Fluoroplastic-low smoke halogen-free composite insulated cable material for new energy and preparation method of fluoroplastic-low smoke halogen-free composite insulated cable material

Abstract

The invention discloses a fluoroplastic-low-smoke halogen-free composite insulated cable material for new energy and a preparation method of the fluoroplastic-low-smoke halogen-free composite insulated cable material, and relates to the technical field of polymer composite insulating materials. Aiming at the problems of thermodynamic incompatibility and mutual performance restriction of fluoroplastic and low-smoke halogen-free polyolefin, a modified filler with a core-shell-crown three-stage structure is prepared through Mg < 2 + > homologous catalysis, polydopamine-melamine formaldehyde in-situ interpenetrating network polymerization and ethylene-vinyl acetate oligomer grafting; and a double-screw step-by-step melt blending process is combined, so that molecular-level compatibility of fluoroplastic and polyolefin is realized. A synergistic flame retardant or a dispersing agent does not need to be additionally added, interface compatibility, flame-retardant synergistic and anti-agglomeration functions are integrated, the product has high temperature resistance, excellent flame retardance, mechanical toughness and low-smoke characteristics, the process is compatible with an existing production line, the industrialization cost is low, and the composite material is suitable for the new energy fields of electric automobile high-voltage wiring harnesses, photovoltaic / wind power cables and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer composite insulation materials technology, specifically to a fluoroplastic-low smoke halogen-free composite insulating cable material suitable for the new energy field and its preparation method. Background Technology

[0002] The rapid development of the new energy industry has placed stringent demands on cable insulation materials: they must simultaneously possess the high temperature resistance, weather resistance, and low-smoke halogen-free flame retardant properties of fluoroplastics, while also maintaining excellent mechanical toughness and electrical insulation performance. However, fluoroplastics have extremely low surface energy, resulting in severe thermodynamic incompatibility with low-smoke halogen-free polyolefin matrices and inorganic flame-retardant fillers. This leads to defects such as phase separation, delamination, and mechanical property degradation in traditional composite systems.

[0003] In existing technologies, the core approach to solving the aforementioned interfacial incompatibility problem is to add compatibilizers such as silane coupling agents and maleic anhydride-grafted polyolefins. However, these compatibilizers can only achieve interfacial bonding through single chemical grafting or physical adsorption, and they are still difficult to suppress agglomeration under high filler loading, resulting in a trade-off between the flame retardant efficiency and mechanical toughness of the composite material. For example, when increasing the amount of inorganic filler to improve flame retardancy, the elongation at break will significantly decrease to below 180%; when increasing the amount of fluoroplastics to improve temperature resistance, the smoke density easily exceeds 70, failing to meet the low smoke requirements.

[0004] Therefore, developing an integrated modification scheme that can simultaneously solve interface compatibility, flame retardancy enhancement, and anti-agglomeration has become a key technological bottleneck in the field of new energy cable insulation materials. Summary of the Invention

[0005] In view of this, the present invention proposes a fluoroplastic-low smoke halogen-free composite insulating cable material for new energy and its preparation method. The aim is to overcome the interface compatibility bottleneck between fluoroplastic and low smoke halogen-free polyolefin by designing a core-shell-crown three-level structure modified filler and combining it with a stepwise melt blending process, so as to achieve synergistic improvement of multiple properties.

[0006] The technical solution of this invention is achieved as follows: This invention provides a method for preparing a fluoroplastic-low-smoke halogen-free composite insulating cable material for new energy applications, comprising two core steps: the preparation of a three-level structure modified filler and the melt blending and granulation of the composite cable material. Specifically, this is achieved through Mg... 2+ A three-step modification process involving directional activation, PDA-melamine formaldehyde (MF) in-situ interpenetrating network (IPN) shell polymerization, and EVA oligomer canopy grafting, combined with twin-screw stepwise lateral feeding extrusion, yields a high-performance composite insulated cable material. The method also provides a composite insulated cable material that achieves a quadruple balance of temperature resistance, flame retardancy, toughness, and low smoke through specific raw material ratios and structural design.

