A multi-layered alternating basalt fiber / resin electromagnetic shielding composite material and a method of manufacturing the same

Abstract

The present application belongs to the technical field of polymer composite materials, and particularly relates to a kind of multilayer alternating basalt fiber / resin electromagnetic shielding composite material and a preparation method thereof.The present application prepares conductive and magnetically conductive films by blending basalt fibers with electroless conductive and magnetically conductive plating layers with resin respectively, and further obtains a multilayer electromagnetic shielding composite material by alternately hot-pressing and assembling the conductive basalt fiber / resin composite film and the magnetically conductive basalt fiber / resin composite film.The electromagnetic shielding composite material of the present application simultaneously realizes high electromagnetic interference shielding efficiency, low reflection and wide electromagnetic interference resistance frequency band, and has great application potential in the fields of buildings and smart homes.In addition, the use of basalt fiber, a widely available and low-cost natural mineral material, not only reduces costs but also has extremely important significance for efficient comprehensive utilization of natural resources, promotion of sustainable green high-tech industries and development of new material science.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polymer composites, and particularly relates to a multi-layer alternating basalt fiber / resin electromagnetic shielding composite material and a preparation method thereof. BACKGROUND

[0002] Basalt fiber (BF) is one of the four key developed fiber materials in China (including carbon fiber, aramid fiber and ultra-high molecular weight polyethylene fiber), has excellent mechanical properties, acid and alkali corrosion resistance, high temperature resistance and insulation performance, and is widely sourced, low cost, environmentally friendly and degradable, and is known as "21st century green industrial new material", and has broad application prospects in transportation, construction, chemical industry, electronics, national defense and aviation fields.

[0003] In the practical application of basalt fiber, the performance characteristics of the fiber itself and the interfacial behavior in the composite material are the key factors affecting the performance of the final product. Surface modification can not only improve the interfacial behavior between basalt fiber and the matrix, but also can impart functionality to some special surface modification methods, broaden its application in the fields of electromagnetic wave protection, water treatment and catalysis. Among them, the chemical plating process for modification not only has simple equipment, no external power input, uniform and dense coating, few pores, high hardness, and excellent chemical and physical properties, but also is more conducive to industrial production, so it is widely used.

[0004] In recent years, with the rapid development of Internet of Things, autonomous driving, and human-machine devices, it brings convenient life but also serious electromagnetic pollution, which causes a series of environmental and social problems. Therefore, it is important to develop high-efficiency and low-cost electromagnetic shielding composites. According to Schelkunoff's transmission theory, conductivity is the key to shielding effectiveness (SE). Therefore, improving conductivity is considered as the main strategy to improve SE, but it will cause impedance mismatch and strong electromagnetic wave reflection, resulting in serious secondary pollution. In order to coordinate the trade-off between high EMI SE and low reflectivity, so as to minimize secondary pollution, researchers have proposed various strategies. In general, there are three strategies: the first is to introduce magnetic particles to increase EMW absorption through electromagnetic synergistic coupling and impedance matching. However, uniform blending of conductive and magnetic materials is difficult to optimize the impedance matching between free space and composites, and cannot fundamentally break the contradiction between high EMI SE and low reflection, so the key is the reasonable arrangement of hybrid particles. The second is to construct a reasonable multi-interface structure of the material (such as a porous structure) to extend the transmission path of electromagnetic waves and bring additional electromagnetic loss, but these methods often require super-high pressure, complex process or chemical reaction, which is not convenient for actual production. The other method is to construct a multi-layer structure, which provides a simpler and more effective method to construct a multi-interface electromagnetic shielding material. However, if only a multi-layer material using a single attenuation mechanism (for example, using a single layer material with high conductivity), it is still difficult to effectively reduce the reflection value.

[0005] Therefore, there is still a need to develop new high-efficiency and low-cost electromagnetic shielding composites. SUMMARY

[0006] In view of the above problems, the present application provides a promising solution, that is, adding a magnetic absorption layer behind the reflection layer for the reabsorption of electromagnetic waves, and further alternating the conductive layer and the magnetic layer to extend the electromagnetic wave loss path and maximize the electromagnetic wave loss in the system, so as to obtain a multi-layer composite material with high electromagnetic shielding efficiency and low reflection. Benefiting from the multiple alternating "absorption-reflection-reabsorption" structure of electromagnetic coupling, not only the impedance matching is greatly improved, so that most of the electromagnetic waves enter the material inside, but also the multiple heterogeneous interfaces are introduced for polarization loss, and in addition, the repeated absorption, reflection and scattering greatly prolong the transmission path of electromagnetic waves and further limit the escape of electromagnetic waves, so as to realize the high electromagnetic shielding efficiency and low reflection value of the multi-layer material.

