Modified PBT composite material with low dielectric constant and preparation method thereof

Abstract

The invention relates to the technical field of resin, in particular to a low-dielectric-constant modified PBT composite material and a preparation method thereof. The low-dielectric constant modified PBT composite material is prepared from the following components: PBT resin, modified PBT resin, PET resin, PC resin, copolymerized PP resin, composite glass fibers, a flame retardant, a flexibilizer, a basic magnesium sulfate whisker silane coupling agent, an antioxidant and propylene-octylene copolymer grafted glycidyl methacrylate. The modified PBT resin is prepared through swelling treatment and carboxyl-terminated butyronitrile glue solution grafting modification, through the synergistic effect of the modified PBT resin and the composite glass fiber, the dielectric constant at the frequency of 1 MHz is as low as 2.30-2.48, the dielectric loss is only 0.0020-0.0032, and the composite requirements for low dielectric, high mechanics, high flame retardance and high temperature resistance in multiple fields such as automobiles, electronic appliances and aerospace can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resin, in particular to a low dielectric constant modified PBT composite material and a preparation method thereof. BACKGROUND

[0002] As one of the five engineering plastics, polybutylene terephthalate (PBT) has high heat resistance and is widely used in the fields of automobiles, electronic and electrical components, etc. However, with the increasing use of PBT resin, the defects of poor flame retardant performance, insufficient heat distortion temperature, insufficient notched impact strength, and the need to improve the mechanical and surface properties of PBT materials become increasingly apparent. In addition, in some specific application scenarios, PBT materials also need to have low dielectric constant and dielectric loss, excellent solvent resistance and other characteristics. Therefore, it is of great practical significance to modify PBT to improve its performance.

[0003] CN118271806A discloses a PBT composite material, a preparation method and application thereof, which comprises PBT resin, PC resin, copolymerized PP resin, glass fiber and propylene-octene copolymer grafted glycidyl methacrylate. The technical solution mainly focuses on improving the dielectric properties and processing fluidity of the composite material by selecting low dielectric constant glass fiber and specific melt index copolymerized PP resin. However, PBT resin as an organic polymer has poor interfacial compatibility with glass fiber, and the interfacial bonding force is weak. In order to improve the interface, the conventional method such as using silane coupling agent for interface treatment is used, but the improvement degree of silane coupling agent in the complex multi-component system, especially under harsh conditions such as high frequency and high temperature, is limited. SUMMARY

[0004] The present application aims to provide a low dielectric constant modified PBT composite material and a preparation method thereof to solve the problems raised in the background art.

[0005] To achieve the above-mentioned purpose, on the one hand, the present application provides the following technical solution: a low dielectric constant modified PBT composite material, consisting of the following components by mass fraction: PBT resin 28-35 parts, modified PBT resin 5-8 parts, PET resin 2-4 parts, PC resin 2-3 parts, copolymerized PP resin 2-3 parts, composite glass fiber 22-38 parts, flame retardant 6-12 parts, toughening agent 2-4 parts, basic magnesium sulfate whisker 3-4 parts, silane coupling agent 1-2 parts, antioxidant 0.5-1 part, propylene-octene copolymer grafted glycidyl methacrylate 2-12 parts. The modified PBT resin is prepared by a method comprising the following steps: (a) soaking 100 parts by mass of polybutylene terephthalate in a plastic swelling agent at 72-78℃ for 32-38 min, and then heating to 90-100℃, and performing ultrasonic-assisted swelling, with an ultrasonic power of 300-400 W, a frequency of 40 kHz, and a time of 20-30 min, to obtain swollen PBT; and (b) placing the swollen PBT and 5-15 parts by mass of carboxyl-terminated butyronitrile glue solution in a twin-screw extruder, and performing melt extrusion at an extrusion temperature of 230-250℃ and a screw rotation speed of 150-200 rpm to obtain the modified PBT resin.

[0006] Optionally, in (a), the plastic swelling agent is toluene or dichloromethane, and the amount thereof is 15-20% of the mass of polybutylene terephthalate.

