A flame-retardant and highly sensitive GO fire alarm sensor material and its preparation method

Abstract

The present invention discloses a flame-retardant, highly sensitive GO fire alarm sensor material and its preparation method. The method comprises adding graphite to concentrated sulfuric acid in an ice bath, cooling, adding potassium nitrate or sodium nitrate in portions, cooling and stirring, then adding potassium permanganate in portions, stirring at an oxidation temperature, adding hydrogen peroxide, allowing the mixture to stand, centrifuging to remove the supernatant, adding deionized water, and ultrasonically dispersing the mixture to obtain a GO dispersion; mixing a phase change material with a natural antioxidant, ball milling the mixture to obtain antioxidant-phase change material microcapsules; and mixing the GO dispersion with the antioxidant-phase change material microcapsules and a water-soluble phosphorus flame retardant, ultrasonically dispersing the mixture to obtain a flame-retardant, highly sensitive GO fire alarm sensor material. The GO fire alarm sensor material prepared by the present invention has the advantages of low response temperature, short response time, and good durability, providing new ideas for the design and development of high-performance fire alarm sensor materials.

Description

Technical Field

[0001] The present invention belongs to the field of flame-retardant sensing materials and relates to a flame-retardant and highly sensitive GO fire alarm sensing material and a preparation method thereof. Background Art

[0002] Fires have become increasingly frequent in recent years, posing a significant threat to people's lives and property. Therefore, reducing fire risks is imperative. Currently, two primary strategies are used to mitigate fire risks: fire alarms and flame retardant technologies. The former leverages the ability of fire alarm sensor materials to respond to abnormal temperatures or smoke concentrations to provide early warnings in the early stages of a fire, playing a crucial role in fire safety and prevention. The latter, on the other hand, utilizes flame retardant technologies such as polymer modification and the addition of flame retardant fillers to enhance the flame retardancy of combustible materials after a fire has occurred, preventing combustion. Enhancing the thermal stability of combustible materials and improving their self-extinguishing ability in a fire scene is crucial.

[0003] As a representative of new intelligent fire alarm sensor materials, graphene oxide (GO) can rapidly transform from an electrically insulating state to conductive reduced GO (rGO) at high temperatures, showing broad application prospects in fire alarms. However, due to GO's thermal reduction process, the response temperature of GO fire alarm sensor materials is mostly above 300°C. At this point, most combustible materials have already burned, which is not conducive to avoiding fire risks. In addition, GO has poor flame retardancy and thermal stability and will burn at high temperatures, making it difficult to meet the alarm needs of actual fire scenes. Therefore, it is crucial to lower GO's thermal reduction temperature, shorten the thermal reduction process, and improve its flame retardancy, so that GO fire alarm sensor materials can connect the circuit to fire alarm at lower temperatures and in a shorter time, and have long-lasting warning at high temperatures. Summary of the Invention

[0004] The purpose of the present invention is to provide a flame-retardant and highly sensitive GO fire alarm sensor material and a preparation method thereof, so as to solve the problem that the response temperature of the existing GO fire alarm sensor material is too high.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material comprises:

[0007] Graphite was added to concentrated sulfuric acid in an ice bath, cooled, potassium nitrate or sodium nitrate was added in portions, cooled and stirred, potassium permanganate was added in portions, stirred at the oxidation temperature, hydrogen peroxide was added, allowed to stand, the supernatant was removed by centrifugation, deionized water was added, and ultrasonic dispersion was performed to obtain a GO dispersion;

[0008] The phase change material and the natural antioxidant are mixed and ball-milled to obtain antioxidant@phase change material microcapsules;

[0009] GO dispersion was mixed with antioxidant@phase change material microcapsules and water-soluble phosphorus flame retardant, uniformly dispersed by ultrasonication and dried to prepare a flame-retardant and highly sensitive GO fire alarm sensor material.

[0010] Furthermore, the added mass-to-volume ratio of the graphite to concentrated sulfuric acid is 1:24, the added mass ratio of the graphite to potassium nitrate is 1:0.5, the added mass ratio of the graphite to sodium nitrate is 1:1, the added mass ratio of the graphite to potassium permanganate is 1:4.5, and the added mass-to-volume ratio of the graphite to hydrogen peroxide is 1:1.4.

[0011] Furthermore, the mass fraction of the concentrated sulfuric acid is 98%, and the mass fraction of the hydrogen peroxide is 30%.

