High-rigidity and high-toughness heat-conducting polypropylene composite material, preparation method thereof and power solid-sealed pole application

Abstract

This invention belongs to the field of polymer composite materials and electrical insulation materials, and relates to a high-rigidity, high-toughness, and thermally conductive polypropylene composite material, its preparation method, and its application in electrical sealing terminals. The preparation steps are as follows: A mixture of PP matrix, elastomer, GF, and hBN raw materials is placed in an 80℃ oven and dried for 8 hours. Then, PP, elastomer, GF, and a composite antioxidant are added to a high-speed mixer and mixed evenly. The mixture is then melt-blended and granulated using a twin-screw extruder to obtain component A. Component A, hBN, and the composite antioxidant are then added back to the high-speed mixer in a specific ratio, and the mixture is melt-blended, extruded, and granulated again using a twin-screw extruder to obtain the high-rigidity, high-toughness, and high-thermal-conductivity polypropylene composite material. This invention provides a simple preparation method, produces a composite material with good comprehensive mechanical properties, a lower melting temperature, a relatively constant melt flow rate, and improved thermal conductivity, which is beneficial for increasing the product molding rate. Simultaneously, it reduces energy consumption and production costs during the production process.

Description

Technical Field

[0001] This invention belongs to the field of polymer composite materials and electrical insulation materials, and relates to the preparation of a composite material for solid-sealed poles in the power industry. Background Technology

[0002] Solid-sealed terminals are core components of vacuum circuit breakers, typically integrating the vacuum interrupter, conductive circuit, and operating mechanism into a single unit using a polymer insulating encapsulation material. The primary polymer material used in manufacturing solid-sealed terminals is thermosetting epoxy resin, which suffers from drawbacks such as long processing cycles, heavy components, and inability to be recycled and reused, failing to meet mainstream environmental protection requirements. Therefore, utilizing recyclable, high-strength thermoplastics to replace epoxy resin in the production of solid-sealed terminals is an inevitable trend. Currently, commercially available thermoplastic solid-sealed terminals have emerged, primarily using high-melting-point thermoplastic materials, including polyamide (PA), polyphenylene sulfide (PPS), and polycarbonate (PC). These polymer materials offer advantages such as high strength, low energy consumption, and fast molding speed, but they have poor thermal conductivity, and their molding temperatures and pressures are significantly higher than those of epoxy resin. Therefore, there is an urgent need to develop new low-melting-point, high-flowability, and high-thermal-conductivity recyclable thermoplastic polymer materials for solid-sealed terminals.

[0003] Polypropylene (PP), as one of the fastest-growing general-purpose plastics, boasts advantages such as low density, good chemical stability, excellent electrical insulation, convenient molding and processing, and low cost, making it a highly promising matrix material for solid-state electrode packaging. It commonly comes in three types: homopolymer PP (PPH), random copolymer PP (PPR), and block copolymer PP (PPB). PPH, polymerized from propylene monomers, is characterized by its light weight, low cost, high rigidity, and poor toughness. PPB, obtained through block copolymerization of propylene and ethylene, exhibits improved toughness compared to PPH due to the addition of ethylene segments, but its rigidity is reduced. Melt blending PPH and PPB can improve the mechanical properties of polypropylene to some extent, but its low impact toughness and low-temperature brittleness still limit its application in the solid-state electrode field. Therefore, toughening modification of PP is necessary to improve its performance.

[0004] Currently, commonly used methods for toughening PP mainly include blending modification, filler modification, and nucleating agent-induced crystallization. Among these, blending modification involves thoroughly mixing and melt-extruding PP with tough thermoplastics, rubbers, or elastomers, and is the simplest, most effective, and most widely used physical modification method in actual production. Existing technologies commonly use plastics, rubbers, or elastomers for toughening PP include high-density polyethylene (HDPE), ethylene propylene diene monomer (EPR), ethylene propylene diene monomer (EPDM), hydrogenated styrene-butadiene block copolymer (SEBS), ethylene-octene copolymer (POE), ethylene-octene block copolymer (OBC), and propylene-based elastomers (PBE). The addition of these modifiers can effectively improve the impact resistance and low-temperature brittleness of PP, but it will significantly reduce its rigidity and strength. Therefore, it is usually necessary to simultaneously toughen and reinforce PP to achieve a balance between rigidity and toughness as much as possible.

