Water-based sericin-graphene ink, graphene modified rubber and preparation method of water-based sericin-graphene ink

Abstract

The invention provides a preparation method of graphene modified rubber. The method comprises the following steps: dissolving sericin powder in deionized water to prepare a uniform solution (A); the preparation method comprises the following steps: adding a sericin solution (A), graphite powder and zirconium oxide ball-milled beads into a ball-milling tank, then putting the ball-milling tank into a planetary ball mill, carrying out ball-milling stripping to obtain aqueous sericin / graphene ink (B), adding the ink (B) and a vulcanizing agent into rubber emulsion while stirring, carrying out ultrasonic treatment to obtain a mixture (C), and carrying out vacuum drying to obtain the aqueous sericin / graphene ink. And drying the mixture (C) to constant weight, and carrying out hot press molding to obtain the graphene modified rubber (D). According to the present invention, the expensive graphene or the graphene derivative is not required to be adopted as the raw material, and the sericin-assisted ball milling method is adopted to peel the graphite into the high-quality graphene during the liquid phase processing process, such that the tedious modification process of the graphene is avoided, the peeling and the modification of the graphene are organically combined so as to achieve the integrated preparation of the graphene modified rubber;

Description

Technical Field

[0001] The present invention relates to water-based sericin-graphene ink, graphene-modified rubber prepared therefrom, and methods for preparing the same. More specifically, the invention relates to a method for preparing graphene-modified rubber and the prepared graphene-modified rubber, and in particular to a method for preparing sericin-assisted graphene exfoliation, a method for preparing graphene-modified carboxylated styrene-butadiene rubber, and the resulting graphene-modified carboxylated styrene-butadiene rubber. These inventions belong to the field of rubber compositions. Background Art

[0002] Multifunctional flexible wearable sensing materials can respond to a variety of stimuli such as strain, pressure, and temperature, and have received widespread attention in the fields of personal health monitoring, human motion monitoring, and electronic skin. At present, sensors based on metal and semiconductor materials are widely used in the commercial field, but their high hardness, poor ductility, and low sensitivity have become bottlenecks in their application in wearable electronic devices. In order to meet the application needs of sensors in the field of wearable electronics, people are committed to combining conductive nanomaterials such as graphene, carbon nanotubes, and precious metals with rubber to prepare sensing films with better sensing performance. Graphene is a two-dimensional nanomaterial composed of tightly stacked carbon atoms with many excellent properties, such as an ultra-large specific surface area (2630m 2 / g), ultra-high Young's modulus (1TPa) and fracture strength (130GPa), ultra-large carrier mobility (200,000cm 2 / (V·s)) and ultra-high thermal conductivity (5300W / (m·K)). Therefore, adding graphene as a functional filler to traditional rubber is expected to significantly improve its thermal conductivity, electrical conductivity, electromagnetic shielding, and UV aging resistance while maintaining its strength and toughness, thereby preparing multifunctional flexible sensors with excellent performance.

[0003] Complete exfoliation of graphene and its good dispersion in the matrix are key factors for the effective formation of percolation networks at low filler loadings, thus posing challenges to the high-quality, scalable preparation and high-performance applications of graphene. In recent years, solution-based preparation processes based on functional inks have provided a simple, economical, efficient, and reliable solution for the large-scale and customized production of advanced multifunctional devices. Graphene is widely used in conductive inks to fabricate high-performance flexible electronic devices due to its excellent conductivity, good mechanical flexibility, high stability, and low cost. However, the strong van der Waals forces and π–π interactions between graphene sheets often make alternating dispersions unstable and prone to aggregation. Furthermore, achieving uniform dispersion in rubber is difficult, which compromises the mechanical properties of the composites. Furthermore, conventional processes often separate the exfoliation of graphene from the preparation of conductive inks, and the redispersion of graphene is difficult and costly, making them unsuitable for large-scale production and application. In comparison, the liquid phase exfoliation method can flexibly achieve low-cost, high-throughput production and good dispersion of graphene, and adjust the rheological and physical properties of the conductive ink as needed. However, there are still problems such as low yield, low exfoliation concentration, and long processing time. It usually requires cumbersome and time-consuming post-processing processes (including repeated exfoliation, centrifugation, redispersion, evaporation concentration, etc.) to increase the concentration of the conductive ink, which greatly limits its large-scale application.

[0004] Related products in the existing technology face the following challenges: First, the low-cost, scalable production of graphene-based functional inks is difficult. Traditionally, to improve the stability of graphene-based functional inks, the preparation process typically involves three steps: a) exfoliating bulk graphite to obtain graphene flakes of appropriate particle size; b) using a surfactant to disperse the graphene flakes in a suitable solvent to obtain a uniform and stable graphene dispersion; and c) adding various additives to adjust the ink's physical properties. However, this process decouples the exfoliation of graphene from the preparation of the conductive ink, and redispersing the graphene is difficult and costly, making it unsuitable for large-scale production and application. Second, graphene exhibits uneven dispersion in the rubber matrix and is prone to agglomeration. To promote good dispersion of graphene in the rubber matrix and enhance interfacial interaction between the graphene and the matrix, existing methods commonly employ chemical modification methods such as oxidation, plasma treatment, and polymer grafting to modify the graphene surface before compounding with the rubber. However, such surface modification significantly reduces the functionality of the graphene, compromising the effectiveness of the graphene-modified rubber. In addition, the existing surface chemical modification methods generally have the problems of cumbersome process, poor operability, high cost, no environmental protection, etc., which cannot meet the large-scale production demand of graphene-modified rubber. On the other hand, poor compatibility and poor interface interaction between graphene and rubber matrix can not give full play to the function of graphene and matrix to improve composite material comprehensive performance. Due to the low quality and poor dispersibility of the graphene peeled off, to obtain the desired graphene-modified rubber performance, higher graphene mass fraction is usually required, which not only increases cost, but also makes the inherent performance of rubber itself decline, such as mechanical strength, fracture toughness, processing properties, etc., thereby affecting the comprehensive performance of composite material.

[0005] Therefore, a simpler and more efficient method is needed to prepare highly exfoliated and stably dispersed graphene-modified rubber, especially a scalable production method that combines graphene exfoliation, interface modification, and compounding to achieve high-performance, green, and economically feasible graphene-modified rubber. Summary of the Invention

[0006] To address the above issues, the present invention provides a method for preparing graphene-modified rubber that is easily scalable and cost-effective. Specifically, a high-concentration, high-performance aqueous graphene / sericin (SG) ink is obtained by ball milling with sericin-assisted exfoliation, and then blended with rubber latex to obtain the graphene-modified rubber.

[0007] This invention effectively combines high-quality exfoliation and interface modification of flake graphite with the preparation of high-performance graphene-modified rubber, providing a method for preparing graphene-modified rubber that is easily scalable, low-cost, and high-yield. In this system, the invention utilizes a sericin solution, leveraging the amphiphilic nature of sericin molecules, the non-covalent interaction between sericin and graphene, and the appropriate viscosity of the sericin solution to promote graphene exfoliation and stable dispersion, resulting in a high-yield, ultra-high-concentration aqueous graphene / sericin ink. This ink is then blended with a rubber latex and hot-pressed to achieve efficient preparation of the graphene-modified rubber material. This invention features a short process flow, simple operation, and is environmentally friendly and economical, enabling the low-cost, scalable preparation of graphene-modified rubber.

