Polyimide nano short fiber and preparation method thereof

Abstract

The invention provides polyimide nano short fibers and a preparation method thereof. The preparation method of the polyimide short nanofibers comprises the following steps: (1) preparing polyimide long nanofibers; (2) carrying out high-temperature treatment on the polyimide nano long fiber; and (3) the polyimide nano long fibers after high-temperature treatment are crushed to obtain polyimide nano short fibers, the diameter of the polyimide nano short fibers is 100-1000 nm, and the length of the polyimide nano short fibers is 5-200 [mu] m. Compared with the prior art, the preparation method comprises the following steps: preparing polyimide nano long fibers from a polyamide acid solution through an electrostatic spinning or centrifugal spinning process, carrying out high-temperature treatment, and carrying out laser cutting, ball milling, high-speed cutting and other external force crushing processes to prepare polyimide nano short fibers, the diameter of the fibers is 100-1000 nm, the length is 5-200 [mu] m, and the diameter of the fibers is 1-10 [mu] m. And the product can be completely dispersed in an aqueous solution.

Description

Technical Field

[0001] The invention relates to the technical field of fiber preparation, in particular to a polyimide nano short fiber and a preparation method thereof. Background Art

[0002] As a special engineering material, polyimide has been widely used in aviation, aerospace, microelectronics, nanotechnology, liquid crystal, separation membrane, laser and other fields. In the 1960s, all countries listed the research, development and utilization of polyimide as one of the most promising engineering plastics in the 21st century. In particular, as one of the most high-temperature resistant materials at the top of the pyramid, polyimide has shown increasing potential in the field of high-temperature resistance.

[0003] However, the high cost of polyimide has limited its further application. One solution is to prepare polyimide into short-cut nanofibers and compound them with a second component. Electrospinning technology and centrifugal spinning technology are common methods for preparing polyimide. The polyimide fibers prepared by these two methods are usually long nanofibers. If the long polyimide fibers are directly cut and dispersed in an aqueous solution, the polyimide fibers will show obvious agglomeration and cannot be completely dispersed in the aqueous solution. See Figure 1 When the polyimide nano short fibers prepared by this method are compounded with the second component, the uniformity of the composite material will be affected. Summary of the invention

[0004] Based on this, the object of the present invention is to provide a polyimide nano short fiber and a preparation method thereof.

[0005] In a first aspect, the present invention provides a method for preparing polyimide short nanofibers, comprising the following steps:

[0006] (1) Preparing polyimide nanofibers;

[0007] (2) subjecting the polyimide nanofibers to high temperature treatment;

[0008] (3) The polyimide nano long fibers after high temperature treatment are crushed to obtain polyimide nano short fibers, wherein the polyimide nano short fibers have a diameter of 100-1000 nm and a length of 5-200 μm.

[0009] In one embodiment, in step (3), laser cutting, ball milling or high-speed crusher is used to crush the polyimide nano-long fibers after high-temperature treatment.

[0010] In one of the embodiments, the laser cutting speed is 10-1000 cm / min, nitrogen or argon is assisted, the cutting slit width is 20-100 μm, and the laser cutting power is 20-2000W.

[0011] In one embodiment, in the ball milling, the ball milling medium is one or more of water, ethanol, ethyl acetate, and petroleum ether.

[0012] In one of the embodiments, in the ball milling, the ball-to-material ratio is 100:1-10000:1, the ball milling time is 1-24h, and the ball milling speed is 200-2000r / min.

[0013] In one embodiment, zirconium oxide balls are added during the ball milling, and the zirconium oxide balls include zirconium balls with a diameter of 10 mm, zirconium balls with a diameter of 6 mm, zirconium balls with a diameter of 2 mm, and zirconium balls with a diameter of 0.5 mm, and the mass ratio of each zirconium ball is at most 30% and at least 5%.

[0014] In one embodiment, the rotation speed of the high-speed crusher is 1000-100000 r / min, the crushing temperature is (-50)-(+120)°C, the crushing time is 1-60 min, and the crushing medium is one or more of water, methanol, ethanol, ethyl acetate, petroleum ether, dichloromethane, dimethylformamide, N-methylpyrrolidone, or no medium.

[0015] In one embodiment, in step (1), polyimide nanofibers are prepared by a centrifugal spinning process or an electrospinning process.

[0016] In one embodiment, in step (2), the high temperature treatment is performed at a temperature of 100-400° C. and for a time of 200-500 min.

[0017] In a second aspect, the present invention provides a polyimide short nanofiber, which is prepared by any of the aforementioned methods for preparing polyimide short nanofibers.

