CN114642973B - Air filtering material with temperature and humidity response performance and preparation and application thereof - Google Patents

Abstract

The invention relates to an air filter material with temperature and humidity response performance and its preparation and application. The air filter material is made of more than one polymer (polyamide, polyurethane, polyacrylonitrile, polyoxyethylene and polyvinylpyrrolidone) ) and protonic acid (phytic acid and/or phosphoric acid) uniformly dispersed and dissolved in the polymer; the preparation method is: adding protonic acid and polymer to a solvent to form a spinning solution for electrospinning to obtain the Air filter material; the application is: connecting the air filter material in series with an alarm device to form a fire alarm circuit; the air filter material has a thickness of 20-30 μm and a breaking strength of 2-5 MPa. The air filter material of the present invention has better temperature and humidity response performance, and the filtering performance is also better. Compared with the coating method in the prior art, the method of the present invention can ensure , can still guarantee stable and excellent response performance.

Description

Air filter material with temperature and humidity response performance and its preparation and application

technical field

The invention belongs to the technical field of filter materials, and relates to an air filter material with temperature and humidity response performance and its preparation and application.

Background technique

With the increasingly prominent air pollution and residents' health problems, people's demand for multifunctional air filter materials is increasing. Especially in some extreme working conditions, such as fire fighting or high humidity conditions, there will be certain potential hazards to equipment operation and human health. Common temperature-responsive materials are usually coated on the surface of fabrics or airgel materials with materials that are subject to change in thermal resistance, such as heat-sensitive materials such as graphene oxide (GO), aminated carbon nanotubes (such as CN111019187 A), through Utilizing the state of some functional groups of such conductive materials that are easily reduced by heat under high temperature conditions to form a low resistance value (such as reduced graphene oxide, carbon nanotubes, etc.) to make the resistance value of the entire material show a significant drop, and then turn on the external circuit and trigger a fire alarm. However, this type of material can only achieve sensitive alarm performance under high temperature conditions (>500°C), and when the temperature is relatively low, its thermal reduction speed is slow, and it takes a long time to reach the critical value of early warning resistance, even without early warning ability. In addition, these materials used for thermal reduction are irreversible, and it is easy to cause the heat-sensitive materials to spontaneously reduce and become invalid in a hot environment for a long time. In addition, the humidity state inside the car is closely related to the health of the occupants in the car, and long-term high humidity conditions will have a negative impact on human health; therefore, it is very important to monitor the humidity conditions in the car. Common fiber-based humidity-responsive materials are mostly composed of graphene or silver nanoparticles combined with fibers, but due to the combination of these materials and the matrix, their stability in use is not good, and their manufacturing costs are also high.

At present, there are few studies on the fire response performance of air filter materials. If the above-mentioned materials with variable heating resistance are processed into the current air filter materials, from the perspective of the factors affecting the filter performance, these additives will affect the fiber. The pore size and porosity of the aggregates have an effect, thus affecting the filtration performance.

Therefore, it is of great significance to study a high-performance air filter material with temperature and humidity responsiveness.

Contents of the invention

In order to overcome the shortcomings of the existing technical solutions, the present invention provides a filter material with temperature and humidity responsiveness and its preparation and application. The present invention utilizes electrospinning technology to dissolve small-molecule protonic acid (phytic acid and/or phosphoric acid) in the polymer matrix, so the protonic acid can be evenly distributed in the polymer matrix, and the protonic acid can be evenly distributed in the polymer matrix. When poorly stimulated, since these small molecules are evenly distributed in the matrix, it is easier to form proton transport channels, promote proton transport, and make its temperature and humidity response performance more sensitive; and compared with the coating method in the prior art , the method of the present invention can ensure stable and excellent response performance under the condition of external mechanical force or long-term use.

In order to achieve the above object, the scheme adopted by the present invention is as follows:

An air filter material with temperature and humidity response performance, the air filter material is composed of a polymer and a protonic acid uniformly dispersed in the polymer;

The polymer is an amorphous polymer or a partially crystalline polymer with relatively low crystallinity, preferably one or more of polyamide, polyurethane, polyacrylonitrile, polyoxyethylene and polyvinylpyrrolidone in the present invention.

