Polycarbonate-based composite material as well as preparation method and application thereof

Abstract

The invention discloses a polycarbonate-based composite material as well as a preparation method and application thereof, and belongs to the technical field of high polymer materials. The composite material is prepared from the following components in parts by mass: 65 to 80 parts of polycarbonate, 10 to 25 parts of long glass fibers, 1 to 7 parts of nano magnetic particles, 0 to 3 parts of carbon nanotubes, 1 to 3 parts of a flame retardant, 0.1 to 1 part of a flame-retardant anti-dripping agent and 1 to 2 parts of an insulating agent, wherein the weight-average molecular weight of the polycarbonate is 2 * 10 < 4 > g / mol to 4 * 10 < 4 > g / mol, and the particle size of the nano magnetic particles is 20 nm to 50 nm. The composite material and the injection molding structural member prepared from the composite material not only have good strength, heat resistance, flame retardance and insulativity, but also have the electromagnetic wave absorption characteristic, and can be widely applied to new energy vehicles, especially battery packs of the new energy vehicles.

Description

Technical Field

[0001] The present application relates to the technical field of polymer materials, and in particular to a composite material based on polycarbonate and a preparation method and application thereof. Background Art

[0002] Polycarbonate (PC) has the characteristics of high light transmittance, high refractive index, excellent mechanical properties, good heat resistance, flame retardancy and insulation. Its products are dimensionally stable and easy to process, and are widely used in the automotive field.

[0003] In the related art, PC materials can be modified to have good flame retardancy so that they can be used in battery pack covers.

[0004] Since there is electromagnetic wave radiation inside the battery pack, if the battery pack cover is given electromagnetic wave absorption performance, it is very important to achieve electromagnetic wave shielding of the battery pack and then eliminate the impact of electromagnetic wave signals on the driving of the entire vehicle and the personal safety of passengers.

[0005] However, there is currently a lack of PC materials that have both good flame retardancy and electromagnetic wave absorption properties. Summary of the invention

[0006] The present application provides a composite material based on polycarbonate and a preparation method and application thereof to solve the technical problems existing in the related art. Specifically, it includes the following technical solutions.

[0007] In a first aspect, the present application provides a composite material based on polycarbonate, characterized in that the composite material comprises the following components in parts by mass: 65-80 parts of polycarbonate, 10-25 parts of long glass fibers, 1-7 parts of nanomagnetic particles, 0-3 parts of carbon nanotubes, 1-3 parts of flame retardant, 0.1-1 parts of flame retardant and anti-dripping agent, and 1-2 parts of insulating agent; wherein the weight average molecular weight of the polycarbonate is 2×10 4 g / mol-4×10 4 g / mol, and the particle size of the nano magnetic particles is 20nm-50nm.

[0008] In some possible implementations, the nanomagnetic particles are ferrite particles.

[0009] In some possible implementations, the length of the long glass fiber is 10 mm-25 mm.

[0010] In some possible implementations, the carbon nanotubes are single-walled carbon nanotubes, and the length of the single-walled carbon nanotubes is 10 nm-20 nm.

[0011] In some possible implementations, the flame retardant includes triphenyl phosphate and polysiloxane, and the mass ratio of the triphenyl phosphate to the polysiloxane is 3-5:1.

[0012] In some possible implementations, the insulating agent includes one or more of polytetrafluoroethylene, polyethylene and its modified products, organic silicon, and nano-silicon dioxide.

[0013] In some possible implementations, the flame retardant and anti-dripping agent includes one or more of modified polytetrafluoroethylene, talc, and organic montmorillonite.

