High-performance polypropylene fiber reinforced composite material for vehicles and method for preparing the same

Abstract

This application discloses a high-performance automotive polypropylene fiber-reinforced composite material and its preparation method, belonging to the field of polymer material modification technology. By weight, the polypropylene fiber-reinforced composite material comprises the following components: 60-80 parts of low-volatile polypropylene matrix resin; 15-30 parts of graded hybrid reinforcing fibers; 2-5 parts of composite adsorbent; 0.5-2 parts of aminosilane coupling agent; and 0.2-0.5 parts of antioxidant.

Description

Technical Field

[0001] This application relates to the field of polymer material modification technology, and more specifically, to a high-performance automotive polypropylene fiber-reinforced composite material and its preparation method. Background Technology

[0002] As the automotive industry accelerates its development towards lightweighting, low emissions, and high comfort, the quality of the in-vehicle environment and the green performance of materials have become important indicators for vehicle evaluation. Polypropylene (PP), due to its advantages such as low density, excellent molding and processing performance, controllable cost, and strong recyclability, is widely used in automotive interior and exterior trim, gradually becoming a core matrix in automotive polymer material systems. However, conventional polypropylene materials still suffer from insufficient low-temperature impact resistance, noticeable odor, and high emissions of volatile organic compounds (VOCs) in practical applications, making it difficult to meet the stringent environmental and overall performance requirements of high-end passenger vehicles.

[0003] To improve the overall performance of polypropylene materials, existing technologies typically employ fiber reinforcement methods, including glass fiber, carbon fiber, and natural fibers. While glass fiber reinforcement significantly improves the rigidity and strength of the material, its limited interfacial compatibility with the matrix makes it prone to fiber breakage and interfacial debonding during processing, leading to significant fluctuations in mechanical properties. Carbon fiber reinforcement, although possessing excellent mechanical properties, is costly and requires stricter control of volatile substances during processing and use, limiting its large-scale application. Natural fibers such as flax and bamboo fibers offer advantages in terms of renewability and low density, but their strong hydrophilicity and poor thermal stability make them prone to degradation and the release of small molecules during high-temperature processing, exacerbating odor and VOC emissions.

[0004] Meanwhile, existing polypropylene composite material preparation processes mostly employ conventional melt blending and single-stage or simple multi-stage vacuum devolatilization methods, which have limited ability to remove low-molecular-weight volatiles. This makes it difficult to efficiently remove residual monomers, oligomers, and processing degradation products from the material system, further restricting the material's application in high-end automotive interiors. Furthermore, existing technical solutions often focus on optimizing single properties, such as improving material mechanical properties or individually reducing VOC emission levels. They lack a systematic design for the synergistic optimization of reinforcement system construction, interface control, volatile matter control, and processing technology, making it difficult to balance material performance stability with industrial production suitability.

[0005] In summary, how to achieve synergistic optimization of reinforced structure design, interface compatibility control, and efficient removal of volatile substances while ensuring good processing performance and industrial feasibility of polypropylene materials, so as to simultaneously meet multiple performance requirements such as low odor, low VOC emissions, high rigidity, and high toughness, has become an urgent technical problem to be solved. Summary of the Invention

[0006] In order to overcome a series of defects in the existing technology, the purpose of this application is to provide a high-performance automotive polypropylene fiber-reinforced composite material, which comprises the following components by mass parts: 60-80 parts of low-volatile polypropylene matrix resin; Graded and blended reinforcing fibers, 15-30 parts; 2-5 parts of composite adsorbent; 0.5–2 parts of aminosilane coupling agent; Antioxidant 0.2 to 0.5 parts.

[0007] Furthermore, the low-volatile polypropylene matrix resin is hydrogenated polypropylene or high-purity polypropylene, with a small molecule residue of ≤0.5%.

[0008] Furthermore, the graded hybrid reinforcing fibers include: Modified short glass fibers, with a length of 3–5 mm; Short flax fiber is a high-degummed grade fiber with a degumming rate of ≥95%, a moisture content of ≤5%, and a length of 3–5 mm. Modified long glass fibers, 10–15 mm in length; The total mass ratio of short fiber components to long fiber components is (2-4):1; The total mass ratio of glass fiber to flax fiber is (3-5):1; The surfaces of the modified long glass fibers and modified short glass fibers are coated with an aminosilane coupling agent after plasma treatment.

