Regenerated carbon fiber modified nylon composite material as well as preparation method and application thereof

Abstract

The invention provides a regenerated carbon fiber modified nylon composite material as well as a preparation method and application thereof, and belongs to the technical field of polymer composite materials and resource recycling. According to the invention, the regenerated carbon fiber is used as a reinforcing main body, interface reinforcing elements (interface modifiers: carbon nanomaterials, inorganic nanoparticles and reactive compatibilizers) are introduced, and a plurality of auxiliaries such as the flexibilizer, the lubricant and the antioxidant and process optimization are combined, so that the mechanical properties and comprehensive properties of a nylon matrix are improved. Compared with pure nylon, the tensile strength and modulus of the composite material are remarkably improved (the strength can reach 150-200 MPa, and the modulus is gt and 8 GPa), and meanwhile, through toughening and interface optimization, the impact strength is improved (notch impact is improved by 50% or above) and the excellent wear-resisting and friction-reducing performance is achieved (the friction coefficient is reduced by 30% or above).

Description

Technical Field

[0001] This invention relates to the fields of polymer composite materials and resource recycling technology, and in particular to a recycled carbon fiber modified nylon composite material, its preparation method and application. Background Technology

[0002] Carbon fiber reinforced composites (CFRPs) are widely used in aerospace, high-end automotive, and other fields due to their advantages such as high specific strength, high specific modulus, and lightweight. However, the large-scale use of CFRPs has also brought about the problem of waste recycling. Traditional methods for processing waste CFRPs include pyrolysis and chemical dissolution, which can separate recycled carbon fibers from the matrix resin. The effective utilization of recycled carbon fibers can not only save expensive carbon fiber raw materials and reduce costs, but also has important environmental significance.

[0003] Nylon (polyamide) plastic is an important class of engineering plastics, with common varieties including PA6, PA66, PA11, PA12, and PA610. Nylon materials possess good toughness, wear resistance, self-lubrication, and resistance to oil and chemicals, making them widely used in automobiles, electronics, and mechanical parts. However, nylon still suffers from insufficient rigidity and strength compared to metals, especially in applications requiring high strength and high modulus. Adding fiber reinforcement can significantly improve the mechanical properties of nylon. While glass fiber is a commonly used reinforcement material and is inexpensive, carbon fiber has higher specific strength and specific modulus, as well as lower density and higher heat resistance. Therefore, carbon fiber reinforced nylon composites are more advantageous in applications requiring high performance.

[0004] In recent years, some research and patents have begun to focus on the use of recycled carbon fibers to reinforce nylon. For example, Chinese patent CN103554904A discloses a recycled carbon fiber reinforced nylon composite material and its preparation method. This method involves adding recycled carbon fibers from waste CFRP to a nylon matrix and using a surface treatment agent (coupling agent) to improve interfacial bonding, achieving high-performance nylon materials at a lower cost. This technology uses silane, titanate, or aluminate coupling agents to surface-treat the recycled carbon fibers, then blends them with nylon resin and additives such as lubricants and antioxidants, followed by extrusion granulation. The resulting composite material has low density and excellent mechanical properties. However, existing technologies still have some shortcomings: First, the original resin surface coating (sizing agent) of the recycled carbon fibers is burned off or destroyed during the recycling process, reducing and potentially damaging the polar functional groups on the fiber surface. Even with coupling agent treatment, there is still room for improvement in the interfacial adhesion between the carbon fibers and the nylon matrix, limiting further improvement in mechanical properties. Second, the addition of carbon fibers often leads to a decrease in the toughness (impact strength) of the nylon composite material, limiting its application in applications requiring impact loads. In addition, the properties of recycled carbon fibers from different sources vary greatly. How to make them compatible with various reinforcing materials and broaden the application range of materials is also a challenge faced by existing technologies.

[0005] Furthermore, traditional carbon fiber reinforced nylon composites mostly focus on improving static mechanical strength and modulus, while there is still room for improvement in areas such as wear resistance, friction reduction, dimensional stability, and thermal properties. For example, patent CN107189428A describes a graphene / carbon fiber reinforced nylon wear-resistant composite material, which simultaneously introduces carbon fibers, graphene, and a solid lubricant into nylon, significantly improving the material's self-lubricating and wear-resistant properties. This suggests that doping with nanomaterials can synergistically enhance specific properties of composite materials (such as wear resistance and thermal conductivity). However, the above technologies mainly target new carbon fibers and are not specifically geared towards recycled carbon fiber applications. Additionally, while emphasizing lubrication and wear resistance, there are few reports on their effects on improving interfacial bonding strength and impact toughness.

[0006] In summary, the existing technologies for modifying nylon with recycled carbon fiber have the following shortcomings: (1) The interfacial compatibility between recycled carbon fiber and nylon matrix needs to be further enhanced. Existing coupling agent treatment can improve polarity but chemical bonding is limited; (2) The impact toughness of the composite material is low and there is a lack of effective toughening measures; (3) Most existing solutions use carbon fiber reinforcement alone and have not fully utilized the potential of multiple reinforcing materials or nanoparticle doping to improve multiple properties at the same time; (4) There is a lack of targeted modification combinations for different application scenarios (such as high-strength structural parts, wear-resistant parts, etc.) and the scope of patent protection is relatively limited.

[0007] Therefore, it is necessary to develop modified nylon composite materials with high strength, high modulus, and good toughness. Summary of the Invention

[0008] The purpose of this invention is to provide a recycled carbon fiber modified nylon composite material, its preparation method and application. By utilizing the reinforcing effect of recycled carbon fiber, combined with interface modifiers and multi-component composite modification (such as toughening agents and fiber reinforcing materials), the mechanical properties (including tensile strength, flexural strength, modulus, etc.) and impact toughness of the nylon matrix are significantly improved through unique material combinations and modification methods, while also taking into account performance requirements such as wear resistance and dimensional stability.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a recycled carbon fiber modified nylon composite material, comprising the following raw materials in parts by weight: Nylon resin 50-95 parts, recycled carbon fiber 5-50 parts, interface modifier 0.1-10 parts, coupling agent 0.1-5 parts, lubricant 0.1-2 parts, antioxidant 0.1-1 part, toughening agent 0-20 parts, additives 0-10 parts; The interface modifier includes one or more of carbon nanomaterials, inorganic nanoparticles, and reactive compatibilizers.

[0010] Preferably, the nylon resin includes one or more of nylon 6, nylon 66, nylon 11, nylon 12, nylon 610, and nylon 1010; The length of the recycled carbon fiber is 0.1~100mm.

[0011] Preferably, the carbon nanomaterials include one or more of graphene, graphene oxide, reduced graphene oxide, carbon nanofibers, and carbon nanotubes; the inorganic nanoparticles include one or more of nano-silica, nano-alumina, and nano-clay; and the reactive compatibilizer includes compounds containing epoxy groups, compounds containing maleic anhydride groups, or compounds containing isocyanate groups.

[0012] Preferably, the epoxy-containing compound includes bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, phenolic epoxy resin, or aliphatic diglycidyl ether. The compounds containing maleic anhydride groups include maleic anhydride-grafted polyolefins (PP-g-MAH), maleic anhydride-grafted polyolefin elastomers (POE-g-MAH), maleic anhydride-grafted SEBS (SEBS-g-MAH), or styrene-maleic anhydride copolymers (SMA). The isocyanate-containing compounds include diisocyanates or polyisocyanates.

[0013] Preferably, the coupling agent includes one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents; The lubricant includes one or more of stearic acid, stearic acid metal salts, paraffin wax, microcrystalline wax, polyethylene wax, and amide wax; The antioxidants include primary antioxidants and secondary antioxidants. The primary antioxidants include hindered phenolic antioxidants; the secondary antioxidants include phosphite antioxidants or thioether antioxidants. The toughening agent includes one or more of maleic anhydride-grafted polyolefin elastomers, styrene-based thermoplastic elastomers, and rubber granules. The additives include one or more of ultraviolet absorbers, heat stabilizers, and flame retardants.

[0014] Preferably, the material further includes 5 to 30 parts of fiber reinforcing material, wherein the fiber reinforcing material includes one or more of glass fiber, aramid fiber and basalt fiber.

[0015] Preferably, it also includes 0.5 to 5 parts of solid lubricant additive, wherein the solid lubricant additive includes one or more of molybdenum disulfide, graphite and polytetrafluoroethylene micro powder.