[0012] Furthermore, in the antioxidant@phase change material microcapsules, the phase change material is 25 to 75 parts, and the natural antioxidant is 25 to 75 parts.

[0013] Furthermore, in the GO fire alarm sensor material, the GO dispersion is 40-62 parts, the antioxidant@phase change material microcapsule is 37-56 parts, and the water-soluble phosphorus flame retardant is 1-4 parts.

[0014] Furthermore, the oxidation temperature is 0°C, 30°C or 95°C.

[0015] Furthermore, the phase change material is one or more of palm wax, polyethylene wax, naphthalene, shellac, paraffin, and beeswax.

[0016] Furthermore, the natural antioxidant is one or more of daidzein, tartaric acid, tannic acid, tea polyphenols, and vitamin C.

[0017] Furthermore, the water-soluble phosphorus-based flame retardant is one or more of ammonium polyphosphate, ammonium phytate, phytic acid, phosphoric acid, and pyrophosphoric acid.

[0018] A flame-retardant and highly sensitive GO fire alarm sensor material prepared by the preparation method.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a method for preparing a flame-retardant, highly sensitive GO fire alarm sensor material. A GO dispersion with a moderate degree of oxidation is prepared using a self-developed Hummers method. Core-shell microcapsules with an antioxidant as the core material and a phase change material as the wall material are then prepared. The GO dispersion is compounded with the antioxidant@phase change material microcapsules and a water-based phosphorus-containing flame retardant. The flame-retardant, highly sensitive GO fire alarm sensor material is prepared using evaporation self-assembly technology. At room temperature, the presence of the wall material isolates the antioxidant from contact with GO, preventing GO from being reduced and generating false alarms. Under heat stimulation, the phase change material transforms from a solid state to a liquid state, rapidly releasing the antioxidant from the core material. The antioxidant is released by the phase transition of the antioxidant@phase change material microcapsule shell. Combined with the rapid reduction of GO with a moderate degree of oxidation, the time required to form a conductive path is shortened, enabling the GO fire alarm sensor material to generate fire alarms at lower temperatures and in a shorter time. Among them, the moderate oxidation degree of GO makes it in an insulating state at room temperature, and it can be quickly reduced to conductive rGO under the stimulation of heat source; at the same time, the core-shell structure of the antioxidant@phase change material microcapsule ensures that GO will not be reduced by the antioxidant at room temperature and cause false alarms. In addition, by adding water-soluble phosphorus-based flame retardants to GO, the water-based phosphorus-containing flame retardants can be used to catalyze GO to form a dense carbon layer to resist flame roasting, thereby improving the flame retardant properties and thermal stability of the GO fire alarm sensor material, and making it have a long-lasting warning in high-temperature fire environments. The flame-retardant and highly sensitive responsive GO fire alarm sensor material prepared by the present invention has a more sensitive and lasting fire alarm response capability to abnormally high temperatures than untreated GO. The time it takes to form a conductive path to connect the alarm at 175°C is 1s, and the time it takes to form a conductive path to connect the alarm at 150°C is 50s; the time it takes to form a conductive path to connect the alarm under flame roasting is 0.5s, and the continuous fire alarm time is greater than 1800s. Therefore, the GO fire alarm sensor material prepared by the present invention has the advantages of low response temperature, short response time and good durability. It reduces the thermal reduction temperature of GO, shortens the thermal reduction process and improves the flame retardant performance, so that the sensor material can perform fire alarm at a lower temperature and in a shorter time, and has warning persistence at high temperature, providing new ideas for the design and development of high-performance fire alarm sensor materials.

[0021] Furthermore, the antioxidants selected in the present invention are all natural materials, which have the characteristics of high safety, strong antioxidant capacity, no side effects, and green and renewable, providing a reference for the green reduction of GO. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is the resistance diagram of GO with different oxidation degrees at room temperature according to the present invention.

[0024] Figure 2 These are the SEM photographs and EDS images of the vitamin C@shellac prepared in Example 10 of the present invention.

[0025] Figure 3 This is a graph showing the change in circuit resistance of GO and the GO fire alarm sensor material prepared in Example 10 of the present invention at 175°C over time.

[0026] Figure 4 This is a graph showing the change in circuit resistance of GO and the GO fire alarm sensor material prepared in Example 10 of the present invention at 150°C over time.

