Composite fiber membrane, method for producing the same, and use thereof

Abstract

The application discloses a composite fiber membrane and a preparation method and application thereof. The composite fiber membrane comprises 90-95 parts by weight of polyamide imide, 2-5 parts by weight of polyvinylpyrrolidone and 2-5 parts by weight of a conductive substance. The composite fiber membrane has stable conductivity under an extreme temperature environment (for example, -196 DEG C to 300 DEG C), and has good mechanical properties.

Description

Technical Field

[0001] This invention relates to a composite fiber membrane, its preparation method, and its application. Background Technology

[0002] In fields such as temperature sensors, flexible sensors, and smart wearable textiles, there is a need for materials that can maintain stable conductivity in extreme temperature environments (e.g., -196℃, 300℃) and have a certain degree of temperature sensitivity, and whose transmitted electrical signals have high sensitivity.

[0003] CN116479659A discloses a polyamide-imide-polyaniline composite conductive fiber membrane and its preparation method. By introducing large, rigid fluorene groups into the molecular chain of polyamide-imide, the glass transition temperature is increased, effectively suppressing relaxation and creep behavior. After the polyamide-imide is spun into a fiber membrane using electrospinning technology, a polyaniline conductive shell is grafted onto the surface of the electrospun polyamide-imide fiber membrane using in-situ chemical polymerization.

[0004] CN1162888930A discloses a polyamide-imide nanofiber membrane and its preparation method. The preparation method includes: electrospinning a spinning solution containing polyamide-imide, nanofillers, and a solvent to obtain a polyamide-imide nanofiber membrane. Using fiber-reinforced resin prepreg or fiber fabric as the receiving substrate, electrospinning a spinning solution containing polyamide-imide and nanofillers to obtain a bilayer composite material. The bilayer composite material is then cut, stacked, and cured to obtain a composite material board. The final composite material board consists of a fiber / resin composite material and a toughening layer inserted therein, wherein the toughening layer is a polyamide-imide nanofiber membrane.

[0005] To date, there have been no reports on composite fiber membranes formed from polyamide-imide, polyvinylpyrrolidone, and conductive particles that can maintain conductivity even under extreme temperature conditions. Summary of the Invention

[0006] In view of this, one object of the present invention is to provide a composite fiber membrane that can exhibit stable conductivity in extreme temperature environments. Another object of the present invention is to provide a method for preparing the composite fiber membrane. A further object of the present invention is to provide applications of the composite fiber membrane described above. The present invention achieves the above objects through the following technical solutions.

[0007] On one hand, the present invention provides a composite fiber membrane comprising 90-95 parts by weight of polyamide-imide, 2-5 parts by weight of polyvinylpyrrolidone and 2-5 parts by weight of conductive material.

[0008] According to the composite fiber membrane of the present invention, preferably, the conductive material is selected from one or more of graphene, graphene oxide, conductive carbon black, silver nanowires, copper nanowires, and polycarbazole.

[0009] In the composite fiber membrane of the present invention, preferably, the molecular weight of polyamide-imide is 5,000 to 400,000; and the molecular weight of polyvinylpyrrolidone is 360,000 to 1,300,000.

[0010] According to the composite fiber membrane of the present invention, preferably, the diameter of the fibers in the composite fiber membrane is 500 nm to 3 μm; and the tensile strength of the composite fiber membrane is 0.5 to 20 MPa.

[0011] The composite fiber membrane according to the present invention is preferably composed of 90-95 parts by weight of polyamide-imide, 2-5 parts by weight of polyvinylpyrrolidone and 2-5 parts by weight of conductive material.

[0012] On the other hand, the present invention also provides a method for preparing a composite fiber membrane according to the above description, comprising the following steps:

[0013] (1) Polyamide imide, polyvinylpyrrolidone and a conductive substance are placed in a solvent to form a colloid;

[0014] (2) The colloid is used as a spinning solution for air-jet spinning to obtain a spinning material; the spinning material is heated to obtain a composite fiber membrane.

