Leather with conductive gradient structure and preparation method and application thereof

Abstract

The application discloses a kind of leathers with conductive gradient structure and its preparation method and application, the method is by ultrasonic and physical mechanical action, makes hydrotalcite, carbon black, polypyrrole etc. Conductive material enters the inside of leather collagen fiber, the modification of collagen fiber of leather is carried out.The preparation method provided by the application can increase the porosity of leather fiber structure, facilitate multiple reflection of electromagnetic wave in leather inside;Meanwhile, conductive material constructs conductive network in the inside of collagen fiber, and the leather with conductive gradient structure is prepared, which is conducive to enhancing the absorption loss of electromagnetic wave by conductive material.The electromagnetic shielding leather prepared by the preparation method provided by the application has a shrinkage temperature of 77 DEG C and an electromagnetic shielding effectiveness of 45 dB, indicating that the leather has good thermal stability and electromagnetic shielding performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of leather tanning, and relates to a leather with a conductive gradient structure and a preparation method and application thereof. BACKGROUND

[0002] Leather has rich multi-scale pores, which can provide a suitable propagation channel for incident electromagnetic waves; the complex three-dimensional network cross-linking structure in the fibers can form multiple diffuse reflections on electromagnetic waves. The synergistic effect of the two can effectively reduce the number of outgoing electromagnetic waves, achieving the purpose of electromagnetic shielding. In addition, the collagen fibers in the leather are rich in carboxyl and amino groups, which can act as electric dipoles to enhance the dielectric loss of collagen fibers to incident electromagnetic waves. At the same time, the carboxyl and amino groups can act as active groups to chemically bond with conductive materials, facilitating the construction of a stable and continuous conductive network, enhancing the number of electromagnetic waves entering the interior of the leather, and being conducive to the absorption loss of electromagnetic waves by the leather.

[0003] The prior art for preparing electromagnetic shielding leather is usually to coat or filter conductive materials on the surface of the leather to prepare a conductive coating, thereby obtaining electromagnetic shielding leather. For example, a nano metal powder (silver, copper, silver-coated copper, ferrite, nickel and zinc) dispersion liquid and a film-forming agent are sprayed on the surface of the leather, and after drying, a leather material with electromagnetic shielding performance is obtained (CN105219895A); multi-walled carbon nanotubes coated with metal nanoparticles are dip-coated on the leather substrate by filtration to develop a lightweight, high-performance electromagnetic shielding leather, which has an excellent electromagnetic shielding efficiency of 76dB. However, the above method has harsh preparation conditions and a complicated procedure, and the conductive material only exists on the surface of the material, which can easily damage the softness and durability of the leather itself, limiting its application in intelligent wearable materials. Therefore, it is of great significance to provide an electromagnetic shielding leather that can fully utilize the advantages of leather materials in the field of electromagnetic shielding, directly construct a conductive network in the interior of the leather, and has excellent performance. SUMMARY

[0004] The present application aims to provide a leather with a conductive gradient structure and a preparation method and application thereof. The leather utilizes conductive materials such as hydrotalcite, carbon black and polypyrrole, and through ultrasonic or physical and mechanical action, the conductive materials enter the interior of the collagen fibers of the leather, modifying the collagen fibers of the leather. This method can increase the porosity of the fiber structure of the leather, facilitating multiple reflections of electromagnetic waves in the interior of the leather; at the same time, the conductive materials construct a conductive network in the interior of the collagen fibers, reducing the resistance of the prepared electromagnetic shielding leather and being conducive to enhancing the dielectric loss of electromagnetic waves. This method can endow the finished leather with thermal stability and electromagnetic shielding performance.

[0005] The first aspect of the present application provides a method for preparing leather with a conductive gradient structure, comprising: a method for preparing leather with a conductive gradient structure, characterized by comprising: adding a dielectric material with wave-absorbing performance to a pretreated crust bath solution for first dipping treatment to obtain dielectric leather;

[0006] placing the dielectric leather in a solution containing conductive material for second dipping treatment to obtain conductive leather;

[0007] placing the conductive leather in a solution containing polymer monomers for third dipping treatment, adding an oxidizing agent for polymerization reaction to obtain leather with a conductive gradient structure.

