A method for preparing a carbon nanotube-doped PSPAN nanofiber air filtration material

Abstract

The application discloses a preparation method of a carbon nanotube-doped PSPAN nanofiber air filtration material, the nanofiber membrane material prepared by doping CNT into a PAN spinning solution and blending with PS nanofiber has high filtration efficiency and high porosity, and can achieve good filtration efficiency on PM2.5, pollen, viruses and other harmful particles; and adding CNT in the spinning solution can improve the fiber surface structure, the roughness of the fiber significantly improves the sound absorption performance of the nanofiber membrane material, and the combination of the hydrophobicity of the PS fiber and the hydrophilicity of the PAN / CNT fiber can form a relatively close three-dimensional network structure, which is beneficial to improving the service life of the material, also makes the composite nanofiber membrane material have advantages in filtration performance, and by adjusting the proportion of the two fibers, the best efficiency and resistance balance point is found, so that the overall strength and durability of the composite nanofiber membrane material are improved.

Description

Technical Field

[0001] This invention relates to the field of fiber materials technology, and in particular to a method for preparing PSPAN nanofiber air filter material doped with carbon nanotubes. Background Technology

[0002] In the 21st century, air pollution remains the most critical factor endangering human health, and many countries around the world still experience varying degrees of air pollution. Currently, the main protective equipment used in daily life consists of masks, anti-smog window screens, and air purifiers, all of which can intercept a certain amount of dust and other fine particulate matter in the air. They are used according to different occasions; for example, anti-smog window screens or air purifiers are mostly used indoors, while masks are mainly used in outdoor public places. The filter core of masks and air purifiers on the market is mainly made of meltblown nonwoven materials, while anti-smog window screens are made of nylon and polyester mesh. However, these materials have problems such as low interception accuracy, filtration performance being easily affected by the environment, unstable filtration efficiency, and non-degradability. But the performance characteristics of electrospun nanofibers can effectively solve this problem.

[0003] Electrospun nanofiber materials are characterized by high efficiency and low resistance filtration. Many nanomaterials and composite nanomaterials have excellent sound absorption properties, such as carbon nanotubes and graphene oxide. Since carbon nanotubes are a non-toxic and harmless material with an extremely high specific surface area and porosity, they have good sound absorption performance. The C=C covalent bond in carbon nanotubes is the most stable chemical bond in nature. High-efficiency sound-absorbing filter media made of nanofibers can be used in air conditioning systems to reduce the noise of the filtration system, thereby reducing the harmful effects of noise on the human body.

[0004] With the updating and development of electrospinning technology, more than 100 kinds of polymers can now be used to prepare nanofibers. Among them, polystyrene (PS) is one of the most commonly used polymer raw materials in electrospinning. Polystyrene is a thermoplastic polymer produced by the polymerization reaction of styrene monomers. PS is widely used because of its good mechanical properties and relatively low cost. In the electrospinning process, electrospun PS nanofibers have good morphologies, such as uniform planar structure, bead structure, and porous structure, thus having broad application potential in air filtration.

[0005] However, during the preparation process, due to the different properties of various fiber materials, such as PAN / CNT fibers, which are hydrophilic mainly because the carboxyl groups of carbon nanotubes make the membrane surface easily absorb water, and the cross-linking between CNT and PAN molecules also enhances the hydrophilicity of the membrane, this fiber is effective in capturing water particles, but it is more likely to cause higher airflow resistance. At the same time, hydrophilic groups such as carboxyl groups will adsorb water, and long-term excessive water adsorption will reduce the fiber strength, thereby affecting the mechanical properties of the fiber and the filtration effect. On the other hand, the obtained PS fiber is a hydrophobic fiber, which allows airflow to pass through more easily, thereby reducing resistance. By adjusting the ratio of the two types of fibers, the optimal resistance balance point can be found, thereby improving the overall strength and durability of the filter material. Summary of the Invention

[0006] This invention overcomes the shortcomings of the prior art and provides a method for preparing PSPAN nanofiber air filter material doped with carbon nanotubes.

