Composite nanofiber with skin-core structure as well as preparation method and application of composite nanofiber

Abstract

The invention relates to the technical field of composite fibers, in particular to a composite nanofiber with a skin-core structure and a preparation method and application of the composite nanofiber. In the composite nanofiber structure of the skin-core structure, a skin layer comprises modified boron nitride and a high-molecular polymer, and the modified boron nitride is modified boron nitride of which the surface is modified with polydopamine; and the core layer is a pyrazine compound solution. The nanofiber material prepared by the method disclosed by the invention shows excellent and stable heat conduction performance and hydrophobic performance. The material has a remarkable industrial application prospect in the fields of controlled release of tobacco essence, moisture-proof packaging and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of composite fibers, and in particular to a composite nanofiber with a skin-core structure, a preparation method thereof, and applications thereof. Background Art

[0002] In the tobacco industry, the rapid release of high-boiling-point flavor components is a key factor in improving product quality. Traditional aroma carrier materials, such as porous particles or polymer films, suffer from unstable release rates, poor thermal stability, and insufficient mechanical strength.

[0003] Among related technologies, electrospinning technology has shown potential for sustained fragrance release due to its ability to produce nanofiber materials with high specific surface area and porous structures. The spinning solution used in electrospinning is a polymer solution, which has excellent hydrophobicity and chemical stability. However, using this solution to encapsulate high-boiling-point flavors such as pyrazine compounds can result in delayed release of the flavor. Summary of the Invention

[0004] In order to solve or partially solve the problems existing in the related art, the present invention provides a composite nanofiber with a skin-core structure and a preparation method and application thereof.

[0005] The invention provides a composite nanofiber with a skin-core structure, wherein the skin layer comprises modified boron nitride and a high molecular polymer, wherein the modified boron nitride is a modified boron nitride with polydopamine modified on the surface; and the core layer is a pyrazine compound solution.

[0006] Furthermore, the high molecular polymer is one or two of polyvinylidene fluoride, polyacrylonitrile, polyurethane, polyvinyl pyrrolidone, polyamide and polyimide; and / or, in the skin layer, the weight ratio of modified boron nitride to the high molecular polymer is 0.01-7:100.

[0007] Furthermore, the pyrazine compound is one or more of 2-phenethylpyrazine, 2-styrylpyrazine, 2-(4-ethylstyryl)pyrazine, 2-(4-isopropylstyryl)pyrazine, 2-(4-methoxystyryl)pyrazine, 2-(4-methylphenethyl)pyrazine, 2-(4-ethylphenethyl)pyrazine, 2-(3-methylphenethyl)pyrazine, and 2-(2-methylphenethyl)pyrazine, and the concentration of the pyrazine compound solution is 5-50wt%; and / or, The solvent of the pyrazine compound solution is acetone, methanol, tetrahydrofuran, ethyl acetate, cyclohexane, acetonitrile or ethanol.

[0008] Furthermore, its diameter is 0.6-2 μm.

[0009] The present invention also provides a method for preparing the composite nanofiber, which comprises: Step a), using lithium fluoride as an intercalation agent, hydrothermally exfoliating boron nitride to obtain exfoliated boron nitride nanosheets; Step b), dispersing the exfoliated boron nitride nanosheets and dopamine hydrochloride in a solvent, adjusting the pH to alkaline, and collecting the precipitate after the reaction to obtain modified boron nitride with surface modified polydopamine; Step c), dissolving the modified boron nitride in a polymer solution to obtain a modified boron nitride / polymer mixed solution; Step d) preparing composite nanofibers by electrospinning using a pyrazine compound solution as a core layer solution and the modified boron nitride / high molecular polymer mixed solution as a skin layer solution.

[0010] Furthermore, in step a), the mass ratio of boron nitride to lithium fluoride is 1:0.5-5, the concentration of lithium fluoride in the hydrothermal exfoliation system is 10-90 g / L, and the temperature is 80-300°C; and / or, in step b), the mass ratio of the exfoliated boron nitride nanosheets to dopamine hydrochloride is 1:0.3-4.

[0011] Furthermore, in the step c), the concentration of the high molecular polymer solution is 6-30 wt %, and the mass ratio of the modified boron nitride to the high molecular polymer is 0.01-7:100.

[0012] Furthermore, in step d), the pyrazine compound is one or more of 2-phenethylpyrazine, 2-styrylpyrazine, 2-(4-ethylstyryl)pyrazine, 2-(4-isopropylstyryl)pyrazine, 2-(4-methoxystyryl)pyrazine, 2-(4-methylphenethyl)pyrazine, 2-(4-ethylphenethyl)pyrazine, 2-(3-methylphenethyl)pyrazine, and 2-(2-methylphenethyl)pyrazine; and the concentration of the pyrazine compound solution is 5-50 wt%.

[0013] Furthermore, in the step d), the process conditions for electrospinning are: a liquid feeding rate of 0.5-2 mL / h, and a receiving distance of 15-30 cm.

[0014] The present invention also provides an application of the composite nanofiber in cigarette flavoring, antibacterial textiles, environmental pollutant adsorption materials, high-sensitivity sensors or controlled-release carriers.

[0015] The composite nanofiber and preparation method thereof provided by the present invention can have the following beneficial effects: 1. Exfoliation-DA modification of boron nitride improves the dispersibility of BN in polymer solution and enhances its interfacial bonding with the matrix, breaking through the bottleneck of easy agglomeration of traditional thermal conductive fillers, thereby improving the overall performance of the composite material, enhancing its waterproof and breathable properties, improving the thermal conductivity of the composite material, and improving its thermal management performance.

