CN113862816B - Preparation method of short-rod-shaped aramid nanofiber and application - Google Patents

Abstract

The invention discloses a preparation method of short rod-shaped aramid nanofibers, the aramid nanofibers and application thereof, and belongs to the technical field of polymer nanomaterials. The aramid nanofiber prepared by the invention is a short rod-shaped aramid nanofiber with the diameter of 100-800 nm. The preparation method comprises the steps of pulping para-aramid fibers in a PFI machine, adding the obtained slurry into KOH solution, heating, stirring and dispersing uniformly, then carrying out vacuum filtration on the obtained aramid fiber dispersion to be slightly alkaline, and finally placing the aramid fiber dispersion in a steam explosion feeding bin to obtain the aramid nanofibers through regulating and controlling the pressure, time and other conditions. The aramid nanofiber prepared by the method is in a short rod shape and can be dispersed in water or a hydrophilic solvent, so that the diversified application of the aramid nanofiber is greatly expanded. The preparation process does not use organic solvent, is environment-friendly, has low cost, high treatment efficiency and simple process, and is suitable for large-scale process production mainly by a mechanical method.

Description

A kind of preparation method of short rod-shaped aramid nanofiber, aramid nanofiber and application

Technical field

The invention belongs to the technical field of polymer nanomaterials, and specifically relates to a preparation method of short rod-shaped aramid nanofibers, aramid nanofibers and applications.

Background technique

One-dimensional aramid fiber, especially aramid nanofiber ANF, not only maintains the excellent properties of light weight, high strength, high temperature resistance, corrosion resistance, high flame retardancy and insulation of the above-mentioned macro aramid fiber PPTA fiber, but also has the properties of polymer nanofiber Unique nanometer effect, large aspect ratio and high specific surface area, excellent mechanical properties. It can serve as one of the most promising building blocks comparable to carbon nanotubes (CNTs) and cellulose nanofibers. Nanoscale ANF brings mechanical and optical properties that cannot be achieved by aramid fibers. In addition, the abundant active groups, large aspect ratio and specific surface area of ANF give it excellent properties as a nanomaterial.

Aramid fiber PPTA is an excellent high-performance chemical fiber with high strength, excellent flame retardant properties, good heat resistance and good chemical stability. It is an important material in the fields of national defense, aerospace, petrochemical and other fields. The rigid chain structure formed by π-π conjugation between molecular chains within the aramid fiber, intermolecular hydrogen bonds and van der Waals forces give the aramid fiber high strength and high temperature resistance, but it also leads to active groups on the surface of the aramid fiber. It has few groups and is difficult to combine with other materials, which limits its application in composite materials, nanomaterials, biomedical materials and other fields. Aramid nanofiber is a polymer nanofiber material that has emerged this year. The chemical alkali dissolution method first proposed by Professor Nicholas A. Kotov's research group in the United States (Yang M, Cao K, Sui L, et al. Dispersions of aramid nanofibers: a new nanoscale buildingblock [J]. Acs Nano, 2011, 5 (9 ): 6945-54.), by mixing aramid fiber with KOH and dimethyl sulfoxide and continuously stirring at room temperature for 7-10 days, an ANFs/DMSO dispersion is obtained. Although aramid nanofibers prepared by deprotonation method have obvious advantages in terms of diameter and distribution, nanofiber quality and method operability, they have been used by many researchers. However, in the process of preparing aramid nanofibers through the deprotonation reaction of aramid fibers, there are many problems such as long reaction cycle (7-10 days) and low reaction concentration (mass concentration is generally 0.2%). Moreover, during the replacement process of ANF from DMSO, the size of aramid nanofibers increases, and even partially reduces to macro-aramid fibers, which greatly destroys the excellence of its nanostructure.