[0007] To achieve the above objectives, the technical solution adopted by this invention is as follows: a method for preparing PSPAN nanofiber air filter material doped with carbon nanotubes, comprising the following steps:

[0008] S1. Pretreatment of carbon nanotubes (CNTs): Carbon nanotubes are mixed with deionized water and dispersed using an ultrasonic water bath. Then, ammonium persulfate (APS) and concentrated NH4OH are added to the mixture to adjust the pH of the mixed solution and stir at a suitable temperature to denature the CNT surface.

[0009] S2. Improve the dispersibility of CNTs: After diluting the mixed solution obtained above, disperse it again using an ultrasonic water bath, then separate the CNTs from the solution by centrifugation, filter it with a hydrophilic polytetrafluoroethylene filter membrane and wash it with distilled water to remove residual APS and NH4OH, and then dry it in a vacuum oven to obtain modified CNTs.

[0010] S3. Preparation of PS solution: Weigh an appropriate amount of PS particles, put them into a clean glass bottle, put them into a drying oven to dry, then add an appropriate amount of N,N-dimethylformamide (DMF), put them into a magnetic stirrer and heat until the solution is completely transparent.

[0011] S4. Mixing CNTs with DMF: Add the obtained modified CNTs to a DMF solution and treat with an ultrasonic water bath to ensure that the CNTs are completely dispersed in the DMF solution.

[0012] S5. Electrospinning: The CNT-DMF solution obtained in step S4 is mixed with polyacrylonitrile PAN and then placed in a magnetic stirrer and stirred until the PAN is completely dissolved to obtain a mixed solution. The mixed solution is then electrospinned to obtain PS nanofibers and PAN / CNT nanofibers, which are then spun onto wood pulp fiber paper.

[0013] S6. Fiber bonding: The obtained PS nanofibers, PAN / CNT nanofibers and wood pulp fiber paper are bonded together by ultrasonic bonding technology to form the final fluffy and multi-scale composite nanofiber membrane material.

[0014] In a preferred embodiment of the present invention, during the electrospinning process in step S5, the voltage of the high-voltage generator is controlled at 10-30kV, the distance between the nozzle and the receiving base fabric is controlled at 12-25cm, the nozzle diameter is controlled at 0.4-1.0mm, the flow rate of the electrospinning solution is controlled at 0.5-3mL / h, and the receiving time is controlled at 5-18min, thereby controlling the diameter and structure of the fiber.

[0015] In a preferred embodiment of the present invention, in step S1, 15-30 mg of carbon nanotubes are selected and dispersed in 80-110 mL of deionized water in an ultrasonic water bath for 50-65 min.

[0016] In a preferred embodiment of the present invention, in step S1, 0.4-0.8 g of ammonium persulfate (APS) is added, concentrated NH4OH is added to adjust the pH of the solution to 12, and the solution is stirred at 80-90°C for 1.5-2 hours.

[0017] In a preferred embodiment of the present invention, in step S2, after the mixed solution is diluted with water, it is dispersed in an ultrasonic water bath for 5-6 hours. During centrifugation, the speed is controlled at 3500-4000 rpm and the centrifugation time is controlled at 10-12 minutes. When drying in a vacuum oven, the temperature is selected to be 70-80°C for 23-25 ​​hours.

[0018] In a preferred embodiment of the present invention, in step S3, 35-40g of PS granules are weighed, the temperature inside the drying oven is controlled at 90-100℃, and the drying time is 5-6h.

[0019] In a preferred embodiment of the present invention, in step S3, 155-165g of DMF is weighed and added to the corresponding glass bottle, and the heating temperature in the magnetic stirrer is controlled at 60-90°C for about 24 hours.

[0020] In a preferred embodiment of the present invention, in step S4, 0.1 to 0.5 g of modified CNTs are added to a DMF solution and treated with an ultrasonic water bath for 22 to 24 hours.

[0021] In a preferred embodiment of the present invention, the amount of PAN added in step S5 is 12-20g, and the stirring temperature in the magnetic stirrer is 60-80℃, the stirring time is about 24h, and the stirring speed is selected as medium to high speed.

[0022] In a preferred embodiment of the present invention, the electrospinning equipment mainly consists of a liquid accumulator, a receiving device, a ground receiver, and a high-voltage power transmitting device.

