Continuous fiber reinforced polyhexahydrotriazine 3d printed thermally conductive composites

Abstract

The present application belongs to the technical field of 3D printing of composite materials, and particularly relates to a continuous fiber reinforced polyhexahydrotriazine 3D printing heat-conducting composite material. The composite material uses a polyhexahydrotriazine prepolymer / heat-conducting filler mixed solution to impregnate continuous fiber filaments or tapes, adjusts the glue solution content and the filament / tape shape, removes the solvent through a heat flow channel, completely solidifies the resin, adjusts the cross-sectional shape of the consumable through a shaping mechanism, and obtains a 3D printing consumable after cooling. The printing consumable has good plasticity, can not rely on thermoplastic plastic as an adhesive, and can be printed through 3D printing technology alone to obtain a continuous fiber reinforced resin-based heat-conducting composite material. The consumable structure includes 25% to 75% of heat-conducting continuous fiber filaments or tapes in terms of volume percentage, 5% to 30% of heat-conducting fillers, and 20% to 70% of completely solidified intrinsic heat-conducting polyhexahydrotriazine resin. The 3D printing heat-conducting composite material has excellent heat-conducting, mechanical and chemical resistance, and can be degraded and recycled under special conditions.

Description

Technical Field

[0001] This invention relates to the field of composite material 3D printing technology, specifically to a continuous fiber reinforced polyhexahydrotriazine 3D printed thermally conductive composite material. Background Technology

[0002] Continuous fiber-reinforced thermosetting resin matrix composites possess high specific strength and stiffness, as well as stable structural dimensions, and have been widely used in high-tech fields such as aerospace, transportation, and military defense. However, these composites have relatively low thermal conductivity, which cannot yet meet the requirements of certain applications. 3D printing is an advanced manufacturing technology that uses digitally driven methods to deposit materials layer by layer. Printing consumables are the material basis of 3D printing and are mainly divided into powders, liquids, sheets, and filaments. Commonly used 3D printing filaments are mainly pure plastic filaments (such as nylon filaments and polylactic acid filaments) and chopped fiber reinforced composite plastic filaments (such as chopped carbon fiber reinforced nylon filaments). When using these filaments to print composite materials with high mechanical performance requirements, significant defects such as weak load-bearing capacity, poor interlayer properties, and low tensile strength have been found, severely limiting their further application and development in the field of composite materials. Patent applications US20150165691 and US2022001587A1 disclose 3D printing technology for composite materials using continuous carbon fiber filaments as reinforcement and thermoplastic plastics as the resin matrix. During the printing process, the high viscosity of the plastic leads to poor wetting of the carbon fiber filaments, low fiber volume content, and poor thermal conductivity of the composite material. However, during printing, the plastic melts upon heating, allowing for good adhesion between the filaments and between layers, resulting in relatively high interlayer shear strength. Furthermore, using thermoplastic plastics as the resin matrix enables the composite material to be recycled. Patent applications US2020283591A1 and CN111163921A disclose 3D printing technology for composite materials using continuous carbon fiber reinforced epoxy resin as the printing filament and thermoplastic plastics as the binder. This improves the resin's wetting of the carbon fiber filaments, increases the fiber volume content, and enhances the mechanical properties of the composite material. However, the use of traditional thermosetting resins to wet the carbon fiber results in poor thermal conductivity and non-recyclability of the composite material. Compared to thermoplastics, traditional thermosetting resins typically form prepolymers first. During molding, the latent functional groups within these prepolymers continue to react, forming a cross-linked structure and solidifying. This transformation is irreversible; the resins cannot melt or plasticize upon heating and are insoluble in solvents, making the composites difficult to recycle. Furthermore, thermosetting epoxy resins cannot melt upon heating, requiring molten thermoplastics as adhesives between filaments and layers to achieve good bonding. Composite material waste is typically disposed of as filler, landfilled, or incinerated, resulting in significant resource waste and severe environmental pollution. Summary of the Invention

[0003] The purpose of this invention is to provide a continuous fiber-reinforced polyhexahydrotriazine 3D-printed thermally conductive composite material. By combining thermally conductive continuous fibers, thermally conductive fillers, and intrinsically thermally conductive polyhexahydrotriazine resin, the thermal conductivity of the printing consumable and its composite material is synergistically improved. Utilizing the dynamic covalent bond structure of the hexahydrotriazine ring contained in the special thermosetting intrinsically thermally conductive polyhexahydrotriazine resin, the consumable is endowed with good plasticity under printing conditions, enabling the continuous fiber-reinforced thermosetting resin-based thermally conductive composite material printed using 3D technology to possess degradation and recycling capabilities under special conditions.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A continuous fiber reinforced polyhexahydrotriazine 3D printed thermally conductive composite material is characterized by using 3D printing technology with continuous fiber reinforced polyhexahydrotriazine resin as the 3D printing thermally conductive consumable to obtain the continuous fiber reinforced polyhexahydrotriazine resin 3D printed thermally conductive composite material; the thermally conductive composite material has a tensile strength of ≥1200MPa and an in-plane thermal conductivity of ≥80W / (m·K) in the direction parallel to the fibers.