[0007] Specifically, the present application provides a preparation method of a multi-layer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection, which comprises the following steps:

[0008] (1) Preparation of conductive basalt fiber / resin composite film: electroless plating of conductive coating on basalt fiber, such as electroless copper plating (or other conductive coatings such as silver plating), to obtain conductive basalt fiber, surface activation of the obtained conductive basalt fiber using a compatibilizer, then melt blending or solution blending with thermoplastic resin, and using mold pressing or doctor blade forming to prepare a conductive basalt fiber / resin composite film;

[0009] (2) Preparation of magnetically permeable basalt fiber / resin composite film: electroless plating of magnetically permeable coating on basalt fiber, such as electroless iron plating (or other magnetically permeable coatings such as cobalt plating, nickel plating, etc.), to obtain magnetically permeable basalt fiber, surface activation of the obtained magnetically permeable basalt fiber using a compatibilizer, then melt blending or solution blending with thermoplastic resin, and using mold pressing or doctor blade forming to prepare a magnetically permeable basalt fiber / resin composite film;

[0010] (3) Preparation of multi-layer alternating basalt fiber / resin electromagnetic shielding composite material: stacking and laying of conductive basalt fiber / resin composite film and magnetically permeable basalt fiber / resin composite film alternately, and obtaining the multi-layer alternating basalt fiber / resin electromagnetic shielding composite material by hot pressing.

[0011] Further, the conductive coating includes a copper plating layer, a silver plating layer, or other conductive coatings.

[0012] Further, the magnetically permeable coating includes an iron plating layer, a cobalt plating layer, a nickel plating layer, or other magnetically permeable coatings.

[0013] Further, the method for electroless plating of conductive or magnetically permeable coating on basalt fiber includes:

[0014] S1: surface etching of the cleaned basalt fiber with an alkaline solution, and then cleaning with deionized water;

[0015] S2: surface coupling modification treatment of the basalt fiber obtained in step S1 in an amino silane coupling agent solution;

[0016] S3: activation treatment of the basalt fiber obtained in step S2 in an activation solution;

[0017] S4: reduction treatment of the basalt fiber obtained in step S3 in a reduction solution;

[0018] S5: electroless plating of conductive or magnetically permeable coating, such as electroless copper plating or electroless iron plating, on the basalt fiber obtained in step S4, and then cleaning with deionized water and drying.

[0019] Further, the cleaned basalt fiber in step S1 is cleaned sequentially with acetone, ethanol, and deionized water.

[0020] Further, the alkaline solution is a sodium hydroxide or potassium hydroxide solution with a concentration of 1M.

[0021] Further, the surface etching is performed at room temperature for 10-30min.

[0022] Further, the amino silane coupling agent solution is an aqueous ethanol solution with an amino silane coupling agent content of 15ml / L.

[0023] Further, the amino silane coupling agent is at least one of KH550, KH792 or KH602.

[0024] Further, the aqueous ethanol solution is 95% ethanol + 5% deionized water.

[0025] Further, the surface coupling modification treatment is performed at room temperature for 10-30min.

[0026] Further, the activation solution is an aqueous hydrochloric acid solution containing 0.2g / L PbCl2.

[0027] Further, the content of HCl in the aqueous hydrochloric acid solution is 15ml / L.

[0028] Further, the activation treatment is performed at room temperature for 10-30min.

[0029] Further, the reduction solution is a 2-10g / L sodium hypophosphite solution, a 2-10g / L potassium hypophosphite solution or a 3-8g / L sodium borohydride solution.

[0030] Further, the reduction treatment is performed at 25-50℃ for 10-30min.

[0031] Further, the plating solution for electroless copper plating contains 30g / L NiSO4·6H2O, 2g / L CuSO4·5H2O, 25g / L NaH2PO2·H2O, 50g / L KNaC4H4O6·4H2O and 30g / L (NH4)2SO4, and the plating solution for electroless iron plating contains 30g / L NiSO4·6H2O, 15g / L (NH4)2Fe(SO4)2·6H2O, 25g / L NaH2PO2·H2O, 50g / L KNaC4H4O6·4H2O and 30g / L (NH4)2SO4.

[0032] Further, the electroless plating, such as electroless copper plating or electroless iron plating, is performed at 60-80℃ for 10-30min.

[0033] Further, the electroless plating such as electroless copper plating or electroless iron plating is also performed at a stirring speed of 200 rpm.

[0034] Further, the compatibilizer is selected from one or more of silane coupling agent, phosphonic acid coupling agent, higher fatty acid, dopamine, maleic anhydride, acrylic, epoxy or isocyanate.

[0035] Further, the mass fraction of the conductive or magnetically conductive basalt fiber in the blend of the conductive or magnetically conductive basalt fiber and the thermoplastic resin is 30-70 wt%.

[0036] Further, the thermoplastic resin is selected from one or more of polylactic acid resin, phenolic resin, epoxy resin, polyester resin, styrene resin, polyamide resin, polyurethane thermoplastic elastomer, polyether resin or polycarbonate resin.

[0037] Further, the thickness of the conductive or magnetically conductive basalt fiber / resin composite film prepared in steps (1) and (2) is 1-5 mm.

[0038] Further, the total number of layers of the conductive basalt fiber / resin composite film and the magnetically conductive basalt fiber / resin composite film stacked alternately is 3-9 layers. As used herein, the manner of stacking alternately requires a stacking manner that keeps the magnetic layer on the outer layer and the conductive layer on the inner layer.

[0039] Further, the mold pressing strength of the hot-pressing forming is 10-20 MPa, the preheating time is 3-8 min, the hot-pressing time is 2-6 min and the cold-pressing time is 2-5 min.

[0040] The present application also provides a multilayer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection prepared by the preparation method described herein.

