Composite board and preparation method and application thereof

Abstract

The application relates to a composite board and a preparation method and application thereof. The preparation method of the composite board comprises the following steps: providing a base board, wherein the base board comprises thermoplastic resin; performing surface activation treatment on a composite surface of the base board; heating the composite surface subjected to the surface activation treatment until the thermoplastic resin of the surface layer is melted; laminating expanded fireproof felt on the melted thermoplastic resin; performing compression at a temperature lower than the melting point of the thermoplastic resin; and cooling and shaping to prepare the composite board. The preparation method can help realize firm combination between the fireproof felt and the base board, reduce the risk of delamination and peeling during service, and ensure that the expansion function of the fireproof felt is completely reserved and the mechanical properties and size precision of the base board are not influenced.

Description

Technical Field

[0001] This application relates to the field of functional panel technology, specifically to a composite panel and its preparation method and application. Background Technology

[0002] Continuous fiber reinforced thermoplastic composites possess advantages such as lightweight, high strength, and recyclability, and have broad application prospects in transportation, aerospace, and other fields. However, the inherent flammability of thermoplastic resins limits their use in fire-resistant applications. To improve the fire resistance of these materials, a feasible approach is to laminate them with intumescent fire-resistant felt. This utilizes the property of the fire-resistant felt to expand upon contact with fire, forming a heat-insulating char layer to protect the internal structure.

[0003] Related technologies have attempted to combine flame-retardant fiber felt as a surface layer with the composite material matrix, for example, through resin transfer molding, vacuum infusion, or compression molding, to form the fireproof felt and reinforcement together. However, when the composite material matrix is ​​a thermoplastic material, due to the low surface energy and strong chemical inertness of thermoplastic resins, the interfacial bonding strength between the fireproof felt and the supporting layer (such as a board) is often insufficient after direct lamination. This can easily lead to delamination during service, resulting in the failure of the fireproof function. To address this, related technologies use adhesives to bond the fireproof felt to the surface of the supporting layer to reinforce the composite structure. However, the adhesive layer is prone to aging and cracking under long-term vibration, alternating high and low temperatures, and humid aging conditions, causing the fireproof felt to fall off. Furthermore, adhesives themselves are often flammable organic materials, which may actually worsen the overall flame-retardant performance.

[0004] Therefore, how to achieve a strong and durable integrated composite between intumescent fireproof felt and thermoplastic composite materials is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, this application provides a composite board, its preparation method, and its application to solve the above-mentioned technical problems.

[0006] To achieve the above objectives, in a first aspect, this application provides a method for preparing a composite board, comprising the following steps: providing a base board comprising a thermoplastic resin; performing surface activation treatment on the surface of the base board to be composited; heating the surface of the base board to be composited after surface activation treatment until the surface thermoplastic resin melts; stacking an intumescent fireproof felt on the molten thermoplastic resin; pressing the felt together at a temperature lower than the melting point of the thermoplastic resin; and cooling and shaping to prepare the composite board.

[0007] Based on the first aspect, in some embodiments, the surface energy of the composite surface after surface activation treatment is greater than or equal to 55 mN / m.

[0008] Based on the first aspect, in some embodiments, the surface activation treatment includes one of plasma treatment and flame treatment.

[0009] Based on the first aspect, in some embodiments, the plasma treatment power is 300 W to 500 W, and the time is 3 min to 8 min.

[0010] Based on the first aspect, in some embodiments, heating is performed to a temperature 10°C to 30°C above the melting point of the thermoplastic resin, and the holding time is 3 min to 5 min, thereby melting the surface thermoplastic resin.

[0011] Based on the first aspect, in some embodiments, the pressing temperature is 10°C to 30°C below the melting point of the thermoplastic resin.

[0012] Based on the first aspect, in some embodiments, the pressing pressure is from 1 MPa to 15 MPa.

[0013] Based on the first aspect, in some embodiments, the holding time for pressing is 2 to 10 minutes.

[0014] Based on the first aspect, in some embodiments, the thermoplastic resin includes at least one of polypropylene, polyamide, and polycarbonate.

[0015] Based on the first aspect, in some embodiments, the base plate also includes reinforcing fibers.

[0016] Based on the first aspect, in some embodiments, the reinforcing fiber includes at least one of glass fiber, basalt fiber, aramid fiber and carbon fiber.

[0017] Based on the first aspect, in some embodiments, the reinforcing fibers include continuous reinforcing fibers.

[0018] Based on the first aspect, in some embodiments, the intumescent fireproof felt includes an intumescent flame retardant, which includes a composite system of expandable graphite and zirconium phosphate and / or a composite system of ammonium polyphosphate, melamine and pentaerythritol.

[0019] Based on the first aspect, in some embodiments, the expansion initiation temperature of the intumescent fireproof felt is greater than or equal to 200°C.

[0020] Secondly, this application provides a composite board, which is prepared according to the above-described preparation method and has a single-sided composite structure or a double-sided composite structure.

[0021] Thirdly, this application provides the application of the aforementioned composite sheet material in battery casings and / or vehicle interior parts.