[0023] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0024] (1) This invention provides a method for preparing PSPAN nanofiber air filter material doped with carbon nanotubes. By combining the hydrophobicity of PS fibers with the hydrophilicity of PAN / CNT fibers, a relatively tight three-dimensional network structure can be formed, which is beneficial to improving the service life of the material and also makes the composite nanofiber membrane material have advantages in filtration performance. Furthermore, by adjusting the ratio of the two fibers, the optimal balance point between efficiency and resistance can be found, thereby improving the overall strength and durability of the composite nanofiber membrane material. At the same time, the hydrophobic PS fiber helps to capture oily particles, while the hydrophilic PAN / CNT fiber can effectively capture watery particles, making the material suitable for various filtration scenarios.

[0025] (2) This invention achieves the best balance between air permeability and filtration efficiency by precisely controlling electrospinning parameters, such as voltage, distance between nozzle and receiving base fabric, nozzle diameter and solution flow rate, thereby adjusting the diameter and structure of nanofibers.

[0026] (3) The present invention prepares a nanofiber membrane material by doping CNT into PAN spinning solution and blending it with PS nanofibers. The nanofiber membrane material has high filtration efficiency and high porosity, and can achieve good filtration efficiency for harmful particles such as PM2.5, pollen, and viruses. Furthermore, adding CNT to the spinning solution can improve the fiber surface structure, and the roughness of the fiber significantly improves the sound absorption performance of the nanofiber membrane material. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart illustrating the preparation method of the composite nanofiber filter material according to a preferred embodiment of the present invention.

[0029] Figure 2 This is a scanning electron microscope image of the carbon nanotube-doped PSPAN nanofibers prepared by electrospinning technology according to the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0032] like Figure 1 As shown, a method for preparing a carbon nanotube-doped PSPAN nanofiber air filter material includes the following steps:

[0033] S1. Pretreatment of carbon nanotubes (CNTs): Carbon nanotubes are mixed with deionized water and dispersed using an ultrasonic water bath. Then, ammonium persulfate (APS) and concentrated NH4OH are added to the mixture to adjust the pH of the mixed solution and stir at a suitable temperature to denature the CNT surface.

[0034] S2. Improve the dispersibility of CNTs: After diluting the mixed solution obtained above, disperse it again using an ultrasonic water bath, then separate the CNTs from the solution by centrifugation, filter it with a hydrophilic polytetrafluoroethylene filter membrane and wash it with distilled water to remove residual APS and NH4OH, and then dry it in a vacuum oven to obtain modified CNTs.

[0035] S3. Preparation of PS solution: Weigh an appropriate amount of PS particles, put them into a clean glass bottle, put them into a drying oven to dry, then add an appropriate amount of N,N-dimethylformamide (DMF), put them into a magnetic stirrer and heat until the solution is completely transparent.

[0036] S4. Mixing CNTs with DMF: Add the obtained modified CNTs to a DMF solution and treat with an ultrasonic water bath to ensure that the CNTs are completely dispersed in the DMF solution.

[0037] S5. Electrospinning: The CNT-DMF solution obtained in step S4 is mixed with polyacrylonitrile PAN and then placed in a magnetic stirrer and stirred until the PAN is completely dissolved to obtain a mixed solution. The mixed solution is then electrospinned to obtain PS nanofibers and PAN / CNT nanofibers, which are then spun onto wood pulp fiber paper.

[0038] S6. Fiber bonding: The obtained PS nanofibers, PAN / CNT nanofibers and wood pulp fiber paper are bonded together by ultrasonic bonding technology to form the final fluffy and multi-scale composite nanofiber membrane material.

[0039] In step S1, 15–30 mg of carbon nanotubes are selected and dispersed in 80–110 mL of deionized water in an ultrasonic water bath for 50–65 min. 0.4–0.8 g of ammonium persulfate (APS) is added, and concentrated NH4OH is added to adjust the pH of the solution to 12. The solution is then stirred at 80–90 °C for 1.5–2 h.

[0040] In step S2, after diluting the mixed solution with water, it is dispersed in an ultrasonic water bath for 5-6 hours. During centrifugation, the speed is controlled at 3500-4000 rpm and the centrifugation time is controlled at 10-12 minutes. When drying in a vacuum oven, the temperature is selected to be 70-80℃ for 23-25 ​​hours.

