Preparation method of high-toughness crosslinked polyethylene insulated power cable

Abstract

The invention relates to the technical field of cable preparation, in particular to a preparation method of a high-toughness crosslinked polyethylene insulated power cable. The preparation method comprises the following main steps in sequence: preparing a modified material, preparing modified crosslinked polyethylene and modified high-density polyethylene, and preparing the high-toughness crosslinked polyethylene insulated power cable. The polyethylene insulated power cable prepared by the method has high toughness, mainly due to the mechanical interlocking synergistic effect of the silicon dioxide fibers and the silicon dioxide nanoparticles, the interface bonding strength of a modified material and a polyethylene matrix is improved; meanwhile, the surface of the modified material is chemically modified, so that chemical bridging is generated between the modified material and a polyethylene matrix, and the bonding strength of the modified material and the polyethylene matrix is further improved; according to the invention, different doped XLPE and HDPE are compounded and combined, and through the combined action of the fiber reinforced phase and the particle toughening phase, the cable outer sheath material has a high-strength skeleton, so that the overall toughness of the cable is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cable preparation, and in particular to a method for preparing a high-toughness cross-linked polyethylene insulated power cable. Background Art

[0002] With the rapid development of the power industry, cables play an irreplaceable role in various fields. Therefore, improving the quality of wires and cables is particularly important. Currently, methods to prevent cable damage include physical, biological, and chemical control. However, biological and chemical control methods can cause soil pollution and environmental damage, while physical control methods use expensive materials and complex processing. Therefore, developing a low-cost, environmentally friendly, and easily processable cable outer sheath is of great significance.

[0003] In recent years, polymers have attracted attention for insulating composite materials in applications such as power cables due to their excellent insulation properties. To ensure the economic and environmental sustainability of cables, polymer materials must possess low electrical conductivity, a low dielectric constant and dissipation factor, high dielectric breakdown strength, and the ability to operate at elevated temperatures. While many materials exhibit nonlinear electrical conductivity, high thermal conductivity, and the ability to absorb UV light emitted by partial discharge, limited research has examined how polymers can enhance cable toughness and, therefore, resistance to physical damage.

[0004] Therefore, the present invention attempts to use a melt blending method to prepare a fiber / particle modified cross-linked polyethylene composite material, and use it as the outer sheath of the cable to improve the mechanical properties of the cable. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a method for preparing a high-toughness cross-linked polyethylene insulated power cable.

[0006] S1. Preparation of modified materials:

[0007] S1-1. Pretreatment of modified materials:

[0008] First, the silica fibers and silica particles were immersed in an acetone solution for 2 h, then ultrasonicated for 1 h, washed with deionized water, and finally dried at 60-65 ° C for 24 h.

[0009] S1-2, silica fiber modification:

[0010] Polydopamine and nano-SiO2 were used to synergistically modify silica fibers to obtain modified silica fibers;

[0011] S1-3, Silica Particle Modification:

[0012] Using KH560 to modify silica particles to obtain modified silica particles;

[0013] S2. Preparation of modified cross-linked polyethylene and modified high-density polyethylene:

[0014] S2-1, Doping and Modification Materials in Polyethylene

[0015] XLPE (cross-linked polyethylene) and HDPE (high-density polyethylene) are dried at 60-65°C for 8 hours, HDPE is mixed with modified silica fibers, and XLPE is mixed with modified silica particles.

[0016] S2-2, melt granulation:

[0017] XLPE mixed with modified silica particles and HDPE mixed with silica fibers are placed in a torque rheometer and mixed in layers, and then the mixed product is granulated to obtain raw material particles;

[0018] S2-3, injection molding:

[0019] The raw material particles are added into an injection molding machine for injection molding, and then the obtained sample is pressed into a mold to obtain a specimen;

[0020] S3. Preparation of high-toughness cross-linked polyethylene insulated power cable:

[0021] S3-1. Preparation of high-toughness cross-linked polyethylene:

[0022] Firstly, the cable outer sheath material was prepared by supercritical foaming method using the S2-3 strips as foaming material and CO2 as foaming agent;

[0023] S3-2, secondary extrusion coating:

[0024] The cable outer sheath material is coated on the cable surface by secondary extrusion coating to obtain a high-toughness cross-linked polyethylene insulated power cable.