[0016] This invention provides a method for preparing the recycled carbon fiber modified nylon composite material described in the above technical solution, comprising the following steps: Regenerated carbon fiber is mixed with a coupling agent for the first modification, and the resulting modified fiber is mixed with an interface modifier for the second modification to obtain modified recycled carbon fiber. The modified recycled carbon fiber is mixed with the required proportions of nylon resin, lubricant, antioxidant, toughening agent and additives, and then melt-blended to obtain carbon fiber-nylon melt; The carbon fiber-nylon melt is extruded and shaped to obtain a recycled carbon fiber modified nylon composite material; Alternatively, after the first modification, the obtained modified fibers are mixed with an interface modifier and nylon resin, and then the required amounts of lubricant, antioxidant, toughening agent and additives are added, extruded and molded to obtain a recycled carbon fiber modified nylon composite material.

[0017] Preferably, the melt mixing and extrusion granulation are carried out continuously in a co-rotating twin-screw extruder, wherein the temperature of each temperature zone of the co-rotating twin-screw extruder is independently 190~290℃, the screw speed is 150~400 rpm, and the screw length-to-diameter ratio L / D is 30~50:1.

[0018] This invention provides the application of the recycled carbon fiber modified nylon composite material described in the above technical solution or the recycled carbon fiber modified nylon composite material prepared by the preparation method described in the above technical solution in high-performance products, including automotive structural parts, aerospace structural parts, load-bearing gears, load-bearing bushings, or housings of electronic and electrical devices.

[0019] This invention provides a recycled carbon fiber modified nylon composite material. The composite material uses recycled carbon fiber as the main reinforcement, introduces interface reinforcing elements (interface modifiers: carbon nanomaterials, inorganic nanoparticles and reactive compatibilizers), and combines various additives such as toughening agents, lubricants and antioxidants with process optimization to improve the mechanical properties and overall performance of the nylon matrix.

[0020] This invention optimizes the characteristics of recycled carbon fiber. The preparation method includes steps such as modified treatment of recycled carbon fiber, melt mixing, extrusion, and molding. Furthermore, it employs a twin-screw extrusion process and side-feeding technology to protect fiber length, enabling the efficient and stable preparation of nylon composite materials with high specific strength, high modulus, and excellent self-lubricating and wear-resistant properties, suitable for industrial production. The modified nylon composite material prepared by this invention exhibits significantly improved tensile strength and modulus compared to pure nylon (strength can reach 150~200MPa, modulus >8GPa). Simultaneously, through toughening and interface optimization, it achieves improved impact strength (notched impact strength increased by more than 50%) and excellent wear resistance and friction reduction properties (friction coefficient reduced by more than 30%).

[0021] The modified nylon composite material prepared by this invention has low density and customizable properties, making it suitable for replacing metal and new carbon fiber composite materials in the automotive, aerospace and other fields. It has the advantages of high efficiency, low cost and environmental protection, and significantly expands the application range of recycled carbon fiber in high-performance engineering plastics.

[0022] Through the synergistic effect of the components of this invention, the various properties of the recycled carbon fiber modified nylon composite material are significantly improved, specifically as follows: Significantly improved mechanical properties: Compared with pure nylon without added reinforcement, the tensile strength and flexural strength of the composite material of this invention are significantly improved, reaching 2 to 3 times or more of pure nylon; the flexural modulus is even more significantly improved, reaching the level of several GPa (depending on the carbon fiber content), making the material rigidity close to that of metallic aluminum, indicating that this material can be used to manufacture structural components that need to withstand high loads and require light weight.

[0023] Enhanced interfacial bonding strength: The combined action of interfacial modifiers and coupling agents ensures a strong bond between the carbon fibers and the nylon matrix. Even under stress or during prolonged use, the fibers are less prone to pull-out from the matrix. Furthermore, the interfacial reinforcement is also reflected in improved flexural and shear strength. Moreover, due to the synergistic effect of interfacial chemical bonding and roughening, the composite material of this invention exhibits better interfacial stability under high-temperature or humid conditions.

[0024] Improved Impact Toughness: This invention, through the addition of toughening agents and interfacial toughening design, significantly improves the notched impact strength of carbon fiber reinforced nylon materials with the same carbon fiber content, achieving a good balance between high strength and high toughness. This indicates that the material is less prone to brittle fracture under impact loads, thereby expanding its application range.

[0025] Excellent wear resistance and friction properties: Carbon fiber itself has self-lubricating and friction-reducing properties, while the graphene (especially graphene flakes formed by the partial reduction of graphene oxide during processing) in the interface modifier introduced in this invention further acts as a solid lubricant. Experimental tests show that the coefficient of friction of the composite material of this invention is reduced by about 30% compared with pure nylon, and the wear consumption is significantly reduced. This makes it very suitable for manufacturing bearing seats, gears, sliding guides, and other parts that require wear resistance. The composite material with added graphene modifier exhibits a significantly reduced wear rate and demonstrates excellent wear resistance.

[0026] Improved dimensional stability and thermal properties: Carbon fibers have an extremely low coefficient of thermal expansion, approximately zero or even negative. Therefore, adding carbon fibers significantly reduces the linear thermal expansion coefficient of nylon composites, improving the dimensional stability of the products. The material of this invention exhibits significantly smaller dimensional changes than pure nylon products within the tested temperature range (-40℃ to 120℃), making it suitable for precision parts applications. Simultaneously, the addition of carbon fibers increases the material's heat distortion temperature (HDT), meeting the requirements for high-temperature environments. Furthermore, the improved thermal conductivity of the nano-interface agent (graphene enhances the thermal conductivity of the composite material) facilitates faster heat dissipation. These thermal improvements enable the application of the material of this invention in high-temperature components such as engine compartments and heater housings.

[0027] Low density and good processability: Compared to traditional metallic materials, the composite material of this invention has a density of only about 1.2~1.3 g / cm³. 3 (Varies with fiber content) It is only half that of aluminum alloy and about one-fifth that of steel, yet it provides strength close to that of metal. Furthermore, this invention maintains good melt flow properties and processability even with high fiber content through lubricant and process optimization. The composite material of this invention can be processed using conventional injection molding machines, and the product molding cycle is not significantly different compared to pure nylon. Simultaneously, due to good interfacial bonding, fiber shedding is reduced during processing and use, resulting in lower mold wear.

[0028] In summary, the recycled carbon fiber modified nylon composite material provided by this invention exhibits outstanding performance in terms of strength, modulus, toughness, and wear resistance, while also being lightweight and processable, achieving the expected technical effects. Compared to existing solutions (such as carbon fiber reinforced nylon using only coupling agents), this invention significantly improves the performance of the composite material through interface modification doping + toughening + multi-component synergistic technology improvements. Detailed Implementation

[0029] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0030] This invention provides a recycled carbon fiber modified nylon composite material, comprising the following raw materials in parts by weight: Nylon resin 50-95 parts, recycled carbon fiber 5-50 parts, interface modifier 0.1-10 parts, coupling agent 0.1-5 parts, lubricant 0.1-2 parts, antioxidant 0.1-1 part, toughening agent 0-20 parts, additives 0-10 parts; The interface modifier includes one or more of carbon nanomaterials, inorganic nanoparticles, and reactive compatibilizers.

[0031] The raw materials for preparing the recycled carbon fiber modified nylon composite material provided by the present invention, by weight, include 50-95 parts of nylon resin, preferably 60-90 parts, and more preferably 75-88.5 parts; the nylon resin (thermoplastic polyamide) preferably includes one or more of nylon 6, nylon 66, nylon 11, nylon 12, nylon 610 and nylon 1010; more preferably nylon 66, and more preferably a blend of nylon 66 and nylon 6 in a weight ratio of 7:3 to 3:7.

[0032] This invention preferably uses nylon 6 (PA6) or nylon 66 (PA66) due to their high mechanical strength and good heat resistance, making them suitable as structural material matrices. Nylon 66 has a higher glass transition temperature and melting point, resulting in composite materials with superior rigidity retention at high temperatures. For applications requiring low water absorption and dimensional stability, aliphatic long-chain nylons such as nylon 11 and nylon 12 can be selected; for applications requiring special properties, semi-aromatic nylons (such as nylon 610T) can also be used.

[0033] The raw materials for preparing the recycled carbon fiber modified nylon composite material provided by the present invention, by weight, include 5 to 50 parts of recycled carbon fiber, preferably 10 to 40 parts, and more preferably 15 to 25 parts; the length of the recycled carbon fiber is preferably 0.1 to 100 mm.

