A multifunctional repeated fire warning flame-retardant plant fiber and its preparation method and application

Abstract

The present invention relates to a multifunctional repeated fire warning flame-retardant plant fiber and its preparation method and application. The preparation method includes: S1: reducing GO to obtain a reduced GO solution; S2: obtaining modified PEDOT:PSS using an organic solvent; S3: mixing the reduced GO solution and the modified PEDOT:PSS, adding chitosan and reacting to obtain a PGO@CCS solution; impregnating the plant fiber with the PGO@CCS solution to obtain PGO@CCS@PF; S4: performing hydrophobic treatment on the PGO@CCS@PF obtained in step S3 using DA and Hf-SiO2 to obtain Hf-SiO2 / PDA / PGO@CCS@PF, which is the target product. It can be used as a sensor in a fire warning device or a human motion monitoring device. Compared with the prior art, the preparation method of the present invention is simple, has good stability, strong thermal stability, good surface hydrophobicity, has a wide sensing range, a sensitive repeated fire warning function, and has the function of monitoring human motion.

Description

Technical Field

[0001] The present invention relates to the technical field of functional materials, and particularly relates to a multifunctional repeated fire warning flame-retardant plant fiber and its preparation method and application. Background Art

[0002] In recent years, fiber interior decoration designed and manufactured from plant fibers has become increasingly popular. Indoor fiber products include curtains, tablecloths, bedding, carpets, etc. Natural fibers have attracted people's interest due to their excellent renewability, reasonable price, biodegradability, and good mechanical properties. However, due to the inherent flammability of plant fibers, it may pose potential fire safety hazards to many applications. To reduce the high fire risk, on the one hand, flame retardants are added to improve the flame retardancy of plant fibers. On the other hand, a fire warning system is developed to achieve early abnormal temperature warning and reduce unnecessary fires.

[0003] Adding flame retardants to the material substrate is a common method to improve flame retardancy. Flame retardant additives play a role in delaying or extinguishing flames when encountering high temperatures or fires. This means that flame retardants play an important role in the high-temperature combustion process, and the corresponding decomposition temperature is to a certain extent higher than the ignition temperature (350°C - 500°C) of combustible materials. However, the introduction of additive flame retardants will bring some disadvantages to substances, such as poor compatibility, complex preparation process, and unsatisfactory performance balance. In contrast, a fire alarm system can monitor abnormal temperatures before a fire occurs in an intelligent way to prevent the fire from spreading further. In addition, integrating conductive flame-retardant plant fibers onto fire-fighting suits can be used to monitor the movements of firefighters and play a certain guiding role in extinguishing fires. They can provide sufficient time and opportunities for escape and rescue.

[0004] In recent years, intelligent and sensitive fire warning temperature sensors have been widely studied and reported. Chinese Patent Publication No. CN109021983A discloses a preparation method of a modified graphene oxide flame-retardant film, which uses silanization treatment to achieve the synergistic flame retardancy enhancement of the structure thermal stability of GO (Graphene Oxid, graphene oxide) and organosilicon. Adding L-ascorbic acid can promote the thermal reduction of graphene oxide at low temperature and shorten the warning time, but an external power supply is required to convert the resistance change before and after thermal reduction into an electrical signal, which increases the complexity of the fire alarm system and cannot achieve repeated warning and be used to monitor human movements. Chinese Patent Publication No. CN111254737A discloses a multifunctional MXene coating and its preparation method and application in fire cycle detection and warning, mainly using MXene (Ti3C2T x)In the presence of the polymer PVP (polyvinylpyrrolidone), when the thin film or coating contacts the flame in the air, the coating is rapidly oxidized into a stable ordered structure of titanium metal oxide, which can stably cycle and switch when attacked by the flame subsequently. However, due to the easy oxidation of MXene in the air, the sensitivity of the temperature sensor is weakened, and the preparation process is complex, with organic pollution and high costs. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned existing technologies and provide a preparation method and application of a multifunctional repeated fire warning flame-retardant plant fiber. The preparation process of this method is simple, highly controllable, the raw materials are green and environmentally friendly, and there is no pollution in the preparation process. The repeated fire warning flame-retardant plant fiber can be applied to a fire warning device to repeatedly emit warning signals and has real-time monitoring of abnormal temperatures. In addition, the prepared flame-retardant plant fiber has excellent electrical conductivity and can be used to monitor human movement.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] The present invention provides a preparation method of a multifunctional repeated fire warning flame-retardant plant fiber, including the following steps:

[0008] S1: Reduce GO with a reducing agent to obtain a reduced GO solution;

[0009] S2: Modify PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid)) with an organic solvent to obtain modified PEDOT:PSS;

[0010] S3: Mix the reduced GO solution obtained in step S1 and the modified PEDOT:PSS obtained in step S2, add CCS (chitosan) and react to obtain a PGO@CCS solution; impregnate the plant fiber with the PGO@CCS solution to obtain PGO@CCS@PF;

[0011] S4: Perform hydrophobic treatment on the PGO@CCS@PF obtained in step S3 with DA (Dopamine) and Hf-SiO2 (hydrophobic fumed silica) to obtain Hf-SiO2 / PDA / PGO@CCS@PF, which is the target product.

