Preparation process of thermoplastic carbon fiber reinforced composite material

Abstract

The invention relates to the technical field of high polymer material synthesis, and discloses a preparation process of a thermoplastic carbon fiber reinforced composite material, a coupling agent KH-550 and nanoscale silicon dioxide are adopted for premixing modification of epoxy resin, the interface bonding force between carbon fibers and a matrix is significantly improved, and the thermal conductivity of the composite material is improved. Functional modification is performed on the carbon short fibers through oxidation treatment and electrophoretic deposition, and synergistic improvement of electrical conductivity and mechanical properties is realized under a relatively mild condition.

Description

Technical Field

[0001] This invention belongs to the field of polymer material synthesis technology, and particularly relates to a preparation process of thermoplastic carbon fiber reinforced composite material. Background Technology

[0002] As people's demands for seating comfort and environmental friendliness continue to increase, the application of thermoplastic carbon fiber reinforced composite seat frames in office furniture, home furnishings, and other fields is also gradually expanding. Carbon fiber composites, with their excellent properties such as high strength, low density, corrosion resistance, and fatigue resistance, have become an ideal alternative to traditional metal materials for seat frames. With continuous improvements and innovations in processing technologies such as injection molding and hot pressing, the processing efficiency and yield of thermoplastic carbon fiber reinforced composites will be further enhanced.

[0003] Existing thermoplastic carbon fiber reinforced composite materials possess excellent processability and high-temperature resistance, but they still suffer from insufficient interfacial bonding between the carbon fibers and the matrix resin. This leads to interlayer delamination under stress, affecting the overall mechanical properties. For example, CN106433107A discloses a "high-strength carbon fiber reinforced thermoplastic resin composite material particle and its preparation method," which involves treating carbon fibers with oxidation, coating them with a graphene or carbon nanotube functional coating using an epoxy emulsion sizing process, and then encapsulating them with thermoplastic resin via twin-screw extrusion to form a "functional coating + resin layer" encapsulation structure. This technology improves interfacial bonding by coating nanomaterials on the surface, but the coating process relies on the wettability of the epoxy emulsion, which can easily lead to uneven distribution of graphene or carbon nanotubes, limiting the improvement of functional properties such as conductivity and making it difficult to meet the requirements of high-end applications for synergistic mechanical and functional properties. Summary of the Invention

[0004] To address the issues mentioned in the background section regarding insufficient interfacial bonding between carbon fibers and the matrix resin, which leads to interlaminar delamination of the composite material under stress and affects its overall mechanical properties, and the lack of optimization of functional properties (such as conductivity and flame retardancy) in conventional carbon fiber composites, making it difficult to meet the special requirements of high-end applications, this invention provides a preparation process for thermoplastic carbon fiber reinforced composite materials. This process uses coupling agent KH-550 and nano-sized silica to premix and modify epoxy resin, significantly improving the interfacial bonding between carbon fibers and the matrix. Furthermore, the carbon short fibers are functionalized through oxidation treatment and electrophoretic deposition (carbon nanotubes / graphene), achieving a synergistic improvement in conductivity and mechanical properties without the need for stringent conditions.

[0005] The specific technical solution of this invention is: a preparation process for thermoplastic carbon fiber reinforced composite materials, comprising the following steps: 1) Mix epoxy resin, coupling agent KH-550 and nano-sized silica, heat to 180~240℃ to melt, and obtain a premix. Add functional carbon short fiber, petroleum coke powder and high temperature asphalt powder according to the weight parts, stir evenly, and obtain a prepreg tape. 2) Lay a prepreg tape flat in the mold, insert a thermoplastic electrospun fiber film into the prepreg tape, hot press and then perform high-temperature carbonization and curing, and demold to obtain thermoplastic carbon fiber reinforced composite material.

[0006] This invention employs coupling agent KH-550 and nano-sized silica to premix and modify epoxy resin, significantly improving the interfacial bonding force between carbon fibers and the matrix. Functional carbon short fibers, petroleum coke powder, high-temperature asphalt powder, and premixed modified epoxy resin are mixed in a specific ratio, and a thermoplastic electrospun fiber membrane is added to the prepreg tape to enhance interlayer bonding. The mixture is then placed in a hot press mold for hot pressing and demolded after high-temperature curing and carbonization. The self-resistance heating characteristic of the reinforcing carbon fibers provides a uniform temperature field, ultimately achieving integrated molding of carbon fiber reinforced thermoplastic composite components.