[0034] In this invention, the recycled carbon fiber is preferably derived from recycled fibers of waste fiber reinforced composite materials, and preferably includes aerospace carbon fiber prepreg scraps and scrapped carbon fiber reinforced resin components (such as wind turbine blades, automobile parts, etc.).

[0035] The present invention does not have any particular limitation on the method of obtaining recycled carbon fiber. It is preferred to obtain carbon fiber by high temperature pyrolysis (such as pyrolysis of matrix resin in an inert atmosphere at 500~600℃), or preferably by chemical solvent dissolution or enzymatic hydrolysis to gently remove the matrix in order to retain the strength of carbon fiber to the greatest extent. It is also preferred to use a pyrolysis + oxidation combined recycling process to fully remove residual resin and generate certain oxygen-containing functional groups on the fiber surface, which is beneficial to subsequent surface modification and grafting.

[0036] In this invention, the recycled carbon fiber is preferably in the form of continuous long fibers or chopped fibers, and the length of the recycled carbon fiber used in this invention is more preferably 0.1~50 mm. Specifically, for the melt blending granulation process, chopped carbon fibers with a length of 3~10 mm are more preferably used to balance fiber length and mixing uniformity; if long fibers (>50 mm) are used, a higher aspect ratio can be maintained during blending, thereby further improving the reinforcing effect. These recycled carbon fibers typically have a diameter of 5~7 micrometers and mechanical properties close to those of the original fibers (tensile strength can reach 80~90% of the original). In particular, recycled carbon fibers from aerospace composite materials (such as T700 grade or higher carbon fibers) are preferred, as they have higher modulus and strength, which can impart superior performance to the composite materials.

[0037] The raw materials for preparing the recycled carbon fiber modified nylon composite material provided by this invention, by weight, include 0.1-10 parts of an interface modifier, preferably 0.2-5 parts, and more preferably 0.5-3 parts; the interface modifier includes one or more of carbon nanomaterials, inorganic nanoparticles, and reactive compatibilizers. This invention utilizes the interface modifier for doping or grafting new elements. The interface modifier is a substance that can construct interfacial bonds and enhance the interfacial function between the carbon fiber and the nylon matrix.

[0038] In this invention, the carbon nanomaterials preferably include one or more of graphene, graphene oxide (GO), reduced graphene oxide (rGO), carbon nanofibers, and carbon nanotubes (CNTs). During material preparation, graphene oxide is attached to the surface of recycled carbon fibers and partially reduced to form graphene, thereby enhancing the interfacial bonding between the fibers and the nylon matrix. Graphene-based two-dimensional materials possess extremely high specific surface area and mechanical strength. Their surface contains oxygen-containing functional groups (in the case of GO), which can interact with polar groups in nylon through hydrogen bonding and other interactions. Simultaneously, when graphene is attached to the carbon fiber surface, it can form a nanoscale transition layer between the fiber and the resin, improving stress transfer efficiency. This invention preferably uses graphene oxide as an interfacial nanomodifier because: graphene oxide is easily dispersed and contains hydroxyl and carboxyl groups, which can interact with the carbon fiber surface and nylon molecules through covalent or non-covalent mechanisms, thereby further improving interfacial bonding. The incorporation of a small amount of graphene oxide can also improve the wear resistance and self-lubricating properties of the composite material, which is difficult to achieve with other coupling agents acting alone. To improve compatibility with the nylon matrix and modification efficiency, the interface modifier is more preferably graphene or carbon nanotubes.

[0039] When using graphene-based interface modifiers, too low a content (<0.1 parts) is unlikely to be effective, while too high a content (>5 parts) may lead to difficulties in dispersion and increased viscosity, which is detrimental to processing. It is preferable to add 0.5 to 3 parts of graphene-based interface modifiers to achieve significant results.

[0040] In this invention, the inorganic nanoparticles preferably include one or more of nano-silica, nano-alumina, and nano-clay, more preferably nano-silica, and are combined with a coupling agent to form a firmly attached layer on the fiber surface. By depositing these nanoparticles on the carbon fiber surface, a rough surface and bonding effect are formed, thereby improving the interfacial strength.

[0041] In this invention, the reactive compatibilizer preferably includes an epoxy-containing compound, a maleic anhydride-containing compound, or an isocyanate-containing compound; when the reactive compatibilizer is added to the carbon fiber / nylon system, it can react during processing to "bridge" the fiber surface with the nylon molecular chain.

[0042] In this invention, the epoxy-containing compound preferably includes bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, phenolic epoxy resin, or aliphatic diglycidyl ether, and more preferably epoxy resin E-51. During the blending process of the composite material, the epoxy-containing compound reacts with the surface of the recycled carbon fiber and nylon molecules to form a chemically bonded interfacial layer.

[0043] In this invention, the compound containing maleic anhydride groups preferably includes maleic anhydride-grafted polyolefin (PP-g-MAH), maleic anhydride-grafted polyolefin elastomer (POE-g-MAH), maleic anhydride-grafted SEBS (SEBS-g-MAH), or styrene-maleic anhydride copolymer (SMA).

[0044] In this invention, the isocyanate-containing compound preferably includes diisocyanate or polyisocyanate, more preferably MDI, TDI, IPDI, or HDI. During high-temperature compounding, these substances can react with the carboxyl / hydroxyl groups on the carbon fiber surface (derived from recycling or surface oxidation), and also with the carboxyl or amino groups at the ends of nylon molecules, thereby forming chemical bonds and achieving true interfacial bonding.

[0045] In this invention, the interface modifier is preferably a mixture of graphene-based nanomaterials (especially graphene oxide) and reactive compatibilizers. The mass ratio of the graphene-based nanomaterials to the reactive compatibilizers is preferably 0.05~5:0.05~5, more preferably 0.1~2:0.1~2. This invention utilizes graphene to provide structural reinforcement and surface area, and the reactive compatibilizer to provide chemical bonding; the combination of the two maximizes the interfacial bonding strength.

[0046] The raw materials for preparing the recycled carbon fiber modified nylon composite material provided by the present invention, by weight, include 0.1 to 5 parts of coupling agent, more preferably 0.5 to 3 parts, and even more preferably 1 to 2 parts; the coupling agent preferably includes one or more of silane coupling agent, titanate coupling agent and aluminate coupling agent; more preferably one or more of γ-aminopropyltriethoxysilane (KH550), γ-glycidoxypropyltrimethoxysilane (KH560), isopropyltris(dioctylphosphoyloxy)titanate and isopropyldistearate aluminate.

[0047] This invention utilizes coupling agents to improve the compatibility of inorganic / organic interfaces. The silane coupling agent has a silane group at one end that can condense with oxygen-containing groups on the carbon fiber surface, while the functional groups (such as amino or epoxy groups) at the other end can form hydrogen bonds or react with nylon molecules, thereby forming molecular bridges between the fiber and resin. KH550 is preferably used in this invention because it contains an amino group, which can form amide bonds or strong polar interactions with the terminal carboxyl groups of nylon, resulting in a significant coupling effect. Titanate coupling agents (such as isopropyltris(alkylbenzenesulfonyl)titanate) and aluminate coupling agents have excellent heat resistance and lubrication properties. It is further preferred to use silane coupling agents in combination with titanate coupling agents, as both synergistically improve the interfacial effect. Pre-treating regenerated carbon fibers with coupling agents can compensate for the insufficient interfacial polarity caused by the lack of size-enhancing agents on the surface of regenerated fibers. Combined with the aforementioned interfacial modifiers, multi-level interfacial reinforcement is achieved.

[0048] The raw materials for preparing the recycled carbon fiber modified nylon composite material provided by the present invention, by weight, include 0.1 to 2 parts of lubricant, preferably 0.2 to 1 part, and more preferably 0.3 to 0.6 parts; the lubricant preferably includes one or more of stearic acid, stearic acid metal salts, paraffin wax, microcrystalline wax, polyethylene wax, and amide wax. The stearic acid metal salt is preferably zinc stearate or calcium stearate; the amide wax is preferably ethylene bis-stearamide (EBS) or erucamide.

[0049] This invention improves melt flowability, reduces wear between fibers and equipment, and enhances the surface quality of the finished product by adding a lubricant. Preferably, this invention uses 0.1-0.5 parts of EBS lubricant due to its thermal stability, good compatibility with nylon, and ability to form a coating on the carbon fiber surface, reducing fiber breakage. It can also be used in conjunction with stearic acid metal salts to achieve a comprehensive lubrication effect both internally and externally. This invention limits the above-mentioned amount of lubricant addition to avoid reducing the interfacial adhesion between the fiber and the matrix.