[0041] In step S3, weigh 35-40g of PS granules, control the temperature in the drying oven at 90-100℃, and dry for 5-6 hours; weigh 155-165g of DMF and add it to the corresponding glass bottle, and control the heating temperature in the magnetic stirrer at 60-90℃ for about 24 hours.

[0042] In step S4, 0.1–0.5 g of modified CNT is added to the DMF solution and treated with an ultrasonic water bath for 22–24 h; in step S5, 12–20 g of PAN is added and stirred in a magnetic stirrer at a temperature of 60–80 °C for about 24 h, with a stirring speed of medium to high speed.

[0043] During the electrospinning process, the voltage of the high-voltage generator is controlled at 10–30 kV, the distance between the nozzle and the receiving base fabric is controlled at 12–25 cm, the nozzle diameter is controlled at 0.4–1.0 mm, the flow rate of the electrospinning solution is controlled at 0.5–3 mL / h, and the receiving time is controlled at 5–18 min. These conditions are used to control the diameter and structure of the fiber. The electrospinning equipment mainly consists of a liquid accumulator, a receiving device, a ground receiver, and a high-voltage power transmission device.

[0044] Example:

[0045] I. Testing Methods

[0046] The air permeability of the final composite nanofiber membrane material was tested using an air permeability tester.

[0047] The filtration efficiency and airflow resistance were tested using an automatic filter resistance and efficiency tester, and the TSI8130 A model was selected.

[0048] Tensile strength was tested using a tensile testing machine, model ISO 527-4.

[0049] II. Material Selection

[0050] 20 mg of carbon nanotubes, 100 mL of deionized water, and 0.5 g of ammonium persulfate (APS) were selected.

[0051] Weigh out 36g of PS granules; add 160g of DMF to the corresponding glass bottles;

[0052] Add 0.5g of modified CNT to DMF solution, and take 18g of PAN;

[0053] The voltage of the high-voltage generator was adjusted to 15kV, the distance between the nozzle and the receiving base fabric was controlled to 12cm, the nozzle diameter was 0.4mm, the flow rate of the electrospinning solution was 1mL / h, and the receiving time was 12min.

[0054] III. Experimental Section

[0055] Example 1:

[0056] 20 mg of carbon nanotubes (CNTs) were mixed with 100 mL of deionized water and dispersed in an ultrasonic water bath for 60 min. Then, 0.5 g of ammonium persulfate (APS) was added to the mixture, and concentrated NH4OH was added to adjust the pH of the mixed solution to 12. The mixture was stirred at 90 °C for 2 h to denature the CNT surface. The resulting mixed solution was diluted with water and dispersed again in an ultrasonic water bath for 6 h. The CNTs were then separated from the solution by centrifugation at 4000 rpm for 12 min. The mixture was then filtered through a hydrophilic polytetrafluoroethylene (PTFE) filter membrane and washed with distilled water. Finally, the CNTs were dried in a vacuum oven at 80 °C for 24 h to obtain the modified CNTs.

[0057] Weigh 36g of PS granules, put them into a clean glass bottle, place them in a drying oven, maintain the temperature at 90℃, and dry for 5 hours; then add 160g of N,N-dimethylformamide (DMF), place it in a magnetic stirrer and heat it at 75℃ for 24 hours until the solution is completely transparent.

[0058] 0.5g of the modified CNT was added to a DMF solution and treated with an ultrasonic water bath for 23h to ensure complete dispersion of CNT in the DMF solution. The resulting CNT-DMF solution was then mixed with 14g of PAN and placed in a magnetic stirrer. The stirring temperature was 70℃ and the stirring time was 24h. The stirring speed was set to medium to high speed until the PAN was completely dissolved to obtain a mixed solution.

[0059] Electrospinning was performed on the mixed solution. The electrospinning equipment mainly consisted of a liquid accumulator, a receiving device, a ground receiver, and a high-voltage power transmitter. The voltage of the high-voltage generator was adjusted to 15kV, the distance between the nozzle and the receiving base fabric was 12cm, the nozzle diameter was 0.4mm, the flow rate of the electrospinning solution was 1mL / h, and the receiving time was 9min. PS nanofibers with a diameter of 1056.4nm and PAN / CNT nanofibers with a diameter of 121.7nm were obtained. These nanofibers were then spun onto wood pulp fiber paper. The obtained PS nanofibers, PAN / CNT nanofibers, and wood pulp fiber paper were then bonded together using ultrasonic bonding technology to form the final fluffy and multi-scale composite nanofiber membrane material.

