Forest fireproof material based on organic silicon MC composite hydrogel and preparation method thereof

Abstract

The invention provides a forest fireproof material based on organic silicon MC composite hydrogel and a preparation method thereof, and the forest fireproof material comprises the following raw materials in parts by weight: 0.05-0.3 wt% of an organic silicon wetting agent, 1.2-1.6 wt% of methyl cellulose, 1.8-2.5 wt% of a flame retardant, 1.8-2.3 wt% of an ionic cross-linking agent, and the balance of water, mC is used as a basic framework of the composite hydrogel, an organic silicon wetting agent 5211 is used as a dynamic wetting regulation and control unit, and DMMP is used as an efficient chemical flame-retardant core. The hydrogel has a shear thinning (0 lt; nlt; the viscosity is reduced during pipeline conveying, the flow-adhesion requirement of a fire extinguishing scene is met, the temperature response characteristic is achieved, balance of shear thinning flowability, high-temperature adhesion and rapid phase change response is achieved through concentration gradient regulation and control of methyl cellulose and an organic silicon wetting agent, thermal stability is achieved, DMMP chemical flame retardance and MC hydrogel self-assembly are achieved, and the temperature response characteristic is achieved; the thermal stability and the carbon layer forming ability are enhanced, the residual yield is synergistically increased from 6.51% to 13.91%, a heat-insulation oxygen-barrier layer is formed, and the method is suitable for a complex fire scene environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of fireproof materials, and in particular relates to a forest fireproof material based on organosilicon MC composite hydrogel, and a preparation method and application thereof. Background Art

[0002] As a type of solid fire, forest fire is characterized by rapid spread and difficulty in control. It can easily pose a threat to the ecosystem and human life and property, and have a wide-ranging impact on social development.

[0003] Traditional fire extinguishing agents, such as water, chemical extinguishing agents, and foams, while effective to a certain extent, have limitations when responding to high-intensity fires in complex environments. For example, while water is widely available and highly mobile, its high volatility at high temperatures limits its effectiveness in reaching the high-temperature zones within a flame, resulting in high water consumption, low fire extinguishing efficiency, and a high risk of rekindling. Dry powder and foams have difficulty penetrating deep into a fire, and residual residue from dry powder sprays is difficult to clean, potentially causing environmental pollution. Foams are also less stable and struggle to maintain their fire extinguishing effectiveness. The effectiveness of traditional fire extinguishing agents is often significantly reduced, particularly in drought and high-temperature complex environments. Furthermore, many forest fire extinguishing agents have negative environmental impacts. For example, long-lasting chemical extinguishing agents such as ammonium sulfate, ammonium phosphate, and halogenated hydrocarbons can cause water pollution, long-term damage to the soil, and even harm humans.

[0004] Hydrogel is a new, clean, and highly effective fire-fighting material with excellent adhesion, strong water absorption, and water retention. During firefighting operations, it can rapidly cool and reduce temperatures while simultaneously acting as an oxygen barrier and blockage barrier, significantly improving water utilization and overall firefighting effectiveness. However, the poor fluidity of traditional hydrogels hinders their penetration and sprayability, resulting in incomplete coverage of ignition points and difficulty in handling residual debris.

[0005] Therefore, on the basis of improving fire extinguishing efficiency, reducing usage costs and reducing the impact on the ecological environment are important goals for the subsequent development of forest fire prevention and extinguishing materials. Summary of the Invention

[0006] This application addresses the problems of poor environmental degradability, low flame retardant efficiency and insufficient anti-reignition ability of traditional forest fire extinguishing agents, and provides a forest fire prevention material based on silicone MC composite hydrogel. It constructs an environmentally responsive composite hydrogel system based on methyl cellulose and trisiloxane wetting agent. On the basis of improving fire extinguishing efficiency, it controls application costs and reduces negative impacts on the environment. It has the advantages of flow and penetration characteristics, green and efficient, low cost, strong thermal stability and the ability to dynamically respond to temperature changes.

[0007] The present invention is achieved through the following technical solutions: A forest fire prevention material based on silicone MC composite hydrogel, comprising the following raw materials in parts by weight: 0.05-0.3wt% silicone wetting agent, 1.2-1.6wt% methyl cellulose, 1.8-2.5wt% flame retardant, 1.8-2.3wt% ionic crosslinking agent, and the balance being water.

[0008] Another object of the present application is to provide a preparation method of the above-mentioned forest fire prevention material based on silicone MC composite hydrogel, comprising the following steps: S1. Take methyl cellulose, flame retardant, silicone wetting agent and ionic crosslinking agent according to the mass fraction ratio; S2. Use the one-pot method to mix the above materials with deionized water, stir evenly until hydrated, and then stand at room temperature to allow it to fully swell and crosslink; S3. Disperse the swollen hydrogel by high-speed stirring until it becomes a uniform sol state, and stand at room temperature to defoam it to obtain the product.

[0009] Compared with the prior art, the present invention has the following advantages: The present application provides a forest fire prevention material based on silicone MC composite hydrogel, comprising the following raw materials in parts by weight: 0.05-0.3wt% silicone wetting agent, 1.2-1.6wt% methyl cellulose, 1.8-2.5wt% flame retardant, 1.8-2.3wt% ionic crosslinking agent, and the balance being water. It is a composite hydrogel system with MC as the basic framework of the composite hydrogel, silicone wetting agent 5211 as the dynamic wetting regulation unit, and DMMP as the high-efficiency chemical flame retardant core. This hydrogel has the characteristics of shear thinning (0 < n < 1), reducing the viscosity during pipeline transportation, meeting the flow-adhesion requirements of the fire extinguishing scenario, having temperature-responsive characteristics, achieving the balance of shear-thinning fluidity, high-temperature adhesion and rapid phase change response through the concentration gradient regulation of methyl cellulose and silicone wetting agent, having thermal stability, the chemical flame retardation of DMMP and the self-assembly of MC hydrogel, enhancing the thermal stability and the ability to form a carbon layer, synergistically increasing the residual yield from 6.51% to 13.91%, forming a heat-insulating and oxygen-blocking layer, and being suitable for complex fire field environments.

[0010] The present application provides a preparation method of a forest fire prevention material based on silicone MC composite hydrogel, preparing a silicone MC composite hydrogel with flow penetration characteristics, being green and efficient, having low cost, strong thermal stability and being able to dynamically respond to temperature changes. This hydrogel is in a sol state when the temperature is lower than the lower critical solution temperature (LCST), has strong fluidity, is easy to spray and cover the fire point, becomes a gel state when the temperature exceeds LCST, has an increased viscosity, can firmly adhere to the surface of combustibles, and at the same time releases a highly permeable liquid when heated to carry the flame retardant component into the depth of the fire source for fire extinguishing. Description of the Drawings

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments.

[0012] Figure 1 This is the gelation mechanism of the organosilicon MC composite hydrogel in the embodiment of the present application; Figure 2 This is a schematic diagram of fire extinguishing of the organosilicon MC composite hydrogel in the embodiment of the present application; Figure 3 is a graph showing the relationship between surface tension and concentration of four wetting agent solutions in the examples of the present application; Figure 4 1 is a graph showing the spreading trend and dynamic contact angle change of SDBS on a pine wood surface in an embodiment of the present application; Figure 5 This is a graph showing the spreading trend and dynamic contact angle change of APG-0810 on a pine wood surface in an embodiment of the present application; Figure 6 This is a graph showing the spreading trend and dynamic contact angle change of 5211 on a pine wood surface in an embodiment of the present application; Figure 7 This is a graph showing the spreading trend and dynamic contact angle change of 8008 on a pine wood surface in an embodiment of the present application; Figure 8 is a graph showing the relationship between the spreading coefficient and the wetting agent concentration in the embodiments of the present application; Figure 9 is a graph showing the penetration time of different wetting agent solutions in the examples of the present application; Figure 10 is a graph showing the relationship between viscosity, shear stress, and shear rate for hydrogels A1-A4 in the examples of the present application (solid graphs show viscosity, hollow graphs show stress); Figure 11 This is a graph showing the effect of DMMP concentration on hydrogel viscosity in the examples of this application; Figure 12 This is a graph showing the effect of 5211 concentration on hydrogel viscosity in the examples of the present application; Figure 13 is a graph showing the relationship between shear stress and shear rate for the A2 hydrogel and the C3 hydrogel in the examples of the present application; Figure 14 2 is a temperature scanning curve diagram of the hydrogels A2 (a) and C3 (b) in the examples of the present application; Figure 15 is the dynamic contact angle of water separation and dehydration of each hydrogel system in the embodiment of this application Figure 16 TG and DTG curves of A2 and C3 hydrogels in the examples of the present application; Figure 17 This is the fire extinguishing process of working conditions 1, 2, and 3 in the embodiments of the present application. DETAILED DESCRIPTION

[0013] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are intended only to explain the present invention and are not intended to limit the present invention. It should be noted that, unless there is a conflict, the embodiments and features in the embodiments of this application may be combined with each other.