[0007] In some embodiments, the preparation of the tertiary structure modified filler includes: mixing magnesium hydroxide and aluminum hydroxide in a mass ratio of 1:1 to form an inorganic flame retardant filler core, dispersing it in deionized water (solid-liquid ratio 1:10-15), ultrasonically dispersing for 30 min, adding 3-6 wt% magnesium nitrate of the inorganic flame retardant filler weight, and stirring for 20-40 min for surface activation.

[0008] Magnesium hydroxide / aluminum filler itself contains Mg 2+ Exogenously added magnesium nitrate provides additional Mg 2+ It can form stable coordination bonds with the hydroxyl groups on the filler surface, providing directional catalytic sites for subsequent PDA polymerization (accelerating the oxidation and quinone conversion of catechols), and can also form a Mg3N2 / MgO composite carbon layer with the nitrogen element of the MF prepolymer during combustion. This achieves a synergistic effect of catalysis, interface enhancement, and flame retardancy, unlike the Cu in existing technologies that only perform a single catalytic function. 2+ Fe 3+ Catalysts solve the compatibility problem between catalysts and systems from the source.

[0009] In some implementations, Mg 2+ After activation, in-situ polymerization is carried out: the activated filler is transferred to a mixture of Tris-HCl buffer solution at pH 8.0-8.5 and ethanol (ethanol volume percentage 5-15%, solid-liquid ratio 1:12-18), nitrogen is purged for 15 min, and then 2-4 wt% of dopamine is added. The mixture is stirred at 20-30℃ for 8-12 h, then heated to 45-55℃ and 6-10 wt% of MF prepolymer is added. The mixture is stirred for another 12-18 h, and then centrifuged, washed with water and dried to obtain the core-shell structure filler.

[0010] In an alkaline environment, PDA in Mg 2+ Catalytic directional polymerization forms a base coating, whose catechol groups can form π-π stacking and hydrogen bonding with the fluoroplastic surface. During the heating process, the MF prepolymer undergoes a cross-linking reaction with the amino and quinone groups of PDA to form an interpenetrating network (IPN) composite shell. This structure not only improves the density and temperature resistance of the coating, but also enhances the carbonization efficiency through the synergistic effect of nitrogen and phosphorus. It can achieve flame retardant enhancement without the need to add additional synergistic flame retardants, solving the defect of conventional PDA modification that can only adhere but cannot simultaneously retard flame. At the same time, the ethanol in the mixed buffer can regulate the porosity of the coating, avoiding the decrease in flame retardant efficiency caused by excessive densification of the PDA coating, and achieving a balance between adhesion and flame retardancy.

[0011] In some embodiments, the core-shell structured filler is grafted to form a tertiary structure: the core-shell filler is dispersed in anhydrous ethanol (solid-liquid ratio 1:15-20), heated to 65-75°C under nitrogen protection, and 8-12 wt% of EVA oligomer (VA content 20-30%, number average molecular weight 1000-3000) of inorganic flame retardant filler is added. The mixture is kept at this temperature and stirred for 18-24 hours. After filtration, washing, and drying, the tertiary structure modified filler is obtained.

[0012] The quinone groups on the surface of the PDA-MF composite shell are strong free radical initiation sites, which can directly initiate the carbon-carbon bond breakage of EVA oligomers at 65-75℃, forming free radicals that are grafted onto the shell surface without the need for additional initiators (such as AIBN), thus avoiding the impact of initiator residues on the electrical properties of the cable material. The EVA oligomers are homologous to the polyolefin matrix (EVA, POE) of the composite cable material, forming a canopy through the principle of like dissolves like. This not only improves the compatibility between the modified filler and the polyolefin matrix, but also inhibits filler agglomeration through the steric hindrance effect of the canopy, solving the dispersion problem under high filler filling conditions.