[0007] Preferably, the particle size of the high-temperature asphalt powder is 10~50μm.

[0008] Further, in step 1), the preparation method of functional carbon short fibers is as follows: heating the carbon short fibers to 200~300℃ and oxidizing them in air for 30~60min; using the oxidized carbon short fibers as the cathode and a stainless steel plate as the anode for electrophoretic deposition, and drying them to obtain functional carbon short fibers. The carbon short fibers are functionalized by oxidation treatment and electrophoretic deposition (carbon nanotubes / graphene), achieving a synergistic improvement in conductivity and mechanical properties without the need for harsh conditions.

[0009] Furthermore, the electrophoretic suspension used during electrophoretic deposition is a carbon nanotube or graphene solution with a concentration of 0.5~2 g / L.

[0010] Preferably, the purity of carbon nanotubes or graphene is ≥5%.

[0011] Furthermore, the electrophoretic deposition conditions are deposition at 40~60V for 1~3min. Traditional addition of nanofillers is prone to agglomeration, leading to performance degradation. This solution ensures uniform distribution of nanomaterials on the fiber surface through positive electrochemical treatment and epoxy emulsion stabilization, thereby improving the conductivity, thermal stability and fatigue resistance of the composite material.

[0012] Further, in step 1), the amount of coupling agent KH-550 added is 5~15wt% of epoxy resin, and the amount of nano-sized silica added is 0.1~1wt% of epoxy resin.

[0013] Further, in step 1), 8-10 parts by weight of functional carbon short fiber, 0.8-1.2 parts by weight of petroleum coke powder, 0.8-1.2 parts by weight of high-temperature asphalt powder and 0.5-0.7 parts by weight of premix are mixed.

[0014] Furthermore, in step 2), the high-temperature curing and carbonization conditions are maintained at 800~1500℃ for 24~48h.

[0015] Furthermore, in step 2), the thickness of the thermoplastic electrospun fiber membrane is 20~100μm.

[0016] Furthermore, the preparation method of the thermoplastic electrospun fiber membrane in step 2) is as follows: dissolve the thermoplastic polymer in dichloromethane, add 5-15 wt% of the flame retardant aluminum hydroxide to the thermoplastic polymer, stir evenly, and then use an electrospinning device to spin the fiber. After spinning, a thermoplastic electrospun fiber membrane is obtained. While enhancing the interlayer bonding force, the introduction of flame retardant into the thermoplastic electrospun fiber membrane can directly improve the fire resistance rating of the material, reduce the risk of fire, and also form a protective film during combustion to prevent oxygen from entering and slow down or stop the spread of flames.

[0017] Furthermore, the thermoplastic polymer is one or more of polyamide, polyacrylonitrile, and polylactic acid, with a molecular weight of 3000-5000.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1) This invention uses coupling agent KH-550 and nano-sized silica to premix and modify epoxy resin, which significantly improves the interfacial bonding force between carbon fiber and matrix. Functional carbon short fiber, petroleum coke powder, high temperature asphalt powder and premixed modified epoxy resin are mixed in proportion, and thermoplastic electrospun fiber film is added to the prepreg tape to enhance interlayer bonding force.

[0019] 2) This invention functionalizes carbon short fibers by oxidizing and electrophoretically depositing them, thereby achieving a synergistic improvement in conductivity and mechanical properties without the need for harsh conditions.

[0020] 3) By introducing flame retardants into thermoplastic electrospun fiber membranes, this invention can directly improve the fire resistance rating of the material and reduce the risk of fire. Attached Figure Description

[0021] The present invention will be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 This is a process flow diagram of the present invention.

[0022] Figure 2 This is a schematic diagram of the carbon short fiber structure of the present invention.

[0023] The attached figures are: 1. Carbon short fibers; 2. Oxidation treatment layer; 3. Electrophoretic deposition layer. Detailed Implementation

[0024] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.

[0025] The present invention will be further described below with reference to embodiments.

[0026] Example 1 The process flow diagram of this embodiment is as follows: Figure 1 As shown.

