GO-coated LNS / phosphorylated cellulose fibril composite flame-retardant film, preparation method and application

Abstract

The invention discloses a GO-coated LNS / phosphorylated cellulose fibril composite flame-retardant film as well as a preparation method and application thereof. The film is mainly formed by compounding lignin, graphene oxide and phosphorylated cellulose nanofibril. The preparation method comprises the following specific preparation steps: (1) dropwise adding an aqueous solution of graphene oxide into a mixed solution of lignin and tetrahydrofuran, and stirring to obtain an aqueous solution of GO-coated LNS; (2) adding a phosphorylated cellulose nanofibril prepared aqueous solution into the GO-coated LNS aqueous solution prepared in the step (1) to obtain a GO-coated LNS / PCNF mixed solution; (3) exhausting bubbles and drying to obtain a GO-coated LNS / phosphorylated cellulose filament composite flame-retardant film attached to the inner wall of the container; the film obtained by the scheme of the invention has the advantage of improving the mechanical property and flame retardant property of the composite material.

Description

Technical Field

[0001] This application relates to the technical field of polymer materials, specifically to a GO@LNS / phosphorylated cellulose filament composite flame retardant film, its preparation method, and its application. Background Technology

[0002] With increasing societal demands for material safety, the research and application of flame-retardant materials has become a crucial direction in the field of polymer materials. While traditional flame-retardant materials can meet fire protection requirements to some extent, they often suffer from insufficient mechanical properties, poor thermal stability, and unsatisfactory environmental friendliness. Therefore, developing a novel composite material that combines excellent flame-retardant properties, mechanical properties, and environmental friendliness is of significant practical importance.

[0003] Graphene oxide (GO), a two-dimensional nanomaterial, has attracted widespread attention in the field of composite materials due to its excellent mechanical properties, thermal stability, and flame retardant properties. However, single graphene oxide materials suffer from poor dispersibility and high cost in practical applications, limiting their further application. Lignin (LNS), a natural polymer material, is widely available, inexpensive, and environmentally friendly. Its molecular structure contains abundant aromatic rings and hydroxyl groups, which can form strong interactions with graphene oxide, thereby improving the performance of composite materials. Phosphorylated cellulose nanofibers (PCNF) are nanomaterials with high specific surface area, excellent mechanical properties, and flame retardant properties, but they suffer from insufficient thermal stability when used alone.

[0004] In recent years, researchers have attempted to combine graphene oxide, lignin, and cellulose nanofibers to develop high-performance flame-retardant composite materials. However, existing technologies still face the following challenges: first, the interfacial compatibility between graphene oxide and cellulose nanofibers is poor, resulting in limited improvement in the mechanical properties of the composite materials; second, the flame-retardant properties and thermal stability of the composite materials still need further improvement; and third, there is a lack of research combining flame-retardant materials with fire warning functions, making it difficult to meet the practical needs for intelligent fire-resistant materials. Summary of the Invention

[0005] To address the aforementioned shortcomings of the prior art, this application provides a GO@LNS / phosphorylated cellulose filament composite flame-retardant film that improves the interfacial compatibility between graphene oxide and phosphorylated cellulose nanofibers by introducing lignin, while simultaneously enhancing the mechanical and flame-retardant properties of the composite material by utilizing the nano-reinforcing effect of graphene oxide.

[0006] To solve the above-mentioned technical problems, the technical solution adopted in this application is: a GO@LNS / phosphorylated cellulose filament composite flame retardant film, which is mainly composed of lignin, graphene oxide and phosphorylated cellulose nanofibers.

[0007] This application also provides a method for preparing the above-mentioned GO@LNS / phosphorylated cellulose filament composite flame retardant film, the specific steps of which include: (1) Add the aqueous solution of graphene oxide to a mixed solution of lignin and tetrahydrofuran, stir, and obtain an aqueous solution of GO@LNS; (2) Add the aqueous solution of phosphorylated cellulose nanofibers to the GO@LNS aqueous solution prepared in step (1) to obtain a GO@LNS / PCNF mixture; (3) Remove the air bubbles and dry to obtain a GO@LNS / phosphocellulose fiber composite flame retardant film adhering to the inner wall of the container.

