Preparation method and application of flame-retardant graphene oxide composite film with sensitive fire warning function

Abstract

The application belongs to the technical field of flame-retardant materials, and more particularly relates to a preparation method and application of a flame-retardant graphene oxide composite film with a sensitive fire early warning function. The flame-retardant graphene oxide composite film is obtained by uniformly mixing graphene oxide, tannic acid and cyclotriphosphazene flame retardant at a certain ratio, and then vacuum drying at room temperature. The flame-retardant graphene oxide composite film provided by the application has multiple chemical bond effects, excellent film forming performance and flexibility. Due to the synergistic flame-retardant effect of the cyclotriphosphazene flame retardant and the tannic acid, the integrity of the composite film skeleton structure is effectively maintained at high temperature or in a flame, and the response speed and continuous response time of the fire early warning / detection are greatly improved. The preparation process of the flame-retardant graphene oxide composite film provided by the application is simple, the operation conditions are mild, the energy consumption is low, the process is green and environmentally friendly, and the flame-retardant graphene oxide composite film is suitable for large-scale production and popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials technology, and more specifically relates to the preparation method and application of a flame retardant graphene oxide composite film with sensitive fire early warning function. Background Technology

[0002] Flammable lightweight materials widely used in daily life and production environments, such as plastics, rubber, wood, and textiles, are key factors in the ignition and rapid spread of fires. Therefore, sensitive monitoring and early warning of these materials in the early stages of a fire are of great scientific significance and immense practical value.

[0003] Highly sensitive early warning systems for fires are one of the most effective ways to improve the fire safety of flammable lightweight materials. Traditional fire alarms based on smoke and infrared thermal imaging detect fire characteristic parameters such as smoke concentration and ambient temperature in the target area. When the detected concentration exceeds the sensor's threshold, a fire alarm is triggered. However, traditional fire alarms are relatively large and are typically installed on ceilings or walls far from the fire source. They suffer from poor penetration, slow response speed (>100s), and insufficient response time, often leading to missed opportunities for fire extinguishing and escape. In recent years, with the development of science and technology and the widespread application of new materials, fire detection technology has entered a new stage of development, and research on new fire alarm systems has become a hot topic.

[0004] Graphene oxide is a layered nanomaterial that can be rapidly reduced to highly conductive reduced graphene oxide (rGO) when heated to high temperatures, thus improving its thermal conductivity and making it a potential application in fire warning sensors. However, fire warning materials prepared from pure graphene oxide have poor mechanical properties, low thermal stability, and are easily combustible, resulting in short fire warning durations. Therefore, improving the sensitivity and stability of graphene oxide-based fire warning devices is a pressing issue that needs to be addressed.

[0005] Chinese patent application CN 109021983 B discloses a method for preparing a modified graphene oxide flame-retardant film and its application in fire early warning. The method includes the following steps: 1 part graphene oxide is dissolved in an aqueous solution, then 0.1-0.5 parts silane coupling agent and 0.1-0.6 parts L-ascorbic acid are added and stirred to remove air bubbles, followed by drying. A low-temperature fire early warning device is constructed based on this method, consisting of a low-voltage safety battery, an alarm light, and the modified graphene oxide film connected sequentially by wires. The fire early warning device prepared by this method rapidly reduces the modified graphene oxide flame-retardant film at 200°C for 100 seconds, triggering an alarm signal from the light bulb to complete the fire early warning.

[0006] Chinese patent application CN 110540198 B discloses a graphene oxide-based self-healing flame-retardant composite film, its preparation, and a fire alarm. The specific steps include: 1) partially reducing graphene oxide by mixing it with a solvent and a reducing agent to obtain modified graphene oxide; 2) mixing the modified graphene oxide with a conductive material and performing a film-forming treatment to obtain a graphene oxide-based composite film; 3) coating the surface of the graphene oxide-based composite film with a self-healing flame-retardant polymer to obtain a graphene oxide-based self-healing flame-retardant film. The prepared graphene oxide-based self-healing flame-retardant composite film, a DC regulated power supply, a switch, and an alarm light are connected in series with wires to assemble a fire alarm. The response time for the alarm light to illuminate upon flame exposure is 35-43 seconds.

