Oil-stain-resistant and anti-aging cable sheath composition, preparation method and photovoltaic cable

Abstract

The invention discloses an oil-resistant and anti-aging cable sheath composition, a preparation method and a photovoltaic cable. Raw materials of the rubber material comprise the following components in parts by mass: 60-70 parts of ethylene propylene diene monomer, 4-6 parts of an antioxidant, 0.5-2 parts of sulfur, 0.8-1.5 parts of an accelerant CZ, 6-8 parts of a di-iso-decylphthalate plasticizer, 12-14 parts of modified nano calcium carbonate, 1-2 parts of alkyl naphthalene sulfonate and 1-2 parts of a perfluoropolyether-based surfactant, wherein the modified nano calcium carbonate is modified by a thiol-based silane coupling agent; the oil-stain-resistant and anti-aging cable sheath composition prepared from the raw materials has strong oil-stain-resistant and anti-aging capabilities.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic cables, and in particular to an oil-resistant and aging-resistant cable sheath composition, a preparation method, and a photovoltaic cable. Background Art

[0002] Cable sheathing, a critical protective layer surrounding the cable insulation or conductor, is a key area of technological development focused on continuously improving the material's comprehensive protective properties. From early natural materials to modern synthetic polymers, sheathing technology has significantly enhanced the mechanical strength, flame retardancy, and electrical insulation reliability of cables. These advancements have greatly expanded the application range of cables, enabling them to adapt to complex and demanding outdoor, industrial, and mobile environments. They have become the foundation for ensuring the safe, stable, and long-lasting operation of modern power and information transmission.

[0003] However, when cable sheaths are used in oily environments, they face a significant and increasingly prominent drawback: insufficient tolerance to oil contamination and the resulting accelerated aging. Many commonly used sheath materials swell, soften, and experience a sharp decline in mechanical properties after prolonged exposure to oil. This oil-induced aging not only destroys the sheath's physical barrier properties but can also lead to insulation degradation, cracking, and even failure, ultimately creating safety hazards such as exposed cables, short circuits, and electrical leakage. Summary of the Invention

[0004] In order to solve the problem that traditional cable sheaths are aged due to contact with oil when used in the photovoltaic field, resulting in a decrease in various performances of the cable sheaths, an oil-resistant and aging-resistant cable sheath composition, a preparation method, and a photovoltaic cable are provided.

[0005] A cable sheath composition that is resistant to oil pollution and aging, the raw materials comprising the following components in parts by weight: 60-70 parts of EPDM rubber; 4-6 parts of antioxidant; 0.5-2 parts of sulfur; Accelerator CZ 0.8-1.5 parts; 6-8 parts of diisodecyl phthalate plasticizer; 12-14 parts of modified nano calcium carbonate; 1-2 parts of alkylnaphthalene sulfonate; 1-2 parts of perfluoropolyether surfactant, The modified nano calcium carbonate is modified by a thiol silane coupling agent.

[0006] Through the above technical solution, the saturated structure of the EPDM main chain imparts ozone resistance and heat resistance; the -SH groups on the surface of nano-calcium carbonate modified by thiol silane coupling agent participate in vulcanization cross-linking to form an organic-inorganic hybrid network; the sulfonic acid groups of alkylnaphthalene sulfonate prevent the agglomeration of nano-fillers through electrostatic repulsion, ensure uniform dispersion in the rubber matrix, and enhance the oil permeability resistance of the sheath; the alkyl chain of thiol silane forms a low surface energy hydrophobic layer, but there are microscopic defects. The helical fluorocarbon chain of perfluoropolyether migrates to the defects of the silane layer and is directionally filled through van der Waals force to form a composite barrier with continuously decreasing surface energy. It is not easy for oil to penetrate the barrier and damage the cable sheath.

[0007] Optionally, the modified nano calcium carbonate is prepared by the following method: Drying the nano-calcium carbonate until the moisture content is less than or equal to 0.3 wt % to obtain dry nano-calcium carbonate; Add dry nano-calcium carbonate and stir to disperse, add mercaptan-based silane coupling agent by spraying after heating, and stir and shear at high speed for 10 to 15 minutes; The mixture is allowed to stand for 1 to 3 hours to obtain modified nano calcium carbonate.

[0008] Through the above technical solution, drying and dehydration are carried out to avoid silane hydrolysis and failure; spray feeding and high-speed shearing ensure monolayer coating and directional exposure of thiol groups, achieve high reactivity of nanofillers, reduce agglomeration, and enhance reinforcement efficiency.

[0009] Optionally, the mercaptan-based silane coupling agent is γ-mercaptopropyltriethoxysilane.