[0027] 1) Preparation of functional carbon short fibers Carbon short fibers were oxidized in air at 250℃ for 40 min. Using the oxidized carbon short fibers as the cathode and a stainless steel plate as the anode, electrophoretic deposition was performed in a 40V, 1.5g / L carbon nanotube electrophoresis solution for 2 min. After electrophoretic deposition, the fibers were dried at 80℃ for 20 min to obtain functional carbon short fibers. The structure of the functional carbon short fibers is as follows. Figure 2 As shown, it includes carbon short fibers 1, an oxidation treatment layer 2, and an electrophoretic deposition layer 3, wherein the purity of the carbon nanotubes is 95%.

[0028] 2) Preparation of thermoplastic electrospun fiber membranes Polylactic acid with a molecular weight of 3000-3500 was dissolved in dichloromethane to prepare a 7% solution. 10 wt% of aluminum hydroxide, a flame retardant, was added to the solution. After mixing evenly, the solution was spun using an electrospinning device to obtain a thermoplastic electrospun fiber membrane with a thickness of 50 μm.

[0029] 3) Preparation of prepreg tape Epoxy resin was mixed with 5 wt% coupling agent KH-550 and 0.5 wt% nano-sized silica, and heated to 230°C in an inert nitrogen atmosphere to melt the mixture, thus obtaining a premix. 10 parts by weight of the functional carbon short fiber obtained in step 1), 1 part of petroleum coke powder, 1 part of high-temperature asphalt powder and 0.5 parts of the premix were mixed and stirred until homogeneous to obtain a prepreg tape.

[0030] 4) Hot pressing and shaping The prepreg tape prepared in step 3) is laid flat in the preheated mold. Five layers of thermoplastic electrospun film prepared in step 2) are inserted into the prepreg tape. The film is hot-pressed at 240℃ and 10MPa for 10 min, heated to 1000℃, and held for 40 h before demolding to obtain thermoplastic carbon fiber reinforced composite material.

[0031] 5) Performance Testing The performance of the thermoplastic reinforced composite material obtained in step 4) was tested.

[0032] Comparative Example 1 The only difference between this comparative example and Example 1 is that the carbon short fibers are not functionalized in this comparative example; all other processes are the same as in Example 1. The specific steps are as follows: 1) Preparation of thermoplastic electrospun fiber membrane Polylactic acid with a molecular weight of 3000-3500 was dissolved in dichloromethane to prepare a 7% solution. 10 wt% of aluminum hydroxide, a flame retardant, was added to the solution. After mixing evenly, the solution was spun using an electrospinning device to obtain a thermoplastic electrospun fiber membrane with a thickness of 50 μm.

[0033] 2) Preparation of prepreg tape Epoxy resin was mixed with 5 wt% coupling agent KH-550 and 0.5 wt% nano-sized silica, and then heated to 230°C in an inert nitrogen atmosphere to melt the mixture, thus obtaining a premix. 10 parts by weight of carbon short fiber, 1 part of petroleum coke powder, 1 part of high-temperature asphalt powder and 0.5 parts of the premix were mixed and stirred until homogeneous to obtain a prepreg tape.

[0034] 3) Hot pressing and shaping The prepreg tape prepared in step 2) is laid flat in the preheated mold. Five layers of thermoplastic electrospun film prepared in step 1) are inserted into the prepreg tape. The film is hot-pressed at 240℃ and 10MPa for 10min, heated to 1000℃, and held for 40h before demolding to obtain thermoplastic carbon fiber reinforced composite material.

[0035] 4) Performance Testing The thermoplastic carbon fiber reinforced composite material obtained in step 3) was subjected to performance testing.

[0036] Table 1. Effects of surface functionalization modification of carbon short fibers on the final synthesized composite material. Should the carbon short fibers be surface modified? Tensile strength / MPa Elongation at break % Example 1 yes 1495 2.5 Comparative Example 1 no 1178 2 The data in Table 1 show that the mechanical properties (tensile strength and elongation at break) of the synthesized thermoplastic carbon fibers are significantly improved after surface functionalization of carbon short fibers by electrophoretic deposition. The reason for this is that surface functionalization of carbon short fibers increases the interfacial bonding force with epoxy resin, thereby enhancing mechanical properties.

[0037] Comparative Example 2 The only difference between this comparative example and Example 1 is that, in this comparative example, a thermoplastic electrospun fiber membrane is not inserted into the prepreg tape. All other processes are the same as in Example 1. The specific steps are as follows: 1) Preparation of functional carbon short fibers Carbon short fibers were oxidized in air at 250°C for 40 min. The oxidized carbon short fibers were used as the cathode and a stainless steel plate as the anode. Electrophoretic deposition was carried out in a 40V, 1.5g / L carbon nanotube electrophoresis solution for 2 min. After electrophoretic deposition, the carbon nanotubes were dried at 80°C for 20 min to obtain functional carbon short fibers with a purity of 95%.

