Preparation method of fluorine-containing porous micro-nano fiber

Abstract

The invention discloses a preparation method of fluorine-containing porous micro-nano fibers, which is characterized in that natural polysaccharide (cassava starch) is used as a matrix, and is blended with fluorine-containing polymer emulsion, and centrifugal spinning and controllable sintering processes are combined, so that integrated construction of fiber forming and a porous structure is realized. The main principle of the method is as follows: natural polysaccharide (cassava starch) has excellent spinnability in a centrifugal spinning system and is used as a fluorine-containing emulsion spinning carrier. Meanwhile, by utilizing the characteristic that the melting points of PTFE and PVDF are different, PTFE and PVDF particles in the precursor fibers are promoted to form fibers and pore parts in different flowing states in the sintering and melting process, and finally the fluorine-containing porous micro-nano fibers are obtained.

Description

Technical Field

[0001] This invention belongs to the field of micro / nanofiber material preparation technology, specifically relating to a method for preparing fluorinated micro / nanofibers with porous structures based on a blend system of natural polysaccharides and fluorinated polymers via centrifugal spinning and sintering. The porous fibers obtained by this method possess high specific surface area, good chemical stability, and tunable pore structure, making them suitable for applications such as high-efficiency filtration, adsorption separation, and biomedical materials. Background Technology

[0002] Micro and nanofibers, due to their excellent specific surface area, pore structure, and surface activity, have shown broad application prospects in fields such as filtration, catalysis, sensing, energy, and biomedicine. In recent years, introducing porous structures to further enhance the specific surface area and functional properties of fibers has become one of the important directions in fiber material modification.

[0003] Currently, the main methods for preparing porous fibers include thermally induced phase separation and post-processing etching. While these methods can construct porous structures, they often suffer from problems such as complex processes, limited applicability to polymers, the need for organic solvents or highly corrosive reagents, and environmental unfriendliness. For example, traditional phase separation methods have strict requirements on solvent systems, temperature gradients, and polymer compatibility, and it is difficult to achieve precise control over pore size and pore distribution.

[0004] In addition, fluoropolymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) have excellent chemical stability, hydrophobicity, and weather resistance, and are widely used in high-performance filter membranes, lithium battery separators, protective clothing, and other fields. However, their insoluble and refractory properties make the fiberization process difficult, usually requiring high-temperature sintering or special solvent treatment, with harsh process conditions, and the fiber morphology and pore structure are not easy to control.

[0005] Therefore, developing a method that is simple in process, environmentally friendly, widely applicable, and can effectively control the porous structure of fluoropolymer fibers is of great scientific significance and practical application value. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing fluorinated porous micro / nanofibers. This method uses natural polysaccharide (cassava starch) as a matrix, blending it with a fluorinated polymer emulsion, and combining centrifugal spinning and controlled sintering processes to achieve integrated fiber forming and porous structure construction. The main principle of this method is to utilize the excellent spinnability of natural polysaccharide (cassava starch) in a centrifugal spinning system as a carrier for the fluorinated emulsion spinning. Simultaneously, taking advantage of the different melting points of PTFE and PVDF, the PTFE and PVDF particles in the precursor fiber form fibers and porous portions in different flow states during the sintering and melting process, ultimately obtaining fluorinated porous micro / nanofibers.

[0007] To solve the above technical problems, the following technical solution is adopted:

[0008] A method for preparing fluorine-containing porous micro / nanofibers, characterized by comprising the following steps:

[0009] (1) Preparation of centrifugal spinning solution:

[0010] Tapioca starch was mixed with NaOH solution, and high molecular weight polyethylene oxide (PEO, molecular weight 5 million) was added to fully dissolve and disperse it to obtain a mixture. Then, polytetrafluoroethylene emulsion and polyvinylidene fluoride emulsion were added to the mixture to obtain a uniform spinning solution.

[0011] (2) Preparation of centrifugally spun micro / nanofibers:

[0012] The above spinning solution was placed in a centrifugal spinning device, and micro / nanofibers were prepared by centrifugal spinning.

[0013] (3) Formation of porous fibers:

[0014] The prepared fibers are placed in a tube furnace for sintering, and fluorinated fibers with a porous structure are obtained after sintering.

[0015] After optimization, in step 1, the mixture contains 8%–10% cassava starch at a total mass of 10.0g.

[0016] After optimization, in step (1), a 2% NaOH solution is used to replenish the remaining amount of the mixture.

[0017] After optimization, in step (1), the molecular weight of the polyethylene oxide is 5 million, and its addition amount is 8%-12% of the mass of the cassava starch.

