PBT composite material with high electromagnetic shielding effectiveness and preparation method thereof

Abstract

The invention discloses a PBT (polybutylene terephthalate) composite material with high electromagnetic shielding effectiveness and a preparation method thereof, and belongs to the technical field of functional polymer composites.The PBT composite material is prepared from the following raw materials in parts by weight: 50-90 parts of PBT resin; 10 to 30 parts of chopped carbon fiber; 10-20 parts of a composite conductive filler; 1-10 parts of a toughening agent; 0.2 to 0.5 part of an antioxidant; 0.2 to 0.5 part of a lubricant; the prepared composite material is excellent in shielding effectiveness and low in reflectivity, and synergistic enhancement of dielectric loss and magnetic loss is achieved through a conductive-magnetic hybrid network constructed by the composite filler, namely the carbon nanotubes-graphene nanosheets-ferroferric oxide. Within the frequency range of 1-18 GHz, the electromagnetic shielding effectiveness of the composite material can reach 60-75 dB and is far higher than the level of 50 dB reported in an existing patent; the electromagnetic wave reflectivity is lower than 25%, and secondary electromagnetic pollution is effectively reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of functional polymer composites, and particularly relates to a PBT composite material with high electromagnetic shielding efficiency and a preparation method thereof. BACKGROUND

[0002] As one of the five engineering plastics, polybutylene terephthalate (PBT) has excellent mechanical strength, chemical corrosion resistance, thermal stability and rapid molding property, and is widely used in the fields of electronic appliances and automobile industry. With the popularization of 5G communication technology and the increasing integration of electronic devices, the problem of electromagnetic interference (EMI) is becoming increasingly prominent, which not only leads to the decline of device operation stability and information leakage, but also poses a potential threat to human health. Therefore, the development of PBT composite materials with excellent electromagnetic shielding performance and mechanical properties has become a research hotspot in the industry.

[0003] Currently, the preparation of electromagnetic shielding PBT composite materials mainly involves adding conductive fillers to construct a conductive network, so as to realize the reflection and absorption of electromagnetic waves. Commonly used conductive fillers include carbon-based materials (carbon black, carbon nanotubes, graphene, etc.), metal-based materials (stainless steel fibers, aluminum powder, etc.) and magnetic materials (ferrite, Fe3O4, etc.). Patent application CN109135207A discloses a PBT composite material using fullerene-PPTA fiber composite filler, but its shielding efficiency can only reach 35-45 dB, which is difficult to meet the needs of high-end electronic devices; patent application CN112940464A discloses the use of a combination of carbon nanotubes, Fe3O4 and stainless steel fibers to improve the shielding efficiency to more than 50 dB, but the addition of metal fibers increases the density of the material, and the electromagnetic wave reflectivity is as high as more than 40%, which easily causes secondary electromagnetic pollution; patent application CN115536998A discloses the use of flake graphite, zinc oxide and barium ferrite as functional fillers, which realizes the combination of shielding and heat conduction, but the high filling amount (14-16 parts) of graphite leads to a decrease in the tensile strength of the material to below 45 MPa and a significant reduction in processing flowability.

[0004] In addition, the poor interface compatibility between the fillers and the PBT matrix is a common problem in the prior art. The interface bonding force between the non-polar carbon-based fillers and the polar PBT matrix is weak, which leads to low stress transfer efficiency and reduced impact toughness of the material. Although some studies have used silane coupling agents for surface treatment, a single modifier cannot simultaneously improve the dispersibility of carbon-based and magnetic fillers, and the modification process is mostly simple mixing, which has limited modification effect. Therefore, the development of an electromagnetic shielding PBT composite material that can achieve high shielding efficiency at low filler content, while maintaining excellent mechanical properties and low electromagnetic wave reflectivity, is the key to solving the current technical bottleneck. SUMMARY

[0005] The present application aims to provide a PBT composite material with high electromagnetic shielding effectiveness and a preparation method thereof, and the prior art electromagnetic shielding PBT composite material has the problem of imbalance between shielding effectiveness and mechanical properties.

