Low-smoke halogen-free flame-retardant crosslinked polyethylene cable and silane crosslinking preparation method thereof

Abstract

The invention belongs to a low-smoke halogen-free flame-retardant crosslinked polyethylene cable and a silane crosslinking preparation method. A sheath layer is prepared from the following raw materials: 40 to 60 parts of LDPE (Low-Density Polyethylene), 20 to 30 parts of LLDPE (Linear Low-Density Polyethylene), 120 to 160 parts of compound flame retardant (ATH / MDF = 2: 1 to 1: 1, and KH-550 modification), 5 to 10 parts of flame-retardant synergist (zinc borate / organic silicon resin = 3: 1), 1.5 to 3 parts of VTMS (Vinyl Trimethylsilyl Sulfonate) and 0.05 to 0.15 part of dibutyltin dilaurate. During preparation, a dynamic crosslinking process is adopted and comprises the following steps: premixing a base material at 110-125 DEG C, dispersing a flame retardant at 130-140 DEG C, injecting a catalyst and silane at 85-95 DEG C in stages, carrying out extrusion coating, carrying out crosslinking with warm water at 90-95 DEG C, and carrying out gradient cooling. The design realizes triple breakthrough: (1) the dispersibility is improved by surface modification of the flame retardant, and the oxygen index is greater than 35%; (2) the catalyst is injected in stages, so that the crosslinking efficiency is improved by 23.3%; and (3) the synergist forms a ceramic carbon layer in a synergistic manner, and the heat release peak value is less than 100kW / m < 2 >. The tensile retention rate after the cable is aged at 136 DEG C is greater than 85%, and the cable is suitable for extreme scenes such as fire-fighting wiring of nuclear power stations and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer material modification, and specifically relates to a halogen-free flame-retardant polyolefin cable material and a silane cross-linking preparation process thereof, which is suitable for manufacturing special cables for extreme environments such as subways and high-rise buildings. Background Art

[0002] In special scenarios such as subway tunnel power supply networks and high-rise building fire protection wiring, cables must simultaneously meet multiple extreme performance requirements: zero smoke toxicity release (light transmittance ≥ 80%), halogen-free flame retardancy (oxygen index ≥ 32%), and long-term stability at high temperatures (mechanical property retention rate > 85% at 105°C). Although traditional polyvinyl chloride (PVC) cables have basic flame retardancy, the hydrogen halide gas and thick smoke released during combustion can seriously hinder evacuation. Halogen-free polyolefin cables face a core contradiction - to achieve the same flame retardancy level, they must be filled with a large amount of inorganic hydroxide (such as more than 150 parts of ATH / MDH). However, the extremely high filling content will lead to three fatal defects:

[0003] (1) Deterioration of processability: High-hardness particles experience severe abrasion during mixing, and the risk of melt fracture increases during screw extrusion.

[0004] (2) Mechanical performance collapse: The tensile strength drops by more than 40%, and the sheath layer's crack resistance cannot meet dynamic laying requirements;

[0005] (3) Cross-linking inhibition effect: The flame retardant surface adsorbs silane cross-linking agent, making the warm water cross-linking degree less than 60%, resulting in a heat deformation temperature lower than 90°C.

[0006] The current technical route has systemic limitations:

[0007] Although the irradiation cross-linking solution can improve the material's temperature resistance, the investment in electron accelerator equipment exceeds 10 million yuan, and the high-density flame retardant causes uneven radiation penetration, with cross-linking degree fluctuations exceeding 30%.

[0008] Peroxide chemical crosslinking requires high-temperature vulcanization above 170°C, but ATH / MDH begins to dehydrate and decompose at 140°C, causing bubbles in the jacket layer and flame retardant failure;

[0009] Although silane grafting cross-linking technology has the advantage of low-temperature processing, the competitive reaction between flame retardants and silanes in conventional processes reduces the cross-linking efficiency by more than 50%, and catalyst poisoning causes the cross-linking cycle to be as long as 24 hours.

[0010] In addition, existing flame retardant systems often add antimony-based synergists to compensate for performance defects, which violates the halogen-free environmental protection requirements; and the zinc borate compounding technology does not solve the compatibility problem with the polyethylene matrix, and loses flame retardancy after migration and precipitation.

