Flame-retardant high-sensitivity response type GO fire alarm sensing material and preparation method thereof

Abstract

The invention discloses a flame-retardant high-sensitivity response type GO fire alarm sensing material and a preparation method thereof.The preparation method comprises the steps that under the ice bath condition, graphite is added into concentrated sulfuric acid, cooling is conducted, potassium nitrate or sodium nitrate is added in batches, cooling and stirring are conducted, potassium permanganate is added in batches, stirring is conducted at the oxidation temperature, hydrogen peroxide is added, standing is conducted, supernate is removed through centrifugation, and the flame-retardant high-sensitivity response type GO fire alarm sensing material is obtained; adding deionized water, and ultrasonically dispersing uniformly to obtain GO dispersion liquid; mixing the phase-change material with a natural antioxidant, and carrying out ball milling to obtain an antioxidant-phase-change material microcapsule; mixing the GO dispersion liquid with the antioxidant phase-change material microcapsule and a water-soluble phosphorus flame retardant, ultrasonically dispersing uniformly, and drying to obtain the flame-retardant high-sensitivity response type GO fire alarm sensing material. The GO fire alarm sensing material prepared by the invention has the advantages of low response temperature, short response time and good durability, and provides a new idea for design and development of high-performance fire alarm sensing materials.

Description

Technical Field

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

[0002] In recent years, fire accidents have occurred frequently, posing a major threat to people's lives and property. Therefore, it is imperative to reduce the risk of fire. At present, the fire risk is mainly reduced through two strategies: fire alarm and flame retardant technology. The former is to use the fire alarm sensor material's ability to respond to abnormal temperature or smoke concentration to warn in the early stage of a fire, playing an important role in fire safety and prevention; while the latter is to use polymer modification, adding flame retardant fillers and other flame retardant technologies to improve the flame retardancy of combustible materials and prevent them from burning after the fire occurs. It is extremely important to enhance the thermal stability of combustibles and improve their self-extinguishing ability in the fire scene.

[0003] As a representative of new intelligent fire alarm sensor materials, graphene oxide (GO) can be rapidly converted from an electrically insulating state to a conductive reduced GO (rGO) at high temperatures, and has broad application prospects in fire alarms. However, limited by the thermal reduction process of GO, the response temperature of GO fire alarm sensor materials is mostly higher than 300°C. At this time, 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 the thermal reduction temperature of GO, shorten the thermal reduction process, and improve its flame retardant properties, so that the GO fire alarm sensor material can connect the circuit for fire alarm at a lower temperature and in a shorter time, and have warning persistence 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: A method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material, comprising: In an ice bath, graphite is added to concentrated sulfuric acid, cooled, potassium nitrate or sodium nitrate is added in portions, cooled and stirred, potassium permanganate is added in portions, stirred at an oxidation temperature, hydrogen peroxide is added, allowed to stand, supernatant is removed by centrifugation, deionized water is added, and ultrasonic dispersion is 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, dispersed evenly by ultrasonication, and dried to obtain a flame-retardant and highly sensitive GO fire alarm sensor material.

[0006] 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.

[0007] Furthermore, the mass fraction of the concentrated sulfuric acid is 98%, and the mass fraction of the hydrogen peroxide is 30%.

[0008] Furthermore, in the antioxidant@phase change material microcapsule, the phase change material is 25-75 parts and the natural antioxidant is 25-75 parts.

[0009] 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.

[0010] Furthermore, the oxidation temperature is 0°C, 30°C or 95°C.

[0011] Furthermore, the phase change material is one or more of palm wax, polyethylene wax, naphthalene, shellac, paraffin, and beeswax.

[0012] Furthermore, the natural antioxidant is one or more of daidzein, tartaric acid, tannic acid, tea polyphenols, and vitamin C.

[0013] Furthermore, the water-soluble phosphorus-based flame retardant is one or more of ammonium polyphosphate, ammonium phytate, phytic acid, phosphoric acid, and pyrophosphoric acid.

