Synergistic flame-retardant epoxy resin-based porous sound insulation composite material and application thereof

Abstract

The invention relates to the technical field of composite materials, in particular to a synergistic flame-retardant epoxy resin-based porous sound insulation composite material and application thereof. The raw materials comprise 100 parts of bisphenol A epoxy resin, 15 parts of an aliphatic amine curing agent, 12 parts of ammonium dihydrogen phosphate, 6 parts of melamine, 4 parts of nano silicon dioxide, 5 parts of sodium chloride, 2 parts of ammonium bicarbonate, 0.8 part of carbon nanotubes and 0.5 part of a silane coupling agent. The synergistic flame-retardant epoxy resin-based porous sound-insulation composite material provided by the invention effectively solves the technical bottleneck that the flame-retardant, sound-insulation and mechanical properties of an epoxy resin-based material in the prior art are difficult to synergistically improve, and has remarkable beneficial effects in multiple aspects.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to a synergistic flame-retardant epoxy resin-based porous sound-insulating composite material and its application. Background Technology

[0002] Epoxy resin-based composite materials are widely used in sound insulation and protection scenarios in fields such as construction and transportation due to their excellent mechanical properties and good formability. As the requirements for material safety performance in related fields continue to increase, epoxy resin-based composite materials with both flame retardant and sound insulation functions have become a research and development focus. However, in the existing technology, there are many technical bottlenecks in the research and development of such composite materials, making it difficult to achieve a synergistic improvement in flame retardancy, sound insulation and mechanical properties.

[0003] Traditional flame-retardant epoxy resin-based materials often employ a single type of flame-retardant system, resulting in limited flame-retardant effects and a tendency to produce excessively high smoke densities, failing to meet the requirements of high-safety-level applications. While porous epoxy resin-based materials possess sound-insulating properties, their porous structure accelerates heat transfer and flame spread, significantly reducing their flame-retardant performance. Furthermore, the porous structure often leads to a decrease in the material's mechanical strength, making it prone to pore collapse and structural damage.

[0004] In addition, the compatibility between the functional components of existing materials is poor, and agglomeration and precipitation are prone to occur, which seriously affects the performance stability of the materials. Moreover, the preparation process is mostly a simple component mixing and direct curing, which cannot achieve precise control of pore formation, curing and modification, making it difficult to form a multi-level pore structure with uniform structure. This limits the sound insulation effect and further leads to mutual constraints between various properties, making it difficult to achieve a balance.

[0005] Therefore, developing an epoxy resin-based composite material that can achieve synergistic improvement in flame retardancy, sound insulation, and mechanical properties, while also being structurally stable and adaptable to multiple application scenarios, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] The primary objective of this invention is to provide a synergistic flame-retardant epoxy resin-based porous sound-insulating composite material and its applications.

[0007] A further objective of this invention is to provide a synergistic flame-retardant epoxy resin-based porous sound-insulating composite material, wherein, by weight, the raw materials include 100 parts of bisphenol A type epoxy resin, 15 parts of aliphatic amine curing agent, 12 parts of ammonium dihydrogen phosphate, 6 parts of melamine, 4 parts of nano-silica, 5 parts of sodium chloride, 2 parts of ammonium bicarbonate, 0.8 parts of carbon nanotubes, and 0.5 parts of silane coupling agent.

[0008] Preferably, the amount of ammonium dihydrogen phosphate is adjusted to 10 parts, 8 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are added, melamine is adjusted to 8 parts, nano-silica is adjusted to 5 parts, 1 part of layered double hydroxide is added, and the remaining raw materials and weight parts are the same as in claim 1.

[0009] Preferably, sodium chloride is replaced with 6 parts potassium chloride and 2 parts calcium chloride, ammonium bicarbonate is replaced with 4 parts azodicarbonamide, and the remaining raw materials and weight parts are the same as in claim 2.

[0010] Preferably, the carbon nanotubes are adjusted to 1.2 parts, graphene is added to 0.6 parts, silane coupling agent is adjusted to 0.6 parts, titanate coupling agent is added to 0.2 parts, and the remaining raw materials and weight parts are the same as in claim 3.

[0011] Preferably, the bisphenol A type epoxy resin is replaced with 60 parts of bisphenol A type, 30 parts of bisphenol F type, and 10 parts of bisphenol S type, and the aliphatic amine curing agent is replaced with 10 parts of ethylenediamine, 6 parts of m-phenylenediamine, and 2 parts of isophorone diamine, and the remaining raw materials and weight parts are the same as in claim 4.

[0012] A method for preparing the aforementioned synergistic flame-retardant epoxy resin-based porous sound-insulating composite material includes the following steps: (1) Raw material pretreatment: Add nano-silica and carbon nanotubes to silane coupling agent and stir for 30 minutes at 60°C and 250 rpm to obtain modified mixed filler; pulverize ammonium dihydrogen phosphate and melamine to a particle size of 45 micrometers and mix to obtain synergistic flame retardant; pulverize sodium chloride to a particle size of 90 micrometers and mix with ammonium bicarbonate to obtain composite porogen; (2) Mixing and dispersion: heat bisphenol A epoxy resin to 50°C and stir at 300 rpm, add modified mixed filler and synergistic flame retardant in sequence and stir for 60 minutes, then add composite porogen and stir for 30 minutes to obtain mixed slurry; (3) Step-by-step pore formation: Pour the mixed slurry into the mold, let it stand at room temperature of 23°C for 20 minutes, and then keep it at 80°C for 30 minutes; (4) Curing and molding: Add aliphatic amine curing agent to the mold and stir evenly. First, cure at 80℃ for 2 hours, then cure at 120℃ for 4 hours. Cool down to room temperature at a rate of 1.5℃ / minute to obtain a preliminary porous composite material. (5) Post-treatment: The pre-formed porous composite material is soaked in deionized water for 48 hours, during which the deionized water is replaced 3 times, and then dried at 100°C for 12 hours to obtain the composite material.

