High-temperature-resistant flame-retardant wire harness and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant flame-retardant wire harness and a preparation method thereof, and relates to the technical field of electric harnesses. The method comprises the following steps: firstly, introducing phosphorus and silicon flame-retardant elements on a polyethylene molecular chain through plasma activation and free radical grafting reaction to prepare phosphorus-silicon grafted modified polyethylene, then compounding aminated silicon dioxide and organic intercalated montmorillonite by using isophorone diisocyanate as a bridging agent to prepare the phosphorus-silicon grafted modified polyethylene composite material. The preparation method comprises the following steps: preparing an isocyanate-bridged silicon dioxide-montmorillonite composite filler to improve the dispersity and compatibility of the filler in a matrix, carrying out extrusion granulation on modified polyethylene, an ethylene-butyl acrylate copolymer, maleic anhydride grafted polyethylene, the composite filler, nano magnesium hydroxide and other additives to prepare polyethylene wire harness particles, and finally, carrying out extrusion granulation on the polyethylene wire harness particles to prepare the cable harness. And coating the surface of a copper core wire with the particles through a single-screw extrusion coating machine, and carrying out subsequent water cooling, steam treatment, drying and rolling to obtain a finished wire harness. The wire harness prepared by the invention has excellent high temperature resistance and flame retardance.

Description

Technical Field

[0001] This invention relates to the field of wire harness technology, specifically to a high-temperature resistant flame-retardant wire harness and its preparation method. Background Technology

[0002] As the core carrier of power transmission and signal transmission, wire harnesses are widely used in many fields such as industrial automation, special vehicles, rail transportation, and high-end equipment. In these application scenarios, wire harnesses often face harsh conditions such as high temperatures and potential fire sources. Their high-temperature resistance and flame-retardant safety are directly related to the stable operation of equipment and the safety of personnel.

[0003] Currently, most mainstream wire harnesses on the market use polyethylene as the core material for insulation and sheathing. This material is widely used in low-voltage wire harnesses due to its excellent electrical insulation properties, good chemical stability, and cost advantages. However, the linear molecular structure of traditional polyethylene materials results in significant performance limitations, making it difficult to meet the stringent requirements of high-temperature resistance and flame retardancy in high-end applications.

[0004] Regarding high-temperature resistance, ordinary polyethylene (PE) wire harnesses are prone to softening and deformation in high-temperature environments such as engine compartments and near laser equipment, leading to insulation failure and equipment malfunctions such as short circuits. In severe cases, this can even affect the operational stability of the entire system. In contrast, industrial equipment and special vehicles often require wire harnesses to withstand much higher temperatures, a requirement that traditional PE wire harnesses cannot meet. In terms of flame retardancy, pure polyethylene has a low limiting oxygen index, making it a flammable material. In the event of a fire, PE wire harnesses are easily ignited, and the flame spreads rapidly, potentially accompanied by melting and dripping, accelerating the fire's spread. More importantly, its combustion process releases large amounts of smoke and toxic gases, significantly reducing escape visibility and endangering human health, greatly hindering evacuation and rescue efforts. Therefore, addressing the technical shortcomings of existing PE wire harnesses—insufficient high-temperature resistance, low flame retardancy, and difficulty in balancing practicality—developing a wire harness with excellent high-temperature resistance, high flame retardancy, and stable overall performance has become a key technological breakthrough direction to meet the application needs of high-end fields. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature resistant and flame-retardant wire harness and its preparation method, thereby solving the technical problems mentioned in the background section. The wire harness prepared by this invention has excellent high-temperature resistance and flame-retardant properties.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a high-temperature resistant flame-retardant wire harness includes the following steps: S1. Polyethylene powder is activated by plasma in an argon-oxygen mixed atmosphere and then mixed with a monomer premix consisting of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and vinyltriethoxysilane. Free radical grafting reaction is carried out under the initiation of benzoyl peroxide. The reaction product is precipitated and dried to obtain phosphorus-silicon grafted modified polyethylene. S2. Nano-silica was aminated with γ-aminopropyltriethoxysilane, and sodium-based montmorillonite was organically intercalated with hexadecyltrimethylammonium bromide. Then, using isophorone diisocyanate as a bridging agent, the aminated silica and organically intercalated montmorillonite under the action of a catalyst underwent a bridging composite reaction. The reaction product was centrifuged, washed, dried and heat-treated to obtain isocyanate-bridged silica-montmorillonite composite filler. S3. Phosphorus-silicon grafted modified polyethylene, ethylene-butyl acrylate copolymer, maleic anhydride grafted polyethylene, isocyanate-bridged silica-montmorillonite composite filler, nano magnesium hydroxide, antioxidant, zinc stearate and triglyceride are mixed evenly, and then melt-extruded, water-cooled and pelletized by a twin-screw extruder to obtain polyethylene wire harness granules. S4. Polyethylene wire harness granules are added to a single-screw extruder and coated onto the surface of copper core wires at the melting temperature. After water cooling, the wire harness is treated in a steam environment, dried, and wound up to obtain a high-temperature resistant and flame-retardant wire harness.