[0016] 2. The modified BN is mixed with a high molecular polymer as the sheath layer spinning solution, and a pyrazine compound solution is used as the core layer spinning solution to perform electrospinning to form a composite nanofiber with a sheath-core structure. The high molecular polymer in the sheath layer structure isolates the core material from the environment to avoid thermal / light degradation of the core material. The modified BN is uniformly dispersed in the sheath layer to construct a continuous heat conduction network, and the heat is quickly conducted to the core layer after heating to promote the thermal motion of pyrazine molecules, thereby accelerating the release of pyrazine molecules with high boiling point fragrances.

[0017] 3. The preparation method has wide raw material sources and significant cost advantages, and the preparation process is simple and easy to operate, and has good scalability and operation convenience. The nanofiber material prepared by the method has excellent and stable heat conduction performance and hydrophobic performance. The material has a significant industrial application prospect in the fields of tobacco fragrance controlled release, moisture-proof packaging and the like.

[0018] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the SEM image of BN, exfoliated BN nanosheet and modified BN in Example 1 of the present application; Figure 2 is the XRD image of the modified BN in Example 1 of the present application; Figure 3 is the SEM image of the fibers prepared in Example 1 of the present application and the control group; Figure 4 is the TEM image and mapping image of the PVDF / modified BN fibers prepared in Example 1 of the present application; Figure 5 is the FTIR spectrum image of the fibers prepared in Example 1 of the present application and the control group; Figure 6 is the water contact angle image of the fibers prepared in Example 1 of the present application and the control group; Figure 7 is the thermal equilibrium time comparison image and thermal response characteristic image of the fibers prepared in Example 1 of the present application and the control group; Figure 8 is the standard absorption curve of 2-phenylethylpyrazine at 270 nm; Figure 9 is the aroma release rate (a) and aroma intensity value (b) of the fibers prepared in Example 1 of the present application and the control group. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] The terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the invention. The singular forms "a," "the," and "the" used in this invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0022] It should be understood that although the terms "first", "second", "third", etc. may be used to describe various information in the present invention, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0023] The invention provides a composite nanofiber with a skin-core structure, wherein the skin layer comprises modified boron nitride and a high molecular polymer, wherein the modified boron nitride is a modified boron nitride with polydopamine modified on the surface; and the core layer is a pyrazine compound solution.

[0024] The sheath-core nanofiber material of the present invention comprises a polymer with high chemical stability and gas barrier properties. Using this polymer as the sheath coating material effectively encapsulates fragrances at room or low temperatures, preventing premature volatilization or decomposition during storage or processing. The polymer is preferably one or two of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyurethane (TPU), polyvinylpyrrolidone (PVP), polyamide (PA), and polyimide (PI). These polymers exhibit excellent chemical stability and gas barrier properties.

[0025] The inventors of this application have found through research that the use of high molecular weight polymers as the cortex to wrap pyrazine compounds has the problem of poor release effect. Pyrazine compounds have a high boiling point. When heated to 40-50°C, the wrapping effect of the high molecular weight polymer will hinder heat conduction, resulting in delayed release of pyrazine.

[0026] To address the above-mentioned issues, the inventors of this application considered modifying the polymer by mixing it with a thermally conductive material. Further research revealed that conventional thermally conductive materials, such as graphene / graphene oxide, have poor dispersibility, and the mechanical properties of the fiber materials obtained after mixing with the polymer need to be improved. Phase change materials release heat slowly, and mixing with polymers has little effect on accelerating the release of fragrances. The inventors of this application ultimately considered using BN, a two-dimensional material with high thermal stability. The addition of BN can improve the mechanical properties of the material and has excellent thermal conductivity and biocompatibility. However, BN has poor interfacial compatibility with polymers and is prone to agglomeration in polymer solutions, affecting the uniformity and performance of the fiber. The addition of high concentrations of BN increases the viscosity of the solution, affecting the processing properties of the fiber. The inventors of this application have further discovered that exfoliation-DA modification of BN significantly improves its dispersibility in polymer solutions and enhances its interfacial bonding with the matrix, thereby enhancing the overall performance of the composite material, enhancing its waterproof and breathable properties, increasing its thermal conductivity, and improving its thermal management properties. The resulting nanofiber material with a skin-core structure exhibits significant improvements in waterproofing, heat transfer, thermal volatilization, and fragrance release. Preferably, the weight ratio of modified boron nitride to polymer in the skin layer is 0.01-7:100, more preferably 3-8:100, and most preferably 5:100.

[0027] In the pyrazine compound solution of the core layer, the pyrazine compound is preferably one or more of 2-phenylethylpyrazine, 2-phenylvinylpyrazine, 2-(4-ethylphenylvinyl)pyrazine, 2-(4-isopropylphenylvinyl)pyrazine, 2-(4-methoxyphenylvinyl)pyrazine, 2-(4-methylphenylethyl)pyrazine, 2-(4-ethylphenylethyl)pyrazine, 2-(3-methylphenylethyl)pyrazine, and 2-(2-methylphenylethyl)pyrazine. The concentration of the pyrazine compound solution is preferably 5-50wt%, that is, the content of the pyrazine compound in the pyrazine compound solution is 5-50wt%, preferably 10-25wt%, and more preferably 20-25wt%. The solvent of the pyrazine compound solution is preferably acetone, methanol, tetrahydrofuran, ethyl acetate, cyclohexane, acetonitrile or ethanol. The core layer can be coated in the skin layer by coaxial electrospinning to finally obtain a composite nanofiber with a skin-core structure. The diameter of the composite nanofiber with a skin-core structure provided by the embodiment of the present invention is preferably 0.6-2 μm.

