Crosslinked polyethylene insulation material with intrinsic self-repairing and recyclable properties, and preparation method and application thereof

Abstract

The application provides a crosslinked polyethylene insulating material with intrinsic self-repairing and recyclable characteristics, a preparation method and application thereof, and relates to the technical field of cable materials.The crosslinked polyethylene insulating material with intrinsic self-repairing and recyclable characteristics is prepared from the following components in parts by weight: 99.7 parts by weight of low-density polyethylene, 1.0-2.6 parts by weight of peroxide, 0.1-0.5 parts by weight of antioxidant, 5-20 parts by weight of maleimide monomer, 0.35-0.7 parts by weight of catalyst, 0.5-3.0 parts by weight of ligand and 0.5-3.0 parts by weight of furan-based small molecule.The low-density polyethylene is functionally modified through catalytic amination reaction, so that the chain breaking and crosslinking in the modification process are avoided, and the mechanical properties, insulating properties and dielectric properties of the crosslinked polyethylene are enhanced through the post-absorption of the introduced peroxide.Meanwhile, the dynamic reversible Diels-Alder reaction introduced by the post-absorption of the furan-based small molecule enables the polyethylene insulating material to have good intrinsic self-repairing effect on mechanical damage and electrical damage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cable materials, in particular to a cross-linked polyethylene insulation material with intrinsic self-repairing and recyclable properties, and a preparation method and application thereof. BACKGROUND

[0002] Cross-linked polyethylene (XLPE) is a widely used insulation material in modern cable industry. Due to its excellent electrical properties, heat resistance and mechanical strength, it has become the first choice for high-voltage and ultra-high-voltage cables. However, the cross-linked structure of XLPE material is irreversible, which is difficult to repair and recycle, causing many problems in actual use and disposal.

[0003] During the service of XLPE cables, micro-cracks or local damage may occur in the XLPE insulation layer due to mechanical stress, electrical treeing effect or thermal aging, etc. These defects may further develop into a breakdown path, significantly shortening the service life of the cable. The existing XLPE materials generally rely on irreversible chemical cross-linking and lack self-repairing ability, and must be restored to insulation performance through complex repair processes (such as replacing the damaged part or re-injecting external repair agents or microcapsules, such as the invention patent with publication number CN106750829A, which realizes self-repairing for electrical treeing defects by introducing microcapsules inside the cross-linked polyethylene), increasing the difficulty and cost of maintenance. In addition, the chemical cross-linking network of XLPE makes it impossible to be recycled by simple thermoplastic processing, which not only causes a lot of waste cable resources, but also causes serious environmental pollution problems. Currently, the recycling of XLPE materials is mainly through high-energy consumption cracking method to decompose into small molecular compounds, which has low recycling efficiency and is easy to produce secondary pollution.

[0004] Therefore, how to realize the intrinsic self-repairing of cross-linked polyethylene insulation material after damage and recycling after retirement has become a big problem in the prior art. SUMMARY

[0005] In view of the deficiencies in the prior art, the purpose of the present application is to provide a cross-linked polyethylene insulation material and a preparation method and application thereof. The cross-linked polyethylene cable insulation material has the characteristics of self-repairing after electrical damage and mechanical damage and recycling after retirement.

[0006] In order to achieve the above-mentioned application purpose, the present application provides the following technical solutions:

[0007] A cross-linked polyethylene insulation material with intrinsic self-repairing and recyclable properties is prepared from the following components by weight fraction:

[0008] Low density polyethylene 99.7 parts by weight, peroxide 1.0-2.6 parts by weight, antioxidant 0.1-0.5 parts by weight, maleimide monomer 5-20 parts by weight, catalyst 0.35-0.7 parts by weight, ligand 0.5-3.0 parts by weight, furan small molecule 0.5-3.0 parts by weight.

[0009] Preferably, the catalyst is one of copper chloride and copper iodide; the ligand is 1,10-phenanthroline; the furan small molecule is one of 2,2-bis(2-tetrahydrofuryl)propane, bis(2-methyl-3-furyl) disulfide, di(2-furan) chlorophosphine and tris(2-furyl) phosphine; the peroxide is one of dicumyl peroxide, di(hexadecyl) dicarbonate peroxide and di-tert-butyl peroxide.

