Carbon fiber nylon composite material and preparation method thereof

Abstract

The invention discloses a carbon fiber nylon composite material and a preparation method thereof. The preparation method comprises the following steps: step 01, adding 35-75 parts by weight of nylon resin, 1-4 parts by weight of an epoxy group-containing copolymer, 0.05-1 part by weight of an antioxidant and 0.1-3 parts by weight of other auxiliary agents into an extruder, and premixing to form an intermediate mixture; 02, sequentially adding 1-10 parts by weight of a plasticizer, 0.5-5 parts by weight of a coupling agent and 15-55 parts by weight of carbon fibers into the extruder, and blending with the intermediate mixture; and step 03, extruding and granulating through an extruder. The tensile strength of the carbon fiber nylon composite material prepared through the preparation method can reach 350 MPa or above, and meanwhile the carbon fiber nylon composite material has excellent injection molding performance, dimensional stability and electromagnetic shielding performance and can meet the requirements of electric structural components with complex structures.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material preparation, and in particular relates to a carbon fiber nylon composite material and a preparation method thereof. Background Art

[0002] With the continuous development of new energy vehicles and 3C electronic products, people have an increasing demand for lightweight, high precision and high structural strength products, especially in the field of electronics and electrical appliances. Since the circuit board is the core component of electronic equipment and has many electronic components on it, it is the control core of the entire electrical equipment, and thus a stable support structure is required to ensure the flatness and stability of the entire circuit board. In addition, as the design structure of electrical components is getting smaller and more complex, the housing of the electronic equipment that protects the electronic components not only needs to match the structural shape, but also needs sufficient strength and rigidity. Moreover, when the electronic components are running, it is necessary to avoid electromagnetic interference between various electronic components and prevent external shock and vibration so that the electronic equipment can work stably. Therefore, there is a need for a structural support component that can effectively support and protect the circuit board and electronic components.

[0003] At present, this type of structural support components are mainly made of metal alloys or carbon fiber reinforced materials. However, due to the high melting point and rapid cooling of metal alloys, it is difficult to form components with more complex structures, and the production cost is high. Its surface also needs to be reprocessed, which makes the production process cumbersome. For more complex structural components, short carbon fiber reinforced thermoplastic polymer materials are usually used, such as carbon fiber nylon materials. Although short carbon fiber reinforced thermoplastic polymer materials are easier to form than metal alloy materials, the tensile strength of existing short carbon fiber reinforced thermoplastic polymer materials is ≤250MPa, which is still a certain distance compared with the tensile strength of alloys of about 350MPa, thus limiting the further application of carbon fiber reinforced polymer materials.

[0004] For example, in patent CN 117050516 A, maleic anhydride-grafted carbon fiber was prepared. The chemical reaction between maleic anhydride and the amino group end of nylon was used to significantly increase the interfacial force between the carbon fiber and nylon. Under the action of external force, the carbon fiber was difficult to pull out, thereby obtaining a carbon fiber nylon composite material with higher specific strength. It is used as a material for lightweight automotive structural load-bearing components. However, the tensile strength of the carbon fiber nylon composite material is still less than 300 MPa.

[0005] In patent CN 118459988 B, nylon is melt-blended and modified using KH550 modified carbon fiber and epoxidized polyaramid-ethersulfone copolymer to form a stable chemically cured cross-linked network, which significantly improves the strength and modulus, thermal decomposition temperature and heat resistance of nylon. However, the tensile strength of the nylon composite material reinforced with modified carbon fiber is still less than 300 MPa. Summary of the Invention

[0006] In view of the above problems, the present invention discloses a carbon fiber nylon composite material and a preparation method thereof, so as to overcome the above problems or at least partially solve the above problems.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In one aspect, the present invention discloses a method for preparing a carbon fiber nylon composite material, the method comprising the following steps:

[0009] Step 01, adding 35-75 parts of nylon resin, 1-4 parts of epoxy-containing copolymer, 0.05-1 parts of antioxidant and 0.1-3 parts of other additives into an extruder by weight, and premixing to form an intermediate mixture;

[0010] Step 02, adding 1 to 10 parts of a plasticizer, 0.5 to 5 parts of a coupling agent, and 15 to 55 parts of carbon fibers, in parts by weight, into the extruder and blending them with the intermediate mixture;

[0011] Step 03, extruding and granulating through the extruder.

[0012] Furthermore, the epoxy group-containing copolymer is one or more of methyl ethylene oxide polymer, bisphenol A-epichlorohydrin copolymer, o-cresol novolac epoxy resin, and dicyclopentadiene phenol epoxy resin.

[0013] Furthermore, the epoxy equivalent of the epoxy group-containing copolymer is 600 to 10,000 g / eq, preferably 1,000 to 3,000 g / eq.

[0014] Furthermore, the weight average molecular weight of the epoxy group-containing copolymer is 1,000 to 20,000, preferably 4,000 to 10,000, and more preferably 6,000 to 8,000.

[0015] Furthermore, in step 02, the extruder is vacuumed from the front end and / or the rear end of the extruder to maintain the vacuum degree in the extruder at 10 to 60 kPa.

[0016] Furthermore, the nylon resin includes aromatic nylon resin and aliphatic nylon resin.