[0006] The object of the present application can be achieved by the following technical solutions: The present application provides a PBT composite material with high electromagnetic shielding effectiveness, which is prepared from the following raw materials by weight: PBT resin 50-90 parts; Short carbon fibers 10-30 parts; Composite conductive filler 10-20 parts; Toughening agent 1-10 parts; Antioxidant 0.2-0.5 parts; Lubricant 0.2-0.5 parts; The composite conductive filler adopts a multi-dimensional synergistic system of "carbon nanotube-graphene nanosheet-ferroferric oxide": CNT has excellent aspect ratio and can be used as a "connecting line" of the conductive path to form a continuous conductive network in the matrix; GNPs have a large specific surface area and can fill the gaps between CNTs to form a "plane-line" interlaced structure to improve the interface contact area and the conductive efficiency; ferroferric oxide particles are uniformly dispersed in the conductive network to significantly enhance the electromagnetic wave absorption capacity and reduce the reflectivity through the synergistic effect of magnetic hysteresis loss and dielectric loss.

[0007] In some possible implementation manners, the PBT resin is 66.5 parts; the short carbon fibers are 20 parts; the composite conductive filler is 10 parts; the toughening agent is 3 parts; the antioxidant is 0.2 parts; and the lubricant is 0.3 parts.

[0008] In some possible implementation manners, the mass ratio of graphene nanosheet, carbon nanotube and ferroferric oxide in the composite conductive filler is 3:1:1.

[0009] In some possible implementation manners, the shielding effectiveness of the PBT composite material is all greater than or equal to 60 dB, and the reflectivity is less than or equal to 24%.

[0010] In some possible implementation manners, the PBT resin is selected from PBT resin with an intrinsic viscosity of 0.8-1.2 dL / g, because an excessively low intrinsic viscosity (<0.8 dL / g) will result in insufficient mechanical strength of the composite material, and an excessively high intrinsic viscosity (>1.2 dL / g) will increase the melt viscosity, reduce the processing fluidity, and result in uneven dispersion of the filler. The PBT resin selected in the present application has an intrinsic viscosity of 1.0 dL / g, which takes into account the processability and matrix strength.

[0011] In some possible implementation manners, the short-cut carbon fiber is selected from a PAN-based high-strength carbon fiber with a single-wire diameter of 7-12 microns and a length of 3-6 millimeters. If the diameter is too small (<7 microns), the carbon fiber is prone to be broken during processing, affecting the reinforcing effect. If the diameter is too large (>12 microns), the interface bonding area between the carbon fiber and the PBT matrix is reduced, and stress concentration is prone to occur. The length is controlled to be 3-6 millimeters, so that a continuous "fiber bridging" structure can be formed in the composite material, that is, the tensile modulus of the composite material is improved through the high modulus (≥230 GPa) of the fiber itself, and a main network for electrical conduction is formed through the lapping between the fibers, to provide a basic path for electromagnetic shielding. Meanwhile, the tensile strength of the carbon fiber is ≥3500 MPa, so that the composite material is not prone to be broken when bearing load.

[0012] In some possible implementation manners, the toughening agent is ethylene-butyl acrylate-glycidyl methacrylate (EMA-GMA) as a compatibilizer. The epoxy groups in the molecular chain of the toughening agent can react with the terminal hydroxyl groups of the PBT, and the non-polar chain segment has a certain compatibility with the carbon filler, so that the interfacial bonding force between the filler and the matrix can be effectively improved.

[0013] In some possible implementation manners, the antioxidant is at least one of a hindered phenolic antioxidant 1010, a phosphite antioxidant 168, and an organic thioester antioxidant DLTP. In some embodiments, a mixture of the antioxidant 1010 and the antioxidant 168 is preferred.

[0014] In some possible implementation manners, the lubricant is ethylene bis-stearamide (EBS) or pentaerythritol stearate (PETS). Such a lubricant has good compatibility with the PBT matrix, can reduce the melt viscosity, reduce the wear of the screw caused by the filler, and reduce the shear fracture of the carbon fiber during the extrusion process, and at the same time, the surface finish of the injection molded product is improved.

