A forest fire prevention material based on silicone MC composite hydrogel and a preparation method thereof

Abstract

The application provides a forest fire prevention material based on a silicone MC composite hydrogel and a preparation method thereof, and comprises the following raw materials in parts by weight: 0.05-0.3wt% of a silicone wetting agent, 1.2-1.6wt% of methyl cellulose, 1.8-2.5wt% of a flame retardant, 1.8-2.3wt% of an ionic crosslinking agent, and the balance of water, and the MC is used as the basic skeleton of the composite hydrogel, the silicone wetting agent 5211 is used as a dynamic wetting regulation unit, and DMMP is used as a high-efficiency chemical flame retardation core. The composite hydrogel system has the shear thinning (0<n<1) property, the viscosity is reduced during pipeline transportation, the flow-adhesion requirement of the fire extinguishing scene is met, the temperature response property is provided, the balance of the shear thinning flowability, the high-temperature adhesion and the rapid phase change response is realized through the concentration gradient regulation of the methyl cellulose and the silicone wetting agent, the thermal stability is provided, the DMMP chemical flame retardation is self-assembled with the MC hydrogel, the thermal stability and the carbon layer formation capacity are enhanced, the residual yield is increased from 6.51% to 13.91% in cooperation, a heat insulation oxygen resistance layer is formed, and the composite hydrogel is suitable for complex fire scene environments.

Description

Technical Field

[0001] This invention belongs to the field of fireproof materials technology, specifically relating to a forest fireproof material based on organosilicon MC composite hydrogel, its preparation method, and its application. Background Technology

[0002] Forest fires, as a type of solid fire, are characterized by their rapid spread and difficulty in control. They pose a significant threat to ecosystems and human life and property, and have a wide-ranging impact on social development.

[0003] Traditional fire extinguishing agents, such as water, chemical fire extinguishing agents, and foam agents, while effective to some extent, have limitations when dealing with high-intensity and complex fires. For example, although water is widely available and highly mobile, its high volatility at high temperatures limits its effectiveness in reaching the high-temperature zones inside the flames, resulting in high water consumption, low extinguishing efficiency, and a high risk of reignition. Dry powder and foam agents struggle to penetrate deep into the fire, and the residue from dry powder sprays is difficult to clean, potentially causing environmental pollution. Foam agents have poor stability, making it difficult to maintain their extinguishing effect. Especially under arid and high-temperature complex environmental conditions, the effectiveness of traditional fire extinguishing agents is often significantly reduced. Furthermore, many forest fire extinguishing agents have negative environmental impacts. For example, long-acting chemical fire extinguishing agents such as ammonium sulfate, ammonium phosphate, and halogenated hydrocarbons may cause water pollution or long-term soil damage, and may even pose health risks.

[0004] Hydrogels are a new type of clean and efficient fire-fighting material with good adhesion, strong water absorption, and water retention. In firefighting operations, they can quickly achieve cooling and temperature reduction effects, while also acting as an oxygen barrier and sealing agent, thus significantly improving water utilization efficiency and overall fire-fighting effectiveness. However, traditional hydrogels have poor flowability, hindering their penetration and sprayability, resulting in incomplete coverage of the ignition point and difficulty in handling residues.

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

[0006] This application addresses the problems of poor environmental biodegradability, low flame retardant efficiency, and insufficient resistance to reignition of traditional forest fire extinguishing agents. It provides a forest fire prevention material based on organosilicon MC composite hydrogel, constructing an environmentally responsive composite hydrogel system based on methylcellulose and trisiloxane wetting agent. While improving fire extinguishing efficiency, it controls application costs and reduces negative environmental impacts. It has the advantages of flow and penetration characteristics, green efficiency, low cost, strong thermal stability, and dynamic response to temperature changes.

[0007] This invention is achieved through the following technical solution:

[0008] 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 of water.

[0009] 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:

[0010] S1. Take methyl cellulose, flame retardant, silicone wetting agent and ionic crosslinking agent according to the mass fraction ratio;

[0011] S2. Mix the above materials with deionized water by the one-pot method, stir evenly until hydrated, and then stand at room temperature to fully swell and crosslink;

[0012] S3. Stir the swollen hydrogel at high speed until it is dispersed into a uniform sol state, and then stand at room temperature to defoam, thus obtaining the product.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 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 of water. It is a composite hydrogel system with MC as the basic skeleton of the composite hydrogel, silicone wetting agent 5211 as the dynamic wetting regulation unit, and DMMP as the efficient chemical flame retardant core. This hydrogel has the characteristics of shear thinning (0 < n < 1), reduces viscosity during pipeline transportation, meets the flow-adhesion requirements of the fire extinguishing scenario, has temperature response characteristics, realizes 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, has thermal stability, the chemical flame retardance of DMMP and the self-assembly of MC hydrogel enhance the thermal stability and the ability to form a carbon layer, synergistically increase the residual yield from 6.51% to 13.91%, form a heat insulation and oxygen barrier layer, and is suitable for complex fire field environments.

[0015] This application provides a method for preparing forest fire prevention materials based on organosilicon MC composite hydrogel. The method prepares an organosilicon MC composite hydrogel with flow permeability, green efficiency, low cost, strong thermal stability and dynamic response to temperature changes. The hydrogel is in sol form below the critical transition temperature (LCST), with strong fluidity, easy to spray and cover fire points. Above the LCST, it becomes gel form with increased viscosity, which can firmly adhere to the surface of combustibles. At the same time, when heated, it releases a highly permeable liquid that carries flame-retardant components into the depths of the fire source for fire extinguishing. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0017] Figure 1 This describes the gelation mechanism of the organosilicon MC composite hydrogel in the embodiments of this application;

[0018] Figure 2 This is a schematic diagram of the fire extinguishing process of the organosilicon MC composite hydrogel in the embodiments of this application;

[0019] Figure 3 This is a graph showing the relationship between the surface tension and concentration of four wetting agent solutions in the embodiments of this application;

[0020] Figure 4 This is a diagram showing the spreading trend and dynamic contact angle variation of SDBS on the pine wood surface in the embodiments of this application;

[0021] Figure 5 This is a diagram showing the spreading trend and dynamic contact angle change of APG-0810 on the pine wood surface in the embodiments of this application;

[0022] Figure 6 This is a diagram showing the spreading trend and dynamic contact angle change of 5211 on the pine wood surface in the embodiment of this application;

[0023] Figure 7 This is a diagram showing the spreading trend and dynamic contact angle change of 8008 on the pine wood surface in the embodiments of this application;

[0024] Figure 8 This is a graph showing the relationship between the spreading coefficient and the wetting agent concentration in the embodiments of this application;

[0025] Figure 9 These are penetration time diagrams for different wetting agent solutions in the embodiments of this application;

[0026] Figure 10 This is a graph showing the relationship between viscosity, shear stress, and shear rate for hydrogels A1-A4 in the embodiments of this application (solid graph - viscosity, hollow graph - stress).

[0027] Figure 11This is a graph showing the effect of DMMP concentration on the viscosity of the hydrogel in the embodiments of this application;

[0028] Figure 12 This is a graph showing the effect of 5211 concentration on the viscosity of the hydrogel in the embodiments of this application;

[0029] Figure 13 This is a graph showing the relationship between shear stress and shear rate for hydrogels A2 and C3 in the embodiments of this application;

[0030] Figure 14 These are temperature scan curves of hydrogels A2(a) and C3(b) in the embodiments of this application;

[0031] Figure 15 This refers to the dynamic contact angle of water separation and dehydration in each hydrogel system in the embodiments of this application.

