Modified aramid fiber composite material and preparation method thereof

Abstract

The invention discloses a modified aramid composite material and a preparation method thereof, and relates to the technical field of aramid composite material production, and the modified aramid composite material is prepared from aramid fibers, a resin matrix, an interface enhancement layer, a weather-resistant-flame-retardant synergistic system and a functional auxiliary agent; according to the preparation method, plasma activation and microwave-assisted in-situ grafting are combined, the limitation of a traditional single interface modification technology is broken through, the interlayer bonding strength and fatigue resistance of the composite material are remarkably improved, a multi-element compounding technology of the hindered amine light stabilizer, the hindered phenol antioxidant and the nanofiller is adopted, and the composite material is prepared. According to the present invention, the integrated improvement of the weather resistance and the flame retardant property of the material is achieved through the intermolecular synergistic effect, and the space customization of the mechanical property and the functional characteristic of the composite material is achieved through the combination of the 3D printing technology and the magnetic field orientation curing, such that the impact resistance and the size stability of the composite material under the complex working condition achieve the collaborative optimization.

Description

Technical Field

[0001] This invention relates to the field of aramid composite material production technology, and in particular to a modified aramid composite material and its preparation method. Background Technology

[0002] Aramid fiber is a new type of high-tech synthetic fiber, officially known as aromatic polyamide fiber. In its molecular structure, at least 85% of the amide bonds (-CONH-) are directly linked to two benzene rings, forming a stable molecular chain structure. This unique structure endows aramid with a series of outstanding properties, including high strength, high modulus, high temperature resistance, corrosion resistance, lightweight, insulation, and flame retardancy. These properties make it widely applicable in aerospace, safety protection, electronics, and automotive industries.

[0003] Aramid composite materials are made by combining aramid fibers with resins or other matrix materials. They possess excellent properties such as high strength, high modulus, high temperature resistance, corrosion resistance, wear resistance, flame retardancy, and insulation. In the aerospace field, they can be used to manufacture structural components and thermal insulation materials for aircraft, satellites, rockets, and other aerospace vehicles. In the automotive industry, they can be used to manufacture lightweight body structural components. In the electronics and electrical fields, they can be used to manufacture high-performance electronic components and insulating materials. In the safety and protection field, they can be used to manufacture high-temperature protective clothing, fire-fighting suits, and cut-resistant gloves.

[0004] Existing aramid composite materials generally suffer from the following defects: insufficient interfacial bonding leads to easy delamination between the fiber and the resin matrix; traditional coupling agent treatment or single nanoparticle modification fails to achieve synergistic effects of chemical bonding and mechanical interlocking; weather resistance and flame retardancy are difficult to improve synergistically, conventional anti-aging agents and flame retardants exhibit functional antagonism, and photo-oxidative aging or thermal decomposition failure easily occurs under extreme environments; manufacturing processes are limited to homogenized structural design, and traditional compression molding or injection molding cannot precisely control fiber orientation and gradient distribution of functional fillers, resulting in insufficient overall material performance and adaptability to complex working conditions. Therefore, this invention proposes a modified aramid composite material and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to propose a modified aramid composite material and its preparation method, thereby solving the problems of insufficient interfacial bonding strength leading to easy delamination between the fiber and resin matrix, difficulty in synergistically improving weather resistance and flame retardant properties, and insufficient overall performance and adaptability to complex working conditions of existing aramid composite materials.

[0006] To achieve the objective of this invention, the invention is implemented through the following technical solution: a modified aramid composite material, comprising the following raw materials in parts by weight: 40-60 parts of aramid fiber, 30-50 parts of resin matrix, 1-5 parts of interface reinforcement layer, 1-3 parts of weather-resistant and flame-retardant synergistic system, and 0.5-2 parts of functional additives;

[0007] The resin matrix is ​​selected from one of epoxy resin, polyimide or vinyl ester resin, the interface reinforcement layer is composed of nanoparticles grafted onto the surface of aramid fiber and an in-situ generated polydopamine coating, and the functional additives include an anti-ultraviolet agent, an antistatic agent and a thermally conductive filler mixed in a mass ratio of 1:1:2.

[0008] A further improvement is that 0.1 to 1 part by weight of a crosslinking agent is added to the resin matrix, wherein the crosslinking agent is selected from one of dicumyl peroxide, glycidyl methacrylate, or styrene ether maleic anhydride.

[0009] A further improvement is that the weather-resistant and flame-retardant synergistic system comprises hindered amine light stabilizers, hindered phenolic antioxidants, and nano-titanium dioxide compounded in a mass ratio of 2-4:1-2:0.5-1.5.