[0012] Further, in step S1, the reducing agent includes one or several of L-ascorbic acid, L-tryptophan, sodium citrate, hydrazine hydrate or sodium borohydride. Further, it is ascorbic acid.

[0013] Further, in step S1, the GO exists in the form of an aqueous solution with a concentration of 2-10 mg / mL.

[0014] Further, in step S1, the dosage of the reducing agent is 5-40% of the mass dosage of the GO.

[0015] Further, in step S2, the organic solvent includes one or more of ethylene glycol, dimethylformamide, dimethyl sulfoxide, and glycerol. More preferably, it is ethylene glycol.

[0016] Further, in step S2, the PEDOT:PSS exists in the form of an aqueous solution with a mass fraction of 1-4 wt%.

[0017] Further, in step S2, the dosage of the organic solvent is 5-20% of the mass dosage of the PEDOT:PSS.

[0018] Further, in step S2, the modification treatment can enhance the conductivity of the PEDOT:PSS.

[0019] Further, the specific process of step S3 is as follows:

[0020] S31: Wash and dry the plant fiber;

[0021] S32: Stir and mix the reduced GO solution obtained in step S1 and the modified PEDOT:PSS solution obtained in step S2 to obtain a PGO solution;

[0022] S33: Add a CCS solution to the PGO solution obtained in step S32 and stir to obtain a PGO@CCS solution;

[0023] S34: Put the dried plant fiber in step S31 into the PGO@CCS solution obtained in step S33 for impregnation and assembly, take it out and dry to obtain PGO@CCS@PF.

[0024] More preferably, in step S31, the detergent includes one or more of ethanol and water.

[0025] More preferably, in step S31, the drying temperature is 40-80°C.

[0026] More preferably, in step S32, the volume ratio of the modified PEDOT:PSS solution to the reduced GO solution is 1:(2-10), preferably 1:(2-5).

[0027] More preferably, in step S32, the stirring and mixing method includes mechanical stirring or magnetic stirring, the time is 1-24 h, and the temperature is 20-30°C.

[0028] Further, in step S33, the CCS exists in the form of an aqueous solution with a concentration of 1-5 mg / mL.

[0029] Further, in step S33, the volume ratio of the PGO solution to the CCS solution is (1-10):1.

[0030] Further, in step S33, the stirring and mixing method includes mechanical stirring or magnetic stirring, the time is 1-24 h, and the temperature is 20-30 °C.

[0031] Further, in step S34, the number of times the plant fiber is impregnated and assembled in the PGO@CCS solution is 2-10 times, the temperature is room temperature, and the time is 3-7 min.

[0032] Further, in step S34, the dosage ratio of the plant fiber mass to the volume of the PGO@CCS solution is 1 g:(5-10) mL.

[0033] Further, in step S34, the drying temperature is 40-80 °C.

[0034] Further, the specific process of the hydrophobic treatment in step S4 is as follows:

[0035] S41: Prepare a DA-Tris buffer solution by taking DA and Tris (Tris(hydroxymethyl)aminomethane) solution;

[0036] S42: Add the PGO@CCS@PF obtained in step S3 to the DA-Tris buffer solution for a polymerization reaction to obtain PDA / PGO@CCS@PF;

[0037] S43: Transfer the PDA / PGO@CCS@PF obtained in step S43 to the Hf-SiO2 organic dispersion, ultrasonicate, and dry to obtain the hydrophobic Hf-SiO2 / PDA / PGO@CCS@PF, which is the target product.

[0038] Further, in step S41, the concentration of the DA-Tris buffer solution is 5-30 mg / mL.

[0039] Further, in step S42, the mass ratio of PGO@CCS@PF to DA in the DA-Tris buffer solution is (1-5):1.

[0040] Further, in step S42, the polymerization reaction time is 12-48 h, and the temperature is room temperature to modify the plant fiber with DA.

[0041] Further, in step S43, the concentration of the Hf-SiO2 organic dispersion is 0.01 to 1 g / mL.

[0042] Further, in step S43, the organic solvent used in the Hf-SiO2 organic dispersion includes one or more of ethanol, ethyl acetate, toluene, methyl ethyl ketone, solvent oil, and isopropanol. Further, it is ethanol.

[0043] Further, in step S43, the mass ratio of PDA / PGO@CCS@PF to Hf-SiO2 in the Hf-SiO2 organic dispersion is (1 to 5):1.

[0044] The present invention also provides a repeat fire warning flame-retardant plant fiber prepared by the above preparation method.

[0045] The present invention also provides an application of the multifunctional repeat fire warning flame-retardant plant fiber as a sensor for a fire warning device.