[0028] Another embodiment of the present invention further provides a method for preparing the above-mentioned composite nanofiber with a skin-core structure, which comprises the following steps: Step a), using lithium fluoride as an intercalation agent, hydrothermally exfoliating boron nitride to obtain exfoliated boron nitride nanosheets; Step b), dispersing the exfoliated boron nitride nanosheets and dopamine hydrochloride in a solvent, adjusting the pH to alkaline, and collecting the precipitate after the reaction to obtain modified boron nitride with surface modified polydopamine; Step c), dissolving the modified boron nitride in a polymer solution to obtain a modified boron nitride / polymer mixed solution; Step d) preparing composite nanofibers by electrospinning using a pyrazine compound solution as a core layer solution and the modified boron nitride / high molecular polymer mixed solution as a skin layer solution.

[0029] Step a) above involves hydrothermal exfoliation of boron nitride. Lithium fluoride (LiF) acts as an intercalant, ionizing into Li⁺ and F⁻ under high-temperature hydrothermal conditions. Li⁺ is embedded between the h-BN layers, weakening the interlayer van der Waals forces through electrostatic interactions and increasing the interlayer spacing. The hydrothermal conditions promote the penetration of solvent molecules into the expanded interlayers, generating expansion stress and producing exfoliated boron nitride nanosheets. The exfoliated boron nitride nanosheets exhibit reduced thickness, increased in-plane thermal conductivity, and exposed surface hydroxyl groups (-OH groups), providing active sites for subsequent surface modification.

[0030] Preferably, in this step, the mass ratio of boron nitride to lithium fluoride is 1:0.5-5; the concentration of lithium fluoride in the hydrothermal stripping system is 10-90 g / L, and the temperature is 80-300°C. More preferably, the mass ratio of boron nitride to lithium fluoride is 1:2; the concentration of lithium fluoride in the hydrothermal stripping system is 60-80 g / L, and the temperature is 180-220°C. The hydrothermal stripping time is preferably 10-15 hours.

[0031] Step a) is preferably as follows: Boron nitride and lithium fluoride are dispersed in deionized water and heated for hydrothermal exfoliation. After the reaction is complete, the mixture is centrifuged for the first time to remove the supernatant and then centrifuged for a second time to collect the precipitate. The precipitate is then washed and dried to obtain exfoliated BN nanosheets. The first centrifugation speed is preferably 1000-6000 rpm, and the second centrifugation speed is preferably 8000-15000 rpm. Washing is preferably performed multiple times with ethanol-water solution. The drying temperature is preferably 60-90°C, and the drying time is preferably 20-30 hours.

[0032] Step b) above involves surface-modifying the boron nitride nanosheets with polydopamine. Dopamine hydrochloride (DA-HCl) undergoes oxidation and self-polymerization under alkaline conditions to form polydopamine (PDA). Its quinone (C=O) groups react with the B-OH groups at the edges of the boron nitride nanosheets to form BOC covalent bonds, while the amino groups (-NH2) form hydrogen bonds with the BN surface, achieving strong interfacial bonding. PDA contains phenolic hydroxyl / amino groups, which form hydrogen bonds or entanglements with subsequent polymers (such as PVDF and PA6), reducing interfacial thermal resistance. The polydopamine-modified boron nitride obtained in this step significantly improves the dispersibility of BN in polymer solutions and strengthens its interfacial bonding with the substrate.

[0033] In this step, the mass ratio of the exfoliated boron nitride nanosheets to dopamine hydrochloride is preferably 1:0.3-4, more preferably 1:0.6-2, and most preferably 1:0.6. The mixing ratio of the exfoliated boron nitride nanosheets to the solvent is preferably 0.5-2 mg:1 ml. To ensure a more uniform dispersion of the exfoliated boron nitride nanosheets and dopamine hydrochloride in the solvent, the exfoliated boron nitride nanosheets and dopamine hydrochloride are preferably ultrasonically dispersed in the solvent in this step, and the ultrasonic dispersion time is preferably 1-1.5 hours.

[0034] The solvent is preferably pre-chilled to 0-5°C. Pre-cooling the solvent lowers the reaction temperature, significantly inhibiting the oxidative polymerization of dopamine salt (HCl-DA) under alkaline conditions and delaying its formation into a polydopamine structure. This facilitates more uniform adsorption or covalent bonding of the dopamine salt (HCl-DA) to the BN nanosheet surface in either monomeric or oligomeric forms, thereby enhancing the modification effect and the structural uniformity of the material. The solvent is preferably a mixture of isopropanol and deionized water. The pH of this reaction is preferably 7-9, most preferably 8.5. The buffer solution used to adjust the pH is preferably selected from tris(hydroxymethyl)aminomethane, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, N,N-dihydroxyethylglycine, N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid, or a sodium bicarbonate / sodium carbonate buffer system.

[0035] The reaction time for this step is preferably 6-24 hours. After the reaction is completed, the lower precipitate can be collected by centrifugation to obtain modified boron nitride with surface modified polydopamine. The centrifugal speed is preferably 4000-8000 rpm. After collecting the lower precipitate, washing and drying steps are preferably included to remove impurities on the surface of the modified boron nitride. Washing is preferably performed multiple times with an ethanol solution. Drying is preferably performed under vacuum, and the drying temperature is preferably 40-60°C.