[0013] Preferably, in step (1), the preparation temperature of the modified mixed filler is adjusted to 70°C, the stirring time is adjusted to 40 minutes, the particle size of the synergistic flame retardant after pulverization is adjusted to 35 micrometers, and the particle size of the composite porogen after pulverization is adjusted to 70 micrometers; in step (2), the stirring speed is increased to 400 rpm, the stirring time is extended to 70 minutes after adding the synergistic flame retardant, and the stirring time is extended to 40 minutes after adding the composite porogen.

[0014] Preferably, in step (3), the room temperature standing time is extended to 30 minutes, and the 80℃ heat preservation time is extended to 40 minutes; in step (4), the curing process is adjusted to first cure at 90℃ for 1.5 hours, then cure at 130℃ for 3 hours, and the programmed cooling rate is adjusted to 1.0℃ / minute; in step (5), the deionized water soaking time is extended to 60 hours, during which the deionized water is replaced 4 times, the drying temperature is adjusted to 110℃, and the drying time is adjusted to 10 hours; ammonium dihydrogen phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10 - After mixing oxides and melamine, add 0.3 parts of silane coupling agent and stir at 80°C and 250 rpm for 50 minutes to obtain a modified synergistic flame retardant; modify silicon powder with silane coupling agent to obtain silane coupling agent modified silicon powder, then compound nano-silica, layered double hydroxide and the silane coupling agent modified silicon powder in a ratio of 2:1:0.5, add 0.2 parts of titanate coupling agent, and stir at 75°C and 250 rpm for 35 minutes to obtain a modified silicon-based flame retardant. Mix the modified synergistic flame retardant and the modified silicon-based flame retardant to form a synergistic flame retardant system.

[0015] Preferably, the composite material is used in sound insulation and flame retardant applications in the construction and transportation sectors.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. The synergistic flame-retardant epoxy resin-based porous sound insulation composite material provided by the present invention effectively solves the technical bottleneck of the difficulty in synergistically improving the flame retardancy, sound insulation and mechanical properties of epoxy resin-based materials in the prior art, and has many significant beneficial effects.

[0017] 2. This invention constructs a multi-element synergistic flame retardant system, which achieves synergistic effects through the scientific compounding of different types of flame retardants, greatly improving the flame retardant performance of the material and improving the smoke suppression effect, fundamentally solving the problem of limited flame retardant effect of a single flame retardant system.

[0018] 3. The combination of the composite pore-forming system and the stepwise pore-forming process of this invention forms a multi-level pore structure with uniform structure, which significantly improves the sound insulation performance of the material. Moreover, the pore structure design takes into account the flame retardant requirements and avoids the decline in flame retardant performance caused by the porous structure.

[0019] 4. The introduction of the modified and enhanced system of this invention optimizes the compatibility of each functional component, effectively avoids component aggregation and precipitation, and improves the mechanical strength of the material, solving the industry pain points of insufficient mechanical properties and easy collapse of pores in porous materials.

[0020] 5. By optimizing the preparation process parameters, this invention achieves precise control over modification, pore formation, and curing, thereby improving the structural stability and performance durability of the material. Furthermore, the material formulation and process can be flexibly adjusted according to the application scenario to meet the different needs of various fields such as construction and transportation. Overall, this invention achieves a comprehensive and synergistic improvement in the flame retardancy, sound insulation, mechanical properties, and stability of composite materials. The process is highly operable and has good practical application value. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1: Raw material dosage: 100 parts of bisphenol A type epoxy resin (epoxy value 0.52 eq / 100g), 15 parts of aliphatic amine curing agent (ethylenediamine), 12 parts of ammonium dihydrogen phosphate (purity 98%), 6 parts of melamine (purity 99%), 4 parts of nano silica (particle size 30nm), 5 parts of sodium chloride (purity 99%), 2 parts of ammonium bicarbonate (purity 98%), 0.8 parts of carbon nanotubes (tube diameter 15nm, length 8μm), and 0.5 parts of silane coupling agent (KH-550).

[0023] Raw material selection criteria: Bisphenol A type epoxy resin (epoxy value 0.52 eq / 100g) is selected, which has excellent mechanical strength and molding performance, and is suitable for the mechanical performance requirements of the basic formulation; ethylenediamine, as an aliphatic amine curing agent, has a moderate curing speed and good compatibility with bisphenol A type epoxy resin, which can ensure the curing and molding effect; ammonium dihydrogen phosphate (phosphorus-based), melamine (nitrogen-based), and nano silica (silicon-based) are compounded to form a basic synergistic flame retardant system, in which ammonium dihydrogen phosphate releases phosphoric acid form during combustion. The carbon layer is formed by melamine releasing ammonia to dilute flammable gases, and nano-silica strengthening the stability of the carbon layer. The three work together to achieve a basic flame-retardant effect. Sodium chloride, as a soluble salt porogen, has a particle size that is easy to control and can be completely removed by washing with water. Ammonium bicarbonate, as a foam-type porogen, has a moderate decomposition temperature and can initially decompose at room temperature to form micropores. Carbon nanotubes can improve the mechanical strength of the material, and silane coupling agent KH-550 can improve the compatibility of carbon nanotubes, nano-silica, and epoxy resin, preventing the components from being exfoliated.

[0024] Preparation steps: Raw material pretreatment: Nano-silica and carbon nanotubes are added to a silane coupling agent and placed in a high-speed shear stirring vessel. The mixture is stirred for 30 minutes at 60°C and 250 rpm to perform surface modification, obtaining a modified mixed filler. The temperature is set at 60°C to allow the silane coupling agent to fully function and achieve surface modification of the filler. The 250 rpm ensures uniform modification and prevents agglomeration, while the 30-minute stirring time ensures sufficient modification. Ammonium dihydrogen phosphate and melamine are pulverized to a particle size of 45 micrometers using a universal pulverizer and mixed evenly to obtain a synergistic flame retardant. Pulverizing to 45 micrometers ensures that the flame retardant is uniformly dispersed in the epoxy resin matrix, avoiding excessively high or low concentrations that could affect the flame retardant effect. Sodium chloride is pulverized to a particle size of 90 micrometers using a universal pulverizer and then mixed evenly with ammonium bicarbonate to obtain a composite pore-forming agent. The 90-micrometer particle size of sodium chloride ensures that the pore size formed subsequently is moderate and suitable for basic sound insulation requirements. Mixing it with ammonium bicarbonate can achieve a uniform distribution of the two pore-forming agents.

