PPy@PVA conductive fiber membrane and its preparation method and application

Abstract

The present invention discloses a PPy@PVA conductive fiber membrane and a preparation method and application thereof. The PVA fiber membrane is obtained by electrostatic spinning technology. The preparation of the PPy@PVA conductive fiber membrane adopts an in-situ polymerization method, which is carried out in two steps of adsorption and oxidation. First, the PVA fiber membrane is impregnated with a pyrrole / DMF solution to adsorb pyrrole monomers, and then oxidized by ferric chloride to generate polypyrrole by in-situ polymerization to obtain the PPy@PVA conductive fiber membrane. The PPy@PVA fiber preparation method proposed by the present invention is simple. The PVA electrostatic spinning fiber is obtained by electrostatic spinning technology; and the PPy@PVA spinning fiber is obtained by simple in-situ polymerization. The mechanical and electrical properties of the spinning fiber membrane can be easily regulated by the number of polymerizations. The PPy@PVA spinning fiber membrane sensor of the present invention has a large deformation amount, a high linearity between the resistance change amount and the deformation, and exhibits stable, durable and reversible strain sensing performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and in particular relates to a preparation method and application of a PPy@PVA conductive fiber membrane. Background Art

[0002] Electronic skin can sense external information such as ambient temperature and pressure, and convert it into electrical signals. It has great application prospects in the fields of human-computer interaction, robotics, virtual reality, etc. Among the existing stress / strain sensors such as resistors, capacitors, and piezoelectric sensors, resistive stress / strain sensors have attracted much attention due to their high sensitivity, large linear area, and convenient signal acquisition. The emerging polymer matrix resistance sensor has the advantages of light weight, large strain, high flexibility, and good comfort. It has shown an increasingly high application feasibility in the field of human health detection such as human joint movement, pulse beating, and vocal cord vibration.

[0003] Polyvinyl alcohol (PVA) is a widely used medical polymer material with high biocompatibility and hydrophilicity. Its surface contains a large number of negatively charged -OH groups, which can produce hydrogen bonding forces with positively charged -NH functional groups (such as -NH on the pyrrole ring). Utilizing this strong intermolecular force, a dense and uniform PPy particle film can be in situ polymerized on the surface of PVA electrospun fibers to obtain PVA fibers coated with conductive PPy particles. Since the PPy particles are firmly fixed on the surface of the PVA fibers, when the PVA is deformed, the PPy particles change with the deformation, and the distance between the particles changes, which is reflected in the tested resistance. Therefore, the PPy@PVA fiber film can be used as a resistive strain / stress sensor. By adjusting the mechanical and electrical properties, stable, durable and reversible strain sensing performance can be obtained, which can be used in flexible electrodes, wearable electronic devices and other fields in the future.

[0004] In this field, the most mature is polyurethane (PU) electrospun fibers. PU spun fibers can absorb conductive components such as conductive carbon black (CB) particles or conductive poly (3,4-ethylenedioxythiophene) - poly (styrene sulfonic acid) (PEDOT:PSS), forming a conductive path on its surface, and the electrical properties of the composite fiber membrane change from an insulator to a semiconductor and conductor. When subjected to stress / strain, the conductivity of the fiber membrane will change with stretching, so it can be used as a strain sensor. Existing PU spun membrane sensors have shown advantages such as a wide response range (0-225% strain), response sensitivity (GF = 1.08-3186.4), and fast response time (0-70ms). Polymer fibers such as polyacrylonitrile (PAN), polyaniline (PANI), and polydimethylsiloxane (PDMS) fibers have also been reported to be used to prepare strain sensors. Lee et al. prepared PAN fiber membrane by electrospinning, and then carbonized it at high temperature (~1000℃) to obtain conductive carbon nanofiber (CNF), which was used for strain sensor, and obtained strain sensor with high transparency, sensitivity of 0.5-180, and deformation of 30%. Yu et al. polymerized PANI in situ on the surface of polyvinylidene fluoride (PVDF) fiber with the participation of sulfonated salicylic acid, and obtained strain sensor with large linear region (0-22%) and recyclable use. Niu et al. used vapor deposition technology to produce strain sensor with high transparency, sensitivity of 0.5-180, and deformation of 30%. 3 The adsorbed PDMS fiber surface was in situ polymerized with polypyrrole (PPy) to obtain a strain sensor with sensitive resistance response signal and large deformation. The above research fully demonstrates the application prospects of polymer fiber membrane in the field of flexible large displacement strain sensing. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a preparation method and application of PPy@PVA conductive fiber membrane. The PPy@PVA spinning fiber membrane is prepared by electrospinning technology and in-situ polymerization technology, which has simple preparation technology and low material cost. The PPy@PVA spinning fiber sensor has high stability and strong durability.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A PPy@PVA conductive fiber membrane is obtained by electrospinning a PVA fiber membrane, and polypyrrole PPy is polymerized and grown on the fiber surface to obtain the PPy@PVA conductive fiber membrane, which is used for a strain sensor.

