Corrosion-resistant cable jacket material and method of making same

Abstract

The application discloses a kind of corrosion-resistant cable sheath material and preparation method thereof, comprising the following weight parts of material: high-density polyethylene 50~70 parts, maleic anhydride grafting ethylene-octene copolymer 15~25 parts, polyketone resin 8~18 parts, modified layered double hydroxide-hexagonal boron nitride composite nanosheet 6~12 parts, amino-terminated hyperbranched polysiloxane 3~8 parts, microencapsulated latent crosslinking agent 2~5 parts, compatibilizer 3~6 parts, antioxidant 0.5~1.5 parts and lubricant 1~3 parts;Through the physical barrier of HDPE hydrophobic layer, the labyrinth effect and ion exchange capture of LDH-BNNS, the selective adsorption and chemical chelation of Mg-NH2-4A molecular sieve to acidic gas, and the in-situ self-repairing function of dynamic hydrogen bond network, multi-level and multi-mechanism synergistic protection to acid, base, salt mist, acidic gas and organic solvent and other corrosion media is realized, and the corrosion resistance grade and service life of the sheath material are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of cable material technology, specifically referring to a corrosion-resistant cable sheath material and its preparation method. Background Technology

[0002] Cables are indispensable basic components in power transmission and signal control systems, with their sheaths directly bearing multiple stresses from the external environment, including physical, chemical, and thermal stresses. In typical corrosive service environments such as chemical industrial parks, offshore wind power, sewage treatment plants, underground utility tunnels, and marine engineering projects, cable sheaths need to withstand the combined erosion of various corrosive media, including acids, alkalis, salt spray, industrial waste gases, oil, and microbial metabolic products, over long periods. Once the sheath material deteriorates and cracks due to corrosion, moisture and corrosive ions will rapidly penetrate the insulation layer, causing electrical treeing or water treeing, ultimately leading to cable breakdown and resulting in serious economic losses and safety hazards.

[0003] Therefore, developing cable sheath materials with excellent long-term corrosion resistance has always been an important research direction in the fields of cable materials and electrical insulation.

[0004] Currently, the corrosion-resistant cable sheath materials disclosed in existing technologies can be mainly divided into the following categories.

[0005] Category 1: Polyvinyl chloride (PVC) based sheathing materials. PVC is inexpensive, has mature processing capabilities, and good flame retardant properties, making it one of the most widely used cable sheathing materials. However, PVC molecules contain a large number of chlorine atoms, which are prone to dehydrochlorination under long-term thermal aging and ultraviolet irradiation, producing conjugated double bonds that cause discoloration, embrittlement, and a sharp decline in mechanical properties. Furthermore, PVC has limited tolerance to acidic and alkaline media; in strong acid or alkaline environments, plasticizer migration and molecular chain degradation easily occur, making it difficult to meet the long-term service requirements under harsh corrosive conditions.

[0006] The second category is polyolefin-based sheathing materials, mainly including polyethylene (PE) and cross-linked polyethylene (XLPE). Polyolefin materials have excellent hydrophobicity, electrical insulation and processing fluidity. Their non-polar molecular structure gives them a certain physical barrier ability against polar corrosive media. In order to improve the heat resistance and environmental stress cracking resistance of polyolefins, existing technologies generally use peroxide chemical cross-linking or silane cross-linking processes to prepare XLPE. However, the corrosion protection mechanism of existing polyolefin-based sheathing materials is mainly concentrated on the passive barrier level, that is, by increasing the crystallinity or cross-linking density to reduce the diffusion coefficient of corrosive media. This mechanism has the following inherent defects: (1) The barrier effect on acidic gases with small molecular size (such as HCl, SO2, H2S) is limited; (2) There is a lack of chemical bonding between the filler and the polyolefin matrix, poor interfacial compatibility, and the filler is prone to agglomeration under high filling amount, which becomes a penetration channel for corrosive media; (3) It does not have any function of actively capturing or in-situ repairing corrosion damage. Once microcracks appear on the sheath surface, corrosive media will quickly penetrate along the cracks, accelerating cable failure.

[0007] The third category consists of fluoroplastic-based sheathing materials, such as perfluoroethylene propylene (FEP) and fusible polytetrafluoroethylene (PFA). Fluoroplastics possess extremely high chemical inertness, are virtually unaffected by any acidic or alkaline media and organic solvents, and have high temperature resistance, making them one of the most corrosion-resistant cable sheathing materials currently available. However, fluoroplastics are extremely expensive (typically 10 to 20 times the cost of ordinary polyolefins), require high processing temperatures, have poor melt flowability, and demand special processing equipment, significantly limiting their large-scale application in conventional industrial cables. They are primarily used in special cables for extreme environments such as aerospace and nuclear industries.

[0008] Category 4: High-performance engineering plastic-based sheathing materials, such as polyetheretherketone (PEEK) and polyketone (PK). Polyketone resins possess excellent chemical resistance and low water absorption due to the alternating carbonyl groups in their molecular backbone. However, pure polyketone materials have poor flexibility and impact resistance, a narrow processing window, and are significantly more expensive than polyolefin materials. While there have been attempts to blend polyketone with polyolefins in existing technologies, the significant difference in polarity between the two results in weak interfacial bonding after simple blending, failing to achieve a synergistic improvement in mechanical properties and corrosion resistance.

[0009] In summary, the corrosion-resistant cable sheath materials disclosed in the prior art have the following main technical defects: I. Limited Corrosion Protection Mechanisms. Existing technologies mainly employ a single path of passive barrier or physical shielding, failing to construct an active and synergistic protection system integrating barrier-capture-self-healing. This makes it difficult to simultaneously cope with the synergistic erosion of multiple corrosive media (acids, alkalis, salt spray, organic solvents, acidic gases, etc.).

[0010] Second, insufficient synergistic effect between components. Most multi-component compound systems are simple physical blends, lacking cross-component network designs with chemical bonds or strong physical interactions. The synergistic effect between fillers and matrix, between different fillers, and between polymer components is not fully utilized.

