Ceramifiable silicone foams containing montmorillonite and phosphorus-nitrogen flame retardant powder, and methods of making and using the same

Abstract

The application discloses a ceramicizable organic silicon foam containing montmorillonite and phosphorus-nitrogen flame-retardant powder and a preparation method and application thereof, and belongs to the technical field of organic silicon composite materials. The foam is prepared by a room-temperature chemical foaming method from raw materials containing the following components: a polydimethylsiloxane matrix, montmorillonite MMT, a nitrogen-phosphorus flame-retardant powder, a low-melting-point glass powder GP, water, a Karstedt platinum catalyst and an inhibitor. The foam material maintains high resilience at room temperature, forms a dense ceramic layer in situ on the surface under a high-temperature flame, and still maintains a porous elastic structure inside, realizes gradient thermal protection of "a hard shell on the outside and a soft core on the inside", and simultaneously reaches a UL-94 V-0 level of the flame-retardant grade, and can provide long-acting thermal protection of more than 30 minutes under a 1200 DEG C flame.

Description

Technical Field

[0001] This invention belongs to the field of organosilicon composite material technology, specifically relating to a ceramicizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame retardant powder, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles, aerospace, and power transmission, higher demands are being placed on the comprehensive protective performance of materials under extreme conditions, such as high heat flux impact, mechanical vibration, and oxidizing environments. For example, in the thermal runaway events of lithium-ion batteries, the internal temperature of the battery pack can soar to over 1000°C within seconds, necessitating a lightweight material that can both buffer mechanical impact and provide long-term thermal protection. Silicone foam is considered an ideal candidate material due to its excellent high and low temperature resistance, flexibility, electrical insulation, and certain flame retardancy. However, under direct impact from high-temperature flames, the polymer skeleton of traditional silicone foam rapidly degrades, forming loose silica residue, leading to structural collapse and rendering it unable to provide continuous and effective thermal protection.

[0003] To overcome this deficiency, researchers have developed ceramicizable polymers. The principle is to add ceramic fillers (such as mica, wollastonite, etc.) and fluxes to the polymer matrix. At high temperatures, the polymer matrix decomposes, and the fillers and decomposition products undergo a eutectic reaction, sintering to form a ceramic body with a certain strength, thereby playing a role in isolating flames and heat. For example, inspired by the "clay-flux" synergistic ceramic-forming mechanism in traditional pottery, Chen et al. introduced montmorillonite and low-melting-point glass powder into organosilicon foam, successfully achieving long-term thermal protection. However, the existing ceramicizable polymer system still has the following problems: (1) The flame retardant function and the ceramic-forming function are separated, the early flame retardant effect is insufficient, and it is not possible to effectively suppress the rapid destruction of the matrix by the flame, affecting the integrity of the subsequent ceramic structure; (2) In order to achieve a good ceramicization effect, a large amount of filler is often required, which usually damages the flexibility and resilience of the foam material at room temperature.

[0004] Chinese patent CN112210156B discloses a halogen-free flame-retardant polymer composite material that can be ceramicized. It uses low-softening-point glass powder and silicate minerals as ceramic fillers, and adds a halogen-free flame retardant and organomontmorillonite as synergistic flame retardants. However, this material is a dense thermoplastic elastomer, lacking a porous structure and resilience, and cannot meet the dual requirements of "room-temperature buffering and energy absorption" and "high-temperature ceramicized insulation" in battery thermal runaway protection. Furthermore, its preparation method, using melt blending, is greatly affected by the heat history of filler dispersion and cannot produce lightweight foam materials. Therefore, how to introduce a ceramicized-flame-retardant system into an organosilicon foam matrix with excellent resilience, and achieve low-temperature foaming-crosslinking integrated molding while ensuring a gradient ceramicized structure, remains an unsolved technical problem in this field.

[0005] Therefore, how to achieve a balance between early-stage high-efficiency flame retardancy and long-term ceramic protection through ingenious multi-component synergistic design while ensuring excellent and exceptionally gentle toughness remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention provides a ceramicizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame retardant powder, its preparation method, and its application. The foam material maintains high resilience at room temperature (stress retention rate ≥90% after 1000 cycles of 50% strain), and forms a dense ceramic layer on the surface in situ under high-temperature flame while maintaining a porous elastic structure inside, achieving gradient thermal protection of "a hard outer shell and a soft inner core". At the same time, the flame retardant rating can reach UL-94 V-0 level, and it can provide long-lasting thermal protection for more than 30 minutes under a flame at 1200℃.

