A radome with a moisture-proof layer and a preparation method thereof

Abstract

The invention relates to the technical field of moisture-proof layers of high-temperature resistant and wave-transparent ceramic-based composite materials for aerospace, and in particular to a radome with a moisture-proof layer and a preparation method thereof. The preparation method of the radome with a moisture-proof layer comprises the following steps: coating a first moisture-proof slurry on the surface of the radome, curing, and forming a first moisture-proof layer; preparing a moisture-proof film mold; polishing the first moisture-proof layer, arranging the radome with the first moisture-proof layer on a male mold protrusion, arranging a female mold cover above the radome with the first moisture-proof layer, through each male mold positioning hole and each female mold positioning hole; evacuating the gap enclosed by the female mold and the first moisture-proof layer and pouring a second moisture-proof slurry, cooling and demoulding, forming a second moisture-proof layer, and obtaining the radome with a moisture-proof layer; after preparing a sealing moisture-proof coating on the surface of the radome, the invention uses a hot melt adhesive process to prepare a moisture-proof film, which solves the problem that the effect of a single moisture-proof method is not durable, and avoids the defects of overlapping, bulging, peeling, etc. existing in traditional bonding methods.

Description

Technical Field

[0001] The invention belongs to the technical field of moisture-proof layers of high-temperature resistant and wave-transmitting ceramic-based composite materials for aerospace use, and in particular relates to a radome with a moisture-proof layer and a preparation method thereof. Background Art

[0002] The ceramic-based high-temperature wave-transmitting radome is a streamlined or conical structural part used in the head of a missile or rocket, which integrates rectification, load-bearing, wave-transmitting and heat-insulating. The continuous quartz fiber reinforced nitride ceramic-based radome has the excellent properties of quartz fiber and boron nitride ceramic, and has excellent mechanical properties, dielectric properties and ablation resistance. It has great application prospects in the field of high-temperature resistant wave transmission. This material is mostly prepared using the PIP process. However, the composite material prepared using the PIP process has many pores, especially after processing, the surface roughness is large, which affects the appearance of the product and is easy to absorb moisture, which will have a serious impact on the electrical properties of the composite material, thereby affecting the wave-transmitting performance of the radome. In order to ensure the good wave-transmitting performance of the radome, it is first necessary to seal the surface of the radome to reduce the surface pores and provide a smooth contact surface for the moisture-proof film. Secondly, the moisture-proof film is coated on the basis of the surface sealing. The combination of the two realizes the system moisture-proof of the radome.

[0003] At present, research on moisture-proofing of antenna covers has made some progress.

[0004] For example: Chinese patent document CN202111580330.9 discloses a method for forming a moisture-proof layer of an antenna cover. This method overlaps and covers the outer surface of the antenna cover with a PVDC high-barrier composite film adhesive layer cut according to the surface shape of the antenna cover, and places it in a hot pressing device after evacuation through a contoured vacuum bag. The composite film is pressurized and heated to form a moisture-proof layer on the surface of the antenna cover. The moisture-proof layer prepared by this method can reduce the moisture absorption rate to below 0.2%; however, this forming method requires overlap when coating the surface of the antenna cover, which requires high accuracy of the process, and the overlap position is prone to defects such as overlap seams and protrusions, making it difficult to ensure the uniformity and consistency of the moisture-proof film.

[0005] For example: Chinese patent document CN111564698A discloses a method for forming a special-shaped ceramic antenna cover with high barrier and moisture-proof film. The method first uses PA, PP, PVDC and the like as raw materials to make a PVDC high barrier composite film, and then uses a co-extrusion blow molding method to make a sheet. The sheet is then attached to the antenna cover and fixedly cut to achieve pre-forming, and finally hot-pressed and bonded in a vacuum drying oven. The moisture absorption rate of the moisture-proof film prepared by this method is less than 0.5; however, the manufacturing process of the composite film in this molding method is relatively complicated. In addition, the pre-forming step requires the use of multiple fixtures and tooling, which increases the difficulty and time of operation and has high requirements.

