A tracking-resistant halogen-free flame-retardant bio-based PBT composite material, a preparation method and application thereof

Abstract

The application discloses a kind of halogen-free flame-retardant bio-based PBT composite material resistant to tracking and its preparation method and application.The composition of the halogen-free flame-retardant bio-based PBT composite material resistant to tracking of the application includes bio-based PBT, glass fiber, aluminum diethyl hypophosphite, melamine polyphosphate, two-dimensional layered material, toughening agent, plasticizer and antioxidant, and its preparation method includes the following steps: the raw materials except glass fiber are added into a mixer to mix uniformly, then the obtained mixture is added into a twin-screw extruder from a main feeding port, and glass fiber is added into the twin-screw extruder from a side feeding port, then melt extrusion granulation is carried out.The halogen-free flame-retardant bio-based PBT composite material resistant to tracking of the application has excellent tracking resistance, excellent flame retardance and excellent mechanical properties, and has a wide application prospect in the field of electronics and electrical appliances, and its preparation process is simple, the raw materials are widely sourced, and it is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of PBT composite material technology, specifically relating to a halogen-free flame-retardant bio-based PBT composite material resistant to tracking and leakage current, its preparation method, and its application. Background Technology

[0002] Polybutylene terephthalate (PBT) is an important engineering plastic with excellent mechanical properties, superior electrical insulation, and good heat resistance and processability, making it widely used in the electronics and electrical fields. However, when the surface of PBT composite materials is exposed to moisture or contaminated by salt spray, dust, etc., it is prone to leakage current and arc discharge under the influence of a high-voltage electric field. This can lead to tracking damage and even fire, ultimately seriously endangering the safety of equipment. Therefore, it is urgent to improve the flame retardant properties and tracking resistance of PBT composite materials.

[0003] Currently, the flame retardant properties of PBT composites are mainly improved by adding large amounts of flame retardants. However, adding large amounts of flame retardants severely impairs the tracking resistance of PBT composites. For example, CN 114891326 A discloses a flame-retardant glass fiber reinforced PBT composite material, which imparts excellent flame retardant properties (self-extinguishing within 2 seconds after flame removal) by adding 23wt% phosphorus-nitrogen flame retardant and 2wt% silicon-based flame retardant. However, the tracking resistance of the PBT composite material is significantly reduced, with a tracking index (CTI) of only 500V. CN 117659649 A discloses a halogen-free flame-retardant glass fiber reinforced PBT composite material, which imparts excellent flame retardant properties (vertical burning rating reaches UL 94 V-0) by adding 13wt% phosphorus-based composite flame retardant and 2wt% calcium oxide. However, the CTI value of the PBT composite material is only 550V. Therefore, how to simultaneously improve the flame retardant properties and tracking resistance of PBT composites is an urgent problem to be solved.

[0004] Bio-based PBT can reduce the carbon footprint of materials throughout their entire life cycle from the source, demonstrating good environmental sustainability, and its research and application are steadily advancing. However, the bio-based monomers (butanediol or terephthalic acid) required for the synthesis of bio-based PBT inevitably contain impurities that are difficult to remove (the fermentation process for preparing bio-based monomers requires the addition of nutrients to maintain the growth and enzyme activity of microorganisms, and even after multiple purification steps such as filtration, evaporation, crystallization, and ion exchange of the fermentation broth, it is still difficult to completely remove residual nutrients and microbial metabolites). Although these impurities have little impact on the mechanical properties of PBT composites, they can severely damage the tracking resistance of PBT composites, which seriously limits the application of bio-based PBT in the electronics and electrical fields.

[0005] Therefore, it is of great significance to develop a bio-based PBT composite material that combines excellent resistance to tracking, excellent flame retardancy, and excellent mechanical properties. Summary of the Invention

[0006] The purpose of this invention is to provide a halogen-free flame-retardant bio-based PBT composite material resistant to tracking and leakage current, its preparation method, and its application.