[0007] In this invention, the high-temperature resistance of the wire harness is improved through two synergistic effects: Firstly, the carbon-carbon double bond of vinyltriethoxysilane, initiated by the free radicals from the decomposition of benzoyl peroxide, undergoes an addition reaction with oxygen-containing active groups generated by plasma activation on the polyethylene surface, and is stably grafted onto the polyethylene molecular chain via covalent bonds. Secondly, the phosphorus heterocyclic structure of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) contains active PH bonds, which can undergo an addition reaction with the carbon-carbon double bond of vinyltriethoxysilane, forming a phosphorus-silicon synergistic molecular structure. Under high-temperature conditions, DOPO decomposes thermally to generate viscous substances such as phosphoric acid and polyphosphoric acid, forming a dense phosphorus-based protective film on the material surface, effectively blocking heat transfer to the interior and inhibiting the thermal oxidative breakage of the polyethylene molecular chain. Thirdly, the grafted silicon monomer slowly hydrolyzes and condenses under high temperature and humidity, forming a Si-O-Si cross-linked network with extremely high bond energy. This network strongly restricts the movement of the high-temperature segments of the polyethylene molecular chain, reducing the thermal deformation of the material at high temperatures. It reduces heat penetration through physical barriers and enhances molecular chain stability through chemical cross-linking, significantly improving the high-temperature resistance of the polyethylene matrix.

[0008] On the other hand, the high-temperature resistance of the matrix is ​​further improved by constructing rigid supports and layered barrier structures. Firstly, montmorillonite with hexadecyltrimethylammonium bromide organic intercalation expands the interlayer spacing and introduces organic groups to the surface, allowing it to disperse uniformly in the matrix and form a layered barrier network. This extends the heat transfer path and hinders oxygen diffusion, reducing the thermal oxidative degradation of the polyethylene matrix. Nano-silica, after ammoniation modification, is bridged with isophorone diisocyanate to form a composite structure. The Si-O bonds of silica exhibit excellent high-temperature stability and can act as rigid support points to suppress thermal shrinkage and deformation of the material at high temperatures. Furthermore, the isocyanate bridging structure can react with the hydrolysis products of silicon monomers and the polar groups of maleic anhydride-grafted polyethylene through urea bonds, strengthening the interfacial bonding between the composite filler and the organic matrix and preventing heat concentration caused by interfacial separation at high temperatures. Nano-sized magnesium hydroxide has a high specific surface area and high dispersibility. It undergoes endothermic decomposition at high temperatures, absorbing heat from the surface and interior of the material, reducing the local temperature, and slowing down the thermal decomposition rate of the main matrix. At the same time, the decomposition product, magnesium oxide, forms a dense inorganic protective layer on the material surface. This layer works synergistically with the phosphorus-based protective film generated by the phosphorus-silicon modified matrix to further block heat and oxygen, thereby improving the flame retardant rating.

[0009] Preferably, in step S1, the plasma activation power is 120-150W and the plasma activation time is 15-20min.

[0010] Preferably, in step S1, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to vinyltriethoxysilane is 10:5 to 8.

[0011] Preferably, in step S2, the mass ratio of nano-silica to γ-aminopropyltriethoxysilane is 10:0.3-0.8.

[0012] Preferably, in step S2, the mass ratio of sodium montmorillonite to hexadecyltrimethylammonium bromide is 10:3 to 5.

[0013] Preferably, the catalyst used in step S2 is dibutyltin dilaurate.

[0014] Preferably, in step S3, the isocyanate-bridged silica-montmorillonite composite filler undergoes modification treatment, including the following steps: Isocyanate-bridged silica-montmorillonite composite filler was added to an ethanol aqueous solution and ultrasonically dispersed evenly. Then, γ-methacryloyloxypropyltriethoxysilane was added, and the mixture was heated and stirred to react. After centrifugation, washing, and drying, the final product was obtained.

[0015] In the technical solution of this invention, the research team discovered through in-depth research that under long-term high-temperature environments, due to the significant difference in the thermal expansion coefficients of phosphorus-silicon synergistic grafted modified polyethylene and isocyanate-bridged silica-montmorillonite composite filler, the interface will generate continuous stress due to the difference in expansion. When the stress exceeds the interfacial bonding strength that relies solely on the maleic anhydride-amino reaction of the grafted polyethylene, microcracks will form. These microcracks will accelerate heat penetration and oxygen intrusion, triggering local thermal oxidation degradation of the matrix, resulting in a sharp drop in the high-temperature stability of the wire harness. They will also destroy the synergistic effect of the phosphorus-based protective film of the phosphorus-silicon matrix and the physical barrier layer of the filler, thereby indirectly affecting the high-temperature resistance of the material. To further address this technical problem, this invention performs graft modification on the isocyanate-bridged silica-montmorillonite composite filler. γ-methacryloxypropyltriethoxysilane reacts with the hydroxyl groups on the surface of the composite filler, thereby grafting it onto the surface of the composite filler. γ-methacryloxypropyltriethoxysilane has flexible alkyl chains, which act like interface springs. When the organic matrix expands at high temperatures, it absorbs interface stress through its own deformation, preventing the generation of microcracks, thereby further improving the high-temperature resistance of the wire harness.

