A composite material for an electric fence and a method of making the same

Abstract

The present application relates to the technical field of high polymer composite material, and particularly relates to a composite material for electrical fence and a preparation method thereof, the composite material is composed of the following components by weight: 100-120 parts by weight of bisphenol A type epoxy resin, 40-60 parts by weight of polyurethane prepolymer, 10-15 parts by weight of carboxyl terminated butylnitrile liquid rubber CTBN, 5-20 parts by weight of polyether amine, 0.3-0.8 parts by weight of aminated graphene nanosheet, 1.0-3.0 parts by weight of nano alumina, 10-30 parts by weight of short glass fiber, 20-30 parts by weight of 4,4'-diamino diphenyl 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, a multi-scale toughening network is formed, and the toughness and strength are simultaneously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer composite materials, in particular to a composite material for electric fence and a preparation method thereof. The composite material is toughened by liquid rubber and reinforced by graphene functionalization on the basis of epoxy resin, and a polyurethane interpenetrating network structure is introduced, so that the composite material has excellent mechanical properties, weather resistance, impact resistance and electrical insulation performance, and is particularly suitable for electric fence insulation support materials in outdoor environment. BACKGROUND

[0002] As a common security device, one of the key components of the electric fence system is a composite material component for support and insulation. Such materials need to have excellent mechanical properties, weather resistance, impact resistance and electrical insulation performance to ensure long-term reliable operation in outdoor harsh environment. At present, the insulation materials for electric fence mainly use engineering plastics or epoxy resin composite materials, but the existing technology still has some obvious deficiencies.

[0003] US5891367A discloses a conductive epoxy resin adhesive based on a silver flake filled polymer reaction product, which uses a liquid bisphenol A epoxy resin containing very low hydrolytic chlorine content and a polypropylene oxide amine curing agent to achieve high impact resistance and stable resistance characteristics. However, this technology is mainly optimized for conductive performance and is not suitable for electric fence applications that require insulation performance, and its weather resistance in outdoor environment is poor.

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

[0005] US4771137A discloses an electric fence wire insulator made of a one-piece body of non-conductive synthetic resin, which includes a transverse spark shield layer. Although this product has certain insulation performance, it lacks a composite reinforcement structure, has insufficient strength, and poor aging resistance, which cannot meet the requirements of long-term outdoor use.

[0006] International patent WO1992008760A1 describes an acrylic modified epoxy resin adhesive, which uses acrylic ester modification to improve rheological control and introduce the interaction effect of hydroxyl functional reinforcement and rheological control agent. However, this material is mainly optimized for adhesive applications and does not consider the comprehensive performance required for electric fence materials.

[0007] In recent years, graphene, as a new type of nanomaterial, has attracted much attention due to its excellent mechanical, thermal and electrical properties. For example, Chinese patent CN111187587A discloses a composite wall joint sealing glue based on epoxy resin modification, which uses graphene carrier modification technology to improve weather resistance and hydrophobicity. However, this technology does not consider the synergistic toughening mechanism of multiple phases, and cannot achieve balanced optimization of mechanical properties and electrical properties.

[0008] Currently, the existing technologies for electrical fence applications mainly have the following shortcomings:

[0009] 1) Conventional epoxy resin materials have excellent insulating properties, but their inherent brittleness leads to poor impact resistance, especially in low temperature environments, which can easily crack;

[0010] 2) Single modification methods (such as liquid rubber toughening or filler reinforcement) often lead to unbalanced material properties, 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, leading to a decrease in long-term performance;

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

[0013] Therefore, it is urgent to develop a composite material with high toughness, high strength, aging resistance and excellent electrical insulation performance to meet the special requirements of electrical fence systems. SUMMARY

[0014] The purpose of the present application is to overcome the shortcomings of the prior art and provide a graphene / liquid rubber synergistically modified epoxy resin interpenetrating network composite material for electrical fences and a preparation method thereof. The material has excellent mechanical properties, weather resistance, impact resistance and electrical insulation performance through the synergistic effect of multiple modification technologies, and is particularly suitable for electrical fence systems in outdoor environments.

[0015] To achieve the above-mentioned purpose, the present application provides a composite material for electrical fences, which is composed of the following components by weight:

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

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

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

[0019] 5-20 parts by weight of polyether amine,

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

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

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

[0023] 20-30 parts by weight of 4,4'-diamino diphenyl 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 type epoxy resin is 170-280 g / eq, the acrylonitrile content of the carboxyl-terminated butyronitrile liquid rubber is 24-28 wt%, the average lateral size of the aminated graphene nanosheet is 1-5 μm, and the thickness is 2-8 nm.