[0008] Furthermore, the PVA fiber membrane obtained by electrospinning has an optical color of white, a uniform fiber diameter, an average diameter of 0.22 microns, a smooth surface and no Taylor cone morphology; the fiber diameter of the PPy@PVA spun fiber membrane is between 0.52-0.92 microns, which is an increase of 0.30-0.70 microns relative to the original PVA spinning diameter, an increase of between 136.3-318.2%.

[0009] Furthermore, the PPy@PVA conductive fiber membrane is prepared by an in-situ polymerization method, which is carried out in two steps: adsorption and oxidation. The PVA fiber membrane is immersed in a pyrrole / DMF solution to adsorb pyrrole monomers, and then oxidized by ferric chloride to generate polypyrrole by in-situ polymerization.

[0010] Furthermore, the specific preparation process of the PPy@PVA conductive fiber membrane includes: adsorption step: cut a PurePVA spinning membrane of 1cm×4cm, place it in a Py / DMF solution with a volume ratio of 10%, and immerse and adsorb at 60°C for 20 minutes; oxidation step: place the Pure PVA spinning membrane adsorbed with Py in a saturated ferric chloride solution at 60°C, polymerize for 2 hours, take out, wash, and dry to obtain a PPy@PVA1 sample; repeat the above adsorption-oxidation operation 2-4 times to obtain PPy@PVA2, PPy@PVA3, PPy@PVA4, and PPy@PVA5 samples in turn.

[0011] Furthermore, the specific preparation method of the PVA conductive fiber membrane is as follows: prepare a 0.1g / ml PVA deionized water solution and inject it into a syringe with a stainless steel needle (spinneret). Use a grounded aluminum foil (size 30cm×50cm) as a receiving plate, apply a DC voltage of 20.0kV to the spinneret, fix the distance between the spinneret and the receiver to 20.0cm, use an injection peristaltic pump to control the feed of the PVA solution, set the rate to 3μl / min, and perform electrospinning. After 12 hours of spinning, a large area of ​​uniform pure PVA spun fiber membrane is obtained. In order to improve its water solubility and mechanical properties, the pure PVA spun fiber membrane is placed at 120°C, annealed for 5 hours, and set aside.

[0012] Furthermore, after three times of PPy deposition, the obtained PPy@PVA3 fiber membrane had an average tensile modulus of 7.71 MPa, a surface resistivity of 840 Ω / sq, and a conductivity of 32.1 mS / cm.

[0013] The polyvinyl alcohol conductive fiber membrane prepared by the preparation method is used in a strain sensor.

[0014] Furthermore, within 30% deformation, the linear deviation of the resistance change and deformation of the PPy@PVA3 conductive fiber membrane sensor is only 0.9%, and the linear value is 1.85. When deformations of 5, 10, 15, 20, 25, and 30% occur, the resistance changes are 9.07, 18.55, 27.81, 37.32, 46.47, and 56.01%, respectively.

[0015] Furthermore, the PPy@PVA3 conductive fiber membrane sensor signal is stable. During the 1000 stretching experiments, except for the initial stage, the sensing signal profile does not drift significantly for a long time (e.g., 5000 seconds), and the calculated sensitivity does not change significantly.

