An aging-resistant resin core rod for composite insulators and its preparation method

Abstract

This application provides an aging-resistant resin core rod for composite insulators and its preparation method. The aging-resistant resin core rod comprises modified glass fiber and epoxy resin compound. The modified glass fiber is obtained by modifying glass fiber with imidazolium-phosphate. The epoxy resin compound comprises the following raw materials in parts by weight: 100 parts epoxy resin, 70-90 parts anhydride curing agent, and 0.1-1 parts curing accelerator. By introducing an imidazolium-phosphate interface layer onto the glass fiber surface and combining it with an anhydride-cured epoxy resin system, the bonding performance of the fiber / resin interface can be significantly improved, the interfacial shear load-bearing capacity can be increased, and the attenuation of interfacial strength under humid and hot conditions can be effectively suppressed. This allows the core rod material to maintain high interfacial bonding stability and mechanical load-bearing capacity under long-term hydrothermal conditions.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, specifically to an aging-resistant resin core rod for composite insulators and its preparation method. Background Technology

[0002] Composite insulators have been widely used in high-voltage transmission lines due to their advantages such as light weight, excellent resistance to flashover, and high mechanical strength. The core load-bearing component, the mandrel, must withstand tension, bending, vibration, and electric field effects during long-term service; its performance changes directly affect the safety and stability of the line operation. Existing mandrels mainly adopt a glass fiber reinforced epoxy resin structure, with the glass fiber providing a high-strength skeleton and the resin matrix handling stress transfer and environmental protection. However, under long-term outdoor operation conditions, the mandrel is inevitably exposed to complex environments such as humidity, heat, ultraviolet radiation, and electrolytic corrosion. Performance degradation easily occurs at the interface, leading to a decline in the mechanical properties of the insulator or even fracture failure.

[0003] Under the combined effects of high humidity and high temperature, the interfacial layer between glass fiber and epoxy resin is susceptible to moisture penetration, leading to decreased interfacial bonding and failure modes such as microcrack propagation and interfacial delamination. Changes in interfacial properties often precede the decline in overall mechanical properties; therefore, interfacial shear strength and its retention after hygrothermal aging are key indicators for evaluating the long-term reliability of mandrel materials. In existing technologies, to improve interfacial bonding and aging resistance, optimization methods are typically employed, such as improving the crosslinking density of the resin matrix, introducing hydrolysis-resistant structural units, or using silane coupling agents to enhance interfacial adhesion. Although these methods can improve initial interfacial bonding, under long-term hygrothermal conditions, problems such as bond relaxation, coupling layer hydrolysis, and resin segment migration may still occur in the interfacial region, gradually weakening the initial reinforcing effect.

[0004] Therefore, while maintaining high initial interfacial adhesion performance, further improving the stability of the glass fiber / resin interface to humid and hot environments, especially enhancing the interfacial shear strength retention rate after humid and hot aging, is an important problem that current composite insulator core rod material technology urgently needs to solve. Summary of the Invention

[0005] This application provides an aging-resistant resin core rod for composite insulators and its preparation method, aiming to solve the problem of interface strength decay of composite insulator core rods under long-term humid and hot and complex service environments.

[0006] In a first aspect, this application provides an aging-resistant resin core rod for composite insulators, comprising modified glass fiber and epoxy resin compound, wherein the modified glass fiber is obtained by modifying glass fiber with imidazolium-phosphate; the epoxy resin compound comprises the following raw materials in parts by weight: 100 parts epoxy resin, 70-90 parts acid anhydride curing agent, and 0.1-1 parts curing accelerator.

[0007] According to this application, by introducing an imidazolium-phosphate interface layer on the surface of glass fiber and combining it with an anhydride-cured epoxy resin system, the bonding performance of the fiber / resin interface can be significantly improved, the interfacial shear load-bearing capacity can be increased, and the attenuation of interfacial strength under humid and hot conditions can be effectively suppressed, so that the mandrel material can maintain high interfacial bonding stability and mechanical load-bearing capacity under long-term hydrothermal conditions.

[0008] Specifically, after the glass fiber is introduced with imidazole groups, these groups are protonated under the action of phosphoric acid to form an imidazole-onium structure, resulting in a stable positively charged center at the interface. A stable ion-pairing structure is formed between the imidazole-onium cation and the phosphate anion, giving the interface charge-dependent characteristics. On the one hand, this interface layer can adhere more firmly to the silica-oxygen structure on the glass fiber surface, enhancing interfacial compatibility and adhesion stability; on the other hand, the imidazole-onium structure can interact with the polar segments in the epoxy resin curing network, helping to improve the interfacial stress transfer efficiency and thus increasing the initial interfacial shear strength.