[0022] In this application, surface activation treatment of the base material helps to increase the density of polar functional groups on the surface of the thermoplastic resin, which is originally chemically inert and has low surface energy, creating good chemical affinity for subsequent fusion bonding. Heating the surface-activated surface melts the surface resin on the side closest to the surface while the base material remains solid, which helps to avoid dimensional instability and mechanical property degradation of the base material caused by overall heating. Intumescent fireproof felt is laminated on the molten thermoplastic resin and pressed at a temperature below the resin melting point. After pressing, the molten surface resin impregnates the fireproof felt. This process utilizes the fluidity of the molten resin to form a physically interwoven anchoring structure with the fibers and bonding resin of the fireproof felt. At the same time, since the fireproof felt does not need to be heated during the composite process and the pressing process is carried out at a low temperature, it also helps to keep the overall temperature of the fireproof felt below its expansion initiation temperature, thereby reducing the risk of premature irreversible expansion reaction of the intumescent flame retardant leading to a decrease in expansion ratio when exposed to fire. Finally, cooling and shaping solidify the impregnated resin to obtain an integrated composite material. Compared with traditional techniques that involve heating and pressing the dry fireproof felt and the support layer together or using adhesives, the preparation method of this application helps to achieve a firm bond between the fireproof felt and the base plate while ensuring that the expansion function of the fireproof felt is fully preserved and the mechanical properties and dimensional accuracy of the base plate are basically unaffected, thereby reducing the risk of delamination during service. Attached Figure Description

[0023] Figure 1 The appearance test results of the composite board provided in Embodiment 1 of this application before and after combustion; wherein, Figure 1 Image (a) is a front view of the composite panel before combustion. Figure 1 (b) in the image is a front view of the composite panel after combustion. Figure 1 (c) in the figure is a side view of the composite panel after combustion. Detailed Implementation

[0024] To facilitate understanding of the technical solutions of this application, a more comprehensive description of the technical solutions of this application will be provided below with reference to the accompanying drawings, which illustrate preferred embodiments of the technical solutions of this application. However, the technical solutions of this application can be implemented in many different forms and are not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and comprehensive understanding of the disclosure of the technical solutions of this application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] To address the technical problem of poor bonding strength between intumescent fireproof felt and thermoplastic composite materials, this application found that while thermal bonding can improve the bonding strength, heating both the intumescent fireproof felt and the thermoplastic composite material as a whole causes the intumescent flame retardant to undergo an irreversible expansion reaction prematurely at high temperatures, significantly reducing its expansion ratio upon exposure to fire and even completely eliminating its fire-protective function. Simultaneously, overall heating also leads to overall softening and dimensional instability of the thermoplastic base material, impairing its mechanical properties and product precision. Therefore, it is necessary to achieve a strong and durable integrated composite between the intumescent fireproof felt and the thermoplastic base material without compromising the expansion function of the fireproof felt or reducing the mechanical properties and dimensional precision of the thermoplastic base material.

[0027] Based on this, one embodiment of this application provides a method for preparing a composite board, comprising the following steps:

[0028] Step 1: Provide a base board, which includes thermoplastic resin, and perform surface activation treatment on the surface of the base board to be laminated.

[0029] In the above steps, surface activation treatment of the base plate helps to increase the density of polar functional groups on the surface of the thermoplastic resin, which is originally chemically inert and has low surface energy, thus creating good chemical affinity for subsequent melt bonding.

[0030] In some embodiments, the surface energy of the composite surface after surface activation treatment is greater than or equal to 55 mN / m. Furthermore, after surface activation treatment of the base plate, controlling the surface energy of the composite surface to be composite within a range greater than or equal to a preset value is beneficial for transforming the originally hydrophobic, low-energy thermoplastic surface into a high-energy surface, and further enhancing the wetting and spreading ability of the molten resin on the fireproof felt fibers and bonding resin, thereby providing favorable conditions for improving the interfacial bonding strength.

[0031] In some embodiments, surface activation treatment includes one of plasma treatment and flame treatment. Furthermore, the above-mentioned surface activation treatment methods are all dry, environmentally friendly surface modification technologies. They help to break the molecular chains on the surface of thermoplastic resins and introduce polar functional groups such as hydroxyl and carbonyl groups without introducing additional chemical substances, thereby effectively increasing surface energy. Compared with methods such as chemical etching or mechanical polishing, plasma or flame treatment is beneficial for achieving controllable surface treatment levels and batch consistency, reducing the risk of damage to the strength of the base material.

[0032] In some embodiments, the plasma treatment power is 300 W to 500 W, and the time is 3 min to 8 min. For example, the plasma treatment power can be 300 W, 320 W, 340 W, 360 W, 380 W, 400 W, 420 W, 440 W, 460 W, 480 W, 500 W, or any value within the range of any two of the above values, and the plasma treatment time can be 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, or any value within the range of any two of the above values. Furthermore, when using plasma treatment, controlling the treatment power and time within the above ranges helps to fully remove surface contaminants and introduce sufficient polar functional groups while reducing the risk of excessive etching or thermal oxidative degradation of the thermoplastic resin surface when the power is high or the time is long. This maintains the integrity of the base material's structural strength while increasing the surface energy to an ideal level.