[0032] Figure 16 These are the TG and DTG curves of hydrogels A2 and C3 in the embodiments of this application;

[0033] Figure 17 This describes the fire extinguishing process under conditions 1, 2, and 3 in the embodiments of this application. Detailed Implementation

[0034] 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 merely illustrative of the invention and are not intended to limit the invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0035] This application provides a forest fire prevention material based on organosilicon MC composite hydrogel, comprising the following raw materials by weight: 0.05-0.3 wt% organosilicon wetting agent (5211), 1.2-1.6 wt% methylcellulose (MC), 1.8-2.5 wt% flame retardant (DMMP), 1.8-2.3 wt% ionic crosslinking agent (NaCl), and the balance being water. The main components of the composite hydrogel prepared in this application include methylcellulose (MC), trisiloxane wetting agent (5211), dimethyl methylphosphonate (DMMP), and sodium chloride (NaCl), which respectively act as gelling agent, wetting agent, flame retardant, and crosslinking agent, playing a synergistic role in the fire prevention and extinguishing process of the composite hydrogel.

[0036] The gelation mechanism of the organosilicon MC composite hydrogel in this application embodiment is as follows: The physical cross-linking network of the organosilicon MC composite hydrogel is mainly constructed by methylcellulose (MC). The hydrophilic groups of MC form hydrogen bonds with water molecules, promoting their orderly arrangement within the MC network. The organosilicon wetting agent is a high-molecular-weight polymer, and the hydrophobic siloxane backbone also contributes to the formation of the cross-linking network. The ethoxy groups on the hydrophilic polyether chains adsorb and aggregate water molecules through electrostatic interactions and hydrogen bonding. Uniformly dispersed sodium ions in the solution interact with the MC methoxy groups, forming a structured network. Due to molecular interactions (hydrogen bonds, hydrophobic interactions, van der Waals forces, etc.), the organosilicon MC composite hydrogel undergoes a sol-gel transition according to temperature changes, such as... Figure 1 As shown, at lower temperatures, hydrogen bonds between water molecules dominate, resulting in a sol state characterized by a water-covered surface. With increasing temperature, the increased heat absorption disrupts these hydrogen bonds, leading to entanglement of the 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 the MC. Subsequently, hydrophobic association dominates, leading to gel formation.

[0037] The fire extinguishing mechanism of organosilicon MC composite hydrogel: Organosilicon MC composite hydrogel has a three-dimensional cross-linked structure and adhesiveness. Methylcellulose (MC) forms the basic morphology of the composite hydrogel, while siloxane chains participate in the formation of the cross-linked structure. Flame retardants and water are encapsulated within the composite hydrogel. The composite hydrogel, possessing shear-thinning properties, can be sprayed at high speed through pipes onto forest fires, forming a film on the fire surface to isolate 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 combustible materials. Simultaneously, as the temperature further increases, the highly efficient flame retardant and organosilicon wetting water loaded in the composite hydrogel are slowly released. This highly wetting and highly permeable water penetrates through the pores of the vegetation fuel layer, reaching deep into the fire source to continue absorbing heat from the depths of the fire. The flame retardant DMMP decomposes upon heating and reacts with free radicals, halting the chain reaction and preventing further combustion. During the fire extinguishing process, the organosilicon MC composite hydrogel fully utilizes the fire extinguishing efficacy of each component from both physical and chemical perspectives. Figure 2 As shown.

[0038] The methylcellulose used in this application's embodiments is derived from natural polymer cellulose, which can be extracted from natural wood or refined cotton. It is inexpensive and environmentally degradable. Utilizing cellulose-based hydrogels to synthesize forest fire-fighting materials is essentially using readily available resources.

[0039] The hydrophilic groups (hydroxyl groups -OH) of MC form hydrogen bonds with water molecules, promoting their orderly arrangement within the MC network, which is beneficial for storage, transportation, and penetration at room temperature. Simultaneously, above a certain threshold, due to the interactions between MC molecules (hydrogen bonds, hydrophobic interactions, van der Waals forces, etc.), it transforms into an adhesive gel, effectively inhibiting oxygen supply and smoke release, thus overcoming the limitations of traditional fire extinguishing methods. Relying on its characteristics of flowing at room temperature and gelling upon heating, MC hydrogel mainly plays a physical role in fire extinguishing by isolating oxygen, smoke, and heat.

[0040] Methylcellulose (MC) is a nonionic cellulose ether produced by introducing methyl groups into cellulose molecules through an etherification reaction. Cellulose is the main structural component of plant cell walls, accounting for 40%-50% of wood. Methylcellulose is a natural high-molecular-weight polymer with good adhesive properties and cost-effectiveness. It is non-toxic, readily biodegradable, and undergoes a reversible sol-gel phase transition at certain temperatures. At room temperature, MC absorbs moisture and swells, forming a stable, low-viscosity solution; at high temperatures, MC undergoes a physical transformation, forming a high-viscosity gel.

[0041] Trisiloxane wetting agent 5211 is a type of organosilicon surfactant with a flexible -Si-O-Si- chain as the backbone and one or more hydrophilic groups connected to it. Due to its strong surface activity and the characteristics of corrosion resistance, high temperature resistance and non-toxicity, it is added as a wetting agent to hydrogel fire extinguishing agents to adjust and improve the fluidity and diffusivity of MC hydrogel so as to form a film quickly, enhance the thermal stability of hydrogel, and promote the wetting and penetration of fuel by water carrying flame retardant after the hydrogel is dehydrated, so as to achieve the effect of cooling and fire extinguishing.

[0042] Dimethyl methyl phosphonate (DMMP) is an organophosphorus flame retardant with extremely high phosphorus content. It exhibits excellent flame retardant properties and boasts advantages such as being environmentally friendly, low in toxicity, and highly compatible, meeting the development requirements for green and efficient flame retardants. When heated, DMMP first decomposes to generate PO and PO2. These two substances can react with free OH radicals, accelerating chain termination reactions and thus playing a flame-retardant role. Dimethyl methyl phosphonate (DMMP, C3H9O3P, CH3PO[OCH3]2) is a comprehensive flame retardant with good water solubility. It possesses advantages such as high efficiency, low toxicity, and good compatibility with polymers, functioning in both the gas and condensed phases. Simultaneously, DMMP generates a phosphate layer during decomposition. This non-volatile phosphate layer acts as a protective layer on the surface of combustible materials, effectively isolating oxygen supply and thus extinguishing the flame. Furthermore, the polymetaphosphoric acid produced during DMMP decomposition can promote the combustion decomposition process of polymers towards carbonization, while releasing a large amount of moisture, effectively inhibiting the continued combustion reaction.

[0043] Sodium chloride (NaCl) generates chemical bonds between linear polymer hydrogels through ionic cross-linking, linking linear molecules together to form a three-dimensional physical cross-linked network structure. Salting out and interaction promote the dehydration process, thereby accelerating the formation of gel and carbonized layers and improving the gel strength of the composite hydrogel.