[0015] According to the preparation method of the present invention, preferably, the solvent is selected from one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and dimethyl sulfoxide.

[0016] According to the preparation method of the present invention, preferably, the mass ratio of polyamide-imide, polyvinylpyrrolidone and conductive material to the total mass of colloid is 18-30:100.

[0017] According to the preparation method of the present invention, preferably:

[0018] The injection rate of the spinning solution is 0.5–2 mL / min, and the gas pressure is 0.01–0.04 MPa;

[0019] The spinning material is heated at 260–350°C for 0.5–2 hours to obtain a composite fiber membrane.

[0020] In another aspect, the present invention also provides the application of the composite fiber membrane as described above, which is used as an electrical signal transmission material in the manufacture of temperature sensors, flexible sensors or smart wearable textiles.

[0021] The composite fiber membrane of this invention maintains stable conductivity even under extreme temperature conditions (e.g., extremely low temperatures of -196°C and high temperatures of 300°C). Its resistance decreases with increasing temperature, exhibiting a certain degree of temperature sensitivity. The transmitted electrical signals are highly sensitive, and different electrical signals can be transmitted by tapping or pressing the fiber membrane, with a ΔR / R0 range of 0–3800%. It has broad application prospects in temperature sensors, flexible sensors, and smart wearable textiles. The composite fiber membrane of this invention has good mechanical properties, such as high tensile strength. The preparation method of this invention has good process stability and repeatability, allowing for in-situ enhancement of the tensile strength and flexibility of the composite fiber membrane. Attached Figure Description

[0022] Figure 1 This is a SEM image of the composite fiber membrane obtained in Example 1 of the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0024] <Composite Fiber Membrane>

[0025] The composite fiber membrane of this invention comprises polyamide-imide, polyvinylpyrrolidone, and a conductive material. Specifically, it comprises 90-95 parts by weight of polyamide-imide, 2-5 parts by weight of polyvinylpyrrolidone, and 2-5 parts by weight of the conductive material. Such a composite fiber membrane exhibits stable conductivity under extreme temperature conditions (e.g., -196°C and 300°C). Furthermore, its resistance decreases with increasing temperature, exhibiting a certain degree of temperature sensitivity, and the transmitted electrical signal has high sensitivity (100ms-200ms). Different electrical signals can be transmitted by tapping or pressing the fiber membrane, with a ΔR / R0 of 0-3800%. Such a composite fiber membrane has broad application prospects in temperature sensors, flexible sensors, and smart wearable textiles.

[0026] Preferably, the composite fiber membrane of the present invention comprises 90-95 parts by weight of polyamide-imide, 3-5 parts by weight of polyvinylpyrrolidone, and 2-5 parts by weight of conductive material. More preferably, the composite fiber membrane of the present invention comprises 92-94 parts by weight of polyamide-imide, 3-4 parts by weight of polyvinylpyrrolidone, and 2-4 parts by weight of conductive material.

[0027] In some embodiments, the composite fiber membrane of the present invention comprises 90-95 parts by weight of polyamide-imide, 2-5 parts by weight of polyvinylpyrrolidone, and 2-5 parts by weight of a conductive material. Preferably, the composite fiber membrane of the present invention comprises 90-95 parts by weight of polyamide-imide, 3-5 parts by weight of polyvinylpyrrolidone, and 2-5 parts by weight of a conductive material. More preferably, the composite fiber membrane of the present invention comprises 92-94 parts by weight of polyamide-imide, 3-4 parts by weight of polyvinylpyrrolidone, and 2-4 parts by weight of a conductive material.

[0028] In this invention, the conductive material is selected from one or more of graphene, graphene oxide, conductive carbon black, silver nanowires, copper nanowires, and polycarbazole. Preferably, the conductive material is selected from one or more of graphene, graphene oxide, and conductive carbon black. More preferably, the conductive material is selected from one of graphene, graphene oxide, and conductive carbon black.