[0011] Third, the self-healing function is lacking. Existing sheath materials are all "passive protection". Once the sheath layer develops microcracks under external force or thermal stress, the corrosive medium will spread rapidly along the cracks, and the existing technology does not have any mechanism to repair cracks in situ.

[0012] Fourth, it is difficult to balance cost and performance. High-performance materials such as fluoroplastics or polyketones have excellent corrosion resistance, but their cost is too high, making it difficult to promote them in industrial scenarios with moderate requirements; while low-cost polyolefin-based materials have good processability, but their corrosion resistance is limited.

[0013] Therefore, developing a cable sheath material and its preparation method that combines low cost, high corrosion resistance, multi-media tolerance, self-healing function, and excellent filler dispersibility has significant industrial application value and innovative significance. Summary of the Invention

[0014] To address the needs and problems mentioned in the background above, the present invention provides a corrosion-resistant cable sheath material and a method for preparing the same, thereby at least partially solving the aforementioned problems.

[0015] According to the technical solution of the present invention, a corrosion-resistant cable sheath material is provided, comprising the following components by weight: 50-70 parts of high-density polyethylene (HDPE); 15-25 parts of maleic anhydride-grafted ethylene-octene copolymer (POE-g-MAH); Polyketone resin (PK) 8-18 parts; Modified layered double hydroxide-hexagonal boron nitride composite nanosheets (LDH-BNNS) 6-12 parts; 3-8 parts of amino-terminated hyperbranched polysiloxane (NH2-HBPSi); 2-5 parts of microencapsulated latent cross-linking agent; 3-6 parts compatibilizer; Antioxidant 0.5–1.5 parts; 1 to 3 parts lubricant.

[0016] Preferably, the sheath material further comprises the following functional fillers: 4-8 parts by weight of magnesium ion exchange type A molecular sieve (Mg-NH2-4A) with aminohydride; and 3-6 parts by weight of polydopamine-coated hollow glass microspheres (PDA@HGM).

[0017] Preferably, the modified layered double hydroxide-hexagonal boron nitride composite nanosheets (LDH-BNNS) have the following structure: hexagonal boron nitride nanosheets serve as a two-dimensional template, and layered double hydroxide nanosheets are epitaxially grown on the surface of the hexagonal boron nitride nanosheets to form an island-like distributed hybrid nanosheet structure; wherein the lateral dimension of the hexagonal boron nitride nanosheets is 200-500 nm, the thickness is 2-10 nm, the chemical composition of the layered double hydroxide is Mg3Al1-LDH, and the interlayer anion is CO3²⁻.

[0018] Preferably, the terminal amino hyperbranched polysiloxane (NH2-HBPSi) has a molecular weight of 2000-8000 g / mol and an amino content of 1.5-3.5 mmol / g; the polyketide resin (PK) has a melt index of 10-30 g / 10 min at 240°C and a load of 2.16 kg; the maleic anhydride grafting rate of the maleic anhydride-grafted ethylene-octene copolymer (POE-g-MAH) is 0.8-1.5%; the microencapsulated latent crosslinking agent is epoxy resin-coated dicumyl peroxide microcapsules with an average particle size of 10-50 μm and a core-shell mass ratio of 1:0.5-1:2; and the compatibilizer is an ethylene-methyl acrylate-glycidyl methacrylate terpolymer.

[0019] Preferably, the modified layered double hydroxide-hexagonal boron nitride composite nanosheets (LDH-BNNS) and the aminated magnesium ion exchange type A molecular sieve (Mg-NH2-4A) undergo integrated surface modification treatment to form a polymethyl methacrylate grafted functionalized composite filler. The integrated surface modification treatment includes: firstly, hydrolysis and activation with γ-methacryloyloxypropyltrimethoxysilane, and then in-situ graft polymerization of methyl methacrylate in the presence of an initiator.

[0020] In a second aspect, the present invention also provides a method for preparing the corrosion-resistant cable sheath material according to the above, comprising the following steps: (1) Preparation of modified layered double hydroxide-hexagonal boron nitride composite nanosheets (LDH-BNNS). (2) High-density polyethylene, maleic anhydride-grafted ethylene-octene copolymer, polyketide resin and compatibilizer are melt-mixed, and then LDH-BNNS, amino-terminated hyperbranched polysiloxane, microencapsulated latent crosslinking agent, antioxidant and lubricant are added and blended to obtain a premixed material. (3) The premixed material is subjected to a grafting reaction under ultraviolet irradiation to obtain an irradiated grafted material; (4) The irradiated grafted material is extruded and granulated to obtain sheath material masterbatch; (5) After the sheath material masterbatch is extruded and coated onto the outer layer of the cable core, it is subjected to steam post-crosslinking treatment to obtain a corrosion-resistant cable sheath.

[0021] Preferably, the conditions for ultraviolet irradiation in step (3) are: wavelength 365nm, light intensity 15~20mW / cm², irradiation time 8~12min, and N2 protective atmosphere; the conditions for post-steam crosslinking treatment in step (5) are: saturated steam, temperature 85~95℃, relative humidity 95~98%, and treatment time 12~24h.

[0022] Preferably, in step (1), an amino-modified magnesium ion exchange type A molecular sieve (Mg-NH2-4A) and polydopamine-coated hollow glass microspheres (PDA@HGM) are also prepared; and before step (2), the LDH-BNNS and the Mg-NH2-4A are mixed and then subjected to integrated surface modification treatment: first, γ-methacryloyloxypropyltrimethoxysilane accounting for 1.5-2.5% of the total mass of the filler is hydrolyzed and activated at pH 4.0-5.0 and 60-70℃ for 2-4 hours, then benzoyl peroxide accounting for 0.2-0.5% of the total mass of the filler and methyl methacrylate accounting for 5-10% of the total mass of the filler are added, and in-situ graft polymerization is carried out at 80-85℃ for 4-6 hours to obtain polymethyl methacrylate grafted functionalized composite filler; in step (2), the functionalized composite filler and the PDA@HGM are added together for blending.

[0023] Preferably, the melting and mixing temperature in step (2) is 145-155°C and the rotor speed is 60-80 rpm; the extrusion granulation in step (4) uses a twin-screw extruder with a barrel temperature of 155-185°C and a screw speed of 200-300 rpm.

