Conductive yarn and preparation method thereof

Abstract

The invention discloses a conductive yarn and a preparation method thereof, relates to the technical field of functional textile materials and composite conductive fiber preparation, and can solve the problems that an existing conductive yarn is poor in flexibility, insufficient in durability, prone to oxidation failure and difficult to integrate multiple functional performances. The preparation method comprises the following steps that S1, PBO yarn is soaked in a dopamine solution, a PDA modification layer is formed on the surface of the PBO yarn through a polydopamine self-polymerization reaction, and the PDA modification layer provides a chelation site and a bonding interface for metal deposition; s2, the PDA modified PBO yarn obtained in the step S1 is subjected to chemical silver plating, silver is deposited on a PDA modified layer to form a continuous conductive layer, and conductive PBO core yarn is prepared; s3, carrying out melt blending and granulation on the low-dielectric-constant flame-retardant filler and thermoplastic polymer resin to prepare flame-retardant composite particles; and S4, spinning by taking the conductive PBO core yarn prepared in the step S2 as a core layer and a melt formed by melting the flame-retardant composite particles prepared in the step S3 as a skin layer to prepare the conductive yarn.

Description

Technical Field

[0001] This application relates to the technical field of functional textile materials and the preparation of composite conductive fibers, specifically to a conductive yarn and its preparation method. Background Technology

[0002] Conductive yarn refers to fibrous materials or fiber assemblies that possess stable electrical conductivity at the yarn scale. Its conductive pathways typically originate from the continuous distribution of functional phases such as metal layers, carbon-based conductive networks, or conductive polymers on the fiber surface or from effective connections within the yarn. Compared to ordinary fibers, conductive yarn not only enables the transmission of charge or signals but also endows fabrics with functions such as antistatic properties, heating capabilities, flexible interconnects, electromagnetic shielding, and signal acquisition. It has wide applications in smart wearables, flexible electronics, electromagnetic protection, sensing, and medical monitoring.

[0003] The main routes for preparing conductive yarns using existing technologies include: Metal fiber blends: Conductivity is achieved by blending or compounding with stainless steel wire, copper wire, or silver-plated filaments. These yarns have a high metal content and strong conductivity, but the metal monofilaments have a large bending modulus and a small bending radius, resulting in poor overall yarn flexibility, a stiff feel, and low wearing comfort. Surface coating with conductive materials: A conductive layer is formed by coating the surface of ordinary yarn with carbon-containing materials (such as carbon paste) or conductive polymers. This method is simple and low-cost, and the initial resistance can be reduced to a low level. However, the coating mainly relies on physical adhesion and is prone to cracking and peeling after bending / friction / washing. At the same time, the dense and continuous coating can easily block fiber pores, reduce breathability and comfort, and has insufficient stability in long-term use. Electroless or electroplating of metals: Depositing metal layers such as silver, copper, and nickel on the surface of polymer fibers (such as polyester, nylon, and aramid) can achieve high conductivity. However, the interfacial bonding between the metal layer and the polymer matrix is ​​limited, and the mechanical properties of the two differ significantly. Under repeated bending, stretching, and friction, the metal layer is prone to microcracks and localized peeling, disrupting the conductive pathway. In addition, most metal layers are easily oxidized / sulfurized in air, sweat, or humid and hot environments, resulting in increased resistance and decreased shielding effectiveness.

[0004] Existing technologies generally struggle to achieve synergy and balance of multiple properties within the same material system. On the one hand, improving conductivity often relies on continuous, dense metal layers or high-conductive phases, which can increase rigidity or sacrifice breathability and comfort. On the other hand, finishing processes or surface coatings used to achieve flame retardancy, water / hydrophobicity, low dielectric properties, and environmental stability often cover, cut off, or weaken the existing conductive network, leading to a significant increase in resistance and a decrease in washability and bending stability. Summary of the Invention

[0005] Therefore, this application provides a conductive yarn and its preparation method to solve the problems of poor flexibility, insufficient durability, easy oxidation failure, and difficulty in integrating multiple functional properties of existing conductive yarns.

