Composite 3D printing ink and preparation method and application thereof

Abstract

The application provides a kind of composite 3D printing ink and its preparation method and application, belong to 3D printing technical field.The composite 3D printing ink provided by the application includes polyamide acid salt, graphene oxide, photoinitiator and organic solvent;The polyamide acid salt has the structure shown in formula I.Using the composite 3D printing ink provided by the application for 3D printing, the printing product with excellent mechanical properties, thermal performance and high-precision customized geometric shape can be obtained, which greatly expands the application of 3D printing technology in high temperature and high strength field.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of 3D printing, and particularly relates to a composite 3D printing ink as well as a preparation method and application thereof. BACKGROUND

[0002] 3D printing is a layer-by-layer manufacturing process for converting a 3D virtual model into a three-dimensional object by using computer-aided design (CAD), and can produce customized structures that cannot be achieved by traditional manufacturing techniques. Direct ink writing (DIW printing) is a kind of 3D printing technology based on the principle of extrusion, which applies a movable printing nozzle to deposit polymer slurry on a printing platform according to a 3D designed model, and then the polymer chains are entangled or bonded to solidify, thereby obtaining the target object.

[0003] At present, the materials used for DIW printing are mainly hydrogels, elastomers or thermoplastic plastics, etc. These materials have many obvious shortcomings, such as poor printing performance, low mechanical properties and insufficient thermal stability, which cannot meet the actual application in most industrial fields.

[0004] Polyimide (PI) has excellent mechanical properties, high and low temperature resistance, chemical resistance and corrosion resistance, flexibility and excellent dielectric properties, and thus becomes one of the commonly used engineering polymer materials in the field. However, due to the poor solubility and meltability of polyimide, and the lack of photocuring groups in its molecular structure, it is difficult to directly use polyimide as a 3D printing raw material for processing and molding to prepare high-performance polymers. SUMMARY

[0005] The purpose of the present application is to provide a composite 3D printing ink as well as a preparation method and application thereof. The 3D printing ink provided by the present application can be used for 3D printing, and can obtain a printing product with excellent mechanical properties, thermal properties and high-precision customized geometric shape, greatly expanding the application of 3D printing technology in high-temperature and high-strength fields.

[0006] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0007] The present application provides a composite 3D printing ink, which comprises a polyamide acid salt, graphene oxide, a photoinitiator and an organic solvent; the polyamide acid salt has a structure shown in Formula I:

[0008]

[0009] In Formula I, n is 13-65.

[0010] Preferably, the preparation method of the polyamide acid salt comprises the following steps:

[0011] The hexafluorodianhydride and 2,2'-bis(trifluoromethyl)-(1,1'-biphenyl)-4,4'-diamine are mixed with N,N-dimethylformamide to perform a polycondensation reaction to obtain a polyamic acid solution;

[0012] The polyamic acid solution is mixed with dimethylaminoethyl methacrylate to perform electrostatic interaction to obtain the polyamic acid salt.

[0013] Preferably, the molar ratio of the hexafluorodianhydride to 2,2'-bis(trifluoromethyl)-(1,1'-biphenyl)-4,4'-diamine is 1:0.9-1; and the mass ratio of the polyamic acid solution to dimethylaminoethyl methacrylate is 1:0.02-0.08.

[0014] Preferably, the mass ratio of the polyamic acid salt to graphene oxide is 20-200:1.

[0015] Preferably, the photoinitiator comprises at least one of diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone and 2,4,6-trimethylbenzoyl phosphonic acid ethyl ester; and the mass ratio of the polyamic acid salt to the photoinitiator is 30-100:1.

[0016] Preferably, the organic solvent comprises at least one of N,N-dimethylformamide, N-methylpyrrolidone and N,N-dimethylacetamide.

[0017] The application provides a preparation method of the composite 3D printing ink.

[0018] The polyamic acid salt, graphene oxide, photoinitiator and organic solvent are mixed to obtain the composite 3D printing ink.

[0019] The application provides an application of the composite 3D printing ink or the composite 3D printing ink prepared by the preparation method in 3D printing.

[0020] Preferably, the 3D printing is DIW printing.

[0021] Preferably, the printing layer height of the 3D printing is 200-400 mu m, the printing speed is 0.2-1.2 mm / s, and the extrusion pressure is 0.5-2 MPa.