[0009] Furthermore, the composite adsorbent is a mixture of molecular sieve and metal-organic framework material, with a mass ratio of (2-3):1, and a BET specific surface area ≥850m². 2 / g; the molecular sieve is 13X type molecular sieve with a particle size of 1-3μm; the metal-organic framework material is ZIF-8 with a particle size of 50-100nm.

[0010] The purpose of this application is also to provide a method for preparing high-performance automotive polypropylene fiber-reinforced composite materials, comprising the following steps: Short glass fibers are treated in a low-temperature plasma treatment device with a plasma power of 300–500W and a treatment area of ​​1000–1500 cm². 2 The atmosphere is air, and the treatment lasts for 5 to 10 minutes. The fiber is then immersed in a partial aminosilane coupling agent solution at room temperature for 1 to 2 hours and then dried to obtain modified short glass fibers. Flax fibers are soaked in a 5%–8% NaOH solution for 2–3 hours, washed with water until neutral, dried, and cut to a length of 3–5 mm to obtain short flax fibers. Long glass fibers are treated in a low-temperature plasma treatment device with a plasma treatment power of 400–600W and a treatment area of ​​1000–1500 cm². 2 The atmosphere is air, the treatment time is 8-12 minutes, and the modified long glass fiber is obtained by immersing it in the remaining aminosilane coupling agent solution at room temperature for 1.5-2.5 hours and then drying it. The modified long glass fiber is then cut to a length of 10-15 mm. Modified short glass fiber, short flax fiber, and partially modified long glass fiber are mixed in a mixer for 5-10 minutes, wherein the amount of modified long glass fiber added is 70%-80% of its total amount, to obtain premixed graded hybrid reinforcing fiber. Low-volatile polypropylene matrix resin, composite adsorbent, and antioxidant are added to a high-speed mixer and mixed for 10-15 minutes at 80-100℃ and 300-500 r / min to obtain a uniform premix. The uniform premix and the premixed graded reinforcing fiber are added to a twin-screw extruder and melt-blended at 180-220℃ and 200-300r / min. The melt is then filtered through an 80-120 mesh filter to obtain the filtered melt material. The remaining 20%–30% of modified long glass fibers are side-fed into the filtered molten material at a temperature of 190–210℃; Finally, the melt is subjected to hot cutting and granulation at a die temperature of 190–220°C, and then dried at 80–100°C for 2–3 hours to obtain polypropylene fiber reinforced composite material.

[0011] Furthermore, the aminosilane coupling agent solution is prepared according to the following steps: Anhydrous ethanol and deionized water were mixed at a volume ratio of (85–95):(5–15) to prepare a mixed solvent, wherein the conductivity of the deionized water was ≤5 μS / cm; Slowly add glacial acetic acid dropwise to the mixed solvent, adjusting the pH to 3.5–4.5 while stirring at a speed of 200–300 rpm for 10–15 minutes. The aminosilane coupling agent is slowly added to the mixed solvent with the pH value adjusted. The mass concentration of the aminosilane coupling agent is 0.5% to 3%, and the addition rate is controlled at 5 to 10 mL / min. At 20–30°C, stir continuously at 300–400 r / min for 30–60 min to fully hydrolyze the aminosilane coupling agent and form an aminosilane coupling agent solution. Let the hydrolysate stand and mature for 2 to 4 hours, stirring once every 30 minutes for 3 to 5 minutes each time, so that the hydrolysate reaches the optimal active state. Stir the solution again for 5-10 minutes before use to ensure uniformity. The prepared coupling agent solution should be used within 24 hours.

[0012] Furthermore, when impregnating short glass fibers, the amount of aminosilane coupling agent solution used is 30% to 40% of the total amount, and when impregnating long glass fibers, the amount of aminosilane coupling agent solution used is 60% to 70% of the total amount; The drying temperature after impregnation of short glass fibers is 100-120℃, and the drying time is 2-3 hours; the drying temperature after impregnation of long glass fibers is 110-130℃, and the drying time is 2.5-3.5 hours.

[0013] Furthermore, the twin-screw extruder adopts a combined screw configuration, which includes a feeding section, a compression section, a metering section, and a devolatilization section in sequence along the material conveying direction. The feeding section uses a deep groove conveying screw, the compression section uses a gradient compression screw, the metering section uses a barrier screw, and the devolatilization section is equipped with a dedicated exhaust structure.

[0014] Furthermore, the exhaust ports of the dedicated exhaust structure are all equipped with demisters, which are filled with activated carbon-alumina composite adsorption fillers in a 1:1 mass ratio. The outlet temperature of the demister is controlled at 80-100℃.

