A carbon fiber reinforced PA6 composite material for 3D printing and its preparation method

Abstract

The present invention provides a carbon fiber reinforced PA6 composite material for 3D printing and a preparation method thereof, relating to the technical fields of additive manufacturing and polymer materials. The method includes performing surface modification treatment on carbon fibers, introducing the modified carbon fiber tow into a twin-screw extruder for melt mixing and granulation with PA6 and SEBS to obtain the carbon fiber reinforced PA6 composite material. The present invention has the prospect of continuous production, and is expected to provide technical reference for customized sizing treatment of carbon fibers for the reinforcement of thermoplastic plastics; the carbon fiber reinforced PA6 composite material and the preparation method provided by the present invention are expected to become a technology popularization and application demonstration for producing strong and tough integrated engineering plastics and further 3D printing into engineering parts with high interlayer adhesion strength.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing and polymer materials, and in particular to a carbon fiber reinforced PA6 composite material for 3D printing and a preparation method thereof. Background Art

[0002] Fused deposition modeling (FDM) is a commonly used 3D printing process with the advantages of low cost, simple operation and maintenance, high user penetration rate and wide material applicability. At present, commonly used FDM 3D printing materials include polylactic acid, acrylonitrile-butadiene-styrene copolymer, thermoplastic polyurethane, polyamide 6 (PA6), polyphenylene sulfide (PPS) and polyetheretherketone (PEEK). Therefore, the FDM process is favored in cultural and creative industries, personalized medical protective gear, personalized consumer products, new energy vehicles, aerospace and other fields.

[0003] PA6 has excellent mechanical properties and good wear resistance and corrosion resistance, and is a widely used engineering plastic. The mechanical strength of PA6 can be greatly improved after being reinforced with carbon fiber, further broadening its application field and is expected to become an important engineering plastic to replace metals such as steel and iron. The combination of carbon fiber reinforced PA6 composite materials and FDM technology will make the low-cost and efficient production of complex-shaped high-performance engineering parts a reality.

[0004] By mixing in polyolefin elastomers, the impact strength of carbon fiber reinforced PA6 composite 3D printed parts can be greatly improved to 21 kJ / m2, but its tensile strength is reduced to 94.1 MPa (Polymer Composites 2024;1–15.doi:10.1002 / pc.28783). This is mainly due to the weak interface bonding between carbon fiber and PA6 matrix. In addition, the above research work did not mention the interlayer bonding of 3D printed parts (z-direction tensile strength), which is particularly important for the service performance of 3D printed parts.

[0005] The carbon fiber currently on the market is mainly used to strengthen thermosetting plastics, using low molecular weight epoxy resin as the surface sizing agent. The affinity between the sizing agent and thermoplastics such as PA6 is weak, so it is difficult to form a strong interface effect during compounding, and its reinforcing effect cannot be fully exerted. Therefore, it is urgent to develop a carbon fiber surface modification method suitable for thermoplastics such as PA6 and the corresponding carbon fiber reinforced PA6 composite material, so as to be used for 3D printing of strong and tough, high-inter-layer bonding strength PA6 parts. Summary of the invention

[0006] In order to overcome the deficiencies of the prior art, an object of the present invention is to provide a carbon fiber reinforced PA6 composite material for 3D printing and a preparation method thereof.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] The present invention provides a carbon fiber reinforced PA6 composite material for 3D printing, comprising: the composite material is composed of the following components in weight percentage;

[0009] PA6: 50wt% - 95wt%;

[0010] Carbon fiber: 1wt% - 45wt%;

[0011] SEBS: 3wt% - 30wt%.

[0012] Preferably, the SEBS is at least one of unmodified SEBS and SEBS-g-MAH.

[0013] The present invention also provides a preparation method of a carbon fiber reinforced PA6 composite material for 3D printing, comprising:

[0014] Performing surface modification treatment on the carbon fiber;

[0015] Introducing the surface-modified carbon fiber tow into a twin-screw extruder to perform melt mixing and pelletizing with PA6 and SEBS to obtain a carbon fiber reinforced PA6 composite material.

