CN104458815A - High-molecular gas sensitive material as well as preparation method and application thereof - Google Patents

Abstract

The invention belongs to the field of gas sensitive materials, and particularly relates to a high-molecular gas sensitive material as well as a preparation method and application thereof. The invention provides the high-molecular gas sensitive material which is a composite material having a conductive network structure and prepared from electro-woven nylon nanometer fiber films modified by conductive fillers. The high-molecular gas sensitive material disclosed by the invention can be used for solving the problem of impossible coexistence of high responsibility and good reversibility and is quite high in responsibility, response rate, resilience speed and recycle rate.

Description

Polymer gas sensitive material and its preparation method and application

technical field

The invention belongs to the field of gas-sensing materials, and in particular relates to a polymer gas-sensing material and its preparation method and application.

Background technique

Advanced chemical gas detection materials need to have low detection limit, high responsivity and response rate, good recovery and good physical properties (flexibility, lightness, etc.). Traditional chemical gas-sensitive materials often use semiconductor oxides as conductive fillers, and rigid materials such as quartz and ceramics as substrates. This inorganic composite material has a high response to chemical gases, but its high processing temperature and poor flexibility greatly limit the application of this material; in addition, this sensitive material generally has a low response to organic gases.

Conductive polymer composite (CPC) refers to a multi-phase composite system with conductive function obtained by adding various conductive fillers through dispersion, mixing and molding with polymer materials as the matrix. It has many excellent properties of polymer materials and can The electrical, mechanical and other properties of the material can be adjusted according to the needs of use in a large range, and the cost is low, easy to form and mass-produced, so it has been widely valued by people. CPC has many unique physical phenomena, such as resistance sensitivity to temperature, pressure, and gas concentration, current-voltage nonlinear behavior, current noise, and frequency dependence of charge dielectric properties. This makes the conductive polymer composite material have high practical application value as a functional polymer material, and also has high theoretical research value.

The good physical properties of CPC and its sensitivity to organic gases have made it widely used in the field of chemical gas detection. Among them, the emergence of processing technologies such as spin coating and inkjet printing in recent years has enabled nanomaterials (carbon nanotubes (CNTs), graphene (GNPs)) to be well distributed on different flexible substrates (polyethylene terephthalate Ethylene glycol formate, polyamide, paper, etc.); lower processing temperature and simple processing technology make these methods have been widely used in the production of flexible gas-sensing devices. For example, "Journal of The American Chemical Society" disclosed a preparation method of an advanced toxic gas detection device in a document titled "Flexible, All-Organic Chemiresistor for Detecting Chemically Aggressive Vapors" in 2012 134 (4553): Ink-printing CNTs distributed on cellulose substrates. This composite material shows excellent selectivity and stability to harmful gases (Cl ₂ , NO ₂ ), but the slow response rate has become a common problem of this type of material, which greatly limits the flexible substrate composite material. Application in organic gas detection.

For CPC gas-sensitive materials, the contradiction between responsivity and recovery has always existed: the strong interaction between chemical gases and composite materials is the cause of high responsivity and high response rate; however, the strong interaction greatly prolongs the material’s lifetime. The recovery time will even destroy the structure of the material and reduce the reuse rate of the material. Therefore, how to improve the responsivity, response rate and recovery rate of the material has always been an important topic in the field of CPC gas-sensitive materials.

Contents of the invention

Aiming at the above defects, the present invention provides a new polymer gas sensitive material, which solves the problem that high responsivity and good recovery cannot be possessed at the same time; it has prepared a material with high responsivity, response rate, recovery rate and reusability. Very high polymer gas sensitive material.

The technical scheme that the present invention takes is as follows:

The first technical problem to be solved by the present invention is to provide a polymer gas-sensing material, which is a composite material with a conductive network structure formed of conductive fillers and electrospun nylon nanofiber membranes.

The electrospun nylon nanofiber membrane is selected from the group consisting of electrospun nylon 6 (PA6) nanofiber membrane, electrospun nylon 66 (PA66) nanofiber membrane, electrospun nylon 1010 (PA1010) nanofiber membrane, electrospun nylon 610 (PA610) At least one of nanofiber membranes or electrospun nylon 1212 (PA1212) nanofiber membranes; the conductive filler is selected from at least one of graphene nanosheets, carbon black, carbon fibers or carbon nanotubes. In the present invention, the electrospun nylon nanofiber membrane is an electrospun nylon nanofiber membrane; the electrospun nanofiber membrane is a fiber membrane prepared by electrospinning.