[0050] The raw materials for preparing the recycled carbon fiber modified nylon composite material provided by the present invention, by weight, include 0.1 to 1 part of antioxidant, preferably 0.2 to 0.8 parts, more preferably 0.5 to 0.6 parts; the antioxidant preferably includes a primary antioxidant and a secondary antioxidant, the primary antioxidant preferably includes a hindered phenolic antioxidant; the secondary antioxidant preferably includes a phosphite antioxidant or a thioether antioxidant; the hindered phenolic antioxidant is preferably antioxidant 1010 or 1076; the phosphite antioxidant is preferably antioxidant 168; the thioether antioxidant is preferably DLTDP / DSTDP. Since nylon and toughening agents may undergo oxidative degradation during processing (high-temperature melt extrusion) and long-term use, the present invention adds antioxidants to improve the thermo-oxidative aging life of the material.

[0051] This invention preferably combines hindered phenolic antioxidants with phosphite antioxidants, for example, adding 0.3 parts of antioxidant 1010 and 0.1 parts of antioxidant 168 per 100 parts of the composite material. This combination provides long-lasting processing and thermal stability protection. This invention controls the amount of antioxidants added to avoid insufficient addition resulting in poor performance, and to avoid excessive addition affecting polymer color and processing stability.

[0052] The raw materials for preparing the recycled carbon fiber modified nylon composite material provided by this invention, by weight, include 0-20 parts of toughening agent, preferably 2-15 parts, and more preferably 5-10 parts. In this invention, the toughening agent preferably includes one or more of maleic anhydride-grafted polyolefin elastomers, styrene-based thermoplastic elastomers, and rubber particles; more preferably, it is a maleic anhydride-grafted ethylene-α-olefin copolymer elastomer, maleic anhydride-grafted SEBS, functionalized polyether, polyurethane elastomer, or core-shell structure rubber particles (such as CSR toughening agent, typically represented by MBS resin); even more preferably, it is a maleic anhydride-grafted ethylene-octene copolymer POE-g-MAH or a maleic anhydride-grafted ethylene-propylene copolymer, in which case the mass of the toughening agent is preferably 5-15% of the mass of the nylon resin. The interaction between the maleic anhydride groups in the toughening agent and the nylon molecules improves compatibility.

[0053] To overcome the low impact strength of carbon fiber reinforced nylon materials, this invention incorporates a toughening agent to improve the fracture toughness and impact performance of the composite material. A relatively flexible toughening agent is used, possessing compatibility with nylon or chemically bonded to it to avoid significant phase separation. The toughening agent disperses within the nylon matrix to form a microphase. Maleic anhydride groups can form amide bonds or strong polar interactions with nylon molecules, thereby improving the interfacial adhesion between the toughening agent and the matrix, achieving effective toughening without excessively sacrificing strength. When the carbon fiber content is high (>30 parts), approximately 5 parts of toughening agent can significantly improve the notched impact strength; for composites with low carbon fiber content, the toughening agent can be added less or omitted to avoid reducing the modulus. This invention preferably adds 5-10 parts of toughening agent, which can increase the notched impact strength by at least 50% while maintaining material stiffness, thus broadening the material's application range (e.g., for automotive structural components requiring a certain level of toughness).

[0054] The raw materials for preparing the recycled carbon fiber modified nylon composite material provided by the present invention include 0 to 10 parts by weight of additives; the additives preferably include one or more of ultraviolet absorbers, heat stabilizers and flame retardants.

[0055] Depending on the specific application requirements, this invention preferably incorporates additives into the composite material to impart special properties. For example, adding ultraviolet absorbers (such as diphenylvinylbenzotriazoles) improves weather resistance; adding heat stabilizers (such as copper salts and HALS light stabilizers) further improves aging resistance; and in applications requiring flame retardancy, adding flame retardants (such as organophosphorus flame retardants, brominated flame retardants, and antimony trioxide synergists, or halogen-free flame retardants such as expanded graphite and polyphosphazene) is preferred. Specifically, when the composite material is used in electronic and electrical components or vehicle interior trim, it is preferable to add organophosphorus flame retardants (such as 9,10-dihydro-9-oxophosphazene-10-oxide DOPO) in combination with nitrogen-containing flame retardants to impart flame retardancy while maintaining mechanical properties. This invention does not limit the specific types and sources of additives, but rather uses commercially available additives well-known in the art, controlling the amount of additives to within 10 parts to avoid adverse effects on the carbon fiber reinforcement effect.

[0056] The raw materials for preparing the recycled carbon fiber modified nylon composite material provided by the present invention preferably include 5-30 parts, more preferably 10-20 parts, of fiber reinforcing material by weight. The fiber reinforcing material preferably includes one or more of glass fiber, aramid fiber, and basalt fiber. The fiber reinforcing material is preferably the corresponding virgin fiber or recycled fiber, more preferably recycled aramid fiber or recycled basalt fiber. The glass fiber is preferably chopped glass fiber with a length of 3-6 mm, and the mass ratio of the recycled carbon fiber to the glass fiber is preferably 1:1.

[0057] By weight, the raw materials for preparing the recycled carbon fiber modified nylon composite material provided by this invention preferably include 0.5 to 5 parts of a solid lubricant additive, wherein the solid lubricant additive includes one or more of molybdenum disulfide, graphite, and polytetrafluoroethylene micro powder; when the solid lubricant additive is two or more of the above, this invention does not have a special limitation on the proportion of different types, and can be adjusted according to requirements. This invention utilizes solid lubricant additives to give the composite material a low coefficient of friction and excellent wear resistance.

[0058] This invention provides a method for preparing the recycled carbon fiber modified nylon composite material described in the above technical solution, comprising the following steps: Regenerated carbon fiber is mixed with a coupling agent for the first modification, and the resulting modified fiber is mixed with an interface modifier for the second modification to obtain modified recycled carbon fiber. The modified recycled carbon fiber is mixed with the required proportions of nylon resin, lubricant, antioxidant, toughening agent and additives, and then melt-blended to obtain carbon fiber-nylon melt; The carbon fiber-nylon melt is extruded and shaped to obtain a recycled carbon fiber modified nylon composite material; Alternatively, after the first modification, the obtained modified fibers are mixed with an interface modifier and nylon resin, and then the required amounts of lubricant, antioxidant, toughening agent and additives are added, extruded and molded to obtain a recycled carbon fiber modified nylon composite material.

[0059] Before mixing the recycled carbon fiber with the coupling agent, the present invention preferably pre-treats the recycled carbon fiber obtained from the recycling process. The pre-treatment preferably involves sequentially subjecting the recycled carbon fiber to surface cleaning and oxidation treatment to obtain recycled carbon fiber with polar groups such as carboxyl and hydroxyl groups on the fiber surface (polar groups are introduced during oxidation treatment). The present invention does not impose specific limitations on the specific parameters of the surface cleaning and oxidation treatment; procedures well known in the art can be followed. In an embodiment of the present invention, specifically, acetone ultrasonic cleaning is first used to remove dust and organic impurities, followed by drying and immersion in 98% concentrated nitric acid at room temperature for 30 minutes. Then, it is repeatedly rinsed with deionized water until neutral, and vacuum dried at 105°C to obtain the pre-treated recycled carbon fiber.

[0060] The present invention preferably involves mixing pretreated recycled carbon fibers with a coupling agent to perform a first modification, thereby allowing the coupling agent to adsorb or react on the fiber surface to form a modified layer, and then adding an interface modifier to the resulting modified fiber for a second modification.

[0061] In this invention, the first modification is preferably carried out at 20~60°C for 10~120 min, more preferably at 25°C for 15 min; when the coupling agent is a silane coupling agent, it is preferably pre-hydrolyzed in ethanol / water, then sprayed onto the surface of recycled carbon fiber, and dried at 60~120°C for 0.5~4 h.

[0062] In this invention, the second modification is preferably carried out by mixing the aqueous dispersion of the interface modifier with the modified fiber at 20-50°C for 10-180 min (with possible ultrasonication for 0.5-30 min), and then drying at 60-110°C for 0.5-6 h.

