High-strength high-toughness nanofiber composite membrane and preparation method thereof

Abstract

The application provides a high-strength and high-toughness nanofiber composite film and a preparation method thereof, and belongs to the technical field of functional materials. First, a PVA-co-PE nanofiber suspension is prepared, then the prepared PVA-co-PE nanofiber suspension is mixed with glutaraldehyde and is subjected to first-step crosslinking, deionized water with a specific ratio is added, PVA-co-PE nanofibers are subjected to second-step crosslinking with water molecules, the obtained solution is subjected to vacuum-assisted filtration to form a film, after drying, heat pressing treatment is performed, further crosslinking of the PVA-co-PE nanofibers is generated, and a high-strength and high-toughness nanofiber composite film is obtained. The successful preparation of the high-strength and high-toughness nanofiber composite film not only solves the problem of insufficient mechanical properties of nanofiber materials, but also provides a new approach for preparing high-performance materials.

Description

Technical Field

[0001] This invention relates to the field of nanofiber membrane material preparation, and particularly to a high-strength and high-toughness nanofiber composite membrane and its preparation method. Background Technology

[0002] With the continuous advancement of science and technology and the development of new materials science, the demand for high-performance materials is increasing, especially in fields such as smart wearables, flexible electronic devices, biomedicine, and environmental protection. However, insufficient mechanical properties of materials often limit their application areas. Among numerous new materials, nanofiber materials have attracted widespread attention due to their unique physicochemical properties, ultra-high specific surface area, and excellent mechanical properties. Polyvinyl alcohol-co-polyethylene (PVA-co-PE) nanofibers, as an important polymer composite material, have shown great application potential in fields such as biomedical engineering, filtration materials, environmental protection, and flexible electronic devices due to their unique physical and chemical properties, good biocompatibility, and environmentally friendly and sustainable development characteristics.

[0003] In the prior art, patent CN 107620212 A discloses a method for preparing phase change nanofibers. This patent grafts a phase change medium onto a carrier via condensation polymerization to form phase change nanofibers with a cross-linked network structure. The carrier is prepared by dissolving PVA-co-PE nanofibers into a suspension, mixing it with the phase change material, adding a cross-linking agent for cross-linking, centrifuging and washing with a solvent, and then drying to obtain the phase change nanofibers. This fiber membrane is prepared through only one cross-linking reaction, resulting in poor strength and toughness, which limits its application range to some extent.

[0004] In view of this, it is necessary to design an improved nanofiber composite membrane and its preparation method to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength and high-toughness nanofiber composite membrane and its preparation method. A PVA-co-PE nanofiber composite membrane is prepared by a "two-step crosslinking method" and hot pressing process. The nanofiber composite membrane has the characteristics of high strength and good toughness. Moreover, the preparation process is simple and does not require the addition of other chemical reagents to undergo further crosslinking. This not only solves the problem of insufficient mechanical properties of nanofiber materials, but also provides a new way to prepare high-performance materials.

[0006] To achieve the above-mentioned objectives, this invention provides a high-strength, high-toughness nanofiber composite membrane and its preparation method, comprising the following steps:

[0007] S1. Disperse PVA-co-PE nanofibers in a solvent to obtain a first nanofiber suspension;

[0008] S2. Add the crosslinking agent to the first nanofiber suspension to carry out the first crosslinking. After the reaction is complete, the second nanofiber suspension is obtained.

[0009] S3. Add a predetermined amount of deionized water to the second nanofiber suspension to carry out a second cross-linking. After the reaction is complete, a third nanofiber suspension is obtained.

[0010] S4. Perform solid-liquid separation on the third nanofiber suspension to obtain a PVA-co-PE nanofiber composite membrane;

[0011] S5. The nanofiber composite membrane is subjected to hot pressing treatment to obtain a high-strength and high-toughness nanofiber composite membrane.

