Flame retardant rigidified glass fiber cloth and method for manufacturing the same

Abstract

The application discloses a kind of flame retardant fixed type glass fiber cloth and preparation method thereof, it is related to high polymer composite material technical field, scheme constructs fixed type flame retardant interface layer on the surface of glass fiber cloth and between fiber bundle, including the anchoring layer formed by epoxy silane, crosslinking solidified water-based epoxy film-forming fixed layer, and the halogen-free flame-retardant component and shielding skeleton component dispersed therein;Method includes desizing drying pretreatment, coupling agent impregnation heat curing, preparation fixed coating liquid, impregnation extrusion liquid gradient drying and solidification after.The interface "anchoring-film-forming-fixing" of the present application improves component retention and layer integrity, shortens afterburning and improves the oxygen concentration required for maintaining combustion, and stably improves the flame-retardant grade;Continuous dense carbon layer is formed under heat and cracks are inhibited, so that heat release and smoke release are simultaneously reduced;Pyrolysis process is postponed and high-temperature residue is increased, which embodies synergistic carbon promotion / carbon preservation;Interfacial load transfer is more continuous, so that interlaminar shear, bending and impact performance remain at a high level with less dispersion.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and in particular to a flame retardant-fixed glass fiber cloth and its preparation method. Background Technology

[0002] Fiberglass reinforced composites are widely used in electronic and electrical laminates, rail transportation and aerospace interiors, construction and new energy equipment, and other fields due to their advantages such as high specific strength, good dimensional stability, corrosion resistance and electrical insulation. However, fiberglass reinforced systems face multi-dimensional coupling risks of "heat-smoke-structure" under fire conditions: on the one hand, the matrix resin and interface phase are combustible phases, which will produce combustible volatiles after heating and drive flame propagation; on the other hand, the layered structure of the fabric and the interlayer interface can easily form channels for the escape of pyrolysis gases, leading to combustion development and amplified smoke production; at the same time, many application scenarios have clear requirements for halogen-free, low smoke and low heat release, and the manufacturing end requires controllable processes, environmental friendliness, and no significant sacrifice to the mechanical load-bearing capacity of the composite. Therefore, the industry is gradually shifting from "simply improving the flame retardant rating" to a comprehensive goal of "inhibiting combustion development, controlling heat release, reducing smoke toxicity, and maintaining interfacial mechanical properties" in the flame retardant and smoke reduction technology of fiberglass reinforced composites, and showing a development trend from solvent-based to water-based, from halogen-based to halogen-free, and from bulk phase addition to precise construction of interface / fabric layers.

[0003] In existing technologies, flame retardant treatments for fiberglass cloth and its composites can be broadly categorized into two types: bulk modification and surface / coating modification. However, both still generally fall short in achieving synergistic effects between flame retardancy, smoke reduction, and interfacial mechanics. Bulk modification typically achieves flame retardancy by introducing flame-retardant components into the resin system, but this can lead to problems such as increased resin viscosity, decreased wetting and penetration capabilities, curing shrinkage, and increased internal stress. Ultimately, this can easily induce porosity, dry spots, and interlayer defects, resulting in decreased interlayer shear capacity. Furthermore, bulk flame-retardant components may migrate or precipitate under thermal cycling or humid environments, affecting the long-term stability and repeatability of the flame-retardant effect. Surface / coating modification, on the other hand, often employs methods such as coating "flame-retardant adhesive layers / bonding layers / composite layers" to enhance flame retardancy. CN104441845A, "High Flame Retardant Glass Fiber Knitted Fabric," discloses a flame-retardant adhesive layer set on the surface of a glass fiber base fabric and bonded to the surface material, emphasizing the flame-retardant coating structure at the fabric level. However, this type of solution is more geared towards the flame-retardant requirements of textiles / covering materials, with the coating mostly concentrated on the outer surface, making it difficult to effectively penetrate between fiber bundles and interlayer interfaces. Therefore, under composite stress scenarios, it is prone to forming a modulus mismatch between a "hard and brittle coating and a flexible matrix," resulting in microcracks and debonding channels. Cracking of the coating during combustion also weakens the shielding continuity. CN104401101A, "Preparation Method of Flame Retardant Fabric," mainly obtains flame-retardant fabric by compositing a glass fiber base fabric with a non-woven layer. Its advantage lies in the flame-retardant durability of the fabric structure, but its technical focus is not on the interfacial load transfer and interlayer shear failure of composite materials. Faced with key failure mechanisms of composite materials such as resin wetting, interlayer slip, and crack propagation, it is still difficult to avoid the contradiction of "the flame-retardant layer exists, but the interfacial load is weakened." CN104140770A, "A Flame-Retardant Thermally Conductive Double-Sided Adhesive for Glass Fiber Cloth," uses glass fiber fabric as the substrate and forms a flame-retardant and thermally conductive adhesive layer on its surface, focusing on adhesive / thermal conduction applications. However, for glass fiber cloth reinforced structural composites, this type of pressure-sensitive / adhesive layer system is more prone to softening, flowing, or carbonizing and shrinking under heat exposure, forming pores and through-hole defects, making it easier for pyrolysis gases to exchange with oxygen, which in turn leads to accelerated combustion development and increased smoke production. Overall, existing patent solutions either favor flame-retardant coatings on fabrics / materials or adhesive products, or flame retardancy in the resin phase. In composite material scenarios, they often encounter three main challenges: First, insufficient "retention and continuity" of the flame-retardant component in the fiber bundles and interface regions makes it difficult to form a stable, dense, and non-detachable / crackable heat-insulating and oxygen-barrier layer during combustion. Second, insufficient interfacial compatibility and stress transfer between the flame-retardant layer and the matrix / fiber result in interface defects and stress concentration, manifesting as performance degradation under multi-field coupled forces such as interlayer shear, bending, and impact. Third, it is difficult to simultaneously achieve synergistic suppression of heat release and smoke release, especially in halogen-free systems. Without effective control over the pyrolysis path and char layer structure, situations often arise where "the flame-retardant rating is barely met, but the overall heat-smoke hazard remains high."The root cause of the above shortcomings is that the combustion and failure of composite materials is not a simple chemical flame retardant problem, but a systemic problem jointly determined by the continuity of the interface structure, the migration of pyrolysis products, the integrity of the char layer and the transfer of mechanical loads. Once the interface layer is discontinuous or not firmly bonded to the fiber bundle, the shielding layer is easily destroyed by thermal shrinkage and gas erosion during combustion. At the same time, under mechanical loading, it is more likely to propagate cracks along the interface defects, making it difficult to improve flame retardancy and mechanical properties simultaneously.