[0007] The technical solution adopted in this invention is: A tracking-resistant, halogen-free, flame-retardant, bio-based PBT composite material comprising the following components by weight percentage: Bio-based PBT: 48.3%–52.3%; Glass fiber: 25.0%~35.0%; Aluminum diethylphosphite (ADP): 8.0%–15.0%; Melamine polyphosphate (MPP): 2.0%–4.0%; Two-dimensional layered materials: 1.0%–5.0%; Toughening agent: 2.0%–4.0%; Plasticizer: 0.4%–0.6%; Antioxidant: 0.1%–0.3%.

[0008] Preferably, the bio-based PBT has a terminal carboxyl group content ≤25mol / t, a melt index of 50g / 10min~75g / 10min, and a melt index test condition of 250℃ / 2.16kg.

[0009] Preferably, the bio-based PBT has an intrinsic viscosity of 0.85 dL / g ± 0.02 dL / g, a melting point of 225.0℃ ± 2.0℃, a colorimetric L ≥ 64, a colorimetric D ≤ 5.0, and a density of 1.30 g / cm³. 3 ~1.32g / cm 3 .

[0010] Preferably, the average monofilament diameter of the glass fiber is 9μm to 11μm.

[0011] Preferably, the two-dimensional layered material is at least one of fluorophlogopite, muscovite, and phlogopite.

[0012] Preferably, the average particle size (sheet diameter) of the two-dimensional layered material is 5 μm to 20 μm.

[0013] Preferably, the toughening agent is at least one of ethylene-methyl acrylate copolymer (EMA) and ethylene-butyl acrylate copolymer (EBA).

[0014] Preferably, the plasticizer is at least one of pentaerythritol stearate (PETS) and oxidized polyethylene wax (OPE wax).

[0015] Preferably, the antioxidant is at least one of pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (antioxidant 1010) and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene (antioxidant 1330).

[0016] A method for preparing the above-described halogen-free flame-retardant bio-based PBT composite material with tracking resistance includes the following steps: Bio-based PBT, diethyl aluminum hypophosphite, melamine polyphosphate, two-dimensional layered material, toughening agent, plasticizer and antioxidant are added to a mixer and mixed evenly. The resulting mixture is then fed into a twin-screw extruder through the main feed port, and glass fiber is fed into the twin-screw extruder through the side feed port. The mixture is then melt-extruded and granulated to obtain a halogen-free flame-retardant bio-based PBT composite material that is resistant to tracking and leakage current.

[0017] Preferably, the melt extrusion is carried out at a temperature of 230°C to 260°C.

[0018] Application of a halogen-free flame-retardant bio-based PBT composite material with tracking resistance as described above in the field of electronics and electrical engineering.

[0019] The beneficial effects of this invention are: the halogen-free flame-retardant bio-based PBT composite material of this invention has excellent tracking resistance, excellent flame retardancy and excellent mechanical properties, and has broad application prospects in the field of electronics and electrical engineering. Moreover, its preparation process is simple and the raw materials are widely available, making it suitable for large-scale industrial production.

[0020] Specifically: 1) The tracking-resistant, halogen-free, flame-retardant bio-based PBT composite material of this invention contains a two-dimensional layered material. This material, uniformly dispersed within the bio-based PBT, provides excellent barrier properties, delaying the release of pyrolysis products and heat transfer. More importantly, the two-dimensional layered material, together with glass fiber, forms a skeletal structure. Under the high temperatures generated by arc discharge, it combines with the halogen-free flame retardant and residues formed by polymer thermal decomposition to generate a robust and dense ceramic-like barrier layer. This layer resists arc erosion and blocks the transfer of heat, combustible gases, and oxygen, thus improving the flame-retardant and tracking-resistant properties of the PBT composite material (vertical burning rating reaches UL 94). (V-0 rating, CTI value reaches 600V); In addition, during arc discharge, a large number of electrons, ions and other charges are injected into the surface of PBT composite material. The two-dimensional layered structure provides a fast channel for charge migration, making it easier for charges to migrate and dissipate in PBT composite material. This reduces the accumulation of charges on the surface, thereby delaying the occurrence of electric field distortion, avoiding the continuous formation of arc, effectively reducing the damage of arc discharge to PBT composite material, and significantly improving the tracking resistance of PBT composite material. 2) The tracking-resistant, halogen-free, flame-retardant bio-based PBT composite material of the present invention has excellent mechanical properties (tensile strength, flexural strength, and notched impact strength ≥100.4MPa, ≥150.2MPa, and ≥7.7kJ / m, respectively). 2 ) and excellent processing performance; 3) The tracking-resistant, halogen-free, flame-retardant bio-based PBT composite material of the present invention has a low carbon footprint and good environmental friendliness; 4) The preparation process of the tracking-resistant, halogen-free, flame-retardant bio-based PBT composite material of the present invention is simple, the raw materials are readily available, and it is easy to realize industrial production, which has a very broad application prospect. Attached Figure Description

