Polycarbonate composite material for 3D printing of granules and preparation method of polycarbonate composite material

Abstract

The invention provides a polycarbonate composite material for particle 3D printing. The polycarbonate composite material comprises the following substances in parts by weight: 75-85 parts of polycarbonate, 5-10 parts of polyketone resin, 3-5 parts of thermoplastic polyurethane, 15-25 parts of carbon fibers, 0.05-0.5 part of an antioxidant, 0.5-1.5 parts of a lubricant and 0.5-1.5 parts of a surface improver, and the melt index of the polycarbonate is 15-20g / min. The polycarbonate composite material prepared by the invention still has excellent dimensional stability under the condition of high-temperature repeated heating, and has excellent mechanical strength and heat resistance, and when the polycarbonate composite material prepared by the invention is used for printing, the buckling deformation is less, and the interlayer cracking is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and in particular to a polycarbonate composite material for granular 3D printing and a preparation method thereof. Background Art

[0002] Industrial 3D printers are faster and more accurate, and are widely used in industrial machinery, aerospace, automobile manufacturing, wind power, construction, medical and other fields. In particular, they have unique advantages in the field of molds. For example, the current traditional mold making process includes mold design-main mold construction-main mold trimming-main mold gel coat curing-main mold grinding-production mold preparation-main mold demoulding wax-mold gel coat-mold laying, mold curing and reinforcement-production mold surface treatment-qualified main mold-finished product production and other processes, which generally take no less than 2 months and require a lot of manpower. However, with the 3D printing process, as long as the mold design-model processing-3D printing-CNC processing-gel coat grinding-qualified main mold-finished product production and other processes are experienced, it takes basically one week to solve, and only one person is required to operate it. Moreover, because they are all calculated and evaluated by computer-generated software, the product is more accurate, the mold is close to the final contour, and the milling gantry five-axis is used for the final processing and molding of the mold. Less material is removed and the efficiency is higher. It can also reduce the time and cost to the greatest extent, and can also reduce the use of materials to the greatest extent. It has the characteristics of low cost, fast forming speed, strong forming ability and high degree of automation.

[0003] In the automotive, aerospace and other fields, the autoclave molding molds used usually require the materials to have the following characteristics: (1) excellent dimensional stability under high-temperature repeated heating; (2) high temperature resistance, with the heat deformation temperature (ISO 75, 1.8MPa) required to be above 135°C; (3) high mechanical strength, with the bending strength of the part required to be 150MPa and the bending modulus required to be 7000MPa (ISO178).

[0004] Compared with traditional removal processes such as turning, milling, planing and grinding, the typical feature of 3D printing is the use of a material addition process that accumulates materials layer by layer. The 3D printing process uses thermoplastic composite material particles to melt and stack them layer by layer to prepare autoclave molding molds. In order to ensure that the mold has excellent properties: (1) the printing process needs to be smooth and stable, and the print head must discharge the material smoothly and evenly; (2) there should be little warping and deformation during the printing process, and no cracking between layers; (3) the surface of the printed object is smooth and free of burrs; the bonding between layers is strong; (4) the printed parts are dense, and the density of the parts reaches 95% of the density of injection molded parts. Therefore, this field is in urgent need of additive manufacturing materials and manufacturing methods with improved mechanical properties. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a polycarbonate composite material for granular 3D printing and a preparation method thereof, which can improve the mechanical strength, heat resistance and dimensional stability of polycarbonate.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions:

[0007] A polycarbonate composite material for pellet 3D printing comprises the following substances in parts by weight: 75-85 of polycarbonate, 5-10 of polyketone resin, 3-5 of thermoplastic polyurethane, 15-25 of carbon fiber, 0.05-0.5 of antioxidant, 0.5-1.5 of lubricant, and 0.5-1.5 of surface improver. The melt index of the polycarbonate is between 15 g / min and 20 g / min.

[0008] The present invention is further configured as follows: the lubricant is one or more of soaps, stearyl stearate, montan wax soap ester, paraffin, pentaerythritol stearate, silicone oil, and silicone.

[0009] The present invention is further configured as follows: the antioxidant is one or more of a hindered phenol antioxidant and a phosphite.

[0010] The present invention is further configured as follows: the surface improver is an organic fluorine polymer additive.

