A new method of making a conductive chest strap

Abstract

The application discloses a novel conductive chest strap preparation method, a permeable conductive reinforcing composition and a surface micro-erosion pretreatment gel. The method first weaves a segmented belt containing stretchable areas and non-stretchable electrode collection areas; then a thixotropic pretreatment gel is coated on the surface of the electrode area, a micro-erosion layer is formed on the surface of the fiber by using a solvent; then the permeable conductive reinforcing composition is forcedly absorbed into the fiber bundle under the condition of vacuum negative pressure; finally, the resin and the fiber form an interpenetrating network and chemical bonding through gradient temperature curing. Through the synergistic effect of physical structure restriction and micro-chemical anchoring, the application solves the problems of easy delamination and cracking of the conductive layer and unstable contact impedance in the traditional process, meanwhile, the gel characteristics are used to block the solvent wicking and diffusion, the elasticity of the substrate is effectively protected, and the durability and signal collection accuracy of the product are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of smart wearable devices and electronic textile manufacturing technology, specifically a novel method for weaving a conductive chest strap. Background Technology

[0002] Heart rate monitors, as common biosignal monitoring devices, have a core component that is a flexible conductive webbing capable of collecting bioelectrical signals from the human body surface. Currently, the mainstream manufacturing process for heart rate monitors typically uses elastic webbing as the base material, employing lamination or screen printing processes to sequentially laminate an insulating layer, a conductive rubber layer, or a conductive coating onto the webbing surface. To ensure comfort and a secure fit, the base webbing usually possesses high elasticity and tensile properties throughout.

[0003] However, this full-length elastic structure and multi-layer composite process have significant technical limitations in practical applications. Because the elastic modulus of the conductive layer material (such as carbon black silicone or silver paste coating) often does not match that of the substrate fabric, continuous shear stress is generated between the different material layers when the heart rate monitor experiences frequent stretching and contraction during wear. Under this dynamic stress environment for extended periods, coupled with sweat immersion and mechanical friction during washing, the conductive functional layer is highly susceptible to interfacial separation from the fabric substrate, resulting in delamination, blistering, and even coating cracking and peeling. This not only shortens the product's lifespan but also causes signal acquisition failure due to the broken conductive pathways.

[0004] Furthermore, existing conductive fabric manufacturing technologies primarily rely on physical bonding to attach conductive agents to the fiber surface. Due to the high crystallinity and low surface energy of synthetic fibers such as nylon or polyester, they exhibit chemical inertness, making it difficult for ordinary conductive adhesives to wet and penetrate the fiber bundles; they remain only on the fabric surface. This weak interfacial bonding is insufficient to resist external mechanical forces, and the surface conductive material is directly exposed to air and sweat, making it prone to oxidation and corrosion. This leads to an increase in contact resistance over time, resulting in problems such as heart rate data drift and increased dynamic noise. Therefore, how to solve the problems of interlayer bonding strength and signal stability in the electrode area while maintaining the comfort of heart rate monitor wearers is a pressing technical challenge in this field. Summary of the Invention

[0005] The technical problem solved by this invention is that existing conductive chest straps are mainly manufactured using surface bonding technology, and the conductive layer and the elastic webbing substrate rely only on physical bonding. Under long-term tensile rebound and water washing shear force, delamination and cracking are prone to occur. At the same time, the surface of the elastic fabric is smooth and highly crystalline, which cannot achieve high-strength chemical anchoring, resulting in unstable contact impedance and affecting the accuracy of heart rate signal acquisition.

[0006] To address the above problems, the present invention provides the following technical solution: First aspect This invention provides a novel method for weaving a conductive chest strap, employing the following technical solution: A novel method for weaving a conductive chest strap includes the following steps: Step S1, Weaving of segmented conductive substrate: Weaving a segmented webbing containing a non-electrode area (Area A) and an electrode data acquisition area (Area B) using a knitting process; wherein, Area A is woven into a stretchable structure, and Area B is woven into a fixed-length non-stretchable structure; conductive yarn is woven into Area B, and the conductive yarn is wrapped from the front to the back of the webbing at the edge of Area B. Step S2, Solvent-induced differential crystallinity pretreatment: The surface micro-etching pretreatment gel is coated on the surface of area B, left to stand for treatment, then cleaned and dried to form a micro-etching layer on the fiber surface of area B. Step S3, Vacuum-assisted deep impregnation: Under vacuum negative pressure conditions, a permeable conductive reinforcing composition is coated on the surface of region B, and the composition is drawn into the fiber bundle by the pressure difference; Step S4, in-situ gradient curing: The impregnated webbing is cured by gradient heating to form an interpenetrating network structure and chemical bonding between the composition and the fiber.

