A high-strength polylactic acid-based electrospun nanofiber membrane and its preparation method

Abstract

The present invention discloses a high-strength polylactic acid-based electrospun nanofiber membrane and a preparation method thereof. The high-strength electrospun nanofiber membrane comprises a polylactic acid matrix resin and a reinforcing nanofiller, wherein the reinforcing nanofiller is a modified cellulose nanocrystal, which is prepared by first TEMPO-oxidizing the cellulose nanocrystal and then introducing a carboxyl group, and then reacting with amino polyethylene glycol under the dehydration condensation of 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide and N-hydroxysuccinate to obtain the modified cellulose nanocrystal. The preparation steps of the electrospun nanofiber membrane are as follows: a polylactic acid solution and a modified cellulose nanocrystal solution dissolved in a chloroform / acetone (volume ratio of 1:1) mixed solvent are respectively prepared, the two are mixed in a certain proportion, a mixed spinning solution with different modified cellulose nanocrystal contents is prepared, and then the corresponding high-strength nanofiber membrane is prepared using electrospinning technology. Compared with pure polylactic acid fiber membrane, the tensile strength of polylactic acid / modified cellulose nanocrystal fiber membrane is significantly improved, while the elongation at break is kept relatively small. In addition, the product is biodegradable, the preparation method is simple, low-cost, and easy to control, and it has broad application prospects in biomedicine and other fields.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of electrospun nanofibers, and in particular relates to a high-strength polylactic acid-based electrospun nanofiber membrane and a preparation method thereof. Background Art

[0002] Polylactic acid (PLA) is a green, environmentally friendly, biodegradable thermoplastic resin with the greatest potential for development and application. Due to its excellent biodegradability and biocompatibility, it has attracted widespread attention in biomedical engineering applications, such as tissue engineering scaffolds and drug delivery. To date, various techniques have been reported for preparing PLA-based tissue engineering scaffolds, including solvent casting, particle leaching, membrane layering, injection molding, and extrusion. Among them, PLA fiber scaffolds prepared by electrospinning exhibit higher porosity and larger surface area, providing a larger surface area for cell growth. The structural morphology of electrospun fibers also closely mimics the natural extracellular matrix. Therefore, electrospun PLA fiber scaffolds are considered promising for tissue engineering applications, including bone, blood vessels, and skin. However, the performance of single electrospun PLA fibers is gradually failing to meet the demands of applications requiring higher performance. For example, their mechanical properties fall far short of the required performance for hard tissue repair, limiting their further application.

[0003] To improve the mechanical properties of electrospun polylactic acid (PLA) fibers without compromising their biocompatibility, a number of biocompatible nanoscale fillers, such as hydroxyapatite, bioactive ceramics, nanodiamonds, and cellulose nanocrystals, have been used to reinforce the PLA matrix. Cellulose nanocrystals, among others, have garnered significant interest. Cellulose nanocrystals, a biomass material, are not only widely available, simple to prepare, low-cost, and environmentally friendly, but also possess advantages such as high crystallinity, high strength, high elastic modulus, lightweight, biodegradable, and biocompatible, making them highly suitable as reinforcing agents for polymer matrices. However, the interfacial adhesion between the hydrophilic cellulose nanocrystals and the hydrophobic PLA matrix results in poor compatibility, hindering the proper dispersion of the nanofillers within the matrix. Therefore, modification of the nanofillers is necessary to enhance the mechanical properties of the material and expand the potential applications of electrospun PLA-based fiber scaffolds. Previous studies have reported that polylactic acid / modified cellulose nanocrystal nanofibers were prepared by electrospinning polylactic acid / modified cellulose nanocrystal nanofibers using polyethylene glycol to modify cellulose nanocrystals. Using chloroform and N,N-dimethylformamide as a mixed solvent, a uniform spinning solution was obtained. Compared with pure polylactic acid electrospun fiber membranes, the tensile strength of polylactic acid electrospun fiber membranes with 5% modified cellulose nanocrystals increased by approximately 68%, demonstrating a certain reinforcing effect. However, as the content increased further, the tensile strength of the polylactic acid electrospun fiber membrane decreased significantly (C. Zhang et al., Materials Science and Engineering C 49 (2015) 463–471). This suggests that only a high content (5%) of modified cellulose nanocrystals can effectively enhance the electrospun polylactic acid fibers. The modified cellulose nanocrystals, prepared by TEMPO oxidation, are grafted with polyethylene glycol via an EDC / NHS coupling reaction. Compared to unmodified cellulose nanocrystals, the modified cellulose nanocrystals exhibit improved dispersibility in non-polar organic solvents, forming a clear, transparent suspension. Consequently, the modified cellulose nanocrystals can be even more effectively dispersed in polylactic acid (PLA), making it easier to achieve enhanced mechanical strength in electrospun PLA fibers at lower filler loadings without compromising their excellent biocompatibility. Summary of the Invention

