Continuous fiber reinforced polyimide structure type core material composite material and 3D printing method thereof

Abstract

The invention discloses a continuous fiber reinforced polyimide structure type core material composite material and a 3D printing method thereof.The method comprises the steps that firstly, a polyamide acid salt solution is adopted for preimpregnation of continuous fiber tows, and continuous fibers are transferred to a printing nozzle for printing of a continuous fiber layer; the viscosity of the polyamide acid hydrogel is adjusted, the extrusion amount of glue solution printing is adjusted, a core material printing path is adjusted in combination with a 3D printing control system, volatile solvents in resin are removed through an external heat flow source, partial curing of the resin is completed, and a polyimide structure type core material preformed body is printed in a sizing mode; and finally, obtaining a continuous fiber reinforced polyimide structure type core material composite material preform by adopting a 3D printer, and heating and curing to obtain the continuous fiber reinforced polyimide structure type core material composite material. The composite material has the characteristics of excellent heat resistance, mechanical corrosion resistance and chemical corrosion resistance, good printing quality and high working efficiency, and is suitable for the fields of aerospace, automobiles, ships, semiconductors and the like.

Description

Technical Field

[0001] The present invention belongs to the field of 3D printing of composite materials, and in particular relates to a continuous fiber reinforced polyimide structural core material composite material and a 3D printing method thereof. Background Art

[0002] Heat-resistant polyimide resin has excellent high-temperature resistance, especially when it is compounded with continuous fibers, it can give the material stronger mechanical properties and is widely used in aerospace, military missiles, automobiles and other fields. However, the structural manufacturing process of such composite materials prepared by traditional manufacturing technology is complex, the process is cumbersome, the production efficiency is low, and the structural design is complex, which cannot meet the production requirements of certain small parts. 3D printing technology uses digital drive to stack materials layer by layer, and lightweight and multifunctional three-dimensional structures can be designed by optimizing the printing path. Among high-temperature resistant materials, due to the characteristics of polyimide resin being difficult to melt and having poor fluidity, one-time 3D printing is still difficult, and direct printing is quite challenging. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention innovatively develops a continuous fiber reinforced polyimide structural core material composite material and its 3D printing method. The present invention combines the characteristics of high temperature resistance, anti-oxidation aging and chemical corrosion resistance of the polyimide matrix resin itself, which will greatly improve the heat resistance of the printed composite material. By utilizing the good temperature thixotropy of polyamic acid salt hydrogel, the continuous fiber reinforced polyimide composite material printed by 3D printing technology has structural designability, and the prepared structure gives the composite material the characteristics of lightweight while ensuring the mechanical properties.

[0004] To achieve the above object, the present invention is implemented by the following technical solutions:

[0005] The present invention provides a 3D printing method for a continuous fiber reinforced polyimide structural core material composite material, the 3D printing method comprising:

[0006] Step 1: Evenly dissolving aromatic amine and aromatic anhydride in an aprotic solvent, stirring at 70-90° C. for 2 hours for prepolymerization, and obtaining a prepolymer impregnation solution; evenly dissolving aromatic amine and aromatic anhydride in an aprotic solvent, stirring at 70-90° C. for 4 hours for polymerization reaction, and obtaining a resin glue solution for 3D printing;

[0007] Step 2: impregnating the continuous fiber tow with the prepolymer impregnation liquid obtained in step 1, performing homogenization and filtration treatment on the excess impregnation liquid on the surface of the continuous fiber tow, and then transmitting it to the printing nozzle through a guide wheel for continuous fiber tow printing;

[0008] Step 3: The resin glue obtained in step 1 is transferred to another printing syringe, the viscosity of the resin glue is adjusted by the printing heating device, the air piston pressure is given by the pressure output system to control the extrusion amount of the glue printing, the 3D printing system adjusts the printing path, and the volatile solvent in the printed resin layer is removed by the external heat flow source to complete the partial curing of the resin, and the polyimide structure core material preform is initially shaped and printed;

[0009] Step 4: Based on the continuous fiber tow and polyimide core material preform obtained in step 2 and step 3, a continuous fiber reinforced polyimide structural core material composite material preform is obtained by alternately stacking and printing layer by layer using a 3D printer, and then the preform is moved to a heating device for curing reaction. After curing, a continuous fiber reinforced polyimide structural core material composite material is obtained.