[0007] By employing the above technical solution, the synergistic effect of physical structure design and microscopic chemical modification improves the mechanical stability and electrical properties of the conductive layer. The specific principle is as follows: First, the non-stretchable structure constructed in step S1 provides a mechanical basis for subsequent deep chemical curing. Region B restricts axial deformation, allowing for deep filling with a conductive resin system that offers greater penetration and higher modulus after curing, thus avoiding brittle fracture caused by stretching. The combination of the non-stretchable substrate and the rigid anchoring layer eliminates the risk of cracking caused by modulus mismatch in traditional elastomer surface coatings.

[0008] Secondly, step S2 utilizes the directional etching effect of the solvent on the fiber surface to reduce the crystallinity of the nylon fiber surface, transforming the fiber surface into a loose amorphous state and generating microscopic roughness. In step S3, the conductive composition fills the gaps between the fiber monofilaments under vacuum negative pressure and diffuses into the amorphous regions of the fiber surface that are swollen by the solvent. After curing in step S4, the resin molecular chains and fiber molecular chains form a physically entangled interpenetrating polymer network at the interface, achieving molecular-level mechanical interlocking.

[0009] Finally, through the gradient curing in step S4, the crosslinking agent in the system undergoes chemical reactions in two directions simultaneously: one end grafts onto the active groups on the surface of the webbing fibers, and the other end crosslinks with the resin matrix in the conductive composition. Covalent bonding integrates the conductive filler, resin matrix, and webbing substrate into a single composite material structure capable of withstanding repeated washing and mechanical friction.

[0010] Preferably, in step S1, area A adopts a plain or rib weave structure with a spandex content of 15-20%; area B adopts a double-sided overlock weave structure with a spandex content of <5%; and the conductive yarn is a composite yarn of silver-plated nylon and carbon fiber.

[0011] By adopting the above technical solutions, the spandex content in area B is reduced and a lock-in coil structure is used to ensure that the electrode area maintains constant size when subjected to external force, preventing contact resistance fluctuations in the conductive network due to substrate deformation. At the same time, silver-plated nylon provides high conductivity and carbon fiber provides a wear-resistant skeleton, and the combination of the two enhances the stability of signal acquisition.

[0012] Preferably, in step S2, the coating amount of the surface micro-etching pretreatment gel is 50-80 g / m, the dwell time is 15-30 seconds, and the drying temperature is 80-90℃.

[0013] By adopting the above technical solution, the etching process can be controlled within a specific time window and coating amount range, which can destroy the highly crystalline layer on the fiber surface to form anchor points, while avoiding excessive solvent penetration that could damage the core structure inside the yarn.

[0014] Preferably, in step S3, the pressure range of the vacuum negative pressure is -0.06MPa to -0.08MPa; the thickness of the coated wet film is 0.12-0.20mm; and the negative pressure suction holding time is 10-20 seconds.

[0015] By employing the above technical solution, controlled fluid penetration is achieved using a specific negative pressure range. This pressure range ensures that the conductive composition precisely fills the internal voids of the fiber bundle in region B, avoiding insufficient penetration due to excessively low negative pressure, or excessively high negative pressure causing the slurry to penetrate the webbing and resulting in backside adhesive overflow.

[0016] Preferably, in step S4, the gradient temperature curing specifically includes: pre-drying at 60-70℃ for 3-5 minutes, forming a film at 100-110℃ for 2-3 minutes, and cross-linking curing at 130-140℃ for 3-5 minutes.

[0017] By adopting the above technical solution, the reaction process is controlled in stages: the low-temperature stage slowly removes the solvent to prevent coating blistering; the medium-temperature stage promotes the fusion and demulsification of waterborne polyurethane particles to form a film; and the high-temperature stage activates the blocked isocyanate or silane groups to complete the chemical crosslinking reaction.

[0018] Second aspect This invention provides a permeable conductive reinforcing composition for use in the novel conductive chest strap weaving method described in the first aspect, employing the following technical solution: A permeable conductive enhancement composition, comprising component A and component B; Component A comprises the following raw materials in parts by weight: 45.0-55.0 parts of aqueous polyurethane dispersion, 25.0-35.0 parts of flake silver powder, 2.0-4.0 parts of conductive carbon black, 10.0-15.0 parts of water / ethanol mixed solvent, 1.0-2.0 parts of thixotropic modifier, and 0.3-0.5 parts of wetting and leveling agent; Component B is 3-isocyanopropyltriethoxysilane, and its addition amount is 2.0%-3.0% of the total weight of component A.

