High-temperature-resistant waterproof PVDF-based flexible triboelectric material and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant waterproof PVDF-based flexible triboelectric material and a preparation method thereof, and belongs to the technical field of triboelectric materials. The preparation method provided by the invention comprises the following technical steps: (1) adding carboxylated multi-walled carbon nanotubes into acetone and N-N dimethyl formamide solvents, and carrying out ultrasonic dispersion to obtain a dispersion liquid; (2) adding polyvinylidene fluoride into the dispersion liquid, and carrying out magnetic stirring to obtain a PVDF / C-MWCNT (P / CM) spinning solution; (3) filling the spinning solution into an injector, and carrying out electrostatic spinning to obtain a P / CM nanofiber membrane; and (4) drying in a drying box to obtain the PVDF-based flexible triboelectric material. The material prepared by the invention has excellent high temperature resistance, self-extinguishing property, hydrophobicity, flexibility and triboelectric property.

Description

Technical Field

[0001] The present invention relates to the technical field of triboelectric materials, and in particular to a high-temperature resistant and waterproof PVDF-based flexible triboelectric material and a preparation method thereof. Background Art

[0002] Catastrophic fires and rainstorms can easily pose a serious threat to public safety, property and the environment. Traditional alarm and rescue equipment powered by lithium-ion batteries is heavy and has limited capacity. It is not only easy to fail in high temperature and water environments, but also releases flammable, explosive or toxic gases such as methane, ethylene and carbon monoxide when the temperature exceeds 90°C. Therefore, it is urgent to develop portable self-powered sensors with high temperature resistance and waterproof functions.

[0003] Triboelectric nanogenerators (TENGs) are self-powered devices that collect tiny mechanical energy from the environment and convert it into electrical energy based on friction electrification and electrostatic induction effects. They provide an environmentally friendly, energy-saving and sustainable solution for self-powered sensing and monitoring of human motion. However, the performance of TENGs is often affected by the harsh environment of fire and rain. It has thermionic emission effect and softening and deformation of the friction layer in high-temperature fires; it dissipates its own charge in high humidity or water, which reduces the efficiency of charge transfer and leads to reduced electrical output performance or even failure. Therefore, in order to achieve smart rescue in fire and rain, it is very important to design a triboelectric material and device that can withstand the dual harsh environments of high temperature and high humidity.

[0004] High temperature resistant and hydrophobic polyvinylidene fluoride (PVDF) is one of the most promising materials for fire and rainy day scenes. Its polar β phase has the strongest triboelectric properties. However, PVDF membranes prepared by traditional processing methods such as casting, spin coating, and casting are not suitable for use as triboelectric materials due to the small amount of electroactive β phase. At the same time, PVDF-based triboelectric materials that can be used in high temperature rain environments have yet to be studied.

[0005] Due to the high voltage electric field between the positive and negative electrodes of electrospinning, the mechanical stretching effect of the drum collector on the spun fibers, and the hydrogen bonds formed between carboxylated multi-walled carbon nanotubes (C-MWCNT) as nucleating agents and PVDF, a large amount of β phase is induced, which improves the triboelectric properties and flexibility of the composite film.

[0006] Therefore, based on electrospinning technology, the present invention prepares PVDF / C-MWCNT5 (P / CM5) triboelectric materials with self-extinguishing, high temperature resistance, hydrophobicity and high triboelectric properties, providing new ideas for the construction and application of triboelectric materials in the dual harsh environments of high-temperature fires and rainy days. Summary of the invention

[0007] In view of the above problems, the present invention provides a method for preparing a high-temperature resistant and waterproof PVDF-based flexible triboelectric material. Based on the electrospinning technology, a P / CM5 triboelectric material with high temperature resistance, self-extinguishing, hydrophobicity and high triboelectric properties is prepared by electrospinning a PVDF / C-MWCNT (P / CM) precursor solution.

