Preparation method of a highly elastic and compressible polylactic acid micro-nano fiber aerogel material

Abstract

The present invention discloses a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, its preparation method and application. The method includes: in a compound solvent, using a polycyclic chain extender to in-situ phase interface compatibilize a polylactic acid blend with a thermoplastic elastomer to obtain a spinning precursor solution of the polylactic acid blend with the thermoplastic elastomer; obtaining toughened polylactic acid micro-nano fibers by subjecting the spinning precursor solution to high-voltage electrospinning; dispersing the toughened polylactic acid micro-nano fibers broken by a homogenizer into an aqueous tert-butanol solution to obtain a micro-nano fiber dispersion liquid, and then using it as a gel framework and using aqueous polyurethane as a micro-nano fiber crosslinking agent to prepare a toughened polylactic acid micro-nano fiber gel, and finally obtaining the highly elastic and compressible polylactic acid micro-nano fiber aerogel material by vacuum freeze-drying. The in-situ phase interface compatibilization improves the mechanical properties of the polylactic acid fibers and the polylactic acid micro-nano fiber aerogel material, and the highly elastic and compressible polylactic acid micro-nano fiber aerogel material exhibits long-term oil-water separation performance.

Description

Technical Field

[0001] The present invention relates to the field of aerogel materials, in particular to a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, the phenomenon of oily sewage pollution caused by factory emissions, maritime transportation, and oil exploration has become increasingly common. This not only has a negative impact on the economy but also causes extremely serious ecological damage. At the same time, it has caused irreversible harm to the environment, organisms, and human health. Currently, the discharge of oily wastewater continues to deteriorate the water environment. To solve the problem of waste oil pollution, a large number of studies have been conducted on oil-water separation methods and materials. Traditional oil-water separation methods include gravity separation, centrifugation, air flotation, biological treatment, and fiber membrane separation. The fiber membrane separation method has the advantages of energy conservation, high cost performance, and easy mass production. At present, the preparation methods of oil-water separation fiber membranes mainly include the metal mesh method, sol-gel method, and electrospinning method. Electrospinning is a simple and inexpensive method for preparing micro-nano fiber membranes. The micro / nano fiber membranes prepared by electrospinning have excellent filtration and adsorption capabilities due to their superior properties such as light weight, high porosity, and large specific surface area, and show great potential in oil-water separation. However, most of the current electrospinning oil-water separation fiber membranes rely on non-degradable polymer materials synthesized from coal, petroleum, and natural gas chemical raw materials, which brings secondary environmental pollution. Therefore, it is crucial to prepare an efficient and green oil-water separation material using renewable, degradable, and environmentally friendly raw materials.

[0003] Polylactic acid (PLA) is a thermoplastic biodegradable polymer material formed by the polymerization of small molecule lactic acid obtained from biomass raw materials such as corn stalks, rice straws, wheat straws, sugar canes, and cassavas through microbial fermentation. Polylactic acid has excellent biodegradability, biocompatibility, non-toxicity, and renewability. Compared with current petrochemical plastics, it is more in line with the concept of sustainable development and economic recycling. At the same time, polylactic acid has excellent hydrophobic properties. Therefore, developing oil-water separation fiber membrane materials using polylactic acid has significant advantages. Zhu Ranran et al. prepared nanofiber membranes by electrospinning PLA / PCL. When the blending ratio of PLA / (polycaprolactone) PCL was 7:3, the oil retention rates of the prepared PLA nanofiber membranes for machine oil, peanut oil, and rapeseed oil were 76.16%, 70.83%, and 67.17% respectively (New Chemical Materials in Chemical Industry (2023), 51(04): 137 - 141). However, the mechanical properties of this product and the reusability of PLA-based adsorption materials were not analyzed. Meng Linlin et al. prepared porous hollow polylactic acid nanofiber membranes using coaxial electrospinning technology. Through the tests of the tensile fracture strength, tearing, air permeability, and moisture permeability of the fiber membranes, it was found that the tensile fracture strength of the porous hollow polylactic acid nanofiber membrane was 36.250 cN, and the elongation at break was 3.238 mm. The tearing strength of the porous hollow PLA nanofiber membrane was 90.16 cN. In the tests of the adsorption properties for peanut oil, silicone oil, and machine oil, the oil retention rates of the porous hollow PLA nanofiber membranes were 42.51%, 37.89%, and 49.49% respectively. Due to the brittleness of polylactic acid, the mechanical properties of the porous hollow PLA nanofiber membrane are not ideal, which leads to poor reusability of the porous hollow PLA nanofiber membrane in oil-water separation applications (Advanced Textile Technology (2019), 27(3): 1 - 4). The application of polylactic acid micro-nano fiber materials in the field of oil-water separation mainly has problems such as poor oil absorption selectivity, low oil absorption capacity, poor oil retention rate, difficult recovery, and poor recyclability, which seriously restrict their practical applications. Therefore, there is an urgent need to develop a polylactic acid micro-nano fiber oil-water separation material with high mechanical properties and long-term effectiveness.

[0004] Aerogel is a three-dimensional porous material with extremely low density, high porosity, high pore volume, and adjustable mechanical properties. This structure is beneficial for storing adsorbed oil and is an ideal material for oil-water separation. Biomass-based aerogels simultaneously possess the environmental protection, renewable, and biodegradable characteristics of biomass materials and the advantages of a three-dimensional porous structure, having unique advantages in oil-water separation and attracting extensive attention from researchers. For example, cellulose aerogel has an excellent porous structure and is currently widely used in the field of oil-water separation. However, natural cellulose has hydrophilic characteristics and needs to be given good oil absorption performance through complex hydrophobic modification, lipophilic modification, or compounding. At the same time, most biomass-based polymers lack intermolecular cross-linking in aqueous solutions, and the aerogels prepared from them are difficult to form or have poor mechanical properties, resulting in unsatisfactory use effects of aerogel materials in an aqueous solution environment. The present invention prepares a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, which combines the advantages of micro-nano fibers and aerogel materials. First, a polylactic acid blend thermoplastic elastomer spinning precursor solution is obtained by in-situ phase interface compatibilization of polylactic acid blend thermoplastic elastomer using a polycyclic chain extender, and then tough polylactic acid micro-nano fibers are obtained by high-voltage electrospinning. The tough polylactic acid micro-nano fibers are broken and dispersed into an aqueous tert-butanol solution using a homogenizer to obtain a micro-nano fiber dispersion liquid. Then, using this as a gel framework, a tough polylactic acid micro-nano fiber gel is prepared using aqueous polyurethane as a micro-nano fiber cross-linking agent. At the same time, aqueous polyurethane can synergistically improve the hydrophobicity and lipophilicity of the aerogel. Finally, a highly elastic and compressible polylactic acid micro-nano fiber aerogel material is obtained by vacuum freeze-drying. The prepared polylactic acid micro-nano fiber aerogel material has excellent elastic recovery, high compressibility, high mechanical strength, large specific surface area, high porosity, superhydrophobicity, and lipophilicity, and has an efficient oil absorption effect. At the same time, in-situ interface compatibilization significantly improves the mechanical properties of polylactic acid fibers and micro-nano fiber aerogels. The micro-nano fiber aerogel material exhibits long-term oil-water separation performance and has the characteristics of easy recovery and recyclability. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of a highly elastic and compressible polylactic acid micro-nano fiber aerogel material to solve the problems mentioned in the above background technology.