[0019] By employing the above technical solution, the composition is specifically designed for deep impregnation processes. The higher proportion of waterborne polyurethane and solvent content reduces the initial viscosity of the slurry, facilitating flow and penetration under vacuum. The introduction of highly conductive carbon black as a bridging agent compensates for the reduced contact of flake silver powder caused by the high resin content, constructing a three-dimensional conductive network within the polymer matrix. Furthermore, component B, as a bifunctional crosslinking agent, allows its isocyanate groups to react with the terminal amino groups of the nylon substrate and the hard segments of the polyurethane resin to form urea bonds. After hydrolysis, the siloxane groups can condense with the hydroxyl groups on the silver powder and carbon black surfaces, as well as the polar groups on the fabric surface. This chemical bridging effect locks the inorganic conductive particles within the organic polymer network.

[0020] Preferably, the aqueous polyurethane dispersion is an aliphatic polycarbonate polyurethane with a solid content of 40%±1% and a 100% tensile modulus of 3.0-5.0 MPa; the average particle size D50 of the flake silver powder is 2.0-5.0 μm; and the BET specific surface area of ​​the conductive carbon black is 800-1000 m² / g.

[0021] By adopting the above technical solution, polycarbonate-type polyurethane has hydrolysis resistance and weather resistance, making it suitable for use in sweaty environments; micron-sized silver powder provides the main conductive path, and high specific surface area carbon black fills the tiny gaps. The combination of the two achieves low resistivity with low filling amount.

[0022] Preferably, the preparation method of the permeable conductive reinforced composition includes: (1) mixing the aqueous polyurethane dispersion, mixed solvent and wetting leveling agent, and stirring and dispersing at 500 rpm; (2) adding conductive carbon black and thixotropic modifier, increasing the speed to 1500 rpm and dispersing for 20 minutes; (3) reducing the speed to 800 rpm, adding flake silver powder, mixing evenly and grinding to a fineness of less than 15 μm, and vacuum degassing to obtain component A; (4) before use, adding component B to component A and mechanically stirring evenly.

[0023] By adopting the above technical solutions, the stepwise dispersion process avoids the breakage of flake silver powder under high shear, while ensuring the uniform distribution of difficult-to-disperse carbon black particles; the two-component, on-the-spot preparation method avoids the premature hydrolysis and failure of active silanes in the aqueous system.

[0024] Third aspect This invention provides a surface micro-etching pretreatment gel for use in the novel conductive chest strap weaving method described in the first aspect, employing the following technical solution: A surface micro-etching pretreatment gel comprises the following raw materials in weight percentages: formic acid 10.0%-15.0%; hydroxyethyl cellulose 1.5%-2.5%; anhydrous ethanol 5.0%-8.0%; and deionized water as the balance; the viscosity of the pretreatment gel is 8000-12000 mPa·s.

[0025] By employing the above technical solution, the gel system solves the technical problem of uncontrolled solvent diffusion on porous fabrics. The high-viscosity gel network constructed from hydroxyethyl cellulose imparts thixotropy to the system. During the coating and settling stage, the yield stress generated by the high viscosity balances the suction force generated by the fabric capillaries, preventing the acidic solvent from wicking away from the adjacent stretchable region (Area A), thereby protecting the polyurethane elastic fibers in Area A from chemical corrosion and maintaining the overall elasticity of the heart rate belt. Simultaneously, the formic acid and ethanol compound system can adjust the dissolution parameters for the polyamide fibers, ensuring that the solvent only swells the fiber skin layer without dissolving the fiber mass, providing a rough interface for subsequent resin penetration.

[0026] Preferably, the preparation method of the surface micro-etching pretreatment gel includes: mixing anhydrous ethanol and deionized water, adding hydroxyethyl cellulose powder, heating to 40°C and stirring to dissolve to form a base liquid; cooling to 25°C and adding formic acid dropwise, stirring evenly and allowing to stand under vacuum to defoam.

[0027] By adopting the above technical solution, the low-temperature acid addition process prevents the degradation of polymer thickeners under acidic conditions, ensuring gel viscosity stability and shelf life.

