Gel spinning preparation method of ultra-high molecular weight polyethylene fiber and application of ultra-high molecular weight polyethylene fiber in high-strength rope

Abstract

The invention discloses a preparation method of an ultra-high molecular weight polyethylene fiber with a gradient structure, which is characterized in that by introducing polytetrafluoroethylene modified by a silane coupling agent as a wear-resistant component, the dispersity and interfacial compatibility of the polytetrafluoroethylene in a matrix are improved, and the wear resistance of the fiber is improved while high strength and high modulus of the fiber are maintained. The wear resistance, the cutting resistance, the strength retention rate and the fatigue resistance are remarkably improved, and the method is suitable for the field of high-performance fibers and ropes.

Description

Technical Field

[0001] This invention relates to the technical field of ultra-high molecular weight polyethylene (UHMWPE) fibers, and in particular to a gel spinning method for preparing UHMWPE fibers and their application in high-strength ropes and cables. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) fiber, due to its quasi-one-dimensional crystal structure formed by the highly oriented molecular chains, exhibits extremely high specific strength, specific modulus, and excellent chemical corrosion resistance, and has been widely used in bulletproof protection, high-performance composite materials, and high-strength ropes and cables. Among existing technologies, gel spinning is considered one of the key technical routes for preparing high-performance UHMWPE fibers. Its basic principle involves dissolving ultra-high molecular weight polyethylene in a specific solvent to form a polymer solution, which is then extruded and cooled to form gel-state nascent fibers. Through multi-stage high-ratio stretching, the molecular chains are highly oriented and crystallized, thereby obtaining high-strength, high-modulus fiber materials. With the continuous development of gel spinning technology, researchers have conducted extensive optimizations in areas such as raw material molecular weight control, solvent system selection, stretching ratio, and heat treatment conditions to continuously improve the mechanical properties of the fibers, making UHMWPE fiber a gradually emerging candidate material to replace steel wire cables and aramid fibers. Especially in the field of high-strength ropes and cables, UHMWPE fiber, with its low density, high breaking strength and excellent fatigue resistance, has shown good application prospects in marine engineering, deep-sea mooring, lifting and hoisting, and load-bearing components in extreme environments.

[0003] However, as the application scenarios of UHMWPE fibers in high-strength ropes and cables continue to expand, the complexity of their service environments and safety requirements have significantly increased, and some structural deficiencies in existing technologies have gradually become apparent. Specifically, UHMWPE fibers prepared by existing gel spinning typically exhibit a homogeneous overall structure, with consistent molecular orientation, crystallinity, and mechanical response within their cross-sections. This homogeneous structure can achieve high strength under uniaxial tensile testing conditions, but in actual rope and cable service, the types of stresses borne by the fibers exhibit significant spatial distribution differences: the fiber surface is more susceptible to corrosion from environmental factors such as friction and wear, sharp edge cutting, ultraviolet aging, and seawater, while the fiber interior mainly bears continuous or periodic axial tensile loads. Because existing UHMWPE fibers cannot achieve functional zoning design for different service stresses at the microscopic or macroscopic structural level, their surface structure is highly susceptible to rapid attenuation of overall load-bearing capacity after wear or localized damage, and may even experience sudden fracture without significant macroscopic deformation, posing a potential risk to the safe use of high-strength ropes and cables. Furthermore, the homogeneous structure limits the synergistic optimization space between abrasion resistance, cut resistance, and load-bearing strength, making it difficult to simultaneously meet the application requirements of long life, high reliability, and high safety. Therefore, how to maintain the high strength advantage of UHMWPE fibers while finely controlling the fiber structure through the gel spinning process to achieve differentiated design in structure and function between the fiber surface and interior has become an important technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] This application provides a method for preparing ultra-high molecular weight polyethylene fibers with a gradient structure, comprising the following steps: Step S1. Preparation of surface modification solution: First, the polytetrafluoroethylene (PTFE) micro powder is modified to obtain modified PTFE micro powder. Then, ultra-high molecular weight polyethylene (UHMWPE) is mixed with the modified PTFE micro powder and dissolved in a solvent to form a surface modification solution. Step S2. Preparation of core solution: Dissolve ultra-high molecular weight polyethylene in a solvent to form a homogeneous core solution; Step S3. Gel spinning: Using a coaxial spinning nozzle, the core solution is used as the inner flowing phase and the surface modified solution is used as the outer flowing phase for extrusion spinning. After cooling, gel-state nascent fibers are formed, wherein the surface thickness of the nascent fibers accounts for 10-30% of the total fiber diameter. Step S4. Infrared-assisted solvent extraction: Place the gel-state nascent fibers in an extraction bath and use infrared radiation to assist in solvent removal; Step S5. Multi-stage stretching: The extracted fibers are subjected to multi-stage thermal stretching; Step S6. Heat setting: The stretched fibers are heat-set using infrared radiation to obtain ultra-high molecular weight polyethylene fibers with a gradient structure.