[0012] As a further improvement of the present invention, in step S3, the amount of deionized water added accounts for 5 to 15 wt% of the mass of the second nanofiber suspension.

[0013] As a further improvement of the present invention, in step S5, during the hot pressing process, the hot pressing temperature is 85-95°C, the pressure is 8-12 MPa, and the hot pressing time is 55-65 s.

[0014] As a further improvement of the present invention, in step S1, the mass fraction of PVA-co-PE nanofibers in the first nanofiber suspension is 1 to 2 wt%.

[0015] As a further improvement of the present invention, in step S1, the solvent includes isopropanol and deionized water; the mass ratio of isopropanol to deionized water is 60-70:40-30.

[0016] As a further improvement of the present invention, in step S2, the crosslinking agent is glutaraldehyde.

[0017] As a further improvement of the present invention, in step S2, the amount of crosslinking agent added accounts for 1wt% to 4wt% of the mass of the PVA-co-PE nanofibers.

[0018] As a further improvement of the present invention, in step S4, the solid-liquid separation method is: vacuum-assisted filtration is used for suction filtration.

[0019] The present invention also provides a high-strength and high-toughness nanofiber composite membrane, which is prepared by the above-mentioned method for preparing nanofiber composite membrane. The membrane undergoes a first crosslinking reaction with a crosslinking agent, followed by a second crosslinking reaction with deionized water through hydrogen bonding, and then is obtained by hot pressing.

[0020] As a further improvement of the present invention, the high-strength and high-toughness nanofiber composite membrane has a tensile strength of 17.8 MPa to 35.6 MPa and a tensile fracture strain of 9.3% to 34.9%.

[0021] The beneficial effects of this invention are:

[0022] 1. The method for preparing high-strength and high-toughness nanofiber composite membrane provided by the present invention first prepares a stable PVA-co-PE nanofiber suspension, then adds a crosslinking agent to generate a first crosslinking reaction. After the reaction is complete, deionized water is added to break the equilibrium state of the mixed solution, so that the polar groups (hydroxyl groups) in the PVA-co-PE nanofibers interact with water molecules, resulting in a large number of hydrogen bonds between the PVA-co-PE nanofibers and generating a second self-crosslinking reaction. This step greatly increases the physical and mechanical properties of the PVA-co-PE nanofiber composite membrane. Moreover, this method does not require the addition of other chemical reagents, the preparation method is simple, and it provides convenience for industrial applications.

[0023] 2. The method for preparing the high-strength and high-toughness nanofiber composite membrane provided by the present invention involves hot-pressing the PVA-co-PE nanofiber composite membrane after secondary cross-linking. This allows water molecules inside the PVA-co-PE nanofiber membrane to evaporate rapidly, reducing porosity without damaging the PVA-co-PE nanofibers. Furthermore, at a specific temperature, the PVA-co-PE nanofibers exhibit a molten state. Applying pressure further promotes cross-linking between the PVA-co-PE nanofibers, thereby further improving the strength of the PVA-co-PE nanofiber composite membrane.

[0024] 3. This invention combines a two-step crosslinking method with a hot-pressing process to prepare a high-strength and high-toughness nanofiber composite membrane, which makes up for the lack of mechanical properties of most polymer composite materials. Moreover, its preparation process is simple, providing a new way to prepare high-performance materials. Attached Figure Description

[0025] Figure 1 A schematic flowchart illustrating the preparation method of the high-strength and high-toughness nanofiber composite membrane provided by the present invention.

[0026] Figure 2 The images show high-magnification and low-magnification SEM images of the nanofiber composite membranes prepared in Examples 1-4 and Comparative Examples 1-2.

[0027] Figure 3 Stress-strain diagrams of the nanofiber composite membranes prepared in Examples 1-4 and Comparative Examples 1-2 are shown.

