Preparation method of polyimide nanofiber aerogel

Abstract

The invention relates to a preparation method of polyimide nanofiber aerogel, and belongs to the technical field of high polymer materials. According to the preparation method of the polyimide nanofiber aerogel, an aerogel material with super-hydrophobicity and a stable structure is prepared through electrostatic spinning, freeze drying and thermal imidization. The triethylamine cross-linked polyimide aerogel has excellent mechanical properties, can bear the weight exceeding 10000 times, and can be applied to the fields of high-temperature filtration, protective fabrics, industrial flame retardance and heat insulation, insulation, aerospace and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to a method for preparing polyimide nanofiber aerogel. Background Art

[0002] Polyimide refers to a series of organic polymers containing imide rings on the main chain. According to the different structures, it can be simply divided into two categories, including linear polyimide and cyclic polyimide. Among them, aromatic polyimide has excellent thermodynamic properties due to the presence of a large number of benzene rings on the molecular chain, and has been widely studied and applied in many fields. Compared with other aromatic heterocyclic polymers, polyimide has unique advantages: good high and low temperature resistance, the thermal decomposition temperature can reach 600℃, and it will not be brittle in liquid nitrogen environment; strong corrosion resistance, can withstand corrosion from various organic solvents and acids and alkalis; has high insulation, the dielectric constant is generally less than 3.5, and is an ideal material for high-voltage insulation; has a variety of synthetic routes; has a variety of processing and molding methods, and can adopt cast film method, molding method, lamination method, injection molding method and extrusion method; has a very wide range of applications, such as high-temperature filtration, protective fabrics, industrial flame retardant insulation, insulation and aerospace. Therefore, it is of great significance to prepare a polyimide nanofiber aerogel with large aspect ratio and specific surface area, excellent mechanical, thermal durability, and chemical properties. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for preparing polyimide nanofiber aerogel.

[0004] The technical solution of the present invention to solve the above technical problem is as follows: A method for preparing polyimide nanofiber aerogel comprises the following steps:

[0005] Step 1: preparing a polyamic acid spinning solution using 1,2,4,5-pyromellitic dianhydride and diaminodiphenyl ether;

[0006] Step 2: electrospinning a polyamic acid nanofiber membrane, cutting it into pieces and dispersing it in water to evenly disperse it, and adding a certain amount of triethylamine to the dispersion for cross-linking;

[0007] Step 3: freeze-dry the dispersion obtained in step 2 to obtain polyamic acid nanofiber aerogel, and perform thermal imidization under nitrogen to obtain polyimide nanofiber aerogel.

[0008] Beneficial effects: The aerogel prepared by electrospinning in the present invention has good mechanical properties, hydrophobicity and shape stability;

[0009] Based on the above technical solution, the present invention can also be improved as follows.

[0010] Preferably, the spinning solution solvent in step 1 may be selected from N,N-dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and tetrahydrofuran.

[0011] Preferably, the solubility of the spinning solution in step 1 is 25-30wt%.

[0012] Preferably, the electrospinning parameter in step 2 is a voltage of 26-32 kV.

[0013] Preferably, the receiving distance in step 2 is 15-17 cm.

[0014] Preferably, the feeding amount in step 2 is 0.5-1.0 mL / h.

[0015] Preferably, the air humidity in step 2 is controlled at 20-30% RH.

[0016] Preferably, the receiving roller in step 2 rotates at a speed of 10-20 rpm.

[0017] Preferably, the concentration of the polyamic acid dispersion in step 2 is 0.5wt%-1.5wt%.

[0018] Preferably, the mass ratio of triethylamine in step 2 is 50%-70% of the mass of the polyamic acid.

[0019] Preferably, the freezing time in step three is 12-24 hours, and the freeze-drying time is 24-48 hours.

[0020] The purpose of the present invention is to provide a method for preparing polyimide nanofiber aerogel, and the polyimide nanofiber aerogel is prepared by the method for preparing polyimide nanofiber aerogel.