[0014] A flame-retardant and highly sensitive GO fire alarm sensor material prepared by the preparation method.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material. A GO dispersion with a moderate oxidation degree is prepared by a self-improved Hummers method, and then a core-shell structure microcapsule with an antioxidant as a core material and a phase change material as a wall material is prepared. The GO dispersion is compounded with an antioxidant@phase change material microcapsule and an aqueous phosphorus-containing flame retardant, and a flame-retardant and highly sensitive GO fire alarm sensor material is prepared by evaporation self-assembly technology. At room temperature, the presence of the wall material isolates the contact between the antioxidant and GO, and prevents GO from being reduced and generating false alarms. Under the stimulation of a heat source, the phase change material changes from a solid state to a liquid state, and quickly releases the antioxidant of the core material. The release of the antioxidant is achieved by utilizing the phase transition of the shell layer of the antioxidant@phase change material microcapsule, and combined with the rapid reduction of GO with a moderate oxidation degree, the time for forming a conductive path is shortened, so that the GO fire alarm sensor material can perform a fire alarm at a lower temperature 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 flame retardants to GO, the water-based phosphorus flame retardants can be used to catalyze GO to form a dense carbon layer to resist flame roasting, improve the flame retardant properties and thermal stability of GO fire alarm sensor materials, and make it have warning durability 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, reduces the thermal reduction temperature of GO, shortens the thermal reduction process and improves the flame retardant performance, enables the sensor material to 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.

[0016] 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

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is the resistance diagram of GO with different oxidation degrees at room temperature according to the present invention.

[0019] Figure 2 These are the SEM photograph and EDS graph of the vitamin C@shellac prepared in Example 10 of the present invention.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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

[0025] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0026] 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.

[0027] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0028] In this document, unless otherwise specified, “includes,” “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.”

[0029] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0030] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it 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 within the scope limited by the appended claims of the application equally.

[0031] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0032] The present invention is further described in detail below in conjunction with the accompanying drawings: 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: Step 1: In an ice bath, add graphite slowly and in small amounts to a beaker containing concentrated sulfuric acid at a mass volume ratio of 1:24, with a mass fraction of 98%. Cool after adding; then add potassium nitrate at a mass ratio of 1:0.5 or sodium nitrate at a mass ratio of 1:1 to graphite (time 30min), cool and stir for 2h after adding; then add potassium permanganate in small amounts at a mass ratio of 1:4.5 to graphite (addition takes about 3h), stir at the oxidation temperature for 2h, add hydrogen peroxide at a mass volume ratio of 1:1.4 to graphite, with a mass fraction of 30%, and let stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour deionized water at a mass volume ratio of 1:20 to graphite and deionized water, and disperse evenly by ultrasonication to obtain a GO dispersion.

[0033] Step 2: Mix 25-75 parts of phase change material and 25-75 parts of natural antioxidant in a 50 ml stainless steel jar. Add 5-10 stainless steel balls with a diameter of 5-10 mm to the jar, and run the vibration ball mill at 25-35 Hz for 5-30 minutes. Stop the ball milling every 5 minutes to avoid excessive temperature in the jar, thereby preparing antioxidant @ phase change material microcapsules.

[0034] 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, dry the moisture at 30-60°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0035] 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.

[0036] Preferably, the phase change material is one or more of palm wax, polyethylene wax, naphthalene, shellac, paraffin, and beeswax.

[0037] Preferably, the natural antioxidant is one or more of daidzein, tartaric acid, tannic acid, tea polyphenols, and vitamin C.

[0038] Preferably, the water-soluble phosphorus-based flame retardant is one or more of ammonium polyphosphate, ammonium phytate, phytic acid, phosphoric acid, and pyrophosphoric acid.

[0039] The technical solution of the present invention is further described in detail below through specific embodiments: Embodiment 1: A flame retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps: 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 after addition; then add 4.5g of potassium permanganate in small amounts and multiple times (add in about 3h), stir at 0℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let 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 a GO dispersion for use.

[0040] Step 2: 25 parts of palm wax and 75 parts of daidzein were mixed in a 50 ml stainless steel jar. Five stainless steel balls with a diameter of 5 mm were added to the jar, and a vibrating ball mill was operated at 35 Hz for 30 min. The ball milling was stopped every 5 min to avoid the jar temperature from being too high, thereby obtaining daidzein@palm wax microcapsules.

[0041] 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.

[0042] Embodiment 2: A flame retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps: Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after adding; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h after adding; then add 4.5g of potassium permanganate in small amounts several times (add in about 3h), stir at 35℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let 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.

[0043] Step 2: 50 parts of polyethylene wax and 50 parts of tartaric acid were mixed in a 50 ml stainless steel jar. Ten stainless steel balls with a diameter of 10 mm were added to the jar, and a vibrating ball mill was operated at 25 Hz for 5 minutes. The ball milling was stopped every 5 minutes to avoid the jar temperature from being too high, thereby obtaining tartaric acid@polyethylene wax microcapsules.

[0044] 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.