[0014] This embodiment of the present application provides a forest fire prevention material based on an organosilicon MC composite hydrogel, comprising the following raw materials by weight: 0.05-0.3wt% organosilicon wetting agent (5211), 1.2-1.6wt% methylcellulose (MC), 1.8-2.5wt% flame retardant (DMMP), 1.8-2.3wt% ionic crosslinker (NaCl), and the balance water. The composite hydrogel prepared in this application primarily comprises methylcellulose (MC), trisiloxane wetting agent (5211), dimethyl methylphosphonate (DMMP), and sodium chloride (NaCl), which act as a gelling agent, wetting agent, flame retardant, and crosslinking agent, respectively, and exert a synergistic effect in the composite hydrogel's fire prevention and extinguishing process.

[0015] The gelation mechanism of the silicone MC composite hydrogel in the embodiment of the present application: The physical cross-linking network of the silicone MC composite hydrogel is mainly constructed by methyl cellulose (MC). The hydrophilic groups of MC form hydrogen bonds with water molecules to promote their orderly arrangement within the MC network. The silicone wetting agent is a high molecular polymer. The hydrophobic siloxane main chain also participates in the formation of the cross-linked grid. The ethoxy groups on the hydrophilic polyether chain adsorb and aggregate water molecules through electrostatic interactions and hydrogen bonds. The sodium ions uniformly dispersed in the solution and the methoxy groups of MC undergo ionic interactions to form a structured network. Due to molecular interactions (hydrogen bonds, hydrophobic interactions, van der Waals forces, etc.), the silicone MC composite hydrogel will produce a sol-gel transition according to temperature changes, such as Figure 1 As shown, at lower temperatures, hydrogen bonding between water molecules predominates, leading to a sol state characterized by water coverage. As the temperature increases, increased heat absorption disrupts hydrogen bonding, causing entanglement between MC and siloxane molecular chains. This, combined with an enhanced salting-out effect, disrupts the ordered water arrangement, gradually exposing the hydrophobic methoxy groups on MC. Subsequently, hydrophobic associations predominate, leading to gel formation.

[0016] Fire extinguishing mechanism of silicone MC composite hydrogel: Silicone MC composite hydrogel has a three-dimensional cross-linked structure and adhesive properties. Methylcellulose (MC) forms the basic morphology of the composite hydrogel, while siloxane chains participate in the formation of the hydrogel's cross-linked structure. Flame retardants and water are encapsulated in the composite hydrogel. The composite hydrogel, which exhibits shear-thinning properties, can be sprayed at high speed through a pipeline onto a forest fire site, forming a film covering the fire point and isolating it from oxygen. When subjected to changes in the fire environment temperature, the thermally responsive composite hydrogel begins to condense and undergo a sol-gel transition, firmly adhering to the surface of the combustible material. At the same time, as the temperature continues to rise, the highly effective flame retardant and silicone wetting water loaded into the composite hydrogel are slowly released. This highly wettable, highly permeable water penetrates the pores of the vegetation fuel layer, penetrates deep into the fire source, and continues to absorb heat from deep within the fire point. The flame retardant DMMP decomposes upon exposure to heat and reacts with free radicals, terminating the chain reaction and preventing further combustion. During the fire extinguishing process, the silicone MC composite hydrogel fully utilizes the fire extinguishing efficiency of each component at both the physical and chemical levels. Figure 2 shown.

[0017] The methylcellulose used in the examples of this application is derived from the natural polymer cellulose, which can be extracted from natural wood or refined cotton. It is inexpensive and environmentally biodegradable. Using cellulose-based hydrogels to synthesize forest fire extinguishing materials is like taking the material and using it for its own benefit.

[0018] MC's hydrophilic groups (hydroxyl groups) form hydrogen bonds with water molecules, promoting their orderly arrangement within the MC network and facilitating storage, transport, and permeation at room temperature. Furthermore, above this threshold, MC molecules interact (hydrogen bonding, hydrophobic interactions, van der Waals forces, etc.) to transform into an adhesive gel, effectively suppressing oxygen supply and smoke release, thus overcoming the limitations of traditional firefighting methods. By virtue of its ability to flow at room temperature and gel upon heating, MC hydrogels primarily serve the physical functions of isolating oxygen, smoke, and heat during firefighting.

[0019] Methylcellulose (MC) is a non-ionic cellulose ether produced by introducing methyl groups into the cellulose molecule through an etherification reaction. Cellulose is the primary structural component of plant cell walls, accounting for 40%-50% of wood. Methylcellulose is a natural polymer with excellent adhesiveness and cost-effectiveness. It is non-toxic, easily degradable, and undergoes a reversible sol-gel phase transition at a certain temperature. At room temperature, MC absorbs water and swells to form a stable, low-viscosity solution. At elevated temperatures, MC undergoes a physical transformation, forming a highly viscous gel.

[0020] Trisiloxane wetting agent 5211 is a type of silicone surfactant with a flexible -Si-O-Si-chain as the skeleton and one or more hydrophilic groups connected. Due to its strong surface activity, corrosion resistance, high temperature resistance and non-toxicity, it is added as a wetting agent in hydrogel fire extinguishing agent to adjust and improve the fluidity and diffusivity of MC hydrogel for rapid film formation, enhance the thermal stability of hydrogel, and promote the moisture carrying flame retardant to wet and penetrate the fuel after the hydrogel is dehydrated to achieve the effect of cooling and extinguishing fire.

[0021] Dimethyl methylphosphonate (DMMP) is an organophosphorus flame retardant with an extremely high phosphorus content. It boasts excellent flame retardancy, environmental friendliness, low toxicity, and excellent compatibility, meeting the development requirements for green and efficient flame retardancy. Upon exposure to heat, DMMP first decomposes to form PO and PO2. These two compounds react with free OH radicals, accelerating chain termination reactions and thus providing a flame retardant effect. Dimethyl methylphosphonate (DMMP, C3H9O3P, CH3PO[OCH3]2) is a comprehensive flame retardant with good water solubility, high efficiency, low toxicity, and good compatibility with polymers. It can function in both the gas and condensed phases. During its decomposition, DMMP forms a non-volatile phosphoric acid layer that acts as a protective layer on the surface of combustible materials, effectively isolating them from oxygen and extinguishing the flame. Furthermore, the polymetaphosphoric acid produced by DMMP decomposition can promote the carbonization of polymer combustion decomposition, while simultaneously releasing a large amount of water, effectively suppressing the continued combustion reaction.

[0022] Sodium chloride (NaCl) generates chemical bonds between linear polymer hydrogels in the form of ionic cross-linking, connecting the linear molecules to each other to form a three-dimensional physically cross-linked network structure. Salting out and interaction promote the dehydration process, thereby accelerating the formation of gel and carbonized layer and improving the gel strength of the composite hydrogel.

[0023] This application utilizes a trisiloxane wetting agent with a simple, stable chemical structure and excellent biocompatibility as its core, and methylcellulose (MC), a natural cellulose derivative, as the hydrogel's base material. Highly fire-resistant and flame-retardant additives are added to create an environmentally friendly, highly effective, thermally insulating, and dynamically responsive silicone hydrogel structural material. This application prepares a silicone-MC composite hydrogel with fluidity and permeability, demonstrating green efficiency, low cost, strong thermal stability, and the ability to dynamically respond to temperature changes. Below the critical transition temperature (LCST), the hydrogel exhibits a sol-like state, exhibiting high fluidity and ease of spraying and covering fire points. Above the LCST, it transforms into a gel-like state with increased viscosity, allowing it to adhere firmly to combustible surfaces. Upon heating, it releases a hypertonic liquid, carrying the flame-retardant components deep into the fire source to extinguish it.

