CN108638619A - Impact-resistant electromagnetic shielding laminate of one kind and the preparation method and application thereof - Google Patents

Abstract

The invention discloses an impact-resistant electromagnetic shielding laminate, a preparation method and application thereof. The impact-resistant electromagnetic shielding laminate comprises two outermost insulating resin layers (1), and n+1 carbon fiber felt shielding layers (2) stacked alternately between the two insulating resin layers (1) and n aramid cloth reinforcing layers (3), an insulating resin layer (1) is also arranged between the adjacent carbon fiber felt shielding layer (2) and the aramid cloth reinforcing layer (3); the value of n The range is 3≥n≥1. The product of the invention combines the advantages of carbon fiber felt and aramid fiber cloth, has excellent electromagnetic shielding performance, tensile performance and impact resistance performance, and is a thinner, corrosion-resistant new lightweight material.

Description

A kind of impact-resistant electromagnetic shielding laminate and its preparation method and application

technical field

The invention belongs to the field of electromagnetic shielding materials, and in particular relates to an impact-resistant electromagnetic shielding laminate and a preparation method and application thereof.

Background technique

With the advent of various electronic devices, electromagnetic radiation pollution has become a new type of pollution. Electromagnetic radiation not only interferes with the normal operation of electronic equipment, but also endangers human health. In order to reduce the impact of electromagnetic radiation on human life, some electromagnetic shielding materials such as chopped carbon fiber mats have gradually received widespread attention. For example, Chinese patent application CN201710028677 discloses a chopped carbon fiber electromagnetic shielding composite material and its preparation method. The two layers of insulating resin layer and one layer of carbon fiber felt shielding layer have good electrical conductivity and electromagnetic shielding performance. However, in order to pursue excellent electromagnetic shielding performance, the prior art often ignores the mechanical properties of electromagnetic shielding materials, and mechanical properties are the basic guarantee for the application of electromagnetic shielding materials in various fields. For the housing of military aircraft and precision electronic equipment, in addition to excellent electromagnetic shielding, good impact resistance is also a must. Since 1988, hundreds of people have died as a result of birds striking aircraft. Due to the brittle nature of carbon fibers, the impact resistance of chopped carbon fiber mats is poor, and its practical application is severely limited.

Aramid fiber is a new type of material with corrosion resistance, high temperature resistance and excellent mechanical properties. It is widely used in bulletproof armor and building reinforcement. Due to its excellent properties, aramid fibers can be made into various bulletproof clothing, cut-resistant gloves and flame-retardant fabrics, etc. However, the performance of aramid fiber will decrease after being exposed to long-term visible light and absorbing water in a humid environment, and the non-conductive nature of aramid fiber hinders its application in fields that require electromagnetic shielding, such as stealth aircraft and precision electronic equipment housings. Chinese patent application CN201210297876.8 discloses a blended cloth of aramid fiber and carbon fiber, which solves the problem that carbon fiber is not resistant to impact. However, since the aramid fiber in the mixed fabric has no electromagnetic shielding ability, electromagnetic radiation can directly pass through the area occupied by the aramid fiber, resulting in the failure of the mixed fabric to shield electromagnetic radiation. Therefore, the mixed cloth only has the ability of impact resistance but not the ability of electromagnetic shielding. In addition, light weight, corrosion resistance, and weather resistance have gradually become key technical issues that need to be solved in the aerospace field. Therefore, the current prior art still lacks a material that has the advantages of impact resistance, excellent electromagnetic shielding performance, and corrosion resistance.

Contents of the invention

In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide an impact-resistant electromagnetic shielding laminate and its preparation method, as well as the application of the impact-resistant electromagnetic shielding laminate in the aerospace field.

The object of the present invention is achieved through the following technical solutions:

An impact-resistant electromagnetic shielding laminate, comprising two outermost insulating resin layers 1, and n+1 carbon fiber felt shielding layers 2 and n aramid fibers stacked alternately between the two insulating resin layers 1 A layer of insulating resin layer 1 is provided between the adjacent carbon fiber felt shielding layer 2 and the aramid cloth reinforcement layer 3; the range of n is 3≥n≥1.