[0027] Figure 5 Response sensitivity diagram of GO (a) and GO fire alarm sensor material prepared in Example 10 of the present invention (b) at 175°C.

[0028] Figure 6 Response sensitivity diagram of GO (a) and GO fire alarm sensor material prepared in Example 10 of the present invention (b) at 150°C.

[0029] Figure 7 Schematic diagram of the response sensitivity and durability of GO (a) and the GO fire alarm sensor material prepared in Example 10 of the present invention (b) under flame roasting. DETAILED DESCRIPTION

[0030] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0031] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0032] All features, such as values, amounts, contents, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0033] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0034] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0035] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0036] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0037] The present invention is described in further detail below with reference to the accompanying drawings:

[0038] The present invention provides a method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material, which specifically comprises the following steps:

[0039] Step 1: Under ice bath conditions, slowly and in small amounts, add graphite to a beaker containing concentrated sulfuric acid with a mass fraction of 98% at a mass volume ratio of 1:24, and cool after addition; then add potassium nitrate in batches at a mass ratio of graphite to potassium nitrate of 1:0.5 or sodium nitrate at a mass ratio of graphite to sodium nitrate of 1:1 (time 30min), and cool and stir for 2h after addition; then add potassium permanganate in small amounts at a mass ratio of graphite to potassium permanganate of 1:4.5 (addition is completed in about 3h), stir at the oxidation temperature for 2h, add hydrogen peroxide at a mass volume ratio of graphite to hydrogen peroxide of 1:1.4, and the mass fraction of hydrogen peroxide is 30%, and let it stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour deionized water at a mass volume ratio of graphite to deionized water of 1:20, and ultrasonically disperse it evenly to obtain a GO dispersion.

[0040] Step 2: Combine 25-75 parts phase change material and 25-75 parts natural antioxidant in a 50ml stainless steel jar. Add 5-10 stainless steel balls with a diameter of 5-10 mm to the jar and run a vibrating ball mill at 25-35 Hz for 5-30 minutes. Stop the milling every 5 minutes to prevent the jar from overheating. This will produce antioxidant-phase change material microcapsules.

[0041] Step 3: Mix 40-62 parts of GO dispersion with 37-56 parts of antioxidant@phase change material microcapsules and 1-4 parts of water-soluble phosphorus flame retardant, disperse them evenly by ultrasonication, and dry the moisture at 30-60°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0042] Preferably, different graphene oxides are synthesized using graphite as a starting material and three different oxidation temperatures of 0°C, 30°C and 95°C.

[0043] Preferably, the phase change material is one or more of palm wax, polyethylene wax, naphthalene, shellac, paraffin, and beeswax.

[0044] Preferably, the natural antioxidant is one or more of daidzein, tartaric acid, tannic acid, tea polyphenols, and vitamin C.

[0045] Preferably, the water-soluble phosphorus-based flame retardant is one or more of ammonium polyphosphate, ammonium phytate, phytic acid, phosphoric acid, and pyrophosphoric acid.

[0046] The technical solution of the present invention is further described in detail below through specific embodiments:

[0047] Example 1:

[0048] A flame-retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps:

[0049] Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a beaker containing 24ml of concentrated sulfuric acid, and cool after addition; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h; then add 4.5g of potassium permanganate in small amounts and in multiple times (addition takes about 3h), stir at 0℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let it stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour in 20ml of deionized water, ultrasonically disperse and bottle to obtain GO dispersion for use.

[0050] Step 2: Combine 25 parts palm wax and 75 parts daidzein in a 50 ml stainless steel jar. Add five 5 mm diameter stainless steel balls to the jar and run a vibrating ball mill at 35 Hz for 30 minutes. Stop the milling every 5 minutes to prevent the jar from overheating. This yields daidzein@palm wax microcapsules.

[0051] Step 3: Mix 62 parts of GO dispersion with 37 parts of daidzein@palm wax microcapsules and 1 part of ammonium polyphosphate, disperse them evenly by ultrasonication, and dry the moisture at 30°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0052] Example 2:

[0053] A flame-retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps:

[0054] Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after addition; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h; then add 4.5g of potassium permanganate in small amounts several times (addition time about 3h), stir at 35℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let it stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour in 20ml of deionized water, ultrasonically disperse and bottle to obtain GO dispersion for use.

