Preparation method of natural rubber composite material and application thereof

Abstract

The application discloses a preparation method of natural rubber composite material and application thereof, and mixes natural rubber with modified carbon nanotube dispersion liquid, stirs, blends, and then dries and dehydrates to obtain the natural rubber composite material. The application has simple equipment and simple process, the natural rubber composite material after silk fibroin modified carbon nanotube is manufactured has electromagnetic shielding performance, the mechanical property is obviously improved, the application of the natural rubber material in the electromagnetic shielding field is expanded, and the application has the prospect of large-scale preparation.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic shielding materials and is a preparation method with simple processing technology and strong shielding effectiveness. By using sericin-assisted composite materials, higher flexibility, improved conductivity and equivalent or better shielding performance are achieved simultaneously without vulcanization. This invention demonstrates an environmentally friendly and scalable high-performance, flexible EMI shielding elastomer preparation route through protein-medium nanofiller engineering. Background Technology

[0002] With the increasing frequency and integration of 5G / 6G communication and electronic equipment, electromagnetic interference and radiation problems are becoming increasingly prominent, creating an urgent need for lightweight, flexible, and corrosion-resistant high-efficiency electromagnetic shielding materials. Traditional metal shielding materials suffer from drawbacks such as high density, susceptibility to corrosion, and poor flexibility. Natural rubber, on the other hand, is widely available, possesses excellent elasticity, good mechanical properties, and excellent molding and processing characteristics, making it an ideal matrix material for preparing flexible electromagnetic shielding composite materials. Carbon nanotubes, with their high electrical conductivity, high aspect ratio, excellent mechanical properties, and electromagnetic loss characteristics, can significantly improve the electromagnetic shielding effectiveness of composite materials as conductive fillers. However, due to their large specific surface area and high surface energy, they are prone to aggregation and have poor dispersion in rubber matrices. This not only damages the material's mechanical properties but also affects the stability of the conductive network construction and the electromagnetic shielding effect.

[0003] Therefore, there is an urgent need to develop natural rubber / carbon nanotube electromagnetic shielding composite materials that can improve the dispersion of carbon nanotubes and enhance their interfacial compatibility with natural rubber, so as to meet the application requirements of modern electronic devices for flexible and efficient electromagnetic shielding materials. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a method for preparing natural rubber composite materials and their applications. The method uses natural rubber as the matrix and combines simple processing technology with high performance, making it suitable for electromagnetic shielding applications.

[0005] The technical solution provided by this invention is as follows: A method for preparing a natural rubber composite material, comprising the following specific steps: Natural rubber and modified carbon nanotube dispersion are mixed and stirred for 50-80 minutes, and then dried in a constant temperature drying oven at 50-70℃ for more than 24 hours to obtain natural rubber composite material.

[0006] The natural rubber and modified carbon nanotube dispersion are mixed at a mass ratio of 100:5-20.

[0007] The natural rubber has not undergone vulcanization and has a solids content of 60%.

[0008] The modified carbon nanotube dispersion is prepared as follows: After mixing the carbon nanotube dispersion and the sericin dispersion, stir at 1000 rpm for 30-40 minutes using a rotor stirrer to obtain the modified carbon nanotube dispersion.

[0009] The carbon nanotubes are carboxylated carbon nanotubes with a diameter of 5-10 nm.

[0010] The mass fraction of the carbon nanotube dispersion and the sericin dispersion is 4-6 wt%.

[0011] The mass ratio of the carbon nanotube dispersion to the sericin dispersion is 1:4.

[0012] The present invention also provides the application of the natural rubber composite material prepared by the above preparation method as an electromagnetic shielding material. The natural rubber composite material has excellent electromagnetic shielding and mechanical properties. The carbon nanotubes modified with sericin have excellent dispersibility and interfacial compatibility in the natural rubber matrix. Moreover, compared with the natural rubber composite material without carbon nanotube modification, not only is the electromagnetic shielding performance significantly improved, but the mechanical properties are also effectively improved.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The equipment used in this invention is simple and inexpensive; carbon nanotubes modified with sericin have excellent dispersibility and interfacial bonding ability in natural rubber matrix, thus achieving high electromagnetic shielding performance even with low carbon nanotube addition. Attached Figure Description

[0014] Figure 1 The scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) elemental distribution diagrams of the products obtained in the examples and comparative examples are shown. Figure 2 Transmission electron microscopy (TEM) of the products obtained in the examples and comparative examples. Figure 3 Zeta potential diagrams of the products obtained in the examples and comparative examples; Figure 4 The graph shows the change of total electromagnetic shielding loss of the product obtained in the example with frequency and a comparison of electromagnetic shielding absorption, reflection and total loss. Figure 5 A diagram illustrating the Tesla coil of the product obtained in the example; Figure 6 A comparison diagram showing the total electromagnetic shielding loss of the products obtained in the examples and comparative examples; Figure 7 This is a comparison of the mechanical properties of the examples and comparative examples. Detailed Implementation

[0015] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. These embodiments are further illustrations of the present invention, but not intended to limit its scope.