[0041] Advantages of the present application

[0042] In practice, it is found that the double-structure material with the magnetic layer as the outer impedance layer and the conductive layer as the internal reflection layer attenuates electromagnetic waves by constructing an "absorption-reflection-reabsorption" transmission path inside the system. Although most of the electromagnetic waves are reflected and re-enter the absorption layer for loss when the electromagnetic waves pass through the surface absorption layer to reach the reflection layer, part of the electromagnetic waves still penetrate the reflection layer into the air for secondary transmission. Obviously, the effective dissipation of this part of the penetrating electromagnetic waves is conducive to further improving the high-efficiency electromagnetic shielding performance of the composite material mainly by absorption. However, there is no research to find and solve the problem of the retransmission of this part of the penetrating electromagnetic waves.

[0043] The product designed by the application solves the above problems, compared with the double-structure material with the magnetic layer as the outer impedance layer and the conductive layer as the internal reflection layer, it simultaneously realizes more excellent high electromagnetic interference shielding efficiency, low reflection and wide electromagnetic interference frequency band, and has reliable joule heating performance, and has great application potential in buildings and smart homes and other fields. In addition, using basalt fiber, a widely available, low-cost, environmentally friendly and degradable natural mineral material, not only reduces costs but also has extremely important significance for efficient comprehensive utilization of natural resources, promoting the development of sustainable green high-tech industries and new material science. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 The basalt fiber electron microscope images are shown, (a) original basalt fiber, (b) chemical plating Ni-Fe-P basalt fiber, (c) chemical plating Ni-Cu-P basalt fiber.

[0045] Figure 2 The element distribution maps of the plated basalt fiber are shown, (a) chemical plating Ni-Fe-P basalt fiber, (a2) Ni element distribution, (a3) Fe element distribution, (a4) P element distribution, (b) chemical plating Ni-Cu-P basalt fiber, (b2) Ni element distribution, (b3) Cu element distribution, (b4) P element distribution.

[0046] Figure 3 The graph showing the measured electromagnetic shielding efficiency values of the samples in the experimental examples is shown. DETAILED DESCRIPTION

[0047] Unless otherwise defined, all terms used herein have the meanings commonly understood by those skilled in the art. For the purposes of the present application, some terms used herein are defined below.

[0048] All numerical designations, including numerical ranges, are approximate values. It is to be understood that, although the numerical designations are recited precisely, the approximations are accepted. Also, it is to be understood that the reagents described herein are merely examples and equivalents are known in the art.

[0049] The application will be described in detail below with reference to the embodiments.

[0050] Example 1

[0051] A method for preparing a high electromagnetic shielding efficiency and low reflection multilayer alternating basalt fiber / resin electromagnetic shielding composite material, comprising the following steps:

[0052] (1) Preparation of conductive basalt fiber / resin composite film: S1: basalt fibers were sequentially cleaned with acetone, ethanol and deionized water, and then etched with 1M NaOH solution at room temperature for 30 min; S2: the basalt fibers were treated in an ethanol solution (95% ethanol + 5% deionized water) containing 15 ml / L KH550 at room temperature for 10 min; S3: the basalt fibers were activated in a hydrochloric acid solution (HCl content of 15 ml / L) containing 0.2 g / L PbCl2 at room temperature for 10 min; S4: the basalt fibers were immersed in a 4 g / L sodium hypophosphite solution at 40°C for 10 min; S5: the basalt fibers were treated in a plating solution (30 g / L NiSO4·6H2O, 2 g / L CuSO4·5H2O, 25 g / L NaH2PO2·H2O, 50 g / L KNaC4H4O6·4H2O and 30 g / L (NH4)2SO4) at 70°C for 30 min, and then rinsed with deionized water, followed by vacuum drying in an oven at 80°C to obtain conductive basalt fibers;

[0053] The obtained conductive basalt fibers were surface-activated with an ethanol solution (95% ethanol + 5% deionized water) containing 6 g / L KH550 to improve their compatibility with the resin matrix;

[0054] The conductive basalt fibers with a mass fraction of 30 wt% were melt-blended with polylactic acid resin at 180°C, and a conductive basalt fiber / resin composite film with a thickness of 3 mm was prepared by a molding process;

[0055] (2) Preparation of magnetically conductive basalt fiber / resin composite film: S1: basalt fibers were sequentially cleaned with acetone, ethanol and deionized water, and then etched with 1M NaOH solution at room temperature for 30 min; S2: the basalt fibers were treated in an ethanol solution (95% ethanol + 5% deionized water) containing 15 ml / L KH550 at room temperature for 10 min; S3: the basalt fibers were activated in a hydrochloric acid solution (HCl content of 15 ml / L) containing 0.2 g / L PbCl2 at room temperature for 10 min; S4: the basalt fibers were immersed in a 4 g / L sodium hypophosphite solution at 40°C for 10 min; S5: the basalt fibers were treated in a plating solution (30 g / L NiSO4·6H2O, CuSO4·5H2O, 15 g / L (NH4)2Fe(SO4)2·6H2O, 25 g / L NaH2PO2·H2O, 50 g / L KNaC4H4O6·4H2O and 30 g / L (NH4)2SO4) at 70°C for 30 min, and then rinsed with deionized water, followed by vacuum drying in an oven at 80°C to obtain magnetically conductive basalt fibers;

