Surface-coated modified ultra-high molecular weight polyethylene fiber, preparation method, preparation system device and application

Abstract

This invention discloses a surface-coated modified ultra-high molecular weight polyethylene fiber, its preparation method, preparation system, and applications. This method deeply integrates the fundamental mechanism of "surface chemical grafting" to strengthen the interface with an "online continuous integrated" industrial production model, solving the core bottleneck of large-scale preparation of high-performance modified UHMWPE fibers. The preparation method of this invention includes the following steps: 1) preparing a water-based modification solution; 2) immersing the fiber bundle in the water-based modification solution for 5-10 seconds; 3) passing it through a first heat-setting oven at 120-130℃ for 60-180 seconds; 4) impregnating the fiber in an amination treatment tank containing an aqueous solution of adipic acid dihydrazide; 5) passing the impregnated fiber through a second heat-setting oven at 80-100℃ for 5-8 minutes; 6) collecting the surface-crosslinked modified ultra-high molecular weight polyethylene fiber online.

Description

Technical Field

[0001] This invention relates to an ultra-high molecular weight polyethylene fiber and its preparation method, and more specifically to a surface-coated modified ultra-high molecular weight polyethylene fiber, its preparation method, preparation system and apparatus, and its application, belonging to the field of high-performance fiber material manufacturing and surface modification technology. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) fibers are widely used in defense, aerospace, marine engineering, and security fields as reinforcements for high-performance composite materials due to their extremely high specific strength, specific modulus, excellent impact resistance, and chemical corrosion resistance. However, the chemically inert surface of UHMWPE fibers, low surface energy, and lack of active functional groups result in extremely poor interfacial bonding strength with commonly used matrix resins such as epoxy resins and unsaturated polyesters. This "weak interfacial" problem severely restricts the effective transfer of stress in the composite material, causing the interlaminar shear strength, impact resistance, and flexural strength of the composite material to be far lower than theoretical expectations, becoming a major bottleneck limiting its wider application in high-performance structures.

[0003] To improve interfacial properties, various surface modification methods have been proposed in the prior art, mainly including: corona treatment, plasma treatment, chemical oxidation (such as chromic acid etching), and surface graft polymerization. However, these methods generally have the following limitations: (1) the treatment effect is not durable or has poor uniformity (such as corona treatment and plasma treatment); (2) the process may damage the strength of the fiber itself (such as strong acid oxidation); (3) toxic reagents are used, resulting in significant environmental pollution; (4) most importantly, most of these methods are offline, batch-based "post-processing" steps, which are incompatible with modern, high-speed, and continuous UHMWPE fiber spinning-drawing production lines. For example, a recent study (Y. Yu, et al., Polymer Composites, 2025) disclosed a method that uses an amphiphilic macromolecular initiator to initiate the copolymerization of diacetone acrylamide (DAAM) and trimethylolpropane triacrylate (TMPTA) on the surface of UHMWPE fibers, followed by post-crosslinking with adipic dihydrazide (ADH) to construct an interfacial transition layer. While this method can significantly improve the interfacial properties of composite materials, its process is cumbersome and extremely time-consuming: it requires immersion polymerization of the fiber fabric at 90°C for up to 5 hours, followed by 2 hours of ADH crosslinking treatment and prolonged drying, totaling over 7 hours. This completely offline, batch-process mode results in low production efficiency, fundamentally restricting the large-scale industrial application of this technology. Furthermore, some surface coating or physical coating methods, while improving the interface to some extent, rely primarily on van der Waals forces or mechanical interlocking, which are physical bonds and prone to failure under humid and hot environments or long-term stress, resulting in insufficient interfacial durability. Therefore, developing a surface modification method and apparatus system that can be seamlessly integrated with existing UHMWPE fiber production lines, continuously completed online, and sequentially achieves efficient surface polymerization and chemical crosslinking in a short time, with temperature control throughout the process to protect the fiber matrix, has become a core technological challenge urgently needing breakthroughs in this field, and has significant industrial application value. Summary of the Invention