[0009] Meanwhile, anhydride-cured epoxy resins belong to a stepwise crosslinking curing system, and their crosslinking process is closely related to the local polar environment. The highly polar region constructed by imidazolium-phosphate at the interface allows the resin to preferentially form a dense curing network near the fiber surface, constituting an "interface reinforcement zone." This region is denser than the crosslinked structure inside the resin, restricting chain segment movement and effectively reducing the rate of water penetration, thus enhancing the interface's resistance to hydrolysis and microcrack propagation.

[0010] In addition, phosphate groups have multi-site adsorption characteristics, which can generate auxiliary interactions with the polar structures in the curing system, so that the interface layer can maintain high structural stability under humid and hot conditions, avoid interface softening, debonding and microcrack accumulation, and thus maintain excellent humid and hot interface strength retention rate.

[0011] Based on the combined effects of the aforementioned interfacial charge structure, polar-induced curing, and interfacial dense layering effect, this application achieves a significant improvement in initial interfacial shear strength without changing the fiber ratio and resin matrix system. It also maintains a high level of interfacial load-bearing capacity under humid heat aging conditions and maintains good mechanical properties of the core rod material, thereby significantly improving the long-term operational reliability of the composite insulator core rod material.

[0012] In some embodiments, the method for preparing the modified glass fiber includes the following steps:

[0013] S1: React glass fiber with imidazole silane coupling agent to graft imidazole groups onto the surface of glass fiber, thereby obtaining imidazole modified glass fiber.

[0014] S2: Phosphorylation reaction is carried out on imidazole-modified glass fiber to protonate the imidazole matrix and obtain modified glass fiber.

[0015] In some of the above embodiments, an imidazole-based silane coupling agent is first used to form siloxane bonds with the silanol groups on the glass fiber surface, thereby stably and directionally anchoring the imidazole groups to the fiber surface and constructing initial polar interface sites. Subsequently, the imidazole groups are phosphorylated, protonating the imidazole nitrogen atoms to form an imidazole-onium structure, which then forms an ion-paired bond with the phosphate group. Because the imidazole structure is first fixed to the fiber surface via covalent bonds, the problem of an unstable interface layer caused by hydrolysis or reversible adsorption when phosphate is directly applied to the glass fiber surface can be avoided, thus making the subsequently formed imidazole-onium phosphate interface layer more stable.

[0016] It should be noted that imidazole silane coupling agent has the meaning known in the art, that is, a silane coupling agent containing an imidazole group. As an example, in one embodiment of this application, N-(trimethoxysilylpropyl)imidazolium is used as an imidazole silane coupling agent.

[0017] In some embodiments, step S1 includes:

[0018] 100 parts of glass fiber and 5-10 parts of imidazole silane coupling agent are dispersed in 500-1000 parts of ethanol aqueous solution and reacted at 40-60℃ for 2-4 hours to obtain imidazole modified glass fiber.

[0019] In some of the above embodiments, the ethanol-water mixture can promote the moderate hydrolysis and uniform dispersion of the silane coupling agent, allowing the imidazole groups to be more stably fixed to the glass fiber surface. Controlling the reaction temperature and time allows for sufficient condensation of the silane with the glass fiber surface while reducing silane aggregation. This treatment method can form a uniform and robust imidazole functional layer on the glass fiber surface, laying the foundation for subsequent phosphorylation and interface reinforcement.

[0020] In some implementations, step S2 includes:

[0021] 100 parts of imidazole-modified glass fiber were impregnated in 500-1000 parts of 0.1wt%-1wt% composite phosphoric acid aqueous solution for 0.5-2 min to obtain modified glass fiber;

[0022] The composite phosphoric acid aqueous solution comprises phosphoric acid and polyphosphoric acid with an average degree of polymerization of 5 to 10, and the mass ratio of phosphoric acid to polyphosphoric acid is 1.5 to 2.5:1.