[0006] The 3D printed thermally conductive consumable is composed of thermally conductive continuous fiber filaments or tapes, thermally conductive fillers, and an intrinsically thermally conductive polyhexahydrotriazine resin matrix; the volume percentage of the continuous fiber filaments or tapes in the composite material is 25% to 75%, the content of the thermally conductive fillers is 5% to 30%, and the content of the matrix is ​​20% to 70%; the matrix is ​​the following structural formula (1) or (2) or a mixture thereof:

[0007]

[0008] At least one of R1, R2, and R3 is any of the following structures:

[0009]

[0010]

[0011]

[0012] The R4 is at least one of the following structures:

[0013]

[0014] Preferably, the thermally conductive composite material has a fiber volume percentage of 45% to 75%, a thermally conductive filler content of 5% to 30%, and a matrix content of 20% to 50%; the in-plane thermal conductivity parallel to the fiber direction is ≥100W / (m·K).

[0015] Preferably, the 3D printed thermal conductive consumable is prepared through the following steps:

[0016] (1) Dissolve formaldehyde and aromatic amine uniformly in a proton / water mixed solvent, stir and react at 40-90℃ for 10-60 minutes to carry out prepolymerization, add thermally conductive filler and disperse uniformly for 5-30 minutes to obtain prepolymer / thermally conductive filler mixed solution.

[0017] (2) Impregnate the prepolymer / thermal filler mixture obtained in step (1) with continuous fiber filaments or continuous fiber strips, adjust the glue content and ribbon shape through the glue extrusion mechanism, remove the solvent through the hot flow channel, completely cure the polyhexahydrotriazine resin, adjust the cross-sectional shape of the consumable through the shaping mechanism, and roll it up after cooling to obtain 3D printed thermal consumable.

[0018] Preferably, the impregnation in step (2) is carried out in an impregnation device at an impregnation speed of 0.1 to 5 m / min; the temperature range of the hot flow channel is divided into three sections, with temperatures of 60 to 150, 160 to 300, and 40 to 100°C for each section; the heating temperature of the shaping mechanism is 200 to 300°C, and the filament shaping mechanism is located between the second and third sections of the hot flow channel.

[0019] Preferably, the continuous fiber filament or tape is one or more of the following: continuous carbon fiber filament or tape, continuous graphite fiber filament or tape, or continuous metal fiber filament or tape with an axial thermal conductivity greater than 100 W / m·K.

[0020] Preferably, the thermally conductive filler is one or more of the following: alumina 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, carbon nanofibers, diamond, carbon black, carbon nanotubes, graphene, and graphynylene.

[0021] Preferably, the formaldehyde has a molar ratio of 2:1 to an aromatic diamine and a molar ratio of 3:1 to an aromatic triamine, wherein the aromatic amine has at least one or more of the following structures:

[0022]

[0023]

[0024]

[0025] Preferably, the aprotic solvent is one or more of N-methylpyrrolidone, dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, 2,5-dimethylfuran, and hexamethylphosphoramide; the water content in the mixed solvent is 1% to 30% by volume; the volume of solvent added per gram of reactant is 0.5 to 10 ml; the 3D printing technology includes fused deposition modeling or automatic filament placement and automatic tape placement; the shaping mechanism is a circle with a diameter of 0.1 to 1 mm, or a rectangle with a length of 1 mm to 5 cm and a width of 0.1 mm to 1 mm.

[0026] Preferably, the thermally conductive composite material is degradable and recyclable; the degradation and recycling method is as follows: soaking in a strong acid / solvent mixed solution, separating the fiber from the degradation acid solution, washing with acid solution, water, alkali solution, and water, and then drying to recover the fiber; further filtering or centrifuging the degradation acid solution, washing with acid solution, water, alkali solution, and water, and then drying to recover the thermally conductive filler; finally, neutralizing the degradation acid solution with alkali solution, precipitation, filtration, water washing, and drying to obtain the aromatic amine, the resin synthesis raw material.

[0027] Preferably, the strong acid is sulfuric acid and hydrochloric acid, and the alkaline solution is a saturated solution of sodium carbonate or sodium bicarbonate; the amount of the strong acid / solvent mixture is 5-30 ml per gram of composite material, the concentration of the strong acid is 0.1-12 mol / L, and the solvent is one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dichloromethane, tetrahydrofuran, 2,5-dimethylfuran, and hexamethylphosphoramide; the soaking temperature is 20-95°C, and the soaking time is 0.5-24 hours.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] (1) The continuous fiber-reinforced polyhexahydrotriazine 3D printing thermal conductive consumable prepared by this invention has adjustable content of continuous fiber and thermally conductive filler, good wettability of the matrix resin to the fiber, and complete curing of the matrix resin. The filaments and tapes have excellent thermal conductivity and mechanical properties. The filaments and tapes have good plasticity and can be printed independently of thermoplastic plastics as binders, using 3D printing technologies such as fused deposition modeling or automatic filament / tape laying.