[0013] In some embodiments, the preparation of composite cable material includes: mixing a low-smoke halogen-free polyolefin matrix with a tertiary structure modified filler, adding additives, mixing at room temperature for 30-50 minutes in a high-speed mixer, adding the mixture to the low-temperature zone (180-220°C) of Zone 1-4 of a co-rotating twin-screw extruder, adding fluoroplastics with a melting point ≥260°C laterally in the high-temperature zone (240-280°C) of Zone 5-8, with a screw speed of 250-400 rpm, and extruding and granulating after vacuum degassing.

[0014] The stepwise melt blending process precisely matches the processing temperature difference between polyolefins (melting point 120-180℃) and fluoroplastics (melting point ≥260℃). In the low-temperature section, the polyolefin matrix and modified fillers can be fully dispersed, avoiding the degradation of low-melting-point polyolefins. In the high-temperature section, after the fluoroplastics are added laterally, the catechol groups of the PDA-MF shell undergo quinone bonding under high-temperature shearing, forming a stable chemical bond with the fluoroplastic surface. Finally, a uniform structure of continuous fluoroplastic phase - polyolefin / modified filler dispersed phase is formed, with the phase domain size controlled below 0.6μm, which completely solves the phase separation problem caused by temperature mismatch in traditional processes.

[0015] In some implementations, the high-speed mixer operates at a speed of 1500-2000 rpm.

[0016] This rotational speed can generate sufficient shear force to ensure that the canopy of the tertiary structure modified filler is in full contact with the polyolefin matrix, further enhancing the dispersion effect, avoiding local agglomeration caused by uneven mixing, and laying the foundation for the interfacial reaction of subsequent melt blending.

[0017] In some embodiments, the fluoroplastic is FEP, the low-smoke halogen-free polyolefin matrix is ​​one or both of EVA and POE, and the VA content of the polyolefin matrix is ​​20-30% and the melt index is 5-15 g / 10min.

[0018] FEP possesses excellent temperature resistance (long-term operating temperature ≥180℃) and chemical stability, making it the optimal choice for the temperature-resistant matrix of new energy cables. The polyolefin matrix with VA content of 20-30% provides sufficient polar groups to form hydrogen bonds with the canopy of the modified filler. The melt index range of 5-15 g / 10min can balance processing fluidity and mechanical strength, avoiding insufficient strength due to excessively high melt index or dispersion difficulties due to excessively low melt index.

[0019] In some embodiments, the additive is a mixture of antioxidant 1010 / 168 composite and silicone masterbatch lubricant, with a total dosage of 3-6 parts.

[0020] The antioxidant 1010 / 168 composite system can synergistically inhibit the oxidative degradation of polyolefins and fluoroplastics during high-temperature processing, extending product service life; the silicone masterbatch lubricant can reduce melt viscosity, reduce friction between the screw and the material, improve processing stability, and at the same time, it does not affect the interfacial bonding strength and electrical properties.

[0021] In some implementations, the twin-screw extruder has an L / D ratio of ≥48:1, and the screw assembly includes a kneading block.

[0022] Extruders with an aspect ratio ≥ 48:1 can provide sufficient residence time to ensure adequate interfacial reaction; the shearing action of the kneading block can further refine the phase domain size, promote the formation of continuous fluoroplastic phase, and avoid performance fluctuations caused by insufficient dispersion.

[0023] In some embodiments, an irradiation crosslinking step is also included: the extruded granulated particles are subjected to electron beam irradiation crosslinking with an irradiation dose of 5-15 Mrad.

[0024] Irradiation crosslinking can form a three-dimensional network structure in the polyolefin matrix, further improving the heat resistance and mechanical strength of the composite material, meeting the higher heat resistance requirements of applications such as high-voltage wiring harnesses for electric vehicles, and the crosslinking process does not affect the low smoke halogen-free and flame retardant properties.

[0025] In some embodiments, the present invention also provides a fluoroplastic-low-smoke halogen-free composite insulating cable material for new energy applications, prepared by any of the above methods, and composed of the following raw materials in parts by weight: 50-60 parts of fluoroplastic, 40-50 parts of low-smoke halogen-free polyolefin matrix, 110-140 parts of tertiary structure modified filler, and 3-6 parts of additives; wherein the tertiary structure modified filler has a magnesium hydroxide / aluminum core, a polydopamine-melamine-formaldehyde interpenetrating network composite shell, and an ethylene-vinyl acetate oligomer grafted crown layer.