[0016] Beneficial effects of the present invention: 1. The materials used in the PPy@PVA fiber proposed in the present invention are simple, including only: PVA raw material, Py monomer, anhydrous FeCl 3 Powder, DMF solution and ultrapure water. 2. The preparation method of PPy@PVA fiber proposed in the present invention is simple. Through electrospinning technology, PVA electrospinning fibers are obtained under certain conditions; and PPy@PVA spinning fibers are obtained through simple in situ polymerization technology. The mechanical and electrical properties of the spinning fiber membrane can be easily regulated by the number of polymerizations. 3. The PPy@PVA spinning fiber membrane sensor of the present invention has a large deformation amount, a high linearity between the resistance change and the deformation, and exhibits stable, durable and reversible strain sensing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the preparation process and strain sensing of PPy@PVA conductive fiber membrane, where a: schematic diagram of PVA electrospinning device; b: front SEM image of pure PVA spun fiber membrane; c: front SEM image of PPy@PVA fiber membrane; d: PPy@PVA sensing signals collected under different deformations.

[0018] Figure 2 FTIR spectrum of PVA related fiber membrane.

[0019] Figure 3 Raman spectrum of PVA related fiber membrane.

[0020] Figure 4 Observation of the morphology of PVA-related fiber membranes; front SEM images of Pure PVA (a), PPy@PVA1 (b), PPy@PVA3 (c), and PPy@PVA5 (d) fibers and mapping analysis of the N element.

[0021] Figure 5 Mechanical properties analysis of PVA related fiber membrane; a: stress-strain curve of PVA related fiber membrane; b: elastic modulus bar graph.

[0022] Figure 6 Comparison of surface resistance and volume conductivity of PVA related fiber membranes.

[0023] Figure 7 Characteristic sensing curve of PPy@PVA conductive fiber film sensor under 5% deformation.

[0024] Figure 8 is the relationship between the resistance change rate and deformation of the sensor.

[0025] Fig. 9 The sensing curve of PPy@PVA3 conductive fiber membrane sensor for 5000 seconds under 20% deformation. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention, and those skilled in the art in this field can make some non-essential improvements and adjustments based on the content of the above invention.

[0027] Example 1

[0028] Preparation of PVA spinning fiber membrane: Prepare 0.1g / ml PVA deionized water solution and inject it into a syringe with a stainless steel needle (spinneret). Figure 1 As shown in a, a grounded aluminum foil (size 30cm×50cm) was used as a receiving plate, a DC voltage of 20.0kV (DW-P303-1ACDFO) was applied to the spinneret, the distance between the spinneret and the receiver was fixed at 20.0cm, and the feed of the PVA solution was controlled by a syringe peristaltic pump (SPLab-02-E) at a set rate of 3μl / min for electrospinning. After 12 hours of spinning, a large area of ​​uniform pure PVA spinning fiber membrane (Pure PVA) was obtained ( Figure 1 b). In order to improve its water solubility resistance and mechanical properties, the Pure PVA fiber was placed at 120°C for annealing for 5 hours and then set aside.

[0029] Example 2

[0030] Preparation of PPy@PVA conductive fiber membrane: The preparation of PPy@PVA conductive fiber membrane adopts in-situ polymerization method, which is divided into two steps: adsorption and oxidation. Adsorption stage: Cut pure PVA spinning membrane 1cm×4cm, place it in a Py / DMF solution with a volume ratio of 10%, and soak it at 60℃ for 20 minutes. Oxidation stage: Place the pure PVA spinning membrane adsorbed with Py in a saturated ferric chloride solution at 60℃. After polymerization for 2 hours, take it out, wash it, and dry it for use. The sample changes from white to gray ( Figure 1c), named PPy@PVA1. In order to regulate the mechanical and electrical properties of PPy@PVA fiber membrane, this polymerization was repeated 4 times on this basis to prepare a series of black PPy@PVA composite spinning membranes, which were defined as PPy@PVA2, PPy@PVA3, PPy@PVA4, and PPy@PVA5.