[0010] A further improvement is that the UV-resistant agent is selected from 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole or 2-hydroxy-4-n-octyloxybenzophenone, and the antistatic agent is a polyaniline / carbon nanotube composite.

[0011] A method for preparing a modified aramid composite material includes the following steps:

[0012] Step 1: Place the aramid fiber in a plasma treatment device and treat it with a power of 100-300W for 5-15 minutes in a mixed atmosphere of nitrogen and helium to obtain surface-activated aramid fiber.

[0013] Step 2: The pretreated aramid fibers are immersed in Tris buffer containing dopamine hydrochloride and reacted under microwave assistance. Then, they are immersed in a dispersion containing nanoparticles and ultrasonically oscillated. After centrifugation and drying, the nanoparticles are grafted in situ onto the surface of the aramid fibers through amide bonds or epoxy reactions to form an interface modification layer, thus obtaining modified fibers.

[0014] Step 3: The resin matrix, crosslinking agent, and weather-resistant-flame retardant synergistic system are melt-blended in a twin-screw extruder to obtain functionalized resin masterbatch;

[0015] Step 4: Modified fibers and functionalized resin masterbatch are stacked layer by layer using 3D printing technology, and then oriented and cured in an alternating magnetic field to obtain a modified aramid composite material with a gradient structure.

[0016] A further improvement is that, in step one, the total working gas pressure of the plasma processing equipment is 0.1 to 0.5 Pa, and the moving speed of the aramid fiber is 0.1 to 0.5 m / min.

[0017] A further improvement is that, in step two, the dispersion is further supplemented with 0.05 to 0.2 wt% of a silane coupling agent, and the frequency of the ultrasonic oscillation is 20 to 40 kHz.

[0018] A further improvement is that, in step four, the 3D printing process adopts a coaxial extrusion nozzle structure, with the inner layer being extruded as a modified aramid fiber-resin mixture, and the outer layer being simultaneously extruded as a coating layer containing 5-10 wt% thermotropic liquid crystal polymer, forming a core-shell reinforced structure.

[0019] The beneficial effects of this invention are as follows: This invention combines plasma activation with microwave-assisted in-situ grafting to construct a composite interface layer on the surface of aramid fibers, consisting of a polydopamine coating and functionalized nanoparticles. The catechol groups of polydopamine form stable covalent bonds with the functional groups on the surface of the nanoparticles. At the same time, the micro-nano structure formed by plasma etching enhances the mechanical interlocking effect between the fiber and the resin. This design breaks through the limitations of traditional single interface modification technology (such as coupling agent coating), significantly improves the interlayer bonding strength and fatigue resistance of the composite material, and solves the problem of poor interfacial compatibility between aramid fibers and the resin matrix.

[0020] Furthermore, by employing a multi-component compounding technology of hindered amine light stabilizers, hindered phenolic antioxidants, and nanofillers, the material's weather resistance and flame retardant properties are integrated and improved through intermolecular synergistic effects. Hindered amine compounds inhibit photo-oxidative degradation by capturing free radicals, hindered phenolic antioxidants block the thermo-oxidative aging chain reaction, and nanofillers enhance flame retardant efficiency through physical barriers and catalytic char formation. This system significantly extends the service life of the composite material in extreme environments such as humid heat and ultraviolet radiation while maintaining mechanical properties.

[0021] Furthermore, by combining 3D printing technology with magnetic field orientation curing, and by programmatically controlling the gradient distribution of fiber-resin and the directional arrangement of nanofillers, spatial customization of the mechanical properties and functional characteristics of composite materials is achieved. The magnetic field induces nanoparticles to arrange themselves in an orderly manner along the stress direction, and the interlayer staggered structure of 3D printing effectively inhibits crack propagation. This process breaks through the homogenization limitations of traditional compression molding products, enabling composite materials to achieve synergistic optimization of impact resistance and dimensional stability under complex working conditions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the preparation method of the modified aramid composite material of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Aramid (aromatic polyamide fiber) is a type of high-performance organic fiber with ultra-high tensile strength, high modulus, and excellent high-temperature resistance and chemical corrosion resistance. It is widely used in aerospace, rail transportation, bulletproof protection and other fields. However, its strong surface inertness (high chemical stability) and few polar functional groups result in weak interfacial bonding with the resin matrix; and its simple structure leads to low functional integration, making it difficult to meet the multifunctional requirements of materials in complex scenarios.

[0025] Aramid composites are mostly prepared using traditional processes such as molding and autoclaving. Coupling agents are used to treat the aramid surface to improve interfacial bonding, but this method suffers from limited bonding strength and insufficient weather resistance. In addition, traditional processes are difficult to use for precise molding of complex structures, and the materials have limited functionality, which restricts their application in high-end equipment (such as high-frequency electronic devices and lightweight load-bearing structures).