[0044] This application uses a trisiloxane wetting agent with a simple, stable chemical structure and good biocompatibility as the core, and methylcellulose (MC), a natural cellulose derivative, as the basic raw material for the hydrogel. Highly efficient fire-resistant and flame-retardant additives are added to construct an environmentally friendly, highly efficient, and dynamically responsive siloxane hydrogel structural material. This application prepares an organosilicon-MC composite hydrogel with flow permeability, green efficiency, low cost, strong thermal stability, and dynamic response to temperature changes. Below the critical transition temperature (LCST), the hydrogel is in a sol state with high fluidity, easy to spray and cover fire points; above the LCST, it becomes a gel with increased viscosity, adhering firmly to the surface of combustible materials. Simultaneously, upon heating, it releases a highly permeable liquid carrying flame-retardant components deep into the fire source for extinguishing.

[0045] Specifically, organosilicon wetting agents are the core components of organosilicon MC composite hydrogels. Wetting agents primarily enhance water permeability by reducing the surface or interfacial tension of water, allowing the solid surface to be wetted. Organosilicon wetting agents have long Si-C bonds and high methyl coverage in their main chain, exhibiting excellent hydrophobicity. They can effectively reduce the surface tension of solutions (down to below 20 mN / m, while the surface tension of conventional surfactants is generally around 30 mN / m). As a novel type of surfactant, organosilicon wetting agents are biodegradable and are commonly used as spray modifiers, pesticide adjuvants, and defoamers.

[0046] In a specific embodiment, the organosilicon wetting agent used is a trisiloxane wetting agent, preferably a nonionic organosilicon from Dow Corning, specifically model 5211. Siloxanes possess stable physicochemical properties, and the dispersion of 5211 in the MC hydrogel enhances the hydrogel's thermal stability. During the hydrogel's heating and dehydration process, water containing 5211 and the flame retardant detaches from the hydrogel. The hydrophilic ethylene oxide (-C2H6O-) groups of the trisiloxane wetting agent 5211 tilt towards the aqueous phase, while the hydrophobic groups (chains) adsorb onto the wood surface, covering the surface with hydrophobic groups such as methoxy groups and benzene rings, thus transforming the wood surface from hydrophobic to hydrophilic. This helps the water removed from the gel to penetrate and wet the surface fuel of forest vegetation, extinguishing deeper smoldering fires and achieving a physical cooling and extinguishing effect.

[0047] Example 1: Performance analysis of organosilicon wetting agents:

[0048] Using pine, the most abundant tree species in forests, as the experimental subject, this study investigated the effects of four water-based wetting agents on the wettability of wood. Nonionic siloxane surfactants, anionic hydrocarbon surfactants, and nonionic hydrocarbon surfactants were selected as comparative test subjects. Surface tension data was used to preliminarily determine the wettability of the monomer solution. The dynamic contact angles of three pine wood cross-sections were tested to analyze the spreading trend of the water-based wetting agents, and the spreading coefficient was calculated using tension and contact angle data. Combined with the results of water-based wetting agent penetration time tests, the effect of solution concentration on the wettability of wood was studied, and the expected type and concentration range of organosilicon wetting agents were selected.

[0049] To improve the diffusion and penetration properties of hydrogels, this application determined the wetting properties and suitable addition concentration of organosilicon wetting agents in organosilicon MC composite hydrogels. Two organosilicon wetting agents (trisiloxane wetting agent 5211 and polyether-modified polysiloxane wetting agent 8008) were selected and compared with common hydrocarbon wetting agents (sodium dodecylbenzenesulfonate SDBS and alkyl glycoside APG) to identify the type of wetting agent with superior wetting, diffusion, and penetration properties and select a suitable concentration range as a 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 investigated. Based on experimental test results, a novel organosilicon wetting agent, 5211, with superior diffusion and penetration capabilities was identified, and its suitable addition concentration range was determined as a key component for improving the fire extinguishing efficiency of the hydrogel fire extinguishing agent.

[0050] (1) Surface tension test

[0051] Surface tension is a crucial parameter affecting penetration and wetting effects; lower surface tension generally results in better wetting properties of the wetting agent. In this experiment, surface tension (IFT) was measured using a KRUSS K20 surface tension meter. The ring method was employed to test the dynamic surface tension values ​​of solutions at different concentrations at 25°C. The instrument calculates the surface tension value based on the maximum tensile force applied during the measurement. Seven concentrations were set for hydrocarbon-based wetting agents, and eight concentrations were set for silicone-based wetting agents. To ensure data accuracy, each experiment 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 compared.

[0052] Analysis of surface tension test results:

[0053] like Figure 3As 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 surfactant concentration; in the stable range, the surface tension of the solution decreases to the lowest and then remains stable with the increase of surfactant concentration. The minimum surface tensions of the 4 surfactants from small to large are: 5211 < 8008 < SDBS < APG-0810. It can be found that the decrease in surface tension of silicone wetting agents is greater than that of hydrocarbon wetting agents with the increase of concentration. Among them, 5211 has the lowest surface tension and the strongest ability to reduce surface tension. The minimum surface tension at 0.05% is 19 mN / m.

[0054] It can be found that with the continuous increase of the wetting agent concentration, the surface tension of the solution will no longer continue to decrease with the increase of its concentration, but instead shows 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 gather together, with their hydrophobic groups facing inside the liquid surface and their hydrophilic groups facing outside the liquid surface to form micelles. At this time, the solution reaches the critical micelle concentration. After reaching this stage, the surfactant mainly consumes itself by forming micelles rather than further reducing the surface tension of the solution. In order to further compare the four wetting agents, according to the surface tension test results in the figure, the critical micelle concentration CMC and the corresponding critical surface tension γCMC of each type of wetting agent can be obtained. The specific values are shown in Table 1.

[0055] Table 1 CMC and γCMC of different wetting agent solutions

[0056]

[0057] As can be seen from Table 1, there are significant differences in the critical micelle concentration CMC and the critical surface tension γCMC of different types of wetting agent solutions. The critical micelle concentration CMC of silicone wetting agents is much smaller than that of hydrocarbon wetting agents, and the γCMC of silicone wetting agents is also lower than that of hydrocarbon wetting agents; among hydrocarbon wetting agents, the CMC and γCMC of SDBS are slightly larger than those of APG-0810; for silicone wetting agents, the CMC of 5211 and 8008 is the same, while the critical surface tension γCMC: 5211 < 8008. This means that silicone wetting agents can greatly reduce the surface tension of liquids with extremely low addition amounts. Compared with hydrocarbon wetting agents, silicone wetting agents have less dosage and lower usage costs. According to the data results of the critical micelle concentration CMC and the critical surface tension γCMC, it can be preliminarily judged that silicone wetting agents meet the expected effects.

[0058] (2)Dynamic contact angle measurement

[0059] The contact angle is an important parameter characterizing the wettability of a solid surface, reflecting the interaction between a liquid and a solid. Due to the anisotropy of wood and variations in processing techniques, the roughness and hydrophobicity of wood cross-sections differ. Generally, the roughness of the cross-section of wood is greater than that of the radial and tangential sections. Therefore, the dynamic contact angles of wood with different cross-sections are measured for comparison. For a surface with the same roughness, the smaller the contact angle, the better the wettability of the wood surface. In this experiment, pine strips were selected as the substrate for the contact angle test. The pine strip samples were in two sizes: 100mm×50mm×10mm and 50mm×50mm×50mm. Each strip underwent polishing, ultrasonic cleaning, and vacuum drying, maintaining a moisture content of 10%–14% and a wood density of 0.45–0.55 g / cm³. 3 Different concentrations of wetting agent solutions were prepared using deionized water. To ensure randomness of the testing, various locations were selected on the sample surface. The dynamic contact angle of the different concentrations of wetting agent on the pine strip surface was measured from 0 to 20 seconds using an SDC-350 optical contact angle meter. The contact angle resolution reached 0.001°. All tests were repeated at least three times to obtain the 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 wetting effect of the wetting agent solutions on the wood was compared and verified.

