CN114150435A

CN114150435A - Electrostatic spinning nano composite fiber membrane and preparation method thereof

Info

Publication number: CN114150435A
Application number: CN202111480961.3A
Authority: CN
Inventors: 韩广萍; 王栋; 程万里; 王庆香; 杨海英; 颜婕
Original assignee: Northeast Forestry University
Current assignee: Northeast Forestry University
Priority date: 2021-12-06
Filing date: 2021-12-06
Publication date: 2022-03-08

Abstract

The invention relates to the field of membrane separation and purification, and discloses an electrostatic spinning nano composite fiber membrane and a preparation method thereof. The method comprises the following steps: (1) adding CNC into DMF, carrying out ultrasonic treatment to obtain CNC suspension, then adding PAN into the CNC suspension in a stirring state, and after the PAN is added, continuously stirring in a sealing state to obtain a CNC/PAN spinning precursor solution; (2) stirring the CNC/PAN spinning precursor solution obtained in the step (1) at room temperature for 18-22 h, and then carrying out electrostatic spinning to obtain a CNC/PAN-based electrostatic spinning nanofiber membrane; (3) completely immersing the CNC/PAN-based electrostatic spinning nanofiber membrane obtained in the step (2) in a sodium hydroxide solution for hydrolysis treatment, then washing the CNC/PAN-based electrostatic spinning nanofiber membrane subjected to hydrolysis treatment to be neutral by using deionized water, then completely immersing the CNC/PAN-based electrostatic spinning nanofiber membrane in a hydrochloric acid solution for treatment, then washing the CNC/PAN-based electrostatic spinning nanofiber membrane to be neutral by using the deionized water, and then drying the CNC/PAN-based electrostatic spinning nanofiber membrane. By adopting the method, the obtained fiber membrane has better hydrophilicity and underwater super oleophobic property.

Description

Electrostatic spinning nano composite fiber membrane and preparation method thereof

Technical Field

The invention relates to the field of membrane separation and purification, in particular to an electrostatic spinning nano composite fiber membrane and a preparation method thereof.

Background

The membrane separation technology has the advantages of simple process operation, low energy consumption, good cost benefit and the like, and therefore, has wide application prospect in the field of solving the problem of oily wastewater. Among many membrane preparation techniques, electrospinning has attracted a great deal of interest because of its simplicity, efficiency, and desirable nanometer size. These nanofibers can be assembled into ordered arrays or layered structures by manipulating their spinning parameters. In addition, Electrospun Nanofiber Membranes (ENMs) have specific advantages such as high surface area to volume ratio, interconnected pore structure and well controlled composition. These advantages make it the best choice for a low resistance liquid filter material. The key factor for preparing the high-efficiency oil-water separation material is the design of a selective wettability interface.

The electrostatic spinning technology is introduced into the Polyacrylonitrile (PAN) film forming process, the prepared PAN fiber film has a one-dimensional nano structure, the diameter can reach hundreds of nanometers, and the preparation of the superfine PAN nano composite fiber is realized. PAN nanofibers have excellent affinity for water and oil in air, and are one of the advanced representatives of the filtration field. However, PAN nanofibers have poor fatigue and abrasion resistance. Cellulose Nanocrystals (CNC) have a higher young's modulus, which can increase the tensile strength of PAN nanofibers. In addition, CNC is derived from the most abundant natural renewable lignocellulosic resources on earth, and thus it is common to compound CNC with PAN to make nanofiber membranes, but CNC/PAN nanofiber membranes are generally poorly resistant to contamination. The PAN nanofiber membrane can be partially hydrolyzed under certain conditions, so that nitrile groups (-CN) existing on the surface are converted into carboxyl groups (-COOH), and the anti-pollution capacity of the PAN nanofiber membrane is improved, but the hydrolysis can cause the change of the original structure of the PAN, so that the research on how to obtain the electrostatic spinning nanofiber membrane which is high in mechanical strength, good in anti-pollution performance and capable of being repeatedly used is not sufficient, and further deep exploration is needed.

Disclosure of Invention

The invention aims to solve the problems of low mechanical strength, poor pollution resistance and poor reusable effect of an electrostatic spinning nano composite fiber membrane in the prior art, and provides a preparation method of the electrostatic spinning nano composite fiber membrane.

In order to achieve the above objects, one aspect of the present invention provides a method for preparing an electrospun nanocomposite fiber membrane, the method comprising the steps of:

(1) adding CNC into DMF (dimethyl formamide), carrying out ultrasonic treatment to obtain CNC suspension, then adding PAN into the CNC suspension in a stirring state, and after the PAN is added, continuously stirring in a sealing state to obtain a CNC/PAN spinning precursor solution, wherein the weight ratio of the CNC to the DMF is 0.008-0.032: 1, the weight ratio of the CNC to the PAN is 0.05-0.2: 1, and the weight ratio of the PAN to the DMF is 0.14-0.18: 1;

(2) stirring the CNC/PAN spinning precursor solution obtained in the step (1) at room temperature for 18-22 h, and then carrying out electrostatic spinning to obtain a CNC/PAN-based electrostatic spinning nanofiber membrane;

(3) completely immersing the CNC/PAN-based electrostatic spinning nanofiber membrane obtained in the step (2) in a sodium hydroxide solution with the concentration of 0.25-1.5 mol/L, carrying out hydrolysis treatment at 50-70 ℃ for 15-45 min, then washing the CNC/PAN-based electrostatic spinning nanofiber membrane subjected to hydrolysis treatment to be neutral by using deionized water, completely immersing the CNC/PAN-based electrostatic spinning nanofiber membrane washed to be neutral in a hydrochloric acid solution with the concentration of 0.25-1 mol/L, carrying out treatment at 18-25 ℃ for 15-45 min, then washing to be neutral by using deionized water, and then drying.

Preferably, in the step (1), the power of the ultrasonic treatment is 200-800W, the temperature of the ultrasonic treatment is-4-0 ℃, and the time of the ultrasonic treatment is 1-20 min.

Preferably, in the step (1), the stirring speed in the stirring state is 900 to 1100 rpm.

Preferably, in the step (1), the stirring temperature in the continuous stirring process is 45-60 ℃, the stirring time is 6-12 h, and the stirring rotation speed is 450-550 rpm.

Preferably, in the step (2), the type of the needle of the injector used in the electrostatic spinning is 18-22G.

Preferably, in the step (2), the process parameters of the electrostatic spinning are as follows: the positive high voltage is 8-15 kV, the negative high voltage is-1.5-3 kV, the spinning speed is 0.04-0.12 mm/min, the rotating speed of a roller is 50-100 rpm, the spinning distance is 20-30 cm, the spinning time is 10-12 h, the spinning temperature is 18-30 ℃, and the relative humidity is 18-28%.

Preferably, in step (3), the drying manner is freeze drying or vacuum drying.

Preferably, the temperature of the freeze drying is-60 to-50 ℃, and the time of the freeze drying is 24 to 48 hours.

Preferably, the pressure of the vacuum drying is-0.2 to-0.05 MPa, the temperature of the vacuum drying is 45 to 60 ℃, and the time of the vacuum drying is 23 to 25 hours.

In a second aspect, the invention provides an electrospun nanocomposite fiber membrane prepared by the above method.

The method can simply and efficiently realize the preparation of the electrostatic spinning nano composite fiber membrane, the obtained fiber membrane has better hydrophilicity and underwater super oleophobic property, the composite fiber membrane is more stable in water environment due to the introduction of CNC, good nano fiber shape and mechanical strength can be kept, meanwhile, the preparation of a spinning precursor is fast, the CNC suspension solution is stable, the preparation process of electrostatic spinning is simple, and the hydrolysis process of the fiber surface is mild. Provides theoretical basis for relevant research, greatly increases the application range and the application prospect of PAN, and the obtained electrostatic spinning product can be applied to the fields of membrane separation and purification, microfiltration and the like.

