An electromagnetic wave absorbing patch and its preparation and bonding methods

Abstract

The present invention provides a microwave absorbing patch and its preparation and bonding methods, belonging to the technical field of microwave absorbing materials. The preparation raw materials of the microwave absorbing patch include the following compositions in parts by weight: 100 parts of aliphatic polyurethane resin, 10 - 12 parts of conductive carbon black, 0.2 - 0.4 parts of coupling agent, 1 - 1.5 parts of cellulose acetate butyrate, 2 - 3 parts of curing agent, and 100 - 200 parts of diluent. The present invention provides a flexible microwave absorbing patch with small thickness, light weight, good microwave absorbing performance, and large interfacial bonding strength, which can be smoothly attached to the surface of a curved part, facilitating construction and mass production, and having broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of microwave absorbing materials, and particularly relates to a microwave absorbing patch and its preparation and bonding methods. Background Art

[0002] Microwave absorbing patches are widely used in the field of microwave absorbing materials because of their simpler construction process and easy repair. However, the existing microwave absorbing patches are mainly suitable for bonding flat parts and are difficult to fit smoothly on the surface of curved parts, and are prone to warping, voids, detachment and other phenomena, which will affect the appearance, usability and reliability of the products.

[0003] Therefore, there is an urgent need to provide a microwave absorbing patch that can fit smoothly on the surface of curved parts. Summary of the Invention

[0004] In view of one or more technical problems existing in the prior art, the present invention provides a microwave absorbing patch and its preparation and bonding methods. The present invention provides a flexible microwave absorbing patch with small thickness, light weight, good microwave absorbing performance and high interfacial bonding strength, which can fit smoothly on the surface of curved parts, is convenient for construction and mass production, and has broad application prospects.

[0005] In the first aspect, the present invention provides a microwave absorbing patch, and the preparation raw materials of the microwave absorbing patch include the following compositions in parts by weight: 100 parts of aliphatic polyurethane resin, 10 - 12 parts of conductive carbon black, 0.2 - 0.4 parts of coupling agent, 1 - 1.5 parts of cellulose acetate butyrate, 2 - 3 parts of curing agent, and 100 - 200 parts of diluent.

[0006] Preferably, the iodine adsorption value of the conductive carbon black is 900 - 1300 mg / g, and the pH value is 6.5 - 8.0.

[0007] Preferably, the coupling agent is a silane coupling agent; preferably, the silane coupling agent is one or more of Si69, Si75, and KH550;

[0008] The diluent is one or more of acetone, xylene, and ethyl acetate; and / or

[0009] The curing agent is 2,2 - dimethylolbutyric acid.

[0010] Preferably, the thickness of the microwave absorbing patch is 0.28 - 0.3 mm; preferably, the surface density of the microwave absorbing patch ≤ 320 g / m 2 ; and / or

[0011] The peel strength of the microwave absorbing patch ≥ 30 N / cm.

[0012] In a second aspect, the present invention provides a method for preparing the absorbing patch according to the first aspect, the preparation method comprising the following steps:

[0013] S1. The composition is fully mixed to obtain an absorbing slurry;

[0014] S2. The absorbing slurry is subjected to casting and a first curing to obtain the absorbing patch.

[0015] Preferably, the release paper is laid on a casting machine, and the absorbing slurry is coated on the release paper, and then subjected to doctor blade coating and first curing to obtain the absorbing patch.

[0016] The present invention provides a method for bonding the absorbing patch according to the first aspect in a third aspect, the bonding method comprising the following steps:

[0017] (i) applying adhesive on the surface of the absorbing patch and the surface of the curved surface member respectively;

[0018] (ii) bonding the dried absorbing patch to the surface of the curved surface member;

[0019] (iii) Performing a second curing.

[0020] Preferably, the adhesive is a polyurethane adhesive;

[0021] The amount of the adhesive on the surface of the absorbing patch is 15-25 g / m 2 The amount of adhesive on the surface of the curved surface is 40 to 60 g / m 2 .