[0005] It should be noted that this preparation method constructs a core-shell gradient structure for UHMWPE fibers through coaxial gel spinning combined with selective infrared radiation treatment, achieving radial functional partitioning to address structural deficiencies under complex service environments. In step S1, PTFE micropowder is first modified with a silane coupling agent, whose hydrolyzed silanol groups form chemical bonds with defect sites on the PTFE surface, and the amino terminus enhances compatibility with UHMWPE, thereby improving micropowder dispersibility and interfacial adhesion. The resulting surface modification solution introduces durable self-lubricating and wear-resistant components. In step S2, the core solution remains pure UHMWPE, ensuring that the internal molecular chains form highly oriented quasi-one-dimensional crystals in subsequent processing to provide excellent axial load-bearing capacity. In step S3, coaxial spinning precisely controls the surface thickness to 10–30 μm through the difference in flow rates between the inner and outer layers. Step S4 involves infrared-assisted extraction, which utilizes the selective and strong absorption of infrared radiation by modified PTFE to preferentially heat the surface layer, promoting enhanced vibration and rapid diffusion of solvent molecules. Simultaneously, it optimizes the uniform distribution of PTFE and controls solvent residue to an extremely low level, avoiding damage to the internal structure. Step S5 involves multi-stage thermal stretching, which gradually induces molecular chain untangling, straightening, orientation, and crystallization, improving overall strength and modulus. Step S6 involves infrared thermal setting, which further drives local rearrangement of surface molecules to form a stable lubricating transfer film, while the core crystal structure remains unchanged. This effectively resists friction, cutting, and environmental erosion on the fiber surface, preventing damage from spreading inwards, significantly reducing strength attenuation rate and the risk of sudden fracture, achieving synergistic optimization of wear resistance, cut resistance, and high load-bearing strength.

[0006] A preferred technical solution for preparing ultra-high molecular weight polyethylene fibers with a gradient structure is provided, wherein the ultra-high molecular weight polyethylene has a molecular weight of 1×10⁻⁶. 6 ~5×10 6 The concentration of the surface modification solution and the core solution was 2–10 wt%, and the solution was stirred and heated to 120–150 °C.

[0007] It should be noted that this parameter range ensures that ultra-high molecular weight polyethylene is fully dissolved in dehydronaphthalene solvent to form a uniform and stable gel solution, avoiding molecular chain degradation or aggregation, thereby promoting the efficient preparation of high-strength, high-modulus and structurally gradient fiber materials in the subsequent gel spinning process.

[0008] In a preferred embodiment of a method for preparing ultra-high molecular weight polyethylene fiber with a gradient structure, the amount of polytetrafluoroethylene micro powder added is 0.5 to 5 wt% of the mass of ultra-high molecular weight polyethylene.

[0009] It should be noted that this addition range ensures the uniform dispersion of polytetrafluoroethylene micropowder in the surface modification solution and effectively enhances wear resistance, while avoiding phase separation or reduction in fiber mechanical strength caused by excessive addition.

[0010] As a preferred technical solution for the preparation of ultra-high molecular weight polyethylene fiber with a gradient structure, the method for preparing the modified polytetrafluoroethylene micro powder is as follows: dispersing polytetrafluoroethylene micro powder in ethanol, adding a silane coupling agent, stirring and reacting for 1-3 h at a temperature of 50-80℃, and then filtering and drying to obtain the modified polytetrafluoroethylene micro powder, wherein the amount of silane coupling agent added is 1-5 wt% of the mass of the polytetrafluoroethylene micro powder, and the silane coupling agent is KH-550.

[0011] It should be noted that the preparation method of this modified polytetrafluoroethylene (PTFE) micropowder is based on the surface functionalization achieved by the bifunctional structure of the silane coupling agent KH-550 (3-aminopropyltriethoxysilane): after dispersing PTFE micropowder in ethanol medium, the ethoxy groups of KH-550 undergo partial hydrolysis to form active silanol groups. These silanol groups bind to the defect sites on the PTFE surface through hydrogen bonds or weak chemical bonds. At the same time, the amino groups easily lose electrons to form empty orbitals, which pair with electron-rich fluorine atoms on the PTFE surface to form coordinate bonds, thereby introducing polar amino groups on the low surface energy PTFE micropowder surface and improving its hydrophilicity and dispersion stability. Heating and stirring (50-80℃, 1-3 h) promotes reaction kinetics, avoids agglomeration, and ensures uniform coverage with an addition amount of 1-5 wt%. Subsequent filtration and drying remove the solvent, and the modified layer is cured, ultimately improving the interfacial compatibility and self-lubricating properties of the modified PTFE micropowder in the UHMWPE matrix.

[0012] In a preferred embodiment of a method for preparing ultra-high molecular weight polyethylene fiber with a gradient structure, during the gel spinning process, extrusion spinning is performed with an inner layer flow rate of 0.5–2 mL / min and an outer layer flow rate of 0.1–0.5 mL / min, at a spinning temperature of 130–160°C. After cooling through an air gap, the fiber enters a cooling bath with a temperature of -10–10°C and an air gap length of 5–20 cm. The cooling bath is composed of n-decane or mineral oil.

[0013] It should be noted that the parameter settings of this gel spinning process are designed to optimize the formation and stability of the core-shell gradient structure: the difference between the inner layer flow rate (0.5–2 mL / min) and the outer layer flow rate (0.1–0.5 mL / min) ensures a thinner outer layer, avoiding excessive extrusion of the core solution leading to structural inhomogeneity, while maintaining spinning continuity; the spinning temperature (130–160℃) promotes uniform flow of the polymer solution and initial gelation of nascent fibers without causing thermal degradation; the air gap length (5–20 cm) provides sufficient cooling time, allowing the solution to partially solidify before entering the cooling bath, reducing diffusion and interface blurring; the cooling bath temperature (-10–10℃) and the choice of n-decane or mineral oil as the medium rapidly lock the molecular chain conformation, forming stable gel-state nascent fibers, preventing premature crystal growth or uneven solvent evaporation, thereby improving the overall microscopic uniformity of the fiber and its subsequent tensile properties.