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

[0030] The composite material has an interpenetrating network structure, including an epoxy resin network and a polyurethane network interpenetrating each other; the carboxyl-terminated butyronitrile liquid rubber reacts with the epoxy resin to form a microphase separation structure, and the microphase size is 0.5-2 μm. This multi-phase structure is the key to achieving comprehensive performance optimization of the present application.

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

[0032] The present application also provides a method for preparing the above-mentioned composite material, comprising the following steps:

[0033] (1) vacuum dehydrating the bisphenol A type epoxy resin at 80±2℃ for 2-3 hours, and controlling the moisture content to be ≤0.05%;

[0034] (2) ultrasonically dispersing the aminated graphene nanosheet in acetone for 30-40 minutes, and the ultrasonic power is 300-400 W, and then performing solvent replacement to obtain a graphene / methyl ethyl ketone dispersion;

[0035] (3) Preheat the carboxyl-terminated butadiene acrylonitrile liquid rubber (CTBN) to 70±2°C to reduce viscosity and treat under reduced pressure for 15-20 minutes to remove 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, mix uniformly, then increase the temperature to 120±2°C and pre-react for 40-60 minutes, control the pre-reaction conversion rate at 20%-30%;

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

[0038] (6) In a three-necked reaction kettle, react the 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, feeding rate is 2-3 g / min, blend for 20-30 minutes, then degas under reduced pressure;

[0040] (8) Cool the mixture in step (7) to 90±2°C, add the imidazole catalyst and polyether amine, mix uniformly, then increase the temperature to 120±2°C, add 4,4'-diamino diphenyl sulfone, stir until completely dissolved, add nano-alumina, chopped glass fiber and other additives, mix uniformly;

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

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

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

[0044] More preferably, the graphene dispersion in step (5) adopts a high-shear disperser, and the dispersion process includes an initial low-speed dispersion of 2,000 rpm for 10-15 minutes, a high-speed dispersion of 4,000-5,000 rpm for 15-20 minutes, and a final low-speed dispersion of 2,000 rpm for 10 minutes. This multi-stage dispersion process can effectively prevent graphene agglomeration and ensure uniform dispersion.

[0045] Further, the preparation of the polyurethane prepolymer in step (6) adopts a mixed polyol of polyether diol (molecular weight 2000) 70-80 parts by weight and polyether triol (molecular weight 450) 20-30 parts by weight, and the amount 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, the segmented curing process in step (9) is monitored by differential scanning calorimetry (DSC) to determine the crosslinking degree, and dynamic mechanical analysis (DMA) is used to determine the glass transition temperature, ensuring that the crosslinking degree is ≥95%. This precise control can ensure stable material performance.

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

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

[0049] 2) The interpenetrating network structure formed by epoxy resin and polyurethane significantly improves the environmental tolerance and mechanical property balance of the material, and is 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 covalent bonding is formed between the amino functional groups and the epoxy groups, enhancing the interfacial bonding force;

[0051] 4) Multi-temperature stage curing process, precise control of different network formation sequence and crosslinking degree, realization of complex phase structure formation and regulation, optimization of final material performance;

[0052] 5) Multiple weather resistance improvement measures, including anti-UV additives, interface stability improvement and polyurethane network introduction, realizing the stable work of the material in the temperature range of -40°C to 80°C, meeting the application requirements of different climate zones for electrical fence. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1XPS survey spectrum of the aminated graphene of the present application, showing C1s (284.5 eV) main peak, O1s (532 eV) peak and N1s (399.6 eV) peak. The N1s peak area of the aminated graphene sample is clearly visible, corresponding to a nitrogen content of about 2.1%.

[0054] Figure 2 C1s high resolution spectrum of the aminated graphene of the present application: peak deconvolution 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). The C-N peak area is clearly increased compared to the unmodified graphene.

[0055] Figure 3 N1s high resolution spectrum of the aminated graphene of the present application: peak deconvolution into primary amines (399.1 eV), secondary amines (399.8 eV) and quaternary amines (401.2 eV), with the primary amines peak area dominating, indicating successful introduction of amino functional groups.