[0006] In the first aspect, the present invention provides a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, characterized in that the highly elastic and compressible polylactic acid micro-nano fiber aerogel material is a three-dimensional network composed of tough polylactic acid micro-nano fibers and aqueous polyurethane, where the tough polylactic acid micro-nano fibers are the gel framework and aqueous polyurethane is the cross-linking network.

[0007] In the second aspect, the present invention provides a preparation method of a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, which includes the following steps:

[0008] S1: Dissolve polylactic acid and thermoplastic elastomer into a compound solvent to obtain a polymer solution. Add a polycyclic chain extender to the polymer solution, ultrasonically disperse the solution for in-situ phase interface compatibilization, and perform vacuum degassing to obtain a spinning precursor solution.

[0009] S2: Obtain toughened polylactic acid micro-nano fibers by high-voltage electrospinning of the spinning precursor solution.

[0010] S3: Disperse the toughened polylactic acid micro-nano fibers into an aqueous tert-butanol solution by using a homogenizer, add aqueous polyurethane as a crosslinking agent to the aqueous solution to obtain a toughened polylactic acid micro-nano fiber hydrogel, and vacuum freeze-dry the hydrogel material to obtain a highly elastic and compressible polylactic acid micro-nano fiber aerogel material.

[0011] Preferably, in step S1, the compound solvent is composed of tetrahydrofuran and N,N'-dimethylformamide, and the mass ratio is 1-3:1; the amounts of polylactic acid and the thermoplastic elastomer in the compound solvent in step S1 are 10-15 wt%, and the mass ratio of polylactic acid to the thermoplastic elastomer is 3:2; the amount of the polycyclic chain extender in polylactic acid and the thermoplastic elastomer in step S1 is 0.5-2 wt%.

[0012] Preferably, the conditions for the ultrasonic dispersion treatment in step S1 are: the power is set to 500-1200 W, and the treatment time is 1-10 h.

[0013] Preferably, the thermoplastic elastomer in step S1 is at least one of aliphatic polyether urethane TPU, aromatic polyether urethane TPU, aliphatic polycarbonate urethane TPU, and aromatic polycarbonate urethane TPU, and the polycyclic chain extender is a styrene-glycidyl methacrylate oligomer.

[0014] Preferably, the parameters of the high-voltage electrospinning in step S2 are set as follows: the high-voltage static electricity is 10-20 kV, the glue-pushing speed is 1-5 ml / h, the receiving distance is 8-15 cm, and the spinning needle head is any one of the models 19G, 20G, 21G, 22G, and 23G.

[0015] Preferably, the amount of the toughened polylactic acid micro-nano fibers in the aqueous tert-butanol solution in step S3 is 0.5-2 wt%.

[0016] Preferably, the aqueous tert-butanol solution in step S3 is composed of tert-butanol and an aqueous solution, and the mass ratio is 1:4. The treatment conditions of the homogenizer are: 10000-20000 rpm, and the treatment time is 0.5-2 h.

[0017] Preferably, in step S3, the mass ratio of the aqueous polyurethane to the toughened polylactic acid micro-nano fibers is 0.1-1:1, and the aqueous polyurethane is at least one of aromatic isocyanate type WPU, aliphatic isocyanate type WPU, and alicyclic isocyanate type WPU.

[0018] Thirdly, the present invention provides an application of a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, and an application of the highly elastic and compressible polylactic acid nano fiber aerogel material prepared by using the aforementioned highly elastic and compressible polylactic acid nano fiber aerogel material in the field of oil-water separation.

[0019] The highly elastic and compressible polylactic acid micro-nano fiber aerogel material of the present invention has the following beneficial effects:

[0020] (1) By using the electrospun micro-nano fibers of polylactic acid to synergistically form the aerogel, a structure with the advantages of both micro-nano fibers and aerogels is constructed, realizing the preparation of a polylactic acid micro-nano fiber aerogel material with excellent elastic recovery, high compressibility, high mechanical strength, large specific surface area, high porosity, superhydrophobicity and high lipophilicity.

[0021] (2) In the stage of constructing the electrospun micro-nano fibers of polylactic acid, the polycyclic ring-expanding chain extender contains epoxy groups in its molecule, which have high reactivity. During the in-situ compatibilization reaction, the epoxy groups are ring-opened and react with the functional groups (-OH and -COOH) of polylactic acid and thermoplastic elastomer to form new -CO-ester chemical bonds, realizing the covalent bridging between polylactic acid, thermoplastic elastomer and polycyclic ring-expanding chain extender. By using the in-situ phase interface compatibilization of the polycyclic ring-expanding chain extender and electrospinning synergistically, toughened polylactic acid micro-nano fibers are prepared. The in-situ phase interface compatibilization significantly improves the mechanical properties of polylactic acid fibers and polylactic acid micro-nano fiber aerogel materials. In the construction of the polylactic acid micro-nano fiber aerogel, the aqueous polyurethane, as a crosslinking agent for the gel framework, further improves the mechanical properties of the polylactic acid micro-nano fiber aerogel and significantly improves the lipophilicity of the polylactic acid micro-nano fibers.

[0022] (3) Using renewable, degradable and environmentally friendly polylactic acid as the raw material, a highly elastic and compressible polylactic acid micro-nano fiber aerogel material with high oil absorption capacity and long-lasting oil absorption effect is constructed by using the electrospun micro-nano fibers of polylactic acid to synergistically form the aerogel. The present invention solves the problem of poor application effect caused by the brittleness of polylactic acid fibers, and at the same time solves the problems of the electrospun oil-water separation fiber membrane relying on non-degradable polymer materials synthesized from coal, petroleum and natural gas chemical raw materials, and the secondary environmental pollution caused by the oil-water separation materials. Description of the Drawings

[0023] Figure 1 Scanning electron microscope images and water contact angle photos of toughened polylactic acid micro-nano fibers;

[0024] Figure 2 It is a scanning electron micrograph of a highly elastic and compressible polylactic acid micro-nano fiber aerogel material;

[0025] Figure 3 They are photos of the water contact angle and oil contact angle of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material;

[0026] Figure 4 They are the compression-rebound stress-strain diagram and height retention rate diagram of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material;

[0027] Figure 5 It is an infrared spectrum diagram of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material;

[0028] Figure 6 They are the oil absorption amount in water and cyclic adsorption performance diagram of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material;

[0029] Figure 7 They are the dynamic separation data diagram of immiscible oil-water mixtures of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material;

[0030] Figure 8 They are the separation data diagram of miscible oil-water emulsions of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material. Specific embodiments

[0031] The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be construed as a limitation of the present invention.

[0032] In a first aspect, in an embodiment of the present invention, a highly elastic and compressible polylactic acid micro-nano fiber aerogel material is provided, which consists of a three-dimensional network composed of toughened polylactic acid micro-nano fibers and aqueous polyurethane, wherein the toughened polylactic acid micro-nano fibers are the gel framework and the aqueous polyurethane serves as the cross-linking network.

