阅读说明：本技术 一种芳纶纳米纤维分散液的制备方法 (Preparation method of aramid nanofiber dispersion liquid ) 是由 张美云 聂景怡 黄连青 宋顺喜 杨斌 谭蕉君 梁建涛 刘佳伟 于 2020-11-19 设计创作，主要内容包括：本发明属于聚合物纳米材料领域,具体公开一种芳纶纳米纤维分散液的制备方法,包括以下步骤：(1)将对位芳纶纤维加入强碱性溶液中浸润10-30s,使得芳纶分子链上至少有一个酰胺基团脱去质子,得到碱处理芳纶纤维；(2)向碱处理芳纶纤维中加入二甲基亚砜,在25～60℃反应温度下进行搅拌5～20min,得到芳纶纳米纤维分散液；其中,对位芳纶纤维与二甲基亚砜的固液比为0.1g:50mL。芳纶分子链中酰胺键与强碱反应脱除质子,破坏芳纶分子链间氢键,形成氮负离子,分子链间的静电斥力得以将分子链解离,有助于去质子化过程快速进行,缩短了超碱体系中强碱的离解时间及去质子化时间,使得ANF制备时间大大缩短,从原来的4h缩短至5-20min。(The invention belongs to the field of polymer nano materials, and particularly discloses a preparation method of an aramid nano-fiber dispersion liquid, which comprises the following steps: (1) adding para-aramid fibers into a strong alkaline solution for soaking for 10-30s, so that at least one amide group on an aramid molecular chain is deprotonated to obtain alkali-treated aramid fibers; (2) adding dimethyl sulfoxide into the alkali-treated aramid fiber, and stirring for 5-20min at the reaction temperature of 25-60 ℃ to obtain an aramid nanofiber dispersion liquid; wherein the solid-to-liquid ratio of the para-aramid fiber to the dimethyl sulfoxide is 0.1g to 50 mL. The amido bond in the aramid fiber molecular chain reacts with strong base to remove proton, so that the hydrogen bond between the aramid fiber molecular chains is destroyed to form nitrogen anions, the molecular chain is dissociated by electrostatic repulsion between the molecular chains, the rapid implementation of the deprotonation process is facilitated, the dissociation time and the deprotonation time of the strong base in an ultra-alkali system are shortened, the preparation time of the ANF is greatly shortened, and the original 4h is shortened to 5-20 min.)

1. The preparation method of the aramid nanofiber dispersion liquid is characterized by comprising the following steps of:

(1) adding para-aramid fibers into a strong alkaline solution for soaking for 10-30s, so that at least one amide group on an aramid molecular chain is deprotonated to obtain alkali-treated aramid fibers;

(2) adding dimethyl sulfoxide into the alkali-treated aramid fiber, and stirring for 5-20min at the reaction temperature of 25-60 ℃ to obtain an aramid nanofiber dispersion liquid; wherein the solid-to-liquid ratio of the para-aramid fiber to the dimethyl sulfoxide is 0.1g to 50 mL.

2. The preparation method of the aramid nanofiber dispersion liquid as claimed in claim 1, wherein in the step (1), the mass fraction of the strongly basic solution is (4.8-25) wt.%.

3. The preparation method of the aramid nanofiber dispersion liquid as claimed in claim 1, wherein the strongly alkaline solution is prepared by dissolving a strongly alkaline substance in a solvent.

4. The preparation method of the aramid nanofiber dispersion liquid as claimed in claim 3, wherein the strongly basic substance is one or more of potassium tert-butoxide, potassium hydroxide and potassium ethoxide.

5. The preparation method of the aramid nanofiber dispersion liquid as claimed in claim 3, wherein the solvent is one or more of deionized water, methanol and ethanol.

6. The preparation method of the aramid nanofiber dispersion liquid as claimed in claim 1, wherein in the step (1), the para-aramid fiber is one or more of aramid chopped fiber, para-aramid fibrid and para-aramid yarn.

7. The preparation method of the aramid nanofiber dispersion liquid as claimed in claim 1, wherein in the step (2), the stirring speed is 500-1500 r/min.

