Low-temperature fast-curing radar wave-absorbing repair coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of stealth materials, and particularly discloses a radar wave-absorbing repair coating capable of being rapidly cured at low temperature as well as a preparation method and application of the radar wave-absorbing repair coating. Comprising the following raw materials: 18%-22% of organic silicon resin, 3%-7% of epoxy modified organic silicon resin, 4%-8% of a diluent, 56%-64% of an absorbent, 2.5%-3.5% of a curing agent, 1.5%-2.5% of an accelerant, 1.5%-2.5% of a thermal initiator and 1%-3% of an auxiliary agent. Wherein the curing agent is formed by compounding a reaction type curing agent and a catalytic type curing agent, and the mass percent of the reaction type curing agent to the catalytic type curing agent is (2-3): (1-1.5). The radar wave-absorbing repair coating provided by the invention can realize low-temperature rapid curing, has good tensile bonding strength, impact resistance and long-term test temperature resistance, is mature and controllable in process, and completely meets the application of external field rapid repair of radar wave-absorbing coatings of various equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of stealth materials, and specifically relates to a low-temperature fast-curing radar absorbing repair coating and a preparation method and application thereof. Background Art

[0002] In today's era of rapid technological development, advanced electronic detection technologies such as infrared and radar have made continuous breakthroughs, which has brought higher requirements and challenges to the concealment of many high-end equipment in specific environments. In recent years, countries around the world have regarded low-detectability technology of equipment as one of the key factors to measure the comprehensive performance of equipment, especially in the field of high-end equipment such as aerospace, which has extremely demanding technical requirements and huge investments.

[0003] To this end, researchers from various countries have conducted a lot of in-depth research and practice around stealth materials, and have successfully integrated absorbing coatings into the design and application of equipment, which has not only revolutionized the application mode of equipment, but also triggered profound changes in the field of military technology. In addition, a wide range of positive results have been achieved in the civilian field. For example, in radio and television transmitters, absorbing coatings can effectively control the diffusion range of electromagnetic radiation and ensure the electromagnetic safety of the surrounding environment; in microwave darkrooms, it can help accurately eliminate various types of electromagnetic interference generated by equipment and create an ideal environment for experiments and tests; in communication and navigation systems, absorbing coatings can significantly reduce electromagnetic interference and greatly improve the accuracy and reliability of system operation.

[0004] Taking aircraft engines and other equipment as an example, the radar absorbing coating on its surface in the medium and high temperature area will be subjected to complex and harsh working conditions such as high temperature baking, high-speed airflow impact, continuous vibration and frequent temperature fluctuations for a long time, which makes it very easy to have local delamination, shedding and wear and other undesirable phenomena. Once the radar absorbing coating is damaged or even fails, the target reflection characteristics of the equipment will be significantly enhanced, and its key performance such as low detectability will be reduced accordingly. The risk of being detected will also increase significantly. In some special scenarios with high requirements for concealment, it may trigger a series of chain reactions. Therefore, radar absorbing coating repair technology is crucial to ensure the stealth capability of equipment. The current practice is to use a single-component silicone resin system radar absorbing coating to repair the damaged area, but the coating has defects such as high curing temperature, long curing time, insufficient mechanical properties and temperature resistance. These defects make it difficult for the coating to meet the needs of rapid repair in emergency situations. In the subsequent use of the equipment, it is also easy to have secondary damage problems such as cracking or shedding of the interface between the original coating and the repair coating, which seriously affects the repair effect and the overall operation efficiency of the equipment.

[0005] In view of this, this invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a low-temperature, fast-curing radar absorbing repair coating and a preparation method and application, which are mainly used to solve the many disadvantages of existing radar absorbing repair coatings, such as high curing temperature, long curing time, poor mechanical properties and temperature resistance, which make it difficult to meet the needs of field repair of stealth equipment.

[0007] The purpose of the present invention is to be solved by the following technical solutions:

[0008] In a first aspect, the present invention provides a low-temperature fast-curing radar absorbing repair coating, wherein the radar absorbing repair coating comprises the following component raw materials by mass percentage:

[0009] Silicone resin 18% to 22%;

[0010] Epoxy modified silicone resin 3% to 7%;

[0011] Diluent 4% to 8%;

[0012] Absorbent 56% to 64%;

[0013] Curing agent 2.5% to 3.5%;

[0014] Accelerator 1.5%~2.5%;

[0015] Thermal initiator 1.5% to 2.5%;

[0016] Additives 1% to 3%;

[0017] Among them, the curing agent is composed of a reaction-type curing agent and a catalytic curing agent, and the mass percentage of the reaction-type curing agent to the catalytic curing agent is (2-3): (1-1.5). When the radar absorbing repair coating is sprayed to a thickness of 1 mm, the curing temperature is less than 85°C and the curing time is less than 5.5 hours.