[0016] The parts mentioned in the examples are parts by mass (phr, based on 100 parts of dry natural rubber), and the actual operation uses the weight unit g; the natural rubber used in the examples has not undergone vulcanization process and its solid content is 60%; the carbon nanotubes are carboxylated carbon nanotubes with a diameter of 5-10 nm.

[0017] Example 1 A method for preparing a natural rubber composite material includes the following steps: (1) Mix 5 parts of carbon nanotube dispersion with 5 wt% mass fraction and 1.25 parts of sericin dispersion with 5 wt% mass fraction, and stir at 1000 rpm for 30 minutes under a rotor stirrer to obtain modified carbon nanotube dispersion, named CNTSS-5phr. (2) The prepared modified carbon nanotube dispersion was mixed with 100 parts of natural rubber at 1000 rpm for 60 minutes, and then dried in a constant temperature drying oven at 60°C for 24 hours to produce a natural rubber composite material, named NR / CNTSS-5phr.

[0018] Example 2 A method for preparing a natural rubber composite material includes the following steps: (1) Mix 10 parts of carbon nanotube dispersion with a mass fraction of 5wt% and 2.5 parts of sericin dispersion with a mass fraction of 5wt%, and stir at 1000rpm for 30 minutes under a rotor stirrer to obtain modified carbon nanotube dispersion, named CNTSS-10phr. (2) The prepared modified carbon nanotube dispersion was mixed with 100 parts of natural rubber at 1000 rpm for 60 minutes, and then dried in a constant temperature drying oven at 60°C for 24 hours to produce a natural rubber composite material, named NR / CNTSS-10phr.

[0019] Example 3 A method for preparing a natural rubber composite material includes the following steps: (1) Mix 15 parts of carbon nanotube dispersion with 5 wt% mass fraction and 3.75 parts of sericin dispersion with 5 wt% mass fraction, and stir at 1000 rpm for 30 minutes under a rotor stirrer to obtain modified carbon nanotube dispersion, named CNTSS-15phr. (2) The prepared modified carbon nanotube dispersion was mixed with 100 parts of natural rubber at 1000 rpm for 60 minutes, and then dried in a constant temperature drying oven at 60°C for 24 hours to make a natural rubber composite material, named NR / CNTSS-15phr.

[0020] Example 4 A method for preparing a natural rubber composite material includes the following steps: After mixing 20 parts of 5wt% carbon nanotube dispersion and 5 parts of 5wt% sericin dispersion, the mixture was stirred at 1000rpm for 30 minutes under a rotor stirrer to obtain a modified carbon nanotube dispersion, named CNTSS-20phr. The prepared modified carbon nanotube dispersion was mixed with 100 parts of natural rubber at 1000 rpm for 60 minutes, and then dehydrated in a constant temperature drying oven at 60℃ for 24 hours to produce a natural rubber composite material, named NR / CNTSS-20phr.

[0021] Example 5 A method for preparing a natural rubber composite material includes the following steps: (1) Mix 15 parts of carbon nanotube dispersion with a mass fraction of 4wt% and 3.75 parts of sericin dispersion with a mass fraction of 6wt%, and stir at 1000rpm for 30 minutes under a rotor stirrer to obtain modified carbon nanotube dispersion, named CNTSS-15phr. (2) The prepared modified carbon nanotube dispersion was mixed with 100 parts of natural rubber at 1000 rpm for 50 minutes, and then dried in a constant temperature drying oven at 60℃ for 24 hours to make a natural rubber composite material, named NR / CNTSS-15phr-50min.

[0022] Example 6 A method for preparing a natural rubber composite material includes the following steps: (1) Mix 15 parts of carbon nanotube dispersion with a mass fraction of 4wt% and 3.75 parts of sericin dispersion with a mass fraction of 6wt%, and stir at 1000rpm for 40 minutes under a rotor stirrer to obtain modified carbon nanotube dispersion, named CNTSS-15phr. (2) The prepared modified carbon nanotube dispersion was mixed with 100 parts of natural rubber at 1000 rpm for 80 minutes, and then dried in a constant temperature drying oven at 60℃ for 24 hours to make a natural rubber composite material, named NR / CNTSS-15phr-80min.

[0023] Example 7 A method for preparing a natural rubber composite material includes the following steps: (1) Mix 15 parts of carbon nanotube dispersion with a mass fraction of 6wt% and 3.75 parts of sericin dispersion with a mass fraction of 5wt%, and stir at 1000rpm for 35 minutes under a rotor stirrer to obtain modified carbon nanotube dispersion, named CNTSS-15phr. (2) The prepared modified carbon nanotube dispersion was mixed with 100 parts of natural rubber at 1000 rpm for 60 minutes, and then dried in a constant temperature drying oven at 50℃ for 24 hours to make a natural rubber composite material, named NR / CNTSS-15phr-50℃.