[0056] Figure 4 Fourier transform infrared spectroscopy (FTIR) spectra, unreacted mixture spectrum: clear display of the characteristic peaks of epoxy groups (915 cm-1 and 830 cm-1), C-H stretching vibration (2930 cm-1 and 2870 cm-1), aromatic ring C=C stretching vibration (1610 cm-1 and 1510 cm-1), and amino characteristic peak (3400-3500 cm-1); cured composite material spectrum: the intensity of the characteristic peak of epoxy groups (915 cm-1) is significantly weakened (decreased by about 92%); a new characteristic peak of C-N bond (1230 cm-1) appears; the intensity of the characteristic broad peak of hydroxyl groups (3200-3600 cm-1) increases, indicating epoxy ring-opening reaction; the intensity of the C-O-C stretching vibration peak (1100 cm-1) is enhanced, indicating the formation of crosslinking network.

[0057] Figure 5 Dynamic mechanical analysis (DMA) spectrum Figure 1 , storage modulus (E') vs. temperature curve of Examples 1-4: showing a typical double-step drop, the first transition interval is at -40°C to -20°C, corresponding to the Tg of the polyurethane phase; the second transition interval is at 150°C to 180°C, corresponding to the Tg of the epoxy phase.

[0058] Figure 6 Dynamic mechanical analysis (DMA) spectrum Figure 2Tan Delta (Tan Delta) curves of Examples 1-4: two distinct peaks are present, a low temperature peak at about -30°C and a high temperature peak at about 165°C, with a peak intensity ratio of about 1:3 to 1:2. Curve of Comparative Example 3 (no interpenetrating network): only one major tan delta peak (about 160°C) is present, lacking a distinct low temperature peak, demonstrating no interpenetrating network structure formation.

[0059] Figure 7 Scanning Electron Microscope (SEM) image of the present application.

[0060] Figure 8 Transmission Electron Microscope (TEM) image of the present application.

[0061] Figure 9 Single temperature cure DSC curve (180°C isotherm). The exothermic peak at the beginning of the cure stage is strong and gradually weakens over time, with the exotherm essentially complete at about 30 minutes, but not fully cured.

[0062] Figure 10 Staged cure DSC curve of the present application. The 120°C stage shows a moderate intensity exothermic peak, with an integrated heat of reaction of about 35-40% of the total; the 150°C stage shows a second exothermic peak, with a heat of reaction of about 45-50%; the 180°C stage shows the final exothermic peak, with a heat of reaction of about 10-15%.

[0063] Figure 11 Volume resistivity comparison plot of composites with different graphene content. DETAILED DESCRIPTION

[0064] The application will be further described in connection with the specific embodiments, but the scope of the application is not limited thereto.

[0065] Reference should be made to Figures 1-11 The composite material for electrical fencing provided by the present application is a graphene / liquid rubber synergistically modified epoxy resin interpenetrating network composite material. The material realizes comprehensive performance optimization through the following key technologies: first, carboxyl-terminated butyl nitrile liquid rubber (CTBN) is used to pre-react with epoxy resin to form a microphase separation structure, providing basic toughness; second, amino-functionalized graphene nanosheet reinforcing material is introduced to enhance strength and thermal conductivity; third, a polyurethane interpenetrating network structure is used to further enhance the environmental adaptability and aging resistance of the material; finally, a multi-component synergistic formulation design and precise control preparation process is used to ensure the formation of the best phase structure and interfacial interaction between the components.

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

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

[0068] Reference Figures 1-3 XPS data clearly showed that the amino functional groups were successfully grafted onto the surface of graphene, with a nitrogen content of 2.1%, which was consistent with the theoretical expectation. The presence of C-N bonds in the C1s spectrum directly proved the introduction of amino groups, and these amino functional groups would react with the epoxy groups to form covalent bonding in the subsequent reaction. Amination reduced the electrical conductivity of graphene, which was consistent with the results of the electrical resistivity test.

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

[0070] The main raw materials used in the present application are as follows:

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

[0072] 2) Carboxy-terminated butynitrile liquid rubber (CTBN): acrylonitrile content 26%, carboxyl equivalent 1600 g / mol COOH, viscosity 110 Pa-s (27°C), provided by Emerald Performance Materials, Inc., trade name Hypro 1300X13;

[0073] 3) Aminated graphene nanoplatelets: nitrogen content 2.1%, amino content 0.8 mmol / g, specific surface area 600 m 2 / g, lateral size 3 pm, 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, 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 Aldrich Reagent;

