyl methacrylate and tripropylene glycol diacrylate.

[0007] Optionally, the mass ratio of β-hydroxyethyl methacrylate to tripropylene glycol diacrylate is 1:1-3.

[0008] Optionally, the absorbent includes iron-silicon-aluminum alloy, iron-silicon-chromium alloy, iron-silicon alloy, carbonyl iron, carbonyl nickel, iron-aluminum-boron alloy, iron-nickel-molybdenum alloy, iron-chromium-nickel alloy, iron-nickel alloy or iron-cobalt-chromium alloy.

[0009] Optionally, the epoxy acrylate includes bisphenol A epoxy acrylate or novolac epoxy acrylate.

[0010] Optionally, the polyurethane acrylate is hydroxy polyurethane acrylate, wherein the mass of hydroxyl groups accounts for 2%-4% of the solid content.

[0011] Optionally, the isocyanate includes one or a combination of isophorone diisocyanate, toluene diisocyanate and diphenylmethane diisocyanate; the auxiliary agent includes a defoamer and a dispersant; the photoinitiator includes a long-wave photoinitiator with an absorption wavelength of 350nm-420nm, and a short-wave photoinitiator with an absorption wavelength of 260nm-320nm.

[0012] Optionally, the mass ratio of the long-wave photoinitiator to the short-wave photoinitiator is 1:1-3; the mass ratio of the defoamer to the dispersant is 1:1-3.

[0013] To achieve the above objectives, the present application also provides a method for preparing the above-mentioned photothermal dual-curing absorbing coating, comprising: mixing polyurethane acrylate, epoxy acrylate, isocyanate and reactive diluent to obtain slurry A; adding a photoinitiator, an absorber and an auxiliary agent to slurry A to obtain the photothermal dual-curing absorbing coating.

[0014] To achieve the above-mentioned purpose, the present application also provides an application of the above-mentioned photothermal dual-curing absorbing coating, including: spraying the photothermal dual-curing absorbing coating on the surface of a substrate; wherein, after each spraying of a coating of a preset thickness, the coating surface is ultraviolet-cured; and the sprayed substrate is placed at 70-90°C for thermal curing for 2-4 hours.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The light-heat dual-curing radar-absorbing coating of the present invention realizes the combination of ultraviolet light curing and thermal curing mechanisms through the coordination between the components, so that the radar-absorbing coating formed by the coating has a fast curing speed and good mechanical properties, and can meet the emergency repair construction requirements of the radar-absorbing coating; polyurethane acrylate and epoxy acrylate contain unsaturated double bonds, which can react with active free radicals generated by photoinitiators under ultraviolet light to polymerize and achieve rapid curing; hydroxyl polyurethane acrylate contains a large number of active hydroxyl groups, which can undergo condensation reaction with isocyanate curing agents when heated, and continue to improve the cross-linking degree of the resin after light curing, thereby improving the mechanical properties of the coating. The polyurethane acrylate, epoxy acrylate and isocyanate curing agent form a resin binder with a dual curing mechanism; epoxy acrylate contains groups such as epoxy and hydroxyl groups, which can form chemical bonds with the hydroxyl and amino groups on the surface of the substrate, thereby strengthening the adhesion performance of the coating and the substrate; the active diluent can not only adjust the viscosity of the system, but also contains active groups that can participate in the polymerization reaction to improve the cross-linking degree of the resin; the auxiliary agent is a composite auxiliary agent composed of a defoamer and a dispersant, among which the defoamer can eliminate bubbles inside the coating and improve the film-forming quality; the dispersant can prevent the absorbent from agglomerating and improve the uniformity of the mixing of the absorbent and the resin binder.

[0017] The application of the photothermal dual-curing absorbing coating of the present invention allows the coating to form a film quickly through ultraviolet light curing, and obtains higher initial mechanical properties in a short period of time; the coating is then heated to allow the active groups in the resin chain segments to continue the cross-linking reaction until it is completely cured, which further improves the mechanical properties of the coating and greatly shortens the overall curing time of the coating.