[0008] Furthermore, the mass ratio of lignin to graphene oxide in step (1) is 0.25-4:1.

[0009] Furthermore, in step (1), the aqueous solution of graphene oxide is dripped in using a micro-injection pump, with the dripping standard of the micro-injection pump being in the range of 150ul / min-200ul / min.

[0010] Furthermore, in step (2), the concentration of the aqueous solution of phosphorylated cellulose nanofibers is 0.1-5 mg / mL (where "0.1-5 mg / mL" refers to the mass concentration of phosphorylated cellulose nanofibers in water in the aqueous solution of phosphorylated cellulose nanofibers).

[0011] Furthermore, in step (2), the mass ratio of solid solute in the aqueous solution of phosphorylated cellulose nanofibers and the aqueous solution of GO@LNS is 20%-50% (i.e., the mass ratio of solid solute in the two aqueous solutions).

[0012] Furthermore, the preparation of phosphorylated cellulose nanofibers in step (2) is as follows: bamboo powder is chemically pretreated with a phosphorylation reagent and then mechanically ground to obtain cellulose nanofibers.

[0013] Furthermore, the preparation of phosphorylated cellulose nanofibers in step (2) is more specifically carried out as follows: First, bamboo powder is soaked in deionized water to wash away soluble impurities, and then dried to remove excess water; after the bamboo powder reaches constant weight, it is placed in deionized water for dispersion and soaking; then, urea and phosphorylation reagent are added to the suspension and mechanically stirred to dissolve them completely, and then the suspension is dried; after the mixture of phosphorylation reagent and bamboo powder reaches constant weight, it is subjected to high-temperature curing treatment; the bamboo powder after high-temperature curing treatment is thoroughly washed with deionized water until neutral, and the washed bamboo powder is mixed with deionized water to form a suspension, which is then ground to obtain a uniform aqueous solution of phosphorylated cellulose nanofibers.

[0014] Furthermore, the phosphorylation reagent is at least one of potassium dihydrogen phosphate, sodium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0015] Furthermore, the amount of urea and phosphorylation reagent added is 5-6 times the mass of bamboo powder, and the mass ratio of urea to phosphorylation reagent is 1-3:1.

[0016] Furthermore, the high-temperature curing temperature is 130-170℃, and the time is 20-40 minutes.

[0017] Furthermore, the mass concentration of the bamboo powder after high-temperature curing and washing in the suspension water is 0.6-1.0wt%; when using, take a portion of the suspension containing bamboo powder (i.e., the phosphorylated cellulose nanofiber aqueous solution prepared above) and mix it with water to prepare a phosphorylated cellulose nanofiber aqueous solution with a concentration of 0.1-5mg / mL for use, i.e., the phosphorylated cellulose nanofiber aqueous solution used in step (2).

[0018] This application also provides an application of the GO@LNS / phosphocellulose filament composite flame-retardant film prepared by the above method in a fire early warning device.

[0019] Furthermore, the fire warning device includes a low-voltage power supply, the aforementioned GO@LNS / phosphocellulose fiber composite flame-retardant film, and an alarm light. The low-voltage power supply, the GO@LNS / phosphocellulose fiber composite flame-retardant film, and the alarm light are sequentially connected by wires to form a closed circuit.

[0020] Furthermore, the fire warning device is equipped with a fire source simulator at the location corresponding to the GO@LNS / phosphocellulose fiber composite flame retardant film.

[0021] The advantages and beneficial effects of this application are as follows: 1. The composite film of this application uses lignin (LNS) as the raw material, which contains abundant aromatic rings and hydroxyl groups in its molecular structure, enabling it to form strong interactions with graphene oxide, thereby improving the performance of the composite material. Simultaneously, phosphorylated cellulose nanofibers are prepared through a combination of chemical pretreatment and mechanical grinding, possessing advantages such as abundant active groups, good water dispersibility, and high aspect ratio. Introducing these nanofibers into the GO@LNS system as nano-reinforcements allows them to form strong interactions with the GO@LNS molecular chains through chemical covalent bonds and physical interactions, thereby enhancing the film's network structure. Experimental results show that the mechanical properties of the obtained GO@LNS / phosphorylated cellulose filament composite flame-retardant film are significantly improved, confirming the reinforcing effect of phosphorylated cellulose nanofibers. Furthermore, the prepared GO@LNS / phosphorylated cellulose filament composite film not only exhibits excellent flame-retardant properties but also maintains its skeletal structure in high-temperature or flame environments, thus achieving a continuous alarm function.

