Flame-retardant intelligent temperature early warning fiber based on waste aramid fiber, preparation method and application

Abstract

The invention discloses a flame-retardant intelligent temperature early-warning fiber based on waste aramid fibers, a preparation method and application. The method comprises the following steps: preparing an ANF dispersion liquid with a first concentration and an ANF dispersion liquid with a second concentration through proton donor assisted deprotonation; the single-layer MXene DMSO dispersion liquid is added into the ANF dispersion liquid with the first concentration, and an MXene / ANF spinning solution is prepared; taking the MXene / ANF spinning solution as a core layer, taking the ANF dispersion solution with the second concentration as a skin layer, and carrying out coaxial wet spinning to prepare the ANF-coated MXene / ANF coaxial composite fiber with the skin-core structure. The outer layer of the skin-core structure not only can improve the mechanical property of the whole fiber, but also provides a protection effect for the core layer, and isolates most of air and moisture to delay oxidation of MXene of the core layer, so that the application value is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal protection materials and relates to a flame-retardant intelligent temperature warning fiber based on waste aramid, a preparation method and an application thereof. Background Art

[0002] Extreme heat and flames are a ubiquitous threat in modern industry, aerospace, defense, and everyday life, making thermal protection materials increasingly important. Rapid advances in electronic information, functional materials, and high-performance fiber technologies are driving the development of intelligent thermal protection textiles. New materials, such as graphene oxide (GO), carbon nanotubes (CNT), and MXene, exhibit unique negative temperature coefficient (NTC) thermosensitivity, meaning their electrical resistance decreases dramatically at high temperatures. This property enables them to automatically sense temperature changes and provide rapid high-temperature warnings in aerospace, security, and emergency response, surpassing traditional passive protection.

[0003] In recent years, MXene has emerged as an ideal candidate for the development of efficient sensors and flame retardants due to its dual functional advantages. It not only offers passive flame retardancy but also proactive fire warning capabilities. Unlike the one-time limitations of GO and CNT-based sensors, MXene undergoes thermal oxidation at high temperatures to form a TiO2 network. As the temperature rises, the electrons in this network are excited, causing cyclic changes in resistance, giving it repeatable warning capabilities.

[0004] Currently, the preparation methods of MXene-based fibers include coating, wet spinning, electrospinning, double curling and 3D printing.

[0005] Coating technology: When preparing functional fibers through coating, it is necessary to optimize interfacial interactions to increase MXene loading and adhesion stability. Furthermore, MXene exhibits poor adhesion to certain materials, such as polyethylene terephthalate (PET) fibers.

[0006] Spinning technology: Because MXene is an inorganic compound, its flakes are small and have weak interlayer forces, making it difficult to assemble MXene dispersions into fibers individually through wet spinning. Furthermore, MXene particles or flakes are prone to agglomeration and re-accumulation, which can lead to inconsistent fiber diameter and morphology. Therefore, obtaining a relatively stable and uniform spinning solution is crucial.

[0007] Double-curling technology: CNT sheet production is expensive and poses biosafety concerns. Its application in wearable electronics faces stringent safety requirements and requires further consideration. Furthermore, the fiber length produced using this method is limited, making it applicable only to small devices with high electrochemical performance requirements, making large-scale commercial applications difficult.

[0008] In summary, MXene's unique interlayer structure leads to weak interlayer interactions, which directly affects the overall mechanical properties of the fiber. Furthermore, MXene sheets have poor environmental resistance and are susceptible to oxidation failure in high temperatures and fires, severely impacting their performance. Furthermore, most thermal protection materials focus on a single function. Common flame-retardant materials cannot provide temperature change information, while some temperature monitoring and early warning materials are primarily designed for temperature measurement and lack flame retardancy.

[0009] Therefore, developing an intelligent fiber material that is both tough and environmentally stable, as well as flame retardant and has fire warning properties, can provide more powerful protection for thermal protection fields such as firefighting, aerospace, emergency rescue, metallurgy, and mining, thereby protecting people's lives and property safety to the greatest extent. Summary of the Invention

[0010] In view of the problems existing in the prior art, the present invention provides a flame-retardant intelligent temperature warning fiber based on waste aramid and its preparation method and application. A single-layer Ti3C2T3O3 fiber is prepared by mild etching with hydrochloric acid (HCl) and lithium fluoride (LiF). x MXene; MXene is mixed with the organic solvent dimethyl sulfoxide (DMSO) to prepare a single layer of Ti3C2T x Xene DMSO dispersion; then, waste aramid 1414 para-fiber PPTA is deprotonated by a proton donor-assisted method to prepare a stable ANF dispersion; the MXene DMSO dispersion and the ANF dispersion are evenly mixed in proportion to prepare a MXene / ANF spinning solution; finally, the intrinsic flame retardant waste aramid nanofiber ANF dispersion is used as the skin layer and the semiconductor material MXene / ANF is used as the core layer. The ANF@MXene / ANF coaxial composite fiber with the skin-core structure is prepared by a coaxial wet spinning method. The composite fiber has the dual functions of outer layer flame retardant protection and inner layer temperature warning, thereby solving the technical problems in the prior art of MXene as a thermal protection material, such as insufficient mechanical properties, poor environmental stability, and single function.