[0022] The application provides a composite 3D printing ink, which comprises a polyamide acid salt, graphene oxide, a photoinitiator and an organic solvent, and the polyamide acid salt has a structure shown in formula I. In the application, the polyamide acid salt has a large number of rigid benzene ring structures in the structure, which endows the obtained printing product with excellent mechanical properties; meanwhile, the graphene oxide (GO) as a reinforcing filler can improve the forming properties and mechanical properties of the obtained printing product; and the photoinitiator can make the obtained printing product have higher resolution, and can realize fine printing of complex structures. The composite 3D printing ink provided by the application is used for 3D printing, and a printing product with excellent mechanical properties, thermal properties and high printing resolution and high-precision customized geometric shape can be obtained, which greatly expands the application of 3D printing technology in the field of high temperature and high strength.

[0023] Further, the application provides a preparation method of the composite 3D printing ink. In the application, a polyamide acid (PAA) as a polyimide precursor is used as a polymer matrix, and a polyamide acid salt (PAAS) with printing properties is formed through electrostatic interaction with dimethylaminoethyl methacrylate (DMAEMA); meanwhile, the graphene oxide (GO) is introduced into the polyamide acid salt as a reinforcing filler, and a high-performance polyamide acid salt / graphene oxide composite 3D ink with excellent printing forming properties is prepared. The composite 3D ink provided by the application has excellent printability, and the printing product obtained by using the composite 3D ink provided by the application for 3D printing has excellent mechanical strength (high strength and high toughness), thermal stability and shape retention capacity. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0025] Figure 1 NMR spectra of polyamide acid and polyamide acid salt;

[0026] Figure 2 Stress-strain curve of PAAS / GO composite ink with different contents of graphene oxide;

[0027] Figure 3 Modulus and toughness spectrum of PAAS / GO composite material with different contents of graphene oxide;

[0028] Figure 4 Actual product picture of a printing product obtained by DIW printing from PAAS / GO composite ink;

[0029] Figure 5 Stress-strain curves of polyamic acid salts with different DMAEMA contents;

[0030] Figure 6 Modulus and toughness spectra of polyamic acid salts with different DMAEMA contents. DETAILED DESCRIPTION

[0031] The application provides a composite 3D printing ink, which comprises a polyamic acid salt, graphene oxide, a photoinitiator and an organic solvent; the polyamic acid salt has the structure shown in formula I.

[0032]

[0033] In formula I, n is 13-65, and is preferably 50-65.

[0034] In the application, if no special description is given, all raw materials used are commercially available or are prepared by methods known to those skilled in the art.

[0035] The preparation raw material of the composite 3D printing ink provided by the application comprises a polyamic acid salt. In the application, the polyamic acid salt has the structure shown in formula I. The preparation raw material of the polyamic acid salt provided by the application preferably comprises hexafluorodiphthalic anhydride, 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine, N,N-dimethylformamide and dimethylaminoethyl methacrylate.

[0036] The preparation method of the polyamic acid salt provided by the application preferably comprises the following steps: mixing hexafluorodiphthalic anhydride, 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine and N,N-dimethylformamide, and performing polycondensation reaction to obtain a polyamic acid solution; mixing the polyamic acid solution with dimethylaminoethyl methacrylate, and performing electrostatic interaction to obtain the polyamic acid salt.

[0037] The present application mixes hexafluorodiphthalic anhydride and 2,2'-bis(trifluoromethyl)-(1,1'-biphenyl)-4,4'-diamine with N,N-dimethylformamide to carry out polycondensation reaction to obtain a polyamic acid solution. In the present application, the molar ratio of the hexafluorodiphthalic anhydride to 2,2'-bis(trifluoromethyl)-(1,1'-biphenyl)-4,4'-diamine is preferably 1:0.9-1, more preferably 1:1. The present application preferably dissolves 2,2'-bis(trifluoromethyl)-(1,1'-biphenyl)-4,4'-diamine in N,N-dimethylformamide to obtain a first feed solution; the present application preferably carries out the dissolution of 2,2'-bis(trifluoromethyl)-(1,1'-biphenyl)-4,4'-diamine under a nitrogen atmosphere. The present application preferably adds hexafluorodiphthalic anhydride into the first feed solution in batches under ice water bath conditions to carry out polycondensation reaction to obtain a polyamic acid solution. In the present application, the temperature of the polycondensation reaction is preferably 0-5°C, more preferably 0°C; the time is preferably 8-24 hours, more preferably 12 hours. The polycondensation reaction of the present application is preferably carried out under stirring conditions. The present application does not have special limitations on the stirring mode and conditions, and any stirring mode known to those skilled in the art can be used.