[0018] Compared with the prior art, the present invention first prepares polyimide nano-long fibers from a polyamic acid solution through an electrostatic spinning or centrifugal spinning process, then treats it at high temperature, and then breaks it through external forces such as laser cutting, ball milling, and high-speed cutting processes to prepare polyimide nano-short fibers, the fiber diameter of which is 100-1000nm, the length of which is 5-200μm, and can be completely dispersed in an aqueous solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of directly cutting polyimide nanofibers and dispersing them in aqueous solution;

[0020] Figure 2 This is a SEM electron microscope image of the polyimide nano short fibers prepared in Example 1 of the present invention;

[0021] Figure 3This is a schematic diagram of polyimide short nanofibers prepared in Example 1 of the present invention dispersed in an aqueous solution;

[0022] Figure 4 This is a SEM electron microscope image of the polyimide short nanofibers prepared in Example 4 of the present invention;

[0023] Figure 5 This is a schematic diagram of polyimide short nanofibers prepared in Example 4 of the present invention dispersed in an aqueous solution;

[0024] Figure 6 This is a SEM electron microscope image of the polyimide nano short fibers prepared in Example 7 of the present invention;

[0025] Figure 7 This is a schematic diagram of polyimide short nanofibers prepared in Example 7 of the present invention dispersed in an aqueous solution. DETAILED DESCRIPTION

[0026] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0027] The preparation method of the polyimide nano short fibers of the present invention comprises the following steps: preparing polyimide nano long fibers by conventional methods, first subjecting the fibers to high temperature treatment, and then subjecting the fibers to external force crushing, thereby obtaining polyimide nano short fibers with a fiber diameter of 100-1000 mm and a fiber length of 5-200 μm.

[0028] Specifically, the method for preparing the polyimide short nanofibers of the present invention comprises the following steps:

[0029] (1) Preparation of polyimide nanofibers.

[0030] Specifically, the polyimide nano-long fibers are prepared by a centrifugal spinning process or an electrostatic spinning process.

[0031] Preferably, in the centrifugal spinning process, the solid content of the glue solution is 5%-30%, the rotating aperture is 0.1-1.5 mm, the centrifuge speed is 1000-10000 r / min, the feed rate is 0.1-2 g / min, the temperature is 10-50°C, and the air humidity is 30%-70% RH.

[0032] Preferably, in the electrospinning process, the solid content of the glue is 5%-30%, the needle diameter is 0.2-2mm, the feed speed is 0.2-2mL / h, the receiving distance is 5-20cm, the positive electrode voltage is (+5)kV-(+25)kV, the negative electrode voltage is (-1)kV-(-10)kV, the roller speed is 50-3000r / min, the temperature is 10-50℃, and the air humidity is 30%-70% RH.

[0033] (2) The polyimide nanofibers are subjected to high temperature treatment.

[0034] The temperature of the high temperature treatment is 100-400°C and the time is 200-500min.

[0035] Preferably, a step-by-step heating method is adopted with a heating rate of 5°C / min, heating from 25°C to 150°C and staying for 1 hour; heating from 150°C to 200°C and staying for 1 hour; heating from 200°C to 300°C and staying for 1 hour; heating from 300°C to 350°C and staying for 30 minutes.

[0036] (3) The polyimide nano long fibers after high temperature treatment are crushed to obtain polyimide nano short fibers, wherein the polyimide nano short fibers have a diameter of 100-1000 nm and a length of 5-200 μm.

[0037] Specifically, laser cutting, ball milling or high-speed crusher is used to crush the polyimide nano-long fibers after high-temperature treatment.

[0038] Preferably, the laser cutting speed is 10-1000 cm / min, nitrogen or argon is used as an auxiliary, the cutting slit width is 20-100 μm, and the laser cutting power is 20-2000W.

[0039] Preferably, in the ball milling, the ball milling medium is one or more of water, ethanol, ethyl acetate, petroleum ether, or there is no ball milling medium.

[0040] Preferably, in the ball milling, the ball-to-material ratio is 100:1-10000:1, the ball milling time is 1-24h, and the ball milling speed is 200-2000r / min.

[0041] Preferably, during the ball milling, zirconium oxide balls are added, and the zirconium oxide balls include zirconium balls with a diameter of 10 mm, zirconium balls with a diameter of 6 mm, zirconium balls with a diameter of 2 mm, and zirconium balls with a diameter of 0.5 mm, and the mass ratio of each zirconium ball is at most 30% and at least 5%.

