阅读说明：本技术 一种通过共价键交联提升芳纶纳米纤维机械性能的方法 (Method for improving mechanical properties of aramid nano-fiber through covalent bond crosslinking ) 是由 陆赵情 马秦 俄松峰 李娇阳 王亚芳 王丹妮 高坤 杨凯伦 于 2019-12-03 设计创作，主要内容包括：本发明公开了一种通过共价键交联提升芳纶纳米纤维机械性能的方法,包括以下步骤：1)将二甲基亚砜、芳纶纤维和KOH混合,室温下搅拌一周至溶液呈现暗红色,得到芳纶纳米纤维悬浮液；2)加入去离子水稀释ANF悬浮液后搅拌；3)将ANF悬浮液抽滤后再分散于NaOH水溶液,使其内部酰胺键部分水解,得到水解后的芳纶纳米纤维；4)对水解后的芳纶纳米纤维加入HCl酸化至pH中性,抽滤；5)将抽滤水解后的芳纶纳米纤维分散在Tris缓冲液中,加入DA室温反应；6)通过真空辅助过滤、压榨、干燥得到PDA-ANF复合材料。制得的复合材料具有制备工艺简单、机械性能优异等特点。(The invention discloses a method for improving the mechanical property of aramid nano-fiber through covalent bond crosslinking, which comprises the following steps: 1) mixing dimethyl sulfoxide, aramid fiber and KOH, and stirring for one week at room temperature until the solution is dark red to obtain an aramid nanofiber suspension; 2) adding deionized water to dilute the ANF suspension and stirring; 3) carrying out suction filtration on the ANF suspension, and then dispersing in NaOH aqueous solution to hydrolyze part of the amide bond in the ANF suspension to obtain hydrolyzed aramid nano-fiber; 4) adding HCl into the hydrolyzed aramid nano-fiber, acidifying until the pH is neutral, and performing suction filtration; 5) dispersing the aramid fiber nanofibers subjected to suction filtration and hydrolysis in a Tris buffer solution, and adding DA for reaction at room temperature; 6) and (3) carrying out vacuum-assisted filtration, squeezing and drying to obtain the PDA-ANF composite material. The prepared composite material has the characteristics of simple preparation process, excellent mechanical property and the like.)

1. A method for improving the mechanical property of aramid nano-fiber through covalent bond crosslinking is characterized by comprising the following steps:

1) mixing dimethyl sulfoxide, aramid fiber and KOH, and stirring for one week at room temperature until the solution is dark red to obtain an aramid nanofiber suspension;

2) adding deionized water to dilute the ANF suspension and stirring;

3) carrying out suction filtration on the ANF suspension, and then dispersing in NaOH aqueous solution to hydrolyze part of the amide bond in the ANF suspension to obtain hydrolyzed aramid nano-fiber;

4) adding HCl into the hydrolyzed aramid nano-fiber to acidify to make the pH value neutral, and performing suction filtration;

5) dispersing the aramid fiber nanofibers subjected to suction filtration and hydrolysis in a Tris buffer solution, and adding DA for reaction at room temperature;

6) and carrying out vacuum-assisted filtration, squeezing and drying treatment to obtain the composite material.

2. The method for improving the mechanical property of the aramid nanofiber through covalent bond crosslinking as claimed in claim 1, wherein the aramid fiber is para-aramid fiber.

3. The method for improving the mechanical property of the aramid nano-fiber through covalent bond crosslinking according to claim 1, wherein in the step 1), the mass ratio of the aramid fiber to KOH is 1: 1.5.

4. The method for improving the mechanical property of the aramid nano-fiber through covalent bond crosslinking is characterized in that in the step 2), the addition amount of deionized water is 3-5 times of the mass of the aramid nano-fiber suspension; the stirring time is 0.5-2 h.

5. The method for improving the mechanical property of the aramid nano-fiber through covalent bond crosslinking according to claim 1, wherein in the step 3), the concentration of the NaOH aqueous solution is 1% -15%, and the hydrolysis time is 5-30 min.