[0016] Preferably, based on the carbon fiber reinforced PA6 composite material for 3D printing, the surface modification treatment of the carbon fiber is specifically:

[0017] Performing desizing treatment on the carbon fiber tow;

[0018] Performing alkali treatment on the desized carbon fiber tow;

[0019] Performing silane treatment on the alkali-treated desized carbon fiber tow;

[0020] Grafting the silane-treated desized carbon fiber tow with maleic anhydride;

[0021] Performing re-sizing on the grafted desized carbon fiber tow.

[0022] Preferably, the desizing treatment of the carbon fiber tow is specifically:

[0023] Driving the carbon fiber tow through a high-temperature furnace by traction to complete desizing, wherein the temperature is 200 - 400 °C and the time passing through the high-temperature furnace is 0.5 - 3 minutes.

[0024] Preferably, the alkali treatment of the desized carbon fiber tow is specifically:

[0025] The desized carbon fiber tow is driven by traction to pass through an aqueous sodium hydroxide solution, wherein the concentration of the aqueous sodium hydroxide solution is 10 mol / L, the passing time is 0.5 - 3 minutes, and after passing through, it enters a water tank for cleaning.

[0026] Preferably, the desized carbon fiber tow after alkali treatment is subjected to silane treatment, specifically:

[0027] The desized carbon fiber tow after cleaning is driven by traction to pass through a silane solution, wherein the silane is at least one of trimethoxysilane and triethoxysilane, the solvent of the silane solution is a mixed solution including water and ethanol or methanol, the volume ratio of water / ethanol or methanol is 90 / 10 - 20 / 80, the silane content in the silane solution is 0.5 wt% - 20 wt%, and the passing time through the silane solution is 5 - 30 minutes.

[0028] Preferably, the desized carbon fiber tow after silane treatment is grafted with maleic anhydride, specifically:

[0029] The desized carbon fiber tow after silane treatment is driven by traction to pass through an aqueous maleic anhydride solution, wherein the maleic anhydride content is 1 wt% - 30 wt%, the content of the Kester catalyst in the aqueous maleic anhydride solution is 0.1 wt%, the temperature of the aqueous maleic anhydride solution is 40 - 80 °C, and the passing time through the aqueous maleic anhydride solution is 5 - 30 minutes.

[0030] Preferably, the desized carbon fiber tow after grafting is re - sized, specifically:

[0031] The desized carbon fiber tow after grafting is driven by traction to pass through a blast high - temperature furnace for drying, wherein the temperature is 120 - 180 °C, the passing time is 2 minutes, and the dried desized carbon fiber passes through a low - molecular - weight PA6 melt for impregnation, wherein the molecular weight of PA6 is 1000 - 11000 g / mol, the temperature of the low - molecular - weight PA6 melt is 220 - 260 °C, and the passing time is 1 - 5 minutes to complete re - sizing.

[0032] Preferably, the modified carbon fiber tow is introduced into a twin - screw extruder and melt - compounded and pelletized with PA6 and SEBS to obtain a carbon fiber - reinforced PA6 composite material, specifically:

[0033] The re - sized carbon fiber tow is introduced into a twin - screw extruder and melt - compounded and pelletized with PA6 and SEBS to obtain a carbon fiber - reinforced PA6 composite material, wherein the molecular weight of PA6 is 12000 - 57000 g / mol, and the extrusion compounding temperature is 220 - 270 °C.

[0034] According to the specific embodiments provided by the present invention, the following technical effects of the present invention are disclosed:

[0035] The present invention provides a carbon fiber reinforced PA6 composite material for 3D printing and a preparation method thereof. The method includes performing surface modification treatment on carbon fibers, introducing the modified carbon fiber filaments into a twin-screw extruder for melt mixing and granulation with PA6 and SEBS to obtain the carbon fiber reinforced PA6 composite material. The present invention has the prospect of continuous production, and is expected to provide technical reference for customized sizing treatment of carbon fibers for the reinforcement of thermoplastic plastics; the carbon fiber reinforced PA6 composite material and the preparation method provided by the present invention are expected to become a technology for producing tough and integral engineering plastics and further promoting the application of 3D printing to form engineering parts with high interlayer bonding strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0037] Figure 1 It is a schematic flow chart of the preparation method of the carbon fiber reinforced PA6 composite material for 3D printing provided by the embodiment of the present invention;

[0038] Figure 2 It is a SEM micrograph of the brittle fracture surface of the carbon fiber reinforced PA6 composite material in Example 2 and Comparative Example 2;

[0039] Figure 3 It is a schematic diagram of the DSC curves of the carbon fiber reinforced PA6 composite materials in Example 4, Comparative Example 4, Example 5 and Comparative Example 5. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0041] The object of the present invention is to provide a carbon fiber reinforced PA6 composite material for 3D printing. The prepared composite material can be 3D printed by the FDM process. The parts printed with the carbon fiber reinforced PA6 composite material prepared by the present invention have the advantages of being tough and integral and having high interlayer bonding strength.

