Composite material automobile outer plate and preparation method thereof

Abstract

The invention relates to the technical field of automobile plate materials, in particular to a composite automobile outer plate and a preparation method thereof.The composite automobile outer plate comprises a resin glass fiber laminated plate and a polypropylene outer layer which are hot-pressed together, a transition layer is arranged between the resin glass fiber laminated plate and the polypropylene outer layer, and a three-layer composite structure of functional layering and gradient transition is adopted; the performance bottleneck of a traditional single material is broken through, the total thickness of the three layers is 2.5-3.0 mm, the thickness of the three layers is equal to that of a traditional steel plate outer plate, but the weight is reduced by more than 70%, and the structural advantages of equal strength, half weight and controllable cost are achieved.

Description

Technical Field

[0001] This invention relates to the field of automotive panel materials technology, and in particular to a composite material automotive outer panel and its preparation method. Background Technology

[0002] Lightweighting of automobiles is a core requirement for environmental protection and energy conservation, and composite materials are a key path to achieving this. Traditional outer panel materials have limitations: metal materials do not achieve sufficient weight reduction, and thermosetting materials are not recyclable. High-performance, recyclable outer panel materials have become an industry necessity.

[0003] Polypropylene, a thermoplastic with excellent chemical stability, high impact resistance, and good processability, is widely used in the manufacture of automotive parts. However, polypropylene alone still has certain shortcomings in terms of strength, rigidity, and impact resistance, limiting its application in automotive exterior panels. To improve the performance of polypropylene, combining it with glass fiber can effectively enhance the properties of the composite material.

[0004] However, the interfacial compatibility between glass fiber and polypropylene matrix is ​​poor, which easily leads to delamination; and the orientation of glass fiber is difficult to control, which can easily cause uneven performance and warping problems, thus restricting large-scale application. Therefore, how to improve the bonding force between glass fiber and polypropylene and improve the performance of the sheet has become a problem that needs to be solved. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a composite material automotive outer panel and its preparation method to solve the problem of poor bonding between glass fiber and polypropylene.

[0006] To achieve the above objectives, the present invention provides a composite material automotive outer panel, comprising a resin fiberglass laminate and a polypropylene outer layer hot-pressed together, wherein a transition layer is provided between the resin fiberglass laminate and the polypropylene outer layer.

[0007] A further improvement is that the resin fiberglass laminate has a thickness of 1.5-2.0 mm, and the resin fiberglass laminate has a mixed layup structure, with the surface layer having a bidirectional layup structure at 0° and 90°, and the middle layer having a ±45° oblique layup structure.

[0008] A further improvement is that the outer layer of polypropylene has a thickness of 0.5-1.0 mm and is injection molded using polypropylene with a crystallinity of 60-70%.

[0009] A further improvement is that the transition layer is a maleic anhydride-grafted polypropylene compatibilizer layer with a thickness of 0.05-0.1 mm.

[0010] This invention also provides a method for preparing a composite material automotive outer panel, characterized by comprising the following steps: Step 1: Material preparation, consisting of the following components by mass percentage: glass fiber 30-40%, epoxy resin 25-35%, polypropylene 15-25%, carboxyl-terminated nitrile butadiene rubber 10-15% of epoxy resin mass, maleic anhydride-grafted polypropylene 3-5% of polypropylene mass, and curing agent 10-15% of epoxy resin mass; Step 2: Glass fiber pretreatment. Soak the glass fiber in KH550 silane coupling agent aqueous solution for 30-60 minutes, then dry it in an oven for 2-3 hours at a temperature of 100℃-120℃. Step 3: Preparation of resin solution: Mix epoxy resin, carboxyl-terminated nitrile rubber and curing agent in proportion and stir evenly at 60℃-80℃. Step 4: Preparation of resin-glass fiber laminate. The glass fibers and resin liquid treated in Step 1 and Step 2 are impregnated, prepregned, and hot-pressed to form a laminate. Step 5: Preparation of the transition layer: Maleic anhydride-grafted polypropylene is coated onto the surface of the laminate prepared in Step 3 and dried at 80℃-100℃ for 10-20 minutes. Step 6: Composite molding. The outer polypropylene layer is injection molded using polypropylene and placed in a hot press with the laminate obtained in Step 4. The hot press is then applied at 180-200℃ and 5-8MPa for 10-20 minutes. Step 7: Post-processing. After cooling to room temperature, adjust the size and appearance.

[0011] A further improvement is that, in step one, the glass fiber is alkali-free glass fiber with a diameter of 10-15 μm.

[0012] A further improvement is that, in step two, the concentration of the KH550 silane coupling agent aqueous solution is 2-3%.