[0060] Example 2:

[0061] The operation steps are largely the same as in Example 1, except that the amount of PAN added is changed. 16g of PAN is mixed with CNT-DMF solution to obtain PS and PAN / CNT in different proportions. Electrospinning is then performed on these mixtures. The voltage of the high-voltage generator is adjusted to 15kV, the distance between the nozzle and the receiving base fabric is controlled to 12cm, the nozzle diameter is 0.4mm, the flow rate of the electrospinning solution is 1mL / h, and the receiving time is 9min. The diameter of the PS nanofibers obtained is 1129.7nm, and the diameter of the PAN / CNT nanofibers is 137.6nm.

[0062] Example 3:

[0063] The operation steps are largely the same as in Example 1, except that the amount of PAN added is changed again. 20g of PAN is mixed with CNT-DMF solution to obtain PS and PAN / CNT in different proportions. Electrospinning is then performed on these mixtures. The voltage of the high-voltage generator is adjusted to 15kV, the distance between the nozzle and the receiving base fabric is controlled to 12cm, the nozzle diameter is 0.4mm, the flow rate of the electrospinning solution is 1mL / h, and the receiving time is 9min. The diameter of the PS nanofibers obtained is 1154.2nm, and the diameter of the PAN / CNT nanofibers is 143.5nm.

[0064] The obtained composite nanofiber membrane material was tested according to the above method, and the following results were obtained;

[0065]

[0066] Analyzing the data obtained above, different proportions of PS and PAN / CNT are formed based on the different amounts of PAN added, which in turn affect the final performance of the composite nanofiber membrane material. The table shows that as the amount of PAN added increases, the diameter of the resulting nanofibers also increases, leading to decreased air permeability, decreased filtration efficiency, and decreased airflow resistance. Tensile strength initially increases and then decreases. It should be noted that PS fibers typically have strong hydrophobicity due to the presence of non-polar benzene rings in the chemical structure of polystyrene, which gives polystyrene its overall hydrophobic properties. When polystyrene forms fibers, this hydrophobicity is maintained, resulting in a larger contact angle of PS fibers with water, making them less susceptible to wetting.

[0067] Furthermore, the PS fiber membrane prepared by electrospinning further exhibits superhydrophobic properties, mainly due to the rough structure and hierarchical composite structure of the fiber surface. This structure can increase the air trapping capacity of the fiber surface, thereby reducing the actual contact area between water droplets and the fiber surface, making it more difficult for water droplets to spread on the fiber surface, thus enhancing the hydrophobic properties of the fiber membrane.

[0068] The resulting PAN / CNT fibers are hydrophilic primarily because the carboxyl groups of carbon nanotubes facilitate water absorption on the membrane surface. Simultaneously, the cross-linking between CNT and PAN molecules enhances the membrane's hydrophilicity. Furthermore, the addition of hydrophilic CNTs improves the PAN / CNT membrane's water absorption capacity, widening the membrane pores and facilitating the absorption of more water, thus increasing the membrane's porosity. These factors work together to give the PAN / CNT membrane its superior hydrophilicity.

[0069] It should be noted that hydrophilic fibers are more effective at capturing water particles, but this results in higher airflow resistance. Conversely, hydrophobic fibers may allow airflow to pass through more easily, thus reducing resistance. By adjusting the ratio of the two types of fibers, the optimal balance between efficiency and resistance can be found.

[0070] The tensile strength initially increased and then decreased because the increased amount of PAN effectively encapsulates the carbon nanotubes, leveraging their strength advantage to improve the tensile strength of the composite fiber. However, the amount of PAN added needs to be controlled. If too much PAN is added, exceeding a certain concentration, the nanotubes become difficult to distribute evenly, clump together, and lose their strength transfer function, thus reducing the tensile strength. It can be seen that the composite nanofiber membrane material obtained according to Example 2 achieves a better balance between filtration efficiency and airflow resistance, while also exhibiting enhanced tensile strength.

[0071] Since the electrospinning process also has a direct impact on the fabrication of composite nanofiber membrane materials, after obtaining the optimal content of PAN, the following experiments were conducted.