[0018] Furthermore, the organic silicone resin is methylphenyl polysilicone resin.

[0019] Furthermore, the epoxy value of the epoxy-modified silicone resin is 0.02 to 0.16.

[0020] Furthermore, the diluent is selected from any one of xylene, PMA or acetone.

[0021] Furthermore, the absorbent is selected from any one of carbonyl iron powder and Sendust aluminum alloy powder with flattened flake morphology, or a mixture of the two.

[0022] Furthermore, the reactive curing agent is selected from any one of polysilazane and tetraethyl orthosilicate;

[0023] The catalytic curing agent is selected from any one of diethylenetriamine and dibutyltin dilaurate.

[0024] Further, the accelerator is dimethyl phthalate;

[0025] The thermal initiator is a peroxide thermal initiator.

[0026] Preferably, the peroxide thermal initiator is dibenzoyl peroxide.

[0027] Furthermore, the auxiliary agent is a composite auxiliary agent composed of a leveling agent, a defoaming agent and a dispersant, and the mass percentage of the leveling agent, the defoaming agent and the dispersant is (4-7): (3-7): (3-6).

[0028] Preferably, the leveling agent is polydimethylsiloxane, the defoaming agent is polyethylene glycol, and the dispersant is polyacrylamide.

[0029] In a second aspect, the present invention provides a method for preparing a low-temperature fast-curing radar absorbing repair coating, the preparation method comprising the following steps: weighing the component raw materials included in the above-mentioned radar absorbing repair coating and the corresponding mass percentages of the component raw materials:

[0030] Step 1, first weigh 18% to 22% of silicone resin, 3% to 7% of epoxy modified silicone resin, and 4% to 8% of diluent according to mass percentage and place them in a container, stir them manually for 3min to 7min, and then use a high-speed disperser to mix them until they are uniform to obtain a first slurry, the speed of the high-speed disperser is set to 500r / min to 700r / min, and the dispersion time is 10min to 20min;

[0031] Step 2: Add 56% to 64% of the absorbent to the first slurry obtained in step 1, stir manually for 3 to 7 minutes, and then use a high-speed disperser to mix until it is uniform to obtain a second slurry. The speed of the high-speed disperser is set at 1200 r / min to 1400 r / min, and the dispersion time is 60 to 75 minutes.

[0032] Step three: Finally, add 2.5% to 3.5% of curing agent, 1.5% to 2.5% of accelerator, 1.5% to 2.5% of thermal initiator, and 1% to 3% of auxiliary agent to the second slurry obtained in step two, and stir manually for 5 to 10 minutes until it is uniform to obtain the target product, a low-temperature fast-curing radar absorbing repair coating.

[0033] In a third aspect, the present invention provides an application of the above-mentioned low-temperature fast-curing radar absorbing repair coating, wherein the radar absorbing repair coating is applied to the missing repair position of the stealth coating on the surface of the aircraft engine medium-temperature area equipment to form a radar absorbing repair coating for radar stealth.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The radar absorbing repair coating provided by the present invention is mainly composed of silicone resin, epoxy modified silicone resin, diluent, absorbent, curing agent, promoter, thermal initiator and auxiliary agent. Compared with the traditional radar absorbing coating (single component silicone resin system) which relies on dehydration polycondensation between Si-OH at high temperature for crosslinking and curing, the radar absorbing repair coating of the present invention adds curing agent, accelerator and thermal initiator components to participate in or catalyze the curing reaction, that is, the resin system is coordinated and coordinated with the curing agent, accelerator and thermal initiator, so that the radar absorbing repair coating prepared by the present invention has the advantages of low curing temperature (less than 85°C), short curing time (less than 5.5h), and excellent preparation process stability when forming a radar absorbing repair coating on a metal substrate. The specific analysis is as follows:

[0036] 1. In the present invention, the organic silicon resin and epoxy modified organic silicon resin are compounded to form a resin binder system. The main chain of the organic silicon resin is composed of Si and O atoms, and the side chain is connected with an organic group. Its skeleton structure is Si-O-Si, wherein the bond energy of the Si-O bond (450kJ / mol) is higher than the bond energy of the CC bond (307kJ / mol), so the organic silicon resin has higher heat resistance than other organic resins. The methylphenyl polysilicone resin selected in the present invention further improves the heat resistance and adhesion of the organic silicon resin due to the introduction of the phenyl organic group, and enhances the compatibility of the silicone resin with the organic polymer, making it easier to mix with the absorbent filler; the epoxy modified organic silicon resin has excellent chemical corrosion resistance, strong bonding strength and better mechanical properties than ordinary thermosetting materials. The epoxy modified organic silicon resin selected in the present invention further improves the mechanical properties and rapid curing performance of the resin due to the introduction of the epoxy bond. The resin binder system of methylphenyl polysilicone resin and modified epoxy resin provides excellent mechanical properties and long-term heat resistance for low-temperature fast-curing radar absorbing repair coatings.

[0037] 2. The diluent is a mailing solvent that dissolves the resin binder system, and its function is to adjust the coating viscosity to a suitable processing state. In the present invention, the diluent is selected from xylene, PMA and acetone, which have a fast volatilization rate and provide excellent synergistic effect for the low-temperature rapid curing system.

[0038] 3. The absorbent determines the stealth performance of the radar absorbing repair coating. According to the loss mechanism, the absorbent can be divided into electric loss type and magnetic loss type. The absorbents of the present invention select carbonyl iron powder and iron silicon aluminum alloy powder, both of which are magnetic loss type absorbers. Among them, carbonyl iron powder has the advantages of high saturation magnetization, high Curie temperature and high natural resonance frequency, and provides excellent absorbing performance in the X and Ku bands; iron silicon aluminum alloy powder also has high saturation magnetization, Curie temperature and natural resonance frequency, provides excellent absorbing performance in the S and C bands, and has excellent temperature resistance and stability.

[0039] 4. Curing agent is a direct parameter or an indirect catalyst for the cross-linking reaction of the resin system, and is a key component for reducing the curing temperature and curing time. The present invention selects a reactive curing agent and a catalytic curing agent for compound use, wherein the reactive curing agent includes polysilazane and tetraethyl orthosilicate, and the -OH and other groups introduced by the curing agent undergo dehydration and dealcoholization condensation reactions with the silicone resin, thereby increasing the cross-linking density to reduce the curing temperature and time; the catalytic curing agent includes diethylenetriamine and dibutyltin dilaurate, which accelerate the dehydration condensation reaction of the silicone resin by activating Si-OH, thereby further reducing the curing temperature and time.

[0040] 5. The main component of the accelerator is dimethyl phthalate, which is a commonly used plasticizer with good film-forming properties and adhesion. The accelerator of the present invention reacts with the epoxy group in the epoxy-modified silicone resin to form a cross-linked structure by introducing active hydrogen atoms on the one hand; on the other hand, it activates the cross-linking groups in the system, and the two synergistically reduce the curing temperature and time.

[0041] 6. The main component of the thermal initiator is dibenzoyl peroxide, which is an organic peroxide initiator. The electron cloud density of the OO bond in the thermal initiator is large and repulsive, and it is easy to break. Generally, it decomposes at 60℃~80℃ to produce benzoic acid free radicals, which can initiate the polymerization reaction of the resin and curing agent components and reduce the curing temperature and time.

[0042] 7. The auxiliary agent of the present invention is a combination of a leveling agent, a defoaming agent and a dispersant, which can improve the appearance and structural density of the coating prepared by the low-temperature fast-curing radar absorbing repair coating, and is conducive to the improvement of mechanical properties;

[0043] In summary, the radar absorbing repair coating provided by the present invention has the functional characteristics of low curing temperature, short curing time, high tensile bonding strength, excellent impact resistance, excellent flexibility, and excellent long-term temperature resistance stability. It can meet the needs of emergency construction of various equipment in the field and quickly restore stealth performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the present invention.

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] Figure 1 The present invention is a flow chart of a method for preparing a low-temperature fast-curing radar absorbing repair coating. DETAILED DESCRIPTION

[0047] Here, exemplary embodiments will be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are only examples consistent with some aspects of the present invention as detailed in the appended claims.

[0048] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0049] The invention provides a low-temperature fast-curing radar absorbing repair coating. The radar absorbing repair coating comprises the following component raw materials in terms of mass percentage: 18% to 22% of silicone resin, 3% to 7% of epoxy-modified silicone resin, 4% to 8% of diluent, 56% to 64% of absorbent, 2.5% to 3.5% of curing agent, 1.5% to 2.5% of accelerator, 1.5% to 2.5% of thermal initiator and 1% to 3% of auxiliary agent.