[0038] After the polycondensation reaction, the present application does not need to carry out post-treatment, and directly mixes the obtained polyamic acid solution with dimethylaminoethyl methacrylate to carry out electrostatic interaction to obtain the polyamic acid salt. In the present application, the mass ratio of the polyamic acid solution to dimethylaminoethyl methacrylate is preferably 1:0.02-0.08, more preferably 1:0.04-0.08. In the present application, the temperature of the electrostatic interaction is preferably room temperature; the time is preferably 10-24 hours, more preferably 24 hours. The electrostatic interaction of the present application is preferably carried out under stirring conditions. The present application does not have special limitations on the stirring mode and conditions, and any stirring mode known to those skilled in the art can be used. After the electrostatic interaction, the present application preferably pours the obtained polyamic acid salt solution into water to precipitate a solid, and then carries out solid-liquid separation on the obtained feed solution to collect the solid material; the obtained solid material is dried to obtain a polyamic acid salt. In the present application, the solid-liquid separation mode is preferably filtration; the drying temperature is preferably 50-100°C, more preferably 80°C; the time is preferably 10-24 hours, more preferably 24 hours.

[0039] The preparation raw material of the composite 3D printing ink of the present application comprises graphene oxide. In the present application, the mass ratio of the polyamic acid salt to graphene oxide is preferably 20-200:1, more preferably 50-200:1. In the present application, the mass fraction of graphene oxide in the composite 3D printing ink is preferably 0.5-3%, and can be 0.5%, 1%, 2% or 3% in particular.

[0040] The preparation raw material of the composite 3D printing ink provided by the present application comprises a photoinitiator. In the present application, the photoinitiator preferably comprises at least one of diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide (photoinitiator TPO), 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone (photoinitiator 819) and 2,4,6-trimethylbenzoyl ethyl phosphinate, and more preferably diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide. In the present application, the mass ratio of the polyamic acid salt to the photoinitiator is preferably 30-100:1, and more preferably 50-80:1.

[0041] The preparation raw material of the composite 3D printing ink provided by the present application comprises an organic solvent. In the present application, the organic solvent preferably comprises at least one of N,N-dimethylformamide, N-methylpyrrolidone and N,N-dimethylacetamide, and more preferably N,N-dimethylformamide.

[0042] The present application also provides a preparation method of the composite 3D printing ink as described in the above technical solution, which comprises the following steps:

[0043] The polyamic acid salt, graphene oxide, photoinitiator and organic solvent are mixed to obtain the composite 3D printing ink.

[0044] In the present application, the mass ratio of the polyamic acid salt to the part of the organic solvent is preferably 1-4:1, and more preferably 1-3:1; and the mass ratio of the acetone to the part of the organic solvent is preferably 3-7:1-3, and more preferably 5:1.5. The acetone is used in the present application to improve the fluidity of the ink, so that the graphene oxide and the photoinitiator can be more uniformly dispersed in the ink.

[0045] In the present application, the mass fraction of the graphene oxide in the graphene oxide dispersion is preferably 5-20%, and specifically can be 5%, 10%, 15% or 20%.

[0046] The polyamic acid salt solution, graphene oxide dispersion and photoinitiator are mixed to obtain the composite 3D printing ink. The mixing method is not particularly limited in the present application, and any mixing method known to those skilled in the art can be used. After the mixing, the acetone in the obtained liquid is preferably removed, and the removal method of the acetone is preferably drying the liquid. In the present application, the drying is preferably vacuum drying.

[0047] The application further provides application of the composite 3D printing ink or the composite 3D printing ink prepared by the preparation method in 3D printing.

[0048] In the application, the 3D printing is preferably DIW printing. In the application, the printer used for the 3D printing is preferably an ultraviolet-assisted-ink direct writing printer (UV-assisted-DIW printer); the diameter of the pneumatic nozzle used for the printer is preferably 250-500 μm, and can be specifically 250 μm, 350 μm, 400 μm or 500 μm. In the application, the printing layer height of the 3D printing is preferably 200-400 μm, and can be specifically 200 μm, 300 μm or 400 μm; the printing speed is preferably 0.2-1.2 mm / s, and more preferably 0.6 mm / s; and the extrusion pressure is preferably 0.5-2 MPa, and more preferably 1 MPa.

[0049] The technical solutions in the application will be described clearly and completely in combination with the embodiments in the application. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0050] The reagents used in the embodiments are as follows:

[0051] Hexafluorodianhydride (6FDA), 2,2'-bis(trifluoromethyl)-(1,1'-biphenyl)-4,4'-diamine (TFDB), dimethylaminoethyl methacrylate (DMAEMA), N,N-dimethylformamide (DMF), graphene oxide (GO), acetone, water and diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide (photoinitiator TPO);

[0052] The printer used in the embodiments is a UV-assisted-DIW printer available on the market.

