High performance glass fiber reinforced polypropylene composites and methods for making the same

Abstract

The application discloses a kind of high-performance glass fiber reinforced polypropylene composite material and preparation method thereof, it is related to high molecular composite material technical field;The application constructs the co-continuous gradient transition layer by polypropylene oligomer between glass fiber surface and polypropylene matrix, the polypropylene oligomer in the transition layer is gradually decreased in concentration in the direction from glass fiber surface to polypropylene matrix, concentration adjacent glass fiber surface is higher than adjacent polypropylene matrix concentration, so that there is no clear interface boundary between glass fiber and polypropylene matrix;The application passes through high concentration and low concentration polypropylene oligomer solution by layer gradient impregnation process in sequence by glass fiber, after drying, and polypropylene matrix is fused and is compounded so that gradient transition layer and matrix form molecular chain entanglement network, stress transmission mode is changed from jumping type to continuous type, and stress concentration point in traditional two-phase structure is eliminated.

Description

Technical Field

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

[0002] Glass fiber reinforced polypropylene (GFRP) composites are widely used in automotive structural components such as dashboard frames, front-end modules, underbody panels, and electronic housings due to their high specific strength, good corrosion resistance, and ease of molding and processing. With the accelerating trend of automotive lightweighting and the increasing demands for material reliability in electronic products, the industry has placed higher requirements on the mechanical properties and long-term service stability of GFRP composites. In practical applications, these composite structural components are subjected to long-term dynamic cyclic loads; interlaminar shear strength and fatigue life are the core indicators determining their service safety and service life.

[0003] However, glass fiber is an inorganic polar material with a surface rich in silanol groups, while polypropylene is a non-polar crystalline polymer. The significant difference in surface energy between the two leads to a clear two-phase separation interface structure between the glass fiber and the polypropylene matrix after melt composite bonding. This interface region relies solely on weak van der Waals forces for bonding, lacking chemical bonding or sufficient molecular chain entanglement. Under external forces, stress cannot be effectively transferred from the polypropylene matrix to the glass fiber, resulting in severe stress concentration at the interface. In existing technologies, silane coupling agents are typically used to treat the glass fiber surface, or maleic anhydride-grafted polypropylene is added to the polypropylene matrix as a compatibilizer to improve interfacial bonding. However, the silane coupling agent treatment layer is only a nanometer-scale monolayer, with limited compatibilizing effect. While maleic anhydride-grafted polypropylene can improve bonding through the reaction of anhydride groups with the hydroxyl groups on the glass fiber surface, it is randomly dispersed in the matrix and cannot form a continuous transition layer on the glass fiber surface. Furthermore, excessively high grafting rates can lead to polypropylene molecular chain breakage due to the catalytic degradation of residual anhydride groups, resulting in yellowing and toughness degradation of the composite material. None of the above methods have fundamentally eliminated the clear interface between glass fiber and the matrix. Stress concentration remains a prominent problem, and the defects of insufficient interlaminar shear strength and low fatigue life have long restricted the widespread application of this type of material in load-bearing structural components.

[0004] Therefore, developing a composite material and its preparation method that can fundamentally eliminate the clear two-phase interface between glass fiber and polypropylene matrix and realize the efficient and continuous transfer of stress from matrix to fiber has important practical application value. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a high-performance glass fiber reinforced polypropylene composite material and its preparation method. This method constructs a co-continuous gradient transition layer composed of polypropylene oligomers between the glass fiber surface and the polypropylene matrix. In this transition layer, the polypropylene oligomers exhibit a continuously decreasing concentration gradient distribution from the glass fiber surface to the polypropylene matrix, with a higher concentration near the glass fiber surface than near the polypropylene matrix, thus eliminating a clear interface boundary between the glass fiber and the polypropylene matrix. This invention uses a layer-by-layer gradient impregnation process to sequentially pass the glass fiber through high-concentration and low-concentration polypropylene oligomer solutions. After drying, the fiber is melt-composite with the polypropylene matrix, forming a molecular chain entanglement network between the gradient transition layer and the matrix. This transforms the stress transmission mode from a jump-like to a continuous one, eliminating stress concentration points in traditional two-phase structures, significantly improving the interlaminar shear strength of the composite material, and significantly extending its fatigue life.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a high-performance glass fiber reinforced polypropylene composite material, made from the following raw materials in parts by weight:

[0007] The invention comprises glass fiber and a polypropylene matrix, wherein a co-continuous gradient transition layer is provided between the glass fiber surface and the polypropylene matrix, the co-continuous gradient transition layer is composed of polypropylene oligomers, and the polypropylene oligomers are distributed in a continuous gradient from the glass fiber surface to the polypropylene matrix, wherein the concentration of polypropylene oligomers adjacent to the glass fiber surface is higher than the concentration of polypropylene oligomers adjacent to the polypropylene matrix.

