Composite material for electrical fence and preparation method thereof

Abstract

The invention relates to the technical field of polymer composite materials, in particular to a composite material for an electrical fence and a preparation method thereof.The composite material is prepared from, by weight, 100-120 parts of bisphenol A epoxy resin, 40-60 parts of polyurethane prepolymer, 10-15 parts of carboxyl-terminated butyronitrile liquid rubber CTBN and 5-20 parts of polyether amine, a multi-scale toughening network is formed by 0.3-0.8 part by weight of aminated graphene nanosheets, 1.0-3.0 parts by weight of nanometer aluminum oxide, 10-30 parts by weight of chopped glass fibers, 20-30 parts by weight of 4, 4 '-diaminodiphenyl sulfone, 0.5-1.5 parts by weight of an imidazole catalyst, 0.2-0.6 part by weight of an antioxidant, 0.3-0.7 part by weight of an ultraviolet light absorber and 0.5-1.5 parts by weight of a dispersing agent, and meanwhile the toughness and the strength are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer composite materials, and particularly to a composite material for an electric fence and a preparation method thereof. The composite material is toughened by liquid rubber and strengthened by graphene functionalization on the basis of epoxy resin, and a polyurethane interpenetrating network structure is introduced. It has excellent mechanical properties, weather resistance, impact resistance and electrical insulation properties, and is particularly suitable for insulating support materials of electric fences in outdoor environments. Background Art

[0002] As a common security device, one of the key components of an electric fence system is a composite material member for support and insulation. Such materials need to have excellent mechanical properties, weather resistance, impact resistance and electrical insulation properties at the same time to ensure long-term reliable operation in harsh outdoor environments. At present, engineering plastics or epoxy resin-based composite materials are mainly used as insulating materials for electric fences, but there are still some obvious deficiencies in the existing technologies.

[0003] U.S. Patent US5891367A discloses a conductive epoxy resin adhesive, which is based on a polymer reaction product filled with silver flakes and uses a liquid bisphenol A epoxy resin and a polypropyleneoxyamine curing agent with a very low hydrolyzable chlorine content to achieve high impact resistance and stable resistance characteristics. However, this technology is mainly optimized for conductive performance, is not suitable for electric fence applications that require insulating performance, and has poor weather resistance in outdoor environments.

[0004] Chinese Patent CN104774429A introduces an electrical insulating epoxy resin composite material, which contains 0.85 - 1.05 parts of epoxy resin, 1 - 1.1 parts of curing agent and 3.05 - 3.3 parts of filler by weight, and has good DC voltage surface flashover and internal breakdown tolerance capabilities. However, this material does not solve the inherent brittleness problem of epoxy resin, is prone to cracking in low-temperature environments, and has limited environmental adaptability.

[0005] U.S. Patent US4771137A discloses an electric fence wire insulator, which is made of a non-conductive synthetic resin into an integral body and includes a transverse spark shielding layer. Although this product has certain insulating properties, it lacks a composite reinforcement structure, has insufficient strength, and has poor aging resistance, and cannot meet the requirements of long-term outdoor use.

[0006] International Patent WO1992008760A1 describes an acrylic-modified epoxy resin adhesive, which is modified with acrylate to improve rheological control and introduce the interaction effect of hydroxyl functionality enhancement and rheological control agent. However, this material is mainly optimized for bonding applications and does not consider the comprehensive performance required for electric fence materials.

[0007] In recent years, as a new type of nanomaterial, graphene has attracted much attention due to its excellent mechanical, thermal, and electrical properties. For example, Chinese Patent CN111187587A discloses a composite wall caulking sealant based on epoxy resin modification, which improves weather resistance and hydrophobicity by using graphene carrier modification technology. However, this technology does not consider the multi-phase synergistic toughening mechanism and cannot achieve the balanced optimization of mechanical and electrical properties.

[0008] Currently, the existing technologies for electric fence applications mainly have the following deficiencies:

[0009] 1) Although conventional epoxy resin materials have excellent insulation properties, their inherent brittleness leads to poor impact resistance, especially prone to cracking in low-temperature environments;

[0010] 2) Single modification methods (such as liquid rubber toughening or filler reinforcement) often lead to material property imbalance, such as increased toughness but decreased strength, or increased strength but insufficient toughness;

[0011] 3) The aging problem of epoxy resin in outdoor environments has not been solved, resulting in a decline in long-term use performance;

[0012] 4) There is a lack of a comprehensive performance optimization scheme for the special application environment of electric fences (large temperature fluctuations and drastic humidity changes).

[0013] Therefore, there is an urgent need to develop a composite material with high toughness, high strength, aging resistance, and excellent electrical insulation performance to meet the special requirements of electric fence systems. Summary of the Invention

[0014] The purpose of the present invention is to address the deficiencies of the existing technologies and provide a graphene / liquid rubber synergistically modified epoxy resin interpenetrating network composite material for electric fences and its preparation method. Through the synergistic effect of multiple modification technologies, this material simultaneously possesses excellent mechanical properties, weather resistance, impact resistance, and electrical insulation performance, and is particularly suitable for electric fence systems in outdoor environments.

[0015] To achieve the above purpose, the present invention provides a composite material for electric fences, which is composed of the following components in parts by weight:

[0016] 100 - 120 parts by weight of bisphenol A epoxy resin,

[0017] 40 - 60 parts by weight of polyurethane prepolymer,

[0018] 10 - 15 parts by weight of carboxyl-terminated butadiene acrylonitrile liquid rubber (CTBN),

[0019] 5 - 20 parts by weight of polyetheramine,

[0020] 0.3 - 0.8 parts by weight of amino-functionalized graphene nanosheets,

[0021] 1.0 - 3.0 parts by weight of nano-aluminum oxide,

[0022] 10 - 30 parts by weight of chopped glass fibers,

[0023] 20 - 30 parts by weight of 4,4'-diaminodiphenyl sulfone,

[0024] 0.5 - 1.5 parts by weight of imidazole catalyst,

[0025] 0.2 - 0.6 parts by weight of antioxidant,

[0026] 0.3 - 0.7 parts by weight of ultraviolet absorber,

[0027] 0.5 - 1.5 parts by weight of dispersant.

[0028] Preferably, the epoxy equivalent of the bisphenol A epoxy resin is 170 - 280 g / eq, the acrylonitrile content of the carboxyl-terminated nitrile liquid rubber is 24 - 28 wt%, the average lateral size of the amino-functionalized graphene nanosheets is 1 - 5 μm, and the thickness is 2 - 8 nm.

[0029] Furthermore, the polyetheramine includes polyether diamine D400 and polyether diamine D2000, and their weight ratio is 30:70 to 70:30. This combination can provide flexible chain segments with different chain lengths, effectively balancing strength and toughness.

[0030] The composite material has an interpenetrating network structure, including the interpenetration of an epoxy resin network and a polyurethane network; the carboxyl-terminated nitrile liquid rubber reacts with the epoxy resin to form a microphase separation structure, and its microphase size is 0.5 - 2 μm. This multiphase structure is the key to achieving the optimization of comprehensive performance in the present invention.

[0031] The composite material of the present invention maintains stable electrical insulation performance in the temperature range of -40°C to 80°C, with a volume resistivity greater than 10 12 Ω·cm and a dielectric strength greater than 20 kV / mm, and is particularly suitable for electrical fence applications under extreme weather conditions.