[0053] Embodiment 1

[0054] (1) Preparation of polyamic acid salt (PAAS): TFDB (5 mmol, 1.6 g) was dissolved in 16 g DMF to obtain a first feed solution; 6FDA (5 mmol, 2.22 g) was added to the first feed solution in batches under the condition of ice water bath and the reaction was continuously stirred for 12 hours, and a polyamic acid (PAA) solution was obtained after the reaction was completed. DMAEMA (10 mmol, 1.57 g) was added to the PAA solution, and electrostatic interaction was carried out under the condition of stirring at room temperature for 24 hours, and a polyamic acid salt (PAAS) solution was obtained after the end. The PAAS solution was poured into water to precipitate a solid, which was filtered and collected, and then placed in a vacuum oven and treated at 80°C for 24 hours, and a white solid, i.e. PAAS solid, was obtained after the end.

[0055] (2) Preparation of polyamic acid salt (PAAS) / graphene oxide (GO) composite ink:

[0056] The PAAS solid (2 g) obtained in the above step was dissolved in a mixed solvent of 1.5 g DMF and 5 g acetone to obtain a PAAS solution; 1 g of graphene oxide (GO) was dissolved in 9 g of DMF solvent to obtain a GO dispersion with a mass fraction of 10%; the PAAS solution, 0.1 g of GO dispersion and 0.04 g of photoinitiator TPO were mixed, and the obtained feed solution was placed in a vacuum oven to completely remove acetone, and a PAAS / GO composite 3D printing ink (GO content of 0.5 wt%) was obtained, which was ready for use.

[0057] The nuclear magnetic resonance spectrum of PAA and PAAS is shown in Figure 1 .

[0058] As can be seen from Figure 1 , 1 H NMR (DMSO, 400 MHz, δ (ppm)): 7-8 ppm is the hydrogen on the benzene ring in PAA, and 11 ppm is the carboxyl hydrogen in PAA. With the addition of DMAEMA, the peak at 11 ppm disappears, and a vinyl hydrogen peak appears at 6 ppm, indicating that PAA and DMAEMA have electrostatic interaction, proving the successful preparation of PAAS.

[0059] Application Example 1

[0060] (1) Preparation of DIW printed high-resolution parts

[0061] The PAAS / GO composite 3D printing ink prepared in Example 1 was loaded into the normal temperature cartridge of the printer, a pneumatic nozzle with a diameter of 250 μm was selected, the printing layer height was set to 200 μm, the printing speed was 0.6 mm / s, and the extrusion pressure was 1 MPa, and DIW printing was carried out to obtain a DIW printed product.

[0062] The results show that the PAAS / GO composite 3D printing ink has excellent printability, the ink can be continuously extruded from the nozzle smoothly, and the shape of the ink is maintained after being extruded into a filament. When the UV light source is irradiated subsequently, the photochemical sites inside the ink are crosslinked, and the bonding between the filaments and the layers is formed, so that the obtained DIW printing product has excellent self-supporting performance and becomes a whole component with strong bonding force.

[0063] (2) Post-thermal curing treatment

[0064] The DIW printing product obtained in (1) is naturally air-dried at room temperature for 48 hours, and then dried in an oven at 80°C for 12 hours to obtain a 3D molded part.

[0065] During the post-thermal curing treatment, the solvent in the DIW printing product is continuously removed, and the free radical polymerization reaction between the photochemical sites is further promoted, so that a more dense crosslinked network structure is formed inside the DIW printing product, and the mechanical properties and thermal stability of the obtained 3D molded part are improved.

[0066] Test Example 1

[0067] The tensile strength, toughness and modulus of the 3D molded part were tested by the method of ISO527-2 / 1BB, and the test results are shown in Figure 2 and Figure 3 .

[0068] As shown in Figure 2 and Figure 3 , the tensile strength of the 3D printing part with a GO content of 0.5wt% is 57MPa, the modulus is 1.8GPa, and the toughness is 6.2MJ / m 3 .

[0069] The actual figure of the high-resolution printing product obtained by DIW printing of the PAAS / GO composite 3D printing ink prepared by the present application is shown in Figure 4 .

[0070] Example 2

[0071] (1) The preparation conditions of PAAS solid are the same as those in Example 1.

[0072] (2) Preparation of polyamide acid salt (PAAS) / graphene oxide (GO) composite ink:

[0073] The PAAS solid obtained in the above step (2 g) was dissolved in a mixed solvent of 1.5 g DMF and 5 g acetone to obtain a PAAS solution; 2 g of graphene oxide (GO) was dissolved in 8 g of DMF solvent to obtain a GO dispersion with a mass fraction of 20%; the PAAS solution, 0.1 g of the GO dispersion, and 0.04 g of a photoinitiator TPO were mixed, and the obtained solution was placed in a vacuum oven to completely remove the acetone after uniform stirring, to obtain a PAAS / GO composite 3D printing ink (GO content of 1 wt%), which was ready for use.

