Ultra-high molecular weight polyethylene conductive composite fiber based on blending spinning and preparation and application thereof

Abstract

The present application relates to a kind of based on blend spinning ultra-high molecular weight polyethylene conductive composite fiber and its preparation and application, through " three-step dispersion method " filler dispersion process, i.e., first to the surface of conductive filler Pre-coated treatment, then realize microscale mixing by high-energy ball milling, further homogenization in swelling process, effectively solve the dispersion problem of conductive filler in UHMWPE high viscosity matrix. By the compounding of zero-dimensional carbon black, one-dimensional carbon nanotube and two-dimensional graphene, a perfect three-dimensional conductive network is constructed at low filler content, achieving the synergy of high conductivity and high mechanical property. The fiber breaking strength is ≥1.8 GPa, the electrical conductivity is ≥5 S / cm, and the electrical conductivity retention rate is ≥80% after 100 cycles of cyclic tension at 20% strain. It can be used in antistatic fabric, electromagnetic shielding material, flexible sensor and other fields.

Description

Technical Field

[0001] This invention belongs to the field of functional fiber materials technology, and relates to an ultra-high molecular weight polyethylene conductive composite fiber based on blend spinning, its preparation and application. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) fiber, renowned as the "king of high-performance fibers" due to its ultra-high strength (2-4 GPa), high modulus, low density, and excellent chemical resistance and abrasion resistance, is widely used in bulletproof protection, marine engineering, aerospace, and other fields. However, the highly crystalline molecular chains, surface inertness, and lack of polar groups in UHMWPE result in a volume resistivity as high as 10⁻⁶. 16 ~10 18 With a conductivity of Ω·cm, UHMWPE fibers are typical insulating materials. This characteristic severely limits their application in fields requiring conductivity, such as antistatic properties, electromagnetic shielding, and flexible sensing. To impart conductivity to UHMWPE fibers, researchers have developed various methods, primarily surface coating and blend spinning. Surface coating achieves conductivity by coating the surface of pre-formed UHMWPE fibers with a conductive layer (such as a metal plating or conductive polymer coating), but it suffers from weak adhesion between the conductive layer and the matrix, easy peeling, and poor wear resistance. Blend spinning involves mixing conductive fillers with UHMWPE resin before spinning, and then directly producing conductive fibers through a spinning process. This method allows the conductive fillers to be evenly distributed within the fiber, resulting in a strong bond between the conductive layer and the matrix, and thus better durability.

[0003] Chinese patent application CN104711696A discloses a heat-resistant and antistatic ultra-high molecular weight polyethylene fiber and its preparation method. The method involves spinning a mixture of conductive nanoparticles and UHMWPE powder to obtain fibers with antistatic properties. However, this method has the following drawbacks: (1) The melt viscosity of UHMWPE is extremely high (10... 8 ~10 9 Pa·s), conductive fillers are difficult to disperse uniformly during melt blending and are prone to forming agglomerates, which affects the construction of conductive networks and fiber mechanical properties; (2) The addition of high content conductive fillers often leads to a significant decrease in the tensile strength and elongation at break of fibers; (3) The interface between conductive fillers and UHMWPE matrix is ​​weak, and the conductive network is easily destroyed during tensile deformation, resulting in poor conductive stability.

[0004] Therefore, developing a conductive composite fiber that maintains the excellent mechanical properties of UHMWPE, has high conductivity, and features uniformly dispersed conductive fillers and a stable conductive network has significant application value. Summary of the Invention