[0015] The second aspect of the present application provides a preparation method of a PBT composite material with high electromagnetic shielding efficiency, specifically comprising the following steps: Step S1, pre-mixing: PBT is vacuum dried at 120-130 DEG C for 4-6 hours to remove water (to avoid hydrolytic degradation during processing); the composite conductive filler, the toughening agent, the antioxidant, and the optional lubricant are added into a high-speed mixer, stirred at 1000-1500 r / min for 5-8 minutes, and preliminary dispersion is realized by using shear force, to obtain a pre-mixed material.

[0016] Step S2, Melt Blending Extrusion: The premixed material is added to a twin-screw extruder with an aspect ratio of 40~48:1, which ensures sufficient mixing and plasticization. The extrusion temperature is set as follows: Zone 1 180~200℃ (feeding zone, to avoid premature melting of the raw material), Zone 2 230~250℃ (melting zone), Zone 3 240~260℃ (mixing zone), Zone 4 240~260℃ (homogenization zone), Zone 5 230~250℃ (metering zone); die temperature 230~240℃; screw speed 300~500 r / min; interlocking screw elements are used; the mixing section length accounts for 30%~40% of the total screw length, which can generate strong shearing and mixing effects, further improving filler dispersion; to avoid excessive shearing of carbon fibers and ensure their integrity, short-cut carbon fibers are fed from the side. After melt extrusion, the material is water-cooled and pelletized to obtain composite material particles.

[0017] Step S3, Molding: Dry the composite material particles at 110~120℃ for 2~3 hours to remove the moisture absorbed during storage; then mold them by injection molding or extrusion, matching the injection molding temperature with the extrusion temperature, and controlling the mold temperature at 60~80℃ to obtain a PBT composite material with high electromagnetic shielding performance.

[0018] The beneficial effects of this invention are: This invention provides an electromagnetic shielding PBT composite material with excellent shielding effectiveness and superior mechanical properties. This composite material achieves synergistic enhancement of dielectric loss and magnetic loss by constructing a conductive-magnetic hybrid network, thereby obtaining excellent electromagnetic shielding and absorption performance with a low filler content.

[0019] Compared with existing technologies, the composite material prepared in this invention exhibits superior shielding effectiveness and low reflectivity: a conductive-magnetic hybrid network constructed using composite fillers (carbon nanotubes-graphene nanosheets-ferric oxide) achieves synergistic enhancement of dielectric and magnetic losses. Within the 1–18 GHz frequency range, the electromagnetic shielding effectiveness of the composite material reaches 60–75 dB, far exceeding the 50 dB level reported in existing patents; the electromagnetic wave reflectivity is less than 25%, effectively reducing secondary electromagnetic pollution and overcoming the technical deficiency of traditional shielding materials that are primarily "reflective."

[0020] High tensile modulus: The “bridging reinforcement” and interface bonding optimization of carbon fiber enable the composite material to have a tensile modulus of ≥8GPa, which is 15-60% higher than that of existing materials (5-7GPa), and can be used as a structural load-bearing component.

[0021] It also possesses thermal conductivity: the carbon nanotubes and graphene in the composite filler have excellent thermal conductivity, and barium ferrite can also assist in heat transfer, making the thermal conductivity of the composite material ≥2.5W. m -1 K -1It can simultaneously solve the electromagnetic shielding and heat dissipation problems of electronic devices, thus extending the service life of the devices.

[0022] Good processing performance: By optimizing the filler ratio (total filler ≤ 20 parts) and adding lubricant, the melt flow rate of the composite material (250℃, 2.16kg) is ≥ 15g / 10min, which can be formed by conventional injection molding and extrusion processes, making it suitable for large-scale industrial production.

[0023] Wide range of applications: The composite material of this invention can be made into electronic device housings, integrated circuit packages, battery pack separators for new energy vehicles, shielding covers for 5G communication equipment, etc., and is especially suitable for high-end application scenarios with stringent requirements for electromagnetic compatibility, mechanical properties and heat dissipation. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] The following is a detailed description of the embodiments of this application.