[0022] 2. In the process of adding the graphene oxide aqueous solution, this application uses a micro-injection pump with a dropping rate in the range of 150ul / min-200ul / min. Using this type of micro-injection pump can achieve a slow dropping state of the graphene oxide aqueous solution, thereby allowing lignin to be more uniformly dispersed in the graphene oxide aqueous solution, improving the uniformity and dispersion of the materials.

[0023] 3. The raw material used in this application for preparing phosphorylated cellulose filaments is bamboo powder. The reasons for using this raw material are as follows: Firstly, bamboo powder is obtained from the processing waste of bamboo products through a sieve, and it is inexpensive and readily available; secondly, the cellulose nanofibers prepared from bamboo powder have the advantages of high aspect ratio, high mechanical strength, high specific surface area, high hydrophilicity, and controllable performance.

[0024] 4. The preparation method of this application has the characteristics of simple and efficient preparation process, controllable reaction process, and green and environmentally friendly product. Moreover, the entire preparation process has no waste discharge, which is in line with the concept of green environmental protection. In summary, the GO@LNS / phosphocellulose fiber composite flame retardant film prepared by this application not only has excellent mechanical properties, but also has excellent flame retardant properties and fire warning function, which is suitable for market promotion and application.

[0025] 5. The GO@LNS / phosphocellulose filament composite flame-retardant film prepared by this process is used in a fire warning simulation device. When a flame approaches and contacts the film prepared in Example 1, the bulb rapidly emits a bright signal within one second, completing the fire warning, and the bright signal remains lit for 30 seconds. This phenomenon is due to the rapid reduction of graphene oxide in the composite film to highly conductive graphene under the action of flame, thereby forming a conductive path, causing the bulb to emit a strong alarm signal and realizing the fire warning function. At the same time, this result further verifies that the composite film has excellent flame-retardant properties and can maintain its stable skeleton structure in a flame environment, ensuring the realization of the continuous alarm function. Attached Figure Description

[0026] Figure 1 A macroscopic digital photograph of the GO@LNS / phosphorylated cellulose filament composite film prepared in Example 1.

[0027] Figure 2 The stress-strain curves are for the composite films prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0028] Figure 3 Comparative experimental photographs of the combustion process of the composite films prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0029] Figure 4 This is a digital photograph of the GO@LNS / phosphocellulose fiber composite film prepared in Example 1 when it is exposed to fire in a simulated fire warning.

[0030] Figure 5 A schematic diagram of the structure of a simulation device that applies the fire warning function of the thin film prepared in Example 1 of this application.

[0031] As shown in the attached diagram: 1. Low-voltage power supply; 2. GO@LNS / phosphocellulose filament composite flame-retardant film; 3. Alarm light; 4. Fire source simulator. Detailed Implementation

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the technical solutions of this application will be described in detail below with reference to the embodiments and accompanying drawings; wherein the technical solutions in the embodiments of this application are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments; based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application; the warning devices corresponding to the accompanying drawings are also described in detail. Obviously, the accompanying drawings described below are only one embodiment of this application. For those of ordinary skill in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0033] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0034] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0035] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0036] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0037] To better understand this application, the following embodiments are provided for further detailed explanation of this application, but they should not be construed as limiting this application. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of this application.

