Dielectric loss coupling magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material and preparation method thereof

Abstract

The invention belongs to the field of polymer composite material preparation, and particularly relates to a dielectric loss coupling magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material and a preparation method thereof. The preparation method comprises the following steps: mixing basalt fibers modified by magnetic particles, basalt fibers modified by conductive fibers and resin, banburying, and carrying out hot press molding to respectively prepare a magnetic basalt fiber / resin film and a conductive basalt fiber / resin film with different mass fractions; and the magnetic basalt fiber / resin film and the conductive basalt fiber / resin film are subjected to electromagnetic gradient alternate hot-pressing assembly to obtain the multilayer electromagnetic shielding film. The basalt fiber-based electromagnetic shielding composite material with the asymmetric structure has the advantage that the preparation method is simple and easy to control, shows excellent electromagnetic shielding performance in a K wave band, and is suitable for the fields of electronic communication, aerospace, automobiles and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of polymer composites, and specifically relates to a dielectric loss-coupled magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material and a preparation method thereof. Background Art

[0002] Although traditional electromagnetic shielding materials (such as metals) have good shielding effects, they have disadvantages such as high density, poor corrosion resistance, and weak bonding force with matrix materials, and it is difficult to meet the modern electromagnetic shielding requirements. In contrast, multifunctional polymer composites not only overcome these deficiencies, but also have advantages such as easy processing and excellent electromagnetic properties, so they have become the key development direction of electromagnetic shielding materials.

[0003] At present, by simple mechanical mixing, adding conductive and magnetic fillers into a polymer matrix can achieve a certain electromagnetic shielding effect, but the problem of impedance matching between electromagnetic waves in free space and the material surface impedance is ignored, resulting in a large amount of electromagnetic waves being reflected, causing secondary harm to the environment. To reduce secondary electromagnetic wave pollution, by introducing magnetic nanoparticles (such as Fe 3 O 4 ) and hybridizing them, the electromagnetic wave absorption performance of polymer composites can be significantly enhanced. Magnetic nanoparticles can provide magnetic loss, and carbon nanotube fillers contribute to dielectric loss, which can dissipate electromagnetic waves more effectively through absorption. Although composites containing magnetic hybrid fillers can reduce reflection to a certain extent, this kind of composite with a uniform conductive network always shows uniform conductivity under fixed impedance mismatch conditions, which is useless for reducing electromagnetic wave reflection for shielding composites with high electromagnetic shielding performance. According to the electromagnetic shielding principle, relying on the design of a layered structure of magnetic / conductive gradient structure, placing the wave-absorbing material in the incident layer and the highly conductive layer at the bottom layer can effectively adjust the impedance matching between free space and the material interface. At the same time, electromagnetic waves form multiple reflections and absorptions inside the material, forming an "absorption-reflection-absorption" process, achieving a multi-level synergistic mechanism and achieving a high electromagnetic shielding effect in the high-frequency band.

[0004] Mechanical properties are crucial for the shielding effect of electromagnetic shielding materials. However, the addition of magnetic nanoparticles and conductive nanoparticles to the resin will cause stress concentration, which will seriously damage the mechanical properties of the composite material. Basalt fiber has mechanical properties comparable to those of carbon fiber, and is inexpensive, sourced from nature, and environmentally friendly.

[0005] The hybridization of functional nanoparticles and basalt fiber provides a new idea for the development of electromagnetic shielding materials. This kind of composite material not only overcomes the disadvantages of traditional materials, but also realizes the dual improvement of electromagnetic shielding performance and mechanical properties through optimizing the structure design and material combination, and is expected to become an important development direction of electromagnetic shielding materials. Summary of the Invention

[0006] The object of the present invention is to provide a preparation method of a dielectric loss coupled magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material that can effectively solve one of the problems in view of the above problems. During the preparation process, the basalt fibers are modified by magnetic nanoparticles and conductive nanoparticles respectively, which can reduce the stress concentration caused by the nanoparticles in the resin and improve the mechanical properties of the film. By alternately stacking the magnetic film and the conductive film prepared from the modified basalt fibers, a high-performance electromagnetic shielding material can be obtained. This material uses the magnetic layer as the incident layer. By regulating the magnetism of the magnetic layer and the conductivity of the conductive layer, impedance matching with electromagnetic waves can be achieved, enabling the electromagnetic waves to enter the material interior more effectively, and achieving high-efficiency attenuation through a step-by-step absorption mechanism. At the same time, the polarization effect of the electromagnetic heterogeneous interface can convert a large amount of electromagnetic waves into heat energy dissipation, thereby significantly improving the electromagnetic shielding and absorption performance of the composite material.