[0030] (2) The continuous fiber reinforced intrinsically thermally conductive polyhexahydrotriazine thermosetting resin-based 3D printing thermally conductive composite material prepared by the present invention has excellent thermal conductivity, mechanical properties, heat resistance and chemical resistance, and can be degraded and recycled under special conditions. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the intrinsically thermally conductive polyhexahydrotriazine matrix resin structure in Example 1.

[0032] Figure 2 This is a schematic diagram of the cross-section of the continuous fiber reinforced polyhexahydrotriazine 3D printed thermally conductive filament in Example 1. (a) Cross-section of the thermally conductive continuous fiber monofilament, (b) Thermally conductive filler particles, and (c) Fully cured intrinsically thermally conductive polyhexahydrotriazine resin.

[0033] Figure 3 This is a schematic diagram of the intrinsically thermally conductive polyhexahydrotriazine matrix resin structure in Example 2.

[0034] Figure 4 This is a schematic diagram of the intrinsically thermally conductive polyhexahydrotriazine matrix resin structure in Example 3.

[0035] Figure 5 This is a schematic diagram of the cross-section of the continuous fiber reinforced polyhexahydrotriazine 3D printed heat-conducting material in Example 3. (d) Continuous fiber bundle impregnated with fully cured intrinsically thermally conductive polyhexahydrotriazine resin, (e) Fully cured intrinsically thermally conductive polyhexahydrotriazine resin, and (f) Thermally conductive filler particles.

[0036] Figure 6 This is a schematic diagram of the intrinsically thermally conductive polyhexahydrotriazine matrix resin structure in Example 4.

[0037] Figure 7 This is a schematic diagram of the intrinsically thermally conductive polyhexahydrotriazine matrix resin structure in Example 5.

[0038] Figure 8 This is a schematic diagram of the polyhexahydrotriazine matrix resin structure for Comparative Example 2. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments, but the content of the present invention is not limited to the following embodiments.

[0040] Example 1

[0041] 10 mol of paraformaldehyde and 5 mol of 4,4′-diaminobenzoylaniline were dissolved sequentially in 2 L of a N-methylpyrrolidone / water mixed solvent (water content 5% by volume). The mixture was stirred at 60 °C for 30 minutes. Thermally conductive carbon nanotubes were then added and uniformly dispersed for 20 minutes to obtain a prepolymer / thermally conductive filler solution. The prepolymer solution was poured into an impregnation tank, and continuous graphite fibers (1 kJ, fiber axial thermal conductivity approximately 250 W / (m·K)) were impregnated at a rate of 0.5 m / min. The resin content and fiber shape were adjusted using a resin extrusion mechanism. The solvent was removed by passing the fibers through hot flow channels at 120, 270, and 60 °C, and the polyhexahydrotriazine resin was completely cured. The shape of the filament was adjusted at 290 °C using a 0.4 mm diameter circular orifice shaping mechanism. After cooling, a continuous linear printing filament was obtained. The filament diameter was approximately 0.40 mm, the fiber content was approximately 55%, the carbon nanotube content was approximately 6%, and the resin content was approximately 39%. A schematic diagram of the intrinsic thermally conductive matrix resin structure is shown below. Figure 1 As shown, the thermal conductivity is 0.43 W / (m·K). The tensile strength of the filament is approximately 1387 MPa, and the axial thermal conductivity is 132.5 W / (m·K). A schematic diagram of the cross-sectional structure of the filament is shown below. Figure 2 As shown. Using this filament, a unidirectional thermally conductive composite material plate was printed using a 3D printer, with the print head temperature set to 280℃. The fiber volume percentage in the composite material is approximately 52%. The tensile strength of the composite material is 1218 MPa (tensile properties determined according to ASTM D638-14 standard); the interlaminar shear strength is 56 MPa (interlaminar shear test determined according to ASTM D2344 / D2344M-2016 standard); the heat distortion temperature of the composite material is 235℃ (determined according to ASTM D648-07 standard); the 5wt% thermal decomposition temperature of the composite material is 359℃; the out-of-plane, in-plane perpendicular to fiber direction, and in-plane parallel to fiber direction thermal conductivity of the composite material are 6.5, 45.7, and 128.4 W / (m·K), respectively (determined according to ISO22007-2 standard). The composite material can withstand corrosion from acidic aqueous solutions, alkaline aqueous solutions, salt aqueous solutions, and solvents, except for concentrated sulfuric acid and concentrated nitric acid. After immersing each gram of the composite material in a 1 mol / L hydrochloric acid / water / tetrahydrofuran mixed solution (tetrahydrofuran volume content 80%) at room temperature for 12 hours, the composite material was completely degraded. Graphite fibers were removed from the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution, and water, and then dried to recover the graphite fibers with a recovery rate of 99.6%. Further filtration and centrifugation of the degradation acid solution, followed by washing with tetrahydrofuran / hydrochloric acid solution, water, saturated sodium carbonate solution, and water, and drying, yielded the thermally conductive filler with a recovery rate of 88.5%. Finally, the acid solution was neutralized with saturated sodium carbonate solution, precipitated, filtered, washed with water, and dried to obtain 4,4′-diaminobenzoylaniline with a recovery rate of 94.8%.