[0046] Further, the fire warning device is composed of a voltage millivoltmeter, an alarm, and a repeat fire warning flame-retardant plant fiber connected in sequence by wires. When one end of the plant fiber with a warning function is heated with an alcohol lamp, the carriers of the thermoelectric material coated on the plant fiber will move from the high-temperature area at the heating end to the low-temperature area, thus forming a potential difference. There will be a certain voltage signal in the voltage millivoltmeter connected by wires. When the voltage signal exceeds the set value of 0.5 mv, the alarm will emit a warning signal.

[0047] The present invention also provides an application of the multifunctional repeat fire warning flame-retardant plant fiber as a sensor for a human motion monitoring device.

[0048] Further, the human motion monitoring device is composed of a multimeter and a repeat fire warning flame-retardant plant fiber attached to body activity parts such as fingers, wrists, knees, etc. to monitor their movements. The repeat fire warning flame-retardant plant fiber prepared by the present invention has good electrical conductivity, and slight deformations such as stretching, pressing, bending, etc. can cause sensitive changes in its impedance.

[0049] Compared with the prior art, the present invention has the following advantages:

[0050] (1) The PEDOT:PSS adopted by the present invention has a relatively high conductivity (200 - 7000 S·cm -1 ) and good water dispersibility (1.1 - 1.7 wt%), and is considered to be one of the most promising conductive polymer materials. The PEDOT:PSS modified by GO has good thermoelectric conversion performance, so the reversible change between thermoelectricity can be realized.

[0051] (2) The present invention uses a method of low-temperature induced self-assembly to improve the thermoelectric performance of PEDOT:PSS with GO, which is simple, green, has good stability, low cost and strong controllability.

[0052] (3) The PEDOT:PSS adopted by the present invention has excellent thermoelectric performance, endowing the repeatable fire warning flame-retardant plant fiber with the ability to monitor abnormal temperature in real time and sensitive warning response time. When applied to a fire warning device, the quantitative relationship between the output voltage and the temperature difference in the fire warning device provides the repeatable and real-time fire warning ability of PEDOT:PSS, which can repeatedly issue an alarm before the material reaches the ignition temperature and can also be reused without an external power source. When applied to a human motion monitoring device, under the action of an external force, the internal distance of the prepared conductive plant fiber is reduced, and the number of conductive paths formed by the collision of the inner walls increases, and finally the resistance rapidly decreases. On the contrary, when the applied force disappears, the number of formed conductive circuits decreases, so the resistance rapidly increases and the resistance returns to the initial state.

[0053] (4) In the repeatable fire warning flame-retardant plant fiber provided by the present invention, the thermoelectric layer forms an ordered hierarchical structure through the self-assembly of chitosan and PGO at low temperature. When applied to a fire warning device, it creates high efficiency for the carrier. The carrier quickly transmits through the transmission channel from the high-temperature region to the low-temperature region, generating a potential difference to trigger an alarm and achieving high sensing efficiency. During combustion, the fire alarm system can be quickly triggered 3 times repeatedly within 7 seconds. When applied to a human motion monitoring device, it also makes the resistance change more sensitive for human monitoring.

[0054] (5) The multifunctional repeatable fire warning flame-retardant plant fiber provided by the present invention is assembled with DA and Hf-SiO2 on the outer layer, which improves the flame retardancy on the one hand and increases the surface hydrophobicity on the other hand. When applied to a fire warning device and human motion monitoring, it is beneficial to improve the long-term stability.

[0055] (6) The preparation process of the present invention is simple, has strong controllability, the raw materials are green and environmentally friendly, and the preparation process is pollution-free. Description of the Drawings

[0056] Figure 1 XRD pattern of GO reduced by L-ascorbic acid in Example 1;

[0057] Figure 2 Graph of the real-time relationship between output voltage and time in Example 2;

[0058] Figure 3 Graph of the relationship between output voltage and time at different temperatures in Example 3;

[0059] Figure 4 Repeat monitoring graph of fire warning in Example 3;

[0060] Figure 5 It is the human body movement monitoring diagram in Example 4. Detailed implementation manners

[0061] To make the invention object, features, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all embodiments. Based on the given embodiments, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0062] In the following embodiments, L-ascorbic acid and DA (purity ≥ 99.0%) are both purchased from Sinopharm Chemical Reagent Co., Ltd., PEDOT:PSS is purchased from China Reagent Network, and the surface density is 200 g·m -2 The plant fiber is purchased from Libeco-Lagae Co., Ltd. (Belgium), and Hf-SiO2 (diameter 16 nm, specific surface area 110 m 2 ·g -1 ) is purchased from Evonik Industries AG, Germany.