[0005] The purpose of this invention is to provide a conductive composite fiber of ultra-high molecular weight polyethylene based on blend spinning and its preparation method. Through an innovative "three-step dispersion method" filler dispersion process and "interface reinforcement" formulation design, the problem of uniform dispersion of conductive fillers in UHMWPE matrix is ​​solved, achieving a synergy of high mechanical properties and high conductivity, and exhibiting good conductive stability.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing ultra-high molecular weight polyethylene conductive composite fibers based on blend spinning, comprising the following steps: S1. The conductive filler, nucleating agent, dispersing agent and surface modifier are dry-mixed to uniformly coat the conductive filler and nucleating agent surface to obtain pre-dispersed conductive composite powder. S2. The pre-dispersed conductive composite powder obtained in S1 is ball-milled and mixed with UHMWPE (ultra-high molecular weight polyethylene) powder, and then added to a solvent and stirred to swell, so as to obtain a uniform spinning solution. S3. The spinning solution is extruded through a spinneret, cooled and solidified in a coagulation bath to form gel fiber. After extraction and drying, it undergoes multi-stage hot stretching and finally heat setting to obtain ultra-high molecular weight polyethylene conductive composite fiber.

[0007] Furthermore, the conductive filler is a mixture of conductive carbon black, carbon nanotubes, and graphene in a mass ratio of (1-5):(1-3):(0.5-2). Preferably, the mass ratio of the three components can be 3:2:1.

[0008] Furthermore, the dispersing agent is hyperbranched polyethylene or maleic anhydride-grafted polyethylene, the surface modifier is a silane coupling agent or a titanate coupling agent, and the nucleating agent is an organophosphate nucleating agent.

[0009] Furthermore, the amount of conductive filler added satisfies the following: its mass fraction in the ultra-high molecular weight polyethylene conductive composite fiber is 0.5%~8%; the amount of nucleating agent added also satisfies the following: its mass fraction in the ultra-high molecular weight polyethylene conductive composite fiber is 0.3%~0.6%, for example, it can be 0.45%, etc.

[0010] Furthermore, ultra-high molecular weight polyethylene (UHMWPE), as a matrix material, provides mechanical support for the fibers, with a viscosity-average molecular weight of 1 million to 6 million.

[0011] Furthermore, in S2, the ball milling and blending process uses a planetary high-energy ball mill with a ball-to-material ratio of (5-10):1, the ball milling media being zirconia balls, the ball milling speed being 200-500 rpm, and the ball milling time being 1-4 hours.

[0012] Furthermore, in S2, the solvent is white oil or decahydronaphthalene, and the stirring and swelling process is as follows: the solid content is controlled at 6~10wt%, and the mixture is stirred at 80~120℃ for 2~6h.

[0013] Furthermore, in S3, the multi-stage hot stretching process is carried out in three stages. The first stage stretching temperature is 100℃~110℃, and the stretching ratio is 3~5 times; the second stage stretching temperature is 110℃~120℃, and the stretching ratio is 4~6 times; the third stage stretching temperature is 120℃~140℃, and the stretching ratio is 5~8 times.

[0014] Furthermore, in S3, the heat setting process is as follows: treatment at 120℃~150℃ for 10~30 minutes.

[0015] In a second aspect, the present invention provides an ultra-high molecular weight polyethylene conductive composite fiber based on blend spinning, which is prepared by the preparation method described in the first aspect. The fiber has a tensile strength ≥1.8 GPa, an electrical conductivity ≥5 S / cm, and an electrical conductivity retention rate ≥80% after 100 cycles of cyclic stretching at 20% strain.

[0016] In a third aspect, the present invention provides the application of ultra-high molecular weight polyethylene conductive composite fibers based on blend spinning in the preparation of antistatic fabrics, electromagnetic shielding materials, flexible sensors, and smart wearable devices.

[0017] Compared with the prior art, the present invention has the following advantages: (1) Significantly improved uniformity of conductive filler dispersion: This invention adopts a "three-step dispersion method", namely, firstly, the conductive filler is pre-coated on the surface, then the microscale mixing of the filler and UHMWPE is achieved by high-energy ball milling, and finally, further homogenization is achieved during the swelling process, which effectively solves the problem of difficult filler dispersion under high viscosity of UHMWPE. SEM observation shows that the conductive filler is uniformly distributed in the fiber cross section and there are no obvious agglomerates.