[0014] In a preferred embodiment of a method for preparing ultra-high molecular weight polyethylene fibers with a gradient structure, the infrared radiation wavelength of the infrared-assisted solvent extraction is 3–8 μm, and the power density is 0.3–1.5 W / cm². 2 The extraction time is 10–30 min, the extraction bath is heptane or hexane, and the temperature is 40–60℃.

[0015] It should be noted that the parameter settings for this infrared-assisted solvent extraction utilize the selective and strong absorption of modified PTFE by infrared wavelengths of 3–8 μm to achieve preferential heating of the surface layer (power density 0.3–1.5 W / cm²). 2 Within 10–30 min in an extraction bath (heptane or hexane) at 40–60 °C, it significantly accelerates the vibration and diffusion rate of solvent molecules, promotes rapid removal of surface solvent and uniform distribution of PTFE, while limiting heat conduction to the core, avoiding premature crystallization or damage of internal molecular chains, ensuring a low level of solvent residue and maintaining the integrity of the gradient structure.

[0016] In a preferred embodiment of a method for preparing ultra-high molecular weight polyethylene fiber with a gradient structure, the total stretching ratio of the multi-stage thermal stretching is 20 to 100 times, the first-stage stretching temperature is 80 to 100°C with a stretching ratio of 5 to 10 times, the second-stage stretching temperature is 100 to 120°C with a stretching ratio of 5 to 10 times, and the third-stage stretching temperature is 120 to 140°C with a stretching ratio of 4 to 10 times.

[0017] It should be noted that the parameters of this multi-stage thermal stretching are set with gradual heating and staged multiple distribution (total multiple 20 to 100 times). The first stage is low stretching (5 to 10 times) at 80 to 100℃ to initially untangle the molecular chains and avoid defects. The second stage is medium stretching (5 to 10 times) at 100 to 120℃ to promote chain segment straightening and orientation. The third stage is high stretching (4 to 10 times) at 120 to 140℃ to induce high crystallinity and quasi-one-dimensional crystal formation, thereby maximizing the axial strength and modulus of the fiber, while maintaining the integrity of the core-shell gradient structure and achieving a synergistic improvement in overall mechanical properties.

[0018] In a preferred embodiment of a method for preparing ultra-high molecular weight polyethylene fiber with a gradient structure, the infrared radiation wavelength for heat setting is 2–10 μm, the power density is 0.5–2 W / cm², the time is 1–5 min, and the temperature is 140–160℃.

[0019] It should be noted that the heat setting parameters utilize the selective and strong absorption of infrared radiation with wavelengths of 2–10 μm by the modified PTFE surface layer, at a range of 0.5–2 W / cm². 2 Treating the surface molecular chains at 140–160℃ for 1–5 min at power density promotes local rearrangement of the surface molecular chains and the formation of a durable lubricating transfer film. At the same time, it limits the excessive heat conduction to the core, avoids excessive relaxation of the internal molecular chains or crystal damage, thereby optimizing the stability of the gradient structure and further improving the fiber's wear resistance and cut resistance.

[0020] This invention introduces polytetrafluoroethylene (PTFE) modified with the silane coupling agent KH-550 as a wear-resistant component into ultra-high molecular weight polyethylene (UHMWPE) fibers. Without compromising the low-friction and self-lubricating properties of PTFE, it significantly improves the interfacial compatibility and dispersion stability between PTFE and the matrix. This allows the wear-resistant phase to be uniformly distributed within the fibers and ropes, forming a stable structure, thereby effectively reducing frictional wear and cutting damage during use. Simultaneously, this modified wear-resistant component alleviates localized stress concentration and inhibits the generation and propagation of microcracks. While maintaining high monofilament strength and modulus, it significantly improves the overall breaking strength, post-damage strength retention, and fatigue resistance of the ropes, ultimately achieving a synergistic improvement in the wear resistance, mechanical properties, and service reliability of the fibers and ropes. Attached Figure Description

[0021] Figure 1 The infrared spectrum of the modified polytetrafluoroethylene micropowder prepared in step S1 of Example 1; Figure 2 Infrared spectrum of fiber with modified silica introduced as a control example 3. Detailed Implementation

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0024] Secondly, the term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single embodiment or an embodiment selectively excluded from other embodiments.

[0025] Example Example 1

[0026] This embodiment provides a method for preparing ultra-high molecular weight polyethylene fibers via gel spinning and its application in high-strength ropes, wherein... The preparation methods include the following; Step S1. Preparation of surface modification solution: First, modify the polytetrafluoroethylene (PTFE) micropowder by dispersing it in ethanol, adding silane coupling agent KH-550 (1 wt% of the PTFE micropowder mass), stirring for 1 h at 50℃, then filtering and drying to obtain modified PTFE micropowder; then, a surface modification solution with a molecular weight of 1×10⁻⁶ is prepared. 6 g / mol of ultra-high molecular weight polyethylene and the modified polytetrafluoroethylene micro powder (added at 0.5 wt% of the mass of ultra-high molecular weight polyethylene) are mixed and dissolved in dehydronaphthalene solvent at a concentration of 2 wt%, stirred and heated to 120°C to form a surface modification solution. Step S2. Prepare the core solution: [The following text appears to be unrelated and possibly machine-translated:] ...with a molecular weight of 1×10... 6 g / mol of ultra-high molecular weight polyethylene was dissolved in dehydronaphthalene solvent at a concentration of 2 wt%, and stirred and heated to 120°C to form a homogeneous core solution. Step S3. Gel spinning: Using a coaxial spinning nozzle, the core solution is used as the inner mobile phase (flow rate of 0.5 mL / min), and the surface modification solution is used as the outer mobile phase (flow rate of 0.1 mL / min). Extrusion spinning is performed at a spinning temperature of 130℃. After cooling through an air gap (length of 5 cm), the fibers enter a cooling bath (temperature of -10℃, cooling bath is n-decane) to form gel-state nascent fibers. The surface layer thickness of the nascent fibers accounts for 10% of the total fiber diameter. Step S4. Infrared-assisted solvent extraction: The gel-state nascent fibers were placed in an extraction bath (heptane, temperature 40℃), and infrared radiation (wavelength 3 μm, power density 0.3 W / cm²) was applied. 2 ) To assist in solvent removal, the extraction time is 10 min; Step S5. Multi-stage stretching: The extracted fibers are subjected to multi-stage thermal stretching with a total stretching ratio of 20 times. The first stage stretching temperature is 80℃ and the stretching ratio is 5 times. The second stage stretching temperature is 100℃ and the stretching ratio is 5 times. The third stage stretching temperature is 120℃ and the stretching ratio is 4 times. Step S6. Heat setting: The stretched fibers are subjected to infrared radiation (wavelength 2 μm, power density 0.5 W / cm²). 2 Heat setting was performed by heating for 1 minute at a temperature of 140°C to obtain ultra-high molecular weight polyethylene fibers with a gradient structure.

