Crosslinked polyethylene flexible control cable for humanoid robots

Abstract

The present application relates to the technical field of cable, and discloses a crosslinked polyethylene flexible control cable for humanoid robot, which aims to solve the problem of early breakdown caused by dynamic strain induced electrical tree growth in the bending and twisting motion of the existing cable, and the cable comprises a conductor, an inner interface layer, an outer interface layer and an insulation layer, the inner interface layer is an EVA semiconductive layer containing double-component microcapsules, after the microcapsules are broken, the core material repairs the interface microcracks through Diels-Alder reaction, the outer interface layer is the same as the insulation layer in material but has a lower radiation dose, a permanent C-C crosslinked skeleton and a Diels-Alder dynamic covalent crosslinking network double-network structure are constructed in the insulation layer, the fur exposed after the Diels-Alder bond breaks and the maleimide pendant group act as deep electron traps to capture high-energy electrons, so that the bending and twisting fatigue life, self-repairing efficiency and partial discharge inception voltage of the cable are improved, and the cable is suitable for high dynamic scenes such as humanoid robot joints.

Description

Technical Field

[0001] This invention relates to the field of cable technology, and in particular to a cross-linked polyethylene flexible control cable for humanoid robots. Background Technology

[0002] The joints of humanoid robots need to perform high-frequency bending and twisting movements in confined spaces, which requires the control cables laid within them to have strong flexibility and durability.

[0003] Cross-linked polyethylene (XLPE) is widely used in the field of power cables due to its excellent insulation properties and thermal stability. In recent years, researchers have been trying to introduce XLPE into flexible control cables for humanoid robots to replace traditional rubber or polyvinyl chloride. For example, Chinese patent CN121122834A discloses a cross-linked polyethylene insulated power cable for humanoid robots. In response to the problem that the cable is prone to early breakage when subjected to repeated bending and torsion at the robot joints, the patent proposes to introduce cross-linked polyethylene insulation material and improves the heat dissipation structure of the conductor.

[0004] The academic community has also revealed the microscopic nature of this failure phenomenon. In the paper "The Influence of Dynamic Mechanical Strain on the Electrical Treeing Characteristics in XLPE Insulation" published in IEEE Transactions on Dielectrics and Electrical Insulation, Frances Hu et al. proved that dynamic mechanical strain accelerates the growth of electrical trees inside the insulation layer and changes its geometry by simultaneously applying dynamic tensile strain and AC voltage to XLPE samples.

[0005] To address the issue of XLPE's susceptibility to damage under dynamic stress, existing technologies attempt to extend cable life through material self-healing. For example, Chinese patent CN119798727B discloses a cross-linked polyethylene insulation material with intrinsic self-healing and recyclability, its preparation method, and applications. By absorbing furanyl small molecules to introduce a dynamic reversible Diels-Alder reaction, the polyethylene insulation material exhibits intrinsic self-healing effects against mechanical and electrical damage. In their paper "Covalent Adaptable Network Enables Sustainable Polyethylene for Next-Generation Cable Insulation" published in *Advanced Materials*, Zhang Wenye et al. proposed a dual-network cross-linked polyethylene based on dynamic covalent bonds, which can self-heal existing electrical tree damage under thermal triggering conditions. However, these self-healing mechanisms all rely on external thermal stimuli and cannot be autonomously executed in real time during continuous humanoid robot movement; they are passive response strategies after damage occurs. Summary of the Invention

[0006] The technical problem to be solved by this invention is: how to enable XLPE insulated control cables to actively suppress the growth of electrical treeing caused by nanocracks induced by dynamic strain when subjected to repeated bending and twisting of humanoid robot joints. To this end, we propose a cross-linked polyethylene flexible control cable for humanoid robots.

[0007] To achieve the above objectives, this application adopts the following technical solution: a cross-linked polyethylene flexible control cable for humanoid robots, comprising, from the inside out, a conductor, an inner interface layer, an outer interface layer, and an insulation layer. The insulation layer is a cross-linked polyethylene layer, which has a dual-network structure formed inside with a CC permanent covalent cross-linked backbone and a Diels-Alder dynamic covalent cross-linked network. The Diels-Alder dynamic covalent cross-linked network is formed by the furan group in the furan norbornene copolymer and the maleimide group in the cross-linking aid containing maleimide end groups through a [4+2] cycloaddition reaction. When the cable is subjected to bending and torsional strain, the Diels-Alder dynamic covalent cross-linked network breaks preferentially over the CC main cross-linking bond to dissipate strain energy, and the suspended groups generated by the breakage can capture high-energy electrons.

[0008] Preferably, the insulating layer is composed of 100 parts by weight of polyethylene matrix resin, 5-15 parts of furan-norbornene copolymer, 2-8 parts of crosslinking aid, 0.5-2.0 parts of radiation sensitizer and 0.3-0.8 parts of antioxidant.

[0009] Preferably, the furanonorbornene copolymer is an ethylene-norbornene copolymer with furan groups in the side chain, obtained by copolymerizing ethylene with 5-norbornene-2-carboxylic acid furfuryl ester under the action of a metallocene catalyst, wherein the molar content of furan side groups is 0.3-1.5 mol%, and the weight average molecular weight is 80,000-200,000 g / mol.

[0010] Preferably, the crosslinking aid is N,N'-(1,3-phenylene)dimaleimide, and the irradiation sensitizer is trimethylolpropane triacrylate.

[0011] Preferably, the polyethylene matrix resin is a blend of low-density polyethylene and linear low-density polyethylene, with a mass ratio of low-density polyethylene to linear low-density polyethylene of 70:30-85:15.

[0012] Preferably, the antioxidant is selected from hindered phenolic antioxidants and phosphite antioxidants, wherein the hindered phenolic antioxidant is antioxidant 1010 and the phosphite antioxidant is antioxidant 168.

[0013] Preferably, the material composition of the insulating layer is the same as that of the outer interface layer, and the outer interface layer and the insulating layer are integrally formed by an irradiation crosslinking process. The irradiation dose of the outer interface layer is 10-30% lower than that of the main insulating layer, so that the degree of crosslinking of the outer interface layer is lower than that of the main insulating layer.

[0014] Preferably, the inner interface layer is a semi-conductive layer containing microcapsules, and the core material of the microcapsules is a mixture of polyethylene glycol polymer and furan polyethylene oligomer at a mass ratio of 1:0.8-1.2.

[0015] Preferably, the polyethylene glycol polymer is maleimide polyethylene glycol maleimide, with a number average molecular weight of 600-2000.

[0016] Preferably, the furan polyethylene oligomer is a polyethylene oligomer containing furan groups in its side chains, obtained by copolymerizing ethylene with 6-furan-1-hexene under the action of a metallocene catalyst, wherein the grafting rate of furan groups in the side chains is 5-15 mol.

