High-strength weather-resistant cable composite material and preparation method thereof

Abstract

The application discloses a kind of high-strength weather-resistant cable composite material and preparation method thereof, belong to cable material technical field.The composite material is composed of linear low density polyethylene, high density polyethylene, ethylene-octene copolymer, modified nano-silica, carboxylic acid modified ethylene-octene copolymer, antioxidant, light stabilizer and carbon black.Modified nano-silica surface is grafted with maleic anhydride grafted polyethylene wax short chain and glycidyl methacrylate grafted ethylene-octene copolymer long chain simultaneously, and short chain is neutralized to form zinc carboxylate site by zinc;The number average molecular weight of carboxylic acid modified ethylene-octene copolymer is less than the number average molecular weight of long chain.In the state of no loading, long chain forms spatial shielding to zinc carboxylate site;Under the action of stress, the degree of spatial shielding of long chain is reduced, and reversible interaction occurs between trapped chain and zinc site, which is beneficial to improve interface slip resistance and mechanical energy dissipation capacity.

Description

Technical Field

[0001] This invention belongs to the field of cable material technology, and relates to a high-strength weather-resistant cable composite material and its preparation method. Background Technology

[0002] Cables are widely used in overhead power transmission, cross-regional cabling, mountainous laying, and outdoor communication. In special laying environments such as long-span overhead lines and complex mountainous terrain, cables not only need to bear their own weight but also need to withstand complex mechanical stresses such as construction traction, continuous tensile loads, wind loads, and ice loads over long periods. Therefore, cable sheaths and insulation materials should not only have high initial mechanical strength but also good long-term load-bearing capacity to ensure that the materials maintain high mechanical properties and structural integrity during long-term service.

[0003] Currently, cable sheaths and insulation layers are typically made of polymer materials such as polyethylene, cross-linked polyethylene, polyvinyl chloride, and thermoplastic elastomers. To improve the mechanical properties of these materials, existing technologies often employ the addition of glass fibers, inorganic fillers, or other reinforcing materials to enhance the tensile strength, tear resistance, and load-bearing capacity of the composite material. Simultaneously, weather-resistant additives such as antioxidants, UV absorbers, and light stabilizers can be added to improve the material's resistance to UV aging and thermo-oxidative aging, thereby extending the cable's outdoor service life.

[0004] However, in long-term suspended conditions such as overhead lines in mountainous areas and long-span lines, the cable sheath material is subjected to continuous tensile stress and cyclic mechanical loads caused by wind vibration. This results in the interface between the reinforcing phase and the polymer matrix being under repeated stress for an extended period. As service time increases, fatigue damage gradually occurs in the interface area, making it prone to interface debonding and microcracks, which further induce crack propagation. This leads to a continuous decline in the material's tensile strength, elongation at break, and other mechanical properties, making it difficult to maintain a high load-bearing capacity over a long period. Consequently, the long-term service safety and service life of the cable are affected. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength weather-resistant cable composite material and its preparation method. This composite material can resist interface fatigue damage during long-term cable service while maintaining high initial mechanical strength, and improve the mechanical property retention rate and long-term load-bearing capacity under cyclic load conditions.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a high-strength weather-resistant cable composite material, comprising the following raw materials in parts by weight: 52-58 parts of linear low-density polyethylene, 27-33 parts of high-density polyethylene, 12-20 parts of ethylene-octene copolymer, 1.5-2.5 parts of modified nano-silica, 0.05-0.15 parts of carboxylic acid modified ethylene-octene copolymer, 0.35-0.55 parts of antioxidant, 0.30-0.50 parts of light stabilizer, and 2.0-2.8 parts of carbon black;

[0008] The preparation of the modified nano-silica includes the following steps:

[0009] S1. Amide nano-silica to obtain aminated nano-silica;

[0010] S2. The aminated nano-silica is reacted with maleic anhydride-grafted polyethylene wax in an organic solvent, and after washing and drying, the grafted short-chain nano-silica is obtained.

[0011] S3. The grafted short-chain nano-silica was reacted with glycidyl methacrylate-grafted ethylene-octene copolymer in an organic solvent, and after washing and drying, grafted short-chain and long-chain nano-silica were obtained.

[0012] S4. React the grafted short-chain and long-chain nano-silica with zinc salt in an alcohol solvent or an alcohol-water mixture, and then wash and dry to obtain modified nano-silica.

[0013] The number-average molecular weight of the carboxylic acid-modified ethylene-octene copolymer is lower than that of the glycidyl methacrylate-grafted ethylene-octene copolymer.

[0014] In this invention, for ease of description, the maleic anhydride-grafted polyethylene wax grafted onto the surface of nano-silica is referred to as a "short chain," the glycidyl methacrylate-grafted ethylene-octene copolymer grafted onto the surface of nano-silica is referred to as a "long shielding chain" (hereinafter referred to as "long chain"), and the carboxylic acid-modified ethylene-octene copolymer is referred to as a "capture chain." The name "long shielding chain" is based on its function: in the unloaded state, the long chain extends into the polyolefin matrix through its longer molecular chain segments and entangles and interpenetrates with the matrix molecular chains, thereby spatially shielding the short-chain carboxylic acid zinc sites located on the nano-silica surface, thus providing a shielding effect. The name "capture chain" is based on its function: when the long chain deshields under stress, the capture chain forms reversible ion association or dynamic coordination with the short-chain carboxylic acid zinc sites through the carboxylic acid groups on its molecular chain, effectively "capturing" the zinc sites, thereby providing additional sliding resistance and dissipating mechanical energy at the particle-matrix interface.