[0011] The present invention is achieved through the following technical solutions:

[0012] A method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid, comprising the following steps:

[0013] S1: KOH, PPTA, water and DMSO are mixed and stirred to prepare an ANF dispersion of a first concentration and an ANF dispersion of a second concentration, wherein the first concentration is less than the second concentration;

[0014] S2: adding the monolayer MXene DMSO dispersion to the first concentration of ANF dispersion to prepare the MXene / ANF spinning solution;

[0015] S3: Using the MXene / ANF spinning solution as the core layer and the ANF dispersion of the second concentration as the skin layer, coaxial wet spinning is performed to obtain the ANF@MXene / ANF coaxial composite fiber with the skin-core structure.

[0016] Preferably, the concentration of the ANF dispersion at the first concentration is 15 mg / mL.

[0017] Preferably, the concentration of the ANF dispersion at the second concentration is 30 mg / mL.

[0018] Preferably, in step S1, after KOH, PPTA, water and DMSO are mixed, and stirred to prepare the ANF dispersion of the first concentration and the ANF dispersion of the second concentration, the stirring temperature is 60° C., the stirring speed is 1200 rpm, and the stirring time is 7 days.

[0019] Preferably, the solid content of the monolayer MXene DMSO dispersion is 5 wt% to 30 wt%.

[0020] Preferably, the preparation of the monolayer MXene DMSO dispersion is specifically as follows: MXene is added to dimethyl sulfoxide, ultrasonicated in an ice bath under nitrogen protection for 6 hours, and then centrifuged at a centrifugal speed of 3000 rpm for 30 minutes to obtain the monolayer MXene DMSO dispersion.

[0021] Preferably, the preparation of the MXene is specifically as follows: using Ti3AlC2 MAX phase precursor as a raw material, etching with lithium fluoride and hydrochloric acid to obtain the MXene.

[0022] Preferably, in step S3, in the coaxial wet spinning, the inner needle is 16G, the outer needle is 12G, and the spinning speeds of the inner needle and the outer needle are 200 μL / min and 350 μL / min, respectively.

[0023] A flame-retardant intelligent temperature warning fiber based on waste aramid is prepared by the above-mentioned preparation method.

[0024] The above-mentioned application of the flame-retardant intelligent temperature warning fiber based on waste aramid in fireproof materials.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] A method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid. This method uses high-concentration aramid nanofibers (ANF) as the outer spinning solution for coaxial spinning, leveraging the inherent high strength and high modulus properties of aramid. The skin and core layers are both based on ANF, and seamless bonding is achieved through coaxial spinning, enhancing interfacial adhesion and avoiding mechanical defects caused by slippage between MXene layers. In addition, the highly dense ANF outer layer isolates oxygen and moisture, significantly slowing the oxidation rate of the core layer MXene under high temperature / flame. Moreover, when the skin layer ANF burns, a char layer is formed, further blocking the penetration of heat and oxygen into the core layer. The outer layer of the skin-core structure in the present invention can not only significantly improve the mechanical properties of the entire fiber, but also provide protection for the fiber core layer and isolate most of the air and moisture to delay the oxidation of the core layer MXene, effectively solving the technical problems of insufficient mechanical properties, poor environmental stability, and single function of MXene as a thermal protection material in the prior art.

[0027] Furthermore, the concentration of the first concentration of the ANF dispersion is 15 mg / mL, and the concentration of the second concentration of the ANF dispersion is 30 mg / mL, which can ensure that the fiber cortex has better overall mechanical properties without blocking the coaxial needle, while having little impact on the electrical properties of the core layer.

[0028] Furthermore, in step S1, after KOH, PPTA, water and DMSO are mixed, the first concentration of ANF dispersion and the second concentration of ANF dispersion are prepared by stirring at a stirring temperature of 60°C, a stirring speed of 1200 rpm and a stirring time of 7 days, so that the PPTA fiber can be fully dissolved.

[0029] Furthermore, the solid content of the single-layer MXene DMSO dispersion is 5 wt% to 30 wt%. Within this range, the electrical properties and carrier concentration of the core fiber can achieve a high-temperature alarm effect.