[0010] Through the above technical solution, the ethoxy group is hydrolyzed into silanol, which condenses with the hydroxyl group on the CaCO3 surface to form a -Si-O-Ca bond. The thiol group captures the sulfur free radical during vulcanization to form a rubber-filler-SS-bridging structure. The interfacial chemical bonding eliminates the weak boundary layer, and the lipophilic molecules are not easy to penetrate along the filler interface.

[0011] Optionally, the antioxidant is a hindered phenolic antioxidant.

[0012] Through the above technical solution, the hindered phenol antioxidant captures alkyl radicals through the phenolic hydroxyl group, inhibits the oxidation chain reaction, and improves the antioxidant capacity of the cable sheath.

[0013] Optionally, the raw materials further include 0.2 to 0.6 parts by weight of a benzotriazole ultraviolet absorber.

[0014] Through the above technical solution, the hydrogen bonds within the molecules of the benzotriazole ultraviolet absorber cyclically absorb 290-400nm ultraviolet light, converting it into low-energy heat energy for release, inhibiting the photodegradation and breakage of the rubber molecular chain, and enhancing the anti-aging property.

[0015] Optionally, the raw materials further include 3 to 5 parts by mass of organic modified montmorillonite.

[0016] Through the above technical solution, the montmorillonite flakes are peeled and dispersed in the matrix, forming a tortuous barrier to hinder the diffusion path of lipophilic molecules and oxygen, reducing the permeability of oil pollution, and improving thermal stability and flame retardancy.

[0017] The second object of the present invention is achieved by the following technical solutions: A method for preparing an oil-resistant and aging-resistant cable sheath composition comprises the following steps: S1: Cutting EPDM rubber into pieces and preheating it until softened to obtain pretreated EPDM rubber; S2: adding the pretreated EPDM rubber into an internal mixer, heating and performing internal mixing, gradually adding other raw materials during the internal mixing process, and obtaining the rubber material after the internal mixing is completed.

[0018] Through the above technical solution, the movement ability of the amorphous chain segments is enhanced by heating the EPDM rubber blocks, the intermolecular force is weakened, the shear stress transfer efficiency is improved during mixing, and the heat capacity of the rubber is homogenized after pre-softening, thereby preventing the high viscosity area from suddenly rising in temperature due to shear heat in the early stage of mixing, causing thermal decomposition of the antioxidant; gradual addition of materials realizes the molecular-level directional assembly of the oleophobic barrier and the construction of a multi-stage cross-linked network, reducing the problems of oil penetration and thermal oxidative aging.

[0019] Optionally, in step S2, modified nano-calcium carbonate is added at 100-102°C.

[0020] Through the above technical solution, the interface reaction can be prioritized, and the silane coupling agent completes the -SH pre-crosslinking with the EPDM rubber before vulcanization. The pre-bonding eliminates the filler-matrix gap and reduces the penetration of lipophilic molecules into the interface.

[0021] The third object of the present invention is achieved through the following technical solutions: A photovoltaic cable, wherein the cable protective sheath is prepared from any one of the above-mentioned oil-resistant and aging-resistant cable sheath compositions.

[0022] Through the above technical solution, this photovoltaic cable is not easily damaged by contamination by oleophilic molecules and aging, and its safety, reliability and durability are higher than those of ordinary cables.

[0023] In summary, this application has at least the following beneficial effects: (1) EPDM rubber gives the cable sheath weather resistance and anti-aging ability, and modified nano-calcium carbonate fills the chain gaps; (2) The helical fluorocarbon chains of perfluoropolyether migrate to the defects of the silane layer and fill them in a directional manner through van der Waals forces, forming a composite barrier with a continuously decreasing surface energy. It is difficult for oil and dirt to penetrate the barrier and damage the cable sheath. (3) Alkylnaphthalene sulfonates improve processing fluidity, while their sulfonic acid groups prevent nanofillers from agglomerating through electrostatic repulsion, ensuring uniform dispersion in the rubber matrix. DETAILED DESCRIPTION