Technical Field

The invention belongs to the field of polymer nano materials, and particularly relates to a preparation method of an aramid nano fiber dispersion liquid.

Background

Aramid Fiber (AF) is a synthetic fiber with excellent performance, and has the advantages of high temperature resistance, high modulus, high strength, chemical corrosion resistance, good insulating property and the like. Aramid fibers are used in many important areas including body armor, special protective apparel, building reinforcement, special ropes, cables and cables, reinforced thermoplastic pipes, and the like. Due to the special molecular structure, the aramid fiber has smooth surface and low chemical activity. The application of aramid fiber in the fields of composite reinforcement, super capacitors, electrical insulation and the like is hindered.

Aramid Nanofibers (ANFs) are one-dimensional nanoscale fibers of Aramid fibers, have the advantages of high strength, high length-diameter ratio, high specific surface area, good thermochemical stability, flame retardance and the like, and have good application prospects in the fields of composite reinforcement, electrical insulation, absorption and filtration, battery diaphragms, flexible electrodes, biological tissues and the like. Therefore, the rapid and efficient preparation of the ANFs is beneficial to promoting the industrialization and large-scale application of the aramid nanofibers. Currently, ANF has preparation methods such as polymerization-induced self-assembly, electrospinning, mechanical separation, and deprotonation. The Nicholas A.Kotov group of America proposed a deprotonation method for preparing aramid nanofibers (Yang M, Cao K, Sui L, et al.dispersions of aramid nanofibers: a new nanoscale building block [ J ]. ACS nano,2011,5(9):6945-54.), and the aramid fibers were continuously stirred in dimethyl sulfoxide (DMSO) with strong base (KOH) for 7-10 days. A homogeneous, stable and transparent dark red dispersion of ANFs/DMSO was obtained. The obtained ANF has the advantages of good size uniformity, maintenance of the basic characteristics of aramid fibers, large amount of active groups on the surface and the like, but has the problems of overlong reaction time (7-10 days), low reaction concentration (less than or equal to 0.2 percent), low preparation efficiency and the like. Zhang Mei Yun subject group of Shanxi university of science and technology proposes a proton donor assisted deprotonation method for preparing ANF, which shortens the preparation period of ANF with the mass fraction of 0.2% to 4h by means of proton donor assisted strong base dissociation (Yang B, Wang L, Zhang M, et al. Timesaving, High-Efficiency approach to Fabric Amides (ANFs) [ J ]. ACS Nano,2019,13 (7)). Greatly shortens the preparation period of ANF and improves the preparation efficiency.

However, the existing method has the problems that the proton donor assisted strong base has long dissociation time and can not be deprotonated quickly, so that the preparation efficiency is low, therefore, the method is only in the laboratory research stage at present, large-scale industrial production is difficult to realize, and the commercial utilization is difficult.

Disclosure of Invention

The invention aims to provide a preparation method of an aramid nano-fiber dispersion liquid, which shortens the reaction time and solves the problem of low preparation efficiency.

The invention is realized by the following technical scheme:

a preparation method of an aramid nanofiber dispersion liquid comprises the following steps:

(1) adding para-aramid fibers into a strong alkaline solution for soaking for 10-30s, so that at least one amide group on an aramid molecular chain is deprotonated to obtain alkali-treated aramid fibers;

(2) adding dimethyl sulfoxide into the alkali-treated aramid fiber, and stirring for 5-20min at the reaction temperature of 25-60 ℃ to obtain an aramid nanofiber dispersion liquid; wherein the solid-to-liquid ratio of the para-aramid fiber to the dimethyl sulfoxide is 0.1g to 50 mL.

Further, in the step (1), the mass fraction of the strongly alkaline solution is (4.8-25) wt.%.

Further, the strongly alkaline solution is prepared by dissolving a strongly alkaline substance in a solvent.

Further, the strong alkaline substance is one or more of potassium tert-butoxide, potassium hydroxide and potassium ethoxide.

Further, the solvent is one or more of deionized water, methanol and ethanol.

Further, in the step (1), the para-aramid fiber is one or more of aramid chopped fiber, para-aramid fibrid and para-aramid yarn.

Further, in the step (2), the stirring speed is 500-1500 r/min.

