Engine bottom guard plate and preparation method thereof

Abstract

The invention relates to the technical field of bottom protection plates, and provides an engine bottom protection plate and a preparation method thereof. The engine bottom protection plate is prepared from the following raw materials in parts by weight: 40 to 50 parts of polypropylene, 15 to 20 parts of glass fiber, 5 to 10 parts of silicon carbide modified carbon fiber, 5 to 9 parts of nano silicon dioxide, 2 to 3 parts of compatilizer, 0.5 to 1 part of antioxidant, 0.3 to 0.5 part of calcium stearate and 0.4 to 0.6 part of polyethylene wax. The engine bottom guard plate provided by the invention is high in hardness, also has certain acid and alkali resistance, keeps good mechanical properties, and meets the development of the modern automobile industry and the change of consumer demands.

Description

Technical Field

[0001] The present invention relates to the technical field of engine underbody shields, and specifically, to an engine underbody shield and a preparation method thereof. Background Art

[0002] The engine underbody shield, also known as the deflector, is usually an engine protection device designed according to various different vehicle models and installed at the bottom of the engine to prevent the engine from being damaged by external factors (such as road potholes, sand and stone impacts, etc.) during driving, thereby avoiding vehicle breakdowns. In addition, the engine underbody shield can also keep the engine compartment clean to a certain extent, prevent road surface water and dust from entering the engine compartment, and improve the operating efficiency of the engine. With the rapid development of the automotive industry and the continuous changes in consumer demands, the performance requirements for engine underbody shields are also getting higher and higher, including lightweight, high strength, impact resistance, noise reduction, and good heat dissipation performance, etc.

[0003] At present, the common materials for engine underbody shields on the market mainly include steel plates, aluminum alloys, hard plastic resins, and plastic steels. These materials are different in terms of weight, price, protection effect, etc. Among them, hard plastic resins have low cost and light weight, but the ability to protect against foreign object impacts is relatively weak. In addition, the existing underbody shields are restricted in material selection and it is difficult to meet the performance requirements in multiple aspects such as lightweight, high strength, impact resistance, and resistance to complex environments at the same time. Based on this, the present invention proposes an engine underbody shield and a preparation method thereof. Summary of the Invention

[0004] In order to solve the foregoing problems, the present invention proposes an engine underbody shield with high hardness, certain acid and alkali resistance, and good mechanical properties maintained at the same time.

[0005] The technical solution of the present invention is as follows: In a first aspect, the present invention proposes a high-strength mudguard, which comprises the following raw materials in parts by weight: 40 - 50 parts of polypropylene, 15 - 20 parts of glass fiber, 5 - 10 parts of silicon carbide modified carbon fiber, 5 - 9 parts of nano-silica, 2 - 3 parts of compatibilizer, 0.5 - 1 part of antioxidant, 0.3 - 0.5 part of calcium stearate, and 0.4 - 0.6 part of polyethylene wax.

[0006] As a further technical solution, the preparation method of the silicon carbide modified carbon fiber includes: mixing tetraethyl orthosilicate with ethanol and water, adding an aqueous hydrochloric acid solution, and stirring for 20 - 24 h under the condition of a rotation speed of 200 - 300 rpm to form a transparent sol; immersing 1 - 2 g of carbon fiber pretreated with nitric acid into 10 - 20 mL of the transparent sol, ultrasonicating for 30 - 40 min under the condition of 30 - 40 kHz, then drying under vacuum at 60 - 80 °C for 120 - 140 min, then heating to 500 - 600 °C at a rate of 3 - 5 °C / min under argon atmosphere, holding for 50 - 60 min, continuing to heat to 1100 - 1200 °C at a rate of 3 - 5 °C / min, holding for 50 - 60 min, and cooling to room temperature to obtain the product.

[0007] As a further technical solution, the preparation method of the pretreated carbon fiber includes: immersing the carbon fiber into acetone, ultrasonic cleaning for 30 - 40 min under the conditions of a power of 90 - 100 W and a frequency of 30 - 40 kHz, drying at 70 - 80 °C for 2 - 3 h, then immersing into an aqueous nitric acid solution with a mass concentration of 60 - 70%, treating at 75 - 85 °C for 50 - 70 min, rinsing with deionized water until neutral, and drying at 100 - 120 °C for 3 - 4 h to obtain the product.

[0008] As a further technical solution, the length of the glass fiber is 200 - 400 μm, and the diameter is 20 - 30 μm; the length of the carbon fiber is 3 - 5 mm, and the diameter is 7 - 9 μm.