Drawings

FIG. 1 is a micro-topography and an infrared spectrum of cellulose nanocrystal CNC used in the present invention;

FIG. 2 is a photograph of spinning precursor solutions prepared in step (1) of comparative example 1 and examples 1 to 4 according to the present invention;

FIG. 3 is a micro-topography of the PAN-based electrospun nanofiber membrane obtained in step (2) of comparative example 1 and the CNC/PAN-based electrospun nanofiber membrane obtained in step (2) of examples 1-4 of the present invention;

FIG. 4 is a fiber diameter profile of the PAN-based electrospun nanofiber membrane of the present invention in comparative example 1 step (2) and the CNC/PAN-based electrospun nanofiber membrane obtained in examples 1-4 step (2);

FIG. 5 is a photograph of the PAN-based electrospun nanofiber membrane of comparative example 1 of the present invention after being treated with a sodium hydroxide solution, treated with a hydrochloric acid solution, and rinsed with deionized water to neutrality, respectively;

FIG. 6 is a photograph of the CNC/PAN-based electrospun nanofiber membrane of example 1 of the present invention after being treated with sodium hydroxide solution, hydrochloric acid solution and deionized water to neutral, respectively;

FIG. 7 is a photograph of the CNC/PAN-based electrospun nanofiber membrane of example 2 of the present invention after being treated with sodium hydroxide solution, hydrochloric acid solution and deionized water to neutral, respectively;

FIG. 8 is a photograph of the CNC/PAN-based electrospun nanofiber membrane of example 3 of this invention after being treated with sodium hydroxide solution, hydrochloric acid solution and deionized water to neutral respectively;

FIG. 9 is a photograph of the CNC/PAN-based electrospun nanofiber membrane of example 4 of this invention after being treated with sodium hydroxide solution, hydrochloric acid solution and deionized water to neutral respectively;

FIG. 10 is a micro-topography of the H-PAN-based electrospun nanofiber membrane obtained in comparative example 1 and the CNC/H-PAN-based electrospun nanocomposite fiber membrane obtained in examples 1-4 of the present invention;

FIG. 11 is a fiber diameter distribution graph of the H-PAN-based electrospun nanofiber membrane obtained in comparative example 1 and the CNC/H-PAN-based electrospun nanocomposite fiber membrane obtained in examples 1-4 of the present invention;

FIG. 12 is a micro-topography of the CNC/H-PAN based electrospun nano-composite fiber membranes obtained from examples 5-6 of the present invention;

FIG. 13 is a micro-topography of the CNC/H-PAN based electrospun nano-composite fiber membranes obtained from comparative examples 2-3 of the present invention;

FIG. 14 is a microscopic morphology of PAN-based electrospun nanofiber membranes obtained in comparative examples 4-6, comparative example 1, step (2), and comparative example 7 of the present invention;

FIG. 15 is a pre-wetting microstructure of the CNC/H-PAN-based electrospun nano-composite fiber membrane obtained in example 2 of the present invention;

FIG. 16 is an infrared spectrum of electrospun nanofiber membranes from comparative example 1 and electrospun nanocomposite fiber membranes from example 1 of the present invention along with PAN-based electrospun nanofiber membrane from comparative example 1 and CNC/PAN-based electrospun nanofiber membrane from step (2) of example 1;

FIG. 17 is a stress-strain force curve for electrospun nanofiber membranes obtained in comparative example 1 and electrospun nanocomposite fiber membranes obtained in examples 1-4 of the present invention;

FIG. 18 is a graph showing the pore size distribution of electrospun nanofiber membranes obtained in comparative example 1 and electrospun nanocomposite fiber membranes obtained in examples 1-4 according to the present invention;

FIG. 19 is a graph of the wetting performance of electrospun nanocomposite fiber membranes obtained in example 2 of the present invention and CNC/PAN-based electrospun nanofiber membranes obtained in step (2) of example 2;

FIG. 20 is a flow chart of the process for preparing the electrospun nano-composite fiber membrane of the present invention.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a preparation method of an electrostatic spinning nano composite fiber membrane, which comprises the following steps:

In the present invention, a process flow diagram of the method for preparing the electrospun nanocomposite fiber membrane is shown in fig. 20.

In a specific embodiment, in step (1), the weight ratio of the CNC to the DMF (N, N-dimethylformamide) may be 0.008:1, 0.01:1, 0.012:1, 0.016:1, 0.02:1, 0.024:1, 0.028:1, or 0.032: 1.

In a specific embodiment, in step (1), the weight ratio of the CNC to the PAN may be 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, 0.18:1, 0.19:1, or 0.2: 1.

In particular embodiments, in step (1), the weight ratio of the PAN to the DMF may be 0.14:1, 0.15:1, 0.16:1, 0.17:1, or 0.18: 1.

In the present invention, in step (1), the sonication power is too low, or the time is too short, so that CNC cannot be completely dispersed in DMF, and then subsequent experiments cannot be performed, so that the sonication conditions should be reasonably controlled.

Specifically, in the step (1), the power of the ultrasonic treatment may be 200W, 250W, 300W, 350W, 400W, 450W, 500W, 550W, 600W, 650W, 700W, 750W or 800W, the temperature of the ultrasonic treatment may be-4 ℃, -3 ℃, -2 ℃, -1 ℃ or 0 ℃, and the time of the ultrasonic treatment is 1min, 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min or 20 min.

In the present invention, in step (1), the equipment used for the ultrasonic treatment may be conventionally selected in the art, and preferably, the ultrasonic treatment is performed in an ultrasonic cell disruptor.

Preferably, in the step (1), the stirring speed in the stirring state is 900 to 1100 rpm. Specifically, the stirring rotation speed in the stirring state may be 900rpm, 920rpm, 950rpm, 980rpm, 1000rpm, 1020rpm, 1050rpm, 1080rpm, or 1100 rpm.

In the invention, in step (1), in order to prevent DMF from volatilizing, adding PAN into the CNC suspension, sealing and continuing stirring to obtain the CNC/PAN spinning precursor solution.

Preferably, in the step (1), the stirring temperature in the continuous stirring process is 45-60 ℃, the stirring time is 6-12 h, and the stirring rotation speed is 450-550 rpm. Specifically, the temperature of stirring during the continuous stirring process can be 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃, 55 ℃, 56 ℃, 57 ℃, 58 ℃, 59 ℃ or 60 ℃, the stirring time can be 6h, 7h, 8h, 9h, 10h, 11h or 12h, and the stirring speed can be 450rpm, 460rpm, 470rpm, 480rpm, 490rpm, 500rpm, 510rpm, 520rpm, 530rpm, 540rpm or 550 rpm.

Preferably, in step (2), the room temperature is 20 to 30 ℃. Specifically, the room temperature may be 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃ or 30 ℃.

In a specific embodiment, in the step (2), the CNC/PAN spinning precursor solution obtained in the step (1) may be stirred at room temperature for 18h, 18.5h, 19h, 19.5h, 20h, 20.5h, 21h, 21.5h or 22 h.

In a preferred embodiment, in the step (2), the needle of the syringe used in the electrospinning may have a size of 18G, 19G, 20G, 21G, or 22G.

In the invention, in the step (2), the electrostatic spinning process can affect the fiber diameter and the fiber morphology of the finally obtained electrostatic spinning nano composite fiber membrane, so that the electrostatic spinning process parameters are optimized in the invention.

Preferably, in step (2), the process parameters of the electrostatic spinning are as follows: the positive high voltage is 8-15 kV, the negative high voltage is-1.5-3 kV, the spinning speed is 0.04-0.12 mm/min, the rotating speed of a roller is 50-100 rpm, the spinning distance is 20-30 cm, the spinning time is 10-12 h, the spinning temperature is 18-30 ℃, and the relative humidity is 18-28%.

Specifically, the positive high voltage may be 8kV, 9kV, 10kV, 11kV, 12kV, 13kV, 14kV or 15kV, the negative high voltage may be-1.5 kV, -1.6kV, -1.7kV, -1.8kV, -1.9kV, -2kV, -2.1kV, -2.2kV, -2.3kV, -2.4kV, -2.5kV, -2.6kV, -2.7kV, -2.8kV, -2.9kV or-3 kV, the spinning rate may be 0.04mm/min, 0.05mm/min, 0.06mm/min, 0.07mm/min, 0.08mm/min, 0.09mm/min, 0.1mm/min, 0.11mm/min or 0.12mm/min, the drum rotation speed may be 50rpm, 55rpm, 60rpm, 65rpm, 70rpm, 75rpm, 80rpm, 85rpm, 90rpm, 95rpm, or 100 cm, and the spinning distance may be 20cm, 21cm, 22cm, 23cm, 24cm, 25cm, 26cm, 27cm, 28cm, 29cm or 30cm, the spinning time may be 10h, 10.25h, 10.5h, 10.75h, 11h, 11.25h, 11.5h, 11.75h or 12h, the spinning temperature may be 18 ℃, 19 ℃, 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, 28 ℃, 29 ℃ or 30 ℃, the relative humidity may be 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27% or 28%.

In the invention, in the step (3), no special requirement is made on the dosage of the sodium hydroxide solution, and the CNC/PAN-based electrospun nanofiber membrane is completely immersed.

In the invention, in the step (3), no special requirement is imposed on the dosage of the hydrochloric acid solution, and the CNC/PAN-based electrospun nanofiber membrane washed to be neutral is completely immersed.

In a specific embodiment, in step (3), the concentration of the sodium hydroxide solution may be 0.25mol/L, 0.3mol/L, 0.35mol/L, 0.4mol/L, 0.45mol/L, 0.5mol/L, 0.55mol/L, 0.6mol/L, 0.65mol/L, 0.7mol/L, 0.75mol/L, 0.8mol/L, 0.85mol/L, 0.9mol/L, 0.95mol/L, 1mol/L, or 1.5 mol/L.

In a specific case, in the step (3), the temperature of the hydrolysis treatment may be 50 ℃, 52.5 ℃, 55 ℃, 57.5 ℃, 60 ℃, 62.5 ℃, 65 ℃, 67.5 ℃ or 70 ℃, and the time of the hydrolysis treatment may be 15min, 17.5min, 20min, 22.5min, 25min, 27.5min, 30min, 32.5min, 35min, 37.5min, 40min, 42.5min or 45 min.