[0060] Dynamic contact angle measurement and analysis:

[0061] Figures 4-7 The study demonstrates the spreading trends of wetting agents of different concentrations on pine wood surfaces. As the wetting agent concentration increases, the contact angle of the wetting agent solution continuously decreases. With increasing contact time, under the influence of gravity and the adsorption effect of the wood's microporous structure, the wetting agent aqueous solution gradually diffuses until complete spreading. Due to the layered porosity and anisotropic structure of wood, the contact angle of the same concentration of wetting agent on the cross-section of pine wood is greater than that on the radial / tangential section, and it is more difficult for the cross-section to spread completely within the same time. On the radial / tangential section of pine wood, 0.2% SDBS and 0.2% APG can spread completely within 15 seconds, while the silicone wetting agents 5211 and 8008 at a concentration of 0.01% can spread completely within 15 seconds. On the cross-section of pine wood, at the same 0.5% mass fraction, SDBS takes more than 20 seconds to spread completely, APG takes 10 seconds, while the complete spreading time of 5211 and 8008 is less than 5 seconds.

[0062] On the same hydrophobic surface, the addition of wetting agents can effectively enhance the wettability of aqueous solutions on wood. The mass fraction of silicone wetting agents that can fully spread in the same amount of time is much lower than that of hydrocarbon wetting agents. At the same mass fraction, the time required for silicone wetting agents to fully spread is also shorter than that for hydrocarbon wetting agents.

[0063] Figures 4-7The changes in dynamic contact angle values ​​of different wetting agents on pine wood surfaces from 0 to 20 seconds are shown. The decrease in contact angle of the four wetting agents on the cross-section of pine wood is less than that on the radial / tangential section, indicating that the wetting agent solution is more difficult to diffuse on cross-sections with greater roughness. Using the dynamic contact angle of the pine wood cross-section at 0.1% mass fraction as a reference, the contact angle value of SDBS decreased from 95.079° to 33.112° within 20 seconds, a decrease of 3.1° / s; the contact angle value of APG decreased from 112.387° to 89.954° within 20 seconds, a decrease of 1.12° / s; the contact angle value of 5211 decreased from 95.512° to 0° within 5 seconds, a decrease of 19.1° / s; and the contact angle value of 8008 decreased from 90.742° to 0° within 10 seconds, a decrease of 9.07° / s. By comparing the dynamic contact angle variation and spreading trend of the four wetting agents on the pine wood surface, it can be concluded that the diffusion and wetting performance of the organosilicon wetting agent is better than that of common hydrocarbon wetting agents, and the wetting performance is ranked from strong to weak as follows: 5211 > 8008 > SDBS > APG-0810.

[0064] (3) Spreading coefficient analysis

[0065] Based on the surface tension and contact angle data measured in this paper, the spreading coefficients of the four wetting agents on the wood surface were analyzed, as shown in Table 2. A larger spreading coefficient indicates better wettability of the solution. When S≥0, it indicates that the solution can spontaneously spread and wet; conversely, it indicates that the solution cannot spontaneously spread and wet. The formula for calculating the spreading coefficient is as follows:

[0066] (1.1)

[0067] in: S The spreading factor is (mN / m).

[0068] The surface tension of the surfactant solution is (mN / m).

[0069] The contact angle value is (°).

[0070] Table 2 Static contact angles (°) of four wetting agents at different concentrations

[0071]

[0072] Depend on Figure 8It can be seen that the spreading coefficients of all four wetting agents are less than 0, indicating that the solutions of the four wetting agents cannot spontaneously diffuse 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 spread more easily on the pine wood surface; the solution concentrations required for SDBS and APG to obtain the maximum spreading coefficient are both greater than those for 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, consistent with the contact angle measurement data.

[0073] (4) Permeability test

[0074] This application's embodiments studied and evaluated the velocity of liquid penetrating a 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 compressed to the same volume for later use. 3ml of the room-temperature wetting agent aqueous solution was added to the test tube. Due to gravity and the influence of pore structure, the solution penetrated into the sample, and the change in liquid column height was observed (foam height was negligible). The time taken for different wetting agent solutions to completely penetrate into the sawdust sample from 0% to 100% was recorded. Three sets were repeated, and the average value was taken.

[0075] Penetration performance test analysis:

[0076] Forest fires ignite not only on the surface of the ground or trees, but also in smoldering fires caused by burning underground peat layers or flames inside dense vegetation. These fires are often covered by layers of obstacles, making them even more dangerous. Only fire extinguishing agents with penetrating properties can achieve better fire extinguishing effectiveness. The penetrating properties of wetting agents determine whether they can quickly penetrate the fuel layer and reach the depths of the fire source. Figure 9(a)-(d) are the times for four wetting agents to penetrate through the sawdust layer at different mass fractions. The shorter the time for the wetting agent solution to penetrate through the sawdust layer with the same density, the stronger the penetration performance of the wetting agent. As the mass fraction of the wetting agent increases, the penetration time of the same volume of wetting agent solution from 0-100% gradually decreases and the penetration rate is faster. The penetration rate during the 75%-100% penetration progress is significantly slower than that during the 0-25% penetration. This is because as the mass fraction of the wetting agent increases, the surfactants in the aqueous solution are arranged more closely. Under the action of hydrogen bonds and van der Waals forces, the surfactants combine with the hydrophobic groups on the wood surface to change the interfacial state of the solid-liquid interface of the wood structure. Hydrophobic wood is more likely to adsorb water molecules. At the same time, as the liquid gradually penetrates into the sawdust, the influence of the gravity on the liquid column gradually weakens, and the penetration rate in the latter half of the liquid penetration process will also slow down.

[0077] According to Figure 9 the data, at a low concentration of 0.05%, for the four wetting agents, the complete penetration time of SDBS 100% is 687 s, the complete penetration time of APG is 729 s, while the complete penetration time of the silicone wetting agent 5211 is 413 s, and the complete penetration time of 8008 is 452 s; at a high concentration of 0.5%, the complete penetration times are: 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 wood structure surface. This 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 stronger hydrogen bond interactions 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 strong adhesion with the hydrophobic groups on the wood molecules, 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.

[0078] The embodiments of this application explore the effects of different types of wetting agents on enhancing the wetting performance and penetration performance of water on wood, and determine a new type of silicone wetting agent 5211 with more excellent diffusion and penetration capabilities according to the experimental test results, and determine the suitable concentration range for its addition, as the key component to improve the fire extinguishing efficiency of the hydrogel fire extinguishing agent.