[0023] In some of the above embodiments, the inventors discovered that when imidazole groups are protonated using a certain ratio of phosphoric acid and polyphosphoric acid, the resulting material exhibits higher interfacial shear strength and better retention of interfacial strength during wet heat aging. This may be because the combination of phosphoric acid and polyphosphoric acid possesses both rapid protonation capability and interfacial densification capability. Phosphoric acid has a high degree of dissociation, enabling it to rapidly react with imidazole groups to form an imidazole-onium structure, thereby establishing an initial interfacial charge layer. Polyphosphoric acid, with a degree of polymerization of 5-10, has a longer-chain phosphoric acid structure, which can form further multi-site adsorption and spatial barriers around the imidazole-onium structure, contributing to improved interfacial layer compactness and hydrolytic stability. By controlling the ratio of the two to 1.5-2.5:1, a stable and ordered interfacial protective layer can be constructed while ensuring rapid protonation efficiency.

[0024] In systems using only phosphoric acid, while single-phosphoric acid treatment can achieve imidazole protonation, the interfacial layer thickness is limited and prone to ion migration under humid and hot conditions, resulting in insufficient long-term water resistance and decreased interfacial stability. Using only polyphosphoric acid, the protonation rate in pure polyphosphoric acid systems is slow, making it difficult to achieve a uniform reaction. Furthermore, the high viscosity and low degree of dissociation may lead to uneven treatment layer distribution and limited interfacial reaction efficiency. The composite interfacial layer formed by the synergistic effect of phosphoric acid and moderately polymerized polyphosphoric acid possesses the dual advantages of rapidly fixing the imidazole onium structure and gradually building a stable interfacial network, resulting in a denser, more uniform interfacial layer with stronger resistance to water erosion.

[0025] Therefore, the interface regulation method achieved through the composite phosphoric acid system helps to construct a stable imidazolium-phosphate network, enabling the modified glass fiber to maintain a high interfacial bonding capacity under high humidity and high temperature environments. Compared with the traditional single acid treatment method, it can achieve higher interfacial shear strength and better wet heat aging effect.

[0026] In some embodiments, the epoxy resin includes alicyclic epoxy resin and aromatic epoxy resin, wherein the mass ratio of the alicyclic epoxy resin to the aromatic epoxy resin is 0.1 to 0.3:1.

[0027] In the above embodiments, the inventors discovered that introducing a certain proportion of alicyclic epoxy resin into the aromatic epoxy resin system can further improve the interfacial shear strength and resistance to humid heat aging. This may be because the aromatic ring skeleton in the network formed after the aromatic epoxy resin cures has high structural rigidity and dimensional stability, which makes it easy for network segments to form localized stress concentration areas under curing shrinkage and service loads. Furthermore, since the segment conformation is difficult to adjust, when moisture penetrates the interface and disturbs the interfacial polarity under humid heat, the cured network is more prone to microscale debonding or interfacial energy weakening at localized stress concentration sites, manifested as a decrease in interfacial shear strength with aging time.

[0028] In contrast, alicyclic epoxy resins, after curing, have a molecular backbone composed of saturated ring structures, exhibiting greater chain segment flexibility and conformational adjustment capabilities. During curing and service, their network can disperse interfacial stress through localized chain segment relaxation, preventing the formation of high-stress concentration areas. Under humid and hot conditions, the alicyclic epoxy interfacial region can maintain interfacial adhesion energy through chain segment-mediated micro-stress release and synergistic structural adjustment, making it less prone to interfacial micro-cracks or debonding.

[0029] Meanwhile, the imidazolium-phosphate interface structure possesses localized charge and polar field effects, providing a local proton source and polar activation for the epoxy ring-opening process in the early stages of the epoxy-anhydride curing reaction. Alicyclic epoxides, due to their higher saturated ring strain, exhibit more sensitive epoxy groups to proton-induced ring-opening, and their chain flexibility makes them more prone to enrichment and conformational adjustment in the interfacial region. Therefore, in this interfacial environment, alicyclic epoxides tend to preferentially undergo ring-opening curing compared to aromatic epoxides, forming a locally dense cross-linked structure.

[0030] Therefore, under the induction of imidazolium-phosphate modified interface, alicyclic epoxy is more prone to early curing and network densification in the interface region, forming a gradient structure with the aromatic epoxy network, giving the interface layer the effects of high adhesion, stress dispersion, and resistance to damp heat. Compared with using aromatic epoxy alone, this embodiment can significantly improve the interface performance under damp heat aging while maintaining the overall mechanical strength, and compared with using alicyclic epoxy alone, it can maintain the necessary stiffness and dimensional stability and enhance the heat resistance of the outer layer of the interface, demonstrating the complementary and synergistic effect of the two in the interface region.

