A bend-resistant flexible cable and method of making the same

Abstract

The application belongs to the technical field of power cables, and particularly relates to a bending-resistant flexible cable and a preparation method thereof. The cable comprises, from inside to outside, a conductor, an insulation layer, a buffer layer, a shielding layer and a protective layer. The insulation layer is divided into an inner layer, a middle layer and an outer layer in the radial direction. The inner layer of the insulation layer comprises the following components in parts by weight: cross-linked polyethylene 100 parts, amino-modified light-responsive graphene quantum dots 6-10 parts and plasticizer DOS 2-4 parts. The content of the amino-modified light-responsive graphene quantum dots is 2-3 parts, the content of the cross-linked polyethylene is 100 parts, and the content of the plasticizer DOS is 2-4 parts. The protective layer comprises the following components in parts by weight: shape memory polyurethane 100 parts, composite microspheres 15-22 parts and light stabilizer 0.5-1.0 part. The insulation layer adopts a 'cross-linked polyethylene + amino-modified light-responsive graphene quantum dots gradient distribution + plasticizer' system. Three-channel co-extrusion and three-stage ultraviolet light curing are used to avoid 'insufficient cross-linking of the inner layer and excessive cross-linking of the outer layer'.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power cables, and particularly relates to an anti-bending flexible cable and a preparation method thereof. BACKGROUND

[0002] As a key component for power and signal transmission under dynamic conditions, the anti-bending fatigue performance of the flexible cable directly determines the reliability and service life of the equipment.

[0003] The traditional conductor is twisted by pure metal wire bundles, and stress concentration occurs between the metal wires due to rigid contact when bending, which is prone to micro-fracture. The insulation layer and the protective sleeve are mainly single polymer materials, which are prone to interlayer peeling or material fatigue cracking after repeated bending. Although the soft insulation material improves flexibility, it lacks mechanical strength and is easily punctured by the conductor. Although the hard protective material is wear-resistant, it is poor in flexibility, resulting in large bending resistance of the cable and accelerating the damage of the internal structure. Therefore, it is a technical problem to be solved in the field to develop a flexible cable with high anti-bending fatigue and long service life. SUMMARY

[0004] In view of the above problems in the prior art, the application provides an anti-bending flexible cable and a preparation method thereof to solve the problems in the background.

[0005] In order to solve the above technical problems, the application adopts the following technical scheme:

[0006] An anti-bending flexible cable comprises, from inside to outside, a conductor, an insulation layer, a buffer layer, a shielding layer and a protective layer. The conductor is composed of an elastic core and an embedded twisted metal wire bundle. The elastic core is a thermoplastic elastomer (thermoplastic polyurethane TPU / styrene-butadiene-styrene block copolymer SBS) containing 0.5-1.5wt% light-responsive crosslinking agent, and a spiral groove is provided on the surface of the elastic core. The groove depth is 0.08-0.12mm, and the tolerance is ±0.005mm. The metal wire bundle is a nickel-plated copper-titanium alloy wire with a single wire diameter of 0.04-0.07mm, which is embedded and twisted in the spiral groove. The twisting pitch is 6-8 times the diameter of the metal wire bundle.

[0007] The insulation layer is divided into an inner layer, a middle layer and an outer layer along the radial direction. According to the weight parts, the inner layer contains 100 parts of crosslinked polyethylene, 6-10 parts of amino-modified light-responsive graphene quantum dots with a particle size of 3-8nm, 2-5wt% azobenzene modified groups and 2-4 parts of plasticizer dioctyl sebacate. The middle layer contains 4-6 parts of amino-modified light-responsive graphene quantum dots. The outer layer contains 2-3 parts of amino-modified light-responsive graphene quantum dots. The insulation layer is formed by gradient co-extrusion and segmented light curing process.

[0008] The buffer layer is a silicone rubber-barium titanate composite system, the content of barium titanate is 5-8wt%, the thickness is 0.3-0.5mm, and the interface with the insulating layer is pretreated by plasma;

[0009] The shielding layer is a tinned copper wire braided layer, the single wire diameter is 0.07-0.10mm, and the braiding density is 95%±0.5%;

[0010] The protective layer contains, by weight parts, 100 parts of shape memory polyurethane, 15-22 parts of composite microspheres, a particle size of 50-100nm, a proportion of graphene quantum dots of 15-20wt%, a light stabilizer of 0.5-1.0 parts, an axial orientation degree of the composite microspheres of ≥98%, and a self-repairing efficiency (tearing strength recovery rate) of ≥92% after 30min of segmented irradiation of 365-405nm ultraviolet light.

[0011] Further, the spiral groove of the elastic core is formed by ultraviolet laser micro-machining, the laser wavelength is 355nm, the power is 10-15W, and the groove wall roughness Ra is ≤0.8μm; the elongation at break of the elastic core is ≥650%, and the crosslinking degree is improved by 40-45% after 365nm ultraviolet light irradiation.

[0012] Further, the nickel-plated copper-titanium alloy wire is prepared by a "vacuum melting-continuous wire drawing-electroplating" process, and the tensile strength is ≥850MPa, and the thickness of the nickel-plated layer is 3-5μm.

[0013] Further, the segmented light curing process parameters of the insulating layer are as follows: the first stage is irradiated at 30-40mW / cm² for 5-8s, the second stage is irradiated at 80-100mW / cm² for 10-12s, and the third stage is irradiated at 120-150mW / cm² for 3-5s; the thickness ratio of the inner layer, the middle layer and the outer layer of the insulating layer is 1:1.2:1, and the total thickness is 0.8-1.2mm.

[0014] Further, the plasma pretreatment process of the buffer layer is as follows: Ar / O2 mixed gas (volume ratio 3:1) is used, the power is 50-80W, the treatment time is 10-15s, and the dielectric loss tangent is ≤0.015.

[0015] Further, the composite microspheres are of a core-shell structure, the core is a mixture of hydroxylated graphene quantum dots and dithiodipropionic acid dihydrazide, and the shell is melamine formaldehyde resin; the composite microspheres are axially oriented by magnetic field assistance, and the magnetic field strength is 0.1-0.2T.

[0016] The application also provides a preparation method of the anti-bending flexible cable.

[0017] S1. Conductor preparation:

[0018] S11. Thermoplastic elastomer, photoresponsive crosslinking agent (4, 4'-bis (azido) benzene methane), antioxidant 1010 are added into a double screw extruder in proportion, melt blended at 180-200℃, and extruded into an elastic core rough blank with a diameter of 0.4-0.6mm;

[0019] S12. When the elastic core rough blank is cooled to 80-90℃, a spiral groove is processed by using an ultraviolet laser (355nm, 10-15W), and then pre-irradiated by 365nm ultraviolet light for 10-15s;

[0020] S13. The metal wire bundle is controlled in tension by a multi-channel tension feedback system, and is twisted into the spiral groove at a constant temperature environment of 40-50℃ to obtain a conductor;

[0021] S2. Insulating layer preparation:

[0022] S21. Insulating layer inner, middle and outer layer slurries are respectively prepared, and are deaerated after ultrasonic dispersion for 30-40min; the three-channel gradient co-extruder is used to coat the conductor periphery, and the co-extruder is controlled in three sections (inner layer 170-180℃, middle layer 160-170℃, outer layer 150-160℃), and the near-infrared online detection module is used to adjust the feeding speed of each channel in real time;

