A 3D printing material capable of regulating PBT crystallinity and a preparation method thereof

Abstract

This invention discloses a 3D printing material with adjustable PBT crystallinity and its preparation method, relating to the field of polymer materials technology. This 3D printing material with adjustable PBT crystallinity utilizes a terpolymer containing epoxy functional groups as a crystallinity regulator, blended with PBT resin in a specific ratio, to achieve precise control over the crystallization behavior of PBT. During melt blending, the epoxy groups on the crystallinity regulator molecular chain can chemically react with the terminal carboxyl or hydroxyl groups of the PBT resin, forming appropriate grafting or crosslinking points. Simultaneously, by controlling the amount of crystallinity regulator added, the crystallinity of the final composite material can be continuously and precisely adjusted within the range of 25% to 40%, thereby fundamentally balancing the warping force caused by crystallization shrinkage with the material's ability to maintain its shape, solving the problems of large crystallization shrinkage, narrow processing window, and poor performance stability in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a 3D printing material with controllable PBT crystallinity and its preparation method. Background Technology

[0002] Polybutylene terephthalate (PBT) is an excellent semi-crystalline thermoplastic engineering plastic with excellent mechanical properties, chemical resistance, electrical insulation and processing flow. It is widely used in the automotive, electronics and electrical fields. In recent years, with the rapid development of 3D printing technology, the application of PBT in fused deposition modeling (FDM) technology has received widespread attention.

[0003] However, the inherent rapid crystallization characteristics of PBT pose a significant challenge to the FDM printing process:

[0004] 1. Large crystallization shrinkage: PBT will produce a large volume shrinkage during the cooling and crystallization process from the melt. This shrinkage can easily cause the product to warp, deform, or even fall off the printing platform in the FDM process of layer-by-layer printing, resulting in a high printing failure rate.

[0005] 2. Narrow processing window: The crystallization temperature (Tc) and melting point (Tm) of PBT are relatively close, and its supercooling (Tm-Tc) is small. Supercooling, or ΔT, means that the melt crystallizes rapidly after extrusion, and the interlayer bonding time is short. If the printing platform temperature is set too low, the crystallization is too fast, and the interlayer bonding is not strong. If it is set too high, the product will solidify slowly and is prone to collapse. This narrow process window places extremely stringent requirements on the setting of printing parameters.

[0006] 3. Poor performance stability: Uneven cooling conditions during the printing process can lead to large differences in crystallinity in different parts of the product, resulting in uneven distribution of internal stress and anisotropy of performance, which affects the dimensional accuracy and mechanical property stability of the final product.

[0007] Currently, the main methods to improve PBT printing performance include adding inorganic nucleating agents (such as talc and montmorillonite) and polymer toughening agents (such as elastomers). While adding nucleating agents can refine the grains, it often further accelerates the crystallization rate and exacerbates the risk of warping. While adding elastomers can improve toughness, it usually reduces the rigidity and heat resistance of the material, and the control of crystallinity is not precise enough.

[0008] Therefore, developing a new method that can effectively control the crystallization kinetics and final crystallinity of PBT to fundamentally solve its FDM printing problem has significant industrial application value. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention provides a 3D printing material with controllable PBT crystallinity and its preparation method. By using a terpolymer containing epoxy functional groups as a crystallinity regulator and blending it with PBT resin in a specific ratio, precise control of PBT crystallization behavior is achieved. During melt blending, the epoxy groups on the crystallinity regulator molecular chain can chemically react with the terminal carboxyl or hydroxyl groups of the PBT resin to form appropriate grafting or crosslinking points. This chemical bonding effectively restricts the movement and orderly arrangement of PBT molecular chains during cooling, thereby significantly slowing down the crystallization rate and increasing the supercooling ΔT. At the same time, by controlling the amount of crystallinity regulator added, the crystallinity of the final composite material can be continuously and precisely adjusted within the range of 25% to 40%, rather than simply inhibiting or promoting crystallization. This fundamentally balances the warping force caused by crystallization shrinkage with the material's ability to maintain its shape, solving the problems of large crystallization shrinkage, narrow processing window, and poor performance stability in existing technologies.