[0033] In some embodiments, the thermoplastic resin includes at least one of polypropylene, polyamide, and polycarbonate. Furthermore, selecting the above-mentioned substances as thermoplastic resins is advantageous due to the good processing and mechanical properties of these two resins.

[0034] In some embodiments, the base board further includes reinforcing fibers. When the base board also includes reinforcing fibers, the preparation method of this application can reduce the risk of orientation disorder of the reinforcing fibers caused by high temperatures during overall heating, thereby helping to maintain the mechanical properties of the reinforcing fibers and thus facilitating further improvement of the mechanical strength of the resulting composite board.

[0035] In some embodiments, the reinforcing fiber includes at least one selected from glass fiber, basalt fiber, aramid fiber, and carbon fiber. Furthermore, selecting the above-mentioned materials for the reinforcing fiber helps to utilize the cost advantage of glass fiber or the high specific strength and high specific modulus properties of carbon fiber.

[0036] In some embodiments, the reinforcing fibers include continuous reinforcing fibers. Furthermore, when the reinforcing fibers include continuous reinforcing fibers, it is advantageous to fully utilize the high strength and high modulus of continuous fibers in the load-bearing direction, enabling the composite panel to maintain good structural mechanical properties while achieving lightweight design.

[0037] In some embodiments, the intumescent fireproof felt includes an intumescent flame retardant, which includes a composite system of expandable graphite and zirconium phosphate and / or a composite system of ammonium polyphosphate, melamine, and pentaerythritol. Furthermore, the intumescent flame retardant is selected from the above systems, which can rapidly expand upon contact with fire to form a dense, porous char layer, thereby providing heat insulation and oxygen barrier fire protection.

[0038] In some embodiments, the expansion initiation temperature of the intumescent fireproof felt is greater than or equal to 200 °C. Furthermore, controlling the expansion initiation temperature of the intumescent fireproof felt to be greater than or equal to a preset value helps ensure that, even if the base material is heated above the resin melting point during the composite process, the fireproof felt will not undergo irreversible premature expansion due to contact with the heated base material surface during lamination and pressing. This ensures its expansion ratio and char layer integrity when exposed to fire, reducing the risk of loss of fireproof function.

[0039] Understandably, the combination of the above material selection with the preparation method of this application is beneficial to endowing the base plate with more reliable fire-resistant function while maintaining its original excellent mechanical properties.

[0040] Step 2: Heat the surface to be laminated after surface activation treatment until the surface thermoplastic resin melts.

[0041] In the above steps, the surface to be laminated is heated after surface activation treatment, so that the surface resin on the side closest to the surface to be laminated melts, while the main body of the base board remains solid. This helps to avoid dimensional instability and decreased mechanical properties of the base board caused by overall heating.

[0042] In some embodiments, the material is heated to a temperature 10°C to 30°C above the melting point of the thermoplastic resin, and held at that temperature for 3 to 5 minutes, thereby melting the surface thermoplastic resin. For example, the surface-activated base material can be heated to a temperature 10°C, 12°C, 14°C, 16°C, 18°C, 20°C, 22°C, 24°C, 26°C, 28°C, or 30°C above the melting point of the thermoplastic resin, or any value within the range of any two of the above values, and the holding time can be 3 minutes, 3.2 minutes, 3.4 minutes, 3.6 minutes, 3.8 minutes, 4 minutes, 4.2 minutes, 4.4 minutes, 4.6 minutes, 4.8 minutes, or 5 minutes, or any value within the range of any two of the above values. Furthermore, heating the surface to be laminated to the above-mentioned temperature range and controlling the holding time within the above-mentioned range for the surface activation treatment helps to allow the surface resin on the side close to the surface to be laminated to melt more fully and maintain appropriate fluidity. This also reduces the risk of the base board softening excessively or the fireproof felt expanding prematurely due to heat radiation when the heating temperature is high. At the same time, the main body of the base board remains solid because it has not reached the overall melting temperature. Thus, during the subsequent pressing process, the molten resin can more effectively wet the fiber gaps of the intumescent fireproof felt under pressure, forming a mechanical anchor, while the base board as a whole does not soften or deform.

[0043] Step 3: Lay the intumescent fireproof felt on the molten thermoplastic resin and press it at a temperature lower than the melting point of the thermoplastic resin.

[0044] In the above steps, an intumescent fireproof felt is laminated onto molten thermoplastic resin and pressed at a temperature below the resin's melting point. After pressing, the molten surface resin impregnates the fireproof felt. This process utilizes the fluidity of the molten resin to form a physically interwoven anchoring structure with the fibers and bonding resin of the fireproof felt. At the same time, since the fireproof felt does not require heating during the composite process and the pressing process is carried out at a lower temperature, it also helps to keep the overall temperature of the fireproof felt below its expansion initiation temperature, thereby reducing the risk of the intumescent flame retardant undergoing an irreversible expansion reaction prematurely, leading to a decrease in the expansion ratio when exposed to fire.

