阅读说明：本技术 一种三维交联的超浸润纳米纤维膜及其制备方法 (Three-dimensional cross-linked super-wetting nanofiber membrane and preparation method thereof ) 是由 王建强 刘富 丁雅杰 林海波 于 2018-07-25 设计创作，主要内容包括：本发明涉及纳米纤维膜制备和改性技术领域,公开了一种三维交联的超浸润纳米纤维膜,其由不同取向的纳米纤维堆叠交叉构成,具有纳米纤维构成的三维交联网络结构,所述纳米纤维的交叉处具有表面活性剂粘结点,本发明利用双亲表面活性剂,一步法制备具有三维交联结构和高强度、超浸润特性的纳米纤维膜的方法。该方法工艺过程简单易行,可大幅提升纳米纤维膜的机械强度,并实现膜表面的超浸润特性。(The invention relates to the technical field of nanofiber membrane preparation and modification, and discloses a three-dimensional cross-linked super-infiltration nanofiber membrane which is formed by stacking and crossing nanofibers with different orientations and has a three-dimensional cross-linked network structure formed by the nanofibers, wherein the intersections of the nanofibers are provided with surfactant bonding points. The method has simple and easy technical process, can greatly improve the mechanical strength of the nanofiber membrane and realize the super-wetting characteristic of the membrane surface.)

1. A three-dimensional crosslinked super-infiltrated nanofiber membrane, characterized in that: the nano-fiber structure is formed by stacking and crossing nano-fibers with different orientations, has a three-dimensional cross-linked network structure formed by the nano-fibers, and has surfactant bonding points at the crossing positions of the nano-fibers.

2. The three-dimensionally crosslinked, super-infiltrated nanofiber membrane according to claim, characterized in that: the diameter of the nanofiber is 20-1000 nm.

3. The three-dimensional crosslinked, super-infiltrated nanofiber membrane of claim 1, wherein: the contact angle is less than 10 DEG or more than 150 deg.

4. A method of preparing the three-dimensional crosslinked super-infiltrated nanofiber membrane of claims 1-3, characterized in that: the method comprises the following steps:

1) preparing a matrix nanofiber membrane by the prior art;

2) weighing a certain amount of surfactant, dissolving in a solvent, and preparing a surfactant solution;

3) fixing the matrix nanofiber membrane obtained in the step 1) on a suction filtration device, pouring the surfactant solution obtained in the step 2), and filtering for a period of time;

4) taking the substrate nanofiber membrane subjected to the filtration treatment in the step 3) down from the suction filtration device, placing the substrate nanofiber membrane in water for cleaning, and then drying to obtain the three-dimensional crosslinked super-infiltrated nanofiber membrane.

5. The method of preparing a three-dimensional crosslinked super-infiltrated nanofiber membrane of claim 4, wherein: the material of the matrix nanofiber membrane is one or a mixture of polyvinylidene fluoride, polyacrylonitrile, polytetrafluoroethylene, polyvinyl chloride, polymethyl methacrylate, polyether sulfone, polysulfone and polystyrene; the preparation method comprises but is not limited to electrostatic spinning, melt spinning and mechanical stirring growth.

6. The method of preparing a three-dimensional crosslinked super-infiltrated nanofiber membrane of claim 4, wherein: the surfactant is one or more of span 20-85, tween 20-80, sorbitan tristearate, polyoxyethylene cetyl alcohol and sodium dodecyl sulfate.

7. The method of preparing a three-dimensional crosslinked super-infiltrated nanofiber membrane of claim 4, wherein: the solvent is one or more of n-hexane, toluene, ethanol, ethylene glycol, tetrahydrofuran, water, chloroform, acetone, dichloromethane, 1, 2-dichloroethane and methanol.

8. The method of preparing a three-dimensional crosslinked super-infiltrated nanofiber membrane of claim 4, wherein: the concentration of the surfactant in the surfactant solution is as follows: 1-80 g/L.

9. The method of preparing a three-dimensional crosslinked super-infiltrated nanofiber membrane of claim 4, wherein: in the filtering process of the surfactant solution in the step 3, the filtering speed is as follows: 0.1-100 mL cm-2 min-1, and the filtration time is as follows: 30 minutes to 6 hours.

Technical Field

The invention relates to the technical field of preparation and modification of nanofiber membranes, in particular to a three-dimensional crosslinked super-wetting nanofiber membrane and a preparation method thereof.

Background

In the 20 th century and 30 s, a patent (U.S. Pat. No. 1,975,504) applied by Formhals et al on a method and apparatus for preparing artificial nanowires, the nanofiber membrane prepared by the technology has unique properties of high porosity, high specific surface area, easily-regulated structure, wide application range, low cost and the like. In recent years, nanofiber membranes have attracted much attention in the fields of biomedical use, energy sources, environment and the like.