Preferably, the mass ratio of the single-layer carbon fiber felt shielding layer 2 to the single-layer aramid cloth reinforcement layer 3 is 4:9˜1:1.

Preferably, the insulating resin layer 1 is made of thermoplastic resin and has a thickness of 0.10-0.13 mm.

Preferably, the carbon fiber felt shielding layer 2 is made of chopped carbon fibers with a length of 4-8 mm through wet papermaking, and its surface density is 40-60 g/m ² .

Preferably, the aramid cloth reinforcing layer 3 is a plain weave cloth woven with aramid fiber tows.

The preparation method of the impact-resistant electromagnetic shielding laminate comprises the following steps:

(1) Add chopped carbon fibers into 0.6-1.4 wt% carboxyethyl cellulose dispersion at a ratio of 0.09-0.12 g/L, stir and disperse evenly, and then form carbon fiber felt shielding layer 2 by wet papermaking;

(2) Stack n+1 carbon fiber felt shielding layers 2 obtained in step (1) and n aramid cloth reinforcement layers 3 alternately, and place a layer between adjacent carbon fiber felt shielding layers 2 and aramid cloth reinforcement layers 3 an insulating resin layer 1, and then place a layer of insulating resin layer 1 on the upper and lower surfaces of the obtained multilayer structure;

(3) Laminating the multi-layer material obtained in step (2), the lamination temperature is 180-200° C., and the lamination pressure is 1-6 MPa.

Preferably, the chopped carbon fibers in step (1) are first treated with acetone for 30-50 minutes, then ultrasonically treated for 40-60 minutes, and then dried at 30-50°C for 1-2 hours; the stirring speed is 600-700rmp, and the stirring time For 4 ~ 6min.

Preferably, before step (3) lamination, the multi-layer materials are pressed back and forth with pressure rollers to remove the gas between the layers.

In general, laminates are often used to join the layers of material by applying a layer of water-soluble adhesive or hot-melt adhesive to one side of each layer of material. However, the mechanical properties of aramid fibers will be affected after absorbing water, which makes it unsuitable to use water-soluble adhesives. With hot melt adhesives, the melt temperature used in lamination is critical. Insufficient temperature will make the fluidity of the adhesive poor, resulting in poor bonding between materials, layering defects, and affecting the mechanical properties of the material; while the temperature is too high and the fluidity of the adhesive is too strong, it will drive the carbon fiber felt shielding layer to expand outward. , so that the conductive mesh of the carbon fiber felt is destroyed, so the electromagnetic shielding performance will be attenuated. However, within the temperature range defined by the present invention, the obtained laminate can simultaneously have good electromagnetic shielding performance and mechanical performance.

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

(1) The present invention makes the laminate possess the electromagnetic shielding of the carbon fiber felt shielding layer and the impact resistance of the aramid cloth reinforcing layer by superimposing the carbon fiber felt shielding layer and the aramid cloth reinforcing layer.

(2) The outermost layer of the laminate is an insulating resin layer, which isolates the contact between the aramid cloth reinforcement layer and the outside air, and overcomes the disadvantage that the mechanical properties of the aramid fiber will decrease after absorbing water. And the outermost insulating resin layer provides good protection for the material.

(3) There is a carbon fiber felt shielding layer outside the aramid cloth reinforcement layer to block the light, which solves the problem of poor light resistance of the aramid fiber.

(4) The carbon fiber and aramid fiber used in the present invention are lightweight materials, which are beneficial to the development of the aerospace field.

Description of drawings

FIG. 1 is a schematic structural view of the impact-resistant electromagnetic shielding laminate obtained in Example 1 of the present invention.

Fig. 2 is an SEM image of the carbon fiber felt shielding layer in Example 1 of the present invention.

Fig. 3 is a structural schematic diagram of the aramid cloth reinforcement layer of the present invention.

Fig. 4 is a digital picture showing the destruction of the continuous conductive network of the laminate obtained in Comparative Example 3 of the present invention.