[0004] In response to the current problems of small strength improvement of electrospun polylactic acid nanofiber membrane, high content of reinforcing nanofillers, and impact on polylactic acid biocompatibility, the present invention provides a method for preparing high-strength polylactic acid-based electrospun nanofiber membrane.

[0005] The present invention provides a method for preparing a high-strength polylactic acid-based electrospun nanofiber membrane. The high-strength polylactic acid-based electrospun nanofiber membrane is composed of polylactic acid and modified cellulose nanocrystals. The preparation method comprises the following specific steps:

[0006] (1) Preparation of polylactic acid electrospun fibers with uniform diameter and no beaded structure: Using chloroform and acetone in different volume ratios as mixed solvents, a polylactic acid spinning solution was prepared for electrospinning, and then the optimal process conditions for electrospinning polylactic acid fibers were determined based on the morphological characteristics of the electrospun fibers. The volume ratios of the mixed solvents were 3:1, 2:1, and 1:1. The electrospinning conditions were: polylactic acid concentration of 10 wt%, voltage of 18 kV, flow rate of 1.5 ml / h, receiving distance of 18 cm, and the optimal process conditions were: chloroform and acetone volume ratio of 1:1.

[0007] (2) The preparation method of carboxylated cellulose nanocrystals is as follows: dispersing cellulose nanocrystals in water to obtain a dispersion; then dissolving an appropriate amount of tetramethylpiperidinium oxide (TEMPO) and sodium bromide (NaBr) in distilled water to obtain a solution; finally, gradually dropping the solution into the cellulose nanocrystal dispersion, adjusting the pH of the dispersion to alkaline with sodium hydroxide solution, and then adding sodium hypochlorite to react to obtain carboxylated cellulose nanocrystals.

[0008] (3) The preparation method of modified cellulose nanocrystals is as follows: dispersing carboxylated cellulose nanocrystals in an aqueous dispersion of amino polyethylene glycol, then adding 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide (EDC) and N-hydroxysuccinate (NHS) to the aqueous dispersion, and reacting with the amino polyethylene glycol under the dehydration condensation of EDC and NHS to obtain cellulose nanocrystals grafted with polyethylene glycol, i.e., modified cellulose nanocrystals.

[0009] (4) Preparation of polylactic acid / modified cellulose nanocrystal spinning solution: preparing composite materials of polylactic acid and modified cellulose nanocrystals in different mass ratios, and dissolving polylactic acid and modified cellulose nanocrystals in a mixed solvent in a volume ratio of 1:1, respectively, to obtain a solution and a dispersion, and fully stirring the polylactic acid solution and the modified cellulose nanocrystal dispersion to obtain a spinning solution, wherein the concentration of polylactic acid in the spinning solution is 10 wt%.

[0010] (5) Electrospinning of polylactic acid / modified cellulose nanocrystal spinning solution: The polylactic acid / modified cellulose nanocrystal spinning solution was electrospun with a voltage of 18 kV, a flow rate of 1.5 ml / h, and a receiving distance of 18 cm to obtain a high-strength polylactic acid / modified cellulose nanocrystal electrospun nanofiber membrane.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] (1) The present invention uses a mixed solvent of chloroform and acetone with a solvent volume ratio of 1:1. Polylactic acid can be quickly dissolved in the mixed solvent in a short time, saving the dissolution time of polylactic acid;

[0013] (2) The present invention uses carboxylated cellulose nanocrystals prepared by TEMPO oxidation as a substrate and grafts polyethylene glycol through an EDC / NHS coupling reaction to obtain modified cellulose nanocrystals. Compared with unmodified cellulose nanocrystals, the modified cellulose nanocrystals have better dispersibility in non-polar organic solvents, forming a clear and transparent suspension. In addition, the modified cellulose nanocrystals also have better dispersibility in polylactic acid.