[0017] Furthermore, the relative viscosity of the aromatic nylon resin is 1.9 to 3.5, and the relative viscosity of the aliphatic nylon resin is 1.7 to 2.7; preferably, the relative viscosity of the aromatic nylon resin is 1.9 to 2.7, and the relative viscosity of the aliphatic nylon resin is 1.9 to 2.3.

[0018] Furthermore, the aromatic nylon resin is one or more of PA4T, PA5T, PA6T, PA9T, PA10T, PPA and PAMXD6, and the aliphatic nylon resin is one or more of PA6, PA66, PA11, PA12, PA610, PA1010 and PA1212.

[0019] Furthermore, the diameter of the carbon fiber is 5 to 10 μm, the carbon fiber is T400H grade carbon fiber, T700S grade carbon fiber, T800H grade carbon fiber or T1000G grade carbon fiber, and the tow of the carbon fiber is 3 to 24 k.

[0020] Furthermore, the plasticizer is one or more of N-ethyl-p-toluenesulfonamide, N-butylbenzenesulfonamide, polyoxypropylenediamine, polycaprolactone, epoxy soybean oil, 1-ethyl-3-methylimidazolium tetrafluoroborate, epoxy fatty acid methyl ester, sorbitol, and xylitol.

[0021] Furthermore, the coupling agent is at least two of a silane coupling agent, a titanate coupling agent, a maleic anhydride grafted polymer and an ionic liquid coupling agent.

[0022] Furthermore, the silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane;

[0023] The titanate coupling agent is at least one of isopropyl tris(dioctylphosphoyl)titanate and di(dioctylpyrophosphoyl)oxyacetate titanium;

[0024] The maleic anhydride grafted polymer is one or more of maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene and maleic anhydride grafted POE;

[0025] The ionic liquid coupling agent is at least one of 1-butyl-3-methylimidazolium hexafluorophosphate and choline carboxylate.

[0026] Furthermore, the antioxidant is one or more of hindered phenol antioxidants, phosphite antioxidants and thioester antioxidants; preferably, the antioxidant is a hindered phenol antioxidant and a phosphite antioxidant in a mass ratio of 1:2 to 2:1.

[0027] Furthermore, the other auxiliary agents are one or more of lubricants, toughening agents and nucleating agents.

[0028] Furthermore, the internal temperature of the extruder during the mixing and extrusion process is 260-320°C.

[0029] Furthermore, the premixing time of the nylon resin, the epoxy-containing copolymer, the antioxidant and the other auxiliary agents in the extruder is 10 to 15 minutes.

[0030] Furthermore, the distance between the total feeding port of the nylon resin, the epoxy-containing copolymer, the antioxidant and the other additives and the feeding port of the plasticizer is 10D to 16D, the distance between the feeding port of the plasticizer and the feeding port of the coupling agent is 4D to 8D, and the distance between the feeding port of the coupling agent and the feeding port of the carbon fiber is 0 to 6D.

[0031] Furthermore, in step 02, before adding the carbon fiber to the extruder, the surface of the carbon fiber is oxidized and the carbon fiber is treated with a sizing agent.

[0032] Another aspect of the present invention discloses a carbon fiber nylon composite material, which is prepared by the above-mentioned method for preparing the carbon fiber nylon composite material.

[0033] The advantages and beneficial effects of the present invention are:

[0034] In the preparation method of the present invention, preset amounts of nylon resin, epoxy-containing copolymer, antioxidant and other additives are added to an extruder to melt-mix and graft the nylon resin and epoxy-containing copolymer. Then, preset amounts of plasticizer, coupling agent and carbon fiber are added to the extruder in sequence to connect the epoxy polymer grafted to the nylon chain end with the carbon fiber, thereby enhancing the interfacial strength between the nylon and carbon fiber and improving the bonding force between the nylon resin and the carbon fiber. As a result, the tensile strength of the prepared carbon fiber nylon composite material can reach above 350 MPa. At the same time, the composite material has excellent injection molding performance, dimensional stability and electromagnetic shielding performance, and can meet the requirements of electrical structural components with complex structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0036] Figure 1 This is a diagram of the implementation steps of a method for preparing a carbon fiber nylon composite material in one embodiment of the present invention. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the present invention more clear, the following will provide a clear and complete description of the technical solutions of the present invention in conjunction with specific embodiments of the present invention and corresponding drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] The technical solutions provided by various embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0039] In one embodiment of the present invention, a method for preparing a carbon fiber nylon composite material is provided, such as Figure 1 As shown, the preparation method comprises the following steps:

[0040] Step 01, by weight, add 35 to 75 parts of nylon resin, 1 to 4 parts of epoxy-containing copolymer, 0.05 to 1 part of antioxidant and 0.1 to 3 parts of other additives into an extruder, and premix to form an intermediate mixture.

[0041] Among them, after the preset amounts of nylon resin, epoxy-containing copolymer, antioxidant and other additives are added to the twin-screw extruder through the total feeding port (main feeding port) of the extruder, the components are melted and mixed to form an intermediate mixture; during this process, the epoxy groups in the epoxy-containing copolymer are ring-opened and undergo a grafting reaction with the functional group -NH in the nylon resin.

[0042] Step 02: Add 1 to 10 parts of plasticizer, 0.5 to 5 parts of coupling agent, and 15 to 55 parts of carbon fiber into the extruder in order by weight, and blend with the intermediate mixture.