[0072] Example 4:

[0073] The operation steps are largely the same as in Example 1. The difference is that, based on Example 2, the electrospinning process is changed, that is, the voltage of the high voltage generator is adjusted to 18kV, while the other data remain unchanged. Accordingly, the diameter of PS nanofibers is 1045.2nm and the diameter of PAN / CNT nanofibers is 113.2nm.

[0074] Example 5:

[0075] The operation steps are largely the same as in Example 1. The difference is that, based on Example 2, the electrospinning process is changed, that is, the voltage of the high voltage generator is adjusted to 22kV, while the other data remain unchanged. Accordingly, the diameter of PS nanofibers is 1026.3nm and the diameter of PAN / CNT nanofibers is 109.5nm.

[0076] The obtained composite nanofiber membrane material was tested according to the above method, and the following results were obtained;

[0077]

[0078]

[0079] Therefore, it can be concluded that when the composite nanofiber membrane material is prepared according to Example 2, the performance conditions are more balanced. Although the voltage of the high-voltage generator is increased, which makes the diameter of the nanofiber smaller, its air permeability is reduced and the airflow resistance is increased, which to some extent reduces the overall strength of the filter material.

[0080] Based on the above experiments, the distance between the nozzle and the receiving base fabric during the electrospinning process was adjusted, and the following experiments were conducted.

[0081] Example 6:

[0082] The operation steps are largely the same as in Example 1. The difference is that, based on Example 2, the electrospinning process is changed, that is, the distance between the nozzle and the receiving base fabric is 16cm, while the other data remain unchanged. Accordingly, the diameter of PS nanofibers is 1136.7nm and the diameter of PAN / CNT nanofibers is 146.3nm.

[0083] Example 7:

[0084] The operation steps are largely the same as in Example 1. The difference is that, based on Example 2, the electrospinning process is changed, that is, the distance between the nozzle and the receiving base fabric is 20cm, while the other data remain unchanged. Accordingly, the diameter of PS nanofibers is 1159.2nm and the diameter of PAN / CNT nanofibers is 149.5nm.

[0085] The obtained composite nanofiber membrane material was tested according to the above method, and the following results were obtained;

[0086]

[0087] Therefore, it can be concluded that when the composite nanofiber membrane material is prepared according to Example 2, the performance conditions are more balanced. Adjusting the distance between the nozzle and the receiving base cloth to increase it increases the diameter of the nanofibers, which reduces the airflow resistance to a certain extent. However, the filtration efficiency also decreases accordingly, and the tensile strength also decreases, resulting in a decline in the overall performance of the composite nanofiber membrane material.

[0088] Based on the above experiments, the following experiments were conducted to further investigate the changes in nozzle diameter during electrospinning.

[0089] Example 8:

[0090] The operation steps are largely the same as in Example 1. The difference is that, based on Example 2, the electrospinning process is changed, that is, the nozzle diameter is 0.7 mm, while the other data remain unchanged. Accordingly, the diameter of PS nanofibers is 1167.3 nm and the diameter of PAN / CNT nanofibers is 151.2 nm.

[0091] Example 9:

[0092] The operation steps are largely the same as in Example 1. The difference is that, based on Example 2, the electrospinning process is changed, that is, the nozzle diameter is 1 mm, while the other data remain unchanged. Accordingly, the diameter of PS nanofibers is 1183.2 nm and the diameter of PAN / CNT nanofibers is 163.8 nm.

[0093] The obtained composite nanofiber membrane material was tested according to the above method, and the following results were obtained;

[0094]

[0095] Therefore, it can be concluded that by adjusting the nozzle diameter to increase it, the diameter of the resulting nanofibers becomes larger, and the airflow resistance is reduced to a certain extent. However, the filtration efficiency is also reduced accordingly, while the tensile strength is significantly reduced, resulting in a decline in the overall performance of the composite nanofiber membrane material.

[0096] Based on the above experimental process, the flow rate of the electrospinning solution was changed, and the following experiments were continued;

[0097] Example 10:

[0098] The operation steps are largely the same as in Example 1. The difference is that, based on Example 2, the electrospinning process is changed, that is, the flow rate of the electrospinning solution is 1.8 mL / h, while the other data remain unchanged. Accordingly, the diameter of PS nanofibers is 1013.5 nm and the diameter of PAN / CNT nanofibers is 116.7 nm.