[0014] (3) The present invention achieves a significant increase in the tensile strength of the electrospun polylactic acid nanofiber membrane by adding a small amount of modified cellulose nanocrystals, with the highest increase reaching ~323%, and the elongation at break decreases slightly. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 For comparison, the SEM image of the polylactic acid fiber in Experimental Example 1 was prepared by mixing chloroform and acetone in a volume ratio of 3:1 to prepare the spinning solution.

[0016] Figure 2 For comparison, the SEM image of the polylactic acid fiber in Experimental Example 1 was prepared by mixing chloroform and acetone in a volume ratio of 2:1 to prepare the spinning solution.

[0017] Figure 3 For comparison, the SEM image of the polylactic acid fiber in Experimental Example 1 is obtained by mixing chloroform and acetone in a volume ratio of 1:1 to prepare the spinning solution.

[0018] Figure 4 This is an SEM image of polylactic acid / modified cellulose nanocrystalline fibers prepared by mixing chloroform and acetone in a volume ratio of 1:1 to prepare the spinning solution in Example 6.

[0019] Specific implementation cases

[0020] The present invention will be described in detail below with reference to specific embodiments and drawings, but is not limited to these embodiments.

[0021] Comparative Experiment Example 1:

[0022] 1) Preparation of electrospinning solution: Polylactic acid was dissolved in a mixed solvent of chloroform and acetone in a volume ratio of 3:1 to prepare a polylactic acid solution with a concentration of 10 wt %. After the solution was completely dissolved and uniformly dissolved, it was used for electrospinning.

[0023] 2) Electrospinning process: The polylactic acid spinning solution prepared in step 1) was placed in a fume hood for electrospinning. The prepared spinning solution was loaded into a syringe, the spinning voltage was set to 18 kV, the flow rate of the electrospinning solution was set to 1.5 ml / h, the receiving distance was 18 cm, and aluminum foil was used as a receiving device. Polylactic acid nanofibers were prepared by electrospinning. The SEM morphology is shown in FIG. Figure 1 As shown, the average fiber diameter is 1646 nm.

[0024] Comparative Experiment Example 2:

[0025] 1) Preparation of electrospinning solution: Polylactic acid was dissolved in a mixed solvent of chloroform and acetone in a volume ratio of 2:1 to prepare a polylactic acid solution with a concentration of 10 wt %. After the solution was completely dissolved and uniformly prepared, it was used for electrospinning.

[0026] 2) Electrospinning process: The polylactic acid spinning solution prepared in step 1) was placed in a fume hood for electrospinning. The prepared spinning solution was loaded into a syringe, the spinning voltage was set to 18 kV, the flow rate of the electrospinning solution was set to 1.5 ml / h, the receiving distance was 18 cm, and aluminum foil was used as a receiving device. Polylactic acid nanofibers were prepared by electrospinning. The SEM morphology is shown in FIG. Figure 2 As shown, the average fiber diameter is 1153 nm.

[0027] Comparative Experiment Example 3:

[0028] 1) Preparation of electrospinning solution: Polylactic acid was dissolved in a mixed solvent of chloroform and acetone in a volume ratio of 1:1 to prepare a polylactic acid solution with a concentration of 10 wt %. After the solution was completely dissolved and uniformly dissolved, it was used for electrospinning.

[0029] 2) Electrospinning process: The polylactic acid spinning solution prepared in step 1) was placed in a fume hood for electrospinning. The prepared spinning solution was loaded into a syringe, the spinning voltage was set to 18 kV, the flow rate of the electrospinning solution was set to 1.5 ml / h, the receiving distance was 18 cm, and aluminum foil was used as a receiving device. Polylactic acid nanofibers were prepared by electrospinning. The SEM morphology is shown in FIG. Figure 3 As shown, the average fiber diameter is 1068nm. Tensile property test results: tensile strength is 1.59MPa, and elongation at break is 99.61%.