[0009] As a further technical solution, the dosage ratio of tetraethyl orthosilicate, ethanol, water and the aqueous hydrochloric acid solution is 10 - 11 g : 18 - 20 g : 3 - 4 g : 5 - 6 mL.

[0010] As a further technical solution, the concentration of the aqueous hydrochloric acid solution is 0.1 - 0.2 M.

[0011] As a further technical solution, the compatibilizer is maleic anhydride grafted polypropylene.

[0012] As a further technical solution, the antioxidant is antioxidant 1010.

[0013] In the second aspect, the present invention provides a preparation method of a high-strength mudguard, and the steps include: mixing polypropylene, glass fiber, silicon carbide modified carbon fiber, nano - silica, compatibilizer, antioxidant, calcium stearate, and polyethylene wax under the condition of a rotation speed of 400 - 500 rpm for 5 - 15 min; performing melt blending through a twin - screw extruder, extruding and pelletizing, and molding to obtain an engine under - shield.

[0014] As a further technical solution, the temperature settings of the twin-screw extruder are as follows: Zone 1: 155 - 165 °C, Zone 2: 185 - 195 °C, Zone 3: 205 - 215 °C, and the die head temperature: 200 - 210 °C.

[0015] The working principle and beneficial effects of the present invention are as follows: In the present invention, the pretreatment of carbon fiber is a key step to improve the interfacial bonding strength with the matrix material. The present invention adopts a method combining ultrasonic cleaning with acetone and nitric acid oxidation treatment. Among them, ultrasonic cleaning with acetone effectively removes impurities such as grease and dust on the surface of carbon fiber by using the dissolution effect of the solvent and the cavitation effect of ultrasonic waves, providing a clean surface for subsequent treatment. The nitric acid oxidation treatment introduces oxygen-containing functional groups (such as carboxyl groups, hydroxyl groups, etc.) by oxidizing the carbon atoms on the surface of carbon fiber. These functional groups can form chemical bonds with the polar groups in the matrix material, thus significantly enhancing the interfacial bonding strength.

[0016] On the basis of the pretreatment, the present invention forms a silicon carbide coating on the surface of carbon fiber through a specific sol-gel method and heat treatment process. The sol-gel method uses the chemical reaction of tetraethyl orthosilicate, ethanol, water, and hydrochloric acid aqueous solution to form a transparent sol. After the carbon fiber is immersed in the sol, it undergoes ultrasonic treatment and vacuum drying, and then high-temperature heat treatment, finally forming a dense silicon carbide coating on the surface of carbon fiber. This coating not only improves the thermal expansion coefficient matching degree between carbon fiber and polypropylene matrix, reducing the interfacial stress caused by thermal expansion differences. This silicon carbide coating can also form a chemically inert protective layer, which can resist the erosion of harsh environments such as acids and alkalis, improve the acid-base retention rate of the material, and increase the surface roughness and activity of carbon fiber, which is beneficial to forming a stronger interfacial bond with the matrix material, thereby improving the overall mechanical properties of the material.

[0017] In the present invention, through the synergistic effect of the multi-dimensional reinforcement network, glass fiber has a relatively high modulus and can resist deformation under external force, providing a stable support structure for the fender; carbon fiber has extremely high strength and can withstand large tensile and compressive loads, complementing glass fiber and jointly improving the overall mechanical properties of the fender. Glass fiber and carbon fiber are intertwined and distributed in three-dimensional space to form a multi-dimensional reinforcement network, effectively dispersing and transmitting loads, and improving the impact resistance of the material.

[0018] In addition, the present invention also uses nano-silica as a heterogeneous nucleating agent, which can promote the refinement of grains in the polypropylene matrix, improve the crystallinity and mechanical properties of the material. Grain refinement can not only improve the strength and toughness of the material, but also help to improve the processing performance and heat resistance of the material. In addition, nano-silica particles can fill the interfacial defects between carbon fibers and the matrix material, reduce stress concentration points, and thus improve the overall strength and toughness of the material. This interfacial strengthening effect further enhances the overall performance of the composite material. Detailed implementation mode

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0020] It should be noted that in the present invention, the polypropylene model is k7003; the polyethylene wax model is GY-303.

[0021] Example 1 In this example, an engine underbody shield is provided, which includes the following raw materials in parts by weight: 45 parts of polypropylene, 17 parts of glass fiber, 8 parts of silicon carbide-modified carbon fiber, 7 parts of nano-silica, 2.5 parts of compatibilizer, 0.7 part of antioxidant, 0.4 part of calcium stearate, and 0.5 part of polyethylene wax.