Fig. 5 is an SEM image showing delamination defects of the laminate obtained in Comparative Example 4 of the present invention.

reference sign

1 is insulating resin layer; 2 is carbon fiber felt shielding layer; 3 is aramid cloth reinforcement layer

Detailed ways

The present invention will be further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

Example 1

An impact-resistant electromagnetic shielding laminate, including two outermost insulating resin layers 1, and three carbon fiber felt shielding layers 2 and two aramid cloth reinforcements alternately stacked between the two insulating resin layers 1 Layer 3, a layer of insulating resin layer 1 is also arranged between the adjacent carbon fiber felt shielding layer 2 and the aramid cloth reinforcement layer 3;

The material of the insulating resin layer 1 is a polycarbonate film with a thickness of 0.1 mm, which has the advantages of corrosion resistance and weather resistance;

The carbon fiber felt shielding layer is made of chopped carbon fibers with a length of 6mm, and the surface density is 50g/m ² ;

The aramid cloth reinforcement layer 3 is a plain weave cloth woven by aramid fiber tows.

The mass ratio of the carbon fiber felt shielding layer to the aramid cloth reinforcing layer is 5:7.

The preparation method of the impact-resistant electromagnetic shielding laminate comprises the following steps:

(1) The carbon fiber tow in the continuous state was chopped to a length of 6 mm by radial chopping technology, then the chopped carbon fiber was soaked in acetone solution for 30 min, and ultrasonic treatment was performed for 40 min to remove the slurry on the surface of the chopped carbon fiber. The treated chopped carbon fibers were placed in a constant temperature drying oven at 40°C for 1 h.

(2) Weigh 1.57 g of dried chopped carbon fiber, place it in 15 L of carboxyethyl cellulose dispersion with a concentration of 1%, and uniformly disperse the chopped carbon fiber by mechanical stirring at a stirring speed of 600rmp. Stirring time is 5min. Then, the carbon fiber felt shielding layer 2 is made by wet papermaking technology, and the surface density of the carbon fiber felt shielding layer is 50g/m ² .

(3) The plain weave cloth woven by aramid fiber tow is used as the aramid cloth reinforcement layer 3 .

(4) The three carbon fiber felt shielding layers 2 and the two aramid cloth reinforcement layers 3 are stacked alternately, and the outermost is the carbon fiber felt shielding layer 2 . An insulating resin layer 1 is placed between the adjacent carbon fiber felt shielding layer 2 and the aramid cloth reinforcement layer 3 as an adhesive, and the material is polycarbonate on the upper and lower surfaces of the outermost layer of the laminated structure after bonding. The insulating resin layer 1 of the film acts as a protective film, thereby obtaining a multilayer material.

(5) Squeeze the multi-layer material back and forth with pressure rollers to remove the gas between the layers. Then the multi-layer material is placed in a flat vulcanizing machine for lamination, the lamination temperature is 180° C., and the lamination pressure is 6 MPa.

In this example, thickness, density, electromagnetic shielding, tensile, and impact tests were performed on impact resistant electromagnetic shielding laminates. The test results showed that the laminated board had a thickness of 1.02 mm and a density of 1.27 g/cm ³ . In the frequency range of 30-1500MHz, its shielding effectiveness reaches 62dB, that is, it can block 99.9% of incident electromagnetic waves. The tensile strength is 223MPa, the impact peak force is 802.9N, and the impact damage area is 255mm ² . Therefore, the laminate prepared in this embodiment has excellent electromagnetic shielding properties, tensile properties and impact resistance properties, and is a thinner, corrosion-resistant and lightweight material.

Example 2

An impact-resistant electromagnetic shielding laminate, comprising two outermost insulating resin layers 1, and two carbon fiber felt shielding layers 2 and an aramid cloth reinforcement layer alternately stacked between the two insulating resin layers 1 3. There is also an insulating resin layer 1 between the adjacent carbon fiber felt shielding layer 2 and the aramid cloth reinforcement layer 3;

The material of the insulating resin layer 1 is a polycarbonate film with a thickness of 0.12 mm, which has the advantages of corrosion resistance and weather resistance;

The carbon fiber felt shielding layer is made of chopped carbon fibers with a length of 8mm, and the surface density is 60g/m ² ;

The aramid cloth reinforcement layer 3 is a plain weave cloth woven by aramid fiber tows.