[0038] The phosphorylated cellulose nanofibers used in the following examples of this application are prepared through the following steps: First, commercially available bamboo powder is soaked in deionized water to remove soluble impurities. Then, it is filtered and dried in a forced-air oven to remove excess moisture. After the bamboo powder reaches a constant weight, it is dispersed and soaked in deionized water to obtain a suspension. Next, urea and a phosphorylation reagent are added to the suspension. Specifically, the amount of bamboo powder is 10-12g, and the amount of urea and phosphorylation reagent added is 5-6 times the mass of the bamboo powder. The ratio of urea to phosphorylation reagent is generally 2:1. Then, it is mechanically stirred to ensure complete dissolution. The suspension is then dried in a forced-air oven. After the mixture reaches a constant weight, it undergoes high-temperature curing treatment at 150℃ for 30 minutes. The treated bamboo powder is thoroughly washed with deionized water until neutral, and the washed bamboo powder is then mixed with deionized water to prepare a suspension. At this point, the mass concentration of bamboo powder in the suspension is 0.8%. Finally, the solution was ground using an ultrafine pulverizer to obtain a uniform aqueous solution of phosphorylated cellulose nanofibers (PCNF aqueous solution). Example 1

[0039] (1) First, weigh 50 mg of LNS (lignin) powder, add 100 ml of tetrahydrofuran and mix with magnetic stirring, then place in a fume hood; then weigh 50 mg of GO (graphene oxide) at a mass ratio of 1:1 and prepare an aqueous solution with a concentration of 0.5 mg / mL in a container. Then, add the graphene oxide aqueous solution dropwise into the lignin and tetrahydrofuran mixed solution through a micro-injection pump, stir for 24 h, and then sonicate for 5 min to obtain GO@LNS aqueous solution; (2) Take the ground PCNF and prepare an aqueous solution with a concentration of 5 mg / ml. The PCNF is added at 50% of the mass of the GO@LNS aqueous solution (the PCNF is added at 50% of the mass of GO@LNS in the GO@LNS aqueous solution). Then, stir magnetically for 40 min-60 min to make it fully dispersed and uniform, and then dispersed by ultrasonication. (3) Then remove the air bubbles 2-3 times in the vacuum drying oven to remove all air bubbles from the solution; (4) Finally, the treated solution was placed in a petri dish and placed in a vacuum oven at 40°C for 48 hours to dry and obtain the GO@LNS / phosphocellulose fiber composite film. The GO@LNS / phosphocellulose fiber composite film is bendable and can maintain its original mechanical properties. When placed in a simulated fire warning device, the bulb brightens and remains lit when a flame approaches. Example 2

[0040] First, weigh 40 mg of LNS powder, add 100 ml of tetrahydrofuran and mix with magnetic stirring. Place the mixture in a fume hood. Then, weigh 40 mg of GO at a mass ratio of 1:1 and prepare an aqueous solution with a concentration of 0.4 mg / mL in a container. Add the solution to the lignin and tetrahydrofuran mixture dropwise using a micro-injection pump. After stirring for 24 h, disperse the solution by ultrasonication for 5 min to obtain the GO@LNS aqueous solution. Next, take the ground PCNF and prepare an aqueous solution with a concentration of 4 mg / ml. The PCNF is added at 40% of the mass of GO@LNS. Stir magnetically for 40-60 minutes to ensure that it is fully dispersed and uniform, and then dispersed by ultrasonication. Then, remove the air bubbles 2-3 times in a vacuum drying oven to remove all air bubbles from the solution; Finally, the treated solution was placed in a petri dish and dried in a vacuum oven at 50°C for 40 hours to obtain the GO@LNS / phosphocellulose filament composite film. The GO@LNS / phosphocellulose filament composite film is bendable and retains its original mechanical properties. When placed in a simulated fire warning device, the bulb brightens and remains lit when a flame approaches. Example 3

