Multi-element modified polypropylene composition, multi-element modified polypropylene material and preparation method

Abstract

The invention relates to a multi-element modified polypropylene composition, a multi-element modified polypropylene material and a preparation method. The polypropylene material comprises the following components in parts by weight: 50-80 parts of base resin, 20-40 parts of modified resin, 0.5-2 parts of an antioxidant, 0.1-2 parts of nano powder and 0.1-0.6 part of a modifier, the base resin is one or more of isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), atactic polypropylene (aPP), block polypropylene (PP-B) and rubber co-polypropylene (PP-R); the modified resin is one or more of an ethylene-octylene copolymer (EOC), a polyolefin elastomer (POE), metallocene polypropylene (MAO-PP), an ethylene-butylene copolymer (SEBS), styrene-isoprene-styrene (SIS) and high density polyethylene (HDPE); the modifier is dopamine. According to the polypropylene material, the crystal structure is greatly improved, and the breakdown performance, mechanical flexibility and thermal performance of the compound polypropylene insulating material are improved.

Description

Technical Field

[0001] The present invention belongs to the field of environmentally friendly polypropylene insulation materials, and in particular relates to a multinary modified polypropylene composition, a multinary modified polypropylene material and a preparation method. Background Art

[0002] With the national "dual carbon" strategy and the construction of a new power system, large-capacity, long-distance, and high-load transmission networks will be vigorously developed, and higher requirements will be placed on the insulation voltage resistance, temperature resistance, and current carrying capacity of high-voltage cables. However, the current power grid generally uses cross-linked polyethylene (XLPE) cables, whose long-term stable operating temperature does not exceed 70°C, which is difficult to meet the current ultra-high voltage transmission requirements of 90°C or even 105°C full-load operating conditions. In addition, traditional XLPE cables are prepared by high-temperature cross-linking and degassing of polyethylene base materials and cross-linking agents. The product is a thermosetting insulation material that cannot be recycled and can only be landfilled and incinerated in the later stage, which poses the risk of environmental pollution. Therefore, there is an urgent need to develop environmentally friendly polypropylene insulation materials with high voltage resistance, high temperature resistance, and excellent thermal properties that meet the requirements of ultra-high voltage AC and DC transmission.

[0003] Polypropylene (PP) is a new environmentally friendly thermoplastic insulating material derived from the polymerization of propylene as a monomer. Its melting point is generally above 150°C, and its long-term operating temperature can reach 90-110°C. It exhibits excellent compressive strength and electrical conductivity (≥1016Ω·m). However, the high crystallinity and large crystal size of PP base materials, coupled with their brittleness and rigidity, make them difficult to use directly as cable insulation materials. Currently, a number of novel modification methods, such as copolymerization, blending, and grafting, are being investigated to improve the comprehensive properties of environmentally friendly PP cable insulation materials. Copolymerization can improve the toughness and impact resistance of PP base materials from a molecular segment perspective; grafting modification can functionalize the segments to modify the amorphous regions of the base material, thereby enhancing overall performance. Elastomer blending and nanocomposites are currently the most commonly used methods to improve the crystal structure and mechanical flexibility of insulation materials. However, the inevitable phase separation problem associated with multicomponent blending can lead to weak interfacial compatibility, resulting in agglomeration, gel phases, and interfacial polarization defects, which can affect the overall electrical, mechanical, and thermal properties of the composite insulation material.

[0004] Dopamine is an important environmentally friendly bioactive molecule with excellent adhesion and self-assembly capabilities. Its surface groups, such as catechol and hydroxyl groups, impart excellent functional interfacial compatibility. Currently, some researchers have directly used dopamine to improve polypropylene base materials (CN 105255010 B) or modified nanoparticle polypropylene insulation materials (CN 117820762A), aiming to optimize the base material's crystal structure and enhance the material's electrical strength. However, the resulting composite insulation materials have not significantly improved their mechanical flexibility, and improvements in the thermal performance of the resulting composite polypropylene have not yet been addressed. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of poor mechanical flexibility and thermal performance of existing environmentally friendly polypropylene insulation materials.