[0016] Preferably, the mass ratio of the isocyanate-bridged silica-montmorillonite composite filler to γ-methacryloyloxypropyltriethoxysilane is 10:0.5-1.5.

[0017] Preferably, the heating and stirring reaction temperature is 65-70°C, and the heating and stirring reaction time is 2-3 hours.

[0018] A high-temperature resistant and flame-retardant wire harness is prepared by the method described above.

[0019] Compared with the prior art, the beneficial effects of the present invention are: (1) Through the synergistic effect of phosphorus and silicon elements, a dense phosphorus-based protective film and a strong silicon-oxygen cross-linking network can be formed on the surface of the material at high temperature, which can effectively block heat and oxygen and enhance the thermal stability of molecular chains, thereby significantly improving the high temperature resistance of the wire harness.

[0020] (2) The composite filler (silica-montmorillonite) constructs layered barriers and rigid support points in the matrix, extending the heat transfer path and inhibiting the thermal deformation of the material. At the same time, the endothermic decomposition of nano-magnesium hydroxide further reduces the material temperature, and the overall heat resistance and flame retardancy are improved through multiple pathways.

[0021] (3) Flexible interface treatment is applied to the composite filler. This technology effectively absorbs the internal stress caused by the difference in thermal expansion, prevents the generation of microcracks at the interface under high temperature, and ensures the integrity of the material structure and the stability of its performance under long-term high temperature environment. Attached Figure Description

[0022] Figure 1 This is a SEM image of the brittle fracture surface of the wire harness prepared according to the present invention. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0024] Example 1 A method for preparing a high-temperature resistant flame-retardant wire harness includes the following steps: Step 1: Weigh 50g of polyethylene powder and place it in a low-temperature plasma treatment instrument. Introduce an argon-oxygen mixed atmosphere (volume ratio 3:1), set the activation power to 130W and the activation time to 18min, and obtain activated polyethylene after treatment. 10 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 7 g of vinyltriethoxysilane, and 180 mL of toluene were added to a three-necked flask and stirred at 55 °C for 30 min to prepare a monomer premix. 30 g of activated polyethylene, 220 mL of toluene, and 0.25 g of benzoyl peroxide were added to a four-necked flask. After purging with nitrogen three times, the temperature was raised to 85 °C, and the monomer premix was added dropwise and the reaction was maintained at this temperature for 2 h. After the reaction, the mixture was poured into 500 mL of anhydrous ethanol to precipitate the precipitate. After filtration, the precipitate was dried in a vacuum environment at 82 °C for 13 h to obtain phosphorus-silicon grafted modified polyethylene.

[0025] Step 2: Weigh 10g of nano-silica, add 300mL of ethanol aqueous solution (ethanol:water = 1:1), sonicate for 22min, then add 0.7g of γ-aminopropyltriethoxysilane, stir and react at 72℃ for 3.5h, centrifuge (7500r / min, 12min), wash 3 times with ethanol, and vacuum dry at 78℃ for 9h to obtain aminated silica; Weigh 10g of sodium montmorillonite, add 220mL of deionized water and ultrasonically disperse for 35min, add 4.5g of hexadecyltrimethylammonium bromide aqueous solution, stir and react at 78℃ for 2.5h, centrifuge (9000r / min, 18min), wash with deionized water until no bromide ions are present, and vacuum dry at 88℃ for 11h to obtain organic intercalated montmorillonite; 10g of aminated silica, 8g of organic intercalated montmorillonite, 0.4g of isophorone diisocyanate, 0.01g of dibutyltin dilaurate, and 160mL of anhydrous toluene were added to a four-necked flask. The mixture was reacted at 70℃ for 3.5h, then heated to 80℃ and reacted for another 5.5h. The mixture was centrifuged (9500r / min, 22min), washed four times with ethanol, dried under vacuum at 92℃ for 13h, and then heat-treated at 155℃ under nitrogen atmosphere for 2.5h to obtain isocyanate-bridged silica-montmorillonite composite filler. Take 10g of isocyanate-bridged silica-montmorillonite composite filler, add 200mL of ethanol aqueous solution (ethanol:water = 3:1), ultrasonically disperse for 15min, add 1.2g of γ-methacryloyloxypropyltriethoxysilane, stir and react at 68℃ for 2.5h, centrifuge (8000r / min, 15min), wash 3 times with ethanol, and vacuum dry at 85℃ for 8h to obtain the modified composite filler.

[0026] Step 3: Weigh out 60 parts by weight of phosphosilicone grafted modified polyethylene, 20 parts by weight of ethylene-butyl acrylate copolymer, 10 parts by weight of maleic anhydride grafted polyethylene, 12 parts by weight of modified composite filler, 4 parts by weight of nano magnesium hydroxide, 1.0 part by weight of antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 1:1), 1.0 part by weight of zinc stearate, and 0.5 parts by weight of tristearate. Add them to a high-speed mixer, set the speed to 1650 r / min and the temperature to 85℃, and mix for 18 min. Add the mixture to a twin-screw extruder, set the temperature of each zone to 165℃, 180℃, 190℃, 195℃, and 190℃ at the die head, and set the screw speed to 320 r / min. After melt extrusion, cool the mixture in a 22℃ water cooling tank, and then cut it into polyethylene wire bundle granules with a particle size of 3-5 mm using a pelletizer.