[0025] Furthermore, the steps of modifying the silica fiber in S1-2 are:

[0026] S1-2-1. Add the silica fibers treated with S1-1 to a sodium hydroxide solution at pH 8 and ultrasonically disperse for 15 minutes; then add dopamine hydrochloride and allow the coating reaction to proceed for 24 hours; then remove the reaction product, wash it with deionized water, and finally dry it at 100°C to obtain polydopamine-modified silica fibers;

[0027] S1-2-2. Anhydrous ethanol and deionized water were mixed in a reactor and stirred for 30 minutes, and then ethyl orthosilicate was added and stirred for 2 hours to obtain solution A. Deionized water, glacial acetic acid, and KH560 were mixed in a reactor and stirred for 30 minutes to obtain solution B.

[0028] S1-2-3. Mix the solution A and solution B and stir for 30 minutes, then add the polydopamine-modified silica fiber in S1-2-1 and stir evenly, and react in a water bath at 65°C for 3 hours; then take out the reaction product and wash and dry it to obtain modified silica fiber.

[0029] Description: The present invention adopts a synergistic modification strategy to treat silica fibers to improve the mechanical strength of polyethylene composites; the mechanical properties of dopamine hydrochloride modified silica fibers gradually increase with the increase of dopamine coverage concentration, and gradually decrease after reaching a peak; then SiO2 is grown on the surface of the dopamine-modified silica fibers to prepare a composite material, and it is found that: compared with the unmodified polyethylene material, the tensile strength of the synergistically modified composite material is improved, which is due to the strong interfacial interaction between the modified silica fibers and polyethylene.

[0030] Furthermore, the addition amount of each component in S1-2-1 is:

[0031] Let n be the rate coefficient and n∈R+, then the amount of silica fiber added is [10, 15] ng, the amount of sodium hydroxide solution added is [100, 150] n mL, and the amount of dopamine hydrochloride added is [0.2, 0.3] ng;

[0032] The amount of each component added to solution A of S1-2-3 is:

[0033] Let n be the rate coefficient and n∈R+, then the amount of anhydrous ethanol added is [100,110]n mL, the amount of deionized water added is [20,30]n mL, and the amount of ethyl orthosilicate added is [10,20]n mL;

[0034] The amount of each component added to solution B of S1-2-2 is:

[0035] Let n be the rate coefficient and n∈R+, then the amount of deionized water added is [110,130]n mL, the amount of glacial acetic acid added is [5,10]n mL, and the amount of KH560 added is [3,5]n mL;

[0036] The amount of polydopamine modified silica fiber added in S1-2-3 was [15,20] ng.

[0037] Furthermore, the step of modifying the silica particles in S1-3 is:

[0038] First, anhydrous ethanol and deionized water were mixed in a reactor and stirred for 30 minutes, then glacial acetic acid and KH560 were added and stirred for 30 minutes; then the silica particles treated with S1-1 were added and reacted in a water bath at 65°C for 2 hours; finally, the reaction product was taken out and washed and dried to obtain modified silica particles.

[0039] Description: Silica particles were surface modified using KH560 with epoxy groups. Modifiers of varying mass fractions were introduced onto the surface of the silica particles to prepare composite materials. It was found that the mechanical properties of the modified composite materials were significantly enhanced. This is presumably because the chemical bonds formed between the amide and epoxy groups improve the interfacial interactions.

[0040] Furthermore, the addition amount of each component in S1-3 is:

[0041] Let n be the rate coefficient and n∈R+, then the amount of anhydrous ethanol added is [80,90]n mL, the amount of deionized water added is [20,30]n mL, the amount of glacial acetic acid added is [5,10]n mL, the amount of KH560 added is [3,5]n mL; and the amount of silica particles added is [10,15] ng.

[0042] Furthermore, the addition amount of each component in S2-1 is: XLPE: 100 phr, modified silica fiber: 20-25 phr, HDPE: 100 phr, modified silica particles: 10-15 phr.

[0043] Furthermore, when laying in layers in S2-2, the mass ratio of XLPE mixed with modified silica particles to HDPE mixed with silica fibers is 3 to 5:1;

[0044] The parameters of the torque rheometer in S2-2 are: temperature of 190-200°C, rotor speed of 80-90 rpm, and blending time of 5-7 min.

[0045] Furthermore, the parameters of the injection molding machine in S2-3 are: temperature of 190-195°C, mold temperature of 65-70°C, injection temperature of 170-175°C, injection pressure of 700-750 bar, and holding time of 9-10 seconds;

[0046] The parameters of the press molding in S2-3 are: first pressurizing at a pressure of 3 to 4 MPa for 3 to 4 minutes, and then pressurizing at a pressure of 15 to 17 MPa for 5 to 7 minutes.

[0047] Furthermore, the parameters of the supercritical foaming method in S3-1 are: the reaction atmosphere is CO2 atmosphere, the immersion temperature is 145-150°C, the foaming temperature is 115-120°C, the foaming pressure is 10-11 MPa, and the time is 1-1.5 h.