[0031] 1. Chemical composition characterization

[0032] Figure 2 This is the infrared spectrum of PPy before and after polymerization on the surface of PVA fiber. For Pure PVA fiber, the infrared spectrum is between 3050 and 3450 cm -1 The large and broad bands in the region are attributed to the stretching vibration of hydroxyl groups in the intramolecular and intermolecular hydrogen bonds. -1 The absorption peak observed at 2 Stretching vibration peak, 1437 cm -1 The band is attributed to the characteristic bending vibration peak of C–H. After depositing PPy once, in the infrared spectrum of PPy@PVA1 film, 1533 cm –1 and 1170cm –1 The characteristic peaks of pyrrole ring vibration and =CH stretching vibration appeared at 1680cm –1 and 1294cm -1 The C═C and CN bond stretching vibration peaks in the pyrrole ring appeared at 1025 cm -1 The N–H in-plane bending vibration peak appeared at the surface of the PVA fiber. The above results show that after one in-situ polymerization, Py components appeared on the surface of PVA fibers. With the increase of polymerization times, the two characteristic peaks of PPy (1680cm -1 and 1294cm -1 ) gradually increased, while the characteristic peaks of PVA such as -OH and -CH 2 The stretching vibration of PVA gradually disappears. This is because: with the increase of polymerization times, the content of polypyrrole increases, and the generated PPy film becomes thicker and thicker, which prevents the detection of the internal PVA signal, so the PVA signal intensity gradually weakens.

[0033] Raman spectroscopy measurements further confirmed the polymerization of PPy on the PVA surface ( Figure 3 ). Since PVA is not sensitive to Raman signals, there is no obvious Raman scattering peak on the Raman curve of Pure PVA. After grafting PPy, the Raman peak of the pyrrole ring appears in the Raman spectrum of PPy@PVA. -1 The scattering peak at 1580cm is attributed to the deformation vibration of the pyrrole ring; -1 and 1400cm –1The scattering peaks are attributed to the C═C and CN stretching vibrations of pyrrole; 1319 cm –1 The scattering peak at 1050cm is attributed to the NH in-plane deformation vibration; –1 The scattering peak at is attributed to the CH in-plane bending vibration of the pyrrole ring. As with infrared, with the increase of polymerization times, the peak signal of the pyrrole ring becomes stronger and stronger, indicating that the pyrrole content gradually increases.

[0034] 2. Morphology Characterization

[0035] The surface of pure PVA spun fibers is smooth, with a diameter between 0.17-0.25 microns and an average diameter of 0.22 microns ( Figure 4 a). After impregnation with Py, in-situ polymerization of PPy, etc., a granular film grows on the surface of PVA spinning. According to the aforementioned IR, Raman, XPS analysis, and the energy spectrum test results of the SEM here (the N element content is 18.67, 22.27, and 22.80%, respectively), the film is a PPy granular film. According to the aforementioned hydrogen bond adsorption mechanism, the possible growth process of the PPy granular film is as follows: PVA uses the surface hydroxyl groups to form hydrogen bonds with the amine groups in the pyrrole molecules, and a large amount of pyrrole is bound to the surface of the PVA fiber; in FeCl 3 Under the catalysis of , the pyrrole molecules on the surface of PVA fiber and in the solution are continuously oxidized to generate PPy, which gathers on the surface of PVA fiber in the form of tiny particles. Therefore, the optical color of PPy@PVA fiber membrane changes from white of PPy fiber membrane to gray of PPy@PVA1 fiber membrane, and then to black; with the continuous polymerization of PPy, the diameter of PPy@PVA fiber continues to increase. PPy@PVA1( Figure 4 b) PPy@PVA3( Figure 4 c) PPy@PVA5( Figure 4 The average fiber diameters of the PVA fibers (d) are 0.52, 0.78, and 0.92 μm, respectively. Compared with the original PVA spinning diameter, they increase by 0.30, 0.56, and 0.70 μm, respectively, with increases of 136.3, 254.5, and 318.2%. The increased PPy content can significantly affect the mechanical and electrical properties of the PPy fiber membrane.

