Melt spinning preparation method of flexible piezoelectric fiber with core-sheath structure

Abstract

The invention discloses a melt spinning preparation method of a flexible piezoelectric fiber with a core-sheath structure, and relates to the field of electronic materials and sensors. The problems of rigidity and brittleness of an existing piezoelectric material are solved. The preparation method comprises the following steps: mixing and stirring potassium sodium niobate piezoelectric powder, polylactic acid powder and a titanate coupling agent, banburying at a high temperature, and carrying out melt spinning, evaporation of an external copper electrode and polarization treatment by using a coaxial spinning nozzle and a copper wire to prepare the flexible piezoelectric fiber with a core-sheath structure. The fiber takes potassium sodium niobate as a piezoelectric active material, the core part is a copper wire, the outer layer is an evaporation copper layer with the thickness of 100-200nm, and the diameter is 50-200mu m. An electrode structure can be arranged in the fiber core part, so that an electric signal can be conveniently obtained; and the selected polylactic acid material has degradability and biocompatibility, so that the fiber can be applied to the field of biomedical sensors, is low in treatment difficulty after being discarded, and has wide application prospects in the fields of intelligent fabrics, intelligent robots with bodies and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of flexible piezoelectric fibers, in particular to a melt spinning preparation method of flexible piezoelectric fibers with core-sheath structure. BACKGROUND

[0002] As a functional material capable of realizing the mutual conversion between mechanical energy and electrical energy, piezoelectric materials have shown significant practicality in many fields such as sensing, driving, acoustics, signal processing, and energy harvesting. Traditional piezoelectric materials are mainly crystals and ceramic materials. Although these materials have good piezoelectric properties, they have typical rigidity and brittleness. In practical applications, rigidity and brittleness greatly limit their use range. For example, in scenarios where materials need to be deformed, traditional piezoelectric materials are prone to breakage and damage, which cannot meet the actual demand.

[0003] In recent years, with the rapid development of flexible electronics, higher requirements have been put forward for the deformability of materials. In order to adapt to conformal installation and large deformation conditions, the development of high-performance flexible piezoelectric materials has become a research hotspot and important development direction in this field. As a key material for manufacturing intelligent fabrics, flexible piezoelectric fibers can be implanted into fabrics to endow fabrics with functions such as sensing and energy harvesting, which has great significance for manufacturing frontier fields such as wearable intelligent robots. In addition, clothes made of flexible piezoelectric fibers will also have rich intelligent characteristics and have broad market prospects. However, the existing preparation methods of flexible piezoelectric fibers still have some problems, such as difficulty in embedding electrode structure, poor biological compatibility, etc., which need to be further improved and optimized. SUMMARY

[0004] The purpose of the present application is to solve the problems of rigidity and brittleness of existing piezoelectric materials, and to overcome the shortcomings of existing preparation methods of flexible piezoelectric fibers, and to provide a melt spinning preparation method of flexible piezoelectric fibers with core-sheath structure. The flexible piezoelectric fibers prepared by this method not only have good flexibility, but also can easily obtain electrical signals, and have advantages such as biodegradability and biological compatibility, and can be widely applied in many fields.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] A melt spinning preparation method of flexible piezoelectric fibers with core-sheath structure, comprising the following steps:

[0007] 1) Mix and stir potassium sodium niobate piezoelectric powder, polylactic acid powder and titanate coupling agent;

[0008] 2) Load the stirred powder into an internal mixer for high-temperature mixing;

[0009] 3) Install a coaxial spinning nozzle at the bottom end of a melt spinning barrel;

[0010] 4) passing the copper wire through the center hole of the coaxial spinning nozzle;

[0011] 5) feeding the mixed material into the cylinder of the melt spinning machine;

[0012] 6) pulling the copper wire and winding it on the winding drum;

[0013] 7) heating the melt spinning cylinder and starting to spin by rotating the winding drum;

[0014] 8) performing the evaporation of the outer copper electrode on the above spinning;

[0015] 9) applying a high direct current voltage to the copper core and the outer copper layer for polarization treatment.