[0056] The obtained magnetically conductive basalt fibers were surface-activated with an ethanol aqueous solution (95% ethanol + 5% deionized water) containing 6 g / L of KH550 to improve the compatibility with the resin matrix;

[0057] The magnetically conductive basalt fibers with a mass fraction of 30 wt% were melt-blended with polylactic acid resin at 180°C to prepare a magnetically conductive basalt fiber / resin composite film with a thickness of 3 mm by a mold pressing process;

[0058] (3) The stacking mode of keeping the magnetic layer on the outer layer and the conductive layer on the inner layer, the conductive basalt fiber / resin composite film and the magnetically conductive basalt fiber / resin composite film were alternately stacked in 3 layers (i.e., the total number of layers was 3), and a multilayer alternating basalt fiber / resin electromagnetic shielding composite material (represented by Fe-Cu-Fe) with high electromagnetic shielding efficiency and low reflection was obtained by preheating for 5 min, hot pressing for 4 min, and cold pressing for 3 min under the conditions of a temperature of 170°C and a pressure of 10 MPa.

[0059] Example 2:

[0060] A preparation method of a multilayer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection, comprising the following steps:

[0061] (1) Preparation of a conductive basalt fiber / resin composite film: S1: The basalt fibers were sequentially cleaned with acetone, ethanol, and deionized water, and then etched with a 1M sodium hydroxide solution at room temperature for 30 min; S2: The basalt fibers were treated in an ethanol aqueous solution (95% ethanol + 5% deionized water) containing 15 ml / L of KH550 at room temperature for 10 min; S3: The basalt fibers were activated in a hydrochloric acid aqueous solution (HCl content was 15 ml / L) containing 0.2 g / L of PbCl2 at room temperature for 10 min; S4: The basalt fibers were soaked in a 4 g / L sodium hypophosphite solution at 40°C for 10 min; S5: The basalt fibers were treated in a plating solution (30 g / L of NiSO4·6H2O, 2 g / L of CuSO4·5H2O, 25 g / L of NaH2PO2·H2O, 50 g / L of KNaC4H4O6·4H2O, and 30 g / L of (NH4)2SO4) at 70°C for 30 min, and then rinsed with deionized water, followed by vacuum drying in an 80°C oven to obtain conductive basalt fibers;

[0062] The obtained conductive basalt fibers were surface-activated with a 2.0 mg / mL dopamine solution (pH value was adjusted to 8.5 with a tris buffer) to improve the compatibility with the resin matrix;

[0063] Conductive basalt fiber with a mass fraction of 40 wt% was melt-blended with epoxy resin at 150°C, and a conductive basalt fiber / resin composite film with a thickness of 2 mm was prepared by compression molding process.

[0064] (2) Preparation of magnetically conductive basalt fiber / resin composite film: S1: Basalt fibers were cleaned sequentially with acetone, ethanol, and deionized water, and then etched with a 1M sodium hydroxide solution at room temperature for 30 min; S2: Basalt fibers were treated with an ethanol aqueous solution (95% ethanol + 5% deionized water) with a KH550 content of 15 ml / L for 10 min at room temperature; S3: Basalt fibers were activated with a hydrochloric acid aqueous solution (HCl content of 15 ml / L) containing 0.2 g / L PbCl2 at room temperature for 10 min; S4: Basalt fibers were immersed in a 4 g / L sodium hypophosphite solution at 40℃ for 10 min; S5: Basalt fibers were coated with a 30 g / L sodium hypophosphite solution at 70℃. The basalt fibers were treated with NiSO4·6H2O, CuSO4·5H2O, 15g / L(NH4)2Fe(SO4)2·6H2O, 25g / LNaH2PO2·H2O, 50g / LKNaC4H4O6·4H2O and 30g / L(NH4)2SO4) for 30min, rinsed with deionized water, and then placed in an 80℃ oven for vacuum drying to obtain magnetic basalt fibers.

[0065] The obtained magnetically conductive basalt fibers were surface activated with a 2.0 mg / mL dopamine solution (pH adjusted to 8.5 with Tris buffer) to improve their compatibility with the resin matrix.

[0066] Magnetic basalt fiber with a mass fraction of 40 wt% was melt-blended with epoxy resin at 150℃, and a magnetic basalt fiber / resin composite film with a thickness of 2 mm was prepared by compression molding process.

[0067] (3) Maintaining the stacking method of magnetic layer on the outer layer and conductive layer on the inner layer, the conductive basalt fiber / resin composite film and the magnetic basalt fiber / resin composite film are stacked alternately in 5 layers. Under the conditions of temperature of 150℃ and pressure of 10MPa, the preheating time is 5min, the hot pressing time is 4min, and the cold pressing time is 3min, the multilayer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection is obtained by hot pressing.