[0048] Description: The cable outer sheath material was prepared by supercritical CO2 foaming technology. The results showed that when the immersion temperature was 145-150℃, the foaming temperature was 115-120℃, and the foaming pressure was 10-11MPa, the cable outer sheath material had good pore morphology, an average pore diameter of 100-105pm, and an expansion ratio of 30.

[0049] Furthermore, the layer thickness of the cable outer sheath material is 0.8-0.85 mm, the extrusion speed is 40-50 m / min, and the temperature of each process section during extrusion is: feeding section: 80-90°C / min, compression section: 110-130°C / min, homogenization section: 115-130°C / min, die head and mold sleeve section: 115-130°C / min, and curing section: 135-150°C / min.

[0050] Note: Based on the processing direction of the cable outer sheath, the selection of the temperature of each process section must meet the following process requirements: prevent the material from plasticizing prematurely, promote the plasticization of the material and eliminate volatiles, ensure uniform flow of the melt, avoid scorching caused by high temperature or poor plasticization caused by low temperature, and balance the reaction rate and material stability.

[0051] Compared with the existing cross-linked polyethylene insulated power cable, the beneficial effects of the present invention are:

[0052] (1) On the one hand, the present invention improves the interfacial bonding strength between the modified material and the polyethylene matrix through the mechanical interlocking synergistic effect of silica fibers and silica nanoparticles; at the same time, by chemically modifying the surface of the modified material, a chemical bridge is generated between the modified material and the polyethylene matrix, thereby further improving the bonding strength between the two.

[0053] (2) The present invention adopts a composite combination of XLPE and HDPE with different doping, and through the combined action of the fiber reinforcement phase and the particle toughening phase, the cable outer sheath material has a high-strength skeleton, thereby being able to improve the overall mechanical strength of the cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a preparation flow chart of the present invention. DETAILED DESCRIPTION

[0055] In order to further illustrate the approach and effects achieved by the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with experiments.

[0056] Example 1: This example describes a method for preparing a high-toughness cross-linked polyethylene insulated power cable.

[0057] S1. Preparation of modified materials:

[0058] S1-1. Pretreatment of modified materials:

[0059] First, the silica fibers and silica particles were immersed in acetone solution for 2 h, then ultrasonicated for 1 h, washed with deionized water, and finally dried at 60 ° C for 24 h.

[0060] S1-2, silica fiber modification:

[0061] S1-2-1. Add 10 g of silica fiber treated with S1-1 to 100 mL of sodium hydroxide solution at pH 8 and ultrasonically disperse for 15 min; then add 0.2 g of dopamine hydrochloride and carry out coating reaction for 24 h; then take out the reaction product and wash it with deionized water, and finally dry it at 100°C to obtain polydopamine-modified silica fiber;

[0062] S1-2-2. Mix 100 mL of anhydrous ethanol and 20 mL of deionized water in a reactor and stir for 30 min. Then, add 10 mL of ethyl orthosilicate and continue stirring for 2 h to obtain solution A. Mix 110 mL of deionized water, 5 mL of glacial acetic acid, and 3 mL of KH560 in a reactor and stir for 30 min to obtain solution B.

[0063] S1-2-3. Mix solution A and solution B and stir for 30 minutes, then add 15 g of polydopamine-modified silica fiber prepared in S1-2-1 and stir evenly. React in a water bath at 65°C for 3 hours. Then, remove the reaction product, wash, and dry it to obtain modified silica fiber.

[0064] S1-3, Silica Particle Modification:

[0065] First, 80 mL of anhydrous ethanol and 20 mL of deionized water were mixed in a reactor and stirred for 30 minutes. Then, 5 mL of glacial acetic acid and 3 mL of KH560 were added and stirred for 30 minutes. Then, 10 g of silica particles treated with S1-1 were added and reacted in a water bath at 65°C for 2 hours. Finally, the reaction product was taken out, washed, and dried to obtain modified silica particles.

