Preparation method of FRP basalt fiber walkway plate

Abstract

The invention discloses a preparation method of an FRP basalt fiber walkway plate, and relates to the technical field of fiber reinforced composites.The preparation method is technically characterized by comprising the following steps that S1, basalt fibers are prepared into a three-dimensional gradient fiber preformed body with a surface layer structure, a middle layer structure and a core layer structure through a three-dimensional weaving technology; wherein the surface layer is formed by tightly weaving fine denier basalt fibers with the linear density higher than 600 tex; the middle layer is formed by weaving continuous basalt fibers at a weaving angle of + / -45 degrees to + / -60 degrees; the core layer is of a loose three-dimensional grid structure formed by compounding basalt fiber chopped strand mats and axial continuous fibers; the technical effect is that the three-dimensional gradient fiber preforming body with the dense weaving surface layer, the large-angle weaving middle layer and the loose core layer is designed and prepared in advance, so that the material is endowed with a heterogeneous mechanical structure from the source. The densely-woven surface layer provides good surface hardness and local impact resistance.

Description

Technical Field

[0001] This invention relates to the field of fiber reinforced composite materials technology, specifically to a method for preparing an FRP basalt fiber walkway panel. Background Technology

[0002] Railway bridge walkways are crucial facilities for ensuring the safe passage of maintenance personnel, and their performance directly affects maintenance efficiency and operational safety. Currently, commonly used walkway slabs mainly include precast concrete walkway slabs and steel grating walkway slabs.

[0003] Precast concrete walkway slabs present challenges due to their heavy weight and difficulties in installation and transportation. More seriously, under harsh outdoor conditions such as prolonged exposure to sun and rain, freeze-thaw cycles, and salt and ice corrosion, concrete is prone to carbonation, weathering, and cracking, leading to steel reinforcement corrosion, structural failure, and serious safety hazards. Furthermore, subsequent maintenance costs are high. While steel grating walkway slabs offer high strength, they also suffer from drawbacks such as heavy weight, high cost, and inconvenient installation. Their grating structure results in poor foot comfort, easily accumulates ice, snow, and debris, and the steel itself is susceptible to electrochemical corrosion in humid and salt spray environments, leading to insufficient durability.

[0004] Therefore, developing a method for manufacturing FRP walkway panels that can overcome the above-mentioned defects and achieve designable performance, balanced mechanical properties in all directions, and excellent durability has important engineering application value. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing FRP basalt fiber walkway panels, which solves the problem of preparing FRP basalt fiber walkway panels.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing an FRP basalt fiber walkway panel, comprising the following steps: S1. Basalt fibers are woven into a three-dimensional gradient fiber preform having a surface layer, an intermediate layer, and a core layer structure through a three-dimensional weaving process; wherein, the surface layer is made of fine denier basalt fibers tightly woven with a linear density higher than 600 tex; the intermediate layer is made of continuous basalt fibers woven at a weaving angle of ±45° to ±60°; the core layer is composed of basalt fiber chopped strand mat and axial continuous fibers to form a loose three-dimensional mesh structure; S2. The three-dimensional gradient fiber preform obtained in step S1 is drawn through a first impregnation tank and impregnated with a surface functional resin system; the surface functional resin system comprises, by weight, 100 parts of modified polyurethane resin, 15-30 parts of anti-slip sand, 5-15 parts of core-shell toughening microspheres, and nano-oxidation 3-10 parts aluminum, 1-3 parts UV absorber, 0.5-2 parts antioxidant; the impregnated preform enters the first curing zone and is pre-cured at 80-110℃ to make the surface resin reach a gel state and form a pre-cured surface layer; S3. The profile with the pre-cured surface layer obtained in step S2 is pulled through the second impregnation tank and impregnated with the main structural resin system; the main structural resin system includes, by weight, 100 parts modified polyurethane resin, 8-20 parts hyperbranched polymer toughening agent, 1-5 parts silane coupling agent, and 1-3 parts release agent; the impregnated profile enters the second curing zone and is mainly cured at 130-160℃ to make the main resin completely cured and react with the pre-cured surface layer through an interpenetrating network to form an integrated plate; S4. The integrated plate obtained in step S3 is cooled and cut to a set length to obtain the FRP basalt fiber walkway board.