[0045] Embodiment 3: In an ice bath, add 1g of graphite slowly and in small amounts to a 24ml beaker, and cool after adding; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h after adding; then add 4.5g of potassium permanganate in small amounts and multiple times (add in about 3h), stir at 95℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let stand for 12h; remove the supernatant, centrifuge and wash until the waste liquid is neutral; pour in 5ml of deionized water, ultrasonically disperse and bottle to obtain GO dispersion for use.

[0046] Step 2: 75 parts of naphthalene and 25 parts of tannic acid were mixed in a 50 ml stainless steel jar. Five stainless steel balls with a diameter of 5 mm were added to the jar, and a vibrating ball mill was operated at 35 Hz for 10 min. The ball milling was stopped every 5 min to avoid the jar temperature from being too high, thereby obtaining tannic acid@naphthalene microcapsules.

[0047] 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 by ultrasonication, and dry the moisture at 60°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0048] Embodiment 4: A flame retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps: Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after adding; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h after adding; then add 4.5g of potassium permanganate in small amounts several times (add in about 3h), stir at 35℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let 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.

[0049] Step 2: Mix 50 parts of shellac and 50 parts of tea polyphenols in a 50 ml stainless steel jar. Add 10 stainless steel balls with a diameter of 5 mm into the jar, and run the vibration ball mill at 35 Hz for 10 minutes. Stop the ball milling every 5 minutes to avoid the jar temperature from being too high, thereby obtaining tea polyphenols @ shellac microcapsules.

[0050] 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 by ultrasonication, and dry the moisture at 50°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0051] Embodiment 5: A flame retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps: Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after adding; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h after adding; 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 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.

[0052] Step 2: 45 parts of paraffin wax and 55 parts of vitamin C were mixed in a 50 ml stainless steel jar. Ten stainless steel balls with a diameter of 5 mm were added to the jar, and the vibration ball mill was operated at 35 Hz for 10 min. The ball milling was stopped every 5 min to avoid the jar temperature from being too high, thereby obtaining vitamin C@paraffin wax microcapsules.

[0053] 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.

[0054] Embodiment 6: A flame retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps: Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after adding; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h after adding; then add 4.5g of potassium permanganate in small amounts several times (add in about 3h), stir at 35℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let 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: 55 parts of beeswax and 45 parts of tea polyphenols were mixed in a 50 ml stainless steel jar. Ten stainless steel balls with a diameter of 10 mm were added to the jar, and a vibrating ball mill was operated at 25 Hz for 10 min. The ball milling was stopped every 5 min to avoid the jar temperature from being too high, thereby obtaining tea polyphenols@beeswax microcapsules.

[0056] 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.

[0057] Embodiment 7: A flame retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps: Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after adding; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h after adding; 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 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.

[0058] Step 2: 65 parts of palm wax and 35 parts of vitamin C were mixed in a 50 ml stainless steel jar. Five stainless steel balls with a diameter of 5 mm were added to the jar, and the vibration ball mill was operated at 35 Hz for 10 minutes. The ball milling was stopped every 5 minutes to avoid the jar temperature from being too high, thereby obtaining vitamin C@palm wax microcapsules.

[0059] 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.

[0060] Embodiment 8: A flame retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps: Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after adding; then add 0.5g of potassium nitrate in portions (time 30min), cool and stir for 2h after adding; then add 4.5g of potassium permanganate in small amounts several times (add in about 3h), stir at 35℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let 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.

[0061] Step 2: 70 parts of palm wax and 30 parts of tea polyphenols were mixed in a 50 ml stainless steel jar. Ten stainless steel balls with a diameter of 10 mm were added to the jar, and a vibrating ball mill was operated at 30 Hz for 10 min. The ball milling was stopped every 5 min to avoid the jar temperature from being too high, thereby obtaining tea polyphenols @ palm wax microcapsules.

[0062] 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.

[0063] Embodiment 9: A flame retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps: Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after adding; then add 0.5g of potassium nitrate in portions (time 10min), cool and stir for 2h after adding; then add 4.5g of potassium permanganate in small amounts several times (add in about 3h), stir at 35℃ for 2h, add 1.4ml of hydrogen peroxide (30%), and let 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: 40 parts of shellac and 60 parts of tea polyphenols were mixed in a 50 ml stainless steel jar. Five stainless steel balls with a diameter of 5 mm were added to the jar, and the vibration ball mill was operated at 35 Hz for 10 minutes. The ball milling was stopped every 5 minutes to avoid the jar temperature from being too high, thereby obtaining tea polyphenols @ shellac microcapsules.