[0010] To achieve the above objectives, the present invention provides the following technical solution: a 3D printing material with adjustable PBT crystallinity, comprising the following components by weight:

[0011] Polybutylene terephthalate (PBT) resin: 80-95 parts;

[0012] Crystallization regulator: 5-20 parts;

[0013] Antioxidant: 0.1 to 1 part;

[0014] The crystallization regulator is a terpolymer containing epoxy functional groups. The crystallization regulator reacts chemically with the end groups of PBT resin during melt blending to regulate the crystallization kinetics and final crystallinity of PBT resin.

[0015] Preferably, the terpolymer containing epoxy functional groups is a terpolymer of glycidyl methacrylate (GMA), ethylene, and methyl acrylate (MA).

[0016] Preferably, in the terpolymer of glycidyl methacrylate, ethylene, and methyl acrylate, the content of each structural unit is as follows: glycidyl methacrylate unit accounts for 5% to 15% of the total weight of the terpolymer, ethylene unit accounts for 60% to 75% of the total weight of the terpolymer, and methyl acrylate unit accounts for 20% to 30% of the total weight of the terpolymer.

[0017] Preferably, the epoxy value of the terpolymer of glycidyl methacrylate, ethylene, and methyl acrylate is 0.1 to 0.3 eq / 100g.

[0018] Preferably, the intrinsic viscosity of the polybutylene terephthalate resin is 0.9 to 1.0 dL / g, and the end carboxyl group content of the polybutylene terephthalate resin is ≤30 mmol / kg.

[0019] Preferably, the crystallinity of the 3D printing material can be continuously controlled within the range of 25% to 40% by adding the amount of the crystallization regulator, and its supercooling degree ΔT measured by differential scanning calorimetry is above 35°C.

[0020] This invention also discloses a method for preparing the 3D printing material with adjustable PBT crystallinity, the method comprising the following steps:

[0021] Step S1, raw material pretreatment: vacuum dry the polybutylene terephthalate resin at 100-120°C for 4-6 hours, and control its moisture content to be below 100ppm;

[0022] Step S2, Premixing: Place the dried polybutylene terephthalate resin, crystallization regulator and antioxidant in a high-speed mixer and mix for 5 to 10 minutes at room temperature to obtain a uniform premix.

[0023] Step S3, melt reaction blending and granulation: The premix obtained in step S2 is fed into a twin-screw extruder for melt blending, devolatilization, extrusion, cooling, stringing and pelletizing to obtain modified polybutylene terephthalate masterbatch;

[0024] Step S4, Masterbatch post-processing: The modified polybutylene terephthalate masterbatch obtained in step S3 is dried at 80-100°C for 3-5 hours to obtain the 3D printing material.

[0025] Preferably, in step S3, the screw length-to-diameter ratio (L / D) of the twin-screw extruder is 36:1 to 40:1; its processing temperature is set as follows: feeding section 210 to 225°C, melt plasticizing section 230 to 240°C, homogenizing and metering section 235 to 245°C, die head temperature 240 to 250°C; screw speed 200 to 400 rpm; and a vacuum port is provided in the homogenizing and metering section to control the vacuum degree at -0.06 to -0.08 MPa.

[0026] Preferably, the preparation method further includes step S5, which involves processing the 3D printing material obtained in step S4 into a printing filament suitable for fused deposition modeling (FDM) technology.

[0027] Step S5, melt drawing: The dried modified polybutylene terephthalate masterbatch is fed into a single-screw extruder, melt-plasticized, and then extruded through a die with a specific aperture. After cooling, traction, and winding, a printing filament with a diameter of 1.75 mm or 2.85 mm is obtained. The barrel temperature of the single-screw extruder is controlled at 220-235℃, the die temperature is controlled at 230-240℃, the traction speed is 5-8 m / min, and the cooling method is constant temperature water bath cooling with a cooling water temperature of 25-30℃.