[0005] Fiber reinforcement significantly improves the tensile strength, flexural strength, and flexural modulus of polypropylene composites, while also enhancing creep resistance and dimensional stability. Commonly used fibers include glass fiber (GF), carbon fiber (CF), and natural fibers. However, these fibers are prone to interfacial incompatibility with elastomers, leading to a decrease in the toughness and fluctuations in processing flowability of PP composites. Furthermore, conventional PP has a low thermal conductivity, which can cause heat accumulation within the sealed electrode structure's internal circuitry and components, resulting in thermal stress. This can reduce the material's strength and toughness, cause aging and cracking, and ultimately fail to meet the long-term safe operation requirements of sealed electrodes.

[0006] CN121450015A discloses a high-rigidity, high-toughness polypropylene composite material and its preparation method. It achieves a balance between rigidity and toughness in polypropylene materials using homopolymer polypropylene, impact copolymer polypropylene, talc, glass fiber, ethylene-octene copolymer, and maleic anhydride-grafted polypropylene at high filler content. CN112552604B discloses a thermally conductive and insulating polypropylene composite material, its preparation method, and its applications. Using polypropylene as the matrix, it achieves high thermal conductivity by compounding boron nitride, inorganic nanoparticles, aerobic nucleating agents, grafted modified resins, inorganic whiskers, antioxidants, and lubricants, but does not provide data on its toughness and strength.

[0007] In summary, the above analysis shows that existing publicly available technologies mostly focus on binary systems such as toughening and strengthening modification or thermal conductivity modification of PP, without specifically constructing a ternary synergistic system that combines toughening and strengthening with thermal conductivity enhancement. This makes it impossible to simultaneously achieve a balance between high toughness, high rigidity, high thermal conductivity, and processing stability. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a high-rigidity, high-toughness, and thermally conductive polypropylene composite material, its preparation method, and its application in power solid-sealing poles.

[0009] The technical solution of this invention is implemented as follows:

[0010] On one hand, the present invention provides a method for preparing a high-rigidity, high-toughness, and thermally conductive polypropylene composite material, comprising the following raw materials in parts by weight:

[0011] The mixed polypropylene matrix consists of 56-72 parts, which is a blend of homopolymer polypropylene (PPH) and block copolymer polypropylene (PPB) in a 1:1 mass ratio.

[0012] 14-18 parts of thermoplastic elastomer, selected from one of SEBS, POE3020, and POE3980;

[0013] 10-30 parts of alkali-free chopped glass fiber (GF);

[0014] 5-20 parts of hexagonal boron nitride (hBN); the median particle size of the hBN is 20 μm, and its density is 2.27 g·cm³. -3 .

[0015] 0.1-0.2 parts of compound antioxidant.

[0016] The preparation steps are as follows:

[0017] (1) Raw material drying: The mixed polypropylene matrix, thermoplastic elastomer, GF, hBN and other raw materials are placed in an 80℃ oven and dried for 8 h;

[0018] (2) High-speed premixing and twin-screw extrusion granulation: First, the mixed polypropylene matrix, thermoplastic elastomer, GF and composite antioxidant are added to the high-speed mixer in proportion and mixed evenly. Then, the mixture is melt-blended and granulated through a twin-screw extruder to obtain component A (M-PP).

[0019] (3) Components A, hBN and composite antioxidants are added to a high-speed mixer in proportion, and then melt-blended and extruded by a twin-screw extruder to obtain a high-rigidity, high-toughness and high-thermal-conductivity polypropylene composite material.

[0020] Furthermore, in step (2) above, the ratio of PP, elastomer, GF and composite antioxidant is 56-71:14-19:10-30:0.1, and the ratio of component A, hBN and composite antioxidant is 80-95:5-20:0.1.

[0021] Furthermore, in step (2) above, the speed of the high-speed mixer is 500-1200 r / min, and the mixing time is 1-10 minutes.

[0022] Furthermore, in step (2) above, the temperatures of the first to fourth zones of the twin-screw extruder are 165℃-170℃, 180℃-190℃, 190℃-200℃, and 185℃-190℃, respectively, and the main engine speed is 40-500 r / min.

[0023] Secondly, a high-rigidity, high-toughness, and thermally conductive polypropylene composite material was prepared using the above method.

[0024] Thirdly, the aforementioned high-rigidity, high-toughness, and thermally conductive polypropylene composite material is used in the preparation of power solid-sealed electrode posts.