[0008] Further, in the method for preparing leather with a conductive gradient structure, the pretreatment is acid immersion treatment;

[0009] The bath solution pH in the acid immersion treatment is 2.5-3.5.

[0010] Further, in the method for preparing leather with a conductive gradient structure, the dielectric material with wave-absorbing performance is hydrotalcite;

[0011] The mass of the hydrotalcite is 5%-10% of the mass of water.

[0012] Further, in the method for preparing leather with a conductive gradient structure, the first dipping treatment comprises: rotation, pH adjustment, and standing;

[0013] The adjusted pH is 4-6;

[0014] The rotation time is 2-4 h;

[0015] The standing time is 6-24 h.

[0016] Further, in the method for preparing leather with a conductive gradient structure, the conductive material is carbon black.

[0017] Further, in the method for preparing leather with a conductive gradient structure, the second dipping treatment comprises: pH adjustment, ultrasonic treatment, and rotation;

[0018] The adjusted pH is 5.5-7;

[0019] The ultrasonic treatment time is 15 min;

[0020] The rotation time is 2-6 h.

[0021] Further, in the preparation method of the leather with the conductive gradient structure, the polymer monomer is pyrrole, and the oxidizing agent is ferric chloride.

[0022] Further, in the preparation method of the leather with the conductive gradient structure, the third dipping treatment comprises rotating.

[0023] The rotating time is 1-2 hours.

[0024] In a second aspect, the application further provides the leather with the conductive gradient structure prepared by the preparation method of the leather with the conductive gradient structure.

[0025] Further, in the SEM diagram of the cross section of the leather with the conductive gradient structure, the hydrotalcite has a hexagonal lamellar structure, the carbon black has a spherical structure, and the poly-pyrrole wraps the fibers, which indicates that the conductive material enters the leather and stably exists on the collagen fibers.

[0026] In a third aspect, the application provides the leather with the conductive gradient structure for preparing electromagnetic shielding materials.

[0027] Further, the electromagnetic shielding efficiency of the leather with the conductive gradient structure is 45 dB, and the electromagnetic shielding performance of the leather with the conductive gradient structure is mainly absorption loss, which effectively avoids reflection loss of high-conductive materials and is more conducive to reducing electromagnetic pollution.

[0028] Compared with the prior art, the technical scheme provided by the application at least has the following beneficial effects or advantages:

[0029] The application makes the hydrotalcite penetrate into the leather by dipping, the hydroxyl and metal ions on the hydrotalcite are combined with the amino and carboxyl on the collagen protein of the leather through chemical bonds, the dielectric property of the leather is improved, the collagen fiber structure of the leather is moderately relaxed, and favorable conditions are created for deep penetration of the carbon black and pyrrole monomers. In addition, the obtained hydrotalcite dielectric leather has more active sites on the fibers than the acid skin, can be electrostatically adsorbed and chemically combined with the modified carbon black, and is convenient for constructing a continuous conductive network inside. Finally, the pyrrole penetrates into the inside and polymerizes in situ on the fibers, can fill the defects of the nano-conductive material, the poly-pyrrole uniformly covers the collagen fibers, and effectively enhances the conductivity.

[0030] The poly-pyrrole / carbon black / hydrotalcite conductive leather prepared in the application constructs a conductive gradient structure of high-conductive (conductive polymer layer)-well-conductive (conductive nanomaterial layer)-dielectric (absorbing material layer) in the inside of leather fibers, can effectively reduce the surface resistance of leather, form a good impedance match with air, and make electromagnetic waves fully incident to the inside of leather for loss. The gradient structure can make leather obtain good electromagnetic shielding efficiency while reducing reflection loss and increasing absorption loss, thereby solving the problem that the reflection loss of high-conductive electromagnetic shielding materials is higher than the absorption loss.

