Continuous fiber reinforced aromatic polyimide 3D printing heat conducting composite material and preparation method thereof

Abstract

The application belongs to the technical field of 3D printing of composite materials, and particularly relates to a continuous fiber reinforced aromatic polyimide 3D printing heat-conducting composite material and a preparation method thereof. The method adopts an aromatic polyimide prepolymer / heat-conducting filler mixed solution to impregnate continuous fiber filaments or tapes, adjusts the glue content and the filament / tape shape through a glue extrusion mechanism, removes the solvent and completely solidifies the resin through a heat flow channel, adjusts the cross section shape of the consumable through a shaping mechanism, and obtains the 3D printing heat-conducting consumable after cooling. The consumable structure comprises 10%-75% of heat-conducting continuous fiber filaments or tapes in terms of volume percentage, 0-30% of heat-conducting fillers, and 25%-90% of completely solidified intrinsic heat-conducting aromatic polyimide resin. The consumable has good plasticity, can be printed through 3D printing technology without the aid of thermoplastic plastic as an adhesive, and the heat-conducting composite material printed by using the consumable has excellent heat-conducting, mechanical, heat-resistant and chemical-resistant properties, and can be degraded and recycled under special conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of 3D printing of composite materials, in particular to a continuous fiber reinforced aromatic polyimide 3D printing heat-conducting composite material and a preparation method thereof. BACKGROUND

[0002] Continuous fiber reinforced thermosetting resin-based composite materials have high specific strength and specific stiffness, stable structure size, and other characteristics, and have been widely used in high-tech fields such as aerospace, transportation, military defense, etc. However, such composite materials have low heat conduction performance and cannot meet the requirements of some use fields. 3D printing is an advanced manufacturing technology that uses digital driving to accumulate materials layer by layer to form a shape. The printing consumables are the material basis for 3D printing, mainly divided into powder materials, liquid materials, sheet materials, and filament materials. Commonly used 3D printing filament materials are pure plastic filament materials (such as nylon filament materials, polylactic acid filament materials) and short-cut fiber reinforced composite plastic filament materials (such as short-cut carbon fiber reinforced nylon filament materials). When printing composite materials with high mechanical performance requirements using the above filament materials, it is found that there are obvious defects such as weak bearing capacity, poor interlayer performance, and low tensile strength, which seriously limit the further application and development of composite materials in this field. Patent applications US20150165691 and US2022001587A1 disclose a composite material 3D printing technology using continuous carbon fiber filament as reinforcing material and thermoplastic plastic as resin matrix. During the printing process, the viscosity of the plastic is relatively high, resulting in poor wettability of the carbon fiber filament, low fiber volume content, and poor heat conduction performance of the composite material. However, during the printing process, the plastic is melted by heat, and good adhesion can be formed between the filament materials and between the layers, and the interlayer shear strength is relatively high. In addition, the use of thermoplastic plastic as the resin matrix can make the composite material recyclable. Patent applications US2020283591A1 and CN111163921A disclose a composite material 3D printing technology using continuous carbon fiber reinforced epoxy resin as a printing filament and thermoplastic plastic as an adhesive, which improves the wettability of the resin to the carbon fiber filament, increases the fiber volume content and the mechanical properties of the composite material. However, due to the use of traditional thermosetting resin to wet the carbon fiber, the heat conduction performance of the composite material is poor and it cannot be recycled. In addition, the thermosetting epoxy resin cannot be melted by heat, and good adhesion can only be formed between the filament materials and between the layers by relying on the melted thermoplastic plastic as an adhesive. Compared with thermoplastic plastic, traditional thermosetting resin generally forms a prepolymer first, and during molding, the latent functional groups continue to react to form a crosslinked body structure and solidify. This transformation is irreversible, and the composite material cannot be melted and plasticized by heating, nor can it be dissolved in a solvent, making it difficult to recycle. Composite material waste is usually treated as filler, buried as garbage, or incinerated, which not only causes a huge waste of resources, but also causes serious environmental pollution. SUMMARY

[0003] The application aims to provide a continuous fiber reinforced aromatic polyimide 3D printing heat-conducting material, a heat-conducting composite material and a preparation method thereof. The heat-conducting performance of the printing material and the composite material thereof is improved by combining the heat-conducting continuous fiber, the heat-conducting filler and the intrinsic heat-conducting aromatic polyimide resin. The imine dynamic covalent bond structure contained in the special thermosetting intrinsic heat-conducting aromatic polyimide resin is used to give the material good plasticity similar to that of the thermoplastic plastic under the printing condition, so that the continuous fiber reinforced heat-conducting composite material printed by the 3D technology has the degradation and recycling function under special conditions.