Compared with the prior art, the invention has the following beneficial technical effects:

the invention discloses a preparation method of an aramid nano-fiber dispersion liquid, wherein a strong base and DMSO super-base system is difficult to rapidly release proton receptors to perform deprotonation reaction with aramid molecules due to poor solubility of the strong base in DMSO, so that the strong base is firstly dissociated by utilizing small molecules such as alcohol or water and the like, then amide bonds in aramid molecular chains are reacted with the strong base to remove protons, hydrogen bonds among the aramid molecular chains are destroyed to form nitrogen anions, the molecular chains are dissociated by electrostatic repulsion among the molecular chains, the dissociation time and the deprotonation time of the strong base in the super-base system are shortened, the ANF preparation time is greatly shortened, and the ANF preparation time is shortened to 5-20min from original 4 h. The method is simple and convenient to operate, and is beneficial to promoting large-scale industrial production and commercial application of the aramid nano-fiber.

Furthermore, the invention utilizes co-solvents such as micromolecular alcohols, water molecules and the like to enable the solvent and the strong base in the super-alkali system to interact, clarifies the preparation mechanism of the aramid nano-fiber and regulates and controls the preparation of the aramid nano-fiber from the mechanism.

Drawings

FIG. 1 is a schematic diagram of a preparation process of an aramid nanofiber dispersion according to the present invention;

FIG. 2 is a graph of UV absorption at various times during the reaction of example 1 of the present invention;

FIG. 3 is a graph of UV absorption at various times during the reaction of example 2 of the present invention;

FIG. 4 is a graph of UV absorption at various times during the reaction of example 3 of the present invention;

FIG. 5 is a graph of UV absorption at various times during the reaction of example 4 of the present invention;

FIG. 6 is a graph of UV absorption at various times during the reaction of example 5 of the present invention;

FIG. 7 is a graph of UV absorption at various times during the reaction of example 6 in accordance with the present invention;

FIG. 8 is a graph of UV absorption at various times during the reaction of example 7 in accordance with the present invention;

FIG. 9 is a graph of UV absorption at various times during the reaction of example 8 of the present invention;

FIG. 10 is a graph of UV absorption at various times during the reaction of example 9 in accordance with the present invention;

FIG. 11 is a graph of UV absorption at various times during the reaction of example 10 in accordance with the present invention;

FIG. 12 is an ANF TEM image obtained by the preparation of example 11 of the present invention;

FIG. 13 is an atomic force microscope image of ANF prepared in example 12 of the present invention.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

As shown in fig. 1, the invention discloses a preparation method of an aramid nanofiber dispersion liquid, which comprises the following steps:

(1) weighing strong base powder, and fully dissociating in a solvent to obtain a strong base solution;

wherein the strong base is one or more of potassium tert-butoxide, potassium hydroxide and potassium ethoxide; the solvent is one or more of deionized water, methanol and ethanol. The mass concentration of the strong alkaline solution is 4.8-25 wt.%.

(2) Weighing para-aramid fibers, adding the para-aramid fibers into strong alkali liquor, and soaking for a certain time;

wherein the para-aramid fiber is one or more of para-aramid chopped fiber, para-aramid fibrid and para-aramid yarn, and the soaking time is 10-30 s.

(3) Dimethyl sulfoxide (DMSO) is added into a mixed system of strong base and aramid fiber to react for a certain time at a certain temperature and a certain stirring rate, and uniform and stable red transparent dispersion liquid is obtained.

Wherein the solid-to-liquid ratio of the para-aramid fiber to the dimethyl sulfoxide is 0.1g:50mL, and stirring for 5-20min under a sealed condition; until the system becomes clear transparent dark red dispersion liquid, the reaction temperature is 25-60 ℃; the stirring speed is 500-1500 r/min.

The present invention is described in further detail below with reference to examples:

example 1

(1) Weighing 0.3g of potassium tert-butoxide, and fully dissociating in 2ml of methanol to obtain a potassium tert-butoxide methanol solution;

(2)0.1g of para-aramid chopped fiber is added into the methanol solution of potassium tert-butoxide obtained in the step (1) to be soaked for 30 s;

(3) adding 50ml of dimethyl sulfoxide into the system, applying magnetic stirring at 1500r/min, wherein the reaction temperature is 25 ℃, and the stirring time is 20min, so as to obtain the aramid nano-fibers dispersed in the DMSO system.