[0024] In a third aspect, the present invention also provides a cable comprising the corrosion-resistant cable sheath material described above, or comprising a corrosion-resistant cable sheath prepared by the preparation method described above. Beneficial effects

[0025] 1. This invention achieves multi-level and multi-mechanism synergistic protection against various corrosive media such as acids, alkalis, salt spray, acidic gases and organic solvents through the physical barrier of the HDPE hydrophobic layer, the labyrinth effect and ion exchange capture of LDH-BNNS, the selective adsorption and chemical chelation of acidic gases by Mg-NH2-4A molecular sieve, and the in-situ self-healing function of the dynamic hydrogen bond network. This significantly improves the corrosion resistance and service life of the sheath material. 2. This invention utilizes an integrated modification technology of silane coupling-in-situ polymerization to construct a PMMA polymer graft layer on the surface of inorganic fillers, achieving chemical bonding and compatibility between the fillers and the polyolefin matrix, fundamentally solving the problem of nanofiller dispersion; through the hydrogen bond network design between PK and NH2-HBPSi, a dual-network structure with both dynamic physical crosslinking and covalent crosslinking is constructed, which enhances the material's impermeability while endowing it with self-healing function; 3. This invention realizes hydrogen bond-driven in-situ self-repair function in cable sheath materials. When microcracks (width ≤ 50 μm) are generated on the sheath surface, under moderate temperature and humidity conditions, hydrogen bonds can break and rearrange, causing the crack interface to close autonomously, which significantly extends the service life of the sheath material and reduces the frequency of cable replacement and maintenance. Detailed Implementation

[0026] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] This invention provides a corrosion-resistant cable sheath material, comprising the components listed in Table 1 below by weight.

[0028] Table 1 High-density polyethylene (HDPE) 50-70 servings Maleic anhydride-grafted ethylene-octene copolymer (POE-g-MAH) 15-25 servings Polyketone (PK) resin 8-18 servings Modified layered double hydroxide-hexagonal boron nitride composite nanosheets (LDH-BNNS) 6-12 servings <![CDATA[Amino-terminated hyperbranched polysiloxane (NH₂-HBPSi)]]> 3 to 8 servings Microencapsulated latent crosslinking agents 2 to 5 servings Ethylene-methyl acrylate-glycidyl methacrylate terpolymer compatibilizer (E-GMA-MA) 3 to 6 portions Antioxidant compound 0.5 to 1.5 parts lubricant 1 to 3 servings Furthermore, the corrosion-resistant cable sheath material also includes the following functional fillers: Magnesium ion-exchange type A molecular sieve (Mg-NH2-4A): 4-8 parts by weight; Polydopamine-coated hollow glass microspheres (PDA@HGM): 3-6 parts by weight.

[0029] The specific definitions and preferred ranges of each component are as follows.

[0030] The high-density polyethylene (HDPE) has a melt index of 0.5–5.0 g / 10 min and a density of 0.945–0.965 g / cm³ at 190°C and a load of 2.16 kg. HDPE, as the main component of the matrix resin, provides mechanical strength and water / chemical barrier properties.

[0031] The maleic anhydride-grafted ethylene-octene copolymer (POE-g-MAH) has a maleic anhydride grafting rate of 0.8-1.5% and a melt index of 1.0-5.0 g / 10 min at 190℃ and 2.16 kg load. POE-g-MAH possesses both high elasticity and polar reactivity. Its MAH groups can chemically react with hydroxyl and amino groups on the surface of functional fillers to form a flexible interfacial bridging layer between the HDPE matrix and the polar filler, while simultaneously imparting excellent impact toughness to the sheath material.

[0032] The polyketone resin (PK) is an alternating copolymer of carbon monoxide, ethylene, and propylene, with a melt index of 10–30 g / 10 min, preferably 10–20 g / 10 min, at 240°C and a load of 2.16 kg. The PK molecule's main chain contains alternating carbonyl groups, giving it excellent resistance to acids, alkalis, organic solvents, and low water absorption. Simultaneously, its carbonyl groups can form hydrogen bonds with the amino groups in the terminal amino hyperbranched polysiloxane for physical cross-linking.

[0033] The terminal amino hyperbranched polysiloxane (NH2-HBPSi) has a molecular weight of 2000–8000 g / mol and an amino content of 1.5–3.5 mmol / g. NH2-HBPSi, under ultraviolet irradiation, forms a Si-O-Si hybrid crosslinking network by covalently grafting with polyolefin chains through free radical reactions; additionally, its terminal amino groups form dynamic reversible hydrogen bonds with the carbonyl groups of PK, constructing a physical crosslinking network.

[0034] The microencapsulated latent crosslinking agent is epoxy resin-coated dicumyl peroxide (DCP) microcapsules with an average particle size of 10–50 μm, a core-shell mass ratio of 1:0.5–1:2, and an encapsulation efficiency of ≥90%. Microencapsulation avoids premature release and pre-crosslinking of the crosslinking agent during melt blending, ensuring the crosslinking reaction proceeds controllably during the UV irradiation stage.

[0035] The ethylene-methyl acrylate-glycidyl methacrylate terpolymer compatibilizer (E-GMA-MA) contains 20-30% by weight of methyl acrylate units, 5-10% by weight of glycidyl methacrylate units, and the remainder being ethylene units. This compatibilizer can simultaneously produce good interfacial compatibility with HDPE, POE-g-MAH, and PK.

[0036] The antioxidant compound is a mixture of Irganox1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) and Irgafos168 (tris(2,4-di-tert-butylphenyl)phosphite) in a weight ratio of 1:2.

[0037] The lubricant is a compound of zinc stearate and polyethylene wax in a 1:1 weight ratio.