[0004] Based on the above situation, there is an urgent need in related fields for a technical approach for the application of fiberglass reinforced composite materials: without relying on halogen-based flame retardancy or excessively sacrificing processing wetting and interfacial load-bearing capacity, to achieve higher stability and continuity of flame retardant function on the fabric surface and between fiber bundles / interfacial regions, thereby facilitating self-extinguishing after ignition and inhibiting flame development, while reducing the combined risks of heat and smoke release; and possessing stronger pyrolysis stability and high-temperature char retention capacity under heat exposure, making the heat-insulating and oxygen-barrier structure formed during combustion more continuous, denser, and less prone to cracking or detachment; furthermore, it should avoid the increase in interfacial defects and exacerbation of interlaminar slippage caused by surface treatment, ensuring that interlaminar shear load-bearing capacity, flexural load-bearing capacity, and impact energy dissipation capacity remain at an engineering-usable level with controllable dispersion. The core technical problem to be solved by this invention is: how to simultaneously achieve the unity of "flame retardancy and self-extinguishing with suppression of combustion development," "synergistic reduction of heat and smoke," "pyrolysis stability and char retention enhancement," and "interfacial load-bearing capacity retention" in a fiberglass reinforced composite material system, and to stably achieve this unity under conditions of process feasibility and repeatable quality. Summary of the Invention

[0005] To achieve the above-mentioned objectives and address the aforementioned technical problems, this invention provides a flame-retardant-fixed glass fiber cloth, wherein a fixed flame-retardant interface layer is provided on the surface of the glass fiber cloth and between the fiber bundles, the fixed flame-retardant interface layer comprising: An anchoring layer, which is formed by treating the surface of glass fiber cloth with an epoxy silane coupling agent; A film-forming and bonding layer, wherein the film-forming and bonding layer is a cross-linked and cured aqueous epoxy resin film; The halogen-free flame retardant component and the shielding skeleton component are dispersed in the film-forming and immobilizing layer, wherein the halogen-free flame retardant component includes ammonium polyphosphate and melamine polyphosphate, and the shielding skeleton component includes organobentonite.

[0006] The present invention also provides a method for preparing the flame retardant-fixed glass fiber cloth as described above, comprising the following steps: (1) Desizing and drying pretreatment of glass fiber cloth; (2) The pretreated glass fiber cloth is immersed in a treatment solution containing epoxy silane coupling agent, and after removing the excess liquid by squeezing with a pressure roller, it is heat-cured to obtain glass fiber cloth forming an anchoring layer. (3) Prepare a curing coating solution, wherein the curing coating solution comprises an aqueous epoxy resin dispersion, an aqueous curing agent, ammonium polyphosphate, melamine polyphosphate and organic bentonite; (4) The glass fiber cloth obtained in step (2) is immersed in the fixation coating liquid, and after the excess coating liquid is removed by squeezing with a pressure roller, it is subjected to gradient drying and curing to obtain flame retardant fixed glass fiber cloth.

