A porous conductive epoxy resin composite material and a preparation method and application thereof

Abstract

The present application belongs to the technical field of polymer materials, and particularly relates to a porous conductive epoxy resin composite material and a preparation method and application thereof. The material comprises the following components: 30 parts of epoxy resin E44, 10-50 parts of dimethylbenzene, 0.398-1.587 parts of expanded microspheres, 0-3.035 parts of multi-walled carbon nanotubes and 9.675 parts of polyether amine curing agent T403. In the present study, expanded microspheres (EM) and multi-walled carbon nanotubes (CNT) are simultaneously introduced into the epoxy resin matrix as composite fillers, and a lightweight porous conductive epoxy resin composite material (PCEP) with high conductivity is successfully prepared. Specifically, lightweight EM with a unique closed pore structure is selected as a foaming and weight-reducing filler, which can significantly reduce the overall density of the composite material while maintaining the high strength and high toughness of the epoxy matrix, and the pore size and distribution can be accurately controlled. Then, high-quality dispersed CNT is uniformly introduced into the system, and by constructing a continuous and efficient conductive channel, the conductivity of the composite material is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a porous conductive epoxy resin composite material, its preparation method, and its application. Background Technology

[0002] Epoxy resins, due to their excellent mechanical strength, superior bonding properties, and excellent chemical stability, have been widely used in coatings, adhesives, and composite materials. However, their high rigidity and brittleness, as well as their inherent insufficient conductivity, severely restrict their development in high-end applications such as electronic devices, electromagnetic shielding, and energy storage systems. With the increasing demand for lightweight and multifunctional materials, the development of epoxy resin composites with both controllable porous structures and excellent conductivity has become a research hotspot in academia and industry. Porous conductive epoxy resins, as an advanced material combining the excellent mechanical properties of epoxy resins with the functional characteristics of conductive fillers, possess a unique porous structure that endows them with lightweight, high specific surface area, and controllable conductivity. Through biomimetic structural design, porous network construction, and synergistic optimization of conductive fillers, this type of material has made significant progress in lightweighting, functional integration, and high performance, showing broad prospects in flexible electronics, electromagnetic shielding, and energy storage.

[0003] In porous conductive epoxy composites, precise control of the pore structure can reduce material density, increase specific surface area, and provide spatial support for the construction of an efficient network of conductive fillers. The type, content, and dispersion state of the conductive fillers directly affect the overall electrical and mechanical properties of the material. However, existing research often struggles to achieve an ideal balance between mechanical strength and conductivity, and the contradiction between the two has not been effectively alleviated. Especially considering the common problems of insufficient tensile strength, low electrical conductivity, and limited functionality in existing materials, the development of high-performance, functionalized porous conductive epoxy resin composites is particularly important and urgent. Therefore, this study proposes a composite strategy based on the synergistic effect of closed-cell expanded microspheres (EM) and multi-walled carbon nanotubes (CNTs) to seek a new balance between lightweight and high conductivity. Furthermore, porous conductive epoxy resin composites have great potential in the integration of structure and function. In the future, through interdisciplinary collaborative innovation, they are expected to break through current bottlenecks and provide key material support for next-generation electronic devices, intelligent equipment, and green energy technologies.

[0004] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the inventors studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0005] This invention belongs to the field of polymer materials technology, specifically relating to a porous conductive epoxy resin composite material, its preparation method, and its application.

[0006] To address the aforementioned technical problems, one objective of this invention is to provide a porous conductive epoxy resin composite material. This porous conductive epoxy resin composite material with a uniform closed-cell structure comprises the following components by weight: 30 parts epoxy resin E44, 10-50 parts xylene, 0.398-1.587 parts closed-cell expanded microspheres, 0-3.035 parts multi-walled carbon nanotubes, and 9.675 parts polyetheramine curing agent T403. The closed-cell expanded microspheres are fully foamed and have a diameter of 20-40 μm.

[0007] According to a preferred embodiment, the porous conductive epoxy resin composite material is selected from the group consisting of: by weight,

[0008] 30 parts epoxy resin E44, 10 parts xylene, 0.794 parts expanded microspheres and 9.675 parts polyetheramine curing agent T403;

[0009] 30 parts epoxy resin E44, 10-50 parts xylene, 0.794 parts expanded microspheres, 1.012 parts multi-walled carbon nanotubes and 9.675 parts polyetheramine curing agent T403;

[0010] 30 parts epoxy resin E44, 25 parts xylene, 0.794 parts expanded microspheres, 2.023 parts multi-walled carbon nanotubes and 9.675 parts polyetheramine curing agent T403;

[0011] 30 parts epoxy resin E44, 45 parts xylene, 0.794 parts expanded microspheres, 3.035 parts multi-walled carbon nanotubes and 9.675 parts polyetheramine curing agent T403;

[0012] 30 parts epoxy resin E44, 70 parts xylene, 0.398 parts expanded microspheres, 2.004 parts multi-walled carbon nanotubes, and 9.675 parts polyetheramine curing agent T403; or

[0013] 30 parts epoxy resin E44, 45 parts xylene, 1.587 parts expanded microspheres, 2.063 parts multi-walled carbon nanotubes and 9.675 parts polyetheramine curing agent T403.

[0014] One of the objectives of this invention is to provide the use of the aforementioned porous conductive epoxy resin composite material in improving the mechanical and electrical properties of equipment or components. The porous conductive epoxy resin composite material combines lightweight, porous structure, and excellent electrical conductivity. By precisely controlling the pore structure and filler content, the synergistic optimization of mechanical and electrical properties can be achieved, thus showing broad application prospects in multiple fields.

[0015] According to a preferred embodiment, the device or component is an electronic and communication device with electromagnetic shielding and anti-static functions, a lightweight conductive structural component, an electric heating and temperature control component, a conductive buffer vibration damping and energy absorption component, or a piezoresistive / strain sensing component.

[0016] One of the objectives of this invention is to provide a method for preparing a porous conductive epoxy resin composite material, comprising the following steps:

[0017] 30 parts of epoxy resin E44 in the S1 fluid state were dissolved in 10-50 parts of xylene solvent, and then 0.398-1.587 parts of expanded microspheres and 0-3.035 parts of multi-walled carbon nanotubes were uniformly mixed.