[0015] In this invention, by limiting the number-average molecular weight of the trapping chain to be lower than that of the long chain, the trapping chain possesses higher segmental mobility and a faster response speed than the long chain. When the composite material is subjected to tension, bending, or cyclic loading, interfacial shear stress is generated between the polyolefin matrix and the rigid nano-silica particles. This stress is transmitted to the long chain through the matrix molecular chain, causing the long chain to tilt, deflect, or partially de-interpenetrate with the matrix chain. The spatial shielding of the zinc carboxylate site by the long chain is reduced, i.e., "deshielding" occurs. At this time, the trapping chain with a smaller molecular weight can quickly approach the zinc carboxylate site and form reversible ion association through local segment conformation adjustment. If the molecular weight of the trapping chain is too large, its segmental mobility is limited, the response speed decreases, and it cannot effectively approach the zinc carboxylate site within a short time under stress loading, resulting in reduced ion association efficiency and affecting interfacial resistance and energy dissipation.

[0016] Preferably, the amination treatment in step S1 uses γ-aminopropyltriethoxysilane, and the mass ratio of γ-aminopropyltriethoxysilane to nano-silica is (3-6):100.

[0017] Preferably, the grafting rate of the maleic anhydride-grafted polyethylene wax on the nano-silica surface is 1.5%-3.5%, and the grafting rate of the glycidyl methacrylate-grafted ethylene-octene copolymer on the nano-silica surface is 4.0%-7.0%.

[0018] Preferably, in step S4, the zinc neutralization degree of the short chains in the grafted short-chain and long-chain nano-silica is 10%-30%.

[0019] Preferably, the maleic anhydride-grafted polyethylene wax has a number average molecular weight of 1500-5000 and a maleic anhydride grafting amount of 0.8-1.2 wt%.

[0020] Preferably, the number average molecular weight of the glycidyl methacrylate-grafted ethylene-octene copolymer is 30,000-50,000, and the amount of glycidyl methacrylate grafted is 0.30-0.40 wt%.

[0021] Preferably, the number average molecular weight of the carboxylic acid modified ethylene-octene copolymer is 5000-10000, and the carboxylic acid group content is 0.4-0.6 wt%.

[0022] Preferably, the particle size of the nano-silica is 20-50 nm.

[0023] Preferably, it further includes 0.02-0.08 parts of a processing aid, wherein the processing aid is a vinylidene fluoride copolymer.

[0024] In a second aspect, the present invention provides a method for preparing a high-strength weather-resistant cable composite material as described in the first aspect, comprising the following steps:

[0025] Y1. Modified nano-silica, carboxylic acid-modified ethylene-octene copolymer and a portion of ethylene-octene copolymer are melt-blended and granulated to obtain functional masterbatch;

[0026] Y2. The functional masterbatch is melt-blended with linear low-density polyethylene, high-density polyethylene, residual ethylene-octene copolymer, antioxidant, light stabilizer and carbon black, and granulated to obtain a high-strength weather-resistant cable composite material.

[0027] The beneficial effects of this invention are:

[0028] (1) In this invention, short chains and long shielding chains are simultaneously grafted onto the surface of nano-silica. After being neutralized by zinc, the short chains provide association sites for zinc carboxylate ions, while the long shielding chains form spatial shielding of the zinc carboxylate sites in the unloaded state. In long-term suspended laying scenarios such as long-span overhead lines and complex mountainous terrain, cable sheath materials bear their own weight and complex mechanical stresses such as wind loads and ice loads for a long time. Under such conditions, traditional reinforced composite materials gradually suffer fatigue damage at the interface between the reinforcing phase and the polymer matrix due to long-term repeated stress, manifested as interface debonding and microcrack propagation, resulting in a continuous decline in mechanical properties such as tensile strength and elongation at break. In this invention, when the material is subjected to tensile or cyclic loads, interfacial shear stress is generated between the polyolefin matrix and the rigid nano-silica particles. The long shielding chains tilt, deflect, or partially de-interpenetrate, reducing the degree of spatial shielding of the zinc carboxylate sites (i.e., "de-shielding"), causing the interface to change from a low-association compliant state to a high-association resistance-increasing state. This stress-induced interfacial dynamic response mechanism enables the composite material to actively increase interfacial slip resistance and delay interfacial debonding when under stress, thereby improving the material's mechanical property retention rate and fatigue resistance under long-term cyclic loading.

[0029] (2) In this invention, the surface grafting rate of the long shielding chain is controlled at 4.0%-7.0%, and the surface grafting rate of the short chain is controlled at 1.5%-3.5%. A lower short chain grafting rate helps to reduce excessive aggregation between short chains on the particle surface and reserves a certain space for capturing the zinc carboxylate sites near the links; a higher long chain grafting rate helps to improve the effective coverage of the long chain on the particle surface, so that it can form a spatial shielding of the adjacent zinc carboxylate sites in the unloaded state. The above combination of grafting rates helps to keep the interface relatively compliant under normal conditions and generate interfacial interaction changes when under stress, thereby taking into account the initial strength, flexibility and cyclic load durability of the material.

[0030] (3) In this invention, the grafting amount of glycidyl methacrylate onto the long chain of ethylene-octene copolymer is controlled at 0.30-0.40 wt%, and the number-average molecular weight of the long chain is controlled at 30,000-50,000. Within this range, calculated by number-average molecular weight and average grafting amount, the average number of GMA units contained in each long chain is close to 1, which statistically reduces the probability of multi-point anchoring of a single long chain, so that at least some long chains can be fixed to the surface of nano-silica with single point or fewer anchoring points, and retain a long free chain segment. This free chain segment is conducive to tilting, deflection or local de-interpenetration under stress. When the GMA grafting amount is too high, the probability of multi-point anchoring of long chains and interfacial cross-linking may increase, thereby limiting the conformational adjustment ability of long chains and being detrimental to the maintenance of interfacial flexibility and cyclic load durability.