[0024] raw material EPDM rubber, with an ethylene content of 53% and an ENB content of 4.0%, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. The accelerator CZ was purchased from Wuhan Jixin Yibang Biotechnology Co., Ltd.; Sulfur was purchased from Anqing Quanmin Chemical Trading Co., Ltd. Alkylnaphthalene sulfonate, sodium dodecylnaphthalene sulfonate, with a purity of ≥97.0% and a loss on drying of ≤1.0%, was purchased from Guangdong Guanghua Technology Co., Ltd. Hindered phenolic antioxidant, antioxidant 1076, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Hindered amine antioxidant, antioxidant 4720, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Benzotriazole UV absorber, 2-(2-hydroxy-5-benzyl)benzotriazole, was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. Perfluoropolyether-based surfactant, Mn = 2800 ± 300, PDI = 1.28, purchased from Zhejiang Juhua Co., Ltd. Sodium polyacrylate, Mw 1900-2300, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Nano-calcium carbonate was purchased from Shandong Yuxin Nanotechnology Co., Ltd.; γ-Mercaptopropyltriethoxysilane and γ-mercaptopropyltrimethoxysilane were purchased from Hangzhou Jessica Chemical Co., Ltd. Aminosilane coupling agent, γ-aminopropyltriethoxysilane, purchased from Hangzhou Jessica Chemical Co., Ltd. Sodium montmorillonite, with a layer aspect ratio of 200-400 and a specific surface area of 700-750m 2 / g, interlayer spacing of 1.2-1.4 nm, purchased from Beijing Yiwei Special Chemical Technology Development Co., Ltd.; Diisodecyl phthalate plasticizer and dioctadecyl methyl ammonium chloride were purchased from Jiangsu Runfeng Synthetic Technology Co., Ltd.; 10 wt % HCl solution was commercially available.

[0025] Preparation Example 1 A modified nano calcium carbonate, the preparation method of which is as follows: 100 kg of nano calcium carbonate was evenly spread on an oven tray and dried at 100°C until the moisture content was ≤ 0.3% to obtain dry nano calcium carbonate; Add the dried nano calcium carbonate into a high-speed mixer and disperse it at 1000 rpm for 8 minutes to obtain dispersed nano calcium carbonate; Raising the temperature to 95° C., spraying 100 L of a γ-mercaptopropyltriethoxysilane coupling agent solution into a mixer through a double-nozzle atomization system at an atomization pressure of 0.3 MPa and a droplet size of ≤50 μm, while simultaneously subjecting the mixture to high-speed shearing at a speed of 2500 rpm for 10 minutes, wherein the γ-mercaptopropyltriethoxysilane coupling agent solution is an ethanol-water solution of γ-mercaptopropyltriethoxysilane coupling agent, wherein the γ-mercaptopropyltriethoxysilane coupling agent content is 2.8 wt %, the ethanol content is 75 wt %, and the remainder is water; The modified nano-calcium carbonate was obtained by standing at 80°C for 2 hours.

[0026] Preparation Example 2 A modified nano calcium carbonate, the preparation method of which is as follows: 100 kg of nano calcium carbonate was evenly spread on an oven tray and dried at 100°C until the moisture content was ≤ 0.3% to obtain dry nano calcium carbonate; Add the dried nano calcium carbonate into a high-speed mixer and disperse it at 1000 rpm for 8 minutes to obtain dispersed nano calcium carbonate; Raising the temperature to 95°C, spraying 100 L of γ-aminopropyltriethoxysilane coupling agent solution into the mixer through a double-nozzle atomization system with an atomization pressure of 0.3 MPa and a droplet size of ≤50 μm, while high-speed shearing at 2500 rpm for 10 minutes, wherein the γ-aminopropyltriethoxysilane coupling agent solution is an ethanol-water solution of γ-aminopropyltriethoxysilane coupling agent, with a γ-aminopropyltriethoxysilane coupling agent content of 2.8 wt%, an ethanol content of 75 wt%, and the remainder being water; The modified nano-calcium carbonate was obtained by standing at 80°C for 2 hours.

[0027] Preparation Example 3 A modified nano calcium carbonate, the preparation method of which is as follows: 100 kg of nano calcium carbonate was evenly spread on an oven tray and dried at 100°C until the moisture content was ≤ 0.3% to obtain dry nano calcium carbonate; Add the dried nano calcium carbonate into a high-speed mixer and disperse it at 1000 rpm for 8 minutes to obtain dispersed nano calcium carbonate; Raising the temperature to 95°C, spraying 100 L of γ-mercaptopropyltrimethoxysilane coupling agent solution into the mixer through a double-nozzle atomization system with an atomization pressure of 0.3 MPa and a droplet size of ≤50 μm, while high-speed shearing at 2500 rpm for 10 minutes, wherein the γ-mercaptopropyltrimethoxysilane coupling agent solution is an ethanol aqueous solution of γ-mercaptopropyltrimethoxysilane coupling agent, the γ-mercaptopropyltrimethoxysilane coupling agent content is 2.8 wt %, the ethanol content is 75 wt %, and the remainder is water; The modified nano-calcium carbonate was obtained by standing at 80°C for 2 hours.

[0028] Preparation Example 4 A modified nano-calcium carbonate, the preparation method of which is different from Preparation 1 in that the weighed nano-calcium carbonate is directly added into a high-speed mixer without drying.