[0026] The abbreviations and components used in this invention are as follows: PBT resin was purchased from Kanghui New Materials (PBTKH2100). Short-cut carbon fiber T300 was purchased from Aurora Composite Materials (CK60CP006). Toughening agent PTW was purchased from Dow Chemical Company, USA. Antioxidant 1010 (hindered phenol) and antioxidant 168 (phosphite) were purchased from Xinxiu Chemical. Ferric oxide was purchased from Anhui Kerun Nanotechnology Co., Ltd. Carbon nanotubes were purchased from Shanghai Dazhan New Materials. The graphene nanosheets were purchased from Xiamen Kaina New Materials.

[0027] The following is a detailed description with reference to specific examples.

[0028] Example 1

[0029] This embodiment describes a PBT composite material with high electromagnetic shielding effectiveness, prepared from the following raw materials in parts by weight: 66.5 parts of PBT resin; 20 parts of chopped carbon fiber; 3 parts toughening agent; Antioxidant 168, 0.1 parts; Antioxidant 1010, 0.1 parts; 0.3 parts of PETS lubricant; Five parts of graphene nanosheets; Two portions of carbon nanotubes; 3 parts of iron(III) oxide; The preparation method of the above-mentioned high shielding effectiveness PBT composite material includes the following steps: Step S1, Premixing: The PBT resin is vacuum dried at 120°C for 4 hours; the PBT resin, toughening agent, lubricant, antioxidant 168, antioxidant 1010, and composite conductive filler (graphene nanosheets, carbon nanotubes, and iron oxide) are added to a high-speed mixer for mixing; the mixture is stirred at 1000 r / min for 5 minutes to obtain a premix. Step S2: The premixed material from step S1 is passed through a twin-screw extruder. Short carbon fibers are side-fed, melt-extruded, and granulated. The extrusion temperature is set as follows: Zone 1 180~200℃ (feeding zone, to avoid premature melting of raw materials), Zone 2 230~250℃ (melting zone), Zone 3 240~260℃ (mixing zone), Zone 4 240~260℃ (homogenization zone), Zone 5 230~250℃ (metering zone), and die temperature 230~240℃; screw speed 300~500 r / min.

[0030] Step S3, Molding: The composite material particles prepared in step S2 are dried at 110°C for 2 hours and then extruded to obtain a PBT composite material with high electromagnetic shielding performance.

[0031] Example 2

[0032] This embodiment describes a PBT composite material with high electromagnetic shielding effectiveness, prepared from the following raw materials in parts by weight: 66.5 parts of PBT resin; 20 parts of chopped carbon fiber; 3 parts toughening agent; Antioxidant 168, 0.1 parts; Antioxidant 1010, 0.1 parts; 0.3 parts of PETS lubricant; Four portions of graphene nanosheets; Three parts of carbon nanotubes; 3 parts of iron(III) oxide; The preparation method of the above-mentioned high shielding effectiveness PBT composite material includes the following steps: (1) Premixing: The PBT resin was vacuum dried at 120°C for 4 hours; the PBT resin, toughening agent, lubricant, antioxidant 168, antioxidant 1010, and composite conductive filler (graphene nanosheets, carbon nanotubes, and iron oxide) were added to a high-speed mixer for mixing; the mixture was stirred at 1000 r / min for 5 min to obtain the premix. (2) The premixed material from step (1) is passed through a twin-screw extruder. Short carbon fibers are fed through the side, melt extruded, and granulated. The extrusion temperature is set as follows: Zone 1 180~200℃ (feeding zone, to avoid premature melting of raw materials), Zone 2 230~250℃ (melting zone), Zone 3 240~260℃ (mixing zone), Zone 4 240~260℃ (homogenization zone), Zone 5 230~250℃ (metering zone), and die temperature 230~240℃; screw speed 300~500r / min.

[0033] (3) Molding: The composite material particles prepared in step (2) are dried at 110°C for 2 hours and then extruded to obtain PBT composite material with high electromagnetic shielding performance.