[0023] S22. After co-extrusion, three-stage ultraviolet curing is immediately carried out: 30-40mW / cm² irradiation for 5-8s→80-100mW / cm² irradiation for 10-12s→120-150mW / cm² irradiation for 3-5s, and then dried in an oven at 85-95℃ for 1-2h to obtain an insulating wire core;

[0024] S3. Buffer layer coating:

[0025] S31. The surface of the insulating wire core is treated by Ar / O2 plasma at 50-80W for 10-15s;

[0026] S32. The silicone rubber-barium titanate composite slurry is coated on the periphery of the treated insulating wire core by an extruder, the extrusion temperature is 130-140℃, the pulling speed is 4-6m / min, and the cooling is set;

[0027] S4. Shielding layer weaving:

[0028] S41. The tinned copper wire is woven by using a double-shaft servo synchronous system, and the synchronization error between the pulling speed and the spindle speed is ≤0.1%;

[0029] S42. The weaving density is detected online by a high-speed camera, and the spindle speed is automatically adjusted to ensure that the weaving density is 95%±0.5%, thereby obtaining a shielding wire core;

[0030] S5. Protective layer preparation:

[0031] S51. The shape memory polyurethane, composite microspheres, and light stabilizer are added to a supercritical CO2 reactor (45 DEG C, 18 MPa), and ultrasonic assistance (20 kHz, 300 W) is used to mix for 40-50 min;

[0032] S52. The mixed system is coated on the shielding wire core by an extruder, a permanent magnet array (magnetic field strength 0.1-0.2 T, length 50-80 mm) is arranged at the outlet section of the extruder, the extrusion temperature is 175-190 DEG C, the screw rotation speed is 30-40 r / min, and cooling and shaping are performed;

[0033] S6. Post-processing:

[0034] S61. First, 365 nm ultraviolet light (80-100 mW / cm²) is used for irradiation for 10-15 s to activate the photoresponsive crosslinking agent of the conductor elastic core;

[0035] S62. Then, 405 nm ultraviolet light (100-120 mW / cm²) is used for irradiation for 10-15 s to activate the photoresponsive components of the insulating layer and the protective layer, and the preparation is completed.

[0036] Further, in step S13, the multi-channel tension feedback system dynamically adjusts the wire bundle pay-off speed through a servo motor.

[0037] Further, in step S21, the near-infrared online detection module is linked with a PLC system, the response time of the feeding screw rotation speed adjustment is less than or equal to 0.5 s, and the concentration deviation of the graphene quantum dots in each layer of the insulating layer is less than or equal to 0.3 wt%.

[0038] Further, in step S52, the magnetic field strength of the permanent magnet array is monitored online by a magnetometer, and the distance between the permanent magnets is adjusted in real time to ensure that the axial orientation degree of the composite microspheres is greater than or equal to 98%.

[0039] Compared with the prior art, the present application has the following beneficial effects:

[0040] 1. The insulating layer adopts a "crosslinked polyethylene + amino-modified photoresponsive graphene quantum dot gradient distribution + plasticizer" system; combined with three-channel co-extrusion and three-stage ultraviolet light curing, the risk of breakdown caused by electric field concentration is avoided.

[0041] 2. The conductor is designed with "thermoplastic elastomer elastic core containing 0.5-1.5 wt% light-responsive crosslinking agent + spiral groove embedded nickel-plated copper-titanium alloy wire bundle": the elastic core can absorb more than 70% of the bending stress, the light-responsive crosslinking agent can increase the crosslinking degree by 40-45%, and the spiral groove can avoid collapse; the metal wire bundle is embedded and arranged to reduce rigid contact wear. Combined with the gradient distribution of the insulating layer quantum dots and the 0.1-0.2T magnetic field axial orientation of the protective layer composite microspheres, the cable bending resistance life far exceeds that of traditional cables, meeting the dynamic wiring needs of industrial robots, mobile devices, etc.

[0042] 3. The shielding layer is a tinned copper wire braided layer, which has good shielding effectiveness, and the tin plating layer prevents oxidation, solving the problem of corrosion of bare copper wire; the protective layer contains shape memory polyurethane, core-shell structure composite microspheres and light stabilizer 770, and the performance retention rate is high after 1000h ultraviolet aging, which is suitable for outdoor, humid and other harsh working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 It is a structural diagram of the anti-bending flexible cable of the present application;

[0044] Figure 2 It is a schematic diagram of the insulating layer of the anti-bending flexible cable of the present application;

[0045] Figure 3 It is a flow chart of the preparation method of the insulating layer of the anti-bending flexible cable of the present application;

[0046] The reference signs in the drawings of the specification include:

[0047] 1. Conductor; 2. Insulating layer; 21. Inner layer of insulating layer; 22. Middle layer of insulating layer; 23. Outer layer of insulating layer; 3. Buffer layer; 4. Shielding layer; 5. Protective layer. DETAILED DESCRIPTION

[0048] In order for those skilled in the art to better understand the present application, the technical solutions of the present application are further described below in conjunction with the drawings and examples.

[0049] The traditional conductor is twisted with pure metal wire bundle, and stress concentration occurs between the metal wires due to rigid contact when bending, which easily causes micro-fracture; the insulating layer and the protective sleeve are mainly single polymer material, which is prone to interlayer peeling or material fatigue cracking after repeated bending; although the soft insulating material improves flexibility, its mechanical strength is insufficient and it is easily pierced by the conductor; although the hard protective material is wear-resistant, it has poor flexibility, resulting in high bending resistance of the cable and accelerating damage to the internal structure; therefore, it is a technical problem to be solved in the field to develop a flexible cable with high bending fatigue resistance and long service life

[0050] The application provides a bending-resistant flexible cable, which comprises a conductor, an insulation layer, a buffer layer, a shielding layer and a protective layer from inside to outside, characterized in that the conductor comprises an elastic core and a wire bundle twisted on the periphery of the elastic core.

[0051] The insulation layer is divided into an inner layer, a middle layer and an outer layer in the radial direction, wherein the inner layer of the insulation layer comprises the following components by weight: 100 parts of cross-linked polyethylene, 6-10 parts of amino-modified light-responsive graphene quantum dots and 2-4 parts of plasticizer DOS.

[0052] The middle layer of the insulation layer comprises the following components by weight: 4-6 parts of amino-modified light-responsive graphene quantum dots, 100 parts of cross-linked polyethylene and 2-4 parts of plasticizer DOS.

[0053] The outer layer of the insulation layer comprises the following components by weight: 2-3 parts of amino-modified light-responsive graphene quantum dots, 100 parts of cross-linked polyethylene and 2-4 parts of plasticizer DOS.