[0042] Preferably, the rotation speed of the high-speed crusher is 1000-100000 r / min, the crushing temperature is (-50)-(+120)°C, the crushing time is 1-60 min, and the crushing medium is one or more of water, methanol, ethanol, ethyl acetate, petroleum ether, dichloromethane, dimethylformamide, N-methylpyrrolidone, or no medium.

[0043] In order to further understand the present invention, the preparation method of the polyimide nano short fibers provided by the present invention is described in detail below in conjunction with the examples. The protection scope of the present invention is not limited by the following examples.

[0044] Example 1

[0045] Weigh 2.1812g of pyromellitic anhydride and add it to 34mL of DMF solution containing 2.0024g of 4,4-diaminodiphenyl ether, with a solid content of 12%. React for 24h, then transfer it to a 10mL syringe and electrospin it. Control the voltage to +15kV, -2kV, needle diameter to 0.5mm, receiving distance to 15cm, temperature to 25℃, air humidity to 50%, roller speed to 200r / min, and propulsion speed to 1mL / h. Electrospinning time is 2h, and polyimide nanofibers with a diameter of 300-500nm are obtained.

[0046] The polyimide nanofibers prepared as above were subjected to high temperature treatment by step-wise heating at a heating rate of 5°C / min, from 25°C to 150°C, and stayed for 1 hour; from 150°C to 200°C, and stayed for 1 hour; from 200°C to 300°C, and stayed for 1 hour; from 300°C to 350°C, and stayed for 30 minutes.

[0047] The high-temperature treated polyimide nano long fibers were placed on a laser cutting machine, and the laser cutting speed was set to 60 cm / min, nitrogen assisted, the cutting slit width was 100 μm, and the laser cutting power was 300 W to obtain polyimide nano short fibers.

[0048] See also Figure 2 As shown in the SEM electron microscope image, in Example 1, laser dot matrix is ​​used to uniformly cut polyimide into short fibers, and the fiber length is about 50 μm. The polyimide nano short fibers prepared in Example 1 are dispersed in an aqueous solution, such as Figure 3 As shown, the polyimide nano short fibers of Example 1 are completely and evenly dispersed in the aqueous solution.

[0049] Example 2

[0050] Weigh 2.1812g of pyromellitic anhydride and add it to 34mL of DMF solution containing 2.0024g of 4,4-diaminodiphenyl ether, with a solid content of 28%. React for 24h, then transfer it to a 10mL syringe and electrospin it. Control the voltage to +5kV, -8kV, needle diameter to 1.8mm, receiving distance to 6cm, temperature to 15℃, air humidity to 70%, roller speed to 2800r / min, and propulsion speed to 0.2mL / h. Electrospinning time is 2h, and polyimide nanofibers with a diameter of 500nm are obtained.

[0051] The polyimide nanofibers prepared as above were subjected to high temperature treatment by step-wise heating at a heating rate of 5°C / min, from 25°C to 150°C, and stayed for 1 hour; from 150°C to 200°C, and stayed for 1 hour; from 200°C to 300°C, and stayed for 1 hour; from 300°C to 350°C, and stayed for 30 minutes.

[0052] The high-temperature treated polyimide nanofibers were placed on a laser cutting machine, and the laser cutting speed was set to 800 cm / min, argon gas was assisted, the cutting slit width was 260 μm, and the laser cutting power was 2000 W to obtain polyimide nanofibers with a length of 200 μm.

[0053] Example 3

[0054] Weigh 2.1812g of pyromellitic anhydride and add it to 34mL of DMF solution containing 2.0024g of 4,4-diaminodiphenyl ether, with a solid content of 5%, react for 24h, then transfer it to a 10mL syringe, and electrospin it with a controlled voltage of +25kV, -6kV, a needle diameter of 1mm, a receiving distance of 20cm, a temperature of 40℃, an air humidity of 40%, a roller speed of 1200r / min, and a propulsion speed of 2mL / h. The electrospinning time is 2h, and polyimide nanofibers with a diameter of 100nm are obtained.

[0055] The polyimide nanofibers prepared as above were subjected to high temperature treatment by step-wise heating at a heating rate of 5°C / min, from 25°C to 150°C, and stayed for 1 hour; from 150°C to 200°C, and stayed for 1 hour; from 200°C to 300°C, and stayed for 1 hour; from 300°C to 350°C, and stayed for 30 minutes.

[0056] The high-temperature treated polyimide nanofibers were placed on a laser cutting machine, and the laser cutting speed was set to 500 cm / min, nitrogen assisted, the cutting slit width was 20 μm, and the laser cutting power was 50 W to obtain polyimide nanofibers with a length of 10 μm.

