A low-smoke, halogen-free, high-voltage-resistant flexible cable with short-circuit temperature rise tolerance and its preparation method.

Abstract

This invention belongs to the field of cable technology and provides a low-smoke halogen-free high-voltage flexible cable with short-circuit temperature rise tolerance and its manufacturing method. The flexible cable includes a cable core, a low-smoke halogen-free elastomer support strip wrapping layer, and a low-smoke halogen-free outer sheath layer. The cable core includes an insulated core, which comprises a soft copper conductor and a cross-linked low-smoke halogen-free insulation layer covering the soft copper conductor. The low-smoke halogen-free elastomer support strip wrapping layer is formed by spirally overlapping and wrapping the low-smoke halogen-free elastomer support strip. The support strip includes a continuous phase of low-smoke halogen-free elastomer, sheet-like inorganic filler, and chopped inorganic fibers. The sheet-like inorganic filler is distributed along the in-plane direction of the support strip, which can limit insulation layer indentation, core wire displacement, and local insulation thickness reduction under the combined effects of short-circuit temperature rise and radial compression, while maintaining the cable's flexibility, low-smoke halogen-free performance, and electrical safety margin.

Description

Technical Field

[0001] This invention belongs to the field of cable technology and relates to a low-smoke halogen-free high-voltage flexible cable with short-circuit temperature rise tolerance and its preparation method. Background Technology

[0002] In practical applications, flexible cables are often installed in cable trays, wire ducts, control cabinets, and internal wiring harnesses or clamping positions within equipment. The cable exterior may be subjected to prolonged localized pressure from cable ties, clamps, clamping plates, wire harness stacking, or bending during wiring. Current design focuses on flame retardancy, low smoke, halogen-free properties, electrical insulation, aging resistance, and room-temperature bending performance. To meet the requirements for low smoke, halogen-free, and flame retardancy, a significant amount of inorganic flame-retardant filler is typically added to the insulation or sheath layer. To maintain the flexibility of the flexible cable, low-modulus polyolefin or elastomer material systems are required. While these material systems can meet general laying and usage requirements at room temperature, when a short circuit or abnormal overcurrent causes a short-term temperature rise in the conductor, the insulation layer and its outer structure are affected by internal heat transfer, reducing the material's thermomechanical support capacity. If the cable is still under clamping, stacking, binding, or bending pressure at this time, localized radial pressure can easily cause thermal indentation, cross-sectional deformation, and core wire misalignment in the insulation layer.

[0003] Furthermore, existing technologies also include methods to improve compressive strength by thickening the sheath, increasing its rigidity, or adding a rigid protective layer. However, these methods tend to weaken the flexibility and laying adaptability of flexible cables. Additionally, since the outer sheath is located on the outermost side of the cable, it is difficult to effectively constrain thermal indentation and insulation thickness reduction near the insulation layer after a short-circuit temperature rise. If only a common extruded reinforcement layer is used in the cable, the sheet-like or fibrous filler tends to distribute along the extrusion flow direction, making it difficult to form a circumferential support structure around the cable core. This results in insufficient limitation of local deformation under the combined effects of short-circuit temperature rise and radial pressure.

[0004] Therefore, existing low-smoke halogen-free flexible cables still have the following problems: how to improve the cable's resistance to indentation after the combined effects of short-circuit temperature rise and external radial pressure, limit the local thinning of the insulation layer and the core wire displacement, and maintain the electrical safety margin after short-circuit temperature rise, while maintaining the low-smoke halogen-free performance and flexibility. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a low-smoke halogen-free high-voltage flexible cable with short-circuit temperature rise tolerance and its manufacturing method. This flexible cable features a low-smoke halogen-free elastomer support strip wrapping around the cable core, and is further covered by a low-smoke halogen-free outer sheath. The support strip wrapping is formed by spirally overlapping and wrapping a low-smoke halogen-free elastomer support strip containing sheet-like inorganic fillers and chopped inorganic fibers. The sheet-like inorganic fillers are distributed along the in-plane direction of the strip, limiting insulation layer indentation, core wire displacement, and insulation thickness reduction after short-circuit temperature rise and radial compression.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a low-smoke halogen-free high-voltage flexible cable with short-circuit temperature rise tolerance, comprising a cable core, a low-smoke halogen-free elastomer support strip wrapping layer, and a low-smoke halogen-free outer sheath layer.

[0008] The cable core includes at least one insulated core, which includes a soft copper conductor and a cross-linked low-smoke halogen-free insulation layer covering the soft copper conductor.

[0009] The low-smoke halogen-free elastomer support strip wrapping layer is disposed outside the cable core, and the low-smoke halogen-free outer sheath layer covers the low-smoke halogen-free elastomer support strip wrapping layer.

[0010] The low-smoke halogen-free elastomer support strip wrapping layer is formed by spirally overlapping and wrapping the low-smoke halogen-free elastomer support strip material, which includes a low-smoke halogen-free elastomer continuous phase, sheet-like inorganic filler and chopped inorganic fibers.

[0011] Preferably, the low-smoke halogen-free elastomer support strip is a single-layer spiral overlap wrapping layer or a double-layer reverse spiral overlap wrapping layer, and the overlap rate of the low-smoke halogen-free elastomer support strip is 20%-50%.

[0012] Preferably, the thickness of the low-smoke halogen-free elastomer support strip is 0.10-0.40 mm and the width is 5-30 mm.

[0013] Preferably, the low-smoke halogen-free elastomer continuous phase is one or more of ethylene-vinyl acetate copolymer, ethylene-octene copolymer, ethylene propylene diene monomer (EPDM) rubber, and thermoplastic polyolefin elastomer.

[0014] Preferably, the sheet-like inorganic filler is one or more of sheet-like magnesium hydroxide, sheet-like aluminum hydroxide, mica powder, and talc powder; the aspect ratio of the sheet-like inorganic filler is (10-80):1, and the average particle size is 2-40 μm.

[0015] Preferably, the chopped inorganic fiber is one or more of basalt fiber, glass fiber and aluminosilicate fiber; the length of the chopped inorganic fiber is 0.3-2.0 mm and the diameter is 5-20 μm.

[0016] Preferably, the low-smoke halogen-free elastomer support tape is an irradiated cross-linked support tape.

[0017] Preferably, a low-smoke halogen-free conductor insulating layer is provided between the soft copper conductor and the cross-linked low-smoke halogen-free insulation layer. The low-smoke halogen-free conductor insulating layer is formed by extrusion of ethylene-vinyl acetate copolymer cable material, and the thickness of the low-smoke halogen-free conductor insulating layer is 0.05-0.20 mm. The cross-linked low-smoke halogen-free insulation layer is a silane cross-linked low-smoke halogen-free polyolefin insulation layer or an irradiated cross-linked low-smoke halogen-free polyolefin insulation layer. The low-smoke halogen-free outer sheath layer is a low-smoke halogen-free flexible polyolefin sheath layer.

[0018] In a second aspect, the present invention provides a method for preparing the short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable described in the first aspect, comprising the following steps:

[0019] S1, low-smoke halogen-free elastomer continuous phase, sheet-like inorganic filler, chopped inorganic fiber, non-sheet-like halogen-free flame retardant, compatibilizer and halogen-free coupling agent are mixed and then calendered into strip to obtain low-smoke halogen-free elastomer support strip.