[0063] When the interface modifier is a nanomaterial (carbon nanomaterial, inorganic nanoparticle), the modified fiber is compounded with a dispersion of the nanomaterial, and then dried to allow the nanoparticles to adhere to the fiber surface. The compounding method is preferably impregnation or spraying; there are no specific limitations on impregnation or spraying, as long as the required proportions of raw materials are met. This invention does not impose specific limitations on the solvent and concentration used in the dispersion of the nanomaterial; adjustments can be made according to requirements. When graphene oxide is used as the interface modifier, the specific steps are as follows: the modified recycled carbon fiber is impregnated in an aqueous dispersion of graphene oxide, allowing the graphene oxide sheets to adsorb onto the fiber surface, and then dried at low temperature to remove the solvent; or the aqueous dispersion of graphene oxide is sprayed onto the modified recycled fiber and dried to obtain recycled carbon fiber with graphene oxide loaded on its surface.

[0064] When the interface modifier is a reactive compatibilizer, the interface modifier is directly mixed with the modified fiber.

[0065] In this invention, it is preferred to add and mix the materials by main feeding, side feeding or segmented feeding, and then perform melt mixing.

[0066] In this invention, the melt mixing and extrusion are preferably carried out continuously in a co-rotating twin-screw extruder; when the average length of the recycled carbon fiber is ≥3 mm (more preferably ≥6 mm, more preferably ≥12 mm), it is preferable to use a side-feeding method to introduce the modified recycled carbon fiber after the resin melt is formed, so as to reduce fiber breakage in the high shear zone and improve the aspect ratio retention rate.

[0067] In this invention, the melt mixing preferably includes one or more of the following: segmented plasticizing, dispersion, impregnation, and degassing, selected according to actual needs.

[0068] In this invention, the temperature of each temperature zone of the co-rotating twin-screw extruder is preferably 190~290℃, more preferably 210~230℃, the screw speed is 150~400 rpm, more preferably 250~350 rpm, and the screw length-to-diameter ratio L / D is 30~50:1, more preferably 30~40:1.

[0069] As another preferred embodiment of the present invention, recycled carbon fibers are treated with a coupling agent, impregnated with nylon melt (containing nylon resin and interface modifier) ​​impregnation device, cooled and shaped, and then granulated to obtain long fiber masterbatch. The required lubricant, antioxidant, toughening agent and additives are added, and the mixture is extruded and shaped to obtain recycled carbon fiber modified nylon composite material.

[0070] As another preferred embodiment of the present invention, the method improves impact toughness, fatigue life and creep resistance by constructing a short fiber / long fiber bimodal length distribution.

[0071] In this invention, the molding method is preferably injection molding, extrusion molding, or compression molding. This invention does not impose any particular limitation on the specific molding process; any process well-known in the art can be followed. This invention further improves the effective fiber length retention rate and orientation consistency in the composite material through molding.

[0072] In this invention, when the raw materials for preparing the recycled carbon fiber modified nylon composite material also include fiber reinforcing materials, it is preferred to use any of the following methods for mixing: (1) after premixing the recycled carbon fiber and the fiber reinforcing materials, perform the first modification and the second modification treatment in sequence; (2) after performing the first modification and the second modification on the recycled carbon fiber and the fiber reinforcing materials in sequence, mix them, and then add the modified fibers to the extruder for melt mixing by the main feed or the side feed method to obtain the hybrid fiber reinforced nylon composite material.

[0073] This invention provides the application of the recycled carbon fiber modified nylon composite material described in the above-described technical solutions, or the recycled carbon fiber modified nylon composite material prepared by the preparation method described in the above-described technical solutions, in high-performance products. These high-performance products include automotive structural components, aerospace structural components, load-bearing gears, load-bearing bushings, or housings for electronic and electrical devices. This invention does not impose any specific limitations on the methods used for these applications; methods well-known in the art can be followed.

[0074] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0075] In different embodiments, the specific raw materials and process parameters used can be adjusted according to actual needs. Unless otherwise specified, conventional conditions in the art or manufacturer's recommended conditions are used. Percentages in the embodiments refer to mass percentages, and performance tests are conducted in accordance with relevant ASTM or GB standards unless otherwise stated.

[0076] Raw material sources and pretreatment in the examples: All recycled carbon fibers used were derived from waste carbon fiber reinforced composite materials. The recycled carbon fibers used in Comparative Examples 1-2 and Examples 2-4 were derived from scraps of aerospace-grade epoxy resin-based carbon fiber prepreg (fiber type T700, diameter 7μm) that had undergone high-temperature pyrolysis treatment. The resulting fibers retained 85% of their strength, had a relatively rough surface, and contained trace amounts of carbonized residue. The specific preparation method was as follows: the scraps of T700 aerospace-grade epoxy prepreg were cut to 20 mm and dried at 100°C for 3 h; the temperature was increased to 550°C at 5°C / min under a nitrogen atmosphere and held for 2 h; then the carbon fibers were treated at 420°C for 20 min under an air atmosphere to remove residual carbonized material, and after washing and drying, recycled carbon fibers were obtained.

[0077] The recycled carbon fiber used in Example 1 was derived from chemically recycled thermosetting composite material waste (fiber type T300, diameter 7 μm), and the resulting fiber retained 90% of its strength. The specific preparation method was as follows: the T300 thermosetting composite material waste was sheared to 15 mm; an ethylene glycol / water (volume ratio 9:1) mixed solvent was added at a solid-liquid ratio of 1:20, and NaOH (2 wt% by solvent mass) was added as a catalyst; the reaction was carried out in a closed reactor at 180°C for 4 h; after cooling, the fibers were separated by filtration, washed successively with ethanol and deionized water until neutral, and dried at 120°C for 2 h to obtain recycled carbon fiber.

[0078] In all embodiments, the recycled carbon fibers were subjected to surface cleaning and oxidation treatment before use. Specifically, the carbon fibers were first ultrasonically cleaned with acetone to remove dust and organic impurities, dried, and then immersed in 98% concentrated nitric acid at room temperature for 30 minutes. After that, they were repeatedly rinsed with deionized water until neutral and then vacuum dried at 105°C to obtain pretreated recycled carbon fibers.

[0079] The nylon resin used in Comparative Examples 1-2 and Examples 2-3 was PA66 (injection molding grade, relative molecular weight 25,000, supplier: DuPont, USA), in Example 1 it was PA6 (relative molecular weight 30,000, supplier: BASF), and in Example 4 it was a blend of PA66 and PA6 in a 7:3 mass ratio. All nylon resins were dried in a vacuum drying oven at 80°C for 12 hours before use, with the moisture content controlled to be below 0.1%.

[0080] The temperature of each zone in the extruder needs to be selected according to the type of matrix resin: generally controlled within the range of 200~280℃ (the processing temperature of PA66 is higher, reaching 280℃; PA6 is slightly lower, around 230℃). Excessive temperature may cause nylon degradation or fiber damage. The screw speed should be medium to high to ensure good mixing and fiber dispersion, while avoiding excessive fiber shearing and breakage; a speed of 200~350 rpm is preferred. The extruder die temperature should be slightly lower than the highest melt temperature zone to facilitate smooth extrusion and molding. After the molten blend is extruded through the die, it is immediately cooled and stretched into strands via a water bath, and then pelletized (particle length 3~5mm).

[0081] It is important to note that to prevent the recycled carbon fiber from absorbing moisture and the nylon from becoming damp and affecting processing, the materials should be kept dry throughout the entire batching and extrusion process (and the side-fed fibers should be dried if necessary). Additionally, during extrusion, the vacuum exhaust system should be activated to remove volatiles and prevent melt bubbles caused by the evaporation of coupling agents, solvents, etc.

[0082] Performance testing: Mechanical properties: Tensile strength and modulus (ASTM D638), flexural strength and flexural modulus (ASTM D790), and notched impact strength of simply supported beams (ASTM D256 or GB / T 1043) were tested according to ASTM or GB standards. Five specimens were taken for each test group, and the average value was taken.

[0083] Wear performance: Refer to ASTM D3702 (ring block method) to test the sliding friction coefficient and volumetric wear rate of the material; alternatively, a pin-disc friction and wear tester can be used to slide the material for a certain period of time under specific load and speed, and measure the wear track width or weight loss to calculate the wear rate.

[0084] Thermal properties: Thermomechanical property changes were determined using DMA, and the heat distortion temperature (HDT) was determined according to ASTM D648 (load 1.8 MPa); the coefficient of linear thermal expansion (CTE) was tested using a thermal dilatometer.