[0018] Add 9.675 parts of polyetheramine curing agent T403 to S2, stir for no less than 1 hour, and then pour the mixture into a polytetrafluoroethylene mold to cure and shape.

[0019] S3 was cured at room temperature for 12 hours and then transferred to an oven at 60~80℃ for 48 hours.

[0020] S4. Place the sample in a vacuum oven at 80~100℃ and evacuate it to remove residual xylene solvent.

[0021] According to a preferred embodiment, epoxy resin E44 is heated at 80°C to obtain epoxy resin E44 in a flowable state.

[0022] According to a preferred embodiment, in S3, after curing at room temperature for 12 h, the mixture is transferred to a 60°C oven for curing for 48 h.

[0023] According to a preferred embodiment, in S4, the sample is placed in an 80°C vacuum oven and vacuumed to remove residual xylene solvent.

[0024] One of the objectives of this invention is to provide a flexible sensor, which is prepared based on the above-mentioned porous conductive epoxy resin composite material or the porous conductive epoxy resin composite material prepared by the above-mentioned preparation method.

[0025] According to a preferred embodiment, a flexible sensor is used to monitor human movement behaviors including finger bending or wrist swinging. The flexible sensor is used in wearable devices for health monitoring.

[0026] Preferably, the wearable device obtains the bending angle or swing dynamics of the limb by detecting the change in electrical signal generated by the deformation of the porous conductive epoxy resin composite material.

[0027] The beneficial effects of this technical solution are:

[0028] The porous conductive epoxy resin composite material (PCEP) involved in this application optimizes and improves the conductivity of epoxy resin E44 by introducing expanded microspheres. During processing, thermal expansion forms a uniformly dispersed microporous structure within the polymer matrix, directly resulting in a significant reduction in material density (PCEP-EM2%@CNT5% density is only 0.723 g / cm³). 3 This material achieves excellent lightweight properties. It is worth noting that this microporous structure created by expanded microspheres does not come at the expense of mechanical properties. The material simultaneously forms a robust cross-linked network, effectively coating and fixing the expanded microspheres, allowing the material to maintain high hardness (44 D) and excellent mechanical properties (fracture strength 4.01 MPa, elongation at break 53.76%) while remaining lightweight, overcoming the drawback of poor strength in traditional porous materials.

[0029] The expanded microspheres used in this application are unique; they are not inert fillers in the traditional sense, but rather structural functional units capable of forming uniform closed-cell structures in situ within the matrix upon thermal expansion. This controllable foaming characteristic allows for the orderly distribution of conductive fillers along the pore walls while reducing density, thereby maintaining the integrity of the conductive network over a wide density range. By precisely controlling the ratio of expanded microspheres to conductive fillers, the density, conductivity, and mechanical properties of the material can be synergistically optimized, without needing to unilaterally pursue a single performance indicator by simply changing the filler content. This design strategy based on multiphase synergy is the key to achieving high-performance, lightweight conductive epoxy resin composite materials in this application.

[0030] Compared to interconnected open-cell structures, closed-cell structures, due to their integrity and isolation, can more effectively block stress transmission paths and significantly delay or prevent crack propagation. This structural advantage allows the material to maintain excellent mechanical integrity while drastically reducing density and achieving significant weight reduction. The material's mechanical properties, especially compressive and tensile strength, are far superior to open-cell foam materials of the same density, thus truly achieving a coexistence of "lightweight" and "high strength and high rigidity," overcoming the common problem of a sharp decline in strength in traditional porous materials.

[0031] Meanwhile, the closed-pore structure introduced by the expanded microspheres greatly enhances the material's thermal insulation performance. These micropores effectively impede air convection and increase the path resistance of heat conduction, resulting in an extremely low thermal conductivity [0.1737 W / (m·K)]. This combination of lightweight and thermal insulation makes the material a promising candidate for application in lightweight equipment requiring thermal insulation and energy saving.

[0032] Furthermore, the addition of expanded microspheres provides a unique interface for the construction of the conductive network. Conductive components can selectively distribute at the interface between the polymer matrix and the expanded microspheres, forming a stable and sensitive three-dimensional conductive network, resulting in suitable surface resistivities of 2 kΩ and 2.6 kΩ for the upper and lower surfaces, respectively. When the sensor prepared based on this is used to monitor human movements such as finger bending and wrist swinging, its porous structure easily deforms, leading to significant changes in the conductive pathways, thereby generating a strong and stable electrical signal response with high sensitivity and reliability.

[0033] In addition, the expanded microspheres themselves have a certain degree of thermal stability, good compatibility with the polymer matrix and the cross-linking network they induce, together ensuring the overall thermal stability of the material. The initial decomposition temperature is as high as 320℃, which meets the application requirements of wearable devices in complex environments.

[0034] In summary, the application of expanded microspheres is not a simple physical blending, but rather a synergistic enhancement of multiple advantages such as lightweight, mechanical strength, thermal insulation, and conductivity by inducing multi-scale structural regulation (micropore formation and interface design), laying a solid foundation for their application in cutting-edge fields such as flexible wearable electronic sensors. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the synthesis route for PCEP;

[0036] Figure 2 The images show the FTIR spectra of PCEP and its raw materials, where a is the PCEP-EM spectrum. 2% @CNT 0% PCEP-EM 2% @CNT 5% The FTIR spectra of the raw materials and c are shown; c is the PCEP-EM spectrum. 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% and PCEP-EM 2% @CNT 7.5% b is the FTIR spectrum; b is the PCEP-EM spectrum. 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% FTIR spectra;

[0037] Figure 3 For PCEP-EM 2% @CNT0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM 1% @CNT 5% and PCEP-EM 4% @CNT 5% Photos taken before and after immersion in DMF solvent for 10 days, with the top image showing before immersion and the bottom image showing after immersion;