[0014] In a second aspect, the present application provides a method for preparing a composite material based on polycarbonate, the preparation method comprising: weighing the following components in parts by mass and mixing them uniformly: 65-80 parts of polycarbonate, 10-25 parts of long glass fibers, 1-7 parts of nanomagnetic particles, 0-3 parts of carbon nanotubes, 1-3 parts of flame retardant, 0.1-1 parts of flame retardant and anti-dripping agent, and 1-2 parts of insulating agent; wherein the weight average molecular weight of the polycarbonate is 2×10 4 g / mol-4×10 4 g / mol, the particle size of the nano magnetic particles is 20nm-50nm; at a set temperature, the components after being evenly mixed are melt-kneaded to obtain a melt of the composite material; after the melt is cooled and solidified, the composite material is obtained.

[0015] In a third aspect, the present application provides an injection-molded structural component, wherein the injection-molded structural component is prepared using the composite material described in any one of the first aspects of the present application.

[0016] In a fourth aspect, the present application provides a battery pack, comprising a shell, a cover and a battery cell, wherein the cover is connected to an open end of the shell, and the battery cell is accommodated in a accommodating space between the cover and the shell; wherein the cover adopts the injection molded structural member described in the third aspect of the present application.

[0017] In a fifth aspect, the present application provides a new energy vehicle, which includes the battery pack described in the fourth aspect of the present application.

[0018] The beneficial effects of the technical solution provided by this application include at least: The composite material provided in this application is based on an improved formula. By using PC as the matrix and matching it with glass fiber, flame retardant, flame retardant anti-drip agent, and insulating agent in a specific ratio, the composite material can have good mechanical properties, heat resistance, insulation, and flame retardancy; at the same time, through the specific ratio of nano-magnetic particles and carbon nanotubes, the composite material can effectively absorb electromagnetic waves in a wider frequency range and show good electromagnetic shielding performance. The above-mentioned PC-based composite material and its injection molded structural parts, when applied to new energy vehicles, especially battery packs of new energy vehicles, can not only be used as a cover to provide a reliable and stable working space for electrical components, but also can effectively shield the electromagnetic interference between the battery pack and other electrical equipment, avoid the potential dangers caused by electromagnetic interference, and improve the safety factor of new energy vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 is the test result of the reflectivity of the injection molded structural part of Example 1 provided in the present application in the frequency band of 2 GHz-18 GHz; Figure 2 is the test result of the reflectivity of the injection molded structural part of Example 2 provided in the present application in the frequency band of 2 GHz-18 GHz; Figure 3 is the test result of the reflectivity of the injection molded structural part of Example 3 provided in the present application in the frequency band of 2 GHz-18 GHz; Figure 4 This is the test result of the reflectivity of the injection-molded structural component of Example 4 provided in the present application in the frequency band of 2 GHz-18 GHz. DETAILED DESCRIPTION

[0021] In response to the current technical problem of the lack of PC materials that have both flame retardancy and electromagnetic wave absorption properties, an embodiment of the present invention provides a PC-based composite material, which not only has good mechanical properties, heat resistance, insulation and flame retardancy, but also has good shielding performance for electromagnetic waves in a wider frequency range and has good electromagnetic wave absorption properties.

[0022] The first aspect of the present application discloses a composite material based on polycarbonate, the composite material comprising the following components in parts by weight: 65-80 parts of polycarbonate, 10-25 parts of long glass fibers, 1-7 parts of nano-magnetic particles, 0-3 parts of carbon nanotubes, 1-3 parts of flame retardant, 0.1-1 parts of flame retardant and anti-dripping agent, and 1-2 parts of insulating agent.

[0023] Among them, the weight average molecular weight of polycarbonate is 2×10 4 g / mol-4×10 4 g / mol, and the particle size of the nanomagnetic particles is 20nm-50nm.

[0024] For example, the total amount of the composite material may be 100 parts by weight.

[0025] The composite material provided in this application is based on an improved formula. By using PC as the matrix and matching it with glass fiber, flame retardant, flame retardant anti-drip agent, and insulating agent in a specific ratio, the composite material can have good mechanical properties, heat resistance, insulation, and flame retardancy; at the same time, through the specific ratio of nano-magnetic particles and carbon nanotubes, the composite material can effectively absorb electromagnetic waves in a wider frequency range and show good electromagnetic shielding performance. The above-mentioned PC-based composite material and its injection molded structural parts, when applied to new energy vehicles, especially battery packs of new energy vehicles, can not only be used as a cover to provide a reliable and stable working space for electrical components, but also can effectively shield the electromagnetic interference between the battery pack and other electrical equipment, avoid the potential dangers caused by electromagnetic interference, and improve the safety factor of new energy vehicles.