[0079] The main conclusions of Example 1 are as follows:

[0080] (1) The surface tensions of four wetting agent solutions were analyzed. The results showed that as the concentration increased, the decrease in the surface tension of the silicone wetting agent was greater than that of the hydrocarbon wetting agent. The CMCs of 5211 and 8008 were 0.01 wt%, and the γCMCs could be as low as 19.7 and 19.8 mN / m respectively. While the CMCs of SDBS and APG were 0.6 wt% and 0.5 wt%, and the γCMCs reached 27.6 and 26.8 mN / m. The critical micelle concentration CMC of the silicone wetting agent was much smaller than that of the hydrocarbon wetting agent, and the γCMC of the silicone wetting agent was also lower than that of the hydrocarbon wetting agent. After comparison, it was preliminarily obtained that the wetting properties of the silicone wetting agents 5211 and 8008 were better than those of the hydrocarbon wetting agents SDBS and APG.

[0081] (2) The spreading trends and changes in contact angles of four wetting agent solutions were explored. 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 sections, and it was more difficult for the solution to completely spread on the cross-section within the same time. On the radial / tangential sections 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 and spreading trends of the four wetting agents 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.

[0082] (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, which was close to spontaneous spreading and was the largest among the four wetting agents.

[0083] (4) The penetration times of four wetting agent solutions into 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. At the same mass fraction, the penetration performance of the silicone wetting agent is better than that of the ordinary hydrocarbon wetting agent.

[0084] Example 2: Preparation of composite hydrogel materials:

[0085] The process includes the following steps: Appropriate amounts of dried methylcellulose (MC), dimethyl methylphosphonate (DMMP), trisiloxane wetting agent (5211), and sodium chloride (NaCl) are taken according to the mass fraction ratio. These are mixed with 70°C deionized water using a one-pot method, stirring constantly to ensure complete polymer hydration. The mixture is then allowed to stand at room temperature for 6 hours to allow for full swelling and crosslinking. The swollen hydrogel is then dispersed into a uniform sol state using a high-speed disperser at 5000 r / min. After defoaming, the mixture is allowed to stand at room temperature for 24 hours before use. Table 3 shows the mass composition of MC, DMMP, 5211, and NaCl in each system of the composite hydrogel.

[0086] Table 3 Mass composition of each system in the composite hydrogel

[0087]

[0088] The prepared composite hydrogel material was subjected to the following performance tests:

[0089] (1) Rheological test

[0090] All rheological tests were performed using a Discovery HR-2 hybrid rheometer (TA Instruments, USA). For testing hydrogel samples, stainless steel parallel plates with a diameter of 25 mm and a gap of 1 mm were used. Before testing, the samples were thoroughly stirred to ensure complete gel dispersion. During kinetic viscosity testing in rotational mode, the temperature was controlled at 25 °C, and the shear rate range was set to 0.1–100 s⁻¹. In the oscillating frequency scan, a constant strain of 2% was applied with an angular frequency of 0.1–100 rad·s⁻¹ to determine the storage modulus (G') and loss modulus (G'') of the gel. In the temperature scan 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.

[0091] Analysis of the influence of each component incorporation on the viscosity of the hydrogel:

[0092] In composite hydrogel systems, methylcellulose (MC) is a key factor affecting viscosity, which directly relates to the effectiveness of fire extinguishing. Therefore, we investigated the relationship between methylcellulose content and the viscosity of the composite hydrogel to determine the optimal methylcellulose concentration. Figure 10As shown, the viscosity of the pure gel increases exponentially with increasing methylcellulose content. Methylcellulose hydrogels are formed through non-covalent crosslinking, and the increase in viscosity mainly stems from chain entanglement in the microstructure. Higher methylcellulose content leads to more severe chain entanglement, resulting in a significant increase in viscosity. This viscosity characteristic allows the gel to adhere firmly to the burning surface during fire extinguishing, rather than flowing away rapidly like water, thus significantly improving extinguishing efficiency. However, excessively high viscosity can also cause problems, such as difficulty in spraying and even potential blockage of delivery pipelines. Therefore, selecting an appropriate viscosity is crucial for practical applications. At specific methylcellulose contents, the hydrogel exhibits significant shear-thinning behavior with increasing shear rate. As shear force increases, the degree of polymer chain entanglement gradually weakens and tends towards directional alignment, causing a rapid decrease in viscosity. This characteristic allows the gel to pass through relatively easily under strong shear forces (such as when flowing in pipelines).

[0093] from Figure 11 In 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, insufficient to significantly alter the gel's rheological behavior. In contrast, as... Figure 12 As shown, the concentration of wetting agent 5211 has a significant impact on the viscosity of the hydrogel system. With the increase of 5211 content, the viscosity of the hydrogel first increases, with C1 and C2 hydrogels exhibiting higher viscosity than A2 hydrogel with the same MC content. As the 5211 content continues to increase, the viscosity of 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: Under low concentration conditions, 5211 can form a physically entangled network with the MC matrix polymer. The hydrogen bonds between MC and 5211, as well as the hydrophobic interaction of the siloxane, promote hydrogel formation. 5211 joins the cross-linked network through hydrogen bonds and molecular interactions. This physically entangled structure restricts the movement of polymer chain segments in the hydrogel, thus leading to an increase in system viscosity. Under high concentration conditions, the interaction between the hydrophilic groups (ethylene oxide) and hydrophobic groups (siloxane) of 5211 molecules is enhanced, causing 5211 molecules to tend 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 original polymer chain entanglement structure, leading to a loosening of the network structure. Finally, under shear stress, the addition of 5211 increases the spacing between polymer chains, further weakening intermolecular interactions, ultimately leading to a decrease in system viscosity.

[0094] 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.

[0095] The shear-thinning behavior of composite hydrogels of different concentrations was evaluated based on the power-law fitting of viscosity and shear rate. Figure 13 This reflects the relationship between shear stress and shear rate of the A2 and C3 composite hydrogels at room temperature. The viscosity of both A2 and C3 hydrogels decreases with increasing shear rate. A power-law model equation was used to fit the A2 and C3 hydrogels. The power-law model is described as follows:

[0096] τ = Kγ ^n(2.1)

[0097] In the formula: τ It is shear stress (Pa);

[0098] K It is the consistency index (Pa.s) n );

[0099] γ It is the shear rate (1 / s);

[0100] n is the rheological index of the fluid (dimensionless), 0 <n<1。

[0101] The lower the value of n, the more pronounced the non-Newtonian rheological behavior of the hydrogel. Data fitting demonstrates that the composite hydrogel is a power-law fluid, exhibiting a high correlation coefficient (C3 hydrogel R...). 2 >0.98, A2 hydrogel R 2 A value >0.99 indicates a strong relationship, suggesting that the hydrogel exhibits pseudoplastic fluid behavior (n<1). This fluid behavior is significant because it means that the hydrogel will not flow before exceeding the critical stress (yield stress), and begins to flow and diffuse above the yield stress, highlighting its potential for effective deployment in fire suppression scenarios where rapid activation is required. Compared to A2 hydrogel, the 0.3% concentration of 5211 in C3 hydrogel increases the spacing of the MC crosslinking network, reduces the viscosity of the composite hydrogel, and does not change the rheological properties of the composite hydrogel, effectively enhancing its flowability and diffusivity.