[0004] The application aims to provide a continuous fiber reinforced aromatic polyimide 3D printing heat-conducting material, a heat-conducting composite material and a preparation method thereof. The heat-conducting performance of the printing material and the composite material thereof is improved by combining the heat-conducting continuous fiber, the heat-conducting filler and the intrinsic heat-conducting aromatic polyimide resin. The imine dynamic covalent bond structure contained in the special thermosetting intrinsic heat-conducting aromatic polyimide resin is used to give the material good plasticity similar to that of the thermoplastic plastic under the printing condition, so that the continuous fiber reinforced heat-conducting composite material printed by the 3D technology has the degradation and recycling function under special conditions.

[0005] A preparation method of a continuous fiber reinforced aromatic polyimide 3D printing heat-conducting composite material, characterized in that the method comprises the following steps:

[0006] (1) uniformly dissolving aromatic aldehyde and aromatic amine in an aprotic solvent, stirring and reacting at 30-90 DEG C for 5-60 minutes to pre-polymerize, adding heat-conducting fillers to uniformly disperse for 5-30 minutes to obtain a pre-polymer / heat-conducting filler mixed solution;

[0007] (2) dipping the continuous fiber yarn or tape with the pre-polymer / heat-conducting filler mixed solution obtained in step (1), adjusting the glue content and the yarn tape shape through a glue extrusion mechanism, removing the solvent and completely solidifying the aromatic polyimide resin through a heat flow channel, adjusting the cross-sectional shape of the material through a shaping mechanism, and winding after cooling to obtain a 3D printing heat-conducting material;

[0008] (3) using the 3D printing heat-conducting material obtained in step (2) to print a continuous fiber reinforced aromatic polyimide 3D printing heat-conducting composite material by 3D printing technology.

[0009] Preferably, the molar amount of the aldehyde group in the aromatic aldehyde structure is equal to that of the primary amine group in the aromatic amine structure; the reactants contain at least one of aromatic tri-aldehyde, aromatic tetra-aldehyde, aromatic hexa-aldehyde and aromatic tri-amine; the aromatic aldehyde is one or two or more of the following structures:

[0010]

[0011] The aromatic amine is one or two or more of the following structures:

[0012]

[0013]

[0014]

[0015] Preferably, the continuous fiber yarn or tape in step (2) is impregnated by a glue dipping device, the dipping speed is 0.1-5 m / min; the temperature range of the heat flow channel is divided into three sections, the temperature of each section is 60-150, 160-300, 40-100℃ respectively; the heating temperature of the shaping mechanism is 200-300℃, and the shaping mechanism is located between the second and third sections of the heat flow channel.

[0016] Preferably, the aprotic solvent in step (1) is one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, dichloromethane, ethyl acetate; the volume of solvent added per gram of reactant is 0.5-10 ml.

[0017] Preferably, the continuous fiber yarn or tape in step (2) is one or more of continuous carbon fiber yarn or tape, continuous graphite fiber yarn or tape, continuous metal fiber yarn or tape with axial thermal conductivity greater than 100 W / m·K; the thermally conductive filler is one or more of aluminum oxide particles, aluminum nitride particles, silicon nitride particles, boron nitride particles, silicon carbide particles, magnesium oxide particles, zinc oxide particles, silver particles, copper particles, aluminum particles, iron particles, zinc particles, nickel particles, chopped carbon fibers, chopped graphite fibers, nanocarbon fibers, diamond, carbon black, carbon nanotubes, graphene, graphyne.

[0018] Preferably, the shape of the shaping mechanism in step (2) is a circle with a diameter of 0.1-1 mm, or an oblong with a length of 1 mm-5 cm and a width of 0.1 mm-1 mm; the 3D printing technology in step (3) is fused deposition or automatic fiber laying, automatic tape laying.

[0019] A continuous fiber reinforced aromatic polyimide 3D printed thermally conductive composite material is composed of a thermally conductive continuous fiber yarn or tape, a thermally conductive filler, and an intrinsic thermally conductive aromatic polyimide resin matrix; the volume percentage content of the continuous fiber yarn or tape in the composite material is 10%-75%, the content of the thermally conductive filler is 5-30%, and the content of the matrix is 25%-85%; the matrix has the following structural formula:

[0020]

[0021] wherein R1 and R2 are aromatic structures containing benzene rings.

[0022] Preferably, the heat-conducting composite material can be degraded and recycled; the degradation and recycling method is: soaking with a strong acid / solvent mixed solution, separating the fibers from the degradation acid solution, cleaning with acid solution, water, alkali solution, and water, and then drying to recover the fibers; further filtering or centrifuging the degradation acid solution, cleaning with acid solution, water, alkali solution, and water, and then drying to recover the heat-conducting filler; and finally, neutralizing the degradation acid solution with an alkali solution, precipitating, filtering, washing with water, and drying to obtain the aromatic amine raw material for resin synthesis.