[0043] Specifically, a preset amount of plasticizer is first added to the twin-screw extruder through a plasticizer feed port, and then a preset amount of coupling agent is added to the twin-screw extruder through a coupling agent feed port downstream of the plasticizer feed port. Finally, a preset amount of carbon fiber is added to the twin-screw extruder through a carbon fiber feed port downstream of the coupling agent feed port. During this process, the epoxy polymer grafted on the end of the nylon chain can be connected to the carbon fiber, thereby enhancing the interface strength between the nylon resin and the carbon fiber, and improving the bonding force between the nylon resin and the carbon fiber, so that the prepared carbon fiber nylon composite material has excellent tensile strength.

[0044] Among them, the plasticizer is injected into the twin-screw extruder in liquid form, which can reduce the melt viscosity and increase the mobility of the nylon molecular chain; the coupling agent is injected into the melt in the twin-screw extruder in a spray state through a liquid high-pressure injection pump. Due to the high temperature in the extruder, the coupling agent liquid is heated to form a high-temperature and high-pressure gas instantly, and a high-pressure mixing reaction is carried out instantly in the extruder, so that the nylon resin and the carbon fiber entering the extruder are mixed, infiltrated and connected; the carbon fiber is added to the twin-screw extruder by side feeding.

[0045] Step 03: extrude and granulate through an extruder.

[0046] During the preparation process, the main function of plasticizers in carbon fiber nylon composites is to increase the mobility of nylon molecular chains, reduce melt viscosity, improve dispersibility, enhance compatibility, and enhance rheological properties, thereby improving processing fluidity, thereby improving the wetting of nylon resin and carbon fiber, and improving the interfacial bonding between nylon resin and carbon fiber. The function of coupling agents is to improve the interfacial bonding between carbon fiber and nylon resin, thereby enhancing the mechanical properties, heat resistance, and durability of the composite material. The use of antioxidants can effectively help the material to age under high temperature and high pressure during extrusion, extending the long-term service life of the material.

[0047] In summary, in the preparation method of this embodiment, by adding a preset amount of nylon resin, epoxy-containing copolymer, antioxidant and other additives into an extruder, the nylon resin and the epoxy-containing copolymer are melt-mixed and grafted, and then by sequentially adding a preset amount of plasticizer, coupling agent and carbon fiber into the extruder, the epoxy polymer grafted on the nylon chain end is connected to the carbon fiber, thereby enhancing the interface strength between nylon and carbon fiber, and improving the bonding force between nylon resin and carbon fiber, thereby enabling the tensile strength of the prepared carbon fiber nylon composite material to reach more than 350MPa, while having excellent injection molding performance, dimensional stability and electromagnetic shielding performance, and can meet the needs of complex electrical structural components. The carbon fiber nylon composite material reaches or even exceeds the tensile strength of magnesium-aluminum alloy, can realize the "plastic-replacing-steel" in the field of electronic and electrical structural components, and can expand a wider range of applications.

[0048] In this embodiment, the epoxy-containing copolymer is one or more of methyl oxirane polymer, bisphenol A-epichlorohydrin copolymer, o-cresol novolac epoxy resin, and dicyclopentadiene (DCPD) phenol epoxy resin. Selecting these epoxy-containing copolymers improves the bonding strength between the nylon resin and the carbon fibers while also providing excellent carbon fiber wetting.

[0049] Moreover, the epoxy equivalent of the epoxy-containing copolymer is 600 to 10,000 g / eq, preferably 1,000 to 3,000 g / eq. The inventors have found that the epoxy equivalent of the epoxy-containing copolymer has a great influence on the bonding strength between nylon resin and carbon fiber. The epoxy-containing copolymer in a reasonable epoxy equivalent range can improve the bonding strength between nylon resin and carbon fiber, while having excellent carbon fiber wetting performance. When using an epoxy-containing copolymer with a lower epoxy equivalent (epoxy equivalent less than 1,000 g / eq), nylon resin maintains good carbon fiber wetting performance, but has less bonding strength with carbon fiber; when using an epoxy-containing copolymer with a higher epoxy equivalent (epoxy equivalent greater than 5,000 g / eq), the fluidity of the nylon resin is greatly reduced, and affects the wetting effect of carbon fiber in the nylon resin.

[0050] In addition, the weight average molecular weight of the epoxy-containing copolymer is 1,000 to 20,000, preferably 4,000 to 10,000, and more preferably 6,000 to 8,000. The weight average molecular weight of the epoxy-containing copolymer has a significant impact on the mechanical properties, processing properties, heat resistance, compatibility, molecular weight distribution, and softening point of the carbon fiber nylon composite material. The epoxy-containing copolymer with a weight average molecular weight within the above range can improve the overall performance of the carbon fiber nylon composite material, such as mechanical properties and processing properties.

[0051] Furthermore, in step 02, the extruder is vacuumed by the front end and / or the rear end of the extruder to maintain the vacuum degree in the extruder at 10 to 60 kPa. In detail, a vacuum exhaust port is set at one end or both ends of the extruder, and the extruder is vacuumed through the vacuum exhaust port to maintain the extruder in an absolute vacuum of 10 to 60 kPa; in this way, the instantaneously formed high-temperature and high-pressure gas of the plasticizer and the coupling agent reacts with a mixed reaction at instant high temperature and high pressure in the extruder. In the vacuum state, the rate of the grafting chemical reaction is promoted kinetically, and a certain grafting conversion rate is ensured thermodynamically, thereby improving the reaction rate of the mixed grafting reaction after the injection molding of the liquid injection plasticizer and the coupling agent; and, in the vacuum state, the gas molecules that fail to react with the grafting reaction are extracted by steam stripping technology to reduce the content of free small molecules, thereby further improving the subsequent wetting and interface bonding effect of the carbon fiber after entry.