[0063] Example 1

[0064] A preparation method and application of a multifunctional repeated fire warning flame-retardant plant fiber, including the following steps:

[0065] S1: Reducing GO: Weigh 0.2 g of GO and add it to 100 mL of water to prepare a 2 mg / mL uniformly dispersed aqueous solution; add 12 mg of the reducing agent L-ascorbic acid, and magnetically stir at room temperature for 12 h at a stirring speed of 600 r / min to fully reduce GO and obtain reduced GO;

[0066] S2: Modifying PEDOT:PSS: Add 5 mL of ethylene glycol to 50 mL of a 1.7 wt% PEDOT:PSS aqueous solution, and magnetically stir at room temperature for 10 h at a stirring speed of 600 r / min to enhance the conductivity of PEDOT:PSS and obtain modified PEDOT:PSS;

[0067] S3: PGO@CCS Treatment: Wash the surface impurities of the plant fiber with ethanol and water, and then place it in an oven at 60 °C for drying for 12 h; Weigh 0.2 g of carboxymethyl chitosan and add it to 200 mL of water to prepare a 1 mg / mL carboxymethyl chitosan solution; Measure 6 mL of the reduced GO obtained in step S1 and 3 mL of the modified PEDOT:PSS obtained in step S2 and mix them to obtain a PGO solution. Then add 1.4 mL of the carboxymethyl chitosan solution and magnetically stir it at room temperature for 6 h at a stirring speed of 600 r / min to obtain a uniform PGO@CCS solution; Put 1.5 g of the dried plant fiber into 10.4 mL of the PGO@CCS solution and impregnate it at room temperature for 5 min. Take it out and place it in an oven at 60 °C for drying for 30 min. Repeat this process 6 times to obtain PGO@CCS@PF;

[0068] S4: Hydrophobic Treatment: Weigh 1.5 g of DA and dissolve it in 100 mL of Tris solution with a pH of 8.5 to prepare a 15 mg / mL DA-Tris buffer solution, and magnetically stir it at room temperature for 12 h; Add 1.64 g of PGO@CCS@PF obtained in step S3 to 50 mL of the DA-Tris buffer solution and magnetically stir it for 1 h, and carry out polymerization at room temperature for 24 h. Take it out and place it in an oven at 60 °C for drying for 1 h. Obtain PDA / PGO@CCS@PF; Weigh 2 g of Hf-SiO2 and dissolve it in 200 mL of ethanol solution to prepare a 0.01 g / mL silicon dioxide ethanol solution; Put 1.7 g of the obtained PDA / PGO@CCS@PF into 50 mL of the silicon dioxide ethanol solution and ultrasonicate it for 10 min. Take it out and place it in an oven at 60 °C for drying for 1 h to obtain Hf-SiO2 / PDA / PGO@CCS@PF, which is the target product.

[0069] Example 2

[0070] A preparation method and application of a multifunctional repeated fire warning flame-retardant plant fiber, comprising the following steps:

[0071] S1: Reduction of GO: Weigh 0.3 g of GO and add it to 100 mL of water to prepare a uniformly dispersed aqueous solution of 3 mg / mL; Add 24 mg of the reducing agent L-ascorbic acid and magnetically stir it at room temperature for 12 h at a stirring speed of 700 r / min to fully reduce GO and obtain reduced GO;

[0072] S2: Modification of PEDOT:PSS: Add 5 mL of ethylene glycol to 50 mL of a 1.7 wt% PEDOT:PSS aqueous solution and magnetically stir it at room temperature for 10 h at a stirring speed of 700 r / min to enhance the conductivity of PEDOT:PSS and obtain modified PEDOT:PSS;

[0073] S3: PGO@CCS Treatment: Wash the surface impurities of plant fibers with ethanol and water, and place them in an oven at 60 °C for drying for 12 h; Weigh 0.4 g of carboxymethyl chitosan and add it to 200 mL of water to prepare a 2 mg / mL carboxymethyl chitosan solution; Measure 6 mL of the reduced GO obtained in step S1 and 3 mL of the modified PEDOT:PSS obtained in step S2 respectively for mixing to obtain a PGO solution, then add 2.5 mL of the carboxymethyl chitosan solution, and stir magnetically at room temperature for 6 h with a stirring speed of 700 r / min to obtain a uniform PGO@CCS solution; Put 1.8 g of the dried plant fibers into 11.5 mL of the PGO@CCS solution and impregnate them at room temperature for 5 min, take them out and place them in an oven at 60 °C for drying for 30 min, and repeat this process 8 times to obtain PGO@CCS@PF;

[0074] S4: Hydrophobic Treatment: Weigh 2 g of DA and dissolve it in 100 mL of Tris solution with a pH of 8.5 to prepare a 20 mg / mL DA-Tris buffer solution, and stir magnetically at room temperature for 12 h; Add 1.95 g of PGO@CCS@PF obtained in step S3 to 50 mL of the DA-Tris buffer solution and stir magnetically for 1 h, and carry out polymerization at room temperature for 24 h, then take it out and place it in an oven at 60 °C for drying for 1 h. Obtain PDA / PGO@CCS@PF; Weigh 2 g of Hf-SiO2 and dissolve it in 100 mL of ethanol solution to prepare a 0.02 g / mL silicon dioxide ethanol solution; Put the obtained 2.04 g of PDA / PGO@CCS@PF into 50 mL of the silicon dioxide ethanol solution and ultrasonicate for 10 min, then take it out and place it in an oven at 60 °C for drying for 1 h to obtain Hf-SiO2 / PDA / PGO@CCS@PF, which is the target product.

