Nano PAN fiber stable preparation method based on high-frequency piezoelectric jet

Abstract

The invention discloses a nano PAN fiber stable preparation method based on high-frequency piezoelectric jet, which comprises the following steps: S1, preparing raw materials and equipment, the raw materials comprising PAN powder and DMF; s2, solution preparation: mixing PAN powder and DMF according to a mass ratio of 13: 87, S3, device preheating and parameter setting, starting a temperature control device, and setting parameters of a high-frequency piezoelectric driving device: starting a jet drafting device; s4, nanometer PAN fiber spinning is carried out, nanometer fibers are collected through a roller winding device, and tensile deformation of the fibers is avoided; s5, fiber performance monitoring is carried out, and stable performance in the continuous spinning process is guaranteed, the spinneret hole structure and heating control are optimized, the blocking rate is reduced to be smaller than or equal to 1%, and the continuous spinning time is prolonged to be larger than or equal to 8 h; piezoelectric parameters are matched with rheological characteristics of a PAN solution, so that the diameter deviation of the nano PAN fiber is smaller than or equal to 10%; the fiber mechanical property is improved.

Description

Technical Field

[0001] This invention belongs to the field of nanofiber preparation technology, specifically relating to a stable preparation method of nano-PAN fibers based on high-frequency piezoelectric jet. Background Technology

[0002] PAN nanofibers, due to their excellent chemical resistance and carbonizability, have important applications in air filtration, medical and health (energy storage) fields. However, existing preparation technologies face three major bottlenecks: 1. Spinneret clogging: The high viscosity of PAN solutions (500-1000 cP) makes it easy for residual solution to solidify in conventional straight-hole spinnerets (>10 μm), resulting in a clogging rate >10%; 2. Poor diameter uniformity: The frequency of existing piezoelectric jets does not match the rheological properties of PAN solutions, leading to fiber diameter deviations >20%; 3. Low spinnability: Conventional piezoelectric modules have low vibration transmission efficiency (<60%), failing to provide stable extrusion power, resulting in continuous spinning time <3 hours. These problems hinder the industrial production of PAN nanofibers and limit the application expansion of cross-scale fiber assemblies. Summary of the Invention

[0003] The purpose of this invention is to provide a stable preparation method for nano-PAN fibers based on high-frequency piezoelectric jets, which optimizes the spinneret structure and heating control to reduce the clogging rate to ≤1% and extend the continuous spinning time to ≥8h; matches the piezoelectric parameters with the rheological properties of the PAN solution to ensure that the diameter deviation of the nano-PAN fibers is ≤10%; and improves the mechanical properties of the fibers to ensure that the breaking strength is ≥2.5cN / dtex and the breaking elongation is 16-20%.

[0004] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution:

[0005] A method for the stable preparation of nano-PAN fibers based on high-frequency piezoelectric jets includes the following steps:

[0006] S1. Raw material and equipment preparation: Raw materials include PAN powder and DMF; Equipment includes magnetic stirring device, high-frequency piezoelectric drive device, temperature control device, rotational viscometer, 3D printed microchannels, anti-clogging spinneret with spinneret orifice, jet stretching device, vacuum degassing tank, micro pump, roller winding device, scanning electron microscope, laser displacement sensor and micro tensile testing machine.

[0007] S2, Solution preparation: Mix PAN powder and DMF at a mass ratio of 13:87, and stir magnetically at 100°C for 3 hours using a magnetic stirrer. Test the viscosity using a rotational viscometer and adjust the viscosity to 700 cP. Then transfer the solution to a vacuum degassing tank and let it stand for 2 hours to remove bubbles and prevent yarn breakage during spinning.

[0008] S3, device preheating and parameter setting, start the temperature control device, raise the spinneret temperature to 105℃, keep it at that temperature for 30 minutes to ensure temperature stability;

[0009] Set the parameters for the high-frequency piezoelectric drive device: frequency 6kHz, voltage 120V;

[0010] Start the jet stretching device, adjust the airflow velocity to 10m / s, air pressure to 0.35MPa, and airflow temperature to 80℃;

[0011] S4, nano-PAN fiber spinning is carried out. The degassed PAN solution from S2 is injected into the microchannel and stably delivered to the spinneret through a micro-pump. After the PAN solution is piezoelectrically driven and extruded by a high-frequency piezoelectric drive device, it is stretched into nanofibers by the jet flow of the jet stretching device. The nanofibers are collected by a roller winding device to avoid fiber stretching and deformation.