Aramid nanofibers can be dispersed in organic solvents, which greatly broadens the application range of aramid nanofibers. However, organic solvents pollute the environment. If aramid nanofiber materials are to be applied on a large scale, they will inevitably cause harm to the environment. At the same time, because aramid nanofibers cannot be dispersed in water and cannot be blended well with water-soluble polymers, the application of aramid nanofibers in water-soluble polymers and hydrophilic materials is limited. The special properties of nanomaterials are closely related to the morphology of nanoparticles. In order to make full use of the excellent properties of aramid and prepare high-performance composite materials, new aramid nanomaterials with simple processes, low costs, and suitable for large-scale industrial use are on the market. Urgent needs.

Contents of the invention

In order to overcome the shortcomings of preparing aramid nanofibers in the prior art, such as long reaction cycles, low yields, and environmental pollution by organic solvents, the present invention provides a preparation method and application of short rod-shaped aramid nanofibers. The method is simple and easy to operate. , can quickly and successfully prepare aramid nanofibers, greatly shorten the reaction cycle, and promote the large-scale production and diversified applications of aramid nanofibers.

In order to achieve the above technical objectives, the technical solutions adopted by the present invention are:

A preparation method of short rod-shaped aramid nanofibers, including the following steps:

(1) Add water to the para-aramid fiber and beat it in a PFI machine to obtain para-aramid fiber A;

(2) Add para-aramid fiber A to the KOH aqueous solution to obtain a mixed system of para-aramid fiber A and KOH aqueous solution. Place it in a water bath for heating and stirring to obtain para-aramid fiber dispersion A;

(3) Wash the para-aramid fiber dispersion A obtained in step (2) with vacuum filtration until it is weakly alkaline to obtain para-aramid fiber dispersion B;

(4) Put the para-aramid fiber dispersion B obtained in step (3) into a steam explosion feeding bin and explode to obtain a short rod-shaped aramid nanofiber aqueous solution. After drying, the final product is obtained.

Further, in step (1), the para-aramid fibers are para-chopped fibers with an average length of 1-10 mm, and the mass concentration of the para-aramid fibers is 1%-20%.

Further, in step (2), add 2-5g para-aramid fiber and 10-100 g KOH per 100 mL of water.

Further, the water bath temperature in step (2) is maintained at 50-80°C, the stirring speed is 200-500r/min, and the stirring time is 2-5h.

Further, the pH of para-aramid fiber dispersion B after suction filtration in step (3) is 8-12.

Further, in step (4), 2.8-3.6L of water is introduced, the burst pressure is 0.5-3.5MPa, and the pressure maintenance time is 1-20 minutes.

Further, in step (4), the drying method is spray drying or freeze drying.

A short rod-shaped aramid nanofiber preparation method obtains short rod-shaped aramid nanofibers.

Application of a short rod-shaped aramid nanofiber preparation method in the preparation of nanomaterials.

beneficial effects

The method of efficiently preparing aramid nanofibers developed by the present invention using new technology and new methods solves the problems of the existing technology such as too long reaction time, low preparation efficiency, and inability of aramid nanofibers to be dispersed in water. The method proposed by the present invention to quickly and efficiently prepare new aramid nanofibers is easy to operate, can quickly and successfully prepare aramid nanofibers, greatly shortens the reaction cycle, improves production efficiency, and enables batch preparation of aramid nanofibers, which is expected to promote The large-scale production and diversified applications of aramid nanofibers have strong market promotion value.

Description of the drawings

Figure 1 is a transmission electron microscope SEM image of aramid nanofibers obtained in Example 6 of the present invention;

Figure 2 is a transmission electron microscope TEM image of the aramid nanofibers obtained in Example 6 of the present invention.

Detailed ways

The technical solutions of the present invention will be further described below with reference to specific embodiments, but are not limited thereto.