[0006] To achieve the above objectives, this application provides the following technical solution: A method for preparing conductive yarn includes the following steps: S1, PBO yarn is immersed in dopamine solution, and a PDA modification layer is formed on the surface of PBO yarn through the self-polymerization reaction of polydopamine. This PDA modification layer provides chelation sites and binding interfaces for metal deposition. S2, chemically silver-plating the PDA-modified PBO yarn obtained in step S1, so that silver is deposited on the PDA-modified layer to form a continuous conductive layer, thus obtaining conductive PBO core yarn. S3, low dielectric constant flame retardant filler is melt-blended with thermoplastic polymer resin and granulated to obtain flame retardant composite particles; S4. Using the conductive PBO core yarn obtained in step S2 as the core layer and the melt formed by melting the flame-retardant composite particles obtained in step S3 as the skin layer, conductive yarn is prepared by spinning.

[0007] Optionally, in step S1, the dopamine solution is a Tris-HCl buffer solution of dopamine hydrochloride, the concentration of dopamine hydrochloride is 1-4 mg / mL, the pH of the Tris-HCl buffer solution is 8.0-8.8, the reaction temperature is 25-40℃, and the reaction time is 6-24 hours.

[0008] Optionally, in step S2, the electroless silver plating includes sensitization, activation and electroless plating steps, the reaction temperature is 30-60℃, the reaction time is 10-40 minutes, and the surface resistance of the obtained conductive PBO core yarn is 0.1-5 Ω / cm.

[0009] Optionally, in step S3, the low dielectric constant flame retardant filler is selected from one or more of silica, boron nitride, boehmite, aluminum hydroxide, and magnesium hydroxide; The thermoplastic polymer resin is selected from one or more of polyimide, polyetherimide, fluorinated ethylene propylene copolymer, thermoplastic polyurethane, polypropylene, polyethylene, and polyethylene terephthalate; Furthermore, the low dielectric constant flame retardant filler accounts for 10%-50% of the mass of the flame retardant composite particles.

[0010] Optionally, in step S4, the sheath-to-core mass ratio of the conductive yarn is 30:70 to 70:30; the melting temperature of the flame-retardant composite particles is set in the range of 150-360°C according to the melting point of the thermoplastic polymer resin.

[0011] Optionally, in step S3, the low dielectric constant flame retardant filler and thermoplastic polymer resin are melt-blended, extruded, cooled, and pelletized using a twin-screw extruder at a temperature higher than the melting point of the thermoplastic polymer resin to obtain flame retardant composite particles.

[0012] Optionally, in step S4, the conductive PBO core yarn is unwound at a constant speed and fed into the core-sheath composite spinning machine. The flame-retardant composite particles obtained in step S3 are fed into the sheath screw extruder of the core-sheath composite spinning machine and heated to a molten state. The molten polymer is transported to the core-sheath structure spinneret through a metering pump and merges with the conductive PBO core yarn that has passed through the core, so that it is covered by the melt. After co-extrusion, it is cooled and solidified in a cooling tank, stretched by a stretching roller, and entangled by a networker.

[0013] This application also discloses a conductive yarn, comprising a conductive PBO core yarn and a sheath covering the conductive PBO core yarn; The conductive PBO core yarn has an Ag@PDA@PBO structure, wherein PBO is the core material, PDA is the modification layer, and Ag is the continuous conductive layer; The skin layer is a flame-retardant composite polymer layer covering the conductive PBO core yarn, and the flame-retardant composite polymer layer is composed of thermoplastic polymer resin and low dielectric constant flame-retardant filler.

[0014] Optionally, the conductive yarn has a surface resistivity of less than 5 Ω / cm, a limiting oxygen index of greater than 28%, a water contact angle of greater than 110°, and an electromagnetic shielding effectiveness of greater than 30 dB at a frequency of 1 GHz.