[0017] The technical effects and advantages of this invention are as follows: In this invention, a dual-network structure of a CC permanent crosslinked backbone and a Diels-Alder dynamic covalent crosslinked network is constructed, actively introducing mechanochemical sacrificial bonds into the insulation layer. When the cable is subjected to bending and torsional strain, the lower-energy Diels-Alder bonds break preferentially over the CC main crosslinked bonds to dissipate strain energy. The furan rings and maleimide dangling groups generated by the breakage act as deep electron traps to capture high-energy electrons at the microcrack tips, inhibiting the initiation of partial discharge and thus blocking the evolution of nanocracks into electrical trees. In contrast, existing technologies introduce furan-based small molecules to form Diels-Alder dynamic bonds through catalytic amination reactions and post-absorption. The function of Diels-Alder bonds is positioned as passive repair and material recovery after damage occurs, relying on external thermal stimulation for triggering. However, this invention changes the function of Diels-Alder bonds from passive repair to active sacrificial energy dissipation and electron capture passivation, thus shifting the resistance to electrical tree growth from post-repair to pre-inhibition. Attached Figure Description

[0018] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts: Figure 1 This is a bar chart showing the combined bending and torsional fatigue life test results of the cable sample of the present invention. Figure 2 This is a stereomicroscopic image of the crack surface at the interface layer of the cable sample in Embodiment 1 of the present invention. Figure 3 This is a line graph showing the insulation resistance recovery rate of the cable sample of the present invention at different repair times; Figure 4 This is a bar chart showing the test results of the electrical tree initiation voltage of the insulating layer sample under dynamic strain. Figure 5 This is a peak-and-trough diagram showing the partial discharge initiation voltage test results of the cable sample of the present invention under bending and torsional motion. Figure 6 The graph shows the Diels-Alder bond retention rate of the insulating layer sample after different cycles of strain loading according to the present invention. Detailed Implementation

[0019] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0020] This invention provides a cross-linked polyethylene flexible control cable for humanoid robots, which, from the inside out, includes a conductor, an inner interface layer, an outer interface layer, an insulation layer, a shielding layer, and a sheath layer.

[0021] The conductor includes a central tensile reinforcement, a first strand, a second strand, and a wrapping layer surrounding the second strand.

[0022] The central tensile reinforcement is an aramid fiber bundle with a linear density of 1000-3000D.

[0023] The first strand is made of copper monofilaments with a diameter of 0.05-0.10 mm, which are bundled into strands at a pitch of 30 times the diameter of the monofilaments. Then, multiple strands are concentrically bundled on the outer periphery of the central tensile reinforcement at a pitch of 10 times the outer diameter of the bundle.

[0024] The second strand is made of bare copper wires with a diameter of 0.05-0.08 mm, which are bundled into strands at a pitch of 40 times the diameter of a single wire. Several strands are then bundled together at a pitch of 8 times the outer diameter of the bundle on the outer periphery of the first strand.

[0025] The stranding direction of the second strand is opposite to that of the first strand, which is used to balance the torsional stress of the conductor as a whole and avoid the accumulation of unidirectional torsion.

[0026] The material of the wrapping layer is selected from one of semi-conductive nylon tape and semi-conductive polyester tape, with a thickness of 0.02-0.05mm and a wrapping overlap rate of 20-35%. The wrapping layer serves as a buffer layer between the conductor and the inner interface layer at the physical level, and is used to homogenize the electric field distribution on the outer surface of the conductor.

[0027] The inner interface layer is located on the outer periphery of the wrapping layer, with a thickness of 0.10-0.25 mm. This inner interface layer is a semi-conductive layer of ethylene-vinyl acetate copolymer containing microcapsules. Its matrix material is ethylene-vinyl acetate copolymer (EVA), CAS number 24937-78-8, and 18-22 wt% conductive carbon black is added to adjust the volume resistivity. The volume resistivity of this inner interface layer at 23±2℃ is 1×10⁻⁶. 2 -1×10 4 Ω·m.

[0028] The microcapsules have a content of 3-8 wt% in the inner interface layer and a particle size of 5-20 μm. The wall material of the microcapsules is urea-formaldehyde resin with a wall thickness of 0.5-2 μm. The core material is a mixture of polyethylene glycol polymer and furan polyethylene oligomer at a mass ratio of 1:0.8-1.2.

[0029] The polyethylene glycol polymer is maleimide polyethylene glycol maleimide (MAL-PEG-MAL), with a number average molecular weight of 600-2000.

[0030] The furan polyethylene oligomer is a polyethylene oligomer containing furan groups in its side chains. It is obtained by copolymerizing ethylene with 6-furan-1-hexene (FH) under the action of a metallocene catalyst (rac-Et(Ind)2ZrCl2). The grafting rate of furan groups in the side chains is 5-15 mol%. The specific preparation method refers to the article "Synthesis of Thermally Reversible Crosslinked Polyethylene Based on Diels-Alder Reaction" published by Liu Liying and Niu Hui in Polymer Bulletin.

[0031] The preparation steps of 6-furan-1-hexene are as follows: Under nitrogen protection, tetrahydrofuran is added to the reaction flask as a solvent. After adding furan, the system temperature is lowered to -80 to -70°C using a mixed cold bath of liquid nitrogen and ethanol. A 1.6 mol / L n-butyllithium solution is added dropwise. After reacting at room temperature for 3-4 hours, the first reaction mixture is obtained. Subsequently, a pre-mixed solution of 6-bromo-1-hexene and tetrahydrofuran is added dropwise to the first reaction mixture. The volume ratio of 6-bromo-1-hexene to tetrahydrofuran is 1:1.19. The reaction is carried out overnight at room temperature to obtain the second reaction mixture. After removing the nitrogen protection, deionized water and ethyl acetate are added to the second reaction mixture for extraction to obtain an organic phase. The organic phase is dried with anhydrous sodium sulfate and then subjected to rotary evaporation to remove the solvent. The obtained product is then subjected to secondary drying with calcium hydride to remove water. Finally, the target fraction is collected by vacuum distillation to obtain the finished product 6-furan-1-hexene.