[0022] Preferably, the second curing is curing at room temperature for 7 days; or

[0023] The second curing step is curing at 70° C. for 8 hours.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] The present invention uses an aliphatic polyurethane resin with good flexibility, strength and ductility as a matrix, uses light-weight, high-absorption conductive carbon black as an absorbent, improves the dispersibility of the conductive carbon black by using a coupling agent and cellulose acetate butyrate, and can achieve low filling of the absorbent, thereby obtaining a flexible absorbing patch with small thickness, light weight, high absorption performance and high interface bonding strength. The absorbing patch is easy to "stretch" and can be smoothly attached to the surface of a curved surface part, is convenient for construction and mass production, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 is a physical diagram of the wave-absorbing patch provided by the present invention;

[0028] Figure 2 is a preparation flow chart of the wave-absorbing patch provided by the present invention;

[0029] Figure 3 is a bonding flow chart of the curved surface part of the wave-absorbing patch provided by the present invention;

[0030] Figure 4 is a physical diagram of the bonded curved surface part of the wave-absorbing patch provided by the present invention;

[0031] Figure 5 is the reflectivity curve of the wave-absorbing patch provided in Embodiment 1 of the present invention;

[0032] Figure 6 is the reflectivity curve of the wave-absorbing patch provided in Embodiment 2 of the present invention;

[0033] Figure 7 is the reflectivity curve of the wave-absorbing patch provided in Embodiment 3 of the present invention. Detailed implementation manners

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0035] The present invention provides a microwave absorbing patch in a first aspect. The raw materials for preparing the microwave absorbing patch include the following compositions in parts by weight: 100 parts of aliphatic polyurethane resin, 10-12 parts of conductive carbon black (for example, it can be 10 parts, 10.2 parts, 10.4 parts, 10.5 parts, 10.6 parts, 10.8 parts, 11 parts, 11.2 parts, 11.4 parts, 11.5 parts, 11.6 parts, 11.8 parts or 12 parts), 0.2-0.4 parts of coupling agent (for example, it can be 0.2 parts, 0.3 parts or 0.4 parts), 1-1.5 parts of cellulose acetate butyrate (for example, it can be 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts or 1.5 parts), 2-3 parts of curing agent (for example, it can be 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts or 3 parts), 100-200 parts of diluent (for example, it can be 100 parts, 110 parts, 120 parts, 130 parts, 140 parts, 150 parts, 160 parts, 170 parts, 180 parts, 190 parts or 200 parts).

[0036] The present invention uses aliphatic polyurethane resin with good flexibility, strength and ductility as the matrix, and conductive carbon black with light weight and high microwave absorption performance as the microwave absorber. By using a coupling agent and cellulose acetate butyrate to improve the dispersion of conductive carbon black, low filling of the microwave absorber can be achieved, and a flexible microwave absorbing patch with small thickness, light weight, high microwave absorption performance and large interfacial bonding strength can be obtained. The microwave absorbing patch is easy to be "stretched" and can be smoothly attached to the surface of a curved part, which is convenient for construction and mass production, and has broad application prospects.

[0037] The present invention controls the content of each component in the composition within the above range to ensure that a microwave absorbing patch with small thickness, large peel strength, light weight and excellent microwave absorption performance is obtained.

[0038] According to some preferred embodiments, the iodine adsorption value of the conductive carbon black is 900-1300 mg / g (for example, it can be 900 mg / g, 950 mg / g, 1000 mg / g, 1050 mg / g, 1100 mg / g, 1150 mg / g, 1200 mg / g, 1250 mg / g or 1300 mg / g), and the pH value is 6.5-8.0 (for example, it can be 6.5, 6.6, 6.7, 6.8, 6.9, 7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9 or 8.0). It should be noted that the conductive carbon black of the present invention is conductive carbon black AC30, purchased from Zongze Supply Chain Management (Shanghai) Co., Ltd., and the country of origin is the Czech Republic.

[0039] The present invention selects the iodine adsorption value and pH of the conductive carbon black with the above iodine adsorption value and pH, which is more conducive to the dispersion of the conductive carbon black, and is more conducive to achieving high dispersion and low filling of the absorber in the absorbing patch, thereby obtaining a thin and lightweight absorbing patch.