[0011] The present invention is further configured as follows: the melt index of the polycarbonate is selected to be 10 g / min.

[0012] The present invention also provides a method for preparing a polycarbonate composite material for pellet 3D printing, the steps of which are: the raw materials are mixed evenly in a high-speed mixer, and then added to a twin-screw extruder for extrusion and granulation to obtain the polycarbonate composition, wherein the twin-screw has a length-to-diameter ratio of 32:1 to 44:1.

[0013] The polycarbonate composite material prepared by the present invention still has excellent dimensional stability under high temperature repeated heating, and has excellent mechanical strength and heat resistance. During the printing process using the polycarbonate composite material prepared by the present invention, there is little warping deformation and no cracking between layers. DETAILED DESCRIPTION

[0014] The technical solution of the present invention is further described below in conjunction with embodiments.

[0015] The present invention relates to a thermoplastic material 3D printing system that directly uses thermoplastic material as a building material. This system can control the relative movement between molten plastic and a matrix. By applying the molten material according to a pre-set position plan, the system can construct products in a layer-by-layer manner.

[0016] Using a 3D printing method to form at least one layer of thermoplastic material that can be fused to the next adjacent layer, multiple layers in a predetermined pattern can be fused to provide an article, and any method that effectively fuses multiple layers during additive manufacturing can be used. Fusion occurs during the formation of each layer, or fusion occurs while subsequent layers are formed, or after all layers are formed. Multiple layers are formed in a preset pattern by an additive manufacturing process, and "multiple" in the context of additive manufacturing includes 2 or more layers. For example, the maximum number of layers can vary and can be determined by, for example, considering factors such as the size of the manufactured article, the technology used, the capabilities of the equipment used, and the level of detail required in the final article. For example, 20 to 100,000 layers can be formed, or 50 to 50,000 layers can be formed. As used herein, "layer" is a convenient term that includes any regular or irregular shape with at least a predetermined thickness. In some embodiments, the size and setting of two dimensions are predetermined, and in some embodiments, the size and shape of all three dimensions of the layer are predetermined. Depending on the additive manufacturing method, the thickness of each layer can vary widely. In some embodiments, the thickness of each layer formed is different from the previous or subsequent layer. In some embodiments, the thickness of each layer is the same. As is known in the art and will be described in further detail below, the preset pattern can be determined by a three-dimensional digital representation of the desired article. Such an image can be created by the user, or can be based at least in part on a scan made from a three-dimensional real object.

[0017] The present invention is applicable to large format 3D printing systems (LF-3DP) because such systems can form parts using thermoplastic materials according to the present disclosure. In LF-3DP systems, a relatively large extruder-type print head converts pellets into a molten form, which is then deposited on a printing platform. The LF-3DP system may include a frame or gantry, which in turn includes a print head that is movable in the x, y and / or z directions. (The print head may also be rotatable.) Alternatively, the print head may be stationary, and the part (or part holder) is movable in the x, y and / or z axes (the part may also be rotatable). The print head uses pellets as a direct feed material. The feed material may be stored in a hopper (for pellets) or other suitable storage container near the print head. The LF-3DP device may include a nozzle for extruding the material. The polymer material is heated and extruded through the nozzle and deposited directly on a building surface, which may be a movable (or stationary) platform, or may also be a pre-deposited material. A heat source may be positioned on or connected to the nozzle to heat the material to a desired temperature and / or flow rate. The platform or bed may be heated, cooled or maintained at room temperature.

[0018] The present invention adopts Cool Eagle BRAM-P300 pellet printer for 3D printing. During the printing process, the materials used need to be dried to ensure that the moisture content of the materials is less than 0.02%. The melt temperature of the extruder print head is 310C, the extrusion amount of the printing material is 10KG / h, the print head diameter is 8mm, the print head moving speed is 4m / min, the print layer height is 3mm, and the print line width is 12mm. The size of the printed part: the XY plane is a rectangular frame of 200*400mm, and the height in the Z direction is 300mm. Single-circle printing in the XY direction.

[0019] The extruder used for extrusion is Coperion STS35 machine, the screw length-diameter ratio of the twin-screw extruder is 40:1, the speed is 500rpm; the extrusion processing temperature is 200-280℃, and the output is 50 kg / hour. Among them, the carbon fiber is fed from the downstream side, and the remaining raw materials are mixed evenly and added from the upstream main feed port.