[0007] While many researchers are currently combining graphene oxide with flame-retardant materials to improve their thermal stability and fire warning response, the response speed of fire detectors prepared using these methods is still not ideal, and the response time during alarm activation is not short enough to fully meet practical application requirements. Therefore, optimizing the construction of graphene oxide composite materials to further improve their strength and toughness, fire warning sensitivity, and sustained stable response time remains a challenge. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing and applying a flame-retardant graphene oxide composite film with sensitive fire early warning function, addressing the shortcomings of the prior art.

[0009] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a flame-retardant graphene oxide composite film with a sensitive fire early warning function, comprising the following steps:

[0010] (1) Preparation of cyclotriphosphazene flame retardant: Alkylamine compounds and acid-binding agents are added to an organic solvent. Under nitrogen atmosphere protection, hexachlorocyclotriphosphazene dissolved in the organic solvent is added dropwise. After the addition is complete, the reaction is carried out. The mixture is filtered, distilled under reduced pressure, and dried under vacuum to obtain cyclotriphosphazene flame retardant.

[0011] (2) Preparation of flame-retardant graphene oxide composite film: Add graphene oxide to deionized water, disperse it by ultrasonication, add pH adjuster to make graphene oxide aqueous solution, then add tannic acid and cyclotriphosphazene flame retardant to the system, stir at room temperature to obtain a uniform graphene oxide mixed suspension, and dry to obtain flame-retardant graphene oxide composite film.

[0012] The mass ratio of graphene oxide, tannic acid and cyclotriphosphazene flame retardant is 10:(1-10):(1-10).

[0013] The general structural formula of the cyclotriphosphazene flame retardant is:

[0014]

[0015] R1 is selected from any one of −CH2−OH, −(CH2)2−OH, −(CH2)3−OH, −(CH2)4−OH or −CH(CH2−OH)2.

[0016] In the above preparation method, the cyclotriphosphazene flame retardant contains phosphorus, nitrogen, and terminal hydroxyl groups, which can not only endow the graphene oxide composite film with excellent thermal stability and flame retardant properties, but also enhance its interaction with the graphene oxide composite film. Tannic acid is a natural plant polyphenol widely distributed in the skin, shell, roots, leaves, and pulp of plants. Its structure is rich in phenolic hydroxyl groups and benzene ring structures, and it has a certain reducing property. By utilizing the cross-linking, hydrogen bonding, and π-π conjugation of tannic acid phenolic hydroxyl groups and benzene ring structures with graphene oxide, the connection between graphene oxide sheets can be realized, effectively enhancing the film-forming ability and mechanical properties of the graphene oxide composite film. At the same time, tannic acid can generate phenoxy free radicals during thermal oxidative degradation, which can capture reactive oxygen free radicals and block the free radical chain reaction during polymer combustion. Furthermore, its rich polyphenol structure can promote the formation of a thermally stable aromatic carbon layer during combustion, which plays a synergistic flame retardant role with the cyclotriphosphazene flame retardant, thereby improving the flame retardant performance and fire response time of the graphene oxide composite film.

[0017] Preferably, the alkanolamine compound in step (1) is selected from any one of methanolamine, 2-aminoethanol, 3-aminopropanol, 4-aminobutanol, and 2-amino-1,3-propanediol.

[0018] Preferably, the acid-binding agent in step (1) is selected from any one of triethylamine, cyclohexylamine, pyridine, and 4-dimethylaminopyridine.

[0019] Preferably, the organic solvent in step (1) is selected from any one of 1,4-dioxane, tetrahydrofuran, and dichloromethane.

[0020] Preferably, in the preparation step of the cyclotriphosphazene flame retardant in step (1), the system temperature is maintained at 0℃~5℃, and the reaction is carried out for 12h~24h after the addition is completed.

[0021] Preferably, the pH adjuster mentioned in step (2) is any one of ammonia, sodium hydroxide, sodium carbonate, sodium bicarbonate, and tris(hydroxymethyl)aminomethane.