[0004] This invention addresses the problems and shortcomings of existing technologies by providing a surface-coated modified ultra-high molecular weight polyethylene fiber, its preparation method, preparation system, and applications. This method creatively integrates the fundamental mechanism of "surface chemical grafting" for strengthening the interface with the industrial production form of "online continuous integration." Simultaneously, the online continuous process integrating polymerization and amination, and its deep integration with the upstream spinning process, achieves truly uninterrupted continuous production, solving the core bottleneck of large-scale preparation of high-performance modified UHMWPE fibers.

[0005] This invention is achieved through the following technical solution: The method for preparing surface-crosslinked modified ultra-high molecular weight polyethylene fibers according to the present invention includes the following steps: 1) Prepare a water-based modified solution, which is composed of diacetone acrylamide, trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, an azo-based amphiphilic free radical initiator and water; 2) Immerse the high-stretch fiber bundles in the water-based modification solution for 5-10 seconds; 3) Immediately guide the impregnated fiber bundle through the first heat setting tunnel at a temperature of 120~130℃, control the fiber passage speed, and make its residence time in the first tunnel 60~180 seconds, so that the fiber bundle aggregates on the fiber surface and forms an initial coating layer, thus obtaining a fiber with an initial coating layer. 4) The fibers with the initial coating layer are then guided through an amination treatment tank containing an aqueous solution of adipic acid dihydrazide for impregnation treatment. 5) The fiber impregnated with adipic acid dihydrazide is then guided through a second heat-setting oven at a temperature of 80~100℃ and left for 5~8 minutes to allow the ketone carbonyl groups in the initial coating layer to react with the adipic acid dihydrazide to form a final cross-linked coating layer with active amino groups. 6) Surface-crosslinked coated and modified ultra-high molecular weight polyethylene fibers were obtained by online collection.

[0006] A further technical solution of the method for surface crosslinking and modifying ultra-high molecular weight polyethylene fibers described above in this invention is that the concentration of diacetone acrylamide in the water-based modification solution is 10-30 g / L, the concentration of trimethylolpropane triacrylate is 2-5 g / L, the concentration of 1,6-hexanediol diacrylate is 2-10 g / L, and the concentration of an azo-based amphiphilic free radical initiator is 0.2-0.9 g / L. A further technical solution is that the azo-based amphiphilic free radical initiator is composed of 4,4'-azobis(4-cyanopentanoic acid) and fatty alcohol polyoxyethylene ether (R–[OCH2CH2)). n Amphiphilic compounds are prepared by the reaction of 4,4'-azobis(4-cyanopentanoic acid) with fatty alcohol polyoxyethylene ether (R–[OCH2CH2)). Specific azo-based amphiphilic free radical initiators, with their unique amphiphilic structures, are key to achieving chemical grafting. This initiator is composed of 4,4'-azobis(4-cyanopentanoic acid) and fatty alcohol polyoxyethylene ether (R–[OCH2CH2)). nIt is prepared by reacting -OH (R = C12~C18, n = 5~10). In its molecule, the long-chain fatty alcohol provides a strongly hydrophobic end, enabling it to efficiently adsorb and accumulate on the hydrophobic surface of the UHMWPE fiber during the impregnation stage; the polyoxyethylene chain and polar end groups ensure its dispersion stability in the water-based modified liquid. In the first heat-setting oven at 120~130℃, the free radicals generated by the initiator decomposition can capture hydrogen atoms from the fiber surface, forming macromolecular free radical active centers, which in turn initiate the graft copolymerization of DAAM, TMPTA, and HDDA monomers. Thus, the polymer coating layer is firmly bonded to the fiber body through covalent bonds. Based on the above mechanism, this method achieves the following on an operational UHMWPE fiber spinning-drawing production line: The highly stretched fiber bundle is immersed in a modifying solution for several seconds, followed by surface grafting polymerization at 120-130°C for 60-180 seconds; immediately afterward, the fiber is guided through an ADH solution and subjected to amination crosslinking at 80-100°C for 5-8 minutes, introducing active amino groups into the grafted layer. Ultimately, this achieves a fully online, continuous, and uninterrupted production process from fiber forming, surface chemical grafting, to functional modification.

