A pet composite material and a preparation method and application thereof

Abstract

The application discloses a PET composite material and a preparation method and application thereof, and belongs to the technical field of high polymer materials. The product is prepared by using PET and PC resin as a base resin, and glass fiber as a reinforcing filler, and then introducing specific compatilizer and hyperbranched polyester as a lubricant to be mutually synergistic, so that the whole product has excellent weld line strength, high toughness and strength, and good processing forming property. When the product is applied to 3D printing, especially 3D printing of some large parts, the quality is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of polymer alloy materials technology, specifically to a PET composite material and its preparation method and application. Background Technology

[0002] 3D printing is a popular forming method that uses programmed control to rapidly deposit materials according to specific coordinates. PET, with its excellent mechanical, electrical, and solvent resistance properties, is a popular material for 3D printing.

[0003] However, current PET composite materials for 3D printing are prone to warping during the 3D printing process, and their processing performance is not ideal, requiring special modification. Furthermore, some existing PET composite materials are not suitable for 3D printing large parts (such as garden landscape components, bridge components, etc., with a single part weighing more than 100 kg). This is because these parts are generally prepared using open-mold 3D printing processes, lacking mold pressure holding and shaping. During the cooling process, the molecular chains in the product tend to stack neatly, reducing the bonding strength of the weld lines between layers. Most existing PET composite materials cannot maintain acceptable weld line bonding strength under this process, and the lower structural parts are prone to cracking due to insufficient mechanical properties. Summary of the Invention

[0004] Based on the deficiencies of existing technologies, the purpose of this invention is to provide a PET composite material. In this product, PET and PC resins are used as the matrix resin, glass fiber is used as the reinforcing filler, and then specific compatibilizers and hyperbranched polyesters are introduced as lubricants to work synergistically. This allows the overall product to have excellent weld line strength, as well as high toughness and strength, good processability, and ensures quality when used in 3D printing, especially in the 3D printing of some large parts.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A PET composite material comprising the following components in parts by weight:

[0007] 30-75 parts PET resin, 15-45 parts PC resin, 3-9 parts compatibilizer, 0.1-1 part hyperbranched polyester, 4-16 parts glass fiber, and 0.1-0.3 parts transesterification accelerator;

[0008] The compatibilizer comprises the following structural units:

[0009]

[0010] Where A is -H or -CH2-CHOH-; B is -H or -CH2-CHOH-; A and B are not both -H;

[0011] n = 10 ~ 2000;

[0012] The hyperbranched polyester is a four-arm polyester copolymer with pentaerythritol as the core and polydimethylolpropionic acid as the branched chain.

[0013] Preferably, the compatibilizer comprises the following structural units:

[0014]

[0015] A is -CH2-CHOH-, B is -CH2-CHOH-, and R group is a residue of ethylene-methyl acrylate-glycidyl methacrylate;

[0016] More preferably, the compatibilizer has the following structural formula:

[0017]

[0018] The compatibilizer is a terpolymer of ethylene-methyl acrylate-glycidyl methacrylate grafted with polybutylene succinate, where R group is a residue of ethylene-methyl acrylate-glycidyl methacrylate, and n = 100 to 2000.

[0019] Preferably, the decomposition temperature of the hyperbranched polyester is ≥340℃.

[0020] In the PET composite material described in this invention, PET and PC are blended as the matrix resin. With the introduction of glass fiber as a reinforcing filler, a compatibilizer with a specific structure is used as a modifying component. Because it contains a molecular chain structure with extremely high compatibility with both PET and PC, this component can directly react and compatibilize with the two matrix resins, effectively connecting the PET and PC resins and improving their compatibility, thus significantly improving the processing fluidity of the product. On the other hand, this component melts and forms a bonding layer during 3D printing, improving the interlayer adhesion of the printed material. Another modifying component in the product, hyperbranched polyester, not only effectively improves the overall product's fluidity and assists in better and more uniform dispersion of the glass fiber, exhibiting excellent strength and support after 3D printing, but also coordinates with the compatibilizer to jointly improve the overall material's compatibility, ultimately achieving excellent weld line strength and mechanical properties.

[0021] Meanwhile, experiments have shown that simply using hyperbranched polyester to improve the product's fluidity does not necessarily result in the product having good weld line strength. The two are actually different properties, so both specific modifying components are indispensable in the product.