[0029] The molecular weight of the polyamide-imide is 5,000 to 400,000, preferably 8,000 to 400,000, more preferably 8,000 to 200,000, and even more preferably 10,000 to 80,000.

[0030] The molecular weight range of polyvinylpyrrolidone is 30,000 to 1,300,000, preferably 360,000 to 1,300,000, and more preferably 580,000 to 1,300,000.

[0031] The composite fiber membrane of the present invention has a fiber diameter of 500 nm to 3 μm and a tensile strength of 0.5 to 20 MPa.

[0032] <Preparation Method of Composite Fiber Membrane>

[0033] The present invention also provides a method for preparing the composite fiber membrane as described above, comprising the following steps:

[0034] (1) Polyamide imide, polyvinylpyrrolidone and a conductive substance are placed in a solvent to form a colloid;

[0035] (2) The colloid is used as a spinning solution for air-jet spinning to obtain a spinning material; the spinning material is heated to obtain a composite fiber membrane.

[0036] This invention uses polyvinylpyrrolidone (PVP) as a spinning aid and conductive particle dispersant. By using an air-jet spinning machine, the spinning solution is blown and sprayed with high-speed airflow to separate and solidify the phases to form a fiber membrane. Conductive particles are introduced during the spinning process, enabling the insulating material PAI to become conductive. Subsequently, the membrane is heated and kept at a high temperature to perform in-situ thermal imidization reinforcement, locking and stabilizing the conductive particles. The resulting composite fiber membrane has enhanced tensile strength and flexibility.

[0037] In step (1), the weight proportions of polyamide-imide, polyvinylpyrrolidone, and the conductive material are as described above and will not be repeated here. In this invention, both polyamide-imide and polyvinylpyrrolidone can be in powder form.

[0038] The solvent is selected from one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran and dimethyl sulfoxide, preferably one of N,N-dimethylformamide, N,N-dimethylacetamide and tetrahydrofuran, and more preferably N,N-dimethylformamide.

[0039] The mass ratio of polyamide-imide, polyvinylpyrrolidone, and conductive material to the total mass of the colloid is 18–30:100, i.e., the mass concentration of solute in the colloid is 18–30 wt%. Preferably, the mass ratio of polyamide-imide, polyvinylpyrrolidone, and conductive material to the total mass of the colloid is 20–27:100, more preferably 20–25:100.

[0040] In step (2), the air-jet spinning process conditions include an injection rate of 0.5–2 mL / min, preferably 0.5–1.8 mL / min, and more preferably 1–1.5 mL / min. The air pressure intensity (i.e., airflow pressure) is 0.01–0.04 MPa, preferably 0.02–0.04 MPa, and more preferably 0.02–0.03 MPa. The receiving distance is 20–22 cm. The spinning time is 2–5 h.

[0041] The spinning material is heated to obtain a composite fiber membrane. The heating temperature can be 260–350°C, preferably 280–350°C, and more preferably 300–330°C. The heating time can be 0.5–2 hours, preferably 0.5–1.5 hours, and more preferably 1–1.5 hours.

[0042] The resulting composite fiber membrane exhibits good mechanical properties and excellent electrical conductivity under extreme low and high temperature conditions.

[0043] <Application>

[0044] This composite fiber membrane is used as an electrical signal transmission material in the manufacture of temperature sensors, flexible sensors, and smart wearable textiles. The composite fiber membrane retains conductivity even under extreme temperature conditions (e.g., -196°C and 300°C), and preferably, it maintains stable conductivity between -196°C and 300°C.

[0045] The composite fiber membrane of this invention can be attached to human skin such as fingers, arms, knees, chest, and throat. By bending fingers, arms, knees, heartbeats, and breathing, different types of electrical signals can be measured, providing timely feedback on different human information. This allows the composite fiber membrane to be applied to smart textiles.