[0040] According to some preferred embodiments, the coupling agent is a silane coupling agent; preferably, the silane coupling agent is one or more of Si69, Si75, and KH550;

[0041] The diluent is one or more of acetone, xylene and ethyl acetate; and / or

[0042] The curing agent is 2,2-dihydroxymethylbutyric acid; it should be noted that the curing agent of the present invention was purchased from Zhangjiagang Yarui Chemical Co., Ltd.

[0043] According to some preferred embodiments, the thickness of the absorbing patch is 0.28-0.3 mm (for example, 0.28 mm, 0.29 mm or 0.3 mm); preferably, the surface density of the absorbing patch is ≤320 g / m 2 ; and / or

[0044] The peel strength of the absorbing patch is ≥30N / cm.

[0045] The absorbing patch prepared by the present invention has a small thickness (only 0.28-0.3 mm) and a light weight (surface density ≤ 320 g / m 2 ), high peel strength (≥30N / cm), absorption value ≤-8dB in Ku band, peak absorption value ≤-20dB, the absorbing patch is lightweight, has high peel strength and excellent absorbing performance. If the thickness of the absorbing patch is too large, the absorbing performance of the absorbing patch will be reduced, and the weight of the absorbing patch will be increased.

[0046] In a second aspect, the present invention provides a method for preparing the absorbing patch according to the first aspect, the preparation method comprising the following steps:

[0047] S1. The composition is fully mixed to obtain an absorbing slurry;

[0048] S2. The absorbing slurry is subjected to casting and a first curing to obtain the absorbing patch.

[0049] According to some preferred embodiments, the conductive carbon black is sequentially mixed with a diluent, a coupling agent, an aliphatic polyurethane resin, butyl acetate cellulose, a diluent and a curing agent to obtain the microwave absorbing slurry.

[0050] According to some preferred embodiments, a release paper is laid on a casting machine, and the absorbing slurry is coated on the release paper, and then subjected to doctor blading and first curing to obtain the absorbing patch.

[0051] Specifically: PP or PE release paper is transported on a casting machine, and the wave-absorbing slurry is poured onto the release paper. The coating thickness is adjusted and controlled by a knife coater, and then it enters a hot drying channel at 100-110 °C for curing to obtain the wave-absorbing patch.

[0052] The present invention provides, in a third aspect, a bonding method for the wave-absorbing patch described in the first aspect, and the bonding method includes the following steps:

[0053] (i) Brush adhesives on the surface of the wave-absorbing patch and the surface of the curved part respectively;

[0054] (ii) Bond the dried wave-absorbing patch to the surface of the curved part;

[0055] (iii) Perform secondary curing.

[0056] The present invention adopts the "double-sided brushing" method, and adhesives must be brushed on the surface of the wave-absorbing patch with release paper and the surface of the curved part respectively. After drying, the release paper is peeled off and then bonded to the surface of the curved part, which can reduce the deformation and warping of the wave-absorbing patch; if the adhesive is only brushed on the surface of the wave-absorbing patch, the wave-absorbing patch is prone to serious shrinkage after bonding; if the adhesive is only brushed on the surface of the curved part, it is not easy to bond. Brushing the adhesive on the surface of the wave-absorbing patch with the release paper retained, and then peeling it off after drying, the release paper serves as a carrier, which can reduce the shrinkage problem of the wave-absorbing patch caused by brushing the adhesive and play a shaping role; if it is directly bonded without peeling off the release paper, due to the poor ductility and flexibility of the release paper, after the wave-absorbing patch is bonded to the curved surface, phenomena such as bulging and warping occur.

[0057] According to some preferred embodiments, the adhesive is a polyurethane adhesive; the polyurethane adhesive of the present invention is Tie Mao 101 glue, purchased from Shanghai Xinguang Chemical Co., Ltd.; this polyurethane adhesive is a two-component, including component A and component B; it is obtained by mixing component A, component B and a diluent in a mass ratio of 100:(10-20):(40-70).