Example 1

A preparation method of short rod-shaped aramid nanofibers, including the following steps:

(1) Put 20g of absolutely dry para-aramid fiber with an average length of 3mm into a beaker, add water to 200g, mix evenly and add it to the PFI beater, and the beating speed is 5000r to obtain para-aramid fiber A;

(2) Take 1g of para-aramid fiber A, 5g of KOH, add 50 mL of water into a beaker, place the beaker in a water bath, stir with a stirrer to obtain para-aramid fiber dispersion A; the processing conditions are: water bath The temperature is 80°C, the stirrer speed is 500r, and the processing time is 3h;

(3) Vacuum filter the para-aramid fiber dispersion A obtained in step (2) until the pH is 8 to obtain para-aramid fiber dispersion B;

(4) Put the para-aramid fiber dispersion B obtained in step (3) into a steam explosion feeding bin and explode to obtain a short rod-shaped aramid nanofiber aqueous solution. After drying, the final product is obtained; the steam explosion treatment conditions are: Add 3.6L of water, the burst pressure is 1.5MPa, and the pressure maintenance time is 5 minutes.

Example 2

A preparation method of short rod-shaped aramid nanofibers, including the following steps:

(1) Put 20g of absolutely dry para-aramid fiber with an average length of 1mm into a beaker, add water to 200g, mix evenly and add it to the PFI beater, and the beating speed is 10000r to obtain para-aramid fiber A;

(2) Take 1g of para-aramid fiber A, 10g of KOH and add 50mL of water into a beaker;

(3) Place the beaker containing para-aramid fiber and KOH solution system obtained in step (2) into a water bath, and stir with the help of a stirrer to obtain para-aramid fiber dispersion A; the processing conditions As follows: the water bath temperature is 80°C, the stirrer speed is 500r, and the processing time is 3h;

(4) Vacuum filter the para-aramid fiber dispersion A obtained in step (3) until the pH is 8 to obtain para-aramid fiber dispersion B;

(5) Put the para-aramid fiber dispersion B obtained in step (4) into a steam explosion feeding bin and explode to obtain a short rod-shaped aramid nanofiber aqueous solution. After drying, the final product is obtained; the steam explosion treatment conditions are: Add 3.6L of water, the burst pressure is 2.0MPa, and the pressure maintenance time is 10 minutes.

Example 3

A preparation method of short rod-shaped aramid nanofibers, including the following steps:

(1) Put 20g of absolutely dry para-aramid fiber with an average length of 1mm into a beaker, add water to 200g, mix evenly and add it to the PFI beater, and the beating speed is 20000r to obtain para-aramid fiber A;

(2) Take 1g of para-aramid fiber A, 20g of KOH and add 50mL of water into a beaker;

(3) Place the beaker containing para-aramid fiber and KOH solution system obtained in step (2) into a water bath, and stir with the help of a stirrer to obtain para-aramid fiber dispersion A; the processing conditions As follows: the water bath temperature is 80°C, the stirrer speed is 500r, and the processing time is 3h;

(4) Vacuum filter the para-aramid fiber dispersion A obtained in step (3) until the pH is 8 to obtain para-aramid fiber dispersion B;

(5) Put the para-aramid fiber dispersion B obtained in step (4) into a steam explosion feeding bin and explode to obtain a short rod-shaped aramid nanofiber aqueous solution. After drying, the final product is obtained; the steam explosion treatment conditions are: Add 3.6L of water, the burst pressure is 2.0MPa, and the pressure maintenance time is 10 minutes.

Example 4

A preparation method of short rod-shaped aramid nanofibers, including the following steps:

(1) Put 20g of absolutely dry para-aramid fiber with an average length of 1mm into a beaker, add water to 200g, mix evenly and add it to the PFI beater, and the beating speed is 50000r to obtain para-aramid fiber A;

(2) Take 1g of para-aramid fiber A, 50g of KOH and add 50mL of water into a beaker;

(3) Place the beaker containing para-aramid fiber and KOH solution system obtained in step (2) into a water bath, and stir with the help of a stirrer to obtain para-aramid fiber dispersion A; the processing conditions As follows: the water bath temperature is 80°C, the stirrer speed is 500r, and the processing time is 3h;

(4) Vacuum filter the para-aramid fiber dispersion A obtained in step (3) until the pH is 8 to obtain para-aramid fiber dispersion B;

(5) Put the para-aramid fiber dispersion B obtained in step (4) into a steam explosion feeding bin and explode to obtain a short rod-shaped aramid nanofiber aqueous solution. After drying, the final product is obtained; the steam explosion treatment conditions are: Add 3.6L of water, the burst pressure is 2.0MPa, and the pressure maintenance time is 10 minutes.