[0031] (4) This invention limits the number-average molecular weight of the trapping chain to 5000-10000, making it smaller than the number-average molecular weight of the long chain, thus giving the trapping chain a relatively high segmental mobility. The trapping chain has a polyolefin backbone and has good compatibility with the POE carrier and polyolefin matrix. In the functional masterbatch preparation stage, the trapping chain is pre-blended with modified nano-silica, which can shorten the initial distance between the two and increase the probability of the trapping chain being distributed in the vicinity of the particle. When the long chain undergoes conformational changes under stress, increasing the accessibility of the zinc carboxylate site, the trapping chain can approach the zinc carboxylate site through local segment adjustment and participate in reversible ion association or dynamic coordination. This dynamic interfacial interaction is beneficial to improving interfacial slip resistance, dispersing local stress, and dissipating some mechanical energy during the formation, rearrangement, and dissociation of association points, thereby improving the cyclic load durability of the material.

[0032] (5) This invention employs a masterbatch preparation process, in which modified nano-silica, carboxylic acid-modified ethylene-octene copolymer, and a portion of ethylene-octene copolymer are pre-prepared into functional masterbatches, which are then blended a second time with the matrix resin. This process is beneficial for improving the dispersion state of modified nano-silica in the final composite material and reducing the risk of agglomeration when nanoparticles are directly added. At the same time, the trapping chains are pre-mixed with modified nano-silica during the masterbatch preparation stage, which is beneficial for increasing the initial distribution probability of the trapping chains in the vicinity of the particles, thereby promoting the dynamic interaction of the interface. In addition, antioxidants, light stabilizers, and carbon black are added to the formulation to form a conventional weather-resistant additive system, which is beneficial for improving the material's resistance to thermal and photo-oxidative aging. However, the main improvement of this invention lies in the interface regulation and mechanical property maintenance under cyclic loading conditions. Detailed Implementation

[0033] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0034] The following descriptions of some of the raw materials used in the examples and comparative examples are as follows:

[0035] The linear low-density polyethylene (LLDPE) used is DFH-2076 from Maoming Petrochemical.

[0036] The high-density polyethylene (HDPE) used is Borealis HE6061;

[0037] The ethylene-octene copolymer (POE) used is ENGAGE™ 8200 from Dow Chemical.

[0038] The particle size of nano-silica is 20-50 nm, and the specific surface area is 180±50 m² / g;

[0039] The carbon black used is Cabot's N550;

[0040] The preparation steps of maleic anhydride-grafted polyethylene wax are as follows: 1000g of polyethylene wax with a number average molecular weight of 3000, 100g of maleic anhydride, and 5g of dicumyl peroxide are added to a reaction vessel and heated to 160℃ under nitrogen protection, and stirred for 3 hours. After the reaction is completed, the product is dissolved in hot xylene, filtered while hot to remove insoluble matter, and the filtrate is precipitated with acetone. After suction filtration and washing, it is dried under vacuum at 70℃ to constant weight to obtain maleic anhydride-grafted polyethylene wax with a maleic anhydride grafting amount of 1.0 wt%.

[0041] The preparation steps of glycidyl methacrylate grafted ethylene-octene copolymer are as follows: 100 parts by weight of ethylene-octene copolymer with a number average molecular weight of 40,000 are premixed with 1.2 parts by weight of glycidyl methacrylate, 0.05 parts by weight of dicumyl peroxide, and 0.08 parts by weight of antioxidant 168. The mixture is then added through the main feed port of a twin-screw extruder. Glycidyl methacrylate is injected through the liquid side feed port. Dicumyl peroxide is premixed with a portion of the ethylene-octene copolymer powder and added after preparation. The temperatures of each section of the twin-screw extruder are set as follows: feeding section 80℃, conveying section 120℃, melting section 145℃, reaction section 160℃, homogenization section 165℃, venting section 165℃, and die head section 160℃. The screw speed is 200 rpm, the residence time is 2 min, and the extruder is equipped with a vacuum degassing device with a vacuum degree of −0.08 MPa. The extrudate was water-cooled and pelletized, then vacuum-dried at 70°C to constant weight. The dried product was extracted in acetone for 18 hours, with the solvent changed three times to remove free glycidyl methacrylate and homopolymer. It was then vacuum-dried at 60°C to constant weight to obtain purified glycidyl methacrylate-grafted ethylene-octene copolymer with a glycidyl methacrylate grafting amount of 0.35 wt% and a gel content ≤0.5 wt%.

[0042] The preparation of carboxylic acid-modified ethylene-octene copolymer was as follows: 100 parts by weight of low molecular weight ethylene-octene copolymer with a number average molecular weight of 8000 were added with 1.0 part of maleic anhydride and 0.05 parts of dicumyl peroxide, premixed, and then fed into a twin-screw extruder. The temperatures of each section of the twin-screw extruder were set as follows: feeding section 80℃, conveying section 140℃, melting section 170℃, reaction section 185℃, homogenization section 190℃, venting section 190℃, and die head section 185℃. The screw speed was 200 rpm, the residence time was 2 min, and the extruder was equipped with a vacuum degassing device with a vacuum degree of −0.08 MPa. After cooling and pelletizing, the extrudate was extracted in acetone for 18 hours to remove free maleic anhydride and homopolymer. Then, it was subjected to hydrolysis and ring-opening treatment in an alcohol-water system (ethanol:water = 80:20, volume ratio) at 90℃ for 3 hours to convert the maleic anhydride groups into carboxylic acid groups. After washing, devolatilization and drying, a carboxylic acid-modified ethylene-octene copolymer with a carboxylic acid group content of 0.5 wt% was obtained.