[0007] Preferably, the desizing in step (1) is performed using an aqueous sodium carbonate solution.

[0008] Preferably, the desizing in step (1) is performed by treating with a 2 wt% sodium carbonate aqueous solution at 60°C for 15–25 min and drying at 110°C for 20–40 min.

[0009] Preferably, after the desizing process in step (1), the glass fiber cloth is rinsed with clean water until the washing solution is neutral in order to remove residual sodium carbonate and soluble impurities; then it is dried.

[0010] Preferably, the epoxy silane coupling agent in step (2) is 3-glycidyl ether propyltrimethoxysilane with a mass fraction of 0.2–3.0 wt%, and the solvent of the treatment solution is ethanol and water with a volume ratio of 90:10–95:5.

[0011] Preferably, the pH of the treatment solution of the epoxy silane coupling agent is adjusted to 4.3–4.8.

[0012] Preferably, the treatment solution in step (2) is allowed to stand before impregnation for 10–60 min.

[0013] Preferably, the thermosetting conditions in step (2) are 80°C for 8–12 min, followed by curing at 120°C for 15–25 min.

[0014] Preferably, in step (2), the glass fiber cloth is immersed in the treatment solution for 2–5 minutes.

[0015] Preferably, the waterborne epoxy resin dispersion in step (3) has a solid content of 45–55 wt%.

[0016] Preferably, the mass ratio of ammonium polyphosphate to melamine polyphosphate in step (3) is 1.2:1–2.5:1, and the two together account for 30–55 wt% of the solid content in the fixation coating solution.

[0017] Preferably, the amount of organic bentonite added in step (3) is 3–10 wt% of the solid content in the fixation coating solution.

[0018] Preferably, the amount of waterborne curing agent added in step (3) is 5–25 wt% of the solid epoxy resin in the waterborne epoxy resin dispersion.

[0019] Preferably, the preparation of the fixation coating solution in step (3) includes the following sub-steps: a) Organic bentonite is added to an aqueous dispersion medium for pre-dispersion to form a stable lamellar dispersion; b) Add ammonium polyphosphate and melamine polyphosphate under stirring conditions to ensure uniform dispersion of the halogen-free flame retardant components; c) Add the water-based epoxy resin dispersion and mix thoroughly; d) Finally, add the water-based curing agent and mix well.

[0020] Preferably, the immersion time in step (4) is 1–3 min, and after removing excess coating liquid, the product is subjected to gradient drying at 80°C, 8–12 min, 120°C, and 12–18 min, followed by curing at 160°C for 15–25 min.

[0021] Preferably, by adjusting the degree of liquid squeezing by the pressure roller, the weight gain of the fixed flame-retardant interface layer relative to the glass fiber cloth is 8–15 wt%.

[0022] The beneficial effects of the technical solution provided by this invention are as follows: 1) Achieving the unity of flame retardancy, self-extinguishing, and combustion development inhibition: The material of this invention can enter the self-extinguishing state more quickly under vertical combustion conditions and significantly weaken afterflame behavior. At the same time, it corresponds to a higher oxygen concentration required to maintain combustion, indicating that the combustion chain reaction after ignition is suppressed and the flame development is more difficult to enter the intense stage, thereby improving the stability and repeatability of the flame retardancy rating.

[0023] 2) Achieving a synergistic reduction in heat and smoke release: Consistent with the self-extinguishing trend, the overall combustion development risk indicators are more favorable and the overall smoke release related indicators are lower, indicating that the generation and escape of combustible pyrolysis products during the heating and combustion process of the material are restricted. The combustion mode has changed from "rapid development accompanied by significant smoke production" to "controlled pyrolysis and smoke reduction", thereby reducing the comprehensive heat and smoke hazards of the combustion process.

[0024] 3) Improved pyrolysis stability and enhanced high-temperature char retention: The pyrolysis initiation and main decomposition process of the material of this invention are shifted to the later stage, and the high-temperature residue is significantly improved. Moreover, the experimental residue is generally higher than the calculated value obtained by linear superposition of components, indicating that the system has a synergistic char-promoting and char-retaining effect. This synergistic effect can build a more continuous and stable barrier structure during heating, thereby further supporting the realization of combustion inhibition and smoke reduction effects.