[0021] Figure 1 The images show the surface corrosion state of the bio-based PBT composite material of Comparative Example 2 and the halogen-free flame-retardant bio-based PBT composite material of Example 1 after a 600V tracking resistance test.

[0022] Figure 2 The image shows the surface of the halogen-free flame-retardant bio-based PBT composite material of Example 1 after a 600V tracking resistance test.

[0023] Figure 3 The isothermal surface potential decay curves are those of the halogen-free flame-retardant bio-based PBT composite material resistant to tracking in Example 1 and the bio-based PBT composite material in Comparative Example 2.

[0024] Figure 4The image shows the SEM image of the impact fracture surface of the halogen-free flame-retardant bio-based PBT composite material resistant to tracking in Example 1. Detailed Implementation

[0025] The present invention will be further explained and described below with reference to specific embodiments.

[0026] Example 1: A halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking, with the composition shown in the table below: Table 1. Composition of a halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking.

[0027] The preparation method of the above-mentioned tracking-resistant, halogen-free, flame-retardant, bio-based PBT composite material is as follows: Bio-based PBT, diethyl aluminum hypophosphite, melamine polyphosphate, fluorophlogopite, ethylene-methyl acrylate copolymer, pentaerythritol stearate, and pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) ester were added to a mixer and mixed evenly. The resulting mixture was then fed into a twin-screw extruder through the main feed port, and glass fiber was fed into the twin-screw extruder through the side feed port. The mixture was then melt-extruded and granulated at a temperature of 250°C to obtain a halogen-free flame-retardant bio-based PBT composite material resistant to tracking.

[0028] Example 2: A halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking, with the composition shown in the table below: Table 2. Composition of a halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking.

[0029] The preparation method of the above-mentioned tracking-resistant, halogen-free, flame-retardant, bio-based PBT composite material is as follows: Bio-based PBT, diethylaluminum hypophosphite, melamine polyphosphate, fluorophlogopite, ethylene-butyl acrylate copolymer, oxidized polyethylene wax, and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene were added to a mixer and mixed evenly. The resulting mixture was then fed into a twin-screw extruder through the main feed port, and glass fiber was fed into the twin-screw extruder through the side feed port. The mixture was then melt-extruded and granulated at a temperature of 230°C to obtain a halogen-free flame-retardant bio-based PBT composite material resistant to tracking.

[0030] Example 3: A halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking, with the composition shown in the table below: Table 3. Composition of a halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking.

[0031] The preparation method of the above-mentioned tracking-resistant, halogen-free, flame-retardant, bio-based PBT composite material is as follows: Bio-based PBT, diethyl aluminum hypophosphite, melamine polyphosphate, fluorophlogopite, ethylene-methyl acrylate copolymer, pentaerythritol stearate, and pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) ester were added to a mixer and mixed evenly. The resulting mixture was then fed into a twin-screw extruder through the main feed port, and glass fiber was fed into the twin-screw extruder through the side feed port. The mixture was then melt-extruded and granulated at a temperature of 250°C to obtain a halogen-free flame-retardant bio-based PBT composite material resistant to tracking.

[0032] Example 4: A halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking, with the composition shown in the table below: Table 4. Composition of a halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking.

[0033] The preparation method of the above-mentioned tracking-resistant, halogen-free, flame-retardant, bio-based PBT composite material is as follows: Bio-based PBT, diethyl aluminum hypophosphite, melamine polyphosphate, fluorophlogopite, ethylene-methyl acrylate copolymer, pentaerythritol stearate, and pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) ester were added to a mixer and mixed evenly. The resulting mixture was then fed into a twin-screw extruder through the main feed port, and glass fiber was fed into the twin-screw extruder through the side feed port. The mixture was then melt-extruded and granulated at a temperature of 260°C to obtain a halogen-free flame-retardant bio-based PBT composite material resistant to tracking.