[0041] First, weigh 30 mg of LNS powder, add 100 ml of tetrahydrofuran and mix with magnetic stirring. Place the mixture in a fume hood. Then, weigh 30 mg of GO at a mass ratio of 1:1 and prepare an aqueous solution with a concentration of 0.3 mg / mL in a container. Add the solution to the lignin and tetrahydrofuran mixture using a micro-injection pump. After stirring for 24 h, disperse the solution by ultrasonication for 5 min to obtain the GO@LNS aqueous solution. Next, take the ground PCNF and prepare an aqueous solution with a concentration of 3 mg / ml. The PCNF is added at 30% of the mass of GO@LNS. Stir magnetically for 40-60 minutes to ensure that it is fully dispersed and uniform, and then dispersed by ultrasonication. Then, remove the air bubbles 2-3 times in a vacuum drying oven to remove all air bubbles from the solution; Finally, the treated solution was placed in a petri dish and dried in a vacuum oven at 45°C for 72 hours to obtain the GO@LNS / phosphocellulose filament composite film. The GO@LNS / phosphocellulose filament composite film is bendable and retains its original mechanical properties. When placed in a simulated fire warning device, the bulb brightens and remains lit when a flame approaches. Example 4

[0042] First, weigh 45 mg of LNS powder, add 100 ml of tetrahydrofuran and mix with magnetic stirring. Place the mixture in a fume hood. Then, weigh the same amount of 45 mg of GO at a mass ratio of 1:1 and prepare an aqueous solution with a concentration of 0.4 mg / mL in a container. Add the solution to the lignin and tetrahydrofuran mixture dropwise using a micro-injection pump. After stirring for 24 h, disperse the solution by ultrasonication for 5 min to obtain the GO@LNS aqueous solution. Next, take the ground PCNF and prepare an aqueous solution with a concentration of 5 mg / ml. The PCNF is added at 20% of the mass of GO@LNS. Stir magnetically for 40-60 minutes to ensure that it is fully dispersed and uniform, and then dispersed by ultrasonication. Then, remove the air bubbles 2-3 times in a vacuum drying oven to remove all air bubbles from the solution; Finally, the treated solution was placed in a petri dish and dried in a vacuum oven at 40°C for 64 hours to obtain the GO@LNS / phosphocellulose filament composite film. The GO@LNS / phosphocellulose filament composite film is bendable and retains its original mechanical properties. When placed in a simulated fire warning device, the bulb brightens and remains lit when a flame approaches.

[0043] To further illustrate the superior performance of the GO@LNS / phosphocellulose filament composite flame-retardant film intended to be protected in this application, the following comparative experiments were conducted. Comparative Example 1

[0044] First, 50 mg of LNS powder was weighed and mixed with 100 ml of tetrahydrofuran using magnetic stirring. The mixture was placed in a fume hood. Then, 50 mg of GO (Glycol of Oxide) was weighed in a 1:1 ratio and dissolved in a 0.5 mg / mL aqueous solution. This solution was then added dropwise to the LNS / Tetrahydrofuran mixture using a micro-injection pump. After stirring for 24 hours, the solution was ultrasonically dispersed for 5 minutes to obtain a GO@LNS aqueous solution. The solution was then degassed 2-3 times in a vacuum drying oven to remove all air bubbles. Finally, the treated solution was placed in a petri dish and dried in a 45°C vacuum oven for 24 hours to obtain a GO@LNS film. The GO@LNS film exhibited poor bending resistance and failed to maintain its original mechanical properties after bending. When placed in a simulated fire warning device, the bulb brightened upon approaching a flame but the effect was short-lived. Comparative Example 2

[0045] First, weigh out the ground PCNF to prepare an aqueous solution with a concentration of 0.5 mg / ml. Take 125 ml of the PCNF aqueous solution and magnetically stir for 40-60 minutes to ensure thorough and uniform dispersion, followed by ultrasonic dispersion. Then, remove air bubbles 2-3 times in a vacuum drying oven to eliminate all air bubbles from the solution. Finally, place the treated solution in a petri dish and put it in a vacuum oven at 45°C for 48 hours to dry, obtaining a phosphorylated cellulose fiber film. The phosphorylated cellulose fiber composite film is flexible and retains its original mechanical properties. When placed in a simulated fire warning device, the bulb fails to light up when a flame approaches.

[0046] See appendix Figure 1 This is a digital photograph of the GO@LNS / phosphocellulose filament composite flame-retardant film prepared in Example 1 of this application. Figure 1 It is evident that the product prepared in Example 1 is bendable and exhibits no mechanical damage during bending. This demonstrates that the GO@LNS / phosphocellulose filament composite flame-retardant film prepared by the process of this application possesses excellent flexibility and deformation capabilities, further confirming its outstanding mechanical properties.