[0007] In order to achieve the above invention object, the specific technical solution of the present invention is as follows:

[0008] A preparation method of a dielectric loss coupled magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material, comprising the following steps:

[0009] (1) Fiber dispersion: Short-cut basalt fibers are dispersed in a high-speed pulverizer, washed and then placed in an oven for drying, and reserved for use;

[0010] (2) Preparation of magnetic basalt fiber / resin film: The basalt fibers reserved in step (1) and magnetic nanoparticles are added into an adhesive together, and the basalt fibers are modified by the adhesive under ultrasonic stirring conditions to obtain modified basalt fibers; the obtained modified basalt fibers are washed and dried to obtain magnetic basalt fibers; finally, the magnetic basalt fibers and the resin are mixed and kneaded in different proportions and hot-pressed to prepare magnetic basalt fiber / resin films (layers) with different mass fractions;

[0011] (3) Preparation of conductive basalt fiber / resin film: The basalt fibers reserved in step (1) and conductive nanoparticles are added into an adhesive together, and the basalt fibers are modified by the adhesive under ultrasonic stirring conditions to obtain modified basalt fibers; the obtained modified basalt fibers are washed and dried to obtain conductive basalt fibers; finally, the conductive basalt fibers and the resin are mixed and kneaded in different proportions and hot-pressed to prepare conductive basalt fiber / resin films (layers) with different mass fractions;

[0012] (4) Prepare basalt fiber / resin composites with asymmetric multi-layer gradient electromagnetic alternation: By controlling variables and two variables, that is, in an alternating stacking manner, gradually increase the mass fraction of conductive basalt fibers or magnetic basalt fibers, or increase the mass fractions of both simultaneously, and then through a hot pressing process, prepare basalt fiber / resin composites with a multi-layer asymmetric gradient electromagnetic alternation structure from the magnetic basalt fiber / resin films with different mass fractions prepared in step (2) and the conductive basalt fiber / resin films prepared in step (3).

[0013] Further, in step (1), the dispersion time of the chopped basalt fibers is 1.5 - 2 min, the rotation speed of the high-speed grinder is 30000 - 34000 r / min; the length of the reserved basalt fibers is 100 - 130 μm.

[0014] Further, in steps (2) and (3), the solvent used for cleaning is any one of deionized water, acetone, and ethanol.

[0015] Further, in steps (2) and (3), the drying temperature is 60 - 80 °C, and the time is 24 h.

[0016] Further, in step (2), the magnetic nanoparticles are any one or several of nano-ferroferric oxide, nano-nickel oxide, and nano-iron carbonyl.

[0017] Further, in step (2), the mass ratio of the magnetic nanoparticles to the basalt fibers obtained in step (1) is 1:1 - 1:10 (specifically, it can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.).

[0018] Further, in step (2), the mass fraction of the magnetic basalt fibers in the film is 2.5 - 50% (specifically, it can be 2.5%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.).

[0019] Further, in step (3), the conductive nanoparticles are any one of graphene, carbon nanotubes, and carbon black.

[0020] Further, in step (3), the mass ratio of the conductive nanoparticles to the basalt fibers obtained in step (1) is 1:8 - 1:16 (specifically, it can be 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, etc.).

[0021] Further, in step (3), the mass fraction of the conductive basalt fiber in the film is 9-50% (specifically, it can be 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc.).

[0022] Further, the adhesive in step (2) and step (3) is any one or several of waterborne polyurethane (W909580), waterborne acrylic acid (LA 133), and waterborne polyester (EM-110).

[0023] Further, the addition amount of the adhesive is 2.5-15% of the mass of the obtained basalt fiber (specifically, it can be 2.5%, 5%, 7.5%, 10%, 12.5%, 15%, etc.).

[0024] Further, the ultrasonic stirring time is 30-60 min.

[0025] Further, the resins in step (2) and step (3) are any one or a mixture of multiple ones of polylactic acid resin (4032D), epoxy resin (E20), and polyamide-based resins (E1105 and TP-4208).

[0026] Further, the kneading time in step (2) and step (3) is 15-20 min, the rotation speed is 130-150 r / min, and the kneading temperature is 160-250 °C.

[0027] Further, the thicknesses of the magnetic basalt fiber / resin film prepared in step (2) and the conductive basalt fiber / resin film prepared in step (3) are both 0.1-0.5 mm.