[0026] This formulation ensures temperature resistance through a continuous fluoroplastic phase, flame retardancy and low smoke through a high-filling-content tertiary structure modified filler, and mechanical toughness through the synergistic effect of the polyolefin matrix and the canopy. The dosage of each component has been optimized and matched to avoid the degradation of other properties due to the improvement of a single performance, thus achieving a balance of four properties.

[0027] The present invention has the following advantages over the prior art: This invention, through the synergistic design of a "core-shell-crown" three-level structure modified filler and a stepwise melt blending process, completely changes the interfacial incompatibility of traditional fluoroplastic-low-smoke halogen-free polyolefin composite systems. Compared to existing technologies that rely on a single compatibilizer, have complex formulations, and are prone to phase separation and delamination, this invention achieves a synergistic breakthrough in temperature resistance, flame retardancy, mechanical toughness, and low smoke characteristics, breaking the industry bottleneck that previous single-performance improvements inevitably led to the deterioration of other properties. Simultaneously, the modified filler integrates multiple functions such as interfacial compatibility, flame retardant enhancement, and anti-agglomeration, eliminating the need for additional synergistic flame retardants or dispersants, significantly simplifying the formulation composition. Furthermore, the preparation process is fully compatible with existing production lines, requiring no additional specialized equipment, greatly reducing the industrialization threshold and cost. In addition, this invention incorporates Mg... 2+ The innovative combination of homologous catalysis, PDA-MF in-situ interpenetrating network polymerization, and EVA oligomer self-initiated grafting forms a non-obvious technical path that cannot be easily conceived by existing technologies. Its overall technical solution and application effect far exceed conventional improvements, providing a brand-new solution for new energy cable insulation materials that combines high performance and high practicality. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1 Step 1: Preparation of tertiary structure modified filler: 100 parts of inorganic flame retardant filler were prepared by mixing magnesium hydroxide and aluminum hydroxide in a 1:1 mass ratio. This mixture was dispersed in deionized water (solid-liquid ratio 1:12) and ultrasonically dispersed for 30 min. Then, 5 parts of magnesium nitrate were added and stirred for 30 min for surface activation to obtain Mg. 2+ Activated filler.

[0030] Step 2: Add Mg 2+The activated packing material was transferred to a mixture of Tris-HCl buffer (10 mmol / L) at pH 8.2 and ethanol (ethanol volume percentage 10%, solid-liquid ratio 1:15). After purging with nitrogen for 15 min, 3 parts of dopamine hydrochloride were added, and the mixture was stirred at 25 °C for 10 h. The temperature was then raised to 50 °C and 8 parts of melamine-formaldehyde prepolymer (solid content 35%) were added. The mixture was stirred for another 15 h for in-situ polymerization. After centrifugation and washing with water 4 times, the mixture was vacuum dried at 90 °C for 9 h to obtain the core-shell structure packing material.

[0031] Step 3: Disperse the core-shell structured filler in anhydrous ethanol (solid-liquid ratio 1:18), heat to 70°C under nitrogen protection, add 10 parts of ethylene-vinyl acetate oligomer (VA content 25%, number average molecular weight 2000), keep warm and stir for 20 h to carry out the grafting reaction, filter, wash with ethanol 3 times, and vacuum dry at 100°C for 9 h to obtain the tertiary structure modified filler.

[0032] Step 4: Preparation of composite cable material: Mix 45 parts of EVA / POE (mass ratio 1:1, VA content 25%, melt index 10 g / 10min) with 120 parts of tertiary structure modified filler, add 4 parts of additives (3 parts of antioxidant 1010 / 168 composite + 1 part of silicone masterbatch lubricant), mix at room temperature for 40 min in a high-speed mixer at 1800 rpm, add the mixture to the low temperature zone 1-4 (temperature 190-210℃) of a co-rotating twin-screw extruder (L / D=48:1, including kneading block), add 55 parts of FEP (melting point 260℃) laterally in the high temperature zone 5-8 (temperature 250-270℃), screw speed 300 rpm, extrude and granulate after vacuum degassing to obtain composite insulated cable material.