[0023] Preferably, the strong acid is sulfuric acid and hydrochloric acid, and the alkali solution is a saturated solution of sodium carbonate or sodium bicarbonate; the amount of the strong acid / solvent mixed solution is 5-30 ml per gram of the composite material, the concentration of the strong acid is 0.1-10 mol / L, the solvent is one or more than two of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dichloromethane, tetrahydrofuran, 2,5-dimethylfuran, and hexamethylphosphoramide, the soaking temperature is 20-100 DEG C, and the soaking time is 0.5-48 hours.

[0024] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0025] (1) The continuous fiber-reinforced aromatic polyimide 3D printing heat-conducting consumable prepared by the present application has adjustable continuous fiber and heat-conducting filler contents, good fiber wetting property of the matrix resin, and completely cured matrix resin. The filament and tape have excellent heat-conducting and mechanical properties. The printing consumable has good plasticity, can be printed by 3D printing technologies such as melt deposition or automatic fiber laying and automatic tape laying without relying on thermoplastic plastic as an adhesive.

[0026] (2) The continuous fiber-reinforced intrinsic heat-conducting aromatic polyimide thermosetting resin-based 3D printing heat-conducting composite material prepared by the present application has excellent heat-conducting, mechanical, heat-resistant, and chemical-resistant properties, and can be degraded and recycled under special conditions. DETAILED DESCRIPTION

[0027] The present application will be further described below in combination with specific examples, but the content of the present application is not limited to the following examples.

[0028] Example 1

[0029] The intrinsic thermal conductive matrix resin has a thermal conductivity of 0.51 W / (m·K). The filament has a tensile strength of about 1265 MPa, and the axial thermal conductivity of the filament is 146.3 W / (m·K). Using the filament, a unidirectional thermal conductive composite material plate is printed by a 3D printer, and the printing head temperature is set to 280°C. The fiber volume percentage in the composite material is about 50%. The tensile strength of the composite material is 1126 MPa (the tensile properties are determined according to the ASTM D638-14 standard); the interlaminar shear strength of the composite material is 78 MPa (the interlaminar shear test is determined according to the ASTM D2344 / D2344M-2016 standard); the thermal distortion temperature of the composite material is 231°C (determined according to the ASTM D648-07 standard); the 5wt% thermal decomposition temperature of the composite material is 481°C; and the out-of-plane, in-plane perpendicular to the fiber direction, and in-plane parallel to the fiber direction thermal conductivities of the composite material are 7.6, 52.8, and 139.7 W / (m·K), respectively (determined according to the ISO 22007-2 standard). The composite material can withstand corrosion of acid aqueous solutions, alkali aqueous solutions, salt aqueous solutions, and solvents except concentrated sulfuric acid and concentrated nitric acid. After each gram of the composite material is immersed in 20 ml of a mixed solution of hydrochloric acid / water / tetrahydrofuran (the volume content of tetrahydrofuran is 80%) with a concentration of 1 mol / L at room temperature for 24 hours, the composite material is completely degraded, the continuous graphite fiber filament is taken out of the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution, and water, and then dried, and the continuous graphite fiber filament is recovered, with a recovery rate of 99.8%. The degradation acid solution is further filtered and centrifuged, washed with tetrahydrofuran / hydrochloric acid solution, water, saturated sodium carbonate solution, and water, and then dried, and the thermal conductive filler short-cut graphite fiber is recovered, with a recovery rate of 98.1%; finally, the acid solution is neutralized by saturated sodium carbonate solution, precipitated, filtered, washed with water, and dried to obtain tri[(4-formylphenoxy)-methyl]ethane, p-xylylene diamine, and 4,4'-diaminobenzanilide, with a recovery rate of 95.9%.