[0050] Specifically, the organosilicon resin in the present invention is selected from methylphenyl polysilicone resin with excellent coating structural strength, heat resistance and weather resistance. In the embodiment of the present invention, the methylphenyl polysilicone resin is specifically selected from SH-9601 organosilicon resin or SH-9603 organosilicon resin produced by Hubei Xinsihai Chemical.

[0051] The epoxy resin selected in the present invention is an epoxy-modified silicone resin, which has excellent coating structural strength and high and low temperature resistance. In the embodiment of the present invention, the epoxy-modified silicone resin is specifically selected from SH-023-4 epoxy-modified silicone resin or SH-023-7 epoxy-modified silicone resin of Hubei Xinsihai Chemical, and the epoxy value is required to be in the range of 0.02 to 0.16.

[0052] The diluent in the present invention is selected from any one of xylene, PMA, and acetone, which can adjust the coating viscosity to a suitable processing state, and has a faster volatilization rate, providing excellent synergistic effects for the low-temperature rapid curing system. In the embodiment of the present invention, the diluent is specifically selected from xylene, PMA or acetone of Beijing Chemical.

[0053] The absorbent in the present invention is any one or a mixture of carbonyl iron powder and sendust aluminum alloy powder with flattened flaky morphology. In the embodiment of the present invention, the carbonyl iron powder is specifically selected from 4# iron powder of Wuhan Magnetics, and the sendust aluminum alloy powder is specifically selected from the flake F02 of Wuhan Magnetics.

[0054] The curing agent in the present invention is a composite curing agent composed of a reactive curing agent and a catalytic curing agent, and the mass percentage of the reactive curing agent and the catalytic curing agent is (2-3): (1-1.5). Preferably, the reactive curing agent is polysilazane or tetraethyl orthosilicate, and the catalytic curing agent is diethylenetriamine or dibutyltin dilaurate. The reactive curing agent increases the crosslinking density of the resin, and the catalytic curing agent activates the crosslinking group to reduce the curing temperature and time through the synergistic effect. In the embodiment of the present invention, the reactive curing agent specifically selects polysilazane or tetraethyl orthosilicate from Beijing Chemical, and the catalytic curing agent specifically selects diethylenetriamine or dibutyltin dilaurate from Beijing Chemical.

[0055] The accelerator in the present invention is dimethyl phthalate, which reacts with the epoxy group in the epoxy-modified silicone resin by introducing active hydrogen atoms to form a cross-linked structure and simultaneously activate the cross-linked groups in the system, and the two synergistically reduce the curing temperature and time. In the embodiment of the present invention, the accelerator is specifically selected from dimethyl phthalate DMP of Kain Chemical.

[0056] The thermal initiator in the present invention is dibenzoyl peroxide, which generates benzoic acid radicals by decomposing and breaking the OO bond in the thermal initiator at 60°C to 80°C, thereby initiating the polymerization reaction of the resin and curing agent components and reducing the curing temperature and time. In the embodiment of the present invention, the thermal initiator is specifically selected from dibenzoyl peroxide BPO of Kain Chemical.

[0057] The auxiliary agent in the present invention is a composite auxiliary agent composed of a leveling agent, a defoaming agent and a dispersant, and the mass percentage of the leveling agent, the defoaming agent and the dispersant is (4-7): (3-7): (3-6). Preferably, the leveling agent is polydimethylsiloxane, the defoaming agent is polyethylene glycol, and the dispersant is polyacrylamide. The leveling agent can cause the coating to form a flat, smooth and uniform coating during the drying and film-forming process; the defoaming agent can inhibit the generation of foam in the coating or eliminate the generated foam; the dispersant can improve the uniform mixing state of the absorbent and the resin. In the embodiment of the present invention, the leveling agent is polydimethylsiloxane from Kain Chemical, the defoaming agent is polyethylene glycol from Kain Chemical, and the dispersant is polyacrylamide from Kain Chemical.

[0058] like Figure 1 As shown, the present invention also provides a method for preparing the above-mentioned low-temperature fast-curing radar absorbing repair coating, which specifically comprises the following steps:

[0059] Step 1, first weigh 18% to 22% of silicone resin, 3% to 7% of epoxy modified silicone resin, and 4% to 8% of diluent according to mass percentage and place them in a container, stir them manually for 3min to 7min, and then use a high-speed disperser to mix them until they are uniform to obtain a first slurry, the speed of the high-speed disperser is set to 500r / min to 700r / min, and the dispersion time is 10min to 20min;

[0060] Step 2: Add 56% to 64% of the absorbent to the first slurry obtained in step 1, stir manually for 3 to 7 minutes, and then use a high-speed disperser to mix until it is uniform to obtain a second slurry. The speed of the high-speed disperser is set at 1200 r / min to 1400 r / min, and the dispersion time is 60 to 75 minutes.