[0012] S5, fiber performance monitoring: samples are taken every 1 hour, fiber diameter is observed using a scanning electron microscope, and breaking strength is tested using a micro tensile testing machine; if the diameter deviation is >10%, the piezoelectric frequency or airflow rate is finely adjusted to ensure stable performance during continuous spinning.

[0013] In one or more embodiments of the present invention, the high-frequency piezoelectric drive device includes a piezoelectric controller and three barium ferrite piezoelectric ceramics connected in parallel. The size of the barium ferrite piezoelectric ceramics is 10mm×5mm×2mm. The piezoelectric controller operates at a frequency of 3-8kHz and a voltage of 100-180V. The displacement of the barium ferrite piezoelectric ceramics is monitored in real time by a laser displacement sensor, and the parameters are dynamically adjusted according to the viscosity of the PAN solution to ensure stable extrusion power.

[0014] In one or more embodiments of the present invention, the diameter of the spinneret hole of the anti-clogging spinneret device is 4μm, the spinneret hole is processed by ultrafast laser thermo-coupling, the laser power during processing is 40-60W, and the heat-affected zone is ≤5μm; the inlet of the spinneret hole channel is provided with a hemispherical flare with a radius of 0.5mm; the inner wall is plasma polished; the body material of the spinneret hole is 304 stainless steel.

[0015] In one or more embodiments of the present invention, the temperature control device uses a 20W polyimide heating film wrapped around the outside of the spinneret body, and is further equipped with a PT100 temperature sensor and a PID controller, controlling the temperature range of the spinneret to 80-120℃.

[0016] In one or more embodiments of the present invention, the jet extrusion device is designed with a turbulent flow channel based on Bernoulli's principle. After the compressed air is filtered by a 5μm filter element, the flow velocity is 8-12m / s and the air pressure is 0.3-0.4MPa. The outlet of the flow channel is provided with a horn-shaped airflow guide cavity with a diameter of 3mm to guide the airflow to uniformly wrap the extruded PAN solution.

[0017] In one or more embodiments of the present invention, the molecular weight of PAN in step S1 is 80,000, and the water content of DMF is ≤0.1%; the flow rate accuracy of the micro pump in step S4 is ±2%, and the tension fluctuation of the roller winding device D is ≤±0.1cN.

[0018] In one or more embodiments of the present invention, the piezoelectric controller has a frequency of 6kHz and a voltage of 120V, and the laser displacement sensor monitors the ceramic displacement of 0.3mm; the compressed air of the jet stretching device is filtered through a 5μm filter element, with a flow rate of 10m / s, an air pressure of 0.35MPa, and an airflow temperature of 80℃.

[0019] In one or more embodiments of the present invention, the jet stretching device is equipped with a gas pressure regulating valve to ensure that the airflow velocity fluctuation is ≤5%.

[0020] In one or more embodiments of the present invention, the piezoelectric controller of the high-frequency piezoelectric drive device has an output accuracy of ±0.1V; the heating film of the temperature control device has a 100% coverage rate, and the heating film insulation layer is made of ceramic fiber with a thickness of 1mm.

[0021] Compared with the prior art, the present invention provides a method for the stable preparation of nano-PAN fibers based on high-frequency piezoelectric jets, which has the following advantages:

[0022] 1. Low clogging: The 4μm spinneret structure and heating and insulation design result in a clogging rate of ≤1% and a continuous spinning time of ≥8h, which extends the maintenance cycle by 2 times compared to conventional spinnerets (clogging rate of 12% and continuous spinning for 3h).

[0023] 2. High uniformity: The diameter of the nano-PAN fiber is 180±15nm with a deviation of ≤10%, which improves the uniformity by 60% compared with the existing technology (deviation of 25%); the fiber surface is smooth and free of bead defects;

[0024] 3. High mechanical properties: The obtained nano-PAN fibers have a breaking strength ≥2.8cN / dtex and a breaking elongation of 16-20%. The surface is free of bead knots and broken filaments. They can be used as nano-raw materials for polypropylene / PAN, polyester / PAN, and nylon / PAN multi-scale fiber assemblies. Compared with conventional piezoelectric jet products (1.5cN / dtex), the strength is improved, meeting the mechanical requirements of multi-scale fiber assemblies.