[0007] The technical solution of this invention is as follows: In a first aspect, a ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame retardant powder is disclosed. The organosilicon foam is an elastic foam with a gradient porous structure, prepared from raw materials containing the following components via a room-temperature chemical foaming method: The polydimethylsiloxane (PDMS matrix) comprises at least vinyl-terminated polydimethylsiloxane and hydrogen-terminated polydimethylsiloxane; Montmorillonite (MMT) is used as a ceramic skeleton filler. Nitrogen-phosphorus flame retardant powder, as a dual-function synergist of flame retardant and ceramic formation, produces acidic substances when it decomposes at high temperatures. These substances first catalyze the degradation of the PDMS matrix to generate silica, and then act as a mineralizer / fluxant to promote the eutectic reaction between the silica and montmorillonite and low-melting-point glass powder to form a dense ceramic layer. Low-melting-point glass powder GP is used as a high-temperature flux; Water, as a foaming agent, reacts with hydrogen-terminated polydimethylsiloxane to produce hydrogen gas for foaming; Karstedt platinum catalyst; Inhibitors, used to control the rate of hydrosilylation crosslinking reactions.

[0008] Preferably, based on 100 parts of total polydimethylsiloxane body, the mass parts of each component are: 20-40 parts of montmorillonite, 20-40 parts of nitrogen-phosphorus flame retardant powder, 10-30 parts of low melting point glass powder, 1-10 parts of water, 0.1-2 parts of Karstedt platinum catalyst, and 0.5-1 parts of inhibitor.

[0009] Preferably, the nitrogen-phosphorus flame retardant powder is a compound mixture of ammonium polyphosphate and melamine phosphate, with a mass ratio of (1-2):(1-2). The nitrogen-phosphorus flame retardant powder decomposes at high temperature to produce phosphoric acid / polyphosphoric acid, which induces the degradation of the PDMS matrix and generates amorphous silica. Subsequently, these acidic substances act as mineralizers / fluxants, participating in and promoting the eutectic reaction between the silica generated by degradation and montmorillonite and low-melting-point glass powder to form a dense ceramic layer.

[0010] Preferably, the inhibitor is 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-1,3,5,7-tetraoxatetrasilcyclooctane.

[0011] Secondly, a method for preparing the ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame-retardant powder is disclosed, comprising the following steps: 1) Preparation of premix: The polydimethylsiloxane (PDMS) matrix is ​​mixed with the inhibitor, followed by the addition of montmorillonite, nitrogen-phosphorus flame retardant powder, low-melting-point glass powder and water, and mechanical stirring is carried out to form a uniform slurry; 2) Catalytic foaming and curing: Add Karstedt platinum catalyst to the uniform slurry obtained in step 1), stir and pour into a mold, let it stand at room temperature to foam; then heat to cure, and obtain ceramicizable organosilicon foam containing montmorillonite and phosphorus nitrogen flame retardant powder.

[0012] Preferably, in step 1), the mechanical stirring speed is 2000-2400 rpm and the time is 60-120 s.

[0013] Preferably, in step 2), the stirring speed is 2000-2400 rpm, the stirring time is 60-120 s, the standing foaming time is 10-20 min, the heating curing temperature is 70-90℃, and the heating curing time is 1-3 h.

[0014] Thirdly, the application of the ceramicizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame retardant powder is disclosed in the preparation of fireproof materials for cables or thermal runaway protection materials for lithium-ion batteries.

[0015] Compared with the prior art, the present invention has the following advantages: (1) Synergistic mechanism of "flame retardant-ceramic integration": This invention introduces nitrogen-phosphorus flame retardant (ammonium polyphosphate / melamine phosphate), ceramic skeleton (montmorillonite), and high-temperature flux (low-melting-point glass powder) into polydimethylsiloxane foam. Under high-temperature flame, the nitrogen-phosphorus flame retardant decomposes first, releasing inert gas to dilute combustibles on the one hand, and catalyzing the polymer matrix to form char on the other, forming a preliminary protective layer and achieving the UL-94 V-0 flame retardant standard; as the temperature rises, montmorillonite and low-melting-point glass powder undergo a melting reaction, and eutectic reaction with the previously formed char layer and the silica produced by polymer degradation, forming a dense, continuous, and gradient porous ceramic layer in situ. This mechanism integrates flame retardancy and ceramicization functions, avoiding the high-temperature structural collapse problem caused by a single ceramic filler in traditional materials, and achieving long-term thermal protection.