[0030] Example 1:

[0031] 1) Preparation of a polylactic acid / cellulose nanocrystal spinning solution: Cellulose nanocrystals were dissolved in a 1:1 chloroform / acetone mixed solvent to prepare a solution, and polylactic acid was dissolved in a 1:1 chloroform / acetone mixed solvent to prepare a solution. After the cellulose nanocrystals were evenly dispersed and the polylactic acid was completely dissolved, the two solutions were mixed and stirred to prepare an electrospinning solution with a modified cellulose nanocrystal and polylactic acid mass ratio of 0.5:100, and the concentration of polylactic acid in the mixed solution was maintained at 10 wt%.

[0032] 2) Electrospinning of the spinning solution: The polylactic acid / modified cellulose nanocrystal spinning solution prepared in step 2) was electrospun in a fume hood. The prepared spinning solution was loaded into a syringe and the spinning voltage was set to 18 kV, the flow rate of the electrospinning solution was 1.5 ml / h, the receiving distance was 18 cm, and aluminum foil was used as the receiving device. The spinning time was 0.5 h to produce polylactic acid / modified cellulose nanocrystal fibers, which were then dried in a 50°C oven to remove the solvent. Tensile properties testing results showed a tensile strength of 3.15 MPa and an elongation at break of 86.84%.

[0033] Example 2:

[0034] 1) Preparation of a polylactic acid / cellulose nanocrystal spinning solution: Cellulose nanocrystals were dissolved in a 1:1 chloroform / acetone mixed solvent to prepare a solution, and polylactic acid was dissolved in a 1:1 chloroform / acetone mixed solvent to prepare a solution. After the cellulose nanocrystals were evenly dispersed and the polylactic acid was completely dissolved, the two solutions were mixed and stirred to prepare an electrospinning solution with a modified cellulose nanocrystal and polylactic acid mass ratio of 1:100. The concentration of polylactic acid in the mixed solution was maintained at 10 wt%.

[0035] 2) Electrospinning of the spinning solution: The polylactic acid / modified cellulose nanocrystal spinning solution prepared in step 2) was electrospun in a fume hood. The prepared spinning solution was loaded into a syringe and the spinning voltage was set to 18 kV, the flow rate of the electrospinning solution was 1.5 ml / h, the receiving distance was 18 cm, and aluminum foil was used as the receiving device. The spinning time was 0.5 h to produce polylactic acid / modified cellulose nanocrystal fibers, which were then dried in a 50°C oven to remove the solvent. Tensile properties testing results showed a tensile strength of 3.86 MPa and an elongation at break of 87.56%.

[0036] Example 3:

[0037] 1) Preparation of a polylactic acid / cellulose nanocrystal spinning solution: Cellulose nanocrystals were dissolved in a 1:1 chloroform / acetone mixed solvent to prepare a solution, and polylactic acid was dissolved in a 1:1 chloroform / acetone mixed solvent to prepare a solution. After the cellulose nanocrystals were evenly dispersed and the polylactic acid was completely dissolved, the two solutions were mixed and stirred to prepare an electrospinning solution with a modified cellulose nanocrystal:polylactic acid mass ratio of 3:100. The concentration of polylactic acid in the mixed solution was maintained at 10 wt%.

[0038] 2) Electrospinning of the spinning solution: The polylactic acid / modified cellulose nanocrystal spinning solution prepared in step 2) was electrospun in a fume hood. The prepared spinning solution was loaded into a syringe and the spinning voltage was set to 18 kV, the flow rate of the electrospinning solution was 1.5 ml / h, the receiving distance was 18 cm, and aluminum foil was used as the receiving device. The spinning time was 0.5 h to produce polylactic acid / modified cellulose nanocrystal fibers, which were then dried in a 50°C oven to remove the solvent. Tensile properties testing results showed a tensile strength of 5.20 MPa and an elongation at break of 20.84%.