[0030] Furthermore, the preparation of the single-layer MXene DMSO dispersion is specifically as follows: using Ti3AlC2 MAX phase precursor as a raw material, etching with lithium fluoride and hydrochloric acid to obtain the MXene, then adding the MXene to DMSO, under a nitrogen atmosphere, and ultrasonically treating in an ice bath for 6 hours, and then centrifuging at a centrifugal rate of 3000 rpm for 30 minutes to obtain the single-layer MXeneDMSO dispersion. The MXene DMSO dispersion can be successfully prepared, and the same solvent can be better combined with the ANF spinning solution, and its concentration can be formed by wet spinning.

[0031] Furthermore, in step S3, in the coaxial wet spinning, the inner needle is 16G, the outer needle is 12G, and the spinning speeds of the inner needle and the outer needle are 200 μL / min and 350 μL / min respectively, which can make the spinning continuous and the fibers more uniform.

[0032] The outer layer of the skin-core structure in the present invention not only improves the mechanical properties of the entire fiber, but also provides protection for the core layer and isolates most of the air and moisture to delay the oxidation of the core layer MXene, effectively improving the application value. At the same time, it also realizes the efficient recycling of waste aramid fibers, which is in line with the current green and environmental protection concept. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] Figure 1 This is a schematic diagram of a process for preparing a flame-retardant intelligent temperature warning fiber in a specific embodiment of the present invention;

[0035] Figure 2 This is an exemplary surface morphology super-depth image of the flame-retardant intelligent temperature warning fiber produced by the present invention;

[0036] Figure 3 is an electron microscope image of an exemplary fiber cross section of the flame-retardant intelligent temperature warning fiber prepared in the present invention;

[0037] Figure 4 It is a schematic diagram of the process preparation of the coaxial wet spinning of the present invention.

[0038] Reference numerals:

[0039] 1-coagulation bath; 2-roller one; 3-deionized water; 4-roller two; A-ANF spinning solution; B-MXene / ANF spinning solution; C-ANF@MXene / ANF coaxial composite fiber. DETAILED DESCRIPTION

[0040] 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.

[0041] 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.

[0042] 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).

[0043] 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.”

[0044] 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.

[0045] Unless otherwise specified in the following examples, all raw materials were purchased commercially or prepared by conventional methods in the art. Titanium aluminum carbide (Ti3AlC2) powder was purchased from Foshan Xinxin Technology Co., Ltd. with a specification of 200 mesh; lithium fluoride (LiF) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with a specification of AR; concentrated hydrochloric acid (HCl) was purchased from Sinopharm Chemical Reagent Co., Ltd. with a purity of 97 wt%; dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH) were both purchased from Chengdu Kelong Chemical Co., Ltd. with a specification of AR; waste aramid 1414 para-polypropylene (PPTA) was purchased from Hubei Jiateng Textile Co., Ltd.; and ammonium chloride (NH4Cl) was purchased from Sinopharm Chemical Reagent Co., Ltd. with a specification of AR.

[0046] like Figure 1 As shown, the present invention provides a method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid, comprising the following steps:

[0047] S1: Preparation of single-layer Ti3C2T by mild etching with hydrochloric acid (HCl) and lithium fluoride (LiF) x MXene;

[0048] Specifically, Ti3AlC2 MAX phase precursor is used as raw material, and lithium fluoride (LiF) and hydrochloric acid (HCl) are used to etch the Al layer in the MAX phase to prepare a single-layer Ti3AlC2 MXene.

[0049] In a specific embodiment, 2g of MAX phase precursor Ti3AlC2 was used as raw material, 2g of LiF was slowly added to 40mL of 9.0M HCl aqueous solution, and a single layer of Ti3C2T was prepared by ultrasonication, centrifugation and freeze drying. x MXene solid powder.

[0050] MXene is a general term for graphene-like two-dimensional transition metal carbides and nitrides. x MXene is relatively easy to synthesize, has high stability and the best electrical conductivity, so it has been widely studied. x MXene has semiconductor properties and its resistance drops sharply at high temperatures. This thermistor material with a negative temperature coefficient can automatically monitor temperature changes and quickly warn of high temperatures and fires. It has wide application value in firefighting, aerospace, emergency rescue and other fields.

[0051] S2: Mixing MXene with an organic solvent, dimethyl sulfoxide (DMSO), to prepare a single-layer Ti3C2T x MXene DMSO dispersion;

[0052] Specifically, dimethyl sulfoxide (DMSO) solvent was added, nitrogen was continuously supplied, and ultrasonic treatment was performed in an ice bath for 6 h, followed by centrifugation at 3000 rpm for 30 min to obtain a single-layer Ti3C2T x DMSO dispersion of MXene layered nanosheets;

[0053] Prepared single-layer Ti3C2T x The concentration of MXene DMSO dispersion was 35 mg / mL.