[0020] S2, a cross-linked low-smoke halogen-free insulation layer is formed on the outside of the soft copper conductor to obtain an insulated wire core;

[0021] S3, at least one insulated wire core is cabled to obtain a cable core;

[0022] S4, the low-smoke halogen-free elastomer support tape is wrapped around the cable core in a spiral overlapping manner to obtain a support tape wrapped cable core;

[0023] S5, a low-smoke halogen-free outer sheath layer is extruded over the cable core wrapped with the support strip to obtain a low-smoke halogen-free high-pressure-resistant flexible cable with short-circuit temperature rise tolerance.

[0024] Preferably, the mass ratio of the low-smoke halogen-free elastomer continuous phase, sheet-like inorganic filler, chopped inorganic fiber, non-sheet-like halogen-free flame retardant, compatibilizer and halogen-free coupling agent is 100: (20-80): (3-15): (40-140): (2-12): (0.5-5).

[0025] Preferably, the compatibilizer is maleic anhydride-grafted polyolefin; the halogen-free coupling agent is one or both of vinyl silane coupling agents and epoxy silane coupling agents.

[0026] Preferably, in S1, the mixing temperature is 110-150℃, the rotation speed is 40-80 r / min, and the time is 8-20 min; the temperature of the calendering rolls for rolling into strip is 80-120℃, the calendering roll gap is 0.08-0.45 mm, the calendering linear speed is 2-10 m / min, and the speed ratio of adjacent calendering rolls is 1:(1.1-1.2).

[0027] Preferably, after S1 and before S4, the low-smoke halogen-free elastomer support strip is subjected to crosslinking treatment; the crosslinking treatment is irradiation crosslinking treatment, the irradiation dose of the irradiation crosslinking treatment is 80-150kGy, and the irradiation crosslinking aid is triallyl isocyanurate.

[0028] Preferably, in S2, when forming the cross-linked low-smoke halogen-free insulation layer, the barrel temperature of the insulation extruder is 120-180℃, the die head temperature is 160-180℃, and the extrusion line speed is 5-30m / min; when the cross-linked low-smoke halogen-free insulation layer is formed by silane cross-linking, the material of the cross-linked low-smoke halogen-free insulation layer contains dibutyltin dilaurate catalyst, the cross-linking treatment temperature is 80-95℃, the relative humidity is 85%-100%, and the cross-linking treatment time is 4-12h.

[0029] Preferably, in S3, the pitch of the cable forming is 8-18 times the outer diameter of the cable core; in S4, the wrapping speed of the low-smoke halogen-free elastomer support tape is 3-20 m / min; in S5, when extruding the low-smoke halogen-free outer sheath layer, the barrel temperature of the sheath extruder is 120-170℃, the die head temperature is 150-185℃, the extrusion speed is 3-25 m / min, and after extruding the low-smoke halogen-free outer sheath layer, segmented cooling is performed, with the first stage cooling water temperature being 35-55℃ and the second stage cooling water temperature being 15-30℃.

[0030] Irradiation treatment induces free radical reactions in the polymer segments of the low-smoke halogen-free elastomer continuous phase. Free radicals on ethylene, octene, vinyl acetate, and rubber segments recombine between adjacent segments, forming carbon-carbon crosslinking points. These crosslinking points connect the polymer segments, which would otherwise be subject to relative slippage, into a three-dimensional network structure. This prevents the elastomer continuous phase from undergoing melt flow as the primary deformation mode when short-circuit temperature rise is transferred to the support strip. Instead, the deformation is primarily characterized by segment conformational changes and the tensile recovery of the crosslinked network. The crosslinked network restricts the flow of the polymer phase between the sheet-like inorganic filler and the chopped inorganic fibers, reducing relative misalignment between filler layers and interfacial separation around the fibers. This ensures that the support strip maintains a continuous load-bearing interface during compression and cooling.

[0031] The ethylene segments in the continuous phase of low-smoke halogen-free elastomers share similar nonpolar segmental structures with ethylene-octene copolymers, EPDM rubber, or thermoplastic polyolefin elastomers, enabling entanglement and interdiffusion between these segments. The vinyl acetate structure in ethylene-vinyl acetate copolymers introduces ester groups, which enhance the wettability of the elastomer continuous phase on the inorganic filler surface and improve the dispersion stability of flake inorganic fillers and non-flake halogen-free flame retardants in the polymer phase during mixing. The nonpolar elastomer segments provide a flexible continuous phase, while the ester-containing segments provide contact capability with the polar filler surface. The network formed after irradiation crosslinking fixes both types of segments within the same continuous phase, reducing interfacial slippage between the elastomer and inorganic phases after short-circuit temperature rise.

[0032] The polyolefin backbone in maleic anhydride-grafted polyolefin is compatible with the continuous phase of the low-smoke, halogen-free elastomer, allowing it to enter the elastomer phase and entangle with the polyolefin segments. The grafted anhydride groups are polar, enabling them to form hydrogen bonds and dipole interactions with hydroxyl groups, adsorbed water layers, and metal-oxygen bond surface sites on the surfaces of flake magnesium hydroxide, flake aluminum hydroxide, mica, talc, and inorganic fibers. They can also undergo partial ring-opening esterification or acid-base interactions with surface hydroxyl groups. This maleic anhydride-grafted polyolefin thus forms an interfacial transition layer between the non-polar elastomer phase and the polar inorganic surface, continuously coating the filler surface with the polymer phase. This interfacial transition layer transfers shear loads under radial compression, transferring the load from the continuous elastomer phase to the flake inorganic filler and chopped inorganic fibers, rather than concentrating the load within the elastomer phase and causing localized indentation.

[0033] Vinyl silane coupling agents or epoxy silane coupling agents undergo alkoxyl hydrolysis under the influence of moisture to generate silanol groups. These silanol groups condense with hydroxyl groups on the surfaces of sheet-like inorganic fillers, non-sheet-like halogen-free flame retardants, and chopped inorganic fibers, forming siloxane bonds. Simultaneously, adjacent silanols can also condense to form a siloxane-silicon structure. The organic end of the silane molecule is located on the outer side of the inorganic surface. The vinyl end can participate in free radical reactions or entangle with elastomer segments during irradiation. The epoxy end can interact with hydroxyl groups on the filler surface, carboxyl groups after anhydride ring-opening, or polar groups in the system through polar interactions, hydrogen bonding, or partial ring-opening reactions in localized high-temperature regions. The silane coupling layer reduces the surface energy of the inorganic filler and fiber surfaces, improves their interfacial compatibility with the elastomer phase, reduces filler agglomeration during mixing, and participates in interfacial fixation after irradiation crosslinking. Since the system does not use aminosilane, the ring-opening reaction between the primary amine group and the maleic anhydride group is avoided at the mixing temperature, thus preserving the interfacial bridging effect of maleic anhydride-grafted polyolefin and the coupling effect of the silane coupling agent on the inorganic surface.

[0034] In the compounding process, the lamellar inorganic filler is co-wetted by the elastomer continuous phase, maleic anhydride-grafted polyolefin, and silane coupling layer, with the lamellar particles separated by the polymer phase. Compounding provides dispersion shear, while calendering provides in-plane shear and normal compression. The lamellar particles tend to distribute in a manner parallel to the strip surface within the roll gap shear field. This distribution is not an isolated lamellar arrangement but rather forms a multiphase layered structure along the strip thickness direction, consisting of lamellar filler, non-lamellar flame-retardant particles, and a cross-linked elastomer phase. Non-lamellar halogen-free flame retardants are distributed between and around the lamellar filler layers, filling the spaces between the layers and reducing stress concentration caused by direct contact between the lamellar particles. Chopped inorganic fibers are dispersed along the in-plane and locally inclined directions of the strip during calendering. The fibers span the polymer phase regions between the lamellar filler layers, forming a bridging structure that restricts in-plane slippage and edge warping of the layers under pressure.