[0015] Compared with the prior art, this application has at least the following beneficial effects: In step S1, the PBO yarn undergoes self-polymerization of polydopamine to form a PDA modification layer. The surface contains abundant active groups such as catechol and amino groups, which can chelate with metal ions, thereby providing a large number of binding sites for subsequent silver deposition. At the same time, the PDA modification layer forms a flexible buffer interface between the PBO yarn and the metal layer, which improves the adhesion and flexibility of the metal deposition layer and avoids the problems of easy peeling and cracking of the metal layer when directly silvering. In step S2, silver ions are uniformly reduced and deposited on the PDA modification layer using a chemical silver plating process. Silver nanoparticles nucleate, grow, and interconnect on the PDA modification layer to form a continuous and dense conductive film layer (continuous conductive layer), thus constructing a stable electron transport pathway. Due to the presence of the PDA modification layer, the interfacial stress between the silver layer and the substrate is buffered, so that the resulting conductive PBO core yarn can still maintain a low surface resistance and stable conductivity under bending, stretching, and washing conditions. In step S3, the low dielectric constant flame retardant filler and thermoplastic polymer resin are melt-blended and granulated to obtain a flame retardant composite masterbatch. The low dielectric constant flame retardant filler is uniformly dispersed in the thermoplastic polymer resin and can endothermally decompose and generate an oxygen barrier layer when heated, thereby improving the flame retardancy and thermal stability of the material. At the same time, the low dielectric constant flame retardant filler can reduce the dielectric loss of the skin layer, giving the yarn excellent electromagnetic shielding performance and signal transmission stability. In step S4, the conductive PBO core yarn and the sheath are spun together to form a conductive yarn. This structure provides comprehensive protection for the conductive core layer, while the sheath effectively isolates oxygen and moisture, preventing silver layer oxidation or sulfidation, and improving washability and environmental stability. Simultaneously, the sheath imparts comprehensive properties to the PBO core yarn, including flame retardancy, water resistance, low dielectric constant, and electromagnetic interference resistance. Compared to traditional single-layer conductive yarns, the conductive yarn of this invention significantly improves conductive durability and multifunctional stability while maintaining softness and weavability. Attached Figure Description

[0016] Figure 1 A process flow diagram of a method for preparing conductive yarn provided in one embodiment of this application; Figure 2 SEM image of a conductive yarn provided in one embodiment of this application; Figure 3 This is a carbon element energy spectrum corresponding to the SEM image of a conductive yarn provided in one embodiment of this application; Figure 4 This is the silicon energy spectrum corresponding to the SEM image of the conductive yarn provided in one embodiment of this application; Figure 5 This is the fluorine energy spectrum corresponding to the SEM image of the conductive yarn provided in one embodiment of this application; Figure 6 The energy spectrum of silver element is shown in the SEM image of the conductive yarn provided in one embodiment of this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0018] In the description of this application: unless otherwise stated, "multiple" means two or more. Expressions such as "including", "comprising", and "having" also mean "not limited to" (certain units, components, materials, steps, etc.).

[0019] Example 1: refer to Figure 1 and Figure 2This application discloses a method for preparing conductive yarn, comprising the following steps: S1, PBO (poly(p-phenylenebenzodioxazole)) yarn is impregnated in dopamine solution, and PDA (polydopamine) modification layer is formed on the surface of PBO yarn through the self-polymerization reaction of polydopamine. This PDA modification layer provides chelation sites and binding interfaces for metal deposition. S2, chemically silver-plating the PDA-modified PBO yarn obtained in step S1, so that silver is deposited on the PDA-modified layer to form a continuous conductive layer, thus obtaining conductive PBO core yarn. S3, low dielectric constant flame retardant filler is melt-blended with thermoplastic polymer resin and granulated to obtain flame retardant composite particles; S4. Using the conductive PBO core yarn obtained in step S2 as the core layer and the melt formed by melting the flame-retardant composite particles obtained in step S3 as the skin layer, conductive yarn is prepared by spinning.