[0030] Example 2

[0031] 5 mol of isophthaldehyde and 3.5 mol of p-aminophenyl p-aminobenzoate, 1 mol of 1,3,5-tris(4-aminophenoxy)benzene were sequentially dissolved in 3 L of N,N-dimethylformamide, stirred at 80°C for 10 minutes, graphene nanosheets were added, and uniformly dispersed for 20 minutes to obtain a prepolymer / thermally conductive filler solution. The prepolymer solution was poured into a sizing tank, and continuous carbon fiber yarn (M60JB-3k, fiber axial thermal conductivity about 150 W / (m·K)) was passed through the sizing tank at 0.5 m / min for sizing, the sizing content and the shape of the yarn were adjusted by a sizing extrusion mechanism, and the solvent was removed, the aromatic polyimide resin was completely cured by passing through the 80, 270, 80°C heat flow channels, the shape of the consumable was adjusted by passing through a 0.8 mm diameter round hole shaping mechanism at 280°C, and the continuous linear printing yarn was obtained after cooling. The diameter of the yarn was about 0.80 mm, the fiber content was about 75%, the graphene content was about 6%, and the resin content was about 19%. The intrinsic thermal conductivity of the matrix resin was 0.48 W / (m·K). The tensile strength of the yarn was about 2185 MPa, and the axial thermal conductivity of the yarn was 123.2 W / (m·K). Using the yarn, a unidirectional thermally conductive composite material plate was printed by a 3D printer, and the printing head temperature was set to 290°C. The volume percentage of the fiber in the composite material was about 73%. The tensile strength of the composite material was 1855 MPa (the tensile properties were determined according to ASTM D638-14 standard); the interlaminar shear strength of the composite material was 75 MPa (the interlaminar shear test was determined according to ASTM D2344 / D2344M-2016 standard); the heat distortion temperature of the composite material was 237°C (determined according to ASTM D648-07 standard); the 5wt% thermal decomposition temperature of the composite material was 489°C; and the thermal conductivities of the composite material in the out-of-plane, in-plane perpendicular to the fiber direction, and in-plane parallel to the fiber direction were 10.5, 60.7, and 115.3 W / (m·K), respectively (determined according to ISO22007-2 standard). The composite material can withstand corrosion of acid aqueous solution, alkali aqueous solution, salt aqueous solution, and solvent, except concentrated sulfuric acid and concentrated nitric acid. After 10 ml of 1 mol / L sulfuric acid / water / tetrahydrofuran mixed solution (tetrahydrofuran volume content of 60%) was immersed in 1 g of composite material at 80°C for 2 hours, the composite material was completely degraded, the carbon fiber yarn was taken out from the acid solution, washed with 0.5 mol / L sulfuric acid, water, saturated sodium carbonate solution, and water, and then dried, the carbon fiber yarn was recovered, and the recovery rate was 99.5%. The degradation acid solution was further filtered and centrifuged, washed with tetrahydrofuran / hydrochloric acid solution, water, saturated sodium carbonate solution, and water, and then dried, the thermally conductive filler was recovered, and the recovery rate was 86.8%; finally, the acid solution was neutralized by saturated sodium carbonate solution, precipitated, filtered, washed with water, and dried to obtain p-aminophenyl p-aminobenzoate, and the recovery rate was 93.4%.

[0032] Example 3

[0033] The 3 mol of tri[(4-formylphenoxy)-methyl]ethane, 2 mol of N,N'-bis(4- aminophenyl)terephthalamide, and 2.5 mol of terephthalic acid dip-aminophenyl ester were sequentially dissolved in 2 L of N-methylpyrrolidone and 2 L of N,N- dimethylformamide, and stirred at 60°C for 20 minutes. Boron nitride nanosheets were added and uniformly dispersed for 15 minutes to obtain a prepolymer / thermally conductive filler solution. The prepolymer solution was poured into a dipping tank, and 30 continuous carbon fiber filaments (M60JB-3k, fiber axial thermal conductivity of about 150 W / (m·K)) were dipped through the tank at a speed of 0.2 m / min. The glue content and belt shape were adjusted by a glue extrusion mechanism, and the solvents were removed and the aromatic polyimide resin was completely cured by passing through the 150, 280, and 80°C heat flow channels. The shape of the consumables was adjusted by a 10 mm long and 1 mm wide rectangular shaping mechanism at 280°C, and a continuous printing tape was obtained after cooling. The tape width was about 20 mm, the thickness was about 0.3 mm, the fiber content was about 62%, the boron nitride content was about 11%, and the resin content was about 27%. The intrinsic thermal conductivity of the matrix resin was 0.53 W / (m·K). The tensile strength of the tape was about 1985 MPa, and the thermal conductivity of the tape parallel to the fiber direction was 105.6 W / (m·K). Using the tape, a unidirectional thermally conductive composite plate was printed by a 3D printer, and the printing head temperature was set to 270°C. The fiber volume percentage in the composite was about 59%. The tensile strength of the composite was 1631 MPa (tensile properties were determined according to ASTM D638-14 standard), the interlaminar shear strength of the composite was 81 MPa (interlaminar shear test was determined according to ASTM D2344 / D2344M-2016 standard), the thermal distortion temperature of the composite was 230°C (determined according to ASTM D648-07 standard), the 5 wt% thermal decomposition temperature of the composite was 488°C, and the out-of-plane, in-plane perpendicular to the fiber direction, and in-plane parallel to the fiber direction thermal conductivities of the composite were 8.8, 48.3, and 88.5 W / (m·K), respectively (determined according to ISO22007-2 standard). The composite could withstand corrosion of acid aqueous solution, alkali aqueous solution, salt aqueous solution, and solvent, except concentrated sulfuric acid and concentrated nitric acid. After 20 ml of 1 mol / L hydrochloric acid / water / tetrahydrofuran mixed solution (tetrahydrofuran volume content of 80%) was soaked in 1 g of composite at room temperature for 10 hours, the composite was completely degraded, the carbon fiber filaments were taken out of the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution, and water, and then dried, and the carbon fiber filaments were recovered with a recovery rate of 99.8%.The degradation acid solution is further filtered and centrifuged, washed by tetrahydrofuran / hydrochloric acid solution, water, saturated sodium carbonate solution, water, and dried to recover the heat-conducting filler with a recovery rate of 83.6%; finally, the acid solution is neutralized by saturated sodium carbonate solution, precipitated, filtered, washed by water, and dried to obtain N,N'-bis(4-aminophenyl)terephthalamide and terephthalic acid dip-aminophenyl ester with a recovery rate of 94.1%.