[0022] Preferably, the total mass content of PET resin and PC resin in the PET composite material is not less than 50%.

[0023] Preferably, the PET composite material comprises the following components by weight:

[0024] 35-45 parts PET resin, 25-35 parts PC resin, 4-5 parts compatibilizer, 0.2-0.6 parts hyperbranched polyester, 8-12 parts glass fiber, and 0.1-0.3 parts transesterification accelerator.

[0025] Preferably, the PET resin is in the range of 35 parts, 38 parts, 40 parts, 42 parts, and 45 parts by weight, or any two of these values; the PC resin is in the range of 25 parts, 28 parts, 30 parts, 32 parts, and 35 parts by weight, or any two of these values; the compatibilizer is in the range of 4 parts, 4.2 parts, 4.5 parts, 4.8 parts, and 5 parts by weight, or any two of these values; the hyperbranched polyester is in the range of 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, and 0.6 parts by weight, or any two of these values; and the glass fiber is in the range of 8 parts, 9 parts, 10 parts, 11 parts, and 12 parts by weight, or any two of these values.

[0026] While increasing the amount of hyperbranched polyester improves the overall performance of the product, it also significantly increases the production cost. Furthermore, tests have shown that when the amount of hyperbranched polyester added exceeds 0.6 parts, the performance improvement decreases. Therefore, considering all factors, an addition amount of 0.2 to 0.6 parts of hyperbranched polyester offers better cost-effectiveness.

[0027] Preferably, the glass fiber has an average length of 3-6 mm and an average diameter of 9-13 μm.

[0028] More preferably, the average diameter of the glass fiber is 10 to 11 μm.

[0029] In the PET composite material described in this invention, the main function of glass fiber is to enhance the overall strength and maintain the toughness of the product. However, when 3D printing large parts, the required strength and toughness are much higher than those of general glass fiber reinforced PET composite materials. Therefore, even with the introduction of new compatible compound components, the size of the glass fiber can be further examined. The inventors have found that when the length and diameter of the glass fiber are maintained within the above-mentioned preferred range, the weld line strength of the product is higher, making it more suitable for use in the 3D printing of some larger parts. However, the amount of glass fiber introduced should not be too much, otherwise, although the mechanical properties of the product will be improved, the weld line strength of the product may not meet the requirements.

[0030] Preferably, the intrinsic viscosity of the PET resin at 25°C is 0.5–1.0 dL / g, and the test standard for the intrinsic viscosity is GB / T 14189-2008, with the solvent being phenol: 1,1,2,2-tetrachloroethane (mass ratio 60:40).

[0031] Specifically, the intrinsic viscosity of the PET resin at 25°C can be one or any two of the following: 0.5 dL / g, 0.6 dL / g, 0.8 dL / g, 1.0 dL / g.

[0032] More preferably, the intrinsic viscosity of the PET resin at 25°C is 0.6 to 0.8 dL / g.

[0033] If the viscosity range of PET resin, as the matrix resin, is selected within the above-mentioned preferred range, the product will not only have better processing performance, but also achieve better melt strength.

[0034] Preferably, the number average molecular weight of the PC resin is 16,000 to 22,000, and the melt index is 20 to 25 g / 10 min. The test standard for the melt index is ISO 1133-2011, and the test conditions are 300°C and 1.2 kg load.

[0035] The number-average molecular weight of the PC resin was directly tested and confirmed using GPC liquid chromatography, with tetrahydrofuran as the solvent.

[0036] Specifically, the number average molecular weight of the PC resin is any two of the values ​​of 16,000, 17,000, 18,000, 19,000, 20,000, 21,000, and 22,000, and the melt index is any two of the values ​​of 20 g / 10 min, 21 g / 10 min, 22 g / 10 min, 23 g / 10 min, 24 g / 10 min, and 25 g / 10 min.

[0037] Preferably, the PET composite material further comprises 0.1 to 0.3 parts of antioxidant.

[0038] To ensure the stability of the product during preparation and subsequent application, those skilled in the art may add appropriate amounts of antioxidants according to actual needs.

[0039] More preferably, the antioxidant is at least one of hindered phenolic antioxidants, hindered amine antioxidants, and phosphite antioxidants;

[0040] Preferably, the transesterification promoter is tetrabutyl titanate.