[0007] Preferably, in step S1, the fiber volume content of the surface layer, the intermediate layer and the core layer are distributed in a gradient, wherein the fiber volume content of the surface layer is 50%-60%, the fiber volume content of the intermediate layer is 65%-75%, and the fiber volume content of the core layer is 30%-45%.

[0008] Preferably, the core-shell toughened microspheres have a particle size of 50-200 nm, with the core being polybutyl acrylate rubber and the shell being a polyurethane prepolymer with hydroxyl groups.

[0009] Preferably, the hyperbranched polymer toughening agent is a hydroxyl-terminated hyperbranched polyester with a molecular weight of 2000-6000 g / mol and a branching degree of 0.4-0.6.

[0010] Preferably, in the surface functional resin system, the modified polyurethane resin is a hydrophobic polyurethane resin modified by organosilicon segments, and the grafting rate of the organosilicon segments is 5%-15%.

[0011] Preferably, in step S2, the pre-curing time is 3-10 minutes; in step S3, the main curing time is 5-15 minutes.

[0012] Preferably, the main structural resin system further includes 0.5-3 parts by weight of color paste.

[0013] Preferably, when preparing the three-dimensional gradient fiber preform in step S1, fiber-reinforced polymer sleeves or channels are pre-woven into the core layer for subsequent installation and connection.

[0014] Compared with existing technologies, this invention provides a method for preparing FRP basalt fiber walkway panels, which has the following beneficial effects: By pre-designing and preparing a three-dimensional gradient fiber preform with a densely woven surface layer, a large-angle woven intermediate layer, and a loose core layer, a heterogeneous mechanical structure is endowed to the material from the source. The densely woven surface layer provides good surface hardness and resistance to localized impacts; the ±45° to ±60° woven intermediate layer greatly improves the shear and torsional resistance of the panel; the loose core layer ensures lightweight and a certain degree of compression resilience. This structural design fundamentally solves the problem of weak lateral and interlayer properties in traditional pultruded panels, enabling the product to withstand more complex dynamic loads.

[0015] The core of this invention is a two-stage impregnation-multi-stage curing process. First, a preform is impregnated with a resin system rich in wear-resistant and anti-aging components and pre-cured to a gel state, forming a functionalized surface shell. Then, a high-strength and tough base resin is used for a second impregnation and high-temperature curing. At the interface, the gel-state surface resin and the flowing base resin undergo an interpenetrating network (IPN) reaction, forming strong chemical bonds. This achieves seamless integration of the wear-resistant and weather-resistant surface layer with the high-strength and tough base, avoiding the risk of delamination.

[0016] A resin system with specific modifications is used for different functional areas. The surface resin is modified with organosilicon grafting and toughened with core-shell elastic microspheres, simultaneously improving hydrophobicity, weather resistance, and impact resistance; the main resin is toughened with hyperbranched polymers, significantly improving toughness without affecting the resin's wettability to complex preforms. The two-component system works synergistically to achieve superior results.

[0017] The product combines the advantages of being lightweight and high-strength, corrosion-resistant, fatigue-resistant, paint-free, and long-lasting anti-slip. It is easy to install and requires almost no maintenance, which greatly reduces the costs of transportation, installation, and subsequent maintenance and replacement. Its economic efficiency throughout the entire life cycle is significantly better than that of concrete and steel products. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the preparation method of the present invention; Figure 2 This is a schematic diagram of the two-stage impregnation and curing process of the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figure 1 and Figure 2 This invention provides a technical solution for the preparation of FRP basalt fiber walkway panels:

[0021] Flexural strength testing reference standards: ISO 14125 (Determination of flexural properties of fiber-reinforced plastic composites) or ASTM D7264 (Standard test method for flexural properties of polymer-based composites).