[0034] Example 4

[0035] The 4 mol of terephthaldehyde, 1 mol of m-trimesic aldehyde, 4 mol of p-aminobenzoic acid p-aminophenyl ester, 1 mol of 1,3,5-tris(4-aminophenyl)benzene are sequentially dissolved in 4 L of N-methylpyrrolidone, 2 L of dichloromethane solvent, stirred at 40℃ for 30 minutes, add the thermal conductive filler carbon nanotube, uniformly dispersed for 10 minutes, obtain the prepolymer / thermal conductive filler solution. Pour the prepolymer solution into the impregnation tank, pass the continuous graphite fiber yarn (2k, fiber axial thermal conductivity about 800 W / (m·K)) through the glue tank at 3 m / min for impregnation, adjust the glue content and the shape of the yarn through the glue extrusion mechanism, respectively through the 120, 270, 100℃ heat flow channel to remove the solvent, completely cure the aromatic polyimide resin, pass through the 0.8 mm diameter round hole shaping mechanism at 280℃ to adjust the shape of the consumable, after cooling, obtain the continuous linear printing yarn. The yarn diameter is about 0.80 mm, the continuous graphite fiber content is about 51%, the carbon nanotube content is about 10%, and the resin content is about 39%. The intrinsic thermal conductivity of the matrix resin is 0.46 W / (m·K). The tensile strength of the yarn is about 1603 MPa, and the axial thermal conductivity of the yarn is 430.1 W / (m·K). Using the yarn, a unidirectional thermal conductive composite material plate is printed by a 3D printer, and the printing head temperature is set to 280℃. The fiber volume percentage in the composite material is 47%. The tensile strength of the composite material is 1225 MPa (the tensile properties are determined according to the ASTM D638-14 standard); the interlaminar shear strength of the composite material is 77 MPa (the interlaminar shear test is determined according to the ASTM D2344 / D2344M-2016 standard); the thermal deformation temperature of the composite material is 236℃ (determined according to the ASTM D648-07 standard); the 5wt% thermal decomposition temperature of the composite material is 490℃; the out-of-plane, in-plane perpendicular to the fiber direction, and in-plane parallel to the fiber direction thermal conductivities of the composite material are 14.9, 75.8, and 410.3 W / (m·K), respectively (determined according to the ISO22007-2 standard). The composite material can withstand corrosion of acid aqueous solution, alkali aqueous solution, salt aqueous solution, and solvent except concentrated sulfuric acid and concentrated nitric acid. After each gram of composite material is immersed in 20 ml of 1 mol / L hydrochloric acid / water / tetrahydrofuran mixed solution (tetrahydrofuran volume content is 80%) at room temperature for 12 hours, the composite material is completely degraded, the graphite fiber yarn is taken out from the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution, and water, and then dried, the recovered graphite fiber yarn has a recovery rate of 99.9%. Further filtering and centrifuging the degradation acid solution, washing with tetrahydrofuran / hydrochloric acid solution, water, saturated sodium carbonate solution, and water, and then drying, the recovered thermal conductive filler has a recovery rate of 88.6%; finally, the acid solution is neutralized by saturated sodium carbonate solution, precipitated, filtered, washed with water, and dried to obtain terephthaldehyde, m-trimesic aldehyde, p-aminobenzoic acid p-aminophenyl ester, and 1,3,5-tris(4-aminophenyl)benzene, with a recovery rate of 92.3%.