In the present invention, the hydrolysis conditions (sodium hydroxide solution concentration, hydrolysis temperature and hydrolysis time) affect the degree of fiber hydrolysis, and the hydrolysis degree is large, and the fiber structure is damaged, so that the hydrolysis conditions are reasonably controlled.

In the present invention, in step (3), the hydrolysis process is a partial hydrolysis process, the cyano group on the PAN surface is converted into a sodium carboxylate group by a sodium hydroxide solution, and the purpose of the hydrochloric acid treatment is to convert the sodium carboxylate group into a carboxyl group. When the hydrolysis treatment with sodium hydroxide solution is not used, the CNC/PAN-based electrospun nanofiber membrane cannot be hydrolyzed even with the subsequent treatment with hydrochloric acid solution, and thus the hydrolysis with sodium hydroxide solution must be performed in advance.

In a specific embodiment, in step (3), the concentration of the hydrochloric acid solution may be 0.25mol/L, 0.3mol/L, 0.35mol/L, 0.4mol/L, 0.45mol/L, 0.5mol/L, 0.55mol/L, 0.6mol/L, 0.65mol/L, 0.7mol/L, 0.75mol/L, 0.8mol/L, 0.85mol/L, 0.9mol/L, 0.95mol/L, or 1 mol/L.

In a specific case, in the step (3), the temperature of the treatment may be 18 ℃, 18.5 ℃, 19 ℃, 19.5 ℃, 20 ℃, 20.5 ℃, 21 ℃, 21.5 ℃, 22 ℃, 22.5 ℃, 23 ℃, 23.5 ℃, 24 ℃, 24.5 ℃ or 25 ℃, and the time of the treatment may be 15min, 17.5min, 20min, 22.5min, 25min, 27.5min, 30min, 32.5min, 35min, 37.5min, 40min, 42.5min or 45 min.

In the invention, in the step (3), the step of washing the CNC/PAN-based electrospun nano-fiber membrane subjected to hydrolysis treatment to be neutral by using deionized water refers to washing the CNC/PAN-based electrospun nano-fiber membrane subjected to hydrolysis treatment by using deionized water until the pH value of the solution obtained after washing is neutral.

In the invention, in the step (3), the step of washing with deionized water to be neutral refers to washing the CNC/PAN-based electrostatic spinning nanofiber membrane treated by the hydrochloric acid solution with deionized water until the pH value of the solution obtained after washing is neutral.

Preferably, in step (3), the drying manner is freeze drying or vacuum drying.

Preferably, the temperature of the freeze drying is-60 to-50 ℃, and the time of the freeze drying is 24 to 48 hours. Specifically, the temperature of the freeze-drying may be-60 ℃, -59 ℃, -58 ℃, -57 ℃, -56 ℃, -55 ℃, -54 ℃, -53 ℃, -52 ℃, -51 ℃, or-50 ℃, and the time of the freeze-drying may be 24h, 28h, 32h, 36h, 40h, 44h, or 48 h.

Preferably, the pressure of the vacuum drying is-0.2 to-0.05 MPa, the temperature of the vacuum drying is 45 to 60 ℃, and the time of the vacuum drying is 23 to 25 hours. Specifically, the pressure of the vacuum drying can be-0.2 MPa, -0.19MPa, -0.18MPa, -0.17MPa, -0.16MPa, -0.15MPa, -0.14MPa, -0.13MPa, -0.12MPa, -0.11MPa, -0.1MPa, -0.09MPa, -0.08MPa, -0.07MPa, -0.06MPa or-0.05 MPa, the temperature of the vacuum drying can be 45 ℃, 46 ℃, 47 ℃, 48 ℃, 49 ℃, 50 ℃, 51 ℃, 52 ℃, 53 ℃, 55 ℃, 56 ℃, 57 ℃, 58 ℃, 59 ℃ or 60 ℃, and the time of the vacuum drying can be 23h, 23.25h, 23.5h, 23.75h, 24h, 24.25h, 24.5h, 24.75h or 25 h.

In the present invention, the pressure is an absolute pressure.

In the present invention, CNC and DMF are first mixed in order to disperse CNC. If PAN is dissolved first, the solution concentration is relatively viscous and CNC cannot be uniformly dispersed at all.

The invention discloses a stable, controllable and efficient preparation method of an electrostatic spinning nano composite fiber membrane. Hydrophilic CNC is uniformly introduced into the PAN nanofiber matrix using electrospinning. And then, modifying the CNC/PAN-based electrostatic spinning nano-fiber membrane by using a sodium hydroxide solution to prepare the underwater super-hydrophobic oil type electrostatic spinning nano-composite fiber membrane. Compared with the prior art, the electrostatic spinning nano composite fiber membrane prepared by the method has the following advantages:

1. the CNC and PAN are uniformly mixed by adopting an ultrasonic crushing method, so that the problem of nonuniform distribution of the CNC in a polymer matrix is solved;

2. and through a partial hydrolysis mode, the composite nanofiber membrane is endowed with better hydrophilicity and underwater lipophobicity (antifouling capacity).

3. The CNC is introduced to ensure that the composite fiber membrane is more stable in water environment and can keep good nanofiber shape and mechanical strength.

The invention expands the practical application of the electrostatic spinning nano composite fiber membrane technology and provides a theoretical basis for the electrostatic spinning nano composite fiber membrane technology in the field of membrane separation and filtration.

The present invention will be described in detail below by way of examples, but the method of the present invention is not limited thereto.

Cellulose Nanocrystals (CNC) used in the examples and comparative examples of the present invention were obtained from acid hydrolyzed microcrystalline cellulose (MCC), wherein MCC (moisture content of 75%) was obtained from major xylonite investment company ltd, and the brand number is KY100S, and polyacrylonitrile (PAN, Mw 85,000) was obtained from shanghai di-cypress biotechnology ltd, and the brand number is K100301;

the preparation method of the cellulose nanocrystal CNC comprises the following steps:

80g of MCC and 9.4g of deionized water were added to a three-necked flask placed in an ice-water bath environment, stirred at a medium speed (600rpm) by an IKARW20 type overhead stirrer, 65.3g of concentrated sulfuric acid was slowly dropped into the three-necked flask through a constant pressure titration funnel, and the dropping of the concentrated sulfuric acid was completed within 0.5 hour. And then, quickly placing the three-neck flask in a water bath heating environment for reaction, wherein the reaction temperature is 45 ℃, adding a large amount of deionized water into the three-neck flask for dilution after the reaction is carried out for 90min, then pouring the solution in the three-neck flask into a beaker, and continuously diluting with the deionized water, wherein the total consumption of the deionized water is 10 times that of the solution obtained after the reaction is carried out for 90 min. Storing the diluted solution in a low-temperature environment (4 ℃) for 24 hours, centrifuging the suspended substance at the lower layer by utilizing a TG-16WS table-type high-speed centrifuge (centrifugation conditions: 10000r/min, 25 ℃ and 10min), repeatedly centrifuging for 2 times, adding water into the solid substance collected after centrifugation (the solid substance precipitated at the bottom of the centrifuge tube after the centrifugation is finished and the upper layer is aqueous solution), then carrying out ultrasonic treatment by utilizing a JY92-IIDN type ultrasonic cell crusher (the ultrasonic treatment conditions: 500W and 15min), then dialyzing for 2 days, adding water into the dialyzed suspension for dilution, controlling the diluted suspension to contain 0.2 wt% of the solid substance collected after centrifugation, carrying out freeze drying by utilizing a Scientz-N type vacuum freeze dryer, collecting the dried CNC, and storing in the low-temperature environment (4 ℃) for later use.

Example 1

(1) 20g of DMF was added to the beaker, then 0.16g of CNC was added to the DMF, performing ultrasonic treatment with an ultrasonic cell pulverizer under ice water bath condition to obtain CNC suspension (the ultrasonic treatment power is 800W, the ultrasonic treatment temperature is 0 deg.C, and the ultrasonic treatment time is 5min), then placing the CNC suspension on a magnetic stirring device, slowly adding 3.2g of PAN into the CNC suspension under the stirring state (the stirring speed is 1000rpm), sealing the beaker after the PAN is added, then placing the sealed beaker into a water bath kettle to continue stirring (the stirring temperature is 50 ℃, the stirring time is 12h, and the stirring rotating speed is 500rpm) to obtain uniform CNC/PAN spinning precursor solution, wherein the weight ratio of the CNC to the DMF is 0.008:1, the weight ratio of the CNC to the PAN is 0.05:1, and the weight ratio of the PAN to the DMF is 0.16: 1;

(2) stirring the CNC/PAN spinning precursor solution obtained in the step (1) at room temperature (25 ℃) for 20 hours, then placing the solution into a 10mL syringe with a needle head and a model of 18G for electrostatic spinning (the technological parameters of electrostatic spinning are that positive high voltage is 12.6kV, negative high voltage is-2.54 kV, the spinning speed is 0.06mm/min, the rotating speed of a roller is 80rpm, the spinning distance is 20cm, the spinning time is 12 hours, the spinning temperature is 25 ℃, and the relative humidity is 23%), and obtaining a CNC/PAN-based electrostatic spinning nanofiber membrane B1;

(3) completely immersing the CNC/PAN-based electrospun nano-fiber membrane obtained in the step (2) of 5cm multiplied by 5cm in a sodium hydroxide solution with the concentration of 1mol/L, carrying out hydrolysis treatment at 60 ℃ for 30min, then washing the CNC/PAN-based electrospun nano-fiber membrane subjected to hydrolysis treatment to be neutral by using deionized water, completely immersing the CNC/PAN-based electrospun nano-fiber membrane washed to be neutral in a hydrochloric acid solution with the concentration of 1mol/L, carrying out treatment at 25 ℃ for 20min, then washing the CNC/PAN-based electrospun nano-fiber membrane to be neutral by using the deionized water, and then carrying out freeze drying in a freeze dryer for 36 hours at the freeze-drying temperature of-58 ℃ to obtain the electrospun nano-composite fiber membrane A1 (CNC/H-PAN-based electrospun nano-composite fiber membrane).