[0025] Fourthly, the method for preparing the casing of the power solid-sealed pole using the above-mentioned high-rigidity, high-toughness, and thermally conductive polypropylene composite material is as follows: after drying the high-rigidity, high-toughness, and thermally conductive polypropylene composite material, it is subjected to injection molding process to obtain the casing of the power solid-sealed pole.

[0026] The injection molding temperature is 200℃-220℃, the mold temperature is 50-60℃, the injection pressure is 10-15MPa, and the holding time is 6 s-1 min.

[0027] The present invention has the following beneficial effects:

[0028] 1. This invention synthesizes a reinforced and toughened M-PP / hBN composite material with high thermal conductivity, using PPH / PPB as a mixed matrix, SEBS, POE, and GF as toughening and reinforcing phases, and hBN as a thermally conductive filler, through a dual-blending uniform dispersion filler technology. When the hBN filling amount is 10% of component A, the impact strength of the composite material can reach 9.21 kJ·m. -2 The tensile strength reaches 44.55 MPa, the elastic modulus is 2217.02 MPa, and the thermal conductivity is 0.244 W / (m·K), representing increases of 22.7%, 32.2%, 58.4%, and 6.1% respectively compared to pure PP. When the hBN filler content is 20% of component A, the impact strength of the composite material reaches 8.49 kJ·m. -2 The tensile strength reaches 40.48 MPa, the elastic modulus is 2134.51 MPa, and the thermal conductivity is 0.34 W / (m·K), which are 13.2%, 20.1%, 52.5%, and 47.8% higher than those of pure PP, respectively.

[0029] 2. The POE and SEBS elastomers used in this invention possess excellent aging resistance and good compatibility with polypropylene, significantly improving the toughness and transparency of polypropylene materials. The three-dimensional network structure formed by GF acts as a skeletal reinforcement, increasing the stress and load of the composite material. GF also promotes PP crystallization, acting as a heterogeneous nucleation agent, which to some extent also improves the strength of the composite material. Furthermore, the secondary blending filler technology effectively achieves uniform dispersion of hBN nanosheets, GF, and elastomers in the PP matrix, facilitating the construction of a highly efficient thermally conductive network of hBN nanosheets and the formation of a "rigid filler-fiber" load transfer path with GF, thereby synergistically improving its tensile and thermal conductivity properties.

[0030] 3. The preparation method of this invention is simple, and the resulting composite material has good comprehensive mechanical properties. The melting temperature is reduced, the melting flow rate remains basically unchanged, and the thermal conductivity is improved, which is conducive to improving the product molding rate. At the same time, it can reduce energy consumption and production costs during the production process. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 The impact strength comparison charts show the M-PP / hBN composite materials with different hBN contents prepared in Examples 1-4, as well as Comparative Examples 1, 2, and pure PP materials.

[0033] Figure 2 The tensile strength and elastic modulus of the M-PP / hBN composite materials with different hBN contents prepared in Examples 1-4, and Comparative Examples 1, 2, and pure PP materials are compared.

[0034] Figure 3 The graph shows a comparison of the thermal conductivity of M-PP / hBN composite materials with different hBN contents prepared in Examples 1-4, and that of Comparative Example 1 and pure PP.

[0035] Figure 4 The graph shows a comparison of the melt flow rates of the M-PP / hBN composite materials with different hBN contents prepared in Examples 1-4, and Comparative Examples 1, 2, and pure PP materials.

[0036] Figure 5 The figures show a comparison of the crystallization (a) and melting curves (b) of the M-PP / hBN composite materials with different hBN contents prepared in Examples 1-4 and Comparative Example 1. Detailed Implementation

[0037] The technical solution 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.

[0038] Unless otherwise specified, the experimental methods used in the following experimental examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0039] The purchase information for the raw materials used in this application is as follows:

[0040] Homopolymer polypropylene (PPH, model: T30S, purchased from Sinopec Shanghai Petrochemical Co., Ltd.), block copolymer polypropylene (PPB, model: K8303, purchased from Sinopec Beijing Yanshan Branch), SEBS (model: 688, purchased from Meite Polymer Materials Co., Ltd.), POE3020 (model: 3020, purchased from ExxonMobil), POE3980 (model: 3980, purchased from ExxonMobil), alkali-free chopped glass fiber (GF, model: GFRP-M, purchased from Bazhou Qihaili Rubber & Plastics Products Co., Ltd.), hexagonal boron nitride (hBN, model: CG20, median particle size: 20 μm, density: 2.27 g·cm³). -3 (Purchased from Suzhou Napu Materials Technology Co., Ltd.) and composite antioxidant (model: 1010+168, purchased from Hubei Kemaidi Chemical Co., Ltd.).