[0085] Comparative Example 1

[0086] Recycled carbon fiber reinforced PA66 (no interface modifier, no toughening agent)

[0087] Formula: 80 parts Nylon 66 (PA66); 20 parts recycled carbon fiber (pyrolysis recovery, 6mm length); 0.1 parts coupling agent KH550; 0.1 parts calcium stearate lubricant; 0.3 parts antioxidant 1010; 0.3 parts antioxidant 168; Preparation: Place the required amount of recycled carbon fiber in a high-speed mixer, add KH550 silane coupling agent (diluted with ethanol to a 2% solution and sprayed evenly), stir for 10 minutes, then add PA66 resin particles, lubricant, and antioxidant, and continue mixing evenly. The resulting mixture is then melt-blended and extruded through a twin-screw extruder. The extruder temperature zones are set as follows: Zone 1 220℃, Zone 2 235℃, Zone 3 250℃, Zone 4 260℃, Zone 5 270℃, Zone 6 270℃, Zone 7 260℃, Zone 8 250℃, and the die head 260℃. The screw speed is set to 300 rpm, and the screw length-to-diameter ratio L / D = 40. The carbon fiber is fed from the main hopper in one go, extruded into strands, cooled, and then pelletized to obtain slightly black cylindrical granules with a glossy finish. After injection molding, a nylon composite material is obtained.

[0088] Performance test results: Standard dumbbell specimens were injection molded using the above method (injection temperature 285℃, mold temperature 80℃). The test results are summarized in Table 1. Table 1. Comparison of material properties between Comparative Example 1 and unreinforced pure PA66

[0089] As shown in Table 1, the introduction of 20 parts of recycled carbon fiber increased the tensile strength of PA66 by approximately 76%, the flexural strength by approximately 80%, and the Young's modulus by approximately 168%. This demonstrates that recycled carbon fiber effectively restores and enhances the load-bearing capacity of nylon. The notched impact strength decreased slightly (by approximately 24%), which is related to the increased rigidity and the introduction of interfacial notches by the carbon fiber. This provides a comparative basis for subsequent toughening modifications. In terms of wear performance, the addition of carbon fiber reduced the coefficient of friction (self-lubricating effect), and the wear rate was only 1 / 3 that of pure nylon, showing good friction-reducing and wear-resistant properties. The dimensional stability at high temperatures was also significantly improved (HDT increased by nearly 3 times). Comparative Example 1, as the base composite material, has already demonstrated significant advantages over pure nylon.

[0090] Example 1

[0091] Graphene-modified recycled carbon fiber / nylon composite material (high interfacial bonding and wear resistance) introduces interfacial modifiers at a low carbon fiber content (10%) to strengthen the interface and improve wear resistance. In this embodiment, the interface modifier is graphene oxide (GO) nanosheets, which are derived from commercially available aqueous graphene oxide dispersion (content 2wt%, sheet diameter 5μm, thickness <2nm). Formula: 88.5 parts of Nylon 6 (PA6); 10 parts of recycled carbon fiber (chemically recycled, length 0.5 mm); 0.5 parts of interface modifier, graphene oxide (solid content); 1.0 part of coupling agent KH560; 0.3 parts of lubricant ethylene-acrylic acid copolymer wax (A-C540A); 0.1 parts of antioxidant 1076 and antioxidant 168.

[0092] Preparation method: The required amount of recycled carbon fiber (short fiber powder with an average length of 0.5 mm) and KH560 silane coupling agent were added to a high-speed mixer and stirred at room temperature for 15 min. Then, aqueous graphene oxide dispersion was added dropwise, and stirring was continued for 30 min to allow a layer of GO colloid to be uniformly adsorbed on the fiber surface. The mixture was then placed in an 80℃ vacuum oven and dried for 2 h. Subsequently, PA6 resin, A-C540A lubricant, antioxidants 1076 and 168 were added and mixed evenly before being fed into a twin-screw extruder. The extruder temperature distribution was as follows: Zone 1 210℃, Zone 2 220℃, Zone 3 230℃, Zone 4 240℃, Zone 5 240℃, Zone 6 235℃, Die head 230℃, Screw speed 250 rpm, Screw length-to-diameter ratio L / D = 40. Due to the extremely short length and low content of the fibers, in this embodiment, the fibers and resin were mixed and added directly from the main feed port. The cooling, drawing, and pelletizing processes were the same as in Comparative Example 1.

[0093] Performance test results: Standard injection molded sample (PA6 injection temperature 240℃). Test results are shown in Table 2: Table 2. Performance comparison of nylon composite materials in Example 1 and Comparative Example 1

[0094] As shown in Table 2, Example 1, containing only 10% carbon fiber, achieved a mechanical strength, such as tensile strength, of 95 MPa, significantly higher than pure PA6 (approximately 60 MPa), but lower than the PA66 composite containing 20% ​​fiber (Comparative Example 1). This is because the fiber content is lower and the PA6 matrix itself has slightly lower strength than PA66. However, it is worth noting that the notched impact strength of Example 1 was 5.0 kJ / m. 2The result is higher than that of Comparative Example 1 (4.2), indicating that while the fiber content is reduced, the toughness of the material does not decrease as it would with typical carbon fiber reinforcement, but is closer to that of pure resin. This reflects the microscopic toughening effect that GO nanosheets may play (GO may induce crazes or crack deflection in the matrix, thereby dissipating energy).

[0095] Furthermore, the most significant advantage of Example 1 lies in its wear resistance: the coefficient of friction further decreased from 0.25 in Comparative Example 1 to 0.18, a reduction of 28%; the wear rate was only half that of Comparative Example 1. This verifies that the synergistic effect of graphene oxide and carbon fiber significantly improves the friction reduction and wear resistance of the composite material. Simultaneously, due to the improved interfacial bonding of GO, the flexural strength / modulus is high despite the low fiber content. Therefore, in applications requiring lightweighting or high toughness with low fiber content, the introduction of an interfacial modifier can effectively compensate for the performance loss caused by the reduced fiber content and bring additional functional improvements (such as wear resistance).

[0096] Comparative Example 2 (no interface modifier added, only toughening agent added)

[0097] Elastomer toughening of recycled carbon fiber / nylon composites

[0098] Toughening agent: POE-g-MAH maleic anhydride grafted polyolefin elastomer (trade name: DuPont™ Fusabond® EMB226D, containing 0.5% MAH, melt index MI=3).

[0099] Formula: 70 parts Nylon 66 (PA66); 25 parts recycled carbon fiber (pyrolysis recovery, length 6mm); 5 parts toughening agent POE-g-MAH; 0.5 parts coupling agent KH550; 0.3 parts lubricant EBS; 0.2 parts antioxidant 1098; 0.2 parts antioxidant 168.

[0100] The key point of this comparative example is that the high fiber content (25%) combined with elastomer toughening achieves a balanced improvement in strength and toughness.

[0101] Preparation method: The required amount of recycled carbon fiber was put into a high-speed mixer, and KH550 coupling agent (5% ethanol solution spray) was added to treat the fiber for 10 min. The fiber was dried at 100℃ for 2 h. Then, PA66 resin and toughening agent POE-g-MAH were added, followed by lubricant EBS, antioxidant 1098 and antioxidant 168. After mixing, the mixture was fed into a twin-screw extruder. The extruder settings were similar to those of Comparative Example 1, but due to the increased melt viscosity from the addition of elastomer, the temperatures of zones three to five were increased by 5℃, and the screw speed was reduced to 200 rpm. The fiber was added by side feeding: the main hopper fed a molten mixture of PA66, elastomer and additives, and the recycled carbon fiber was added from the side feed port in zone four to mix with the molten resin, which reduced the excessive breakage of the fiber under high shear in the first few zones. Other aspects were the same as those of Comparative Example 1.

[0102] Performance test results: The material was tested after injection molding, and the results were compared with those of Comparative Example 1 to evaluate the toughening effect. The results are shown in Table 3. Table 3 Comparison of mechanical properties of composite materials in Comparative Example 2 and Comparative Example 1

[0103] As shown in Table 3, Comparative Example 2, with a higher carbon fiber content (25%) and the addition of an elastomer toughening agent, achieved a comprehensive performance improvement, particularly in toughness: the notched impact strength reached 8.5 kJ / m², approximately twice that of Comparative Example 1; the unnotched impact strength (reflecting overall toughness) reached 54 kJ / m², a 145% increase compared to Comparative Example 1. This indicates a significant enhancement in the material's ability to absorb energy under impact loads, exhibiting clear ductile fracture characteristics under impact. On the other hand, regarding strength, Comparative Example 2's tensile strength was 140 MPa, slightly higher than Comparative Example 1's 132 MPa. This is mainly attributed to the reinforcing effect contributed by increasing the carbon fiber content from 20% to 25%, demonstrating that although the introduction of elastomers generally reduces strength, this embodiment, through a reasonable formulation (increased recycled carbon fiber content and appropriate elastomer amount), not only did not decrease but actually increased the strength. The flexural strengths of both examples are similar (180, 185 MPa), while the flexural modulus of Comparative Example 2 is slightly lower than that of Comparative Example 1 (7.5, 8.2 GPa), reflecting that the addition of the elastomer slightly reduces the stiffness, but the decrease is not significant (approximately 9%). Considering the substantial gain of doubling the impact performance, this loss of stiffness is acceptable.