[0027] Step 4: Add polyethylene wire harness granules to a single-screw extruder for coating. Set the barrel temperature to 190℃, the die head temperature to 195℃, and the die temperature to 190℃. Introduce 1.5mm diameter copper core wires into the die at a speed of 3m / min using a traction device, so that the molten wire harness granules are evenly coated on the surface of the wires to form a 0.4mm thick coating layer. After coating, the wire harness is cooled in a 28℃ water cooling bath, then placed in a steam environment for 30 minutes, followed by drying at 80℃ for 1 hour. Finally, it is wound up using a winding device to obtain a high-temperature resistant and flame-retardant wire harness.

[0028] Example 2 A method for preparing a high-temperature resistant flame-retardant wire harness includes the following steps: Step 1: Weigh 50g of polyethylene powder and place it in a low-temperature plasma treatment instrument. Introduce an argon-oxygen mixed atmosphere (volume ratio 3:1), set the activation power to 130W and the activation time to 18min, and obtain activated polyethylene after treatment. 10 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 6 g of vinyltriethoxysilane, and 180 mL of toluene were added to a three-necked flask and stirred at 55 °C for 30 min to prepare a monomer premix. 30 g of activated polyethylene, 220 mL of toluene, and 0.25 g of benzoyl peroxide were added to a four-necked flask. After purging with nitrogen three times, the temperature was raised to 85 °C, and the monomer premix was added dropwise and the reaction was maintained at this temperature for 2 h. After the reaction, the mixture was poured into 500 mL of anhydrous ethanol to precipitate the precipitate. After filtration, the precipitate was dried in a vacuum environment at 82 °C for 13 h to obtain phosphorus-silicon grafted modified polyethylene.

[0029] Step 2: Weigh 10g of nano-silica, add 300mL of ethanol aqueous solution (ethanol:water = 1:1), ultrasonically disperse for 22min, then add 0.5g of γ-aminopropyltriethoxysilane, stir and react at 72℃ for 3.5h, centrifuge (7500r / min, 12min), wash 3 times with ethanol, and vacuum dry at 78℃ for 9h to obtain aminated silica; Weigh 10g of sodium montmorillonite, add 220mL of deionized water and ultrasonically disperse for 35min, add 3.5g of hexadecyltrimethylammonium bromide aqueous solution, stir and react at 78℃ for 2.5h, centrifuge (9000r / min, 18min), wash with deionized water until no bromide ions are found, and vacuum dry at 88℃ for 11h to obtain organic intercalated montmorillonite; 10g of aminated silica, 8g of organic intercalated montmorillonite, 0.4g of isophorone diisocyanate, 0.01g of dibutyltin dilaurate, and 160mL of anhydrous toluene were added to a four-necked flask. The mixture was reacted at 70℃ for 3.5h, then heated to 80℃ and reacted for another 5.5h. The mixture was centrifuged (9500r / min, 22min), washed four times with ethanol, dried under vacuum at 92℃ for 13h, and then heat-treated at 155℃ under nitrogen atmosphere for 2.5h to obtain isocyanate-bridged silica-montmorillonite composite filler. Take 10g of isocyanate-bridged silica-montmorillonite composite filler, add 200mL of ethanol aqueous solution (ethanol:water = 3:1), ultrasonically disperse for 15min, add 0.8g of γ-methacryloyloxypropyltriethoxysilane, stir and react at 68℃ for 2.5h, centrifuge (8000r / min, 15min), wash 3 times with ethanol, and vacuum dry at 85℃ for 8h to obtain the modified composite filler.

[0030] Step 3: Weigh out 60 parts by weight of phosphosilicone grafted modified polyethylene, 20 parts by weight of ethylene-butyl acrylate copolymer, 10 parts by weight of maleic anhydride grafted polyethylene, 12 parts by weight of modified composite filler, 4 parts by weight of nano magnesium hydroxide, 1.0 part by weight of antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 1:1), 1.0 part by weight of zinc stearate, and 0.5 parts by weight of tristearate. Add them to a high-speed mixer, set the speed to 1650 r / min and the temperature to 85℃, and mix for 18 min. Add the mixture to a twin-screw extruder, set the temperature of each zone to 165℃, 180℃, 190℃, 195℃, and 190℃ at the die head, and set the screw speed to 320 r / min. After melt extrusion, cool the mixture in a 22℃ water cooling tank, and then cut it into polyethylene wire bundle granules with a particle size of 3-5 mm using a pelletizer.