Example 2

(1) Weighing 0.5g of potassium tert-butoxide, and fully dissolving in a mixed solvent of 2ml of methanol, 0.5ml of deionized water and 0.5ml of ethanol to obtain a potassium tert-butoxide mixed solution;

(2) adding 0.04g of para-aramid chopped fiber, 0.04g of aramid fibrid and 0.02g of aramid yarn fiber into the mixed solution of potassium tert-butoxide obtained in the step (1) and soaking for 25 s;

(3) adding 50ml of dimethyl sulfoxide into the system, and applying magnetic stirring at 1500r/min, wherein the reaction temperature is 25 ℃, and the stirring time is 10 min; and obtaining the aramid nano-fiber dispersed in a DMSO system.

Example 3

(1) Weighing 0.6g of potassium tert-butoxide, and fully dissociating in 2ml of methanol to obtain a potassium tert-butoxide methanol solution;

(2)0.1g of para-aramid chopped fibers are added into the potassium tert-butoxide methanol solution obtained in the step (1) to be soaked for 10 s;

(3) adding 50ml of dimethyl sulfoxide into the system, and applying magnetic stirring at 1500r/min, wherein the reaction temperature is 25 ℃, and the stirring time is 5 min; and obtaining the aramid nano-fiber dispersed in a DMSO system.

Example 4

(1) Weighing 0.5g of potassium tert-butoxide, and fully dissociating in 1.5ml of deionized water to obtain a potassium tert-butoxide solution;

(2)0.1g of para-aramid chopped fibers are added into the potassium tert-butoxide solution obtained in the step (1) to be soaked for 10 s;

(3) adding 50ml of dimethyl sulfoxide into the system, and applying magnetic stirring at 1500r/min, wherein the reaction temperature is 25 ℃, and the stirring time is 5 min; and obtaining the aramid nano-fiber dispersed in a DMSO system.

Example 5

(1) Weighing 0.1g of potassium hydroxide, and fully dissolving the potassium hydroxide in 2ml of deionized water to obtain a potassium hydroxide aqueous solution;

(2)0.1g of para-aramid yarn is added into the potassium hydroxide aqueous solution obtained in the step (1) to be soaked for 30 s;

(3) adding 50ml of dimethyl sulfoxide into the system, and applying magnetic stirring at 500r/min, wherein the reaction temperature is 25 ℃, and the stirring time is 20 min; and obtaining the aramid nano-fiber dispersed in a DMSO system.

Example 6

(1) Weighing 0.2g of potassium hydroxide, and fully dissociating in 0.5ml of deionized water to obtain a potassium hydroxide solution;

(2)0.1g of para-aramid chopped fibers are added into the potassium tert-butoxide solution obtained in the step (1) to be soaked for 10 s;

(3) adding 50ml of dimethyl sulfoxide into the system, and applying magnetic stirring at 1000r/min, wherein the reaction temperature is 25 ℃, and the stirring time is 10 min; obtain the aramid nano-fiber dispersed in a DMSO system

Example 7

(1) Weighing 0.2g of potassium hydroxide, and fully dissociating in 1ml of deionized water to obtain a potassium hydroxide solution;

(2)0.1g of para-aramid chopped fiber is added into the potassium hydroxide solution obtained in the step (1) to be soaked for 10 s;

(3) adding 50ml of dimethyl sulfoxide into the system, and applying magnetic stirring at 1000r/min, wherein the reaction temperature is 25 ℃, and the stirring time is 10 min; obtain the aramid nano-fiber dispersed in a DMSO system

Example 8

(1) Weighing 0.2g of potassium hydroxide, and fully dissociating in 1.5ml of deionized water to obtain a potassium hydroxide solution;

(2)0.1g of para-aramid chopped fiber is added into the potassium hydroxide solution obtained in the step (1) to be soaked for 10 s;