[0038] It should be noted that the modified layered boron double hydroxide-hexagonal boron nitride composite nanosheets (LDH-BNNS) have the following structural characteristics: Hexagonal boron nitride nanosheets (BNNS) serve as a two-dimensional template, and layered boron double hydroxide (LDH) nanosheets are epitaxially grown on the surface of BNNS, forming an island-like dispersed hybrid nanosheet structure. The lateral dimensions of BNNS are 200–500 nm, and the thickness is 2–10 nm; the chemical composition of LDH is Mg3Al1-LDH, and the interlayer anion is CO3²⁻. The LDH-BNNS composite nanosheets were prepared by the following method: Oxidized BNNS were ultrasonically dispersed in deionized water, and a mixed salt solution of Mg(NO3)2·6H2O and Al(NO3)3·6H2O (molar ratio Mg:Al=3:1) was added. The pH was adjusted to 9.0-10.0 with 0.5M NaOH solution under N2 protection, and the reaction was carried out hydrothermally at 80℃ for 24 hours. After centrifugation, washing and drying, the nanosheets were obtained.

[0039] The synergistic anti-corrosion mechanism of this composite nanosheet is as follows: the two-dimensional layered structure of BNNS forms a labyrinthine physical barrier layer in the polymer matrix, extending the diffusion path of corrosive media (such as water molecules, Cl⁻, H⁺, etc.); simultaneously, the LDH interlayer has anion exchange capacity, which can exchange ions with the penetrating corrosive anions (Cl⁻, SO₄²⁻, etc.), fixing the corrosive ions in the interlayer channels and achieving active capture. The lattice-matched interface between BNNS and LDH enables their synergistic effect to be realized at the nanoscale, avoiding the problem of filler agglomeration in simple physical blending.

[0040] The preparation method of the Mg-NH2-4A molecular sieve is as follows: 4A molecular sieve (particle size 0.5-3 μm) is dispersed in 1 MM MgCl2 solution, and ion exchange is performed at 60℃ for 24 hours. After washing and drying, Mg-4A molecular sieve is obtained. Then, Mg-4A molecular sieve is dispersed in toluene, and 15-20% of 3-aminopropyltriethoxysilane (APTES) is added. The mixture is refluxed at 110℃ for 12 hours. After washing and drying, Mg-NH2-4A is obtained.

[0041] The functional mechanism of Mg-NH2-4A is as follows: the micropore size of the 4A molecular sieve is approximately 0.4 nm, which can selectively adsorb acidic gas molecules with a kinetic diameter of less than 0.4 nm, such as HCl, SO2, and H2S; Mg²⁺ ion exchange enhances the electrostatic adsorption capacity of the molecular sieve for H⁺; after surface amylation modification, the NH2 groups can further coordinate and chelate with invading corrosive cations. Mg-NH2-4A and LDH-BNNS complement each other in terms of size and mechanism of action—LDH-BNNS mainly targets ion diffusion capture at the nanoscale, while the molecular sieve mainly targets the adsorption of acidic gases at the molecular scale. Together, they constitute a triple capture mechanism of spatial screening—ion exchange—chemical chelation.

[0042] The preparation method of PDA@HGM is as follows: hollow glass microspheres (particle size 10-50 μm, wall thickness 2-5 μm, true density 0.2-0.4 g / cm³) are dispersed in Tris buffer (pH=8.5), and dopamine hydrochloride (5-10% of the mass of microspheres) is added. The mixture is stirred and reacted at room temperature for 24 hours. After centrifugation, washing and drying, PDA@HGM is obtained.

[0043] The functions of PDA@HGM are as follows: the low density of hollow glass microspheres can compensate for the increase in density caused by the addition of inorganic fillers, thus maintaining the lightweight of cable sheath materials; the polydopamine coating layer has abundant catechol and amino functional groups, which on the one hand enhances the interfacial adhesion with the matrix resin, and on the other hand provides additional active sites to participate in the hydrogen bond network.

[0044] To address the dispersion challenges of multi-scale inorganic fillers in polyolefin matrices, this invention employs a silane coupling-in-situ free radical polymerization integrated surface modification method to treat a mixture of LDH-BNNS composite nanosheets and Mg-NH2-4A molecular sieves. The specific steps are as follows: Step 1, Hydrolysis Activation: LDH-BNNS composite nanosheets are mixed with Mg-NH2-4A molecular sieve and dispersed in a mixed solvent of ethanol and water at a volume ratio of 7:3. The mixture is ultrasonically dispersed for 30 minutes. γ-methacryloyloxypropyltrimethoxysilane (KH-570) is added at 1.5-2.5% of the total mass of the filler. The pH is adjusted to 4.0-5.0 with acetic acid. The mixture is hydrolyzed at 60-70℃ for 2-4 hours, causing the silanoxy groups of KH-570 to condense with the hydroxyl groups on the filler surface to form Si-OM (M=Al, Mg, B) covalent bonds. Step 2, in-situ graft polymerization: Add 0.2-0.5% benzoyl peroxide (BPO) and 5-10% methyl methacrylate (MMA) to the above reaction system and stir continuously at 80-85°C for 4-6 hours. MMA initiates graft polymerization on the surface of the filler to form a polymethyl methacrylate (PMMA) graft layer. Step 3, Post-processing: After cooling, the reaction system was centrifuged, washed three times with acetone, and vacuum dried (60℃, 12 hours) to obtain PMMA-g-(LDH / BNNS / Mg-NH2-4A) functionalized composite filler.

[0045] The technical advantages of this integrated modification method are as follows: the silanol end of KH-570 is covalently bonded to the hydroxyl groups on the filler surface, forming stable anchoring points. The grafted PMMA polymer shell exhibits good compatibility with the HDPE / POE-g-MAH matrix (the MAH groups of POE-g-MAH and the ester groups of PMMA exhibit dipole interactions), achieving chemical bonding-level compatibility between the filler and the matrix. Compared to conventional physical adsorption or simple coating treatment of silane coupling agents, the covalent bonding interface strength of this invention is increased by more than 300%, and desorption does not occur under high shear processing conditions.

[0046] The sheath material of the present invention simultaneously constructs a dual structure in the polymer matrix, consisting of a covalent cross-linked network and a dynamic reversible hydrogen bond physical network.