[0031] Step 4: Add polyethylene wire harness granules to a single-screw extruder for coating. Set the barrel temperature to 190℃, the die head temperature to 195℃, and the die temperature to 190℃. Introduce 1.5mm diameter copper core wires into the die at a speed of 3m / min using a traction device, so that the molten wire harness granules are evenly coated on the surface of the wires to form a 0.4mm thick coating layer. After coating, the wire harness is cooled in a 28℃ water cooling bath, then placed in a steam environment for 30 minutes, followed by drying at 80℃ for 1 hour. Finally, it is wound up using a winding device to obtain a high-temperature resistant and flame-retardant wire harness.

[0032] Example 3 A method for preparing a high-temperature resistant flame-retardant wire harness includes the following steps: Step 1: Weigh 50g of polyethylene powder and place it in a low-temperature plasma treatment instrument. Introduce an argon-oxygen mixed atmosphere (volume ratio 3:1), set the activation power to 130W and the activation time to 18min, and obtain activated polyethylene after treatment. 10 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 6.5 g of vinyltriethoxysilane, and 180 mL of toluene were added to a three-necked flask and stirred at 55 °C for 30 min to prepare a monomer premix. 30 g of activated polyethylene, 220 mL of toluene, and 0.25 g of benzoyl peroxide were added to a four-necked flask. After purging with nitrogen three times, the temperature was raised to 85 °C, and the monomer premix was added dropwise and the reaction was maintained at this temperature for 2 h. After the reaction, the mixture was poured into 500 mL of anhydrous ethanol to precipitate the precipitate. After filtration, the precipitate was dried in a vacuum environment at 82 °C for 13 h to obtain phosphorus-silicon grafted modified polyethylene.

[0033] Step 2: Weigh 10g of nano-silica, add 300mL of ethanol aqueous solution (ethanol:water = 1:1), ultrasonically disperse for 22min, then add 0.6g of γ-aminopropyltriethoxysilane, stir and react at 72℃ for 3.5h, centrifuge (7500r / min, 12min), wash 3 times with ethanol, and vacuum dry at 78℃ for 9h to obtain aminated silica; Weigh 10g of sodium montmorillonite, add 220mL of deionized water and ultrasonically disperse for 35min, add 4g of hexadecyltrimethylammonium bromide aqueous solution, stir and react at 78℃ for 2.5h, centrifuge (9000r / min, 18min), wash with deionized water until no bromide ions are present, and vacuum dry at 88℃ for 11h to obtain organic intercalated montmorillonite; 10g of aminated silica, 8g of organic intercalated montmorillonite, 0.4g of isophorone diisocyanate, 0.01g of dibutyltin dilaurate, and 160mL of anhydrous toluene were added to a four-necked flask. The mixture was reacted at 70℃ for 3.5h, then heated to 80℃ and reacted for another 5.5h. The mixture was centrifuged (9500r / min, 22min), washed four times with ethanol, dried under vacuum at 92℃ for 13h, and then heat-treated at 155℃ under nitrogen atmosphere for 2.5h to obtain isocyanate-bridged silica-montmorillonite composite filler. Take 10g of isocyanate-bridged silica-montmorillonite composite filler, add 200mL of ethanol aqueous solution (ethanol:water = 3:1), ultrasonically disperse for 15min, add 1.0g of γ-methacryloyloxypropyltriethoxysilane, stir and react at 68℃ for 2.5h, centrifuge (8000r / min, 15min), wash 3 times with ethanol, and vacuum dry at 85℃ for 8h to obtain the modified composite filler.

[0034] Step 3: Weigh out 60 parts by weight of phosphosilicone grafted modified polyethylene, 20 parts by weight of ethylene-butyl acrylate copolymer, 10 parts by weight of maleic anhydride grafted polyethylene, 12 parts by weight of modified composite filler, 4 parts by weight of nano magnesium hydroxide, 1.0 part by weight of antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 1:1), 1.0 part by weight of zinc stearate, and 0.5 parts by weight of tristearate. Add them to a high-speed mixer, set the speed to 1650 r / min and the temperature to 85℃, and mix for 18 min. Add the mixture to a twin-screw extruder, set the temperature of each zone to 165℃, 180℃, 190℃, 195℃, and 190℃ at the die head, and set the screw speed to 320 r / min. After melt extrusion, cool the mixture in a 22℃ water cooling tank, and then cut it into polyethylene wire bundle granules with a particle size of 3-5 mm using a pelletizer.

[0035] Step 4: Add polyethylene wire harness granules to a single-screw extruder for coating. Set the barrel temperature to 190℃, the die head temperature to 195℃, and the die temperature to 190℃. Introduce 1.5mm diameter copper core wires into the die at a speed of 3m / min using a traction device, so that the molten wire harness granules are evenly coated on the surface of the wires to form a 0.4mm thick coating layer. After coating, the wire harness is cooled in a 28℃ water cooling bath, then placed in a steam environment for 30 minutes, followed by drying at 80℃ for 1 hour. Finally, it is wound up using a winding device to obtain a high-temperature resistant and flame-retardant wire harness.