6. The method for improving the mechanical property of the aramid nano-fiber through covalent bond crosslinking according to claim 1, wherein in the step 4), the concentration of HCl is 1-4 mol/L.

7. The method for improving the mechanical property of the aramid nano-fiber through covalent bond crosslinking according to claim 1, wherein in the step 5), the concentration of Tris buffer solution is 0.4-1.2 g/L, and the reaction time is 2-24 h after DA is added.

8. The method for improving the mechanical property of the aramid nano-fiber through covalent bond crosslinking is characterized in that in the step 6), vacuum-assisted suction filtration is carried out for forming, then, squeezing is carried out for 8-10 min under the pressure of less than or equal to 4MPa, and finally, drying is carried out for 5-10 min at the temperature of 100-110 ℃.

9. The method for improving the mechanical property of the aramid nano-fiber through covalent bond crosslinking as claimed in claim 1, wherein the tensile strength of the composite material is 234.90MPa, and the toughness is 32.03MJ/m³。

Technical Field

The invention relates to the field of crossing of paper making industry and material industry, in particular to a method for improving the mechanical property of aramid nano-fiber through covalent bond crosslinking.

Background

The aramid nano-fiber has excellent mechanical property, temperature resistance and flexible designability, and is widely applied to the reinforcement of polymers, however, the research on the improvement of the strength of the aramid nano-fiber is very little, and the application of the aramid nano-fiber is greatly limited due to the interface combination problem of the aramid nano-fiber. Compared with macroscopic aramid fibers, the nano aramid fibers are improved to a certain extent, but the problem of too few active groups still exists, and the number of groups capable of playing a role in combination with a matrix is limited, so that the advantages of the nano aramid fibers are difficult to play.

At present, methods for surface modification of aramid nanofibers are not yet researched, but ultrasonic cavitation, acid-base solution treatment, plasma bombardment and the like are already available for surface treatment of aramid fibers, but the methods all damage the aramid fibers to a certain extent, and simultaneously the ultrasonic cavitation has the defects of high energy consumption and expensive equipment, so that a new surface modification method is urgently needed to be searched for, and the strength of the aramid nanofibers is essentially improved.

Disclosure of Invention

In order to solve the problem of poor mildness of the aramid nano-fiber in the prior art, the invention aims to provide a method for improving the mechanical property of the aramid nano-fiber through covalent bond crosslinking, and the composite material obtained by the method has the mechanical property (tensile strength: 234.90MPa, toughness: 32.03 MJ/m)³) Excellent performance, simple preparation process and the like, improves the binding capacity between the aramid nano-fiber and the polymer, and widens the application of the aramid nano-fiber in the fields of light weight and high strength.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method for improving the mechanical properties of aramid nanofibers through covalent bond crosslinking comprises the following steps:

1) mixing dimethyl sulfoxide, aramid fiber and KOH, and stirring for one week at room temperature until the solution is dark red to obtain an aramid nanofiber suspension;

2) adding deionized water to dilute the ANF suspension and stirring;

3) carrying out suction filtration on the ANF suspension, and then dispersing in NaOH aqueous solution to hydrolyze part of the amide bond in the ANF suspension to obtain hydrolyzed aramid nano-fiber;

4) adding HCl into the hydrolyzed aramid nano-fiber to acidify to make the pH value neutral, and performing suction filtration;

5) dispersing the aramid fiber nanofibers subjected to suction filtration and hydrolysis in a Tris buffer solution, and adding DA for reaction at room temperature;

6) and carrying out vacuum-assisted filtration, squeezing and drying treatment to obtain the composite material.

As a further improvement of the present invention, the aramid fiber is a para-aramid fiber.

As a further improvement of the invention, in the step 1), the mass ratio of the aramid fiber to KOH is 1: 1.5.

As a further improvement of the method, in the step 2), the addition amount of deionized water is 3-5 times of the mass of the aramid nano-fiber suspension; the stirring time is 0.5-2 h.