[0006] The purpose of the present invention is to adopt the following technical solutions to achieve:

[0007] A multi-component modified polypropylene composition comprises the following components in parts by weight: 50-80 parts of base resin, 20-40 parts of modified resin, 0.5-2 parts of antioxidant, 0.1-2 parts of nano powder, and 0.1-0.6 parts of modifier;

[0008] The base resin is one or more of isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), atactic polypropylene (aPP), segmented polypropylene (PP-B), and rubber copolymer polypropylene (PP-R);

[0009] The modified resin is one or more of ethylene-octene copolymer (EOC), polyolefin elastomer (POE), metallocene polypropylene (MAO-PP), ethylene-butene copolymer (SEBS), styrene-isoprene-styrene (SIS), and high-density polyethylene (HDPE);

[0010] The modifier is dopamine.

[0011] Preferably, the nanopowder is selected from one or more of nano-aluminum oxide, nano-boron nitride, nano-magnesium oxide, nano-zinc oxide, nano-titanium dioxide, and nano-silicon carbide.

[0012] Preferably, the particle size of the nanopowder is 50 to 500 nm. When the filler particle size is lower than the preferred value, the van der Waals force between the particles is too strong, causing the filler to easily agglomerate together. Even if a modifier is used for interface modification, its specific area and surface energy are still large, and it is easy for agglomeration to occur in the polypropylene base material, resulting in difficulty in its extrusion processing and easy accumulation of defects inside the material. When the filler particle size is greater than the preferred value, the filler particle size is too large, and sedimentation is likely to occur during the melt extrusion process, making it difficult to distribute evenly. At the same time, a large particle size means a reduction in the amount of filler, which is not conducive to internal β crystal nucleation and difficult to optimize the material structure and overall performance.

[0013] Preferably, the base resin is a propylene-ethylene block copolymer.

[0014] Preferably, the ethylene content of the propylene-ethylene block copolymer is 5% to 20%. When the ethylene content is lower than the preferred value, the material has greater rigidity, higher crystallinity, and poor low-temperature impact resistance, making it unsuitable for selection as a cable insulation base material. When the ethylene content is higher than the preferred value, the internal crystal structure is irregular, lacks cohesion, and processing and mechanical toughness are significantly reduced. The molecular chains are more likely to move at high temperatures, resulting in poor thermal stability and making it unsuitable for use as a high-temperature resistant polypropylene base material.

[0015] Preferably, the antioxidant is one or more of antioxidant 300, antioxidant 1076, antioxidant 1035, antioxidant 1330 and antioxidant 802.

[0016] The present invention also provides a method for preparing a multinary modified polypropylene material using the composition, comprising the following steps:

[0017] Nanopowder pretreatment: The nanopowder is heated and dried in a vacuum environment to obtain dry powder;

[0018] Nanopowder modification: adding a modifier dropwise to the dispersion, mixing uniformly to obtain a modifier solution, adding the dry powder, ultrasonically treating and stirring at high speed, washing several times, filtering, and freeze-drying to obtain modified nanopowder;

[0019] Preparation of powder-filled elastomer: uniformly mixing the modified nanopowder and modified resin to obtain a powder-filled elastomer;

[0020] Granulation: the powder is filled with elastomer, base resin and antioxidant and extruded and granulated at a temperature of 150-220° C. to obtain the polypropylene material.

[0021] Preferably, the pretreatment of the nanopowder specifically includes: placing the nanopowder in a vacuum drying oven, heating the nanopowder at a temperature ranging from 50 to 300° C., and treating the nanopowder for 6 to 12 hours to obtain dry powder.