[0015] Furthermore, the preparation method further includes: During the melt extrusion process, the melt undergoes pre-devouring, main devouring, and fine devouring treatments in a devouring section to remove volatile substances from the melt. Specifically, the vacuum degree of the pre-devouring treatment is 0.05–0.07 MPa, and the temperature is 160–180 °C; the vacuum degree of the main devouring treatment is 0.08–0.09 MPa, and the temperature is 200–220 °C; and the vacuum degree of the fine devouring treatment is 0.095–0.098 MPa, and the temperature is 210–230 °C.

[0016] Compared with the prior art, this application has the following beneficial effects: 1) Significantly improved environmental performance: This invention constructs a synergistic system of low-volatile polypropylene matrix resin, 13X molecular sieve / ZIF-8 metal-organic framework composite adsorbent, and three-stage vacuum devolvation process. It achieves full-chain control of volatile organic compounds (VOCs) from three levels: source inhibition, process adsorption, and end-of-pipe deep removal. This makes the odor level of the material consistently reach ≤3, and the key indicators such as benzene, toluene, and formaldehyde are significantly better than existing technologies. It effectively solves the problems of strong odor and VOC exceeding the standard in automotive polypropylene materials.

[0017] 2) Achieving a synergistic balance of high strength, high rigidity and high toughness in mechanical properties: By constructing a graded hybrid reinforcement system of glass fiber and flax fiber and combining it with interface modification technology, while maintaining the high strength and high rigidity advantages of glass fiber, the toughening and lightweight characteristics of natural fibers are introduced, overcoming the performance defects of a single reinforcement system. This enables the composite material to have excellent mechanical strength and impact resistance at the same time, and can replace engineering plastics such as ABS and PC / ABS for structural applications.

[0018] 3) Simultaneous improvement of devolatilization efficiency and processing stability: The three-stage devolatilization process combining gradient temperature and gradient vacuum, along with a low-shear screw configuration design, improves the volatile matter removal efficiency while effectively reducing fiber shear breakage. Under the premise of ensuring the effective fiber length and mechanical properties, the devolatilization efficiency is increased by more than 30% compared with the traditional process, breaking through the technical bottleneck of the traditional process where it is difficult to balance devolatilization efficiency and material properties.

[0019] 4) Strong industrial adaptability and superior economic efficiency: The raw materials used in this invention are all readily available bulk industrial materials, without relying on high-cost carbon fiber or special additives. The preparation process is compatible with existing twin-screw extrusion production lines. Only the devolatilization system needs to be optimized and upgraded to achieve large-scale production. It has the advantages of low investment cost and short implementation cycle. At the same time, the overall material cost is reduced by 10% to 20% compared with similar products, and it has good engineering application prospects.

[0020] 5) Combining green, low-carbon, healthy, and safe performance: The resulting composite material does not contain toxic or harmful additives, meets the relevant standards for limiting harmful substances, and has good compatibility with the in-vehicle environment; at the same time, the material has a low density, which is conducive to the lightweighting of the whole vehicle and the reduction of energy consumption. While reducing VOC emissions, it also takes into account the needs of energy conservation and emission reduction, and plays a positive role in achieving the goals of green manufacturing and healthy cabin. Detailed Implementation

[0021] The technical solution of this application will be clearly and completely described below with reference to the embodiments of this application, but these embodiments should not be construed as limiting the scope of protection of this application.

[0022] Information on raw materials used in the following examples: Hydrogenated polypropylene: Yanshan Petrochemical HHP-20, melt flow rate of 20g / 10min (230℃, 2.16kg); General-purpose polypropylene: Lanzhou Petrochemical PP-H9018H; High-purity polypropylene: Zhejiang Petrochemical HP-P1000; Short glass fiber: Chongqing International Composite Materials ECS10-3.0, diameter Φ10~15μm; Long glass fiber: Chongqing International Composite Materials ER4305N–2400; Flax fiber: Heilongjiang Jin Flax Textile, chopped strand grade, degumming rate ≥95%; Molecular sieve: Shanghai Molecular Sieve Factory 13XHP, particle size 1~3μm; Aminosilane coupling agent: Nanjing Shuguang Chemical KH550; Antioxidant: BASF 1010; Activated carbon: Fujian Yuanli Activated Carbon, coal-based granular carbon; Activated alumina: Shandong Tainuo Technology, 2-3mm spherical shape.