[0007] Optionally, in (b), the mass fraction of acrylonitrile in the carboxyl-terminated butyronitrile glue solution is 20-24%, and the mass fraction of carboxyl groups is 2.2-2.8%.

[0008] Optionally, in (b), the barrel temperature of the twin-screw extruder is set as follows: zone 1, 210-220℃; zone 2, 220-230℃; zone 3, 230-240℃; zone 4, 240-250℃; and die head, 230-250℃.

[0009] Optionally, the composite glass fiber is made by mixing short-cut flat glass fibers and glass fiber short-cut filaments at a mass ratio of 1:1-3:1.

[0010] Optionally, the flame retardant is made by mixing aluminum diethyl phosphinate and melamine polyphosphate at a mass ratio of 1:1-5:1.

[0011] Optionally, the toughening agent is selected from ethylene-butyl acrylate copolymer or ethylene-vinyl acetate copolymer.

[0012] Optionally, the antioxidant is made by mixing a hindered phenolic antioxidant and a phosphite antioxidant at a mass ratio of 1:1-2:1.

[0013] In another aspect, the present application also provides a preparation method of the low-dielectric-constant modified PBT composite material, comprising the following steps: S1, raw material mixing: first, the PBT resin, modified PBT resin, PET resin, PC resin, copolymer PP resin, flame retardant, toughening agent, silane coupling agent, antioxidant, propylene-octene copolymer grafted glycidyl methacrylate are placed in a high-speed stirrer, stirred at 600-800 rpm for 10-30 min, then composite glass fiber and basic magnesium sulfate whisker are added, stirred at 300-400 rpm for 5-8 min, to obtain a mixture; S2, extrusion granulation: the mixture is subjected to twice melt extrusion granulation to prepare modified PBT plastic particles, wherein in the first extrusion granulation, the barrel temperature of the double screw extruder is controlled as follows: feeding section 180-190 DEG C, compression section 200-215 DEG C, homogenization section 215-225 DEG C, die head 220-230 DEG C, and the screw speed is 220-280 rpm; in the second extrusion granulation, the barrel temperature of the double screw extruder is controlled as follows: feeding section 190-200 DEG C, compression section 210-225 DEG C, homogenization section 225-235 DEG C, die head 230-240 DEG C, and the screw speed is 280-330 rpm; S3, injection molding: the obtained modified PBT plastic particles are vacuum dried at 125-135 DEG C for 60-90 min, then injection molding is carried out using an improved mold cavity with flow guide groove and exhaust passage, the mold cavity temperature is maintained at 85-110 DEG C by a heat conduction oil circulation temperature control system, the injection pressure is 80-120 MPa, the pressure maintaining time is 10-30 s, the heat preservation and shaping time is 30-50 s, finally the product is demolded and trimmed, to obtain the low dielectric constant modified PBT composite material.

[0014] Compared with the prior art, the present application has the following advantages: 1. The modified PBT resin is prepared by swelling treatment and carboxyl-terminated nitrile glue solution grafting modification, and through the synergistic effect of the modified PBT resin and the composite glass fiber, the dielectric constant at 1 MHz frequency is as low as 2.30-2.48, and the dielectric loss is only 0.0020-0.0032, which can meet the composite requirements of low dielectric, high mechanics, high flame retardance and high temperature resistance in many fields such as automobiles, electronic appliances and aerospace; 2. The modified PBT resin improves the interfacial compatibility of the resin and the composite glass fiber, and through the combination of the reinforcing effect of the composite glass fiber and the toughening effect of the toughening agent, the tensile strength of the material reaches 119-134 MPa, the impact strength reaches 28-33 kJ / m², and the heat distortion temperature is improved to 132-153 DEG C, which improves the defects of insufficient mechanical strength and poor thermal stability of traditional PBT materials; 3. The injection molding process of two times of extrusion granulation by sectional temperature control, combined with the flow guide and exhaust design of the improved mold cavity, reduces the processing difficulty and ensures the product forming quality. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0016] Embodiment 1 The present application provides a low dielectric constant modified PBT composite material, which is composed of the following components in parts by mass: PBT resin 30 parts, modified PBT resin 8 parts, PET resin 3 parts, PC resin 2 parts, copolymerized PP resin 2 parts, composite glass fiber 30 parts, flame retardant 9 parts, toughening agent 3 parts, basic magnesium sulfate whisker 4 parts, silane coupling agent 1.2 parts, antioxidant 0.8 parts, propylene-octene copolymer grafted glycidyl methacrylate 7 parts.