[0054] The amino-modified light-responsive graphene quantum dots are functional nanomaterials obtained by performing amino chemical modification on graphene quantum dots (basic carrier) and endowing the graphene quantum dots with light-responsive characteristics. The graphene quantum dots provide mechanical / electrical basis, the amino modification solves the compatibility problem with the matrix, and the light-responsive characteristics adapt to the segmented light-curing process of the insulating layer, so that the triple effects of "enhanced tear resistance + auxiliary crosslinking + stable dispersion" are finally achieved in the insulating layer. Graphene quantum dots (GQDs) are nanoscale fragments of graphene (usually 3-8 nm in size, spherical or flaky, with excellent properties of graphene, but due to quantum size effect, additional optical response ability; the atomically dense structure makes the tensile strength reach 130 GPa, and when added to the crosslinked polyethylene matrix, it can disperse bending stress like "nanometer steel bar", which is the key to the insulating layer tear strength ≥40 MPa; the nanoscale size enables it to absorb specific wavelength ultraviolet light (365-405 nm, matching the segmented light-curing wavelength), providing the basis for "light response"; the amino-modified light-responsive graphene quantum dots are formed by grafting amino groups (-NH2) onto the surface of graphene quantum dots through chemical methods (such as ammonia reduction method and amine coupling reaction); the amino group (polar group) can form hydrogen bonds with the hydroxyl group (-OH) and ester group (-COO-) in the crosslinked polyethylene matrix, avoiding the agglomeration of quantum dots in the slurry, and the amino modification can further reduce the agglomeration rate; the modified quantum dots are not easy to "channel layer" in the molten slurry, ensuring that the concentration deviation of the inner layer (6-10 wt%), middle layer (4-6 wt%) and outer layer (2-3 wt%) is ≤0.2 wt% during gradient co-extrusion; the amino group can react with the active free radicals of crosslinked polyethylene during light-curing process, indirectly improving the crosslinking efficiency (making the inner layer crosslinking degree reach 75%-85% faster). The amino-modified graphene quantum dots will undergo "photo-induced electron transfer" under 365-405 nm ultraviolet light (the core wavelength of segmented light-curing): after absorbing light energy, the electrons of the surface amino group are excited and can be transferred to the crosslinked polyethylene molecular chain or photoinitiator, accelerating the crosslinking reaction; the inner layer (high addition amount 6-10 wt%): under high light intensity (120-150 mW / cm²), the light response of quantum dots is more significant, which assists the rapid and deep crosslinking of the inner layer and strengthens the tear resistance; the middle / outer layer (low addition amount): under low light intensity (30-100 mW / cm²), the response is mild, avoiding excessive crosslinking leading to the embrittlement of the outer layer; without light: the quantum dots only play a mechanical strengthening role and do not interfere with the storage or co-extrusion process of the slurry (such as good stability at 170-180°C inner layer temperature control).

[0055] The protective layer comprises the following components by weight: 100 parts of shape memory polyurethane, 15-22 parts of composite microspheres, and 0.5-1.0 parts of light stabilizer.

[0056] The shape memory polyurethane is a kind of polyurethane polymer material with "light / thermal stimulus response shape memory function", which can recover from the "temporary deformation" caused by bending to the initial structure morphology under 405nm ultraviolet light (corresponding to the post-processing step S62 "405nm ultraviolet light irradiation activation") or a specific temperature, and the molecule chain contains a light-activated cross-linking site, which has excellent compatibility with composite microspheres and light stabilizers; although ordinary polyurethane has good flexibility, it is easy to produce irreversible deformation (such as wrinkles and cracks) after repeated bending, and cannot recover automatically; while the shape memory polyurethane can recover to the original shape through light activation, avoiding the accumulation of deformation leading to the failure of the protective layer; the amino and ester groups in the molecular structure of the shape memory polyurethane can form hydrogen bonds with the hydroxyl groups in the shell layer (melamine formaldehyde resin) of the composite microspheres, and at the same time, the dispersion of the light stabilizer 770 is compatible, ensuring the uniformity of the overall components of the protective layer and avoiding delamination.

[0057] The composite microspheres have a core-shell structure, and the parameters and compositions are as follows: size: particle size 50-100 nm;

[0058] The core layer is a mixture of hydroxylated graphene quantum dots (15-20wt%) and dithiodipropionic acid dihydrazide (containing a disulfide bond, a self-repairing active component), and after 30 minutes of segmented irradiation with 365-405nm ultraviolet light, the disulfide bond breaks and recombines, and the tear strength recovery rate of the protective layer is ≥92%, which can repair the microcracks (width ≤5μm) caused by bending;

[0059] The shell layer is melamine formaldehyde resin (rigid support layer), which can block external water vapor and oxygen, and slow down the oxidation and aging of the protective layer matrix (shape memory polyurethane);

[0060] Orientation: axial orientation (along the length direction of the cable) is achieved by 0.1-0.2T magnetic field assistance during preparation, and the orientation degree is ≥98%.

[0061] The shell layer (melamine formaldehyde resin) can prevent the loss of the disulfide bond component in the core, while providing rigid support; the hydroxylated graphene quantum dots (high mechanical strength) in the core can specifically enhance the tear resistance of the protective layer, and the disulfide bond of dithiodipropionic acid dihydrazide can break and recombine under ultraviolet light to achieve self-repairing; when the cable is bent, the stress is transmitted along the length direction, and the axial arrangement of the microspheres can maximize the dispersion of the bending stress (avoiding stress concentration leading to cracking), and the anti-bending fatigue life is improved by more than 40% compared with random dispersion.

[0062] In the dynamic bending working condition of the cable, the stress is mainly transmitted along the length direction (axial direction) (such as the bending force of the cable is distributed along the axial direction when the industrial robot joint swings or the equipment moves), if the composite microspheres are randomly dispersed: the amount of core layer hydroxylated graphene quantum dots (high mechanical strength) cannot be arranged in the stress direction, and is easy to form "stress concentration points" on the inside / outside of the bending, causing the local tearing of the protective layer, axial orientation (along the length direction of the cable): the "axial orientation degree of the composite microspheres is ≥98%" after the magnetic field assistance, in any unit volume (such as 1 mm3) of the protective layer, the included angle between the long axis of at least 98% of the composite microspheres and the length direction (axial direction) of the cable is ≤5°, only less than 2% of the microspheres deviate slightly (included angle > 5°) or arrange randomly due to dispersion error, which can be understood as "more than 98% of the 100 microspheres are neatly oriented in the extension direction of the cable, only 1-2 microspheres are slightly arranged", and the whole presents a highly unified axial arrangement state, which is realized through 0.1-0.2T magnetic field assistance. When the protective layer generates microcracks (extend along the radial direction or the axial direction) due to bending, the cracks at any position can contact the disulfide bond component, and after irradiation by 365-405 nm ultraviolet light, the disulfide bond breaks and recombines. The graphene quantum dots can evenly disperse the axial bending stress like "axial nanometer steel bars", avoiding local stress from being too high to cause cracking; at the same time, the core layer disulfide bond (self-repairing active component) is also evenly distributed along the axial direction, and when activated by subsequent ultraviolet light, it can cover the microcracks comprehensively, ensuring the self-repairing efficiency, the core layer of the composite microspheres containing hydroxylated graphene quantum dots has weak magnetism, and sufficient magnetic field force is needed to drive the directional arrangement. If the magnetic field strength <0.1T (such as 0.05T), the magnetic field force is not enough to overcome the van der Waals force between the microspheres, and the orientation degree will decrease to below 80%, which cannot form effective axial arrangement, and the anti-tearing performance of the protective layer decreases, if the magnetic field strength >0.2T (such as 0.3T), the magnetic field force is too strong, which can cause the microspheres to attract each other and form agglomerates with a diameter >1μm (the particle size of the microspheres is required to be 50-100nm). The agglomerates not only destroy the continuity of the protective layer, but also form "dielectric / mechanical defects" at the local position - such as the self-repairing component is missing in the agglomerate (the disulfide bond is concentrated in the agglomerate), which causes the cracks to be unable to be repaired; at the same time, the agglomerates can also scratch the inner shielding layer, causing the shielding efficiency to fluctuate. The axially oriented composite microspheres can complement the "light-induced shape recovery" function of the shape memory polyurethane - after bending, the shape memory polyurethane restores the original shape, and the axially oriented microspheres simultaneously disperse the elastic recovery stress, avoiding the accumulation of deformation; the 0.1-0.2T magnetic field orientation process does not affect the function of the light stabilizer 770 (the light stabilizer 770 "does not react with the composite microspheres"), and when activated by subsequent ultraviolet light, it can not only ensure the self-repairing / shape memory functions, but also inhibit aging through the light stabilizer, prolonging the service life of the protective layer.