[0020] In step S1, the PBO yarn undergoes self-polymerization of polydopamine to form a PDA modification layer. The surface contains abundant active groups such as catechol and amino groups, which can chelate with metal ions, thereby providing a large number of binding sites for subsequent silver deposition. At the same time, the PDA modification layer forms a flexible buffer interface between the PBO yarn and the metal layer, which improves the adhesion and flexibility of the metal deposition layer and avoids the problems of easy peeling and cracking of the metal layer when directly silvering. In step S2, silver ions are uniformly reduced and deposited on the PDA modification layer using a chemical silver plating process. Silver nanoparticles nucleate, grow, and interconnect on the PDA modification layer to form a continuous and dense conductive film layer (continuous conductive layer), thus constructing a stable electron transport pathway. Due to the presence of the PDA modification layer, the interfacial stress between the silver layer and the substrate is buffered, so that the resulting conductive PBO core yarn can still maintain a low surface resistance and stable conductivity under bending, stretching, and washing conditions. In step S3, the low dielectric constant flame retardant filler and thermoplastic polymer resin are melt-blended and granulated to obtain a flame retardant composite masterbatch. The low dielectric constant flame retardant filler is uniformly dispersed in the thermoplastic polymer resin and can endothermally decompose and generate an oxygen barrier layer when heated, thereby improving the flame retardancy and thermal stability of the material. At the same time, the low dielectric constant flame retardant filler can reduce the dielectric loss of the skin layer, giving the yarn excellent electromagnetic shielding performance and signal transmission stability. In step S4, the conductive PBO core yarn and the sheath are spun together to form a conductive yarn. This structure provides comprehensive protection for the conductive core layer, while the sheath effectively isolates oxygen and moisture, preventing silver layer oxidation or sulfidation, and improving washability and environmental stability. Simultaneously, the sheath imparts comprehensive properties to the PBO core yarn, including flame retardancy, water resistance, low dielectric constant, and electromagnetic interference resistance. Compared to traditional single-layer conductive yarns, the conductive yarn of this invention significantly improves conductive durability and multifunctional stability while maintaining softness and weavability.

[0021] In step S1, the dopamine solution is a Tris-HCl buffer solution of dopamine hydrochloride, the concentration of dopamine hydrochloride is 1-4 mg / mL, the pH of the Tris-HCl buffer solution is 8.0-8.8, the reaction temperature is 25-40℃, and the reaction time is 6-24 hours.

[0022] Surface modification under these conditions allows dopamine to undergo a self-polymerization reaction in a weakly alkaline environment and deposit on the surface of PBO yarn, forming a uniform, dense, and firmly adhered PDA-modified layer (PDA film). The PDA-modified layer itself has good hydrophilicity and chemical stability, which can improve the inertness of the PBO yarn surface and enhance the interfacial bonding strength between the metal deposition layer and the fiber matrix.

[0023] In step S2, the electroless silver plating includes sensitization, activation and electroless plating steps, the reaction temperature is 30-60℃, the reaction time is 10-40 minutes, and the surface resistance of the obtained conductive PBO core yarn is 0.1-5 Ω / cm.

[0024] Through three steps—sensitization, activation, and electroless plating—silver can uniformly nucleate, grow, and ultimately form a continuous and dense conductive film on the surface of the PDA-modified layer. The PDA-modified PBO yarn is sequentially immersed in a sensitizer solution (such as SnCl2) and an activator solution (such as PdCl2) for activation treatment to attach catalytic active centers to the surface. Subsequently, it is placed in an electroless silver plating solution (such as a mixed solution composed of silver nitrate, reducing agents (glucose, sodium borohydride), complexing agents (ammonia, potassium sodium tartrate), and stabilizers). Reacting within a temperature range of 30–60℃ ensures a balance between the silver ion reduction rate and the grain growth rate, resulting in a dense silver layer with uniform grains. Silver ions are reduced to silver nanoparticles (AgNPs) and uniformly and densely deposited on the PDA modification layer, forming a robust conductive network with a resistance as low as 0.1–5 Ω / cm. Due to the strong chemical bond and good mechanical matching between the silver layer and the PDA modification layer, the conductive PBO core yarn can maintain stable conductivity after bending, stretching and repeated washing, and there will be no phenomenon of silver layer peeling or cracking.