[0022] Preferably, in the nanopowder modification step, the dispersion is prepared by mixing deionized water and anhydrous ethanol in a volume ratio of 4:1; the mass concentration of the modifier solution is 2-10% and the pH is 7-10.

[0023] Preferably, in the nanopowder modification step, the ultrasonic treatment temperature is 20-40° C., and the time is 0.5-2 h; the stirring temperature is 20-80° C., and the stirring time is 6-48 h; and the freeze-drying time is 24-48 h.

[0024] Preferably, in the step of preparing the powder-filled elastomer, the modified nanopowder and the modified resin are uniformly mixed in a blender, the blender has a stirring temperature of 150-190° C., a blender speed of 600-1000 rpm, and a stirring time of 10-15 min.

[0025] Preferably, in the granulation step, a twin-screw extruder is used to produce the extruded strips, which are then cooled underwater for pelletizing. The extrusion temperature range is 150-220°C, and the extrusion speed is 40-200 rpm. When the extrusion temperature is lower than the preferred value, the insulating material is difficult to effectively plasticize, and the surface of the extruded strips and pellets is rough, making them difficult to shape. When the extrusion temperature is higher than the preferred value, the internal molecular chain structure of the insulating material is easily damaged, resulting in thermal decomposition and thermal oxidation of the material. Internal defects will affect the mechanical and electrical properties of the material.

[0026] Preferably, the twin-screw extruder's filter mesh combination is: 40 / 80 / 200 / 100 / 40 mesh, and the material is stainless steel. When the mesh size is lower than the preferred value, the extrusion pressure is too low, the filtration effect of the filter is poor, and the extrusion rate is too fast, which is not conducive to effective blending of the materials within the screw. When the mesh size is higher than the preferred value, the filtration rate is significantly reduced, the yield of the prepared polypropylene insulation material decreases, and the extrusion pressure fluctuates greatly over a long period of time, which is not conducive to homogeneous extrusion of the material.

[0027] The present invention also provides a multinary modified polypropylene material prepared by adopting the composition or the preparation method.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The multi-component modified polypropylene material of the present invention comprises the following components in parts by weight: 50-80 parts of a base resin, 20-40 parts of a modified resin, 0.5-2 parts of an antioxidant, 0.1-2 parts of a nanopowder, and 0.1-0.6 parts of a modifier; the base resin is one or more of isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), atactic polypropylene (aPP), segmented polypropylene (PP-B), and rubber copolymer polypropylene (PP-R); the modified resin is one or more of ethylene-octene copolymer (EOC), polyolefin elastomer (POE), metallocene polypropylene (MAO-PP), ethylene-butene copolymer (SEBS), styrene-isoprene-styrene (SIS), and high-density polyethylene (HDPE); and the modifier is dopamine. The polypropylene material of the present invention uses dopamine, a bio-based environmentally friendly modifier obtained from marine fermentation within a specific range, to modify the surface of the nanopowder, so that the surface of the nanopowder is rich in unsaturated groups such as catechol, hydroxyl and amino groups. The nanopowder can not only be evenly dispersed in the elastomer resin, but also synergistically enhance the interfacial compatibility and dispersibility of the filler and the non-polar block polypropylene base material; at the same time, the nano-coated modified elastomer can also improve the nucleation efficiency of the β crystals of the block polypropylene base material in the form of a nucleating agent, thereby achieving the purpose of uniformly refining the grains, thereby significantly improving the crystal structure and enhancing the breakdown performance, mechanical flexibility and thermal properties of the compounded polypropylene insulation material.

[0030] The modified resin is a low-melting-point thermoplastic elastomer. The polydopamine-coated modified nanopowder is uniformly blended with the low-melting-point thermoplastic elastomer at low temperature to achieve uniform mixing in the elastomer, effectively avoiding carbonization of the coating layer and thermal degradation of the molecular chain segments, and laying the foundation for subsequent high-temperature multi-component blending and extrusion with a polypropylene base material.