[0024] Specifically, silicone wetting agents are the core component of silicone-MC composite hydrogels. They primarily reduce the surface tension or interfacial tension of water, enhancing water penetration and making solid surfaces wettable. The long Si-C bond length and high methyl coverage in the silicone wetting agent's backbone contribute to its excellent hydrophobicity, effectively reducing the surface tension of solutions (to below 20 mN / m, compared to the 30 mN / m typical of conventional surfactants). As a novel biodegradable surfactant, silicone wetting agents are commonly used as spray modifiers, pesticide adjuvants, and defoaming agents.

[0025] In a specific embodiment, the organosilicon wetting agent used is a trisiloxane wetting agent, preferably Dow Corning's 5211 nonionic organosilicon. Siloxane has stable physical and chemical properties, and the dispersion of 5211 in the MC hydrogel enhances the hydrogel's thermal stability. During the hydrogel's thermal dehydration process, water from 5211 and the flame retardant escapes the hydrogel. The hydrophilic ethylene oxide (-C2H6O-) groups of the trisiloxane wetting agent 5211 migrate toward the aqueous phase, while the hydrophobic groups (chains) adsorb onto the wood surface, covering the methoxy and benzene ring hydrophobic groups on the wood surface, transforming the wood's surface from hydrophobic to hydrophilic. This water removed from the gel helps penetrate the surface fuel layer of the forest vegetation, extinguishing deeper smoldering fires and achieving a physical cooling effect.

[0026] Example 1, Performance Analysis of Silicone Wetting Agent: Using pine, the wood with the highest forest coverage, as the test specimen, the study examined the effects of four water-wetting agents on the penetrating wettability of wood, selecting nonionic silicone surfactants, anionic hydrocarbon surfactants, and nonionic hydrocarbon surfactants as comparison test objects. Surface tension data provided a preliminary assessment of the wettability of the monomer solution. Dynamic contact angle measurements on three sections of pine wood were used to analyze the spreading tendency of the water-wetting agent. Tension and contact angle data were used to calculate the spreading coefficient. Combined with the results of water-wetting agent penetration time tests, the effect of solution concentration on the penetrating wettability of wood was investigated, allowing the selection of the desired silicone wetting agent type and concentration range.

[0027] To improve the diffusion and penetration properties of the hydrogel, determine the wetting properties of the silicone wetting agent in the silicone MC composite hydrogel and the suitable addition concentration, this application selects two silicone wetting agents (trisiloxane wetting agent 5211, polyether-modified polysiloxane wetting agent 8008), compares common hydrocarbon wetting agents (sodium dodecyl benzene sulfonate SDBS, alkyl polyglycoside APG), determines the wetting agent type with more excellent wetting, diffusion, and penetration properties and selects a suitable concentration range as the key component of the fire-fighting hydrogel. The effects of different types of wetting agents on enhancing the wetting and penetration properties of water on wood were explored, and based on the experimental test results, a new type of silicone wetting agent 5211 with more excellent diffusion and penetration ability was determined, and its suitable addition concentration range was determined as the key component to improve the fire extinguishing efficiency of the hydrogel fire extinguishing agent.

[0028] (1) Surface tension test Surface tension is an important parameter affecting the penetration and wetting effect. The lower the surface tension, the better the wetting property of the wetting agent. In this experiment, the surface tension (IFT) was tested using a KRUSS K20 type surface tension meter, and the dynamic surface tension values of solutions with different concentrations at 25°C were measured by the ring method. The instrument calculates the surface tension value based on the maximum tensile force received during the measurement process. Seven concentrations were set for the hydrocarbon wetting agents, and eight concentrations were set for the silicone wetting agents. To ensure the accuracy of the data, each group of experiments was repeated three times to obtain the average surface tension value. After measuring the surface tension data, the critical micelle concentration and critical surface tension of the four solutions were calculated, and then the two were compared.

[0029] Analysis of surface tension test results: As Figure 3 shown, the change of surface tension with concentration can be divided into two concentration ranges: the decreasing range and the stable range. In the decreasing range, the surface tension of the solution decreases significantly with the increase of the surfactant concentration; in the stable range, the surface tension of the solution decreases to the lowest and then remains stable with the increase of the surfactant concentration. The lowest surface tensions of the four surfactants from small to large are: 5211 < 8008 < SDBS < APG-0810. It can be found that the decrease in surface tension of the silicone wetting agent is greater than that of the hydrocarbon wetting agent with the increase of concentration. Among them, 5211 has the lowest surface tension and the strongest ability to reduce the surface tension. The lowest surface tension is 19 mN / m at 0.05%.

[0030] It can be found that as the wetting agent concentration continues to increase, the surface tension of the solution no longer decreases continuously with its concentration, but instead exhibits a stable trend. This is because the adsorption density of surfactant molecules at the gas-liquid interface gradually reaches saturation. The surfactant molecules in the solution will aggregate together, with their hydrophobic groups facing inward and their hydrophilic groups facing outward, forming micelles. At this point, the solution reaches the critical micelle concentration. When this stage is reached, the surfactant mainly consumes itself by forming micelles, rather than further reducing the surface tension of the solution. To further compare the four wetting agents, the surface tension test results in Figure 1 can be used to obtain the critical micelle concentration (CMC) and the corresponding critical surface tension (γCMC) corresponding to each wetting agent. The specific values are detailed in Table 1.

[0031] Table 1 CMC and γCMC of different wetting agent solutions

[0032] Table 1 shows significant differences in the critical micelle concentration (CMC) and critical surface tension (γCMC) of different wetting agent solutions. Silicone wetting agents exhibit significantly lower CMC and γCMC values than hydrocarbon wetting agents. Among hydrocarbon wetting agents, SDBS exhibits slightly higher CMC and γCMC values than APG-0810. Among silicone wetting agents, 5211 and 8008 exhibit similar CMC values, while γCMC values for 5211 and 8008 are comparable. This suggests that silicone wetting agents can significantly reduce the surface tension of liquids at very low addition levels. Compared to hydrocarbon wetting agents, silicone wetting agents offer lower cost and lower dosage. Based on the CMC and γCMC data, we can preliminarily conclude that silicone wetting agents meet expectations.

[0033] (2) Dynamic contact angle measurement The contact angle is an important parameter to characterize the wettability of solid surfaces and can reflect the interaction between liquid and solid. Due to the anisotropy of wood and different wood processing processes, the roughness of wood sections is different, and the surface hydrophobicity is also different. Usually, the cross-section roughness of wood is greater than the radial section and tangential section. Therefore, the dynamic contact angles of wood with different sections are measured for comparison. The smaller the contact angle of the surface with the same roughness, the better the wettability of the wood surface. In this experiment, pine strips were selected as the contact angle test substrate. The pine strip specimens were of two specifications: 100mm×50mm×10mm and 50mm×50mm×50mm. Each strip was polished, ultrasonically cleaned, and vacuum dried. Its moisture content was maintained at 10%~14% and the wood density was maintained at 0.45~0.55g / cm 3Wetting agent solutions of varying concentrations were prepared using deionized water. Random testing was performed at various locations on the specimen surface. The dynamic contact angles of the different wetting agent concentrations on the pine wood surfaces were measured using an SDC-350 optical contact angle meter over a period of 0-20 seconds. The contact angle resolution was 0.001°. All tests were repeated at least three times to obtain an average value. Based on the surface tension and contact angle data, the spreading coefficients of the four solutions on the wood surface were calculated, and the enhanced wetting effects of the wetting agent solutions on wood were compared and verified.

[0034] Dynamic contact angle measurement analysis: Figure 4-Figure 7 The spreading trends of different wetting agent concentrations on pine wood surfaces were demonstrated. With increasing wetting agent concentration, the contact angle of the wetting agent solution decreased. With increasing contact time, the wetting agent solution gradually diffused and spread completely due to the effects of gravity and adsorption within the wood's microporous structure. Due to the layered porosity and anisotropic structure of wood, the contact angle of the same wetting agent concentration on pine wood cross sections was greater than that on radial / tangential sections, and it was more difficult for the cross sections to spread completely within the same time. On radial / tangential sections of pine wood, 0.2% SDBS and 0.2% APG spread completely within 15 seconds, while silicone wetting agents 5211 and 8008 spread completely within 15 seconds at a concentration of 0.01%. On pine wood cross sections, at the same 0.5% mass concentration, SDBS spread completely in over 20 seconds, APG in 10 seconds, and 5211 and 8008 in less than 5 seconds.

