Polypropylene material, method for preparing the same and use thereof

Abstract

The application relates to a kind of polypropylene material and its preparation method and application, belong to the technical field of polymer material modification, overcome the problem that the mechanical property and high transmittance of polypropylene material in prior art are difficult to consider simultaneously.The raw material of the polypropylene material includes, by weight parts: 40-90 parts of polypropylene, 0.5-5 parts of maleic anhydride grafted polypropylene, 5-15 parts of modified magnesium sulfate whisker, 0.2-1.0 parts of transparent nucleating agent, 5-15 parts of toughening agent, 0.2-0.8 parts of antioxidant;The modified magnesium sulfate whisker is the magnesium sulfate whisker modified by dispersant, surfactant and gamma-aminopropyl triethoxysilane.The polypropylene material has higher transmittance and mechanical property simultaneously.

Description

Technical Field

[0001] This invention belongs to the field of polymer material modification technology, specifically relating to a polypropylene material, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of the automotive industry, the proportion of new energy vehicles has been increasing. Compared with traditional gasoline vehicles, new energy vehicles have undergone significant changes in their power systems, and intelligence and technology have become major distinguishing features. Traditional car bumper materials mainly serve as energy-absorbing and protective materials when a car is impacted, improving the vehicle's safety factor. The development of new energy vehicles is no longer limited to this; while fulfilling the protective function, materials need to be given new roles. For example, while meeting safety performance requirements, materials can be made to have a certain degree of light transmission, allowing for the design of unique patterns or logos, and the placement of backlighting components behind them, thus presenting a cool, intelligent, and technological feel.

[0003] Existing bumper materials improve their mechanical properties by adding whiskers to a polypropylene matrix, but this results in poor light transmission. Without whiskers, the mechanical properties are poor, making it difficult to provide protection. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the difficulty in achieving both mechanical properties and high light transmittance of polypropylene materials in the prior art, thereby providing a polypropylene material, its preparation method and application.

[0005] To this end, the present invention provides the following technical solution.

[0006] In a first aspect, the present invention provides a polypropylene material, wherein the raw materials comprise, by weight, the following:

[0007] 40-90 parts polypropylene, 0.5-5 parts maleic anhydride-grafted polypropylene, 5-15 parts modified magnesium sulfate whiskers, 0.2-1.0 parts transparent nucleating agent, 5-15 parts toughening agent, 0.2-0.8 parts antioxidant;

[0008] The modified magnesium sulfate whiskers are magnesium sulfate whiskers modified with dispersant, surfactant and γ-aminopropyltriethoxysilane.

[0009] Furthermore, the preparation method of the modified magnesium sulfate whiskers includes:

[0010] S1: Mix magnesium sulfate whiskers, water and dispersant, adjust the pH to 4-6, react, then separate the solid and liquid, wash and dry the solid to obtain pre-dispersed magnesium sulfate whiskers;

[0011] S2: Pre-dispersed magnesium sulfate whiskers, surfactant, γ-aminopropyltriethoxysilane and solvent are mixed and reacted, then the solid and liquid are separated, and the solid is washed and dried to obtain modified magnesium sulfate whiskers.

[0012] Furthermore, the method for preparing the modified magnesium sulfate whiskers satisfies at least one of the following conditions:

[0013] (1) In S2, the mass ratio of pre-dispersed magnesium sulfate whiskers, surfactant and γ-aminopropyltriethoxysilane is (100-300):(0.1-0.5):(5-25), preferably (100-200):(0.1-0.3):(15-25);

[0014] (2) The reaction conditions for S2 are: reacting at a temperature of 60-80℃ for 12-24 hours;

[0015] (3) The reaction atmosphere of S2 is nitrogen;

[0016] (4) The step of mixing the pre-dispersed magnesium sulfate whiskers, surfactant, γ-aminopropyltriethoxysilane and solvent in S2 includes: first, adding the pre-dispersed magnesium sulfate whiskers to the solvent and dispersing them by ultrasonication, and then adding the surfactant and γ-aminopropyltriethoxysilane; ultrasonication can further disperse the pre-dispersed magnesium sulfate whiskers, so that the substances added later can have a more complete contact reaction.