[0032] The microcapsules are prepared by in-situ polymerization, specifically including the following steps: C1: Mix the core material with deionized water at a volume ratio of 1:3-5, add 2%-5% sodium dodecyl sulfate emulsifier by weight of the core material, and emulsify at high speed of 8000-12000 r / min in an ice-water bath for 10-20 min to obtain a stable oil-in-water emulsion. C2: Dissolve urea and formaldehyde in deionized water at a molar ratio of 1:1.5-2.0, adjust the pH to 8.0-9.0 with triethanolamine, and stir the reaction at 70-80℃ for 60-90 min to obtain a urea-formaldehyde prepolymer solution. C3: Transfer the oil-in-water emulsion to the reactor, adjust the pH to 3.5-4.5, and slowly add the wall material prepolymer solution while stirring. The addition time is controlled at 30-45 min. Then raise the temperature to 55-75℃ and continue the reaction for 3-5 h to allow the wall material to polymerize and solidify on the surface of the oil droplets to form microcapsule walls. C4: After the reaction is complete, cool to room temperature, wash the product 3-4 times with deionized water, filter, and vacuum dry at 40-50℃ for 12-24 hours to obtain microcapsule powder.

[0033] When a cable is subjected to bending and torsional motion, microcracks are generated at the interface between the conductor and the insulation layer due to stress concentration. The stress at the crack tip causes the microcapsules to rupture, releasing the core material to the crack surface. The polyethylene glycol polymer and the furan polyethylene oligomer come into contact at the crack surface and undergo a Diels-Alder cycloaddition reaction, rebonding the crack surface. This self-healing process occurs spontaneously at room temperature without the need for external heating or light triggering.

[0034] The outer interface layer is disposed on the outer periphery of the inner interface layer, located between the inner interface layer and the insulating layer, and has a thickness of 0.02-0.08 mm.

[0035] The outer interface layer is a cross-linked polyethylene thin layer containing reversible Diels-Alder dynamic covalent bonds. The material composition of the outer interface layer is the same as that of the insulating layer, both containing polyethylene matrix, furan norbornene copolymer, cross-linking aid, radiation sensitizer and antioxidant, and the weight ratio of each component is consistent with that of the insulating layer.

[0036] The outer interface layer and the insulating layer are integrally formed by radiation crosslinking process, but the radiation dose during radiation crosslinking is 10-30% lower than the radiation dose of the main body of the insulating layer, so that its crosslinking degree is lower than that of the main body of the insulating layer.

[0037] The density of Diels-Alder dynamic covalent bonds in the outer interface layer is positively correlated with the degree of crosslinking. When the propagation depth of the microcrack exceeds the repair range of the inner interface layer, the outer interface layer, due to its lower density of Diels-Alder dynamic covalent bonds compared to the insulating layer, preferentially dissociates from the covalent bonds of the polyethylene main chain under dynamic strain, dissipating strain energy through chemical bond breakage.

[0038] After the bending and torsional stresses are unloaded, the dissociated Diels-Alder bonds undergo a thermally reversible Diels-Alder reaction at the cable's service temperature to re-bond, restoring the structural integrity of the outer interface layer.

[0039] The insulating layer is located on the outer periphery of the outer interface layer and has a thickness of 0.4-0.6 mm. Its material, by weight, consists of 100 parts of polyethylene matrix resin, 5-15 parts of furan-norbornene copolymer, 2-8 parts of crosslinking aid, 0.5-2.0 parts of radiation sensitizer, and 0.3-0.8 parts of antioxidant.

[0040] The polyethylene matrix resin is a blend of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), with a mass ratio of LDPE to LLDPE of 70:30-85:15; and the melt index of LDPE is 1.5-2.5 g / 10 min, while the melt index of LLDPE is 1.0-2.0 g / 10 min.

[0041] The furan-norbornene copolymer is an ethylene-norbornene copolymer with furan groups in its side chains. It is obtained by copolymerizing ethylene with 5-norbornene-2-carboxylic acid furfuryl ester under the action of a metallocene catalyst (rac-Et(Ind)2ZrCl2). The CAS number of 5-norbornene-2-carboxylic acid furfuryl ester is 684282-41-5, the molar content of furan side groups is 0.3-1.5 mol%, the weight average molecular weight is 80,000-200,000 g / mol, and the molecular weight distribution is 2.0-4.0. The specific preparation method is consistent with the above-mentioned furan-polyethylene oligomer, except that 5-norbornene-2-carboxylic acid furfuryl ester is used instead of 6-furan-1-hexene as a comonomer.

[0042] The crosslinking aid is N,N'-(1,3-phenylene)dimaleimide, CAS number 3006-93-7, used to form Diels-Alder sacrificial bond sites with the furan side groups in the furan norbornene copolymer after crosslinking.

[0043] The irradiation sensitizer is trimethylolpropane triacrylate, CAS number 15625-89-5, which is used to promote the uniform generation of free radicals during irradiation and improve crosslinking efficiency and crosslinking uniformity.

[0044] The antioxidant is one of hindered phenolic antioxidants and phosphite antioxidants, used to prevent oxidative degradation of materials during processing and use. The hindered phenolic antioxidant is preferably antioxidant 1010, and the phosphite antioxidant is preferably antioxidant 168.

[0045] After being cross-linked by irradiation, the insulating layer forms a dual-network structure inside, consisting of a CC cross-linked backbone and a Diels-Alder dynamic covalent cross-linked network.

[0046] The CC crosslinked backbone is constructed by the formation of CC covalent bonds through intermolecular recombination of polyethylene backbone free radicals during irradiation.

[0047] The Diels-Alder dynamic covalent crosslinking network is formed by the [4+2]Diels-Alder cycloaddition reaction between the furan side group in the furan norbornene copolymer and the maleimide end group in the crosslinking aid during irradiation.

[0048] The bond energy of the Diels-Alder adduct is lower than that of the CC main crosslinking bond. When the cable is bent and twisted, the insulation layer is subjected to dynamic mechanical strain. The Diels-Alder bond breaks preferentially and dissipates the strain energy in the form of chemical bond breakage.

[0049] After the Diels-Alder bond breaks, the furan ring and maleimide group exist on both sides of the fracture surface in the form of suspended groups. The electron affinity of the conjugated diene system of the furan ring and the maleimide is higher than that of the polyethylene matrix.

[0050] The suspended group acts as a deep electron trap to capture high-energy field-emitted electrons emitted under the influence of the electric field at the tip of the microcrack, thereby increasing the threshold of the initial field strength of the partial discharge and blocking the evolution of the microcrack into an electric tree.

[0051] After the bending and torsional stress disappears, under the combined effect of the cable's operating temperature and the thermal motion of the molecular chain segments, the furan groups and maleimide groups near the fracture site undergo a new Diels-Alder cycloaddition reaction, rebuilding the Diels-Alder dynamic covalent crosslinking network and restoring the integrity of the insulation layer crosslinking network.

[0052] The shielding layer is located on the outer periphery of the insulation layer and is woven from tin-plated copper wire with a diameter of 0.10-0.20 mm and a weaving density of 80%-95%.