[0036] 3. Mechanical properties characterization

[0037] The unannealed PVA spun fiber membrane has poor mechanical properties, high water solubility, and cannot undergo aqueous polymerization. After annealing at 120°C for 5 hours, the crystallinity of PVA was significantly improved, and intramolecular hydrogen bonds were also formed. Therefore, the mechanical properties of the PVA spun fiber membrane were also significantly improved, and it has good water solubility and can withstand 60°C water without dissolving. Figure 5a and 5b record the stress-strain curve and elastic modulus of PVA-related fiber membranes, respectively. The elastic modulus of PurePVA spun fiber membrane is 3.12MPa, and the elongation at break is 92.2%, showing good mechanical properties. With the increase of polymerization times, PPy is deposited thicker on PVA fibers, and the elastic modulus of PPy@PVA fiber membrane increases, which are 3.55, 4.92, 7.71, 7.88, and 8.78MPa ( Figure 5 b, Table 1); the elongation at break decreased, and the data decreased from 92.2% of Pure PVA spun fiber membrane to 65.7, 60.4, 33.2, 23.9, and 18.8% of Py@PVA fiber membrane ( Figure 5 a, Table 1). The reason for the increase in elastic modulus and the decrease in elongation at break is that due to the strong hydrogen bonding force between PPy particles and PVA fibers, the rigid PPy chains limit the elongation of PVA chains and increase the elastic modulus of PPy@PVA fibers.

[0038] Table 1 Mechanical properties data of PVA related fiber membranes

[0039]

[0040]

[0041] 4. Electrical performance characterization

[0042] Since a conductive path can be formed between PPy particles, the PPy@PVA fiber has certain conductive properties. Figure 6 The relationship between the number of in-situ polymerizations and the resistance and conductivity is shown. The results show that as the number of polymerizations increases, the surface resistance of the PPy@PVA composite fiber membrane decreases and the volume conductivity increases. The spinning fiber membrane of pure PVA is an insulator, and its resistance and conductivity cannot be measured using a four-probe resistance tester. After one PPy deposition, the PPy@PVA1 obtained shows certain conductivity, but the tested surface resistance is relatively high, at 38kΩ / sq. After 2-5 PPy depositions, more and more PPy particles are fixed on the surface of the PVA fiber, and a large number of conductive particles are connected to each other to form a network of electron transmission pathways. The detected surface resistance decreases and the volume conductivity increases. Among them, the detected surface resistance of PPy@PVA5 obtained after 5 PPy depositions is 0.63kΩ / sq and the volume conductivity is 0.0345S / cm, showing a high degree of conductivity.

[0043] 5. Sensor performance characterization

[0044] Since the PPy particles are firmly fixed on the surface of the PVA fiber, when the PVA is deformed, the distance between the PPy particles changes as they deform, which is reflected in the resistance of the test. Therefore, the PPy@PVA fiber film can be used as a resistive strain / stress sensor. In order to evaluate the sensor performance, we used a flexible electronic tester to test the sensing performance of PPy@PVA. The initial spacing of the sample test was 30mm and the stretching speed was 1mm / s. The results are listed in Figure 7-9 and Table 2. Figure 7 The relative resistance change rate (ΔR / R) of the PPy@PVA sensor is shown when the deformation is 5%. 0 , ΔR is the resistance difference on the stretching curve, R 0 is the initial resistance). It can be seen from the figure that during the periodic stretching process, as the number of polymerizations increases, the resistance change rate of the PPy@PVA sensor shows a trend of first increasing and then decreasing. The maximum value appears on PPy@PVA3, and its relative resistance change rate reaches the maximum value of 9.47%. This change trend is related to the change in the contact tightness between the PPy particles on the surface of the PVA fiber during the stretching process. The resistance change rates of PPy@PVA1 and PPy@PVA2 are small. This is because after 1-2 polymerizations, the polypyrrole content of the PPy@PVA film is relatively low, and the contact between the PPy particles is not very close, R 0 The value is large, resulting in a small relative resistance change rate. After 5 polymerizations, the relative resistance change rate of PPy@PVA5 decreased to 5.09%. This is because a large amount of polypyrrole is attached to the fiber surface, forming a multi-channel conductive connection. When the material is deformed, the fiber membrane still maintains a high conductivity, and the ΔR change is small, so the resistance change rate is low. In addition, it can be seen from the figure that with the extension of working time, the sensing signal of PPy@PVA1 drifts and becomes unstable. This is because the modulus of PPy@PVA1 is low, the material has high viscoelasticity, and there is mechanical loss during the working process, resulting in creep. With the increase in the number of polymerizations, a large number of PPy particles are attached to the surface of the PVA fiber, which increases the modulus of the PPy@PVA fiber membrane and reduces the viscoelasticity. Therefore, the more stable the response signal of the sensor, the smaller the signal drift. Therefore, for the PPy@PVA sensor, the higher the PPy content, the smaller the creep, and the less obvious the signal drift phenomenon.