[0033] Example 2 Step 1: Preparation of tertiary structure modified filler: 100 parts of inorganic flame retardant filler were prepared by mixing magnesium hydroxide and aluminum hydroxide in a 1:1 mass ratio, dispersing in deionized water (solid-liquid ratio 1:10), and ultrasonically dispersing for 30 min. Then, 3 parts of magnesium nitrate were added, and the mixture was stirred for 20 min to activate the filler, yielding Mg. 2+ Activated filler.

[0034] Step 2: Transfer to a mixture of pH 8.0 Tris-HCl buffer (10 mmol / L) and ethanol (ethanol volume percentage 5%, solid-liquid ratio 1:12), purge with nitrogen for 15 min, add 2 parts of dopamine hydrochloride, stir at 20℃ for 8 h, raise the temperature to 45℃ and add 6 parts of melamine-formaldehyde prepolymer, stir for 12 h, centrifuge and wash with water 3 times, and vacuum dry at 80℃ for 8 h to obtain core-shell structured packing material.

[0035] Step 3: Disperse in anhydrous ethanol (solid-liquid ratio 1:15), add 8 parts of ethylene-vinyl acetate oligomer (VA content 20%, number average molecular weight 1000) at 65°C under nitrogen protection, keep warm and stir for 18 hours, and obtain the tertiary structure modified filler after washing and drying.

[0036] Step 4: Preparation of composite cable material: Mix 50 parts of EVA (VA content 20%, melt index 5 g / 10min) with 110 parts of tertiary structure modified filler, add 3 parts of additives, mix at high speed of 1500 rpm for 30 min, add to the low temperature section (180-200℃) and high temperature section (240-260℃) of a twin-screw extruder, add 50 parts of FEP laterally, and extrude and granulate at a screw speed of 250 rpm.

[0037] Example 3 Step 1: Preparation of tertiary structure modified filler: 100 parts magnesium hydroxide / aluminum (1:1) were dispersed in deionized water (solid-liquid ratio 1:15), sonicated for 30 min, and then 6 parts magnesium nitrate were added and stirred for 40 min to activate.

[0038] Step 2: Transfer to a mixture of pH 8.5 Tris-HCl buffer (10 mmol / L) and ethanol (ethanol volume percentage 15%, solid-liquid ratio 1:18), purge with nitrogen for 15 min, add 4 parts of dopamine hydrochloride, stir at 30℃ for 12 h, raise the temperature to 55℃ and add 10 parts of melamine-formaldehyde prepolymer, stir for 18 h, centrifuge and wash with water 5 times, and vacuum dry at 100℃ for 10 h.

[0039] Step 3: Disperse in anhydrous ethanol (solid-liquid ratio 1:20), add 12 parts of ethylene-vinyl acetate oligomer (VA content 30%, number average molecular weight 3000) at 75°C under nitrogen protection, keep warm and stir for 24 hours, wash and dry.

[0040] Step 4: Mix 40 parts of POE (VA content 30%, melt index 15 g / 10min) with 140 parts of tertiary structure modified filler, add 6 parts of additives, mix at high speed of 2000 rpm for 50 min, add to the low temperature section (200-220℃) and high temperature section (260-280℃) of a twin-screw extruder, add 60 parts of FEP laterally, and extrude and granulate at a screw speed of 400 rpm.

[0041] Example 4 Steps 1-3: The preparation of the tertiary structure modified filler is the same as in Example 1.

[0042] Step 4: Mix 48 parts of EVA (VA content 25%, melt index 8 g / 10min) with 125 parts of tertiary structure modified filler, add 5 parts of additives, mix at high speed of 1700 rpm for 35 min, add to the low temperature section (190-210℃) and high temperature section (250-270℃) of a twin-screw extruder, add 52 parts of FEP laterally, screw speed 350 rpm, after extrusion and granulation, perform electron beam irradiation crosslinking (irradiation dose 10Mrad).