[0053] The sheath layer is located on the outer periphery of the shielding layer and is made of thermoplastic polyurethane elastomer (TPU) with a thickness of 0.4-0.8 mm.

[0054] The present invention also provides a method for preparing the above-mentioned cross-linked polyethylene flexible control cable for humanoid robots, specifically including the following steps: S1: Use a single screw extruder to coat the outer periphery of the wrapping layer with the inner interface layer material to form the inner interface layer. Set the barrel temperature of the extruder to 110-130℃, the die head temperature to 120-140℃, and the extrusion line speed to 5-15m / min. S2: The insulating layer material is fed into two extruders respectively, and is sequentially wrapped around the outer periphery of the inner interface layer through a double-layer co-extrusion die head. The inner layer is the outer interface layer and the outer layer is the insulating layer. The barrel temperature of the insulating layer extruder is set to 150-195℃ and the die head temperature is set to 165-200℃. The barrel temperature of the outer interface layer extruder is set to 135-165℃ and the die head temperature is set to 150-180℃. S3: The cable is cross-linked by electron beam irradiation using an electron accelerator. The electron beam energy is 1.5-3.0 MeV and the beam current intensity is 10-30 mA. By controlling the linear velocity of the cable, the irradiation dose received by the main body of the insulation layer reaches 80-120 kGy. Since the energy of the electron beam gradually decreases when penetrating the insulation layer, the irradiation dose received by the outer interface layer located inside the insulation layer is 10%-30% lower than that of the main body of the insulation layer. After irradiation, the cable is kept in an oven at 60-70℃ for 12-24 hours to eliminate residual free radicals. S4: After irradiation, a shielding layer is woven around the outer periphery of the cable. A single-screw extruder is used to coat the outer periphery of the shielding layer with thermoplastic polyurethane elastomer to form a sheath layer. The barrel temperature of the extruder is set to 160-190℃, the die head temperature to 180-200℃, and the extrusion line speed to 10-20m / min to obtain the finished product.

[0055] The present invention will be described in detail below with reference to specific embodiments. It should be noted that these embodiments are only used to explain the present invention and do not constitute any limitation on the scope of protection of the present invention. Those skilled in the art can make adaptive adjustments to the embodiments based on their understanding of the technical solutions of the present invention, and these adjustments still fall within the scope of protection of the present invention.

[0056] Example 1: This example provides a cross-linked polyethylene flexible control cable for humanoid robots, which includes, from the inside out, a conductor, an inner interface layer, an outer interface layer, an insulation layer, a shielding layer, and a sheath layer.

[0057] The conductor's central tensile reinforcement has a linear density of 2000D. The first strand is made of copper monofilament bundles with a diameter of 0.07mm, which are twisted into strands. Multiple strands are then concentrically twisted around the outer periphery of the central tensile reinforcement at a pitch of 10 times the outer diameter of the bundle. The second strand is made of bare copper wire bundles with a diameter of 0.06mm, which are twisted into strands. Several strands are then twisted around the outer periphery of the first strand at a pitch of 8 times the outer diameter of the bundle. The wrapping material is semi-conductive nylon tape with a thickness of 0.03mm and a wrapping overlap rate of 28%.

[0058] The thickness of the inner interface layer is 0.18 mm, wherein the VA content of the ethylene-vinyl acetate copolymer is 22 wt%, and 20 wt% conductive carbon black is added to control the volume resistivity of the inner interface layer to be 5 × 10⁻⁶. 3 Ω·m; the microcapsules in the inner interface layer contain 5wt%, have a particle size of 10μm, a wall thickness of 1μm, and the core material is a mixture of polyethylene glycol polymer and furan polyethylene oligomer in a mass ratio of 1:1.

[0059] The polyethylene glycol polymer is maleimide polyethylene glycol maleimide, with a number average molecular weight of 1000.

[0060] The furan-polyethylene oligomer is a polyethylene oligomer with furan groups in its side chains. It is obtained by copolymerization of ethylene and 6-furan-1-hexene in a metallocene catalytic system. The specific preparation method is as follows: Before the polymerization reaction, the reaction flask, feeding pipeline and stirring device were dried and purged with nitrogen three times to remove moisture and oxygen from the system. Then, ethylene gas was introduced into the 250mL polymerization reaction flask to maintain an ethylene atmosphere in the reaction system. 50mL of dehydrated toluene, 0.80g of 6-furan-1-hexene and 8mL of 1mol / L methylaluminoxane toluene solution were added in sequence. The mixture was stirred for 5min under an ethylene atmosphere to ensure that 6-furan-1-hexene and the co-catalyst were evenly dispersed in the toluene. Subsequently, a toluene solution of 4 μmol (rac-Et(Ind)2ZrCl2) was added to initiate the copolymerization reaction of ethylene and 6-furan-1-hexene. The polymerization temperature was controlled at 60 °C and the reaction time was controlled at 15 min. After the reaction was completed, the reaction system was poured into an acid-alcohol solution with a hydrochloric acid / ethanol volume ratio of 1:4 to terminate the reaction. The obtained polymer was washed with ethanol and distilled water in sequence, filtered, and vacuum dried at 50 °C to constant weight to obtain furan polyethylene oligomer. The grafting rate of furan groups in the side chain of the obtained furan polyethylene oligomer was 5.0 mol as determined by 1H NMR spectroscopy.

[0061] Before preparing the microcapsules, maleimide polyethylene glycol maleimide and furan polyethylene oligomer were mixed at a mass ratio of 1:1 and stirred evenly at room temperature to serve as the core material of the microcapsules. The microcapsules were prepared by in-situ polymerization, specifically including the following steps: C1: Mix the core material with deionized water at a volume ratio of 1:4, add 3% sodium dodecyl sulfate emulsifier by weight of the core material, and emulsify at a high speed of 10000 r / min for 15 min in an ice-water bath to obtain a stable oil-in-water emulsion. C2: Dissolve urea and formaldehyde in deionized water at a molar ratio of 1:1.8, adjust the pH to 8.5 with triethanolamine, and stir the reaction at 75°C for 75 min to obtain a urea-formaldehyde prepolymer solution. C3: Transfer the oil-in-water emulsion to the reactor, adjust the pH to 4.0, and slowly add the wall material prepolymer solution while stirring. The addition time is controlled at 40 min. Then, raise the temperature to 65℃ and continue the reaction for 4 h to allow the wall material to polymerize and solidify on the surface of the oil droplets to form microcapsule walls. C4: After the reaction is complete, cool to room temperature, wash the product three times with deionized water, filter, and vacuum dry at 45°C for 18 hours to obtain microcapsule powder.