[0057] Example 4

[0058] The preparation and high temperature treatment process of the polyimide nano long fibers in this embodiment are the same as those in Embodiment 1, except that the preparation of the polyimide nano short fibers is as follows:

[0059] 2 g of high-temperature treated polyimide nano-long fibers were placed in a ball mill containing 40 g of ethyl acetate solvent, and 200 g of zirconia balls were added, wherein the mass ratio of 10 mm diameter zirconium balls: 6 mm diameter zirconium balls: 2 mm diameter zirconium balls: 0.5 mm diameter zirconium balls was 1:1:1:1. The ball milling time was 24 h, and the ball milling speed was 600 r / min to obtain polyimide nano-short fibers.

[0060] See also Figure 4 As shown in the SEM electron microscope image, in Example 4, high-speed ball milling was used to break the polyimide nano-long fibers, and the fiber length was about 5-20 μm. The polyimide nano-short fibers prepared in Example 4 were dispersed in an aqueous solution, such as Figure 5 As shown, the polyimide nano short fibers of Example 4 are completely and evenly dispersed in the aqueous solution.

[0061] Example 5

[0062] Weigh 2.1812g of pyromellitic anhydride and add it to 34mL of DMF solution containing 2.0024g of 4,4-diaminodiphenyl ether, with a solid content of 10%, react for 24h, then transfer it to a 10mL syringe, pass it through a centrifugal spinning device, control the centrifugal spinning machine speed to 2000r / min, the diameter of the outlet is 0.1mm, the distance between the outlet and the receiver is 20cm, the temperature is 15℃, the air humidity is 50%, and the propulsion speed is 1g / min. The electrospinning time is 5min, and polyimide nanofibers with a diameter of 300nm are obtained.

[0063] The polyimide nanofibers prepared as above were subjected to high temperature treatment by step-wise heating at a heating rate of 5°C / min, from 25°C to 150°C, and stayed for 1 hour; from 150°C to 200°C, and stayed for 1 hour; from 200°C to 300°C, and stayed for 1 hour; from 300°C to 350°C, and stayed for 30 minutes.

[0064] 2g of high-temperature treated polyimide nano-long fibers were placed in a ball mill without ball milling media, and 20,000g of zirconium oxide balls were added, wherein the mass percentage of zirconium balls with a diameter of 10mm was 35%, the mass percentage of zirconium balls with a diameter of 6mm was 20%, the mass percentage of zirconium balls with a diameter of 2mm was 15%, and the mass percentage of zirconium balls with a diameter of 0.5mm was 30%. The ball milling time was 2h, and the ball milling speed was 2000r / min to obtain polyimide nano-short fibers with a length of 20-30μm.

[0065] Example 6

[0066] Weigh 2.1812g of pyromellitic anhydride and add it to 34mL of DMF solution containing 2.0024g of 4,4-diaminodiphenyl ether, with a solid content of 10%, react for 24h, then transfer it to a 10mL syringe, pass it through a centrifugal spinning device, control the centrifugal spinning machine speed to 1000r / min, the diameter of the outlet is 0.5mm, the distance between the outlet and the receiver is 20cm, the temperature is 15℃, the air humidity is 50%, and the propulsion speed is 0.5g / min. The electrospinning time is 5min, and polyimide nanofibers with a diameter of 500nm are obtained.

[0067] The polyimide nanofibers prepared as above were subjected to high temperature treatment by step-wise heating at a heating rate of 5°C / min, from 25°C to 150°C, and stayed for 1 hour; from 150°C to 200°C, and stayed for 1 hour; from 200°C to 300°C, and stayed for 1 hour; from 300°C to 350°C, and stayed for 30 minutes.

[0068] 2g of high-temperature treated polyimide nano-long fibers were placed in a ball mill containing 40g of ethanol solvent, and 2000g of zirconium oxide balls were added, wherein the mass percentage of zirconium balls with a diameter of 10mm was 5%, the mass percentage of zirconium balls with a diameter of 6mm was 30%, the mass percentage of zirconium balls with a diameter of 2mm was 30%, and the mass percentage of zirconium balls with a diameter of 0.5mm was 35%. The ball milling time was 12h, and the ball milling speed was 1500r / min to obtain polyimide nano-short fibers with a length of 5-10μm.

[0069] Example 7

[0070] The preparation and high temperature treatment process of the polyimide nano long fibers in this embodiment are the same as those in Embodiment 1, except that the preparation of the polyimide nano short fibers is as follows:

[0071] 2 g of high-temperature treated polyimide nanofibers were placed in 100 g of ethanol, and the nanofibers were crushed by a high-speed crusher at a crushing speed of 20,000 r / min, a crushing temperature of 50° C., and a crushing time of 30 min to obtain polyimide nanofibers.