[0063] Light stabilizer 770 (Hindered amine HALS, Hindered amine light stabilizer), the amount of addition is 0.5-1.0 parts by weight, the chemical property is stable, does not absorb 365-405 nm ultraviolet light (avoid interfering with the light activated self-repair, shape memory function), and does not react with shape memory polyurethane, composite microspheres.Chemical reaction. Ultraviolet light will cause the molecular chain of shape memory polyurethane to break (inducing embrittlement, flexibility decreases), and will also damage the double sulfur bond of the core layer of the composite microspheres (lose self-repair function); ordinary light stabilizers (such as ultraviolet absorbers) may absorb 365-405 nm ultraviolet light, interfere with the light activation process of the post-processing step; and light stabilizer 770 inhibits aging by "capturing free radicals", without affecting the function of the light responsive component.

[0064] In an embodiment, the buffer layer is a silicone rubber-barium titanate composite system, with a thickness of 0.3-0.5 mm, and the interface thereof in contact with the insulating layer is pretreated by plasma. The buffer layer uses methyl vinyl silicone rubber as the matrix, and barium titanate particles as the functional filler uniformly dispersed in the matrix. The mass fraction of barium titanate on the side of the buffer layer close to the insulating layer is 7-8 wt%, and the mass fraction of barium titanate on the side of the buffer layer close to the shielding layer is 5-6 wt%. The dielectric constant of the buffer layer decreases from the side of the insulating layer to the side of the shielding layer, forming a micro-graded distribution of the dielectric constant along the radial direction.

[0065] It is explained that the traditional buffer layer matrix (such as ordinary nitrile rubber) is not flexible enough and is prone to hardening and cracking after repeated bending. The molecular chain of methyl vinyl silicone rubber contains flexible Si-O bonds, with a Shore hardness of only 30-50A at room temperature and an elongation at break of ≥500%. It can produce elastic deformation with the cable bending, effectively absorbing the bending stress between the insulating layer and the shielding layer (reducing stress transmission loss by more than 40%), while having excellent high and low temperature resistance (stable at -60-200°C), suitable for cable use in multiple working conditions.

[0066] The dielectric constant of the insulating layer (crosslinked polyethylene-based) is about 2.3-2.5, and the dielectric constant of the shielding layer (tinned copper wire) is close to infinity. Direct contact between the two will cause "electric field concentration" due to the sudden change in dielectric constant (the local field strength can be 3-5 times the average field strength), which is prone to cause breakdown of the insulating layer. Barium titanate is a high dielectric filler (dielectric constant ≥1000). Through the gradient design of "high content (7-8 wt%) on the side close to the insulating layer and low content (5-6 wt%) on the side close to the shielding layer", the dielectric constant of the buffer layer decreases from 30-40 to 15-20 along the radial direction, forming a dielectric constant transition zone from "insulating layer → buffer layer → shielding layer", avoiding electric field concentration. If barium titanate is uniformly distributed, the dielectric constant of the buffer layer is single, and the dielectric sudden change between the insulating layer and the buffer layer cannot be eliminated.

[0067] If the interface between the buffer layer and the insulating layer is not firmly combined, interlayer peeling is likely to occur when bending (peeling strength of traditional process ≤1.5 N / mm); by treating the surface of the insulating layer with Ar / O2 plasma (volume ratio 3:1, power 50-80 W, time 10-15 s), two key effects can be achieved: etching the surface of the insulating layer (roughness Ra increases from 0.2 μm to 0.8-1.0 μm), and increasing the contact area between the buffer layer and the insulating layer; introducing active groups such as hydroxyl (-OH) and carboxyl (-COOH) on the surface of the insulating layer, and chemically bonding with the silicon hydroxyl (-SiOH) of the methyl vinyl silicone rubber, so that the interfacial peeling strength is increased to ≥3.0 N / mm, avoiding interlayer peeling.

[0068] The preparation method of the silicone rubber-barium titanate composite system comprises the following steps:

[0069] Pre-treatment: insulating layer interface plasma treatment equipment: low-temperature plasma treatment machine (equipped with Ar / O2 gas mixing system); process parameters: Ar / O2 volume ratio 3:1, treatment power 50-80 W, treatment time 10-15 s, treatment distance (nozzle to the surface of the insulating layer) 5-8 mm; etching the surface of the insulating layer and introducing active groups, preparing for the subsequent combination of the buffer layer.

[0070] Composite slurry preparation: prepare gradient barium titanate slurry in batches

[0071] High-content slurry (corresponding to the side of the buffer layer close to the insulating layer, 7-8 wt% barium titanate): take 100 parts by weight of methyl vinyl silicone rubber, 7-8 parts by weight of barium titanate, and 1.5-2.0 parts by weight of vulcanizing agent (such as dicumyl peroxide), add them into a high-speed mixer (rotation speed 1000-1200 r / min), mix at 80-90°C for 30-40 min, and form a uniform slurry;

[0072] Low-content slurry (corresponding to the side of the buffer layer close to the shielding layer, 5-6 wt% barium titanate): keep the amounts of methyl vinyl silicone rubber and vulcanizing agent unchanged, adjust the amount of barium titanate to 5-6 parts by weight, and prepare the slurry according to the same mixing process; transfer the two kinds of slurry into a 20 kHz, 300 W ultrasonic device respectively, and ultrasonically disperse for 20-30 min to ensure uniform dispersion of barium titanate particles (no agglomerates with particle size >5 μm).

[0073] Gradient extrusion coating: double-channel gradient extruder (equipped with independent temperature control system and coaxial die, two channels conveying high content and low content slurry respectively); extrusion temperature: 130-140°C (adapt to the melt flowability of methyl vinyl silicone rubber, avoid the decomposition of vulcanizing agent in advance); traction speed: 4-6 m / min (synchronous with the co-extrusion insulation layer traction speed, avoid uneven thickness of buffer layer); high content slurry is conveyed in the inner channel of coaxial die (close to the insulation layer), low content slurry is conveyed in the outer channel (close to the shielding layer), the channel cross-sectional area ratio is 1:1.2, ensuring the total thickness of the buffer layer is 0.3-0.5 mm;

[0074] Cooling and shaping: the buffer layer after extrusion immediately enters the 25-30°C cooling water tank (cooling length 1-1.5 m), cooled to surface temperature ≤50°C, fixed gradient structure and shape.