[0018] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of this application clearer, the technical solution in this application is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] The first embodiment of the present invention provides a light-heat dual-curing absorbing coating, the raw materials of which include the following components in terms of mass fraction: 10%-14% polyurethane acrylate, 2%-4% epoxy acrylate, 3%-7% isocyanate, 3%-7% photoinitiator, 2%-6% active diluent, 65%-75% absorbent, and 0.5%-1.5% additive.

[0021] Among them, the active diluent includes β-hydroxyethyl methacrylate (HEMA) and tripropylene glycol diacrylate (TPGDA); it contains active acrylate functional groups, can participate in the photocuring reaction, and improve the mechanical properties of the coating. The absorbent includes iron silicon aluminum alloy, iron silicon chromium alloy, iron silicon alloy, carbonyl iron, carbonyl nickel, iron aluminum boron alloy, iron nickel molybdenum alloy, iron chromium nickel alloy, iron nickel alloy or iron cobalt chromium alloy. Epoxy acrylate includes bisphenol A epoxy acrylate or phenolic epoxy acrylate. Polyurethane acrylate is hydroxy polyurethane acrylate, in which the mass of hydroxyl accounts for 2%-4% of the solid content; isocyanate includes one or more of isophorone diisocyanate (IPDI), toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). The auxiliary agent includes a defoamer and a dispersant; the photoinitiator is a free radical photoinitiator. The photoinitiator includes a long-wave photoinitiator with an absorption wavelength of 350nm-420nm and a short-wave photoinitiator with an absorption wavelength of 260nm-320nm.

[0022] It can be understood that the solid content in this embodiment refers to the mass percentage of the remaining part of the coating or resin after drying.

[0023] Furthermore, the mass ratio of β-hydroxyethyl methacrylate to tripropylene glycol diacrylate is 1:1-3. The mass ratio of long-wave photoinitiator to short-wave photoinitiator is 1:1-3. The mass ratio of defoamer to dispersant is 1:1-3.

[0024] Exemplarily, the defoamer is polydimethylsiloxane, the dispersant is polyacrylamide, the hydroxy polyurethane acrylate is UV-3076 or UV-3609, the bisphenol A epoxy acrylate can be EBECRYL 3701, the phenolic epoxy acrylate can be EBECRYL 9636, the long-wave photoinitiator is 1-hydroxycyclohexyl phenyl ketone, also known as photoinitiator 184, and the short-wave photoinitiator is phenyl bis 2,4,6-trimethylbenzoylphosphine oxide, also known as photoinitiator 819; the absorber has a spherical or flaky morphology with a particle size of 3-40 μm.

[0025] The second embodiment of the present invention provides a method for preparing the above-mentioned light-thermal dual-curing radar absorbing coating, which specifically includes the following steps:

[0026] Step S1, mixing polyurethane acrylate, epoxy acrylate, isocyanate and reactive diluent to obtain slurry A;

[0027] Specifically, polyurethane acrylate, epoxy acrylate, isocyanate, reactive diluent, photoinitiator, absorbent and additives are weighed according to the above mass fractions, polyurethane acrylate, epoxy acrylate, isocyanate and reactive diluent are placed in a paint mixing cup and mixed, manually stirred for 4-6 minutes, and then dispersed with a mechanical stirrer at a speed of 800-1200 rpm for 8-12 minutes to obtain slurry A.

[0028] In this embodiment, polyurethane acrylate and epoxy acrylate contain unsaturated double bonds, which can react with the active free radicals generated by the photoinitiator under ultraviolet light to produce a polymerization reaction and achieve rapid curing; further, the hydroxyl groups contained in hydroxy polyurethane acrylate can undergo a condensation reaction with the isocyanate curing agent when heated, thereby continuing to improve the cross-linking degree of the resin after light curing, thereby improving the mechanical properties of the coating. Epoxy acrylate also contains unsaturated double bonds that can undergo ultraviolet light curing, and also contains groups such as epoxy and hydroxyl groups, which can form chemical bonds with hydroxyl and amino groups on the surface of metal substrates such as iron and aluminum, thereby strengthening the adhesion performance of the coating to the substrate. The active diluent can not only adjust the viscosity of the system, but also contains active groups that can participate in the polymerization reaction to increase the cross-linking degree of the resin, thereby improving the mechanical properties of the coating.