[0028] Further, in step (4), the multi-layer is 3-7 layers; when stacking, the magnetic layer is used as the incident layer, and the magnetic basalt fiber / resin film layer and the conductive basalt fiber / resin film layer are stacked alternately in an asymmetric gradient, and stacking is carried out with the mass fraction of the modified basalt fiber in the magnetic basalt fiber / resin film layer and the conductive basalt fiber / resin film layer as a variable (preferably showing an upward trend).

[0029] Further, in step (4), the molding pressure of the hot pressing is 3-10 MPa, and the hot pressing time is 3-6 min.

[0030] The present invention also protects a dielectric loss-coupled magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material that can be prepared by any of the above methods or any arbitrary combination of the above method steps.

[0031] Compared with the existing technology, the beneficial effects of the present invention are:

[0032] (1) By adopting organic / inorganic hybrid fibers, the present invention significantly improves the surface roughness of the fibers, enhances the mechanical biting force between the fibers and the matrix, thereby improving the mechanical properties of the resin matrix, which plays a key role in the electromagnetic shielding effect of the composite material.

[0033] (2) By using the mass fraction of modified basalt fibers as a gradient variable, the present invention alternately stacks controllable magnetic layers and conductive layers to prepare a high-performance electromagnetic shielding composite material. The material uses a low magnetic layer as the incident absorption layer, which can achieve good impedance matching with electromagnetic waves, prompting more electromagnetic waves to enter the material interior and gradually attenuating in the structure with increasing gradient. At the same time, the electromagnetic synergy effect between the magnetic layer and the conductive layer further enhances the absorption performance of the material, ultimately achieving an efficient electromagnetic shielding effect dominated by absorption.

[0034] (3) The electromagnetic shielding material of the present invention has the advantages of wide shielding range, strong adaptability, simple preparation process, etc., and meets the requirements of green and sustainable development. By regulating the ratio of conductive nanoparticles and magnetic nanoparticles to basalt fibers, the electromagnetic shielding performance of the composite material can be precisely controlled, thereby realizing the personalized customization of electromagnetic shielding composite materials. Brief Description of the Drawings

[0035] Figure 1 It is the micrograph of basalt fibers. (a) Dispersed basalt fibers, (b) Single basalt fiber (BF), (c) Basalt fiber loaded with nano-ferroferric oxide (BF@Fe 3 O 4 ₃) and (d) Basalt fiber loaded with carbon nanotubes (BF@CNT).

[0036] Figure 2 It is the XRD of basalt fiber loaded with nano-ferroferric oxide and basalt fiber loaded with carbon nanotubes.

[0037] Figure 3 It is the stress-strain curve of the mechanical tension of modified basalt fiber reinforced polylactic acid. (a) Different mass fractions of basalt fiber loaded with nano-ferroferric oxide reinforced polylactic acid (BF@Fe 3 O 4 ₃ / PLA) and (b) Different mass fractions of basalt fiber loaded with carbon nanotubes reinforced polylactic acid (BF@CNT / PLA).

[0038] Figure 4 It is the conductivity of different mass fractions of basalt fiber loaded with carbon nanotubes reinforced polylactic acid (BF@CNT / PLA).

[0039] Figure 5Arrangement of the magnetic layer and the conductive layer in Example 6, where the blue series represents the magnetic layer and the red series represents the conductive layer, and the mass fraction of the modified basalt fiber increases with the deepening of the color.

[0040] Figure 6 Electromagnetic shielding effectiveness of the sample prepared in Example 6. Detailed implementation manners

[0041] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates the present invention in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, it should be understood that after reading the content of the present invention, those skilled in the art can make various changes and modifications to the present invention, but these equivalent forms also fall within the scope defined by the appended claims of this application.

[0042] The raw materials used in the following embodiments are all commercially available products, the equipment used is all conventional equipment, and the methods or devices not specifically required can be realized through the prior art.

[0043] Example 1:

[0044] Preference of magnetic nanoparticles and conductive nanoparticles, including the following steps:

[0045] (1) Dispersing fibers: Take 100 g of chopped basalt fibers and disperse them in a high-speed grinder for 1.5 min. Wash the dispersed fibers with deionized water and put them in an 80°C oven to dry, obtaining basalt fibers with a length of 100 - 130 μm.