[0027] Specific applications The ultra-high molecular weight polyethylene fibers with a gradient structure prepared in Example 1 were bundled into 12-strand ropes as monofilament bundles: First, about 5,000 monofilaments were twisted into a single rope (twist pitch 15 mm), and then the 12 strands were braided into a 12-strand braided rope with alternating S / Z twist directions, and the outer layer was protected with a polyurethane coating (coating thickness 0.2 mm). The heat setting temperature was 120°C for 5 min, and finally a pre-stretching treatment was performed (loaded to 30% of the breaking strength and held for 10 min) to obtain the rope.

[0028] Example 2

[0029] This embodiment provides a method for preparing ultra-high molecular weight polyethylene fibers via gel spinning and its application in high-strength ropes, wherein... The preparation methods include the following; Step S1. Preparation of surface modification solution: First, modify the polytetrafluoroethylene (PTFE) micropowder by dispersing it in ethanol, adding silane coupling agent KH-550 (3 wt% of the PTFE micropowder mass), stirring for 2 h at 65℃, then filtering and drying to obtain modified PTFE micropowder; then, a surface modification solution with a molecular weight of 3×10⁻⁶ is prepared. 6 g / mol of ultra-high molecular weight polyethylene and the modified polytetrafluoroethylene micro powder (added at 2.75 wt% of the mass of ultra-high molecular weight polyethylene) are mixed and dissolved in dehydronaphthalene solvent at a concentration of 6 wt%, and stirred and heated to 135°C to form a surface modification solution. Step S2. Preparation of core solution: [The following text appears to be incomplete and requires further context: "to prepare the core solution with a molecular weight of 3×10..."] 6g / mol of ultra-high molecular weight polyethylene was dissolved in dehydronaphthalene solvent at a concentration of 6 wt%, and stirred and heated to 135°C to form a homogeneous core solution. Step S3. Gel spinning: Using a coaxial spinning nozzle, the core solution is used as the inner mobile phase (flow rate of 1.25 mL / min), and the surface modification solution is used as the outer mobile phase (flow rate of 0.3 mL / min). Extrusion spinning is performed at a spinning temperature of 145℃. After cooling through an air gap (length of 12.5 cm), the fibers enter a cooling bath (temperature of 0℃, cooling bath is mineral oil) to form gel-state nascent fibers. The surface layer thickness of the nascent fibers accounts for 20% of the total fiber diameter. Step S4. Infrared-assisted solvent extraction: The gel-like nascent fibers were placed in an extraction bath (hexane, temperature 50°C), and infrared radiation (wavelength 5.5 μm, power density 0.9 W / cm²) was applied. 2 ) To assist in solvent removal, the extraction time is 20 min; Step S5. Multi-stage stretching: The extracted fibers are subjected to multi-stage thermal stretching with a total stretching ratio of 60 times. The first stage stretching temperature is 90℃ and the stretching ratio is 7.5 times. The second stage stretching temperature is 110℃ and the stretching ratio is 7.5 times. The third stage stretching temperature is 130℃ and the stretching ratio is 7 times. Step S6. Heat setting: The stretched fibers are subjected to infrared radiation (wavelength 6 μm, power density 1.25 W / cm²). 2 Heat setting was performed by heating for 3 minutes at a temperature of 150°C to obtain ultra-high molecular weight polyethylene fibers with a gradient structure.

[0030] Specific applications The ultra-high molecular weight polyethylene fibers with a gradient structure prepared in Example 2 were bundled into a double-braided rope as monofilament bundles: First, about 12,000 monofilaments were twisted into a single rope (twist distance 25 mm). Then, 24 strands of the rope were first primary braided into an inner core rope. Then, 32 strands of the rope were wrapped in a double-layer braid to form a rope with a diameter of 32 mm. The outer layer was impregnated with a low-friction polytetrafluoroethylene emulsion (solid content 15 wt%), dried at 150°C for 10 min, and finally hot-stretched under tension (loaded to 40% of the breaking strength, temperature 130°C, held for 15 min) to obtain the rope.