[0062] The outer interface layer has a thickness of 0.05 mm, and the insulating layer has a thickness of 0.5 mm. The two layers have the same material composition, including 100 parts by weight of polyethylene matrix resin, 10 parts of furan norbornene copolymer, 5 parts of N,N'-(1,3-phenylene)dimaleimide, 1.0 part of trimethylolpropane triacrylate, and 0.5 parts of antioxidant 1010.

[0063] The mass ratio of LDPE to LLDPE in the polyethylene matrix resin is 80:20. The melt index of LDPE is 2.0 g / 10 min, and the melt index of LLDPE is 1.5 g / 10 min.

[0064] The furanonorbornene copolymer was obtained by copolymerization of ethylene and 5-norbornene-2-carboxylic acid furfuryl ester in a metallocene catalytic system, and the specific preparation method is as follows: Before the polymerization reaction, the reaction flask, feeding pipeline and stirring device were dried and purged with nitrogen three times to remove moisture and oxygen from the system. Then, ethylene gas was introduced into the 250mL polymerization reaction flask to maintain an ethylene atmosphere in the reaction system. 50mL of dehydrated toluene, 0.15g of 5-norbornene-2-carboxylic acid furfuryl ester and 8mL of 1mol / L methylaluminoxane toluene solution were added in sequence. The mixture was stirred for 5min under an ethylene atmosphere to ensure that 5-norbornene-2-carboxylic acid furfuryl ester and the co-catalyst were evenly dispersed in the toluene. Subsequently, a toluene solution of 4 μmol (rac-Et(Ind)2ZrCl2) was added to initiate the copolymerization reaction of ethylene and 5-norbornene-2-carboxylic acid furfuryl ester. The polymerization temperature was controlled at 60℃ and the reaction time was controlled at 15 min. After the reaction was completed, the reaction system was poured into an acid-alcohol solution with a hydrochloric acid / ethanol volume ratio of 1:4 to terminate the reaction. The obtained polymer was washed with ethanol and distilled water in sequence, filtered, and vacuum dried at 50℃ to constant weight to obtain furan-norbornene copolymer. The molar content of furan side groups in the obtained furan-norbornene copolymer was 1.0 mol% by nuclear magnetic resonance spectroscopy. The weight average molecular weight was 130,000 g / mol and the molecular weight distribution was 3.2 by gel permeation chromatography.

[0065] This embodiment also provides a method for preparing the above-mentioned flexible control cable, specifically including the following steps: S1: Use a single screw extruder to coat the outer periphery of the wrapping layer with the inner interface layer material. Set the extruder barrel temperature to 120℃, the die head temperature to 130℃, and the extrusion line speed to 10m / min. S2: The outer interface layer material and the insulating layer material are respectively fed into two extruders and sequentially coated on the outer periphery of the inner interface layer through a double-layer co-extrusion die head. The inner layer is the outer interface layer and the outer layer is the insulating layer. The barrel temperature of the insulating layer extruder is set to 170℃ and the die head temperature is set to 180℃. The barrel temperature of the outer interface layer extruder is set to 150℃ and the die head temperature is set to 165℃. S3: The cable was cross-linked by electron beam irradiation using an electron accelerator. The electron beam energy was 2.0 MeV, the beam current intensity was 20 mA, and the cable's linear velocity was controlled at 8 m / min. The irradiation dose received by the main insulation layer was tested to be 100 kGy, and the irradiation dose received by the outer interface layer was tested to be 80 kGy. After irradiation, the cable was kept in an oven at 65°C for 18 hours to allow the polyethylene segments in the outer interface layer and insulation layer to complete the irradiation cross-linking. This also allowed the furan groups in the furan norbornene copolymer to form a Diels-Alder dynamic covalent cross-linking network with the maleimide groups in N,N'-(1,3-phenylene)dimaleimide. S4: A shielding layer is woven around the irradiated cable using tinned copper wire with a diameter of 0.15mm and a weaving density of 90%. A single-screw extruder is used to coat the shielding layer with thermoplastic polyurethane elastomer to form a sheath layer. The extruder barrel temperature is set to 175℃, the die head temperature to 190℃, the extrusion line speed to 15m / min, and the sheath layer thickness is controlled to be 0.6mm to obtain the finished product.

[0066] Example 2: This example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that the amount of microcapsules added in the inner interface layer is reduced to 3wt%, and the amount of ethylene-vinyl acetate copolymer added is increased accordingly, while keeping the total weight unchanged.

[0067] Example 3: This example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that the amount of microcapsules added in the inner interface layer is increased to 8 wt%, and the amount of ethylene-vinyl acetate copolymer added is reduced accordingly, while keeping the total weight unchanged.

[0068] Example 4: This example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that in step S3, while maintaining the irradiation dose received by the main body of the insulation layer at 100 kGy, the combination of electron beam energy, beam current intensity, cable passing linear velocity, and irradiation number is adjusted to make the irradiation dose received by the outer interface layer 90 kGy. That is, the irradiation dose received by the outer interface layer is 10% lower than that of the main body of the insulation layer. The remaining structure, material composition, and preparation steps are the same as in Example 1.

[0069] Example 5: This example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that in step S3, while maintaining the irradiation dose received by the main body of the insulation layer at 100 kGy, the combination of electron beam energy, beam current intensity, cable linear velocity, and irradiation times is adjusted to make the irradiation dose received by the outer interface layer 70 kGy. That is, the irradiation dose received by the outer interface layer is 30% lower than that of the main body of the insulation layer. The remaining structure, material composition, and preparation steps are the same as in Example 1.

[0070] Example 6: This example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that the amount of furanorbornene copolymer added in the insulation layer and the outer interface layer is reduced to 5 parts.

[0071] Example 7: This example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that the amount of furanorbornene copolymer added to the insulation layer and the outer interface layer is increased to 15 parts.

[0072] Comparative Example 1 This comparative example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that it does not have an inner interface layer and an outer interface layer. The insulation layer is a common cross-linked polyethylene insulation layer, which is composed of 100 parts by weight of polyethylene matrix resin, 1.0 part of trimethylolpropane triacrylate and 0.5 parts of antioxidant 1010. The remaining conductor, shielding layer, sheath layer and preparation method are the same as in Example 1.

[0073] Comparative Example 2

[0074] This comparative example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that no outer interface layer is provided, and the insulation layer is the same as that of Comparative Example 1, while the other materials and preparation methods are the same as those of Example 1.

[0075] Comparative Example 3 This comparative example provides a cross-linked polyethylene flexible control cable for a humanoid robot. The difference from Example 1 is that the inner interface layer is not provided, but the outer interface layer is retained. Both the outer interface layer and the insulation layer are made of the same ordinary cross-linked polyethylene material as in Comparative Example 1. The remaining materials and preparation methods are consistent with those in Example 1.