[0042] To make the above objects, features, and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] The present invention provides a carbon fiber reinforced PA6 composite material for 3D printing, and the composite material is composed of the following components in weight percentage;

[0044] PA6: 50wt% - 95wt%;

[0045] Carbon fiber: 1wt% - 45wt%;

[0046] SEBS: 3wt% - 30wt%.

[0047] The SEBS is at least one of unmodified SEBS and SEBS-g-MAH (maleic anhydride grafted SEBS).

[0048] Figure 1 It is a flowchart of the method provided by the embodiment of the present invention. As Figure 1 shown, the present invention also provides a preparation method of a carbon fiber reinforced PA6 composite material for 3D printing, including:

[0049] Step 100: Modify the surface of the carbon fiber;

[0050] Step 200: Introduce the modified carbon fiber tow into a twin-screw extruder and melt-mix and pelletize it with PA6 and SEBS to obtain a carbon fiber reinforced PA6 composite material.

[0051] In step 100, based on the carbon fiber reinforced PA6 composite material for 3D printing, the surface of the carbon fiber is modified specifically as follows:

[0052] Step 101: Desize the carbon fiber tow;

[0053] Step 102: Alkaline-treat the desized carbon fiber tow;

[0054] Step 103: Silane-treat the alkaline-treated desized carbon fiber tow;

[0055] Step 104: Graft the silane-treated desized carbon fiber tow with maleic anhydride;

[0056] Step 105: Resize the grafted desized carbon fiber tow.

[0057] In step 101, the desizing treatment of the carbon fiber tow is specifically as follows:

[0058] The carbon fiber tow is driven by traction to pass through a high-temperature furnace to complete desizing. Among them, the temperature is 200 - 400 °C, preferably 300 - 360 °C, and the time for passing through the high-temperature furnace is 0.5 - 3 minutes, preferably 1 - 2 minutes.

[0059] In step 102, the desized carbon fiber tow is subjected to alkali treatment. Specifically:

[0060] The desized carbon fiber tow is driven by traction to pass through an aqueous sodium hydroxide solution. Among them, the concentration of the aqueous sodium hydroxide solution is 10 mol / L, the passing time is 0.5 - 3 minutes, preferably 1 - 2 minutes, and after passing through, it enters a clear water tank for cleaning.

[0061] In step 103, the desized carbon fiber tow after alkali treatment is subjected to silane treatment. Specifically:

[0062] The desized carbon fiber tow after cleaning is driven by traction to pass through a silane solution. Among them, the silane is at least one of trimethoxysilane and triethoxysilane, the solvent of the silane solution is a mixed solution including water and ethanol or methanol, the volume ratio of water / ethanol (methanol) is 90 / 10 - 20 / 80, preferably 30 / 70 - 60 / 40, the silane content in the silane solution is 0.5 wt% - 20 wt%, preferably 5 wt% - 10 wt%, and the time for passing through the silane solution is 5 - 30 minutes, preferably 15 minutes.

[0063] In step 104, the desized carbon fiber tow after silane treatment is grafted with maleic anhydride. Specifically:

[0064] The maleic anhydride grafting reaction on the surface of the carbon fiber tow is that maleic anhydride reacts with the silane on the surface of the carbon fiber tow and is grafted onto its surface through a silicon-hydrogen reaction. The desized carbon fiber tow after silane treatment is driven by traction to pass through an aqueous maleic anhydride solution. Among them, the maleic anhydride content is 1 wt% - 30 wt%, preferably 10 wt%, the silicon-hydrogen reaction is initiated by a Karstedt catalyst dispersed in the aqueous maleic anhydride solution, the Karstedt catalyst content in the aqueous maleic anhydride solution is 0.1 wt%, the temperature of the aqueous maleic anhydride solution is 40 - 80 °C, preferably 55 °C, and the time for passing through the aqueous maleic anhydride solution is 5 - 30 minutes, preferably 15 minutes.