[0025] In step S3, the low dielectric constant flame retardant filler is selected from one or more of silica, boron nitride, boehmite, aluminum hydroxide, and magnesium hydroxide; The thermoplastic polymer resin is selected from one or more of polyimide, polyetherimide, fluorinated ethylene propylene copolymer, thermoplastic polyurethane, polypropylene, polyethylene, and polyethylene terephthalate; Furthermore, the low dielectric constant flame retardant filler accounts for 10%-50% of the mass of the flame retardant composite particles.

[0026] Low dielectric constant flame-retardant fillers possess excellent thermal stability and flame-retardant properties. When heated or burning, they can absorb heat, release moisture, or generate an oxygen barrier layer, thereby effectively delaying heat transfer and inhibiting combustion reactions, improving the flame-retardant rating and thermal protection performance of the skin layer. The low dielectric properties significantly reduce the overall dielectric loss of the skin layer material, making the final conductive yarn more stable in signal transmission under high-frequency conditions and providing higher electromagnetic shielding effectiveness. Thermoplastic polymer resin has good film-forming properties and flexibility, and can be used as a skin layer matrix to provide mechanical support and spinnability. The resulting flame-retardant composite particles endow the conductive yarn with excellent flame retardancy, dielectric stability, and anti-electromagnetic interference capabilities.

[0027] In addition, by selecting specific materials such as low dielectric constant flame-retardant fillers and thermoplastic polymer resins, the softness, elasticity, cost, and performance focus of conductive yarns can be precisely customized, making them applicable to a wide range of fields from consumer electronics to defense and military industries.

[0028] In step S4, the core-sheath mass ratio of the conductive yarn is 30:70 to 70:30; the melting temperature of the flame-retardant composite particles is set in the range of 150-360℃ according to the melting point of the thermoplastic polymer resin.

[0029] In step S3, the low dielectric constant flame retardant filler and thermoplastic polymer resin are melt-blended, extruded, cooled, and pelletized using a twin-screw extruder at a temperature higher than the melting point of the thermoplastic polymer resin to obtain flame retardant composite particles.

[0030] By using a twin-screw extruder for melt blending at temperatures above the melting point of thermoplastic polymer resins, low-dielectric-constant flame-retardant fillers can be fully dispersed and coated within the polymer matrix, forming a composite system with a uniform structure and good interfacial bonding. The twin-screw extruder possesses strong mixing and high shear capabilities, effectively breaking down agglomerates of inorganic fillers and ensuring that micron or nano-sized particles are uniformly distributed in the resin melt, thereby improving the overall consistency and processing stability of the composite material. During melt blending, the filler and polymer matrix can form interfacial interactions through hydrogen bonds, van der Waals forces, or interfacial modifiers, resulting in a tighter bond between the low-dielectric-constant flame-retardant filler and the thermoplastic polymer resin.

[0031] The flame-retardant composite particles obtained after cooling and pelletizing have uniform particle size and good flowability, and can be stably melt-extruded and uniformly coated with conductive PBO core yarn in the subsequent spinning process.

[0032] In step S4, the conductive PBO core yarn is unwound at a constant speed and fed into the core-sheath composite spinning machine. The flame-retardant composite particles obtained in step S3 are fed into the sheath screw extruder of the core-sheath composite spinning machine and heated to a molten state. The molten polymer is transported to the core-sheath structure spinneret through a metering pump and merges with the conductive PBO core yarn that has passed through the core, so that it is covered by the melt. After co-extrusion, it is cooled and solidified in a cooling tank, stretched by a stretching roller, and entangled by a networker.

[0033] By using a core-sheath composite spinning machine for coaxial coating, the conductive PBO core yarn and the sheath layer are simultaneously fused and extruded at the spinning nozzle, achieving an integrated structural bond between the core and sheath layers. This process ensures that the conductive PBO core yarn maintains stable tension and positional accuracy at the center of the sheath melt, resulting in uniform outer coating and consistent thickness.

[0034] In this process, the metering pump ensures a stable flow rate of the molten polymer, making the sheath thickness controllable; the rapid setting of the cooling tank and the synchronous traction of the drafting rollers ensure that the sheath adheres tightly to the core yarn during the curing process, preventing bubbles, holes, or peeling. Subsequently, the yarn is entangled by the networker, forming a fine interlaced structure on the yarn surface, improving the overall density and weaving adaptability of the yarn.