[0031] The poly-pyrrole / carbon black / hydrotalcite conductive leather prepared in the application has a continuous and stable three-dimensional conductive network in the inside, can increase the transmission path of electromagnetic waves in the inside of leather, make electromagnetic energy further dissipate in the form of heat energy, and effectively avoid electromagnetic wave transmission. The method is simple to operate, does not need expensive equipment, and has low production cost, and can be used for large-scale production. Therefore, the application provides a simple and smart leather preparation method, and has important significance for the reform and development of traditional leather industry. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The figure is a cross-sectional optical photograph and SEM image of poly-pyrrole / carbon black / hydrotalcite conductive leather, carbon black / hydrotalcite conductive leather, hydrotalcite dielectric leather and acid skin with a conductive gradient structure. A is a cross-sectional image of acid skin; B is a cross-sectional SEM image of acid skin under a scale of 5 μm; C is a cross-sectional SEM image of acid skin under a scale of 100 nm; D is a cross-sectional image of hydrotalcite dielectric leather; E is a cross-sectional SEM image of hydrotalcite dielectric leather under a scale of 2 μm; F is a cross-sectional SEM image of hydrotalcite dielectric leather under a scale of 500 nm; G is a cross-sectional image of carbon black / hydrotalcite conductive leather; H is a cross-sectional SEM image of carbon black / hydrotalcite conductive leather under a scale of 5 μm; I is a cross-sectional SEM image of carbon black / hydrotalcite conductive leather under a scale of 1 μm; J is a cross-sectional image of poly-pyrrole / carbon black / hydrotalcite conductive leather; K is a cross-sectional SEM image of poly-pyrrole / carbon black / hydrotalcite conductive leather under a scale of 2 μm; L is a cross-sectional SEM image of poly-pyrrole / carbon black / hydrotalcite conductive leather under a scale of 200 nm; SP is acid skin; LDHs-L is hydrotalcite dielectric leather; CB / LDHs-L is carbon black / hydrotalcite conductive leather; PPy / CB / LDHs-L is poly-pyrrole / carbon black / hydrotalcite conductive leather.

[0033] Figure 2 The figure is a shrinkage temperature diagram of poly-pyrrole / carbon black / hydrotalcite conductive leather, carbon black / hydrotalcite conductive leather, hydrotalcite dielectric leather and acid skin with a conductive gradient structure.

[0034] Figure 3 The figure is an electromagnetic shielding efficiency diagram of poly-pyrrole / carbon black / hydrotalcite conductive leather, carbon black / hydrotalcite conductive leather, hydrotalcite dielectric leather and acid skin with a conductive gradient structure.

[0035] Figure 4 Shielding factor diagrams of polypyrrole / carbon black / hydrotalcite conductive leather, carbon black / hydrotalcite conductive leather and hydrotalcite dielectric leather. DETAILED DESCRIPTION

[0036] Hereinafter, the technical solutions of the present application will be described in conjunction with examples, but the present application is not limited to the following examples. The experimental methods and detection methods described in each example are all conventional methods unless otherwise specified; and the reagents and materials described are all commercially available unless otherwise specified.

[0037] Example 1

[0038] The present embodiment provides a preparation method of electromagnetic shielding leather with a conductive gradient structure.

[0039] 1. Preparation of hydrotalcite dielectric leather

[0040] Put 30 g of goat skin (naked skin) into a rotating drum, and then add 60 mL of water and 4.2 g of salt as a bath liquid in sequence. Use a small amount of 1 mol / L formic acid solution to adjust the pH of the bath liquid in the rotating drum for multiple times until the pH of the bath liquid is 3. Rotate the rotating drum for 30 min, and the pickling treatment of the goat skin is completed to obtain a pickled skin. Then add 4.8 g of hydrotalcite into the rotating drum, rotate for 4 h, and then add 1 mol / L sodium bicarbonate solution to adjust the pH to 6. After standing for 24 h to make the hydrotalcite uniformly combined with the collagen fibers of the goat skin, hydrotalcite dielectric leather is obtained.

[0041] 2. Preparation of carbon black / hydrotalcite conductive leather

[0042] Put the hydrotalcite dielectric leather into a 1 mol / L conductive carbon black aqueous solution, and use 1 mol / L sodium bicarbonate solution to adjust the pH of the conductive carbon black aqueous solution to 7. After ultrasonic treatment for 15 min, rotate the rotating drum for 4 h to make the conductive carbon black combined with the collagen fibers through physical and mechanical action, and carbon black / hydrotalcite conductive leather is obtained.

[0043] 3. Preparation of polypyrrole / carbon black / hydrotalcite conductive leather

[0044] At 5℃, disperse 1 mol / L pyrrole monomer in a mixed solution of 20 mL of ethanol and 20 mL of water to obtain a mixed solution. Put the carbon black / hydrotalcite conductive leather into the mixed solution, and rotate the rotating drum vigorously for 2 h. Then add 1 mol / L ferric chloride solution, and slowly rotate the rotating drum for 6 h to obtain polypyrrole / carbon black / hydrotalcite conductive leather.