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

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

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

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

[0083] 13) Methyl ethyl ketone (MEK): analytical pure, boiling point 79-80°C, provided by National Pharmaceutical Group 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 type 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 butylnitrile liquid rubber (CTBN, acrylonitrile content 26%, Emerald CVCCTBN 1300X13),

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

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

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

[0091] 10 parts by weight of chopped glass fiber (length 3 mm, surface silane treatment),

[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 tetrakis [beta-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol antioxidant,

[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): 5 g of natural flake graphite was slowly added to 120 ml of concentrated sulfuric acid in an ice bath; 15 ml of concentrated nitric acid was slowly added with stirring, controlling the temperature at 0-5°C; 25 g of potassium permanganate was gradually added, controlling the temperature at <20°C; the temperature was raised to 35±2°C and the reaction was stirred for 2 hours; the temperature was raised to 65±2°C and the reaction was continued for 4 hours; it was cooled to room temperature, 250 ml of deionized water was slowly added; 30 ml of hydrogen peroxide (30%) was added to terminate the reaction; it was washed by centrifugation until neutral, obtaining graphene oxide;

[0098] Preparation of amino-graphene:

[0099] 2 g of graphene oxide was dispersed in 200 ml of deionized water; ultrasonic treatment for 1 hour to form a uniform dispersion; add 2 g of stannous chloride and 2.5 g of cobalt hexammine complex; stirring at 60°C for 1 hour; add 10 ml of ethylenediamine, heated to 85±2°C for 6 hours; centrifugal washing, deionized water, ethanol, acetone in turn; 50°C vacuum drying for 24 hours to obtain aminated graphene.

[0100] The aminated graphene nanosheet used in the present application contains a large number of amino functional groups on the surface, which interact with the π-conjugated structure of graphene, partially destroying the conductive network of graphene. When the aminated graphene reacts with the epoxy group, a covalent bond is formed, further interrupting the electron transport channel. In addition, the addition amount of graphene in the present application (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, the low content and high dispersion state of aminated graphene mainly play the role of enhancing the material interface and improving the thermal stability, which actually increases the volume resistivity. This phenomenon has been verified by four-probe resistance test and transmission electron microscope observation.

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

[0102] Aminated graphene indeed has significantly different electrical properties from ordinary graphene. The introduction of amino functional groups will destroy part of the sp 2 conjugated structure of graphene, reducing its conductivity. At the same time, the addition amount below the percolation threshold isolates the graphene nanosheets from each other, and they cannot form a conductive network. These factors together lead to the phenomenon that the volume resistivity increases after adding aminated graphene, which is consistent with the principles of material science under certain conditions.

[0103] Unmodified graphene conductivity data: the measured conductivity is about 1.2×10 4 S / m, close to the reported value.

[0104] Aminated graphene conductivity data: the measured conductivity is significantly reduced to about 2.3×10 2 S / m, which decreases by about two orders of magnitude.

[0105] Comparison of volume resistivity of composites with different graphene content: The volume resistivity slightly increases as the amount of aminated graphene increases from 0.3 to 0.8 parts by weight, but remains in the order of 1014Ω·cm, confirming that the percolation threshold has not been reached.

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

[0107] The preparation method of the composite comprises the following steps:

[0108] (1) Dehydrate bisphenol A epoxy resin at 80°C under vacuum (15 mbar) for 2 hours, with moisture content controlled at 0.03%;

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

[0110] (3) Preheat CTBN liquid rubber to 70°C to reduce viscosity, with a stirring speed of 120 rpm, for 30 minutes, and then treat under reduced pressure (60 mbar) for 15 minutes to remove bubbles;

[0111] (4) Heat the epoxy resin treated in step (1) to 90°C, slowly add the preheated CTBN in step (3) at a rate of 1.5 g / min, with a stirring speed of 100 rpm, mix uniformly, and then heat to 120°C for 50 minutes to control the pre-reaction conversion rate at about 25%, at which 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 (initial 2,000 rpm for 15 minutes, then 4,000 rpm for 20 minutes, and 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, with the solvent residue controlled below 0.3%;

[0113] (6) In a three-necked reaction kettle, 75 parts by weight of polyether diol (molecular weight 2000) and 25 parts by weight of polyether triol (molecular weight 450) were mixed and stirred uniformly, and then dry nitrogen was passed at 60°C for 30 minutes. Then, isophorone diisocyanate (IPDI) was slowly added dropwise at 60°C for 30 minutes, with an NCO / OH equivalent ratio of 1.08. After the addition was completed, the temperature was raised to 70°C and the reaction was continued for 90 minutes, and samples were taken periodically 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, and blended for 25 minutes, and then degassed at 15 mbar for 5 minutes;

