Wave-absorbing slurry, polyurethane-based radar wave-absorbing foam as well as preparation method and application of polyurethane-based radar wave-absorbing foam

Abstract

The invention belongs to the technical field of electromagnetic wave-absorbing materials, and relates to wave-absorbing slurry, polyurethane-based radar wave-absorbing foam as well as a preparation method and application. By adjusting the content ratio of the purified water, the polyurethane resin, the conductive carbon black / acetylene carbon black powder, the silane coupling agent, the anti-adhesion additive and the defoaming agent, the movement of the absorption peak of the polyurethane-based radar wave-absorbing foam between high frequency and low frequency in the frequency range of 2-18 GHz can be adjusted; the optimal average radar reflectivity performance at 2-18 GHz can reach-20 dB, the optimal average radar reflectivity performance at 8-18 GHz can be smaller than or equal to-23 dB, and the optimal radar reflectivity wave-absorbing performance at 13.6 GHz can reach-35 dB. The low-density polyurethane foam is used as a base body, the wave-absorbing slurry is immersed into a grid framework of the base body, the wave-absorbing layer is formed after drying, and meanwhile, the overall weight gain of the sponge is small, so that the polyurethane-based radar wave-absorbing foam achieves the light wave-absorbing effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic absorbing materials, and in particular relates to an absorbing slurry, a polyurethane-based radar absorbing foam, and a preparation method and application thereof. Background Art

[0002] Electromagnetic absorbing materials are gaining increasing attention among researchers. Traditional absorbing materials, however, are limited in their application due to their inherent limitations, such as high density and poor absorption performance. The porous structure of foam absorbing materials effectively reduces the density of the composite material while also optimizing impedance matching by introducing air into the system, achieving multiple reflections of electromagnetic waves and significantly improving the absorption efficiency of the absorbing foam material.

[0003] [He Shan, Xiong Kemin, et al. Research on foam-type absorbing materials for radomes [J]. Journal of Aeronautical Materials, 2001, 09(21): 20-23] mentioned a broadband lightweight foam material with a radar reflectivity of ≤-15dB in the 8-18GHz frequency band and a surface density of 1.5kg / m 2 However, the broadband lightweight foam material still has the problem of high surface density, and the radar performance needs to be further improved.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide an absorbing slurry, a polyurethane-based radar absorbing foam, and a preparation method and application thereof.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] On the one hand, the present invention provides an absorbing slurry, which includes the following components, calculated by weight: 650-750 parts of water, 200-250 parts of polyurethane resin, 20-30 parts of conductive carbon black / acetylene black powder, 50 parts of additives, and 10-15 parts of polyurethane resin curing agent; wherein the additives include 5-10 parts of silane coupling agent, 10-15 parts of anti-adhesion additive, and 25-35 parts of defoaming agent.

[0008] Specifically, the conductive carbon black / acetylene carbon black powder is a mixture of conductive carbon black powder and acetylene carbon black powder, and the mass ratio of the conductive carbon black powder to the acetylene carbon black powder in the mixture is 1:1.

[0009] In another aspect, the present invention provides a method for preparing the above-mentioned absorbing slurry, wherein the preparation method is as follows;

[0010] First, the required raw materials are weighed according to weight, and then the polyurethane resin, conductive carbon black / acetylene carbon black powder, silane coupling agent, anti-adhesion agent, and defoaming agent are added to water in sequence. After the first stirring and dispersion, the polyurethane resin curing agent is added, and then the second stirring and dispersion is performed to finally prepare the absorbing slurry.

[0011] Specifically, an appropriate amount of grinding beads needs to be added before the first stirring and dispersing. The speed of the first dispersing and stirring is 600-1200 r / min, and the time is 2-2.5 h; the speed of the second dispersing and stirring is 600-1200 r / min, and the time is 10-30 min.

[0012] In another aspect, the present invention provides a polyurethane-based radar absorbing foam, which is prepared by using the absorbing slurry prepared by the preparation method described above and the polyurethane foam.

[0013] In another aspect, the present invention provides a method for preparing the polyurethane-based radar absorbing foam as described above, comprising the following steps:

[0014] Step 1: Select a polyurethane foam block of specific thickness and density;

[0015] Step 2: completely immersing the polyurethane foam block in the microwave absorbing slurry and repeatedly squeezing the block until no more bubbles emerge, thereby obtaining an impregnated polyurethane foam.

[0016] Step 3: Using a fixed-distance extrusion device, squeeze the impregnated polyurethane foam multiple times;

[0017] Step 4: Dry and solidify the extruded polyurethane foam to obtain polyurethane-based radar absorbing foam.

[0018] Specifically, in step 1, the polyurethane foam block is a square low-density polyurethane foam with a thickness of 2 to 8 cm, a density of 40 to 80 ppi, and a size of 180×180 mm to 1000×1000 mm.

[0019] Specifically, in step 2, the polyurethane foam block is repeatedly squeezed in the microwave absorbing slurry for 3 to 5 times, each time for 1 to 2 minutes.

[0020] Specifically, in step 4, the drying and curing is performed at a temperature of 50 to 100° C. for 24 to 48 hours.

[0021] In another aspect, the present invention provides the polyurethane-based radar absorbing foam as described above, or the use of the polyurethane-based radar absorbing foam prepared by the preparation method as described above, in the field of absorbing radar.

[0022] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0023] 1) The present invention adjusts the content ratio of each component of pure water, polyurethane resin, conductive carbon black / acetylene carbon black powder, silane coupling agent, anti-adhesion additive, and defoaming agent to adjust the movement of the absorption peak of the polyurethane-based radar absorbing foam between high frequency or low frequency in the frequency band of 2 to 18 GHz; the average radar reflectivity performance at 2 to 18 GHz is the best up to -20 dB, the average radar reflectivity performance at 8 to 18 GHz is the best up to ≤-23 dB, and the best radar reflectivity absorption performance at 13.6 GHz can reach -35 dB.

[0024] 2) The present invention uses low-density polyurethane foam as the matrix, and the matrix is a porous grid skeleton structure. The structure itself is lightweight and porous. By impregnating the absorbing slurry, the absorbing slurry is immersed in the grid skeleton. After drying, the water in the absorbing slurry evaporates, and the absorbing agent is attached and fixed on the surface of the porous grid skeleton to form a thin absorbing layer. At the same time, the overall weight gain of the sponge is small. The surface density of the 2cm thick polyurethane-based radar absorbing foam is 1.1kg / ㎡, so that the polyurethane-based radar absorbing foam achieves the effect of lightweight absorbing.

[0025] 3) The present invention adopts a fixed-spacing extrusion device to extrude the impregnated low-density polyurethane foam. First, the excess absorbing slurry in the low-density polyurethane foam can be removed, thereby reducing the content of the absorbing slurry in the low-density polyurethane foam, reducing the solid content of the low-density polyurethane foam after drying, and reducing the weight of the polyurethane-based radar absorbing foam. Secondly, the fixed-spacing extrusion can make all parts of the low-density polyurethane foam be subjected to uniform pressure, thereby ensuring the uniformity of the distribution of the absorbing slurry in the low-density polyurethane foam, avoiding the formation of lumps in the low-density polyurethane foam due to uneven distribution of the absorbing slurry, thereby preventing the influence of lumps on radar waves, and further improving the radar performance of the polyurethane-based radar absorbing foam. Finally, the fixed-spacing extrusion can better protect the original structure of the low-density polyurethane foam, avoid the destruction of the pore structure of the low-density polyurethane foam due to excessive extrusion, and ensure the structural stability of the polyurethane-based radar absorbing foam. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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 invention.

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0028] Figure 1This is a flow chart of the method for preparing the polyurethane-based radar absorbing foam of the present invention;

[0029] Figure 2 This is a radar performance curve of the polyurethane-based radar absorbing foam prepared in Example 1 in the range of 2 to 18 GHz. DETAILED DESCRIPTION

[0030] Exemplary embodiments will now be described in detail, with examples shown in the accompanying drawings. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present invention. Instead, they are merely examples consistent with some aspects of the present invention as detailed in the appended claims.

[0031] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is described in further detail below with reference to the accompanying drawings and embodiments.

[0032] On the one hand, the present invention provides an absorbing slurry, which includes the following components, calculated by weight: 650-750 parts of water, 200-250 parts of polyurethane resin, 20-30 parts of conductive carbon black / acetylene black powder, 50 parts of additives, and 10-15 parts of polyurethane resin curing agent; wherein the additives include 5-10 parts of silane coupling agent, 10-15 parts of anti-adhesion additive, and 25-35 parts of defoaming agent.

[0033] Specifically, the conductive carbon black / acetylene carbon black powder is a mixture of conductive carbon black powder and acetylene carbon black powder, and the mass ratio of the conductive carbon black powder to the acetylene carbon black powder in the mixture is 1:1.

[0034] In another aspect, the present invention provides a method for preparing the above-mentioned absorbing slurry, wherein the preparation method is as follows;

[0035] First, the required raw materials are weighed according to weight, and then the polyurethane resin, conductive carbon black / acetylene carbon black powder, silane coupling agent, anti-adhesion agent, and defoaming agent are added to water in sequence. After the first stirring and dispersion, the polyurethane resin curing agent is added, and then the second stirring and dispersion is performed to finally prepare the absorbing slurry.

[0036] Specifically, an appropriate amount of grinding beads needs to be added before the first stirring and dispersing. The speed of the first dispersing and stirring is 600-1200 r / min, and the time is 2-2.5 h; the speed of the second dispersing and stirring is 600-1200 r / min, and the time is 10-30 min.

[0037] In another aspect, the present invention provides a polyurethane-based radar absorbing foam, which is prepared by using the absorbing slurry prepared by the preparation method described above and the polyurethane foam.

[0038] In another aspect, the present invention provides a method for preparing the polyurethane-based radar absorbing foam as described above, comprising the following steps:

[0039] Step 1: Select a polyurethane foam block of specific thickness and density;

[0040] Step 2: completely immersing the polyurethane foam block in the microwave absorbing slurry and repeatedly squeezing the block until no more bubbles emerge, thereby obtaining an impregnated polyurethane foam.

[0041] Step 3: Using a fixed-distance extrusion device, squeeze the impregnated polyurethane foam multiple times;

[0042] Step 4: Dry and solidify the extruded polyurethane foam to obtain polyurethane-based radar absorbing foam.

[0043] Specifically, in step 1, the polyurethane foam block is a square low-density polyurethane foam with a thickness of 2 to 8 cm, a density of 40 to 80 ppi, and a size of 180×180 mm to 1000×1000 mm.

[0044] Specifically, in step 2, the polyurethane foam block is repeatedly squeezed in the microwave absorbing slurry for 3 to 5 times, each time for 1 to 2 minutes.

[0045] Specifically, in step 4, the drying and curing is performed at a temperature of 50 to 100° C. for 24 to 48 hours.

[0046] In order to verify the effectiveness of the preparation method of the polyurethane-based radar absorbing foam of the present invention, the following examples are provided for verification.

[0047] Example 1

[0048] See also Figure 1 As shown, this embodiment provides a method for preparing a polyurethane-based radar absorbing foam, and the specific steps are as follows:

[0049] Step 1, weighing 694.5 parts of pure water, adding 217.1 parts of low-density polyurethane resin (BLJ-716), 25.2 parts of conductive carbon black / acetylene black powder, 6.3 parts of silane coupling agent (KH560), 13.7 parts of anti-adhesion additive (LH-333), 30 parts of defoamer (6203), and adding an appropriate amount of grinding beads, passing through a disperser at a speed of 1200r / min and fully grinding and stirring for 2h, then adding 13.1 parts of polyurethane resin curing agent (L75), and then after dispersion stirring at a speed of 1200r / min and a dispersion stirring time of 10min, the absorbing slurry is prepared;

[0050] Step 2: Select a low-density polyurethane foam with a thickness of 2 cm and a density of 60 ppi, and cut it into blocks with a size of 180 mm × 180 mm using a cutting knife to obtain a low-density polyurethane foam block;

[0051] Step 3: first pour the absorbing slurry into an open container, then completely immerse the low-density polyurethane foam block in the absorbing slurry, and repeatedly squeeze it in the absorbing slurry for 3 to 5 times, each time lasting 1 to 2 minutes, and finally squeeze until no bubbles emerge, to obtain the impregnated low-density polyurethane foam;

[0052] Step 4: Using a fixed-pitch extrusion device, adjust the extrusion pitch to 10 mm, and extrude the impregnated low-density polyurethane foam twice through the extrusion device to obtain extruded low-density polyurethane foam;

[0053] Step 5: Place the extruded low-density polyurethane foam in a drying room at 80° C. and dry and cure it for 24 hours. After it is completely dried and cured, a polyurethane-based radar absorbing foam A is obtained.

[0054] Example 2

[0055] This embodiment provides a method for preparing a polyurethane-based radar absorbing foam, and the specific steps are as follows:

[0056] Step 1, weighing 750 parts of pure water, adding 250 parts of polyurethane resin (BLJ-716), 30 parts of conductive carbon black / acetylene carbon black powder, 10 parts of silane coupling agent (KH560), 15 parts of anti-adhesion additive (LH-333), 25 parts of defoamer (6203), and adding an appropriate amount of grinding beads, passing through a disperser at a speed of 600r / min and fully grinding and stirring for 2.5h, then adding 15 parts of polyurethane resin curing agent (L75), and then after dispersion stirring at a speed of 600r / min and a dispersion stirring time of 30min, the absorbing slurry is prepared;

[0057] Step 2: Select a low-density polyurethane foam with a thickness of 6 cm and a density of 80 ppi, and cut it into blocks with a size of 1000 mm × 1000 mm using a cutting knife to obtain a low-density polyurethane foam block;

[0058] Step 3: first pour the absorbing slurry into an open container, then completely immerse the low-density polyurethane foam block in the absorbing slurry, and repeatedly squeeze it in the absorbing slurry for 3 to 5 times, each time lasting 1 to 2 minutes, and finally squeeze until no bubbles emerge, to obtain the impregnated low-density polyurethane foam;

[0059] Step 4: Using a fixed-pitch extrusion device, adjust the extrusion pitch to 14 mm, and extrude the impregnated low-density polyurethane foam twice through the extrusion device to obtain extruded low-density polyurethane foam;

[0060] Step 5: Place the extruded low-density polyurethane foam in a drying room at 100° C. and dry and cure it for 48 hours. After it is completely dried and cured, a polyurethane-based radar absorbing foam B is obtained.

[0061] Example 3

[0062] This embodiment provides a method for preparing a polyurethane-based radar absorbing foam, and the specific steps are as follows:

[0063] Step 1, weighing 650 parts of pure water, adding 200 parts of polyurethane resin (BLJ-716), 20 parts of conductive carbon black / acetylene carbon black powder, 5 parts of silane coupling agent (KH560), 10 parts of anti-adhesion additive (LH-333), 35 parts of defoamer (6203), and adding an appropriate amount of grinding beads, passing through a disperser at a speed of 900r / min and fully grinding and stirring for 2h, then adding 10 parts of polyurethane resin curing agent (L75), and then after dispersion stirring at a speed of 900r / min and a dispersion stirring time of 20min, the absorbing slurry was prepared;

[0064] Step 2: Select low-density polyurethane foam with a thickness of 8 cm and a density of 40 ppi, and cut it into blocks of 500 mm × 500 mm using a cutting knife to obtain low-density polyurethane foam blocks;

[0065] Step 3: first pour the absorbing slurry into an open container, then completely immerse the low-density polyurethane foam block in the absorbing slurry, and repeatedly squeeze it in the absorbing slurry for 3 to 5 times, each time lasting 1 to 2 minutes, and finally squeeze until no bubbles emerge, to obtain the impregnated low-density polyurethane foam;

[0066] Step 4: Using a fixed-pitch extrusion device, adjust the extrusion pitch to 6 mm, and extrude the impregnated low-density polyurethane foam twice through the extrusion device to obtain extruded low-density polyurethane foam;

[0067] Step 5: Place the extruded low-density polyurethane foam in a drying room at 50° C. and dry and cure for 36 hours. After it is completely dried and cured, a polyurethane-based radar absorbing foam C is obtained.