[0045] Figure 8 The relationship between the relative resistance change rate and deformation of the five groups of PPy@PVA sensors was compared, and the relevant data are summarized in Table 2. Since the ΔR value increases rapidly with the increase of tensile deformation, the sensitivity of all sensors (GF = (ΔR / R 0) / ε, ε is the deformation variable) all show a trend of increasing with the increase of deformation. For PPy@PVA1, its sensing curve can be approximately divided into three linear regions: in the range of 0-31%, there is a high linear relationship between the relative resistance change rate and the deformation variable, and the deviation value is only 0.2%. The sensitivity of this region is relatively small, only 0.91; for the 32%-64% region, the sensitivity linearity decreases and the sensitivity increases; in the 64%-65.7% deformation range, the sensitivity increases to 21.74, and the linear deviation is 90.3%. This unstable sensing curve is due to the large R of PPy@PVA1. 0 and low modulus. The former causes low sensitivity; the latter produces high viscoelasticity, resulting in large mechanical losses during stretching, so the sensor's sensing signal drifts greatly and the linear sensing area accounts for a small proportion. There is a large linear area on the sensing curves of the PPy@PVA2 and PPy@PVA3 composite fiber membranes. Among them, the linear area of ​​PPy@PVA2 is 0-60%, and the sensitivity is 1.72; while the linear area of ​​PPy@PVA3 is 0-33%, and the sensitivity is 1.85. It should be noted that the PPy@PVA3 sensor has a high degree of linearity, and the deviation after linear fitting is only 0.9%. When the deformation is 5, 10, 15, 20, 25, and 30%, the resistance changes are 9.07, 18.55, 27.81, 37.32, 46.47, and 56.01%, respectively, showing a high linear relationship. Compared with other electrospun membrane sensors, such as PANI / PVDF nanofiber membrane with a linear deformation area of ​​0-22% and a sensitivity between 0.045-0.84, and TPU / PEDOT:PSS nanofiber with a linear deformation area of ​​0-40% and a sensitivity between 0-20%, our PPy@PVA2 and PPy@PVA3 sensors show an ideal linear deformation area and high sensitivity, and are more suitable for making flexible displacement sensors with large deformations. For PPy@PVA4 and PPy@PVA5, due to the deposition of too many PPy particles, the stretching of the material is limited and large deformation cannot be produced, so their linear deformation area is small. At the same time, the high density of PPy particles makes the ΔR value smaller during the stretching process and reduces the sensitivity.

[0046] Taking PPy@PVA3 as an example, the stability of PVA fiber sensor was tested. Fig. 9The sensing curve of PPy@PVA3 with a deformation of 20% and cyclic stretching within 5000 seconds is shown. The results show that the resistance change rate is basically maintained at about 37% within 1000 cycles; there is no obvious drift in the profile of the sensing curve (except for the initial stretching, when the sensing curve has a short drift due to polymer creep), showing a very stable sensing performance. This is because the PPy conductive network is periodically destroyed and reconstructed during the stretching and contraction of the conductive film. When the deformation range is fixed, the destruction and reorganization of the conductive network are fixed, so the sensing signal can remain stable for a long time.