[0033] In a second aspect, an embodiment of the present invention provides a method for preparing a highly elastic and compressible polylactic acid micro-nano fiber aerogel material. In a complex solvent, a polycyclic chain extender is used to in-situ phase interface compatibilize a polylactic acid blend with a thermoplastic elastomer to obtain a spinning precursor solution of the polylactic acid blend with the thermoplastic elastomer; the spinning precursor solution is subjected to high-voltage electrospinning to obtain toughened polylactic acid micro-nano fibers; the toughened polylactic acid micro-nano fibers broken by a homogenizer are dispersed into an aqueous tert-butanol solution to obtain a micro-nano fiber dispersion, and then, using this as a gel framework, an aqueous polyurethane is used as a micro-nano fiber crosslinking agent to prepare a toughened polylactic acid micro-nano fiber gel, and finally, a highly elastic and compressible polylactic acid micro-nano fiber aerogel material is obtained through vacuum freeze-drying. The polylactic acid micro-nano fiber aerogel material simultaneously has the advantages of polylactic acid micro-nano fibers and aerogel materials, and has the high specific surface area of micro-nano fibers and the high porosity of aerogels. In-situ interface compatibilization significantly improves the mechanical properties of polylactic acid fibers and polylactic acid micro-nano fiber aerogel materials. The highly elastic and compressible polylactic acid micro-nano fiber aerogel material has excellent elastic recovery, high compressibility, high mechanical strength, large specific surface area, high porosity, superhydrophobicity and high lipophilicity, and shows a high-efficiency oil absorption effect when applied to the field of oil-water separation. The highly elastic and compressible polylactic acid micro-nano fiber aerogel material exhibits long-term oil-water separation performance and is easy to recycle and reusable at the same time.

[0034] Specifically, the method for preparing the highly elastic and compressible polylactic acid micro-nano fiber aerogel material includes the following steps:

[0035] S1: Dissolve polylactic acid and a thermoplastic elastomer into a complex solvent obtained by mixing tetrahydrofuran and N,N'-dimethylformamide in a mass ratio of 1 to 3:1. The amount of polylactic acid and the thermoplastic elastomer in the complex solvent is 10 to 15 wt%, and the mass ratio of polylactic acid to the thermoplastic elastomer is 3:2; add a polycyclic chain extender to the polymer solution, and the amount of the polycyclic chain extender in polylactic acid and the thermoplastic elastomer is 0.5 to 2 wt%. Ultrasonically disperse the solution for in-situ phase interface compatibilization and perform vacuum degassing to obtain a spinning precursor solution.

[0036] S2: Subject the spinning precursor solution to high-voltage electrospinning to obtain toughened polylactic acid micro-nano fibers;

[0037] S3: Use a homogenizer to disperse the toughened polylactic acid micro-nano fibers into an aqueous tert-butanol solution (the aqueous tert-butanol solution is composed of tert-butanol and water, and the mass ratio is 1:4), and the amount of the toughened polylactic acid micro-nano fibers in the aqueous tert-butanol solution is 0.5 to 2 wt%; continue to add an aqueous polyurethane as a crosslinking agent to the aqueous solution of tert-butanol, and the mass ratio of the aqueous polyurethane to the toughened polylactic acid micro-nano fibers is 0.1 to 1:1 to obtain a toughened polylactic acid micro-nano fiber hydrogel, and vacuum freeze-dry the hydrogel material to obtain a highly elastic and compressible polylactic acid micro-nano fiber aerogel material.

[0038] In a preferred embodiment of the present invention, the thermoplastic elastomer is at least one of aliphatic polyether urethane TPU, aromatic polyether urethane TPU, aliphatic polycarbonate urethane TPU, and aromatic polycarbonate urethane TPU, but is not limited thereto; and the polycyclic chain extender is styrene-glycidyl methacrylate oligomer.

[0039] In a preferred embodiment of the present invention, in the above steps, the ultrasonic dispersion treatment conditions are: the power is set to 500-1200W, and the treatment time is 1-10h.

[0040] In a preferred embodiment of the present invention, in the above steps, the high-voltage electrospinning parameters are set as follows: high-voltage electrostatic 10-20 kV, a pushing speed of 1-5 ml / h, a receiving distance of 8-15 cm, and a spinning needle according to any one of the models 19G, 20G, 21G, 22G, and 23G, but not limited thereto.

[0041] In a preferred embodiment of the present invention, in the above steps, the processing conditions of the homogenizer are: 10000-20000 rpm, and the processing time is 0.5-2h.

[0042] In a preferred embodiment of the present invention, in the above steps, the waterborne polyurethane is at least one of aromatic isocyanate type WPU, aliphatic isocyanate type WPU, and alicyclic isocyanate type WPU, but is not limited thereto.

[0043] In the third aspect, the present invention provides an application of a highly elastic compressible polylactic acid micro-nano fiber aerogel material prepared by the aforementioned method in the field of oil-water separation. The highly elastic compressible polylactic acid micro-nano fiber aerogel material has excellent elastic recovery, high compressibility, high mechanical strength, large specific surface area, high porosity, super hydrophobicity and high lipophilicity, and is applied to the field of oil-water separation to show efficient oil absorption effect. The highly elastic compressible polylactic acid micro-nano fiber aerogel material exhibits long-term oil-water separation performance, and is also easy to recycle and reusable.

[0044] The following embodiments are some specific implementation cases of the present invention in practical applications, but are not limited thereto.

[0045] Embodiment 1:

[0046] This embodiment provides a method for preparing a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, which specifically includes the following steps:

[0047] Step 1: Preparation of in-situ phase interface compatibilized spinning precursor solution

[0048] Dissolve polylactic acid and aliphatic polyether polyurethane TPU into a compound solvent obtained by mixing tetrahydrofuran and N,N'-dimethylformamide at a mass ratio of 2:1. The amount of polylactic acid and aliphatic polyether polyurethane TPU in the compound solvent is 14 wt%, and the mass ratio of polylactic acid to thermoplastic elastomer is 3:2. Add a chain extender, styrene-glycidyl methacrylate oligomer, to the polymer solution. The amount of styrene-glycidyl methacrylate oligomer in polylactic acid and thermoplastic elastomer is 1 wt%. Ultrasonically disperse the solution for in-situ phase interface compatibilization, set the ultrasonic power to 1000 W, and the treatment time to 5 h. Then perform vacuum degassing to obtain a spinning precursor solution.

[0049] Step 2: Strengthening polylactic acid micro-nano fibers

[0050] Load the spinning precursor solution into a syringe for high-voltage electrospinning. The high voltage is 15 kV, the pushing speed of the glue is 2 ml / h, the receiving distance is 10 cm, and the spinning needle head is of model 20G to obtain strengthened polylactic acid micro-nano fibers.

