Preparation method and application of high-crystallinity PVDF piezoelectric fiber reinforced by Tris

Abstract

The invention discloses a preparation method and application of a high-crystallinity PVDF piezoelectric fiber enhanced by tris(hydroxymethyl)aminomethane (Tris). The invention belongs to the field of organic materials. The piezoelectric fiber is prepared by an electrostatic spinning method, and shows an increase in crystallinity and crystalline β-phase. Preparation steps: Tris is ultrasonically dissolved in a mixed solution of acetone and N,N-dimethylformamide as an additive, and then PVDF powder is added to dissolve and prepared into a spinning solution, and a Tris-enhanced PVDF piezoelectric fiber is prepared by an electrostatic spinning method. The present invention adopts an electrostatic spinning method to prepare a high-crystallinity Tris@PVDF piezoelectric fiber, and the preparation method is simple. The obtained Tris@PVDF piezoelectric fiber has a crystallinity of 45.4% and a β-phase content of 92%, while pure PVDF piezoelectric fiber has only a crystallinity of 36.6% and a β-phase content of 84%. The present invention introduces Tris into PVDF for the first time to obtain a highly crystalline PVDF piezoelectric fiber, which has certain potential in flexible nanogenerators and flexible piezoelectric sensors.

Description

Technical Field

[0001] The invention belongs to the field of organic materials and relates to a preparation method and application of a high-crystallinity polymer piezoelectric material reinforced by tris(hydroxymethyl)aminomethane (Tris): polyvinylidene fluoride (PVDF) piezoelectric fiber. Background Art

[0002] With the development of small, wireless, wearable, and self-powered electronic devices, nanogenerators have attracted much attention due to their excellent ability to convert mechanical energy into electrical energy. Polyvinylidene fluoride (PVDF) has excellent electrical properties (ferroelectric, dielectric, piezoelectric), and its light weight, easy processing, and flexibility make it widely used in flexible nanogenerators. Its excellent electrical properties are due to the high content of β phase, so how to obtain a high content of β phase has always been the focus of research. In previous studies, most researchers increased the electroactive β phase content of PVDF by adding carbon materials (carbon nanotubes, graphene, etc.) to PVDF. For example, Kunming Shi et al. from Shanghai Jiaotong University obtained a 91.1% relative content of β phase by electrospinning PVDF nanofibers through the synergistic effect of graphene and barium titanate; Sumanta Kumar Karan et al. obtained a 95% relative content of β phase by casting a synergistic rGO and AlO blended solution with PVDF. The present invention adds tris(hydroxymethyl)aminomethane (Tris) to PVDF and utilizes the interaction between -NH2 in Tris and -CF2 on PVDF to increase the content and crystallinity of the electroactive β phase, so that it has certain potential in the application of energy collection and flexible piezoelectric sensors. Summary of the invention

[0003] Purpose of the invention: The first purpose of the present invention is to provide a high-performance piezoelectric nanofiber; the second purpose of the present invention is to provide a simple method for preparing the above-mentioned PVDF piezoelectric fiber by electrospinning through Tris to increase the crystallinity; the third purpose of the present invention is to provide the application of the above-mentioned Tris-enhanced PVDF piezoelectric fiber in piezoelectric energy collection and flexible piezoelectric sensors.

[0004] Technical solution: The high-crystallinity polyvinylidene fluoride (PVDF) piezoelectric fiber reinforced with tris(hydroxymethyl)aminomethane (Tris) described in the present invention is formed by using Tris as an additive to improve the crystallinity of the PVDF piezoelectric fiber.

[0005] Furthermore, the diameter of the PVDF piezoelectric fiber is 200 nm.

[0006] Furthermore, the content of Tris as an additive accounts for 0wt% to 1.5wt% of Tris@PVDF.

[0007] Furthermore, a method for preparing a high-crystallinity PVDF piezoelectric fiber reinforced by Tris is provided, and the specific operation steps are as follows:

[0008] (1) dissolving Tris in a mixed solvent containing N,N-dimethylformamide (DMF) and acetone to prepare a Tris solvent;

[0009] (2) dissolving the prepared PVDF in the prepared Tris solvent to prepare a Tris-PVDF solution;

[0010] (3) electrospinning the prepared Tris-PVDF solution to obtain spun Tris@PVDF piezoelectric fibers;

[0011] (4) Drying and cutting the prepared Tris@PVDF piezoelectric fibers, encapsulating them to obtain piezoelectric devices, and testing the piezoelectric output.