[0028] Figure 4Stress-strain diagrams of the nanofiber composite membranes prepared in Example 1 and Comparative Examples 3-4. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0031] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0032] Please see Figure 1 As shown, the present invention provides a method for preparing a high-strength and high-toughness nanofiber composite membrane, comprising the following steps:

[0033] S1. The solvent and PVA-co-PE nanofibers are dispersed and mixed in a high-speed shear mixer to obtain the first nanofiber suspension;

[0034] S2. Add the crosslinking agent to the first nanofiber suspension obtained in step S1 to carry out the first crosslinking. After the reaction is complete, the second nanofiber suspension is obtained.

[0035] S3. Add a predetermined amount of deionized water to the second nanofiber suspension to carry out a second cross-linking. After the reaction is complete, a third nanofiber suspension is obtained.

[0036] S4. Perform solid-liquid separation on the third nanofiber suspension to obtain a PVA-co-PE nanofiber composite membrane;

[0037] S5. The nanofiber composite membrane is subjected to hot pressing treatment to obtain a high-strength and high-toughness nanofiber composite membrane.

[0038] Through the above methods, the present invention can obtain a high-strength and high-toughness nanofiber composite membrane. The preparation process is simple, and the physical and mechanical properties of the obtained nanofiber composite membrane are greatly improved.

[0039] Preferably, in step S1, the solvent includes isopropanol and deionized water, the mass ratio of isopropanol to deionized water is 60-70:40-30, and the mass fraction of PVA-co-PE nanofibers is 1-2 wt%, so as to obtain a stable PVA-co-PE nanofiber suspension.

[0040] In step S2, the crosslinking agent is preferably glutaraldehyde, and the amount of crosslinking agent added accounts for 1 wt% to 4 wt% of the mass of the PVA-co-PE nanofibers.

[0041] In step S3, the addition of deionized water disrupts the phase equilibrium of the second nanofiber suspension, causing numerous hydrogen bonds to form between the PVA-co-PE nanofibers. The preferred mass fraction of the deionized water is 5–15 wt%.

[0042] If too little deionized water is added, the PVA-co-PE nanofibers cannot fully interact with water molecules, and a large number of hydrogen bonds cannot be formed between the PVA-co-PE nanofibers, resulting in poor cross-linking effect. Consequently, the mechanical properties of the PVA-co-PE nanofiber composite membrane cannot be well improved. If too much deionized water is added, the dispersion effect of the PVA-co-PE nanofibers will be poor, and they will not form a solution state, but will instead exhibit a solid-liquid separation state.

[0043] In step S4, the preferred method for solid-liquid separation is vacuum-assisted filtration, specifically using a vacuum filter.

[0044] In step S5, during the hot pressing process, the hot pressing temperature is preferably 85-95℃, the hot pressing pressure is preferably 8-12MPa, and the hot pressing time is preferably 55-65s. If the hot pressing temperature and pressure are too high, the PVA-co-PE nanofiber membrane will not be able to form and its strength will be reduced. If the temperature and pressure are too low, the mechanical properties of the PVA-co-PE nanofiber membrane will hardly change, and the purpose of assisting in promoting cross-linking and enhancing the mechanical properties of the PVA-co-PE nanofiber membrane will not be achieved.

[0045] The present invention also provides a high-strength and high-toughness nanofiber composite membrane, which is prepared by the above-mentioned method for preparing nanofiber composite membranes. The high-strength and high-toughness nanofiber composite membrane is obtained by a two-step crosslinking method combined with a hot pressing process.

[0046] The present invention will now be described in detail with reference to specific embodiments.

[0047] Example 1

[0048] This embodiment provides a method for preparing a high-strength and high-toughness nanofiber composite membrane, including the following steps:

[0049] S1. Isopropanol and deionized water were mixed at a ratio of 60:40 to prepare a solvent; PVA-co-PE nanofibers were dispersed and mixed with the prepared solvent in a high-speed shear mixer to obtain a first nanofiber suspension. The mass fraction of PVA-co-PE nanofibers in the first nanofiber suspension was 1 wt%.