[0038] 2) Preparation of prepreg tape Epoxy resin was mixed with 5 wt% coupling agent KH-550 and 0.5 wt% nano-sized silica, and heated to 230°C in an inert nitrogen atmosphere to melt the mixture, thus obtaining a premix. 10 parts by weight of the functional carbon short fiber obtained in step 1), 1 part of petroleum coke powder, 1 part of high-temperature asphalt powder and 0.5 parts of the premix were mixed and stirred until homogeneous to obtain a prepreg tape.

[0039] 3) Hot pressing and shaping The prepreg tape prepared in step 2) is laid flat in the preheated mold, hot-pressed at 240℃ and 10MPa for 10min, heated to 1000℃, held for 40h and then demolded to obtain thermoplastic carbon fiber reinforced composite material.

[0040] Table 2. Effects of thermoplastic electrospun fiber membranes on the properties of thermoplastic carbon fiber reinforced composites. Whether to insert thermoplastic electrospun fiber membrane Limiting oxygen index High temperature resistance Example 1 yes 28% After high-temperature carbonization and curing, the mass loss is less than 3%. Comparative Example 2 no 24% After high-temperature carbonization and curing, the mass loss is 10%. The data in Table 2 show that the introduction of thermoplastic electrospun fiber membranes can significantly improve the flame retardant properties (limiting oxygen index) and high temperature resistance of the material, thus expanding its application range.

[0041] Example 2 1) Preparation of functional carbon short fibers Carbon short fibers were oxidized in air at 250°C for 40 min. The oxidized carbon short fibers were used as the cathode and a stainless steel plate as the anode. Electrophoretic deposition was carried out in a 40V, 1.5g / L graphene electrophoresis solution for 2 min. After electrophoretic deposition, the fibers were dried at 80°C for 20 min to obtain functional carbon short fibers with a graphene purity of 95%.

[0042] 2) Preparation of thermoplastic electrospun fiber membranes Polyamide with a molecular weight of 3000-3500 was dissolved in dichloromethane to prepare a 5% solution. 5 wt% of aluminum hydroxide flame retardant was added to the polylactic acid solution. After mixing evenly, the solution was spun using an electrospinning device to obtain a thermoplastic electrospun fiber membrane with a thickness of 30 μm.

[0043] 3) Preparation of prepreg tape Epoxy resin was mixed with 7 wt% coupling agent KH-550 and 0.1 wt% nano-sized silica, and heated to 180°C in an inert nitrogen atmosphere to melt the mixture, thus obtaining a premix. 10 parts by weight of the functional carbon short fiber obtained in step 1), 1 part of petroleum coke powder, 1 part of high-temperature asphalt powder and 0.5 parts of the premix were mixed and stirred until homogeneous to obtain a prepreg tape.

[0044] 4) Hot pressing and shaping The prepreg tape prepared in step 3) is laid flat in the preheated mold. Five layers of thermoplastic electrospun film prepared in step 2) are inserted into the prepreg tape. The film is hot-pressed at 240℃ and 10MPa for 10 min, heated to 1000℃, and held for 40 h before demolding to obtain thermoplastic carbon fiber reinforced composite material.

[0045] Measurements show that the limiting oxygen index of the thermoplastic carbon fiber reinforced composite material prepared in step 4) of this embodiment is 26%.

[0046] Example 3 1) Preparation of functional carbon short fibers Carbon short fibers were oxidized in air at 300℃ for 30 min. The oxidized carbon short fibers were used as the cathode and a stainless steel plate as the anode. Electrophoretic deposition was carried out in a 60V, 1.5g / L carbon nanotube electrophoresis solution for 1 min. After electrophoretic deposition, the carbon nanotubes were dried at 80℃ for 20 min to obtain functional carbon short fibers with a purity of 95%.

[0047] 2) Preparation of thermoplastic electrospun fiber membranes Polyacrylonitrile with a molecular weight of 3000-3500 was dissolved in dichloromethane to prepare an 8% solution. 30 wt% of aluminum hydroxide, a flame retardant, was added to the solution. After mixing evenly, the solution was spun using an electrospinning device to obtain a thermoplastic electrospun fiber membrane with a thickness of 100 μm.