[0031] The modifier, dopamine, self-polymerizes into polydopamine during the preparation process. The surface of polydopamine is rich in functional groups such as catechol, hydroxyl, and amino groups, which can react with the hydroxyl groups on the surface of the nanoparticles to form hydrogen bonds, thereby firmly adhering to the surface of the powder, significantly reducing the van der Waals forces between the powders, effectively promoting the dispersion of the modified powder in the polypropylene base material, and avoiding the formation of agglomeration defects. At the same time, the nanopowder coated with the polydopamine coating contains a benzene ring structure. The π electron cloud on the benzene ring can interact with the electron cloud on the surface of the non-polar material, generating a π-π stacking interaction force, thereby enhancing the interfacial adsorption between the powder and the base material.

[0032] The base resin is selected from segmented polypropylene (BPP), which has high energy and activity. The polydopamine-coated powder promotes the aggregation and crystallization of BPP molecular chains on its surface, reducing the size and increasing the number of β-spherulites. The spherulites collide and inhibit each other, ultimately resulting in a spherulite morphology with higher crystallinity and a more regular crystal structure. The significantly improved crystal morphology, significantly enhanced interfacial compatibility, and uniform filler dispersion are key to synergistically improving the material's breakdown field strength, mechanical properties, and thermal conductivity.

[0033] The preparation method of the multinary modified polypropylene material of the present invention uses dopamine derived from abundant nature, and the modification process does not require an organic solvent. The preparation raw materials involved, such as nanopowders and thermoplastic base resins, are all recyclable, inexpensive, and readily available. The preparation process is simple to operate, and no toxic by-products are produced. Therefore, the method is environmentally friendly and has the potential for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a flow chart of a method for preparing a multinarily modified polypropylene material according to Example 3 of the present invention;

[0035] Figure 2 Schematic diagram of the cross section SEM of the polypropylene materials of Example 3 of the present invention and Comparative Example 3.

[0036] Among them, 1 is nano powder, 2 is modified nano powder, 3 is powder-filled elastomer, and 4 is multi-component modified polypropylene material. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] like Figure 1 As shown, it is a flow chart of the preparation method of multi-component modified polypropylene material, 1 is nano powder, 2 is modified nano powder, 3 is powder-filled elastomer, and 4 is multi-component modified polypropylene material.

[0039] A multi-component modified polypropylene composition comprises the following components in parts by weight: 50-80 parts of base resin, 20-40 parts of modified resin, 0.5-2 parts of antioxidant, 0.1-2 parts of nano powder, and 0.1-0.6 parts of modifier;

[0040] The base resin is one or more of isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), atactic polypropylene (aPP), segmented polypropylene (PP-B), and rubber copolymer polypropylene (PP-R);

[0041] The modified resin is one or more of ethylene-octene copolymer (EOC), polyolefin elastomer (POE), metallocene polypropylene (MAO-PP), ethylene-butene copolymer (SEBS), styrene-isoprene-styrene (SIS), and high-density polyethylene (HDPE);

[0042] The modifier is dopamine.

[0043] In one embodiment, the nanopowder is one or more of nano-aluminum oxide, nano-boron nitride, nano-magnesium oxide, nano-zinc oxide, nano-titanium dioxide, and nano-silicon carbide.

[0044] In one embodiment, the base resin is a propylene-ethylene block copolymer.

[0045] In one embodiment, the propylene-ethylene block copolymer has an ethylene content of 5% to 20%.

[0046] In one embodiment, the antioxidant is one or more of antioxidant 300, antioxidant 1076, antioxidant 1035, antioxidant 1330, and antioxidant 802.

