A method for preparing a modified cellulose acetate electrospun membrane

Abstract

The application relates to a preparation method of a modified cellulose acetate electrospun membrane, which comprises the following steps: mixing N,N-dimethylacetamide and acetone in a certain proportion, adding cellulose acetate into the transparent solution, and fully stirring to obtain a mixed solution; adding a certain amount of eggshell membrane powder into the mixed solution, fully stirring to obtain a spinning stock solution; adopting an electrospinning technology to obtain a cellulose acetate electrospun membrane; and after deacetylation treatment, washing and drying, a modified cellulose acetate electrospun membrane is obtained. The preparation method is simple, the steps are easy to operate, the prepared electrospun membrane has excellent fiber aspect ratio, large specific surface area and high porosity, and the fiber membrane has good air permeability; the blending with the eggshell membrane rich in hydrophilic groups enhances the hydrophilicity of the fiber membrane and improves the mechanical properties; and the modified cellulose acetate electrospun membrane has enhanced piezoelectric response and can be used as a potential green energy source for energy supply.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanocellulose film preparation, and particularly relates to a preparation method of modified cellulose acetate electrospun film. BACKGROUND

[0002] With the increasing demand for clean energy and the development of portable micro devices, environmentally friendly energy technologies and new materials have attracted a lot of exploration, which can obtain energy from the surrounding environment, including solar energy, wind energy, sea waves and mechanical energy. Among them, some mechanical energy in nature and living environment, such as mechanical vibration, sound wave and body movement, is considered as a potential renewable energy. Among them, piezoelectric materials with micro or nano structure have attracted great attention due to their portability, sustainability, simple structure and wide application environment.

[0003] Among naturally occurring polymers, cellulose is an abundant polymer with excellent biocompatibility and biodegradability, and provides non-toxic, low cost, excellent chemical resistance and mechanical properties. In addition, cellulose contains abundant and high crystallinity polar hydroxyl groups, resulting in a large number of dipoles with strong electron-donating ability, which endows it with intrinsic piezoelectric effect. However, due to the limited solubility of cellulose in solvents, the processing of cellulose is very difficult, but the acetylation of cellulose helps the resulting polymer to be soluble in organic solvents. Cellulose acetate is a derivative of cellulose, which has good fiber-forming properties when the acetylation degree reaches a certain level.

[0004] Electrospun nanofibers have a large surface-to-volume ratio, high porosity, variable pore size and highly interconnected porous structure, so they are attractive in textiles, biomedical and sensors. Due to its non-toxicity, solubility in organic solvents, good stability, biocompatibility and biodegradability, cellulose acetate has become a promising branch of electrospun fiber membranes. Cellulose shows limited piezoelectricity with a piezoelectric coefficient d33 of only 0.4 pC / N, which limits its application in high-performance piezoelectric energy harvesting. Therefore, it is very necessary to improve the piezoelectric performance of cellulose acetate to manufacture renewable and biocompatible piezoelectric sensors. Current researches are mostly focused on the application of cellulose acetate film in medical dressings, filtration, adsorption and other fields, and there are few studies on improving the intrinsic piezoelectricity of cellulose acetate film. SUMMARY

[0005] The application is to solve the problem of limited piezoelectric performance of existing cellulose acetate film, and provides a preparation method of modified cellulose acetate electrospun film with good piezoelectric performance.

[0006] The application adopts the following technical scheme:

[0007] A method for preparing a modified cellulose acetate electrospun membrane, comprising the following steps:

[0008] (1) mixing N, N-dimethylacetamide and acetone at a volume ratio of 2:1-3:1, and stirring at room temperature to obtain a transparent solution;

[0009] (2) adding a certain amount of cellulose acetate into the transparent solution, and stirring to obtain a mixed solution, wherein the concentration of cellulose acetate is 15-20%;

[0010] (3) adding eggshell membrane powder into the mixed solution to obtain a spinning solution, wherein the concentration of eggshell membrane is 0.1-0.5%;

[0011] (4) electrospinning the spinning solution in an electrospinning machine to obtain a cellulose acetate electrospun membrane;

[0012] (5) immersing the cellulose acetate electrospun membrane into a NaOH / ethanol solution for deacetylation treatment; removing the deacetylated cellulose acetate membrane, and washing with deionized water and ethanol to remove residual NaOH solution until the solution is neutral;

[0013] (6) drying the washed membrane to obtain the prepared modified cellulose acetate electrospun membrane.