[0028] This invention provides a novel method for weaving a conductive chest strap. It has the following beneficial effects: 1. This invention significantly improves the bonding strength between the conductive layer and the webbing substrate by combining solvent micro-etching with vacuum deep impregnation technology. Gel pretreatment creates micro-roughened areas on the nylon fiber surface, and vacuum negative pressure forces the conductive resin into the fiber bundle. This results in the cured conductive layer no longer merely adhering to the fabric surface, but forming a physically entangled interpenetrating network structure with the fibers. This deep anchoring mechanism, combined with the chemical bonding effect of the silane coupling agent, effectively solves the delamination and cracking problems that occur after long-term use and washing in traditional surface bonding processes, extending the product's service life.

[0029] 2. This invention ensures high fidelity in heart rate signal acquisition through the synergistic effect of a segmented, non-stretchable structure and a silver / carbon composite conductive system. The non-stretchable braided structure in the electrode area physically restricts the dimensional deformation of the conductive layer during movement, avoiding resistance fluctuations caused by stretching. Simultaneously, the three-dimensional conductive network constructed from flake silver powder and high-structure carbon black maintains a stable conductive path under minute vibrations. The combination of these two elements significantly reduces dynamic contact impedance and motion artifacts, ensuring the accuracy of heart rate data during strenuous exercise.

[0030] 3. The thixotropic gel pretreatment process employed in this invention effectively protects the elasticity of the substrate. By controlling the viscosity and rheological properties of the etchant, the yield stress of the gel is used to block the capillary wicking effect of the solvent in the porous fabric, strictly confining the chemical reaction to the surface layer of the electrode area. This process feature prevents the diffusion of highly polar solvents to adjacent stretchable areas and prevents the swelling or breakage of the internal polyurethane elastic fibers (spandex) due to chemical corrosion, thereby improving electrode durability while fully preserving the overall wearing elasticity required for the heart rate monitor. Attached Figure Description

[0031] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] See attached document Figure 1 The main raw materials and reagents used in the following examples and comparative examples are sourced and specified as follows. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0034] Flake silver powder, purity ≥99.9%, average particle size D50 2.0μm-5.0μm, tap density ≥2.5g / cm³. Conductive carbon black, BET specific surface area 800m² / g-1000m² / g, DBP oil absorption value 300mL / 100g-350mL / 100g. Aqueous polyurethane dispersion, an anionic aliphatic polycarbonate polyurethane aqueous dispersion, solid content 40%±1%, 100% tensile modulus 3.0MPa-5.0MPa, elongation at break ≥500%, pH 7.0-8.0. 3-isocyanopropyltriethoxysilane, purity ≥98%. Hydrophobically modified fumed silica, surface grafted with dimethyldichlorosilane, specific surface area 100m² / g-150m² / g. Hydroxyethyl cellulose, with a 2% aqueous solution viscosity of 30000 mPa·s-50000 mPa·s at 25℃. Formic acid, purity ≥88%. Silver-plated nylon and carbon fiber composite conductive yarn, linear density 70D, silver content 15%-20%, resistivity <10Ω / cm. Nylon 66 filament, linear density 70D; spandex filament, linear density 40D.

[0035] Preparation Example 1: This preparation example provides a surface micro-etching pretreatment gel, including the following preparation steps: Add 83.5 kg of deionized water and 5.0 kg of anhydrous ethanol to a reactor equipped with a disperser, and start stirring until the mixture is homogeneous; slowly add 1.5 kg of hydroxyethyl cellulose powder, heat to 40°C and continue stirring for 40 minutes until completely dissolved to form a transparent base liquid; cool to 25°C, and slowly add 10.0 kg of formic acid dropwise under low-speed stirring. After the addition is complete, continue stirring for 15 minutes, let stand and defoam under vacuum for 2 hours to obtain a pretreated gel with a viscosity of 8000 mPa·s.

[0036] Preparation Example 2: This preparation example provides a surface micro-etching pretreatment gel, including the following preparation steps: Add 79.0 kg of deionized water and 6.5 kg of anhydrous ethanol to a reactor equipped with a disperser, and start stirring until the mixture is homogeneous; slowly add 2.0 kg of hydroxyethyl cellulose powder, heat to 40°C and stir continuously for 40 minutes until completely dissolved to form a transparent base liquid; cool to 25°C, and slowly add 12.5 kg of formic acid dropwise under low-speed stirring. After the addition is complete, continue stirring for 15 minutes, let stand and defoam under vacuum for 2 hours to obtain a pretreated gel with a viscosity of 10000 mPa·s.