[0025] Mixing and Dispersion: Bisphenol A type epoxy resin is added to a high-speed shear mixer, heated to 50°C, and the stirring speed is adjusted to 300 rpm. Modified mixed filler and synergistic flame retardant are added sequentially, and stirring is continued for 60 minutes to ensure uniform dispersion. Heating to 50°C reduces the viscosity of the epoxy resin, facilitating the dispersion of each component. The 300 rpm speed prevents component agglomeration, and stirring for 60 minutes ensures thorough integration of the modified mixed filler, synergistic flame retardant, and epoxy resin. Then, a composite pore-forming agent is added, and stirring continues for 30 minutes to obtain a mixed slurry. Stirring for 30 minutes ensures uniform dispersion of the composite pore-forming agent, avoiding excessive or insufficient local pores and guaranteeing a uniform material structure.

[0026] Stepwise pore formation: The mixed slurry is poured into a metal mold and first allowed to stand at room temperature (23°C) for 20 minutes to allow the foam-based pore-forming agent to initially decompose and generate micropores. Room temperature (23°C) facilitates operation, and the 20-minute standing time allows ammonium bicarbonate to slowly decompose, forming uniform micropores, laying the foundation for the subsequent multi-level pore structure. The mold is then placed in a constant-temperature curing oven, heated to 80°C, and held for 30 minutes to promote the uniform dispersion of soluble salt pore-forming agents and simultaneously allow the foam-based pore-forming agent to completely decompose, forming a multi-level pore structure. 80°C ensures complete decomposition of ammonium bicarbonate while preventing premature curing of the epoxy resin due to excessive temperature. Holding for 30 minutes ensures uniform pore formation, resulting in a multi-level pore structure consisting of macropores (formed after sodium chloride removal) and micropores (formed by the decomposition of ammonium bicarbonate), thus improving sound insulation performance.

[0027] Curing and Molding: Add aliphatic amine curing agent to the mold, stir evenly, first cure at 80℃ for 2 hours, then raise the temperature to 120℃ for 4 hours. After curing, use a programmed cooling method with a cooling rate of 1.5℃ per minute to cool to room temperature, thus obtaining a pre-formed porous composite material. Curing at 80℃ for 2 hours first allows the curing agent to react initially with the epoxy resin, avoiding the formation of bubbles due to excessively rapid reaction. Raising the temperature to 120℃ for 4 hours ensures complete curing and improves the structural stability of the material. The programmed cooling rate of 1.5℃ per minute reduces internal stress in the material and prevents cracking.

[0028] Post-processing: The pre-formed composite material is removed from the mold and soaked in deionized water for 48 hours, changing the deionized water three times during this period to remove soluble salts and pore-forming agents. Soaking for 48 hours and changing the deionized water three times ensures that sodium chloride is completely dissolved and removed, avoiding residues that could affect material performance. It is then placed in a 100℃ forced-air drying oven for 12 hours to remove moisture, obtaining a synergistic flame-retardant epoxy resin-based porous sound-insulating composite material. Drying at 100℃ for 12 hours completely removes moisture from the material, preventing residual moisture from causing structural instability and affecting flame retardancy, sound insulation, and mechanical properties.

[0029] Example 2: Based on the basic formula and process of Example 1, the flame retardant performance and smoke suppression effect are further improved, while the amount of other raw materials and preparation steps remain the same as in Example 1.

[0030] Raw material dosage adjustments: The phosphorus-based flame retardant is a compound of 10 parts ammonium dihydrogen phosphate (98% purity) and 8 parts 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) (98% purity), for a total dosage of 18 parts; the nitrogen-based flame retardant is a compound of 8 parts melamine (99% purity); the silicon-based flame retardant is a compound of 5 parts nano-silica (30nm particle size) and 1 part layered double hydroxide (80nm particle size), for a total dosage of 6 parts; the total dosage of the synergistic flame retardant system is 32 parts; the dosage of other raw materials is the same as in Example 1.

[0031] Compared to Example 1, this example increases the total amount of phosphorus-based, nitrogen-based, and silicon-based flame retardants. It also employs a combination of two phosphorus-based flame retardants (ammonium dihydrogen phosphate and DOPO) and two silicon-based flame retardants (nano-silica and layered double hydroxides) to enhance their synergistic effect. DOPO exhibits excellent flame-retardant and smoke-suppressing properties; its combination with ammonium dihydrogen phosphate improves the flame-retardant efficiency of phosphorus-based flame retardants and reduces smoke generation. The layered double hydroxide has a layered structure, further enhancing char layer stability; its combination with nano-silica improves the synergistic flame-retardant effect of silicon-based flame retardants. The increased amount of melamine releases more inert gas, further diluting combustible gases and inhibiting combustion chain reactions. Simultaneously, the total amount of flame retardants is controlled within a reasonable range to avoid a decrease in mechanical properties due to increased flame retardant dosage, ensuring the compatibility of the flame retardants with the epoxy resin matrix.

[0032] This embodiment enhances the synergistic effect of phosphorus-based, nitrogen-based, and silicon-based flame retardants by increasing the dosage of two phosphorus-based flame retardants and two silicon-based flame retardants, thereby improving flame retardant efficiency and smoke suppression effect. At the same time, it maintains the compatibility between the flame retardants and the epoxy resin matrix, avoiding the decline in mechanical properties caused by the increase in the amount of flame retardants.

[0033] Example 3: Based on the optimized formulation and process of Example 2, the type, ratio and particle size of the composite pore-forming agent were optimized to achieve a synergistic improvement in flame retardant and sound insulation performance. The amount of other raw materials and preparation steps remained the same as in Example 2.

[0034] Raw material dosage adjustment: The composite porogen is composed of 6 parts potassium chloride (99% purity) and 2 parts calcium chloride (99% purity) as a soluble salt porogen, with a total dosage of 8 parts; the foam porogen is composed of 4 parts azodicarbonamide (98% purity), with a total dosage of 4 parts; the total dosage of the composite porogen is 12 parts; the particle size of potassium chloride is adjusted to 80 micrometers, the particle size of calcium chloride is adjusted to 70 micrometers, and the particle size of azodicarbonamide is adjusted to 60 micrometers; the dosage of other raw materials is the same as in Example 2.