[0052] In this embodiment, the nylon resin includes an aromatic nylon resin and an aliphatic nylon resin. The aromatic nylon resin is one or more of PA4T, PA5T, PA6T, PA9T, PA10T, PPA, and PAMXD6, and the aliphatic nylon resin is one or more of PA6, PA66, PA11, PA12, PA610, PA1010, and PA1212.

[0053] The inventors found that in the carbon fiber nylon composite material system, when the carbon fiber content is less than 30%, the tensile strength of the aromatic nylon carbon fiber reinforced composite material is greater than that of the aliphatic nylon composite material, and when the carbon fiber content is greater than 30%, the tensile strength of the aliphatic nylon carbon fiber composite material is greater than that of the aromatic nylon carbon fiber reinforced composite material.

[0054] In addition, the relative viscosity of the aromatic nylon resin is 1.9 to 3.5, and the relative viscosity of the aliphatic nylon resin is 1.7 to 2.7; preferably, the relative viscosity of the aromatic nylon resin is 1.9 to 2.7, and the relative viscosity of the aliphatic nylon resin is 1.9 to 2.3. When aromatic nylon resin and aliphatic nylon resin with a relative viscosity lower than 2.1 are combined, the prepared carbon fiber nylon composite material can achieve the maximum tensile strength.

[0055] In a preferred embodiment, a carbon fiber nylon composite material is prepared by using, by weight, 30 to 55 parts of aromatic nylon resin, 5 to 20 parts of aliphatic nylon resin, 1 to 4 parts of epoxy-containing copolymer, 1 to 10 parts of plasticizer, 1 to 3 parts of coupling agent, 25 to 55 parts of carbon fiber, 0.2 to 0.6 parts of antioxidant and 0.1 to 3 parts of other additives.

[0056] In this embodiment, the diameter of the carbon fiber is 5 to 10 μm, the carbon fiber is T400H grade carbon fiber, T700S grade carbon fiber, T800H grade carbon fiber, or T1000G grade carbon fiber, and the carbon fiber tow is 3 to 24k. Selecting carbon fiber with the above parameters can increase the tensile strength of the carbon fiber nylon composite material.

[0057] In addition, the plasticizer is one or more of N-ethyl-p-toluenesulfonamide (N-ETSA), N-butylbenzenesulfonamide (N-BBSA), polyoxypropylenediamine (Jeffamine D series), polycaprolactone (PCL), epoxidized soybean oil (ESO), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF-]), epoxy fatty acid methyl ester (EFAME), sorbitol, and xylitol.

[0058] In addition, the coupling agent is at least two of a silane coupling agent, a titanate coupling agent, a maleic anhydride grafted polymer (compatibilizer-type coupling agent), and an ionic liquid coupling agent.

[0059] Furthermore, the silane coupling agent is one or more of γ-aminopropyltriethoxysilane (KH-550, APTES), γ-glycidoxypropyltrimethoxysilane (KH-560, GPTMS), and γ-mercaptopropyltrimethoxysilane (KH-590); the titanate coupling agent is at least one of isopropyl tris(dioctylphosphoyl) titanate (KR-12) and di(dioctylpyrophosphoyl) titanium oxyacetate (KR-138S); the maleic anhydride grafted polymer (compatibilizer coupling agent) is one or more of maleic anhydride grafted polyethylene (MAH-g-PE), grafted polypropylene (MAH-g-PP), and maleic anhydride grafted POE (MAH-g-POE); and the ionic liquid coupling agent is at least one of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF-]) and choline carboxylate.

[0060] The alkoxy group (-OR) of silane in the silane coupling agent hydrolyzes to form silanol (-SiOH), which forms a silanol bond (-Si-OC) with the hydroxyl group (-OH) or carboxyl group (-COOH) on the surface of the carbon fiber. The -NH2 of aminosilane or the epoxy group of epoxysilane reacts with the terminal carboxyl group (-COOH) or terminal amino group (-NH2) of nylon to form a covalent bond. The alkoxy group (-OR) of titanate in the titanate coupling agent reacts with the hydroxyl group on the surface of the carbon fiber to form a Ti-OC bond. Its long-chain organic part (such as phosphate group) physically entangles with the nylon resin or forms a hydrogen bond, and can catalyze the end group reaction of nylon, promoting the formation of interfacial chemical bonds. The anhydride group of maleic anhydride (MAH) in the compatibilizer coupling agent reacts with the active group (-OH / -COOH) on the surface of the carbon fiber to form an ester bond or an amide bond. The polymer chain segment (such as PE, PP) is physically blended with the nylon resin to form an interpenetrating network, which can reduce the interfacial tension between the carbon fiber and nylon and promote the dispersion of the carbon fiber. The cations of the ionic liquid in the ionic liquid coupling agent and the negative charges on the carbon fiber surface (such as the oxidized -COO - ) combined with the anion part (such as PF6 - ) forms hydrogen bonds with the amide bonds of nylon, which can enhance interfacial adhesion.