[0006] For example: Chinese patent document CN108493605A discloses a method for forming a moisture-proof heat shrink film for a special-shaped antenna cover. The forming method first cuts the heat shrink film according to a two-dimensional diagram of the transformation of the three-dimensional model of the antenna cover and covers it on the surface of the antenna cover, welds it into an integral film and then takes it off, then puts the integral film on the antenna cover with a silicone resin on the outer surface and wrapped with a non-stick polytetrafluoroethylene film for pre-shrinkage, and finally pulls out the non-stick polytetrafluoroethylene film for vacuum curing to obtain a moisture-proof heat shrink film. The performance of the moisture-proof film of the product prepared by this method is controlled within 0.3%; but due to the different shrinkage amounts of the heat shrink film at different parts of the antenna cover, wrinkles and excessive shrinkage allowance will be caused. Therefore, this method requires a subsequent process for wrinkle removal, which is not conducive to improving production efficiency.

[0007] Therefore, in view of the above problems, the present invention urgently needs to provide a radome with a moisture-proof layer and a preparation method thereof. Summary of the invention

[0008] The present invention provides an antenna cover with a moisture-proof layer and a preparation method thereof, wherein a sealing moisture-proof coating is prepared on the surface of the antenna cover, and at the same time, a method for integrated molding of a ceramic antenna cover moisture-proof film with a simple process and a short molding time is provided, and the dual effects of the double-layer moisture-proof layer are utilized to improve the moisture-proof performance of the antenna cover.

[0009] The present invention provides a method for preparing a radome with a moisture-proof layer, comprising the following steps:

[0010] 1) uniformly coating the first moisture-proof slurry on the surface of the radome, and curing the slurry to form a first moisture-proof layer on the outer surface of the radome;

[0011] 2) preparing a moisture-proof film mold, including a male mold and a female mold, wherein the male mold includes a male mold bottom plate, a male mold protrusion matching the inner surface of the antenna cover is provided above the male mold bottom plate, and a plurality of male mold positioning holes are arranged at intervals around the male mold bottom plate, and the female mold includes a conical cover, and a circular female mold bottom plate is provided at the bottom of the conical cover extending horizontally outward in the circumferential direction, and a plurality of female mold positioning holes corresponding to the male mold positioning holes are arranged at intervals on the female mold bottom plate, and a glue inlet is also provided at the top of the conical cover;

[0012] 3) polishing the first moisture-proof layer, placing the antenna cover with the first moisture-proof layer on the male mold protrusion, placing the female mold cover above the antenna cover with the first moisture-proof layer, and forming a gap of uniform width between the inner mold surface of the female mold and the first moisture-proof layer through each male mold positioning hole and each female mold positioning hole;

[0013] 4) After vacuuming the gap between the female mold and the first moisture-proof layer through the glue inlet, the second moisture-proof slurry is poured into the gap between the female mold and the first moisture-proof layer through the glue inlet, cooled and demolded to form a second moisture-proof layer, thereby obtaining a radome with a moisture-proof layer.

[0014] Preferably, in step 1), the first moisture-proof slurry comprises silicone resin, silicon nitride powder, xylene and ethylene glycol ethyl ether acetate; the mass ratio of the silicone resin, silicon nitride powder, xylene and ethylene glycol ethyl ether acetate is 10:26:7:13.

[0015] Preferably, the width of the gap between the inner molding surface of the female mold and the first moisture-proof layer is 0.1-1 mm.

[0016] Preferably, in step 4), the material of the second moisture-proof slurry is hot melt adhesive, the type of the hot melt adhesive is HA490, and the melting temperature is 120±3°C.

[0017] Preferably, in step 1), the curing process includes, in sequence, a temperature of 80° C. and a curing time of 0.5-1 h; a temperature of 130° C. and a curing time of 0.5-1 h; and a temperature of 160° C. and a curing time of 0.5-1 h.

[0018] Preferably, in step 1), after curing is completed, the surface of the cured first moisture-proof layer is polished smooth using 200-mesh fine sandpaper and then purged clean with high-purity nitrogen.