[0010] As a further optimization scheme of the present invention, the amount of the amine group in the structure of the aromatic amine is equal to the amount of the anhydride group in the structure of the aromatic anhydride; the reactant of the aromatic amine contains at least one of aromatic diamine, aromatic triamine and aromatic anhydride; the aromatic amine is one or more of the following structures:

[0011]

[0012] The aromatic anhydrides are one or more of the following structures:

[0013]

[0014] As a further optimization scheme of the present invention, in step 1, the aprotic solvent is one or more of 2-ethyl-4-methylimidazole, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, 1,2-dimethylimidazole, dimethyl sulfoxide, dichloromethane, and triethylamine.

[0015] As a further optimization scheme of the present invention, in step 2, the continuous fiber bundle is impregnated in an impregnation tank, the impregnation speed is set to 0.2-6 m / min, and the impregnation temperature is set to 40-50°C.

[0016] As a further optimization scheme of the present invention, in step 2, the continuous fiber tow is one or more of polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber, graphene fiber and carbon fiber.

[0017] As a further optimization scheme of the present invention, in step 3, the shape of the polyimide structural core material preform is one of a hexagon, a rhombus, a triangle, a square matrix, and a grid structure; the preliminary finalized printing conditions are: using a printing needle with an outer diameter of 0.54 mm, a printing rate of 5 mm / s, a printing syringe temperature of 56°C, and a pressure output system pressure value of 0.15 MPa; the 3D printing technology is molten deposition, ink direct writing or inkjet technology.

[0018] As a further optimization scheme of the present invention, in step 4, the curing conditions are: placing the continuous fiber reinforced polyimide structural core material composite material preform into a heating device, and post-curing at a heating rate of 5°C / min under a temperature gradient of 80°C / 8h, 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h, 300°C / 1h, and 400°C / 1h.

[0019] As a further optimization scheme of the present invention, in step 4, the heating equipment is one of a high-temperature blast oven, a vacuum oven, a heating blanket, and a heating furnace.

[0020] The present invention also provides a continuous fiber reinforced polyimide structural core material composite material, the composite material is prepared by the 3D printing method, and the composite material consists of high-strength continuous fiber bundles and high-temperature resistant polyimide structural core material.

[0021] As a further optimization scheme of the present invention, the volume percentage of the continuous fiber tow in the composite material is 25% to 60%, and the volume percentage of the polyimide structural core material is 25% to 40%; the structural formula of the polyimide structural core material is as follows:

[0022]

[0023] Wherein, R and R' are aromatic structures containing a benzene ring.

[0024] The density of the structural composite material can be controlled by setting the length of the topological unit of the printing core material or adding continuous fibers; the input parameter conditions of the printing instrument are set as follows: matrix resin is 4-6mm / s, continuous fiber is 3-5mm / s, printing temperature is 50℃~60℃, hot air gun blowing temperature: 100℃~150℃, pressure output system air pressure: 0.1MPa~0.15MPa.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The polyamic acid salt hydrogel matrix resin for 3D printing prepared by the present invention is not only green and environmentally friendly, but also has good interfacial compatibility with continuous fibers due to the use of aqueous polymerization, and has good heat resistance while ensuring mechanical properties; on the other hand, the matrix resin has good thixotropy and shear thinning behavior, and the content of continuous fibers and matrix resin can be adjusted during printing. The "secondary reaction" printing method combining double-needle direct writing printing with high-temperature thermal imidization makes the prepared composite material have a complete structure, high precision and low shrinkage. At the same time, the polyamic acid salt hydrogel for printing has good thermoplasticity, does not rely on thermoplastic plastics as adhesives, and can be printed alone through 3D printing technologies such as melt deposition, direct writing, and inkjet.