[0007] A further technical solution of the method for surface crosslinking and coating modified ultra-high molecular weight polyethylene fiber described above in this invention may be that the concentration of the adipic acid dihydrazide aqueous solution is 5~10 g / L, and the immersion treatment time of the fiber in the amination treatment tank is 10~20 seconds.

[0008] The present invention relates to a method for preparing surface-crosslinked coated and modified ultra-high molecular weight polyethylene (UHMWPE) fibers. A further technical solution involves a crosslinked polymer coating layer containing active amino groups on the fiber surface, wherein the mass percentage of this coating layer is 3% to 10% of the total fiber mass. This crosslinked polymer coating layer containing active amino groups on the fiber surface enables it to form strong chemical bonds with the resin matrix.

[0009] This invention relates to the application of surface-crosslinked coated and modified ultra-high molecular weight polyethylene fibers as reinforcements in composite materials. The resulting composite material exhibits superior interlaminar properties and overall mechanical properties due to fundamentally strengthened interfaces.

[0010] This invention discloses a system apparatus for preparing the aforementioned surface-crosslinked coated and modified ultra-high molecular weight polyethylene (UHMWPE) fibers. This system apparatus is integrated into a UHMWPE fiber spinning-drawing production line and is arranged sequentially along the fiber travel direction: an impregnation device for holding the water-based modification solution and immersing the fiber; a first heat-setting oven (set at 120-130°C) for polymerizing the modification solution and forming an initial coating layer; an amination treatment device for holding an aqueous solution of adipate dihydrazide and immersing the fiber; a second heat-setting oven (set at 80-100°C) for completing the hydrazone crosslinking reaction and forming the final crosslinked coating layer; and a winding device. The impregnation device, first heat-setting oven, amination treatment device, and second heat-setting oven operate synchronously with the upstream spinning-drawing device and the downstream winding device to achieve continuous production. This system apparatus is constructed in a modular manner, aiming for seamless integration with existing UHMWPE fiber spinning-drawing production lines. The system, along the fiber travel direction, sequentially includes: an impregnation device for holding the water-based modification solution and immersing the fiber bundle during operation; a first heat-setting oven set at 120-130°C for rapidly polymerizing the fiber surface modification solution to form an initial coating layer; an amination treatment device for holding an aqueous solution of adipate dihydrazide (ADH) and immersing the initial coating layer fiber; and a second heat-setting oven set at 80-100°C for promoting hydrazone crosslinking reactions to form the final crosslinked coating layer. All of the above devices work in synergy and synchronously with the upstream spinning-drawing unit and the downstream winding device, thereby integrating the two key processes of surface chemical grafting polymerization and amination functionalization online, continuously, and in an integrated manner into the main fiber production line, realizing uninterrupted operation throughout the entire process from fiber forming and online surface modification to finished product winding.

[0011] Compared with the prior art, the present invention has the following advantages: 1. Achieved chemical grafting bonding between the coating layer and fiber: This invention utilizes an amphiphilic initiator with fatty alcohol polyoxyethylene ether as the hydrophobic segment, achieving directional enrichment and efficient initiation of the initiator on the fiber surface. Active sites are generated in situ on the fiber surface, initiating monomer grafting polymerization. This ensures that the polymer coating layer is chemically linked to the fiber through covalent bonds, fundamentally improving interfacial strength. 2. Highly efficient continuous production: A pioneering online continuous process integrating polymerization and amination is implemented and deeply integrated with the upstream spinning process, achieving truly uninterrupted continuous production and solving the core bottleneck in the large-scale preparation of high-performance modified UHMWPE fibers. 3. A qualitative leap in interfacial performance: Through the online formation of a chemically grafted-crosslinked coating layer containing active amino groups, a complete chemical bonding "bridge" is established between the fiber and resin, from the fiber to the coating layer (covalent bond) and then to the resin (covalent bond). Experiments show that the interfacial shear strength (IFSS) of the resulting fiber and epoxy resin can be increased by more than 150%, while the flexural modulus and impact toughness of the composite material are synergistically enhanced, resulting in excellent overall performance. 4. Low industrialization implementation cost and strong adaptability: The process of this invention makes full use of or draws on the heat setting equipment of existing production lines. The system has a high degree of modularity, low transformation cost, and is easy to promote and implement on various existing UHMWPE fiber production lines, with broad industrialization prospects. Attached Figure Description