[0055] Step 2: Mix 50 parts polyethylene wax and 50 parts tartaric acid in a 50 ml stainless steel jar. Add 10 stainless steel balls (10 mm in diameter) to the jar and run a vibrating ball mill at 25 Hz for 5 minutes. Stop the milling every 5 minutes to prevent the jar from overheating. This yields tartaric acid@polyethylene wax microcapsules.

[0056] Step 3: Mix 54 parts of GO dispersion with 44 parts of tartaric acid@polyethylene wax microcapsules and 2 parts of ammonium phytate, disperse them evenly by ultrasonication, and dry the moisture at 60°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0057] Example 3:

[0058] In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker and cool it down. Then, add 0.5g of potassium nitrate in portions (30min), cool and stir for 2h. Then, add 4.5g of potassium permanganate in small amounts (about 3h to complete), stir at 95℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let it stand for 12h. Remove the supernatant, centrifuge and wash until the waste liquid is neutral. Pour in 5ml of deionized water, disperse evenly by ultrasonication, and bottle to obtain a GO dispersion for later use.

[0059] Step 2: Mix 75 parts naphthalene and 25 parts tannic acid in a 50 ml stainless steel jar. Add five 5 mm diameter stainless steel balls to the jar and run a vibrating ball mill at 35 Hz for 10 minutes. Stop the milling every 5 minutes to prevent the jar from overheating. This yields tannic acid-naphthalene microcapsules.

[0060] Step 3: Mix 50 parts of GO dispersion with 46 parts of tannic acid@naphthalene microcapsules and 4 parts of phytic acid, disperse them evenly under ultrasonication, and dry the moisture at 60°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0061] Example 4:

[0062] A flame-retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps:

[0063] Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after addition; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h; then add 4.5g of potassium permanganate in small amounts several times (addition time about 3h), stir at 35℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let it stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour in 20ml of deionized water, ultrasonically disperse and bottle to obtain GO dispersion for use.

[0064] Step 2: Mix 50 parts shellac and 50 parts tea polyphenols in a 50ml stainless steel jar. Add 10 5mm diameter stainless steel balls to the jar and run a vibrating ball mill at 35Hz for 10 minutes. Stop the milling every 5 minutes to prevent the jar from overheating. This produces tea polyphenols@shellac microcapsules.

[0065] Step 3: Mix 44 parts of GO dispersion with 52 parts of tea polyphenols@shellac microcapsules and 4 parts of phosphoric acid, disperse them evenly under ultrasonication, and dry the moisture at 50°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0066] Example 5:

[0067] A flame-retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps:

[0068] Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after addition; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h; then add 4.5g of potassium permanganate in small amounts several times (add in about 3h), stir at 0℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let it stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour in 20ml of deionized water, ultrasonically disperse evenly and bottle to obtain GO dispersion for use.

[0069] Step 2: Mix 45 parts paraffin wax and 55 parts vitamin C in a 50ml stainless steel jar. Add 10 5mm diameter stainless steel balls to the jar and run a vibrating ball mill at 35Hz for 10 minutes. Stop the milling every 5 minutes to prevent the jar from overheating. This yields vitamin C@paraffin wax microcapsules.

[0070] Step 3: Mix 40 parts of GO dispersion with 56 parts of vitamin C@paraffin microcapsules and 4 parts of pyrophosphoric acid, disperse them evenly by ultrasonication, and dry the moisture at 50°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0071] Example 6:

[0072] A flame-retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps:

[0073] Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after addition; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h; then add 4.5g of potassium permanganate in small amounts several times (addition time about 3h), stir at 35℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let it stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour in 20ml of deionized water, ultrasonically disperse and bottle to obtain GO dispersion for use.

[0074] Step 2: Mix 55 parts beeswax and 45 parts tea polyphenols in a 50ml stainless steel jar. Add 10 stainless steel balls (10 mm in diameter) to the jar and run a vibrating ball mill at 25 Hz for 10 minutes. Stop the milling every 5 minutes to prevent the jar from overheating. This yields tea polyphenols@beeswax microcapsules.

[0075] Step 3: Mix 62 parts of GO dispersion with 37 parts of tea polyphenols@beeswax microcapsules and 1 part of ammonium polyphosphate, disperse them evenly by ultrasonication, and dry the moisture at 50°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0076] Example 7:

[0077] A flame-retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps:

[0078] Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after addition; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h; then add 4.5g of potassium permanganate in small amounts several times (add in about 3h), stir at 0℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let it stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour in 20ml of deionized water, ultrasonically disperse evenly and bottle to obtain GO dispersion for use.