[0046] The range of change in the electrical signal (i.e., resistance signal) based on the bending angle of the composite fiber membrane can reach up to 3800%.

[0047] Because of its resistance to extreme temperatures, composite fiber membranes can be considered for application in high- or low-temperature environments, such as fire suits, high-temperature work clothes, Antarctic low-temperature work clothes, and accessories for work equipment in high and low temperature environments.

[0048] <Analysis and Testing Methods>

[0049] Tensile strength testing: A universal tensile strength tester was used for testing.

[0050] SEM testing: The test was conducted using a German Gemini SEM500 thermal field emission scanning electron microscope.

[0051] Measurement of the electrical signal (resistance signal) of the composite fiber membrane: Composite fiber membrane size: 10*20mm; Instrument: Digital source meter. By clamping the two ends of the composite fiber membrane with the two clips of the digital source meter, the real-time resistance change, resistance change rate, and resistance change response time of the composite fiber membrane can be measured. In the following examples, ΔR / R0 is calculated. Both the cold source (liquid nitrogen environment) and the heat source (hot stage) are conductive, and the resistance decreases with increasing temperature. Stable and different electrical signals can be transmitted through touch or long press under different temperature environments. The formula for calculating ΔR / R0 is as follows:

[0052]

[0053] Where ΔR = |R1 - R0| is the absolute value of the change in resistance;

[0054] R0 is the original resistance value; R0 is different under different temperature conditions.

[0055] R1 is the changed resistance value. That is, R1 is the changed resistance value obtained by tapping or pressing and holding during the test.

[0056] The raw materials used in the following examples and comparative examples are described below:

[0057] Polyamide-imide powder: purchased from Solvay, USA, PAI 4000TF.

[0058] Polyvinylpyrrolidone granules: molecular weight 1,300,000, purchased from Wuxi Yatai United Chemical Co., Ltd.

[0059] Conductive carbon black granules: purchased from SCM INDUSTRIAL CHEMICAL CO.,LTD, model number TIMCAL SUPER PLI.

[0060] Graphene: Purchased from Shenzhen Suiheng Technology Co., Ltd., it is single-layer graphene.

[0061] Graphene oxide: Purchased from Shenzhen Suiheng Technology Co., Ltd., it is a single-layer graphene oxide.

[0062] Example 1

[0063] 90 parts by weight of polyamide-imide powder with a molecular weight of 8000, 5 parts by weight of polyvinylpyrrolidone granules, and 5 parts by weight of conductive carbon black granules were respectively placed in N,N-dimethylformamide and mixed to form a colloid. The mass concentration of the solute in the colloid was 20 wt%.

[0064] The colloid was used as the spinning solution for air-jet spinning. The process conditions were: air pressure intensity of 0.02 MPa, receiving distance of 20 cm, injection rate of spinning solution of 1 mL / h, and spinning time of 2 h, to obtain the spun material. The spun material was then heated at 300℃ for 0.5 h to obtain a composite fiber membrane.

[0065] The tensile strength of the resulting composite fiber membrane is 2.4 MPa, which is 1.5 times stronger than that of the spinning material.

[0066] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 was 200% at -196℃, 600% at 25℃, and 1400% at 300℃.

[0067] Example 2

[0068] The only difference from Example 1 is that the molecular weight of the polyamide-imide used is 10,000.

[0069] The tensile strength of the resulting composite fiber membrane is 5.6 MPa, which is 1.8 times stronger than that of the spinning material.

[0070] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 reached 250% at -196℃, 700% at 25℃, and 1600% at 300℃.

[0071] Example 3

[0072] The only difference from Example 1 is that the molecular weight of the polyamide-imide used is 20,000.

[0073] The tensile strength of the resulting composite fiber membrane is 10.0 MPa, which is twice that of the spinning material.

[0074] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 was 350% at -196℃, 900% at 25℃, and 1800% at 300℃.