[0043] Except for the raw materials explicitly mentioned above, all other raw materials not specifically mentioned are conventional industrial-grade products that can be easily obtained through commercial channels.

[0044] Grafting rate determination: Thermogravimetric analysis was performed on aminated nano-silica, nano-silica grafted with short chains, and nano-silica grafted with both short and long chains. Each sample was thoroughly washed with the appropriate solvent or extracted using a Soxhlet extract and dried to constant weight before testing. The short-chain grafting rate was calculated based on the increase in organic component mass of the short-chain grafted sample relative to the aminated sample; the long-chain grafting rate was calculated based on the increase in organic component mass of the double-chain grafted sample relative to the short-chain grafted sample. The grafting rate is based on the mass of the unmodified nano-silica and represents the percentage of the corresponding organic chain mass retained on the surface of the nano-silica after thorough washing or extraction relative to the mass of the unmodified nano-silica.

[0045] The degree of zinc neutralization is calculated as the percentage of carboxylic acid groups converted to zinc carboxylate in the short chain relative to the total amount of carboxylic acid groups in the short chain; the amount of zinc acetate added is calculated based on 1 mol Zn 2+ This corresponds to a 2 mol carboxylic acid group quantification.

[0046] Example 1

[0047] A high-strength weather-resistant cable composite material comprises the following raw materials in parts by weight: 55 parts of linear low-density polyethylene (Maoming Petrochemical DFH-2076), 30 parts of high-density polyethylene (Borealis HE6061), 15 parts of ethylene-octene copolymer (Dow Chemical ENGAGE™ 8200), 2.0 parts of modified nano-silica, 0.08 parts of carboxylic acid modified ethylene-octene copolymer, 0.20 parts of antioxidant 1010, 0.25 parts of antioxidant 168, 0.40 parts of light stabilizer 944, 0.05 parts of processing aid for vinylidene fluoride copolymer, and 2.30 parts of carbon black (Cabot N550).

[0048] The preparation of modified nano-silica includes the following steps:

[0049] S1. The nano-silica was vacuum dried at 110℃ for 6 hours. 100g of the dried nano-silica was dispersed in an ethanol-water mixture (ethanol:water = 95:5, volume ratio), and 4.0g of γ-aminopropyltriethoxysilane (KH-550) was added. The pH was adjusted to 4.5-5.0 with glacial acetic acid, and the reaction was carried out at 70℃ for 4 hours. After the reaction was complete, the mixture was filtered, washed three times with ethanol, pre-dried at 80℃, and vacuum dried at 105℃ for 6 hours to obtain aminated nano-silica.

[0050] S2. Aminated nano-silica was dispersed in xylene, and 10g of maleic anhydride-grafted polyethylene wax (mass ratio of maleic anhydride-grafted polyethylene wax to nano-silica was 10:100) was added. The reaction was carried out at 120℃ for 6 hours under nitrogen protection. After the reaction was completed, the mixture was filtered while hot, and then extracted with hot xylene using a Soxhlet extracter for 12 hours. After drying, the grafting rate of maleic anhydride-grafted polyethylene wax on the surface of nano-silica was determined to be 2.5% according to the thermogravimetric analysis method described above.

[0051] S3. The grafted short-chain nano-silica was redispersed in xylene, and 22g of glycidyl methacrylate-grafted ethylene-octene copolymer (mass ratio of glycidyl methacrylate-grafted ethylene-octene copolymer to nano-silica was 22:100) was added. The reaction was carried out at 130℃ for 8 hours under nitrogen protection. After the reaction was completed, the mixture was filtered while hot, and Soxhlet extracted with hot xylene for 12 hours. After drying, the grafting rate of glycidyl methacrylate-grafted ethylene-octene copolymer on the surface of nano-silica was determined to be 5.5% according to the above thermogravimetric analysis method.

[0052] S4. Disperse the double-linked nano-silica in an alcohol-water mixed solvent (ethanol:water = 90:10, volume ratio), add zinc acetate (the amount added is determined according to the above stoichiometric relationship and based on the short link branching rate of 2.5% and the zinc neutralization degree of 20%), and react at 60°C for 3 hours. After the reaction is complete, filter and wash three times with ethanol.

[0053] S5. The modified nano-silica after zinc neutralization is pre-dried under reduced pressure at 70°C, and then vacuum dried at 100°C for 6 hours to obtain modified nano-silica.

[0054] A method for preparing a high-strength weather-resistant cable composite material includes the following steps:

[0055] Y1. Weigh 2.0 parts of the above-mentioned modified nano-silica, 0.08 parts of carboxylic acid modified ethylene-octene copolymer (capture chain), and 7.92 parts of ethylene-octene copolymer carrier. First, premix the modified nano-silica with part of the ethylene-octene copolymer carrier in a high-speed mixer, then add the capture chain and continue mixing, followed by adding the remaining ethylene-octene copolymer carrier and mixing thoroughly. Add the mixture to a twin-screw extruder and melt-blend at 160°C. After extrusion, cooling, and pelletizing, obtain the functional masterbatch.