[0047] Construction of the covalent crosslinking network: Under ultraviolet irradiation, microencapsulated DCP releases free radicals, which initiate the breakage of CH bonds on the HDPE and POE-g-MAH chains. The resulting active free radicals undergo grafting reactions with unsaturated double bonds or active hydrogens in the NH2-HBPSi end groups, forming an organosilicon hybrid crosslinking structure with Si-O-Si as the main chain. The bond energy of the Si-O-Si bond is 452 kJ / mol, which endows the material with excellent heat aging resistance and chemical penetration resistance. At the same time, the crosslinking structure significantly reduces the free volume of polymer chain segments, inhibiting the diffusion of small molecule corrosive media.

[0048] Construction of a dynamic and reversible hydrogen bond network: Dense hydrogen bonds are formed between the alternating carbonyl groups (C=O) in the PK molecular chain and the terminal amino groups (-NH2) of NH2-HBPSi. The hydrogen bonds have low bond energies (approximately 20–40 kJ / mol) and exhibit dynamic and reversible characteristics—when microcracks appear on the surface of the sheathing material due to mechanical stress or thermo-oxidative aging, the hydrogen bonds can undergo an adaptive process of breakage, chain slippage, and rebonding, causing the crack interface to close again and achieving in-situ self-repair. After crack healing, the hydrogen bond network recovers without affecting the overall mechanical properties and protective function. The density and distribution of this hydrogen bond network can be controlled by adjusting the relative amounts of PK and NH2-HBPSi.

[0049] HDPE (surface energy approximately 31 mJ / m²) exhibits hydrophobic and nonpolar characteristics, POE-g-MAH (surface energy approximately 33–35 mJ / m²) is amphiphilic, and PK (surface energy approximately 42–45 mJ / m²) has moderate polarity. These three components form a gradient interfacial energy distribution structure from hydrophobic to polar, upgrading the dispersion of the functionalized composite filler in the matrix from a random, point-like distribution to a layered, cascaded, ordered distribution—the more polar functionalized composite filler preferentially distributes in the PK-rich region, while the hydrophobic HDPE forms a continuous outer hydrophobic barrier. When corrosive media penetrates from the outside, it first encounters the hydrophobic barrier layer of HDPE, then penetrates into the POE-g-MAH transition layer, where it is further trapped by ion capture and chemisorption in the more polar PK / functional filler composite region. This gradient structure upgrades corrosion protection from a single-layer barrier to a multi-level synergistic buffer, significantly improving protection efficiency.

[0050] In a second aspect, embodiments of the present invention also provide a method for preparing the above-mentioned corrosion-resistant cable sheath material, comprising the following steps: (1) Preparation of LDH-BNNS composite nanosheets: Oxidized BNNS was ultrasonically dispersed in deionized water to form a BNNS suspension with a concentration of 0.5 mg / mL. Mg(NO3)2·6H2O and Al(NO3)3·6H2O were dissolved in deionized water at a molar ratio of Mg:Al = 3:1 to form a mixed salt solution. The BNNS suspension and the mixed salt solution were mixed, and the pH was adjusted to 9.0–10.0 with 0.5 M NaOH solution under N2 protection. The mixture was then subjected to hydrothermal reaction at 80 °C for 24 hours. After the reaction, the mixture was centrifuged, washed three times alternately with deionized water and ethanol, and then vacuum dried at 80 °C for 12 hours to obtain LDH-BNNS composite nanosheets.

[0051] (2) Preparation of Mg-NH2-4A molecular sieve: Mg-4A molecular sieve was dispersed in 1 mmol MgCl2 solution at a solid-liquid ratio of 1:10 (g / mL) and stirred for ion exchange at 60℃ for 24 hours. After centrifugation, the sieve was washed with deionized water until no Cl⁻ was detected (tested with AgNO3 solution) and dried at 100℃ for 12 hours to obtain Mg-4A molecular sieve. Mg-4A molecular sieve was dispersed in anhydrous toluene at a solid-liquid ratio of 1:15 (g / mL). APTES, accounting for 15-20% of the molecular sieve mass, was added, and the mixture was refluxed at 110℃ for 12 hours under N2 protection. After the reaction was completed, the mixture was centrifuged, washed three times alternately with toluene and anhydrous ethanol, and dried under vacuum at 80℃ for 12 hours to obtain Mg-NH2-4A molecular sieve.

[0052] (3) Preparation of PDA@HGM: Hollow glass microspheres were dispersed in Tris buffer (pH=8.5, concentration 10mM) at a solid-liquid ratio of 1:20 (g / mL) and ultrasonically dispersed for 15 minutes. Dopamine hydrochloride at 5-10% of the mass of the microspheres was added and the mixture was stirred at room temperature for 24 hours. After the reaction was completed, the microspheres were centrifuged, washed three times with deionized water, and vacuum dried at 50°C for 24 hours to obtain PDA@HGM.

[0053] (4) Integrated surface modification treatment: The LDH-BNNS composite nanosheets prepared in step (1) are mixed with the Mg-NH2-4A molecular sieve prepared in step (2) to obtain a composite filler. The composite filler was dispersed in a mixed solvent of ethanol and water at a volume ratio of 7:3 and a solid-liquid ratio of 1:20 (g / mL), and ultrasonically dispersed for 30 minutes. KH-570 at a mass of 1.5-2.5% of the total mass of the composite filler was added, and the pH was adjusted to 4.0-5.0 with acetic acid. The mixture was then hydrolyzed at 60-70℃ for 2-4 hours. Add 0.2-0.5% BPO and 5-10% MMA by mass of the composite filler to the above reaction system, and stir continuously for 4-6 hours under N2 protection at 80-85℃. After the reaction was completed, the product was centrifuged, washed three times with acetone, and vacuum dried at 60°C for 12 hours to obtain PMMA-g-(LDH / BNNS / Mg-NH2-4A) functionalized composite filler.

[0054] (5) Melt blending and ultraviolet irradiation grafting: Weigh each component according to the following parts by weight: HDPE: 50-70 parts POE-g-MAH (grafting rate 0.8-1.5%): 15-25 parts. PK (MFR 10~30g / 10min, 240℃ / 2.16kg): 8~18 parts, E-GMA-MA ternary copolymer compatibilizer: 3-6 parts The functionalized composite filler prepared in step (4) is 6 to 12 parts based on LDH-BNNS (which is converted to a total addition of 9 to 18 parts of functionalized composite filler, of which LDH-BNNS:Mg-NH2-4A=2:1).