[0035] refer to Figure 2-6 This application also discloses a conductive yarn, comprising a conductive PBO core yarn and a sheath covering the conductive PBO core yarn; The conductive PBO core yarn has an Ag@PDA@PBO structure, where PBO is the core material, PDA is the modification layer, and Ag is the continuous conductive layer. The outer layer is a flame-retardant composite polymer layer covering the conductive PBO core yarn. The flame-retardant composite polymer layer is composed of thermoplastic polymer resin and low dielectric constant flame-retardant filler.

[0036] Figure 2 This is a SEM image (image obtained by scanning electron microscopy) of a conductive yarn with Ag@PDA@PBO core yarn and SiO2@FEP sheath.

[0037] The conductive yarn has a surface resistivity of less than 5 Ω / cm, a limiting oxygen index of greater than 28%, a water contact angle of greater than 110°, and an electromagnetic shielding effectiveness of greater than 30 dB at a frequency of 1 GHz.

[0038] Conductive yarns possess flame-retardant, waterproof, and electromagnetic interference-resistant properties, and can be used in the manufacture of products including but not limited to: weaving flexible circuits and connecting wires; integrating them into smart clothing, smart gloves, and smart insoles for data transmission and power supply, while ensuring the safety and comfort of wearable smart devices and fashion technology. Utilizing their Joule heating effect, they can be used to create fast-responding, uniformly heated, safe, and reliable (flame-retardant) electrically heated clothing, skiwear, mountaineering clothing, blankets, car heated seats, and other personal thermal management textiles.

[0039] It can be used as a flexible, dry electrode, woven into clothing for long-term, stable collection of physiological signals such as electrocardiogram (ECG), electromyography (EMG), and electroencephalography (EEG), for use in telemedicine and health management. It can also be woven into highly flexible, lightweight electromagnetic shielding fabrics for use in making covers for secure communication equipment, military stealth tents, EMI protective clothing, and shielding layers inside aerospace vehicles.

[0040] Its flame-retardant, waterproof, and sensing properties can be utilized to create smart protective clothing for firefighters, welders, and petrochemical workers, providing both protection and monitoring of environmental hazards (such as overheating) and vital signs. It can also be used as a braided flexible antenna in wearable communication devices, or integrated as a flexible component into energy harvesting devices. Furthermore, it can be used in smart carpets (pressure sensing), smart sofas, and smart car seats (occupant monitoring and heating), providing concealed sensing and heating functions.

[0041] Example 2: The method for preparing conductive yarn includes the following steps:

[0042] S1. Take 1 km of 150D PBO filament yarn and immerse it in a 10 mM Tris-HCl buffer solution (pH=8.5) containing 2 mg / mL dopamine hydrochloride. Stir slowly at 30°C for 16 hours. After removal, ultrasonically clean with deionized water for 5 minutes and dry at 60°C.

[0043] S2. First, immerse the above yarn in SnCl2 sensitization solution and PdCl2 activation solution for 10 minutes each. After washing, transfer it to chemical silver plating solution (containing AgNO3 5g / L, appropriate amount of ammonia water until the solution is clear, and glucose 8g / L) and react at 50℃ for 25 minutes. After taking it out, wash and dry it. The surface resistance is measured to be 0.5 Ω / cm. Conductive PBO core yarn is obtained.

[0044] S3 involves premixing boron nitride (BN) powder with an average particle size of 1.5 μm with thermoplastic polyurethane particles at a mass ratio of 25:75, then melting and extruding the mixture using a twin-screw extruder at 185-195℃, followed by water cooling and pelletizing to obtain flame-retardant TPU composite masterbatch.

[0045] S4. The conductive PBO core yarn is fed into the core-sheath composite spinning machine at a speed of 60 m / min; the flame-retardant TPU composite masterbatch is fed into the sheath extruder and melted at 195℃, and then coated and spun through the core-sheath spinneret (the core-sheath ratio is designed to be 50:50); after cooling with cold water at 20℃, 1.6 times drafting, and twisting with a networker, it is wound into a bobbin; the final conductive yarn linear density is approximately 300 D.