[0025] 4. Ease of operation: The device parameters can be adjusted in real time, equipped with a blockage alarm function (pressure sensor monitoring), and have a high degree of automation. One person can operate 3-5 devices, making it suitable for industrial mass production. Attached Figure Description

[0026] 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.

[0027] Figure 1 This is a design drawing of the high-frequency piezoelectric jet stretching module of the present invention;

[0028] Figure 2 This is a simulation diagram of the structure and flow field of the drawing assembly of the present invention;

[0029] Figure 3 This is a comparative experimental data table of the present invention and existing conventional piezoelectric jet devices. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0031] A method for the stable preparation of nano-PAN fibers based on high-frequency piezoelectric jets includes the following steps:

[0032] S1. Raw material and equipment preparation: Raw materials include PAN powder and DMF; Equipment includes magnetic stirring device, high-frequency piezoelectric drive device, temperature control device, rotational viscometer, 3D printed microchannels, anti-clogging spinneret with spinneret orifice, jet stretching device, vacuum degassing tank, micro pump, roller winding device, scanning electron microscope, laser displacement sensor and micro tensile testing machine.

[0033] S2, Solution preparation: Mix PAN powder and DMF at a mass ratio of 13:87. In this example: 13g PAN + 87g DMF are added to a 500mL three-necked flask and magnetically stirred at 100°C for 3 hours. The viscosity is tested using a rotational viscometer (NDJ-5S) and adjusted to 700cP. If the viscosity is >700cP, add a small amount of DMF. If the viscosity is <700cP, heat to concentrate and finally adjust to 700cP. Then, transfer the solution to a vacuum degassing tank (-0.09MPa) and let it stand for 2 hours to remove bubbles and prevent yarn breakage during spinning.

[0034] S3, device preheating and parameter setting, start the temperature control device, power on the polyimide heating film, raise the spinneret temperature to 105℃ through the PID controller, the PT100 sensor provides real-time feedback, temperature fluctuation ±1℃; keep warm for 30 minutes to ensure uniform temperature of the spinneret body.

[0035] Set the parameters of the high-frequency piezoelectric drive device: frequency 6kHz, voltage 120V, and calibrate the ceramic displacement to 0.3mm using a laser displacement sensor;

[0036] Start the jet stretching device, adjust the airflow velocity to 10m / s, air pressure to 0.35MPa, and airflow temperature to 80℃;

[0037] S4, PAN nanofiber spinning is carried out continuously for 8 hours. The PAN solution after degassing in S2 is injected into the microchannel and stably delivered to the spinneret through a micro pump. After the PAN solution is piezoelectrically driven and extruded by a high-frequency piezoelectric drive device, it is stretched into nanofibers by the jet airflow of the jet stretching device. The nanofibers are collected by a roller winding device, and the winding tension is controlled at 0.5cN to avoid fiber stretching and deformation.

[0038] S5, fiber performance monitoring: samples are taken every 1 hour, and the fiber diameter is observed using a scanning electron microscope (SU8010). The breaking strength is tested using a micro tensile testing machine (50N range). If the diameter deviation is >10%, the piezoelectric frequency (±0.5kHz) or airflow velocity (±0.5m / s) is finely adjusted to ensure stable performance during continuous spinning.

[0039] like Figure 1-2 As shown, the design and flow field simulation diagram of the high-frequency piezoelectric jet stretching module (including sub-diagrams a, b, and c) are presented. Figure 1 In the diagram, 'a' represents the overall design of the high-frequency piezoelectric jet stretching module, indicating the compressed air inlet, sealing ring, and installation location of the high-frequency piezoelectric ceramic. Figure 2 b is a cross-sectional view of the internal structure of the key drawing component, with 4μm spinneret micro-holes and compressed air flow channels marked; Figure 2 c is a simulation diagram of the drawn flow field, showing the airflow velocity distribution cloud map to prove the rationality of the flow channel design.

[0040] Specifically, the high-frequency piezoelectric drive device includes a piezoelectric controller and three barium ferrite piezoelectric ceramics connected in parallel. The size of the barium ferrite piezoelectric ceramics is 10mm×5mm×2mm. The piezoelectric controller operates at a frequency of 3-8kHz and a voltage of 100-180V. The displacement of the barium ferrite piezoelectric ceramics is monitored in real time by a laser displacement sensor, and the parameters are dynamically adjusted according to the viscosity of the PAN solution to ensure stable extrusion power.