[0029] Preparation Example 5 A modified nano calcium carbonate and its preparation method: 100 kg of nano calcium carbonate was evenly spread on an oven tray and dried at 100°C until the moisture content was ≤ 0.3% to obtain dry nano calcium carbonate; Add the dried nano calcium carbonate into a high-speed mixer and disperse it at 1000 rpm for 8 minutes to obtain dispersed nano calcium carbonate; Raising the temperature to 95° C., spraying 100 L of a γ-mercaptopropyltriethoxysilane coupling agent solution into the mixer at a rate of 10 L / min, and simultaneously high-speed shearing at a speed of 2500 rpm for 10 min, wherein the γ-mercaptopropyltriethoxysilane coupling agent solution is a γ-mercaptopropyltriethoxysilane coupling agent ethanol aqueous solution, with a γ-mercaptopropyltriethoxysilane coupling agent content of 2.8 wt %, an ethanol content of 75 wt %, and the remainder being water; The modified nano-calcium carbonate was obtained by standing at 80°C for 2 hours.

[0030] Preparation Example 6 An organic modified montmorillonite and its preparation method: 10 kg of sodium montmorillonite and 90 L of deionized water were added to a reactor, and ultrasonic dispersion was performed at 400 W for 30 min to obtain a slurry with a solid content of 10%. 50 g of sodium polyacrylate was added to the slurry. 4 L of dioctadecyl methyl ammonium chloride solution was dropwise added to the slurry at a rate of 100 mL / min, while heating in a water bath at 80° C. and magnetically stirring at 500 rpm for 2 h, and the pH was adjusted to 6.8-7.0 using 10% HCl to obtain a reaction solution, wherein the dioctadecyl methyl ammonium chloride solution is a dioctadecyl methyl ammonium chloride ethanol aqueous solution, with a dioctadecyl methyl ammonium chloride content of 20 wt %, an ethanol content of 75 wt %, and the remainder being water; The reaction solution was filtered using filter paper with a pore size of 0.45 μm to obtain a filter cake, which was then washed with 50% ethanol aqueous solution until no white precipitate was left when AgNO3 was added to the filtrate. The filter cake was scraped off and placed in an oven to dry at 80°C for 5 h, and then crushed and passed through an 80-mesh sieve to obtain organically modified montmorillonite.

[0031] Example 1 A cable sheath composition that is resistant to oil pollution and aging is prepared from the following raw materials: 650kg of EPDM rubber, 50kg of antioxidant 1076, 15kg of sulfur, 10kg of accelerator CZ, 10kg of diisodecyl phthalate plasticizer, 130kg of modified nano-calcium carbonate, 15kg of sodium dodecylnaphthalenesulfonate, 15kg of perfluoropolyether-based surfactant, 4kg of 2-(2-hydroxy-5-benzyl)benzotriazole, and 40kg of organically modified montmorillonite, wherein the modified nano-calcium carbonate is the modified nano-calcium carbonate in Preparation Example 1, and the organically modified montmorillonite is the organically modified montmorillonite in Preparation Example 6.

[0032] A cable sheath composition that is resistant to oil pollution and aging, and a preparation method thereof is as follows: Cut the EPDM rubber into pieces and preheat to 60°C to soften it to obtain the pretreated EPDM rubber; Add the pretreated EPDM rubber into the internal mixer, set the initial temperature to 60°C, start the internal mixer, rotate the rotor at 50 rpm, and increase the temperature at a rate of 8°C / min; Before 100°C, antioxidant 1076, sulfur, accelerator CZ, sodium dodecylnaphthalene sulfonate, perfluoropolyether-based surfactant, 2-(2-hydroxy-5-benzyl)benzotriazole, and diisodecyl phthalate plasticizer were added in sequence, and modified nano-calcium carbonate was added at 100°C; At 118°C, the binder was discharged and the timing started after the pretreated EPDM rubber was added into the internal mixer. The total mixing time until the end of the binder discharge was 7 minutes.

[0033] Comparative Example 1 A cable sheath composition that is resistant to oil pollution and aging is disclosed. The difference between the cable sheath composition and Example 1 is that the modified nano-calcium carbonate in the raw material is the modified nano-calcium carbonate in Preparation Example 2.

[0034] Comparative Example 2 A cable sheath composition that is resistant to oil stains and aging, which differs from Example 1 in that no perfluoropolyether-based surfactant is added to the raw materials.

[0035] Example 2 A cable sheath composition that is resistant to oil pollution and aging is disclosed. The difference between the cable sheath composition and Example 1 is that the modified nano-calcium carbonate in the raw material is the modified nano-calcium carbonate in Preparation Example 3.