[0046] (2) Preparing magnetic films: Add the basalt fibers obtained in step (1) and nano-ferroferric oxide, nano-nickel oxide, and nano-iron carbonyl to the aqueous polyurethane aqueous dispersion with a mass fraction of 10% at a mass fraction of 1:1. After ultrasonic stirring for 1 h, take out the fibers, wash them with deionized water, and put them in an 80°C oven for drying to obtain magnetic basalt fibers. Respectively mix magnetic basalt fibers with mass fractions of 5%, 10%, 30%, and 50% with polylactic acid in a mixer at 180°C for 15 min, and then press them into a 0.3-mm-thick magnetic basalt fiber / polylactic acid film under a pressure of 3 MPa in a hot press at 180°C. The test results of their electromagnetic shielding effectiveness are shown in Table 1:

[0047] Table 1. Total electromagnetic shielding effectiveness of basalt fiber-loaded magnetic nanoparticle composite polylactic acid films

[0048]

[0049] (3) Preparation of conductive thin films: The basalt fibers obtained in step (1) were respectively added to the aqueous polyurethane aqueous dispersion with a mass fraction of 10% together with graphene, carbon nanotubes, and carbon black at a mass ratio of 8:1. After ultrasonic stirring for 1 h, the fibers were taken out, washed with deionized water, and dried in an oven at 80 °C to obtain conductive basalt fibers. Conductive basalt fibers with mass fractions of 9%, 18%, 27%, and 36% were respectively kneaded with polylactic acid in a kneader at 180 °C for 15 min, and then pressed into a 0.3-mm-thick conductive basalt fiber / polylactic acid film under a pressure of 3 MPa in a hot press at 180 °C. The test results of its electromagnetic shielding effectiveness are shown in Table 2:

[0050] Table 2. Total electromagnetic shielding effectiveness of basalt fiber-loaded magnetic nanoparticle composite polylactic acid films

[0051] Mass fraction of conductive basalt fiber Basalt fiber / graphene Basalt fiber / carbon nanotube Basalt fiber / carbon black 9％ 4.6 dB 5.5 dB 3.2 dB 18％ 9.4 dB 10.6 dB 5.8 dB 27％ 10.2 dB 11.4 dB 7.6 dB 36％ 13.9 dB 13.4 dB 8.9 dB

[0052] As can be seen from Table 1 and Table 2, after basalt fibers are respectively loaded with nano-ferroferric oxide and carbon nanotubes, they show significant advantages in electromagnetic wave shielding, which is mainly attributed to the high magnetic loss characteristics of nano-ferroferric oxide and the high dielectric loss characteristics of carbon nanotubes. The composite films prepared from the two can enhance the electromagnetic synergistic effect between them and achieve good electromagnetic wave shielding effects.

[0053] Example 2

[0054] A preparation method of a dielectric loss-coupled magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material, comprising the following steps:

[0055] (1) Fiber dispersion: Take 100 g of chopped basalt fibers and disperse them in a high-speed pulverizer (rotation speed: 34000 r / min) for 1.5 min. The dispersed fibers are washed with deionized water and dried in an oven at 80 °C for 24 h to obtain basalt fibers with lengths of 100 - 130 μm for standby;

[0056] (2) Preparation of magnetic thin films: The basalt fibers obtained in step (1) and nano-ferroferric oxide nanoparticles are added to the aqueous acrylic acid aqueous dispersion with a mass fraction of 12.5% at a mass ratio of 1:1. After ultrasonic stirring for 1 h, the fibers are taken out, washed with deionized water, and dried in an oven at 80 °C to obtain magnetic basalt fibers. Magnetic basalt fibers with mass fractions of 5%, 10%, 30%, and 50% are respectively kneaded with polylactic acid (commercially available product, Nature Works 4032D) in a kneader at 180 °C for 15 min, and then pressed into a 0.3-mm-thick magnetic basalt fiber / polylactic acid film under a pressure of 3 MPa in a hot press at 180 °C;

[0057] (3) Preparation of conductive thin film: The basalt fibers obtained in step (1) and carbon nanotubes were added to an aqueous acrylic acid aqueous dispersion with a mass fraction of 12.5% at a mass ratio of 8:1, ultrasonically stirred for 1 h, then the fibers were taken out, washed with deionized water, and dried in an oven at 80 °C to obtain conductive basalt fibers. Conductive basalt fibers with mass fractions of 9%, 18%, 27%, 36%, and 45% were respectively kneaded with polylactic acid in a kneader at 180 °C for 15 min, and then pressed into a 0.3-mm-thick conductive basalt fiber / polylactic acid film under a pressure of 3 MPa in a hot press at 180 °C.