[0008] The present invention aims to solve the problems existing in the prior art in the preparation of graphene-modified rubber, such as difficulty in dispersing graphene, complicated graphene modification process, high cost, and difficulty in industrial application. The present invention combines the high-quality and high-yield production of graphene with the preparation process of high-performance rubber materials to obtain a graphene-modified rubber composite material with better overall performance.

[0009] To achieve the above objectives, the sericin introduced in the present invention has a molecular structure that combines both hydrophilic and hydrophobic moieties, acting like a surfactant in aqueous solution, reducing the surface energy of water. Furthermore, the sericin interacts with graphene through certain π-π and hydrophobic interactions, reducing the exfoliation energy of the graphite. Furthermore, the viscous sericin solution constrains the movement of zirconia milling beads, absorbing normal impact forces and increasing shear forces, acting like a "liquid tape," thereby achieving high-quality exfoliation, stable dispersion, and surface modification of the graphene. This further promotes uniform dispersion of the graphene in the rubber matrix and forms a strong hydrogen-bonded crosslinked network with the matrix, effectively improving the modulus, toughness, electrical conductivity, and thermal conductivity of the graphene-modified rubber. This invention streamlines the production process of graphene-modified rubber, reduces production costs, and has the potential to achieve industrialized production.

[0010] According to a first embodiment of the present invention, there is provided a method for preparing a graphene-modified rubber, the method comprising:

[0011] (1) Dissolving sericin powder in deionized water to prepare a uniform solution (A);

[0012] (2) ball milling the sericin solution (A), graphite powder, and ball milling beads to obtain a water-based sericin / graphene ink (B);

[0013] (3) adding ink (B) and (rubber) vulcanizing agent to rubber latex while stirring, and then ultrasonically treating to obtain a mixture (C);

[0014] (4) The mixture (C) is dried to a constant weight and hot-pressed to obtain a graphene-modified rubber (D).

[0015] Preferably, in step (1), the concentration of sericin in the sericin solution (A) is 0.1-400 mg / ml, 0.5-395 mg / ml, preferably 1-393 mg / ml, preferably 5-391 mg / ml, preferably 10-390 mg / ml, more preferably 20-380 mg / ml, more preferably 30-370 mg / ml, more preferably 40-360 mg / ml, more preferably 50-350 mg / ml, more preferably 60-340 mg / ml, more preferably 70-330 mg / ml, more preferably 80-320 mg / ml. 200 mg / mL.

[0016] Preferably, in step (2), the fineness (or particle size) of the graphite powder is 0.1-500 μm, preferably 0.15-400 μm, preferably 0.2-300 μm, preferably 0.25-200 μm, preferably 0.3-200 μm, preferably 0.35-100 μm, preferably 0.4-50 μm, preferably 0.45-40 μm, preferably 0.5-30 μm, preferably 0.55-20 μm, preferably 0.6-18 μm, more preferably 1-15 μm, more preferably 1.5-10 μm, more preferably 2-6 μm, most preferably 3-5 μm.

[0017] Preferably, step (2) is performed as follows: adding the sericin solution (A), graphite powder and ball milling beads into a ball milling jar, then placing the ball milling jar into a planetary ball mill for ball milling and exfoliation to obtain a water-based sericin / graphene ink (B).

[0018] Preferably, the rubber emulsion in step (3) is one or more selected from styrene-butadiene rubber emulsion, chloroprene rubber emulsion, nitrile rubber emulsion, natural rubber emulsion, vinyl acetate emulsion, and ethylene-vinyl acetate copolymer (EVA) emulsion.

[0019] Preferably, the (rubber) vulcanizing agent in step (3) is an organic peroxide (e.g. dicumyl peroxide, DCP) or a sulfur-containing vulcanizing agent (e.g. sulfur, carbon disulfide, diethyl thioacetate, dimethyl disulfide or diethyl sulfide, etc.).

[0020] Preferably, the ball milling beads are zirconia ball milling beads.

[0021] Preferably, in step (2), the mass ratio of the solid component (i.e., sericin) in the sericin solution to the graphite powder is (0.01-10):1, preferably (0.05-9):1, preferably (0.1-8):1, preferably (0.2-7):1, preferably (0.3-6):1, preferably (0.4-5):1, preferably (0.5-4):1, preferably (0.6-3):1, preferably (0.7-2.5):1, preferably (0.8-2):1, preferably (0.9-1.5):1, and most preferably (1-1.2):1. Therefore, in the aqueous sericin / graphene ink (B) obtained in step (2), the mass ratio of sericin to graphite powder is (0.01-10):1, preferably (0.05-9):1, preferably (0.1-8):1, preferably (0.2-7):1, preferably (0.3-6):1, preferably (0.4-5):1, preferably (0.5-4):1, preferably (0.6-3):1, preferably (0.7-2.5):1, preferably (0.8-2):1, preferably (0.9-1.5):1, and most preferably (1-1.2):1.

[0022] Preferably, in step (2), the amount of graphite powder relative to the sericin solution should be such that the concentration of graphene in the resulting aqueous sericin / graphene ink (B) is 0.1-400 mg / ml, 0.5-396 mg / ml, preferably 1-394 mg / ml, preferably 1.5-392 mg / ml, preferably 2-390 mg / ml, preferably 10-385 mg / ml, more preferably 20-380 mg / ml, more preferably 30-370 mg / ml, more preferably 40-360 mg / ml, more preferably 50-350 mg / ml, more preferably 60-340 mg / ml, more preferably 70-330 mg / ml, more preferably 80-320 mg / ml, more preferably 90-310 mg / ml, more preferably 100-300 mg / ml, more preferably 110-290 mg / ml, more preferably 120-280 mg / ml, more preferably 130-270 mg / ml, more preferably 140-260 mg / ml, more preferably 150-250 mg / ml, more preferably 160-240 mg / ml, more preferably 170-230 mg / ml, more preferably 180-220 mg / ml, more preferably 190-210 mg / ml, most preferably 200 mg / mL. For example, 0.01-400 mg / ml, preferably 0.05-360 mg / ml, preferably 0.1-340 mg / ml, preferably 0.5-320 mg / ml, preferably 1-300 mg / ml, preferably 1.5-280 mg / ml, preferably 2.0-260 mg / ml.

[0023] Preferably, in step (3), the amount of aqueous sericin / graphene ink (B) relative to the rubber emulsion should be such that in the resulting graphene / modified rubber (D), the mass percentage or weight percentage of graphene is 0.05-25 wt%, preferably 0.1-22 wt%, preferably 0.15-20 wt%, preferably 0.20-18 wt%, preferably 0.25-16 wt%, preferably 0.30-15 wt%, preferably 0.35-12 wt%, preferably 0.40-10 wt%, preferably 0.60-8 wt%, preferably 0.80-7 wt%, preferably 0.90-6 wt%, preferably 1-5 wt%, preferably 1.5-4.5 wt%, preferably 2-4 wt%, preferably 2.5-3.5 wt%, such as 3 wt%, based on the total weight of the modified rubber (D).