[0017] The modified PBT resin is prepared by a method comprising the following steps: (a) soaking 100 parts by mass of polybutylene terephthalate in a plastic swelling agent at 75℃ for 35 min, and then increasing the temperature to 95℃ for ultrasonic-assisted swelling, with an ultrasonic power of 350 W, a frequency of 40 kHz, and a time of 25 min, to obtain swollen PBT; (b) placing the swollen PBT and 10 parts by mass of carboxyl-terminated butyronitrile glue solution in a twin-screw extruder for melt extrusion at an extrusion temperature of 240℃ and a screw rotation speed of 180 rpm to obtain the modified PBT resin.

[0018] In (a), the plastic swelling agent is toluene, and its amount is 18% of the mass of polybutylene terephthalate. In (b), the mass fraction of acrylonitrile in the carboxyl-terminated butyronitrile glue solution is 22%, and the mass fraction of carboxyl is 2.5%. The barrel temperature of the twin-screw extruder is set as follows: zone 1 215℃, zone 2 225℃, zone 3 235℃, zone 4 245℃, and die 240℃.

[0019] The composite glass fiber is made by mixing short-cut flat glass fiber and glass fiber short-cut original wire at a mass ratio of 2:1. The flame retardant is made by mixing aluminum diethyl phosphinate and melamine polyphosphate at a mass ratio of 3:1. The toughening agent is selected from ethylene-butyl acrylate copolymer. The antioxidant is made by mixing hindered phenolic antioxidant and phosphite antioxidant at a mass ratio of 1.5:1.

[0020] The preparation method of the low dielectric constant modified PBT composite material comprises the following steps: S1, raw material mixing: first, the PBT resin, modified PBT resin, PET resin, PC resin, copolymer PP resin, flame retardant, toughening agent, silane coupling agent, antioxidant, propylene-octene copolymer grafted glycidyl methacrylate are placed in a high-speed stirrer, stirred at 700 rpm for 20 min, then composite glass fiber and basic magnesium sulfate whisker are added, stirred at 350 rpm for 6 min, to obtain a mixture; S2, extrusion granulation: the mixture is subjected to twice melt extrusion granulation to prepare modified PBT plastic particles, wherein in the first extrusion granulation, the barrel temperature of the double screw extruder is controlled to be 185℃ for the feeding section, 208℃ for the compression section, 220℃ for the homogenization section, and 225℃ for the die head, and the screw speed is 250 rpm, and in the second extrusion granulation, the barrel temperature of the double screw extruder is controlled to be 195℃ for the feeding section, 218℃ for the compression section, 230℃ for the homogenization section, and 235℃ for the die head, and the screw speed is 300 rpm; S3, injection molding: the obtained modified PBT plastic particles are vacuum dried at 130℃ for 75 min, then injection molding is carried out using an improved mold cavity with flow guide groove and exhaust passage, the mold cavity temperature is maintained at 95℃ by a heat conduction oil circulation temperature control system, the injection pressure is 100 MPa, the pressure maintaining time is 20 s, the heat preservation and shaping time is 40 s, finally demolding and trimming are carried out, to obtain a low dielectric constant modified PBT composite material.