[0025] 4) Maintaining the load-bearing capacity of composite material structure while achieving flame retardancy and smoke reduction: The interfacial shear load, flexural load and impact resistance of the material of the present invention can be maintained at a high level with small dispersion, indicating that the interfacial transition layer is more continuous, the load transfer path is more stable, and the tendency of interlayer slip and crack propagation is suppressed, thereby avoiding the obvious interfacial weakening problem caused by surface flame retardant treatment. Attached Figure Description

[0026] Figure 1 This is a SEM image of the cross section of Comparative Example 1 of this invention after ILSS testing.

[0027] Figure 2 This is a SEM image of the cross section after ILSS testing in Example 1 of the present invention.

[0028] Figure 3 These are photographs of the carbon residue of the material of the present invention after UL94V testing, where a: Comparative Example 4; b: Comparative Example 1; c: Comparative Example 2; d: Comparative Example 3; e: Example 1.

[0029] Figure 4 The images show the combustion of the material of the present invention during the UL94V test, where a: Example 1; b: Comparative Example 2.

[0030] Figure 5 The images show the char residue after combustion of the material of the present invention, where a: Example 1; b: Comparative Example 2. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] Example 1 Preparation steps of flame retardant-fixed fiberglass cloth: Step (1) Desizing and Drying Pretreatment a) Arrange glass fibers in a 2 wt% sodium carbonate aqueous solution and treat at 60°C for 20 min.

[0033] b) After removal, rinse with clean water until the washing solution is neutral to remove residual sodium carbonate and soluble impurities.

[0034] c) Arrange the rinsed glass fibers in an oven and dry them at 110°C for 30 min to obtain pretreated glass fiber cloth.

[0035] Step (2) Silane treatment to form an anchoring layer a) Preparation of silane treatment solution: Ethanol and water were used as solvents in a volume ratio of 92:8. Add 3-glycidyl ether propyltrimethoxysilane to it, making its mass fraction 1.2 wt%. Adjust the pH of the solution to 4.6 and stir well.

[0036] b) Let the above treatment solution stand for 30 minutes to allow the silane to be in a state that is more conducive to surface treatment.

[0037] c) Immerse the pretreated glass fiber cloth obtained in step (1) in a silane treatment solution for 3 minutes.

[0038] d) After impregnation, remove excess liquid by squeezing with pressure rollers, followed by heat curing: First 80℃ for 10 minutes; Then 120℃ for 20 minutes.

[0039] A glass fiber cloth with an anchoring layer formed on its surface is obtained.

[0040] Step (3) Prepare the fixation coating solution a) Pre-dispersed organic bentonite: Organic bentonite is added to an aqueous dispersion medium for pre-dispersion to obtain a sheet dispersion; wherein, the amount of organic bentonite added is set to 6 wt% (based on the solid content of the fixation coating liquid). b) Add ammonium polyphosphate (APP) and melamine polyphosphate (MPP) under stirring conditions to ensure uniform dispersion of the halogen-free flame retardant components; wherein: The quality ratio of APP to MPP is set at 1.8:1; The combined content of APP and MPP in the solids of the fixation coating solution is 45 wt%.

[0041] c) Add an aqueous epoxy resin dispersion (50 wt% solids) and mix thoroughly to make it the main body for film formation and provide a continuous phase basis for the film-forming fixation layer.

[0042] d) Finally, add the water-based curing agent and mix thoroughly; the amount of water-based curing agent added is based on the mass of epoxy resin solids in the water-based epoxy resin dispersion, and is taken as 15 wt.

[0043] The fixation coating is now obtained.

[0044] Step (4) Adhesion coating, gradient drying and curing a) Immerse the glass fiber cloth that forms the anchoring layer obtained in step (2) in the fixation coating solution in step (3) for 2 minutes.

[0045] b) After impregnation, excess coating liquid is removed by squeezing with pressure rollers, and after gradient drying and curing, the dry weight gain of the fixed flame retardant interface layer relative to the glass fiber cloth is 12 wt%, and the dry weight gain is controlled by adjusting the degree of squeezing with pressure rollers.

[0046] c) The extruded glass fiber cloth is subjected to gradient drying and curing in sequence: 80℃ for 10 min, used to initially remove moisture and stabilize the coating morphology; 120℃ for 15 min, to further dry and reduce defects; Subsequently, it is cured at 160℃ for 20 min to crosslink the waterborne epoxy into a film, forming a crosslinked and cured waterborne epoxy resin film, and fixing APP, MPP and organic bentonite to the surface of glass fiber cloth and between fiber bundles.

[0047] The flame retardant-fixed glass fiber cloth of Example 1 was obtained.