[0061] Step three: Finally, add 2.5% to 3.5% of curing agent, 1.5% to 2.5% of accelerator, 1.5% to 2.5% of thermal initiator, and 1% to 3% of auxiliary agent to the second slurry obtained in step two, and stir manually for 5 to 10 minutes until it is uniform to obtain the target product, a low-temperature fast-curing radar absorbing repair coating.

[0062] In order to further verify the efficacy of the powder metallurgy method of the present invention, the inventors conducted the following specific experiments:

[0063] Example 1

[0064] The present embodiment 1 provides a low-temperature fast-curing radar absorbing repair coating, the composition and proportion of which are shown in the following table 1:

[0065] Table 1

[0066]

[0067] The preparation process of the radar absorbing repair coating of this embodiment is as follows:

[0068] 1) 18% of silicone resin (SH-9601 silicone resin), 7% of epoxy-modified silicone resin (SH-023-4 epoxy-modified silicone resin), and 4% of diluent (xylene) were weighed according to mass percentage and placed in a container, manually stirred for 3 minutes, and then mixed with a high-speed disperser until uniform to obtain a first slurry, the speed of the high-speed disperser was set to 500 r / min, and the dispersion time was 10 minutes;

[0069] 2) Add 64% of the absorbent (4# iron powder) to the first slurry obtained in step 1), stir manually for 7 minutes, and then use a high-speed disperser to mix until uniform to obtain a second slurry. The speed of the high-speed disperser is set at 1400 r / min and the dispersion time is 75 minutes;

[0070] 3) Finally, 2.5% of curing agent (1.65% of polysilazane, 0.85% of diethylenetriamine), 1.5% of accelerator (dimethyl phthalate), 1.5% of thermal initiator (dibenzoyl peroxide), and 1.5% of auxiliary agent (0.4% of polydimethylsiloxane, 0.7% of polyethylene glycol, and 0.4% of polyacrylamide) are added to the second slurry obtained in step 2), and manually stirred for 10 minutes until it is in a uniform state to obtain the target product, a low-temperature fast-curing radar absorbing repair coating.

[0071] Example 2

[0072] This embodiment 2 provides a low-temperature fast-curing radar absorbing repair coating, the composition and proportion of which are shown in Table 2 below:

[0073] Table 2

[0074]

[0075]

[0076] The preparation process of the radar absorbing repair coating of this embodiment is as follows:

[0077] 1) 20% of silicone resin (SH-9601 silicone resin), 3% of epoxy-modified silicone resin (SH-023-7 epoxy-modified silicone resin), and 4% of diluent (PMA) were weighed according to mass percentage and placed in a container, manually stirred for 5 minutes, and then mixed with a high-speed disperser until uniform to obtain a first slurry, the speed of the high-speed disperser was set to 600 r / min, and the dispersion time was 15 minutes;

[0078] 2) Add 62% of the absorbent (45% of 4# iron powder and 17% of F02) to the first slurry obtained in step 1), stir manually for 5 minutes, and then use a high-speed disperser to mix until uniform to obtain a second slurry. The speed of the high-speed disperser is set at 1300 r / min and the dispersion time is 70 minutes;

[0079] 3) Finally, 3% of curing agent (2% of polysilazane, 1% of dibutyltin dilaurate), 2% of accelerator (dimethyl phthalate), 2% of thermal initiator (dibenzoyl peroxide), and 2% of auxiliary agent (0.7% of polydimethylsiloxane, 0.7% of polyethylene glycol, and 0.6% of polyacrylamide) are added to the second slurry obtained in step 2), and manually stirred for 7 minutes until it is uniform to obtain the target product, a low-temperature fast-curing radar absorbing repair coating.