[0026] The following is a further exemplary description of the content of each component in the PC-based composite material.

[0027] As mentioned above, the matrix PC of the composite material can be used for, but not limited to, making the composite material have good heat resistance, insulation and flame retardancy.

[0028] In some embodiments, the weight average molecular weight of PC can be 2×10 4 g / mol-4×10 4 g / mol, for example, may include 2×10 4 g / mol, 2.2×10 4 g / mol, 2.4×10 4 g / mol, 2.6×10 4 g / mol, 2.8×10 4 g / mol, 3×10 4 g / mol, 3.1×10 4 g / mol, 3.2×10 4 g / mol, 3.3×10 4 g / mol, 3.4×10 4g / mol, 3.5×10 4 g / mol, 3.6×10 4 g / mol, 3.7×10 4 g / mol, 3.8×10 4 g / mol, 3.9×10 4 g / mol, 4×10 4 g / mol, etc., or other values ​​within the above range, which are not limited in this application.

[0029] In some embodiments, the mass fraction of PC in the composite material can be 65 parts to 80 parts, for example, it can include but is not limited to 65 parts, 67 parts, 69 parts, 71 parts, 73 parts, 75 parts, 77 parts, 80 parts, etc., or other values ​​within the above range, and the present application does not impose any limitation on this.

[0030] Long glass fiber (LGF) can be used for, but is not limited to, improving the mechanical properties and dimensional stability of composite materials, as well as improving the heat resistance and fatigue resistance of composite materials.

[0031] In some embodiments, the mass fraction of LGF in the composite material can be 10 parts to 25 parts, for example, it can include 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 25 parts, etc., or other values ​​within the above range.

[0032] In some embodiments, the length of the LGF in the composite material can be 10-25 mm, for example, it can include 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, etc., or other values ​​within the above range, and the present application does not impose any limitations on this.

[0033] In some embodiments, the diameter of the LGF in the composite material can be 10 μm-20 μm, for example, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, etc., or other values ​​within the above range, so that the LGF in the composite material has good dispersion and retention length while providing good reinforcement effect.

[0034] In some embodiments, the LGF may be prepared, for example, by a LGT-D (long fiber reinforced thermoplastics-Direct) process.

[0035] Nano-magnetic particles can be used for, but not limited to, enhancing the mechanical properties of composite materials and making composite materials have electromagnetic wave absorption properties.

[0036] In some embodiments, the mass proportion of the nanomagnetic particles in the composite material may be 1 part to 7 parts, for example, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, etc., or other values ​​within the above range.

[0037] In some embodiments, the particle size of the nanomagnetic particles can be 20 nm-50 nm, for example, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, 30 nm, 31 nm, 32 nm, 33 nm, 34 nm, 35 nm, 36 nm, 37 nm, 38 nm, 39 nm, 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm, 50 nm, etc., or other values ​​within the above range, and the present application does not impose any limitation on this.

[0038] In some embodiments, the nanomagnetic particles may be, for example, ferrite particles.

[0039] Carbon nanotubes can be used for, but are not limited to, enhancing the mechanical properties of composite materials, improving the thermal stability of composite materials, and making composite materials have electromagnetic wave absorption properties.

[0040] In some embodiments, the mass fraction of carbon nanotubes in the composite material can be 0-3 parts, for example, can include 0, 0.4, 0.8, 1.2, 1.6, 2.0, 2.4, 2.8, 3, etc., or other values ​​within the above range.