[0027] (2) The continuous fiber reinforced polyimide structural core material composite material prepared by the present invention has excellent heat resistance, mechanical, flame retardant and chemical resistance properties, and has flexible structural designability, which is conducive to material lightweighting. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a temperature thixotropic performance diagram of the polyamic acid salt hydrogel resin for 3D printing prepared in Example 1.

[0029] Figure 2 This is the double needle 3D printing flow chart in Example 3.

[0030] Figure 3 This is a product picture of the continuous fiber reinforced polyimide structural core material composite material prepared in Example 3.

[0031] Figure 4 This is a graph showing the relationship between the topological unit length and density of the continuous fiber reinforced polyimide structural core material composite material in Example 3.

[0032] Figure 5 This is a side SEM image of the continuous fiber reinforced polyimide structural core material composite material in Example 3.

[0033] Figure 6 This is a compressive stress-strain curve of the continuous fiber reinforced polyimide structural core material composite material in Example 3.

[0034] Figure 7 This is the DMA test chart of the continuous fiber reinforced polyimide structural core material composite material in Example 3.

[0035] Figure 8 This is the thermal weight loss diagram of the continuous fiber reinforced polyimide structural core material composite material in Example 3 after being heat-resistant at 300°C for 30 hours. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred implementation scheme of the present invention is described below in conjunction with specific embodiments, but it should not be understood as limiting the present invention and is only used as an example.

[0037] Materials used:

[0038] Continuous carbon fiber (T300, 1K) was purchased from Toray Industries, Japan.

[0039] The instruments used are as follows:

[0040] The 3D printer was purchased from Fisnar, USA, model F4000N.1 series.

[0041] Thermomechanical Analyzer (DMA): purchased from TA Company, USA, model Q800.

[0042] Water bath: Changzhou Aohua Instrument Co., Ltd.; agitator: Shanghai Lichen Instrument Technology Co., Ltd.; rotational rheometer: TA Instruments, USA, model: Discovery HR-1; universal testing machine: Instron Instruments, USA, model: 5960; vacuum oven: Shanghai Mous Experimental Equipment Co., Ltd., model: DZF-610N; scanning electron microscope: FEI Company, USA, model: Nova nano450; thermogravimetric analyzer: TA Instruments, USA, model: Q50 series.

[0043] Example 1

[0044] A method for preparing a high temperature resistant polyamic acid salt hydrogel resin is as follows:

[0045] S1. Use an electronic balance to weigh 80g of 1,2-dimethylimidazole catalyst and pour it into 392.5g of deionized water. Stir with a glass rod until 1,2-dimethylimidazole is completely dissolved. Pour it into a 1000ml three-necked flask immediately and set the heating device temperature to 60°C:

[0046] S2. After the water bath temperature is constant, weigh 29.40g of p-phenylenediamine (PDA) and slowly add it into the three-necked flask. Stir mechanically until p-phenylenediamine (PDA) is completely dissolved. Then add 80g of 3,3',4,4'-biphenyltetracarboxylic anhydride (s-BPDA) in batches. Control the solid content of the system at 21.8wt%. Raise the water bath temperature from 60℃ to 85℃ and continue stirring for 4h. Finally, obtain a polyamic acid salt hydrogel resin for 3D printing with viscoelasticity. The temperature thixotropic properties of the synthesized polyamic acid salt hydrogel resin are as follows: Figure 1As shown, the resin has good viscosity reversibility during the printing heating-cooling process, which can ensure that the resin will not collapse due to gravity in a short period of time after flowing out of the printing needle, and can ensure that the basic printing path shape of the resin is maintained. The composite material printed with this resin has excellent heat resistance, mechanical and chemical corrosion resistance, good printing quality and high work efficiency. The prepared composite material is suitable for aerospace, automobile, shipbuilding, semiconductor and other fields.