[0076] Comparative Example 4 This comparative example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that it does not have an inner interface layer and an outer interface layer, while the remaining conductor, shielding layer, sheath layer, insulation layer and preparation method are the same as in Example 1.

[0077] Comparative Example 5 This comparative example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that the inner interface layer is retained, but the outer interface layer is not provided. The other materials and preparation methods are the same as in Example 1.

[0078] Comparative Example 6 This comparative example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that the inner interface layer is not provided, but the outer interface layer and the insulation layer are retained. The remaining materials and preparation methods are consistent with those of Example 1.

[0079] Comparative Example 7 This comparative example provides a cross-linked polyethylene flexible control cable for humanoid robots. The difference from Example 1 is that the microcapsule core material in the inner interface layer contains only maleimide polyethylene glycol maleimide and does not contain furan polyethylene oligomer. The remaining materials and preparation methods are consistent with those in Example 1.

[0080] To verify the technical effect of the flexible control cables prepared in the above embodiments and comparative examples of the present invention, the cables prepared in the embodiments and comparative examples were tested respectively to evaluate the actual effect of the technical solution of the present invention in suppressing the growth of electrical trees caused by dynamic strain-induced nanocracks.

[0081] Experiment Example 1: This experiment aims to evaluate the combined bending and torsional fatigue life of various cable samples under simulated humanoid robot joint service conditions.

[0082] Cable samples prepared in Examples 1-7 and Comparative Examples 1-7 were selected. Three parallel samples were prepared for each group of samples, and the length of each sample was 2m.

[0083] Fix both ends of the cable sample to the moving end and the fixed end of the bending and torsion combined fatigue testing machine, respectively. Adjust the bending radius guide wheel to 5 times the outer diameter of the cable, set the bending angle to ±90°, the torsion angle to ±180° / m, and the movement frequency to 30 times / min. Connect the high-voltage power supply to the cable conductor, ground the shielding layer, and stabilize for 5 minutes after power-on. Record the initial insulation resistance value and partial discharge quantity. After confirming that the initial state of the sample is normal, start the testing machine to begin bending and torsion cycling. When the insulation resistance drops below 50% of the initial value, or the partial discharge quantity continuously exceeds 100 pC, or a breakdown short circuit occurs, the cable is deemed to have failed. Stop the test and record the current number of cycles as the bending and torsion fatigue life of the sample. Test 3 parallel samples in each group, and record the number of cycles at failure for each sample. The results are shown in Table 1 below. Figure 1 As shown.

[0084] Table 1. Results of combined bending and torsion fatigue life test (unit: cycles)

[0085] From Table 1 and Figure 1 The data shows that the bending and torsional fatigue life of Examples 1-7 is higher than that of the comparative examples. The results of three parallel tests of Example 1 are about 8.8 times that of Comparative Example 1 and about 2.4 times that of Comparative Example 4. The lifespan of Example 2 was lower than that of Example 1, while the lifespan of Example 3 was slightly higher than that of Example 1, indicating a positive correlation between microcapsule content and cable lifespan. The lifespan of Example 6 was the lowest among all examples, while the lifespan of Example 7 was higher than that of Example 6 but lower than that of Example 1.

[0086] Experimental Example 2: This experimental example aims to evaluate the self-healing ability of urea-formaldehyde resin microcapsules in the inner interface layer of the present invention under room temperature conditions.

[0087] Cable samples prepared in Examples 1-3, Comparative Examples 2 and 7 were selected, and a positive control group was set up. The inner interface layer of the control group did not contain microcapsules, but only 80 wt% ethylene-vinyl acetate copolymer and 20 wt% conductive carbon black were added.

[0088] The cable sample from Example 1 was placed on the bending fixture of the testing machine with a support point spacing of 200 mm. The pressure head was pressed vertically downwards at a speed of 5 mm / min, and monitored in real time using a stereomicroscope until a visible crack with a width of approximately 0.1 mm and a length of approximately 10-15 mm appeared on the outer surface of the cable insulation layer. The peak load was recorded and then immediately unloaded. After unloading, the crack partially closed, forming a stable interfacial microcrack inside the cable. The surrounding black spherical objects were microcapsules. Figure 2 As shown.

[0089] Subsequently, the cable samples with pre-formed microcracks were placed in a constant temperature and humidity chamber and left to stand at a temperature of 23±2℃ and a relative humidity of 50±10%. During this period, the samples were taken out every 4 hours for insulation resistance testing, the insulation resistance values ​​at different repair time points were recorded, and the corresponding repair efficiency was calculated.

[0090] Insulation resistance was tested using a ZC-90G high insulation resistance meter. During measurement, a voltage was applied to the cracked area for 1 minute, and a stable reading was taken. For each measurement, three different locations within the cracked area were selected, and the arithmetic mean was calculated. The repair efficiency was calculated using the following formula:

[0091] Where η is the repair efficiency, R initial R is the initial insulation resistance measured before the pre-crack formation. crack R is the insulation resistance measured immediately after unloading when the crack is still present. t The insulation resistance measured after time t is used for repair. The test results are shown in Table 2 below. Figure 3 As shown.

[0092] Table 2. Insulation resistance recovery rate of cable samples at different times (unit: %)

[0093] From Table 2 and Figure 3 The data shows that during the room temperature resting process, the insulation resistance recovery rate of Examples 1-3 and Comparative Example 2 gradually increased with the extension of the repair time, and all reached more than 80% after 24 hours. However, Comparative Example 7 and the positive control showed almost no recovery within 24 hours. This indicates that the presence of both maleimide and furan reactive functional groups in the microcapsule core material is a necessary condition for achieving room temperature self-repair. After the two come into contact with the crack surface, a Diels-Alder cycloaddition reaction occurs, forming a cross-linked network that rebonds the crack surface.

[0094] In addition, different microcapsule contents have a certain impact on the repair rate and final repair efficiency. Example 3 showed a slightly higher early recovery rate than Example 1, but the final efficiency was similar. Example 2 showed both a lower repair rate and a lower final efficiency, indicating that there is an optimal window for microcapsule content. If the content is too low, the repair will be insufficient, and if it is too high, the gain will be limited.

[0095] Experimental Example 3 aims to evaluate the ability of the cable insulation layers of each embodiment and comparative example to resist the initiation of electrical treeing under dynamic mechanical strain conditions.

[0096] Cable samples prepared in Examples 1, 4-7, Comparative Examples 1 and 4-7 were selected. Insulation layer body sheets were prepared from each cable sample. Five test sheets were prepared for each group of samples. A positive control group was also set up. The positive control group used the same material formulation and electron beam irradiation dose treatment as the insulation layer in Example 1 to obtain an insulation layer body sheet containing a CC permanent cross-linked backbone and a Diels-Alder dynamic covalent cross-linked network, without conductors, inner interface layers, outer interface layers, shielding layers, and sheath layers.