[0018] (2) Optimization of three-dimensional conductive network structure: By combining zero-dimensional carbon black, one-dimensional carbon nanotubes and two-dimensional graphene, a more complete three-dimensional conductive network is constructed with low filler content by utilizing the synergistic effect of materials of different dimensions. Carbon black fills the gaps between carbon nanotubes, and graphene provides in-plane conductive pathways. The three work together to reduce the percolation threshold to 0.3 wt%.

[0019] (3) High mechanical property retention rate: Due to the uniform dispersion of filler and low addition amount (≤8 wt%), the addition of nucleating agent reduces the undercooling of UHMWPE, promotes heterogeneous nucleation, improves interfacial bonding, and the fiber breaking strength retention rate can reach more than 85%, which solves the problem of large mechanical property loss in traditional blending method.

[0020] (4) Excellent electrical conductivity: The uniformly dispersed conductive network and good interfacial bonding give the fiber excellent electrical conductivity under dynamic deformation. After 100 cycles of cyclic stretching at 20% strain, the conductivity retention rate can still reach more than 80%.

[0021] (5) The process is highly controllable and suitable for industrial production: The method of this invention is based on the mature gel spinning process, and only adds filler pre-dispersion and ball milling and blending steps at the front end. The process window is wide and it is easy to realize continuous production. Detailed Implementation

[0022] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0024] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0025] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0026] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0027] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0028] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0029] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0030] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0031] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0032] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0033] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0034] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and ingredients may be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0035] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0036] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0037] Explanation of the source of raw materials used in this embodiment: (1) The preparation process of hyperbranched polyethylene is as follows: Catalyst preparation: α-diimine nickel complex (i.e., bis-(2,6-diisopropylphenyl)-butadiimine nickel dibromide) was synthesized according to the method in reference

[11] and purified before use; methylaluminoxane (MAO) was a commercially available product and was not further processed before use.

[0038] Polymerization reaction: In a 250 mL Schlenk flask fully purged with nitrogen, 100 mL of dry toluene was added, followed by MAO (Al / Ni molar ratio = 800:1) and 0.01 mmol of α-diimine nickel complex. After purging with ethylene gas three times, the ethylene pressure was maintained at 1 atm, and the reaction was stirred in a 30°C water bath for 2 hours. Ethylene was continuously introduced during the reaction to maintain a constant pressure.

[0039] Product post-treatment: After polymerization, 10 mL of acidified ethanol (containing 5 wt% hydrochloric acid) was added to terminate the reaction. The reaction solution was poured into 200 mL of ethanol to precipitate the polymer. The polymer was filtered, washed 3-5 times with a large amount of ethanol, and dried under vacuum at 60°C to constant weight to obtain a white powdery hyperbranched polyethylene with a yield of approximately 85%.

[0040] Product characterization: The obtained hyperbranched polyethylene was characterized by gel permeation chromatography (GPC). The number-average molecular weight was approximately 800 g / mol, and the molecular weight distribution (PDI) was approximately 1.4. The degree of branching was approximately 120 / 1000C (as indicated by...). 13 (C NMR determination).

[0041] The specific references mentioned above are:

[11] Xiao, Anguo. Preparation, characterization and performance study of novel hyperbranched polyolefins [D]. Doctoral dissertation, Zhejiang University, 2009.

[12] North China Huajin Chemical Industry Co., Ltd. A method for preparing a post-transition metal catalyst for the synthesis of hyperbranched polyethylene: CN120484163A[P]. 2025-08-15. (2) UHMWPE powder: purchased from Shanghai Lianle Chemical Technology Co., Ltd., grade X-300.

[0042] (3) Nucleating agent: Organic phosphate nucleating agent (brand name NA-21), commercially available industrial product.