[0035] In this embodiment, the single soluble salt porogen (sodium chloride) in Example 1 is replaced with a combination of two soluble salt porogens (potassium chloride and calcium chloride). The solubility of potassium chloride and calcium chloride is similar to that of sodium chloride, and their combination can control the pore size distribution, forming a more uniform macroporous structure. The foam-type porogen is replaced with azodicarbonamide, whose decomposition temperature is slightly higher than that of ammonium bicarbonate, making it better suited to the stepwise porogenization process. The decomposition produces more uniform gas, resulting in more regular micropore sizes. Adjusting the particle size of the porogen (potassium chloride 80 microns, calcium chloride 70 microns, azodicarbonamide 60 microns) allows for a more reasonable matching of macropore and micropore sizes, improving sound insulation performance. Macropores absorb low-to-mid-frequency noise, while micropores absorb high-frequency noise, achieving improved sound insulation across the entire frequency range. Simultaneously, potassium chloride and calcium chloride are both inorganic salts with certain heat resistance, which can complement the synergistic flame-retardant system, further optimizing the flame-retardant effect and avoiding the decrease in flame-retardant performance caused by the porous structure.

[0036] In this embodiment, the single soluble salt porogen in Example 1 is replaced with a combination of two soluble salt porogens, and the foam porogen is replaced with azodicarbonamide. The particle size and dosage of the porogens are adjusted to form a more uniform macroporous and microporous multi-level pore structure, which significantly improves the sound insulation performance. At the same time, potassium chloride and calcium chloride improve the heat resistance of the composite material and complement the synergistic flame retardant system, further optimizing the flame retardant effect.

[0037] Example 4: Based on the optimized formulation and process of Example 3, the types and ratios of the modifiers and reinforcing agents were optimized, and the amount of modifiers was adjusted to achieve a synergistic improvement in mechanical properties, flame retardancy, and sound insulation properties. The amount of other raw materials and the preparation steps remained the same as in Example 3.

[0038] Raw material dosage adjustment: 1.2 parts of carbon nanotubes (15nm diameter, 8μm length) and 0.6 parts of graphene (8 layers) were used as the modifier, with a total dosage of 1.8 parts; 0.6 parts of silane coupling agent (KH-550) and 0.2 parts of titanate coupling agent (NDZ-101) were used as the modifier, with a total dosage of 0.8 parts; the dosage of other raw materials was the same as in Example 3.

[0039] This embodiment incorporates a modified reinforcing agent that combines graphene and carbon nanotubes. Graphene possesses excellent sheet structure and mechanical properties; when combined with carbon nanotubes, it forms a three-dimensional reinforcing network, significantly improving the tensile and impact strength of the material and addressing the weakness of porous materials in terms of mechanical strength. Simultaneously, the sheet structure of graphene can form a denser char layer during combustion, further enhancing the flame-retardant effect and creating a synergistic effect with the synergistic flame-retardant system. A composite modifier system (a combination of silane coupling agent KH-550 and titanate coupling agent NDZ-101) is used. KH-550 focuses on improving the compatibility between inorganic fillers (flame retardants, reinforcing agents) and epoxy resin, while NDZ-101 focuses on enhancing the organic-inorganic interfacial bonding force. The combination of these two agents further reduces component exudation, improves material structural stability, optimizes pore structure stability, prevents pore collapse, and enhances the durability of sound insulation performance.

[0040] This embodiment incorporates a modified reinforcing agent that combines graphene and carbon nanotubes. A composite modifier system is used, and through the synergistic modification effect of the composite modifier, the reinforcing agent is uniformly dispersed in the epoxy resin matrix. The layered structure of graphene enhances the density of the carbon layer, further improving the flame retardant effect. Simultaneously, it synergistically enhances tensile strength and impact strength with carbon nanotubes, addressing the weakness of insufficient mechanical strength in porous materials. Furthermore, it optimizes the stability of the pore structure, preventing pore collapse and improving the durability of sound insulation performance.

[0041] Example 5: Based on the optimized formulation and process of Example 4, the compounding ratio and type of epoxy resin and curing agent were optimized to improve the molding performance and scene adaptability of the material. The amount of other raw materials and the preparation steps remained the same as in Example 4.

[0042] Raw material dosage adjustment: 60 parts of bisphenol A epoxy resin (epoxy value 0.52 eq / 100g), 30 parts of bisphenol F epoxy resin (epoxy value 0.51 eq / 100g), and 10 parts of bisphenol S epoxy resin (epoxy value 0.50 eq / 100g) were used in combination for a total dosage of 100 parts; 10 parts of aliphatic amine curing agent (ethylenediamine), 6 parts of aromatic amine curing agent (m-phenylenediamine), and 2 parts of alicyclic amine curing agent (isophorone diamine) were used in combination for a total dosage of 18 parts; the dosage of other raw materials was the same as in Example 4.

[0043] In this embodiment, a single bisphenol A epoxy resin is replaced with a three-element epoxy resin blend. The bisphenol A epoxy resin retains its high strength advantage, the bisphenol F epoxy resin exhibits high toughness and low viscosity, improving the material's molding performance and facilitating the mixing and dispersion of the components, and the bisphenol S epoxy resin possesses excellent high-temperature resistance, enhancing the material's heat resistance. This three-element blend is suitable for complex environments such as high-temperature and high-impact conditions. The curing agent uses a blend of three types: ethylenediamine, which cures quickly and ensures effective initial curing; m-phenylenediamine, which enhances the mechanical strength and heat resistance of the cured material; and isophorone diamine, which improves the material's toughness. This three-element blend allows for precise control of the curing speed, preventing uneven pore structure, while simultaneously improving the material's heat resistance and aging resistance. It also works synergistically with the blended epoxy resin to further optimize the material's overall performance.