[0036] Example 4 A method for preparing a high-temperature resistant flame-retardant wire harness includes the following steps: Step 1: Weigh 50g of polyethylene powder and place it in a low-temperature plasma treatment instrument. Introduce an argon-oxygen mixed atmosphere (volume ratio 3:1), set the activation power to 150W and the activation time to 20min, and obtain activated polyethylene after treatment. 10 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 8 g of vinyltriethoxysilane, and 180 mL of toluene were added to a three-necked flask and stirred at 55 °C for 30 min to prepare a monomer premix. 30 g of activated polyethylene, 220 mL of toluene, and 0.25 g of benzoyl peroxide were added to a four-necked flask. After purging with nitrogen three times, the temperature was raised to 85 °C, and the monomer premix was added dropwise and kept at this temperature for 2 h. After the reaction, the mixture was poured into 500 mL of anhydrous ethanol to precipitate the precipitate. After filtration, the precipitate was dried in a vacuum environment at 82 °C for 13 h to obtain phosphorus-silicon grafted modified polyethylene.

[0037] Step 2: Weigh 10g of nano-silica, add 300mL of ethanol aqueous solution (ethanol:water = 1:1), sonicate for 22min, then add 0.8g of γ-aminopropyltriethoxysilane, stir and react at 72℃ for 3.5h, centrifuge (7500r / min, 12min), wash 3 times with ethanol, and vacuum dry at 78℃ for 9h to obtain aminated silica; Weigh 10g of sodium montmorillonite, add 220mL of deionized water and ultrasonically disperse for 35min, add 5g of hexadecyltrimethylammonium bromide aqueous solution, stir and react at 78℃ for 2.5h, centrifuge (9000r / min, 18min), wash with deionized water until no bromide ions are present, and vacuum dry at 88℃ for 11h to obtain organic intercalated montmorillonite; 10g of aminated silica, 8g of organic intercalated montmorillonite, 0.4g of isophorone diisocyanate, 0.01g of dibutyltin dilaurate, and 160mL of anhydrous toluene were added to a four-necked flask. The mixture was reacted at 70℃ for 3.5h, then heated to 80℃ and reacted for another 5.5h. The mixture was centrifuged (9500r / min, 22min), washed four times with ethanol, dried under vacuum at 92℃ for 13h, and then heat-treated at 155℃ under nitrogen atmosphere for 2.5h to obtain isocyanate-bridged silica-montmorillonite composite filler. Take 10g of isocyanate-bridged silica-montmorillonite composite filler, add 200mL of ethanol aqueous solution (ethanol:water = 3:1), ultrasonically disperse for 15min, add 1.5g of γ-methacryloyloxypropyltriethoxysilane, stir and react at 70℃ for 3h, centrifuge (8000r / min, 15min), wash 3 times with ethanol, and vacuum dry at 85℃ for 8h to obtain the modified composite filler.

[0038] Step 3: Weigh out 60 parts by weight of phosphosilicone grafted modified polyethylene, 20 parts by weight of ethylene-butyl acrylate copolymer, 10 parts by weight of maleic anhydride grafted polyethylene, 12 parts by weight of modified composite filler, 4 parts by weight of nano magnesium hydroxide, 1.0 part by weight of antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 1:1), 1.0 part by weight of zinc stearate, and 0.5 parts by weight of tristearate. Add them to a high-speed mixer, set the speed to 1650 r / min and the temperature to 85℃, and mix for 18 min. Add the mixture to a twin-screw extruder, set the temperature of each zone to 165℃, 180℃, 190℃, 195℃, and 190℃ at the die head, and set the screw speed to 320 r / min. After melt extrusion, cool the mixture in a 22℃ water cooling tank, and then cut it into polyethylene wire bundle granules with a particle size of 3-5 mm using a pelletizer.

[0039] Step 4: Add polyethylene wire harness granules to a single-screw extruder for coating. Set the barrel temperature to 190℃, the die head temperature to 195℃, and the die temperature to 190℃. Introduce 1.5mm diameter copper core wires into the die at a speed of 3m / min using a traction device, so that the molten wire harness granules are evenly coated on the surface of the wires to form a 0.4mm thick coating layer. After coating, the wire harness is cooled in a 28℃ water cooling bath, then placed in a steam environment for 30 minutes, followed by drying at 80℃ for 1 hour. Finally, it is wound up using a winding device to obtain a high-temperature resistant and flame-retardant wire harness.

[0040] Example 5 A method for preparing a high-temperature resistant flame-retardant wire harness includes the following steps: Step 1: Weigh 50g of polyethylene powder and place it in a low-temperature plasma treatment instrument. Introduce an argon-oxygen mixed atmosphere (volume ratio 3:1), set the activation power to 120W and the activation time to 15min, and obtain activated polyethylene after treatment. 10g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 5g of vinyltriethoxysilane, and 180mL of toluene were added to a three-necked flask and stirred at 55℃ for 30min to prepare a monomer premix. 30g of activated polyethylene, 220mL of toluene, and 0.25g of benzoyl peroxide were added to a four-necked flask, purged with nitrogen three times, and then heated to 85℃. The monomer premix was added dropwise and the reaction was maintained at this temperature for 2h. After the reaction, the mixture was poured into 500mL of anhydrous ethanol to precipitate the precipitate. After filtration, the precipitate was dried in a vacuum environment at 82℃ for 13h to obtain phosphorus-silicon grafted modified polyethylene.