[0008] The present invention is achieved through the following technical solutions:

[0009] A method for preparing a high temperature resistant and waterproof PVDF-based flexible triboelectric material, characterized by comprising the following steps:

[0010] (1) adding carboxylated multi-walled carbon nanotubes (C-MWCNT) into N-N-dimethylformamide (DMF) and acetone (ACET) solvents for ultrasonic dispersion to obtain a dispersion;

[0011] (2) adding polyvinylidene fluoride (PVDF) into the above dispersion and performing magnetic stirring to obtain a P / CM spinning solution;

[0012] (3) loading the spinning solution of step (2) into a syringe and performing electrospinning to obtain a P / CM nanofiber membrane;

[0013] (4) Drying the P / CM nanofiber membrane obtained in step (3) in a drying oven to obtain a PVDF-based flexible triboelectric material.

[0014] As a further preferred solution, in step (1), 0 to 82 g of C-MWCNT is added per liter of solvent.

[0015] As a further preferred solution, in step (1), the volume ratio of DMF and ACET is 8:2. The amount of solvent used needs to be strictly controlled in the present invention. If the volume ratio of the solvent is too large, the volatility of the spinning solution is large, which can easily clog the needle and cause uneven spinning. However, if the volume ratio of the solvent is too small, the volatility is too small, the surface tension and viscosity are large, and the solution has a large jet resistance under the action of a high-voltage electric field. Therefore, the injection and stretching are inhibited, and the spinning can easily clog the needle and has poor film-forming properties. Almost no fiber is collected by the drum collector within 30 minutes. The present invention selects a volume ratio of 8:2 as the optimal ratio obtained by experimentally exploring different ratios.

[0016] As a further preferred embodiment, in step (1), the C-MWCNT accounts for 0-9 wt % of the PVDF.

[0017] As a further preferred embodiment, in step (1), the ultrasonication time is 1.5-2 h.

[0018] As a further preferred solution, in step (2), the mass fraction of PVDF is 9%. The mass fraction of PVDF is too small, the viscosity is too small, the molecular entanglement is insufficient, and the macroscopic observation during the experiment is electrostatic spraying rather than electrostatic spinning. Secondly, after the preparation is completed, it cannot be completely peeled off from the aluminum foil during SEM measurement, and it appears in powder form without forming a film. The mass fraction of PVDF is too large, and the viscosity is too large. During the experiment, the needle is very easy to clog and normal spinning cannot be performed. After spinning for 30 minutes, there is almost no fiber on the drum collector. Selecting a PVDF dosage of 9wt% is the most effective dosage.

[0019] As a further preferred solution, in step (2), the temperature of the magnetic stirring is 60-65° C. and the stirring time is 10-12 h.

[0020] As a further preferred solution, in step (3), the injection speed of the spinning solution is set to 0.5 mL h -1 , the receiving distance was set to 15 cm, the spinning voltage was set to 15 kV, the ambient temperature was controlled at 25 °C, and the relative humidity was 40%.

[0021] As a further preferred solution, in step (4), the vacuum drying temperature is 60-65°C, and the drying time is 20-24h.

[0022] The PVDF-based flexible triboelectric material prepared by the preparation method of the present invention has the properties of high temperature resistance and waterproofness, and can be used in high temperature fire scenes and rainy environments.

[0023] The preparation principle of the PVDF-based flexible triboelectric material suitable for high-temperature fire and rainy environments of the present invention is as follows:

[0024] Nanofiber materials prepared by electrospinning technology have the characteristics of high specific surface area and high porosity, and are considered to be ideal for loading conductive nanoparticles. The present invention uses electrospinning technology to electrospin P / CM solution to adjust the surface structure and performance of the material. High voltage electric field, mechanical stretching and C-MWCNT polarize the dipoles in the PVDF molecular chain in situ, thereby increasing the content of β-phase PVDF. In addition, C-MWCNT can be used as a nucleating agent to induce the formation of β phase. Electrospinning and C-MWCNT have complementary effects on the formation of β-phase PVDF. When PVDF-based flexible triboelectric materials are burned, the thermal decomposition products contain F·flame retardant free radicals that need to consume HO· and H·active free radicals; at the same time, a dense carbon layer can also be formed after combustion to block external heat sources and thus improve flame retardancy. In addition, PVDF-based flexible triboelectric materials contain abundant CF bonds and are hydrophobic. Therefore, the triboelectric performance in high-temperature fire and water environments is greatly improved. At the same time, electrospinning overcomes the brittleness of C-MWCNT, so that the film has sufficient flexibility.