[0034] Example 5: A halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking, with the composition shown in the table below: Table 5. Composition of a halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking.

[0035] The preparation method of the above-mentioned tracking-resistant, halogen-free, flame-retardant, bio-based PBT composite material is as follows: Bio-based PBT, diethyl aluminum hypophosphite, melamine polyphosphate, muscovite, ethylene-butyl acrylate copolymer, pentaerythritol stearate, and pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) ester were added to a mixer and mixed evenly. The resulting mixture was then fed into a twin-screw extruder through the main feed port, and glass fiber was fed into the twin-screw extruder through the side feed port. The mixture was then melt-extruded and granulated at a temperature of 240°C to obtain a halogen-free flame-retardant bio-based PBT composite material resistant to tracking.

[0036] Comparative Example 1: A bio-based PBT composite material, the composition of which is shown in the table below: Table 6 Composition of a bio-based PBT composite material

[0037] The preparation method of the above-mentioned bio-based PBT composite material is as follows: Bio-based PBT, ethylene-methyl acrylate copolymer, pentaerythritol stearate and pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) ester were added to a mixer and mixed evenly. The resulting mixture was then fed into a twin-screw extruder through the main feed port, and glass fiber was fed into the twin-screw extruder through the side feed port. The mixture was then melt-extruded and granulated at a temperature of 250°C to obtain the bio-based PBT composite material.

[0038] Comparative Example 2: A bio-based PBT composite material, the composition of which is shown in the table below: Table 7 Composition of a bio-based PBT composite material

[0039] The preparation method of the above-mentioned bio-based PBT composite material is as follows: Bio-based PBT, diethyl aluminum hypophosphite, melamine polyphosphate, ethylene-methyl acrylate copolymer, pentaerythritol stearate, and pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) ester were added to a mixer and mixed evenly. The resulting mixture was then fed into a twin-screw extruder through the main feed port, and glass fiber was fed into the twin-screw extruder through the side feed port. The mixture was then melt-extruded and granulated at a temperature of 250°C to obtain the bio-based PBT composite material.

[0040] Comparative Example 3: A bio-based PBT composite material, the composition of which is shown in the table below: Table 8 Composition of a bio-based PBT composite material

[0041] The preparation method of the above-mentioned bio-based PBT composite material is as follows: Bio-based PBT, fluorophlogopite, ethylene-methyl acrylate copolymer, pentaerythritol stearate, and pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid) ester were added to a mixer and mixed evenly. The resulting mixture was then fed into a twin-screw extruder through the main feed port, and glass fiber was fed into the twin-screw extruder through the side feed port. The mixture was then melt-extruded and granulated at a temperature of 250°C to obtain the bio-based PBT composite material.

[0042] Performance testing: 1) The surface corrosion state of the bio-based PBT composite material of Comparative Example 2 and the halogen-free flame-retardant bio-based PBT composite material of Example 1 after a 600V tracking resistance test is shown in the figure. Figure 1 (a is Comparative Example 2, b is Example 1) As shown, the scanning electron microscope (SEM) image of the surface of the halogen-free flame-retardant bio-based PBT composite material of Example 1 after a 600V tracking resistance test is shown below. Figure 2 (a is a SEM image near the electrode, b and c are SEM images of the electro-erosion area) As shown, the isothermal surface potential decay curves of the halogen-free flame-retardant bio-based PBT composite material resistant to tracking in Example 1 and the bio-based PBT composite material of Comparative Example 2 are as follows: Figure 3 As shown in the table below, the test results of the tracking resistance (CTI value) and flame retardant properties (UL 94 flame retardant rating) of the halogen-free flame-retardant bio-based PBT composite materials of Examples 1-5 and the bio-based PBT composite materials of Comparative Examples 1-3 are as follows: Table 9 Test results of tracking resistance and flame retardant properties

[0043] Note: Tracking resistance: Tested according to "GB / T 4207-2022 Test method for tracking resistance and determination of comparative tracking index of solid insulating materials".