[0115] (8) The mixture of step (7) was cooled to 90°C, 2-methylimidazole (previously dissolved in a small amount of epoxy resin) and polyether amine were added, and stirred for 10 minutes. Then the temperature was raised to 120°C, and 4,4'-diamino diphenyl sulfone was added in two portions, and stirred until completely dissolved (about 15 minutes). Subsequently, nano-alumina, chopped glass fiber, antioxidant, ultraviolet absorber and dispersant were added, and stirred for 15 minutes until uniformly 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. The curing was carried out in stages: first at 120°C for 40 minutes, then at a rate of 1°C / min to 150°C for 90 minutes, and finally at a rate of 0.8°C / min to 180°C for 180 minutes;

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

[0118] The composite material of the present application has a two-component interpenetrating network structure (IPN), i.e. a three-dimensional network structure formed by interpenetration of the epoxy resin network and the polyurethane network. By controlling the epoxy resin and the curing agent to partially crosslink first (about 60-70% crosslinking degree), and then making the NCO groups in the polyurethane prepolymer react with the remaining active sites and form a second network, the interpenetration of the two independent crosslinking networks is finally realized.

[0119] The formation of interpenetrating network structure was confirmed by dynamic mechanical analysis (DMA). DMA thermograms of Examples 1-4 showed two distinct tan δ peaks, corresponding to the glass transition temperatures of polyurethane phase (-30°C) and epoxy phase (165°C), respectively. Comparative Example 3 (without interpenetrating network) showed only one major tan δ peak, confirming the absence of dual network structure. Transmission electron microscopy (TEM) observation showed that the epoxy phase and polyurethane phase formed interpenetrating structure with a size of about 50-100 nm, with blurred phase boundary and no distinct interface, further confirming the formation of interpenetrating network.

[0120] Characterization of interpenetrating network structure:

[0121] Dynamic mechanical analysis (DMA): TA Instruments DMA Q800 dynamic mechanical analyzer was used, dual cantilever mode, frequency 1 Hz, temperature ramp rate 3°C / min, temperature range -80°C to 250°C.

[0122] Transmission electron microscopy (TEM): JEOL JEM-2100F transmission electron microscope was used, and the sample was observed after epoxy embedding, ultrathin sectioning (thickness about 80 nm), and Ru04staining.

[0123] Interpenetrating network structure is a specific microstructure in material science, and its existence needs to be proved by suitable characterization methods. Dynamic mechanical analysis (DMA) is one of the most commonly used methods for characterizing interpenetrating networks, and the existence of different network phases can be proved by observing multiple peaks on the tan δ curve. Transmission electron microscopy (TEM) can directly observe the interpenetration of network structure. The addition of these characterization methods can effectively prove the formation of interpenetrating network structure.

[0124] Curing kinetics analysis curve: it shows that about 40% crosslinking degree can be reached at 120°C for 40 minutes, about 85% crosslinking degree can be reached at 150°C for 90 minutes, and more than 95% crosslinking degree can be reached at 180°C for 180 minutes.

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

[0126] Example 2

[0127] A graphene / liquid rubber synergistically modified epoxy resin interpenetrating network composite for electrical fence, consisting of the following components:

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

[0129] 12 parts by weight of carboxyl-terminated butylnitrile 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 nanoplatelets (lateral size 4 pm, thickness 6 nm),

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

[0133] 20 parts by weight of chopped glass fiber (length 4 mm, surface silane treatment),

[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 tetrakis[β-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate] antioxidant,

[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 method for preparing the composite material comprises the following steps:

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

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

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

[0143] (4) The epoxy resin treated in step (1) is heated to 90°C, and CTBN preheated in step (3) is slowly added at a rate of 1.2 g / min, with a stirring speed of 120 rpm. After mixing, the temperature is raised to 120°C, and pre-reaction is carried out for 45 minutes. The change in the content of epoxy groups is monitored by infrared spectroscopy, and the pre-reaction conversion rate is controlled to be about 22%;

[0144] (5) The pre-reaction system in step (4) is dispersed with graphene in a three-stage dispersion process, with the temperature controlled at 60±2°C, and the total dispersion time being 38 minutes. After completion, the solvent is removed under reduced pressure, and the residual amount of solvent is controlled to be less than 0.4%;

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

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

[0147] (8) The mixture is cooled to 90°C, and a catalyst and a polyether amine are added, and then other fillers and auxiliaries are added, and the mixture is mixed uniformly;

[0148] (9) The mixture is poured into a preheated mold, and is subjected to three-stage curing: 120°C / 35 minutes, 150°C / 80 minutes, and 180°C / 150 minutes;

[0149] (10) After demolding, stress relief treatment is carried out at 160°C for 80 minutes, and then slow cooling is carried out.