[0047] See appendix Figure 2 These are the stress-strain curves of the thin films prepared in Example 1, Comparative Examples 1 and 2 of this application. Figure 2 As can be seen, compared with Comparative Example 1 and Comparative Example 2, the film prepared in Example 1 of this application has excellent mechanical properties. Its tensile strength and elongation at break are both greater than those of the comparative examples. This further illustrates that by introducing lignin to improve the interfacial compatibility between graphene oxide and phosphorylated cellulose nanofibers, the interaction between graphene oxide and phosphorylated cellulose nanofibers is strengthened. Combined with the nano-reinforcing effect of graphene oxide, the mechanical properties of the composite film are further improved.

[0048] See appendix Figure 3These are comparative experimental photographs of the combustion processes of the composite films prepared in Example 1, Comparative Example 1, and Comparative Example 2. A comparison of the combustion test results of Comparative Example 1, Comparative Example 2, and Example 1 reveals that: the GO@LNS film in Comparative Example 1 began to burn immediately after contact with the flame and burned out rapidly; the PCNF film in Comparative Example 2 began to burn after contact with the flame for 3 seconds. Although it maintained a certain degree of structural stability and integrity during combustion, it was accompanied by a noticeable flame, and its network skeleton underwent significant thermal decomposition and shrinkage after being removed from the flame; in contrast, the GO@LNS film in Example 1 of this application… The @LNS / phosphocellulose filament composite flame-retardant film exhibits excellent flame-retardant properties. Under continuous exposure to an alcohol lamp flame for one minute, no flame spread was observed, and the film self-extinguished after being removed from the flame, maintaining its good morphology without significant damage. This superior performance is attributed to the synergistic flame-retardant effect of the introduction of GO@LNS into the composite film and the formation of phosphorus-containing groups, which further protects the polymer skeleton, resulting in no obvious flame generation during combustion. This characteristic is of great significance in practical applications for suppressing flame spread. Furthermore, the composite film maintains its skeletal structure in a flame environment, thus achieving a continuous alarm function.

[0049] See appendix Figure 4 , Figure 5 This is a simulation device for the fire early warning function of the GO@LNS / phosphocellulose fiber composite flame-retardant film prepared in Example 1, during the simulation alarm process. The fire early warning device includes a low-voltage power supply 1, the aforementioned GO@LNS / phosphocellulose fiber composite flame-retardant film 2, and an alarm light 3. The low-voltage power supply 1 (within the safe voltage range for the human body), the GO@LNS / phosphocellulose fiber composite flame-retardant film 2, and the alarm light 3 are sequentially connected by wires to form a closed circuit. A fire source simulator 4 is installed at a corresponding position on the GO@LNS / phosphocellulose fiber composite flame-retardant film. Specifically, the fire source simulator can use an alcohol lamp to obtain other fire sources to simulate flames. Figure 4 As can be seen, when the flame approaches and contacts the film prepared in Example 1, the bulb rapidly emits a bright signal within one second, completing the fire warning, and the bright signal continues to burn for 30 seconds. This phenomenon is due to the rapid reduction of graphene oxide in the composite film to highly conductive graphene under the action of the flame, thereby forming a conductive path, causing the bulb to emit a strong alarm signal and realizing the fire warning function. At the same time, this result further verifies that the composite film has excellent flame-retardant properties and can maintain its stable skeleton structure in a flame environment, ensuring the realization of the continuous alarm function.

[0050] The above description of the disclosed embodiments and comparative examples enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A GO@LNS / phosphocellulose filament composite flame-retardant film, characterized in that: The film is mainly composed of lignin, graphene oxide and phosphorylated cellulose nanofibers.