[0044] Flame retardancy: Tested in accordance with "UL 94 Standard Test for Flammability of Plastic Materials for Equipment and Electrical Components".

[0045] From Table 9 and Figures 1-3 It can be known that: a) The bio-based PBT composite material without diethylaluminum hypophosphite, melamine polyphosphate, and two-dimensional layered materials (Comparative Example 1) and the bio-based PBT composite material with fluorophlogopite added alone (Comparative Example 3) both exhibited poor tracking resistance and flame retardancy, failing the 600V tracking resistance test and vertical burning test. The bio-based PBT composite material with only diethylaluminum hypophosphite and melamine polyphosphate added (Comparative Example 2) achieved a UL 94 V-0 flame retardancy rating, but its tracking resistance was poor, failing the 600V tracking resistance test (from...). Figure 1 As can be seen from a in Figure 2, the bio-based PBT composite material in Comparative Example 2 suffered severe tracking damage during the tracking resistance test, indicating extremely serious electrical erosion of the composite material. b) Bio-based PBT composites with the simultaneous addition of diethylaluminum hypophosphite, melamine polyphosphate, and a small amount of two-dimensional layered material (Examples 1-5) all exhibited excellent resistance to tracking. The halogen-free flame-retardant bio-based PBT composite of Example 1, which is resistant to tracking, passed the 600V tracking resistance test. No tracking damage occurred on the surface of the composite material, only slight traces of electrical erosion were observed (see...). Figure 1 b and Figure 2 (a) In this context, the electro-erosion debris, supported by two-dimensional layered materials and glass fibers, forms a protective barrier, protecting the internal matrix from further erosion by heat, contaminated liquids, and strong electric arcs, thereby improving the tracking resistance of the composite material (see [reference]). Figure 2 (b and c in the original text); Compared with the bio-based PBT composite material with only diethylaluminum hypophosphite and melamine polyphosphate added (Comparative Example 2), the tracking-resistant, halogen-free, flame-retardant bio-based PBT composite material of Example 1 exhibits significantly enhanced charge dissipation capability, and its surface potential decreases rapidly over time, reaching 1284V at 2000s and only 380V at 10000s (see b and c in the original text). Figure 3 The reason is that two-dimensional layered materials make it easier for electrons, ions and other charges to migrate and dissipate in composite materials, effectively suppressing the local accumulation of charges on the material surface. The reduction in the degree of charge accumulation weakens the electric field distortion effect, reduces the formation of high-energy electric arcs, and thus reduces the destructive effect of electric arcs on the polymer matrix. Therefore, the tracking resistance of composite materials is significantly improved. c) Bio-based PBT composites (Examples 1-5) with the simultaneous addition of diethylaluminum hypophosphite, melamine polyphosphate, and a small amount of two-dimensional layered material all exhibit excellent flame retardant properties, achieving a UL 94 rating of V-0. This is because: diethylaluminum hypophosphite and melamine polyphosphate play a flame-retardant role in both the gas and condensed phases; on the one hand, they release phosphorus-containing free radicals in the gas phase, quenching the combustion chain reaction; on the other hand, they promote the dehydration and char formation of the polymer matrix, forming a barrier layer; simultaneously, the two-dimensional layered material, with its good skeletal support, can enhance the density of the barrier layer, effectively blocking the transfer of heat, combustible gases, and oxygen. Under the synergistic effect of the above multiple flame-retardant effects, the composite material achieves excellent flame-retardant properties.

[0046] 2) SEM image of the impact fracture surface of the halogen-free flame-retardant bio-based PBT composite material resistant to tracking in Example 1 is shown below. Figure 4 As shown in the table below, the mechanical properties (tensile strength, flexural strength, and cantilever beam notched impact strength) and melt flow rate test results of the halogen-free flame-retardant bio-based PBT composites of Examples 1-5 and Comparative Examples 1-3 are as follows: Table 10 Test results of mechanical properties and melt flow rate

[0047] Note: Tensile strength: Tested in accordance with "GB / T 1040.1-2025 Determination of tensile properties of plastics - Part 1: General".

[0048] Bending strength: Tested in accordance with "GB / T 9341-2008 Determination of bending properties of plastics".