[0014] Further, the acetyl content in the cellulose acetate is 37-39wt%, and the hydroxyl content is 2.5-3.5wt%.

[0015] Further, the voltage for electrospinning in step (4) is 18-22V.

[0016] Further, the concentration of the NaOH / ethanol solution in step (5) is 0.05-0.08mol / L, and the deacetylation treatment time is 8-10h.

[0017] Further, the drying time in step (6) is 20-24h.

[0018] Further, the preparation method of the eggshell membrane powder is as follows: stripping fresh eggshell membrane and dissolving it in a mixture containing 1.5 M 3-mercaptopropionic acid and 10% acetic acid, keeping at 85-95℃ for 6-8h, cooling to room temperature, centrifuging to remove insoluble components, adjusting the pH of the solution to 5, filtering the supernatant, washing the precipitant with pure methanol, and freeze-drying to obtain the eggshell membrane powder.

[0019] Principle of enhancing piezoelectric properties of eggshell membrane modified cellulose acetate: The eggshell membrane itself is a material with certain piezoelectricity. The piezoelectricity inside the eggshell membrane is attributed to the strong correlation between the amide, -OH and carbonyl groups in the eggshell membrane through dipole arrangement and strong hydrogen bonds inside the microfibers. The eggshell membrane contains a large amount of high collagen fibers (type I, V and X collagen), including other different proteins, which endow the eggshell membrane with piezoelectricity. Among them, the type I collagen fiber exhibits shear piezoelectricity due to the presence of N-terminal and C-terminal peptides and C6 symmetry in its crystal chain. In addition, the pores between the well-oriented and tightly packed peptide fibers make the eggshell membrane more easily displace under external force, thereby making the eggshell membrane have higher piezoelectric properties.

[0020] The eggshell membrane is used to modify the cellulose acetate, and the eggshell membrane is crosslinked with the cellulose. Due to the hydrogen bond molecular interaction between the soluble eggshell membrane and the cellulose, the cellulose nanofiber is polarized and arranged under the action of external mechanical excitation, thereby generating more positive and negative electrons, and further generating higher piezoelectric output. The piezoelectric properties of the modified cellulose acetate are enhanced.

[0021] The electrospun membrane prepared in the application has excellent fiber aspect ratio, large specific surface area and high porosity, which endows the fiber membrane with good air permeability; by blending with the eggshell membrane rich in hydrophilic groups, the hydrophilicity of the fiber membrane is enhanced, and the strong hydrogen bond interaction between molecules also improves the mechanical properties of the electrospun membrane; in addition, the prepared modified cellulose acetate electrospun membrane has enhanced piezoelectric response, which can be used as a potential green energy source for energy supply.

[0022] The advantages of the application are as follows:

[0023] (1) The modified cellulose membrane prepared by the electrospinning technology of the application has high fiber aspect ratio, large specific surface area and high porosity, good water absorption and air permeability, good biocompatibility and degradability;

[0024] (2) The eggshell membrane is used to modify the cellulose in the application, which improves the mechanical properties and piezoelectric properties of the fiber membrane, and can be applied to human motion detection and intelligent wearable field. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a flowchart of the preparation method of the modified cellulose acetate electrospun membrane of the application.

[0026] Figure 2 is a scanning electron microscope image of the modified cellulose acetate electrospun membrane of the application.

[0027] Figure 3 It is an XRD graph of the modified cellulose acetate electrospun membrane without adding eggshell membrane and the modified cellulose acetate electrospun membrane with adding eggshell membrane of the application.

[0028] Figure 4 Figure of water contact angle test results of the modified cellulose acetate electrospun membrane without adding eggshell membrane of the comparative example of the present application and the modified cellulose acetate electrospun membrane adding eggshell membrane of Example 2.

[0029] Figure 5 Figure of piezoelectric performance test results of the modified cellulose acetate electrospun membrane without adding eggshell membrane of the comparative example of the present application and the modified cellulose acetate electrospun membrane adding eggshell membrane of Example 2.