[0037] Preparation Example 3: This preparation example provides a surface micro-etching pretreatment gel, including the following preparation steps: Add 74.5 kg of deionized water and 8.0 kg of anhydrous ethanol to a reactor equipped with a disperser, and start stirring until the mixture is homogeneous; slowly add 2.5 kg of hydroxyethyl cellulose powder, heat to 40°C and continue stirring for 40 minutes until completely dissolved to form a transparent base liquid; cool to 25°C, and slowly add 15.0 kg of formic acid dropwise under low-speed stirring. After the addition is complete, continue stirring for 15 minutes, let stand and defoam under vacuum for 2 hours to obtain a pretreated gel with a viscosity of 12000 mPa·s.

[0038] Preparation Example 4: This preparation example provides a slurry of component A of a permeable conductive enhancement composition, comprising the following preparation steps: 55.0 parts by weight of aqueous polyurethane dispersion, 10.0 parts by weight of water / ethanol mixed solvent (mass ratio 3:1), and 0.3 parts by weight of polyether-modified polydimethylsiloxane were added to a dispersion tank and stirred at 500 rpm for 5 minutes. 2.0 parts by weight of conductive carbon black and 1.0 parts by weight of hydrophobic modified fumed silica were gradually added, and the speed was increased to 1500 rpm for 20 minutes. The speed was reduced to 800 rpm, and 25.0 parts by weight of flake silver powder were added in batches. The mixed slurry was ground to a fineness of less than 15 μm using a three-roll mill. Finally, it was stirred at low speed and degassed for 10 minutes under a vacuum of -0.09 MPa to obtain component A slurry.

[0039] Preparation Example 5: This preparation example provides a slurry of component A of a permeable conductive enhancement composition, comprising the following preparation steps: 50.0 parts by weight of aqueous polyurethane dispersion, 12.5 parts by weight of water / ethanol mixed solvent (mass ratio 3:1), and 0.4 parts by weight of polyether modified polydimethylsiloxane were added to a dispersion tank and stirred at 500 rpm for 5 minutes. 3.0 parts by weight of conductive carbon black and 1.5 parts by weight of hydrophobic modified fumed silica were gradually added, and the speed was increased to 1500 rpm for 20 minutes. The speed was reduced to 800 rpm, and 30.0 parts by weight of flake silver powder were added in batches. The mixed slurry was ground to a fineness of less than 15 μm using a three-roll mill. Finally, it was stirred at low speed and degassed for 10 minutes under a vacuum of -0.09 MPa to obtain component A slurry.

[0040] Preparation Example 6: This preparation example provides a slurry of component A of a permeable conductive enhancement composition, comprising the following preparation steps: 45.0 parts by weight of aqueous polyurethane dispersion, 15.0 parts by weight of water / ethanol mixed solvent (mass ratio 3:1), and 0.5 parts by weight of polyether-modified polydimethylsiloxane were added to a dispersion tank and stirred at 500 rpm for 5 minutes. 4.0 parts by weight of conductive carbon black and 2.0 parts by weight of hydrophobic modified fumed silica were gradually added, and the speed was increased to 1500 rpm for dispersion for 20 minutes. The speed was reduced to 800 rpm, and 35.0 parts by weight of flake silver powder were added in batches. The mixed slurry was ground to a fineness of less than 15 μm using a three-roll mill. Finally, it was stirred at low speed and degassed for 10 minutes under a vacuum of -0.09 MPa to obtain component A slurry.

[0041] Example 1 This embodiment provides a novel method for weaving a conductive chest strap, including the following steps: Step S1: Weaving of segmented conductive substrate The weave is performed using a 28-gauge / inch seamless circular knitting machine, employing 70D nylon 66 filament and 40D spandex yarn. In the non-electrode area (Area A), a plain weave with 18% spandex content is used to maintain high tensile resilience. In the electrode data acquisition area (Area B), a high-density double-sided overlock weave is used, reducing the spandex content to 4% and restricting deformation through a coil-locking structure, forming a fixed-length, non-stretchable area. Simultaneously, 70D silver-plated nylon / carbon fiber composite conductive yarn is woven into Area B as a filler yarn. Through jacquard weaving, the conductive yarn is controlled to wrap from the front to the back of the weave at the edge of Area B, forming a continuous conductive path.

[0042] Step S2: Solvent-induced differential crystallinity pretreatment The webbing was laid flat and fixed on the mold, covering area A and exposing only the conductive surface of area B. Using a precision screen printing machine, the surface micro-etching pretreatment gel (formic acid concentration 10%, viscosity 8000 mPa·s) obtained in Preparation Example 1 was uniformly coated onto the surface of area B. The coating amount was controlled at 50 g / m, and the treatment time was 20 seconds. After the time was up, area B was immediately cleaned with deionized water using high-pressure atomization spray to remove residual gel, and then quickly dried with 80°C hot air to form a micro-rough etched layer on the fiber surface of area B.