As a further improvement of the invention, in the step 3), the concentration of the NaOH aqueous solution is 1-15%, and the hydrolysis time is 5-30 min.

As a further improvement of the invention, in the step 4), the concentration of HCl is 1-4 mol/L.

As a further improvement of the invention, in the step 5), the concentration of Tris buffer solution is 0.4-1.2 g/L, and the reaction time is 2-24 h after DA is added.

As a further improvement of the invention, in the step 6), vacuum-assisted suction filtration molding is carried out, then squeezing is carried out for 8-10 min under the pressure of less than or equal to 4MPa, and finally drying is carried out for 5-10 min at the temperature of 100-110 ℃.

As a further improvement of the invention, the composite material has a tensile strength up toThe toughness reaches 32.03MJ/m when the pressure is 234.90MPa³。

The invention has the following advantages:

the method selects para-aramid fiber (PPTA) and dopamine hydrochloride (DA) as raw materials. Processing the para-aramid fiber under a mixed system of dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH) to obtain para-Aramid Nanofiber (ANF) suspension, and then processing the ANF through NaOH aqueous solution; obtaining hydrolyzed para-aramid nano-fiber (ANF (h))]A suspension; and then mixing DA and ANF (h) and performing ultrasonic treatment, and performing vacuum-assisted suction filtration to obtain a PDA-ANF (h) film, wherein dopamine autopolymerization has adhesiveness, and the surface of the dopamine autopolymerization has a large number of active functional groups, performing alkali solution treatment to obtain hydrolyzed aramid nanofibers (the surface of which has carboxyl functional groups), connecting the hydrolyzed aramid nanofibers with hydroxyl groups on the polydopamine through covalent bonds, and meanwhile, coating the dopamine autopolymerization on the surface of the aramid nanofibers, and preparing the PDA/ANF (h) composite material with high strength and high toughness by adopting a vacuum-assisted suction filtration method, thereby providing a new idea for the application of the aramid nanofibers in the field of reinforcement. The prepared composite material has simple preparation process and mechanical properties (tensile strength: 234.90MPa, toughness: 32.03 MJ/m)³) Excellent and the like.

Drawings

FIG. 1: a physical map of the PDA-ANF (h) composite;

FIG. 2: scanning electron microscope image of PDA-ANF (h) composite material section;

FIG. 3: PDA-ANF (h) mechanical properties of the composite material.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention relates to a method for improving the mechanical property of aramid nano-fiber through covalent bond crosslinking, which comprises the following steps:

(1) adding 500mLDMSO, 1.0g of aramid fiber and 1.5g of KOH into a beaker, and stirring for one week at room temperature until the solution is dark red to obtain an Aramid Nanofiber (ANF) suspension;

(2) adding deionized water of which the amount is about 3-5 times that of the suspension liquid to dilute the suspension liquid, and stirring (time: 0.5-2 h);

(3) carrying out suction filtration on the ANF suspension, and then dispersing in NaOH aqueous solution (the concentration is 1-15%), so that the internal amido bond of the ANF suspension is partially hydrolyzed, and obtaining the hydrolyzed aramid nano-fiber [ ANF (h) (the time is 5-30 min);

(4) adding HCl (the concentration is 1-4 mol/L) into the hydrolyzed aramid nano-fibers, acidifying until the pH is neutral, and performing suction filtration;

(5) dispersing ANF (h) in a Tris buffer solution (0.4-1.2 g/L), adding DA for reaction at room temperature (time: 2-24 h);

(6) and (3) carrying out vacuum-assisted suction filtration molding, then squeezing for 8-10 min under the pressure of less than or equal to 4MPa, and finally drying for 5-10 min at the temperature of 100-110 ℃ to obtain the PDA-ANF (alpha-amino-vinyl acetate) (h) composite material.

The invention discloses a method for improving the mechanical property of aramid nano-fiber through covalent bond crosslinking, which further describes the following specific embodiments: