A wave-absorbing patch with high flame-retardant performance and a preparation method thereof

Abstract

The application provides a wave-absorbing patch with high flame-retardant performance and a preparation method, and belongs to the technical field of wave-absorbing materials. The technical problem that traditional wave-absorbing materials are difficult to realize excellent electromagnetic wave absorption and high flame-retardant performance under the premise of good usability and processability due to poor mechanical performance, processing difficulty and the like caused by simply increasing the filling amount of absorbents and flame-retardants in the application of light weight and miniaturization is solved. The wave-absorbing patch comprises a rubber matrix, a multi-dimensional electromagnetic wave absorbent, white carbon black, an inorganic hydroxide flame-retardant and a vulcanizing agent. By constructing a multi-scale network structure of the absorbent, electronic transition is effectively promoted, and the hetero-interface is increased, so that the electromagnetic wave loss capacity of the material is significantly improved; the flame-retardant and the multi-dimensional electromagnetic wave absorbent synergistically act to form a uniform and dense carbon layer in the condensed phase, and the gas phase flame-retardant effect is exerted. The application is suitable for the field of electronic devices and communication with high requirements for light weight, miniaturization and safety.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, specifically to a microwave absorbing patch with high flame retardant properties and its preparation method. Background Technology

[0002] With the rapid development and widespread adoption of 5G communication, the Internet of Things, and high-power electronic devices, electromagnetic radiation pollution has become an increasingly prominent issue. Therefore, developing microwave absorbing materials that combine thinness, lightweight properties, and wide-bandwidth, strong absorption characteristics is of significant application value. At the same time, the high integration of electronic and communication equipment also places higher demands on material safety, making microwave absorbing materials with excellent flame-retardant properties a necessary choice for ensuring the safety of equipment and personnel.

[0003] Currently, a simple and direct approach in existing technologies is to fill flexible polymers with absorbers that absorb electromagnetic losses and flame retardants that have flame-retardant properties. This process typically requires a high filler content to achieve the desired microwave absorption and flame retardancy for industrial applications. However, polymer substrates, such as silicone rubber, usually have upper limits on filler addition. Simultaneously adding large amounts of absorbers and flame retardants significantly reduces the mechanical properties of the composite material, drastically worsening its processability, such as hardness and resilience, severely impacting processability and making it difficult to meet the stringent requirements for comprehensive material performance in modern electronic equipment and aerospace applications. Therefore, how to synergistically achieve high-efficiency microwave absorption and high flame retardancy without compromising processability has become a critical issue that urgently needs to be addressed in this technological field. Summary of the Invention

[0004] This invention aims to resolve the contradiction in existing microwave absorbing materials that simultaneously possess flame-retardant properties, mechanical properties, and processability. Its technical objective is to provide a microwave absorbing patch with high flame-retardant performance. This invention, through the synergistic design of multi-dimensional electromagnetic wave absorbers and flame retardants, aims to overcome the problems of significantly reduced mechanical properties and processing difficulties caused by simply increasing the amount of absorber and flame retardant in traditional technologies. Thus, while ensuring processability and usability, it simultaneously achieves excellent electromagnetic wave absorption capacity and high flame-retardant properties.

[0005] To achieve the above-mentioned objectives of this invention, the following technical solution is adopted: A microwave absorbing patch with high flame retardant properties comprises the following raw materials: a rubber matrix, a multidimensional electromagnetic wave absorber, silica, an inorganic hydroxide flame retardant, and a vulcanizing agent; the multidimensional electromagnetic wave absorber is mainly composed of nano-graphite with a size of 30-100 nm, and includes one or more of sheet graphene with a transverse dimension of 35-50 μm or carbon fiber or iron fiber with an aspect ratio of 4:1 to 8:1.

[0006] Preferably, the rubber matrix is ​​silicone rubber, and more preferably one of methyl silicone rubber, methyl vinyl silicone rubber, and methyl phenyl vinyl silicone rubber.

[0007] Preferably, the inorganic hydroxide flame retardant is one or more of aluminum hydroxide and magnesium hydroxide.

[0008] Preferably, the total amount of the multidimensional electromagnetic wave absorber added to the raw material of the microwave absorbing patch is 60-100 parts, with 100 parts of the rubber matrix.

[0009] Preferably, the total amount of the inorganic hydroxide flame retardant added to the microwave absorbing patch raw material is 30-60 parts, based on 100 parts of the rubber matrix.

[0010] More preferably, when the multidimensional electromagnetic wave absorber contains sheet graphene, the mass ratio of the nanographite to the sheet graphene is 15:1 to 30:1.

[0011] In a further preferred embodiment, the amount of silica added to the microwave absorbing patch raw material is 5-20 parts, based on 100 parts of the rubber matrix.

[0012] To achieve the objective of this invention, another technical solution is adopted: a method for preparing a microwave absorbing patch with high flame retardant performance, wherein a rubber matrix, a multidimensional electromagnetic wave absorber, silica and an inorganic hydroxide flame retardant are premixed, the premixed materials are then mixed evenly in a two-roll mill, a vulcanizing agent is added and the mixing is continued, and after vulcanization, the microwave absorbing patch is obtained.

[0013] Preferably, the vulcanization includes a first-stage vulcanization at 10 MPa pressure and 175°C for 10 minutes, and a second-stage vulcanization at 200°C for 2 hours.

[0014] The invention also provides the use of the aforementioned high flame-retardant absorbing patch in the preparation of electromagnetic wave absorbing or electromagnetic protection materials.

[0015] Compared with the prior art, the present invention achieves the following technical effects: 1. This invention introduces a multidimensional electromagnetic wave absorber consisting primarily of nano-graphite of a specific size (30-100 nm) and supplemented with sheet-like graphene of a specific lateral size (35-50 μm) or fibers of a specific aspect ratio (4:1 to 8:1), thereby constructing a highly efficient multi-scale conductive network and heterogeneous interface within the material. This structure effectively promotes electronic transitions and increases interfacial polarization, thus significantly improving the electromagnetic wave absorption performance of the composite material while maintaining a controllable total filler content.

[0016] 2. This invention utilizes the synergistic effect of inorganic hydroxide flame retardants with materials such as zero-dimensional nano-graphite, one-dimensional fibers, and two-dimensional sheet graphene in the system. During combustion, it can catalyze the formation of a dense and uniform char barrier layer and release flame-inhibiting components, while simultaneously exerting both condensed-phase and gas-phase flame-retardant effects. This dual flame-retardant mechanism endows the material with extremely high flame-retardant properties, with a limiting oxygen index exceeding 46.6%, thus ensuring the safety of the material while achieving efficient wave absorption. Attached Figure Description

[0017] For ease of explanation, the present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0018] Figure 1 The diagram shows a comparison of reflection loss in Examples 1-3.

[0019] Figure 2 This is a comparison chart of reflection loss in Examples 1-4. Detailed Implementation

[0020] The following are specific embodiments of the present invention, in conjunction with the appendix. Figure 1-2 The technical solutions of the present invention will be further described below, but the present invention is not limited to these embodiments; in the following description, specific details such as specific configurations are provided only to help to fully understand the embodiments of the present invention. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present invention.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0022] Unless otherwise specified, the materials, practices, and experimental equipment involved in the embodiments of this invention are all commercially available products in the relevant chemical and biotechnology fields.

[0023] The microwave absorbing patch with high flame retardant properties provided by this invention is specifically prepared by the following steps: (1) Weigh each raw material component by weight: 100 parts of rubber matrix, 60-100 parts of multidimensional electromagnetic wave absorber (of which the size of nano-graphite is 30-100 nm, the transverse dimension of the contained sheet graphene is 35-50 μm, and the aspect ratio of carbon fiber or iron fiber is 4:1 to 8:1), 5-20 parts of fumed silica, and 30-60 parts of inorganic hydroxide flame retardant; (2) Transfer all the raw materials weighed in step (1) to a container for physical stirring and premixing; (3) Transfer the premixed mixture from step (2) to a rolling mill and repeatedly pass through and mix it at room temperature until it is uniform. Then add the amount of vulcanizing agent (corresponding to 100 parts of rubber matrix, usually 1-2 parts) and continue to mix until it is evenly dispersed to obtain the compound rubber and sheet it to form a rubber sheet. (4) Place the rubber sheet obtained in step (3) into a mold that has been pre-sprayed with release agent, place it in a flat vulcanizing machine at 175 ℃, and vulcanize it at 10 MPa pressure for 10 min. (5) After vulcanization, the sample is placed in an oven at 200 ℃ and kept warm for 2 h for two-stage vulcanization treatment; finally, it is naturally cooled to room temperature and demolded to obtain a rubber sheet of 300mm×300mm×3mm, which is the microwave absorbing patch with high flame retardant performance.

[0024] Example 1 A microwave absorbing patch with high flame retardant properties is prepared as follows: 100 parts by weight of methyl vinyl silicone rubber is selected as the matrix, 40 parts by weight of aluminum hydroxide as the flame retardant filler, 50 parts by weight of nano-graphite (particle size 30-100 nm) and 20 parts by weight of conductive carbon fiber (length-to-diameter ratio 4:1 to 6:1) as multidimensional electromagnetic wave absorbers, and 20 parts by weight of silica as a reinforcing filler. First, the filler and rubber matrix are premixed; then, the premix is ​​transferred to a two-roll mill for thorough blending to form a homogeneous mixture; finally, the mixture is vulcanized at high temperature to obtain the flame retardant microwave absorbing patch.

[0025] Example 2 A microwave absorbing patch with high flame retardant properties is prepared as follows: 100 parts by weight of methyl vinyl silicone rubber is selected as the matrix, 40 parts by weight of aluminum hydroxide as the flame retardant filler, 50 parts by weight of nano-graphite (particle size 30-100 nm) and 30 parts by weight of iron fiber (length-to-diameter ratio 4:1 to 8:1) as multidimensional electromagnetic wave absorbers, and 20 parts by weight of silica as a filler and reinforcing agent. First, the filler and rubber matrix are premixed; then, the premix is ​​transferred to a two-roll mill for thorough blending to form a homogeneous mixture; finally, the mixture is vulcanized at high temperature to obtain the flame retardant microwave absorbing patch.

[0026] Example 3 A microwave absorbing patch with high flame retardant properties is prepared as follows: 100 parts by weight of methyl vinyl silicone rubber is selected as the matrix, 30 parts by weight of aluminum hydroxide as the flame retardant filler, 57 parts by weight of nano-graphite (particle size 30-100 nm) and 3 parts by weight of sheet graphene (lateral dimension 35-50 μm) as multidimensional electromagnetic wave absorbers, and 15 parts by weight of silica as a filler and reinforcing agent. First, the filler and rubber matrix are premixed; then, the premix is ​​transferred to a two-roll mill for thorough blending to form a homogeneous mixture; finally, the mixture is vulcanized at high temperature to obtain the flame retardant microwave absorbing patch.

[0027] Comparative Example 1 This comparative example aims to examine the material performance when two absorbents of the same dimension (both fibrous) are combined and the total filler content is significantly increased. The preparation method is as follows: 100 parts by weight of methyl vinyl silicone rubber was selected as the matrix, 40 parts by weight of aluminum hydroxide as the flame-retardant filler, 60 parts by weight of conductive carbon fiber (aspect ratio 4:1 to 8:1) and 100 parts by weight of iron fiber (aspect ratio 4:1 to 8:1) as absorbents, and 10 parts by weight of silica as reinforcing filler. All the fillers were premixed with the rubber matrix; subsequently, the premix was transferred to a two-roll mill for thorough blending to form a homogeneous mixture; finally, the mixture was vulcanized at high temperature to obtain the microwave absorbing patch.

[0028] Comparative Example 2 This comparative example aims to examine the performance of the material when using a single absorbent, and its preparation method is as follows: 100 parts by weight of methyl vinyl silicone rubber were selected as the matrix, 30 parts by weight of aluminum hydroxide as the flame retardant filler, 75 parts by weight of nano-graphite (particle size 30-100 nm) as the absorbent, and 10 parts by weight of silica as the reinforcing filler. All the fillers were premixed with the rubber matrix; subsequently, the premix was transferred to a two-roll mill for thorough blending to form a homogeneous mixture; finally, the mixture was vulcanized at high temperature to obtain the flame-retardant microwave absorbing patch.

[0029] Comparative Example 3 This comparative example aims to investigate the effect of the ratio of nano-graphite to graphene on flame retardant and microwave absorption properties. The preparation method is as follows: A microwave absorbing patch with high flame retardant properties is prepared as follows: 100 parts by weight of methyl vinyl silicone rubber is selected as the matrix, 30 parts by weight of aluminum hydroxide as the flame retardant filler, 50 parts by weight of nano-graphite (particle size 30-100 nm) and 10 parts by weight of sheet graphene (lateral dimension 35-50 μm) as multidimensional electromagnetic wave absorbers, and 15 parts by weight of silica as a filler and reinforcing agent. First, the filler and rubber matrix are premixed; then, the premix is ​​transferred to a two-roll mill for thorough blending to form a homogeneous mixture; finally, the mixture is vulcanized at high temperature to obtain the flame retardant microwave absorbing patch.

[0030] Comparative Example 4 This comparative example aims to investigate the effect of the aspect ratio of carbon fiber and iron fiber on flame retardant and microwave absorption properties. The preparation methods are as follows: A microwave absorbing patch with high flame retardant properties is prepared as follows: 100 parts by weight of methyl vinyl silicone rubber is selected as the matrix, 40 parts by weight of aluminum hydroxide as the flame retardant filler, 50 parts by weight of nano-graphite (particle size 30-100 nm) and 30 parts by weight of iron fiber (length-to-diameter ratio 1:1 to 2:1) as multidimensional electromagnetic wave absorbers, and 20 parts by weight of silica as a reinforcing filler. First, the filler and rubber matrix are premixed; then, the premix is ​​transferred to a two-roll mill for thorough blending to form a homogeneous mixture; finally, the mixture is vulcanized at high temperature to obtain the flame retardant microwave absorbing patch.

[0031] Figure 1 The diagrams show the reflection loss of Examples 1-3. The results indicate that, thanks to the synergistic effect of the multidimensional electromagnetic wave absorber, the patches prepared in Examples 1-3 all exhibited good absorption performance. Specifically, the rubber patch of Example 1 achieved a reflection loss of less than -5 dB in the 2-3.7 GHz range. The rubber patch of Example 2 achieved a reflection loss of less than -5 dB in the 3.7-6 GHz and 12.4-18 GHz ranges. The rubber patch of Example 3 achieved a reflection loss of less than -5 dB in the 4.2-6 GHz and 14.4-17.4 GHz ranges. However, the rubber patches in Comparative Examples 1-4 did not achieve a reflection loss of less than -5 dB in the 2-18 GHz range. In Comparative Example 1, using a fibrous absorber of the same dimension resulted in a poorer absorption effect. Figure 2 In Comparative Example 2, the rubber patch using single nano-graphite as the absorber also exhibited poor microwave absorption performance, further confirming the importance of synergistic effects of multi-dimensional absorbers. Comparative Example 3 shows that when the ratio of nano-graphite to graphene is not within the optimal range, the prepared patch also has poor microwave absorption performance. Figure 2 Comparative Example 4 shows a microwave absorbing patch prepared with fibrous absorbent filler outside the optimal aspect ratio range. Figure 2It can be seen that, compared with Example 2 with the same formula, the microwave absorption performance of Comparative Example 4 is significantly reduced.

[0032] Table 1 shows the limiting oxygen index (LOI) of Examples 1-3 and Comparative Examples 1-4. The LIOIs of Examples 1 and 2 are 46.6% and 40.9%, respectively, higher than that of Comparative Example 1 (40.4%). This may be because the composite of 0-dimensional nanographite and 1-dimensional carbon fiber creates a denser and more uniform carbon layer, resulting in excellent flame retardant performance even with a much lower filler content than Comparative Example 1. Furthermore, the LIOI of Example 3 is 41.8%, and that of Comparative Example 2 is 40.6%. This also indicates that when the functional filler is single-dimensional, the flame retardant performance of the microwave absorbing patch is lower than that of the multi-scale composite rubber sheet. The LIOI of Comparative Example 3 is 41.1%, lower than that of Example 3. This indicates that the ratio of sheet graphene to nanographite affects its flame retardant performance. The LIOI of Comparative Example 4 is 39.8%, significantly lower than that of Example 2. This indicates that when the aspect ratio of the fiber material is not within the optimal range, it also has a significant effect on the flame retardant performance. This demonstrates that the multi-dimensional, multi-scale filler synergistic design described in this invention can simultaneously achieve and significantly improve the high flame retardant performance of microwave absorbing patches while ensuring the processability and usability of rubber.

[0033] Table 1: Limiting Oxygen Index of Examples and Comparative Examples

[0034] Those skilled in the art to which this application pertains may modify or supplement the specific embodiments described or use similar methods to replace them, but without departing from the inventive concept of this application or exceeding the scope defined by the appended claims.

Claims

1. A microwave absorbing patch with high flame retardant properties, characterized in that, Its raw material composition includes: rubber matrix, multidimensional electromagnetic wave absorber, fumed silica, inorganic hydroxide flame retardant and vulcanizing agent; the main body of the multidimensional electromagnetic wave absorber is nano-graphite with a size of 30-100nm, and contains one or more of sheet graphene with a transverse size of 35-50μm or carbon fiber or iron fiber with an aspect ratio of 4:1 to 8:

1.

2. The microwave absorbing patch with high flame retardant properties according to claim 1, characterized in that, The rubber matrix is ​​silicone rubber, preferably one of methyl silicone rubber, methyl vinyl silicone rubber, and methyl phenyl vinyl silicone rubber.

3. The microwave absorbing patch with high flame retardant properties according to claim 1, characterized in that, The inorganic hydroxide flame retardant is one or more of aluminum hydroxide and magnesium hydroxide.

4. The microwave absorbing patch with high flame retardant properties according to claim 1, characterized in that, The total amount of the multidimensional electromagnetic wave absorber added to the raw material of the microwave absorbing patch is 60-100 parts, with 100 parts of the rubber matrix.

5. The microwave absorbing patch with high flame retardant properties according to claim 1, characterized in that, The total amount of the inorganic hydroxide flame retardant added to the microwave absorbing patch raw material is 30-60 parts, with 100 parts of rubber matrix.

6. The microwave absorbing patch with high flame retardant properties according to claim 1, characterized in that, When the multidimensional electromagnetic wave absorber contains sheet graphene, the mass ratio of the nanographite to the sheet graphene is 15:1 to 30:

1.

7. The microwave absorbing patch with high flame retardant properties according to claim 1, characterized in that, The amount of silica added to the microwave absorbing patch raw material is 5-20 parts, based on 100 parts of rubber matrix.

8. A method for preparing a microwave absorbing patch with high flame retardant properties according to any one of claims 1-7, characterized in that, The preparation method includes: premixing a rubber matrix, a multidimensional electromagnetic wave absorber, silica and an inorganic hydroxide flame retardant; then mixing the premixed materials evenly in a two-roll mill; adding a vulcanizing agent and continuing to mix; and finally vulcanizing the sheet to obtain the microwave absorbing patch.

9. The preparation method according to claim 8, characterized in that, The vulcanization process includes a first-stage vulcanization at 10 MPa pressure and 175°C for 10 minutes, and a second-stage vulcanization at 200°C for 2 hours.

10. The use of a microwave absorbing patch with high flame retardant properties according to any one of claims 1-7 in the preparation of electromagnetic wave absorbing or electromagnetic protection materials.

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