[0047] Example 2

[0048] A method for preparing a polyamic acid salt impregnation solution is as follows:

[0049] S1. Use an electronic balance to weigh 50 g of 1,2-dimethylimidazole catalyst and pour it into 615.42 g of deionized water. Stir with a glass rod until 1,2-dimethylimidazole is completely dissolved. Pour it immediately into a 1000 ml three-necked flask and set the heating device temperature to 60 ° C.

[0050] S2. After the temperature of the water bath is constant, slowly add 18.38 g of p-phenylenediamine (PDA) into a three-necked flask and stir mechanically until the p-phenylenediamine (PDA) is completely dissolved. Then add 50 g of 3,3',4,4'-biphenyltetracarboxylic anhydride (s-BPDA) in batches and control the solid content of the system to 10 wt%. Raise the temperature of the water bath from 60°C to 85°C and continue stirring for 2 hours to obtain a polyacrylamide hydrochloride solution for the impregnation process of continuous fibers, which is beneficial to increase the interfacial compatibility between the continuous fiber layer and the resin.

[0051] Example 3

[0052] The present invention is described in detail below in conjunction with Embodiment 1 and Embodiment 2 and the accompanying drawings.

[0053] In this embodiment, the continuous fiber tow adopts T300-1K continuous carbon fiber.

[0054] Reference Figure 2, a 3D printing system for continuous fiber reinforced polyimide structural core composite material, mainly including a continuous carbon fiber bundle frame, an impregnation tank, a fiber pulling device, a filter, a continuous carbon fiber printer (i.e., a 3D printer), and a post-curing device. Under the action of the pulling force of the fiber pulling device 4, the continuous carbon fiber 1 is sized on the surface of the fiber bundle through the impregnation tank 2, and the resin impregnation liquid is evenly impregnated into the continuous carbon fiber 1 under the pressure of the extrusion roller group 3, and the conical aperture tube 5 homogenizes the excess slurry on the surface of the fiber bundle to obtain the impregnated continuous carbon fiber bundle 6 for 3D printing; the impregnated continuous fiber bundle 6 is sent to the printing nozzle 8 of the 3D printing device through the wire feeding roller group 7; on the other hand, the printing resin synthesized in Example 1 is pre-loaded into the syringe 10, and under the air pressure applied by the air pressure input system 11 and the heating and melting action of the heating device 12 in the syringe, the resin is melted and extruded from the needle, At the same time, the hot air gun 13 is moved to heat and pre-cure the printed resin layer so that it can quickly adhere to the printing platform 14; by adjusting the printing system, the double needles are alternately printed in layers, and after each layer of fiber layer is printed, the fiber is cut 9 and then the resin layer is printed, and a continuous fiber reinforced polyimide structural core material composite preform 15 is gradually and alternately layered on the platform according to the printing trajectory, and then the continuous fiber reinforced polyimide structural core material composite preform 15 is placed in a vacuum oven 16 for programmed temperature rise and curing, so that it undergoes a complete thermal imidization reaction and is converted into a continuous fiber reinforced polyimide structural core material composite material 17 with high temperature resistance and excellent mechanical properties.

[0055] A 3D printing method for a continuous fiber reinforced polyimide structural core material composite material comprises the following steps:

[0056] Step 1: Pour the polyamic acid salt hydrogel resin obtained in Example 1 into the printing syringe, and set the printing syringe temperature to 56°C for preheating. Pour the polyamic acid salt solution obtained in Example 2 into the impregnation tank, pass the continuous carbon fiber through the impregnation tank at 0.4m / min to size the fiber filaments, and use a 0.30mm diameter conical aperture tube to homogenize the excess slurry on the surface of the fiber bundle, and then feed the continuous carbon fiber bundle into the printing nozzle through the wire feeding roller device in turn, and control the fiber filament width to be 0.30mm, the fiber content to be 80%, and the sizing agent content to be 20%.