[0099] Example 11:

[0100] The operation steps are largely the same as in Example 1. The difference is that, based on Example 2, the electrospinning process is changed, that is, the flow rate of the electrospinning solution is 2.5 mL / h, while the other data remain unchanged. Accordingly, the diameter of PS nanofibers is 1008.3 nm and the diameter of PAN / CNT nanofibers is 112.4 nm.

[0101] The obtained composite nanofiber membrane material was tested according to the above method, and the following results were obtained;

[0102]

[0103] Based on the table above, it can be concluded that during the electrospinning process, changing the flow rate of the electrospinning solution to increase it results in a decrease in the diameter of the obtained nanofibers, which reduces air permeability, increases filtration efficiency, increases airflow resistance, and decreases tensile strength. Considering that airflow resistance and filtration efficiency need to be in a better balance, in the case of Example 10, the overall performance of the material is in a better balance.

[0104] Meanwhile, the porous structure formed by PS nanofibers has a positive effect on improving the interfacial adhesion strength between them and PAN / CNT fibers. Comparative experiments were conducted on the porous structure of PS nanofibers. Before the experiments, relevant tests were performed on the composite nanofiber material obtained in Example 10: the porosity and the interfacial adhesion strength between PS fibers and PAN / CNT fibers were tested.

[0105] The cross-section of the membrane was observed using a scanning electron microscope to directly observe and count the size and distribution of pores. The pores were analyzed using SEM software to obtain approximate values. Based on the above method, the porosity of the composite nanofiber membrane material in Example 10 was approximately 95%.

[0106] By preparing the composite fiber sample, a tensile test was conducted on a uniaxial tensile tester, and the stress-strain curve of the sample during the tensile process was recorded. The maximum stress value of the interface fracture during the tensile test was read from the curve. Then, the tensile fracture or adhesive interface was observed by SEM to see if it separated. The SEM image further confirmed the interface strength. According to the above method, the adhesive strength of the composite nanofiber membrane material in Example 10 was approximately 32 N / cm.

[0107] After obtaining the porosity and viscous strength in Example 10, the following experiments were conducted;

[0108] Example 12:

[0109] The operation steps are largely the same as in Example 1. The difference is that, based on Example 10, 15g of polyethylene glycol PEG2000 is added to the mixed solution in a soft solid state before the electrospinning begins to form. The rest of the process remains unchanged.

[0110] Example 13:

[0111] The operation steps are largely the same as in Example 1. The difference is that, based on Example 10, 20g of polyethylene glycol PEG2000 is added to the mixed solution in a soft solid state before the electrospinning begins to form. The rest of the process remains unchanged.

[0112] The obtained composite nanofiber membrane material was tested according to the above method, and the following results were obtained;

[0113] Porosity (%) 95 96 98 Viscous strength (N / cm) 32 34 30

[0114] As can be seen from the table above, the presence of porous structures can increase the interfacial adhesion strength between PS fibers and PAN / CNT fibers. This is because porous structures can increase the contact area between the two types of fibers, thereby providing more adhesion sites, and also help to form mechanical interlocking between the fibers, further improving the interfacial adhesion strength.

[0115] However, the porous structure also affects the overall mechanical and filtration properties of the fiber. Excessive pores may reduce the fiber's strength and durability, while also affecting the material's air permeability and filtration efficiency. The air permeability and filtration efficiency of the composite nanofiber material obtained in Example Twelve were tested, yielding a value of 335 L / m³. 2 / s and 94.31%, the filtration efficiency decreased, while the air permeability increased, but the overall performance improved relatively, resulting in a composite nanofiber membrane material with better overall strength, such as Figure 2As shown, observation of the final composite nanofiber material reveals that with the increase of PS addition, the nanofibers form a three-dimensional spatial membrane structure with alternating coarse and fine fibers. This nanofiber composite membrane material has a very wide range of applications in air filtration. Nanofiber air filter paper is very suitable for use in fresh air systems, biomedicine, indoor purification, and replaceable air purifier filters, making it a highly commercially valuable air filtration material.