[0150] Example 3

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

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

[0153] 60 parts by weight of a polyurethane prepolymer,

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

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

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

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

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

[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 light absorber,

[0163] 1.5 parts by weight of dispersant.

[0164] The composite material was prepared in a similar way as in Example 1, but with adjustments in key parameters:

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

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

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

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

[0169] (5) The curing used a higher post-curing temperature (185 °C) and a longer time (180 minutes) to ensure a high degree of cross-linking.

[0170] Example 4

[0171] A graphene / liquid rubber synergistically modified epoxy resin interpenetrating network composite material for electrical fencing, consisting of the following components:

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

[0173] 45 parts by weight of polyurethane prepolymer,

[0174] 13 parts by weight of carboxyl-terminated butylnitrile 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 nanoplatelets (2 pm in lateral size, 4 nm in thickness),

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

[0178] 15 parts by weight of chopped glass fiber (length 3.5 mm, surface silane treatment),

[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 adopted a higher proportion of polyetheramine D400, which can provide higher crosslinking density and better temperature resistance. At the same time, the graphene nanoplatelets have a small size, which is beneficial to more uniform dispersion and higher specific surface area, enhancing the interfacial interaction. In the preparation process, moderate conditions were adopted, such as a pre-reaction time of 55 minutes, a conversion rate controlled at 28%, and a three-stage curing 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 with amine groups; at the 150°C stage, a second exothermic peak was observed, corresponding to the formation of epoxy and residual amine groups and polyurethane network; at the 180°C stage, the final exothermic peak was observed, corresponding to complete crosslinking. By integrating the enthalpy change of each stage, it was determined that the crosslinking degree at the 120°C stage was about 40%, at the 150°C stage reached 85%, and at the 180°C stage reached more than 95%. The different temperature stages controlled the reaction rate of different reactions, ensuring the ordered formation of the network structure.

[0186] Comparative Example 1 (without graphene)

[0187] To verify the synergistic reinforcing effect of graphene, a comparative formulation without graphene was designed, with the following composition:

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

[0189] 40 parts by weight of polyurethane prepolymer,

[0190] 10 parts by weight of carboxyl-terminated butylnitrile 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 nanoplatelets,

[0193] 1.0 parts by weight of nano-alumina,

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

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

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

[0197] 0.2 parts by weight of antioxidant,

[0198] 0.3 parts by weight of ultraviolet absorber,

[0199] 0.5 parts by weight of dispersant.

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

[0201] Comparative Example 2 (without liquid rubber)

[0202] In order to verify the toughening effect of liquid rubber, a comparative formula without liquid rubber is designed:

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

[0204] 40 parts by weight of polyurethane prepolymer,

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

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

[0207] 0.3 parts by weight of amino-functionalized graphene nanoplatelets,

[0208] 1.0 parts by weight of nano-alumina,

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

[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 dispersing agent.

[0215] The preparation method is the same as 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] In order to verify the importance of the interpenetrating network structure, a comparative formula without a polyurethane network is designed:

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

[0219] 0 parts by weight of polyurethane prepolymer,

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

[0221] 25 parts by weight of polyether amine (as a curing agent, not forming a polyurethane network),

[0222] 0.3 parts by weight of amino-functionalized graphene nanoplatelets,

[0223] 1.0 parts by weight of nano-alumina,

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

[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 dispersing agent.

[0230] The preparation method is the same as Example 1, but the polyurethane prepolymer preparation and introduction steps are omitted, and the amount of polyether amine 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] In order to comprehensively evaluate the performance of the example and comparative example materials, the following tests were conducted:

[0232] 1. Mechanical property test: Tensile property was tested according to ASTM D638 standard, impact strength was tested according to ASTM D256 standard, and the test was conducted at 23 °C and -40 °C.

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

[0234] 3. Weathering resistance test: UV aging test was conducted according to ASTM G154 standard (500 hours), and the mechanical property retention rate before and after aging was tested; salt spray test was conducted according to ASTM B117 standard (500 hours); temperature and humidity cycle test was conducted (-40 °C to 85 °C, 95% RH, 50 cycles), and the performance change after aging was tested.