[0017] Optionally, the ultrasonic dispersion time is 0.25 to 0.75 hours;

[0018] Optionally, the solvent is anhydrous ethanol.

[0019] Furthermore, the method for preparing the modified magnesium sulfate whiskers satisfies at least one of the following conditions:

[0020] (1) In S1, the step of mixing magnesium sulfate whiskers, water and dispersant includes: adding magnesium sulfate whiskers to water and dispersing them ultrasonically, and then adding the dispersant;

[0021] Optionally, the ultrasonic dispersion time is 0.5–1.0 h;

[0022] (2) The reaction conditions in S1 are to react at a temperature of 50-70℃ for 1-3 hours;

[0023] (3) In S1, the mass of the dispersant is 5.0 to 10.0% of the mass of magnesium sulfate whiskers;

[0024] (4) In S1, the aspect ratio of the magnesium sulfate whiskers is >30, preferably 35-100.

[0025] Furthermore, at least one of the following conditions must be met:

[0026] (1) The dispersant is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide and tetrapropylammonium hydroxide;

[0027] (2) The surfactant is selected from at least one of sodium dodecyl sulfonate (SDS), sodium dodecyl sulfate and sodium stearate.

[0028] Furthermore, the melt flow rate of the maleic anhydride-grafted polypropylene is >15 g / 10 min, and the maleic anhydride grafting rate is 0.5% to 2.0%.

[0029] Furthermore, the polypropylene is selected from one or more of homopolymer polypropylene and copolymer polypropylene;

[0030] Optionally, the polypropylene is compounded from high-stiffness homopolymer polypropylene and random copolymer polypropylene in a mass ratio of (30-50):(20-40).

[0031] The high-rigidity homopolymer polypropylene resin has a melt flow rate of 5-100 g / 10 min and a flexural modulus >1800 MPa.

[0032] The random copolymer polypropylene is a polymer obtained by random copolymerization of propylene and ethylene, with a melt flow rate of 1 to 10 g / 10 min.

[0033] Furthermore, at least one of the following conditions must be met:

[0034] (1) The transparent nucleating agent is selected from one or more of carboxylic acid metal salt nucleating agents, sorbitol nucleating agents, and aryl phosphate nucleating agents;

[0035] (2) The toughening agent is selected from one or more of vinyl-polydiene-styrene block copolymer, styrene-ethylene-butadiene-styrene copolymer, ethylene-octene copolymer, and ethylene-butene copolymer;

[0036] (3) The antioxidant is selected from one or more of hindered phenolic antioxidants, hindered amine antioxidants, phosphite antioxidants, thiodipropionate antioxidants, and thiol antioxidants, preferably hindered phenolic antioxidants and phosphite antioxidants;

[0037] Preferably, the mass ratio of hindered phenolic antioxidant to phosphite antioxidant is (0.1-0.3):(0.1-0.3).

[0038] Secondly, the present invention provides a method for preparing a polypropylene material, characterized by comprising the following steps:

[0039] S1: Add each raw material component to a high-speed mixer according to the formula and mix.

[0040] S2: Add the premixed material from step S1 to a twin-screw extruder, melt-blend, and extrude granulate to obtain the polypropylene material;

[0041] Optionally, the mixing conditions for the high-speed mixer are: a speed of 600–1000 r / min and a mixing time of 2–5 min;

[0042] Optionally, the twin-screw extruder has a temperature of 180℃ to 220℃ and a screw speed of 500 to 900 r / min.

[0043] Thirdly, the present invention provides a bumper comprising the aforementioned polypropylene material or polypropylene material prepared according to the aforementioned method.

[0044] The technical solution of this invention has the following advantages:

[0045] 1. The polypropylene material raw materials of the present invention comprise, by weight, 40-90 parts polypropylene, 0.5-5 parts maleic anhydride-grafted polypropylene, 5-15 parts modified magnesium sulfate whiskers, 0.2-1.0 parts transparent nucleating agent, 5-15 parts toughening agent, and 0.2-0.8 parts antioxidant; wherein the modified magnesium sulfate whiskers are magnesium sulfate whiskers modified by dispersant, surfactant and γ-aminopropyltriethoxysilane.

[0046] This invention employs a dispersant, a surfactant, and γ-aminopropyltriethoxysilane to modify magnesium sulfate whiskers. The dispersant adsorbs onto the surface of the magnesium sulfate whiskers, significantly improving their dispersibility under electrostatic repulsion and preventing agglomeration. This promotes the amination modification of the magnesium sulfate whiskers by the surfactant and γ-aminopropyltriethoxysilane. The amination modification allows the anhydride groups on the maleic anhydride-grafted polypropylene in the formulation to undergo an interfacial compatibilization reaction with the -NH2 groups on the surface of the magnesium sulfate whiskers. This further improves the dispersibility and compatibility of the magnesium sulfate whiskers in the matrix, resulting in polypropylene materials with both high light transmittance and mechanical properties.

[0047] Furthermore, the modified magnesium sulfate whiskers have a needle-like structure, which acts as a support in the material, restricting the movement of polymer molecules during the heating process, thereby improving the thermal stability of the material.

[0048] 2. Polypropylene is a compound of high-strength homopolymer polypropylene and random copolymer polypropylene in a mass ratio of (30-50):(20-40);

[0049] High-rigidity polypropylene (PP) has a high modulus, while random PP has high toughness. When combined, the high rigidity and high heat resistance of high-rigidity homopolymer polypropylene are utilized to improve the material's heat resistance and rigidity. Combined with a transparent nucleating agent to reduce the grain size of spherulites, the light transmittance is further increased, resulting in polypropylene materials with excellent comprehensive properties such as light transmittance, toughness, and rigidity.

[0050] 3. The mass ratio of pre-dispersed magnesium sulfate whiskers, surfactant, and γ-aminopropyltriethoxysilane is (100–200):(0.1–0.3):(15–25). Within this range, the dispersibility of modified magnesium sulfate whiskers in the material and its compatibility with the matrix are optimal, thereby promoting the overall rigidity, toughness, and light transmittance of the polypropylene material to reach their best. Detailed Implementation

[0051] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0052] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0053] The main testing methods involved in the following embodiments of the present invention are as follows:

[0054] <1> Mechanical property testing:

[0055] Bending performance: Tested using a ZWICK Z010 universal testing machine according to ISO 178:2019 standard;

[0056] Cantilever beam notched impact: Tested using a ZWICK HIT25P impact testing machine according to ISO 180:2019 standard.

[0057] <2> Transmittance test: Using an X-Rite desktop CI7860 colorimeter, 2mm and 3mm color samples from injection molded scales were tested in transmission mode according to the ASTM D1003-2013 standard.

[0058] <3> Load heat distortion temperature test: The test was conducted using an INSTRON HV6M thermal analyzer at a pressure of 0.45 MPa, in accordance with the ISO 75-2:2013 standard.

[0059] <4> Shrinkage test: The extruded particles were injection molded into 350*70*3mm sheets using a single screw injection molding machine, and conditioned under constant temperature and humidity conditions for 48 hours. The dimensional changes were then detected using a gauge.

[0060] The main raw material information in the following embodiments of the present invention is as follows:

[0061] (1)PP-6012: High-rigidity homopolymer polypropylene, melt flow rate of 10g / 10min (230℃, 2.16kg), Tianjin Petrochemical;

[0062] (2)PP-M60T: High-rigidity homopolymer polypropylene, melt flow rate of 60g / 10min (230℃, 2.16kg), Zhenhai Refining & Chemical.

[0063] (3) QCT02N: Random copolymer polypropylene, melt flow rate of 5g / 10min (230℃, 2.16kg), Ningqilu Petrochemical;

[0064] (4) 5012XT: Random copolymer polypropylene, melt flow rate of 3g / 10min (230℃, 2.16kg), Ningbo Formosa Plastics;

[0065] (5) WS-152: Magnesium sulfate whiskers, diameter 1.0 μm, L / D = 50, Kangru Technology Co., Ltd.;

[0066] (6) GPM200A: Maleic anhydride grafted polypropylene, melt flow rate of 144g / 10min (230℃, 2.16kg), grafting rate of 0.8%, Ningbo Guangzhi Energy New Material Technology Co., Ltd.