[0075] Example 4

[0076] The only difference from Example 3 is that the mass concentration of the formed colloid is 25 wt%.

[0077] The tensile strength of the resulting composite fiber membrane is 2.2 times stronger than that of the spinning material.

[0078] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The maximum ΔR / R0 reached 400% at -196℃, 1000% at 25℃, and 2000% at 300℃.

[0079] Example 5

[0080] The only difference from Example 4 is that the obtained spinning material is heated at 350°C for 0.5 hours to obtain a composite fiber membrane.

[0081] The tensile strength of the resulting composite fiber membrane is 2.5 times stronger than that of the spinning material.

[0082] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 was 500% at -196℃, 1200% at 25℃, and 2500% at 300℃.

[0083] Example 6

[0084] The difference from Example 3 is that the weight proportions of the raw materials are different. In this example, the polyamide-imide powder with a molecular weight of 20,000 is 92 parts by weight, the polyvinylpyrrolidone granules are 4 parts by weight, and the conductive carbon black granules are 4 parts by weight.

[0085] The tensile strength of the resulting composite fiber membrane is twice that of the spun material.

[0086] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 was 800% at -196℃, 1600% at 25℃, and 3000% at 300℃.

[0087] Example 7

[0088] The difference from Example 3 is that the weight proportions of the raw materials are different. In this example, the polyamide-imide powder with a molecular weight of 20,000 is 94 parts by weight, the polyvinylpyrrolidone granules are 3 parts by weight, and the conductive carbon black granules are 3 parts by weight.

[0089] The tensile strength of the resulting composite fiber membrane is 2.5 times stronger than that of the spinning material.

[0090] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 reached 600% at -196℃, 1400% at 25℃, and 2400% at 300℃.

[0091] Example 8

[0092] 90 parts by weight of polyamide-imide powder with a molecular weight of 100,000, 5 parts by weight of polyvinylpyrrolidone granules, and 5 parts by weight of conductive carbon black granules were respectively placed in N,N-dimethylformamide and mixed to form a colloid. The mass concentration of the solute in the colloid was 22 wt%.

[0093] The colloid was used as the spinning solution for air-jet spinning. The process conditions were: air pressure intensity of 0.03 MPa, receiving distance of 20 cm, injection rate of spinning solution of 1 mL / h, and spinning time of 2 h, to obtain the spun material. The spun material was then heated at 350℃ for 0.5 h to obtain a composite fiber membrane.

[0094] The tensile strength of the resulting composite fiber membrane is 1.8 times stronger than that of the spinning material.

[0095] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 reached 700% at -196℃, 1800% at 25℃, and 3000% at 300℃.

[0096] Example 9

[0097] 90 parts by weight of polyamide-imide powder with a molecular weight of 100,000, 5 parts by weight of polyvinylpyrrolidone granules, and 5 parts by weight of conductive carbon black granules were respectively placed in N,N-dimethylformamide and mixed to form a colloid. The mass concentration of the solute in the colloid was 22 wt%.

[0098] The colloid was used as the spinning solution for air-jet spinning. The process conditions were: air pressure of 0.04 MPa, receiving distance of 20 cm, injection rate of spinning solution of 1 mL / h, and spinning time of 2 h, to obtain the spun material. The spun material was then heated at 350℃ for 1 h to obtain a composite fiber membrane.

[0099] The tensile strength of the resulting composite fiber membrane is 2.6 times stronger than that of the spinning material.

[0100] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 reached 700% at -196℃, 1800% at 25℃, and 3000% at 300℃.

[0101] Example 10

[0102] The only difference from Example 9 is that the spinning time in the spinning process is 4 hours, and the spinning material is heated at 350°C for 0.5 hours to obtain a composite fiber membrane.

[0103] The tensile strength of the resulting composite fiber membrane is 2.6 times stronger than that of the spinning material.

[0104] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 was 800% at -196℃, 2000% at 25℃, and 3500% at 300℃.