(3) adding 50ml of dimethyl sulfoxide into the system, and applying magnetic stirring at 900r/min, wherein the reaction temperature is 25 ℃, and the stirring time is 10 min; obtain the aramid nano-fiber dispersed in a DMSO system

Example 9

(1) Weighing 0.2g of potassium hydroxide, and fully dissociating in 2ml of deionized water to obtain a potassium hydroxide solution;

(2)0.1g of para-aramid chopped fiber is added into the potassium hydroxide solution obtained in the step (1) to be soaked for 10 s;

(3) adding 50ml of dimethyl sulfoxide into the system, and applying magnetic stirring at 1500r/min, wherein the reaction temperature is 25 ℃, and the stirring time is 15 min; obtain the aramid nano-fiber dispersed in a DMSO system

Example 10

(1) Weighing 0.2g of potassium hydroxide, and fully dissociating in 2.5ml of deionized water to obtain a potassium hydroxide solution;

(2)0.1g of para-aramid chopped fiber is added into the potassium hydroxide solution obtained in the step (1) to be soaked for 10 s;

(3) adding 50ml of dimethyl sulfoxide into the system, and applying magnetic stirring at 900r/min, wherein the reaction temperature is 25 ℃, and the stirring time is 10 min; and obtaining the aramid nano-fiber dispersed in a DMSO system.

Example 11

(1) Weighing 0.1g of potassium hydroxide and 0.1g of potassium tert-butoxide, and fully dissociating in 1ml of deionized water and 1ml of ethanol mixed solvent to obtain strong base mixed solution;

(2)0.1g of para-aramid fibrid is added into the strong base mixed solution obtained in the step (1) to be soaked for 10 s;

(3) adding 50ml of dimethyl sulfoxide into the system, and applying magnetic stirring at 1500r/min, wherein the reaction temperature is 35 ℃, and the stirring time is 20 min; and obtaining the aramid nano-fiber dispersed in a DMSO system.

Example 12

(1) Weighing 0.1g of potassium hydroxide, 0.1g of potassium tert-butoxide and 0.1g of potassium ethoxide, and fully dissociating in 2.5ml of methanol to obtain a strong alkali mixed solution;

(2) adding 0.05g of para-aramid chopped fiber and 0.05g of para-aramid yarn into the strong base mixed solution obtained in the step (1) and soaking for 20 s;

(3) adding 50ml of dimethyl sulfoxide into the system, and applying magnetic stirring at 1500r/min, wherein the reaction temperature is 25 ℃, and the stirring time is 15 min; and obtaining the aramid nano-fiber dispersed in a DMSO system.

The prepared aramid nano-fiber is characterized, and the preparation time of the aramid nano-fiber is shortened to 5min at least. The aramid nanofiber prepared by the method has the characteristics of large length-diameter ratio of one-dimensional nano materials, good heat resistance and the like. The method for quickly preparing the aramid nano-fiber through alkaline pretreatment greatly shortens the preparation period, improves the preparation efficiency of the aramid nano-fiber, and is expected to promote large-scale industrial production and commercial utilization.

And (3) judging whether the reaction end point is reached or not by using the ultraviolet absorption spectrum of the ANF/DMSO solution, if the reaction end point is reached, preparing the ANF, and if the reaction end point is not reached, repeating the previous step until the reaction end point is reached.

Sampling and diluting the reaction process of the examples 1-10 to a certain multiple at a certain time interval, representing the reaction process in an ultraviolet spectrometer (shown in figures 2-11), and taking the trend of the absorption intensity of the characteristic peak as a judgment basis for reflecting the reaching of an end point, wherein the balance is achieved within 20min, which shows that the invention can rapidly prepare the aramid nano-fiber within 20 min.

As shown in fig. 12, the aramid nanofibers prepared by the present invention were characterized by transmission electron microscopy, and the comparison with a scale shows that the fibers were obtained in nanoscale, indicating that the aramid nanofibers were successfully prepared by the present invention.

As shown in fig. 13, the aramid nanofibers prepared by the present invention were characterized by an atomic force microscope, and the comparison with a scale shows that the fibers were obtained in a nanoscale, indicating that the aramid nanofibers were successfully prepared by the present invention.