[0067] (7) Polybond7200: Maleic anhydride-grafted polypropylene, melt flow rate of 250 g / 10 min (230 °C, 2.16 kg), grafting rate of 2.0%, from Kotria Corporation, USA;

[0068] (8) SEBS1657M: Toughening agent, styrene-ethylene-butene-styrene, melt flow rate of 20g / 10min (230℃, 2.16kg), Kraton Polymers, Inc., USA;

[0069] (9) SEBS6014: Toughening agent, styrene-ethylene-butene-styrene polymer, melt flow rate of 5 g / 10 min (230℃, 2.16 kg), TSRC;

[0070] (10) SEBS7311F: Toughening agent, styrene-ethylene-butene-styrene polymer, melt flow rate of 1g / 10min (230℃, 2.16kg), Kuraray International Trading (Shanghai) Co., Ltd.;

[0071] (11) NX8000: Transparent nucleating agent, Meiliken Chemical Co., Ltd.;

[0072] (12) N04GT: Transparent nucleating agent, Ningbo Hengze Chemical Co., Ltd.;

[0073] (13) SunShow1010: Antioxidant, Lianlong New Materials Co., Ltd.;

[0074] (14) SunShow168: Antioxidant, Lianlong New Materials Co., Ltd.;

[0075] Unless otherwise specified, all other raw materials and reagents were purchased through commercial channels.

[0076] Preparation Example 1

[0077] The preparation method of modified magnesium sulfate whiskers A is as follows:

[0078] 1) Disperse 30g of magnesium sulfate whiskers WS-152 in 1500g of deionized water, add 1.5g of tetramethylammonium hydroxide (5% of magnesium sulfate whiskers), adjust the pH to 5 with dilute hydrochloric acid, react in a constant temperature water bath at 60℃ for 2h, and obtain pre-dispersed magnesium sulfate whiskers after filtration, washing and drying.

[0079] 2) Disperse 30g of pre-dispersed magnesium sulfate whiskers in 1000g of anhydrous ethanol solution, and sonicate in an ultrasonic cleaner for 0.75h. Slowly add sodium dodecyl sulfonate and γ-aminopropyltriethoxysilane (the mass ratio of pre-dispersed magnesium sulfate whiskers: sodium dodecyl sulfonate: γ-aminopropyltriethoxysilane is 100:0.3:20), and react in a constant temperature water bath at 70℃ for 24h. After filtration, washing and drying, modified magnesium sulfate whiskers A are obtained.

[0080] Preparation Example 2

[0081] The preparation method of modified magnesium sulfate whiskers B is as follows:

[0082] 1) Disperse 30g of magnesium sulfate whiskers WS-152 in 1500g of deionized water, add 3g of tetraethylammonium hydroxide (10% of magnesium sulfate whiskers), adjust the pH to 6 with dilute hydrochloric acid, react in a constant temperature water bath at 70℃ for 1h, and obtain pre-dispersed magnesium sulfate whiskers after filtration, washing and drying.

[0083] 2) Disperse 30g of pre-dispersed magnesium sulfate whiskers in 1000g of anhydrous ethanol solution, and sonicate in an ultrasonic cleaner for 0.45h. Slowly add sodium dodecyl sulfate and γ-aminopropyltriethoxysilane (the mass ratio of pre-dispersed magnesium sulfate whiskers: sodium dodecyl sulfate: γ-aminopropyltriethoxysilane is 200:0.2:15), and react in a constant temperature water bath at 60℃ for 12h. After filtration, washing and drying, modified magnesium sulfate whiskers B are obtained.