[0012] Figure 1 A schematic diagram of a system device (integrated complete type) for preparing surface crosslinked coated and modified ultra-high molecular weight polyethylene fibers. In the figure: 1-UHMWPE fiber spinning section, 2-water-based modification liquid tank, 3-first heat setting oven, 4-ammoniation treatment tank, 5-second heat setting oven, 6-winding machine; Figure 2 This is a SEM image of the surface-crosslinked coated and modified ultra-high molecular weight polyethylene fiber prepared in Example 1 of the present invention. Detailed Implementation

[0013] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the following embodiments. This embodiment demonstrates the integrated online process of the present invention, aiming to clarify the proportions, process steps, and parameters of each key component in the modified liquid. In actual industrial production, it is necessary to scale up according to the production line scale, impregnation tank volume, and processing throughput.

[0014] Example 1 1) Preparation of water-based polymerization modification solution: Weigh the following components according to the following concentration ratios: diacetone acrylamide (DAAM) 20 g / L, trimethylolpropane triacrylate (TMPTA) 4 g / L, 1,6-hexanediol diacrylate (HDDA) 6 g / L, and amphiphilic free radical initiator synthesized from 4,4'-azobis(4-cyanopentanoic acid) and lauryl alcohol polyoxyethylene ether (C12, n=7) via the acyl chloride method. Prepare 1 liter of this modification solution and magnetically stir at room temperature for 20 minutes to obtain a homogeneous and transparent polymerization modification solution. In actual production, the volume of the amination treatment tank and the total amount of ADH solution need to be scaled up according to this concentration ratio based on the processing throughput of the production line. 2) Online continuous polymerization: Start the production line and run the UHMWPE fiber bundles, which have already undergone high-ratio stretching, at a linear speed of 30 meters per minute. The fibers are guided into an impregnation tank completely immersed in the above-mentioned polymerization modification solution for approximately 6 seconds. Subsequently, the impregnated wet fibers are immediately introduced into a first heat-setting tunnel at 130°C, where they remain for 90 seconds (i.e., polymerization drying time), forming a fiber intermediate with an initial polymer coating. 3) Online continuous amination treatment: a. Preparation of the amination treatment solution: Prepare an aqueous solution of adipic acid dihydrazide (ADH) with a concentration of 6 g / L and inject it into the amination treatment tank. In actual production, the volume of the amination treatment tank and the total amount of ADH solution need to be scaled up according to the processing throughput of the production line and prepared in this concentration ratio; b. Online impregnation: The fiber intermediate (linear speed still 30 m / min) coming out of the first drying tunnel is guided to be immersed in the above ADH solution for about 10 seconds; c. Online reaction and drying: Subsequently, the fiber is immediately introduced into the second heat setting drying tunnel at a temperature of 90°C, and the residence time of the fiber in the second drying tunnel is controlled to be 7 minutes to complete the hydrazone crosslinking reaction and drying. 4) Online winding: The fiber coming out of the second drying tunnel is wound up by the winding device after passing through the cooling guide rollers to obtain the final modified fiber, denoted as Fiber-PA-1. 5) Fiber characterization and performance testing: It was determined that the mass fraction of the crosslinked coating layer on the surface of Fiber-PA-1 is about 6.5%. After thorough THF cleaning to remove physically adsorbed polymers from the surface, the fiber was characterized using X-ray photoelectron spectroscopy (XPS). The C 1s fine spectrum showed new characteristic peaks attributable to CN bonds (~285.5 eV), C=O bonds (~288 eV), and OC=O bonds (~289 eV), confirming that the polymer layer is covalently bonded to the fiber substrate. A composite material was prepared using E-44 epoxy resin and polyamide 651 curing agent, compared to the unmodified fiber composite. Tests showed that, compared to the unmodified fiber composite, the Fiber-PA-1 composite exhibited approximately 230% higher interfacial shear strength (IFSS), approximately 220% higher flexural modulus, and approximately 75% higher unnotched impact strength.