[0050] S2. Add glutaraldehyde to the first nanofiber suspension obtained in step S1 to perform the first crosslinking, stir for 2 hours to allow it to react fully, and obtain the second nanofiber suspension; wherein, the amount of crosslinking agent added accounts for 1 wt% of the mass of the PVA-co-PE nanofibers.

[0051] S3. Weigh a predetermined amount of deionized water, such that the weighed deionized water accounts for 5 wt% of the mass of the second nanofiber suspension, add the deionized water to the second nanofiber suspension obtained in step S2, perform a second crosslinking, stir for 2 hours to allow it to react fully, and obtain the third nanofiber suspension.

[0052] S4. The third nanofiber suspension obtained in step S3 is filtered by a vacuum filter to obtain a PVA-co-PE nanofiber composite membrane.

[0053] S5. The PVA-co-PE nanofiber composite membrane obtained in step S4 is hot-pressed at 90°C and 10MPa for 60s using a hot press to obtain a high-strength and high-toughness nanofiber composite membrane.

[0054] Examples 2-4 and Comparative Examples 1-2

[0055] Examples 2-4 and Comparative Examples 1-2 each provide a method for preparing a high-strength, high-toughness nanofiber composite membrane. Compared with Example 1, the difference lies in the amount of deionized water added in step S3. The amount of deionized water added in each example and Comparative Examples 1-2 is shown in Table 1. Other steps are roughly the same as in Example 1 and will not be described again here.

[0056] Table 1 shows the amount of deionized water added in Examples 1-4 and Comparative Examples 1-2.

[0057]

[0058] The morphology of the high-strength and high-toughness nanofiber composite membranes prepared in Examples 1-4 and Comparative Examples 1-2 are as follows: Figure 2 As shown, its stress-strain curve was measured as follows: Figure 3 As shown.

[0059] Figure 2 and Figure 3In the text, PVA-co-PE, PVA-co-PE-S, PVA-co-PE-S1, PVA-co-PE-S2, PVA-co-PE-S3, and PVA-co-PE-S4 represent the high-strength and high-toughness nanofiber composite membranes prepared in Comparative Example 1, Example 1, Example 2, Example 3, Example 4, and Comparative Example 2, respectively.

[0060] Figure 3 In Table 2, the specific values ​​of tensile strength and tensile fracture strain of the high-strength and high-toughness nanofiber composite membranes prepared in Examples 1-4 and Comparative Examples 1-2 are shown.

[0061] Table 2 shows the tensile strength and tensile fracture strain of the composite membranes in Examples 1-4 and Comparative Examples 1-2.

[0062]

[0063] Combination Figure 2 and Figure 3 It can be seen that with the increase of the amount of deionized water added, the tensile strength and tensile fracture strain of the high-strength and high-toughness nanofiber composite membrane gradually increase, indicating that the strength and flexibility of the nanofiber composite membrane gradually improve. However, when the amount of deionized water added reaches 15wt%, if it is further increased to 25wt%, the dispersion effect of PVA-co-PE nanofibers will be worse, and they will not be able to form a solution state, but will exhibit a solid-liquid separation state. As a result, the nanofiber composite membrane is difficult to form, and both tensile strength and flexibility decrease.

[0064] Comparative Examples 3-4

[0065] Comparative Examples 3 and 4 respectively provide methods for preparing high-strength and high-toughness nanofiber composite membranes. Compared with Example 1, the difference lies in the change of the hot-pressing treatment method in step S5: in Comparative Example 3, the hot-pressing treatment is replaced by drying treatment at 50°C; in Comparative Example 4, the hot-pressing temperature is changed to 120°C and the pressure is changed to 20 MPa. The other steps are roughly the same as in Example 1, and will not be described again here.

[0066] The stress-strain curves of the high-strength and high-toughness nanofiber composite membranes prepared in Comparative Examples 3-4 are shown below. Figure 4 As shown in Table 3, the specific values ​​of its tensile strength and tensile fracture strain are as follows.