Example 2

(1) 20g of DMF was added to the beaker, then 0.32g of CNC was added to the DMF, performing ultrasonic treatment with an ultrasonic cell pulverizer under ice water bath condition to obtain CNC suspension (the ultrasonic treatment power is 800W, the ultrasonic treatment temperature is 0 deg.C, and the ultrasonic treatment time is 5min), then placing the CNC suspension on a magnetic stirring device, slowly adding 3.2g of PAN into the CNC suspension under the stirring state (the stirring speed is 1000rpm), sealing the beaker after the PAN is added, then placing the sealed beaker into a water bath kettle to continue stirring (the stirring temperature is 50 ℃, the stirring time is 12h, and the stirring rotating speed is 500rpm) to obtain uniform CNC/PAN spinning precursor solution, wherein the weight ratio of the CNC to the DMF is 0.016:1, the weight ratio of the CNC to the PAN is 0.1:1, and the weight ratio of the PAN to the DMF is 0.16: 1;

(2) stirring the CNC/PAN spinning precursor solution obtained in the step (1) at room temperature (25 ℃) for 20 hours, then placing the solution into a 10mL syringe with a needle head and a model of 18G for electrostatic spinning (the technological parameters of electrostatic spinning are that positive high voltage is 12.6kV, negative high voltage is-2.54 kV, the spinning speed is 0.06mm/min, the rotating speed of a roller is 80rpm, the spinning distance is 20cm, the spinning time is 12 hours, the spinning temperature is 25 ℃, and the relative humidity is 23%), and obtaining a CNC/PAN-based electrostatic spinning nanofiber membrane B2;

(3) completely immersing the CNC/PAN-based electrospun nano-fiber membrane obtained in the step (2) of 5cm multiplied by 5cm in a sodium hydroxide solution with the concentration of 1mol/L, carrying out hydrolysis treatment at 60 ℃ for 30min, then washing the CNC/PAN-based electrospun nano-fiber membrane subjected to hydrolysis treatment to be neutral by using deionized water, completely immersing the CNC/PAN-based electrospun nano-fiber membrane washed to be neutral in a hydrochloric acid solution with the concentration of 1mol/L, carrying out treatment at 25 ℃ for 20min, then washing the CNC/PAN-based electrospun nano-fiber membrane to be neutral by using the deionized water, and then carrying out freeze drying in a freeze dryer for 36 hours at the freeze-drying temperature of-58 ℃ to obtain the electrospun nano-composite fiber membrane A2 (CNC/H-PAN-based electrospun nano-composite fiber membrane).

Example 3

(1) 20g of DMF was added to the beaker, then 0.48g of CNC was added to the DMF, performing ultrasonic treatment by using an ultrasonic cell crusher under the condition of ice-water bath to obtain CNC suspension (the power of ultrasonic treatment is 800W, the temperature of ultrasonic treatment is 0 ℃, and the time of ultrasonic treatment is 5 min.), then placing the CNC suspension on a magnetic stirring device, slowly adding 3.2g of PAN into the CNC suspension under the stirring state (the stirring speed is 1000rpm), sealing the beaker after the PAN is added, then placing the sealed beaker into a water bath kettle to continue stirring (the stirring temperature is 50 ℃, the stirring time is 12h, and the stirring rotating speed is 500rpm) to obtain uniform CNC/PAN spinning precursor solution, wherein the weight ratio of the CNC to the DMF is 0.024:1, the weight ratio of the CNC to the PAN is 0.15:1, and the weight ratio of the PAN to the DMF is 0.16: 1;

(2) stirring the CNC/PAN spinning precursor solution obtained in the step (1) at room temperature (25 ℃) for 20 hours, then placing the solution into a 10mL syringe with a needle head and a model of 18G for electrostatic spinning (the technological parameters of electrostatic spinning are that positive high voltage is 12.6kV, negative high voltage is-2.54 kV, the spinning speed is 0.06mm/min, the rotating speed of a roller is 80rpm, the spinning distance is 20cm, the spinning time is 12 hours, the spinning temperature is 25 ℃, and the relative humidity is 23%), and obtaining a CNC/PAN-based electrostatic spinning nanofiber membrane B3;

(3) completely immersing the CNC/PAN-based electrospun nano-fiber membrane obtained in the step (2) of 5cm multiplied by 5cm in a sodium hydroxide solution with the concentration of 1mol/L, carrying out hydrolysis treatment at 60 ℃ for 30min, then washing the CNC/PAN-based electrospun nano-fiber membrane subjected to hydrolysis treatment to be neutral by using deionized water, completely immersing the CNC/PAN-based electrospun nano-fiber membrane washed to be neutral in a hydrochloric acid solution with the concentration of 1mol/L, carrying out treatment at 25 ℃ for 20min, then washing the CNC/PAN-based electrospun nano-fiber membrane to be neutral by using the deionized water, and then carrying out freeze drying in a freeze dryer for 36 hours at the freeze-drying temperature of-58 ℃ to obtain the electrospun nano-composite fiber membrane A3 (CNC/H-PAN-based electrospun nano-composite fiber membrane).

Example 4

(1) 20g of DMF was added to the beaker, then 0.64g of CNC was added to the DMF, performing ultrasonic treatment by using an ultrasonic cell crusher under the condition of ice-water bath to obtain CNC suspension (the power of ultrasonic treatment is 800W, the temperature of ultrasonic treatment is 0 ℃, and the time of ultrasonic treatment is 5 min.), then placing the CNC suspension on a magnetic stirring device, slowly adding 3.2g of PAN into the CNC suspension under the stirring state (the stirring speed is 1000rpm), sealing the beaker after the PAN is added, then placing the sealed beaker into a water bath kettle to continue stirring (the stirring temperature is 50 ℃, the stirring time is 12h, and the stirring rotating speed is 500rpm) to obtain uniform CNC/PAN spinning precursor solution, wherein the weight ratio of the CNC to the DMF is 0.032:1, the weight ratio of the CNC to the PAN is 0.2:1, and the weight ratio of the PAN to the DMF is 0.16: 1;

(2) stirring the CNC/PAN spinning precursor solution obtained in the step (1) at room temperature (25 ℃) for 20 hours, then placing the solution into a 10mL syringe with a needle head and a model of 18G for electrostatic spinning (the technological parameters of electrostatic spinning are that positive high voltage is 12.6kV, negative high voltage is-2.54 kV, the spinning speed is 0.06mm/min, the rotating speed of a roller is 80rpm, the spinning distance is 20cm, the spinning time is 12 hours, the spinning temperature is 25 ℃, and the relative humidity is 23%), and obtaining a CNC/PAN-based electrostatic spinning nanofiber membrane B4;

(3) completely immersing the CNC/PAN-based electrospun nano-fiber membrane obtained in the step (2) of 5cm multiplied by 5cm in a sodium hydroxide solution with the concentration of 1mol/L, carrying out hydrolysis treatment at 60 ℃ for 30min, then washing the CNC/PAN-based electrospun nano-fiber membrane subjected to hydrolysis treatment to be neutral by using deionized water, completely immersing the CNC/PAN-based electrospun nano-fiber membrane washed to be neutral in a hydrochloric acid solution with the concentration of 1mol/L, carrying out treatment at 25 ℃ for 20min, then washing the CNC/PAN-based electrospun nano-fiber membrane to be neutral by using the deionized water, and then carrying out freeze drying in a freeze dryer for 36 hours at the freeze-drying temperature of-58 ℃ to obtain the electrospun nano-composite fiber membrane A4 (CNC/H-PAN-based electrospun nano-composite fiber membrane).

Example 5

(1) 20g of DMF was added to the beaker, then 0.32g of CNC was added to the DMF, performing ultrasonic treatment with an ultrasonic cell pulverizer under ice water bath condition to obtain CNC suspension (ultrasonic treatment power is 200W, ultrasonic treatment temperature is 0 deg.C, ultrasonic treatment time is 20min), then placing the CNC suspension on a magnetic stirring device, slowly adding 2.8g of PAN into the CNC suspension under the stirring state (the stirring speed is 900rpm), sealing the beaker after the PAN is added, then placing the sealed beaker into a water bath kettle to continue stirring (the stirring temperature is 45 ℃, the stirring time is 12h, and the stirring rotating speed is 550rpm) to obtain uniform CNC/PAN spinning precursor solution, wherein the weight ratio of the CNC to the DMF is 0.016:1, the weight ratio of the CNC to the PAN is 0.11:1, and the weight ratio of the PAN to the DMF is 0.14: 1;

(2) stirring the CNC/PAN spinning precursor solution obtained in the step (1) at room temperature (25 ℃) for 21h, then placing the solution into a 10mL syringe with a 19G needle head for electrostatic spinning (the technological parameters of electrostatic spinning are that positive high voltage is 8kV, negative high voltage is-2 kV, the spinning speed is 0.04mm/min, the rotating speed of a roller is 75rpm, the spinning distance is 25cm, the spinning time is 10h, the spinning temperature is 30 ℃, and the relative humidity is 20%), and obtaining the CNC/PAN-based electrostatic spinning nanofiber membrane;

(3) completely immersing the CNC/PAN-based electrospun nano-fiber membrane obtained in the step (2) of 5cm multiplied by 5cm in a sodium hydroxide solution with the concentration of 0.5mol/L, carrying out hydrolysis treatment at 70 ℃ for 15min, then washing the CNC/PAN-based electrospun nano-fiber membrane subjected to hydrolysis treatment with deionized water to be neutral, completely immersing the CNC/PAN-based electrospun nano-fiber membrane washed to be neutral in a hydrochloric acid solution with the concentration of 0.25mol/L, carrying out treatment at 20 ℃ for 45min, then washing with deionized water to be neutral, and then carrying out vacuum drying in a vacuum oven for 23H at the temperature of 60 ℃ and the pressure of-0.2 MPa to obtain the electrospun nano-composite fiber membrane A5 (CNC/H-PAN-based electrospun nano-composite fiber membrane).

Example 6

(1) 20g of DMF was added to the beaker, then 0.32g of CNC was added to the DMF, performing ultrasonic treatment with an ultrasonic cell pulverizer under ice water bath condition to obtain CNC suspension (ultrasonic treatment power is 750W, ultrasonic treatment temperature is 0 deg.C, ultrasonic treatment time is 1min), then placing the CNC suspension on a magnetic stirring device, slowly adding 3.6g of PAN into the CNC suspension under the stirring state (the stirring speed is 1000rpm), sealing the beaker after the PAN is added, then placing the sealed beaker into a water bath kettle to continue stirring (the stirring temperature is 60 ℃, the stirring time is 6h, and the stirring rotating speed is 450rpm) to obtain uniform CNC/PAN spinning precursor solution, wherein the weight ratio of the CNC to the DMF is 0.016:1, the weight ratio of the CNC to the PAN is 0.09:1, and the weight ratio of the PAN to the DMF is 0.18: 1;

(2) stirring the CNC/PAN spinning precursor solution obtained in the step (1) at room temperature (25 ℃) for 22h, then placing the CNC/PAN spinning precursor solution into a syringe with the model of 22G and a needle head for electrostatic spinning (the technological parameters of electrostatic spinning are that positive high voltage is 10kV, negative high voltage is-1.5 kV, the spinning speed is 0.052mm/min, the rotating speed of a roller is 50rpm, the spinning distance is 28cm, the spinning time is 11h, the spinning temperature is 25 ℃, and the relative humidity is 18%), and obtaining the CNC/PAN-based electrostatic spinning nanofiber membrane;

(3) completely immersing the CNC/PAN-based electrospun nano-fiber membrane obtained in the step (2) of 5cm multiplied by 5cm in a sodium hydroxide solution with the concentration of 0.25mol/L, carrying out hydrolysis treatment at 50 ℃ for 45min, then washing the CNC/PAN-based electrospun nano-fiber membrane subjected to hydrolysis treatment with deionized water to be neutral, completely immersing the CNC/PAN-based electrospun nano-fiber membrane washed to be neutral in a hydrochloric acid solution with the concentration of 0.5mol/L, carrying out treatment at 20 ℃ for 30min, then washing with deionized water to be neutral, and then carrying out vacuum drying in a vacuum oven for 25 hours at the temperature of 50 ℃ and the pressure of-0.05 MPa to obtain the electrospun nano-composite fiber membrane A6 (CNC/H-PAN-based electrospun nano-composite fiber membrane).

Comparative example 1

(1) Adding 20g of DMF (dimethyl formamide) into a beaker, then adding 3.2g of PAN into the DMF, sealing the beaker after the PAN is added, and then placing the sealed beaker into a water bath kettle to be stirred (the stirring temperature is 50 ℃, the stirring time is 12h, and the stirring rotating speed is 500rpm) to obtain a uniform PAN spinning precursor solution, wherein the weight ratio of the PAN to the DMF is 0.16: 1;

(2) stirring the PAN spinning precursor solution obtained in the step (1) at room temperature (25 ℃) for 20h, then placing the solution into a 10mL syringe with a needle head and a model number of 18G for electrostatic spinning (the technological parameters of electrostatic spinning are that positive high voltage is 12.6kV, negative high voltage is-2.54 kV, the spinning speed is 0.06mm/min, the rotating speed of a roller is 80rpm, the spinning distance is 20cm, the spinning time is 12h, the spinning temperature is 25 ℃, and the relative humidity is 23%), and obtaining PAN-based electrostatic spinning nanofiber membrane C1;

(3) and (3) completely immersing the PAN electrospun nanofiber membrane obtained in the step (2) of 5cm multiplied by 5cm in a sodium hydroxide solution with the concentration of 1mol/L, carrying out hydrolysis treatment at 60 ℃ for 30min, then washing the PAN electrospun nanofiber membrane subjected to hydrolysis treatment to be neutral by using deionized water, then completely immersing the PAN electrospun nanofiber membrane washed to be neutral in a hydrochloric acid solution with the concentration of 1mol/L, carrying out treatment at 25 ℃ for 20min, then washing the PAN electrospun nanofiber membrane to be neutral by using the deionized water, and then carrying out freeze drying in a freeze dryer for 36 hours at the freeze drying temperature of-58 ℃ to obtain the electrospun nanofiber membrane D1 (H-PAN-based electrospun nanofiber membrane).

Comparative example 2

The procedure was followed as described in example 2, except that in step (3), the temperature of the hydrolysis treatment was 85 ℃ to obtain electrospun nanocomposite fiber membrane D2.

Comparative example 3

The procedure was as described in example 2, except that in step (3), the hydrolysis treatment was carried out at 85 ℃ for 60min to obtain electrospun nanocomposite fiber membrane D3.

Comparative example 4

(1) Adding 20g of DMF (dimethyl formamide) into a beaker, then adding 2.0g of PAN into the DMF, sealing the beaker after the PAN is added, and then placing the sealed beaker into a water bath kettle to be stirred (the stirring temperature is 50 ℃, the stirring time is 12h, and the stirring rotating speed is 500rpm) to obtain a uniform PAN spinning precursor solution, wherein the weight ratio of the PAN to the DMF is 0.10: 1;

(2) stirring the PAN spinning precursor solution obtained in the step (1) at room temperature (25 ℃) for 20h, then placing the solution into a 10mL syringe with a needle head and a model number of 18G for electrostatic spinning (the technological parameters of electrostatic spinning are that positive high voltage is 12.6kV, negative high voltage is-2.54 kV, the spinning speed is 0.06mm/min, the rotating speed of a roller is 80rpm, the spinning distance is 20cm, the spinning time is 12h, the spinning temperature is 25 ℃, and the relative humidity is 23%), and obtaining PAN-based electrostatic spinning nanofiber membrane D4;

comparative example 5

(1) Adding 20g of DMF (dimethyl formamide) into a beaker, then adding 2.4g of PAN into the DMF, sealing the beaker after the PAN is added, and then placing the sealed beaker into a water bath kettle to be stirred (the stirring temperature is 50 ℃, the stirring time is 12h, and the stirring rotating speed is 500rpm) to obtain a uniform PAN spinning precursor solution, wherein the weight ratio of the PAN to the DMF is 0.12: 1;

(2) stirring the PAN spinning precursor solution obtained in the step (1) at room temperature (25 ℃) for 20h, then placing the solution into a 10mL syringe with a needle head and a model number of 18G for electrostatic spinning (the technological parameters of electrostatic spinning are that positive high voltage is 12.6kV, negative high voltage is-2.54 kV, the spinning speed is 0.06mm/min, the rotating speed of a roller is 80rpm, the spinning distance is 20cm, the spinning time is 12h, the spinning temperature is 25 ℃, and the relative humidity is 23%), and obtaining PAN-based electrostatic spinning nanofiber membrane D5;

comparative example 6

(1) Adding 20g of DMF (dimethyl formamide) into a beaker, then adding 2.8g of PAN into the DMF, sealing the beaker after the PAN is added, and then placing the sealed beaker into a water bath kettle to be stirred (the stirring temperature is 50 ℃, the stirring time is 12h, and the stirring rotating speed is 500rpm) to obtain a uniform PAN spinning precursor solution, wherein the weight ratio of the PAN to the DMF is 0.14: 1;

