Preparation method of toughened polylactic acid nanofiber electrostatic spinning membrane

Abstract

The invention relates to a preparation method of a toughened polylactic acid nanofiber electrostatic spinning membrane, which comprises the following steps: (1) adding an elastic component monomer, lactic acid and cellulose into deionized water, heating and stirring to obtain a compatibilizer; (2) adding the compatibilizer, the elastic component and the polylactic acid in the step (1) into an organic solvent, stirring, dissolving and uniformly mixing to obtain a spinning solution; and (3) carrying out electrostatic spinning on the spinning solution to obtain the toughened polylactic acid nanofiber electrostatic spinning membrane. The preparation method is simple, the defect that the polylactic acid material is too large in brittleness is overcome, and the obtained nanofiber electrostatic spinning membrane has better toughness, elastic recovery performance and fatigue resistance.

Description

Technical Field

[0001] The invention belongs to the field of nanofiber membranes, and particularly relates to a method for preparing a toughened polylactic acid nanofiber electrospinning membrane. Background Art

[0002] Polylactic acid (PLA) is a synthetic polymer material made from corn, with excellent biodegradability and biocompatibility. PLA can be decomposed by bacteria, molds and other microorganisms in nature, and can eventually be degraded into carbon dioxide and water that are harmless to the environment. As a bio-based material that originates from nature and can eventually be degraded back to nature, PLA has great development potential in the current process of focusing on environmental protection and promoting new bio-based environmentally friendly materials.

[0003] The existing preparation technology of PLA nanofibers can select electrospinning technology. PLA nanofibers spun by existing electrospinning technology have the characteristics of large specific surface area and excellent biocompatibility. They are widely used in the biomedical field as tissue scaffolds and mixed drugs to promote human tissue repair. However, some parts that require scaffolds, such as muscle ligament tissue, require the tissue scaffolds to have a certain toughness.

[0004] However, due to the low crystallization rate of electrospun PLA, its mechanical properties are poor. Although it has high hardness, its toughness is obviously insufficient, it is relatively brittle, and its bending resistance is also poor. In addition, under high wind speed conditions, there are high requirements for the strength and toughness of air filter materials.

[0005] At present, the method of toughening PLA mainly includes polymer blending. In order to ensure that the prepared PLA composite material is still degradable, the toughening material used must have the performance of natural harmless and easy to degrade, and elastic components such as PCL and PBAT are often selected for blending. CN111748181B discloses a material made by blending biodegradable flexible macromolecules PBAT, PBF and PBls in PLA, and epoxidized cellulose fibers through melt reaction. However, PLA and elastic components such as PBAT are thermodynamically incompatible systems, so that the blend obtained by melt blending PLA and elastic components has poor mechanical properties, is not tightly connected, and the connection of amorphous regions is insufficient, which is easy to cause interface separation and thus affects the toughening effect.

[0006] In order to improve the mechanical properties of the blends of PLA and elastic components, it is necessary to introduce a compatibilizer during the blending process to reduce the tension at the interface between PLA and the elastic component and enhance the adhesion of the interface, thereby achieving the purpose of improving the compatibility of the blending system. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing a toughened polylactic acid nanofiber electrospinning membrane. By introducing a compatibilizer, the tension at the interface between PLA and an elastic component is reduced, the adhesion of the interface is improved, and the elastic component and the compatibilizer work together to achieve a toughening effect.

[0008] The present invention provides a method for preparing a toughened polylactic acid nanofiber electrospinning membrane, comprising:

[0009] (1) adding an elastic component monomer, lactic acid and cellulose into deionized water, heating and stirring, to obtain a compatibilizer;

[0010] (2) adding the compatibilizer, the elastic component and the polylactic acid into an organic solvent, stirring and dissolving them, and obtaining a spinning solution;

[0011] (3) The spinning solution is subjected to electrospinning to obtain a toughened polylactic acid nanofiber electrospinning membrane.

[0012] Preferably, the elastic component monomer in step (1) includes one of butanediol, caprolactone, succinic acid or adipic acid; and the cellulose includes one of microcrystalline cellulose, cellulose nanocrystals or cellulose nanofibers.

[0013] Preferably, in step (1), the mass ratio of the elastic component monomer, lactic acid and cellulose is 1-3:7-9:1, and the mass ratio of cellulose to deionized water is 1:10-20.

[0014] More preferably, in step (1), the mass ratio of the elastic component monomer, lactic acid and cellulose is 2:8:1, and the mass ratio of cellulose to deionized water is 1:20.

[0015] Preferably, the organic solvent in step (2) is a volatile solvent, including one of a mixed solvent of dichloromethane and DMF or chloroform and DMF, and the mass ratio of the components in the mixed solvent is 6:4, 7:3 or 8:2.

[0016] Preferably, the weight average molecular weight of the elastic component and the polylactic acid in step (2) is 80,000 to 120,000.

[0017] Preferably, the elastic component in step (2) corresponds to an elastic component monomer, including one of polybutylene terephthalate-adipate (PBAT), polycaprolactone (PCL), polybutylene succinate (PBS) or polybutylene succinate-adipate (PBSA). The elastic component has a toughening effect on PLA.