[0016] (2) Low cost and easy to scale up: This invention adopts a room temperature chemical foaming method, which uses water to react with hydrogen-containing silicone oil to generate hydrogen gas for foaming and simultaneously completes cross-linking and curing. The process is simple and does not require complex equipment such as supercritical drying, making it easy to achieve industrial production. All fillers used are commercially available industrial-grade raw materials, which are inexpensive and have good economic benefits.

[0017] (3) By optimizing the total amount and ratio of multi-scale fillers, the resulting foam material maintains excellent flexibility and resilience over a wide temperature range, meeting the requirements for wide temperature range adaptability of materials, such as those for battery thermal runaway protection. Simultaneously, under direct impact from a butane flame at 1200℃, the material maintains structural integrity for over 30 minutes, with the back temperature rise controlled below 300℃, demonstrating excellent long-term thermal protection capabilities. This enables it to meet the dual requirements of "room temperature buffering - high temperature protection" for materials under extreme conditions such as battery thermal runaway protection.

[0018] (4) This invention successfully applies the ceramic-flame retardant system to the silicone foam matrix, and constructs a gradient porous structure using a room temperature chemical foaming method, realizing the integration of the functions of "room temperature elastic buffer" and "high temperature ceramic protection". Experiments show that the stress retention rate of the material of this invention is as high as 97% after 1000 cycles of 50% strain compression, and the temperature rise on the back side of the material is less than 300°C within 30 minutes under a 1200°C flame. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the "flame retardant-ceramic integration" synergistic mechanism.

[0020] Figure 2 The compressive stress-strain curve of the ceramicizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame retardant powder prepared in Example 1 is shown.

[0021] Figure 3This is a comparison chart of the flame retardant performance of Example 1 and Comparative Example 1, in which... Figure 3 a is a photograph of the sample from Example 1 undergoing vertical combustion. Figure 3 b is a photograph of the vertical combustion of sample 1 in Comparative Example 1.

[0022] Figure 4 Figure (a) shows a cross-sectional view of the materials obtained in Example 1 and Comparative Example 5 after high-temperature burning. Figure (b) shows a cross-sectional view of the material obtained in Example 1 after burning.

[0023] Figure 5 The back-side temperature-time curve of the ceramicizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame retardant powder prepared in Example 1 under a butane flame at 1200°C. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions will be clearly and completely described below in conjunction with the embodiments of this invention.

[0025] Polydimethylsiloxane (PDMS) matrix: Vinyl-terminated polydimethylsiloxane (Vi-PDMS) and hydrogen-terminated polydimethylsiloxane (H-PDMS) are used as base polymers; vinyl-terminated polydimethylsiloxane was purchased from Ningbo Runhe High-Tech Materials Technology Co., Ltd., model number RH-Vi1305; hydrogen-terminated polydimethylsiloxane was purchased from Ningbo Runhe High-Tech Materials Technology Co., Ltd., model number RH-vi321.

[0026] Inhibitor: 2,4,6,8-Tetramethyl-2,4,6,8-Tetravinyl-1,3,5,7-Tetraoxatetrasilcyclooctane, used to control the rate of platinum-catalyzed reactions.

[0027] Montmorillonite (MMT): Sodium-based montmorillonite, used as a ceramic framework.

[0028] Nitrogen-phosphorus flame retardant powder: It is a compound of ammonium polyphosphate (APP) and melamine phosphate (MP) in a mass ratio of 2:1, and serves as a dual-function synergist for flame retardancy and ceramic formation.

[0029] Low melting point glass powder (GP): Purchased from Anmi Micro-Nano New Materials (Guangzhou) Co., Ltd. as a high-temperature flux, model number DM95-G750.

[0030] The Karstedt platinum catalyst, model PT-3000SW, was purchased from Guangzhou Silicon Friends New Materials Technology Co., Ltd.

[0031] Deionized water: used as a foaming agent.