[0054] More specifically, the above step S2 is:

[0055] S21, multilayer Ti3C2T x After grinding the MXene powder, pour it into a centrifuge tube, add 30 mL of deionized water, and centrifuge at 5000 rpm for 5 min. After centrifugation, pour out the upper liquid;

[0056] S22, add 30mL DMSO solvent, shake well and ultrasonicate for 1h, centrifuge at 3000rpm for 10min, and the upper liquid is the single layer Ti3C2T x MXene DMSO dispersion solution.

[0057] S23. If the upper liquid is clear, pour out the DMSO, add water and centrifuge again at high speed. After centrifugation, pour out the water and add DMSO, and repeat the above steps.

[0058] S3: waste aramid 1414 para-fiber PPTA is deprotonated using a proton donor-assisted method to prepare a stable ANF dispersion;

[0059] Specifically, a proton donor-assisted deprotonation method was used to prepare a stable ANF dispersion. KOH, PPTA, deionized water, and DMSO were mixed and magnetically stirred at 1200 rpm at 60°C for one week to prepare the ANF dispersion. The ratio of KOH, PPTA, and deionized water was 1:1 (1-2):1.

[0060] In a specific embodiment, KOH, PPTA, deionized water and 40 mL of DMSO were mixed together and magnetically stirred at 1200 rpm at 60° C. for one week to obtain a dark red ANFs dispersion.

[0061] The concentration of the ANF dispersion in the core layer of the coaxial composite fiber is 15 mg / mL, and the concentration in the skin layer is 30 mg / mL.

[0062] S4: The MXene DMSO dispersion and the ANF dispersion were uniformly mixed in proportion to prepare the MXene / ANF spinning solution;

[0063] Specifically: Ti3C2T was added to 15 mg / mL dark red ANFs dispersion. x The MXene DMSO dispersion was magnetically stirred at 600 rpm at room temperature for 48 h to prepare the MXene / ANF core spinning solution.

[0064] Among them, Ti3C2T x The solid content of the MXene DMSO dispersion is 5 wt% to 30 wt%, preferably 25 wt%.

[0065] In a specific embodiment, 5 wt%, 15 wt%, and 25 wt% Ti3C2 MXene DMSO dispersions were added to 15 mg / mL ANF dispersion, respectively, and were labeled as M5A, M 15 A.M. 25 A; and magnetically stirred at 600 rpm for 6 h at room temperature to finally prepare the MXene / ANF spinning solution for the fiber core layer.

[0066] The MXene / ANF spinning solution prepared by mixing Ti3C2 MXene DMSO dispersion and ANF dispersion, and the subsequent wet spinning process, make the final fiber have excellent thermal stability, mechanical properties and fire warning performance, such as Figure 2-Figure 3 As shown in the figure, the coaxial fiber has a uniform surface structure and a diameter of 360 μm; the skin and core are tightly fused, with no obvious gaps and holes, and the interface bonding performance is good; the overall cross-section presents a structure with a dense outer layer and a relatively loose inner layer.

[0067] Compared with traditional thermal protection fiber materials, when the smart fiber encounters high temperature or flame attack, the polymer ANF in the core layer of the MXene / ANF temperature sensing fiber is burned to form a carbon network, and the Ti3C2T x Thermal oxidation of MXene nanosheets in situ generates TiO2, an indirect bandgap semiconductor. This in turn stimulates the release of charge carriers, significantly increasing the carrier concentration. During this process, the resistance decreases by several orders of magnitude in a very short period of time, enabling the circuit to conduct and ultimately triggering a response from the fire alarm system.

[0068] S5: Using the intrinsic flame retardant waste aramid nanofiber ANF dispersion as the skin layer and the semiconductor material MXene / ANF as the core layer, the ANF@MXene / ANF coaxial composite fiber with the skin-core structure is prepared by the coaxial wet spinning method. The fiber has the dual-layer effect of outer layer flame retardant protection and inner layer temperature warning.

[0069] Specifically, the coaxial wet spinning parameters were: a constant draw ratio of 1.1, a coaxial inner needle of 16G (inner diameter ≈ 1.15 mm), an outer needle of 12G (inner diameter ≈ 2.3 mm), and the spinning speeds connected to the inner and outer needles were 200 and 350 μL / min, respectively. The coaxial fibers were treated with a 5 wt % NH 4 Cl solution, washed three times in deionized water, collected on a bobbin, and dried at room temperature.

[0070] In a specific embodiment, the above step S5 is specifically as follows:

[0071] S51. The wet spinning preform obtained in steps S3 and S4 is evenly injected into two syringes and installed in a wet spinning machine. Wet spinning parameters are as follows: the pumps connected to the inner and outer needles have feed rates of 200 and 350 μL / min, respectively; the draw ratio R is 1.1; and the coagulation bath for wet spinning is deionized water containing 5 wt% NH4Cl.