[0047] Table 2 Sensing data of PPy@PVA related fiber membranes

[0048]

[0049]

[0050] Compared with the prior art, the present invention is creative in the following aspects:

[0051] (1) PPy@PVA spinning fiber membrane was prepared by electrospinning technology and in situ polymerization technology. The preparation technology is simple and the material cost is low.

[0052] (2) PPy and PVA are tightly bonded and do not separate.

[0053] (3) PPy@PVA spun fibers have large deformation and excellent sensing performance, and there is a highly linear relationship between the resistance change and deformation.

[0054] (4) PPy@PVA spun fiber sensor has high stability and strong durability.

[0055] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a PPy@PVA conductive fiber membrane, characterized in that: The PPy@PVA conductive fiber membrane is obtained by electrostatic spinning technology to obtain a PVA fiber membrane, and polypyrrole PPy is polymerized and grown on the fiber surface to obtain a PPy@PVA conductive fiber membrane. The preparation of the PPy@PVA conductive fiber membrane adopts an in-situ polymerization method, which is divided into two steps of adsorption and oxidation. First, the PVA fiber membrane is immersed in a pyrrole / DMF solution to adsorb pyrrole monomer, and then ferric chloride is used to oxidize and in-situ polymerize to generate polypyrrole; the adsorption step is as follows: the pure PVA spinning membrane is placed in a Py / DMF solution with a volume ratio of 10%, and immersed and adsorbed at 60°C for 20 minutes; the oxidation step is as follows: the pure PVA spinning membrane adsorbed with Py is placed in a saturated ferric chloride solution at 60°C, and after polymerization for 2 hours, it is taken out, washed, and dried to obtain a PPy@PVA1 sample, and the adsorption-oxidation operation is repeated 1-4 times to obtain PPy@PVA2, PPy@PVA3, PPy@PVA4, and PPy@PVA5 samples.

2. The method for preparing the PPy@PVA conductive fiber membrane according to claim 1, characterized in that: The PVA fiber membrane obtained by electrospinning has an optical color of white, a uniform fiber diameter, an average diameter of 0.22 microns, a smooth surface and no Taylor cone morphology; the fiber diameter of the PPy@PVA conductive fiber membrane is between 0.52 and 0.92 microns, which is an increase of 0.30 to 0.70 microns relative to the original PVA spinning diameter, an increase of between 136.3 and 318.2%.

3. The method for preparing the PPy@PVA conductive fiber membrane according to claim 1, characterized in that: The specific preparation method of the PVA spun fiber membrane is as follows: prepare a 0.1 g / ml PVA deionized water solution, inject it into a syringe with a stainless steel needle, use a grounded aluminum foil as a receiving plate, apply a DC voltage of 20.0 kV to the spinneret, fix the distance between the spinneret and the receiver to 20.0 cm, use an injection peristaltic pump to control the feed of the PVA solution, set the rate to 3 μL / min, and perform electrostatic spinning; after 12 hours of spinning, a uniform PVA spun fiber membrane is obtained; in order to improve the water solubility and mechanical properties of the PVA spun fiber membrane, the PVA spun fiber membrane is placed at 120°C, annealed for 5 hours, and set aside.

4. The method for preparing the PPy@PVA conductive fiber membrane according to claim 1, characterized in that: After three times of PPy deposition, the obtained PPy@PVA3 fiber membrane has an average tensile modulus of 7.71 MPa, a surface resistivity of 840 Ω / sq, and a conductivity of 32.1 mS / cm.

5. Application of the PPy@PVA conductive fiber film prepared according to any one of the preparation methods described in claims 1-4 in strain sensors.

6. The use according to claim 5, characterized in that: Within 30% deformation, the linear deviation of the resistance change and deformation of the PPy@PVA3 fiber membrane sensor is only 0.9%, and the linear value is 1.

85. When the deformations are 5, 10, 15, 20, 25, and 30%, the resistance changes are 9.07, 18.55, 27.81, 37.32, 46.47, and 56.01%, respectively.

7. The use according to claim 6, characterized in that: The PPy@PVA3 fiber membrane sensor signal is stable. During the 1000 stretching experiments, except for the initial stage, the sensing signal profile did not drift significantly for 5000 seconds, and the calculated sensitivity did not change significantly.

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