[0051] Step 3: Preparation of highly elastic and compressible polylactic acid micro-nano fiber aerogel

[0052] Use a homogenizer to disperse the strengthened polylactic acid micro-nano fibers into an aqueous tert-butanol solution. The aqueous tert-butanol solution is composed of tert-butanol and water solution, and the mass ratio is 1:4. The amount of strengthened polylactic acid micro-nano fibers in the aqueous tert-butanol solution is 1 wt%. The treatment conditions of the homogenizer are: 15000 rpm, and the treatment time is 1 h. Then continue to add aliphatic isocyanate type WPU as a cross-linking agent to the aqueous solution of tert-butanol. The mass ratio of aliphatic isocyanate type WPU to the strengthened polylactic acid micro-nano fibers is 0.5:1 to obtain a strengthened polylactic acid micro-nano fiber hydrogel. Vacuum freeze-dry the hydrogel material to obtain a highly elastic and compressible polylactic acid micro-nano fiber aerogel material.

[0053] Example 2:

[0054] This example provides a method for preparing a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, which specifically includes the following steps:

[0055] Step 1: Preparation of in-situ phase interface compatibilized spinning precursor solution

[0056] Dissolve polylactic acid and aromatic polyether polyurethane TPU into a compound solvent obtained by mixing tetrahydrofuran and N,N'-dimethylformamide in a mass ratio of 3:1. The amount of polylactic acid and aromatic polyether polyurethane TPU in the compound solvent is 10 wt%, and the mass ratio of polylactic acid to thermoplastic elastomer is 3:2. Add a chain extender, styrene-glycidyl methacrylate oligomer, to the polymer solution. The amount of styrene-glycidyl methacrylate oligomer in polylactic acid and thermoplastic elastomer is 1.5 wt%. Ultrasonically disperse the solution for in-situ phase interface compatibilization, set the ultrasonic power to 1500 W, and the treatment time to 3 h. Then perform vacuum degassing to obtain a spinning precursor solution.

[0057] Step 2: Strengthening polylactic acid micro-nano fibers

[0058] Load the spinning precursor solution into a syringe for high-voltage electrospinning. The high voltage is 12 kV, the glue-pushing speed is 1.5 ml / h, the receiving distance is 9 cm, and the spinning needle head is of model 22G to obtain strengthened polylactic acid micro-nano fibers.

[0059] Step 3: Preparation of highly elastic and compressible polylactic acid micro-nano fiber aerogel

[0060] Use a homogenizer to disperse the strengthened polylactic acid micro-nano fibers into an aqueous tert-butanol solution. The aqueous tert-butanol solution is composed of tert-butanol and water, with a mass ratio of 1:4. The amount of strengthened polylactic acid micro-nano fibers in the aqueous tert-butanol solution is 1.5 wt%. The treatment conditions of the homogenizer are: 10000 rpm and the treatment time is 1 h; continue to add aromatic isocyanate-based WPU as a crosslinking agent to the aqueous solution of tert-butanol. The mass ratio of aromatic isocyanate-based WPU to strengthened polylactic acid micro-nano fibers is 0.2:1 to obtain a strengthened polylactic acid micro-nano fiber hydrogel. Vacuum freeze-dry the hydrogel material to obtain a highly elastic and compressible polylactic acid micro-nano fiber aerogel material.

[0061] Example 3:

[0062] This example provides a method for preparing a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, which specifically includes the following steps:

[0063] Step 1: Preparation of in-situ phase interface compatibilized spinning precursor solution

[0064] Dissolve polylactic acid and aliphatic polycarbonate urethane TPU into a compound solvent obtained by mixing tetrahydrofuran and N,N'-dimethylformamide at a mass ratio of 2:1. The amount of polylactic acid and aliphatic polycarbonate urethane TPU in the compound solvent is 14 wt%, and the mass ratio of polylactic acid to thermoplastic elastomer is 3:2. Add a chain extender, styrene-glycidyl methacrylate oligomer, to the polymer solution. The amount of styrene-glycidyl methacrylate oligomer in polylactic acid and thermoplastic elastomer is 1.6 wt%. Ultrasonically disperse the solution for in-situ phase interface compatibilization, set the ultrasonic power to 1100 W, and the treatment time to 8 h. Then carry out vacuum degassing to obtain a spinning precursor solution.

[0065] Step 2: Strengthening polylactic acid micro-nano fibers

[0066] Load the spinning precursor solution into a syringe for high-voltage electrospinning. The high voltage is 13 kV, the glue-pushing speed is 2.2 ml / h, the receiving distance is 12 cm, and the spinning needle head is of model 22G to obtain strengthened polylactic acid micro-nano fibers.

[0067] Step 3: Preparation of highly elastic and compressible polylactic acid micro-nano fiber aerogel

[0068] Use a homogenizer to disperse the strengthened polylactic acid micro-nano fibers into an aqueous tert-butanol solution. The aqueous tert-butanol solution is composed of tert-butanol and water, with a mass ratio of 1:4. The amount of strengthened polylactic acid micro-nano fibers in the aqueous tert-butanol solution is 1.7 wt%. The treatment conditions of the homogenizer are: 18000 rpm and the treatment time is 1 h. Then continue to add alicyclic isocyanate-based WPU as a cross-linking agent to the aqueous solution of tert-butanol. The mass ratio of alicyclic isocyanate-based WPU to the strengthened polylactic acid micro-nano fibers is 0.6:1 to obtain a strengthened polylactic acid micro-nano fiber hydrogel. Vacuum freeze-dry the hydrogel material to obtain a highly elastic and compressible polylactic acid micro-nano fiber aerogel material.

[0069] Example 4:

[0070] This example provides a method for preparing a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, which specifically includes the following steps:

[0071] Step 1: Preparation of in-situ phase interface compatibilized spinning precursor solution

[0072] Dissolve polylactic acid and aromatic polycarbonate urethane TPU into a compound solvent obtained by mixing tetrahydrofuran and N,N'-dimethylformamide at a mass ratio of 1.5:1. The amount of polylactic acid and aromatic polycarbonate urethane TPU in the compound solvent is 11 wt%, and the mass ratio of polylactic acid to thermoplastic elastomer is 3:2. Add a chain extender, styrene-glycidyl methacrylate oligomer, to the polymer solution. The amount of styrene-glycidyl methacrylate oligomer in polylactic acid and thermoplastic elastomer is 1.8 wt%. Ultrasonically disperse the solution for in-situ phase interface compatibilization, set the ultrasonic power to 900 W, and the treatment time to 6 h. Then carry out vacuum degassing to obtain a spinning precursor solution.

[0073] Step 2: Strengthening polylactic acid micro-nano fibers

[0074] Load the spinning precursor solution into a syringe for high-voltage electrospinning. The high voltage is 14 kV, the pushing speed of the glue is 2.3 ml / h, the receiving distance is 9 cm, and the spinning needle head is of model 23G to obtain strengthened polylactic acid micro-nano fibers.