[0055] Step (3) Preparation of PDA@HGM: 3 to 6 portions.

[0056] NH2-HBPSi: 3-8 parts Microencapsulated DCP: 2-5 parts Antioxidant compound (Irganox1010:Irgafos168=1:2): 0.5–1.5 parts, Lubricant (zinc stearate: polyethylene wax = 1:1): 1-3 parts, HDPE, POE-g-MAH, PK and E-GMA-MA compatibilizer are put into an internal mixer, the mixing temperature is set to 145-155℃, the rotor speed is 60-80rpm, and the mixture is melt-mixed for 5-8 minutes. Then add the functionalized composite filler prepared in step (4) and the PDA@HGM prepared in step (3), and continue mixing for 3 to 5 minutes; Then add the antioxidant compound and lubricant, and continue mixing for 2 minutes; Finally, add NH2-HBPSi and microencapsulated DCP, mix rapidly for 2-3 minutes, and then discharge to obtain the premixed material; The premixed material was transferred to an ultraviolet irradiation chamber and irradiated for 8 to 12 minutes in a N2 protective atmosphere at a wavelength of 365 nm and a light intensity of 15 to 20 mW / cm² to initiate a covalent grafting reaction and obtain the irradiated grafted material.

[0057] (6) Extrusion granulation: After cooling and crushing, the irradiated grafted material is fed into a twin-screw extruder for melt extrusion granulation. The extruder barrel temperature is set as follows: Zone 1 155-165℃, Zone 2 165-175℃, Zone 3 175-185℃, Zone 4 180-185℃, Die head temperature 175-180℃, and screw speed 200-300 rpm. The extruded material is then water-cooled, stretched, granulated, sieved, and dried to obtain sheath material masterbatch.

[0058] (7) Post-steam crosslinking: The aforementioned sheath material masterbatch is extruded onto the outer layer of the cable core using a cable extruder to form a cable sheath layer. Then, the cable with the sheath layer is placed in a saturated steam treatment chamber and treated for 12 to 24 hours at a temperature of 85–95°C and a relative humidity of 95–98% to perform post-steam crosslinking, which promotes the full release of the crosslinking agent encapsulated in the residual microcapsules and completes the covalent crosslinking of the matrix, ultimately obtaining a corrosion-resistant cable sheath.

[0059] The following provides specific examples 1-10 and comparative examples 1-4. The formulation composition of each example and comparative example is shown in Table 2.

[0060] Table 2

[0061] *Note: Comparative Example 4 did not use microcapsule DCP, nor did it undergo UV irradiation or post-steam crosslinking; it only used ordinary melt blending extrusion.

[0062] Explanation of Examples 1-4: Comparative Example 1: No polyketone resin (PK) and amino-terminated hyperbranched polysiloxane (NH2-HBPSi) were added, i.e. there was no hydrogen bond physical network and no gradient compatibility design.

[0063] Comparative Example 2: Without the addition of LDH-BNNS, Mg-NH2-4A, and PDA@HGM, i.e., without a multi-scale functional filler synergistic corrosion protection system.

[0064] Comparative Example 3: The 4234 type silane cross-linked polyethylene (XLPE) compound produced by Shanghai Xinshanghua Polymer Materials Co., Ltd. was used as the sheath material.

[0065] Comparative Example 4: The same formulation as Example 1 was used, but without the use of microencapsulation crosslinking agent, without UV irradiation and steam crosslinking, and directly extruded into a sheath after ordinary melt blending extrusion granulation.

[0066] The following are the specific preparation methods for Examples 1-10 and Comparative Examples 1-4: (1) Preparation of LDH-BNNS: Oxidized BNNS (lateral size 200-500nm) was ultrasonically dispersed in deionized water (0.5mg / mL), Mg(NO3)2·6H2O and Al(NO3)3·6H2O (molar ratio 3:1) were added, pH was adjusted to 9.5, hydrothermal reaction was carried out at 80℃ for 24h, and then washed and dried.

[0067] (2) Preparation of Mg-NH2-4A: 4A molecular sieve (1-3μm) was ion exchanged in 1MMgCl2 at 60℃ for 24h, washed and dried; then refluxed in toluene with 15% APTES at 110℃ for 12h, washed and dried.

[0068] (3) Preparation of PDA@HGM: Hollow glass microspheres (particle size 10-50μm) were dispersed in Tris buffer (pH=8.5), 8% dopamine hydrochloride was added and stirred at room temperature for 24h, then washed and dried.

[0069] (4) Integrated surface modification: LDH-BNNS and Mg-NH2-4A were mixed and dispersed in ethanol / water (7:3), 2% KH-570 was added, pH=4.5, and hydrolyzed at 65℃ for 3h; then 0.3% BPO and 8% MMA were added, and polymerization was carried out at 82℃ for 5h. After washing and drying, PMMA-g-(LDH / BNNS / Mg-NH2-4A) functionalized composite filler was obtained.

[0070] (5) Melt blending and UV irradiation grafting: In a Banbury mixer at 150℃ and 70rpm, first add HDPE, POE-g-MAH, PK, and E-GMA-MA and mix for 6min; then add functionalized composite filler and PDA@HGM and mix for 4min; then add antioxidant and lubricant and mix for 2min; finally add NH2-HBPSi and microcapsule DCP and mix for 2.5min before discharging. Place the premix in a UV irradiation chamber (365nm, 18mW / cm², N2 protection) and irradiate for 10min.

[0071] (6) Extrusion granulation: Twin screw extruder, zone 1 160℃, zone 2 170℃, zone 3 180℃, zone 4 182℃, die head 178℃, speed 250rpm, granulation.

[0072] (7) Steam crosslinking: After the sheath material is wrapped around the cable core on the cable extruder, it is placed in a saturated steam chamber (90℃, RH i.e., relative humidity 96%) for 18h.

[0073] Comparative Examples 1, 2, and 4: Except for the formulation being adjusted according to Table 1, the other steps are the same as in Example 1. Among them, Comparative Example 4 does not add microcapsule DCP, and does not undergo ultraviolet irradiation and steam crosslinking (i.e., no crosslinking agent is added in step 5, no irradiation is performed, and step 7 is omitted).