[0011] Therefore, it is urgent to develop a sheath material system that combines processability with ultra-high flame retardant filling content, high efficiency of silane cross-linking reaction and long-term thermal stability. Through innovations in flame retardant surface engineering and dynamic cross-linking processes, a breakthrough in the overall performance of cables for special scenarios can be achieved. Summary of the Invention

[0012] In order to solve the above problems, the present invention discloses a low-smoke, halogen-free, flame-retardant cross-linked polyethylene cable and a silane cross-linking preparation method thereof.

[0013] The purpose of the present invention is achieved through the following technical solutions.

[0014] A low-smoke, halogen-free, flame-retardant cross-linked polyethylene cable, comprising a conductor and a sheath layer from the inside out, wherein the raw materials of the sheath layer include, by weight:

[0015]

[0016]

[0017] The compound halogen-free flame retardant is composed of aluminum hydroxide ATH and magnesium hydroxide MDH in a mass ratio of 2:1-1:1, has a particle size D50 of 1-5 μm, and is surface-modified with a silane coupling agent KH-550.

[0018] Furthermore, in the above-mentioned cable, the silane crosslinking agent is vinyltrimethoxysilane VTMS with a purity of ≥99%, and the organic tin catalyst is dibutyltin dilaurate.

[0019] Furthermore, in the above-mentioned cable, the flame retardant synergist is compounded by zinc borate and silicone resin in a mass ratio of 3:1.

[0020] The present invention also discloses a silane cross-linking preparation method of the low-smoke halogen-free flame-retardant cross-linked polyethylene cable, comprising the following steps:

[0021] (1) Premixing of base materials: Add LDPE, LLDPE, antioxidant 1010, and zinc stearate lubricant into an internal mixer and mix at 110-125°C for 5-8 minutes;

[0022] (2) Flame retardant dispersion: Add compound halogen-free flame retardant and flame retardant synergist, heat to 130-140℃ and mix for 10-15 minutes;

[0023] (3) Dynamic crosslinking: Cool to 85-95°C, add silane crosslinker and organotin catalyst, and continue mixing for 3-5 minutes;

[0024] (4) Extrusion granulation: The mixed material is granulated by a twin-screw extruder, and the barrel temperature is controlled at 100 / 115 / 125 / 135°C;

[0025] (5) Cable forming: The pellets are extruded and coated on the conductor to form a sheath layer;

[0026] (6) Warm water crosslinking: Place the formed cable in a 90-95℃ hot water bath for crosslinking for 8-12 hours.

[0027] Furthermore, in the above preparation method, in step (3), the catalyst is added in two stages: 70% of the total amount is added first and premixed with the base material, and the remaining 30% is injected 2 minutes before the addition of silane.

[0028] Furthermore, in the above preparation method, step (6) is followed by gradient cooling after cross-linking: 75°C water bath for 1 hour → 50°C water bath for 0.5 hour → air cooling at room temperature.

[0029] The present invention also discloses the application of the low-smoke, halogen-free, flame-retardant cross-linked polyethylene cable, which is used for wiring of fire protection systems in nuclear power plants, subway tunnels, and high-rise buildings, with an operating temperature range of -40°C to 105°C.

[0030] Furthermore, the above-mentioned low-smoke halogen-free flame-retardant cross-linked polyethylene cable has a light transmittance of ≥80% after being tested for smoke density according to GB / T 17651.2; and a self-extinguishing time of ≤30 seconds when burning vertically according to GB / T 18380.12.

[0031] Furthermore, the above-mentioned low-smoke halogen-free flame-retardant cross-linked polyethylene cable has an oxygen index of ≥32% (GB / T 2406.2) and a tensile strength retention rate of ≥85% after heat aging at 136°C for 168h, GB / T 2951.12.

[0032] Compared with the existing technology, the present invention has the following advantages and beneficial effects:

[0033] 1. The present invention achieves a breakthrough improvement in low-smoke, halogen-free, flame-retardant, cross-linked polyethylene cables through the innovation of compound flame retardant surface engineering and dynamic cross-linking process:

[0034] 2. Synergistic flame retardancy: ATH / MDH compound (120-160 parts) modified with KH-550, synergized with zinc borate / silicone resin synergist, the oxygen index reaches 35.2% and the self-extinguishing time is ≤ 22 seconds (Test Example 1), the peak heat release is reduced by more than 34%, and a continuous ceramic carbon layer is formed during combustion to isolate oxygen;

[0035] 3. Improved cross-linking efficiency: The staged catalyst injection process achieves a gel content of 78.5%, shortening the cross-linking cycle to 10 hours (Test Example 2), solving the problem of cross-linking inhibition caused by high-filled flame retardants.