[0068] Example 3:

[0069] A method for preparing a multilayer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection includes the following steps:

[0070] (1) Preparation of conductive basalt fiber / resin composite film: S1: Basalt fiber was cleaned sequentially with acetone, ethanol, and deionized water, and then etched with 1M sodium hydroxide solution at room temperature for 30 min; S2: Basalt fiber was treated with 15 ml / L KH550 ethanol aqueous solution (95% ethanol + 5% deionized water) at room temperature for 10 min; S3: Basalt fiber was activated with 0.2 g / L PbCl2 hydrochloric acid aqueous solution (HCl content of 15 ml / L) at room temperature for 10 min; S4: Basalt fiber was immersed in 4 g / L sodium hypophosphite solution at 40℃ for 10 min; S5: Basalt fiber was plated in 70℃ plating solution (30 g / L NiSO4·6H2O, 2 g / L sodium hydroxide solution) The basalt fibers were treated with CuSO4·5H2O, 25g / LNaH2PO2·H2O, 50g / LKNaC4H4O6·4H2O and 30g / L(NH4)2SO4) for 30min, rinsed with deionized water, and then placed in an 80℃ oven for vacuum drying to obtain conductive basalt fibers.

[0071] The obtained conductive basalt fibers were surface activated with an ethanol aqueous solution of KH550 (6 g / L) (95% ethanol + 5% deionized water) to improve their compatibility with the resin matrix.

[0072] Conductive basalt fiber with a mass fraction of 40 wt% was melt-blended with epoxy resin at 150℃, and a conductive basalt fiber / resin composite film with a thickness of 2 mm was prepared by hot pressing molding process.

[0073] (2) Preparation of magnetically conductive basalt fiber / resin composite film: S1: Basalt fibers were cleaned sequentially with acetone, ethanol, and deionized water, and then etched with a 1M sodium hydroxide solution at room temperature for 30 min; S2: Basalt fibers were treated with an ethanol aqueous solution (95% ethanol + 5% deionized water) with a KH550 content of 15 ml / L for 10 min at room temperature; S3: Basalt fibers were activated with a hydrochloric acid aqueous solution (HCl content of 15 ml / L) containing 0.2 g / L PbCl2 at room temperature for 10 min; S4: Basalt fibers were immersed in a 4 g / L sodium hypophosphite solution at 40℃ for 10 min; S5: Basalt fibers were coated with a 30 g / L sodium hypophosphite solution at 70℃. The basalt fibers were treated with NiSO4·6H2O, CuSO4·5H2O, 15g / L(NH4)2Fe(SO4)2·6H2O, 25g / LNaH2PO2·H2O, 50g / LKNaC4H4O6·4H2O and 30g / L(NH4)2SO4) for 30min, rinsed with deionized water, and then placed in an 80℃ oven for vacuum drying to obtain magnetic basalt fibers.

[0074] The obtained magnetically conductive basalt fibers were surface activated with an ethanol aqueous solution of KH550 (6 g / L) (95% ethanol + 5% deionized water) to improve their compatibility with the resin matrix.

[0075] Magnetic basalt fiber with a mass fraction of 40 wt% was melt-blended with epoxy resin at 150℃, and a magnetic basalt fiber / resin composite film with a thickness of 2 mm was prepared by hot pressing molding process.

[0076] (3) Maintaining the stacking method of magnetic layer on the outer layer and conductive layer on the inner layer, the conductive basalt fiber / resin composite film and the magnetic basalt fiber / resin composite film are stacked alternately in 5 layers. Under the conditions of temperature of 150℃ and pressure of 10MPa, the preheating time is 5min, the hot pressing time is 4min, and the cold pressing time is 3min, the multilayer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection is obtained by hot pressing.

[0077] Example 4:

[0078] A method for preparing a multilayer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection includes the following steps:

[0079] (1) Preparation of conductive basalt fiber / resin composite film: S1: Basalt fiber was cleaned sequentially with acetone, ethanol, and deionized water, and then etched with 1M sodium hydroxide solution at room temperature for 30 min; S2: Basalt fiber was treated with 15 ml / L KH550 ethanol aqueous solution (95% ethanol + 5% deionized water) at room temperature for 10 min; S3: Basalt fiber was activated with 0.2 g / L PbCl2 hydrochloric acid aqueous solution (HCl content of 15 ml / L) at room temperature for 10 min; S4: Basalt fiber was immersed in 4 g / L sodium hypophosphite solution at 40℃ for 10 min; S5: Basalt fiber was plated in 70℃ plating solution (30 g / L NiSO4·6H2O, 2 g / L sodium hydroxide solution) The basalt fibers were treated with CuSO4·5H2O, 25g / LNaH2PO2·H2O, 50g / LKNaC4H4O6·4H2O and 30g / L(NH4)2SO4) for 30min, rinsed with deionized water, and then placed in an 80℃ oven for vacuum drying to obtain conductive basalt fibers.

[0080] The obtained conductive basalt fibers were surface activated with a 2.0 mg / mL dopamine solution (pH adjusted to 8.5 with Tris buffer) to improve their compatibility with the resin matrix.

[0081] Conductive basalt fiber with a mass fraction of 60 wt% was solution blended with polylactic acid resin (using dimethyl carbonate as solvent, treated at 60℃ and 200 rpm for 6 h), and a conductive basalt fiber / resin composite film with a thickness of 2 mm was prepared by a scraping film forming process.