[0031] In some embodiments, the alicyclic epoxy resin includes at least one of hydrogenated bisphenol A type epoxy resin and hydrogenated bisphenol F type epoxy resin;

[0032] The aromatic epoxy resin includes at least one of bisphenol A type epoxy resin and bisphenol F type epoxy resin.

[0033] In some of the above embodiments, the alicyclic epoxy resin is preferably hydrogenated bisphenol A type epoxy resin or hydrogenated bisphenol F type epoxy resin, whose saturated ring structure is beneficial to improving the resin's resistance to damp heat and its interfacial stress relief ability; the aromatic epoxy resin is preferably bisphenol A type epoxy resin or bisphenol F type epoxy resin, which can provide higher matrix strength and stiffness, making it easier to maintain the stability of the mandrel structure performance. By combining the two types of epoxy resins, a balance can be achieved between interfacial toughening and overall mechanical properties, enabling the composite material to maintain a high initial interfacial shear strength while improving the interfacial strength retention rate after damp heat aging.

[0034] As an example, in one embodiment of this application, commercially available Eponex® 1510 hydrogenated bisphenol A epoxy resin is used as an alicyclic epoxy resin, and E51 bisphenol A type epoxy resin is used as an aromatic epoxy resin.

[0035] In some embodiments, the epoxy resin compound further includes 1 to 2 parts of epoxy-terminated polysiloxane.

[0036] In some of the above embodiments, adding a small amount of epoxy-terminated polysiloxane to the resin system can improve the wetting and spreading of the glass fiber bundles, enhance the resin's impregnation and coating effect on the fiber surface, reduce interfacial gaps and dry spots, thereby improving the initial interfacial bonding quality. Simultaneously, the epoxy-terminated structure can participate in resin curing, fixing it within the resin phase near the fiber interface during the curing process.

[0037] Because the imidazolium-phosphate interface layer has strong polarity and charge interaction, it preferentially attracts highly polar epoxy resin segments to the fiber surface, while relatively low-polarity silica segments tend to be distributed on the outer side of the interface. During the curing reaction, the silica segments participate in cross-linking and are fixed through end-group epoxy, forming a gradient interface structure that gradually transitions from the ion-exchange interface layer on the glass fiber surface to the flexible silica segments.

[0038] This gradient interface structure can alleviate curing shrinkage stress through the flexible adjustment and local relaxation of the silicon-oxygen segments. Furthermore, the hydrophobicity of the silicon-oxygen segments slows down the penetration and diffusion of moisture along the interface, and, in conjunction with the heat resistance of the benzene rings, maintains higher interfacial adhesion stability under humid and hot conditions. Through these synergistic effects, the interfacial shear strength of the material after humid and hot aging can be further improved.

[0039] In some embodiments, the epoxy-terminated polysiloxane comprises a propylene oxide-terminated polydimethylsiloxane with a number average molecular weight of 1000-3000. As an example, this application uses a propylene oxide-terminated polydimethylsiloxane with a number average molecular weight of 2000 as the epoxy-terminated polysiloxane.

[0040] In some embodiments, the modified glass fiber comprises 70% to 80% by mass in the aging-resistant resin core rod. Based on the above embodiments, a higher fiber content can significantly improve the load-bearing capacity and axial strength of the core rod, which is beneficial for leveraging the interfacial bonding advantages, enhancing interfacial shear strength, and maintaining stable interfacial load-bearing capacity under humid and hot conditions.

[0041] In some embodiments, the glass fiber comprises ECR glass fiber with an average diameter of 12-18 μm. Based on the above embodiments, ECR glass fiber has a low alkali content and excellent water erosion resistance, and can maintain fiber strength stability in humid and hot environments; the fiber diameter in the range of 12-18 μm can provide a high interfacial bonding area while ensuring wettability and formability, thereby facilitating the function of the interfacial modification system and improving interfacial shear strength and humid and hot aging retention rate.

[0042] In some embodiments, the anhydride curing agent includes at least one of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride. Based on the above embodiments, the resin network structure obtained by curing with the above anhydride curing agent is uniform, has moderate polarity, and has low curing stress and good water resistance, which can cooperate with the interface structure of this application to form a dense and stable cured layer.