[0074] Comparative Example 3: Commercially available silane crosslinked polyethylene (XLPE) sheath material, processed using conventional methods: after extrusion, it was placed in a 90℃ hot water bath for 8 hours for crosslinking.

[0075] The products obtained from Examples 1-10 and Comparative Examples 1-4 were tested according to the following test methods, and the data are shown in Tables 3 and 4 below.

[0076] Mechanical properties: According to GB / T1040.3-2018 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", the tensile speed is 50 mm / min, and the tensile strength (MPa) and elongation at break (%) of the sheath material are tested.

[0077] Corrosion resistance: The sheath material was made into dumbbell-shaped samples and immersed in: A 10% (w / w) H₂SO₄ solution was incubated at 60°C for 72 hours. A 10% NaOH solution was incubated at 60°C for 72 hours. Salt spray with 5% NaCl by mass, 35℃, 72h (salt spray chamber).

[0078] After soaking, remove the product, wipe the surface dry, test the tensile strength and elongation at break, and calculate the retention rate. Retention rate (%) = (value after soaking / initial value) × 100%.

[0079] Self-healing performance: Microcracks approximately 50 μm wide and 5 mm long were etched onto the surface of the specimen using a Razorblade tool. The specimen was then placed in a constant temperature and humidity chamber (60℃, 90%RH) for 48 hours. The tensile strength of the repaired specimen was tested, and the strength recovery rate was calculated. Recovery rate (%) = (Repaired strength / Original strength) × 100%.

[0080] Thermo-oxidative aging performance: The sample was placed in a thermal aging chamber and aged at 100°C for 500 hours. After being removed, the tensile strength and elongation at break retention were tested.

[0081] Table 3 Initial mechanical properties and properties after thermo-oxidative aging for each embodiment and comparative example. Example 1 24.5 520 88.6 86.5 Example 2 23.8 510 87.2 85.0 Example 3 25.1 490 89.5 87.2 Example 4 24.2 515 88.1 85.8 Example 5 24.6 510 87.9 86.0 Example 6 26.0 470 90.0 88.0 Example 7 22.5 540 86.7 84.5 Example 8 24.3 525 88.3 86.2 Example 9 22.0 550 85.5 82.5 Example 10 25.8 460 89.2 87.5 Comparative Example 1 20.5 480 78.0 74.5 Comparative Example 2 18.2 450 82.5 80.0 Comparative Example 3 21.0 480 81.0 78.5 Comparative Example 4 20.8 550 72.0 65.0 Table 4. Corrosion resistance (retention rate after 72h immersion) and self-healing properties of each example and comparative example.

[0082] In summary, the initial tensile strength of all embodiments is between 22.0 and 26.0 MPa, and the elongation at break is between 460 and 550%, which meets the requirements for use of cable sheath materials.

[0083] Example 6 (50 parts HDPE, 18 parts PK, 12 parts LDH-BNNS, 8 parts NH2-HBPSi, 5 parts microcapsule DCP) exhibited the highest tensile strength (26.0 MPa) and the best corrosion resistance retention (95.5% strength retention in acid), but its elongation at break was relatively low (470%). This was because the higher crosslinking density and filler content improved strength but slightly reduced toughness. Example 7 (70 parts HDPE, 8 parts PK, lower filler content) showed the best toughness (540% elongation at break), but its corrosion resistance retention was slightly lower than Example 6 (92.5% in acid). Example 9 (lower limit formulation) had the highest initial elongation at break (550%), but its corrosion resistance retention was slightly lower (92.0% in acid), indicating that moderate PK and filler content can achieve the best balance between mechanical properties and corrosion resistance (Examples 1-5).

[0084] Comparative Example 1 (without PK and NH2-HBPSi): Compared with Example 1, the initial tensile strength decreased (20.5 MPa vs 24.5 MPa), and the corrosion resistance significantly declined, with a strength retention rate in acid of only 72.5% (compared to 94.2% in Example 1). This is because of the lack of chemical inertness and hydrogen bond network of PK, the absence of gradient compatibility design, and the ease with which corrosive media can penetrate. The self-healing recovery rate was only 35%, far lower than the 78.5% of Example 1, indicating that the dynamic hydrogen bond network is key to the self-healing function.

[0085] Comparative Example 2 (non-functional filler LDH-BNNS and molecular sieve): This sample exhibited the worst corrosion resistance, with a strength retention rate of only 68.0% in acid and 66.5% in alkali. This indicates that despite the presence of cross-linked networks and hydrogen bonds, the lack of ion trapping and physical barrier fillers allows corrosive media to penetrate relatively quickly. The self-healing recovery rate (76.0%) was still relatively high due to the presence of the hydrogen bond network, but the overall protective capability was insufficient.

[0086] Comparative Example 3 (commercially available XLPE): Initial mechanical properties were acceptable (21.0 MPa, 480%), but corrosion resistance was significantly inferior to that of the embodiments of the present invention, with a strength retention rate of only 65.0% in acid and 62.0% in alkali. It also lacked self-healing function (recovery rate 42%). The retention rate after thermo-oxidative aging was also low (81%).

[0087] Comparative Example 4 (no crosslinking network, physical blending only): The same formulation as Example 1 was used, but without UV irradiation and post-vapor crosslinking. Initial elongation at break was high (550%), but performance declined sharply after thermo-oxidative aging (strength retention rate 72%), and corrosion resistance was also far lower than Example 1 (strength retention rate in acid 70.5% vs 94.2%). The self-healing recovery rate was 45%, indicating that without covalent crosslinking and a fully established hydrogen bond network, the self-healing effect is limited.

[0088] The corrosion-resistant cable sheath material provided by this invention (Examples 1-10) significantly improves its resistance to acid, alkali, and salt spray corrosion (retention rate ≥88%, mostly ≥92%) while maintaining excellent initial mechanical properties, far exceeding the performance of the prior art comparative example 3 (retention rate ≤70%). Simultaneously, it achieves excellent self-healing function (recovery rate ≥74%) through a dynamic hydrogen bond network, which is completely absent in existing technologies. Its performance retention rate after thermo-oxidative aging is also significantly better than the comparative example.