[0066] S2. Preparation of modified cross-linked polyethylene and modified high-density polyethylene:

[0067] S2-1, Doping and Modification Materials in Polyethylene

[0068] XLPE and HDPE were dried at 60℃ for 8h, 100phr of HDPE was mixed with 20phr of modified silica fiber, and 100phr of XLPE was mixed with 10phr of modified silica particle;

[0069] S2-2, melt granulation:

[0070] According to the mass ratio of HDPE mixed with silica fiber to XLPE mixed with modified silica particle is 3:1; by the way of layered laying, XLPE mixed with modified silica particle and HDPE mixed with silica fiber are laid into the torque rheometer for mixing, and then the mixed product is granulated to obtain raw material particles;

[0071] When layered laying, the total number of layers is 8, the mass of HDPE in each layer is the same, and the mass of XLPE in each layer is the same, and the specific layering is: layer 1: HDPE, layer 2: HDPE, layer 3: XLPE, layer 4: HDPE, layer 5: HDPE, layer 6: XLPE, layer 7: HDPE, layer 8: HDPE;

[0072] The parameters of the torque rheometer are: temperature is 190℃, rotor speed is 80rpm, and blending time is 5min;

[0073] S2-3, injection compression:

[0074] The raw material particles are added to the injection molding machine for injection molding, and then the sample is molded in the mold to obtain a sample bar;

[0075] The parameters of the injection molding machine are: temperature is 190℃, mold temperature is 65℃, injection temperature is 170℃, injection pressure is 700bar, and holding pressure time is 9s;

[0076] The parameters of the compression molding are: first pressurized at 3MPa for 3min, and then pressurized at 15MPa for 5min;

[0077] S3, preparation of high-toughness crosslinked polyethylene insulated power cable:

[0078] S3-1, preparation of high-toughness crosslinked polyethylene:

[0079] First, the sample bar in S2-3 is used as a foaming material, CO2 is used as a foaming agent, and a cable outer sheath material is prepared by supercritical foaming method;

[0080] The parameters of the supercritical foaming method are: reaction atmosphere is CO2 atmosphere, soaking temperature is 145℃, foaming temperature is 115℃, foaming pressure is 10MPa, and time is 1h;

[0081] S3-2, secondary extrusion coating:

[0082] The cable outer sheath material is coated on the cable surface by secondary extrusion coating to obtain a high-toughness cross-linked polyethylene insulated power cable;

[0083] The parameters of the secondary extrusion coating are: the layer thickness of the cable outer sheath material is 0.8 mm, the extrusion speed is 40 m / min, and the temperature of each process section during extrusion is: feeding section: 80°C / min, compression section: 110°C / min, homogenization section: 115°C / min, head and mold sleeve section: 115°C / min, and curing section: 135°C / min.

[0084] Example 2: This example describes a method for preparing a high-toughness cross-linked polyethylene insulated power cable under another parameter.

[0085] S1. Preparation of modified materials:

[0086] S1-1. Pretreatment of modified materials:

[0087] First, the silica fibers and silica particles were immersed in acetone solution for 2 h, then ultrasonicated for 1 h, washed with deionized water, and finally dried at 63 ° C for 24 h.

[0088] S1-2, silica fiber modification:

[0089] S1-2-1. Add 12 g of silica fiber treated with S1-1 to 125 mL of sodium hydroxide solution at pH 8 and ultrasonically disperse for 15 min; then add 0.25 g of dopamine hydrochloride and carry out coating reaction for 24 h; then take out the reaction product and wash it with deionized water, and finally dry it at 100° C. to obtain polydopamine-modified silica fiber;

[0090] S1-2-2. Mix 105 mL of anhydrous ethanol and 25 mL of deionized water in a reactor and stir for 30 min. Then add 15 mL of ethyl orthosilicate and continue stirring for 2 h to obtain solution A. Mix 120 mL of deionized water, 7 mL of glacial acetic acid, and 4 mL of KH560 in a reactor and stir for 30 min to obtain solution B.

[0091] S1-2-3. Mix solution A and solution B and stir for 30 minutes, then add 17 g of polydopamine-modified silica fiber in S1-2-1 and stir evenly. React in a water bath at 65°C for 3 hours. Then, take out the reaction product, wash and dry it to obtain modified silica fiber.

[0092] S1-3, Silica Particle Modification:

[0093] First, 85 mL of anhydrous ethanol and 25 mL of deionized water were mixed in a reactor and stirred for 30 minutes. Then, 7 mL of glacial acetic acid and 4 mL of KH560 were added and stirred for 30 minutes. Then, 13 g of silica particles treated with S1-1 were added and reacted in a water bath at 65°C for 2 hours. Finally, the reaction product was taken out, washed, and dried to obtain modified silica particles.