[0058] (4) Preparation of basalt fiber / resin composite material with asymmetric multi-layer gradient electromagnetic alternation:

[0059] Taking the magnetic layer as the incident layer, from top to bottom are magnetic basalt fiber / polylactic acid films with a mass fraction of 5%, conductive basalt fiber / polylactic acid films with a mass fraction of 9%, and magnetic basalt fiber / polylactic acid films with a mass fraction of 10%, alternately and asymmetrically stacked in 3 layers, and a basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency mainly for absorption was prepared under a pressure of 3 MPa in a hot press at 180 °C.

[0060] After testing, the electromagnetic shielding efficiency of this composite material is 15.7 dB.

[0061] Example 3

[0062] A preparation method of a dielectric loss-coupled magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material, which includes the following steps:

[0063] (1) Fiber dispersion: Take 100 g of chopped basalt fibers, disperse them in a high-speed grinder for 1.5 min, wash the dispersed fibers with deionized water, and dry them in an oven at 80 °C to obtain basalt fibers with a length of 100 - 130 μm;

[0064] (2) Preparation of magnetic thin film: The basalt fibers obtained in step (1) and iron oxide nanoparticles were added to an aqueous polyurethane aqueous dispersion with a mass fraction of 10% at a mass ratio of 1:1, ultrasonically stirred for 1 h, then the fibers were taken out, washed with deionized water, and dried in an oven at 80 °C to obtain magnetic basalt fibers. Magnetic basalt fibers with mass fractions of 5%, 10%, 30%, and 50% were respectively kneaded with epoxy resin in a kneader at 160 °C for 15 min, and then pressed into a 0.3-mm-thick magnetic basalt fiber / epoxy resin film under a pressure of 3 MPa in a hot press at 160 °C;

[0065] (3) Preparation of conductive thin film: The basalt fibers obtained in step (1) and carbon nanotubes were added to an aqueous polyurethane aqueous dispersion with a mass fraction of 10% at a mass ratio of 8:1. After ultrasonic stirring for 1 h, the fibers were taken out, washed with deionized water, and dried in an oven at 80 °C to obtain conductive basalt fibers. Conductive basalt fibers with mass fractions of 9%, 18%, 27%, 36% and 45% were respectively kneaded with epoxy resin in a kneader at 160 °C for 15 min, and then pressed into a 0.3-mm-thick conductive basalt fiber / epoxy resin film under a pressure of 3 MPa in a hot press at 160 °C.

[0066] (4) Preparation of asymmetric multi-layer gradient electromagnetic alternating basalt fiber / resin composite material:

[0067] Taking the magnetic layer as the incident layer, five layers of magnetic basalt fiber / epoxy resin films with mass fractions of 5%, 10% and 30% and a conductive basalt fiber / epoxy resin film with a mass fraction of 9% were alternately stacked asymmetrically in an electromagnetic manner. A basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency mainly for absorption was prepared under a pressure of 3 MPa in a hot press at 160 °C.

[0068] After testing, the electromagnetic shielding efficiency of this composite material is 21.5 dB.

[0069] Example 4

[0070] A preparation method of a dielectric loss-coupled magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material, which includes the following steps:

[0071] (1) Fiber dispersion: 100 g of chopped basalt fibers were dispersed in a high-speed grinder for 1.5 min. The dispersed fibers were washed with deionized water and dried in an oven at 80 °C to obtain basalt fibers with a length of 100-130 μm;

[0072] (2) Preparation of magnetic thin film: The basalt fibers obtained in step (1) and iron oxide nanoparticles were added to an aqueous polyurethane aqueous dispersion with a mass fraction of 10% at a mass ratio of 1:1. After ultrasonic stirring for 1 h, the fibers were taken out, washed with deionized water, and dried in an oven at 80 °C to obtain magnetic basalt fibers. Magnetic basalt fibers with mass fractions of 5%, 10%, 30% and 50% were respectively kneaded with polylactic acid in a kneader at 180 °C for 15 min, and then pressed into a 0.3-mm-thick magnetic basalt fiber / polylactic acid film under a pressure of 3 MPa in a hot press at 180 °C;

[0073] (3) Preparation of conductive thin film: The basalt fibers obtained in step (1) and carbon nanotubes were added to an aqueous polyurethane aqueous dispersion with a mass fraction of 10% at a mass ratio of 8:1. After ultrasonic stirring for 1 h, the fibers were taken out, washed with deionized water, and dried in an oven at 80 °C to obtain conductive basalt fibers. Conductive basalt fibers with mass fractions of 9%, 18%, 27%, 36% and 45% were respectively kneaded with polylactic acid in a kneader at 180 °C for 15 min, and then pressed into a 0.3-mm-thick conductive basalt fiber / polylactic acid film under a pressure of 3 MPa in a hot press at 180 °C.