[0041] The anti-clogging spinneret device has a spinneret orifice diameter of 4μm. The spinneret orifice is processed by ultrafast laser thermo-coupling, with a laser power of 40-60W and a heat-affected zone of ≤5μm. The inlet of the spinneret orifice is provided with a hemispherical flare with a radius of 0.5mm. The inner wall is plasma polished. The body of the spinneret orifice is made of 304 stainless steel.

[0042] The temperature control device uses a 20W polyimide heating film wrapped around the outside of the spinneret body, and is equipped with a PT100 temperature sensor and a PID controller to control the temperature range of the spinneret orifice from 80 to 120°C.

[0043] The jet extrusion device is designed with a turbulent flow channel based on Bernoulli's principle. After the compressed air is filtered through a 5μm filter element, the flow velocity is 8-12m / s and the air pressure is 0.3-0.4MPa. The outlet of the flow channel is provided with a horn-shaped airflow guide cavity with a diameter of 3mm to guide the airflow to uniformly wrap the extruded PAN solution, avoid fiber adhesion, and ensure uniform diameter.

[0044] The PAN powder in step S1 has a molecular weight of 80,000 and a purity of 99%; it is of analytical grade DMF and has a water content of ≤0.1%.

[0045] In step S4, the flow rate accuracy of the micro-pump is ±2%, which delivers the PAN solution to the spinneret. The tension fluctuation of the roller winding device D is ≤ ±0.1cN. In this embodiment, the roller winding speed is 15r / min and the tension is 0.5cN (controlled by a tension sensor). Continuous spinning is carried out for 8 hours without machine downtime for cleaning, and there is no blockage in the spinneret.

[0046] The piezoelectric controller has a frequency of 6kHz and a voltage of 120V, and the laser displacement sensor monitors the ceramic displacement of 0.3mm. The compressed air of the jet stretching device is filtered through a 5μm filter element, with a flow rate of 10m / s, an air pressure of 0.35MPa, and an air temperature of 80℃.

[0047] The jet stretching device is equipped with a gas pressure regulating valve to ensure that the airflow velocity fluctuation is ≤5%.

[0048] The piezoelectric controller of the high-frequency piezoelectric drive device has an output accuracy of ±0.1V; the heating film of the temperature control device has a 100% coverage rate, and the insulation layer of the heating film is made of ceramic fiber with a thickness of 1mm.

[0049] In step S5, when performing performance testing, the following needs to be tested:

[0050] Diameter: SEM observation of 10 fields of view (20 fibers measured in each field of view), diameter 180±15nm, deviation 8.3%;

[0051] Mechanical properties: tested by a micro tensile testing machine, tensile strength 2.8 cN / dtex, elongation at break 18%;

[0052] Morphology: The fiber surface is smooth, without bead knots or broken filaments.

[0053] contrast Figure 3 It can be seen that, compared with the prior art, this embodiment has the following advantages:

[0054] With a 4μm spinneret structure and heating and insulation design, the clogging rate is ≤1% and the continuous spinning time is ≥8h, which extends the maintenance cycle by 2 times compared to conventional spinnerets (clogging rate 12%, 3h continuous spinning). The diameter of the nano-PAN fiber is 180±15nm with a deviation of ≤10%, which improves the uniformity by 60% compared to the existing technology (deviation 25%). The fiber surface is smooth and free of bead defects. The obtained nano-PAN fiber has a breaking strength ≥2.8cN / dtex and a breaking elongation of 16-20%. The surface is free of bead and broken fiber defects, which can be used as a nano-raw material for polypropylene / PAN, polyester / PAN, and nylon / PAN multi-scale fiber assemblies. Compared with conventional piezoelectric jet products (1.5cN / dtex), the strength is improved, meeting the mechanical requirements of multi-scale fiber assemblies. The overall equipment energy consumption is also lower than that of existing devices.