[0035] Under fire or abnormally high temperature conditions, flake magnesium hydroxide, flake aluminum hydroxide, and non-flake halogen-free flame retardants undergo endothermic decomposition upon heating, releasing bound water. The released water vapor dilutes the small-molecule combustibles released from the polymer's thermal decomposition, and the resulting metal oxides remain inside the support strip. These metal oxide residues, along with mica and talc, constitute the inorganic phase framework, reducing the continuous flow path of the polymer phase under heating conditions. The halogen-free flame retardant system does not produce hydrogen halide gas. The inorganic phase barrier structure inside the support strip extends the path of thermal decomposition volatiles to migrate outwards and reduces the source of halogenated acidic components in the flue gas during combustion. This low-smoke, halogen-free reaction process occurs within the support strip itself, ensuring that the intermediate support layer does not become a source of flue gas and halogen release during low-smoke, halogen-free cabling tests.

[0036] Short-cut basalt fibers, glass fibers, or aluminosilicate fibers maintain their inorganic fiber morphology within the support tape. Their surfaces, after silane coupling, form an interfacial bond with the elastomer continuous phase. The fibers act as bridges and provide tear resistance within the support tape. When the support tape is subjected to bending, overlapping, and radial compression after wrapping, the fibers can cross the polymer phase regions between the sheet fillers, transferring localized shear stress to adjacent areas. The fiber ends are covered by the cross-linked elastomer continuous phase, and the interfacial layer restricts fiber pull-out. The fibers and sheet fillers together form a composite structure characterized by sheet-borne pressure, fiber bridging, and cross-linked elastomer constraint. Under pressure after a short-circuit temperature rise, this structure does not rely solely on the elastomer phase to withstand compression; instead, the load is transferred through the combined action of the inorganic sheets and fibers.

[0037] After the support tape is spirally wrapped around the cable core, the sheet-like filler distributed within the tape surface no longer exhibits only a layered structure within the planar sheet, but instead forms a circumferentially stacked support structure around the outer periphery of the cable core. Adjacent wrapping loops overlap in the overlapping area, and the sheet-like filler layer, chopped fibers, and cross-linked elastomer phase within the overlapping area form a multi-layered contact interface. During the extrusion of the outer sheath, the molten sheath material applies covering pressure to the support tape wrapping layer, causing the support tape to adhere to the outer surface of the cable core and maintaining tight contact in the overlapping area. After cooling, a radially bonded structure is formed between the outer sheath layer, the support tape wrapping layer, and the cable core, and a pressure-bearing path continuously distributed along the circumference of the cable is formed at the support tape overlap.

[0038] When the cable is subjected to external radial pressure, the pressure first acts on the low-smoke halogen-free outer sheath, which then transmits the pressure to the support tape wrapping. The in-plane structure of the lamellar filler in the support tape wrapping transforms the local radial load into compressive, shear, and circumferentially distributed loads along the in-plane direction of the tape. The overlap area allows adjacent wrapping loops to share the load. Short-cut inorganic fibers limit shear cracking at the tape edges and overlap interfaces, while the continuous phase of the cross-linked elastomer restricts the relative displacement of the inorganic sheets and fibers. Therefore, the pressure is not directly concentrated in localized areas of the cross-linked low-smoke halogen-free insulation layer, but rather diffuses within the support tape surface and overlap area, reducing localized compressive deformation of the insulation layer.

[0039] When the short-circuit temperature rise is transmitted outward from the soft copper conductor, the cross-linked low-smoke halogen-free insulation layer first bears the internal thermal shock. The cross-linked network in the cross-linked insulation layer restricts the flow of the insulating material chains under heat, but the insulation layer still tends to undergo thermal compression due to radial pressure. The support tape wrapping layer is located on the outside of the insulation layer, providing peripheral restraint when the insulation layer softens due to heat. Because the support tape itself is irradiated and cross-linked, the continuous phase of the elastomer does not form a continuous melt flow channel under temperature rise, and the sheet-like inorganic filler and chopped inorganic fibers are still fixed within the cross-linked network. The support tape wrapping layer forms a circumferential restraint on the outer periphery of the insulation layer, making it less likely for the insulation layer to bulge outward or inward locally when short-circuit temperature rise and external pressure are present simultaneously, thus limiting the offset of the soft copper conductor relative to the center of the insulation layer.

[0040] When a low-smoke halogen-free conductor insulating layer is placed between a soft copper conductor and a cross-linked low-smoke halogen-free insulation layer, the insulating layer penetrates the recessed area on the outer periphery of the stranded soft copper conductor, filling the local gaps formed by the stranding of copper wires. Under the influence of short-circuit temperature rise and electromagnetic force, the individual filaments in the soft copper conductor may experience slight relative displacement, and the protrusions and burrs on the outer periphery of the conductor can create localized stress concentration on the inner surface of the insulation. The conductor insulating layer, with a flexible low-smoke halogen-free polymer phase covering the outer periphery of the conductor, separates the discontinuous protrusions on the surface of the copper wires from the inner surface of the cross-linked insulation layer, changing the stress on the inner side of the insulation layer from point contact to surface contact. This interface structure reduces the penetration effect of conductor thermal expansion and filament fretting on the inner surface of the insulation layer, and together with the outer support strip wrapping layer, limits localized damage on both the inner and outer sides of the insulation layer.

[0041] When the outer sheath uses a low-smoke halogen-free flexible polyolefin system, its polyolefin segments have a similar non-polar structure to the low-smoke halogen-free elastomer continuous phase in the support strip. During extrusion, the molten sheath material wets into contact with the surface of the support strip. The surface of the support strip contains a cross-linked elastomer phase, compatibilizer, and a small amount of polar groups. After the outer sheath cools, a mechanical interlocking and segment contact interface is formed between it and the support strip. This interface does not need to form a rigid adhesive layer; instead, the support strip is restricted from loosening within the outer sheath by the covering pressure and surface adhesion. When the cable bends, the support strip wrapping layer can continuously bend along with the outer sheath and the cable core. When the cable is under pressure, the outer sheath transmits the pressure to the support strip wrapping layer, which then bears the load diffusion and circumferential constraint.

[0042] The support tape is first calendered into a strip and then irradiated for crosslinking. This allows the in-plane distribution structure of the sheet filler to form first in the processing flow field, and then be fixed by irradiation crosslinking. If crosslinking is performed before the formation of the sheet filler orientation structure, the reduced fluidity of the polymer phase will limit the rearrangement of the filler in the calendering shear field; if crosslinking is not performed, the continuous elastomer phase will experience significant chain segment slippage during short-circuit temperature rise, increasing the relative displacement between the sheet filler and the fibers. The process sequence of calendering followed by irradiation ensures that the in-plane distribution of the sheet filler, the bridging distribution of the chopped fibers, and the elastomer crosslinking network are retained in the same support tape. After wrapping, the support tape forms a circumferential laminated support structure that can bend with the cable and maintain interfacial continuity under heat and pressure.