[0075] Post-vulcanization: the cooled and shaped cable is sent into a hot air circulating oven, vulcanized at 150-160°C for 2-3 h, so that the methyl vinyl silicone rubber is fully crosslinked, and at the same time, the titanium dioxide particles are firmly combined with the matrix, finally forming a silicone rubber-barium titanate composite buffer layer with gradient distribution of dielectric constant.

[0076] In an embodiment, the shielding layer is a tinned copper wire braid layer. The cable is susceptible to external electromagnetic interference (EMI) and radio frequency interference (RFI) in power / signal transmission, and the shielding layer needs to have high electrical conductivity to "ground and lead away interference current" - the volume resistivity of copper is only 1.72 x 10 -8 Ω·m (much lower than aluminum, iron and other metals), which can efficiently absorb and conduct interference signals, is the optimal base material selection to achieve "low interference transmission", adapts to the functional positioning of the cable "stable transmission", and bare copper wire is easily oxidized to form copper oxide (resistivity increases sharply, shielding performance decreases) in humid and high temperature environments, while tin has excellent chemical stability: a dense protective film can be formed on the surface of the copper wire by the tin plating layer, which isolates the contact of air, water vapor and copper, preventing oxidation and rust; at the same time, tin has good ductility, and the plating layer is not easy to crack during subsequent braiding and bending, ensuring long-term stable shielding performance and adapting to the needs of cable "multi-environment application". The braided layer is made of multiple thin copper wires (single wire diameter 0.07-0.10 mm) interlaced, and the single wire can slide slightly along the interlaced gap during bending, following the overall deformation of the cable (no risk of breaking when the bending radius is ≤10 times the cable diameter), avoiding the problem of "easy breakage and shielding failure" of traditional metal foil when bending; the buffer layer (silicone rubber-barium titanate system) is a flexible elastomer, the mesh structure of the braided layer can fully adhere to the surface of the buffer layer, and the two are deformed synchronously during bending, reducing the risk of interlayer peeling and controlling the "braiding density 95% ± 0.5%": balancing the shielding effect and flexibility.

[0077] In an embodiment, the elastic core is a thermoplastic elastomer containing 0.5-1.5 wt% of a light-responsive crosslinking agent. The wire bundle is a nickel-plated copper-titanium alloy wire with a single wire diameter of 0.04-0.07 mm and a twisting pitch of 6-8 times the diameter of the wire bundle.

[0078] It is noted that traditional conductor cores are mostly rigid metals or pure rubber, the former is prone to stress concentration when bending, and the latter is difficult to process. Thermoplastic elastomer (TPU / SBS) has both "rubber elasticity" and "plastic hot processing" - at room temperature, the soft segment of the molecular chain is free to move, showing high flexibility (elongation at break ≥650%), which can absorb the stress of wire bundle twisting and cable bending; at high temperature (180-200℃), it can be melt-extruded, which meets the process requirements of the "spiral groove processing" of the elastic core. If no light-responsive crosslinking agent is added, the elastic core is prone to "permanent deformation" (such as spiral groove collapse) after long-term bending, and cannot stably support the wire bundle; if the amount of light-responsive crosslinking agent is less than 0.5 wt%, the crosslinking degree is insufficient (the crosslinking degree increases by less than 30% after 365 nm ultraviolet irradiation), and the anti-deformation ability of the elastic core is weak.

[0079] If the amount of light-responsive crosslinking agent is more than 1.5 wt%, the crosslinking degree is too high, and the rigidity of the elastic core increases (Shore hardness >75A), increasing the bending resistance of the cable. The high elasticity of the elastic core can absorb more than 70% of the radial stress when the cable is bent, avoiding micro-fracture of the wire bundle (nickel-plated copper-titanium alloy wire) due to rigid contact. After 10-15 s of 365 nm ultraviolet pre-irradiation, the light-responsive crosslinking agent activates crosslinking, the hardness of the elastic core increases from 60A to 75A, and the deformation of the spiral groove decreases from 15% to less than 5%, which can stably embed the wire bundle (avoiding wire bundle slipping during twisting); subsequent post-processing can further strengthen the support.

[0080] The core composition of the elastic core is as follows: the type of thermoplastic elastomer matrix (main body) is one of thermoplastic polyurethane (TPU) or styrene-butadiene-styrene block copolymer (SBS).

[0081] TPU: The molecular chain contains "hard segment (polyurethane segment, providing basic strength) + soft segment (polyether / polyester segment, providing elasticity)", with a temperature resistance range of -50-150℃, suitable for extreme working conditions.

[0082] SBS: composed of "rigid styrene segment (S segment, physical crosslinking point) + flexible butadiene segment (B segment, source of elasticity)", with an optimal flexibility when the butadiene segment content is 30-40%, and a lower processing temperature (160-180℃).

[0083] The photo-responsive crosslinking agent is 4,4'-bis(azido) benzene methane; the azido (-N3) photoactive group is broken to generate free radicals under 365 nm ultraviolet light irradiation, and crosslinking reaction occurs with the molecular chain of TPU / SBS to form a three-dimensional network structure, thereby realizing performance regulation; the addition amount is 0.5-1.5 wt% (relative to the mass of the thermoplastic elastomer base).

[0084] In an embodiment, the thickness ratio of the inner layer, the middle layer and the outer layer of the insulation layer is 1:1.2:1, and the total thickness is 0.8-1.2 mm. The preparation method of the insulation layer comprises the following steps: preparing inner layer, middle layer and outer layer slurries of the insulation layer, ultrasonic dispersion for 30-40 min and then defoaming; using a three-channel co-extrusion machine, segmenting temperature control at 170-180℃ for the inner layer, 160-170℃ for the middle layer and 150-160℃ for the outer layer, synchronously coating the three layers of slurry on the conductor and then shaping in 20-25℃ cold water; after shaping in cold water, three-stage ultraviolet light curing is used, and the irradiation is performed in sequence at 30-40 mW / cm² for 5-8 seconds, 80-100 mW / cm² for 10-12 seconds and 120-150 mW / cm² for 3-5 seconds; finally, the insulation wire core is dried in hot air at 85-95℃ for 1-2 hours.

[0085] The total thickness of the insulation layer is less than 0.8 mm: the insulation layer is too thin to meet the insulation requirement of a breakdown field strength of greater than or equal to 35 kV / mm (the electric field is concentrated due to insufficient thickness, which causes breakdown); if the total thickness is greater than 1.2 mm: the insulation layer is too thick, which increases the overall diameter of the cable and the bending resistance (violates the design goal of a flexible cable, the bending radius needs to be increased by more than 20%, which cannot adapt to dynamic working conditions); the thickness ratio of the inner layer (tear resistance), the middle layer (transition), and the outer layer (flexibility) makes the radial "tear resistance strength-flexibility" of the insulation layer transition smoothly (the tear resistance strength of the inner layer is greater than or equal to 45 MPa, the outer layer is greater than or equal to 30 MPa, and the middle layer is greater than or equal to 38 MPa), which avoids the bending delamination (interlayer peeling strength is greater than or equal to 3.0 N / mm, which is much higher than the 1.5 N / mm of ordinary equal-thickness structures) caused by performance mutations in traditional "equal-thickness three-layer" structures. Under the control of the total thickness, the breakdown field strength of the insulation layer is stably greater than or equal to 35 kV / mm (satisfies the power transmission insulation requirement), and at the same time, the overall bending radius of the cable can be reduced to 8-10 times the diameter (ordinary thick insulation cables need 12-15 times), which adapts to dynamic bending working conditions (such as industrial robot joints and mobile device wiring). The amino-modified light-responsive graphene quantum dots are prone to agglomeration due to van der Waals forces, and if they are not evenly dispersed, it will cause local quantum dots to be excessive (brittle) or insufficient (poor tear resistance / insulation). If air bubbles remain in the slurry, "air bubble defects" will be formed after co-extrusion, which directly reduces the breakdown field strength (the electric field is concentrated at the air bubbles, which easily causes breakdown) by 20 kHz ultrasonic dispersion, which can break the agglomeration and make the quantum dots have a dispersion uniformity of greater than or equal to 90% and a concentration deviation of each layer of less than or equal to 0.3 wt%. After degassing, there are no visible air bubbles in the slurry, and the insulation layer formed by co-extrusion has no air bubble defects, and the qualified rate of the breakdown field strength is increased to more than 98% (when not degassed, the qualified rate is only 75%)