[0032] The present invention also provides a method for preparing the above composite material, including the following steps:

[0033] (1) Vacuum dehydrate the bisphenol A epoxy resin at 80 ± 2°C for 2 - 3 hours, and control the moisture content to be ≤ 0.05%;

[0034] (2) Ultrasonically disperse the amino-functionalized graphene nanosheets in acetone for 30 - 40 minutes, with an ultrasonic power of 300 - 400 W, and then perform solvent replacement to obtain a graphene / methyl ethyl ketone dispersion;

[0035] (3) Preheat the carboxyl-terminated nitrile liquid rubber (CTBN) to 70 ± 2 °C to reduce viscosity, and carry out decompression treatment for 15 - 20 minutes to remove air bubbles;

[0036] (4) Heat the epoxy resin treated in step (1) to 90 ± 2 °C, slowly add the preheated CTBN in step (3) at a feeding rate of 1 - 2 g / min. After mixing evenly, raise the temperature to 120 ± 2 °C for pre-reaction for 40 - 60 minutes, and control the pre-reaction conversion rate at 20% - 30%;

[0037] (5) Cool the pre-reaction system in step (4) to 60 ± 2 °C, and batchwise add the graphene dispersion liquid in step (2) under high-shear dispersion. The dispersion time is 30 - 40 minutes, and then remove the solvent under reduced pressure, controlling the solvent residue < 0.5%;

[0038] (6) In a three-necked reaction kettle, react polyether polyol with isophorone diisocyanate at 70 ± 2 °C for 80 - 100 minutes to prepare a polyurethane prepolymer;

[0039] (7) Slowly add the polyurethane prepolymer in step (6) to the mixed system in step (5) at 70 ± 2 °C at a feeding rate of 2 - 3 g / min, blend for 20 - 30 minutes, and then carry out decompression degassing;

[0040] (8) Cool the mixture in step (7) to 90 ± 2 °C, add an imidazole catalyst and polyetheramine, mix evenly, then raise the temperature to 120 ± 2 °C, add 4,4'-diaminodiphenyl sulfone, stir until completely dissolved, add nano-aluminum oxide, chopped glass fibers and other additives, and mix evenly;

[0041] (9) Pour the mixture in step (8) into a mold preheated to 120 ± 5 °C at 80 ± 2 °C for segmented curing: first maintain at 120 ± 2 °C for 30 - 40 minutes, then raise the temperature to 150 ± 2 °C and maintain for 60 - 90 minutes, and finally raise the temperature to 180 ± 2 °C and maintain for 120 - 180 minutes;

[0042] (10) Demold the cured material, carry out stress relief treatment at a temperature of Tg - 20 °C for 60 - 90 minutes, and slowly cool to room temperature.

[0043] Preferably, the degree of pre-reaction in step (4) is controlled by monitoring the changes in the viscosity of the mixture and the epoxy group content. When the viscosity increases to 1.5 - 2 times the initial value, the pre-reaction is terminated. This control method can ensure that CTBN and epoxy resin form an optimal block copolymer structure, providing a basis for subsequent microphase separation.

[0044] More preferably, in step (5), a high-shear disperser is used for graphene dispersion. The dispersion process includes initial low-speed dispersion at 2,000 rpm for 10 - 15 minutes; high-speed dispersion at 4,000 - 5,000 rpm for 15 - 20 minutes; and final low-speed dispersion at 2,000 rpm for 10 minutes. This multi-stage dispersion process can effectively prevent graphene agglomeration and ensure dispersion uniformity.

[0045] Furthermore, in step (6), for the preparation of the polyurethane prepolymer, a mixed polyol of 70 - 80 parts by weight of polyether diol (molecular weight 2,000) and 20 - 30 parts by weight of polyether triol (molecular weight 450) is used, and the dosage of isophorone diisocyanate is 1.05 - 1.10 times the calculated amount, and the equivalent ratio of NCO groups to OH groups is 1.05 - 1.10. This ratio can ensure the optimal crosslinking density of the polyurethane network.

[0046] Preferably, in step (9), the crosslinking degree is monitored by differential scanning calorimetry (DSC) during the segmented curing process, and the glass transition temperature is measured by dynamic mechanical analysis (DMA) to ensure that the crosslinking degree ≥ 95%. This precise control can ensure stable material properties.

[0047] The beneficial effects of the present invention include:

[0048] 1) Through the synergistic effect of amino-functionalized graphene and liquid rubber, a multi-scale toughening network is formed, simultaneously improving toughness and strength, and still maintaining excellent impact strength in a low-temperature environment of -40°C, solving the brittleness problem of traditional epoxy materials;

[0049] 2) Epoxy resin and polyurethane form an interpenetrating network structure, significantly improving the environmental tolerance and mechanical property balance of the material, and being particularly suitable for the harsh environmental requirements of outdoor electrical fence applications;

[0050] 3) Through a specific dispersion process and surfactant system, uniform dispersion of graphene in the epoxy matrix is achieved, and at the same time, covalent bonding is formed between amino functional groups and epoxy groups to enhance the interfacial bonding force;

[0051] 4) The multi-temperature stage curing process precisely controls the formation sequence and crosslinking degree of different networks, realizes the formation and regulation of complex phase structures, and optimizes the final material properties;

[0052] 5) Multiple weather resistance improvement measures, including anti-UV additives, improved interface stability, and the introduction of polyurethane network, enable the material to work stably in the temperature range of -40°C to 80°C, meeting the application requirements of electrical fences in different climate zones. Description of the Drawings

[0053] Figure 1This is the XPS full spectrum of the amino-functionalized graphene of the present invention, showing the main peak of C1s (284.5 eV), the peak of O1s (532 eV), and the peak of N1s (399.6 eV). The N1s peak area of the amino-functionalized graphene sample is clearly visible, corresponding to a nitrogen content of approximately 2.1%.

[0054] Figure 2 This is the high-resolution spectrum of C1s of the amino-functionalized graphene of the present invention: It can be deconvoluted and fitted into four components: C═C / C-C bonds (284.5 eV, main peak), C-N bonds (285.8 eV), C-O bonds (286.6 eV), and C═O bonds (288.2 eV). Compared with the unmodified graphene, the area of the C-N peak has increased significantly.

[0055] Figure 3 This is the high-resolution spectrum of N1s of the amino-functionalized graphene of the present invention: It can be deconvoluted and fitted into primary amine (399.1 eV), secondary amine (399.8 eV), and quaternary amine (401.2 eV). The area of the primary amine peak is dominant, indicating the successful introduction of amino functional groups.

[0056] Figure 4 This is the Fourier transform infrared spectroscopy (FTIR) graph of the unreacted mixture: It clearly shows the characteristic peaks of epoxy groups (915 cm-1 and 830 cm-1), C-H stretching vibrations (2930 cm-1 and 2870 cm-1), aromatic ring C═C stretching vibrations (1610 cm-1 and 1510 cm-1), and the characteristic peak of amino groups (3400 - 3500 cm-1); the FTIR graph of the cured composite material: The intensity of the characteristic peak of epoxy groups (915 cm-1) has decreased significantly (decreased by approximately 92%); a new characteristic peak of C-N bonds (1230 cm-1) appears; the intensity of the broad characteristic peak of hydroxyl groups (3200 - 3600 cm-1) has increased, indicating the epoxy ring-opening reaction; the intensity of the C-O-C stretching vibration peak (1100 cm-1) has increased, indicating the formation of a crosslinked network.