2. A method for preparing a GO@LNS / phosphocellulose filament composite flame-retardant film, characterized in that: The specific steps of this method include: (1) Add the aqueous solution of graphene oxide to a mixed solution of lignin and tetrahydrofuran, stir, and obtain an aqueous solution of GO@LNS; (2) Add the aqueous solution of phosphorylated cellulose nanofibers to the GO@LNS aqueous solution prepared in step (1) to obtain a GO@LNS / PCNF mixture; (3) Remove the air bubbles and dry to obtain a GO@LNS / phosphocellulose fiber composite flame retardant film adhering to the inner wall of the container.

3. The method for preparing the GO@LNS / phosphocellulose filament composite flame-retardant film according to claim 2, characterized in that: The mass ratio of lignin to graphene oxide in step (1) is 0.25-4:

1.

4. The method for preparing the GO@LNS / phosphocellulose filament composite flame-retardant film according to claim 2, characterized in that: The aqueous solution of graphene oxide mentioned in step (1) is added by dripping using a micro-injection pump. The standard dripping rate of the micro-injection pump is in the range of 150ul / min-200ul / min.

5. The method for preparing the GO@LNS / phosphocellulose filament composite flame-retardant film according to claim 2, characterized in that: Step (2) The concentration of the aqueous solution of phosphorylated cellulose nanofibers is 0.1-5 mg / mL; the mass ratio of solid solute in the aqueous solution of phosphorylated cellulose nanofibers and the aqueous solution of GO@LNS is 20%-50%.

6. The method for preparing the GO@LNS / phosphocellulose filament composite flame-retardant film according to claim 2, characterized in that: The preparation of the aqueous solution of phosphorylated cellulose nanofibers in step (2) is as follows: bamboo powder is chemically pretreated with a phosphorylation reagent and then mechanically ground to prepare cellulose nanofibers.

7. The method for preparing the GO@LNS / phosphocellulose filament composite flame-retardant film according to claim 6, characterized in that: The preparation of the phosphorylated cellulose nanofibers is more specifically carried out as follows: First, bamboo powder is soaked in deionized water to wash away soluble impurities, and then dried to remove excess water; after the bamboo powder reaches a constant weight, it is placed in deionized water for dispersion and soaking; next, urea and phosphorylation reagent are added to the suspension and mechanically stirred to dissolve them completely, and then the suspension is dried; after the mixture of phosphorylation reagent and bamboo powder reaches a constant weight, it is subjected to high-temperature curing treatment; the bamboo powder after high-temperature curing treatment is thoroughly washed with deionized water until neutral, and the washed bamboo powder is mixed with deionized water to form a suspension, which is then ground to obtain a uniform aqueous solution of phosphorylated cellulose nanofibers.

8. The method for preparing the GO@LNS / phosphocellulose filament composite flame-retardant film according to claim 7, characterized in that: The phosphorylation reagent is at least one of potassium dihydrogen phosphate, sodium dihydrogen phosphate, and diammonium hydrogen phosphate.

9. The method for preparing the GO@LNS / phosphocellulose filament composite flame-retardant film according to claim 7, characterized in that: The amount of urea and phosphorylation reagent added is 5-6 times the mass of bamboo powder, and the mass ratio of urea to phosphorylation reagent is 1-3:

1.

10. The method for preparing the GO@LNS / phosphorylated cellulose filament composite flame-retardant film according to claim 7, characterized in that: The high-temperature curing temperature is 130-170℃, and the time is 20-40 minutes.

11. The method for preparing the GO@LNS / phosphocellulose filament composite flame-retardant film according to claim 7, characterized in that: The mass concentration of the bamboo powder after high-temperature curing and washing in the suspension water is 0.6-1.0 wt%.

12. The application of the GO@LNS / phosphocellulose filament composite flame-retardant film according to claim 1 in a fire early warning device.

13. The application according to claim 12, characterized in that: The fire warning device includes a low-voltage power supply, the aforementioned GO@LNS / phosphocellulose fiber composite flame-retardant film, and an alarm light. The low-voltage power supply, the GO@LNS / phosphocellulose fiber composite flame-retardant film, and the alarm light are sequentially connected by wires to form a closed circuit.

14. The application according to claim 12, characterized in that: The fire warning device is equipped with a fire source simulator corresponding to the GO@LNS / phosphocellulose fiber composite flame retardant film.

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