[0008] Furthermore, the number-average molecular weight of the polypropylene oligomer is 500-5000, which is determined by gel permeation chromatography using polystyrene as a standard, trichlorobenzene as the mobile phase, and the test temperature is 150°C.

[0009] Furthermore, the thickness of the co-continuous gradient transition layer is 0.5~10μm. This thickness range is obtained by observing the etched sample of the frozen brittle fracture section of the composite material using a scanning electron microscope. For specific testing methods, please refer to the detailed implementation section of the specification.

[0010] Furthermore, the glass fiber is alkali-free glass fiber with a fiber diameter of 5~25μm and a fiber length of 3~50mm.

[0011] Furthermore, the polypropylene matrix is ​​at least one of homopolymer polypropylene or copolymer polypropylene.

[0012] On the other hand, a method for preparing a high-performance glass fiber reinforced polypropylene composite material is characterized by comprising the following steps:

[0013] Prepare at least two solutions containing polypropylene oligomers of different concentrations, wherein the solutions include at least a high-concentration solution and a low-concentration solution, wherein the mass percentage concentration of polypropylene oligomers in the high-concentration solution is 5% to 30%, and the mass percentage concentration of polypropylene oligomers in the low-concentration solution is 0.5% to 5%.

[0014] The glass fiber is impregnated sequentially through the high-concentration solution and the low-concentration solution;

[0015] The modified glass fiber after impregnation is dried to remove the solvent;

[0016] The dried modified glass fiber is melt-composite with the polypropylene matrix to form a molecular chain entanglement network between the gradient transition layer and the polypropylene matrix.

[0017] Furthermore, the solution also includes a medium-concentration solution, wherein the mass percentage concentration of polypropylene oligomer in the high-concentration solution, medium-concentration solution and low-concentration solution decreases sequentially, and the glass fiber passes through the high-concentration solution, medium-concentration solution and low-concentration solution sequentially.

[0018] Furthermore, the solvent of the solution is at least one of toluene, xylene, or tetrahydrofuran.

[0019] Furthermore, the immersion treatment time is 1~30 min, and the immersion temperature is 20~80℃.

[0020] Furthermore, the temperature of the melt composite is 180~250℃, the pressure is 1~10MPa, and the holding time is 5~30min.

[0021] Compared with existing technologies, this high-performance glass fiber reinforced polypropylene composite material and its preparation method have the following advantages:

[0022] I. This invention constructs a co-continuous gradient transition layer composed of polypropylene oligomers between the glass fiber surface and the polypropylene matrix. The concentration of polypropylene oligomers in this transition layer decreases continuously from the glass fiber surface to the polypropylene matrix. This eliminates the clear interface boundary between the glass fiber and the polypropylene matrix, transforming stress transmission from a jump-like to a continuous process. This significantly reduces stress concentration points in traditional two-phase structures, thereby greatly improving the interlaminar shear strength of the composite material.

[0023] II. This invention controls the number-average molecular weight of polypropylene oligomers to 500-5000 and the thickness of the gradient transition layer to 0.5-10 μm. Combined with the sequential impregnation of high-concentration and low-concentration solutions in the layer-by-layer gradient impregnation process and the coordinated control of temperature, pressure and holding time in the subsequent melt composite process, a sufficient molecular chain entanglement network is formed between the gradient transition layer and the polypropylene matrix. This effectively suppresses the initiation and propagation of fatigue cracks at the interface under cyclic loading and significantly extends the fatigue life of the composite material.

[0024] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0026] Figure 1 A flowchart of a high-performance glass fiber reinforced polypropylene composite material;

[0027] Figure 2 This is a schematic diagram of the gradient transition layer thickness parameters for a high-performance glass fiber reinforced polypropylene composite material.