[0031] Example 3

[0032] This embodiment provides a method for preparing ultra-high molecular weight polyethylene fibers via gel spinning and its application in high-strength ropes, wherein... The preparation methods include the following; Step S1. Preparation of surface modification solution: First, modify the polytetrafluoroethylene (PTFE) micropowder by dispersing it in ethanol, adding silane coupling agent KH-550 (5 wt% of the PTFE micropowder mass), stirring for 3 h at 80℃, then filtering and drying to obtain modified PTFE micropowder; then, a surface modification solution with a molecular weight of 5×10⁻⁶ is prepared. 6 g / mol of ultra-high molecular weight polyethylene and the modified polytetrafluoroethylene micro powder (added at 5 wt% of the mass of ultra-high molecular weight polyethylene) are mixed and dissolved in dehydronaphthalene solvent at a concentration of 10 wt%, stirred and heated to 150°C to form a surface modification solution. Step S2. Prepare the core solution: [The following text appears to be unrelated and possibly machine-translated:] ...with a molecular weight of 5×10... 6 g / mol of ultra-high molecular weight polyethylene was dissolved in dehydronaphthalene solvent at a concentration of 10 wt%, and stirred and heated to 150°C to form a homogeneous core solution. Step S3. Gel spinning: Using a coaxial spinning nozzle, the core solution is used as the inner mobile phase (flow rate of 2 mL / min), and the surface modification solution is used as the outer mobile phase (flow rate of 0.5 mL / min). Extrusion spinning is performed at a spinning temperature of 160℃. After cooling through an air gap (length of 20 cm), the fibers enter a cooling bath (temperature of 10℃, cooling bath is n-decane) to form gel-state nascent fibers. The surface thickness of the nascent fibers accounts for 30% of the total fiber diameter. Step S4. Infrared-assisted solvent extraction: The gel-like nascent fibers were placed in an extraction bath (heptane, temperature 60℃), and infrared radiation (wavelength 8 μm, power density 1.5 W / cm²) was applied. 2 ) To assist in solvent removal, the extraction time is 30 min; Step S5. Multi-stage stretching: The extracted fibers are subjected to multi-stage thermal stretching with a total stretching ratio of 100 times. The first stage stretching temperature is 100℃ and the stretching ratio is 10 times. The second stage stretching temperature is 120℃ and the stretching ratio is 10 times. The third stage stretching temperature is 140℃ and the stretching ratio is 10 times. Step S6. Heat setting: The stretched fibers are subjected to infrared radiation (wavelength 10 μm, power density 2 W / cm²). 2 Heat setting was performed by heating for 5 minutes at a temperature of 160°C to obtain ultra-high molecular weight polyethylene fibers with a gradient structure.

[0033] Specific applications The ultra-high molecular weight polyethylene fibers with a gradient structure prepared in Example 3 were bundled into heavy-duty ropes as monofilament bundles: First, about 20,000 monofilaments were twisted into a single rope (twist pitch 40 mm), and then 48 strands of the rope were woven into a 48-strand rope with a diameter of 80 mm by multiple alternating twist directions. An additional protective sheath (high-strength polyester tape, 20 mm wide) was wrapped around the outer layer, and a two-component polyurethane protective coating (thickness 0.5 mm) was applied. The curing temperature was 100°C and the time was 20 min. Finally, a high-load pre-stretching treatment was performed (loaded to 50% of the breaking strength and held for 30 min) to obtain the rope.

[0034] Example 4

[0035] This embodiment provides a method for preparing ultra-high molecular weight polyethylene fibers via gel spinning and its application in high-strength ropes, wherein... The preparation methods include the following; Step S1. Preparation of surface modification solution: First, the polytetrafluoroethylene (PTFE) micropowder is modified by dispersing the PTFE micropowder in ethanol, adding silane coupling agent KH-550 (2 wt% of the PTFE micropowder mass), stirring and reacting for 1.5 h at 60℃, then filtering and drying to obtain modified PTFE micropowder; then, a molecular weight of 2×10 6 g / mol of ultra-high molecular weight polyethylene and the modified polytetrafluoroethylene micro powder (added at 1.5 wt% of the mass of ultra-high molecular weight polyethylene) are mixed and dissolved in dehydronaphthalene solvent at a concentration of 4 wt%, stirred and heated to 130°C to form a surface modification solution. Step S2. Prepare the core solution: [The following text appears to be unrelated and possibly machine-translated:] ...with a molecular weight of 2×10... 6 g / mol of ultra-high molecular weight polyethylene was dissolved in dehydronaphthalene solvent at a concentration of 4 wt%, and stirred and heated to 130°C to form a homogeneous core solution. Step S3. Gel spinning: Using a coaxial spinning nozzle, the core solution is used as the inner mobile phase (flow rate of 1 mL / min), and the surface modification solution is used as the outer mobile phase (flow rate of 0.2 mL / min). Extrusion spinning is performed at a spinning temperature of 140℃. After cooling through an air gap (length of 10 cm), the fibers enter a cooling bath (temperature of -5℃, cooling bath is mineral oil) to form gel-state nascent fibers. The surface layer thickness of the nascent fibers accounts for 15% of the total fiber diameter. Step S4. Infrared-assisted solvent extraction: The gel-like nascent fibers were placed in an extraction bath (hexane, temperature 45°C), and infrared radiation (wavelength 4 μm, power density 0.6 W / cm²) was applied. 2 ) To assist in solvent removal, the extraction time is 15 min; Step S5. Multi-stage stretching: The extracted fibers are subjected to multi-stage hot stretching with a total stretching ratio of 40 times. The first stage stretching temperature is 85℃ and the stretching ratio is 6 times. The second stage stretching temperature is 105℃ and the stretching ratio is 6 times. The third stage stretching temperature is 125℃ and the stretching ratio is 5 times. Step S6. Heat setting: The stretched fiber is heat-set using infrared radiation (wavelength 4 μm, power density 1 W / cm²) for 2 min at a temperature of 145℃ to obtain ultra-high molecular weight polyethylene fiber with a gradient structure.