[0074] Application Example 2

[0075] (1) DIW printing of high-resolution parts

[0076] The PAAS / GO composite 3D printing ink prepared in Example 2 was loaded into the normal-temperature cartridge of the printer, a pneumatic nozzle with a diameter of 350 μm was selected, the printing layer height was set to 300 μm, the printing speed was 0.6 mm / s, and the extrusion pressure was 1 MPa, and DIW printing was performed to obtain a DIW printed product.

[0077] The results show that the PAAS / GO composite 3D printing ink has excellent printability, the ink can be continuously extruded from the nozzle smoothly, and the shape of the filament is maintained after extrusion. When the UV light source is irradiated subsequently, the photochemical sites inside the ink are crosslinked, and the keying action between the filaments and between the layers is formed, so that the obtained DIW printed product has excellent self-supporting performance and becomes a whole part with strong binding force.

[0078] (2) Post-thermal curing treatment

[0079] The DIW printed product obtained in (1) was naturally air-dried at room temperature for 48 hours, and then dried in an oven at 80°C for 12 hours to obtain a 3D molded part.

[0080] During the post-thermal curing treatment, the solvent in the DIW printed product is continuously removed, and the free radical polymerization reaction between the photo-reaction sites is further promoted, so that a more dense crosslinked network structure is formed inside the DIW printed product, and the mechanical properties and thermal stability of the obtained 3D molded part are improved.

[0081] Test Example 2

[0082] The performance of the 3D printed part with a GO content of 1 wt% was tested according to the conditions of Test Example 1, and the test results are shown in Figure 2 and Figure 3 , as follows: the tensile strength is 62 MPa, the modulus is 1.95 GPa, and the toughness is 9.3 MJ / m 3 .

[0083] Example 3

[0084] (1) Preparation conditions of PAAS solid are the same as those in Example 1.

[0085] (2) Preparation of polyamide acid salt (PAAS) / graphene oxide (GO) composite ink:

[0086] The PAAS solid (2 g) obtained in the above step was dissolved in a mixed solvent of 1.4 g DMF and 5 g acetone to obtain a PAAS solution; 2 g of graphene oxide (GO) was dissolved in 8 g of DMF solvent to obtain a GO dispersion with a mass fraction of 20%; the PAAS solution, 0.2 g of GO dispersion and 0.04 g of photoinitiator TPO were mixed, and the obtained solution was placed in a vacuum oven after uniform stirring to completely remove the acetone, thereby obtaining a PAAS / GO composite 3D printing ink (GO content: 2 wt%) for standby.

[0087] Application Example 3

[0088] (1) DIW printing of high-resolution parts

[0089] The PAAS / GO composite 3D printing ink prepared in Example 3 was loaded into the normal-temperature cartridge of the printer, a pneumatic nozzle with a diameter of 400 μm was selected, the printing layer height was set to 300 μm, the printing speed was set to 0.6 mm / s, and the extrusion pressure was set to 1 MPa, and then DIW printing was performed to obtain a DIW printed product.

[0090] The results show that the PAAS / GO composite 3D printing ink has excellent printability, the ink can be continuously extruded from the nozzle smoothly, and the shape of the filament is maintained after extrusion. When the UV light source is irradiated subsequently, the photochemical sites inside the ink are crosslinked, and the keying action between the filaments and between the layers is formed, so that the obtained DIW printed product has excellent self-supporting performance and becomes an integral part with strong binding force.

[0091] (2) Post-thermal curing treatment

[0092] The DIW printed product obtained in (1) was naturally air-dried at room temperature for 48 hours, and then dried in an oven at 80°C for 12 hours to obtain a 3D molded part.

[0093] During the post-thermal curing treatment, the solvent in the DIW printed product is continuously removed, and the free radical polymerization reaction between the photochemical sites is further promoted, so that a more dense crosslinked network structure is formed inside the DIW printed product, thereby improving the mechanical properties and thermal stability of the obtained 3D molded part.

[0094] Test Example 3

[0095] The performance of 3D printed parts with 2wt% GO content was tested according to the conditions of Test Example 1. The test results are as follows: Figure 2 and Figure 3 As shown, the specifics are as follows: tensile strength is 54 MPa, modulus is 1.7 GPa, and toughness is 3.4 MJ / m. 3 .

[0096] Example 4

[0097] (1) The preparation conditions of PAAS solid were the same as those in Example 1.