[0045] In some embodiments, the pressing temperature is 10°C to 30°C below the melting point of the thermoplastic resin. For example, the pressing temperature can be 10°C, 12°C, 14°C, 16°C, 18°C, 20°C, 22°C, 24°C, 26°C, 28°C, or 30°C below the melting point of the thermoplastic resin, or any value within the range of any two of the above values. Furthermore, by controlling the pressing temperature within the above temperature range, since the pressing temperature is below the resin melting point, the pressing action has a cooling effect on the base plate as a whole, and is conducive to further promoting the formation of a physically interwoven anchoring structure between the molten thermoplastic resin and the fibers and bonding resin of the fireproof felt, followed by cooling to form a strong bonding interface.

[0046] In some embodiments, the pressing pressure is from 1 MPa to 15 MPa. For example, the pressing pressure can be 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, or any value within the range of any two of the above values. In some embodiments, the holding time for pressing is from 2 min to 10 min. For example, the holding time can be 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, or any value within the range of any two of the above values. Furthermore, controlling the pressing pressure and holding time within the above range helps the molten surface resin to penetrate into the fiber network and bonding resin of the intumescent fireproof felt before cooling during the pressing process, further promoting the formation of a dense interfacial interpenetrating layer, and reducing the risk of insufficient resin wetting when the pressure is too low or the holding time is too short, or excessive resin extrusion or deformation of the base plate when the pressure is too high or the holding time is too long.

[0047] Step 4: Cool and solidify to prepare composite board.

[0048] In the above steps, the impregnated resin is cured by cooling and shaping to obtain an integrated composite board.

[0049] Compared with traditional techniques that involve heating and pressing the dry fireproof felt and the support layer together or using adhesives, the preparation method of this application helps to achieve a firm bond between the fireproof felt and the base plate while ensuring that the expansion function of the fireproof felt is fully preserved and the mechanical properties and dimensional accuracy of the base plate are basically unaffected, thereby reducing the risk of delamination during service.

[0050] One embodiment of this application also provides a composite board, which is prepared according to the above-described preparation method and has a single-sided composite structure or a double-sided composite structure.

[0051] In this application, the composite panel has a single-sided or double-sided composite structure, allowing for flexible selection of either composite fireproof felt only on the side requiring fire protection or composite on both sides, depending on specific application needs. Due to the use of surface activation treatment combined with selective heating and low-temperature pressing, the interface between the intumescent fireproof felt and the base panel in this composite panel is firmly bonded, which helps resist the risk of delamination under long-term vibration and alternating high and low temperature environments. Simultaneously, the expansion ratio of the fireproof felt is maintained, which helps provide reliable fire protection. The mechanical properties and dimensional accuracy of the base panel are largely unaffected by the composite process, thus enabling the entire composite panel to possess both excellent structural load-bearing capacity and fire safety.

[0052] One embodiment of this application also provides the application of the above-described composite sheet material in battery casings and / or vehicle interior parts.

[0053] In this application, the composite sheet material can be used in battery casings and / or vehicle interior components (such as automotive interior components, aerospace interior components, and rail transit vehicle interior components), which helps meet the comprehensive requirements of these fields for lightweight materials, high mechanical strength, and stringent fire safety performance. For example, its use in the casings of new energy vehicle battery packs helps to delay the spread of fire in the event of battery thermal runaway and reduces the risk of damage to adjacent battery cells; its use in aerospace and rail transit interior components helps to meet the stringent requirements of relevant industry standards (such as UL94 V0, EN45545, etc.) for the flame retardancy rating and smoke emission of materials, while maintaining the lightweight and high-strength characteristics of the composite sheet material, which helps to improve the energy efficiency and safety level of vehicles.

[0054] The present application will be described below through specific embodiments and comparative examples. Those skilled in the art should understand that the preparation methods described in this application are merely examples, and any other suitable preparation methods are within the scope of this application.

[0055] Example 1:

[0056] A composite board is prepared by the following method:

[0057] Materials preparation:

[0058] (1) Base board: Continuous glass fiber reinforced polypropylene (GF / PP) composite board with a glass fiber content of 50 wt%, a unidirectional continuous fiber layup, a board thickness of 2 mm, and a size of 300 mm × 300 mm. The melting point of polypropylene is 167 ℃ (DSC test, heating rate 10 ℃ / min). The original surface energy of the surface to be composited is 28 mN / m (contact angle method, 25 ℃); (2) Intumescent fireproof felt: Intumescent fireproof felt with glass fiber chopped strand mat as the base, a thickness of 0.8 mm, and a surface weight of 150 g / m 2 The intumescent flame retardant is a composite system of ammonium polyphosphate / melamine / pentaerythritol (APP / MEL / PER) in a mass ratio of 3:1:1. The initial expansion temperature is greater than 200 ℃ (thermogravimetric analysis, air atmosphere, heating rate 10 ℃ / min), and the ultimate expansion ratio is 20 times (flame burn at 800 ℃ for 3 min). The binding resin is an acrylic thermoplastic resin, with a content of approximately 15 wt%.