[0030] Figure 6 Application of the modified cellulose acetate electrospun membrane prepared for the present application in textiles.

[0031] Figure 7 Application of the modified cellulose acetate electrospun membrane prepared for the present application in the field of smart wearable, such as detecting the movement of different parts of the human body, such as fingers, wrist parts, elbows, knees, etc.

[0032] Figure 8 Figure of the influence of the modified cellulose acetate electrospun membrane prepared for the present application on cell growth. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be further described below in combination with examples.

[0034] Preparation method of eggshell membrane powder: including the following steps:

[0035] (1) Fresh eggshell membrane is stripped and dissolved in a mixture containing 1.5 M 3-mercaptopropionic acid and 10% acetic acid, and kept at 90°C for half a day;

[0036] (2) After cooling to room temperature, centrifuge at 15000 rpm for 15 minutes, and take the supernatant by centrifugation;

[0037] (3) Add NaOH solution (5M) to adjust the pH of the solution to 5, discard the supernatant after filtration, and wash the precipitant with pure methanol;

[0038] (4) After freeze-drying, soluble eggshell membrane powder is obtained.

[0039] Example 1: A preparation method of a modified cellulose acetate electrospun membrane, including the following steps: (1) At room temperature, 8g of cellulose acetate (acetyl content of 37 wt %, hydroxyl content of 3.5 wt %) powder is dissolved in 40ml of a mixed solution of N, N-dimethylacetamide and acetone with a volume ratio of 3:1 to be fully stirred, to obtain a transparent solution with a concentration of 16.7%;

[0040] (2) 6 g of eggshell membrane powder was added to the transparent solution described in step (1) and stirred until fully dissolved to obtain an electrospinning stock solution;

[0041] (3) The electrospinning stock solution prepared in step (2) was filled into a 10 mL syringe equipped with a 19-gauge needle, and after removing the bubbles, it was fixed on the syringe pump. A composite nanofiber membrane was prepared using an electrospinning machine. The voltage was adjusted to 18 kV during spinning, and the spinning flow rate was set to 1 mL / h. The distance between the needle and the collection roller was 15 cm. The spinning temperature was 25-30°C, and the relative humidity was 50-60%. After electrospinning, the nanofiber membrane was dried in air for 48 hours;

[0042] (4) The dried nanofiber membrane in step (3) was placed in a 0.08 M NaOH / ethanol solution for 10 h for deacetylation treatment;

[0043] (5) The deacetylated composite fiber membrane in step (4) was taken out and washed thoroughly with deionized water and ethanol to remove residual NaOH solution until the pH of the composite nanofiber reached neutral;

[0044] (6) The deacetylated composite nanofiber after washing in step (5) was dried in a drying oven at 50°C for 24 h to obtain the modified composite nanofiber membrane.

[0045] Example Two: A method for preparing a modified cellulose acetate electrospun membrane, comprising the following steps:

[0046] (1) At room temperature, 8 g of cellulose acetate (acetyl content of 39.8 wt %, hydroxyl content of 3.5 wt%) powder was dissolved in 40 ml of a mixed solution of N, N-dimethylacetamide and acetone with a volume ratio of 2:1 and stirred thoroughly to obtain a transparent solution with a concentration of 16.7%;

[0047] (2) 10 g of eggshell membrane powder was added to the transparent solution described in step (1) and stirred until fully dissolved to obtain an electrospinning stock solution;

[0048] (3) The electrospinning stock solution prepared in step (2) was filled into a 10 mL syringe equipped with a 19-gauge needle, and after removing the bubbles, it was fixed on the syringe pump. A composite nanofiber membrane was prepared using an electrospinning machine. The voltage was adjusted to 20 kV during spinning, and the spinning flow rate was set to 1 mL / h. The distance between the needle and the collection roller was 15 cm. The spinning temperature was 25-30°C, and the relative humidity was 50-60%. After electrospinning, the nanofiber membrane was dried in air for 48 hours;

[0049] (4) The dried nanofiber membrane in step (3) is immersed in a 0.05M NaOH / ethanol solution for 18h for deacetylation treatment;

[0050] (5) The deacetylated composite nanofiber membrane in step (4) is taken out and washed with deionized water and ethanol to remove the residual NaOH solution until the pH of the composite nanofiber reaches neutral;

[0051] (6) The deacetylated composite nanofiber membrane washed in step (5) is dried in a drying oven at 50°C for 24h to obtain the modified composite nanofiber membrane.