[0045] Figure 1Cross-sectional optical photographs and SEM images of polypyrrole / carbon black / hydrotalcite conductive leather (PPy / CB / LDHs-L), carbon black / hydrotalcite conductive leather (CB / LDHs-L), hydrotalcite dielectric leather (LDHs-L), and acid leather (SP) with conductive gradient structure prepared in this embodiment. It can be seen intuitively from the cross-sectional optical photographs that the acid leather cross section is yellow-white ( Figure 1 A), the cross section of the hydrotalcite dielectric leather is uniform orange-yellow ( Figure 1 D), the cross section of carbon black / hydrotalcite conductive leather is black ( Figure 1 G in the figure), the black color of the cross section of the polypyrrole / carbon black / hydrotalcite conductive leather is further deepened ( Figure 1 The above phenomenon shows that the conductive materials such as hydrotalcite, carbon black and polypyrrole evenly enter the leather collagen fibers and modify the leather collagen fibers. The SEM images of the cross section at different scales further confirm this conclusion. The collagen fibers in the SEM image of the acid leather cross section are closely arranged ( Figure 1 B and C in the figure); SEM images of the cross section of the hydrotalcite dielectric leather show the presence of hexagonal lamellar hydrotalcite on the leather collagen fibers ( Figure 1 E and F in the figure); The SEM image of the cross section of the carbon black / hydrotalcite conductive leather shows both hexagonal lamellar structure of hydrotalcite and spherical structure of carbon black ( Figure 1 H and I in the figure); the SEM image of the cross section of the polypyrrole / carbon black / hydrotalcite conductive leather includes hexagonal layer structure of hydrotalcite, spherical structure of carbon black and fiber-wrapped polypyrrole ( Figure 1 K and L in the leather), which indicates that the conductive material enters the leather and exists stably on the collagen fibers.

[0046] Figure 2 This graph shows the shrinkage temperatures of the conductive leathers with a conductive gradient structure (polypyrrole / carbon black / hydrotalcite), carbon black / hydrotalcite, hydrotalcite dielectric, and acid leather, all produced in this example. The graph shows that the hydrotalcite dielectric leather has the highest shrinkage temperature, reaching 85°C. While the shrinkage temperature decreases with repeated loading of the conductive material, the final shrinkage temperature of the polypyrrole / carbon black / hydrotalcite conductive leather reaches 77°C, significantly higher than that of the acid leather. This demonstrates that the conductive leather produced using this method exhibits excellent resistance to moisture and heat.

[0047] Figure 3The electromagnetic shielding efficiency diagram of the poly-pyrrole / carbon black / hydrotalcite conductive leather, carbon black / hydrotalcite conductive leather and hydrotalcite dielectric leather prepared in the embodiment is shown in the figure. It can be seen from the figure that the combination of collagen fibers and hydrotalcite, carbon black and poly-pyrrole can effectively improve the electromagnetic shielding performance of the leather, and the electromagnetic shielding performance of the poly-pyrrole / carbon black / hydrotalcite conductive leather is obviously improved with the complete construction of the conductive gradient, and can reach 45 dB.

[0048] Figure 4 The shielding coefficient diagram of the poly-pyrrole / carbon black / hydrotalcite conductive leather, carbon black / hydrotalcite conductive leather and hydrotalcite dielectric leather prepared in the embodiment is shown in the figure. It can be seen from the figure that the conductive gradient structure of high conductivity (conductive polymer layer, poly-pyrrole layer)-good conductivity (conductive nanomaterial layer, carbon black layer)-dielectric (absorbing material layer, hydrotalcite layer) makes the absorption coefficient in the electromagnetic shielding process greater than the reflection coefficient, which indicates that the electromagnetic shielding performance of the poly-pyrrole / carbon black / hydrotalcite leather is mainly dominated by absorption loss, effectively avoiding the reflection loss of high-conductive materials, and more conducive to reducing electromagnetic pollution.