[0057] Figure 5 This is the dynamic mechanical analysis (DMA) spectrum Figure 1 For the storage modulus (E') vs. temperature curves of Examples 1 - 4: It shows a typical double-step decline. The first transition interval is from -40 °C to -20 °C, corresponding to the Tg of the polyurethane phase; the second transition interval is from 150 °C to 180 °C, corresponding to the Tg of the epoxy phase.

[0058] Figure 6 This is the dynamic mechanical analysis (DMA) spectrum Figure 2, Loss factor (tanδ) vs. temperature curves for Examples 1 - 4: There are two distinct peaks. The low - temperature peak is located at approximately - 30°C, and the high - temperature peak is located at approximately 165°C. The peak intensity ratio is approximately 1:3 to 1:2. The curve for Comparative Example 3 (without interpenetrating network): There is only one main tanδ peak (at approximately 160°C), lacking an obvious low - temperature peak, demonstrating that no interpenetrating network structure is formed.

[0059] Figure 7 This is the scanning electron microscope (SEM) image of the present invention.

[0060] Figure 8 This is the transmission electron microscope (TEM) image of the present invention.

[0061] Figure 9 This is the DSC curve for single - temperature curing (isothermal at 180°C). In the initial stage of curing, the exothermic peak has a large intensity, which gradually weakens over time. The exothermic reaction is basically completed at about 30 minutes, but complete curing is not achieved.

[0062] Figure 10 This is the DSC curve for step - by - step curing of the present invention. The 120°C stage shows an exothermic peak with medium intensity, and the integrated heat of reaction accounts for about 35 - 40% of the total heat of reaction; the 150°C stage shows a second exothermic peak, with the heat of reaction accounting for about 45 - 50%; the 180°C stage shows the final exothermic peak, with the heat of reaction accounting for about 10 - 15%.

[0063] Figure 11 This is a comparison chart of the volume resistivity of composites with different graphene contents. Detailed implementation manners

[0064] The present invention will be further described in detail below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0065] Please refer to Figures 1-11 , The composite material for an electric fence provided by the present invention is a graphene / liquid rubber synergistically modified epoxy resin interpenetrating network composite material. The comprehensive performance of this material is optimized through the following key technologies: First, carboxyl - terminated nitrile liquid rubber (CTBN) is pre - reacted with epoxy resin to form a micro - phase separation structure, providing basic toughness; second, amino - functionalized graphene nanosheets are introduced to enhance the material strength and thermal conductivity; third, the environmental adaptability and aging resistance of the material are further enhanced through a polyurethane interpenetrating network structure; finally, a multi - component synergistic formulation design and a precisely controlled preparation process are adopted to ensure the formation of the best phase structure and interfacial interaction among the components.

[0066] In addition, liquid rubber (CTBN) and polyetheramine (D400 / D2000) form a dual toughening network, improving toughness through the dual mechanisms of microphase separation and interfacial toughening. Aminated graphene forms covalent bonds with epoxy groups to construct a conductive network with a low percolation threshold, while enhancing the interfacial bonding force. The epoxy network and the polyurethane network form an interpenetrating structure, improving the comprehensive mechanical properties and environmental tolerance of the material. Through the synergistic effect of functional groups, the multifunctional integration of conductivity, mechanical properties, and environmental stability is achieved.

[0067] The covalent bonding between aminated graphene and epoxy groups was confirmed by Fourier transform infrared spectroscopy (FTIR) characterization. Characteristic peaks of epoxy groups (915 cm-1) and amino groups (3400 - 3500 cm-1) were observed in the mixture before curing; while in the cured sample, the intensity of the epoxy group peak decreased significantly, and at the same time, characteristic peaks of C-N bonds (1230 cm-1) and hydroxyl groups (3200 - 3600 cm-1) appeared, indicating that the epoxy groups and amino groups underwent a ring-opening reaction to form covalent bonds. X-ray photoelectron spectroscopy (XPS) further confirmed the formation of C-N bonds, and characteristic peaks of C-N bonds (285.8 eV) and C-O-C bonds (286.5 eV) appeared in the C1s spectrum.

[0068] Refer to Figures 1-3 , the XPS data clearly show that amino functional groups were successfully grafted onto the graphene surface, and the nitrogen content of 2.1% is consistent with the theoretical expectation. The presence of C-N bonds in the C1s spectrum directly proves the introduction of amino groups, and these amino functional groups will react with epoxy groups to form covalent bonds in the subsequent process. Amination reduces the conductivity of graphene, which is consistent with the resistivity test results.

[0069] Refer to Figure 4 , the changes in the FTIR spectrum directly prove the chemical reaction between epoxy groups and amino functional groups. The significant weakening of the epoxy peak combined with the appearance of C-N bond and hydroxyl peaks confirms the occurrence of the epoxy ring-opening reaction, forming a stable covalent bond network. This chemical bonding is the key mechanism for achieving good dispersion and interfacial enhancement of graphene.

[0070] The main raw materials used in this invention are as follows:

[0071] 1) Bisphenol A epoxy resin: The epoxy equivalent is 182 - 192 g / eq, and the viscosity is 10 - 13 Pa·s (25 °C), provided by Dow Chemical Company, with the trade name D.E.R. TM 332;

[0072] 2) Carboxyl-terminated butadiene acrylonitrile liquid rubber (CTBN): acrylonitrile content 26%, carboxyl equivalent 1600 g / mol·COOH, viscosity 110 Pa·s (27 °C), provided by Emerald Performance Materials, trade name Hypro1300X13;

[0073] 3) Amino-functionalized graphene nanosheets: nitrogen content 2.1%, amino content 0.8 mmol / g, specific surface area 600 m 2 / g, lateral size 3 μm, thickness about 5 nm;

[0074] 4) Polyether diol: average molecular weight about 2000, hydroxyl value 56 mg KOH / g, provided by BASF, trade name Pluracol TM P2000;

[0075] 5) Polyether triol: average molecular weight about 450, hydroxyl value 370 mg KOH / g, provided by BASF, trade name Pluracol TM TP440;

[0076] 6) Isophorone diisocyanate (IPDI): NCO content 37.8%, provided by Evonik Industries AG, trade name IPDI;

[0077] 7) 4,4'-Diaminodiphenyl sulfone (DDS): purity ≥99%, melting point 175 - 178 °C, provided by Sigma-Aldrich;

[0078] 8) 2-Methylimidazole: purity ≥99%, provided by Aladdin Reagent Co., Ltd.;

[0079] 9) Antioxidant: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], provided by BASF, trade name Irganox 1010;

[0080] 10) Ultraviolet absorber: 2-(2-hydroxy-5-methylphenyl)benzotriazole, provided by BASF, trade name Tinuvin P;

[0081] 11) Dispersant: polyurethane amide salt, provided by BYK-Chemie GmbH, trade name DISPERBYK-2150;

[0082] 12) Acetone: analytically pure, boiling point 56 - 57 °C, provided by Sinopharm Chemical Reagent Co., Ltd.;

[0083] 13) Methyl ethyl ketone (MEK): analytically pure, boiling point 79 - 80 °C, provided by Sinopharm Chemical Reagent Co., Ltd.