[0024] Example 8 A method for preparing a natural rubber composite material includes the following steps: (1) Mix 15 parts of carbon nanotube dispersion with 4wt% mass fraction and 3.75 parts of sericin dispersion with 4wt% mass fraction, and stir at 1000rpm for 30 minutes under a rotor stirrer to obtain modified carbon nanotube dispersion, named CNTSS-15phr. (2) The prepared modified carbon nanotube dispersion was mixed with 100 parts of natural rubber at 1000 rpm for 60 minutes, and then dried in a constant temperature drying oven at 70℃ for 24 hours to make a natural rubber composite material, named NR / CNTSS-15phr-70℃.

[0025] Comparative Example 1 100 parts of natural rubber were dehydrated in a constant temperature drying oven at 60°C for 24 hours, and the resulting material was named NR.

[0026] Comparative Example 2 Five parts of carbon nanotube dispersion with a mass fraction of 5 wt% were mixed with 100 parts of natural rubber at a speed of 1000 rpm for 60 minutes. Finally, the mixture was dehydrated in a constant temperature drying oven at 60℃ for 24 hours. The resulting material was named NR / CNT-5phr.

[0027] Comparative Example 3 Ten parts of a 5 wt% carbon nanotube dispersion were mixed with 100 parts of natural rubber at 1000 rpm for 60 minutes, and then dehydrated in a constant temperature drying oven at 60°C for 24 hours. The resulting material was named NR / CNT-10phr.

[0028] Comparative Example 4 15 parts of carbon nanotube dispersion with a mass fraction of 5 wt% were mixed with 100 parts of natural rubber at a speed of 1000 rpm for 60 minutes, and then dried in a constant temperature drying oven at 60℃ for 24 hours. The resulting material was named NR / CNT-15phr.

[0029] Comparative Example 5 20 parts of carbon nanotube dispersion with a mass fraction of 5 wt% were mixed with 100 parts of natural rubber at a speed of 1000 rpm for 60 minutes, and finally dehydrated in a constant temperature drying oven at 60℃ for 24 hours. The resulting material was named NR / CNT-20phr.

[0030] The effect verification experiment showed the dispersion of carbon nanotubes in the products of the above examples and comparative examples, such as... Figure 1 Morphological characterization of the nanocomposites shown: SEM images of NR / CNTSS-5phr (a1), NR / CNTSS-10phr (b1), NR / CNTSS-15phr (c1), and NR / CNTSS-20phr (d1); oxygen (O) surface distribution maps of NR / CNTSS-5phr (a2), NR / CNTSS-10phr (b2), NR / CNTSS-15phr (c2), and NR / CNTSS-20phr (d2); SEM images of NR / CNT-5phr (e1), NR / CNT-10phr (f1), NR / CNT-15phr (g1), and NR / CNT-20phr (h1). Images; surface distribution maps of oxygen (O) in NR / CNT-5phr (e2), NR / CNT-10phr (f2), NR / CNT-15phr (g2), and NR / CNT-20phr (h2), with attached... Figure 1 It can be seen that the dispersion of carbon nanotubes modified with sericin in the natural rubber matrix has changed significantly. Moreover, in the EDS energy spectrum, the O element represents the carboxylated carbon nanotubes of the raw material, and the distribution of the O element also shows that the modified carbon nanotubes have a more uniform dispersion.

[0031] like Figure 2 As shown in the transmission electron microscopy (TEM) characterization results of the products of Example 3 and Comparative Example 4, the results show that the carbon nanotubes of Example 3 are well dispersed in the NR matrix without obvious agglomeration, forming a continuous nanotube network, which is conducive to exerting the nano-reinforcement effect; while the unmodified carbon nanotubes in Comparative Example 4 form large-sized agglomerates due to inter-tube van der Waals forces, and there are interfacial gaps between them and the matrix, resulting in poor bonding.

[0032] Figure 3 The zeta potential diagram of the material is shown in the figure. Figure 3As shown, under neutral conditions, the original carbon nanotubes have a negative charge on their surface, with a Zeta potential of -30.8 eV. Meanwhile, the isoelectric point of sericin is approximately 4.3, and its surface also exhibits negative charge in a neutral environment. After sericin modification, the Zeta potential of the sericin-modified carbon nanotubes (CNTSS-15phr) prepared in Example 3 decreased slightly to -32.3 eV, and the potential distribution peak broadened significantly, indicating that the charge density on the carbon nanotube surface was significantly increased, and the surface properties became more uniform and stable. Natural rubber latex particles themselves also have a high negative potential, with a Zeta potential reaching -62.3 eV. When sericin-modified carbon nanotubes were added to the rubber latex system, the Zeta potential of the entire dispersion system became -47.4 eV. This change indicates that there is a strong electrostatic repulsion between the carbon nanotubes and the rubber particles. This electrostatic repulsion effectively hinders the aggregation of carbon nanotubes and promotes their uniform dispersion in the latex system, significantly improving the stability of the composite system.