[0059] Step 1: Cut the GF / PP sheet into 300 mm × 300 mm pieces, wipe the surface to be laminated with anhydrous ethanol, and allow it to air dry. Treat one side of the sheet using an atmospheric plasma treatment device (equipped with a rotating nozzle). Treatment parameters: power 400 W, nozzle scanning speed 50 mm / s, treatment distance 10 mm, treatment time 5 min (covering the entire surface to be laminated). After treatment, the surface water contact angle decreased from 105° to 35°, and the surface energy increased from 28 mN / m to 58 mN / m.

[0060] Step 2: The plasma-treated GF / PP sheet is placed in an infrared heating furnace (2 kW power, wavelength 1 μm~3 μm) and heated to 190 ℃ (23 ℃ higher than the PP melting point of 167 ℃), with a heating rate of approximately 15 ℃ / s and a holding time of 4 min. The surface temperature is monitored in real time using an infrared thermometer, with temperature fluctuations controlled within ±3 ℃. After heating, only the surface and near-surface layer (approximately 0.3 mm~0.5 mm depth) of the resin melts, while the main body of the sheet remains solid. The intumescent fireproof felt is kept at room temperature (approximately 25 ℃) without any preheating treatment.

[0061] Step 3: Preheat the flatbed press to 150℃ (17℃ lower than the PP melting point of 167℃) and maintain a constant temperature. Quickly stack the heated GF / PP sheet (treated side up) with the room temperature intumescent fireproof felt, ensuring direct contact between the activated surface to be laminated and the fireproof felt. Place it in the center of the mold and press: initially pre-press at 1 MPa for 10 seconds to release air, then increase the pressure to 5 MPa and hold for 5 minutes. During the pressing process, control the mold temperature fluctuation within ±2℃. A small amount of molten resin will be visible being extruded from the surface of the base sheet and impregnating the fireproof felt fibers.

[0062] Step 4: After the pressure holding period, immediately introduce circulating cooling water (inlet temperature 20 ℃, outlet temperature 25 ℃), with a cooling rate of approximately 10 ℃ / min. The temperature at mold opening is 45 ℃. After demolding, trim the edges to obtain a single-sided fireproof composite board with a total thickness of approximately 2.5 mm.

[0063] Example 2:

[0064] Materials preparation:

[0065] (1) Base plate: Continuous carbon fiber reinforced polyamide 6 (CF / PA6) composite material plate, the carbon fiber is T700 grade, plain weave, carbon fiber content is 55 vol%, the plate thickness is 2.0 mm, and the size is 400 mm × 400 mm. The melting point of polyamide 6 is 220 ℃, and the original surface energy is 35 mN / m; (2) Intumescent fireproof felt: Stainless steel wire mesh-aramid fiber composite felt, the wire diameter is 0.05 mm, the mesh number is 50 mesh, and the aramid fiber is in short-cut form. The thickness is 1.0 mm, and the surface weight is 250 g / m. 2 The intumescent flame retardant is a compound system of expandable graphite (EG, 50 mesh, expansion ratio 250 times) and zirconium phosphate (ZrP, flake diameter 1μm~2μm) in a mass ratio of 5:1. The expansion initiation temperature is greater than 220 ℃, and the ultimate expansion ratio is greater than 30 times. The bonding resin is polyamide 6 (the same as the base board resin), with a content of approximately 12wt%.

[0066] Step 1: Both sides of the CF / PA6 sheet were treated using a flame treatment device (propane / air mixed burner, flame temperature approximately 1000℃~1200℃). Treatment parameters: flame distance 25 mm, treatment speed 100 mm / s, 2 treatment passes (cross-direction), oxygen / fuel ratio optimized to achieve a blue flame (smokeless). After treatment, the surface energy increased from 35 mN / m to 62 mN / m (dyne pen test), and XPS analysis showed an increase in surface oxygen content from 8% to 22%.

[0067] Step 2: Place the CF / PA6 sheet in a hot air circulating oven and heat it to 245 ℃ (25 ℃ higher than the PA6 melting point of 220 ℃) ​​for 5 minutes to melt the resin on the surface and near the surface of the sheet. The intumescent fireproof felt is kept at room temperature (about 25 ℃) and is not heated.

[0068] Step 3: Prepare two pieces of intumescent fireproof felt (same size as the base board), both kept at room temperature. Preheat the flatbed press mold to 200℃ (20℃ lower than the PA6 melting point of 220℃). Lay them in the following order: lower mold → fireproof felt → heated CF / PA6 base board → fireproof felt → upper mold, ensuring that the two surfaces of the base board to be laminated are in contact with the two pieces of fireproof felt, and press them together: use segmented pressurization, first pre-press at 2 MPa for 20 seconds, then increase the pressure to 10 MPa and hold for 8 minutes.