[0012] Further, in step (1), in a mixed solvent containing DMF and acetone,

[0013] The mass ratio of DMF to acetone is 3:2.

[0014] Furthermore, in step (2), the conditions for dissolving the PVDF in the Tris solvent are: the dissolving temperature is 45°C-65°C, and the dissolving time is 1.5-3.5 hours;

[0015] The mass ratio of the PVDF to the mass ratio of the Tris solvent is 10-15 wt %.

[0016] Furthermore, in step (3), the specific operation of the electrospinning is as follows: the distance from the needle tip to the drum is 17 cm, the electric field strength is 1.2 kV / cm, the needle is 25G, the solution feed rate is 1 ml / h, and the drum speed is 1000 rpm.

[0017] Furthermore, a Tris-reinforced PVDF piezoelectric fiber is applied as energy harvester and flexible piezoelectric sensor.

[0018] Beneficial effects: Compared with the prior art, the present invention is characterized in that: the preparation method of the present invention is simple, the preparation time is short, a high performance improvement can be obtained, and the repeatability is good; the prepared high-performance Tris@PVDF piezoelectric fiber has high crystallinity and crystalline β phase; the present invention introduces Tris as an additive for the first time through a simple electrospinning method to enhance the performance of PVDF piezoelectric fibers, and the obtained piezoelectric fibers have certain potential for application in energy collection and flexible piezoelectric sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a SEM photo of the Tris@PVDF piezoelectric fiber prepared in Example 1-4;

[0020] Figure 2 This is a mapping element distribution photo of the Tris@PVDF piezoelectric fiber prepared in Example 3;

[0021] Figure 3 XRD patterns of Tris@PVDF piezoelectric fibers prepared in Examples 1-4;

[0022] Figure 4 FTIR spectrum of Tris@PVDF piezoelectric fiber prepared in Example 1-4;

[0023] Figure 5 DSC spectra of Tris@PVDF piezoelectric fibers prepared in Examples 1-4;

[0024] Figure 6 The crystallinity, relative β-phase content, and the relationship between β-phase crystallinity and tris content of the Tris@PVDF piezoelectric fibers prepared in Examples 1-4 are shown in FIG.

[0025] Figure 7 Schematic diagram of the Tris@PVDF piezoelectric fiber package prepared in Example 4;

[0026] Figure 8 This is a voltage output diagram of the Tris@PVDF piezoelectric fiber prepared in Example 1-4 after packaging and testing. DETAILED DESCRIPTION

[0027] In order to more clearly illustrate the technical solution of the present invention, the technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

[0028] As shown in the figure, the Tris-reinforced PVDF piezoelectric fiber of the present invention has high crystallinity and crystalline β phase.

[0029] Furthermore, the diameter of the nanofiber (PVDF piezoelectric fiber) is 200 nm.

[0030] Furthermore, the highest crystallinity of the nanofibers is 45.4%; the crystalline β phase is 92%.

[0031] In the present invention, when the content of Tris is 0wt%, it is pure PVDF nanofiber with a low crystallinity of 36.6%; when the content of Tris is higher than 0wt%, the crystallinity begins to increase; when the content of Tris reaches 1wt%, the crystallinity is the highest, which is 45.4%; when the content of Tris is higher than 1wt%, the crystallinity begins to decrease. The introduction of an appropriate amount of Tris can improve the crystallinity of PVDF nanofibers.

[0032] The preparation principle of the present invention is: the present invention adopts electrospinning method to prepare Tris-enhanced coaxial high-crystallinity PVDF piezoelectric fibers; the specific steps are as follows:

[0033] First, Tris is dissolved in a mixed solution containing DMF and acetone to prepare a Tris solvent, wherein Tris is dispersed in the mixed solution to form a single molecule;

[0034] Secondly, PVDF is added to the mixed solution (Tris solvent). Under heating and stirring, PVDF dissolves, the long chain stretches and contacts with Tris, and hydrogen bonds are formed between -NH2 on Tris and -CF2 on PVDF to obtain Tris-PVDF solution.

[0035] Then, the prepared Tris-PVDF solution was electrospun to prepare spun Tris@PVDF piezoelectric fibers;

[0036] Finally, the prepared Tris@PVDF piezoelectric fibers were dried, cut, and packaged to obtain piezoelectric devices and the piezoelectric output was tested.