[0038] Figure 4 This is a microstructure diagram of PCEP, where a is the PCEP-EM. 2% @CNT 0% a) is the SEM image; b) is the PCEP-EM image. 2% @CNT 2.5% SEM image; c is PCEP-EM 2% @CNT 5% SEM image; d is PCEP-EM 2% @CNT 7.5% SEM image; e is PCEP-EM 1% @CNT 5% SEM image; f is PCEP-EM 4% @CNT 5% SEM image;

[0039] Figure 5 This is a bar chart of PCEP density, where a represents PCEP-EM. 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% and PCEP-EM 2% @CNT 7.5% histogram of density; b is PCEP-EM 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% A histogram of density;

[0040] Figure 6 This is a bar chart of PCEP compression ratios, where a represents PCEP-EM. 2% @CNT 0% PCEP-EM2% @CNT 2.5% PCEP-EM 2% @CNT 5% and PCEP-EM 2% @CNT 7.5% a histogram of compression ratios; b is PCEP-EM 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% A histogram of compression ratios;

[0041] Figure 7 This is a bar chart of PCEP hardness, where a represents PCEP-EM. 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% and PCEP-EM 2% @CNT 7.5% Bar chart of hardness; b is PCEP-EM 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% A bar chart of hardness;

[0042] Figure 8 Here is the tensile stress-strain curve of PCEP, where a is the PCEP-EM. 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% and PCEP-EM 2% @CNT 7.5% The tensile stress-strain curve; b is the PCEP-EM. 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% The tensile stress-strain curve;

[0043] Figure 9 Here is the compressive stress-strain curve of PCEP, where a is the PCEP-EM. 2%@CNT 0% and PCEP-EM 2% @CNT 5% b is the compressive stress-strain curve; b is the PCEP-EM 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% The compressive stress-strain curve;

[0044] Figure 10 Here is the DSC curve for PCEP, where a is the PCEP-EM curve. 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% and PCEP-EM 2% @CNT 7.5% The DSC curve; b is the PCEP-EM curve. 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% The DSC curve;

[0045] Figure 11 Here is the TG curve for PCEP, where a is the PCEP-EM curve. 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% and PCEP-EM 2% @CNT 7.5% b is the TG curve; b is PCEP-EM 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% The TG curve;

[0046] Figure 12 The results are the thermal conductivity test results for PCEP, where a represents the thermal conductivity of PCEP-EM. 2% @CNT 0% PCEP-EM 2% @CNT 2.5%PCEP-EM 2% @CNT 5% and PCEP-EM 2% @CNT 7.5% Thermal conductivity; b is PCEP-EM 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% Thermal conductivity;

[0047] Figure 13 This is a histogram of resistance, where, Figure 13 a and Figure 13 b represents PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM 1% @CNT 5% and PCEP-EM 4% @CNT 5% Resistance histograms of the upper and lower surfaces;

[0048] Figure 14 The changes in ΔR / R0 signal of the material prepared for PCEP during sensing tests, where a represents the changes in ΔR / R0 signal when the finger is bent at different angles; and b represents the changes in ΔR / R0 signal when monitoring wrist swing behavior. Detailed Implementation

[0049] In the description of this invention, the terminology used is for descriptive purposes only and should not be construed as indicating or implying relative importance, or implicitly specifying the number of indicated technical features. In the description of this invention, "a plurality of" means two or more, unless otherwise expressly defined.

[0050] Unless otherwise stated, the experimental methods used in the following embodiments are all conventional methods; the materials, reagents, or instruments used, unless otherwise specified by the manufacturer, are all products that can be obtained from commercial channels; where specific conditions are not specified in the embodiments, experiments were conducted according to conventional conditions or conditions recommended by the manufacturer. Furthermore, the present invention does not limit the source of the raw materials used; unless otherwise specified, the raw materials used in the present invention are all conventional commercially available products in this technical field.

[0051] The density of conductive epoxy resin is not an independent variable with the final properties of the material (especially conductivity). Rather, it is a comprehensive indicator determined by the internal microstructure of the material and strongly correlated with other properties. Adjusting the filler dosage or replacing the filler solely for the purpose of reducing density may disrupt the carefully designed three-phase system (resin matrix, conductive filler, and pores) within the material, leading to performance degradation or even failure. The achievement of conductivity is highly dependent on the integrity and continuity of the conductive network within the matrix. This property does not increase linearly with the increase of filler content; rather, there is a critical point—the percolation threshold. When the filler content is below this threshold, the particles are isolated and cannot form effective electron transport paths, and the material still exhibits insulating properties. Only when the filler concentration reaches and exceeds the percolation threshold can a continuous three-dimensional conductive network be constructed, thus enabling the composite material to conduct electricity. If the amount of conductive filler (such as carbon nanotubes or carbon black) is reduced below the percolation threshold to reduce density, even if the apparent density of the material reaches the preset target, its conductivity will be lost, failing to meet application requirements. Conversely, if the filler content is excessively increased in pursuit of high conductivity, the conductive network will be strengthened, but the material density will also increase significantly, which is not conducive to the goal of lightweighting and may cause problems in processing technology and performance.

[0052] In particular, the interaction between fillers and the resin matrix is ​​a key factor determining the mechanical properties of composite materials. Epoxy resin itself is inherently brittle, and the addition of fillers not only imparts conductivity but also plays a role in reinforcement and toughening. The type, geometry, and surface chemical properties of the filler directly affect the interfacial bonding strength with the matrix. For example, changing the filler type without considering compatibility (such as replacing spherical particles with flakes, or using fillers with mismatched surface energy) may lead to a decrease in interfacial bonding, thereby significantly reducing the strength and toughness of the material. Furthermore, excessive filler addition can easily cause particle agglomeration, forming localized stress concentration points that become crack initiation points under load, thus increasing the brittleness of the material. From a process perspective, excessively high filler content will significantly increase the viscosity of the composite system, reduce the fluidity of the slurry, and consequently reduce its feasibility in processes such as potting, casting, or coating.