[0043] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention provides a support strip wrapping layer outside the cable core, formed by a spiral overlap of low-smoke halogen-free elastomer support strip. This allows the sheet-like inorganic filler in the support strip to be distributed along the in-plane direction of the strip, forming a circumferentially stacked support structure outside the cable core. This structure can disperse external radial pressure to the circumferential and overlapping areas, reducing local pressure concentration on the insulation layer under short-circuit temperature rise conditions, and limiting thermal indentation, core wire displacement, and local thickness reduction of the insulation layer. After radiation cross-linking, the continuous phase of the elastomer in the support strip maintains structural continuity when heated and forms a stable interface with the sheet-like inorganic filler and chopped inorganic fibers, improving the recovery capability of the support strip under pressure. This flexible cable maintains low-smoke halogen-free performance and flexible laying performance while improving the compressive strength and electrical safety margin under combined short-circuit temperature rise and mechanical compression conditions. Attached Figure Description

[0044] Figure 1 This is an SEM image of the cross-section of the low-smoke halogen-free elastomer support strip prepared in Example 1 of the present invention. Detailed Implementation

[0045] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0046] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0047] The ethylene-vinyl acetate copolymer used in the embodiments and comparative examples of this invention is 7470K from Formosa Plastics Ningbo or a commercially available product with equivalent performance; the ethylene-octene copolymer is commercially available POE for cable materials; the ethylene propylene diene monomer (EPDM) rubber is commercially available EPDM for cable materials; the thermoplastic polyolefin elastomer is commercially available TPO for cable materials; the vinyl silane coupling agent is WD-21 from Hubei Wuda Organosilicon New Materials Co., Ltd.; the epoxy silane coupling agent is WD-60 from Hubei Wuda Organosilicon New Materials Co., Ltd.; the cross-linked low-smoke halogen-free polyolefin insulation material is 101H from Zhejiang Wanma Polymer Materials Group Co., Ltd.; and the low-smoke halogen-free flexible polyolefin sheathing material is WM-Z125PA from Zhejiang Wanma Polymer Materials Group Co., Ltd.

[0048] Example 1

[0049] This embodiment provides a short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable and its preparation method. The preparation method specifically includes the following steps:

[0050] S1, a low-smoke halogen-free elastomer continuous phase, sheet-like inorganic filler, chopped inorganic fibers, non-sheet-like halogen-free flame retardant, compatibilizer, halogen-free coupling agent, and radiation crosslinking aid are mixed and then calendered into a strip to obtain a low-smoke halogen-free elastomer support strip; wherein, the low-smoke halogen-free elastomer continuous phase is ethylene-vinyl acetate copolymer, the compatibilizer is maleic anhydride-grafted polyolefin, the halogen-free coupling agent is vinyl silane coupling agent, and the radiation crosslinking aid is triallyl isocyanurate; the sheet-like inorganic filler is sheet-like magnesium hydroxide with a diameter-to-thickness ratio of 10:1 and an average particle size of 2μm; the chopped inorganic fibers are basalt fibers, short... The length of the cut inorganic fiber is 0.3 mm and the diameter is 5 μm; the non-flaky halogen-free flame retardant is non-flaky aluminum hydroxide; the mass ratio of the low-smoke halogen-free elastomer continuous phase, flaky inorganic filler, chopped inorganic fiber, non-flaky halogen-free flame retardant, compatibilizer, halogen-free coupling agent and radiation crosslinking aid is 100:20:3:40:2:0.5:1.5; the mixing temperature is 110℃, the rotation speed is 40 r / min, and the time is 8 min; the temperature of the calendering rolls for calendering the strip is 80℃, the calendering roll gap is 0.08 mm, the calendering linear speed is 2 m / min, and the speed ratio of adjacent calendering rolls is 1:1.1; Figure 1 The image shows an SEM photograph of the cross-section of the low-smoke halogen-free elastomer support strip. As shown, the sheet-like inorganic filler is distributed along the in-plane direction of the strip, forming a roughly layered structure. The continuous elastomer phase fills the spaces between the sheet-like filler layers, and the chopped inorganic fibers span multiple sheet-like regions along the in-plane direction or locally at an angle. After being calendered into a strip, the low-smoke halogen-free elastomer support strip is subjected to irradiation crosslinking treatment with an irradiation dose of 80 kGy to obtain an irradiated crosslinked support strip. The low-smoke halogen-free elastomer support strip has a thickness of 0.10 mm and a width of 5 mm.

[0051] S2, a low-smoke halogen-free conductor isolation layer is extruded over a Class 5 soft copper conductor, and then a cross-linked low-smoke halogen-free insulation layer is formed over the low-smoke halogen-free conductor isolation layer to obtain an insulated wire core; wherein, the low-smoke halogen-free conductor isolation layer is formed by extruding ethylene-vinyl acetate copolymer cable material, and the thickness of the low-smoke halogen-free conductor isolation layer is 0.05mm; the cross-linked low-smoke halogen-free insulation layer is formed using silane cross-linked low-smoke halogen-free polyolefin insulation material containing dibutyltin dilaurate catalyst; when forming the cross-linked low-smoke halogen-free insulation layer, the barrel temperature of the insulation extruder is 120℃, the die head temperature is 160℃, the extrusion line speed is 5m / min; the cross-linking treatment temperature is 80℃, the relative humidity is 85%, and the cross-linking treatment time is 4h;

[0052] S3, the three insulated wire cores are bundled together to obtain the cable core; wherein, the pitch of the bundled cable is 8 times the outer diameter of the cable core;

[0053] S4, the low-smoke halogen-free elastomer support tape is wrapped around the cable core in a spiral overlap manner to obtain the support tape wrapped cable core; wherein, the low-smoke halogen-free elastomer support tape wrapping layer is a single-layer spiral overlap wrapping layer, the overlap rate of the low-smoke halogen-free elastomer support tape is 20%; the wrapping line speed is 3m / min.

[0054] S5, a low-smoke halogen-free outer sheath layer is extruded over the support tape wrapped around the cable core to obtain a low-smoke halogen-free high-voltage-resistant flexible cable with short-circuit temperature rise resistance; wherein, the low-smoke halogen-free outer sheath layer is a low-smoke halogen-free flexible polyolefin sheath layer; during the extrusion of the low-smoke halogen-free outer sheath layer, the barrel temperature of the sheath extruder is 120℃, the die head temperature is 150℃, and the extrusion line speed is 3m / min; after the low-smoke halogen-free outer sheath layer is extruded, segmented cooling is performed, with the first stage cooling water temperature being 35℃ and the second stage cooling water temperature being 15℃.