[0024] Preferably, the solid content of the rubber emulsion is 10-60wt%, preferably 15-58wt%, preferably 20-56wt%, preferably 25-55wt%, preferably 30-53wt%, preferably 35-52wt%, preferably 40-50wt%, preferably 42-48wt%, preferably 43-45wt%, for example 12, 18, 22, 28, 32, 38, 44wt%.

[0025] Preferably, in step (2), the mass ratio of the ball milling beads (preferably, zirconia beads or zirconia ball milling beads) to the graphite powder is (5-40):1, preferably (7-35):1, preferably (10-30):1, more preferably (15-25):1, preferably (18-20):1.

[0026] Preferably, the diameter of the ball milling beads (preferably, zirconia beads or zirconia ball milling beads) in step (2) is 0.5-3 mm, preferably 0.6-2.7 mm, preferably 0.7-2.5 mm, preferably 0.8-2.2 mm, preferably 1-2 mm, for example 1.2, 1.5, 1.8 mm.

[0027] Preferably, in step (2), the sericin solution (A), graphite powder and ball milling beads are added to a ball milling jar, and then the ball milling jar is placed in a planetary ball mill. Ball milling and exfoliation are performed at a set speed of the planetary ball mill to obtain a water-based sericin / graphene ink (B). The set speed is in the range of 20 to 1000 rpm, preferably 40 to 900 rpm, more preferably 50 to 800 rpm, more preferably 70 to 700 rpm, more preferably 100 to 750 rpm, more preferably 150 to 700 rpm, more preferably 180 to 650 rpm, more preferably 200 to 600 rpm, more preferably 250 to 550 rpm, more preferably 300 to 500 rpm, more preferably 350 to 450 rpm, such as 400 rpm.

[0028] Preferably, the ball milling stripping time in step (2) is 0.5 to 72 hours, preferably 1 to 65 hours, preferably 5 to 60 hours, preferably 7 to 55 hours, preferably 10 to 50 hours, preferably 12 to 45 hours, preferably 15 to 40 hours, preferably 18 to 35 hours, preferably 20 to 30 hours, preferably 22 to 26 hours, such as 24 hours.

[0029] Preferably, the speed of mechanical stirring in step (3) is 20 to 2000 rpm, preferably 50 to 1500 rpm, preferably 100 to 1200 rpm, preferably 200 to 1000 rpm, preferably 400 to 900 rpm, preferably 500 to 800 rpm, preferably 550 to 750 rpm, preferably 600 to 700 rpm.

[0030] Preferably, the stirring time in step (3) is 0.5-120 min, preferably 1-100 min, preferably 5-90 min, preferably 7-70 min, preferably 10-60 min, preferably 15-50 min, more preferably 20-40 min, such as 30 minutes.

[0031] Preferably, the time of ultrasonic treatment in step (3) is 0.5-120 min, preferably 1-100 min, preferably 5-90 min, preferably 7-70 min, preferably 10-60 min, preferably 15-50 min, more preferably 20-40 min, such as 30 or 35 minutes.

[0032] Preferably, the drying temperature in step (4) is 25-100°C, preferably 30-90°C, preferably 35-80°C, preferably 38-70°C, preferably 40-60°C, such as 50°C.

[0033] Preferably, the hot pressing temperature in step (4) is 100-400°C, preferably 110-350°C, preferably 120-300°C, preferably 130-250°C, more preferably 140-200°C, more preferably 150-180°C.

[0034] Preferably, the hot pressing time in step (4) is 0.5-100 min, preferably 1-90 min, preferably 1.5-70 min, preferably 2-60 min, preferably 3-50 min, preferably 4-40 min, preferably 5-30 min, preferably 6-20 min, more preferably 8-15 min, such as 10 or 12 minutes.

[0035] According to a second embodiment of the present invention, there is provided a graphene-modified rubber obtained by the above method, wherein the mass percentage of graphene, i.e. the mass fraction of graphene in the modified rubber D, is 0.05-25 wt %, preferably 0.1-22 wt %, preferably 0.15-20 wt %, preferably 0.20-18 wt %, preferably 0.25-15 wt %, preferably 0.30-12 wt %, preferably 0.35-10 wt %, preferably 0.40-9 wt %, for example 0.50, 0.60, 0.70, 0.80, 0.90, 1.0, 1.2, 1.5, 1.8, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8 or 8.5 wt %, based on the total weight of the modified rubber (D).

[0036] Preferably, the graphene-modified rubber is in the form of a film, sheet or plate. The tensile strength of the graphene-modified rubber (e.g., in the form of a film, sheet or plate) is 5-13 MPa, preferably 5.5-12.9 MPa, preferably 6-12.8 MPa, preferably 6.5-12.7 MPa, preferably 7-12.6 MPa, preferably 7.5-12.5 MPa, preferably 8-12.4 MPa, for example 9, 10, 11 MPa. The Young's modulus of the graphene-modified rubber (e.g., in the form of a film, sheet or plate) is 0.25-1.5 MPa, preferably 0.28-1.4 MPa, preferably 0.3-1.2 MPa, preferably 0.35-1.1 MPa, preferably 0.4-1.0 MPa, preferably 0.5-0.9 MPa, preferably 0.6-0.85 MPa, preferably 0.65-0.83 MPa, preferably 0.7-0.8 MPa, preferably 0.74-0.79 MPa.

[0037] According to a third embodiment of the present invention, the use of the graphene-modified rubber obtained by the above method is provided, which is used to reinforce modified rubber, to prepare polymer nanocomposites, to produce functional inks and coatings, and as a raw material for producing multifunctional flexible sensors suitable for electronic skin, human health monitoring and wearable electronics through hot pressing technology.

[0038] According to a fourth embodiment of the present invention, there is provided a sericin / graphene ink (B), which is prepared by a preparation method comprising the following steps:

[0039] (1) Dissolving sericin powder in deionized water to prepare a uniform solution (A);

[0040] (2) Adding sericin solution (A), graphite powder and zirconium oxide ball milling beads into a ball milling jar, and then placing the ball milling jar into a planetary ball mill for ball milling and exfoliation to obtain a water-based sericin / graphene ink (B).

[0041] According to a fourth embodiment of the present invention, there is provided a sericin / graphene ink (B), which is prepared by steps (1) and (2) in the above preparation method.

[0042] The preparation method of the present invention has the following advantages compared with the prior art:

[0043] By combining graphene exfoliation with the preparation of water-based sericin / graphene ink, the technical solution not only avoids the high cost of graphene or its derivatives, but also streamlines the process, greatly reducing the production cost of graphene-modified rubber and making the production process integrated and green.

[0044] Compared with the complex process of traditional graphene surface modification, this scheme adopts the method of sericin-assisted ball milling exfoliation to prepare water-based sericin / graphene ink, which introduces abundant hydrophilic groups. It can not only achieve efficient exfoliation of graphene and its stable dispersion in the matrix, but also induce the formation of hydrogen bond network between graphene and rubber matrix, enhance the interaction between graphene and rubber, and improve the comprehensive performance of modified rubber.