[0042] Example 2

[0043] 10 mol of paraformaldehyde and 5 mol of p-aminobenzoic acid (p-aminophenyl ester) were dissolved sequentially in 3 L of N,N-dimethylformamide / water mixed solvent (water volume content 10%). The mixture was stirred at 80 °C for 20 minutes. Graphene nanosheets were then added and uniformly dispersed for 10 minutes to obtain a prepolymer / thermally conductive filler solution. The prepolymer solution was poured into an impregnation tank, and continuous carbon fiber filaments (M60JB-3k, fiber axial thermal conductivity approximately 150 W / (m·K)) were impregnated with the resin at a rate of 1 m / min. The resin content and filament shape were adjusted using a resin extrusion mechanism. The solvent was removed by passing the filaments through hot flow channels at 100, 260, and 80 °C, respectively, and the polyhexahydrotriazine resin was completely cured. The shape of the filament was adjusted at 250 °C using a 0.8 mm diameter circular orifice shaping mechanism. After cooling, a continuous linear printing filament was obtained. The filament diameter was approximately 0.81 mm, the fiber content was approximately 74%, the graphene content was approximately 5%, and the resin content was approximately 21%. A schematic diagram of the intrinsic thermally conductive matrix resin structure is shown below. Figure 3 As shown, the thermal conductivity is 0.38 W / (m·K). The tensile strength of the filament is approximately 2159 MPa, and the axial thermal conductivity is 110.3 W / (m·K). Using this filament, a unidirectional thermally conductive composite material plate was printed using a 3D printer, with the print head temperature set to 250℃. The fiber volume percentage in the composite material is approximately 72%. The tensile strength of the composite material is 1756 MPa (tensile properties were determined according to ASTM D638-14); the interlaminar shear strength is 54 MPa (interlaminar shear test was determined according to ASTM D2344 / D2344M-2016); the heat distortion temperature is 188℃ (determined according to ASTM D648-07); the 5wt% thermal decomposition temperature is 353℃; the out-of-plane, in-plane perpendicular to fiber, and in-plane parallel to fiber thermal conductivity are 9.7, 56.8, and 106.2 W / (m·K), respectively (determined according to ISO 22007-2). The composite material can withstand corrosion from acidic solutions, alkaline solutions, salt solutions, and solvents, except for concentrated sulfuric acid and concentrated nitric acid. After immersing each gram of the composite material in 10 ml of a 1 mol / L sulfuric acid / water / tetrahydrofuran mixed solution (tetrahydrofuran volume content 60%) at 80°C for 2 hours, the composite material completely degrades. Carbon fiber filaments are removed from the acid solution, washed with 0.5 mol / L sulfuric acid, water, saturated sodium carbonate solution, and water, and then dried to recover the carbon fiber filaments, achieving a recovery rate of 99.5%. Further filtration and centrifugation of the degradation acid solution, followed by washing with tetrahydrofuran / hydrochloric acid solution, water, saturated sodium carbonate solution, and water, and drying, yields the thermally conductive filler, achieving a recovery rate of 86.8%. Finally, the acid solution is neutralized with saturated sodium carbonate solution, precipitated, filtered, washed with water, and dried to obtain p-aminobenzoic acid p-phenyl ester, achieving a recovery rate of 93.4%.