[0086] The inner layer slurry has the highest quantum dot content (6-10 parts), and the viscosity is 30-50% higher than that of the middle and outer layers. Higher temperature (170-180°C) is needed to reduce the viscosity and ensure uniform flow during extrusion (to avoid thickness fluctuations in the inner layer). The outer layer slurry has the lowest quantum dot content (2-3 parts) and low viscosity. If the temperature is too high (>160°C), it will cause excessive melting, and the cooled layer will be brittle (contrary to the positioning of the outer layer as "flexible"). The middle layer uses a transition temperature (160-170°C) to eliminate the temperature difference between the inner and outer layers, promote molecular chain diffusion and fusion at the three-layer interface (to avoid delamination between the layers). After co-extrusion, the slurry is in a molten viscous state at 150-180°C. If it is cooled naturally, the high-viscosity inner layer slurry and the low-viscosity outer layer slurry will easily "channel" due to the difference in flowability (quantum dot distribution is chaotic, which destroys the thickness ratio of 1:1.2:1 and the gradient concentration). The molten slurry is prone to deformation due to tension during the pulling process, causing the insulation layer to be eccentric (uneven thickness). Cold water at 20-25°C can quickly solidify the surface of the slurry (surface hardness reaches Shore D30) through rapid heat exchange (cooling rate ≥10°C / s), locking the three-layer structure. After cold water shaping, the insulation layer gradient structure (thickness ratio, quantum dot concentration) has no channeling, and the eccentricity is ≤0.05mm (much lower than the industry standard of 0.1mm).

[0087] The solidified structure provides "rigid support" for subsequent photocuring, avoiding uneven crosslinking caused by material flow during light irradiation. The outer layer requires high flexibility, and the crosslinking degree needs to be controlled at 30-40% (excessive crosslinking will cause brittleness), so low light intensity (30-40mW / cm²) is used for short time (5-8s) irradiation to achieve initial crosslinking. The middle layer requires "balance between tear resistance and flexibility", and the crosslinking degree needs to be 60-70%, so medium light intensity (80-100mW / cm²) is used for medium time (10-12s) irradiation to achieve full crosslinking. The inner layer requires "high tear resistance + voltage resistance", and the crosslinking degree needs to be 75-85%. Since the inner layer is located at the innermost side, the light needs to penetrate the middle and outer layers, so high light intensity (120-150mW / cm²) is used for short time (3-5s) irradiation to ensure deep crosslinking and avoid excessive crosslinking of the middle and outer layers.

[0088] The slurry contains plasticizer DOS (2-4 parts). DOS is the abbreviation of Dioctyl Sebacate, CAS number 122-62-3, molecular formula C 26 H 50 O4, which is a colorless or pale yellow transparent oily liquid. After co-extrusion and photocuring, a small amount of low-boiling-point solvent (such as impurities in DOS) may be left. If not removed, the solvent will evaporate during long-term use, causing the insulation layer to shrink and produce micro-cracks. Hot air at 85-95°C can promote further crosslinking of the quantum dots and crosslinked polyethylene molecular chains that have not fully reacted (crosslinking degree increased by 5-10%), reducing internal stress.

[0089] The application further provides a preparation method of the anti-bending flexible cable.

[0090] S1. Conductor preparation:

[0091] S11. Thermoplastic elastomer, light response crosslinking agent and antioxidant 1010 are proportionally added into a double screw extruder, melt blended at 180-200 DEG C, and extruded into an elastic core rough blank with a diameter of 0.4-0.6 mm;

[0092] S12. When the elastic core rough blank is cooled to 80-90 DEG C, a spiral groove is processed by using ultraviolet laser, and then pre-irradiated by 365 nm ultraviolet light for 10-15 s;

[0093] S13. Metal wire bundles are embedded and twisted in the spiral groove in a constant temperature environment of 40-50 DEG C to obtain a conductor;

[0094] S2. Insulating layer preparation:

[0095] S21. Insulating layer inner, middle and outer layer slurries are respectively prepared, and ultrasonic dispersion is carried out for 30-40 min and then defoaming; a three-channel gradient co-extruder is used to coat the conductor periphery, and after extrusion, 20-25 DEG C cold water is used for shaping, and the co-extruder is controlled in three sections, wherein the inner layer temperature is controlled at 170-180 DEG C, the middle layer temperature is controlled at 160-170 DEG C, and the outer layer temperature is controlled at 150-160 DEG C;

[0096] S22. Three-stage ultraviolet light curing is adopted: 30-40 mW / cm² is sequentially irradiated for 5-8 s, 80-100 mW / cm² is sequentially irradiated for 10-12 s, and 120-150 mW / cm² is sequentially irradiated for 3-5 s, and then dried in an oven at 85-95 DEG C for 1-2 h to obtain an insulating wire core;

[0097] S3. Buffer layer coating:

[0098] S31. The surface of the insulating wire core is treated by Ar / O2 plasma;

[0099] S32. The silicone rubber-barium titanate composite slurry is coated on the periphery of the treated insulating wire core by an extruder, the extrusion temperature is 130-140 DEG C, the pulling speed is 4-6 m / min, and the cooling shaping is carried out;

[0100] S4. Shielding layer weaving:

[0101] S41. The tinned copper wire is woven by using a double-shaft servo synchronous system to obtain a shielding wire core;

[0102] S5. Protective layer preparation:

[0103] S51. Add shape memory polyurethane, composite microspheres, and light stabilizer into a supercritical CO2 reactor, and mix for 40-50 min with ultrasonic assistance;

[0104] S52. Coat the mixed system on the periphery of the shielded wire core through an extruder, set a permanent magnet array at the outlet section of the extrusion die, set the extrusion temperature to 175-190℃, and cool and shape;

[0105] S6. Post-processing:

[0106] S61. First, irradiate with 365 nm ultraviolet light for 10-15 s to activate the light-responsive crosslinking agent of the conductor elastic core;

[0107] S62. Then, irradiate with 405 nm ultraviolet light for 10-15 s to activate the light-responsive components of the insulating layer and protective layer, and complete the preparation

[0108] Example 1 provides a bending-resistant flexible cable, which comprises, from inside to outside, a conductor, an insulating layer, a buffer layer, a shielding layer, and a protective layer. The conductor: the elastic core is TPU (thermoplastic polyurethane, Shore hardness 58A) containing 0.8 wt% of light-responsive crosslinking agent (4,4'-bis(azido)diphenylmethane), and is processed with a 355 nm ultraviolet laser to form a spiral groove (depth 0.1 mm ± 0.005 mm) and pre-irradiated with 365 nm ultraviolet light for 12 s. The wire bundle is a nickel-plated copper-titanium alloy wire (single wire diameter 0.06 mm) twisted by 130 strands (twisting pitch 7 mm, constant temperature embedding at 45℃, tension deviation ≤3%).