[0043] Example 5 Steps 1-3: The preparation of the tertiary structure modified filler is the same as in Example 1.

[0044] Step 4: Mix 45 parts of EVA / POE (1:1) with 120 parts of tertiary structure modified filler, add 4 parts of additives, mix at high speed of 1800 rpm for 40 min, and add to the low temperature section (185-215℃) and high temperature section (245-275℃) of a co-rotating twin-screw extruder (L / D=52:1, including kneading blocks). Add 55 parts of FEP laterally at the high temperature section (245-275℃), and extrude and granulate at a screw speed of 320 rpm.

[0045] Comparative Example 1 Step 1: Preparation of unmodified filler, using 120 parts of unmodified magnesium hydroxide / aluminum (1:1).

[0046] Step 2: Mix 55 parts FEP, 45 parts EVA / POE (1:1) and 120 parts unmodified filler, add 3 parts silane coupling agent KH560 and 4 parts additives, mix at high speed of 1800 rpm for 40 min, and then extrude in a twin-screw extruder in a single step (temperature 190-260℃). Mix and feed, screw speed 300 rpm, and granulate by extrusion.

[0047] Comparative Example 2 Step 1: 100 parts magnesium hydroxide / aluminum (1:1) were dispersed in deionized water (1:12), sonicated for 30 min, and then 5 parts magnesium nitrate were added. After stirring for 30 min, the mixture was activated and transferred to Tris-HCl buffer (pH 8.2, ethanol-free). After purging with nitrogen for 15 min, 3 parts dopamine hydrochloride were added. The mixture was stirred at 25 °C for 10 h, centrifuged, washed with water, and then vacuum dried at 90 °C to obtain PDA single-coating modified filler (MF prepolymer-free).

[0048] Step 2: No EVA oligomer grafting step, directly use the above-mentioned PDA single-coating modified filler.

[0049] Step 3: The preparation of composite cable material is the same as in Example 1, and the step-by-step extrusion process remains unchanged.

[0050] Comparative Example 3 Steps 1-2: Same as Steps 1-2 of Example 1, to prepare a core-shell structured filler (without EVA oligomer grafting).

[0051] Step 3: The preparation of composite cable material is the same as in Example 1, with the stepwise extrusion process remaining unchanged, except that the core-shell structure filler is used instead of the three-level structure modified filler.

[0052] Comparative Example 4 Steps 1-3: The preparation of the tertiary structure modified filler is the same as in Example 1.

[0053] Step 2: Mix 55 parts FEP, 45 parts EVA / POE (1:1), 120 parts tertiary structure modified filler and 4 parts additives, mix at high speed of 1800 rpm for 40 min, add to twin-screw extruder for single-step extrusion (temperature 200-260℃), all raw materials are mixed and fed, screw speed is 300 rpm, extrusion granulation.

[0054] Comparative Example 5 Step 1: Disperse 100 parts of magnesium hydroxide / aluminum (1:1) in deionized water (1:12), sonicate for 30 min, then add 3 parts of copper nitrate (instead of magnesium nitrate), stir for 30 min to activate.

[0055] Steps 2-3: Same as steps 2-3 in Example 1, to prepare a tertiary structure modified filler (Cu). 2+ catalytic).

[0056] Step 4: The preparation of composite cable material is the same as in Example 1, and the step-by-step extrusion process remains unchanged.

[0057] Comparative Example 6 Step 1: 100 parts magnesium hydroxide / aluminum (1:1) were dispersed in deionized water (1:12), sonicated for 30 min, and then 5 parts magnesium nitrate were added. After stirring for 30 min, the mixture was activated and transferred to Tris-HCl buffer at pH 8.2. After purging with nitrogen for 15 min, 3 parts dopamine hydrochloride were added. The mixture was stirred at 25°C for 10 h, centrifuged, washed with water, and then vacuum dried at 90°C to obtain PDA single-coated filler.