[0082] (2) Preparation of magnetically conductive basalt fiber / resin composite film: S1: Basalt fibers were cleaned sequentially with acetone, ethanol, and deionized water, and then etched with a 1M sodium hydroxide solution at room temperature for 30 min; S2: Basalt fibers were treated with an ethanol aqueous solution (95% ethanol + 5% deionized water) with a KH550 content of 15 ml / L for 10 min at room temperature; S3: Basalt fibers were activated with a hydrochloric acid aqueous solution (HCl content of 15 ml / L) containing 0.2 g / L PbCl2 at room temperature for 10 min; S4: Basalt fibers were immersed in a 4 g / L sodium hypophosphite solution at 40℃ for 10 min; S5: Basalt fibers were coated with a 30 g / L sodium hypophosphite solution at 70℃. The basalt fibers were treated with NiSO4·6H2O, CuSO4·5H2O, 15g / L(NH4)2Fe(SO4)2·6H2O, 25g / LNaH2PO2·H2O, 50g / LKNaC4H4O6·4H2O and 30g / L(NH4)2SO4) for 30min, rinsed with deionized water, and then placed in an 80℃ oven for vacuum drying to obtain magnetic basalt fibers.

[0083] The obtained magnetically conductive basalt fibers were surface activated with a 2.0 mg / mL dopamine solution (pH adjusted to 8.5 with Tris buffer) to improve their compatibility with the resin matrix.

[0084] Magnetic basalt fiber with a mass fraction of 60 wt% was solution blended with polylactic acid resin (using dimethyl carbonate as solvent, and treated for 6 h at a temperature of 60℃ and a rotation speed of 200 rpm), and a magnetic basalt fiber / resin composite film with a thickness of 2 mm was prepared by a scraping film forming process.

[0085] (3) Maintaining the stacking method of magnetic layer on the outer layer and conductive layer on the inner layer, the conductive basalt fiber / resin composite film and the magnetic basalt fiber / resin composite film are stacked alternately for 7 layers. Under the conditions of temperature of 170℃ and pressure of 10MPa, the preheating time is 5min, the hot pressing time is 4min, and the cold pressing time is 3min, the multilayer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection is obtained by hot pressing.

[0086] Example 5:

[0087] A method for preparing a multilayer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection includes the following steps:

[0088] (1) Preparation of conductive basalt fiber / resin composite film: S1: Basalt fiber was cleaned sequentially with acetone, ethanol, and deionized water, and then etched with 1M sodium hydroxide solution at room temperature for 30 min; S2: Basalt fiber was treated with 15 ml / L KH550 ethanol aqueous solution (95% ethanol + 5% deionized water) at room temperature for 10 min; S3: Basalt fiber was activated with 0.2 g / L PbCl2 hydrochloric acid aqueous solution (HCl content of 15 ml / L) at room temperature for 10 min; S4: Basalt fiber was immersed in 4 g / L sodium hypophosphite solution at 40℃ for 10 min; S5: Basalt fiber was plated in 70℃ plating solution (30 g / L NiSO4·6H2O, 2 g / L sodium hydroxide solution) The basalt fibers were treated with CuSO4·5H2O, 25g / LNaH2PO2·H2O, 50g / LKNaC4H4O6·4H2O and 30g / L(NH4)2SO4) for 30min, rinsed with deionized water, and then placed in an 80℃ oven for vacuum drying to obtain conductive basalt fibers.

[0089] The obtained conductive basalt fibers were stirred at room temperature for 24 hours in a 2.0 mg / mL dopamine solution, and then 0.6 mg / mL KH550 was added dropwise for surface activation treatment to improve their compatibility with the resin matrix.

[0090] Conductive basalt fiber with a mass fraction of 70 wt% was melt-blended with polyethylene terephthalate at 240℃, and a conductive basalt fiber / resin composite film with a thickness of 1 mm was prepared by compression molding process.

[0091] (2) Preparation of magnetically conductive basalt fiber / resin composite film: S1: Basalt fiber was cleaned sequentially with acetone, ethanol and deionized water, and then etched with 1M sodium hydroxide solution at room temperature for 30 min; S2: Basalt fiber was treated with ethanol aqueous solution (95% ethanol + 5% deionized water) with KH550 content of 15 ml / L at room temperature for 10 min; S3: Basalt fiber was activated with hydrochloric acid aqueous solution (HCl content of 15 ml / L) containing 0.2 g / L PbCl2 at room temperature for 10 min; S4: Basalt fiber was soaked in sodium hypophosphite solution of 4 g / L at 40℃ for 10 min;

[0092] S5: Basalt fibers were treated in a 70℃ plating solution (30g / L NiSO4·6H2O, CuSO4·5H2O, 15g / L (NH4)2Fe(SO4)2·6H2O, 25g / L NaH2PO2·H2O, 50g / L KNaC4H4O6·4H2O and 30g / L (NH4)2SO4) for 30min. The plating basalt fibers were then rinsed with deionized water and placed in an 80℃ oven for vacuum drying to obtain magnetic basalt fibers.

[0093] The obtained magnetically conductive basalt fibers were stirred in a 2.0 mg / mL dopamine solution at room temperature for 24 h, and then 0.6 mg / mL KH550 was added dropwise for surface activation treatment to improve their compatibility with the resin matrix.