[0036] Example 3 A cable sheath composition that is resistant to oil pollution and aging is disclosed, which differs from Example 1 in that 50 kg of antioxidant 1076 is replaced by 50 kg of antioxidant 4720 in the raw materials.

[0037] Example 4 A cable sheath composition that is resistant to oil pollution and aging is disclosed. The difference between the cable sheath composition and Example 1 is that 2-(2-hydroxy-5-benzyl)benzotriazole is not added to the raw materials.

[0038] Example 5 A cable sheath composition that is resistant to oil pollution and aging is disclosed, which differs from Example 1 in that organic modified montmorillonite is not added to the raw materials.

[0039] Example 6 A cable sheath composition that is resistant to oil pollution and aging is disclosed. The difference between the cable sheath composition and Example 1 is that the modified nano-calcium carbonate in the raw material is the modified nano-calcium carbonate in Preparation Example 4.

[0040] Example 7 A cable sheath composition that is resistant to oil pollution and aging is disclosed. The difference between the cable sheath composition and Example 1 is that the modified nano-calcium carbonate in the raw material is the modified nano-calcium carbonate in Preparation Example 5.

[0041] Comparative Example 3 A cable sheath composition that is resistant to oil pollution and aging is disclosed. The difference between the cable sheath composition and Example 1 is that, in the preparation method, after pretreated EPDM rubber is added to an internal mixer, antioxidant 1076, sulfur, accelerator CZ, sodium dodecylnaphthalenesulfonate, perfluoropolyether-based surfactant, 2-(2-hydroxy-5-benzyl)benzotriazole, diisodecyl phthalate plasticizer, and modified nano-calcium carbonate are added at one time.

[0042] Example 8 A cable sheath composition that is resistant to oil pollution and aging is disclosed. The difference between the cable sheath composition and Example 1 is that the modified nano-calcium carbonate is added into the internal mixer before the temperature is raised to 100°C.

[0043] Example 9 A cable sheath composition that is resistant to oil pollution and aging is disclosed. The composition differs from Example 1 in that the raw materials are 600 kg of EPDM rubber, 40 kg of antioxidant 1076, 5 kg of sulfur, 8 kg of accelerator CZ, 60 kg of diisodecyl phthalate plasticizer, 120 kg of modified nano-calcium carbonate, 10 kg of sodium dodecylnaphthalenesulfonate, 10 kg of perfluoropolyether-based surfactant, 2 kg of 2-(2-hydroxy-5-benzyl)benzotriazole, and 30 kg of organically modified montmorillonite.

[0044] Example 10 A cable sheath composition that is resistant to oil pollution and aging is disclosed. The composition differs from Example 1 in that the raw materials are 700 kg of EPDM rubber, 60 kg of antioxidant 1076, 30 kg of sulfur, 15 kg of accelerator CZ, 80 kg of diisodecyl phthalate plasticizer, 140 kg of modified nano-calcium carbonate, 20 kg of sodium dodecylnaphthalenesulfonate, 20 kg of perfluoropolyether-based surfactant, 6 kg of 2-(2-hydroxy-5-benzyl)benzotriazole, and 50 kg of organically modified montmorillonite.

[0045] The cable sheath compositions of Examples 1 to 10 and Comparative Examples 1 to 3 were all prepared into cable sheaths in the following manner: the cable sheath composition was added to an open mill, preheated and plasticized at 80° C. for 15 minutes, and the Mooney viscosity was controlled to be reduced to 35 to 45 MU; A pin-type extruder was used with zone temperature control: feeding section 60°C, compression section 85°C, metering section 105°C, die section 110°C, screw speed 25 rpm, die pressure 18 MPa, extrusion speed 28 m / min; Use saturated steam continuous vulcanization, pressure 1.2MPa, temperature 160±2℃, vulcanization time 6min; The cable sheath was obtained after spray cooling at 70°C for 10s and main cooling in a 50°C water bath for 5min.

[0046] The cable sheaths made from the cable sheath compositions of Examples 1 to 10 and Comparative Examples 1 to 3 were tested for oil resistance and aging resistance.

[0047] According to GB / T 2951.21-2008 "General test methods for insulation and sheathing materials of electric and optical cables Part 12: Special test methods for elastomeric mixtures - Mineral oil immersion test", the sheath immersion test was carried out in mineral oil. The compressive strength retention rate and volume expansion rate are shown in Table 1.