[0022] Preferably, the pH of the graphene oxide aqueous solution in step (2) is adjusted to 8-10, and the concentration is 2mg / mL-10mg / mL.

[0023] Preferably, the drying step of the graphene oxide mixed suspension in step (2) is to dry it in a vacuum oven at 30℃~50℃ for 8h~24h.

[0024] Secondly, this invention also provides the application of the flame-retardant graphene oxide composite film with sensitive fire early warning function in fire early warning and detection. A fire early warning / detection device can be formed by connecting a low-voltage power supply, an alarm light, the flame-retardant graphene oxide composite film with sensitive fire early warning function, and wires. This fire early warning / detection device differs from traditional smoke and infrared thermal imaging fire alarms; it can quickly issue an alarm after a fire occurs, and the alarm duration is long.

[0025] The principle behind the application of the flame-retardant graphene oxide composite film with sensitive fire early warning function in fire early warning / detection is that the insulating flame-retardant graphene oxide composite film can be rapidly reduced into a highly conductive reduced graphene oxide network when heated, thereby achieving a rapid, sensitive, and long-term fire early warning / detection response.

[0026] Compared with the prior art, the present invention has the following innovative features:

[0027] (1) The flame-retardant graphene oxide composite film provided by the present invention is obtained by mixing graphene oxide, tannic acid and cyclotriphosphazene flame retardant in a certain proportion at room temperature and then drying. The preparation process is simple, the operating conditions are mild, the energy consumption is low, and it is green and environmentally friendly, making it suitable for large-scale production and promotion.

[0028] (2) The graphene oxide composite film provided by the present invention has multiple chemical bond interactions and excellent mechanical flexibility; at the same time, due to the synergistic flame retardant effect of cyclotriphosphazene flame retardant and tannic acid, it can effectively maintain the integrity of its skeleton structure in high temperature or flame, thereby greatly improving the response speed and continuous response time of fire early warning / detection.

[0029] (3) The fire early warning / detection device provided by the present invention has the advantages of good strength and toughness, fast response speed and long continuous response time, and can be applied to fields such as intelligent fire protection, modern home and national defense industry. Attached Figure Description

[0030] Figure 1 The images shown are photographs and scanning electron microscope images of the flame-retardant graphene oxide composite film prepared in Example 1.

[0031] Figure 2 This is a comparison chart of the film-forming properties of the flame-retardant graphene oxide composite films of Example 3 and Comparative Example 3.

[0032] Figure 3 A schematic diagram of a fire early warning / detection device and its early warning mechanism;

[0033] Figure 4 The images shown are screenshots from fire warning tests of the flame-retardant graphene oxide composite films prepared in Example 1, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0034] The present invention will now be described in detail through embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Those skilled in the art can make some non-essential improvements and adjustments based on the above content of the present invention, which still fall within the scope of protection of the present invention.

[0035] Example 1

[0036] (1) Add 0.6 mol of 2-aminoethanol and 0.72 mol of triethylamine to tetrahydrofuran. Under nitrogen atmosphere protection, keep the system temperature at 0℃~5℃ and add 0.1 mol of hexachlorocyclotriphosphazene dissolved in tetrahydrofuran dropwise. After the addition is complete, continue the reaction at 0℃~5℃ for 18 h. Filter, distill under reduced pressure and dry under vacuum to obtain cyclotriphosphazene flame retardant.

[0037] (2) 10 parts by weight of graphene oxide prepared by the modified Hummer's method were added to deionized water, ultrasonically dispersed, and sodium hydroxide was added as a pH adjuster to prepare an aqueous solution of graphene oxide with a pH of 8 and a concentration of 10 mg / mL. Then, 5 parts by weight of tannic acid and 7 parts by weight of cyclotriphosphazene flame retardant were added to the system. The mixture was stirred at room temperature to obtain a uniform graphene oxide suspension. After vacuum drying at 50°C for 8 hours, a flame-retardant graphene oxide composite film was obtained.