[0018] Preferably, in step (2), the mass ratio of the compatibilizer, the elastic component and the polylactic acid is 1:1-3:6-8, and the spinning solution concentration is 10-14wt%.

[0019] More preferably, in step (2), the mass ratio of the compatibilizer, the elastic component and the polylactic acid is 1:2:7.

[0020] Preferably, in step (1), the heating temperature is 80-100° C. and the stirring time is 10-20 h; in step (2), the stirring time is 10-12 h and the mixture is allowed to stand for 5-10 min until all bubbles disappear.

[0021] Furthermore, the spinning solution in step (2) can be refrigerated and stored at 4-8° C. for no more than 24 hours.

[0022] Preferably, in step (3), the electrospinning voltage is 8 to 14 kV, the propulsion speed is 0.8 to 1.4 mL / h, the total liquid volume is 4 to 6 mL, and the time is 4 to 5 h.

[0023] The present invention also provides a toughened polylactic acid nanofiber electrospinning membrane prepared by the above method, which is obtained by grafting lactic acid and elastic component monomers on cellulose to obtain a compatibilizer, and then mixing the compatibilizer with polylactic acid and the elastic component and performing electrospinning.

[0024] Beneficial Effects

[0025] (1) The low molecular weight PLA and low molecular weight elastic component segments on the side chains of the compatibilizer used in the present invention are respectively compatible with the PLA and the elastic component in the blend, so that the compatibilizer acts as a bridge between the amorphous regions of the PLA and the elastic component, reduces the tension at the interface between the PLA and the elastic component, increases the adhesion of the interface, improves the interfacial force of the blend, and greatly improves the mechanical properties of the PLA film;

[0026] (2) The elastic component and compatibilizer added in the present invention do not damage the excellent biocompatibility and degradability of PLA, and preserve its application ability in biomedicine;

[0027] (3) The present invention uses electrospinning technology to shape the spinning solution, and the nanofiber membrane has the advantages of large specific surface area, high porosity, etc.

[0028] (4) The preparation method of the present invention is simple, easy to operate, and easy to scale up for production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the infrared spectrum of microcrystalline cellulose and modified cellulose in Example 1 of the present invention.

[0030] Figure 2 This is an electron microscope photograph of the PLA nanofiber electrospun membrane in Example 1 of the present invention.

[0031] Figure 3Comparison of tensile properties between the modified and toughened PLA nanofiber electrospun membrane (right) and the unmodified PLA nanofiber electrospun membrane (left) in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0033] The PLA nanofiber electrospun membranes in the examples and comparative examples were subjected to a tensile test. The specific method was as follows: the nanofiber membranes were cut into rectangles of 10 mm*50 mm, and clamped in a universal testing machine with a range of 5 N for a tensile test at a speed of 15 mm / min.

[0034] Example 1

[0035] Weigh 8 g of lactic acid, 2 g of ε-caprolactone, and 1 g of microcrystalline cellulose (MCC), add 20 g of deionized water, and stir at 80° C. for 10 h until the grafting and synthesis reactions are complete to obtain a compatibilizer (i.e., modified cellulose mMCC). Figure 1 The infrared spectra of microcrystalline cellulose and modified cellulose show the carbon-oxygen double bonds of modified cellulose. The grafting is complete. The electron microscope photos are shown in Figure 2 As shown. Then weigh 7g of dichloromethane and 3g of DMF to mix into a volatile organic solvent, then weigh 0.16g of mMCC, 0.33g of PCL (weight average molecular weight 80,000) and 1.14g of PLA (weight average molecular weight 80,000) in turn and add them to the organic solvent, stir at room temperature for 12h until all particles are completely dissolved in the organic solvent, and prepare a 14wt% spinning solution. Finally, take 4mL of spinning solution for electrospinning, the voltage is 10KV, the propulsion speed is 1mL / h, and the time is 4h, to obtain a modified and toughened PLA nanofiber electrospinning membrane, the maximum breaking stress is 8.8mPA, and the maximum deformation is 120%.

[0036] Example 2

[0037] Weigh 8g lactic acid, 2g butanediol, 1g microcrystalline cellulose, add 20g deionized water, stir at 80℃ for 10h until the grafting and synthesis reaction are complete to obtain the compatibilizer (i.e., modified cellulose mMCC). Then weigh 7g chloroform and 3g DMF to mix into a volatile organic solvent, then weigh 0.14g mMCC, 0.27g PBAT (weight average molecular weight 120000) and 0.95g PLA (weight average molecular weight 80000) in turn and add them to the organic solvent, stir at room temperature for 10h until all particles are completely dissolved in the organic solvent, and prepare a 12wt% spinning solution. Finally, take 4mL spinning solution for electrospinning, the voltage is 10kV, the propulsion speed is 1mL / h, and the time is 4h, and the modified toughened PLA nanofiber electrospinning membrane is obtained, the maximum breaking stress is 8.1mPA, and the maximum deformation is 98%.