[0074] (4) Preparation of basalt fiber / resin composite material with asymmetric multi-layer gradient electromagnetic alternation:

[0075] Taking the magnetic layer as the incident layer, five layers of magnetic basalt fiber / polylactic acid films with mass fractions of 5%, 10% and 30% and conductive basalt fiber / polylactic acid films with mass fractions of 9% and 18% were alternately stacked asymmetrically in an electromagnetic manner. A basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency mainly for absorption was prepared in a hot press at 180 °C under a pressure of 3 MPa.

[0076] After testing, the electromagnetic shielding efficiency of this composite material was 25.8 dB.

[0077] Example 5

[0078] A preparation method of a dielectric loss-coupled magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material, which comprises the following steps:

[0079] (1) Fiber dispersion: 100 g of chopped basalt fibers were taken and dispersed in a high-speed grinder for 1.5 min. The dispersed fibers were washed with deionized water and dried in an oven at 80 °C to obtain basalt fibers with a length of 100 - 130 μm;

[0080] (2) Preparation of magnetic thin film: The basalt fibers obtained in step (1) and magnetite nanoparticles were added to an aqueous polyurethane aqueous dispersion with a mass fraction of 10% at a mass ratio of 1:1. After ultrasonic stirring for 1 h, the fibers were taken out, washed with deionized water, and dried in an oven at 80 °C to obtain magnetic basalt fibers. Magnetic basalt fibers with mass fractions of 5%, 10%, 30% and 50% were kneaded with polylactic acid in a kneader at 180 °C for 15 min, and then pressed into a 0.3-mm-thick magnetic basalt fiber / polylactic acid film under a pressure of 3 MPa in a hot press at 180 °C;

[0081] (3) Preparation of conductive thin film: The basalt fibers obtained in step (1) and carbon nanotubes were added to an aqueous polyurethane aqueous dispersion with a mass fraction of 10% at a mass ratio of 8:1. After ultrasonic stirring for 1 h, the fibers were taken out, washed with deionized water, and dried in an oven at 80 °C to obtain conductive basalt fibers. Conductive basalt fibers with mass fractions of 9%, 18%, 27%, 36%, and 45% were respectively kneaded with polylactic acid in a kneader at 180 °C for 15 min, and then pressed into a 0.3-mm-thick conductive basalt fiber / polylactic acid thin film under a pressure of 3 MPa in a hot press at 180 °C.

[0082] (4) Preparation of basalt fiber / resin composite material with asymmetric multi-layer gradient electromagnetic alternation:

[0083] Using the magnetic layer as the incident layer, seven layers of magnetic basalt fiber / polylactic acid thin films with mass fractions of 5%, 10%, 30%, and 50% and conductive basalt fiber / polylactic acid thin films with mass fractions of 9%, 27%, and 45% were alternately stacked asymmetrically in terms of electromagnetics. A basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency mainly for absorption was prepared in a hot press at 180 °C under a pressure of 3 MPa.

[0084] After testing, the electromagnetic shielding efficiency of this composite material was 31.1 dB.

[0085] Example 6

[0086] A preparation method of a dielectric loss-coupled magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material, which comprises the following steps:

[0087] (1) Fiber dispersion: 100 g of chopped basalt fibers were taken and dispersed in a high-speed crusher for 1.5 min. The dispersed fibers were washed with deionized water and dried in an oven at 80 °C to obtain basalt fibers with a length of 100 - 130 μm;

[0088] (2) Preparation of magnetic thin film: The basalt fibers obtained in step (1) and magnetite nanoparticles were added to an aqueous polyurethane aqueous dispersion with a mass fraction of 10% at a mass ratio of 1:1. After ultrasonic stirring for 1 h, the fibers were taken out, washed with deionized water, and dried in an oven at 80 °C to obtain magnetic basalt fibers. Magnetic basalt fibers with mass fractions of 5%, 10%, 30%, and 50% were respectively kneaded with polylactic acid in a kneader at 180 °C for 15 min, and then pressed into a 0.3-mm-thick magnetic basalt fiber / polylactic acid thin film under a pressure of 3 MPa in a hot press at 180 °C;