[0036] Specific applications The ultra-high molecular weight polyethylene fibers with a gradient structure prepared in Example 4 were bundled into lightweight ropes as monofilament bundles: First, about 8,000 monofilaments were twisted into a single rope (twist distance 20 mm), and then 16 strands of rope were formed into a rope with a diameter of 18 mm using a circular weaving process. The outer layer was coated with a silicone low-friction coating (solid content 10 wt%), dried at 140°C for 8 min, and finally subjected to a low-temperature flexible shaping treatment (loaded to 35% of the breaking strength, temperature 110°C, held for 12 min) to obtain the rope.

[0037] Comparison Example

[0038] Compare with Example 1 This control example, compared to Example 1, contains no surface-modified PTFE, only homogeneous pure UHMWPE fibers. Preparation method: Except for steps S1 and S3, which do not introduce modified polytetrafluoroethylene micropowder and coaxial spinning, the remaining steps are the same as in Example 1. Specifically, only a single core solution (molecular weight 1×10⁻⁶) is prepared. 6 Ultra-high molecular weight polyethylene (UHMWPE) of g / mol was dissolved in dehydronaphthalene at a concentration of 2 wt% and heated to 120°C. The mixture was then extruded and spun using a conventional uniaxial spinning nozzle (flow rate 0.6 mL / min, with other spinning, extraction, stretching, and heat setting parameters the same as in Example 1) to obtain homogeneous UHMWPE fibers with a diameter of 10 μm.

[0039] Rope preparation: The homogeneous fiber is made into a rope in the same way (about 5,000 single fibers twisted into one strand, 12 strands of S / Z alternating braiding, diameter 8 mm, outer polyurethane coating 0.2 mm, heat set at 120℃ / 5 min, pre-stretched to 30% breaking strength / 10 min).

[0040] Compare with Example 2 This control example is compared with Example 1: no PTFE modification was performed, and unmodified PTFE micropowder was directly added. Preparation method: Step S1 is changed to directly mixing and dissolving unmodified polytetrafluoroethylene micro powder (addition amount 0.5 wt%) with ultra-high molecular weight polyethylene in dehydronaphthalene (the remaining parameters are the same as in Example 1). Steps S2 to S6 are the same as in Example 1, and fibers with a diameter of 10 μm and a surface thickness of 1 μm are obtained (but the surface PTFE dispersibility is poor).

[0041] Rope preparation: A 12-strand rope with a diameter of 8 mm was prepared in the same manner as in Example 1.

[0042] Compare with Example 3 Comparative Example 3 with Example 1: Polytetrafluoroethylene was replaced with silicon dioxide. This comparative example provides a method for preparing ultra-high molecular weight polyethylene fibers via gel spinning and its application in high-strength ropes, wherein... The preparation methods include the following; Step S1. Preparation of surface modification solution: First, modify the silica micro powder by dispersing it in ethanol, adding silane coupling agent KH-550 (1 wt% of the silica micro powder mass), stirring for 1 h at 50℃, then filtering and drying to obtain modified silica micro powder; then, a surface modification solution with a molecular weight of 1×10⁻⁶ is prepared. 6 g / mol of ultra-high molecular weight polyethylene and the modified silica micro powder (added at 0.5 wt% of the mass of ultra-high molecular weight polyethylene) are mixed and dissolved in dehydronaphthalene solvent at a concentration of 2 wt%, stirred and heated to 120°C to form a surface modification solution. Step S2. Prepare the core solution: [The following text appears to be unrelated and possibly machine-translated:] ...with a molecular weight of 1×10... 6 g / mol of ultra-high molecular weight polyethylene was dissolved in dehydronaphthalene solvent at a concentration of 2 wt%, and stirred and heated to 120°C to form a homogeneous core solution. Step S3. Gel spinning: Using a coaxial spinning nozzle, the core solution is used as the inner mobile phase (flow rate of 0.5 mL / min), and the surface modification solution is used as the outer mobile phase (flow rate of 0.1 mL / min). Extrusion spinning is performed at a spinning temperature of 130℃. After cooling through an air gap (length of 5 cm), the fibers enter a cooling bath (temperature of -10℃, cooling bath is n-decane) to form gel-state nascent fibers. The surface layer thickness of the nascent fibers accounts for 10% of the total fiber diameter. Step S4. Infrared-assisted solvent extraction: The gel-state nascent fibers were placed in an extraction bath (heptane, temperature 40℃), and infrared radiation (wavelength 3 μm, power density 0.3 W / cm2) was used to assist in the removal of solvent for 10 min. Step S5. Multi-stage stretching: The extracted fibers are subjected to multi-stage thermal stretching with a total stretching ratio of 20 times. The first stage stretching temperature is 80℃ and the stretching ratio is 5 times. The second stage stretching temperature is 100℃ and the stretching ratio is 5 times. The third stage stretching temperature is 120℃ and the stretching ratio is 4 times. Step S6. Heat setting: The stretched fibers are subjected to infrared radiation (wavelength 2 μm, power density 0.5 W / cm²). 2 Heat setting was performed by heating for 1 minute at a temperature of 140°C to obtain ultra-high molecular weight polyethylene fibers with a gradient structure.