[0041] Example 1

[0042] The method for preparing a high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to this embodiment is carried out according to the following steps:

[0043] (1) Raw material drying: The mixed PP matrix, elastomer POE3020, GF, hBN and other raw materials are placed in an 80℃ oven and dried for 8 h;

[0044] (2) High-speed premixing and twin-screw extrusion granulation: First, 40 g of mixed PP matrix (homopolymer PP and block copolymer PP compounded at a mass ratio of 1:1), 16 g of POE3020, 24 g of GF and 0.08 g of composite antioxidant were added to a high-speed mixer at a speed of 1200 r / min for 2 minutes. After uniform mixing, the mixture was melt-blended and granulated through a twin-screw extruder to obtain component A (M-PP). The temperatures of zones one to four of the twin-screw extruder were 165℃, 180℃, 190℃ and 185℃, respectively, and the main extruder speed was 40 r / min.

[0045] (3) 80 g of component A, 20 g of hBN and 0.1 g of composite antioxidant were added to a high-speed mixer in proportion, and then melt-blended and extruded by a twin-screw extruder to obtain M-PP / hBN composite material. The parameters of the high-speed mixer and the twin-screw extruder were the same as those described above.

[0046] A method for preparing a solid-state electrode shell for power applications includes the following steps: drying the prepared M-PP / hBN composite material in an oven at 80℃ for 3 h, followed by injection molding. The injection temperature is 220℃, the mold temperature is 50℃, the injection pressure is 15MPa, and the holding time is 6 s.

[0047] The material prepared in this application has an impact strength of up to 8.49 kJ·m. -2 Compared to pure PP, it is 13.2% higher; its tensile strength can reach 40.48 MPa, which is similar to component A and 20.1% higher than pure PP; its elastic modulus is 2134.51 MPa, which is 52.5% higher than pure PP; its thermal conductivity is 0.34 W / (m·K), which is 60.2% higher than component A and 47.8% higher than pure PP.

[0048] Example 2

[0049] The method for preparing a high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to this embodiment is carried out according to the following steps:

[0050] (1) Raw material drying: The mixed PP matrix, elastomer POE3020, GF, hBN and other raw materials are placed in an 80℃ oven and dried for 8 h;

[0051] (2) High-speed premixing and twin-screw extrusion granulation: First, 45 g of mixed PP matrix (homopolymer PP and block copolymer PP compounded at a mass ratio of 1:1), 18 g of POE3020, 27 g of GF and 0.09 g of composite antioxidant were added to a high-speed mixer at a speed of 1200 r / min for 2 minutes. After uniform mixing, the mixture was melt-blended and granulated through a twin-screw extruder to obtain component A. The temperatures of zones one to four of the twin-screw extruder were 165℃, 180℃, 190℃ and 185℃, respectively, and the main extruder speed was 40 r / min.

[0052] (3) 90 g of component A, 10 g of hBN and 0.1 g of composite antioxidant were added to a high-speed mixer in proportion, and then melt-blended and extruded by a twin-screw extruder to obtain M-PP / hBN composite material. The parameters of the high-speed mixer and the twin-screw extruder were the same as those described above.

[0053] A method for preparing a solid-state electrode shell for power applications includes the following steps: drying M-PP / hBN composite material granules in an oven at 80℃ for 3 hours, followed by injection molding. The injection temperature is 220℃, the mold temperature is 50℃, the injection pressure is 15MPa, and the holding time is 6 seconds.

[0054] The material prepared in this application has an impact strength of up to 9.21 kJ·m. -2 Compared to pure PP, it is 22.7% higher; the tensile strength reaches 44.55 MPa, which is 32.2% higher than pure PP; the elastic modulus is 2217.02 MPa, which is 58.4% higher than pure PP; and the thermal conductivity is 0.244 W / (m·K), which is 6.1% higher than pure PP.