[0084] Preparation Example 3

[0085] The preparation method of modified magnesium sulfate whiskers C is as follows:

[0086] 1) Disperse 30g of magnesium sulfate whiskers WS-152 in 1500g of deionized water, add 2.4g of tetrapropylammonium hydroxide (8% of magnesium sulfate whiskers), adjust the pH to 4 with dilute hydrochloric acid, react in a constant temperature water bath at 50℃ for 3h, and obtain pre-dispersed magnesium sulfate whiskers after filtration, washing and drying.

[0087] 2) Disperse 30g of pre-dispersed magnesium sulfate whiskers in 1000g of anhydrous ethanol solution, and sonicate in an ultrasonic cleaner for 0.25h. Slowly add sodium stearate and γ-aminopropyltriethoxysilane (the mass ratio of pre-dispersed magnesium sulfate whiskers: sodium stearate: γ-aminopropyltriethoxysilane is 150:0.1:25), and react in a constant temperature water bath at 80℃ for 18h. After filtration, washing and drying, modified magnesium sulfate whiskers C are obtained.

[0088] Preparation Example 4

[0089] The preparation method of modified magnesium sulfate whiskers D is basically the same as that in Example 1, except that the mass ratio of pre-dispersed magnesium sulfate whiskers: sodium dodecyl sulfonate: γ-aminopropyltriethoxysilane is 300:0.5:5.

[0090] Preparation of Comparative Example 1

[0091] The preparation method of modified magnesium sulfate whiskers E is as follows:

[0092] 1) Disperse 30g of magnesium sulfate whiskers WS-152 in 1500g of deionized water, add 1.5g of tetramethylammonium hydroxide (5% of magnesium sulfate whiskers), adjust the pH to 5 with dilute hydrochloric acid, react in a constant temperature water bath at 60℃ for 2h, and obtain modified magnesium sulfate whiskers E after filtration, washing and drying.

[0093] Preparation of Comparative Example 2

[0094] The preparation method of modified magnesium sulfate whiskers F is as follows:

[0095] 1) Disperse 30g of magnesium sulfate whiskers WS-152 in 1000g of anhydrous ethanol solution, and sonicate in an ultrasonic cleaner for 0.75h. Slowly add sodium dodecyl sulfonate and γ-aminopropyltriethoxysilane (the mass ratio of magnesium sulfate whiskers: sodium dodecyl sulfonate: γ-aminopropyltriethoxysilane is 100:0.3:20), and react in a constant temperature water bath at 70℃ for 24h. After filtration, washing and drying, modified magnesium sulfate whiskers F are obtained.

[0096] Example

[0097] The polypropylene material of the preparation example was prepared according to the proportions shown in Table 1 (the amount of each component in the table is expressed in parts by weight). The preparation process is as follows:

[0098] Weigh each raw material according to the weight proportions shown in the table below, then put them into a high-speed mixer. Mix the materials at a certain time and speed, and then put them into a twin-screw extruder. Extrusion granulation is carried out at a specified temperature and speed to obtain polypropylene material.

[0099] Example 5 is basically the same as Example 1, except that in Example 5, all polypropylene used is high-stiffness homopolymer polypropylene, and no random copolymer polypropylene is added.

[0100] Table 1. Raw material ratios and processing conditions for Examples 1-5

[0101]

[0102]

[0103] The comparative polypropylene material was prepared according to the proportions shown in Table 2. The preparation process is as follows: each raw material was weighed according to the weight parts shown in Table 2, and then put into a high-speed mixer. After mixing the materials at a certain time and speed, the mixture was put into a twin-screw extruder and extruded and granulated at a specified temperature and speed to obtain the polypropylene material.

[0104] Comparative Example 1

[0105] This comparative example is basically the same as Example 1, except that the modified magnesium sulfate whiskers A are replaced with modified magnesium sulfate whiskers E.

[0106] Comparative Example 2

[0107] This comparative example is basically the same as Example 1, except that the modified magnesium sulfate whiskers A are replaced with modified magnesium sulfate whiskers F.

[0108] Comparative Example 3

[0109] This comparative example is basically the same as Example 1, except that the modified magnesium sulfate whiskers A are replaced with unmodified magnesium sulfate whiskers WS-152.