[0075] Example 3

[0076] A preparation method and application of a multifunctional repeated fire warning flame-retardant plant fiber, comprising the following steps:

[0077] S1: Reduction of GO: Weigh 0.3 g of GO and add it to 100 mL of water to prepare a 3 mg / mL uniformly dispersed aqueous solution; Add 36 mg of the reducing agent L-ascorbic acid, and stir magnetically at room temperature for 12 h with a stirring speed of 800 r / min to fully reduce GO and obtain reduced GO;

[0078] S2: Modification of PEDOT:PSS: Add 5 mL of ethylene glycol to 50 mL of a 1.7 wt% PEDOT:PSS aqueous solution, and stir magnetically at room temperature for 10 h with a stirring speed of 800 r / min to enhance the conductivity of PEDOT:PSS and obtain modified PEDOT:PSS;

[0079] S3: PGO@CCS Treatment: Wash the surface impurities of the plant fiber with ethanol and water, and place it in an oven at 60 °C for drying for 12 h; weigh 0.2 g of carboxymethyl chitosan and add it to 200 mL of water to prepare a 1 mg / mL carboxymethyl chitosan solution; measure 6 mL of the reduced GO obtained in step S1 and 3 mL of the modified PEDOT:PSS obtained in step S2 respectively for mixing to obtain a PGO solution, then add 3.7 mL of the carboxymethyl chitosan solution, and magnetically stir at room temperature for 6 h with a stirring speed of 800 r / min to obtain a uniform PGO@CCS solution; put the dried 1.8 g of plant fiber into 12.7 mL of the PGO@CCS solution and impregnate it at room temperature for 5 min, take it out and place it in an oven at 60 °C for drying for 30 min, and repeat this process 10 times to obtain PGO@CCS@PF;

[0080] S4: Hydrophobic Treatment: Weigh 2 g of DA and dissolve it in 100 mL of Tris solution with a pH of 8.5 to prepare a 20 mg / mL DA-Tris buffer solution, and magnetically stir at room temperature for 12 h; add 1.98 g of PGO@CCS@PF obtained in step S3 to 50 mL of the DA-Tris buffer solution and magnetically stir for 1 h, and carry out polymerization at room temperature for 24 h, then take it out and place it in an oven at 60 °C for drying for 1 h. Obtain PDA / PGO@CCS@PF; weigh 2 g of Hf-SiO2 and dissolve it in 50 mL of ethanol solution to prepare a 0.04 g / mL silicon dioxide ethanol solution; put the obtained 2.08 g of PDA / PGO@CCS@PF into 50 mL of the silicon dioxide ethanol solution and ultrasonicate for 10 min, then take it out and place it in an oven at 60 °C for drying for 1 h to obtain Hf-SiO2 / PDA / PGO@CCS@PF, which is the target product.

[0081] Example 4

[0082] Compared with Example 1, most of them are the same, except that in step S1, the reducing agent ascorbic acid is changed to L-tryptophan.

[0083] Example 5

[0084] Compared with Example 1, most of them are the same, except that in step S1, the mass of GO is adjusted to 1.0 g, and 100 mL of water is added to prepare a uniformly dispersed aqueous solution of 10 mg / mL.

[0085] Example 6

[0086] Compared with Example 2, most of them are the same, except that in step S1, the dosage of the reducing agent L-ascorbic acid is adjusted to 10 mg.

[0087] Example 7

[0088] Compared with Example 2, most of them are the same, except that in step S1, the dosage of the reducing agent L-ascorbic acid is adjusted to 80 mg.

[0089] Example 8

[0090] Compared with Example 2, most of them are the same, except that the mass fraction of the PEDOT:PSS solution in step S2 is adjusted to 1 wt%.

[0091] Example 9

[0092] Compared with Example 2, most of them are the same, except that the amount of ethylene glycol in step S2 is adjusted to 5 ml.

[0093] Example 10

[0094] Compared with Example 2, most of them are the same, except that the mass of carboxymethyl chitosan weighed in step S3 is adjusted to 1.0 g, and 200 mL of water is added to prepare a 5 mg / mL carboxymethyl chitosan solution.

[0095] Example 11

[0096] Compared with Example 2, most of them are the same, except that the volume of the carboxymethyl chitosan solution added in step S3 is adjusted to 9 mL.

[0097] Example 12

[0098] Compared with Example 2, most of them are the same, except that the volume of the reduced GO obtained in step S1 measured in step S3 is adjusted to 15 mL.

[0099] Example 13

[0100] Compared with Example 2, most of them are the same, except that the number of impregnation and assembly times in step S3 is adjusted to 2 times.