[0084] Example 1

[0085] A composite material for an electric fence, consisting of the following components:

[0086] 100 parts by weight of bisphenol A epoxy resin (epoxy equivalent 175 g / eq, Dow Chemical DER 331), 40 parts by weight of polyurethane prepolymer,

[0087] 10 parts by weight of carboxyl-terminated nitrile liquid rubber (CTBN, acrylonitrile content 26%, Emerald CVCCTBN1300X13),

[0088] 5 parts by weight of polyetheramine (polyether diamine D400 and D2000, weight ratio 30:70),

[0089] 0.3 parts by weight of amino-functionalized graphene nanosheets (lateral size 3 μm, thickness 5 nm),

[0090] 1.0 parts by weight of nano-aluminum oxide (average particle size 50 nm),

[0091] 10 parts by weight of chopped glass fibers (length 3 mm, surface silanized),

[0092] 20 parts by weight of 4,4'-diaminodiphenyl sulfone (DDS),

[0093] 0.5 parts by weight of 2-methylimidazole,

[0094] 0.2 parts by weight of pentaerythritol antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],

[0095] 0.3 parts by weight of 2-(2-hydroxy-5-methylphenyl)benzotriazole ultraviolet absorber,

[0096] 0.5 parts by weight of polyurethane amide salt dispersant.

[0097] Preparation of graphene oxide (modified Hummers method): Slowly add 5 g of natural flake graphite to 120 ml of concentrated sulfuric acid in an ice bath; slowly add 15 ml of concentrated nitric acid with stirring, and control the temperature at 0-5 °C; gradually add 25 g of potassium permanganate, and control the temperature at <20 °C; raise the temperature to 35 ± 2 °C and stir for 2 hours; raise the temperature to 65 ± 2 °C and continue to react for 4 hours; cool to room temperature, slowly add 250 ml of deionized water; add 30 ml of hydrogen peroxide (30%) to terminate the reaction; centrifuge and wash until neutral to obtain graphene oxide;

[0098] Preparation of amino-functionalized graphene:

[0099] Disperse 2 g of graphene oxide in 200 ml of deionized water; sonicate for 1 hour to form a homogeneous dispersion; add 2 g of stannous chloride and 2.5 g of hexaamminecobalt complex; stir at 60 °C for 1 hour; add 10 ml of ethylenediamine, raise the temperature to 85 ± 2 °C and react for 6 hours; centrifuge and wash, successively wash with deionized water, ethanol, and acetone; dry in vacuum at 50 °C for 24 hours to obtain amino-functionalized graphene.

[0100] The amino-functionalized graphene nanosheets used in the present invention have a large number of amino functional groups on their surface. These functional groups interact with the π-conjugated structure of graphene, partially disrupting the conductive network of graphene. When the amino-functionalized graphene reacts with epoxy groups, covalent bonding is formed, further blocking the electron transport channels. In addition, the addition amount of graphene in the present invention (0.3 - 0.8 parts by weight) is significantly lower than the percolation threshold (usually 2 - 3 parts by weight), so a continuous conductive network is not formed. On the contrary, this low-content, highly dispersed amino-functionalized graphene mainly plays the role of enhancing the material interface and improving thermal stability, actually increasing the volume resistivity. This phenomenon has been verified by four-probe resistance testing and transmission electron microscopy observation.

[0101] X-ray photoelectron spectroscopy (XPS) analysis of the amino-functionalized graphene sample shows that the amino-functionalization process makes the nitrogen content on the surface of graphene reach 2.1%, and the amino content is 0.8 mmol / g. This surface functionalization significantly changes the electronic structure of graphene. Further four-probe conductivity testing shows that the conductivity of pure graphene is about 1×10 4 S / m, while the conductivity of the amino-functionalized graphene drops to about 2×10 2 S / m, a decrease of about two orders of magnitude. This explains why the volume resistivity of the sample increases after adding amino-functionalized graphene.

[0102] Amino-functionalized graphene does have significantly different electrical properties from ordinary graphene. The introduction of amino functional groups will disrupt part of the sp 2 conjugated structure of graphene and reduce its conductivity. At the same time, the addition amount below the percolation threshold isolates the graphene nanosheets from each other and cannot form a conductive network. These factors together lead to the phenomenon of increased volume resistivity after adding amino-functionalized graphene, which is in line with the principles of materials science under specific conditions.

[0103] Conductivity data of unmodified graphene: The measured conductivity is about 1.2×10 4 S / m, which is close to the reported value in the literature.

[0104] Conductivity data of amino-functionalized graphene: The measured conductivity is significantly reduced to about 2.3×10 2 S / m, a decrease of about two orders of magnitude.

[0105] Composite volume resistivity comparison chart with different graphene contents: As the content of amino-functionalized graphene increases from 0.3 parts by weight to 0.8 parts by weight, the volume resistivity slightly increases, but remains in the order of 10^14 Ω·cm, confirming that the conductive percolation threshold has not been reached.

[0106] The four-probe test data directly proves that the amino-functionalization treatment significantly reduces the conductivity of graphene, which explains why the volume resistivity of the composite material slightly increases after adding amino-functionalized graphene. The introduction of amino functional groups disrupts part of the π-conjugated structure of graphene. Coupled with the addition amount below the percolation threshold, graphene mainly plays a reinforcing and stabilizing role in the composite material rather than a conductive role. This finding is consistent with the design goal of the material (maintaining high insulation).

[0107] The preparation method of this composite material includes the following steps:

[0108] (1) Vacuum dehydrate bisphenol A epoxy resin at 80 °C (15 mbar) for 2 hours, and control the moisture content at 0.03%;

[0109] (2) Ultrasonically disperse amino-functionalized graphene nanosheets in acetone at a mass ratio of 1:100 for 35 minutes, with an ultrasonic power of 350 W, using an intermittent mode (working for 30 seconds and pausing for 10 seconds), and control the dispersion temperature below 25 °C. Then add an equal amount of methyl ethyl ketone (MEK) to the dispersion, and distill off part of the acetone under reduced pressure (150 mbar) at 45 °C. Repeat this process until the acetone content is below 3%;

[0110] (3) Preheat CTBN liquid rubber to 70 °C to reduce viscosity, with a stirring speed of 120 rpm, and maintain for 30 minutes. Then carry out a reduced pressure treatment (60 mbar) for 15 minutes to remove air bubbles;

[0111] (4) Heat the epoxy resin treated in step (1) to 90 °C, and slowly add the preheated CTBN in step (3) at a rate of 1.5 g / min, with a stirring speed of 100 rpm. After mixing evenly, raise the temperature to 120 °C for a pre-reaction for 50 minutes, and control the pre-reaction conversion rate at about 25%. At this time, the viscosity increases to about 1.8 times the initial value;

[0112] (5) Cool the pre-reaction system in step (4) to 60 °C, start the high-shear disperser (initially 2,000 rpm for 15 minutes; then 4,000 rpm for 20 minutes; finally 2,000 rpm for 10 minutes), and add the graphene dispersion in step (2) in batches, with a total dispersion time of 40 minutes. After completion, remove the solvent under reduced pressure (60 - 80 mbar) at 70 °C, and control the solvent residue content below 0.3%;