[0094] S2. Preparation of modified cross-linked polyethylene and modified high-density polyethylene:

[0095] S2-1, Doping and Modification Materials in Polyethylene

[0096] XLPE and HDPE were dried at 63° C. for 8 h, respectively, and then 100 phr of HDPE was mixed with 23 phr of modified silica fiber, and 100 phr of XLPE was mixed with 13 phr of modified silica fiber for further use;

[0097] S2-2, melt granulation:

[0098] According to the mass ratio of HDPE mixed with silica fibers to XLPE mixed with modified silica particles being 4:1, the XLPE mixed with modified silica particles and the HDPE mixed with silica fibers were layered and mixed in a torque rheometer, and then the mixed product was granulated to obtain raw material particles;

[0099] When laying in layers, the total number of layers is 8, each layer of HDPE has the same quality, and each layer of XLPE has the same quality. The specific layers are: 1 layer: HDPE, 2 layers: HDPE, 3 layers: XLPE, 4 layers: HDPE, 5 layers: HDPE, 6 layers: XLPE, 7 layers: HDPE, 8 layers: HDPE;

[0100] The parameters of the torque rheometer were: temperature 195 °C, rotor speed 85 rpm, and blending time 6 min;

[0101] S2-3, injection molding:

[0102] The raw material pellets are added to an injection molding machine for injection molding, and then the obtained sample is pressed into a mold to obtain a specimen;

[0103] The parameters of the injection molding machine are: temperature 193°C, mold temperature 67°C, injection temperature 173°C, injection pressure 730 bar, and holding time 9.5 seconds.

[0104] The compression molding parameters were as follows: first, pressurizing at 3.5 MPa for 3.5 min, then at 16 MPa for 6 min;

[0105] S3. Preparation of high-toughness cross-linked polyethylene insulated power cable:

[0106] S3-1, Preparation of high-toughness crosslinked polyethylene:

[0107] First, the spline in S2-3 is used as a foaming material, and CO2 is used as a foaming agent to prepare a cable outer sheath material by a supercritical foaming method;

[0108] The parameters of the supercritical foaming method are: the reaction atmosphere is CO2 atmosphere, the soaking temperature is 148℃, the foaming temperature is 117℃, the foaming pressure is 10.5MPa, and the time is 1.3h;

[0109] S3-2, Secondary extrusion coating:

[0110] The cable outer sheath material is coated on the surface of the cable by secondary extrusion coating to obtain a high-toughness crosslinked polyethylene insulated power cable;

[0111] The parameters of the secondary extrusion coating are: the layer thickness of the cable outer sheath material is 0.83mm, the extrusion speed is 45m / min, and the temperature of each process section during extrusion is: feeding section: 85℃ / min, compression section: 120℃ / min, homogenization section: 123℃ / min, head and die section: 125℃ / min, curing section: 145℃ / min.

[0112] Example 3: The content described in this example is a preparation method of a high-toughness crosslinked polyethylene insulated power cable under another parameter.

[0113] S1, Preparation of modified material:

[0114] S1-1, Pretreatment of modified material:

[0115] First, the silica fibers and silica particles are soaked in acetone solution for 2h, then ultrasonic treatment for 1h, then washed with deionized water, and finally dried at 65℃ for 24h for standby;

[0116] S1-2, Modification of silica fibers:

[0117] S1-2-1, 15g of silica fibers treated by S1-1 are added to 150mL of sodium hydroxide solution with pH=8, and ultrasonic dispersion is carried out for 15min; Then 0.3g of dopamine hydrochloride is added and a 24h coating reaction is carried out; Then the reaction product is taken out and washed with deionized water, and finally dried at 100℃ to obtain polydopamine modified silica fibers;

[0118] S1-2-2. Mix 110 mL of anhydrous ethanol and [20,30] mL of deionized water in a reactor and stir for 30 min. Then add 20 mL of ethyl orthosilicate and continue stirring for 2 h to obtain solution A. Mix 130 mL of deionized water, 10 mL of glacial acetic acid, and 5 mL of KH560 in a reactor and stir for 30 min to obtain solution B.

[0119] S1-2-3. Mix solution A and solution B and stir for 30 minutes, then add 20 g of polydopamine-modified silica fiber prepared in S1-2-1 and stir evenly. React in a water bath at 65°C for 3 hours. Then, remove the reaction product, wash, and dry it to obtain modified silica fiber.

[0120] S1-3, Silica Particle Modification:

[0121] First, 90 mL of anhydrous ethanol and 30 mL of deionized water were mixed in a reactor and stirred for 30 minutes. Then, 10 mL of glacial acetic acid and 5 mL of KH560 were added and stirred for 30 minutes. Then, 15 g of silica particles treated with S1-1 were added and reacted in a water bath at 65°C for 2 hours. Finally, the reaction product was taken out, washed, and dried to obtain modified silica particles.