[0021] Example 2 The present application provides a low dielectric constant modified PBT composite material, which is composed of the following components in mass parts: PBT resin 28 parts, modified PBT resin 5 parts, PET resin 4 parts, PC resin 2 parts, copolymer PP resin 3 parts, composite glass fiber 38 parts, flame retardant 11 parts, toughening agent 2 parts, basic magnesium sulfate whisker 3 parts, silane coupling agent 1 part, antioxidant 1 part, propylene-octene copolymer grafted glycidyl methacrylate 2 parts.

[0022] The modified PBT resin is prepared by a method comprising the following steps: (a) 100 parts by mass of polybutylene terephthalate is soaked in a plastic swelling agent at 72℃ for 38 min, then the temperature is raised to 90℃, ultrasonic assisted swelling is carried out, the ultrasonic power is 400 W, the frequency is 40 kHz, and the time is 30 min, to obtain swollen PBT; (b) the swollen PBT and 8 parts by mass of carboxyl-terminated butyronitrile glue solution are placed in a double screw extruder, melt extrusion is carried out at an extrusion temperature of 230℃ and a screw speed of 150 rpm, to prepare the modified PBT resin.

[0023] In (a), the plastic swelling agent is dichloromethane, and its amount is 15% of the mass of polybutylene terephthalate. In (b), the mass fraction of acrylonitrile in the carboxyl-terminated butyronitrile glue solution is 20%, and the mass fraction of carboxyl is 2.2%. The barrel temperature of the twin-screw extruder is set as follows: 210℃ for zone 1, 220℃ for zone 2, 230℃ for zone 3, 240℃ for zone 4, and 230℃ for the head, and the extrusion temperature is 230℃.

[0024] The composite glass fiber is made by mixing short-cut flat glass fiber and glass fiber chopped strands at a mass ratio of 3:1. The flame retardant is made by mixing aluminum diethyl phosphinate and melamine polyphosphate at a mass ratio of 1:1. The toughening agent is selected from ethylene-vinyl acetate copolymer. The antioxidant is made by mixing hindered phenolic antioxidant and phosphite antioxidant at a mass ratio of 1:1.

[0025] The preparation method of the low dielectric constant modified PBT composite material comprises the following steps: S1, raw material mixing: first, put PBT resin, modified PBT resin, PET resin, PC resin, copolymer PP resin, flame retardant, toughening agent, silane coupling agent, antioxidant, propylene-octene copolymer grafted glycidyl methacrylate into a high-speed stirrer, stir at 600 rpm for 30 min, then add composite glass fiber and basic magnesium sulfate whisker, stir at 300 rpm for 8 min, to obtain a mixture; S2, extrusion granulation: the mixture is subjected to twice melt extrusion granulation to prepare modified PBT plastic particles, wherein in the first extrusion granulation, the barrel temperature of the twin-screw extruder is controlled as follows: 180℃ for the feeding section, 200℃ for the compression section, 215℃ for the homogenization section, and 220℃ for the head, and the screw speed is 220 rpm; in the second extrusion granulation, the barrel temperature of the twin-screw extruder is controlled as follows: 190℃ for the feeding section, 210℃ for the compression section, 225℃ for the homogenization section, and 230℃ for the head, and the screw speed is 280 rpm; S3, injection molding: the obtained modified PBT plastic particles are vacuum dried at 125℃ for 90 min, then injection molded by using an improved mold cavity with a flow guide groove and an exhaust passage, the mold cavity temperature is maintained at 85℃ by a heat conduction oil circulation temperature control system, the injection pressure is 120 MPa, the pressure maintaining time is 10 s, the heat preservation and shaping time is 30 s, finally demolding and trimming, to obtain the low dielectric constant modified PBT composite material.

[0026] Example 3 The application provides a low dielectric constant modified PBT composite material which is composed of the following components in parts by mass: 35 parts of PBT resin, 6 parts of modified PBT resin, 2 parts of PET resin, 3 parts of PC resin, 3 parts of copolymerized PP resin, 22 parts of composite glass fiber, 6 parts of flame retardant, 4 parts of toughening agent, 4 parts of basic magnesium sulfate whisker, 2 parts of silane coupling agent, 1 part of antioxidant, and 12 parts of propylene-octene copolymer grafted glycidyl methacrylate.