[0038] The flame-retardant graphene oxide composite film has a strength of 103.6 MPa and a toughness of 15.1 MJ / cm. 3 A fire warning / detection device is constructed by connecting a low-voltage power supply, an alarm light, a flame-retardant graphene oxide composite film with sensitive fire warning function, and wires. After contact with flame, the fire warning response speed of the flame-retardant graphene oxide composite film is 0.6s, and the fire warning duration is 1620s.

[0039] Example 2

[0040] (1) 0.6 mol of 2-amino-1,3-propanediol and 0.6 mol of pyridine were added to 1,4-dioxane. Under nitrogen atmosphere protection, the system temperature was kept at 0℃~5℃. 0.1 mol of hexachlorocyclotriphosphazene dissolved in 1,4-dioxane was added dropwise. After the addition was completed, the reaction was continued at 0℃~5℃ for 24 h. The mixture was filtered, distilled under reduced pressure and dried under vacuum to obtain the cyclotriphosphazene flame retardant.

[0041] (2) 10 parts by weight of graphene oxide prepared by the modified Hummer's method were added to deionized water, ultrasonically dispersed, and sodium bicarbonate was added as a pH adjuster to prepare an aqueous solution of graphene oxide with a pH of 9 and a concentration of 2 mg / mL. Then, 3 parts by weight of tannic acid and 1 part by weight of cyclotriphosphazene flame retardant were added to the system. The mixture was stirred at room temperature to obtain a uniform graphene oxide mixed suspension. After vacuum drying at 30°C for 24 h, a flame-retardant graphene oxide composite film was obtained.

[0042] The flame-retardant graphene oxide composite film has a strength of 82.6 MPa and a toughness of 11.4 MJ / cm. 3 A fire warning / detection device is constructed by connecting a low-voltage power supply, an alarm light, a flame-retardant graphene oxide composite film with sensitive fire early warning function, and wires. After contact with flame, the fire warning response speed of the flame-retardant graphene oxide composite film is 0.6s, and the fire warning duration is 1060s.

[0043] Example 3

[0044] (1) Add 0.6 mol of 4-aminobutanol and 0.6 mol of 4-dimethylaminopyridine to dichloromethane. Under nitrogen atmosphere protection, keep the system temperature at 0℃~5℃. Add 0.1 mol of hexachlorocyclotriphosphazene dissolved in dichloromethane dropwise. After the addition is complete, continue the reaction at 0℃~5℃ for 24 h. Filter, distill under reduced pressure and dry under vacuum to obtain cyclotriphosphazene flame retardant.

[0045] (2) 10 parts by weight of graphene oxide prepared by the modified Hummer's method were added to deionized water, ultrasonically dispersed, and ammonia water was added as a pH adjuster to prepare an aqueous solution of graphene oxide with a pH of 10 and a concentration of 5 mg / mL. Then, 1 part by weight of tannic acid and 5 parts by weight of cyclotriphosphazene flame retardant were added to the system. The mixture was stirred at room temperature to obtain a uniform graphene oxide mixed suspension. After vacuum drying at 40°C for 18 h, a flame-retardant graphene oxide composite film was obtained.

[0046] The flame-retardant graphene oxide composite film has a strength of 70.8 MPa and a toughness of 7.2 MJ / cm. 3 A fire warning / detection device is constructed by connecting a low-voltage power supply, an alarm light, a flame-retardant graphene oxide composite film with sensitive fire early warning function, and wires. After contact with flame, the fire warning response speed of the flame-retardant graphene oxide composite film is 0.5s, and the fire warning duration is 660s.

[0047] Example 4

[0048] (1) Add 0.6 mol methanolamine and 0.75 mol triethylamine to 1,4-dioxane. Under nitrogen atmosphere protection, keep the system temperature at 0℃~5℃ and add 0.1 mol hexachlorocyclotriphosphazene dissolved in 1,4-dioxane dropwise. After the addition is complete, the reaction continues at 0℃~5℃ for 12 h. Filter, distill under reduced pressure and dry under vacuum to obtain cyclotriphosphazene flame retardant.