[0035] On the same hydrophobic surface, the addition of wetting agent can effectively enhance the wettability of aqueous solution on wood. The mass fraction of organosilicon wetting agent required for complete spreading of solution at the same time is much lower than that of hydrocarbon wetting agent. At the same mass fraction, the time required for organosilicon wetting agent to completely spread is also lower than that of hydrocarbon wetting agent.

[0036] Figure 4-Figure 7The dynamic contact angle changes of different wetting agents on a pine wood surface over a period of 0-20 seconds are shown. The contact angles of the four wetting agents on pine wood cross sections decreased less significantly than those on tangential and radial sections, indicating that wetting agent solutions have greater difficulty spreading on rougher cross sections. Using the dynamic contact angles of pine wood cross sections at the same mass fraction of 0.1% as a reference, the contact angle of SDBS decreased from 95.079° to 33.112° over 20 seconds, a decrease of 3.1° / s. The contact angle of APG decreased from 112.387° to 89.954° over 20 seconds, a decrease of 1.12° / s. The contact angle of 5211 decreased from 95.512° to 0° over 5 seconds, a decrease of 19.1° / s. The contact angle of 8008 decreased from 90.742° to 0° over 10 seconds, a decrease of 9.07° / s. By comparing the dynamic contact angle changes and spreading trends of the four wetting agents on the pine wood surface, it can be concluded that the diffusion and wetting properties of silicone wetting agents are better than those of common hydrocarbon wetting agents, and the wetting properties are ranked from strong to weak as follows: 5211>8008>SDBS>APG-0810.

[0037] (3) Spreading coefficient analysis Based on the surface tension and contact angle data measured in this paper at 0 seconds, the spreading coefficients of the four wetting agents on the wood surface were analyzed, as shown in Table 2. The larger the spreading coefficient, the better the wettability of the solution. When S ≥ 0, it indicates that the solution can spontaneously spread and wet; otherwise, it indicates that the solution cannot spontaneously spread and wet. The spreading coefficient is calculated as follows: (1.1) in: S is the spreading coefficient (mN / m); is the surface tension of the surfactant solution (mN / m); is the contact angle value (°).

[0038] Table 2 Static contact angles of four wetting agents at different concentrations (°)

[0039] Depend on Figure 8It can be seen that the spreading coefficients of the four wetting agents are all less than 0, indicating that the four wetting agent solutions cannot spread spontaneously on the wood surface. When the concentration of 5211 reaches 0.01%, the spreading coefficient of the pine wood diameter / tangential section is the largest, Smax=-0.04; when the concentration of 5211 reaches 0.5%, the spreading coefficient of the pine wood cross section is the largest, Smax=-0.09. The maximum spreading coefficient of SDBS is -7.12, and the maximum spreading coefficient of APG is -6.99. Overall, 5211 and 8008 are easier to spread on the pine wood surface; the solution concentrations required for SDBS and APG to obtain the maximum spreading coefficient are greater than those of 5211 and 8008. Figure 8 It can also be seen that the maximum spreading coefficient of 5211 is -0.04, which is the largest among the four wetting agents, which is consistent with the contact angle measurement data.

[0040] (4) Penetration performance test The examples in this application studied and evaluated the speed at which liquids penetrated the surface fuel layer. Forest vegetation environments are complex, and the pore size of the fuel layer is not uniform. After screening and drying pine sawdust powder in the laboratory, 1g samples of the sawdust powder were placed in test tubes and pressed to the same volume for later use. A 3ml room-temperature aqueous solution of the wetting agent to be tested was measured and dripped into the test tube. Under the influence of gravity and the pore structure, the solution penetrated the sample, and the change in liquid column height was observed (excluding foam height). The time it took for different wetting agent solutions to fully penetrate the sawdust sample from 0% to 100% was recorded. Three repeated sets were repeated and the average value was taken.

[0041] Penetration performance test analysis: The ignition point of a forest fire is not only on the surface of the ground or trees. The smoldering fire caused by the burning of the underground peat layer or the flames inside the high-density vegetation are more difficult to extinguish. They are usually covered with layers of obstacles and are more dangerous. Only fire extinguishing agents with penetrating properties can exert better fire extinguishing efficiency. The penetrating performance of the wetting agent can determine whether it can quickly penetrate the fuel layer to reach the deep of the fire source. Figure 9 (a)-(d) show the time it takes for four wetting agents to penetrate a wood chip layer at different mass fractions. The shorter the time it takes for a wetting agent solution to penetrate a wood chip layer of the same density, the stronger the wetting agent's penetration performance. As the wetting agent mass fraction increases, the time it takes for the same volume of wetting agent solution to penetrate from 0-100% gradually decreases, and the penetration rate increases. The penetration rate from 75%-100% penetration is significantly slower than the 0-25% penetration rate. This is because increasing the wetting agent mass fraction results in a more compact arrangement of surfactants in the aqueous solution. Through hydrogen bonding and van der Waals forces, the surfactants bind to the hydrophobic groups on the wood surface, altering the solid-liquid interface of the wood structure. Hydrophobic wood is more susceptible to water adsorption. Furthermore, as the liquid gradually penetrates the wood chips, the influence of gravity on the liquid column gradually weakens, slowing the penetration rate in the latter half of the penetration process.

[0042] According to Figure 9 the data, at a low concentration of 0.05%, for the four wetting agents, it took 687 s for 100% SDBS to fully penetrate, 729 s for APG to fully penetrate, 413 s for the silicone wetting agent 5211 to fully penetrate, and 452 s for 8008 to fully penetrate; at a high concentration of 0.5%, the time taken for full penetration was: 5211 < 8008 < SDBS < APG. The data shows that at the same mass fraction, the silicone wetting agent has a faster penetration rate, indicating that the silicone wetting agent has a stronger hydrophilic modification effect on the surface of the wooden structure, which is related to the unique molecular structure of the silicone surfactant. Compared with the anionic surfactant SDBS and the non-ionic surfactant APG, the single molecular chain of the silicone surfactant is longer. The longer hydrophilic polyether chain contains a large number of oxygen-containing functional groups, resulting in a stronger hydrogen bond effect and easily forming a dense water molecule adsorption layer; the methyl group on the hydrophobic group Si-C bond has a larger coverage area than that of hydrocarbon surfactants, generating a strong adhesion force with the hydrophobic group on the wood molecule, promoting the interaction between water and wood. The above results show that the penetration characteristics of the wetting agent are affected by the chemical structure of the wetting agent, the concentration of the wetting agent, and the chemical properties of the wood. At the same mass fraction, the penetration performance of the silicone wetting agent is better than that of hydrocarbon wetting agents, which can effectively improve the fire extinguishing efficiency of the fire extinguishing agent.

[0043] In the embodiments of this application, the effects of different types of wetting agents on enhancing the wetting performance and penetration performance of water on wood were explored, and based on the experimental test results, a new type of silicone wetting agent 5211 with more excellent diffusion and penetration capabilities was determined, and the suitable addition concentration range was determined as the key component to improve the fire extinguishing efficiency of the hydrogel fire extinguishing agent.

[0044] The main conclusions of Example 1 are as follows: (1) The surface tensions of the four wetting agent solutions were analyzed. The results show that as the concentration increases, the decrease in the surface tension of the silicone wetting agent is greater than that of the hydrocarbon wetting agent; the CMC of 5211 and 8008 is 0.01 wt%, and γCMC can be as low as 19.7 and 19.8 mN / m respectively, while the CMC of SDBS and APG is 0.6 wt% and 0.5 wt%, and γCMC reaches 27.6 and 26.8 mN / m. The critical micelle concentration CMC of the silicone wetting agent is much smaller than that of the hydrocarbon wetting agent, and γCMC of the silicone wetting agent is also lower than that of the hydrocarbon wetting agent. After comparison, it was initially obtained that the wetting performance of the silicone wetting agents 5211 and 8008 is better than that of the hydrocarbon wetting agents SDBS and APG.