[0041] In some embodiments, the carbon nanotubes may be, for example, single-walled carbon nanotubes; the length of the single-walled carbon nanotubes may be 10nm-20nm, such as 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, etc., or other values ​​within the above range; the diameter of the single-walled carbon nanotubes may be 0.7nm-2nm, such as 0.7nm, 0.9nm, 1.1nm, 1.3nm, 1.5nm, 1.7nm, 2nm, etc., or other values ​​within the above range.

[0042] Flame retardants can be used for, but are not limited to, improving the flame retardant properties of composite materials, so that the composite materials can have better fire resistance.

[0043] In some embodiments, the mass fraction of the flame retardant in the composite material can be, for example, 1 part to 3 parts, for example, can include 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, etc., or other values ​​within the above range.

[0044] In some embodiments, the flame retardant can be a compound halogen-free flame retardant. The compound halogen-free flame retardant can not only avoid the harmful gases produced by halogens during combustion and improve the environmental protection of the composite material, but also utilize the synergistic effect of multiple flame retardants to improve the flame retardant efficiency and avoid the influence of a high addition of a single flame retardant on the mechanical properties of the composite material.

[0045] In some embodiments, the composite halogen-free flame retardant may include, for example, triphenylphosphate (TPP) and polysiloxane, and the mass ratio of TPP to polysiloxane may be 3-5:1, for example, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4:1, 4.2:1, 4.4:1, 4.6:1, 4.8:1, 5:1, etc., or other values ​​within the above range.

[0046] The insulating agent can be used for, but is not limited to, isolating the composite material from the conduction of electric current and / or heat energy, thereby improving the safety of the composite material when in use.

[0047] In some embodiments, the mass fraction of the insulating agent in the composite material can be 1 part to 2 parts, for example, it can include 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2 parts, etc., or other values ​​within the above range.

[0048] In some embodiments, the insulating agent may include, for example, one or more of polytetrafluoroethylene (PTFE), polyethylene and its modified products, organic silicon, and nano-silicon dioxide.

[0049] The flame retardant and anti-dripping agent can be used for, but is not limited to, improving the melt strength and elastic modulus of the composite material and preventing the composite material from producing dripping melt when burning.

[0050] In some embodiments, the mass fraction of the flame retardant and anti-drip agent in the composite material can be 0.1 part to 1 part, for example, it can include 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1 part, etc., or other values ​​within the above range.

[0051] In some embodiments, the flame retardant and anti-dripping agent may include, for example, one or more of modified polytetrafluoroethylene, talc, and montmorillonite.

[0052] For example, the total amount of the composite material may be 100 parts by weight.

[0053] In some examples, the PC-based composite material mentioned above can be prepared by the following preparation method.

[0054] Step 1: Weigh the following components in parts by mass and mix them evenly: 65-80 parts of polycarbonate, 10-25 parts of long glass fiber, 1-7 parts of nano magnetic particles, 0-3 parts of carbon nanotubes, 1-3 parts of flame retardant, 0.1-1 parts of flame retardant and anti-drip agent, 1-2 parts of insulating agent. The weight average molecular weight of polycarbonate is 2×10 4 g / mol-4×10 4 g / mol, and the particle size of the nanomagnetic particles is 20nm-50nm.

[0055] It should be understood that the preparation method of the composite material provided in the above embodiment belongs to the same concept as the composite material embodiment, and its specific implementation method can refer to the composite material embodiment, which will not be repeated here. For example, the properties and amounts of components such as polycarbonate, long glass fiber, nano magnetic particles, carbon nanotubes, flame retardant, flame retardant anti-drip agent, and insulating agent.

[0056] In some embodiments, the method for preparing the composite material of the embodiment of the present application may further include: before uniformly mixing the components of the composite material, drying the weighed components in a vacuum drying atmosphere.

[0057] In some embodiments, the drying time of the weighed components in a vacuum drying atmosphere can be 3.8 h to 4.2 h, for example, 3.8 h, 3.9 h, 4 h, 4.1 h, 4.2 h, etc., or other values ​​within the above range.