[0069] Step 4: After the pressure holding period, start the water cooling circulation (cooling water temperature 15 ℃), with a cooling rate of approximately 15 ℃ / min. The temperature at the time of mold opening is 60 ℃. After demolding, a double-sided fireproof composite board is obtained with a total thickness of approximately 3.8 mm.

[0070] Example 3:

[0071] The difference from Example 2 is that in the second step, the heating temperature is adjusted to 230 ℃ (that is, 10 ℃ higher than the melting point of PA6 220 ℃), and the heating time is 8 min; in the third step, the hot pressing temperature is adjusted to 210 ℃ (that is, 10 ℃ lower than the melting point of PA6 220 ℃), the pressure is adjusted to 5 MPa, and the pressure is held for 2 min.

[0072] Example 4:

[0073] The difference from Example 2 is that in the second step, the heating temperature is adjusted to 250 ℃ (that is, 30 ℃ higher than the melting point of PA6 220 ℃), and the heating time is 3 min; in the third step, the hot pressing temperature is adjusted to 190 ℃ (that is, 30 ℃ lower than the melting point of PA6 220 ℃), the pressure is adjusted to 1 MPa, and the pressure is held for 10 min.

[0074] Comparative Example 1:

[0075] The same base board (GF / PP, without any surface activation treatment) and intumescent fireproof felt as in Example 1 were used.

[0076] Overall heating: The GF / PP sheet was directly heated to 190 ℃ (same as in Example 1) and held at that temperature for 4 min to bring the entire sheet to the set temperature. Simultaneously, the intumescent fireproof felt was also heated to 190 ℃ in the same oven. The heated GF / PP sheet and the heated fireproof felt were then stacked together and placed in a flatbed press preheated to 190 ℃. A pressure of 5 MPa was applied and held for 5 min. After pressure holding, water cooling was performed. The mold opening temperature was 45 ℃, and the composite sheet was obtained after demolding.

[0077] Comparative Example 2:

[0078] The same base board (GF / PP, without surface activation treatment) and intumescent fireproof felt as in Example 1 were used. A two-component epoxy resin adhesive (A / B adhesive) with a nominal shear strength of 12 MPa was also prepared.

[0079] Apply adhesive: Apply epoxy resin evenly to the surface of the GF / PP sheet to be laminated and the corresponding surface of the intumescent fireproof felt, with an adhesive application rate of approximately 100 g / m² on each side. 2 (Total adhesive application amount 200 g / m) 2 The two materials were then laminated at room temperature. The laminated sample was placed in a flatbed press, subjected to a pressure of 0.5 MPa, heated to 80 °C, and cured for 2 hours. After curing, it was allowed to cool naturally to room temperature to obtain the composite board.

[0080] The testing method for this application is as follows:

[0081] 1. Interface peel strength: Refer to GB / T 2790-1995, use the 180° peel method, test width 25 mm, peel speed 100 mm / min.

[0082] 2. Thermal cycling aging test: Referring to GB / T 2423.22, the sample was kept at -40 ℃ for 1 hour, followed by 80 ℃ for 1 hour, with each cycle lasting 2 hours. The peel strength retention rate was tested after 0, 200, 500, 800, and 1000 cycles respectively.

[0083] 3. Fireproof felt expansion ratio test: Carefully peel off the fireproof felt layer from the composite board, and vertically burn the peeled fireproof felt with an 800 ℃ propane flame for 3 minutes. Measure the thickness before and after burning and calculate the expansion ratio.

[0084] 4. Flame retardant performance test: Vertical burning test according to UL94; cone calorimeter test according to ISO 5660 to measure maximum average heat release rate and total heat release; fire resistance limit test according to GB / T 9978.

[0085] 5. Mechanical property testing: Tensile strength and tensile modulus are tested according to ISO 527-5; flexural strength and flexural modulus are tested according to ISO 14125. The retention rate of mechanical properties is calculated using unreinforced virgin GF / PP sheets as a control.

[0086] Based on the above testing methods, the following performance tests were conducted in this application:

[0087] 1. The composite plates of Example 1 and Comparative Examples 1-2 were subjected to interfacial peel strength tests, and the interface failure modes under extreme conditions were recorded. Please refer to Table 1.

[0088] 2. The composite boards of Example 1 and Comparative Example 2 were subjected to thermal cycling aging tests, please refer to Table 2.

[0089] 3. The fireproof felt expansion ratio test was conducted on the composite boards of Example 1 and Comparative Example 1, and the original fireproof felt (uncomposite) was added as a control. Please refer to Table 3.

[0090] 4. Flame retardant performance tests were conducted on Example 1, and a GF / PP base board without fireproof felt was added as a control. Please refer to Table 4.

[0091] 5. Mechanical performance tests were conducted on Example 1, and a GF / PP base board without fireproof felt was added as a control. Please refer to Table 5.

[0092] 6. Five batches (10 boards per batch) of Example 1 were prepared continuously, and the batch-to-batch variation of key performance indicators was tested. Please refer to Table 6.

[0093] 7. Single-sided interfacial peel strength, tensile properties, flexural properties, UL94 flame retardant rating, limiting oxygen index, maximum heat release rate, and fire resistance limit were tested for Examples 2-4. CF / PA6 base board without fireproof felt was added as a control. Please refer to Table 7.