[0045] The preparation method proposed in this scheme is simple, efficient, green, environmentally friendly, low-cost, and has strong application potential. The polymer nanocomposite material obtained by this scheme has excellent comprehensive performance and a wide range of applications.

[0046] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0047] 1. The present invention does not require expensive graphene or graphene derivatives as raw materials, and can produce high-quality, high-yield and ultra-high-concentration graphene through a simple ball milling method;

[0048] 2. The present invention combines graphene exfoliation and modification, avoiding the complex graphene modification process. It also combines graphene exfoliation with the preparation of water-based sericin / graphene ink, achieving the integration of material production and application.

[0049] 3. The preparation method proposed in the present invention is simple, efficient, green, environmentally friendly, low-cost, and has important industrial application value.

[0050] 4. The graphene is evenly dispersed in the rubber composite obtained by the present invention, and has a strong interface interaction with the matrix. The comprehensive performance of the material is superior and the application range is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 (a) Transmission electron microscopy (TEM) image and (b) High-resolution transmission electron microscopy (HRTEM) image of the edge of the exfoliated graphene of Example 1 of the present invention.

[0052] Figure 2 1 is the X-ray diffraction (XRD) pattern of the graphite and SG ink of Example 1 of the present invention.

[0053] Figure 3 1 is a size distribution histogram and a fitting curve of the exfoliated graphene sheets of Example 1 of the present invention.

[0054] Figure 4 is the tensile strength of modified rubber with different graphene contents.

[0055] Figure 5 is the Young’s modulus of modified rubber with different graphene contents. DETAILED DESCRIPTION

[0056] The present invention further illustrates the technical solution in detail through the following examples, but the present invention is not limited to these examples.

[0057] All raw materials involved in the present invention can be purchased on the market, for example: high-purity graphite powder (Qingdao Tianheda Graphite Co., Ltd.) and sericin powder (Xi'an Ruierli Bioengineering Co., Ltd.).

[0058] Unless otherwise specified, the devices used in the examples are all commonly used in the art and commercially available.

[0059] The present invention provides a method for preparing graphene-modified rubber, which comprises the following steps:

[0060] (1) dissolving sericin powder in deionized water to prepare a homogeneous solution (A); preferably, the concentration of sericin in the sericin solution (A) is 0.01-400 mg / ml, preferably 0.1-350 mg / ml, more preferably 1-300 mg / ml, more preferably 5-250 mg / ml, more preferably 10-200 mg / ml, and most preferably 200 mg / mL;

[0061] (2) adding the sericin solution (A), graphite powder, and zirconium oxide ball milling beads into a ball milling jar, and then placing the ball milling jar into a planetary ball mill. After ball milling and exfoliation at a certain speed, a water-based sericin / graphene ink (B) is obtained;

[0062] (3) adding ink (B) and (rubber) vulcanizing agent to rubber latex while stirring, and then ultrasonically treating the mixture to obtain a mixture (C);

[0063] (4) The mixture (C) is dried to a constant weight and then hot-pressed to obtain graphene-modified rubber (D).

[0064] The above-mentioned preparation method of the present invention is particularly suitable for preparing graphene-modified carboxylated styrene-butadiene rubber. Therefore, the present invention provides a preparation method of graphene-modified carboxylated styrene-butadiene rubber, which comprises the following steps:

[0065] (1) dissolving sericin powder in deionized water to prepare a homogeneous solution (A); preferably, the concentration of sericin in the sericin solution (A) is 0.01-400 mg / ml, preferably 0.1-350 mg / ml, more preferably 1-300 mg / ml, more preferably 5-250 mg / ml, more preferably 10-200 mg / ml, and most preferably 200 mg / mL;

[0066] (2) adding the sericin solution (A), graphite powder, and zirconium oxide ball milling beads into a ball milling jar, and then placing the ball milling jar into a planetary ball mill. After ball milling and exfoliation at a certain speed, a water-based sericin / graphene ink (B) is obtained;

[0067] (3) adding the ink (B) and the vulcanizing agent to the carboxylated styrene-butadiene rubber latex while stirring, and then ultrasonically treating the mixture to obtain a mixture (C);

[0068] (4) The mixture (C) is dried to a constant weight and then hot-pressed to obtain graphene-modified rubber (D).

[0069] More specifically, the present invention provides a method for preparing graphene-modified carboxylated styrene-butadiene rubber, the method comprising the following steps:

[0070] (1) dissolving sericin powder in deionized water to prepare a homogeneous solution (A); preferably, the concentration of sericin in the sericin solution (A) is 0.01-400 mg / ml, preferably 0.1-350 mg / ml, more preferably 1-300 mg / ml, more preferably 5-250 mg / ml, more preferably 10-200 mg / ml, and most preferably 200 mg / mL;

[0071] (2) adding the sericin solution (A), graphite powder, and zirconium oxide ball milling beads into a ball milling jar, and then placing the ball milling jar into a planetary ball mill. After ball milling and exfoliation at a certain speed, a water-based sericin / graphene ink (B) is obtained;

[0072] (3) adding the ink (B) and the vulcanizing agent to the carboxylated styrene-butadiene rubber latex while stirring, and then ultrasonically treating the mixture to obtain a mixture (C);

[0073] (4) The mixture (C) is dried to a constant weight and then hot-pressed to obtain graphene-modified rubber (D).

[0074] In the present application, the rubber latex selected in step (3) is one or more selected from styrene-butadiene rubber latex, chloroprene rubber latex, nitrile rubber latex, natural rubber latex, vinyl acetate latex, and ethylene-vinyl acetate copolymer (EVA) latex;

[0075] In the present application, the (rubber) vulcanizing agent in step (3) is an organic peroxide (such as dicumyl peroxide, DCP) or a sulfur-containing vulcanizing agent (such as sulfur, carbon disulfide, diethyl thioacetate, dimethyl disulfide, diethyl sulfide, etc.).

[0076] Preferably, the fineness of the graphite powder used in step (2) is 1-20 μm, preferably 1-10 μm, more preferably 1-5 μm, and most preferably 3 μm.

[0077] Preferably, in step (2), the mass ratio of the solid component in the sericin solution to the graphite powder is (0.01-10):1, preferably (0.1-8); 1, preferably (0.2-6):1, preferably (0.4-4):1, preferably (0.8-2):1, and most preferably 1:1.

[0078] Preferably, in step (2), the mass ratio of the zirconia beads to the graphite powder is (5-40):1, preferably (10-30):1, more preferably (15-25):1, and the diameter ranges from 0.6-2.5 mm, preferably 0.6-2 mm, more preferably 0.6-1 mm. Preferably, the rotation speed ranges from 1 to 1000 rpm, preferably 10 to 800 rpm, more preferably 20 to 600 rpm; and preferably, the stripping time ranges from 0 to 72 hours, preferably 0 to 48 hours, more preferably 0 to 36 hours.