[0113] (6) In a three-necked reaction flask, 75 parts by weight of polyether diol (molecular weight 2000) and 25 parts by weight of polyether triol (molecular weight 450) were mixed. After stirring evenly, dry nitrogen was introduced at 60 °C for 30 minutes. Then, at 60 °C, isophorone diisocyanate (IPDI) was slowly added dropwise over 30 minutes, with an NCO to OH equivalent ratio of 1.08. After the addition was complete, the temperature was raised to 70 °C and the reaction continued for 90 minutes. Samples were taken regularly to detect the NCO content until the theoretical value was reached;

[0114] (7) The polyurethane prepolymer in step (6) was slowly added to the mixed system in step (5) at a rate of 2.5 g / min at 70 °C, with a stirring speed of 130 rpm. The blending was carried out for 25 minutes, and then degassing was performed at 15 mbar for 5 minutes;

[0115] (8) The mixture in step (7) was cooled to 90 °C, and 2-methylimidazole (previously dissolved in a small amount of epoxy resin) and polyetheramine were added. Stirring was carried out for 10 minutes. Then the temperature was raised to 120 °C, and 4,4'-diaminodiphenyl sulfone was added in two portions and stirred until completely dissolved (about 15 minutes). Subsequently, nano-aluminum oxide, chopped glass fibers, antioxidant, ultraviolet absorber, and dispersant were added, and stirring was carried out for 15 minutes until evenly mixed;

[0116] (9) The mixture in step (8) was poured into a steel mold preheated to 125 °C at 80 °C, degassed at 15 mbar for 5 minutes, and then a pressure of 0.3 MPa was applied. Segmented curing was carried out: first maintained at 120 °C for 40 minutes, then heated at a rate of 1 °C / min to 150 °C and maintained for 90 minutes, and finally heated at a rate of 0.8 °C / min to 180 °C and maintained for 180 minutes;

[0117] (10) After the curing was completed, demolding was carried out at 100 °C, and then stress relief treatment was carried out at 155 °C for 90 minutes. Finally, it was slowly cooled to room temperature at a rate of 0.2 °C / min.

[0118] The composite material of the present invention has a two-component interpenetrating network structure (IPN), that is, a three-dimensional network structure formed by the interpenetration of an epoxy resin network and a polyurethane network. By controlling the epoxy resin and the curing agent to first undergo partial crosslinking (about 60 - 70% crosslinking degree), and then on this basis, the NCO groups in the polyurethane prepolymer react with the remaining active sites to form a second network, ultimately realizing the interpenetration of two independent crosslinked networks.

[0119] The formation of the interpenetrating network structure was confirmed by dynamic mechanical analysis (DMA) in this invention. The DMA thermograms of Examples 1 - 4 showed two distinct tanδ peaks, corresponding to the glass transition temperatures of the polyurethane phase (around -30 °C) and the epoxy phase (around 165 °C), respectively. While Comparative Example 3 (without an interpenetrating network) showed only one main tanδ peak, confirming the absence of a double network structure. Transmission electron microscopy (TEM) observations showed that the epoxy phase and the polyurethane phase formed an interpenetrating structure of approximately 50 - 100 nm, with blurred boundaries between the two phases and no obvious interface, further confirming the formation of the interpenetrating network.

[0120] Characterization of the interpenetrating network structure:

[0121] Dynamic mechanical analysis (DMA): A TA Instruments DMA Q800 dynamic mechanical analyzer was used, in double-cantilever mode, with a frequency of 1 Hz, a heating rate of 3 °C / min, and a temperature range of -80 °C to 250 °C.

[0122] Transmission electron microscopy (TEM): A JEOL JEM-2100F transmission electron microscope was used. The samples were observed after being embedded in epoxy, ultrathin sectioned (thickness approximately 80 nm), and stained with RuO4.

[0123] The interpenetrating network structure is a specific microstructure in materials science and its existence needs to be proven by appropriate characterization methods. Dynamic mechanical analysis (DMA) is one of the most commonly used methods to characterize the interpenetrating network. The existence of different network phases can be proven by observing multiple peaks on the tanδ curve. Transmission electron microscopy (TEM) can visually observe the interpenetration of the network structure. The addition of these characterization methods can strongly prove the formation of the interpenetrating network structure.

[0124] Curing kinetics analysis curve: It shows that a crosslinking degree of approximately 40% can be achieved in 40 minutes at 120 °C, approximately 85% in 90 minutes at 150 °C, and over 95% in 180 minutes at 180 °C.

[0125] The DSC curve clearly shows the process of the gradual formation of different network structures during the staged curing process. Different temperature stages correspond to the activation of different reaction mechanisms: at 120 °C, it is mainly the initial reaction of epoxy and amine groups; at 150 °C, it promotes the formation of epoxy and the remaining amine groups as well as the polyurethane network; at 180 °C, it ensures complete crosslinking. This staged curing process is crucial for the formation of an ordered interpenetrating network structure and directly affects the final material properties.

[0126] Example 2

[0127] A graphene / liquid rubber co-modified epoxy resin interpenetrating network composite for an electric fence, which consists of the following components:

[0128] 110 parts by weight of bisphenol A epoxy resin (epoxy equivalent: 220 g / eq, Shell Chemical Epon 828), 50 parts by weight of polyurethane prepolymer,

[0129] 12 parts by weight of carboxyl-terminated butadiene acrylonitrile liquid rubber (CTBN, acrylonitrile content: 27%, Lubrizol Hycar CTBN),

[0130] 10 parts by weight of polyetheramine (polyether diamine D400 and D2000, weight ratio: 50:50),

[0131] 0.5 parts by weight of amino-functionalized graphene nanosheets (lateral size: 4 μm, thickness: 6 nm),

[0132] 2.0 parts by weight of nano-aluminum oxide (average particle size: 80 nm),

[0133] 20 parts by weight of chopped glass fibers (length: 4 mm, surface silanized),

[0134] 25 parts by weight of 4,4'-diaminodiphenyl sulfone (DDS),

[0135] 1.0 parts by weight of 2-methylimidazole,

[0136] 0.4 parts by weight of pentaerythritol antioxidant tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],

[0137] 0.5 parts by weight of 2-(2-hydroxy-5-methylphenyl)benzotriazole ultraviolet absorber,

[0138] 1.0 parts by weight of polyurethane amide salt dispersant.