[0029] Step S2, adding a photoinitiator, an absorber and an auxiliary agent into slurry A to obtain a light-thermal dual-curing absorbing coating.

[0030] Specifically, the photoinitiator, absorber and auxiliary agent are added to slurry A according to the above mass fractions, manually stirred for 4-6 minutes, and then dispersed at a speed of 1000-1200 rpm using a mechanical stirrer for 20-35 minutes to obtain a light-thermal dual-cured absorbing coating.

[0031] In this embodiment, the photoinitiator is excited and generates active free radicals when exposed to ultraviolet light, which triggers the polymerization reaction of unsaturated double bonds and realizes the rapid photocuring process of the resin. Long-wave photoinitiators have strong penetrating power and can penetrate deep into the coating to achieve curing; short-wave photoinitiators have higher photon energy but weaker penetrating power, and are suitable for rapid curing on the surface of the coating; the compounding of the two photoinitiators effectively improves the photocuring speed of the absorbing coating. The absorbent can provide electromagnetic wave loss performance. The absorbent of this embodiment can be a magnetic loss type absorbent with strong wave absorbing performance. The defoaming agent can eliminate bubbles inside the coating and improve the film quality. The dispersant can prevent the absorbent from agglomerating and improve the uniformity of the absorbent and the resin binder.

[0032] The third embodiment of the present invention provides an application of the above-mentioned photothermal dual-curing absorbing coating, which is characterized by comprising: spraying the photothermal dual-curing absorbing coating on the surface of a metal substrate; wherein, after each spraying of a coating of a preset thickness, the coating surface is ultraviolet-cured; and the substrate after spraying is placed at 70-90°C for 2-4 hours.

[0033] Example 1

[0034] The types and proportions of raw materials are shown in Table 1 below.

[0035] Table 1 Example 1 Raw material components

[0036]

[0037] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0038] According to the mass percentage in Table 1, polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed respectively, polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 5 minutes, and then dispersed at a speed of 1000 rpm for 10 minutes using a mechanical stirrer to obtain slurry A; photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 5 minutes, and then dispersed at a speed of 1200 rpm for 25 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0039] Example 2

[0040] The types and proportions of raw materials are shown in Table 2 below.

[0041] Table 2 Example 2 Raw material components

[0042]

[0043] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0044] Polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed respectively according to the mass percentage in Table 2, polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 5 minutes, and then dispersed at a speed of 1000 rpm for 12 minutes using a mechanical stirrer to obtain slurry A; photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 5 minutes, and then dispersed at a speed of 1100 rpm for 30 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0045] Example 3

[0046] This embodiment provides a light-heat dual-curing radar absorbing coating, and the types and proportions of raw materials are shown in Table 3 below.

[0047] Table 3 Example 3 Raw material components

[0048]

[0049]

[0050] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0051] Polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed according to the mass percentage in Table 3, and polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 4 minutes, and then dispersed at a speed of 1200 rpm for 12 minutes using a mechanical stirrer to obtain slurry A. Photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 6 minutes, and then dispersed at a speed of 1200 rpm for 30 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0052] Example 4

[0053] This embodiment provides a light-heat dual-curing radar absorbing coating, and the types and proportions of raw materials are shown in Table 4 below.

[0054] Table 4 Example 4 Raw material components

[0055]

[0056]

[0057] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0058] Polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed according to the mass percentage in Table 4, polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 5 minutes, and then dispersed at a speed of 900 rpm for 10 minutes using a mechanical stirrer to obtain slurry A; photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 4 minutes, and then dispersed at a speed of 1000 rpm for 25 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0059] Example 5

[0060] This embodiment provides a light-heat dual-curing radar absorbing coating, and the types and proportions of raw materials are shown in Table 5 below.