[0080] Example 3

[0081] This embodiment 3 provides a low-temperature fast-curing radar absorbing repair coating, the composition and proportion of which are shown in Table 3 below:

[0082] Table 3

[0083]

[0084] The preparation process of the radar absorbing repair coating of this embodiment is as follows:

[0085] 1) 22% of silicone resin (SH-9601 silicone resin), 5% of epoxy-modified silicone resin (SH-023-4 epoxy-modified silicone resin), and 8% of diluent (acetone) were weighed according to mass percentage and placed in a container, and then manually stirred for 5 minutes and then mixed with a high-speed disperser until uniform to obtain a first slurry, the speed of the high-speed disperser was set to 600 r / min, and the dispersion time was 15 minutes;

[0086] 2) Add 56% of the absorbent (4# iron powder) to the first slurry obtained in step 1), stir manually for 5 minutes, and then use a high-speed disperser to mix until uniform to obtain a second slurry. The speed of the high-speed disperser is set at 1300 r / min and the dispersion time is 70 minutes;

[0087] 3) Finally, 3.5% of curing agent (2.3% of tetraethyl orthosilicate, 1.2% of dibutyltin dilaurate), 2.2% of accelerator (dimethyl phthalate), 2.3% of thermal initiator (dibenzoyl peroxide), and 1% of auxiliary agent (0.4% of polydimethylsiloxane, 0.3% of polyethylene glycol, and 0.3% of polyacrylamide) are added to the second slurry obtained in step 2), and manually stirred for 5 minutes until it is uniform to obtain the target product, a low-temperature fast-curing radar absorbing repair coating.

[0088] Example 4

[0089] This embodiment 4 provides a low-temperature fast-curing radar absorbing repair coating, the composition and proportion of which are shown in Table 4 below:

[0090] Table 4

[0091]

[0092] The preparation process of the radar absorbing repair coating of this embodiment is as follows:

[0093] 1) 18% of silicone resin (SH-9603 silicone resin), 7% of epoxy-modified silicone resin (SH-023-7 epoxy-modified silicone resin), and 4% of diluent (acetone) were weighed according to mass percentage and placed in a container, manually stirred for 5 minutes, and then mixed with a high-speed disperser until uniform to obtain a first slurry, the speed of the high-speed disperser was set to 600 r / min, and the dispersion time was 15 minutes;

[0094] 2) Add 63% of the absorbent (43% of 4# iron powder and 20% of F02) to the first slurry obtained in step 1), stir manually for 5 minutes, and then use a high-speed disperser to mix until uniform to obtain a second slurry. The speed of the high-speed disperser is set at 1300 r / min and the dispersion time is 70 minutes;

[0095] 3) Finally, 2.5% of curing agent (1.65% of tetraethyl orthosilicate, 0.85% of dibutyltin dilaurate), 1.5% of accelerator (dimethyl phthalate), 1.5% of thermal initiator (dibenzoyl peroxide), and 2.5% of auxiliary agent (1.4% of polydimethylsiloxane, 0.5% of polyethylene glycol, and 0.6% of polyacrylamide) are added to the second slurry obtained in step 2), and manually stirred for 10 minutes until it is in a uniform state to obtain the target product, a low-temperature fast-curing radar absorbing repair coating.

[0096] Example 5

[0097] This embodiment 5 provides a low-temperature fast-curing radar absorbing repair coating, the composition and proportion of which are shown in the following Table 5:

[0098] Table 5

[0099]

[0100]

[0101] The preparation process of the radar absorbing repair coating of this embodiment is as follows:

[0102] 1) 21% of silicone resin (SH-9603 silicone resin), 4% of epoxy-modified silicone resin (SH-023-4 epoxy-modified silicone resin), and 6% of diluent (PMA) were weighed according to mass percentage and placed in a container, manually stirred for 7 minutes, and then mixed with a high-speed disperser until uniform to obtain a first slurry, the speed of the high-speed disperser was set to 700 r / min, and the dispersion time was 20 minutes;

[0103] 2) Add 60% of the absorbent (4# iron powder) to the first slurry obtained in step 1), stir manually for 7 minutes, and then use a high-speed disperser to mix until uniform to obtain a second slurry. The speed of the high-speed disperser is set at 1400 r / min and the dispersion time is 75 minutes;

[0104] 3) Finally, 3% of curing agent (2% of tetraethyl orthosilicate, 1% of diethylenetriamine), 1.8% of accelerator (dimethyl phthalate), 1.9% of thermal initiator (dibenzoyl peroxide), and 2.3% of auxiliary agent (0.6% of polydimethylsiloxane, 0.8% of polyethylene glycol, and 0.9% of polyacrylamide) are added to the second slurry obtained in step 2), and manually stirred for 10 minutes until it is in a uniform state to obtain the target product, a low-temperature fast-curing radar absorbing repair coating.