[0053] For porous conductive epoxy resin systems, density control is more complex, essentially depending on structural design rather than simply adjusting filler ratios. In such materials, achieving lightweighting relies primarily on introducing controllable pores. Pores can be considered a type of extremely low-density "filler," significantly reducing the overall density of the material. The presence of pores also provides space for the directional enrichment of conductive fillers on the pore walls or framework, thus contributing to the formation of efficient conductive pathways. However, there is an inherent trade-off between porosity and mechanical strength: higher porosity results in lower density, but also reduces the material's load-bearing capacity; therefore, an optimal balance must be found. The structural characteristics of the pores (e.g., whether they are open or closed pores, and the uniformity of pore size distribution) not only affect the material density but also directly determine the effectiveness of the conductive pathways and the material's thermal insulation, sound absorption, and other functional properties. More importantly, the distribution of conductive fillers within the pore structure is crucial to performance. If the compatibility of the filler with the foaming process or template method is not considered when changing the type of filler, it may result in uneven dispersion of the filler in the voids. Even if the apparent density of the material meets the requirements, its conductivity may not meet the application requirements.

[0054] Therefore, the density of conductive epoxy resin is not a parameter that can be adjusted independently, but rather a reflection of the combined effect of material formulation and microstructure. Any adjustment to the filler must be comprehensively considered within a design framework that coordinates the resin matrix, conductive phase, and pore structure.

[0055] This study successfully prepared a lightweight porous conductive epoxy resin composite material (PCEP) with high conductivity by simultaneously introducing expanded microspheres (EM) and multi-walled carbon nanotubes (CNTs) as composite fillers into an epoxy resin matrix. This preparation process allows for precise control of pore size and distribution, and optimizes the overall performance of PCEP by adjusting the content of expanded microspheres (EM, industrial grade) and CNTs, thereby achieving systematic regulation of key parameters such as material conductivity, mechanical behavior, and density. This study successfully prepared a series of PCEP materials with high strength, low density, and excellent conductivity, and systematically investigated their chemical structure, microstructure, mechanical properties, density, hardness, compressibility, electrical conductivity, thermal conductivity, and sensing properties. Experimental results show that the prepared PCEP materials not only possess good conductivity and mechanical strength but also significantly reduce the brittleness of epoxy resin, thus demonstrating good application potential in flexible electronics, smart packaging, and new energy devices.

[0056] Example 1

[0057] This embodiment relates to the preparation of porous conductive epoxy resin (PCEP).

[0058] (a) Experimental materials

[0059] Epoxy resin E44 (EP-E44, industrial grade) was purchased from Nantong Xingchen Synthetic Materials Co., Ltd. Xylene (analytical grade) and ethyl acetate (EAC, analytical grade) were purchased from Chengdu Kelong Chemical Co., Ltd. Multi-walled carbon nanotubes (CNT, industrial grade) were purchased from Shanghai Xiyan Technology Service Center. Expanded microspheres (EM, industrial grade) were purchased from AkzoNobel. Polyetheramine curing agent T403 (PEA-T403, industrial grade) was purchased from Shenzhen Huite Chemical Co., Ltd.

[0060] (II) Preparation of porous conductive epoxy resin (PCEP)

[0061] The synthetic route of PCEP is as follows Figure 1 As shown. Using PCEP-EM 2% @CNT 5% Taking sample preparation as an example, the synthesis process is as follows:

[0062] First, EP-E44 was heated to a fluid state at 80 °C. 30 g of EP-E44 and 45 g of xylene solvent were weighed and added to a beaker, followed by 0.794 g of EM and 2.023 g of CNT. The mixture was stirred thoroughly at room temperature using a high-speed dispersing disc mechanical stirrer, and then 9.675 g of T403 curing agent was added. Stirring continued for 1 h, and the mixture was then poured into a polytetrafluoroethylene mold for curing. After curing at room temperature for 12 h, the mixture was transferred to a 60 °C oven for 48 h. Finally, the sample was placed in an 80 °C vacuum oven to remove residual xylene solvent, yielding the final product PCEP-EM. 2% @CNT 5% Based on the different proportions of microspheres and CNTs used in the synthesis process, the prepared porous epoxy resin materials can be named as: PCEP-EM 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM 1% @CNT 5% PCEP-EM 4% @CNT 5% The specific formula is listed in Table 1.

[0063] Table 1. Formulation of PCEP

[0064]

[0065] Example 2

[0066] This embodiment relates to the testing and characterization of the PCEP prepared in Example 1.

[0067] (a) Fourier Transform Infrared Spectroscopy (FTIR)

[0068] PCEP-EM was analyzed using a Nicolet-560 Fourier transform infrared spectrometer from Nicolet Corporation, USA, in total reflectance (ATR) mode. 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM 1% @CNT 5% PCEP-EM 4% @CNT 5% The test was conducted, with a measurement range of 4000~400 cm. -1 The resolution is 4 cm. -1 The test temperature was room temperature.

[0069] The results are as follows Figure 2 As shown in the figure, the stretching vibration absorption peak of the epoxy group -O-CH2-CH-O- in EPE-44 appears at 912 cm⁻¹. -1 PCEP-EM 2% @CNT 0% In the FTIR spectrum, the stretching vibrations of -O-CH2-CH-O- in EPE-44 are at 912 cm⁻¹. -1 The absorption peak at that location completely disappears; this phenomenon also occurs in PCEP-EM. 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM 1% @CNT 5% PCEP-EM 4% @CNT 5% The sample indicates that the epoxy group in EPE-44 undergoes a reverse ring-opening reaction with the amino group in T403, and unreacted EPE-44 is not present in the product. The stretching vibration absorption peak of -NH2 in T403 in the figure shows a double peak, appearing at 3372 cm⁻¹. -1 and 3295 cm -1 PCEP-EM 2% @CNT0% In the FTIR spectrum, the stretching vibration of -NH2 in T4O3 is at 3372 cm⁻¹. -1 and 3295 cm -1 The absorption peak intensity at 3407 cm⁻¹ weakened, and the double peak transformed into a broad peak, which was attributed to the stretching vibration of -NH at 3407 cm⁻¹. -1 This phenomenon also occurs in PCEP-EM. 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM 1% @CNT 5% PCEP-EM 4% @CNT 5% In the sample, at 3402 cm -1 3402 cm -1 3393 cm -1 3393 cm -1 and 3388 cm -1 Characteristic absorption peaks belonging to -NH in PCEP appeared at [locations]. Meanwhile, PCEP-EM [data / images]... 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM 1% @CNT 5% PCEP-EM 4% @CNT 5% In the FTIR spectrum, at 3407 cm⁻¹ -1 3402 cm -1 3402 cm -1 3393 cm -1 3393 cm -1 and 3388 cm -1 A characteristic absorption peak belonging to the ring-opening product with an epoxide group appeared. At 1174 cm⁻¹ -1 1106 cm -1 1179 cm -1 1181 cm -1 1179 cm -1 and 1177 cm -1The characteristic absorption peak at 1601 cm⁻¹ is attributed to the ether bond COC. -1 1608 cm -1 1612 cm -1 1608 cm -1 1605 cm -1 and 1610 cm -1 The six absorption peaks at the FITR spectrum are attributed to the stretching vibrations of the benzene ring skeleton. As the CNT content increases, it affects the scattering or absorption of infrared light, and the vibrational intensity of the absorption peaks in the FITR spectrum weakens. These peaks correspond one-to-one with the characteristic infrared absorption peaks of the designed PCEP, indicating that the PCEP was successfully synthesized.