[0043] Step S3: Vacuum-assisted deep impregnation Take 100 parts by weight of the slurry of component A prepared in Preparation Example 4, add 2.0 parts by weight of 3-isocyanopropyltriethoxysilane (component B), and mechanically stir until homogeneous to prepare a penetrating conductive reinforcing composition. Place the dried webbing region B on a porous vacuum suction cup, turn on the vacuum pump to maintain the chamber negative pressure at -0.07 MPa. Under the negative pressure condition, use a doctor blade to coat the conductive composition onto region B, with a wet film thickness of 0.15 mm. Maintain the negative pressure suction for 15 seconds, and use the pressure difference to force the composition into the fiber bundle.

[0044] Step S4: In-situ gradient curing The impregnated webbing is sent into a multi-temperature drying tunnel and sequentially undergoes pre-drying at 60°C for 3 minutes, film formation at 100°C for 2 minutes, and cross-linking and curing at 135°C for 3 minutes, so that the resin and fiber form an interpenetrating network structure and chemical bonding, resulting in the finished conductive chest strap.

[0045] Example 2 This embodiment provides a novel conductive chest strap weaving method. Compared with Embodiment 1, the pretreatment strength and conductive composition formulation are adjusted (focusing on verification of low-limit process conditions), including the following steps: Step S1: Weaving of segmented conductive substrate The weaving process is consistent with that of Example 1 to ensure that a segmented webbing substrate with the non-stretchable characteristics of region B is obtained.

[0046] Step S2: Solvent-induced differential crystallinity pretreatment The surface micro-etching pretreatment gel (formic acid concentration 12.5%, viscosity 10000 mPa·s) obtained in Preparation Example 2 was used. The coating amount was controlled at 60 g / m, and the dwell time was shortened to 15 seconds (the lower limit of the time range of the test claims). Cleaning and drying were then performed immediately.

[0047] Step S3: Vacuum-assisted deep impregnation Take 100 parts by weight of the slurry of component A (high silver content / low resin ratio) prepared in Preparation Example 6, add 2.5 parts by weight of 3-isocyanopropyltriethoxysilane (component B), and stir until homogeneous. Place the webbing area B on a vacuum suction cup, and adjust the vacuum degree to **-0.06 MPa** (testing the lower limit of the negative pressure range of the claim). Coat a wet film thickness of 0.12 mm, and maintain negative pressure suction for 10 seconds.

[0048] Step S4: In-situ gradient curing The curing process parameters were kept the same as in Example 1: pre-drying at 60°C for 3 minutes, film formation at 100°C for 2 minutes, and cross-linking curing at 135°C for 3 minutes.

[0049] Example 3 This embodiment provides a novel conductive chest strap weaving method, which, compared with Embodiment 1, enhances pretreatment strength and increases the amount of crosslinking agent (focusing on verification of high-limit process conditions), and includes the following steps: Step S1: Weaving of segmented conductive substrate The weaving process is consistent with that of Example 1 to ensure that a segmented webbing substrate with the non-stretchable characteristics of region B is obtained.

[0050] Step S2: Solvent-induced differential crystallinity pretreatment The surface micro-etching pretreatment gel (formic acid concentration 15%, viscosity 12000 mPa·s) obtained in Preparation Example 3 was used. The coating amount was controlled at 80 g / m, and the dwell time was extended to 30 seconds (testing the upper limit of the claimed time range to verify safety for deep spandex). Cleaning and drying were then performed immediately.

[0051] Step S3: Vacuum-assisted deep impregnation Take 100 parts by weight of component A slurry prepared in Preparation Example 5, add 3.0 parts by weight of 3-isocyanopropyltriethoxysilane (component B, for testing high crosslinking density), and stir until homogeneous. Place region B of the webbing on a vacuum suction cup, and adjust the vacuum level to -0.08 MPa (for testing the upper limit of the negative pressure range of the claim). Coat a wet film thickness of 0.20 mm, and maintain negative pressure suction for 20 seconds.

[0052] Step S4: In-situ gradient curing To match the high crosslinking agent content, the curing temperature was slightly increased: the product was pre-dried at 60°C for 3 minutes, film-forming at 110°C for 2 minutes, and crosslinking and curing at 140°C for 3 minutes.

[0053] Comparative Example 1 (Verifying the necessity of solvent pretreatment) Compared with Example 1, the difference is that step S2 (solvent-induced differential crystallinity pretreatment) is omitted. That is, the B region of the ribbon is not etched by formic acid gel, the surface of the original fiber is kept smooth, and the vacuum-assisted deep impregnation in step S3 is performed directly, while the rest are the same.