[0110] Comparative Example 4

[0111] This comparative example is basically the same as Example 1, except that modified magnesium sulfate whiskers A were not added, and were replaced with an equal amount of random copolymer polypropylene 5012XT.

[0112] Comparative Example 5

[0113] This comparative example is basically the same as Example 1, except that maleic anhydride-grafted polypropylene was not added, and it was replaced with an equal amount of random copolymer polypropylene 5012XT.

[0114] Table 2 Raw material ratios and processing conditions for Comparative Examples 1-5

[0115]

[0116] The polypropylene materials obtained in Examples 1-5 and Comparative Examples 1-5 were subjected to performance tests, and the results are shown in Tables 3 and 4 below.

[0117] Table 3 Performance test results of each embodiment

[0118]

[0119] HDT stands for Heat Deflection Temperature.

[0120] Table 4. Performance test results of each comparative example

[0121]

[0122] Comparative Example 4 shows that the polypropylene material without magnesium sulfate whiskers has very poor mechanical properties. Comparative Example 3 shows that although the mechanical properties of the polypropylene material with added unmodified magnesium sulfate whiskers are improved, its light transmittance is significantly reduced. Although Comparative Examples 1 and 2 modified the magnesium sulfate whiskers to some extent, their improvement on light transmittance was limited.

[0123] As can be seen from the comparison of data from the embodiments and comparative examples, the optical performance of this application is significantly improved compared to the comparative examples, and its mechanical properties are also improved to a certain extent, while taking into account both mechanical properties and light transmittance.

[0124] Comparing Example 1 with Comparative Examples 3 and 5, it can be seen that the rigidity, toughness, light transmittance, heat resistance, and dimensional stability of the material in Example 1 are greatly improved. This indicates that after two-step modification, the -NH2 on the whiskers and the anhydride groups on the maleic anhydride-grafted polypropylene undergo an interfacial compatibilization reaction, which greatly improves the dispersibility of magnesium sulfate in the material and its compatibility with the matrix.

[0125] Comparing Examples 1-3 with Example 4, it can be seen that when the mass ratio of pre-dispersed magnesium sulfate whiskers, surfactant and γ-aminopropyltriethoxysilane is in the range of (100-200):(0.1-0.3):(15-25), the polypropylene material has higher rigidity, toughness and light transmittance.

[0126] Comparing Example 1 and Example 5, it can be seen that using a blend of high-rigidity polypropylene and random copolymer polypropylene can further improve the toughness and light transmittance of the material.

[0127] As shown in Table 3, the polypropylene material prepared by this invention has high light transmittance, high mechanical properties, and high heat resistance.

[0128] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A polypropylene material, characterized in that, The raw materials, by weight, include: 40-90 parts polypropylene, 0.5-5 parts maleic anhydride-grafted polypropylene, 5-15 parts modified magnesium sulfate whiskers, 0.2-1.0 parts transparent nucleating agent, 5-15 parts toughening agent, 0.2-0.8 parts antioxidant; The modified magnesium sulfate whiskers are magnesium sulfate whiskers modified with dispersant, surfactant and γ-aminopropyltriethoxysilane; The mass ratio of magnesium sulfate whiskers, surfactant, and γ-aminopropyltriethoxysilane is (100~200):(0.1~0.3):(15~25); The polypropylene is compounded from high-rigidity homopolymer polypropylene and random copolymer polypropylene in a mass ratio of (30~50):(20~40); the high-rigidity homopolymer polypropylene resin has a melt flow rate of 5~100g / 10min and a flexural modulus >1800MPa; the random copolymer polypropylene is a polymer obtained by random copolymerization of propylene and ethylene, with a melt flow rate of 1~10g / 10min. The dispersant is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide; The surfactant is selected from at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, and sodium stearate.