[0061] Table 5 Example 5 Raw material components

[0062]

[0063]

[0064] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0065] Polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed according to the mass percentage in Table 5, and polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 6 minutes, and then dispersed at a speed of 800 rpm for 10 minutes using a mechanical stirrer to obtain slurry A. Photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 6 minutes, and then dispersed at a speed of 1000 rpm for 30 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0066] Example 6

[0067] This embodiment provides a light-heat dual-curing radar absorbing coating, and the types and proportions of raw materials are shown in Table 6 below.

[0068] Table 6 Example 6 Raw material components

[0069]

[0070]

[0071] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0072] Polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed according to the mass percentage in Table 6, and polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 5 minutes, and then dispersed at a speed of 800 rpm for 12 minutes using a mechanical stirrer to obtain slurry A. Photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 4 minutes, and then dispersed at a speed of 1200 rpm using a mechanical stirrer for 30 minutes to obtain a light-thermal dual-cured absorbing coating.

[0073] Example 7

[0074] This embodiment provides a light-heat dual-curing radar absorbing coating, and the types and proportions of raw materials are shown in Table 7 below.

[0075] Table 7 Example 7 Raw material components

[0076]

[0077] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0078] Polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed according to the mass percentage in Table 7, and polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 5 minutes, and then dispersed at a speed of 1100 rpm for 9 minutes using a mechanical stirrer to obtain slurry A. Photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 5 minutes, and then dispersed at a speed of 1100 rpm for 30 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0079] Example 8

[0080] This embodiment provides a light-heat dual-curing radar absorbing coating, and the types and proportions of raw materials are shown in Table 8 below.

[0081] Table 8 Example 8 Raw material components

[0082]

[0083] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0084] Polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed according to the mass percentage in Table 8, and polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 5 minutes, and then dispersed at a speed of 1000 rpm for 9 minutes using a mechanical stirrer to obtain slurry A. Photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 4 minutes, and then dispersed at a speed of 1200 rpm for 30 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0085] Example 9

[0086] This embodiment provides a light-heat dual-curing radar absorbing coating, and the types and proportions of raw materials are shown in Table 9 below.

[0087] Table 9 Example 9 Raw material components

[0088]

[0089] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0090] Polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed according to the mass percentage in Table 9, and polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 6 minutes, and then dispersed at a speed of 800 rpm for 12 minutes using a mechanical stirrer to obtain slurry A. Photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 6 minutes, and then dispersed at a speed of 1200 rpm for 25 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0091] Example 10

[0092] This embodiment provides a light-heat dual-curing radar absorbing coating, and the types and proportions of raw materials are shown in Table 10 below.

[0093] Table 10 Raw material components of Example 10

[0094]

[0095] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0096] Polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed according to the mass percentage in Table 10, and polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 4 minutes, and then dispersed at a speed of 1000 rpm for 10 minutes using a mechanical stirrer to obtain slurry A. Photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 5 minutes, and then dispersed at a speed of 1000 rpm for 30 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0097] Comparative Example 1

[0098] This comparative example provides a photocurable radar absorbing coating, and the types and proportions of raw materials are shown in Table 11 below.

[0099] Table 11 Comparative Example 1 Raw material types and ratios

[0100]

[0101] In this embodiment, the light-cured microwave absorbing coating is prepared according to the following steps:

[0102] Polyurethane acrylate, diluent, photoinitiator, absorbent and additives were weighed according to the mass percentage in Table 11. The polyurethane acrylate and diluent were placed in a paint mixing cup, manually stirred for 4 minutes, and then dispersed at a speed of 800 rpm for 12 minutes using a mechanical stirrer to obtain slurry A. The photoinitiator, absorbent and additives were added to slurry A, manually stirred for 5 minutes, and then dispersed at a speed of 1000 rpm for 25 minutes using a mechanical stirrer to obtain a light-cured absorbing coating.