[0027] The modified PBT resin is prepared by a method comprising the following steps: (a) soaking 100 parts by mass of polybutylene terephthalate in a plastic swelling agent at 78 DEG C for 32 min, then increasing the temperature to 100 DEG C, and performing ultrasonic-assisted swelling with an ultrasonic power of 300 W and a frequency of 40 kHz for 20 min to obtain swollen PBT; and (b) placing the swollen PBT and 15 parts by mass of carboxyl-terminated butyronitrile glue solution in a double-screw extruder, and performing melt extrusion at an extrusion temperature of 250 DEG C and a screw rotation speed of 200 rpm to obtain the modified PBT resin.

[0028] In (a), the plastic swelling agent is toluene, and the amount of the plastic swelling agent is 20% of the mass of polybutylene terephthalate.

[0029] The composite glass fiber is prepared by mixing short-cut flat glass fiber and glass fiber short-cut filaments at a mass ratio of 1:1. The flame retardant is prepared by mixing aluminum diethyl phosphinate and melamine polyphosphate at a mass ratio of 5:1. The toughening agent is selected from ethylene-butyl acrylate copolymer. The antioxidant is prepared by mixing hindered phenolic antioxidant and phosphite antioxidant at a mass ratio of 2:1.

[0030] The preparation method of the low dielectric constant modified PBT composite material comprises the following steps: S1, raw material mixing: first, the PBT resin, modified PBT resin, PET resin, PC resin, copolymerized PP resin, flame retardant, toughening agent, silane coupling agent, antioxidant, propylene-octene copolymer grafted glycidyl methacrylate are placed in a high-speed mixer, stirred at 800 rpm for 10 min, then the composite glass fiber and the basic magnesium sulfate whisker are added, stirred at 400 rpm for 5 min, and a mixture is obtained; S2, extrusion granulation: the mixture is subjected to twice melt extrusion granulation, to obtain modified PBT plastic particles, wherein in the first extrusion granulation, the barrel temperature of the twin-screw extruder is controlled as follows: feeding section 190℃, compression section 215℃, homogenization section 225℃, die head 230℃, screw rotation speed 280 rpm, and in the second extrusion granulation, the barrel temperature of the twin-screw extruder is controlled as follows: feeding section 200℃, compression section 225℃, homogenization section 235℃, die head 240℃, screw rotation speed 330 rpm; S3, injection molding: the obtained modified PBT plastic particles are vacuum dried at 135℃ for 60 min, then injection molding is performed using a modified mold cavity with flow guide grooves and exhaust channels, the mold cavity temperature is maintained at 110℃ by a heat conduction oil circulation temperature control system, the injection pressure is 80 MPa, the pressure maintaining time is 30 s, the heat preservation and shaping time is 50 s, finally the mold is opened and the product is trimmed, to obtain a low dielectric constant modified PBT composite material.

[0031] Example 4 The present application provides a low dielectric constant modified PBT composite material, which is composed of the following components in parts by mass: PBT resin 31 parts, modified PBT resin 7 parts, PET resin 4 parts, PC resin 1 part, copolymerized PP resin 2 parts, composite glass fiber 26 parts, flame retardant 12 parts, toughening agent 2 parts, basic magnesium sulfate whisker 3 parts, silane coupling agent 1.5 parts, antioxidant 0.5 parts, propylene-octene copolymer grafted glycidyl methacrylate 10 parts.

[0032] The modified PBT resin is prepared by a method comprising the following steps: (a) 100 parts by mass of polybutylene terephthalate is soaked in a plastic swelling agent at 76℃ for 36 min, then the temperature is raised to 98℃, ultrasonic assisted swelling is performed, the ultrasonic power is 380 W, the frequency is 40 kHz, and the time is 22 min, to obtain swollen PBT; (b) the swollen PBT and 12 parts by mass of carboxyl-terminated butyronitrile glue solution are placed in a twin-screw extruder, melt extrusion is performed at an extrusion temperature of 245℃ and a screw rotation speed of 190 rpm, to obtain the modified PBT resin.