[0025] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0026] 1. The P / CM5 triboelectric material prepared by the present invention has excellent self-extinguishing properties, based on the fact that the F·flame-retardant free radicals released by its combustion and decomposition capture the HO· and H· free radicals required for the combustion chain reaction, interrupting the combustion, and the formation of a dense carbon layer with a physical barrier effect. It also contains abundant CF bonds with strong binding force, resulting in a low surface energy, and thus has excellent hydrophobicity (WCA=123°).

[0027] 2. The P / CM5 triboelectric material prepared by the present invention also has excellent flexibility.

[0028] 3. The P / CM5 triboelectric material prepared by the present invention has an increased content of PVDFβ phase due to high voltage electric field, mechanical stretching and hydrogen bonding between C-MWCNT and PVDF, and has excellent triboelectric properties at room temperature (117.97V), high temperature (200℃, 44.17V; after combustion, 22.33V), and in water (8.90V). It is expected to realize rapid human-machine intelligent interaction in emergency rescue in fire and rainy days, and scientifically and effectively improve the rescue efficiency of firefighters. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the preparation of PVDF-based flexible triboelectric material in Example 2.

[0030] Figure 2 This is the SEM image of the PVDF-based flexible triboelectric material of Example 3 at a magnification of 2000.

[0031] Figure 3 This is the EDS element distribution diagram of the PVDF-based flexible triboelectric material of Example 3.

[0032] Figure 4 This is a combustion self-extinguishing diagram of the PVDF-based flexible triboelectric material of Example 3 under the flame of an alcohol lamp.

[0033] Figure 5 This is the voltage diagram of the PVDF-based flexible triboelectric material of Example 3 at room temperature.

[0034] Figure 6 This is a voltage diagram of the PVDF-based flexible triboelectric material of Example 3 at different high temperatures.

[0035] Figure 7 The voltage diagram of the PVDF-based flexible triboelectric material of Example 3 when immersed in water at different areas. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below by way of examples. These examples are only used to illustrate the present invention and do not limit the protection scope of the present invention.

[0037] Example 1

[0038] Preparation of PVDF-based flexible triboelectric materials:

[0039] 9 wt% PVDF powder was dissolved in a mixed solvent of DMF and ACET (8:2, v / v) and stirred continuously for 12 h in a water bath at 60 °C using a magnetic stirrer to obtain a uniform spinning solution. Subsequently, the solution was injected into a 10 mL plastic syringe equipped with a 22G needle for electrospinning. The voltage of the electrospinning process was 15 kV and the propulsion speed was 0.5 mL h -1 , collection speed is 120r min -1 The distance between the needle and the roller collector was 15 cm. The temperature and humidity were maintained at 25°C and 40%, respectively. Finally, after drying in an oven at 60°C for 24 h, the product was obtained and named P / CM0.

[0040] Example 2

[0041] Preparation of PVDF-based flexible triboelectric materials:

[0042] C-MWCNTs accounting for 1 wt% of PVDF powder were ultrasonically dispersed in a mixed solvent of DMF and ACET (8:2, v / v). Then 9 wt% of PVDF powder was dissolved in the solution, stirred continuously for 12 h in a water bath at 60 °C with a magnetic stirrer, and then ultrasonically dispersed for 2 h to obtain a uniform P / CM1 mixed solution. Subsequently, the P / CM solution was injected into a 10 mL plastic syringe equipped with a 22G needle for electrospinning. The voltage of the electrospinning process was 15 kV and the propulsion speed was 0.5 mL h -1 , collection speed is 120r min -1 The distance between the needle and the roller collector was 15 cm. The temperature and humidity were maintained at 25°C and 40%, respectively. Finally, after drying in a drying oven at 60°C for 24 hours, it was obtained and named P / CM1.