[0109] The insulating layer: inner layer (100 parts of crosslinked polyethylene + 8 parts of amino-modified light-responsive graphene quantum dots + 3 parts of DOS), middle layer (100 parts of crosslinked polyethylene + 5 parts of quantum dots + 3 parts of DOS), and outer layer (100 parts of crosslinked polyethylene + 2.5 parts of quantum dots + 3 parts of DOS), thickness ratio 1:1.2:1, total thickness 1.0 mm; three-channel co-extrusion (inner layer 175℃, middle layer 165℃, outer layer 155℃), 20-25℃ cold water shaping, three-stage ultraviolet light curing (35 mW / cm²×6 s→90 mW / cm²×11 s→130 mW / cm²×4 s), and 90℃ hot air drying for 1.5 h.

[0110] The buffer layer: 100 parts of methyl vinyl silicone rubber + 7.5 wt% of barium titanate on the side of the insulating layer and 5.5 wt% of barium titanate on the side of the shielding layer, thickness 0.4 mm; the interface of the insulating layer is treated with Ar / O2 plasma (volume ratio 3:1, 70 W, 12 s), and is extruded and coated at 135℃ with a pulling speed of 5 m / min.

[0111] The shielding layer: tin-plated copper wire (single wire diameter 0.09 mm) is biaxially servo-synchronously woven (weaving density 96%, synchronization error 0.08%).

[0112] Protective layer: shape memory polyurethane 100 parts + composite microspheres (50-100 nm, hydroxylated graphene quantum dots account for 18 wt%) 18 parts + 0.8 parts of light stabilizer 770; the composite microspheres are axially oriented (orientation degree ≥98%) by 0.15T magnetic field assistance, mixed by supercritical CO2 (45℃, 18MPa), and then extruded at 185℃.

[0113] Post-processing: 365nm ultraviolet light (90mW / cm²×12s)→405nm ultraviolet light (110mW / cm²×12s) activates functional components.

[0114] Example 2 differs from Example 1 only in that; ① the elastic core matrix is replaced by SBS (styrene-butadiene-styrene block copolymer, butadiene segment content 35%, processing temperature 180℃); ② the protective layer composite microsphere addition amount is increased to 22 parts, and the magnetic field strength is increased to 0.2T (orientation degree ≥99%); ③ the total thickness of the insulating layer is 1.2mm, and the light intensity of the three-stage photocuring third stage is 150mW / cm²×5s. The rest of the raw materials, process parameters are consistent with Example 1.

[0115] Example 3 differs from Example 1 only in that; ① the total thickness of the insulating layer is 0.8mm, and the thickness ratio is kept at 1:1.2:1; ② the buffer layer barium titanate gradient is adjusted to 8wt% on the side close to the insulating layer and 6wt% on the side close to the shielding layer, with a thickness of 0.3mm; ③ the protective layer composite microsphere addition amount is reduced to 15 parts, and the magnetic field strength is reduced to 0.1T (orientation degree ≥98%). The rest of the raw materials, process parameters are consistent with Example 1.

[0116] Comparative Example 1 differs from Example 1 only in that: the elastic core does not add 4,4'-bis(azido)diphenylmethane (only TPU + antioxidant 1010), there is no 365nm ultraviolet light pre-irradiation step, and the spiral groove is directly embedded with metal wire after processing. The rest of the raw materials, process parameters are consistent with Example 1.

[0117] Comparative Example 2 differs from Example 1 only in that; ① the inner / middle / outer layers of the insulating layer are all "crosslinked polyethylene 100 parts + amino modified quantum dots 5 parts + DOS 3 parts" (no gradient); ② the photocuring is changed to a single condition (100mW / cm²×20s), without segmented control; ③ the three-section temperature control of the co-extruder is unified to 165℃. The rest of the raw materials, process parameters are consistent with Example 1.

[0118] Comparative Example 3 differs from Example 1 only in that; ① the surface of the insulating layer is not treated by Ar / O2 plasma; ② the buffer layer barium titanate is uniformly added by 6.5wt% (no gradient distribution), and the extrusion temperature is 140℃. The rest of the raw materials, process parameters are consistent with Example 1.

[0119] The difference between Comparative Example 4 and Example 1 is only that: ① the protective layer composite microspheres are not treated by 0.1-0.2T magnetic field (random dispersion); ② no light stabilizer 770 is added; ③ the supercritical CO2 mixing time is shortened to 30 min. The rest of the raw materials, process parameters are consistent with Example 1.

[0120] The difference between Comparative Example 5 and Example 1 is only that: ① the conductor is pure copper wire (single wire diameter 0.08 mm) twisted (no elastic core, no spiral groove, twisted pitch 10 mm); ② the insulating layer is ordinary crosslinked polyethylene (no quantum dots, no DOS); ③ the buffer layer is ordinary nitrile rubber (no barium titanate); ④ the protective layer is ordinary TPE (no shape memory function, no composite microspheres). The rest of the process parameters are simplified as industry conventional process (such as single-channel extrusion, natural cooling).

[0121] Performance comparison table

[0122]

[0123]

[0124] Bending life: Example (17.8-19.5 million times) because of the use of "elastic core light response crosslinking + insulating layer quantum dot gradient + buffer layer barium titanate gradient + protective layer composite microspheres magnetic field orientation", dispersing bending stress; Comparative Example 1 lacks elastic core light response crosslinking agent (10.5 million times), and Comparative Example 5 is a traditional structure (5.1 million times), and the stress is concentrated, resulting in a sharp decrease in life.

[0125] Insulating layer performance: Example (breakdown field strength 35.2-37.5 kV / mm, tear strength 40.5-43.8 MPa) "quantum dot gradient + segmented photocuring", strong crosslinking voltage resistance and tear resistance in the inner layer; Comparative Example 2 has no gradient + single photocuring (29.7 kV / mm, 33.2 MPa), and Comparative Example 5 has no quantum dots (20.3 kV / mm, 21.7 MPa), and the performance is not up to standard.

[0126] Buffer layer peeling strength: Example (3.0-3.3 N / mm) uses Ar / O2 plasma pretreatment to strengthen the interface; Comparative Example 3 has no pretreatment (1.6 N / mm), and the layers are easy to peel off.

[0127] Protective layer self-repair: Example (92.1-94.8%) relies on core-shell composite microspheres + magnetic field orientation; Comparative Example 4 has no magnetic field + no light stabilizer (75.3%), and the repair efficiency is low.