[0057] Step 2: Using the fiber tow and the polyamic acid salt hydrogel resin for printing, a continuous fiber reinforced polyimide structural core composite material preform is prepared by a direct writing 3D printer, and the printing instrument input conditions are set as follows: printing rate: 6mm / s, printing needle temperature: 56°C, mobile hot air gun blowing temperature: 150°C, air output system pressure value: 0.15MPa. The volume percentage of continuous fiber in the structural composite material is about 50%, and a continuous fiber reinforced polyimide grid core composite material preform is printed by alternating lamination.

[0058] Step 3: Place the continuous fiber reinforced polyimide grid core composite material preform into a vacuum oven, and perform post-curing at a temperature gradient of 80°C / 8h, 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h, 300°C / 1h, and 400°C / 1h at a heating rate of 5°C / min to convert it into the following through a thermal imidization reaction process: Figure 3 The product shown is a continuous fiber reinforced polyimide grid core composite material with high temperature resistance and excellent mechanical properties. The topological unit length of the printed core material can be freely controlled by adjusting the printing path, such as Figure 4 The relationship between the topological unit length and density of the continuous fiber reinforced polyimide grid core composite material was explored. The results showed that the topological unit length and density of the composite material followed a certain linear proportional relationship. By adjusting the printed grid unit length (3-10 mm), the density can be controlled to be 0.19-0.36 g / cm 3 Range, can realize the controllable printing of low-density products.

[0059] Reference Figure 5 and Figure 6 , Figure 5 The electron microscope photo of the side of the 3D printed continuous fiber reinforced polyimide grid core composite material of this embodiment is given, which proves the feasibility of preparing the continuous fiber reinforced polyimide core composite material by 3D printing of the present invention. Figure 6As shown, the compressive mechanical properties of the continuous carbon fiber reinforced polyimide core material and the non-fiber reinforced polyimide core material were compared through mechanical property tests. The test results show that the compressive yield stress values ​​of the non-fiber reinforced polyimide core material at different test temperatures are 30.80MPa (25°C), 23.37MPa (200°C), and 19.79MPa (250°C), respectively. The compressive yield stresses of the continuous fiber reinforced polyimide grid core composite material prepared by this embodiment are 65.45MPa (25°C), 49.07MPa (200°C), and 37.81MPa (250°C), respectively. The compressive resistance is improved by about 50%, indicating that the continuous fiber reinforced polyimide grid core composite material has excellent compressive resistance due to its I-beam structure.

[0060] Reference Figure 7 and Figure 8 , Figure 7 The glass transition temperature of the continuous fiber reinforced polyimide grid core composite material in the DMA test of this embodiment is 382.39°C, indicating that the continuous fiber reinforced polyimide grid core composite material prepared in this embodiment can be used for a long time at 350°C. Figure 8 As shown, the continuous fiber reinforced polyimide grid core composite material prepared in this embodiment is kept at 300° C. for 30 hours, and the thermal weight loss only decreases by 5wt%, which proves that the composite material has good heat resistance.

[0061] In summary, the present invention takes into account the existence of a transition state of polyamic acid salt in the process of synthesizing polyimide, and explores the "secondary reaction" process of direct writing 3D printing combined with thermal imidization, so that the prepared continuous fiber reinforced polyimide structural core material composite material has the characteristics of high temperature resistance and high strength. In order to ensure excellent mechanical properties while giving the material the characteristics of light weight, starting from the structural design, 3D printing of hollow and other structural core materials, so that it can give the material comprehensive properties such as light weight and high strength by virtue of its unique grid structure.