[0039] Example 4:

[0040] 1) Preparation of a polylactic acid / cellulose nanocrystal spinning solution: Cellulose nanocrystals were dissolved in a 1:1 chloroform / acetone mixed solvent to prepare a solution, and polylactic acid was dissolved in a 1:1 chloroform / acetone mixed solvent to prepare a solution. After the cellulose nanocrystals were evenly dispersed and the polylactic acid was completely dissolved, the two solutions were mixed and stirred to prepare an electrospinning solution with a modified cellulose nanocrystal:polylactic acid mass ratio of 5:100. The concentration of polylactic acid in the mixed solution was maintained at 10 wt%.

[0041] 2) Electrospinning of the spinning solution: The polylactic acid / modified cellulose nanocrystal spinning solution prepared in step 2) was electrospun in a fume hood. The prepared spinning solution was loaded into a syringe and the spinning voltage was set to 18 kV, the flow rate of the electrospinning solution was 1.5 ml / h, the receiving distance was 18 cm, and aluminum foil was used as the receiving device. The spinning time was 0.5 h to produce polylactic acid / modified cellulose nanocrystal fibers, which were then dried in a 50°C oven to remove the solvent. Tensile properties testing results showed a tensile strength of 2.87 MPa and an elongation at break of 18.16%.

[0042] Example 5:

[0043] 1) Preparation of carboxylated cellulose nanocrystals: 2 g of cellulose nanocrystals were ultrasonically dispersed in water. 0.032 g of TEMPO and 0.2 g of sodium bromide (previously dissolved in distilled water) were added to the aqueous dispersion and stirred thoroughly for 10 min to mix thoroughly. 15 mmol of sodium hypochlorite solution was then added dropwise. During the reaction, the pH was maintained at 10.0 with 0.5 mol / L sodium hydroxide solution. The reaction was continued until all the sodium hypochlorite was consumed. 4 ml of ethanol was added to terminate the reaction. The mixture was washed with water and centrifuged several times. 1 mol / L hydrochloric acid was added to the precipitate, and the mixture was reacted with magnetic stirring for 30 min. Finally, the mixture was washed several times with 0.1 mol / L hydrochloric acid and distilled water until neutral, and freeze-dried to obtain carboxylated cellulose nanocrystals.

[0044] 2) Preparation of modified cellulose nanocrystals: 4 g of amino-polyethylene glycol was dissolved in 200 ml of water, followed by the addition of 2 g of carboxylated cellulose nanocrystals, 0.76 g of NHS, and 0.46 g of EDC, followed by stirring and reaction. During the reaction, the pH value was maintained at 7.5-8.0 with 0.5 mol / L sodium chloride and sodium hydroxide solutions. After the reaction, the mixture was washed with water, centrifuged several times, and freeze-dried to obtain modified cellulose nanocrystals.

[0045] 3) Preparation of polylactic acid / modified cellulose nanocrystal spinning solution: The modified cellulose nanocrystals were dissolved in a mixed solvent of chloroform and acetone in a volume ratio of 1:1 to prepare a solution, and the polylactic acid was dissolved in a mixed solvent of chloroform and acetone in a volume ratio of 1:1 to prepare a solution. After the modified cellulose nanocrystals were evenly dispersed and the polylactic acid was completely dissolved, the above two solutions were mixed and stirred to prepare an electrospinning solution with a modified cellulose nanocrystal and polylactic acid mass ratio of 0.5:100, and the concentration of polylactic acid in the mixed solution was maintained at 10 wt%.

[0046] 4) Electrospinning of the spinning solution: The polylactic acid / modified cellulose nanocrystal spinning solution prepared in step 2) was electrospun in a fume hood. The prepared spinning solution was loaded into a syringe and the spinning voltage was set to 18 kV, the electrospinning solution flow rate to 1.5 ml / h, the receiving distance to 18 cm, and aluminum foil as the receiving device. The spinning time was 0.5 h to produce polylactic acid / modified cellulose nanocrystal fibers, which were then dried in a 50°C oven to remove the solvent. Tensile properties testing results showed a tensile strength of 4.48 MPa and an elongation at break of 87.91%.