[0043] In some embodiments, the curing accelerator is selected from at least one of 2-methylimidazole and 2-ethyl-4-methylimidazole. Based on the above embodiments, imidazole accelerators can synergistically work with the imidazole-phosphate interface of this application to ensure that the curing rate of the interface and the bulk phase matches during the resin curing process, forming a stable curing network and improving the density and continuity of the interfacial adhesive layer.

[0044] Secondly, this application provides a method for preparing an aging-resistant resin core rod for composite insulators, comprising:

[0045] Provides the raw materials comprising the modified glass fiber and epoxy resin compound in the aging-resistant resin core rod according to any embodiment of the first aspect;

[0046] The raw materials are mixed to obtain an epoxy resin compound;

[0047] The epoxy resin compound is mixed with the modified glass fiber, pultruded and then cured to obtain an aging-resistant resin core rod.

[0048] According to this application, by employing the above-described preparation method, effective matching between the modified glass fiber surface functional layer and the resin curing process can be achieved, thereby enabling the fiber-resin interface to form a stable and continuous interfacial adhesive layer structure during molding. During the pultrusion stage, the imidazolium-phosphate modified glass fiber and epoxy resin compound are in full contact, allowing the imidazolium structure at the interface to generate an interfacial induced effect with the epoxy-anhydride curing system. This causes the resin to preferentially cure in the fiber interface region and form a dense transition layer. During curing, this cured interfacial layer is further fixed and continuously covers the fiber surface, helping to reduce voids and micro-defects at the fiber-resin interface and improve interfacial bonding quality. The core rod resin prepared by this method exhibits high interfacial shear strength in its initial state and maintains a high interfacial strength retention rate after damp heat aging, contributing to improved long-term service reliability of the composite insulator core rod material.

[0049] Compared with the prior art, the beneficial effects of this application are at least as follows:

[0050] This application constructs an imidazolium-phosphate interface layer on the surface of glass fiber and works synergistically with an anhydride-cured epoxy resin system to form a denser interface curing structure on the fiber surface. This interface structure can improve the resin spreadability and curing uniformity at the fiber / resin interface, enhance interfacial adhesion, and thus significantly improve the initial interfacial shear strength of the mandrel material. At the same time, the ion pairing structure of the imidazolium-phosphate interface layer and the gradient transition interface formed after resin curing can effectively relieve interfacial stress and inhibit moisture penetration, so that the interface maintains high structural stability under long-term humid heat conditions and significantly improves the interfacial strength retention rate after humid heat aging. Detailed Implementation

[0051] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0052] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0053] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0054] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0055] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0056] Hydrogenated bisphenol A epoxy resin, Eponex® 1510;

[0057] Bisphenol A epoxy resin, E51;

[0058] N-(trimethoxysilylpropyl)imidazolium, CAS No. 70851-51-3;

[0059] Polyphosphoric acid, with an average degree of polymerization of 6;

[0060] The number-average molecular weight of the epoxypropoxypropyl-terminated polydimethylsiloxane is approximately 2000.

[0061] ECR glass fiber, with an average diameter of approximately 16 μm.

[0062] Preparation Example 1

[0063] Preparation of modified glass fibers:

[0064] Add 700 parts of ethanol and 300 parts of deionized water to a reaction vessel and stir to form a transparent mixture; add 7 parts of imidazole silane coupling agent and stir evenly to form a transparent hydrolysis solution; heat the system to 50°C and maintain the temperature; immerse 100 parts of ECR ​​glass fiber in the solution; maintain 50°C and circulate the solution for 3 hours; remove the fiber and remove excess liquid; place the impregnated fiber in a 60°C hot air oven and dry for 2 hours to obtain imidazole modified glass fiber;

[0065] Add 994 parts of deionized water to a reaction vessel; add 4 parts of phosphoric acid and 2 parts of polyphosphoric acid in sequence, and stir to form a 0.6 wt% composite phosphoric acid solution; immerse 100 parts of imidazole-modified glass fiber in the composite phosphoric acid solution; immerse for 1 min, keeping the solution gently stirred; remove the fiber, and remove excess solution from the surface by gently pressing with a rubber roller; pre-dry at room temperature under ventilation for 30 min; then dry at 60℃ for 1.5 h to obtain imidazole-phosphate modified glass fiber.