[0034] Example 3

[0035] This embodiment describes a PBT composite material with high electromagnetic shielding effectiveness, prepared from the following raw materials in parts by weight: 66.5 parts of PBT resin; 20 parts of chopped carbon fiber; 3 parts toughening agent; Antioxidant 168, 0.1 parts; Antioxidant 1010, 0.1 parts; 0.3 parts of PETS lubricant; 7 parts of graphene nanosheets; One part of carbon nanotubes; Two parts of iron(III) oxide; The preparation method of the above-mentioned high shielding effectiveness PBT composite material includes the following steps: (1) Premixing: The PBT resin was vacuum dried at 120°C for 4 hours; the PBT resin, toughening agent, lubricant, antioxidant 168, antioxidant 1010, and composite conductive filler (graphene nanosheets, carbon nanotubes, and iron oxide) were added to a high-speed mixer for mixing; the mixture was stirred at 1000 r / min for 5 min to obtain the premix. (2) The premixed material from step (1) is passed through a twin-screw extruder. Short carbon fibers are fed through the side, melt extruded, and granulated. The extrusion temperature is set as follows: Zone 1 180~200℃ (feeding zone, to avoid premature melting of raw materials), Zone 2 230~250℃ (melting zone), Zone 3 240~260℃ (mixing zone), Zone 4 240~260℃ (homogenization zone), Zone 5 230~250℃ (metering zone), and die temperature 230~240℃; screw speed 300~500r / min.

[0036] (3) Molding: The composite material particles prepared in step (2) are dried at 110°C for 2 hours and then extruded to obtain PBT composite material with high electromagnetic shielding performance.

[0037] Example 4

[0038] This embodiment describes a PBT composite material with high electromagnetic shielding effectiveness, prepared from the following raw materials in parts by weight: 66.5 parts of PBT resin; 20 parts of chopped carbon fiber; 3 parts toughening agent; Antioxidant 168, 0.1 parts; Antioxidant 1010, 0.1 parts; 0.3 parts of PETS lubricant; Six parts of graphene nanosheets; Two portions of carbon nanotubes; Two parts of iron(III) oxide; The preparation method of the above-mentioned high shielding effectiveness PBT composite material includes the following steps: (1) Premixing: The PBT resin was vacuum dried at 120°C for 4 hours; the PBT resin, toughening agent, lubricant, antioxidant 168, antioxidant 1010, and composite conductive filler (graphene nanosheets, carbon nanotubes, and iron oxide) were added to a high-speed mixer for mixing; the mixture was stirred at 1000 r / min for 5 min to obtain the premix. (2) The premixed material from step (1) is passed through a twin-screw extruder. Short carbon fibers are fed through the side, melt extruded, and granulated. The extrusion temperature is set as follows: Zone 1 180~200℃ (feeding zone, to avoid premature melting of raw materials), Zone 2 230~250℃ (melting zone), Zone 3 240~260℃ (mixing zone), Zone 4 240~260℃ (homogenization zone), Zone 5 230~250℃ (metering zone), and die temperature 230~240℃; screw speed 300~500r / min.

[0039] (3) Molding: The composite material particles prepared in step (2) are dried at 110°C for 2 hours and then extruded to obtain PBT composite material with high electromagnetic shielding performance.

[0040] Comparative Example 1

[0041] This comparative example describes a PBT composite material with high electromagnetic shielding effectiveness, prepared from the following raw materials in parts by weight: 66.5 parts of PBT resin; 3 parts toughening agent; Antioxidant 168, 0.1 parts; Antioxidant 1010, 0.1 parts; 0.3 parts of PETS lubricant; 10 parts of graphene nanosheets; 20 parts of chopped carbon fiber; The preparation method of the above-mentioned high shielding effectiveness and high tensile modulus PBT composite material is basically the same as that in the examples, except that the conductive filler is graphene nanosheets.

[0042] Comparative Example 2

[0043] This comparative example describes a PBT composite material with high electromagnetic shielding effectiveness, prepared from the following raw materials in parts by weight: 66.5 parts of PBT resin; 3 parts toughening agent; Antioxidant 168, 0.1 parts; Antioxidant 1010, 0.1 parts; 0.3 parts of PETS lubricant; 10 parts of carbon nanotubes; 20 parts of chopped carbon fiber; The preparation method of the above-mentioned high shielding effectiveness and high tensile modulus PBT composite material is basically the same as that in the examples, except that the conductive filler is carbon nanotubes.