[0052] Example Three: A method for preparing a modified cellulose acetate electrospun membrane, comprising the following steps:

[0053] (1) At room temperature, 8g of cellulose acetate (acetyl content of 39.8 wt%, hydroxyl content of 3.5 wt%) powder is dissolved in 40ml of a mixed solution of N, N-dimethylacetamide and acetone with a volume ratio of 2:1 for sufficient stirring to obtain a transparent solution with a concentration of 16.7%;

[0054] (2) 15g of eggshell membrane powder is added to the transparent solution in step (1) for stirring until fully dissolved to obtain an electrospinning stock solution;

[0055] (3) The electrospinning stock solution prepared in step (2) is filled into a 10mL syringe equipped with a 19-gauge needle, and after removing the air bubbles, it is fixed on the syringe pump to prepare a composite nanofiber membrane using an electrospinning machine. The voltage is adjusted to 22kV during spinning, and the spinning flow rate is set to 1mL / h. The distance between the needle and the collection roller is 15cm. The spinning temperature is 25-30°C, and the relative humidity is 50%-60%. After electrospinning, the nanofiber membrane is dried in air for 48 hours;

[0056] (4) The dried nanofiber membrane in step (3) is immersed in a 0.05M NaOH / ethanol solution for 8h for deacetylation treatment;

[0057] (5) The deacetylated composite nanofiber membrane in step (4) is taken out and washed with deionized water and ethanol to remove the residual NaOH solution until the pH of the composite nanofiber reaches neutral;

[0058] (6) The deacetylated composite nanofiber membrane washed in step (5) is dried in a drying oven at 50°C for 20h to obtain the modified composite nanofiber membrane.

[0059] Comparative Example: The same as steps in Example Two, but without adding eggshell membrane powder.

[0060] The modified cellulose acetate electrospun membranes prepared in Example 2 and the comparative example were subjected to performance testing.

[0061] Depend on Figure 2A The scanning electron microscope images show that the fiber membrane obtained in Comparative Example 2 has a smooth fiber surface, a relatively uniform diameter distribution, and good fiber morphology and porosity. This indicates that the preparation method can yield nanofiber membranes with good fiber morphology. Figure 2B It can be seen that the modified cellulose acetate without eggshell membrane in the comparative example has a rough fiber surface and uneven diameter, with many microdroplets on the surface, and the fiber breakage phenomenon is relatively serious. By crosslinking the eggshell membrane with cellulose, the electrospun nanofiber membrane exhibits a continuous and uniformly distributed fiber state.

[0062] Depend on Figure 3 It can be seen that the XRD spectrum of the modified cellulose acetate in the comparative example matches that of cellulose I. Cellulose I shows peaks at 15.08, 16.65, 22.68, and 34.48 corresponding to the (101), (10), (002), and (040) planes, respectively. Compared with the diffraction peaks of the modified cellulose acetate in the comparative example, the X-ray diffraction peaks of the composite film after adding the eggshell membrane in Example 2 are more obvious, indicating that the presence of the eggshell membrane enhances the crystallinity of cellulose acetate, thereby producing a stronger piezoelectric effect.

[0063] Depend on Figure 4 The water contact angle test results of the modified cellulose acetate electrospun membranes prepared in Example 2 and the comparative example are shown. A smaller water contact angle indicates better wettability of the material. The water contact angle of the modified cellulose acetate electrospun membrane prepared in the comparative example was 80.3°. After adding the eggshell membrane in Example 2, the water contact angle of the modified cellulose acetate electrospun membrane decreased to 65.4°, indicating that the addition of the eggshell membrane in Example 2 improved the wettability of the composite membrane.