[0047] A preparation method of a multinary modified polypropylene material is as follows:

[0048] S01. The nanopowder is placed in a vacuum drying oven at a heating temperature range of 50 to 300 ° C for 6 to 12 hours to obtain a dry powder;

[0049] S02. The modifier is added dropwise to a dispersion prepared by mixing deionized water and anhydrous ethanol in a volume ratio of 4:1. The weight concentration of the modifier solution is 2 to 10%. The pH is adjusted to 7 to 10. After mixing, the dried nanopowder obtained in step S01 is added, and the mixture is ultrasonically treated at 20 to 40°C for 0.5 to 2 hours. After high-speed stirring at 20 to 80°C for 6 to 48 hours, the mixture is washed several times with the dispersion and filtered. Finally, the mixture is freeze-dried for 24 to 48 hours to obtain a modified nanopowder.

[0050] S03. The modified nanopowder obtained in step S02 is mixed with the modified resin in a blender at a stirring temperature of 150 to 180°C, a stirring speed of 600 to 1000 rpm, and a stirring time of 10 to 15 min to obtain a powder-filled elastomer;

[0051] S04. The powder-filled elastomer, base resin and antioxidant in step S03 are uniformly extruded in a twin-screw extruder, and the extrusion multi-section temperature range is 150-190°C, the feed inlet: 150-170°C, the melting section: 170-190°C, the extrusion section: 180-190°C, and the outlet temperature: 190°C; the extrusion speed is 40-200rpm, and the filter screen combination of the twin-screw extruder is: 40 / 80 / 200 / 100 / 40 mesh, and the material is stainless steel; the polypropylene insulation material is extruded into long strips, and is cooled and pelletized underwater, the underwater pelletizing temperature is 20°C, and the pellet diameter is 1-2mm to obtain a multi-component modified polypropylene insulation material.

[0052] Example 1

[0053] The multi-component modified polypropylene composition of this embodiment includes the following components in parts by weight: 65 parts of base resin, 32 parts of modified resin, 1 part of antioxidant, 1.5 parts of nanopowder, and 0.5 part of modifier; the base resin is block polypropylene (PP-B); the modified resin is ethylene-octene copolymer; the modifier is dopamine; the nanopowder is nano-alumina; and the antioxidant is antioxidant 300.

[0054] The preparation method of the multinary modified polypropylene material of this embodiment is as follows:

[0055] S01. The average particle size of 100nm nano-alumina was placed in a vacuum drying oven at 100 ° C and dried for 12h to obtain a dry powder;

[0056] S02. 3 g of the dry powder obtained in step S01 was dissolved in 300 ml of dispersion solution with 0.5 g of tris(hydroxymethyl)aminomethane. The pH was then adjusted to 8.5 by adding sodium hydroxide tablets. 1.2 g of dopamine hydrochloride was added and ultrasonicated at room temperature for 2 h. The mixture was stirred at high speed for 24 h. The mixture was washed several times with the dispersion solution and filtered. The mixture was freeze-dried for 24 h to obtain a modified nanopowder.

[0057] S03. The modified nanopowder described in step S02 is mixed with ethylene-octene copolymer (EOC) in a blender, wherein the total mass content of the modified nanopowder is 0.1%, the stirring temperature is 150 ° C, the mixer speed is 800 rpm, and the stirring is carried out for 15 min to obtain a powder-filled elastomer;

[0058] S04. The powder-filled elastomer, block polypropylene (PP-B), and antioxidant 300 in step S03 are uniformly extruded in a twin-screw extruder. The extrusion multi-stage temperature range is 150-190°C, the extrusion speed is 40-200rpm, and long strips are extruded. The strips are cooled and pelletized underwater. The pellets have a diameter of 2mm to obtain a multi-modified polypropylene material.

[0059] Example 2

[0060] The preparation method of this embodiment is basically the same as that of Example 1, except that the total mass content of the modified nanopowder is 0.5%.

[0061] Example 3

[0062] The preparation method of the multi-component modified polypropylene material in this embodiment is basically the same as that in Example 1, except that the total mass content of the modified nanopowder is 1.0%.

[0063] Example 4

[0064] The preparation method of the multi-component modified polypropylene material in this embodiment is basically the same as that in Example 1, except that the total mass content of the modified nanopowder is 1.5%.