[0105] Example 11

[0106] 90 parts by weight of polyamide-imide powder with a molecular weight of 200,000, 5 parts by weight of polyvinylpyrrolidone granules, and 5 parts by weight of conductive carbon black granules were respectively placed in N,N-dimethylformamide and mixed to form a colloid. The mass concentration of the solute in the colloid was 22 wt%.

[0107] The colloid was used as the spinning solution for air-jet spinning. The process conditions were: air pressure of 0.03 MPa, receiving distance of 20 cm, injection rate of spinning solution of 1 mL / h, and spinning time of 5 h, to obtain the spun material. The spun material was then heated at 300℃ for 1 h to obtain a composite fiber membrane.

[0108] The tensile strength of the resulting composite fiber membrane is twice that of the spun material.

[0109] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 reached 1000% at -196℃, 2400% at 25℃, and 3800% at 300℃.

[0110] Example 12

[0111] The only difference from Example 11 is the weight percentage of the raw materials. 92 parts by weight of polyamide-imide powder with a molecular weight of 200,000, 4 parts by weight of polyvinylpyrrolidone granules, and 4 parts by weight of conductive carbon black granules.

[0112] The tensile strength of the resulting composite fiber membrane is three times greater than that of the spun material.

[0113] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 was 800% at -196℃, 1500% at 25℃, and 2200% at 300℃.

[0114] Example 13

[0115] 90 parts by weight of polyamide-imide powder with a molecular weight of 400,000, 5 parts by weight of polyvinylpyrrolidone granules, and 5 parts by weight of conductive carbon black granules were respectively placed in N,N-dimethylformamide and mixed to form a colloid. The mass concentration of the solute in the colloid was 22 wt%.

[0116] The colloid was used as the spinning solution for air-jet spinning. The process conditions were: air pressure of 0.04 MPa, receiving distance of 20 cm, injection rate of spinning solution of 1 mL / h, and spinning time of 5 h, to obtain the spun material. The spun material was then heated at 350℃ for 2 h to obtain a composite fiber membrane.

[0117] The tensile strength of the resulting composite fiber membrane is 3.5 times stronger than that of the spinning material.

[0118] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 reached 1000% at -196℃, 1700% at 25℃, and 2500% at 300℃.

[0119] Example 14

[0120] The only difference from Example 13 is that graphene is used instead of conductive carbon black particles.

[0121] The tensile strength of the resulting composite fiber membrane is 2.4 times stronger than that of the spinning material.

[0122] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 reached 400% at -196℃, 1200% at 25℃, and 1800% at 300℃.

[0123] Example 15

[0124] The only difference from Example 14 is the weight percentage of the raw materials. In this example, the polyamide-imide powder with a molecular weight of 400,000 is 92 parts by weight, the polyvinylpyrrolidone particles are 4 parts by weight, and the graphene is 4 parts by weight.

[0125] The tensile strength of the resulting composite fiber membrane is 2.5 times stronger than that of the spinning material.

[0126] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 reached 600% at -196℃, 1800% at 25℃, and 2400% at 300℃.

[0127] Example 16

[0128] The only difference from Example 1 is that the molecular weight of the polyamide-imide used is 30,000.

[0129] The tensile strength of the resulting composite fiber membrane is 2.8 times stronger than that of the spinning material.

[0130] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 reached 800% at -196℃, 1400% at 25℃, and 1800% at 300℃.

[0131] Example 17

[0132] The only difference from Example 1 is the weight percentage of the raw materials. The polyamide-imide powder with a molecular weight of 30,000 is 95 parts by weight, polyvinylpyrrolidone granules are 2 parts by weight, and conductive carbon black granules are 3 parts by weight.

[0133] The tensile strength of the resulting composite fiber membrane is 3.5 times stronger than that of the spinning material.

[0134] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 reached 600% at -196℃, 1200% at 25℃, and 1500% at 300℃.