[0036] 4. Adaptability to extreme environments: Tensile strength retention rate after heat aging at 136°C > 88% (Test Example 3), no damage after impact at -40°C (Test Example 4), volume resistivity after wet heat aging remains at 2.1×1015 Ω·m (Test Case 6), meeting the long-term operation requirements of nuclear power plants at 105°C;

[0037] 5. Qualitative improvement in safety performance: smoke transmittance ≥ 83.5% (national standard ≥ 60%), HCl / HCN release is undetectable (test case 5), and the escape time window for personnel in fire scenes is extended by 3 times.

[0038] 6. Comprehensively solve the impossible triangle of "processability-mechanical properties-crosslinking degree" of highly filled flame retardant systems, filling the gap in cable technology for scenarios such as nuclear power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Comparison of oxygen index (OI) (%) for flame retardant synergistic effect verification;

[0040] Figure 2 Comparison of self-extinguishing time (s) for flame retardant synergistic effect verification;

[0041] Figure 3 Peak HRR (kW / m 2 ) comparison;

[0042] Figure 4 Tensile strength retention rate (%) of the performance retention rate test after heat aging;

[0043] Figure 5 Elongation at break retention (%) of performance retention test after heat aging. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below. However, it should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the scope of the invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention. All raw materials in the embodiments of the present invention can be obtained through commercial channels.

[0045] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0046] Table 1 List of raw materials

[0047]

[0048] Example 1

[0049] A low-smoke, halogen-free, flame-retardant cross-linked polyethylene cable sheath layer material, comprising, by weight:

[0050]

[0051]

[0052] Preparation of compound halogen-free flame retardant:

[0053] Aluminum hydroxide (ATH) and magnesium hydroxide (MDH) were mixed in a mass ratio of 2:1 (80 parts of ATH + 40 parts of MDH), with a particle size D50 of 5 μm, and surface-modified with a silane coupling agent KH-550 (added in an amount of 1.5 wt%).

[0054] Flame retardant synergist: zinc borate: silicone resin = 3:1 (3.75 parts of zinc borate + 1.25 parts of silicone resin).

[0055] Preparation method:

[0056] 1. Premix base materials: Add LDPE, LLDPE, antioxidant 1010 and zinc stearate into internal mixer and mix at 110℃ for 8 minutes;

[0057] 2. Flame retardant dispersion: Add compound flame retardant and synergist, heat to 130℃ and mix for 15 minutes;

[0058] 3. Dynamic crosslinking: Cool down to 85°C, inject the catalyst in two stages (first add 70% premix, then add the remaining 30% and VTMS after 2 minutes), and mix for 5 minutes;

[0059] 4. Extrusion granulation: twin-screw extruder (temperature zone 100 / 115 / 125 / 135℃);

[0060] 5. Cable forming: sheath layer extrusion coating;

[0061] 6. Warm water crosslinking: crosslink in a 90°C water bath for 12 hours → gradient cooling (75°C / 1 hour → 50°C / 0.5 hour → air cooling).

[0062] Example 2

[0063] A low-smoke, halogen-free, flame-retardant cross-linked polyethylene cable sheath layer material, comprising, by weight:

[0064]

[0065] Compound flame retardant: ATH:MDH=1.5:1 (84 parts of ATH+56 parts of MDH), D50=3 μm, KH-550 modified (2 wt%).

[0066] Flame retardant synergist: zinc borate: silicone resin = 3:1 (6 parts zinc borate + 2 parts silicone resin).

[0067] Preparation method:

[0068] 1. Premixing of base materials: Mixing at 125℃ for 5 minutes;

[0069] 2. Flame retardant dispersion: Mix at 140°C for 10 minutes;

[0070] 3. Dynamic crosslinking: inject catalyst + VTMS in stages at 95℃ and mix for 3 minutes;

[0071] 4.5 Extrusion granulation and cable forming (same as in Example 1);

[0072] 6. Warm water crosslinking: crosslink at 95℃ for 10 hours → gradient cooling.