[0079] Step 2: Mix 65 parts palm wax and 35 parts vitamin C in a 50ml stainless steel jar. Add five 5mm diameter stainless steel balls to the jar and run a vibrating ball mill at 35Hz for 10 minutes. Stop the milling every 5 minutes to prevent the jar from overheating. This produces vitamin C@palm wax microcapsules.

[0080] Step 3: Mix 48 parts of GO dispersion with 48 parts of vitamin C@palm wax microcapsules and 4 parts of phytic acid, disperse them evenly by ultrasonication, and dry the moisture at 50°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0081] Example 8:

[0082] A flame-retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps:

[0083] Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after addition; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h; then add 4.5g of potassium permanganate in small amounts several times (addition time about 3h), stir at 35℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let it stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour in 20ml of deionized water, ultrasonically disperse and bottle to obtain GO dispersion for use.

[0084] Step 2: Combine 70 parts palm wax and 30 parts tea polyphenols in a 50ml stainless steel jar. Add 10 stainless steel balls (10 mm in diameter) to the jar and run a vibrating ball mill at 30 Hz for 10 minutes. Stop the milling every 5 minutes to prevent the jar from overheating. This yields tea polyphenols@palm wax microcapsules.

[0085] Step 3: Mix 44 parts of GO dispersion with 52 parts of tea polyphenols @ palm wax microcapsules and 4 parts of ammonium phytate, disperse them evenly by ultrasonication, and dry the moisture at 50°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0086] Example 9:

[0087] A flame-retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps:

[0088] Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after addition; then add 0.5g of potassium nitrate in portions (time 10min), cool and stir for 2h; then add 4.5g of potassium permanganate in small amounts several times (addition time about 3h), stir at 35℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let it stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour in 20ml of deionized water, ultrasonically disperse and bottle to obtain GO dispersion for use.

[0089] Step 2: Mix 40 parts shellac and 60 parts tea polyphenols in a 50ml stainless steel jar. Add five 5mm diameter stainless steel balls to the jar and run a vibrating ball mill at 35Hz for 10 minutes. Stop the milling every 5 minutes to prevent the jar from overheating. This produces tea polyphenols@shellac microcapsules.

[0090] Step 3: 40 parts of GO dispersion, 56 parts of tea polyphenols@shellac microcapsules and 4 parts of ammonium phytate were mixed and dispersed evenly by ultrasonication, and the moisture was dried at 50°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0091] Example 10:

[0092] A flame-retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps:

[0093] Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after addition; then add 1g of sodium nitrate in portions (time 30min), cool and stir for 2h; then add 4.5g of potassium permanganate in small amounts several times (addition time about 3h), stir at 0℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let it stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour in 20ml of deionized water, ultrasonically disperse and bottle to obtain GO dispersion for use.

[0094] Step 2: Mix 70 parts shellac and 30 parts vitamin C in a 50ml stainless steel jar. Add 10 stainless steel balls (10 mm in diameter) to the jar and run a vibrating ball mill at 30 Hz for 10 minutes. Stop the milling every 5 minutes to prevent the jar from overheating. This produces vitamin C@shellac microcapsules.

[0095] Step 3: Mix 48 parts of GO dispersion with 48 parts of vitamin C@shellac microcapsules and 4 parts of ammonium phytate, disperse them evenly by ultrasonication, and dry the moisture at 50°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0096] Different oxidation temperatures were used in the preparation of GO dispersions in Examples 1 to 10 of the present invention. Figure 1 It can be seen that GO with different oxidation degrees exhibits different electrical conductivity at room temperature, and by controlling the oxidation degree of GO, its resistance can be adjusted within a certain range. For GO fire alarm sensor materials, they should be in an insulating state at room temperature (i.e., meeting the insulation resistance requirement of >1 MΩ for low-voltage electrical equipment, its connected circuits, and secondary circuits). At high temperatures, they rapidly undergo reduction to form conductive rGO. This process is closely related to the GO's oxidation degree. When the oxidation degree is too high, the thermal reduction process is slow and the response time is long. When the oxidation degree is too low, the insulation requirements are not met, which can easily lead to false alarms. In contrast, GO with a moderate oxidation degree exhibits a rapid thermal reduction process and a short response time while still meeting the insulation resistance requirement for typical circuits (>1 MΩ). GO with a low oxidation degree can undergo rapid thermal reduction under heat stimulation, shortening the time it takes to form a conductive path.