[0079] Preferably, in step (2), the amount of graphite powder relative to the sericin solution should be such that the concentration of graphene in the resulting aqueous sericin / graphene ink (B) is 0.01-400 mg / ml, preferably 0.05-360 mg / ml, preferably 0.1-340 mg / ml, preferably 0.5-320 mg / ml, preferably 1-300 mg / ml, preferably 1.5-280 mg / ml, preferably 2.0-260 mg / ml.

[0080] In step (3), the amount of aqueous sericin / graphene ink (B) relative to the rubber emulsion should be such that the mass percentage or weight percentage of graphene in the resulting graphene / modified rubber (D) is 0.05-25 wt%, preferably 0.1-20 wt%, preferably 0.15-15 wt%, preferably 0.20-13 wt%, preferably 0.25-12 wt%, preferably 0.30-10 wt%, preferably 0.35-9 wt%, preferably 0.40-8 wt%, based on the total weight of the modified rubber (D).

[0081] In the present invention, the mechanical stirring speed in step (3) is 1-2000 rpm, preferably 10-1000 rpm, more preferably 20-800 rpm, and the stirring time is 0-60 min, preferably 10-50 min, more preferably 20-40 min.

[0082] In the present invention, the ultrasonic time in step (3) is 0-60 min, preferably 0-50 min, more preferably 5-40 min;

[0083] In the present invention, the drying temperature in step (4) is in the range of 25-100°C, preferably in the range of 30-90°C, more preferably in the range of 40-60°C;

[0084] The hot pressing temperature in step (4) of the present invention is 100-400°C, preferably 110-350°C, more preferably 120-300°C, more preferably 130-250°C, more preferably 140-200°C.

[0085] In step (4), the amount of sericin-assisted exfoliated graphene relative to the rubber should be such that the mass percentage or weight percentage of graphene in the resulting graphene-modified rubber (e.g., carboxylated styrene-butadiene rubber) (i.e., the mass fraction or content of graphene in the modified composite rubber D) is 0.05-25 wt %, preferably 0.1-20 wt %, preferably 0.15-15 wt %, preferably 0.20-13 wt %, preferably 0.25-12 wt %, preferably 0.30-10 wt %, preferably 0.35-9 wt %, preferably 0.40-8 wt %, for example, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0, 1.2, 1.5, 1.8, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5 wt %, based on the total weight of the modified rubber (D).

[0086] More specifically, the present invention provides a method for preparing graphene-modified rubber (e.g., carboxylated styrene-butadiene rubber), characterized in that the specific steps are as follows:

[0087] (1) Dissolving sericin powder in deionized water to prepare a uniform solution (A);

[0088] (2) Adding sericin solution (A), graphite powder, and zirconium oxide ball milling beads into a ball milling jar, then placing the ball milling jar in a planetary ball mill, and ball milling and exfoliation at a certain speed to obtain a water-based sericin / graphene ink (B), wherein the graphene concentration is controlled to be 0.01-200 mg / mL;

[0089] (3) The ink (B) and the vulcanizing agent are added to the carboxylated styrene-butadiene rubber latex while stirring, and then ultrasonically treated to obtain a mixture (C); the mixture (C) is dried to a constant weight and then hot-pressed to obtain the graphene-modified rubber (D).

[0090] Preferably, the concentration of the sericin solution in step (1) is 200 mg / mL.

[0091] Preferably, the fineness of the graphite powder used in step (2) is 3 μm.

[0092] Preferably, the mass ratio of the solid component to the graphite powder in the sericin solution in step (2) is 1:1.

[0093] Preferably, in step (2), the mass ratio of the zirconium oxide beads to the graphite powder is 22:1, and the diameter ranges from 0.6 to 0.8 mm. Preferably, the rotation speed is ∼400 rpm; and preferably, the stripping time is ∼24 h.

[0094] Preferably, in step (2), the amount of graphite powder relative to the sericin solution should be such that the concentration of graphene in the resulting aqueous sericin / graphene ink (B) is 0.01-400 mg / ml, preferably 0.05-360 mg / ml, preferably 0.1-340 mg / ml, preferably 0.5-320 mg / ml, preferably 1-300 mg / ml, preferably 1.5-280 mg / ml, preferably 2.0-260 mg / ml.

[0095] Preferably, the rubber latex selected in step (3) is one or more selected from styrene-butadiene rubber latex, chloroprene rubber latex, nitrile rubber latex, natural rubber latex, vinyl acetate latex, and ethylene-vinyl acetate copolymer (EVA) latex;

[0096] Preferably, the vulcanizing agent in step (3) is one or more of dicumyl peroxide (DCP), sulfur, carbon disulfide, diethyl thioacetate, dimethyl disulfide, and diethyl sulfide.

[0097] Preferably, in step (3), the mechanical stirring speed is 1 to 2000 rpm, preferably 10 to 1000 rpm, more preferably 20 to 800 rpm, and the stirring time is 0 to 60 min, preferably 10 to 50 min, more preferably 20 to 40 min;

[0098] Preferably, the ultrasonic time in step (3) is 0-60 min, preferably 0-50 min, more preferably 5-40 min;

[0099] Preferably, the drying temperature in step (3) is in the range of 25-100°C, preferably 30-90°C, more preferably 40-60°C; and the hot pressing temperature is in the range of 140-200°C;

[0100] Preferably, the graphene content in the graphene / modified rubber (such as carboxylated styrene-butadiene rubber) obtained in step (3) is 0.40-8wt%.

[0101] In addition, the present invention also provides a graphene-modified rubber material obtained by the above method, wherein the mass percentage or weight percentage of the sericin-assisted exfoliated graphene (i.e., the mass fraction or content of graphene in the modified composite rubber D) is 0.05-25 wt %, preferably 0.1-20 wt %, preferably 0.15-15 wt %, preferably 0.20-13 wt %, preferably 0.25-12 wt %, preferably 0.30-10 wt %, preferably 0.35-9 wt %, preferably 0.40-8 wt %, for example, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0, 1.2, 1.5, 1.8, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5 wt %, based on the total weight of the modified rubber (D).

[0102] In addition, the present invention also provides a water-based sericin / graphene ink prepared by ball milling and exfoliation. The ink is prepared by a method comprising the following steps:

[0103] (1) Dissolving sericin powder in deionized water to prepare a uniform solution (A);

[0104] (2) Adding sericin solution (A), graphite powder and zirconium oxide ball milling beads into a ball milling jar, and then placing the ball milling jar into a planetary ball mill, and milling and peeling at a certain speed to obtain water-based sericin / graphene ink (B).

[0105] That is, the aqueous sericin / graphene ink (B) is prepared by the above-mentioned methods (1)-(2) according to the first embodiment.

[0106] The technical solution of the present invention can be directly used to reinforce rubber (such as rubber matrices such as carboxylated styrene-butadiene rubber emulsion or natural rubber emulsion), used for the preparation of polymer nanocomposites, and can also be directly used in the production of functional inks and coatings, or the products of this solution can be used as raw materials to produce multifunctional flexible sensors suitable for electronic skin, human health monitoring, wearable electronics and other fields.

[0107] In the present application, "high-purity graphite powder" refers to graphite powder with a purity higher than 98.5% or higher than 98.7%, preferably higher than 99%.