[0010] Preferably, the low density polyethylene has a number average molecular weight of 10000-100000 g / mol, and has excellent flexibility and processability.

[0011] The application also provides a preparation method of crosslinked polyethylene insulation material with intrinsic self-repairing and recyclable properties, comprising the following steps:

[0012] (1) mixing low density polyethylene, peroxide, antioxidant, maleimide monomer, catalyst, ligand and solvent to perform catalytic amination reaction, pouring the mixed solution into methanol solution after reaction to cool and reduce elimination, and then drying to obtain functionalized polyethylene material;

[0013] (2) mixing the functionalized polyethylene obtained in step (1) with furan small molecule and peroxide, and sequentially performing post-absorption treatment and hot pressing treatment to obtain crosslinked polyethylene insulation material.

[0014] Preferably, in step (1), the mass ratio of maleimide monomer to the total mass of low density polyethylene and antioxidant is (5-20):100; the mass ratio of peroxide to the total mass of low density polyethylene and antioxidant is (1.0-2.6):100; the mass ratio of catalyst to the total mass of low density polyethylene and antioxidant is preferably (0.35-0.7):100; the molar ratio of ligand to catalyst is 1:1; the mass ratio of antioxidant to the total mass of low density polyethylene and antioxidant is (0.1-0.5):100.

[0015] Preferably, in step (1), the catalyst is one of copper chloride and copper iodide.

[0016] Preferably, in step (1), the solvent is one of toluene, o-dichlorobenzene and p-xylene.

[0017] Preferably, in the step (1), the ligand is 1,10-phenanthroline.

[0018] Preferably, in the step (1), the peroxide is one of dicumyl peroxide, dicetyl peroxide and di-tert-butyl peroxide.

[0019] Preferably, in the step (1), the temperature of catalytic amination reaction is 115-125℃, and the time of catalytic amination reaction is 80-120min.

[0020] Preferably, in the step (1), the drying temperature is 60-80℃, and the drying time is 12-24h.

[0021] Preferably, in the step (2), the furan small molecule is one of 2,2-bis(2-tetrahydrofurfuryl)propane, bis(2-methyl-3-furyl)disulfide, di(2-furan)chlorophosphine and tri(2-furyl)phosphine.

[0022] Preferably, in the step (2), the ratio of the mass of the furan small molecule to the total mass of the low-density polyethylene and the antioxidant is (0.5-3.0):100.

[0023] Preferably, in the step (2), the ratio of the mass of the peroxide to the total mass of the low-density polyethylene and the antioxidant is (1.0-2.6):100.

[0024] Preferably, in the step (2), the post-absorption sequence is furan small molecule and peroxide in turn, the temperature of post-absorption treatment is 60-80℃, and the time of post-absorption treatment is 12-28h.

[0025] Preferably, in the step (2), the temperature of hot-pressing treatment is 120-180℃, and the hot-pressing time is 6-120min.

[0026] The application further provides application of the cross-linked polyethylene insulating material with intrinsic self-repairing and recyclable functions in the field of cable insulating materials.

[0027] The technical scheme of the application has the following beneficial effects:

[0028] The application provides a crosslinked polyethylene insulating material with intrinsic self-repairing and recyclable properties. The low-density polyethylene is functionally modified through a catalytic amination reaction, chain breaking and crosslinking in the modification process are avoided, and the mechanical properties, insulating properties and dielectric properties of the crosslinked polyethylene are enhanced through the introduction of peroxide through post-absorption. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0030] Figure 1 The Fourier infrared spectrum of the crosslinked polyethylene prepared for the application examples 1-3 and the comparative example 1;

[0031] Figure 2 The SEM images of the crosslinked polyethylene prepared for the application example 1 before and after mechanical and corona damage and self-repairing, wherein (a) is the SEM image after mechanical damage, (b) is the SEM image after repair after mechanical damage, (c) is the SEM image after corona damage, and (d) is the SEM image after repair after corona damage;

[0032] Figure 3 The stress-strain curves of the crosslinked polyethylene prepared for the application example 1 before and after mechanical damage repair;

[0033] Figure 4 The stress-strain curves of the crosslinked polyethylene prepared for the application example 1 after different mechanical and solution recycling times. DETAILED DESCRIPTION

[0034] In order to make the technical problems, technical solutions and advantages of the application more clear, the following will be described in detail in combination with the drawings and specific embodiments.