[0036] Example 5

[0037] The 3 mol of tri[(4-formylphenoxy)-methyl]ethane, 1 mol of 4,4'-diaminobenzanilide, and 3.5 mol of 2,2-bis[4-(4-aminophenoxy)phenyl]propane were sequentially dissolved in 6 L of N-methylpyrrolidone, stirred at 50°C for 30 minutes, 50 μm short-cut graphite fibers were added as a thermal conductive filler, and uniformly dispersed for 10 minutes to obtain a prepolymer / thermal conductive filler solution. The prepolymer solution was poured into a dipping tank, and continuous graphite fiber filaments (1k, fiber axial thermal conductivity of about 250 W / (m·K)) were dipped through the tank at a speed of 1 m / min, the content of the glue and the shape of the filament were adjusted by a glue extrusion mechanism, and the solvent was removed and the aromatic polyimide resin was completely cured by passing through 120, 290, and 80°C heat flow channels, respectively. The shape of the consumable was adjusted by a 0.4 mm diameter round hole shaping mechanism at 280°C, and the continuous linear printing filament was obtained after cooling. The filament diameter was about 0.40 mm, the fiber content was about 53%, the short-cut graphite fiber content was about 10%, and the resin content was about 37%. The intrinsic thermal conductivity of the matrix resin was 0.37 W / (m·K). The tensile strength of the filament was about 1296 MPa, and the axial thermal conductivity of the filament was 127.5 W / (m·K). Using this filament, a unidirectional thermal conductive composite material plate was printed by a 3D printer, and the printing head temperature was set to 280°C. The fiber volume content in the composite material was about 51%. The tensile strength of the composite material was 1206 MPa (tensile properties were determined according to ASTM D638-14 standard); the interlaminar shear strength of the composite material was 80 MPa (interlaminar shear test was determined according to ASTM D2344 / D2344M-2016 standard); the heat distortion temperature of the composite material was 230°C (determined according to ASTM D648-07 standard); the 5 wt% thermal decomposition temperature of the composite material was 478°C; and the out-of-plane, in-plane perpendicular to the fiber direction, and in-plane parallel to the fiber direction thermal conductivities of the composite material were 5.9, 45.7, and 118.2 W / (m·K), respectively (determined according to ISO22007-2 standard). The composite material can withstand corrosion of acid aqueous solutions, alkali aqueous solutions, salt aqueous solutions, and solvents except concentrated sulfuric acid and concentrated nitric acid. After each gram of the composite material was immersed in 20 ml of a mixed solution of hydrochloric acid / water / tetrahydrofuran (tetrahydrofuran content of 80%) with a concentration of 1 mol / L at room temperature for 24 hours, the composite material was completely degraded, the continuous graphite fiber filament was taken out of the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution, and water, and then dried, and the continuous graphite fiber filament was recovered, with a recovery rate of 99.7%.The degradation acid solution is further filtered and centrifuged, washed by tetrahydrofuran / hydrochloric acid solution, water, saturated sodium carbonate solution, water, and dried to recover the heat-conducting filler short-cut graphite fiber with a recovery rate of 98.5%; finally, the acid solution is neutralized by saturated sodium carbonate solution, precipitated, filtered, washed by water, dried, and treated to obtain tri[(4-formylphenoxy)-methyl]ethane, 4,4'-diaminobenzanilide and 2,2-bis[4-(4-aminophenoxy)phenyl]propane with a recovery rate of 95.5%.

[0038] Comparative Example 1

[0039] Aromatic polyimide prepolymer solution was obtained by dissolving 1 mol of tris[(4-formylphenoxy)-methyl]ethane, 4 mol of terephthaldehyde and 5.5 mol of 4,4'-diaminobenzanilide in 6 L of N-methylpyrrolidone successively at 50 °C and stirring for 30 min. The prepolymer solution was poured into a dipping tank, and continuous carbon fiber filaments (T300-1k, fiber axial thermal conductivity about 10 W / (m·K)) were dipped through the tank at 1 m / min, the content of the glue and the shape of the filaments were adjusted by a glue extrusion mechanism, and the solvent was removed and the aromatic polyimide resin was completely cured by passing through 120, 290 and 80 °C heat flow channels, respectively. The shape of the consumables was adjusted by a 0.4 mm diameter round hole shaping mechanism at 280 °C, and the continuous linear printing filaments were obtained after cooling. The filament diameter was about 0.40 mm, the fiber content was about 50%, and the resin content was about 50%. The intrinsic thermal conductivity of the matrix resin was 0.51 W / (m·K). The tensile strength of the filament was about 1215 MPa, and the axial thermal conductivity of the filament was 7.3 W / (m·K). Using this filament, a unidirectional composite material plate was printed by a 3D printer, and the printing head temperature was set to 280 °C. The fiber volume fraction in the composite material was about 48%. The tensile strength of the composite material was 1054 MPa (tensile properties were determined according to ASTM D638-14 standard); the interlaminar shear strength of the composite material was 76 MPa (interlaminar shear test was determined according to ASTM D2344 / D2344M-2016 standard); the heat distortion temperature of the composite material was 230 °C (determined according to ASTM D648-07 standard); the 5 wt% thermal decomposition temperature of the composite material was 479 °C; and the thermal conductivities of the composite material in the out-of-plane, in-plane perpendicular to the fiber direction, and in-plane parallel to the fiber direction were 1.3, 1.9 and 6.7 W / (m·K), respectively (determined according to ISO22007-2 standard). The composite material could withstand corrosion of acid aqueous solution, alkali aqueous solution, salt aqueous solution and solvent except concentrated sulfuric acid and concentrated nitric acid. After each gram of the composite material was immersed in 20 ml of a mixed solution of hydrochloric acid / water / tetrahydrofuran (tetrahydrofuran content 80%) with a concentration of 1 mol / L at room temperature for 24 hours, the composite material was completely degraded, the carbon fiber filaments were taken out of the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution and water, and then dried, and the carbon fiber filaments were recovered, with a recovery rate of 99.9%. After the acid solution was neutralized by saturated sodium carbonate solution, precipitated, filtered, washed with water and dried, tris[(4-formylphenoxy)-methyl]ethane, terephthaldehyde and 4,4'-diaminobenzanilide were obtained, with a recovery rate of 96.3%.