[0061] In particular, after the carbon fiber surface is oxidized, the use of a strongly reactive coupling agent (silane coupling agent, titanate coupling agent or ionic liquid coupling agent) in combination with a silane coupling agent, titanate coupling agent or ionic coupling agent can further improve the wetting and bonding strength between the nylon resin and the carbon fiber, making the tensile strength of the carbon fiber nylon composite material exceed 300MPa.

[0062] In the present embodiment, antioxidant is one or more of hindered phenol antioxidant, phosphite antioxidant and thioester antioxidant;Preferably, antioxidant is hindered phenol antioxidant and phosphite antioxidant of mass ratio 1:2~2:1.Wherein, adopt the combination of hindered phenol antioxidant and phosphite antioxidant of 1:2~2:1, can meet the long-term high strength of material while, have less influence on the acid value in composite material system.It should be noted that, when the total dosage of hindered phenol antioxidant and phosphite antioxidant exceeds 0.8% (mass ratio), the acid value in material system will increase, hindered phenol antioxidant and phosphite antioxidant are derived from phenol and isobutylene synthesis, with free phenolic hydroxyl group in product, affected by aromatic ring, phenolic hydroxyl group acidity is stronger than alcohol hydroxyl group, when material is in high temperature extrusion environment, excessive phenolic hydroxyl group will affect the interface bonding force of coupling agent to nylon resin and carbon fiber, thereby reducing composite material tensile strength.

[0063] Furthermore, the other additives are one or more of lubricants, toughening agents, and nucleating agents. Since all commercially available lubricants, toughening agents, and nucleating agents used to prepare composite materials are suitable for the present invention, their detailed types are not listed here.

[0064] Furthermore, the internal temperature of the extruder during the mixing and extrusion process is 260-320°C. That is, in steps 01, 02, and 03, the temperature within the extruder is consistently maintained at 260-320°C, resulting in the prepared carbon fiber nylon composite material system having excellent tensile strength. Simultaneously, this temperature allows the coupling agent liquid to instantly transform into a high-temperature, high-pressure gas, which undergoes an instantaneous, high-pressure mixing reaction within the extruder, thereby allowing the nylon matrix to be mixed, infiltrated, and connected with the incoming carbon fibers.

[0065] In this embodiment, the nylon resin, epoxy-containing copolymer, antioxidant and other additives are pre-mixed in the extruder for 10 to 15 minutes, which allows for a more complete grafting reaction between the epoxy-containing copolymer and the nylon resin. The extruder's main engine speed is preferably 200 to 550 rpm.

[0066] In addition, the distance between the total feed port for nylon resin, epoxy-containing copolymer, antioxidant, and other additives and the feed port for plasticizer is 10D to 16D, so that the nylon resin, epoxy-containing copolymer, antioxidant, and other additives can be fully mixed before adding the plasticizer. The distance between the feed port for plasticizer and the feed port for coupling agent is 4D to 8D, and the distance between the feed port for coupling agent and the feed port for carbon fiber is 0 to 6D. Wherein, D represents the screw diameter of the extruder (unit: mm).

[0067] In this way, by setting the distance of the above-mentioned feeding ports, the molecular chains in the material preparation process are made more flexible, and the wetting effect of the carbon fiber in the nylon matrix resin is improved, and the interface bonding effect between the carbon fiber and the nylon matrix is ​​increased.

[0068] Further, in step 02, before carbon fiber is added to extruder, oxidation treatment is carried out on carbon fiber surface, and sizing agent is used to process carbon fiber.By oxidation treatment is carried out on carbon fiber surface, not only polar groups such as carboxyl (-COOH), hydroxyl (-OH) can be generated on carbon fiber surface, the chemical bonding ability with nylon resin is improved, and microscopic groove structure can also be formed on carbon fiber surface, the mechanical intercalation effect of carbon fiber and nylon resin is increased.When sizing agent is processed to carbon fiber, one end of its molecular structure is combined with carbon fiber surface functional group, and the other end is compatible with nylon resin, promotes interfacial stress transmission, improves the bonding force between carbon fiber and nylon resin.

[0069] Another embodiment of the present invention provides a carbon fiber nylon composite material, which is prepared using the method for preparing the carbon fiber nylon composite material described in the above embodiment. The carbon fiber nylon composite material has excellent tensile strength and injection molding properties, can meet the requirements of complex electrical structural components, and has excellent dimensional stability and electromagnetic shielding performance.

[0070] The raw materials and processes used in the following examples and comparative examples are as follows:

[0071] Aliphatic nylon resin A uses PA6 with a relative viscosity of 1.9, aliphatic nylon resin B uses PA6 with a relative viscosity of 2.4, aliphatic nylon resin C uses PA66 with a relative viscosity of 2.1, aliphatic nylon resin D uses PA66 with a relative viscosity of 2.7, aliphatic nylon resin E uses PA610 with a relative viscosity of 1.9, aliphatic nylon resin F uses PA1010 with a relative viscosity of 1.9, epoxy resin 0199 is used as the epoxy group-containing copolymer, N-ethyl p-toluenesulfonamide (N-ETSA) is used as the plasticizer, γ-aminopropyltriethoxysilane (KH-550, APTES) is used as the silane coupling agent, 1-butyl-3-methylimidazole hexafluorophosphate ([BMIM][PF-]) is used as the ionic liquid coupling agent, SYT55-6K is used as the carbon fiber, RIANOX1098 is used as the antioxidant A, and RIANOX168 is used as the antioxidant B.