[0058] Step 2: Disperse the PDA single-coated filler in anhydrous ethanol (1:18), add 10 parts of EVA oligomer at 70°C under nitrogen protection, and stir for 20 hours to obtain "Mg 2+ "Activation + PDA single coating + EVA crown" modified filler (without MF prepolymer).

[0059] Step 3: The preparation of composite cable material is the same as in Example 1, and the step-by-step extrusion process remains unchanged.

[0060] Comparative Example 7 Step 1: Preparation of unmodified filler using 120 parts of unmodified magnesium hydroxide / aluminum (1:1).

[0061] Step 2: Mix 55 parts FEP, 45 parts EVA / POE (1:1), 120 parts unmodified filler, 3 parts silane coupling agent KH560 and 4 parts additives at 1800 rpm for 40 min. Add the mixture to the low temperature section (190-210℃) and the high temperature section (250-270℃) of the twin-screw extruder. Add FEP laterally and extrude in stages (process is the same as in Example 1).

[0062] Performance verification 1. Oxygen Index Test According to GB / T 2406.2-2009 standard, a sample with dimensions of 100mm×10mm×4mm is prepared. The mixing ratio of oxygen and nitrogen is adjusted in an oxygen index tester, and the lowest oxygen concentration when the sample maintains combustion for 3 minutes or the combustion length reaches 50mm is recorded, which is the oxygen index.

[0063] 2. Elongation at break test According to GB / T 1040.3-2006 standard, dumbbell-shaped Type I specimens were prepared and tested on a universal tensile testing machine at a tensile speed of 50 mm / min. The ratio of the elongation at break to the initial gauge length was recorded, and the elongation at break was calculated.

[0064] 3. Smoke density test According to GB / T 8627-2007 standard, a sample with a size of 25mm×25mm×4mm was prepared and tested in a smoke density tester. The maximum smoke density value was recorded after 4 minutes of combustion.

[0065] 4. Test for retention of elongation at break after thermal aging According to GB / T 32129-2015 standard, the sample was placed in a 180℃ thermal aging chamber for 168 hours. After being taken out and cooled to room temperature, the elongation at break after aging was measured according to the above-mentioned method. The ratio of the elongation at break before and after aging was calculated, which is the retention rate.

[0066] 5. Phase domain size observation The cross-section of the composite cable material was observed using a transmission electron microscope (TEM). Five fields of view were randomly selected, and the particle size of the dispersed phase was measured. The average value was taken as the phase domain size.