[0098] (2) Preparation of polyamic acid salt (PAAS) / graphene oxide (GO) composite ink:

[0099] The PAAS solid (2g) obtained in the previous step was dissolved in a mixed solvent of 1.3g DMF and 5g acetone to obtain a PAAS solution; 2g graphene oxide (GO) was dissolved in 8g DMF to obtain a GO dispersion with a mass fraction of 20%; the PAAS solution, 0.3g GO dispersion and 0.04g photoinitiator TPO were mixed and stirred evenly, and the resulting liquid was placed in a vacuum oven to completely remove acetone to obtain PAAS / GO composite 3D printing ink (GO content of 3wt%) for later use.

[0100] Application Example 4

[0101] (1) DIW printing of high-resolution components

[0102] The PAAS / GO composite 3D printing ink prepared in Example 3 was loaded into the room temperature barrel of the printer. A pneumatic nozzle with a diameter of 500 μm was selected, the printing layer height was set to 400 μm, the printing speed was 0.6 mm / s, and the extrusion pressure was 1 MPa. DIW printing was performed to obtain DIW printed products.

[0103] The results show that the PAAS / GO composite 3D printing ink has excellent printability. The ink can be smoothly and continuously extruded from the nozzle and maintain its shape after being extruded into filaments. When irradiated by a UV light source, the photochemical sites inside the ink cross-link, forming bonds between filaments and between layers. This results in DIW printed products with excellent self-supporting properties and become a strongly bonded integral part.

[0104] (2) Post-heat curing treatment

[0105] The DIW printed product obtained in (1) was air-dried at room temperature for 48 hours, and then placed in an oven at 80°C for 12 hours to obtain a 3D molded part.

[0106] During the post-thermo-curing process, the solvent in the DIW printed product is continuously removed, and the free radical polymerization reaction between the photoreactive sites is further promoted, resulting in a denser cross-linked network structure inside the DIW printed product, which improves the mechanical properties and thermal stability of the obtained 3D molded parts.

[0107] Test Example 4

[0108] The performance of 3D printed parts with 3wt% GO content was tested according to the conditions of Test Example 1. The test results are as follows: Figure 2 and Figure 3 As shown, the specifics are as follows: tensile strength is 46 MPa, modulus is 1.75 GPa, and toughness is 1.5 MJ / m. 3 .

[0109] Comparative Example 1

[0110] TFDB (5 mmol, 1.6 g) was dissolved in 16 g DMF under a nitrogen atmosphere to obtain the first solution. 6 FDA (5 mmol, 2.22 g) was added in batches to the first solution under ice-water bath conditions with continuous stirring for 12 hours. After the reaction was complete, a polyamic acid (PAA) solution was obtained. DMAEMA (10 mmol, 1.57 g) was added to the PAA solution, and electrostatic interaction was carried out with stirring at room temperature for 24 hours. After the reaction was completed, a polyamic acid salt (PAAS) solution was obtained. The PAAS solution was poured into water to precipitate a solid. After filtration, the solid was collected and placed in a vacuum oven at 80°C for 24 hours. After the treatment, a white solid was obtained, which was the PAAS solid.

[0111] The PAAS solid (2g) was dissolved in a mixed solvent of 1.6g DMF and 5g acetone to obtain a PAAS solution; 0.04g photoinitiator TPO was added to the PAAS solution, and after stirring evenly, the resulting liquid was placed in a vacuum oven to completely remove the acetone, thus obtaining pure PAAS ink.

[0112] Comparative Application Example 1

[0113] The pure PAAS ink obtained in Comparative Example 1 was loaded into the room temperature cartridge of the printer and subjected to UV-assisted direct ink writing printing (UV-assisted DIW printing) to obtain a 3D printed product.

[0114] The 3D printed product was air-dried at room temperature for 48 hours, and then placed in an oven at 80°C for 12 hours to obtain a 3D molded part.

[0115] Comparative Test Example 1

[0116] The 3D shaped part was tested for tensile strength, toughness and modulus using the method of ISO527-2 / 1BB.

[0117] Figure 5 Stress-strain curves of polyamide acid salts with different DMAEMA contents;

[0118] Figure 6 Modulus and toughness spectra of polyamide acid salts with different DMAEMA contents;

[0119] As shown in Figure 5 With Figure 6 The tensile strength of the 3D shaped part was 58 MPa, the modulus was 1.6 GPa, and the toughness was 2.4 MJ / m 3 .

[0120] Comparative Example 2

[0121] TFDB (5 mmol, 1.6 g) was dissolved in 16 g of DMF under a nitrogen atmosphere to obtain a first feed solution; 6FDA (5 mmol, 2.22 g) was added to the first feed solution in batches under ice water bath conditions and the reaction was continuously stirred for 12 hours, and a polyamide acid (PAA) solution was obtained after the reaction was completed. DMAEMA (7.5 mmol, 1.18 g) was added to the PAA solution and electrostatic interaction was carried out under stirring at room temperature for 24 hours, and a polyamide acid salt (PAAS) solution was obtained after the end. The PAAS solution was poured into water to precipitate a solid, which was filtered and collected, and then placed in a vacuum oven for treatment at 80°C for 24 hours, and a white solid, i.e. PAAS solid, was obtained after the end.