Taking polyacrylonitrile as an example, the traditional polyacrylonitrile material is non-conductive and extremely flammable, but protonic acid and polyacrylonitrile are doped together and prepared into nanofibers, and small molecules of protonic acid can be uniformly dispersed in polyacrylonitrile. In the molecular chain of acrylonitrile, since the protonic acid molecule has abundant hydroxyl functional groups, it can form a hydrogen bond with the cyano group on the molecular chain of polyacrylonitrile, thus forming a hydrogen bond network inside the molecular chain of polyacrylonitrile; A large number of hydrogen ions can be generated under high temperature conditions, and these hydrogen ions can migrate along the formed hydrogen bond network under high temperature conditions, thus significantly reducing the resistance value of the filter material. At the same time, due to the presence of phytic acid in the nanofiber, the flame retardancy of the final nanofiber material is significantly improved.

The protonic acid is phytic acid and/or phosphoric acid; the protonic acid is also rich in phosphorus, so it can also endow the polymer with excellent flame retardancy.

The temperature-humidity response performance means that the resistance value of the air filter material changes when the ambient temperature and/or ambient humidity (relative humidity) changes.

As a preferred technical solution:

According to the above-mentioned air filter material with temperature and humidity response performance, the air filter material is a nanofiber membrane composed of nanofibers. First of all, the micro-nano scale of the fiber makes it have a super large specific surface area, which makes it easier for the air filter material to sense and respond to changes in external temperature or humidity conditions; secondly, continuous nanofibers (super large long Diameter ratio) also provides a continuous channel for the proton transport of protonic acid, and due to its small fiber diameter and porosity, it can efficiently intercept fine particles in the air.

According to the above-mentioned air filter material with temperature and humidity response performance, the average pore diameter of the nanofiber membrane is 0.5-3 μm; the average diameter of the nanofiber is 200-600 nm.

According to the above-mentioned air filter material with temperature and humidity response performance, the mass content of protonic acid in the nanofiber membrane is 25-85%.

The present invention also provides a method for preparing an air filter material with temperature and humidity responsiveness as described above. Protonic acid and polymer are added into a solvent to form a spinning solution for electrostatic spinning to obtain the air filter material.

The specific process is as follows:

(1) dissolving the protonic acid in a solvent and dispersing it evenly;

The solvent is DMF, acetone, formic acid, ethanol or water;

(2) Add polymer to the material obtained in step (1), and stir to form a homogeneous solution;

When stirring, the temperature of the mixture is 20-100°C, and the stirring time is 5-10 hours;

(3) Use a syringe pump to transport the solution obtained in step (2) to the nozzle at a certain flow rate. Under certain high pressure conditions, the solution is drawn by the force of the electric field at the end of the nozzle to form nanofibers, and receive it on the receiving device for a period of time. Afterwards, a fiber aggregate with random arrangement is formed;

The spinning temperature is room temperature, the relative humidity of spinning is 20-80%, the certain flow rate is 0.1-3ml/h, the certain high pressure is 10-30kV, and the receiving device is a drum;

(4) Vacuum-dry the obtained fiber assembly in an oven for 5-8 hours and then take it out to obtain the air filter material.

The present invention also provides the application of the above-mentioned air filter material with temperature and humidity response performance, and the air filter material is connected in series with the alarm device to form a fire alarm circuit.

As a preferred technical solution:

For the application of the air filter material with temperature and humidity response performance as described above, the thickness of the air filter material is 20-30 μm, and the breaking strength of the air filter material is 2-5 MPa.

The above-mentioned application of an air filter material with temperature and humidity response performance, the air filter material has an interception efficiency of more than 99.9% for particulate matter (PM2. efficiency). Test method of interception efficiency: put the air filter material on an automatic filter material tester for testing, the size of the test area is 10×10cm, and the air flow rate is 5.3cm/s.

According to the above-mentioned application of an air filter material with temperature and humidity response performance, the fire alarm circuit is composed of a DC power supply, a warning lamp with a rated voltage of 12V and the air filter material connected in series.

Principle of the present invention is as follows:

The air filter material of the present invention is by adding a class of protonic acid materials (phytic acid and/or phosphoric acid) in amorphous polymers or some partially crystalline polymer solutions with lower crystallinity, and then is prepared by electrospinning technology to have Nano-scale fiber filter material; due to the addition of protonic acid, the filter material can ionize hydrogen ions under certain conditions, such as when the temperature rises, and the generated hydrogen ions will move directional within the molecular chain, which makes The resistance value of the originally highly resistive polymer fiber material changes rapidly. Specifically, when the temperature rises, a large number of hydrogen ions are ionized on the protonic acid molecules, and the transmission speed and mobility of the hydrogen ions are improved. The directional transmission of the hydrogen ions makes the resistance value of the material significantly lower. When the temperature returns to the original condition, the resistance value will return to the original state due to the decrease in the number of hydrogen ion ionization and the decrease in the moving rate of hydrogen ions. In this way, the material will have different resistance value states under different temperature conditions, which makes the material have the performance of temperature sensing, and can be sensitive to external temperature conditions and temperature changes.