[0066] Preparation Example 2

[0067] Preparation of modified glass fibers:

[0068] Add 700 parts of ethanol and 300 parts of deionized water to a reaction vessel and stir to form a transparent mixture; add 7 parts of imidazole silane coupling agent and stir evenly to form a transparent hydrolysis solution; heat the system to 50°C and maintain the temperature; immerse 100 parts of ECR ​​glass fiber in the solution; maintain 50°C and circulate the solution for 3 hours; remove the fiber and remove excess liquid; place the impregnated fiber in a 60°C hot air oven and dry for 2 hours to obtain imidazole modified glass fiber;

[0069] Add 994 parts of deionized water to the reaction vessel; add 6 parts of phosphoric acid sequentially and stir to form a 0.6 wt% phosphoric acid solution; immerse 100 parts of imidazole-modified glass fiber in the composite phosphoric acid solution; immerse for 1 min while keeping the solution gently stirred; remove the fiber and gently press it with a rubber roller to remove excess solution from the surface; pre-dry at room temperature under ventilation for 30 min; then dry at 60℃ for 1.5 h to obtain imidazole-phosphate modified glass fiber.

[0070] Preparation Example 3

[0071] Preparation of modified glass fibers:

[0072] Add 700 parts of ethanol and 300 parts of deionized water to a reaction vessel and stir to form a transparent mixture; add 7 parts of imidazole silane coupling agent and stir evenly to form a transparent hydrolysis solution; heat the system to 50°C and maintain the temperature; immerse 100 parts of ECR ​​glass fiber in the solution; maintain 50°C and circulate the solution for 3 hours; remove the fiber and remove excess liquid; place the impregnated fiber in a 60°C hot air oven and dry for 2 hours to obtain imidazole modified glass fiber;

[0073] Add 996 parts of deionized water to a reaction vessel; add 6 parts of polyphosphoric acid sequentially and stir to form a 0.6 wt% polyphosphoric acid solution; immerse 100 parts of imidazole-modified glass fiber in the composite phosphoric acid solution; immerse for 1 min while keeping the solution gently stirred; remove the fiber and gently press it with a rubber roller to remove excess solution from the surface; pre-dry at room temperature under ventilation for 30 min; then dry at 60℃ for 1.5 h to obtain imidazole-phosphate modified glass fiber.

[0074] Example 1

[0075] Preparation of aging-resistant resin core rods for composite insulators:

[0076] The epoxy resin compound is prepared as follows: 85 parts of bisphenol A type epoxy resin, 15 parts of hydrogenated bisphenol A type epoxy resin, 80 parts of methyl hexahydrophthalic anhydride, 0.5 parts of 2-ethyl-4-methylimidazolium and 1.5 parts of epoxypropoxypropyl-terminated polydimethylsiloxane are stirred evenly at 50°C and degassed for later use.

[0077] The modified glass fiber prepared in Preparation Example 1 was introduced into the resin impregnation tank to fully wet the epoxy resin. The resin content was controlled by the guide plate and the extrusion die so that the fiber accounted for about 75 wt% of the final cured mandrel.

[0078] After being impregnated with resin, the fiber bundles enter a pultrusion mold for continuous molding. The mold is sequentially set as a preheating zone, a reaction zone, and a post-curing zone along the fiber travel direction. The temperature and time are controlled at 90℃ / 2h, 140℃ / 3h, and 170℃ / 4h, respectively. The fiber bundles are oriented and gradually cured in the mold cavity to form a mandrel with a diameter of approximately 20mm. Subsequently, it is continuously output by a traction device, cooled at room temperature, and cut into the required length to obtain an aging-resistant resin mandrel.

[0079] Example 2

[0080] Preparation of aging-resistant resin core rods for composite insulators:

[0081] It is largely the same as Example 1, except that the modified glass fiber obtained in Preparation Example 2 is used instead of the modified glass fiber obtained in Preparation Example 1.

[0082] Example 3

[0083] Preparation of aging-resistant resin core rods for composite insulators:

[0084] It is largely the same as Example 1, except that the modified glass fiber obtained in Preparation Example 3 is used instead of the modified glass fiber obtained in Preparation Example 1.