[0043] Example 3

[0044] Preparation of PVDF-based flexible triboelectric materials:

[0045] C-MWCNTs accounting for 3 wt% of PVDF powder were ultrasonically dispersed in a mixed solvent of DMF and ACET (8:2, v / v). Then 9 wt% of PVDF powder was dissolved in the solution, stirred continuously for 12 h in a water bath at 60 °C with a magnetic stirrer, and then ultrasonically dispersed for 2 h to obtain a uniform P / CM3 mixed solution. Subsequently, the P / CM solution was injected into a 10 mL plastic syringe equipped with a 22G needle for electrospinning. The voltage of the electrospinning process was 15 kV and the propulsion speed was 0.5 mL h -1 , collection speed is 120r min -1 The distance between the needle and the roller collector was 15 cm. The temperature and humidity were maintained at 25°C and 40%, respectively. Finally, after drying in a drying oven at 60°C for 24 hours, the product was obtained and named P / CM3.

[0046] Example 4

[0047] Preparation of PVDF-based flexible triboelectric materials:

[0048] C-MWCNTs accounting for 5 wt% of PVDF powder were ultrasonically dispersed in a mixed solvent of DMF and ACET (8:2, v / v). Then 9 wt% of PVDF powder was dissolved in the solution, stirred continuously for 12 h in a water bath at 60 °C with a magnetic stirrer, and then ultrasonically dispersed for 2 h to obtain a uniform P / CM5 mixed solution. Subsequently, the P / CM solution was injected into a 10 mL plastic syringe equipped with a 22G needle for electrospinning. The voltage of the electrospinning process was 15 kV and the propulsion speed was 0.5 mL h -1 , collection speed is 120r min -1The distance between the needle and the roller collector was 15 cm. The temperature and humidity were maintained at 25°C and 40%, respectively. Finally, after drying in a drying oven at 60°C for 24 hours, the product was obtained and named P / CM5.

[0049] Example 5

[0050] Preparation of PVDF-based flexible triboelectric materials:

[0051] C-MWCNTs accounting for 7 wt% of PVDF powder were ultrasonically dispersed in a mixed solvent of DMF and ACET (8:2, v / v). Then 9 wt% of PVDF powder was dissolved in the solution, stirred continuously for 12 h in a water bath at 60 °C with a magnetic stirrer, and then ultrasonically dispersed for 2 h to obtain a uniform P / CM7 mixed solution. Subsequently, the P / CM solution was injected into a 10 mL plastic syringe equipped with a 22G needle for electrospinning. The voltage of the electrospinning process was 15 kV and the propulsion speed was 0.5 mL h -1 , collection speed is 120r min -1 The distance between the needle and the roller collector was 15 cm. The temperature and humidity were maintained at 25°C and 40%, respectively. Finally, after drying in a drying oven at 60°C for 24 hours, the product was obtained and named P / CM7.

[0052] Example 6

[0053] Preparation of PVDF-based flexible triboelectric materials:

[0054] C-MWCNTs accounting for 9 wt% of PVDF powder were ultrasonically dispersed in a mixed solvent of DMF and ACET (8:2, v / v). Then 9 wt% of PVDF powder was dissolved in the solution, stirred continuously for 12 h in a water bath at 60 °C with a magnetic stirrer, and then ultrasonically dispersed for 2 h to obtain a uniform P / CM9 mixed solution. Subsequently, the P / CM solution was injected into a 10 mL plastic syringe equipped with a 22G needle for electrospinning. The voltage of the electrospinning process was 15 kV and the propulsion speed was 0.5 mL h -1 , collection speed is 120r min -1 The distance between the needle and the roller collector was 15 cm. The temperature and humidity were maintained at 25°C and 40%, respectively. Finally, after drying in a drying oven at 60°C for 24 hours, the product was obtained and named P / CM9.