[0056] Y2. Weigh out linear low-density polyethylene, high-density polyethylene, 7.08 parts of residual ethylene-octene copolymer, 10 parts of functional masterbatch, antioxidant 1010, antioxidant 168, light stabilizer 944, processing aids for vinylidene fluoride copolymer, and carbon black according to the above formula. After premixing in a high-speed mixer, feed the mixture into a twin-screw extruder. Set the temperatures of each section as follows: feeding section 145℃, conveying section 155℃, melting section 170℃, reaction section 175℃, homogenization section 180℃, venting section 180℃, and die head section 175℃. The screw speed is 200 rpm. After extrusion, cooling, and pelletizing, obtain the cable composite material.

[0057] Example 2

[0058] A high-strength weather-resistant cable composite material comprises the following raw materials in parts by weight: 53 parts of linear low-density polyethylene (Maoming Petrochemical DFH-2076), 31 parts of high-density polyethylene (Borealis HE6061), 14 parts of ethylene-octene copolymer (Dow Chemical ENGAGE™ 8200), 1.8 parts of modified nano-silica, 0.10 parts of carboxylic acid modified ethylene-octene copolymer, 0.25 parts of antioxidant 1010, 0.25 parts of antioxidant 168, 0.35 parts of light stabilizer 944, 0.04 parts of processing aid for vinylidene fluoride copolymer, and 2.50 parts of carbon black (Cabot N550).

[0059] The preparation of modified nano-silica includes the following steps:

[0060] S1. The nano-silica was vacuum dried at 110℃ for 6 hours. 100g of the dried nano-silica was dispersed in an ethanol-water mixture (ethanol:water = 95:5, volume ratio), and 3.5g of γ-aminopropyltriethoxysilane (KH-550) was added. The pH was adjusted to 4.5-5.0 with glacial acetic acid, and the reaction was carried out at 70℃ for 4 hours. After the reaction was complete, the mixture was filtered, washed three times with ethanol, pre-dried at 80℃, and vacuum dried at 105℃ for 6 hours to obtain aminated nano-silica.

[0061] S2. Aminated nano-silica was dispersed in xylene, and 8g of maleic anhydride-grafted polyethylene wax (mass ratio of maleic anhydride-grafted polyethylene wax to nano-silica was 8:100) was added. The reaction was carried out at 120℃ for 6 hours under nitrogen protection. After the reaction was completed, the mixture was filtered while hot, and then extracted with hot xylene using a Soxhlet extracter for 12 hours. After drying, the grafting rate of maleic anhydride-grafted polyethylene wax on the surface of nano-silica was determined to be 1.8% according to the thermogravimetric analysis method described above.

[0062] S3. The grafted short-chain nano-silica was redispersed in xylene, and 18g of glycidyl methacrylate-grafted ethylene-octene copolymer (mass ratio of glycidyl methacrylate-grafted ethylene-octene copolymer to nano-silica was 18:100) was added. The reaction was carried out at 130℃ for 8 hours under nitrogen protection. After the reaction was completed, the mixture was filtered while hot, and Soxhlet extracted with hot xylene for 12 hours. After drying, the grafting rate of glycidyl methacrylate-grafted ethylene-octene copolymer on the surface of nano-silica was determined to be 4.5% according to the above thermogravimetric analysis method.

[0063] S4. Disperse the double-linked nano-silica in an alcohol-water mixed solvent (ethanol:water = 90:10, volume ratio), add zinc acetate (the amount added is determined according to the above stoichiometric relationship and based on the short link branching rate of 1.8% and the zinc neutralization degree of 15%), and react at 60°C for 3 hours. After the reaction is complete, filter and wash 3 times with ethanol.

[0064] S5. The modified nano-silica after zinc neutralization is pre-dried under reduced pressure at 70°C, and then vacuum dried at 100°C for 6 hours to obtain modified nano-silica.

[0065] A method for preparing a high-strength weather-resistant cable composite material includes the following steps:

[0066] Y1. Weigh 1.8 parts of the above-mentioned modified nano-silica, 0.10 parts of carboxylic acid modified ethylene-octene copolymer (capture chain), and 8.10 parts of ethylene-octene copolymer carrier. First, premix the modified nano-silica with part of the ethylene-octene copolymer carrier in a high-speed mixer, then add the capture chain and continue mixing, followed by adding the remaining ethylene-octene copolymer carrier and mixing thoroughly. Add the mixture to a twin-screw extruder and melt-blend at 155°C. After extrusion, cooling, and pelletizing, obtain the functional masterbatch.

[0067] Y2. Weigh out linear low-density polyethylene, high-density polyethylene, 5.90 parts of residual ethylene-octene copolymer, 10 parts of functional masterbatch, antioxidant 1010, antioxidant 168, light stabilizer 944, processing aids for vinylidene fluoride copolymer, and carbon black according to the above formula. After premixing in a high-speed mixer, feed the mixture into a twin-screw extruder. Set the temperatures of each section as follows: feeding section 145℃, conveying section 155℃, melting section 165℃, reaction section 170℃, homogenization section 175℃, venting section 175℃, and die head section 170℃. The screw speed is 200 rpm. After extrusion, cooling, and pelletizing, obtain the cable composite material.

[0068] Example 3

[0069] A high-strength weather-resistant cable composite material comprises the following raw materials in parts by weight: 57 parts of linear low-density polyethylene (Maoming Petrochemical DFH-2076), 29 parts of high-density polyethylene (Borealis HE6061), 16 parts of ethylene-octene copolymer (Dow Chemical ENGAGE™ 8200), 2.2 parts of modified nano-silica, 0.06 parts of carboxylic acid modified ethylene-octene copolymer, 0.20 parts of antioxidant 1010, 0.20 parts of antioxidant 168, 0.45 parts of light stabilizer 944, 0.06 parts of processing aid for vinylidene fluoride copolymer, and 2.10 parts of carbon black (Cabot N550).