[0045] (2) The spreading trends and contact angle changes of four wetting agent solutions were investigated. The results showed that the contact angles of the wetting agents with the same concentration on the cross-section of pine wood were greater than those on the radial / tangential section, and it was more difficult for the solution to completely spread on the cross-section within the same time; on the radial / tangential section of pine wood, 0.2% SDBS and 0.2% APG could completely spread within 15 s, while the silicone wetting agents 5211 and 8008 could completely spread within 15 s at a concentration of 0.01%; on the cross-section of pine wood, at the same mass fraction of 0.5%, the complete spreading time of SDBS exceeded 20 s, that of APG was 10 s, while the complete spreading times of 5211 and 8008 were both within 5 s; by comparing the dynamic contact angle change ranges of the four wetting agents and their spreading trends on the pine wood surface, it can be concluded that the diffusion and wetting properties of the silicone wetting agents are stronger than those of common hydrocarbon wetting agents, and the wetting properties are ranked from strong to weak as 5211 > 8008 > SDBS > APG-0810.

[0046] (3) The spreading coefficients of the wetting agents were calculated based on the surface tension and contact angle measurement results, and the influence of the wetting agent concentration on the solution spreading coefficient was analyzed. The results showed that the solution concentrations required for SDBS and APG to obtain the maximum spreading coefficient were both greater than those of 5211 and 8008; the maximum spreading coefficient of 5211 was -0.04, close to spontaneous spreading, and it had the largest spreading coefficient among the four wetting agents.

[0047] (4) The penetration times of the four wetting agent solutions through the sawdust layer with the same density were analyzed, and the influencing factors of the penetrated wood structure were explored. The results showed that: at a low concentration of 0.05%, the complete penetration time of SDBS was 687 s, that of APG was 729 s, while the complete penetration time of the silicone wetting agent 5211 was 413 s, and that of 8008 was 452 s; at a high concentration of 0.5%, the complete penetration times from small to large were: 5211 < 8008 < SDBS < APG. The penetration characteristics of the wetting agent are affected by the chemical structure of the wetting agent, the concentration of the wetting agent, and the chemical properties of the wood. The penetration performance of the silicone wetting agent is better than that of the ordinary hydrocarbon wetting agent under the same mass fraction.

[0048] Example 2: Preparation of the composite hydrogel material: It includes the following steps: Take appropriate amounts of dried methylcellulose (MC), dimethyl methylphosphonate (DMMP), trisiloxane wetting agent (5211), and sodium chloride (NaCl) according to the mass fraction ratio, and mix them with deionized water at 70 °C using the one-pot method, stir evenly to ensure that the polymer is completely hydrated, and stand still at room temperature for 6 h to fully swell and crosslink. Use a high-speed disperser to disperse the swollen hydrogel into a uniform sol state at 5000 r / min, and stand still at room temperature for 24 h to defoam and then reserve. Table 3 shows the mass compositions of MC, DMMP, 5211, and NaCl in each system of the composite hydrogel.

[0049] Table 3 Mass composition of each system of composite hydrogel

[0050] The prepared composite hydrogel material was subjected to the following performance tests: (1) Rheological test All rheological tests were performed using a Discovery HR-2 hybrid rheometer (TA Instruments, USA). For testing the hydrogel samples, stainless steel parallel plates with a diameter of 25 mm and a gap of 1 mm were used. Prior to testing, the samples were thoroughly stirred to ensure complete dispersion of the gel. Dynamic viscosity measurements were performed in rotational mode with the temperature controlled at 25°C and a shear rate range of 0.1–100 s⁻¹. An oscillatory frequency sweep was applied with an angular frequency of 0.1–100 rad·s⁻¹ at a constant strain of 2% to determine the storage modulus (G') and loss modulus (G'') of the gel. For the temperature sweep portion of the experiment, the heating step was performed from 5°C to 85°C at a constant rate of 5°C / min and a fixed frequency of 1 Hz.

[0051] Analysis of the effect of each component on the viscosity of the hydrogel: In the composite hydrogel system, methylcellulose (MC) is a key factor affecting viscosity, which is directly related to the fire extinguishing effect. Therefore, we have conducted an in-depth study on the relationship between methylcellulose content and composite hydrogel viscosity to determine the optimal methylcellulose concentration. Figure 10 As shown, the viscosity of the neat hydrogel increases exponentially with increasing methylcellulose content. Methylcellulose hydrogels are formed through non-covalent crosslinking, and the increase in viscosity is primarily due to chain entanglement within their microstructure. Higher methylcellulose content leads to greater chain entanglement, resulting in a significant increase in viscosity. This viscosity allows the gel to adhere firmly to burning surfaces during firefighting, rather than rapidly dissipating like water, significantly improving firefighting efficiency. However, excessively high viscosity can also pose problems, such as difficulty in spraying and even possible clogging of delivery pipes. Therefore, selecting the appropriate viscosity is crucial for practical applications. At a specific methylcellulose content, the hydrogel exhibits pronounced shear-thinning behavior with increasing shear rate. As shear increases, the degree of entanglement of the polymer chains decreases, leading to a more oriented alignment, resulting in a rapid decrease in viscosity. This property allows the gel to pass easily under intense shear forces, such as when flowing through a pipe.

[0052] from Figure 11In the rheological test results, we can see that DMMP slightly increases the viscosity of the hydrogel. However, DMMP does not affect the rheological properties of the gel. This phenomenon may be attributed to the weak interaction between DMMP molecules and the hydrogel network structure, which is not enough to significantly change the rheological behavior of the gel. Figure 12 As shown in the figure, the concentration of the wetting agent 5211 has a significant effect on the viscosity of the hydrogel system. As the 5211 content increases, the viscosity of the hydrogel first increases, with the C1 and C2 hydrogels showing higher viscosities than the A2 hydrogel with the same MC content. As the 5211 content continues to increase, the viscosity of the C3 and C4 hydrogels begins to decrease significantly. Considering that 5211 is also a high-molecular-weight chain polymer, this anomalous phenomenon may be related to the following factors: At low concentrations, 5211 can form a physical entanglement network with the MC matrix polymer. Hydrogen bonding between MC and 5111, as well as the hydrophobic interaction of siloxane, promotes hydrogel formation. 5211 joins the cross-linked network through hydrogen bonding and molecular interactions. This physical entanglement restricts the movement of polymer chains within the hydrogel, leading to an increase in the viscosity of the system. At high concentrations, the interactions between the hydrophilic (ethylene oxide) and hydrophobic (siloxane) groups of 5211 molecules are enhanced, leading to a tendency for 5211 molecules to form self-assembled structures. These structures competitively adsorb water molecules, thus affecting the integrity of the hydrogel network. Secondly, excessive 5211 may disrupt the existing polymer chain entanglement, leading to a loosening of the network structure. Finally, under shear, the addition of 5211 increases the spacing between polymer chains, further weakening intermolecular interactions and ultimately reducing the viscosity of the system.

[0053] Therefore, we believe that the concentrations of methylcellulose MC and 5211 have a greater impact on the rheological behavior of the composite hydrogel system, while the effect of DMMP content is almost negligible.

[0054] The shear thinning behavior of the composite hydrogels at different concentrations was evaluated based on the power law fitting of viscosity and shear rate. Figure 13 The relationship between the shear stress and shear rate of the A2 and C3 composite hydrogels at room temperature is reflected. The viscosity of the A2 and C3 hydrogels decreases with increasing shear rate. The A2 and C3 hydrogels are fitted according to the power law model equation. The power law model is described as follows: τ = Kγ ^n (2.1) Where: τ is the shear stress (Pa); K is the consistency index (Pa.s n ); γ is the shear rate (1 / s); n is the rheological index of the fluid (dimensionless), 0 <n<1。

[0055] The lower the n, the more obvious the non-Newtonian rheological behavior of the hydrogel. Data fitting proves that the composite hydrogel is a power-law fluid with a high correlation coefficient (C3 hydrogel R 2 >0.98, A2 hydrogel R 2 >0.99), indicating a strong relationship, indicating that the hydrogel behaves as a pseudoplastic fluid (n < 1). This fluid behavior is significant because it means that the hydrogel will not flow until a critical stress (yield stress) is exceeded, at which point the hydrogel begins to flow and diffuse, highlighting its potential for effective deployment in firefighting scenarios where rapid activation is essential. Compared to hydrogel A2, a 0.3% concentration of 5211 in hydrogel C3 increases the spacing of the MC cross-linked network and reduces the viscosity of the composite hydrogel without changing its rheological properties, effectively enhancing the fluidity and diffusivity of the composite hydrogel.

