阅读说明：本技术 一种基于微结构有序的高气体阻隔性复合材料及其制备方法 (Microstructure-order-based high-gas-barrier-property composite material and preparation method thereof ) 是由 秦余杨 袁凤 史纪新 曹振兴 徐森 朱凯 曹东升 郑玉斌 于 2020-05-08 设计创作，主要内容包括：本发明公开了一种基于微结构有序的高气体阻隔性复合材料及其制备方法,利用剪切力破坏三维块体纳米片间的层间作用力,将三维块体纳米片剥离成二维纳米片；在碱性水溶液中盐酸多巴胺会在纳米片表面发生自聚合,生成的聚多巴胺与纳米片间具有强烈的π-π相互作用,从而同时实现纳米片表面聚多巴胺π-π共轭改性,同时聚多巴胺修饰的二维纳米片表面羟基和胺基可以与聚乙烯醇分子链上的羟基形成大量的氢键,从而有效提高了纳米片在基体中的分散性和界面结合力,再借助真空辅助抽滤产生的重力作用可有效实现纳米片在基体的定向排列,这方面效应可有效延长气体的扩散路径,从而显著提高复合材料的气体阻隔性能。(The invention discloses a microstructure-ordered high-gas-barrier composite material and a preparation method thereof, wherein a shearing force is utilized to destroy an interlayer acting force between three-dimensional block nanosheets, and the three-dimensional block nanosheets are stripped into two-dimensional nanosheets; in an alkaline aqueous solution, hydrochloric acid dopamine is subjected to self-polymerization on the surfaces of the nano sheets, strong pi-pi interaction is formed between the generated polydopamine and the nano sheets, so that the pi-pi conjugate modification of the polydopamine on the surfaces of the nano sheets is realized, meanwhile, hydroxyl and amino on the surfaces of the two-dimensional nano sheets modified by the polydopamine can form a large number of hydrogen bonds with hydroxyl on a polyvinyl alcohol molecular chain, the dispersity and the interface binding force of the nano sheets in a matrix are effectively improved, the directional arrangement of the nano sheets on the matrix can be effectively realized by means of the gravity effect generated by vacuum-assisted suction filtration, the effect on the aspect can effectively prolong the diffusion path of gas, and the gas barrier property of the composite material is remarkably improved.)

1. A preparation method of a two-dimensional nanosheet with a surface modified with polydopamine is characterized by comprising the following steps:

(1) dispersing the flaky three-dimensional nano particles in absolute ethyl alcohol and continuously stirring, then adding a trihydroxymethyl aminomethane hydrochloride buffer solution, and continuously stirring to obtain a mixed solution;

(2) adding dopamine hydrochloride into the mixed solution prepared in the step (1), and uniformly stirring and mixing;

(3) placing the mixed solution prepared in the step (2) in a high-speed shearing emulsifying instrument, and shearing at a high speed for a plurality of hours to obtain a sheared dispersion liquid;

(4) and (4) carrying out centrifugal separation on the dispersion liquid prepared in the step (3), and then taking supernatant liquid to carry out filtration, washing and drying to obtain the surface modified polydopamine two-dimensional nanosheet.

2. A method for preparing two-dimensional nanoplatelets according to claim 1 wherein in step (1) the platelet-shaped three-dimensional nanoparticles are any one of hexagonal boron nitride powder and natural graphite.

3. A preparation method of two-dimensional nanosheets as claimed in claim 1, wherein in step (1), the ratio of the amount of the flaky three-dimensional nanoparticles to the amount of absolute ethanol is 10-50 mg: 1 ml.

4. A method for preparing two-dimensional nano-sheets according to claim 1, wherein in step (1), the concentration of tris hydrochloride buffer is 0.01-0.04 mol/l, and the pH is 8.5-10.

5. A preparation method of two-dimensional nano-sheets as claimed in claim 1, wherein in the step (1), the dosage ratio of the flaky three-dimensional nano-particles to the tris hydrochloride buffer solution is 6-20 mg: 1 ml.

6. A preparation method of two-dimensional nano-sheets according to claim 1, wherein in the step (2), the mass ratio of the flaky three-dimensional nano-particles to dopamine hydrochloride is 2-6: 1.

7. a method of preparing two-dimensional nanoplatelets according to claim 1 wherein in step (3) the high shear is carried out at a high shear rate of 6000 to 8000rpm for 3 to 6 hours.

8. A preparation method of two-dimensional nano-sheet according to claim 1, wherein in the step (4), the centrifugal rotation speed is 2000-5000 rpm, and the centrifugal time is 10-30 min.

9. Two-dimensional nanoplatelets of surface-modified polydopamine prepared according to the process of any of claims 1 to 8.