[0065] In step 105, the desized carbon fiber tow after grafting is re-sized. Specifically:

[0066] The sized carbon fiber tow after grafting is driven by traction and dried in a blast high-temperature furnace, where the temperature is 120 - 180 °C, the passing time is 2 minutes. The dried sized carbon fiber is impregnated in a low-molecular-weight PA6 melt, where the molecular weight of PA6 is 1000 - 11000 g / mol, preferably 8000 g / mol, the temperature of the low-molecular-weight PA6 melt is 220 - 260 °C, preferably 240 °C, and the passing time is 1 - 5 minutes, preferably 2 minutes. In the low-molecular-weight PA6 melt, maleic anhydride grafted on the surface of the carbon fiber tow reacts with the amino group on the PA6 molecular chain, thereby generating a covalent bond interaction between the molecular chains. After winding, re-sizing is completed.

[0067] In step 200, the modified carbon fiber tow is introduced into a twin-screw extruder and melt-mixed and granulated with PA6 and SEBS to obtain a carbon fiber reinforced PA6 composite material. Specifically:

[0068] The re-sized carbon fiber tow is introduced into a twin-screw extruder and melt-mixed and granulated with PA6 and SEBS to obtain a carbon fiber reinforced PA6 composite material. Among them, the molecular weight of PA6 is 12000 - 57000 g / mol, the extrusion and mixing temperature is 220 - 270 °C, preferably 240 - 255 °C. The basic formula of the extruded carbon fiber reinforced PA6 composite material is: PA6 accounts for 50 - 95 wt%, carbon fiber accounts for 1 - 45 wt%, and SEBS accounts for 3 - 30 wt%; the SEBS is at least one of unmodified SEBS or maleic anhydride grafted SEBS (SEBS-g-MAH);

[0069] The carbon fiber reinforced PA6 composite material prepared by extrusion and mixing can be further prepared into wire rods with standard diameters (1.75 or 2.80 mm) for 3D printing, or directly printed and formed using a particle extrusion type 3D printer.

[0070] The present invention provides six examples. According to the above method, a carbon fiber reinforced PA6 composite material is prepared. Among them, the FDM process is used to 3D print and form the carbon fiber reinforced PA6 composite material, and the mechanical properties of the test piece, especially the interlayer adhesion strength, are analyzed. Six examples are introduced respectively:

[0071] Example 1:

[0072] 1. The re-sized carbon fiber tow is introduced into a twin-screw extruder and melt-mixed and granulated with PA6 and SEBS-g-MAH to obtain a carbon fiber reinforced PA6 composite material, where the carbon fiber content is 10 wt%, the PA6 content is 70 wt%, and the SEBS-g-MAH content is 20 wt%. A differential scanning calorimeter (DSC) is used to test the crystallization temperature of the composite material.

[0073] 2. The carbon fiber reinforced PA6 composite material was printed into standard mechanical splines by the FDM process. The printing nozzle size was 0.4 mm, the nozzle temperature was 240 °C, the printing speed was 60 mm / s, and the printing direction was the x-axis direction; the printing direction of the standard mechanical splines for evaluating the interlayer adhesion strength was the z-axis direction. The tensile strength of the splines was tested using an electronic tensile testing machine, and the notched impact strength of the splines was tested using an impact testing machine.

[0074] Example 2:

[0075] 1. The re-sized carbon fiber tow was introduced into a twin-screw extruder and melt-blended with PA6 and SEBS-g-MAH to produce pellets of a carbon fiber reinforced PA6 composite material, where the carbon fiber content was 20 wt%, the PA6 content was 60 wt%, and the SEBS-g-MAH content was 20 wt%. The crystallization temperature of the composite material was tested using a differential scanning calorimeter (DSC).

[0076] 2. The carbon fiber reinforced PA6 composite material was printed into standard mechanical splines by the FDM process. The printing nozzle size was 0.4 mm, the nozzle temperature was 240 °C, the printing speed was 60 mm / s, and the printing direction was the x-axis direction; the printing direction of the standard mechanical splines for evaluating the interlayer adhesion strength was the z-axis direction. The tensile strength of the splines was tested using an electronic tensile testing machine, and the notched impact strength of the splines was tested using an impact testing machine.