[0019] Preferably, the material of the male mold and the female mold is polytetrafluoroethylene.

[0020] Preferably, in step 4), before pouring the second moisture-proof slurry into the pouring cavity surrounded by the female mold and the first moisture-proof layer, the male mold, the female mold and the first moisture-proof layer are placed in an oven and heated to the melting temperature of the hot melt adhesive.

[0021] Preferably, in step 4), the cooling method is natural cooling.

[0022] The present invention also provides a radome with a moisture-proof layer, comprising a first moisture-proof layer and a second moisture-proof layer sequentially arranged around the outer surface of the radome.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention provides a radome with a moisture-proof layer and a preparation method thereof. A first moisture-proof slurry is first coated on the surface of the radome to prepare a sealing moisture-proof coating, namely the first moisture-proof layer. A moisture-proof film, namely the second moisture-proof layer, is prepared by a hot melt adhesive process with a simple process and a short molding time. The radome is moisture-proofed by utilizing the dual effects of the moisture-proof coating and the moisture-proof film, thereby improving the moisture-proof performance of the radome and solving the problem of the short-lasting effect of a single moisture-proof method. In terms of the molding method of the second moisture-proof layer, the present invention adopts integrated molding to avoid the defects of overlapping, bulging, peeling, etc. existing in the traditional bonding method, while saving labor costs, and having a fast laminating speed and good moisture-proof performance.

[0025] 2. Before pouring the second moisture-proof slurry, the present invention polishes the first moisture-proof layer and vacuumizes the mold, thereby improving the adhesion effect between the second moisture-proof layer and the first moisture-proof layer, making the second moisture-proof layer and the first moisture-proof layer evenly bonded, avoiding debonding phenomena such as bubbles. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram (cross-sectional view) of the male mold and the female mold according to an embodiment of the present invention;

[0027] Figure 2 It is a structural schematic diagram (cross-sectional view) of the antenna cover with a moisture-proof layer according to an embodiment of the present invention;.

[0028] Among them: 1. antenna cover; 2. first moisture-proof layer; 3. second moisture-proof layer; 401. male mold bottom plate; 402. male mold protrusion; 403. male mold positioning hole; 501. female mold bottom plate; 502. conical cover; 503. female mold positioning hole; 504. glue inlet. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] like Figure 1 As shown, the method for preparing a radome with a moisture-proof layer described in this embodiment includes the following steps:

[0031] 1) coating the first moisture-proof slurry on the surface of the radome 1 and curing the slurry to form a first moisture-proof layer 2 on the outer surface of the radome 1;

[0032] 2) preparing a moisture-proof film mold, including a male mold and a female mold, wherein the male mold includes a male mold bottom plate 401, a male mold protrusion 402 matching the inner surface of the antenna cover 1 is provided above the male mold bottom plate 401, and a plurality of male mold positioning holes 403 are spaced around the male mold bottom plate 401, and the female mold includes a conical cover 502, and a circular female mold bottom plate 501 is provided at the bottom of the conical cover 502 extending outward in the circumferential direction horizontally, and a plurality of female mold positioning holes 503 corresponding to the male mold positioning holes 403 are spaced on the female mold bottom plate 501, and a glue inlet 504 is also provided at the top of the conical cover 502;

[0033] 3) polishing the first moisture-proof layer 2, placing the antenna cover 1 with the first moisture-proof layer 2 on the male mold protrusion 402, placing the female mold cover on the antenna cover 1 with the first moisture-proof layer 2, and forming a gap of uniform width between the inner mold surface of the female mold and the first moisture-proof layer 2 through each male mold positioning hole 403 and each female mold positioning hole 503;

[0034] 4) After the gap between the female mold and the first moisture-proof layer 2 is evacuated through the glue inlet 504, the second moisture-proof slurry is poured into the gap between the female mold and the first moisture-proof layer 2 through the glue inlet 504, cooled and demolded to form the second moisture-proof layer 3, and obtain the antenna cover 1 with a moisture-proof layer.