[0065] Example 5

[0066] The method for preparing the polypropylene material of this embodiment is substantially the same as that of embodiment 1, except that the base resin is isotactic polypropylene, the extrusion temperature range is 150-220°C, and the extrusion speed is 40-180 rpm.

[0067] Example 6

[0068] The method for preparing the polypropylene material of this embodiment is substantially the same as that of embodiment 1, except that the base resin is syndiotactic polypropylene, the extrusion temperature range is 150-205°C, and the extrusion speed is 40-160 rpm.

[0069] Example 7

[0070] The preparation method of the polypropylene material in this embodiment is basically the same as that in Example 1, except that the average particle size of the aluminum oxide powder is 50 nm.

[0071] Example 8

[0072] The preparation method of the polypropylene material in this embodiment is basically the same as that in Example 1, except that the average particle size of the aluminum oxide powder is 200 nm.

[0073] Example 9

[0074] The preparation method of the polypropylene material in this embodiment is basically the same as that in Example 1, except that the nano powder is nano boron nitride with an average particle size of 50 nm.

[0075] Example 10

[0076] The preparation method of the polypropylene material in this embodiment is basically the same as that in Example 1, except that the nano powder is nano magnesium oxide with an average particle size of 50 nm.

[0077] Examples 11 to 15

[0078] The preparation method of the polypropylene material in this embodiment is basically the same as that in Example 1, except for the raw material ratio, as shown in Table 1.

[0079] Table 1 Different ratios of raw materials

[0080]

[0081] Examples 16 to 20

[0082] The raw material ratio of the polypropylene material preparation method of this embodiment is basically the same as that of Example 1, except for the preparation conditions, which are shown in Table 2 for details.

[0083] Table 2 Differences in preparation conditions

[0084]

[0085] Comparative Example 1

[0086] The preparation method of the polypropylene material in this comparative example is basically the same as that in Example 1, except that the modification step is not included.

[0087] Comparative Example 2

[0088] The preparation method of the polypropylene material in this comparative example is basically the same as that in Example 2, except that the modification step is not included.

[0089] Comparative Example 3

[0090] The preparation method of the polypropylene material in this comparative example is basically the same as that in Example 3, except that the modification step is not included.

[0091] Comparative Example 4

[0092] The preparation method of the polypropylene material in this comparative example is basically the same as that in Example 4, except that the modification step is not included.

[0093] Comparative Analysis

[0094] The micromorphology of the polypropylene materials obtained in Example 3 and Comparative Example 3 was observed using a scanning electron microscope (SEM, Hitachi, S-4800). Figure 2 As shown in the figure, it can be found that the interface compatibility between the unmodified nano-alumina and the polypropylene matrix is poor, and there are obvious gaps and nano-aggregates inside (such as the area in the red circle in the figure), which will lead to obvious local defects, thereby causing electric field distortion, heat accumulation, etc. under the electric field, thereby causing electrical tree breakdown; while the nano-powder modified with dopamine is evenly distributed in the composite insulation material and no obvious agglomeration phenomenon is observed, as shown in the figure. Figure 2As shown on the right, the good interfacial compatibility between the modified filler and the matrix can enhance interfacial polarization and effectively suppress local electric field distortion, thereby strengthening the material's breakdown field strength and interfacial phonon transmission efficiency, achieving electrothermal synergistic optimization.

[0095] A spherical electrode breakdown system was used to test the breakdown field strength of the samples in an insulating oil environment at room temperature. An electronic universal testing machine was used to test the tensile properties of the insulating materials prepared under different conditions. A laser thermal conductivity meter was used to test the effective thermal conductivity of the materials. The test results are shown in Table 3.