The mass ratio of the carbon fiber felt shielding layer to the aramid cloth reinforcing layer is 2:3.

The preparation method of the impact-resistant electromagnetic shielding laminate comprises the following steps:

(1) The carbon fiber tow in the continuous state was chopped to a length of 8 mm by radial chopping technology, then the chopped carbon fiber was soaked in acetone solution for 50 min, and ultrasonic treatment was performed for 60 min to remove the slurry on the surface of the chopped carbon fiber. The treated chopped carbon fibers were placed in a constant temperature drying oven at 30°C for 2 h.

(2) Weigh 1.884g of chopped carbon fiber and place it in 16L of carboxyethyl cellulose dispersion with a concentration of 1.4%, and uniformly disperse the chopped carbon fiber by mechanical stirring at a stirring speed of 700rmp for 6 minutes. Then, the carbon fiber felt shielding layer 2 is made by wet papermaking technology, and the surface density of the carbon fiber felt shielding layer is 60g/m ² .

(3) The plain weave cloth woven by aramid fiber tow is used as the aramid cloth reinforcement layer 3 .

(4) Two carbon fiber felt shielding layers 2 and one aramid cloth reinforcement layer 3 are stacked alternately, and the outermost is the carbon fiber felt shielding layer 2 . Between the adjacent carbon fiber felt shielding layer 2 and the aramid cloth reinforcement layer 3, an insulating resin layer 1 is placed as an adhesive, and an insulating resin layer 1 is placed as a protective film on the upper and lower surfaces of the multilayer structure obtained, thereby obtaining multiple layer material.

(5) Squeeze the multi-layer material back and forth with pressure rollers to remove the gas between the layers. Then the multi-layer material is placed in a flat vulcanizing machine for lamination, the lamination temperature is 200° C., and the lamination pressure is 3 MPa.

In this example, thickness, density, electromagnetic shielding, tensile, and impact tests were performed on impact resistant electromagnetic shielding laminates. The test results showed that the thickness of the laminated board was 0.652 mm, and the density was 1.32 g/cm ³ . In the frequency range of 30-1500MHz, its shielding effectiveness reaches 53dB, that is, it can block 99.9% of incident electromagnetic waves. The tensile strength is 178MPa, the impact peak force is 545N, and the impact damage area is 230mm ² . Therefore, the laminate prepared in this embodiment has excellent electromagnetic shielding properties, tensile properties and impact resistance properties, and is a thinner, corrosion-resistant and lightweight material.

Example 3

An impact-resistant electromagnetic shielding laminate, comprising two outermost insulating resin layers 1, and two carbon fiber felt shielding layers 2 and an aramid cloth reinforcement layer alternately stacked between the two insulating resin layers 1 3. There is also an insulating resin layer 1 between the adjacent carbon fiber felt shielding layer 2 and the aramid cloth reinforcement layer 3;

The material of the insulating resin layer 1 is a polycarbonate film with a thickness of 0.125 mm, which has the advantages of corrosion resistance and weather resistance;

The carbon fiber felt shielding layer is made of chopped carbon fibers with a length of 4mm and an area density of 40g/m ² ;

The aramid cloth reinforcement layer 3 is a plain weave cloth woven by aramid fiber tows.

The mass ratio of the carbon fiber felt shielding layer to the aramid cloth reinforcing layer is 4:9.

A method for preparing an impact-resistant electromagnetic shielding laminate, comprising the following steps:

(1) The carbon fiber tow in the continuous state was chopped to a length of 4 mm by radial chopping technology, then the chopped carbon fiber was soaked in acetone solution for 40 min, and ultrasonic treatment was performed for 50 min to remove the slurry on the surface of the chopped carbon fiber. The treated chopped carbon fibers were placed in a constant temperature drying oven at 50°C for 1 h.