[0036] Step c) above involves blending the modified boron nitride with a polymer. The resulting mixed solution subsequently serves as the skin layer solution. The polymer acts as a continuous phase, encapsulating the modified boron nitride. The modified boron nitride is oriented within the polymer, forming a continuous thermal pathway and improving in-plane thermal conductivity. Furthermore, the modified boron nitride acts as a nanoreinforcement, enhancing fiber breaking strength through stress transfer.

[0037] In this step, the polymer is preferably one or more of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyurethane (TPU), polyvinyl pyrrolidone (PVP), polyamide (PA), and polyimide (PI). The concentration of the polymer solution is preferably 6-30 wt%, more preferably 10-14 wt%, and even more preferably 12-13 wt%. The mass ratio of modified boron nitride to polymer is 0.01-7:100, preferably 3-8:100, and most preferably 5:100.

[0038] The above-mentioned step d) is a coaxial electrospinning forming step. In this step, the cortex solution is the modified BN / polymer mixed solution prepared in step c), which is used to form the fiber skeleton. The modified BN provides thermal conductivity, and the polymer isolates the core material from the environment to avoid thermal / photodegradation; the core layer solution is a pyrazine compound, which is used to release fragrance after the fiber is heated. As a preferred embodiment of this step, the pyrazine compound is preferably one or more of 2-phenylethylpyrazine, 2-phenylvinylpyrazine, 2-(4-ethylphenylvinyl)pyrazine, 2-(4-isopropylphenylvinyl)pyrazine, 2-(4-methoxyphenylvinyl)pyrazine, 2-(4-methylphenylethyl)pyrazine, 2-(4-ethylphenylethyl)pyrazine, 2-(3-methylphenylethyl)pyrazine, and 2-(2-methylphenylethyl)pyrazine; the concentration of the pyrazine compound solution is preferably 5-50wt%. The solvent of the pyrazine compound solution can be one of acetone, methanol, tetrahydrofuran, ethyl acetate, cyclohexane, acetonitrile and ethanol.

[0039] In this step, the process conditions for electrospinning are preferably: the liquid feed rate is 0.5-2 mL / h, and the receiving distance is 15-30 cm. The liquid feed rate is preferably 0.8-1.2 mL / h, more preferably 1.0-1.1 mL / h. The spinning voltage is preferably 18-20 kV. Most preferably, the liquid feed rate is 1.0 mL / h, the spinning voltage is 20 kV, and the receiving distance is 17 cm. The temperature of electrospinning is preferably 26±2°C, the relative humidity is preferably 30±2%, and the needles used in the spinning process are preferably coaxial 20-gauge needles. The above-mentioned composite nanofibers with a skin-core structure are prepared by step d).

[0040] Another embodiment of the present invention further provides a use of the composite nanofiber in cigarette flavoring, antibacterial textiles, environmental pollutant adsorption materials, high-sensitivity sensors or controlled-release carriers.

[0041] The composite nanofibers and the preparation method thereof provided by the embodiments of the present invention have the following advantages: 1. Exfoliation-DA modification of boron nitride improves the dispersibility of BN in polymer solution and enhances its interfacial bonding with the matrix, breaking through the bottleneck of easy agglomeration of traditional thermal conductive fillers, thereby improving the overall performance of the composite material, enhancing its waterproof and breathable properties, improving the thermal conductivity of the composite material, and improving its thermal management performance.

[0042] 2. The modified BN is mixed with a high molecular polymer as the sheath spinning solution, and a pyrazine compound solution is used as the core spinning solution to perform electrospinning to form a composite nanofiber with a sheath-core structure. The high molecular polymer in the sheath structure isolates the core material from the environment to prevent thermal / photodegradation of the core material. The modified BN is evenly dispersed in the sheath to construct a continuous heat conduction network. After heating, the heat is quickly transferred to the core layer, promoting the thermal motion of the pyrazine molecules, thereby accelerating the release of high-boiling-point flavors such as pyrazine molecules.

[0043] 3. This preparation method utilizes a wide range of raw materials with significant cost advantages. The preparation process is simple and easy to implement, with good scalability and ease of operation. The nanofiber material produced by this method exhibits excellent and stable thermal conductivity and hydrophobicity. This material has significant industrial application prospects in areas such as controlled release of tobacco flavors and moisture-proof packaging.

[0044] The technical solution of the present invention will be further described below in conjunction with specific embodiments: Example 1 1. Preparation of modified BN 0.5 g of BN and 1 g of LiF were dispersed in 15 mL of deionized water. The mixture was ultrasonically treated at room temperature for 2 h. The resulting dispersion was then transferred to a polytetrafluoroethylene autoclave and reacted at 200°C for 12 h. After the reaction, the mixture was cooled to room temperature and centrifuged at 4000 rpm for 5 min. The supernatant was collected and then centrifuged again at 9000 rpm for 5 min to obtain the precipitate. The precipitate was washed five times with a mixture of ethanol and deionized water (1:1 by volume) and dried at 80°C for 24 h to obtain exfoliated BN nanosheets.

[0045] 40 mg of exfoliated BN nanosheets and 24 mg of HCl-DA were added to 40 mL of a precooled 0-5°C isopropanol / deionized water mixture (volume ratio 2:3) and sonicated at room temperature for 1 hour to obtain a mixed dispersion. The pH of the dispersion was adjusted to 8.5 using tris(hydroxymethylaminomethane), and the mixture was reacted at 30°C for 10 hours. The mixture was then centrifuged at 8000 rpm for 5 minutes, and the lower precipitate was collected. The precipitate was washed five times with a mixture of ethanol / deionized water (volume ratio 1:1) and dried in a vacuum oven at 60°C for 24 hours to obtain the modified BN.