[0068] The radar reflectivity of the polyurethane-based radar absorbing foam A prepared in Example 1 was tested in the frequency range of 2 to 18 GHz. Figure 2As shown in the figure, the horizontal axis represents frequency and the vertical axis represents radar reflectivity; in the range of 2 to 18 GHz, the average value of the radar reflectivity of the polyurethane-based radar absorbing foam A is ≤-20 dB; in the range of 8 to 18 GHz, the average value of the radar reflectivity of the polyurethane-based radar absorbing foam A is ≤-23 dB; at 13.6 GHz, the radar reflectivity of the polyurethane-based radar absorbing foam A can reach -35 dB; therefore, the polyurethane-based radar absorbing foam prepared by the preparation method meets the use requirements in the field of radar absorption.

[0069] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0070] It should be understood that the present invention is not limited to the above description and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A microwave absorbing slurry, characterized in that: The composition includes the following components in parts by weight: 650-750 parts of water, 200-250 parts of polyurethane resin, 20-30 parts of conductive carbon black / acetylene black powder, 50 parts of auxiliary agent, and 10-15 parts of polyurethane resin curing agent; wherein the auxiliary agent includes 5-10 parts of silane coupling agent, 10-15 parts of anti-adhesion auxiliary agent, and 25-35 parts of defoaming agent.

2. The microwave absorbing slurry according to claim 1, characterized in that: The conductive carbon black / acetylene carbon black powder is a mixture of conductive carbon black powder and acetylene carbon black powder, and the mass ratio of the conductive carbon black powder to the acetylene carbon black powder in the mixture is 1:

1.

3. The method for preparing the microwave absorbing slurry according to claim 1 or 2, characterized in that: The preparation method is as follows: First, the required raw materials are weighed according to weight, and then the polyurethane resin, conductive carbon black / acetylene carbon black powder, silane coupling agent, anti-adhesion agent, and defoaming agent are added to water in sequence. After the first stirring and dispersion, the polyurethane resin curing agent is added, and then the second stirring and dispersion is performed to finally prepare the absorbing slurry.

4. The method for preparing the microwave absorbing slurry according to claim 1, wherein: Before the first stirring and dispersing, an appropriate amount of grinding beads needs to be added. The speed of the first dispersing and stirring is 600-1200 r / min, and the time is 2-2.5 hours; the speed of the second dispersing and stirring is 600-1200 r / min, and the time is 10-30 minutes.

5. A polyurethane-based radar absorbing foam, characterized in that: The microwave absorbing slurry and polyurethane foam are prepared by the preparation method according to claim 3 or 4.

6. The method for preparing the polyurethane-based radar absorbing foam according to claim 5, characterized in that: The steps include: Step 1: Select a polyurethane foam block of specific thickness and density; Step 2: completely immersing the polyurethane foam block in the microwave absorbing slurry and repeatedly squeezing the block until no more bubbles emerge, thereby obtaining an impregnated polyurethane foam. Step 3: Using a fixed-distance extrusion device, squeeze the impregnated polyurethane foam multiple times; Step 4: Dry and solidify the extruded polyurethane foam to obtain polyurethane-based radar absorbing foam.

7. The preparation method according to claim 6, characterized in that In step 1, the polyurethane foam block is a square low-density polyurethane foam with a thickness of 2 to 8 cm, a density of 40 to 80 ppi, and a size of 180×180 mm to 1000×1000 mm.

8. The preparation method according to claim 6, characterized in that In step 2, the polyurethane foam block is repeatedly squeezed in the microwave absorbing slurry for 3 to 5 times, each time for 1 to 2 minutes.

9. The preparation method according to claim 6, characterized in that In step 4, drying and curing are performed at a temperature of 50 to 100° C. for 24 to 48 hours.

10. Use of the polyurethane-based radar absorbing foam according to claim 5, or the polyurethane-based radar absorbing foam prepared by the preparation method according to any one of claims 6 to 9, characterized in that: Application in the field of wave absorption.

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