[0043] (4) Silane coupling agent: KH-550 (γ-aminopropyltriethoxysilane), commercially available industrial product.

[0044] (5) Conductive carbon black: Grade VXC72, commercially available industrial product.

[0045] (6) Multi-walled carbon nanotubes: grade TNIM4, commercially available industrial product.

[0046] (7) Graphene: Grade SE1231, commercially available industrial product.

[0047] (8) White oil: 68# industrial grade white oil, commercially available industrial product.

[0048] (9) Other reagents: Dichloromethane, etc. are all commercially available analytical grade.

[0049] Unless otherwise specified, all other raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in this field.

[0050] Example 1: (1) Pre-dispersion treatment of conductive filler: Conductive carbon black (average particle size 30 nm), multi-walled carbon nanotubes (diameter 10-20 nm, length 10-30 μm) and graphene (sheet diameter 1-5 μm, thickness 1-3 nm) were mixed at a mass ratio of 3:2:1, with a total mass of 100 g. 5 g of organophosphate nucleating agent NA-21, 10 g of hyperbranched polyethylene as a dispersing aid, and 2 g of silane coupling agent KH-550 as a surface modifier were added. The mixture was placed in a high-speed mixer and mixed at 1000 rpm for 20 minutes at 80°C to uniformly coat the conductive filler and nucleating agent surfaces, thus obtaining a pre-dispersed conductive composite powder.

[0051] (2) UHMWPE pretreatment: Take 1000 g of UHMWPE powder with a viscosity-average molecular weight of 3 million and vacuum dry it at 100℃ for 3 hours.

[0052] (3) Multi-stage blending: The pre-dispersed conductive composite powder (total conductive filler 100 g, corresponding to filler content of about 8.5 wt% in the fiber) obtained in step (1) and the UHMWPE powder treated in step (2) are added to a planetary high-energy ball mill with a ball-to-material ratio of 8:1 and a ball milling medium of zirconia balls (5 mm in diameter). The mixture is ball-milled at 300 rpm for 2 hours under nitrogen protection to obtain a uniform blended material.

[0053] (4) Swelling treatment: Add the blended material obtained in step (3) to white oil (solid content 8 wt%), stir and swell at 100°C for 4 hours to form a uniform spinning solution.

[0054] (5) Gel spinning: The spinning solution obtained in step (4) is extruded through a spinneret (orifice diameter 0.8 mm), and then solidified and cooled in a water bath to form gel fibers.

[0055] (6) Super-expansion heat stretching: After solvent extraction (using dichloromethane to extract white oil) and drying, the gel fiber obtained in step (5) is subjected to three-stage heat stretching: the first stage stretching temperature is 105℃ and the stretching ratio is 4 times; the second stage stretching temperature is 115℃ and the stretching ratio is 5 times; the third stage stretching temperature is 130℃ and the stretching ratio is 6 times; the total stretching ratio is 120 times.

[0056] (7) Heat setting treatment: The fiber is heat set at 140℃ for 20 minutes to obtain conductive UHMWPE composite fiber.

[0057] Performance testing: The electrical conductivity and mechanical properties of the fiber prepared in Example 1 were tested. The electrical conductivity was tested using the four-probe method, and the results showed that the fiber conductivity was 8.5 S / cm. Tensile testing showed that the fiber's breaking strength was 2.1 GPa (compared to 2.4 GPa for the pure UHMWPE fiber control sample), and the elongation at break was 4.2%. After 100 cycles of tensile testing at 20% strain, the electrical conductivity retention rate was 85%. SEM observation showed that the conductive filler was uniformly distributed in the fiber cross-section, with no obvious agglomerates.

[0058] Example 2 The results are basically the same as in Example 1, except that in step (1), the total mass of the conductive filler is reduced to 60 g (corresponding to a filler content of about 5.6 wt% in the fiber), and the mass ratio of conductive carbon black, carbon nanotubes and graphene is adjusted to 2:1:1.