[0015] Example 2 1) Preparation of water-based polymerization modification solution: Except for replacing the amphiphilic initiator with the product synthesized by the acyl chloride method from 4,4'-azobis(4-cyanopentanoic acid) and hexadecyl polyoxyethylene ether (C16, n=5), the concentrations of other components are the same as in Example 1. 2) Online continuous polymerization: The process parameters are the same as step (2) in Example 1, the fiber linear speed is 30 m / min, the impregnation time is 6 seconds, and the polymerization time in the 120°C drying tunnel is 150 seconds. 3) Online continuous amination treatment: a. The concentration of ADH solution is the same as in Example 1; b. Online impregnation: the impregnation time is about 20 seconds; c. Online reaction and drying: the temperature of the second heat setting drying tunnel is set to 100°C; the residence time of the fiber in the drying tunnel is controlled to be 5 minutes by adjusting the length of the drying tunnel and the fiber speed. 4) Online winding to obtain modified fiber, denoted as Fiber-PA-2. 5) Fiber characterization and performance testing: the mass fraction of the surface coating layer of Fiber-PA-2 is about 5.8%. Composite material tests show that, compared with unmodified fiber composites, its IFSS is increased by about 235%, flexural modulus by about 210%, and impact strength by about 70%.

[0016] Example 3 This embodiment aims to demonstrate the combined effects of using different monomer concentrations, lower fiber running speeds, and longer amination times. 1) Preparation of water-based polymerization modification solution: Adjust the concentrations of each component to: DAAM 30 g / L, TMPTA 2 g / L, HDDA 2 g / L, and amphiphilic initiator (same as in Example 1) 0.3 g / L. 2) Online continuous polymerization: Adjust the production line speed to 15 m / min. Adjust the length of the impregnation tank accordingly to make the online impregnation time approximately 8 seconds. Then, introduce the fiber into the first heat-setting tunnel at 120°C, and design the tunnel length to ensure a residence time of 180 seconds. 3) Online continuous amination treatment: a. Prepare an 8 g / L ADH aqueous solution; b. Online impregnation: Impregnation time approximately 15 seconds; c. Online reaction and drying: Set the temperature of the second heat-setting tunnel to 80°C. Control the fiber speed to ensure a residence time of 8 minutes in the tunnel. 4) Online winding yields the modified fiber, denoted as Fiber-PA-3. 5) Fiber characterization and performance testing: The surface coating mass fraction of Fiber-PA-3 is approximately 4.5%. Composite material testing shows that compared to the unmodified fiber composite, its IFSS is increased by approximately 205%, flexural modulus by approximately 185%, and impact strength by approximately 68%. The above embodiments demonstrate that the online integrated process provided by this invention possesses high flexibility and adjustability, and strong industrial applicability. By adjusting the fiber linear speed, drying tunnel temperature, and length, the impregnation, polymerization, and amination times can be flexibly controlled to adapt to production lines with different capacity and performance requirements. This process can be fully integrated into existing UHMWPE fiber spinning-drawing production lines, achieving continuous, efficient, and stable production from fiber to high-performance modified products, and has broad prospects for industrial application.