[0048] 3) Preparation of prepreg tape Epoxy resin was mixed with 15 wt% coupling agent KH-550 and 1 wt% nano-sized silica, and heated to 230°C in an inert nitrogen atmosphere to melt the mixture, thus obtaining a premix. 10 parts by weight of the functional carbon short fiber obtained in step 1), 1 part of petroleum coke powder, 1 part of high-temperature asphalt powder and 0.5 parts of the premix were mixed and stirred until homogeneous to obtain a prepreg tape.

[0049] 4) Hot pressing and shaping The prepreg tape prepared in step 3) is laid flat in the preheated mold. Five layers of thermoplastic electrospun film prepared in step 2) are inserted into the prepreg tape. The film is hot-pressed at 240℃ and 10MPa for 10 min, heated to 1000℃, and held for 40 h before demolding to obtain thermoplastic carbon fiber reinforced composite material.

[0050] Measurements show that the limiting oxygen index of the thermoplastic carbon fiber reinforced composite material prepared in step 4) of this embodiment is 30%.

[0051] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0052] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A process for the production of a thermoplastic carbon fiber reinforced composite material, characterized in that, The method comprises the following steps: 1) mixing epoxy resin, coupling agent KH-550 and nano-sized silicon dioxide, melting in inert gas at 180-240 DEG C to obtain a premix, adding functional carbon short fibers, petroleum coke powder and high-temperature pitch powder by weight, stirring uniformly to obtain a prepreg tape; 2) laying the prepreg tape in a mold, inserting a thermoplastic electrospun fiber membrane in the prepreg tape, hot pressing, high-temperature carbonization and curing, demolding to obtain a thermoplastic carbon fiber reinforced composite material.

2. The process for the preparation of thermoplastic carbon fiber reinforced composites according to claim 1, characterized in that, In step 1), the functional carbon short fibers are prepared by heating carbon short fibers to 200-300 DEG C, oxidizing in air for 30-60 min, using the oxidized carbon short fibers as a cathode, and performing electrophoretic deposition with a stainless steel plate as an anode, and drying to obtain functional carbon short fibers.

3. The process for the production of thermoplastic carbon fiber reinforced composites according to claim 2, characterized in that, The electrophoretic suspension for electrophoretic deposition is a carbon nanotube or graphene solution with a concentration of 0.5-2 g / L.

4. The preparation process of a thermoplastic carbon fiber reinforced composite material according to claim 2, characterized in that, The electrophoretic deposition conditions are 40-60 V for 1-3 min.

5. The preparation process of a thermoplastic carbon fiber reinforced composite material according to claim 1, characterized in that, In step 1), the amount of coupling agent KH-550 added is 5-15 wt% of the epoxy resin, and the amount of nano-sized silicon dioxide added is 0.1-1 wt% of the epoxy resin.

6. The preparation process of a thermoplastic carbon fiber reinforced composite material according to claim 1, characterized in that, In step 1), 8-10 parts of functional carbon short fibers, 0.8-1.2 parts of petroleum coke powder, 0.8-1.2 parts of high-temperature pitch powder and 0.5-0.7 parts of the premix are mixed by weight.

7. The preparation process of a thermoplastic carbon fiber reinforced composite material according to claim 1, characterized in that, In step 2), the high-temperature curing and carbonization conditions are 800-1500 DEG C for 24-48 h.

8. The preparation process of a thermoplastic carbon fiber reinforced composite material according to claim 1, characterized in that, In step 2), the thickness of the thermoplastic electrospun fiber membrane is 20-100 μm.

9. The preparation process of a thermoplastic carbon fiber reinforced composite material according to claim 1, characterized in that, In step 2), the thermoplastic electrospun fiber membrane is prepared by dissolving a thermoplastic polymer in dichloromethane, adding 5-15 wt% of a flame retardant aluminum hydroxide, stirring uniformly, and then using an electrospinning device to spin, and obtaining a thermoplastic electrospun fiber membrane after spinning.

10. The process for the production of thermoplastic carbon fiber reinforced composites according to claim 9, characterized in that, The thermoplastic polymer is one or more of polyamide, polyacrylonitrile and polylactic acid, and the molecular weight is 3000-5000.

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