[0055] Example 2

[0056] This embodiment provides a short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable and its preparation method. The preparation method specifically includes the following steps:

[0057] S1. A low-smoke halogen-free elastomer continuous phase, sheet-like inorganic filler, chopped inorganic fibers, non-sheet-like halogen-free flame retardant, compatibilizer, halogen-free coupling agent, and radiation crosslinking aid are blended and then calendered into a strip to obtain a low-smoke halogen-free elastomer support strip. The low-smoke halogen-free elastomer continuous phase consists of ethylene-vinyl acetate copolymer and ethylene-octene copolymer, with a mass ratio of ethylene-vinyl acetate copolymer to ethylene-octene copolymer of 70:30. The compatibilizer is maleic anhydride-grafted polyolefin, the halogen-free coupling agent is an epoxy silane coupling agent, and the radiation crosslinking aid is triallyl isocyanurate. The sheet-like inorganic filler is sheet-like aluminum hydroxide with a diameter-to-thickness ratio of 30:1 and an average particle size of 12 μm. The chopped inorganic fibers are glass fibers with a length of 0.8 mm and a diameter of 10 μm. The non-flaky halogen-free flame retardant is non-flaky magnesium hydroxide; the mass ratio of the low-smoke halogen-free elastomer continuous phase, flaky inorganic filler, chopped inorganic fiber, non-flaky halogen-free flame retardant, compatibilizer, halogen-free coupling agent, and irradiation crosslinking aid is 100:40:7:70:5:1.5:2.5; the mixing temperature is 125℃, the rotation speed is 55r / min, and the time is 12min; the calendering roll temperature is 95℃, the calendering roll gap is 0.18mm, the calendering linear speed is 4.5m / min, and the speed ratio of adjacent calendering rolls is 1:1.2; after calendering, the low-smoke halogen-free elastomer support strip is subjected to irradiation crosslinking treatment with an irradiation dose of 100kGy to obtain the irradiated crosslinked support strip; the thickness of the low-smoke halogen-free elastomer support strip is 0.20mm, and the width is 12mm;

[0058] S2, a low-smoke halogen-free conductor isolation layer is extruded over a Class 5 soft copper conductor, and then a cross-linked low-smoke halogen-free insulation layer is formed over the low-smoke halogen-free conductor isolation layer to obtain an insulated wire core; wherein, the low-smoke halogen-free conductor isolation layer is formed by extruding ethylene-vinyl acetate copolymer cable material, and the thickness of the low-smoke halogen-free conductor isolation layer is 0.10 mm; the cross-linked low-smoke halogen-free insulation layer is formed using silane cross-linked low-smoke halogen-free polyolefin insulation material containing dibutyltin dilaurate catalyst; when forming the cross-linked low-smoke halogen-free insulation layer, the barrel temperature of the insulation extruder is 140℃, the die head temperature is 167℃, the extrusion line speed is 12 m / min; the cross-linking treatment temperature is 85℃, the relative humidity is 90%, and the cross-linking treatment time is 7 h;

[0059] S3, the four insulated wire cores are bundled together to obtain the cable core; wherein, the pitch of the bundled cable is 11 times the outer diameter of the cable core;

[0060] S4, the low-smoke halogen-free elastomer support tape is wrapped around the cable core in a spiral overlap manner to obtain the support tape wrapped cable core; wherein, the low-smoke halogen-free elastomer support tape wrapping layer is a single-layer spiral overlap wrapping layer, the overlap rate of the low-smoke halogen-free elastomer support tape is 30%; the wrapping line speed is 8m / min.

[0061] S5, a low-smoke halogen-free outer sheath layer is extruded over the cable core wrapped with a support strip to obtain a low-smoke halogen-free high-voltage-resistant flexible cable with short-circuit temperature rise tolerance; wherein, the low-smoke halogen-free outer sheath layer is a low-smoke halogen-free flexible polyolefin sheath layer; during the extrusion of the low-smoke halogen-free outer sheath layer, the barrel temperature of the sheath extruder is 140℃, the die head temperature is 162℃, and the extrusion line speed is 9m / min; after the low-smoke halogen-free outer sheath layer is extruded, segmented cooling is performed, with the first stage cooling water temperature being 42℃ and the second stage cooling water temperature being 20℃.

[0062] Example 3

[0063] This embodiment provides a short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable and its preparation method. The preparation method specifically includes the following steps:

[0064] S1. A low-smoke halogen-free elastomer continuous phase, sheet-like inorganic filler, chopped inorganic fibers, non-sheet-like halogen-free flame retardant, compatibilizer, halogen-free coupling agent, and radiation crosslinking aid are blended and then calendered into a strip to obtain a low-smoke halogen-free elastomer support strip. The low-smoke halogen-free elastomer continuous phase consists of ethylene-octene copolymer and ethylene propylene diene monomer (EPDM) rubber, with a mass ratio of 60:40. The compatibilizer is maleic anhydride-grafted polyolefin. The halogen-free coupling agent consists of vinyl silane coupling agent and epoxy silane coupling agent, with a mass ratio of 1:1. The radiation crosslinking aid is triallyl isocyanurate. The sheet-like inorganic filler is mica powder, with an aspect ratio of 50:1 and an average particle size of 25 μm. The chopped inorganic fibers are aluminosilicate fibers, with a length of 1.4 m. The diameter is 15 μm; the non-flaky halogen-free flame retardant is non-flaky magnesium hydroxide and zinc borate; the mass ratio of low-smoke halogen-free elastomer continuous phase, flaky inorganic filler, chopped inorganic fiber, non-flaky halogen-free flame retardant, compatibilizer, halogen-free coupling agent and irradiation crosslinking aid is 100:60:11:105:8:3:3.5; the mixing temperature is 140℃, the rotation speed is 70 r / min, the time is 16 min, and the speed ratio of adjacent calendering rolls is 1:1.13; the calendering roll temperature for calendering the strip is 110℃, the calendering roll gap is 0.30 mm, and the calendering linear speed is 7 m / min; after calendering, the low-smoke halogen-free elastomer support strip is subjected to irradiation crosslinking treatment with an irradiation dose of 125 kGy to obtain irradiated crosslinked support strip; the thickness of the low-smoke halogen-free elastomer support strip is 0.30 mm and the width is 20 mm;

[0065] S2, a low-smoke halogen-free conductor isolation layer is extruded over a Class 5 soft copper conductor, and then a cross-linked low-smoke halogen-free insulation layer is formed over the low-smoke halogen-free conductor isolation layer to obtain an insulated wire core; wherein, the low-smoke halogen-free conductor isolation layer is formed by extruding ethylene-vinyl acetate copolymer cable material, and the thickness of the low-smoke halogen-free conductor isolation layer is 0.15mm; the cross-linked low-smoke halogen-free insulation layer is formed using silane cross-linked low-smoke halogen-free polyolefin insulation material containing dibutyltin dilaurate catalyst; when forming the cross-linked low-smoke halogen-free insulation layer, the barrel temperature of the insulation extruder is 160℃, the die head temperature is 174℃, the extrusion line speed is 20m / min; the cross-linking treatment temperature is 90℃, the relative humidity is 95%, and the cross-linking treatment time is 10h;

[0066] S3, the six insulated wire cores are bundled together to obtain the cable core; wherein, the pitch of the bundled cable is 15 times the outer diameter of the cable core;

[0067] S4, the low-smoke halogen-free elastomer support tape is wrapped around the cable core in a spiral overlapping manner to obtain the support tape wrapped cable core; wherein, the low-smoke halogen-free elastomer support tape wrapping layer is a double-layer reverse spiral overlapping wrapping layer, the overlap rate of the low-smoke halogen-free elastomer support tape is 40%; the wrapping line speed is 14m / min.

[0068] S5, a low-smoke halogen-free outer sheath layer is extruded over the cable core wrapped with a support strip to obtain a low-smoke halogen-free high-voltage-resistant flexible cable with resistance to short-circuit temperature rise conditions; wherein, the low-smoke halogen-free outer sheath layer is a low-smoke halogen-free flexible polyolefin sheath layer; during the extrusion of the low-smoke halogen-free outer sheath layer, the barrel temperature of the sheath extruder is 155℃, the die head temperature is 174℃, and the extrusion line speed is 16m / min; after the low-smoke halogen-free outer sheath layer is extruded, segmented cooling is performed, with the first stage cooling water temperature being 48℃ and the second stage cooling water temperature being 25℃.