[0041] Step 2: Weigh 10g of nano-silica, add 300mL of ethanol aqueous solution (ethanol:water = 1:1), sonicate for 22min, then add 0.3g of γ-aminopropyltriethoxysilane, stir and react at 72℃ for 3.5h, centrifuge (7500r / min, 12min), wash 3 times with ethanol, and vacuum dry at 78℃ for 9h to obtain aminated silica; Weigh 10g of sodium montmorillonite, add 220mL of deionized water and ultrasonically disperse for 35min, add 3g of hexadecyltrimethylammonium bromide aqueous solution, stir and react at 78℃ for 2.5h, centrifuge (9000r / min, 18min), wash with deionized water until no bromide ions are present, and vacuum dry at 88℃ for 11h to obtain organic intercalated montmorillonite; 10g of aminated silica, 8g of organic intercalated montmorillonite, 0.4g of isophorone diisocyanate, 0.01g of dibutyltin dilaurate, and 160mL of anhydrous toluene were added to a four-necked flask. The mixture was reacted at 70℃ for 3.5h, then heated to 80℃ and reacted for another 5.5h. The mixture was centrifuged (9500r / min, 22min), washed four times with ethanol, dried under vacuum at 92℃ for 13h, and then heat-treated at 155℃ under nitrogen atmosphere for 2.5h to obtain isocyanate-bridged silica-montmorillonite composite filler. Take 10g of isocyanate-bridged silica-montmorillonite composite filler, add 200mL of ethanol aqueous solution (ethanol:water = 3:1), ultrasonically disperse for 15min, add 0.5g of γ-methacryloyloxypropyltriethoxysilane, stir and react at 65℃ for 2h, centrifuge (8000r / min, 15min), wash 3 times with ethanol, and vacuum dry at 85℃ for 8h to obtain the modified composite filler.

[0042] Step 3: Weigh out 60 parts by weight of phosphosilicone grafted modified polyethylene, 20 parts by weight of ethylene-butyl acrylate copolymer, 10 parts by weight of maleic anhydride grafted polyethylene, 12 parts by weight of modified composite filler, 4 parts by weight of nano magnesium hydroxide, 1.0 part by weight of antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 1:1), 1.0 part by weight of zinc stearate, and 0.5 parts by weight of tristearate. Add them to a high-speed mixer, set the speed to 1650 r / min and the temperature to 85℃, and mix for 18 min. Add the mixture to a twin-screw extruder, set the temperature of each zone to 165℃, 180℃, 190℃, 195℃, and 190℃ at the die head, and set the screw speed to 320 r / min. After melt extrusion, cool the mixture in a 22℃ water cooling tank, and then cut it into polyethylene wire bundle granules with a particle size of 3-5 mm using a pelletizer.

[0043] Step 4: Add polyethylene wire harness granules to a single-screw extruder for coating. Set the barrel temperature to 190℃, the die head temperature to 195℃, and the die temperature to 190℃. Introduce 1.5mm diameter copper core wires into the die at a speed of 3m / min using a traction device, so that the molten wire harness granules are evenly coated on the surface of the wires to form a 0.4mm thick coating layer. After coating, the wire harness is cooled in a 28℃ water cooling bath, then placed in a steam environment for 30 minutes, followed by drying at 80℃ for 1 hour. Finally, it is wound up using a winding device to obtain a high-temperature resistant and flame-retardant wire harness.

[0044] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that step 1 is omitted in the preparation process of the high temperature resistant flame retardant wire harness, and the phosphorus silicon grafted modified polyethylene in step 3 is replaced with ordinary polyethylene.

[0045] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that step 2 is omitted in the preparation process of the high temperature resistant flame retardant wire harness, and the modified composite filler in step 3 is removed.

[0046] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that in the preparation process of the high temperature resistant flame retardant wire harness, the modified composite filler is replaced with isocyanate-bridged silica-montmorillonite composite filler in step 3.

[0047] Performance testing: 1. High-Temperature Resistance Test: The test was conducted according to the national standard GB / T 1633-2000 "Determination of Vicat Softening Temperature of Thermoplastic Plastics". The coating layer was peeled off from the wire harnesses prepared in each embodiment and comparative example, and cut into standard specimens of 10mm × 10mm × 0.4mm (length × width × thickness). Five samples were tested in parallel for each group. The test conditions were: load 4kg, heating rate 50℃ / h, silicone oil medium, and the temperature at which the specimen was penetrated 1mm by the indenter was recorded. The average value of the five samples was taken as the final Vicat softening point. The higher the Vicat softening point value, the better the high-temperature resistance. The test results are shown in Table 1.