[0105] Example 6

[0106] This embodiment 6 provides a low-temperature fast-curing radar absorbing repair coating, the composition and proportion of which are shown in the following Table 6:

[0107] Table 6

[0108]

[0109] The preparation process of the radar absorbing repair coating of this embodiment is as follows:

[0110] 1) 22% of silicone resin (SH-9603 silicone resin), 3% of epoxy-modified silicone resin (SH-023-7 epoxy-modified silicone resin), and 8% of diluent (xylene) were weighed according to mass percentage and placed in a container, manually stirred for 7 minutes, and then mixed with a high-speed disperser until uniform to obtain a first slurry, the speed of the high-speed disperser was set to 500 r / min, and the dispersion time was 10 minutes;

[0111] 2) Add 57% of the absorbent (40% of 4# iron powder and 17% of F02) to the first slurry obtained in step 1), stir manually for 3 minutes, and then use a high-speed disperser to mix until uniform to obtain a second slurry. The speed of the high-speed disperser is set at 1200r / min and the dispersion time is 60min.

[0112] 3) Finally, 3.5% of curing agent (2.3% of polysilazane, 1.2% of diethylenetriamine), 2.5% of accelerator (dimethyl phthalate), 2.5% of thermal initiator (dibenzoyl peroxide), and 1.5% of auxiliary agent (0.5% of polydimethylsiloxane, 0.4% of polyethylene glycol, and 0.6% of polyacrylamide) are added to the second slurry obtained in step 2), and manually stirred for 7 minutes until it is uniform to obtain the target product, a low-temperature fast-curing radar absorbing repair coating.

[0113] Performance Testing

[0114] The present invention takes part of the samples of the low-temperature fast-curing radar absorbing repair coatings prepared in Examples 1 to 6 for performance testing. It should be noted that the performance test of the low-temperature fast-curing radar absorbing repair coatings uses compressed air spraying technology to spray the coating on the surface of the sample, repeatedly spraying to a thickness of 1mm, and testing the performance after curing in an oven at 60℃ to 80℃. The test requirements are as follows.

[0115] A. Curing time:

[0116] The overall curing time of the coating with a thickness of 1 mm was recorded using a timer.

[0117] B. Tensile bond strength:

[0118] The test is carried out according to the "Pull-out Method" in GJB 5210 "Tensile Bond Strength Test of Paint and Varnish by Pull-off Method". It should be noted that at least 6 samples are tested in the test, and the average value of 6 measurements is used to represent the tensile bond strength of the coating.

[0119] C. Impact resistance:

[0120] The test is carried out in accordance with GB / T 1732 "Test method for impact resistance of paint film", and the highest height that does not cause cracking and damage to the coating is used to indicate the impact resistance of the coating.

[0121] D. Temperature resistance test:

[0122] The test is carried out in accordance with GB / T 1735 "Determination of Heat Resistance of Paints and Varnishes". The specific temperature resistance requirements are: Place the coating in a 250℃ or 270℃ forced air drying oven or muffle furnace, keep it warm for 100 hours, then cool it down with the furnace. After it drops to room temperature, take it out and observe whether the coating has cracking, delamination, shedding and other damage. If no damage is found to the coating, place it in a 250℃ forced air drying oven or muffle furnace for continuous heat resistance, observe the appearance of the coating every 100 hours, and stop the test until the coating cracks.

[0123] The performance test results of the low-temperature fast-curing radar absorbing repair coatings prepared in Examples 1 to 6 of the present invention are shown in Table 7 below:

[0124] Table 7

[0125]

[0126] From the analysis of the curing time test results in Examples 1 to 6 in Table 7, it can be seen that the low-temperature fast-curing radar absorbing repair coating provided by the present invention has a low curing temperature (less than 85°C) and a short curing time (less than 5.5h), which completely solves the problems of high curing temperature and long curing time of conventional radar absorbing coatings, and provides fast curing capability for outdoor radar absorbing coating repair.

[0127] From the analysis of the tensile bonding strength and impact resistance test results in Examples 1 to 6 in Table 7, it can be seen that the coating prepared by the low-temperature fast-curing radar absorbing repair coating provided by the present invention has good tensile bonding strength (greater than 16 MPa) and impact resistance (greater than 45 mm), and the tensile bonding strength and impact resistance are improved with the increase of the mass percentage of the epoxy-modified silicone resin, thereby ensuring the structural strength stability of the coating prepared by the low-temperature fast-curing radar absorbing repair coating under external force loads and vibration forces.

[0128] From the analysis of the heat resistance test results at 250°C and 270°C in Examples 1 to 6 in Table 7, it can be seen that the coating prepared by the low-temperature fast-curing radar absorbing repair coating provided by the present invention has good heat resistance, which fully solves the problem of conventional radar absorbing coatings being resistant to temperature differences and peeling off after service, and ensures the performance stability of the coating prepared by the low-temperature fast-curing radar absorbing repair coating under thermal stress.