[0070] (II) Scanning Electron Microscopy (SEM) Analysis

[0071] PCEP-EM was observed using an Apreo S HiVoc field emission scanning electron microscope from Thermo Fisher Scientific, USA. 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM 1% @CNT 5% PCEP-EM 4% @CNT 5% The microscopic morphology.

[0072] Figure 4 PCEP-EM was demonstrated 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM 1% @CNT 5% PCEP-EM 4% @CNT 5% SEM images of the cross-section of the sample at different magnifications. (Source: [Insert source here]) Figure 4 As can be seen from b, when the CNT content is low, the CNTs are relatively uniformly distributed in the epoxy resin matrix, the microspheres are unaffected and exist independently, and there is no obvious interaction between the two. Figure 4As can be seen from c, as the CNT content increases, the CNTs begin to interact and form a local conductive network, and the microspheres begin to be encapsulated in the gaps between the local CNT networks. Figure 4 As can be seen from d, when the CNT content is high, van der Waals forces intensify aggregation, forming large-area aggregation regions, with microspheres being significantly pushed to the edges of these regions. This indicates that as the CNT content increases, conductive pathways are initially formed, enhancing the conductivity of the porous conductive epoxy resin material. However, when the CNT content reaches a certain level, it leads to large-area CNT aggregation, which obstructs conductive pathways, resulting in decreased conductivity. Furthermore, it pushes out microspheres, forming noticeable pores or defects, thus deteriorating mechanical properties. Figure 4 As shown in e, 4c, and 4f, when the added expanded microspheres increase from 1% to 4%, the porous conductive epoxy resin cross-section exhibits a closed-cell structure with a relatively large diameter. With increasing microsphere content, the number of pores formed in the porous conductive epoxy resin cross-section increases, but a large number of closed-cell structures still exist, and the pore structure does not change significantly. This is because the microspheres are encapsulated by the epoxy resin during the curing process, preventing them from connecting and forming isolated small pores. This indicates that the microsphere content affects the CNT distribution, thereby affecting the conductivity of the porous conductive epoxy resin material.

[0073] (iii) Density test

[0074] The density of different samples was tested using a MAY-D80 densitometer from China Miaozhun Scientific Instruments Co., Ltd. The test temperature was room temperature, and each sample was tested three times, with the average value taken.

[0075] Depend on Figure 5 As can be seen from a and 5b, the addition of EM effectively reduced the density of PCEP, resulting in all samples having a density below 0.9 g / cm³. 3 While keeping the EM addition amount constant, the density of PCEP increased slightly with increasing CNT content in the matrix resin, and decreased significantly with increasing microsphere content. This is because the density of CNT is slightly higher than that of the epoxy resin matrix, so increasing its volume fraction slightly increases the density of PCEP. The density of microspheres is much lower than that of the epoxy resin matrix; after adding microspheres, they form a porous structure within the resin, resulting in a significant decrease in the overall density of the PCEP composite material due to the introduction of lightweight fillers.

[0076] (iv) Differential Scanning Calorimetry (DSC)

[0077] A Netzsch DSC204 differential scanning calorimeter was used. Under a nitrogen atmosphere, the sample was first heated to 100°C at a heating rate of 40°C / min and held for 3 minutes to eliminate thermal history. Then, the sample was cooled to -60°C at a cooling rate of 10°C / min, and then heated to 180°C at a heating rate of 10°C / min. The mass of each sample was approximately 6 mg.

[0078] Depend on Figure 10 It can be seen that PCEP-EM 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM1%@CNT 5% and PCEP-EM 4% @CNT 5% The glass transition temperatures (Tg) are 80℃, 90℃, 95℃, 92℃, 90℃, and 85℃, respectively. Figure 10 It was observed that when the added EM content remained constant, the Tg of PCEP significantly increased with increasing CNT content; however, when the CNT content increased further, the Tg of PCEP decreased slightly. This is because the interaction between CNTs and epoxy resin molecular chains in the matrix restricts the movement of epoxy resin segments, thus increasing Tg. Additionally, excessive CNTs can aggregate in the matrix, forming local defects and weakening interfacial bonding, thereby decreasing Tg. Figure 10 As shown in b, when the added CNT content remains constant at 5%, the Tg of PCEP gradually increases as the EM content increases from 1% to 4%, but the Tg decreases slightly when the EM content increases further. This is because uniform dispersion of EM in the matrix enhances the physical filling effect, thus increasing the Tg. Additionally, excessive EM can aggregate, leading to an increase in free volume and easier activation of chain segment movement, resulting in a decrease in Tg.

[0079] (v) Resistance test

[0080] The surface resistance of the upper and lower surfaces of different PCEP samples was tested using a KEITHLEY DMM6500 digital multimeter.