[0022] Detailed steps:

[0023] Sample preparation: Cut rectangular samples of specified dimensions (approximately 1.2 times the span, according to standard requirements) from the finished walkway slab along both the longitudinal and transverse directions.

[0024] Test setup: Use a three-point or four-point bending test apparatus. For anisotropic materials, three-point bending is typically used. Calculate and set the span between the support rollers precisely according to standards (such as ISO 14125 or ASTM D7264) and the specimen thickness (typically 16-40 times the thickness to ensure that failure is dominated by bending stress).

[0025] Test Procedure: Place the specimen symmetrically on the support rollers. Apply a load at a constant rate (e.g., 2 mm / min) at the center or one-third of the span until the specimen fails. The test should be conducted in a standard laboratory environment (e.g., temperature 23 ± 2°C, humidity 50 ± 10%).

[0026] Data recording: Continuously record the load-displacement curve. Based on the curve and specimen dimensions, calculate the bending strength (maximum bending stress) and bending modulus (stress-strain ratio within the elastic range).

[0027] Interlaminar shear strength testing reference standard: The short beam shear method is commonly used, referring to ASTM D2344 (Standard Test Method for Short Beam Strength of Polymer-Based Composites and Laminates). This method is a commonly used approach for evaluating the interlaminar shear properties of fiber-reinforced composites.

[0028] Detailed steps:

[0029] Sample preparation: Cut short, thick rectangular samples, the length of which is usually 6 times the thickness.

[0030] Test setup: A three-point bending apparatus is used, but with an extremely short span-to-thickness ratio (typically 4:1 or 5:1). This short span design is intended to cause the specimen to fail due to interlaminar shear stress before significant bending deformation occurs.

[0031] Test: Place the sample on the support roller and apply a load at the center at a relatively fast loading rate (e.g., 1 mm / min).

[0032] Data logging: Record the maximum load at which the specimen fails. The interlaminar shear strength is calculated using a specific formula that relates the maximum load, specimen width, and thickness.

[0033] Impact strength testing reference standards: ISO 179-1 (Plastics—Determination of impact strength of simply supported beams) or ASTM D6110 (Standard test method for Charpy impact strength of notched specimens in plastics).

[0034] Detailed steps:

[0035] Sample preparation: Process rectangular samples of specified dimensions, with or without a V-notch.

[0036] Test setup: A pendulum impact testing machine was used. The specimen was placed horizontally on the machine support, acting as a simply supported beam.

[0037] Test: Release a pendulum with known energy and strike the middle of the specimen (or the back of the notch).

[0038] Data recording: Measure the remaining oscillation energy after the pendulum breaks the specimen. Impact strength is calculated by dividing the energy absorbed during specimen fracture by the cross-sectional area (or width) of the notch in the specimen.

[0039] Density testing reference standard: ISO 1183-1 (Plastics—Determination of density—Part 1: Impregnation method).

[0040] Detailed steps:

[0041] Weigh the sample in air (m1).

[0042] Immerse the sample in distilled water (if the material does not absorb water, a very thin hydrophobic coating can be applied to prevent air bubbles), and determine its apparent mass (m2) in water using a buoyancy balance or weighing device.

[0043] According to Archimedes' principle, the bulk density of the sample is calculated using the formula density = m1 / (m1-m2)*ρwater (ρwater is the density of water at the test temperature).

[0044] Hardness testing (Barcol hardness) reference standard: ASTM D2583 (Standard test method for testing the indentation hardness of hard plastics using a Barcol hardness tester).

[0045] Detailed steps:

[0046] Instrument calibration: Ensure accurate readings of the Barcol hardness tester on the glass standard.

[0047] Sample placement: Place the finished walkway slab or a sufficiently thick, flat sample on a sturdy table.

[0048] Test procedure: Hold the hardness tester perpendicular to the sample surface and press down quickly and steadily until the indenter is fully inserted. Record the maximum reading on the dial.

[0049] Multi-point measurement: Measure at least 5 times at different locations on the same sample surface, and take the average value as the Barcol hardness value of the sample.