[0047] Example 6:

[0048] 1) Preparation of carboxylated cellulose nanocrystals: 2 g of cellulose nanocrystals were ultrasonically dispersed in water. 0.032 g of TEMPO and 0.2 g of sodium bromide (previously dissolved in distilled water) were added to the aqueous dispersion and stirred thoroughly for 10 min to mix thoroughly. 15 mmol of sodium hypochlorite solution was then added dropwise. During the reaction, the pH was maintained at 10.0 with 0.5 mol / L sodium hydroxide solution. The reaction was continued until all the sodium hypochlorite was consumed. 4 ml of ethanol was added to terminate the reaction. The mixture was washed with water and centrifuged several times. 1 mol / L hydrochloric acid was added to the precipitate, and the mixture was reacted with magnetic stirring for 30 min. Finally, the mixture was washed several times with 0.1 mol / L hydrochloric acid and distilled water until neutral, and freeze-dried to obtain carboxylated cellulose nanocrystals.

[0049] 2) Preparation of modified cellulose nanocrystals: 4 g of amino-polyethylene glycol was dissolved in 200 ml of water, followed by the addition of 2 g of carboxylated cellulose nanocrystals, 0.76 g of NHS, and 0.46 g of EDC, followed by stirring and reaction. During the reaction, the pH value was maintained at 7.5-8.0 with 0.5 mol / L sodium chloride and sodium hydroxide solutions. After the reaction, the mixture was washed with water, centrifuged several times, and freeze-dried to obtain modified cellulose nanocrystals.

[0050] 3) Preparation of polylactic acid / modified cellulose nanocrystal spinning solution: The modified cellulose nanocrystals were dissolved in a mixed solvent of chloroform and acetone in a volume ratio of 1:1 to prepare a solution, and the polylactic acid was dissolved in a mixed solvent of chloroform and acetone in a volume ratio of 1:1 to prepare a solution. After the modified cellulose nanocrystals were evenly dispersed and the polylactic acid was completely dissolved, the above two solutions were mixed and stirred to prepare an electrospinning solution with a modified cellulose nanocrystal and polylactic acid mass ratio of 1:100, and the concentration of polylactic acid in the mixed solution was maintained at 10 wt%.

[0051] 4) Electrospinning process of spinning solution: The polylactic acid / modified cellulose nanocrystal spinning solution prepared in step 2) is placed in a fume hood for electrospinning. The prepared spinning solution is loaded into a syringe, the spinning voltage is set to 18kV, the flow rate of the electrospinning solution is 1.5ml / h, the receiving distance is 18cm, and aluminum foil is used as a receiving device. The spinning time is 0.5h to prepare polylactic acid / modified cellulose nanocrystal fibers, which are then placed in a 50°C oven to dry and remove the solvent. Tensile performance test results: tensile strength is 4.69MPa, and elongation at break is 91.83%. The SEM morphology of the spun fiber is shown in Figure 2. Figure 4 As shown, the average fiber diameter is 629 nm.

[0052] Example 7:

[0053] 1) Preparation of carboxylated cellulose nanocrystals: 2 g of cellulose nanocrystals were ultrasonically dispersed in water. 0.032 g of TEMPO and 0.2 g of sodium bromide (previously dissolved in distilled water) were added to the aqueous dispersion and stirred thoroughly for 10 min to mix thoroughly. 15 mmol of sodium hypochlorite solution was then added dropwise. During the reaction, the pH was maintained at 10.0 with 0.5 mol / L sodium hydroxide solution. The reaction was continued until all the sodium hypochlorite was consumed. 4 ml of ethanol was added to terminate the reaction. The mixture was washed with water and centrifuged several times. 1 mol / L hydrochloric acid was added to the precipitate, and the mixture was reacted with magnetic stirring for 30 min. Finally, the mixture was washed several times with 0.1 mol / L hydrochloric acid and distilled water until neutral, and freeze-dried to obtain carboxylated cellulose nanocrystals.

[0054] 2) Preparation of modified cellulose nanocrystals: 4 g of amino-polyethylene glycol was dissolved in 200 ml of water, followed by the addition of 2 g of carboxylated cellulose nanocrystals, 0.76 g of NHS, and 0.46 g of EDC, followed by stirring and reaction. During the reaction, the pH value was maintained at 7.5-8.0 with 0.5 mol / L sodium chloride and sodium hydroxide solutions. After the reaction, the mixture was washed with water, centrifuged several times, and freeze-dried to obtain modified cellulose nanocrystals.