[0094] This application also includes fire performance tests on the composite panels of the embodiments. Please refer to [link / reference]. Figure 1 Taking Example 1 as an example, by comparing... Figure 1 (a) and Figure 1 As can be seen from the comparison of (b) and (c), the composite panel of this application expands after combustion and does not separate from the base panel.

[0095] Table 1. Test results of interfacial peel strength of composite panels of Example 1 and Comparative Examples 1-2 of this application

[0096]

[0097] According to Table 1, the interfacial peel strength of Example 1 of this application is higher than that of Comparative Examples 1-2, and the failure mode is the cohesive tensile breakage of the fireproof felt fibers themselves, while the comparative samples all showed interfacial peeling or adhesive layer failure. This result indicates that a strong interfacial bond cannot be obtained solely through direct hot pressing or adhesive bonding. The preparation method of this application allows the molten surface resin to fully wet the fireproof felt fibers and form a physical anchor. Simultaneously, the activated high surface energy enhances the chemical affinity between the resin and the fireproof felt, thereby achieving an interfacial bond strength superior to that of conventional technologies.

[0098] Table 2. Results of thermal cycling aging tests on the composite panels of Example 1 and Comparative Example 2 of this application.

[0099]

[0100] According to Table 2, Example 1 of this application maintained a high peel strength retention rate after 1000 cycles, while Comparative Example 2 showed a significant decrease in strength retention rate during the cycling process and localized cracking occurred in the later stages of the cycle. This result indicates that the adhesive layer of traditional adhesive composites is prone to aging, becoming brittle, or developing internal stress cracking under drastic temperature alternation, leading to an increased risk of fireproof felt detachment. In contrast, the anchoring structure formed by the integrated fusion bonding of this application has better thermomechanical stability, which helps reduce the risk of interface failure due to environmental aging during long-term service.

[0101] Table 3. Test results of fireproof felt expansion ratio of the composite board and the original fireproof felt in Example 1 and Comparative Example 1 of this application.

[0102]

[0103] According to Table 3, the expansion ratio of the fireproof felt in Example 1 of this application is basically the same as that of the original fireproof felt, while the expansion ratio of the fireproof felt in Comparative Example 1 is significantly reduced. This result indicates that in the direct integral hot-pressing process, the high temperature experienced by the fireproof felt causes the intumescent flame retardant to undergo an irreversible expansion reaction prematurely, preventing it from fully forming a heat-insulating char layer when exposed to fire. In contrast, the preparation method of this application keeps the fireproof felt in a low-temperature environment throughout the entire composite process, effectively avoiding premature pyrolysis of the flame retardant and thus fully preserving the fireproof felt's expansion function upon exposure to fire.

[0104] Table 4. Flame retardant performance test results of the composite board and GF / PP base board of Example 1 of this application

[0105]

[0106] According to Table 4, the flame retardant rating of Example 1 of this application reaches V0, the limiting oxygen index is improved, the maximum average heat release rate and total heat release are significantly reduced, and the fire resistance limit exceeds that of the GF / PP base board. This result indicates that after the intumescent fireproof felt is firmly bonded to the surface of the thermoplastic composite material, the fireproof felt can rapidly expand to form a dense, heat-insulating char layer when exposed to fire, effectively blocking the transfer of flames and heat to the base board, thereby improving the overall fire safety of the composite board; simultaneously, since the expansion function of the fireproof felt is not damaged by the process, its protective effect is fully realized.

[0107] Table 5. Mechanical property test results of the composite board and GF / PP base board of Example 1 of this application

[0108]

[0109] According to Table 5, the tensile strength, tensile modulus, flexural strength, and flexural modulus of Example 1 of this application all remain at high levels, with a smaller decrease compared to the GF / PP base board. This result indicates that the preparation method used in this application prevents the base board from reaching its melting temperature, avoiding fiber orientation disorder, resin degradation, or board warping caused by overall softening. Simultaneously, low-temperature pressing further suppresses thermal damage, thus endowing the board with excellent fire resistance while almost completely preserving the original load-bearing capacity and structural precision of the base board, achieving a unity of fire resistance and structural performance.

[0110] Table 6. Process stability test results of Example 1 of this application

[0111]

[0112] According to Table 6, taking Example 1 as an example, the average values ​​of key performance indicators such as interfacial peel strength, expansion ratio, and tensile strength of the five batches are consistent with the results of a single batch in Example 1. The coefficients of variation of each indicator are controlled at a low level (less than 2%), and the UL94 flame retardant rating of all batches consistently reaches V0. This result indicates that the process of this application has good controllability and repeatability. The fluctuation range of each process parameter (such as plasma treatment power and time, heating temperature and time, pressing pressure and mold temperature, etc.) has little impact on the final product quality, which is beneficial to reducing the risk of batch-to-batch differences in industrial production. In contrast, the direct integral hot pressing or adhesive bonding method in traditional technologies often makes it difficult to guarantee batch stability because the pre-expansion degree of the fireproof felt is greatly affected by temperature fluctuations and the curing conditions of the adhesive are sensitive to interface quality. The preparation method of this application keeps the fireproof felt in a low-temperature environment, avoiding the uncontrollable influence of high temperature on the performance of the fireproof felt, and at the same time providing a stable interfacial chemical state, thus making the entire composite process more tolerant to fluctuations in process parameters. This result fully demonstrates that the method of this application has good prospects for engineering application and can meet the requirements of large-scale production for product consistency and reliability.