The nanofiber membrane is obtained by randomly stacking nanofibers, and due to the ultralow mass transfer resistance and the microstructure formed by random stacking of the nanofibers, the nanofiber membrane is favored in the fields of preparation and application of super-infiltration separation membranes. Although the super-infiltrated nanofiber membrane can be easily obtained through surface microstructure construction and membrane surface energy regulation, the mechanical strength of the membrane is poor due to the fact that only physical accumulation exists among the nanofibers and no interaction force exists, and practical application of the super-infiltrated nanofiber membrane is greatly limited. At present, methods for enhancing the mechanical strength of nanofiber membranes are mainly solved by methods for three-dimensional welding of nanofibers, such as ultraviolet light induced crosslinking (CN 105536577A, CN 104497330 a), thermal induced crosslinking (CN 102574037 a), chemical induced crosslinking (CN 1062227980A, CN 101929037A, CN 104988606A), solvent evaporation induced crosslinking (CN 103861145A), and calcination induced crosslinking (CN 107098333 a). Although these methods can successfully improve the mechanical strength of the nanofiber membrane, the effectiveness of the methods is limited to specific polymers or specific reactions, and the crosslinking process is complicated, high in energy consumption and not suitable for large-scale industrial application. In addition, limited by the spinnability of the material, the nanofiber membrane is usually required to be surface-modified to give it super-hydrophilic or super-hydrophobic properties, but the surface modification process is often complex and expensive. Therefore, the development of a new method for simply and efficiently three-dimensionally crosslinking and wettability modification of the nanofiber membrane is an urgent problem to be solved for pushing the high-performance nanofiber membrane to industrial application.

Disclosure of Invention

Aiming at the problems of poor mechanical strength, complex surface functionalization process and the like of a functional nanofiber membrane, the invention provides a method for preparing a nanofiber membrane with a three-dimensional cross-linked structure, high strength and super-infiltration characteristics by using an amphiphilic surfactant through a one-step method. The method has simple and easy technical process, can greatly improve the mechanical strength of the nanofiber membrane and realize the super-wetting characteristic of the membrane surface.

The technical solution of the invention is as follows: a three-dimensional cross-linked super-infiltrated nanofiber membrane is formed by stacking and crossing nanofibers with different orientations, has a three-dimensional cross-linked network structure formed by the nanofibers, and has surfactant bonding points at the crossing positions of the nanofibers.

The diameter of the nanofiber is 20-1000 nm.

The contact angle of the three-dimensional crosslinked super-wetting nanofiber membrane is less than 10 degrees or more than 150 degrees.

The preparation method of the three-dimensional cross-linked super-wetting nanofiber membrane comprises the following steps:

1) preparing a matrix nanofiber membrane by the prior art;

2) weighing a certain amount of surfactant, dissolving in a solvent, and preparing a surfactant solution;

3) fixing the matrix nanofiber membrane obtained in the step 1) on a suction filtration device, pouring the surfactant solution obtained in the step 2), and filtering for a period of time;

4) taking the substrate nanofiber membrane subjected to the filtration treatment in the step 3) down from the suction filtration device, placing the substrate nanofiber membrane in water for cleaning, and then drying to obtain the three-dimensional crosslinked super-infiltrated nanofiber membrane.

The material of the matrix nanofiber membrane is one or a mixture of polyvinylidene fluoride, polyacrylonitrile, polytetrafluoroethylene, polyvinyl chloride, polymethyl methacrylate, polyether sulfone, polysulfone and polystyrene; the preparation method comprises but is not limited to electrostatic spinning, melt spinning and mechanical stirring growth.

The surfactant is one or more of span 20-85, tween 20-80, sorbitan tristearate, polyoxyethylene cetyl alcohol and sodium dodecyl sulfate.

The solvent is one or more of n-hexane, toluene, ethanol, ethylene glycol, tetrahydrofuran, water, chloroform, acetone, dichloromethane, 1, 2-dichloroethane and methanol.

The concentration of the surfactant in the surfactant solution is as follows: 1-80 g/L.

The filtering speed of the filtering process of the surfactant solution is as follows: 0.1-100 mL cm-2 min-1, and the filtration time is as follows: 30 minutes to 6 hours.

The invention has the beneficial effects that: through the selection of amphiphilic molecule chain segments of the surfactant and the slightly swelling effect of the organic solvent, surfactant bonding points are formed at the intersections of the adjacent polymer nanofibers, which is equivalent to the fact that the adjacent polymer nanofibers are welded, so that the polymer nanofibers which are only physically and crossly stacked form an integral three-dimensional cross-linked network structure. The three-dimensional cross-linked network structure formed by the plurality of nano fibers can effectively enhance the physical and mechanical properties of the polymer nano fiber membrane and effectively reduce various physical losses of the polymer nano fiber membrane in the processes of water treatment and the like. Meanwhile, through the selection of the nanofiber polymer material and the surfactant amphiphilic molecule chain segment and the regulation and control of the selective combination of the surfactant molecule chain segment and the nanofiber matrix, the selective orientation arrangement of the surfactant characteristic groups can be effectively realized: for example, the polyvinylidene fluoride nanofiber membrane has a polyvinylidene fluoride matrix, which is a high polymer with strong hydrophobicity, when an amphiphilic surfactant is slightly swollen and adsorbed on the surface of a nanofiber, the hydrophobic group of the surfactant tends to be loaded on the polyvinylidene fluoride nanofiber matrix, and the hydrophilic group of the surfactant tends to be away from the polyvinylidene fluoride nanofiber matrix, so that an outward arrangement trend of the hydrophilic group is formed on the surface of the polyvinylidene fluoride nanofiber matrix, and the wettability of the polyvinylidene fluoride nanofiber membrane is effectively changed from hydrophobicity to super-hydrophilicity.