[0048] 2. Tensile property retention rate test after long-term high-temperature aging: The test was conducted according to the national standards GB / T 1040-1992 "Test Method for Tensile Properties of Plastics" and GB / T 7141-2021 "Test Method for Thermal Aging of Plastics". First, the wire harness covering layer was cut into Type I standard tensile specimens (effective length 25 mm, width 4 mm), and the initial tensile strength and elongation at break were tested (tensile speed 50 mm / min, temperature 23℃). Then, specimens of the same specifications were placed in a 150℃ constant temperature oven and aged without load for 1000 h. After aging, they were removed and cooled to room temperature, and the tensile property test was repeated. The percentage of tensile strength and elongation at break after aging relative to the initial values ​​was calculated, i.e., tensile strength retention rate and elongation at break retention rate. Five samples were tested in parallel for each group, and the average value was taken. The high-temperature stability of the wire harness was characterized sequentially. The test results are shown in Table 1.

[0049] 3. Limiting Oxygen Index (LOI) Test: The test was conducted according to the national standard GB / T 2406.2-2009 "Determination of Combustion Behavior by Oxygen Index Method for Plastics". The wire harness coating was cut into standard specimens of 80mm × 10mm × 0.4mm (length × width × thickness), with three samples tested in parallel for each group. During the test, the volume fraction of oxygen in the oxygen-nitrogen mixture was adjusted gradually from low to high. The lowest oxygen volume fraction at which the specimen could burn continuously for 30 seconds or reach a burning length of 50mm was recorded. The average value of the three samples was taken as the limiting oxygen index. This was used to characterize the flame-retardant performance of the wire harness. The test results are shown in Table 1.

[0050] Table 1: Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 process for the preparation of a high temperature resistant, flame retardant wire harness, characterized in that, The method comprises the following steps: S1, polyethylene powder is mixed with a monomer pre-mixed solution composed of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and vinyltriethoxysilane after plasma activation in argon-oxygen mixed atmosphere, and a free radical grafting reaction is carried out under the initiation of dibenzoyl peroxide, and the reaction product is precipitated and dried to obtain phosphorus-silicon grafted modified polyethylene; S2, nano-silicon dioxide is modified by amino with gamma-aminopropyl triethoxysilane, and sodium-based montmorillonite is modified by organic intercalation with cetyltrimethylammonium bromide; then, with isophorone diisocyanate as a bridging agent, the amino-modified silicon dioxide and the organic intercalation montmorillonite are subjected to a bridging and compounding reaction under the action of a catalyst, and the reaction product is subjected to centrifugation, washing, drying and heat treatment to obtain an isocyanate-bridged silicon dioxide-montmorillonite composite filler; S3, the isocyanate-bridged silicon dioxide-montmorillonite composite filler is added into an ethanol aqueous solution, ultrasonically dispersed uniformly, then gamma-methacryloxypropyl triethoxysilane is added, heated and stirred to react, and then subjected to centrifugal separation, washing and drying to obtain a modified isocyanate-bridged silicon dioxide-montmorillonite composite filler; The phosphorus-silicon grafted modified polyethylene, ethylene-butyl acrylate copolymer, maleic anhydride grafted polyethylene, modified isocyanate-bridged silicon dioxide-montmorillonite composite filler, nano-magnesium hydroxide, antioxidant, zinc stearate and glycerol tristearate are uniformly mixed, then subjected to melt extrusion through a double-screw extruder, water cooling and pelletizing to obtain polyethylene wire bundle particles; S4, the polyethylene wire bundle particles are added into a single-screw extrusion coating machine, coated on the surface of a copper core conductor at a melting temperature, treated in a steam environment after water cooling, and dried and wound to obtain a high-temperature-resistant flame-retardant wire bundle.

2. The method for preparing a high-temperature resistant flame-retardant wire harness according to claim 1, characterized in that, In the step S1, the plasma activation power is 120-150 W, and the plasma activation time is 15-20 min.

3. The method for preparing a high-temperature resistant flame-retardant wire harness according to claim 1, characterized in that, In the step S1, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to vinyltriethoxysilane is 10:5-8.

4. The method for preparing a high-temperature resistant flame-retardant wire harness according to claim 1, characterized in that, In the step S2, the mass ratio of nano-silicon dioxide to gamma-aminopropyl triethoxysilane is 10:0.3-0.

8.

5. The method for preparing a high-temperature resistant flame-retardant wire harness according to claim 1, characterized in that, In the step S2, the mass ratio of sodium-based montmorillonite to cetyltrimethylammonium bromide is 10:3-5.

6. The method for preparing a high-temperature resistant flame-retardant wire harness according to claim 1, characterized in that, In the step S2, the catalyst used is dibutyltin dilaurate.

7. The method for preparing a high-temperature resistant flame-retardant wire harness according to claim 1, characterized in that, In the step S3, the mass ratio of the isocyanate-bridged silicon dioxide-montmorillonite composite filler to gamma-methacryloxypropyl triethoxysilane is 10:0.5-1.

5.

8. The method for preparing a high-temperature resistant flame-retardant wire harness according to claim 1, characterized in that, In the step S3, the heating and stirring reaction temperature is 65-70℃, and the heating and stirring reaction time is 2-3 h.

9. A high temperature resistant, flame resistant wire harness characterized in that, The method is prepared by the method in any one of the above claims 1-8.

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