[0070] The preparation of modified nano-silica includes the following steps:

[0071] S1. The nano-silica was vacuum dried at 110℃ for 6 hours. 100g of the dried nano-silica was dispersed in an ethanol-water mixture (ethanol:water = 95:5, volume ratio), and 4.5g of γ-aminopropyltriethoxysilane (KH-550) was added. The pH was adjusted to 4.5-5.0 with glacial acetic acid, and the reaction was carried out at 70℃ for 4 hours. After the reaction was complete, the mixture was filtered, washed three times with ethanol, pre-dried at 80℃, and vacuum dried at 105℃ for 6 hours to obtain aminated nano-silica.

[0072] S2. Aminated nano-silica was dispersed in xylene, and 12g of maleic anhydride-grafted polyethylene wax (mass ratio of maleic anhydride-grafted polyethylene wax to nano-silica was 12:100) was added. The reaction was carried out at 120℃ for 6 hours under nitrogen protection. After the reaction was completed, the mixture was filtered while hot, and then extracted with hot xylene using a Soxhlet extracter for 12 hours. After drying, the grafting rate of maleic anhydride-grafted polyethylene wax on the surface of nano-silica was determined to be 3.2% according to the thermogravimetric analysis method described above.

[0073] S3. The grafted short-chain nano-silica was redispersed in xylene, and 26g of glycidyl methacrylate-grafted ethylene-octene copolymer (mass ratio of glycidyl methacrylate-grafted ethylene-octene copolymer to nano-silica was 26:100) was added. The reaction was carried out at 130℃ for 8 hours under nitrogen protection. After the reaction was completed, the mixture was filtered while hot, and Soxhlet extracted with hot xylene for 12 hours. After drying, the grafting rate of glycidyl methacrylate-grafted ethylene-octene copolymer on the surface of nano-silica was determined to be 6.5% according to the above thermogravimetric analysis method.

[0074] S4. Disperse the double-linked nano-silica in an alcohol-water mixed solvent (ethanol:water = 90:10, volume ratio), add zinc acetate (the amount added is determined according to the above stoichiometric relationship and based on the short link branching rate of 3.2% and the zinc neutralization degree of 25%), and react at 60°C for 3 hours. After the reaction is complete, filter and wash three times with ethanol.

[0075] S5. The modified nano-silica after zinc neutralization is pre-dried under reduced pressure at 70°C, and then vacuum dried at 100°C for 6 hours to obtain modified nano-silica.

[0076] A method for preparing a high-strength weather-resistant cable composite material includes the following steps:

[0077] Y1. Weigh 2.2 parts of the above-mentioned modified nano-silica, 0.06 parts of carboxylic acid modified ethylene-octene copolymer (capture chain), and 7.74 parts of ethylene-octene copolymer carrier. First, premix the modified nano-silica with part of the ethylene-octene copolymer carrier in a high-speed mixer, then add the capture chain and continue mixing, followed by adding the remaining ethylene-octene copolymer carrier and mixing thoroughly. Add the mixture to a twin-screw extruder and melt-blend at 165°C. After extrusion, cooling, and pelletizing, obtain the functional masterbatch.

[0078] Y2. Weigh out linear low-density polyethylene, high-density polyethylene, 8.26 parts of residual ethylene-octene copolymer, 10 parts of functional masterbatch, antioxidant 1010, antioxidant 168, light stabilizer 944, processing aids for vinylidene fluoride copolymer, and carbon black according to the above formula. After premixing in a high-speed mixer, feed the mixture into a twin-screw extruder. Set the temperatures of each section as follows: feeding section 145℃, conveying section 155℃, melting section 175℃, reaction section 180℃, homogenization section 185℃, venting section 185℃, and die head section 180℃. The screw speed is 200 rpm. After extrusion, cooling, and pelletizing, obtain the cable composite material.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that the nano-silica was not subjected to any surface modification treatment. The unmodified nano-silica was directly granulated with carboxylic acid modified ethylene-octene copolymer (capture chain) and ethylene-octene copolymer carrier in the same proportion to prepare functional masterbatch. The other raw material types, amounts and preparation processes were the same as in Example 1.

[0081] Comparative Example 2

[0082] The difference from Example 1 is that the nano-silica is only subjected to KH-550 amination treatment (i.e. only the S1 step in Example 1 is completed), without short chain and long chain branching. The amination nano-silica is directly granulated with carboxylic acid modified ethylene-octene copolymer (capture chain) and ethylene-octene copolymer carrier in the same proportion to prepare functional masterbatch. The other raw material types, amounts and preparation processes are the same as in Example 1.

[0083] Comparative Example 3

[0084] The difference from Example 1 is that: only short chains (maleic anhydride grafted with polyethylene wax) are grafted onto nano silica and neutralized with zinc, and long chains (glycidyl methacrylate grafted with ethylene-octene copolymer) are not grafted onto it, that is, step S3 in Example 1 is omitted, and the other raw material types, amounts and preparation processes are the same as in Example 1.

[0085] Comparative Example 4

[0086] The difference from Example 1 is that after grafting short and long chains onto nano-silica, zinc neutralization treatment is not performed (i.e., step S4 in Example 1 is omitted). After direct drying, it is granulated with carboxylic acid-modified ethylene-octene copolymer (capture chain) and ethylene-octene copolymer carrier to prepare functional masterbatch. The types, amounts and preparation processes of other raw materials are the same as in Example 1.