[0028] Preferably, the diameter tolerance of the printing filament obtained in step S5 is controlled within ±0.05mm, and it is suitable for fused deposition modeling printing process with a hot bed temperature in the range of 60℃~90℃, and the printed products are free from warping.

[0029] The technical effects and advantages of this invention are as follows:

[0030] 1. This 3D printing material with adjustable PBT crystallinity achieves precise control over PBT crystallization behavior by using a terpolymer containing epoxy functional groups as a crystallization regulator and blending it with PBT resin in a specific ratio. During melt blending, the epoxy groups on the crystallization regulator molecular chain can chemically react with the terminal carboxyl or hydroxyl groups of the PBT resin to form appropriate grafting or cross-linking points. This chemical bonding effectively restricts the movement and orderly arrangement of PBT molecular chains during cooling, thus significantly slowing down the crystallization rate and increasing the supercooling ΔT. Furthermore, by controlling the amount of this crystallization regulator added, the crystallinity of the final composite material can be continuously and precisely adjusted within the range of 25% to 40%, rather than simply inhibiting or promoting crystallization. This fundamentally balances the warping force caused by crystallization shrinkage with the material's ability to maintain its shape.

[0031] 2. This 3D printing material with adjustable PBT crystallinity, through optimized preparation methods, especially the setting of process parameters for the twin-screw extruder, ensures the full realization of modification effects and material homogeneity. The method specifies the temperature control range from the feeding section to the die head section, the appropriate screw speed, and the vacuum applied in the high-speed stirring section. These process conditions work together to ensure that PBT and the terpolymer can fully contact and undergo the expected chemical reaction in the molten state. At the same time, it removes any small molecule byproducts that may be generated in a timely manner, avoiding material performance degradation or defects caused by volatiles or degradation products. The resulting material has uniform composition and stable performance, providing a reliable raw material basis for subsequent filament drawing and printing.

[0032] 3. This 3D printing material with adjustable PBT crystallinity is produced by creating printing filaments from modified PBT composite materials using a specific melt-drawing process. This process gives the printing filaments excellent FDM printing adaptability and product quality. The process controls the barrel and die temperature, traction speed, and cooling water temperature of the single-screw extruder, thereby producing high-precision filaments with diameter tolerances strictly controlled within ±0.05mm. Based on the material's broadened supercooling and adjustable crystallinity, this filament exhibits a wide process window during FDM printing, successfully printing within a hotbed temperature range of 60℃ to 90℃ or even wider. During the printing process, the material crystallizes gradually, and the interlayer fusion time is long, effectively suppressing warpage and deformation. This results in high dimensional accuracy, strong interlayer bonding, and stable and uniform mechanical properties in the final product. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the material composition of the present invention;

[0035] Figure 2 This is a flowchart of the preparation method of the present invention;

[0036] Figure 3 This is a schematic diagram showing the specific parameters of step S3 of the present invention;

[0037] Figure 4 This is a logic diagram illustrating the characteristics and applications of the printing filament material in this invention. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] This embodiment discloses a 3D printing material with adjustable PBT crystallinity, according to the attached... Figure 1 To be continued Figure 4As shown, the material includes polybutylene terephthalate (PBT) resin, crystallization regulator, antioxidant, and other optional additives. The crystallization regulator is a terpolymer containing epoxy functional groups, which can chemically react with the terminal carboxyl or hydroxyl groups of PBT resin during melt blending, thereby achieving precise control over the crystallization kinetics and final crystallinity of PBT, and thus significantly improving the printing adaptability, warpage resistance, and product performance stability of the material in the fused deposition modeling (FDM) process.

[0040] Furthermore, the terpolymer containing epoxy functional groups is preferably a terpolymer of glycidyl methacrylate (GMA), ethylene (E), and methyl acrylate (MA). In this terpolymer, the weight content of each structural unit is as follows: glycidyl methacrylate unit accounts for 5% to 15%, ethylene unit accounts for 60% to 75%, and methyl acrylate unit accounts for 20% to 30%. This composition design makes the copolymer reactive, compatible, and moderately flexible: the GMA unit provides epoxy groups that can react with PBT end groups; the ethylene unit has good compatibility with nonpolar PBT segments; and the MA unit imparts a certain degree of flexibility to the copolymer, which is beneficial to improving the toughness of the composite material.