[0072] See also Figure 6 As shown in the SEM electron microscope image, Example 7 is cut by a high-speed crusher, and the polyimide nano long fibers are completely broken, and the fiber length is about 20-50 μm. The polyimide nano short fibers prepared in Example 7 are dispersed in an aqueous solution, such as Figure 7 As shown, the polyimide nano short fibers of Example 7 are completely and evenly dispersed in the aqueous solution.

[0073] Example 8

[0074] The preparation and high temperature treatment process of the polyimide nano long fibers in this embodiment are the same as those in embodiment 5, except that the preparation of the polyimide nano short fibers is as follows:

[0075] 2g of high-temperature treated polyimide nanofibers were placed in 100g of ethyl acetate and crushed by a high-speed crusher at a crushing speed of 80,000 r / min, a crushing temperature of 120°C, and a crushing time of 10 min to obtain polyimide nanofibers with a length of 5-10 μm.

[0076] Example 9

[0077] The preparation and high temperature treatment process of the polyimide nano long fibers in this embodiment are the same as those in Embodiment 6, except that the preparation of the polyimide nano short fibers is as follows:

[0078] 2g of high-temperature treated polyimide nanofibers were crushed into nanofibers by a high-speed crusher at a crushing speed of 1000r / min, a crushing temperature of 80°C, and a crushing time of 60min to obtain polyimide nanofibers with a length of 50-60μm.

[0079] The results show that the present invention first prepares polyimide nano-long fibers from a polyamic acid solution through an electrostatic spinning or centrifugal spinning process, then performs a high-temperature treatment, and then crushes the fibers through external forces such as laser cutting, ball milling, and high-speed cutting processes to prepare polyimide nano-short fibers, the fiber diameter of which is 100-1000nm, the length of which is 5-200μm, and which can be completely dispersed in an aqueous solution.

[0080] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for preparing polyimide short nanofibers, characterized in that: The following steps are involved: (1) Preparing polyimide nanofibers; (2) subjecting the polyimide nanofibers to high temperature treatment; (3) The polyimide nano long fibers after high temperature treatment are crushed to obtain polyimide nano short fibers, wherein the polyimide nano short fibers have a diameter of 100-1000 nm and a length of 5-200 μm.

2. The method for preparing polyimide short nanofibers according to claim 1, characterized in that: In step (3), laser cutting, ball milling or high-speed crusher is used to crush the polyimide nano-long fibers after high-temperature treatment.

3. The method for preparing polyimide short nanofibers according to claim 2, characterized in that: The laser cutting speed is 10-1000 cm / min, nitrogen or argon is used as an auxiliary, the cutting slit width is 20-100 μm, and the laser cutting power is 20-2000 W.

4. The method for preparing polyimide short nanofibers according to claim 2, characterized in that: In the ball milling, the ball milling medium is one or more of water, ethanol, ethyl acetate, petroleum ether, or there is no ball milling medium.

5. The method for preparing polyimide short nanofibers according to claim 4, characterized in that: In the ball milling, the ball-to-material ratio is 100:1-10000:1, the ball milling time is 1-24h, and the ball milling speed is 200-2000r / min.

6. The method for preparing polyimide short nanofibers according to claim 4, characterized in that: During the ball milling, zirconium oxide balls are added, including zirconium oxide balls with a diameter of 10 mm, zirconium oxide balls with a diameter of 6 mm, zirconium oxide balls with a diameter of 2 mm and zirconium oxide balls with a diameter of 0.5 mm, and the mass ratio of each zirconium oxide ball is at most 30% and at least 5%.

7. The method for preparing polyimide short nanofibers according to claim 2, characterized in that: The rotation speed of the high-speed crusher is 1000-100000 r / min, the crushing temperature is (-50)-(+120)°C, the crushing time is 1-60 min, and the crushing medium is one or more of water, methanol, ethanol, ethyl acetate, petroleum ether, dichloromethane, dimethylformamide, N-methylpyrrolidone, or no medium.

8. The method for preparing polyimide short nanofibers according to any one of claims 2 to 7, characterized in that: In step (1), polyimide nanofibers are prepared by centrifugal spinning or electrostatic spinning.

9. The method for preparing polyimide short nanofibers according to any one of claims 2 to 7, characterized in that: In step (2), the high temperature treatment is performed at a temperature of 100-400° C. and for a time of 200-500 min.

10. A polyimide short nanofiber, characterized in that: The polyimide nano short fibers are prepared by the preparation method of any one of claims 1 to 9.

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