[0035] The application provides a preparation method of a crosslinked polyethylene insulating material with intrinsic self-repairing and recyclable properties, comprising the following steps:

[0036] (1) mixing low-density polyethylene, peroxide, antioxidant, maleimide monomer, catalyst, ligand and solvent to perform catalytic amination reaction, pouring the mixed solution into methanol solution after reaction to cool and reduce elimination, and then drying to obtain functionalized polyethylene material;

[0037] (2) mixing the functionalized polyethylene obtained in step (1) with furan small molecule and peroxide to perform post-absorption treatment and hot-pressing treatment in sequence to obtain cross-linked polyethylene insulating material.

[0038] Unless otherwise specified, the source of each component is not particularly limited in the present application, and commercially available products well known to those skilled in the art can be used.

[0039] In the present application, low-density polyethylene, peroxide, antioxidant, maleimide monomer, catalyst, ligand and solvent are mixed to perform catalytic amination reaction.

[0040] In the present application, the mass ratio of the maleimide monomer to the total mass of low-density polyethylene and antioxidant is preferably (5-20):100, i.e., the mass of the maleimide monomer to the mass of (low-density polyethylene + antioxidant) is (5-20):100, and more preferably (10-15):100. By limiting the mass of the maleimide monomer within the above range, the structure of the polyethylene can be adjusted, and the mechanical properties and insulating properties of the functionalized polyethylene can be enhanced.

[0041] In the present application, the catalyst is preferably copper chloride and copper iodide, and more preferably copper iodide. By combining with the ligand, the chain scission and cross-linking of low-density polyethylene during the catalytic amination process can be inhibited, and the molecular weight of the functionalized polyethylene can be ensured not to change significantly.

[0042] In the present application, the mass ratio of the catalyst to the total mass of low-density polyethylene and antioxidant is preferably (0.35-0.7):100, i.e., the mass of the catalyst to the mass of (low-density polyethylene + antioxidant) is (0.35-0.7):100, and more preferably 0.35:100. By limiting the mass ratio of the catalyst to the total mass of low-density polyethylene and antioxidant within the above range, the catalytic amination reaction can be ensured to proceed smoothly to realize the functionalization of the material, and at the same time, the insulating material can have higher insulating properties.

[0043] In the present application, the molar ratio of the ligand to the catalyst is preferably 1:1. By limiting the molar ratio of the ligand to the catalyst within the above range, the chain scission and cross-linking of low-density polyethylene during the catalytic amination process can be inhibited, and the molecular weight of the functionalized polyethylene can be ensured not to change significantly.

[0044] In the present application, the ratio of the mass of the antioxidant to the mass of the low-density polyethylene and the antioxidant is (0.1-0.5):100, i.e. the mass of the antioxidant: the mass of (low-density polyethylene + antioxidant) is (0.1-0.5):100.

[0045] In the present application, the solvent is preferably toluene, o-dichlorobenzene and p-xylene, and more preferably o-dichlorobenzene. By using the high boiling point of the o-dichlorobenzene solvent, the full dissolution of the low-density polyethylene is promoted, and the catalytic amination reaction can be carried out more fully.

[0046] In the present application, the temperature of the catalytic amination reaction is preferably 115-125°C, and more preferably 120°C; and the reaction time of the catalytic amination is preferably 80-120 min, and more preferably 90 min. By limiting the catalytic amination temperature and time within the above range, the amination process can be carried out more fully.

[0047] In the present application, the catalytic amination reaction is preferably carried out in an air atmosphere.

[0048] In the present application, after the catalytic amination reaction, the mixed solution is poured into a methanol solution for cooling and reduction elimination to obtain a functionalized polyethylene material.

[0049] In the present application, the time of the reduction elimination is preferably 60-180 min, and more preferably 120 min.

[0050] In the present application, the cooling and reduction elimination are preferably natural cooling, and the end point of the cooling is preferably room temperature.