[0058] The present invention uses a polyurethane adhesive as the bonding adhesive. Utilizing the principle of "similar compatibility", it enables better affinity and higher peel strength between the surface of the wave-absorbing patch and the curved part, thereby improving the reliability and environmental adaptability of the product.

[0059] The dosage of the adhesive on the surface of the wave-absorbing patch is 15-25 g / m 2 (For example, it can be 15 g / m 2 、16 g / m 2 、17 g / m 2 、18 g / m 2 、19 g / m 2 、20 g / m2 , 21 g / m 2 , 22 g / m 2 , 23 g / m 2 , 24 g / m 2 or 25 g / m 2 ); The amount of the adhesive on the surface of the curved surface part is 40 - 60 g / m 2 (For example, it can be 40 g / m 2 , 42 g / m 2 , 44 g / m 2 , 45 g / m 2 , 46 g / m 2 , 48 g / m 2 , 50 g / m 2 , 52 g / m 2 , 54 g / m 2 , 55 g / m 2 , 56 g / m 2 , 58 g / m 2 or 60 g / m 2 ).

[0060] By controlling the brushing amount of the adhesive on the surface of the wave - absorbing patch and the surface of the curved surface part within the above - mentioned range, the present invention can ensure that the wave - absorbing patch can be better bonded to the surface of the curved surface part, improving the bonding performance between the wave - absorbing patch and the curved surface part.

[0061] According to some preferred embodiments, the second curing is curing at room temperature for 7 days; or

[0062] the second curing is curing at 70 °C for 8 h.

[0063] In order to more clearly illustrate the technical solutions and advantages of the present invention, the present invention will be further described below with reference to embodiments.

[0064] The materials and reagents in the present invention can all be directly purchased on the market or synthesized by oneself, and no specific models are restricted.

[0065] Example 1

[0066] 1) Stir the conductive carbon black AC30, coupling agent and diluent thoroughly to obtain a first mixture; add the aliphatic polyurethane resin to the first mixture and stir thoroughly to obtain a second mixture; add cellulose acetate butyrate to the second mixture and stir thoroughly to obtain a third mixture; add the diluent to the third mixture and stir thoroughly, then grind it on a three-roll mill at a speed of 200 r / min for 20 minutes to obtain a fourth mixture; add a curing agent to the fourth mixture and stir evenly to obtain the wave-absorbing paste; wherein, the mass ratio of the aliphatic polyurethane resin, conductive carbon black, coupling agent, diluent, cellulose acetate butyrate and curing agent is 100:10:0.2:50:1:2;

[0067] 2) Transfer the PP or PE release paper on a casting machine, pour the wave-absorbing paste onto the release paper, adjust and control the coating thickness through a doctor blade, and cure it in a hot drying oven to obtain a wave-absorbing patch;

[0068] 3) Cut the wave-absorbing patch (with release paper) into a suitable size, brush a layer of polyurethane adhesive (mass ratio of component A: component B: diluent = 100:10:40) on the surface of the wave-absorbing patch, and the weight gain per unit area is 15 g / m 2 ; brush a layer of polyurethane adhesive on the surface of the curved part, and the weight gain per unit area is 40 g / m 2 , and leave it to dry for 20 minutes;

[0069] 4) After drying, peel the wave-absorbing patch from the release paper, and bond the patch to the surface of the curved part. When bonding, first align one end of the wave-absorbing patch with the corresponding end of the curved part for bonding, and along the direction of the intended bonding, first press with the palm, and then use a squeegee to press and move back and forth along the bonding direction on the surface of the patch to remove air bubbles until the other end is completely adhered. Add an appropriate amount of weight and cure at 70 °C for 8 hours.

[0070] The reflectivity curve of the wave-absorbing patch prepared in Example 1 is as Figure 5 shown.