[0044] In this embodiment, a single bisphenol A epoxy resin is replaced with a three-element epoxy resin blend system, combined with a three-curing agent blend system. This retains the high strength advantage of bisphenol A epoxy resin, utilizes the high toughness and low viscosity of bisphenol F epoxy resin, and leverages the high temperature resistance of bisphenol S epoxy resin to improve molding performance, toughness, and heat resistance. The blended curing agents precisely control the curing speed, avoiding uneven pore structure and improving heat resistance and aging resistance.

[0045] Example 6: Based on the optimized formulation of Example 5, the preparation process parameters were optimized to improve the material's structural stability and overall performance consistency. The amount of other raw materials and steps remained the same as in Example 5.

[0046] Process parameter adjustment: Raw material pretreatment: The modification temperature was adjusted to 70℃, the stirring time was extended to 40 minutes, and the rotation speed was maintained at 250 rpm; the synergistic flame retardant was pulverized to a particle size of 35 micrometers; the particle size of the composite pore-forming agent was adjusted to 70 micrometers.

[0047] Mixing and dispersion: The stirring speed is increased to 400 rpm, the stirring time after adding the synergistic flame retardant is extended to 70 minutes, and the stirring time after adding the composite porogen is extended to 40 minutes.

[0048] Step-by-step pore formation: extend the room temperature standing time to 30 minutes and the 80℃ heat preservation time to 40 minutes.

[0049] Curing and molding: First cure at 90℃ for 1.5 hours, then cure at 130℃ for 3 hours, with the programmed cooling rate adjusted to 1.0℃ per minute.

[0050] Post-treatment: The soaking time in deionized water was extended to 60 hours, and the deionized water was replaced 4 times; the drying temperature in the oven was adjusted to 110℃, and the drying time was extended to 10 hours.

[0051] The core objective of optimizing process parameters in this embodiment is to improve the uniformity of dispersion of each component, enhance component compatibility, optimize pore structure, and reduce internal stress in the material. In the raw material pretreatment stage, increasing the modification temperature to 70°C and extending the stirring time to 40 minutes allows the modifier to fully exert its effect, further improving the compatibility between the filler and epoxy resin. Pulverizing the synergistic flame retardant to 35 micrometers and adjusting the particle size of the composite pore-forming agent to 70 micrometers further improves the uniformity of component dispersion and prevents agglomeration. In the mixing and dispersion stage, increasing the stirring speed to 400 rpm and extending the stirring time ensures thorough integration of each component and avoids uneven local component concentrations. In the stepwise pore-forming stage, extending the room temperature standing time and the 80°C holding time allows for more complete decomposition of the pore-forming agent, a more uniform pore structure, and improved pore connectivity. In the curing and molding stage, adjusting the curing temperature and time ensures complete curing and reduces internal bubbles; reducing the programmed cooling rate to 1.0°C per minute further reduces internal stress in the material and prevents cracking. In the post-treatment stage, extending the soaking time and increasing the number of water changes can ensure the complete removal of soluble pore-forming agents; adjusting the drying temperature and time can thoroughly remove moisture while avoiding the degradation of material properties caused by high temperatures.

[0052] This embodiment improves the dispersion uniformity of each component and reduces agglomeration by optimizing process parameters; enhances the compatibility of flame retardants, reinforcing agents and epoxy resin matrix; optimizes the step-by-step pore-forming process to make the pore structure more uniform and the connectivity better; and reduces the internal stress of the material.

[0053] Example 7: Based on the optimized formulation and process of Example 6, the synergistic flame retardant system was deeply modified. At the same time, the ratio of composite pore-forming agent and modifier was optimized to achieve a deep synergistic improvement in flame retardancy, sound insulation and mechanical properties. The amount of other raw materials and preparation steps were kept the same as in Example 6.

[0054] Optimization and adjustments: Synergistic flame retardant system modification: Ammonium dihydrogen phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and melamine were mixed, and 0.3 parts of silane coupling agent were added. The mixture was stirred at 80℃ and 250 rpm for 50 minutes to perform surface modification and obtain a modified synergistic flame retardant. Nano-silica, layered double hydroxide, and silane coupling agent modified silicon powder were compounded at a mass ratio of 2:1:0.5, and 0.2 parts of titanate coupling agent were added. The mixture was stirred at 75℃ and 250 rpm for 35 minutes to obtain a modified silicon-based flame retardant. The modified synergistic flame retardant and the modified silicon-based flame retardant were mixed evenly and added as a synergistic flame retardant system, with a total dosage of 38 parts.

[0055] Adjustment of composite porogen: For soluble salt porogen, use 5 parts potassium chloride and 3 parts calcium chloride, for a total of 8 parts; for foam porogen, use 3 parts azodicarbonamide and 1 part azobisisobutyronitrile, for a total of 4 parts; the total amount of composite porogen is 12 parts, and the particle size is adjusted to 65 micrometers.

[0056] Modifier adjustment: The modifier is a compound of 1.5 parts carbon nanotubes, 0.8 parts graphene and 0.5 parts carbon fiber, with a total amount of 2.8 parts; the modifier is a compound of 0.8 parts silane coupling agent and 0.4 parts titanate coupling agent, with a total amount of 1.2 parts.

[0057] In this embodiment, each component of the synergistic flame retardant system is individually modified and then compounded. The phosphorus-nitrogen flame retardant is modified with a silane coupling agent, and the silicon-based flame retardant is modified with a titanate coupling agent. This further improves the compatibility between the flame retardant and the epoxy resin matrix, reduces flame retardant precipitation, and enhances flame retardant durability. Simultaneously, the modified phosphorus-nitrogen-silicon flame retardants exhibit stronger synergistic effects, resulting in a denser and more stable char layer during combustion and a more significant smoke suppression effect. The composite porogen uses a combination of two foam-type porogens (azodicarbonamide and azobisisobutyronitrile), whose decomposition temperatures differ slightly, allowing for better compatibility with the stepwise porogenization process and the formation of a more uniform multi-level porous structure, further improving sound insulation performance. Adjusting the porogen particle size to 65 micrometers optimizes the matching degree between macropores and micropores. Adding a modifier to carbon fiber forms a three-dimensional reinforcing network with carbon nanotubes and graphene, further improving the mechanical properties of the material. Increasing the amount of modifier ensures the compatibility of the three reinforcing agents with epoxy resin, avoids agglomeration, and strengthens the bonding force between the components, thereby improving the structural stability of the material.