The air filter material prepared by the present invention can not have an impact on the aperture of the nanofibers that are finally formed because the additive protonic acid wherein can be completely dissolved in the polymer solution, so it is less than 2.5 μm in size (PM2.5 ) interception efficiency can reach more than 99.9%, with high air filtration efficiency.

The air filter material of the present invention also has good humidity response performance, and this is because the protonic acid material in the present invention contains abundant hydroxyl or carboxyl functional groups, and these functional groups easily absorb water molecules in the air and combine to form hydronium ions (H ₃ O+), the formation of these hydronium ions provides a channel for proton transport, and the directional transport of protons changes the resistance value of the material; for example, under high humidity conditions, the material will absorb more water molecules to form hydronium ions , which provides more channels for proton transmission inside the material, so the resistance value of the material will drop to a very low level quickly; and under low humidity conditions, the adsorbed water molecules will desorb into the air again, making the protons There are fewer transmission channels, and the resistance value of the filter material will quickly return to the original level. In this way, the material will have different resistance values under different humidity conditions, which makes the material have the performance of humidity sensing, and can sensitively perceive the change of external humidity.

The additive protonic acid in the air filter material with temperature and humidity response performance of the present invention plays a major role in flame retardancy and fire response performance. It can not only play a role in flame retardancy under high temperature conditions, but also change in external conditions Time (temperature change or humidity change), the resistance value of the air filter material decreases rapidly and is connected to the external circuit to form a conductive circuit, and then the alarm device is triggered.

Beneficial effect

(1) A kind of air filter material with temperature and humidity response performance of the present invention has higher air filter efficiency compared with traditional automobile interior air filter material, because the additive protonic acid wherein can be dissolved in polymer solution completely In the process, it will not affect the pore size of the final nanofiber, so its interception efficiency for particles (PM2.5) with a size less than 2.5 μm can reach more than 99.9%; and in the present invention, by introducing protonic acid materials, using protons Under certain conditions, the directional transmission can realize the temperature and humidity response performance. Compared with the traditional doped conductive nanomaterials to realize the temperature and humidity response, the humidity response material of the present invention has the advantages of low cost, non-toxic and harmless, etc., and It has excellent response performance;

(2) A method for preparing an air filter material with temperature and humidity response performance of the present invention, which is prepared by doping a low-cost, green and renewable protonic acid material in a polymer solution and utilizing electrospinning technology ; The preparation process is simple, and the preparation of a functional air filter material with temperature and humidity response performance can be realized without post-treatment process;

(3) An air filter material with temperature and humidity response performance of the present invention is used to form a fire alarm circuit. Compared with traditional graphene-based fire early warning products, it has a faster early warning time in fire early warning, and can be used in fire alarms. The fire is detected faster and the alarm is given quickly before the fire occurs; in addition, its excellent flame retardant performance can also inhibit the further spread of the flame.

Description of drawings

Fig. 1 is the schematic diagram of the electrospinning device that the present invention adopts;

Fig. 2 is the SEM picture of the nanofibrous film that embodiment 1 makes;

Fig. 3 is the fire alarm circuit schematic diagram of the present invention;

Fig. 4 is the change trend diagram of the resistance value of the air filter material made by embodiment 1 after contacting the fire source after cutting;

Fig. 5 is the resistance change curve of the air filter material prepared in Example 1 in the repeated transfer process under different temperature conditions; wherein, the resistance at the peak corresponds to the normal temperature condition (30°C), and the resistance at the peak to the valley corresponds to Object surface at 60°C;

Fig. 6 is the resistance change curve of the air filter material prepared in Example 1 under different humidity conditions; wherein, the resistance at the peak corresponds to the relative humidity of 0% and a temperature of 20°C, and the resistance at the peak to the valley corresponds to The relative humidity is 95% and the temperature is 20°C.