[0085] Example 4

[0086] Preparation of aging-resistant resin core rods for composite insulators:

[0087] It is largely the same as Example 1, except that:

[0088] The epoxy resin compound is prepared as follows: 100 parts of bisphenol A type epoxy resin, 80 parts of methyl hexahydrophthalic anhydride, 0.5 parts of 2-ethyl-4-methylimidazolium and 1.5 parts of epoxypropoxypropyl-terminated polydimethylsiloxane are taken, stirred evenly at 50°C and degassed for later use.

[0089] Example 5

[0090] Preparation of aging-resistant resin core rods for composite insulators:

[0091] It is largely the same as Example 1, except that:

[0092] The epoxy resin compound is prepared as follows: Take 50 parts of bisphenol A type epoxy resin, 50 parts of hydrogenated bisphenol A type epoxy resin, 80 parts of methyl hexahydrophthalic anhydride, 0.5 parts of 2-ethyl-4-methylimidazolium and 1.5 parts of epoxypropoxypropyl-terminated polydimethylsiloxane, stir evenly at 50°C and degas for later use.

[0093] Example 6

[0094] Preparation of aging-resistant resin core rods for composite insulators:

[0095] It is largely the same as Example 1, except that:

[0096] The epoxy resin compound is prepared as follows: Take 85 parts of bisphenol A type epoxy resin, 15 parts of hydrogenated bisphenol A type epoxy resin, 80 parts of methylhexahydrophthalic anhydride and 0.5 parts of 2-ethyl-4-methylimidazole, stir evenly at 50°C and degas for later use.

[0097] Comparative Example 1

[0098] Preparation of aging-resistant resin core rods for composite insulators:

[0099] It is largely the same as Example 1, except that:

[0100] Unmodified ECR glass fibers were used instead of the modified glass fibers prepared in Preparation Example 1.

[0101] Test section

[0102] Interfacial shear strength test: Using the aging-resistant resin mandrels obtained in each example and comparative example, round rod specimens with a diameter of approximately 20 mm and a length of approximately 120 mm were cut from the mandrel body. Horizontal shear tests were performed on a three-point bending apparatus according to ASTM D4475 standard, with the span distance set to approximately 5 times the specimen diameter and the loading speed at 1~2 mm / min. The maximum load at specimen failure was recorded, and the interfacial shear strength τ (MPa) was calculated. The results are shown in Table 1.

[0103] Interfacial shear strength retention rate test after damp heat aging: A round rod sample with a diameter of approximately 20 mm and a length of approximately 120 mm was cut from the core rod of each of the same batch of aging-resistant resin core rods obtained in various examples and comparative examples. The sample was immersed in deionized water and kept at a constant temperature of (95±2)℃ for 168 h. After aging, the surface moisture was washed off, the sample was allowed to cool naturally to room temperature and dried, and the interfacial shear strength was tested again using the same method described above. The shear strength τ1 (MPa) after aging was obtained, and the interfacial shear strength retention rate R (%) after damp heat aging was calculated as R = τ1 / τ × 100%. The results are shown in Table 1.

[0104] Table 1

[0105]

[0106] According to Table 1, the interfacial shear strength τ and the interfacial shear strength retention rate R after damp heat aging of each embodiment are significantly higher than those of Comparative Example 1, indicating that the aging-resistant resin core provided in this application has high interfacial shear performance and good damp heat aging retention effect. The possible reason is that in Comparative Example 1, the interfacial active sites on the glass fiber surface are insufficient, making it difficult to form a stable interfacial structure during resin curing; and in a high-temperature water environment, the glass fiber surface is prone to hydrolysis and interfacial debonding, leading to a decrease in interfacial stress transfer capacity, thus exhibiting lower initial bonding strength and damp heat retention rate.

[0107] As shown in Examples 1-3, under the same imidazole modification conditions, the combination treatment of phosphoric acid and polyphosphoric acid is more beneficial to improving interfacial performance. Example 1, using a combination of phosphoric acid and polyphosphoric acid, showed the highest interfacial shear strength and wet heat retention; Example 2, using only phosphoric acid, showed the second-best performance; and Example 3, using only polyphosphoric acid, showed a further decline in performance. This indicates that phosphoric acid provides rapid protonation capability, while polyphosphoric acid can further form a dense multi-point adsorption structure at the interface. The combination of the two can achieve more stable interfacial bonding and resistance to hydrolysis.