[0139] The preparation method of the composite material comprises the following steps:

[0140] (1) Dehydrate bisphenol A epoxy resin under vacuum (10 mbar) at 80 °C for 2.5 hours, and control the water content at 0.04%;

[0141] (2) Ultrasonically disperse amino-functionalized graphene nanosheets in acetone at a mass ratio of 1:90 for 40 minutes, with an ultrasonic power of 380 W, using an intermittent mode (working for 25 seconds and pausing for 10 seconds), and control the dispersion temperature below 28 °C. Then carry out the solvent replacement process to obtain graphene / MEK dispersion, and control the residual acetone content below 2%;

[0142] (3) Preheat CTBN liquid rubber to 70 °C to reduce viscosity, with a stirring speed of 140 rpm, maintain for 40 minutes, add 0.08% of dibutyltin dilaurate as an activator, stir gently (90 rpm) for 5 minutes, and then carry out a decompression (50 mbar) treatment for 20 minutes to remove bubbles;

[0143] (4) Heat the epoxy resin treated in step (1) to 90 °C, and slowly add the preheated CTBN in step (3) at a rate of 1.2 g / min. The stirring speed is 120 rpm. After mixing evenly, raise the temperature to 120 °C and pre-react for 45 minutes. Monitor the change of epoxy group content by infrared spectroscopy, and control the pre-reaction conversion rate at about 22%;

[0144] (5) Disperse graphene in the pre-reaction system in step (4) according to the three-stage dispersion process, control the temperature at 60 ± 2 °C, and the total dispersion time is 38 minutes. After completion, remove the solvent under reduced pressure, and control the solvent residue below 0.4%;

[0145] (6) Prepare a polyurethane prepolymer in a three-necked reaction kettle, using 72 parts by weight of polyether diol (molecular weight 2000) and 28 parts by weight of polyether triol (molecular weight 450), react with isophorone diisocyanate, the NCO to OH equivalent ratio is 1.06, the reaction temperature is 70 °C, and the total reaction time is 85 minutes;

[0146] (7) Add the prepared polyurethane prepolymer to the epoxy / CTBN / graphene system at a rate of 2.2 g / min at 70 °C, blend for 28 minutes, and then degas under reduced pressure;

[0147] (8) Cool the mixture to 90 °C, add a catalyst and polyetheramine, and then add other fillers and additives, and mix evenly;

[0148] (9) Pour the mixture into a preheated mold and carry out three-stage curing: 120 °C / 35 minutes, 150 °C / 80 minutes, 180 °C / 150 minutes;

[0149] (10) After demolding, carry out stress relief treatment, treat at 160 °C for 80 minutes, and then cool slowly.

[0150] Example 3

[0151] A graphene / liquid rubber synergistically modified epoxy resin interpenetrating network composite material for an electric fence, which is composed of the following components:

[0152] 120 parts by weight of bisphenol A epoxy resin (epoxy equivalent 280 g / eq),

[0153] 60 parts by weight of polyurethane prepolymer,

[0154] 15 parts by weight of carboxyl-terminated butadiene acrylonitrile liquid rubber (CTBN, acrylonitrile content 28%),

[0155] 15 parts by weight of polyetheramine (polyether diamine D400 and D2000, weight ratio 40:60),

[0156] 0.8 parts by weight of amino-functionalized graphene nanosheets (lateral size 5 μm, thickness 8 nm),

[0157] 3.0 parts by weight of nano-aluminum oxide (average particle size 100 nm),

[0158] 30 parts by weight of chopped glass fibers (length 5 mm, surface silanized),

[0159] 30 parts by weight of 4,4'-diaminodiphenyl sulfone (DDS),

[0160] 1.5 parts by weight of 2-methylimidazole,

[0161] 0.6 parts by weight of antioxidant,

[0162] 0.7 parts by weight of ultraviolet absorber,

[0163] 1.5 parts by weight of dispersant.

[0164] The preparation method of this composite material is similar to that of Example 1, but adjustments are made to the key parameters:

[0165] (1) The dehydration temperature of the epoxy resin is increased to 82 °C and the time is extended to 3 hours;

[0166] (2) For graphene dispersion, a higher ultrasonic power (400 W) and a longer dispersion time (45 minutes) are used;

[0167] (3) The pre-reaction temperature of CTBN is increased to 125 °C, the time is extended to 60 minutes, and the conversion rate is controlled at 30%;

[0168] (4) For the synthesis of the polyurethane prepolymer, 70 parts by weight of polyether diol and 30 parts by weight of polyether triol are used, and the NCO to OH equivalent ratio is increased to 1.10;

[0169] (5) For curing, a higher post-curing temperature (185 °C) and a longer time (180 minutes) are used to ensure a high degree of crosslinking.

[0170] Example 4

[0171] A graphene / liquid rubber synergistically modified epoxy resin interpenetrating network composite material for electric fences, which is composed of the following components:

[0172] 115 parts by weight of bisphenol A epoxy resin (epoxy equivalent 200 g / eq),

[0173] 45 parts by weight of polyurethane prepolymer,

[0174] 13 parts by weight of carboxyl-terminated butadiene acrylonitrile liquid rubber (CTBN, acrylonitrile content 25%),

[0175] 20 parts by weight of polyetheramine (polyether diamine D400 and D2000, weight ratio 70:30),

[0176] 0.6 parts by weight of amino-functionalized graphene nanosheets (lateral size 2 μm, thickness 4 nm),

[0177] 1.5 parts by weight of nano-aluminum oxide (average particle size 30 nm),

[0178] 15 parts by weight of chopped glass fibers (length 3.5 mm, surface silanized),

[0179] 22 parts by weight of 4,4'-diaminodiphenyl sulfone (DDS),

[0180] 0.8 parts by weight of 2-methylimidazole,

[0181] 0.5 parts by weight of antioxidant,

[0182] 0.4 parts by weight of ultraviolet absorber,

[0183] 0.8 parts by weight of dispersant.

[0184] This example uses a higher proportion of polyetheramine D400. This low-molecular-weight polyetheramine can provide a higher crosslinking density and better temperature resistance. At the same time, the graphene nanosheets are smaller in size, which is beneficial for more uniform dispersion and a higher specific surface area, enhancing the interfacial interaction. In the preparation process, medium condition parameters are adopted, such as a pre-reaction for 55 minutes, the conversion rate is controlled at 28%, and the curing adopts a three-stage process of 120 °C / 38 minutes, 150 °C / 75 minutes, and 180 °C / 160 minutes.

[0185] The segmented curing process was monitored in real time by differential scanning calorimetry (DSC). At the 120 °C stage, an exothermic peak was observed, corresponding to the initial reaction of epoxy and amine groups; at the 150 °C stage, a second exothermic peak was observed, corresponding to the reaction of epoxy with the remaining amine groups and the formation of the polyurethane network; at the 180 °C stage, a final exothermic peak was observed, corresponding to complete crosslinking. By integrating and calculating the enthalpy change of each stage of the reaction, it was determined that the crosslinking degree at the 120 °C stage was about 40%, reached 85% at the 150 °C stage, and reached more than 95% at the 180 °C stage. Different reaction rates of different reactions were controlled at different temperature stages, ensuring the orderly formation of the network structure.

[0186] Comparative Example 1 (without graphene)

[0187] To verify the synergistic strengthening effect of graphene, a comparative formulation without graphene was designed, and the composition is as follows:

[0188] 100 parts by weight of bisphenol A epoxy resin (epoxy equivalent 175 g / eq),

[0189] 40 parts by weight of polyurethane prepolymer,

[0190] 10 parts by weight of carboxyl-terminated nitrile liquid rubber (CTBN, acrylonitrile content 26%),

[0191] 5 parts by weight of polyetheramine (polyether diamine D400 and D2000, weight ratio 30:70),

[0192] 0 parts by weight of amino-functionalized graphene nanosheets,

[0193] 1.0 part by weight of nano-aluminum oxide,

[0194] 10 parts by weight of chopped glass fibers,

[0195] 20 parts by weight of 4,4'-diaminodiphenyl sulfone (DDS),

[0196] 0.5 part by weight of 2-methylimidazole,

[0197] 0.2 part by weight of antioxidant,

[0198] 0.3 part by weight of ultraviolet absorber,

[0199] 0.5 part by weight of dispersant.