(2) Weigh 1.256g of chopped carbon fiber and place it in 14L of carboxyethyl cellulose dispersion with a concentration of 0.6%, and uniformly disperse the chopped carbon fiber by mechanical stirring at a stirring speed of 650rmp for 4 minutes. Then, the carbon fiber felt shielding layer 2 is made by wet papermaking technology, and the surface density of the carbon fiber felt shielding layer is 40g/m ² .

(3) The plain weave cloth woven by aramid fiber tow is used as the aramid cloth reinforcement layer 3 .

(4) Two carbon fiber felt shielding layers 2 and one aramid cloth reinforcement layer 3 are stacked alternately, and the outermost is the carbon fiber felt shielding layer 2 . Between the adjacent carbon fiber felt shielding layer 2 and the aramid cloth reinforcement layer 3, an insulating resin layer 1 is placed as an adhesive, and an insulating resin layer 1 is placed as a protective film on the upper and lower surfaces of the multilayer structure obtained, thereby obtaining multiple layer material.

(5) Squeeze the multi-layer material back and forth with pressure rollers to remove the gas between the layers. Then the multi-layer material is placed in a flat vulcanizer for lamination, the lamination temperature is 190° C., and the lamination pressure is 1 MPa.

In this example, thickness, density, electromagnetic shielding, tensile, and impact tests were performed on impact resistant electromagnetic shielding laminates. The test results showed that the laminated board had a thickness of 0.660 mm and a density of 1.21 g/cm ³ . In the frequency range of 30-1500MHz, its shielding effectiveness reaches 49dB, that is, it can block 99.9% of incident electromagnetic waves. The tensile strength is 172.2MPa, the impact peak force is 536.8N, and the impact damage area is 239mm ² . Therefore, the laminate prepared in this embodiment has excellent electromagnetic shielding properties, tensile properties and impact resistance properties, and is a thinner, corrosion-resistant and lightweight material.

Comparative example 1

An impact-resistant laminate, except that the carbon fiber felt shielding layer 2 is completely removed, the other conditions and preparation methods refer to Example 2.

In Comparative Example 1, the shielding effectiveness of the material in the frequency range of 30-1500MHz is 0.24dB, that is, only 5.4% of incident electromagnetic waves can be blocked. It can be seen that the electromagnetic shielding performance of the laminate prepared in Comparative Example 1 is far worse than that of the embodiment. 2. The carbon fiber felt shielding layer 2 in the present invention greatly improves the electromagnetic shielding performance of the laminate.

Comparative example 2

An impact-resistant laminate, except that the aramid cloth reinforcing layer 3 is completely removed, the other conditions and preparation methods refer to Example 2.

In Comparative Example 2, the peak impact force obtained by the material test was only 213N, and the area of impact damage was enlarged to 850mm ² . It can be seen that the impact performance of the laminate prepared in Comparative Example 2 was far worse than that of Example 2. The aramid fabric reinforced in the present invention Layer 3 greatly improves the mechanical properties of the laminate.

Comparative example 3

An impact-resistant electromagnetic shielding laminate, comprising two outermost insulating resin layers 1, and two carbon fiber felt shielding layers 2 and an aramid cloth reinforcement layer alternately stacked between the two insulating resin layers 1 3. There is also an insulating resin layer 1 between the adjacent carbon fiber felt shielding layer 2 and the aramid cloth reinforcement layer 3;

The lamination temperature is 230° C., and refer to Example 2 for other conditions and preparation methods.

In Comparative Example 3, as shown in FIG. 4 , the destruction of the carbon fiber conductive network due to the high lamination temperature can be observed with the naked eye. After the electromagnetic shielding test, the shielding effectiveness of the material is 36dB in the frequency range of 30-1500MHz. It can be seen that the electromagnetic shielding performance of the laminate prepared in Comparative Example 3 is far worse than that of Example 2, and the attenuation of the electromagnetic shielding performance of the laminate can be prevented within the lamination temperature range defined by the present invention.