[0023] The above-mentioned raw materials and reagents are merely examples of some specific embodiments of the present invention, making the technical solution of the present invention clearer, and do not mean that the present invention can only use the above-mentioned reagents. The specific scope is subject to the claims. In addition, unless otherwise specified, "parts" in the examples and comparative examples refer to parts by weight.

[0024] Each embodiment is prepared according to the following general process, and the specific parameters are described in detail in each embodiment: Step 1: Preparation of aminosilane coupling agent solution Anhydrous ethanol and deionized water were mixed at a volume ratio of (85–95):(5–15) to prepare a mixed solvent, wherein the conductivity of the deionized water was ≤5 μS / cm. Glacial acetic acid was slowly added dropwise to the mixed solvent while stirring to adjust the pH to 3.5–4.5 at a stirring speed of 200–300 r / min for 10–15 min. An aminosilane coupling agent, with a mass concentration of 0.5%–3%, was slowly added to the pH-adjusted mixed solvent at a rate of 5–10 mL / min. The mixture was stirred continuously at 300–400 r / min for 30–60 min at 20–30 °C to ensure complete hydrolysis of the aminosilane coupling agent, forming an aminosilane coupling agent solution. The hydrolysate was allowed to stand for 2–4 h, stirring every 30 min for 3–5 min each time, to allow the hydrolysate to reach its optimal activity state. Stir the solution again for 5-10 minutes before use to ensure uniformity. The prepared coupling agent solution should be used within 24 hours.

[0025] Step 2: Pretreatment of short glass fibers Short glass fibers are treated in a low-temperature plasma treatment device with a plasma power of 300–500W and a treatment area of ​​1000–1500 cm². 2The atmosphere is air, and the treatment time is 5-10 minutes. Immerse in the aminosilane coupling agent solution prepared in step 1 (30%-40% of the total amount) at room temperature for 1-2 hours. Dry at 100-120℃ for 2-3 hours to obtain modified short glass fibers.

[0026] Step 3: Pretreatment of short flax fibers Flax fibers are soaked in a 5%–8% NaOH solution for 2–3 hours, washed with deionized water until neutral, and dried at 100°C until the moisture content is ≤5%. They are then cut to a length of 3–5 mm to obtain short flax fibers.

[0027] Step 4: Pretreatment of long glass fibers Long glass fibers are treated in a low-temperature plasma treatment device with a plasma treatment power of 400–600W and a treatment area of ​​1000–1500 cm². 2 The atmosphere is air, and the treatment time is 8–12 minutes. Immerse in the remaining aminosilane coupling agent solution prepared in step 1 (60%–70% of the total amount) at room temperature for 1.5–2.5 hours. Dry at 110–130°C for 2.5–3.5 hours, and cut to a length of 10–15 mm to obtain modified long glass fibers.

[0028] Step 5: Preparation of pre-mixed graded hybrid reinforcing fibers Modified short glass fibers, short flax fibers, and a portion of modified long glass fibers (70%–80% of the total modified long glass fibers) are mixed in a mixer for 5–10 minutes to obtain premixed graded hybrid reinforcing fibers.

[0029] Step 6: Preparation of Resin Premix Low-volatile polypropylene matrix resin, composite adsorbent, and antioxidant are added to a high-speed mixer and mixed for 10-15 minutes at 80-100℃ and 300-500 r / min to obtain a uniform premix.

[0030] Step 7: Melt blending and multi-stage devolatilization The uniform premixed material and premixed graded reinforcing fibers are added to the main feed inlet of a twin-screw extruder and melt-blended at 180–220°C and a screw speed of 200–300 r / min. The twin-screw extruder adopts a combined screw configuration, which includes, in sequence along the material conveying direction, a feeding section (using a deep-groove conveying screw), a compression section (using a gradient compression screw), a metering section (using a barrier screw), and a devolatilization section. The devolatilization section is equipped with a dedicated exhaust structure, and each exhaust port is equipped with a demister. The internal structure is filled with activated carbon-alumina composite adsorption packing material at a mass ratio of 1:1, and the outlet temperature of the demister is controlled at 80–100°C.

[0031] During the melt extrusion process, the melt undergoes three stages of devolatilization treatment in the devolatilization section: the pre-devolatilization section has a vacuum of 0.05–0.07 MPa and a temperature of 160–180℃; the main devolatilization section has a vacuum of 0.08–0.09 MPa and a temperature of 200–220℃; and the fine devolatilization section has a vacuum of 0.095–0.098 MPa and a temperature of 210–230℃.