[0041] In particular, the epoxy value of the ternary copolymer glycidyl ester is preferably controlled within the range of 0.1 to 0.3 eq / 100g. Within this range, the epoxy value can ensure sufficient reaction with the PBT end groups, effectively restrict molecular chain movement and delay crystallization, and avoid excessive cross-linking that could lead to a significant decrease in material processing fluidity or complete inhibition of crystallization.

[0042] It is particularly important to emphasize that the intrinsic viscosity of polybutylene terephthalate resin is preferably 0.9–1.0 dL / g, and its terminal carboxyl group content should be controlled at ≤30 mmol / kg. The appropriate intrinsic viscosity ensures that the material has good melt strength and processing fluidity. As the main active site for chemical reaction with the epoxy groups in the terpolymer, the content of the terminal carboxyl groups must meet certain requirements to ensure the modification effect.

[0043] Furthermore, by adjusting the amount of crystallization regulator added, the crystallinity of the 3D printing material of this invention can be continuously and precisely controlled within the range of 25% to 40%. At the same time, the crystallization peak temperature (Tc) of the modified material is significantly reduced, and the supercooling (ΔT, i.e., Tm-Tc) increases to above 35°C, indicating that the crystallization process is effectively delayed and the crystallization rate is significantly slowed down. This characteristic is the key to broadening the FDM printing process window and suppressing product warping.

[0044] Specifically, the material preparation method includes the following core steps:

[0045] Raw material pretreatment: Vacuum dry PBT resin at 100-120℃ for 4-6 hours to ensure that the water content is below 100ppm to prevent hydrolysis and degradation during high-temperature processing.

[0046] Premixing: The dried PBT resin, crystallization regulator, antioxidant and other optional additives are mixed in a high-speed mixer at room temperature for 5 to 10 minutes to obtain a premix with uniform components.

[0047] Melt reaction blending and granulation: The premixed material is fed into a twin-screw extruder. The extrusion process parameters are crucial for achieving full reaction and uniform blending: the screw length-to-diameter ratio (L / D) is preferably 36:1 to 40:1; the temperature is set progressively along the screw axis: 210 to 225°C in the feeding section, 230 to 240°C in the melt plasticizing section, 235 to 245°C in the homogenizing and metering section, and 240 to 250°C in the die head; the screw speed is 200 to 400 rpm. A vacuum port is set in the homogenizing and metering section to maintain a vacuum of -0.06 to -0.08 MPa to remove small molecule byproducts and residual moisture generated during the reaction in a timely manner, ensuring the purity and performance of the material.

[0048] Masterbatch post-processing: After the extruded strips are cooled in a water bath and granulated, the resulting modified PBT masterbatch needs to be dried at 80-100℃ for 3-5 hours to further remove surface moisture and prevent air bubbles from forming during subsequent stringing or printing.

[0049] Melt drawing (optional): The dried masterbatch is melt-drawn using a single-screw extruder. The barrel temperature is 220-235℃ and the die temperature is 230-240℃. After the melt is extruded through the die, it is cooled in a constant temperature (25-30℃) water bath, and then drawn (speed 5-8m / min) and wound up to finally produce FDM printing filament with high diameter accuracy (such as 1.75mm or 2.85mm, tolerance ±0.05mm).

[0050] It is particularly important to emphasize that the printing filament made using the material of this invention exhibits extremely wide process adaptability in FDM printing. Its successful printing platform temperature window is significantly widened to 60℃~90℃ or even wider (such as 55℃~90℃ and above), which is far superior to the extremely narrow printing window of pure PBT (about 85℃~90℃). When printed within this wide window, the product has no visible warping, high dimensional accuracy, and strong interlayer adhesion, fundamentally solving the problem of FDM printing of PBT materials.