[0022] Among them, the preparation method of the silicon carbide-modified carbon fiber includes: immersing the carbon fiber in acetone, ultrasonic cleaning for 35 min under the conditions of a power of 95 W and a frequency of 35 kHz, drying at 75 °C for 2.5 h, then immersing it in a nitric acid aqueous solution with a mass concentration of 65%, treating it at 80 °C for 60 min, rinsing with deionized water until neutral, and drying at 110 °C for 3.5 h to obtain the pretreated carbon fiber; mixing tetraethyl orthosilicate with ethanol and water, adding a hydrochloric acid aqueous solution with a concentration of 0.15 M, and stirring at a rotation speed of 250 rpm for 22 h to form a transparent sol; the dosage ratio of tetraethyl orthosilicate, ethanol, water, and hydrochloric acid aqueous solution is 10.5 g: 19 g: 3.5 g: 5.5 mL; immersing 1.5 g of the carbon fiber pretreated with nitric acid in 15 mL of the transparent sol, ultrasonicating at 35 kHz for 35 min, then drying at 70 °C under vacuum conditions for 130 min, then heating to 550 °C at a rate of 4 °C / min under argon conditions, holding for 55 min, continuing to heat to 1150 °C at a rate of 4 °C / min, holding for 55 min, and cooling to room temperature to obtain the product.

[0023] Among them, the glass fiber has a length of 300 μm and a diameter of 25 μm; the carbon fiber has a length of 4 mm and a diameter of 8 μm; the compatibilizer is maleic anhydride grafted polypropylene; the antioxidant is antioxidant 1010.

[0024] The preparation method of this engine underbody guard plate includes: mixing polypropylene, glass fiber, silicon carbide modified carbon fiber, nano-silica, compatibilizer, antioxidant, calcium stearate, and polyethylene wax for 10 min under the condition of a rotation speed of 450 rpm; performing melt blending through a twin-screw extruder, extruding and pelletizing, and then forming after adding to a mold; the temperature settings of the twin-screw extruder include: zone 1 at 160 °C, zone 2 at 190 °C, zone 3 at 210 °C, and the die head temperature at 205 °C.

[0025] Example 2 In this example, an engine underbody guard plate is provided, which comprises the following raw materials in parts by weight: 40 parts of polypropylene, 15 parts of glass fiber, 5 parts of silicon carbide modified carbon fiber, 5 parts of nano-silica, 2 parts of compatibilizer, 0.5 part of antioxidant, 0.3 part of calcium stearate, and 0.4 part of polyethylene wax.

[0026] Among them, the preparation method of the silicon carbide modified carbon fiber includes: immersing the carbon fiber in acetone, ultrasonically cleaning for 30 min under the conditions of a power of 90 W and a frequency of 30 kHz, drying at 70 °C for 2 h, then immersing in a nitric acid aqueous solution with a mass concentration of 60%, treating at 75 °C for 50 min, rinsing with deionized water until neutral, drying at 100 °C for 3 h to obtain the pretreated carbon fiber; mixing tetraethyl orthosilicate with ethanol and water, adding a hydrochloric acid aqueous solution with a concentration of 0.1 M, and stirring at a rotation speed of 200 rpm for 20 h to form a transparent sol; the dosage ratio of tetraethyl orthosilicate, ethanol, water, and hydrochloric acid aqueous solution is 10 g: 18 g: 3 g: 5 mL; immersing 1 g of the carbon fiber pretreated with nitric acid in 10 mL of the transparent sol, ultrasonically treating at 30 kHz for 30 min, then drying at 60 °C under vacuum conditions for 120 min, then heating to 500 °C at a rate of 3 °C / min under argon conditions, holding for 50 min, continuing to heat to 1100 °C at a rate of 3 °C / min, holding for 50 min, and cooling to room temperature to obtain the product.

[0027] Among them, the glass fiber has a length of 200 μm and a diameter of 20 μm; the carbon fiber has a length of 3 mm and a diameter of 7 μm; the compatibilizer is maleic anhydride grafted polypropylene; the antioxidant is antioxidant 1010.

[0028] The preparation method of this engine underbody guard plate includes: mixing polypropylene, glass fiber, silicon carbide modified carbon fiber, nano-silica, compatibilizer, antioxidant, calcium stearate, and polyethylene wax at a rotation speed of 400 rpm for 5 minutes; performing melt blending through a twin-screw extruder, extruding and pelletizing, and then forming after adding into a mold; the temperature settings of the twin-screw extruder include: zone 1 at 155 °C, zone 2 at 185 °C, zone 3 at 205 °C, and the die head temperature at 200 °C.