[0094] 70 wt% magnetic basalt fiber and polyethylene terephthalate were melt-blended at 240°C and then molded to form a magnetic basalt fiber / resin composite film with a thickness of 1 mm.

[0095] (3) Maintaining the stacking method of magnetic layer on the outer layer and conductive layer on the inner layer, 9 layers of conductive basalt fiber / resin composite film and magnetic basalt fiber / resin composite film are stacked alternately. Under the conditions of temperature of 240℃ and pressure of 10MPa, the preheating time is 5min, the hot pressing time is 4min, and the cold pressing time is 3min, the multilayer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection is obtained by hot pressing.

[0096] Experimental Example

[0097] Conductive basalt fiber / resin composite films (copper-plated basalt fiber / resin composite film) and magnetic basalt fiber / resin composite films (iron-plated basalt fiber / resin composite film) were prepared according to the method in Example 1. To demonstrate the superior performance of the alternating magnetic and conductive layer structure proposed in this invention, control samples were prepared according to the following method for comparative study:

[0098] (1) Preparation method of reference sample 1: Three conductive layers are stacked together, and under the conditions of 170℃ and 10MPa, the multilayer composite material (represented by Cu-Cu-Cu) is obtained after 5min preheating, 4min hot pressing and 3min cold pressing.

[0099] (2) Preparation method of reference sample 2: The three magnetic conductive layers are stacked together and subjected to a temperature of 170℃ and a pressure of 10MPa. The composite material is preheated for 5 minutes, hot-pressed for 4 minutes, and cold-pressed for 3 minutes (represented as Fe-Fe-Fe).

[0100] (3) Preparation method of control sample 3: Keep the conductive layer on the outer layer and the magnetic layer on the inner layer in a stacking manner. The conductive basalt fiber / resin composite film and the magnetic basalt fiber / resin composite film are stacked alternately in 3 layers (i.e., the total number of layers is 3). Under the conditions of temperature of 170℃ and pressure of 10MPa, after 5min of preheating, 4min of hot pressing and 3min of cold pressing, a multilayer alternating basalt fiber / resin electromagnetic shielding composite material (represented by Cu-Fe-Cu) is obtained.

[0101] (4) Preparation method of control sample 4: Keep the conductive layer on the outer layer and the magnetic layer on the inner layer in a stacking manner. Stack the conductive basalt fiber / resin composite film and the magnetic basalt fiber / resin composite film together (i.e., the total number of layers is 2). Under the conditions of temperature of 170℃ and pressure of 10MPa, after 5min of preheating, 4min of hot pressing and 3min of cold pressing, a multilayer alternating basalt fiber / resin electromagnetic shielding composite material (represented by Cu-Fe) is obtained.

[0102] (5) Preparation method of control sample 5: Keep the magnetic layer on the outer layer and the conductive layer on the inner layer in the stacking mode, and alternately stack the conductive basalt fiber / resin composite film and the magnetic basalt fiber / resin composite film (i.e., the total number of layers is 2). Under the conditions of temperature of 170℃ and pressure of 10MPa, after 5min of preheating, 4min of hot pressing and 3min of cold pressing, a multilayer alternating basalt fiber / resin electromagnetic shielding composite material (represented by Fe-Cu) is obtained.

[0103] The electromagnetic shielding effectiveness of control samples 1 to 5 and the Fe-Cu-Fe sample from Example 1 were tested, and the results are as follows: Figure 3 As shown.

[0104] The Fe-Cu-Fe sample exhibits the best overall shielding effectiveness (SE). T Meanwhile, its electromagnetic reflection value SE R The smallest result fully demonstrates the superior performance of the alternating structure with the magnetic layer on the outer layer and the conductive layer on the inner layer. Compared to the two-layer Fe-Cu, all performance indices show a significant improvement. Next is the Cu-Fe-Cu sample. Although it has a conductive layer on the outer layer and a magnetic layer on the inner layer, which is not the stacking method commonly used in the art, its electromagnetic interference shielding performance and reflection value are better than the Cu-Fe and even Fe-Cu samples, indicating that the alternating structure of the present invention can bring unexpected superior performance. In summary, the above experiments demonstrate that the multilayer alternating basalt fiber / resin electromagnetic shielding composite materials of Examples 1-5, with high electromagnetic shielding efficiency and low reflection, possess high electromagnetic interference shielding efficiency, low reflection, and a wide electromagnetic interference resistance bandwidth.

[0105] It should be noted that while the preferred embodiments of the present invention are provided in this specification, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of the present invention; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of the present invention. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of the present invention. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a multilayer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection, characterized in that, Includes the following steps: (1) Preparation of conductive basalt fiber / resin composite film: Chemically plate basalt fiber with conductive coating to obtain conductive basalt fiber, surface activation of the obtained conductive basalt fiber with compatibilizer, and then melt-blending or solution-blending with thermoplastic resin, and preparing conductive basalt fiber / resin composite film by compression molding or scraping molding, wherein the conductive coating includes copper plating or silver plating. (2) Preparation of magnetic basalt fiber / resin composite film: Chemically plate the basalt fiber with a magnetic coating to obtain magnetic basalt fiber. Surface activation of the obtained magnetic basalt fiber is performed using a compatibilizer. Then, it is melt-blended or solution-blended with thermoplastic resin and prepared into a magnetic basalt fiber / resin composite film by compression molding or scraping molding. The magnetic coating includes an iron plating layer, a cobalt plating layer, or a nickel plating layer. The mass fraction of conductive or magnetic basalt fiber in the blend of conductive or magnetic basalt fiber and thermoplastic resin is 30-70 wt%. (3) Preparation of multilayer alternating basalt fiber / resin electromagnetic shielding composite material: Conductive basalt fiber / resin composite film and magnetic basalt fiber / resin composite film are alternately stacked and layered, and the multilayer alternating basalt fiber / resin electromagnetic shielding composite material is obtained by hot pressing. The alternating stacking method requires that the magnetic layer is on the outer layer and the conductive layer is on the inner layer.