[0033] In (a), the plastic swelling agent is dichloromethane, and the amount is 17% of the mass of polybutylene terephthalate. In (b), the mass fraction of acrylonitrile in the carboxyl-terminated butyronitrile glue solution is 23%, and the mass fraction of carboxyl is 2.6%. The barrel temperature of the twin-screw extruder is set as follows: zone 1 218℃, zone 2 228℃, zone 3 238℃, zone 4 248℃, die head 245℃.

[0034] The composite glass fiber is made by mixing short-cut flat glass fiber and glass fiber short-cut roving at a mass ratio of 2.5:1. The flame retardant is made by mixing aluminum diethyl phosphinate and melamine polyphosphate at a mass ratio of 4:1. The toughening agent is selected from ethylene-vinyl acetate copolymer. The antioxidant is made by mixing hindered phenolic antioxidant and phosphite antioxidant at a mass ratio of 1.8:1.

[0035] The preparation method of the low dielectric constant modified PBT composite material comprises the following steps: S1, raw material mixing: first, the PBT resin, modified PBT resin, PET resin, PC resin, copolymer PP resin, flame retardant, toughening agent, silane coupling agent, antioxidant, propylene-octene copolymer grafted glycidyl methacrylate are placed in a high-speed stirrer, stirred at 750 rpm for 15 min, then composite glass fiber and basic magnesium sulfate whisker are added, stirred at 380 rpm for 6 min, to obtain a mixture; S2, extrusion granulation: the mixture is subjected to twice melt extrusion granulation to prepare modified PBT plastic particles, wherein in the first extrusion granulation, the barrel temperature of the double screw extruder is controlled to be 188℃ for the feeding section, 212℃ for the compression section, 222℃ for the homogenization section, and 228℃ for the die head, and the screw speed is 260 rpm; in the second extrusion granulation, the barrel temperature of the double screw extruder is controlled to be 198℃ for the feeding section, 222℃ for the compression section, 232℃ for the homogenization section, and 238℃ for the die head, and the screw speed is 310 rpm; S3, injection molding: the obtained modified PBT plastic particles are vacuum dried at 132℃ for 70 min, then injection molding is carried out using an improved mold cavity with flow guide groove and exhaust passage, the mold cavity temperature is maintained at 105℃ by a heat conduction oil circulation temperature control system, the injection pressure is 90 MPa, the pressure maintaining time is 25 s, the heat preservation and shaping time is 45 s, finally the mold is demolded and the blank is trimmed, to obtain the low dielectric constant modified PBT composite material.

[0036] Comparative Example 1 The PBT composite material is prepared in the same way as Example 1. The PBT composite material is composed of the following components: PBT resin 30 parts, PC resin 15 parts, copolymer PP resin 10 parts, glass fiber 30 parts, propylene octene copolymer grafted glycidyl methacrylate 8 parts, antioxidant 1 part, lubricant 1 part.

[0037] Comparative Example 2 The PBT composite material is prepared in the same way as Example 1, with the only difference being that the modified PBT resin is replaced by PBT resin.

[0038] The compositions of the low dielectric constant modified PBT composite materials in Examples 1-4 are shown in Table 1.

[0039] Table 1 Component Table Test Example Test Content: The low dielectric constant modified PBT composite prepared in Examples 2-3 and the PBT composite prepared in Comparative Examples 1-2 were taken as test samples for performance testing, and the test standards were as follows: Tensile strength: in accordance with ISO 527 standard; Impact strength: in accordance with ISO 180 standard; Flame retardant grade: in accordance with UL 94 standard; Heat distortion temperature: in accordance with ISO 75 standard, test load is 1.80 MPa; Warpage: the height difference H and the measurement span L were measured by contacting the four corners and the center of the sample with a micrometer, and the maximum difference was taken as the warpage value, and the calculation formula was as follows: Wherein H is the height difference, and L is the measurement span; Dielectric constant: in accordance with GB / T 1409 standard, test frequency is 1 MHz, and sample thickness is 10 mm; Dielectric loss: in accordance with GB / T 1409 standard, test frequency is 1 MHz, and sample thickness is 10 mm; Solvent resistance: in accordance with ISO 175 standard, and the test grading standard is shown in Table 2.