2. The polypropylene material according to claim 1, characterized in that, The method for preparing the modified magnesium sulfate whiskers includes: S1: Mix magnesium sulfate whiskers, water and dispersant, adjust the pH to 4-6, react, then separate the solid and liquid, wash and dry the solid to obtain pre-dispersed magnesium sulfate whiskers; S2: Pre-dispersed magnesium sulfate whiskers, surfactant, γ-aminopropyltriethoxysilane and solvent are mixed and reacted, then the solid and liquid are separated, and the solid is washed and dried to obtain modified magnesium sulfate whiskers.

3. The polypropylene material according to claim 2, characterized in that, The method for preparing the modified magnesium sulfate whiskers satisfies at least one of the following conditions: (1) The reaction conditions for S2 are: reacting at a temperature of 60~80℃ for 12~24h; (2) The reaction atmosphere of S2 is nitrogen; (3) The step of mixing the pre-dispersed magnesium sulfate whiskers, surfactant, γ-aminopropyltriethoxysilane and solvent in S2 includes: first, adding the pre-dispersed magnesium sulfate whiskers to the solvent and ultrasonically dispersing them, and then adding the surfactant and γ-aminopropyltriethoxysilane.

4. The polypropylene material according to claim 3, characterized in that, The ultrasonic dispersion time is 0.25~0.75h.

5. The polypropylene material according to claim 3, characterized in that, The solvent is anhydrous ethanol.

6. The polypropylene material according to claim 2, characterized in that, The method for preparing the modified magnesium sulfate whiskers satisfies at least one of the following conditions: (1) In S1, the step of mixing magnesium sulfate whiskers, water and dispersant includes: adding magnesium sulfate whiskers to water and ultrasonically dispersing them, and then adding the dispersant; (2) The reaction conditions in S1 are to react at a temperature of 50~70℃ for 1-3 hours; (3) In S1, the mass of the dispersant is 5.0~10.0% of the mass of magnesium sulfate whiskers; (4) In S1, the aspect ratio of the magnesium sulfate whiskers is >30.

7. The polypropylene material according to claim 6, characterized in that, In S1, the ultrasonic dispersion time is 0.5~1.0h.

8. The polypropylene material according to claim 6, characterized in that, The magnesium sulfate whiskers have an aspect ratio of 35-100.

9. The polypropylene material according to any one of claims 1-8, characterized in that, The maleic anhydride-grafted polypropylene has a melt flow rate >15g / 10min and a maleic anhydride grafting rate of 0.5%~2.0%.

10. The polypropylene material according to any one of claims 1-8, characterized in that, At least one of the following conditions must be met: (1) The transparent nucleating agent is selected from one or more of carboxylic acid metal salt nucleating agents, sorbitol nucleating agents, and aryl phosphate nucleating agents; (2) The toughening agent is selected from one or more of vinyl-polydiene-styrene block copolymer, styrene-ethylene-butadiene-styrene copolymer, ethylene-octene copolymer, and ethylene-butene copolymer; (3) The antioxidant is selected from one or more of the following: hindered phenolic antioxidants, hindered amine antioxidants, phosphite antioxidants, thiodipropionate antioxidants, and thiol antioxidants.

11. The polypropylene material according to claim 10, characterized in that, The antioxidants are hindered phenolic antioxidants and phosphite antioxidants.

12. The polypropylene material according to claim 11, characterized in that, The mass ratio of hindered phenolic antioxidants to phosphite antioxidants is (0.1-0.3):(0.1-0.3).

13. A method for preparing the polypropylene material according to any one of claims 1-12, characterized in that, Includes the following steps: S1: Add each raw material component to a high-speed mixer according to the formula and mix. S2: Add the premixed material from step S1 to a twin-screw extruder, melt-blend, and extrude granulate to obtain the polypropylene material.

14. The method for preparing polypropylene material according to claim 13, characterized in that, The mixing conditions for a high-speed mixer are 600~1000 r / min and 2~5 min.

15. The method for preparing polypropylene material according to claim 13, characterized in that, The twin-screw extruder operates at a temperature of 180℃~220℃ and a screw speed of 500~900 r / min.

16. A bumper, characterized in that, Includes the polypropylene material according to any one of claims 1-12 or the polypropylene material prepared by the method according to any one of claims 13-15.

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