Preferably, the thickness of the electrospun nylon nanofiber membrane is 0.3-3 μm, the average diameter of the fiber membrane is 100-400 nm, and the pore diameter of the fiber membrane is 1-6 μm.

Further, the preparation method of the electrospun nylon nanofiber membrane is as follows: firstly mix nylon and formic acid to prepare a spinning solution with a mass concentration of 15-25%; Fiber membrane; wherein, the electrospinning conditions are: the distance between electrodes is 15-30cm, the voltage is 15-35KV, and the spinning time is 1.5-5 hours.

Preferably, the method for forming a composite material between the conductive filler and the electrospun nylon nanofiber film is: the conductive filler is distributed on the surface of the electrospun nylon nanofiber by means of ultrasonic dispersion, and the method of ultrasonic dispersion is: first mix the conductive filler with deionized water A conductive filler dispersion liquid with a mass concentration of 0.03-0.2% is prepared, and then the electrospun nylon nanofiber membrane is placed in the conductive filler dispersion liquid for ultrasonic treatment for 2-10 minutes.

Preferably, the mass concentration of the conductive filler dispersion is 0.1%.

More preferably, the average size of the conductive filler in the conductive filler dispersion should not be greater than 5 μm.

Preferably, the electrospun nylon nanofiber membrane is a PA6 nanofiber membrane, and the conductive filler is a graphene nanosheet.

More preferably, the number of layers of the graphene nanosheets is less than 30, the thickness is less than 20nm, and the purity is greater than 99.5wt%.

Preferably, when the electrospun nylon nanofiber membrane is a PA6 nanofiber membrane, the preparation method of the PA6 nanofiber membrane is: first mix PA6 with formic acid, and stir at 65-75°C for 1-2.5 hours to obtain a PA6 solution ; Then the resulting PA6 solution was prepared by electrospinning PA6 nanofiber membrane.

More preferably, when the electrospun nylon nanofiber membrane is a PA6 nanofiber membrane, the electrospinning conditions are: the distance between electrodes is 25cm, the voltage is 30KV, and the spinning time is 3 hours; covered rollers.

The second technical problem to be solved by the present invention is to provide a preparation method for the above-mentioned polymer gas-sensing material. The electrospun nylon nanofiber membrane is placed in a conductive filler dispersion and ultrasonically treated for 2-10 minutes, and then washed and dried to obtain a polymer gas-sensing material. Gas-sensitive material; wherein, the preparation method of the conductive filler dispersion is: after mixing the conductive filler and deionized water, ultrasonically disperse in an environment of 0-5°C for 1.5-3.5 hours, and the ultrasonic power is 285W-570W.

Preferably, in the above method, the electrospun nylon nanofiber membrane is placed in the conductive filler dispersion and the ultrasonic treatment is performed in an ice-water bath.

Preferably, in the above method, the electrospun nylon nanofiber membrane is placed in the conductive filler dispersion solution for ultrasonication, rinsed repeatedly with deionized water for 2-5 times, and then dried naturally to obtain the polymer gas-sensitive material.

The third technical problem to be solved by the present invention is to provide the use of the above-mentioned polymer gas-sensing material: the polymer gas-sensing material of the present invention is used for detecting polar gases.

Further, the polar gas includes formic acid, acetic acid, methanol, ethanol or ammonia.

Beneficial effects of the present invention:

The invention uses conductive filler and nylon as raw materials, and uses electrospinning and ultrasonic dispersion to distribute the conductive filler on the surface of the nylon fiber to form a good conductive network and prepare a novel nanometer gas-sensitive material.

The present invention has the following advantages:

1. The conductive filler/nylon composite material of the present invention is used as a gas-sensitive material. Since both the conductive filler and the electrospun fiber have a smaller size, the composite material has a large specific surface area and porosity, and can interact rapidly with the external gas atmosphere ; Therefore, the responsivity, response rate, recovery rate and reuse rate of the composite material are ingeniously improved at the same time.