[0235] 4. Special performance test for electric fence: Tracking index was tested (IEC 60112 standard); insulation strength test under high and low temperature impact was conducted (from -40 °C to 80 °C, 30 cycles).

[0236] The test results are summarized in Tables 1-3:

[0237] Table 1 Mechanical property test results

[0238]

[0239] Table 2 Electrical property test results

[0240]

[0241] Table 3 Weathering resistance and special performance test results

[0242]

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

[0244] ** High and low temperature impact resistance cycle number refers to the maximum cycle number that maintains insulation strength up to standard in cycle test, > 30 indicates that the performance is still up to standard after 30 cycles;

[0245] Table 4 Material structure characterization and analysis method summary

[0246]

[0247]

[0248] From the test results, it can be seen that:

[0249] 1. Mechanical properties: All examples 1-4 exhibit excellent mechanical property balance, especially maintaining good impact strength at low temperature (-40°C). Example 3, with the highest content of graphene and liquid rubber, shows the highest impact strength and elongation at break. Comparative example 1 (without graphene) and comparative example 2 (without liquid rubber) show a significant decrease in impact strength at low temperature, demonstrating the synergistic toughening effect of graphene and liquid rubber. Comparative example 2, while having higher tensile strength, shows lower elongation at break and higher brittleness.

[0250] 2. Electrical properties: All samples show good electrical insulation properties, but examples 2 and 3 maintain higher volume resistivity under high temperature and high humidity conditions, mainly due to the synergistic effect of interpenetrating network structure and graphene, improving the environmental stability of the material. Comparative example 3 (without interpenetrating network) shows a significant decrease in volume resistivity under high temperature and high humidity conditions, demonstrating the important contribution of interpenetrating network structure to the stability of electrical properties.

[0251] 3. Weather resistance and special performance: Example 3 shows the most excellent weather resistance, with strength retention rate of 98.1% after UV aging, resistivity retention rate of 98.5% after salt spray test, and performance index of 95.3% after temperature and humidity cycling. In contrast, comparative example 3 (without interpenetrating network) performs the worst in various weather resistance tests, especially with a performance index of only 61.2% after temperature and humidity cycling, indicating that the polyurethane interpenetrating network structure is crucial to improving the aging resistance of the material. In the electrical fence special performance test, examples 2-4 can complete 30 high and low temperature impact cycles while maintaining insulation performance, while the comparative materials show varying degrees of performance degradation.

[0252] Through comparative analysis, the following conclusions can be drawn:

[0253] 1. Synergistic toughening mechanism of graphene / liquid rubber: 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 basic toughness through microphase separation, while graphene further improves the toughness and strength of the material by bridging microcracks and enhancing interfacial adhesion. The performance difference between comparative examples 1 and 2 proves this. Scanning electron microscopy (SEM) observation confirms the microphase separation structure formed by CTBN and epoxy resin. After fracture, extraction (using acetone at 70°C for 24 hours to remove unreacted components) and gold sputtering treatment, uniform spherical phases with a diameter range of 0.8-1.5 μm are observed under SEM, which is consistent with the theoretical expectation of 0.5-2 μm. Energy dispersive spectroscopy (EDS) confirms that these spherical phases are rich in nitrogen elements, indicating that they are mainly composed of CTBN. This microphase structure is a key factor in providing toughness and low temperature impact strength

[0254] 2. Importance of 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 significant performance decline of Comparative Example 3 proves the importance of the interpenetrating network structure for materials used in electrical 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 performed best 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 synergy of graphene / liquid rubber / polyurethane interpenetrating network produces unexpected performance improvements, especially in low-temperature impact strength and electrical performance stability under high-temperature and high-humidity conditions. This synergistic effect, which is difficult to predict by simply adding the individual contributions of each component, is an important innovation of the present invention.

[0257] Example 3 is determined to be the best implementation of the present invention, with the most comprehensive performance advantages. However, depending on the specific application environment and cost requirements, appropriate formulations and process parameters can be selected within the scope of Examples 1-4.