[0128] The above is only an embodiment of the present application, and relates to circuits and electronic components and modules, which are all prior art. Those skilled in the art can implement the present application without further description. The present application does not involve improvement of software and methods. Commonly known specific structures and characteristics in the scheme are not described in detail herein. Those skilled in the art know all common technical knowledge in the technical field of the present application before the filing date or the priority date, can know all prior art in the field, and have the ability to apply conventional experimental means before the date. Those skilled in the art can perfect and implement the present scheme based on their own ability under the guidance of the present application. Some typical known structures or known methods should not be an obstacle for those skilled in the art to implement the present application. It should be pointed out that, for those skilled in the art, a number of modifications and improvements can be made without departing from the structure of the present application. These should also be considered as the protection scope of the present application, and these will not affect the implementation effect and practicality of the present application.

Claims

1. A bending-resistant flexible cable comprising, from inside to outside, a conductor, an insulation layer, a buffer layer, a shielding layer and a protective layer, characterized in that: The conductor comprises an elastic core and a wire bundle twisted on the periphery of the elastic core; The inner layer of the insulation layer comprises the following components by weight: 100 parts of cross-linked polyethylene, 6-10 parts of amino-modified light-responsive graphene quantum dots, and 2-4 parts of plasticizer DOS; The middle layer of the insulation layer comprises the following components by weight: 100 parts of cross-linked polyethylene, 4-6 parts of amino-modified light-responsive graphene quantum dots, and 2-4 parts of plasticizer DOS; The outer layer of the insulation layer comprises the following components by weight: 100 parts of cross-linked polyethylene, 2-3 parts of amino-modified light-responsive graphene quantum dots, and 2-4 parts of plasticizer DOS; The protective layer comprises the following components by weight: 100 parts of shape memory polyurethane, 15-22 parts of composite microspheres, and 0.5-1.0 parts of light stabilizer, wherein the composite microspheres have a core-shell structure, the core is a mixture of hydroxylated graphene quantum dots and dithiodipropionic acid dihydrazide, and the shell is melamine formaldehyde resin.

2. A kink-resistant flexible electrical cable as claimed in claim 1, characterized in that: The buffer layer is a silicone rubber-barium titanate composite system with a thickness of 0.3-0.5 mm, and the interface between the buffer layer and the insulation layer is pretreated by plasma.

3. A kink-resistant flexible electrical cable as claimed in claim 2, characterized in that; The buffer layer uses methyl vinyl silicone rubber as a matrix and uniformly disperses barium titanate particles as a functional filler in the matrix, the mass fraction of barium titanate on the side of the buffer layer close to the insulation layer is 7-8 wt%, the mass fraction of barium titanate on the side of the buffer layer close to the shielding layer is 5-6 wt%, and the dielectric constant of the buffer layer decreases from the side of the insulation layer to the side of the shielding layer, forming a micro-graded distribution of the dielectric constant along the radial direction.

4. A kink-resistant flexible electrical cable as defined in claim 1, wherein: The shielding layer is a braided layer of tin-plated copper wires.

5. A kink-resistant flexible electrical cable according to claim 1, wherein: The elastic core is a thermoplastic elastomer containing 0.5-1.5 wt% of a light-responsive cross-linking agent.

6. A kink-resistant flexible electrical cable according to claim 5, wherein: The wire bundle is a nickel-plated copper-titanium alloy wire with a single wire diameter of 0.04-0.07 mm and a twisting pitch of 6-8 times the diameter of the wire bundle.

7. A kink-resistant flexible electrical cable according to claim 1, wherein: The thickness ratio of the inner layer, the middle layer, and the outer layer of the insulation layer is 1:1.2:1, and the total thickness is 0.8-1.2 mm.

8. A kink-resistant flexible electrical cable according to claim 7, wherein: The preparation method of the insulation layer comprises the following steps: Prepare the slurry of the inner layer, the middle layer, and the outer layer of the insulation layer, and perform ultrasonic dispersion for 30-40 min and then degassing; Use a three-channel co-extrusion machine to segmentally control the temperature of the inner layer at 170-180°C, the middle layer at 160-170°C, and the outer layer at 150-160°C, synchronously coat the three layers of slurry on the conductor, and then perform cold water shaping at 20-25°C; After cold water shaping, perform three-stage ultraviolet light curing by sequentially irradiating at 30-40 mW / cm² for 5-8 seconds, 80-100 mW / cm² for 10-12 seconds, and 120-150 mW / cm² for 3-5 seconds; finally, dry the insulation wire core at 85-95°C with hot air for 1-2 hours.

9. A kink-resistant flexible electrical cable according to claim 1, wherein: The composite microspheres are axially oriented by magnetic field assistance, and the magnetic field strength is 0.1-0.2 T.

10. A method for the production of a kink-resistant flexible electrical cable for the production of a kink-resistant flexible electrical cable according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: S1. Conductor preparation: S11. Add the thermoplastic elastomer, the light-responsive cross-linking agent, and the antioxidant 1010 into a double-screw extruder in proportion, melt blend at 180-200°C, and extrude into an elastic core rough blank with a diameter of 0.4-0.6 mm; S12. When the elastic core rough blank is cooled to 80-90℃, a helical groove is processed by using ultraviolet laser, and then the helical groove is pre-irradiated by 365nm ultraviolet light for 10-15s; S13. The metal wire bundle is embedded and twisted in the helical groove in a constant temperature environment of 40-50℃ to obtain a conductor; S2. Insulating layer preparation: S21. The inner, middle and outer layer slurries of the insulating layer are respectively prepared, and after ultrasonic dispersion for 30-40min, they are degassed; the three-channel gradient co-extrusion machine is used to coat the conductor periphery, and after extrusion, the 20-25℃ cold water is used for shaping, and the co-extrusion machine is controlled in three sections, wherein the inner layer temperature is controlled at 170-180℃, the middle layer temperature is controlled at 160-170℃, and the outer layer temperature is controlled at 150-160℃; S22. Adopt three-stage ultraviolet light curing: 30-40 mW / cm2 irradiation for 5-8 seconds, 80-100 mW / cm2 irradiation for 10-12 seconds, 120-150 mW / cm2 irradiation for 3-5 seconds, and then drying in an 85-95 °C oven for 1-2 h to obtain an insulated wire core. 2 30-40 mW / cm2 irradiation for 5-8 seconds, 80-100 mW / cm2 irradiation for 10-12 seconds, 120-150 mW / cm2 irradiation for 3-5 seconds, and then drying in an 85-95 °C oven for 1-2 h to obtain an insulated wire core. S3. Buffer layer coating: S31. The surface of the insulating wire core is treated by Ar / O2 plasma; S32. The silicone rubber-barium titanate composite slurry is coated on the periphery of the treated insulating wire core by using an extruder, the extrusion temperature is 130-140℃, the pulling speed is 4-6m / min, and the cooling shaping is performed; S4. Shielding layer weaving: S41. The tinned copper wire is woven by using a double-shaft servo synchronous system to obtain a shielding wire core; S5. Protective layer preparation: S51. The shape memory polyurethane, composite microspheres and light stabilizer are added into a supercritical CO2 reaction kettle, and ultrasonic assisted mixing is performed for 40-50min; S52. The mixed system is coated on the periphery of the shielding wire core by using an extruder, a permanent magnet array is arranged at the outlet section of the extrusion die, the extrusion temperature is 175-190℃, and the cooling shaping is performed; S6. Post-processing: S61. First, the conductor elastic core is activated by 365nm ultraviolet light for 10-15s to activate the light response crosslinking agent; S62. Then, the light response components of the insulating layer and the protective layer are activated by 405nm ultraviolet light for 10-15s, and the preparation is completed.

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