[0056] Temperature dependence analysis: Because MC hydrogel is a temperature-responsive material, temperature has a great influence on the hydrogel. Figure 14 Temperature sweeps for gels A2 and C3 are shown. Interestingly, the addition of 5211 significantly alters the thermorheological behavior of the composite hydrogels. Below 55°C, the modulus and viscosity of the neat gels show little change with increasing temperature. Starting at 55°C, both the modulus and viscosity increase dramatically, indicating a transition from sol to gel. As the temperature continues to rise, the modulus and viscosity of both composite hydrogels increase dramatically. Unlike the neat MC gel, the silicone-MC composite hydrogel exhibits some differences in the temperature sweep. Initially, the modulus and viscosity of the composite hydrogels are similar to those of the neat gel. While the MC hydrogels complete the sol-gel transition in the 40°C-55°C temperature range, the silicone-MC composite hydrogels extend this transition temperature range to 40°C-60°C. After 60°C, both the modulus and viscosity undergo a similar sol-gel transition, resulting in increases in both modulus and viscosity. The flow tests above demonstrate that 5211 exhibits a degree of thermal stability, delaying the sol-gel transition of the MC hydrogel. This, to a certain extent, allows the hydrogel to flow and diffuse under high-temperature fire conditions, suggesting that the silicone-based MC hydrogel can cover a wider range. The increase in modulus and viscosity is due to increased chain entanglement. As the temperature rises, the increased heat absorption disrupts hydrogen bonds, leading to entanglement between the MC and siloxane chains. Subsequently, the hydrophobic methoxylated groups on the MC are gradually exposed, and hydrophobic association predominates, leading to gel formation. This suggests that the addition of 5211 enhances the flowability of the composite hydrogel on combustible materials and, through temperature-dependent adhesion, allows it to firmly adhere to the surface of the burning material.

[0057] (2) Dynamic contact angle test of gel water separation 100ml of the composite hydrogel was placed in a beaker and continuously heated using an alcohol burner. Heat was transferred to the hydrogel via an asbestos mesh. A thermocouple was inserted into the center of the hydrogel, providing continuous temperature feedback via a temperature recorder. When the center temperature of the composite hydrogel in the beaker reached 90°C, the hydrogel gelled and aggregated, and some liquid precipitated out of the hydrogel. This liquid was then aspirated and loaded into a contact angle meter to measure the dynamic contact angle over 50 seconds.

[0058] Figure 15 The dynamic contact angle trends of water released from each hydrogel system upon heating on the pine wood surface from 0 to 50 seconds are shown. Under uniform heating conditions at 90°C, each hydrogel system has already transformed into a gel, the three-dimensional cross-linked structure of the gel further shrinks, and some of the water stored in the gel is discharged. Taking the dynamic contact angle of pure water as a reference, the pure water contact angle on the pine wood cross section decreased from 133.839° to 123.836° within 50 seconds. As the methylcellulose concentration increases, the contact angle of the released water begins to increase. The contact angle of the pine wood cross section released by the A4 hydrogel drops from 136.958° to 126.4°, while the spreading properties of the released water from the A1 hydrogel are similar to those of pure water. This indicates that as the MC concentration increases, the presence of MC with hydrophobic methyl groups in the released liquid slightly increases the contact angle of the liquid on the wood surface. According to the changes in the dynamic contact angles of hydrogels C1-C4, it can be seen that the addition of 5211 significantly enhances the wetting properties of water, and as the amount of addition increases, the contact angle of the water precipitated from the gel becomes smaller. The contact angle of the pine wood cross-section where the water precipitated from the C4 hydrogel decreased from 106.979° to 0° within 40s.

[0059] (3) Thermal stability test A thermogravimetric analyzer was used in an air atmosphere with a protective gas flow rate of 50 mL / min and a reaction gas flow rate of 50 mL / min. The temperature was increased from room temperature (25°C) to 800°C at a rate of 10 K / min. The composite hydrogel sample mass was 5-10 mg.

[0060] Thermal stability analysis of composite hydrogel: The thermal stability of the prepared composite hydrogel was studied using TGA thermogravimetric analysis. Figure 16The TG and DTG curves of the A2 and C3 hydrogels are shown. The initial degradation temperature (T-5%) and the maximum degradation temperature (Tmax) are primarily used to assess the thermal stability of hydrogels. Thermal stability is defined by the temperature at which the mass loss reaches 5 wt% and the temperature at which the mass loss rate reaches its maximum. These temperatures mark the onset of significant mass loss and the critical point of most drastic mass loss, respectively, as shown in Table 4.4. As can be seen, the two hydrogels exhibit similar weight loss phases. The A2 hydrogel exhibits a weight loss phase from room temperature to 141°C, while the C3 hydrogel exhibits a weight loss phase from room temperature to 116°C. During this phase, the continuous evaporation of free water in the hydrogel and the destruction of bound water in the solute are the primary factors. The A2 hydrogel loses 92.7% of its weight, while the C3 hydrogel loses 86.3% of its weight. This helps lower the temperature and dilutes oxygen, thereby reducing combustion. From 150°C to 350°C, the volatilization and degradation of some polymers and salts are predominant. The thermal degradation of methylcellulose usually occurs between 200°C and 410°C. At around 300°C, methylcellulose will experience significant weight loss. This is because the ether bonds and methoxy groups in its molecular structure break and decompose at high temperatures, resulting in mass loss. DMMP has good thermal stability. The thermal decomposition rate of hydrogen bonds within the DMMP molecule is slow between 200 and 300°C. At 300°C, the thermal decomposition of DMMP is significantly accompanied by the formation of volatile products. The flame temperature of wood burning can be higher than 900°C, so the DMMP dissolved in the gel can take effect immediately when it comes into contact with the flame, forming a structurally stable carbonized layer. The carbonized layer acts as a physical barrier to prevent further thermal decomposition of the polymer and the release of thermal decomposition products into the gas phase, thereby inhibiting combustion and smoke emissions. This explains Figure 16 The A2 and C3 hydrogels lost about 0.5% of their weight at 300℃.

[0061] The C3 hydrogel exhibited fluctuating DTG mass loss rates during the initial weightlessness period (25–48°C). This is due to the excellent thermal stability of the organosilicon wetting agent 5211. As heat transfer from the hydrogel surface to the interior occurs, the strong Si-O bonds of the 5211 at the gel interface act as a thermal barrier. The sodium chloride (NaCl) in the hydrogel exhibited excellent thermal stability below 800°C, resulting in minimal mass loss throughout the weightlessness period. The weights of both hydrogels remained nearly constant after reaching 400°C. The addition of 5211 and DMMP increased the residual product from 6.51% in A2 to 13.91% in C3 (Table 4). Considering that C3 contained 0.3% 5211 wetting agent and 2% DMMP, the C3 hydrogel still achieved an increase in the residual yield from 6.51% to 13.91%. The catalytic carbonization ability of DMMP and the high heat resistance of the organosilicon wetting agent 5211 contribute to the increased residual yield, facilitating the formation of a thermal barrier on the combustible surface.