[0058] In some embodiments, the flame retardant may include, for example, a compound halogen-free flame retardant. The method for preparing the composite material provided in the embodiment of the present application may further include: preparing the compound halogen-free flame retardant before uniformly mixing the components of the composite material.

[0059] In some embodiments, the compound halogen-free flame retardant may include TPP and polysiloxane, and the method for preparing the compound halogen-free flame retardant may include: mixing TPP and polysiloxane by a mixer; drying the mixed TPP and polysiloxane to obtain the compound halogen-free flame retardant.

[0060] In some embodiments, the mass ratio of TPP to polysiloxane can be 3-5:1, for example, can include 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4:1, 4.2:1, 4.4:1, 4.6:1, 4.8:1, 5:1, etc., or other values ​​within the above range.

[0061] In some embodiments, the temperature for drying the mixed TPP and polysiloxane can be 95°C-105°C, for example, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, etc., or other values ​​within the above range.

[0062] In some embodiments, the drying time for the mixed TPP and polysiloxane can be 35 min-45 min, for example, 35 min, 36 min, 37 min, 38 min, 39 min, 40 min, 41 min, 42 min, 43 min, 44 min, 45 min, etc., or other values ​​within the above range, and the present application does not impose any limitation on this.

[0063] Step 2: Melt and knead the uniformly mixed components at a set temperature to obtain a molten composite material.

[0064] In some embodiments, the set temperature for melt mixing of the components after uniform mixing can be 220°C-260°C, for example, it can include 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, 260, etc., or other values ​​within the above range.

[0065] In some embodiments, the time length for melt kneading the components after uniform mixing can be 3.5h-4.5h, for example, it can include 3.5h, 3.6h, 3.7h, 3.8h, 3.9h, 4.0h, 4.1h, 4.2h, 4.3h, 4.4h, 4.5h, etc., or other values ​​within the above range.

[0066] In some embodiments, the method of melt-kneading the uniformly mixed components may include, for example, melt-kneading the uniformly mixed components through an extruder. The extruder may include, for example, a twin-screw extruder, and the present application does not impose any limitation in this regard.

[0067] Step 3: After the melt is cooled and solidified, a composite material is obtained.

[0068] In some embodiments, the method of cooling and solidifying the melt of the composite material may include, for example, water cooling, air cooling, mold cooling, etc., and the present application does not impose any limitation in this regard.

[0069] The present application also provides an injection-molded structural component prepared using the composite material as described above.

[0070] The injection-molded structural parts may include any injection-molded structural parts having specific structures and sizes that can meet specific usage requirements.

[0071] For example, it may include plates, profiles, tubes, rods, etc. used for bearing and / or supporting, or it may include injection-molded structural parts used for vehicle windows and transparent parts, interior and exterior parts, and headlights, or it may include injection-molded structural parts for the cover of the battery pack of a new energy vehicle.

[0072] When preparing the injection molded structural part, it can be directly prepared based on the components in the composite material, such as the method involved in the above composite material. After obtaining the molten body of the composite material, it can be directly injection molded to obtain the injection molded structural part. Alternatively, the composite material prepared in advance can be melted or softened, and then injection molded to obtain the injection molded structural part.

[0073] As described above, the composite material provided in the embodiment of the present application can show excellent mechanical properties, processing properties, heat resistance, insulation, and good electromagnetic wave absorption characteristics through the specific ratio of PC, LGF, nanomagnetic particles, carbon nanotubes, flame retardants, flame retardant anti-dripping agents and insulating agents. In view of this, the injection molded structural parts prepared by the composite material described above provided in the embodiment of the present application can also have good strength, heat resistance, insulation and electromagnetic wave absorption characteristics at the same time.

[0074] The present application also provides a method for preparing the injection-molded structural component as described above, comprising the following steps.

[0075] Step 1: providing an injection mold, placing the composite material or the molten body of the composite material in the cavity of the injection mold, and making the cavity in a vacuum-sealed state.

[0076] Step 2: Preheat and hold the cavity at a given injection temperature and pressure.