[0077] Example 3:

[0078] 1. The re-sized carbon fiber tow was introduced into a twin-screw extruder and melt-blended with PA6 and SEBS-g-MAH to produce pellets of a carbon fiber reinforced PA6 composite material, where the carbon fiber content was 30 wt%, the PA6 content was 50 wt%, and the SEBS-g-MAH content was 20 wt%. The crystallization temperature of the composite material was tested using a differential scanning calorimeter (DSC).

[0079] 2. The carbon fiber reinforced PA6 composite material was printed into standard mechanical splines by the FDM process. The printing nozzle size was 0.4 mm, the nozzle temperature was 240 °C, the printing speed was 60 mm / s, and the printing direction was the x-axis direction; the printing direction of the standard mechanical splines for evaluating the interlayer adhesion strength was the z-axis direction. The tensile strength of the splines was tested using an electronic tensile testing machine, and the notched impact strength of the splines was tested using an impact testing machine.

[0080] Example 4:

[0081] 1. Introduce the re-sized carbon fiber tow into a twin-screw extruder and melt-knead and granulate it with PA6 and SEBS-g-MAH to obtain a carbon fiber-reinforced PA6 composite material, where the carbon fiber content is 20 wt%, the PA6 content is 75 wt%, and the SEBS-g-MAH content is 5 wt%. Use a differential scanning calorimeter (DSC) to measure the crystallization temperature of the composite material.

[0082] 2. Use the FDM process to print the carbon fiber-reinforced PA6 composite material into standard mechanical splines. The print nozzle size is 0.4 mm, the nozzle temperature is 240 °C, the printing speed is 60 mm / s, and the printing direction is the x-axis direction; the standard mechanical splines for evaluating the interlayer adhesion strength are printed in the z-axis direction. Use an electronic tensile machine to measure the tensile strength of the splines and an impact testing machine to measure the notched impact strength of the splines.

[0083] Example 5:

[0084] 1. Introduce the re-sized carbon fiber tow into a twin-screw extruder and melt-knead and granulate it with PA6 and SEBS-g-MAH to obtain a carbon fiber-reinforced PA6 composite material, where the carbon fiber content is 20 wt%, the PA6 content is 65 wt%, and the SEBS-g-MAH content is 15 wt%. Use a differential scanning calorimeter (DSC) to measure the crystallization temperature of the composite material.

[0085] 2. Use the FDM process to print the carbon fiber-reinforced PA6 composite material into standard mechanical splines. The print nozzle size is 0.4 mm, the nozzle temperature is 240 °C, the printing speed is 60 mm / s, and the printing direction is the x-axis direction; the standard mechanical splines for evaluating the interlayer adhesion strength are printed in the z-axis direction. Use an electronic tensile machine to measure the tensile strength of the splines and an impact testing machine to measure the notched impact strength of the splines.

[0086] Example 6:

[0087] 1. Introduce the re-sized carbon fiber tow into a twin-screw extruder and melt-knead and granulate it with PA6 and SEBS-g-MAH to obtain a carbon fiber-reinforced PA6 composite material, where the carbon fiber content is 20 wt%, the PA6 content is 50 wt%, and the SEBS-g-MAH content is 30 wt%. Use a differential scanning calorimeter (DSC) to measure the crystallization temperature of the composite material.

[0088] 2. The carbon fiber reinforced PA6 composite material was printed into standard mechanical splines by the FDM process. The printing nozzle size was 0.4 mm, the nozzle temperature was 240 °C, the printing speed was 60 mm / s, and the printing direction was the x-axis direction; the printing direction of the standard mechanical splines for evaluating the interlayer adhesion strength was the z-axis direction. The tensile strength of the splines was tested using an electronic tensile testing machine, and the notched impact strength of the splines was tested using an impact testing machine.

[0089] The present invention additionally provides six comparative examples, which are respectively:

[0090] Comparative Example 1:

[0091] The difference from Example 1 is only that: commercially available epoxy-sized carbon fiber tows were used.

[0092] Comparative Example 2:

[0093] The difference from Example 2 is only that: commercially available epoxy-sized carbon fiber tows were used.