[0044] Example 3

[0045] 10 mol of paraformaldehyde, 2.5 mol of N,N′-bis(4-aminophenyl)terephthalamide, and 2.5 mol of di-p-aminophenyl terephthalate were dissolved sequentially in 2 L of N-methylpyrrolidone / water mixed solvent (water volume content 8%). The mixture was stirred at 50 °C for 60 minutes. Boron nitride nanosheets were then added and uniformly dispersed for 10 minutes to obtain a prepolymer / thermally conductive filler solution. The prepolymer solution was poured into an impregnation tank, and 30 bundles of continuous carbon fiber filaments (M60JB-3k, fiber axial thermal conductivity approximately 150 W / (m·K)) were impregnated in the tank at a speed of 0.3 m / min. The resin content and bundle shape were adjusted by a resin extrusion mechanism. The solvent was removed by passing the polyhexahydrotriazine resin through hot flow channels at 120, 270, and 80 °C, respectively, and the resin was completely cured. The shape of the consumable was adjusted by a 10 mm long and 1 mm wide rectangular shaping mechanism at 270 °C. After cooling, a continuous printing tape was obtained. The strip is approximately 20 mm wide and 0.3 mm thick, with a fiber content of approximately 60%, boron nitride content of approximately 10%, and resin content of approximately 30%. A schematic diagram of the intrinsic thermally conductive matrix resin structure is shown below. Figure 4 As shown, the thermal conductivity is 0.48 W / (m·K). The tensile strength of the strip is approximately 1937 MPa, and the thermal conductivity parallel to the fiber direction is 98.4 W / (m·K). A schematic diagram of the strip's cross-sectional structure is shown below. Figure 5As shown. Using this strip, a unidirectional thermally conductive composite material plate was printed using a 3D printer, with the print head temperature set to 270℃. The fiber volume percentage in the composite material is approximately 56%. The tensile strength of the composite material is 1652 MPa (tensile properties determined according to ASTM D638-14 standard); the interlaminar shear strength is 59 MPa (interlaminar shear test determined according to ASTM D2344 / D2344M-2016 standard); the heat distortion temperature of the composite material is 205℃ (determined according to ASTM D648-07 standard); the 5wt% thermal decomposition temperature of the composite material is 368℃; the out-of-plane, in-plane perpendicular to fiber direction, and in-plane parallel to fiber direction thermal conductivity of the composite material are 8.2, 46.5, and 86.9 W / (m·K), respectively (determined according to ISO22007-2 standard). The composite material can withstand corrosion from acidic aqueous solutions, alkaline aqueous solutions, salt aqueous solutions, and solvents, except for concentrated sulfuric acid and concentrated nitric acid. After immersing each gram of the composite material in a 20 ml solution of 1 mol / L hydrochloric acid / water / tetrahydrofuran (tetrahydrofuran volume content 80%) at room temperature for 10 hours, the composite material was completely degraded. Carbon fiber filaments were removed from the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution, and water, and then dried to recover the carbon fiber filaments with a recovery rate of 99.8%. Further filtration and centrifugation of the degradation acid solution, followed by washing with tetrahydrofuran / hydrochloric acid solution, water, saturated sodium carbonate solution, and water, and drying, yielded the thermally conductive filler with a recovery rate of 83.6%. Finally, the acid solution was neutralized with saturated sodium carbonate solution, precipitated, filtered, washed with water, and dried to obtain N,N′-bis(4-aminophenyl)terephthalamide and di-p-aminophenyl terephthalate with a recovery rate of 94.1%.

[0046] Example 4

[0047] 11 mol of paraformaldehyde, 4 mol of p-aminobenzoic acid, and 1 mol of 1,3,5-tris(4-aminophenyl)benzene were dissolved sequentially in a mixed solvent of 1 L N-methylpyrrolidone / 0.96 L dichloromethane / 0.04 L water. The mixture was stirred at 40 °C for 30 minutes. Then, 50 μm short-cut graphite fibers, a thermally conductive filler, were added and dispersed uniformly for 10 minutes to obtain a prepolymer / thermally conductive filler solution. The prepolymer solution was poured into an impregnation tank, and continuous graphite fibers (2 kJ, with an axial thermal conductivity of approximately 800 W / (m·K)) were impregnated in the tank at a rate of 3 m / min. The resin content and fiber shape were adjusted using a resin extrusion mechanism. The solvent was removed by passing the fibers through hot flow channels at 150, 280, and 100 °C, and the polyhexahydrotriazine resin was completely cured. The shape of the filament was adjusted at 260 °C using a 0.8 mm diameter circular orifice shaping mechanism. After cooling, a continuous linear printing filament was obtained. The filament diameter is approximately 0.81 mm, with continuous graphite fiber content of approximately 50%, chopped graphite fiber content of approximately 15%, and resin content of approximately 35%. A schematic diagram of the intrinsic thermally conductive matrix resin structure is shown below. Figure 6As shown, the thermal conductivity is 0.45 W / (m·K). The tensile strength of the filament is approximately 1546 MPa, and the axial thermal conductivity is 416.3 W / (m·K). Using this filament, a unidirectional thermally conductive composite material plate was printed using a 3D printer, with the print head temperature set to 280℃. The fiber volume percentage in the composite material is 48%. The tensile strength of the composite material is 1286 MPa (tensile properties were determined according to ASTM D638-14); the interlaminar shear strength is 55 MPa (interlaminar shear test was determined according to ASTM D2344 / D2344M-2016); the heat distortion temperature is 215℃ (determined according to ASTM D648-07); the 5wt% thermal decomposition temperature is 382℃; the out-of-plane, in-plane perpendicular to fiber, and in-plane parallel to fiber thermal conductivity are 12.6, 68.2, and 396.3 W / (m·K), respectively (determined according to ISO 22007-2). The composite material can withstand corrosion from aqueous solutions of acids, alkalis, salts, and solvents, except for concentrated sulfuric acid and concentrated nitric acid. After immersing each gram of the composite material in 20 ml of a 1 mol / L hydrochloric acid / water / tetrahydrofuran mixed solution (tetrahydrofuran volume content 80%) at room temperature for 12 hours, the composite material completely degrades. Graphite fibers are extracted from the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution, and then dried to recover the graphite fibers, achieving a recovery rate of 99.9%. Further filtration and centrifugation of the degradation acid solution, followed by washing with tetrahydrofuran / hydrochloric acid solution, water, saturated sodium carbonate solution, and then drying, yields the thermally conductive filler, achieving a recovery rate of 90.7%. Finally, the acid solution is neutralized with saturated sodium carbonate solution, precipitated, filtered, washed with water, and dried to obtain p-aminobenzoic acid p-phenyl ester and 1,3,5-tris(4-aminophenyl)benzene, achieving a recovery rate of 91.8%.