[0055] Example 3

[0056] The method for preparing a high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to this embodiment is carried out according to the following steps:

[0057] (1) Raw material drying: The mixed PP matrix, elastomer POE3020, GF, hBN and other raw materials are placed in an 80℃ oven and dried for 8 h;

[0058] (2) High-speed premixing and twin-screw extrusion granulation: First, 42.5 g (homopolymer PP and block copolymer PP compounded at a mass ratio of 1:1), 17 g POE3020, 25.5 g GF and 0.085 g composite antioxidant were added to a high-speed mixer at a speed of 1200 r / min for 2 minutes. After uniform mixing, the mixture was melt-blended and granulated through a twin-screw extruder to obtain component A. The temperatures of zones one to four of the twin-screw extruder were 165℃, 180℃, 190℃ and 185℃, respectively, and the main extruder speed was 40 r / min.

[0059] (3) 85 g of component A, 15 g of hBN and 0.1 g of composite antioxidant were added to a high-speed mixer in proportion, and then melt-blended and extruded by a twin-screw extruder to obtain M-PP / hBN composite material. The parameters of the high-speed mixer and the twin-screw extruder were the same as those described above.

[0060] A method for preparing a solid-state electrode shell for power applications includes the following steps: drying the prepared M-PP / hBN / hBN composite material granules in an oven at 80℃ for 3 hours, and then adding them to an injection molding machine for injection molding. The injection temperature is 220℃, the mold temperature is 50℃, the injection pressure is 15MPa, and the holding time is 6 seconds.

[0061] The material prepared in this application has an impact strength of 8.62 kJ·m. -2 Compared to pure PP, it is 14.9% higher; the tensile strength can reach 42.75 MPa, which is 26.9% higher than pure PP; the elastic modulus is 2204.64 MPa, which is about 57.5% higher than pure PP; and the thermal conductivity is 0.321 W / (m·K), which is 39.6% higher than pure PP.

[0062] Example 4

[0063] The method for preparing a high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to this embodiment is carried out according to the following steps:

[0064] (1) Raw material drying: The mixed PP matrix, elastomer POE3020, GF, hBN and other raw materials are placed in an 80℃ oven and dried for 8 h;

[0065] (2) High-speed premixing and twin-screw extrusion granulation: First, 47.5 g of mixed PP matrix (homopolymer PP and block copolymer PP compounded at a mass ratio of 1:1), 19 g of POE3020, 28.5 g of GF and 0.095 g of composite antioxidant were added to a high-speed mixer at a speed of 1200 r / min for 2 minutes. After uniform mixing, the mixture was melt-blended and granulated through a twin-screw extruder to obtain component A. The temperatures of zones one to four of the twin-screw extruder were 165℃, 180℃, 190℃ and 185℃, respectively, and the main extruder speed was 40 r / min.

[0066] (3) 95 g of component A, 5 g of hBN and 0.1 g of composite antioxidant were added to a high-speed mixer in proportion, and then melt-blended and extruded by a twin-screw extruder to obtain M-PP / hBN composite material. The parameters of the high-speed mixer and the twin-screw extruder were the same as those described above.

[0067] A method for preparing a solid-state electrode shell for power applications includes the following steps: drying the prepared M-PP / hBN composite material granules in an oven at 80℃ for 3 hours, and then adding them to an injection molding machine for injection molding. The injection temperature is 220℃, the mold temperature is 50℃, the injection pressure is 15MPa, and the holding time is 6 seconds.

[0068] Comparative Example 1

[0069] The preparation method of a high-rigidity, high-toughness, and thermally conductive polypropylene composite material in this comparative example is carried out according to the following steps:

[0070] (1) Raw material drying: Place the mixed PP matrix, elastomer POE3020, GF and other raw materials in an 80℃ oven and dry for 8 h;

[0071] (2) High-speed premixing and twin-screw extrusion granulation: First, 64 g of mixed PP matrix (homopolymer PP and block copolymer PP compounded at a mass ratio of 1:1), 16 g of POE3020, 20 g of GF and 0.1 g of composite antioxidant were added to a high-speed mixer at a speed of 1200 r / min for 2 minutes. After uniform mixing, the mixture was melt-blended and granulated through a twin-screw extruder to obtain component A (PP / POE / GF). The temperatures of zones one to four of the twin-screw extruder were 165℃, 180℃, 190℃ and 185℃, respectively, and the main extruder speed was 40 r / min.