[0016] In step 1), the potassium sodium niobate is used as a piezoelectric active material; the mass ratio of the potassium sodium niobate piezoelectric powder, the polylactic acid powder and the titanate coupling agent is (30-50):(49-69):(1-2).

[0017] In step 4), the copper wire is passed through the center hole of the coaxial spinning nozzle, and the core of the piezoelectric fiber is the copper wire.

[0018] In step 7), the spinning speed is 2-3 m / min.

[0019] In step 8), the outer copper electrode is evaporated, the outer electrode of the piezoelectric fiber is the evaporated copper layer, and the thickness is 100-200 nm.

[0020] In step 9), the high direct current voltage is applied, and the applied electric field strength is 3-3.5 kV / mm.

[0021] The flexible piezoelectric fiber material with a core-sheath structure prepared by the application has the following characteristics:

[0022] The potassium sodium niobate is used as a piezoelectric active material to ensure the piezoelectric performance of the fiber.

[0023] The diameter of the piezoelectric fiber is controlled to be 50-200 μm to adapt to various application scenarios.

[0024] The core of the piezoelectric fiber is a copper wire, which is used as an internal electrode.

[0025] The outer electrode of the piezoelectric fiber is an evaporated copper layer with a thickness of 100-200 nm, which can effectively conduct electrical signals.

[0026] Compared with the prior art, the technical scheme of the application has the following beneficial effects:

[0027] 1) The present application adopts melt spinning technology to prepare flexible piezoelectric fiber with core-sheath structure. Through unique process design, the electrode structure can be embedded in the fiber core during preparation. This embedded electrode structure makes it easier and more efficient to obtain electrical signals during the operation of the piezoelectric fiber, avoiding signal transmission loss and poor contact caused by external electrodes in traditional methods, greatly improving the performance and stability of the fiber.

[0028] 2) The selected polylactic acid material has the characteristics of biodegradability and biocompatibility. Biodegradability allows the piezoelectric fiber to easily degrade after disposal, reducing the difficulty and cost of disposal, and meeting environmental protection requirements; biocompatibility allows the piezoelectric fiber to be applied in the field of biomedical sensors, such as wearable bioelectric signal monitoring equipment, etc., expanding its application range. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application more clear, the following examples will further illustrate the present application. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0030] Example 1

[0031] This example includes the following steps:

[0032] 1) Take 49 parts by mass of potassium sodium niobate powder, 50 parts by mass of polylactic acid, and 1 part by mass of titanate coupling agent. Before mixing, the potassium sodium niobate piezoelectric powder is dried in a 80℃ air drying oven for 4h, and the polylactic acid powder is vacuum dried at 60℃ for 6h to remove the water in the raw materials, preventing decomposition or performance degradation of the materials due to water during subsequent processing. The three raw materials are put into a high-speed mixer and stirred at a speed of 800r / min for 15min to ensure that the components are fully mixed and uniform.

[0033] 2) Transfer the stirred powder to a laboratory type internal mixer, set the mixing temperature to 180℃, the rotor speed to 60r / min, and the mixing time to 15min. During the mixing process, observe the state of the material to ensure that the material reaches a good melt mixing state and forms a uniform material mass with certain plasticity.

[0034] 3) Install the coaxial spinning nozzle (inner tube diameter 0.5mm, outer tube diameter 1.2mm) at the bottom end of the barrel of the single screw melt spinning machine. During installation, ensure that the nozzle is tightly connected to the barrel without leakage risk.

[0035] 4) Select a pure copper wire with a diameter of 0.3mm, polish one end of it smooth, and pass it through the center hole of the coaxial spinning nozzle. Then fix the copper wire on the wire drum and wrap it around it to ensure that the copper wire does not slip or deflect during the spinning process.

[0036] 5) Carefully put the mixed material into the barrel of the melt spinning machine to avoid spilling the material.

[0037] 6) Turn on the melt-spinning machine's heating system and raise the barrel temperature to 200°C. Once the material is completely melted, start the fiber drum and spin at a speed of 3 m / min. During the spinning process, observe the fiber's formation in real time and adjust the spinning temperature and speed to ensure fiber uniformity and stability.