[0026] It should be noted that the technical means not described in detail in the embodiments of the present invention can be implemented by conventional means and are not the key points of the invention, so they will not be elaborated upon. Example 1

[0027] This embodiment provides a modified aramid composite material, comprising the following raw materials in parts by weight: 40 parts aramid fiber, 30 parts resin matrix, 1 part interface reinforcement layer, 1 part weather-resistant and flame-retardant synergistic system, and 0.5 parts functional additives. The resin matrix is ​​epoxy resin. The interface reinforcement layer consists of nanoparticles grafted onto the surface of the aramid fiber and an in-situ generated polydopamine coating (the nanoparticles are selected from boron nitride nanosheets with a particle size of 10-50 nm). The weather-resistant and flame-retardant synergistic system is composed of a hindered amine light stabilizer, a hindered phenolic antioxidant, and nano-titanium dioxide, with a mass ratio of 2:1:0.5. The functional additives are a mixture of an anti-UV agent, an antistatic agent, and a thermally conductive filler, with a mass ratio of 1:1:2.

[0028] In this embodiment, the surface of the nanoparticles is pretreated with amino (-NH2) functional groups (achieved by modification with silane coupling agent KH550).

[0029] The catechol groups of the polydopamine coating form covalent bonds with the amino groups on the surface of the nanoparticles through a Schiff base reaction (-NH2+catechol-OH→-NH-CO-catechol). The reaction conditions are pH=8, temperature 60℃, and time 1h.

[0030] In this embodiment, the hindered amine light stabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate (Tinuvin 770).

[0031] The hindered phenolic antioxidant is β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol ester (BHT).

[0032] The crystal form of nano-titanium dioxide is rutile, and the particle size is 20-50 nm.

[0033] In this embodiment, 0.1 parts by weight of a crosslinking agent, namely dicumyl peroxide (DCP), is also added to the resin matrix.

[0034] The UV stabilizer is 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole (UV-327), the antistatic agent is a polyaniline / carbon nanotube composite (CNT content 5wt%), and the thermally conductive filler is graphene microsheets. The addition of the thermally conductive filler makes the composite material's thermal conductivity ≥1.5W / (m·K) and volume resistivity ≤1×10⁻⁶. 8 Ω·cm.

[0035] See Figure 1 This embodiment also provides a method for preparing modified aramid composite materials, including the following steps:

[0036] Step 1: Surface activation pretreatment of aramid fibers

[0037] Weigh each raw material according to the preset mass ratio, place the aramid fiber in the plasma treatment equipment, and treat it for 5 minutes at 100W power under a mixed atmosphere of nitrogen and helium (volume ratio 4:1). The total working gas pressure of the plasma treatment equipment is 0.1Pa, and the moving speed of the aramid fiber is 0.1m / min. After the treatment is completed, surface-activated aramid fiber is obtained.

[0038] Step 2: Construct an interface reinforcement layer on the surface of aramid fibers

[0039] The pretreated aramid fibers were immersed in Tris buffer (pH=8.5) containing 0.1 mol / L dopamine hydrochloride and reacted with shaking for 2 h under microwave assistance (power 200W, frequency 2.45GHz). The intermittent power control mode of the microwave-assisted reaction was: high power (500W) for 10 s, then switched to low power (200W) for 50 s, and the number of cycles was 20.

[0040] Subsequently, it was immersed in a dispersion containing nanoparticles (the solvent of the dispersion was ethanol, and the concentration of nanoparticles was 0.5wt%), ultrasonically vibrated at 60℃ for 30 min, and after centrifugation and drying, the nanoparticles were in situ grafted onto the surface of aramid fibers through amide bonds or epoxy reactions to form an interface modification layer.

[0041] The dispersion in this embodiment also contains 0.05 wt% silane coupling agent (KH550), and the ultrasonic oscillation frequency is 20 kHz;

[0042] Step 3: Modify the resin matrix to obtain functionalized resin masterbatch.

[0043] Functionalized resin masterbatch was prepared by melt blending resin matrix with crosslinking agent and weather-resistant-flame retardant synergistic system in a twin-screw extruder (temperature 150℃, speed 200rpm).

[0044] Step 4: Guided molding of modified fiber and functionalized resin masterbatch structure

[0045] Modified fibers and functionalized resin masterbatches were stacked layer by layer using a 3D printing process (printing temperature 180℃, layer thickness 0.1mm), and then oriented and cured in an alternating magnetic field (frequency 1kHz, intensity 0.5T) to finally obtain a modified aramid composite material with a gradient structure.