[0029] Example 3 In this example, an engine underbody guard plate is provided, which includes the following raw materials in parts by weight: 50 parts of polypropylene, 20 parts of glass fiber, 10 parts of silicon carbide modified carbon fiber, 9 parts of nano-silica, 3 parts of compatibilizer, 1 part of antioxidant, 0.5 part of calcium stearate, and 0.6 part of polyethylene wax.

[0030] Among them, the preparation method of the silicon carbide modified carbon fiber includes: immersing carbon fiber in acetone, performing ultrasonic cleaning at a power of 100 W and a frequency of 40 kHz for 40 minutes, drying at 80 °C for 3 hours, then immersing it in a nitric acid aqueous solution with a mass concentration of 70%, treating it at 85 °C for 70 minutes, rinsing with deionized water until neutral, and drying at 120 °C for 4 hours to obtain the pretreated carbon fiber; mixing tetraethyl orthosilicate with ethanol and water, adding a hydrochloric acid aqueous solution with a concentration of 0.2 M, and stirring at a rotation speed of 300 rpm for 24 hours to form a transparent sol; the dosage ratio of tetraethyl orthosilicate, ethanol, water, and hydrochloric acid aqueous solution is 11 g: 20 g: 4 g: 6 mL; immersing 2 g of the carbon fiber pretreated with nitric acid in 20 mL of the transparent sol, performing ultrasonic treatment at 40 kHz for 40 minutes, then drying at 80 °C under vacuum for 140 minutes, then heating to 600 °C at a rate of 5 °C / min under argon atmosphere, holding for 60 minutes, continuing to heat to 1200 °C at a rate of 5 °C / min, holding for 60 minutes, and cooling to room temperature to obtain it.

[0031] Among them, the glass fiber has a length of 400 μm and a diameter of 30 μm; the carbon fiber has a length of 5 mm and a diameter of 9 μm; the compatibilizer is maleic anhydride grafted polypropylene; the antioxidant is antioxidant 1010.

[0032] The preparation method of this engine underbody guard plate includes: mixing polypropylene, glass fiber, silicon carbide modified carbon fiber, nano-silica, compatibilizer, antioxidant, calcium stearate, and polyethylene wax at a rotation speed of 500 rpm for 15 minutes; performing melt blending through a twin-screw extruder, extruding and pelletizing, and then forming after adding into a mold; the temperature settings of the twin-screw extruder include: zone 1 at 165 °C, zone 2 at 195 °C, zone 3 at 215 °C, and the die head temperature at 210 °C.

[0033] Example 4 In this embodiment, an engine underbody shield is provided, which comprises raw materials in the following parts by weight: 40 parts of polypropylene, 20 parts of glass fiber, 5 parts of silicon carbide modified carbon fiber, 9 parts of nano-silica, 2 parts of compatibilizer, 1 part of antioxidant, 0.3 part of calcium stearate, and 0.6 part of polyethylene wax.

[0034] Among them, the preparation method of the silicon carbide modified carbon fiber includes: immersing the carbon fiber in acetone, ultrasonically cleaning for 30 min under the conditions of a power of 90 W and a frequency of 40 kHz, drying at 80 °C for 2 h, then immersing it in a nitric acid aqueous solution with a mass concentration of 70%, treating at 75 °C for 70 min, rinsing with deionized water until neutral, and drying at 100 °C for 4 h to obtain the pretreated carbon fiber; mixing tetraethyl orthosilicate with ethanol and water, adding a hydrochloric acid aqueous solution with a concentration of 0.1 M, and stirring at a rotation speed of 300 rpm for 20 h to form a transparent sol; the dosage ratio of tetraethyl orthosilicate, ethanol, water, and hydrochloric acid aqueous solution is 11 g: 18 g: 4 g: 5 mL; immersing 2 g of the carbon fiber pretreated with nitric acid in 10 mL of the transparent sol, ultrasonically treating at 40 kHz for 30 min, then drying at 80 °C under vacuum conditions for 120 min, then heating to 500 °C at a rate of 5 °C / min under argon conditions, holding for 60 min, continuing to heat to 1200 °C at a rate of 3 °C / min, holding for 50 min, and cooling to room temperature to obtain the product.

[0035] Among them, the glass fiber has a length of 400 μm and a diameter of 20 μm; the carbon fiber has a length of 5 mm and a diameter of 7 μm; the compatibilizer is maleic anhydride grafted polypropylene; the antioxidant is antioxidant 1010.