[0122] The PAAS solid (2 g) was dissolved in a mixed solvent of 1.6 g of DMF and 5 g of acetone to obtain a PAAS solution; 0.04 g of a photoinitiator TPO was added to the PAAS solution, and after stirring uniformly, the obtained feed solution was placed in a vacuum oven to completely remove the acetone, and a pure PAAS ink was obtained.

[0123] Comparative Example 2

[0124] The pure PAAS ink obtained in Comparative Example 2 was loaded into a normal-temperature cartridge of a printer, and ultraviolet-assisted direct ink writing printing (UV-assisted-DIW printing) was carried out to obtain a 3D printed product.

[0125] The 3D printed product was naturally air-dried at room temperature for 48 hours, and then placed in an oven for drying at 80°C for 12 hours to obtain a 3D shaped part.

[0126] Comparative Test Example 2

[0127] The 3D shaped part was tested for tensile strength, toughness and modulus in the same manner and under the same conditions as Comparative Test Example 1, and the test results are shown in Table 1 as follows: tensile strength of 53 MPa, modulus of 1.65 GPa, and toughness of 2.15 MJ / m Figure 5 As shown in Table 1, specifically as follows: tensile strength of 53 MPa, modulus of 1.65 GPa, and toughness of 2.15 MJ / m Figure 6 As shown in Table 1, specifically as follows: tensile strength of 53 MPa, modulus of 1.65 GPa, and toughness of 2.15 MJ / m 3 .

[0128] Comparative Example 3

[0129] TFDB (5 mmol, 1.6 g) was dissolved in 16 g of DMF under a nitrogen atmosphere to obtain a first solution; 6FDA (5 mmol, 2.22 g) was added to the first solution in batches under an ice water bath and the reaction was continuously stirred for 12 hours, and a polyamic acid (PAA) solution was obtained after the reaction was completed. DMAEMA (5 mmol, 0.79 g) was added to the PAA solution, and electrostatic interaction was carried out under stirring at room temperature for 24 hours, and a polyamic acid salt (PAAS) solution was obtained after the end. The PAAS solution was poured into water to precipitate a solid, which was filtered and collected, and then placed in a vacuum oven and treated at 80°C for 24 hours, and a white solid, i.e. PAAS solid, was obtained after the end.

[0130] The PAAS solid (2 g) was dissolved in 1.6 g of DMF and 5 g of acetone to obtain a PAAS solution; 0.04 g of a photoinitiator TPO was added to the PAAS solution, and after stirring uniformly, the obtained solution was placed in a vacuum oven to completely remove the acetone, and a pure PAAS ink was obtained.

[0131] Comparative Application Example 3

[0132] The pure PAAS ink obtained in Comparative Example 3 was loaded into a normal-temperature cartridge of a printer, and ultraviolet-assisted direct ink writing printing (UV-assisted DIW printing) was carried out to obtain a 3D printed product.

[0133] The 3D printed product was naturally air-dried at room temperature for 48 hours, and then placed in an oven and dried at 80°C for 12 hours to obtain a 3D shaped part.

[0134] Comparative Test Example 3

[0135] The 3D shaped part was tested for tensile strength, toughness and modulus in the same manner and under the same conditions as Comparative Test Example 1, and the test results are shown in Table 1 as follows: tensile strength of 53 MPa, modulus of 1.65 GPa, and toughness of 2.15 MJ / m Figure 5 As shown in Table 1, specifically as follows: tensile strength of 53 MPa, modulus of 1.65 GPa, and toughness of 2.15 MJ / m Figure 6 As shown in Table 1, specifically as follows: tensile strength of 53 MPa, modulus of 1.65 GPa, and toughness of 2.15 MJ / m 3 .

[0136] Comparative Example 4

[0137] The TFDB (5 mmol, 1.6 g) was dissolved in 16 g of DMF to obtain a first solution; the 6FDA (5 mmol, 2.22 g) was added to the first solution in batches under the condition of ice water bath and the reaction was continuously stirred for 12 hours, and a polyamic acid (PAA) solution was obtained after the reaction was completed. The DMAEMA (2.5 mmol, 0.4 g) was added to the PAA solution and the electrostatic interaction was carried out under the condition of stirring at room temperature for 24 hours, and a polyamic acid salt (PAAS) solution was obtained after the end. The PAAS solution was poured into water to precipitate a solid, the solid was collected by filtration and was placed in a vacuum oven under the condition of 80℃ for 24 hours, and a white solid, i.e. the PAAS solid, was obtained after the end.