[0018] After optimization, in step (1), under the condition that the emulsion mass is fixed at 6.0 g, the mass ratio of polytetrafluoroethylene emulsion to polyvinylidene fluoride emulsion is 1:5 to 3:3.

[0019] After optimization, the solid content of both polytetrafluoroethylene emulsion and polyvinylidene fluoride emulsion is 60%.

[0020] After optimization, the magnetic stirring in step (1) is divided into two stages: the stirring time is 2 hours before adding the fluorinated emulsion in the first stage, and the stirring time is 45 minutes after adding the fluorinated emulsion in the second stage.

[0021] After optimization, in step (2), the needle diameter is 25G, the rotation speed is 1200-1400rpm, and the spinning temperature is 60℃.

[0022] After optimization, in step (3), the sintering process is carried out in a nitrogen-free environment, the sintering temperature is 380°C, and the sintering time is 5 hours.

[0023] The above technical solution has the following beneficial effects:

[0024] Using natural starch as the spinning matrix, which is widely available, low in cost, and environmentally friendly, the fiber completely decomposes after sintering, forming a rich porous structure. The fiber structure is formed by utilizing the inexhaustible melting point of two fluoropolymers. The resulting fiber has a high specific surface area, excellent chemical stability, and hydrophobicity, making it suitable for a variety of high-end applications such as high-temperature filtration, oil-water separation, battery separators, and tissue engineering scaffolds. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of the fluorine-containing porous nanofibers prepared in Example 1 of this invention.

[0026] Figure 2 This is a scanning electron microscope image of the fluorine-containing nanofibers prepared in Comparative Example 1 of this invention. Detailed Implementation

[0027] This invention uses natural polysaccharide (cassava starch) as a matrix, and achieves integrated construction of fiber forming and porous structure by blending it with a fluoropolymer emulsion and combining centrifugal spinning and controlled sintering processes. The main principle of this method is to utilize the excellent spinnability of natural polysaccharide (cassava starch) in a centrifugal spinning system as a carrier for the fluoropolymer emulsion spinning. Simultaneously, by utilizing the different melting points of PTFE and PVDF, the PTFE and PVDF particles in the precursor fiber form fibers and porous portions in different flow states during the sintering and melting process, ultimately obtaining fluoropolymer porous micro / nanofibers.

[0028] The present invention will be further described below with reference to specific embodiments:

[0029] Example 1

[0030] (1) Weigh 0.8g of cassava starch, add 9.2g of 2% NaOH solution, and then add 0.08g of PEO (molecular weight 5 million). Stir magnetically at room temperature for 2 hours to obtain a uniform and transparent starch-alkali-PEO solution.

[0031] (2) Add 2g of 60% PTFE emulsion and 4g of 60% PVDF emulsion to the above solution in sequence, and continue to stir magnetically for 45 minutes to obtain a milky white and uniform spinning solution.

[0032] (3) Inject the spinning solution into a 5mL syringe, install a 25G stainless steel needle, and place it on a centrifugal spinning machine. Set the spinning temperature to 60℃ and the rotation speed to 1300rpm, and perform centrifugal spinning to obtain nascent fibers.

[0033] (4) Place the nascent fibers in a muffle furnace, heat them to 380°C in the air, keep them at that temperature for 45 minutes, and then let them cool naturally to room temperature to obtain porous fluorinated fiber material.

[0034] Example 2

[0035] (1) Weigh 0.8g of cassava starch, add 9.2g of 2% NaOH solution, and then add 0.08g of PEO (molecular weight 5 million). Stir magnetically at room temperature for 2 hours to obtain a uniform and transparent starch-alkali-PEO solution.

[0036] (2) Add 1g of 60% PTFE emulsion and 5g of PVDF emulsion to the above solution in sequence, and continue to stir magnetically for 45 minutes to obtain a milky white and uniform spinning solution.

[0037] (3) Inject the spinning solution into a 5mL syringe, install a 25G stainless steel needle, and place it on a centrifugal spinning machine. Set the spinning temperature to 60℃ and the rotation speed to 1300 rpm, and perform centrifugal spinning to obtain nascent fibers.

[0038] (4) Place the nascent fibers in a muffle furnace, heat them to 380°C in the air, keep them at that temperature for 45 minutes, and then let them cool naturally to room temperature to obtain porous fluorinated fiber material.