[0037] Under the action of the electric field, the -NH2 on Tris is positively charged, and produces electrostatic attraction with the negatively charged -CF2 on PVDF, which enhances the interaction between Tris and PVDF. At the same time, intermolecular hydrogen bonds are generated between Tris molecules and PVDF, which guide the all-trans (TTTT') arrangement of PVDF chains, increase the β-phase content and improve the crystallinity, and finally form piezoelectric fibers with high crystallinity.

[0038] Example 1

[0039] PVDF piezoelectric fiber

[0040] DMF and acetone were weighed and mixed in a mass ratio of 3:2, and 12 wt% of PVDF powder was added to the mixed solution, which was sealed and stirred at 60°C for 2 h to obtain an electrospinning solution;

[0041] Take 5 ml of electrospinning liquid into a 10 ml syringe, select a 25G needle, set the distance from the needle tip to the roller to 17 cm, the roller speed to 1000 rpm, the solution flow rate to 1 ml / h, the electric field strength to 1.2 kV / cm, and spin at 40% humidity. Dry the obtained spun fiber felt in a vacuum drying oven at 80°C to obtain pure PVDF piezoelectric fiber.

[0042] Example 2

[0043] Preparation of 0.5wt% Tris@PVDF piezoelectric fibers

[0044] DMF and acetone were weighed and mixed in a mass ratio of 3:2, 0.5 wt% Tris was weighed and added to the mixed solvent of DMF and acetone, and ultrasonically dissolved for 5 min to prepare a mixed solution, and then 12 wt% PVDF powder was added to the mixed solution, which was sealed and stirred at 60°C for 2 h to obtain an electrospinning solution;

[0045] Take 5 ml of electrospinning liquid into a 10 ml syringe, select a 25G needle, set the distance from the needle tip to the roller to 17 cm, the roller speed to 1000 rpm, the solution flow rate to 1 ml / h, the electric field strength to 1.2 kV / cm, and spin at 40% humidity. Dry the obtained spun fiber felt in a vacuum drying oven at 80°C to obtain 0.5 wt% Tris@PVDF piezoelectric fiber.

[0046] Example 3

[0047] 1.0wt% Tris@PVDF piezoelectric fiber

[0048] DMF and acetone were weighed and mixed in a mass ratio of 3:2, 1.0 wt% Tris was weighed and added to the mixed solvent of DMF and acetone, and dissolved by ultrasonic for 5 min to prepare a mixed solution, and then 12 wt% PVDF powder was added to the mixed solution, which was sealed and stirred at 60° C. for 2 h to obtain an electrospinning solution;

[0049] Take 5 ml of electrospinning liquid into a 10 ml syringe, select a 25G needle, set the distance from the needle tip to the roller to 17 cm, the roller speed to 1000 rpm, the solution flow rate to 1 ml / h, the electric field strength to 1.2 kV / cm, and spin at 40% humidity. Dry the obtained spun fiber felt in a vacuum drying oven at 80°C to obtain 1.0 wt% Tris@PVDF piezoelectric fiber.

[0050] Example 4

[0051] 1.5wt% Tris@PVDF piezoelectric fiber

[0052] DMF and acetone were weighed and mixed in a mass ratio of 3:2, 1.5 wt% Tris was weighed and added to the mixed solvent of DMF and acetone, and ultrasonically dissolved for 5 min to prepare a mixed solution, and then 12 wt% PVDF powder was added to the mixed solution, which was sealed and stirred at 60°C for 2 h to obtain an electrospinning solution;

[0053] Take 5 ml of electrospinning liquid into a 10 ml syringe, select a 25G needle, set the distance from the needle tip to the roller to 17 cm, the roller speed to 1000 rpm, the solution flow rate to 1 ml / h, the electric field strength to 1.2 kV / cm, and spin at 40% humidity. Dry the obtained spun fiber felt in a vacuum drying oven at 80°C to obtain 1.5 wt% Tris@PVDF piezoelectric fiber.

[0054] in, Figure 1 For Examples 1 to 4, the scanning electron microscopy images of PVDF piezoelectric fibers with Tris contents of 0wt%, 0.5wt%, 1wt%, and 1.5wt% respectively show that the diameter of the obtained products is about 200nm; Figure 2 Element distribution diagram of piezoelectric fiber with 1wt% Tris, proving the presence of N element.

[0055] The product was subjected to XRD phase analysis. Figure 3 As shown in the figure, pure PVDF shows two peaks at 17.7° and 20.6°, corresponding to the (100) crystal plane of the α phase and the (110) / (200) crystal plane of the β phase of PVDF, respectively; with the addition of a small amount of Tris, such as 0.5wt% Tris, the peak intensity of the 17.7° peak representing the α phase weakens, indicating that the α phase content is reduced.