[0040] Comparative Example 2

[0041] Aromatic polyimide prepolymer solution was obtained by dissolving 4 mol of tris[(4-formylphenoxy)-methyl]ethane and 6 mol of 2,2'-bis[4-(4-aminophenoxyphenyl)]propane in 5 L of N-methylpyrrolidone at 50 °C with stirring for 30 min. The prepolymer solution was poured into a dipping tank, and continuous carbon fiber filaments (T300-1k, fiber axial thermal conductivity of about 10 W / (m·K)) were dipped through the tank at a speed of 1 m / min. The filament shape and the content of the glue were adjusted by a glue extrusion mechanism, and the solvent and the aromatic polyimide resin were removed by passing through the 100, 270, and 60 °C heat flow channels, respectively. The shape of the consumable was adjusted by passing through a 0.4 mm diameter round hole shaping mechanism at 280 °C, and the continuous linear printing filament was obtained after cooling. The filament diameter was about 0.40 mm, the fiber content was about 51%, and the resin content was about 49%. The thermal conductivity of the matrix resin was 0.22 W / (m·K). The tensile strength of the filament was about 1486 MPa, and the axial thermal conductivity of the filament was 5.1 W / (m·K). Using this filament, a unidirectional composite material plate was printed by a 3D printer, and the printing head temperature was set to 280 °C. The fiber volume content in the composite material was about 48%. The tensile strength of the composite material was 1285 MPa (the tensile properties were determined according to ASTM D638-14 standard); the interlaminar shear strength of the composite material was 79 MPa (the interlaminar shear test was determined according to ASTM D2344 / D2344M-2016 standard); the heat distortion temperature of the composite material was 235 °C (determined according to ASTM D648-07 standard); the 5 wt% thermal decomposition temperature of the composite material was 481 °C; and the thermal conductivities of the composite material in the out-of-plane, in-plane perpendicular to the fiber direction, and in-plane parallel to the fiber direction were 0.3, 0.5, and 4.9 W / (m·K), respectively (determined according to ISO 22007-2 standard). The composite material could withstand corrosion of acid solutions, alkali solutions, salt solutions, and solvents except concentrated sulfuric acid and concentrated nitric acid. After 20 ml of 1 mol / L hydrochloric acid / water / tetrahydrofuran mixed solution (tetrahydrofuran content of 80%) was used to soak 1 g of the composite material at room temperature for 36 hours, the composite material was completely degraded, the carbon fiber filament was taken out of the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution, and water, and then dried, and the carbon fiber filament was recovered with a recovery rate of 99.7%. After the acid solution was neutralized by saturated sodium carbonate solution, precipitated, filtered, washed with water, and dried, tris[(4-formylphenoxy)-methyl]ethane and 2,2'-bis[4-(4-aminophenoxyphenyl)]propane were obtained with a recovery rate of 95.8%.

[0042] Table 1. Comparison of thermal conductivity of 3D printing consumables and their composite materials.

[0043]

[0044] As shown in Table 1, increasing the content and thermal conductivity of the heat-conducting continuous fibers, the content and thermal conductivity of the heat-conducting fillers, and the intrinsic thermal conductivity of the aromatic polyimide resin are all conducive to improving the thermal conductivity of the composite material. By combining the synergistic thermal conductivity advantages of the heat-conducting continuous fibers, the heat-conducting fillers, and the intrinsic thermal conductivity of the aromatic polyimide resin, the thermal conductivity of the 3D printing consumables and the composite material thereof can be greatly improved.