[0021] Beneficial effects: The prepared polyimide nanofiber aerogel has good mechanical properties, hydrophobicity and shape stability; BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 is a SEM picture of the polyamic acid nanofiber membrane obtained in Example 1 of the present invention;

[0024] Figure 2This is a SEM image of the polyimide nanofiber aerogel prepared in Example 1;

[0025] Figure 3 This is a picture of the mechanical properties of the polyimide nanofiber aerogel of Example 1;

[0026] Figure 4 This is a picture of the water contact angle of the polyimide nanofiber aerogel in Example 1. DETAILED DESCRIPTION

[0027] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0028] Example 1

[0029] A method for preparing a polyimide nanofiber aerogel comprises the following steps:

[0030] Step 1: preparing a polyamic acid spinning solution using 1,2,4,5-pyromellitic dianhydride and diaminodiphenyl ether;

[0031] Step 2: electrospinning a polyamic acid nanofiber membrane, cutting it into pieces and dispersing it in water to evenly disperse it, and adding a certain amount of triethylamine to the dispersion for cross-linking;

[0032] Step 3: freeze-dry the dispersion obtained in step 2 to obtain polyamic acid nanofiber aerogel, and perform thermal imidization under nitrogen to obtain polyimide nanofiber aerogel.

[0033] The polyamic acid nanofiber membrane prepared in Example 1 was observed by electron microscope. Figure 1 As shown, the polyamic acid nanofibers prepared by electrospinning present a uniform and smooth surface, an average fiber diameter of 262.8 nm, and a CV value of 26.609%.

[0034] The polyimide nanofiber aerogel prepared in Example 1 was observed by electron microscope. Figure 2 As shown, the polyimide nanofiber aerogel with triethylamine added exhibits three-dimensional porosity and a smooth lamellar pore wall structure inside, due to the fact that the polyamic acid organic salt dissolved by triethylamine is attached to the nanofibers as a binder.

[0035] The mechanical properties of the polyimide nanofiber aerogel prepared in Example 1 were tested. A 500 g weight was placed on the surface of the aerogel. After the weight was removed, the aerogel basically returned to its original shape without deformation, and it could withstand more than 10,000 times its own weight.

[0036] The water contact angle of the polyimide nanofiber aerogel prepared in Example 1 was tested. Figure 4It can be seen that the water contact angle of the aerogel is 155°, showing excellent hydrophobic properties.

[0037] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing polyimide nanofiber aerogel, characterized in that: The following steps are involved: Step 1: preparing a polyamic acid spinning solution using 1,2,4,5-pyromellitic dianhydride and diaminodiphenyl ether; Step 2: electrospinning a polyamic acid nanofiber membrane, cutting it into pieces and dispersing it in water to evenly disperse it, and adding a certain amount of triethylamine to the dispersion for cross-linking; Step 3: freeze-dry the dispersion obtained in step 2 to obtain polyamic acid nanofiber aerogel, and perform thermal imidization under nitrogen to obtain polyimide nanofiber aerogel.

2. The method for preparing polyimide nanofiber aerogel according to claim 1, characterized in that: The ratio of 1,2,4,5-pyromellitic dianhydride to diaminodiphenyl ether in step 1 is 1:1, and the concentration of the spinning solution is 25-30wt%.

3. The method for preparing polyimide nanofiber aerogel according to claim 1, characterized in that: The electrospinning parameters in step 2 are as follows: voltage of 26-32 kV, receiving distance of 15-17 cm, liquid feeding volume of 0.5-1.0 mL / h, air humidity controlled at 20-30% RH, and the receiving roller collecting the nanofiber membrane at a rotation speed of 10-20 rpm.

4. The method for preparing polyimide nanofiber aerogel according to claim 1, characterized in that: The concentration of the polyamic acid dispersion in step 2 is 0.5wt%-1.5wt%.

5. The method for preparing polyimide nanofiber aerogel according to claim 1, characterized in that: The mass ratio of triethylamine in the step 2 is 50%-70% of the mass of the polyamic acid.

6. The method for preparing polyimide nanofiber aerogel according to claim 1, characterized in that: The thermal imidization temperature in step 3 is 300° C. and the time is 3 h.

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