[0072] A method for preparing a solid-state electrode shell for power applications includes the following steps: drying the prepared PP / POE / GF composite material granules in an oven at 80℃ for 3 hours, and then injection molding them using an injection molding machine. The injection temperature is 220℃, the mold temperature is 50℃, the injection pressure is 15MPa, and the holding time is 6 seconds.

[0073] The PP / POE / GF material prepared in this comparative example has an impact strength of 12.04 kJ·m. -2 Compared to pure PP, it is 60.5% higher; the tensile strength can reach 40.98 MPa, which is 21.6% higher than pure PP; the elastic modulus is 2100.21 MPa, which is 50.0% higher than pure PP; while the thermal conductivity is 0.212 W / (m·K), which is 7.8% lower than pure PP.

[0074] Comparative Example 2

[0075] The preparation method of a high-rigidity, high-toughness, and thermally conductive polypropylene composite material in this comparative example is carried out according to the following steps:

[0076] (1) Raw material drying: Place the mixed PP matrix and elastomer POE3020 raw materials in an 80℃ oven and dry for 8 h;

[0077] (2) High-speed premixing and twin-screw extrusion granulation: First, 80 g of mixed PP matrix (homopolymer PP and block copolymer PP compounded at a mass ratio of 1:1), 20 g of POE3020 and 0.1 g of composite antioxidant were added to a high-speed mixer at a speed of 1200 r / min for 2 minutes. After uniform mixing, the mixture was melt-blended and granulated through a twin-screw extruder to obtain PP / POE composite material. The temperatures of zones one to four of the twin-screw extruder were 165℃, 180℃, 190℃ and 185℃, respectively, and the main extruder speed was 40 r / min.

[0078] A method for preparing a solid-state electrode shell for power applications includes the following steps: drying the prepared PP / POE composite material granules in an oven at 80℃ for 3 hours, and then adding them to an injection molding machine for injection molding. The injection temperature is 220℃, the mold temperature is 50℃, the injection pressure is 15MPa, and the holding time is 6 seconds.

[0079] The PP / POE material prepared in this comparative example has an impact strength of 50.68 kJ·m. -2 Compared to pure PP, it is 575.7% higher; however, the tensile strength is only 30.5 MPa, which is 9.5% lower than that of pure PP; and the elastic modulus is 807.01 MPa, which is 42.4% lower than that of pure PP.

[0080] Example 5

[0081] The method for preparing a high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to this embodiment is carried out according to the following steps:

[0082] (1) Raw material drying: The mixed PP matrix, elastomer POE3980, GF, hBN and other raw materials are placed in an 80℃ oven and dried for 8 h;

[0083] (2) High-speed premixing and twin-screw extrusion granulation: First, 40 g of mixed PP matrix (homopolymer PP and block copolymer PP compounded at a mass ratio of 1:1), 16 g of POE3980, 24 g of GF and 0.08 g of composite antioxidant were added to a high-speed mixer at a speed of 1200 r / min for 2 minutes. After uniform mixing, the mixture was melt-blended and granulated through a twin-screw extruder to obtain component A. The temperatures of zones one to four of the twin-screw extruder were 165℃, 180℃, 190℃ and 185℃, respectively, and the main extruder speed was 60 r / min.

[0084] (3) 80 g of component A, 20 g of hBN and 0.1 g of composite antioxidant were added to a high-speed mixer in proportion, and then melt-blended and extruded by a twin-screw extruder to obtain M-PP / hBN composite material. The parameters of the high-speed mixer and the twin-screw extruder were the same as those described above.

[0085] A method for preparing a solid-state electrode shell for power applications includes the following steps: drying the prepared M-PP / hBN composite material granules in an oven at 80℃ for 3 hours, and then adding them to an injection molding machine for injection molding. The injection temperature is 210℃, the mold temperature is 60℃, the injection pressure is 10MPa, and the holding time is 1 min.

[0086] Example 6

[0087] The method for preparing a high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to this embodiment is carried out according to the following steps:

[0088] (1) Raw material drying: The mixed PP matrix, elastomer POE3980, GF, hBN and other raw materials are placed in an 80℃ oven and dried for 8 h;

[0089] (2) High-speed premixing and twin-screw extrusion granulation: First, 45 g of mixed PP matrix (homopolymer PP and block copolymer PP compounded at a mass ratio of 1:1), 18 g of POE3980, 27 g of GF and 0.09 g of composite antioxidant were added to a high-speed mixer at a speed of 1200 r / min for 2 minutes. After uniform mixing, the mixture was melt-blended and granulated through a twin-screw extruder to obtain component A. The temperatures of zones one to four of the twin-screw extruder were 165℃, 185℃, 195℃ and 185℃, respectively, and the main extruder speed was 50 r / min.