[0046] Example 3: The method for preparing conductive yarn includes the following steps:

[0047] S1 and S2 are prepared using the same methods as steps S1 and S2 in Example 2, to produce conductive PBO core yarn.

[0048] S3. Boehmite powder and polyetherimide (PEI) particles are premixed at a mass ratio of 30:70, and then melt-blended, extruded, cooled, and pelletized using a twin-screw extruder at 340-360℃ to obtain flame-retardant PEI composite masterbatch.

[0049] S4, the process is the same as step S4 in Example 2, the temperature of the skin extruder is set to 345℃, and the skin-to-core ratio is 40:60.

[0050] Example 4: The method for preparing conductive yarn includes the following steps:

[0051] S1 and S2 are prepared using the same methods as steps S1 and S2 in Example 2, to produce conductive PBO core yarn.

[0052] S3 involves premixing BN with polypropylene (PP) granules and an appropriate amount of flame retardant synergist for PP at a mass ratio of 20:75:5, and then granulating the mixture using a twin-screw extruder at 190-210℃.

[0053] S4, the process is the same as step S4 in Example 2, the temperature of the skin extruder is set to 200℃, and the skin-to-core ratio is 55:45.

[0054] Example 5: The method for preparing conductive yarn includes the following steps:

[0055] S1 and S2 are prepared using the same methods as steps S1 and S2 in Example 2, to produce conductive PBO core yarn.

[0056] S3 involves premixing oleophilic silica (SiO2) nanoparticles (20nm) with fluorinated ethylene propylene copolymer (FEP) powder at a mass ratio of 15:85, and then granulating the mixture using a twin-screw extruder at 280-300℃. FEP exhibits excellent chemical corrosion resistance.

[0057] S4, the process is the same as step S4 in Example 2, the temperature of the skin extruder is set to 295℃, and the skin-to-core ratio is 60:40.

[0058] By comparing the proportions and examples: Comparative Example 1 (without PDA modification layer): Step S1 in Example 2 is omitted. Pure PBO yarn is directly subjected to chemical silver plating in step S2. Uneven silver layer distribution and significant agglomeration were observed, resulting in poor adhesion to the fibers. After gentle bending and rubbing, a large amount of silver powder was detached. The initial surface resistivity was measured to be 5 Ω / cm, which increased to over 50 Ω / cm after one wash, and completely failed after five washes.

[0059] Comparative Example 2 (without cortical protection): The conductive PBO core yarn prepared in steps S1 and S2 of Example 2 was used only, without subsequent sheathing. This yarn exhibits: good initial conductivity (0.5 Ω / cm); flame retardancy derived solely from the PBO core (LOI = 38%); no hydrophobicity, with a contact angle less than 90°; and after one week in air, the surface resistivity increased to 2 Ω / cm (silver oxidation). After one wash, the surface resistivity increased to 8 Ω / cm, and was severely damaged after five washes.

[0060]

[0061] Through thorough comparison of the above embodiments and comparative examples (see Table 1), it can be clearly concluded that the PDA modification layer is the key to achieving a firm bond between the silver layer and the PBO yarn; without this layer, both conductivity and durability are substandard (Comparative Example 1). The flame-retardant composite polymer sheath provides crucial protection for the internal conductive core layer, giving it excellent hydrophobicity, resistance to environmental aging, and abrasion resistance. Without the sheath protection, conductivity will rapidly decay (Comparative Example 2). This invention, through a three-step design of "PDA modification + chemical silver plating + flame-retardant composite sheath-core spinning," successfully produces conductive yarns with comprehensive and excellent overall performance, far superior to the comparative examples and existing technologies.

[0062] The technical features of the above embodiments can be combined in any way (as long as there is no contradiction in the combination of these technical features). For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; these embodiments not explicitly written should also be considered to be within the scope of this specification.

[0063] The present application has been described in a relatively specific and detailed manner above through general descriptions and specific embodiments. It should be understood that, based on the technical concept of the present application, several conventional adjustments or further innovations can be made to these specific embodiments; however, as long as they do not depart from the technical concept of the present application, the technical solutions obtained by these conventional adjustments or further innovations also fall within the protection scope of the claims of the present application.