2. Since the conductive filler is attached to the surface of the electrospun nylon fiber, the conductivity of the composite material is greatly enhanced.

3. The thickness of the gas-sensitive material obtained by the method of the present invention is only 1.7 μm, which is soft and light.

4. The processing method of the present invention is simple. Using the processing method of the present invention, the flexibility of the electrospun nylon nanofiber membrane is retained, and the application range of the conductive filler/nylon composite material is greatly improved.

Description of drawings:

Fig. 1: Fig. 1 a is the scanning electron microscope (SEM) picture of the obtained electrospun PA6 nanofiber of the embodiment of the present invention 1, Fig. 1 b is the SEM picture of the GNPs/PA6 composite material obtained in the embodiment 1, Fig. 1c, Fig. 1 e are GNPs/ Partial SEM pictures of PA6 composite materials, Figure 1d and Figure 1f are enlarged views of Figure 1c and Figure 1e, respectively.

Figure 2: Time-resistance curves of GNPs/PA6 under different concentrations of formic acid gas atmosphere.

Figure 3: Time-resistance curves of GNPs/PA6 under 500ppm of different organic gas atmospheres.

Figure 4: The response time and recovery time of GNPs/PA6 to different organic gases under the atmosphere of 500ppm different organic gases.

Figure 5: The response intensity of GNPs/PA6 to different organic gases under the atmosphere of 500ppm different organic gases.

Detailed ways

The first technical problem to be solved by the present invention is to provide a polymer gas-sensing material, which is a composite material with a conductive network structure formed by modifying electrospun nylon nanofiber membranes with conductive fillers. The conductive filler can be evenly distributed on the surface of the electrospun nylon nanofiber membrane to form a material with a conductive network structure.

The second technical problem to be solved by the present invention is to provide a preparation method for the above-mentioned polymer gas-sensing material. The electrospun nylon nanofiber membrane is placed in a conductive filler dispersion and ultrasonically treated for 2-10 minutes, and then washed and dried to obtain a polymer gas-sensing material. Gas-sensitive material; wherein, the preparation method of the conductive filler dispersion is: after mixing the conductive filler and deionized water, ultrasonically disperse in an environment of 0-5°C for 1.5-3.5 hours, and the ultrasonic power is 285W-570W.

The third technical problem to be solved by the present invention is to provide the use of the above-mentioned polymer gas-sensing material: the polymer gas-sensing material of the present invention is used for detecting polar gases.

In the present invention, the electrospun nylon nanofiber membrane is used as the base, and then the conductive filler is evenly distributed on the surface of the electrospun nylon nanofiber membrane to form a conductive network structure.

The present invention proposes to use electrospun nylon nanofiber membrane as the base, and modify electrospun nylon nanofibers with conductive fillers to increase the contact area between the composite material and the external atmosphere by increasing the specific surface area of the composite material, thereby shortening the response of the composite material to the external atmosphere Time, improve the responsiveness and response rate of the composite material to the external atmosphere. The large porosity of electrospun nylon nanofibers and the large specific surface area of ultrafine fibers greatly increase the contact area between nylon fibers and the external atmosphere. In the solvent gas atmosphere, the volume of nylon fibers expands rapidly, and the overlap between the conductive fillers on the fiber surface is destroyed to a certain extent in a very short time, and the resistance of the composite material increases rapidly; thus, the composite material has a high response to the solvent gas atmosphere. speed and response rate. In the air atmosphere, the large porosity between the nylon fibers and the large specific surface area of the superfine fibers promote the separation of organic gases from the composite material, and the material and electrical properties of the composite material can be quickly restored. The method proposed by the present invention cleverly increases the specific surface area of the composite material, thereby greatly increasing the contact area between the composite material and the external atmosphere, shortening the response time of the composite material to the external atmosphere, and improving the response rate of the composite material to the external atmosphere. The problem that high responsivity and good recovery cannot be achieved at the same time is solved; gas-sensitive materials with high responsivity, response rate, recovery rate and reusability are prepared.