[0071] Example 2

[0072] 1) Conductive carbon black AC30, a coupling agent and a diluent are stirred and fully mixed to obtain a first mixture; an aliphatic polyurethane resin is added to the first mixture and stirred and fully mixed to obtain a second mixture; cellulose acetate butyrate is added to the second mixture and stirred and fully mixed to obtain a third mixture; the diluent is added to the third mixture and stirred and fully mixed, and then ground on a three-roll mill at a speed of 200 r / min for 25 minutes to obtain a fourth mixture; a curing agent is added to the fourth mixture and stirred evenly to obtain a wave absorbing material; wherein the mass ratio of the aliphatic polyurethane resin, the conductive carbon black, the coupling agent, the diluent, the cellulose acetate butyrate and the curing agent is 100:11:0.3:75:1.3:2.5;

[0073] 2) PP or PE release paper is transferred on the casting machine, and the absorbing slurry is poured on the release paper. The coating thickness is adjusted and controlled by a doctor blade coater, and the film is cured in a hot drying oven to obtain an absorbing patch.

[0074] 3) Cut the absorbing patch (with release paper) into a suitable size, and apply a layer of polyurethane adhesive (mass ratio of component A: component B: diluent = 100:15:55) on the surface of the absorbing patch, with a unit area weight gain of 20g / m 2 ; Apply a layer of polyurethane adhesive on the surface of the curved part, with a unit area weight gain of 50g / m 2 , let it dry for 40 minutes;

[0075] 4) After drying, peel off the absorbing patch from the release paper and bond the patch to the surface of the curved part. When bonding, first align one end of the absorbing patch with the corresponding end of the curved part, and apply pressure with your palm along the intended bonding direction, and then use a scraper to press back and forth on the surface of the patch along the bonding direction to remove bubbles until the other end is completely bonded, add appropriate weight, and cure at room temperature for 7 days.

[0076] The reflectivity curve of the absorbing patch obtained in Example 2 is as follows: Figure 6 shown.

[0077] Example 3

[0078] 1) Conductive carbon black AC30, a coupling agent and a diluent are stirred and fully mixed to obtain a first mixture; an aliphatic polyurethane resin is added to the first mixture and stirred and fully mixed to obtain a second mixture; cellulose acetate butyrate is added to the second mixture and stirred and fully mixed to obtain a third mixture; the diluent is added to the third mixture and stirred and fully mixed, and then ground on a three-roll mill at a speed of 200 r / min for 25 minutes to obtain a fourth mixture; a curing agent is added to the fourth mixture and stirred evenly to obtain a wave absorbing material; wherein the mass ratio of the aliphatic polyurethane resin, the conductive carbon black, the coupling agent, the diluent, the cellulose acetate butyrate and the curing agent is 100:12:0.4:100:1.5:3;

[0079] 2) PP or PE release paper is transferred on the casting machine, and the absorbing slurry is poured on the release paper. The coating thickness is adjusted and controlled by a doctor blade coater, and the film is cured in a hot drying oven to obtain an absorbing patch.

[0080] 3) Cut the absorbing patch (with release paper) into a suitable size, and apply a layer of polyurethane adhesive (mass ratio of component A: component B: diluent = 100:20:70) on the surface of the absorbing patch, with a unit area weight gain of 25g / m 2 ; Apply a layer of polyurethane adhesive on the surface of the curved part, with a unit area weight gain of 60g / m 2 , leave to air for 60 minutes;

[0081] 4) After drying, peel off the absorbing patch from the release paper and bond the patch to the surface of the curved part. When bonding, first align one end of the absorbing patch with the corresponding end of the curved part, and apply pressure with your palm along the intended bonding direction, and then use a scraper to press back and forth on the surface of the patch along the bonding direction to remove bubbles until the other end is completely bonded, add appropriate weight, and cure at 70°C for 8 hours.

[0082] The reflectivity curve of the absorbing patch obtained in Example 3 is as follows: Figure 7 shown.

[0083] Comparative Example 1

[0084] Comparative Example 1 is substantially the same as Example 2, except that in step 1), the conductive carbon black is replaced with ordinary thermal cracking carbon black N990.