(2) stirring the PAN spinning precursor solution obtained in the step (1) at room temperature (25 ℃) for 20h, then placing the solution into a 10mL syringe with a needle head and a model number of 18G for electrostatic spinning (the technological parameters of electrostatic spinning are that positive high voltage is 12.6kV, negative high voltage is-2.54 kV, the spinning speed is 0.06mm/min, the rotating speed of a roller is 80rpm, the spinning distance is 20cm, the spinning time is 12h, the spinning temperature is 25 ℃, and the relative humidity is 23%), and obtaining PAN-based electrostatic spinning nanofiber membrane D6;

comparative example 7

(1) Adding 20g of DMF (dimethyl formamide) into a beaker, then adding 3.6g of PAN into the DMF, sealing the beaker after the PAN is added, and then placing the sealed beaker into a water bath kettle to be stirred (the stirring temperature is 50 ℃, the stirring time is 12h, and the stirring rotating speed is 500rpm) to obtain a uniform PAN spinning precursor solution, wherein the weight ratio of the PAN to the DMF is 0.18: 1;

(2) stirring the PAN spinning precursor solution obtained in the step (1) at room temperature (25 ℃) for 20h, then placing the solution into a 10mL syringe with a needle head and a model number of 18G for electrostatic spinning (the technological parameters of electrostatic spinning are that positive high voltage is 12.6kV, negative high voltage is-2.54 kV, the spinning speed is 0.06mm/min, the rotating speed of a roller is 80rpm, the spinning distance is 20cm, the spinning time is 12h, the spinning temperature is 25 ℃, and the relative humidity is 23%), and obtaining PAN-based electrostatic spinning nanofiber membrane D7;

test example 1

The micro-morphology of the cellulose nanocrystal CNC used in the examples and comparative examples was analyzed using a Transmission Electron Microscope (TEM) of Hitachi-7650 model japan; characteristic absorption peaks of the cellulose nanocrystal CNC used in the examples and comparative examples were measured by a fourier infrared spectrometer;

the transmission electron microscope analysis result is shown in FIG. 1(a), and it can be seen from FIG. 1(a) that the CNC has a rod-like structure, a clear profile, an average length of 90nm and an average diameter of 6.2 nm.

The measurement result of the Fourier Infrared spectrometer is shown in FIG. 1(b), and it can be seen from FIG. 1(b) that for CNC, 3336cm^-1The absorption peak at (a) corresponds to the-OH stretching vibration absorption peak of the CNC unit. 1031cm^-1The absorption peak at (A) is assigned to the C-OH stretching vibration absorption peak (the strongest band of the cellulose unit).

Test example 2

The photographs of the spinning precursor solutions prepared in the step (1) of the examples 1 to 4 and the comparative example 1 are shown in fig. 2, and the photographs of the spinning precursor solutions prepared in the step (1) of the comparative example 1 and the examples 1 to 4 correspond to the spinning precursor solutions of the comparative example 1 and the examples 1 to 4 in sequence from left to right in fig. 2;

from fig. 2, the spinning precursor solution gradually became turbid from a translucent state with the increase of the CNC dosage, indicating that the CNC was fully dispersed into the PAN spinning precursor solution.

Test example 3

Respectively observing the micro-morphological structures of C1 and B1-B4 by a scanning electron microscope (SEM, JSM-7500F, Japan);

the micro-topographic structures of C1 and B1-B4 are shown in FIG. 3, respectively, and from FIG. 3, thicker and thinner fibers appear in the fiber film as the amount of CNC is increased. When the weight ratio of CNC to PAN reaches 0.2:1, the interaction between oleophilic nitrile groups (-C [ identical to ] N) on the PAN chain and hydrophilic hydroxyl groups (-OH) on the CNC chain is poor, so that the instability of jet flow in the spinning process is caused, and the nonuniformity of fiber diameter is increased.

Test example 4

Respectively detecting the fiber diameter distribution maps of C1 and B1-B4 by using Nanomeasure software, wherein the detection method comprises the following steps: the average diameter was calculated by taking 100 random points on the film, measuring the fiber diameter, and counting the diameter distribution.

The fiber diameter distribution plots of C1, B1-B4 are shown as a-e in fig. 4, respectively, from fig. 4, the diameter difference (maximum diameter value-minimum diameter value) of the electrospun nanocomposite fiber membranes becomes larger with increasing CNC usage. With the increase of the CNC content, both coarser and finer fibers are present in the electrospun nanocomposite fiber film, the diameter of the nanofibers tends to be non-uniform, and the distribution tends to be wider.

Test example 5

The photo of the PAN-based electrospun nanofiber membrane C1 in the comparative example 1 immersed in deionized water after being hydrolyzed by a sodium hydroxide solution is shown as a in FIG. 5, the photo of immersed in deionized water after being treated by a hydrochloric acid solution is shown as b in FIG. 5, and the photo of deionized water after being washed to be neutral after being treated by the hydrochloric acid solution is shown as C in FIG. 5;

the photo of the CNC/PAN-based electrospun nanofiber membrane B1 in example 1 immersed in deionized water after being hydrolyzed by sodium hydroxide solution is shown as a in fig. 6, the photo of immersed in deionized water after being treated by hydrochloric acid solution is shown as B in fig. 6, and the photo of deionized water after being washed to neutrality after being treated by hydrochloric acid solution is shown as c in fig. 6;

the photo of the CNC/PAN-based electrospun nanofiber membrane B2 in example 2 immersed in deionized water after being hydrolyzed by sodium hydroxide solution is shown as a in fig. 7, the photo of immersed in deionized water after being treated by hydrochloric acid solution is shown as B in fig. 7, and the photo of deionized water after being washed to neutrality after being treated by hydrochloric acid solution is shown as c in fig. 7;

the photo of the CNC/PAN-based electrospun nanofiber membrane B3 in example 3 immersed in deionized water after being hydrolyzed by sodium hydroxide solution is shown as a in fig. 8, the photo of immersed in deionized water after being treated by hydrochloric acid solution is shown as B in fig. 8, and the photo of deionized water after being washed to neutrality after being treated by hydrochloric acid solution is shown as c in fig. 8;

the photo of the CNC/PAN based electrospun nanofiber membrane B4 in example 4 immersed in deionized water after being hydrolyzed by sodium hydroxide solution is shown as a in fig. 9, the photo of immersed in deionized water after being treated by hydrochloric acid solution is shown as B in fig. 9, and the photo of deionized water after being washed to neutrality after being treated by hydrochloric acid solution is shown as c in fig. 9;

from fig. 5-9, after CNC is added, the stability of the fiber membrane in water is enhanced, and the basic composite fiber membrane structure can still be maintained under the interference of external force; and the fiber film is easy to loosen in water without adding CNC.

Test example 6

Respectively observing the microstructure of D1 and A1-A4 by adopting a scanning electron microscope (SEM, JSM-7500F, Japan);

the micro-morphological structures of D1 and A1-A4 are respectively shown in FIG. 10. from FIG. 10, the electrospun nano composite fiber membrane prepared by the invention can still maintain the original nano fiber structure.

Test example 7

Respectively detecting the fiber diameter distribution maps of D1 and A1-A4 by using Nanomeasure software, wherein the detection method comprises the following steps: the average diameter was calculated by taking 100 random points on the film, measuring the fiber diameter, and counting the diameter distribution.

The fiber diameter distribution patterns of D1 and A1-A4 are respectively shown as a-e in FIG. 11, and the average diameter of the fibers is increased from 296.32 + -34 nm to 330.19 + -61 nm in FIG. 11. D1(H-PAN based electrospun nanocomposite fiber membrane) nanofiber diameter was 295nm, and when the weight ratio of CNC to PAN was 0.05:1, the fiber diameter slightly increased to 308 nm. When the weight ratio of CNC to PAN is 0.1:1, the fiber diameter is 314 nm. When the weight ratio of CNC to PAN is 0.15:1, the fiber diameter is slightly reduced, the prepared fiber has 600nm of fiber with larger diameter and 150nm of fiber with smaller diameter, and the fiber distribution range is enlarged. When the weight ratio of CNC to PAN is 0.2:1, the average diameter of the obtained fiber is about 331nm, the minimum fiber diameter is about 151nm, and the maximum fiber diameter is about 566 nm.

The addition of CNC increases the viscosity of the spinning solution, resulting in larger fiber diameters. Meanwhile, the high viscosity can also make the density of the long molecular chains of the fluid higher, which provides an important factor for the Rayleigh instability of the jet flow. On the other hand, after the CNC is added, the conductivity and the surface tension of the spinning solution tend to increase, and the lipophilic nitrile group (-C [ identical to ] N) on the PAN chain and the hydrophilic hydroxyl group (-OH) on the CNC chain are subjected to ineffective integration. This further increases the instability of the jet during spinning and thus increases the non-uniformity of the fiber diameter.

Test example 8

Respectively observing the micro-morphology structures of A5-A6 by adopting a scanning electron microscope (SEM, JSM-7500F, Japan);

the micro-morphology structures of A5-A6 are respectively shown in FIG. 12, and the structure between the nano-fibers is still clear after the electrostatic spinning nano-composite fiber membrane prepared by the invention is hydrolyzed in FIG. 12.