[0087] Comparative Example 5

[0088] The difference from Example 1 is that the functional masterbatch does not contain carboxylic acid modified ethylene-octene copolymer (capture chain). That is, the functional masterbatch is composed only of modified nano silica and ethylene-octene copolymer carrier (modified nano silica 20.0 wt%, ethylene-octene copolymer carrier 80.0 wt%). The types, amounts and preparation processes of the other raw materials are the same as those in Example 1.

[0089] Comparative Example 6

[0090] The difference from Example 1 is that the amount of glycidyl methacrylate grafted onto the ethylene-octene copolymer is different, specifically 2.8 wt%.

[0091] The preparation steps of the glycidyl methacrylate-grafted ethylene-octene copolymer in Comparative Example 6 were as follows: 100 parts by weight of ethylene-octene copolymer with a number average molecular weight of 40,000 were added, along with 8.0 parts of glycidyl methacrylate, 0.12 parts of dicumyl peroxide, and 0.08 parts of antioxidant 168. After premixing, the mixture was added through the main feed port of a twin-screw extruder. Glycidyl methacrylate was injected through the liquid side feed port, and dicumyl peroxide was added after being premixed with a portion of the ethylene-octene copolymer powder. The temperatures of each section of the twin-screw extruder were set as follows: feeding section 80℃, conveying section 120℃, melting section 145℃, reaction section 160℃, homogenization section 165℃, venting section 165℃, and die head section 160℃. The screw speed was 200 rpm, the residence time was 2 min, and the extruder was equipped with a vacuum degassing device with a vacuum degree of −0.08 MPa. The extrudate was water-cooled and pelletized, then vacuum-dried to constant weight at 70°C. The dried product was extracted in acetone for 18 hours, with the solvent changed three times to remove free glycidyl methacrylate and homopolymer. It was then vacuum-dried to constant weight at 60°C to obtain a high-grafted glycidyl methacrylate-grafted ethylene-octene copolymer. The glycidyl methacrylate grafting amount was determined to be 2.8 wt%, and the gel content was ≤0.5 wt%.

[0092] Test case

[0093] The following performance tests were performed on the cable composite materials prepared in Examples 1-3 and Comparative Examples 1-6.

[0094] Test Example 1: Mechanical Property Test

[0095] The tensile strength and elongation at break of the composite material were tested according to GB / T 1040.2 standard. The composite material was hot-pressed into a sheet approximately 1 mm thick on a flat vulcanizing machine at 180℃ and 10 MPa, and then cut into 1A-type dumbbell-shaped specimens. The tensile rate was 50 mm / min, and the test temperature was room temperature (23±2℃). Five specimens were tested in each group, and the average value was taken.

[0096] Test Example 2: Cyclic Load Durability Test

[0097] Referring to GB / T 1040.2 standard, type 1A dumbbell-shaped specimens were prepared using the same method described above. Load-unloading cyclic tests were performed on an electronic universal testing machine at a loading rate of 50 mm / min and an unloading rate of 50 mm / min. The upper limit of the load was set to 60% of the initial tensile strength, and the lower limit of the load was set to 5% of the initial tensile strength. After 500 and 1000 cycles of loading, respectively, the tensile strength of the specimens was tested according to the method in Test Example 1, and the strength retention rate was calculated.

[0098] Strength retention rate (%) = (Tensile strength after cycles / Initial tensile strength) × 100%

[0099] Five samples were tested in each group, and the average value of the results was taken.

[0100] Test Example 3: Dynamic Mechanics Analysis (DMA)

[0101] Following ISO 6721-1 standards, the composite material was hot-pressed into a sheet approximately 2 mm thick on a flat vulcanizing machine at 180°C and 10 MPa. This sheet was then cut into rectangular strips measuring 30 mm × 10 mm × 2 mm. A dynamic mechanical analyzer was used to perform temperature scanning in tensile mode, ranging from -80°C to 120°C, with a heating rate of 3°C / min, a frequency of 1 Hz, and a strain amplitude of 0.05%. The loss factor (tan δ) was recorded as a function of temperature, and the peak value (tan δ_max) was read.

[0102] The data for each test case are shown in Table 1.

[0103] Table 1

[0104]

[0105] As shown in Table 1:

[0106] The tensile strength of Examples 1-3 was 23.8-25.1 MPa, and the elongation at break was 580%-650%, which were generally higher than those of the comparative examples. Among them, Comparative Example 1 (unmodified SiO2) and Comparative Example 2 (KH-550 only) showed lower mechanical properties, indicating that double-link grafting modification is beneficial to improving the interfacial compatibility and stress transfer between nano-silica and the polyolefin matrix. Comparative Example 6 used a higher GMA grafting amount, and its elongation at break was lower than that of Example 1, indicating that excessively high GMA grafting amount is not conducive to maintaining the material's flexibility. This may be related to the increased probability of multi-point anchoring and the limited adjustment of long-chain conformation.

[0107] Regarding cyclic load durability, the strength retention rates of Examples 1-3 were 89.5%-92.0% after 500 cycles and 83.2%-86.5% after 1000 cycles, both higher than the corresponding comparative examples. Specifically, the strength retention rates of Comparative Example 5 (lacking a trapping chain), Comparative Example 3 (lacking a long shielding chain), and Comparative Example 6 (using a high GMA grafting amount) after 1000 cycles were 68.5%, 63.5%, and 58.4%, respectively, lower than the 85.6% of Example 1. These results indicate that the trapping chain, long shielding chain, zinc carboxylate sites, and appropriate GMA grafting amount have a synergistic effect on improving the mechanical property retention rate after cyclic loading, consistent with the stress-induced interface regulation mechanism proposed in this invention.