[0104] Furthermore, the elongation at break of the material in Comparative Example 2 reached 3.5%, a significant increase compared to 2.1% in Comparative Example 1, confirming the improvement in toughness. However, the improvement is limited, the stability is insufficient, and the interface remains weak. Morphological results show that Comparative Example 2 exhibits obvious streaks and signs of plastic deformation around the fibers, with shorter fiber pull-out lengths. Most fibers remain firmly encapsulated in the matrix, indicating that the elastomer phase at the interface plays a role in passivating cracks and synergistically deforming, while maintaining interfacial adhesion together with the coupling agent. This high-strength and high-toughness material is well-suited for impact-resistant structural components, such as automotive front-end frames and collision buffer components. In these applications, pure carbon fiber reinforcement materials are often unsuitable due to their high brittleness, while the material in this embodiment provides a feasible solution.

[0105] Example 2 (with interface modifier)

[0106] The only difference from Comparative Example 2 is that 0.5 parts of the interface modifier GO nanosheets from Example 1 were added to Comparative Example 2: after treating the regenerated carbon fiber with KH550 coupling agent, the GO nanosheet aqueous dispersion was added, stirred and mixed for 30 min, and then placed in an 80℃ vacuum oven to dry for 2 h. The rest was the same as Comparative Example 2.

[0107] The results show that the performance data of the composite material prepared in this embodiment (under the same conditions as Table 3) are as follows: Tensile strength: 148 MPa; Tensile modulus: 7.6 GPa; Flexural strength: 225 MPa; Flexural modulus: 9.0 GPa; Notched impact strength: 9.6 kJ / m 2 Unnotched impact strength: 57 kJ / m 2 The elongation at break was 3.8%. Compared with Comparative Example 2, the interface modifier GO further enhanced the interfacial bonding, and the impact energy absorption capacity and strength / rigidity were improved simultaneously.

[0108] Example 3 (with interface modifier, no toughening agent)

[0109] Ultra-high strength recycled carbon fiber reinforced nylon composite material (high fiber, high filler type)

[0110] Formula: 54 parts Nylon 66 (PA66); 45 parts recycled carbon fiber (pyrolysis recovery, long fiber bundles, average length 100mm); interface modifier: 1 part E-51 epoxy resin (epoxy equivalent 190); aluminate coupling agent: 3 parts distearyloxydi(ethylethoxysilyl) aluminate; 0.5 parts lubricant white oil; 0.3 parts antioxidant DSTDP; 0.2 parts antioxidant 168.

[0111] This embodiment pursues the ultimate strength and modulus in the formulation, adopts a fiber content close to the upper limit (45%), and maintains the fiber aspect ratio through a special process.

[0112] In this embodiment, continuous long fiber (100mm) bundles are used as raw materials, and the fibers are kept continuous through pultrusion blending technology.

[0113] Since conventional twin-screw extruders have difficulty directly melting and blending high proportions of long fibers, this embodiment employs a long fiber impregnation + LFT molding method: First, the recycled carbon fiber bundles are impregnated in an ethanol solution of aluminate coupling agent and dried by roller heating at 60°C. The pretreated long fiber bundles are then tensioned and arranged, and passed through an impregnation tank containing molten nylon 66 containing E-51 epoxy resin (54 parts PA66 and 1 part E-51 epoxy resin are mixed at 280°C). The fiber bundles are drawn through the impregnation tank at a constant speed, cooled and shaped, and cut into 10mm long composite masterbatches. After drying, lubricant and antioxidant are added and mixed, and then extruded to obtain composite granules.

[0114] Performance test results: The composite granules prepared in this embodiment were used to injection mold standard samples using an LFT injection molding machine (because the fibers are very long, a long gate and slow injection are required to reduce uneven fiber orientation).

[0115] The test results are as follows: Tensile strength: 212 MPa; Tensile modulus: 17.5 GPa; Flexural strength: 280 MPa; Flexural modulus: 18.9 GPa; Notched impact strength: 3.5 kJ / m 2 Unnotched impact strength: 21 kJ / m 2 Density: 1.35 g / cm³ 3 .

[0116] The results show that this process maximizes fiber length retention, achieving extremely high reinforcement efficiency. The static strength and stiffness of the material in Example 3 are very high: tensile strength exceeds 200 MPa, which is more than 80% higher than some aluminum alloys (such as 6061 aluminum, which typically has a tensile strength of about 240 MPa), and flexural strength is close to 300 MPa. In terms of modulus, the tensile modulus of 17.5 GPa is about half that of aluminum alloys (aluminum is about 70 GPa), but considering that the material density is only about one-third that of aluminum, the specific stiffness (stiffness / density) of the material in this example is comparable to or even better than that of aluminum alloys. This means that in applications requiring extremely low weight, this material can replace some metal components.

[0117] On the other hand, impact toughness decreases significantly with high fiber content (notched impact strength 3.5 kJ / m). 2 Comparison Example 1: 4.2 kJ / m 2 (Low), but still retains some toughness and is not completely brittle (unnotched impact 21 kJ / m 2This demonstrates that the material itself still possesses plastic deformation capability. This is attributed to the action of epoxy compatibilizer and aluminate coupling agent, which ensures a strong bond between the fiber and the matrix, preventing premature debonding of the interface even with extremely long fibers. Morphological results show that most carbon fibers continue to penetrate the cross-section upon sample failure, with both ends firmly anchored in the matrix, requiring tensile testing to break. This verifies the very high interfacial strength and effective fiber utilization. Example 3 demonstrates that the material and process of this invention can achieve extremely high reinforcement effects, making it suitable for manufacturing ultra-high strength components (such as replacement materials for aerospace parts, automotive body frames, etc.). Although the process is complex, its core lies in maintaining the fiber aspect ratio and reinforcing the interface, which is completely different from the general short fiber reinforcement route.

[0118] Example 4 (Interface modification + toughening + multi-component)

[0119] Multi-component composite reinforced recycled carbon fiber nylon material (mixed fiber + lubricating and wear-resistant type)

[0120] Formula: 85 parts of Nylon 66 / Nylon 6 blend (PA66:PA6 mass ratio = 7:3); 15 parts of recycled carbon fiber (T700 long fiber pyrolysis recovery, length 6mm); 1.0 part of interface modifier (nano SiO2, particle size 20nm); 0.2 parts of coupling agent KH550; 0.3 parts of lubricant EBS; 0.3 parts of antioxidant 1010, 0.1 parts of antioxidant 168; 6.0 parts of toughening agent (core-shell structure acrylate impact modifier CSR) (core is acrylate rubber microparticles, shell is PMMA, particle size 100nm); 15 parts of glass fiber (alkali-free glass fiber chopped strands, length 4.5mm, KH550 impregnation treatment); 2 parts of molybdenum disulfide powder (solid lubricant); 1 part of polytetrafluoroethylene (PTFE) micro powder (auxiliary lubricant, particle size 10μm).

[0121] This embodiment demonstrates multiple reinforcements and functional composites: recycled carbon fiber and glass fiber are used together, and solid lubricants MoS2 and PTFE are added to improve friction performance, so as to cover a wider range of applications (such as high-strength and wear-resistant transmission components).

[0122] Preparation: Take the required proportions of recycled carbon fiber, glass fiber and KH550 and mix them evenly. Add nano-SiO2 sol to the fiber mixture, then add nylon 66 / 6 blended resin (prepared in advance in a twin-screw extruder as a 7:3 PA66 / PA6 blended granule), MoS2, PTFE micro powder, toughening agent, EBS lubricant and antioxidant, mix evenly in a mixer, and feed into a twin-screw extruder for granulation. The extruder temperature is set between the processing temperatures of PA66 and PA6: Zone 1 230℃, Zone 2 245℃, Zone 3 255℃, Zone 4 260℃, Zone 5 250℃, die head 250℃, screw speed 300 rpm. Since it contains two kinds of fibers, the main feed is added in its entirety. MoS2 and PTFE are both high-temperature resistant solids and will not decompose during mixing, but ensure uniform dispersion. After cooling and pelletizing, gray-black granules are obtained (because MoS2 is dark gray).