[0103] Comparative Example 2

[0104] This comparative example provides a thermally cured radar absorbing coating, and the types and proportions of raw materials are shown in Table 12 below.

[0105] Table 12 Example 12 Raw material types and ratios

[0106]

[0107]

[0108] In this comparative example, a heat-cured microwave absorbing coating was prepared according to the following steps:

[0109] Weigh polyurethane acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and additives according to the mass percentage in Table 12, put polyurethane acrylate, isocyanate curing agent and diluent in a paint mixing cup, stir manually for 5 minutes, and then use a mechanical stirrer to disperse at a speed of 800 rpm for 12 minutes to obtain slurry A; add the photoinitiator, absorbent and additives to slurry A, stir manually for 4 minutes, and then use a mechanical stirrer to disperse at a speed of 1200 rpm for 20 minutes to obtain a thermally cured absorbing coating.

[0110] Comparative Example 3

[0111] This comparative example provides a light-heat dual-curing absorbing coating, and the types and proportions of raw materials are shown in Table 13 below.

[0112] Table 13 Comparative Example 3 Raw Materials

[0113]

[0114] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0115] According to the mass percentage in Table 13, polyurethane acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed respectively, and polyurethane acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 5 minutes, and then dispersed at a speed of 1000 rpm for 10 minutes using a mechanical stirrer to obtain slurry A; photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 5 minutes, and then dispersed at a speed of 1200 rpm for 25 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0116] Comparative Example 4

[0117] The types and proportions of raw materials are shown in Table 14 below.

[0118] Table 14 Comparative Example 4 Raw Materials

[0119]

[0120] This comparative example prepares a light-heat dual-curing microwave absorbing coating according to the following steps:

[0121] Polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed respectively according to the mass percentage in Table 14, polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 5 minutes, and then dispersed at a speed of 1000 rpm for 10 minutes using a mechanical stirrer to obtain slurry A; photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 5 minutes, and then dispersed at a speed of 1200 rpm for 25 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0122] Comparative Example 5

[0123] The types and proportions of raw materials are shown in Table 15 below.

[0124] Table 15 Comparative Example 15 Raw Material Composition

[0125]

[0126] In this embodiment, the light-heat dual-curing microwave absorbing coating is prepared according to the following steps:

[0127] According to the mass percentage in Table 15, polyurethane acrylate, epoxy acrylate, isocyanate curing agent, diluent, photoinitiator, absorbent and auxiliary agent were weighed respectively, polyurethane acrylate, epoxy acrylate, isocyanate curing agent and diluent were placed in a paint mixing cup, manually stirred for 5 minutes, and then dispersed at a speed of 1000 rpm for 10 minutes using a mechanical stirrer to obtain slurry A; photoinitiator, absorbent and auxiliary agent were added to slurry A, manually stirred for 5 minutes, and then dispersed at a speed of 1200 rpm for 25 minutes using a mechanical stirrer to obtain a light-thermal dual-cured absorbing coating.

[0128] The absorbing coatings of Examples 1-10 and Comparative Examples 1-5 were respectively prepared by compressed air spraying to prepare absorbing coatings with a thickness of 1 mm. The specific method is as follows: pour the absorbing coating into a W-71 spray gun, adjust the spraying pressure to 0.5 MPa, the spraying distance to 15-20 cm, the spray gun moving speed to 30-40 cm / s, and spray evenly on the surface of the substrate in an S-shaped path; after each spraying of 100 μm of coating, use an ultraviolet surface light source to irradiate the coating surface for 5-10 minutes to complete light curing, and then repeat the above spray curing process until the thickness of the obtained prefabricated layer reaches 1 mm. Then, keep the sample at 80° C. for 2 hours to completely cure the coating sprayed on the surface of the substrate.