[0048] Table 1 Oil resistance test results Tensile strength retention rate (%) Volume expansion rate (%) Example 1 94.8 4.6 Example 2 92.5 6.8 Example 3 89.7 7.5 Example 4 87.3 9.2 Example 5 84.1 13.6 Example 6 78.3 18.5 Example 7 91 7.1 Example 8 85.4 11.3 Example 9 91.5 7.0 Example 10 94.2 5.9 Comparative Example 1 81.6 15.4 Comparative Example 2 75.3 22.7 Comparative Example 3 83.2 14.9 According to GB / T 2951.12-2008 “General test methods for insulation and sheathing materials of electric and optical cables Part 12: General test methods — Thermal aging test methods”, thermal aging tests were conducted, and the tensile strength retention rate and elongation at break retention rate were obtained, as shown in Table 2.

[0049] Table 2 Anti-aging test results Tensile strength retention rate (%) Retention rate of elongation at break (%) Example 1 92.3 88.4 Example 2 91.6 86.5 Example 3 88.7 83.2 Example 4 80.1 72.8 Example 5 82.5 75.6 Example 6 76.9 68.3 Example 7 87.8 82 Example 8 83.9 77.4 Example 9 89.6 84.5 Example 10 90.5 85.1 Comparative Example 1 79.4 71.5 Comparative Example 2 74.8 66.3 Comparative Example 3 82.1 74.9 In combination with Table 1 and Table 2, comparing Example 1 and Comparative Example 1, the tensile strength retention rate of the cable sheath made of the cable sheath composition of Example 1 after the oil immersion test is greater than the tensile strength retention rate of the cable sheath made of the cable sheath composition of Comparative Example 1, and the volume expansion rate of the corresponding cable sheath of Example 1 is less than the volume expansion rate of the corresponding cable sheath of Comparative Example 1, and the tensile strength retention rate and elongation at break retention rate of the cable sheath made of the cable sheath composition of Example 1 after the heat aging test are greater than the tensile strength retention rate and elongation at break retention rate of the cable sheath made of the cable sheath composition of Comparative Example 1.

[0050] The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, an aminosilane coupling agent solution is used instead of a thiolsilane coupling agent solution. In the thiolsilane coupling agent solution, the thiol group captures the sulfur free radical during vulcanization to form a rubber-filler-SS-bridge structure. The interfacial chemical bonding eliminates the weak boundary layer, and the oil molecules cannot penetrate along the filler interface, resulting in stronger anti-oil performance. Therefore, it can be seen that it is necessary to modify the nano-calcium carbonate with a thiolsilane coupling agent solution.

[0051] Comparing Example 1 and Comparative Example 2, the tensile strength retention rate of the sheath of Example 1 after the oil immersion test is greater than the tensile strength retention rate of the sheath of Comparative Example 2, and the volume expansion rate of the sheath of Example 1 is less than the volume expansion rate of the sheath of Comparative Example 2, and the tensile strength retention rate and elongation at break retention rate of the sheath of Example 1 after the heat aging test are greater than the tensile strength retention rate and elongation at break retention rate of the sheath of Comparative Example 2.

[0052] The difference between Comparative Example 2 and Example 1 is that no perfluoropolyether-based surfactant is added to the raw materials of Comparative Example 2. The helical fluorocarbon chains of the perfluoropolyether migrate to the defects of the silane layer and are filled in a directionally manner through van der Waals forces to form a composite barrier with a continuously decreasing surface energy. Oil stains are not easy to penetrate into the barrier and damage the cable sheath. Therefore, it can be seen that it is necessary to add a perfluoropolyether-based surfactant to the raw materials.

[0053] Comparing Example 1 and Example 2, the tensile strength retention rate of the sheath of Example 1 after the oil immersion test is greater than the tensile strength retention rate of the sheath of Example 2, and the volume expansion rate of the sheath of Example 1 is less than the volume expansion rate of the sheath of Example 2, and the tensile strength retention rate and elongation at break retention rate of the sheath of Example 1 after the heat aging test are greater than the tensile strength retention rate and elongation at break retention rate of the sheath of Example 2.

[0054] The difference between Example 2 and Example 1 is that Example 2 selects γ-mercaptopropyltrimethoxysilane instead of γ-mercaptopropyltriethoxysilane to modify nano-calcium carbonate. The ethoxy group is hydrolyzed into silanol, which condenses with the surface hydroxyl groups of CaCO3 to form a -Si-O-Ca bond, and the interface bonding is more firm. It can be seen that it is necessary to use γ-mercaptopropyltriethoxysilane to modify nano-calcium carbonate.

[0055] Comparing Example 1 with Examples 3 to 5, the tensile strength retention rate of the sheath of Example 1 after the oil immersion test is greater than the tensile strength retention rate of the sheath of Examples 3 to 5, and the volume expansion rate of the sheath of Example 1 is less than the volume expansion rate of the sheath of Examples 3 to 5. The tensile strength retention rate and elongation at break retention rate of the sheath of Example 1 after the heat aging test are greater than the tensile strength retention rate and elongation at break retention rate of the sheath of Examples 3 to 5.