[0050] For anti-slip performance testing (wet friction coefficient), the reference standard is GB / T4100-2015 (ceramic tiles) Appendix M (wet method for determining static friction coefficient), or the more general ASTM E303 (standard test method for measuring surface friction properties using a British pendulum tester).

[0051] Detailed steps (using the pendulum method):

[0052] Sample preparation: Fix the sample horizontally on the surface of the walkway slab.

[0053] Wetting the surface: Use standard methods (such as spraying) to form a uniform water film on the sample surface.

[0054] Release the pendulum: After raising the rubber slider of the pendulum to a fixed height, release it so that it slides over the wet and slippery sample surface.

[0055] Data recording: Record the height the pendulum swings after gliding over a wet surface. By comparing the energy loss when gliding on a standard smooth surface, calculate and convert it into an anti-slip value (BPN) or coefficient of friction. The higher the value, the better the anti-slip performance.

[0056] Reference standards for UV aging resistance testing: ISO 4892-2 (Plastics—Laboratory light source exposure methods—Part 2: Xenon arc lamps) or ASTM G155 (Standard procedure for operation of xenon arc lamp equipment for exposure of nonmetallic materials).

[0057] Detailed steps:

[0058] Sample preparation: Prepare multiple sets of parallel samples.

[0059] Aging Cycle: Place the sample in a xenon lamp aging test chamber. Set the illumination cycle (e.g., continuous illumination or alternating light and dark), chamber temperature (e.g., 65°C), blackboard temperature, and relative humidity. Simulate a rain spray cycle. The total aging time can be set as needed (e.g., 2000 hours in this application).

[0060] Performance evaluation: At aging time points of 0 hours, 500 hours, 1000 hours, and 2000 hours, the samples were removed, conditioned in a standard environment for at least 24 hours, and then the bending strength test was performed.

[0061] Calculation result: Strength retention rate = (average strength after aging / average initial strength) × 100%.

[0062] Example 1: Preparation of a three-dimensional gradient fiber preform: A 400mm wide and 25mm thick board was woven. The surface layer used 1200 tex basalt fiber, plain weave, with a fiber volume content of 50%; the middle layer used 2400 tex fiber, woven at ±45° angles, with a fiber volume content of 65%; the core layer used a mixture of basalt chopped strand mat (150g / m²) and axial fibers, with a volume content of 30%. A pre-woven FRP sleeve was used for the core layer.

[0063] 100 parts of polyurethane resin with 5% organosilicon grafting rate, 15 parts of 80-mesh corundum, 5 parts of core-shell toughened microspheres (particle size 50nm), 3 parts of nano alumina, 1 part of UV stabilizer, and 0.5 parts of antioxidant.

[0064] 100 parts of ordinary polyurethane resin, 8 parts of hyperbranched polyester (molecular weight 2000, branching degree 0.4), 1 part of silane coupling agent, 1 part of release agent, and 0.5 parts of color paste.

[0065] The preform is pulled at 0.4 m / min, first impregnated with resin A, and then pre-cured in the first curing zone at 80°C for 10 minutes; then impregnated with resin B and pre-cured in the second curing zone at 130°C for 15 minutes.

[0066] Post-processing: After cooling, cut into standard lengths.

[0067] Example 2, Preform: The structure is the same as in Example 1, but the fiber volume content is adjusted to: surface layer 55%, middle layer 70%, core layer 40%.

[0068] 100 parts of polyurethane resin with 10% organosilicon grafting rate, 22 parts of 60-mesh corundum, 10 parts of core-shell toughened microspheres (particle size 100nm), 6 parts of nano alumina, 2 parts of UV stabilizer, and 1.2 parts of antioxidant.

[0069] 100 parts of ordinary polyurethane resin, 15 parts of hyperbranched polyester (molecular weight 4000, branching degree 0.5), 3 parts of silane coupling agent, 2 parts of release agent, and 1.5 parts of color paste.

[0070] Traction speed: 0.6 m / min. Pre-curing conditions: 100℃, 7 minutes. Main curing conditions: 150℃, 10 minutes.

[0071] The rest is the same as in Example 1.