[0028] Figure 3 This is a flowchart of a method for preparing a high-performance glass fiber reinforced polypropylene composite material. Detailed Implementation

[0029] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0030] The sources of the raw materials used in the following examples and comparative examples are as follows:

[0031] Alkali-free glass fiber, 13μm in diameter and 10mm in length: Jushi Group Co., Ltd.; Homopolymer polypropylene, melt flow index (MFR) = 10g / 10min, 230℃ / 2.16kg: Sinopec Zhenhai Refining & Chemical Co., Ltd.; Copolymer polypropylene, MFR = 8g / 10min, 230℃ / 2.16kg: Sinopec Zhenhai Refining & Chemical Co., Ltd.; Polypropylene oligomers, number average molecular weights of 500, 2000, and 5000 respectively: self-made in the laboratory, using propylene as monomer and hydrogen as molecular weight regulator, and bulk polymerization using Ziegler-Natta catalyst. Specific polymerization conditions are shown in Table A.

[0032] PP-500 70 1.2 4 520 PP-2000 75 0.6 6 2100 PP-5000 80 0.2 8 4900

[0033] The test methods used in the following examples and comparative examples are as follows:

[0034] (1) Interlaminar shear strength: The short beam shear method was tested according to ASTM D2344 standard. The specimen size was 20mm×10mm×4mm, the span-to-thickness ratio was 4:1, and the loading rate was 1mm / min. Five specimens were tested for each example and comparative example. The results are expressed as mean ± standard deviation.

[0035] (2) Fatigue life: Three-point bending fatigue loading test was performed according to ASTM D3479 standard, with stress ratio R=0.1, frequency of 5Hz, and maximum stress set to 60% of static bending strength. Five specimens were tested for each example and comparative example, and the results are expressed as mean ± standard deviation.

[0036] (3) Determination of the thickness and concentration distribution of the gradient transition layer: The composite material sample was frozen in liquid nitrogen for 30 minutes and then subjected to brittle fracture. After gold sputtering, the cross-section morphology was observed and photographed using a scanning electron microscope. Subsequently, energy-dispersive X-ray spectroscopy line scanning analysis was performed on the same cross-section. The Si element signal was used as a marker for the location of the glass fiber, and the C element signal intensity was used as an indicator of the relative concentration of polypropylene oligomers. The distance from the outer edge of the Si signal peak in the EDS line scanning data to the point where the C signal intensity drops to 95% of the stable matrix value was defined as the thickness of the transition layer. At least 10 fibers were selected for measurement for each sample, and the average value was taken.

[0037] (4) Determination of the number-average molecular weight of polypropylene oligomers: The determination was performed using gel permeation chromatography with polystyrene as standard, 1,2,4-trichlorobenzene as mobile phase, flow rate 1.0 mL / min, and column temperature 150 ℃.

[0038] Example 1

[0039] This embodiment provides a high-performance glass fiber reinforced polypropylene composite material and its preparation method.

[0040] In this embodiment, alkali-free glass fiber with a diameter of 13 μm and a length of 10 mm is used. The polypropylene matrix is ​​homopolymer polypropylene. The number average molecular weight of the polypropylene oligomer is 2000. The thickness of the continuous gradient transition layer is approximately 3 μm.

[0041] The preparation method of the high-performance glass fiber reinforced polypropylene composite material in this embodiment includes the following steps.

[0042] Preparation of gradient impregnation solutions. Using toluene as the solvent, three solutions containing different concentrations of polypropylene oligomer were prepared. The high-concentration solution contained 20% polypropylene oligomer by mass. The medium-concentration solution contained 10% polypropylene oligomer by mass. The low-concentration solution contained 2% polypropylene oligomer by mass. The specific preparation methods for the three solutions were as follows: The corresponding mass of polypropylene oligomer was weighed and dissolved in toluene, and the solution was stirred until completely dissolved under a 40°C water bath heating condition, yielding a clear and transparent solution.

[0043] Pretreatment of glass fiber: Alkali-free glass fiber is ultrasonically cleaned in acetone for 15 minutes to remove surface organic contaminants. After removal, it is rinsed repeatedly with deionized water 3 times and dried in an 80℃ forced-air oven for 4 hours for later use.