[0046] 2. Preparation of modified PVDF / BN@2-phenylethylpyrazine composite nanofibers 1.2 g of PVDF was dissolved in a mixed solution of 8.8 g of DMF and acetone (the volume ratio of DMF to acetone was 6:4), and stirred at 80°C for 5 h to obtain a PVDF / DMF / acetone mixed solution; 0.06 g of modified BN was uniformly dispersed in the PVDF / DMF / acetone mixed solution and stirred at 40°C for 10 h to obtain a uniform electrospinning cortex solution.

[0047] 1 g of 2-phenylethylpyrazine was dissolved in 4 g of acetone to obtain the core electrospinning solution.

[0048] PVDF / modified BN@2-phenylethylpyrazine composite nanofibers were prepared by electrospinning technology with a liquid feed rate of 1.0 mL / h, a spinning voltage of 20 kV, and a receiving distance of 17 cm, denoted as PVDF / modified BN.

[0049] Control group: Control group A: Step 1 was omitted, and the modified BN in step 2 was replaced by BN. The prepared nanofibers were designated as PVDF / BN.

[0050] Control group B: The step of modifying the exfoliated BN nanosheets in step 1 was omitted, and the prepared nanofibers were recorded as PVDF / exfoliated BN.

[0051] Control group C: Step 1 was omitted, and no modified BN was added to the electrospinning cortex solution in step 2, that is, PVDF / DMF / acetone was directly used as the cortex solution; the electrospinning process parameters were the same as above, and the prepared nanofibers were recorded as PVDF.

[0052] The SEM images of BN, exfoliated BN nanosheets and modified BN in this example are shown in Figure 2. Figure 1 As shown, Figure 1 In the middle: (a) is BN; (b) is the peeled BN nanosheet; (c) is the modified BN. Figure 1The results show that the thickness of the exfoliated BN nanosheets dropped below 200 nm, with significant surface wrinkling and edge curling, increasing the specific surface area and active sites. PDA modification formed a uniform coating, whose steric hindrance inhibited nanosheet aggregation, resulting in surface granulation and reduced transparency.

[0053] The X-ray diffraction (XRD) of the modified BN in this embodiment is as follows: Figure 2 As shown. Figure 2 The XRD pattern shows distinct peaks at 2θ ≈ 26.8°, 41.6°, 50.2°, and 55.1°, corresponding to the (002), (100), (004), and (110) planes of h-BN, respectively (JCPDS 34-0421). XRD characterization reveals that the sample retains the h-BN hexagonal form after exfoliation and modification, with the characteristic diffraction peak positions and intensities remaining essentially consistent, indicating that the crystal structure is intact.

[0054] The SEM images of the fibers prepared in this example and the control group and the corresponding Figure 3 As shown, Figure 3 In the figure, (a) is PVDF; (b) is PVDF / BN; (c) is PVDF / exfoliated BN; (d) is PVDF / modified BN.

[0055] The diameters of the fibers prepared in this example and the control group were measured using ImageJ software to measure the diameters of 100 nanofibers, and the average value was taken as the fiber diameter. The measurement results are as follows: PVDF: 0.895 μm PVDF / BN: 1.164μm PVDF / peeled BN: 1.210μm PVDF / modified BN: 1.118μm Depend on Figure 3 Diameter measurements show that when PVDF is incorporated with unmodified BN, the fiber diameter increases to 1.164 μm. However, when exfoliated BN is added, the diameter reaches 1.210 μm due to the high aspect ratio and enhanced interfacial entanglement of the BN sheets. The diameter of the PVDF nanofibers modified with PDA decreases to 1.118 μm, attributed to the PDA promoting covalent bonding between the BN and the matrix, achieving uniform dispersion and inhibiting phase separation.

[0056] The TEM and mapping images of the fiber PVDF / modified BN prepared in this example are shown in Figure 2. Figure 4 As shown. Figure 4 It can be seen that the B / N elements in PVDF / modified BN are evenly distributed, and the optimized interfacial adhesion effectively improves the thermal conductivity and mechanical performance potential of the material.

[0057] The fibers prepared in this example and the control group were analyzed using a Nicolet 6700 Fourier transform infrared spectrometer at 500-4000 cm -1 The structure of the powder samples was tested by KBr pellet method within the range of 100 nm. The FTIR spectra of different fibers were as follows: Figure 5 As shown. Figure 5 It can be seen that h-BN at 808 cm -1 and 1370 cm -1 The B–N–B out-of-plane bending vibration and the B–N in-plane stretching vibration correspond to the B–N in-plane stretching vibration, respectively. The PVDF composite nanofibers have the following vibrations at 877, 1174, and 1402 cm -1 The characteristic absorption peaks of CH2 vibration, CF2 symmetric stretching and CH2 vibration are shown at 808 cm -1 The peak shifts to high frequency and overlaps with the PVDF peak at 877 cm⁻¹ and 1370 cm -1 The peak is close to 1402 cm -1 However, the characteristic peaks of PVDF are still clearly visible, indicating that the introduction of h-BN does not significantly destroy its crystalline structure. When the exfoliated and modified h-BN is further added, the peaks at 808 cm -1 The peak is red-shifted to 1402 cm -1 The peak at OH further broadens. -1 ) confirmed the presence of the dopamine coating; 840 cm -1 The enhancement of the peak indicates that there is a strong hydrogen bond between the –CF2 group in PVDF and the –OH / –NH2 of dopamine.