[0102] Temperature dependence analysis:

[0103] Because MC hydrogel is a temperature-responsive material, temperature has a significant impact on the hydrogel. Figure 14Temperature scans of A2 and C3 gels are shown. Interestingly, the addition of 5211 significantly alters the thermorheological behavior of the composite gels. Below 55°C, the modulus and viscosity of the pure gel show little change with increasing temperature. From 55°C onwards, both modulus and viscosity increase sharply, indicating a transition from sol to gel. With further increases in temperature, the modulus and viscosity of both composite hydrogels increase dramatically. Unlike the pure MC gel, the silicone MC composite hydrogel exhibits some differences in the temperature scan. Initially, the modulus and viscosity of the composite hydrogel are similar to those of the pure gel. In the temperature range of 40°C–55°C, the MC hydrogel completes the sol-gel transition, while the silicone MC composite hydrogel extends this transition temperature range to 40°C–60°C. After 60°C, both modulus and viscosity undergo a similar sol-gel transition process, leading to an increase in modulus and viscosity. The flow tests described above indicate that 5211 possesses a certain degree of thermal stability, delaying the sol-gel transition of the MC hydrogel and providing time for flow diffusion in high-temperature fire environments. This means that the organosilicon composite MC hydrogel can cover a wider area. The increase in modulus and viscosity is due to the increased degree of chain entanglement. As the temperature rises, the increased heat absorption disrupts hydrogen bonds, leading to entanglement of MC and siloxane molecular chains. Subsequently, the hydrophobic methoxylated groups on the MC are gradually exposed, and hydrophobic association becomes dominant, resulting in gel formation. This demonstrates that the addition of 5211 can improve the flowability of the composite hydrogel on combustible materials and, with the aid of temperature, allow it to adhere firmly to the surface of the burning material.

[0104] (2) Dynamic contact angle test of gel water separation

[0105] 100 ml of the composite hydrogel was placed in a beaker and continuously heated using an alcohol lamp. The heat was transferred to the hydrogel in the beaker through an asbestos mesh. A thermocouple was inserted into the center of the hydrogel, and the temperature was continuously monitored using 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 collected and loaded into a contact angle measuring instrument to measure its dynamic contact angle over 50 seconds.

[0106] Figure 15The dynamic contact angle of the water released from the hydrogel systems on the pine wood surface from 0 to 50 seconds was shown. Under uniform heating at 90°C, each hydrogel system underwent a phase transition to gelation, and the three-dimensional cross-linked structure of the gel further shrank, releasing some of the water stored in the gel. Using the dynamic contact angle of pure water as a reference, the contact angle of pure water on the pine wood cross-section decreased from 133.839° to 123.836° within 50 seconds. As the concentration of methylcellulose increased, the contact angle of the released water began to increase. The contact angle of the A4 hydrogel on the pine wood cross-section decreased from 136.958° to 126.4°, while the spreading properties of the A1 hydrogel were similar to those of pure water. This indicates that as the concentration of MC increases, the presence of hydrophobic methyl groups in the released liquid slightly increases the contact angle of the liquid on the wood surface. The dynamic contact angle changes of hydrogels C1-C4 show that the addition of 5211 significantly enhances the wetting properties of water. As the amount of 5211 added increases, the contact angle of the water exuded from the gel decreases. The contact angle of the pine wood cross section of the C4 hydrogel that exudes water decreases from 106.979° to 0° within 40 seconds.

[0107] (3) Thermal stability test

[0108] Thermogravimetric analysis was used under 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 mass of the composite hydrogel sample was 5-10 mg.

[0109] Thermal stability analysis of composite hydrogels:

[0110] The thermal stability of the prepared composite hydrogel was studied using thermogravimetric analysis (TGA). Figure 16The TG and DTG curves of hydrogels A2 and C3 are shown. The initial degradation temperature (T-5%) and the maximum degradation temperature (Tmax) are mainly used to evaluate the thermal stability of the 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 is maximum, marking the starting point and the critical point of most severe mass loss, respectively (see Table 4.4). It can be seen that both hydrogels exhibit similar weight loss stages. Hydrogel A2 shows a weight loss stage from room temperature to 141℃, while hydrogel C3 shows a weight loss stage from room temperature to 116℃. In this stage, the main processes are the continuous evaporation of free water in the hydrogel and the destruction of bound water in the solute. Hydrogel A2 loses 92.7% of its weight, and hydrogel C3 loses 86.3%. This helps to lower the temperature and dilute oxygen, thereby reducing combustion. In the stage from 150℃ to 350℃, the main processes are the volatilization and degradation of some polymers and salts. The thermal degradation of methylcellulose typically occurs between 200°C and 410°C. Around 300°C, methylcellulose undergoes significant weight loss due to the breakage and decomposition of ether bonds and methoxy groups in its molecular structure at high temperatures, leading to mass loss. DMMP exhibits better thermal stability; the rate of thermal decomposition due to the breaking of intramolecular hydrogen bonds is slow between 200 and 300°C, but significant thermal decomposition at 300°C is accompanied by the formation of volatile products. Since the flame temperature during wood combustion can exceed 900°C, DMMP dissolved in a gel can immediately take effect upon contact with the flame, forming a structurally stable carbonized layer. This carbonized layer acts as a physical barrier, preventing further pyrolysis 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 approximately 0.5% of their weight at 300℃.

[0111] During the initial weight loss phase (25–48 °C), the C3 hydrogel exhibited fluctuations in its DTG mass loss rate. This was due to the excellent thermal stability of the silicone wetting agent 5211; as heat transferred from the hydrogel surface to the interior, the strong Si-O bonds allowed 5211 distributed at the gel interface to act as a thermal barrier. Sodium chloride (NaCl) in the hydrogel exhibited good thermal stability below 800 °C, resulting in minimal mass loss throughout the weight loss phase. Both hydrogels maintained almost constant weight 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 increased the residual yield from 6.51% to 13.91%. The catalytic carbonization ability of DMMP and the high heat resistance of the silicone wetting agent 5211 both contribute to increased residual yield and facilitate the formation of a heat-insulating layer on the surface of combustible materials.

[0112] Table 4. TGA data for A2 and C3 in air atmosphere

[0113]

[0114] Performance Test Summary

[0115] This application systematically studies the influence mechanisms of methylcellulose (MC), organosilicon wetting agent 5211, and flame retardant DMMP on the rheological behavior, temperature response, interfacial wetting, and thermal stability of a composite hydrogel system, revealing the synergistic effect mechanism and performance regulation mechanism of the components of the composite hydrogel. Based on various experimental analyses, the hydrogel combination with the optimal C3 mass ratio was selected. The main research conclusions are summarized as follows:

[0116] (1) Rheological behavior and viscosity regulation mechanism

[0117] 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, ultra-high viscosity (>1.6wt%) can lead to spray clogging, requiring a balance between adhesion and flowability. The system exhibits pseudoplastic fluid characteristics (power-law model fitting R²>0.98), with a significant shear thinning effect (n<1). Viscosity can be reduced during pipeline transport (shear rate>100s⁻¹), and high viscosity is restored upon reaching the target, meeting the flow-adhesion synergy requirements of fire extinguishing scenarios. The concentration threshold effect of wetting agent 5211: low concentrations of 5211 (<0.05%) enhance the network structure through physical entanglement, increasing viscosity; high concentrations (>0.3%) induce self-assembly and competitive adsorption of water molecules, weakening network integrity and causing a sharp drop in viscosity. 5211 also possesses wetting function, reducing shear resistance by increasing interchain spacing and optimizing spray performance.