[0013] A further improvement is that in step four, the impregnation speed is 0.5-1 m / min.

[0014] The beneficial effects of this invention are as follows: 10-15μm alkali-free glass fiber is modified with a silane coupling agent, and the surface hydroxyl groups form chemical bonds with the coupling agent, solving the problem of easy debonding of traditional glass fiber and resin physical bonding, and improving the interfacial shear strength by more than 30%; Epoxy resin and carboxyl-terminated nitrile rubber are mixed in a ratio of 100:(10-15), and CTBN forms a nanoscale "island structure" in the resin. Impact energy is dissipated through the island interface, which improves the resin toughness by 50% while retaining more than 90% of the strength; Maleic anhydride-grafted polypropylene bifunctional structure is used, with one end entangled with the non-polar segments of polypropylene and the other end esterified with the polar groups of epoxy resin, increasing the interlayer peel strength from 5kN / m to 12kN / m, completely solving the industry pain point of incompatibility between polypropylene and resin interfaces; All materials are thermoplastic or thermosetting biodegradable types, and after disposal, glass fiber and resin can be separated by pyrolysis, with a glass fiber recycling rate of 90%, solving the environmental problem of non-recyclability of traditional thermosetting composite materials.

[0015] Employing a three-layer composite structure with functional layering and gradient transition, it breaks through the performance bottlenecks of traditional single materials: the 1.5-2.0mm resin-fiberglass laminate uses a mixed layup of 0°, 90°, and ±45° to form a three-dimensional stress-bearing network, with an in-plane tensile strength ≥180MPa and a flexural strength ≥220MPa, providing the outer panel with core mechanical support for impact resistance and deformation resistance. Meanwhile, its density of 1.8-2.0g / cm³ is only 1 / 4 that of high-strength steel; the 0.05-0.1mm maleic anhydride-grafted polypropylene compatibilizer layer is produced through solvent evaporation. A gradient diffusion layer is then formed, with maleic anhydride-grafted polypropylene molecules diffusing 5-10 μm into the resin-fiberglass laminate and 3-5 μm into the outer polypropylene layer, achieving a smooth transition of interfacial properties and avoiding interlaminar cracking caused by stress concentration. The 0.5-1.0 mm highly crystalline polypropylene outer layer has a density of only 0.9 g / cm³, reducing the overall structural density to 1.2-1.25 g / cm³. Simultaneously, the injection molding flowability of polypropylene allows for the molding of complex outer panel contours, and the surface can be directly painted, reducing costs by more than 60% compared to carbon fiber composites. The total thickness of the three layers is 2.5-3.0 mm, comparable to the thickness of traditional steel outer panels, but with a weight reduction of more than 70%, achieving structural advantages of comparable strength, halved weight, and controllable cost. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of an embodiment of the present invention.

[0018] The diagram is marked as follows: 1. Resin fiberglass laminate; 2. Polypropylene outer layer; 3. Transition layer. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0020] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly. Example

[0021] like Figure 1 As shown, this embodiment provides a composite material automotive outer panel, comprising a resin-fiberglass laminate 1 and a polypropylene outer layer 2 hot-pressed together, with a transition layer 3 disposed between the resin-fiberglass laminate 1 and the polypropylene outer layer 2. The resin-fiberglass laminate 1 has a thickness of 1.5-2.0 mm and is a hybrid layup structure, with the surface layer being a bidirectional layup structure at 0° and 90°, and the middle layer being a ±45° oblique layup structure, forming a three-dimensional stress-bearing network. After hot pressing, the laminate density is controlled at 1.8-2.0 g / cm3, and the tensile strength can reach 180-220 MPa, providing core support for the overall structure in terms of impact and bending resistance.

[0022] The outer polypropylene layer 2 has a thickness of 0.5-1.0 mm and is injection molded from polypropylene with a crystallinity of 65%. The use of polypropylene serves two purposes: firstly, its density of only 0.9-0.91 g / cm³ reduces the overall structural density; secondly, its excellent injection molding flow facilitates the molding of complex outer panel contours. The outer polypropylene layer can be directly treated with painting, coating, and other surface treatments, while also protecting the inner fiberglass layer from mechanical damage. Furthermore, the recyclability of polypropylene ensures that the entire structure has a recycling rate of over 95%.

[0023] The transition layer 3 is a maleic anhydride-grafted polypropylene compatibilizer layer with a thickness of 0.05-0.1 mm, which enhances the interlayer bonding force.

[0024] This embodiment provides a method for preparing a composite material automotive outer panel, characterized by the following steps: Step 1: Material preparation, consisting of the following components by mass percentage: glass fiber 35%, epoxy resin 30%, polypropylene 25%, carboxyl-terminated nitrile rubber 12% of epoxy resin mass, maleic anhydride-grafted polypropylene 4% of polypropylene mass, and curing agent 12% of epoxy resin mass; The glass fiber is alkali-free with a diameter of 12μm and an alkali content of 0.6%; the bisphenol A type epoxy resin has an epoxy value of 0.55eq / 100g; the carboxyl-terminated butadiene-acrylonitrile rubber has a carboxyl content of 1.8mmol / g; the amine curing agent has a purity of 99.2%; the polypropylene has a crystallinity of 65% and a melting point of 168℃; and the maleic anhydride-grafted polypropylene has a grafting rate of 1.2%.

[0025] Step 2: Glass fiber pretreatment. 12μm alkali-free glass fibers were immersed in a 2.5% KH550 silane coupling agent aqueous solution for 45 minutes, followed by drying in an oven at 110℃ for 2.5 hours. After cooling, the grafting rate of the coupling agent on the glass fiber surface was measured to be ≥1.5%. Step 3: Preparation of resin solution. 100 parts of epoxy resin, 12 parts of carboxyl-terminated nitrile rubber and 12 parts of amine curing agent are added to the reaction vessel in sequence. The mixture is stirred at a constant temperature of 70°C for 1.5 hours at a speed of 250 r / min. The viscosity of the resin solution is controlled at 500-800 mPa·s at 25°C. Step 4: Preparation of resin-coated fiberglass laminate. Pretreated fiberglass is impregnated with resin using an impregnation machine at a speed of 0.8 m / min to form a prepreg. The surface layer is laid up with a bidirectional ply structure of 0° and 90°, and the middle layer is laid up with a ±45° oblique ply structure. Then, it is hot-pressed at 135℃ and 12MPa for 45 minutes to obtain a 1.8 mm thick laminate with a porosity of 0.8%. Step 5: Preparation of transition layer: 8% maleic anhydride-grafted polypropylene toluene solution is sprayed onto the surface of the laminate to form a 0.08mm thick coating, and dried at 90℃ for 15 minutes to remove the solvent. Step 6: Composite molding. Inject a 0.8mm thick polypropylene outer layer into the injection molding machine at a temperature of 220℃. Place the laminate with the transition layer into a hot press and laminate at 190℃ and 6MPa for 15 minutes to achieve interlayer fusion bonding. Step 7: Post-processing. After natural cooling to 25℃, trim the edges to achieve a dimensional accuracy of ±0.1mm.

[0026] The automotive outer panel material properties obtained through the above methods are as follows: 1. Tensile strength (GB / T1040.2-2006): dumbbell-shaped specimen, gauge length 50mm, tensile speed 5mm / min, test value 120MPa; 2. Flexural strength (GB / T9341-2008): 80mm×10mm×4mm specimen, span 64mm, loading speed 2mm / min, test value 180MPa; 3. Impact strength: A-notch specimen, impact energy 5J, test value 8kJ / m²; 4. Density: 1.2g / cm³ measured by the water displacement method, weight reduction 84.6%; 5. Salt spray test (GB / T10125-2012): 35℃, 5% NaCl solution, after 720h, no rust or blistering on the surface, corrosion resistance level reaches 10. All indicators meet the technical requirements for passenger car outer panel components. Example

[0027] This embodiment provides step one: material preparation, with the material ratios the same as in embodiment one; the glass fiber is alkali-free with a diameter of 13μm and an alkali content of 0.7%; the bisphenol A type epoxy resin has an epoxy value of 0.6eq / 100g; the carboxyl-terminated butadiene-acrylonitrile rubber has a carboxyl content of 2.0mmol / g; the acid anhydride curing agent has a purity of 99.0%; the polypropylene has a crystallinity of 68% and a melting point of 170℃; and the maleic anhydride-grafted polypropylene has a grafting rate of 1.5%.

[0028] Step 2: Glass fiber pretreatment. 13μm alkali-free glass fibers were immersed in a 3% KH550 silane coupling agent aqueous solution for 60 minutes, followed by drying in an oven at 120℃ for 3 hours. After cooling, the grafting rate of the coupling agent on the glass fiber surface was measured to be ≥1.6%. Step 3: Preparation of resin solution: 100 parts of epoxy resin, 15 parts of carboxyl-terminated nitrile rubber, and 15 parts of amine curing agent are added to the reaction vessel in sequence, and stirred at 80°C for 2 hours at a speed of 300 r / min. The viscosity of the solution is 700 mPa·s. Step 4: Preparation of resin-coated fiberglass laminate. Pretreated fiberglass is impregnated with resin using an impregnation machine at a speed of 0.8 m / min to form a prepreg. The prepreg is then laid up with a bidirectional layup structure of 0° and 90° on the surface and a ±45° oblique layup structure in the middle layer. The laminate is then hot-pressed at 145℃ and 13MPa for 50 minutes to obtain a 1.9 mm thick laminate with a porosity of 0.7%. Step 5: Preparation of transition layer: A 10% maleic anhydride-grafted polypropylene xylene solution is sprayed onto the surface of the laminate to form a 0.09mm thick coating. The solvent is removed by drying at 100℃ for 20 minutes. Step 6: Composite molding. Inject a 0.9mm thick polypropylene outer layer into the injection molding machine at a temperature of 230℃. Place the laminate with the transition layer into a hot press and composite it at 200℃ and 7MPa for 18 minutes to achieve interlayer fusion bonding. Step 7: Post-processing, forced air cooling to 30℃, edge trimming, dimensional accuracy to ±0.1mm.

[0029] The automotive outer panel material properties obtained through the above methods are as follows: 1. Tensile strength (GB / T 1040.2-2006): Tensile speed 6 mm / min, test value 125 MPa; 2. Flexural strength (GB / T 9341-2008): Loading speed 3 mm / min, test value 185 MPa; 3. Impact strength (GB / T 1843-2008): Test value 8.5 kJ / m²; 4. Density 1.22 g / cm³; 5. Salt spray test (GB / T 10125-2012): No corrosion after 720h salt spray test. Compared with Example 1, the performance fluctuation is ≤4%, proving that the structural performance remains stable and controllable when the material grade and process parameters are finely adjusted, adapting to the equipment and material supply conditions of different manufacturers.

[0030] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity. Any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A composite material automotive outer panel, characterized in that, It includes a resin fiberglass laminate (1) and a polypropylene outer layer (2) that are hot-pressed together, with a transition layer (3) provided between the resin fiberglass laminate (1) and the polypropylene outer layer (2).

2. The composite material automotive outer panel according to claim 1, characterized in that, The resin fiberglass laminate (1) has a thickness of 1.5-2.0 mm. The resin fiberglass laminate (1) has a mixed layup structure, with the surface layer having a bidirectional layup structure at 0° and 90°, and the middle layer having a ±45° oblique layup structure.

3. The composite material automotive outer panel according to claim 1, characterized in that, The outer polypropylene layer (2) has a thickness of 0.5-1.0 mm and is injection molded from polypropylene with a crystallinity of 60-70%.

4. A composite material automotive outer panel according to claim 1, characterized in that, The transition layer (3) is a maleic anhydride-grafted polypropylene compatibilizer layer with a thickness of 0.05-0.1 mm.

5. A method for preparing a composite material automotive outer panel according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Material preparation, consisting of the following components by mass percentage: glass fiber 30-40%, epoxy resin 25-35%, polypropylene 15-25%, carboxyl-terminated nitrile butadiene rubber 10-15% of epoxy resin mass, maleic anhydride-grafted polypropylene 3-5% of polypropylene mass, and curing agent 10-15% of epoxy resin mass; Step 2: Glass fiber pretreatment. Soak the glass fiber in KH550 silane coupling agent aqueous solution for 30-60 minutes, then dry it in an oven for 2-3 hours at a temperature of 100℃-120℃. Step 3: Preparation of resin solution: Mix epoxy resin, carboxyl-terminated nitrile rubber and curing agent in proportion and stir evenly at 60℃-80℃. Step 4: Preparation of resin-glass fiber laminate. The glass fibers and resin liquid treated in Step 1 and Step 2 are impregnated, prepregned, and hot-pressed to form a laminate. Step 5: Preparation of the transition layer: Maleic anhydride-grafted polypropylene is coated onto the surface of the laminate prepared in Step 3 and dried at 80℃-100℃ for 10-20 minutes. Step 6: Composite molding. The outer polypropylene layer is injection molded using polypropylene and placed in a hot press with the laminate obtained in Step 4. The hot press is then applied at 180-200℃ and 5-8MPa for 10-20 minutes. Step 7: Post-processing. After cooling to room temperature, adjust the size and appearance.

6. The method for preparing a composite material automotive outer panel according to claim 5, characterized in that, In step one, the glass fiber is alkali-free glass fiber with a diameter of 10-15 μm.

7. The method for preparing a composite material automotive outer panel according to claim 5, characterized in that, In step two, the concentration of the KH550 silane coupling agent aqueous solution is 2-3%.

8. The method for preparing a composite material automotive outer panel according to claim 5, characterized in that, Step four, the impregnation speed is 0.5-1m / min.

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