[0035] 1. The present invention provides a radome with a moisture-proof layer and a preparation method thereof. A first moisture-proof slurry is first coated on the surface of the radome 1 to prepare a sealing moisture-proof coating, namely, a first moisture-proof layer 2. A moisture-proof film, namely, a second moisture-proof layer 3, is prepared by a hot melt adhesive process with a simple process and a short molding time. The radome 1 is moisture-proofed by utilizing the dual effects of the moisture-proof coating and the moisture-proof film, thereby improving the moisture-proof performance of the radome 1 and solving the problem of the short-lasting effect of a single moisture-proof method. In terms of the molding method of the second moisture-proof layer 3, the present invention adopts integrated molding to avoid defects such as overlapping, bulging, and peeling in traditional bonding methods, while saving labor costs, and having a fast laminating speed and good moisture-proof performance.

[0036] 2. Before pouring the second moisture-proof slurry, the present invention performs operations such as polishing the prefabricated antenna cover and vacuuming the mold, thereby improving the adhesion effect between the second moisture-proof layer 3 and the first moisture-proof layer 2, so that the second moisture-proof layer 3 and the first moisture-proof layer 2 are evenly bonded, avoiding debonding phenomena such as bubbles.

[0037] The antenna cover 1 described in the present invention is mostly conical or hood-shaped. The setting of the male mold positioning hole 403 and the female mold positioning hole 503 ensures the centering effect of the female mold, the male mold and the antenna cover 1 during the mold assembly process, ensures the uniform thickness of the second moisture-proof layer 3, and further improves the moisture-proof effect of the antenna cover with a moisture-proof layer described in the present invention; in the present invention, the inner diameter of the glue inlet 504 is 8mm and the outer diameter is 14mm.

[0038] In this embodiment, in step 1), the first moisture-proof slurry includes silicone resin, silicon nitride powder, xylene and ethylene glycol ethyl ether acetate; the mass ratio of silicone resin, silicon nitride powder, xylene and ethylene glycol ethyl ether acetate is 10:26:7:13.

[0039] In some embodiments, silicone resin, silicon nitride powder, xylene and ethylene glycol ethyl ether acetate are mixed in a mass ratio of 10:26:7:13 as the first moisture-proof slurry; the prepared antenna cover with a moisture-proof layer is subjected to a moisture absorption test for 120 hours at a temperature of 25°C and a humidity of 90%, and the results show that the moisture absorption rate is less than 0.2; the national standard GB / T9286-1998 cross-cut test for color paint and varnish film is adopted, and after inspection, the coating surface adhesion reaches level 0.

[0040] In the comparative example, silicone resin, silicon nitride powder and xylene were mixed in a mass ratio of 10:35:10 as the first moisture-proof slurry; the moisture absorption rate of the prepared antenna cover with a moisture-proof layer was tested for 120 hours at a temperature of 25°C and a humidity of 90%, and the results showed that the moisture absorption rate was greater than 0.5; the national standard GB / T9286-1998 cross-cut test for color paint and varnish film was adopted, and after inspection, the coating surface adhesion reached level 1.

[0041] Compared with the comparative example, the antenna cover with a moisture-proof layer prepared by the ratio of the first moisture-proof slurry proposed in the present invention in this embodiment has a lower moisture absorption rate, which means that the moisture-proof performance is stronger; at the same time, the antenna cover with a moisture-proof layer prepared by the ratio of the first moisture-proof slurry proposed in the present invention has a higher coating surface adhesion, which means that the second moisture-proof layer 3 and the first moisture-proof layer 2 have better bonding.

[0042] In some embodiments, the width of the gap between the inner molding surface of the female mold and the prefabricated radome is controlled to be 0.1-1 mm.

[0043] If the second moisture-proof layer 3 is too thick, it will affect the wave transmittance of the antenna cover, which is not conducive to wave transmission; according to the data of coated antenna covers with different thicknesses, the thickness of the second moisture-proof layer 3 meets 0.1-1mm, and preferably, the thickness of the second moisture-proof layer 3 is 0.1-0.15mm.