[0044] The glass fiber undergoes a layer-by-layer gradient impregnation treatment. First, the alkali-free glass fiber is immersed in a high-concentration solution for 5 minutes at 40°C. After removal and draining excess solution, it is then immersed in a medium-concentration solution for 5 minutes at 40°C. After draining again, it is finally immersed in a low-concentration solution for 5 minutes at 40°C. After this layer-by-layer gradient impregnation treatment, polypropylene oligomers form a continuous gradient distribution from high to low concentration on the glass fiber surface. As the glass fiber passes through solutions of different concentrations, the higher concentration of polypropylene oligomers in the high-concentration solution adheres to the glass fiber surface first. With subsequent immersion in medium- and low-concentration solutions, the concentration of polypropylene oligomers on the outer layer gradually decreases, thus forming a continuous gradient transition layer with decreasing concentration from the inside to the outside on the glass fiber surface.

[0045] The impregnated modified glass fibers were dried to remove the solvent. The modified glass fibers were placed in a vacuum drying oven at 60°C for 12 hours to allow the toluene solvent to evaporate completely.

[0046] The dried modified glass fiber was melt-bonded with a polypropylene matrix. 30 parts by weight of modified glass fiber and 70 parts by weight of homopolymer polypropylene were weighed. Both were placed in a mold and melt-bonded on a hot press. The melt-bonding temperature was 200℃, the pressure was 5MPa, and the holding time was 15 minutes. During the melt-bonding process, the polypropylene oligomer gradient transition layer on the glass fiber surface and the polypropylene matrix under high temperature and pressure underwent molecular chain interdiffusion and entanglement, forming a molecular chain entanglement network. Because the concentration of polypropylene oligomers in the gradient transition layer gradually decreases from the glass fiber surface to the outside, the concentration difference between the outermost layer and the polypropylene matrix is ​​small, and the two have good compatibility. Therefore, there is no clear interface boundary between the glass fiber and the polypropylene matrix, but rather a continuous transition structure is formed.

[0047] In the high-performance glass fiber reinforced polypropylene composite material prepared in this embodiment, a co-continuous gradient transition layer is provided between the glass fiber surface and the polypropylene matrix. This co-continuous gradient transition layer is composed of polypropylene oligomers, and the polypropylene oligomers are continuously gradient distributed in the direction from the glass fiber surface to the polypropylene matrix, with the polypropylene oligomer concentration near the glass fiber surface being higher than that near the polypropylene matrix. This structure allows for a smooth transition of stress from the polypropylene matrix to the glass fiber, avoiding the stress concentration phenomenon caused by the clear two-phase interface in traditional composite materials.

[0048] Example 2

[0049] This embodiment provides a high-performance glass fiber reinforced polypropylene composite material and its preparation method.

[0050] In this embodiment, alkali-free glass fiber with a diameter of 13 μm and a length of 10 mm is used. The polypropylene matrix is ​​homopolymer polypropylene. The number average molecular weight of the polypropylene oligomer is 500. The thickness of the continuous gradient transition layer is approximately 2 μm.

[0051] The preparation method of the high-performance glass fiber reinforced polypropylene composite material in this embodiment includes the following steps.

[0052] Prepare gradient impregnation solutions. Using toluene as a solvent, prepare two solutions containing different concentrations of polypropylene oligomer. The high-concentration solution contains 30% polypropylene oligomer by mass, while the low-concentration solution contains 5% polypropylene oligomer by mass. The specific preparation methods for the two solutions are as follows: weigh the corresponding mass of polypropylene oligomer and dissolve it in toluene, stirring in a 25°C water bath until completely dissolved, yielding a clear and transparent solution.

[0053] The glass fibers underwent a layer-by-layer gradient impregnation treatment. The alkali-free glass fibers were first immersed in a high-concentration solution for 2 minutes at 25°C. After removal and draining excess solution, they were then immersed in a low-concentration solution for 2 minutes at 25°C. Following this layer-by-layer gradient impregnation treatment, a continuous gradient distribution of polypropylene oligomers from high to low concentration was formed on the glass fiber surface. Compared to Example 1, this example uses two concentration solutions for impregnation, resulting in fewer gradient layers and therefore a relatively thinner gradient transition layer.

[0054] The impregnated modified glass fibers were dried to remove the solvent. The modified glass fibers were placed in a vacuum drying oven at 60°C for 12 hours to allow the toluene solvent to evaporate completely.