[0122] S2. Preparation of modified cross-linked polyethylene and modified high-density polyethylene:

[0123] S2-1, Doping and Modification Materials in Polyethylene

[0124] XLPE and HDPE were dried at 65°C for 8 h, respectively, and then 100 phr of HDPE was mixed with 25 phr of modified silica fibers, and 100 phr of XLPE was mixed with 15 phr of modified silica particles.

[0125] S2-2, melt granulation:

[0126] According to the mass ratio of HDPE mixed with silica fibers to XLPE mixed with modified silica particles being 5:1, the XLPE mixed with modified silica particles and the HDPE mixed with silica fibers were layered and mixed in a torque rheometer, and then the mixed product was granulated to obtain raw material particles;

[0127] When laying in layers, the total number of layers is 8, and the quality of each HDPE layer is the same, and the quality of each XLPE layer is the same. The specific layers are: 1 layer: HDPE, 2 layers: HDPE, 3 layers: XLPE, 4 layers: HDPE, 5 layers: HDPE, 6 layers: XLPE, 7 layers: HDPE, 8 layers: HDPE; 9 layers: XLPE, 10 layers: HDPE, 11 layers: HDPE;

[0128] The parameters of the torque rheometer were: temperature 200 °C, rotor speed 90 rpm, and blending time 7 min;

[0129] S2-3, injection molding:

[0130] The raw material pellets are added to an injection molding machine for injection molding, and then the obtained sample is pressed into a mold to obtain a specimen;

[0131] The parameters of the injection molding machine are: temperature 195℃, mold temperature 70℃, injection temperature 175℃, injection pressure 750bar, and holding time 10s;

[0132] The parameters for the compression molding were as follows: first, pressurizing at 4 MPa for 4 min, then at 17 MPa for 7 min;

[0133] S3. Preparation of high-toughness cross-linked polyethylene insulated power cable:

[0134] S3-1. Preparation of high-toughness cross-linked polyethylene:

[0135] Firstly, the cable outer sheath material was prepared by supercritical foaming method using the S2-3 strips as foaming material and CO2 as foaming agent;

[0136] The parameters of the supercritical foaming method are as follows: reaction atmosphere is CO2 atmosphere, soaking temperature is 150℃, foaming temperature is 120℃, foaming pressure is 11MPa, and time is 1.5h;

[0137] S3-2, secondary extrusion coating:

[0138] The cable outer sheath material is coated on the cable surface by secondary extrusion coating to obtain a high-toughness cross-linked polyethylene insulated power cable;

[0139] The parameters of the secondary extrusion coating are: the layer thickness of the cable outer sheath material is 0.85 mm, the extrusion speed is 50 m / min, and the temperature of each process section during extrusion is: feeding section: 90°C / min, compression section: 130°C / min, homogenization section: 130°C / min, head and mold sleeve section: 130°C / min, and curing section: 150°C / min.

[0140] Experimental Example: The description of this experimental example is based on the scheme described in Example 2, and is intended to illustrate the practical application effect of the present invention.

[0141] 1. Mechanical properties test

[0142] Experimental design: The mechanical properties of composite materials are also important indicators for evaluating material performance indicators. In order to illustrate that the cable outer sheath material prepared by the present invention can improve the toughness of the cable, an experimental group is designed to test the overall mechanical properties of the cable outer sheath material.

[0143] Experimental group 1: The addition ratio of HDPE mixed with silica fibers and XLPE mixed with silica particles in S2-2 was 3:1;

[0144] Control group 1: Only pure HDPE and XLPE were used as the base material without adding any modified materials, and the addition ratio of the two was 3:1;

[0145] In experimental group 2:2-2, the addition ratio of HDPE mixed with silica fibers and XLPE mixed with silica particles was 4:1;

[0146] Control group 2: Only pure HDPE and XLPE were used as the base material without adding any modified materials, and the addition ratio of the two was 4:1;

[0147] In experimental group 3:2-2, the addition ratio of HDPE mixed with silica fibers and XLPE mixed with silica particles was 5:1;

[0148] Control group 3: Only pure HDPE and XLPE were used as the base materials without adding any modified materials, and the addition ratio of the two was 5:1.

[0149] The tensile strength, tensile modulus, elongation at break, flexural strength, flexural modulus and hardness of the samples in each group were tested to obtain the data in Table 1.

[0150] Table 1 Mechanical properties of cable outer sheath materials

[0151]

[0152] Comparing control groups 1 to 3, it can be seen that as the proportion of XLPE in the composite material decreases, the tensile strength and tensile modulus of the composite material gradually decrease. This is because the cross-linking structure of XLPE itself is denser and more rigid. And as the proportion of XLPE decreases, the breaking strength and elongation of the composite material gradually increase. This is because HDPE itself has better ductility. As its proportion increases, the overall ductility of the material is improved. For the same reason, because the cross-linking density of XLPE is greater, the higher the proportion of XLPE in the composite material, the overall hardness of the material will show an upward trend.