[0048] Example 2 Prepared using the same method as in Example 1, except that: In step (3), the water-based epoxy resin dispersion contains 45 wt% solids; the water-based curing agent is added at 5 wt% of the solid mass of the epoxy resin.

[0049] Step (4) The immersion time for the fixation coating is 1 min; the gradient drying and curing conditions are adjusted to 80℃ for 8 min, 120℃ for 12 min, and 160℃ for 15 min.

[0050] By adjusting the degree of liquid squeezing by the pressure roller, the dry weight gain of the fixed flame-retardant interface layer relative to the glass fiber cloth after drying and curing is 8 wt%.

[0051] Example 3 Prepared using the same method as in Example 1, except that: In step (3), the water-based epoxy resin dispersion contains 55 wt% solids; the water-based curing agent is added at 25 wt% of the solid mass of the epoxy resin.

[0052] Step (4) The immersion time for the fixation coating is 3 min; the gradient drying and curing conditions are adjusted to 80℃ for 12 min, 120℃ for 18 min, and 160℃ for 25 min.

[0053] By adjusting the degree of liquid squeezing by the pressure roller, the dry weight gain of the fixed flame-retardant interface layer relative to the glass fiber cloth after drying and curing is 15 wt%.

[0054] Example 4 Prepared using the same method as in Example 1, except that: In step (3), the mass ratio of APP to MPP is adjusted to 1.2:1.

[0055] Example 5 Prepared using the same method as in Example 1, except that: In step (3), the mass ratio of APP to MPP is adjusted to 2.5:1, and the total amount of APP+MPP in the solid content of the fixation coating is adjusted to 30 wt%.

[0056] Example 6 Prepared using the same method as in Example 1, except that: In step (3), the total amount of APP+MPP in the solid content of the fixation coating liquid is adjusted to 55 wt%, and the amount of organic bentonite added is adjusted to 3 wt%. Example 7 Prepared using the same method as in Example 1, except that: In step (2), the mass fraction of 3-glycidyl ether propyltrimethoxysilane in the silane treatment solution is 0.2 wt%; the volume ratio of ethanol to water is 95:5; and the pH of the treatment solution is adjusted to 4.8.

[0057] Step (2) Soaking time is 2 min.

[0058] Example 8 Prepared using the same method as in Example 1, except that: In step (2), the mass fraction of 3-glycidyl ether propyltrimethoxysilane in the silane treatment solution is 3.0 wt%; the volume ratio of ethanol to water is 90:10; and the pH of the treatment solution is adjusted to 4.3.

[0059] Step (2) Soaking time is 5 min.

[0060] Comparative Example 1 Flame retardant-fixed glass fiber cloth was prepared using the same preparation method as in Example 1, except that: In step (2), the surface treatment of epoxy silane coupling agent is not performed to form an anchoring layer. Instead, the pretreated glass fiber cloth obtained in step (1) is directly immersed in the fixation coating liquid prepared in step (3) and subjected to pressure roller squeezing, gradient drying and curing in step (4). The remaining steps and parameters are the same as in Example 1, thereby obtaining the glass fiber cloth of Comparative Example 1 without an anchoring layer.

[0061] Comparative Example 2 Prepared using the same method as in Example 1, except that: In step (3), when preparing the fixation coating solution, do not add ammonium polyphosphate (APP) and melamine polyphosphate (MPP), but only add organic bentonite, waterborne epoxy resin dispersion and waterborne curing agent to prepare the fixation coating solution. And in step (4), after drying and curing, control the dry weight gain to 12 wt%.

[0062] Comparative Example 3 Prepared using the same method as in Example 1, except that: In step (3), when preparing the fixation coating solution, do not add organic bentonite, but only add APP and MPP, waterborne epoxy resin dispersion and waterborne curing agent to prepare the fixation coating solution.

[0063] Comparative Example 4 Prepared using the same method as in Example 1, except that: In step (3), when preparing the fixation coating solution, no waterborne epoxy resin dispersion and waterborne curing agent are added. Instead, APP, MPP and organic bentonite are dispersed in an aqueous dispersion medium to obtain the fixation coating solution. The glass fiber cloth after squeezing was then subjected to gradient drying and heat treatment in sequence: 80℃ for 10 min, 120℃ for 15 min, and 160℃ for 20 min, in order to remove moisture and allow the inorganic flame retardant / lamellar filler to form a deposited layer.

[0064] Experimental test: 1. Mechanical properties Impact strength was tested using a domestically produced XJJ-40 impact testing machine according to GB / T1043-1993 standard. Bending strength and interlaminar shear strength were tested using a domestically produced KQL microcomputer-controlled electronic universal testing machine according to GB / T9341-2000, at a test speed of 2 mm / min. At least five valid results were obtained for each set of mechanical property tests, and the average value was taken as the final result.