[0041] Preferably, the PET composite material further comprises 8-12 parts of a brominated flame retardant and 2-4 parts of an antimony-based flame retardant synergist.

[0042] Existing PET composite materials have unsatisfactory flame retardant properties and poor fire resistance. When introducing flame retardants, it is necessary to consider their compatibility and whether they may weaken the product's flowability and mechanical properties. However, in the product described in this invention, based on a specific compounding system, the product can achieve a V-0 level flame retardant effect after introducing the above-mentioned flame retardant components, without weakening other product properties, making it more practical.

[0043] More preferably, the brominated flame retardant is at least one of brominated epoxy, brominated polystyrene, decabromodiphenyl ethane, polypentabromobenzyl methacrylate, and brominated imine.

[0044] More preferably, the antimony-based flame retardant synergist is antimony white.

[0045] Preferably, the compatibilizer is obtained by mixing and reacting polybutylene succinate (PBS) and ethylene-methyl acrylate-glycidyl methacrylate terpolymer.

[0046] Preferably, the temperature during the mixing reaction is 170-190℃ and the time is 2-4 minutes.

[0047] More preferably, the mass ratio of polybutylene succinate and ethylene-methyl acrylate-glycidyl methacrylate terpolymer is (8.5:1.5) to (9.5:0.5).

[0048] For example, the mixing reaction can be carried out in an internal mixer at a temperature of 180°C, a mixing speed of 600-800 r / min, and a reaction time of 3 min.

[0049] More preferably, the density of the polybutylene succinate is 1.20–1.30 g / cm³. 3 Its melting point is 110-120℃.

[0050] More preferably, the ethylene-methyl acrylate-glycidyl methacrylate terpolymer, according to ASTM-D1238 2010, has a melt flow rate of 5-7 g / 10 min at 190°C and a load of 2.16 kg, and a density of 0.935-0.955 g / cm³. 3 The melting temperature is 60-70℃.

[0051] More preferably, the ethylene-methyl acrylate-glycidyl methacrylate terpolymer can be selected from AX8900 produced by Arkema, France.

[0052] Based on the structural and functional group requirements, the compatibilizer described in this invention can use the two substances mentioned above as raw materials. Since polybutylene succinate has a carboxyl group at the end and ethylene-methyl acrylate-glycidyl methacrylate terpolymer has an epoxy group, the inventors have verified that the two can react to generate the compatibilizer described in this invention. However, those skilled in the art can choose other types of compounds as raw materials according to the actual situation, and prepare compatibilizer products with the same unit through grafting / condensation / dissociation reactions, etc., and are not limited to the two raw materials and reaction process preferred in this invention.

[0053] Preferably, the hyperbranched polyester is CYD-5300 produced by Weihai Chenyuan Molecular New Materials Co., Ltd.

[0054] As a key component in this invention used to synergistically work with compatibilizers and improve the overall flowability of the product, the hyperbranched polyester can be a four-arm polyester copolymer obtained by compounding pentaerythritol as the core and polydimethylolpropionic acid as the branched chain, or other hyperbranched polyesters with different configurations and compositions, as long as the same technical effect can be achieved.

[0055] Another object of the present invention is to provide a method for preparing the PET composite material, comprising the following steps:

[0056] The PET composite material is obtained by mixing the components, melt extruding, and granulating.

[0057] The preparation method of the PET composite material described in this invention has simple operation steps and can realize large-scale industrial production.

[0058] Preferably, the mixing rate is 700-800 rpm and the time is 2-4 min.

[0059] Preferably, the melt extrusion is carried out in a twin-screw extruder, and the temperatures of each zone in the twin-screw extruder are set as follows: 210–240°C, zone 2 250–270°C, zone 3 245–265°C, zone 4 245–265°C, zone 5 245–265°C, zone 6 250–270°C, zone 7 250–270°C, zone 8 230–250°C, zone 9 230–250°C, and zone 10 250–270°C. The screw speed of the twin-screw extruder is 200–450 rpm.

[0060] Another object of the present invention is to provide the application of the PET composite material in the 3D printing of large parts.

[0061] Preferably, the large parts include garden landscape components, garden sculpture components, and bridge components.