[0089] (3) Preparation of conductive thin film: The basalt fibers obtained in step (1) and carbon nanotubes were added to an aqueous polyurethane aqueous dispersion with a mass fraction of 10% at a mass ratio of 8:1, ultrasonically stirred for 1 h, then the fibers were taken out, washed with deionized water, and dried in an oven at 80 °C to obtain conductive basalt fibers. Conductive basalt fibers with mass fractions of 9%, 18%, 27%, 36% and 45% were respectively kneaded with polylactic acid in a kneader at 180 °C for 15 min, and then pressed into a 0.3-mm-thick conductive basalt fiber / polylactic acid film under a pressure of 3 MPa in a hot press at 180 °C.

[0090] (4) Preparation of basalt fiber / resin composite material with asymmetric multi-layer gradient electromagnetic alternation:

[0091] Taking the magnetic layer as the incident layer, seven layers of magnetic basalt fiber / polylactic acid films with mass fractions of 5%, 10%, 30% and 50% and conductive basalt fiber / polylactic acid films with mass fractions of 9%, 18% and 27% were stacked asymmetrically with electromagnetic alternation, and a basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency mainly for absorption (denoted as F-C-F) was prepared under a pressure of 3 MPa in a hot press at 180 °C.

[0092] To prove the performance superiority of the electromagnetic asymmetric multi-layer gradient composite material proposed by the present invention, control samples were prepared by the following method:

[0093] (1) Preparation of control sample 1: Seven layers of conductive basalt fiber / polylactic acid films with a mass fraction of 27% were stacked and hot-pressed at 180 °C under a pressure of 3 MPa to obtain a multi-layer electromagnetic shielding composite material (denoted as C).

[0094] (2) Preparation of control sample 2: Seven layers of magnetic basalt fiber / polylactic acid films with a mass fraction of 30% were stacked and hot-pressed at 180 °C under a pressure of 3 MPa to obtain a multi-layer electromagnetic shielding composite material (denoted as F).

[0095] (3) Preparation of control sample 3: Taking the conductive layer as the incident layer, three layers of magnetic basalt fiber / polylactic acid films with a mass fraction of 30% and four layers of conductive basalt fiber / polylactic acid films with a mass fraction of 27% were alternately stacked and hot-pressed at 180 °C under a pressure of 3 MPa to obtain a multi-layer electromagnetic shielding composite material (denoted as C-F).

[0096] (4) Preparation of control sample 4: Taking the magnetic layer as the incident layer, four layers of magnetic basalt fiber / polylactic acid films with a mass fraction of 30% and three layers of conductive basalt fiber / polylactic acid films with a mass fraction of 27% were alternately stacked and hot-pressed at 180 °C under a pressure of 3 MPa to obtain a multi-layer electromagnetic shielding composite material (denoted as F-C).

[0097] The electromagnetic shielding effectiveness of the sample prepared in Example 6 was tested, and the test results are shown in Figure 6 .

[0098] The total electromagnetic shielding effectiveness (SE T ) of Sample C-F is the largest, but its reflection shielding effectiveness (SE R ) is relatively high, reaching 9.8 dB, and the absorption rate of the electromagnetic shielding effectiveness is 74%. Through the design of the electromagnetic asymmetric gradient layered structure, although the total electromagnetic shielding effectiveness decreases, the reflection shielding effectiveness significantly drops to 2.4 dB, and at the same time, the absorption rate of the electromagnetic shielding effectiveness of F-C-F increases to 91%. This indicates that the design of the asymmetric gradient structure can prompt the electromagnetic wave to gradually attenuate inside the composite material, thereby achieving efficient absorption. In summary, the multi-layer asymmetric basalt fiber / resin composites prepared in Examples 2-5 have the characteristics of mainly absorption, a wide anti-electromagnetic interference band, and excellent electromagnetic shielding performance.

[0099] The above-described embodiments only represent the specific implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the protection scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the technical solution of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application.

[0100] This background technology section is provided to generally present the context of the present invention. The work of the currently named inventors, to the extent described in this background technology section, and aspects described in this section that do not constitute prior art at the time of filing this application are neither expressly nor impliedly admitted to be prior art of the present invention.