[0077] In some embodiments, the injection molding temperature can be 140°C-160°C, for example, it can include 140°C, 142°C, 144°C, 146°C, 148°C, 150°C, 152°C, 154°C, 156°C, 158°C, 160°C, etc., or other values ​​within the above range.

[0078] In some embodiments, the injection pressure can be 11 MPa-13 MPa, for example, can include 11 MPa, 11.2 MPa, 11.4 MPa, 11.6 MPa, 11.8 MPa, 12 MPa, 12.2 MPa, 12.4 MPa, 12.6 MPa, 12.8 MPa, 13 MPa, etc., or other values ​​within the above range.

[0079] In some embodiments, the preheating time for preheating the cavity can be 55s-65s, for example, it can include 55s, 56s, 57s, 58s, 59s, 60s, 61s, 62s, 63s, 64s, 65s, etc., or other values ​​within the above range.

[0080] In some embodiments, the holding time for the pressure-holding treatment of the cavity can be 580s-620s, for example, it can include 580s, 585s, 590s, 595s, 600s, 605s, 610s, 615s, 616s, 617s, 618s, 619s, 620s, etc., or other values ​​within the above range.

[0081] Step 3: Open the mold cavity to obtain the injection molded structural parts.

[0082] The present application also provides a battery pack, which includes a shell, a cover and a battery cell, wherein the cover is connected to the open end of the shell, and the battery cell is accommodated in the accommodation space between the cover and the shell.

[0083] The cover body adopts the injection-molded structural parts as described above. The battery pack provided in the embodiment of the present application has good strength, heat resistance, insulation and electromagnetic wave absorption characteristics, which can provide a reliable and stable working space for the operation of the battery pack and effectively shield the electromagnetic interference between the battery pack and other electrical equipment.

[0084] The present application also provides a new energy vehicle, which adopts the battery pack as described above.

[0085] The new energy vehicle provided in the embodiment of the present application has a battery pack cover with good strength, heat resistance, insulation and electromagnetic wave absorption characteristics, which can provide a reliable and stable working space for the operation of the battery pack and can effectively shield the electromagnetic interference between the battery pack and other electrical equipment, greatly improving the safety factor of the new energy vehicle.

[0086] The exemplary embodiments of the present invention will be described in more detail below. Although the exemplary embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. In the embodiment, if specific techniques or conditions are not indicated, the techniques or conditions described in the document in this area or the product instructions are carried out. The reagents used or the instruments that are not indicated by the manufacturer are all conventional products that can be obtained commercially.

[0087] Example 1 Example 1 provides an injection molded structural part using a PC-based composite material. The flame retardant involved in the composite material is a compound halogen-free flame retardant, and the compound halogen-free flame retardant is prepared by the following method: TPP and polysiloxane are weighed according to a mass ratio of 5:1; TPP and polysiloxane are mixed by a mixer, and the mixed TPP and polysiloxane are dried at 100°C for 40 minutes to obtain a compound halogen-free flame retardant.

[0088] Step 1: Weigh the following components by mass and dry them in a vacuum drying atmosphere for 4 hours: PC70.9 parts, LGF (prepared by LFT-D process) 20 parts, ferrite particles 1 part, single-walled carbon nanotubes 6 parts, compound halogen-free flame retardant 1 part, flame retardant anti-dripping agent 0.1 part, PTFE 1 part. Among them, the weight average molecular weight of PC meets 2×10 4 g / mol-4×10 4 The particle size of the nanomagnetic particles is within the range of 20nm-50nm.

[0089] Step 2: Put the dried components into a blender and stir repeatedly to mix them evenly.

[0090] Step 3: Send the uniformly mixed components into a twin-screw extruder, set the working temperature of the twin-screw extruder to 240° C., melt-mix the uniformly mixed components in the twin-screw extruder for 4 hours to obtain a molten composite material.

[0091] Step 4: Extruding the composite material melt through a twin-screw extruder, cooling it in a water tank, and pelletizing it to obtain a granular composite material.