[0051] In the present application, the drying is preferably vacuum drying, the drying temperature is preferably 70°C, and the drying time is preferably 12 h.

[0052] After obtaining the functionalized polyethylene material, the functionalized polyethylene material is subjected to post-absorption of furan-based small molecules and peroxide treatment, followed by heat pressing to obtain a dynamic crosslinking polyethylene insulation material.

[0053] In the present application, the furan-based small molecules are preferably 2,2-bis(2-tetrahydrofuryl)propane, bis(2-methyl-3-furyl) disulfide, di(2-furan) chlorophosphine and tri(2-furyl) phosphine, and more preferably bis(2-methyl-3-furyl) disulfide and tri(2-furyl) phosphine, and most preferably bis(2-methyl-3-furyl) disulfide. In the present application, bis(2-methyl-3-furyl) disulfide, on the basis of the Diels-Alder reaction of furan groups with maleimide, also contains a dynamic disulfide bond, which can further improve the dynamic reversibility of the crosslinked polyethylene material and enhance the self-repairing and recycling properties of the crosslinked polyethylene material.

[0054] In the present application, the peroxide is preferably dicumyl peroxide, dihexadecyl peroxydicarbonate and di-tert-butyl peroxide, more preferably dicumyl peroxide and di-tert-butyl peroxide, most preferably dicumyl peroxide.

[0055] In the present application, the order of the post-absorption treatment is dicumyl peroxide and di-tert-butyl peroxide.

[0056] In the present application, the ratio of the mass of the furan-based small molecule to the total mass of the low-density polyethylene and the antioxidant is preferably (0.5-3.0):100, i.e., the mass of the furan-based small molecule:(the mass of the low-density polyethylene + the mass of the antioxidant) = (0.5-3.0):100, more preferably (1.0-2.0):100, and most preferably 1.5:100. By limiting the ratio of the mass of the furan-based small molecule to the total mass of the low-density polyethylene and the antioxidant to the above range, the present application can effectively retain the mechanical properties and insulation properties of the cross-linked polyethylene while imparting self-repairing and recycling properties to the cross-linked polyethylene.

[0057] In the present application, the ratio of the mass of the peroxide to the total mass of the low-density polyethylene and the antioxidant is preferably (1.0-2.6):100, i.e., the mass of the peroxide:(the mass of the low-density polyethylene + the mass of the antioxidant) = (0.5-3.0):100, more preferably (1.2-2.2):100, and most preferably 1.8:100. By limiting the ratio of the mass of the peroxide to the total mass of the low-density polyethylene and the antioxidant to the above range, the present application can improve the comprehensive performance of the cross-linked polyethylene by adjusting the ratio of covalent cross-linking and dynamic cross-linking by changing the mass of the peroxide.

[0058] In the present application, the temperature of the post-absorption treatment is preferably 60-80°C, and more preferably 70°C; and the time of the post-absorption treatment is preferably 12-28h, and more preferably 24h. By limiting the temperature and time of the post-absorption treatment to the above range, the present application can promote the absorption of the furan-based small molecule and the peroxide by the functionalized polyethylene material.

[0059] In the present application, the temperature of the heat pressing treatment is preferably 120-180°C, and the heat pressing time is preferably 6-120min; more preferably, the heat pressing is performed at 120°C for 6min and at 140°C for 120min in sequence. By limiting the temperature and time of the heat pressing treatment to the above range, the present application can make the Diels-Alder reaction and the covalent cross-linking reaction proceed sufficiently to obtain a cross-linked polyethylene insulation material.

[0060] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work belong to the protection scope of the present application.