10. A preparation method of a microstructure-ordered high-gas-barrier-property composite material specifically comprises the following steps:

(a) dispersing the two-dimensional nano-sheets of the surface-modified polydopamine prepared by the method according to any one of claims 1 to 8 in distilled water, performing ultrasonic dispersion for 20-50 min at room temperature, adding a certain amount of polyvinyl alcohol resin, and continuing the ultrasonic dispersion for 30-60 min to obtain a uniform aqueous solution;

(b) and (b) carrying out vacuum filtration on the aqueous solution prepared in the step (a), and drying the obtained filter membrane in a vacuum oven for several hours to obtain the high-gas-barrier-property composite material with ordered microstructure.

Technical Field

The invention belongs to the field of nano composite materials, and particularly relates to a high-gas-barrier-property composite material with an ordered microstructure and a preparation method thereof.

Background

Since the birth of composite material pressure vessels, the composite material pressure vessels are widely used in the fields of national defense, traffic, petrochemical industry and the like. In recent years, with the development of advanced technologies and equipment such as advanced engine systems and new energy vehicles, in order to meet the severe requirements of high airtightness, low weight, multifunction and the like, researchers have gained more and more favor of a novel ultra-light linerless polymer composite pressure vessel. Generally, the inner liner of the composite pressure vessel accounts for more than 30% of the total weight of the vessel, and therefore, the non-liner design can greatly improve the structural efficiency and realize effective weight reduction. However, the gas tightness of the composite pressure vessel is seriously reduced by adopting a linerless design, so that the composite pressure vessel cannot meet the strict gas tightness requirement under the action of high-pressure load, and therefore, a high-gas-barrier polymer material is urgently needed. In addition, due to the advantages of light weight, easy processing, and being not easy to break, the demand of high-barrier polymer materials in the fields of packaging, agriculture, industry, medical treatment, etc. is increasing. For this reason, the development of polymer materials with high gas barrier properties has been one of the hot spots of research.

At present, various methods for improving the barrier property of materials have been reported, such as a filling modification method, a blending method, a multilayer compounding method, a surface treatment method, and the like. The filling method is to fill inorganic nanoparticles serving as a filler into a polymer matrix by a certain method to prepare the nanocomposite with excellent barrier property, and is an internationally recognized effective means for improving the gas barrier property of the material at present. Researchers focused on the filling modification method two points: firstly, selecting and processing nano filler; secondly, the dispersity and orientation of the filler in the matrix are controlled. The two-dimensional layered nano material can form the largest contact area with a matrix due to the larger length-diameter ratio of the two-dimensional layered nano material, and can effectively prolong the diffusion path of gas molecules, so that the two-dimensional layered nano material becomes the most ideal nano filler of the gas barrier composite material. Sheet-like nano-graphite, graphene, layered silicate and boron nitride nanosheets have been widely used to prepare gas barrier polymer composites. However, the prior art has the following problems: (1) the nano filler has poor dispersibility and is easy to agglomerate seriously, so that the barrier property of the obtained composite material is far lower than a theoretical value; (2) the nano-fillers are arranged in disorder in the matrix, so that the effect of prolonging the gas diffusion path is limited. Therefore, how to effectively improve the dispersibility of the nano filler in the resin matrix so as to realize the highly ordered and oriented arrangement of the nano filler in the resin matrix is a research hotspot in the field of high-gas-barrier nano composite materials.

Disclosure of Invention

The invention aims to provide a simple and effective high-gas-barrier composite material based on microstructure order and a preparation method thereof.

The purpose of the invention is realized by the following technical scheme.

A two-dimensional nanosheet with a surface modified with polydopamine is prepared by the following steps:

(1) dispersing the flaky three-dimensional nano particles in absolute ethyl alcohol and continuously stirring, then adding a trihydroxymethyl aminomethane hydrochloride buffer solution, and continuously stirring to obtain a mixed solution;

(2) adding dopamine hydrochloride into the mixed solution prepared in the step (1), and uniformly stirring and mixing;

(3) placing the mixed solution prepared in the step (2) in a high-speed shearing emulsifying instrument, and shearing at a high speed for a plurality of hours to obtain a sheared dispersion liquid;

(4) and (4) carrying out centrifugal separation on the dispersion liquid prepared in the step (3), and then taking supernatant liquid to carry out filtration, washing and drying to obtain the surface modified polydopamine two-dimensional nanosheet.

Preferably, in the step (1), the flaky three-dimensional nanoparticles are any one of hexagonal boron nitride powder and natural graphite.

Preferably, in the step (1), the dosage ratio of the flaky three-dimensional nanoparticles to the absolute ethyl alcohol is 10-50 mg: 1 ml.