[0051] Example 1: This example uses the addition of 8 parts by weight of a terpolymer as an example, combined with the attached... Figure 1 To be continued Figure 4 The material preparation, performance characterization, and printing verification process is described in detail below.

[0052] Raw material preparation: Prepare the raw materials according to the proportions in Example 1 in Table 1. The intrinsic viscosity of PBT resin is 0.95 dL / g, the end carboxyl group content is 25 mmol / kg, the content of GMA unit in the ternary copolymer glycidyl ester is 8 wt%, the content of MA unit is 28 wt%, and the remainder is ethylene unit. The epoxy value is about 0.18 eq / 100g. The antioxidant is 1010 and 168 compounded in a weight ratio of 1:2.

[0053] Pretreatment and premixing: PBT resin was vacuum dried at 110°C for 5 hours, and then all raw materials were put into a high-speed mixer and mixed at room temperature for 8 minutes to obtain a premix.

[0054] Melt blending and granulation: Blending is carried out using a twin-screw extruder (L / D=40:1). Temperature settings: feeding section 220℃, melting section 235℃, homogenization section 240℃, die head 245℃, screw speed 300rpm. Vacuum is drawn in the homogenization section with a vacuum degree of -0.07MPa. The melt is extruded through the die head, water-cooled, drawn into strips, and pelletized to obtain modified PBT masterbatch.

[0055] Masterbatch drying: Dry the masterbatch at 90℃ for 4 hours.

[0056] Performance testing:

[0057] DSC test: Differential scanning calorimetry analysis was performed on the dried masterbatch. The results are shown in Table 2. The melting point (Tm) was 223.1℃, the crystallization peak temperature (Tc) was 182.5℃, the supercooling ΔT reached 40.6℃, and the crystallinity Xc was calculated to be 34.2%.

[0058] Compared with pure PBT, the crystallization peak of the sample in this embodiment shifts significantly towards lower temperatures, and the crystallization process is significantly delayed.

[0059] Printing filament preparation and printing verification:

[0060] The dried masterbatch was drawn into filaments using a single-screw extruder with a barrel temperature of 225℃, a die temperature of 235℃, a traction speed of 6.5m / min, and a water bath cooling temperature of 28℃, to obtain filaments with a diameter of 1.75±0.03mm.

[0061] Using a general-purpose FDM printer, single-walled rectangular templates with dimensions of 60mm×20mm×10mm were printed. Starting from 50℃, the printing platform temperature was tested, increasing by 5℃ each time. It was found that when the platform temperature was 65℃, a warp-free template could be successfully printed. Further testing showed that printing was successful in the range of 65℃ to 90℃ and above without warping. The minimum successful platform temperature was determined to be 65℃, and the "printing process window width" exceeded 25℃ (65-90+℃).

[0062] Comparison of results: The spline printed in Comparative Example 1 (pure PBT) was severely warped, with the corners detaching from the platform; while the spline printed in this embodiment was flat, with no visible warping, and the dimensions were stable.

[0063] Example 2: This example uses the addition of 12 parts by weight of terpolymer as an example to illustrate in detail the impact of further increasing the addition amount on material properties and printing process. The workflow is as follows:

[0064] Raw materials and preparation: According to the proportions in Table 1 Example 2, there are 88 parts of PBT and 12 parts of terpolymer. The antioxidant formulation is the same as in Example 1. The specifications of PBT resin and terpolymer are the same as in Example 1. The preparation process steps and parameters are basically the same as in Example 1.

[0065] Performance testing: The DSC test results (Table 2) show that Tm is 222.8℃, Tc further decreases to 179.3℃, ΔT increases to 43.5℃, and the crystallinity Xc is calculated to be 31.0%, indicating that as the amount of regulator increases, the delay effect on crystallization is enhanced, and the crystallinity further decreases.

[0066] Printing verification: The wire drawing process is the same as in Example 1. Printing tests show that the minimum successful platform temperature is further reduced to 60°C, and the temperature range (process window) for successful printing is widened to 60°C to 90°C or more, with a width of 30°C. All printed strips are free of warping and have good interlayer bonding.