[0058] The fiber samples prepared in this embodiment and the control group were tested for wettability using a Shanghai JC2000D1 dynamic contact angle meter. The average value was taken from the test at 5 different locations. The water contact angle images of different fibers are shown in Figure 2. Figure 6 shown. Figure 6 In the figure, (a) is PVDF; (b) is PVDF / BN; (c) is PVDF / exfoliated BN; (d) is PVDF / modified BN.

[0059] Depend on Figure 6 The hydrophobicity of the four PVDF-based nanofibers was significantly enhanced. This is attributed to the PDA coating inhibiting BN aggregation and synergistically enhancing surface roughness and hydrogen bonding. The ingress of water vapor absorbs heat from the nanofiber system, reducing its heat and hindering the volatilization of the flavor. Therefore, the increased hydrophobicity of the nanofibers can reduce the impact of water vapor on the fiber system during cigarette smoking.

[0060] The fiber samples prepared in this example and the control group were processed as follows: The samples were placed in an oven preheated to 50°C. The temperature of the nanofibers was recorded every 30 seconds using a Fluke temperature monitoring system from the United States, and their thermal response behavior was observed. The time required for each sample to reach 50°C was also recorded. The thermal equilibrium time comparison and thermal response characteristics of different fibers are shown in the figure below. Figure 7 As shown. Figure 7 The PVDF membrane exhibited the longest equilibration time (293 seconds), attributed to its inherently low thermal conductivity (~0.19 W / mK) and lack of thermally conductive fillers. Adding h-BN to PVDF reduced the equilibration time to 261 seconds, as the layered structure of h-BN provides moderate thermal conductivity (~30 W / mK) and promotes heat transfer through filler-matrix interactions. However, the PVDF-exfoliated BN membrane experienced a further reduction (226 seconds), highlighting the critical role of filler exfoliation. Notably, the PVDF-modified BN membrane reached equilibrium in just 118 seconds, demonstrating the fastest thermal response. The h-BN filler primarily enhances bulk thermal conductivity, while the dopamine modification optimizes interfacial heat transfer at the molecular level.

[0061] The fiber samples prepared in this example and the control group were subjected to mechanical tests, and the test results are listed in Table 1.

[0062] Table 1 Mechanical properties of different nanofibers

[0063] As shown in Table 1, the breaking strength and elongation of the four PVDF-based nanofibers increase from left to right, which is closely related to the uniform dispersion of BN and the molecular entanglement between PDA and PVDF. In addition, BN is oriented under the action of the electric field during electrospinning.

[0064] The release performance and aroma retention ability of the fiber samples prepared in this example and the control group were tested using the following test methods: 1) Construction of 2-phenylethylpyrazine standard curve: The release kinetics of 2-phenylethylpyrazine from electrospun nanofibers was studied using a Shanghai Model 752 UV-visible spectrophotometer. A standard calibration curve for 2-phenylethylpyrazine was established ( Figure 8). The results showed that in the concentration range of 0~90 mg / L, the absorbance and the concentration of 2-phenethylpyrazine showed a good linear relationship and could be used for quantitative analysis. The UV-visible absorption spectrum of 2-phenethylpyrazine was recorded by wavelength scanning (200~800nm), and it was found that it had an obvious absorption peak at 270 nm, so this wavelength was selected for quantitative analysis. Anhydrous ethanol was used for stepwise dilution to prepare a series of standard solutions with concentrations of 0, 20, 40, 60, 80, 100 and 120 mg / L. Each concentration was measured three times to determine its absorbance. A linear fitting curve was drawn with absorbance (Y-axis) versus concentration (X-axis) ( Figure 8 ), and the regression line equation is calculated as Y = 0.017786 X + 0.03142 , correlation coefficient R² = 0.996411 .

[0065] 2) Ten fiber samples (1.5 g each) pre-equilibrated at 50 °C were placed in a 50 °C oven. One sample was taken out every 1 min and transferred to a 10 mL centrifuge tube filled with 50 °C ethanol. The tube was shaken continuously to facilitate the extraction of 2-phenylethylpyrazine. The absorbance of 2-phenylethylpyrazine in the extract at 270 nm ( Y ) to quantify its release rate ( Re ). Calculated using the following equation Re .

[0066]

[0067] Where Y represents the absorbance of the nanofiber membrane extract at different times, Y 10 Representative absorbances of nanofiber membrane extracts measured immediately after spinning.

[0068] The aroma release characteristics of skin-core nanofibers were measured using a Japanese XP-329 odor detection system. A 1-gram sample of nanofiber was placed in a sealed glass chamber (10 × 20 × 20 cm³) and tested at 50°C. Data was recorded every 1 minute until the fluctuation in the values ​​for three consecutive measurements was less than 2%, indicating that the sample had reached a stable state.

[0069] The aroma release rate (a) and aroma intensity value (b) of the fibers prepared in the embodiment and the control group are shown in Figures 1 and 2. Figure 9 As shown in (a) and (b).