The preparation of embodiment 1 polymer gas-sensitive material

Preparation method: the specific preparation steps are as follows:

(1) Configuration of PA6 formic acid solution: Mix 1.5g of nylon 6 and 5ml of formic acid in a 50ml round bottom flask, then mechanically blend at 75°C for 1.5 hours to prepare a nylon 6 solution with a mass fraction of 20%.

(2) Electrospinning: under the action of high-voltage static electricity, the PA6 solution obtained in step 1 will form a Taylor cone at the spinneret. When the electric field strength reaches a critical value, the electric field force can overcome the surface tension of the liquid. A charged jet stream is formed at the thread opening; during the jetting process, due to the rapid increase in the surface area of the jet stream, the solvent volatilizes, the fibers solidify and are arranged in disorder on the collecting device, thereby obtaining a fiber film with a thickness of 0.3-3 μm and an average The diameter is 100-400nm, the pore diameter of the fiber membrane is 1-6μm nanofiber; the electrospinning parameters: the distance between electrodes is 25cm, the voltage is 30KV; the receiving device is a copper mesh.

(3) Preparation of GNPs dispersion: in an ice-water bath, place GNPs in deionized water for ultrasonic dispersion for 1 hour to form a GNPs dispersion (the mass concentration of the dispersion is 0.1%).

(4) Preparation of GNPs/PA6 conductive network: In an ice-water bath, the PA6 fiber membrane was placed in the dispersed GNPs dispersion solution for ultrasonic treatment for 3 minutes, and then placed in the air to dry naturally to make a GNPs/PA6 conductive composite Material (thickness distribution 0.3-3 μm; average thickness 1.7 μm).

Figure 1a is a scanning electron microscope (SEM) image of PA6 electrospun fiber membrane. It can be seen from Figure 1a that: PA6 fibers are uniform and smooth, and the fiber morphology is good; Figure 1b: SEM image of GNPs/PA6, as can be seen from Figure 1b : GNPs are distributed on PA6 fibers, with very little distribution between pores; Figure 1c, Figure 1e: Local SEM images of GNPs/PA6, Figure 1d, Figure 1f are the enlarged images of Figure 1c and Figure 1e, respectively, from Figure 1c, Figure 1d , Figure 1e, and Figure 1f, it can be seen that a good connection has been formed between GNPs and fibers.

Performance Testing:

The composite material obtained in Example 1 was placed in different concentrations of formic acid gas atmosphere for 150s and then placed in air atmosphere for 150s, and the test was repeated like this; the concentration of formic acid was respectively 25ppm, 50ppm, 100ppm, 200ppm, 500ppm, 1000ppm, and its electrical properties were measured The change.

Fig. 2 is the time-resistance curves of the gas-sensitive material obtained in Example 1 under different concentrations of formic acid gas atmosphere. It can be seen from Figure 2 that the resistance of the gas-sensing material increases rapidly after being placed in the formic acid gas atmosphere; and the resistance of the gas-sensing material recovers quickly after being placed in the air atmosphere. And the responsivity of the sensitive material has a positive linear relationship with the concentration of formic acid gas.

The GNPs/PA6 gas-sensing material obtained in Example 1 was placed in a gas atmosphere of ethanol, methylene chloride, cyclohexane, and ethyl acetate at 500 ppm to study its time-resistance behavior. Fig. 3 is a time-resistance curve of the gas-sensing material under different organic gas atmospheres of 500ppm. It can be seen from Figure 3 that: for different gases, the response of the sensitive material is very different, that is, the selectivity of the sensitive material is good.

FIG. 4 shows the response time and recovery time of the gas-sensitive material obtained in Example 1 to different organic gases under the atmosphere of 500 ppm of different organic gases. It can be seen from Figure 3 that for different gases, the response time and recovery time of sensitive materials are different, but the overall response rate is very fast.

FIG. 5 shows the response intensity of the gas-sensitive material obtained in Example 1 to different organic gases under the atmosphere of 500 ppm of different organic gases. It can be seen from Figure 3 that for different gases, the responsivity of the sensitive material is different, further indicating that the selectivity of the sensitive material is good.