[0062] Another object of the present invention is to provide a 3D printed part comprising the PET composite material described herein.

[0063] The PET composite material described in this invention has excellent processing fluidity and mechanical properties, and can reach a maximum of over 50 MPa in the weld line strength test. Therefore, it can be used with confidence in the 3D printing of large parts without worrying about reduced weld line strength due to the lack of mold fixation or cracking due to excessive volume. In addition, the product can achieve V-0 level flame retardant performance when flame retardant components are introduced.

[0064] The beneficial effects of this invention are that it provides a PET composite material in which PET and PC resins are used as the matrix resin, glass fiber is used as the reinforcing filler, and specific compatibilizers and hyperbranched polyesters are introduced as lubricants to work synergistically. This results in an overall product with excellent weld line strength, high toughness and strength, good processability, and guaranteed quality when used in 3D printing, especially in the 3D printing of some large parts. Detailed Implementation

[0065] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0066] Examples 1-17

[0067] Examples of the PET composite material and its preparation method according to the present invention are shown in Table 1.

[0068] The preparation method of the PET composite material includes the following steps:

[0069] The PET composite material is obtained by mixing the components, melt extruding, and granulating.

[0070] The mixing rate is 700-800 rpm, and the time is 3 min;

[0071] The melt extrusion is carried out in a twin-screw extruder, and the temperatures of each zone in the twin-screw extruder are set as follows: 210-240℃, zone 2 250-270℃, zone 3 245-265℃, zone 4 245-265℃, zone 5 245-265℃, zone 6 250-270℃, zone 7 250-270℃, zone 8 230-250℃, zone 9 230-250℃, and zone 10 250-270℃. The screw speed of the twin-screw extruder is 350 rpm.

[0072] Comparative Examples 1-10

[0073] The only difference between each comparative example and the embodiment is the type and ratio of components, as shown in Table 2.

[0074] In the components described in each embodiment and comparative example,

[0075] The PC resin 1 is FN1700, manufactured by Idemitsu Corporation, Taiwan, with a number average molecular weight of 17,000 and a melt index of 26 g / 10 min at 300°C and a load of 1.2 kg.

[0076] The PC resin 2 is PC 1300-22NP, manufactured by LG Corporation, with a number average molecular weight of 20,000 and a melt index of 22 g / 10 min at 300°C and a load of 1.2 kg.

[0077] The PET resin 1 is PET FG600, made by Sichuan Dongcai, with an intrinsic viscosity of 0.67 dL / g at 25°C;

[0078] The PET resin 2 is PET FG720, made by Sichuan Dongcai, with an intrinsic viscosity of 0.74 dL / g at 25°C;

[0079] The PET resin 3 is PET BG85, produced by Yizheng Chemical Fiber in China, with an intrinsic viscosity of 0.87 dL / g at 25°C.

[0080] The PET resin 4 is PET CR-7702, manufactured by China Resources Packaging Materials Co., Ltd., with an intrinsic viscosity of 0.5 dL / g at 25°C.

[0081] The compatibilizer 1 is a terpolymer of ethylene-methyl acrylate-glycidyl methacrylate grafted with polybutylene succinate, with the following structural formula:

[0082]

[0083] The R group is a residue of ethylene-methyl acrylate-glycidyl methacrylate;

[0084] The compatibilizer is obtained by mixing and reacting PBS and an ethylene-methyl acrylate-glycidyl methacrylate terpolymer. The specific steps are as follows:

[0085] PBS and ethylene-methyl acrylate-glycidyl methacrylate terpolymer were mixed at a mass ratio of 9:1 in a high-speed mixer at 700 rpm and 130°C for 3 minutes. After cooling and crushing, the mixture was then fed into an extruder for extrusion granulation.

[0086] The compatibilizer is formed through the following reaction:

[0087]

[0088] The PBS in question is product A200 NC801 manufactured by Zhuhai Kingfa Biomaterials Co., Ltd., with a density of 1.26 g / cm³. 3 Its melting point is 114℃;

[0089] The ethylene-methyl acrylate-glycidyl methacrylate terpolymer is Arkema AX8900 from France. According to ASTM-D1238 2010, its melt flow rate at 190°C and 2.16 kg load is 6 g / 10 min, and its density is 0.940 g / cm³. 3 The melting temperature is 65℃.