[0069] Example 4

[0070] This embodiment provides a short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable and its preparation method. The preparation method specifically includes the following steps:

[0071] S1. A low-smoke halogen-free elastomer continuous phase, sheet-like inorganic filler, chopped inorganic fibers, non-sheet-like halogen-free flame retardant, compatibilizer, halogen-free coupling agent, and radiation crosslinking aid are blended and then calendered into a strip to obtain a low-smoke halogen-free elastomer support strip. The low-smoke halogen-free elastomer continuous phase consists of ethylene-vinyl acetate copolymer, ethylene propylene diene monomer (EPDM) rubber, and thermoplastic polyolefin elastomer, with a mass ratio of 40:20:40. The compatibilizer is maleic anhydride-grafted polyolefin, the halogen-free coupling agent is an epoxy silane coupling agent, and the radiation crosslinking aid is triallyl isocyanurate. The sheet-like inorganic filler is talc powder with a diameter-to-thickness ratio of 80:1 and an average particle size of 40 μm. The chopped inorganic fibers are basalt fiber and glass fiber, with a length of 2.0 m. The diameter is 20 μm; the non-flaky halogen-free flame retardant is non-flaky magnesium hydroxide and zinc borate; the mass ratio of low-smoke halogen-free elastomer continuous phase, flaky inorganic filler, chopped inorganic fiber, non-flaky halogen-free flame retardant, compatibilizer, halogen-free coupling agent and irradiation crosslinking aid is 100:80:15:140:12:5:5; the mixing temperature is 150℃, the rotation speed is 80 r / min, and the time is 20 min; the calendering roll temperature is 120℃, the calendering roll gap is 0.45 mm, the calendering linear speed is 10 m / min, and the speed ratio of adjacent calendering rolls is 1:1.17; after calendering, the low-smoke halogen-free elastomer support strip is subjected to irradiation crosslinking treatment with an irradiation dose of 150 kGy to obtain irradiated crosslinked support strip; the thickness of the low-smoke halogen-free elastomer support strip is 0.40 mm and the width is 30 mm;

[0072] S2, a low-smoke halogen-free conductor isolation layer is extruded over a Class 5 soft copper conductor, and then a cross-linked low-smoke halogen-free insulation layer is formed over the low-smoke halogen-free conductor isolation layer to obtain an insulated wire core; wherein, the low-smoke halogen-free conductor isolation layer is formed by extruding ethylene-vinyl acetate copolymer cable material, and the thickness of the low-smoke halogen-free conductor isolation layer is 0.20 mm; the cross-linked low-smoke halogen-free insulation layer is formed using silane cross-linked low-smoke halogen-free polyolefin insulation material containing dibutyltin dilaurate catalyst; when forming the cross-linked low-smoke halogen-free insulation layer, the barrel temperature of the insulation extruder is 180°C, the die head temperature is 180°C, the extrusion line speed is 30 m / min; the cross-linking treatment temperature is 95°C, the relative humidity is 100%, and the cross-linking treatment time is 12 h;

[0073] S3, eight insulated wire cores are bundled together to obtain a cable core; wherein, the pitch of the bundled cable is 18 times the outer diameter of the cable core;

[0074] S4, the low-smoke halogen-free elastomer support tape is wrapped around the cable core in a spiral overlapping manner to obtain the support tape wrapped cable core; wherein, the low-smoke halogen-free elastomer support tape wrapping layer is a double-layer reverse spiral overlapping wrapping layer, the overlap rate of the low-smoke halogen-free elastomer support tape is 50%; the wrapping line speed is 20m / min.

[0075] S5, a low-smoke halogen-free outer sheath layer is extruded over the support tape wrapped cable core to obtain a low-smoke halogen-free high-voltage-resistant flexible cable with short-circuit temperature rise resistance; wherein, the low-smoke halogen-free outer sheath layer is a low-smoke halogen-free flexible polyolefin sheath layer; during the extrusion of the low-smoke halogen-free outer sheath layer, the barrel temperature of the sheath extruder is 170℃, the die head temperature is 185℃, and the extrusion line speed is 25m / min; after the low-smoke halogen-free outer sheath layer is extruded, segmented cooling is performed, with the first stage cooling water temperature being 55℃ and the second stage cooling water temperature being 30℃.

[0076] Comparative Example 1

[0077] This comparative example provides a low-smoke halogen-free high-voltage flexible cable with short-circuit temperature rise tolerance and its preparation method. The difference between this and Example 1 is that the low-smoke halogen-free elastomer support layer is not provided. Specifically, steps S1 and S4 in Example 1 are omitted. After obtaining the cable core in step S3, a low-smoke halogen-free outer sheath layer is directly extruded over the cable core to obtain the low-smoke halogen-free flexible cable. All other materials, structures, and process parameters are the same as in Example 1.

[0078] Comparative Example 2

[0079] This comparative example provides a low-smoke halogen-free high-voltage flexible cable with short-circuit temperature rise tolerance and its preparation method. The difference between this and Example 1 is that the low-smoke halogen-free elastomer support tape is not subjected to radiation crosslinking treatment after being calendered. Specifically, in step S1, the low-smoke halogen-free elastomer continuous phase, sheet-like inorganic filler, chopped inorganic fibers, non-sheet-like halogen-free flame retardant, compatibilizer, halogen-free coupling agent, and radiation crosslinking aid are mixed and calendered into a tape to directly obtain an uncrosslinked low-smoke halogen-free elastomer support tape. This uncrosslinked low-smoke halogen-free elastomer support tape is used for the spiral overlap wrapping in step S4. All other materials, structures, and process parameters are the same as in Example 1.

[0080] Comparative Example 3

[0081] This comparative example provides a low-smoke halogen-free high-voltage flexible cable with short-circuit temperature rise tolerance and its preparation method. The difference between this and Example 1 is that the low-smoke halogen-free elastomer support strip does not contain sheet-like inorganic fillers. Specifically, in step S1, the sheet-like magnesium hydroxide in Example 1 is replaced with an equal mass of non-sheet-like magnesium hydroxide, so that no sheet-like structure formed in the support strip due to the distribution of sheet-like inorganic fillers along the in-plane direction of the strip is formed. All other materials, structures, and process parameters are the same as in Example 1.

[0082] Comparative Example 4

[0083] This comparative example provides a low-smoke halogen-free high-voltage flexible cable with short-circuit temperature rise tolerance and its preparation method. The difference between this and Example 1 is that the low-smoke halogen-free elastomer support tape does not contain chopped inorganic fibers. Specifically, in step S1, basalt fibers are omitted and replaced with an equal mass of low-smoke halogen-free elastomer continuous phase. The remaining materials, structures, and process parameters are the same as in Example 1.

[0084] Comparative Example 5

[0085] This comparative example provides a low-smoke halogen-free high-voltage flexible cable with short-circuit temperature rise tolerance and its preparation method. The difference between this and Example 1 is that the low-smoke halogen-free elastomer support tape does not employ a spiral overlapping wrapping structure. Specifically, in step S4, the low-smoke halogen-free elastomer support tape is wrapped around the cable core in a spiral, non-overlapping manner, with the edges of adjacent support tapes but not overlapping, so that the low-smoke halogen-free elastomer support tape wrapping layer does not form a continuous overlapping area. All other materials, structures, and process parameters are the same as in Example 1.

[0086] Performance testing:

[0087] The cables prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to performance tests. The test items included the low smoke halogen-free and combustion performance of the finished cables, the indentation depth after short-circuit temperature rise cycle, the outer diameter recovery rate after short-circuit temperature rise cycle, the insulation thickness retention rate after short-circuit temperature rise cycle, and the power frequency withstand voltage after short-circuit temperature rise cycle.