[0038] Comparative Example 1

[0039] The preparation method of the unmodified PLA nanofiber electrospinning membrane in this comparative example is: weigh 7g of dichloromethane and 3g of DMF to mix into a volatile organic solvent, then weigh 1.63g of PLA (weight average molecular weight 80000) and add the organic solvent to prepare a 14wt% spinning solution. Finally, take 4mL of spinning solution for electrospinning, the voltage is 10KV, the propulsion speed is 1mL / h, and the time is 4h to obtain an unmodified PLA nanofiber electrospinning membrane. Comparison of the tensile properties of the modified and toughened PLA nanofiber electrospinning membrane in Example 1 of the present invention and the unmodified PLA nanofiber electrospinning membrane in this example Figure 3 As shown, the toughness of the modified and toughened PLA nanofiber electrospun membrane in Example 1 is significantly better than that of the unmodified PLA nanofiber electrospun membrane.

[0040] Comparative Example 2

[0041] In this comparative example, the preparation method of the PLA nanofiber electrospinning membrane toughened only by the elastic component is as follows: 7g of dichloromethane and 3g of DMF are weighed and mixed into a volatile organic solvent, and then 0.49g of PCL (weight average molecular weight 80000) and 1.14g of PLA (weight average molecular weight 80000) are weighed in turn and added to the organic solvent, and stirred at room temperature for 12h until all particles are completely dissolved in the organic solvent to obtain a 14wt% spinning solution. Finally, 4mL of the spinning solution is taken for electrospinning, the voltage is 10KV, the propulsion speed is 1mL / h, and the time is 4h to obtain a modified and toughened PLA / PCL nanofiber electrospinning membrane, the maximum breaking stress is 7.3mPA, the maximum deformation is 100%, and the performance is significantly worse than the nanofiber electrospinning membrane in Example 1.

Claims

1. A method for preparing a toughened polylactic acid nanofiber electrospinning membrane, comprising: (1) adding an elastic component monomer, lactic acid and cellulose into deionized water, heating and stirring, to obtain a compatibilizer; (2) adding the compatibilizer, elastic component and polylactic acid in step (1) into an organic solvent, stirring and dissolving them to obtain a spinning solution; (3) The spinning solution is subjected to electrospinning to obtain a toughened polylactic acid nanofiber electrospinning membrane.

2. The method for preparing the toughened polylactic acid nanofiber electrospinning membrane according to claim 1, characterized in that: In the step (1), the elastic component monomer includes one of butanediol, caprolactone, succinic acid or adipic acid; and the cellulose includes one of microcrystalline cellulose, cellulose nanocrystals or cellulose nanofibers.

3. The method for preparing the toughened polylactic acid nanofiber electrospinning membrane according to claim 1, characterized in that: In the step (1), the mass ratio of the elastic component monomer, lactic acid and cellulose is 1-3:7-9:1; the mass ratio of cellulose to deionized water is 1:10-20.

4. The method for preparing the toughened polylactic acid nanofiber electrospinning membrane according to claim 1, characterized in that: The organic solvent in step (2) is a volatile solvent, including one of a mixed solvent of dichloromethane and DMF or chloroform and DMF, and the mass ratio of the components in the mixed solvent is 6:4, 7:3 or 8:

2.

5. The method for preparing the toughened polylactic acid nanofiber electrospinning membrane according to claim 1, characterized in that: The weight average molecular weight of the elastic component and the polylactic acid in the step (2) is 80,000 to 120,000.

6. The method for preparing the toughened polylactic acid nanofiber electrospinning membrane according to claim 1, characterized in that: The elastic component in step (2) corresponds to an elastic component monomer, which includes one of polybutylene terephthalate-adipate, polycaprolactone, polybutylene succinate or polybutylene succinate-adipate.

7. The method for preparing toughened polylactic acid nanofiber electrospinning membrane according to claim 1, characterized in that: In the step (2), the mass ratio of the compatibilizer, the elastic component and the polylactic acid is 1:1-3:6-8; and the spinning solution concentration is 10-14wt%.

8. The method for preparing toughened polylactic acid nanofiber electrospinning membrane according to claim 1, characterized in that: In the step (1), the heating temperature is 80-100° C. and the stirring time is 10-20 h. In the step (2), the stirring time is 10-12 h and the mixture is allowed to stand for 5-10 min until all bubbles disappear.

9. The method for preparing toughened polylactic acid nanofiber electrospinning membrane according to claim 1, characterized in that: In the step (3), the electrospinning voltage is 8 to 14 kV, the propulsion speed is 0.8 to 1.4 mL / h, the total liquid volume is 4 to 6 mL, and the time is 4 to 5 h.

10. A toughened polylactic acid nanofiber electrospinning membrane prepared by the method according to any one of claims 1 to 9, characterized in that: The compatibilizer is obtained by grafting lactic acid and elastic component monomers on cellulose, and then the compatibilizer is mixed with polylactic acid and the elastic component and then subjected to electrostatic spinning.

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