[0138] The PAAS solid (2 g) was dissolved in a mixed solvent of 1.6 g of DMF and 5 g of acetone to obtain a PAAS solution; 0.04 g of a photoinitiator TPO was added to the PAAS solution, and the obtained solution was placed in a vacuum oven after being uniformly stirred to completely remove the acetone, and a pure PAAS ink was obtained.

[0139] Comparative application example 4

[0140] The pure PAAS ink obtained in Comparative Example 4 was loaded into a normal-temperature cartridge of a printer, and ultraviolet-assisted direct ink writing printing (UV-assisted DIW printing) was carried out to obtain a 3D printed product.

[0141] The 3D printed product was naturally air-dried at room temperature for 48 hours, and then was placed in an oven to be dried at 80℃ for 12 hours, and a 3D molded part was obtained.

[0142] Comparative test example 4

[0143] The 3D molded part was tested for tensile strength, toughness and modulus in the manner and under the conditions of Comparative Test Example 1, and the test results were as shown in Table 1 and Table 2. Figure 5 and Figure 6 Specifically, the tensile strength was 41 MPa, the modulus was 1.4 GPa, and the toughness was 0.5 MJ / m 3 .

[0144] As can be seen from the above examples and comparative examples, a high-performance composite 3D printing ink is prepared by the present application, and the high performance of the composite 3D printing ink is reflected in the excellent printing formability of the ink and the super-high mechanical properties of the 3D printed product obtained therefrom.

[0145] The excellent mechanical performance of the 3D printing part printed by the composite 3D printing ink is due to two aspects of design: 1. The polyimide precursor-polyamide acid (PAA) is designed as the matrix of the composite 3D printing ink, and a large number of rigid benzene ring structures are contained therein to improve the strength of the printing part; 2. The graphene oxide (GO) is used as the reinforcing filler of the composite 3D printing ink; the composite 3D printing ink prepared in this way obtains the 3D formed part with high resolution and excellent mechanical performance through DIW printing. In summary, the application prepares a high-performance composite 3D printing ink for DIW printing, and the customized printing product obtained thereby has excellent comprehensive performance and is expected to be used in high-temperature, high-strength and other high-performance fields.

[0146] Although the above embodiment has made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiment without creativity, which all belong to the protection scope of the present application.

Claims

1. A method for preparing a composite 3D printing ink, characterized in that, Includes the following steps: Hexafluorodianhydride, 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine and N,N-dimethylformamide were mixed and subjected to a polycondensation reaction to obtain a polyamic acid solution. The polyamic acid solution is mixed with dimethylaminoethyl methacrylate and subjected to electrostatic interaction. After electrostatic interaction, the resulting polyamic acid salt solution is poured into water to precipitate solids. The resulting liquid is then subjected to solid-liquid separation, and the solid material is collected. The obtained solid material is dried to obtain polyamic acid salt. The polyamic acid salt has the structure shown in Formula I: In Equation I, n ranges from 13 to 65; The polyamic acid salt is dissolved in acetone and a portion of the organic solvent to obtain a polyamic acid salt solution; graphene oxide is dispersed in the remaining organic solvent to obtain a graphene oxide dispersion; the organic solvent includes at least one of N,N-dimethylformamide, N-methylpyrrolidone, and N,N-dimethylacetamide; The polyamic acid salt solution, graphene oxide dispersion, and photoinitiator are mixed to obtain the composite 3D printing ink; the mass ratio of polyamic acid salt to graphene oxide is 20-200:1, and the mass fraction of graphene oxide in the composite 3D printing ink is 0.5-3%.

2. The preparation method according to claim 1, characterized in that, The molar ratio of hexafluorodianhydride to 2,2'-bis(trifluoromethyl)-(1,1'-diphenyl)-4,4'-diamine is 1:0.9-1; the mass ratio of polyamic acid solution to dimethylaminoethyl methacrylate is 1:0.02-0.

08.

3. The preparation method according to claim 1, characterized in that, The photoinitiator includes at least one of diphenyl-(2,4,6-trimethylbenzoyl)phosphine, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholino)-1-propanone, and ethyl 2,4,6-trimethylbenzoylphosphonate; the mass ratio of the polyamic acid salt to the photoinitiator is 30 to 100:

1.

4. The application of the composite 3D printing ink prepared by the preparation method according to any one of claims 1 to 3 in 3D printing.

5. The application according to claim 4, characterized in that, The 3D printing is DIW printing.

6. The application according to claim 4 or 5, characterized in that, The 3D printing layer height is 200–400 μm, the printing speed is 0.2–1.2 mm / s, and the extrusion pressure is 0.5–2 MPa.

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