[0090] The compatibilizer 2 is PBS, and its source is the same as that of compatibilizer 1;

[0091] The compatibilizer 3 is a terpolymer of ethylene-methyl acrylate-glycidyl methacrylate, and its source is the same as that of compatibilizer 1;

[0092] The compatibilizer 4 is an ethylene methyl acrylate copolymer, manufactured by DuPont. product;

[0093] The hyperbranched polyester 1 is a four-arm polyester copolymer obtained by compounding pentaerythritol as the core and polydimethylolpropionic acid as the branched chain. Weihai Chenyuan Molecular New Materials Co., Ltd. produces CYD-5300 products.

[0094] The lubricant is a hyperbranched ester substance, specifically Hyper C100 produced by Wuhan Hyperbranched Resin Technology Co., Ltd.

[0095] The glass fiber 1 has an average length of 6 mm and an average diameter of 10 μm, and is HMG436S-10-6.0 produced by Taishan Fiberglass.

[0096] The glass fiber 2 has an average length of 3 mm and an average diameter of 11 μm, and is ECS11-3.0-T436CP produced by Taishan Fiberglass.

[0097] The glass fiber 3 has an average length of 3 mm and an average diameter of 13 μm, and is ECS13-3.0-T436W produced by Taishan Fiberglass.

[0098] The glass fiber 4 has an average length of 3mm and an average diameter of 9μm. It is a custom-made alkali-free glass fiber from Taian Songze Composite Materials Co., Ltd.

[0099] The antioxidant is a commercially available hindered phenolic antioxidant.

[0100] The transesterification promoter is commercially available tetrabutyl titanate;

[0101] The bromine-based flame retardant is commercially available decabromodiphenyl ethane;

[0102] The antimony-based flame retardant synergist is commercially available antimony white;

[0103] The only difference between Comparative Example 8 and Example 1 is the composition of the components, as shown in Table 2. The PBS and ethylene-methyl acrylate-glycidyl methacrylate terpolymer were not prepared as compatibilizers in advance.

[0104] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0105] Table 1

[0106]

[0107]

[0108] Table 2

[0109]

[0110] To verify the performance of the PET composite material described in this invention, the products prepared in each embodiment and comparative example were subjected to the following performance tests, with the specific steps as follows:

[0111] (1) Molding fluidity test: The spiral length of each sample was measured by injection molding at 260℃ and 80MPa pressure. After 51 consecutive injection moldings, the spiral length of the last molded product was tested. The longer the spiral length, the better the molding fluidity of the product.

[0112] (2) Cantilever beam notched impact strength test: The cantilever beam notched impact strength of the material was tested according to ISO-180-2019, with a V-notch and an impact pendulum capacity of 2.75J;

[0113] (3) Tensile strength test: The test was conducted in accordance with ISO 527-2-2012 standard, with a tensile speed of 10 mm / min, a specimen size of 150*10*4 mm, and a dumbbell-shaped specimen.

[0114] (4) Weld line strength test: Non-standard test. Each sample is prepared according to step (3) to prepare a standard tensile strength test strip. The strip size is 150*10*4mm. The dumbbell-shaped strip is glued on both sides and melted in the middle to form a weld line. Then, the test is carried out according to ISO 527-2-2012 standard with a tensile speed of 10mm / min.

[0115] The test results are shown in Tables 3 and 4.

[0116] Table 3

[0117]

[0118] Table 4

[0119]