[0059] The obtained fiber has an electrical conductivity of 3.2 S / cm, a breaking strength of 2.2 GPa, and a breaking elongation of 4.5%. After 100 cycles of cyclic tensile testing at 20% strain, the electrical conductivity is retained at 88%.

[0060] Example 3 The results are basically the same as in Example 1, except that in step (1), the total mass of the conductive filler is increased to 160 g (corresponding to a filler content of about 13.6 wt% in the fiber), and the mass ratio of conductive carbon black, carbon nanotubes and graphene is adjusted to 4:3:1.

[0061] The obtained fiber has an electrical conductivity of 15.6 S / cm, a tensile strength of 1.9 GPa, and an elongation at break of 3.8%. After 100 cycles of tensile testing at 20% strain, the electrical conductivity is retained at 76%.

[0062] Comparative Example 1 (without pre-dispersion treatment) The process is basically the same as in Example 1, except that the pre-dispersion treatment in step (1) is omitted, and conductive carbon black, carbon nanotubes, graphene and UHMWPE powder are directly added to a ball mill for blending.

[0063] The obtained fiber had an electrical conductivity of 1.2 S / cm, a tensile strength of 1.5 GPa, and an elongation at break of 3.0%. SEM observation showed obvious filler agglomerates in the fiber. After 100 cycles of tensile testing at 20% strain, the electrical conductivity retention rate was only 42%.

[0064] Comparative Example 2 (Single Packing Material) It is basically the same as Example 1, except that in step (1), the conductive filler is only carbon nanotubes (without carbon black and graphene), and the total mass is still 100 g.

[0065] The obtained fiber had an electrical conductivity of 2.8 S / cm and a breaking strength of 2.0 GPa. The percolation threshold was approximately 1.2 wt%, higher than the 0.3 wt% of Example 1.

[0066] Comparative Example 3 (without nucleating agent) It is basically the same as Example 1, except that no nucleating agent is added in step (1).

[0067] The obtained fiber had an electrical conductivity of 8.1 S / cm, comparable to that of Example 1, but a breaking strength of 1.9 GPa, lower than the 2.1 GPa of Example 1. After 100 cycles of cyclic tensile testing at 20% strain, the conductivity retention rate was 81%, also lower than the 85% of Example 1. This indicates that the addition of the nucleating agent helps to improve interfacial bonding and enhance mechanical properties and electrical conductivity stability.

[0068] Comparative Example 4 (without ball milling process) The process is basically the same as in Example 1, except that the ball milling and blending process is omitted in step (3), and the pre-dispersed composite powder obtained in step (1) and UHMWPE powder are directly added to the solvent for swelling treatment.

[0069] The obtained fibers had an electrical conductivity of 3.5 S / cm, a tensile strength of 1.8 GPa, and an elongation at break of 3.5%. After 100 cycles of cyclic stretching at 20% strain, the electrical conductivity was retained at 65%. This indicates that the ball milling process is crucial for achieving uniform mixing at the microscale.

[0070] Comparative Example 5 (without multi-walled carbon nanotubes) The method is basically the same as in Example 1, except that multi-walled carbon nanotubes are not added to the conductive filler, and the total amount of conductive carbon black and graphene is still 100g, with a mass ratio of conductive carbon black to graphene of 3:1.

[0071] The prepared fibers exhibited a conductivity of 4.2 S / cm, a tensile strength of 2.0 GPa, and an elongation at break of 4.0%. After 100 cycles of tensile testing at 20% strain, the conductivity retention was 72%. This indicates that the incorporation of carbon nanotubes contributes to the construction of a more complete three-dimensional conductive network.

[0072] Comparative Example 6 (without surface modifier added) It is basically the same as Example 1, except that no surface modifier is added in step (1).