[0073] Example 3

[0074] Sheath layer materials by weight:

[0075]

[0076] Compound flame retardant: ATH:MDH=1:1 (80 parts of ATH+80 parts of MDH), D50=1 μm, KH-550 modified (2.5 wt%).

[0077] Flame retardant synergist: zinc borate: silicone resin = 3:1 (7.5 parts of zinc borate + 2.5 parts of silicone resin).

[0078] Preparation method: Same as Example 2, except that the mixing temperature was adjusted to 135°C.

[0079] Comparative Example 1

[0080] (missing flame retardant synergist)

[0081] The components are the same as those in Example 2, except that the flame retardant synergist is deleted (zinc borate and silicone resin are not added).

[0082] Comparative Example 2

[0083] (Unmodified flame retardant)

[0084] The components are the same as those in Example 2, but the compounded flame retardant is not surface treated with KH-550.

[0085] Comparative Example 3

[0086] (Catalyst is added at one time)

[0087] The components are the same as those in Example 2. In the preparation method, the catalyst is added all at once (not injected in stages).

[0088] Comparative Example 4

[0089] (Single flame retardant)

[0090] Component adjustment:

[0091] The compound flame retardant was replaced with 160 parts of ATH (without MDH).

[0092] The rest is the same as Example 2.

[0093] Comparative Example 5

[0094] (Commercial reference)

[0095] Commercially available halogen-free flame-retardant polyolefin sheathing materials (Dow Engage TM 8400), flame retardant content 140 parts (mainly aluminum hydroxide).

[0096] Test Example 1

[0097] Verification of flame retardant synergistic effect

[0098] Objective: To evaluate the synergistic effect of compound flame retardants (ATH / MDH) and synergists (zinc borate / silicone resin).

[0099] method:

[0100] Sample: Example 2 (complete formulation) vs. Comparative Examples 1-5

[0101] Test standard:

[0102] Oxygen index (OI): GB / T 2406.2

[0103] Vertical combustion: GB / T 18380.12 (flame applied for 60 seconds)

[0104] Heat release rate (HRR): Cone calorimeter (ISO 5660, 50kW / m 2 radiation).

[0105] The results are shown in Table 2 and Figure 1-3 As shown:

[0106] Table 2 Comparison of flame retardant properties

[0107] Group Oxygen index OI (%) Self-extinguishing time (s) <![CDATA[Peak HRR (kW / m 2 )]]> Example 2 35.2 22 98 Comparative Example 1 31.5 38 148 Comparative Example 2 32.1 35 132 Comparative Example 4 28.7 52 205 Comparative Example 5 30.3 45 182

[0108] in conclusion:

[0109] The peak heat release rate of Example 2 was 34% lower than that of Comparative Example 1 (*P<0.01). Scanning electron microscopy revealed that the synergist promoted the formation of a continuous ceramic carbon layer (thickness >50 μm), which isolated oxygen diffusion. The ATH / MDH blend increased the oxygen index by 22.6% compared to ATH alone (Comparative Example 4), demonstrating the necessity of synergy.

[0110] Test Example 2

[0111] Comparison of cross-linking process efficiency

[0112] Purpose: To verify the effect of catalyst injection in stages on the degree of crosslinking

[0113] method:

[0114] Determination of cross-linking degree: xylene extraction method

[0115] Thermal deformation test: Apply 0.2MPa load in 200℃ oil bath and record the time to 50% deformation

[0116] Comparison group:

[0117] Example 2 (catalyst injection in stages)

[0118] Comparative Example 3 (adding catalyst at one time)

[0119] The results are shown in Table 3:

[0120] Table 3 Comparison of cross-linking process performance

[0121] Group Gel content (%) Thermal deformation time (min) Crosslinking cycle (h) Example 2 78.5±1.2 42±3 10 Comparative Example 3 63.7±2.1 18±2 16

[0122] in conclusion:

[0123] Staged injection increased cross-linking efficiency by 23.3% (*P<0.01) and shortened cross-linking time by 37.5%. Infrared spectroscopy confirmed that staged injection reduced adsorption of the silane coupling agent by the flame retardant (the intensity of the C-Si characteristic peak increased by 1.8 times).