[0065] 2. UL94 Vertical Burning Test: According to the ASTM (D63-77) method, the number of test samples for each material is 5.

[0066] 3. Limiting Oxygen Index (LOI): Tested according to standard GB2406-80. 4. Cone calorimetry: The test was conducted using a standard cone calorimeter (FTT007, Stanton Redcroft, UK).

[0067] According to ISO 5660 and ASTM E1354-94 international standards, the sample is analyzed using specialized analytical software to determine its flammability. The heat release rate (HRR), total heat release rate (THR), and mass loss rate (MRL) or mass loss (ML) of combustion. Characteristic parameters, etc. The test result error is controlled within ±10%, and the data is the average of three results.

[0068] 5. Thermogravimetric Analysis (TG): A PerkinElmer TGA-7 thermogravimetric analyzer was used to test the material under nitrogen atmosphere. Thermal stability in the environment, with a heating rate of 10℃ / min and a temperature range of 50-800℃. Initial thermal decomposition temperature. (T) di It is defined as the temperature at which 5% weight loss occurs.

[0069] Table 1 Sample Combustion Data

[0070] As shown in Table 1, there is a good correlation between the flame retardancy rating, afterflame behavior, oxygen index, and cone calorimetric smoke release index of each sample: The example group as a whole showed a higher UL94 rating and a shorter afterflame time, while the FPI remained at a high level, the SEA and TSR were at a low level, and the LOI was higher overall. This indicates that the material is more likely to self-extinguish under vertical combustion conditions, flame development is suppressed, heat release and smoke release are weakened simultaneously during the heated combustion process, and a higher oxygen concentration is required to maintain continuous combustion. Conversely, the samples with a lower flame retardancy rating or NR showed a significantly longer afterflame time, a lower FPI, a higher SEA and TSR, and a lower LOI. This indicates that combustion is more likely to develop into a violent stage, combustible pyrolysis products are more likely to maintain a combustion chain reaction, and are accompanied by heavier smoke generation. The above results can be explained by the differences in formulation and structure: In the example system, the "silane anchoring layer + waterborne epoxy crosslinking film" provides stable interface fixation and continuous phase coating, making APP / MPP more prone to expansion into carbon and forming a continuous and dense barrier layer when heated. The lamellar structure of organic bentonite further promotes the densification of the carbon layer and the sealing of cracks, thereby constructing a shielding channel for heat insulation, oxygen isolation and smoke suppression on the material surface and between fiber bundles. This shielding channel reduces the pyrolysis rate and inhibits the growth of the heat release peak on the one hand, and reduces the escape of combustible volatiles and the diffusion of oxygen inward on the other hand. Therefore, it is simultaneously reflected in the shortened UL94 afterflame, the reduced cone calorimetric smoke release and the overall increase in LOI value. Comparative Example 1 lacks an anchoring layer, resulting in insufficient interfacial adhesion and easy failure of the flame retardant layer; Comparative Example 2 lacks APP / MPP, causing the absence of a key expansion and char formation mechanism; Comparative Example 3 lacks organobentonite, weakening the density and shielding stability of the char layer; Comparative Example 4 lacks epoxy film formation and cross-linking fixation, making it difficult to form a continuous and stable flame retardant interfacial layer. All of these defects cause discontinuous or easily cracked / detached barrier layers, ultimately resulting in a decrease in flame retardant rating, increased afterflame, increased smoke release, and a decrease in LOI. Furthermore, it can be seen that the different embodiments exhibit certain fluctuations due to variations in parameters such as silane treatment intensity, epoxy / curing conditions, impregnation and dry weight gain, and the ratio and content of APP / MPP. This is consistent with the principle that "interfacial fixation efficiency—char quality—shielding integrity" is highly sensitive to combustion behavior.