[0200] The preparation method is the same as that of Example 1, but the steps related to graphene dispersion are omitted. The purpose of this design is to directly compare the role of graphene while keeping other factors unchanged.

[0201] Comparative Example 2 (without liquid rubber)

[0202] To verify the toughening effect of liquid rubber, a comparative formulation without liquid rubber was designed:

[0203] 100 parts by weight of bisphenol A epoxy resin (epoxy equivalent 175 g / eq),

[0204] 40 parts by weight of polyurethane prepolymer,

[0205] 0 parts by weight of carboxyl-terminated nitrile liquid rubber,

[0206] 5 parts by weight of polyetheramine (polyether diamine D400 and D2000, weight ratio 30:70),

[0207] 0.3 part by weight of amino-functionalized graphene nanosheets,

[0208] 1.0 part by weight of nano-aluminum oxide,

[0209] 10 parts by weight of chopped glass fibers,

[0210] 20 parts by weight of 4,4'-diaminodiphenyl sulfone (DDS),

[0211] 0.5 parts by weight of 2-methylimidazole,

[0212] 0.2 parts by weight of antioxidant,

[0213] 0.3 parts by weight of ultraviolet absorber,

[0214] 0.5 parts by weight of dispersant.

[0215] The preparation method is the same as that of Example 1, but the CTBN pre-reaction step is omitted. This design is to verify the key role of liquid rubber in improving the toughness of the material.

[0216] Comparative Example 3 (without interpenetrating network structure)

[0217] To verify the importance of the interpenetrating network structure, a comparative formulation without a polyurethane network was designed:

[0218] 100 parts by weight of bisphenol A epoxy resin (epoxy equivalent 175 g / eq),

[0219] 0 parts by weight of polyurethane prepolymer,

[0220] 10 parts by weight of carboxyl-terminated butadiene-acrylonitrile liquid rubber (CTBN, acrylonitrile content 26%),

[0221] 25 parts by weight of polyetheramine (as a curing agent, does not form a polyurethane network),

[0222] 0.3 parts by weight of aminated graphene nanosheets,

[0223] 1.0 part by weight of nano-aluminum oxide,

[0224] 10 parts by weight of chopped glass fibers,

[0225] 15 parts by weight of 4,4'-diaminodiphenyl sulfone (DDS),

[0226] 0.5 parts by weight of 2-methylimidazole,

[0227] 0.2 parts by weight of antioxidant,

[0228] 0.3 parts by weight of ultraviolet absorber,

[0229] 0.5 parts by weight of dispersant.

[0230] The preparation method is the same as that of Example 1, but the preparation and introduction steps of the polyurethane prepolymer are omitted, and the amount of polyetheramine is increased to maintain sufficient curing degree. This comparative example aims to verify the influence of the interpenetrating network structure on the weather resistance and environmental adaptability of the material.

[0231] To comprehensively evaluate the properties of the materials in the examples and comparative examples, the following tests were carried out:

[0232] 1. Mechanical property testing: Tensile properties were determined according to ASTM D638 standard, and impact strength was determined according to ASTM D256 standard. The tests were carried out under two temperature conditions of 23 °C and -40 °C.

[0233] 2. Electrical property testing: Volume resistivity was determined according to ASTM D257, dielectric strength was determined according to ASTM D149, and dielectric constant and loss factor were determined according to ASTM D150.

[0234] 3. Weather resistance testing: UV aging test (500 hours) was carried out according to ASTM G154 standard, and the retention rate of mechanical properties before and after aging was determined; Salt spray test (500 hours) was carried out according to ASTM B117 standard; Temperature and humidity cycle test (-40 °C to 85 °C, 95% RH, 50 cycles) was carried out, and the performance change after aging was determined.

[0235] 4. Special performance testing for electric fences: The tracking resistance index (IEC 60112 standard) was determined; Insulation strength test under high and low temperature shock (rapid temperature rise from -40 °C to 80 °C, 30 cycles) was carried out.

[0236] The summary of test results is shown in Table 1-3:

[0237] Table 1 Test Results of Mechanical Properties

[0238]

[0239] Table 2 Test Results of Electrical Properties

[0240]

[0241] Table 3 Test Results of Weather Resistance and Special Properties

[0242]

[0243] * The performance index is the comprehensive score of strength retention rate, resistivity retention rate and appearance rating;

[0244] ** The number of high and low temperature shock tolerance cycles refers to the maximum number of cycles that can maintain the insulation strength up to standard in the cycle test. >30 means that the performance is still up to standard after 30 cycles;

[0245] Table 4 Summary of Material Structure Characterization and Analysis Methods

[0246]

[0247]

[0248] It can be seen from the test results that:

[0249] 1. In terms of mechanical properties: Examples 1-4 all exhibited excellent mechanical property balance, especially maintaining good impact strength under low temperature (-40°C) conditions. Example 3 added the highest content of graphene and liquid rubber, so it showed the highest impact strength and elongation at break. Comparative Example 1 (without graphene) and Comparative Example 2 (without liquid rubber) showed a significant decrease in impact strength under low temperature conditions, demonstrating the synergistic toughening effect of graphene and liquid rubber. Although Comparative Example 2 had a relatively high tensile strength, its elongation at break was low, showing relatively high brittleness.

[0250] 2. In terms of electrical properties: All samples showed good electrical insulation properties, but Examples 2 and 3 maintained higher volume resistivity under high temperature and high humidity conditions. This was mainly due to the synergistic effect of the interpenetrating network structure and graphene, which improved the environmental stability of the material. Comparative Example 3 (without the interpenetrating network) showed a significant decrease in volume resistivity under high temperature and high humidity conditions, demonstrating the important contribution of the interpenetrating network structure to the stability of electrical properties.

[0251] 3. In terms of weather resistance and special properties: Example 3 showed the most excellent weather resistance. After UV aging, the strength retention rate reached 98.1%, after the salt spray test, the resistivity retention rate reached 98.5%, and after the temperature and humidity cycle, the performance index reached 95.3%. In contrast, Comparative Example 3 (without the interpenetrating network) performed the worst in various weather resistance tests. Especially after the temperature and humidity cycle, the performance index was only 61.2%, indicating that the polyurethane interpenetrating network structure was crucial for improving the anti-aging performance of the material. In the special performance test of the electric fence, Examples 2-4 could all complete 30 high-low temperature impact cycles while maintaining insulation performance, while the comparative example materials showed varying degrees of performance degradation.

[0252] The following conclusions can be drawn through comparative analysis:

[0253] 1. Graphene / liquid rubber synergistic toughening mechanism: The synergistic effect of graphene and liquid rubber is the key to achieving high toughness and low temperature performance of the material. Liquid rubber provides the basic toughness through microphase separation, while graphene further improves the toughness and strength of the material by bridging microcracks and enhancing the interfacial bonding force. The performance differences between Comparative Example 1 and Comparative Example 2 proved this point. The microphase separation structure formed by CTBN and epoxy resin was confirmed by scanning electron microscopy (SEM). After the sample was fractured, extracted (using acetone to extract unreacted components at 70°C for 24 hours), and gold sputtered, uniformly distributed spherical phases with a diameter range of 0.8 - 1.5 μm were observed under SEM, which was consistent with the theoretical expectation of 0.5 - 2 μm. Energy dispersive spectroscopy (EDS) confirmed that these spherical phases were rich in nitrogen elements, indicating that they were mainly composed of CTBN. This microphase structure was the key factor providing toughness and low temperature impact strength.