[0101] Example 14

[0102] Compared with Example 2, most of them are the same, except that the amounts of plant fiber and PGO@CCS solution in step S3 are adjusted to 1.8 g and 9 ml.

[0103] Example 15

[0104] Compared with Example 2, most of them are the same, except that the amounts of plant fiber and PGO@CCS solution in step S3 are adjusted to 1.8 g and 18 ml.

[0105] Example 16

[0106] Compared with Example 2, most of them are the same, except that the mass of DA weighed in step S4 is adjusted to 0.5 g, dissolved in 100 mL of Tris solution with a pH of 8.5 to prepare a 5 mg / mL DA-Tris buffer solution. The volume of the added DA-Tris buffer solution is adjusted to 64 mL.

[0107] Example 17

[0108] Compared with Example 2, most of them are the same, except that in step S4, the mass of DA weighed is adjusted to 3.0 g, dissolved in 100 mL of Tris solution with a pH of 8.5 to prepare a 30 mg / mL DA-Tris buffer solution. The volume of the added DA-Tris buffer solution is adjusted to 65 mL.

[0109] Example 18

[0110] Compared with Example 2, most of them are the same, except that in step S4, the polymerization time is adjusted to 12 h.

[0111] Example 19

[0112] Compared with Example 2, most of them are the same, except that in step S4, the polymerization time is adjusted to 48 h.

[0113] Example 20

[0114] Compared with Example 2, most of them are the same, except that in step S4, the mass of Hf-SiO2 weighed is 0.08 g, and the volume of the ethanol solution is adjusted to 50 mL to prepare a 1 g / mL silicon dioxide ethanol solution.

[0115] Comparative Example 1

[0116] Compared with Example 2, most of them are the same, except that in step S2, the volume of the PEDOT:PSS aqueous solution is 0 ml, that is, no PEDOT:PSS is added.

[0117] Comparative Example 2

[0118] Compared with Example 2, most of them are the same, except that in step S2, the PEDOT:PSS aqueous solution is adjusted to a polypyrrole aqueous solution.

[0119] Comparative Example 3

[0120] Compared with Example 2, most of them are the same, except that in step S4, the mass of Hf-SiO2 weighed is 0 g, that is, no Hf-SiO2 is added.

[0121] Performance test:

[0122] I. GO analysis before and after the reduction of L-ascorbic acid

[0123] XRD analysis was performed on GO before and after the reduction of L-ascorbic acid in Example 1, and the results are as Figure 1As shown, it can be seen that after deoxidation with the reducing agent L-ascorbic acid, a relatively flat characteristic peak appears near 2θ = 20° for the reduced GO. This is because the oxygen-containing groups in graphene oxide are removed, reducing the interlayer spacing, making the reduced GO conductive, increasing the output voltage, and improving the thermoelectric performance.

[0124] II. Relationship between voltage and temperature difference

[0125] The Hf-SiO2 / PDA / PGO@CCS@PF obtained in Example 2 was assembled into a fire warning device, which consists of a voltage millivoltmeter, an alarm, and a multifunctional repeated fire warning flame-retardant plant fiber connected in sequence by wires. When one end of the multifunctional repeated fire warning flame-retardant plant fiber is heated with an alcohol lamp, the carriers of the thermoelectric material on the outer layer coated with the multifunctional repeated fire warning flame-retardant plant fiber will move from the high-temperature area at the heating end to the low-temperature area, thus forming an electric potential difference. The millivoltmeter connected by wires will have a certain voltage signal. When the voltage signal exceeds the set value of 0.5 mV, the alarm will emit a warning signal. The relationship between voltage and temperature difference was fitted, and the results are as Figure 2 shown. It can be seen that there is a linear relationship between the generated voltage and the temperature difference. We can accurately calculate the temperature difference between two points based on the voltage. When the output voltage is 3 mV, the temperature difference is 258 °C, thus sensitively sensing the change in temperature.

[0126] The Hf-SiO2 / PDA / PGO@CCS@PF obtained in Example 3 was assembled into a fire warning device, and the relationship between voltage and time at different temperature differences was tested. The results are as Figure 3 shown. It can be seen that the output voltage of Hf-SiO2 / PDA / PGO@CCS@PF increases regularly with the increase of the temperature difference. As the temperature further increases, the voltage generated at both ends of Hf-SiO2 / PDA / PGO@CCS@PF also increases. When the temperature difference increases from 100 °C to 200 °C, the maximum output voltage increases from 1.05 mV to 1.96 mV. The repeated monitoring diagram of fire warning is as Figure 4 shown. When the temperature reaches 250 °C, the alarm emits a danger warning signal within 2.5 s. And due to its excellent fire resistance and combustion stability, when a fire occurs again, the fire alarm system can be triggered again.