[0044] When the thickness of the second moisture-proof layer 3 is 0.06 mm, the water vapor permeability of the radome with the moisture-proof layer is 0.35 g / m2·24 h, the dielectric constant is 2.32, and the dielectric loss tangent is 0.002;

[0045] When the thickness of the second moisture-proof layer 3 is 0.1 mm, the water vapor permeability of the radome with the moisture-proof layer is 0.32 g / m2·24 h, the dielectric constant is 2.36, and the dielectric loss tangent is 0.002;

[0046] When the thickness of the second moisture-proof layer 3 is 0.15 mm, the water vapor permeability of the radome with the moisture-proof layer is 0.28 g / m2·24 h, the dielectric constant is 2.38, and the dielectric loss tangent is 0.002;

[0047] When the thickness of the second moisture-proof layer 3 is 0.2 mm, the water vapor permeability of the radome with the moisture-proof layer is 0.26 g / m2·24 h, the dielectric constant is 2.41, and the dielectric loss tangent is 0.003;

[0048] When the thickness of the second moisture-proof layer 3 is 0.3 mm, the water vapor permeability of the radome with the moisture-proof layer is 0.26 g / m2·24 h, the dielectric constant is 2.56, and the dielectric loss tangent is 0.005;

[0049] When the thickness of the second moisture-proof layer 3 is 1.1 mm, the water vapor permeability of the radome with the moisture-proof layer is 0.12 g / m2·24 h, the dielectric constant is 3.74, and the dielectric loss tangent is 0.013;

[0050] Based on the above data, when the thickness of the second moisture-proof layer 3 is selected to be 0.1-1mm, the dielectric constant is less than 3.74, and the water vapor permeability is less than 0.35g / m2·24h, indicating that when the thickness is selected to be 0.1-1mm, the antenna cover with a moisture-proof layer can ensure a relatively low dielectric constant under the premise of low water vapor permeability, and the thickness of the second moisture-proof layer 3 is selected to be 0.1-1mm, which has a good moisture-proof effect while meeting the wave transmission performance of the antenna cover.

[0051] In this embodiment, the width of the gap between the inner molding surface of the female mold and the first moisture-proof layer 2 is 0.1-1 mm.

[0052] In this embodiment, in step 4), the material of the second moisture-proof slurry is hot melt adhesive, the type of the hot melt adhesive is HA490, and the melting temperature is 120±3°C.

[0053] In this embodiment, in step 1), the curing process includes temperature 80° C., curing time 0.5-1 h; temperature 130° C., curing time 0.5-1 h; temperature 160° C., curing time 0.5-1 h.

[0054] In this embodiment, in step 1), after the curing is completed, the surface of the cured first moisture-proof layer 2 is polished smooth using 200-mesh fine sandpaper and then purged clean with high-purity nitrogen.

[0055] The present invention performs an alignment and grinding process after the first moisture-proof layer 2 is cured and formed, thereby improving the adhesion effect between the second moisture-proof layer 3 and the first moisture-proof layer 2, making the second moisture-proof layer 3 and the first moisture-proof layer 2 evenly bonded, and avoiding debonding phenomena such as bubbles.

[0056] In this embodiment, the material of the male mold and the female mold are both polytetrafluoroethylene.

[0057] In this embodiment, in step 4), before pouring the second moisture-proof slurry into the pouring cavity surrounded by the female mold and the first moisture-proof layer 2, the male mold, the female mold and the first moisture-proof layer 2 are placed in an oven and heated to the melting temperature of the hot melt adhesive.

[0058] In this embodiment, in step 4), the cooling method is natural cooling.

[0059] like Figure 2 As shown, the present invention further provides a radome with a moisture-proof layer, comprising a first moisture-proof layer 2 and a second moisture-proof layer 3 sequentially arranged around the outer surface of the radome 1 .