[0081] Depend on Figure 13 It can be seen that when the added EM content remains constant at 2%, as the CNT content gradually increases to 7.5%, the surface resistance of PCEP changes from PCEP to EM. 2% @CNT 2.5% Reduced from 20 kΩ to PCEP-EM2% @CNT 7.5% It is 2.8 kΩ; the lower surface resistance of the PCEP is from PCEP-EM 2% @CNT 2.5% Reduced from 150 kΩ to PCEP-EM 2% @CNT 7.5% It is 1.3 kΩ.

[0082] The surface resistance of PCEP gradually decreases as the CNT content in the matrix increases, forming continuous conductive pathways. When the added CNT content remains constant at 5%, the resistance of PCEP increases significantly as the EM content gradually increases from 1% to 4%. This is because EM forms a physical barrier in the matrix, promoting CNT aggregation and disrupting the conductive pathways, leading to a gradual increase in PCEP resistance. Simultaneously, due to… Figure 13 It can be observed that the resistance of the lower surface of the sample is generally lower than that of the upper surface. This may be because CNTs settle during the curing process while EM floats during the curing process, resulting in a higher CNT concentration on the lower surface.

[0083] (vi) Monitoring human movement test

[0084] PCEP-EM data was collected using a KEITHLEY DMM6500 digital multimeter. 2% @CNT 5% Sensors are used to monitor signal changes during human movement.

[0085] PCEP has advantages such as high strength, light weight and high sensitivity sensing performance, making it suitable for embedding in wearable electronic devices to monitor various human movement behaviors. Figure 14 a explains the spline PCEP-EM 2% @CNT 5% It is attached to the finger joints to sense changes caused by different bending angles of the fingers.

[0086] Experimental results show that when the fingers are bent into different shapes, PCEP-EM 2% @CNT 5% This will generate different ΔR / R0 signal strengths. This is because a larger bending angle will cause the PCEP-EM to... 2% @CNT 5% This causes greater deformation, resulting in fewer paths in the conductive network, and thus a significant increase in the ΔR / R0 signal strength. Figure 14 b demonstrates PCEP-EM 2% @CNT 5% The spline is attached to the wrist to monitor wrist movement dynamics. As the wrist swings back and forth, the PCEP-EM... 2% @CNT 5%The resistance will change accordingly, resulting in a set of regular ΔR / R0 signal waveforms.

[0087] The experimental results above show that PCEP sensors can be effectively applied to human motion monitoring and recognition devices, meaning that the material can be used not only as a strain sensor but also as a pressure sensor.

[0088] (vii) Tensile mechanical property testing

[0089] The tensile mechanical properties of PCEP samples were tested using an Instron-4302 universal testing machine from Instron Corporation, USA. The dumbbell-shaped specimens (15 mm × 4 mm × 1 mm) were tested at room temperature at a tensile rate of 50 mm / min, and each sample was tested at least 5 times.

[0090] Depend on Figure 8 From Table 2, we can obtain PCEP-EM 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM1%@CNT 5% and PCEP-EM 4% @CNT 5% The fracture strengths were 9.24 MPa, 4.23 MPa, 4.01 MPa, 2.92 MPa, 5.95 MPa, and 1.75 MPa, respectively. When the EM content in the matrix remained constant, the fracture strength of the composite material gradually decreased with increasing CNT content in the matrix. This is because the CNTs added to the matrix aggregate, forming stress concentration points and weakening the reinforcement effect. When the CNT content in the matrix remained constant, the fracture strength of the composite material gradually decreased with increasing EM content in the matrix. This is because microsphere accumulation leads to matrix discontinuity disruption, increases the risk of interfacial debonding, and weakens the overall load-bearing capacity. Figure 8 As shown in Table 2, PCEP-EM 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM1%@CNT 5% and PCEP-EM 4% @CNT5% The Young's moduli of the composite materials were 295.58 MPa, 27.18 MPa, 22.25 MPa, 17.85 MPa, 30.74 MPa, and 6.56 MPa, respectively. When the EM content in the matrix remained constant, the Young's modulus of the composite material gradually decreased with increasing CNT content. This is because the increased CNT content occupies more matrix volume, disrupting the continuity of the resin matrix and hindering effective load transfer, thus reducing the Young's modulus. When the CNT content in the matrix remained constant, the Young's modulus of the composite material gradually decreased with increasing EM content. This is because the low-modulus microspheres diluted the matrix rigidity, leading to a decrease in Young's modulus.

[0091] Furthermore, as shown in Table 2, PCEP-EM was obtained. 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM1%@CNT 5% and PCEP-EM 4% @CNT 5% The elongation at break were 19.68%, 48.96%, 53.76%, 62.33%, 67.54%, and 31.08%, respectively. When the EM content in the matrix remained constant, the elongation at break of the composite material gradually increased with increasing CNT content in the matrix. This is because the high aspect ratio and strong interfacial bonding of CNTs in the matrix can bridge cracks, forcing crack paths to deflect, prolonging crack propagation time, absorbing more energy, and achieving toughening. When the CNT content in the matrix remained constant, the elongation at break of the composite material gradually decreased with increasing EM content in the matrix. This is because the interfacial bonding between microspheres and resin is weak, making them prone to debonding and forming pores under stress, which become crack initiation points and accelerate fracture.

[0092] Table 2

[0093]

[0094] (viii) Thermogravimetric analysis (TGA)

[0095] PCEP samples were tested using a Thermogravimetric Analysis (TGA) SDT-Q600 instrument from Thermogravimetric Analysis Corporation (TAI). Samples ranging from 3 to 8 mg were heated from 25°C to 600°C at a rate of 10°C / min under a nitrogen atmosphere. The mass change of different samples during the heating process was recorded.