[0072] S52, using an intrinsically flame-retardant 30 mg / mL ANF dispersion as the skin layer and a semiconductor material MXene / ANF with a mass ratio of 25 wt% as the core layer, coaxial wet spinning was performed, wherein the coaxial inner needle was 16G (inner diameter ≈ 1.15 mm) and the outer needle was 12G (inner diameter ≈ 2.3 mm).

[0073] S53. After spinning, the fiber was placed in a coagulation bath for displacement for 30 minutes. Finally, the fiber was washed three times in deionized water and collected on a bobbin, and dried at room temperature to obtain an ANF@MXene / ANF coaxial composite fiber with a skin-core structure.

[0074] Due to the oxidation of C and Ti in MXene, a dense carbon layer is formed at high temperatures, which can act as a physical barrier to inhibit the transfer of heat and oxygen. MXene and ANF also form a certain cross-linked network, further improving the overall thermal stability of the ANF@MXene / ANF coaxial composite fiber. Furthermore, the fiber can maintain its original shape during combustion, without melt dripping, and can be quickly extinguished after leaving the alcohol lamp flame. At the same time, the fiber has a limiting oxygen index of 43.2%, which is 1.44 times higher than that of commercial aramid fiber (LOI of 30%) used in firefighting uniforms. These results indicate that the ANF@MXene / ANF coaxial composite fiber has excellent flame retardant properties and has wide application value in special industries such as firefighting, aerospace, and emergency rescue.

[0075] The present invention uses Ti3AlC2 MAX phase precursor as raw material, uses lithium fluoride (LiF) and hydrochloric acid (HCl) to gently etch the Al layer in the MAX phase, and thus prepares a single-layer Ti3C2T x MXene, MXene is mixed with organic solvent DMSO to prepare Ti3C2T x MXene DMSO dispersion; waste aramid 1414 para-fiber (PPTA) is dissolved in a DMSO / KOH / H2O system using a proton donor-assisted deprotonation method to prepare a stable ANF dispersion; the MXene DMSO dispersion and the ANF dispersion are then evenly mixed in proportion to prepare a MXene / ANF solution; using the intrinsic flame retardant waste aramid nanofiber ANF dispersion as the skin layer and the semiconductor material MXene / ANF as the core layer, a smart fiber material with outer flame retardant protection and inner temperature warning is prepared by a coaxial wet spinning method. When this coaxial fiber with a skin-core structure is attacked by high temperature or flame, the outer layer can achieve self-flame retardancy, control the spread of flame, and protect the fiber core layer MXene from rapid thermal oxidation at high temperature, thereby achieving continuous alarm. When the temperature is transmitted to the core layer, the core layer's ANF decomposes and catalyzes the oxidation of MXene. Due to the Ti3C2Tx MXene nanosheets are converted into TiO2 through thermal oxidation. TiO2 has semiconductor properties. When the temperature rises, electron transitions occur, resulting in an increase in carrier density and the formation of a conductive network, thus achieving rapid fire alarm (less than 3 seconds).

[0076] In addition, the present invention utilizes poly-p-phenylene terephthamide (PPTA), a high-strength and high-modulus fiber with a thermal decomposition temperature of 560°C, trade name Kevlar, and aramid 1414 (with the amide group in the para (1,4) position of the benzene ring in the molecular structure) for dissolution and re-spinning, giving full play to the excellent flame retardant and mechanical properties of aramid 1414 fiber. In addition, 35mg / mL of 25-30wt% single-layer Ti3C2T x MXene DMSO dispersions, when exposed to high temperatures or flames, undergo oxidation of carbon and titanium in the MXene, forming a denser carbon layer. This acts as a physical barrier, inhibiting the transfer of heat and oxygen, slowing the spread of flames and thus enhancing thermal stability and flame retardancy. By combining the intrinsically flame-retardant aramid nanofiber (ANF) with the two-dimensional layered nanomaterial MXene, the two exhibit a synergistic flame-retardant effect. This ANF@MXene / ANF composite fiber maintains a high carbon residue of 64.05% at 800°C and exhibits excellent flame retardancy. Shrinkage and deformation only begin after 170 seconds of exposure to an alcohol lamp, with a damage length of less than 0.5 cm, no melt dripping, and the fiber self-extinguishes upon removal from the flame. Furthermore, the fiber has a limiting oxygen index of 43.2%, a 1.44-fold increase compared to aramid fiber (LOI of 30%), making it suitable for use in specialized industries such as firefighting, aerospace, and emergency rescue.