[0129] In order to verify the light-curing performance of the absorbing coating, the curing time of a single spray coating with a thickness of 100 μm was measured with reference to GB / T 1728-2020 "Determination of drying time of paint film and putty film". The tensile strength of the coating sample that was only light-cured was tested with reference to GB / T1040 "Plastic tensile test method", and the results are shown in Table 16 below.

[0130] Table 16 Photocuring time and tensile strength of each embodiment and comparative example

[0131]

[0132] As can be seen from Table 16, the photocuring time of each embodiment and comparative examples 1 and 3 is within 300s, which is much shorter than the several hours of the traditional thermal curing coating. Since ultraviolet light curing generates active free radicals through ultraviolet light excitation of the photoinitiator, which then initiates free radical polymerization, it has high reactivity and extremely fast polymerization speed. Therefore, the curing speed of the photocuring coating is much faster than that of the thermal curing coating. The tensile strength of each embodiment and comparative example 1 after photocuring is at the same level, which is about 2MPa. This is because the excessively fast curing speed of the photocuring causes the internal stress to be released too late, affecting the mechanical properties of the coating.

[0133] In order to verify the thermal curing performance of the absorbing coating, the light-cured coatings of the embodiments and comparative examples were first kept at 80°C for 2 hours, and their tensile strength was tested according to GB / T 1040 "Plastic Tensile Test Methods"; the coatings were kept at 80°C for 10 hours, and then the tensile strength was tested. The test results of the embodiments and comparative examples are shown in Table 17.

[0134] Table 17 Tensile strength of each embodiment and comparative example thermal curing at different times

[0135]

[0136] As can be seen from Table 17, the tensile strength of each embodiment after 2 hours of thermal curing is much greater than that of Comparative Examples 1-3, and at the same time, the tensile strength is greatly improved compared to that after light curing, indicating that the active groups in the resin and the added isocyanate curing agent continue to undergo cross-linking reaction under heating conditions, thereby improving the mechanical properties of the coating. For Comparative Example 1, since it does not contain an isocyanate curing agent, it does not have thermal curing ability, and the tensile strength is basically unchanged from the test results after light curing. After continuing thermal curing for 10 hours, the tensile strength of each embodiment is basically unchanged compared to thermal curing for 2 hours, indicating that it has been completely cured in 2 hours. The tensile strength of the coating in Comparative Example 2 is greatly improved after 12 hours of thermal curing compared to 2 hours, indicating that it has not been completely cured in 2 hours, the degree of cross-linking is low, and the mechanical properties are poor. The curing speed of the absorbing coating in Comparative Example 2 is significantly slower than that of the dual-cured absorbing coating in each embodiment.

[0137] According to the test results in Table 16 and Table 17, the curing time of the dual-cured absorbing coating in each embodiment is much shorter than that of the thermally cured coating in Comparative Example 2, and the mechanical properties are greatly improved compared with the photocured coating in Comparative Example 1, effectively combining the advantages of both photocured and thermally cured coatings.

[0138] In order to fully verify the performance of the light-heat dual-curing absorbing coating in each embodiment, for the fully cured coating samples of each embodiment and comparative example, the adhesion performance of the coating and the substrate was tested with reference to GJB 5210 "Tensile bonding strength test of paint and varnish by pulling apart method"; the reflection loss of the absorbing coating was tested with the bow method with reference to GJB 2038-94 "Test method for reflectivity of radar absorbing materials", and the minimum reflection loss (RL min ) was used to characterize the microwave absorbing performance of the coating. The results are shown in Table 18.