[0118] (2) Surface wettability and thermal stability

[0119] Synergistic enhancement of wettability: 5211 significantly improves the wettability of released water (the contact angle of the C4 system drops to 0° within 40s), overcoming the hydrophobic limitation of the pure MC system (contact angle >120°), enabling rapid penetration of combustibles at high temperatures. Enhanced thermal degradation and flame retardancy: The composite hydrogel undergoes thermal degradation in three stages: water evaporation (25-150℃), polymer decomposition (150-350℃), and char layer stabilization (>350℃). 5211 delays heat transfer, DMMP catalyzes carbonization, synergistically increasing the residual yield to 13.91% (A2: 6.51%), forming a thermally insulating and oxygen-barrier layer.

[0120] (3) Overall performance and fire extinguishing application potential

[0121] Rheology-Thermal Response Synergistic Design: By controlling the concentration gradients of MC and 5211, a balance is achieved between shear-thinning flowability, high-temperature adhesion, and rapid phase change response. Multifunctional Integrated Advantages: The synergistic effect of DMMP flame retardancy and 5211 wetting modification enhances fire extinguishing efficiency. Combined with thermal stability and charcoal formation ability, it is suitable for complex fire environments. The optimal formulation range is 1.2-1.6wt% MC concentration and 0.05-0.3wt% 5211 concentration, balancing spraying efficiency and fire extinguishing performance.

[0122] The prepared composite hydrogel material was subjected to the following fire extinguishing tests:

[0123] Combustion System: A timber stack combustion test platform was constructed according to GB13875-2008 standard, with specifications of a Class 1A experimental reference model. The combustion material selected was pine strips with dimensions of 4cm×4cm×50cm. The pine wood was dried to maintain a moisture content of 10%~14% and a density of 0.45g / cm³. 3 ~0.55g / cm 3 The timber was stacked in 12 layers, with 6 timbers per layer, for a total of 72 timbers. The timbers were evenly spaced and stacked in layers to form a standard 1A timber stack measuring 50cm × 50cm × 48cm. To prevent the timber stack from collapsing due to excessive pressure from the spray gun, the edge timbers were secured with nails. A 40cm high and 10cm side tray containing 1.1L of kerosene (calorific value 45MJ / kg, similar to gasoline 44.2MJ / kg) was used to ignite the timber stack. A 40cm high metal support frame was selected for the combustion.

[0124] 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 water tank volume only needs to meet the extinguishing agent dosage requirements. A plunger-type high-pressure pump is used to provide pressure, and 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.

[0125] This section mainly focuses on the experimental verification of extinguishing Class 1A timber stack fires using self-made organosilicon MC composite hydrogel, water, and foam extinguishing agent. The test site was selected in a semi-enclosed space with a certain net height. A set of Class 1A timber stack fire extinguishing experiments were carried out using organosilicon MC composite hydrogel with a C3 mass ratio, water, and high-expansion Class A foam extinguishing agent (main components: foaming agent, flame retardant, stabilizer, anti-burning agent, and other substances). The amount of water used for extinguishing the fire was 6L, and the amount of organosilicon MC composite hydrogel and high-expansion Class A foam extinguishing agent used for preparation was also 6L. The experimental conditions are shown in Table 5.

[0126] The experimental steps are as follows: Based on the experimental model, construct the experimental system, determining the placement of the woodpile, the installation height of the thermocouples, and the location of the camera equipment. After assembling each system, check its normal operation, including the temperature feedback of the thermocouples and whether parameters such as the experimental pressure and flow rate of the spray system meet the requirements. Before starting the fire extinguishing test, pour water and kerosene into the oil pan as fuel, pre-burning for approximately 200 seconds. When the woodpile reaches a stable burning state (i.e., the thermocouple temperature reaches its maximum and remains stable without rising), extinguish the fire. After pre-burning, turn on the high-pressure plunger pump to release water, silicone MC composite hydrogel, and Class A foam extinguishing agent at the same spray rate, spraying from the front of the woodpile and then towards the top, bottom, and sides. The fire extinguishing is complete when a fixed amount of 6L of the three extinguishing agents has been sprayed. Process and analyze the temperature data and the flame morphology recorded by the camera, and extract relevant data such as extinguishing time and flame morphology involved in the fire extinguishing experiment. The performance of three fire extinguishing agents was compared and analyzed, covering aspects such as extinguishing time, average cooling rate, and resistance to reignition. Their effects on flame morphology and temperature changes during the extinguishing process were also investigated. If no open flame appeared within 10 minutes after the flame was extinguished, the extinguishing was considered successful; otherwise, it was considered a failure. If the woodpile collapsed during the extinguishing test, the experiment was considered invalid and repeated.

[0127] Table 5. Experimental Operating Conditions

[0128]

[0129] Flame morphology changes during pure water fire extinguishing process, such as Figure 17 As shown in Case 1, water exhibits low viscosity during fire extinguishing. Under the same pressure conditions, the water jet from the nozzle has a large impact force, rapidly impacting and suppressing the flames. Simultaneously, the water quickly accumulates at the bottom of the woodpile, dividing the flames into irregular shapes. With continuous spraying of pure water, the flame coverage area gradually shrinks and begins to move irregularly to both sides of the woodpile. Due to the weak adhesion of pure water to the surface of the woodpile, its rate of extinguishing open flames is slow and time-consuming. Experiments observed that 40 seconds after extinguishing, open flames were still burning inside the woodpile, indicating extinguishing failure and smoldering inside. The woodpile began to reignite 150 seconds after extinguishing, with the flames expanding and the amount of smoke generated increasing accordingly.

[0130] Flame morphology changes during the extinguishing process of Class A foam fire extinguishing agents, such as... Figure 17As shown in Case 2, when the extinguishing agent was sprayed onto the fire on the woodpile, the flames were rapidly suppressed. During this process, with continuous spraying of the extinguishing agent, the adhesion of the foam extinguishing agent to the surface of the woodpile improved. The resulting gas-liquid mixed foam layer not only cooled the fire source but also effectively isolated the oxygen supply, thus achieving a high extinguishing rate. Within 40 seconds of the start of extinguishing, the fire was essentially under control, with only a small amount of smoldering remaining inside the woodpile. With continuous spraying of the extinguishing agent, the flames wherever the foam extinguishing agent reached were rapidly suppressed, indicating its good fluidity and encapsulation effect. Finally, at 147 seconds into the extinguishing process, the flames on the woodpile were completely extinguished, and no reignition occurred.

[0131] Flame morphology changes during the fire extinguishing process of organosilicon MC composite hydrogel, such as Figure 17 As shown in Case 3, the composite hydrogel has a relatively higher viscosity than the other three extinguishing agents, resulting in a lower spray rate under the same pressure and a weaker initial impact on the woodpile fire. Due to its high viscosity, the flow rate into the ignition points inside the wood after spraying onto the surface is relatively slow. However, the composite hydrogel has strong adhesion, and its gel strength significantly increases after phase change, resulting in more significant cooling and oxygen-blocking effects. Twenty seconds after extinguishing the fire, the fire was significantly suppressed, and the surface flames were completely extinguished, with only residual ignition points inside the woodpile. With continued spraying of the extinguishing agent, the hydrogel absorbs heat and releases liquid, carrying highly permeable water and DMMP, further suppressing the flames inside the woodpile, successfully extinguishing the fire at 126 seconds.

[0132] Table 6. Flame area changes under different fire extinguishing conditions.