[0067] Example 3 illustrates the material characteristics when the amount of regulator added is close to the upper limit, using the addition of 18 parts by weight of terpolymer as an example.

[0068] The workflow is as follows:

[0069] Raw materials and preparation: According to the proportions in Table 1 Example 3, there are 82 parts of PBT, 18 parts of terpolymer, the antioxidant formulation is the same as before, and the preparation process is the same as in Example 1.

[0070] Performance testing: The DSC results (Table 2) show that Tm is 221.5℃, Tc is significantly reduced to 175.8℃, ΔT reaches 45.7℃, and the crystallinity Xc is 27.8%, achieving a further reduction in crystallinity.

[0071] Printing verification: Printing tests after wire drawing showed that the "lowest successful plateau temperature" was as low as 55℃, and the process window width was further expanded to 35℃ (above 55℃~90℃). Even at the relatively low plateau temperature of 55℃, the printed strip remained flat and without warping, proving the material's excellent anti-warping properties and wide process adaptability.

[0072] Comparative Example 1 uses pure PBT resin as an example as a benchmark to highlight the modification effect of the present invention. The workflow is as follows:

[0073] Raw materials and preparation: 100 parts by weight of the same PBT resin as in the example were used, with the same proportions of antioxidants added (1010:0.2 parts, 168:0.4 parts). The drying, mixing, extrusion granulation process conditions were similar to those in the example.

[0074] Performance testing: DSC test (Table 2) shows that the Tm of pure PBT is 224.5℃, the Tc is as high as 191.2℃, the ΔT is only 33.3℃, ​​and the crystallinity Xc is 38.5%.

[0075] Printing verification: After drawing the wire, printing tests were conducted. It was found that only when the printing platform temperature was set at 85℃ or above could a strip without severe warping be printed. Moreover, the suitable temperature range was extremely narrow (about 85-90℃). When printing at 85℃, the strip still showed obvious warping (corner separation). At slightly lower platform temperatures, the warping was extremely severe, leading to printing failure. This fully demonstrates the inherent defects of using pure PBT for FDM printing.

[0076] Table 1: Component ratios (parts by weight) of the examples and comparative examples

[0077]

[0078] Table 2: Performance Test and Print Verification Results

[0079]

[0080] Summary and Analysis:

[0081] By comparing the above examples with the comparative examples, the following conclusions can be clearly drawn:

[0082] This invention successfully achieves precise control over the crystallization kinetics of PBT (significantly delaying crystallization and increasing supercooling) and the final crystallinity (adjustable within the range of 25% to 40%) by introducing a ternary copolymer glycidyl ester with a specific composition as a crystallization regulator.

[0083] This regulation fundamentally improves the FDM printing performance of PBT materials: the platform temperature required for printing is significantly reduced, and the temperature window for successful printing is significantly widened (from <5℃ to over 25℃), completely solving the core problem of warping and deformation of printed products.

[0084] Terpolymers not only play a role in crystallization regulation through chemical reactions, but their ethylene and methyl acrylate segments also have the effects of compatibilization and moderate toughening, which is beneficial to improving the phase stability of composite materials and the toughness of products.

[0085] The preparation method provided by this invention has mature technology and clear parameters, making it easy to achieve large-scale production. The resulting printing filament has precise specifications and is suitable for a wide range of FDM printing equipment and process conditions.

[0086] In summary, this invention provides a PBT-based 3D printing material with precisely controllable crystallinity, excellent anti-warping properties, and a wide printing process window, as well as its efficient preparation method. This greatly expands the application prospects of PBT in fused deposition modeling (FDM) technology and is suitable for manufacturing engineering parts with high dimensional accuracy and high mechanical property stability.

[0087] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A 3D printing material with adjustable PBT crystallinity, characterized in that, By weight, it comprises the following components: Polybutylene terephthalate resin: 80-95 parts; Crystallization regulator: 5-20 parts; Antioxidant: 0.1 to 1 part; The crystallization regulator is a terpolymer containing epoxy functional groups. The crystallization regulator reacts chemically with the end groups of PBT resin during melt blending to regulate the crystallization kinetics and final crystallinity of PBT resin.