[0094] Comparative Example 3:

[0095] The difference from Example 3 is only that: commercially available epoxy-sized carbon fiber tows were used.

[0096] Comparative Example 4:

[0097] The difference from Example 4 is only that: the toughening phase used was SEBS.

[0098] Comparative Example 5:

[0099] The difference from Example 5 is only that: the toughening phase used was SEBS.

[0100] Comparative Example 6:

[0101] The difference from Example 6 is only that: the toughening phase used was SEBS.

[0102] For the convenience of comparison, re-sized carbon fiber tows prepared by the preferred process were uniformly used in the examples for experiments; the extrusion and mixing temperature was also uniformly 255 °C. The test results of the mechanical properties and crystallization behavior are shown in Table 1.

[0103] Table 1 Tensile strength data of fused deposition molding products prepared in Examples 1-6 and Comparative Examples 1-6

[0104] Case Tensile strength in the x direction Notched impact strength Tensile strength in the z direction Crystallization temperature Example 1 89 ± 1.9 MPa <![CDATA[36±1.6 kJ / m 2 > 55 ± 3.3 MPa 176.6 ℃ Example 2 133 ± 2.6 MPa <![CDATA[35±1.4 kJ / m 2 > 59 ± 2.7 MPa 174.1 ℃ Example 3 139 ± 3.1 MPa <![CDATA[24±1.9 kJ / m 2 > 45 ± 4.4 MPa 174.7 ℃ Example 4 157 ± 3.8 MPa <![CDATA[7.2±2.0 kJ / m 2 > 33 ± 2.2 MPa 181.0 ℃ Example 5 143 ± 4.5 MPa <![CDATA[21±2.4 kJ / m 2 > 37 ± 3.2 MPa 179.3 ℃ Example 6 78 ± 4.9 MPa <![CDATA[33 ± 1.5 kJ / m 2 > 19 ± 1.9 MPa 173.3 ℃ Comparative Example 1 56 ± 2.0 MPa <![CDATA[30±1.8 kJ / m 2 > 17 ± 1.3 MPa 176.9 ℃ Comparative Example 2 63 ± 2.7 MPa <![CDATA[28±1.6 kJ / m 2 > 14 ± 1.3 MPa 176.3 ℃ Comparative Example 3 68 ± 3.3 MPa <![CDATA[23±2.5 kJ / m 2 > 12 ± 1.8 MPa 176.0 ℃ Comparative Example 4 118 ± 0.9 MPa <![CDATA[6.7±2.1 kJ / m 2 > 22 ± 1.3 MPa 183.1 ℃ Comparative Example 5 112 ± 1.6 MPa <![CDATA[6.9±1.1 kJ / m 2 > 19 ± 3.7 MPa 182.6 ℃ Comparative Example 6 97 ± 2.2 MPa <![CDATA[14±1.4 kJ / m 2 > 18 ± 4.1 MPa 179.2 ℃

[0105] As can be seen from Table 1, the carbon fiber reinforced PA6 composite material prepared by the present invention for 3D printing can exhibit excellent tensile strength and impact strength, and the tensile strength in the z direction is also significantly higher, indicating an improvement in the interlayer adhesion strength of the parts. The increase in the tensile strength in the X direction is mainly due to the enhanced interfacial interaction between the re-sized carbon fiber and the PA6 matrix; the increase in the impact strength is mainly due to the reaction between the maleic anhydride on the molecular chain of SEBS-g-MAH and the amino group on the molecular chain of PA6 to form a strong interfacial interaction; the increase in the interlayer adhesion strength is on the one hand because the addition of SEBS-g-MAH reduces the crystallization temperature of PA6, and on the other hand because a strong interaction is formed between SEBS-g-MAH and the PA6 molecular chain at the interlayer interface.

[0106] As Figure 2 shown, Figure 2 Figures a and b in it are respectively SEM micrographs of the brittle fracture surfaces of the carbon fiber reinforced PA6 composite materials in Example 2 and Comparative Example 2. As can be seen from the figure, there is a good interfacial bonding between the re-sized carbon fiber and the PA6 matrix in Example 2, and most of the carbon fibers are well coated by the PA6 matrix; while the carbon fibers with epoxy sizing agent in Comparative Example 2 have a weak bonding with the PA6 matrix, and most of the carbon fibers are exposed outside the PA6 matrix.