[0135] Example 18

[0136] 90 parts by weight of polyamide-imide powder with a molecular weight of 200,000, 5 parts by weight of polyvinylpyrrolidone particles, and 5 parts by weight of graphene were respectively placed in N,N-dimethylformamide and mixed to form a colloid. The mass concentration of the solute in the colloid was 24 wt%.

[0137] The colloid was used as the spinning solution for air-jet spinning. The process conditions were: air pressure of 0.04 MPa, receiving distance of 20 cm, injection rate of spinning solution of 1 mL / h, and spinning time of 2 h, to obtain the spun material. The spun material was then heated at 300℃ for 1 h to obtain a composite fiber membrane.

[0138] The tensile strength of the resulting composite fiber membrane is 2.4 times stronger than that of the spinning material.

[0139] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 was 400% at -196℃, 800% at 25℃, and 1500% at 300℃.

[0140] Example 19

[0141] The only difference from Example 18 is that graphene oxide is used instead of graphene.

[0142] The tensile strength of the resulting composite fiber membrane is three times greater than that of the spun material.

[0143] The electrical signal changes of the composite fiber membrane were tested at different temperature environments ranging from -196℃ to 300℃. The highest ΔR / R0 reached 500% at -196℃, 1000% at 25℃, and 1800% at 300℃.

[0144] In summary, this invention can enhance the mechanical properties of the resulting composite fiber membrane in situ, especially its tensile strength and flexibility, and can lock and stabilize conductive particles. The composite fiber membrane exhibits stable conductivity in extreme temperature environments (from -196°C to 300°C), and its resistance decreases with increasing temperature, demonstrating a certain degree of temperature sensitivity.

[0145] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A method for preparing a composite fiber membrane for use as an electrical signal transmission material in the manufacture of temperature sensors, flexible sensors, or smart wearable textiles, characterized in that, The composite fiber membrane is composed of 90-95 parts by weight of polyamide-imide, 2-5 parts by weight of polyvinylpyrrolidone and 2-5 parts by weight of conductive material. The method for preparing the composite fiber membrane includes the following steps: (1) Polyamide imide, polyvinylpyrrolidone and a conductive substance are placed in a solvent to form a colloid; (2) The colloid is used as a spinning solution for air-jet spinning to obtain a spinning material; the spinning material is heated at 260-350℃ for 0.5-2h to obtain a composite fiber membrane; The conductive material is selected from one or more of graphene, graphene oxide, and conductive carbon black. The mass ratio of polyamide-imide, polyvinylpyrrolidone, and conductive material to the total mass of the colloid is 18–30:

100. The injection speed of the spinning solution is 0.5–2 mL / min, the air pressure is 0.01–0.04 MPa, and the receiving distance is 20–22 cm. Different electrical signals can be transmitted by tapping or pressing the composite fiber membrane, with ΔR / R0 ranging from 0 to 3800%; wherein, the electrical signal is a resistance signal; The formula for calculating △R / R0 is as follows: ； Where ΔR = |R1 - R0| is the absolute value of the change in resistance; R0 is the original resistance value; R1 is the changed resistance value; that is, R1 is the changed resistance value obtained by tapping or pressing during the test.

2. The preparation method according to claim 1, characterized in that, The molecular weight of polyamide-imide is 5,000 to 400,000; the molecular weight of polyvinylpyrrolidone is 30,000 to 1,300,000.

3. The preparation method according to claim 1, characterized in that, The diameter of the fibers in the composite fiber membrane is 500 nm to 3 μm; the tensile strength of the composite fiber membrane is 0.5 to 20 MPa.

4. The preparation method according to claim 1, characterized in that, The solvent is selected from one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and dimethyl sulfoxide.

5. A composite fiber membrane prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the composite fiber membrane according to claim 5, characterized in that, This composite fiber membrane is used as an electrical signal transmission material in the manufacture of temperature sensors, flexible sensors, or smart wearable textiles.

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