2. The 3D printing material with adjustable PBT crystallinity according to claim 1, characterized in that, The terpolymer containing epoxy functional groups is a terpolymer of glycidyl methacrylate, ethylene, and methyl acrylate.

3. The 3D printing material with adjustable PBT crystallinity according to claim 2, characterized in that, In the terpolymer of glycidyl methacrylate, ethylene, and methyl acrylate, the content of each structural unit is as follows: glycidyl methacrylate unit accounts for 5% to 15% of the total weight of the terpolymer, ethylene unit accounts for 60% to 75% of the total weight of the terpolymer, and methyl acrylate unit accounts for 20% to 30% of the total weight of the terpolymer.

4. The 3D printing material with adjustable PBT crystallinity according to claim 3, characterized in that, The epoxy value of the terpolymer of glycidyl methacrylate, ethylene, and methyl acrylate is 0.1 to 0.3 eq / 100g.

5. The 3D printing material with adjustable PBT crystallinity according to claim 1, characterized in that, The intrinsic viscosity of the polybutylene terephthalate resin is 0.9–1.0 dL / g, and the end carboxyl group content of the polybutylene terephthalate resin is ≤30 mmol / kg.

6. The 3D printing material with adjustable PBT crystallinity according to claim 1, characterized in that, The crystallinity of the 3D printing material can be continuously controlled within the range of 25% to 40% by adding the crystallization regulator, and its supercooling degree ΔT measured by differential scanning calorimetry is above 35°C.

7. A method for preparing a 3D printing material with adjustable PBT crystallinity as described in any one of claims 1 to 6, characterized in that, The preparation method includes the following steps: Step S1: Vacuum dry the polybutylene terephthalate resin at 100-120°C for 4-6 hours, controlling its moisture content to be below 100 ppm. Step S2: Place the dried polybutylene terephthalate resin, crystallization regulator and antioxidant in a high-speed mixer and mix for 5 to 10 minutes at room temperature to obtain a uniform premix. Step S3: The premix obtained in step S2 is fed into a twin-screw extruder for melt blending, devolatilization, extrusion, cooling, drawing and pelletizing to obtain modified polybutylene terephthalate masterbatch. Step S4: The modified polybutylene terephthalate masterbatch obtained in step S3 is dried at 80-100°C for 3-5 hours to obtain the 3D printing material.

8. The method for preparing a 3D printing material with adjustable PBT crystallinity according to claim 7, characterized in that, In step S3, the screw length-to-diameter ratio (L / D) of the twin-screw extruder is 36:1 to 40:1; its processing temperature is set as follows: feeding section 210 to 225°C, melt plasticizing section 230 to 240°C, homogenizing and metering section 235 to 245°C, and die head temperature 240 to 250°C; the screw speed is 200 to 400 rpm; and a vacuum port is provided in the homogenizing and metering section to control the vacuum degree at -0.06 to -0.08 MPa.

9. The method for preparing a 3D printing material with adjustable PBT crystallinity according to claim 8, characterized in that, The preparation method further includes step S5, which involves processing the 3D printing material obtained in step S4 into a printing filament suitable for fused deposition modeling (FDM) technology. Step S5: The dried modified polybutylene terephthalate masterbatch is fed into a single-screw extruder. After being melt-plasticized, it is extruded through a die with a specific aperture. After cooling, traction, and winding, a printing filament with a diameter of 1.75 mm or 2.85 mm is obtained. The barrel temperature of the single-screw extruder is controlled at 220-235℃, the die temperature is controlled at 230-240℃, the traction speed is 5-8 m / min, and the cooling method is constant temperature water bath cooling with a cooling water temperature of 25-30℃.

10. The method for preparing a 3D printing material with adjustable PBT crystallinity according to claim 9, characterized in that, The diameter tolerance of the printing filament obtained in step S5 is controlled within ±0.05mm, and it is suitable for fused deposition modeling printing process with a hot bed temperature in the range of 60℃~90℃, and the printed products are free from warping.

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