[0092] Step 5: Place the granular composite material in the cavity of the injection mold prepared in advance, make the temperature of the injection mold to be 150°C, then close the injection mold, evacuate and pressurize to 12 MPa, preheat for 60 seconds, and hold the pressure for 600 seconds.

[0093] Step 6: Open the cavity of the injection mold to obtain the injection molded structural part.

[0094] Example 2 The difference between Example 2 and Example 1 is that the weight parts of the components weighed in step (1) are different, specifically: PC74.9 parts, LGF (prepared by LFT-D process) 15 parts, ferrite particles 3 parts, single-walled carbon nanotubes 5 parts, compound halogen-free flame retardant 1 part, flame retardant and anti-dripping agent 0.1 part, PTFE 1 part.

[0095] Example 3 The difference between Example 3 and Example 1 is that the weight parts of the components weighed in step (1) are different, specifically: PC76.9 parts, LGF (prepared by LFT-D process) 13 parts, ferrite particles 5 parts, single-walled carbon nanotubes 2 parts, compound halogen-free flame retardant 2 parts, flame retardant and anti-dripping agent 0.1 parts, PTFE 1 part.

[0096] Example 4 The difference between Example 4 and Example 1 is that the weight parts of the components weighed in step (1) are different, specifically: 8.9 parts of PC6, 22 parts of LGF (prepared by LFT-D process), 7 parts of ferrite particles, 0 parts of single-walled carbon nanotubes, 1 part of compound halogen-free flame retardant, 0.1 parts of flame retardant and anti-dripping agent, and 1 part of PTFE.

[0097] Test Case 1. The injection molded structural parts obtained in the above-mentioned Examples 1 to 4 were cut into 3 mm thick plates, and the following parameters were tested (see Table 1 for the test results): Density: Tested using the method described in ISO 1183-1:2019; Tensile strength: tested using the method described in ISO 527-2:2024 at a temperature of 23°C; Bending strength: tested using the method described in ISO 178:2019 at a temperature of 23°C; Elongation after fracture: tested using the method described in ISO 527-2:2024; Flame resistance: Tested using the method described in UL94; Notched impact strength: tested using the method described in ISO 179-1:2023, at a test temperature of 23°C; Heat Deflection Temperature: Tested using the method described in ISO 306:2022.

[0098] 2. The injection molded structures obtained in the above Examples 1 to 4 were cut into samples of 300 mm×300 mm×3 mm, and the reflectivity of the samples in the 2 GHz-18 GHz frequency band was tested by the method described in GJB2038A-2011.

[0099] Figure 1 This is the test result of the reflectivity of the injection-molded structural component of Example 1 provided in the present application in the frequency band of 2 GHz-18 GHz.

[0100] Figure 2 This is the test result of the reflectivity of the injection-molded structural component of Example 2 provided in the present application in the 2 GHz-18 GHz frequency band.

[0101] Figure 3 This is the test result of the reflectivity of the injection-molded structural component of Example 3 provided in the present application in the frequency band of 2 GHz-18 GHz.

[0102] Figure 4 This is the test result of the reflectivity of the injection-molded structural component of Example 4 provided in the present application in the frequency band of 2 GHz-18 GHz.

[0103] from Figure 1-Figure 4 It can be seen that the composite material provided in Example 1 exhibits good absorption of low-frequency electromagnetic waves ( Figure 1 ).

[0104] The composite material provided in Example 2 exhibits good absorption of electromagnetic waves in the frequency range of 3 GHz to 18 GHz, and the reflectivity is less than -4.9 db ( Figure 2 ).

[0105] The composite material provided in Example 3 also exhibits good absorption of electromagnetic waves in the frequency range of 5GHz-18GHz, and the reflectivity is less than -7db ( Figure 3 ).

[0106] The composite material provided in Example 4 exhibits good absorption of high-frequency electromagnetic waves and has a low dielectric constant ( Figure 4 ).