[0040] Table 2 Solvent Resistance Grading Standard The results are recorded in Table 3.

[0041] Table 3 Test Results As can be seen from Table 2, in terms of tensile strength and heat distortion temperature: the content of composite glass fiber has a significant effect on the mechanical properties and heat resistance of the material. When the proportion of composite glass fiber in the raw material is gradually increased from 22% (Example 3) to 38% (Example 2), the tensile strength and heat distortion temperature of the corresponding composite material both show a clear upward trend, reflecting the fiber reinforcement effect. Under the condition of similar glass fiber content (the proportion of glass fiber in Comparative Example 1 is 31.58%), the tensile strength and heat distortion temperature of Example 1 (30%), Example 3 (22%) and Comparative Example 2 (30%) are all better than those of Comparative Example 1, which fully proves the positive contribution of modified PBT resin to improving the mechanical properties and heat resistance of the material.

[0042] In terms of impact strength, the comparative example 2 without using the modified PBT resin exhibits the lowest impact strength, while the example 4 by optimizing the modified PBT resin ratio and process parameters achieves the best impact strength, showing that the modified PBT resin and the overall formula system have good compatibility and toughening effect.

[0043] In terms of flame retardant grade, the comparative example 1 without adding a flame retardant has the worst flame retardant effect, and the examples 1-4 and the comparative example 2 all add a flame retardant, and the flame retardant grade all reaches V0 level, confirming the effectiveness of the flame retardant system of the application.

[0044] In terms of warpage rate, the warpage rates of the examples 1-4 are all ≤0.7%, and the low dielectric constant modified PBT composite material prepared by the application has low warpage rate.

[0045] In terms of dielectric constant and dielectric loss, the dielectric constant and dielectric loss of all examples are much lower than those of the comparative examples 1 and 2, and the example 4 performs best, confirming the synergistic effect between the modified PBT resin, the composite glass fiber and other components of the application, which can effectively reduce the polarization rate of the material and plays a decisive role in achieving excellent low dielectric properties.

[0046] In terms of solvent resistance, the solvent resistance of the examples 1-4 all performs well.

[0047] From the above performance test results, it can be seen that the low dielectric constant modified PBT composite material prepared by the application has good mechanical properties, flame retardant properties, heat distortion temperature, low warpage rate, low dielectric constant and dielectric loss, and excellent solvent resistance.

[0048] The low dielectric constant modified PBT composite material of the application can be widely used in the following fields: 1. Automotive field: can be used to manufacture automotive interior and exterior parts, engine peripheral parts, etc., such as instrument panel, door interior panel, bumper, radiator water tank, engine cover, etc. 2. Electronic and electrical field: can be used to manufacture electronic and electrical housings, sockets, switches, connectors, coil frames, etc.

[0049] 3. Aerospace field: can be used to manufacture parts of aerospace equipment, such as aircraft interior parts, satellite parts, etc.

[0050] Although the embodiments of the application have been shown and described, it can be understood by those of ordinary skill in the art that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the application, and the scope of the application is defined by the appended claims and their equivalents.