[0075] Step 3: Preparation of highly elastic and compressible polylactic acid micro-nano fiber aerogel

[0076] Use a homogenizer to disperse the strengthened polylactic acid micro-nano fibers into an aqueous solution of tert-butanol. The aqueous solution of tert-butanol is composed of tert-butanol and water, and the mass ratio is 1:4. The amount of strengthened polylactic acid micro-nano fibers in the aqueous solution of tert-butanol is 1.8 wt%. The treatment conditions of the homogenizer are: 19000 rpm and the treatment time is 1.2 h. Then continue to add aromatic isocyanate type WPU as a crosslinking agent to the aqueous solution of tert-butanol. The mass ratio of aromatic isocyanate type WPU to the strengthened polylactic acid micro-nano fibers is 0.7:1 to obtain a strengthened polylactic acid micro-nano fiber hydrogel. Vacuum freeze-dry the hydrogel material to obtain a highly elastic and compressible polylactic acid micro-nano fiber aerogel material.

[0077] Example 5:

[0078] This example provides a method for preparing a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, which specifically includes the following steps:

[0079] Step 1: Preparation of in-situ phase interface compatibilized spinning precursor solution

[0080] Dissolve polylactic acid and aliphatic polyether polyurethane TPU into a compound solvent obtained by mixing tetrahydrofuran and N,N'-dimethylformamide at a mass ratio of 2.5:1. The amount of polylactic acid and aliphatic polyether polyurethane TPU in the compound solvent is 14 wt%, and the mass ratio of polylactic acid to thermoplastic elastomer is 3:2. Add a chain extender, styrene-glycidyl methacrylate oligomer, to the polymer solution. The amount of styrene-glycidyl methacrylate oligomer in polylactic acid and thermoplastic elastomer is 1.9 wt%. Ultrasonically disperse the solution for in-situ phase interface compatibilization, set the ultrasonic power to 1150 W, and the treatment time to 9 h. Then carry out vacuum degassing to obtain a spinning precursor solution.

[0081] Step 2: Strengthening polylactic acid micro-nano fibers

[0082] Load the spinning precursor solution into a syringe for high-voltage electrospinning. The high voltage is 19 kV, the glue-pushing speed is 1.1 ml / h, the receiving distance is 14 cm, and the spinning needle head is of model 20G to obtain strengthened polylactic acid micro-nano fibers.

[0083] Step 3: Preparation of highly elastic and compressible polylactic acid micro-nano fiber aerogel

[0084] Use a homogenizing disperser to disperse the strengthened polylactic acid micro-nano fibers into an aqueous solution of tert-butanol. The aqueous solution of tert-butanol is composed of tert-butanol and water, with a mass ratio of 1:4. The amount of strengthened polylactic acid micro-nano fibers in the aqueous solution of tert-butanol is 1.9 wt%. The treatment conditions of the homogenizing disperser are: 19500 rpm and the treatment time is 1.6 h. Then continue to add aliphatic isocyanate-based WPU as a crosslinking agent to the aqueous solution of tert-butanol. The mass ratio of aliphatic isocyanate-based WPU to the strengthened polylactic acid micro-nano fibers is 0.8:1 to obtain a strengthened polylactic acid micro-nano fiber hydrogel. Vacuum freeze-dry the hydrogel material to obtain a highly elastic and compressible polylactic acid micro-nano fiber aerogel material.

[0085] Example 6:

[0086] This example provides a method for preparing a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, which specifically includes the following steps:

[0087] Step 1: Preparation of in-situ phase interface compatibilized spinning precursor solution

[0088] Dissolve polylactic acid and aromatic polycarbonate urethane TPU into a compound solvent obtained by mixing tetrahydrofuran and N,N'-dimethylformamide at a mass ratio of 3:1. The amount of polylactic acid and aromatic polyether urethane TPU in the compound solvent is 15 wt%. The mass ratio of polylactic acid to thermoplastic elastomer is 3:2. Add a chain extender, styrene-glycidyl methacrylate oligomer, to the polymer solution. The amount of styrene-glycidyl methacrylate oligomer in polylactic acid and thermoplastic elastomer is 2 wt%. Ultrasonically disperse the solution for in-situ phase interface compatibilization, set the ultrasonic power to 1200 W, and the treatment time to 10 h. Then perform vacuum degassing to obtain a spinning precursor solution.

[0089] Step 2: Strengthen polylactic acid micro-nano fibers

[0090] Load the spinning precursor solution into a syringe for high-voltage electrospinning. The high voltage is 20 kV, the pushing speed of the glue is 5 ml / h, the receiving distance is 15 cm, and the spinning needle head is of model 19G to obtain strengthened polylactic acid micro-nano fibers.

[0091] Step 3: Preparation of highly elastic and compressible polylactic acid micro-nano fiber aerogel

[0092] Use a homogenizing disperser to disperse the strengthened polylactic acid micro-nano fibers into an aqueous solution of tert-butanol. The aqueous solution of tert-butanol is composed of tert-butanol and water, with a mass ratio of 1:4. The amount of strengthened polylactic acid micro-nano fibers in the aqueous solution of tert-butanol is 2 wt%. The treatment conditions of the homogenizing disperser are: 20000 rpm, and the treatment time is 2 h; continue to add alicyclic isocyanate type WPU as a crosslinking agent to the aqueous solution of tert-butanol. The mass ratio of alicyclic isocyanate type WPU to the strengthened polylactic acid micro-nano fibers is 1:1 to obtain a strengthened polylactic acid micro-nano fiber hydrogel. Vacuum freeze-dry the hydrogel material to obtain a highly elastic and compressible polylactic acid micro-nano fiber aerogel material.

[0093] Experimental example:

[0094] Taking the highly elastic and compressible polylactic acid micro-nano fiber aerogel material prepared in Example 1 above as an example, conduct further research and analysis. Apply the highly elastic and compressible polylactic acid micro-nano fiber aerogel material to the field of oil-water separation. In order to comprehensively study the oil-water separation effect of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material, three experiments, namely, oil absorption in water by the highly elastic and compressible polylactic acid micro-nano fiber aerogel, dynamic separation of immiscible oil-water mixtures, and separation of miscible oil-water emulsions, are designed.

[0095] 1. Oil absorption experiment: Weigh 10 g of dimethyl silicone oil, vacuum pump oil, n-hexane, petroleum ether, cyclohexane and 150 mL of deionized water separately using a beaker, and mix them thoroughly to form an oil-water emulsion. Take a 0.1 g high-elastic compressible polylactic acid micro-nano fiber aerogel material body, and completely immerse it in the prepared oil-water emulsion to ensure that the material fully adsorbs the oil. Take out the soaked material from the beaker, let it stand and hang until no liquid droplets drip from the material, ensuring that all excess liquid has been removed. After ensuring that no liquid droplets drip, weigh the treated material and record its mass. Calculate the oil absorption capacity of the high-elastic compressible polylactic acid micro-nano fiber aerogel material using formula (1).

[0096]

[0097] Where: Q is the oil absorption capacity (g / g), m 1 is the mass of the high-elastic compressible polylactic acid micro-nano fiber aerogel material body before adsorption, which is 0.1 g, m 2 is the mass of the high-elastic compressible polylactic acid micro-nano fiber aerogel material sample after soaking in the oil-water emulsion and standing and hanging until no liquid droplets drip.