[0090] (3) 90 g of component A, 10 g of hBN and 0.1 g of composite antioxidant were added to a high-speed mixer in proportion, and then melt-blended and extruded by a twin-screw extruder to obtain M-PP / hBN composite material. The parameters of the high-speed mixer and the twin-screw extruder were the same as those described above.

[0091] A method for preparing a solid-state electrode shell for power applications includes the following steps: drying the prepared M-PP / hBN composite material granules in an oven at 80℃ for 3 hours, and then adding them to an injection molding machine for injection molding. The injection temperature is 200℃, the mold temperature is 55℃, the injection pressure is 13MPa, and the holding time is 1 minute.

[0092] Example 7

[0093] The method for preparing a high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to this embodiment is carried out according to the following steps:

[0094] (1) Raw material drying: Place the mixed PP matrix, elastomer SEBS, GF, hBN and other raw materials in an 80℃ oven and dry for 8 hours;

[0095] (2) High-speed premixing and twin-screw extrusion granulation: First, 40 g of mixed PP matrix (homopolymer PP and block copolymer PP compounded at a mass ratio of 1:1), 16 g of SEBS, 24 g of GF and 0.08 g of composite antioxidant were added to a high-speed mixer at a speed of 1200 r / min for 2 minutes. After uniform mixing, the mixture was melt-blended and granulated through a twin-screw extruder to obtain component A. The temperatures of zones one to four of the twin-screw extruder were 170℃, 190℃, 200℃ and 190℃, respectively, and the main extruder speed was 40 r / min.

[0096] (3) 80 g of component A, 20 g of hBN and 0.1 g of composite antioxidant were added to a high-speed mixer in proportion, and then melt-blended and extruded by a twin-screw extruder to obtain M-PP / hBN composite material. The parameters of the high-speed mixer and the twin-screw extruder were the same as those described above.

[0097] A method for preparing a solid-state electrode shell for power applications includes the following steps: drying the prepared M-PP / hBN composite material granules in an oven at 80℃ for 3 hours, and then adding them to an injection molding machine for injection molding. The injection temperature is 220℃, the mold temperature is 50℃, the injection pressure is 15MPa, and the holding time is 1 min.

[0098] Implementation Results Example

[0099] The impact strength comparison results of a series of reinforced and toughened M-PP / hBN composite materials prepared in Examples 1-4 and Comparative Examples 1-2, and Comparative Examples 1, 2, and pure PP materials are as follows: Figure 1 As shown, the comparison results of tensile strength and elastic modulus are as follows: Figure 2 As shown, the comparison results of thermal conductivity are as follows: Figure 3 As shown, the comparison results of melt flow rates are as follows: Figure 4 As shown, the comparison results of crystallization (a) and melting curve (b) are as follows: Figure 5 As shown.

[0100] It can be seen that adding POE to PP can greatly improve the impact strength of the composite material. However, with the addition of GF and hBN fillers, the impact strength shows a significant downward trend, and the impact strength of the composite material decreases to 8.49 kJ·m when the hBN content is 20%. -2 Compared to PP / POE and M-PP, the impact strength is reduced by 83.2% and 29.5% respectively, but it is still higher than that of pure PP matrix (7.5 kJ·m). -2The tensile strength and elastic modulus of the composite material with only POE added were lower than those of the pure PP matrix. However, with the addition of high-modulus rigid fillers GF and hBN, the tensile strength and elastic modulus of the composite material were greatly improved. As the hBN content increased, the overall trend was first higher and then lower, and the highest tensile strength and elastic modulus were obtained when the hBN content was 10%, reaching 44.55 MPa and 2217.02 MPa, respectively. Compared with pure PP, these were increased by 32.19% and 58.35%, and compared with PP / POE, they were increased by 46.07% and 174.72%, respectively.

[0101] Filling with hBN can effectively improve the thermal conductivity of composite materials. With the increase of hBN content, the thermal conductivity of composite materials continues to increase and the slope becomes larger and larger. When the hBN content is 20%, the thermal conductivity of composite materials reaches a maximum of 0.34 W / (m·K), which is 60.2% higher than that of PP / POE / GF and 47.8% higher than that of pure PP.