[0067] Table 3 shows the tensile strength and tensile fracture strain of the composite membranes in Comparative Examples 3 and 4.

[0068] Comparative Example Comparative Example 3 Comparative Example 4 tensile strength 17.0MPa 5.2MPa Tensile fracture strain 8.6％ 4.6％

[0069] Figure 4In the table, PVA-co-PE-S5 and PVA-co-PE-S6 represent the high-strength and high-toughness nanofiber composite membranes prepared in Comparative Examples 3 and 4, respectively. (From Table 3 and...) Figure 4 As can be seen, compared with Example 1, the temperature in Comparative Example 3 was too low, causing the nanofibers to be unable to exhibit a molten state, and further cross-linking between the nanofibers was not possible. Therefore, the tensile strength and flexibility of Comparative Example 3 both decreased. Compared with Example 1, the temperature and pressure in Comparative Example 4 were too high, causing the nanofibers to be very close to a molten state. This made the nanofiber composite film difficult to form and extremely prone to breakage under high pressure. Therefore, the tensile strength and flexibility of Comparative Example 4 both decreased sharply.

[0070] In summary, this invention combines a two-step crosslinking method with a hot-pressing process to prepare a high-strength and high-toughness nanofiber composite membrane, which overcomes the problem of insufficient mechanical properties in most polymer composite materials. Moreover, its preparation process is simple, requiring only the addition of a specific proportion of deionized water to induce a further self-crosslinking reaction in PVA-co-PE nanofibers, providing a new approach for the preparation of high-performance materials.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a high-strength, high-toughness nanofiber composite membrane, characterized in that, Includes the following steps: S1. PVA-co-PE nanofibers are dispersed in a solvent to obtain a first nanofiber suspension; the mass fraction of PVA-co-PE nanofibers in the first nanofiber suspension is 1~2 wt%. S2. A crosslinking agent is added to the first nanofiber suspension to perform the first crosslinking. After sufficient reaction, a second nanofiber suspension is obtained. The amount of the crosslinking agent added is 1wt% to 4wt% of the mass of the PVA-co-PE nanofibers. S3. A predetermined amount of deionized water is added to the second nanofiber suspension to perform a second cross-linking. After sufficient reaction, a third nanofiber suspension is obtained. The amount of deionized water added is 5-15 wt% of the mass of the second nanofiber suspension. S4. Perform solid-liquid separation on the third nanofiber suspension to obtain a PVA-co-PE nanofiber composite membrane; S5. The nanofiber composite membrane is subjected to hot pressing treatment to obtain a high-strength and high-toughness nanofiber composite membrane; during the hot pressing treatment, the hot pressing temperature is 85~95℃, the pressure is 8~12MPa, and the hot pressing time is 55~65s.

2. The method for preparing the high-strength and high-toughness nanofiber composite membrane according to claim 1, characterized in that, In step S1, the solvent includes isopropanol and deionized water; the mass ratio of isopropanol to deionized water is 60~70:40~30.

3. The method for preparing the high-strength and high-toughness nanofiber composite membrane according to claim 1, characterized in that, In step S2, the crosslinking agent is glutaraldehyde.

4. The method for preparing the high-strength and high-toughness nanofiber composite membrane according to claim 1, characterized in that, In step S4, the solid-liquid separation method is: vacuum-assisted filtration is used for filtration.

5. A high-strength, high-toughness nanofiber composite membrane, characterized in that, The high-strength and high-toughness nanofiber composite membrane was prepared using the preparation method described in any one of claims 1 to 4.

6. The high-strength, high-toughness nanofiber composite membrane according to claim 5, characterized in that, The high-strength and high-toughness nanofiber composite membrane has a tensile strength of 17.8 MPa to 35.6 MPa and a tensile fracture strain of 9.3% to 34.9%.

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