[0062] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A 3D printing method for a continuous fiber reinforced polyimide structural core composite material, characterized in that: The 3D printing method comprises: Step 1: Evenly dissolving aromatic amine and aromatic anhydride in an aprotic solvent, stirring at 70-90° C. for 2 hours for prepolymerization, and obtaining a prepolymer impregnation solution; evenly dissolving aromatic amine and aromatic anhydride in an aprotic solvent, stirring at 70-90° C. for 4 hours for polymerization reaction, and obtaining a resin glue solution for 3D printing; Step 2: impregnating the continuous fiber tow with the prepolymer impregnation liquid obtained in step 1, performing homogenization and filtration treatment on the excess impregnation liquid on the surface of the continuous fiber tow, and then transmitting it to the printing nozzle through a guide wheel for continuous fiber tow printing; Step 3: The resin glue obtained in step 1 is transferred to another printing syringe, the viscosity of the resin glue is adjusted by a printing heating device, the air piston pressure is given by an air pressure input system to control the extrusion amount of the glue printing, the 3D printing system adjusts the printing path, and the volatile solvent in the printed resin layer is removed by an external heat flow source to complete the partial curing of the resin, and the polyimide structural core material preform is initially shaped and printed; Step 4: Based on the continuous fiber tow and polyimide core material preform obtained in step 2 and step 3, a continuous fiber reinforced polyimide structural core material composite material preform is obtained by alternately stacking and printing layer by layer using a 3D printer, and then the preform is moved to a heating device for curing reaction. After curing, a continuous fiber reinforced polyimide structural core material composite material is obtained.

2. The 3D printing method of continuous fiber reinforced polyimide structural core composite material according to claim 1, characterized in that: The amount of the amine group in the structure of the aromatic amine is equal to the amount of the anhydride group in the structure of the aromatic anhydride; the reactant of the aromatic amine contains at least one of aromatic diamine, aromatic triamine and aromatic anhydride; the aromatic amine is one or more of the following structures: The aromatic anhydrides are one or more of the following structures:

3. The 3D printing method of continuous fiber reinforced polyimide structural core composite material according to claim 1, characterized in that: In step 1, the aprotic solvent is one or more of 2-ethyl-4-methylimidazole, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, 1,2-dimethylimidazole, dimethyl sulfoxide, dichloromethane, and triethylamine.

4. The 3D printing method of continuous fiber reinforced polyimide structural core composite material according to claim 1, characterized in that: In step 2, the continuous fiber bundle is immersed in an immersion tank, the immersion speed is set to 0.2-6 m / min, and the immersion temperature is set to 40-50°C.

5. The 3D printing method of continuous fiber reinforced polyimide structural core composite material according to claim 1, characterized in that: In step 2, the continuous fiber tow is one or more of polyacrylonitrile-based carbon fiber, asphalt-based carbon fiber, graphene fiber and carbon fiber.

6. The 3D printing method of continuous fiber reinforced polyimide structural core composite material according to claim 1, characterized in that: In step 3, the shape of the polyimide structural core material preform is one of a hexagon, a rhombus, a triangle, a square matrix, and a grid structure; the preliminary finalized printing conditions are: using a printing needle with an outer diameter of 0.54 mm, a printing rate of 5 mm / s, a printing syringe temperature of 56°C, and a pressure output system pressure value of 0.15 MPa.

7. The 3D printing method of continuous fiber reinforced polyimide structural core composite material according to claim 1, characterized in that: In step 4, the curing conditions are as follows: placing the continuous fiber reinforced polyimide structural core material composite preform into a heating device, and post-curing at a heating rate of 5°C / min under a temperature gradient of 80°C / 8h, 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h, 300°C / 1h, and 400°C / 1h.

8. The 3D printing method of continuous fiber reinforced polyimide structural core composite material according to claim 1 or 7, characterized in that: In step 4, the heating equipment is one of a high-temperature blast oven, a vacuum oven, a heating blanket, and a heating furnace.

9. A continuous fiber reinforced polyimide structural core material composite material, characterized in that: The composite material is prepared by the 3D printing method according to any one of claims 1 to 8, and the composite material consists of high-strength continuous fiber bundles and high-temperature resistant polyimide structural core materials.

10. The continuous fiber reinforced polyimide structural core material composite material according to claim 9, characterized in that: The volume percentage of the continuous fiber bundle in the composite material is 25% to 60%, and the volume percentage of the polyimide structural core material is 25% to 40%; the structural formula of the polyimide structural core material is as follows: Wherein, R and R' are aromatic structures containing a benzene ring.

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