[0055] 3) Preparation of polylactic acid / modified cellulose nanocrystal spinning solution: The modified cellulose nanocrystals were dissolved in a mixed solvent of chloroform and acetone in a volume ratio of 1:1 to prepare a solution, and the polylactic acid was dissolved in a mixed solvent of chloroform and acetone in a volume ratio of 1:1 to prepare a solution. After the modified cellulose nanocrystals were evenly dispersed and the polylactic acid was completely dissolved, the above two solutions were mixed and stirred to prepare an electrospinning solution with a modified cellulose nanocrystal and polylactic acid mass ratio of 3:100, and the concentration of polylactic acid in the mixed solution was maintained at 10 wt%.

[0056] 4) Electrospinning of the spinning solution: The polylactic acid / modified cellulose nanocrystal spinning solution prepared in step 2) was electrospun in a fume hood. The prepared spinning solution was loaded into a syringe and the spinning voltage was set to 18 kV, the flow rate of the electrospinning solution was 1.5 ml / h, the receiving distance was 18 cm, and aluminum foil was used as the receiving device. The spinning time was 0.5 h to produce polylactic acid / modified cellulose nanocrystal fibers, which were then dried in a 50°C oven to remove the solvent. Tensile properties testing results showed a tensile strength of 6.72 MPa and an elongation at break of 59.57%.

Claims

1. A method for preparing a high-strength polylactic acid-based electrospun nanofiber membrane, wherein the high-strength polylactic acid-based electrospun nanofiber membrane is composed of polylactic acid and modified cellulose nanocrystals; the preparation method comprises the following specific steps: (1) Preparation of polylactic acid electrospun fibers with uniform diameter and without beaded structure: using chloroform and acetone in different volume ratios as mixed solvents to prepare polylactic acid spinning solutions for electrospinning, and then determining the optimal process conditions for electrospinning polylactic acid fibers based on the morphological characteristics of the electrospun fibers; (2) The preparation method of carboxylated cellulose nanocrystals is as follows: dispersing cellulose nanocrystals in water to obtain a dispersion liquid, thereby obtaining a cellulose nanocrystal dispersion liquid; then mixing an appropriate amount of tetramethylpiperidinium oxide and sodium bromide and dissolving them in distilled water to obtain a dissolving liquid; finally, gradually dropping the dissolving liquid into the cellulose nanocrystal dispersion liquid, adjusting the pH of the dispersion liquid to alkaline with a sodium hydroxide solution, and then adding sodium hypochlorite for reaction to obtain carboxylated cellulose nanocrystals; (3) The preparation method of modified cellulose nanocrystals is as follows: dispersing carboxylated cellulose nanocrystals in an aqueous dispersion of amino polyethylene glycol, then adding 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide and N-hydroxysuccinate to the aqueous dispersion, and reacting with the amino polyethylene glycol under the dehydration condensation of 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide and N-hydroxysuccinate to obtain cellulose nanocrystals grafted with polyethylene glycol, i.e., modified cellulose nanocrystals; (4) preparing a polylactic acid / modified cellulose nanocrystal spinning solution: preparing a polylactic acid / modified cellulose nanocrystal composite material having different mass ratios and a chloroform / acetone mixed solvent at a volume ratio of 1:1, dissolving the polylactic acid and modified cellulose nanocrystal in the mixed solvent to obtain a solution and a dispersion, respectively; and fully stirring the polylactic acid solution and the modified cellulose nanocrystal dispersion to obtain a spinning solution, wherein the concentration of polylactic acid in the spinning solution is 10 wt %; (5) Electrospinning of polylactic acid / modified cellulose nanocrystal spinning solution: The polylactic acid / modified cellulose nanocrystal spinning solution was electrospun with a voltage of 18 kV, a flow rate of 1.5 ml / h, and a receiving distance of 18 cm to obtain a high-strength polylactic acid / modified cellulose nanocrystal electrospun nanofiber membrane.

2. The high-strength polylactic acid / modified cellulose nanocrystal electrospun nanofiber membrane prepared according to the preparation method of claim 1, characterized in that: The mass fraction of the modified cellulose nanocrystals is 0.5%, 1% or 3% compared to the polylactic acid.

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