[0153] Comparing the data of the experimental group and the corresponding control group, it can be seen that, overall, compared with pure HDPE and pure XLPE as the base material, the composite materials with added silica fibers / particles have different degrees of improvement in tensile strength, tensile modulus, breaking strength, elongation at break, and hardness (among which the improvement in tensile strength and tensile modulus is the most significant). This shows that the addition of silica fibers and silica particles has a reinforcing effect on the polymer matrix material and can significantly enhance the mechanical properties of the composite materials.

[0154] It is noteworthy that the tensile strength and tensile modulus of the composites first increase and then decrease as the material ratios change in Experimental Groups 1 to 3. This is presumably because the ratios of HDPE and pure XLPE added differ, resulting in different ratios of silica fibers to silica particles. As the material ratios change in Experimental Groups 1 to 3, the silica fiber content gradually decreases, while the silica particle content gradually increases. In Experimental Group 2, the ratio of silica fibers to silica particles reaches its optimal value, at which point the silica fibers are embedded in the HDPE matrix. The silica fibers themselves possess excellent strength and stiffness, leading to enhanced tensile strength in the composite. Simultaneously, the addition of silica particles increases the interfacial bonding between the fibers and the matrix, further enhancing the tensile strength and tensile modulus of the composite. However, when the silica fibers are further added, the excessive amount of fibers themselves hinders the uniform distribution of the particles, causing them to agglomerate locally, which in turn reduces the tensile strength and tensile modulus of the composite. At the same time, the fibers themselves have a tandem effect with the matrix, which in turn improves the composite's breaking strength and elongation at break. Therefore, in actual production, the preparation process parameters should be reasonably selected according to the working environment requirements of the cable.

[0155] As for the hardness of the composite material, it can be seen that the hardness of the materials in the experimental group is higher than that in the control group. This is because both silica fibers and silica particles have good interface reinforcement effects, which can significantly improve the overall hardness of the material.

Claims

1. A method for preparing a high-toughness cross-linked polyethylene insulated power cable, characterized in that: The following steps are involved: S1. Preparation of modified materials: S1-1. Pretreatment of modified materials: First, the silica fibers and silica particles were immersed in an acetone solution for 2 h, then ultrasonicated for 1 h, washed with deionized water, and finally dried at 60-65 ° C for 24 h. S1-2, silica fiber modification: Polydopamine and nano-SiO2 were used to synergistically modify silica fibers to obtain modified silica fibers; S1-3, Silica Particle Modification: Using KH560 to modify silica particles to obtain modified silica particles; S2. Preparation of modified cross-linked polyethylene and modified high-density polyethylene: S2-1, Doping and Modification Materials in Polyethylene XLPE and HDPE were dried at 60-65°C for 8 hours respectively, and then HDPE was mixed evenly with modified silica fibers and XLPE was mixed evenly with modified silica particles. S2-2, melt granulation: XLPE mixed with modified silica particles and HDPE mixed with silica fibers are placed in a torque rheometer and mixed in layers, and then the mixed product is granulated to obtain raw material particles; S2-3, injection molding: The raw material particles are added into an injection molding machine for injection molding, and then the obtained sample is pressed into a mold to obtain a specimen; S3. Preparation of high-toughness cross-linked polyethylene insulated power cable: S3-1. Preparation of high-toughness cross-linked polyethylene: Firstly, the cable outer sheath material was prepared by supercritical foaming method using the S2-3 strips as foaming material and CO2 as foaming agent; S3-2, secondary extrusion coating: The cable outer sheath material is coated on the cable surface by secondary extrusion coating to obtain a high-toughness cross-linked polyethylene insulated power cable.

2. The method for preparing a high-toughness cross-linked polyethylene insulated power cable according to claim 1, wherein: The steps for modifying the silica fiber in S1-2 are: S1-2-1. Add the silica fibers treated with S1-1 to a sodium hydroxide solution at pH 8 and ultrasonically disperse for 15 minutes; then add dopamine hydrochloride and allow the coating reaction to proceed for 24 hours; then remove the reaction product, wash it with deionized water, and finally dry it at 100°C to obtain polydopamine-modified silica fibers; S1-2-2. Anhydrous ethanol and deionized water were mixed in a reactor and stirred for 30 minutes, and then ethyl orthosilicate was added and stirred for 2 hours to obtain solution A. Deionized water, glacial acetic acid, and KH560 were mixed in a reactor and stirred for 30 minutes to obtain solution B. S1-2-3. Mix the solution A and solution B and stir for 30 minutes, then add the polydopamine-modified silica fiber in S1-2-1 and stir evenly, and react in a water bath at 65°C for 3 hours; then take out the reaction product and wash and dry it to obtain modified silica fiber.