[0060] The present invention sequentially provides a sealing moisture-proof coating, i.e., a first moisture-proof layer 2, and a moisture-proof film, i.e., a second moisture-proof layer 3, on the antenna cover 1 using a hot melt adhesive process with a simple process and a short molding time. The antenna cover 1 is moisture-proofed by utilizing the dual effects of the moisture-proof coating and the moisture-proof film, thereby improving the moisture-proof performance of the antenna cover 1 and solving the problem of the short-lasting effect of a single moisture-proof method. The second moisture-proof layer 3 uses hot melt adhesive to avoid defects such as overlapping, bulging, and peeling in traditional bonding methods, while saving labor costs, and having a fast laminating speed and good moisture-proof performance.

[0061] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing a radome with a moisture-proof layer, characterized in that: The steps include: 1) coating a first moisture-proof slurry on the surface of the radome (1), and curing the slurry to form a first moisture-proof layer (2) on the outer surface of the radome (1); 2) preparing a moisture-proof film mold, comprising a male mold and a female mold, wherein the male mold comprises a male mold base plate (401), a male mold protrusion (402) matching the inner surface of the antenna cover (1) is provided above the male mold base plate (401), and a plurality of male mold positioning holes (403) are arranged at intervals around the male mold base plate (401), and the female mold comprises a conical cover (502), a circular female mold base plate (501) is provided at the bottom of the conical cover (502) extending outward in a circumferential direction horizontally, and a plurality of female mold positioning holes (503) corresponding to the male mold positioning holes (403) are arranged at intervals on the female mold base plate (501), and a glue inlet (504) is also provided at the top of the conical cover (502); 3) grinding the first moisture-proof layer (2), placing the antenna cover (1) with the first moisture-proof layer (2) on the male mold protrusion (402), placing the female mold cover on the antenna cover (1) with the first moisture-proof layer (2), and forming a gap of uniform width between the inner mold surface of the female mold and the first moisture-proof layer (2) through each male mold positioning hole (403) and each female mold positioning hole (503); 4) After the gap between the female mold and the first moisture-proof layer (2) is evacuated through the glue inlet (504), the male mold, the female mold and the first moisture-proof layer (2) are placed in an oven and heated to the melting temperature of the second moisture-proof slurry, and the second moisture-proof slurry is poured into the gap between the female mold and the first moisture-proof layer (2) through the glue inlet (504), cooled and demoulded to form a second moisture-proof layer (3), thereby obtaining a radome (1) with a moisture-proof layer.

2. The method for preparing a radome with a moisture-proof layer according to claim 1, characterized in that: In step 1), the first moisture-proof slurry includes silicone resin, silicon nitride powder, xylene and ethylene glycol ethyl ether acetate; the mass ratio of the silicone resin, silicon nitride powder, xylene and ethylene glycol ethyl ether acetate is 10:26:7:

13.

3. The method for preparing a radome with a moisture-proof layer according to claim 2, characterized in that: The width of the gap between the inner mold surface of the female mold and the first moisture-proof layer (2) is 0.1-1 mm.

4. The method for preparing a radome with a moisture-proof layer according to claim 3, characterized in that: In step 4), the material of the second moisture-proof slurry is hot melt adhesive, the type of the hot melt adhesive is HA490, and the melting temperature is 120±3°C.

5. The method for preparing a radome with a moisture-proof layer according to claim 4, characterized in that: In step 1), the curing process includes temperature 80°C, curing time 0.5-1h; temperature 130°C, curing time 0.5-1h; temperature 160°C, curing time 0.5-1h.

6. The method for preparing a radome with a moisture-proof layer according to claim 5, characterized in that: In step 1), after curing is completed, the surface of the cured first moisture-proof layer (2) is polished smooth using 200-grit fine sandpaper and then purged clean with high-purity nitrogen.

7. The method for preparing a radome with a moisture-proof layer according to claim 6, characterized in that: The material of the male mold and the female mold is polytetrafluoroethylene.

8. The method for preparing a radome with a moisture-proof layer according to claim 7, characterized in that: In step 4), the cooling method is natural cooling.

9. A radome with a moisture-proof layer obtained based on the method for preparing a radome with a moisture-proof layer according to claims 1 to 8, characterized in that: It comprises a first moisture-proof layer (2) and a second moisture-proof layer (3) which are sequentially arranged around the outer surface of the antenna cover (1).

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