[0038] 7) The spun fibers were transferred to a vacuum coating machine and the vacuum degree was 5×10 -3 Under the conditions of Pa, thermal evaporation coating technology was used to evaporate the external copper electrodes. The evaporation source temperature was set to 1200℃ and the evaporation time was 15 minutes, so that the copper layer was evenly deposited on the fiber surface, forming an evaporated copper layer with a thickness of about 100-200nm.

[0039] 8) Place the fiber with a copper core and outer copper layer in a polarization device, connect it to a DC high-voltage power supply, and polarize it at an electric field strength of 3 kV / mm for 10 minutes to fully polarize the piezoelectric material in the fiber and obtain stable piezoelectric properties.

[0040] A scanning electron microscope was used to observe the surface morphology and cross-sectional structure of the fiber to check whether the fiber diameter was within the range of 50–200 μm. A four-probe tester was used to measure the surface resistance of the fiber and evaluate the conductivity of the electrode. A dynamic mechanical analyzer was used to test the mechanical properties of the fiber, including tensile strength and elongation at break. A piezoelectric test system was used to measure the piezoelectric coefficient of the fiber to verify its piezoelectric performance. After testing, the flexible piezoelectric fiber prepared in this embodiment had an average diameter of 120 μm, a surface resistance of 5 Ω·cm, a tensile strength of 80 MPa, an elongation at break of 15%, and a piezoelectric coefficient d 33 Reaching 15pC / N, meeting the expected performance requirements.

[0041] Example 2

[0042] This embodiment includes the following steps:

[0043] 1) Take 38 parts by mass of potassium sodium niobate piezoelectric powder (average particle size 0.8 μm), 61 parts by mass of polylactic acid (molecular weight 180,000, intrinsic viscosity 1.0 dL / g), and 1 part by mass of titanate coupling agent (type NDZ-201). The raw materials are pretreated according to the same drying method as in Example 1. The raw materials are added to a planetary ball mill and ball-mixed at a speed of 400 r / min for 2 h to make the materials more uniform and improve the dispersibility between the components.

[0044] 2) The mixed powder is placed in an internal mixer, the mixing temperature is set to 175°C, the rotor speed is 50 r / min, and the mixing time is 20 min. During the mixing process, the mixing state of the material is observed periodically to ensure uniform mixing of the material.

[0045] 3) The same coaxial spinning nozzle and copper wire are used as in Example 1.

[0046] 4) The temperature of the barrel is raised to 195°C, and after the material is melted, the fiber is spun at a speed of 2 m / min. During the spinning process, the fiber is closely monitored to prevent problems such as broken fibers and uneven thickness.

[0047] 5) The same vacuum coating machine and polarization device as in Example 1 are used, and the conditions for evaporating the external copper electrode are the same as in Example 1. During the polarization process, the electric field strength is set to 3.5 kV / mm, and the polarization time is 12 min.

[0048] The same detection equipment and method as in Example 1 are used to test the performance of the fiber. The results show that the average diameter of the flexible piezoelectric fiber prepared in this example is 100 μm, the surface resistance is 4 Ω·cm, the tensile strength is 90 MPa, the elongation at break is 12%, the piezoelectric coefficient d 33 reaches 18 pC / N, indicating that the fiber also has good overall performance and can meet the needs of different application scenarios.

[0049] Example 3

[0050] This example includes the following steps:

[0051] 1) Prepare 45 parts by mass of potassium sodium niobate piezoelectric powder with an average particle size of 0.6 μm, 54 parts by mass of poly (L-lactic acid) (PLLA, molecular weight 120,000, intrinsic viscosity 0.7 dL / g), and 1 part by mass of a titanate coupling agent (model NDZ-311). Dry the potassium sodium niobate piezoelectric powder in a 90°C forced air oven for 5 hours, and vacuum dry the poly (L-lactic acid) at 55°C for 7 hours. Then, place the three raw materials in a three-dimensional motion mixer and mix at 120 rpm for 20 minutes to ensure thorough mixing.