[0045] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A continuous fiber-reinforced aromatic polyimide 3D-printed thermally conductive composite material, characterized in that, Consist of heat-conducting continuous fiber filaments or tapes, heat-conducting fillers and intrinsic heat-conducting aromatic polyimide resin matrix; the volume percentage of continuous fiber filaments or tapes in the composite material is 10%~75%, the content of heat-conducting fillers is 5~30%, and the content of the matrix is 25%~85%; the matrix structural formula is as follows: Wherein, R1 and R2 are aromatic structures containing benzene rings; The continuous fiber reinforced aromatic polyimide 3D printing heat-conducting composite material is prepared by the following method: (1) uniformly dissolve aromatic aldehyde and aromatic amine in aprotic solvent, stir and react at 30~90℃ for 5~60 minutes for pre-polymerization, add heat-conducting fillers and uniformly disperse for 5~30 minutes to obtain a pre-polymer / heat-conducting filler mixed solution; (2) impregnate the continuous fiber filaments or tapes with the pre-polymer / heat-conducting filler mixed solution obtained in step (1), adjust the glue content and filament tape shape through a glue extrusion mechanism, remove the solvent through a hot flow channel, completely solidify the aromatic polyimide resin, adjust the cross-sectional shape of the consumables through a shaping mechanism, and obtain 3D printing heat-conducting consumables after cooling and winding; In step (2), the continuous fiber filaments or tapes are impregnated by a glue dipping device, the dipping speed is 0.1~5m / min; the temperature range of the hot flow channel is divided into three sections, and the temperature of each section is 60~150, 160~300 and 40~100℃ respectively; the heating temperature of the shaping mechanism is 200~300℃, and the shaping mechanism is located between the second and third sections of the hot flow channel; (3) use the 3D printing heat-conducting consumables obtained in step (2) to print a continuous fiber reinforced aromatic polyimide 3D printing heat-conducting composite material by 3D printing technology.

2. The continuous fiber-reinforced aromatic polyimide 3D-printed thermally conductive composite material according to claim 1, characterized in that, The number of moles of aldehyde groups in the structure of the aromatic aldehyde is equal to that of primary amine groups in the structure of the aromatic amine; at least one of aromatic tri-aldehyde, aromatic tetra-aldehyde, aromatic hexa-aldehyde and aromatic triamine is contained in the reactants; the aromatic aldehyde is one or two or more of the following structures: ； The aromatic amine is one or two or more of the following structures: 。 3. The continuous fiber-reinforced aromatic polyimide 3D-printed thermally conductive composite material according to claim 1, wherein, In step (1), the aprotic solvent is one or two or more of N-methyl pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, dichloromethane and ethyl acetate; the volume of solvent added per gram of reactant is 0.5~10ml.

4. The continuous-fiber-reinforced, aromatic polyimide 3D-printed thermally conductive composite material according to claim 2 or 3, characterized in that, In step (2), the continuous fiber filaments or tapes are one or two or more of continuous carbon fiber filaments or tapes, continuous graphite fiber filaments or tapes and continuous metal fiber filaments or tapes with axial thermal conductivity greater than 100W / m·K; the heat-conducting fillers are one or two or more of aluminum oxide particles, aluminum nitride particles, silicon nitride particles, boron nitride particles, silicon carbide particles, magnesium oxide particles, zinc oxide particles, silver particles, copper particles, aluminum particles, iron particles, zinc particles, nickel particles, chopped carbon fibers, chopped graphite fibers, nanometer carbon fibers, diamond, carbon black, carbon nanotubes and graphene.

5. The continuous-fiber-reinforced, aromatic polyimide 3D-printed thermally conductive composite material according to claim 2 or 3, characterized in that, In step (2), the shape of the shaping mechanism is a circle with a diameter of 0.1~1mm, or a rectangle with a length of 1mm~5cm and a width of 0.1mm~1mm; in step (3), the 3D printing technology is fused deposition or automatic fiber laying or automatic tape laying.

6. The continuous fiber-reinforced, aromatic polyimide 3D-printed thermally conductive composite material of claim 5, wherein, The heat-conducting composite material can be degraded and recycled; the degradation and recycling method is: soaking in a strong acid / solvent mixed solution, separating fibers from the degradation acid solution, cleaning in acid solution, water, alkali solution, and water, and drying to obtain the fibers; further filtering or centrifugally separating the degradation acid solution, cleaning in acid solution, water, alkali solution, and water, and drying to obtain the heat-conducting filler; finally, neutralizing, precipitating, filtering, washing, and drying the degradation acid solution to obtain the resin synthesis raw material aromatic amine.

7. The continuous fiber-reinforced, thermally conductive, 3D-printed poly(arylene imide) composite of claim 6, wherein, The strong acid is sulfuric acid and hydrochloric acid, and the alkali solution is a saturated solution of sodium carbonate or sodium bicarbonate; the amount of the strong acid / solvent mixed solution is 5-30 ml per gram of the composite material, the concentration of the strong acid is 0.1-10 mol / L, the solvent is one or two or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dichloromethane, tetrahydrofuran, 2,5-dimethylfuran, and hexamethylphosphoramide, the soaking temperature is 20-100 DEG C, and the soaking time is 0.5-48 hours.

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