[0048] Example 5

[0049] 10 mol paraformaldehyde, 1 mol 4,4′-diaminobenzoylaniline, and 4 mol 2,2-bis[4-(4-aminophenoxy)phenyl]propane were dissolved sequentially in 2 L of a mixed solvent of N-methylpyrrolidone / water (water volume content 5%). The mixture was stirred at 60 °C for 30 minutes. Thermally conductive carbon nanotubes were then added and uniformly dispersed for 20 minutes to obtain a prepolymer / thermally conductive filler solution. The prepolymer solution was poured into an impregnation tank, and continuous graphite fibers (1k, fiber axial thermal conductivity approximately 250 W / (m·K)) were impregnated in the tank at a speed of 0.5 m / min. The resin content and fiber shape were adjusted by a resin extrusion mechanism. The solvent was removed by passing the fibers through hot flow channels at 120, 270, and 60 °C, and the polyhexahydrotriazine resin was completely cured. The shape of the filament was adjusted by a 0.4 mm diameter circular hole shaping mechanism at 290 °C. After cooling, a continuous linear printing filament was obtained. The filament diameter is approximately 0.41 mm, with a fiber content of approximately 54%, a carbon nanotube content of approximately 6%, and a resin content of approximately 40%. A schematic diagram of the intrinsically thermally conductive matrix resin structure is shown below. Figure 7As shown, the thermal conductivity is 0.30 W / (m·K). The tensile strength of the filament is approximately 1588 MPa, and the axial thermal conductivity is 109.6 W / (m·K). Using this filament, a unidirectional thermally conductive composite material plate was printed using a 3D printer, with the print head temperature set to 270℃. The fiber volume percentage in the composite material is approximately 52%. The tensile strength of the composite material is 1375 MPa (tensile properties were determined according to ASTM D638-14); the interlaminar shear strength is 58 MPa (interlaminar shear test was determined according to ASTM D2344 / D2344M-2016); the heat distortion temperature is 229℃ (determined according to ASTM D648-07); the 5wt% thermal decomposition temperature is 372℃; the out-of-plane, in-plane perpendicular to fiber, and in-plane parallel to fiber thermal conductivity are 4.9, 33.6, and 98.8 W / (m·K), respectively (determined according to ISO 22007-2). The composite material can withstand corrosion from aqueous solutions of acids, alkalis, salts, and solvents, except for concentrated sulfuric acid and concentrated nitric acid. After immersing each gram of the composite material in 15 ml of a 1 mol / L hydrochloric acid / water / tetrahydrofuran mixed solution (tetrahydrofuran volume content 80%) at room temperature for 12 hours, the composite material completely degrades. Graphite fibers are removed from the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution, and then dried to recover the graphite fibers, achieving a recovery rate of 99.7%. Further filtration and centrifugation of the degradation acid solution, followed by washing with tetrahydrofuran / hydrochloric acid solution, water, saturated sodium carbonate solution, and then drying, yields the thermally conductive filler, achieving a recovery rate of 86.9%. Finally, the acid solution is neutralized with saturated sodium carbonate solution, precipitated, filtered, washed with water, and dried to obtain 4,4′-diaminobenzoylaniline and 2,2-bis[4-(4-aminophenoxy)phenyl]propane, with a recovery rate of 92.5%.