[0065] Step 3: 40 parts of GO dispersion, 56 parts of tea polyphenols @ shellac microcapsules and 4 parts of ammonium phytate are mixed and dispersed evenly by ultrasonication, and the moisture is dried at 50°C to form a flame-retardant and highly sensitive GO fire alarm sensor material.

[0066] Embodiment 10: A flame retardant and highly sensitive GO fire alarm sensor material is prepared according to the following steps: Step 1: In an ice bath, slowly and in small amounts, add 1g of graphite to a 24ml beaker, and cool after adding; then add 1g of sodium nitrate in portions (time 30min), cool and stir for 2h after adding; 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 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.

[0067] Step 2: Mix 70 parts of shellac and 30 parts of vitamin C in a 50 ml stainless steel jar. Add 10 stainless steel balls with a diameter of 10 mm into the jar, and run the vibration ball mill at 30 Hz for 10 minutes. Stop the ball milling every 5 minutes to avoid the jar temperature from being too high, thereby obtaining vitamin C@shellac microcapsules.

[0068] 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.

[0069] In the process of preparing GO dispersion in Examples 1 to 10 of the present invention, different oxidation temperatures are used. Figure 1It can be seen that GO with different oxidation degrees has different 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 (that is, meet the insulation resistance requirement of low-voltage electrical appliances and their connecting circuits and secondary circuits>1MΩ), and quickly reduce to form conductive rGO at high temperature. This process is closely related to the oxidation degree of GO. 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, it is easy to cause false alarms if the insulation requirements are not met. In contrast, GO with a moderate oxidation degree has a fast thermal reduction process and a short response time on the premise of meeting the insulation requirements. On the premise of meeting the daily circuit insulation resistance requirements (>1MΩ), GO with a lower oxidation degree can be quickly thermally reduced under the stimulation of a heat source, shortening the time to form a conductive path.

[0070] The SEM photo and EDS image of the vitamin C@shellac microcapsules prepared in Example 10 of the present invention are as follows: Figure 2 As shown in the figure, the shellac-coated vitamin C prepared by the dry coating method presents a three-dimensional structure. This is because the phase change material shellac has a lower melting temperature than vitamin C and can be melted in advance in the collision heat generated by the rotor, thereby coating vitamin C. At the same time, the EDS spectrum shows that the C, O and Si elements are evenly distributed, indicating that the vitamin C@shellac microcapsules have been successfully prepared. It ensures that GO itself will not be directly reduced by antioxidants at room temperature and affect its alarm sensitivity. At the same time, the phase change material can quickly release antioxidants under the stimulation of heat sources, thereby accelerating the thermal reduction process of GO and shortening the response time.

[0071] Depend on Figures 3 to 6 It can be seen that the GO fire alarm sensor material prepared in Example 10 of the present invention has a lower response temperature and a shorter response time than the unmodified GO. It performs well in the ultra-sensitive early fire alarm response to abnormally high temperatures, wherein the time to form a conductive path to connect the alarm at 175°C is 1s, and the time to form a conductive path to connect the alarm at 150°C is 50s.

[0072] like Figure 7 As shown in the figure, the time for the unmodified GO to form a conductive path to connect the alarm under an open flame is 2s, and the continuous fire alarm time is less than 10s. The GO fire alarm sensor material prepared in Example 10 of the present invention shows a more sensitive and lasting alarm capability, and the time for forming a conductive path to connect the alarm under an open flame is 0.5s, and the continuous fire alarm time is greater than 1800s. This is because the phosphorus-containing flame retardant can catalyze GO to form a dense carbon layer to resist flame roasting, thereby improving its flame retardancy and thermal stability.

[0073] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope 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: In an ice bath, graphite is added to concentrated sulfuric acid, cooled, potassium nitrate or sodium nitrate is added in portions, cooled and stirred, potassium permanganate is added in portions, stirred at an oxidation temperature, hydrogen peroxide is added, allowed to stand, supernatant is removed by centrifugation, deionized water is added, and ultrasonic dispersion is 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, dispersed evenly by ultrasonication, and dried to obtain a flame-retardant and highly sensitive GO fire alarm sensor material.

2. The method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material according to claim 1, characterized in that: 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.

3. 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%.

4. The method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material according to claim 1, characterized in that: In the antioxidant@phase change material microcapsule, the phase change material is 25-75 parts, and the natural antioxidant is 25-75 parts.

5. The method for preparing a flame-retardant and highly sensitive GO fire alarm sensor material according to claim 1, characterized in that: 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. A flame-retardant and highly sensitive GO fire alarm sensor material prepared by the preparation method according to any one of claims 1 to 9.

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