[0077] Moreover, the present invention uses an intrinsically flame-retardant waste aramid nanofiber ANF dispersion as the sheath layer and a semiconductor material MXene / ANF as the core layer to prepare an ANF@MXene / ANF coaxial composite intelligent fiber with a sheath-core structure. The outer layer of the sheath-core structure can improve the mechanical properties of the entire fiber, control the spread of flame to achieve self-flammability, and at the same time provide protection for the fiber core layer, isolating most of the air and moisture to delay the oxidation of the core layer MXene. The presence of ANF in both the sheath and the core gives them excellent interfacial bonding ability, thereby improving the mechanical properties of the overall fiber, enhancing chemical stability, reducing problems such as fiber deformation and cracking caused by thermal stress, and improving the heat resistance and thermal stability of the fiber. This composite fiber material with a sheath-core structure ensures that the carrier density of the core layer MXene increases under high temperature or fire conditions, thereby effectively generating a conductive network and providing a more sensitive and reliable fire warning.

[0078] 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.

[0079] 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.

[0080] Comparative Example 1:

[0081] A method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid, comprising the following steps:

[0082] S1: Using 2g of MAX phase precursor Ti3AlC2 as raw material, 2g of LiF was slowly added to 40mL of 9.0M HCl aqueous solution, and single-layer Ti3C2T was prepared by ultrasonication, centrifugation and freeze drying. x MXene solid powder.

[0083] S2: Mixing MXene with the organic solvent dimethyl sulfoxide (DMSO) to prepare a single-layer Ti3C2T x MXene DMSO dispersion;

[0084] S21, multilayer Ti3C2T x After grinding the MXene powder, pour it into a centrifuge tube, add 30 mL of deionized water, and centrifuge at 5000 rpm for 5 min. After centrifugation, pour out the upper liquid;

[0085] S22, add 30mL DMSO solvent, shake well and ultrasonicate for 1h, centrifuge at 3000rpm for 10min, and the upper liquid is the single layer Ti3C2T x MXene DMSO dispersion solution.

[0086] S23. If the upper liquid is clear, pour out the DMSO, add water and centrifuge again at high speed. After centrifugation, pour out the water and add DMSO, and repeat the above steps.

[0087] S3: Using the proton donor-assisted deprotonation method, KOH, PPTA, deionized water and 40 ml DMSO were mixed together and magnetically stirred at 1200 rpm at 60 °C for one week to prepare a 15 mg / mL ANFs dispersion.

[0088] S4: MXene DMSO dispersion and ANF dispersion were uniformly mixed in proportion to prepare MXene / ANF solution;

[0089] S41, add 25wt% Ti3C2 MXene DMSO dispersion to 15mg / mL ANF dispersion, marked as M 25 A;

[0090] S42, magnetic stirring was performed at 600 rpm at room temperature for 6 h to finally prepare the MXene / ANF spinning solution for the fiber core layer.

[0091] S5: A flame-retardant and temperature-preventing MXene / ANF composite fiber was prepared by wet spinning.

[0092] S51. Inject the wet spinning preform obtained in step S4 into a syringe and install it in a wet spinning machine. Wet spinning parameters are: injection rate 200 μL / min, draw ratio R of 1.1, spinning needle gauge 16G (inner diameter ≈ 1.15 mm), and the coagulation bath for wet spinning is deionized water containing 5 wt% NH4Cl.

[0093] S52. After spinning, the fiber was placed in a coagulation bath for 30 min. Finally, the fiber was washed three times in deionized water and collected on a bobbin, and dried at room temperature to obtain MXene / ANF composite fibers.

[0094] Comparative Example 2:

[0095] The difference between Comparative Example 1 and Comparative Example 1 is:

[0096] S4: Add 15 wt% Ti3C2 MXene DMSO dispersion to 15 mg / mL ANF dispersion, marked as M 15 A, and then magnetically stirred at 600 rpm for 6 h at room temperature to finally prepare the MXene / ANF spinning solution for the fiber core layer.

[0097] Comparative Example 3:

[0098] The difference between Comparative Example 2 and Comparative Example 1 is that:

[0099] S4: A 5 wt% Ti3C2 MXene DMSO dispersion was added to a 15 mg / mL ANF dispersion, labeled M5A, and then magnetically stirred at 600 rpm at room temperature for 6 h to prepare the MXene / ANF spinning solution for the fiber core layer.

[0100] Table 1 shows the performance test results of the composite fibers obtained by comparison 1 to 3.

[0101]

[0102] As can be seen from Table 1, due to the lack of interlayer force between MXene nanosheets, when its content increases, internal stress or interface defects may be generated, and some amorphous regions will be formed, reducing the crystallinity of the MXene / ANF composite fiber, thereby reducing its strength. In Comparative Example 1, the MXene / ANF fiber has the highest conductivity. By connecting the fiber, a regulated DC power supply, and an alarm light in series, a simple fire alarm device was designed. When the alcohol lamp attacks the fiber, MXene generates TiO2 in situ as an indirect bandgap semiconductor, resulting in a significant increase in carrier concentration. At the same time, the resistance value drops rapidly in a very short time, thereby achieving circuit conduction, and the LED light of the fire alarm device can be triggered within 3s. Moreover, when the MXene content is 35%, the fiber strength is about 11MPa, which is difficult to spin and store.