[0032] The melt is filtered through an 80-120 mesh screen to obtain the filtered molten material. The remaining 20%-30% of modified long glass fibers are then added to the filtered molten material through a side feed port at a temperature of 190-210℃.

[0033] Step 8: Granulation and Post-processing The melt is subjected to hot cutting and granulation at a die temperature of 190–220°C, and the particles are dried at 80–100°C for 2–3 hours to obtain composite material particles.

[0034] Step 9: Injection molding Injection temperature 190~210℃, injection pressure 80~100MPa, holding pressure 60~80MPa, cooling time 15~20s, to obtain standard mechanical specimens and VOC test specimens.

[0035] The specific testing method is as follows: Tensile strength: Tested according to GB / T 1040.1 and GB / T 1040.2, using type 1A injection molded specimens, at a test speed of 50 mm / min.

[0036] Flexural modulus: The test was conducted according to GB / T 9341, with a specimen size of 80mm×10mm×(4.0±0.2)mm, a test speed of 2mm / min, and a support span of 64mm.

[0037] Notched impact strength: Tested according to GB / T 1843, with a sample size of 80mm×10mm×(4.0±0.2)mm, type A notch, and the notch was machined.

[0038] Odor: Tested according to GB / T 24149. Test conditions: 80℃ / 2h, ≤3 level.

[0039] VOC: Tested according to GB / T 39885.

[0040] Example 1 (Standard Formulation System) 1. Formula composition (parts by weight) 70 parts hydrogenated polypropylene, 15 parts modified short glass fiber, 5 parts modified long glass fiber, 5 parts short flax fiber, 2 parts 13X molecular sieve, 1 part ZIF-8, 1 part KH-550, and 0.3 parts antioxidant.

[0041] 2. Preparation process The general preparation process was followed, with the following specific parameters: short glass fibers were plasma treated with a power of 400W for 8 minutes, then immersed in a 5% KH-550 solution for 1.5 hours and dried at 80°C; flax fibers were soaked in a 6% NaOH solution for 2.5 hours, washed with water until neutral, and dried; long glass fibers were plasma treated with a power of 450W for 9 minutes, then immersed in the remaining KH-550 solution for 2 hours and dried at 110°C; resin premixing was carried out at 90°C and 400 r / min for 12 minutes; twin-screw extrusion temperature range was 180–220°C, and screw speed was 250 r / min; the three-stage devolatilization parameters were 0.06 MPa / 170°C, 0.085 MPa / 210°C, and 0.096 MPa / 220°C, respectively; and the particles were dried at 90°C for 2.5 hours.

[0042] 3. Performance Test Results Odor rating: Level 3; Benzene: 22 μg / m³ 3 Toluene 45 μg / m 3 Formaldehyde 40 μg / m³ 3 Tensile strength 95 MPa, flexural modulus 7200 MPa, notched impact strength 11 kJ / m 2 .

[0043] Example 2 (Highly Enhanced, Highly Adsorption System) 1. Formula composition (parts by weight) 65 parts high-purity polypropylene, 18 parts modified short glass fiber, 7 parts modified long glass fiber, 5 parts flax fiber, 3 parts 13X molecular sieve, 1 part ZIF-8, 1.2 parts KH-550, and 0.4 parts antioxidant.

[0044] 2. Preparation process The fiber pretreatment was the same as in Example 1; the extrusion screw speed was increased to 280 r / min; the temperature of the fine devolatilization section was adjusted to 230℃, and the other process parameters remained unchanged.

[0045] 3. Performance Test Results Odor rating: Level 3; Benzene: 18 μg / m³ 3 Toluene 40 μg / m 3 Formaldehyde 35μg / m³ 3 Tensile strength 98 MPa, flexural modulus 7300 MPa, notched impact strength 10.5 kJ / m 2 .

[0046] Example 3 (High matrix, low fiber system) 1. Formula composition (parts by weight) 80 parts hydrogenated polypropylene, 11 parts modified short glass fiber, 4 parts modified long glass fiber, 3 parts degummed flax fiber, 2.4 parts 13X molecular sieve, 0.6 parts ZIF-8, 0.8 parts KH-550, and 0.2 parts antioxidant.

[0047] 2. Preparation process The extrusion temperature range is 190–220°C; the vacuum levels for the three-stage devolatilization are 0.05 MPa, 0.09 MPa, and 0.097 MPa, respectively; the remaining process parameters are the same as in Example 1.