Detailed ways

The present invention will be further described below in combination with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

The test method that the embodiment of the present invention adopts is as follows:

(1) The test method for the thickness of the air filter material: use a thickness gauge to measure, clamp and measure at random positions on the sample, and calculate the average value of 3 tests;

(2) The test method for the breaking strength of the air filter material: use a breaking strength meter to measure, select a fiber membrane with a sample size of 20*5mm for three tensile tests, and take the average value of the test results;

(3) Test method of interception efficiency: put the air filter material on an automatic filter material tester for testing, the size of the test area is 10×10cm, and the air flow rate is 5.3cm/s.

Example 1

A method for preparing an air filter material with temperature and humidity response performance, the steps are as follows:

(1) Dissolving phytic acid in solvent N-N dimethylformamide (DMF) to obtain solution A; the concentration of phytic acid in solution A is 10wt%;

(2) Add polyacrylonitrile to the solution A obtained in step (1), and stir for 5 h at a temperature of 60° C. to form a uniform solution B; in solution B, the mass ratio of polyacrylonitrile to phytic acid is 1.2: 1;

(3) As shown in Figure 1, the solution B obtained in step (2) is transported to the nozzle at a flow rate of 1ml/h with a syringe pump, and under the high pressure condition of 20kV, the solution B is drawn by the electric field force at the end of the nozzle Forming nanofibers, and forming fiber aggregates with random arrangement after being received on the receiving device (drum) for a period of time; wherein, the spinning temperature is 20°C, and the relative humidity of spinning is 50%;

(4) Take out the obtained fiber assembly after vacuum drying in an oven for 5 hours to obtain a nanofiber membrane made of nanofibers, i.e. an air filter material; wherein, the average pore diameter of the nanofiber membrane is 0.8 μm, and the nanofiber The average diameter is 250nm, the thickness of the nanofiber membrane is 25μm, and the breaking strength of the nanofiber membrane is 5MPa; the mass content of phytic acid in the nanofiber membrane is 45%;

The air filter material has an interception efficiency of 99.95% for particulate matter (PM2.5) with a size smaller than 2.5 μm.

Example 2

A method for preparing an air filter material with temperature and humidity response performance, the steps are as follows:

(1) phosphoric acid is dissolved in solvent acetone to obtain solution A; the concentration of phosphoric acid in solution A is 7wt%;

(2) Add polyurethane to the solution A obtained in step (1), and stir for 5 hours at 20° C. to form a uniform solution B; in solution B, the mass ratio of polyurethane to phytic acid is 2.2:1;

(3) The solution B obtained in step (2) is delivered to the nozzle with a flow rate of 1.5ml/h by a syringe pump. Under the high pressure condition of 15kV, the solution B is drawn to form nanofibers at the end of the nozzle by electric field force, and After being received on the receiving device (drum) for a period of time, a fiber aggregate with random arrangement is formed; wherein, the spinning temperature is 20° C., and the relative humidity of spinning is 60%;

(4) Take out the obtained fiber assembly after vacuum drying in an oven for 5h to obtain a nanofiber membrane made of nanofibers, i.e. an air filter material, as shown in Figure 2; wherein, the average pore size of the nanofiber membrane is 2 μm, the average diameter of the nanofiber is 500nm, the thickness of the nanofiber membrane is 25 μm, the breaking strength of the nanofiber membrane is 2MPa; the mass content of phosphoric acid in the nanofiber membrane is 31%;

The air filter material has an interception efficiency of 99.9% for particulate matter (PM2.5) with a size smaller than 2.5 μm.

Example 3

A method for preparing an air filter material with temperature and humidity response performance, the steps are as follows:

(1) Dissolving phytic acid and phosphoric acid in solvent formic acid to obtain solution A; in solution A, the mass ratio of phytic acid and phosphoric acid is 1:1, and the sum of the concentrations of phytic acid and phosphoric acid is 8wt%;

(2) Add PA6 (25038-54-4, Ron’s reagent, monomer molecular weight 111.14) to the solution A obtained in step (1), and stir for 8 hours at a temperature of 20°C to form a uniform solution B; solution B Among them, the ratio of polyamide to the sum of the mass of phytic acid and phosphoric acid is 2.5:1;

(3) The solution B obtained in step (2) is delivered to the nozzle with a flow rate of 1.5ml/h by a syringe pump. Under the high pressure condition of 28kV, the solution B is drawn to form nanofibers at the end of the nozzle by electric field force, and After being received on the receiving device (drum) for a period of time, a fiber assembly with random arrangement is formed; wherein, the spinning temperature is 20° C., and the relative humidity of spinning is 50%;