[0056] The difference between Examples 3 to 5 and Example 1 is that in Example 3, hindered amine antioxidants are used instead of hindered phenol antioxidants in the raw materials, no benzotriazole ultraviolet absorber is added in Example 4, and no organic modified montmorillonite is added in Example 5. The hindered phenol antioxidants capture alkyl radicals through phenolic hydroxyl groups, blocking the oxidation chain reaction and improving the antioxidant capacity of the cable sheath. The intramolecular hydrogen bonds of the benzotriazole ultraviolet absorber cycle absorb 290-400nm ultraviolet light, converting it into low-energy heat energy release, inhibiting the photodegradation and breakage of the rubber molecular chain, and enhancing the aging resistance. The montmorillonite flakes are peeled and dispersed in the matrix, forming a tortuous barrier to hinder the diffusion path of oil molecules and oxygen, and synergistically reducing the permeability of oil stains. It can be seen that it is necessary to add hindered phenol antioxidants, benzotriazole ultraviolet absorbers, and benzotriazole ultraviolet absorbers to the raw materials.

[0057] Comparing Example 1 and Examples 6-7, the tensile strength retention rate of the sheath of Example 1 after the oil immersion test is greater than the tensile strength retention rate of the sheath of Examples 6-7, and the volume expansion rate of the sheath of Example 1 is less than the volume expansion rate of the sheath of Examples 6-7. The tensile strength retention rate and elongation at break retention rate of the sheath of Example 1 after the heat aging test are greater than the tensile strength retention rate and elongation at break retention rate of the sheath of Examples 6-7.

[0058] The difference between Examples 6 and 7 and Example 1 is that in Example 6, the nano-calcium carbonate is not dried during the preparation process of the modified nano-calcium carbonate. In Example 7, the coupling agent is added to the mixer by spraying instead of atomizing, and the drying and water removal are performed to avoid the ineffectiveness of silane hydrolysis. The spray feeding and high-speed shearing ensure the monolayer coating and the directional exposure of the thiol group, achieve high reactivity of the nano-filler, eliminate agglomeration, and maximize the reinforcement efficiency. It can be seen that it is necessary to dry the nano-calcium carbonate and add the coupling agent by atomizing in the preparation process of the modified nano-calcium carbonate.

[0059] Comparing Example 1 and Comparative Example 3, the tensile strength retention rate of the sheath of Example 1 after the oil immersion test is greater than the tensile strength retention rate of the sheath of Comparative Example 3, and the volume expansion rate of the sheath of Example 1 is less than the volume expansion rate of the sheath of Comparative Example 3, and the tensile strength retention rate and elongation at break retention rate of the sheath of Example 1 after the heat aging test are greater than the tensile strength retention rate and elongation at break retention rate of the sheath of Comparative Example 3.

[0060] The difference between Comparative Example 3 and Example 1 is that in the preparation process of the cable sheath composition of Comparative Example 3, the remaining raw materials except EPDM rubber are added at one time instead of gradually adding the remaining raw materials except EPDM rubber. The gradual addition realizes the molecular-level directional assembly and multi-stage cross-linking network construction of the oleophobic barrier, solves the problems of oil penetration and thermal oxidation aging. It can be seen that it is necessary to gradually add the remaining raw materials except EPDM rubber during the preparation process of the cable sheath composition.

[0061] Comparing Example 1 and Example 8, the tensile strength retention rate of the sheath of Example 1 after the oil immersion test is greater than the tensile strength retention rate of the sheath of Example 8, and the volume expansion rate of the sheath of Example 1 is less than the volume expansion rate of the sheath of Example 8. The tensile strength retention rate and elongation at break retention rate of the sheath of Example 1 after the heat aging test are greater than the tensile strength retention rate and elongation at break retention rate of the sheath of Example 8.

[0062] The difference between Example 8 and Example 1 is that in Example 8, modified nano-calcium carbonate is added before 10°C instead of adding nano-calcium carbonate at 100°C during the preparation process of the cable sheath composition, which can preferentially react at the interface. The silane coupling agent completes the -SH pre-crosslinking with the EPDM rubber before vulcanization, and the pre-bonding eliminates the filler-matrix gap and prevents oil molecules from preferentially penetrating the interface. Therefore, it can be seen that it is necessary to add modified nano-calcium carbonate at 100°C during the preparation process.