[0097] Referring to the GB / T 2951.11-2008 standard, the testing device was coupled with a miniature dynamic tensile stage, so that each sample was subjected to cyclic tensile strain while a gradually increasing AC voltage was applied, and the voltage value when the electric tree first appeared was recorded.

[0098] During sample preparation, cable segments of 100mm in length were cut from each finished cable product. The sheath, shield, inner interface layer, conductor, and outer interface layer area near the inner interface layer were removed in sequence, leaving only the main body of the insulation layer. The stripped insulation layer was then cut axially and unfolded into a flat sheet with a thickness controlled within the range of 0.49-0.51mm. Finally, it was cut into 20mm×20mm square sheets.

[0099] Each group of thin-film samples was placed between the fixtures of the dynamic stretching table with an initial gauge length of 15 mm. The stainless steel needle electrode was vertically inserted into the center of the insulating layer body thin film. The penetration depth was controlled to be about 0.25 mm by the three-dimensional micro-adjustment frame. The distance between the needle tip and the lower electrode was kept at 0.3-0.5 mm. The lower electrode was made of stainless steel plate and was in close contact with the lower surface of the sample. The needle electrode was connected to the high-voltage power supply and the lower electrode was grounded through the detection resistor.

[0100] During dynamic strain application, a sinusoidal cyclic tensile strain was applied to the thin-sheet sample using a dynamic tensile stage. The strain waveform was sinusoidal, the strain amplitude was 2%, the strain frequency was 1Hz, and the strain direction was perpendicular to the needle electrode axis. Before testing, the dynamic tensile stage was run at the set parameters for 30 seconds. After the strain stabilized, the voltage increase test was started at a rate of 0.5kV / s, continuously increasing the voltage from 0kV. When the discharge instrument detected a continuous discharge pulse, the voltage value at this time was recorded as the initiation voltage of the electrical tree. The results are shown in Table 3 below. Figure 4 As shown.

[0101] Table 3 Results of electrical tree initiation voltage under dynamic strain (unit: kV)

[0102] From Table 3 and Figure 4 The data shows that the initial voltage values ​​of the five sheets in Example 1 fluctuated less, indicating that they could still stably suppress the initiation of electrical treeing under high voltage. The initial voltage of Example 7 was similar to that of Example 1, while that of Example 6 was reduced to 3.77-4.01kV. This indicates that too low content of furanonorbornene copolymer would weaken the electrical treeing suppression ability of the Diels-Alder dynamic covalent crosslinking network and the suspended groups.

[0103] Comparative Example 1 had the lowest starting voltage, indicating that dynamic mechanical strain easily induces the initiation of electrical trees when there are no dynamic bonds or traps. The starting voltage of Comparative Example 4 was 2.79-2.96kV, which was about twice that of Comparative Example 1, but still lower than that of Example 1, indicating that the single insulating layer Diels-Alder dynamic covalent cross-linked network was insufficient to achieve the suppression effect.

[0104] Experiment Example 4 aims to evaluate the partial discharge initiation voltage (PDIV) of the cable of the present invention under simulated humanoid robot joint bending and twisting motion, in order to verify the ability of the complete cable structure to suppress the risk of partial discharge initiation under the combined effect of dynamic bending and twisting and local defects.

[0105] Cable samples prepared in Examples 1-7 and Comparative Examples 1-7 were selected, with 3 cables prepared for each group. Three test areas were set at equal intervals in the middle of each cable. The test areas were created by inserting a medical injection needle into the surface of the insulation layer to about 1 / 3 of its thickness and then scratching it axially. Before testing, the defect areas were wiped with anhydrous ethanol and allowed to air dry naturally to simulate the initial defects caused by local stress concentration, interface microcrack propagation, or external micro-damage during long-term bending and torsion service of the cable.

[0106] Cable samples were mounted on a bending-torsional fatigue testing machine. The bending radius was set to 5 times the cable outer diameter, the bending angle to ±45°, the torsional angle to ±90° / m, and the motion frequency to 20 times / minute. The samples underwent continuous bending and torsional motion during the test. The testing system conformed to IEC 60270-2015 standards. A power frequency high-voltage test transformer was used to uniformly increase the voltage at a rate of 0.2 kV / s. The voltage value (PDIV) was recorded when the local discharge first stably exceeded 10 pC. Three test zones for each sample were tested independently. If a sample broke down during the test, the breakdown voltage was recorded as the PDIV of that test zone. The results are shown in Table 4 below. Figure 5 As shown, where, Figure 5 The horizontal axis represents the partial discharge initiation voltage in kV, and the vertical axis represents the cable sample group.

[0107] Table 4 Partial discharge initiation voltage of each cable sample (unit: kV)

[0108] From Table 4 and Figure 5 The data shows that the PDIV test values ​​of Example 1 are distributed in the range of 6.09-6.41kV, with the highest overall level. This indicates that in the complete cable structure, the microcapsule repair effect of the inner interface layer, the low cross-linking energy dissipation effect of the outer interface layer, and the strain energy dissipation and electron capture effect of the Diels-Alder dynamic covalent cross-linking network in the insulation layer can work together to enable the cable to still have a high partial discharge initiation voltage under bending and torsional motion and local micro-defect conditions.

[0109] Comparing Examples 2, 3 and 1, it is shown that the microcapsule content affects the repair effect of interfacial microcracks. When the microcapsule content is low, the partial discharge initiation voltage decreases, while when the microcapsule content increases to a certain extent, the improvement on the partial discharge initiation voltage tends to be limited.

[0110] Examples 4, 1, and 5 correspond to cases where the irradiation dose of the outer interface layer is 10%, 20%, and 30% lower than that of the main insulating layer, respectively. This shows that when the crosslinking of the outer interface layer is too high, the strain energy dissipation capacity is insufficient, and when the crosslinking is too low, the interface support stability decreases.

[0111] Comparing Examples 6 and 7 with Example 1, it is shown that the amount of furanonorbornene copolymer added affects the formation density of the Diels-Alder dynamic covalent crosslinking network. When the amount added is too low, the number of dynamic bonds and dangling groups is insufficient, while when the amount added is too high, it may affect the dielectric uniformity of the polyethylene matrix.

[0112] The partial discharge initiation voltage of each comparative example was lower than that of Example 1, indicating that it is difficult to achieve the comprehensive effect of Example 1 by using only ordinary cross-linked polyethylene insulation layer, only setting a single interface layer, or only introducing Diels-Alder dynamic covalent cross-linked network in the insulation layer.