[0070] Depend on Figure 9It can be seen that: the thermal equilibrium behavior and the release curve of 2-PEP over time of four kinds of core-shell nanofiber membranes (PVDF, PVDF-BN, PVDF-exfoliated BN and PVDF-modified BN). The thermal equilibrium time reaching 50℃ (previously reported 293 seconds, 261 seconds, 226 seconds and 118 seconds respectively) is in strong inverse proportion to the final aroma release rate (12%, 35.5%, 51.6% and 73.3%) and aroma value (260, 315, 390 and 492). This relationship highlights the synergistic effect of thermal conductivity and membrane permeability in regulating payload release. The rapid thermal equilibrium of dopamine hydrochloride modified polyvinylidene fluoride (118 seconds) directly corresponds to its outstanding release efficiency (73.3%) and aroma intensity (492). This accelerated response is derived from the enhanced thermal conduction mechanism: the polar functional groups (-NH2, -OH) introduced by polydopamine improve the interface phonon coupling, reduce the thermal resistance, and make the heat conduct faster to the core. The exfoliated h-BN nanosheet has a high aspect ratio, reducing stacking defects, thereby forming a continuous heat channel, expanding the accessibility of heat diffusion and solvent.

[0071] Example 2 This example relates to the influence of the change of modified BN content on the performance of the final material in the preparation process of the core-sheath structure nanofiber material. Adjust the mass ratio of modified BN and PVDF in the electrospinning skin layer solution in step 2 of Example 1, and the rest of the preparation steps and condition parameters are the same as those in Example 1. Test the material performance of the prepared fiber, and the results are shown in Table 2 below.

[0072] Table 2 Performance indicators of fibers prepared with different modified BN contents

[0073] As can be seen from Table 2: when the content of BN is 5wt% of the mass of PVDF, the mechanical properties and hydrophobic properties of the nanofiber are best, the heat release is the fastest, and the most perfume is released. This shows that the presence of BN not only improves the thermal conductivity of the nanofiber, but also increases the hydrophobicity and mechanical properties. The increase in hydrophobicity helps to stabilize the nanofiber heat transfer system. The increase in mechanical properties facilitates the use of cigarettes in actual production and processing.

[0074] Example 3 This example relates to the influence of different buffers in the preparation process of nanofiber materials on the performance of the final material. Adjust the buffer (tris-hydroxymethyl aminomethane) in step 1 of Example 1 by using different buffers to adjust the pH value, and the rest of the preparation steps and condition parameters are the same as those in Example 1. Test the material performance of the prepared fiber, and the results are shown in Table 3 below.

[0075] Table 3 Performance indicators of fibers prepared with different buffers

[0076] Table 3 shows that the buffer solution does not affect the modified BN, achieving excellent thermal conductivity. This performance is complemented by excellent fragrance encapsulation, hydrophobicity, and mechanical strength. The various buffer solutions used to prepare the nanofibers showed minimal impact on their properties.

[0077] Example 4 This example describes the influence of electrospinning conditions on the properties of the final nanofiber material during its preparation. In step 2 of Example 1, the solute (the addition and amount of modified BN remained unchanged) and solvent in the electrospinning cortical solution were adjusted. The remaining preparation steps and conditions remained the same as in Example 1. The material properties of the resulting fibers were tested, and the results are shown in Table 4 below.

[0078] Table 4 Performance indicators of fibers prepared from different polymers

[0079] Table 4 shows that modified BN can be evenly dispersed in a variety of polymers, achieving good thermal conductivity. While exhibiting excellent thermal conductivity, it also exhibits good fragrance encapsulation efficiency, hydrophobicity, and mechanical strength.

[0080] Example 5 This example describes the impact of different core layer fragrance materials on the properties of the final nanofiber material during its preparation. In step 2 of Example 1, the type of pyrazine compound in the core electrospinning solution was adjusted. The remaining preparation steps and conditions remained the same as in Example 1. The material properties of the resulting fibers were tested, and the results are shown in Table 5 below.

[0081] Table 5 Performance indicators of samples prepared with different core layer flavor materials

[0082] Table 5 shows that the core flavor material does not affect the thermal conductivity of the modified BN. While exhibiting excellent thermal conductivity, it also exhibits good flavor encapsulation efficiency, hydrophobicity, and mechanical strength. This demonstrates the universal applicability of this nanofiber material. However, the effects on thermal equilibrium time and heat release rate differ slightly, due to the different boiling points of the pyrazine flavor compounds.

[0083] Example 6 This example describes the effects of varying PVDF concentrations on the properties of the final nanofiber material during its preparation. The PVDF concentration in the PVDF / DMF / acetone mixed solution in step 2 of Example 1 was adjusted. The remaining preparation steps and conditions remained the same as in Example 1. The material properties of the resulting fibers were tested, and the results are shown in Table 6 below.

[0084] Table 6 Performance indicators of samples prepared from spinning solutions with different PVDF concentrations

[0085] Table 6 shows that as the PVDF concentration increases, the average fiber diameter and mechanical properties improve overall. Samples with a PVDF concentration in the electrospinning cortex solution of 12–13 wt% exhibit the best breaking strength, good hydrophobicity, and little change in thermal equilibrium time. This suggests that appropriately increasing the PVDF concentration can help optimize fiber structure and overall performance.

[0086] Example 7 This example describes the effect of spinning speed on the final properties of nanofiber materials during the preparation process. The liquid feed rate in step 2 of Example 1 was adjusted, while the remaining preparation steps and conditions remained the same as in Example 1. The material properties were tested, and the results are shown in Table 7 below.

[0087] Table 7 Performance indicators of samples prepared at different spinning speeds

[0088] Table 7 shows that as the spinning speed increases, the fiber diameter and mechanical properties improve. At 1.0–1.1 mL / h, the breaking strength reaches its highest point, and the release rate is also high. The contact angle stabilizes at around 135°, and the thermal equilibrium time remains relatively unchanged. These results indicate that appropriately increasing the spinning speed can enhance fiber density and mechanical properties, while also improving fragrance release.