[0089] Examples 1-5 (preferred range) offer the most balanced overall performance, with Examples 1 and 3 being the best representatives. Example 6 is suitable for scenarios requiring higher strength and slightly lower toughness; Examples 7 and 9 are suitable for applications requiring higher flexibility; Example 10 is suitable for working conditions with extremely high corrosion resistance requirements.

[0090] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A corrosion-resistant cable sheath material, characterized in that, Includes the following materials by weight: The composition includes 50-70 parts of high-density polyethylene, 15-25 parts of maleic anhydride-grafted ethylene-octene copolymer, 8-18 parts of polyketone resin, 6-12 parts of modified layered double hydroxide-hexagonal boron nitride composite nanosheets, 3-8 parts of amino-terminated hyperbranched polysiloxane, 2-5 parts of microencapsulated latent crosslinking agent, 3-6 parts of compatibilizer, 0.5-1.5 parts of antioxidant, and 1-3 parts of lubricant.

2. The corrosion-resistant cable sheath material according to claim 1, characterized in that, The sheath material also includes the following functional fillers: 4-8 parts by weight of amino-modified magnesium ion-exchange type A molecular sieve; 3-6 parts by weight of polydopamine-coated hollow glass microspheres.

3. The corrosion-resistant cable sheath material according to claim 1, characterized in that, The modified layered double hydroxide-hexagonal boron nitride composite nanosheets have the following structure: Using hexagonal boron nitride nanosheets as two-dimensional templates, layered double hydroxide nanosheets are epitaxially grown on the surface of hexagonal boron nitride nanosheets to form an island-like distributed hybrid nanosheet structure. The hexagonal boron nitride nanosheets have a lateral dimension of 200–500 nm and a thickness of 2–10 nm. The chemical composition of the layered double hydroxide is Mg3Al1-LDH, and the interlayer anion is CO3. 2- .

4. The corrosion-resistant cable sheath material according to claim 1, characterized in that, The terminal amino hyperbranched polysiloxane has a molecular weight of 2000–8000 g / mol and an amino content of 1.5–3.5 mmol / g; The polyketone resin has a melt index of 10-30 g / 10 min at 240°C and 2.16 kg load. The maleic anhydride grafting rate of the maleic anhydride-grafted ethylene-octene copolymer is 0.8% to 1.5%. The microencapsulated latent crosslinking agent is epoxy resin-coated dicumyl peroxide microcapsules with an average particle size of 10-50 μm and a core-shell mass ratio of 1:0.5-1:

2. The compatibilizer is an ethylene-methyl acrylate-glycidyl methacrylate terpolymer.

5. The corrosion-resistant cable sheath material according to claim 2, characterized in that, The modified layered double hydroxide-hexagonal boron nitride composite nanosheets and the amino-magnesium ion-exchange type A molecular sieve are subjected to an integrated surface modification treatment to form a polymethyl methacrylate-grafted functionalized composite filler. The integrated surface modification treatment includes: First, it is hydrolyzed and activated with γ-methacryloxypropyltrimethoxysilane, and then in situ grafted polymerization of methyl methacrylate in the presence of an initiator is carried out.

6. A method for preparing a corrosion-resistant cable sheath material as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) Preparation of modified layered double hydroxide-hexagonal boron nitride composite nanosheets; (2) High-density polyethylene, maleic anhydride-grafted ethylene-octene copolymer, polyketide resin and compatibilizer are melt-mixed, and then modified layered double hydroxide-hexagonal boron nitride composite nanosheets, amino-terminated hyperbranched polysiloxane, microencapsulated latent crosslinking agent, antioxidant and lubricant are added and blended to obtain premixed material; (3) The premixed material is subjected to a grafting reaction under ultraviolet irradiation to obtain an irradiated grafted material; (4) The irradiated grafted material is extruded and granulated to obtain sheath material masterbatch; (5) After the sheath material masterbatch is extruded and coated onto the outer layer of the cable core, it is subjected to steam post-crosslinking treatment to obtain a corrosion-resistant cable sheath.

7. The method for preparing the corrosion-resistant cable sheath material according to claim 6, characterized in that, The conditions for ultraviolet irradiation in step (3) are: wavelength 365nm, light intensity 15~20mW / cm², irradiation time 8~12min, and N2 protective atmosphere; The conditions for the steam crosslinking treatment in step (5) are: saturated steam, temperature 85-95℃, relative humidity 95-98%, and treatment time 12-24h.

8. The method for preparing the corrosion-resistant cable sheath material according to claim 6, characterized in that, In step (1), amino-modified magnesium ion-exchange type A molecular sieves and polydopamine-coated hollow glass microspheres are also prepared. Furthermore, prior to step (2), the modified layered double hydroxide-hexagonal boron nitride composite nanosheets are mixed with aminated magnesium ion-exchange type A molecular sieves and then subjected to integrated surface modification treatment: First, γ-methacryloyloxypropyltrimethoxysilane, accounting for 1.5–2.5% of the total mass of the filler, is hydrolyzed and activated at pH 4.0–5.0 and 60–70°C for 2–4 hours. Then, benzoyl peroxide, accounting for 0.2–0.5% of the total mass of the filler, and methyl methacrylate, accounting for 5–10% of the total mass of the filler, are added. In-situ grafting polymerization is carried out at 80–85°C for 4–6 hours to obtain polymethyl methacrylate grafted functionalized composite filler. In step (2), the functionalized composite filler and the polydopamine-coated hollow glass microspheres are added together for blending.

9. The method for preparing the corrosion-resistant cable sheath material according to claim 6, characterized in that, In step (2), the melting and mixing temperature is 145-155℃, and the rotor speed is 60-80 rpm; In step (4), the extrusion granulation is performed using a twin-screw extruder with a barrel temperature of 155-185℃ and a screw speed of 200-300rpm.

10. A cable, characterized in that, It includes the corrosion-resistant cable sheath material according to any one of claims 1-5, or includes the corrosion-resistant cable sheath prepared by the preparation method according to any one of claims 6-9.

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