2. The preparation method according to claim 1, characterized in that, Methods for chemical plating conductive or magnetic coatings onto basalt fibers include: S1: The cleaned basalt fibers are surface-etched with an alkaline solution and then cleaned with deionized water. S2: The basalt fibers obtained in step S1 are subjected to surface coupling modification treatment in an amino-based silane coupling agent solution; S3: Activate the basalt fibers obtained in step S2 in an activation solution; S4: The basalt fibers obtained in step S3 are reduced in a reducing solution; S5: The basalt fibers obtained in step S4 are chemically plated with conductive or magnetic coatings in a plating solution, then washed with deionized water and dried.

3. The preparation method according to claim 2, characterized in that, The basalt fibers cleaned in step S1 are cleaned sequentially with acetone, ethanol and deionized water.

4. The preparation method according to claim 2, characterized in that, The alkaline solution is a 1M sodium hydroxide or potassium hydroxide solution.

5. The preparation method according to claim 2, characterized in that, The surface etching is performed at room temperature for 10-30 minutes.

6. The preparation method according to claim 2, characterized in that, The amino-based silane coupling agent solution is an ethanol-water solution with an amino-based silane coupling agent content of 15 ml / L.

7. The preparation method according to claim 6, characterized in that, The amino-based silane coupling agent is at least one of KH550, KH792, or KH602.

8. The preparation method according to claim 6, characterized in that, The ethanol-water solution is 95% ethanol + 5% deionized water.

9. The preparation method according to claim 2, characterized in that, The surface coupling modification treatment is performed at room temperature for 10-30 minutes.

10. The preparation method according to claim 2, characterized in that, The activation solution is an aqueous solution of hydrochloric acid containing 0.2 g / L PbCl2.

11. The preparation method according to claim 10, characterized in that, The HCl content in the hydrochloric acid aqueous solution is 15 ml / L.

12. The preparation method according to claim 2, characterized in that, The activation treatment is performed at room temperature for 10-30 minutes.

13. The preparation method according to claim 2, characterized in that, The reducing solution is a sodium hypophosphite solution of 2-10 g / L, a potassium hypophosphite solution of 2-10 g / L, or a sodium borohydride solution of 3-8 g / L.

14. The preparation method according to claim 2, characterized in that, The reduction treatment is carried out at 25-50℃ for 10-30 minutes.

15. The preparation method according to claim 2, characterized in that, The plating solution used for electroless copper plating contains 30 g / L NiSO4·6H2O, 2 g / L CuSO4·5H2O, 25 g / L NaH2PO2·H2O, 50 g / L KNaC4H4O6·4H2O, and 30 g / L (NH4)2SO4. The plating solution used for electroless iron plating contains 30 g / L NiSO4·6H2O, 15 g / L (NH4)2Fe(SO4)2·6H2O, 25 g / L NaH2PO2·H2O, 50 g / L KNaC4H4O6·4H2O, and 30 g / L (NH4)2SO4.

16. The preparation method according to claim 2, characterized in that, The electroless plating process is carried out at 60-80℃ for 10-30 minutes.

17. The preparation method according to claim 2, characterized in that, The electroless plating process is also carried out with a stirring speed of 200 rpm.

18. The preparation method according to claim 1, characterized in that, The compatibilizer is selected from one or more of the following: silane coupling agents, titanate coupling agents, higher fatty acids, dopamine, maleic anhydride, acrylic acid, epoxy, or isocyanate.

19. The preparation method according to claim 1, characterized in that, The thermoplastic resin is selected from one or more of polylactic acid resin, phenolic resin, epoxy resin, polyester resin, styrene resin, polyamide resin, polyurethane thermoplastic elastomer, polyether resin or polycarbonate resin.

20. The preparation method according to claim 1, characterized in that, The thickness of the conductive or magnetic basalt fiber / resin composite membrane prepared in steps (1) and (2) is 1 mm to 5 mm.

21. The preparation method according to claim 1, characterized in that, The conductive basalt fiber / resin composite membrane and the magnetic basalt fiber / resin composite membrane are stacked alternately in 3-9 layers.

22. The preparation method according to claim 1, characterized in that, The hot-pressed molding strength is 10-20 MPa, the preheating time is 3-8 min, the hot pressing time is 2-6 min, and the cold pressing time is 2-5 min.

23. A multilayer alternating basalt fiber / resin electromagnetic shielding composite material with high electromagnetic shielding efficiency and low reflection, prepared by the preparation method according to any one of claims 1-22.

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