[0072] Process A: First, nylon resin, epoxy copolymer, antioxidant and other additives are added to the extruder from the main feeding port (total feeding port) of the extruder, and then the plasticizer, coupling agent and carbon fiber are added to the extruder in turn. The distance between the main feeding port (total feeding port) and the plasticizer feeding port is 16D, the distance between the plasticizer feeding port and the coupling agent feeding port is 6D, and the distance between the coupling agent feeding port and the carbon fiber feeding port is 2D. The vacuum degree in the extruder is maintained at 40kPa.

[0073] Process B: First, add nylon resin, epoxy copolymer, antioxidant and other additives into the extruder from the main feeding port (total feeding port) of the extruder, and then add plasticizer, coupling agent and carbon fiber into the extruder in turn. The distance between the main feeding port (total feeding port) and the feeding port of the plasticizer is 16D, the distance between the feeding port of the plasticizer and the feeding port of the coupling agent is 4D, and the distance between the feeding port of the coupling agent and the feeding port of the carbon fiber is 2D. The vacuum degree in the extruder is maintained at 40kPa.

[0074] Process C: First, add nylon resin, epoxy copolymer, antioxidant and other additives into the extruder from the main feeding port (total feeding port) of the extruder, and then add plasticizer, coupling agent and carbon fiber into the extruder in turn. The distance between the main feeding port (total feeding port) and the feeding port of the plasticizer is 16D, the distance between the feeding port of the plasticizer and the feeding port of the coupling agent is 6D, and the distance between the feeding port of the coupling agent and the feeding port of the carbon fiber is 2D. No vacuum is applied in the extruder.

[0075] Process D: First, add nylon resin, epoxy copolymer, antioxidant, plasticizer and other additives into the extruder from the main feeding port (total feeding port) of the extruder, and then add the coupling agent and carbon fiber into the extruder in turn. The distance between the main feeding port (total feeding port) and the feeding port of the coupling agent is 16D, and the distance between the feeding port of the coupling agent and the feeding port of the carbon fiber is 12D. The vacuum degree in the extruder is maintained at 40kPa.

[0076] Process E: First, add nylon resin, epoxy copolymer, antioxidant and other additives into the extruder from the main feeding port (total feeding port) of the extruder, and then add plasticizer, carbon fiber and coupling agent into the extruder in sequence (that is, the feeding port of carbon fiber is located between the feeding port of plasticizer and the feeding port of coupling agent). The distance between the main feeding port (total feeding port) and the feeding port of plasticizer is 14D, the distance between the feeding port of plasticizer and the feeding port of coupling agent is 18D, the distance between the feeding port of carbon fiber and the feeding port of coupling agent is 4D, and the vacuum degree in the extruder is maintained at 40kPa.

[0077] Examples 1 to 10 respectively use the corresponding raw material compositions (in parts by weight) and processes in Table 1 below to prepare carbon fiber nylon composite materials. The specific preparation steps are as follows:

[0078] Step 01: Add nylon resin, epoxy-containing copolymer, antioxidant and other additives into an extruder in parts by weight and premix to form an intermediate mixture.

[0079] Step 02: Add plasticizer, coupling agent and carbon fiber into the extruder in order by weight and blend with the intermediate mixture.

[0080] Step 03: extrude and granulate through an extruder.

[0081] The premixing time of nylon resin, epoxy-containing copolymer, antioxidant and other additives in the extruder is 10 to 15 minutes, the internal temperature of the extruder during the mixing and extrusion process is 260 to 320° C., and the main engine speed of the extruder is 200 to 550 rpm.

[0082] Table 1

[0083]

[0084] Comparative Example 1

[0085] This comparative example uses the raw material composition (in parts by weight) and process corresponding to the following Table 2 to prepare a carbon fiber nylon composite material. The difference from Example 1 is that no low-viscosity aliphatic nylon resin is added, and the rest is the same as Example 1.

[0086] Comparative Example 2

[0087] This comparative example uses the raw material composition (in parts by weight) and process corresponding to the following Table 2 to prepare a carbon fiber nylon composite material. The difference from Example 1 is that the extrusion production process is different, and the rest is the same as Example 1.

[0088] Comparative Example 3

[0089] This comparative example uses the corresponding raw material composition (in parts by weight) and process in Table 2 below to prepare a carbon fiber nylon composite material. The difference from Example 2 is that the extrusion production process is different, and the rest is the same as Example 2.

[0090] Comparative Example 4

[0091] This comparative example uses the corresponding raw material composition (in parts by weight) and process in Table 2 below to prepare a carbon fiber nylon composite material. The difference from Example 3 is that the extrusion production process is different, and the rest is the same as Example 3.

[0092] Comparative Example 5

[0093] This comparative example uses the corresponding raw material composition (in parts by weight) and process in Table 2 below to prepare a carbon fiber nylon composite material. The difference from Example 4 is that the extrusion production process is different, and the rest is the same as Example 4.

[0094] Comparative Example 6

[0095] This comparative example uses the raw material composition (in parts by weight) and process corresponding to the following Table 2 to prepare a carbon fiber nylon composite material. The difference from Example 5 is that the type and proportion of the coupling agent are different, and the rest is the same as Example 5.