[0071] Table 2-1 Thermal Decomposition Data

[0072] As can be seen from the thermal decomposition data in Table 2-1, the thermal stability and char retention capacity of each sample under nitrogen atmosphere vary significantly with the integrity of the system's "fixation-film formation-expansion flame retardancy-layered shielding": the example group generally exhibits a higher initial thermal decomposition temperature and a higher main decomposition peak temperature, indicating that the continuous fixation interface formed by the silane anchoring layer and the waterborne epoxy crosslinking film can weaken the rapid escape of small molecules in the early stage of pyrolysis and improve the structural stability of the pyrolysis process; at the same time, the residual of the example group at high temperature is significantly higher than that of the comparative group, and the experimental values ​​of the residual are generally higher than the calculated values ​​obtained by linear superposition of components, indicating that there is a real synergistic char formation / char retention effect in this system: APP / MPP provides acid and gas sources when heated, inducing resin dehydration and carbonization and forming The expanded char layer, with its layered structure of organic bentonite, further promotes char layer densification, inhibits crack propagation, and enhances the stability of the char layer skeleton. The film-forming fixation and anchoring structure improves the retention and continuity of flame retardants / fillers on the fiber surface and between fiber bundles, making the char layer less prone to breakage or detachment. Conversely, Comparative Example 1 lacks an anchoring layer, resulting in insufficient interfacial fixation and reduced pyrolysis and char retention capacity. Comparative Example 2 lacks APP / MPP, leading to the absence of key char-promoting pathways, manifested as earlier pyrolysis and lower residue with closer linear calculations. Comparative Example 3 lacks organic bentonite, weakening char layer densification and stability, and reducing the synergistic char retention effect. Comparative Example 4 lacks epoxy film formation and cross-linking fixation, making it difficult for flame retardant components to form a continuous and stable interfacial layer, resulting in a pyrolysis process that tends to have "early decomposition and low residue" characteristics. Overall, the consistent trend reflected by TG / DTG—"improved thermal stability + increased high-temperature residue + experimental residue higher than calculated residue"—verifies the synergistic effect of the fixed flame-retardant interface layer of this invention on pyrolysis inhibition and char layer construction from the perspective of thermal decomposition and char formation mechanism.

[0073] Table 3 Mechanical property test data

[0074] As can be seen from the mechanical property data in Table 3, the interlaminar shear strength, flexural strength / modulus, and impact strength of each sample exhibit consistent stratified differences between the example group and the comparative example group: the example group is generally at a higher level with less fluctuation, indicating that the fixed flame-retardant interface layer not only does not weaken the interfacial load-bearing capacity of the composite material, but also enhances the fiber surface wetting and chemical / physical bonding through the "silane anchoring layer + waterborne epoxy crosslinking film", making the load transfer between the fiber bundle and the matrix more continuous, thereby delaying the interfacial shear failure in short beam shear and inhibiting interlaminar slip and microcrack propagation under bending load; at the same time, the lamellar structure of organic bentonite forms microscale reinforcement and crack deflection paths in the fixed film, which is beneficial to improving bending stiffness and improving toughness through crack bifurcation, energy dissipation and interfacial friction during impact. Therefore, the impact strength and bending performance can be maintained at a high level simultaneously. Comparative Example 1, lacking an anchoring layer, resulted in insufficient bonding between the fixed film and the fiberglass surface, making the interface more prone to debonding and interlaminar shear failure, leading to a simultaneous decrease in bending load-bearing capacity and impact energy dissipation capacity. Comparative Example 3, after removing the organic bentonite, showed weakened lamellar reinforcement and crack passivation effects of the fixed film, resulting in an overall decline in bending and impact resistance. Comparative Example 4, lacking epoxy film formation and cross-linking fixation, struggled to form a continuous and stable interface layer, leading to increased interface defects and stress concentration, and the most significant decrease in mechanical properties. While Comparative Example 2 retained the anchoring layer and epoxy cross-linking film, thus maintaining a relatively considerable interfacial load-bearing capacity, the lack of APP / MPP resulted in insufficient filler / component synergy and structural integrity in the fixed layer, making it difficult to achieve the overall mechanical performance of the example group. In summary, the results in Table 3, from the perspectives of shear, bending, and impact stress scenarios, demonstrate that this invention constructs a more stable fiber / fixed film / matrix transition layer through interface anchoring and cross-linking fixation, and achieves a synergistic balance between the flame-retardant interface layer and mechanical properties through the reinforcement and crack control mechanism of the lamellar filler.