[0120] As shown in Tables 3 and 4, the PET composite material of this invention possesses ideal comprehensive properties, including a helix length exceeding 210 mm, high flowability, and a cantilever beam notched impact strength reaching 10 kJ / m. 2 The tensile strength can reach 85 MPa or higher, exhibiting excellent comprehensive mechanical properties. When the product undergoes weld line strength testing, the strength of each embodiment can reach 35 MPa or higher (specifically, the helix length can reach 220–241 mm, and the cantilever beam notched impact strength can reach 10.0–13.5 kJ / m). 2The tensile strength can reach 85-98 MPa, and the weld line strength can reach 36-53 MPa, fully demonstrating that the product can be applied to open-type moldless 3D printing of large parts. According to Examples 2 and 14-16, in the modified system of compatibilizer and hyperbranched polyester, the type of glass fiber also affects the product's performance. The weld line performance is optimal when the glass fiber has an average diameter in the range of 10-11 μm. Simultaneously, the viscosity of the PET resin, as the matrix resin, also has a certain impact on the various properties of the product. The product's performance is optimal when the intrinsic viscosity of the PET resin is maintained in the range of 0.6-0.8 dL / g. In Comparative Examples 1, 2, 4-5, and 2, the compatibilizer gradually increased in content from none to the product. It can be seen that without compatibilizer, Comparative Example 1 exhibits low weld line strength and low tensile strength, failing to meet the requirements for 3D printing large parts. With increased compatibilizer, the weld line strength improves, but the fluidity decreases. Excessive compatibilizer leads to a decline in all product properties, with Comparative Example 2 failing to meet the standards for fluidity, rigidity, and weld line strength. Furthermore, a comparison of Comparative Examples 6-8, 9, and 2 shows that components with similar structures or functions cannot replace the specific compatibilizer described in this invention. Inappropriate compatibilizer selection will still result in unsatisfactory product performance. On the other hand, the compatibilizer described in this invention needs to be used in conjunction with hyperbranched polyester, as in Comparative Examples 4 and 10. If hyperbranched polyester is lacking, or if other types of hyperbranched lubricants are used as substitutes, the weld line strength may not be guaranteed, or the fluidity may be poor. Furthermore, the amount of glass fiber introduced into the product should not be excessive; otherwise, as described in Comparative Example 3, although the tensile strength of the product is high, the toughness and weld line strength are poor due to the excessive bulk density of the glass fiber. Comparative Example 5 shows that the transesterification accelerator in the product is beneficial to the intercalation reaction of PET and PC resins. If this component is lacking, the weld line strength of the prepared product cannot meet the application requirements.

[0121] Furthermore, samples of 150*12.7*1.6mm were injection molded from the products of Examples 1 to 17, and then tested according to the latest UL94-2023 standard. The results showed that the flame retardant rating of each product could reach V-0 after the introduction of flame retardant components. The performance comparison between the products of Examples 2 and 17 showed that the introduction of flame retardant components did not cause a significant change in the original application performance of the products. The products of this invention are practical for both fire-retardant and non-fire-retardant printed parts.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A PET composite material, characterized in that, The components include the following parts by weight: 30-75 parts PET resin, 15-45 parts PC resin, 3-9 parts compatibilizer, 0.1-1 part hyperbranched polyester, 4-16 parts glass fiber, and 0.1-0.3 parts transesterification accelerator; The compatibilizer comprises the following structural units: ； A is -CH2-CHOH-, B is -CH2-CHOH-, and R group is a residue of ethylene-methyl acrylate-glycidyl methacrylate; n=10~2000； The hyperbranched polyester is a four-arm polyester copolymer with pentaerythritol as the core and polydimethylolpropionic acid as the branched chain. The glass fibers have an average length of 3-6 mm and an average diameter of 9-13 μm. The intrinsic viscosity of the PET resin at 25°C is 0.5~1.0 dL / g.

2. The PET composite material as described in claim 1, characterized in that, The PC resin has a weight-average molecular weight of 16,000 to 22,000 and a melt index of 20 to 25 g / 10 min at 300°C and a load of 1.2 kg.

3. The PET composite material as described in claim 1, characterized in that, The PET composite material also includes 0.1 to 0.3 parts of antioxidant; the antioxidant is at least one of hindered phenolic antioxidants, hindered amine antioxidants, and phosphite antioxidants.

4. The PET composite material as described in claim 1, characterized in that, The transesterification promoter is tetrabutyl titanate.

5. The PET composite material as described in claim 1, characterized in that, The PET composite material also includes 8-12 parts of bromine-based flame retardant and 2-4 parts of antimony-based flame retardant synergist.

6. The method for preparing the PET composite material according to any one of claims 1 to 5, characterized in that, Includes the following steps: The PET composite material is obtained by mixing the components, melt extruding, and granulating.

7. The application of the PET composite material as described in any one of claims 1 to 5 in the 3D printing of large parts.

8. The application as described in claim 7, characterized in that, The large components include garden landscape parts and bridge components.

9. A 3D printed part, characterized in that, Includes the PET composite material described in any one of claims 1 to 5.

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