[0049] (2) 10 parts by weight of graphene oxide prepared by the modified Hummer's method were added to deionized water, ultrasonically dispersed, and pH adjuster tris(hydroxymethyl)aminomethane was added to prepare an aqueous solution of graphene oxide with pH of 8.5 and concentration of 6 mg / mL. Then, 10 parts by weight of tannic acid and 10 parts by weight of cyclotriphosphazene flame retardant were added to the system. The mixture was stirred at room temperature to obtain a uniform graphene oxide mixed suspension. After vacuum drying at 40°C for 24 h, a flame-retardant graphene oxide composite film was obtained.

[0050] The flame-retardant graphene oxide composite film has a strength of 94.7 MPa and a toughness of 6.9 MJ / cm. 3 A fire warning / detection device is constructed by connecting a low-voltage power supply, an alarm light, a flame-retardant graphene oxide composite film with sensitive fire early warning function, and wires. After contact with flame, the fire warning response speed of the flame-retardant graphene oxide composite film is 0.6s, and the fire warning duration is 1410s.

[0051] Comparative Example 1

[0052] Compared with Example 1, the only difference is that tannic acid and cyclotriphosphazene flame retardant are not added; all other conditions are the same. The specific preparation method is as follows:

[0053] Ten parts by weight of graphene oxide prepared by the modified Hummer's method were added to deionized water, ultrasonically dispersed, and sodium hydroxide was added as a pH adjuster to prepare an aqueous solution of graphene oxide with a pH of 8 and a concentration of 10 mg / mL. After vacuum drying at 50°C for 8 h, a graphene oxide film was obtained.

[0054] The graphene oxide film exhibits a strength of 41.2 MPa and a toughness of 2.7 MJ / cm. 3 A fire warning / detection device is constructed by connecting a low-voltage power supply, an alarm light, a graphene oxide film, and wires. After contact with a flame, the fire warning response speed of the graphene oxide film is 0.5 seconds, and the fire warning response time is 30 seconds.

[0055] Comparative Example 2

[0056] Compared with Example 1, the only difference is that no cyclotriphosphazene flame retardant is added; all other conditions are the same. The specific preparation method is as follows:

[0057] Ten parts by weight of graphene oxide prepared by the modified Hummer's method were added to deionized water and ultrasonically dispersed. Sodium hydroxide, a pH adjuster, was added to prepare an aqueous solution of graphene oxide with a pH of 8 and a concentration of 10 mg / mL. Then, 5 parts by weight of tannic acid were added to the system and stirred at room temperature to obtain a uniform graphene oxide mixed suspension. After vacuum drying at 50°C for 8 hours, a graphene oxide film was obtained.

[0058] The flame-retardant graphene oxide composite film has a strength of 55.3 MPa and a toughness of 4.5 MJ / cm. 3 A fire warning / detection device is constructed by connecting a low-voltage power supply, an alarm light, a flame-retardant graphene oxide composite film with sensitive fire early warning function, and wires. After contact with flame, the fire warning response speed of the flame-retardant graphene oxide composite film is 0.5s, and the fire warning response time is 100s.

[0059] Comparative Example 3

[0060] Compared with Example 3, the only difference is that tannic acid is not added, while other conditions are the same. The specific preparation method is as follows:

[0061] (1) Add 0.6 mol of 4-aminobutanol and 0.6 mol of 4-dimethylaminopyridine to dichloromethane. Under nitrogen atmosphere protection, keep the system temperature at 0℃~5℃. Add 0.1 mol of hexachlorocyclotriphosphazene dissolved in dichloromethane dropwise. After the addition is complete, continue the reaction at 0℃~5℃ for 24 h. Filter, distill under reduced pressure and dry under vacuum to obtain cyclotriphosphazene flame retardant.

[0062] (2) 10 parts by weight of graphene oxide prepared by the modified Hummer's method were added to deionized water, ultrasonically dispersed, and ammonia water was added as a pH adjuster to prepare an aqueous solution of graphene oxide with a pH of 10 and a concentration of 5 mg / mL. Then, 5 parts by weight of cyclotriphosphazene flame retardant were added to the system and stirred at room temperature to obtain a uniform graphene oxide mixed suspension. After vacuum drying at 40°C for 18 h, a flame-retardant graphene oxide composite film was obtained.