Claims

1. A method for preparing surface-crosslinked coated and modified ultra-high molecular weight polyethylene fiber, characterized in that, Includes the following steps: 1) Prepare a water-based modified solution, which is composed of diacetone acrylamide, trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, an azo-based amphiphilic free radical initiator and water; 2) Immerse the high-stretch fiber bundles in the water-based modification solution for 5-10 seconds; 3) Immediately guide the impregnated fiber bundle through the first heat setting tunnel at a temperature of 120~130℃, control the fiber passage speed, and make its residence time in the first tunnel 60~180 seconds, so that the fiber bundle aggregates on the fiber surface and forms an initial coating layer, thus obtaining a fiber with an initial coating layer. 4) The fibers with the initial coating layer are then guided through an amination treatment tank containing an aqueous solution of adipic acid dihydrazide for impregnation treatment. 5) The fiber impregnated with adipic acid dihydrazide is then guided through a second heat-setting oven at a temperature of 80~100℃ and left for 5~8 minutes to allow the ketone carbonyl groups in the initial coating layer to react with the adipic acid dihydrazide to form a final cross-linked coating layer with active amino groups. 6) Surface-crosslinked coated and modified ultra-high molecular weight polyethylene fibers were obtained by online collection.

2. The method for surface crosslinking and coating modified ultra-high molecular weight polyethylene fibers according to claim 1, characterized in that, In the water-based modified solution, the concentration of diacetone acrylamide is 10~30 g / L, the concentration of trimethylolpropane triacrylate is 2~5 g / L, the concentration of 1,6-hexanediol diacrylate is 2~10 g / L, and the concentration of azo-based amphiphilic free radical initiator is 0.2~0.9 g / L.

3. The method for surface crosslinking and coating modified ultra-high molecular weight polyethylene fibers according to claim 1 or 2, characterized in that, The aforementioned azo-based amphiphilic free radical initiator is composed of 4,4'-azobis(4-cyanopentanoic acid) and fatty alcohol polyoxyethylene ether (R–[OCH2CH2)). n Amphiphilic compounds prepared by the reaction of –OH) via acyl chloride.

4. The method for surface crosslinking and coating modified ultra-high molecular weight polyethylene fibers according to claim 1, characterized in that, The concentration of the adipic acid dihydrazide aqueous solution is 5~10 g / L, and the immersion time of the fiber in the amination treatment tank is 10~20 seconds.

5. A surface-crosslinked coated ultra-high molecular weight polyethylene fiber prepared by a method for surface-crosslinked coated modified ultra-high molecular weight polyethylene fiber as described in any one of claims 1-4.

6. The surface-crosslinked coated modified ultra-high molecular weight polyethylene fiber according to claim 5, characterized in that, The fiber surface has a cross-linked polymer coating layer with active amino groups, and the mass percentage of the coating layer is 3% to 10% of the total fiber mass.

7. The application of surface-crosslinked coated and modified ultra-high molecular weight polyethylene fiber as described in claim 5 or 6 as a reinforcement in composite materials.

8. A system apparatus for preparing surface-crosslinked coated and modified ultra-high molecular weight polyethylene fibers as described in claim 5 or 6, characterized in that, The system is integrated into the spinning-drawing production line of ultra-high molecular weight polyethylene fiber, and is arranged in sequence along the fiber travel direction: an impregnation device for holding water-based modification liquid and immersing the fiber; and a first heat setting oven, which is set at a temperature of 120~130℃ to polymerize the modification liquid and form an initial coating layer. Amination treatment apparatus for holding an aqueous solution of adipate dihydrazide and immersing the fiber; The second heat-setting oven is a drying oven with a temperature set at 80~100℃, used to complete the hydrazone cross-linking reaction and form the final cross-linked coating layer; The device includes a winding device; the impregnation device, the first heat setting oven, the amination treatment device, and the second heat setting oven operate synchronously with the upstream spinning-drawing device and the downstream winding device to achieve continuous production.

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