[0049] Table 1 Comparison of surface resistances of acid leather, hydrotalcite dielectric leather, carbon black / hydrotalcite conductive leather and poly-pyrrole / carbon black / hydrotalcite conductive leather

[0050]

[0051] The surface of the leather material is divided into grain side and flesh side. The grain side has a tight fiber structure and a smooth surface. The flesh side is the reverse side of the leather, and the fiber bundles are loose and rough. There are also different fiber structures inside the leather. The fiber in the nipple layer is fine and loose, and the collagen fiber bundle in the network layer is thick, so the fiber pores are also of different sizes. In order to build a conductive gradient on the leather, it is necessary to ensure that the size of the conductive material can penetrate into different fiber structures and be uniformly combined with the fibers. As can be seen from Table 1, the combination of conductive materials and collagen fibers can effectively reduce the resistance of the leather, and the resistance of the flesh side and the grain side of the conductive leather prepared in the embodiment is not much different, while the resistance of the flesh side and the grain side of the carbon black / hydrotalcite leather obtained by filtering conductive carbon black on the leather flesh side is greatly different. The conclusion can be drawn that the preparation method of the present application learns from the leather tanning method, adjusts the pH to make the conductive material and the collagen fiber have different electrical properties by using the isoelectric point of the collagen fiber, and makes the conductive material enter the tightly woven leather fiber and combine with it through physical and mechanical action and electrostatic action. That is, the present application can make the conductive materials such as hydrotalcite, carbon black and poly-pyrrole uniformly enter the inside of the leather collagen fiber, build a continuous conductive network in the leather, and make the whole leather have stable conductivity.

[0052] Example 2

[0053] The embodiment provides a preparation method of electromagnetic shielding leather with a conductive gradient structure.

[0054] 1. Preparation of hydrotalcite dielectric leather

[0055] 15 g of goat skin is put into a rotating drum, and then 30 mL of water and 2.1 g of salt are sequentially added as a bath solution. A 1 mol / L formic acid solution is used to adjust the pH of the bath solution in the rotating drum in small amounts for multiple times until the pH of the bath solution is 2.5. The rotating drum is rotated for 30 min, and the immersion acid treatment of the goat skin is completed. Then, 2.4 g of hydrotalcite is added into the rotating drum, 1 mol / L sodium bicarbonate solution is added to adjust the pH to 5.5 after the rotating drum is rotated for 2 h, and the hydrotalcite is uniformly combined with collagen fibers of the goat skin after being placed for 24 h, so that hydrotalcite dielectric leather is obtained.

[0056] 2. Preparation of carbon black / hydrotalcite conductive leather

[0057] The hydrotalcite dielectric leather is placed in a 0.5 mol / L conductive carbon black aqueous solution, and the pH of the conductive carbon black aqueous solution is adjusted to 6 by using a 1 mol / L sodium bicarbonate solution. After being ultrasonically treated for 15 min, the rotating drum is rotated for 3 h, so that the conductive carbon black is combined with the collagen fibers through physical and mechanical actions, and carbon black / hydrotalcite conductive leather is obtained.

[0058] 3. Preparation of polypyrrole / carbon black / hydrotalcite conductive leather

[0059] In a 15℃ environment, 0.5 mol / L of pyrrole monomers are dispersed in a mixed solution of 15 mL of ethanol and 15 mL of water, so that a mixed solution is obtained. The carbon black / hydrotalcite conductive leather is placed in the mixed solution, and the rotating drum is rotated vigorously for 2 h. A 1 mol / L ferric chloride solution is added, and the rotating drum is slowly rotated for 3 h, so that polypyrrole / carbon black / hydrotalcite conductive leather is obtained.

[0060] Example 3

[0061] The embodiment provides a preparation method of electromagnetic shielding leather with a conductive gradient structure.

[0062] 1. Preparation of hydrotalcite dielectric leather

[0063] 20 g of goat skin is put into a rotating drum, and then 40 mL of water and 2.8 g of salt are sequentially added as a bath solution. A 1 mol / L formic acid solution is used to adjust the pH of the bath solution in the rotating drum in small amounts for multiple times until the pH of the bath solution is 3. The rotating drum is rotated for 30 min, and the immersion acid treatment of the goat skin is completed. Then, 2.8 g of hydrotalcite is added into the rotating drum, 1 mol / L sodium bicarbonate solution is added to adjust the pH to 6 after the rotating drum is rotated for 2 h, and the hydrotalcite is uniformly combined with collagen fibers of the goat skin after being placed for 24 h, so that hydrotalcite dielectric leather is obtained.