[0133]

[0134] Table 7 shows the data. Comparing the temperature curves during the extinguishing process of the three extinguishing agents reveals differences in their extinguishing efficiency, 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, cannot remain on the surface of the woodpile to absorb heat, resulting in a longer extinguishing time and an average cooling rate of only 3.74°C / s, leading to relatively low extinguishing efficiency. Class A foam extinguishing agent, composed of foaming agents, flame retardants, stabilizers, and anti-burning agents, exhibits excellent foam performance and can form a foam barrier layer on the wood surface. Under the same experimental conditions, it has a faster extinguishing rate, but its foam cannot maintain stability and is prone to defoaming under the high temperature conditions inside the woodpile, resulting in an extinguishing time of 147 seconds. However, its average cooling rate is better than that of water extinguishing agent, at 5.12°C / s. Organosilicon MC composite hydrogel exhibits unique advantages; when sprayed onto the woodpile, it can adhere tightly to the surface of the woodpile, achieving effective cooling. Furthermore, the strength of the hydrogel is further enhanced when it comes into contact with a high-temperature fire source, thereby exerting an oxygen-barrier suffocation effect. The highly wettable water and flame retardant encapsulated inside the hydrogel also play a role in chemical inhibition. The organosilicon MC composite hydrogel has high fire extinguishing efficiency, with a fire extinguishing time of 126 seconds and an average cooling rate of 6.13°C / s, which is superior to other fire extinguishing agents. Under the same experimental conditions, the fire extinguishing efficiency is significantly improved.

[0135] Table 7 Extinguishing efficacy of different extinguishing agents

[0136]

[0137] Summary of fire extinguishing experiment test

[0138] This application investigates the fire extinguishing effect of a C3 mass ratio (MC:5211:DMMP:NaCl:water = 1.2:0.3:2.0:2.0:94.5) composite hydrogel with good rheological properties and thermal stability through a 1A woodpile fire experiment. Fire extinguishing experiments under the same conditions were conducted for comparative verification using water and Class A foam extinguishing agents. Through fire extinguishing experiments under three different conditions, flame and temperature data were used to reveal the synergistic mechanism and dynamic fire extinguishing regulation mechanism of the composite hydrogel components. Based on the analysis of the fire extinguishing efficiency of the three extinguishing agents, the main research conclusions are summarized as follows:

[0139] (1) The burning of a woodpile is a typical decomposition combustion process. The results of three sets of experimental conditions show that when the woodpile is in a burning state, its internal temperature is often the highest. Even if the open flame on the surface is extinguished, the internal temperature is still high, and smoldering occurs. As the moisture gradually evaporates and the heat continues to accumulate, the woodpile becomes susceptible to reignition.

[0140] (2) When using pure water to extinguish a fire, the flames are quickly suppressed and the water is piled up below the woodpile. However, due to the weak adhesion of water to the surface of the woodpile, the rate of extinguishing the open flames is slow, and the woodpile does not cool down completely and reignites 150 seconds after extinguishing the fire. When using Class A foam extinguishing agents, the flames are quickly suppressed. The foam extinguishing agents exhibit wetting ability on the surface of the woodpile, and the gas-liquid mixed foam covering layer formed by the foam can effectively play a cooling role and can isolate oxygen, thereby achieving the purpose of suppressing the fire. The extinguishing rate is relatively high, and the woodpile is extinguished in 147 seconds. Organosilicon MC composite hydrogel has the highest viscosity among the three and a smaller spray rate under the same pressure. The composite hydrogel has strong adhesion ability, and the gel strength is greater after phase change. It has significant cooling and oxygen-blocking effects, and the extinguishing time of the woodpile is 126 seconds, which is the fastest among the three extinguishing agents.

[0141] (3) In the initial stage of fire extinguishing, the temperatures of thermocouples #4 to #7, located far from the center of the woodpile, all showed a rapid downward trend, while the temperatures of thermocouples #2 and #3 in the center of the woodpile remained stable. The temperature of thermocouple #1 steadily decreased after the fuel in the oil pan burned out. Water extinguishing agent has high fluidity and cannot effectively stay on the surface of the woodpile to absorb heat, resulting in a low average cooling rate of 3.74°C / s, eventually leading to reignition. Class A foam extinguishing agent is composed of multiple substances, has excellent foam performance, and a fast extinguishing rate, but the foam is prone to defoaming at high temperatures, with an average cooling rate of 5.12°C / s, which is better than water extinguishing agent. When organosilicon MC composite hydrogel is sprayed onto the woodpile, it has strong adhesion, cools and de-escalates the surface, isolates oxygen and suffocates, and the internal highly wetted water and flame retardant play a chemical inhibitory role, resulting in high extinguishing efficiency and the best average cooling rate of 6.13°C / s.

[0142] Experimental results show that the organosilicon MC composite hydrogel fire extinguishing agent developed in this application has high fire extinguishing efficiency and anti-reignition performance, and its average cooling rate and extinguishing time are superior to water and Class A foam fire extinguishing agents. The experimental results indicate that the organosilicon MC composite hydrogel fire extinguishing agent is a highly efficient fire extinguishing agent with broad application prospects.

[0143] The above description provides one or more embodiments in conjunction with specific content, and does not imply that the specific implementation of the present invention is limited to these descriptions. Any methods or structures that are similar to or identical to those of the present invention, or any technical deductions or substitutions made based on the concept of the present invention, should be considered within the scope of protection of the present invention.

Claims

1. A forest fire-resistant material based on organosilicon MC composite hydrogel, characterized in that: It includes the following raw materials by weight: 0.05-0.3 wt% silicone wetting agent, 1.2-1.6 wt% methylcellulose, 1.8-2.5 wt% flame retardant, 1.8-2.3 wt% ionic crosslinking agent, and the balance being water; The organosilicon wetting agent is a trisiloxane wetting agent or a polyether-modified polysiloxane wetting agent; The flame retardant is dimethyl methylphosphonate.

2. The forest fire-resistant material based on organosilicon MC composite hydrogel according to claim 1, characterized in that: The trisiloxane wetting agent is model 5211.

3. The forest fire-resistant material based on organosilicon MC composite hydrogel according to claim 2, characterized in that: The critical micelle concentration (CMC) of 5211 is 0.01 wt%, and the critical surface tension (γCMC) is 19.7 mN / m.

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

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

6. A method for preparing a forest fire-resistant material based on organosilicon MC composite hydrogel according to any one of claims 1-5, characterized in that: Includes the following steps: S1. Take methylcellulose, flame retardant, organosilicon wetting agent and ionic crosslinking agent according to the mass fraction ratio; S2. Mix the above materials with deionized water using a one-pot method, stir until hydrated, and then let stand at room temperature to allow them to fully swell and crosslink. S3. Stir the swollen hydrogel at high speed to disperse it into a uniform sol state, and let it stand at room temperature to defoam.

7. The method for preparing forest fire-resistant materials based on organosilicon MC composite hydrogel according to claim 6, characterized in that: In step S2, the deionized water is heated to 68-75 ℃ during mixing, and the swelling and cross-linking standing time is 5-8 h.

8. The method for preparing forest fire-resistant materials based on organosilicon MC composite hydrogel according to claim 6, characterized in that: In step S3, a high-speed disperser is used to stir at 4800-5500 r / min, and the defoaming and standing time is 20-30h.

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