[0049] Impact strength of cantilever beam: The test was conducted in accordance with "GB / T 1843-2008 Determination of impact strength of plastic cantilever beam".

[0050] Melt flow rate: The test shall be conducted in accordance with "GB / T 3682.1-2018 Determination of melt mass flow rate (MFR) and melt volumetric flow rate (MVR) of thermoplastics - Part 1: Standard method".

[0051] Depend on Figure 4 It can be seen that the glass fiber and the two-dimensional layered material are uniformly dispersed in the bio-based PBT matrix, and no obvious agglomeration regions were observed. Moreover, the glass fiber and the bio-based PBT matrix are tightly bonded, which helps to transfer stress between the bio-based PBT matrix and the glass fiber, thus significantly improving the mechanical properties of the composite material.

[0052] As shown in Table 10, the bio-based PBT composite materials (Examples 1-5) with the simultaneous addition of diethylaluminum hypophosphite, melamine polyphosphate, and a small amount of two-dimensional layered material exhibit excellent mechanical properties, with tensile strength, flexural strength, and notched impact strength ≥100.4 MPa, ≥150.2 MPa, and ≥7.7 kJ / m, respectively. 2 It also has good processing performance.

[0053] In summary, the halogen-free flame-retardant bio-based PBT composite material of the present invention possesses excellent resistance to tracking, excellent flame retardancy, and excellent mechanical properties, and has a very broad application prospect in the field of electronics and electrical engineering.

[0054] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking, characterized in that, The components include the following percentages by mass: Bio-based PBT: 48.3%–52.3%; Glass fiber: 25.0%~35.0%; Diethylaluminum hypophosphite: 8.0%–15.0%; Melamine polyphosphate: 2.0%–4.0%; Two-dimensional layered materials: 1.0%–5.0%; Toughening agent: 2.0%–4.0%; Plasticizer: 0.4%–0.6%; Antioxidant: 0.1%–0.3%.

2. The halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking as described in claim 1, characterized in that: The bio-based PBT has a terminal carboxyl group content of ≤25mol / t, a melt index of 50g / 10min~75g / 10min, and a melt index test condition of 250℃ / 2.16kg.

3. The halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking as described in claim 1, characterized in that: The average diameter of the glass fiber monofilament is 9μm to 11μm.

4. The halogen-free, flame-retardant, bio-based PBT composite material resistant to tracking as described in claim 1, characterized in that: The two-dimensional layered material is at least one of fluorophlogopite, muscovite, and phlogopite; and / or, the average particle size of the two-dimensional layered material is 5 μm to 20 μm.

5. The halogen-free flame-retardant bio-based PBT composite material resistant to tracking according to any one of claims 1 to 4, characterized in that: The toughening agent is at least one of ethylene-methyl acrylate copolymer and ethylene-butyl acrylate copolymer.

6. The halogen-free flame-retardant bio-based PBT composite material resistant to tracking according to any one of claims 1 to 4, characterized in that: The plasticizer is at least one of pentaerythritol stearate and oxidized polyethylene wax.

7. The halogen-free flame-retardant bio-based PBT composite material resistant to tracking according to any one of claims 1 to 4, characterized in that: The antioxidant is at least one of pentaerythritol tetrakis(β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene.

8. A method for preparing a halogen-free flame-retardant bio-based PBT composite material with tracking resistance as described in any one of claims 1 to 7, characterized in that, The process includes the following steps: adding bio-based PBT, aluminum diethyl phosphite, melamine polyphosphate, two-dimensional layered material, toughening agent, plasticizer and antioxidant into a mixer and mixing them evenly; then feeding the resulting mixture into a twin-screw extruder through the main feed port and feeding glass fiber into the twin-screw extruder through the side feed port; and then performing melt extrusion granulation to obtain a halogen-free flame-retardant bio-based PBT composite material resistant to tracking.

9. The preparation method according to claim 8, characterized in that: The melt extrusion is carried out at a temperature of 230℃ to 260℃.

10. The application of a halogen-free flame-retardant bio-based PBT composite material as described in any one of claims 1 to 7 in the field of electronics and electrical engineering.

Images