[0123] Performance test results: Standard gear-shaped specimens were injection molded from the granules for mechanical and frictional performance evaluation, and standard tensile and impact specimens were also injection molded.

[0124] The results are as follows: tensile strength: 145 MPa; tensile modulus: 9.0 GPa; flexural strength: 200 MPa; flexural modulus: 9.5 GPa; notched impact strength: 5.5 kJ / m²; coefficient of friction (gear to gear, lubricated): 0.05 (when running in with a steel gear); coefficient of dry friction (plane sliding): 0.15.

[0125] Wear resistance: The gear showed no significant wear after 100 hours of continuous operation under a torque of 1 N·m, with a change in tooth surface roughness of <5%. The planar friction specimen slid 1 km under a load of 2 MPa, and its wear track depth was reduced by about 40% compared with the control material without MoS2.

[0126] In summary, the material of Example 4 exhibits slightly superior mechanical strength compared to Comparative Example 1 (tensile strength 145, 132 MPa). This is attributed to the increased total fiber content to 30% and the inclusion of glass fiber. Although glass fiber monofilaments have lower strength than carbon fibers, their higher density and lower volume fraction in the composite material, coupled with the increased transverse reinforcement and impact toughness, result in an impact strength of 5.5 kJ / m² in this example. 2 It is also higher than the 4.2 kJ / m² of Comparative Example 1. 2The hybrid reinforcement of carbon fiber and glass fiber achieved a relatively balanced effect: compared with the purely carbon fiber reinforced Comparative Example 1, rigidity and strength were improved, and toughness was also improved. This shows that the two fibers played a complementary role during fracture – carbon fiber provided high modulus, while glass fiber, due to its slightly better ductility than carbon fiber, could absorb more energy during fracture. This is particularly suitable for structural components requiring both high strength and rigidity as well as a certain degree of toughness. In terms of friction and wear performance, the synergy between MoS2 and PTFE resulted in excellent lubrication and friction reduction: the coefficient of friction was extremely low, with virtually no wear on gears under lubricated conditions; even under dry friction conditions, the coefficient of friction of 0.15 was far lower than that of typical unmodified nylon-fiber composites (usually >0.3). Long-term gear operation tests demonstrated sufficient reliability. This indicates that by adding solid lubricants, the application of the material of this invention can be extended to high-end gears, bushings, and other self-lubricating components. Compared to wear-resistant materials primarily composed of carbon fiber and graphene, this embodiment cleverly utilizes the classic combination of MoS2+PTFE, reinforced with recycled carbon fiber, to achieve similar or even superior friction-reducing effects at a lower cost (MoS2 is inexpensive and readily available). This demonstrates the flexibility and versatility of the material design in this invention: different combinations of reinforcing agents and additives can be selected according to requirements to form new implementation schemes, all of which fall within the protection scope of this invention.

[0127] In summary, the recycled carbon fiber modified nylon composite material proposed in this invention achieves significant performance improvements under different formulations and can be adjusted and optimized for different application scenarios (high-strength structural components, wear-resistant components, high-toughness components, etc.). Comparative Example 1 serves as the basic scheme, Comparative Example 2 adds a toughening agent to improve impact toughness, Example 1 introduces nano-graphene to strengthen the interface and wear resistance, Example 3 pursues ultimate strength modulus, and Example 4 demonstrates multi-component composite reinforcement and lubrication. This invention obtains high-performance nylon composite materials through recycled carbon fiber reinforcement + interface modification + synergistic modification (toughening / wear resistance, etc.).

[0128] Without departing from the principles of this invention, those skilled in the art can make various equivalent substitutions or modifications to the material type, proportions and process parameters, or use the material of this invention in additive manufacturing (3D printing) powder or filaments, and adjust the particle size and viscosity parameters to meet the process requirements.

[0129] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A recycled carbon fiber modified nylon composite material, characterized in that, The preparation raw materials include the following parts by weight: Nylon resin 50-95 parts, recycled carbon fiber 5-50 parts, interface modifier 0.1-10 parts, coupling agent 0.1-5 parts, lubricant 0.1-2 parts, antioxidant 0.1-1 part, toughening agent 0-20 parts, additives 0-10 parts; The interface modifier includes one or more of carbon nanomaterials, inorganic nanoparticles, and reactive compatibilizers.

2. The recycled carbon fiber modified nylon composite material according to claim 1, characterized in that, The nylon resin includes one or more of nylon 6, nylon 66, nylon 11, nylon 12, nylon 610, and nylon 1010; The length of the recycled carbon fiber is 0.1~100mm.

3. The recycled carbon fiber modified nylon composite material according to claim 1, characterized in that, The carbon nanomaterials include one or more of graphene, graphene oxide, reduced graphene oxide, carbon nanofibers, and carbon nanotubes; the inorganic nanoparticles include one or more of nano-silica, nano-alumina, and nano-clay; and the reactive compatibilizers include one or more of epoxy-containing compounds, maleic anhydride-containing compounds, and isocyanate-containing compounds.

4. The recycled carbon fiber modified nylon composite material according to claim 3, characterized in that, The epoxy-containing compound includes bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, phenolic epoxy resin, or aliphatic diglycidyl ether. The compounds containing maleic anhydride groups include maleic anhydride-grafted polyolefins, maleic anhydride-grafted polyolefin elastomers, maleic anhydride-grafted SEBS, or styrene-maleic anhydride copolymers. The isocyanate-containing compounds include diisocyanates or polyisocyanates.

5. The recycled carbon fiber modified nylon composite material according to claim 1, characterized in that, The coupling agent includes one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents; The lubricant includes one or more of stearic acid, stearic acid metal salts, paraffin wax, microcrystalline wax, polyethylene wax, and amide wax; The antioxidants include primary antioxidants and secondary antioxidants. The primary antioxidants include hindered phenolic antioxidants; the secondary antioxidants include phosphite antioxidants or thioether antioxidants. The toughening agent includes one or more of maleic anhydride-grafted polyolefin elastomers, styrene-based thermoplastic elastomers, and rubber granules. The additives include one or more of ultraviolet absorbers, heat stabilizers, and flame retardants.

6. The recycled carbon fiber modified nylon composite material according to claim 1, characterized in that, It also includes 5 to 30 parts of fiber reinforcing material, wherein the fiber reinforcing material includes one or more of glass fiber, aramid fiber and basalt fiber.

7. The recycled carbon fiber modified nylon composite material according to claim 1, characterized in that, It also includes 0.5 to 5 parts of solid lubricant additives, wherein the solid lubricant additives include one or more of molybdenum disulfide, graphite and polytetrafluoroethylene micro powder.

8. A method for preparing the recycled carbon fiber modified nylon composite material according to any one of claims 1 to 7, characterized in that, Includes the following steps: Regenerated carbon fiber is mixed with a coupling agent for the first modification, and the resulting modified fiber is mixed with an interface modifier for the second modification to obtain modified recycled carbon fiber. The modified recycled carbon fiber is mixed with the required proportions of nylon resin, lubricant, antioxidant, toughening agent and additives, and then melt-blended to obtain carbon fiber-nylon melt; The carbon fiber-nylon melt is extruded and shaped to obtain a recycled carbon fiber modified nylon composite material; Alternatively, after the first modification, the obtained modified fibers are mixed with an interface modifier and nylon resin, and then the required amounts of lubricant, antioxidant, toughening agent and additives are added, extruded and molded to obtain a recycled carbon fiber modified nylon composite material.

9. The preparation method according to claim 8, characterized in that, The melt mixing and extrusion granulation are carried out continuously in a co-rotating twin-screw extruder, wherein the temperature of each temperature zone of the co-rotating twin-screw extruder is independently 190~290℃, the screw speed is 150~400 rpm, and the screw length-to-diameter ratio L / D is 30~50:

1.

10. The application of the recycled carbon fiber modified nylon composite material according to any one of claims 1 to 7 or the recycled carbon fiber modified nylon composite material prepared by the preparation method according to any one of claims 8 to 9 in high-performance products, characterized in that, The high-performance products include automotive structural components, aerospace structural components, load-bearing gears, load-bearing bushings, or housings for electronic and electrical devices.

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