Conductive composite material and method for producing the same

Abstract

The present application relates to the technical field of composite materials, in particular to a conductive composite material and a preparation method thereof.The specific technical scheme is as follows: a preparation method of a conductive composite material, polyurethane is electrospun to form a polyurethane film, the film is soaked in FeCl3.6H2O and then dried, then the film is soaked in a pyrrole solution, an oxidant is added after a certain time of soaking, and the film is washed and dried after the reaction is completed.The TPU nanofiber film prepared by electrospinning has a special micro-nano structure, so that it has the characteristics of high roughness, high specific surface area, high porosity and the like, and shows its unique advantages in flexible sensors.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, and specifically to a conductive composite material and its preparation method. Background Technology

[0002] Thermoplastic polyurethane (TPU) is a polymer material composed of alternating rigid and flexible segments. The abundant urethane groups in its soft segments endow the material with excellent elasticity, while the urea groups in its rigid segments contribute high mechanical strength and abrasion resistance. Simultaneously, its microphase-separated structure gives it good biocompatibility, making it a preferred environmentally friendly material for flexible matrices. Polypyrrole (PPy), as an important conductive polymer, has attracted widespread attention due to its simple preparation, high conductivity, good environmental stability, and non-toxicity.

[0003] Flexible composite sensors consist of a flexible matrix and conductive fillers. Changes in the distance of the conductive fillers cause changes in the output resistance or capacitance, thereby enabling the monitoring of sensitive behavior under different external fields. Flexible conductive polymer composites (FCPCs) can be prepared by embedding conductive fillers into a flexible matrix. FCPC-based resistance sensors have simple structural design and manufacturing processes, low cost, and are easy to industrialize.

[0004] The low solubility and inherent brittleness of conductive polymers, along with the low specific surface area and mechanical strength issues of pure PPy, limit their sensing applications. The conductive layer (PPy) is brittle, and continuous conductive layers are prone to breakage during deformation, leading to a decrease in conductivity. PPy / TPU films prepared by casting have a conductivity of 1.93 S / m, a sensing range of 0-110%, a sensitivity of 104.4 (60-80%), and a response recovery time of 470 / 440 ms. Conductive composite materials prepared by continuous film fabrication severely limit their application in wearable strain sensors due to their low conductivity, low sensitivity, long response recovery time, poor biocompatibility, poor air permeability, rigid structure, and large thickness. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a conductive composite material and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention discloses a method for preparing a conductive composite material, which involves electrospinning polyurethane to form a polyurethane film, immersing it in FeCl3·6H2O and then drying it, immersing it in a polypyrrole solution, adding an oxidant after immersion for a certain period of time, and then washing and drying it after the reaction is completed.

[0008] Preferably, the conditions for electrospinning the polyurethane are: solvent ratio DMF:THF = 1:1 to 5:1, polyurethane spinning solution concentration 10 to 30%, spinning distance 10 to 20 cm, spinning voltage 5 to 30 kV, injection speed 0.5 to 1.5 mL / h, and spinning time 1 to 8 h.

[0009] Preferably, the concentration of FeCl3·6H2O is 0.05–0.30 mol / L, and the polyurethane membrane is reacted in FeCl3·6H2O at 70–100 °C for 60–150 min.

[0010] Preferably, the concentration of the pyrrole solution is 0.05–0.25 mol / L.

[0011] Preferably, the oxidant is FeCl3·6H2O with a concentration of 0.05–0.25 mol / L.

[0012] Preferably, the reaction time after adding the oxidant is 30 to 150 minutes.

[0013] Accordingly, the conductive composite material prepared according to the above method.

[0014] The present invention has the following beneficial effects:

[0015] The electrospun membrane in this invention is a three-dimensional structure built from countless loosely connected micro- and nano-sized fibers. It can respond to external strain changes through structural variations between fibers, while the conductive layer remains intact without breakage or peeling. Conductive nanoparticles are wrapped around the fiber surface. From a microscopic perspective, the breakage of the thin conductive network organized by the conductive nanofiller under stretching is caused by the slippage of the nanofiller due to the weak interfacial bonding between the nanofiller and the stretchable polymer substrate. Compared to continuous films formed by casting, this method reduces the possibility of conductive network breakage and damage under large or repeated strain. The unique fibrous network structure of electrospinning combines a tough matrix with a brittle conductive layer. TPU nanofiber membranes prepared by electrospinning possess unique micro- and nanostructures, giving them characteristics such as high roughness, high specific surface area, and high porosity. These characteristics demonstrate their unique advantages in flexible sensors, including excellent tensile properties (0-506.15%), high electrical conductivity (79.69 S / m), high sensitivity (GF=2205, 60-80%), sensitivity to small strains (1%), excellent air permeability, fast response recovery (130 / 170 ms), large active area, and tight bonding to irregular surfaces. Attached Figure Description

[0016] Figure 1 This is a scanning electron microscope image of the FeOOH / PPy / TPU composite fiber membrane prepared in Example 3;

[0017] Figure 2 In order to be in Figure 1 Based on scanning electron microscope images at different magnifications;

[0018] Figure 3 In order to be in Figure 1 Based on scanning electron microscope images at different magnifications;

[0019] Figure 4 The graph shows the change in relative resistance of the sensor made from the FeOOH / PPy / TPU composite fiber membrane prepared in Example 3 as a function of strain.

[0020] Figure 5 The graph shows the change in relative resistance (ΔR / R0) of the FeOOH / PPy / TPU composite fiber membrane prepared in Example 3 under small (0-5%) strain periodic tensile release.