[0096] Table 3 Test results

[0097]

[0098] Compared to Comparative Examples 1-4, the modified multi-component modified environmentally friendly polypropylene insulation materials in Examples 1-4 exhibited higher breakdown field strength and tensile strength. When the filler mass fraction was 1%, the breakdown field strength of the composite insulation material containing the modified alumina nanopowder increased from 312 kV / mm to 377 kV / mm, the tensile strength increased from 15.8 MPa to 25.5 MPa, and the effective thermal conductivity increased from 0.234 W / (m·K) to 0.254 W / (m·K). The main reasons are: ① The polydopamine surface is rich in functional groups such as catechol, hydroxyl, and amino groups, which can react with the hydroxyl groups on the surface of the nanoparticles to form hydrogen bonds, thereby firmly adhering to the powder surface and significantly reducing the van der Waals forces between the powders. This effectively promotes the dispersion of the modified powder in the polypropylene matrix and avoids the formation of agglomeration defects. ② The polydopamine-coated nanopowder contains a benzene ring structure. The π electron cloud on the benzene ring can interact with the electron cloud on the surface of the non-polar material, generating a π sub-cloud stacking interaction force, thereby enhancing the interfacial adsorption between the powder and the matrix. ③ The high energy and activity of the polydopamine-coated powder can promote the aggregation and crystallization of the block polypropylene molecular chains on its surface, reducing the size and increasing the number of β-spherulites. The spherulites collide and inhibit each other, ultimately resulting in a spherulite morphology with higher crystallinity and a more regular crystal structure. The improved crystal morphology, effectively enhanced interfacial compatibility, and uniform filler dispersion structure are the key to synergistically improving the material's breakdown field strength, mechanical toughness, and effective thermal conductivity.

[0099] Comparing Example 3 with Examples 5-6, it is found that the insulation material with the block polypropylene base material formula has better breakdown field strength and mechanical properties than isotactic polypropylene and syndiotactic polypropylene. This is because the unique β crystal form of the block polypropylene base material is the main factor in improving its performance.

[0100] Comparing Example 3 with Examples 7-8 reveals that when using smaller nanopowders, increasing the amount of filler at the same filler mass results in more two-phase interfaces, leading to defects, a decrease in the phonon free path, and a reduction in the electrical and thermal properties of the material. Larger particle sizes significantly reduce the ability to form β-crystals, which also reduces the material's overall breakdown strength and thermal conductivity. However, the tensile properties of the small-particle powder composite insulation material are superior to those of the larger-particle insulation material. This is likely due to the larger number of two-phase interfaces created by small-particle powders, which strengthens the interfacial forces and thus improves the material's tensile strength and elongation at break.

[0101] Comparing Example 3 with Examples 9-10, it is found that, relatively speaking, the effect of aluminum oxide is greater than that of boron carbide and magnesium oxide. This is because aluminum oxide has the most regular spherical structure and the relative density closest to that of polypropylene, which can promote the dispersion ability and interfacial bonding of the filler in the base material. The two-dimensional sheet structure of boron nitride and the irregular structure of magnesium oxide will increase the difficulty of uniform filling of the powder, thereby reducing the electrical and thermal properties of the material. In addition, the comprehensive performance of boron nitride-filled insulating materials is better than that of magnesium oxide-filled insulating materials. This may be because the external forces such as hot pressing and extrusion of the tablet press during the sample preparation process promote the regular orientation of boron nitride, thereby greatly reducing interface defects and optimizing the internal structure, greatly improving the electrical, mechanical and thermal properties of the material.

[0102] Examples 11 to 20 vary the raw material composition and ratio, as well as the preparation conditions within the scope of the present invention. The results show that the breakdown performance, mechanical flexibility, and thermal properties of the obtained polypropylene materials all meet the requirements.