[0254] 2. Importance of the interpenetrating network structure: The interpenetrating network structure formed by epoxy resin and polyurethane significantly improves the environmental stability and aging resistance of the material. The obvious performance decline in Comparative Example 3 proves the importance of the interpenetrating network structure for the materials used in electric fences.

[0255] 3. Optimization of component ratios: The higher graphene content (0.8 parts by weight) and liquid rubber content (15 parts by weight) used in Example 3 showed the best performance in various performance tests, indicating that this ratio achieved the best synergistic effect. However, considering cost and processability, Example 2 may represent the best balance between performance and cost.

[0256] 4. Unexpected technical effects: The triple synergistic effect of the graphene / liquid rubber / polyurethane interpenetrating network has produced a performance improvement beyond expectations, especially in terms of low-temperature impact strength and electrical property stability under high-temperature and high-humidity conditions. This synergistic effect is difficult to predict by simply adding the individual contributions of each component and is an important innovation point of the present invention.

[0257] Example 3 was determined to be the best embodiment of the present invention, having the most comprehensive performance advantages. However, according to the specific application environment and cost requirements, appropriate formulation and process parameters can be selected within the range of Examples 1-4.

[0258] The graphene / liquid rubber synergistically modified epoxy resin interpenetrating network composite material of the present invention has successfully solved the durability problem of materials used in electric fences in harsh environments through innovative multi-component synergistic design and precisely controlled preparation processes, providing a more reliable insulation material solution for electric fence systems.

Claims

1. A composite material for electric fence, characterized in that: The composite material is composed of the following components in parts by weight: 100-120 parts by weight of bisphenol A epoxy resin, 40-60 parts by weight of polyurethane prepolymer, 10-15 parts by weight of carboxyl-terminated nitrile liquid rubber CTBN, 5-20 parts by weight of polyetheramine, 0.3-0.8 parts by weight of amino-modified graphene nanosheets, 1.0-3.0 parts by weight of nano-alumina, 10-30 parts by weight of chopped glass fibers, 20-30 parts by weight of 4,4'-diaminodiphenyl sulfone, 0.5-1.5 parts by weight of imidazole catalyst, 0.2-0.6 parts by weight of antioxidant, 0.3-0.7 parts by weight of ultraviolet absorber, 0.5-1.5 parts by weight of dispersant.

2. The composite material according to claim 1, characterized in that The epoxy equivalent of the bisphenol A epoxy resin is 170-280 g / eq, the acrylonitrile content of the carboxyl-terminated nitrile liquid rubber is 24-28 weight percent, and the average lateral size of the amino graphene nanosheets is 1-5 μm and the thickness is 2-8 nm.

3. The composite material according to claim 1, characterized in that The polyetheramine includes polyetherdiamine D400 and polyetherdiamine D2000, and the weight ratio thereof is 30:70 to 70:

30.

4. The composite material according to claim 1, characterized in that The composite material has an interpenetrating network structure, including an epoxy resin network and a polyurethane network interpenetrating each other; the carboxyl-terminated nitrile liquid rubber reacts with the epoxy resin to form a microphase separation structure, and the microphase size is 0.5-2 μm.

5. The composite material according to claim 1, characterized in that The composite material maintains stable electrical insulation performance within a temperature range of -40°C to 80°C, and a volume resistivity greater than 10 12 Ω·cm, and the dielectric strength is greater than 20kV / mm.

6. A method for preparing the composite material according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) dehydrating bisphenol A epoxy resin under vacuum at 80±2°C for 2-3 hours, and controlling the moisture content to ≤0.05%; (2) ultrasonically dispersing the amino-modified graphene nanosheets in acetone for 30 to 40 minutes at an ultrasonic power of 300 to 400 W, and then performing solvent replacement to obtain a graphene / methyl ethyl ketone dispersion; (3) preheating the carboxyl-terminated nitrile liquid rubber CTBN to 70±2°C to reduce viscosity, and decompressing the liquid rubber for 15 to 20 minutes to remove bubbles; (4) heating the epoxy resin treated in step (1) to 90±2° C., slowly adding the CTBN preheated in step (3) at a rate of 1-2 g / min, and heating to 120±2° C. for pre-reaction for 40-60 minutes after mixing evenly, and controlling the pre-reaction conversion rate to 20%-30%; (5) cooling the pre-reaction system in step (4) to 60±2° C., adding the graphene dispersion in step (2) in batches under high shear dispersion for 30 to 40 minutes, and then removing the solvent under reduced pressure to control the residual solvent content to <0.5%; (6) In a three-mouth reaction kettle, reacting polyether polyol and isophorone diisocyanate at 70±2° C. for 80 to 100 minutes to prepare a polyurethane prepolymer; (7) slowly adding the polyurethane prepolymer in step (6) to the mixed system in step (5) at 70±2° C. at a rate of 2-3 g / min, blending for 20-30 minutes, and then degassing under reduced pressure; (8) Cool the mixture of step (7) to 90±2°C, add the imidazole catalyst and polyetheramine, mix well, then heat to 120±2°C, add 4,4'-diaminodiphenyl sulfone, stir until completely dissolved, add nano-alumina, chopped glass fiber and other additives, and mix well; (9) pouring the mixture in step (8) at 80±2°C into a mold preheated to 120±5°C for staged curing: first, maintaining at 120±2°C for 30 to 40 minutes, then heating to 150±2°C for 60 to 90 minutes, and finally heating to 180±2°C for 120 to 180 minutes; (10) The cured material is demoulded, subjected to stress relief treatment at Tg-20°C for 60 to 90 minutes, and then slowly cooled to room temperature.

7. The method according to claim 6, characterized in that The extent of the pre-reaction in step (4) is controlled by monitoring the viscosity of the mixture and the change in epoxy content, and the pre-reaction is terminated when the viscosity increases to 1.5-2 times of the initial value.

8. The method according to claim 6, characterized in that The graphene dispersion in step (5) adopts a high shear disperser, and the dispersion process includes initial low-speed dispersion at 2,000 rpm for 10 to 15 minutes; high-speed dispersion at 4,000-5,000 rpm for 15 to 20 minutes; and final low-speed dispersion at 2,000 rpm for 10 minutes.

9. The method according to claim 6, characterized in that In step (6), the polyurethane prepolymer is prepared by using a mixed polyol of 70-80 parts by weight of polyether diol and 20-30 parts by weight of polyether triol, the amount of isophorone diisocyanate is 1.05-1.10 times the calculated amount, and the equivalent ratio of NCO group to OH group is 1.05-1.

10.

10. The method according to claim 6, characterized in that The crosslinking degree in the staged curing process in step (9) is monitored by differential scanning calorimetry (DSC), and the glass transition temperature is determined by dynamic mechanical analysis (DMA) to ensure that the crosslinking degree is ≥ 95%.

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