Claims

1. A method for preparing a conductive yarn, characterized in that, Includes the following steps: S1, PBO yarn is immersed in dopamine solution, and a PDA modification layer is formed on the surface of PBO yarn through the self-polymerization reaction of polydopamine. This PDA modification layer provides chelation sites and binding interfaces for metal deposition. S2, chemically silver-plating the PDA-modified PBO yarn obtained in step S1, so that silver is deposited on the PDA-modified layer to form a continuous conductive layer, thus obtaining conductive PBO core yarn. S3, low dielectric constant flame retardant filler is melt-blended with thermoplastic polymer resin and granulated to obtain flame retardant composite particles; S4. Using the conductive PBO core yarn obtained in step S2 as the core layer and the melt formed by melting the flame-retardant composite particles obtained in step S3 as the skin layer, conductive yarn is prepared by spinning.

2. The preparation method according to claim 1, characterized in that, In step S1, the dopamine solution is a Tris-HCl buffer solution of dopamine hydrochloride, the concentration of dopamine hydrochloride is 1-4 mg / mL, the pH of the Tris-HCl buffer solution is 8.0-8.8, the reaction temperature is 25-40℃, and the reaction time is 6-24 hours.

3. The preparation method according to claim 1, characterized in that, In step S2, the electroless silver plating includes sensitization, activation and electroless plating steps, the reaction temperature is 30-60℃, the reaction time is 10-40 minutes, and the surface resistance of the obtained conductive PBO core yarn is 0.1-5 Ω / cm.

4. The preparation method according to claim 1, characterized in that, In step S3, the low dielectric constant flame retardant filler is selected from one or more of silica, boron nitride, boehmite, aluminum hydroxide, and magnesium hydroxide; The thermoplastic polymer resin is selected from one or more of polyimide, polyetherimide, fluorinated ethylene propylene copolymer, thermoplastic polyurethane, polypropylene, polyethylene, and polyethylene terephthalate; Furthermore, the low dielectric constant flame retardant filler accounts for 10%-50% of the mass of the flame retardant composite particles.

5. The preparation method according to claim 1, characterized in that, In step S4, the core-sheath mass ratio of the conductive yarn is 30:70 to 70:30; the melting temperature of the flame-retardant composite particles is set in the range of 150-360℃ according to the melting point of the thermoplastic polymer resin.

6. The preparation method according to claim 1 or 4, characterized in that, In step S3, the low dielectric constant flame retardant filler and thermoplastic polymer resin are melt-blended, extruded, cooled, and pelletized using a twin-screw extruder at a temperature higher than the melting point of the thermoplastic polymer resin to obtain flame retardant composite particles.

7. The preparation method according to claim 1 or 5, characterized in that, In step S4, the conductive PBO core yarn is unwound at a constant speed and fed into the core-sheath composite spinning machine. The flame-retardant composite particles obtained in step S3 are fed into the sheath screw extruder of the core-sheath composite spinning machine and heated to a molten state. The molten polymer is transported to the core-sheath structure spinneret through a metering pump and merges with the conductive PBO core yarn that has passed through the core, so that it is covered by the melt. After co-extrusion, it is cooled and solidified in a cooling tank, stretched by a stretching roller, and entangled by a networker.

8. A conductive yarn, characterized in that, It includes a conductive PBO core yarn and a sheath covering the conductive PBO core yarn; The conductive PBO core yarn has an Ag@PDA@PBO structure, wherein PBO is the core material, PDA is the modification layer, and Ag is the continuous conductive layer; The outer layer is a flame-retardant composite polymer layer covering the conductive PBO core yarn, and the flame-retardant composite polymer layer is composed of thermoplastic polymer resin and low dielectric constant flame-retardant filler.

9. The conductive yarn according to claim 8, characterized in that, The conductive yarn has a surface resistivity of less than 5 Ω / cm, a limiting oxygen index of greater than 28%, a water contact angle of greater than 110°, and an electromagnetic shielding effectiveness of greater than 30 dB at a frequency of 1 GHz.

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