[0055] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0056] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for stable production of nanometer PAN fibers based on high-frequency piezoelectric jet, characterized in that, Includes the following steps: S1. Raw material and equipment preparation: Raw materials include PAN powder and DMF; Equipment includes magnetic stirring device, high-frequency piezoelectric drive device, temperature control device, rotational viscometer, 3D printed microchannels, anti-clogging spinneret with spinneret orifice, jet stretching device, vacuum degassing tank, micro pump, roller winding device, scanning electron microscope, laser displacement sensor and micro tensile testing machine. S2, PAN solution preparation: Mix PAN powder and DMF at a mass ratio of 13:87, and stir magnetically at 100°C for 3 hours using a magnetic stirrer. Use a rotational viscometer to test the viscosity and adjust it to 700 cP. Then transfer the solution to a vacuum degassing tank and let it stand for 2 hours to remove bubbles and prevent yarn breakage during spinning. S3, device preheating and parameter setting, start the temperature control device, raise the spinneret temperature to 105℃, keep it at that temperature for 30 minutes to ensure temperature stability; Set the parameters for the high-frequency piezoelectric drive device: frequency 6kHz, voltage 120V; Start the jet stretching device, adjust the airflow velocity to 10m / s, air pressure to 0.35MPa, and airflow temperature to 80℃; S4, nano-PAN fiber spinning is carried out. The degassed PAN solution from S2 is injected into the microchannel and stably delivered to the spinneret through a micro-pump. After the PAN solution is piezoelectrically driven and extruded by a high-frequency piezoelectric drive device, it is stretched into nanofibers by the jet flow of the jet stretching device. The nanofibers are collected by a roller winding device to avoid fiber stretching and deformation. S5, fiber performance monitoring: samples are taken every 1 hour, fiber diameter is observed using a scanning electron microscope, and breaking strength is tested using a micro tensile testing machine; if the diameter deviation is >10%, the piezoelectric frequency or airflow rate is finely adjusted to ensure stable performance during continuous spinning.

2. The method according to claim 1, wherein the method is characterized by, The high-frequency piezoelectric drive device includes a piezoelectric controller and three barium ferrite piezoelectric ceramics connected in parallel. The size of the barium ferrite piezoelectric ceramics is 10mm×5mm×2mm. The piezoelectric controller operates at a frequency of 3-8kHz and a voltage of 100-180V. The displacement of the barium ferrite piezoelectric ceramics is monitored in real time by a laser displacement sensor, and the parameters are dynamically adjusted according to the viscosity of the PAN solution to ensure stable extrusion power.

3. The method according to claim 2, wherein the method is characterized by, The anti-clogging spinneret device has a spinneret orifice diameter of 4μm. The spinneret orifice is processed by ultrafast laser thermo-coupling, with a laser power of 40-60W and a heat-affected zone of ≤5μm. The inlet of the spinneret orifice is provided with a hemispherical flare with a radius of 0.5mm. The inner wall is plasma polished. The body of the spinneret orifice is made of 304 stainless steel.

4. The method according to claim 3, wherein the method is characterized by, The temperature control device uses a 20W polyimide heating film wrapped around the outside of the spinneret body, and is equipped with a PT100 temperature sensor and a PID controller to control the temperature range of the spinneret orifice from 80 to 120°C.

5. The method according to claim 4, wherein the method is characterized by, The jet extrusion device is designed with a turbulent flow channel based on Bernoulli's principle. After the compressed air is filtered through a 5μm filter element, the flow velocity is 8-12m / s and the air pressure is 0.3-0.4MPa. The outlet of the flow channel is provided with a horn-shaped airflow guide cavity with a diameter of 3mm to guide the airflow to uniformly wrap the extruded PAN solution.

6. The method according to claim 5, wherein the method is characterized by, The magnetic stirring device has a stirring speed of 500 r / min.

7. The method according to claim 6, wherein the method is characterized by, In step S1, the molecular weight of PAN is 80,000, and the water content of DMF is ≤0.1%; in step S4, the flow rate accuracy of the micro pump is ±2%, and the tension fluctuation of the roller winding device is ≤±0.1cN.

8. The method according to claim 5, wherein the method is characterized by, The piezoelectric controller has a frequency of 6kHz and a voltage of 120V, and the laser displacement sensor monitors the ceramic displacement of 0.3mm. The compressed air of the jet stretching device is filtered through a 5μm filter element, with a flow rate of 10m / s, an air pressure of 0.35MPa, and an air temperature of 80℃.

9. The method for stable preparation of nano-PAN fibers based on high-frequency piezoelectric jet according to claim 7, characterized in that, The jet stretching device is equipped with a gas pressure regulating valve to ensure that the airflow velocity fluctuation is ≤5%.

10. The method for stable preparation of nano-PAN fibers based on high-frequency piezoelectric jet according to claim 7, characterized in that, The piezoelectric controller of the high-frequency piezoelectric drive device has an output accuracy of ±0.1V; the heating film of the temperature control device has a 100% coverage rate, and the insulation layer of the heating film is made of ceramic fiber with a thickness of 1mm.

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