[0036] The preparation method of this engine underbody shield includes: mixing polypropylene, glass fiber, silicon carbide modified carbon fiber, nano-silica, compatibilizer, antioxidant, calcium stearate, and polyethylene wax at a rotation speed of 400 rpm for 15 min; performing melt blending through a twin-screw extruder, extruding and pelletizing, and then forming after adding to a mold; the temperature settings of the twin-screw extruder include: zone 1 at 155 °C, zone 2 at 195 °C, zone 3 at 205 °C, and the die head temperature at 210 °C.

[0037] Example 5 In this comparative example, an engine underbody shield is provided, which comprises raw materials in the following parts by weight: 45 parts of polypropylene, 17 parts of glass fiber, 8 parts of silicon carbide modified carbon fiber, 7 parts of nano-silica, 2.5 parts of compatibilizer, 0.7 part of antioxidant, 0.4 part of calcium stearate, and 0.5 part of polyethylene wax.

[0038] Among them, the preparation method of the silicon carbide modified carbon fiber includes: immersing the carbon fiber in an aqueous nitric acid solution with a mass concentration of 65%, treating it at 80 °C for 60 min, rinsing it with deionized water until neutral, and drying it at 110 °C for 3.5 h to obtain the pretreated carbon fiber; mixing tetraethyl orthosilicate with ethanol and water, adding an aqueous hydrochloric acid solution with a concentration of 0.15 M, and stirring it at a rotation speed of 250 rpm for 22 h to form a transparent sol; the dosage ratio of tetraethyl orthosilicate, ethanol, water, and the aqueous hydrochloric acid solution is 10.5 g: 19 g: 3.5 g: 5.5 mL; immersing 1.5 g of the carbon fiber pretreated with nitric acid in 15 mL of the transparent sol, ultrasonicating it at 35 kHz for 35 min, then drying it at 70 °C under vacuum conditions for 130 min, then heating it to 550 °C at a rate of 4 °C / min under argon conditions, holding it for 55 min, continuing to heat it to 1150 °C at a rate of 4 °C / min, holding it for 55 min, and cooling it to room temperature to obtain it.

[0039] Among them, the length of the glass fiber is 300 um and the diameter is 25 μm; the length of the carbon fiber is 4 mm and the diameter is 8 μm; the compatibilizer is maleic anhydride grafted polypropylene; the antioxidant is antioxidant 1010.

[0040] The preparation method of this engine underbody guard plate includes: mixing polypropylene, glass fiber, silicon carbide modified carbon fiber, nano-silica, compatibilizer, antioxidant, calcium stearate, and polyethylene wax at a rotation speed of 450 rpm for 10 min; performing melt blending through a twin-screw extruder, extruding and granulating, and then forming it after adding it to a mold; the temperature settings of the twin-screw extruder include: zone 1 at 160 °C, zone 2 at 190 °C, zone 3 at 210 °C, and the die head temperature at 205 °C.

[0041] Example 6 In this comparative example, an engine underbody guard plate is provided, which includes the following raw materials in parts by weight: 45 parts of polypropylene, 17 parts of glass fiber, 8 parts of silicon carbide modified carbon fiber, 7 parts of nano-silica, 2.5 parts of compatibilizer, 0.7 part of antioxidant, 0.4 part of calcium stearate, and 0.5 part of polyethylene wax.

[0042] Among them, the preparation method of the silicon carbide modified carbon fiber includes: immersing the carbon fiber in acetone, ultrasonically cleaning for 35 min under the conditions of a power of 95 W and a frequency of 35 kHz, and drying for 2.5 h at 75 °C to obtain the pretreated carbon fiber; mixing tetraethyl orthosilicate with ethanol and water, adding an aqueous hydrochloric acid solution with a concentration of 0.15 M, and stirring for 22 h under the condition of a rotation speed of 250 rpm to form a transparent sol; the dosage ratio of tetraethyl orthosilicate, ethanol, water and the aqueous hydrochloric acid solution is 10.5 g: 19 g: 3.5 g: 5.5 mL; immersing 1.5 g of the carbon fiber pretreated with nitric acid in 15 mL of the transparent sol, ultrasonically treating for 35 min under the condition of 35 kHz, then drying under vacuum at 70 °C for 130 min, then heating to 550 °C at a rate of 4 °C / min under argon conditions, holding for 55 min, continuing to heat to 1150 °C at a rate of 4 °C / min, holding for 55 min, and cooling to room temperature to obtain the product.