Test example 9

Respectively observing the micro-morphology structures of D2-D3 by adopting a scanning electron microscope (SEM, JSM-7500F, Japan);

the microstructure of D2-D3 is shown in FIG. 13, respectively, in FIG. 13, the hydrolysis time is increased to destroy the surface structure of the fiber membrane under the condition of a certain hydrolysis temperature, and in the D2 microstructure, the nanofibers are bonded together, but are not obvious; in the D3 microscopic morphology, the phenomenon of nanofiber adhesion (aggregation) together is serious; in contrast, in the sample A2 in FIG. 10, the structure between nanofibers is clear and well-defined. Therefore, reasonable control of hydrolysis temperature and hydrolysis time is required.

Test example 10

Respectively observing the micro-morphology structures of D4-D6, C1 and D7 by adopting a scanning electron microscope (SEM, JSM-7500F, Japan);

the micro-topographic structures of D4-D6, C1 and D7 are respectively shown in FIG. 14, and in the D4 micro-topographic map, beaded structure fibers appear, and the fiber diameters are uneven; the bead structure in the D5 fiber membrane disappears, the fiber thickness is not uniform, the fiber diameters of the D6, C1 and D7 fiber membranes are uniform, but the diameters of the nano fibers in an SEM image are obviously reduced under the same magnification. The surfaces of the electrostatic spinning nano composite fibers prepared by the method are smooth.

Test example 11

Detecting the pre-wetting morphology of A2;

the detection method comprises the following steps: a2 was immersed in water for 24h and then removed to observe its morphology.

The pre-wetting topography of A2 is shown in FIG. 15, and the CNC/H-PAN based electrospun nano-composite fiber membrane prepared by the method has good wetting property in FIG. 15. Due to the hydrogen bonding interaction force existing between CNC molecules. Therefore, the composite fiber membrane has better stability under the interaction of hydrogen bonds.

Test example 12

Measuring infrared spectrograms of C1, B1, D1 and A1 by a Fourier infrared spectrometer;

as shown in FIG. 16, from FIG. 16, after hydrolysis, the A1 and D1 samples were at 3651cm^-1A new peak appears around, which can be attributed to the hydroxyl (-OH) groups in the H-PAN sample. In addition, 2242cm in A1 and D1 samples^-1Has a reduced absorption peak at 1668cm^-1The absorption peak at (a) disappears due to hydrolysis of the PAN matrix surface. Furthermore, at 1358cm^-1A weak absorption peak appears at (carboxylic acid groups). These changes (including peak intensity, position) in these absorption peaks indicate that amide groups and a portion of nitrile groups in PAN nanofibers are hydrolyzed to carboxylic acid groups.

Test example 13

Respectively detecting stress-strain force curves of D1 and A1-A4 by adopting a WDW-20 microelectronic universal mechanical testing machine (China underwriter mechanical instruments Co., Ltd.);

the detection method comprises the following steps: the fiber membranes were cut into rectangular strip-shaped samples of 30mm × 10mm, and the test was performed at a tensile rate of 5mm/min at room temperature (25 ℃) at a relative humidity of 23% and a tensile force of 5N, and the measurement was repeated 3 times for each fiber membrane, and the test result was an arithmetic average of 3 experiments.

Application of D1 and A1-A4The force-strain force curve is shown in FIG. 17, from FIG. 17, with increasing CNC usage, tensile strength (σ)_max) And elongation at break (. epsilon.)_b) The values increase and decrease, while the Young's modulus (E) tends to increase, σ 1 (electrospun H-PAN nanocomposite fiber membrane)_max、ε_bAnd E values of 1.93MPa, 48.85% and 4.89MPa, respectively. The bulk density of D1 was low and the fiber alignment was loosely disordered. Thus, the interaction forces between adjacent fibers are weak. In the initial stage of drawing, the arrangement between nanofibers changes from loose to tight. With further increase in stress, the nanocomposite fiber film is sufficiently stretched to enable the individual fibers to withstand the same tensile stress, with the strain increasing linearly with stress. When the stress reaches a certain value, the nano composite nano fiber is broken.

For A1, its σ_max、ε_bAnd E values of 3.71MPa, 60.38% and 3.68MPa, respectively. σ of fiber compared to D1_maxAnd ε_bThe values increased by 92.2% and 23.6%, respectively, and the E value decreased by 24.7%.

For A2, its σ_max、ε_bAnd E values of 4.2MPa, 62.83% and 9.8MPa, respectively. In contrast to D1, σ_max、ε_bAnd E values increased 117.6%, 28.6% and 100.4%, respectively. In one aspect, the addition of CNC changes the arrangement and microstructure of the internal fibers of the composite fiber membrane. On the other hand, the intermolecular hydrogen bonding interaction force of CNC in the composite fiber film increases with the increase of the CNC content. As a result, the tensile strength of the composite fiber film is improved.

For A3, its σ_max、ε_bAnd E values of 3.88MPa, 48.24% and 10.36MPa, respectively. σ of fiber compared to D1_maxAnd E values increased by 101.0% and 11.9%, respectively_bThe value was reduced by 1.2%.

For A4, its σ_max、ε_bAnd E values of 3.0MPa, 30.54% and 21.53MPa, respectively. The values of σ max and E of the fibers were increased by 55.4% and 334.2%, ε, respectively, compared to D1_bThe value was reduced by 37.5%.

It can be seen that as the CNC to PAN weight ratio increases to 0.15:1, the mechanical properties begin to degrade. Too much CNC content can change the physical and chemical properties (viscosity, conductivity, surface tension) of the spinning precursor solution, increasing the instability of the jet during spinning. Due to the break-up of the micro-jets, small diameter fibers increase and the fiber diameter becomes non-uniform. Therefore, the tensile strength of the composite fiber membrane is reduced. Due to the CNC hydrogen bonding effect between adjacent fibers, the single fibers are not easy to slip. Therefore, the elongation at break is reduced, and the toughness of the material is deteriorated. As the weight ratio of CNC to PAN was further increased to 0.2:1, the higher the CNC content, the more susceptible the CNC to agglomerate due to hydrogen bond interactions, adversely affecting the interface compatibility of CNC with H-PAN. Therefore, A4 has poor mechanical properties and a high Young's modulus.

Test example 14

Detecting the pore size and the pore size distribution of D1 and A1-A4 respectively;

the aperture detection method comprises the following steps: the pore size of the membrane was measured by a microfiltration membrane pore size analyzer (PSDA-20, tokyo high-performance materials science and technology ltd, china) using a bubble point method.

The pore size distribution curves of D1, A1-A4 are shown in FIG. 18. from FIG. 18, all of the electrospun nanocomposite fiber membranes showed a central peak in the range of 0.5-0.8. mu.m. For D1, A1-A4, the average pore diameters were 0.65, 0.74, 0.60, 0.54, and 0.63 μm, respectively. Obviously, as the CNC content increases, the average pore size of the membrane increases first, then decreases, and finally increases. This is due to the increase in fiber diameter and the wide range of diameter distributions.

For D1, the interaction between the fibers is weak. Therefore, the fiber layer is easily peeled from the film after absorbing water during hydrolysis. At this time, the film shows a loose swollen state under water. For a1, the hydrogen bonding interaction forces in the fiber membrane are relatively weak, and the pore structure of the electrospun nanofiber membrane is mainly influenced by the fiber diameter. Thus, a1 has the largest average pore size and a broader Pore Size Distribution (PSD). When the CNC content is further increased, the pore structure of the membrane is mainly affected by CNC hydrogen bond interactions, the fiber density is increased, and the pore size and PSD range of the electrospun nanocomposite fiber membrane become smaller. When the weight ratio of the CNC to the PAN exceeds 0.15:1, the amount of CNC existing on the surface of the nanofiber is limited, and excessive CNC causes agglomeration, so that the interaction force of hydrogen bonds on the surface of the fiber membrane is weakened. The diameter range and porosity of A3 and a4 were similar, but the average fiber diameter of a4 was larger, which is the main reason for the increase in pore size. Therefore, by incorporating a certain amount of CNC in the composite fiber membrane, the pore size of the composite fiber membrane can be enhanced.