[0050] Comparative Example 1

[0051] 10 mol of paraformaldehyde and 5 mol of 4,4′-diaminobenzoylaniline were dissolved sequentially in 2 L of a mixed solvent of N-methylpyrrolidone / water (water content 5% by volume). The mixture was stirred at 60 °C for 30 minutes to obtain a polyhexane triazine prepolymer solution. The prepolymer solution was poured into an impregnation tank, and continuous carbon fiber filaments (T300-1k, fiber axial thermal conductivity approximately 10 W / (m·K)) were impregnated at a rate of 0.5 m / min. The resin content and filament shape were adjusted using a resin extrusion mechanism. The solvent was removed by passing the filaments through hot flow channels at 120, 270, and 80 °C, and the polyhexane triazine resin was completely cured. The shape of the filament was adjusted at 280 °C using a 0.4 mm diameter circular orifice shaping mechanism. After cooling, a continuous linear printing filament was obtained. The filament diameter was approximately 0.40 mm, the fiber content was approximately 54%, and the resin content was approximately 46%. A schematic diagram of the intrinsically thermally conductive matrix resin structure is shown below. Figure 1 As shown, the thermal conductivity is 0.43 W / (m·K). The tensile strength of the filament is approximately 1628 MPa, and the axial thermal conductivity is 7.6 W / (m·K). Using this filament, a unidirectional composite material plate was printed using a 3D printer, with the print head temperature set to 280℃. The fiber volume percentage in the composite material is approximately 51%. The tensile strength of the composite material is 1455 MPa (tensile properties were determined according to ASTM D638-14 standard); the interlaminar shear strength is 56 MPa (interlaminar shear test was determined according to ASTM D2344 / D2344M-2016 standard); the heat distortion temperature of the composite material is 234℃ (determined according to ASTM D648-07 standard); the 5wt% thermal decomposition temperature of the composite material is 351℃; the out-of-plane, in-plane perpendicular to fiber direction, and in-plane parallel to fiber direction thermal conductivity of the composite material are 0.84, 1.35, and 7.4 W / (m·K), respectively (determined according to ISO22007-2 standard). The composite material can withstand corrosion from acidic solutions, alkaline solutions, salt solutions, and solvents, except for concentrated sulfuric acid and concentrated nitric acid. After immersing each gram of the composite material in 20 ml of a 1 mol / L hydrochloric acid / water / tetrahydrofuran mixed solution (tetrahydrofuran volume content 80%) at room temperature for 12 hours, the composite material completely degraded. The carbon fiber filaments were removed from the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution, and then dried to recover the carbon fiber filaments, achieving a recovery rate of 99.9%. After neutralizing the acid solution with saturated sodium carbonate solution, precipitation, filtration, washing with water, and drying, 4,4′-diaminobenzoylaniline was obtained, with a recovery rate of 93.2%.

[0052] Comparative Example 2

[0053] 10 mol of paraformaldehyde and 5 mol of 2,2-bis[4-(4-aminophenoxy)phenyl]propane were dissolved sequentially in 2 L of a mixed solvent of N-methylpyrrolidone / water (water volume content 10%), and the mixture was stirred at 60 °C for 30 minutes to obtain a polyhexane triazine prepolymer solution. The prepolymer solution was poured into an impregnation tank, and continuous carbon fiber filaments (T300-1k, fiber axial thermal conductivity approximately 10 W / (m·K)) were impregnated at a rate of 0.5 m / min. The resin content and filament shape were adjusted using a resin extrusion mechanism. The solvent was removed by passing the filaments through hot flow channels at 120, 260, and 80 °C, and the polyhexane triazine resin was completely cured. The shape of the filament was adjusted at 270 °C using a 0.4 mm diameter circular orifice shaping mechanism. After cooling, a continuous linear printing filament was obtained. The filament diameter was approximately 0.41 mm, the fiber content was approximately 53%, and the resin content was approximately 47%. A schematic diagram of the matrix resin structure is shown below. Figure 8As shown, the thermal conductivity is 0.24 W / (m·K). The tensile strength of the filament is approximately 1531 MPa, and the axial thermal conductivity is 5.3 W / (m·K). Using this filament, a unidirectional composite material plate was printed using a 3D printer, with the print head temperature set to 280℃. The fiber volume percentage in the composite material is approximately 50%. The tensile strength of the composite material is 1326 MPa (tensile properties were determined according to ASTM D638-14 standard); the interlaminar shear strength is 53 MPa (interlaminar shear test was determined according to ASTM D2344 / D2344M-2016 standard); the heat distortion temperature of the composite material is 226℃ (determined according to ASTM D648-07 standard); the 5wt% thermal decomposition temperature of the composite material is 381℃; the out-of-plane, in-plane thermal conductivity perpendicular to the fiber, and in-plane thermal conductivity parallel to the fiber are 0.38, 0.54, and 5.1 W / (m·K), respectively (determined according to ISO22007-2 standard). The composite material can withstand corrosion from acidic solutions, alkaline solutions, salt solutions, and solvents, except for concentrated sulfuric acid and concentrated nitric acid. After immersing each gram of the composite material in 20 ml of a 1 mol / L hydrochloric acid / water / tetrahydrofuran mixed solution (tetrahydrofuran volume content 80%) at room temperature for 12 hours, the composite material completely degrades. The carbon fiber filaments are then removed from the acid solution, washed with 0.5 mol / L hydrochloric acid, water, saturated sodium carbonate solution, and water, and dried to recover the carbon fiber filaments with a recovery rate of 99.8%. After neutralizing the acid solution with saturated sodium carbonate solution, precipitation, filtration, washing with water, and drying, 2,2-bis[4-(4-aminophenoxy)phenyl]propane is obtained with a recovery rate of 91.5%.

[0054] Table 1. Comparison of thermal conductivity of 3D printing consumables and their composite materials.

[0055]

[0056] As shown in Table 1, increasing the content and thermal conductivity of thermally conductive continuous fibers, the content and thermal conductivity of thermally conductive fillers, and the thermal conductivity of intrinsically thermally conductive polyhexahydrotriazine resin are all beneficial to improving the thermal conductivity of composite materials. By combining the synergistic thermal conductivity advantages of thermally conductive continuous fibers, thermally conductive fillers, and intrinsically thermally conductive polyhexahydrotriazine resin, the thermal conductivity of 3D printing consumables and their composite materials can be significantly improved.