[0039] Example 3

[0040] (1) Weigh 0.8g of cassava starch, add 9.2g of 2% NaOH solution, and then add 0.08g of PEO (molecular weight 5 million). Stir magnetically at room temperature for 2 hours to obtain a uniform and transparent starch-alkali-PEO solution.

[0041] (2) Add 3g of 60% PTFE emulsion and 3g of PVDF emulsion to the above solution in sequence, and continue to stir magnetically for 45 minutes to obtain a milky white and uniform spinning solution.

[0042] (3) Inject the spinning solution into a 5mL syringe, install a 25G stainless steel needle, and place it on a centrifugal spinning machine. Set the spinning temperature to 60℃ and the rotation speed to 1300 rpm, and perform centrifugal spinning to obtain nascent fibers.

[0043] (4) Place the nascent fibers in a muffle furnace, heat them to 380°C in the air, keep them at that temperature for 45 minutes, and then let them cool naturally to room temperature to obtain porous fluorinated fiber material.

[0044] Comparative Example 1

[0045] (1) Weigh 0.8g of cassava starch, add 9.2g of 2% NaOH solution, and then add 0.08g of PEO (molecular weight 5 million). Stir magnetically at room temperature for 2 hours to obtain a uniform and transparent starch-alkali-PEO solution.

[0046] (2) Add 6g of 60% PTFE emulsion to the above solution in sequence, and continue to stir magnetically for 45 minutes to obtain a milky white and uniform spinning solution.

[0047] (3) Inject the spinning solution into a 5mL syringe, install a 25G stainless steel needle, and place it on a centrifugal spinning machine. Set the spinning temperature to 60℃ and the rotation speed to 1300 rpm, and perform centrifugal spinning to obtain nascent fibers.

[0048] (4) Place the nascent fibers in a muffle furnace, heat them to 380°C in the air, keep them at that temperature for 45 minutes, and then let them cool naturally to room temperature to obtain fluorinated fiber materials.

[0049] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A method for preparing fluorine-containing porous micro / nanofibers, characterized in that... The process includes the following steps: (1) Preparation of centrifugal spinning solution: Cassava starch is mixed with NaOH solution, and high molecular weight polyethylene oxide (PEO, molecular weight 5 million) is added to fully dissolve and disperse to obtain a mixed solution; then polytetrafluoroethylene emulsion and polyvinylidene fluoride emulsion are added to the mixed solution to obtain a uniform spinning solution; (2) Preparation of centrifugal spinning micro and nanofibers: The above spinning solution is placed in a centrifugal spinning device to prepare micro and nanofibers by centrifugal spinning; (3) Formation of porous fibers: The prepared fibers are placed in a tube furnace for sintering, and fluorine-containing fibers with porous structures are obtained after sintering.

2. The method for preparing fluorine-containing porous micro / nanofibers according to claim 1, characterized in that: In step 1, the mixture contains 8%–10% cassava starch at a total mass of 10.0g.

3. The method for preparing fluorine-containing porous micro / nanofibers according to claim 1, characterized in that: In step (1), a 2% NaOH solution is used to replenish the remaining amount of the mixture.

4. The method for preparing fluorine-containing porous micro / nanofibers according to claim 1, characterized in that: In step (1), the molecular weight of polyethylene oxide is 5 million, and the amount added is 8%-12% of the mass of cassava starch.

5. The method for preparing fluorine-containing porous micro / nanofibers according to claim 1, characterized in that: In step (1), with the emulsion mass fixed at 6.0 g, the mass ratio of polytetrafluoroethylene emulsion to polyvinylidene fluoride emulsion is 1:5 to 3:

3.

6. The method for preparing fluorine-containing porous micro / nanofibers according to claim 5, characterized in that: Both the polytetrafluoroethylene emulsion and the polyvinylidene fluoride emulsion have a solid content of 60%.

7. The method for preparing fluorine-containing porous micro / nanofibers according to claim 1, characterized in that: Step (1) involves magnetic stirring in two stages: in the first stage, the stirring time is 2 hours before adding the fluorinated emulsion, and in the second stage, the stirring time is 45 minutes after adding the fluorinated emulsion.

8. The method for preparing fluorine-containing porous micro / nanofibers according to claim 1, characterized in that: In step (2), the needle diameter is 25G, the rotation speed is 1200-1400rpm, and the spinning temperature is 60℃.

9. The method for preparing fluorine-containing porous micro / nanofibers according to claim 1, characterized in that: In step (3), the sintering process is carried out in a nitrogen-free environment at a temperature of 380°C for 5 hours, followed by a holding time of 45 minutes and then natural cooling.

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