Thermoplastic wave-absorbing material as well as preparation method and application thereof

Abstract

The invention discloses a thermoplastic wave-absorbing material as well as a preparation method and application thereof. The thermoplastic wave-absorbing material comprises a silane coupling agent modified absorbent and thermoplastic polyurethane, wherein the thermoplastic polyurethane is prepared from the following raw materials in parts by mass: 100 parts of a polyurethane matrix, 2 to 4 parts of an anti-hydrolysis agent, 2 to 4 parts of an antioxidant, 0.1 to 0.5 part of a mildew preventive and 2 to 10 parts of a plasticizer. The thermoplastic wave-absorbing material disclosed by the invention has good wave-absorbing performance in a range of 1-18GHz, has temperature resistance, flexibility, mechanical strength and environmental adaptability which are equivalent to those of a thermosetting material, and has a wide application prospect. According to the preparation method, extrusion molding is adopted, continuous production can be achieved, use of solvents is reduced, the method is more environmentally friendly, the material can be recycled after being damaged, and therefore the material cost is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials, and in particular to a thermoplastic microwave absorbing material, its preparation method, and its application. Background Technology

[0002] Radar-absorbing materials are fundamental to radar-absorbing performance. By using radar-absorbing materials, signal signatures can be significantly reduced without altering the target's shape, decreasing the likelihood of detection by detection systems. In designs containing numerous moving parts (such as hatches and access panels), assembly errors are inevitable due to limitations in machining precision, resulting in gaps. These tiny but significant spaces become potential secondary scattering sources, severely impacting overall stealth performance. By applying specially designed radar-absorbing edge-sealing strips to the joint surfaces, these defects can be effectively filled, ensuring a continuous, smooth, and uninterrupted surface across the entire outer shell. In addition to directly blocking physical openings, high-quality radar-absorbing edge-sealing strips can further absorb the small amounts of electromagnetic waves escaping from these gaps, further enhancing overall stealth capabilities.

[0003] Despite their excellent electrical properties, microwave absorbing edge sealing strips face challenges in practical applications, such as wear and tear caused by frequent opening and closing, especially under extreme temperature variations and harsh environments, where ordinary materials struggle to maintain optimal performance over extended periods. To meet the needs of diverse applications, ideal microwave absorbing edge sealing strips should possess sufficient flexibility to adapt to various complex shapes, while also maintaining high enough mechanical strength to withstand external impacts without damage. Existing edge sealing strips are mostly thermosetting rubber materials, requiring molding, resulting in long production cycles, and the entire product is scrapped upon damage. Current technology involves ultrasonically dispersing oxidized hydrogenated semi-coke powder and graphene oxide separately in water, then mixing the two, followed by stirring, filtration, freeze-drying, and annealing to obtain a composite absorbent. This composite absorbent is then added to a thermoplastic polyurethane solution, followed by ultrasonic treatment, stirring, and drying to obtain a polyurethane-based microwave absorbing composite material. This method, which uses solvent evaporation to combine the composite absorbent with thermoplastic polyurethane, suffers from problems such as high solvent consumption and significant pollution.

[0004] Therefore, there is an urgent need to provide a thermoplastic microwave absorbing material and its preparation method to solve the technical problems that existing microwave absorbing materials cannot simultaneously achieve flexibility, mechanical strength, microwave absorption performance, and that the preparation methods involve large amounts of solvent and significant pollution. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a thermoplastic microwave absorbing material, its preparation method and application, thereby solving the technical problems in the prior art where microwave absorbing materials cannot simultaneously achieve flexibility, mechanical strength, microwave absorption performance, and where the preparation method involves large amounts of solvent and significant pollution.

[0006] In a first aspect, the present invention provides a thermoplastic microwave absorbing material, comprising: a silane coupling agent modified absorber and thermoplastic polyurethane; wherein, by mass parts, the raw materials of the thermoplastic polyurethane include: 100 parts of polyurethane matrix, 2-4 parts of anti-hydrolysis agent, 2-4 parts of antioxidant, 0.1-0.5 parts of antifungal agent, and 2-10 parts of plasticizer.

[0007] Secondly, the present invention provides a method for preparing a thermoplastic microwave absorbing material, comprising the following steps: Mix all raw materials thoroughly to obtain a premix; The premixed material is fed into a twin-screw extruder and extruded through a die to obtain a thermoplastic microwave absorbing material.

[0008] Thirdly, the present invention provides an application of a thermoplastic microwave absorbing material, which is used as a thermoplastic microwave absorbing edge sealing strip.

[0009] Compared with the prior art, the beneficial effects of the present invention include: The thermoplastic microwave absorbing material of this invention exhibits excellent microwave absorption performance in the 1GHz~18GHz range, and possesses temperature resistance, flexibility, mechanical strength, and environmental adaptability comparable to thermosetting materials, showing broad application prospects. The preparation method of this invention employs extrusion molding, enabling continuous production, reducing solvent usage, making it more environmentally friendly, and allowing for material recycling and reuse after damage, thereby effectively reducing material costs. Attached Figure Description

[0010] Figure 1 This is a graph showing the test results of the vertical reflectivity of the thermoplastic absorbing material prepared in Example 1 of the present invention in the range of 1 GHz to 8 GHz. Figure 2 This is a graph showing the vertical reflectivity test results of the thermoplastic absorbing material prepared in Example 1 of the present invention in the range of 8GHz to 18GHz. Detailed Implementation

[0011] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0012] When preparing microwave absorbing materials using thermoplastic polyurethane, a higher absorbent filler content is generally selected to achieve better microwave absorption performance. However, with a higher absorbent filler content, the melt viscosity of the mixture increases and the processing performance deteriorates during extrusion molding. Higher temperatures are required to maintain the fluidity of the compound before injection molding. At these temperatures, the thermoplastic polyurethane is easily degraded due to the thermal accumulation of the absorbent. This invention inhibits chain scission by controlling the addition of anti-hydrolysis agents and antioxidants, and reduces melt viscosity and processing temperature by adding plasticizers to ensure that the molded material still has good mechanical strength and environmental adaptability. By treating the absorbent with a silane coupling agent, the dispersibility of the absorbent in the thermoplastic polyurethane and the binding force between the absorbent and polyurethane molecules are improved, thereby further enhancing flexibility, mechanical strength, and microwave absorption effect. The thermoplastic microwave absorbing material of this invention has excellent physical properties and functional characteristics. The thermoplastic material is recyclable and has broad application prospects.

[0013] In a first aspect, the present invention provides a thermoplastic microwave absorbing material, comprising: a silane coupling agent modified absorber and thermoplastic polyurethane; wherein, by mass parts, the raw materials of the thermoplastic polyurethane include: 100 parts of polyurethane matrix, 2-4 parts of anti-hydrolysis agent, 2-4 parts of antioxidant, 0.1-0.5 parts of antifungal agent, and 2-10 parts of plasticizer.

[0014] In this invention, the thermoplastic polyurethane's resistance to heat and oxygen aging is improved by adding antioxidants, its heat resistance and water vapor resistance are improved by adding anti-hydrolysis agents, its flexibility and absorbent filling performance are improved by adding plasticizers, and its interfacial bonding force between the absorbent and the thermoplastic polyurethane is improved by using silane coupling agents to modify the absorbent, thereby further improving its flexibility, mechanical strength and wave absorption effect.

[0015] In this embodiment, the silane coupling agent is at least one of an aminosilane coupling agent or an epoxysilane coupling agent. The present invention does not limit the type of aminosilane coupling agent or epoxysilane coupling agent; those skilled in the art can select according to the actual situation. For example, the aminosilane coupling agent can be aminopropyltriethoxysilane, aminopropyltrimethoxysilane, etc., and the epoxysilane coupling agent can be glycidyl ether propyltrimethoxysilane, etc.

[0016] In this embodiment, the absorbent is at least one of carbonyl iron powder, iron-silicon-aluminum powder, or iron-silicon-chromium powder.

[0017] In this embodiment, the silane coupling agent accounts for 1%wt to 10%wt of the absorbent mass, including but not limited to 1%wt, 2%wt, 4%wt, 6%wt, 8%wt, 10%wt, etc.

[0018] In this embodiment, the preparation steps of the silane coupling agent modified absorbent include: dispersing the absorbent in a solvent, then adding a silane coupling agent for surface treatment, and drying to obtain the silane coupling agent modified absorbent.

[0019] The mass ratio of absorbent to solvent is 1:(5~20), including but not limited to 1:5, 1:10, 1:15, 1:20, etc.

[0020] The solvent is ethanol.

[0021] The surface treatment temperature is 15℃~40℃, the surface treatment time is 100min~300min, and the stirring speed is 500rpm~1000rpm.

[0022] In this embodiment, the polyurethane matrix is ​​at least one of polyether polyurethane or polyester polyurethane.

[0023] In this embodiment, the anti-hydrolysis agent is polycarbodiimide.

[0024] In some specific embodiments of the present invention, the molecular weight of polycarbodiimide is 500 to 5000.

[0025] In this embodiment, the antioxidant is at least one of antioxidant 1010 and antioxidant 168.

[0026] In this embodiment, the antifungal agent is at least one of salicylaniline or quaternary ammonium silane.

[0027] In this embodiment, the plasticizer is at least one of dioctyl phthalate (DOP), dioctyl sebacate (DOS), and TP-95.

[0028] In this embodiment, the silane coupling agent modified absorber accounts for 40% to 70% of the mass of the thermoplastic microwave absorbing material, including but not limited to 40%, 50%, 60%, 70%, etc.

[0029] Secondly, the present invention provides a method for preparing a thermoplastic microwave absorbing material, comprising the following steps: S1. Mix all raw materials evenly to obtain a premix; S2. The premixed material is fed into a twin-screw extruder and extruded through a die to obtain a thermoplastic microwave absorbing material.

[0030] In this embodiment, during the extrusion process, the extrusion temperature is 170~190℃, including but not limited to 170℃, 180℃, 190℃, etc., and the screw speed is 180~220rpm.

[0031] In this embodiment, the extrusion method is underwater extrusion.

[0032] In this embodiment, both the mixing and extrusion processes are carried out under a protective atmosphere. The present invention does not limit the type of protective atmosphere; those skilled in the art can select one according to the actual situation. For example, the protective atmosphere can be nitrogen, etc.

[0033] Thirdly, the present invention provides an application of a thermoplastic microwave absorbing material, which is used as a thermoplastic microwave absorbing edge sealing strip.

[0034] Example 1 A thermoplastic microwave absorbing material comprises: thermoplastic polyurethane and a silane coupling agent modified absorber, wherein the silane coupling agent modified absorber accounts for 50% of the total mass of the thermoplastic microwave absorbing material; wherein the thermoplastic polyurethane comprises the following raw materials in parts by mass: 100 parts of M580A polyether polyurethane, 3 parts of polycarbodiimide (number average molecular weight 2000~3000), 2 parts of antioxidant 1010, 0.2 parts of salicylaniline, and 5 parts of DOP; the silane coupling agent modified absorber is prepared by the following steps: by mass, 100 parts of carbonyl iron powder are added to 500 parts of anhydrous ethanol, followed by 2 parts of aminopropyltriethoxysilane, stirred for 240 min at a stirring speed of 600 rpm, and then dried to obtain the silane coupling agent modified absorber.

[0035] The preparation method of the above-mentioned thermoplastic microwave absorbing material includes the following steps: (1) After drying each raw material, weigh it according to the weight proportions, add it to a high-speed mixer, fill it with nitrogen for protection, and mechanically mix it evenly to form a premix. (2) The premixed material is fed into a twin-screw extruder, protected by nitrogen, and the extrusion temperature is controlled at 180°C and the screw speed is 200 rpm. After underwater extrusion and drying through the die head, a thermoplastic microwave absorbing material is obtained.

[0036] Example 2 The steps are the same as in Example 1, except that the silane coupling agent modifies the absorbent and accounts for 60% of the total mass of the thermoplastic microwave absorbing material, and the extrusion temperature is controlled at 175°C.

[0037] Example 3 The steps are the same as in Example 1, except that the silane coupling agent modifies the absorbent and accounts for 70% of the total mass of the thermoplastic microwave absorbing material, and the extrusion temperature is controlled at 170°C.

[0038] Example 4 The steps are the same as in Example 1, except that glycidyl ether propyltrimethoxysilane is used instead of aminopropyltriethoxysilane in the preparation of the silane coupling agent modified absorbent.

[0039] Example 5 The steps are the same as in Example 1, except that the amount of DOP added is 2 parts.

[0040] Example 6 The steps are the same as in Example 1, except that the amount of DOP added is 8 parts.

[0041] Example 7 The steps are the same as in Example 1, except that the amount of DOP added is 10 parts.

[0042] Comparative Example 1 The steps are the same as in Example 1, except that carbonyl iron powder is used directly as the absorbent (without modification by silane coupling agent).

[0043] Comparative Example 2 The steps are the same as in Example 1, except that there are 0 parts of polycarbodiimide.

[0044] Comparative Example 3 The steps are the same as in Example 1, except that 1010 parts of antioxidant are used.

[0045] Comparative Example 4 The raw materials are the same as in Example 1, except that the preparation steps are as follows: 100 parts of M580A polyether polyurethane, 3 parts of polycarbodiimide, 2 parts of antioxidant 1010, 0.2 parts of salicylaniline, 5 parts of DOP, and 110.2 parts of silane coupling agent modified absorber were added to 400 parts of xylene. The mixture was sonicated for 60 min, magnetically stirred for 12 h, and the solvent was allowed to evaporate naturally. Then, it was vacuum dried in an oven at 80℃ for 8 h to obtain a thermoplastic microwave absorbing material.

[0046] Performance testing The thermoplastic microwave absorbing materials prepared in the above embodiments and comparative examples were subjected to performance tests. Mechanical properties were tested according to GB / T528-2009, tear strength according to GB / T 529-2008, and vertical reflectivity according to GJB 2038A-2011. The material thickness was 1.0 mm.

[0047] Table 1 Performance test data of different thermoplastic microwave absorbing materials

[0048] Please refer to Table 1. As can be seen from Table 1, the microwave absorbing materials prepared in the embodiments of the present invention all possess good mechanical strength, flexibility, and microwave absorption performance. Examples 1-3 show that a higher proportion of absorber results in better microwave absorption performance, but reduces tensile strength and tear strength. Examples 1 and 4 show that modification with an epoxy-based silane coupling agent is more beneficial for improving tear strength. Examples 1 and 5-7 show that with the increase of plasticizer content, mechanical strength and flexibility exhibit a trend of first increasing and then decreasing, but have little impact on microwave absorption performance. Examples 1 and Comparative Example 1 show that the addition of a silane coupling agent can significantly improve the microwave absorption performance. The tensile strength, tear strength, and microwave absorption properties indicate that the absorbent, after modification with a silane coupling agent, can be more uniformly dispersed in the thermoplastic polyurethane, thereby enhancing the material's mechanical strength, flexibility, and microwave absorption performance. Examples 1 and Comparative Examples 2-3 show that the addition of anti-hydrolysis agents and antioxidants can significantly improve the tensile strength, tear strength, and microwave absorption performance of the microwave absorbing material. Examples 1 and Comparative Example 4 show that, compared with the solvent evaporation method, the present invention, through extrusion molding, can significantly improve the tensile strength, tear strength, and microwave absorption performance of the microwave absorbing material.

[0049] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A thermoplastic microwave absorbing material, characterized in that, include: Silane coupling agents modified absorbents and thermoplastic polyurethanes; among which, The raw materials of the thermoplastic polyurethane, by weight, include: 100 parts of polyurethane matrix, 2-4 parts of anti-hydrolysis agent, 2-4 parts of antioxidant, 0.1-0.5 parts of mildew inhibitor, and 2-10 parts of plasticizer.

2. The thermoplastic microwave absorbing material according to claim 1, characterized in that, The silane coupling agent is at least one of an aminosilane coupling agent or an epoxysilane coupling agent; wherein... The aminosilane coupling agent is at least one selected from aminopropyltriethoxysilane and aminopropyltrimethoxysilane; and / or... The epoxy silane coupling agent is glycidyl ether propyltrimethoxysilane.

3. The thermoplastic microwave absorbing material according to claim 1, characterized in that, The absorbent is at least one of carbonyl iron powder, iron-silicon-aluminum powder, or iron-silicon-chromium powder; and / or, The silane coupling agent accounts for 1% to 10% of the mass of the absorbent.

4. The thermoplastic microwave absorbing material according to claim 1, characterized in that, The preparation steps of the silane coupling agent modified absorbent include: dispersing the absorbent in a solvent, then adding a silane coupling agent for surface treatment, and drying to obtain the silane coupling agent modified absorbent.

5. The thermoplastic microwave absorbing material according to claim 4, characterized in that, The mass ratio of the absorbent to the solvent is 1:(5~20); and / or, The solvent is ethanol; and / or, The surface treatment temperature is 15℃~40℃, the surface treatment time is 100min~300min, and the stirring speed is 500rpm~1000rpm.

6. The thermoplastic microwave absorbing material according to claim 1, characterized in that, The polyurethane matrix is ​​at least one of polyether-type polyurethane or polyester-type polyurethane; and / or The anti-hydrolysis agent is polycarbodiimide; and / or... The antioxidant is at least one of antioxidant 1010 and antioxidant 168; and / or, The antifungal agent is at least one of salicylaniline or quaternary ammonium silane; and / or The plasticizer is at least one of dioctyl phthalate, dioctyl sebacate, and TP-95.

7. The thermoplastic microwave absorbing material according to claim 1, characterized in that, The silane coupling agent modified absorber accounts for 40% to 70% of the mass of the thermoplastic microwave absorbing material.

8. A method for preparing the thermoplastic microwave absorbing material according to any one of claims 1 to 7, characterized in that, Includes the following steps: Mix all raw materials thoroughly to obtain a premix; The premixed material is fed into a twin-screw extruder and extruded through a die to obtain a thermoplastic microwave absorbing material.

9. The method for preparing the thermoplastic microwave absorbing material according to claim 8, characterized in that, The extrusion temperature is 170~190℃, and the screw speed is 180~220rpm; and / or, The extrusion method is underwater extrusion; and / or, Both the mixing and extrusion processes are carried out under a protective atmosphere.

10. An application of the thermoplastic microwave absorbing material as described in any one of claims 1 to 7, characterized in that, The thermoplastic absorbing material is used as a thermoplastic absorbing edge sealing strip.

Images