[0102] Furthermore, the melt flow properties of thermoplastic materials are one of the important reference indicators in industrial production, directly affecting production efficiency and processing costs. Compared to pure PP, the melt flow rate (MFR) of PP / POE composites decreases sharply, while the introduction of GF (growth factor) mitigates this phenomenon to some extent. Simultaneously, the processability of M-PP / hBN composites is further improved with the addition of hBN. When the hBN content in the system is less than 10%, the melt flow rate of the composite remains essentially unchanged. However, with further increasing the hBN content, the MFR of the composite system begins to increase. The MFR reaches its maximum when the hBN content is 20%, approximately 10% higher than that of PP / POE / GF.

[0103] Finally, with the increase of hBN filler content, the crystallization peak temperature of the composite material gradually shifted towards higher temperatures. When the filler content was 20%, the crystallization peak temperature increased by approximately 6.2 °C, and the half-width at half-maximum (FWHM) of the crystallization peak narrowed with the increase of hBN content, indicating that hBN had a significant heterogeneous nucleation effect, reducing the crystallization difficulty of PP and enabling it to crystallize at higher temperatures. The change in the melting peak temperature was not significant. With the increase of hBN content, the melting peak temperature first increased slightly and then shifted towards lower temperatures.

[0104] In summary, when the hBN filling amount is 10 wt% of the total mass of the composite material, the composite material exhibits good overall mechanical properties, with impact strength, tensile strength, and elastic modulus reaching 9.09 kJ·m⁻², 44.55 MPa, and 2217.02 MPa, respectively, while the melt flow rate remains essentially unchanged, and the thermal conductivity is improved. After filling PP / POE / GF with 20 wt% hBN, the thermal conductivity of the composite material is 0.34 W / (m·K), which is 47.8% higher than that of pure PP.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-rigidity, high-toughness, and thermally conductive polypropylene composite material, characterized in that, The steps are as follows: (1) The mixed polypropylene matrix, thermoplastic elastomer, alkali-free chopped glass fiber and hexagonal boron nitride are dried. (2) The mixed polypropylene matrix, thermoplastic elastomer, alkali-free chopped glass fiber and composite antioxidant after step (1) are added to the mixer in proportion, mixed evenly and then extruded and granulated by a twin-screw extruder to obtain component A. (3) After mixing component A, hexagonal boron nitride and composite antioxidant, the high-rigidity, high-toughness, and high-thermal-conductivity polypropylene composite material is obtained by twin-screw extrusion granulation.

2. The method for preparing the high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to claim 1, characterized in that: In step (1), the mixed polypropylene matrix is ​​a blend of homopolymer polypropylene and block copolymer polypropylene in a mass ratio of 1:1; the antioxidant is a blend of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

1.

3. The method for preparing the high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to claim 1, characterized in that: In step (2), the mass ratio of the mixed polypropylene matrix, thermoplastic elastomer, alkali-free chopped glass fiber and antioxidant is 56-71:14-19:10-30:0.

1.

4. The method for preparing the high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to claim 3, characterized in that: The mixer operates at a speed of 500-1200 r / min and a mixing time of 1-10 minutes.

5. The method for preparing the high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to claim 4, characterized in that: The twin-screw extruder has four temperature zones: 165℃-170℃, 180℃-190℃, 190℃-200℃, and 185℃-190℃, respectively, and a screw speed of 40-500 r / min.

6. The method for preparing the high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to claim 5, characterized in that: The mass ratio of component A, hexagonal boron nitride, and composite antioxidant is 80-95:5-20:0.

1.

7. A high-rigidity, high-toughness, and thermally conductive polypropylene composite material prepared by the method according to any one of claims 1-6.

8. The application of the high-rigidity, high-toughness, and thermally conductive polypropylene composite material according to claim 7 in the preparation of power solid-sealed poles.

9. A method for preparing a power solid-sealed electrode shell using the high-rigidity, high-toughness, and thermally conductive polypropylene composite material as described in claim 7, characterized in that, The steps are as follows: After drying the high-rigidity, high-toughness, and thermally conductive polypropylene composite material, an injection molding process is carried out to obtain the power solid-sealed electrode shell.

10. The method according to claim 9, characterized in that: The injection molding temperature is 200℃-220℃, the mold temperature is 50-60℃, the injection pressure is 10-15MPa, and the holding time is 6 s-1 min.

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