[0048] 3. Performance Test Results Odor rating: Level 3; Benzene: 25 μg / m³ 3 Toluene 48 μg / m 3 Formaldehyde 42 μg / m³ 3 Tensile strength 91 MPa, flexural modulus 7050 MPa, notched impact strength 10.2 kJ / m 2 .

[0049] Example 4 (Strongly modified, deeply devolatilized system) 1. Formula composition (parts by weight) 60 parts high-purity polypropylene, 17 parts modified short glass fiber, 7 parts modified long glass fiber, 6 parts degummed flax fiber, 3 parts 13X molecular sieve, 1.5 parts ZIF-8, 1.5 parts KH550, and 0.5 parts antioxidant.

[0050] 2. Preparation process The plasma treatment power for short glass fibers was increased to 500W, and the treatment time was 10 minutes; the plasma treatment power for long glass fibers was increased to 600W, and the treatment time was 12 minutes; flax fibers were treated with 8% NaOH solution for 3 hours; the remaining process parameters were the same as in Example 1.

[0051] 3. Performance Test Results Odor rating: 2.5; Benzene: 17 μg / m³ 3 Toluene 38 μg / m 3 Formaldehyde 32 μg / m³ 3 Tensile strength 99 MPa, flexural modulus 7400 MPa, notched impact strength 11.2 kJ / m 2 .

[0052] Comparative Example 1 (Pure matrix blank control) Formula: 100 parts general-purpose polypropylene, without added reinforcing fibers, composite adsorbents and coupling agents, and without fiber modification and multi-stage devolatilization.

[0053] Process: Conventional extrusion granulation, single-stage vacuum devolatilization (0.08MPa, 210℃).

[0054] Performance: Odor rating: 5; Benzene: 95 μg / m³ 3 Toluene 120 μg / m 3 Formaldehyde 85 μg / m³ 3 Tensile strength 35 MPa, flexural modulus 1800 MPa, notched impact strength 3.5 kJ / m 2 .

[0055] Comparative Example 2 (Single Glass Fiber Reinforced Control) Formula: 70 parts general-purpose polypropylene, 25 parts unmodified glass fiber, 3 parts single 13X molecular sieve, no flax fiber or ZIF-8 added, no multi-stage devolatilization implemented.

[0056] Process: Conventional melt extrusion, single-stage devolatilization.

[0057] Performance: Odor rating 4.5; Benzene 65 μg / m³ 3 Toluene 78 μg / m 3 Formaldehyde 60 μg / m³ 3 Tensile strength 75 MPa, flexural modulus 4800 MPa, notched impact strength 6.5 kJ / m 2 .

[0058] Comparative Example 3 (Control without composite adsorbent) Formula: Completely identical to Example 1, except without the addition of 13X molecular sieve and ZIF-8 composite adsorbent.

[0059] Process: exactly the same as in Example 1.

[0060] Performance: Odor rating 4.5; Benzene 72 μg / m³ 3 Toluene 85 μg / m 3 Formaldehyde 78 μg / m³ 3 Tensile strength 94 MPa, flexural modulus 7150 MPa, notched impact strength 10.8 kJ / m 2 .

[0061] Comparative Example 4 (Traditional Single-Stage Deviation Control) Formula: Completely identical to Example 1.

[0062] Process: Only single-stage vacuum devolatilization (0.09MPa, 210℃) is used, without three-stage gradient devolatilization.

[0063] Performance: Odor rating: 4; Benzene: 45 μg / m³ 3 Toluene 68 μg / m 3 Formaldehyde 55 μg / m³ 3 Tensile strength 95 MPa, flexural modulus 7200 MPa, notched impact strength 11.0 kJ / m 2 .

[0064] Performance Comparison Analysis The performance data for Example 1 are: odor level 3, benzene 22 μg / m³ 3 Formaldehyde 40 μg / m³ 3 Tensile strength 95 MPa, flexural modulus 7200 MPa; Performance data for Example 2: Odor rating 3, benzene 18 μg / m³ 3 Formaldehyde 35μg / m³ 3 Tensile strength 98 MPa, flexural modulus 7300 MPa; Performance data for Example 3: Odor rating 3, benzene 25 μg / m³ 3 Formaldehyde 42 μg / m³ 3 Tensile strength 91 MPa, flexural modulus 7050 MPa; Performance data for Example 4: Odor rating 2.5, benzene 17 μg / m³ 3 Formaldehyde 32 μg / m³ 3 Tensile strength 99MPa, flexural modulus 7400MPa.

[0065] The performance data for Comparative Example 1 (pure matrix) are: odor level 5, benzene 95 μg / m³. 3 Formaldehyde 85 μg / m³ 3 Tensile strength 35 MPa, flexural modulus 1800 MPa; Comparative Example 2 (single glass fiber reinforced) performance data: odor rating 4.5, benzene 65 μg / m³ 3 Formaldehyde 60 μg / m³ 3 Tensile strength 75 MPa, flexural modulus 4800 MPa; Comparative Example 3 (without composite adsorbent) performance data: odor grade 4.5, benzene 72 μg / m³ 3 Formaldehyde 78 μg / m³ 3 Tensile strength 94 MPa, flexural modulus 7150 MPa; Comparative Example 4 (conventional single-stage devolatilization) performance data: odor level 4, benzene 45 μg / m³ 3 Formaldehyde 55 μg / m³ 3 Tensile strength 95MPa, flexural modulus 7200MPa.

[0066] As can be seen from the data above: (1) Compared with Comparative Example 1 (pure matrix), Examples 1 to 4 show significant improvements in all performance indicators, proving the overall effectiveness of the technical solution of the present invention.

[0067] (2) Compared with Comparative Example 2 (single glass fiber reinforcement), Examples 1 to 4 showed a further improvement of 10 to 30% in mechanical properties and a reduction of about 60 to 70% in VOC, demonstrating the synergistic effect of the hybrid fiber reinforcement system and the composite adsorbent.

[0068] (3) Compared with Comparative Example 3 (without composite adsorbent), Example 1 improved the odor level by 1.5 levels and reduced VOC by about 60-70%, which proved the key role of composite adsorbent in reducing volatile substances.

[0069] (4) Compared with Comparative Example 4 (single-stage devolvation), Example 1 improved the odor level by 1 level and reduced VOC by about 40-50%, which proved the technical advantages of the three-stage gradient devolvation process.

[0070] Application and Implementation Methods The composite material of this invention is suitable for structural interior parts such as automotive dashboards, door panels, and pillar guards. It is prepared by injection molding: injection temperature 190-210℃, injection pressure 80-100MPa, holding pressure 60-80MPa, cooling time 15-20s. The product has stable dimensions, low odor, and reliable mechanical properties.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-performance automotive polypropylene fiber-reinforced composite material, characterized in that, It contains the following components by mass: 60-80 parts of low-volatile polypropylene matrix resin; Graded and blended reinforcing fibers, 15-30 parts; 2-5 parts of composite adsorbent; 0.5–2 parts of aminosilane coupling agent; Antioxidant 0.2 to 0.5 parts.

2. The high-performance automotive polypropylene fiber-reinforced composite material according to claim 1, characterized in that, The low-volatile polypropylene matrix resin is hydrogenated polypropylene or high-purity polypropylene, with a small molecule residue of ≤0.5%.

3. The high-performance automotive polypropylene fiber-reinforced composite material according to claim 2, characterized in that, The graded hybrid reinforcing fibers include: Modified short glass fibers, with a length of 3–5 mm; Short flax fiber, with a degumming rate ≥95%, a moisture content ≤5%, and a length of 3–5 mm; Modified long glass fibers, 10–15 mm in length; The total mass ratio of short fiber components to long fiber components is (2-4):1; The total mass ratio of glass fiber to flax fiber is (3-5):1; The surfaces of the modified long glass fibers and modified short glass fibers are coated with an aminosilane coupling agent after plasma treatment.

4. The high-performance automotive polypropylene fiber-reinforced composite material according to claim 3, characterized in that, The composite adsorbent is a mixture of molecular sieve and metal-organic framework material in a mass ratio of (2-3):1, with a BET specific surface area ≥850m². 2 / g; the molecular sieve is 13X type molecular sieve with a particle size of 1-3μm; the metal-organic framework material is ZIF-8 with a particle size of 50-100nm.