[0032] A schematic diagram of the "flame retardant-ceramic integration" synergistic mechanism is shown below. Figure 1 As shown, under the action of high-temperature flame, the nitrogen-phosphorus flame retardant (APP / MP) on the foam surface first decomposes and releases inert gas and catalyzes the formation of a preliminary carbon layer (stage I); as the temperature rises to above 500℃, the low-melting-point glass powder (GP) softens and melts, and the montmorillonite (MMT) sheets begin to participate in the reaction. At the same time, the amorphous SiO2 produced by the decomposition of the PDMS matrix and the phosphorus decomposition products work together to form a molten mixture (stage II); when the temperature reaches 800-1000℃, the above components undergo a eutectic reaction and are sintered in situ to form a dense and continuous gradient ceramic layer. This ceramic layer presents a gradient structure of "dense layer-transition layer-porous elastic layer" from the outside to the inside, thereby achieving long-term thermal protection.

[0033] Example 1 The method for preparing the ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame retardant powder includes the following steps: 1) Preparation of premix: Vinyl-terminated polydimethylsiloxane Vi-PDMS (80g), hydrogen-terminated polydimethylsiloxane H-PDMS (20g) and inhibitor 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-1,3,5,7-tetraoxatetrasilcyclooctane (1g) were mixed. Then, montmorillonite (30g), nitrogen-phosphorus flame retardant powder (30g), low melting point glass powder (20g) and deionized water (10g) were added. The mechanical mixer was started and stirred at 2400 rpm for 1 minute to form a uniform slurry. The nitrogen-phosphorus flame retardant powder was compounded from ammonium polyphosphate (APP) and melamine phosphate (MP) in a mass ratio of 2:1.

[0034] 2) Catalytic foaming and curing: Add Karstedt platinum catalyst (0.8g) to the uniform slurry obtained in step 1), stir rapidly at 2400rpm for 1min, pour into a mold, let stand at room temperature (about 25℃) for 15 minutes to foam, and after the foam is formed, transfer it to an 80℃ forced-air oven for curing for 2 hours to finally obtain a ceramicizable organosilicon foam sample containing montmorillonite and phosphorus nitrogen flame retardant powder, denoted as CSF-Syn.

[0035] Example 2 The method for preparing the ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame retardant powder includes the following steps: 1) Preparation of premix: Vinyl-terminated polydimethylsiloxane Vi-PDMS (40g), hydrogen-terminated polydimethylsiloxane H-PDMS (10g) and inhibitor 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-1,3,5,7-tetraoxatetrasilcyclooctane (0.5g) were mixed. Then, montmorillonite (10g), nitrogen-phosphorus flame retardant powder (20g), low melting point glass powder (5g) and deionized water (5g) were added. The mechanical mixer was started and stirred at 2400 rpm for 1 minute to form a uniform slurry. The nitrogen-phosphorus flame retardant powder was compounded from ammonium polyphosphate (APP) and melamine phosphate (MP) in a mass ratio of 2:1.

[0036] 2) Catalytic foaming and curing: Add Karstedt platinum catalyst (0.8g) to the uniform slurry obtained in step 1), stir rapidly at 2200rpm for 1min, pour into a mold, let stand at room temperature (about 25℃) for 15 minutes to foam, after the foam is formed, transfer to an 80℃ forced-air oven for curing for 2 hours, and finally obtain a ceramicizable organosilicon foam sample containing montmorillonite and phosphorus nitrogen flame retardant powder, denoted as CSF-HFR.

[0037] Example 3 The method for preparing the ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame retardant powder includes the following steps: 1) Preparation of premix: Vinyl-terminated polydimethylsiloxane Vi-PDMS (40g), hydrogen-terminated polydimethylsiloxane H-PDMS (10g) and inhibitor 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-1,3,5,7-tetraoxatetrasilcyclooctane (0.5g) were mixed. Then, montmorillonite (20g), nitrogen-phosphorus flame retardant powder (10g), low melting point glass powder (15g) and deionized water (5g) were added. The mechanical mixer was started and stirred at 2400 rpm for 1 minute to form a uniform slurry. The nitrogen-phosphorus flame retardant powder was compounded from ammonium polyphosphate (APP) and melamine phosphate (MP) in a mass ratio of 2:1.