[0058] In this embodiment, each component of the synergistic flame retardant system is individually modified and then compounded to further improve the compatibility between the flame retardant and the epoxy resin matrix, reduce the precipitation of the flame retardant, and improve the flame retardant durability; the synergistic effect of phosphorus-nitrogen flame retardants and silicon-based flame retardants is strengthened, resulting in a denser and more stable char layer during combustion and a more significant smoke suppression effect; the ratio of composite pore-forming agent and modified reinforcing agent is optimized to further improve the sound insulation and mechanical properties, achieving a deep synergistic improvement in flame retardancy, sound insulation, and mechanical properties.

[0059] Comparative Example 1: Raw material adjustment: Melamine and nano-silica were removed from the synergistic flame retardant system, and only 18 parts of ammonium dihydrogen phosphate were retained. The amount of other raw materials was the same as in Example 1.

[0060] This comparative example does not use the phosphorus-nitrogen-silicon synergistic flame retardant system of the present invention, but only uses a single phosphorus-based flame retardant to simulate the application scheme of a single flame retardant in the prior art.

[0061] Comparative Example 2: Raw material adjustment: The composite pore-forming agent was removed, and the amount of other raw materials was the same as in Example 1; the step-by-step pore-forming and deionized water soaking steps were omitted in the preparation steps, and the material was directly solidified and molded.

[0062] This comparative example did not use the composite porogen and stepwise porogen process of the present invention, and therefore could not form a porous structure, thus simulating the epoxy resin composite material without a porous structure in the prior art.

[0063] Comparative Example 3: Raw material adjustment: Remove the modifier and reinforcing agent, and the amount of the remaining raw materials is the same as in Example 1.

[0064] This comparative example does not include the modifying and reinforcing agent and silane coupling agent of the present invention, and simulates the scheme in the prior art that does not employ the modification and reinforcing process.

[0065] Comparative Example 4: Raw material adjustment: Remove the silane coupling agent, and the amount of the remaining raw materials is the same as in Example 1.

[0066] This comparative example did not include the modifier of the present invention, and simulated a scheme in the prior art that did not consider component compatibility.

[0067] Comparative Example 5: Raw material dosage: 100 parts bisphenol A type epoxy resin, 15 parts aliphatic amine curing agent, 20 parts ammonium dihydrogen phosphate, 8 parts sodium chloride, and 5 parts calcium carbonate; Preparation steps: Mix all raw materials evenly and cure at 100℃ for 5 hours without step-by-step pore-forming and raw material modification steps.

[0068] This comparative example uses conventional epoxy resin flame-retardant composite material formulations and processes in existing technologies. It does not have a synergistic flame-retardant system, no modifiers or reinforcing agents, and no composite pore-forming process, which is a typical solution in existing technologies.

[0069] Comparative Example 6: Raw material dosage: 100 parts bisphenol A type epoxy resin, 15 parts aliphatic amine curing agent, 12 parts ammonium dihydrogen phosphate, 6 parts melamine, 4 parts nano silica, 5 parts sodium chloride, 2 parts ammonium bicarbonate, and 0.8 parts carbon nanotubes; Preparation steps: Mix all raw materials evenly, add to the mold, and cure at 100℃ for 5 hours. No raw material modification or step-by-step pore-forming steps are required.

[0070] This comparative example simulates the simple combination scheme of flame retardant, pore-forming agent and reinforcing agent in the prior art. It does not adopt the modification treatment and step-by-step pore-forming process of the present invention. The components have poor compatibility and the pore structure is not uniform. The flame retardant, sound insulation and mechanical properties are significantly lower than those of the embodiment of the present invention. Moreover, the structural stability is poor and the component analysis and pore collapse phenomenon are easy to occur. It can demonstrate the performance advantages of the synergistic optimization scheme of the present invention compared with the combination scheme of the prior art.

[0071] To fully disclose the preparation process of the silane coupling agent modified silicon powder described in this invention, which can be directly implemented by those skilled in the art, the preparation method is supplemented as follows: The silane coupling agent modified silicon powder uses microsilica powder with a particle size of 3μm and a purity of 99% as raw material. 1.2 parts by weight of silane coupling agent KH-550 are added to every 100 parts by weight of microsilica powder. The two are placed in a high-speed shear stirring vessel and stirred for 35 minutes at 70°C and 250 rpm. After surface modification, the product is dried in an 80°C forced-air drying oven for 6 hours. After cooling to room temperature, the silane coupling agent modified silicon powder is obtained. This silane coupling agent modified silicon powder can be directly used in the preparation of the modified silicon-based flame retardant of this invention and has good compatibility with nano-silica and layered double hydroxides.

[0072] Performance testing and results analysis: The composite materials prepared in the above 7 examples and 6 comparative examples were tested for flame retardancy, sound insulation, mechanical properties, porosity and stability in accordance with relevant national and industry standards. All test samples were of the same size (100 mm × 100 mm × 10 mm), and 3 samples were tested in each group. The average value was taken. The test methods met the requirements of national standards to ensure the accuracy and reliability of the test results.

[0073] Test method: Flame retardant performance testing: The vertical flammability rating is tested according to GB / T2408-2021 Determination of flammability of plastics - Horizontal and vertical flammability methods; the limiting oxygen index is tested according to GB / T2406.2-2009 Determination of flammability of plastics - Oxygen index method - Part 2: Room temperature test; and the smoke density rating is tested according to GB / T16172-2007 Test method for smoke density of building materials during combustion or decomposition.

[0074] Sound insulation performance test: According to GB / T50121-2005 Standard for Evaluation of Building Sound Insulation, the average sound insulation volume in the frequency range of 1000 Hz to 4000 Hz is tested; according to GB / T19889.3-2005 Acoustics of Buildings and Sound Insulation Measurement Part 3: Laboratory Measurement of Airborne Sound Insulation of Building Components, the airborne sound insulation volume is tested.

[0075] Mechanical property testing: Tensile strength and elongation at break were tested in accordance with GB / T1040.1-2018 Determination of tensile properties of plastics Part 1: General principles; and the impact strength of simply supported beams was tested in accordance with GB / T1043.1-2008 Determination of impact strength of simply supported beams Part 1: Non-instrumental impact test.