[0043] Among them, the length of the glass fiber is 300 μm and the diameter is 25 μm; the length of the carbon fiber is 4 mm and the diameter is 8 μm; the compatibilizer is maleic anhydride grafted polypropylene; the antioxidant is antioxidant 1010.

[0044] The preparation method of this engine underbody guard plate includes: mixing polypropylene, glass fiber, silicon carbide modified carbon fiber, nano-silica, compatibilizer, antioxidant, calcium stearate, and polyethylene wax under the condition of a rotation speed of 450 rpm for 10 min; melt-blending through a twin-screw extruder, extruding and pelletizing, and then molding after adding to the mold to obtain the product; the temperature settings of the twin-screw extruder include: zone 1 at 160 °C, zone 2 at 190 °C, zone 3 at 210 °C, and the die head temperature at 205 °C.

[0045] Example 7 In this comparative example, an engine underbody guard plate is provided, which includes the following raw materials in parts by weight: 45 parts of polypropylene, 17 parts of glass fiber, 8 parts of silicon carbide modified carbon fiber, 7 parts of nano-silica, 2.5 parts of compatibilizer, 0.7 part of antioxidant, 0.4 part of calcium stearate, and 0.5 part of polyethylene wax.

[0046] Among them, the preparation method of the silicon carbide modified carbon fiber includes: mixing tetraethyl orthosilicate with ethanol and water, adding an aqueous hydrochloric acid solution with a concentration of 0.15 M, and stirring for 22 h under the condition of a rotation speed of 250 rpm to form a transparent sol; the dosage ratio of tetraethyl orthosilicate, ethanol, water and the aqueous hydrochloric acid solution is 10.5 g: 19 g: 3.5 g: 5.5 mL; immersing 1.5 g of carbon fiber in 15 mL of the transparent sol, ultrasonically treating for 35 min under the condition of 35 kHz, then drying under vacuum at 70 °C for 130 min, then heating to 550 °C at a rate of 4 °C / min under argon conditions, holding for 55 min, continuing to heat to 1150 °C at a rate of 4 °C / min, holding for 55 min, and cooling to room temperature to obtain the product.

[0047] Among them, the glass fiber has a length of 300 μm and a diameter of 25 μm; the carbon fiber has a length of 4 mm and a diameter of 8 μm; the compatibilizer is maleic anhydride grafted polypropylene; the antioxidant is antioxidant 1010.

[0048] The preparation method of this engine underbody guard plate includes: mixing polypropylene, glass fiber, silicon carbide modified carbon fiber, nano-silica, compatibilizer, antioxidant, calcium stearate, and polyethylene wax for 10 min under the condition of a rotation speed of 450 rpm; melting and blending through a twin-screw extruder, extruding and pelletizing, and then forming after adding into a mold; the temperature settings of the twin-screw extruder include: zone 1 at 160 °C, zone 2 at 190 °C, zone 3 at 210 °C, and the die head temperature at 205 °C.

[0049] Comparative Example 1 This comparative example provides an engine underbody guard plate, which includes the following raw materials in parts by weight: 45 parts of polypropylene, 17 parts of glass fiber, 8 parts of carbon fiber, 7 parts of nano-silica, 2.5 parts of compatibilizer, 0.7 part of antioxidant, 0.4 part of calcium stearate, and 0.5 part of polyethylene wax.

[0050] Among them, the glass fiber has a length of 300 μm and a diameter of 25 μm; the carbon fiber has a length of 4 mm and a diameter of 8 μm; the compatibilizer is maleic anhydride grafted polypropylene; the antioxidant is antioxidant 1010.

[0051] The preparation method of this engine underbody guard plate includes: mixing polypropylene, glass fiber, nano-silica, compatibilizer, antioxidant, calcium stearate, and polyethylene wax for 10 min under the condition of a rotation speed of 450 rpm; melting and blending through a twin-screw extruder, extruding and pelletizing, and then forming after adding into a mold; the temperature settings of the twin-screw extruder include: zone 1 at 160 °C, zone 2 at 190 °C, zone 3 at 210 °C, and the die head temperature at 205 °C.

[0052] Comparative Example 2 This comparative example provides an engine underbody guard plate, which includes the following raw materials in parts by weight: 45 parts of polypropylene, 8 parts of silicon carbide modified carbon fiber, 7 parts of nano-silica, 2.5 parts of compatibilizer, 0.7 part of antioxidant, 0.4 part of calcium stearate, and 0.5 part of polyethylene wax.