[0061] Embodiment 1

[0062] 99.7 parts by weight of low-density polyethylene (the number average molecular weight of which is 17371 g / mol), 0.2 parts by weight of antioxidant 300 were added into o-dichlorobenzene solvent under the condition of 30℃, and then the temperature was raised to 120℃, and mechanical stirring was performed until complete dissolution; then 1.8 parts by weight of dicumyl peroxide, 15 parts by weight of maleimide monomer, 0.35 parts by weight of copper iodide catalyst, 1.46 parts by weight of 1,10-phenanthroline ligand were added into the above mixed solution (the mass ratio of the maleimide monomer to the total mass of the low-density polyethylene plus the antioxidant was 15:100, the mass ratio of the copper iodide to the total mass of the low-density polyethylene plus the antioxidant was 0.35:100, and the amount-of-substance ratio of the copper iodide to the 1,10-phenanthroline was 1:1), and mechanical stirring was performed for 90 min at 120℃ in an air atmosphere, to obtain a homogeneous viscous functionalized polyethylene solution, then the above solution was poured into 30 mL of a methanol solution, stirred for 120 min, and allowed to cool naturally, and after filtration, vacuum drying was performed, and the material was placed in a vacuum drying oven at 70℃ for 12 h, and after natural cooling, a functionalized polyethylene material was obtained. Then 1.5 parts by weight of bis(2-methyl-3-furyl) disulfide and 1.8 parts by weight of dicumyl peroxide were added into the above functionalized polyethylene material for post-absorption treatment (the mass ratio of the bis(2-methyl-3-furyl) disulfide to the total mass of the low-density polyethylene plus the antioxidant was 1.5:100, and the mass ratio of the dicumyl peroxide to the total mass of the low-density polyethylene plus the antioxidant was 1.8:100), first stirring at 30℃ for 30 min, and then placing in a 70℃ air-drying oven for 30 min, and repeating the above operation 4 times, and then placing in a 70℃ air-drying oven for 20 h. Finally, the post-absorption treated material was subjected to 120℃, 6 min of hot-pressing pretreatment and 140℃, 120 min of hot-pressing treatment, to obtain a crosslinked polyethylene insulation material, which is denoted as DPPE1.

[0063] Embodiment 2

[0064] The mass of the bis(2-methyl-3-furyl) disulfide in embodiment 1 was replaced by 2.0 parts by weight, and at this time, the mass ratio of the bis(2-methyl-3-furyl) disulfide to the total mass of the low-density polyethylene plus the antioxidant was 2.0:100, and other parameters were the same as in embodiment 1, to obtain a crosslinked polyethylene insulation material, which is denoted as DPPE2.

[0065] Example 3

[0066] The mass of bis(2-methyl-3-furyl) disulfide in Example 1 was replaced by 2.5 parts by weight, at which time the ratio of bis(2-methyl-3-furyl) disulfide to the total mass of low-density polyethylene plus antioxidant was 2.5:100, and the other parameters were the same as in Example 1, to obtain a crosslinked polyethylene insulation material, which is denoted as DPPE3.

[0067] Comparative Example 1

[0068] A crosslinked polyethylene insulated cable differs from Example 1 in that the polyethylene is not functionally modified and post-absorbed with a furan-based small molecule according to the modification method described in Example 1. The specific method is as follows: 99.7 parts by weight of low-density polyethylene and 0.2 parts by weight of antioxidant are mixed, followed by the addition of 1.8 parts by weight of dicumyl peroxide for post-absorption treatment (the ratio of dicumyl peroxide to the total mass of low-density polyethylene plus antioxidant is 1.8:100). Finally, the post-absorbed material is sequentially subjected to a heat pressing pretreatment at 120°C for 6 min and a heat pressing treatment at 140°C for 120 min to obtain a crosslinked polyethylene insulation material, which is denoted as XLPE.

[0069] Comparative Example 2

[0070] After 99.7 parts by weight of low-density polyethylene and 0.2 parts by weight of antioxidant are uniformly mixed, they are sequentially subjected to a heat pressing pretreatment at 120°C for 6 min and a heat pressing treatment at 140°C for 120 min to obtain a low-density polyethylene material, which is denoted as LDPE.