[0072] Example 3, preform: the fiber volume content is adjusted to: surface layer 60%, middle layer 75%, core layer 45%.

[0073] 100 parts of polyurethane resin with 15% organosilicon grafting rate, 30 parts of 46-mesh diamond abrasive, 15 parts of core-shell toughened microspheres (particle size 200nm), 10 parts of nano alumina, 3 parts of UV stabilizer, and 2 parts of antioxidant.

[0074] 100 parts of ordinary polyurethane resin, 20 parts of hyperbranched polyester (molecular weight 6000, branching degree 0.6), 5 parts of silane coupling agent, 3 parts of release agent, and 3 parts of color paste.

[0075] Traction speed: 0.8 m / min. Pre-curing conditions: 110℃, 3 minutes. Main curing conditions: 160℃, 5 minutes.

[0076] The rest is the same as in Example 1.

[0077] Example 4, Preform: The structure and fiber content are the same as in Example 2, the key difference being that the weaving angle of the intermediate layer is increased to ±60°.

[0078] The rest is the same as in Example 2.

[0079] Example 5, Preform: The structure and fiber content are the same as in Example 2, but the core layer does not have pre-woven FRP sleeves, and only the mesh structure is retained.

[0080] The rest is the same as in Example 2.

[0081] Comparative Example 1: The gradient design was eliminated. Basalt fibers of the same total weight as in Example 2 were used, but all were changed to a 0° unidirectional arrangement, supplemented with a small amount of chopped strand mat, to form a homogeneous fiber layup.

[0082] The rest is the same as in Example 2.

[0083] Comparative Example 2: Resin A and Resin B were pre-mixed physically at a solid content ratio (approximately 1:3) to prepare a single resin system C.

[0084] After the preform is impregnated with mixed resin C, it is directly placed in the 150℃ curing zone for curing for 10 minutes at a time, without going through a pre-curing step.

[0085] The rest is the same as in Example 2.

[0086] Comparative Example 3: No core-shell toughening microspheres were added to the surface resin A, while the remaining components and their amounts remained unchanged. Everything else was the same as in Example 2.

[0087] Comparative Example 4: No hyperbranched polymer was added to the main resin B. To ensure the total resin volume, an equal amount of ordinary polyurethane resin was used instead. The rest was the same as in Example 2.

[0088] In Comparative Example 5, an equal amount of unmodified ordinary polyurethane resin was used to replace the silicone-modified polyurethane resin in surface resin A, while the remaining components and their amounts remained unchanged. The rest was the same as in Example 2.

[0089] The walkway panels obtained from Examples 1, 2, 3, 4, 5 and Comparative Examples 1, 2, 3, 4, 5 were grouped together, and the products of the Examples and Comparative Examples were subjected to performance tests, including initial antibacterial rate (%), antibacterial rate after 50 washes (%), contact angle (°), and fiber polymerization degree. The specific test results are detailed in Tables 1 and 2.

[0090] Table 1

[0091]

[0092] Table 2

[0093]

[0094] Comparative Example 1 exhibited the highest longitudinal strength, but its transverse flexural strength and interlaminar shear strength plummeted to less than 1 / 5 and 1 / 3 of those of Example 2, respectively. This demonstrates that the "three-dimensional gradient structure design" of this invention is the decisive factor in solving the anisotropy problem of FRP pultruded sheets and obtaining balanced and excellent mechanical properties, which cannot be achieved by simple material superposition. Comparative Example 2, which used a one-time curing process, showed significantly lower interlaminar shear strength and impact toughness than Example 2. This indicates that the interpenetrating network (IPN) interface formed by "pre-curing-main curing" can more effectively transfer and disperse stress, improving integrity and anti-delamination ability compared to the physical interface formed by one-time curing. The significant decrease in impact strength of Comparative Example 3 indicates that the core-shell microspheres effectively induce microcracks and absorb impact energy on the surface, which is crucial for improving the product's resistance to instantaneous impact. Comparative Example 4 showed a decrease in longitudinal, transverse, and impact strength, proving that the hyperbranched polymer enhanced the toughness of the matrix without compromising its basic strength, thus playing a multifunctional synergistic role. Comparative Example 5 showed a significantly increased water absorption rate and a substantial decrease in strength retention after QUV aging. This verifies the outstanding effect of organosilicon segment modification on improving the hydrophobicity of the resin and its resistance to UV light and moisture erosion, which is the fundamental guarantee for long-term weather resistance. Example 2 showed the best overall performance. Example 4 demonstrated higher transverse strength, confirming the designability of the braid angle for specific properties.