[0116] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A type of carbon nanotube-doped material The method for preparing nanofiber air filter materials is characterized by, Includes the following steps: S1, carbon nanotubes Pretreatment: Carbon nanotubes were mixed with deionized water and dispersed using an ultrasonic water bath. Then, ammonium persulfate was added to the mixture. and Concentrate Adjust its mixed solution The value is adjusted and stirred at a suitable temperature to achieve the desired effect. Surface modification; S2, Improve Dispersibility: The above-obtained mixed solution was diluted and dispersed again using an ultrasonic water bath, and then centrifuged. Separate from the solution, then filter using a hydrophilic polytetrafluoroethylene (PTFE) membrane and wash with distilled water to remove residues. as well as Then, the modified product was obtained by drying in a vacuum oven. ; S3, Preparation Solution: Weigh an appropriate amount The granules were placed in a clean glass bottle and dried in a drying oven. Then, an appropriate amount of N,N-dimethylformamide was added. Place it in a magnetic stirrer and heat until the solution is completely transparent; S4, Mix and The obtained modification Join In the solution, ultrasonic water bath treatment is used to make... Completely dispersed in solution; S5, Electrospinning: The product obtained in step S4... - Solution and polyacrylonitrile After mixing, place the mixture in a magnetic stirrer and stir until... Complete dissolution yields a mixed solution, which is then subjected to electrospinning to obtain... Nanofibers and Nanofibers are spun onto wood pulp fiber paper. S6, Fiber bonding: The obtained Nanofibers Nanofibers and wood pulp fiber paper are bonded together using ultrasonic bonding technology to form a final composite nanofiber membrane material with a fluffy and multi-scale structure. In step S5, during the electrospinning process, the voltage of the high-voltage generator is controlled at 10-30kV, the distance between the nozzle and the receiving base fabric is controlled at 12-25cm, the nozzle diameter is controlled at 0.4-1.0mm, the flow rate of the electrospinning solution is controlled at 0.5-3mL / h, and the receiving time is controlled at 5-18min. The diameter and structure of the fiber are controlled under these conditions.

2. The doped carbon nanotube according to claim 1 The method for preparing nanofiber air filter materials is characterized by: In step S1, 15–30 mg of carbon nanotubes are selected and dispersed in 80–110 mL of deionized water in an ultrasonic water bath for 50–65 min.

3. The doped carbon nanotube according to claim 1 The method for preparing nanofiber air filter materials is characterized by: In step S1, 0.4–0.8 g of ammonium persulfate is added. Add concentrate Adjusting the solution The value is 12, and it is stirred at 80-90℃ for 1.5-2 hours.

4. The doped carbon nanotube according to claim 1 The method for preparing nanofiber air filter materials is characterized by: In step S2, after the mixed solution is diluted with water, it is dispersed in an ultrasonic water bath for 5-6 hours. During centrifugation, the speed is controlled at 3500-4000 rpm and the centrifugation time is controlled at 10-12 minutes. When drying in a vacuum oven, the temperature is selected to be 70-80℃ for 23-25 ​​hours.

5. A doped carbon nanotube according to claim 1 The method for preparing nanofiber air filter materials is characterized by: In step S3, weigh out 35-40g of the sample. For granules, the temperature inside the drying oven is controlled at 90-100℃, and the drying time is 5-6 hours.

6. A doped carbon nanotube according to claim 1 The method for preparing nanofiber air filter materials is characterized by: In step S3, weigh out 155-165g of the sample. Add it to the corresponding glass bottle, and the heating temperature inside the magnetic stirrer is controlled at 60-90℃, with a heating time of about 24 hours.

7. A doped carbon nanotube according to claim 1 The method for preparing nanofiber air filter materials is characterized by: In step S4, 0.1–0.5 g of modified... Join The solution was treated with an ultrasonic water bath for 22–24 hours.

8. A doped carbon nanotube according to claim 1 The method for preparing nanofiber air filter materials is characterized by: Add to step S5 The amount should be 12-20g, and the stirring temperature in the magnetic stirrer should be 60-80℃, the stirring time should be about 24 hours, and the stirring speed should be medium to high.

9. A doped carbon nanotube according to claim 1 The method for preparing nanofiber air filter materials is characterized by: The electrospinning equipment mainly consists of a liquid accumulator, a receiving device, a ground receiver, and a high-voltage power transmission device.

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