It is found from the above experiments that the method proposed by the invention cleverly ensures that the responsivity, response rate, recovery rate and reutilization rate of the composite material are simultaneously improved. The simple processing method and the excellent flexibility of the composite material will help reduce the production cost of the material and promote the application of the material. In addition, the present invention directly uses reduced graphene, and can achieve a good combination of GNPs and PA6, which greatly simplifies the processing process and reduces the processing cost.

Claims (10)

1. macromolecule gas sensitive, is characterized in that, described macromolecule gas sensitive is the compound substance with conductive network structure that conductive filler and electrospinning nylon nano fiber film are formed.

2. macromolecule gas sensitive according to claim 1, it is characterized in that, described electrospinning nylon nano fiber film is selected from least one in electrospinning nylon 6/nanometer tunica fibrosa, electrospinning nylon66 fiber nano fibrous membrane, electrospinning nylon 1010 nano fibrous membrane, electrospinning NYLON610 nano fibrous membrane or electrospinning nylon 1212 nano fibrous membrane; Described conductive filler is selected from least one in graphene nanometer sheet, carbon black, carbon fiber or carbon nano-tube; Preferably, the thickness of described electrospinning nylon nano fiber film is 0.3-3 μm, and tunica fibrosa mean diameter is 100-400nm, and tunica fibrosa aperture is 1-6 μm.

3. macromolecule gas sensitive according to claim 1 and 2, is characterized in that, the preparation method of described electrospinning nylon nano fiber film is: first nylon and formic acid are mixed with the spinning liquid that mass concentration is 15-25%; Then gained spinning liquid is obtained electrospinning nylon nano fiber film by electrostatic spinning; Wherein, electrospinning condition is: interelectrode distance is 15-30cm, and voltage is 15-35KV, spinning time 1.5-5 hour.

4. the macromolecule gas sensitive according to any one of claims 1 to 3, it is characterized in that, the method that conductive filler and electrospinning nylon nano fiber film form compound substance is: conductive filler is distributed in electrospinning nylon nano fiber surface by the mode of ultrasonic disperse, the method of ultrasonic disperse is: first conductive filler is mixed the conductive filler dispersion liquid that obtained mass concentration is 0.03-0.2% with deionized water, then electrospinning nylon nano fiber film is placed in conductive filler dispersion liquid ultrasonic process 2-10min.

5. the macromolecule gas sensitive according to any one of Claims 1 to 4, is characterized in that, the mass concentration of described conductive filler dispersion liquid is 0.1%, and in described conductive filler dispersion liquid, the average-size of conductive filler is not more than 5 μm.

6. the macromolecule gas sensitive according to any one of claim 2 ~ 5, is characterized in that, described electrospinning nylon nano fiber film is electrospinning PA6 nano fibrous membrane, and described conductive filler is graphene nanometer sheet; Preferably, the sheet number of plies of described graphene nanometer sheet is less than 30, and thickness is less than 20nm, and purity is greater than 99.5wt%.

7. macromolecule gas sensitive according to claim 6, is characterized in that, the preparation method of described electrospinning PA6 nano fibrous membrane is: first mixed with formic acid by PA6, within 1-2.5 hour, obtains PA6 solution in 65-75 DEG C of stirring; Then gained PA6 solution is obtained electrospinning PA6 nano fibrous membrane by electrostatic spinning.

8. the preparation method of the macromolecule gas sensitive described in any one of claim 1 ~ 7, is characterized in that, electrospinning nylon nano fiber film is placed in conductive filler dispersion liquid ultrasonic process 2-10min, then washs, is drying to obtain macromolecule gas sensitive; Wherein, the preparation method of described conductive filler dispersion liquid is: after conductive filler and deionized water are mixed in 0-5 DEG C of environment ultrasonic disperse 1.5-3.5 hour, ultrasonic power is 285W-570W.

9. the preparation method of macromolecule gas sensitive according to claim 8, is characterized in that, electrospinning nylon nano fiber film is placed in the ultrasonic process of conductive filler dispersion liquid to carry out at ice-water bath.

10. macromolecule gas sensitive is for detecting polar gas, and described macromolecule gas sensitive is the macromolecule gas sensitive described in any one of claim 1 ~ 7, or the macromolecule gas sensitive adopting the method described in claim 8 or 9 obtained; Described polar gas comprises formic acid, acetic acid, methyl alcohol, ethanol or ammonia.