[0089] Example 8 This example relates to the effects of different thermally conductive materials on the performance of the final nanofiber material during the preparation process. The thermally conductive material, modified BN, in step 2 of Example 1 was replaced with graphene / graphene oxide, respectively. The specific process for preparing the electrospinning shell solution was as follows: 0.06 g of graphene / graphene oxide was added to a PVDF / DMF / acetone mixed solution, and ultrasonic treatment was performed for 30 minutes to promote uniform dispersion in the solution, thereby producing a stable electrospinning shell solution. The remaining preparation steps and conditions were the same as in Example 1. The material properties of the prepared fibers were tested, and the results are shown in Table 8 below.

[0090] Table 8 Performance indicators of samples prepared with different thermal conductive materials

[0091] From Table 8, it can be seen that the modified BN has the best comprehensive performance, with the breaking strength (3.63 MPa), elongation at break (124%), hydrophobicity (contact angle 135.3°) and thermal performance (thermal balance time 118 s, release rate 74%) all better than graphene and graphene oxide, and it is especially suitable for high-strength and high-thermal-conductivity applications; the mechanical and thermal performance of graphene is in the middle, while the strength (3.22 MPa) and release rate (55%) of graphene oxide are the lowest due to structural defects, and the thermal response is the slowest (145 s).

[0092] The above has described various embodiments of the present application, and the above description is exemplary and is not exhaustive, and is also not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles, practical applications, or improvements to the technology in the market of the embodiments, or to enable other ordinary skilled in the art to understand the embodiments disclosed herein.

Claims

1. A composite nanofiber with a skin-core structure, characterized in that: The skin layer comprises modified boron nitride and high molecular polymer, wherein the modified boron nitride is modified boron nitride with polydopamine modified on the surface; and the core layer is a pyrazine compound solution.

2. The composite nanofiber according to claim 1, characterized in that The high molecular polymer is one or two of polyvinylidene fluoride, polyacrylonitrile, polyurethane, polyvinyl pyrrolidone, polyamide and polyimide; and / or, in the skin layer, the weight ratio of modified boron nitride to the high molecular polymer is 0.01-7:

100.

3. The composite nanofiber according to claim 1, characterized in that The pyrazine compound is one or more of 2-phenethylpyrazine, 2-styrylpyrazine, 2-(4-ethylstyryl)pyrazine, 2-(4-isopropylstyryl)pyrazine, 2-(4-methoxystyryl)pyrazine, 2-(4-methylphenethyl)pyrazine, 2-(4-ethylphenethyl)pyrazine, 2-(3-methylphenethyl)pyrazine, and 2-(2-methylphenethyl)pyrazine, and the concentration of the pyrazine compound solution is 5-50wt%; and / or, The solvent of the pyrazine compound solution is acetone, methanol, tetrahydrofuran, ethyl acetate, cyclohexane, acetonitrile or ethanol.

4. The composite nanofiber according to claim 1, characterized in that Its diameter is 0.6-2μm.

5. The method for preparing the composite nanofiber according to any one of claims 1 to 4, characterized in that: include: Step a), using lithium fluoride as an intercalation agent, hydrothermally exfoliating boron nitride to obtain exfoliated boron nitride nanosheets; Step b), dispersing the exfoliated boron nitride nanosheets and dopamine hydrochloride in a solvent, adjusting the pH to alkaline, and collecting the precipitate after the reaction to obtain modified boron nitride with surface modified polydopamine; Step c), dissolving the modified boron nitride in a polymer solution to obtain a modified boron nitride / polymer mixed solution; Step d) preparing composite nanofibers by electrospinning using a pyrazine compound solution as a core layer solution and the modified boron nitride / high molecular polymer mixed solution as a skin layer solution.

6. The preparation method according to claim 5, characterized in that In step a), the mass ratio of boron nitride to lithium fluoride is 1:0.5-5, the concentration of lithium fluoride in the hydrothermal exfoliation system is 10-90 g / L, and the temperature is 80-300° C.; and / or, in step b), the mass ratio of the exfoliated boron nitride nanosheets to dopamine hydrochloride is 1:0.3-4.

7. The preparation method according to claim 5, characterized in that In the step c), the concentration of the high molecular polymer solution is 6-30 wt %, and the mass ratio of the modified boron nitride to the high molecular polymer is 0.01-7:

100.

8. The preparation method according to claim 5, characterized in that In the step d), the pyrazine compound is one or more of 2-phenethylpyrazine, 2-styrylpyrazine, 2-(4-ethylstyryl)pyrazine, 2-(4-isopropylstyryl)pyrazine, 2-(4-methoxystyryl)pyrazine, 2-(4-methylphenethyl)pyrazine, 2-(4-ethylphenethyl)pyrazine, 2-(3-methylphenethyl)pyrazine, and 2-(2-methylphenethyl)pyrazine; and the concentration of the pyrazine compound solution is 5-50 wt%.

9. The preparation method according to claim 5, wherein In the step d), the process conditions for electrospinning are: a liquid feeding rate of 0.5-2 mL / h and a receiving distance of 15-30 cm.

10. Use of the composite nanofiber according to any one of claims 1 to 4 in cigarette flavoring, antibacterial textiles, environmental pollutant adsorption materials, high-sensitivity sensors or controlled-release carriers.

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