[0097] The SEM photos and EDS images of the vitamin C@shellac microcapsules prepared in Example 10 of the present invention are as follows: Figure 2 As shown, the shellac-coated vitamin C prepared using the dry coating method exhibits a three-dimensional structure. This is because the phase-change material shellac has a lower melting temperature than vitamin C, allowing it to melt prematurely in the heat generated by the rotor collisions, thus encapsulating the vitamin C. EDS spectra also reveal uniform distributions of C, O, and Si, demonstrating the successful preparation of vitamin C@shellac microcapsules. This ensures that GO is not directly reduced by antioxidants at room temperature, which would affect its alarm sensitivity. Furthermore, under heat stimulation, the phase-change material rapidly releases antioxidants, accelerating the thermal reduction of GO and shortening response time.

[0098] Depend on Figures 3 to 6As can be seen, the GO fire alarm sensor material prepared in Example 10 of the present invention has a lower response temperature and shorter response time than unmodified GO. It performs well in ultra-sensitive early fire alarm response to abnormally high temperatures, with the time it takes to form a conductive path connecting to the alarm being 1 second at 175°C and 50 seconds at 150°C.

[0099] like Figure 7 As shown, the unmodified GO takes 2 seconds to form a conductive path and connect to the alarm under an open flame, and the fire alarm lasts for less than 10 seconds. However, the GO fire alarm sensor material prepared in Example 10 of the present invention exhibits more sensitive and long-lasting alarm capabilities, forming a conductive path and connecting to the alarm under an open flame in 0.5 seconds, and lasting for more than 1800 seconds. This is because the phosphorus-containing flame retardant can catalyze the formation of a dense carbon layer on GO to resist flame damage, improving its flame retardancy and thermal stability.

[0100] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material, characterized in that: include: Graphite was added to concentrated sulfuric acid in an ice bath, cooled, potassium nitrate or sodium nitrate was added in portions, cooled and stirred, potassium permanganate was added in portions, stirred at the oxidation temperature, hydrogen peroxide was added, allowed to stand, the supernatant was removed by centrifugation, deionized water was added, and ultrasonic dispersion was performed to obtain a GO dispersion; The phase change material and the natural antioxidant are mixed and ball-milled to obtain antioxidant@phase change material microcapsules; The GO dispersion was mixed with antioxidant@phase change material microcapsules and water-soluble phosphorus flame retardant, uniformly dispersed by ultrasonication, and dried to prepare a flame-retardant and highly sensitive GO fire alarm sensor material. The added mass-to-volume ratio of the graphite to concentrated sulfuric acid is 1:24, the added mass ratio of the graphite to potassium nitrate is 1:0.5, the added mass ratio of the graphite to sodium nitrate is 1:1, the added mass ratio of the graphite to potassium permanganate is 1:4.5, and the added mass-to-volume ratio of the graphite to hydrogen peroxide is 1:1.4; In the antioxidant@phase change material microcapsules, the phase change material is 25-75 parts and the natural antioxidant is 25-75 parts; The GO fire alarm sensor material comprises 40 to 62 parts of GO dispersion, 37 to 56 parts of antioxidant@phase change material microcapsules, and 1 to 4 parts of water-soluble phosphorus flame retardant.

2. The method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material according to claim 1, characterized in that: The mass fraction of the concentrated sulfuric acid is 98%, and the mass fraction of the hydrogen peroxide is 30%.

3. The method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material according to claim 1, characterized in that: The oxidation temperature is 0°C, 30°C or 95°C.

4. The method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material according to claim 1, characterized in that: The phase change material is one or more of palm wax, polyethylene wax, naphthalene, shellac, paraffin, and beeswax.

5. The method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material according to claim 1, characterized in that: The natural antioxidant is one or more of daidzein, tartaric acid, tannic acid, tea polyphenols and vitamin C.

6. The method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material according to claim 1, characterized in that: The water-soluble phosphorus-based flame retardant is one or more of ammonium polyphosphate, ammonium phytate, phytic acid, phosphoric acid, and pyrophosphoric acid.

7. A flame-retardant and highly sensitive GO fire alarm sensor material prepared by the preparation method according to any one of claims 1 to 6.

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