[0098] 2. Immiscible oil-water mixture separation experiment: Mix dimethyl silicone oil, vacuum pump oil, n-hexane, petroleum ether, cyclohexane and deionized water in a ratio of 9:1 to prepare an immiscible oil-water mixture. This step ensures the uniformity of the test mixture for accurate evaluation of the performance of the separation material. Cut a circular columnar high-elastic compressible polylactic acid micro-nano fiber aerogel material with a diameter of 4 cm to fit the inner diameter of the separation device. Fix the prepared material in the separation unit (filter element), and the inner diameter of this separation unit is 4 cm. Such a design ensures that the oil-water mixture can pass through the material evenly for separation. Use the material as the filter element and conduct a separation experiment under the action of gravity through a vacuum filtration device. Calculate the separation flux by observing and recording the volume of the filtrate collected within 1 minute. Measure the water content of the filtrate using a Karl Fischer moisture analyzer to calculate the efficiency of oil-water separation.

[0099] 3. Miscible oil-water emulsion separation experiment: 0.5 grams of Span 80 surfactant was accurately weighed and mixed with 1 mL of deionized water in 99 mL of silicone oil (oil-based medium). Subsequently, the mixture was subjected to ultrasonic emulsification treatment for two consecutive hours to prepare a stable surfactant-stabilized emulsion. Using a miscible oil-water emulsion separation device, i.e., a separation device composed of a peristaltic pump and a separation unit, the highly elastic and compressible poly(lactic acid) micro-nano fiber aerogel material was fixed in a separation unit with a diameter of 20 mm, and the separation efficiency and permeation flux of the highly elastic and compressible poly(lactic acid) micro-nano fiber aerogel material were tested. By adjusting the external driving pressure, precise control of the separation conditions was achieved. The quantitative analysis of the permeation flux was carried out using formula (2).

[0100]

[0101] Among them, J is the permeation flux, with the unit of ml / (m 2 ·min). V represents the filtrate volume (mL) within a unit time, a is the test area (m 2 ), and t is the time (min). The final evaluation of the separation performance was carried out by measuring the water content in the filtrate using a Karl Fischer moisture analyzer, thereby accurately characterizing the application performance of the highly elastic and compressible poly(lactic acid) micro-nano fiber aerogel material in the separation of water-in-oil emulsions.

[0102] The toughened poly(lactic acid) micro-nano fibers provided in Example 1 were subjected to scanning electron microscopy (SEM) detection to observe the in-situ phase interface compatibilization effect of poly(lactic acid), and at the same time, the contact angle of the fibers was measured. The results are as Figure 1 shown. Figure 1 (a) is the scanning electron microscope image of the toughened poly(lactic acid) micro-nano fibers. It can be seen from the figure that the diameters of the toughened poly(lactic acid) micro-nano fibers are distributed in the range of 60 nm - 250 nm. The fiber morphology is regular, the thickness is uniform, and there are no beads on the fibers. There is no phase interface separation between poly(lactic acid) and the thermoplastic elastomer. This is attributed to the fact that the polycyclic ring chain extender molecule contains epoxy groups, which have high reactivity. During the in-situ compatibilization reaction, the epoxy groups open the ring and react with the functional groups (-OH and -COOH) of poly(lactic acid) and the thermoplastic elastomer to form new chemical bonds, realizing the covalent bridging between poly(lactic acid), the thermoplastic elastomer, and the polycyclic ring chain extender. The in-situ phase interface compatibilization of the polycyclic ring chain extender and the electrospinning were used together to prepare toughened poly(lactic acid) micro-nano fibers. At the same time, obvious cross-linking points appear between the fibers, which further improves the mechanical properties of the poly(lactic acid) micro-nano fiber membrane. Selective surface superwetting is one of the important prerequisite conditions for materials to achieve efficient oil-water separation. Figure 1(b) is the water contact angle diagram of the toughened polylactic acid micro-nano fibers. It can be seen from the figure that the water contact angle of the toughened polylactic acid micro-nano fibers reaches 137°. Due to the hydrophobicity of polylactic acid and thermoplastic elastomers, the toughened polylactic acid micro-nano fibers have good hydrophobic effects. This observation not only demonstrates the potential high efficiency of the toughened polylactic acid micro-nano fibers in simulated oil-water separation applications, but also highlights their potential for multi-functional self-cleaning, separation, and filtration applications in practical scenarios.

[0103] To prove the structural stability, high specific surface area, and porous structure of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material, its microscopic morphology was characterized. Figure 2 It is the scanning electron microscope image of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material. Figure 2 (a) is the microscopic morphology image of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material magnified 500 times. It can be seen from the figure that there are a large number of pores formed by the cross-linking of polylactic acid micro-nano fibers in the polylactic acid micro-nano fiber aerogel. The toughened polylactic acid micro-nano fibers were broken into micro-nano short fibers by a homogenizer, and then used as the gel framework. Using waterborne polyurethane as the micro-nano fiber cross-linking agent, through freeze-drying, the ice crystals formed by the tert-butanol aqueous solution rapidly sublimated to form a large number of pores. At the same time, the polylactic acid micro-nano fibers cross-linked to form a three-dimensional porous structure. The polylactic acid micro-nano fiber aerogel simultaneously has the high specific surface area of the polylactic acid micro-nano fibers and the porous structure of the aerogel and Figure 2 (b) is the microscopic morphology image of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material magnified 1000 times and locally magnified 5000 times. It can be seen from the figure that in the highly elastic and compressible polylactic acid micro-nano fiber aerogel material, the porous structure formed by the cross-linking of micro-nano fibers and the state of the cross-linking of waterborne polyurethane between the fibers. Through the role of the "bridging agent", waterborne polyurethane binds the micro-nano fibers together, thus maintaining the stable morphology of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material, and at the same time further increasing the mechanical compressibility and elastic recovery of the aerogel material.

[0104] Selective surface superwetting is one of the important prerequisite conditions for materials to achieve efficient oil-water separation. To prove the hydrophobicity and lipophilic effect of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material, the water contact angle and oil contact angle of the material were tested. Figure 3 It is the selective surface superwetting diagram of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material. From Figure 3(a) It can be seen that the toughened polylactic acid micro-nano fibers show a certain degree of hydrophobicity, with a water contact angle of 137°. This is mainly due to the large number of hydrophobic ester groups and alkyl groups present in the PLA molecular chain backbone and the molecular chains of the thermoplastic elastomer. In contrast, the surface of the polylactic acid micro-nano fiber aerogel crosslinked by aqueous polyurethane has a multi-scale nanofiber / porous structure, showing extremely high superhydrophobicity. The water contact angle of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material in air reaches 152°( Figure 3 (b)), while the oil contact angle is close to 0°( Figure 3 (c)). This is attributed to the strong non-polarity of the alkane or aromatic hydrocarbon groups in the thermoplastic elastomer, which can form strong interactions with non-polar substances. This result reflects the superoleophilic / superhydrophobic selective wetting property of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material.