5. A method for preparing a high-performance automotive polypropylene fiber-reinforced composite material, used to prepare the high-performance automotive polypropylene fiber-reinforced composite material as described in claim 4, characterized in that, Includes the following steps: Short glass fibers are treated in a low-temperature plasma treatment device with a plasma treatment power of 300–500W and a treatment area of ​​1000–1500 cm². 2 The atmosphere is air, and the treatment lasts for 5 to 10 minutes. The fiber is then immersed in a partial aminosilane coupling agent solution at room temperature for 1 to 2 hours and then dried to obtain modified short glass fibers. Flax fibers are soaked in a 5%–8% NaOH solution for 2–3 hours, washed with water until neutral, dried, and cut to a length of 3–5 mm to obtain short flax fibers. Long glass fibers are treated in a low-temperature plasma treatment device with a plasma treatment power of 400–600W and a treatment area of ​​1000–1500 cm². 2 The atmosphere is air, the treatment time is 8-12 minutes, and the modified long glass fiber is obtained by immersing it in the remaining aminosilane coupling agent solution at room temperature for 1.5-2.5 hours and then drying it. The modified long glass fiber is then cut to a length of 10-15 mm. Modified short glass fiber, short flax fiber, and partially modified long glass fiber are mixed in a mixer for 5-10 minutes, wherein the amount of modified long glass fiber added is 70%-80% of its total amount, to obtain premixed graded hybrid reinforcing fiber. Low-volatile polypropylene matrix resin, composite adsorbent, and antioxidant are added to a high-speed mixer and mixed for 10-15 minutes at 80-100℃ and 300-500 r / min to obtain a uniform premix. The uniform premix and the premixed graded reinforcing fiber are added to a twin-screw extruder and melt-blended at 180-220℃ and 200-300r / min. The melt is then filtered through an 80-120 mesh filter to obtain the filtered melt material. The remaining 20%–30% of modified long glass fibers are side-fed into the filtered molten material at a temperature of 190–210℃; Finally, the melt is subjected to hot cutting and granulation at a die temperature of 190–220°C, and then dried at 80–100°C for 2–3 hours to obtain polypropylene fiber reinforced composite material.

6. The method for preparing high-performance automotive polypropylene fiber-reinforced composite materials according to claim 5, characterized in that, The aminosilane coupling agent solution is prepared according to the following steps: Anhydrous ethanol and deionized water were mixed at a volume ratio of (85–95):(5–15) to prepare a mixed solvent, wherein the conductivity of the deionized water was ≤5 μS / cm; Slowly add glacial acetic acid dropwise to the mixed solvent, adjusting the pH to 3.5–4.5 while stirring at a speed of 200–300 rpm for 10–15 minutes. The aminosilane coupling agent is slowly added to the mixed solvent with the pH value adjusted. The mass concentration of the aminosilane coupling agent is 0.5% to 3%, and the addition rate is controlled at 5 to 10 mL / min. At 20–30°C, stir continuously at 300–400 r / min for 30–60 min to fully hydrolyze the aminosilane coupling agent and form an aminosilane coupling agent solution.

7. The method for preparing high-performance automotive polypropylene fiber-reinforced composite materials according to claim 6, characterized in that, When impregnating short glass fibers, the amount of aminosilane coupling agent solution used is 30% to 40% of the total amount; when impregnating long glass fibers, the amount of aminosilane coupling agent solution used is 60% to 70% of the total amount. The drying temperature after impregnation of short glass fibers is 100-120℃, and the drying time is 2-3 hours; the drying temperature after impregnation of long glass fibers is 110-130℃, and the drying time is 2.5-3.5 hours.

8. The method for preparing high-performance automotive polypropylene fiber-reinforced composite materials according to claim 5, characterized in that, The twin-screw extruder adopts a combined screw configuration, which includes a feeding section, a compression section, a metering section and a devolatilization section in sequence along the material conveying direction. The feeding section adopts a deep groove conveying screw, the compression section adopts a gradient compression screw, the metering section adopts a barrier screw, and the devolatilization section is equipped with a dedicated exhaust structure.

9. The method for preparing high-performance automotive polypropylene fiber-reinforced composite material according to claim 8, characterized in that, The exhaust ports of the dedicated exhaust structure are all equipped with demisters, which are filled with activated carbon-alumina composite adsorption packing material with a mass ratio of 1:

1. The outlet temperature of the demister is controlled at 80-100℃.

10. The method for preparing high-performance automotive polypropylene fiber-reinforced composite material according to claim 8, characterized in that, The preparation method further includes: During the melt extrusion process, the melt undergoes pre-devouring, main devouring, and fine devouring treatments in a devouring section to remove volatile substances from the melt. Specifically, the vacuum degree of the pre-devouring treatment is 0.05–0.07 MPa, and the temperature is 160–180 °C; the vacuum degree of the main devouring treatment is 0.08–0.09 MPa, and the temperature is 200–220 °C; and the vacuum degree of the fine devouring treatment is 0.095–0.098 MPa, and the temperature is 210–230 °C.