[0067] Performance Results

[0068] Based on the performance verification results of the above embodiments and comparative examples, it can be seen that Embodiments 1-5 of the present invention, due to the complete integration of "Mg 2+The core innovative elements of this invention, namely "homogeneous catalysis + PDA-MF IPN shell + EVA canopy + stepwise extrusion," achieve synergistic compliance in terms of temperature resistance, flame retardancy, mechanical toughness, and low smoke characteristics. The phase domains are uniformly small in size, and the performance remains stable after thermal aging, fully demonstrating the synergistic effect of all innovative elements. In contrast, the comparative examples, lacking one or more core innovative elements, exhibited significant performance degradation even when simulating existing technologies or their combinations, resulting in insufficient flame retardancy and low smoke performance, a substantial decrease in mechanical toughness and aging resistance, or prominent phase separation and agglomeration problems. This indicates that the superior performance of this invention is not a conventional improvement of a single technical element, but rather the result of the non-obvious combination and synergistic effect of core innovative elements. Existing technologies, whether alone or in combination, cannot achieve the same technical effect, further confirming the inventiveness and practicality of this invention.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a fluoroplastic-low-smoke halogen-free composite insulating cable material for new energy applications, characterized in that, Includes the following steps: (1) Mix magnesium hydroxide and aluminum hydroxide in a mass ratio of 1:1 to form an inorganic flame-retardant filler. Disperse the mixture in deionized water at a solid-liquid ratio of 1:10-15. Ultrasonically disperse for 30 min. Add 3-6 wt% magnesium nitrate of the inorganic flame-retardant filler and stir for 20-40 min for surface activation to obtain Mg 2+ Activated filler; (2) The Mg 2+ The activated filler was transferred to a mixture of Tris-HCl buffer solution (pH 8.0-8.5) and ethanol (ethanol volume percentage 5-15%, solid-liquid ratio 1:12-18). After purging with nitrogen for 15 min, 2-4 wt% of dopamine (by weight of inorganic flame retardant filler) was added. The mixture was stirred at 20-30℃ for 8-12 h, then heated to 45-55℃ and 6-10 wt% of melamine-formaldehyde prepolymer (by weight of inorganic flame retardant filler) was added. The mixture was stirred for 12-18 h to carry out in-situ polymerization, forming a polydopamine-melamine-formaldehyde interpenetrating network composite shell. After centrifugation and washing with water 3-5 times, the mixture was vacuum dried at 80-100℃ for 8-10 h to obtain the core-shell structure filler. (3) The core-shell structured filler is dispersed in anhydrous ethanol at a solid-liquid ratio of 1:15-20. Under nitrogen protection, the temperature is raised to 65-75℃. 8-12 wt% of the inorganic flame-retardant filler weight of ethylene-vinyl acetate oligomer with a VA content of 20-30% and a number-average molecular weight of 1000-3000 is added. The mixture is kept at the temperature and stirred for 18-24 h to carry out the grafting reaction. After filtration and washing with ethanol three times, the mixture is vacuum dried at 100℃ for 8-10 h to obtain the modified filler with a core-shell-crown three-level structure. (4) Mix the low-smoke halogen-free polyolefin matrix with the tertiary structure modified filler, add the additives and mix at room temperature for 30-50 min in a high-speed mixer. Add the mixture to the low-temperature zone 1-4 of a co-rotating twin-screw extruder at a temperature of 180-220℃. Add fluoroplastics with a melting point ≥260℃ to the side in the high-temperature zone 5-8 at a screw speed of 250-400 rpm. After vacuum degassing, extrude and granulate to obtain the composite insulated cable material.

2. The preparation method according to claim 1, characterized in that, It also includes an irradiation crosslinking step: electron beam irradiation crosslinking of the extruded granulated particles, with an irradiation dose of 5-15 Mrad.

3. The preparation method according to claim 1, characterized in that, The high-speed mixer operates at a speed of 1500-2000 rpm.

4. The preparation method according to claim 1, characterized in that, The fluoroplastic is FEP, and the low-smoke halogen-free polyolefin matrix is ​​one or both of EVA and POE. The VA content of the low-smoke halogen-free polyolefin matrix is ​​20-30%, and the melt index is 5-15 g / 10 min.

5. The preparation method according to claim 1, characterized in that, The additive is a mixture of antioxidant 1010 / 168 composite and silicone masterbatch lubricant, with a total dosage of 3-6 parts.

6. The preparation method according to claim 1, characterized in that, The twin-screw extruder has an L / D ratio of ≥48:1, and the screw assembly includes a kneading block.

7. A fluoroplastic-low-smoke halogen-free composite insulating cable material for new energy applications, characterized in that, Prepared by the method of any one of claims 1-6, and composed of the following raw materials in parts by weight: 50-60 parts of fluoroplastics, 40-50 parts of low-smoke halogen-free polyolefin matrix, 110-140 parts of tertiary structure modified filler, and 3-6 parts of additives; wherein the tertiary structure modified filler has a magnesium hydroxide / aluminum core, a polydopamine-melamine-formaldehyde interpenetrating network composite shell, and an ethylene-vinyl acetate oligomer grafted crown.

8. The fluoroplastic-low-smoke halogen-free composite insulating cable material for new energy applications according to claim 7, characterized in that, The composite insulated cable material has an oxygen index ≥48% and an elongation at break ≥280%.

9. The fluoroplastic-low-smoke halogen-free composite insulating cable material for new energy applications according to claim 7, characterized in that, The composite insulated cable material retains an elongation at break of >85% and a phase domain size of <0.6μm after heat aging at 180℃ for 168h.

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