[0038] 2) Catalytic foaming and curing: Add Karstedt platinum catalyst (0.8g) to the uniform slurry obtained in step 1), stir rapidly at 2400rpm for 1min, pour into a mold, let stand at room temperature (about 25℃) for 15 minutes to foam, and after the foam is formed, transfer it to an 80℃ forced-air oven for curing for 2 hours to finally obtain a ceramicizable organosilicon foam sample containing montmorillonite and phosphorus nitrogen flame retardant powder, denoted as CSF-HC.

[0039] Comparative Example 1 In this comparative example, pure PDMS foam was used, and the specific preparation method is as follows: (1) Preparation of premix: Vinyl-terminated polydimethylsiloxane Vi-PDMS (40g), hydrogen-terminated polydimethylsiloxane H-PDMS (10g) and inhibitor 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-1,3,5,7-tetraoxatetrasilcyclooctane (0.5g) were mixed, and then deionized water (5g) was added. The mechanical mixer was started and stirred at 2400 rpm for 1 minute to form a uniform slurry; 2) Catalytic foaming and curing: Add Karstedt platinum catalyst (0.8g) to the uniform slurry obtained in step 1), stir rapidly for 1 min and pour into a mold. Let it stand at room temperature (about 25℃) for 15 minutes to foam. After the foam is formed, transfer it to an 80℃ forced-air oven for curing for 2 hours to finally obtain a pure PDMS foam sample, which is denoted as pure SiF.

[0040] Comparative Example 2 This comparative example contains only a flame retardant system. Compared with Example 1, Comparative Example 2 maintains the same amount of flame retardant powder, the only difference being the absence of montmorillonite and low-melting-point glass powder. The specific preparation method is as follows: 1) Preparation of premix: Vinyl-terminated polydimethylsiloxane Vi-PDMS (40g), hydrogen-terminated polydimethylsiloxane H-PDMS (10g) and inhibitor 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-1,3,5,7-tetraoxatetrasilcyclooctane (0.5g) were mixed. Then, nitrogen-phosphorus flame retardant powder (15g) and deionized water (5g) were added. The mechanical mixer was started and stirred at 2400 rpm for 1 minute to form a uniform slurry. The nitrogen-phosphorus flame retardant powder was compounded from ammonium polyphosphate (APP) and melamine phosphate (MP) in a mass ratio of 2:1.

[0041] 2) Catalytic foaming and curing: Add Karstedt platinum catalyst (0.4g) to the uniform slurry obtained in step 1), stir rapidly for 1 min and pour into a mold. Let it stand at room temperature (about 25℃) for 15 minutes to foam. After the foam is formed, transfer it to an 80℃ forced-air oven for curing for 2 hours to finally obtain the foam sample, which is denoted as CSF-FR.

[0042] Comparative Example 3 Unlike Example 1, the flame retardant powder in this comparative example only uses ammonium polyphosphate (30g) and does not add melamine phosphate. The rest of the preparation methods and steps are the same as in Example 1.

[0043] Comparative Example 4 Unlike Example 1, no montmorillonite was added in this comparative example, but the rest of the preparation methods and steps were the same as in Example 1.

[0044] Comparative Example 5 Unlike Example 1, no glass powder was added in this comparative example, but the rest of the preparation methods and steps were the same as in Example 1.

[0045] The following performance tests were performed on the foam samples prepared in the examples and comparative examples: (1) Mechanical property testing: Compression testing was conducted using a universal testing machine. Sample size: 10×10×10mm 3 The compression rate was 0.3 mm / min. Cyclic compression tests were performed 1000 times at 50% strain, and the stress-strain curves were recorded.

[0046] (2) Flame retardant performance test: Cut the sample into strips with a length of 13cm, a width of 1.5cm and a thickness of 3mm. Perform vertical burning test with an alcohol spray gun and blue flame, and record the burning time and melting droplet situation.

[0047] The test results are shown below: The compressive stress-strain curve of the ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame retardant powder prepared in Example 1 is shown in the figure below. Figure 2 As shown, the compressive stress-strain curve of the foam in Example 1 exhibits typical characteristics of elastic foam. After 1000 cycles of compression at 50% strain, the maximum stress retention rate is approximately 97%, and the residual strain is approximately 2.8%, indicating excellent fatigue resistance and elasticity. Examples 2 and 3 also show good elasticity, but their compressive modulus and resilience differ slightly due to different filler ratios. In contrast, the pure SiF foam in Comparative Example 1 has lower strength and is prone to permanent deformation due to the lack of filler reinforcement; the CSF-FR in Comparative Example 2, although having some reinforcing effect due to the addition of only flame retardants, still has mechanical properties inferior to the synergistic system of Example 1. The compressive properties of the examples and comparative examples are shown in Table 1.