[0107] In summary, the composite material provided by the present invention has electromagnetic wave absorption characteristics, so that when it is applied to new energy vehicles, especially in the field of battery packs, it can effectively shield electromagnetic interference between different electronic devices and improve the safety factor of the vehicle. In addition, increasing the content of carbon nanotubes in the composite material can improve the absorption characteristics of the composite material for low-frequency electromagnetic waves, and increasing the content of nano-magnetic materials can improve the absorption characteristics of the composite material for high-frequency electromagnetic waves.

[0108] Table 1

[0109] As shown in Table 1, the combustion performance of the composite material provided by the present invention can reach the V-0 level under the UL94 test standard, and it has good thermal stability and flame retardancy, and the glass fiber has an excellent reinforcing effect on the composite material, and the composite material has excellent performance in specific stiffness, impact toughness, processability, etc. In addition, the composite material provided by the present invention has good insulation, and the environmental protection of the composite material can be improved by using a compound halogen-free flame retardant, and the composite material is given electromagnetic wave absorption characteristics by adding nano magnetic particles and / or carbon nanotubes, so that the composite material has a wide range of application prospects in new energy vehicles, especially in the field of battery packs.

[0110] The above description is only for the purpose of facilitating the technical solution of the present application to be understood by those skilled in the art, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A composite material based on polycarbonate, characterized in that: The composite material comprises the following components in parts by weight: 65-80 parts of polycarbonate, 10-25 parts of long glass fibers, 1-7 parts of nano-magnetic particles, 0-3 parts of carbon nanotubes, 1-3 parts of flame retardant, 0.1-1 parts of flame retardant and anti-dripping agent, 1-2 parts of insulating agent; wherein, The weight average molecular weight of the polycarbonate is 2×10 4 g / mol-4×10 4 g / mol, the particle size of the nano magnetic particles is 20nm-50nm; and the nano magnetic particles are ferrite particles.

2. The composite material according to claim 1, characterized in that The length of the long glass fiber is 10 mm-25 mm.

3. The composite material according to claim 1, characterized in that The carbon nanotubes are single-walled carbon nanotubes, and the length of the single-walled carbon nanotubes is 10nm-20nm.

4. The composite material according to claim 1, characterized in that The flame retardant comprises triphenyl phosphate and polysiloxane, and the mass ratio of the triphenyl phosphate to the polysiloxane is 3-5:

1.

5. The composite material according to claim 1, characterized in that The insulating agent includes one or more of polytetrafluoroethylene, polyethylene and its modified products, organic silicon, and nano silicon dioxide.

6. The composite material according to claim 1, characterized in that The flame retardant and anti-dripping agent includes one or more of modified polytetrafluoroethylene, talcum powder and montmorillonite.

7. A method for preparing a composite material based on polycarbonate, characterized in that: The preparation method comprises: Weigh the following components in parts by mass and mix them evenly: 65-80 parts of polycarbonate, 10-25 parts of long glass fiber, 1-6 parts of nano magnetic particles, 0-3 parts of carbon nanotubes, 1-3 parts of flame retardant, 0.1-1 parts of flame retardant and anti-drip agent, 1-2 parts of insulating agent; wherein the weight average molecular weight of the polycarbonate is 2×10 4 g / mol-4×10 4 g / mol, and the particle size of the nanomagnetic particles is 20nm-50nm; Melting and kneading the uniformly mixed components at a set temperature to obtain a melt of the composite material; After the melt is cooled and solidified, the composite material is obtained.

8. An injection molded structural part, characterized in that: The injection-molded structural component is prepared by using the composite material described in any one of claims 1 to 6.

9. A battery pack, characterized in that: The battery pack comprises a shell, a cover and a battery cell, wherein the cover is connected to the open end of the shell, and the battery cell is accommodated in the accommodation space between the cover and the shell; wherein, The cover body adopts the injection-molded structural component described in claim 8.

10. A new energy vehicle, characterized in that: The new energy vehicle includes the battery pack according to claim 9.

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