[0108] The raw materials in the following examples are:

[0109] High-purity graphite powder: Qingdao Tianheda Graphite Co., Ltd., purity 99wt%;

[0110] Sericin powder (SS): Xi'an Ruierli Bioengineering Co., Ltd., purity 98wt%

[0111] Carboxylated styrene-butadiene rubber (XSBR) emulsion: Two XSBR emulsions were used in a 1:1 mass ratio. The first emulsion had a 50% solids content, including 3% carboxyl-functional monomer, 35% butadiene, and 62% styrene, and was sourced from Wuhan Fengyao Tonghui Chemical Products Co., Ltd. The second emulsion had a 50% solids content, including 7% carboxyl-functional monomer, 35% styrene, and 58% butadiene, and was sourced from Jingjiang Tonggao Chemical Co., Ltd.

[0112] Dipropylbenzene peroxide (DCP): Sinopharm Chemical Reagent Co., Ltd.

[0113] Example 1

[0114] 1) Sericin powder was dissolved in deionized water to a concentration of 200 mg mL -1 A uniform solution is obtained to obtain a sericin aqueous solution;

[0115] 2) Add 25 mL of sericin aqueous solution, 5 g of high-purity graphite powder, and 110 g of zirconia ball milling beads (0.6-0.8 mm in diameter) to a 100 mL ball mill. The mill was then placed in a planetary ball mill (YXQM-1L) and milled at 400 rpm for 24 hours. Finally, the mixture was separated from the ball milling beads using a 200-mesh nylon sieve to obtain a water-based sericin / graphene (SG) ink.

[0116] 3) Slowly add 3 mL of the above-mentioned aqueous SG ink and 0.2 g of dipropylbenzene peroxide (DCP) to 20 g of carboxylated styrene-butadiene rubber latex (50 wt% solids content) and mechanically stir at 650 rpm for 30 minutes. After stirring, sonicate for 5 minutes to remove bubbles and continue sonicating for 30 minutes to uniformly disperse the mixture.

[0117] 4) The mixed solution was poured into a polytetrafluoroethylene mold, heated to 40°C and dried for 24 hours, then heated to 60°C and dried to constant weight, and finally hot-pressed at 160°C for 10 minutes to obtain the final film product.

[0118] The mass percentage (ie, content) of graphene, ie, the mass fraction of graphene in the film product (modified rubber D), is 5 wt %, based on the total weight of the modified rubber (D).

[0119] The tensile strength of the film product of Example 1 is 12.43 MPa and the Young's modulus is 1.09 MPa. Figure 4 The graphene content in the Figure 5The graphene content in the composite is 5wt%.

[0120] Figure 1 (a) Transmission electron microscopy (TEM) image and (b) High-resolution transmission electron microscopy (HRTEM) image of the edge of the exfoliated graphene of Example 1 of the present invention.

[0121] Figure 2 1 is the X-ray diffraction (XRD) pattern of the graphite and sericin / graphene (SG) ink of Example 1 of the present invention.

[0122] Figure 3 1 is a size distribution histogram and a fitting curve of the exfoliated graphene sheets of Example 1 of the present invention.

[0123] Example 2

[0124] 1) Sericin powder was dissolved in deionized water to a concentration of 200 mg mL -1 A uniform solution is obtained to obtain a sericin aqueous solution;

[0125] 2) Add 25 mL of sericin aqueous solution, 5 g of high-purity graphite powder, and 110 g of zirconia ball milling beads (0.6-0.8 mm in diameter) to a 100 mL ball mill. The mill was then placed in a planetary ball mill (YXQM-1L) and milled at 400 rpm for 24 hours. Finally, the mixture was separated from the ball milling beads using a 200-mesh nylon sieve to obtain a water-based sericin / graphene (SG) ink.

[0126] 3) Slowly add 1.5 mL of the above-mentioned aqueous SG ink and 0.2 g of dipropylbenzene peroxide (DCP) to 20 g of carboxylated styrene-butadiene rubber latex and mechanically stir at 650 rpm for 30 minutes. After stirring, sonicate for 5 minutes to remove bubbles and continue sonicating for 30 minutes to uniformly disperse the mixture.

[0127] 4) The mixed solution was poured into a polytetrafluoroethylene mold, heated to 40°C and dried for 24 hours, then heated to 60°C and dried to constant weight, and finally hot-pressed at 160°C for 10 minutes to obtain the final film product.

[0128] The mass percentage of graphene, ie, the mass fraction of graphene in the film product (modified rubber D), is about 3 wt %, based on the total weight of the modified rubber (D).

[0129] The tensile strength of the film product of Example 2 is 8.34 MPa and the Young's modulus is 0.74 MPa. Figure 4 The graphene content in the Figure 5 The graphene content in the composite is 3wt%.

[0130] Example 3

[0131] 1) Sericin powder was dissolved in deionized water to a concentration of 200 mg mL -1 A uniform solution is obtained to obtain a sericin aqueous solution;

[0132] 2) Add 25 mL of sericin aqueous solution, 5 g of high-purity graphite powder, and 110 g of zirconia ball milling beads (0.6-0.8 mm in diameter) to a 100 mL ball mill. The mill was then placed in a planetary ball mill (YXQM-1L) and milled at 400 rpm for 24 hours. Finally, the mixture was separated from the ball milling beads using a 200-mesh nylon sieve to obtain a water-based sericin / graphene (SG) ink.

[0133] 3) Slowly add 4 mL of water-based SG ink and 0.2 g of dipropylbenzene peroxide (DCP) to 20 g of carboxylated styrene-butadiene rubber latex and mechanically stir at 650 rpm for 30 minutes. After stirring, sonicate for 5 minutes to remove bubbles and continue sonicating for 30 minutes to ensure uniform dispersion of the mixture.

[0134] 4) The mixed solution was poured into a polytetrafluoroethylene mold, heated to 40°C and dried for 24 hours, then heated to 60°C and dried to constant weight, and finally hot-pressed at 160°C for 10 minutes to obtain the final film product.

[0135] The mass percentage of graphene, ie, the mass fraction of graphene in the film product (modified rubber D), is about 7 wt %, based on the total weight of the modified rubber (D).

[0136] The tensile strength of the film product of Example 3 is 9.98 MPa and the Young's modulus is 0.79 MPa. Figure 4 、 5 Strength and modulus results for a graphene content of 7 wt%.

[0137] Example 4

[0138] Example 1 was repeated, wherein the mass percentage of graphene, ie, the mass fraction of graphene in the film product (modified rubber D), was 1 wt %, based on the total weight of the modified rubber (D).

[0139] The tensile strength of the film product of Example 4 is 6.97 MPa and the Young's modulus is 0.38 MPa. Figure 4 、 5 The graphene content in the samples was 1 wt%.

[0140] Example 5

[0141] Example 1 was repeated, wherein in step 3), 5.5 mL of the aqueous SG ink and 0.2 g of dipropylbenzene peroxide (DCP) were slowly added to 20 g of the carboxylated styrene-butadiene rubber latex. The mass percentage of graphene, i.e., the mass fraction of graphene in the film product (modified rubber D), was approximately 9 wt %, based on the total weight of the modified rubber (D).