[0139] Table 18 Adhesion and wave absorption performance of each embodiment and comparative example

[0140]

[0141] As can be seen from Table 18, the adhesion of the absorbing coating in each embodiment is good, which is greatly improved compared with Comparative Examples 1, 2, and 3. This is because the epoxy acrylate in the resin system of the embodiment contains groups such as epoxy and hydroxyl groups, which can form chemical bonds with hydroxyl and amino groups on the surface of the metal substrate, thereby strengthening the adhesion performance of the coating and the substrate. Each embodiment has good reflection loss performance and no significant difference from Comparative Examples 1, 2, and 3, indicating that the absorption performance of the absorbing coating mainly comes from the absorbent, and the resin binder component has good wave transmission performance and has no significant effect on the coating's absorbing performance. Comparative Examples 4 and 5 use the same resin binder formula and absorbent type as Example 1, but the reflection loss is significantly reduced, proving that the absorbent morphology and particle size will affect the coating's absorbing performance. Comparative Example 4 shows that the performance of the sheet absorber is better than that of the spherical absorber, and Comparative Example 5 shows that reducing the particle size can improve the absorbing performance.

[0142] In summary, the photo-thermal dual-curing absorbing coating of the present invention combines the advantages of both photo-curing and thermal-curing mechanisms, which can not only meet the demand for rapid curing of the absorbing coating, but also enable the coating to have better mechanical properties, adhesion and absorbing properties, and can meet the use requirements under actual service conditions.

[0143] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A light-heat dual-curing radar absorbing coating, characterized in that: The raw materials include the following components by mass fraction: Polyurethane acrylate 10%-14%, epoxy acrylate 2%-4%, isocyanate 3%-7%, photoinitiator 3%-7%, active diluent 2%-6%, absorbent 65%-75%, auxiliary agent 0.5%-1.5%.

2. The light-heat dual-curing radar absorbing coating according to claim 1, characterized in that: The reactive diluent includes β-hydroxyethyl methacrylate and tripropylene glycol diacrylate.

3. The light-heat dual-curing radar absorbing coating according to claim 2, characterized in that: The mass ratio of the β-hydroxyethyl methacrylate to tripropylene glycol diacrylate is 1:1-3.

4. The light-heat dual-curing radar absorbing coating according to claim 1, characterized in that: The absorbent includes iron-silicon-aluminum alloy, iron-silicon-chromium alloy, iron-silicon alloy, carbonyl iron, carbonyl nickel, iron-aluminum-boron alloy, iron-nickel-molybdenum alloy, iron-chromium-nickel alloy, iron-nickel alloy or iron-cobalt-chromium alloy.

5. The light-heat dual-curing radar absorbing coating according to claim 1, characterized in that: The epoxy acrylate includes bisphenol A epoxy acrylate or novolac epoxy acrylate.

6. The light-heat dual-curing radar absorbing coating according to claim 1, characterized in that: The polyurethane acrylate is hydroxy polyurethane acrylate, wherein the content of hydroxyl groups accounts for 2%-4% of the mass of the solid component.

7. The light-heat dual-curing radar absorbing coating according to claim 1, characterized in that: The isocyanate includes one or a combination of isophorone diisocyanate, toluene diisocyanate and diphenylmethane diisocyanate; The auxiliary agents include defoamers and dispersants; The photoinitiator includes a long-wave photoinitiator with an absorption wavelength of 350nm-420nm and a short-wave photoinitiator with an absorption wavelength of 260nm-320nm.

8. The light-heat dual-curing radar absorbing coating according to claim 7, characterized in that: The mass ratio of the long-wave photoinitiator to the short-wave photoinitiator is 1:1-3; The mass ratio of the defoamer to the dispersant is 1:1-3.

9. A method for preparing the light-heat dual-curing radar absorbing coating according to claim 1, characterized in that: include: Mixing polyurethane acrylate, epoxy acrylate, isocyanate and reactive diluent to obtain slurry A; A photoinitiator, an absorber and an auxiliary agent are added into slurry A to obtain a light-heat-dual-cured microwave-absorbing coating.

10. An application of the light-heat dual-curing microwave absorbing coating as claimed in claim 1, characterized in that: include: Spraying the light-heat dual-curing absorbing coating on the surface of the substrate; Wherein, after each spraying of a coating of a preset thickness, the coating surface is cured by ultraviolet light; The sprayed substrate was placed at 70-90°C for thermal curing for 2-4 hours.

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