[0129] In summary, the low-temperature fast-curing radar absorbing repair coating provided by the present invention can achieve low-temperature fast curing, has good tensile bonding strength, impact resistance and long-term temperature resistance, and the process is mature and controllable, which can fully meet the application of rapid field repair of radar absorbing coatings of various equipment.

[0130] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0131] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A low-temperature fast-curing radar absorbing repair coating, characterized in that: The radar absorbing repair coating comprises the following raw materials by weight percentage: Silicone resin 18% to 22%; Epoxy modified silicone resin 3% to 7%; Diluent 4% to 8%; Absorbent 56% to 64%; Curing agent 2.5% to 3.5%; Accelerator 1.5%~2.5%; Thermal initiator 1.5% to 2.5%; Additives 1% to 3%; Among them, the curing agent is composed of a reaction-type curing agent and a catalytic curing agent, and the mass percentage of the reaction-type curing agent to the catalytic curing agent is (2-3): (1-1.5). When the radar absorbing repair coating is sprayed to a thickness of 1 mm, the curing temperature is less than 85°C and the curing time is less than 5.5 hours.

2. The low-temperature fast-curing radar absorbing repair coating according to claim 1, characterized in that: The organic silicon resin is methylphenyl polysilicone resin.

3. The low-temperature fast-curing radar absorbing repair coating according to claim 1, characterized in that: The epoxy value of the epoxy-modified silicone resin is 0.02 to 0.

16.

4. The low-temperature fast-curing radar absorbing repair coating according to claim 1, characterized in that: The diluent is selected from any one of xylene, PMA or acetone.

5. The low-temperature fast-curing radar absorbing repair coating according to claim 1, characterized in that: The absorbent is selected from any one of carbonyl iron powder and sendust aluminum alloy powder with flattened flake morphology or a mixture of the two.

6. The low-temperature fast-curing radar absorbing repair coating according to claim 1, characterized in that: The reactive curing agent is selected from any one of polysilazane and tetraethyl orthosilicate; The catalytic curing agent is selected from any one of diethylenetriamine and dibutyltin dilaurate.

7. The low-temperature fast-curing radar absorbing repair coating according to claim 1, characterized in that: The accelerator is dimethyl phthalate; The thermal initiator is a peroxide thermal initiator.

8. The low-temperature fast-curing radar absorbing repair coating according to claim 1, characterized in that: The auxiliary agent is a composite auxiliary agent composed of a leveling agent, a defoaming agent and a dispersing agent, and the mass percentage of the leveling agent, the defoaming agent and the dispersing agent is (4-7): (3-7): (3-6).

9. A method for preparing a low-temperature fast-curing radar absorbing repair coating, characterized in that: The preparation method is to weigh the component raw materials included in the radar absorbing repair coating according to any one of claims 1 to 8 and the corresponding mass percentages of the component raw materials, and specifically comprises the following steps: Step 1, first weigh 18% to 22% of silicone resin, 3% to 7% of epoxy modified silicone resin, and 4% to 8% of diluent according to mass percentage and place them in a container, stir them manually for 3min to 7min, and then use a high-speed disperser to mix them until they are uniform to obtain a first slurry, the speed of the high-speed disperser is set to 500r / min to 700r / min, and the dispersion time is 10min to 20min; Step 2: Add 56% to 64% of the absorbent to the first slurry obtained in step 1, stir manually for 3 to 7 minutes, and then use a high-speed disperser to mix until it is uniform to obtain a second slurry. The speed of the high-speed disperser is set at 1200 r / min to 1400 r / min, and the dispersion time is 60 to 75 minutes. Step three: Finally, add 2.5% to 3.5% of curing agent, 1.5% to 2.5% of accelerator, 1.5% to 2.5% of thermal initiator, and 1% to 3% of auxiliary agent to the second slurry obtained in step two, and stir manually for 5 to 10 minutes until it is uniform to obtain the target product, a low-temperature fast-curing radar absorbing repair coating.

10. Use of the radar absorbing repair coating according to any one of claims 1 to 8, or the radar absorbing repair coating prepared by the preparation method according to claim 9, characterized in that: The radar absorbing repair coating is applied to the repair position of the stealth coating missing on the surface of the aircraft engine in the medium temperature area equipment to form a radar absorbing repair coating for radar stealth.

Images