[0048] Table 1: Comparison of compression performance of different samples

[0049] Examples 1-3 all exhibited superior mechanical properties compared to the comparative examples. Example 3, due to its highest total content of ceramic filler (MMT+GP) (35 parts), had the highest compressive modulus, but its resilience was slightly lower (91%). Example 2, due to its high proportion of flame retardant, had a slightly lower modulus but excellent resilience. This demonstrates that the formulation of the present invention can be adjusted within a wide range to meet the balance requirements of "flexibility" and "rigidity" in different scenarios, and the overall mechanical properties of all synergistic systems (Examples 1-3) are significantly better than those of the single-component systems (Comparative Examples 1-2).

[0050] (2) Flame retardant properties The results of the UL-94 vertical burning test are shown in Table 2 below.

[0051] Table 2

[0052] As shown in the table above, the samples from Examples 1 and 2 both met the UL-94 V-0 flame retardant standard, indicating that the addition of nitrogen-phosphorus flame retardants played a highly efficient early flame retardant role. Example 3, focusing on a high content of ceramic filler (35 parts of montmorillonite and glass powder), had a relatively low proportion of flame retardant, achieving a flame retardant rating of V-1, but still superior to pure silicone foam (Comparative Example 1, V-2). This further demonstrates that by adjusting the ratio of flame retardant to ceramic filler, the flame retardant rating of this invention can be flexibly controlled between V-1 and V-0. Comparative Example 1 (pure SiF) had a long burning time and produced molten droplets, achieving only a V-2 rating. Although Comparative Example 2 achieved a V-0 rating, it lacked a ceramic framework and flux, resulting in significantly lower structural stability and long-term thermal protection capabilities at high temperatures compared to Examples 1-3. A comparison of the flame retardant performance of Example 1 and Comparative Example 1 is shown in the figure below. Figure 3 As shown, where Figure 3 a is a photograph of the sample from Example 1 undergoing vertical combustion. Figure 3 b is a photograph of the vertical combustion of sample 1 in Comparative Example 1. As can be seen from the figure, in the vertical combustion test, Figure 3 The sample in Example 1 (synergistic system) of type a exhibited typical V-0 flame retardant behavior, with the afterflame rapidly self-extinguishing within 1-2 seconds after being removed from the flame and no molten dripping. Figure 3 Comparative Example 1 (pure PDMS foam) sample b continued to burn for more than 10 seconds after being removed from the flame, accompanied by melting and dripping, and its flame retardant rating was only V-2. This comparison intuitively demonstrates the significant effect of the 'flame retardant-ceramic integration' strategy of this invention in suppressing flame spread and promoting self-extinguishing.

[0053] (3) Analysis of porcelain formation mechanism Analysis of the samples from Examples 1-3 after combustion revealed the following ceramic formation mechanism: Upon exposure to a high-temperature flame, the phosphorus-nitrogen flame retardant on the foam surface first decomposes, releasing inert gases such as ammonia and water vapor, diluting the combustible gases, and simultaneously catalyzing the formation of a thin carbon layer on the polymer surface. As the temperature continues to rise (>500℃), the PDMS matrix decomposes into amorphous silica, and low-melting-point glass powder begins to soften and melt, penetrating between the montmorillonite layers. At approximately 800-1000℃, the molten glass powder, montmorillonite, silica, and phosphides undergo a complex eutectic reaction, generating high-temperature resistant ceramic crystalline phases such as albite and cordierite, ultimately sintering to form a dense ceramic protective layer with a gradient structure. This ceramic layer effectively blocks heat transfer to the interior and prevents oxygen from contacting the unburned polymer inside, thus achieving long-term thermal protection. In contrast, Comparative Example 5 only forms a loose carbon layer and silica residue at high temperatures, failing to form a dense ceramic structure, thus its long-term heat protection capability is insufficient. A comparative schematic diagram of the cross-sectional structures of the materials obtained in Example 1 and Comparative Example 5 after high-temperature calcination is shown below. Figure 4 As shown, Figure (a) is a schematic cross-sectional view of the material after burning in Example 1 of the present invention, and (b) is a schematic cross-sectional view of the material after burning in Comparative Example 5. Figure 4 (a) It can be seen that the foam of Example 1, after being burned at high temperature, formed a clear three-layer gradient structure: the outermost layer is a dense, continuous ceramic hard shell, the middle layer is a transition layer, and the interior still retains some porous elastic structure, achieving gradient thermal protection of "outer hard shell and inner soft core". And from... Figure 4 (b) It can be seen that after calcination, the foam of Comparative Example 5 (without added low-melting-point glass powder) only formed a loose carbon layer and unsintered silica particles on its surface, failing to form a dense ceramic protective layer, and the foam structure could not be transformed. This intuitively demonstrates that low-melting-point glass powder, as a high-temperature flux, is crucial for forming a dense and continuous ceramic layer and realizing a gradient structure.