[0103] Embodiment 1:

[0104] A method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid, comprising the following steps:

[0105] S1: Using 2g of MAX phase precursor Ti3AlC2 as raw material, 2g of LiF was slowly added to 40mL of 9.0M HCl aqueous solution, and single-layer Ti3C2T was prepared by ultrasonication, centrifugation and freeze drying. x MXene solid powder.

[0106] S2: Mixing MXene with the organic solvent dimethyl sulfoxide (DMSO) to prepare a single-layer Ti3C2T x MXene DMSO dispersion;

[0107] S21, multilayer Ti3C2T x After grinding the MXene powder, pour it into a centrifuge tube, add 30 mL of deionized water, and centrifuge at 5000 rpm for 5 min. After centrifugation, pour out the upper liquid;

[0108] S22, add 30mL DMSO solvent, shake well and ultrasonicate for 1h, centrifuge at 3000rpm for 10min, and the upper liquid is the single layer Ti3C2Tx MXene DMSO dispersion solution.

[0109] S23. If the upper liquid is clear, pour out the DMSO, add water and centrifuge again at high speed. After centrifugation, pour out the water and add DMSO, and repeat the above steps.

[0110] S3: Using the proton donor-assisted deprotonation method, KOH, PPTA, deionized water and 40 ml of DMSO were mixed together and magnetically stirred at 1200 rpm at 60°C for one week to prepare two ANFs dispersions with concentrations of 15 mg / mL (core) and 30 mg / mL (skin).

[0111] S4: MXene DMSO dispersion and ANF dispersion were uniformly mixed in proportion to prepare MXene / ANF solution;

[0112] S41, add 25wt% Ti3C2 MXene DMSO dispersion to 15mg / mL ANF dispersion, marked as M 25 A;

[0113] S42, magnetic stirring was performed at 600 rpm at room temperature for 6 h to finally prepare the MXene / ANF spinning solution for the fiber core layer.

[0114] S5: Using intrinsic flame retardant ANF dispersion as the skin layer and semiconductor material MXene / ANF as the core layer, a coaxial wet spinning method was used to prepare an ANF@MXene / ANF coaxial composite fiber with flame retardant outer layer and temperature warning inner layer. The surface morphology super depth of field image and the electron microscope image of the fiber cross section are shown as follows: Figure 2-Figure 3 As shown by Figure 2-Figure 3 It can be seen that the fiber surface structure is uniform, the cortex is transparent light yellow and the inner layer is black, and it is grooved along the longitudinal direction, which is a typical structural feature of the fiber prepared by wet spinning. The preparation process of the coaxial wet spinning of this embodiment is as follows Figure 4 As shown;

[0115] S51. The wet spinning preform obtained in steps S3 and S4 is evenly injected into two syringes and installed in a wet spinning machine. Wet spinning parameters are as follows: the pumps connected to the inner and outer needles have feed rates of 200 and 350 μL / min, respectively; the draw ratio R is 1.1; and the coagulation bath for wet spinning is deionized water containing 5 wt% NH4Cl.

[0116] S52, using 30mg / mL ANF dispersion as the skin layer and 25wt% of the semiconductor material MXene / ANF as the core layer, coaxial wet spinning was performed, where the coaxial inner needle was 16G (inner diameter ≈1.15mm) and the outer needle was 12G (inner diameter ≈2.3mm).

[0117] S53. After spinning, the fiber was placed in a coagulation bath for 30 minutes. Finally, the fiber was washed three times in deionized water and collected on a bobbin. It was then dried at room temperature to obtain an ANF@MXene / ANF coaxial composite fiber with a core-shell structure. The surface morphology of the ANF@MXene / ANF coaxial composite fiber with a core-shell structure is shown in the super-depth image. Figure 2 shown.

[0118] Table 2 shows the performance test results of the composite fibers obtained in Comparative Example 1 and Example 1

[0119]

[0120] As can be seen from Table 2, compared with Example 1, the ANF@MXene / ANF fiber (product of Example 1) in Comparative Example 1 has a continuous and dense outer layer, and the fiber cortex and core layer are both based on ANF, which makes the fiber skin and core have strong adhesion and good interfacial properties, which can effectively enhance its mechanical strength. At the same time, the ANF concentration in the cortex is higher and has a good flame retardant effect. While improving the strength, the limiting oxygen index of Example 1 is also improved to a certain extent. This is because MXene also forms a tortuous path in the polymer ANF matrix, thereby delaying the heat and mass transfer between the underlying matrix and the gas zone, which can inhibit further combustion of the fiber material and also inhibit the release of smoke and heat, so that the MXene and ANF in the ANF@MXene / ANF coaxial composite fiber have a certain degree of synergistic flame retardant effect.