Preferably, in step (1), the concentration of the tris hydrochloride buffer is 0.01-0.04 mol/l, and the pH is 8.5-10.

Preferably, in the step (1), the dosage ratio of the flaky three-dimensional nanoparticles to the tris hydrochloride buffer solution is 6-20 mg: 1 ml.

Preferably, in the step (2), the mass ratio of the flaky three-dimensional nanoparticles to the dopamine hydrochloride is 2-6: 1.

preferably, in the step (3), the high-speed shearing is carried out at a high-speed shearing speed of 6000 to 8000rpm for 3 to 6 hours.

Preferably, in the step (4), the centrifugal speed is 2000-5000 rpm, and the centrifugal time is 10-30 min.

A high-gas barrier composite material based on microstructure order and a preparation method thereof specifically comprise the following steps:

(a) dispersing the two-dimensional nano sheet modified by the polydopamine in distilled water, performing ultrasonic dispersion for 20-50 min at room temperature, then adding a certain amount of polyvinyl alcohol (PVA), and continuing to perform ultrasonic dispersion for 30-60 min to obtain a uniform aqueous solution;

(b) and (b) carrying out vacuum filtration on the aqueous solution prepared in the step (a), and drying the obtained filter membrane in a vacuum oven for several hours to obtain the high-gas-barrier-property composite material with ordered microstructure.

Preferably, in the step (a), the concentration of the polydopamine-modified two-dimensional nanosheet in distilled water is 2-4 mg/1ml, and the mass ratio of the polydopamine-modified two-dimensional nanosheet to polyvinyl alcohol is 1-4: 20.

preferably, in step (b), the concentration is 50 to 70^oAnd C, drying in a vacuum oven for 24 hours.

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

(1) the invention realizes the stripping and surface modification of the two-dimensional nanosheet at the same time, and has the advantages of simple and easy process, room-temperature operation, low cost and high production efficiency.

(2) The poly-dopamine pi-pi conjugated modified two-dimensional nanosheet can effectively maintain inherent high gas barrier property of the nanosheet, can form hydrogen bonds with a polymer matrix, solves the problems of poor dispersibility and low interface binding force of the nanosheet in the resin matrix, and promotes the application of the nanosheet in the field of high-barrier composite materials.

(3) The directional arrangement of the nano particles in the resin matrix can be realized by simple vacuum filtration, the diffusion path of gas molecules can be prolonged to the maximum extent, and the gas barrier property of the composite material is obviously improved.

Drawings

FIG. 1 is a transmission electron micrograph of BNNSs-PDA prepared in example 1.

FIG. 2 is a graph of the thermogravimetric curves of the original h-BN and the BNNSs-PDA made in example 1.

FIG. 3 is a graph of the thermogravimetric curves of the original h-BN and the BNNSs-PDA made in example 2.

FIG. 4 is a graph of the thermogravimetric curves of the original h-BN and the BNNSs-PDA made in example 3.

Fig. 5 is a transmission electron microscope of the surface-modified poly-dopamine graphene prepared in example 4.

Fig. 6 is a thermogravimetric plot of natural graphite and graphene-PDA prepared in example 4.

FIG. 7 is a transmission electron micrograph of the product prepared in comparative example 1.

FIG. 8 is a graph of the thermal weight loss of virgin h-BN and BNNSs made in comparative example 1.

FIG. 9 is a thermogravimetric plot of the product made from virgin h-BN and comparative example 2.

FIG. 10 is a scanning electron micrograph of the product obtained in comparative example 2.

Detailed Description

The principle of the invention is as follows: in the preparation process of the two-dimensional nanosheet with the surface modified with polydopamine, on one hand, interlaminar acting force among the three-dimensional block nanosheets is destroyed by utilizing shearing force, and the three-dimensional block nanosheets are stripped into the two-dimensional nanosheets; on the other hand, dopamine hydrochloride in an alkaline aqueous solution can undergo self-polymerization on the surfaces of the nano sheets, and the generated polydopamine and the nano sheets have strong pi-pi interaction, so that the pi-pi conjugated modification of the polydopamine on the surfaces of the nano sheets is realized at the same time. In the preparation process of the composite material, on one hand, hydroxyl and amido on the surface of the two-dimensional nano sheet modified by polydopamine can form a large number of hydrogen bonds with hydroxyl on a polyvinyl alcohol molecular chain, so that the dispersibility and the interface binding force of the nano sheet in a matrix are effectively improved; on the other hand, the oriented arrangement of the nano-sheets on the matrix can be effectively realized by means of the gravity effect generated by vacuum-assisted suction filtration. The effect of the aspect can effectively prolong the diffusion path of the gas, thereby obviously improving the gas barrier property of the composite material.