[0054] Comparative Example 2 (Verifying the necessity of vacuum-assisted deep penetration) Compared to Example 1, the difference lies in the fact that a vacuum negative pressure process was not used in step S3. Specifically, the conductive composition was coated onto the surface of area B using a conventional screen printing method, allowing it to flow naturally rather than being forcibly absorbed into the fiber; all other aspects remained the same.

[0055] Comparative Example 3 (verifying the importance of gelation in preventing wicking damage) The difference between Example 1 and Example 2 lies in the form of the pretreatment agent used in step S2. Specifically, the "pretreatment gel of Example 1" was replaced with an aqueous solution of liquid formic acid of the same concentration (without the addition of hydroxyethyl cellulose for thickening), and applied by spraying. All other aspects remained the same. This comparative example is used to demonstrate that the liquid solvent can diffuse to region A due to capillary effect, thereby damaging the elasticity of the spandex.

[0056] Comparative Example 4 (verifying the dual locking effect of the chemical cross-linking agent) Compared to Example 1, the difference lies in that the conductive composition used in step S3 does not contain component B. Specifically, when formulating the conductive composition, only the slurry of component A from Preparation Example 4 is used, without adding 3-isocyanopropyltriethoxysilane (crosslinking agent), and curing is achieved solely through the physical bonding of the PUD resin; all other aspects remain the same.

[0057] Comparative Example 5 (Compared to traditional TPU hot-press lamination process) Compared with Example 1, the difference is that steps S2 to S4 are replaced with a traditional hot-pressing process. Specifically, after weaving in step S1, solvent treatment and slurry impregnation are not performed. Instead, the pre-made TPU conductive film is cut and hot-pressed onto the surface of area B of the webbing at 140°C and 0.4MPa. The rest (such as the substrate structure) are the same.

[0058] Test Example 1: Elasticity Retention Rate and Substrate Damage Assessment in Untreated Area A Samples were taken from the finished heart rate monitors, including samples from Examples 1, 2, 3, Comparative Example 3, and untreated blank webbing. Sampling was performed within a 5mm to 25mm radius from the boundary between electrode area B and stretchable area A, a region most susceptible to solvent penetration. Each sample was cut into rectangular specimens 50mm long and 20mm wide, with 10 parallel samples prepared for each group. The morphology of the spandex fibers at the sample edges was observed using a 200x optical microscope, recording any swelling, breakage, or adhesion. Subsequently, according to GB / T 3923.1-2013, a universal testing machine was used to perform constant-speed tensile tests on the specimens, with a spacing of 20mm and a tensile speed of 100mm / min. The breaking strength and elongation at a constant load of 10N were recorded, and the strength retention rate was calculated based on the data from the blank webbing.

[0059] The specific test data is shown in the table below: Table 1. Influence data of different treatment systems on the mechanical properties of the substrate interface region. ; Based on the analysis of test data and chemical action mechanisms, after treatment with a low-viscosity liquid formic acid solution, the tensile strength of the substrate in Comparative Example 3 decreased to approximately 213.5 N, with a strength retention rate of approximately 60.8%, and the elongation at constant load decreased from approximately 129% to approximately 45%. The performance degradation is attributed to the wicking effect of the low-viscosity solvent under capillary pressure, which migrates and diffuses over long distances to region A through the yarn gaps. Upon contact with the polyurethane elastic fibers, the formic acid causes the spandex to swell, plasticize, and break, damaging the elastic skeleton of the webbing.