[0033] like Figure 4 The graph shows the change of total electromagnetic shielding loss with frequency and the comparison of electromagnetic shielding absorption, reflection, and total loss. As can be seen from the graph, with the gradual increase of CNTSS content, the internal conductive network of the composite material is continuously improved, and its electromagnetic shielding effectiveness shows a continuous upward trend. In particular, the total shielding effectiveness of NR / CNTSS-15phr can reach about 56dB. This result directly confirms that sericin modification can significantly optimize the dispersion state and interfacial bonding of carbon nanotubes in the natural rubber matrix, and greatly improve the electromagnetic shielding performance of the composite material.

[0034] like Figure 5 The diagram shows a Tesla coil for the material, including Example 3 (NR / CNTSS-15phr) and Comparative Example 1 (NR). The results show that Example 3 effectively shields the electromagnetic waves that generate the magnetic field of the Tesla coil.

[0035] Figure 6 The graph shows a comparison of the total electromagnetic shielding loss of the products obtained in the examples and comparative examples. It illustrates the total electromagnetic shielding effectiveness (EMI SE) of the natural rubber composites of Examples 1-4 (NR / CNTSS, sericin-modified system) and Comparative Examples 1-5 (NR / CNT, unmodified system) under different carbon nanotube filling amounts. T The results showed that the EMI SE of the two groups of samples changed. T All showed a significant increasing trend with the increase of CNT filling amount. Among them, the EMI SE of Example 3 (NR / CNTSS-15phr) was... T Reaching 56dB, this is nearly double the 29.1dB of Comparative Example 4 (NR / CNT-15phr) with the same filler content, and far exceeds the performance requirements of commercial electromagnetic shielding materials (SE).T >20dB) can meet the electromagnetic protection requirements of high-end electronic equipment.

[0036] Figure 7 For the comparison of the mechanical properties of Examples 1-4 and Comparative Examples 1-5, the elastic modulus was measured by... Figure 7 a and Figure 7 The stress-strain curve of b is calculated as follows: Figure 7 d and Figure 7 As shown in e, the elastic modulus of the example (NR / CNTSS) was consistently higher than that of the comparative example (NR / CNT) for all carbon nanotube addition amounts. Figure 7 As shown in the tensile strength results in f, the tensile strength of the example (NR / CNTSS) steadily increased with the increase of CNTSS loading, reaching 350% higher than that of Comparative Example 1 (pure NR) at 15 phr. Meanwhile, due to the higher crosslinking density of the example (NR / CNTSS), its elongation at break was lower than that of the corresponding material of the comparative example (NR / CNT) at all carbon nanotube loadings. Furthermore, the fluctuation in the elongation at break of the comparative example (NR / CNT) may be related to poor dispersibility and aggregation. In contrast, the example (NR / CNTSS) showed an elongation at break that was still slightly lower than that of NR / CNT. Figure 7 (c) This is consistent with its higher crosslinking density. Despite this trade-off, the composite material maintains excellent flexibility, achieving an elongation at break of 660% at 15 phr CNTSS.

[0037] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for preparing a natural rubber composite material, characterized in that, The specific steps are as follows: Natural rubber is mixed with modified carbon nanotube dispersion, stirred and blended for 50-80 minutes, and dried at 50-70℃ for more than 24 hours to obtain natural rubber composite material.

2. The method for preparing the natural rubber composite material according to claim 1, characterized in that, The natural rubber and modified carbon nanotube dispersion are mixed at a mass ratio of 100:5-20.

3. The method for preparing the natural rubber composite material according to claim 1, characterized in that, The modified carbon nanotube dispersion is prepared as follows: After mixing the carbon nanotube dispersion and the sericin dispersion, stir for 30-40 minutes to obtain the modified carbon nanotube dispersion.

4. The method for preparing the natural rubber composite material according to claim 3, characterized in that, The carbon nanotubes are carboxylated carbon nanotubes with a diameter of 5-10 nm.

5. The method for preparing the natural rubber composite material according to claim 3, characterized in that, The mass fraction of the carbon nanotube dispersion and the sericin dispersion is 4-6%.

6. The method for preparing the natural rubber composite material according to claim 3, characterized in that, The mass ratio of the carbon nanotube dispersion to the sericin dispersion is 1:

4.

7. The application of the natural rubber composite material prepared by the preparation method of claim 1 as an electromagnetic shielding material.

Images