[0073] The obtained fiber has a conductivity of 5.8 S / cm and a tensile strength of 1.9 GPa. After 100 cycles of tensile testing at 20% strain, the conductivity remains at 68%. This indicates that the addition of the modifier helps improve the interfacial bonding between the conductive filler and the matrix, and enhances dispersibility and stability.

[0074] Comparative Example 7 (without dispersant) It is basically the same as Example 1, except that no dispersing agent is added in step (1), and only a surface modifier is used to treat the conductive material.

[0075] The obtained fiber has a conductivity of 3.6 S / cm, a tensile strength of 1.8 GPa, and an elongation at break of 3.5%. After 100 cycles of tensile testing at 20% strain, the conductivity retention rate is 63%. This indicates that the synergistic effect of the dispersant and surfactant is indispensable, and only by combining the two can the best dispersion effect be achieved.

[0076] Comparative Example 8 (Ultrasonic dispersion instead of ball milling) The process is basically the same as in Example 1, except that in step (3), ultrasonic dispersion (500W, 30 minutes) is used instead of ball milling and mixing. The pre-dispersed composite powder obtained in step (1) and UHMWPE powder are added to a solvent for ultrasonic dispersion.

[0077] The obtained fibers had an electrical conductivity of 3.8 S / cm, a breaking strength of 1.9 GPa, and an elongation at break of 3.6%. After 100 cycles of tensile testing at 20% strain, the electrical conductivity retention rate was 66%. This demonstrates that high-energy ball milling has a more significant promoting effect on the synergy between high mechanical properties and high electrical conductivity compared to mixing methods such as ultrasonic dispersion.

[0078] Application example: Flexible antistatic fabric The conductive UHMWPE composite fiber obtained in Example 1 was blended with ordinary polyester fiber at a ratio of 1:9 and woven into a woven fabric. Its antistatic properties were tested according to GB / T 12703.1-2008 standard. The results showed that the static voltage half-life of the fabric was 1.2 seconds, meeting the national Class B antistatic standard (<2 seconds). After 50 washes, the half-life remained at 1.8 seconds, indicating that the conductive fiber has good wash resistance.

[0079] Seepage threshold determination: To evaluate the promoting effect of the method of the present invention on the formation of conductive networks, the percolation threshold of Examples 1-3 and Comparative Examples 1-8 was determined. Specifically, for each formulation system, a series of fiber samples with different conductive filler contents (0.1-10 wt%) were prepared. The conductivity of each sample was tested using the four-probe method, and the percolation threshold Pc of each system was calculated by nonlinear fitting based on the classical percolation theory formula σ = σ0(P - Pc)^t. The results are summarized in Table 1.

[0080] Table 1: Seepage thresholds for each embodiment and comparative example Note: The critical exponent t is a parameter characterizing the dimension of the conductive network, with a theoretical value of approximately 1.6-2.0 in a three-dimensional system. The t values ​​of Examples 1-3 of this invention are all between 2.0 and 2.2, which is consistent with the characteristics of a three-dimensional conductive network. The comparative examples have lower t values ​​due to uneven packing dispersion or imperfect network, indicating defects in the conductive network structure.

[0081] As can be seen from the data in Table 1: The seepage thresholds of Examples 1-3 of this invention are all as low as 0.3 wt%, which is much lower than that of Comparative Example 1 (no pre-dispersion, 1.0 wt%) and Comparative Example 2 (single CNT, 1.2 wt%), demonstrating the synergistic effect of the "three-step dispersion method" and multi-dimensional filler compounding.

[0082] Comparative Example 3 (without nucleating agent) still had a percolation threshold of 0.3 wt%, indicating that the nucleating agent mainly affects mechanical properties rather than the formation of conductive networks.

[0083] The percolation thresholds of Comparative Examples 4-8 were all between 0.5-0.8 wt%, which was higher than that of Example 1, demonstrating that factors such as ball milling, dispersing agents, and surface modifiers are indispensable for constructing a highly efficient conductive network.