[0127] III. Monitoring human movement

[0128] The low-temperature fire warning device was integrated into a fire-fighting suit for human movement detection. The prepared multifunctional repeated fire warning flame-retardant plant fiber was cut into pieces of 1 * 1 cm in size, pasted on the finger through a copper electrode, and connected to a multimeter through a wire. The finger resistance response curve diagram for human movement detection is as Figure 5As shown, it can be seen that under the action of an external force, the internal distance of Hf-SiO2 / PDA / PGO@CCS@PF decreases, and the number of conductive paths formed by the collision of the inner wall increases, and finally the resistance decreases rapidly. On the contrary, when the external force applied to Hf-SiO2 / PDA / PGO@CCS@PF disappears, the number of formed conductive circuits decreases, so the resistance increases rapidly. The resistance is restored to the initial state.

[0129] The performance of Hf-SiO2 / PDA / PGO@CCS@PF obtained in Examples 1-2 and Comparative Examples 1-3 was detected, and the performance detection methods are as follows:

[0130] Thermoelectric performance: Hf-SiO2 / PDA / PGO@CCS@PF was assembled into a fire warning device, which was composed of a voltage millivoltmeter and an alarm. The multifunctional repeated fire warning flame-retardant plant fibers were connected in sequence by wires. When one end of the plant fiber with a warning function was heated with an alcohol lamp, the carriers of the thermoelectric material on the outer layer coated with the plant fiber would move from the high-temperature area at the heating end to the low-temperature area, thus forming a potential difference. There will be a certain voltage signal on the millivoltmeter connected by wires, that is, the thermoelectric performance is represented by the voltage value of the voltmeter. When the voltage signal exceeds the set value of 0.5 mv, the alarm will send out a warning signal.

[0131] Flame retardant performance: The flame retardant performance is represented by the limiting oxygen index, which is measured by the candle burning test. The plant fiber is burned downward under specific conditions for measurement. The limiting oxygen index refers to the lowest oxygen concentration required for a material to burn with a flame in an oxygen-nitrogen mixed gas stream under specified conditions. It is expressed as the value of the volume percentage of oxygen.

[0132] LOI = Vo2 / (Vo2 + V N2 )

[0133] Surface hydrophobic performance: The hydrophobic performance is represented by the contact angle. The test method is the profile image analysis method. The principle of the profile image analysis method is to drop a liquid droplet on the surface of a solid sample, obtain the profile image of the liquid droplet through a microscope lens and a camera, and then calculate the contact angle of the liquid droplet in the image by using digital image processing.

[0134] γSV = γSL + γLV × cosθ

[0135] Piezoelectric performance: The response law of different movements is represented by the resistance change rate (R - R0) / R0. The initial resistance is R0, and the resistance during the movement change process is R. The resistance change rate is calculated using the formula (R - R0) / R0.

[0136] The test results are as follows:

[0137]

[0138] As can be seen from the above table:

[0139] (1) When PEDOT:PSS is not added in Comparative Example 1, there is no voltage value, that is, no conductivity. Compared with Comparative Example 1, Examples 1 and 2 have excellent thermoelectric performance, which are 2.82 mv and 3.08 mv respectively, and can repeat the warning and real-time monitor abnormal temperature. Since the prepared Hf-SiO2 / PDA / PGO@CCS@PF has good electrical conductivity and piezoresistive sensing performance, it can be applied to fire warning devices and human motion monitoring devices;

[0140] (2) In Comparative Example 2, the PEDOT:PSS aqueous solution is adjusted to a polypyrrole aqueous solution. Compared with Comparative Example 2, Examples 1 and 2 have excellent thermoelectric performance. The output voltage of Comparative Example 2 is only 0.25 mv, and the prepared plant fiber has weak electrical conductivity and cannot be applied to fire warning devices and human motion monitoring devices;

[0141] (3) Compared with Comparative Example 3, Examples 1 and 2 have excellent flame retardant performance. The limiting oxygen indices are 33.6 and 33.5 respectively, and the surfaces are hydrophobic, and the hydrophobic angles are 125° and 127° respectively; Since the amount of Hf-SiO2 added in Comparative Example 20 is 0, the limiting oxygen index is 21.3 and the hydrophobic angle is 9.7°, making the prepared plant fiber flammable and hydrophilic. The sensor is damaged after one response and does not have the function of repeated warning.

[0142] The above are only the preferred embodiments of the present invention, and are not limitations to the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of a multifunctional repeated fire warning flame-retardant plant fiber, characterized in that, It includes the following steps: S1: Reduce GO using a reducing agent to obtain a reduced GO solution; S2: Modify PEDOT:PSS using an organic solvent to obtain modified PEDOT:PSS, where the organic solvent includes one or several of ethylene glycol, dimethylformamide, dimethyl sulfoxide, or glycerol; S3: Mix the reduced GO solution obtained in step S1 and the modified PEDOT:PSS obtained in step S2, add CCS and react to obtain a PGO@CCS solution; impregnate plant fibers with the PGO@CCS solution to obtain PGO@CCS@PF; S4: Perform hydrophobic treatment on the PGO@CCS@PF obtained in step S3 using DA and Hf-SiO2 to obtain Hf-SiO2 / PDA / PGO@CCS@PF, which is the target product.