[0064] 2. Preparation of carbon black / hydrotalcite conductive leather

[0065] The hydrotalcite dielectric leather was placed in a 1 mol / L conductive carbon black aqueous solution, and a 1 mol / L sodium bicarbonate solution was used to adjust the pH of the conductive carbon black aqueous solution to 7. After ultrasonic treatment for 15 min, the drum was rotated for 4 h, and the conductive carbon black was combined with the collagen fibers through physical and mechanical action to obtain the carbon black / hydrotalcite conductive leather.

[0066] 3. Preparation of polypyrrole / carbon black / hydrotalcite conductive leather

[0067] The carbon black / hydrotalcite conductive leather was placed in the mixed solution, and the drum was rotated vigorously for 2 h. A 0.5 mol / L ferric chloride solution was added, and the drum was slowly rotated for 3 h to obtain the polypyrrole / carbon black / hydrotalcite conductive leather.

[0068] Example 4

[0069] The present example provides a preparation method of electromagnetic shielding leather with a conductive gradient structure.

[0070] 1. Preparation of hydrotalcite dielectric leather

[0071] The 15 g of goat skin was placed in a drum, and 30 mL of water and 2.1 g of salt were sequentially added as a bath solution. A 1 mol / L formic acid solution was used to adjust the pH of the bath solution in small amounts and multiple times until the pH of the bath solution was 3.5. The drum was rotated for 30 min, and the acid pickling treatment of the goat skin was completed. Then, 2.4 g of hydrotalcite was added to the drum, and the drum was rotated for 4 h. A 1 mol / L baking soda solution was added to adjust the pH to 6, and the hydrotalcite was uniformly combined with the collagen fibers of the goat skin after standing for 24 h to obtain the hydrotalcite dielectric leather.

[0072] 2. Preparation of carbon black / hydrotalcite conductive leather

[0073] The hydrotalcite dielectric leather was placed in a 0.5 mol / L conductive carbon black aqueous solution, and a 1 mol / L sodium bicarbonate solution was used to adjust the pH of the conductive carbon black aqueous solution to 6. After ultrasonic treatment for 15 min, the drum was rotated for 4 h, and the conductive carbon black was combined with the collagen fibers through physical and mechanical action to obtain the carbon black / hydrotalcite conductive leather.

[0074] 3. Preparation of polypyrrole / carbon black / hydrotalcite conductive leather

[0075] The 1 mol / L pyrrole monomer was dispersed in a mixed solution of 15 mL ethanol and 15 mL water at 5°C to obtain a mixed solution. The carbon black / hydrotalcite conductive leather was placed in the mixed solution, and the rotating drum was rotated rapidly for 2 h. Then, 1 mol / L ferric chloride solution was added, and the rotating drum was rotated slowly for 6 h to obtain a polypyrrole / carbon black / hydrotalcite conductive leather.

[0076] The above-described embodiments are part of the embodiments of the present application, but not all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the application. All other embodiments obtained by persons of ordinary skill in the art based on the relevant deductions and substitutions made under the concept of the present application, without making creative efforts, fall within the scope of the present application.

Claims

1. A method for preparing a leather having a conductive gradient structure, characterized by, The application relates to a preparation method of a leather with a conductive gradient structure. The dielectric material with wave-absorbing performance is hydrotalcite, the conductive material is carbon black, the polymer monomer is pyrrole, and the oxidant is ferric chloride. The pretreatment is acid immersion treatment. The bath solution pH in the acid immersion treatment is 2.5-3.

5. The first dipping treatment comprises rotation, pH adjustment and standing; the adjusted pH is 4-6, the rotation time is 2-4 hours, and the standing time is 6-24 hours. The second dipping treatment comprises pH adjustment, ultrasonic treatment and rotation; the adjusted pH is 5.5-7, the ultrasonic treatment time is 15 minutes, and the rotation time is 2-6 hours. The third dipping treatment comprises rotation; the rotation time is 1-2 hours.

2. The leather with a conductive gradient structure prepared by the preparation method of the leather with a conductive gradient structure in claim 1.

3. The leather with a conductive gradient structure in claim 2 is applied to preparation of electromagnetic shielding materials. ​

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