[0076] Porosity performance testing: Porosity was tested using the density method, and the calculation formula is porosity equals 1 minus apparent density divided by absolute density and then multiplied by 100%; pore size distribution was tested using the BET method, with a test range of 2 nanometers to 100 micrometers, and the average pore size was recorded.

[0077] Stability test: The sample was aged in an environment of 80℃ and 85% humidity for 72 hours. The limiting oxygen index and average sound insulation of the sample after aging were tested, and the performance retention rate was calculated. The sample was repeatedly bent 10 times at a bending angle of 90 degrees. The sample was observed to see if it cracked or fell off. The impact strength retention rate after bending was tested.

[0078] Test results: To ensure the objectivity, repeatability, and adequacy of the test results, the following test-related details are added to improve the disclosed content of the test process, facilitating the complete replication of this test plan by those skilled in the art: (1) Sample preparation consistency control: All samples were prepared using metal molds of the same specifications (100mm×100mm×10mm). After molding, the dimensions were caliped with calipers with an accuracy of 0.01mm to ensure that the sample size deviation did not exceed ±0.05mm, so as to avoid the size difference from interfering with the test results of sound insulation, mechanical and other performance. (2) Test environment control: All performance tests are conducted under standard environmental conditions, namely, temperature 23±2℃ and relative humidity 50±5%. Before the test, all samples are placed in this environment and left to stand for 24 hours to allow the sample state to reach equilibrium with the test environment and eliminate the influence of environmental factors on the test results. (3) Parallel sample testing details: The testing of each group of 3 parallel samples is completed by the same operator and using the same set of metrologically calibrated testing instruments. During the testing process, the test data of each sample is recorded in real time. If the test data of a single sample deviates from the average value of the group by more than 5%, the sample is re-prepared and retested to ensure the reliability of the test data. (4) Test instrument description: Flame retardant performance test adopts vertical combustion tester, oxygen index tester and smoke density tester conforming to GB / T standard; sound insulation performance test adopts building component sound insulation measurement system; mechanical performance test adopts electronic universal testing machine (accuracy 0.01MPa) and simply supported beam impact testing machine; porosity performance test adopts specific surface area and pore size analyzer; stability test adopts constant temperature and humidity aging chamber and bending tester. All instruments are calibrated regularly to ensure that the test accuracy meets the standard requirements. (5) Performance retention rate calculation instructions: performance retention rate = (performance index of sample after aging ÷ corresponding performance index of sample before aging) × 100%, where the samples tested before and after aging are corresponding samples in the same group of parallel samples to ensure that the calculation basis is consistent; impact strength retention rate after bending = (impact strength of sample after 10 bends ÷ corresponding impact strength of sample before bending) × 100%, during the bending process, the bending speed is kept consistent (5 times / minute), and the bending angle is precisely controlled to 90 degrees.

[0079] The test results are shown in Table 1 below: Table 1:

[0080]

[0081]

[0082] Results analysis: Based on the above test data, it can be seen that the composite materials prepared in all embodiments all achieve a vertical combustion rating of V-0, a limiting oxygen index of over 32%, and a smoke density rating of less than 35, demonstrating excellent flame retardant and smoke suppression performance. Furthermore, with the gradual optimization of the embodiments, the flame retardant and smoke suppression effect shows a steady upward trend.

[0083] Example 1 serves as the basic formulation, achieving a basic synergy in flame retardancy, sound insulation, and mechanical properties. All performance indicators are within a reasonable range, providing a reliable benchmark for subsequent optimization.

[0084] Example 2 shows that by optimizing the ratio and type of the synergistic flame retardant system, the limiting oxygen index was increased to over 36.8%, the smoke density level was reduced to below 28, the flame retardant and smoke suppression performance was significantly improved, and good mechanical and sound insulation properties were maintained at the same time.

[0085] In Example 3, after optimizing the type, ratio, and particle size of the composite pore-forming agent, the average sound insulation and airborne sound insulation were significantly improved, and the porosity and average pore size became more reasonable, achieving a synergistic improvement in flame retardant performance and sound insulation performance.

[0086] Example 4 introduced a modified reinforcing agent composed of graphene and carbon nanotubes, which significantly improved tensile strength, elongation at break, and impact strength, solving the problem of insufficient mechanical strength of porous materials, while further optimizing flame retardant and sound insulation properties.

[0087] Example 5 improved the molding performance and heat resistance of the material by compounding epoxy resin and curing agent, making it suitable for more complex application scenarios.

[0088] After optimizing the preparation process parameters in Example 6, the components were more evenly dispersed, the internal stress of the material was reduced, the performance retention rate and the impact strength retention rate after bending were further improved, and the structural stability was better.

[0089] Example 7, as the optimal embodiment, has achieved optimal performance in all aspects after in-depth optimization of the entire system. It has the highest limiting oxygen index, the lowest smoke density level, the best sound insulation and mechanical properties, and the best stability, making it suitable for high-end application requirements.

[0090] Comparing the test data of the examples and comparative examples, it can be seen that the overall performance of each comparative example is significantly inferior to that of the examples. Comparative example 1 uses only a single phosphorus-based flame retardant and does not employ a phosphorus-nitrogen-silicon synergistic flame retardant system, resulting in low flame retardant efficiency, a significantly increased smoke density level, and a substantial decrease in flame retardant performance.

[0091] Comparative Example 2 did not use a composite pore-forming agent and a stepwise pore-forming process, so it could not form a porous structure, resulting in extremely poor sound insulation performance. At the same time, its flame retardant performance also decreased because heat transfer could not be effectively blocked.

[0092] Comparative Example 3, without the addition of modifiers and silane coupling agents, showed significantly insufficient mechanical properties, a pore structure prone to collapse, and adversely affected sound insulation and flame retardant properties.

[0093] Comparative Example 4 did not contain any modifier, resulting in poor compatibility among the components, making it prone to agglomeration and precipitation, and leading to a comprehensive decline in overall performance.