[0084] In summary, this invention has successfully prepared UHMWPE composite fibers with both high mechanical properties and high conductivity through an innovative "three-step dispersion method" filler dispersion process and a composite conductive filler design, which has broad application prospects in fields such as antistatic materials and flexible electronics.

[0085] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing ultra-high molecular weight polyethylene conductive composite fibers based on blend spinning, characterized in that, Includes the following steps: S1. The conductive filler, nucleating agent, dispersing agent and surface modifier are dry-mixed to uniformly coat the conductive filler and nucleating agent surface to obtain pre-dispersed conductive composite powder. S2. The pre-dispersed conductive composite powder obtained in S1 is ball-milled and mixed with UHMWPE powder, then added to a solvent and stirred to swell, to obtain a uniform spinning solution. S3. The spinning solution is extruded through a spinneret, cooled and solidified in a coagulation bath to form gel fiber. After extraction and drying, it undergoes multi-stage hot stretching and finally heat setting to obtain ultra-high molecular weight polyethylene conductive composite fiber.

2. The method for preparing ultra-high molecular weight polyethylene conductive composite fiber based on blend spinning according to claim 1, characterized in that, The conductive filler is a mixture of conductive carbon black, carbon nanotubes and graphene in a mass ratio of (1-5):(1-3):(0.5-2).

3. The method for preparing ultra-high molecular weight polyethylene conductive composite fiber based on blend spinning according to claim 1, characterized in that, The dispersing agent is hyperbranched polyethylene or maleic anhydride-grafted polyethylene, the surface modifier is a silane coupling agent or a titanate coupling agent, and the nucleating agent is an organophosphate nucleating agent.

4. The method for preparing ultra-high molecular weight polyethylene conductive composite fiber based on blend spinning according to claim 1, characterized in that, The amount of conductive filler added satisfies the following condition: its mass fraction in ultra-high molecular weight polyethylene conductive composite fiber is 0.5%~8%.

5. The method for preparing ultra-high molecular weight polyethylene conductive composite fiber based on blend spinning according to claim 1, characterized in that, In S2, the ball milling and blending process uses a planetary high-energy ball mill with a ball-to-material ratio of (5-10):1, the ball milling media being zirconia balls, the ball milling speed being 200-500 rpm, and the ball milling time being 1-4 hours.

6. The method for preparing ultra-high molecular weight polyethylene conductive composite fiber based on blend spinning according to claim 1, characterized in that, In S2, the solvent is white oil or decahydronaphthalene, and the stirring and swelling process is as follows: the solid content is controlled at 6~10wt%, and the mixture is stirred at 80~120℃ for 2~6h.

7. The method for preparing ultra-high molecular weight polyethylene conductive composite fiber based on blend spinning according to claim 1, characterized in that, In S3, the multi-stage hot stretching process is carried out in three stages. The first stage stretching temperature is 100℃~110℃, and the stretching ratio is 3~5 times. The second stage stretching temperature is 110℃~120℃, and the stretching ratio is 4~6 times. The third stage stretching temperature is 120℃~140℃, and the stretching ratio is 5~8 times.

8. The method for preparing ultra-high molecular weight polyethylene conductive composite fiber based on blend spinning according to claim 1, characterized in that, In S3, the heat setting process is as follows: treatment at 120℃~150℃ for 10~30 minutes.

9. A conductive composite fiber of ultra-high molecular weight polyethylene based on blend spinning, characterized in that, The material is prepared by the preparation method described in any one of claims 1-8, and has a fracture strength ≥1.8 GPa, an electrical conductivity ≥5 S / cm, and an electrical conductivity retention rate ≥80% after 100 cycles of cyclic tensile stress at 20% strain.

10. The application of the ultra-high molecular weight polyethylene conductive composite fiber based on blend spinning as described in claim 9 in the preparation of antistatic fabrics, electromagnetic shielding materials, flexible sensors, and smart wearable devices.

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