[0124] Test Example 3

[0125] High temperature long-term stability

[0126] Purpose: To evaluate the mechanical property retention after aging at 136°C

[0127] method:

[0128] Accelerated aging: 136°C hot air aging oven for 168 hours (GB / T 2951.12)

[0129] Detection indicators:

[0130] Tensile strength: GB / T 1040.2

[0131] Elongation at break: GB / T 1040.2

[0132] The results are shown in Table 4:

[0133] Table 4 Performance retention rate after thermal aging

[0134] Group Tensile strength retention rate% Elongation at break retention % Example 2 88.2 85.7 Comparative Example 2 72.3 68.5 Comparative Example 5 65.1 61.9

[0135] in conclusion:

[0136] The flame retardant surface modification (KH-550) increased the tensile strength retention of Example 2 by 22% (*P<0.01) compared to Comparative Example 2. DSC showed that the modified flame retardant increased the crystallinity of polyethylene (melting enthalpy increased by 15.7 J / g).

[0137] Test Example 4

[0138] Dynamic laying adaptability

[0139] Purpose: To simulate the crack resistance of subway tunnels under bending conditions

[0140] method:

[0141] Bending test:

[0142] The cable is bent 10 times around a Φ20D pulley (D = cable diameter)

[0143] Detection of the number of cracks in the sheath layer (observation under a microscope at 50 times magnification)

[0144] Low temperature shock: Drop ball impact at -40°C (1kg steel ball at 1m height)

[0145] The results are shown in Table 5 and Figure 4-5 As shown:

[0146] Table 5 Dynamic mechanical properties

[0147] Group Number of bending cracks (cracks / m) Low temperature impact breakage rate Example 2 0.8±0.3 0％ Comparative Example 1 3.2±0.7 40％ Comparative Example 5 5.1±1.2 100％

[0148] in conclusion:

[0149] The flame retardant synergist (zinc borate / organic silicone resin) improves the toughness of the material, and Example 2 is not damaged by low-temperature impact. Energy spectrum analysis shows that the organosilicone resin forms a SiO2 self-healing layer (Si element enrichment >8at%) at the crack tip.

[0150] Test Example 5

[0151] Smoke toxicity safety verification

[0152] Purpose: To measure smoke transmittance and toxic gases in fire scenes

[0153] method:

[0154] Smoke density: GB / T 17651.2 (flame radiation mode)

[0155] Gas analysis: FTIR online detection of HCl and HCN release (ISO 19702)

[0156] The results are shown in Table 6:

[0157] Table 6 Flue gas safety performance

[0158] Group Light transmittance (%) HCl release (mg / g) HCN release (mg / g) Example 2 83.5±2.1 Not detected Not detected PVC cable 41.2±3.7 28.7±1.5 5.3±0.8

[0159] in conclusion:

[0160] The halogen-free system achieves zero toxic gas release, and the light transmittance exceeds the national standard (≥60%) by 39.2%. Animal exposure experiments (ISO 5659-2) show that the survival rate of mice in the Example 2 group is 100% (60% in the PVC group).

[0161] Test Example 6

[0162] Long-term reliability in hot and humid environments

[0163] Purpose: To verify the electrical performance stability in a high humidity environment of a nuclear power plant

[0164] method:

[0165] Accelerated damp heat aging: 85°C / 85% RH for 1000h (IEC 60216)

[0166] Detection indicators:

[0167] Volume resistivity: IEC 60093

[0168] Dielectric strength: IEC 60243

[0169] The results are shown in Table 7:

[0170] Table 7 Electrical properties after damp heat aging

[0171]

[0172]

[0173] in conclusion:

[0174] The silane cross-linked network inhibits the penetration of water molecules, and the resistivity retention rate of Example 2 is 84% ​​(only 25% in Comparative Example 2).

[0175] From the above test examples, it can be seen that the technical solution of the present invention has the following advantages:

[0176] Flame retardant synergy (Test Example 1): The compound flame retardant + synergist increased the oxygen index by 22.6% (vs. single-component ATH), and the peak HRR dropped to 98kW / m 2 ;

[0177] Process advancement (Test Case 2): Staged catalyst injection shortened the crosslinking cycle by 37.5% and achieved a gel content of 78.5%;

[0178] Long-term reliability (Test Case 3 / 6): 136℃ aging tensile retention rate 88.2%, 85℃ / 85%RH damp heat aging resistivity retention 10 15 Ω·m level;

[0179] Dynamic safety (Test Case 4 / 5): No damage after impact at -40°C, bending cracks <1 / m, smoke transmittance 83.5% and zero toxic gas release.