[0055] The dried modified glass fiber was melt-bonded with a polypropylene matrix. 30 parts by weight of modified glass fiber and 70 parts by weight of homopolymer polypropylene were weighed. Both were placed in a mold and melt-bonded on a hot press. The melt-bonding temperature was 180℃, the pressure was 10MPa, and the holding time was 5 minutes. During the melt-bonding process, the polypropylene oligomer gradient transition layer on the glass fiber surface and the polypropylene matrix under high temperature and pressure underwent molecular chain interdiffusion and entanglement, forming a molecular chain entanglement network.

[0056] In the high-performance glass fiber reinforced polypropylene composite material prepared in this embodiment, a co-continuous gradient transition layer is provided between the glass fiber surface and the polypropylene matrix. This co-continuous gradient transition layer is composed of polypropylene oligomers, and the polypropylene oligomers are distributed in a continuous gradient from the glass fiber surface to the polypropylene matrix, with the polypropylene oligomer concentration near the glass fiber surface being higher than that near the polypropylene matrix. Compared with Example 1, this embodiment uses a shorter impregnation time and a higher melt composite pressure, making it suitable for large-scale production scenarios with high production efficiency requirements.

[0057] Example 3

[0058] This embodiment provides a high-performance glass fiber reinforced polypropylene composite material and its preparation method.

[0059] In this embodiment, alkali-free glass fiber with a diameter of 13 μm and a length of 10 mm is used. The polypropylene matrix is ​​copolymerized polypropylene. The number average molecular weight of the polypropylene oligomer is 5000. The thickness of the co-continuous gradient transition layer is approximately 8 μm.

[0060] The preparation method of the high-performance glass fiber reinforced polypropylene composite material in this embodiment includes the following steps.

[0061] Prepare gradient impregnation solutions. Using xylene as the solvent, prepare three solutions containing different concentrations of polypropylene oligomer. The high-concentration solution contains 5% polypropylene oligomer by mass. The medium-concentration solution contains 2% polypropylene oligomer by mass. The low-concentration solution contains 0.5% polypropylene oligomer by mass. The specific preparation methods for the three solutions are as follows: weigh the corresponding mass of polypropylene oligomer and dissolve it in xylene, stirring under 80°C water bath heating until completely dissolved, obtaining a clear and transparent solution.

[0062] The glass fibers underwent a layer-by-layer gradient impregnation treatment. First, the alkali-free glass fibers were immersed in a high-concentration solution for 30 minutes at 80°C. After removal and draining excess solution, they were then immersed in a medium-concentration solution for 30 minutes at 80°C. After draining excess solution again, they were finally immersed in a low-concentration solution for 30 minutes at 80°C. After this layer-by-layer gradient impregnation treatment, a continuous gradient distribution of polypropylene oligomers from high to low concentration was formed on the glass fiber surface. Compared to Example 1, this example used a higher molecular weight polypropylene oligomer and a longer impregnation time. The higher molecular weight oligomer diffuses more slowly in the solution, requiring a longer impregnation time to achieve sufficient adhesion and penetration; therefore, the gradient transition layer is relatively thicker.

[0063] The impregnated modified glass fibers were dried to remove the solvent. The modified glass fibers were placed in a vacuum drying oven at 60°C for 12 hours to allow the xylene solvent to evaporate completely.

[0064] The dried modified glass fiber was melt-bonded with a polypropylene matrix. 30 parts by weight of modified glass fiber and 70 parts by weight of copolymerized polypropylene were weighed. Both were placed in a mold and melt-bonded on a hot press. The melt-bonding temperature was 250℃, the pressure was 1 MPa, and the holding time was 30 minutes. During the melt-bonding process, the polypropylene oligomer gradient transition layer on the glass fiber surface and the polypropylene matrix under high temperature and pressure underwent molecular chain interdiffusion and entanglement, forming a molecular chain entanglement network.

[0065] In the high-performance glass fiber reinforced polypropylene composite material prepared in this embodiment, a co-continuous gradient transition layer is provided between the glass fiber surface and the polypropylene matrix. This co-continuous gradient transition layer is composed of polypropylene oligomers, and the polypropylene oligomers are distributed in a continuous gradient from the glass fiber surface to the polypropylene matrix, with the polypropylene oligomer concentration near the glass fiber surface being higher than that near the polypropylene matrix. Compared with Example 1, this embodiment uses copolymerized polypropylene as the matrix. Copolymerized polypropylene has better impact resistance and is suitable for applications requiring high toughness.