[0103] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A multinary modified polypropylene composition, characterized in that: The composition comprises the following components in parts by weight: 50-80 parts of base resin, 20-40 parts of modified resin, 0.5-2 parts of antioxidant, 0.1-2 parts of nano powder, and 0.1-0.6 parts of modifier; The base resin is one or more of isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), atactic polypropylene (aPP), segmented polypropylene (PP-B), and rubber copolymer polypropylene (PP-R); The modified resin is one or more of ethylene-octene copolymer (EOC), polyolefin elastomer (POE), metallocene polypropylene (MAO-PP), ethylene-butene copolymer (SEBS), styrene-isoprene-styrene (SIS), and high-density polyethylene (HDPE); The modifier is dopamine.

2. The multinary modified polypropylene composition according to claim 1, characterized in that The nano powder is one or more of nano aluminum oxide, nano boron nitride, nano magnesium oxide, nano zinc oxide, nano titanium dioxide, and nano silicon carbide.

3. The multinary modified polypropylene composition according to claim 2, characterized in that The particle size of the nano powder is 50 to 500 nm.

4. The multinary modified polypropylene composition according to claim 1, characterized in that The base resin is a propylene-ethylene block copolymer.

5. The multinary modified polypropylene composition according to claim 4, characterized in that The ethylene content of the propylene-ethylene block copolymer is 5% to 20%.

6. The multinary modified polypropylene composition according to claim 1, characterized in that The antioxidant is one or more of antioxidant 300, antioxidant 1076, antioxidant 1035, antioxidant 1330 and antioxidant 802.

7. A method for preparing a multinary modified polypropylene material using the composition according to any one of claims 1 to 6, characterized in that: The following steps are involved: Nanopowder pretreatment: The nanopowder is heated and dried in a vacuum environment to obtain dry powder; Nanopowder modification: adding a modifier dropwise to the dispersion, mixing uniformly to obtain a modifier solution, adding the dry powder, ultrasonically treating and stirring at high speed, washing several times, filtering, and freeze-drying to obtain modified nanopowder; Preparation of powder-filled elastomer: uniformly mixing the modified nanopowder and modified resin to obtain a powder-filled elastomer; Granulation: the powder is filled with elastomer, base resin and antioxidant and extruded and granulated at a temperature of 150-220° C. to obtain the polypropylene material.

8. The preparation method according to claim 7, characterized in that The nano powder pretreatment specifically includes: placing the nano powder in a vacuum drying oven, heating the nano powder in a temperature range of 50 to 300° C., and treating the nano powder for 6 to 12 hours to obtain dry powder.

9. The preparation method according to claim 7, characterized in that In the nanopowder modification step, the dispersion is prepared by mixing deionized water and anhydrous ethanol in a volume ratio of 4:1; the mass concentration of the modifier solution is 2-10% and the pH is 7-10.

10. The preparation method according to claim 7, characterized in that In the nanopowder modification step, the ultrasonic treatment temperature is 20-40° C., and the time is 0.5-2 h; the stirring temperature is 20-80° C., and the stirring time is 6-48 h; and the freeze-drying time is 24-48 h.

11. The preparation method according to claim 7, characterized in that In the step of preparing the powder-filled elastomer, the modified nanopowder and the modified resin are uniformly mixed in a mixer. The stirring temperature of the mixer is 150-190° C., the mixer speed is 600-1000 rpm, and the stirring time is 10-15 minutes.

12. The preparation method according to claim 7, characterized in that In the granulation step, a twin-screw extruder is used to extrude long strips, the extrusion temperature range is 150-220° C., and the extrusion speed is 40-200 rpm.

13. The preparation method according to claim 12, characterized in that After the long strips are extruded by a twin-screw extruder, they are cooled and pelletized underwater. The underwater pelletizing temperature is 20°C and the pellet diameter is 1 to 2 mm.

14. The preparation method according to claim 12, characterized in that The filter screen combination of the twin-screw extruder is: 40 / 80 / 200 / 100 / 40 mesh, and the material is stainless steel.

15. A multinary modified polypropylene material prepared by the composition according to any one of claims 1 to 6 or the preparation method according to any one of claims 7 to 14.

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