[0057] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A continuous fiber-reinforced polyhexahydrotriazine 3D-printed thermally conductive composite material, characterized in that, Using 3D printing technology, continuous fiber reinforced polyhexahydrotriazine resin was used as the 3D printing thermal conductive consumable to print a continuous fiber reinforced polyhexahydrotriazine resin 3D printed thermal conductive composite material. The thermally conductive composite material has a tensile strength ≥1200MPa and an in-plane thermal conductivity ≥80W / m·K parallel to the fiber direction; The 3D printed thermally conductive consumable is composed of thermally conductive continuous fiber filaments or tapes, thermally conductive fillers, and an intrinsically thermally conductive polyhexahydrotriazine resin matrix; the volume percentage of the continuous fiber filaments or tapes in the composite material is 25%~75%, the content of the thermally conductive fillers is 5~30%, and the content of the matrix is ​​20%~70%; the matrix is ​​the following structural formula (1) or (2) or a mixture thereof: R1, R2, and R3 can be any of the following structures: R4 can be any of the following structures: ； The 3D printed thermal conductive consumable is prepared through the following steps: (1) Dissolve formaldehyde and aromatic amine uniformly in a proton / water mixed solvent, stir and react at 40-90℃ for 10-60 minutes to carry out prepolymerization, add thermally conductive filler and disperse uniformly for 5-30 minutes to obtain prepolymer / thermally conductive filler mixed solution; (2) Impregnate the continuous fiber filament or continuous fiber tape with the prepolymer / thermal filler mixture obtained in step (1), adjust the glue content and tape shape through the glue extrusion mechanism, remove the solvent through the hot flow channel, completely cure the polyhexahydrotriazine resin, adjust the cross-sectional shape of the consumable through the shaping mechanism, and roll it up after cooling to obtain the 3D printed thermal conductive consumable. The impregnation in step (2) is carried out in the impregnation device at a speed of 0.1~5m / min; the temperature range of the hot flow channel is divided into three sections, with temperatures of 60~150, 160~300, and 40~100℃ respectively; the heating temperature of the shaping mechanism is 200~300℃, and the filament shaping mechanism is located between the second and third sections of the hot flow channel.

2. The thermally conductive composite material according to claim 1, characterized in that, The thermally conductive composite material has a fiber volume percentage of 45%~75%, a thermally conductive filler content of 5%~30%, and a matrix content of 20%~50%; the in-plane thermal conductivity in the direction parallel to the fiber is ≥100W / m·K.

3. The thermally conductive composite material according to claim 1 or 2, characterized in that, The continuous fiber filament or tape is one or more of the following: continuous carbon fiber filament or tape, continuous graphite fiber filament or tape, or continuous metal fiber filament or tape with an axial thermal conductivity greater than 100 W / m·K.

4. The thermally conductive composite material according to claim 1 or 2, characterized in that, The thermally conductive filler is one or more of the following: alumina 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, carbon nanofibers, diamond, carbon black, carbon nanotubes, graphene, and graphynylene.

5. The thermally conductive composite material according to claim 1 or 4, characterized in that, The molar ratio of formaldehyde to aromatic diamine is 2:1, and the molar ratio of formaldehyde to aromatic triamine is 3:

1. The aromatic amine has at least one or more of the following structures: 。 6. The thermally conductive composite material according to claim 1, characterized in that, The aprotic solvent is one or more of N-methylpyrrolidone, dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, 2,5-dimethylfuran, and hexamethylphosphoramide; the water content in the mixed solvent is 1% to 30% by volume; the volume of solvent added per gram of reactant is 0.5 to 10 ml; the 3D printing technology includes fused deposition modeling or automatic filament placement and automatic tape placement; the shaping mechanism is a circle with a diameter of 0.1 to 1 mm, or a rectangle with a length of 1 mm to 5 cm and a width of 0.1 mm to 1 mm.

7. The thermally conductive composite material according to claim 1, characterized in that, This thermally conductive composite material is degradable and recyclable. The degradation and recycling methods are as follows: the fiber is separated from the degradation acid solution by soaking in a strong acid / solvent mixed solution, and then dried after washing with acid solution, water, alkali solution and water to recover the fiber; the degradation acid solution is further filtered or centrifuged, and then dried after washing with acid solution, water, alkali solution and water to recover the thermally conductive filler; finally, the degradation acid solution is neutralized with alkali solution, precipitated, filtered, washed with water and dried to obtain the aromatic amine, the raw material for resin synthesis.

8. The thermally conductive composite material according to claim 7, characterized in that, The strong acid is sulfuric acid and hydrochloric acid, and the alkaline solution is a saturated solution of sodium carbonate or sodium bicarbonate; the amount of the strong acid / solvent mixture is 5-30 ml per gram of composite material, the concentration of the strong acid is 0.1-12 mol / L, and the solvent is one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, dichloromethane, tetrahydrofuran, 2,5-dimethylfuran, and hexamethylphosphoramide; the soaking temperature is 20-95℃, and the soaking time is 0.5-24 hours.

Images