[0052] 2) Transfer the mixed powder to an internal mixer, set the mixing temperature to 170°C, the rotor speed to 55 r / min, and the mixing time to 18 min. During this period, continuously observe the melting and mixing state of the materials to ensure that the materials are uniform and have good plasticity.

[0053] 3) As in Example 1, a coaxial spinning nozzle (inner tube diameter 0.4 mm, outer tube diameter 1.1 mm) was installed. A 0.25 mm diameter pure copper wire was selected, one end of which was polished and passed through the center hole of the nozzle. The wire was then fixed to the receiving drum and wrapped around once.

[0054] 4) Turn on the melt spinning machine heating system and raise the barrel temperature to 190°C. After the material is completely melted, start the fiber drum and spin at a speed of 2.5m / min. Monitor fiber formation in real time and dynamically adjust spinning parameters to ensure fiber quality.

[0055] 5) Place the spun fiber in a vacuum coating machine at a vacuum degree of 6×10 -3 Pa, the external copper electrode was evaporated by magnetron sputtering coating technology with a sputtering power of 80 W and a sputtering time of 12 min to form a uniform copper layer with appropriate thickness.

[0056] 6) Place the fiber with a copper core and an outer copper layer into a polarization device, connect it to a DC high-voltage power supply, and polarize it at an electric field strength of 3.2 kV / mm for 11 minutes to impart stable piezoelectric properties to the fiber.

[0057] The results showed that the flexible piezoelectric fiber had an average diameter of 90 μm, a surface resistance of 6 Ω·cm, a tensile strength of 75 MPa, an elongation at break of 18%, and a piezoelectric coefficient d 33 It is 16pC / N, showing unique performance characteristics.

[0058] Example 4

[0059] 1) Take 42 parts by mass of potassium sodium niobate piezoelectric powder with an average particle size of 1.2 μm, 57 parts by mass of polylactic acid-glycolic acid copolymer (PLGA, lactic acid / glycolic acid molar ratio 75 / 25, molecular weight 160,000, intrinsic viscosity 0.9 dL / g), and 2 parts by mass of titanate coupling agent (model NDZ-401). The potassium sodium niobate piezoelectric powder and PLGA were dried separately and then placed in a double-cone rotary vacuum mixer at a vacuum degree of 1×10 -2 The mixture was mixed for 25 min at 4000 Pa and a rotation speed of 100 r / min to achieve full mixing of the raw materials.

[0060] 2) Place the mixed powder into an internal mixer, set the mixing temperature to 185°C, the rotor speed to 65 r / min, and the mixing time to 16 min. During this period, take samples several times to observe the mixing effect of the materials.

[0061] 3) Install the coaxial spinning nozzle (inner tube diameter 0.6mm, outer tube diameter 1.3mm), select pure copper wire with a diameter of 0.35mm, and process and fix it according to the conventional process.

[0062] 4) Raise the barrel temperature to 205°C. After the material is melted, spin at a wire speed of 3.0 m / min. Deal with any abnormalities that occur during the spinning process in a timely manner.

[0063] 5) Place the fiber in a vacuum coating machine at a vacuum degree of 4×10 -3 Pa, electron beam evaporation technology was used to evaporate the external copper electrode, the evaporation source temperature was 1300℃, and the evaporation time was 13 min to form a high-quality copper layer.

[0064] 6) Place the fiber in a polarization device and polarize it at an electric field strength of 3.3 kV / mm for 9 minutes to give the fiber good piezoelectric properties.

[0065] After testing, the flexible piezoelectric fiber has an average diameter of 130 μm, a surface resistance of 5.5 Ω·cm, a tensile strength of 85 MPa, an elongation at break of 14%, and a piezoelectric coefficient d 33 Reaching 17pC / N, it demonstrates the performance under different raw material and process combinations.