[0055] Material morphology characterization and analysis

[0056] (I) SEM analysis

[0057] The P / CM5 flexible triboelectric material of Example 4 was characterized and analyzed using a scanning electron microscope (SEM). Figure 2 As shown, Figure 2 This is the SEM image of the P / CM5 flexible triboelectric material of Example 4 at a magnification of 2000.

[0058] Depend on Figure 2 It can be seen that C-MWCNT is uniformly dispersed on PVDF nanofibers, and the prepared P / CM5 flexible triboelectric material is a nanofiber membrane.

[0059] The P / CM5 flexible triboelectric material of Example 4 was characterized and analyzed using an energy dispersive spectrometer (EDS). Figure 3 As shown, Figure 3 This is the EDS image of the P / CM5 flexible triboelectric material of Example 4.

[0060] Depend on Figure 3 It can be seen that C-MWCNT is uniformly dispersed on PVDF nanofibers, and the appearance of O element indicates that C-MWCNT is successfully introduced into PVDF.

[0061] Material performance test analysis

[0062] (I) Self-extinguishing test

[0063] The P / CM5 flexible triboelectric material of Example 4 was subjected to a vertical combustion test by placing it under the flame of an alcohol lamp (520° C.) and burning it for 1 min.

[0064] The results are as follows Figure 4 As shown, Figure 4 This is a combustion self-extinguishing diagram of the P / CM5 flexible triboelectric material of Example 4. Figure 4 It can be seen that the P / CM5 flexible triboelectric material has the excellent property of self-extinguishing after ignition.

[0065] (II) Electrical performance test at room temperature

[0066] Polylactic acid (PLA) and PVDF-based flexible triboelectric materials prepared in Examples 1-6 were cut into 2 cm × 2 cm squares and attached to acrylic plates with conductive adhesive to serve as positive and negative electrode materials. The positive and negative plates were respectively mounted on the TENGs electrical test bench to form TENGs in vertical-contact separation mode. The test was conducted at a frequency of 2 Hz. The test results are shown in Figure 2. Figure 5 shown. Figure 5 In the figure, P / CM0, P / CM1, P / CM3, P / CM5, P / CM7, and P / CM9 respectively represent PVDF-based flexible triboelectric materials made from C-MWCNTs with different mass fractions (0-9%) of PVDF in Examples 1-6. Figure 5The voltage diagram of the PVDF-based flexible triboelectric material of Examples 1-6 at room temperature.

[0067] Depend on Figure 5 It can be seen that with the increase of C-MWCNT addition, the voltage of PVDF-based flexible triboelectric material first increases and then decreases, reaching the maximum at 5wt%. P / CM5 flexible triboelectric material has the highest open circuit voltage (117.97V).

[0068] (III) Electrical performance test at different high temperatures

[0069] PLA and P / CM5 flexible triboelectric material prepared in Example 4 were cut into 2cm×2cm squares and attached to acrylic plates with conductive adhesive to be used as positive and negative electrode materials. The positive and negative plates were respectively installed on the TENGs electrical test bench to form TENGs in vertical-contact separation mode. The temperature of the heating plate was controlled by a temperature control box to control the temperature of the system. The test was carried out at a frequency of 2Hz. The test results are shown in Figure 2. Figure 6 shown. Figure 6 This is a voltage diagram of the PVDF-based flexible triboelectric material of Example 4 at different temperatures.

[0070] Depend on Figure 6 It can be seen that as the temperature increases, the voltage of the P / CM5 flexible triboelectric material gradually decreases due to the thermal ion emission effect. It is worth noting that even at a high temperature of 200°C and after combustion, the P / CM5 flexible triboelectric material still has a voltage of 44.17V and 22.33V respectively.