[0060] Examples 1 to 3 introduced hydroxyethyl cellulose to construct a thixotropic gel system. The tensile strength retention rate of the samples remained above 97%, with no statistical difference compared to the control group. The high-viscosity gel system increased the internal viscous resistance of the fluid, reducing the solvent penetration rate in the fiber capillary channels. The three-dimensional polymer network restricted the diffusion path of formic acid molecules, confining the etching reaction to the surface fibers of the coated area. Within the process time of 15 to 30 seconds, the solvent did not undergo lateral migration and did not come into contact with the spandex component inside the adjacent A area. The experiment demonstrates that the gel-based micro-etching pretreatment process can achieve selective etching of nylon fibers on the surface of specific areas by adjusting rheological properties, while avoiding damage to the overall mechanical properties and elastic components of the substrate.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A novel method for weaving a conductive chest strap, characterized in that, Includes the following steps: Step S1, Weaving of segmented conductive substrate: Weaving a segmented webbing containing a non-electrode area A and an electrode data acquisition area B using a knitting process; wherein, area A is woven into a stretchable structure, and area B is woven into a fixed-length non-stretchable structure; conductive yarn is woven into area B, and the conductive yarn is wrapped from the front to the back of the webbing at the edge of area B. Step S2, Solvent-induced differential crystallinity pretreatment: The surface micro-etching pretreatment gel is coated on the surface of area B, left to stand for treatment, then cleaned and dried to form a micro-etching layer on the fiber surface of area B. Step S3, Vacuum-assisted deep impregnation: Under vacuum negative pressure conditions, a permeable conductive reinforcing composition is coated on the surface of region B, and the composition is drawn into the fiber bundle by the pressure difference; Step S4, in-situ gradient curing: The impregnated webbing is cured by gradient heating to form an interpenetrating network structure and chemical bonding between the composition and the fiber.

2. The novel conductive chest strap weaving method according to claim 1, characterized in that, In step S1, area A adopts a plain or rib weave structure with a spandex content of 15-20%; area B adopts a double-sided overlock weave structure with a spandex content of <5%; and the conductive yarn is a composite yarn of silver-plated nylon and carbon fiber.

3. The novel conductive chest strap weaving method according to claim 1, characterized in that, In step S2, the coating amount of the surface micro-etching pretreatment gel is 50-80 g / m, the dwell time is 15-30 seconds, and the drying temperature is 80-90℃.

4. The novel conductive chest strap weaving method according to claim 1, characterized in that, In step S3, the pressure range of the vacuum negative pressure is -0.06MPa to -0.08MPa; the thickness of the coated wet film is 0.12-0.20mm; and the negative pressure suction holding time is 10-20 seconds.

5. The novel conductive chest strap weaving method according to claim 1, characterized in that, In step S4, the gradient temperature curing specifically includes: pre-drying at 60-70℃ for 3-5 minutes, forming a film at 100-110℃ for 2-3 minutes, and cross-linking curing at 130-140℃ for 3-5 minutes.

6. A permeable conductive reinforcing composition, used in the novel conductive chest strap weaving method according to any one of claims 1-4, characterized in that, It consists of component A and component B; Component A comprises the following raw materials in parts by weight: 45.0-55.0 parts of aqueous polyurethane dispersion, 25.0-35.0 parts of flake silver powder, 2.0-4.0 parts of conductive carbon black, 10.0-15.0 parts of water / ethanol mixed solvent, 1.0-2.0 parts of thixotropic modifier, and 0.3-0.5 parts of wetting and leveling agent; Component B is 3-isocyanopropyltriethoxysilane, and its addition amount is 2.0%-3.0% of the total weight of component A.

7. The permeation-type conductive enhancement composition according to claim 6, characterized in that, The aqueous polyurethane dispersion is an aliphatic polycarbonate polyurethane with a solid content of 40%±1% and a 100% tensile modulus of 3.0-5.0MPa; the average particle size D50 of the flake silver powder is 2.0-5.0μm; and the BET specific surface area of ​​the conductive carbon black is 800-1000m² / g.

8. The method for preparing the permeation-type conductive enhancement composition according to claim 6, characterized in that, Includes the following steps: Mix the waterborne polyurethane dispersion, mixed solvent and wetting leveling agent, and disperse by stirring at 500 rpm; Add conductive carbon black and thixotropic modifier, increase the rotation speed to 1500 rpm and disperse for 20 minutes; Reduce the rotation speed to 800 rpm, add flake silver powder, mix evenly and grind until the fineness is less than 15 μm, and degas under vacuum to obtain component A; Before use, add component B to component A and stir mechanically until homogeneous.

9. A surface micro-etching pretreatment gel, used in the novel conductive chest strap weaving method according to any one of claims 1-4, characterized in that, It contains the following raw materials by weight percentage: Formic acid 10.0%-15.0%; Hydroxyethyl cellulose 1.5%-2.5%; Anhydrous ethanol 5.0%-8.0%; Deionized water balance; The viscosity of the pretreated gel is 8000-12000 mPa·s.

10. The method for preparing the surface micro-etching pretreatment gel according to claim 9, characterized in that, Includes the following steps: Anhydrous ethanol and deionized water were mixed, hydroxyethyl cellulose powder was added, and the mixture was heated to 40°C and stirred to dissolve and form a base solution. After cooling to 25°C, formic acid was added dropwise, stirred evenly, and allowed to stand under vacuum to defoam.

Images