[0046] In this embodiment, the 3D printing process uses a coaxial extrusion nozzle structure. The inner layer is extruded with a modified aramid fiber-resin mixture, and the outer layer is simultaneously extruded with a coating layer containing 5 wt% thermotropic liquid crystal polymer (TLCP) to form a core-shell reinforced structure. Example 2

[0047] This embodiment provides a modified aramid composite material, comprising the following raw materials in parts by weight: 60 parts aramid fiber, 50 parts resin matrix, 5 parts interface reinforcement layer, 3 parts weather-resistant and flame-retardant synergistic system, and 2 parts functional additives. The resin matrix is ​​a mixture of polyimide and vinyl ester resin in a mass ratio of 1:3. The interface reinforcement layer consists of nanoparticles grafted onto the surface of the aramid fiber and an in-situ generated polydopamine coating (the nanoparticles are selected from silicon carbide nanowires and nanocellulose with a particle size of 10-50 nm, and the mass ratio of silicon carbide nanowires to nanocellulose is 1:1). The weather-resistant and flame-retardant synergistic system is composed of hindered amine light stabilizers, hindered phenolic antioxidants, and nano-titanium dioxide in a mass ratio of 4:2:1.5. The functional additives are a mixture of UV stabilizers, antistatic agents, and thermally conductive fillers in a mass ratio of 1:1:2.

[0048] In this embodiment, the surface of the nanoparticles is pretreated with amino (-NH2) functional groups (achieved by modification with silane coupling agent KH560).

[0049] The catechol groups of the polydopamine coating form covalent bonds with the amino groups on the surface of the nanoparticles through a Schiff base reaction (-NH2+catechol-OH→-NH-CO-catechol). The reaction conditions are pH=9, temperature 80℃, and time 2h.

[0050] In this embodiment, the hindered amine light stabilizer is polysuccinic acid (4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol) ester (Tinuvin 123).

[0051] The hindered phenolic antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (1010).

[0052] The nano-titanium dioxide has a rutile crystal form and a particle size of 50–80 nm.

[0053] In this embodiment, 1 part by weight of crosslinking agent is also added to the resin matrix. The crosslinking agent is a mixture of glycidyl methacrylate (GMA) and styrene ether maleic anhydride (SMA) with a mixing mass ratio of 1:1.

[0054] The UV stabilizer is 2-hydroxy-4-n-octyloxybenzophenone (UV-531), the antistatic agent is a polyaniline / carbon nanotube composite (CNT content 15wt%), and the thermally conductive filler is aluminum nitride nanoparticles. The addition of the thermally conductive filler makes the composite material's thermal conductivity ≥1.5W / (m·K) and volume resistivity ≤1×10⁻⁶. 8 Ω·cm.

[0055] See Figure 1 This embodiment also provides a method for preparing modified aramid composite materials, including the following steps:

[0056] Step 1: Surface activation pretreatment of aramid fibers

[0057] Weigh each raw material according to the preset mass ratio, place the aramid fiber in the plasma treatment equipment, and treat it for 15 minutes at 300W power under a mixed atmosphere of nitrogen and helium (volume ratio 4:1). The total working gas pressure of the plasma treatment equipment is 0.5Pa, and the moving speed of the aramid fiber is 0.5m / min. After the treatment is completed, surface-activated aramid fiber is obtained.

[0058] Step 2: Construct an interface reinforcement layer on the surface of aramid fibers

[0059] The pretreated aramid fibers were immersed in Tris buffer (pH=8.5) containing 0.5 mol / L dopamine hydrochloride and reacted with shaking for 4 h under microwave assistance (power 600W, frequency 2.45GHz). The intermittent power control mode of the microwave-assisted reaction was: high power (600W) for 10 s, then switching to low power (300W) for 50 s, and the number of cycles was 40.

[0060] Subsequently, the nanoparticles were immersed in a dispersion containing nanoparticles (the dispersion solvent was ethanol or deionized water, and the nanoparticle concentration was 2wt%), ultrasonically vibrated at 80℃ for 60 min, and after centrifugation and drying, the nanoparticles were grafted in situ onto the surface of aramid fibers through amide bonds or epoxy reactions to form an interface modification layer.

[0061] The dispersion in this embodiment also contains 0.2 wt% silane coupling agent (KH560), and the ultrasonic oscillation frequency is 40 kHz;

[0062] Step 3: Modify the resin matrix to obtain functionalized resin masterbatch.

[0063] Functionalized resin masterbatch was prepared by melt blending the resin matrix with crosslinking agent and weather-resistant-flame retardant synergistic system in a twin-screw extruder (temperature 280℃, speed 400rpm).