[0094] Comparative Example 5 uses conventional formulations and processes from existing technologies, lacking key technical features such as synergistic flame retardancy, modified reinforcement, and composite pore formation. Its performance is far lower than that of the examples, and it also suffers from structural instability and other problems.

[0095] Comparative Example 6 did not employ modification treatment or a step-by-step pore-forming process; it simply assembled the components, resulting in poor compatibility among the components, uneven pore structure, and significantly inferior overall performance compared to the Example.

[0096] The above test results fully demonstrate that the present invention achieves a synergistic improvement in the flame retardant, sound insulation, mechanical and stability properties of composite materials through the organic combination of synergistic flame retardant system, composite porous system, modified reinforcement system and optimized process.

[0097] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A synergistic flame-retardant epoxy resin-based porous sound-insulating composite material, characterized in that, By weight, the raw materials include 100 parts of bisphenol A epoxy resin, 15 parts of aliphatic amine curing agent, 12 parts of ammonium dihydrogen phosphate, 6 parts of melamine, 4 parts of nano silica, 5 parts of sodium chloride, 2 parts of ammonium bicarbonate, 0.8 parts of carbon nanotubes, and 0.5 parts of silane coupling agent.

2. The synergistic flame-retardant epoxy resin-based porous sound-insulating composite material according to claim 1, characterized in that, The amount of ammonium dihydrogen phosphate was adjusted to 10 parts, 8 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added, melamine was adjusted to 8 parts, nano-silica was adjusted to 5 parts, and 1 part of layered double hydroxide was added. The remaining raw materials and their weight parts were the same as those in claim 1.

3. The synergistic flame-retardant epoxy resin-based porous sound-insulating composite material according to claim 2, characterized in that, Sodium chloride is replaced with 6 parts potassium chloride and 2 parts calcium chloride, and ammonium bicarbonate is replaced with 4 parts azodicarbonamide. The remaining raw materials and their weight parts are the same as in claim 2.

4. The synergistic flame-retardant epoxy resin-based porous sound-insulating composite material according to claim 3, characterized in that, The carbon nanotubes were adjusted to 1.2 parts, graphene was added to 0.6 parts, silane coupling agent was adjusted to 0.6 parts, titanate coupling agent was added to 0.2 parts, and the remaining raw materials and weight parts were the same as in claim 3.

5. The synergistic flame-retardant epoxy resin-based porous sound-insulating composite material according to claim 4, characterized in that, The bisphenol A type epoxy resin is replaced with 60 parts of bisphenol A type, 30 parts of bisphenol F type, and 10 parts of bisphenol S type; the aliphatic amine curing agent is replaced with 10 parts of ethylenediamine, 6 parts of m-phenylenediamine, and 2 parts of isophorone diamine; the remaining raw materials and their weight parts are the same as in claim 4.

6. A method for preparing the synergistic flame-retardant epoxy resin-based porous sound-insulating composite material according to claim 1, characterized in that, Includes the following steps: (1) Raw material pretreatment: Add nano-silica and carbon nanotubes to silane coupling agent and stir for 30 minutes at 60°C and 250 rpm to obtain modified mixed filler; pulverize ammonium dihydrogen phosphate and melamine to a particle size of 45 micrometers and mix to obtain synergistic flame retardant; pulverize sodium chloride to a particle size of 90 micrometers and mix with ammonium bicarbonate to obtain composite porogen; (2) Mixing and dispersion: heat bisphenol A epoxy resin to 50°C and stir at 300 rpm, add modified mixed filler and synergistic flame retardant in sequence and stir for 60 minutes, then add composite porogen and stir for 30 minutes to obtain mixed slurry; (3) Step-by-step pore formation: Pour the mixed slurry into the mold, let it stand at room temperature of 23°C for 20 minutes, and then keep it at 80°C for 30 minutes; (4) Curing and molding: Add aliphatic amine curing agent to the mold and stir evenly. First, cure at 80℃ for 2 hours, then cure at 120℃ for 4 hours. Cool down to room temperature at a rate of 1.5℃ / minute to obtain a preliminary porous composite material. (5) Post-treatment: The pre-formed porous composite material is soaked in deionized water for 48 hours, during which the deionized water is replaced 3 times, and then dried at 100°C for 12 hours to obtain the composite material.

7. The preparation method according to claim 6, characterized in that, In step (1), the preparation temperature of the modified mixed filler is adjusted to 70℃, the stirring time is adjusted to 40 minutes, the particle size of the synergistic flame retardant after pulverization is adjusted to 35 micrometers, and the particle size of the composite porogen after pulverization is adjusted to 70 micrometers; in step (2), the stirring speed is increased to 400 rpm, the stirring time is extended to 70 minutes after adding the synergistic flame retardant, and the stirring time is extended to 40 minutes after adding the composite porogen.

8. The preparation method according to claim 7, characterized in that, In step (3), the room temperature standing time is extended to 30 minutes, and the 80℃ heat preservation time is extended to 40 minutes; in step (4), the curing process is adjusted to first cure at 90℃ for 1.5 hours, then at 130℃ for 3 hours, and the programmed cooling rate is adjusted to 1.0℃ / minute; in step (5), the deionized water soaking time is extended to 60 hours, during which the deionized water is replaced 4 times, the drying temperature is adjusted to 110℃, and the drying time is adjusted to 10 hours; ammonium dihydrogen phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxa A modified synergistic flame retardant is obtained by mixing a compound with melamine and adding 0.3 parts of silane coupling agent, stirring at 80°C and 250 rpm for 50 minutes; silane coupling agent-modified silicon powder is obtained by modifying silicon powder with silane coupling agent, and then nano-silica, layered double hydroxide and the silane coupling agent-modified silicon powder are compounded at a ratio of 2:1:0.5, and 0.2 parts of titanate coupling agent are added, stirring at 75°C and 250 rpm for 35 minutes. A modified silicon-based flame retardant is obtained by mixing the modified synergistic flame retardant with the modified silicon-based flame retardant as a synergistic flame retardant system.

9. The application of the synergistic flame-retardant epoxy resin-based porous sound-insulating composite material according to any one of claims 1-5, characterized in that, The composite material is used in sound insulation and flame retardant applications in the construction and transportation sectors.

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