[0113] Table 7. Test results of multiple properties of the composite board and CF / PA6 base board in Examples 2-4 of this application.

[0114]

[0115] Based on the test results of Example 1 in Tables 1-6 and Example 2-4 in Table 7, the present application embodiments, by performing surface activation treatment on the base plate, are beneficial to increasing the density of polar functional groups on the originally chemically inert and low-surface-energy thermoplastic resin surface to be laminated, thus creating good chemical affinity for subsequent melt bonding; heating the surface-activated surface to be laminated causes the surface resin on the side closest to the surface to be laminated to melt, while the main body of the base plate remains solid, which helps to avoid dimensional instability and decreased mechanical properties of the base plate caused by overall heating; and the expansion layer is laminated on the molten thermoplastic resin. The fire-retardant felt is expanded and pressed at a temperature below the resin's melting point. During pressing, the molten surface resin impregnates the fire-retardant felt. This process utilizes the fluidity of the molten resin to form a physically interwoven anchoring structure with the fire-retardant felt's fibers and the bonding resin. Furthermore, since the fire-retardant felt does not require heating during the composite process, and the pressing is carried out at a lower temperature, it helps to keep the overall temperature of the fire-retardant felt below its expansion initiation temperature. This reduces the risk of premature irreversible expansion of the intumescent flame retardant, leading to a decrease in expansion ratio upon exposure to fire. Finally, cooling and solidification allow the impregnated resin to cure, resulting in an integrated composite board. Compared to traditional techniques that involve heating and pressing the dry fire-retardant felt and the supporting layer together or using adhesives, the preparation method of this application helps to achieve a strong bond between the fire-retardant felt and the base board while ensuring the complete preservation of the fire-retardant's expansion function and minimal impact on the mechanical properties and dimensional accuracy of the base board. This reduces the risk of delamination during service.

[0116] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0117] The embodiments described above are merely illustrative of several implementations of the technical solution of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the technical solution of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for preparing a composite board, characterized in that, Includes the following steps: A base plate is provided, the base plate comprising thermoplastic resin, and the surface of the base plate to be laminated is subjected to surface activation treatment; The surface to be laminated, which has undergone the surface activation treatment, is heated until the thermoplastic resin on the surface melts; An intumescent fireproof felt is laminated onto molten thermoplastic resin and pressed at a temperature below the melting point of the thermoplastic resin. The composite material is prepared by cooling and shaping.

2. The preparation method according to claim 1, characterized in that, The surface activation treatment is performed under at least one of the following conditions: (1) The surface energy of the composite surface after the surface activation treatment is greater than or equal to 55 mN / m; (2) The surface activation treatment includes plasma treatment, wherein the power of the plasma treatment is 300 W to 500 W and the time is 3 min to 8 min; (3) The surface activation treatment includes flame treatment.

3. The preparation method according to claim 1, characterized in that, The heating process is carried out to a temperature 10°C to 30°C above the melting point of the thermoplastic resin, and the holding time is 3 min to 8 min, thereby melting the thermoplastic resin on the surface layer.

4. The preparation method according to claim 1, characterized in that, The pressing temperature is 10°C to 30°C below the melting point of the thermoplastic resin.

5. The preparation method according to claim 4, characterized in that, The pressing pressure is from 1 MPa to 15 MPa.

6. The preparation method according to claim 5, characterized in that, The pressure holding time for the pressing is 2 to 10 minutes.

7. The preparation method according to claim 1, characterized in that, The base plate satisfies at least one of the following conditions: (1) The thermoplastic resin includes at least one of polypropylene, polyamide and polycarbonate; (2) The base plate also includes reinforcing fibers; (3) The base plate also includes reinforcing fibers, which include at least one of glass fiber, basalt fiber, aramid fiber and carbon fiber; (4) The base plate also includes reinforcing fibers, which include continuous reinforcing fibers.

8. The preparation method according to claim 1, characterized in that, The intumescent fireproof felt meets at least one of the following conditions: (1) The intumescent fireproof felt includes an intumescent flame retardant, which includes a composite system of expandable graphite and zirconium phosphate and / or a composite system of ammonium polyphosphate, melamine and pentaerythritol; (2) The expansion initiation temperature of the intumescent fireproof felt is greater than or equal to 200 ℃.

9. A composite board, characterized in that, The composite board is prepared according to the preparation method described in any one of claims 1-8; The composite material is a single-sided composite structure or a double-sided composite structure.

10. The application of the composite sheet material as described in claim 9 in battery casings and / or vehicle interior trim.

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