[0071] Comparative Example 3

[0072] 99.7 parts by weight of low-density polyethylene and 0.2 parts by weight of antioxidant are added to an o-dichlorobenzene solvent at 30°C, followed by warming to 120°C and mechanical stirring until complete dissolution. Then, 1.8 parts by weight of a peroxide, 15 parts by weight of a maleimide monomer, 0.35 parts by weight of a catalyst, and 1.46 parts by weight of a ligand are sequentially added to the above mixed solution (the ratio of the mass of the maleimide monomer to the total mass of low-density polyethylene plus antioxidant is 15:100, the ratio of the mass of the catalyst to the total mass of low-density polyethylene plus antioxidant is 0.35:100, and the ratio of the amount of substance of the catalyst to the ligand is 1:1), and mechanical stirring is performed in an air atmosphere at 120°C for 90 min to obtain a homogeneous viscous functionalized polyethylene solution. Subsequently, the above solution is poured into a methanol solution, stirred for 120 min, and allowed to cool naturally. After filtration and vacuum drying, the functionalized polyethylene material is placed in a vacuum drying oven at 70°C for 12 h, and after natural cooling, a functionalized low-density polyethylene material is obtained. Subsequently, the above functionalized polyethylene material is sequentially subjected to a heat pressing pretreatment at 120°C for 6 min and a heat pressing treatment at 140°C for 120 min to obtain a functionalized low-density polyethylene material, which is denoted as CAPE.

[0073] Comparative Example 2 is a low-density polyethylene insulation material that is not modified by catalytic amination and post-absorption treatment, relative to Example 1. Comparative Example 3 is a functionalized polyethylene material that is modified by catalytic amination, but is not post-absorbed and heat-pressed crosslinked, relative to Example 1.

[0074] Table 1. Material properties of Example 1 and Comparative Examples 2 and 3

[0075]

[0076] Table 1 discloses the material properties of Example 1, Comparative Example 2 and Comparative Example 3. As can be seen from Table 1, the mechanical properties and breakdown strength of the crosslinked polyethylene insulation material prepared in Example 1 are obviously improved relative to Comparative Examples 2 and 3 which are not crosslinked, and Example 1 also has good self-repairing and recyclable properties. The comparison of the mechanical properties of Comparative Examples 2 and 3 shows that the tensile strength and elongation at break of the samples do not change substantially before and after catalytic amination, confirming that the polyethylene does not break and crosslink during the catalytic amination reaction.

[0077] Fourier infrared spectra of the crosslinked polyethylene prepared in Examples 1-3 and Comparative Example 1 were tested. The crosslinked polyethylene was cut into small pieces of 30 mm x 30 mm, and a Fourier transform infrared spectrometer was used for testing, with a scanning range of 4000-500 cm -1 . The results are shown in Figure 1 . By comparing the changes in the characteristic absorption peaks at 1720 cm -1 and 810 cm -1 in Examples 1-3 and Comparative Example 1, the grafting of maleimide and the introduction of furan-based small molecules in the catalytic amination reaction were confirmed, respectively.

[0078] SEM images of the crosslinked polyethylene prepared in Example 1 before and after corona damage repair were tested. The crosslinked polyethylene was cut into a shape of 70 mm x 70 mm, and a corona resistance test system with a needle plate electrode was used to take SEM images of the surface of the sample after corona damage at a voltage of 2.2 kV for 4 h. Subsequently, the sample after corona damage was placed in a blast drying oven at 120°C for 12 h to repair, and SEM images of the surface of the sample after repair were taken. The results are shown in Figure 2 (a) and Figure 2 (b). As can be seen from Figure 2 (a), after 4 h of corona treatment, the crosslinked polyethylene surface appeared relatively obvious halo marks, and the halo marks on its surface disappeared after thermal stimulation, as shown in Figure 2 (b), indicating that it has good self-repairing performance after electrical damage.

[0079] SEM images of the crosslinked polyethylene prepared in Example 1 before and after being subjected to mechanical damage repair, the prepared crosslinked polyethylene was cut into a shape of 10 mm x 50 mm x 10 mm, a cutter was used to scratch the surface of the sample to a depth of about 7 mm, the surface SEM of the scratch sample was taken, and then the surface SEM image of the sample after mechanical damage was taken after the sample was placed in a blast drying oven at 120°C for 12 h, and the results are shown in Figure 2 (c) and Figure 2 (d) shown. As can be seen from Figure 2 (c), the crosslinked polyethylene can be effectively repaired after receiving severe mechanical damage by applying a thermal stimulus to it, as shown in Figure 2 (d), and has good self-repairing ability.