[0107] As Figure 3 shown, Figure 3 are the DSC curves of the carbon fiber reinforced PA6 composite materials in Example 4, Comparative Example 4, Example 5 and Comparative Example 5. As can be seen from the figure, increasing the content of SEBS or SEBS-g-MAH helps to reduce the crystallization temperature of PA6; and the effect of SEBS-g-MAH is more significant than that of SEBS.

[0108] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0109] Specific examples are used in this article to elaborate on the principles and implementation methods of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A preparation method of a carbon fiber reinforced PA6 composite material for 3D printing, characterized in that, Including: Desizing the carbon fiber tow; Alkali-treating the desized carbon fiber tow: driving the desized carbon fiber tow through an aqueous sodium hydroxide solution by traction; Silane-treating the alkali-treated desized carbon fiber tow: driving the washed desized carbon fiber tow through a silane solution by traction, wherein the silane is at least one of trimethoxysilane and triethoxysilane; Grafting the silane-treated desized carbon fiber tow with maleic anhydride: driving the silane-treated desized carbon fiber tow through an aqueous maleic anhydride solution by traction; Resizing the grafted desized carbon fiber tow: driving the grafted desized carbon fiber tow through a blast high-temperature furnace for drying by traction, and impregnating the dried desized carbon fiber through a low-molecular-weight PA6 melt, wherein the molecular weight of the low-molecular-weight PA6 is 1000-11000 g / mol, the temperature of the low-molecular-weight PA6 melt is 220-260 °C, and the passing time is 1-5 minutes to complete resizing; Drawing the resized carbon fiber tow into a twin-screw extruder to melt-mix and pelletize with PA6 and SEBS to obtain a carbon fiber-reinforced PA6 composite material, wherein the SEBS is SEBS-g-MAH; The specific content of the carbon fiber-reinforced PA6 composite material is: the carbon fiber content is 20 wt%, the PA6 content is 60 wt%, and the SEBS-g-MAH content is 20 wt%.

2. The method according to claim 1, wherein Desizing the carbon fiber tow, specifically: Completing desizing by driving the carbon fiber tow through a high-temperature furnace by traction, wherein the temperature is 200-400 °C, and the passing time through the high-temperature furnace is 0.5-3 minutes.

3. The method according to claim 1, wherein Alkali-treating the desized carbon fiber tow, specifically: Driving the desized carbon fiber tow through an aqueous sodium hydroxide solution by traction, wherein the concentration of the aqueous sodium hydroxide solution is 10 mol / L, the passing time is 0.5-3 minutes, and after passing through, it enters a clear water tank for cleaning.

4. The method according to claim 1, characterized in that Silane-treating the alkali-treated desized carbon fiber tow, specifically: Driving the washed desized carbon fiber tow through a silane solution by traction, wherein the silane is at least one of trimethoxysilane and triethoxysilane, the solvent of the silane solution is a mixed solution including water and ethanol or methanol, the volume ratio of water / ethanol or methanol is 90 / 10-20 / 80, the silane content in the silane solution is 0.5 wt%-20 wt%, and the passing time through the silane solution is 5-30 minutes.

5. The method according to claim 1, characterized in that, Grafting the silane-treated desized carbon fiber tow with maleic anhydride, specifically: Driving the silane-treated desized carbon fiber tow through an aqueous maleic anhydride solution by traction, wherein the maleic anhydride content is 1 wt%-30 wt%, the content of the Kester catalyst in the aqueous maleic anhydride solution is 0.1 wt%, the temperature of the aqueous maleic anhydride solution is 40-80 °C, and the passing time through the aqueous maleic anhydride solution is 5-30 minutes.

6. The method according to claim 1, wherein The drying temperature of the blast high-temperature furnace is 120-180 °C, and the passing time is 2 minutes.

7. The method according to claim 1, characterized in that, The re-sized carbon fiber tow is introduced into a twin-screw extruder for melt mixing and pelletizing with PA6 and SEBS to obtain a carbon fiber reinforced PA6 composite material. Among them, the molecular weight of PA6 is 12,000 - 57,000 g / mol, and the extrusion and mixing temperature is 220 - 270 °C.

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