2. The preparation method of a multifunctional repetitive fire warning flame-retardant plant fiber according to claim 1, characterized in that, In step S1, the reducing agent includes one or several of L-ascorbic acid, L-tryptophan, sodium citrate, hydrazine hydrate, or sodium borohydride; The GO exists in the form of an aqueous solution with a concentration of 2 - 10 mg / mL; The dosage of the reducing agent is 5 - 40% of the mass dosage of the GO.

3. The preparation method of a multifunctional repeated fire warning flame-retardant plant fiber according to claim 1, characterized in that In step S2, the PEDOT:PSS exists in the form of an aqueous solution with a mass fraction of 1 - 4 wt%; The dosage of the organic solvent is 5 - 20% of the mass dosage of the PEDOT:PSS.

4. The preparation method of a multifunctional repeated fire warning and flame retardant plant fiber according to claim 1, characterized in that, The specific process of step S3 is as follows: S31: Wash and dry the plant fibers; S32: Stir and mix the reduced GO solution obtained in step S1 and the modified PEDOT:PSS solution obtained in step S2 to obtain a PGO solution; S33: Add CCS to the PGO solution obtained in step S32 and stir to obtain a PGO@CCS solution; S34: Put the dried plant fibers from step S31 into the PGO@CCS solution obtained in step S33 for impregnation and assembly, take them out and dry to obtain PGO@CCS@PF.

5. The preparation method of a multifunctional repeated fire warning flame retardant plant fiber according to claim 4, characterized in that, In step S31, the detergent includes one or more of ethanol and water; In step S31, the drying temperature is 40 - 80 °C; In step S32, the volume ratio of the modified PEDOT:PSS solution to the reduced GO solution is 1:(2 - 10); In step S32, the stirring and mixing method includes mechanical stirring or magnetic stirring, the time is 1 - 24 h, and the temperature is 20 - 30 °C; In step S33, the CCS exists in the form of an aqueous solution with a concentration of 1 - 5 mg / mL; In step S33, the volume ratio of the PGO solution to the CCS solution is (1 - 10):1; In step S33, the stirring and mixing method includes mechanical stirring or magnetic stirring, the time is 1 - 24 h, and the temperature is 20 - 30 °C; In step S34, the number of times the plant fibers are impregnated and assembled in the PGO@CCS solution is 2 - 10 times, the temperature is room temperature, and the time is 3 - 7 min; In step S34, the dosage ratio of the mass of the plant fibers to the volume of the PGO@CCS solution is 1 g:(5 - 10) mL; In step S34, the drying temperature is 40 - 80 °C.

6. The preparation method of a multifunctional repeated fire warning flame retardant plant fiber according to claim 1, characterized in that, The specific process of the hydrophobic treatment in step S4 is as follows: S41: Prepare a DA-Tris buffer solution by taking DA and Tris solution. S42: Add the PGO@CCS@PF obtained in step S3 into the DA-Tris buffer solution for polymerization reaction to obtain PDA / PGO@CCS@PF. S43: Transfer the PDA / PGO@CCS@PF obtained in step S42 to the Hf-SiO2 organic dispersion, ultrasonicate, and dry to obtain the hydrophobic Hf-SiO2 / PDA / PGO@CCS@PF, which is the target product.

7. The preparation method of a multifunctional repeated fire warning flame-retardant plant fiber according to claim 6, characterized in that, In step S41, the concentration of DA in the DA-Tris buffer solution is 5 - 30 mg / mL. In step S42, the mass ratio of PGO@CCS@PF to DA in the DA-Tris buffer solution is (1 - 5):

1. In step S42, the polymerization reaction time is 12 - 48 h and the temperature is room temperature. In step S43, the concentration of Hf-SiO2 in the Hf-SiO2 organic dispersion is 0.01 - 1 g / mL. In step S43, the organic solvents used in the Hf-SiO2 organic dispersion include one or more of ethanol, ethyl acetate, toluene, methyl ethyl ketone, solvent oil, and isopropanol. In step S43, the mass ratio of PDA / PGO@CCS@PF to Hf-SiO2 in the Hf-SiO2 organic dispersion is (1 - 5):

1.

8. A multifunctional repeated fire warning flame-retardant plant fiber, characterized in that, It is prepared by the preparation method according to any one of claims 1 - 7.

9. The application of a multifunctional repeated fire warning flame-retardant plant fiber as claimed in claim 8, characterized in that, It is used as a sensor in a fire warning device or a human motion monitoring device.

10. The application of a multifunctional repeated fire warning and flame retardant plant fiber according to claim 9, characterized in that, The fire warning device is composed of a millivoltmeter, an alarm, and a repeated fire warning flame-retardant plant fiber connected in sequence by wires. The human motion monitoring device is composed of a multimeter and a repeated fire warning flame-retardant plant fiber attached to the body activity part.

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