[0044] Comparative Example 3

[0045] This comparative example describes a PBT composite material with high electromagnetic shielding effectiveness, prepared from the following raw materials in parts by weight: 66.5 parts of PBT resin; 3 parts toughening agent; Antioxidant 168, 0.1 parts; Antioxidant 1010, 0.1 parts; 0.3 parts of PETS lubricant; 10 parts of iron(III) oxide; 20 parts of chopped carbon fiber; The preparation method of the above-mentioned high shielding effectiveness PBT composite material includes the following steps: The preparation method of the above-mentioned high shielding effectiveness and high tensile modulus PBT composite material is basically the same as that in the examples, except that the conductive filler is iron(III) oxide.

[0046] Comparative Example 4

[0047] This comparative example describes a PBT composite material with high electromagnetic shielding effectiveness, prepared from the following raw materials in parts by weight: 66.5 parts of PBT resin; 3 parts toughening agent; Antioxidant 168, 0.1 parts; Antioxidant 1010, 0.1 parts; 0.3 parts of PETS lubricant; 5 parts of iron(III) oxide; Five parts of graphene nanosheets; 20 parts of chopped carbon fiber; The preparation method of the above-mentioned high shielding effectiveness and high tensile modulus PBT composite material is basically the same as that in the examples, except that the conductive filler is: graphene nanosheets and iron(III) oxide.

[0048] Comparative Example 5

[0049] This comparative example describes a PBT composite material with high electromagnetic shielding effectiveness, prepared from the following raw materials in parts by weight: 66.5 parts of PBT resin; 3 parts toughening agent; Antioxidant 168, 0.1 parts; Antioxidant 1010, 0.1 parts; 0.3 parts of PETS lubricant; 5 parts of iron(III) oxide; 5 parts of carbon nanotubes; 20 parts of chopped carbon fiber; The preparation method of the above-mentioned high shielding effectiveness and high tensile modulus PBT composite material is basically the same as that in the examples, except that the conductive filler is carbon nanotubes and iron oxide.

[0050] Comparative Example 6

[0051] This comparative example describes a PBT composite material with high electromagnetic shielding effectiveness, prepared from the following raw materials in parts by weight: 66.5 parts of PBT resin; 3 parts toughening agent; Antioxidant 168, 0.1 parts; Antioxidant 1010, 0.1 parts; 0.3 parts of PETS lubricant; Five parts of graphene nanosheets; 5 parts of carbon nanotubes; 20 parts of chopped carbon fiber; The preparation method of the above-mentioned high shielding effectiveness and high tensile modulus PBT composite material is basically the same as that in the examples, except that the conductive filler is carbon nanotubes and graphene nanosheets.

[0052] Performance tests were conducted on the splines of Examples 1-4 and Comparative Examples 1-6, and the test standards are as follows: Electromagnetic shielding effectiveness (SE): ASTM D4935-18, test frequency 1~18 GHz; Electromagnetic wave reflectivity (R): coaxial method, test frequency 1~18GHz; Tensile property test: Tested according to ISO 527 standard, speed 50 mm / min; Notched impact strength: Tested according to ISO 180 standard, impact energy: 2.75J; Thermal conductivity: ASTM E1461-13, laser flare method; Melt flow rate (MFR): ISO 1133-1: Test conditions: temperature 250℃, weight of weight 2.16kg.

[0053] The test results are shown in Table 1: Table 1

[0054] As shown in Table 1, the shielding effectiveness of Examples 1-4 is ≥60dB and the reflectivity is ≤24%, which is significantly better than that of Comparative Examples 1-6, proving that the synergistic effect of the composite filler can effectively improve the shielding performance and reduce the reflectivity. Example 4 has the best overall performance, with a shielding effectiveness of 74dB, tensile strength of 62MPa, impact strength of 16kJ / m², and thermal conductivity of 3.5W. m -1 K -1 MFR24g / 10min meets the requirements of high-end applications; in the comparative example (single filler), the shielding effectiveness and reflectivity performance are slightly worse, indicating that the synergistic effect of magnetic filler and multi-dimensional carbon filler is crucial, and the mechanical properties are poor, indicating that carbon fiber has a strong reinforcing effect on the mechanical properties of the material.