[0096] Comparative Example 7

[0097] This comparative example uses the raw material composition (in parts by weight) and process corresponding to the following Table 2 to prepare a carbon fiber nylon composite material. The difference from Example 1 is that the viscosity of the aliphatic nylon resin is different, and the rest is the same as Example 1.

[0098] Comparative Example 8

[0099] This comparative example uses the corresponding raw material composition (in parts by weight) and process in Table 2 below to prepare a carbon fiber nylon composite material. The difference from Example 2 is that the viscosity of the aliphatic resin nylon is different, and the rest is the same as Example 2.

[0100] Comparative Example 9

[0101] This comparative example uses the corresponding raw material composition (in parts by weight) and process in Table 2 below to prepare a carbon fiber nylon composite material. The difference from Example 4 is that no epoxy group-containing copolymer is added, and the rest is the same as Example 4.

[0102] Comparative Example 10

[0103] This comparative example uses the corresponding raw material composition (in parts by weight) and process in Table 2 below to prepare a carbon fiber nylon composite material. The difference from Example 4 is that the type of epoxy group-containing copolymer is different, and the rest is the same as Example 4.

[0104] Comparative Example 11

[0105] This comparative example uses the corresponding raw material composition (in parts by weight) and process in Table 2 below to prepare a carbon fiber nylon composite material. The difference from Example 5 is that the type of epoxy group-containing copolymer is different, and the rest is the same as Example 5.

[0106] Comparative Example 12

[0107] This comparative example uses the raw material composition (in parts by weight) and process corresponding to the following Table 2 to prepare a carbon fiber nylon composite material. The difference from Example 5 is that the proportion of antioxidants is inconsistent, and the rest is the same as Example 5.

[0108] Table 2

[0109]

[0110] The carbon fiber nylon composite materials prepared in Examples 1 to 10 and Comparative Examples 1 to 12 were tested, and the test results are shown in Tables 3 and 4.

[0111] The tensile properties were evaluated by tensile breaking strength, which was measured according to ASTM D638 standard, with sample size of 165 mm × 13 mm × 3.2 mm, a test speed of 10 mm / min, and a universal testing machine.

[0112] The flow properties were tested using a spiral flow mold injection molding test. The testing equipment was an injection molding machine. The injection temperature was 280-320°C, the injection pressure was 60 MPa, and the injection time was 2 s.

[0113] Table 3

[0114]

[0115] Table 4

[0116]

[0117] As shown in Tables 3 and 4, it can be seen from Examples 1 to 10 that by using a low-viscosity aliphatic nylon resin to compound an aromatic nylon resin, selecting an epoxy-containing copolymer with an epoxy equivalent of 1000 to 5000, and compounding two types of coupling agents, and during twin-screw extrusion, after the nylon resin and the epoxy-containing copolymer are mixed, the plasticizer, coupling agent and carbon fiber are gradually added under vacuum conditions, a high-strength carbon fiber nylon composite material can be obtained, and the tensile strength is greater than 350 MPa, and the modified material has better fluidity during injection molding.

[0118] It can be seen from Comparative Examples 1, 7 and 8 that when preparing carbon fiber nylon composite materials, no low-viscosity aliphatic nylon resin is added, which will result in insufficient overall impregnation of the carbon fiber by the nylon resin; it can be seen from Comparative Examples 9 and 10 that when preparing carbon fiber nylon composite materials, no epoxy group-containing copolymer is added or the epoxy equivalent is not properly selected, which will result in poor bonding between the carbon fiber and the nylon resin; it can be seen from Comparative Example 6 that when preparing carbon fiber nylon composite materials, no silane coupling agent and liquid ion coupling agent are compounded in the coupling agent, and the bonding between the carbon fiber and the nylon resin is poor. The interface bonding force is not enough; it can be seen from Comparative Example 12 that when preparing carbon fiber nylon composite materials, adding excessive antioxidants will lead to excessive acid value in the material system, and excessive phenolic hydroxyl groups will affect the interface bonding force of the coupling agent on nylon resin and carbon fiber; it can be seen from Comparative Examples 2, 3, 4 and 5 that when preparing carbon fiber nylon composite materials, the extrusion process is not suitable, the positions for adding plasticizers and coupling agents are not suitable, and the upstream and downstream of the plasticizer / coupling agent addition are not vacuumed to remove small molecules that fail to graft reaction, affecting the bonding between carbon fiber and nylon resin.

[0119] By comparison, it can be seen that the above factors all reduce the tensile strength of the carbon fiber nylon composite material, and it can be seen from Comparative Example 11 that the use of an epoxy group copolymer with an epoxy equivalent greater than 5000 to prepare a carbon fiber nylon composite material will significantly reduce the flow properties of the composite material.

[0120] The above description is only a specific embodiment of the present invention. Under the above teachings of the present invention, those skilled in the art may make other improvements or modifications based on the above embodiments. Those skilled in the art should understand that the above description is only to better explain the purpose of the present invention, and the scope of protection of the present invention shall be based on the scope of protection of the claims.

Claims

1. A method for preparing a carbon fiber nylon composite material, characterized in that: The preparation method comprises the following steps: Step 01, adding 35-75 parts of nylon resin, 1-4 parts of epoxy-containing copolymer, 0.05-1 parts of antioxidant and 0.1-3 parts of other additives into an extruder by weight, and premixing to form an intermediate mixture; Step 02, adding 1 to 10 parts of a plasticizer, 0.5 to 5 parts of a coupling agent, and 15 to 55 parts of carbon fibers, in parts by weight, into the extruder and blending them with the intermediate mixture; Step 03, extruding and granulating through the extruder.