[0062] Table 4. TGA data of A2 and C3 under air atmosphere

[0063] Performance Test Summary This application systematically studies the effects of methylcellulose (MC), silicone wetting agent 5211, and flame retardant DMMP on the rheological behavior, temperature response, interfacial wetting, and thermal stability of a composite hydrogel system. The results reveal the synergistic mechanisms of the components and the performance regulation mechanisms of the composite hydrogel. Based on various experimental analyses, a hydrogel composition with a mass ratio of C3 was selected. The main research conclusions are summarized as follows: (1) Rheological behavior and viscosity control mechanism MC concentration dominates viscosity evolution: The viscosity of the hydrogel increases exponentially with MC content, attributed to the non-covalent cross-linked network formed by molecular chain entanglement. However, extremely high viscosity (>1.6wt%) can lead to spray blockage, necessitating a balance between adhesion and flow properties. The system exhibits pseudoplastic fluid behavior (power-law model fit R² >0.98) with a significant shear-thinning effect (n <1). This reduces viscosity during pipeline transport (shear rates >100s⁻¹) and restores high viscosity upon reaching the target, meeting the flow-adhesion synergy required in firefighting scenarios. The wetting agent 5211 exhibits a threshold concentration effect: Low concentrations of 5211 (<0.05%) enhance the network structure through physical entanglement, increasing viscosity. High concentrations (>0.3%) induce self-assembly, competitively adsorbing water molecules, weakening the network integrity and leading to a sharp drop in viscosity. 5211 also exhibits wetting properties, reducing shear resistance by increasing interchain distance, thereby optimizing spray performance.

[0064] (2) Surface wettability and thermal stability Synergistically Enhanced Wettability: 5211 significantly improves the wettability of precipitated water (the contact angle of the C4 system drops to 0° within 40 seconds), overcoming the hydrophobic limitations of pure MC systems (contact angle >120°), enabling rapid penetration into combustible materials at high temperatures. Thermal Degradation and Flame Retardant Enhancement: The composite hydrogel thermally degrades in three stages: water evaporation (25-150°C), polymer decomposition (150-350°C), and char layer stabilization (>350°C). 5211 delays heat transfer, while DMMP catalyzes carbonization, synergistically increasing the residual yield to 13.91% (A2: 6.51%), forming a thermal and oxygen-barrier layer.

[0065] (3) Comprehensive performance and fire extinguishing application potential Rheological-Thermal Response Co-Design: Achieve a balance of shear-thinning fluidity, high-temperature adhesion, and rapid phase change response through gradient control of MC and 5211 concentrations. Multifunctional Integration: DMMP flame retardancy and 5211 wettability modification synergistically enhance firefighting efficiency. Combined with thermal stability and char formation, the spray is suitable for complex fire environments. The optimal formulation range is 1.2-1.6wt% MC and 0.05-0.3wt% 5211, balancing spray efficiency and firefighting performance.

[0066] The prepared composite hydrogel material was subjected to the following fire extinguishing test: Combustion system: A woodpile combustion test platform was constructed according to GB13875-2008 standard. Its specification is a Class 1A experimental reference model. The combustion material is pine wood strips with a size of 4cm×4cm×50cm. The pine wood has been dried to keep the moisture content at 10%~14% and the density at 0.45g / cm 3 ~0.55g / cm 3 72 wood strips were stacked in 12 layers, 6 strips per layer, evenly spaced, to form a standard 1A woodpile measuring 50cm x 50cm x 48cm. To prevent the woodpile from collapsing due to excessive pressure from the blast gun, the edges of the wood strips were secured with nails. A 40cm by 10cm high oil pan filled with 1.1L of kerosene (calorific value 45MJ / kg, similar to gasoline's 44.2MJ / kg) was used to ignite the woodpile. A 40cm high metal support frame was used for the combustion rack.

[0067] Fire extinguishing system: The fire extinguishing system consists of a high-pressure spray gun, a high-pressure hose, a high-pressure plunger pump, a water tank and related equipment. The volume of the water tank only needs to meet the demand for fire extinguishing agent. A plunger-type high-pressure pump is used to provide pressure. The flow rate of the high-pressure pump is 6~9L / min. A high-pressure hose is used to connect the water gun to extinguish the woodpile fire.

[0068] This section mainly conducts 1A-level woodpile fire extinguishing experimental verification research on the homemade organosilicon MC composite hydrogel, water and foam fire extinguishing agent. The test site is selected in a semi-enclosed space with a certain net height. Organosilicon MC composite hydrogel with a mass ratio of C3, water and high-expansion Class A foam fire extinguishing agent (main components: foaming agent, flame retardant, stabilizer, anti-burning agent and other substances) are selected to carry out a group of 1A woodpile fire extinguishing experiments. The amount of water used for fire extinguishing is 6L, and the preparation amount of organosilicon MC composite hydrogel and high-expansion Class A foam fire extinguishing agent is also 6L. The experimental working conditions are shown in Table 5.

[0069] The experimental steps are as follows: The experimental system was constructed based on the experimental model, determining the placement of the woodpile, the height of the thermocouples, and the location of the camera equipment. After assembly of all systems, the system was checked for proper operation, including the temperature feedback from the thermocouples and the experimental pressure and flow rate of the spray system. Before the fire extinguishing test began, water and kerosene were poured into the oil pan as fuel. A pre-burn period of approximately 200 seconds was allowed. When the woodpile reached a stable combustion state (i.e., the thermocouple temperature reached its maximum and remained stable), the fire was extinguished. After the pre-burn period, the high-pressure plunger pump was activated, releasing water, silicone MC composite hydrogel, and Class A foam fire extinguishing agents at the same rate, starting from the front of the woodpile and then spraying towards the top, bottom, and sides. Extinguishing was completed when a fixed volume of 6L of all three fire extinguishing agents was dispensed. Temperature data and information such as the flame morphology recorded by the camera were processed and analyzed to compile and extract relevant data related to extinguishing time and flame morphology during the fire extinguishing experiment. A comparative analysis of the three fire extinguishing agents examined multiple performance factors, including extinguishing time, average cooling rate, and re-ignition resistance. The authors also explored their impact on flame morphology and temperature changes during the extinguishing process. A successful extinguishing test was considered successful if no open flames reappeared within 10 minutes of extinguishing the flames; otherwise, it was considered a failure. If the woodpile collapsed during the fire extinguishing test, the experiment was deemed invalid and repeated.

[0070] Table 5. Experimental conditions settings

[0071] The flame shape changes during pure water fire extinguishing process Figure 17 As shown in Condition 1, water exhibits low viscosity during fire extinguishing. Under the same pressure, the water jet from the nozzle exerts a greater impact force, quickly impacting and suppressing the flames. Simultaneously, the water rapidly accumulates at the bottom of the woodpile, fragmenting the flames into irregular shapes. With the continued spraying of pure water, the flames gradually shrink in area and begin to move irregularly toward the sides of the woodpile. Due to the weak adhesion of pure water to the woodpile surface, the fire extinguishing process is slow and time-consuming. The experiment observed that flames were still burning within the woodpile 40 seconds after extinguishing the fire, indicating that the fire extinguishing had failed and the interior of the woodpile was still smoldering. 150 seconds after the start of extinguishing, the woodpile began to reignite, and the flames expanded, accompanied by a corresponding increase in smoke generation.

[0072] The flame morphology changes during the fire extinguishing process of Class A foam fire extinguishing agent are as follows Figure 17As shown in Working Condition 2, when it is sprayed onto the woodpile fire as an extinguishing agent, the flame is quickly suppressed. During this process, with the continuous spraying of the extinguishing agent, the adhesion performance of the foam fire extinguishing agent on the surface of the woodpile is improved. The gas-liquid mixed foam layer formed can not only cool the fire source, but also effectively isolate the oxygen supply, thereby achieving a higher fire extinguishing rate. 40 seconds after the start of the fire extinguishing, the fire was basically under control, and only a small amount of smoldering remained inside the woodpile. The fire extinguishing agent was continuously sprayed, and the flames were quickly suppressed wherever the foam fire extinguishing agent reached, indicating that it has good fluidity and wrapping effect. Finally, at the 147th second of the fire extinguishing, the flames on the woodpile were completely extinguished, and there was no re-ignition.

[0073] The flame morphology changes during the fire extinguishing process of silicone MC composite hydrogel are as follows: Figure 17 As shown in working condition 3. The viscosity of the composite hydrogel is relatively higher among the three fire extinguishing agents, resulting in a lower injection rate at the same pressure and a weaker initial impact on the woodpile fire. Due to its high viscosity, after being sprayed onto the surface of the wood, the speed at which it flows into the fire point inside the wood is relatively slow. However, the composite hydrogel has a strong adhesion ability, and the gel strength is significantly improved after the phase change, and the cooling and oxygen-isolating sealing effects are more significant. After 20 seconds of fire extinguishing, the fire was significantly suppressed, the surface flames were completely extinguished, and only fire points remained inside the woodpile. After the fire extinguishing agent was continuously sprayed, the hydrogel absorbed heat and released liquid, carrying highly osmotic water and DMMP, which further suppressed the flames inside the woodpile and successfully extinguished the fire at the 126th second of fire extinguishing.