[0063] The flame-retardant graphene oxide composite film has poor film-forming properties and cracks after drying, therefore its mechanical properties and fire warning performance are not tested.

[0064] The parameters and test results of the sensitive fire early warning function flame-retardant graphene oxide composite films prepared in Examples 1-4 and Comparative Examples 1-3 are statistically summarized and shown in Table 1.

[0065] Table 1. Parameters and properties of the flame-retardant graphene oxide composite films with sensitive fire early warning function prepared in Examples 1-4 and Comparative Examples 1-3.

[0066]

[0067] As shown in Table 1, the flame-retardant graphene oxide with sensitive fire early warning function provided in Examples 1-4 of this invention possesses excellent film-forming properties, mechanical properties, and fire early warning response. The graphene oxide composite film provided by this invention exhibits multiple chemical bonds due to the introduction of tannic acid, giving the composite film good strength and flexibility, such as... Figure 1 and 2 As shown. Meanwhile, due to the synergistic flame-retardant effect of cyclotriphosphazene flame retardant and tannic acid, it effectively maintains the integrity of its skeletal structure in high temperatures or flames, thereby significantly improving the continuous response time of fire early warning / detection, such as... Figure 3 and 4 As shown.

[0068] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a flame-retardant graphene oxide composite film with sensitive fire early warning function, characterized in that, Includes the following steps: (1) Preparation of cyclotriphosphazene flame retardant: Alkylamine compounds and acid-binding agents are added to an organic solvent. Under nitrogen atmosphere protection, hexachlorocyclotriphosphazene dissolved in the organic solvent is added dropwise. After the addition is complete, the reaction is carried out. The mixture is filtered, distilled under reduced pressure, and dried under vacuum to obtain cyclotriphosphazene flame retardant. (2) Preparation of flame-retardant graphene oxide composite film: Add graphene oxide to deionized water, disperse it by ultrasonication, add pH adjuster to make graphene oxide aqueous solution, then add tannic acid and cyclotriphosphazene flame retardant to the system, stir at room temperature to obtain a uniform graphene oxide mixed suspension, and dry to obtain flame-retardant graphene oxide composite film. The mass ratio of graphene oxide, tannic acid and cyclotriphosphazene flame retardant is 10:(1-10):(1-10). The general structural formula of the cyclotriphosphazene flame retardant is: In the formula, R1 is selected from any one of −CH2−OH, −(CH2)2−OH, −(CH2)3−OH, −(CH2)4−OH or −CH(CH2−OH)2; The alkanolamine compound is selected from any one of methanolamine, 2-aminoethanol, 3-aminopropanol, 4-aminobutanol, and 2-amino-1,3-propanediol. The acid-binding agent is selected from any one of triethylamine, cyclohexylamine, pyridine, and 4-dimethylaminopyridine.

2. The preparation method according to claim 1, characterized in that, The organic solvent is selected from any one of 1,4-dioxane, tetrahydrofuran, and dichloromethane.

3. The preparation method according to claim 1, characterized in that, In the preparation steps of cyclotriphosphazene flame retardant, the system temperature is maintained at 0℃~5℃, and the reaction is carried out for 12h~24h after the addition is completed.

4. The preparation method according to claim 1, characterized in that, The pH adjuster is selected from any one of ammonia, sodium hydroxide, sodium carbonate, sodium bicarbonate, and tris(hydroxymethyl)aminomethane.

5. The preparation method according to claim 1, characterized in that, The pH of the graphene oxide aqueous solution is adjusted to 8-10, and the concentration is 2 mg / mL-10 mg / mL.

6. The preparation method according to claim 1, characterized in that, The drying step of the graphene oxide mixed suspension is to dry it in a vacuum oven at 30℃~50℃ for 8h~24h.

7. A flame-retardant graphene oxide composite film with sensitive fire early warning function prepared by the preparation method according to any one of claims 1-6.

8. The application of the flame-retardant graphene oxide composite film with sensitive fire early warning function as described in claim 7 in a sensitive fire early warning device.

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