[0043] Specific applications The ultra-high molecular weight polyethylene fibers with a gradient structure prepared in Comparative Example 3 were bundled into 12-strand ropes as monofilament bundles: First, about 5,000 monofilaments were twisted into a single rope (twist pitch 15 mm), and then the 12 strands were braided into a 12-strand braided rope with alternating S / Z twist directions, and the outer layer was protected with a polyurethane coating (coating thickness 0.2 mm). The heat setting temperature was 120°C for 5 min, and finally a pre-stretching treatment was performed (loaded to 30% of the breaking strength and held for 10 min) to obtain the rope.

[0044] Performance testing

[0045] 1. Tensile strength and elongation at break of fiber monofilaments: UHMWPE monofilaments were tested using a single-fiber tensile testing machine. Before testing, the fibers were conditioned in a standard environment (23±2 ℃, relative humidity 50±5%) for no less than 24 h. An axial load was applied to the fiber at a constant tensile rate, and the maximum load at break was recorded and converted into tensile strength. The elongation at break was also recorded.

[0046] 2. Initial modulus and specific modulus of fiber: During the monofilament tensile test, the initial modulus is calculated through the linear elastic stage of the stress-strain curve; the specific modulus is further calculated in combination with the fiber density.

[0047] 3. Fiber abrasion resistance: The abrasion test is conducted using a grinding wheel to test the friction and wear of the fiber under specified load and stroke conditions. The abrasion resistance is evaluated by the mass loss rate, strength retention rate, or number of abrasion cycles.

[0048] 4. Cut resistance: The constant load cutting test is used to compare the load or time required for the fiber or rope to be cut under the same cutting conditions.

[0049] 5. Overall breaking strength of the rope: The fibers are prepared into ropes of a specified structure and diameter, and the whole rope is subjected to tensile testing on a large tensile testing machine. A constant loading rate is used until the rope breaks, and the maximum breaking load is recorded.

[0050] 6. Strength retention rate (residual strength after damage): After the rope has undergone bending damage, a tensile fracture test is performed, and the fracture strength after damage is compared with the initial fracture strength to calculate the strength retention rate.

[0051] 7. Fatigue resistance: Apply periodic tensile loads (such as cyclic loads that account for a certain proportion of the breaking strength) to the fiber rope and record the strength decay under cyclic loading conditions.

[0052] Table 1 shows the test results of the tensile properties and modulus of the monofilament.

[0053] Table 2 shows the test results of fiber abrasion resistance and cut resistance.

[0054] Table 3. Results of Rope and Cable Performance Tests

[0055] In conjunction with Example 1 and Comparative Example 3, Figure 1 as well as Figure 2 It can be seen that the infrared spectrum of Example 1 shows a significant difference in characteristic peaks compared to that of Control Example 3: Example 1 shows a significant difference in characteristic peaks at 1212 cm⁻¹. -1 and 639 cm -1 Strong CF skeleton vibration and deformation vibration peaks appeared at 3441 cm⁻¹. -1 The broad peak of -NH2 and 1040 cm⁻¹ -1 The Si-O-Si / Si-OC shoulder peak indicates that modified polytetrafluoroethylene (PTFE) was successfully introduced and uniformly distributed on the fiber surface. Its low organic surface energy and the polar groups introduced by silane KH-550 form good hydrogen bonds and van der Waals interactions with the non-polar UHMWPE matrix, promoting stable dispersion and clear interfacial bonding of the surface solution. This makes it easier to form a continuous and stable core-shell gradient structure in coaxial gel spinning, achieving a synergistic function of high core strength and self-lubricating wear resistance of the shell. Control Example 3 mainly shows a 1080 cm⁻¹ peak. -1 The nearby broad Si-O-Si asymmetric stretching peak and 950 cm⁻¹ -1 The residual Si-OH peak and the weak modification-related peaks indicate that the high surface energy and inorganic properties of modified silica lead to poor compatibility with UHMWPE, making it prone to agglomeration and weak interfacial bonding, making it difficult to form a uniform and complete shell. The stability of the core-shell structure is significantly reduced, ultimately affecting the wear resistance, cut resistance and overall mechanical properties of the fiber.

[0056] As can be seen from Examples 1 to 4 and Tables 1 to 3, the fibers and ropes using modified polytetrafluoroethylene (PTFE) as the wear-resistant component exhibit relatively stable mechanical properties such as monofilament tensile strength, elongation at break, initial modulus, and specific modulus. Furthermore, they demonstrate superior overall performance in terms of wear resistance, cut resistance, overall rope breaking strength, strength retention, and fatigue resistance. The small variation in performance among the examples indicates that the modified PTFE maintains good structural stability and performance consistency under different process parameters, demonstrating the repeatability and process adaptability of the present invention.

[0057] As can be seen from Example 1, Comparative Example 1, and Tables 1 to 3, compared with Comparative Example 1 without modified PTFE, Example 1 shows significant improvements in monofilament tensile strength, initial modulus, and overall rope breaking strength. Simultaneously, its abrasion resistance and cut resistance are significantly improved, and it maintains a high strength retention rate after bending or cyclic loading. Analysis suggests this is because the modified PTFE is uniformly dispersed in the fiber matrix, forming a stable abrasion-resistant phase. While maintaining the self-lubricating properties of PTFE, surface functionalization enhances the interfacial interaction with the matrix, thereby effectively reducing wear and localized stress concentration.

[0058] As can be seen from Example 1, Comparative Example 2, and Tables 1 to 3, compared with Comparative Example 4, Example 1 exhibits significant advantages in wear resistance, cut resistance, and fatigue resistance, while maintaining a high strength retention rate under repeated bending or cyclic loading. This is because the modified polytetrafluoroethylene in Example 1 not only provides excellent self-lubricating properties but also effectively shares external friction and cutting loads through good interfacial compatibility, thereby significantly improving the overall service performance of the material.