[0063] Comparing Example 1 and Examples 9 to 10, the tensile strength retention rate of the sheath of Example 1 after the oil immersion test is greater than the tensile strength retention rate of the sheath of Examples 9 to 10, and the volume expansion rate of the sheath of Example 1 is less than the volume expansion rate of the sheath of Examples 9 to 10, and the tensile strength retention rate and elongation at break retention rate of the sheath of Example 1 after the heat aging test are greater than the tensile strength retention rate and elongation at break retention rate of the sheath of Examples 9 to 10.

[0064] The difference between Examples 9 and 10 and Example 1 is that the raw materials of Example 9 are EPDM rubber: antioxidant 1076: sulfur: accelerator CZ: diisodecyl phthalate plasticizer: modified nano calcium carbonate: sodium dodecyl naphthalene sulfonate: perfluoropolyether-based surfactant: 2-(2-hydroxy-5-phenylmethyl)benzotriazole: organic modified montmorillonite is 600:40:5:8:60:120:10:10:2:30, and the raw materials of Example 10 are EPDM rubber: antioxidant 1076: sulfur: accelerator CZ: diisodecyl phthalate plasticizer: modified nano calcium carbonate: sodium dodecyl naphthalene sulfonate The ratio of sodium: perfluoropolyether surfactant: 2-(2-hydroxy-5-benzyl)benzotriazole: organic modified montmorillonite is 700:60:30:15:80:140:20:20:6:50. It can be seen that the optimal ratio of the raw materials is EPDM rubber: antioxidant 1076: sulfur: accelerator CZ: diisodecyl phthalate plasticizer: modified nano-calcium carbonate: sodium dodecylnaphthalene sulfonate: perfluoropolyether surfactant: 2-(2-hydroxy-5-benzyl)benzotriazole: organic modified montmorillonite is 650:50:15:10:10:130:15:15:4:40.

[0065] Example 11 A photovoltaic cable consists of an optical fiber and a cable protective sheath, wherein the cable protective sheath is prepared from the oil-resistant and aging-resistant cable sheath composition of any one of Examples 1 to 10 and Comparative Examples 1 to 3.

[0066] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as the modifications are within the scope of protection required by the present invention, they will be protected by patent law.

Claims

1. A cable sheath composition that is resistant to oil pollution and aging, characterized in that: The raw materials contain the following components in parts by mass: 60~70 parts of EPDM rubber; 4-6 parts of antioxidants; 0.5~2 parts of sulfur; Accelerator CZ 0.8~1.5 parts; 6-8 parts of diisodecyl phthalate plasticizer; 12-14 parts of modified nano calcium carbonate; 1-2 parts of alkylnaphthalene sulfonate; 1~2 parts of perfluoropolyether surfactant, The modified nano calcium carbonate is modified by a thiol-silane coupling agent.

2. The oil-resistant and aging-resistant cable sheath composition according to claim 1, characterized in that: The modified nano calcium carbonate is prepared by the following method: Drying the nano-calcium carbonate to a moisture content of ≤0.3 wt % to obtain dry nano-calcium carbonate; Stir and disperse the dried nano-calcium carbonate, add the thiol silane coupling agent by spraying after heating, and stir and shear at high speed for 10-15 minutes; The mixture was allowed to stand for 1 to 3 hours to obtain modified nano calcium carbonate.

3. The oil-resistant and aging-resistant cable sheath composition according to claim 1, characterized in that: The mercaptan-based silane coupling agent is γ-mercaptopropyltriethoxysilane.

4. The oil-resistant and aging-resistant cable sheath composition according to claim 1, characterized in that: The antioxidant is a hindered phenol antioxidant.

5. The oil-resistant and aging-resistant cable sheath composition according to claim 1, characterized in that: The raw materials further contain 0.2 to 0.6 parts by weight of a benzotriazole ultraviolet absorber.

6. The oil-resistant and aging-resistant cable sheath composition according to claim 1, characterized in that: The raw materials also contain 3 to 5 parts by mass of organic modified montmorillonite.

7. The method for preparing the oil-resistant and aging-resistant cable sheath composition according to any one of claims 1 to 6, characterized in that: The following steps are included: S1: Cutting EPDM rubber into pieces and preheating it until softened to obtain pretreated EPDM rubber; S2: adding the pretreated EPDM rubber into an internal mixer, heating and performing internal mixing, gradually adding other raw materials during the internal mixing process, and obtaining a cable sheath composition after the internal mixing is completed.

8. The method for preparing an oil-resistant and aging-resistant cable sheath composition according to claim 7, characterized in that: In the step S2, modified nano-calcium carbonate is added at 100-102°C.

9. A photovoltaic cable, characterized in that: The cable protective sheath is prepared from the oil-resistant and aging-resistant cable sheath composition according to any one of claims 1 to 6.