3. The method for preparing a high-toughness cross-linked polyethylene insulated power cable according to claim 2, wherein: The addition amount of each component in S1-2-1 is: Let n be the rate coefficient and n∈R+, then the amount of silica fiber added is [10, 15] ng, the amount of sodium hydroxide solution added is [100, 150] n mL, and the amount of dopamine hydrochloride added is [0.2, 0.3] ng; The amount of each component added to solution A of S1-2-3 is: Let n be the rate coefficient and n∈R+, then the amount of anhydrous ethanol added is [100,110]n mL, the amount of deionized water added is [20,30]n mL, and the amount of ethyl orthosilicate added is [10,20]n mL; The amount of each component added to solution B of S1-2-2 is: Let n be the rate coefficient and n∈R+, then the amount of deionized water added is [110,130]n mL, the amount of glacial acetic acid added is [5,10]n mL, and the amount of KH560 added is [3,5]n mL; The amount of polydopamine modified silica fiber added in S1-2-3 was [15,20] ng.

4. The method for preparing a high-toughness cross-linked polyethylene insulated power cable according to claim 1, wherein: The steps for modifying the silica particles in S1-3 are: First, anhydrous ethanol and deionized water were mixed in a reactor and stirred for 30 minutes, then glacial acetic acid and KH560 were added and stirred for 30 minutes; then the silica particles treated with S1-1 were added and reacted in a water bath at 65°C for 2 hours; finally, the reaction product was taken out and washed and dried to obtain modified silica particles.

5. The method for preparing a high-toughness cross-linked polyethylene insulated power cable according to claim 4, characterized in that: The addition amount of each component in S1-3 is: Let n be the rate coefficient and n∈R+, then the amount of anhydrous ethanol added is [80,90]n mL, the amount of deionized water added is [20,30]n mL, the amount of glacial acetic acid added is [5,10]n mL, the amount of KH560 added is [3,5]n mL; and the amount of silica particles added is [10,15] ng.

6. The method for preparing a high-toughness cross-linked polyethylene insulated power cable according to claim 1, wherein: The addition amounts of the components in S2-1 are: HDPE: 100 phr, modified silica fiber: 20-25 phr; XLPE: 100 phr, modified silica particles: 10-15 phr.

7. The method for preparing a high-toughness cross-linked polyethylene insulated power cable according to claim 1, wherein: When laying in layers in S2-2, the mass ratio of HDPE mixed with silica fibers to XLPE mixed with modified silica particles is 3 to 5:1; When laying in layers in S2-2, the total number of layers is 8 or 11, the first and last layers are both XDPE, and there are 2 layers of HDPE between the XLPE layers. The quality of each HDPE layer is the same, and the quality of each XLPE layer is the same; The parameters of the torque rheometer in S2-2 are: temperature of 190-200°C, rotor speed of 80-90 rpm, and blending time of 5-7 min.

8. The method for preparing a high-toughness cross-linked polyethylene insulated power cable according to claim 1, wherein: The parameters of the injection molding machine in S2-3 are: temperature 190-195℃, mold temperature 65-70℃, injection temperature 170-175℃, injection pressure 700-750bar, and holding time 9-10s; The parameters of the press molding in S2-3 are: first pressurizing at a pressure of 3 to 4 MPa for 3 to 4 minutes, and then pressurizing at a pressure of 15 to 17 MPa for 5 to 7 minutes.

9. The method for preparing a high-toughness cross-linked polyethylene insulated power cable according to claim 1, characterized in that: The parameters of the supercritical foaming method in S3-1 are: reaction atmosphere is CO2 atmosphere, immersion temperature is 145-150°C, foaming temperature is 115-120°C, foaming pressure is 10-11 MPa, and time is 1-1.5 h.

10. The method for preparing a high-toughness cross-linked polyethylene insulated power cable according to claim 1, characterized in that: The parameters of the secondary extrusion coating in S3-2 are: the layer thickness of the cable outer sheath material is 0.8~0.85mm, the extrusion speed is 40~50m / min, and the temperature of each process section during extrusion is: feeding section: 80~90℃ / min, compression section: 110~130℃ / min, homogenization section: 115~130℃ / min, head and mold sleeve section: 115~130℃ / min, curing section: 135~150℃ / min.

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