Claims

1. A low dielectric constant modified PBT composite material, characterized in that, The product is composed of the following components by weight: 28-35 parts PBT resin, 5-8 parts modified PBT resin, 2-4 parts PET resin, 2-3 parts PC resin, 2-3 parts copolymer PP resin, 22-38 parts composite glass fiber, 6-12 parts flame retardant, 2-4 parts toughening agent, 3-4 parts basic magnesium sulfate whiskers, 1-2 parts silane coupling agent, 0.5-1 part antioxidant, and 2-12 parts propylene-octene copolymer grafted with glycidyl methacrylate. The modified PBT resin is prepared by a method comprising the following steps: (a) immersing 100 parts by weight of polybutylene terephthalate in a plastic swelling agent at 72–78°C for 32–38 min, then heating to 90–100°C for ultrasonic-assisted swelling, with an ultrasonic power of 300–400 W, a frequency of 40 kHz, and a time of 20–30 min, to obtain swollen PBT; (b) placing the swollen PBT and 5–15 parts by weight of carboxyl-terminated nitrile butadiene rubber solution in a twin-screw extruder, and performing melt extrusion at an extrusion temperature of 230–250°C and a screw speed of 150–200 rpm to obtain the modified PBT resin.

2. The low dielectric constant modified PBT composite material according to claim 1, characterized in that, In (a), the plastic swelling agent is toluene or dichloromethane, and its amount is 15% to 20% of the mass of polybutylene terephthalate.

3. The low dielectric constant modified PBT composite material according to claim 1, characterized in that, In (b), the mass fraction of acrylonitrile in the carboxyl-terminated nitrile rubber solution is 20% to 24%, and the mass fraction of carboxyl groups is 2.2% to 2.8%.

4. The low dielectric constant modified PBT composite material according to claim 1, characterized in that, In (b), the barrel temperature of the twin-screw extruder is set in the following sections: Zone 1 210~220℃, Zone 2 220~230℃, Zone 3 230~240℃, Zone 4 240~250℃, and Die head 230~250℃.

5. The low dielectric constant modified PBT composite material according to claim 1, characterized in that, The composite glass fiber is made by mixing chopped flat glass fibers and chopped glass fiber precursors in a mass ratio of 1:1 to 3:

1.

6. The low dielectric constant modified PBT composite material according to claim 1, characterized in that, The flame retardant is prepared by mixing aluminum diethylphosphonate and melamine polyphosphate in a mass ratio of 1:1 to 5:

1.

7. The low dielectric constant modified PBT composite material according to claim 1, characterized in that, The toughening agent is selected from ethylene-butyl acrylate copolymer or ethylene-vinyl acetate copolymer.

8. The low dielectric constant modified PBT composite material according to claim 1, characterized in that, The antioxidant is prepared by mixing hindered phenolic antioxidants and phosphite antioxidants in a mass ratio of 1:1 to 2:

1.

9. A method for preparing a low dielectric constant modified PBT composite material as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Raw material mixing: First, place PBT resin, modified PBT resin, PET resin, PC resin, copolymer PP resin, flame retardant, toughening agent, silane coupling agent, antioxidant, and propylene-octene copolymer grafted glycidyl methacrylate into a high-speed mixer and stir at 600-800 rpm for 10-30 min. Then add composite glass fiber and basic magnesium sulfate whiskers and stir at 300-400 rpm for 5-8 min to obtain the mixture. S2. Extrusion Granulation: The mixture is subjected to two melt extrusion granulation processes to obtain modified PBT plastic granules. During the first extrusion granulation, the barrel temperature of the twin-screw extruder is controlled as follows: feeding section 180-190℃, compression section 200-215℃, homogenization section 215-225℃, and die head 220-230℃, with a screw speed of 220-280 rpm. During the second extrusion granulation, the barrel temperature of the twin-screw extruder is controlled as follows: feeding section 190-200℃, compression section 210-225℃, homogenization section 225-235℃, and die head 230-240℃, with a screw speed of 280-330 rpm. S3. Injection Molding: The obtained modified PBT plastic granules are vacuum dried at 125-135℃ for 60-90 min, and then injection molded using an improved mold cavity with a guide groove and an exhaust channel. The mold cavity temperature is maintained at 85-110℃ by a heat transfer oil circulation temperature control system, the injection pressure is 80-120 MPa, the holding time is 10-30 s, the heat setting time is 30-50 s, and finally the mold is demolded and trimmed to obtain the low dielectric constant modified PBT composite material.

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