[0108] As shown in Examples 1, 4, and 5, the proportion of alicyclic epoxy resin in the resin system affects the interfacial bonding performance. In Example 1, the interfacial performance was optimal when the ratio of alicyclic to aromatic epoxy resin was moderate; in Example 4, the interfacial performance was slightly lower when no alicyclic epoxy resin was added; and in Example 5, the performance decreased when the proportion of alicyclic epoxy resin was higher. This indicates that alicyclic epoxy resin can improve the crosslinking density and flexibility of the interfacial region, but excessive use will reduce local rigidity and polar interaction, thereby affecting the overall interfacial load-bearing capacity.

[0109] As shown in Examples 1 and 6, the interfacial strength and moisture retention rate are further improved after adding epoxy-terminated polysiloxane. In Example 6, the moisture retention rate was 86.6% without polysiloxane, while in Example 1, it increased to 89.3% after addition. This indicates that an appropriate amount of epoxy-terminated polysiloxane can form a flexible regulating structure in the interfacial region, reduce interfacial stress concentration, and to a certain extent reduce the diffusion rate of moisture in the interfacial region, thereby enhancing interfacial durability.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An age resistant resin core for a composite insulator, characterized by, The modified glass fiber and the epoxy resin sizing material are included, wherein, The modified glass fiber is obtained by modifying glass fiber through imidazolium-phosphate; The preparation method of the modified glass fiber comprises the following steps: S1: reacting glass fiber with imidazole-based silane coupling agent to graft imidazole group on the surface of glass fiber to obtain imidazole-modified glass fiber; S2: phosphating the imidazole-modified glass fiber to protonate the imidazole group to obtain modified glass fiber; The epoxy resin sizing material comprises the following raw materials by mass fraction: 100 parts of epoxy resin, 70-90 parts of acid anhydride curing agent, and 0.1-1 part of curing accelerator.

2. The age-resistant resin mandrel of claim 1, wherein, The step S1 comprises: 100 parts of glass fiber and 5-10 parts of imidazole-based silane coupling agent are dispersed in 500-1000 parts of ethanol aqueous solution to react at 40-60℃ for 2-4h to obtain imidazole-modified glass fiber.

3. The age-resistant resin mandrel of claim 2, wherein, The step S2 comprises: 100 parts of imidazole-modified glass fiber is immersed in 500-1000 parts of 0.1wt%-1wt% composite phosphoric acid aqueous solution for 0.5-2min to obtain modified glass fiber; The composite phosphoric acid aqueous solution comprises phosphoric acid and polyphosphoric acid with an average degree of polymerization of 5-10, and the mass ratio of the phosphoric acid to the polyphosphoric acid is 1.5-2.5:

1.

4. The age resistant resin mandrel of claim 1, wherein, The epoxy resin comprises aliphatic epoxy resin and aromatic epoxy resin, and the mass ratio of the aliphatic epoxy resin to the aromatic epoxy resin is 0.1-0.3:

1.

5. The age resistant resin mandrel of claim 4, wherein, The aliphatic epoxy resin comprises at least one of hydrogenated bisphenol A type epoxy resin and hydrogenated bisphenol F type epoxy resin; The aromatic epoxy resin comprises at least one of bisphenol A type epoxy resin and bisphenol F type epoxy resin.

6. The age resistant resin mandrel of claim 1, wherein, The epoxy resin sizing material further comprises 1-2 parts of epoxy-terminated polysiloxane.

7. The age resistant resin mandrel of claim 6, wherein, The epoxy-terminated polysiloxane comprises epoxy propoxy propyl-terminated polydimethylsiloxane with a number average molecular weight of 1000-3000.

8. The resin core for the aging resistant pipe according to any one of claims 1 to 7, characterized by, The aging-resistant resin mandrel satisfies at least one of the following conditions: 1) the mass percentage content of the modified glass fiber in the aging-resistant resin mandrel is 70%-80%; 2) the glass fiber comprises ECR glass fiber with an average diameter of 12-18μm; 3) the acid anhydride curing agent comprises at least one of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride; 4) the curing accelerator is selected from at least one of 2-methylimidazole and 2-ethyl-4-methylimidazole.

9. A method of making an age resistant resin core for a composite insulator, characterized by, The method comprises: providing raw materials included in the modified glass fiber and the epoxy resin sizing material in the aging-resistant resin mandrel according to any one of claims 1-8; mixing the raw materials to obtain an epoxy resin sizing material; mixing the epoxy resin sizing material with the modified glass fiber, and extruding and forming to obtain an aging-resistant resin mandrel after curing.

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