[0095] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A method for preparing an FRP basalt fiber walkway slab, characterized in that: Includes the following steps: S1. Basalt fibers are processed using a three-dimensional weaving process to create a three-dimensional gradient fiber preform with a surface layer, an intermediate layer, and a core layer; wherein, the surface layer is made of fine denier basalt fibers tightly woven with a linear density higher than 600 tex; the intermediate layer is made of continuous basalt fibers woven at a weaving angle of ±45° to ±60°; and the core layer is made of basalt fiber chopped strand mat and axial continuous fibers to form a loose three-dimensional mesh structure. S2. The three-dimensional gradient fiber preform obtained in step S1 is pulled through the first impregnation tank and impregnated with a surface functional resin system. The surface functional resin system comprises, by weight, 100 parts of modified polyurethane resin, 15-30 parts of anti-slip sand, 5-15 parts of core-shell toughened microspheres, 3-10 parts of nano-alumina, 1-3 parts of UV absorber, and 0.5-2 parts of antioxidant. The impregnated preform enters the first curing zone and is pre-cured at 80-110°C to make the surface resin reach a gel state and form a pre-cured surface layer. S3. The profile with the pre-cured surface layer obtained in step S2 is pulled through the second impregnation tank and impregnated with the main structural resin system; the main structural resin system includes, by weight, 100 parts of modified polyurethane resin, 8-20 parts of hyperbranched polymer toughening agent, 1-5 parts of silane coupling agent, and 1-3 parts of release agent; the impregnated profile enters the second curing zone and is mainly cured at 130-160℃ to completely cure the main resin and react with the pre-cured surface layer through an interpenetrating network reaction to form an integrated plate. S4. Cool the integrated plate obtained in step S3 and cut it to a set length to obtain the FRP basalt fiber walkway plate.

2. The method for preparing an FRP basalt fiber walkway slab according to claim 1, characterized in that: In step S1, the fiber volume content of the surface layer, intermediate layer and core layer is distributed in a gradient, wherein the fiber volume content of the surface layer is 50%-60%, the fiber volume content of the intermediate layer is 65%-75%, and the fiber volume content of the core layer is 30%-45%.

3. The method for preparing an FRP basalt fiber walkway slab according to claim 1, characterized in that: The core-shell toughened microspheres have a particle size of 50-200 nm, with a core of polybutyl acrylate rubber and a shell of polyurethane prepolymer with hydroxyl groups.

4. The method for preparing an FRP basalt fiber walkway slab according to claim 1, characterized in that: The hyperbranched polymer toughening agent is a hydroxyl-terminated hyperbranched polyester with a molecular weight of 2000-6000 g / mol and a branching degree of 0.4-0.

6.

5. The method for preparing an FRP basalt fiber walkway slab according to claim 1, characterized in that: In the surface functional resin system, the modified polyurethane resin is a hydrophobic polyurethane resin modified by organosilicon segments, and the grafting rate of organosilicon segments is 5%-15%.

6. The method for preparing an FRP basalt fiber walkway slab according to claim 1, characterized in that: In step S2, the pre-curing time is 3-10 minutes; in step S3, the main curing time is 5-15 minutes.

7. The method for preparing an FRP basalt fiber walkway slab according to claim 1, characterized in that: The main structural resin system also contains 0.5-3 parts by weight of color paste.

8. The method for preparing an FRP basalt fiber walkway slab according to claim 1, characterized in that: In step S1, when preparing the three-dimensional gradient fiber preform, fiber-reinforced polymer sleeves or channels are pre-woven into the core layer for subsequent installation and connection.

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