[0085] Comparative Example 2

[0086] Comparative Example 2 is substantially the same as Example 2, except that in step 1), the conductive carbon black is replaced by multi-walled carbon nanotubes.

[0087] Comparative Example 3

[0088] Comparative Example 3 is basically the same as Example 2, except that: in step 1), the mass ratio of the aliphatic polyurethane resin, conductive carbon black, coupling agent, diluent, cellulose acetate butyrate and curing agent is 100:7:0.3:75:1.3:2.5.

[0089] Comparative Example 4

[0090] Comparative Example 4 is basically the same as Example 2, except that: in step 1), the mass ratio of the aliphatic polyurethane resin, conductive carbon black, coupling agent, diluent, cellulose acetate butyrate and curing agent is 100:15:0.3:75:1.3:2.5.

[0091] Comparative Example 5

[0092] Comparative Example 5 is basically the same as Example 2, except that: in step 1), cellulose acetate butyrate is not added.

[0093] Comparative Example 6

[0094] Comparative Example 6 is basically the same as Example 2, except that: in step 3), the polyurethane adhesive is replaced with an epoxy resin adhesive (Lord 305, origin is the United States, purchased from Shanghai Watai Economic and Trade Co., Ltd., wherein, the mass ratio of 305-1 component: 305-2 component = 1:1).

[0095] Comparative Example 7

[0096] Comparative Example 7 is basically the same as Example 2, except that: in step 1), the aliphatic polyurethane resin is replaced with an epoxy resin.

[0097] Comparative Example 8

[0098] Comparative Example 8 is basically the same as Example 2, except that: in step 1), the aliphatic polyurethane resin, conductive carbon black, coupling agent, diluent, cellulose acetate butyrate are fully mixed and ground on a three-roll mill at a speed of 200 r / min for 25 minutes to obtain a mixture; the curing agent is added to the mixture and stirred evenly to obtain the wave-absorbing material; wherein, the mass ratio of the aliphatic polyurethane resin, conductive carbon black, coupling agent, diluent, cellulose acetate butyrate and curing agent is 100:11:0.3:75:1.3:2.5.

[0099] Comparative Example 9

[0100] Comparative Example 9 is basically the same as Example 2, except that: in step 3), only a layer of polyurethane adhesive is brushed on the surface of the wave-absorbing patch, and the weight gain per unit area is 20 g / m 2 , and left to dry for 40 minutes.

[0101] Comparative Example 10

[0102] Comparative Example 10 is basically the same as Example 2, except that: in step 3), only one layer of polyurethane adhesive is brushed on the surface of the curved part, and the weight gain per unit area is 50 g / m 2 , and it is left to dry for 40 minutes.

[0103] Comparative Example 11

[0104] Comparative Example 11 is basically the same as Example 2, except that: in step 4), after drying, the absorbent patch is not peeled off from the release paper, and the patch is bonded to the surface of the curved part. When bonding, first align one end of the absorbent patch with the corresponding end of the curved part for bonding, and along the direction of intended bonding, first press with the palm, and then use a squeegee to press and move back and forth along the bonding direction on the surface of the patch to remove air bubbles until the other end is completely adhered. Add appropriate weight and cure at room temperature for 7 days.

[0105] Since the release paper was not peeled off during the bonding process, and the release paper does not have good ductility and flexibility, after the absorbent patch was bonded to the curved surface, phenomena such as bulging and warping occurred.

[0106] The performances of the absorbent patches provided in Examples 1-3 and Comparative Examples 1-10 are shown in Table 1.