[0055] The electromagnetic shielding PBT composite material provided by this invention achieves a balance of high shielding effectiveness, low reflectivity, excellent mechanical properties, and good processability through reasonable component design and process optimization. Its preparation process is mature and can be industrialized using existing plastic processing equipment. The resulting products can meet the stringent requirements for electromagnetic shielding materials in fields such as 5G communication, new energy vehicles, and precision electronics, and have broad market application prospects.

[0056] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A PBT composite material having high electromagnetic shielding effectiveness, characterized by, The PBT composite material is prepared from the following raw materials by weight: PBT resin 50-90 parts; Short carbon fiber 10-30 parts; Composite conductive filler 10-20 parts; Toughening agent 1-10 parts; Antioxidant 0.2-0.5 parts; Lubricant 0.2-0.5 parts; The composite conductive filler includes carbon nanotubes, graphene nanosheets, and ferroferric oxide.

2. The PBT composite material with high electromagnetic shielding efficiency according to claim 1, characterized in that, PBT resin 66.5 parts; short carbon fiber 20 parts; composite conductive filler 10 parts; toughening agent 3 parts; antioxidant 0.2 parts; lubricant 0.3 parts.

3. The PBT composite material with high electromagnetic shielding effectiveness according to claim 1, characterized in that, The mass ratio of graphene nanosheets, carbon nanotubes, and ferroferric oxide in the composite conductive filler is 3:1:

1.

4. The PBT composite material with high electromagnetic shielding effectiveness according to claim 1, characterized in that, The shielding effectiveness of the PBT composite material is ≥60 dB, and the reflectivity is ≤24%.

5. The PBT composite material with high electromagnetic shielding effectiveness according to claim 1, characterized in that, The PBT resin is selected from PBT resin with a specific viscosity of 0.8-1.2 dL / g.

6. The PBT composite material with high electromagnetic shielding effectiveness according to claim 1, characterized in that, The short carbon fiber is selected from PAN-based high-strength carbon fiber with a single filament diameter of 7-12 μm and a length of 3-6 mm.

7. The PBT composite material with high electromagnetic shielding effectiveness according to claim 1, characterized in that, The toughening agent is ethylene-butyl acrylate-glycidyl methacrylate.

8. The PBT composite material with high electromagnetic shielding effectiveness according to claim 1, characterized in that, The antioxidant is at least one of hindered phenolic antioxidant 1010, phosphite antioxidant 168, and organic thioester antioxidant DLTP.

9. The PBT composite material with high electromagnetic shielding effectiveness according to claim 1, characterized in that, The lubricant is ethylene bis-stearamide or pentaerythritol stearate.

10. A process for the production of a PBT composite material having a high electromagnetic shielding effectiveness for the production of a PBT composite material having a high electromagnetic shielding effectiveness according to any one of claims 1 to 9, characterized in that The method comprises the following steps: Step S1, pre-mixing: vacuum drying the PBT resin at 120-130°C for 4-6 h; stirring the composite conductive filler, toughening agent, antioxidant, and lubricant at 1000-1500 r / min for 5-8 min to obtain a pre-mixed material; Step S2, melt blending and extrusion: adding the pre-mixed material to a double-screw extruder with a length-diameter ratio of 40-48:1, feeding the short carbon fiber, setting the extrusion temperature to zone 1 180-200°C, zone 2 230-250°C, zone 3 240-260°C, zone 4 240-260°C, zone 5 230-250°C, and die temperature 230-240°C; screw rotation speed 300-500 r / min, to obtain composite material particles; Step S3, molding: drying the composite material particles at 110-120°C for 2-3 h, and molding by injection molding or extrusion process to obtain a PBT composite material with high electromagnetic shielding effectiveness.

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