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

Claims

1. A composite material for use in an electric fence, characterised in that, The composite material is composed of the following components by weight: 100-120 parts by weight of bisphenol A type epoxy resin, 40-60 parts by weight of polyurethane prepolymer, 10-15 parts by weight of carboxyl-terminated butyl nitrile liquid rubber CTBN, 5-20 parts by weight of polyether amine, 0.3-0.8 parts by weight of aminated graphene nanosheet, 1.0-3.0 parts by weight of nano-alumina, 10-30 parts by weight of chopped glass fiber, 20-30 parts by weight of 4,4'-diamino diphenyl 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; The composite material has an interpenetrating network structure, including an epoxy resin network and a polyurethane network interpenetrating each other; the carboxyl-terminated butyl nitrile liquid rubber reacts with the epoxy resin to form a microphase separation structure, and the microphase size is 0.5-2 μm; The composite material maintains stable electric insulation performance in the temperature range of -40°C to 80°C, with volume resistivity greater than 10 12 Ω·cm, and dielectric strength greater than 20 kV / mm.

2. The composite material of claim 1, wherein, The epoxy equivalent weight of the bisphenol A type epoxy resin is 170-280 g / eq, the acrylonitrile content of the carboxyl-terminated butyl nitrile liquid rubber is 24-28 wt%, and the average lateral size of the aminated graphene nanosheet is 1-5 μm and the thickness is 2-8 nm.

3. The composite material of claim 1, wherein, The polyether amine includes polyether diamine D400 and polyether diamine D2000, and the weight ratio is 30:70 to 70:

30.

4. A method of making the composite material of any one of claims 1-3, characterized in that, The method comprises the following steps: (1) vacuum dehydration of bisphenol A type epoxy resin at 80±2℃ for 2-3 hours, with water content controlled at ≤0.05%; (2) ultrasonic dispersion of amino-functionalized graphene nanosheets in acetone for 30-40 minutes, with ultrasonic power of 300-400W, followed by solvent replacement to obtain graphene / methyl ethyl ketone dispersion; (3) preheating of carboxyl-terminated butyronitrile liquid rubber CTBN to 70±2℃ for viscosity reduction, and vacuum treatment for 15-20 minutes to remove bubbles; (4) heating of the epoxy resin treated in step (1) to 90±2℃, slow addition of the preheated CTBN in step (3) at a feeding rate of 1-2g / min, uniform mixing, heating to 120±2℃, pre-reaction for 40-60 minutes, and control of the pre-reaction conversion rate at 20%-30%; (5) cooling of the pre-reaction system in step (4) to 60±2℃, batch addition of the graphene dispersion in step (2) under high shear dispersion, dispersion time of 30-40 minutes, followed by solvent removal under reduced pressure, and control of the residual solvent amount at <0.5%; (6) preparation of polyurethane prepolymer in a three-necked reaction kettle by reacting polyether polyol with isophorone diisocyanate at 70±2℃ for 80-100 minutes; (7) slow addition of the polyurethane prepolymer in step (6) to the mixture in step (5) at 70±2℃ at a feeding rate of 2-3g / min, blending for 20-30 minutes, and vacuum degassing; (8) cooling of the mixture in step (7) to 90±2℃, addition of imidazole catalyst and polyether amine, uniform mixing, heating to 120±2℃, addition of 4,4'-diamino diphenyl sulfone, stirring until complete dissolution, addition of nano-alumina, chopped glass fiber and other additives, and uniform mixing; (9) pouring of the mixture in step (8) into a mold preheated to 120±5℃ at 80±2℃, and staged curing: first keeping at 120±2℃ for 30-40 minutes, then heating to 150±2℃ for 60-90 minutes, and finally heating to 180±2℃ for 120-180 minutes; and (10) demolding of the cured material, stress relief treatment at Tg-20℃ for 60-90 minutes, and slow cooling to room temperature.

5. The method of claim 4, wherein, The pre-reaction degree in step (4) is controlled by monitoring the viscosity and epoxy group content of the mixture, and the pre-reaction is terminated when the viscosity increases to 1.5-2 times the initial value.

6. The method of claim 4, wherein, The graphene dispersion in step (5) is performed by using a high shear disperser, and the dispersion process comprises initial low-speed dispersion at 2,000rpm for 10-15 minutes, high-speed dispersion at 4,000-5,000rpm for 15-20 minutes, and final low-speed dispersion at 2,000rpm for 10 minutes.

7. The method of claim 4, wherein, The polyurethane prepolymer in step (6) 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, and the amount of isophorone diisocyanate is 1.05-1.10 times the calculated amount, with the equivalent ratio of NCO group to OH group being 1.05-1.

10.

8. The method of claim 4, wherein, The crosslinking degree of the segmented 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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