Claims

1. A method for preparing a dielectric loss coupled magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material, characterized in that: The following steps are involved: (1) Dispersing fibers: Disperse the chopped basalt fibers in a high-speed pulverizer, wash them, and put them into an oven for drying for later use; (2) preparing magnetic basalt fiber / resin film: adding the basalt fiber prepared in step (1) together with the magnetic nanoparticles into an adhesive, and modifying the basalt fiber with the adhesive under ultrasonic stirring conditions to obtain modified basalt fiber; washing and drying the obtained modified basalt fiber to obtain magnetic basalt fiber; finally, mixing and kneading the magnetic basalt fiber and the resin in different proportions, and preparing magnetic basalt fiber / resin films with different mass fractions by hot pressing; (3) Preparing a conductive basalt fiber / resin film: adding the basalt fiber prepared in step (1) together with the conductive nanoparticles into an adhesive, and modifying the basalt fiber with the adhesive under ultrasonic stirring conditions to obtain a modified basalt fiber; washing and drying the obtained modified basalt fiber to obtain a conductive basalt fiber; finally, mixing and kneading the conductive basalt fiber and the resin in different proportions, and performing hot pressing to prepare conductive basalt fiber / resin films with different mass fractions; (4) Preparation of asymmetric multi-layer gradient electromagnetic alternating basalt fiber / resin composite materials: The magnetic basalt fiber / resin films with different mass fractions prepared in step (2) and the conductive basalt fiber / resin films with different mass fractions prepared in step (3) are stacked by controlling variables or dual variables, that is, by alternating stacking, to gradually increase the mass fraction of the conductive basalt fiber or the magnetic basalt fiber, or to increase the mass fractions of both at the same time, and then a basalt fiber / resin composite material with a multi-layer asymmetric gradient electromagnetic alternating structure is prepared by a hot pressing process.

2. The preparation method according to claim 1, characterized in that: In step (1), the dispersion time of the chopped basalt fibers is 1.5 to 2 minutes, the rotation speed of the high-speed pulverizer is 30,000 to 34,000 r / min; the length of the spare basalt fibers is 100 to 130 μm; The solvent used for the cleaning is any one of deionized water, acetone, and ethanol; The drying temperature is 60-80° C. and the drying time is 24 hours.

3. The preparation method according to claim 1, characterized in that: In step (2), the magnetic nanoparticles are any one or more of nano-ferroferric oxide, nano-nickel oxide and nano-carbonyl iron; The mass ratio of the magnetic nanoparticles to the basalt fibers obtained in step (1) is 1:1 to 1:10; The mass fraction of the magnetic basalt fiber in the film is 2.5-50%.

4. The preparation method according to claim 1, characterized in that: In step (3), the conductive nanoparticles are any one of graphene, carbon nanotubes, and carbon black; The mass ratio of the conductive nanoparticles to the basalt fibers obtained in step (1) is 1:8 to 1:16; The mass fraction of the conductive basalt fiber in the film is 9-50%.

5. The preparation method according to claim 1, characterized in that: The adhesive in step (2) and step (3) is a mixture of one or more of waterborne polyurethane, waterborne acrylic acid, and waterborne polyester; The amount of the adhesive added is 2.5-15% of the mass of the obtained basalt fiber; The ultrasonic stirring time is 30 to 60 minutes.

6. The preparation method according to claim 1, characterized in that: The resins described in step (2) and step (3) are any one or more mixtures of polylactic acid resin, epoxy resin, and polyamide resin; The mixing time is 15 to 20 minutes, the rotation speed is 130 to 150 r / min, and the mixing temperature is 160 to 250°C.

7. The preparation method according to claim 1, characterized in that: The thickness of the magnetic basalt fiber / resin film prepared in step (2) and the conductive basalt fiber / resin film prepared in step (3) are both 0.1 to 0.5 mm.

8. The preparation method according to claim 1, characterized in that: In step (4), the multilayer is 3 to 7 layers; when stacking, the magnetic layer is used as the incident layer, and the magnetic basalt fiber / resin film layer and the conductive basalt fiber / resin film layer are stacked alternately in an asymmetric gradient, and the mass fraction of the modified basalt fiber in the magnetic basalt fiber / resin film layer and the conductive basalt fiber / resin film layer is used as a variable for alternating stacking.

9. The preparation method according to claim 1, characterized in that: In steps (2), (3) and (4), the mold compression strength of the hot pressing molding is 3 to 10 MPa, and the hot pressing time is 3 to 6 minutes.

10. A dielectric loss coupled magnetic loss basalt fiber-based asymmetric structure electromagnetic shielding composite material prepared by the method according to any one of claims 1 to 9.

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