[0020] The preparation method of the polycarbonate composite material in the present application is set as follows: the raw materials are mixed evenly in a high-speed mixer, and then added to a twin-screw extruder for extrusion and granulation to obtain the polycarbonate composition, and the length-to-diameter ratio of the twin-screw is 32:1 to 44:1.

[0021] The evaluation method for heating dimensional stability is as follows: the printed object is placed at room temperature for 12 hours, at a high temperature of 120 degrees for 12 hours, and then cooled to room temperature. This cycle is repeated three times. If the dimensional change is within 0.1%, it is considered to be stable. If it is above 0.1%, it is considered to be unqualified.

[0022] Among them, the mechanical properties evaluation method is: flexural strength and flexural modulus, which is carried out in accordance with ISO 178 standard.

[0023] Among them, the thermal performance evaluation method is: the heat deformation temperature is carried out according to ISO 75 standard, and the load is 1.8MPa.

[0024] The evaluation method for the stability of the printing process is to observe four factors: (1) uniform material discharge from the extruder, (2) stable line diameter, (3) smooth line surface, and (4) no material accumulation at the extruder. The result is considered qualified.

[0025] The density test method is as follows: According to ISO 1133, the density percentage is the density of the printed part / the density of the injection molded part * 100%

[0026] Among them, the warping evaluation method for the printing process is: if the average distance between the four feet of the workpiece and the printing platform is more than 2mm, the evaluation result is unqualified.

[0027]

[0028]

[0029] In Comparative Examples 1 and 2, after adjusting the PC melt index, the printing process was not smooth, the surface of the product was not smooth, the density of the printed product was low, and the strength of the printed product was low, which affected the performance of the final printed product, so that the product could not meet the mold requirements. In Comparative Example 3, the carbon fiber ratio was reduced to 10%, the overall strength of the product was low, and the product would warp during the printing process, so that the product could not meet the mold requirements. In Comparative Example 4, the carbon fiber ratio was increased to 30%, the printing process was not smooth, the surface of the product was not smooth, the density of the printed product was low, and the strength of the printed product was low, which affected the performance of the final printed product, so that the product could not meet the mold requirements. In Comparative Example 5, the resin uses PA66 as the base material, the size of the printed product is unstable, the deformation during the thermal cycle process is large, and the printing process will produce warping, which does not meet the mold requirements. In Comparative Example 6, glass fiber is used, the strength of the printed product is low, and the printing process will produce warping, which does not meet the mold requirements. In summary, by using the raw materials and proportions of the polycarbonate composite material described in this application, the obtained parts have a smooth surface, reasonable density, and high strength. The size of the parts is unstable during the printing process, the deformation during the thermal cycle process is small, and no warping occurs during the printing process, which can meet the mold requirements.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A polycarbonate composite material for pellet 3D printing, characterized in that: The invention comprises the following materials in parts by weight: 75-85 parts of polycarbonate, 5-10 parts of polyketone resin, 3-5 parts of thermoplastic polyurethane, 15-25 parts of carbon fiber, 0.05-0.5 parts of antioxidant, 0.5-1.5 parts of lubricant and 0.5-1.5 parts of surface improver. The melt index of the polycarbonate is between 15 g / min and 20 g / min.

2. A polycarbonate composite material for pellet 3D printing according to claim 1, characterized in that: The lubricant is one or more of soaps, stearyl stearate, montan wax soap ester, paraffin, pentaerythritol stearate, silicone oil and silicone.

3. A polycarbonate composite material for pellet 3D printing according to claim 1, characterized in that: The antioxidant is one or more of a hindered phenol antioxidant and a phosphite.

4. A polycarbonate composite material for pellet 3D printing according to claim 1, characterized in that: The surface improver is an organic fluorine polymer additive.

5. A polycarbonate composite material for pellet 3D printing according to claim 1, characterized in that: The melt index of the polycarbonate is selected to be 10 g / min.

6. A method for preparing a polycarbonate composite material for pellet 3D printing as claimed in claims 1 to 5, characterized in that: The raw materials are mixed uniformly in a high-speed mixer, and then added into a twin-screw extruder for extrusion and granulation to obtain the polycarbonate composition, wherein the length-to-diameter ratio of the twin-screw is 32:1 to 44:1.

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