2. The method for preparing a carbon fiber nylon composite material according to claim 1, wherein: The epoxy group-containing copolymer is one or more of methyl ethylene oxide polymer, bisphenol A-epichlorohydrin copolymer, o-cresol novolac epoxy resin, and dicyclopentadiene phenol epoxy resin.

3. The method for preparing a carbon fiber nylon composite material according to claim 1, wherein: The epoxy equivalent of the epoxy group-containing copolymer is 600 to 10,000 g / eq, preferably 1,000 to 3,000 g / eq.

4. The method for preparing a carbon fiber nylon composite material according to claim 1, wherein: The weight average molecular weight of the epoxy group-containing copolymer is 1,000 to 20,000, preferably 4,000 to 10,000, and more preferably 6,000 to 8,000.

5. The method for preparing a carbon fiber nylon composite material according to claim 1, wherein: In the step 02, the extruder is vacuumed from the front end and / or the rear end of the extruder to maintain the vacuum degree in the extruder at 10 to 60 kPa.

6. The method for preparing a carbon fiber nylon composite material according to claim 1, wherein: The nylon resin includes aromatic nylon resin and aliphatic nylon resin.

7. The method for preparing a carbon fiber nylon composite material according to claim 6, characterized in that: The relative viscosity of the aromatic nylon resin is 1.9 to 3.5, and the relative viscosity of the aliphatic nylon resin is 1.7 to 2.7; preferably, the relative viscosity of the aromatic nylon resin is 1.9 to 2.7, and the relative viscosity of the aliphatic nylon resin is 1.9 to 2.

3.

8. The method for preparing a carbon fiber nylon composite material according to claim 6, characterized in that: The aromatic nylon resin is one or more of PA4T, PA5T, PA6T, PA9T, PA10T, PPA and PAMXD6, and the aliphatic nylon resin is one or more of PA6, PA66, PA11, PA12, PA610, PA1010 and PA1212.

9. The method for preparing a carbon fiber nylon composite material according to claim 1, wherein: The diameter of the carbon fiber is 5 to 10 μm, the carbon fiber is T400H grade carbon fiber, T700S grade carbon fiber, T800H grade carbon fiber or T1000G grade carbon fiber, and the tow of the carbon fiber is 3 to 24 k.

10. The method for preparing a carbon fiber nylon composite material according to claim 1, characterized in that: The plasticizer is one or more of N-ethyl-p-toluenesulfonamide, N-butylbenzenesulfonamide, polyoxypropylenediamine, polycaprolactone, epoxy soybean oil, 1-ethyl-3-methylimidazolium tetrafluoroborate, epoxy fatty acid methyl ester, sorbitol, and xylitol.

11. The method for preparing a carbon fiber nylon composite material according to claim 1, wherein: The coupling agent is at least two of a silane coupling agent, a titanate coupling agent, a maleic anhydride grafted polymer and an ionic liquid coupling agent.

12. The method for preparing a carbon fiber nylon composite material according to claim 11, characterized in that: The silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane; The titanate coupling agent is at least one of isopropyl tris(dioctylphosphoyl)titanate and di(dioctylpyrophosphoyl)oxyacetate titanium; The maleic anhydride grafted polymer is one or more of maleic anhydride grafted polyethylene, maleic anhydride grafted polypropylene and maleic anhydride grafted POE; The ionic liquid coupling agent is at least one of 1-butyl-3-methylimidazolium hexafluorophosphate and choline carboxylate.

13. The method for preparing a carbon fiber nylon composite material according to claim 1, wherein: The antioxidant is one or more of hindered phenol antioxidants, phosphite antioxidants and thioester antioxidants; preferably, the antioxidant is a hindered phenol antioxidant and a phosphite antioxidant in a mass ratio of 1:2 to 2:

1.

14. The method for preparing a carbon fiber nylon composite material according to claim 1, wherein: The other auxiliary agents are one or more of lubricants, toughening agents and nucleating agents.

15. The method for preparing a carbon fiber nylon composite material according to claim 1, characterized in that: The internal temperature of the extruder during the mixing and extrusion process was 260-320°C.

16. The method for preparing a carbon fiber nylon composite material according to claim 1, characterized in that: The premixing time of the nylon resin, the epoxy-containing copolymer, the antioxidant and the other auxiliary agents in the extruder is 10 to 15 minutes.

17. The method for preparing a carbon fiber nylon composite material according to claim 1, characterized in that: The distance between the total feeding port of the nylon resin, the epoxy-containing copolymer, the antioxidant and the other additives and the feeding port of the plasticizer is 10D to 16D, the distance between the feeding port of the plasticizer and the feeding port of the coupling agent is 4D to 8D, and the distance between the feeding port of the coupling agent and the feeding port of the carbon fiber is 0 to 6D.

18. The method for preparing a carbon fiber nylon composite material according to any one of claims 1 to 17, characterized in that: In the step 02, before adding the carbon fiber to the extruder, the surface of the carbon fiber is oxidized and the carbon fiber is treated with a sizing agent.

19. A carbon fiber nylon composite material, characterized in that: The carbon fiber nylon composite material is prepared by the preparation method of the carbon fiber nylon composite material according to any one of claims 1 to 18.

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