[0066] This invention aims to achieve efficient electromechanical conversion. Potassium sodium niobate serves as the piezoelectric active material, generating polarization through lattice distortion under stress. Polylactic acid or a copolymer provides flexibility and serves as a matrix, while a titanate coupling agent enhances interfacial bonding. These three elements work together to lay the foundation for piezoelectric performance. A core-sheath structure is formed through melt spinning, with a copper wire as the core and a vapor-deposited copper layer as the outer electrode. This, combined with the intermediate piezoelectric material, forms a circuit, facilitating rapid charge transfer. High-voltage DC polarization aligns the piezoelectric material's electric dipoles, activating and stabilizing piezoelectric properties and enabling conversion between mechanical and electrical energy.

[0067] Experiments have demonstrated that this method, through an innovative melt-spinning process and raw material formulation, has successfully produced flexible piezoelectric fibers with a core-sheath structure exhibiting excellent performance. By adjusting the raw material ratio and process parameters, the resulting fibers exhibit excellent controllability in terms of diameter, mechanical properties, conductivity, and piezoelectric properties. The unique core-sheath structure allows for the integration of electrodes, effectively improving the efficiency of electrical signal acquisition. The polylactic acid-based material imparts biodegradability and biocompatibility to the fibers, expanding their application scenarios and promising prospects in areas such as smart textiles and biomedical sensors.

[0068] The above embodiments are only preferred embodiments of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent of the present invention.

Claims

1. A method for preparing a flexible piezoelectric fiber with a core-sheath structure by melt spinning, characterized in that: The following steps are involved: 1) Mixing potassium sodium niobate piezoelectric powder, polylactic acid powder and titanate coupling agent; 2) Load the stirred powder into the internal mixer for high-temperature internal mixing; 3) Install the coaxial spinning nozzle at the bottom end of the melt spinning barrel; 4) Pass the copper wire through the center hole of the coaxial spinning nozzle; 5) The mixed material is put into the barrel of the melt spinning machine; 6) Pull the copper wire and wind it on the wire drum; 7) Heat the melt spinning barrel and start rotating the spinning barrel to spin; 8) Evaporating the above spinning to form an external copper electrode; 9) Apply a high DC voltage to the copper core and the outer copper layer for polarization.

2. The melt spinning method for preparing a flexible piezoelectric fiber with a core-sheath structure according to claim 1, characterized in that: In step 1), the potassium sodium niobate is used as a piezoelectric active material.

3. The melt spinning method for preparing a flexible piezoelectric fiber with a core-sheath structure according to claim 1, characterized in that: In step 1), the mass ratio of the potassium sodium niobate piezoelectric powder, the polylactic acid powder, and the titanate coupling agent is (30-50): (49-69): (1-2).

4. The melt spinning method for preparing a flexible piezoelectric fiber with a core-sheath structure according to claim 1, wherein: In step 4), the copper wire is passed through the central hole of the coaxial spinning nozzle, and the core of the piezoelectric fiber is the copper wire.

5. The melt spinning method for preparing a flexible piezoelectric fiber with a core-sheath structure according to claim 1, characterized in that: In step 7), the spinning speed is 2-3 m / min.

6. The melt spinning method for preparing a flexible piezoelectric fiber with a core-sheath structure according to claim 1, characterized in that: In step 8), the outer copper electrode is evaporated, and the outer electrode of the piezoelectric fiber is an evaporated copper layer with a thickness of 100-200 nm.

7. The melt spinning method for preparing a flexible piezoelectric fiber with a core-sheath structure according to claim 1, characterized in that: In step 9), the DC high voltage is applied with an electric field strength of 3-3.5 kV / mm.

8. The melt spinning method for preparing a flexible piezoelectric fiber with a core-sheath structure according to claim 1, characterized in that: The diameter of the prepared piezoelectric fiber is 50-200 μm.

9. A flexible piezoelectric fiber material with a core-sheath structure prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The flexible piezoelectric fiber material has a core-sheath structure, uses potassium sodium niobate as the piezoelectric active material, the core is a copper wire, and the outer electrode is a vapor-deposited copper layer with a thickness of 100-200nm and a diameter of 50-200μm.