[0142] The film product of Example 5 has a tensile strength of 7.65 MPa and a Young's modulus of 0.43 MPa.

[0143] Comparative Example 1

[0144] 1) Sericin powder was dissolved in deionized water to a concentration of 200 mg mL -1 A uniform solution is obtained to obtain a sericin aqueous solution;

[0145] 2) Slowly add 5 mL of sericin solution and 0.2 g of dipropylbenzene peroxide (DCP) to 20 g of carboxylated styrene-butadiene rubber latex. Mechanically stir at 650 rpm for 30 minutes. After stirring, sonicate for 5 minutes to remove bubbles. Continue sonicating for 30 minutes to ensure uniform dispersion of the mixture.

[0146] 3) The mixed solution was poured into a polytetrafluoroethylene mold, heated to 40°C and dried for 24 h, then heated to 60°C and dried to constant weight, and finally hot-pressed at 160°C for 10 min to obtain the final film product.

[0147] The tensile strength of the film product of this comparative example is 1.95 MPa, and the Young's modulus is 0.12 MPa. Figure 4 、 5 It can be seen that when no graphite powder is added, the tensile strength and Young's modulus of the film will decrease.

[0148] Comparative Example 2

[0149] 1) Sericin powder was dissolved in deionized water to a concentration of 200 mg mL -1 A uniform solution is obtained to obtain a sericin aqueous solution;

[0150] 2) Add 25 mL of sericin aqueous solution, 5 g of high-purity graphite powder, and 110 g of zirconia ball milling beads (0.6-0.8 mm in diameter) to a 100 mL ball mill. The mill was then placed in a planetary ball mill (YXQM-1L) and milled at 400 rpm for 24 hours. Finally, the mixture was separated from the ball milling beads using a 200-mesh nylon sieve to obtain a water-based sericin / graphene (SG) ink.

[0151] 3) Slowly add 3 mL of the above-mentioned aqueous SG ink to 20 g of carboxylated styrene-butadiene rubber latex (50 wt% solids content) and mechanically stir at 650 rpm for 30 minutes. After stirring, sonicate for 5 minutes to remove bubbles and continue sonicating for 30 minutes to uniformly disperse the mixture.

[0152] 4) The mixed solution was poured into a polytetrafluoroethylene mold, heated to 40°C and dried for 24 hours, then heated to 60°C and dried to constant weight, and finally hot-pressed at 160°C for 10 minutes to obtain the final film product.

[0153] The mass percentage (ie, content) of graphene, ie, the mass fraction of graphene in the film product (modified rubber D) is 5 wt %, based on the total weight of the modified rubber (D).

[0154] The film product of this comparative example has a tensile strength of 3.17 MPa and a Young's modulus of 0.31 MPa.

[0155] It can be seen that without adding vulcanizing agent, the strength of the obtained film will be significantly reduced.

Claims

1. A method for preparing graphene-modified rubber, the method comprising: (1) Dissolving sericin powder in deionized water to prepare a uniform solution (A); (2) ball milling the sericin solution (A), graphite powder, and ball milling beads to obtain a water-based sericin / graphene ink (B); (3) adding the ink (B) and the vulcanizing agent to the rubber latex while stirring, and then ultrasonically treating the mixture to obtain a mixture (C); (4) The mixture (C) is dried to a constant weight and hot-pressed to obtain a graphene-modified rubber (D).

2. The preparation method according to claim 1, wherein In step (1), the concentration of sericin in the sericin solution (A) is 0.1-400 mg / ml, 0.5-395 mg / ml, preferably 1-393 mg / ml, preferably 5-391 mg / ml, preferably 10-390 mg / ml, more preferably 20-380 mg / ml, more preferably 30-370 mg / ml, more preferably 40-360 mg / ml, more preferably 50-350 mg / ml, more preferably 60-340 mg / ml, more preferably 70-330 mg / ml, more preferably 80-320 mg / ml. / ml, more preferably 90-310 mg / ml, more preferably 100-300 mg / ml, more preferably 110-290 mg / ml, more preferably 120-280 mg / ml, more preferably 130-270 mg / ml, more preferably 140-260 mg / ml, more preferably 150-250 mg / ml, more preferably 160-240 mg / ml, more preferably 170-230 mg / ml, more preferably 180-220 mg / ml, more preferably 190-210 mg / ml, most preferably 200 mg / mL; and / or In step (2), the fineness of the graphite powder is 0.1-500 μm, preferably 0.15-400 μm, preferably 0.2-300 μm, preferably 0.25-200 μm, preferably 0.3-200 μm, preferably 0.35-100 μm, preferably 0.4-50 μm, preferably 0.45-40 μm, preferably 0.5-30 μm, preferably 0.55-20 μm, preferably 0.6-18 μm, more preferably 1-15 μm, more preferably 1.5-10 μm, more preferably 2-6 μm, most preferably 3-5 μm; and / or Step (2) is performed as follows: adding the sericin solution (A), graphite powder and ball milling beads into a ball milling jar, and then placing the ball milling jar into a planetary ball mill for ball milling and exfoliation to obtain a water-based sericin / graphene ink (B).

3. The preparation method according to claim 1 or 2, wherein The rubber emulsion in step (3) is one or more selected from styrene-butadiene rubber emulsion, chloroprene rubber emulsion, nitrile rubber emulsion, natural rubber emulsion, vinyl acetate emulsion, and ethylene-vinyl acetate copolymer (EVA) emulsion; and / or The vulcanizing agent in step (3) is an organic peroxide (e.g., dicumyl peroxide, DCP) or a sulfur-containing vulcanizing agent (e.g., sulfur, carbon disulfide, diethyl thioacetate, dimethyl disulfide, diethyl sulfide); and / or The ball milling beads are zirconium oxide ball milling beads.

4. The preparation method according to any one of claims 1 to 3, wherein In step (2), the mass ratio of the solid component in the sericin solution to the graphite powder is (0.01-10):1, preferably (0.05-9):1, preferably (0.1-8):1, preferably (0.2-7):1, preferably (0.3-6):1, preferably (0.4-5):1, preferably (0.5-4):1, preferably (0.6-3):1, preferably (0.7-2.5):1, preferably (0.8-2):1, preferably (0.9-1.5):1, and most preferably (1-1.2):1; and / or In step (2), the amount of graphite powder relative to the sericin solution should be such that the concentration of graphene in the resulting aqueous sericin / graphene ink (B) is 0.1-400 mg / ml, 0.5-396 mg / ml, preferably 1-394 mg / ml, preferably 1.5-392 mg / ml, preferably 2-390 mg / ml, preferably 10-385 mg / ml, more preferably 20-380 mg / ml, more preferably 30-370 mg / ml, more preferably 40-360 mg / ml, more preferably 50-350 mg / ml, more preferably 60-340 mg / ml, more preferably 70- 330 mg / ml, more preferably 80-320 mg / ml, more preferably 90-310 mg / ml, more preferably 100-300 mg / ml, more preferably 110-290 mg / ml, more preferably 120-280 mg / ml, more preferably 130-270 mg / ml, more preferably 140-260 mg / ml, more preferably 150-250 mg / ml, more preferably 160-240 mg / ml, more preferably 170-230 mg / ml, more preferably 180-220 mg / ml, more preferably 190-210 mg / ml, most preferably 200 mg / mL; and / or In step (3), the amount of aqueous sericin / graphene ink (B) relative to the rubber emulsion should be such that the mass percentage or weight percentage of graphene in the resulting graphene / modified rubber (D) is 0.05-25 wt%, preferably 0.1-22 wt%, preferably 0.15-20 wt%, preferably 0.20-18 wt%, preferably 0.25-16 wt%, preferably 0.30-15 wt%, preferably 0.35-12 wt%, preferably 0.40-10 wt%, preferably 0.60-8 wt%, preferably 0.80-7 wt%, preferably 0.90-6 wt%, preferably 1-5 wt%, preferably 1.5-4.5 wt%, preferably 2-4 wt%, preferably 2.5-3.5 wt%, such as 3 wt%, based on the total weight of the modified rubber (D).