[0113] Experimental Example 5 aims to evaluate the degree of structural retention of the Diels-Alder dynamic covalent cross-linked network in the insulating layer after undergoing different numbers of cyclic strain loading.

[0114] Cable products were prepared using Examples 1, 4-5, Comparative Example 1, and Comparative Example 4-6, and insulation layer samples were taken from the above cable products as experimental subjects.

[0115] Take samples from each group, first peel off the sheath and shielding layers to expose the outer surface of the insulation layer, then cut the insulation layer along the cable axis and separate the main body of the insulation layer from the conductor, inner interface layer, and outer interface layer area near the inner interface layer. Only take the main body of the insulation layer without the inner interface layer, outer interface layer, and conductor residue as the test section. Use a standard cutter to cut a thin sample of about 10mm × 10mm in area and about 0.5mm in thickness from the test section. Slightly sand the two ends of the thin sample with fine sandpaper to increase friction, and then install it in the tensile fixture of the dynamic mechanical analyzer. After fixing, the effective test length of the sample is 5mm.

[0116] Start the dynamic mechanical analyzer and set the test temperature to 65℃. After the temperature stabilizes, preheat the sample at this constant temperature for 5 minutes. Apply sinusoidal cyclic tensile strain to the sample with a strain amplitude of 3% and a loading frequency of 1Hz. Load each group of samples for 100, 500, 1000, 5000, and 10000 cycles, respectively. Use three independent parallel samples for each cycle. Immediately after loading, remove the samples and test them using a Fourier transform infrared spectrometer with a spectral acquisition range of 500-4000 cm⁻¹. -1 The resolution is 4cm. -1 The scan was performed 32 times. A clean, empty ATR crystal was used as the background for initial subtraction during the test. The sample was then tightly attached to the ATR crystal window. Spectra for each sample were acquired at three different locations. The average absorbance of the characteristic peak at each location was taken as the representative value for that sample. The wavelength was approximately 1710 cm⁻¹. -1The carbonyl stretching vibration peak of the Diels-Alder adduct is taken as the characteristic absorption peak of the Diels-Alder bond, at approximately 1460 cm⁻¹. -1 The methylene bending vibration peak of the polyethylene backbone was used as an internal reference peak. The absorbance values ​​of each peak were read, and the normalized absorbance was calculated. Using the normalized absorbance of the sample after 0 cycles as a benchmark, the Diels-Alder dynamic covalent bond retention rate of the sample after each number of cycles was calculated. The results are shown in Table 5 below. Figure 6 As shown.

[0117] Table 5. Diels-Alder dynamic covalent bond retention rate results (unit: %)

[0118] From Table 5 and Figure 6 The data shows that there are reasonable fluctuations among the parallel samples of each experimental object, without a clear monotonically increasing or decreasing trend. With the increase of the number of cyclic loading, the retention rate of Diels-Alder dynamic covalent bonds in all samples containing Diels-Alder dynamic covalent crosslinking networks shows a gradual decreasing trend, but the rate of decrease varies among different experimental objects. Comparative Example 1 did not detect 1710 cm⁻¹ throughout the entire test process. -1 Characteristic absorption peaks.

[0119] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A cross-linked polyethylene flexible control cable for humanoid robots, comprising, from the inside out, a conductor, an inner interface layer, an outer interface layer, and an insulation layer, characterized in that, The insulation layer is a cross-linked polyethylene layer, which has a dual network structure formed inside with a CC permanent covalent cross-linked backbone and Diels-Alder dynamic sacrificial cross-linking sites. The Diels-Alder dynamic sacrificial cross-linking sites are formed by the [4+2] cycloaddition reaction between the furan groups in the copolymer containing furan groups and the maleimide groups in the cross-linking aid containing maleimide end groups. When the cable is subjected to bending and torsional strain, the Diels-Alder dynamic sacrificial cross-linking sites break preferentially over the CC main cross-linking bonds to dissipate strain energy, and the suspended groups generated by the breakage can capture high-energy electrons. The outer interface layer and the insulating layer are integrally formed by an irradiation crosslinking process, and the irradiation dose of the outer interface layer is 10-30% lower than that of the main insulating layer. The inner interface layer is a semi-conductive layer containing microcapsules. The core material of the microcapsules is a mixture of polyethylene glycol polymer with bismaleimide end groups and polymer with furan side groups in a mass ratio of 1:0.8-1.

2.

2. The cross-linked polyethylene flexible control cable for humanoid robots according to claim 1, characterized in that: The insulating layer, by weight, consists of 100 parts polyethylene matrix resin, 5-15 parts a copolymer containing furan groups, 2-8 parts a crosslinking aid containing maleimide end groups, 0.5-2.0 parts an irradiation sensitizer, and 0.3-0.8 parts an antioxidant.

3. The cross-linked polyethylene flexible control cable for humanoid robots according to claim 2, characterized in that: The copolymer containing furan groups is an ethylene-norbornene copolymer with furan groups in the side chain, obtained by copolymerizing ethylene with 5-norbornene-2-carboxylic acid furfuryl ester under the action of a metallocene catalyst, wherein the molar content of furan side groups is 0.3-1.5 mol%, and the weight average molecular weight is 80,000-200,000 g / mol.

4. The cross-linked polyethylene flexible control cable for humanoid robots according to claim 2, characterized in that: The crosslinking aid containing maleimide end groups is N,N'-(1,3-phenylene)dimaleimide, and the irradiation sensitizer is trimethylolpropane triacrylate.

5. A cross-linked polyethylene flexible control cable for humanoid robots according to claim 2, characterized in that: The polyethylene matrix resin is a blend of low-density polyethylene and linear low-density polyethylene, and the mass ratio of low-density polyethylene to linear low-density polyethylene is 70:30-85:

15.

6. The cross-linked polyethylene flexible control cable for humanoid robots according to claim 2, characterized in that: The antioxidant is selected from one of hindered phenolic antioxidants and phosphite antioxidants, wherein the hindered phenolic antioxidant is antioxidant 1010 and the phosphite antioxidant is antioxidant 168.

7. The cross-linked polyethylene flexible control cable for humanoid robots according to claim 1, characterized in that: The polyethylene glycol polymer containing bismaleimide end groups is maleimide polyethylene glycol maleimide, with a number average molecular weight of 600-2000.

8. The cross-linked polyethylene flexible control cable for humanoid robots according to claim 1, characterized in that: The polymer containing furan side groups is a polyethylene oligomer with furan groups in the side chain, which is obtained by copolymerizing ethylene with 6-furan-1-hexene under the action of a metallocene catalyst, wherein the grafting rate of furan groups in the side chain is 5-15 mol.

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