Certainly, by selecting different types of surfactants and effective combination of the surfactants and the polymer nanofiber membrane, the polymer nanofiber membrane can be endowed with rich functions, such as super-wetting, positive charge, negative charge and the like.

The preparation method of the three-dimensional cross-linked super-wetting nanofiber membrane has the following advantages:

relative to existing polymer nanofiber membrane crosslinking techniques, such as violetThe method has the defects of complex process, high energy consumption and low efficiency, and simultaneously the nano fiber matrix is extremely easy to lose in the crosslinking modification process. The polymer nanofiber membrane obtained by the method is of a three-dimensional cross-linked integral network structure, meanwhile, the functional modification of the polymer nanofiber membrane can be realized by one-step method, the process flow is simple, the efficiency is high, the energy consumption is low, the universality is strong, the operation and the realization are easy, and the industrial production is easy. The polymer nanofiber membrane provided by the method can exceed 15000 Lm in permeation flux to oil-in-water emulsion^-2h^-1bar^-1The separation rate can reach more than 96.3 percent, and the method has wide application prospect in the oil-water separation and other industrial wastewater treatment processes.

Drawings

FIG. 1 is a Surface Electron Microscope (SEM) photograph of a comparative example of the PVDF nanofiber membrane.

Fig. 2 is a Surface Electron Microscope (SEM) photograph of the superhydrophilic polyvinylidene fluoride nanofiber membrane prepared in example 1.

Fig. 3 is a Contact Angle (CA) photograph of the polyvinylidene fluoride nanofiber membrane according to the comparative example.

Fig. 4 is a Contact Angle (CA) photograph of the superhydrophilic polyvinylidene fluoride nanofiber membrane prepared in example 1.

FIG. 5 is a tensile strength test curve of polyvinylidene fluoride nanofiber membrane described in the comparative example.

FIG. 6 is a tensile strength test curve of the superhydrophilic polyvinylidene fluoride nanofiber membrane prepared in example 1

FIG. 7 is a cross-Sectional Electron Microscope (SEM) photograph of the polyvinylidene fluoride nanofiber membrane of the comparative example.

Fig. 8 is a cross-Sectional Electron Microscope (SEM) photograph of the superhydrophilic polyvinylidene fluoride nanofiber membrane prepared in example 1.

Detailed Description

The present invention will be described in further detail with reference to the following examples, but the present invention is not limited to the following examples.

Comparative example

1) Weighing a certain amount of polyvinylidene fluoride, dissolving the polyvinylidene fluoride in a solvent N, N-dimethylformamide, heating and stirring to prepare a 25wt% solution;

2) measuring a certain volume of the solution obtained in the step (1) and adding the solution into an injector;

3) putting the solution obtained in the step (2) into an injector, and putting the injector on an electrostatic spinning device to perform electrostatic spinning membrane making, wherein electrostatic spinning parameters are as follows: the diameter of a spray head is 0.7 mm, the voltage is 16.5 kV, the receiving distance is 15 cm, the propelling speed is 1 mL/h, the left-right moving speed of spinning equipment is 100 mm/min, the rotating speed of a receiving roller is 80 rpm, the spinning environment temperature is 25 ℃, the spinning environment humidity is 63%, and the spinning time is 14 h;

4) and taking the electrostatic spinning membrane down from the electrostatic spinning equipment to obtain the polyvinylidene fluoride nanofiber membrane which is physically cross-stacked. As shown in figure 1, the prepared polyvinylidene fluoride nanofiber membrane is formed by randomly stacking nanofibers, no crosslinking points exist among the fibers, and the fiber diameter is 50-250 nm. As shown in fig. 3, the contact angle of the resulting film was 141.2 ° ± 2 °. As shown in fig. 5, the tensile strength of the obtained nanofiber membrane was 2.0 MPa. The cross section of the nanofiber membrane obtained is shown in fig. 7, and the entire nanofiber membrane is composed of randomly stacked nanofibers. Under the gravity condition (980 Pa), the polyvinylidene fluoride nanofiber membrane has no permeation flux to 1, 2-dichloroethane-in-water emulsion stabilized by a surfactant.