Example 5

A preparation method of short rod-shaped aramid nanofibers, including the following steps:

(1) Put 20g of absolutely dry para-aramid fiber with an average length of 1mm into a beaker, add water to 200g, mix evenly and add it to the PFI beater, and the beating speed is 50000r to obtain para-aramid fiber A;

(2) Take 1g of para-aramid fiber A, 30g of KOH and add 50mL of water into a beaker;

(3) Place the beaker containing para-aramid fiber and KOH solution system obtained in step (2) into a water bath, and stir with the help of a stirrer to obtain para-aramid fiber dispersion A; the processing conditions As follows: the water bath temperature is 80°C, the stirrer speed is 500r, and the processing time is 3h;

(4) Vacuum filter the para-aramid fiber dispersion A obtained in step (3) until the pH is 8 to obtain para-aramid fiber dispersion B;

(5) Put the para-aramid fiber dispersion B obtained in step (4) into a steam explosion feeding bin and explode to obtain a short rod-shaped aramid nanofiber aqueous solution. After drying, the final product is obtained; the steam explosion treatment conditions are: Add 3.6L of water, the burst pressure is 2.0MPa, and the pressure maintenance time is 10 minutes.

Example 6

A preparation method of short rod-shaped aramid nanofibers, including the following steps:

(1) Put 20g of absolutely dry para-aramid fiber with an average length of 1mm into a beaker, add water to 200g, mix evenly and add it to the PFI beater, and the beating speed is 50000r to obtain para-aramid fiber A;

(2) Take 1g of para-aramid fiber A, 50g of KOH and add 50mL of water into a beaker;

(3) Place the beaker containing para-aramid fiber and KOH solution system obtained in step (2) into a water bath, and stir with the help of a stirrer to obtain para-aramid fiber dispersion A; the processing conditions As follows: the water bath temperature is 80°C, the stirrer speed is 500r, and the processing time is 3h;

(4) Vacuum filter the para-aramid fiber dispersion A obtained in step (3) until the pH is 12 to obtain para-aramid fiber dispersion B;

(5) Put the para-aramid fiber dispersion B obtained in step (4) into a steam explosion feeding bin and explode to obtain a short rod-shaped aramid nanofiber aqueous solution. After drying, the final product is obtained; the steam explosion treatment conditions are: Add 3.6L of water, the burst pressure is 2.5MPa, and the pressure maintenance time is 20 minutes.

The product obtained in Example 6 was subjected to scanning electron microscopy and transmission electron microscopy to analyze the morphological characteristics, as shown in Figure 1-2. From Figure 1-2, we can see that the obtained nanofibers are uniform in size, have clear boundaries, and exhibit an obvious short rod-like morphology. , uniformly dispersed without agglomeration and caking, which can effectively solve the problems existing in the existing technology and fully prove the superiority of the preparation method of the present invention. The method of preparing aramid nanofibers of the present invention fully meets the needs of large-scale market promotion and application. ,Broad prospects.

Example 7

A preparation method of short rod-shaped aramid nanofibers, including the following steps:

(1) Put 20g of absolutely dry para-aramid fiber with an average length of 1mm into a beaker, add water to 200g, mix evenly and add it to the PFI beater, and the beating speed is 50000r to obtain para-aramid fiber A;

(2) Take 1g of para-aramid fiber A, 50g of KOH and add 50mL of water into a beaker;

(3) Place the beaker containing para-aramid fiber and KOH solution system obtained in step (2) into a water bath, and stir with the help of a stirrer to obtain para-aramid fiber dispersion A; the processing conditions As follows: the water bath temperature is 80°C, the stirrer speed is 500r, and the processing time is 3h;

(4) Vacuum filter the para-aramid fiber dispersion A obtained in step (3) until the pH is 8 to obtain para-aramid fiber dispersion B;

(5) Put the para-aramid fiber dispersion B obtained in step (4) into a steam explosion feeding bin and explode to obtain a short rod-shaped aramid nanofiber aqueous solution. After drying, the final product is obtained; the steam explosion treatment conditions are: Add 3.6L of water, the burst pressure is 2.5MPa, and the pressure maintenance time is 5 minutes.