[0053] Among them, the preparation method of the silicon carbide modified carbon fiber includes: immersing the carbon fiber in acetone, ultrasonically cleaning for 35 min under the conditions of a power of 95 W and a frequency of 35 kHz, drying for 2.5 h at 75 °C, then immersing it in a nitric acid aqueous solution with a mass concentration of 65%, treating it at 80 °C for 60 min, rinsing with deionized water until neutral, and drying at 110 °C for 3.5 h to obtain the pretreated carbon fiber; mixing tetraethyl orthosilicate with ethanol and water, adding a hydrochloric acid aqueous solution with a concentration of 0.15 M, and stirring for 22 h under the condition of a rotation speed of 250 rpm to form a transparent sol; the dosage ratio of tetraethyl orthosilicate, ethanol, water, and the hydrochloric acid aqueous solution is 10.5 g: 19 g: 3.5 g: 5.5 mL; immersing 1.5 g of the carbon fiber pretreated with nitric acid in 15 mL of the transparent sol, ultrasonically treating for 35 min at 35 kHz, then drying at 70 °C under vacuum conditions for 130 min, then heating to 550 °C at a rate of 4 °C / min under argon conditions, holding for 55 min, continuing to heat to 1150 °C at a rate of 4 °C / min, holding for 55 min, and cooling to room temperature to obtain the product.

[0054] Among them, the length of the carbon fiber is 4 mm, and the diameter is 8 μm; the compatibilizer is maleic anhydride grafted polypropylene; the antioxidant is antioxidant 1010.

[0055] The preparation method of this engine underbody guard plate includes: mixing polypropylene, silicon carbide modified carbon fiber, nano-silica, compatibilizer, antioxidant, calcium stearate, and polyethylene wax for 10 min under the condition of a rotation speed of 450 rpm; performing melt blending by a twin-screw extruder, extruding and granulating, and then molding after adding it to a mold; the temperature settings of the twin-screw extruder include: zone 1 at 160 °C, zone 2 at 190 °C, zone 3 at 210 °C, and the die head temperature at 205 °C.

[0056] Comparative Example 3 In this comparative example, an engine underbody guard plate is provided, which includes the following raw materials in parts by weight: 45 parts of polypropylene, 17 parts of glass fiber, 8 parts of silicon carbide modified carbon fiber, 2.5 parts of compatibilizer, 0.7 part of antioxidant, 0.4 part of calcium stearate, and 0.5 part of polyethylene wax.

[0057] Among them, the preparation method of the silicon carbide modified carbon fiber includes: immersing the carbon fiber in acetone, ultrasonically cleaning for 35 min under the conditions of a power of 95 W and a frequency of 35 kHz, drying at 75 °C for 2.5 h, then immersing it in a nitric acid aqueous solution with a mass concentration of 65%, treating at 80 °C for 60 min, rinsing with deionized water until neutral, and drying at 110 °C for 3.5 h to obtain the pretreated carbon fiber; mixing tetraethyl orthosilicate with ethanol and water, adding a hydrochloric acid aqueous solution with a concentration of 0.15 M, and stirring for 22 h under the condition of a rotation speed of 250 rpm to form a transparent sol; the dosage ratio of tetraethyl orthosilicate, ethanol, water, and hydrochloric acid aqueous solution is 10.5 g: 19 g: 3.5 g: 5.5 mL; immersing 1.5 g of the carbon fiber pretreated with nitric acid in 15 mL of the transparent sol, ultrasonically treating for 35 min under the condition of 35 kHz, then drying at 70 °C under vacuum for 130 min, then heating to 550 °C at a rate of 4 °C / min under argon conditions, holding for 55 min, continuing to heat to 1150 °C at a rate of 4 °C / min, holding for 55 min, and cooling to room temperature to obtain the product.

[0058] Among them, the length of the glass fiber is 300 um and the diameter is 25 μm; the length of the carbon fiber is 4 mm and the diameter is 8 μm; the compatibilizer is maleic anhydride grafted polypropylene; the antioxidant is antioxidant 1010.

[0059] The preparation method of this engine underbody guard plate includes: mixing polypropylene, glass fiber, silicon carbide modified carbon fiber, compatibilizer, antioxidant, calcium stearate, and polyethylene wax under the condition of a rotation speed of 450 rpm for 10 min; performing melt blending and extrusion granulation through a twin-screw extruder, and then forming after adding it to a mold; the temperature settings of the twin-screw extruder include: zone 1 at 160 °C, zone 2 at 190 °C, zone 3 at 210 °C, and the die head temperature at 205 °C.