[0108] DMA test results showed that the tan δ_max of Examples 1-3 was 0.50-0.54, higher than that of Comparative Examples 1-6 (0.38-0.45); specifically, Comparative Example 4 (lacking zinc neutralization) had a tan δ_max of 0.41, and Comparative Example 5 (lacking the trapping chain) had a tan δ_max of 0.45. These results indicate that the examples possess strong viscoelastic energy dissipation capabilities. Combined with the results of the comparative examples lacking zinc neutralization or the trapping chain, it can be inferred that the reversible interaction between the zinc site of the carboxylic acid and the carboxylic acid group of the trapping chain participates in the dynamic energy dissipation process at the interface. However, these DMA results themselves are not intended to limit specific microscopic interaction mechanisms.

[0109] In summary, this invention is based on a stress-induced interface design that integrates a short chain, a long shielding chain, and a trapping chain. Under unloaded conditions, the long chain spatially shields adjacent zinc carboxylate sites, maintaining a relatively compliant interface. Under stress, the spatial shielding effect of the long chain decreases, and the trapping chain interacts reversibly with the zinc carboxylate sites, which helps improve interface slip resistance and dissipate mechanical energy. After unloading, the interface structure can recover and rearrange to some extent. Test results show that this dynamic interface design is beneficial for improving the initial mechanical properties of the material and the strength retention rate after cyclic loading. The formulation also includes antioxidants, light stabilizers, and carbon black, forming a weather-resistant additive system suitable for outdoor polyolefin cable materials, which helps improve the material's resistance to thermal and photo-oxidative aging. The main technical effect of this invention is to improve interface durability and mechanical property retention under long-term cyclic loading conditions, making it suitable for laying scenarios with high requirements for long-term cable load-bearing capacity, such as long-span overhead lines and complex mountainous terrain.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-strength weather-resistant cable composite material, characterized in that, The raw materials include the following parts by weight: 52-58 parts linear low-density polyethylene, 27-33 parts high-density polyethylene, 12-20 parts ethylene-octene copolymer, 1.5-2.5 parts modified nano-silica, 0.05-0.15 parts carboxylic acid modified ethylene-octene copolymer, 0.35-0.55 parts antioxidant, 0.30-0.50 parts light stabilizer, and 2.0-2.8 parts carbon black; The preparation of the modified nano-silica includes the following steps: S1. Amide nano-silica to obtain aminated nano-silica; S2. The aminated nano-silica is reacted with maleic anhydride-grafted polyethylene wax in an organic solvent, and after washing and drying, the grafted short-chain nano-silica is obtained. S3. The grafted short-chain nano-silica was reacted with glycidyl methacrylate-grafted ethylene-octene copolymer in an organic solvent, and after washing and drying, grafted short-chain and long-chain nano-silica were obtained. S4. React the grafted short-chain and long-chain nano-silica with zinc salt in an alcohol solvent or an alcohol-water mixture, and then wash and dry to obtain modified nano-silica. The number-average molecular weight of the carboxylic acid-modified ethylene-octene copolymer is lower than that of the glycidyl methacrylate-grafted ethylene-octene copolymer.

2. The high-strength weather-resistant cable composite material according to claim 1, characterized in that, The amination treatment in step S1 uses γ-aminopropyltriethoxysilane, and the mass ratio of γ-aminopropyltriethoxysilane to nano-silica is (3-6):

100.

3. The high-strength weather-resistant cable composite material according to claim 1, characterized in that, The grafting rate of the maleic anhydride-grafted polyethylene wax on the nano-silica surface is 1.5%-3.5%, and the grafting rate of the glycidyl methacrylate-grafted ethylene-octene copolymer on the nano-silica surface is 4.0%-7.0%.

4. The high-strength weather-resistant cable composite material according to claim 1, characterized in that, In step S4, the zinc neutralization degree of the short chains in the grafted short-chain and long-chain nano-silica is 10%-30%.

5. The high-strength weather-resistant cable composite material according to claim 1, characterized in that, The maleic anhydride-grafted polyethylene wax has a number average molecular weight of 1500-5000 and a maleic anhydride grafting amount of 0.8-1.2 wt%.

6. The high-strength weather-resistant cable composite material according to claim 1, characterized in that, The glycidyl methacrylate-grafted ethylene-octene copolymer has a number average molecular weight of 30,000-50,000 and a glycidyl methacrylate grafting amount of 0.30-0.40 wt%.

7. The high-strength weather-resistant cable composite material according to claim 1, characterized in that, The carboxylic acid-modified ethylene-octene copolymer has a number average molecular weight of 5,000-10,000 and a carboxylic acid group content of 0.4-0.6 wt%.

8. The high-strength weather-resistant cable composite material according to claim 1, characterized in that, The particle size of the nano-silica is 20-50 nm.

9. The high-strength weather-resistant cable composite material according to claim 1, characterized in that, It also includes 0.02-0.08 parts of processing aid, wherein the processing aid is a vinylidene fluoride copolymer.

10. A method for preparing a high-strength weather-resistant cable composite material as described in any one of claims 1-9, characterized in that, Includes the following steps: Y1. Modified nano-silica, carboxylic acid-modified ethylene-octene copolymer and a portion of ethylene-octene copolymer are melt-blended and granulated to obtain functional masterbatch; Y2. The functional masterbatch is melt-blended with linear low-density polyethylene, high-density polyethylene, residual ethylene-octene copolymer, antioxidant, light stabilizer and carbon black, and then granulated to obtain a high-strength weather-resistant cable composite material.

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