Example 8

A preparation method of short rod-shaped aramid nanofibers, including the following steps:

(1) Put 20g of absolutely dry para-aramid fiber with an average length of 3mm into a beaker, add water to 200g, mix evenly and add it to the PFI beater, and the beating speed is 50000r to obtain para-aramid fiber A;

(2) Take 1g of para-aramid fiber A, 50g of KOH and add 50mL of water into a beaker;

(3) Place the beaker containing para-aramid fiber and KOH solution system obtained in step (2) into a water bath, and stir with the help of a stirrer to obtain para-aramid fiber dispersion A; the processing conditions As follows: the water bath temperature is 80°C, the stirrer speed is 500r, and the processing time is 3h;

(4) Vacuum filter the para-aramid fiber dispersion A obtained in step (3) until the pH is 8 to obtain para-aramid fiber dispersion B;

(5) Put the para-aramid fiber dispersion B obtained in step (4) into a steam explosion feeding bin and explode to obtain a short rod-shaped aramid nanofiber aqueous solution. After drying, the final product is obtained; the steam explosion treatment conditions are: Add 3.6L of water, the burst pressure is 2.5MPa, and the pressure maintenance time is 10 minutes.

It should be noted that the above-mentioned embodiments are only some embodiments of preferred ways to implement the present invention, rather than all embodiments. Obviously, based on the above-mentioned embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts should fall within the scope of protection of the present invention.

Claims (8)

1. The preparation method of the short rod-shaped aramid nanofiber comprises the following steps:

(1) Adding water into the para-aramid fiber, and pulping in a PFI machine to obtain para-aramid fiber A;

(2) Adding para-aramid fiber A into KOH aqueous solution to obtain a mixed system of para-aramid fiber A and KOH aqueous solution, and placing the mixed system in a water bath kettle for heating and stirring treatment to obtain para-aramid fiber dispersion A;

(3) The para-aramid fiber dispersion A obtained in the step (2) is filtered and washed to alkalescence by vacuum to obtain a para-aramid fiber dispersion B;

(4) Putting the para-aramid fiber dispersion B obtained in the step (3) into a steam explosion feeding bin for point explosion to obtain a short rod-shaped aramid nanofiber aqueous solution, and drying to obtain a final product;

2.8-3.6L of water is introduced in the step (4), the bursting pressure is 0.5-3.5MPa, and the maintenance time is 1-20min.

2. The method for preparing the short-rod-shaped aramid nanofiber according to claim 1, wherein the para-aramid fiber in the step (1) is a para-chopped fiber with an average length of 1-10mm, and the mass concentration of the para-aramid fiber is 1% -20%.

3. The method for preparing short rod-shaped aramid nanofibers according to claim 1, wherein 2-5g para-aramid fibers and 10-100 g KOH are added per 100mL of water in step (2).

4. The method for preparing short rod-shaped aramid nanofibers according to claim 1, wherein the water bath temperature in the step (2) is maintained at 50-80 ℃, the stirring speed is 200-500r/min, and the stirring time is 2-5h.

5. The method for producing a short rod-shaped aramid nanofiber according to claim 1, wherein the pH of the para-aramid fiber dispersion B after the suction filtration in the step (3) is 8 to 12.

6. The method for preparing short rod-shaped aramid nanofibers according to claim 1, wherein the drying mode in the step (4) is spray drying or freeze drying.

7. A short rod-shaped aramid nanofiber obtained by the method for preparing a short rod-shaped aramid nanofiber according to any one of claims 1 to 6.

8. Use of the method for preparing short rod-shaped aramid nanofibers according to any one of claims 1 to 6 in the preparation of nanomaterials.