[0059] Combining the test results of Example 1, Comparative Example 3, and Tables 1 to 3, it can be seen that Example 1 is significantly superior to Comparative Example 3 in terms of monofilament mechanical properties, abrasion and cut resistance, and overall service performance of the rope. As shown in Table 1, the tensile strength, initial modulus, and specific modulus of Example 1 are all higher than those of Comparative Example 3, indicating that its molecular chain orientation and load-bearing structure are more perfect. Table 2 shows that the number of abrasion cycles of Example 1 is significantly increased, the mass loss rate is significantly reduced, and the time required for cutting and the cutting load are significantly higher than those of Comparative Example 3, demonstrating superior abrasion resistance and cut resistance. Table 3 further shows that the rope prepared by Example 1 not only has higher overall breaking strength, but also has a significantly better strength retention rate after damage and fatigue cycles than Comparative Example 3, exhibiting better service stability. The modified polytetrafluoroethylene introduced in Example 1 has low surface energy and self-lubricating properties. After modification with a silane coupling agent, it can form a good interfacial bond with the UHMWPE matrix, so that the wear-resistant phase is uniformly distributed on the fiber surface and forms a continuous and stable protective layer. Infrared analysis shows that the characteristic absorption peak of CF of PTFE and the related absorption characteristics introduced by silane modification can be observed in Example 1, indicating that the wear-resistant component was successfully introduced and participated in the interfacial interaction. In contrast, the infrared spectrum of Control Example 3 is mainly dominated by Si-O-Si characteristic peaks and lacks low surface energy organic characteristics, reflecting that the modified silica has poor compatibility with the matrix and is prone to agglomeration and stress concentration, thus limiting its comprehensive performance improvement in wear resistance, cut resistance and long-term strength maintenance.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing ultra-high molecular weight polyethylene fiber with a gradient structure, characterized in that, Includes the following steps: Step S1. Preparation of surface modification solution: First, the polytetrafluoroethylene (PTFE) micro powder is modified to obtain modified PTFE micro powder. Then, ultra-high molecular weight polyethylene (UHMWPE) is mixed with the modified PTFE micro powder and dissolved in a solvent to form a surface modification solution. Step S2. Preparation of core solution: Dissolve ultra-high molecular weight polyethylene in a solvent to form a homogeneous core solution; Step S3. Gel spinning: Using a coaxial spinning nozzle, the core solution is used as the inner flowing phase and the surface modified solution is used as the outer flowing phase for extrusion spinning. After cooling, gel-state nascent fibers are formed, wherein the surface thickness of the nascent fibers accounts for 10-30% of the total fiber diameter. Step S4. Infrared-assisted solvent extraction: Place the gel-state nascent fibers in an extraction bath and use infrared radiation to assist in solvent removal; Step S5. Multi-stage stretching: The extracted fibers are subjected to multi-stage thermal stretching; Step S6. Heat setting: The stretched fibers are heat-set using infrared radiation to obtain ultra-high molecular weight polyethylene fibers with a gradient structure.

2. The preparation method according to claim 1, characterized in that, The molecular weight of the ultra-high molecular weight polyethylene is 1×10⁻⁶. 6 ~5×10 6 The concentration of the surface modification solution and the core solution was 2–10 wt%, and the solution was stirred and heated to 120–150 °C.

3. The preparation method according to claim 1, characterized in that, The amount of polytetrafluoroethylene micro powder added is 0.5 to 5 wt% of the mass of ultra-high molecular weight polyethylene.

4. The preparation method according to claim 1, characterized in that, The modified polytetrafluoroethylene (PTFE) micro powder is prepared by dispersing PTFE micro powder in ethanol, adding a silane coupling agent, stirring and reacting for 1-3 hours at a temperature of 50-80°C, and then filtering and drying to obtain modified PTFE micro powder. The amount of silane coupling agent added is 1-5 wt% of the mass of the PTFE micro powder, and the silane coupling agent is KH-550.

5. The preparation method according to claim 1, characterized in that, During the gel spinning process, extrusion spinning is performed with an inner layer flow rate of 0.5–2 mL / min and an outer layer flow rate of 0.1–0.5 mL / min. The spinning temperature is 130–160℃. After cooling through an air gap, the product enters a cooling bath with a temperature of -10–10℃ and an air gap length of 5–20 cm. The cooling bath is made of n-decane or mineral oil.

6. The preparation method according to claim 1, characterized in that, The infrared radiation wavelength for the infrared-assisted solvent extraction is 3–8 μm, and the power density is 0.3–1.5 W / cm². 2 The extraction time is 10–30 min, the extraction bath is heptane or hexane, and the temperature is 40–60℃.

7. The preparation method according to claim 1, characterized in that, The total stretching ratio of the multi-stage hot stretching is 20 to 100 times, the first stage stretching temperature is 80 to 100°C with a stretching ratio of 5 to 10 times, the second stage stretching temperature is 100 to 120°C with a stretching ratio of 5 to 10 times, and the third stage stretching temperature is 120 to 140°C with a stretching ratio of 4 to 10 times.

8. The preparation method according to claim 1, characterized in that, The infrared radiation wavelength for heat setting is 2–10 μm, and the power density is 0.5–2 W / cm². 2 The time is 1 to 5 minutes, and the temperature is 140 to 160℃.

9. The application of ultra-high molecular weight polyethylene fiber with a gradient structure as described in any one of claims 1 to 8 in high-strength ropes and cables.

Images