[0107] Table 1

[0108]

[0109]

[0110] As can be seen from Table 1, the absorbent agent in Comparative Example 1 is ordinary carbon black, and the absorbent agent in Comparative Example 2 is multi-walled carbon nanotubes. The peel strength and absorbance performance in the Ku band of the prepared absorbent patches are significantly worse than those in Example 2; from Comparative Examples 3 and 4, it can be seen that whether the mass ratio of conductive carbon black to aliphatic polyurethane resin is too large or too small, the absorbance performance in the Ku band of the prepared absorbent patches is significantly worse than that in Example 2; in Comparative Example 5, cellulose acetate butyrate was not added, and the peel strength and absorbance performance in the Ku band of the prepared absorbent patches are significantly worse than those in Example 2; in Comparative Example 6, the adhesive is an epoxy resin adhesive. Due to the poor compatibility between the adhesive and the resin matrix, the peel strength of the prepared absorbent patch is significantly lower than that in Example 2; in Comparative Example 7, since an epoxy resin matrix is used, the prepared absorbent material has high hardness and is easy to break. After bonding to the curved surface, phenomena such as bulging and warping occurred; in Comparative Example 8, each component was directly mixed, and the dispersion of the prepared absorbent slurry was poor. The peel strength and absorbance performance in the Ku band of the prepared absorbent patches are significantly worse than those in Example 2; in Comparative Example 9, only one layer of polyurethane adhesive was brushed on the surface of the absorbent patch during the bonding process, and in Comparative Example 10, only one layer of polyurethane adhesive was brushed on the surface of the curved part during the bonding process. The absorbent patches cannot be well bonded to the surface of the curved part, and the peel strength is significantly less than that in Example 2.

[0111] As can be seen from Figure 4 the above, the microwave absorption patch prepared by the present invention can be smoothly attached to the surface of the curved part.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A microwave absorbing patch, It is characterized in that The raw materials for preparing the absorbing patch include the following composition in parts by weight: 100 parts of aliphatic polyurethane resin, 10-12 parts of conductive carbon black, 0.2-0.4 parts of coupling agent, 1-1.5 parts of cellulose acetate butyrate, 2-3 parts of curing agent, and 100-200 parts of diluent; the iodine adsorption value of the conductive carbon black is 900-1300 mg / g, and the pH value is 6.5-8.0; the curing agent is 2,2-dihydroxymethylbutyric acid; The preparation method of the absorbing patch comprises the following steps: S1. Stirring and mixing the conductive carbon black, the coupling agent and the diluent to obtain a first mixture; adding the aliphatic polyurethane resin to the first mixture and stirring and mixing to obtain a second mixture; adding the cellulose acetate butyrate to the second mixture and stirring and mixing to obtain a third mixture; adding the diluent to the third mixture and stirring and mixing to obtain a fourth mixture; adding the curing agent to the fourth mixture and stirring evenly to obtain an absorbing slurry; S2. Casting and first curing the absorbing slurry to obtain the absorbing patch.

2. The absorbing patch according to claim 1, It is characterized in that The coupling agent is a silane coupling agent; the silane coupling agent is one or more of Si69, Si75, KH550; and / or The diluent is one or more of acetone, xylene and ethyl acetate.

3. The absorbing patch according to claim 1, It is characterized in that The thickness of the absorbing patch is 0.28-0.3 mm.

4. The absorbing patch according to claim 1, It is characterized in that The areal density of the microwave absorbing patch ≤ 320 g / m 2 .

5. The absorbing patch according to claim 1, It is characterized in that The peel strength of the absorbing patch is ≥30N / cm.

6. The absorbing patch according to claim 1, It is characterized in that The release paper is laid on a casting machine, and the absorbing slurry is coated on the release paper, and the absorbing patch is obtained through knife coating and first curing.

7. A method for bonding the absorbing patch according to any one of claims 1 to 6, It is characterized in that The bonding method comprises the following steps: (i) applying adhesive on the surface of the absorbing patch and the surface of the curved surface member respectively; (ii) bonding the dried absorbing patch to the surface of the curved surface member; (iii) Performing a second curing.

8. The bonding method according to claim 7, It is characterized in that The adhesive is a polyurethane adhesive.

9. The bonding method according to claim 8, It is characterized in that The dosage of the adhesive on the surface of the wave-absorbing patch is 15 to 25 g / m 2 ; the dosage of the adhesive on the surface of the curved surface part is 40 to 60 g / m 2 .

10. The bonding method according to claim 7, It is characterized in that The second curing is curing at room temperature for 7 days; or The second curing step is curing at 70° C. for 8 hours.

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