[0180] Conclusion: All performance indicators exceed GB / IEC standards, especially in the highly filled flame retardant system (160 parts):

[0181] Processability (melt flow rate > 0.5g / 10min);

[0182] Safety (UL94 V-0 grade + smoke density level SDR ≤ 15);

[0183] A synergistic breakthrough in durability (lifespan > 40 years at 105°C).

[0184] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, based on the innovative concept of the present invention, changes and modifications to the embodiments described herein, or changes and modifications made using the contents of the present invention, etc.

[0185] Equivalent structure or equivalent process transformation, directly or indirectly apply the above technical solutions to other related

[0186] The relevant technical fields are all included in the protection scope of the patent of this invention.

Claims

1. A low-smoke, halogen-free, flame-retardant cross-linked polyethylene cable, characterized in that: From the inside to the outside, it includes a conductor and a sheath layer, and the raw materials of the sheath layer include, by weight: The compound halogen-free flame retardant is composed of aluminum hydroxide ATH and magnesium hydroxide MDH in a mass ratio of 2:1-1:1, has a particle size D50 of 1-5 μm, and is surface-modified with a silane coupling agent KH-550.

2. The low-smoke, halogen-free, flame-retardant cross-linked polyethylene cable according to claim 1, characterized in that: The silane crosslinking agent is vinyl trimethoxysilane VTMS, with a purity of ≥99%, and the organic tin catalyst is dibutyltin dilaurate.

3. The low-smoke, halogen-free, flame-retardant cross-linked polyethylene cable according to claim 1, characterized in that: The flame retardant synergist is prepared by compounding zinc borate and silicone resin in a mass ratio of 3:

1.

4. The silane cross-linking preparation method of the low-smoke halogen-free flame-retardant cross-linked polyethylene cable according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Premixing of base materials: Add LDPE, LLDPE, antioxidant 1010, and zinc stearate lubricant into an internal mixer and mix at 110-125°C for 5-8 minutes; (2) Flame retardant dispersion: Add compound halogen-free flame retardant and flame retardant synergist, heat to 130-140℃ and mix for 10-15 minutes; (3) Dynamic crosslinking: Cool to 85-95°C, add silane crosslinker and organotin catalyst, and continue mixing for 3-5 minutes; (4) Extrusion granulation: The mixed material is granulated by a twin-screw extruder, and the barrel temperature is controlled at 100 / 115 / 125 / 135°C; (5) Cable forming: The pellets are extruded and coated on the conductor to form a sheath layer; (6) Warm water crosslinking: Place the formed cable in a 90-95℃ hot water bath for crosslinking for 8-12 hours.

5. The preparation method according to claim 4, characterized in that: In step (3), the catalyst is added in two stages: 70% of the total amount is added first and premixed with the base material, and the remaining 30% is injected 2 minutes before the addition of the silane.

6. The preparation method according to claim 4, characterized in that: Step (6) After cross-linking, the temperature was gradually lowered as follows: 75° C. water bath for 1 hour → 50° C. water bath for 0.5 hour → air cooling to room temperature.

7. Use of the low-smoke, halogen-free, flame-retardant cross-linked polyethylene cable according to any one of claims 1 to 3, characterized in that: Used for fire protection system wiring in subway tunnels or high-rise buildings, with an operating temperature range of -40℃ to 105℃.

8. The low-smoke, halogen-free, flame-retardant cross-linked polyethylene cable according to any one of claims 1 to 3, characterized in that: According to the smoke density test of GB / T 17651.2, the light transmittance is ≥80%; according to GB / T 18380.12, the self-extinguishing time of vertical combustion is ≤30 seconds.

9. The low-smoke, halogen-free, flame-retardant cross-linked polyethylene cable according to any one of claims 1 to 3, characterized in that: Oxygen index ≥32% (GB / T 2406.2), tensile strength retention rate ≥85% after heat aging at 136℃×168h, GB / T2951.12.

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