[0060] Test Example 1: For the engine underbody guards prepared in the foregoing Examples 1-7 and Comparative Examples 1-3, the following tests were carried out: Notched impact strength: Tested with reference to GB / T 1843-2008; Hardness: Tested with reference to GB / T 531.1-2008; Thermal aging resistance: Treating in an aging oven at 120 °C for 168 h, testing the impact strength, and calculating the retention rate of the impact strength; Corrosion resistance: Immersing the specimens of the engine underbody guards prepared in Examples 1-7 and Comparative Examples 1-3 in a hydrochloric acid aqueous solution with a mass concentration of 5% and a sodium hydroxide aqueous solution with a mass concentration of 5% for 100 h respectively, testing the impact strength, and calculating the retention rate of the impact strength.

[0061] The results are shown in Table 1 below: Table 1

[0062] Combined with the above data, Examples 5-7 show that acetone ultrasonic cleaning and nitric acid oxidation treatment significantly affect the interfacial bonding strength, and the impact strength of the samples without complete pretreatment decreases. For the unmodified carbon fiber in Comparative Example 1, the impact strength decreases, proving that the SiC coating enhances the performance through the mechanism of improving the thermal expansion coefficient matching degree between the fiber and the matrix and forming a chemically inert protective layer; in addition, the hardness of the glass fiber-free sample in Comparative Example 2 decreases, indicating that the glass fiber and the carbon fiber form a multi-dimensional reinforcement network. In Comparative Example 3, without nano-SiO2, the thermal aging retention rate decreases. The nanoparticles refine the grains through heterogeneous nucleation and simultaneously fill the interfacial defects.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An engine bottom guard plate, characterized in that: The invention comprises the following raw materials in parts by weight: 40-50 parts of polypropylene, 15-20 parts of glass fiber, 5-10 parts of silicon carbide modified carbon fiber, 5-9 parts of nano silicon dioxide, 2-3 parts of compatibilizer, 0.5-1 part of antioxidant, 0.3-0.5 part of calcium stearate and 0.4-0.6 part of polyethylene wax.

2. The engine underbody guard according to claim 1, characterized in that: The preparation method of the silicon carbide modified carbon fiber comprises: mixing tetraethyl orthosilicate with ethanol and water, adding hydrochloric acid aqueous solution, and stirring to form a transparent sol; immersing the carbon fiber pretreated with nitric acid in the transparent sol, ultrasonicating, drying, and then heating to 500-600°C at 3-5°C / min under argon conditions, keeping the temperature for 50-60min, continuing to heat to 1100-1200°C at 3-5°C / min, keeping the temperature for 50-60min, and cooling to room temperature to obtain the carbon fiber.

3. The engine underbody guard plate according to claim 2, characterized in that: The method for preparing the pretreated carbon fiber comprises: immersing the carbon fiber in acetone for ultrasonic cleaning for 30-40 minutes, drying at 70-80° C. for 2-3 hours, immersing in a nitric acid aqueous solution with a mass concentration of 60%-70%, treating at 75-85° C. for 50-70 minutes, rinsing with deionized water until neutral, and drying to obtain the carbon fiber.

4. The engine underbody guard according to claim 3, characterized in that: The glass fiber has a length of 200-400 μm and a diameter of 20-30 μm; the carbon fiber has a length of 3-5 mm and a diameter of 7-9 μm.

5. The engine underbody guard plate according to claim 2, characterized in that: The usage ratio of the tetraethyl orthosilicate, ethanol, water and hydrochloric acid aqueous solution is 10-11 g: 18-20 g: 3-4 g: 5-6 mL.

6. The engine underbody guard according to claim 5, characterized in that: The concentration of the hydrochloric acid aqueous solution is 0.1-0.2M.

7. The engine underbody guard according to claim 1, characterized in that: The compatibilizer is maleic anhydride grafted polypropylene.

8. The engine underbody guard plate according to claim 1, characterized in that: The antioxidant is antioxidant 1010.

9. A method for preparing an engine underbody guard according to any one of claims 1 to 8, characterized in that the steps include: Polypropylene, glass fiber, silicon carbide modified carbon fiber, nano silicon dioxide, compatibilizer, antioxidant, calcium stearate and polyethylene wax are mixed at a rotation speed of 400-500 rpm for 5-15 minutes; melt blending is carried out by a twin-screw extruder, extrusion granulation is carried out, and molding is carried out to obtain an engine bottom guard plate.

10. The method for preparing an engine underbody guard plate according to claim 9, characterized in that: The temperature settings of the twin-screw extruder include: zone one 155-165°C, zone two 185-195°C, zone three 205-215°C, and die head temperature 200-210°C.

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