[0056] Combination Figure 4 As shown in the FTIR infrared spectrum shown, the vibration peak at 763cm-1 corresponds to the non-polar α phase, while the vibration peak at 840cm-1 corresponds to the polar β phase; it can be seen that with the addition of Tris, the peak intensity of 763cm-1 representing the α phase first decreases and then increases, indicating that Tris can inhibit the formation of the α phase, thereby increasing the content of the electroactive β phase.

[0057] According to the formula

[0058] Calculate the relative content of β phase F(β); Aβ and Aα are 849 cm -1 and 763cm -1 The absorbance at the corresponding wave number is 6.1×104 and 7.7×104 cm 2 mol -1 The calculated relative contents of the electroactive β phase F(β) were 84%, 89%, 92%, and 85%, respectively. Excessive addition of Tris would inhibit the formation of the β phase.

[0059] Figure 5 The DSC spectra of Examples 1-4 show the melting temperature of pure PVDF. m is 164.5℃, and with the addition of Tris, Tm First, it moves toward high temperature, and then toward low temperature. This is due to the increase in β content. The high melting point β phase makes the piezoelectric fiber have a higher melting temperature. At the same time, the crystallinity of the piezoelectric fiber is calculated to be 36.6%, 44.3%, 45.4%, and 44.1%, respectively. The addition of Tris makes the piezoelectric fiber obtain higher crystallinity and crystalline β phase, such as Figure 6 Shown is the distribution diagram of the crystallinity, relative β-phase content and crystalline β-phase content of the piezoelectric fibers obtained in Examples 1-4 as a function of Tris content.

[0060] In order to test the piezoelectric output performance of the obtained piezoelectric fiber, it was packaged into a sensor, such as Figure 7 As shown, Figure 7 This is a schematic diagram of the packaged sensor, which has a symmetrical structure from top to bottom. From top to bottom are PI tape, PET substrate, electrode, and piezoelectric fiber.

[0061] The force-electric response test of the sensor is carried out, such as Figure 8 As shown, the piezoelectric output of the piezoelectric fibers of Examples 1-4 was obtained under a cyclic pressure of 2 Hz and 2 N. It can be seen that pure PVDF can generate a voltage of 3 V when the fiber is pressed down. With the addition of Tris, the voltage first increases and then decreases, which is consistent with the changes in crystallinity and crystalline β-phase content. The maximum voltage is about 6 V when 1 wt% Tris is added. This shows that the addition of Tris can obtain higher piezoelectric output and has certain potential in flexible nanogenerators and flexible piezoelectric sensors.

[0062] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a high-crystallinity PVDF piezoelectric fiber reinforced with Tris, characterized in that: The diameter of the PVDF piezoelectric fiber is 200 nm; The content of Tris as an additive accounts for 0.5wt% to 1.5wt% of the Tris and PVDF system; The specific steps are as follows: (1) Dissolving the prepared Tris in a mixed solvent containing DMF and acetone to prepare a Tris solvent; (2) dissolving the prepared PVDF in the prepared Tris solvent to prepare a Tris-PVDF solution; (3) electrospinning the prepared Tris-PVDF solution to obtain spun Tris@PVDF piezoelectric fibers; (4) Dry and cut the prepared Tris@PVDF piezoelectric fibers, encapsulate them to obtain piezoelectric devices, and test the piezoelectric output.

2. The method for preparing a Tris-reinforced high-crystallinity PVDF piezoelectric fiber according to claim 1, characterized in that: In step (1), in a mixed solvent containing DMF and acetone, The mass ratio of DMF to acetone is 3:

2.

3. The method for preparing a Tris-reinforced high-crystallinity PVDF piezoelectric fiber according to claim 1, characterized in that: In step (2), the conditions for dissolving the PVDF in the Tris solvent are: the dissolving temperature is 45°C-65°C, and the dissolving time is 1.5-3.5 hours; The mass ratio of the PVDF to the Tris solvent is 10-15wt%.

4. The method for preparing a Tris-reinforced high-crystallinity PVDF piezoelectric fiber according to claim 1, characterized in that: In step (3), the specific operation of the electrospinning is as follows: the distance from the needle tip to the drum is 17 cm, the electric field strength is 1.2 kV / cm, the needle is 25G, the solution feed rate is 1 ml / h, and the drum speed is 1000 rpm.

Images