[0121] Furthermore, Comparative Examples 1-3 show that when the core layer MXene concentration is 25 wt%, the fiber has the best initial conductivity, with the resistance dropping by approximately 88.16% within 3 seconds under an alcohol lamp, indicating the fastest response speed. Therefore, based on Comparative Example 1, Example 1 prepared a flame-retardant and fire-preventing core-shell intelligent fiber material through coaxial wet spinning, providing a more effective and reliable method for applications in firefighting, aerospace, emergency rescue, safety protection, and other fields.

[0122] In summary, the skin-core structure in Example 1 provides effective protection for the internal MXene by concentrating a higher concentration of ANF in the skin layer to prevent its oxidation, while giving the fiber as a whole higher mechanical strength and flexibility.

[0123] Example 2:

[0124] The difference between this embodiment and embodiment 1 is that:

[0125] S4: Add 15 wt% Ti3C2 MXene DMSO dispersion to 15 mg / mL ANF dispersion, marked as M 15 A, and then magnetically stirred at 600 rpm for 6 h at room temperature to finally prepare the MXene / ANF spinning solution for the fiber core layer.

[0126] S5: Using intrinsic flame-retardant ANF dispersion as the skin layer and semiconductor material MXene / ANF as the core layer, an ANF@MXene / ANF coaxial composite fiber with a flame-retardant outer layer and a temperature warning inner layer was prepared by coaxial wet spinning.

[0127] Example 3:

[0128] The difference between this embodiment and embodiment 1 is that:

[0129] S4: A 5 wt% Ti3C2 MXene DMSO dispersion was added to a 15 mg / mL ANF dispersion, labeled M5A, and then magnetically stirred at 600 rpm at room temperature for 6 h to prepare the MXene / ANF spinning solution for the fiber core layer.

[0130] S5: Using intrinsic flame-retardant ANF dispersion as the skin layer and semiconductor material MXene / ANF as the core layer, an ANF@MXene / ANF coaxial composite fiber with a flame-retardant outer layer and a temperature warning inner layer was prepared by coaxial wet spinning.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing flame-retardant intelligent temperature warning fiber based on waste aramid, characterized in that: The following steps are involved: S1: KOH, waste aramid para-fiber PPTA, water and DMSO are mixed and stirred to prepare an ANF dispersion of a first concentration and an ANF dispersion of a second concentration, wherein the first concentration is less than the second concentration; S2: adding the monolayer MXene DMSO dispersion to the first concentration of ANF dispersion to prepare the MXene / ANF spinning solution; S3: Using the MXene / ANF spinning solution as the core layer and the ANF dispersion of the second concentration as the skin layer, coaxial wet spinning is performed to produce the flame-retardant intelligent temperature warning fiber based on waste aramid.

2. The method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid according to claim 1, characterized in that: The concentration of the ANF dispersion at the first concentration is 15 mg / mL.

3. The method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid according to claim 1, characterized in that: The concentration of the ANF dispersion at the second concentration is 30 mg / mL.

4. The method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid according to claim 1, characterized in that: In step S1, KOH, waste aramid para-fiber PPTA, water and DMSO are mixed and stirred to prepare a first concentration ANF dispersion and a second concentration ANF dispersion. The stirring temperature is 60°C, the stirring speed is 1200 rpm, and the stirring time is 7 days. The mass ratio of KOH, PPTA and water is 1:(1~2):

1.

5. The method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid according to claim 1, characterized in that: A monolayer MXene DMSO dispersion is added to an ANF dispersion of a first concentration to prepare a MXene / ANF spinning solution, wherein the concentration of MXene in the MXene / ANF spinning solution is 5 wt% to 30 wt%.

6. The method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid according to claim 1, characterized in that: The preparation of the monolayer MXene DMSO dispersion is specifically as follows: MXene is added to dimethyl sulfoxide, ultrasonicated in an ice bath under nitrogen protection for 6 hours, and then centrifuged at a centrifugal speed of 3000 rpm for 30 minutes to obtain the monolayer MXene DMSO dispersion.

7. The method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid according to claim 1, characterized in that: The preparation of the MXene is specifically as follows: using Ti3AlC2 MAX phase precursor as a raw material, using lithium fluoride and hydrochloric acid for etching to obtain the MXene.

8. The method for preparing a flame-retardant intelligent temperature warning fiber based on waste aramid according to claim 1, characterized in that: In step S3, in the coaxial wet spinning, the inner needle is 16G, the outer needle is 12G, and the spinning speeds of the inner needle and the outer needle are 200 μL / min and 350 μL / min, respectively.

9. A flame-retardant intelligent temperature warning fiber based on waste aramid, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the flame-retardant intelligent temperature warning fiber based on waste aramid as claimed in claim 9 in fireproof materials.

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