[0064] Figure 5 To compare the piezoelectric properties of the modified cellulose acetate electrospun membranes prepared in the comparative example and Example 2, double-sided conductive aluminum foil tape was adhered to both sides of the composite nanofiber membrane, with a copper wire led out from each side. Finally, it was encapsulated with polyimide tape to obtain a piezoelectric sensor with enhanced piezoelectric effect. Under an excitation pressure of 40 N and a frequency of 1.5 Hz, the modified cellulose acetate electrospun membrane in the comparative example generated an output voltage of ~0.45 V, while the modified cellulose acetate electrospun membrane in Example 2 exhibited a voltage as high as ~1.175 V. This indicates that the intrinsic piezoelectricity of the eggshell membrane in Example 2 and its strong hydrogen bonding interaction with cellulose enhance the piezoelectric properties of the modified cellulose acetate electrospun membrane.

[0065] Depend on Figure 6It can be known that the application diagram of the composite nanofiber membrane prepared by the modified cellulose acetate electrospun membrane preparation method with good air permeability, water absorption and biocompatibility in the textile field is added to the textile products, such as three-dimensional masks, eye masks, face masks and the like according to different application scenarios, has good effects of skin-friendly comfort, air permeability and moisture retention, health care, expands the application of nanofiber membranes in the textile field, the particle counter CEM four-in-one particle counter DT-9880M is used to measure the particle concentration in the gas before the electrospun membrane filtration and the particle concentration in the gas after the electrospun membrane filtration, and the calculation shows that the filtration efficiency of the electrospun membrane on PM2.5 is as high as 95%, which can effectively block the particles above PM0.3 in the air, and meets the T / CTCA1-2015-F95 standard.

[0066] By Figure 7 It can be known that the application diagram of the composite nanofiber membrane prepared by the modified cellulose acetate electrospun membrane preparation method with enhanced piezoelectric effect in the smart wearable field is that the piezoelectric sensor with enhanced piezoelectric effect is adhered to different parts of the human body, such as fingers, wrists, elbows, knees and the like according to different scenes of human motion, generates corresponding piezoelectric response to parts with different amplitude strain, and can effectively identify human motion.

[0067] By Figure 8 It can be known that the cell culture using the electrospun membrane shows that the cell growth condition is good after 10 days, 20 days and 20 days, and the number shows a gradually increasing trend, which indicates that the electrospun membrane has good biocompatibility.

Claims

1. A method for preparing a modified cellulose acetate electrospun membrane, characterized by: The method comprises the following steps: (1) mixing N, N-dimethylacetamide and acetone at a volume ratio of 2:1-3:1, and stirring at room temperature to obtain a transparent solution; (2) adding a certain amount of cellulose acetate into the transparent solution, and stirring to obtain a mixed solution, wherein the mass concentration of cellulose acetate is 15-20%; (3) adding eggshell membrane powder into the mixed solution to obtain a spinning dope, wherein the concentration of eggshell membrane is 0.1-0.5%, and stirring to obtain a spinning dope; (4) electrospinning the spinning dope in an electrospinning machine to obtain a cellulose acetate electrospun membrane; (5) immersing the cellulose acetate electrospun membrane into a NaOH / ethanol solution for deacetylation treatment; removing the deacetylated cellulose fiber membrane, and washing with deionized water and ethanol to remove residual NaOH solution until the solution is neutral; (6) drying the washed fiber membrane to obtain the prepared modified cellulose acetate electrospun membrane; The acetyl content in the cellulose acetate is 37-39 wt%, and the hydroxyl content is 2.5-3.5 wt%; The voltage of electrospinning in step (4) is 18-22 V; The concentration of NaOH / ethanol solution in step (5) is 0.05-0.08 mol / L, and the deacetylation treatment time is 8-10 h; The drying time in step (6) is 20-24 h; The preparation method of the eggshell membrane powder is as follows: stripping fresh eggshell membrane and dissolving it in a mixture containing 1.5 M 3-mercaptopropionic acid and 10% acetic acid, keeping at 85-95°C for 6-8 h, cooling to room temperature, centrifuging to remove insoluble components, adjusting the pH of the solution to 5, filtering the supernatant, washing the precipitant with pure methanol, and freeze-drying to obtain the eggshell membrane powder.

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