5. The preparation method according to any one of claims 1 to 4, wherein The solid content of the rubber emulsion is 10-60wt%, preferably 15-58wt%, preferably 20-56wt%, preferably 25-55wt%, preferably 30-53wt%, preferably 35-52wt%, preferably 40-50wt%, preferably 42-48wt%, preferably 43-45wt%; and / or In step (2), the mass ratio of the ball milling beads (preferably, zirconia beads or zirconia ball milling beads) to the graphite powder is (5-40):1, preferably (7-35):1, preferably (10-30):1, more preferably (15-25):1, preferably (18-20):1; and / or The diameter of the ball milling beads (preferably, zirconia beads or zirconia ball milling beads) in step (2) is 0.5-3 mm, preferably 0.6-2.7 mm, preferably 0.7-2.5 mm, preferably 0.8-2.2 mm, preferably 1-2 mm, for example 1.2, 1.5, 1.8 mm; and / or In step (2), the sericin solution (A), graphite powder and ball milling beads are added to a ball milling jar, and the ball milling jar is then placed in a planetary ball mill for ball milling and exfoliation at a set speed of the planetary ball mill to obtain a water-based sericin / graphene ink (B). The set speed is in the range of 20 to 1000 rpm, preferably 40 to 900 rpm, more preferably 50 to 800 rpm, more preferably 70 to 700 rpm, more preferably 100 to 750 rpm, more preferably 150 to 700 rpm, more preferably 180 to 650 rpm, more preferably 200 to 600 rpm, more preferably 250 to 550 rpm, more preferably 300 to 500 rpm, more preferably 350 to 450 rpm, such as 400 rpm; and / or The ball milling peeling time in step (2) is 0.5 to 72 hours, preferably 1 to 65 hours, preferably 5 to 60 hours, preferably 7 to 55 hours, preferably 10 to 50 hours, preferably 12 to 45 hours, preferably 15 to 40 hours, preferably 18 to 35 hours, preferably 20 to 30 hours, preferably 22 to 26 hours, such as 24 hours.

6. The preparation method according to any one of claims 1 to 5, wherein The speed of mechanical stirring in step (3) is 20 to 2000 rpm, preferably 50 to 1500 rpm, preferably 100 to 1200 rpm, preferably 200 to 1000 rpm, preferably 400 to 900 rpm, preferably 500 to 800 rpm, preferably 550 to 750 rpm, preferably 600 to 700 rpm; and / or The stirring time in step (3) is 0.5-120 min, preferably 1-100 min, preferably 5-90 min, preferably 7-70 min, preferably 10-60 min, preferably 15-50 min, more preferably 20-40 min, such as 30 minutes; and / or The time of ultrasonic treatment in step (3) is 0.5-120 min, preferably 1-100 min, preferably 5-90 min, preferably 7-70 min, preferably 10-60 min, preferably 15-50 min, more preferably 20-40 min, such as 30 or 35 minutes; and / or The drying temperature in step (4) is 25-100°C, preferably 30-90°C, preferably 35-80°C, preferably 38-70°C, preferably 40-60°C, such as 50°C; and / or The hot pressing temperature in step (4) is 100-400°C, preferably 110-350°C, preferably 120-300°C, preferably 130-250°C, more preferably 140-200°C, more preferably 150-180°C; and / or The hot pressing time in step (4) is 0.5-100 min, preferably 1-90 min, preferably 1.5-70 min, preferably 2-60 min, preferably 3-50 min, preferably 4-40 min, preferably 5-30 min, preferably 6-20 min, more preferably 8-15 min, such as 10 or 12 minutes.

7. A graphene-modified rubber obtained by the method of any one of claims 1 to 6, wherein the mass percentage of graphene, i.e. the mass fraction of graphene in the modified rubber (D), is 0.05-25 wt %, preferably 0.1-22 wt %, preferably 0.15-20 wt %, preferably 0.20-18 wt %, preferably 0.25-15 wt %, preferably 0.30-12 wt %, preferably 0.35-10 wt %, preferably 0.40-9 wt %, for example 0.50, 0.60, 0.70, 0.80, 0.90, 1.0, 1.2, 1.5, 1.8, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8 or 8.5 wt %, based on the total weight of the modified rubber (D); Preferably, the tensile strength of the graphene-modified rubber (e.g., in the form of a film, sheet or plate) is 5-13 MPa, preferably 5.5-12.9 MPa, preferably 6-12.8 MPa, preferably 6.5-12.7 MPa, preferably 7-12.6 MPa, preferably 7.5-12.5 MPa, preferably 8-12.4 MPa, and its Young's modulus is 0.25-1.5 MPa, preferably 0.28-1.4 MPa, preferably 0.3-1.2 MPa, preferably 0.35-1.1 MPa, preferably 0.4-1.0 MPa, preferably 0.5-0.9 MPa, preferably 0.6-0.85 MPa, preferably 0.65-0.83 MPa, preferably 0.7-0.8 MPa, preferably 0.74-0.79 MPa.

8. The use of the graphene-modified rubber according to claim 7, characterized in that: It is used to reinforce modified rubber, to prepare polymer nanocomposites, to produce functional inks and coatings, and as a raw material for producing multifunctional flexible sensors for electronic skin, human health monitoring, and wearable electronics through hot pressing technology.

9. A sericin / graphene ink (B), prepared by a method comprising the following steps: (1) Dissolving sericin powder in deionized water to prepare a uniform solution (A); (2) Adding sericin solution (A), graphite powder and zirconium oxide ball milling beads into a ball milling jar, and then placing the ball milling jar into a planetary ball mill for ball milling and exfoliation to obtain a water-based sericin / graphene ink (B).

10. A sericin / graphene ink (B) prepared by steps (1) and (2) of the preparation method according to claims 1 to 6; preferably, in the aqueous sericin / graphene ink (B) obtained in step (2), the mass ratio of sericin to graphene is (0.01-10):1, preferably (0.05-9):1, preferably (0.1-8):1, preferably (0.2-7):1, preferably (0.3-6):1, preferably (0.4-5):1, preferably (0.5-4):1, preferably (0.6-3):1, preferably (0.7-2.5):1, preferably (0.8-2):1, preferably (0.9-1.5):1, and most preferably (1-1.2):1.

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