[0054] Although the present invention has been described in detail by way of preferred embodiments, the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame-retardant powder, characterized in that, The silicone foam is an elastic foam with a gradient porous structure, prepared from raw materials containing the following components by a room temperature chemical foaming method: The polydimethylsiloxane comprises at least vinyl-terminated polydimethylsiloxane and hydrogen-terminated polydimethylsiloxane; Montmorillonite (MMT) is used as a ceramic skeleton filler. Nitrogen-phosphorus flame retardant powder, as a dual-function synergist of flame retardant and ceramic formation, produces acidic substances when it decomposes at high temperatures. These substances first catalyze the degradation of polydimethylsiloxane to generate silica, and then act as a mineralizer / fluxant to promote the eutectic reaction between silica and montmorillonite and low-melting-point glass powder to form a dense ceramic layer. Low-melting-point glass powder GP is used as a high-temperature flux; Water, as a foaming agent, reacts with hydrogen-terminated polydimethylsiloxane to produce hydrogen gas for foaming; Karstedt platinum catalyst; Inhibitors.

2. The ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame-retardant powder as described in claim 1, characterized in that, Based on a total mass of 100 parts of polydimethylsiloxane, the mass fractions of each component are as follows: montmorillonite 20-40 parts, nitrogen-phosphorus flame retardant powder 20-40 parts, low melting point glass powder 10-30 parts, water 1-10 parts, Karstedt platinum catalyst 0.1-2 parts, and inhibitor 0.5-1 parts.

3. The ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame-retardant powder as described in claim 1, characterized in that, The nitrogen-phosphorus flame retardant powder is a compound mixture of ammonium polyphosphate and melamine phosphate, with a mass ratio of (1-2):(1-2).

4. The ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame-retardant powder as described in claim 1, characterized in that, The inhibitor is 2,4,6,8-tetramethyl-2,4,6,8-tetravinyl-1,3,5,7-tetraoxatetrasilcyclooctane.

5. The method for preparing ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame-retardant powder as described in any one of claims 1-4, characterized in that, Includes the following steps: 1) Preparation of premix: Polydimethylsiloxane is mixed with inhibitor, followed by the addition of montmorillonite, nitrogen-phosphorus flame retardant powder, low melting point glass powder and water, and mechanically stirred to form a uniform slurry; 2) Catalytic foaming and curing: Add Karstedt platinum catalyst to the uniform slurry obtained in step 1), stir and pour into a mold, let it stand at room temperature to foam; then heat to cure, and obtain ceramicizable organosilicon foam containing montmorillonite and phosphorus nitrogen flame retardant powder.

6. The method for preparing ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame-retardant powder as described in claim 5, characterized in that, In step 1), the mechanical stirring speed is 2000-2400 rpm and the time is 60-120 s.

7. The method for preparing ceramizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame-retardant powder as described in claim 5, characterized in that, In step 2), the stirring speed is 2000-2400 rpm, the stirring time is 60-120 s, the standing foaming time is 10-20 min, the heating curing temperature is 70-90℃, and the heating curing time is 1-3 h.

8. The application of the ceramicizable organosilicon foam containing montmorillonite and phosphorus-nitrogen flame retardant powder as described in any one of claims 1-4 in the preparation of fire-resistant materials for cables or thermal runaway protection materials for lithium-ion batteries.

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