(4) Take out the obtained fiber assembly after vacuum drying in an oven for 5 hours to obtain a nanofiber membrane made of nanofibers, i.e. an air filter material; wherein, the average pore diameter of the nanofiber membrane is 0.5 μm, and the nanofiber The average diameter is 200nm, the thickness of the nanofiber membrane is 20μm, and the breaking strength of the nanofiber membrane is 3MPa; the mass content of phytic acid and phosphoric acid in the nanofiber membrane is 29%;

The air filter material has an interception efficiency of 99.99% for particulate matter (PM2.5) with a size smaller than 2.5 μm.

Example 4

A method for preparing an air filter material with temperature and humidity response performance, the steps are as follows:

(1) Dissolving phytic acid in solvent ethanol to obtain solution A; the concentration of phytic acid in solution A is 15wt%;

(2) Add polyoxyethylene with a viscosity-average molecular weight of 300,000 to solution A obtained in step (1), and stir for 5 hours at a temperature of 20°C to form a uniform solution B; in solution B, polyoxyethylene and plant The mass ratio of acid is 0.23:1;

(3) The solution B obtained in step (2) is delivered to the nozzle with a flow rate of 1ml/h by a syringe pump. Under the high pressure condition of 15kV, the solution B is drawn to form nanofibers at the end of the nozzle by electric field force, and After being received on the receiving device (drum) for a period of time, a fiber aggregate with random arrangement is formed; wherein, the spinning temperature is 20° C., and the relative humidity of spinning is 50%;

(4) Take out the obtained fiber assembly after vacuum drying in an oven for 5 hours to obtain a nanofiber membrane made of nanofibers, i.e. an air filter material; wherein, the average pore diameter of the nanofiber membrane is 3 μm, and the average diameter of the nanofibers The diameter is 600nm, the thickness of the nanofiber membrane is 20μm, and the breaking strength of the nanofiber membrane is 2MPa; the mass content of phytic acid in the nanofiber membrane is 81%;

The interception efficiency of the air filter material for particulate matter (PM2.5) with a size smaller than 2.5 μm is 99.9%.

Example 5

A method for preparing an air filter material with temperature and humidity response performance, the steps are as follows:

(1) phosphoric acid is dissolved in solvent water to obtain solution A; the concentration of phosphoric acid in solution A is 10wt%;

(2) Add polyvinylpyrrolidone with an average molecular weight of 1.3 million to the solution A obtained in step (1), and stir for 5 hours at a temperature of 20° C. to form a uniform solution B; in solution B, polyvinylpyrrolidone and phosphoric acid The mass ratio is 1.2:1;

(3) The solution B obtained in step (2) is delivered to the nozzle with a flow rate of 1.5ml/h by a syringe pump. Under the high pressure condition of 15kV, the solution B is drawn to form nanofibers at the end of the nozzle by electric field force, and After being received on the receiving device (drum) for a period of time, a fiber assembly with random arrangement is formed; wherein, the spinning temperature is 20° C., and the relative humidity of spinning is 50%;

(4) Take out the obtained fiber assembly after vacuum drying in an oven for 5 hours to obtain a nanofiber membrane made of nanofibers, i.e. an air filter material; wherein, the average pore diameter of the nanofiber membrane is 2.5 μm, and the nanofiber The average diameter is 550nm, the thickness of the nanofiber membrane is 20μm, and the breaking strength of the nanofiber membrane is 2.5MPa; the mass content of phosphoric acid in the nanofiber membrane is 45%;

The air filter material has an interception efficiency of 99.9% for particulate matter (PM2.5) with a size smaller than 2.5 μm.

Example 6

A method for preparing an air filter material with temperature and humidity response performance, the steps are as follows:

(1) Dissolving phytic acid in solvent N-N dimethylformamide (DMF) to obtain solution A; the concentration of phytic acid in solution A is 15wt%;

(2) Add a mixture of PA6 and polyacrylonitrile with a mass ratio of 1:1 to the solution A obtained in step (1), and stir for 8 hours at a temperature of 50°C to form a uniform solution B; in solution B, the The mass ratio of said mixture and phytic acid is 1:1;