[0074] Table 6 Changes in flame area under different fire extinguishing conditions

[0075] The data in Table 7 compares the temperature curves of the three extinguishing agents during the extinguishing process, revealing the fire extinguishing effectiveness of different extinguishing agents, including extinguishing time, stable combustion temperature, and average cooling rate. Under the same extinguishing agent dosage and experimental conditions, water extinguishing agent, due to its high fluidity, is unable to remain on the woodpile surface to absorb heat, resulting in a longer extinguishing time. This results in an average cooling rate of only 3.74°C / s, indicating relatively low extinguishing efficiency. Class A foam extinguishing agent, composed of a foaming agent, flame retardant, stabilizer, and anti-burn agent, has excellent foam properties and can also form a foam insulation layer on the wood surface. Under the same experimental conditions, it has a faster extinguishing rate, but its foam cannot maintain stability and easily defoams under the high temperature conditions inside the woodpile. Its extinguishing time is 147 seconds, but its average cooling rate is superior to that of water extinguishing agent, at 5.12°C / s. The silicone MC composite hydrogel exhibits unique advantages. When sprayed onto the woodpile, it adheres tightly to the surface, achieving effective cooling. Moreover, when exposed to a high-temperature fire source, the strength of the hydrogel will be further enhanced, thereby exerting the effect of oxygen isolation and suffocation. The high wetting water and flame retardant encapsulated inside the hydrogel will also play a role in chemical inhibition. The silicone MC composite hydrogel has a high fire extinguishing efficiency, with an extinguishing time of 126 seconds and an average cooling rate of 6.13°C / s, which is better than other fire extinguishing agents. The fire extinguishing efficiency is significantly improved under the same experimental conditions.

[0076] Table 7 Fire extinguishing efficiency of different fire extinguishing agents

[0077] Fire extinguishing test summary This application investigates the fire-extinguishing effectiveness of a C3 composite hydrogel (MC:5211:DMMP:NaCl:water = 1.2:0.3:2.0:2.0:94.5) with excellent rheological properties and thermal stability through a 1A woodpile fire test. Fire-extinguishing experiments using water and a Class A foam fire extinguishing agent under the same conditions were also conducted for comparative verification. Fire-extinguishing experiments under three different conditions, utilizing flame and temperature data, revealed the synergistic mechanism of the composite hydrogel components and the dynamic fire-extinguishing control mechanism. Based on the experimental analysis of the fire-extinguishing effectiveness of the three fire extinguishing agents, the main research conclusions are summarized as follows: (1) Woodpile combustion is a typical decomposition and combustion process. The results of three sets of working condition experiments show that when the woodpile is in a burning state, the temperature inside it is often the highest. Even if the open flame on the surface is extinguished, the internal temperature remains high, and smoldering occurs. As the water gradually evaporates and the heat continues to accumulate, the woodpile has the possibility of re-ignition.

[0078] (2) When pure water is used to extinguish a fire, the flame is quickly suppressed and accumulates under the woodpile. Due to the weak adhesion of water on the surface of the woodpile, the rate of extinguishing the open flame is slow. The woodpile has not yet cooled down and begins to reignite 150 seconds after the fire is extinguished. When a Class A foam fire extinguishing agent is used to extinguish a fire, the flame is quickly suppressed. The foam fire extinguishing agent exhibits wetting ability on the surface of the woodpile. The gas-liquid mixed foam covering layer formed by it can effectively play a cooling role and isolate oxygen, thereby achieving the purpose of suppressing the fire. The fire extinguishing rate is high, and the woodpile is extinguished in 147 seconds. The silicone MC composite hydrogel has the highest viscosity among the three, and the injection rate is smaller under the same pressure. The composite hydrogel has strong adhesion, and the gel strength is greater after phase change. The cooling and oxygen-isolating sealing effects are significant. The woodpile fire extinguishing time is 126 seconds, which is the fastest among the three fire extinguishing agents.

[0079] (3) In the initial stage of fire extinguishing, the temperatures of the 4#~7# thermocouples located far from the center of the woodpile showed a rapid decline, while the temperatures of the 2# and 3# thermocouples in the center of the woodpile remained stable. The temperature of the 1# thermocouple steadily decreased after the fuel in the oil pan burned out. The water fire extinguishing agent has high fluidity and cannot effectively stay on the surface of the woodpile to absorb heat. The average cooling rate is low, at 3.74°C / s, and eventually re-ignition occurs. Class A foam fire extinguishing agent is composed of multiple substances. It has excellent foam performance and a fast fire extinguishing rate, but the foam is easy to defoam at high temperatures. The average cooling rate is 5.12°C / s, which is better than water fire extinguishing agent. When the silicone MC composite hydrogel is sprayed onto the woodpile, it has strong adhesion, cools the surface, isolates oxygen and suffocates, and the high wettability water and flame retardant inside play a chemical inhibitory role. It has high fire extinguishing efficiency and the best average cooling rate, at 6.13°C / s.

[0080] Experimental results demonstrate that the silicone MC composite hydrogel fire extinguishing agent developed in this application has high fire extinguishing efficiency and anti-reignition performance. Its average cooling rate and fire extinguishing time are superior to those of water and Class A foam fire extinguishing agents. These experimental results demonstrate that the silicone MC composite hydrogel fire extinguishing agent is a highly effective fire extinguishing agent with broad application prospects.

[0081] The above descriptions are provided in conjunction with specific content to provide one or more embodiments, and the specific implementation of the present invention is not limited to these descriptions. Any similarity or similarity with the methods, structures, etc. of the present invention, or any technical deduction or substitution based on the concept of the present invention, shall be considered within the scope of protection of the present invention.

Claims

1. A forest fire prevention material based on organosilicon MC composite hydrogel, characterized by: The invention comprises the following raw materials in parts by weight: 0.05-0.3 wt% of an organosilicon wetting agent, 1.2-1.6 wt% of methyl cellulose, 1.8-2.5 wt% of a flame retardant, 1.8-2.3 wt% of an ion crosslinking agent, and the balance of water.

2. The forest fire prevention material based on organosilicon MC composite hydrogel according to claim 1, characterized in that: The organosilicon wetting agent is a trisiloxane wetting agent or a polyether-modified polysiloxane wetting agent.

3. The forest fire prevention material based on organosilicon MC composite hydrogel according to claim 2, characterized in that: The trisiloxane wetting agent model is 5211.

4. The forest fire prevention material based on organosilicon MC composite hydrogel according to claim 3, characterized in that: The critical micelle concentration CMC of 5211 is 0.01wt%, and the critical surface tension γCMC is 19.7mN / m.

5. The forest fire prevention material based on organosilicon MC composite hydrogel according to claim 1, characterized in that: Methylcellulose is a cellulose derivative.

6. The forest fire prevention material based on organosilicon MC composite hydrogel according to claim 1, characterized in that: The flame retardant is dimethyl methylphosphonate.

7. The forest fire prevention material based on organosilicon MC composite hydrogel according to claim 1, characterized in that: The ionic crosslinking agent is sodium chloride.

8. The method for preparing a forest fire prevention material based on organosilicon MC composite hydrogel according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Take methyl cellulose, flame retardant, silicone wetting agent and ion crosslinking agent according to the mass fraction ratio; S2. Mix the above materials with deionized water using a one-pot method, stir evenly until hydrated, and let stand at room temperature to allow them to fully swell and cross-link; S3. The swollen hydrogel is dispersed by high-speed stirring until it becomes a uniform sol state, and then allowed to stand at room temperature to defoam.

9. The method for preparing a forest fire prevention material based on organosilicon MC composite hydrogel according to claim 8, characterized in that: In step S2, the deionized water is at 68-75° C. during mixing, and the swelling and cross-linking standing time is 5-8 hours.

10. The method for preparing a forest fire prevention material based on organosilicon MC composite hydrogel according to claim 8, characterized in that: In step S3, a high-speed disperser is used for high-speed stirring at 4800-5500 r / min, and the defoaming standing time is 20-30 hours.

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