[0105] To prove the mechanical properties of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material, its compression recovery and elasticity were tested. Figure 4 is the compression-rebound stress-strain diagram and the height retention rate after cyclic compression of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material. As can be seen from Figure 4 (a), when the compression strain in the first cycle is 50%, the maximum stress of the material can reach 21 kPa. When compressed 10 cycles, 100 cycles, 500 cycles, and 1000 cycles, the maximum stress value of the material still reaches about 18.5 kPa, which is significantly higher than that of the same type of materials (Advanced functional materials (2024), 2412424: 1-9). At the same time, it can be seen that the area enclosed by the stress-strain curve when the material is compressed and rebounded is small, indicating that the polylactic acid micro-nano fiber aerogel material has low rebound response hysteresis and high elasticity. The polylactic acid micro-nano fiber aerogel material can achieve a compression effect of 50% strain, which reflects its high compressibility. The excellent mechanical properties of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material are mainly attributed to the toughened polylactic acid micro-nano fibers obtained by in-situ phase interface compatibilization with a polycyclic chain extender and the stability of the three-dimensional porous structure crosslinked by the aerogel. Figure 4 (b) is the height retention rate of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material after 1000 cycles of cyclic compression at a compression strain of 50%. It can be seen from the figure that its height retention rate reaches 66.7%, further indicating that the highly elastic and compressible polylactic acid micro-nano fiber aerogel material has outstanding mechanical properties, which is attributed to the stability of the structure of the polylactic acid micro-nano fiber aerogel material. In summary, the excellent mechanical properties of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material are proved, which provides a basis for its use in suction filtration or emulsion separation driven by external pressure and material reuse in oil-water separation applications.

[0106] To prove the stability of in-situ phase interface compatibilization and the composite of highly elastic and compressible polylactic acid micro-nano fiber aerogel materials through chemical reactions between polylactic acid and thermoplastic elastomers, their microscopic chemical structures were characterized. Figure 5 This is the infrared spectrum of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material. For polylactic acid molecules, the peak at 1755 cm -1 is attributed to C=O, and the peaks at 1450 and 1365 cm -1 come from the -CH 3 vibration peak, and the peak at 1180 cm-1 is attributed to the -CO-ester group. Meanwhile, an obvious vibration peak is seen at 1080 cm -1 which is attributed to the stretching peak of C-O-C in polylactic acid molecules. For thermoplastic elastomers, the peak observed at 3325 cm -1 is related to the -NH stretching vibration. The peak at 1528 cm -1 can be attributed to the -CN stretching vibration, while the peak at 1595 cm -1 indicates the -NH bending vibration of the polyurethane group in the thermoplastic elastomer. In addition, the peaks at 2950 and 2870 cm -1 correspond to the asymmetric and symmetric vibrations of the -CH 2 - group respectively. The doublet at 1,700 - 1730 cm -1 is related to the C=O stretching vibration, where the peak at 1725 cm -1 is related to the free carbonyl group, and the peak at 1700 cm -1 is related to the hydrogen-bonded carbonyl group.

[0107] For the toughened polylactic acid micro-nano fiber molecules, the characteristic peak signals of both polylactic acid and thermoplastic elastomers after mixing can be clearly seen in the infrared spectrum. Among them, the vibration peaks at 3325, 2,950, 2,870, 1725, 1700, 1595 and 1528 cm -1 etc. come from the thermoplastic elastomer, and the vibration peaks at 1755, 1450, 1365 and 1080 come from the polylactic acid molecules. Notably, the peak at 1180 cm -1 is attributed to the -CO-ester group, and the peak signal intensity at this position is significantly higher than that of polylactic acid and thermoplastic elastomers. This is because during the construction stage of electrospun polylactic acid micro-nano fibers, the polycyclic chain extender molecules contain epoxy groups, which have high reactivity. During the in-situ compatibilization reaction process, the epoxy groups open the ring and react with the functional groups (-OH and -COOH) of polylactic acid and thermoplastic elastomers to form new -CO-ester chemical bonds, thus making 1180 cm -1The peak signal intensity at [specific location] increases, which confirms the in-situ phase interface compatibilization between polylactic acid and thermoplastic elastomer through chemical reactions. The covalent bridging between polylactic acid, thermoplastic elastomer, and polycyclic chain extender is achieved by in-situ phase interface compatibilization. Through the in-situ phase interface compatibilization and electrospinning technology, tough polylactic acid micro-nano fibers are prepared. The mechanical properties of polylactic acid fibers and polylactic acid micro-nano fiber aerogel materials are significantly improved by the in-situ phase interface compatibilization and electrospinning technology. For the highly elastic and compressible polylactic acid micro-nano fiber aerogel material, it is mainly composed of toughened polylactic acid micro-nano fibers and waterborne polyurethane. Characteristic signal peaks of toughened polylactic acid micro-nano fiber molecules and waterborne polyurethane molecules can be observed in the highly elastic and compressible polylactic acid micro-nano fiber aerogel material. Since the peak at 1725 cm -1 in polyurethane is related to the free carbonyl group, the vibration signal of this free carbonyl group can be clearly seen in the infrared spectrum of waterborne polyurethane. It is worth noting that when toughened polylactic acid micro-nano fiber molecules and waterborne polyurethane molecules are combined, the peak signal intensity at 1725 cm -1 in the highly elastic and compressible polylactic acid micro-nano fiber aerogel material is significantly enhanced, indicating good compounding of the two. In summary, the successful preparation and stable structure of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material are demonstrated through the microscopic chemical structure.