(3) The solution B obtained in step (2) is delivered to the nozzle with a flow rate of 2ml/h by a syringe pump. Under the high pressure condition of 20kV, the solution B is drawn to form nanofibers at the end of the nozzle by electric field force, and After being received on the receiving device (drum) for a period of time, a fiber aggregate with random arrangement is formed; wherein, the spinning temperature is 20° C., and the relative humidity of spinning is 50%;

(4) Take out the obtained fiber assembly after vacuum drying in an oven for 5 hours to obtain a nanofiber membrane made of nanofibers, that is, an air filter material; wherein, the average pore diameter of the nanofiber membrane is 1 μm, and the average diameter of the nanofiber The diameter is 300nm, the thickness of the nanofiber membrane is 20μm, and the breaking strength of the nanofiber membrane is 4MPa; the mass content of phosphoric acid in the nanofiber membrane is 50%;

The air filter material has an interception efficiency of 99.99% for particulate matter (PM2.5) with a size smaller than 2.5 μm.

The air filter materials prepared in Examples 1 to 6 were respectively cut, and the cut sizes are shown in Table 1. The air filter materials of each embodiment after cutting were respectively connected in series with a DC power supply and a warning light with a rated voltage of 12V to form a fire alarm. Circuit, as shown in Figure 3; When the external open flame contacts with the air filter material after cutting, the resistance value of the air filter material made by embodiment 1 after cutting changes as shown in Figure 4, and the fire alarm The circuit is connected within 0.16s and triggers the alarm light. See Table 1 for the time when the fire alarm circuit made of the air filter material prepared in Examples 2-6 is switched on and the alarm light is triggered.

Under external open flame conditions, the protonic acid in the above-mentioned air filter material of the present invention will ionize a large amount of hydrogen ions, and these hydrogen ions carry out rapid and directional transmission along a certain transmission path inside the polymer, so that the resistance value of the material occurs significantly. Change, and quickly reduce to a level that can turn on the external circuit, and then trigger the alarm system to realize the fire warning function. The fire warning performance is generally evaluated by the fire response time, which is the interval time from when the response material is exposed to an open flame to when the fire alarm light is triggered, and the shorter the response time, the more sensitive the fire response performance is; from the published technologies, The fire response time of common graphene products is usually between 0.5-15s, while the response time of the air filter material of the present invention is 0.1-0.2s under open flame conditions. Compared with traditional conductive nanomaterials that need to be doped with higher cost, such as graphene oxide (GO), aminated multi-walled carbon nanotubes, etc. to achieve fire response performance, the present invention only needs to incorporate low-cost, non-toxic and harmless , The green and renewable phytic acid component can be added to the spinning solution to achieve the ultra-sensitive fire response performance and flame retardancy of the air filter material without affecting its filtration performance.

Table 1

The air filter material prepared in Examples 1～6 is cut respectively, and the size of cutting is shown in Table 2. At first, the left and right sides of the air filter material after cutting in Examples 1～6 are respectively connected with a multimeter (Keeithly DAQ) by a wire. 6510) connection, record the initial resistance value of the material at a temperature of 30°C and a relative humidity of 40%, then transfer the air filter material from a temperature of 30°C and a relative humidity of 40% to the surface of an object at a temperature of 60°C, and then Transfer the air filter material from the surface of the object at a temperature of 60°C to a temperature of 30°C and a relative humidity of 40%, repeat the operation (in this process, keep the relative humidity at 40%), and record the resistance of the material during the process value.

The test results of the air filter material corresponding to Example 1 are shown in Figure 5, as can be seen from Figure 5, when transferred from a temperature of 30°C and a relative humidity of 40% to the surface of an object at a temperature of 60°C, the The resistance value will decrease rapidly, and when it is transferred from the surface of the object at a temperature of 60°C to a temperature of 30°C and a relative humidity of 40%, the resistance value of the material will return to the initial level. And repeating the operation many times, the change of the resistance is very stable. The air filter materials in Examples 2-6 are measured by the same method, and their temperature coefficients of resistance are shown in Table 2. Among them, the calculation method of the temperature coefficient of resistance is: the resistance change rate of the material at 60°C is divided by the temperature difference (30°C).

Generally, the temperature coefficient of resistance (TCR) is used to characterize the thermal resistance change ability of the material. The larger the value, the better the temperature response performance of the material; most of the TCR values of temperature sensing materials in the prior art are 1.2-1.7%/°C .