[0096] Depend on Figure 11 As shown in Table 3, PCEP-EM2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM1%@CNT 5% and PCEP-EM 4% @CNT 5% The initial decomposition temperatures were 290℃, 305℃, 320℃, 315℃, 300℃, and 310℃, respectively; the maximum decomposition rate temperatures were 330℃, 305℃, 320℃, 315℃, 340℃, and 340℃, respectively; and the residual mass fractions at 600℃ were 8%, 12%, 14%, 19%, 16%, and 12%, respectively. Figure 11 It was observed that when the added EM content remained constant at 2%, as the CNT content increased from 0 to 7.5%, the initial decomposition temperature, maximum decomposition rate temperature, and residual amount at 600℃ of the PCEP sample gradually increased. This is because CNTs themselves are carbon materials, which are difficult to degrade at high temperatures, thus significantly increasing carbon residue and thermal stability, leading to an increase in the initial decomposition temperature, maximum decomposition rate temperature, and residual amount at 600℃. Figure 11 As shown in b, when the added CNT content remains constant at 5%, the initial decomposition temperature, maximum decomposition rate temperature, and residual amount at 600℃ of the PCEP sample gradually decrease as the EM content increases from 1% to 4%. This is because EM is a polyacrylonitrile resin material, which has poor thermal stability under high-temperature conditions. Excessive EM will weaken the thermal stability due to interfacial defects, leading to a decrease.

[0097] Table 3

[0098]

[0099] (ix) Compression ratio test

[0100] First, place the digital altimeter probe (model P10) onto a solid and stable horizontal plane, and zero it. Lift the probe, then move the PCEP sample below it. Slowly lower the probe and press a U-shaped weight (500 g or 1000 g) around it to ensure the EPU sample is flat, recording the value T1. Finally, load a 500 g weight onto the central axis of the digital altimeter, wait 60 seconds, and record the value T2. Calculate the compression ratio of the EPU using formula 2-1. Following the above testing procedure, measure at least three times at different locations on the same sample and calculate the average value.

[0101] Compression ratio (%) = (T1-T2) / T1×100% (2-1)

[0102] Where T1 and T2 are the sample thicknesses under the initial load and the 500 g load, respectively, in millimeters (mm).

[0103] Depend on Figure 6 It can be seen that when the EM content is 2%, the compression ratios of PCEP with CNT contents of 0%, 2.5%, 5%, and 7.5% are 5.25%, 13.71%, 14.17%, and 10.41%, respectively. When the CNT content is 5%, as the microsphere content increases from 1% to 4%, the compression ratios of PCEP-EM... 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% The compression rates were 20.74%, 14.17%, and 10.41%, respectively.

[0104] The above results indicate that adding expanded microspheres can effectively improve the compressibility of epoxy resin, while adding a certain amount of CNTs is detrimental to the compressibility of epoxy resin. This is mainly because when expanded microspheres are uniformly dispersed in the epoxy resin matrix, they can form a local porous structure, increasing the matrix toughness and dispersing the external stress. As the microsphere content increases, the overall compression deformation can be reduced, thus lowering the compression ratio. However, when CNTs are added, the added CNTs will agglomerate in the epoxy resin matrix, forming aggregates that develop into crack initiation points, leading to stress concentration and accelerating stress failure. Therefore, excessively high CNT content is detrimental to the material's toughness.

[0105] (x) Swelling test

[0106] The PCEP sample was cut into circular pieces using a circular cutter, and then placed in DMF solvent. After soaking for 7 days, the appearance of the sample before and after swelling was observed and recorded with a mobile phone.

[0107] like Figure 3 As shown, after immersion in DMF solvent for 10 days, all prepared PCEP exhibited significant swelling but none dissolved. This is mainly because the chemical cross-linking network restricts molecular chain movement, preventing dissolution and only causing swelling. Solvent resistance tests indicate that the PCEP formed a stable cross-linked network structure, exhibiting good solvent resistance. Figure 3It can be seen that at the beginning of the experiment, all six samples floated on the surface in DMF liquid. After ten days, they all sank, with most sinking to the bottom. This is because the density of PCEP is less than the density of DMF solvent, so the samples float on the surface. After soaking for ten days, the composite material absorbs DMF molecules and swells. The internal pores of the material are filled with solvent, and the overall density of the sample gradually increases, exceeding the density of DMF solvent, causing it to sink, or even sink to the bottom. Excessive EM will weaken the resin cross-linking network, resulting in a loose structure of the composite material after swelling, forming continuous channels inside. This makes the density of the composite material after swelling close to that of DMF, and it exhibits a suspension phenomenon under the influence of small disturbances. (XI) Hardness Test

[0108] Place the PCEP sample on a firm and stable horizontal plane. Then, load a Shore D hardness tester with a 5 kg weight on its central axis onto the sample under non-impact conditions, ensuring the base is parallel to the PCEP sample and applying sufficient pressure to guarantee tight contact between the base and the sample. Read the hardness tester reading after 15 ± 1 s; if an instantaneous reading is specified, read the maximum value within 1 s after the base and sample reach tight contact. Measure three hardness values ​​at least 6 mm apart on the same sample and calculate their average.

[0109] Depend on Figure 7 It can be seen that when the added EM content is 2%, and the added CNT content is 0%, 2.5%, 5%, and 7.5%, PCEP-EM 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% and PCEP-EM 2% @CNT 7.5% The hardness values ​​were 57.6 D, 38.2 D, 44.0 D, and 28.6 D, respectively. When the CNT content was 5%, and the microsphere content was 1%, 2%, and 4%, the PCEP-EM... 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% The hardness values ​​are 37.0 D, 44.0 D, and 21.7 D, respectively.

[0110] In addition to PCEP-EM 2% @CNT 5%In addition, with an EM content of 2%, the hardness of PCEP gradually decreased with increasing CNT content. This is because CNTs agglomerate in the epoxy resin matrix, and these agglomerates become weak areas, leading to weakened interfacial bonding and easier indentation penetration, thus reducing the hardness of the composite material. With an EM content of 5%, the hardness of PCEP also gradually decreased with increasing EM content. This is because excessively high microsphere content in the epoxy resin matrix leads to increased interfacial defects. Hollow microspheres can rupture, forming pores, causing stress concentration, and becoming crack initiation points, making indentation propagation easier and reducing the hardness of PCEP. PCEP-EM 2% @CNT 5% It is a special case with high hardness because of the synergistic effect of EM and CNT. CNT can fill the gaps between microspheres, forming an interpenetrating reinforcing network, inhibiting interface slippage, and improving the overall hardness.