Test example 15

Detecting the wetting characteristics of A2 and B2;

the method for detecting the affinity of A2 to water and oil comprises the following steps: water was stained with methylene blue and oil (1, 2-dichloroethane) was stained with sudan iii. The membrane is laid on a glass sheet, water and oil are respectively dripped on the surface of the membrane by using a dropper, the existence state of water drops and oil drops is observed, the detection result is shown as a in figure 19, the water drops and the oil drops completely permeate into the fiber membrane, and the composite fiber membrane has good affinity to the water and the oil in the air;

a2 underwater super oleophobic property detection method comprises the following steps: fixing the composite fiber membrane on a glass slide by using a double-sided adhesive tape, then placing the glass slide into the bottom of a quartz glass container filled with water, after the composite fiber membrane is completely soaked and wetted, injecting a certain amount of oil drops on the surface of the membrane in the water by using an injector, dyeing the oil solution by using Sudan red, shaking the quartz glass container back and forth, observing the existence state of the oil drops on the surface of the membrane, wherein the detection result is shown as b in fig. 19, and the interface between the oil drops and the membrane is clear. The film has good oleophobic property to oil drops in water;

the method for detecting the dynamic contact angle of A2 to water (5 muL) in air is as follows: the test was carried out by means of a dynamic contact angle tester (OCA40, Dataphysics, Germany). About 5. mu.L of water was dropped on the surface of the film. Recording Contact Angle (CA) data of the composite fiber membrane on water drops along with the change of time, wherein the detection result is shown as c in fig. 19, and water can rapidly permeate into the composite fiber membrane in a short time, which shows that the composite fiber membrane has good affinity to water;

the method for detecting the dynamic contact angle of A2 to oil (10 muL) in water is as follows: the test was carried out by means of a dynamic contact angle tester (OCA40, Dataphysics, Germany). The membrane was stuck to a glass plate and placed in a quartz glass container containing water, and about 10. mu.L of oil droplets were dropped on the surface of the membrane. Recording Contact Angle (CA) data of the composite fiber membrane on oil drops changing underwater along with time, wherein the detection result is shown as d in fig. 19, which shows that the composite fiber membrane has underwater oleophobic property, and the oil drops can keep relatively stable in aqueous solution for a long time;

the detection method of the adhesion of the B2 underwater oil comprises the following steps: the membrane is adhered to a glass sheet and placed in a quartz glass container filled with water, a 30-degree oblique angle is kept between the glass sheet and the bottom of the quartz glass, oil drops (dyed) are injected onto the surface of the membrane by a 5ml injector, the state of the oil drops on the surface of the membrane is observed, the detection result is shown as e in figure 19, when the oil drops are contacted with the composite fiber membrane, the oil drops are adhered to the surface of the composite fiber membrane, the selective wettability of the composite fiber membrane is seriously reduced by the adhesion behavior, and B2 has poor oleophobic performance underwater;

the detection method of the adhesion of the A2 underwater oil comprises the following steps: the membrane is adhered to a glass sheet and placed in a quartz glass container filled with water, the glass sheet and the bottom of the quartz glass keep a 30-degree oblique angle, oil drops (dyed) are injected on the surface of the membrane by a 5ml syringe, the state of the oil drops on the surface of the membrane is observed, the detection result is shown as f in figure 19, the oil drops can not be completely adhered on the surface of the membrane, and the A2 has good underwater oleophobic performance after hydrolysis treatment, which is mainly because part of nitrile groups (-CN) and amide groups (-C (O) NH can be partially hydrolyzed by alkali on the surface of the membrane₂) To a carboxyl group (-COOH). Hydrolysis can directly change the surface structure and properties of the fiber;

a2 method for detecting the dynamic adhesion performance of underwater oil comprises the following steps: the test was carried out by means of a dynamic contact angle tester (OCA40, Dataphysics, Germany). The film was adhered to a glass plate and placed in a quartz container containing water for testing. After the membrane surface was sufficiently contacted with about 5. mu.L of oil droplets, the syringe (5. mu.L of the discharged droplets at the end of the syringe) was slowly and uniformly lifted, and the state of the droplets when they left the membrane surface was observed in real time. The detection result is shown as g in fig. 19, under the condition of pre-stress, the tail end of the injector is close to the surface of the membrane, the liquid drop still cannot be soaked into the composite fiber membrane, and after the injector is lifted, the liquid drop rises together with the injector until the liquid drop is separated from the surface of the composite fiber membrane, which indicates that the composite fiber membrane has good oil repellency under water.

Test example 16

The viscosity, surface tension and conductivity of the spinning precursor solutions prepared in examples 1 to 6 and comparative example 1 were respectively measured at 25 ℃;

the viscosity was measured by the following method: the viscosity of the spinning precursor solution was measured using a digital viscometer (SNB-1 digital viscometer, gradiometer ltd).

The surface tension was measured by the following method: the surface tension of the spinning precursor solution was measured using an interfacial tension meter (JK 98B full-automatic interfacial tension meter, gyromagnetic instruments ltd).

The conductivity was measured by the following method: the conductivity of the spinning precursor solution was measured using a conductivity meter (DDSJ-318 conductivity meter, shanghai instruments electro scientific instruments ltd.).

The results are shown in Table 1.

TABLE 1

As can be seen from the results in table 1, the spinning precursor solution prepared by the method of the present invention has high surface tension, viscosity and conductivity. From examples 1 to 4, it can be seen that the viscosity of the spinning precursor solution increases significantly with the increase of the CNC amount, while the conductivity decreases and then increases, and the surface tension changes irregularly.

Test example 17

The bulk density and the porosity of A1-A6 and D1 are respectively detected;

the detection method of the bulk density comprises the following steps: cutting the membrane into 4 × 4cm size, and determining the bulk density (ρ) of the membrane according to the mass-to-volume ratio of the fiber membrane by equation calculation

Wherein m is_FilmIs the mass of the fibrous film, A_FilmThe size of the fibrous membrane, i.e. 4X 4cm, T_FilmIs the thickness of the fibrous membrane.

Determination of porosity: the porosity (. epsilon.) of the film was determined by dry-wet gravimetric method from the equation calculation according to the following formula

Where ρ is_wIs the density of ethylene glycol, typically, the fiber membrane is completely immersed in ethylene glycol and then removed and the excess solvent on the membrane surface is wiped off with filter paper. m is₁And m₂The mass of the fiber membrane before and after the fiber membrane is immersed in ethylene glycol.

The results are shown in Table 2.

TABLE 2

Numbering	Bulk Density (g/cm)³)	Porosity/%
			A1	0.139	31.26
A2	0.182	29.58
			A3	0.196	26.66
A4	0.213	25.23
			A5	0.216	27.48
A6	0.181	29.43
			D1	0.133	38.28

As can be seen from the results of table 2, from comparative example 1, examples 1 to 4, it can be seen that as the CNC content increases, the fiber density increases and the porosity decreases, mainly due to the presence of hydrogen bond interaction between CNC, the increase in CNC content increases and the hydrogen bond interaction between adjacent fibers in the composite fiber film increases.

From the above results, SEM results show that the fiber diameter is in a positive correlation with the concentration of PAN spinning solution in comparison with D4, D5, D6, C1, and D7 (fig. 14). Comparing a1-a4 (fig. 6-9) with D1 (fig. 5), the hydrolysis process shows that the fiber membrane has higher stability in water after CNC is added, and CNC hydrogen bond interaction plays an important role; comparing A1-A4 with D1, the mechanics (FIG. 17) result shows that the stability of the composite fiber is obviously enhanced after the CNC is added; comparing the SEM results of A1-A4 and B1-B4 (FIGS. 10 and 3), the nanofiber structure in the composite fiber membrane is unchanged after hydrolysis; comparing a2 with B2 (fig. 19), the wettability structure shows that after hydrolysis, the composite fiber membrane is more hydrophilic under water, while the oleophobicity under water is enhanced; comparing a2, D2, D3 (fig. 10, 13), SEM results show that alkaline hydrolysis conditions affect the composite fiber membrane surface structure morphology.

Compared with a non-hydrolytic composite fiber membrane, the composite fiber membrane obtained in the embodiment has the advantages that the wettability is improved, the underwater oleophobic performance is improved, compared with the composite fiber membrane without CNC, the structural stability is improved, and compared with the fiber membrane without CNC and without hydrolysis, the underwater oleophobic performance, the underwater oil repellency and the structural stability are all obviously improved. Therefore, in order to obtain a composite fiber membrane having a stable structure and oleophobic properties in water, it is necessary to add a certain amount of CNC and to subject the fiber to hydrolysis treatment.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A method for preparing an electrospun nano-composite fiber membrane, comprising the steps of:

2. The method according to claim 1, wherein in the step (1), the power of the ultrasonic treatment is 200-800W, the temperature of the ultrasonic treatment is-4-0 ℃, and the time of the ultrasonic treatment is 1-20 min.

3. The method according to claim 1, wherein in the step (1), the stirring speed in the stirring state is 900 to 1100 rpm.

4. The method as claimed in claim 1, wherein in step (1), the stirring temperature during the continuous stirring process is 45-60 ℃, the stirring time is 6-12 h, and the stirring speed is 450-550 rpm.

5. The method according to claim 1, wherein in the step (2), the needle of the syringe used in the electrospinning has a size of 18 to 22G.

6. The method according to claim 1 or 5, wherein in step (2), the process parameters of the electrospinning are: the positive high voltage is 8-15 kV, the negative high voltage is-1.5-3 kV, the spinning speed is 0.04-0.12 mm/min, the rotating speed of a roller is 50-100 rpm, the spinning distance is 20-30 cm, the spinning time is 10-12 h, the spinning temperature is 18-30 ℃, and the relative humidity is 18-28%.

7. The method according to claim 1, wherein in step (3), the drying means is freeze drying or vacuum drying.

8. The method according to claim 7, wherein the temperature of the freeze drying is-60 to-50 ℃, and the time of the freeze drying is 24 to 48 hours.

9. The method according to claim 7, wherein the pressure of the vacuum drying is-0.2 to-0.05 MPa, the temperature of the vacuum drying is 45 to 60 ℃, and the time of the vacuum drying is 23 to 25 hours.

10. Electrospun nanocomposite fiber membranes obtainable by the process according to any one of claims 1 to 9.