[0066] Comparative Example 1

[0067] This comparative example uses a conventional method to prepare glass fiber reinforced polypropylene composite material, and is used for comparison with the embodiments of the present invention.

[0068] In this comparative example, alkali-free glass fiber with a diameter of 13 μm and a length of 10 mm was used. Homopolymer polypropylene was used as the polypropylene matrix. Maleic anhydride-grafted polypropylene was used as the compatibilizer.

[0069] The preparation method of the glass fiber reinforced polypropylene composite material in this comparative example includes the following steps.

[0070] 30 parts by weight of alkali-free glass fiber, 70 parts by weight of homopolymer polypropylene, and 5 parts by weight of maleic anhydride-grafted polypropylene were mixed. The mixture was placed in a mold and melt-bonded on a hot press. The melt-bonding temperature was 200℃, the pressure was 5MPa, and the holding time was 15 minutes.

[0071] In the glass fiber reinforced polypropylene composite prepared in this comparative example, no co-continuous gradient transition layer was provided between the glass fiber and the polypropylene matrix. The glass fiber was only interfacially bonded to the polypropylene matrix through maleic anhydride-grafted polypropylene. The maleic anhydride groups in the maleic anhydride-grafted polypropylene can react with the hydroxyl groups on the surface of the glass fiber, while the polypropylene segments are compatible with the polypropylene matrix, acting as an interfacial bridge. However, the maleic anhydride-grafted polypropylene is randomly dispersed in the matrix and cannot form a continuous gradient transition layer on the surface of the glass fiber. Therefore, a clear two-phase interface still exists between the glass fiber and the polypropylene matrix, and stress concentrates at this interface, preventing continuous transfer from the matrix to the fiber.

[0072] The difference between Comparative Example 1 and Examples 1-3 is that Comparative Example 1 uses a traditional maleic anhydride-grafted polypropylene compatibilizer to improve interfacial bonding, while Examples 1-3 eliminate the two-phase interface by constructing a co-continuous gradient transition layer of polypropylene oligomers on the glass fiber surface. The technical solution of Comparative Example 1 represents a commonly used method in the prior art for improving the interfacial compatibility between glass fiber and polypropylene.

[0073] The composite materials prepared in Examples 1-3 and Comparative Example 1 were subjected to performance tests, and the test results are shown in Table 1.

[0074] Interlaminar shear strength was tested according to ASTM D2344, using the short beam shear method. The specimen size was 20 mm × 10 mm × 4 mm, the span-to-thickness ratio was 4:1, and the loading rate was 1 mm / min. Five specimens were tested for each example and comparative example, and the average value was taken as the final test result.

[0075] Fatigue life testing was conducted according to ASTM D3479 standard, using a three-point bending fatigue loading method with a stress ratio of 0.1, a frequency of 5 Hz, and a maximum stress set at 60% of the static bending strength. Five specimens were tested for each example and comparative example, and the average value was taken as the final test result.

[0076] Table 1. Interlaminar shear strength and fatigue life of Examples 1-3 and Comparative Example 1

[0077] Interlaminar shear strength / MPa 48.5 45.2 46.8 31.2 Fatigue life / 10 4 Subsequent 8.6 7.8 8.1 4.3

[0078] As can be seen from the test results in Table 1, the interlaminar shear strength of Example 1 is 48.5 MPa, Example 2 is 45.2 MPa, and Example 3 is 46.8 MPa, all significantly higher than the 31.2 MPa of Comparative Example 1. The interlaminar shear strength of Example 1 is approximately 55.4% higher than that of Comparative Example 1. This indicates that the present invention effectively eliminates the clear two-phase interface between the glass fiber and the polypropylene matrix by constructing a co-continuous gradient transition layer on the surface of the glass fiber, thus significantly improving the interfacial bonding strength.

[0079] Based on the fatigue life test results, the fatigue life of Example 1 is 8.6 × 10⁻⁶. 4 Next, Example 2 is 7.8 × 10 4 Next, Example 3 is 8.1 × 10 4 All were significantly longer than the 4.3 × 10⁻⁶ of Comparative Example 1. 4 The fatigue life of Example 1 was improved by approximately 100% compared to Comparative Example 1. This indicates that the co-continuous gradient transition layer eliminated stress concentration points and effectively suppressed the initiation and propagation of fatigue cracks at the interface under cyclic loading.