[0088] The tests for the low-smoke halogen-free and combustion performance of the finished cables included halogen acid gas release testing, combustion gas aqueous solution pH value testing, combustion gas aqueous solution conductivity testing, smoke density testing, and single-strand vertical combustion testing. The results are shown in Table 1.

[0089] The halogen acid gas release test was conducted according to GB / T 17650.1-2021. Non-metallic materials from the finished cable were used as samples and burned in a tube furnace. The gases released during combustion were absorbed by the absorbent liquid, and the total amount of halogen acid gas in the absorbent liquid was measured. A halogen acid gas release of no more than 0.5% was considered a pass; a halogen acid gas release of more than 0.5% was considered a fail.

[0090] The pH value and conductivity of the combustion gas aqueous solution were tested according to GB / T 17650.2-2021. Non-metallic materials from the finished cable were used as samples and burned in a tubular furnace, allowing the combustion-released gases to enter the absorbent liquid. The pH value and conductivity of the absorbent liquid were then tested. A test was considered passed if the pH value of the combustion gas aqueous solution was not less than 4.3 and the conductivity was not greater than 10 μS / mm; a test was considered failed if the pH value was less than 4.3 or the conductivity was greater than 10 μS / mm.

[0091] Smoke density testing was conducted according to GB / T 17651.2-2021. Finished cables were used as samples and burned in a specified smoke density test chamber. Changes in light transmittance during the test were recorded, and the minimum transmittance was taken as the test result. A minimum transmittance of 60% or higher was considered a pass; a minimum transmittance of less than 60% was considered a fail.

[0092] The single-strand vertical combustion test was conducted according to GB / T 18380.12-2022. A finished cable was used as the sample. The sample was fixed vertically, and a 1kW premixed flame was applied for the time corresponding to the sample's outer diameter. After removing the flame, the flame spread and charring range were observed. The sample was considered passed if it could self-extinguish, and the distance from the lower edge of the upper support to the upper starting point of charring was greater than 50mm, the lower end of charring did not extend downwards to a position more than 540mm from the lower edge of the upper support, and the distance from the upper end of charring to the lower end of charring did not exceed 425mm. If any of the above conditions were not met, the test was considered failed.

[0093] The comprehensive evaluation criteria for the low-smoke halogen-free and combustion performance of finished cables are as follows: when the halogen acid gas release, the pH value of the combustion gas aqueous solution, the conductivity of the combustion gas aqueous solution, the smoke density, and the single-strand vertical combustion test all pass, the finished cable is deemed to have passed the low-smoke halogen-free and combustion performance; if any one of these tests fails, the finished cable is deemed to have failed the low-smoke halogen-free and combustion performance.

[0094] The short-circuit temperature rise cyclic compression test was conducted using the following method: A finished cable sample was taken, and a pressure test area was selected in the middle of the sample. The cable outer diameter D0 of the pressure test area before the test was measured. The sample was placed between two parallel pressure plates, and the plates applied radial pressure to the sample. The radial pressure was calculated as 0.5 MPa based on the contact area between the pressure plates and the cable. After the pressure was applied, a pre-calibrated high-current generator was used to supply current to the conductor, raising the conductor temperature to 250℃±10℃ and holding it for 5 seconds. Then, the current was stopped, and the conductor was cooled to room temperature while maintaining the radial pressure. This "heating-holding-cooling" process was repeated 5 times. After completion, the conductor was unloaded and left at room temperature for 30 minutes.

[0095] The test method for indentation depth after short-circuit temperature rise cycle is as follows: After completing the short-circuit temperature rise cycle combined compression test, measure the outer diameter D1 of the pressure test area in the pressure direction after unloading. The indentation depth after short-circuit temperature rise cycle is calculated as D0-D1. At least three test positions are selected for each sample, and the average value is taken as the indentation depth of the sample after short-circuit temperature rise cycle.

[0096] The test method for the outer diameter recovery rate after short-circuit temperature rise cycle is as follows: Calculate the outer diameter of the cable before and after the short-circuit temperature rise cycle combined compression test. The outer diameter recovery rate after short-circuit temperature rise cycle is D1 / D0×100%. Where D0 is the outer diameter of the cable in the pressure test area before the test, and D1 is the outer diameter in the pressure direction after the short-circuit temperature rise cycle combined compression test is completed and the cable is unloaded and placed.

[0097] The test method for insulation thickness retention rate after short-circuit temperature rise cycling is as follows: Take a cable cross-section corresponding to the pressure test area, cut it along the pressure direction, and measure the thinnest point thickness T1 of the cross-linked low-smoke halogen-free insulation layer at the pressure location using a projector or micro-measuring device; take another cable sample from the same batch that has not undergone short-circuit temperature rise cycle composite compression test, and measure the thinnest point thickness T0 of the cross-linked low-smoke halogen-free insulation layer at the corresponding location. The insulation thickness retention rate after short-circuit temperature rise cycling is calculated as T1 / T0 × 100%.

[0098] The power frequency withstand voltage test after short-circuit temperature rise cycle was conducted after the short-circuit temperature rise cycle combined compression test. The ends of the cable samples that had completed the combined compression test were stripped and waterproofed. The samples were then immersed in room temperature water, ensuring the pressure test area was completely submerged. After immersion, a power frequency AC voltage was applied between the conductor and the water electrode. For multi-core cables, power frequency AC voltage was applied sequentially between each conductor and the remaining conductors and the water electrode. The test voltage was 2.5 kV, the frequency was 50 Hz, and the duration was 5 minutes. If no breakdown, flashover, or continuous discharge occurred during the test, the power frequency withstand voltage after short-circuit temperature rise cycle was considered passed; if breakdown, flashover, or continuous discharge occurred, the power frequency withstand voltage after short-circuit temperature rise cycle was considered failed. Specific results are shown in Table 2.

[0099] Table 1. Test results of low-smoke halogen-free and combustion performance of finished cables from Examples 1-4 and Comparative Examples 1-5

[0100]

[0101] Table 2 Performance test results of finished cables after short-circuit temperature rise cycles in Examples 1-4 and Comparative Examples 1-5

[0102]

[0103] As shown in Table 1, the finished cables obtained in Examples 1-4 all meet the requirements for low smoke halogen-free and combustion performance; the finished cables obtained in Comparative Examples 1-5 also passed the low smoke halogen-free and combustion performance tests, indicating that the samples are comparable in terms of low smoke halogen-free and combustion performance.

[0104] As shown in Table 2, compared to Example 1, Comparative Example 1, lacking a low-smoke halogen-free elastomer support strip wrapping layer, experienced increased indentation depth, decreased outer diameter recovery rate and insulation thickness retention rate after short-circuit temperature rise cycles, and failed the power frequency withstand voltage test. Comparative Example 2, without radiation cross-linking of the support strip, also experienced increased indentation depth, decreased outer diameter recovery rate and insulation thickness retention rate after short-circuit temperature rise cycles, and failed the power frequency withstand voltage test. Comparative Example 3, lacking sheet-like inorganic filler, experienced increased indentation depth, decreased outer diameter recovery rate and insulation thickness retention rate after short-circuit temperature rise cycles. Comparative Example 4, lacking chopped inorganic fibers, experienced increased indentation depth, decreased outer diameter recovery rate and insulation thickness retention rate after short-circuit temperature rise cycles. Comparative Example 5, lacking a spiral overlapping wrapping structure, experienced increased indentation depth, decreased outer diameter recovery rate and insulation thickness retention rate after short-circuit temperature rise cycles, and failed the power frequency withstand voltage test.