[0111] (xii) Compression mechanical property testing

[0112] The samples used for compression testing were circular rectangular strips with a diameter of 25 mm and a height of 30 mm. The compression test was conducted using an Instron-4302 (Instron, USA) instrument at room temperature, using a 1 kN sensor, and a pulse velocity of 50 mm / min. -1 By compressing the spline at a certain velocity, the stress-strain curve of the material is obtained.

[0113] from Figure 9 As can be seen, if the added EM content is always 2%, then PCEP-EM with 5% CNT added... 2% @CNT 5% Its elastic modulus and ultimate compressive strength are comparable to those of PCEP-EM without CNTs. 2% @CNT 0% The significant improvement is due to the fact that the added CNTs form a three-dimensional network within the epoxy resin matrix, restricting the movement of molecular chains and thus increasing the material's rigidity. Figure 9 As shown in b, if the added CNT content remains constant at 5%, during the stage when the EM content increases from 1% to 4%, PCEP-EM 1% @CNT 5% PCEP-EM 2% @CNT 5% and PCEP-EM 4% @CNT 5% The compressive stress gradually decreases, mainly because EM can significantly reduce the density of the material. During compression, it absorbs energy through collapse. If the EM content exceeds the normal level, it will cause the porous structure in the epoxy resin matrix to continuously increase, and the material strength will show a downward trend. The above results reflect the performance of PCEP-EM.2% @CNT 5% It is the optimal solution in terms of mechanical performance. CNTs can fill the gaps between microspheres, creating a hierarchical reinforcement structure and enhancing the overall load-bearing capacity.

[0114] (xiii) Thermal conductivity test

[0115] The samples were cut into circular pieces with a thickness greater than 2 mm, and the thermal conductivity of different samples was tested using a Hot Disk 2500S thermal constant analyzer from Hot Disk GmbH, Sweden. The test temperature was room temperature, and the thermal conductivity probe was a Kapton 7577. The appropriate heating power and duration were adjusted according to different samples.

[0116] Thermal conductivity is an important parameter for evaluating the thermal insulation performance of materials. The lower the value, the better the thermal insulation performance of the material. Figure 12 These are the thermal conductivity test results for PCEP. Figure 12 As can be seen from this, PCEP-EM 2% @CNT 0% PCEP-EM 2% @CNT 2.5% PCEP-EM 2% @CNT 5% PCEP-EM 2% @CNT 7.5% PCEP-EM 1% @CNT 5% and PCEP-EM 4% @CNT 5% The thermal conductivity values ​​were 0.09509 W / (mK), 0.1355 W / (mK), 0.1737 W / (mK), 0.1774 W / (mK), 0.1836 W / (mK), and 0.1254 W / (mK), respectively. If the added EM content remained at 2%, the thermal conductivity of PCEP continuously increased as the CNT content gradually increased from 0% to 7.5%, due to the excellent thermal conductivity of CNTs themselves. When the added CNT content remained constant, the thermal conductivity of PCEP decreased sharply as the EM content gradually increased from 1% to 4%. The gradual decrease in the thermal conductivity of the material is mainly attributed to the increase in EM content, which introduces more porous structures into the epoxy resin matrix. These porous structures form a thermal insulation barrier in the material, effectively preventing the transfer of heat within the material. Because PCEP exhibits a low thermal conductivity, it displays excellent thermal insulation properties, making it potentially applicable in various application scenarios that require good thermal insulation performance.

[0117] It should be noted that the specific embodiments described above are exemplary, and those skilled in the art can devise various solutions inspired by the disclosure of this invention. These solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and not intended to limit the scope of the claims. The scope of protection of this invention is defined by the claims and their equivalents.

Claims

1. A porous conductive epoxy resin composite material, characterized in that, The material has a density of less than 0.9 g / cm³. 3 The porous conductive epoxy resin composite material with a uniform closed-cell structure has a tensile strength of 4.01 MPa, a tensile elongation at break of 53.76%, an upper surface resistivity of 2 KΩ, a lower surface resistivity of 2.6 KΩ, and comprises the following components: By weight, the composition includes 30 parts epoxy resin E44, 45 parts xylene, 0.794 parts closed-cell expanded microspheres, 2.023 parts multi-walled carbon nanotubes, and 9.675 parts polyetheramine curing agent T403, wherein the closed-cell expanded microspheres are fully foamed and have a diameter of 20-40 μm. The preparation method of the porous conductive epoxy resin composite material includes the following steps: S1, by weight, 30 parts of epoxy resin E44 in a fluid state are dissolved in 45 parts of xylene solvent, and then 0.794 parts of fully foamed expanded microspheres and 2.023 parts of multi-walled carbon nanotubes are added and mixed evenly. S2 is added with 9.675 parts by weight of polyetheramine curing agent T403, and after stirring for no less than 1 hour, the mixture is poured into a polytetrafluoroethylene mold and cured. After curing S3 at room temperature for 12 hours, it is transferred to an oven at 60-80 ℃ for 48 hours of curing. S4. Place the sample in a vacuum oven at 80-100 ℃ and evacuate to remove residual xylene solvent.

2. The porous conductive epoxy resin composite material according to claim 1, characterized in that, Epoxy resin E44 was heated at 80°C to obtain epoxy resin E44 in a flowable state.

3. The porous conductive epoxy resin composite material according to claim 1, characterized in that, In S3, after curing at room temperature for 12 hours, it is transferred to a 60°C oven for curing for 48 hours.

4. The porous conductive epoxy resin composite material according to claim 1, characterized in that, In S4, the sample is placed in an 80°C vacuum oven and evacuated to remove residual xylene solvent.

5. Use of the porous conductive epoxy resin composite material as described in any one of claims 1-4 in improving the mechanical and electrical properties of equipment or components.

6. The use according to claim 5, characterized in that, The equipment or components are electronic and communication equipment with electromagnetic shielding and anti-static functions, lightweight conductive structural components, electric heating and temperature control components, conductive buffering and vibration damping and energy absorption components, and piezoresistive and / or strain sensing components.

7. A flexible sensor, characterized in that, It is prepared based on the porous conductive epoxy resin composite material according to any one of claims 1-4.

8. The flexible sensor according to claim 7, characterized in that, The flexible sensor is used to monitor human movement behaviors, including finger bending or wrist swinging.

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