[0071] (IV) Electrical performance test of different areas immersed in water

[0072] PLA and P / CM5 flexible triboelectric material prepared in Example 4 were cut into 2 cm × 2 cm squares and attached to acrylic plates with conductive adhesive to be used as positive and negative electrode materials. The positive and negative plates were respectively mounted on the TENGs electrical test bench to form TENGs in vertical-contact separation mode, and different areas were immersed in a beaker containing tap water. The test was carried out at a frequency of 2 Hz. The test results are shown in Figure 2. Figure 7 shown. Figure 7 This is a voltage diagram of the PVDF-based flexible triboelectric material of Example 4 when immersed in water at different areas.

[0073] Depend on Figure 7It can be seen that as the immersion area increases, the voltage of the P / CM5 flexible triboelectric material gradually decreases due to the ion dissipation effect. When the material immersion area is 50%, the voltage change is not obvious; when the material immersion area reaches 75%, it can still maintain 86% of the voltage, controlled at 30.54V. Even after 100% immersion in water, the P / CM5 flexible triboelectric material still has a voltage of 8.90V.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high temperature resistant and waterproof PVDF-based flexible triboelectric material, characterized in that: The following steps are involved: (1) adding carboxylated multi-walled carbon nanotubes to N,N-dimethylformamide and acetone solvents and ultrasonically dispersing them to obtain a dispersion; (2) adding polyvinylidene fluoride to the above dispersion and subjecting it to magnetic stirring to obtain a polyvinylidene fluoride / carboxylated multi-walled carbon nanotube spinning solution; (3) loading the spinning solution of step (2) into a syringe and performing electrospinning to obtain a polyvinylidene fluoride / carboxylated multi-walled carbon nanotube nanofiber membrane; (4) Drying the polyvinylidene fluoride / carboxylated multi-walled carbon nanotube nanofiber membrane obtained in step (3) in a drying oven to obtain a PVDF-based flexible triboelectric material.

2. The method for preparing the high temperature resistant and waterproof PVDF-based flexible triboelectric material according to claim 1, characterized in that: In step (1), 0 to 82 g of carboxylated multi-walled carbon nanotubes are added to each liter of solvent.

3. The method for preparing the high temperature resistant and waterproof PVDF-based flexible triboelectric material according to claim 1, characterized in that: In step (1), the volume ratio of N-N-dimethylformamide to acetone is 8:

2.

4. The method for preparing a high temperature resistant and waterproof PVDF-based flexible triboelectric material according to claim 1, characterized in that: In step (1), the carboxylated multi-walled carbon nanotubes account for 0-9 wt % of the polyvinylidene fluoride.

5. The method for preparing the high temperature resistant and waterproof PVDF-based flexible triboelectric material according to claim 1, characterized in that: In step (1), the ultrasonic time is 1.5-2h.

6. The method for preparing the high temperature resistant and waterproof PVDF-based flexible triboelectric material according to claim 1, characterized in that: In step (2), the mass fraction of the polyvinylidene fluoride is 9%.

7. The method for preparing a high temperature resistant and waterproof PVDF-based flexible triboelectric material according to claim 1, characterized in that: In step (2), the temperature of the magnetic stirring is 60-65° C. and the stirring time is 10-12 h.

8. The method for preparing a high temperature resistant and waterproof PVDF-based flexible triboelectric material according to claim 1, characterized in that: In step (3), the injection speed of the spinning solution is set to 0.5 mL h -1 , the receiving distance was set to 15 cm, the spinning voltage was set to 15 kV, the ambient temperature was controlled at 25 °C, and the relative humidity was 40%.

9. The method for preparing a high temperature resistant and waterproof PVDF-based flexible triboelectric material according to claim 1, characterized in that: In step (4), the vacuum drying temperature is 60-65° C. and the drying time is 20-24 h.

10. A PVDF-based flexible triboelectric material prepared by the method for preparing a high-temperature resistant and waterproof PVDF-based flexible triboelectric material as claimed in any one of claims 1 to 8, wherein the PVDF-based flexible triboelectric material is applied to high-temperature fire scenes and rainy environments.

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