[0105] This is because, in Comparative Example 1, the lack of a circumferential laminated support structure outside the cable core allows external radial pressure to be directly transmitted to the insulation layer under short-circuit temperature rise conditions, resulting in increased insulation layer indentation and localized thinning; in Comparative Example 2, the support strip does not form an irradiated cross-linked network, leading to increased chain segment slippage of the elastomer continuous phase after short-circuit temperature rise, and reduced interfacial constraint of the support strip on the sheet-like inorganic filler and chopped inorganic fibers; in Comparative Example 3, the lack of sheet-like inorganic filler distributed along the in-plane direction of the strip makes it difficult for radial pressure to diffuse to the circumferential and overlapping areas via the support strip; in Comparative Example 4, the lack of bridging effect of chopped inorganic fibers reduces the shear resistance of the support strip in the pressure-bearing and overlapping areas; and in Comparative Example 5, the absence of an overlapping area and the lack of overlapping pressure-bearing paths between adjacent support strips makes it easy for localized radial pressure to be transmitted to the insulation layer via the edge of the support strip.

[0106] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A low-smoke, halogen-free, high-voltage-resistant flexible cable with short-circuit temperature rise tolerance, characterized in that... This includes the cable core, a low-smoke halogen-free elastomer support strip wrapping layer, and a low-smoke halogen-free outer sheath layer; The cable core includes at least one insulated core, which includes a soft copper conductor and a cross-linked low-smoke halogen-free insulation layer covering the soft copper conductor. The low-smoke halogen-free elastomer support strip wrapping layer is disposed outside the cable core, and the low-smoke halogen-free outer sheath layer covers the low-smoke halogen-free elastomer support strip wrapping layer. The low-smoke halogen-free elastomer support strip wrapping layer is formed by spirally overlapping and wrapping the low-smoke halogen-free elastomer support strip material, which includes a low-smoke halogen-free elastomer continuous phase, sheet-like inorganic filler and chopped inorganic fibers.

2. The short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable according to claim 1, characterized in that, The low-smoke halogen-free elastomer support strip is wrapped with a single-layer spiral overlap or a double-layer reverse spiral overlap, and the overlap rate of the low-smoke halogen-free elastomer support strip is 20%-50%.

3. The short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable according to claim 1, characterized in that, The thickness of the low-smoke halogen-free elastomer support strip is 0.10-0.40 mm, and the width is 5-30 mm.

4. The short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable according to claim 1, characterized in that, The continuous phase of the low-smoke halogen-free elastomer is one or more of the following: ethylene-vinyl acetate copolymer, ethylene-octene copolymer, ethylene propylene diene monomer (EPDM) rubber, and thermoplastic polyolefin elastomer.

5. The short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable according to claim 1, characterized in that, The sheet-like inorganic filler is one or more of sheet-like magnesium hydroxide, sheet-like aluminum hydroxide, mica powder, and talc powder; the aspect ratio of the sheet-like inorganic filler is 10-80:1, and the average particle size is 2-40μm.

6. The short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable according to claim 1, characterized in that, The chopped inorganic fibers are one or more of basalt fibers, glass fibers, and aluminosilicate fibers; the length of the chopped inorganic fibers is 0.3-2.0 mm, and the diameter is 5-20 μm.

7. The short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable according to claim 1, characterized in that, A low-smoke halogen-free conductor insulating layer is disposed between the soft copper conductor and the cross-linked low-smoke halogen-free insulation layer. The low-smoke halogen-free conductor insulating layer is formed by extrusion of ethylene-vinyl acetate copolymer cable material, and the thickness of the low-smoke halogen-free conductor insulating layer is 0.05-0.20 mm. The cross-linked low-smoke halogen-free insulation layer is a silane cross-linked low-smoke halogen-free polyolefin insulation layer or an irradiated cross-linked low-smoke halogen-free polyolefin insulation layer. The low-smoke halogen-free outer sheath layer is a low-smoke halogen-free flexible polyolefin sheath layer.

8. A method for preparing a short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable according to any one of claims 1-7, characterized in that, Includes the following steps: S1, low-smoke halogen-free elastomer continuous phase, sheet-like inorganic filler, chopped inorganic fiber, non-sheet-like halogen-free flame retardant, compatibilizer and halogen-free coupling agent are mixed and then calendered into strip to obtain low-smoke halogen-free elastomer support strip. S2, a cross-linked low-smoke halogen-free insulation layer is formed on the outside of the soft copper conductor to obtain an insulated wire core; S3, at least one insulated wire core is cabled to obtain a cable core; S4, the low-smoke halogen-free elastomer support tape is wrapped around the cable core in a spiral overlapping manner to obtain a support tape wrapped cable core; S5, a low-smoke halogen-free outer sheath layer is extruded over the cable core wrapped with the support strip to obtain a low-smoke halogen-free high-pressure-resistant flexible cable with short-circuit temperature rise tolerance.

9. The method for preparing a short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable according to claim 8, characterized in that, In S1, the mass ratio of the low-smoke halogen-free elastomer continuous phase, the sheet-like inorganic filler, the chopped inorganic fiber, the non-sheet-like halogen-free flame retardant, the compatibilizer, and the halogen-free coupling agent is 100:20-80:3-15:40-140:2-12:0.5-5. The mixing temperature is 110-150℃, the rotation speed is 40-80 r / min, and the time is 8-20 min. The temperature of the calendering rolls for calendering the strip is 80-120℃, the calendering roll gap is 0.08-0.45 mm, the calendering linear speed is 2-10 m / min, and the speed ratio of adjacent calendering rolls is 1:1.1-1.

2.

10. The method for preparing a short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable according to claim 8, characterized in that, After S1 and before S4, the low-smoke halogen-free elastomer support strip is subjected to cross-linking treatment. The crosslinking treatment is an irradiation crosslinking treatment, and the irradiation dose of the irradiation crosslinking treatment is 80-150 kGy.

11. The method for preparing a short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable according to claim 8, characterized in that, In S2, when forming the cross-linked low-smoke halogen-free insulation layer, the barrel temperature of the insulation extruder is 120-180℃, the die head temperature is 160-180℃, and the extrusion line speed is 5-30m / min; when the cross-linked low-smoke halogen-free insulation layer is formed by silane cross-linking, the material of the cross-linked low-smoke halogen-free insulation layer contains dibutyltin dilaurate catalyst, the cross-linking treatment temperature is 80-95℃, the relative humidity is 85%-100%, and the cross-linking treatment time is 4-12h.

12. The method for preparing a short-circuit temperature rise resistant, low-smoke, halogen-free, high-voltage-resistant flexible cable according to claim 8, characterized in that, In S3, the cable pitch is 8-18 times the outer diameter of the cable core; in S4, the wrapping speed of the low-smoke halogen-free elastomer support tape is 3-20 m / min; in S5, when extruding the low-smoke halogen-free outer sheath layer, the barrel temperature of the sheath extruder is 120-170℃, the die head temperature is 150-185℃, the extrusion speed is 3-25 m / min, and after extruding the low-smoke halogen-free outer sheath layer, segmented cooling is performed, with the first stage cooling water temperature being 35-55℃ and the second stage cooling water temperature being 15-30℃.

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