[0080] Example 2 used two solutions of different concentrations for impregnation with a shorter impregnation time. Its interlaminar shear strength and fatigue life were slightly lower than Example 1, but still significantly better than Comparative Example 1. Example 3 used a high molecular weight polypropylene oligomer and a copolymerized polypropylene matrix. Its interlaminar shear strength and fatigue life were between those of Examples 1 and 2, and also significantly better than Comparative Example 1. The above results demonstrate that the technical solution of the present invention can achieve good technical effects within a wide range of process parameters.

[0081] In summary, this invention constructs a co-continuous gradient transition layer composed of polypropylene oligomers between the glass fiber surface and the polypropylene matrix, enabling the polypropylene oligomers to be continuously gradient distributed in the direction from the glass fiber surface to the polypropylene matrix. This eliminates the clear two-phase interface present in traditional glass fiber reinforced polypropylene composites, achieving continuous stress transfer from the polypropylene matrix to the glass fiber, thereby significantly improving the interlaminar shear strength of the composite material and extending its fatigue life.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-performance glass fiber reinforced polypropylene composite material, characterized in that, Made from the following raw materials in parts by weight: The invention comprises glass fiber and a polypropylene matrix, wherein a co-continuous gradient transition layer is provided between the glass fiber surface and the polypropylene matrix, the co-continuous gradient transition layer is composed of polypropylene oligomers, and the polypropylene oligomers are distributed in a continuous gradient from the glass fiber surface to the polypropylene matrix, wherein the concentration of polypropylene oligomers adjacent to the glass fiber surface is higher than the concentration of polypropylene oligomers adjacent to the polypropylene matrix.

2. The high-performance glass fiber reinforced polypropylene composite material according to claim 1, characterized in that, The number-average molecular weight of the polypropylene oligomer is 500-5000.

3. The high-performance glass fiber reinforced polypropylene composite material according to claim 1, characterized in that, The thickness of the co-continuous gradient transition layer is 0.5~10μm.

4. The high-performance glass fiber reinforced polypropylene composite material according to claim 1, characterized in that, The glass fiber is alkali-free glass fiber with a diameter of 5~25μm and a length of 3~50mm.

5. The high-performance glass fiber reinforced polypropylene composite material according to claim 1, characterized in that, The polypropylene matrix is ​​at least one of homopolymer polypropylene or copolymer polypropylene.

6. A method for preparing a high-performance glass fiber reinforced polypropylene composite material, used to prepare the high-performance glass fiber reinforced polypropylene composite material according to any one of claims 1-5, characterized in that, Includes the following steps: Prepare at least two solutions containing polypropylene oligomers of different concentrations, wherein the solutions include at least a high-concentration solution and a low-concentration solution, wherein the mass percentage concentration of polypropylene oligomers in the high-concentration solution is 5% to 30%, and the mass percentage concentration of polypropylene oligomers in the low-concentration solution is 0.5% to 5%. The glass fiber is impregnated sequentially through the high-concentration solution and the low-concentration solution; The modified glass fiber after impregnation is dried to remove the solvent; The dried modified glass fiber is melt-composite with the polypropylene matrix to form a molecular chain entanglement network between the gradient transition layer and the polypropylene matrix.

7. The high-performance glass fiber reinforced polypropylene composite material according to claim 6, characterized in that, The solution also includes a medium-concentration solution, wherein the mass percentage concentration of polypropylene oligomer in the high-concentration solution, medium-concentration solution and low-concentration solution decreases sequentially, and the glass fiber passes through the high-concentration solution, medium-concentration solution and low-concentration solution sequentially.

8. The high-performance glass fiber reinforced polypropylene composite material according to claim 6, characterized in that, The solvent of the solution is at least one of toluene, xylene, or tetrahydrofuran.

9. A high-performance glass fiber reinforced polypropylene composite material according to claim 6, characterized in that, The immersion treatment time is 1~30 min, and the immersion temperature is 20~80℃.

10. A high-performance glass fiber reinforced polypropylene composite material according to claim 6, characterized in that, The melting and bonding temperature is 180~250℃, the pressure is 1~10MPa, and the holding time is 5~30min.

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