[0064] Step 4: Guided molding of modified fiber and functionalized resin masterbatch structure

[0065] Modified fibers and functionalized resin masterbatches were stacked layer by layer using a 3D printing process (printing temperature 320℃, layer thickness 0.3mm), and then oriented and cured in an alternating magnetic field (frequency 5kHz, intensity 2T) to finally obtain a modified aramid composite material with a gradient structure.

[0066] In this embodiment, the 3D printing process uses a coaxial extrusion nozzle structure. The inner layer is extruded with a modified aramid fiber-resin mixture, and the outer layer is simultaneously extruded with a coating layer containing 10wt% thermotropic liquid crystal polymer (TLCP) to form a core-shell reinforced structure.

[0067] The modified aramid composite materials prepared in Examples 1 and 2 were subjected to performance tests, and the results are as follows:

[0068] Tensile strength ≥1800MPa (test standard reference ISO 527-4);

[0069] Interlaminar shear strength ≥80MPa (test standard reference ISO 14130), which is 30% to 50% higher than that of unmodified aramid composites;

[0070] After 1000 hours of UV aging (UVB 313nm, 60℃), the tensile strength retention rate is ≥85% (test standard refers to ISO4892-3), and the retention rate of unmodified aramid composite material is ≤60%.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A modified aramid composite material, characterized in that, It includes the following raw materials in parts by weight: 40-60 parts aramid fiber, 30-50 parts resin matrix, 1-5 parts interface reinforcement layer, 1-3 parts weather-resistant and flame-retardant synergistic system, and 0.5-2 parts functional additives; The resin matrix is ​​selected from one of epoxy resin, polyimide or vinyl ester resin, the interface reinforcement layer is composed of nanoparticles grafted onto the surface of aramid fiber and an in-situ generated polydopamine coating, and the functional additives include an anti-ultraviolet agent, an antistatic agent and a thermally conductive filler mixed in a mass ratio of 1:1:

2.

2. The modified aramid composite material according to claim 1, characterized in that: The resin matrix also contains 0.1 to 1 part by weight of a crosslinking agent, which is selected from dicumyl peroxide, glycidyl methacrylate, or styrene ether maleic anhydride.

3. The modified aramid composite material according to claim 1, characterized in that: The weather-resistant and flame-retardant synergistic system comprises hindered amine light stabilizers, hindered phenolic antioxidants, and nano-titanium dioxide compounded in a mass ratio of 2-4:1-2:0.5-1.

5.

4. The modified aramid composite material according to claim 1, characterized in that: The UV stabilizer is selected from 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole or 2-hydroxy-4-n-octyloxybenzophenone, and the antistatic agent is a polyaniline / carbon nanotube composite.

5. A method for preparing a modified aramid composite material according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Place the aramid fiber in a plasma treatment device and treat it with a power of 100-300W for 5-15 minutes in a mixed atmosphere of nitrogen and helium to obtain surface-activated aramid fiber. Step 2: The pretreated aramid fibers are immersed in Tris buffer containing dopamine hydrochloride and reacted under microwave assistance. Then, they are immersed in a dispersion containing nanoparticles and ultrasonically oscillated. After centrifugation and drying, the nanoparticles are grafted in situ onto the surface of the aramid fibers through amide bonds or epoxy reactions to form an interface modification layer, thus obtaining modified fibers. Step 3: The resin matrix, crosslinking agent, and weather-resistant-flame retardant synergistic system are melt-blended in a twin-screw extruder to obtain functionalized resin masterbatch; Step 4: Modified fibers and functionalized resin masterbatch are stacked layer by layer using 3D printing technology, and then oriented and cured in an alternating magnetic field to obtain a modified aramid composite material with a gradient structure.

6. The method for preparing a modified aramid composite material according to claim 5, characterized in that: In step one, the total working gas pressure of the plasma processing equipment is 0.1 to 0.5 Pa, and the moving speed of the aramid fiber is 0.1 to 0.5 m / min.

7. The method for preparing a modified aramid composite material according to claim 5, characterized in that: In step two, the dispersion also contains 0.05–0.2 wt% silane coupling agent, and the frequency of the ultrasonic oscillation is 20–40 kHz.

8. The method for preparing a modified aramid composite material according to claim 5, characterized in that: In step four, the 3D printing process uses a coaxial extrusion nozzle structure. The inner layer is extruded with a modified aramid fiber-resin mixture, and the outer layer is simultaneously extruded with a coating layer containing 5-10 wt% thermotropic liquid crystal polymer to form a core-shell reinforced structure.

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