[0021] Figure 6 The image shows the air permeability test results of the FeOOH / PPy / TPU composite fiber membrane prepared in Example 3.

[0022] Figure 7 The response recovery time diagram of the FeOOH / PPy / TPU composite fiber membrane prepared in Example 3 at 1% strain. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0025] This invention discloses a method for preparing a conductive composite material, specifically including the following steps:

[0026] (1) Preparation of polyurethane (TPU) electrospun film. The spinning conditions are as follows: solvent ratio DMF (dimethylformamide): THF (tetrahydrofuran) = 1:1 to 5:1, polyurethane spinning solution concentration 10 to 30%, spinning distance 10 to 20 cm, spinning voltage 5 to 30 kV, injection speed 0.5 to 1.5 mL / h, and spinning time 1 to 8 h.

[0027] (2) Preparation of FeOOH-TPU composite material: The TPU film was immersed in 0.05-0.30 mol / L FeCl3·6H2O and reacted at 70-100℃ for 60-150 min, then washed and dried. Among them, Fe... 3+ β-FeOOH (Fe) is deposited on polyurethane fibers via in-situ thermal hydrolysis. 3+ +H₂O→β-FeOOH).

[0028] (3) Preparation of FeOOH-PPy-TPU conductive composite material: The FeOOH-TPU composite material was immersed in a Py (pyrrole) solution with a concentration of 0.05-0.25 mol / L for a certain period of time (30-150 min). Then, an oxidant (FeCl3·6H2O, concentration of 0.05-0.25 mol / L) was added and reacted for 30-150 min. The mixture was then washed and dried.

[0029] The present invention will be further described below with reference to specific embodiments.

[0030] The experimental parameters for each step in the preparation of the conductive composite material are shown in Table 1 below, and the properties of the prepared conductive composite material are shown in Table 2.

[0031] Table 1 Parameters of each embodiment

[0032]

[0033] Table 2 Performance of each conductive composite material

[0034] Tensile strength (MPa) 3.94 3.21 3.14 3.32 3.18 Elongation at break (%) 433.09 389.62 397.09 445.89 506.15 <![CDATA[Toughness value (MJ / m 3 )]]> 10.33 7.92 7.74 9.42 9.70 Electrical conductivity (S / m) 45.09 46.78 49.44 79.69 72.38

[0035] The scanning electron microscope (SEM) image of the conductive composite material prepared in Example 3 is shown below. Figure 1 As shown, Figure 2 and Figure 3 These are scanning electron microscope (SEM) images of conductive composite materials at different magnifications. As can be seen from the images, polypyrrole nanospheres are uniformly attached to the fiber surface to form a conductive shell, and the uniform insertion and modification of β-FeOOH and polypyrrole have no negative impact on the structure of electrospun polyurethane nanofibers.

[0036] The relative resistance of the sensor made from the conductive composite material (FeOOH / PPy / TPU composite fiber membrane) prepared in Example 3 changes with strain as follows: Figure 4 As shown in the figure, the sensitivity of the β-FeOOH / PPy / TPU composite fiber membrane increases significantly with increasing elongation. GF calculations indicate that this sensor exhibits good sensitivity and sensing range under both small and large deformations.

[0037] The change in relative resistance (ΔR / R0) of the FeOOH / PPy / TPU composite fiber membrane prepared in Example 3 under small (0-5%) strain cyclic tensile release is as follows: Figure 5 As shown, Figure 5 The sensing performance under five tensile release cycles at different strains was described. The intensity of the response signal increased with increasing strain. The FeOOH / PPy / TPU composite fiber membrane could detect a complete and obvious sensing signal under small deformation (1%-5%).

[0038] The air permeability of the FeOOH / PPy / TPU composite fiber membrane prepared in Example 3 is as follows: Figure 6 As shown, a self-built device was used to test the breathability of the FeOOH / PPy / TPU stretchable fiber membrane. The device consisted of two transparent PET bottles and the fiber membrane. The bottom bottle contained water at 37°C to simulate human skin sweating. After 5 minutes, condensation of water vapor was clearly observed on the inner wall of the bottle above the fiber membrane and at the top of the bottle, indicating that the fiber membrane is breathable.

[0039] The response recovery time of the FeOOH / PPy / TPU composite fiber membrane prepared in Example 3 under 1% strain is as follows: Figure 7 As shown. When the sensor is in normal condition, a 1% strain (at a rate of 400 mm / s) is applied, and after a dwell time of 5 s, the sensor returns to its state before the strain, with a response time of 130 ms and a recovery time of 170 ms.

[0040] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a conductive composite material, characterized in that: Polyurethane is electrospun into a polyurethane membrane, which is then soaked in FeCl3•6H2O and dried. Next, it is soaked in a pyrrole solution for a certain period, followed by the addition of an oxidizing agent to react. After the reaction is complete, the membrane is washed and dried. The concentration of FeCl3•6H2O is 0.05–0.30 mol / L. The polyurethane membrane is reacted in FeCl3•6H2O at 70–100 °C for 60–150 min. The oxidizing agent is FeCl3•6H2O with a concentration of 0.05–0.25 mol / L. The conditions for polyurethane electrospinning are as follows: solvent ratio DMF:THF = 1:1 to 5:1, polyurethane spinning solution concentration 10 to 30%, spinning distance 10 to 20 cm, spinning voltage 5 to 30 kV, injection speed 0.5 to 1.5 mL / h, and spinning time 1 to 8 h.

2. The preparation method according to claim 1, characterized in that: The concentration of the pyrrole solution is 0.05–0.25 mol / L.

3. The preparation method according to claim 1, characterized in that: After adding the oxidant, the reaction time is 30–150 min.

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