Comparative example 4

An impact-resistant electromagnetic shielding laminate, comprising two outermost insulating resin layers 1, and two carbon fiber felt shielding layers 2 and an aramid cloth reinforcement layer alternately stacked between the two insulating resin layers 1 3. There is also an insulating resin layer 1 between the adjacent carbon fiber felt shielding layer 2 and the aramid cloth reinforcement layer 3;

The lamination temperature is 160° C., and refer to Example 2 for other conditions and preparation methods.

In Comparative Example 4, as shown in FIG. 5 , it can be observed through a scanning electron microscope that the laminate has delamination defects. After the mechanical performance test, the tensile strength of the material is 121MPa, the peak impact force is 412N, and the impact damage area is enlarged to 407mm ² . It can be seen that the mechanical properties of the laminate prepared in Comparative Example 4 are far worse than that of Example 2, and the attenuation of the mechanical properties of the laminate can be prevented within the lamination temperature range defined by the present invention.

The table below summarizes some important parameters and technical effects of Examples 1-3 and Comparative Examples 1-4.

Important parameters and technical effects of table 1 embodiment 1～3 and comparative examples 1～4

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (9)

1. An impact-resistant electromagnetic shielding laminate, characterized in that it comprises two layers of insulating resin layers (1) on the outermost layer, and n+1 stacked alternately between the two layers of insulating resin layers (1) A carbon fiber felt shielding layer (2) and n aramid cloth reinforcement layers (3), and an insulating resin layer (1) is arranged between adjacent carbon fiber felt shielding layers (2) and aramid cloth reinforcement layers (3) ; The value range of n is 3≥n≥1. 2. A kind of impact-resistant electromagnetic shielding laminate according to claim 1, characterized in that, the single-layer carbon fiber felt shielding layer (2) and the single-layer aramid cloth reinforcement layer (3) The mass ratio is 4:9～1:1. 3. The impact-resistant electromagnetic shielding laminate according to claim 1, characterized in that the insulating resin layer (1) is made of thermoplastic resin, and the thickness of each layer is 0.10-0.13 mm. 4. A kind of impact-resistant electromagnetic shielding laminate according to claim 1, characterized in that, the carbon fiber felt shielding layer (2) is made by wet-process papermaking from chopped carbon fibers with a length of 4 to 8 mm. Surface density is 40~60g/m ² . 5. An impact-resistant electromagnetic shielding laminate according to claim 1, characterized in that, the aramid cloth reinforcement layer (3) is a plain weave cloth woven by aramid fiber tows. 6. A preparation method of an impact-resistant electromagnetic shielding laminate, characterized in that, comprising the following steps: (1) Add chopped carbon fiber into 0.6-1.4wt% carboxyethyl cellulose dispersion at a ratio of 0.09-0.12g/L, stir and disperse evenly, and then form a carbon fiber felt shielding layer by wet papermaking (2) ; (2) stacking n+1 said carbon fiber felt shielding layers (2) and n aramid cloth reinforcement layers (3) alternately, adjacent carbon fiber felt shielding layers (2) and aramid cloth reinforcement layers (3) ) between placing a layer of insulating resin layer (1) to obtain a multilayer structure, respectively placing a layer of insulating resin layer (1) on the upper and lower surfaces of the multilayer structure to obtain a multilayer material; (3) Laminating the multi-layer materials, the lamination temperature is 180-200° C., and the lamination pressure is 1-6 MPa. 7. The preparation method of a kind of impact-resistant electromagnetic shielding laminate according to claim 6, characterized in that, the chopped carbon fibers described in the step (1) are first treated with acetone for 30-50 min, and then ultrasonically treated for 40-60 min , and then dried at 30-50° C. for 1-2 hours; the stirring speed was 600-700 rpm, and the stirring time was 4-6 minutes. 8. the preparation method of a kind of impact-resistant electromagnetic shielding laminated board according to claim 6, is characterized in that, before carrying out described lamination, multi-layer material is carried out back and forth extruding with pressure roller, drains away interlayer gas. 9. The application of the impact-resistant electromagnetic shielding laminate according to any one of claims 1 to 5 in the field of aerospace.