[0075] from Figures 1-5 It can be seen that the interface-fixed flame retardant layer of this invention, consisting of "silane anchoring layer + water-based epoxy cross-linking film + APP / MPP char formation expansion + organic bentonite sheet densification," does indeed exert a synergistic effect in both the mechanical interface and combustion char / smoke suppression dimensions. ILSS cross-sectional morphology ( Figure 1 , Figure 2The results show that the cross-section of Comparative Example 1 reveals more obvious exposed fiber bundles, interface gaps, and pull-out marks, indicating a discontinuity in interfacial bonding and load transfer, making interlaminar debonding and interfacial slip more likely to occur under shear loads. In contrast, the cross-section of Example 1 is more likely to be "encapsulated / filled by a continuous phase," with more complete matrix / fixation layer residue around the fiber bundles and a more complete interfacial transition. This indicates that the fixation layer achieves more effective wetting, chemical anchoring, and mechanical interlocking on the fiber surface, thus shifting the failure mode from "interfacial debonding-dominated" to "matrix / interface synergistic failure," corresponding to a superior structural basis for ILSS. UL94 residual carbon appearance ( Figure 3 As can be seen, the char residue of Example 1(e) is more continuous, more complete, and has a denser surface, exhibiting stronger barrier and skeletal support; while the comparative sample lacking key components or fixed structures has thinner char residue that is more prone to cracking or localized peeling, suggesting that it is difficult to form a stable shielding layer during combustion. Combustion process and post-combustion morphology ( Figure 4 , Figure 5 Further evidence: In Example 1, the flame was relatively controlled during combustion, with weaker tendency for dripping and violent spread, resulting in a more complete expanded / dense char layer after combustion; in Comparative Example 2, the combustion was more intense, the flame was stronger and harder to "suppress" by the char layer, and the char layer was insufficient / loose or melted after combustion. Based on this visual evidence, we can conclude that when the anchoring layer and epoxy cross-linked film are present, the flame-retardant filler can be more stably fixed on the fiber surface and between the fiber bundles. When heated, APP / MPP promotes char formation and expansion, while organic bentonite promotes densification of the char layer and inhibits crack propagation, thereby constructing a more complete heat-insulating and oxygen-barrier shielding layer. This shielding layer not only reduces combustion development and smoke generation, but also strengthens the continuity of the interface transition layer and its resistance to shear failure, ultimately achieving a simultaneous improvement in flame-retardant performance and mechanical properties.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flame retardant-fixed fiberglass cloth, characterized in that, The surface of the glass fiber cloth and the spaces between the fiber bundles are provided with an adhesive flame-retardant interface layer, the adhesive flame-retardant interface layer comprising: An anchoring layer, which is formed by treating the surface of glass fiber cloth with an epoxy silane coupling agent; A film-forming and bonding layer, wherein the film-forming and bonding layer is a cross-linked and cured aqueous epoxy resin film; The halogen-free flame retardant component and the shielding skeleton component are dispersed in the film-forming and immobilizing layer, wherein the halogen-free flame retardant component includes ammonium polyphosphate and melamine polyphosphate, and the shielding skeleton component includes organobentonite.

2. A method for preparing the flame retardant-fixed glass fiber cloth as described in claim 1, characterized in that, Includes the following steps: (1) Desizing and drying pretreatment of glass fiber cloth; (2) The pretreated glass fiber cloth is immersed in a treatment solution containing epoxy silane coupling agent, and after removing the excess liquid by squeezing with a pressure roller, it is heat-cured to obtain glass fiber cloth forming an anchoring layer. (3) Prepare a curing coating solution, wherein the curing coating solution comprises an aqueous epoxy resin dispersion, an aqueous curing agent, ammonium polyphosphate, melamine polyphosphate and organic bentonite; (4) The glass fiber cloth obtained in step (2) is immersed in the fixation coating liquid, and after the excess coating liquid is removed by squeezing with a pressure roller, it is subjected to gradient drying and curing to obtain flame retardant fixed glass fiber cloth.

3. The preparation method according to claim 2, characterized in that, In step (1), the desizing process is performed using an aqueous sodium carbonate solution.

4. The preparation method according to claim 2, characterized in that, The epoxy silane coupling agent in step (2) is 3-glycidyl ether propyltrimethoxysilane with a mass fraction of 0.2–3.0 wt%, and the solvent of the treatment solution is ethanol and water with a volume ratio of 90:10–95:

5.

5. The preparation method according to claim 2, characterized in that, In step (2), the thermosetting conditions are 80°C for 8–12 min, followed by curing at 120°C for 15–25 min.

6. The preparation method according to claim 2, characterized in that, The waterborne epoxy resin dispersion described in step (3) has a solid content of 45–55 wt%.

7. The preparation method according to claim 2, characterized in that, The mass ratio of ammonium polyphosphate to melamine polyphosphate in step (3) is 1.2:1–2.5:1, and the two together account for 30–55 wt% of the solid content in the fixation coating solution.

8. The preparation method according to claim 2, characterized in that, The amount of organic bentonite added in step (3) is 3–10 wt% of the solid content in the fixation coating solution.

9. The preparation method according to claim 2, characterized in that, In step (4), the immersion time is 1–3 min, and after removing excess coating liquid, the product is dried in a gradient at 80℃, 8–12 min, 120℃, and 12–18 min, and then cured at 160℃ for 15–25 min.

10. The preparation method according to claim 2, characterized in that, By adjusting the degree of liquid squeezing by the pressure roller, the weight gain of the fixed flame-retardant interface layer relative to the glass fiber cloth is 8–15 wt%.

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