[0108] When the highly elastic and compressible polylactic acid micro-nano fiber aerogel material is applied to the field of oil-water separation, the experimental results of its oil absorption in water, dynamic separation of immiscible oil-water mixtures, and separation of miscible oil-water emulsions are shown respectively as Figure 6 、 Figure 7 and Figure 8 shown. As shown in Figure 6 (a), the oil absorption capacities of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material for silicone oil, vacuum pump oil, n-hexane, cyclohexane, and petroleum ether are 21.0, 17.4, 17.5, 20.8, and 15.3 g·g -1 respectively. This result is significantly higher than that of the reported products of the same type (Journal of Dispersion Science and Technology (2019), 41(2), 289–296 and Journal of Porous Materials (2022), 29:241–247). This significantly improved oil absorption performance can be attributed to its high specific surface area and three-dimensional porous structure, which provide additional storage space for oil. The oil can quickly spread on the rough surface of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material and further penetrate into the internal porous network. In addition, as shown in Figure 6(As shown in (b), the highly elastic and compressible polylactic acid micro-nano fiber aerogel material still exhibited excellent and long-lasting oil absorption stability after 10 cycle tests, which was attributed to the excellent mechanical properties of the material. These results not only demonstrated the application potential of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material in the oil-water separation field, but also emphasized its long-term reliability as an environmental purification material. The excellent superhydrophobicity, superoleophilicity, waterproof adhesion of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material, as well as its unique micro-nano fiber high specific surface area and three-dimensional porous structure, jointly made it a highly potential candidate material in the oil-water separation field. Using gravity drive, the immiscible oil / water mixture could be effectively separated. The oil phase could rapidly penetrate through the highly elastic and compressible polylactic acid micro-nano fiber aerogel material, while the water phase was successfully repelled and intercepted by the surface layer of the biomimetic sponge. In the separation tests of five different oil-water mixtures (silicone oil / water, vacuum pump oil / water, n-hexane / water, cyclohexane / water, and petroleum ether / water), the highly elastic and compressible polylactic acid micro-nano fiber aerogel material showed high separation flux characteristics, and the permeation fluxes were as high as 24032, 20628, 20854, 19532, 22563 L·m -2 ·h -1 (as Figure 7 (shown in (a)). This result highlighted the high-efficiency ability of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material in oil-water separation applications, especially in dealing with oil-water mixtures containing oil phases with different densities and viscosities. It should be noted that the density and viscosity of the oil were the key factors affecting the separation performance of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material sponge. Especially for the silicone oil / water mixture, the relatively high separation flux might be due to the relatively high density (0.963 g·cm -3 ) of the silicone oil, which promoted the rapid penetration of its fluid. The unique high specific surface area and three-dimensional porous structure of the highly elastic and compressible polylactic acid micro-nano fiber aerogel material not only provided high-efficiency oil-water separation ability, but also could still maintain a separation efficiency as high as 99.92% after 10 cycle tests, demonstrating its excellent separation stability, as Figure 7(as shown in (b)). This persistent performance indicates that the highly elastic and compressible poly(lactic acid) micro-nano fiber aerogel material has the potential for long-term applications in the field of oil-water separation, providing an effective approach to achieving efficient, long-lasting, and sustainable oil-water separation technologies. The highly elastic and compressible poly(lactic acid) micro-nano fiber aerogel material with superhydrophobic and superoleophilic properties can effectively capture oil droplets at the micro-nano scale and form a stable oil layer, relying on the high specific surface area and three-dimensional porous structure of its micro-nano fibers. This adsorption mechanism promotes the formation of a composite interface between the fiber surface and the oil phase and effectively prevents the adsorption of water molecules by enhancing the capillary retention force. Further, with the help of capillary action, the oil phase can quickly penetrate through the three-dimensional porous structure of the poly(lactic acid) micro-nano fiber aerogel, achieving efficient water-in-oil emulsion separation. Figure 8 (a) shows that when using the highly elastic and compressible poly(lactic acid) micro-nano fiber aerogel material as a filtration medium, the water content of the filtrate treated by the highly elastic and compressible poly(lactic acid) micro-nano fiber aerogel material is less than 60 ppm, and the separation efficiency reaches 99%. As Figure 8 (b) shows, under the condition that the external driving pressure increases from 0 to 20 kPa, the permeation fluxes of the highly elastic and compressible poly(lactic acid) micro-nano fiber aerogel material for the (water / silicone oil) water-in-oil emulsion system reach 1003, 2080, 3500, 4000, 4800 L·m -2 ·h -1 respectively, and the water content of the filtered liquid remains below 88 ppm. This result demonstrates the importance of the high specific surface area structure of the micro-nano fibers in the highly elastic and compressible poly(lactic acid) micro-nano fiber aerogel material, as well as the synergistic effect of the superhydrophobic / superoleophilic selective wetting property and the importance of interconnected porous channels. These factors jointly contribute to the excellent performance of the highly elastic and compressible poly(lactic acid) micro-nano fiber aerogel material in effectively retaining emulsified water droplets and promoting the rapid penetration of the oil phase.

[0109] The structure, characteristics, and effects of the present invention have been described in detail based on the embodiments shown in the drawings. The above are only the preferred embodiments of the present invention, but the present invention is not limited to the scope shown in the drawings. Any changes made according to the concept of the present invention, or equivalent embodiments modified into equivalent changes, should still be within the protection scope of the present invention when they do not exceed the spirit covered by the description and the drawings.

Claims

1. A method for preparing a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, which is used to prepare a highly elastic and compressible polylactic acid micro-nano fiber aerogel material, characterized in that: The following steps are involved: S1: dissolving polylactic acid and a thermoplastic elastomer in a compound solvent to obtain a polymer solution, adding a polycyclic chain extender to the polymer solution, ultrasonically dispersing the solution for in-situ phase interface volume expansion, and vacuum degassing to obtain a spinning precursor solution, wherein the thermoplastic elastomer is at least one of aliphatic polyether urethane TPU, aromatic polyether urethane TPU, aliphatic polycarbonate urethane TPU, and aromatic polycarbonate urethane TPU, and the polycyclic chain extender is styrene-glycidyl methacrylate oligomer; S2: The spinning precursor solution is subjected to high-voltage electrospinning to obtain toughened polylactic acid micro-nanofibers; S3: Use a homogenizer to disperse the toughened polylactic acid micro-nano fibers into a tert-butyl alcohol aqueous solution, add aqueous polyurethane as a cross-linking agent into the aqueous solution to obtain a toughened polylactic acid micro-nano fiber hydrogel, and vacuum freeze-dry the hydrogel material to obtain a highly elastic and compressible polylactic acid micro-nano fiber aerogel material.

2. The method for preparing the highly elastic and compressible polylactic acid micro-nano fiber aerogel material according to claim 1, characterized in that: The composite solvent in step S1 is composed of tetrahydrofuran and N,N'-dimethylformamide in a mass ratio of 1 to 3:1; In step S1, the amount of the polylactic acid and the thermoplastic elastomer in the compounding solvent is 10-15wt%, and the mass ratio of the polylactic acid to the thermoplastic elastomer is 3:2; In step S1, the amount of the polycyclic chain extender in the polylactic acid and the thermoplastic elastomer is 0.5-2 wt%.

3. The method for preparing the highly elastic and compressible polylactic acid micro-nano fiber aerogel material according to claim 1, characterized in that: The ultrasonic dispersion treatment conditions in step S1 are: the power is set to 500-1200W, and the treatment time is 1-10h.

4. The method for preparing the highly elastic and compressible polylactic acid micro-nano fiber aerogel material according to claim 1, characterized in that: The high-voltage electrospinning parameters in step S2 are set as follows: high-voltage electrostatic 10-20 kV, a pushing speed of 1-5 ml / h, a receiving distance of 8-15 cm, and a spinning needle of any one of 19G, 20G, 21G, 22G, and 23G.

5. The method for preparing the highly elastic and compressible polylactic acid micro-nano fiber aerogel material according to claim 1, characterized in that: In step S3, the amount of the toughened polylactic acid micro-nano fibers in the tert-butyl alcohol aqueous solution is 0.5-2 wt %.

6. The method for preparing the highly elastic and compressible polylactic acid micro-nano fiber aerogel material according to claim 1, characterized in that: The tert-butanol aqueous solution in step S3 is composed of tert-butanol and aqueous solution in a mass ratio of 1:

4. The processing conditions of the homogenizer are: 10000-20000 rpm, and the processing time is 0.5-2h.

7. The method for preparing highly elastic and compressible polylactic acid micro-nano fiber aerogel material according to claim 1, characterized in that: The mass ratio of the waterborne polyurethane to the toughened polylactic acid micro-nanofibers in step S3 is 0.1-1:1, and the waterborne polyurethane is at least one of aromatic isocyanate type WPU, aliphatic isocyanate type WPU, and alicyclic isocyanate type WPU.

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