Table 2

The air filter material obtained in Examples 1～6 is cut respectively, and the size of cutting is shown in Table 3. At first, the left and right sides of the air filter material obtained after cutting in Examples 1～6 are utilized to be connected with the multimeter respectively by wires (Ji. Shili DAQ6510), record the initial resistance value of the material at a relative humidity of 0% and a temperature of 20°C, and then transfer the air filter material from a relative humidity of 0% and a temperature of 20°C to a relative humidity of 95% and a temperature of 20°C °C, then transfer the air filter material from a relative humidity of 95% and a temperature of 20 °C to a relative humidity of 0% and a temperature of 20 °C, and repeat the operation (keep the temperature at 20 °C during this process) ), record the resistance value of the material during the process.

The test results of the air filter material corresponding to Example 1 are shown in Figure 6. It can be seen from Figure 6 that when the relative humidity is 0% and the temperature is 20°C, it is transferred to the relative humidity is 95% and the temperature is 20°C. When the temperature is lowered, the resistance value of the material will gradually decrease, and its response time is 8s. The resistance value will increase rapidly again, and its resistance recovery time is 15s. The response time and recovery time of the air filter materials in Examples 2-6 are shown in Table 3 respectively. Among them, the measurement method of the response time is: when the material is transferred from the condition of 0% relative humidity and temperature of 20°C to the condition of relative humidity of 95% and temperature of 20°C, the time interval after the material resistance changes from the beginning to maintain a stable state The measurement method of the recovery time is: when the material is transferred from the condition of 95% relative humidity and temperature of 20°C to the condition of relative humidity of 0% and temperature of 20°C, the resistance of the material returns to the original state of resistance after the change. required time interval.

In the prior art, the resistance change rate of the humidity sensing material (the resistance change rate is obtained by dividing the resistance value of the material at a certain time point under a certain humidity condition and the initial resistance value of the material by the initial resistance value of the material) is mostly in the In the range of 10% to 50%, the calculation method is to subtract the stable resistance value of the material under the condition of 95% relative humidity and temperature of 20°C from the initial resistance value of the material under the condition of 0% relative humidity and temperature of 20°C and then divide Take the initial resistance value of the material and multiply it by 100. In addition, the response time and recovery time of humidity sensing materials are also important indicators to measure their performance. The shorter the time, the better the performance. In the prior art, the response time and recovery time of humidity sensing materials are mostly between 3-50s and 5 ~100s range. And described air filter material of the present invention when environment humidity rises to 95% from 0%, resistance value descends and rate of change is 55～61%; The response time and recovery time of resistance change are respectively 5～10s and 12～ 18s.

table 3

Claims (8)

1. An air filter material having temperature and humidity response characteristics, comprising: the air filtering material is a nanofiber membrane formed by nanofibers; the air filter material is composed of a polymer and a protonic acid uniformly dispersed in the polymer;

the polymer is more than one of polyamide, polyurethane, polyacrylonitrile, polyoxyethylene and polyvinylpyrrolidone;

the protonic acid is phytic acid and/or phosphoric acid;

the temperature and humidity response performance refers to that the resistance value of the air filter material changes when the ambient temperature and/or the ambient humidity changes.

2. The air filter material with temperature and humidity response performance as claimed in claim 1, wherein the average pore diameter of the nanofiber membrane is 0.5 to 3 μm; the average diameter of the nano-fiber is 200 to 600nm.

3. The air filter material with temperature and humidity response performance as claimed in claim 1, wherein the mass content of the protonic acid in the nanofiber membrane is 25-85%.

4. A method of making an air filter material having temperature and humidity response as claimed in any one of claims 1~3 wherein: and adding protonic acid and a polymer into a solvent to prepare a spinning solution for electrostatic spinning, so as to prepare the air filter material.

5. Use of an air filter material having temperature and humidity responsive properties according to any one of claims 1~3 wherein: and the air filtering material is connected with an alarm device in series to form a fire alarm circuit.

6. The use of the air filter material with temperature and humidity response performance according to claim 5, wherein the thickness of the air filter material is 20 to 30 μm, and the breaking strength is 2 to 5MPa.

7. The use of an air filter material with temperature and humidity response performance according to claim 6, wherein the air filter material has an interception efficiency of particulate matter with a size of less than 2.5 μm of 99.9% or more.

8. The use of an air filter material having temperature/humidity response characteristics according to claim 5, wherein the fire alarm circuit is formed by connecting a DC power supply, a 12V rated voltage alarm lamp, and the air filter material in series.

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