[0080] Mechanical properties of the crosslinked polyethylene prepared in Example 1 before and after self-repairing, the prepared crosslinked polyethylene was cut into a dumbbell-shaped sample using a mold, and then subjected to mechanical damage (scratch to two-thirds of its thickness), after the damage, it was placed in a blast drying oven at 120°C for 12 h, and then the mechanical properties of the sample before and after repair were tested using a MARK-10 tester, the tensile test speed was 50 mm / min, and the results are shown in Figure 3 As can be seen from Figure 3 , the tensile strength of the crosslinked polyethylene prepared in Example 1 recovered to more than 93% of the initial value after self-repairing, and the elongation at break recovered to more than 63% of the initial value after self-repairing, and had good self-repairing performance.

[0081] Mechanical properties of the crosslinked polyethylene prepared in Example 1 before and after two mechanical recycling and two solution recycling, the prepared crosslinked polyethylene was cut into a dumbbell-shaped sample using a mold, and the mechanical properties of the sample before and after two mechanical recycling and solution recycling were tested using a MARK-10 tester, the tensile test speed was 50 mm / min, and the results are shown in Figure 4 As can be seen from Figure 4 , the tensile strength of the crosslinked polyethylene prepared in Example 1 was about 100% of the initial state after two mechanical recycling, and the elongation at break was about 90% of the initial state, the tensile strength was about 98% of the initial state after two solution recycling, and the elongation at break was about 80% of the initial state, and had excellent recyclable properties.

[0082] In summary, the crosslinked polyethylene prepared in the present application has excellent self-repairing ability after mechanical damage and electrical damage, and multiple recyclable properties.

[0083] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for producing a crosslinked polyethylene insulation material having intrinsic self-repairing and recyclable properties, characterized in that, It comprises the following steps: (1) mixing low-density polyethylene, peroxide, antioxidant, maleimide monomer, catalyst, ligand and solvent to perform catalytic amination reaction, pouring the mixed solution into methanol solution after reaction for cooling and reductive elimination, and then drying to obtain functionalized polyethylene material; (2) mixing the functionalized polyethylene obtained in step (1) with furan small molecule and peroxide, and sequentially performing post-absorption treatment and hot-pressing treatment to obtain crosslinked polyethylene insulation material; In step (1), the mass ratio of maleimide monomer to the total mass of low-density polyethylene and antioxidant is (5-20):100; the mass ratio of peroxide to the total mass of low-density polyethylene and antioxidant is (1.0-2.6):100; the mass ratio of catalyst to the total mass of low-density polyethylene and antioxidant is (0.35-0.7):100; the molar ratio of ligand to catalyst is 1:1; the mass ratio of antioxidant to the total mass of low-density polyethylene and antioxidant is (0.1-0.5):100; Wherein, the catalyst is one of copper chloride and copper iodide; the solvent is one of toluene, o-dichlorobenzene and p-xylene; the ligand is 1,10-phenanthroline; the peroxide is one of dicumyl peroxide, dihexadecyl peroxide dicarbonate and di-tert-butyl peroxide; the furan small molecule is bis(2-methyl-3-furyl) disulfide; The crosslinked polyethylene insulation material has self-repairing ability after mechanical damage and electrical damage and multiple recyclable characteristics.

2. The method for preparing the cross-linked polyethylene insulating material with intrinsic self-healing and recyclable properties according to claim 1, characterized in that, In step (1), the temperature of catalytic amination reaction is 115-125℃, and the time of catalytic amination reaction is 80-120min.

3. The method for preparing the cross-linked polyethylene insulation material with intrinsic self-healing and recyclable properties according to claim 1, characterized in that, In step (2), the mass ratio of furan small molecule to the total mass of low-density polyethylene and antioxidant is (0.5-3.0):100; the mass ratio of peroxide to the total mass of low-density polyethylene and antioxidant is (1.0-2.6):

100.

4. The method for preparing the cross-linked polyethylene insulating material with intrinsic self-healing and recyclable properties according to claim 1, characterized in that, In step (2), the post-absorption sequence is furan small molecule and peroxide in turn, the temperature of post-absorption treatment is 60-80℃, and the time of post-absorption treatment is 12-28h; the temperature of hot-pressing treatment is 120-180℃, and the hot-pressing time is 6-120min.

5. The application of crosslinked polyethylene insulation material prepared by the method of any one of claims 1-4 in the field of cable insulation materials.

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